The evidence of quasi-free positronium state in GiPS-AMOC spectra of glycerol

We present the results of processing of Age-Momentum Correlation (AMOC) spectra that were measured for glycerol by the Gamma-induced positron spectroscopy (GiPS) facility. Our research has shown that the shape of experimental s(t) curve cannot be explained without introduction of the intermediate state of positronium (Ps), called quasi-free Ps. This state yields the wide Doppler line near zero lifetimes. We discuss the possible properties of this intermediate Ps state from the viewpoint of developed model. The amount of annihilation events produced by quasi-free Ps is estimated to be less than 5% of total annihilations. In the proposed model, quasi-free Ps serves as a precursor for trapped Ps of para- and ortho-states

Measurement of the Casimir force between dissimilar metals

The first precise measurement of the Casimir force between dissimilar metals is reported. The attractive force, between a Cu layer evaporated on a microelectromechanical torsional oscillator, and an Au layer deposited on an Al$_2$O$_3$ sphere, was measured dynamically with a noise level of 6 fN/$\sqrt{\rm{Hz}}$. Measurements were performed for separations in the 0.2-2 $\mu$m range. The results agree to better than 1% in the 0.2-0.5 $\mu$m range with a theoretical model that takes into account the finite conductivity and roughness of the two metals. The observed discrepancies, which are much larger than the experimental precision, can be attributed to a lack of a complete characterization of the optical properties of the specific samples used in the experiment.Comment: 6 pages, 4 figure

First measurement of gravitational lensing by cosmic voids in SDSS

We report the first measurement of the diminutive lensing signal arising from matter underdensities associated with cosmic voids. While undetectable individually, by stacking the weak gravitational shear estimates around 901 voids detected in SDSS DR7 by Sutter et al. (2012a), we find substantial evidence for a depression of the lensing signal compared to the cosmic mean. This depression is most pronounced at the void radius, in agreement with analytical models of void matter profiles. Even with the largest void sample and imaging survey available today, we cannot put useful constraints on the radial dark-matter void profile. We invite independent investigations of our findings by releasing data and analysis code to the public at https://github.com/pmelchior/void-lensingComment: 6 pages, 5 figures, as accepted by MNRA

Precise comparison of theory and new experiment for the Casimir force leads to stronger constraints on thermal quantum effects and long-range interactions

We report an improved dynamic determination of the Casimir pressure between two plane plates obtained using a micromachined torsional oscillator. The main improvements in the current experiment are a significant suppression of the surface roughness of the Au layers deposited on the interacting surfaces, and a decrease in the experimental error in the measurement of the absolute separation. A metrological analysis of all data permitted us to determine both the random and systematic errors, and to find the total experimental error as a function of separation at the 95% confidence level. In contrast to all previous experiments on the Casimir effect, our smallest experimental error ($\sim 0.5$%) is achieved over a wide separation range. The theoretical Casimir pressures in the experimental configuration were calculated by the use of four theoretical approaches suggested in the literature. All corrections to the Casimir force were calculated or estimated. All theoretical errors were analyzed and combined to obtain the total theoretical error at the 95% confidence level. Finally, the confidence interval for the differences between theoretical and experimental pressures was obtained as a function of separation. Our measurements are found to be consistent with two theoretical approaches utilizing the plasma model and the surface impedance over the entire measurement region. Two other approaches to the thermal Casimir force, utilizing the Drude model or a special prescription for the determination of the zero-frequency contribution to the Lifshitz formula, are excluded on the basis of our measurements at the 99% and 95% confidence levels, respectively. Finally, constraints on Yukawa-type hypothetical interactions are strengthened by up to a factor of 20 in a wide interaction range.Comment: 43 pages, 15 figures, elsart.cls is used. Accepted for publication in Annals of Physics. (Several misprints in the text are corrected.

Comment on "Anomalies in electrostatic calibration for the measurement of the Casimir force in a sphere-plane geometry"

Recently W. J. Kim, M. Brown-Hayes, D. A. R. Dalvit, J. H. Brownell, and R. Onofrio [Phys. Rev. A, v.78, 036102(R) (2008)] performed electrostatic calibrations for a plane plate above a centimeter-size spherical lens at separations down to 20-30 nm and observed "anomalous behavior". It was found that the gradient of the electrostatic force does not depend on separation as predicted on the basis of a pure Coulombian contribution. Some hypotheses which could potentially explain the deviation from the expected behavior were considered, and qualitative arguments in favor of the influence of patch surface potentials were presented. We demonstrate that for the large lenses at separations of a few tens nanometers from the plate, the electrostatic force law used by the authors is not applicable due to possible deviations of the mechanically polished and ground lens surface from a perfect spherical shape. A model is proposed which explains the observed "anomalous behavior" using the standard Coulombian force.Comment: 9 pages, 3 figure

The Enamel Ultrastructure of Multituberculate Mammals: A Review

The enamel ultrastructure of multituberculate mammals has been sampled extensively and studied intensively and is better known than for any other group of early mammals. The enamel of the earliest multituberculates, those of the Late Triassic-Early Jurassic suborder Haramiyoidea and the Late Jurassic-early Early Cretaceous suborder Plagiaulacoidea, is preprismatic. With only two exceptions, all Late Cretaceous and early Tertiary genera of multituberculates examined have prismatic enamel. Prisms are either small with circular (complete) boundaries or large with arc-shaped (incomplete) boundaries. There is a remarkably consistent relationship between enamel ultrastructural type and subordinal taxa in that small, circular prisms are usually found within the suborder Ptilodontoidea and large, arc-shaped prisms are usually found in the suborder Taeniolabidoidea and in six Late Cretaceous-Early Tertiary genera of indeterminate subordinal status. Research currently in progress suggests that both small, circular prisms and large, arc-shaped prisms are homologous in all multituberculates in which they occur, with one exception. Neoliotomus, a taeniolabidoid, appears to have evolved small, circular prisms independently. In addition, it appears that large, arc-shaped prisms represent the primitive condition in multituberculates with prismatic enamel, not small, circular prisms as has been proposed previously

Linkages Between the Phenologies of Jack Pine \u3ci\u3e(Pinus Banksiana)\u3c/i\u3e Foliage and Jack Pine Budworm (Lepidoptera: Tortricidae)

A field study conducted in 2001 and 2002 in the Michigan Upper Peninsula investigated seasonal associations between the development of jack pine, Pinus banksiana Lamb., and larvae of the jack pine budworm Choristoneura pinus Freeman (Lepidoptera: Tortricidae). There was almost no active relationship between post-diapause emerging second instars and elongation of vegetative shoots. Early instars were not closely synchronized with the flushing of current-year needle fascicles, which is required to optimize larval feeding. How- ever, there were close feeding and shelter relationships between early instars and year-2 pollen cone development. Associations with, and larval damage to, year-2 seed cones were dependent upon larval population size and posed only minimal and periodic threats to jack pine seed production. As a consequence, early instar jack pine budworm relied almost exclusively on pollen cones for survival. Third to fifth instars vacated pollen cones as soon as they became desiccated. Only then did these larvae start close associations with vegetative shoots. First, they excised partially emerged needles at their base, and when the needle-pairs completely escaped their fascicle sheath, the larvae fed routinely on the complete needle lamina. Late instars, pupae and adults were associated with previous years’ and current-year foliage without any apparent bias. This study has shown that it might be more practical to time insecticide strategies, which are intended to manage jack pine budworm larvae, to the tree’s phenology rather than jack pine budworm larval indices

Social Support Seeking And Early Adolescent Depression And Anxiety Symptoms: The Moderating Role Of Rumination

This study examined how social support seeking and rumination interacted to predict depression and anxiety symptoms 6 months later in early adolescents (N = 118; 11-14 years at baseline). We expected social support seeking would be more helpful for adolescents engaging in low rather than high levels of rumination. Adolescents self-reported on all measures at baseline, and on depression and anxiety symptoms 6 months later. Social support seeking predicted fewer symptoms of depression and anxiety at low rumination levels but was not associated with benefits as rumination increased. For depression symptoms, social support seeking predicted more symptoms at high rumination levels. Results were stronger for emotion-focused than problem-focused support seeking and for depression compared with anxiety symptoms. These findings suggest that cognitive risk factors like rumination may explain some inconsistencies in previous social support literature, and highlight the importance of a nuanced approach to studying social support seeking