Absolute Excitation Cross Sections Of He+ In 20-100-keV He+-He Collisions Using Energy-loss Spectrometry

Application of positive-ion energy-loss spectrometry has been extended to include experimental determination of absolute excitation cross sections of ground-state helium ions. Helium ion-atom collisions were studied for impact energies ranging between 20-100 keV, in 10-keV intervals. The data were taken with an apparatus resolution between 0.6-0.8 eV full width at half-maximum (FWHM). Cross sections for transitions from ground state to the second and third principal quantum levels of the ion plotted as a function of impact energy were still rapidly increasing at 100 keV. The cross sections at this energy were (1.64 ± 0.28) x 10-18 cm2 for He+(1s122)→He+ (n=2) and (3.46 ± 0.45) x 10-19 cm2 for He+(1s122)→He+ (n=3). © 1971 The American Physical Society

Semicrompressible Ocean Thermodynamics and Boussinesq Energy Conservation

Equations more accurate than the Boussinesq set that still filter out sound were recently introduced. While these equations were shown to have a consistent potential energy, their thermodynamical behavior and associated implications were not fully analyzed. These shortcomings are remedied in the present note that argues both sets are fully consistent from a thermodynamic perspective. It is further argued that both sets remain computationally competitive with the Boussinesq set

Collision Cross Sections For The Excitation Of The Schumann-Runge Dissociation Continuum In Molecular Oxygen By 20-110-keV Protons

Absolute cross sections for the excitation of the Schumann-Runge dissociation continuum of molecular oxygen have been obtained from inelastic energy-loss spectra induced by 20-110-keV protons incident on gaseous targets of molecular oxygen. Apparent differential energy loss cross sections, ionization cross sections, and total inelastic cross sections are also obtained from the energy-loss spectra. The proton energy-loss spectra have an energy resolution of about 2 eV. The energy location of the first peak in the energy-loss spectra of O2 is in general agreement with the findings of photo absorption and electron energy-loss-spectra measurements. The cross section for the Schumann-Runge dissociation continuum for 20-110-keV protons varies between 5 and 7 x 10-17 cm2 and has a broad maximum at about 60 keV. Existing theoretical treatments show poor agreement with these reported cross sections for the excitation of the dissociation continuum with respect to both absolute magnitude and curve shape. © 1971 The American Physical Society

Cross Section For Excitation Of The Fourth Positive Band System In Carbon Monoxide By 20-120 KeV Protons

Excitation cross sections for the fourth positive band system in carbon monoxide have been determined from studies of the energy-loss spectra of 20-120-keV protons incident on gaseous CO targets. The energy-loss spectra had an energy resolution of about 2 eV. Prominent peaks in the spectra were observed at 8.5 and 13.8 eV. The first peak is believed to be due to excitation of the fourth positive band system of CO (X+1A 1, while the 13.8-eV peak covers a number of possible states, including the B+2 and the C+1 states. Changes in the slope of the ionization continuum were noted at 16.5 eV, corresponding to the A i2 state of CO+, and at 20.5 eV, corresponding to the B+2 state of CO+. Absolute excitation cross sections for the fourth positive band system of CO are presented, as well as the total inelastic cross sections and the total ionization cross sections for 20-120-keV protons incident on CO. © 1970 The American Physical Society

Functional Architecture of the Inner Pore of a Voltage-gated Ca2+ Channel

The inner pore of voltage-gated Ca2+ channels (VGCCs) is functionally important, but little is known about the architecture of this region. In K+ channels, this part of the pore is formed by the S6/M2 transmembrane segments from four symmetrically arranged subunits. The Ca2+ channel pore, however, is formed by four asymmetric domains of the same (α1) subunit. Here we investigated the architecture of the inner pore of P/Q-type Ca2+ channels using the substituted-cysteine accessibility method. Many positions in the S6 segments of all four repeats of the α1 subunit (Cav2.1) were modified by internal methanethiosulfonate ethyltrimethylammonium (MTSET). However, the pattern of modification does not fit any known sequence alignment with K+ channels. In IIS6, five consecutive positions showed clear modification, suggesting a likely aqueous crevice and a loose packing between S6 and S5 segments, a notion further supported by the observation that some S5 positions were also accessible to internal MTSET. These results indicate that the inner pore of VGCCs is indeed formed by the S6 segments but is different from that of K+ channels. Interestingly some residues in IIIS6 and IVS6 whose mutations in L-type Ca2+ channels affect the binding of dihydropyridines and phenylalkylamines and are thought to face the pore appeared not to react with internal MTSET. Probing with qBBr, a rigid thiol-reactive agent with a dimension of 12 Å × 10 Å × 6 Å suggests that the inner pore can open to >10 Å. This work provides an impetus for future studies on ion permeation, gating, and drug binding of VGCCs

Communication Services and Supports for Individuals With Severe Disabilities: Guidance for Assessment and Intervention

The National Joint Committee for the Communication Needs of People with Severe Disabilities (NJC) reviewed literature regarding practices for people with severe disabilities in order to update guidance provided in documents originally published in 1992. Changes in laws, definitions, and policies that affect communication attainments by persons with severe disabilities are presented, along with guidance regarding assessment and intervention practices. A revised version of the Communication Bill of Rights, a powerful document that describes the communication rights of all individuals, including those with severe disabilities is included in this article. The information contained within this article is intended to be used by professionals, family members, and individuals with severe disabilities to inform and advocate for effective communication services and opportunities

Autonomous multispecies reaction-diffusion systems with more-than-two-site interactions

Autonomous multispecies systems with more-than-two-neighbor interactions are studied. Conditions necessary and sufficient for closedness of the evolution equations of the $n$-point functions are obtained. The average number of the particles at each site for one species and three-site interactions, and its generalization to the more-than-three-site interactions is explicitly obtained. Generalizations of the Glauber model in different directions, using generalized rates, generalized number of states at each site, and generalized number of interacting sites, are also investigated.Comment: 9 pages, LaTeX2

Characterizing mechanical effects of aging damage

This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The goal was to develop and apply several different experimental and theoretical/computational tools to better understand physical and chemical aging phenomena in plastic-bonded high explosives, and to develop a methodology for predicting the likely effects of aging on the mechanical properties of the composite based on input from these fundamental studies. Initial comparisons were done for spectra of fresh and aged Esane, as well as PBX-9501, and the authors found differences in the carbonyl region of the spectrum, which possibly reflect differences in hydrogen bonding due to aging phenomena. The micromechanical model of composites was extended to study various volume fractions of HMX with binders. The results showed that, as the binder fraction increases, there is a decrease in the maximum stress that can be supported but an increase in the percent strain at final fracture. A more realistic microstructural model was obtained through the use of a phase field model. Using this model, the authors have studied the microstructural evolution as a function of the grain boundary energy vs. misorientation relationship. The initial results indicate that there are some changes in the grain growth rate when the grain-boundary energy dependence on the angle is not constant. They also find that solute tends to segregate at the grain boundary and slows the grain growth kinetics

Framing the Real: Lefèbvre and NeoRealist Cinematic Space as Practice

In 1945 Roberto Rossellini's Neo-realist Rome, Open City set in motion an approach to cinema and its representation of real life – and by extension real spaces – that was to have international significance in film theory and practice. However, the re-use of the real spaces of the city, and elsewhere, as film sets in Neo-realist film offered (and offers) more than an influential aesthetic and set of cinematic theories. Through Neo-realism, it can be argued that we gain access to a cinematic relational and multidimensional space that is not made from built sets, but by filming the built environment. On the one hand, this space allows us to "notice" the contradictions around us in our cities and, by extension, the societies that have produced those cities, while on the other, allows us to see the spatial practices operative in the production and maintenance of those contradictions. In setting out a template for understanding the spatial practices of Neo-realism through the work of Henri Lefèbvre, this paper opens its films, and those produced today in its wake, to a spatio-political reading of contemporary relevance. We will suggest that the rupturing of divisions between real spaces and the spaces of film locations, as well the blurring of the difference between real life and performed actions for the camera that underlies much of the central importance of Neo-realism, echoes the arguments of Lefèbvre with regard the social production of space. In doing so, we will suggest that film potentially had, and still has, a vital role to play in a critique of contemporary capitalist spatial practices

Inkjet Metrology: High-Accuracy Mass Measurements of Microdroplets Produced by a Drop-on-Demand Dispenser

We describe gravimetric methods for measuring the mass of droplets generated by a drop-on-demand (DOD) microdispenser. Droplets are deposited, either continuously at a known frequency or as a burst of known number, into a cylinder positioned on a submicrogram balance. Mass measurements are acquired precisely by computer, and results are corrected for evaporation. Capabilities are demonstrated using isobutyl alcohol droplets. For ejection rates greater than 100 Hz, the repeatability of droplet mass measurements was 0.2%, while the combined relative standard uncertainty (uc) was 0.9%. When bursts of droplets were dispensed, the limit of quantitation was 72 μg (1490 droplets) with uc = 1.0%. Individual droplet size in a burst was evaluated by high-speed videography. Diameters were consistent from the tenth droplet onward, and the mass of an individual droplet was best estimated by the average droplet mass with a combined uncertainty of about 1%. Diameters of the first several droplets were anomalous, but their contribution was accounted for when dispensing bursts. Above the limits of quantitation, the gravimetric methods provided statistically equivalent results and permit detailed study of operational factors that influence droplet mass during dispensing, including the development of reliable microassays and standard materials using DOD technologies