Theoretical study of production of unique glasses in space

The potential of producing the glassy form of selected materials in the weightless, containerless nature of space processing is examined through the development of kinetic relationships describing nucleation and crystallization phenomena. Transformation kinetics are applied to a well-characterized system (SiO2), an excellent glass former (B2O3), and a poor glass former (Al2O3) by conventional earth processing methods. Viscosity and entropy of fusion are shown to be the primary materials parameters controlling the glass forming tendency. For multicomponent systems diffusion-controlled kinetics and heterogeneous nucleation effects are considered. An analytical empirical approach is used to analyze the mullite system. Results are consistent with experimentally observed data and indicate the promise of mullite as a future space processing candidate

Perfect coupling of light to surface plasmons with ultra-narrow linewidths

We examine the coupling of electromagnetic waves incident normal to a thin silver film that forms an oscillatory grating embedded between two otherwise uniform, semi-infinite half spaces. Two grating structures are considered, in one of which the mid point of the Ag film remains fixed whereas the thickness varies sinusoidally, while in the other the mid point oscillates sinusoidally whereas the film thicknesses remains fixed. On reducing the light wavelength from the long wavelength limit, we encounter signatures in the transmission, T, and reflection, R, coefficients associated with: i) the short-range surface plasmon mode, ii) the long-range surface plasmon mode, and iii) electromagnetic diffraction tangent to the grating. The first two features can be regarded as generalized (plasmon) Wood's anomalies whereas the third is the first-order conventional (electromagnetic) Wood's anomaly. The energy density at the film surface is enhanced for wavelengths corresponding to these three anomalies, particularly for the long range plasmon mode in thin films. When exciting the silver film with a pair of waves incident from opposite directions, we find that by adjusting the grating oscillation amplitude and fixing the relative phase of the incoming waves to be even or odd, T+R can be made to vanish for one or the other of the plasmon modes; this corresponds to perfect coupling (impedance matching in the language of electrical engineering) between the incoming light and these modes.Comment: 13 pages, 5 figures. accepted J. Chem. Phy

The Foreign Intelligence Surveillance Act of 1978 Compared with the Law of Electronic Surveillance in Europe

The purpose of this article is to compare the fundamental operative provisions of the U.S. Foreign Intelligence Surveillance Act (FISA) with the equivalent directives of European surveillance law in five representative countries. The specific provisions being compared relate to the ability to monitor the content of individual communications within the nation state or citizens outside territorial borders. The author is not greatly concerned at this point with the procedure required before interceptions of noncitizens outside the country as under U.S. law this is not limited in a manner that endangers the nation. Foreign residents outside the country are not protected by the Fourth Amendment and thus there are less obstructive regulations. Nor is there a need at this time to concentrate on metadata collection, which is simply the accumulation of data on numbers dialed, time, and duration of calls made by telephone subscribers. Metadata does not include content. Although the provisions of the USA Freedom Act will increase the burden on the government by directing that this data be stored with the separate telecommunications providers instead of NSA, the threat posed by these provisions is minor compared to the dangers created by the restraints of the FISA statute on the ability of the government to intercept citizens and communications domestically.The Scowcroft Institute of International Affair

Genus-Specific Carbon Fixation Activity Measurements Reveal Distinct Responses to Oxygen among Hydrothermal Vent Campylobacteria

Molecular surveys of low temperature deep-sea hydrothermal vent fluids have shown that Campylobacteria (previously Epsilonproteobacteria) often dominate the microbial community and that three genera, Arcobacter, Sulfurimonas, and Sulfurovum, frequently coexist. In this study, we used replicated radiocarbon incubations of deep-sea hydrothermal fluids to investigate activity of each genus under three experimental conditions. To quantify genus-specific radiocarbon incorporation, we used newly designed oligonucleotide probes for Arcobacter, Sulfurimonas, and Sulfurovum to quantify their activity using catalyzed-reporter deposition fluorescence in situ hybridization (CARD-FISH) combined with fluorescence-activated cell sorting. All three genera actively fixed CO2 in short-term (similar to 20 h) incubations, but responded differently to the additions of nitrate and oxygen. Oxygen additions had the largest effect on community composition, and caused a pronounced shift in community composition at the amplicon sequence variant (ASV) level after only 20 h of incubation. The effect of oxygen on carbon fixation rates appeared to depend on the initial starting community. The presented results support the hypothesis that these chemoautotrophic genera possess functionally redundant core metabolic capabilities, but also reveal finer-scale differences in growth likely reflecting adaptation of physiologically-distinct phylotypes to varying oxygen concentrations in situ. Overall, our study provides new insights into how oxygen controls community composition and total chemoautotrophic activity, and underscores how quickly deep-sea vent microbial communities respond to disturbances. IMPORTANCE Sulfidic environments worldwide are often dominated by sulfur-oxidizing, carbon-fixing Campylobacteria. Environmental factors associated with this group's dominance are now understood, but far less is known about the ecology and physiology of members of subgroups of chemoautotrophic Campylobacteria. In this study, we used a novel method to differentiate the genus-specific chemoautotrophic activity of three subtypes of Campylobacteria. In combination with evidence from microscopic counts, chemical consumption/production during incubations, and DNA-based measurements, our data show that oxygen concentration affects both community composition and chemoautotrophic function in situ. These results help us better understand factors controlling microbial diversity at deep-sea hydrothermal vents, and provide first-order insights into the ecophysiological differences between these distinct microbial taxa

Wearing Knee Sleeves During Back Squats Does Not Improve Mass Lifted or Affect Knee Biomechanics

Purpose:Knee sleeves have become widely popular in the exercise realm, especially for knee support during back squats. Knee sleeves are successful in providing frontal plane knee support during functional tasks, but have not been investigated in back squats. Knee wraps, a somewhat similar elastic material, provide elastic energy that increases weight lifted during back squats. Thus, it is possible the thick neoprene knee sleeves could prove advantageous for back squats. The purpose of this study was to examine the effects of knee sleeves on weight lifted, knee biomechanics, and muscle activations during back squats.Methods:Fifteen resistance trained men and women performed 1-repetition maximum (1-RM) squats to full depth and 80% 1-RM to full and parallel depths during two separate randomized sessions: with/without knee sleeves. Three-dimensional motion capture, force platforms, and electromyography recorded knee biomechanics and activations of the rectus femoris, vastus medialis, biceps femoris long head, and gluteus maximus during all squats.Results:Maximal weight lifted did not improve when using knee sleeves. Frontal plane knee biomechanics did not differ for 1-RM or submaximal squats to either depth between conditions. Knee external rotation moments during descent were larger with sleeves during submaximal squats. Reduced integrated ascent phase gluteus maximus activations occurred during both 1-RM and submaximal squats with knee sleeves.Conclusions:The results of this study show that wearing knee sleeves does not provide additive effects to weight lifted and do not appear to alter frontal plane mechanics during weighted back squats