Probing For Machos of Mass 10−15M⊙10^{-15}M_\odot-10−7M⊙10^{-7}M_\odot with Gamma-Ray Burst Parallax Spacecraft

Two spacecraft separated by \sim 1\,\au and equipped with gamma-ray burst (GRB) detectors could detect or rule out a cosmological density of Massive Compact Halo Objects (MACHOs) in the mass range 10^{-15} M_{\odot}\lsim M \lsim 10^{-7} M_{\odot} provided that GRBs prove to be cosmological. Previously devised methods for detecting MACHOs have spanned the mass range 10^{-16} M_{\odot}\lsim M \lsim 10^{7} M_{\odot}, but with a gap of several orders of magnitude near $10^{-9} M_{\odot}$. For MACHOs and sources both at a cosmological distance, the Einstein radius is \sim 1\,\au\,(M/10^{-7} M_\odot)^{1/2}. Hence, if a GRB lies within the Einstein ring of a MACHO of mass M\lsim 10^{-7}M_\odot as seen by one detector, it will not lie in the Einstein ring as seen by a second detector \sim 1\,\au away. This implies that if GRBs are measured to have significantly different fluxes by the two detectors, this would signal the presence of a MACHO \lsim 10^{-7}M_\odot. By the same token, if the two detectors measured similar fluxes for several hundred events a cosmological abundance of such low-mass MACHOs would be ruled out. The lower limit of sensitivity, M\lsim 10^{-15}M_\odot is set by the finite size of the source. If low-mass MACHOs are detected, there are tests which can discriminate among events generated by MACHOs in the three mass ranges M\lsim 10^{-12}\,M_\odot, 10^{-12}\,M_\odot\lsim M\lsim 10^{-7}\,M_\odot, and M\gsim 10^{-7}\ M_\odot. Further experiments would then be required to make more accurate mass measurements.Comment: 8 pages, uuencoded postscript, no figure

Social Comparison Threat and Interpersonal Attraction

The self-esteem of 80 male subjects was temporarily either raised or lowered by giving them false feedback on an alleged personality test. Subsequently, subjects were led to believe that their attractiveness to a physically attractive female student would be compared with that of a male stimulus person. The perceived ability of the male stimulus person to be attractive to females was varied and subjects were given an opportunity to indicate their liking for the male target either before learning the outcome of the female's comparative evaluation or after learning that the female had indicated a preference for the stimulus person. From an analysis of self-esteem threat based on Festinger's theory of social comparison processes (1954), a three way interaction was predicted. Under conditions where subjects had received negative comparison feedback it was predicted that low self-esteem subjects would indicate greater liking for the stimulus person than high self-esteem subjects, regardless of the stimulus person's perceived ability. In contrast, under conditions where comparative evaluation feedback was anticipated, it was predicted that low self-esteem, relative to high self-esteem, subjects, would indicate greater liking for the target perceived to have high ability, but would indicate less liking for the stimulus person perceived to have low ability. The results supported these predictions and are discussed in with respect to furthering our understanding the self-esteem construct and the process of self-esteem maintenance, and the extension of the applicability of social comparison principles

Tests of pattern separation and pattern completion in humans - a systematic review

OBJECTIVE: To systematically review the characteristics, validity and outcome measures of tasks that have been described in the literature as assessing pattern separation and pattern completion in humans. METHODS: Electronic databases were searched for articles. Parameters for task validity were obtained from two reviews that described optimal task design factors to evaluate pattern separation and pattern completion processes. These were that pattern separation should be tested during an encoding task using abstract, never-before-seen visual stimuli, and pattern completion during a retrieval task using partial cues; parametric alteration of the degree of interference of stimuli or degradation of cues should be used to generate a corresponding gradient in behavioral output; studies should explicitly identify the specific memory domain under investigation (sensory/perceptual, temporal, spatial, affect, response, or language) and account for the contribution of other potential attributes involved in performance of the task. A systematic, qualitative assessment of validity in relation to these parameters was performed, along with a review of general validity and task outcome measures. RESULTS: Sixty-two studies were included. The majority of studies investigated pattern separation and most tasks were performed on young, healthy adults. Pattern separation and pattern completion were most frequently tested during a retrieval task using familiar or recognizable visual stimuli and cues. Not all studies parametrically altered the degree of stimulus interference or cue degradation, or controlled for potential confounding factors. CONCLUSION: This review found evidence that some of the parameters for task validity have been followed in some human studies of pattern separation and pattern completion, but no study was judged to have adequately met all the parameters for task validity. The contribution of these parameters and other task design factors towards an optimal behavioral paradigm is discussed and recommendations for future research are made. This article is protected by copyright. All rights reserved

Size Distributions of Coastal Ocean Suspended Particulate Inorganic Matter: Amorphous Silica and Clay Minerals and their Dynamics

Particulate inorganic matter (PIM) is a key component in estuarine and coastal systems and plays a critical role in trace metal cycling. Better understanding of coastal dynamics and biogeochemistry re-quires improved quantification of PIM in terms of its concentration, size distribution, and mineral species composition. The angular pattern of light scattering contains detailed information about the size and composition of particles. These volume scattering functions (VSFs) were measured in Mobile Bay, Alabama, USA, a dynamic, PIM dominated coastal environment. From measured VSFs, we determined through inversion the particle size distributions (PSDs) of major components of PIM, amorphous silica and clay minerals. An innovation here is the extension of our reported PSDs significantly into the sub-micron range. The PSDs of autochthonous amorphous silica exhibit two unique features: a peak centered at about 0.8mm between 0.2 and 4mm and a very broad shoulder essentially extending from 4mm to\u3e100mm. With an active and steady particle source from blooming diatoms, the shapes of amorphoussilica PSDs for sizes area, but showed more particles of sizes\u3e10mm inside the bay, likely due to wind-induced resuspension of larger frustules that have settled. Compared to autochthonous amorphous silica, the allochthonous clay minerals are denser and exhibit relatively narrower PSDs with peaks located between 1 and 4mm. Preferential settling of larger mineral particles as well as the smaller but denser illite component further narrowed the size distributions of clay minerals as they were being transported outside the bay. The derived PSDs also indicated a very dynamic situation in Mobile Bay when a cold weather front passed through during the experiment. With northerly winds of speeds up to 15 m s-1, both amorphous silica and clay minerals showed a dramatic increase in concentration and broadening in size distribution outside the exit of the barrier islands, indicative of wind-induced resuspension and subsequent advection of particles out of Mobile Bay. While collectively recognized as the PIM, amorphous silica and clay minerals, as shown in this study, possess very different size distributions. Considering how differences in PSDs and the associated particle areas will effect differences in sorption/desorption properties of these components, the results also demonstrate thepotential of applying VSF-inversion in studying biogeochemistry in the estuarine-coastal ocean system

The McDonald Observatory Planet Search: New Long-Period Giant Planets, and Two Interacting Jupiters in the HD 155358 System

We present high-precision radial velocity (RV) observations of four solar-type (F7-G5) stars - HD 79498, HD 155358, HD 197037, and HD 220773 - taken as part of the McDonald Observatory Planet Search Program. For each of these stars, we see evidence of Keplerian motion caused by the presence of one or more gas giant planets in long-period orbits. We derive orbital parameters for each system, and note the properties (composition, activity, etc.) of the host stars. While we have previously announced the two-gas-giant HD 155358 system, we now report a shorter period for planet c. This new period is consistent with the planets being trapped in mutual 2:1 mean-motion resonance. We therefore perform an in-depth stability analysis, placing additional constraints on the orbital parameters of the planets. These results demonstrate the excellent long-term RV stability of the spectrometers on both the Harlan J. Smith 2.7 m telescope and the Hobby-Eberly telescope.Comment: 38 pages, 10 figures, 6 tables. Accepted for publication in Ap

Transformation and patterning of supermicelles using dynamic holographic assembly

Although the solution self-assembly of block copolymers has enabled the fabrication of a broad range of complex, functional nanostructures, their precise manipulation and patterning remain a key challenge. Here we demonstrate that spherical and linear supermicelles, supramolecular structures held together by non-covalent solvophobic and coordination interactions and formed by the hierarchical self-assembly of block copolymer micelle and block comicelle precursors, can be manipulated, transformed and patterned with mediation by dynamic holographic assembly (optical tweezers). This allows the creation of new and stable soft-matter superstructures far from equilibrium. For example, individual spherical supermicelles can be optically held in close proximity and photocrosslinked through controlled coronal chemistry to generate linear oligomeric arrays. The use of optical tweezers also enables the directed deposition and immobilization of supermicelles on surfaces, allowing the precise creation of arrays of soft-matter nano-objects with potentially diverse functionality and a range of applications