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

On the detectability of extragalactic fast radio transients

Recent discoveries of highly dispersed millisecond radio bursts by Thornton et al. in a survey with the Parkes radio telescope at 1.4 GHz point towards an emerging population of sources at cosmological distances whose origin is currently unclear. Here we demonstrate that the scattering effects at lower radio frequencies are less than previously thought, and that the bursts could be detectable at redshifts out to about $z=0.5$ in surveys below 1 GHz. Using a source model in which the bursts are standard candles with bolometric luminosities $\sim 8 \times 10^{44}$ ergs/s uniformly distributed per unit comoving volume, we derive an expression for the observed peak flux density as a function of redshift and use this, together with the rate estimates found by Thornton et al. to find an empirical relationship between event rate and redshift probed by a given survey. The non-detection of any such events in Arecibo 1.4 GHz survey data by Deneva et al., and the Allen Telescope Array survey by Simeon et al. is consistent with our model. Ongoing surveys in the 1--2 GHz band should result in further discoveries. At lower frequencies, assuming a typical radio spectral index $\alpha=-1.4$, the predicted peak flux densities are 10s of Jy. As a result, surveys of such a population with current facilities would not necessarily be sensitivity limited and could be carried out with small arrays to maximize the sky coverage. We predict that sources may already be present in 350-MHz surveys with the Green Bank Telescope. Surveys at 150 MHz with 30 deg$^2$ fields of view could detect one source per hour above 30 Jy.Comment: 5 pages, 2 figures, Accepted for publication in MNRAS on 2013 July 25. Received 2013 July 24; in original form 2013 May 3

XMM-Newton observations of PSr B1259-63 near the 2004 periastron passage

PSR B1259-63 is in a highly eccentric 3.4 year orbit with a Be star and crosses the Be star disc twice per orbit, just prior to and just after periastron. Unpulsed radio, X-ray and gamma-ray emission observed from the binary system is thought to be due to the collision of pulsar wind with the wind of Be star. We present here the results of new XMM-Newton observations of the PSR B1259-63 system during the beginning of 2004 as the pulsar approached the disc of Be star.We combine these results with earlier unpublished X-ray data from BeppoSAX and XMM-Newton as well as with ASCA data. The detailed X-ray lightcurve of the system shows that the pulsar passes (twice per orbit) through a well-defined gaussian-profile disk with the half-opening angle (projected on the pulsar orbit plane) ~18.5 deg. The intersection of the disk middle plane with the pulsar orbital plane is inclined at ~70 deg to the major axis of the pulsar orbit. Comparing the X-ray lightcurve to the TeV lightcurve of the system we find that the increase of the TeV flux some 10--100 days after the periastron passage is unambiguously related to the disk passage. At the moment of entrance to the disk the X-ray photon index hardens from 1.8 up to 1.2 before returning to the steeper value 1.5. Such behaviour is not easily accounted for by the model in which the X-ray emission is synchrotron emission from the shocked pulsar wind. We argue that the observed hardening of the X-ray spectrum is due to the inverse Compton or bremsstrahlung emission from 10-100 MeV electrons responsible for the radio synchrotron emission.Comment: 9 pages, accepted to MNRA