Thermoelectric properties of partly Sb- and Zn-substituted Ba8Ga16Ge30 clathrates

The effects on the thermoelectric properties of n-Ba8Ga16Ge30 when substituting small amounts of the Ga or Ge with Sb or Zn have been investigated. A number of syntheses were prepared in quaternary systems of Ba8Ga16Ge30 substituted with either Sb or Zn but only three samples were found to yield single phase products with nominal compositions of Ba8Ga15Sb1Ge30, Ba8Ga15Zn1Ge30 and Ba8Ga16Ge28Zn2, respectively. When Ge was substituted for Zn the resulting sample remained n-type and an increase in thermopower and a decrease in thermal conductivity were achieved. These positive effects were accompanied with an increased electrical resistivity and thus the ZT was only somewhat improved up to about 400 °C. When substituting Ga with either Sb or Zn samples remained n-type but showed decreased thermopower and increased electrical resistivity and thermal conductivity. It is thus concluded that substitution of Ga with Zn or Sb is detrimental for the thermoelectric properties of Ba8Ga16Ge30, whereas substitution of Ge with Zn appears a potent method for improving its performance

Phenomenological analysis of densification mechanism during spark plasma sintering of MgAl2O4

International audienceSpark plasma sintering (SPS) of MgAl2O4 powder was investigated at temperatures between 1200 and 1300°C. A significant grain growth was observed during densification. The densification rate always exhibits at least one strong minimum, and resumes after an incubation period. Transmission electron microscopy investigations performed on sintered samples never revealed extensive dislocation activity in the elemental grains. The densification mechanism involved during SPS was determined by anisothermal (investigation of the heating stage of a SPS run) and isothermal methods (investigation at given soak temperatures). Grain-boundary sliding, accommodated by an in-series {interface-reaction/lattice diffusion of the O 2-anions} mechanism controlled by the interface reaction step, governs densification. The zero-densification-rate period, detected for all soak temperatures, arise from the difficulty of annealing vacancies, necessary for the densification to proceed. The detection of atomic ledges at grain boundaries and the modification of the stoichiometry of spinel during SPS could be related to the difficulty to anneal vacancies at temperature soaks.

Elevated [11C]-D-Deprenyl Uptake in Chronic Whiplash Associated Disorder Suggests Persistent Musculoskeletal Inflammation

There are few diagnostic tools for chronic musculoskeletal pain as structural imaging methods seldom reveal pathological alterations. This is especially true for Whiplash Associated Disorder, for which physical signs of persistent injuries to the neck have yet to be established. Here, we sought to visualize inflammatory processes in the neck region by means Positron Emission Tomography using the tracer 11C-D-deprenyl, a potential marker for inflammation. Twenty-two patients with enduring pain after a rear impact car accident (Whiplash Associated Disorder grade II) and 14 healthy controls were investigated. Patients displayed significantly elevated tracer uptake in the neck, particularly in regions around the spineous process of the second cervical vertebra. This suggests that whiplash patients have signs of local persistent peripheral tissue inflammation, which may potentially serve as a diagnostic biomarker. The present investigation demonstrates that painful processes in the periphery can be objectively visualized and quantified with PET and that 11C-D-deprenyl is a promising tracer for these purposes

Novel Biochemical Markers of Psychosocial Stress in Women

Background: Prolonged psychosocial stress is a condition assessed through self-reports. Here we aimed to identify biochemical markers for screening and early intervention in women