Of any metal, it has one of the lowest values of thermal conductivity (after manganese, and maybe neptunium and plutonium) and the highest Hall coefficient. It has a high electrical resistivity. When deposited in sufficiently thin layers on a substrate, bismuth is a semiconductor, despite being a post-transition metal. Elemental bismuth is denser in the liquid phase than the solid, a characteristic it shares with germanium, silicon, gallium, and water. Bismuth expands 3.32% on solidification; therefore, it was long a component of low-melting typesetting alloys, where it compensated for the contraction of the other alloying components to form almost isostatic bismuth-lead eutectic alloys. Though virtually unseen in nature, high-purity bismuth can form distinctive, colorful hopper crystals. It is relatively nontoxic and has a low melting point just above 271 °C, so crystals may be grown using a household stove, although the resulting crystals will tend to be of lower quality than lab-grown crystals.At ambient conditions, bismuth shares the same layered structure as the metallic forms of arsenic and antimony, crystallizing in the rhombohedral lattice (Pearson symbol hR6, space group R3m No. 166) of the trigonal crystal system. When compressed at room temperature, this Bi-I structure changes first to the monoclinic Bi-II at 2.55 GPa, then to the tetragonal Bi-III at 2.7 GPa, and finally to the body-centered cubic Bi-V at 7.7 GPa. The corresponding transitions can be monitored via changes in electrical conductivity; they are rather reproducible and abrupt and are therefore used for calibration of high-pressure equipment.
The World Health Organization classes chronic fatigue syndrome as a central nervous system disease.Some neuroimaging studies have observed prefrontal and brainstem hypometabolism; however, sample size was limited. Neuroimaging studies in persons with CFS have identified changes in brain structure and correlations with various symptoms. Results were not consistent across the neuroimaging brain structure studies, and more research is needed to resolve the discrepancies found between the disparate studies.Tentative evidence suggests a relationship between autonomic nervous system dysfunction and diseases such as CFS, fibromyalgia, irritable bowel syndrome, and interstitial cystitis. However, it is unknown if this relationship is causative. Reviews of CFS literature have found autonomic abnormalities such as decreased sleep efficiency, increased sleep latency, decreased slow wave sleep, and abnormal heart rate response to tilt table tests, suggesting a role of the autonomic nervous system in CFS. However, these results were limited by inconsistency.Central sensitization, or increased sensitivity to sensory stimuli such as pain have been observed in CFS. Sensitivity to pain increases after exertion, which is opposite to the normal pattern. Immunological
Immunological abnormalities are frequently observed in those with CFS. Decreased NK cell activity is found more often in people with CFS and this correlates with severity of symptoms. People with CFS have an abnormal response to exercise, including increased production of complement products, increased oxidative stress combined with decreased antioxidant response, and increased Interleukin 10, and TLR4, some of which correlates with symptom severity.