Erythromelalgia is characterized by burning pain, erythema, and increased temperature in acral skin. The pain is aggravated by warming and relieved by cooling. Increased microvascular arteriovenous shunting in deep dermal plexa has been hypothesized as the pathogenetic mechanism of pain in affected skin, inducing hypoxia during pain attacks. The aim of this study was to quantify skin capillary density in erythromelalgic patients before and after heat provocation, as increased skin temperature should increase the need for nutritive blood supply by the capillaries. Fourteen patients and 10 healthy control subjects were studied using an enhanced technique of computer-assisted analysis of capillary bed morphology and temperature measurements before and after central body heating. The increase in acral skin temperature was significantly higher (p < 0.05) in the eight patients where symptoms were induced after heat provocation, compared to asymptomatic patients and healthy control subjects. The number of visible capillaries in a field of view (1.7 mm2) decreased significantly (p = 0.01) in erythromelalgia patients from 105 (62-137) (median with total range) to 89 (49-118) after warming in areas with numerous arteriovenous anastomoses (nail bed region). In symptomatic patients an even more significant reduction was observed (p = 0.01). The capillary size was also significantly reduced (p < 0.05) from 41.0 (31.5-50.5) (arbitrary units) to 37.3 (33.0-46.0) in symptomatic patients. The change in capillary density in the nail bed area was significantly larger in erythromelalgia patients -17 (-49 to 39) compared to controls 0 (-47 to 13) (p < 0.05), and in symptomatic patients -19 (-49 to -12) compared to asymptomatic patients -8 (-48 to 39) (p < 0.05) and controls (p < 0.01). The reduced skin capillary density after heating is compatible with increased microvascular arteriovenous shunting of blood and a corresponding relative deficit in nutritive perfusion (steal phenomenon) with skin hypoxia, causing the symptoms in erythromelalgia.
We have studied the influence of the Mn content on the elastic properties of Fe–Mn random alloys (space group of Fmm) using ab initio calculations. The magnetic effects in Fe–Mn alloys have a strong influence on the elastic properties, even above the Néel temperature. As the Mn content is increased from 5 to 40 at. %, the C44 elastic constant is unaffected, while C11 and C12 decrease. This behavior can be understood based on the magnetovolume effect which softens the lattice. Since the amplitude of local magnetic moments is less sensitive to volume conserving distortions, the softening is not present during shearing.Original publication: Denis Music, Tetsuya Takahashi, Levente Vitos, Christian Asker, Igor A. Abrikosov and Jochen M. Schneider, Elastic properties of Fe–Mn random alloys studied by ab initio calculations, 2007, Applied Physics Letters, (91), 191904. Copyright: The America Institute of Physics, http://www.aip.org
Erythromelalgia is a condition consisting of red, warm, and burning painful extremities. Symptoms are relieved by cold and aggravated by heat. A wide variety of etiologic conditions can cause erythromelalgia, but one common pathogenetic mechanism, microvascular arteriovenous shunting, has been hypothesized. The aim of this study was to test this hypothesis. Quantification of skin microvascular perfusion using laser Doppler perfusion imaging and skin temperature at rest and after central body heating was performed in 14 patients with erythromelalgia and 11 controls. Attacks of erythromelalgia were induced in eight patients after heat provocation. In the plantar region of the foot, the location of numerous anatomical arteriovenous shunts, these patients significantly increased the skin perfusion as compared with asymptomatic patients with erythromelalgia and controls. In the dorsal region with few arteriovenous shunts no significant differences between the groups were demonstrated. The results show a relation between clinical symptoms and increased perfusion in the region of numerous anatomical arteriovenous shunts, and support the hypothesis of increased thermoregulatory arteriovenous shunt flow during attacks in primary erythromelalgia.
The energy differences between the ground state body-centred structure (bcc) and closed-packed face-centred structure (fcc) structures for transition metals in the middle of the series show unusually large disagreements when they are obtained by the thermochemical approach based on the analysis of experimental data or by first-principles electronic structure calculations. Considering a typical example, the lattice stability of Mo, we present a solution to this long-standing problem. In contrast to conventional total energy calculations within Density Functional Theory framework, we carry out ab initio molecular dynamics simulations for the two phases at high temperature. We show that at these conditions both bcc and fcc structures of Mo are dynamically stable, and the difference in their configurational energies decreases dramatically as compared to the zero temperature result, approaching the value derived by means of the thermochmical approach. We show that the main contribution to the effect comes from the modification of the canonical band structure for bcc and fcc phases due to lattice vibrations at high temperature, and discuss consequences of our finding for future first-principles simulations of phase stability.
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