Effect of the spin-orbit interaction on the thermodynamic properties of crystals: The specific heat of bismuth

In recent years, there has been increasing interest in the specific heat $C$ of insulators and semiconductors because of the availability of samples with different isotopic masses and the possibility of performing \textit{ab initio} calculations of its temperature dependence $C(T)$ using as a starting point the electronic band structure. Most of the crystals investigated are elemental (e.g., germanium) or binary (e.g., gallium nitride) semiconductors. The initial electronic calculations were performed in the local density approximation and did not include spin-orbit interaction. Agreement between experimental and calculated results was usually found to be good, except for crystals containing heavy atoms (e.g., PbS) for which discrepancies of the order of 20% existed at the low temperature maximum found for $C/T^3$. It has been conjectured that this discrepancies result from the neglect of spin-orbit interaction which is large for heavy atoms ($\Delta_0\sim$1.3eV for the $p$ valence electrons of atomic lead). Here we discuss measurements and \textit{ab initio} calculations of $C(T)$ for crystalline bismuth ($\Delta_0\sim$1.7 eV), strictly speaking a semimetal but in the temperature region accessible to us ($T >$ 2K) acting as a semiconductor. We extend experimental data available in the literature and notice that the \textit{ab initio} calculations without spin-orbit interaction exhibit a maximum at $\sim$8K, about 20% lower than the measured one. Inclusion of spin-orbit interaction decreases the discrepancy markedly: The maximum of $C(T)$ is now only 7% larger than the measured one. Exact agreement is obtained if the spin-orbit hamiltonian is reduced by a factor of $\sim$0.8.Comment: 4 pages, 3 figure

Age problem in holographic dark energy

We study the age problem of the universe with the holographic DE model introduced in [21], and test the model with some known old high redshift objects (OHRO). The parameters of the model have been constrained using the SNIa, CMB and BAO data set. We found that the age of the old quasar APM 08 279+5255 at z = 3.91 can be described by the model.Comment: 13 page

Lattice Properties of PbX (X = S, Se, Te): Experimental Studies and ab initio Calculations Including Spin-Orbit Effects

During the past five years the low temperature heat capacity of simple semiconductors and insulators has received renewed attention. Of particular interest has been its dependence on isotopic masses and the effect of spin- orbit coupling in ab initio calculations. Here we concentrate on the lead chalcogenides PbS, PbSe and PbTe. These materials, with rock salt structure, have different natural isotopes for both cations and anions, a fact that allows a systematic experimental and theoretical study of isotopic effects e.g. on the specific heat. Also, the large spin-orbit splitting of the 6p electrons of Pb and the 5p of Te allows, using a computer code which includes spin-orbit interaction, an investigation of the effect of this interaction on the phonon dispersion relations and the temperature dependence of the specific heat and on the lattice parameter. It is shown that agreement between measurements and calculations significantly improves when spin-orbit interaction is included.Comment: 25 pages, 12 Figures, 1 table, submitted to PR

Challenging the status quo: women's experiences of opting for a home birth in Andalucia, Spain

Objective To explore the perceptions, beliefs and attitudes of women who opted for a home birth in Andalusia (Spain). Background Home birth is currently an unusual choice among Spanish women. It is not an option covered by the Spanish National Health Service and women who opt for a home birth have to pay for an independent midwife. Design A qualitative study with a phenomenological approach was adopted. All participants who took part in this study had chosen to have a home birth and given written consent to take part in the study. Methods Data collection was conducted in 2015–16. Face-to-face, semi-structured interviews were undertaken with women who chose a home birth in the last 5 years. Findings The sample consisted of thirteen women. Seven themes were created through analysis: 1. Getting informed about home birth; 2. Home birth as a choice, despite feeling unsupported; 3. The best way to have a personalized and a physiological birth; 4. Seeking a healing and empowering experience 5. The need for emotional safety, establishing a relationship and trusting the midwife; 6. Preparing for birth and working on fears; 7. Inequality of access (because of financial implications). Conclusions Women opted to plan birth at home because they wanted a personalised birth and control over their decision-making in labour, which they felt would not have been afforded to them in hospital settings. Andalusian maternity care leaders should strive to ensure that all pregnant women receive respectful and high-quality personalised care, by appropriately trained staff, both in the hospital and in the community

Vibrational and Thermal Properties of ZnX (X=Se, Te): Density Functional Theory (LDA and GGA) versus Experiment

We calculated the phonon dispersion relations of ZnX (X=Se, Te) employing ab initio techniques. These relations have been used to evaluate the temperature dependence of the respective specific heats of crystals with varied isotopic compositions. These results have been compared with mea- surements performed on crystals down to 2 K. The calculated and measured data are generally in excellent agreement with each other. Trends in the phonon dispersion relations and the correspond- ing densities of states for the zinc chalcogenide series of zincblende-type materials are discussed.Comment: 10 pages, submitted to PR

EFFICACY OF ELECTRON BEAM IRRADIATION OF PROCESSED PORK PRODUCTS

The research reported on in this paper was conducted as part of a larger project. That project is on-going and is focused on ascertaining if irradiation of processed meats would be effective and economical. It involved the examination, through modeling, of the irradiation of one of many currently produced ready-to-eat (RTE) convenience-oriented, value-added pork products, sliced boneless ham. The results and findings reported in this paper represent the initial estimates of the cost and potential profitability or economic viability of irradiation of processed meats. The results and findings in this paper should be considered preliminary with extension and verification to be reported in a later paper by the authors. The objective of the portion of that project reported on in this paper was to conduct cost analysis of alternative irradiation methods and to ascertain the cost of each of those methods. Three scenarios were considered for cost analysis. The first scenario was the installation of an X-ray irradiator at an existing meat processing plant. The second scenario was the installation of a Cobalt-60 irradiator at an existing meat processing plant. The third scenario assumed that the meat processor contracted for irradiation services from an off-site company providing such service to a number of clients. For purposes of this study it was assumed that irradiation of sliced boneless ham would result in either a $.06/pound reduction in costs from processor to consumer, a$.06/pound increase in willingness to pay [price] or an equivalent combination of reduced costs and increased price. Total cost per pound for the irradiation process applied to sliced boneless ham ranged from $0.008, at the 200 million pound annual throughput rate using Cobalt-60 irradiation, to$0.069 at the 50 million pound annual throughput rate when contracting with an off-site company.Food Consumption/Nutrition/Food Safety,

Phonons in single and few-layer MoS2 and WS2

We report ab-initio calculations of the phonon dispersion relations of the single-layer and bulk dichalcogenides MoS2 and WS2. We explore in detail the behavior of the Raman active modes, A1g and E2g as a function of the number of layers. In agreement with recent Raman spectroscopy measurements [C. Lee et. al., ACS Nano Vol. 4, 2695 (2010)] we find that the A1g mode increases in frequency with increasing layer number while the E2g mode decreases. We explain this decrease by an enhancement of the dielectric screening of the long-range Coulomb interaction between the effective charges with growing number of layers. This decrease in the long-range part over-compensates the increase of the short-range interaction due to the weak inter-layer interaction.Comment: 8 pages, 6 figure

Detection and isolation of exotic Newcastle disease virus from field-collected flies.

Flies were collected by sweep net from the vicinity of two small groups of "backyard" poultry (10-20 chickens per group) that had been identified as infected with exotic Newcastle disease virus (family Paramyxoviridae, genus avulavirus, ENDV) in Los Angeles County, CA, during the 2002-2003 END outbreak. Collected flies were subdivided into pools and homogenized in brain-heart infusion broth with antibiotics. The separated supernatant was tested for the presence of ENDV by inoculation into embryonated chicken eggs. Exotic Newcastle disease virus was isolated from pools of Phaenicia cuprina (Wiedemann), Fannia canicularis (L.), and Musca domestica L., and it was identified by hemagglutination inhibition with Newcastle disease virus antiserum. Viral concentration in positive pools was low (<1 egg infectious dose50 per fly). Isolated virus demonstrated identical monoclonal antibody binding profiles as well as 99% sequence homology in the 635-bp fusion gene sequence compared with ENDV recovered from infected commercial egg layer poultry during the 2002 outbreak