Photoproduction of π0 on Hydrogen With CLAS From 1.1 GeV - 5.45 GeV Using e+e –γ Decay

Photoproduction of the π0 meson was studied using the CLAS detector at the Thomas Jefferson National Accelerator Facility using tagged incident photon energies spanning the range Eγ = 1.1 GeV - 5.45 GeV. The measurement is performed on a liquid hydrogen target in the reaction γp → pe +e–(γ). The final state of the reaction is the sum of two subprocesses for π0 decay, the Dalitz decay mode of π0 → e +e–γ and conversion mode where one photon from π0 → γγ decay is converted into a e+e – pair. This specific final state reaction avoided limitations caused by single prompt track triggering, while the span of incident photon energies allowed for measurements of π0 photoproduction to a domain never systematically measured before. We report the measurement of the π0 differential cross sections dσ/dΩ and dσ/dt. The angular distributions agree well with the SAID parametrization for incident beam energies below 3 GeV. As a result with this new data, the χ2/p.d.f. of the global fit in the SAID parametrization improved to 3.1 from 3.7. For incident beam energies greater than 3 GeV a comparison of a model based on Generalized Parton Distributions (GPD) with experimental data shows significant discrepancy, requiring further model developments to describe the data

Morphology of the Esophageal Hiatus: Is It Different in 3 Types of Hiatus Hernias?

Background/aimsThe esophageal hiatus is formed by the right crus of the diaphragm in the majority of subjects. Contraction of the hiatus exerts a sphincter-like action on the lower esophageal sphincter (LES). The aim is to study the hiatal anatomy (using CT scan imaging) and function (using high-resolution manometry [HRM]), and esophageal motor function in patients with sliding and paraesophageal hiatal hernia.MethodsWe assessed normal subjects (n = 20), patients with sliding type 1 hernia (n = 18), paraesophageal type 2 hernia (n = 19), and mixed type 3 hernia (n = 19). Hernia diagnosis was confirmed on the upper gastrointestinal series. The hiatal morphology was constructed from the CT scan images. The LES pressure and relaxation, percent peristalsis, bolus pressure, and hiatal squeeze pressure were assessed by HRM.ResultsThe CT images revealed that the esophageal hiatus is formed by the right crus of the diaphragm in all normal subjects and 86% of hernia patients. The hiatus is elliptical in shape with a surface area of 1037 mm2 in normal subjects. The hiatal dimensions were larger in patients compared to normal subjects. The HRM revealed impaired LES relaxation and higher bolus pressure in patients with paraesophageal compared to the sliding hernia. The hiatal pinch on HRM was recognized in significantly higher number of patients with sliding as compared to paraesophageal hernia.ConclusionsUsing a novel approach, we provide details of the esophageal hiatus in patients with various kinds of hiatal hernia. Impaired LES relaxation in paraesophageal hernia may play a role in its pathophysiology and genesis of symptoms

Towards Density Functional Approximations from Coupled Cluster Correlation Energy Densities

(Semi)local density functional approximations (DFAs) are the workhorse electronic structure methods in condensed matter theory and surface science. The correlation energy density ϵc(r) (a spatial function that yields the correlation energy Ec upon integration) is central to defining such DFAs. Unlike Ec, ϵc(r) is not uniquely defined, however. Indeed, there are infinitely many functions that integrate to the correct Ec for a given electron density ρ. The challenge for constructing useful DFAs is thus to find a suitable connection between ϵc(r) and ρ. Herein, we present a new such approach by deriving ϵc(r) directly from the coupled-cluster (CC) energy expression. The corresponding energy densities are analyzed for prototypical two-electron systems. As a proof-of-principle, we construct a semilocal functional to approximate the numerical CC correlation energy densities. Importantly, the energy densities are not simply used as reference data but guide the choice of the functional form, leading to a remarkably simple and accurate correlation functional for the helium isoelectronic series. While the resulting functional is not transferable to many-electron systems (due to a lack of same-spin correlation), these results underscore the potential of the presented approach

Chemokines and the Tissue-Specific Migration of Lymphocytes

AbstractTissue-selective trafficking of memory and effector T and B lymphocytes is mediated by unique combinations of adhesion molecules and chemokines. The discovery of several related epithelial-expressed chemokines (TECK/CCL25 in small intestine, CTACK/CCL27 in skin, and MEC/CCL28 in diverse mucosal sites) now highlights an important role for epithelial cells in controlling homeostatic lymphocyte trafficking, including the localization of cutaneous and intestinal memory T cells, and of IgA plasma cells. Consitutively expressed epithelial chemokines may help determine the character of local immune responses and contribute to the systemic organization of the immune system

Substrate-induced DNA strand misalignment during catalytic cycling by DNA polymerase λ

The simple deletion of nucleotides is common in many organisms. It can be advantageous when it activates genes beneficial to microbial survival in adverse environments, and deleterious when it mutates genes relevant to survival, cancer or degenerative diseases. The classical idea is that simple deletions arise by strand slippage. A prime opportunity for slippage occurs during DNA synthesis, but it remains unclear how slippage is controlled during a polymerization cycle. Here, we report crystal structures and molecular dynamics simulations of mutant derivatives of DNA polymerase λ bound to a primer–template during strand slippage. Relative to the primer strand, the template strand is in multiple conformations, indicating intermediates on the pathway to deletion mutagenesis. Consistent with these intermediates, the mutant polymerases generate single-base deletions at high rates. The results indicate that dNTP-induced template strand repositioning during conformational rearrangements in the catalytic cycle is crucial to controlling the rate of strand slippage

Artifact Rejection Methodology Enables Continuous, Noninvasive Measurement of Gastric Myoelectric Activity in Ambulatory Subjects.

The increasing prevalence of functional and motility gastrointestinal (GI) disorders is at odds with bottlenecks in their diagnosis, treatment, and follow-up. Lack of noninvasive approaches means that only specialized centers can perform objective assessment procedures. Abnormal GI muscular activity, which is coordinated by electrical slow-waves, may play a key role in symptoms. As such, the electrogastrogram (EGG), a noninvasive means to continuously monitor gastric electrical activity, can be used to inform diagnoses over broader populations. However, it is seldom used due to technical issues: inconsistent results from single-channel measurements and signal artifacts that make interpretation difficult and limit prolonged monitoring. Here, we overcome these limitations with a wearable multi-channel system and artifact removal signal processing methods. Our approach yields an increase of 0.56 in the mean correlation coefficient between EGG and the clinical "gold standard", gastric manometry, across 11 subjects (p < 0.001). We also demonstrate this system's usage for ambulatory monitoring, which reveals myoelectric dynamics in response to meals akin to gastric emptying patterns and circadian-related oscillations. Our approach is noninvasive, easy to administer, and has promise to widen the scope of populations with GI disorders for which clinicians can screen patients, diagnose disorders, and refine treatments objectively