Gamma ray line production from cosmic ray spallation reactions

The gamma ray line intensities due to cosmic ray spallation reactions in clouds, the galactic disk and accreting binary pulsars are calculated. With the most favorable plausible assumptions, only a few lines may be detectable to the level of 0.0000001 per sq. cm per sec. The intensities are compared with those generated in nuclear excitation reactions

Feasibility Of One–Dedicated–Lane Bus Rapid Transit ⁄Light–Rail Systems And Their Expansion To Two–Dedicated–Lane Systems: A Focus On Geometric Configuration And Performance Planning, MTI Report 08-01

This report consists primarily of two parts, the first on feasibility and the next on space minimization. In the section on feasibility, we propose the concept of a Bus Rapid Transit (BRT) or light–rail system that effectively requires only one dedicated but reversible lane throughout the system to support two-way traffic in the median of a busy commute corridor with regular provision of left–turn lanes. Based on key ideas proposed in that section, the section on space minimization first addresses how to implement a two–dedicated–lane BRT or light–rail system with minimum right–of–way width and then proposes ways to expand a one–dedicated–lane system to two dedicated lanes. In a one–dedicated–lane system, traffic crossing is accommodated on the otherwise unused or underused median space resulting from provision of the left–turn lanes. Although not necessary, some left–turn lanes can be sacrificed for bus stops. Conceptual design options and geometric configuration sketches for the bus stop and crossing space are provided in the section on feasibility, which also discusses system performance in terms of travel speed, headway of operations, distance between two neighboring crossing spaces, and number of crossing spaces. To ensure practicality, we study implementation of such a system on an existing corridor. Such a system is also useful as an intermediate step toward a two–dedicated–lane system because of its potential for facilitating transit–oriented development. In typical existing or planned BRT or light–rail systems implemented with two dedicated traffic lanes, a space equivalent to four traffic lanes is dedicated for a bus stop. In the section on space minimization, we propose implementations requiring only three lanes at a bus stop, based on two key ideas proposed for a one–dedicated–lane system. That section also discusses ways to expand a one–dedicated–lane system to its corresponding two–dedicated–lane system

A Cortical Region Consisting Entirely of Face-Selective Cells

Face perception is a skill crucial to primates. In both humans and macaque monkeys, functional magnetic resonance imaging (fMRI) reveals a system of cortical regions that show increased blood flow when the subject views images of faces, compared with images of objects. However, the stimulus selectivity of single neurons within these fMRI-identified regions has not been studied. We used fMRI to identify and target the largest face-selective region in two macaques for single-unit recording. Almost all (97%) of the visually responsive neurons in this region were strongly face selective, indicating that a dedicated cortical area exists to support face processing in the macaque

Propagation of cosmic rays and new evidence for distributed acceleration

The origin and propagation of cosmic rays in terms of conventional and supplementary newer assumptions were explored. Cosmic rays are considered to be accelerated by supernoava shock waves and to traverse clouds in the source region. After rigidity-dependent escape from these clouds into interstellar space, cosmic rays are further accelerated by the weakened shocks of old supernova remnants and then pass through additional material. The distributed acceleration hypothesis is discussed with emphasis on recent data on the abundances of cosmic-ray isotopes of N above 1 GeV/u and of He near 6 GeV/u

Curvature dependence of the effect of ionic functionalization on the attraction among nanoparticles in dispersion

Solubilization of nanoparticles facilitates nanomaterial processing and enables new applications. An effective method to improve dispersibility in water is provided by ionic functionalization.We explore how the necessary extent of functionalization depends on the particle geometry. Using molecular dynamics/umbrella sampling simulations, we determine the effect of the solute curvature on solventaveraged interactions among ionizing graphitic nanoparticles in aqueous dispersion. We tune the hydrophilicity of molecular-brush coated fullerenes, carbon nanotubes, and graphane platelets by gradually replacing a fraction of the methyl end groups of the alkyl coating by the ionizing –COOK or –NH3Cl groups. To assess the change in nanoparticles’ dispersibility in water, we determine the potential-of-mean-force profiles at varied degrees of ionization. When the coating comprises only propyl groups, the attraction between the hydrophobic particles intensifies from spherical to cylindrical to planar geometry. This is explained by the increasing fraction of surface groups that can be brought into contact and the reduced access to water molecules, both following the above sequence. When ionic groups are added, however, the dispersibility increases in the opposite order, with the biggest effect in the planar geometry and the smallest in the spherical geometry. These results highlight the important role of geometry in nanoparticle solubilization by ionic functionalities, with about twice higher threshold surface charge necessary to stabilize a dispersion of spherical than planar particles. At 25%–50% ionization, the potential of mean force reaches a plateau because of the counterion condensation and saturated brush hydration. Moreover, the increase in the fraction of ionic groups can weaken the repulsion through counterion correlations between adjacent nanoparticles. High degrees of ionization and concomitant ionic screening gradually reduce the differences among surface interactions in distinct geometries until an essentially curvature-independent dispersion environment is created. Insights into tuning nanoparticle interactions can guide the synthesis of a broad class of nonpolar nanoparticles, where solubility is achieved by ionic functionalization

Implications of cross section errors for cosmic ray propagation

Errors in nuclear interaction cross sections are the single most important limitation on the analysis of cosmic ray composition data. At the 18th International Cosmic Ray Conference, the potential importance of correlations in cross section errors in determining cosmic ray source abundances was demonstrated. In this paper the magnitude of cross section error correlation is estimated. Analysis suggests that cross section errors are essentially uncorrelated for nuclei with Z 29 and that the actual errors may be less than the nominal 35%

A feasibility study of signal processing to improve antenna gain Final report

Feasibility of signal processor with phase isolator for adaptive antenna arra

Calculation of improved spallation cross sections

Several research groups have recently carried out highly precise measurements (to about 10 percent) of high-energy nuclear spallation cross sections. These measurements, above 5 GeV, cover a broad range of elements: V, Fe, Cu, Ag, Ta and Au. Even the small cross sections far off the peak of the isotopic distribution curves have been measured. The semiempirical calculations are compared with the measured values. Preliminary comparisons indicate that the parameters of our spallation relations (Silberberg and Tsao, 1973) for atomic numbers 20 to 83 need modifications, e.g. a reduced slope of the mass yield distribution, broader isotopic distributions, and a shift of the isotopic distribution toward the neutron-deficient side. The required modifications are negligible near Fe and Cu, but increase with increasing target mass

Constraints on large scalar multiplets from perturbative unitarity

We determine the constraints on the isospin and hypercharge of a scalar electroweak multiplet from partial-wave unitarity of tree-level scattering diagrams. The constraint from SU(2)_L interactions yields T <= 7/2 (i.e., n <= 8) for a complex scalar multiplet and T <= 4 (i.e., n <= 9) for a real scalar multiplet, where n = 2T+1 is the number of isospin states in the multiplet.Comment: 10 pages, 1 figure. v2: refs added, minor additions to text, submitted to PR

Neuroimaging Weighs In: Humans Meet Macaques in “Primate” Visual Cortex

It has been only a decade since functional magnetic resonance imaging (fMRI) was introduced, but approximately four fMRI papers are now published every working day. Here we review this progress in a well studied system: primate visual cortex