495 research outputs found

    Confinement and scaling in deep inelastic scattering

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    We show that parton confinement in the final state generates large 1/Q21/Q^2 corrections to Bjorken scaling, thus leaving less room for the logarithmic corrections. In particular, the xx-scaling violations at large xx are entirely described in terms of power corrections. For treatment of these non-perturbative effects, we derive a new expansion in powers of 1/Q21/Q^2 for the structure function that is free of infra-red singularities and which reduces corrections to the leading term. The leading term represents scattering from an off-mass-shell parton, which keeps the same virtual mass in the final state. It is found that this quasi-free term is a function of a new variable xˉ\bar x, which coincides with the Bjorken variable xx for Q2→∞Q^2\to\infty. The two variables are very different, however, at finite Q2Q^2. In particular, the variable xˉ\bar x depends on the invariant mass of the spectator particles. Analysis of the data at large xx shows excellent scaling in the variable xˉ\bar x, and determines the value of the diquark mass to be close to zero. xˉ\bar x-scaling allows us to extract the structure function near the elastic threshold. It is found to behave as F2∼(1−x)3.7F_2\sim (1-x)^{3.7}. Predictions for the structure functions based on xˉ\bar x-scaling are made.Comment: Discussion of target mass corrections is added. Accepted for publication in Phys. Rev.

    Immunogenicity negatively influences the outcome of adalimumab treatment in Crohn's disease

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    Background: Adalimumab is an effective treatment in patients with Crohn's disease; as it is a humanized anti-tumour necrosis factor monoclonal antibody, immunogenicity is thought not to be of any significance. Aim: To assess whether antibodies to adalimumab (ATAs) affect adalimumab treatment outcome in patients with Crohn's disease previously treated with infliximab. Methods: A retrospective study was p

    Perturbative QCD and factorization of coherent pion photoproduction on the deuteron

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    We analyze the predictions of perturbative QCD for pion photoproduction on the deuteron, gamma D -> pi^0 D, at large momentum transfer using the reduced amplitude formalism. The cluster decomposition of the deuteron wave function at small binding only allows the nuclear coherent process to proceed if each nucleon absorbs an equal fraction of the overall momentum transfer. Furthermore, each nucleon must scatter while remaining close to its mass shell. Thus the nuclear photoproduction amplitude, M_{gamma D -> pi^0 D}(u,t), factorizes as a product of three factors: (1) the nucleon photoproduction amplitude, M_{gamma N_1 -> pi^0 N_1}(u/4,t/4), at half of the overall momentum transfer, (2) a nucleon form factor, F_{N_2}(t/4), at half the overall momentum transfer, and (3) the reduced deuteron form factor, f_d(t), which according to perturbative QCD, has the same monopole falloff as a meson form factor. A comparison with the recent JLAB data for gamma D -> pi^0 D of Meekins et al. [Phys. Rev. C 60, 052201 (1999)] and the available gamma p -> pi^0 p data shows good agreement between the perturbative QCD prediction and experiment over a large range of momentum transfers and center of mass angles. The reduced amplitude prediction is consistent with the constituent counting rule, p^11_T M_{gamma D -> pi^0 D} -> F(theta_cm), at large momentum transfer. This is found to be consistent with measurements for photon lab energies E_gamma > 3 GeV at theta_cm=90 degrees and \elab > 10 GeV at 136 degrees.Comment: RevTeX 3.1, 17 pages, 6 figures; v2: incorporates minor changes as version accepted by Phys Rev

    A purely algebraic construction of a gauge and renormalization group invariant scalar glueball operator

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    This paper presents a complete algebraic proof of the renormalizability of the gauge invariant d=4d=4 operator Fμν2(x)F_{\mu\nu}^2(x) to all orders of perturbation theory in pure Yang-Mills gauge theory, whereby working in the Landau gauge. This renormalization is far from being trivial as mixing occurs with other d=4d=4 gauge variant operators, which we identify explicitly. We determine the mixing matrix ZZ to all orders in perturbation theory by using only algebraic arguments and consequently we can uncover a renormalization group invariant by using the anomalous dimension matrix Γ\Gamma derived from ZZ. We also present a future plan for calculating the mass of the lightest scalar glueball with the help of the framework we have set up.Comment: 17 page

    Limited added value of laboratory monitoring in thiopurine maintenance monotherapy in inflammatory bowel disease patients

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    Background: To timely detect myelotoxicity and hepatotoxicity, laboratory monitoring at 3-month intervals is advised throughout thiopurine maintenance treatment for IBD. However, reported incidence rates of myelotoxicity and hepatotoxicity in maintenance treatment are low. Aim: To assess incidence rates and clinical consequences of myelotoxicity and hepatotoxicity in thiopurine maintenance therapy after at least 1 year of thiopurine treatment. Methods: Retrospective analysis of therapy adjustment for laboratory toxicity in adult IBD patients after 12 consecutive months of azathioprine (AZA) or mercaptopurine monotherapy (ie baseline) between 2000 and 2016. Incidence rates of laboratory toxicity (ie myelotoxicity [leucocyte count <4.0 × 10e9/L, and/or platelet count <150 × 10e9/L] and/or hepatotoxicity (gamma-glutamyltransferase [GGT], alkaline phosphatase [AP], ALT and/or AST above ULN, excluding isolated increased AST/AP]) and associated diagnostic procedures and complications were assessed. Results: In total, 12.391 laboratory assessments were performed on 1132 patients (56% female, AZA 74%) during 3.3 years of median follow-up. Median monitoring frequency was 3.1 assessments/treatment year. Only 83/12.391 (0.7%) assessments resulted in therapy adjustment, dose reduction in 46 patients, cessation in 28 and allopurinol initiation in nine; risk of therapy adjustment was 1.9% per treatment year. Incidence rates of myelotoxicity were 7.1% (5.1% mild/1.8% moderate/0.1% severe) and hepatotoxicity 5.1% (3.8% mild/1.1% moderate/0.2% severe) per treatment year. Treatment-related complications with concurrent laboratory toxicity occurred in 12 patients (1.1%) and would not have been prevented by monitoring. Conclusion: Severe laboratory toxicity is uncommon after 1 year of thiopurine monotherapy at 4-month monitoring intervals. Therapy adjustments are rare after detection of laboratory toxicity. After 1 year of thiopurine monotherapy, laboratory monitoring may be lowered to less than a 4-month interval

    Neutron structure function and inclusive DIS from H-3 and He-3 at large Bjorken-x

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    A detailed study of inclusive deep inelastic scattering (DIS) from mirror A = 3 nuclei at large values of the Bjorken variable x is presented. The main purpose is to estimate the theoretical uncertainties on the extraction of the neutron DIS structure function from such nuclear measurements. On one hand, within models in which no modification of the bound nucleon structure functions is taken into account, we have investigated the possible uncertainties arising from: i) charge symmetry breaking terms in the nucleon-nucleon interaction, ii) finite Q**2 effects neglected in the Bjorken limit, iii) the role of different prescriptions for the nucleon Spectral Function normalization providing baryon number conservation, and iv) the differences between the virtual nucleon and light cone formalisms. Although these effects have been not yet considered in existing analyses, our conclusion is that all these effects cancel at the level of ~ 1% for x < 0.75 in overall agreement with previous findings. On the other hand we have considered several models in which the modification of the bound nucleon structure functions is accounted for to describe the EMC effect in DIS scattering from nuclei. It turns out that within these models the cancellation of nuclear effects is expected to occur only at a level of ~ 3%, leading to an accuracy of ~ 12 % in the extraction of the neutron to proton structure function ratio at x ~ 0.7 -0.8$. Another consequence of considering a broad range of models of the EMC effect is that the previously suggested iteration procedure does not improve the accuracy of the extraction of the neutron to proton structure function ratio.Comment: revised version to appear in Phys. Rev. C; main modifications in Section 4; no change in the conclusion

    A two-component pre-seeded dermal-epidermal scaffold

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    We have developed a bilayered dermal-epidermal scaffold for application in the treatment of full-thickness skin defects. The dermal component gels in situ and adapts to the lesion shape, delivering human dermal fibroblasts in a matrix of fibrin and cross-linked hyaluronic acid modified with a cell adhesion-promoting peptide. Fibroblasts were able to form a tridimensional matrix due to material features such as tailored mechanical properties, presence of protease-degradable elements and cell-binding ligands. The epidermal component is a robust membrane containing cross-linked hyaluronic acid and poly-l-lysine, on which keratinocytes were able to attach and to form a monolayer. Amine-aldehyde bonding at the interface between the two components allows the formation of a tightly bound composite scaffold. Both parts of the scaffold were designed to provide cell-type-specific cues to allow for cell proliferation and form a construct that mimics the skin environment.D.S.K. acknowledges funding from the Biotechnology Research Endowment from the Department of Anesthesiology at Boston Children's Hospital. I.P.M. acknowledges the Portuguese Foundation for Science and Technology for the grant BD/39396/2007 and the MIT-Portugal Program. D.G. acknowledges the Swiss National Science Foundation for a post-doctoral fellowship (PBGEP3-129111). B.P.T. acknowledges an NIR Ruth L. Kirschstein National Research Service Award (F32GM096546)

    [Accepted Manuscript] Anthropometry and Malaria among Children in Niger: A Cross-Sectional Study.

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    The complex relationship between malnutrition and malaria affects morbidity and mortality in children younger than 5 years, particularly in parts of sub-Saharan Africa where these conditions occur together seasonally. Previous research on this relationship has been inconclusive. Here, we examine the association between anthropometric indicators and malaria infection in a population-based sample of children younger than 5 years in Niger. This cross-sectional study is a secondary analysis of a cluster-randomized trial comparing treatment strategies for trachoma in Niger. We included children aged 6-60 months residing in the 48 communities enrolled in the trial who completed anthropometric and malaria infection assessments at the final study visit. We evaluated the association between anthropometric indicators, including height-for-age z-score (HAZ) and weight-for-age z-score (WAZ) and indicators of malaria infection, including malaria parasitemia and clinical malaria. In May 2013, we collected data from 1,649 children. Of these, 780 (47.3%) were positive for malaria parasitemia and 401 (24.3%) had clinical malaria. In models of malaria parasitemia, the adjusted odds ratio (aOR) was 1.05 (95% confidence interval [CI]: 1.00-1.10) for HAZ and 1.07 (95% CI: 0.99, 1.15) for WAZ. In models of clinical malaria, the aOR was 1.07 (95% CI: 1.02-1.11) for HAZ and 1.09 (95% CI: 1.01-1.19) for WAZ. Overall, we did not find evidence of an association between most anthropometric indicators and malaria infection. Greater height may be associated with an increased risk of clinical malaria

    Readmissions after general surgery: a prospective multicenter audit

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    Background: Readmission rates after surgical procedures are viewed as a marker of quality of care and as a driver to improve outcomes in the United Kingdom, they are not remunerated. However, readmissions are not wholly avoidable. The aim of this study was to develop a regional overview of readmissions to determine the proportion that might be avoidable and to examine predictors of readmissions at a unit level. Methods: We undertook a prospective multicenter audit of readmissions following National Health Service funded general surgical procedures in five National Health Service hospitals and three independent sector providers over a 2-wk period. Basic demographic and procedure data were captured. Readmissions to hospitals were identified through acute admissions lists. Reason for readmission was identified, and the readmission data assessed by a senior surgical doctor as to whether it was avoidable. Results: We identified 752 operations in the study period with all followed up to 30 d. The overall rate of readmissions was 4.7%, with 40% of these judged as being potentially avoidable. Pain and wound problems accounted for the vast majority of avoidable readmissions. The number of unavoidable readmissions was correlated with the workload of each center (r ¼ 0.63, P ¼ 0.06) and as with the higher (British United Provident Association) complexity of surgery (r ¼ 0.90, P ¼ 0.01). Patient and demographic factors were not associated with readmissions. Conclusions: This prospective audit describes readmission rates after general surgery. Volume and complexity of work are associated with readmission rates. A large proportion of readmissions could be reduced by attention to analgesia and outpatient arrangements for wound management
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