Magnetism, structure, and charge correlation at a pressure-induced Mott-Hubbard insulator-metal transition

We use synchrotron x-ray diffraction and electrical transport under pressure to probe both the magnetism and the structure of single crystal NiS2 across its Mott-Hubbard transition. In the insulator, the low-temperature antiferromagnetic order results from superexchange among correlated electrons and couples to a (1/2, 1/2, 1/2) superlattice distortion. Applying pressure suppresses the insulating state, but enhances the magnetism as the superexchange increases with decreasing lattice constant. By comparing our results under pressure to previous studies of doped crystals we show that this dependence of the magnetism on the lattice constant is consistent for both band broadening and band filling. In the high pressure metallic phase the lattice symmetry is reduced from cubic to monoclinic, pointing to the primary influence of charge correlations at the transition. There exists a wide regime of phase separation that may be a general characteristic of correlated quantum matter.Comment: 5 pages, 3 figure

Autocracies as Mediators in Conflicts

It is puzzling why autocracies, which typically are not renowned for their human rights record or their observance of international norms related to human rights and are frequently inured in their own violent conflicts, would choose to take on the seemingly humanitarian role of peacemaker as often as democracies in the conflicts of other states in the absence of such things as a former colonial relationship or shared geographic proximity with them. I argue that autocracies will offer more often to mediate when they are subjected to international scrutiny, sanctioning, and/or condemnation, as well as materially and immaterially benefitting from their efforts afterwards. I also posit that based on institutional attributes such as the presence of a professional bureaucracy (such as is found in a party “machine” autocracy) or by contrast an all-powerful autocrat (such as is found in personalist regimes), different autocratic regime-types will be more likely to offer to mediate than others. To test my theory, I utilize Large-N datasets about international mediation and autocratic regimes, as well as qualitative sources including information derived from the United Nations, the U.S. State Department, Human Rights Watch, Amnesty International, news articles/reports, and statements and criticisms from various states, in order to investigate when autocracies offer to mediate interstate conflicts, as well as which types of autocracies are most likely to offer to mediate an end to an international conflict. Quantitative analysis yielded some inconclusive results, however finding that Party-based autocracies are most likely to offer to mediate an international conflict when being sanctioned relative to other types of autocracies, while qualitative analysis did indeed uncover evidence that when being subjected to international condemnation and scrutiny, autocracies are likely to offer to mediate international conflict

Universality and Critical Behavior at the Mott transition

We report conductivity measurements of Cr-doped V2O3 using a variable pressure technique. The critical behavior of the conductivity near the Mott-insulator to metal critical endpoint is investigated in detail as a function of pressure and temperature. The critical exponents are determined, as well as the scaling function associated with the equation of state. The universal properties of a liquid-gas transition are found. This is potentially a generic description of the Mott critical endpoint in correlated electron materials.Comment: 3 figure

Learning-Focused Leadership and Leadership Support: Meaning and Practice in Urban Systems

Synthesizes three reports on what good education leadership means and how it can best be supported, including the role of the school leader and the transformation of central district offices to focus more on improving instruction. Outlines key practices

Traceable measurements of the activity concentration in air

The nuclear reactions induced by high energetic protons in heavy targets such as UC/sub 2/ and ThC cause a particular, complex radiation protection task at facilities like ISOLDE: the measurement of a mixture of different isotopes of the radioactive noble gas radon and the radon progenies in air. The knowledge of their respective activity concentration is fundamental for exposure assessments. Due to the complex mixture of activity concentrations in air, its precise determination is quite difficult. Therefore, a new procedure for taking reference samples was developed and implemented for the traceable measurement of the activity concentration of radioactive ions (e.g., radon progenies) in air. This technique is combined by measuring alpha -particles with a multi-wire ionization chamber for the parallel on-line determination of the activity concentration of different radon isotopes. (10 refs)

Agrin isoforms and their role in synaptogenesis

Agrin is thought to mediate the motor neuron-induced aggregation of synaptic proteins on the surface of muscle fibers at neuromuscular junctions. Recent experiments provide direct evidence in support of this hypothesis, reveal the nature of agrin immunoreactivity at sites other than neuromuscular junctions, and have resulted in findings that are consistent with the possibility that agrin plays a role in synaptogenesis throughout the nervous system