Realistic Tunneling States for the Magnetic Effects in Non-Metallic Real Glasses

The discovery of magnetic and compositional effects in the low temperature properties of multi-component glasses has prompted the need to extend the standard two-level systems (2LSs) tunneling model. A possible extension \cite{Jug2004} assumes that a subset of tunneling quasi-particles is moving in a three-welled potential (TWP) associated with the ubiquitous inhomogeneities of the disordered atomic structure of the glass. We show that within an alternative, cellular description of the intermediate-range atomic structure of glasses the tunneling TWP can be fully justified. We then review how the experimentally discovered magnetic effects can be explained within the approach where only localized atomistic tunneling 2LSs and quasi-particles tunneling in TWPs are allowed. We discuss the origin of the magnetic effects in the heat capacity, dielectric constant (real and imaginary parts), polarization echo and SQUID magnetization in several glassy systems. We conclude by commenting on a strategy to reveal the mentioned tunneling states (2LSs and TWPs) by means of atomistic computer simulations and discuss the microscopic nature of the tunneling states in the context of the potential energy landscape of glass-forming systems.Comment: 48 pages, 27 figures; mini-review for the Proceedings of the XIV International Workshop on Complex Systems (Fai della Paganella, Trento, March 2015) (submitted to Phil.Mag.). arXiv admin note: text overlap with arXiv:cond-mat/0210221 by other author

Subluminal to superluminal propagation in a left-handed medium

In this paper we report large group delays in the propagation of narrow-band pulses through a dispersive medium with both dielectric function and magnetic permeability negative. We show how the numerical results can be understood in terms of the phase time as calculated from the complex transmission amplitude. We also demonstrate superluminal passage and saturation of phase time in the same material albeit in a different spectral region.Peer reviewedPhysic

Substituent effects on the in vitro and in vivo genotoxicity of 4-aminobiphenyl and 4-aminostilbene derivatives

4-Amino-4'-substituted biphenyls and 4-aminostilbenes substituted in the 3' or 4' position were studied for their in vitro and in vivo genotoxicity. The in vitro mutagenicity of the biphenyls with and without S9 activation was established with Salmonella strains TA98 and TA100 and that of the stilbenes with the same strains plus TA98/1,8-DNP6. The in vivo genotoxicity assay with both series of compounds was for chromosomal aberrations in the bone-marrow cells of mice following intraperitoneal administration of the chemicals. Hammett values of substituents, partition coefficients and frontier orbital energies (ELUMO and EHOMO) of the compounds were used for correlations with mutagenicity. The Salmonella mutagenicity in TA98 and TA98/1,8-DNP6 with S9 was correlated to Hammett [sigma]+ values for the 4-aminostilbene substituents, showing a strong trend of increasing mutagenicity with an increase in the electron-withdrawing capability of the substituent. Hydrophobicity of the stilbenes, however, had little effect on their relative mutagenicity. The 4-aminobiphenyls showed a correlation between their mutagenicity and Hammett [sigma]+ values of their 4'-substituents in stain TA98 with S9, although the trend was not as strong as for the stilbenes. But unlike the stilbenes, TA98 mutagenicity of the biphenyls could also be correlated to hydrophobicity, and structure-activity correlations for the biphenyls was substantially improved when both [sigma]+ and hydrophobicity data were included. For strain TA100 with S9, little correlation was found between mutagenicity of the stilbenes and any of, the parameters. However, a limited correlation did exist between the mutagenicity of the biphenyls and their hydrophobicity. There was also limited correlations of the mutagenicity for the stilbenes in TA98 and TA98/1,8-DNP6 with S9 to ELUMO or EHOMO. The in vivo genotoxicity results for the biphenyls and stilbenes could not be correlated to electronic effects as for the in vitro results, nor could they be explained by hydrophobicity. However, it is interesting to note that 3'-substituted 4-aminostilbenes were all substantially more genotoxic in vivo than their corresponding 4'-substituted counterparts. The most genotoxic compound in vivo in either series was 4-aminostilbene which would not have been predicted from the in vitro results.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31865/1/0000815.pd

A global experiment on motivating social distancing during the COVID-19 pandemic

Finding communication strategies that effectively motivate social distancing continues to be a global public health priority during the COVID-19 pandemic. This cross-country, preregistered experiment (n = 25,718 from 89 countries) tested hypotheses concerning generalizable positive and negative outcomes of social distancing messages that promoted personal agency and reflective choices (i.e., an autonomy-supportive message) or were restrictive and shaming (i.e. a controlling message) compared to no message at all. Results partially supported experimental hypotheses in that the controlling message increased controlled motivation (a poorly-internalized form of motivation relying on shame, guilt, and fear of social consequences) relative to no message. On the other hand, the autonomy-supportive message lowered feelings of defiance compared to the controlling message, but the controlling message did not differ from receiving no message at all. Unexpectedly, messages did not influence autonomous motivation (a highly-internalized form of motivation relying on one’s core values) or behavioral intentions. Results supported hypothesized associations between people’s existing autonomous and controlled motivations and self-reported behavioral intentions to engage in social distancing: Controlled motivation was associated with more defiance and less long-term behavioral intentions to engage in social distancing, whereas autonomous motivation was associated with less defiance and more short- and long-term intentions to social distance. Overall, this work highlights the potential harm of using shaming and pressuring language in public health communication, with implications for the current and future global health challenges

Improved quality GSC-4 sealing glass

A glass commonly used to make graded seals between fused silica and higher-expansion glasses, General Electric Company GSC-4, was remelted to obtain higher quality glass than is available commercially. Remelting the commercially available glass cane in a platinum crucible at 1700 deg C for periods of 40 to 60 hours produced a homogeneous glass free of crysinlline inclusions and bubbles. During this melting, water was evolved and some constituents were lost from the surface layer. The bulk composition was not substantially changed and the remelted glass had approximately the same thermal expansion coefficient and viscosity as the original glass. (auth

Controlled permeation of hydrogen through glass. Final report

Storing hydrogen inside of hollow glass spheres requires that the gas permeate through the glass walls. Hydrogen permeation through glass is relatively slow and the time to charge a sphere or bed of spheres is dependent on many factors. Permeation processes are strongly temperature dependent with behavior that follows an Arrhenius function., Rate is also dependent on the pressure drop driving force across a membrane wall and inversely proportional to thickness. Once filled, glass spheres will immediately begin to leak once the pressure driving force is reversed. Practical systems would take advantage of the fact that keeping the glass at ambient temperatures can minimize outboard leakage even with significant internal pressures. If hydrogen could be loaded and unloaded from glass microspheres with significantly less energy and particularly at near ambient temperature, some of the key barriers to commercializing this storage concept would be broken and further system engineering efforts may make this approach cost-effective. There were two key objectives for this effort. The first was to evaluate the application of hollow glass microspheres for merchant hydrogen storage and distribution and then determine the hydrogen permeation performance required for practical commercial use. The second objective was to identify, through a series of fundamental experiments, a low energy, low temperature field effect that could significantly enhance hydrogen permeation through glass without application of heat. If such an effect could be found, hollow glass microspheres could be much more attractive for hydrogen storage or possibly gas separation applications