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1. Duan, Lele
Bozoglian, Fernando
Mandal, Sukanta
Stewart, Beverly
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Privalov, Timofei
Llobet, Antoni
Sun, Licheng
A molecular ruthenium catalyst with water-oxidation activity comparable to that of photosystem II2012In: Nature Chemistry, ISSN 1755-4330, E-ISSN 1755-4349, Vol. 4, no 5, p. 418-423Article in journal (Refereed)
Across chemical disciplines, an interest in developing artificial water splitting to O-2 and H-2, driven by sunlight, has been motivated by the need for practical and environmentally friendly power generation without the consumption of fossil fuels. The central issue in light-driven water splitting is the efficiency of the water oxidation, which in the best-known catalysts falls short of the desired level by approximately two orders of magnitude. Here, we show that it is possible to close that 'two orders of magnitude' gap with a rationally designed molecular catalyst [Ru(bda)(isoq)(2)] (H(2)bda = 2,2'-bipyridine-6,6'-dicarboxylic acid; isoq = isoquinoline). This speeds up the water oxidation to an unprecedentedly high reaction rate with a turnover frequency of >300 s(-1). This value is, for the first time, moderately comparable with the reaction rate of 100-400 s(-1) of the oxygen-evolving complex of photosystem II in vivo.
Nyhlén, Jonas
Fischer, Andreas
Xu, Yunhua
Highly Active Mononuclear Ru Catalysts for Water Oxidation: O-O Bond Formation via Direct Radical CouplingIn: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126Article in journal (Refereed)
Heshmat, Mojgan
A Prediction of Proton-Catalyzed Hydrogenation of Ketones in Lewis Basic Solvent through Facile Splitting of Hydrogen Molecules2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 5, p. 1036-1039Article in journal (Refereed)
A ketone's carbonyl carbon is electrophilic and harbors a part of the lowest unoccupied molecular orbital of the carbonyl group, resembling a Lewis acidic center; under the right circumstances it exhibits very useful chemical reactivity, although the natural electrophilicity of the ketone's carbonyl carbon is often not strong enough on its own to produce such reactivity. Quantum chemical calculations predict that a proton shared between a ketone and the Lewis basic solvent molecule (dioxane or THF) activates carbonyl carbon to the point of enabling a facile heterolytic splitting of H-2. Proton-catalyzed hydrogenation of a ketone in Lewis basic solvent is the result. The mechanism involves the interaction of H-2 with the enhanced Lewis acidity of a carbonyl carbon and the free Lewis basic solvent molecule polarizes H-2 and enables the hydride-type attack on carbonyl carbon, which is very strongly influenced by the proton shared between a ketone and solvent. The hydride-type attack on carbon is reminiscent of the splitting of H-2 by singlet carbenes except that, in this case, a Lewis base from the surrounding environment (solvent) is necessary for polarization of H-2 and acceptance of the proton resulting from the heterolytic splitting of H-2.
Carbonyl Activation by Borane Lewis Acid Complexation: Transition States of H-2 Splitting at the Activated Carbonyl Carbon Atom in a Lewis Basic Solvent and the Proton-Transfer Dynamics of the Boroalkoxide Intermediate2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 38, p. 9098-9113Article in journal (Refereed)
By using transition-state (TS) calculations, we examined how Lewis acid (LA) complexation activates carbonyl compounds in the context of hydrogenation of carbonyl compounds by H-2 in Lewis basic (ethereal) solvents containing borane LAs of the type (C6F5)(3)B. According to our calculations, LA complexation does not activate a ketone sufficiently enough for the direct addition of H-2 to the O = C unsaturated bond; but, calculations indicate a possibly facile heterolytic cleavage of H-2 at the activated and thus sufficiently Lewis acidic carbonyl carbon atom with the assistance of the Lewis basic solvent (i.e., 1,4-dioxane or THF). For the solvent-assisted H-2 splitting at the carbonyl carbon atom of (C6F5)(3)B adducts with different ketones, a number of TSs are computed and the obtained results are related to insights from experiment. By using the Born-Oppenheimer molecular dynamics with the DFT for electronic structure calculations, the evolution of the (C6F5)(3)B-alkoxide ionic intermediate and the proton transfer to the alkoxide oxygen atom were investigated. The results indicate a plausible hydrogenation mechanism with a LA, that is, (C6F5)(3)B, as a catalyst, namely, 1) the step of H-2 cleavage that involves a Lewis basic solvent molecule plus the carbonyl carbon atom of thermodynamically stable and experimentally identifiable (C6F5)(3)B-ketone adducts in which (C6F5)(3)B is the Lewis acid promoter, 2) the transfer of the solvent-bound proton to the oxygen atom of the (C6F5)(3)B-alkoxide intermediate giving the (C6F5)(3)B-alcohol adduct, and 3) the S(N)2-style displacement of the alcohol by a ketone or a Lewis basic solvent molecule.
Computational Elucidation of a Role That Bronsted Acidification of the Lewis Acid-Bound Water Might Play in the Hydrogenation of Carbonyl Compounds with H-2 in Lewis Basic Solvents2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 48, p. 11489-11493Article in journal (Refereed)
Bronsted acidification of water by Lewis acid (LA) complexation is one of the fundamental principles in chemistry. Using transition-state calculations (TS), herein we investigate the role that Bronsted acidification of the LA-bound water might play in the mechanism of the hydrogenation of carbonyl compounds in Lewis basic solvents under non-anhydrous conditions. The potential energy scans and TS calculations were carried out with a series of eight borane LAs as well as the commonly known strong LA AlCl3 in 1,4-dioxane or THF as Lewis basic solvents. Our molecular model consists of the dative LA-water adduct with hydrogen bonds to acetone and a solvent molecule plus one additional solvent molecule that participates is the TS structure describing the cleavage of H-2 at acetone's carbonyl carbon atom. In all the molecular models applied here, acetone (O=CMe2) is the archetypical carbonyl substrate. We demonstrate that Bronsted acidification of the LA-bound water can indeed lower the barrier height of the solvent-involving H-2-cleavage at the acetone's carbonyl carbon atom. This is significant because at present it is believed that the mechanism of the herein considered reaction is described by the same mechanism regardless of whether the reaction conditions are strictly anhydrous or non-anhydrous. Our results offer an alternative to this belief that warrants consideration and further study.
H-2 Cleavage by Frustrated Lewis Pairs Characterized by the Energy Decomposition Analysis of Transition States: An Alternative to the Electron Transfer and Electric Field Models2018In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 122, no 36, p. 7202-7211Article in journal (Refereed)
Knowing that the Papai's electron transfer (ET) and the Grimme's electric field (EF) models draw attention to somewhat different physical aspects, we are going to systematically (re)examine interactions in the transition states (TSs) of the heterolytic H-2-cleavage by the Frustrated Lewis Pairs (FLPs). Our main vehicle is the quantitative energy decomposition analysis (EDA), a powerful method for elucidation of interactions, plus the analysis of molecular orbitals (MOs). Herein, the Lewis acid (LA) is B(C6F5)(3) and the Lewis bases (LBs) are tBu(3)P, (o-C6H4Me)(3)P, 2,6-lutidine, 2,4,6-lutidine, MeN=C(Ph)Me imine, MeN(H)-C(H)PhMe amine, THF, 1,4-dioxane, and acetone. For a series of the phosphorus-, nitrogen-, and oxygen-bearing LBs plus B(C6F5)(3), we will show that (i) neither the electrostatic nor the orbital interactions dominate but instead both are essential alongside the Pauli repulsion and (ii) the frontier molecular orbitals (FMOs) of a TS can arise not only from the push-pull molecular orbital scheme by Papai et al., which directly involves the occupied sigma and the empty sigma* MOs of H-2, but also from a more intricate but energetically more fitting orbital interactions which have escaped notice thus far.
Structurally Flexible Oxocarbenium/Borohydride Ion Pair: Dynamics of Hydride Transfer on the Background of Conformational Roaming2018In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 122, no 23, p. 5098-5106Article in journal (Refereed)
We apply Born-Oppenheimer molecular dynamics to the practically significant [dioxane-H(+)-acetone]-[(C6F5)(3)B-H(-)] and [Et2O-H(+)-OCPr2][(C6F5)(3)B-H(-)] ion pair intermediates. Dynamics of hydride transfer in cation/anion ion pair takes place on the background of large amplitude configurational changes. Geometry of oxocarbenium/borohydride ion pairs is flexible, meaning that we uncover significant actual structural disorder at a finite temperature. Therefore, although the starting structure can be fairly close to the configurational area of the hydride transfer transition state (TS) and despite a low potential energy barrier (ca. 1.5 kcal/mol, according to the literature), already at T approximate to 325 K the system can remain ignorant of the TS region and move round and about (roam) in the configurational space for a period of time in the range between 10 and 100 ps. This indicates structural flexibility of oxocarbenium/borohydride ion pair on apparently a flat potential energy landscape of cation/anion interaction, and this has not been taken into consideration by the free energy estimations in static considerations made thus far. The difference between the dynamics-based representation of the system versus the static representation amounts to the difference between quasi-bimolecular versus unimolecular descriptions of the hydride transfer step.
Surprisingly Flexible Oxonium/Borohydride Ion Pair Configurations2018In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 122, no 15, p. 3713-3727Article in journal (Refereed)
We investigate the geometry of oxonium/borohydride ion pairs [ether-H(+) ether] [LA-H(-)] with dioxane, THF, and Et2O as ethers and B(C6F5)(3) as the Lewis acid (LA). The question is about possible location of the disolvated proton [ether -H(+) -ether], with respect to the hydride of the structurally complex [LA -H(-)] anion. Using Born Oppenheimer molecular dynamics and a comparison of the potential and free energies of the optimized configurations, we show that herein considered ion pairs are much more flexible geometrically than previously thought. Conformers with different locations of cations with respect to anions are governed by a flat energy -landscape. We found a novel configuration in which oxonium is below [LA-11((-))], with respect to the direction of borane -> hydride vector, and the proton -hydride distance is ca. 6 A. With calculations of the vibrational spectra of [ether-H(+)-ether][(C6F5)(3)B-H(-)] for dioxane, THF, and Et2O as ethers, we investigate the manifestation of SSLB-type (short, strong, low -barrier) hydrogen bonding in the OHO motif of an oxonium cation.
Theory-Based Extension of the Catalyst Scope in the Base-Catalyzed Hydrogenation of Ketones: RCOOH-Catalyzed Hydrogenation of Carbonyl Compounds with H-2 Involving a Proton Shuttle2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 72, p. 18193-18202Article in journal (Refereed)
As an extension of the reaction mechanism describing the base-catalyzed hydrogenation of ketones according to Berkessel et al., we use a standard methodology for transition-state (TS) calculations in order to check the possibility of heterolytic cleavage of H-2 at the ketone's carbonyl carbon atom, yielding one-step hydrogenation path with involvement of carboxylic acid as a catalyst. As an extension of the catalyst scope in the base-catalyzed hydrogenation of ketones, our mechanism involves a molecule with a labile proton and a Lewis basic oxygen atom as a catalyst-for example, R-C(= O) OH carboxylic acids-so that the heterolytic cleavage of H-2 could take place between the Lewis basic oxygen atom of a carboxylic acid and the electrophilic (Lewis acidic) carbonyl carbon of a ketone/aldehyde. According to our TS calculations, protonation of a ketone/aldehyde by a proton shuttle (hydrogen bond) facilitates the hydride-type attack on the ketone's carbonyl carbon atom in the process of the heterolytic cleavage of H-2. Ketones with electron-rich and electron-withdrawing substituents in combination with a few carboxylic and amino acids-in total, 41 substrate-catalyst couples-have been computationally evaluated in this article and the calculated reaction barriers are encouragingly moderate for many of the considered substrate-catalyst couples.
Water and a Borohydride/Hydronium Intermediate in the Borane-Catalyzed Hydrogenation of Carbonyl Compounds with H-2 in Wet Ether: A Computational Study2018In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 122, no 38, p. 8952-8962Article in journal (Refereed)
We have computationally evaluated water as an active Lewis base (LB) and introduced the borohydride/hydronium intermediate in the mechanism of B(C6F5)(3)-catalyzed hydrogenation of carbonyl compounds with H-2 in wet/moist ether. Our calculations extend the known frustrated Lewis pair mechanism of this reaction toward the inclusion of water as the active participant in all steps. Although the definition of the zero-energy point interweaves in comparison of the scenarios with and without water, we will be able to show that (i) water (hydrogen bonded to its molecular environment) can, in principle, act as a reasonably viable LB in cooperation with the borane Lewis acid such as B(C6F5)(3) but relatively a strong borane-water complexation can be the hindering factor; (ii) the herein-proposed borohydride/hydronium intermediates with the hydronium cation having three OH center dot center dot center dot ether hydrogen bonds or a combination of the OH center dot center dot center dot ether/OH center dot center dot center dot ketone hydrogen bonds appear to be as valid as the previously considered borohydride/oxonium or borohydride/oxocarbenium intermediates; (iii) the proton-coupled hydride transfer from the borohydride/hydronium to a ketone (acetone) has a reasonably low barrier. Our findings could be useful for better mechanistic understanding and further development of the aforementioned reaction.
Karlsson, Erik A.
Oxidation of ethers, alcohols, and unfunctionalized hydrocarbons by the methyltrioxorhenium/H2O2 system: a computational study on catalytic C-H bond activation2009In: Abstracts of Papers, 238th ACS National Meeting, Washington, DC, United States, August 16-20, 2009, Washington DC: American Chemical Society , 2009Conference paper (Other academic)
Oxidation of ethers, alcohols, and unfunctionalized hydrocarbons by the methyltrioxorhenium/H2O2 system: a computational study on catalytic C-H bond activation2009In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 15, no 8, p. 1862-1869Article in journal (Refereed)
A concerted mechanism that does not involve an ionic intermediate was revealed by a DFT study on oxidation of ethers, alcohols, and unfunctionalized hydrocarbons by methyltrioxorhenium/H2O2. Instead, C H insertion occurs through hydride transfer and then turns into a hydroxide transfer/rebound in a concerted fashion. The picture shows selected frames from an intrinsic reaction coordinate scan from the transition state to the product for the oxidation of cis-1,2-dimethylcyclohexane.
The potential-energy surfaces (PESs) of methyltrioxorhenium (MTO)-catalyzed C H insertion reactions in the presence of hydrogen peroxide were studied by accurate DFT methods for a series of substrates including unsaturated hydrocarbons, an ether, and an alcohol. Based on the comprehensive analysis of transition states and intrinsic reaction coordinate (IRC) scans, C H insertion was found to proceed by a concerted mechanism that does not require, as previously thought, a side-on or a butterfly-like transition state. We found that a typical transition state follows requirements of the SN2 reaction instead. Furthermore, by exploring the PESs of several C H insertion reactions, we discovered that no ionic intermediate is formed even in a polar solvent. The latter was modeled within the self-consistent reaction field approach in a polarizable continuum model (PB-SCRF/PCM). According to our study, C H insertion occurs by a concerted but highly asynchronous mechanism that first proceeds by hydride transfer and then turns into hydroxide transfer/rebound. For the oxidation of alcohols, C H bond cleavage occurs without formation of alkoxide intermediates on the dominant pathway. The computed deuterium kinetic isotope effect of 2.9 for the hydride-transfer transition state for alcohol oxidation is in good agreement with the experimental kH/kD ration of 3.2 reported by Zauche and Espenson. As confirmed by IRC and PES scans in different solvents, the OH-rebound phase of the C H insertion pathway demonstrates strong similarities with the rebound mechanism that was previously proposed for cytochrome P450 and metalloporphyrin-catalyzed oxidations.
Kärkäs, Markus D.
Åkermark, Torbjörn
Johnston, Eric V.
Karim, Shams R.
Laine, Tanja M.
Lee, Bao-Lin
Åkermark, Tobias
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
Åkermark, Björn
Water Oxidation by Single-Site Ruthenium Complexes: Using Ligands as Redox and Proton Transfer Mediators2012In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 51, no 46, p. 11589-11593Article in journal (Refereed)
Boschloo, Gerrit
Hagfeldt, Anders
Kloo, Lars
Regeneration of oxidized organic photo-sensitizers in Grätzel solar cells: quantum-chemical portrait of a general mechanism2010In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 11, no 9, p. 1858-1862Article in journal (Refereed)
Duan, Lele
Evolution of O2 in a seven-coordinate RuIV dimer complex with a [HOHOH]- bridge: A computational study2010In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 49, no 10, p. 1773-1777Article in journal (Refereed)
"Frustration" of orbital interactions in Lewis base/Lewis acid adducts: a computational study of H2 uptake by phosphanylboranes R2P=BR'22009In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, no 19, p. 2759-2764Article in journal (Refereed)
The reaction of mol. hydrogen with phosphanylboranes R2P:BR'2 (1) is systematically studied by d. functional theory calcns. and second order Moller-Plesset perturbation theory. The potential energy barriers and the exothermicity of H2 uptake are reported for a series of phosphanylboranes with different electron-donating and -withdrawing groups bound to phosphorus and boron. Systematic MO anal. reveals that the "frustration" between boron and phosphorus can be increased by modifying the substituents, and thus, AO interactions could be exploited in order to increase the reactivity of 1. Addnl., authors found a correlation between the potential energy barrier for H2 uptake and the energy of the HOMO of the P:B complex, which could be relevant for the prediction of the properties of candidate compds. for H2 activation and therefore useful for the development of such systems. [on SciFinder(R)]
Hydrogenation of carbon-heteroatom unsaturated bonds: An assessment of consistency of density functional methods2010In: Journal of Molecular Catalysis A: Chemical, ISSN 1381-1169, E-ISSN 1873-314X, Vol. 324, no 1-2, p. 97-103Article in journal (Refereed)
Hydrogenation of unsaturated carbon-heteroatom bonds, C = X, is the general process for which we assess consistency of quantum chemical calculations in the context of B(C6F5)3-catalyzed reduction of imines with H2. According to the mechanism of the reaction, computational uncertainty of energies of hydrogenation of imines, i.e. the difference between results obtained with different methods, contributes to method related uncertainties of the computed relative energies of key H2-activating species. For this reason, it is desirable to know the magnitude of methodological dependence/uncertainty of energies of hydrogenation. Calculations were performed with a number of different density functionals, such as M05-2X, M06-2X, B3LYP, B3PW91, BH&HLYP, MPW1K, MPW1PW91, HCTH407 and PBE, on a number of relevant imines and ketones/aldehydes. Additionally, second order Møller-Plesset perturbation theory was also evaluated. The results quantitatively reveal the manner in which the form of a method affects the calculated energy change and that there is substantial difference between results obtained with different methods even for structurally simple species.
On the possibility of catalytic reduction of carbonyl moieties with tris(pentafluorophenyl)borane and H2: a computational study2009In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 29, p. 5780-5786Article in journal (Refereed)
The study thoroughly examines the Gibbs free energy surfaces of a new mechanism for redn. of ketones/aldehydes by tris(pentafluorophenyl)borane (1) and H2. Key elements of the proposed mechanism are the proton and the hydride transfer steps similar to Stephan's catalytic redn. of imines by 1. The proton is transferred to the ketone/aldehyde in the process of H2 cleavage by the carbonyl-borane couple and the hydride is transferred in a nucleophilic attack on the carbonyl carbon by the hydridoborate in the ionic pair, [HOCRR']+[HB(C6F5)3]-. The in solvent Gibbs free energy barriers of H2 splitting by adducts of B(C6F5)3 with acetone, acetophenone and benzaldehyde are predicted to be in the range of 24.5 ± 2.5 kcal mol-1, which corresponds to potential energy barriers in the range of 17.0 ± 2.0 kcal mol-1. Significantly lower barrier of H2 activation is predicted in cases of bulky ketones such as 2,2,4,4-tetramethylpentan-3-one. With respect to the hydridoborate intermediate, the nucleophilic attack on the activated carbon is predicted to have a relatively low barrier for the sterically unhindered substrates, while this barrier is considerably higher for the sterically encumbered substrates. Since the formation of the hydridoborate intermediates is found to be endothermic, the transition state of the nucleophilic attack is the highest point of the computed energy profile for all tested substrates. Overall, according to in solvent d. function calcns. the proposed redn. of "compact" ketones/aldehydes by 1 and H2 is allowed both thermodynamically and kinetically at elevated temp., but it is expected to be slower and more substrate specific than the corresponding redn. of imines. [on SciFinder(R)]
Bäckvall, Jan-Erling
Racemization of alcohols catalyzed by [RuCl(CO)2(η5-pentaphenylcyclopentadienyl)] – Mechanistic insights from theoretical modeling2009In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 15, no 21, p. 5220-5229Article in journal (Refereed)
Two possible pathways of inner-sphere racemization of sec-alcohols by using the [RuCl(CO)(2)(eta(5)-pentaphenylcyclopentadienyl)] catalyst (1) have been thoroughly investigated by means of density function calculations. To be able to racemize alcohols, catalyst 1 needs to have a free coordination site on the metal. This can be achieved either by a eta(5)-->eta(3) ring slippage or by dissociation of a carbon monoxide (CO) ligand. The eta(5)-->eta(3) ring-slip pathway was found to have a high potential energy barrier, 42 kcal mol(-1), which can be explained by steric congestion in the transition state. On the other hand, CO dissociation to give a 16-electron complex has a barrier of only 22.6 kcal mol(-1). We have computationally discovered a mechanism involving CO participation that does not require eta(5)-->eta(3) ring slippage. The key features of this mechanism are 1) CO-assisted exchange of chloride for alkoxide, 2) alcohol-alkoxide exchange, and 3) generation of an active 16-electron complex through CO dissociation with subsequent beta-hydride elimination as the racemization step. We have found a low-energy pathway for reaction of 1 with potassium tert-butoxide and a pathway for fast alkoxide exchange with interaction between the incoming/leaving alcohol and one of the two CO ligands. We predict that dissociation of a Ru-bound CO ligand does not occur in these exchange reactions. Dissociation of one of the two Ru-bound CO ligands has been found necessary only at a later stage of the reaction. Though this barrier is still quite high, our results indicate that it is not necessary to cross the CO dissociation barrier for the racemization of each new alcohol. Thus, the dissociation of a CO ligand is interpreted as a rate-limiting reaction step in order to create a catalytically active 16-electron complex.
Hydrogenation of imines by phosphonium borate zwitterions: a theoretical study2009In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. -, no 8, p. 1321-1327Article in journal (Refereed)
On the possibility of conversion of alcohols to ketones and aldehydes by phosphinoboranes R2PBR'R'': a computational study2009In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 15, no 8, p. 1825-1829Article in journal (Refereed)
The role of amine-B(C6F5)3 adducts in the catalytic reduction of imines with H2: a computational study2009In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, no 15, p. 2229-2237Article in journal (Refereed)
Svensson, Per H.
A study of the interactions between I-/I3- redox , mediators amd organometallic sensitizing dyes in solar cells2009In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 2, p. 783-790Article in journal (Refereed)
The O-O Bonding in Water Oxidation: the Electronic Structure Portrayal of a Concerted Oxygen Atom-Proton Transfer Pathway2011In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, no 30, p. 8313-8317Article in journal (Refereed)
25. Pu, Maoping
Liberation of H-2 from (o-C6H4Me)(3)P-H(+) + H(-)-B(p-C6F4H)(3) ion-pair: A transition-state in the minimum energy path versus the transient species in Born-Oppenheimer molecular dynamics2017In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 147, no 1, article id 014303Article in journal (Refereed)
Using Born-Oppenheimer molecular dynamics (BOMD) with density functional theory, transition-state (TS) calculations, and the quantitative energy decomposition analysis (EDA), we examined the mechanism of H-2-liberation from LB-H(+) + H(-)-LA ion-pair, 1, in which the Lewis base (LB) is (o-C6H4Me)(3)P and the Lewis acid (LA) is B(p-C6F4H)(3). BOMD simulations indicate that the path of H-2 liberation from the ion-pair 1 goes via the short-lived transient species, LB center dot center dot center dot H(2 center dot center dot center dot)LA, which are structurally reminiscent of the TS-structure in the minimum-energy-path describing the reversible reaction between H-2 and (o-C6H4Me)(3)P/B(p-C6F4H)(3) frustrated Lewis pair (FLP). With electronic structure calculations performed on graphics processing units, our BOMD data-set covers more than 1 ns of evolution of the ion-pair 1 at temperature T approximate to 400 K. BOMD simulations produced H-2-recombination events with various durations of H-2 remaining fully recombined as a molecule within a LB/LA attractive pocket-from very short vibrational-time scale to time scales in the range of a few hundred femtoseconds. With the help of perturbational approach to trajectory-propagation over a saddle-area, we directly examined dynamics of H-2-liberation. Using EDA, we elucidated interactions between the cationic and anionic fragments in the ion-pair 1 and between the molecular fragments in the TS-structure. We have also considered a model that qualitatively takes into account the potential energy characteristics of H-H recombination and H-2-release plus inertia of molecular motion of the (o-C6H4Me)(3)P/B(p-C6F4H)(3) FLP.
Pu, Maoping
Ab initio dynamics trajectory study of the heterolytic cleavage of H2 by a Lewis acid [B(C6F5)3] and a Lewis base [P(tBu)3]2013In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 138, no 15, article id 154305Article in journal (Refereed)
Activation of H-2 by a frustrated Lewis pair (FLP) composed of B(C6F5)(3) and P(tBu)(3) species has been explored with high level direct ab initio molecular dynamics (AIMD) simulations at finite temperature (T = 300 K) in gas phase. The initial geometrical conditions for the AIMD trajectory calculations, i.e., the near attack conformations of FLP + H-2, were devised using the host-guest model in which suitable FLP conformations were obtained from the dynamics of the B(C6F5)(3)/P(tBu)(3) pair in gas phase. AIMD trajectory calculations yielded microscopic insight into effects which originate from nuclear motion in the reacting complex, e. g., the alternating compression/elongation of the boron-phosphorous distance and the change of the pyramidality of boron in B(C6F5)(3). The ensemble averaged trajectory analysis has been compared with the minimum energy path (MEP) description of the reaction. Similar to MEP, AIMD shows that an attack of the acid/base pair on the H-H bond gives rise to the polarization of the H-2 molecule and as a consequence generates a large dipole moment of the reacting complex. The MEP and AIMD portrayals of the reaction are fundamentally different in terms of the magnitude of the motion of nuclei in B(C6F5)(3) and P(tBu)(3) during the H-2 cleavage. In the AIMD trajectory simulations, geometries of B(C6F5)(3) and P(tBu)(3) appear as nearly frozen on the short time scale of the H-2 cleavage. This is contrary to the MEP picture. Several of the concepts which arise from this work, e. g., separation of time scales of nuclear motion and the time-dependence of the donor-acceptor interactions in the reacting complex, are important for the understanding of chemical reactivity and catalysis.
Ab Initio Molecular Dynamics Study of Hydrogen Cleavage by a Lewis Base [tBu(3)P] and a Lewis Acid [B(C6F5)(3)] at the Mesoscopic Level-Dynamics in the Solute-Solvent Molecular Clusters2014In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 15, no 17, p. 3714-3719Article in journal (Refereed)
With the help of state-of-the-art ab initio molecular dynamics methods, we investigated the reaction pathway of the {tBu(3)P + H-2 + B(C6F5)(3)} system at the mesoscopic level. It is shown that: i) the onset of H-2 activation is at much larger boronphosphorus distances than previously thought; ii) the system evolves to the product in a roaming-like fashion because of quasi-periodic nuclear motion along the asymmetric normal mode of PHHB fragment; iii) transient configurations of a certain type are present despite structural interference from the solvent; iv) transient-state configurations with sub-picosecond lifetime have potentially interesting infrared activity in the organic solvent (toluene) as well as in the gas phase. The presented results should be helpful for future experimental and theoretical studies of frustrated Lewis pair (FLP) activity.
Ab initio molecular dynamics with explicit solvent discovers a two-step pathway in the Frustrated Lewis Pair reactionIn: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765Article in journal (Refereed)
Ab Initio Molecular Dynamics with Explicit Solvent Reveals a Two-Step Pathway in the Frustrated Lewis Pair Reaction2015In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 21, no 49, p. 17708-17720Article in journal (Refereed)
The role solvent plays in reactions involving frustrated Lewis pairs (FLPs)-for example, the stoichiometric mixture of a bulky Lewis acid and a bulky Lewis base-still remains largely unexplored at the molecular level. For a reaction of the phosphorus/boron FLP and dissolved CO2 gas, first principles (Born-Oppenheimer) molecular dynamics with explicit solvent reveals a hitherto unknown two-step reaction pathway-one that complements the concerted (one-step) mechanism known from the minimum-energy-path calculations. The rationalization of the discovered reaction pathway-that is, the stepwise formation of P-C and O-B bonds-is that the environment (typical organic solvents) stabilizes an intermediate which results from nucleophilic attack of the phosphorus Lewis base on CO2. This finding is significant because presently the concerted reaction-path paradigm predominates in the rationalization of FLP reactivity. Herein we point out how to attain experimental proof of our results.
Binding of CO2 by a Mes(2)PCH(2)CH(2)B(C6F5)(2) Species: An Involvement of the Ground State Species in a Low-Energy Pathway2013In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 19, no 49, p. 16512-16517Article in journal (Refereed)
Chemistry of Intermolecular Frustrated Lewis Pairs in Motion: Emerging Perspectives and Prospects2015In: Israel Journal of Chemistry, ISSN 0021-2148, Vol. 55, no 2, p. 179-195Article, review/survey (Refereed)
This feature article describes the chemistry in motion of frustrated Lewis pairs (FLPs). With state-of-the-art ab initio molecular dynamics (AIMD) simulations supplemented by minimum energy path (MEP) and potential energy surface (PES) calculations, we examine the binding of CO2 and the heterolytic cleavage of H-2 by a Lewis base (LB), tBu(3)P, and a Lewis acid (LA), B(C6F5)(3). We strive to uncover and understand mechanistic implications of the physical laws that govern the behavior of a LB and a LA when they react with a third species (e.g., CO2 or H-2) at finite temperature. The approximation that we necessarily must make at present is to forgo the quantization of the movement of atoms in favor of the Born-Oppenheimer molecular dynamics (BOMD), which unfold according to the classical (Newton's) laws of motion. However, strict quantum chemical theory is used to compute all of the forces that govern the dynamics of the macromolecular FLP system. Using physical reasoning and innovative computer simulations, we show that multi-scale motion is the predominant mechanistic aspect in reactions of the tBu(3)P/B(C6F5)(3) FLP, as well as, conceivably, those of other similar intermolecular FLPs. Insight achieved thus far leads to a novel activity model for intermolecular FLPs and specific predictions, which could be useful for future experimental and theoretical studies of FLP and other chemistries.
How Frustrated Lewis Acid/Base Systems Pass through Transition-State Regions: H-2 Cleavage by [tBu(3)P/B(C6F5)(3)]2014In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 15, no 14, p. 2936-2944Article in journal (Refereed)
We investigate the transition-state (TS) region of the potential energy surface (PES) of the reaction tBu(3)P+H-2 +B(C6F5)(3)-> tBu(3)P-H(+)+H(-)-B(C6F5)(3) and the dynamics of the TS passage at room temperature. Owing to the conformational inertia of the phosphane center dot center dot center dot borane pocket involving heavy tBu(3)P and B(C6F5)(3) species and features of the PES E(P center dot center dot center dot H, B center dot center dot center dot H vertical bar B center dot center dot center dot P) as a function of P center dot center dot center dot H, B center dot center dot center dot H, and B center dot center dot center dot P distances, a typical reactive scenario for this reaction is a trajectory that is trapped in the TS region for a period of time (about 350 fs on average across all calculated trajectories) in a quasi-bound state (scattering resonance). The relationship between the timescale of the TS passage and the effective conformational inertia of the phosphane center dot center dot center dot borane pocket leads to a prediction that isotopically heavier Lewis base/Lewis acid pairs and normal counterparts could give measurably different reaction rates. Herein, the predicted quasi-bound state could be verified in molecular collision experiments involving femtosecond spectroscopy.
Multiple-Pathways of Carbon Dioxide Binding by a Lewis Acid [B(C6F5)(3)] and a Lewis Base [P(tBu)(3)]: The Energy Landscape Perspective2014In: International Journal of Quantum Chemistry, ISSN 0020-7608, E-ISSN 1097-461X, Vol. 114, no 4, p. 289-294Article in journal (Refereed)
Using the reaction-relevant two-dimensional potential energy surface, an accurate reaction-pathway mapping and ab inito molecular dynamics, it is shown that CO2 capture by P(tBu)(3) and B(C6F5)(3) species has many nearly degenerate reaction-routes to take. The explanation of that is in the topography of the transition state (saddle) area. An ensemble of asynchronous reaction-routes of CO2 binding is described in fine detail.
Uncovering the Role of Intra- and Intermolecular Motion in Frustrated Lewis Acid/Base Chemistry: Ab Initio Molecular Dynamics Study of CO2 Binding by Phosphorus/Boron Frustrated Lewis Pair [tBu(3)P/B(C6F5)(3)]2014In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 53, no 9, p. 4598-4609Article in journal (Refereed)
The role of the intra- and intermolecular motion, i.e., molecular vibrations and the relative motion of reactants, remains largely unexplored in the frustrated Lewis acid/base chemistry. Here, we address the issue with the ab initio molecular dynamics (AIMD) study of CO2 binding by a Lewis acid (LA) and a Lewis base (LB), i.e., tBu(3)P + CO2 + B(C6F5)(3) -> tBu(3)P-C(O)O-B(C6F5)(3) ([1]). Reasonably large ensemble of AIMD trajectories propagated at 300 K from structures in the saddle region as well as trajectories propagated directly from the reactants region revealed an effect arising from significant recrossing of the saddle area. The effect is that transient complexes composed of weakly interacting reactants nearly cease to progress along the segment of the minimum energy pathway (MEP) at the saddle region for a (subpicosecond) period of time during which the dominant factor is the light-to-heavy type of relative motion of the vibrating reactants, i.e., the bouncing-like movement of CO2 with respect to much heavier phosphine and borane as main contributor to the mode that is perpendicular to the MEP-direction. In terms of how P...C and B...O distances change with time, the roaming-like patterns of typical AIMD trajectories, reactive and nonreactive alike, extend far beyond the saddle region. In addition to the dynamical portrayal of [1], we provide the energy-landscape perspective that takes into account the hierarchy of time scales. The verifiable implication of the effect found here is that the isotopically substituted (heavier) LB/LA pair should be less reactive that the normal and thus lighter counterpart.
Martin-Matute, Belén
Bäckvall, Jan-E.
A computational study of the CO dissociation in cyclopentadienyl ruthenium complexes relevant to the racemization of alcohols2013In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 42, no 4, p. 927-934Article in journal (Refereed)
The formation of an active 16-electron ruthenium sec-alkoxide complex via loss of the CO ligand is an important step in the mechanism of the racemization of sec-alcohols by (eta(5)-Ph5C5) Ru(CO)(2)X ruthenium complexes with X = Cl and OtBu. Here we show with accurate DFT calculations the potential energy profile of the CO dissociation pathway for a series of relevant (eta(5)-Ph5C5) Ru(CO) 2X complexes, where X = Cl, OtBu, H and (COOBu)-Bu-t. We have found that the CO dissociation energy increases in the following order: OtBu (lowest), Cl, COOtBu and H (highest). Using the distance between ruthenium and C-CO, r = Ru-C-CO, as a constraint, and by optimizing all other degrees of freedom for a range of Ru-CO distances, we obtained relative energies, Delta E(r) and geometries of a sufficient number of transient structures with the elongated Ru-CO bond up to r = 3.4 angstrom. Our calculations provide a quantitative understanding of the CO ligand dissociation in (eta(5)-Ph5C5) Ru(CO)(2)Cl and (eta(5)-Ph5C5) Ru(CO) 2(OtBu) complexes, which is relevant to the mechanism of their catalytic activity in the racemization of alcohols. We recently reported that exchange of the CO ligand by isotopically labeled (CO)-C-13 in the Ru-(OBu)-Bu-t complex occurs twenty times faster than that in the Ru-Cl complex. This corresponds to a difference of 1.8 kcal mol(-1) in the CO dissociation energy (at room temperature). This is in very good agreement with the calculated difference between the two potential energy curves for Ru-OtBu and Ru-Cl complexes, which is about 1.8-2 kcal mol(-1) around the corresponding transition states of the CO dissociation. The calculated difference in the total energy for CO dissociation in (eta(5)-Ph5C5) Ru(CO)(2)X complexes is related to the stabilization provided by the X group in the final 16-electron complexes, which are formed via product-like transition states. In addition to the calculated transition states of CO dissociation in Ru-OtBu and Ru-Cl complexes, the calculated transient structures with the elongated Ru-CO bond provide insight into how the geometry of the ruthenium complex with a potent heteroatom donor group (X) gradually changes when one of the COs is dissociating.
36. Tong, Lianpeng
Structural Modifications of Mononuclear Ruthenium Complexes: A Combined Experimental and Theoretical Study on the Kinetics of Ruthenium-Catalyzed Water Oxidation2011In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 50, no 2, p. 445-449Article in journal (Refereed)
37. Wang, Lei
Liu, Jianhui
Toward Controlling Water Oxidation Catalysis: Tunable Activity of Ruthenium Complexes with Axial Imidazole/DMSO Ligands2012In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 134, no 45, p. 18868-18880Article in journal (Refereed)
Using the combinations of imidazole and dimethyl :sulfoxide (DMSO) as axial ligands and 2,2'-bipyridine-6,6'-dicarboxylate (bda) as the equatorial ligand, we have synthesized six novel ruthenium complexes with noticeably different activity as water oxidation catalysts (WOCs). In four C-s symmetric Ru-II(kappa(3)-bda)(DMSO)L-2 complexes L = imidazole (1), N-methylimidazole (2), 5-methylimidazole (3), and 5-bromo-N-methylimidazole (4). Additionally, in two C-2v symmetric Ru-II(kappa(4)-bda)L-2 complexes L = 5-nitroimidazole (5) and 5-bromo-N-methylimidazole (6), that is, fully equivalent axial imidazoles. A detailed characterization of all complexes and the mechanistic investigation of the catalytic water oxidation have been carried out with a number of experimental techniques, that is, kinetics, electrochemistry and high resolution mass spectrometry (HR-MS), and density functional theory (DFT) calculations. We have observed the in situ formation: of a Ru-II-complex with the accessible seventh coordination position. The measured catalytic activities and kinetics of complex 1-6 revealed details about an important structure activity relation: the connection between the nature of axial ligands in the combination and either the increase or decrease of the catalytic activity. In particular, an axial DMSO group substantially increases the turnover frequency of WOCs reported in article, with the ruthenium-complex having one axial 5-bromo-N-methylimidazole and one axial DMSO: (4), we have obtained a high initial turnover frequency of similar to 180 s(-1). DFT modeling Of the binuclear reaction pathway of the O-O bond formation in catalytic Water oxidation further corroborated the concept of the mechanistic significance of the axial ligands and rationalized the experimentally observed difference in the activity of complexes with imidazole/DMSO and imidazole/imidazole combinations of axial ligands.
Åberg, Jenny B.
Martín-Matute, Belén
CO Assistance in ligand exchange of a ruthenium racemization catalyst: identification of an acyl intermediate2009In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 131, no 27, p. 9500-9501Article in journal (Refereed)
An acyl intermediate in the activation of eta(5)-(Ph(5)Cp)Ru(CO)(2)Cl by t-BuOK was identified by means of in situ FT-IR measurements and NMR spectroscopy. This strongly supports the conclusion that the ligand exchange takes place via CO assistance, i.e., that the activation occurs via nucleophilic attack by tert-butoxide on one of the CO ligands. The tert-butoxycarbonyl intermediate shows stretching vibrations at 1933 and 1596 cm(-1), corresponding to the CO and COOt-Bu groups, respectively. In the (13)C NMR spectrum, the CO group appears at 209.5 ppm and the COOt-Bu group at 208.7 ppm. The NMR assignments were confirmed by density functional theory calculations. The subsequent alcohol-alkoxide exchange is also thought to take place via CO assistance. However, no intermediate in that step could be detected.


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A Marxist History of the World part 23: The Abbasid Revolution
Written by Neil Faulkner
Published in A Marxist History of The World
Islam created a single overarching allegiance throughout the Arab-ruled world yet the Middle East came to be a divided region of weak and unpopular states. Neil Faulkner looks at the conflicts that lay behind this process.
The Arab conquests which began in 632 CE (common era) eventually gave Arab rulers and their warrior retinues control of territories that stretched from the Atlantic to Afghanistan. They inherited the wealth of Byzantine Syria, Sassanid Iraq, and Visigothic Spain. Such accretions of power and wealth made a social order based on desert tribes and the caravan trade unsustainable.
The Islamic Empire remained united immediately after Muhammad's death under the leadership of the first caliph (or 'successor'), Abu Bakr, but the second caliph, Umar, was murdered in 644 CE, the third, Uthman, in 656 CE, and the fourth, Ali, in 661 CE.
The crisis of 658-661 CE was decisive. Ali was overthrown after a full-scale civil war, and not only was he murdered, but also his son, Husein, some 19 years later. The victor of the dynastic struggle was Mu'awiya, who founded the Damascus-based Umayyad dynasty in the year of Ali's murder.
These apparently obscure events matter. Ali was the son-in-law of the Prophet. Mu'awiya was a cousin of the murdered caliph Uthman, another onetime intimate of Muhammad. The Islamic politico-religious elite was tearing itself apart.
The split would never heal. There is a direct line from Uthman and Mu'awiya to today's Sunni Muslims, and from Ali and Husein to today's Shi'ites.
The Umayyads wanted to enjoy the fruits of empire. The followers of Ali and Husein wanted to preserve the purity of early Islam. This was, in part, a class split, and the Sunni-Shi'ite division retains something of this character today.
For a century, the Umayyads retained power, held the empire together, and exploited the wealth and skills of the old civilisations. The Arab world enjoyed rich irrigation agriculture, sophisticated urban crafts, a dynamic banking system, and a strong tradition of scholarship, literature, and art. The Western world, by contrast, was living in 'the Dark Ages'.
Two contradictions undermined the Umayyad Empire and eventually brought it down. First, the geography of the Arab world contained several natural economic units, in which separate ruling classes with interests of their own rapidly developed. Distance limited the effectiveness of Umayyad rule. How could armies in Damascus expect to control Baghdad, Cairo, Tunis, and Fez?
Second, the Umayyads represented the Arab warrior aristocracy which had carried out the original Islamic conquests and then settled in the ancient cities of Syria. This elite built themselves palaces and spent lavishly on architecture, art, and luxury goods.
They were supported by the Arab rank-and-file, settled in garrison-towns, exempt from taxation, and supported by pensions paid for out of booty and tribute. The Umayyad ruling class was small and parasitic, and it rested on a narrow base of military freeloaders.
But the economy was booming. War between the old empires had devastated farms, disrupted trade, and drained away taxes and manpower. The Pax Islamica meant that agriculture and trade flourished, ancient towns hollowed out by decay were transformed into commercial powerhouses, and the merchant and artisan classes grew in numbers, prosperity, and assertiveness. Here were the social roots of a new revolution.
Many converted to Islam. Keen to limit the number exempt from taxation, however, the Umayyads created a new category of second-class Muslims: new converts were designated mawali and excluded from Arab privilege.
By the middle of the 8th century CE, the Arabs were a small military aristocracy living off the tribute paid by a growing mass of urban-based Muslim merchants and artisans. The latter provided a ready audience for Islamic dissidents like the Shi'ites, the yet-more-radical Kharijites, and various messianic mahdis ('guided ones').
None of the dissident movements was strong enough to break the power of the Umayyad state; they merely expressed the social discontent and symbolised its instability. What was decisive was an opportunist split in the Arab ruling class.
Abu-I-Abbas, a descendant of Muhammad's family, built an underground network of supporters in Iraq, placed himself at the head of the various dissident groups, and then launched an Islamic insurrection to overthrow the Umayyad dynasty.
The Umayyads were defeated, and a new Abbasid dynasty was founded in 750 CE, with its capital in Baghdad.
Power passed to a more broadly-based and inclusive urban elite of officials, merchants, and Islamic scholars and clerics. Arab ethnicity and warrior status lost much of their significance. Agriculture, trade, and towns continued to grow.
Even so, the two contradictions of Early Islamic empire soon reasserted themselves, albeit on a more elevated level. The towns were the centres of Islamic life, but they were largely self-sufficient and independent, the urban elites preoccupied with agriculture, trade, craft production, religious observance, and the maintenance of order. Their concerns were parochial.
A wide gap separated this social base from the Early Islamic state. The Abbasid caliphs were threatened by secession on the fringes of empire, coups by disaffected elite factions, and revolt from below by religious sectarians or sections of the exploited rural masses. The Early Islamic state therefore acquired an existence over and above society. It became little more than a mechanism for accumulating the military resources necessary to perpetuate the ruling dynasty.
The Umayyads had already separated themselves from civil society by building palaces and consuming luxuries. The Abbasids took this much further.
To free themselves from subordination to the Baghdad urban elite, they built a magnificent new palace-city 120km up the River Tigris at Samarra. The first palace, built in 836-842 CE, was bigger than Louis XIV's Versailles. Yet two more similar palaces were built in the next 40 years.
The Abbasid state was further de-anchored when it replaced the old Arab tribal host with a new army of mercenaries, mainly Turks from Central Asia, quartered at Samarra.
The court and the army were sustained by taxes, especially those levied on non-Muslims. The tribes and towns of Islamic society, meantime, developed strong local identities and ideologies. Though Islam created a single overarching allegiance throughout the Arab-ruled world, no strong ties of any kind bound state and society.
It is this that explains the instability of the Abbasid state. During the 9th and 10th centuries CE, the unity of the Islamic Empire broke up: the Abbasid caliph soon faced a Fatimid rival in Cairo, an Umayyad one at Cordoba, and numerous independent and semi-independent minor rulers elsewhere.
Conflicts between and within these polities increased the cost of state power, drained national treasuries, and further weakened the Early Islamic rulers. During the 11th century, the Abbasid caliphate effectively collapsed. The caliph's Seljuk Turkish mercenaries, reinforced by further drafts from Central Asia, and legitimised by their conversion to Islam, seized power for themselves.
It was a measure of the state's lack of social roots that it could be usurped by its own mercenaries. Among the population at large, hammered by taxes to pay for palaces, soldiers, and dynastic warfare, there was little enthusiasm for any of the ruling regimes. The region, moreover, remained a mosaic of minorities, so that political stress was easily transformed into resistance based on ethnic and religious difference.
By the end of the 11th century, the Middle East was a divided region of weak and unpopular states. For this, it would pay a terrible price.
In November 1095, Pope Urban II, speaking at Clermont in France, issued a call to the Western feudal elite to 'hasten to carry aid to your brethen in the East'. The Crusades were about to begin.
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Tagged under: History Socialism Marxism
Neil Faulkner
Neil Faulkner is a freelance archaeologist and historian. He works as a writer, lecturer, excavator, and occasional broadcaster. His books include 'A Visitor's Guide to the Ancient Olympics' and 'A Marxist History of the World: from Neanderthals to Neoliberals'.
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Able Skills 5 day Carpentry course has been recognised by City & Guilds as a comprehensive introduction to carpentry and as such, they have accredited the course with a C&G 4555-05.
At the end of this Carpentry course you will receive a City & Guilds certificate to confirm the skills that you will have learned.
Able Skills has a fantastic carpentry training facility and we offer lots of different courses that can lead to a variety of carpentry and joinery qualifications. Equally, Able Skills are happy to cater for those of you who have a basic knowledge of carpentry but want something a little more suited to their needs, so something bespoke. If you call with your requirements, we will help if we can.
This course can act as a fantastic introductory to Carpentry and following on from this; it may be that you want to gain carpentry qualifications. If that is the case, you may be able to upgrade to any of the longer programmes of carpentry that we teach. To help you, we will deduct from any course, the time spent on this course and we will also deduct the fees paid for this course.
If you would like to view the facilities at Able Skills, please feel free to visit us at any time. We are open 7 days every week and encourage visitors to the centre. You will not need an appointment, just turn up (08.30 – 16.30) and we will show you around.
The cost for this City & Guilds certificated Carpentry course is £395.00 including VAT. A £150.00 deposit will secure a booking and the balance can be paid on the start date.
Learn Basic Carpentry Skills in 5 Days: what are the dates for this course please?
We are now fully booked for 2018 for the 5 day introductory carpentry course I'm afraid. We will be adding 2019 dates soon.
Hi, is it possible to attend the classes over the weekend ?
We don't offer this course at weekends.
When is the next course scheduled to start?
It will be in the New Year.
I just booked this course online for the week commencing 18th April, but have yet to receive a confirmation. Is this normal? Thanks.
Yes this is normal, you will receive email and post confimation within the next few days.
Dears, I would like to enroll in this course 5 days Introductory to Carpentry. So is it possible I attend from 7 November to 11 November. I would like to learn this skill although I am 50 years old but keen to get engaged with it.
Our next available start date is Monday 2nd January, however, we only have a few spaces left for this course due to popularity.
1. You give the price of the 5-day course plus VAT.
Whats the VAT rate so I can calculate the total cost?
2. Does the accommodation rate of 20 pounds per night include VAT or is VAT added to this rate as well?
All the prices shown include VAT.


Derby County haven't even taken on Hull in the Championship play-off semi-finals yet but one fan is adamant the Rams are not only on their way to Wembley but are poised for glory courtesy of Darren Bent.
The former Ipswich, Tottenham and Aston Villa hitman has bagged just three goals for the iPro Stadium outfit this season but given his knack for scoring late on one punter has requested odds on the 32-year-old having the last word in the final.
Bent's three goals have all come after the 80th minute this season and all have been pretty goals.
His first strike came in the 89th-minute against MK Dons with the game locked at 1-1. His goal spurred the Rams on to win 3-1 thanks to a stoppage-time effort from Tom Ince.
Bent's second strike of the season came in the 85th-minute away to Hartlepool, again with the game all square at one apiece.
And his third and final strike of the season rescued a point against fellow play-off hopefuls Sheffield Wednesday, with his 82nd-minute effort earning a 1-1 draw at Pride Park.
So, while he hasn't exactly been prolific this term this trend has prompted one punter to request a special price through our #WhatAreTheOdds service for Bent to score the final goal in the Championship play-off final.
And given his tendency to turn up late in games the 22/1 offered might tempt more than just this potentially psychic customer.
Derby are 13/8 to win the first leg of their semi-final against the Tigers but 11/4 third favourites to reach the Promised Land that is the Premier League.
Should they defy those odds thanks to another late strike from bent there will be at least one Rams fan laughing all the way to the bank.


SAM is proud to bring back another Summer and Music series favorite, Bicycle Drive-In, featuring cult classic, Harold and Maude! Grab your bike and best gal or guy, fellow film fancier or the entire family and pedal down to Historic Old Pine Ave (HOPA) between 4th and 5th Streets on August 4 to experience that old drive-in magic with some great plot twists!
Known for combining live music, movies and Long Beach's long time love of pedal movement, the event will also have trivia contests with prizes and fun movie themed photo opps! Our free bike valet will have your two-wheeler covered while you select bites from HOPA eateries, Beachwood Brewery craft beers & Publix wines to enjoy before and during the movie. Come early for special live renditions by local artists of songs from the Harold and Maude soundtrack, originally produced by the beloved Cat Stevens - and Don't Be Shy, If You Want to Sing Out, Sing Out!
Always an advocate for alternative transportation and free music, SAM added film to the mix about 6 years go with the very first Bicycle Drive-In and is excited to present it to you again as part of our 10th season of Summer and Music (and Movies!). The event is free but don't forget to bring some coin for candy, peanuts for popcorn or bucks for beer - all proceeds help us keep you flush with local live music and memorable experiences throughout the summer. All ages welcome!
MOVE is a musical collaborative showcasing local talent, capitalizing on the magic of spontaneity. True live music.
Heather Jean Sommerhauser is a Soul/Pop singer and songwriter based in Long Beach, CA. She's front woman to local band, Nothing But Flowers, a high energy funky eclectic pop band.
Miniature Houses are comprised of singer-songwriters Michael Wysong, Lili De La Mora, and multi-instrumentalist Tai Tajima, from Long Beach, California. Mixing elements of folk and pop with delicate harmonies, melodica, bells, and acoustic guitar, their sound draws upon that pre-dawn feeling of melancholy and heartache.


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Kane é uma série de revistas em quadrinhos criada, produzida e publicada de forma independente durante entre 1993 e 2001 pelo ilustrador e roteirista britânico Paul Grist. O protagonista-título é um policial que trabalha como investigador no 39º distrito policial da fictícia cidade americana de "New Eden". Em 1997, foi indicada ao Eisner de "Melhor Série". Grist anunciou em 2013 estar trabalhando numa continuação, mas a série permanece com sua publicação suspensa.

Títulos da Image Comics
Banda desenhada do Reino Unido

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Full-time QA Specialist needed right outside of Nashville, TN!
This Quality Assurance Specialist is responsible for maintenance and oversight of day to day operations quality assurance/quality management program, which includes maintaining documents, records and certifications according to state and federal health care standards in compliance with accreditation guidelines.
- Compile, review, and analyze data related to client concerns, QA events and corrective actions in order to determine areas for quality improvement.
- Evaluate quality control data with appropriate department management to determine trends and issues, and assist with the development of corrective action plans to address these issues.
- Assist in the implementation of corrective action plans for areas that do not meet accreditation standards.
- Assist in review, updates and maintenance of quality assurance plans.
- Assist in the preparation for the quality assurance/quality management committee agenda creation and data collection, with an emphasis on establishing/maintaining a standardized quality management program.
- Participate in coordinating documentation for accreditation reviews.
- Provide education to staff regarding laboratory quality control programs.
- Assist departmental managers and medical directors in implementing and maintaining competency and continuing education for staff.
- Audit laboratory locations or departments for compliance with company quality policy and procedure and CLIA, CAP, State requirements where applicable.
- Attend quarterly meeting for TN Medical Laboratory Board as needed.
- Assist with development, implementation and maintenance of effective departmental QA programs and monitors.
- Assist with coordination of the maintenance, development and implementation of departmental policies and procedures.
* Associates Degree required. Bachelor of Science degree or equivalent work experience.
* National certification by the American Society of Clinical Pathology (ASCP) or American Medical Technologist (AMT) required.
* Must hold a valid Tennessee Laboratory License required; or eligible.
* At least one year of relevant quality control/quality improvement experience preferred.
* Over five years of prior laboratory experience required.
* Must maintain appropriate continuing education for certification/licensure, and be willing to increase basic knowledge.
* Quality Management training/experience is preferred.
* Proficiency in accreditation standards specific to sections of laboratory such as CAP/CLIA required. Knowledge of FDA/GLP standards preferred.
* Some travel will be required.


Boulee Frenchies is not a kennel, however I am a small hobbyist of French Bulldog Breed as of 1998, located in Michigan. I am a responsible, honest person that has been around dogs all my life and have fell in complete love with the French Bulldog Breed. They are everything that a big dog is in a little compact body.
All my dogs will be health screened before I use them in my breeding program because I want to do my best to ensure healthy puppies/dogs. My goal is to produce a consistent French Bulldog that is healthy, temperamentally sound, correct in conformation, because I believe that everyone should have a great looking French Bulldog for a companion. All of my dogs are raised in a home environment with plenty of attention, interaction with people, other dogs to establish a great temperament and socialization skills. They receive unconditional love from the day they are born until the day they are taken away by their new family. My puppies receive all their shots and if needed a Vet Reference will be granted.
Most of my puppies will be placed on a spay or neutered contract. If you choose a puppy from me, I am not only there for the guarantee of the puppy I am there for life of the puppy, to help you in any way that I can. I also have several people that I can reference to show you my concern and passion for my babies. Anyone and everyone is welcome to my home to visit my Frenchies and see how we all live. I live and breathe French Bulldogs!
I do NOT deal with any pet shops, puppy brokers, puppy mills or irresponsible people/breeders. All potential new owners will be screened before I will place one of my puppies/dogs in their home. I am very concerned as to where my puppies are placed. I always stay in contact with the new families, aiding them in any questions, opinions and help they need! Because we cannot be the best unless we have help, learning experiences and advice from others!


text:
package net.sf.jasperreports.engine.util;

import java.util.Comparator;

/**
 * @author Teodor Danciu (teodord@users.sourceforge.net)
 * @version $Id: VersionComparator.java 7199 2014-08-27 13:58:10Z teodord $
 */
public class VersionComparator implements Comparator<String>
{

	@Override
	public int compare(String currentVersion, String oldVersion)
	{
		if (oldVersion == null)
		{
			throw new IllegalArgumentException("Reference version can't be null.");
		}

		if(currentVersion == null || currentVersion.startsWith(oldVersion))
		{
			return 1;
		}
		else
		{
			String[] oldVersionChunks = oldVersion.split("\\.");
			String[] currentVersionChunks = currentVersion.split("\\.");
			int count = Math.min(oldVersionChunks.length, currentVersionChunks.length);
			for (int i = 0, old = 0, current = 0; i < count; i++)
			{
				try
				{
					//numeric comparison
					old = Integer.valueOf(oldVersionChunks[i]);
					current = Integer.valueOf(currentVersionChunks[i]);

					if (current != old)
					{
						return current - old;
					}
				}
				catch (NumberFormatException e)
				{
					//string comparison
					if (currentVersionChunks[i].compareTo(oldVersionChunks[i]) != 0)
					{
						return currentVersionChunks[i].compareTo(oldVersionChunks[i]);
					}
				}
			}
			return currentVersionChunks.length - oldVersionChunks.length;
		}
	}

}

redpajama_set_name: RedPajamaGithub


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The First Steps ??? Permits businessmen to tax exempted profits Listening is Extra Necessary Starting a Graphic Design Company Free platforms like Squidoo, HubPages, Gather and Scribd can make an enormous distinction in your site visitors by attracting people on those sites who are searching for data in your topic.
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Among the finest places in the web to go to when searching for great packages of wholesale shoe is SaleHoo. Present in SaleHoo are many shoe manufacturers, wholesale dealers, suppliers and distributors from different nation across the globe. These shoe wholesale sellers are confirmed to have high quality dropshipping services. They've been screened by SaleHoo crew to ensure that they're professional and reliable.


Your pet is part of your family—and the last thing you want to do when traveling to visit family over the holidays is leave a member behind.
But while your feelings on the matter may be simple, traveling with pets in tow often isn't. No matter how you're getting from point A to point B, there are a number of guidelines, regulations, and fees to prepare for.
A few weeks prior to a trip is a great time to take your pet to the veterinarian for a checkup. This is a perfect time to make sure your pet is in optimal health.
If your pet takes any medications regularly, be sure you have enough to last the full trip. If not, request a refill from the vet during your appointment. This is also a good time to make sure your pet is up to date on all vaccinations, so that s/he is protected against anything s/he might be exposed to while traveling.
And if your pet has not yet been microchipped, get onto it now–microchipping dramatically increases the likelihood of being reunited if your pet bolts out of the car or hotel door.
If you're taking your pet with you on a car trip, one of the first things to consider is how comfortable your pet is while driving. There are ways to help pets who don't love a long ride get more comfortable in the car in the weeks before the trip.
ASPCA recommends feeding anxious dogs one meal a day in the car in the weeks leading up to your big trip, and going for several short rides together. If your pet exhibits signs of carsickness such as vomiting, trembling or drooling, mention it when you visit the veterinarian—they may be able to ease the symptoms with medication.
And don't forget, a tired pet is a content pet—give your pet plenty of exercise prior to the drive to reduce anxiety, barking, and other problem behaviors.
Once you're on the road, don't let your pet wander the care while you drive; it's a lot safer for you both if your pet is securely fastened in the back seat with a harness or crate.
You can help your pet get comfortable by bringing blankets and toys that are familiar and stimulating—kongs and other puzzle toys can be great for dogs. You should take a break to let your pet relieve him/herself and get some exercise at least every four hours while on the road.
Never leave a pet in a hot or cold car alone—the conditions inside a car in these temperatures can be life-threatening.
Before flying with a pet, it's important to be aware of the various rules and restrictions. The Department of Transportation, the Federal Aviation Administration, the Transportation Security Administration all have regulations you must follow when flying with a pet. If you're traveling abroad, you'll also have to comply with rules from the U.S. Department of Agriculture and the International Air Transport Association.
Don't forget the the airline you're flying on, too—each airline will have different requirements for crates, weight limits, and more. The Air Carrier Access Act requires airlines to accommodate animals who provide task and emotional support to people with disabilities. Make sure to research your airline's pet shipping requirements and what documentation is necessary if you need to take a service animal with you on the flight.
Most airlines' availability for pets on a flight are very limited, so book at least six weeks ahead to avoid complications. A few days before your flight, call and confirm that everything is in order for your pet's travel.
Flying is not considered an ideal way to fly for most pets. Never let your pet travel with the baggage, always take your pet on board with you in a carrier. Furthermore, consider anything that might make your pet especially vulnerable while flying—the American Humane Association recommends against bringing puppies or kittens, pets that are sick, or pets that are pregnant onto a plane.
Animals with "pushed-in faces" (think pugs, bulldogs, Persian cats) are at high risk of breathing problems while flying, and many animal advocate groups urge owners not to bring these pets on flights. Some airlines won't even let them on board.
When taking your pet to a hotel with you, always double check its policies and fees—that means calling the hotel itself, not just checking a website. Even pet-friendly hotels often have limits on what types of pets it accepts, and their own policies on pet-related fees. The last thing you want is to show up only to find out that your pet isn't allowed, or to get hit with a massive fee you aren't prepared for.
While you've got a hotel representative on the line, you may want to ask about the condition of the hotel's pet-friendly rooms as well. Some hotels only allow pets in smoking rooms. If that's going to bother you, ask before booking. Call again a few days ahead of your reservation to confirm it, and remind the hotel that you have a furry friend coming along.
To help your pet feel at ease in the hotel room, bring things such as favorite toys and blankets that will smell like home and keep your pet entertained. Most importantly, bring your pet's crate. Dogs, cats and many other pets feel their crate is a safe place, so keep it open for them to rest in as they wish.
And always put your pet in a crate when leaving them alone in the room. Even the most well-behaved pet may act unpredictably in a new environment.
While traveling with a pet can be more complicated, that's no reason why you and your pet can't have a smooth trip. If you hate to leave your pet behind over the holidays, there's plenty of pet-friendly options available.
Just be sure to plan ahead, know the requirements, and bring plenty of food, toys and anything else your pet might need.
Dogs are fun, cuddly and playful. But your pup does much than put a smile on your face. In fact, there are several proven health benefits to owning a dog. So much so, that one insurance company (Midland Life Insurance Company) include dog ownership as a factor in its medical screening for clients 75 years and older.
All of this is good news for dog owners, though the news that time spent with your pup keeps you healthy and feeling good may not be surprising to them. And if you've been considering getting a dog, these health benefits are a slew of great reasons to take action and bring a new furry friend into your home.
What you feed your dog is one of the most important health decisions of dog ownership. A dog's food heavily impacts its energy and overall health. But there are a lot of factors to consider. The right food for your dog depends on size, age, activity level and other special needs your dog may have.
Puppies' growing bodies have special nutritional needs. How well their food meets those needs can shape the dog they grow into and influence their healthy over the full course of their lives.
Look for ingredients that support growth and energy—because they're growing so quickly, puppies need more of both per pound than adult dogs do. That means protein and carbs. A good kibble for puppies also includes healthy fats, which boosts a dog's ability to absorb vitamins.
Improper or imbalanced nutrition in the puppy stage could negatively affect bone and joint growth, which could lead to long-term health issues. This is especially important for large dog breeds because they grow so rapidly as puppies.
Once your puppy has reached is full size and is no longer growing, it is time to switch it to an adult dog food. This is important for meeting your full-grown dog's health needs for weight management, oral care, activity level digestion, and more.
For good adult dog nutrition, look for protein for muscle support, and carbs for energy and fiber. Healthy fats continue to be important too, supporting skin and coat health, energy boosting levels, and enhancing taste.
A food that helps your dog get its needed vitamins and minerals will keep its body strong and working properly. Stick to a dog food made for your dog's type if it is a large or small breed or has other special needs.
As dogs age, their metabolism slows and their activity levels go down. As this happens, dogs' need for calories and fat goes down.
Dogs eight years and older have a higher risk for a number of health issues including obesity, heart disease, kidney disease, dental disease, degenerative hip and joint disease, and more. They're also more prone to digestive irregularities. Stick to a dog food created or seniors to help your dog get the appropriate nutrients, and if your dog has a health issue, look for a food that can help address it.
Senior dogs may also start to lose their appetite. If you notice your dog eating less, talk to your vet about potential health issues and look out for signs of discomfort, such as difficulty chewing. Consider ways to make the food more palatable or easier to consume, such as adding a little water to dry food to soften it and reduce digestive issues.
A dog's nutrition needs can vary significantly based on its size, age and activity level. To make sure your dog is getting the health support it needs from its food, always check that the food's intended consumption matches your dog's life stage, and make note of any special needs it has.
From the puppy stage to adulthood to your dog's silver years, make sure your dog's food is designed to meet its specific health needs. Follow these simple tips, and you'll set your dog up for a long and healthy life.
Are you training a new dog? Stuck with a problem behavior you are having trouble correcting? Read on for some tips to help you effectively train your four-legged friend.
Arguably the most important element in training a dog is consistency. Dogs, like small children, do not do well with mixed signals, and if you are inconsistent your dog is likely to get confused and to not understand what you want them to do. It is also a good idea to make sure that as many family members as possible are using the same training methods. That way, your dog will always know what is expected of them from your entire family.
Always be patient with your dog. Sometimes it is tempting to get frustrated or angry, especially when the dog is misbehaving, but in the long run this does not help the learning process any at all and could actually frighten the dog. Furthermore, behaviors take time to change. Do not expect your pup to have all their commands down quickly. Training a dog takes time. Behaviors that are natural for dogs such as jumping, biting and digging will take longer to correct.
Positive reinforcement is important for any good training routine. Dogs do what works. If sitting when asked, staying and giving a paw will get them a treat, a longer walk, a favorite toy or affection, then they will do it. Be sure to liberally reward your dog when they do something right. You likely have no trouble punishing behaviors you do not like. However, rewarding those behaviors you do like is sometimes harder to remember. Be genuine and sincere with your affection and praise. It is even okay to be a little bit over the top. Make sure your dog knows that you like what they are doing, and they will be much more likely to repeat the behavior.
Listening is an important skill in any relationship. If your dog seems uncomfortable with something you are asking them to do, that is a clear message. Do not force your dog to do something that they are uncomfortable with. They have their reasons. As a human, you may not understand what those reasons are, but it is important to respect them. You can always try again later. Just because they are not comfortable at this moment does not mean they will always be uncomfortable.
These tips may seem basic, but their value cannot be underestimated. If you build a good relationship with your dog now, you are likely to have less incidents of bad behavior. Furthermore, your dog is much more likely to listen to you when you ask them to sit instead of chasing the mailman or jumping on the guests the next time you choose to entertain. Even more importantly, a well-trained dog is a loyal companion who will be at your side for the rest of their life.
Puppies are such adorable bundles of fur, it's hard to imagine that there could ever have be a need for training classes.
After all, training classes are for "bad" or "problem" dogs, not yours. Besides, you can handle teaching a dog a few tricks, right? Wrong—these are common myths, but false ones.
One of the most basic ways a training class can help you and your dog is by pre-empting bad habits—like chewing on your shoes—by establishing positive habits early. Puppies can benefit from training classes and learn simple commands like "sit" as young as seven to eight weeks old.
But even if bad habits do develop in older dogs, a training class can help correct behaviors, too.
For you to have a successful long-term relationship with your dog, it's important to establish yourself as the pack leader. Dogs' social dynamics function within a hierarchy, with an alpha dog at the top as their leader. If no leader is established, your dog will take it upon itself to become that leader.
To establish your authority over the dog, it's important that you claim that leadership role first. A training course can help you learn the confidence and command to do it well.
The nuances of communicating with a dog are not always intuitive. You may think you're communicating clearly, while in fact your dog can't understand it at all.
But taking a training course together can help you and your dog learn to communicate to each other better, serving as a strong foundation for a long happy relationship.
A training class does much more for a dog than teach it to sit. It also exposes them to public spaces where they interact with other people and pets—which gives dogs valuable lessons about how to get along with others, of both the human and canine varieties.
These lessons about appropriate behavior come in handy any time you want to take your pup with you to a parade, park, or other public space, as well as any time you invite someone to your home!
Dogs are meant to be active, and many were even bred to hone instincts for specific jobs, such as sheep-herding. And yet most modern dogs spend their time napping and sitting around the house.
For some dogs, this can cause boredom that leads to acting out in ways that are not acceptable, like tearing up the couch pillows while you're at work. It's not that their "bad," they're just looking for an outlet for their hard-wired instincts.
Along with regular exercise, training classes (and practice time at home with you) can offer your dog the mental stimulation it needs and stave off those negative behaviors. If your dog has already mastered the basics, consider an advanced course.
Training classes for your dog can be beneficial at any age or skill level—and they can be good for you, too! From basic commands to strengthening your line of communication, there's plenty of reasons to get your dog in a training class.
Find a training class for your dog by checking at your local pet shop, adoption center, or searching online.
Why Do Dogs Jump Up on People?
You come home from a long day at work and open the door to your home, and are greeted by the high energy of your dog, who rushes to the door and jumps up to greet you.
Perhaps you enjoy this effusive greeting, taking it as your dog's happiness that you are home. But over time, it's likely become a source of frustration for you, especially if your puppy has grown into a large dog.
Even worse, your dog exhibits the same behavior to guests, and most of them (understandably) don't appreciate it at all.
Dogs communicate differently than us, so it's not uncommon for a behavior to mean something very different to dogs than it does to their owners. In fact, your dog's jumping behavior is not the elated "welcome home" that most of us believe it to be.
When a dog jumps, it is asserting dominance as the pack leader. When it jumps on you, it is asserting dominance over you. When you don't fill the leadership role strongly and consistently, your dog senses that. Instinctively, it has a need to provide that leadership itself.
What do you do when you're nervous? Pace around or fidget? Your dog's jumping may be a similar response, rooted in anxiety or a simple excess of energy.
Fortunately, regardless of what's causing your dog's jumping, the way to stop it is the same.
First, stop reciprocating your dog's jumping with affection. When you do this, you tell your dog this behavior is good and is being rewarded. Worse, if your dog is anxious, you are telling your dog this is an emotional state you want it in, and creating a cycle of anxiety for your dog.
Then, re-establish yourself as the pack leader by exhibiting a calm, positive, and authoritative demeanor when you come home. Don't give your dog attention until it is calm, too—just go about your business as if it isn't there without touching, speaking to or make eye contact.
It will also help to give your dog more exercise on a consistent basis—this will help it manage that extra energy.
By following these simple steps, you'll be communicating with your dog in a way they can understand, while giving them the security of a strong leader and affirming a healthy, calm and happy state of being. In short, in addressing the behavior problem of jumping, you will also create a happier life for your dog by tackling the underlying problems.


text:
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Home / WWARN / About WWARN
About WWARN
May 1, 2017 By Malaria.com Leave a Comment
The WorldWide Antimalarial Resistance Network (WWARN) generates innovative resources and reliable evidence to inform the malaria community on the factors affecting the efficacy of antimalarial medicines.
The WorldWide Antimalarial Resistance Network (WWARN) is a multi-disciplinary, scientifically independent network that provides reliable evidence to inform the malaria community on the factors affecting the efficacy of antimalarial medicines. WWARN, which is part of the Infectious Diseases Data Observatory, provides high-quality analysis, customised research tools and services, and a global platform for exchanging scientific and public health information.
WWARN was founded in 2009 to provide the information necessary to prevent or alleviate antimalarial drug resistance and therefore reduce the number of people falling ill and dying from malaria.
WWARN now works with around 270 collaborators across the world to help optimise the efficacy of antimalarial medicines and treatment regimens, especially for vulnerable groups including pregnant women, infants and malnourished children. WWARN also provides evidence to inform the development of new antimalarial medicines.
The threat of artemisinin resistance
Artemisinin derivatives used in combination with other partner medicines are currently the cornerstone of malaria treatment. However, artemisinin resistance in Plasmodium falciparum malaria is the single greatest threat to efforts to control and eliminate malaria.
Resistance has been identified in Cambodia, Thailand, Vietnam, Laos and Myanmar. The spread or emergence of resistance beyond the Myanmar-Indian border, toward Africa, could derail current efforts to eliminate malaria. Assessing, mapping, and modelling the emergence or spread of artemisinin resistance is essential to limiting the impact of drug resistance on patient illness and mortality rates.
There are currently no new and approved antimalarial drugs and the drug development pipeline is a long and complex process, so it is vital to sustain the efficacy of existing artemisinin combination therapies (ACTs) until new medicines are registered and launched.
Barriers to prevention and control efforts
In the past, assessments of antimalarial resistance were based solely on the success of antimalarial drug treatments. The available data were variable in quality and reliability, and many data files were inaccessible. Geographical gaps in data, and a lack of standardisation in data collection and analysis, make it difficult to track or anticipate resistance before it becomes apparent through treatment failures and deaths.
Life-saving information that enables treatment approaches to be optimised is not always current or readily available in many countries. Furthermore, clinical trial treatment assessments are not always reliable (quality assured), correctly analysed, or made available to global policy makers, donors, pharmaceutical companies and researchers.
Poor quality medicines are also a significant barrier to malaria control and prevention efforts and threaten the lives and livelihood of millions of people globally. These include both substandard medicines – caused by errors during the manufacturing process – and falsified medicines – caused by criminal fraud. Assessing the quality of antimalarial drugs is particularly challenging due to the heterogeneity and paucity of data available.
How is WWARN responding to these challenges?
WWARN provides a unique platform for the sharing and analysis of data on antimalarial medicines. Detection of subtle changes in patient treatment outcomes can provide early warning of emerging drug resistance. This allows prompt implementation of containment efforts to help prolong the usefulness of current antimalarial medicines.
Data sharing partnerships: WWARN has developed a unique model to facilitate data sharing in the research community. The WWARN data-sharing platform is the result of a collaborative effort of more than 250 partners around the world, comprised of research institutions, governmental and non-governmental organisations, product development partnerships, and pharmaceutical companies.
Data repository: WWARN's Data Centre contains the majority of the world's clinical, molecular, pharmacological and drug quality clinical trial results. The Data Centre is a repository for around 80% of ACT clinical trial studies published since 2000 – data from over 120,000 patients. WWARN serves as a long-term data storage facility ensuring that this important information continues to be available to the malaria research community.
Data curation and analysis: WWARN has developed an innovative system for standardising heterogeneous data, enabling detailed analyses of large combined datasets. WWARN's approach to data analysis provides unparalleled statistical power to answer critical public health questions that it would be impossible to answer through analysis of results from individual clinical trials.
Collaborative meta-analyses: WWARN has facilitated 20 active or published collaborative meta-analyses. These meta-analyses have made significant contributions to our understanding of the factors affecting the efficacy of antimalarial medicines. For instance, pooled analyses of artesunate-amodiaquine data showed that providing the artemisinin and amodiaquine as a single pill was more effective than treating people with two separate pills.
Tools and services: To help researchers generate high quality data, WWARN provides resources, services and training free of charge to the malaria community. For example, the WWARN Explorer enables researchers to identify gaps in clinical trial data. The WWARN Toolkit helps to build capacity in malaria endemic countries, to strengthen the collection, analysis, interpretation and dissemination of high quality research data.
Defining artemisinin resistance: WWARN has developed, validated and made available a Parasite Clearance Estimator (PCE), the only online tool currently available for assessing parasite clearance rates, a measure of artemisinin resistance. The PCE has become a standard reference tool and is being used to document the spread or emergence of resistance in the Mekong region. WWARN has developed models of the emergence and spread of known molecular markers of artemisinin resistance, including the K13 Molecular Surveyor which summarises data from over 5,000 samples from 22 countries.
Partnership projects: WWARN is a key partner in the second Tracking Resistance to Artemisinin Collaboration (TRAC II), a project that is investigating the safety, tolerability and efficacy of two Triple ACTs, and monitoring for the extension and emergence of artemisinin and partner drug resistance across Asia and Africa.
Visit www.wwarn.org
Email info@wwarn.org
Follow WWARN on Twitter @wwarn or like WWARN on Facebook at facebook.com/AntimalarialResistance
Filed Under: WWARN
WWARN Corner
The WorldWide Antimalarial Resistance Network (WWARN) generates innovative resources and reliable evidence to inform the malaria community on the factors affecting the efficacy of antimalarial medicines. Learn more…
Fighting Malaria Requires Protecting the Effectiveness of Antimalarial Medicines
Data Sharing at IDDO
Evidence to inform equitable dosing in very young and malnourished children
More WWARN Stories...
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text:
from openstack.tests.unit import base
import uuid

from openstack.load_balancer.v2 import flavor_profile

IDENTIFIER = uuid.uuid4()
EXAMPLE = {
    'id': IDENTIFIER,
    'name': 'acidic',
    'provider_name': 'best',
    'flavor_data': '{"loadbalancer_topology": "SINGLE"}'}

class TestFlavorProfile(base.TestCase):

    def test_basic(self):
        test_profile = flavor_profile.FlavorProfile()
        self.assertEqual('flavorprofile', test_profile.resource_key)
        self.assertEqual('flavorprofiles', test_profile.resources_key)
        self.assertEqual('/lbaas/flavorprofiles', test_profile.base_path)
        self.assertTrue(test_profile.allow_create)
        self.assertTrue(test_profile.allow_fetch)
        self.assertTrue(test_profile.allow_commit)
        self.assertTrue(test_profile.allow_delete)
        self.assertTrue(test_profile.allow_list)

    def test_make_it(self):
        test_profile = flavor_profile.FlavorProfile(**EXAMPLE)
        self.assertEqual(EXAMPLE['id'], test_profile.id)
        self.assertEqual(EXAMPLE['name'], test_profile.name)
        self.assertEqual(EXAMPLE['provider_name'], test_profile.provider_name)
        self.assertEqual(EXAMPLE['flavor_data'], test_profile.flavor_data)

        self.assertDictEqual(
            {'limit': 'limit',
             'marker': 'marker',
             'id': 'id',
             'name': 'name',
             'provider_name': 'provider_name',
             'flavor_data': 'flavor_data'},
            test_profile._query_mapping._mapping)