text:
\section{Introduction}

Single photons are important as a means of transporting quantum information because they interact weakly with their environment and can carry information in many degrees of freedom \cite{OBrien:07}. In order to scale up the complexity of quantum operations, there is now a real need for a source of identical photons, promptly delivered on demand, and ideally integrated in the solid state into a photonic chip. Quantum dots are one promising approach, but despite significant recent progress \cite{HePRL:13}, photons produced by different dots are generally distinguishable. Nitrogen-vacancy (N-V) centres in diamond are also promising \cite{Kurtsiefer:00}, though it is challenging to place colour centres at specific sites in a photonic circuit \cite{Aharonovich:11} and the emitted photons have uncertain frequencies due to phonon-assisted sidebands and the low probability of emission on the zero-phonon line. By contrast, dibenzoterrylene (DBT) molecules embedded in anthracene at cryogenic temperatures produce a high yield of indistinguishable photons \cite{Nicolet1:07} in a 30~MHz-wide line at 785~nm \cite{Tamarat:00,Trebbia:09}.  It has been proposed that these molecules could deliver photons very efficiently into a nearby waveguide \cite{Hwang:11, Verhart:14}.

In pursuit of that idea, we have used the open-source MEEP package \cite{Oskooi:10} to solve Maxwell's equations for a radiating dipole located 32\,nm above a silicon nitride waveguide and embedded in a $2\,\mu$m-square ``crystal" of anthracene, as illustrated in Fig.~\ref{Fig:FDTD}(a). The top panel in Fig.~\ref{Fig:FDTD}(b) illustrates this from the side, and plots the field radiated by the molecule for several different thicknesses of crystal. Unless the crystal is thin, much of the radiation goes into the anthracene instead of the waveguide because the anthracene refractive index -- $n\simeq 1.8$ for the polarisation of interest -- is almost as high as the $n=2.0$ of the silicon nitride. Fig.~\ref{Fig:FDTD}(c) plots the efficiency of coupling into the waveguide as a function of the anthracene thickness and shows an optimum thickness of $\sim150\,$nm. To make such a crystal, we could not use the normal co-sublimation methods \cite{Nicolet1:07,Trebbia:09,Nicolet2:07,Makarewicz:12,Major:15}, which yield crystals that are $1-2\mu\textrm{m}$ thick.  Films of the desired thickness were made by spin coating a solution of DBT and anthracene, and these are known to give stable photon emission from the DBT \cite{Toninelli:10}, but we found that these films are always too rough for our purpose, varying in thickness by as much as 50\% over regions only a few microns across.

\begin{figure}[t!]
\centering\includegraphics[width=12cm]{FDTD.pdf}
\vspace{0.5cm}
\caption{We have numerically solved Maxwell's equations for a radiating dipole embedded in a $2\,\mu$m-square ``crystal" of anthracene. The dipole lies 32\,nm above a silicon nitride waveguide  500\,nm wide and 120\,nm thick on a glass substrate. (a) Sketch of the geometry. (b) Top: side view of substrate, waveguide, anthracene and dipole. Below: Simulation results for several thicknesses of the crystal. (i) Radiation is lost into the substrate. (ii) Radiation propagates in the waveguide. (iii-iv) Radiation is lost into the thick anthracene layer. (c) Graph showing the calculated coupling efficiency as the thickness of the anthracene crystal is varied. This peaks at $\sim 22\%$ (total in both directions) for a thickness of $\sim 150$ nm.
}
\label{Fig:FDTD}
\end{figure}

In this paper we show how to grow a uniformly thin crystal of anthracene containing a controlled density of DBT dopant molecules, and we demonstrate that these molecules are suitable for use as single photon sources on a chip. Section~\ref{sec:growth}  presents our methods for growing and doping the crystal. Section~\ref{sec:microscopy} describes the microscopy used to examine the crystals, image the molecules and investigate the molecular polarisation. In Sec.~\ref{sec:DBToptics} we characterise the antibunching and saturation of the fluorescence and we explore the photobleaching of the molecules. Section~\ref{sec:conclusions} provides a concluding summary of our results.

\section{Growing the crystals}
\label{sec:growth}

Figure \ref{Fig:growth_process}(a) illustrates the steps we follow to produce suitable crystals. We start with (i), a glass cover slip that has been cleaned in an oxygen plasma. Next, we make a 1 mMol solution of the DBT molecules\footnote{7.8,15.16-dibenzoterrylene supplied by the Institute for PAH-Research, Greifenberg, Bavaria} in toluene, which we further dilute in diethyl ether at a ratio of 1:1000 (volume) to reach the desired concentration. In step (ii) we spin-coat the cover slip with  $20\,\mu\mathit{l}$ of this solution, ramping up to 2000 rpm over 5 s, then holding for 60 s before ramping down suddenly. This recipe gives a surface coverage of approximately 0.4 DBT molecules per square micron. In step (iii) we grow a thin anthracene crystal on the cover slip,  inside a glove bag purged of air and filled with nitrogen, as sketched in Fig. \ref{Fig:growth_process}(b).  A temperature-controlled copper block heats the bottom end of a glass vial, containing $3\,$g of anthracene powder, to a temperature $T_b$ that we can set. Once the bottom temperature has stabilised, the DBT-coated cover slip is placed on top of the tube for approximately 1 minute to grow the crystal. During this growth period, the temperature at the top is $T_t\simeq25\,^{\circ}$C. Finally, in step (iv), we mix 4\% by weight of PVA powder in deionised water at $\sim65\,^{\circ}$C and wait (about an hour) until the powder is dissolved. We spin $20\,\mu\mathit{l}$ of this solution on top of the anthracene, ramping up to 3000 rpm and back down again over a minute. This covering is necessary because uncoated anthracene sublimes and is gone in less than a day, whereas the coated crystals last for months (at least) at room temperature.

\begin{figure}
\centering\includegraphics[width=12cm]{growth_process.pdf}
\vspace{-0.5cm}
\caption{Preparing the thin crystal of anthracene doped with DBT.  (a) Steps involved in the processing. (i) clean of the glass substrate in a plasma, (ii) spin-coat DBT molecules onto the surface, (iii)  grow a thin anthracene crystal over the molecules, (vi) spin-coat a protective layer of PVA. (b) The crystal growth apparatus is a test tube with anthracene powder heated at the bottom and the glass substrate covering the open top, all in a nitrogen atmosphere inside a glove bag.}
\label{Fig:growth_process}
\end{figure}

 Changing $T_b$ has a profound effect on the morphology of the crystals that grow, as we demonstrate in  Fig.~\ref{Fig:AllPics} -- a set of atomic force microscope images showing crystals grown at successively higher values of the bottom temperature. With $T_b\le218\,^{\circ}$C (Figs.~\ref{Fig:AllPics}(a-c)), the crystals are long and thin in cross section and stick up from the surface as 3-dimensional structures, reminiscent of those described in \cite{Major:15}. By contrast, when $T_b\ge243\,^{\circ}$C (Figs.~\ref{Fig:AllPics}(e, f)), they change to wide, flat mesas, whose height grows roughly linearly with the deposition time. A typical mesa is shown in Fig.~\ref{Fig:AFM}(a), together with a cut through the centre along $x$, plotted in Fig.~\ref{Fig:AFM}(b). This particular crystal was grown for $50\,$s at $T_b=243\,^{\circ}$C, and is $80\,$nm thick. The roughness measured on the top of the mesa is  $1.1\,$nm rms, but that is about the level of the instrumental noise, so we believe the crystal is smoother than $1\,$nm. Thus, by controlling the temperature $T_b$ and the growth time, we have produced crystals of very uniform thickness in the range $40 - 150\,$nm, a suitable range for coupling the DBT molecules to a waveguide.

 \begin{figure}[t]
\centering\includegraphics[width=13cm]{fivepics.pdf}
\caption{Atomic force microscope images  (taken in tapping mode) of the crystals grown at a variety of bottom temperatures $T_b$ (a) $139\,^{\circ}$C, (b) $197\,^{\circ}$C, (c) $217\,^{\circ}$C, (d) $231\,^{\circ}$C, (e) $243\,^{\circ}$C, and (f) $256\,^{\circ}$C. These images show the transition from tall, thin crystals - similar to those reported in \cite{Major:15} - to wide, flat mesas. The transition occurs between $T_b=220$ and $240\,^{\circ}$C.}
\label{Fig:AllPics}
\end{figure}

\begin{figure}[b]
\hspace{-1.5em}
\includegraphics[width=14cm]{AFM_AC_Crystal2.pdf}
\caption{Atomic force microscope image of a thin anthracene mesa. (a) 3D plot. (b) Section through the centre along $x$, showing  a flat-top profile with a height of $\sim$80~nm and very low roughness.}
\label{Fig:AFM}
\end{figure}

Before turning to the optical properties of the DBT molecules underneath this thin crystal, we digress briefly to comment on the thermodynamics of the crystal growth. The pressure $p_{t}$ of anthracene vapour at the top of the test tube, from which the crystal grows, is controlled by the temperature at the bottom, where we can reasonably suppose  the vapour is in equilibrium with the solid, at the vapour pressure $p_0(T_{b})$. Thus, taking into account the temperature gradient along the test tube, and treating the anthracene vapour as an ideal gas, we expect $p_t=\sqrt{T_t/T_b}p_0(T_{b})$. The chemical potential of this (ideal) vapour at the top of the test tube is $\mu_1=-k_B T_t\ln[p_Q/p_t]$ (with quantum pressure $p_Q=(\frac{m k_B T_t}{2\pi \hbar^2})^{3/2}k_B T_t$). Let us compare this with the chemical potential of a fully covered anthracene surface at temperature $T_t$, for which the vapour pressure is $p_0(T_{t})$, and therefore the chemical potential is $\mu_2=-k_B T\ln[p_Q/p_0(T_{t})]$.  The chemical potential difference is $\mu_1-\mu_2=k_B T_t\ln[p_t/p_0(T_t)]$. We see that when the pressure at the top of the test tube is equal to the vapour pressure for anthracene at temperature $T_t$, there is no chemical potential difference. Then the crystal sits in equilibrium with the vapour and cannot grow, which is the case when $T_b=T_t$.

\begin{figure}[b]
\centering\includegraphics[width=13cm]{oil_confocal.pdf}
\caption{Schematic of our confocal microscope system. 780-BPF: 780~nm band pass filter; PBS: polarising beam splitter; HWP: half wave plate; FC: fiber coupler; PMF: polarisation maintaining fiber; 90:10 BS: 90\% transmission, 10\% reflection cube beam splitter; X-Y SM: X-Y steering mirrors; L1, L2: telecentric lens system $f_1=75\,$mm, $f_2=250\,$mm; Objective: Nikon OFN25 DIC N2 $60\times$ microscope objective; 3D Stage: Thorlabs Nanomax MAX311/M translation stage for positioning the sample ; 792-LPF: Chroma technology RET792LP long pass filter; MMF: multimode fiber; 50:50 Multimode Fiber BS: 50\% transmission, 50\% reflection multimode fiber beam splitter; Si APD: Perkin Elmer SPCM-AQRH-15-FC silicon avalanche photodiode detectors.}
\label{Fig:oil_confocal}
\end{figure}

A rise of $T_b$ increases the vapour pressure at the bottom, which drives up the pressure at the top, and hence increases the chemical potential difference between the crystal and the vapour at the top. When this potential difference is small, the crystal that grows is constrained in its morphology by the need to minimise its surface energy (see \cite{Grimbergen:98,Verlaak:03}, for example) but as more free energy becomes available other conformations become possible. Above a critical value, the crystal is able to grow in a two-dimensional way \cite{Verlaak:03}, and this is the origin of the transition that takes place somewhere between $220$ and $240\,^{\circ}$C. At these temperatures, the ratio $p_0(T_b)/p_0(T_t)$ of vapour pressures is in the range  $(0.4- 3.4)\times 10^7$ \cite{Chen:06,Lide:09,WebBook}, and the corresponding chemical potential difference between the vapour at the top and the infinite anthracene crystal is $0.41(2)\,$eV. Following section 4 of \cite{Sassella:06}, we expect this transition to occur at a chemical potential difference of $2a b(2\gamma-\sigma)$, where $a b$ is the area of $(001)$ plane of the unit cell, while $\gamma$ and $\sigma$ are the surface energies per unit area of the (001) plane and the interface with the substrate, respectively. From \cite{Northrup:02} the values are $a b=51.7\,\AA^2$, $\gamma=3.3\,$meV/$\AA^2$. Comparing this theory with our measurement, we conclude that the energy per unit area of the anthracene binding to the glass is $\sigma=2.6(2)\,$meV/$\AA^2$. We are not aware of any previous determination of this quantity, but note that it is of similar magnitude to the value taken by \cite{Verlaak:03} for other -acenes.

\section{Microscopy}
\label{sec:microscopy}

\begin{figure}[b]
\centering\includegraphics[width=9cm]{confocal.pdf}
\caption{Confocal microscope images. (a) Anthracene crystals viewed in reflected excitation light (long-pass filter removed). (b) The same crystals viewed with the long-pass filter in place. Nearly all the spots are single DBT molecules}
\label{Fig:confocal}
\end{figure}

We turn now to the analysis of the DBT molecules embedded under these thin anthracene crystals, which we image using the confocal microscope setup shown in Fig.~\ref{Fig:oil_confocal}. The light source is an external-cavity continuous-wave diode laser (TEC 100 Littrow - Lynx, Sacher Lasertechnik) producing $8\,$mW at $780\,$nm, filtered by a $10\,$nm-wide bandpass (BPF) to suppress any amplified spontaneous emission at wavelengths longer than $785\,$nm. The light is linearly polarised (PBS) and coupled into a polarisation-maintaining, single-mode fibre (PMF), which filters the spatial mode.  A half-wave plate (HWP) allows us to adjust the polarisation axis so that the light couples only to one of the principle axes of the fibre. The output from the fibre is polarised once again (PBS) and the axis is then adjusted by a second half-wave plate. A polarisation-insensitive beam splitter directs 10\% of the light ($\sim0.5\,$mW) onto two steering mirrors (SM) that raster-scan the beam direction. Lenses L1 and L2  expand the beam size from $2\,$mm to $6.7\,$mm and ensure that it always enters the microscope objective centrally while the angle is being scanned. We use an infinity-corrected, Plan-Apochromat, oil-immersion objective lens. This has  $60\times$ magnification with a numerical aperture of 1.40, and is corrected for 170~$\mu$m cover slips with a working distance of 130~$\mu$m. On fitting the focussed spot to a Gaussian, we typically measure a full width at half maximum intensity of $400\,$nm in the object plane. The steering mirrors allow us to scan this spot over an area of $20\times20\,\mu$m.

The $780\,$nm laser excites molecules from the ground state $S_{0}$ to the first excited singlet $S_{1}$. Although the laser frequency lies  $2\,$THz above the $S_{0,0}-S_{1,0}$ ``zero-phonon" resonance of DBT, the homogeneous linewidth at room temperature is approximately $10\,$THz, so molecules are excited both to the $S_{1,v=0}$ state at the bottom of the upper band and to vibrationally excited states $S_{1,v}$ of the upper electronic level. These relax very rapidly to $S_{1,0}$, which then decays radiatively back to the ground level $S_{0}$. The ``zero-phonon" light is emitted at a wavelength of $\sim785\,$nm, while the transitions to vibrationally excited ground states $S_{0,v}$ produce sidebands further to the red. This fluorescence is collected by the microscope and retraces the path of the incident light back as far as the beam splitter, where 90\% of the photons are transmitted. A $792\,$nm long-pass filter (LPF) rejects scattered excitation light -- and also rejects DBT fluorescence close to the zero-phonon line -- but transmits the more red-shifted sidebands of the fluorescence. This light is coupled into a multimode fibre (MMF) and a fibre beam splitter delivers half the power to each of two silicon avalanche photodiode detectors (Si-APD).

With the long-pass filter removed, there is a strong signal in the detectors from back-scattered $780\,$nm excitation light. Figure~\ref{Fig:confocal}(a) shows six anthracene crystals, viewed in this way after attenuating the excitation power to $\sim1\,$nW. The image in Fig.~\ref{Fig:confocal}(b), taken with the long-pass filter in place and with the attenuator removed,  shows the individual DBT molecules embedded in the same crystals. These scans cover an area of $16\times16\,\mu$m and have a resolution of  $200\times200$ pixels.

\begin{figure}[b]
\centering\includegraphics[width=13cm]{polarization_confocal_3.pdf}
\caption{Test of DBT polarisation. (a) Sum of the two images from Fig.~\ref{Fig:confocal}. (b) Normalised polar plots of molecule emission as the excitation laser polarisation angle is varied. Labels (i-iii) indicate the crystal in which the molecules reside, as shown in (a). The colour of the lines signifies the visibility of the fitted function to the data. Within a given crystal the optical dipoles clearly share a common orientation. (c) Histogram showing the spread of molecule orientations relative to the mean orientation, taken over 58 molecules in 12 crystals.}
\label{Fig:polarization_confocal}
\end{figure}

In order to have good control over the density of photo-emitters, we first deposit the DBT molecules on the glass surface then over-coat them with anthracene, as described in section 2. We therefore needed to establish whether the molecules remain stuck on the surface, underneath the crystal, or are incorporated into the  anthracene matrix. DBT molecules occupying the main site in anthracene have the long axis of the terrylene moiety - and hence the $S_0 - S_1$ optical dipole moment - polarised along the b-axis of the crystal \cite{Nicolet2:07}, whereas they must have a random orientation when we first deposit them on the glass. Thus, our first test was to measure the fluorescence as a function of the polarisation angle of the excitation light, to see whether the DBT molecules in a given crystal share a common orientation. Figure~\ref{Fig:polarization_confocal}(a) sums the two images in Fig.~\ref{Fig:confocal}, to show the DBT molecules and the anthracene crystals simultaneously, and indicates three crystals, labeled (i - iii), where we have measured the DBT polarisation in some detail. In each crystal we identify molecules that are well isolated from each other, and for those molecules we measure the fluorescence intensity, normalised to incident power, as a function of the polarisation angle $\theta$. We determine the background level by measuring the signal from a nearby place on the same crystal where there are no DBT molecules, and this is subtracted. The polar plots in Fig.~\ref{Fig:polarization_confocal}(b) show the angular dependences measured in crystals (i - iii).  In crystal (i) four out of the five molecules exhibit the same orientation, though one of these has quite poor contrast. In crystal (ii) all six molecules have the same orientation, as do the three measured in crystal (iii).  The lines drawn in Fig.~\ref{Fig:polarization_confocal}(b) are fits of the form $A\cos^{2}(\theta+\phi)+B/(A+B)$, with $\phi$ being the direction of the molecular alignment. In all, we looked at 58 molecules in 12 crystals and found, as summarised in Fig.~\ref{Fig:polarization_confocal}(c), that the DBT molecules in a given crystal are indeed closely aligned with each other. This provides strong evidence that the molecules move inside the anthracene as it grows and become aligned with the b-axis of the crystal. It is possible that some of the dispersion in orientation is associated with DBT molecules that occupy the secondary insertion site, known as the red site, where the orientation is rotated by $7^{\circ}$ \cite{Nicolet2:07}, but we have not yet explored that possibility.

\section{Optical properties of the DBT}
\label{sec:DBToptics}

In order to prove that the DBT fluorescence seen in Fig.~\ref{Fig:confocal}(b) comes from individual molecules, we measure the correlation between photon arrival times in the two photodetectors (Fig.~(\ref{Fig:oil_confocal})) using a time-correlated counting card (TCCC, Picoquant Timeharp200) and a 755~nm, 83~ps pulsed laser (Picoquant, PDL-800B). This determines the average probability of detecting a photon in the second detector during a narrow time window $\delta t$ centred on time  $t+\tau$, having previously registered one in the first detector at time $t$. For small enough $\delta t$ this is the discrete approximation to the (unnormalised) second-order correlation function $C^{(2)}(\tau)$ \cite{MigdallBook:13}

\begin{equation}
C^{(2)}(\tau) =\langle \hat{a}^\dagger(t)\hat{a}^\dagger(t+\tau)\hat{a}(t)\hat{a}(t+\tau) \rangle ,
\end{equation}

\noindent where $\hat{a}^\dagger$ and $\hat{a}$ are the photon creation and annihilation operators, respectively.
With $\delta t=106.9\,$ps and an excitation power of 16~$\mu$W we have count rates of order $4\times 10^4\,\mbox{s}^{-1}$ in each detector. Because the pulse repetition time $\Delta t=25\,$ns is substantially longer than the decay time $T_1$ of the excited state, we expect the correlation we measure to be well described by the function

\begin{equation}
C^{(2)}(\tau) \simeq B+ N\sum_{n=-\infty}^{\infty}(1-\frac{\delta_{0n}}{m})  e^{-\frac{|\,\tau-n\,\Delta t |}{T_1}}\,,
\label{eq:g2Function}
\end{equation}
where $B$ is a background due to dark counts in the detector, $N$ is a normalising factor, $n$ is an integer that labels the excitation pulses,  $\delta_{0n}$ is the Kronecker delta, and $m$ is the number of molecules emitting the light.

\begin{figure}[t]
\centering\includegraphics[width=9cm]{pulsedg2zero.pdf}
\caption{Second order correlation function of the light from a single fluorescent spot within a thin anthracene crystal when pumped with a pulsed laser.  The reduced peak in the centre shows that this is a single DBT molecule. Black line: data accumulated over 30 minutes with the timing resolution set to $106.9\,$ps. Red line: fit to Eq.(\ref{eq:g2Function}). Blue dashed line: background level deduced from the fitted function.}
\label{Fig:g2}
\end{figure}

The black line plotted in Fig.~\ref{Fig:g2} shows the experimental result obtained after 30 minutes of measurement, while the red line is the fit of Eq.~(\ref{eq:g2Function}) to this measurement. We see that the central peak is strongly suppressed because we are observing a single molecule that is unable to scatter two photons at once. The fit gives the number of molecule as $m=1.53(15)$, or in terms of the normalised second-order correlation function, $g^{(2)}(0)=1-1/m=0.346(59)$. We interpret this to mean that we are observing a single molecule, but that we also collect a small amount of light from other nearby molecule(s) in the periphery of the field of view. By repeating this experiment on many different fluorescent spots we have established that virtually all the emitters are single molecules when the DBT density is low, as in Fig.~\ref{Fig:confocal}. At higher density, we also see bright spots with higher central $C^{(2)}$ peaks, corresponding to clusters of two or more DBT molecules. Returning to Fig.~\ref{Fig:g2}, the blue dashed line shows the background level $B=44.7(2)$.  The same fit  gives the excited state lifetime as $T_1=4.23(5)\,$ns, and this is typical of the lifetimes for all the emitters. It is also similar to the lifetimes measured in thick crystals \cite{Nicolet1:07,Tamarat:00,Trebbia:09,Major:15} and in spin-coated thin films \cite{Toninelli:10}.

\begin{figure}[b]
\centering\includegraphics[width=9cm]{saturation_v3.pdf}
\caption{A typical plot of detected molecule emission for various illumination intensities, showing a saturation intensity of $I_{sat}=75(3)~$kW/cm$^{2}$ and a maximum count rate of $R_{max}=440~$kC/s. Red line: fit to the data using Eq.~\ref{Eq:sat}.}
\label{Fig:saturation}
\end{figure}

When this same molecule is driven continuously by a laser on resonance, the scattering rate in steady state is given by the optical Bloch equations  \cite{LoudonBook:00} as
\begin{equation}
R = \frac{I}{I+I_{sat}} R_{max}\,,
\label{Eq:sat}
\end{equation}
where $I$ is the laser intensity at the molecule, $I_{sat}$ is the saturation intensity, and $R_{max}$ is the limiting rate at high intensity. The saturation intensity is linked to the Rabi frequency $\Omega$ and to the relaxation times by $I/I_{sat}=\Omega^2 T_1 T_2$. We have determined the saturation intensity of this molecule by measuring the scattered photon rate as a function of the incident intensity, as shown by the points plotted in Fig.~\ref{Fig:saturation}. The red line is a fit of Eq.~(\ref{Eq:sat}) to the data, which gives the result $I_{sat}=75(3)\,$kW/cm$^2$. We are not aware of any other determination of this parameter, but note that closely related data are also presented in \cite{Toninelli:10}.

\begin{figure}[b]
\centering\includegraphics[width=9cm]{photobleachplot.pdf}
\caption{Photo-bleaching of DBT in thin anthracene crystals. The graphs show the number of DBT molecules remaining unbleached as a function of the exposure time. Orange squares: Anthracene grown in an atmosphere of air and excited at 780 nm using an intensity of $10\,\mbox{kW/cm}^2$. Orange line: a fit to exponential decay, giving a lifetime of $5.7\,$s. Blue Circles: Anthracene grown in a nitrogen atmosphere and excited at 780 nm with $130\,\mbox{kW/cm}^2$. Blue line: simple empirical formula $15 e^{(-t/5.7)}+ 31 e^{(-t/10^3)}+ 30$ intended to show that the decay rate per molecule increases with time and hence that the bleaching is not exponential.}
\label{Fig:photobleach}
\end{figure}

When dye molecules are optically excited it is not unusual for them to react with ambient oxygen molecules and stop fluorescing \cite{Kozankiewicz:14}, which is clearly undesirable in a practical single-photon source. In order to see whether oxygen plays an important role here, we grew DBT-doped crystals in an atmosphere of air instead of purging the glove bag with nitrogen. We then illuminated 36 molecules, one at a time, at a wavelength of $780\,$nm and an intensity of $\sim10\,\mbox{kW/cm}^2$ ($s\simeq 0.13$) and recorded how long each molecule survived before photo-bleaching. The orange squares in Fig.~\ref{Fig:photobleach} show the number of molecules remaining unbleached as a function of the illumination time. This evolution is reasonably well described by an exponential decay, with a lifetime of $5.7\,$s, as shown by the solid line. That corresponds to a molecule being excited (on average) $\sim10^7$ times before it photo-bleaches. Nicolet \textit{et al.} \cite{Nicolet1:07} give the  branching ratio for decay from $S_1$ to the triplet state $T_0$  as $\sim10^{-7}$, so our result could indicate that the photobleaching mechanism here is associated with passing through the triplet state of DBT and subsequent reaction with the oxygen. However, DBT molecules on the surface of the slide, without any anthracene on top, bleach so quickly that they do not have time to pass through the triplet state -- indeed so quickly that we could not make a plot of their survival over time -- so, at least in that case, the triplet state of DBT does not seem to be playing a role in the bleaching.

By contrast, the DBT molecules prepared without oxygen are extremely photostable. In order to measure their bleaching, we removed LI and used L2 (shown in Fig.~\ref{Fig:oil_confocal}) to focus the excitation light onto the back aperture of the objective. This illuminated a circle of 9.3~$\mu$m FWHM in the plane of the sample, allowing us to expose all the molecules in a single crystal. We also used much higher laser power ($125~\mbox{mW}$ from a Toptica TA 100 Pro at $780\,$nm) so that the intensity on each molecule increased to $\sim 130$~kW/cm$^2$ ($s\simeq 1.7$). We then interleaved periods of high-intensity exposure with confocal scans to check how many molecules remained unbleached. The result, plotted using blue circles in Fig.~\ref{Fig:photobleach}, shows that these molecules are remarkably stable.  An initial population of 75 molecules, observed in 3 separate crystals, decays to 60 molecules after a minute, to 32 after an hour, and to 30 after 4 hours and 20 minutes. This evolution cannot be described by an exponential: the loss rate per molecule is much higher at early times than it is at later times. To illustrate this, the solid blue line in Fig.~\ref{Fig:photobleach} shows that this data can be described by the simple empirical formula $15 e^{(-t/5.7)}+ 31 e^{(-t/10^3)}+ 30$. At the end of this experiment, the 30 photostable molecules have survived $> 10^{12}$ excitations, and it seems likely that they could have survived many more. It remains to be seen whether all the molecules can be rendered photostable by a more serious effort to remove all the oxygen.

\section{Conclusions}
\label{sec:conclusions}

We have demonstrated a method for growing anthracene crystals that are wide and thin. The thickness, adjustable by the duration of the growth over the range $40 - 150\,$nm  (at least), has excellent uniformity. A highly supersaturated anthracene vapour is used to obtain enough chemical potential difference to favour this morphology. The anthracene is doped with DBT molecules that are spun onto the surface prior to the crystal growth, and this makes it possible to adjust the concentration of the dopant over a wide range. We have shown that after the anthracene is grown, the DBT molecules become aligned with a common axis in the crystal -- presumably the b-axis -- which indicates that they are accepted into the lattice, where most of them occupy the main insertion site. This opens the possibility of aligning the molecules with nano-fabricated optical structures when we seek in the future to insert them into devices. The standard Hanbury Brown and Twiss method has shown that the bright spots seen in the microscope are indeed single molecules, and the decay of the exponentials in the $C^{(2)}$ function have shown that the lifetime in these particular crystals is similar to that in other anthracene matrices. We have also measured the saturation intensity at room temperature and find that it is unremarkable. On subjecting these molecules to a long period of intense illumination, we find that they are extremely photostable as long as we grow the anthracene in a nitrogen atmosphere, rather than in air. We presume that this hinges on the level of oxygen.

In summary, there is a need for quantum emitters able to radiate individual photons on demand into optical nanostructures, and  we have started to pursue the proposal that DBT molecules in an organic matrix might be able to satisfy that need. Having shown that the matrix must be thin to achieve efficient coupling to a waveguide, we have found a way to grow suitable films of anthracene, and how to dope them with DBT. On investigating their optical properties, we find that these molecules are very promising, being both polarised and photostable. Whilst all of the anthracene growth presented in this paper was carried out on a glass substrate we have recently grown crystals on silicon nitride, a material commonly used for nanophotonic devices operating at visible wavelengths. We find that these crystals appear to be the same as those presented here.

\section{Acknowledgements}

We are indebted to Jaesuk Hwang for suggesting this method of crystal growth, to Kiang-Wei Kho for helping to set up the microscope, to Yu Hung Lien for valuable discussions, and to Jon Dyne, Steve Maine, and Valerijus Gerulis for their expert mechanical and electrical workshop support. We acknowledge funding from the Royal Society, the EPSRC, and dstl. The European Commission supports A.S.C. through a Marie Sk{\l}odowska Curie Individual Fellowship (Q-MoPS) and S.G. through the Action-Initial Training Network: Frontiers in Quantum Technology.

\end{document}

redpajama_set_name: RedPajamaArXiv


text:
Might co-living ease the UK countryside's housing disaster?
By linda Last updated Aug 7, 2022 3
© Clare Melinsky
The proportion of the UK categorized as "steady city cloth" — ie cities — is 0.1 per cent. One other 5.3 per cent is taken into account "discontinuous city cloth" (through which 50-80 per cent of the land is constructed on). The remaining is usually countryside. The UK would possibly usually be regarded as one of many extra densely populated locations to reside. It isn't. The densest? That might be Macau. Then Monaco, Singapore, Hong Kong, Gibraltar . . . The UK is available in at quantity 50, eight locations beneath Japan and simply above Pakistan.
But that vast expanse of land is protected vociferously, as if it had been a tiny sliver underneath fixed stress from increasing cities. In some ways, the countryside is struggling a much more acute housing scarcity than the metropolis, which may not less than develop — upwards, outwards (typically) and in density.
The winner of this 12 months's Davidson Prize, a £10,000 annual award for design concepts making an attempt to deal with points in housing, targeted exactly on this query. A staff led by Charles Holland Architects developed a mannequin for co-living within the countryside, which, although it seems to be fairly a modest proposal, when it comes to the precise structure of latest UK housing, is definitely remarkably radical.
The plan is to create a rented lodging mannequin capable of tackle the wants of a disempowered demographic, the (largely) younger who want to proceed dwelling within the countryside, or to maneuver there and to remain there. It's a design that makes an attempt to ask the questions that the mass housebuilders are resolutely not asking. How are households altering? How has WFH affected the necessity for home area? How can lodging be tailored to altering wants all through life to allow a group to place down roots? Can we envisage a extra communal, extra co-operative life-style? What would possibly it appear to be? And what would possibly the neighbours assume?
"There appears to be an actual dearth of concepts about how rural housing may be achieved," Charles Holland tells me. "There's just one mannequin: the mass housebuilders' — largely indifferent, govt homes primarily based round a cul de sac. There are every kind of different points we needed to take a look at: loneliness, childcare, automobile dependency, variety and the dearth of reasonably priced housing within the nation."
The proposed growth may very well be constructed on the sting of the village of Alfriston in East Sussex © Greg Balfour Evans/Alamy
The drawings the group offered are undoubtedly eye-catching. An eccentric, irregular vary of housing round a central communal area, the homes sprout quirky, vibrant, toylike pavilions on their roofs, whereas the yard is a patchwork of inexperienced, allotments, bushes and play areas.
"We had been all for making the structure a framework which permits several types of dwelling to go on — in distinction to most rural housing, which is tough to adapt and aimed squarely at a nuclear household," says Holland. The designs are easy, timber-framed steady models with versatile interiors. The curiosity comes on high. If they should develop, the intention is that they need to develop upwards with an ideal diploma of design freedom in order that the profile of the housing would change over time.
"We needed to construct in adaptability," says Verity-Jane Keefe, an artist who was a part of the profitable proposal and who has labored extensively with communities to know the way in which folks adapt and customise their houses. "What's it to have estates that you could possibly develop with? For those who all of the sudden end up single, you'd be capable to keep [ . . .] All of us have an curiosity in change and adaptation in housing and we needed to maneuver past model and the horrendous debate about conventional structure."
That debate is certainly very reside. The curious factor in regards to the aesthetic architectural discourse within the British countryside is an assumption that the housebuilders are delivering what folks need, as confirmed, they might counsel, by their gross sales. However what if that's all that's obtainable? The default brick homes with pitched roofs set in acres of tarmac have created estates that purport to be "in holding" with their environment (maybe utilizing some native brick, slate or stone) however truly produce bleak, remoted, car-reliant landscapes of painful banality.
That is an try and do one thing completely different. And to do it on an actual web site on the sting of a ravishing village of the South Downs, Alfriston in East Sussex.
Matthew Morgan, one other member of the staff and director of the High quality of Life Basis, says: "We needed to ask, 'What do folks worth and what do they want? Alfriston is on the sting of the Downs, this big pure and social useful resource which is unavailable to most individuals. There's a very excessive proportion of individuals round right here who personal their property outright, it's an older inhabitants and there are only a few alternatives for individuals who develop up right here to grow to be owners."
A picture of the Alfriston venture by Charles Holland Architects © Co-Dwelling In The Countryside
The Davidson Prize, it ought to be famous, awards concepts. This proposal doesn't have planning permission, though its designers are hopeful that profitable could have boosted its probabilities.
One among its actual improvements is its rental-only mannequin. In a panorama affected by rampant house-price inflation and second houses (outsiders outpricing the locals), the concept right here is that there could be no likelihood for residents to purchase these houses. As a substitute, the intention is one thing just like the Group Land Trusts envisaged by the founders of the backyard metropolis motion within the nineteenth century.
This mannequin concerned advantages accruing from enhancements for use for group profit somewhat than particular person revenue. Profitable in locations equivalent to Letchworth Backyard Metropolis within the UK and later in India and the US, curiosity has just lately been revived within the mannequin as an antidote to non-public seize of communal positive factors and the advantages of presidency spending and group work.
"This scheme tries to discover a completely different mannequin for rented co-living," says Holland. "It's involved with taking a look at variety of occupation, a spot which could appeal to individuals who in any other case wouldn't consider, or be capable to reside within the nation."
The adaptable homes of the Alfriston venture can accommodate multigenerational dwelling, prolonged households and different forms of non-nuclear households © Co-Dwelling In The Countryside
The focus of dwellings and their versatile layouts are supposed to deal with an entire barrage of latest points. Proximity and shared play area creates potentialities for childcare, so usually an issue in rural places. In addition to the potential for shared kitchen and eating areas, versatile layouts promise a neater lodging of working from house and domesticity in a single location and workshops make much less domesticated labour accessible on web site.
Co-living is, in fact, nothing new. It's arguably the oldest type of housing, through which residents share areas and facilities. However in its fashionable incarnation (and as an aspiration somewhat than a slum) there are effective examples, from early Soviet structure (equivalent to Moscow's Narkomfin Constructing, constructed 1928-30) via hippy communes and desert cults (famously, Paolo Soleri's Arcosanti in Arizona) to Danish experiments within the Seventies. Extra just lately, it was revived to be used in more and more unaffordable cities, in New York and London, to deal with acute housing shortages.
However its adoption within the British countryside, exterior the occasional cult, is uncommon. It envisages a flexibility within the existence it helps, designed to encourage a higher variety of dwellers than may be anticipated. Homes can accommodate multigenerational dwelling, prolonged households, non-nuclear households and both roughly communal existence.
The proximity of dwellings and the vary of home preparations they may assist are supposed to deal with the issues of loneliness and isolation usually related to rural life.
Range, nonetheless, isn't what you'd affiliate with Alfriston. Or certainly a lot of the English countryside. It's true that since Brexit a lot agricultural labour has come from as far afield as Bangladesh and Nepal however these are typically short-term staff, dwelling in remoted lodging, remaining unintegrated within the communities. In 2020, the "white ethnic" group accounted for 98.6 per cent of the inhabitants of rural areas.
The backyard metropolis motion gave rise to Letchworth Backyard Metropolis, Hertfordshire, amongst others in England © Getty Photos/iStockphoto
Joseph Henry, the ultimate member of the profitable staff, is the capital growth supervisor of the tradition and artistic industries unit of the Better London Authority. He's optimistic about rising rural variety. "Lots of people come to the UK from rural conditions," he says, "however they have a tendency to finish up in cities the place there may be established communities. There are assumptions round the place folks wish to reside."
Change is going on, although. "There are numerous rural ethnic Tory MPs coming via," he laughs — Tory management candidate Rishi Sunak, for example, is MP for Richmond, an prosperous rural North Yorkshire seat. "The countryside will grow to be extra various."
One of many limitations to constructing new homes within the countryside is the neighbours. Everyone seems to be in favour of extra housing. Simply not right here. (The acronym BANANA because the hypertrophied nimby, "construct completely nothing wherever close to anybody", appears to seize it).
"The query," says Henry, "is the way you make folks really feel extra invested." Numerous it's about governance, he provides, in reference to their co-living venture. "The board members [for the housing committee] may very well be anybody, together with folks from the area people. And the positioning ought to grow to be an amenity for the group, with childcare, workshops, services, allotments." Convey the broader public on board, he causes, and you may pre-empt among the antagonism.
Protesters against a brand new housing property exterior Dorchester © Finnbarr Webster/Getty
Although the staff has tried to keep away from too prescriptive an structure, the drawings look fairly wacky — a sort of self-build utopia of half-timbered, mock-Tudor roof extensions, inexperienced greenhouses, inflatables. "Properly, folks do do completely loopy issues to their homes," says Holland.
It's a part of an effort to provide renters, who often have so little management over their environment, a level of company, to permit them to mould their dwellings to their must encourage them to remain and construct group. Holland refers to anarchist architect Colin Ward, "who developed an concept of 'dweller management' and who was vital of the disempowerment created by bureaucratic administration".
It's an intriguing proposal. The location, an deserted farm on what Holland refers to as "the much less fairly facet of the village", is at the moment scrappy but additionally precisely the sort of place for an experiment like this. Keefe says that when she visited the positioning "curtains had been a-twitching and the speedy neighbours had been initially combative".
However you want dedication, she says, meaningfully embedding your self in the neighborhood and figuring out folks for the venture who have already got connections to the village. As but, it's unclear whether or not that assist has been forthcoming, however not less than they're serious about it.
All of them inform me in regards to the significance of figuring out what the group wants. "Not 3D printers and artistic hubs," says Keefe, figuring out one of many purest tropes of latest developer-speak. "We discovered there have been a number of builders round right here — engaged on the massive, costly homes — they usually wanted area. You might construct workshops for them to make use of, integrating the place into the group."
Industrial housing developments may be bleak and isolating © Getty Photos/iStockphoto
"The location is a sort of edge situation, the place housing begins to merge with the agricultural," Holland says. "We had been very impressed by the plotlands, that wealthy panorama between suburban and countryside," he says, referring to the post-first world battle tasks that allotted returning servicemen small rural plots and allowed them to construct their very own dwellings.
That second produced a surprisingly enduring different to the mainstream of builders' housing. The Dunton Plotlands and Jaywick Sands, each in Essex, survive as testomony, although the latter is usually held up as one of the vital disadvantaged locations within the UK. The countryside isn't at all times a bucolic idyll.
The Alfriston web site has already been designated for housing, so this proposal has an opportunity of being realised. However it's a radical departure from the norm, a bottom-up, non-profit strategy to a area that has been delegated nearly totally to industrial builders. Its actual curiosity, nonetheless, will emerge solely with time, as residents transform and reimagine their homes and their group.
That is, in fact, how the chocolate field village itself grew, with its layers accreting over centuries, adapting to altering calls for. Then, by some means, it acquired caught in a single second, its magnificence each blessing and curse. It will be thrilling to see this proposal realised. However even higher to see it a century on, advanced somewhat than designed.
Edwin Heathcote is the FT's design and structure critic
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redpajama_set_name: RedPajamaCommonCrawl


text:
\section{Introduction}\label{sec:intro}

Core-collapse supernova explosion (CCSN) marks the death of massive stars, in which the heavy elements in the order of solar mass are ejected into the interstellar medium.
The explosive nucleosynthesis during the development of explosion and the subsequent neutron star cooling phases are particularly important for the production of heavier elements.
Importantly the direct measurements of some of the heavy elements in young supernova remnants (SNRs) are now possible
and offer valuable insights to understand the explosion mechanism and the possible link with the neutron star (NS) kick~\citep{2006A&A...457..963S, 2006A&A...453..661K, 2013A&A...552A.126W, 2017ApJ...842...13W}.

It is now established that multi-dimensional(D) hydrodynamic instabilities are one of the key ingredients in the explosion mechanism.
They disorganize the post-shock accretion flows including the envelope of the NS, which also produce temporal variations and global asymmetries in the neutrino emissions.
This may also impact on the explosive nucleosynthesis, which has been investigated based on results of 2D simulations of CCSNe~\citep{2005ApJ...623..325P, 2006ApJ...644.1028P, 2011ApJ...738...61F, 2011ApJ...726L..15W, 2013ApJ...767L..26W, 2013ApJ...774L...6W, 2017ApJ...843....2H, 2018JPhG...45a4001E, 2018ApJ...852...40W}.

More recently, the coherent asymmetric neutrino emissions have been witnessed in some CCSN simulations with detailed neutrino transport; for instances, lepton-emission self-sustained asymmetry appears in some 3D CCSN simulations among different groups~\citep{2014ApJ...792...96T, 2018ApJ...865...81O, 2019MNRAS.482..351V}
and large asymmetric neutrino emissions associated with the NS kick are observed in a latest axisymmetric CCSN simulation with full Boltzmann neutrino transport~\citep{2019arXiv190704863N}.
In this {\it Letter},
we examine the impact of the asymmetric neutrino emissions on the explosive nucleosynthesis by axisymmetric hydrodynamic simulations with approximate neutrino transport and by post-processing calculation of the abundance evolution of SN ejecta with a nuclear reaction network combined with the tracer particle method.
In this study, we focus on a representative SN progenitor; 19.4$\Ms$ with the solar metallicity~\citep{2002RvMP...74.1015W}.
Based on our results, we discuss the observational consequences of asymmetric neutrino emissions such as correlations of asymmetric distributions of heavy elements, ejecta morphology and NS kick in SNRs.

This paper is organized as follows. In section 2, we will presents results of 2D axisymmetric simulations of CCSN explosions.
In section 3, we present our results of nucleosynthesis and discuss observational implications in SNRs of our results.
Finally, we will summarize our conclusion in section 4.

\section{Aspherical CCSN explosion}\label{sec:SN explosion}

We employ two-independent numerical codes in our CCSN simulations; one of which is an open-source spherically symmetric CCSN scheme, namely "GR1D"~\citep{2015ApJS..219...24O},
and the other is based on another open-source hydrodynamic scheme, namely "ZEUS-2D"~\citep{1992ApJS...80..791S, 2006ApJ...641.1018O, 2007ApJ...667..375O}, with incorporating required CCSN physics such as neutrino-matter interactions and neutrino transport.
We use the former for the simulation up to $\sim 100$ms after the bounce including the collapsing phase. We then switch to axisymmetric simulations with dynamically-unimportant velocity perturbations.
Most parts of the numerical method are the same as those used in~\citet{2011ApJ...738...61F}, in which we solve axisymmetric hydrodynamic equations with taking into account the feedback from neutrino-matter interactions.
The neutrino distribution function, which is required in the feedback from neutrinos to matter, is computed by a simplified $\nu$ transport model, namely "light-bulb $\nu$ transport"~\citep{2006ApJ...641.1018O},
in which neutrinos are emitted from a sphere with thermal distributions.

In this study, we assume that the neutrino temperatures are spherical symmetric
\footnote{We checked the average energy of neutrinos in some CCSN simulations with full Boltzmann neutrino transport,
and confirmed that its asphericity is much smaller than that in the energy-flux.}
but the luminosities are aspherical;
\begin{eqnarray}
L_{\nue} &=& L_{\nue, \rm ave} (1 +m_{\rm asy} \cos \theta), \\
L_{\nueb} &=& L_{\nueb, \rm ave} (1 -m_{\rm asy} \cos \theta),
\end{eqnarray}
where $L_{\nue}$ and $L_{\nueb}$ are luminosity of $\nue$ and $\nueb$ and $L_{\nue, \rm ave}$ and $L_{\nueb, \rm ave}$ are their angle averages, respectively.
Here the evolution of $L_{\nue, \rm ave}$, $L_{\nueb, \rm ave}$ and neutrino temperatures
are evaluated with a $\nu$-core model from the mass accretion rate at an inner edge of the computational domain of our 2D simulations,
as in systematic studies on CCSN nucleosynthesis in spherical symmetry~\citep{2012ApJ...757...69U, 2016ApJ...821...38S} but with some modifications
(see details in Fujimoto et al. (2019) in preparation).
For instances, $L_{\nue, \rm ave}$ and $L_{\nueb, \rm ave}$ were set to be constant in time and $m_{\rm asy} = 0$ in the previous work~\citep{2011ApJ...738...61F}.
We have tuned two parameters of the $\nu$-core model so that the explosion of the $19.4\Ms$ progenitor for $m_{\rm asy} = 0\%$ (spherical $\nu$ emission) reproduces
observations of SN1987A, or the explosion energy $E_{\rm exp} \sim 10^{51} \rm erg$ and the ejected mass of \nuc{Ni}{56}, $M$(\nuc{Ni}{56}), of $\sim (0.07-0.08) \Ms$.
We set $m_{\rm asy}$ to be 0\%, 10/3\%, 10\%, 30\%, and 50\%\footnote{$m_{\rm asy} \sim 10 \%$ has been observed in the recent multi-D CCSN simulations (see, e.g., \citet{2014ApJ...792...96T}).}.

We have performed the simulations for the progenitor of 19.4$\Ms$ up to $\sim$ 1.2s after the core bounce,
in which shock fronts for all models have reached to a layer with $r = 10,000\km$ in almost all directions by the end of the simulations.
We confirm that the explosion is highly aspherical and $l=1$ and $2$ modes are dominant
as shown in \citet{2006A&A...453..661K, 2006A&A...457..963S, 2007ApJ...667..375O, 2011ApJ...738...61F}.
The aspherical neutrino emission makes ejecta in the high-$\nue$ hemisphere proton($p$)-rich due to enhanced $\nue$-absorptions on neutron($n$)
and declined $\nueb$-absorptions on $p$,
while the enhanced $\nueb$ and the declined $\nue$ emission results in $n$-rich ejecta in the high-$\nueb$ hemisphere (Fig. \ref{fig:schematic}).

In our models, properties of the CCSN explosion weakly depend on $m_{\rm asy}$;
the evolution of shock radii are similar (Fig. \ref{fig:shock radii}) and
$E_{\rm exp}$ and $M$(\nuc{Ni}{56}) are (0.89-1.17)$\times 10^{51} \rm erg$ and (5.2-8.1)$\times 0.01 \Ms$, respectively.
It should be noted, however, the asymmetric neutrino emissions may be associated with the shock morphology in reality (see e.g., \citet{2014ApJ...792...96T}).
This issue can be only addressed by CCSN simulations with more consistent treatments of neutrino-radiation hydrodynamics
such as ~\citet{2018ApJ...854..136N} and \citet{2019arXiv190704863N}.
We postpone these studies to a future paper.

 \begin{figure}
  \begin{center}
   \includegraphics[scale=1.0]{figure1.eps}
  \end{center}
  \caption{
  Schematic picture of CCSN explosion with asymmetric $\nue$ and $\nueb$ emission.
  The asymmetry leads to the compositional differences in SN ejecta, which become $n$($p$)-rich in the high-$\nue$ (high-$\nueb$) hemisphere
  due to the enhancement of $\nue$ ($\nueb$) and the decline of $\nueb$ ($\nue$).}

  \label{fig:schematic}
 \end{figure}

 \begin{figure}
  \begin{center}
   \includegraphics[scale=0.65]{figure2.eps}
  \end{center}
  \caption{Evolution of average shock radius, $r_{\rm sh}$, for cases with $m_{\rm asy}=$ 0\%(solid line), 10/3\%(dashed line), 10\%(dotted line), 30\%(dash-dotted line), and 50\%(double dotted line) as a function of the time from the core bounce $t_{\rm pb}$.
  }
  \label{fig:shock radii}
 \end{figure}

\section{Abundances of SN ejecta}\label{sec:abundances}

For the nucleosynthesis computations, Lagrangian thermodynamic histories are computed by a tracer particle method~\citep{1997ApJ...486.1026N, 2010MNRAS.407.2297S},
in which the particles evolve in accordance with the fluid-velocity while storing their physical quantities such as density, temperature, and electron fraction.
At the beginning of the simulations, 6,000 tracer particles are distributed in the regions from $1,000$km to $10,000$km or an O-rich layer with being weighted to the mass in the shell.
By virtue of the adaptive particle mass distributions, the highest resolution in the particle mass is $\sim 10^{-4} \Ms$ in this study.
Note that 6,000 particles are sufficient to investigate the impact of asymmetric neutrino emissions in CCSN.
Indeed, in our previous study~\citep{2011ApJ...738...61F}, we checked the sensitivity of nuclear abundances to the particle numbers,
and found that the difference of the ejected mass of heavy nuclei between 3,000 and 6,000 particles cases is less than $\sim$ 1\%.
For the initial condition, we take the abundance data of 20 nuclei from the result of stellar evolution in~\citet{2002RvMP...74.1015W}.

In our models, more than 3,500 particles are ejected by explosions.
The nuclear abundances produced by the explosive nucleosynthesis and their masses in the ejecta are estimated in the region $r_{\rm cc} \le 10,000\km$,
where the peak temperature is higher than the required temperature to produce elements heavier than C.
For this reason our nucleosynthesis computations are conducted only for the tracer particles which are located $r \le r_{\rm cc}$ at the initial condition
\footnote{The mass in the region $r > r_{\rm cc}$ for the 19.4 $\Ms$ progenitor is $13.0\Ms$.}.
We compute nucleosynthesis for 2,488 nuclides from $n$, $p$ to Nd by employing the same network as that in \citet{2007ApJ...656..382F}.
Note that, for the ejecta with higher temperature than $9 \times 10^9 \K$,
the chemical composition of the ejecta is set to be that in nuclear statistical equilibrium.
Note also that the number of nuclides in this study is less than that in the previous study ($\sim 4,000$ nuclides),
but we improved some neutrino interactions for He and nuclei from C to Kr as in ~\citet{2011ApJ...738...61F}.
Albeit possessing $Y_e$ data from the hydrodynamic simulations,
we recompute $Y_e$ following the weak interactions employed in the nuclear reaction network, and we adopt them in our network computations.

Below, we present the main results of our nucleosynthetic computation.
Figure \ref{fig:dist-ye-ww19.4} shows mass profiles of $dM_{\rm ej}$ in $Y_{e,1}$ of the ejecta from the inner region ($r_{\rm cc} \le 10,000\km$)
for cases with $m_{\rm asy}=$ 0\%, 10/3\%, 10\%, 30\%, and 50\%.
Here $Y_{e,1}$ is the electron fraction evaluated when the temperature is equal to $10^9 \rm K$ during the ejection
and $dM_{\rm ej}$ is a mass of ejecta integrated with a bin of $dY_{e,1} = 0.005$.
We find that for larger $m_{\rm asy}$, amounts of both $p$- and $n$-rich ejecta become larger with wider range of $Y_{e,1}$.
This is mainly due to the excess of $\nue$ or $\nueb$ absorptions by asymmetric neutrino emissions.

\begin{figure}
  \includegraphics[scale=1.1]{figure3.eps}
  \vspace*{-30pt}
  \caption{Mass profiles of $dM_{\rm ej}$ in $Y_{e,1}$ of the inner ejecta ($r_{\rm cc} \le 10,000 \km$)
 for cases with $m_{\rm asy}=$ 0\%, 10/3\%, 10\%, 30\%, and 50\% in panels from top to bottom, respectively.}
  \label{fig:dist-ye-ww19.4}
\end{figure}

Figure \ref{fig:xfe-ww19.4} shows the composition of the ejecta for our models
in terms of [X/Fe]~\footnote{[A/B] = $\log \left[ (X_{\rm A}/X_{\rm A, \odot})/(X_{\rm B}/X_{\rm B, \odot})\right]$,
where $X_{\rm i}$ and $X_{\rm i,\odot}$ are a mass fraction of element $\rm i$ and its solar value~\citep{1989GeCoA..53..197A}, respectively.}
of the ejecta as a function of an atomic number $Z$ for a model with $m_{\rm asy}=$ 0\%, 10/3\%, 10\%, 30\%, and 50\%.
Here masses of an element of the ejecta are evaluated with the sum of those in the inner ejecta ($r_{\rm cc} < 10,000\km$)
and those of ejecta from the outer layers ($\ge 10,000 \rm km$) with the progenitor abundances.
We find that abundances of the $p$-rich ejecta are similar to those in ejecta with $Y_e \sim 0.49-0.51$.
This is attributed to the fact that the $\nu p$ process is weak and $rp$ process hardly happen
due to the low entropies and long expansion timescales in the ejecta, which results in small proton to seed ratios, as in \citet{2018ApJ...852...40W}. On the other hand,
we find that the $n$-rich ejecta have a largely different composition from the ejecta with $Y_e \sim 0.49-0.51$ and have abundant elements with $Z \ge 29$,
which are abundantly produced through quasi and nuclear statistical equilibrium;
the composition is not largely changed through reactions other than $\beta$ decays even after the break of the equilibrium~\citep{2018ApJ...852...40W}.
We note that dependences of the ejecta composition on $Y_{e,1}$ are similar to those in \citet{2018ApJ...852...40W}.
Elements lighter than Al are chiefly synthesized in the progenitor and abundances of elements lighter than Ca are independent to $m_{\rm asy}$,
because of similar $E_{\rm exp}$ and amounts of ejecta with $Y_{e,1} \sim 0.5$ (Fig. \ref{fig:dist-ye-ww19.4}),
even for cases with large asymmetric $\nu$ emission ($m_{\rm asy} \ge 30\%$).
For cases with small $\nu$ asymmetry ($m_{\rm asy} =$ 10/3\% and 10\%), elements with $Z \ge 29$
can be abundantly produced in the ejecta with some overproduction of elements ($Z=$ 34-37 and $40$),
while models with large asymmetry ($m_{\rm asy} =$ 30\% and 50\%) produce too large elements with $Z \ge 30$ compared with those in the solar system,
due to too large $n$-rich ejecta (Fig. \ref{fig:dist-ye-ww19.4}).
Although the detailed comparison to the solar abundance requires considering the progenitor dependence and taking the IMF-average,
such an extreme overproduction can not be easily diminished.
We thus conclude that $m_{\rm asy} \ge $ 30\% in $\nu$ luminosity is not favorable to yield the solar abundances from CCSNe.

\begin{figure}
 \includegraphics[scale=1.1]{figure4.eps}
 \vspace*{-30pt}
 \caption{
 [X/Fe] of all ejecta for cases with $m_{\rm asy}=$ 0\%, 10/3\%, 10\%, 30\%, and 50\% in panels from top to bottom.
 Cases with large asymmetry ($m_{\rm asy} =$ 30\% (fourth panel) and 50\% (bottom panel)), produce too much elements with $Z \ge 30$.}
 \label{fig:xfe-ww19.4}
\end{figure}

\begin{figure}
 \includegraphics[scale=0.65]{figure5.eps}
 \vspace*{-10pt}
 \caption{
 [X/Fe] of ejecta in the high-$\nue$ (solid lines) and high-$\nueb$ (dotted lines) hemispheres
 for $m_{\rm asy}=$ 0\% (top), 10/3\% (middle), and 10\% (bottom).
 Compositional differences between the high-$\nue$ and high-$\nueb$ hemispheres are prominent for Sc and elements with $Z \ge 29$
 for cases of aspherical $\nu$ emission.
 }
 \label{fig:xfe-ww19.4-ns}
\end{figure}
Figure \ref{fig:xfe-ww19.4-ns} shows [X/Fe] of ejecta in the high-$\nue$ (solid lines) hemisphere and high-$\nueb$ (dotted lines) one,
where $n$-rich ejecta ($Y_{\rm e,1} < 0.49$) are abundantly located, for cases with $m_{\rm asy}=$ 0\% (top panel), 10/3\% (middle panel), and 10\% (bottom panel).
We note that abundances in the high-$\nueb$ hemisphere are very similar to those of all the ejecta (Fig. \ref{fig:xfe-ww19.4}).
For the case with spherical $\nu$ emission (top panel), compositional differences between the northern- and southern- hemisphere is small.
Note that in the spherical case we make a geometrical distinction of northern and southern hemispheres instead of high-$\nue$ and high-$\nueb$ hemispheres.
On the other hand, the differences in Sc and elements with $Z \ge 29$ are prominent for cases with aspherical $\nu$ emission (middle and bottom panels).

In this study, we have adopted the limited number of nuclei as the progenitor composition.
To clarify effects of odd-$Z$ and $s$-process elements synthesized in the outer layers of the 19.4$\Ms$ progenitor, which are not included in our mass estimate,
we evaluate masses of Sc, Cu, Zn, Ga, and Ge in the outer layers ($r_{\rm cc} > 10,000\km$) of a SN progenitor of 19.0$\Ms$,
whose detailed composition are evaluated for nuclei more than 1,200 just before the core collapse~\citep{2002ApJ...576..323R}
and are likely to be comparable to those for the 19.4$\Ms$ progenitor.
When $\nue$ and $\nueb$ are spherically emitted,
the differences of the above elements between northern- and southern- hemispheres possibly disappear,
since the elements are more massive in the outer layers of the progenitor.
For $m_{\rm asy} = $ 10/3\% and 10\% cases,
the differences of Sc, Cu, and Ga are likely to be covered with larger masses of these elements in the outer layers.
It should be noted, however, that the differences are still prominent in masses of Zn and Ge,
even if the elements are taken into account in the outer layers of the progenitor.

Finally we apply our results to the observational consequences in SNRs.
As indicated by some theoretical studies, the asymmetric neutrino emissions may be correlated with the ejecta morphology and NS kick,
in which $\nueb$ is higher in the hemisphere of stronger shock expansion (opposite direction to the NS kick if the mechanism is the hydrodynamic origin)
and $\nue$ is stronger in the opposite hemisphere (see, e.g., \citet{2014ApJ...792...96T} and \citet{2019arXiv190704863N}).
If this is true, the asymmetric distributions of heavy elements found in the present study can be observed with the correlation with the NS kick.
We speculate that the distribution of elements would have the following characteristics;
abundances of elements lighter than Ca are insensitive to the ejecta morphology and NS kick direction, but Zn and Ge would be abundant in the opposite side to the NS kick.
Indeed, a recent observation of asymmetric motion of center of mass of $\alpha$ elements~\citep{2018ApJ...856...18K} may be relevant to our findings.
Note also that observations of abundances of $\alpha$ elements (O, Ne, Mg, Si, and S), and Fe in some SNRs have been proposed to estimate the mass of a SN progenitor~(e.g., \citet{2007ApJ...671.1717T, 2018ApJ...863..127K}),
and we find that their total abundances are insensitive to the asymmetric neutrino emissions.
Thus, the estimate could not be modified even for asymmetric neutrino emissions,
although the systematic study is indispensable in order to assess the impact more quantitatively.

We also note that the ejected mass of Zn found in the present study is not subtle, indeed, it is comparable to that of Cr and even higher than that of Mn,
while the line emissions of the latter two elements from SNRs were observed by Suzaku X-ray satellite~(e.g., \citet{2013ApJ...766...44Y}).
X-Ray Imaging and Spectroscopy Mission (XRISM),
which will be launched at 2021, may detect them with distinguishing Zn-lines from others in young SNRs due to the high energy resolution in a X-ray calorimeter,
which is very similar to that in the Hitomi X-ray observatory.
It should be noted that the last Hitomi X-ray mission showed the ability of the high sensitivity of detecting faint line emissions of Zn from Perseus cluster~\citep{2019PASJ...71...50T}.
More quantitative assessment of the detectability requires detailed computations of the line emissions with multiple progenitors, which will be done in our forthcoming paper.

\section{Conclusion}\label{sec:conclusion}

We have examined explosive nucleosynthesis in CCSNe of the 19.4$\Ms$ progenitor under asymmetric and anti-correlated $\nue$ and $\nueb$ emission,
assuming a dipolar, angular dependence (Eqs. 1 and 2) and varying magnitudes of the asymmetry, $m_{\rm asy}$, from 0\% (spherical emission) to 50\%.
Due to the dipolar and anti-correlated angular dependence of the $\nu$ luminosities,
SN ejecta become $p$-rich and $n$-rich in the high-$\nue$ and high-$\nueb$ hemispheres, respectively.
We also found that elements heavier than Cu ($Z \ge 29$) are abundantly produced in the $n$-rich ejecta (Fig. \ref{fig:xfe-ww19.4}).
The asymmetry ($m_{\rm asy} \ge 30\%$) leads to too much elements heavier than Zn ($Z \ge 30$) (e.g., bottom panel in Fig. \ref{fig:xfe-ww19.4}),
which may imply that such a large asymmetry does not appear in reality.
On the other hand, small asymmetry ($m_{\rm asy} \le 10\%$)
leads to produce elements heavier than Cu in the n-rich ejecta, which are deficit in the case with spherical $\nu$ emissions.

We also apply our results to the observational consequences of SNRs,
in which Zn and Ge would be abundant in the opposite side of NS kick if the kick correlates with asymmetric $\nu$ emissions,
which are seen in some recent multi-D simulations with detailed $\nu$ transport.
Our finding indicates that the correlation between the asymmetric distributions of heavy elements and NS kick may be
not only due to the aspherical shock expansion~\citep{2017ApJ...837...84J} but also asymmetric $\nu$ emissions.
We also speculate that the observation of abundances of $\alpha$ elements, Fe, Zn, and Ge may give us information of asymmetric degree of $\nu$ emissions.

In the present study, we focus on a single representative SN progenitor. Although the qualitative trend may be the same in different progenitors,
amounts of $p$-rich and $n$-rich ejecta depend not only on $m_{\rm asy}$ but also on the neutrino luminosities and the velocities of the ejecta.
Thus, the systematic study of the progenitor dependence with more detailed neutrino transport should be investigated for more quantitative arguments.
We also speculate that the asymmetric neutrino emissions from the PNS core potentially impact on $r$-process nucleosynthesis
in ejecta from the core ($\le 50\,\km$), which were not included in the present computation.
This is also on the to-do-list of future investigations and the result will be published elsewhere.

\vspace*{-20pt}

\section{Acknowledgements}
We thank S. Katsuda for a helpful discussion about observational aspects of Zn in a SNR.
We also thank the anonymous referee for detailed comments that helped us to improve our manuscript.
This work is partly supported by JSPS KAKENHI Grant Number 25400281.

\vspace*{-10pt}

\input{ms.bbl}

\bsp
\label{lastpage}
\end{document}


text:
Q: Почему в разных компиляторах код выводит разные значения?
*

*http://rextester.com/ZZGGK27907

*http://rextester.com/IGXLV67756
В данных ссылках один и тот же код. Но отличается для компиляторов C++ и C++11. В C++ ответ выводится верный. А в C++11 выводится просто 0. По идее, C++ и C++11 не должны сильно отличаться.
Почему может выводится разный ответ в одинаковых кодах? И где может быть ошибка?

A: Не сильно вдавался в алгоритмические подробности, но как минимум одно проблемное место нашел:
stack<int> path;
for(int index = Q.front().idx; index != -1; )
{
   ...

Я попробовал прогнать ваш код на указанном наборе входных данных и обнаружил, что к указанному моменту очередь Q оказывается пуста (не углублялся, должно так быть или нет). Соответственно Q.front().idx обращается к первому элементу пустой очереди. В результате возникает неопределенное поведение. А раз оно неопределенное, то, в зависимости от компилятора, программа ведет себя по разному. Как-то вам нужно этот момент корректно обойти или (если он - не то что вы ожидали), починить код до указанного.

redpajama_set_name: RedPajamaStackExchange


with a celebration of Evening Prayer.
Combining the traditional texts of Psalms, readings, and prayers with contemplative Celtic harp music, this celebration is sure to be a boost for your week.
Evening Prayer (also known as Vespers) is the most commonly celebrated part of the Liturgy of the Hours which together with the Mass, constitutes the official public prayer life of the Church. It is celebrated communally and privately by most Religious orders, as well as by lay people.
The Liturgy of the Hours (also knows as the Divine Office, or Work of God, and often referred to as the Breviary), is the official set of prayers "marking the hours of each day and sanctifying the day with prayer".
It consists primarily of Psalms supplemented by hymns, readings and other prayers and antiphons. The addition of Celtic harp music makes this evening a special blessing.


The review report was a good news story in that it found the organisation was meeting its core purpose of advocating for older persons on the Kapiti Coast with relatively few areas in need of change. The report will be a platform for discussion by Grey Power over the next twelve months and will assist in planning for the future.
Volunteers are the lifeblood of Grey Power and without them Grey Power would be unable to operate. We have about 150 volunteers performing a wide range of tasks they include delivering the Super-people magazine, working in the office and reception and the management committee. All of them do a fantastic job. However, we can always use of more volunteers, the work is stimulating and you meet a wide range of interesting people. Volunteers also reported that they found the work they did for the organisation personally rewarding and uplifting which is always a sign of a healthy culture.
A summary of the review's recommendations will be provided to Grey Power members at the upcoming annual general meeting on 9 May.


text:
Van Breda Trial Update: Evidence of Henri's epileptic fit on night of murders
The Van Breda trial continues to go back and forth. We have the latest updates from the trial. Including information about Henri's seizure.
CAPE TOWN, SOUTH AFRICA – MAY 15: Henri van Breda at the Western Cape High Court during day 11 of his trial on May 15, 2017 in Cape Town, South Africa. Police forensic analyst Henry Stuart who analysed various hair samples from the Van Breda home, had initially testified that his analysis showed that the hair resembles that of Henri's hair, but under cross-examination conceded that it was highly unlikely.
While Judge Siraj Desai wants the trial of Henri Van Breda concluded by the end of the month, expert witnesses are still dropping new bombshells by the day. This time, it has everything to do with Henri and the "seizure" he claims to have had on the night of the murders.
Neurologist Dr James Butler testified for the defence on Monday in the High Court in Cape Town on Monday. Butler said that Van Breda's form of epilepsy might explain his "missing" two hours from his version of events.
While the state has argued that Van Breda's blackout was a convenient explanation for a muddled timeline, Dr Butler said it was more than possible.
"It is possible he wasn't right in the head (nie reg in die kop) if he had had a seizure."
"I made it very clear to both sides I do not wish to receive any remuneration for my part in this process other than being paid for the medical consultation of Mr Van Breda'" he said.
While Van Breda has been accused of feigning medical illness with ulterior motives during the trial, Butler diagnosed Henri "unequivocally" with juvenile myoclonic epilepsy.
"He said he had looked up from his phone while climbing the stairs and remembers seeing Marli at the top of the stairs and he remembered seeing her right arm and leg moving' and quite a bit of blood on her head'" said Butler.
Butler was then asked how Henri appeared in the photo that showed him sitting in the ambulance on the night of the attacks.
"He looked dulled'" said Butler' "just like someone recovering from a seizure".
While Judge Desai hit back and said the look could easily have been common symptoms of dealing with such an event, Butler was adamant.
The doctor stressed that the possibility of Henri faking the illness was so unlikely it "can effectively be disregarded".
Tags: Henri van BredaVan Breda murders


#Ash was removed from the western edition of the game, but remained a playable character with the aid of the Game Genie. They were possibly given these mannerisms because Gracie is a fashion designer and Saharah has long eyelashes that he always brags about.
Click to watch more Amature automobile masturbation videos!


Interactive exposure - college coaches will be on the field with players, running the drills and instructing the athletes.
COST Once an invitation is sent out players will be required to register and pay the $595 per player registration; fee includes 3 hours of college-level practices, skills, 2 games, all games are filmed by StreamSports (they can be purchased pre or post-event for an additional fee) plus all players receive a 77 SOUTH custom reversible, an event T-shirt & 77 South shorts..
Requests for refunds are handled on a case by case basis and must be in writing to info@stickwithus.org In general, however, by registering for any of our programs, the registrants agree and understand that due to the nature and expense of pre-planned events, leagues, tournaments, camps, clinics, workshops, and select teams, StickWithUs.org Lacrosse & The Carolina Lacrosse Association has a policy of no refunds, unless a suitable replacement can be added to the event in your absence.
ALL games played at the Sportsplex at Matthews - 11 turf field at ONE location with plenty of parking! - Best tourney venue in the South East.
All sessions/games played on sports turf & all games guaranteed!


At Home Care Assistance, we are passionate about one thing: providing seniors with meaning and purpose in life. Our goal is to change and improve the way our world ages by providing the best in-home care services throughout the industry. We invite you to use the information on this page to find out why joining our franchise network is the right move for you.
In 2002, the founders of Home Care Assistance were inspired to start their own home care company when they discovered the options for hiring outside care for their own aging parents were not suitable. Most care companies focused on building relationships with hospitals instead of the families of their clients. Our founders saw a need for a home care company that focused on the needs of the consumer—usually adult children searching for the right professional care for their aging parents and loved ones.
Not only were most home care services failing to meet the real needs of their consumers, they were also unprofessional. About 9 in 10 were "mom and pop" companies, and even larger franchises operated in a comparable fashion, running home-based businesses or operating from small business parks off the beaten path. In an effort to professionalize the business of in-home-care, Home Care Assistance was born.
In 2005, we began franchising. Our goal was to deliver our revolutionary home care services to more consumers in territories throughout the world. Each franchise owner receives the resources, training, and support necessary to ensure that their quality mirrors that of the original pilot office. We design each territory and help franchise owners achieve their goals by coaching them with our proven model. To date, we've added over 165 locations around the world.
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text:
, né le  à Tokyo et mort le  à Tallinn (Estonie), est un guitariste et compositeur de jazz japonais.

Biographie

Ryō Kawasaki s'est dirigé vers la musique après avoir étudié durant quelques années pour devenir scientifique. Pendant les années 1960, il joue avec divers groupes japonais de jazz et forme aussi ses propres groupes. Au début des années 1970, il s'installe à New York où il trouve une activité régulière au sein de formations renommées telles que celles de Gil Evans, Elvin Jones, Chico Hamilton, Ted Curson et Joanne Brackeen.

Au milieu des années 1980, il se retire de la scène pour élaborer des logiciels destinés à la musique. Il compose aussi plusieurs singles de musique techno et crée son propre label, Satellites Records, pour les publier.

En 1991 il retourne au jazz en enregistrant des albums pour un label japonais et en montrant qu'il n'avait rien perdu de son habilité. Grâce à sa longue et vaste expérience, Ryō Kawasaki est capable de passer avec une apparente simplicité du hard bop au jazz-rock. Son jeu est reconnu pour sa fluidité et son style parfois vigoureux.

Discographie

Albums en solo

Collaborations

Simples

Notes et références

Liens externes

Naissance en février 1947
Naissance à Suginami
Guitariste japonais de jazz
Compositeur de jazz
Décès à Tallinn
Décès à 73 ans
Décès en avril 2020

redpajama_set_name: RedPajamaWikipedia


Have you ever tried to cook frozen French fries in the oven without preheating the oven? The directions often say preheat to 425 degrees. That can take 15 to 20 minutes. So, after 10 minutes, you lose your patience and in the oven they go. Big mistake! Your French fries take forever to get crispy!
Today I'm going to talk about "conventional" oven settings.
There are many recipes for making fish, chicken, nachos, etc., that will say bake and others that say broil as a method of cooking. Do not confuse them. These are two very different ways to prepare food. With "baking" you always have to start with preheating the oven.
Preheating an oven is essential or you will throw off the cooking times. All cooking times are based on a preheated oven unless otherwise stated in the recipe. Luckily, when most (modern) ovens reach their desired temperature, they beep at you, or a light goes on or off. You then know it is OK to put food in the oven and start the timer.
Before turning the oven on, make sure the oven racks are in the desired position. It's easier to move the racks in a cold oven; you are less likely to get burned that way! Baking is usually done in the middle of the oven. Broiling (see below) is usually done closer to the top of the oven.
Baking is used to cook things like chicken, potatoes, fish, stews, cookies and cakes. Food gets cooked from the outside in. (Unlike a microwave which causes food molecules to vibrate, creating friction that heats and cooks the food in all directions at once.) You check for "done-ness" by examining the internal temperatures, for example by sticking an oven thermometer into the food. While your food is baking, try not to open the door too often to check for done-ness. Every time you open the oven door to see if your food is cooked, your oven temperature will drop and extend the cooking time.
Broiling means to cook food (like steaks, hamburgers, chicken breasts) under very direct heat. With a gas oven, you actually see a flame. An electric oven has coils directly above the food. My oven insists the door be closed for the broil to work. Some ovens you have to leave the door open. The oven manual should tell you what works with your oven.
Obviously, the closer you are to the heat source – the higher the heat. If you have positioned the racks too close to the broiler, your steak may get burned on the outside and still be raw on the inside. Many recipes will tell you how far away from the broiler you should be.
Do make sure that the baking dish you are using is safe to put under the broiler. Pyrex dishes are NOT broiler safe and could possibly explode from the intense heat of the broiler!
You can also broil things on an outdoor grill over charcoal or some other heat source. I have been to many barbeques but I have never actually done any outdoor grilling myself! We live in a condominium and don't do outdoors very well!
As noted above, your oven may have a warming drawer. If you are having a dinner party, this is a great place to keep the food warm while waiting for your guests to arrive. The food is kept warm at a very low temperature. As I don't actually use it very often, I store cooking equipment in my warming drawer.
I hope this brief introduction to conventional oven settings was helpful.
Sarah, broiling chicken can be a bit tricky. Here is a recipes that include some broiling tips. Good Luck!
Your recipes and blogs are always helpful. This might be a simple question, but I hope you help. In a self-cleaning oven, hw do we clean the oven and what solution should we use for the cleaning process.
Self-cleaning ovens don't really clean themselves, per se. What they do is basically turn off the thermostat and change into crematoriums. They get super-hot, and turn all the baked-on grime into dust. That's why you have to lock them, and the lock won't release until the temperature gets down to ambient again.
Once that's complete, all you need to finish up is a damp sponge and some clean rinse water to wipe the interior down.
Thanks KGW for jumping in with a great description of how self cleaning ovens work!
The only thing I would add is that if there is a lot of spillage on the bottom of your oven, the self cleaning "crematorium" can make your kitchen very smoky as it burns everything into dust. (Also some ovens being self-cleaned for the very first time can cause a bit of smoke as well.) An open window and a fan help to keep the air moving. Wipe up any really obvious spills before you start.
Also, pick a cold winter's day to self-clean an oven as it can take 3-4 hours to complete the process.
Be sure to plan on staying home during the entire cleaning process!
Thanx Kathy and KGWagner for the reply…Will have to take time to clean the oven this week ….
You know I was doing the whole thing wrong, but by reading this it helped me out alot thnx!!! Now I can broil my chicken the right way.
That's great Daisy! Remember every time you open the oven door, even for just a peek, the temperature drops significantly and the cooking time gets thrown off!
I am male and am doing lots of cooking as of late. I went to your site to see if I could find information on re-warming food in a conventional oven. I know that that's probably a simple thing to cooks like you, but I can't seem to find anything about what temp to use and how long. I do not have a warming drawer. I do have a microwave, but, I thought for several dishes, or a large dish, like what was left of a low country boil, it would be better to warm it in a conventional oven.
Reheating leftovers is pretty tricky. The texture is never quite the same as when it is freshly cooked.
Reheating most things in the microwave is actually your best bet.
For rice based recipes you can add a few drops of water so that the dish does not dry out too much.
I reheat pizza in a frying pan. It works brilliantly! The crust gets really crispy again.
For conventional oven reheating, set the oven to 325-350 degrees and just about anything should be reheated in about 10 minutes. Depending on what you are reheating, you may want to cover the dish with some tin foil.
Good Luck and thanks for this great question!
P.S. Just remember with leftovers…when in doubt…throw it out!
As Kathy says, reheating leftovers is tricky. With larger quantities and with some foods, the amount of time you'd have to reheat them is roughly equal to the original cooking time, which is no fun.
What I've found is that it's easier to separate things into single servings and microwave them, being careful to separate faster/slower cooking foods. Generally speaking, faster cooking foods would be things with more fat content, and slower cooking foods are more water & solids.
So, for instance, if you want to reheat a single serving of ham and potatoes, you'd give the potatoes a minute or so, then add the ham and 30 seconds. They'll both come out about the same temperature.
Thanks KGW – you are so right about re-heating in single serving size – great tip!
Bobby I would like to also add that it is essential to store leftovers properly.
I have basic baking question. After pre-heating the oven, do I turn it off before I insert food inside the oven?
The quick answer is NO do not turn the oven off!
Pre-heating is just that; getting the oven hot before you put the food in it. It is necessary for the oven to stay hot while you cook your food. Cooking times are based on a pre-heated oven. If you put food in a cold oven, it will totally throw off the outcome of the recipe.
Very interesting. I didn't know about all these little secrets and I was wondering why my French fries didn't have the same taste as those you eat at a restaurant. Mmm, can't wait to taste the first crispy fries made by me in my own oven.
To be absolutely certain what those setting are, you will need to buy an oven thermometer, place it in the oven and do some testing.
Oven thermometers range in price from about $4-$30. You can buy them at the grocery store or a hardware store or on-line.
I would guess that with your settings medium is 350F, but that is only a guess.
Warm is usually about 200F.
I am planning to buy a new oven . i heard that we can even make tea or coffee in this. can you explain how and the usage of oven for different types of food.
I'm having a dinner party and I would like to cook some things about 3 hours ahead one is steaks. .. How do you think I should handle keeping them like they were just cooked when the guest arrive. I don't have a warmer draw. Thanks!
Sandra – Even with a warming drawer, you don't want to hold steaks that long. They'll continue cooking, albeit slowly, and when you go to serve them they'll be seriously overdone. Your best bet might be to just brown them, then let them sit until just before serving time. When that gets to be close, you finish them. That's chancy business, though. If you haven't done that before a few times, a dinner party is no time to start experimenting with new techniques. Any kind of decent steak only takes minutes to cook. Perhaps something else could be made ahead?
Hi KGW – welcome back!
Sandra, KGW offers great advice. I agree completely that you may want to re-thing holding steaks in a warming drawer for 3 hours!
I just found your site searching how to use the "start time" feature on my Kenmore oven. I was wondering how this works, because I was thinking how does it "preheat"? I would like to use it, but I don't want to ruin my food. Have you ever used this feature before?
Some ovens have internal clocks which you can set set for automatic start and stop for oven cleaning.
Generally you would not need to use this for preheating an oven. Preheating an oven usually takes about 15-20 minutes. Once the oven is preheated, in goes the food.
Look on the top or side of the oven door to see what your model number is. Then you can Google Kenmore oven manual and find the specific manual for operating your oven.
Hello, we have a convention oven, I DON'T KNOW HOW TO USE IT, I want to bake chicken, meatloaf, fish, lasagne, chicken parmigan & etc., please tell me what temperature I should set it at, I usually use a regular oven & bake everything @ 350% for whatever time I need.
Please help me, please tell me what temperature & how long it will take.
Are you sure you don't mean a "convection" oven? If so, then what you need to know is a little bit about how they work.
Convection ovens are actually mis-named, because they don't rely on convection at all. They use a fan force the air to circulate in the oven, which can speed up cooking. Regular ovens use convection, which relies on hot air rising and cooler air sinking to circulate the air in the oven. It doesn't need any help for that – it happens naturally. But, it's a slow(er) process.
To make a long story short, you need a good oven thermometer. You'll need to learn to cook to an internal temperature, rather than by time. In other words, you don't put a roast or chicken in for 2.5 hours at 350 degrees, you put it in a 350 degree oven until it reaches a certain number of degrees internally. What those values are for internal temperatures vary by what it is you're cooking, and how you like it done. You don't keep track of time, you keep track of temperature.
The other thing you have to consider is that things will brown (and possibly dry out) much more quickly, so sometimes you do cook at a lower temperature.
Unfortunately, there's no easy conversion you can do. You have to sorta dare to wreck things until you get a feel for it. I suspect that's the reason so many people don't use the feature.
But, for example, you know you don't want a pork roast to get any hotter than about 140-145 degrees internally. So, poke a thermometer in there, and watch it. When it hits that point, take it out and let it rest for 10-15 minutes. It'll climb to 150-155 degrees on its own outside the oven.
When baking a cake, should the oven be preheated? Some recipes specifically say "cold oven" but most simply state "bake for 1 hour at 350 degrees". Should the oven be preheated unless otherwise directed? Thanks.
Unless otherwise directed, ovens should always be pre-heated. It takes a bit of time, too. You can't turn it on and expect it to be up to temp in 5 minutes. Figure 15, easy.
That's probably in the top 3 on the list of reasons things don't turn out: improper starting heat. With baked goods especially, it changes when different fats liquify, which changes rise times and texture, it changes when your leavening does its thing, and it alters the timing (sometimes dramatically). Cookies in particular will punish you for improper heat and timing.
Usually, if the recipe says anything at all about the broiler, it's how far away from the flame you cook the food. Most broilers will allow you to move the pan up or down.
so i will just turn the dial to broil/grill but will not touch the temp setting dial?
With many ovens, the broiler is sort of a drawer with a pan under the oven, so it uses the same burner to broil with that is used to heat the oven above. All setting the dial to "Broil" does is disable the thermostat so the burner runs continuously.
With other ovens, the broiler is actually inside the oven at the top, so there's a separate control. Then, the drawer underneath the oven (if there is one) is used as a warmer or for storage. This feature costs more to build, so you usually only see it on more expensive gas stoves, although it's quite common on electrics.
The only thing I would add is that gas ovens have a "flame" for broiling and electric ovens usually have heated coils and not an actual "flame".
someone asked me if during the preheat period does the broiler works to help preheat the oven and then turns off when the temperature is reached? or is it just the botton oven heating up the oven to the exact temperature?
No, the broiler burner doesn't lend a helping hand. I've sometimes wondered why it doesn't, because I suspect a lot of people's timing errors come from not preheating the oven long enough. If they both ran, the thing would heat up quicker and more likely be up to temp before someone tried cooking something. But, as it is, even modern ovens can take 5-10 minutes to get up to temp.
It's possible that with electric ovens it would take too much power, or with gas ovens it would take too much gas to run both burners at the same time, as they're heavy loads.
Can a microwaveable dish also be used in a converntional oven?
"Microwaveable" means two things. One, it doesn't have any metal in it, and two, it can take high temperatures without melting/deforming. So, the answer to your question is generally 'yes'. But, "high temperatures" in a microwave are different than they are in an oven because it's the food that gets hot rather than the environment, so be aware that there are a lot of things that are "microwave safe" that should never go in an oven. Paper or plastic dishes/plates/bowls/cups/etc. come immediately to mind.


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