Rare k-decays

This article reviews the current situation in the field of rare K decays: the relevant phenomenology, the present experimental situation, and prospects for the near future. Study of rare K decays can make a significant contribution in a number of different frontier areas of research in high-energy physics. In the area of CP violation, study of such rare decays as K(L)0 --> pi0e+e-, K(L)0 --> pi0mu+mu-, K(L)0 --> pi0nunuBAR, and muon polarization in K(L)0 --> mu+mu- can provide important complementary information to what has been learned from the decay K(L)0 --> pipi. Even though experiments with sufficient accuracy to make a meaningful study of CP violation are still a few years away, significant progress has been made in this general area during the last decade. A second major area of interest in the field of rare K decays is the search for processes forbidden in the Standard Model, e.g., K(L)0 --> mue and K+ --> pi+mu+e-. Various extensions of the Standard Model predict that these processes will occur with branching fractions in the range of 10(-10) to 10(-15). Experiments of the last decade have pushed the limits into the 10(-10) to 10(-11) range, and further improvements in sensitivity of one to two orders of magnitude can be expected in the next few years. K decays allow one also to study higher-order weak-interaction processes such as K(L)0 --> mu+mu-, K(L)0 --> e+e-, K+ --> pi+nunuBAR, which are forbidden to first order in the Standard Model. Because of strong suppression, these decay modes offer potential windows on new physics; in addition, they may offer the most reliable measurement of V(td), one of the elements of the weak mixing matrix in the quark sector. The studies of the mu+mu- channel have achieved data samples of close to 1000 events; the other two modes should be observed for the first time in the next few years. Finally, as a byproduct of these studies, one has been able to look simultaneously for new light particles into which the K meson could decay. Limits obtained for various hypothetical particles are summarized.Physic

The Dependence of Coronal Loop Heating on the Characteristics of Slow Photospheric Motions

The Parker hypothesis (Parker (1972)) assumes that heating of coronal loops occurs due to reconnection, induced when photospheric motions braid field lines to the point of current sheet formation. In this contribution we address the question of how the nature of photospheric motions affects heating of braided coronal loops. We design a series of boundary drivers and quantify their properties in terms of complexity and helicity injection. We examine a series of long-duration full resistive MHD simulations in which a simulated coronal loop, consisting of initially uniform field lines, is subject to these photospheric flows. Braiding of the loop is continually driven until differences in behaviour induced by the drivers can be characterised. It is shown that heating is crucially dependent on the nature of the photospheric driver - coherent motions typically lead to fewer large energy release events, while more complex motions result in more frequent but less energetic heating events

Socioeconomic inequalities in childhood exposure to secondhand smoke before and after smoke-free legislation in three UK countries

Background: Secondhand smoke (SHS) exposure is higher among lower socioeconomic status (SES) children. Legislation restricting smoking in public places has been associated with reduced childhood SHS exposure and increased smoke-free homes. This paper examines socioeconomic patterning in these changes.<p></p> Methods: Repeated cross-sectional survey of 10 867 schoolchildren in 304 primary schools in Scotland, Wales and Northern Ireland. Children provided saliva for cotinine assay, completing questionnaires before and 12 months after legislation.<p></p> Results: SHS exposure was highest, and private smoking restrictions least frequently reported, among lower SES children. Proportions of saliva samples containing <0.1 ng/ml (i.e. undetectable) cotinine increased from 31.0 to 41.0%. Although across the whole SES spectrum, there was no evidence of displacement of smoking into the home or increased SHS exposure, socioeconomic inequality in the likelihood of samples containing detectable levels of cotinine increased. Among children from the poorest families, 96.9% of post-legislation samples contained detectable cotinine, compared with 38.2% among the most affluent. Socioeconomic gradients at higher exposure levels remained unchanged. Among children from the poorest families, one in three samples contained > 3 ng/ml cotinine. Smoking restrictions in homes and cars increased, although socioeconomic patterning remained.<p></p> Conclusions Urgent action is needed to reduce inequalities in SHS exposure. Such action should include emphasis on reducing smoking in cars and homes

Experimental position-time entanglement with degenerate single photons

We report an experiment in which two-photon interference occurs between degenerate single photons that never meet. The two photons travel in opposite directions through our fibre-optic interferometer and interference occurs when the photons reach two different, spatially separated, 2-by-2 couplers at the same time. We show that this experiment is analogous to the conventional Franson-type entanglement experiment where the photons are entangled in position and time. We measure wavefunction overlaps for the two photons as high as 94 $\pm$ 3%.Comment: Updated to published version, new fig. 4., corrected typo

Analysis of a short tail type in farmed Atlantic salmon (Salmo salar)

The short tail phenotype represents one of the main causes for downgrading of farmed Atlantic salmon (Salmo salar) at slaughterhouses. Prevalence of short tail is variable and the aetiology is suspected to be multi-factorial. Risk factors have been identified but descriptions of the aetiology and the pathology of the condition are still rare. In the current study, a radiological and histological analysis of short tails has been performed, examining six normal and six downgraded individuals from a slaughterhouse in southern Norway. In the short tail phenotype, vertebral bodies were shifted and bent at the contact zone of adjacent vertebral bodies. Changes either affected the entire spine or were located at the medial caudal-spine. While the internal bone structure of the vertebrae was similar in deformed and non-deformed animals, a lack of intervertebral space apparently caused a shortening of the vertebral column and corresponded to an elevated condition factor in deformed individuals. Histological analysis revealed different degrees of proliferation of cartilaginous tissues, which replaced the intervertebral notochord tissue. The displacement of adjacent vertebral bodies and the development of cartilage in between vertebral bodies suggest mechanical forces as a possible cause for the observed deformations, since mechanically-induced overload and a subsequent direct contact of bones are factors that can stimulate heterotopic cartilage development and pseudoarthrosi

Analysis of lead levels in deciduous teeth from children in Clark County, Nevada.

Background: Elevated blood lead levels (EBLL) are declining in the United States, although some population subgroups continue to exhibit significant health disparities. A childhood lead poisoning prevention program was recently started in Nevada, and many efforts have been made to support this program and increase the screening rates. Methods: To expand the potential pool of children screened for EBLLs, a pilot study was performed to evaluate lead concentrations in extracted deciduous teeth using Graphic Furnace Atomic Absorption Spectrometry (GFAAS), Inductively Coupled Plasma Mass Spectrometry (ICP-MS), and X-Ray Fluorescence (XRF) analysis. Results: Lead concentrations as determined by GFAAS and ICP-MS were found to be within normal ranges (0.585 ppm ± 0.022) and were similar to previous studies. Hispanic patients exhibited higher lead levels (0.580 ppm ± 0.032) than Black (0.478 ppm ± 0.051) patients, and were significantly higher than White (0.275 ppm ± 0.035) patients (p \u3c 0.05). Analysis of a small number of matched saliva samples, however, found no evidence for acute lead poisoning. Although limited by a small initial sample size (n=22), this pilot study provides evidence that teeth can be effectively used to reveal lead exposure in pediatric dentistry patients

ATRX is Required for Maintenance of the Neuroprogenitor Cell Pool in the Embryonic Mouse Brain

Mutations in the alpha-thalassemia mental retardation X-linked (ATRX) gene cause a spectrum of abnormalities including intellectual disability, developmental delay, seizures, and microcephaly. The ATRX protein is highly enriched at heterochromatic repetitive sequences adjacent to the centromere, and ATRX depletion results in chromosome congression, segregation, and cohesion defects. Here, we show that Cre-mediated inactivation of Atrx in the embryonic mouse (Mus musculus) brain results in expansion of cerebral cortical layer VI, and a concurrent thinning of layers II-IV. We observed increased cell cycle exit during early-mid neurogenesis, and a depletion of apical progenitors by late neurogenesis in the Atrx-null neocortex, explaining the disproportionate layering. Premature differentiation was associated with an increased generation of outer radial glia (oRG) and TBR2-expressing basal progenitors, as well as increased generation of early-born post-mitotic projection neurons. Atrx deletion also reduced the fidelity of mitotic spindle orientation in apical progenitors, where mutant cells were often oriented at non-parallel angles of division relative to the ventricular surface. We conclude that ATRX is required for correct lamination of the mouse neocortex by regulating the timing of neuroprogenitor cell differentiation