From War to Integration: Generalizing the Dynamic of Power Transitions

Generalizing the dynamics implied by power transition theory, we characterize the structural conditions that lead nations to initiate conflict or choose to integrate. The relationship between changes in relative power, hierarchical structures, and joint satisfaction are used to identify the structural conditions for conflict and cooperation. Empirical tests for the last two centuries confirm the strength and robustness of this characterization. In addition, long term assessments of Pax Britannica, the Cold War, and China’s potential challenge to the United States in this century are used to illustrate the precision of these findings. The fundamental implication is that structural conditions provide the pre-conditions for conflict and cooperation, but decision makers have leeway in advancing policies that eventually lead to either war or peace.

Physical rehabilitation for critical illness myopathy and neuropathy (Protocol)

Protocol for a review - no abstract

Scanning Tunneling Spectroscopy of Bi2Sr2CuO6+d: New Evidence for the Common Origin of the Pseudogap and Superconductivity

Using scanning tunneling spectroscopy, we investigated the temperature dependence of the quasiparticle density of states of overdoped Bi2Sr2CuO6+δ between 275 mK and 82 K. Below Tc = 10 K, the spectra show a gap with well-defined coherence peaks at ±Δp≃12 meV, which disappear at Tc. Above Tc, the spectra display a clear pseudogap of the same magnitude, gradually filling up and vanishing at T*≃68 K. The comparison with Bi2Sr2CaCu2O8+δ demonstrates that the pseudogap and the superconducting gap scale with each other, providing strong evidence that they have a common origin

Posttraumatic Stress Disorder (PTSD) and Positive and Negative Social Support as Components of the Interpersonal Psychological Theory of Suicide in the United States Military Veterans

Veterans are at a greater risk for suicide compared to the general population. Suicide risk further increases for veterans with posttraumatic stress disorder (PTSD). The Interpersonal Psychological Theory of Suicide (IPTS) states that a combination of higher perceived burden and lower thwarted belonging increases risk for suicidal ideation (SI), and when SI is present, higher acquired capability for suicide (ACFS) increases risk for suicide attempt. The IPTS is well supported in samples of the general population, but understudied in military samples. The current study tested the IPTS, using PTSD severity in place of perceived burden, and bothersomeness of negative social support (BNSS) and satisfaction of positive social support (SPSS) in place of thwarted belonging, and the original measure of ACFS in 290 military service members/veterans. We observed that higher PTSD and BNSS and lower SPSS were associated with SI and higher suicide risk. BNSS demonstrated a nearly equivalent association to both SI and total suicide risk compared to SPSS. Neither the combined effect of PTSD severity and BNSS/SPSS on SI nor the combined effect of PTSD severity, BNSS/SPSS and ACFS on suicide risk were significant. Findings suggest that PTSD and SPSS/BNSS may not be useful variables for testing the IPTS, but that they are useful individually to assess suicidal behavior. Moreover, given the nearly equivalent association of BNSS and SPSS with suicide risk observed in the current study, clinicians and researchers should attend to both the positive and negative facets of social support in place of measuring only aspects of positive social support

The Effect of Acute Alcohol Intoxication on Memory Scan and Memory Span in Working Memory

The efficiency of working memory processes has been studied by many researchers. Verbal ability and intoxication with ethanol are two hypothesized influences on the efficiency of working memory processes. This study looked at these factors across two measures, memory span tasks and memory scan tasks. This study also examined the extent to which verbal ability modulates the effect of alcohol on working memory performance. Seventy-eight male subjects participated in the present study. Subjects who reported drinking at least two drinks on two separate occasions per week were invited to participate. Subjects were administered the WAIS-R Vocabulary subtest and categorized as high verbal or low verbal by a median split of the scores. Subjects were given four memory span tasks. These included digit span forward, digit span backward, word span, and sentence span. Digit span forward and backward were administered as they are in the WAIS-R. Word span was similar to digit span with the exception that there were three trials at each level. Sentence span was that introduced by Daneman and Carpenter (1980). Subjects had to read a group of sentences aloud and remember the last word in each sentence. Subjects received two memory scan tasks. The first required them to judge whether a probe word was one from a stimulus set. The second required them to judge whether a probe word was a member of the categories from the stimulus set. Subjects were tested over twelve sequences consisting of 32 trials per sequence, with three sequences each of set sizes of two, three, and four. One half of the judgements were positive and one half were negative. Verbal ability was a significant factor in all span tasks. Alcohol was a significant factor only for digit span backward. Alcohol did not affect digit span forward, word span, or sentence span. Task and set size were significant factors in the memory scan tasks. Verbal ability and alcohol intoxication were minimally related to the memory scan tasks. Support was found for the elaboration explanation of alcohol intoxication. No support was found for overall cognitive slowing

Controlling hole spin dynamics in two‐dimensional hole systems at low temperatures

With the recent discovery of very long hole spin decoherence times in GaAs/AlGaAs heterostructures of more than 70 ns in two-dimensional hole systems, using the hole spin as a viable alternative to electron spins in spintronic applications seems possible. Furthermore, as the hyperfine interaction with the nuclear spins is likely to be the limiting factor for electron spin lifetimes in zero dimensions, holes with their suppressed Fermi contact hyperfine interaction due to their p-like nature should be able to show even longer lifetimes than electrons. For spintronic applications, electric-field control of hole spin dynamics is desirable. Here, we report on time-resolved Kerr rotation and resonant spin amplification measurements on a two-dimensional hole system in a p-doped GaAs/AlGaAs heterostructure. Via a semitransparent gate, we tune the charge density within the sample. We are able to observe a change in the hole g factor, as well as in the hole spin dephasing time at high magnetic fields

Resonant spin amplification of hole spin dynamics in two‐dimensional hole systems: experiment and simulation

Spins in semiconductor structures may allow for the realization of scalable quantum bit arrays, an essential component for quantum computation schemes. Specifically, hole spins may be more suited for this purpose than electron spins, due to their strongly reduced interaction with lattice nuclei, which limits spin coherence for electrons in quantum dots. Here, we present resonant spin amplification (RSA) measurements, performed on a p-modulation doped GaAs-based quantum well at temperatures below 500 mK. The RSA traces have a peculiar, butterfly-like shape, which stems from the initialization of a resident hole spin polarization by optical orientation. The combined dynamics of the optically oriented electron and hole spins are well-described by a rate equation model, and by comparison of experiment and model, hole spin dephasing times of more than 70 ns are extracted from the measured data

Deformed Skyrme Crystals

The Skyrme crystal, a solution of the Skyrme model, is the lowest energy-per-charge configuration of skyrmions seen so far. Our numerical investigations show that, as the period in various space directions is changed, one obtains various other configurations, such as a double square wall, and parallel vortex-like solutions. We also show that there is a sudden "phase transition" between a Skyrme crystal and the charge 4 skyrmion with cubic symmetry as the period is gradually increased in all three space directions.Comment: 13 pages, 6 figures. To be published in JHE

Baryons and baryonic matter in the large Nc and heavy quark limits

This paper explores properties of baryons and finite density baryonic matter in an artificial world in which Nc, the number of colors, is large and the quarks of all species are degenerate and much larger than {\Lambda}_QCD. It has long been known that in large Nc QCD, baryons composed entirely of heavy quarks are accurately described in the mean-field approximation. However, the detailed properties of baryons in the combined large Nc and heavy quark limits have not been fully explored. Here some basic properties of baryons are computed using a variational approach. At leading order in both the large Nc and heavy quark expansions the baryon mass is computed explicitly as is the baryon form factor. Baryonic matter, the analog of nuclear matter in this artificial world, should also be well described in the mean-field approximation. In the special case where all baryons have an identical spin flavor structure, it is shown that in the formal heavy quark and large Nc limit interactions between baryons are strictly repulsive at low densities. The energy per baryon is computed in this limit and found to be exponentially small. It is shown that when the restriction to baryons with an identical spin-flavor structure is dropped, a phase of baryonic matter exists with a density of 2Nf times that for the restricted case but with the same energy (where Nf is the number of degenerate flavors). It is shown that this phase is at least metastable.Comment: 19 page

Band structure of helimagnons in MnSi resolved by inelastic neutron scattering

A magnetic helix realizes a one-dimensional magnetic crystal with a period given by the pitch length $\lambda_h$. Its spin-wave excitations -- the helimagnons -- experience Bragg scattering off this periodicity leading to gaps in the spectrum that inhibit their propagation along the pitch direction. Using high-resolution inelastic neutron scattering the resulting band structure of helimagnons was resolved by preparing a single crystal of MnSi in a single magnetic-helix domain. At least five helimagnon bands could be identified that cover the crossover from flat bands at low energies with helimagnons basically localized along the pitch direction to dispersing bands at higher energies. In the low-energy limit, we find the helimagnon spectrum to be determined by a universal, parameter-free theory. Taking into account corrections to this low-energy theory, quantitative agreement is obtained in the entire energy range studied with the help of a single fitting parameter.Comment: 5 pages, 3 figures; (v2) slight modifications, published versio