Symmetries of pp-Waves with Distributional Profile

We generalize the classification of (non-vacuum) pp-waves \cite{JEK} based on the Killing-algebra of the space-time by admitting distribution-valued profile functions. Our approach is based on the analysis of the (infinite-dimensional) group of ``normal-form-preserving'' diffeomorphisms.Comment: 10 pages, latex2e, no figures, statement about the combination of symmetry classes of impulsive waves correcte

Glycerol confined in zeolitic imidazolate frameworks: The temperature-dependent cooperativity length scale of glassy freezing

In the present work, we employ broadband dielectric spectroscopy to study the molecular dynamics of the prototypical glass former glycerol confined in two microporous zeolitic imidazolate frameworks (ZIF-8 and ZIF-11) with well-defined pore diameters of 1.16 and 1.46 nm, respectively. The spectra reveal information on the modified alpha relaxation of the confined supercooled liquid, whose temperature dependence exhibits clear deviations from the typical super-Arrhenius temperature dependence of the bulk material, depending on temperature and pore size. This allows assigning well-defined cooperativity length scales of molecular motion to certain temperatures above the glass transition. We relate these and previous results on glycerol confined in other host systems to the temperature-dependent length scale deduced from nonlinear dielectric measurements. The combined experimental data can be consistently described by a critical divergence of this correlation length as expected within theoretical approaches assuming that the glass transition is due to an underlying phase transition.Comment: 14 pages, 5 figures + Supplemental Material (4 pages, 6 figures). Final version as accepted for publicatio

Importance of reorientational dynamics for the charge transport in ionic liquids

Most ionic liquids contain at least one rather complex ion species exhibiting a dipolar moment. In the present work, we provide a thorough evaluation of broadband dielectric spectra of 12 ionic liquids taking into account the often neglected reorientational dynamics of these ions. We confirm that this dynamics leads to a clear relaxational signature in the spectra, a fact that so far only was considered in few previous works. The obtained reorientational relaxation times are well consistent with earlier inelastic light-scattering and high-frequency dielectric investigations. Evaluating our dielectric spectra in terms of reorientational motions reveals a close coupling of the ion-rotation dynamics to the ionic charge transport in a broad temperature range from the low-viscosity liquid above room temperature deep into the high-viscosity supercooled state close to Tg. This coupling does not seem to be mediated by the viscosity but probably is of more direct nature, pointing to a revolving-door mechanism as also considered for plastic-crystalline ionic conductors. Our results show that the reorientational motion of the dipolar ions plays a significant and so far widely overlooked role for the ionic charge transport in ionic liquids.Comment: 10 pages, 9 figures. Revised version according to suggestions of referee

Dielectric study on mixtures of ionic liquids

Ionic liquids are promising candidates for electrolytes in energy-storage systems. We demonstrate that mixing two ionic liquids allows to precisely tune their physical properties, like the dc conductivity. Moreover, these mixtures enable the gradual modification of the fragility parameter, which is believed to be a measure of the complexity of the energy landscape in supercooled liquids. The physical origin of this index is still under debate; therefore, mixing ionic liquids can provide further insights. From the chemical point of view, tuning ionic liquids via mixing is an easy and thus an economic way. For this study, we performed detailed investigations by broadband dielectric spectroscopy and differential scanning calorimetry on two mixing series of ionic liquids. One series combines an imidazole based with a pyridine based ionic liquid and the other two different anions in an imidazole based ionic liquid. The analysis of the glass-transition temperatures and the thorough evaluations of the measured dielectric permittivity and conductivity spectra reveal that the dynamics in mixtures of ionic liquids are well defined by the fractions of their parent compounds.Comment: 9 pages, 4 figure

People making deontological judgments in the Trapdoor dilemma are perceived to be more prosocial in economic games than they actually are

Why do people make deontological decisions, although they often lead to overall unfavorable outcomes? One account is receiving considerable attention: deontological judgments may signal commitment to prosociality and thus may increase people’s chances of being selected as social partners–which carries obvious long-term benefits. Here we test this framework by experimentally exploring whether people making deontological judgments are expected to be more prosocial than those making consequentialist judgments and whether they are actually so. In line with previous studies, we identified deontological choices using the Trapdoor dilemma. Using economic games, we take two measures of general prosociality towards strangers: trustworthiness and altruism. Our results procure converging evidence for a perception gap according to which Trapdoor-deontologists are believed to be more trustworthy and more altruistic towards strangers than Trapdoor-consequentialists, but actually they are not so. These results show that deontological judgments are not universal, reliable signals of prosociality

Characterization of Telehealth Use in Veterans with Spinal Cord Injuries and Disorders

BACKGROUND: Individuals with spinal cord injuries and disorders (SCI/D) require frequent interdisciplinary health care to address impairments in mobility, autonomic functions, and secondary complications. Telehealth has the capacity to substantially transform healthcare delivery and improve care by increasing access and communication. However, relatively little is known about telehealth use in this specific population. Here, we attempt to fill part of this gap. OBJECTIVE: To investigate the frequency and characteristics associated with telehealth use in Veterans with SCI/D. DESIGN: Cross-sectional, descriptive project SETTING: Veterans Health Administration (VHA) facilities. Participants: 15,028 Veterans living with SCI/D whom received services from the VHA SCI/D System of Care. Intervention: Not applicable Outcome Measures: Frequency and characteristics associated with VHA telehealth utilization. Results: Of the 15,028 Veterans with SCI/D included in the evaluation, 17% used some form of telehealth in VHA Fiscal Year (FY)2017. Veterans over the age of 65 had lower odds (OR = 0.88, p \u3c 0.05, CI: 0.80-0.98) of using telehealth. Being Caucasian (OR = 1.29, p \u3c 0.01, CI: 1.09-1.52), living in rural areas (OR =1.16, p \u3c 0.01, CI: 1.05-1.28), living greater distances away from the VHA (p \u3c 0.01 for all distances), and being in priority group 8, meaning that Veterans have higher copayment requirements (OR=1.46, p \u3c 0.001, CI: 1.19-1.81), were all significantly associated with greater odds of telehealth use. The most frequent types of telehealth used were real-time clinical video and store-and-forward between a provider and patient within the same hub network. Conclusion: There are opportunities to increase telehealth adoption in the SCI/D arena. The findings from this project highlight which Veterans are currently using telehealth services, as well as gaps regarding telehealth adoption in this population

Sorption concentration of arsenic ions by magnetite

© The author(s). This paper is focused on the possibility of using magnetite powders obtained by chemical and plasma-chemical method for sorption concentration of arsenic ions. Processes of arsenic concentration by two-site sorption in magnetite-water system have been studied, and the optimal conditions for concentration have been defined. In static mode, effects of pH, temperature and contact time on the adsorption process have been studied. As a result, a method for pre-sorption concentration has been proposed, allowing reducing the lower limit of the atomic absorption determination of arsenic content