Measurement of the Neutron Radius of Pb-208 through Parity Violation in Electron Scattering

We report the first measurement of the parity-violating asymmetry A(PV) in the elastic scattering of polarized electrons from Pb-208. APV is sensitive to the radius of the neutron distribution (R-n). The result A(PV) = 0.656 +/- 0.060(stat) +/- 0.014(syst) ppm corresponds to a difference between the radii of the neutron and proton distributions R-n - R-p = 0.33(-0.18)(+0.16) fm and provides the first electroweak observation of the neutron skin which is expected in a heavy, neutron-rich nucleus

Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to Q^2 = 8.5 GeV^2

Among the most fundamental observables of nucleon structure, electromagnetic form factors are a crucial benchmark for modern calculations describing the strong interaction dynamics of the nucleon's quark constituents; indeed, recent proton data have attracted intense theoretical interest. In this letter, we report new measurements of the proton electromagnetic form factor ratio using the recoil polarization method, at momentum transfers Q2=5.2, 6.7, and 8.5 GeV2. By extending the range of Q2 for which GEp is accurately determined by more than 50%, these measurements will provide significant constraints on models of nucleon structure in the non-perturbative regime

Measurement of the Neutron Radius of 208Pb Through Parity-Violation in Electron Scattering

We report the first measurement of the parity-violating asymmetry A_PV in the elastic scattering of polarized electrons from 208Pb. A_PV is sensitive to the radius of the neutron distribution (Rn). The result A_PV = 0.656 \pm 0.060 (stat) \pm 0.014 (syst) ppm corresponds to a difference between the radii of the neutron and proton distributions Rn - Rp = 0.33 +0.16 -0.18 fm and provides the first electroweak observation of the neutron skin which is expected in a heavy, neutron-rich nucleus.Comment: 6 pages, 1 figur

Protein-Tyrosine Kinase Activity Profiling in Knock Down Zebrafish Embryos

BACKGROUND: Protein-tyrosine kinases (PTKs) regulate virtually all biological processes. PTKs phosphorylate substrates in a sequence-specific manner and relatively short peptide sequences determine selectivity. Here, we developed new technology to determine PTK activity profiles using peptide arrays. The zebrafish is an excellent model system to investigate signaling in the whole organism, given its wealth of genetic tools, including morpholino-mediated knock down technology. We used zebrafish embryo lysates to determine PTK activity profiles, thus providing the unique opportunity to directly compare the effect of protein knock downs on PTK activity profiles on the one hand and phenotypic changes on the other. METHODOLOGY: We used multiplex arrays of 144 distinct peptides, spotted on a porous substrate, allowing the sample to be pumped up and down, optimizing reaction kinetics. Kinase reactions were performed using complex zebrafish embryo lysates or purified kinases. Peptide phosphorylation was detected by fluorescent anti-phosphotyrosine antibody binding and the porous chips allowed semi-continuous recording of the signal. We used morpholinos to knock down protein expression in the zebrafish embryos and subsequently, we determined the effects on the PTK activity profiles. RESULTS AND CONCLUSION: Reproducible PTK activity profiles were derived from one-day-old zebrafiish embryos. Morpholino-mediated knock downs of the Src family kinases, Fyn and Yes, induced characteristic phenotypes and distinct changes in the PTK activity profiles. Interestingly, the peptide substrates that were less phosphorylated upon Fyn and Yes knock down were preferential substrates of purified Fyn and Yes. Previously, we demonstrated that Wnt11 knock down phenocopied Fyn/Yes knock down. Interestingly, Wnt11 knock down induced similar changes in the PTK activity profile as Fyn/Yes knock down. The control Nacre/Mitfa knock down did not affect the PTK activity profile significantly. Our results indicate that the novel peptide chip technology can be used to unravel kinase signaling pathways in vivo

Good agreement of conventional and gel-based direct agglutination test in immune-mediated haemolytic anaemia

<p>Abstract</p> <p>Background</p> <p>The aim of this study was to compare a gel-based test with the traditional direct agglutination test (DAT) for the diagnosis of immune-mediated haemolytic anaemia (IMHA).</p> <p>Methods</p> <p>Canine (n = 247) and feline (n = 74) blood samples were submitted for DAT testing to two laboratories. A subset of canine samples was categorized as having idiopathic IMHA, secondary IMHA, or no IMHA.</p> <p>Results</p> <p>The kappa values for agreement between the tests were in one laboratory 0.86 for canine and 0.58 for feline samples, and in the other 0.48 for canine samples. The lower agreement in the second laboratory was caused by a high number of positive canine DATs for which the gel test was negative. This group included significantly more dogs with secondary IMHA.</p> <p>Conclusions</p> <p>The gel test might be used as a screening test for idiopathic IMHA and is less often positive in secondary IMHA than the DAT.</p

Concentric “microwaves” of Henle's fiber layer: Associated with horizontal folding

Concentric “microwaves” in Henle's fiber layer are found in a case of extensive horizontal folding in the fundus due to tumor pressure on the globe from behind. In addition to horizontal folding of inner choroid and inner retina between disk and fovea, somewhat irregular vertical folds are found next to the fovea in the inner retinal layers. The concentric waves of Henle's fiber layer are a new observation and they are suspected to be a protective adjustment of the central retina to minimize distortion of the foveola. Konzentrische Mikrowellen in Henle's Faserschicht werden in einem Fall von horizontaler Faeltelung im Augenhintergrund bei Tumordruck von hinten dargestellt. Zusätzlich zu horizontalen Falten der Aderhaut und Netzhaut zwischen Sehnerv und Fovea werden leicht unregelmäßige vertikale Falten der inneren Netzhaut im Foveabereich gefunden. Die konzentrischen Mikrowellen in Henle's Faserschicht sind eine neue Beobachtung und dieselben könnten eine mechanische Anpassung der zentralen Netzhaut zur Vermeidung von Verzerrung der Fovea darstellen.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47370/1/417_2004_Article_BF00407774.pd

Somatic health among heroin addicts before and during opioid maintenance treatment: a retrospective cohort study

<p>Abstract</p> <p>Background</p> <p>The long-term impact of opioid maintenance treatment (OMT) on morbidity and health care utilization among heroin addicts has been insufficiently studied. The objective of this study was to investigate whether health care utilization due to somatic disease decreased during OMT, and if so, whether the reduction included all kinds of diseases and whether a reduction was related to abstinence from drug use.</p> <p>Methods</p> <p>Cohort study with retrospective registration of somatic disease incidents (health problems, acute or sub-acute, or acute problems related to chronic disease, resulting in a health care contact). Medical record data were collected from hospitals, Outpatients' Departments, emergency wards and from general practitioners (GPs) and prospective data on substance use during OMT were available from 2001 onwards. The observation period was five years before and up to five years during OMT. The cohort consisted of 35 out of 40 patients who received OMT between April 1999 and January 2005 in a Norwegian district town. Statistical significance concerning changes in number of incidents and inpatient and outpatient days during OMT compared with the pre OMT period was calculated according to Wilcoxon signed rank test. Significance concerning pre/during OMT changes in disease incidents by relation to the type of health service contacts, as well as the impact of ongoing substance use during OMT on the volume of contacts, was calculated according to Pearson chi-square and Fisher's exact tests.</p> <p>Results</p> <p>278 disease incidents were registered. There was a reduction in all incidents by 35% (p = 0.004), in substance-related incidents by 62% (p < 0.001) and in injection-related incidents by 70% (p < 0.001). There was an insignificant reduction in non-fatal overdose incidents by 44% (p = 0.127) and an insignificant increase in non-substance-related incidents by 13% (p = 0.741). Inpatient and outpatient days were reduced by 76% (p = 0.003) and 46% (p = 0.060), respectively. The disease incidents were less often drug-related during OMT (p < 0.001). Patients experienced a reduction in substance-related disease incidents regardless of ongoing substance use, however there was a trend towards greater reductions in those without ongoing abuse.</p> <p>Conclusion</p> <p>Although as few as 35 patients were included, this study demonstrates a significant reduction in health care utilization due to somatic disease incidents during OMT. The reduction was most pronounced for incidents related to substance use and injection. Inpatient and outpatient days were reduced. Most probably these findings reflect somatic health improvement among heroin addicts during OMT.</p

First discovery of Holocene cryptotephra in Amazonia

The use of volcanic ash layers for dating and correlation (tephrochronology) is widely applied in the study of past environmental changes. We describe the first cryptotephra (non-visible volcanic ash horizon) to be identified in the Amazon basin, which is tentatively attributed to a source in the Ecuadorian Eastern Cordillera (0–1°S, 78-79°W), some 500-600 km away from our field site in the Peruvian Amazon. Our discovery 1) indicates that the Amazon basin has been subject to volcanic ash fallout during the recent past; 2) highlights the opportunities for using cryptotephras to date palaeoenvironmental records in the Amazon basin and 3) indicates that cryptotephra layers are preserved in a dynamic Amazonian peatland, suggesting that similar layers are likely to be present in other peat sequences that are important for palaeoenvironmental reconstruction. The discovery of cryptotephra in an Amazonian peatland provides a baseline for further investigation of Amazonian tephrochronology and the potential impacts of volcanism on vegetation

Sea-ice dynamics in an Arctic coastal polynya during the past 6500 years

The production of high-salinity brines during sea-ice freezing in circum-arctic coastal polynyas is thought to be part of northern deep water formation as it supplies additional dense waters to the Atlantic meridional overturning circulation system. To better predict the effect of possible future summer ice-free conditions in the Arctic Ocean on global climate, it is important to improve our understanding of how climate change has affected sea-ice and brine formation, and thus finally dense water formation during the past. Here, we show temporal coherence between sea-ice conditions in a key Arctic polynya (Storfjorden, Svalbard) and patterns of deep water convection in the neighbouring Nordic Seas over the last 6500 years. A period of frequent sea-ice melting and freezing between 6.5 and 2.8 ka BP coincided with enhanced deep water renewal in the Nordic Seas. Near-permanent sea-ice cover and low brine rejection after 2.8 ka BP likely reduced the overflow of high-salinity shelf waters, concomitant with a gradual slow down of deep water convection in the Nordic Seas, which occurred along with a regional expansion in sea-ice and surface water freshening. The Storfjorden polynya sea-ice factory restarted at ~0.5 ka BP, coincident with renewed deep water penetration to the Arctic and climate amelioration over Svalbard. The identified synergy between Arctic polynya sea-ice conditions and deep water convection during the present interglacial is an indication of the potential consequences for ocean ventilation during states with permanent sea-ice cover or future Arctic ice-free conditions

Search for effects beyond the Born approximation in polarization transfer observables in e⃗p\vec{e}p elastic scattering

Intensive theoretical and experimental efforts over the past decade have aimed at explaining the discrepancy between data for the proton electric to magnetic form factor ratio, $G_{E}/G_{M}$, obtained separately from cross section and polarization transfer measurements. One possible explanation for this difference is a two-photon-exchange (TPEX) contribution. In an effort to search for effects beyond the one-photon-exchange or Born approximation, we report measurements of polarization transfer observables in the elastic $H(\vec{e},e'\vec{p})$ reaction for three different beam energies at a fixed squared momentum transfer $Q^2 = 2.5$ GeV$^2$, spanning a wide range of the virtual photon polarization parameter, $\epsilon$. From these measured polarization observables, we have obtained separately the ratio $R$, which equals $\mu_p G_{E}/G_{M}$ in the Born approximation, and the longitudinal polarization transfer component $P_\ell$, with statistical and systematic uncertainties of \Delta R \approx \pm 0.01 \mbox{(stat)} \pm 0.013 \mbox{(syst)} and \Delta P_\ell/P^{Born}_{\ell} \approx \pm 0.006 \mbox{(stat)}\pm 0.01 \mbox{(syst)}. The ratio $R$ is found to be independent of $\epsilon$ at the 1.5% level, while the $\epsilon$ dependence of $P_\ell$ shows an enhancement of $(2.3 \pm 0.6)$ relative to the Born approximation at large $\epsilon$