Neutron interference scattering in crystalline solids Progress report

Neutron elastic and inelastic interference scattering cross section in crystalline lattices of solid

Computer program calculates the effective temperature for a crystalline solid /DETS/

Computer program computes and prints out both the Debye and resulting effective temperatures for each Debye model-dependent average energy per vibrational mode, Debye-Waller factor, and specific heat. The program calculates by the trapezodial rule and then Simpsons rule

Multiple environmental controls explain global patterns in soil animal communities

Soil animals play important roles in ecosystem functioning and stability, but the environmental controls on their communities are not fully understood. In this study, we compiled a dataset of soil animal communities for which the abundance and body mass of multiple soil animal groups were recorded. The mass–abundance scaling relationships were then used to investigate multiple environmental controls on soil animal community composition. The data reveal latitudinal shifts from high abundances of small soil animals at high latitudes to greater relative abundances of large soil animals at low latitudes. A hierarchical linear mixed effects model was applied to reveal the environmental variables shaping these latitudinal trends. The final hierarchical model identified mean annual temperature, soil pH and soil organic carbon content as key environmental controls explaining global mass–abundance scaling relationships in soil animal communities (R2c = 0.828, Ngroup = 117). Such relationships between soil biota with climate and edaphic conditions have been previously identified for soil microbial, but not soil animal, communities at a global scale. More comprehensive global soil community datasets are needed to better understand the generality of these relationships over a broader range of global ecosystems and soil animal groups

Identifying a forward scattering superconductor through pump-probe spectroscopy

Electron-boson scattering that is peaked in the forward direction has been suggested as an essential ingredient for enhanced superconductivity observed in FeSe monolayers. Here, we study the superconducting state of a system dominated by forward scattering in the time-domain and contrast its behavior against the standard isotropic BCS case for both s- and d-wave symmetries. An analysis of the electron's dynamics in the pump-driven non-equilibrium state reveals that the superconducting order in the forward-focused case is robust and persistent against the pump-induced perturbations. The superconducting order parameter also exhibits a non-uniform melting in momentum space. We show that this behavior is in sharp contrast to the isotropic interaction case and propose that time-resolved approaches are a potentially powerful tool to differentiate the nature of the dominant coupling in correlated materials.Comment: Updated the introduction and the methods section, 6 Pages, 5 figure

Polarisation profiles of southern pulsars at 3.1 GHz

We present polarisation profiles for 48 southern pulsars observed with the new 10-cm receiver at the Parkes telescope. We have exploited the low system temperature and high bandwidth of the receiver to obtain profiles which have good signal to noise for most of our sample at this relatively high frequency. Although, as expected, a number of profiles are less linearly polarised at 3.1 GHz than at lower frequencies, we identify some pulsars and particular components of profiles in other pulsars which have increased linear polarisation at this frequency. We discuss the dependence of linear polarisation with frequency in the context of a model in which emission consists of the superposition of two, orthogonally polarised modes. We show that a simple model, in which the orthogonal modes have different spectral indices, can explain many of the observed properties of the frequency evolution of both the linear polarisation and the total power, such as the high degree of linear polarisation seen at all frequencies in some high spin-down, young pulsars. Nearly all the position angle profiles show deviations from the rotating vector model; this appears to be a general feature of high-frequency polarisation observations.Comment: Accepted for publication in MNRA

Origin of the transient unpulsed radio emission from the PSR B1259-63 binary system

We discuss the interpretation of transient, unpulsed radio emission detected from the unique pulsar/Be-star binary system PSR B1259-63. Extensive monitoring of the 1994 and 1997 periastron passages has shown that the source flares over a 100-day interval around periastron, varying on time-scales as short as a day and peaking at 60 mJy (~100 times the apastron flux density) at 1.4 GHz. Interpreting the emission as synchrotron radiation, we show that (i) the observed variations in flux density are too large to be caused by the shock interaction between the pulsar wind and an isotropic, radiatively driven, Be-star wind, and (ii) the radio emitting electrons do not originate from the pulsar wind. We argue instead that the radio electrons originate from the circumstellar disk of the Be star and are accelerated at two epochs, one before and one after periastron, when the pulsar passes through the disk. A simple model incorporating two epochs of impulsive acceleration followed by synchrotron cooling reproduces the essential features of the radio light curve and spectrum and is consistent with the system geometry inferred from pulsed radio data.Comment: To be published in Astrophysical Journal Letters 7 pages, 1 postscript figur

Absence of structural correlations of magnetic defects in heavy fermion LiV2O4

Magnetic defects have pronounced effects on the magnetic properties of the face-centered cubic compound LiV2O4. The magnetic defects arise from crystal defects present within the normal spinel structure. High-energy x-ray diffraction studies were performed on LiV2O4 single crystals to search for superstructure peaks or any other evidence of periodicity in the arrangement of the crystal defects present in the lattice. Entire reciprocal lattice planes are mapped out with help of synchrotron radiation. No noticeable differences in the x-ray diffraction data between a crystal with high magnetic defect concentration and a crystal with low magnetic defect concentration have been found. This indicates the absence of any long-range periodicity or short-range correlations in the arrangements of the crystal/magnetic defects.Comment: 6 pages, 4 figure