Scattering from a Domain Wall in a Spontaneously Broken Gauge Theory

We study the interaction of particles with a domain wall at a symmetry-breaking phase transition by perturbing about the domain wall solution. We find the particulate excitations appropriate near the domain wall and relate them to the particles present far from the wall in the uniform broken and unbroken phases. For a quartic Higgs potential we find analytic solutions to the equations of motion and derive reflection and transmission coefficients. We discover several bound states for particles near the wall. Finally, we apply our results to the electroweak phase transition in the standard model.Comment: 48 pages, 10 figures, LaTeX / epsf, revised to include references to earlier related wor

Spectroscopic applications and frequency locking of THz photomixing with distributed-Bragg-reflector diode lasers in low-temperature-grown GaAs

A compact, narrow-linewidth, tunable source of THz radiation has been developed for spectroscopy and other high-resolution applications. Distributed-Bragg-reflector (DBR) diode lasers at 850 nm are used to pump a low-temperature-grown GaAs photomixer. Resonant optical feedback is employed to stabilize the center frequencies and narrow the linewidths of the DBR lasers. The heterodyne linewidth full-width at half-maximum of two optically locked DBR lasers is 50 kHz on the 20 ms time scale and 2 MHz over 10 s; free-running DBR lasers have linewidths of 40 and 90 MHz on such time scales. This instrument has been used to obtain rotational spectra of acetonitrile (CH3CN) at 313 GHz. Detection limits of 1 × 10^–4 Hz^1/2 (noise/total power) have been achieved, with the noise floor dominated by the detector's noise equivalent power

Fiscal and economic stability in the eurozone.

yesEvery day the news is filled with increasingly depressing news about the economy. The recent Autumn Statement (29 November 2011) to the House of Commons by UK Chancellor of the Exchequer, George Osborne, confirmed that the cause of a potential ?double dip? recession in the British economy lay largely at the doors of the European Union and, in particular, the eurozone. It is easy to understand why some commentators feel that perhaps the European single currency is in its death-throes, and that the European Union itself needs major structural revisions. But for the sake of perspective it is important to remember the underlying rationale behind the ?European project? which remains as relevant today as it did in the 1950s

Quorum sensing influences growth and photosynthetic membrane production in high-cell-density cultivations of Rhodospirillum rubrum

BACKGROUND: The facultative anoxygenic photosynthetic bacterium Rhodospirillum rubrum exhibits versatile metabolic activity allowing the adaptation to rapidly changing growth conditions in its natural habitat, the microaerobic and anoxic zones of stagnant waters. The microaerobic growth mode is of special interest as it allows the high-level expression of photosynthetic membranes when grown on succinate and fructose in the dark, which could significantly simplify the industrial production of compounds associated with PM formation. However, recently we showed that PM synthesis is no longer inducible when R. rubrum cultures are grown to high cell densities under aerobic conditions. In addition a reduction of the growth rate and the continued accumulation of precursor molecules for bacteriochlorophyll synthesis were observed under high cell densities conditions. RESULTS: In the present work, we demonstrate that the cell density-dependent effects are reversible if the culture supernatant is replaced by fresh medium. We identified six N-acylhomoserine lactones and show that four of them are produced in varying amounts according to the growth phase and the applied growth conditions. Further, we demonstrate that N-acylhomoserine lactones and tetrapyrrole compounds released into the growth medium affect the growth rate and PM expression in high cell density cultures. CONCLUSIONS: In summary, we provide evidence that R. rubrum possesses a Lux-type quorum sensing system which influences the biosynthesis of PM and the growth rate and is thus likely to be involved in the phenotypes of high cell density cultures and the rapid adaptation to changing environmental conditions

Phosphocholine – an agonist of metabotropic but not of ionotropic functions of alpha9-containing nicotinic acetylcholine receptors

We demonstrated previously that phosphocholine and phosphocholine-modified macromolecules efficiently inhibit ATP-dependent release of interleukin-1beta from human and murine monocytes by a mechanism involving nicotinic acetylcholine receptors (nAChR). Interleukin-1beta is a potent pro-inflammatory cytokine of innate immunity that plays pivotal roles in host defence. Control of interleukin-1beta release is vital as excessively high systemic levels cause life threatening inflammatory diseases. In spite of its structural similarity to acetylcholine, there are no other reports on interactions of phosphocholine with nAChR. In this study, we demonstrate that phosphocholine inhibits ion-channel function of ATP receptor P2X7 in monocytic cells via nAChR containing alpha9 and alpha10 subunits. In stark contrast to choline, phosphocholine does not evoke ion current responses in Xenopus laevis oocytes, which heterologously express functional homomeric nAChR composed of alpha9 subunits or heteromeric receptors containing alpha9 and alpha10 subunits. Preincubation of these oocytes with phosphocholine, however, attenuated choline-induced ion current changes, suggesting that phosphocholine may act as a silent agonist. We conclude that phophocholine activates immuno-modulatory nAChR expressed by monocytes but does not stimulate canonical ionotropic receptor functions

Do Maternal Vitamin D Levels Influence Vitamin D Levels in Preterm Neonates?

Objective To determine the prevalence of Vitamin D (VitD) deficiency/insufficiency in mothers of preterm neonates less than or equal to 32 weeks of gestation and determine if the current level of VitD supplementation used for preterm neonates is appropriate. Design Prospective study from 10th May 2015 to 1st November 2016. Setting Neonatal Intensive Care Unit at the Canberra Hospital. Patients Mothers and their preterm neonates born less than or equal to 32 weeks gestation. Interventions Maternal VitD levels were obtained within 3-4 days following delivery. Neonatal VitD levels were obtained in the first 3-4 days of life, at 3-4 weeks of age, and at 6-8 weeks of age. Demographic data and data on VitD intake from parenteral nutrition, enteral feeds, and vitamin supplementation agents were collected. Results 70 neonates were enrolled into the study. Median gestation was 29 (27-30) weeks and median birth weight 1197 (971.2-1512.5) grams. Median maternal VitD level was 54.5 (36-70.7) nmol/L, median neonatal Vit D level at birth was 57 (42-70) nmol/L. Median Vit D level at 3 weeks and 6 weeks were 63.5 nmol/L (53-80.2) nmol/L and 103 (71.5-144) nmol/L respectively. 22/55 (40%) mothers were VitD deficient/insufficient. 25/70 (36%) neonates were VitD deficient/insufficient at birth. Of those neonates who were VitD deficient/insufficient at birth 5/25(10%) were deficient/insufficient at 6 weeks. The median intake of VitD at 6 weeks was 826.5 (577.5-939.5) IU/day. Conclusions VitD deficiency/insufficiency in mothers of preterm neonates and in preterm neonates at birth is common. Routine screening of maternal VitD and their preterm neonates along with individualized supplementation regimens in mothers and preterm infants may optimize VitD status and reduce risk of ongoing VitD deficiency/insufficiency