Universality in edge-source diffusion dynamics

We show that in edge-source diffusion dynamics the integrated concentration N(t) has a universal dependence with a characteristic time-scale tau=(A/P)^2 pi/(4D), where D is the diffusion constant while A and P are the cross-sectional area and perimeter of the domain, respectively. For the short-time dynamics we find a universal square-root asymptotic dependence N(t)=N0 sqrt(t/tau) while in the long-time dynamics N(t) saturates exponentially at N0. The exponential saturation is a general feature while the associated coefficients are weakly geometry dependent.Comment: 4 pages including 4 figures. Minor changes. Accepted for PR

Short Bowel Patients Treated for Two Years with Glucagon-Like Peptide 2 (GLP-2): Compliance, Safety, and Effects on Quality of Life

Background and aims. Glucagon-like peptide 2 (GLP-2) has been shown to improve intestinal absorption in short bowel syndrome (SBS) patients in a short-term study. This study describes safety, compliance, and changes in quality of life in 11 SBS patients at baseline, week 13, 26, and 52 during two years of subcutaneous GLP-2 treatment, 400 microgram TID, intermitted by an 8-week washout period. Methods. Safety and compliance was evaluated during the admissions. The Sickness Impact Profile (SIP), Short Form 36 (SF 36), and Inflammatory Bowel Disease Questionnaire (IBDQ) evaluated quality of life. Results. The predominant adverse event was transient abdominal discomfort in 5 of 11 patients, but in 2, both suffering from Crohns disease, it progressed to abdominal pain and led to discontinuation of GLP-2 treatment. One had a fibrostenotic lesion electively resected at the jejuno-ascendo-anastomosis. The investigator excluded a patient due to unreliable feedback. Stoma nipple enlargement was seen in all 9 jejunostomy patients. Reported GLP-2 compliance was excellent (>93%). GLP-2 improved the overall quality of life VAS-score (4.1 ± 2.8 cm versus 6.0 ± 2.4 cm, P < .01), the overall SIP score (10.3 ± 8.9% versus 6.2 ± 9.5%, P < .001), the mental component of the SF-36 (45 ± 13% versus 53 ± 11%, P < .05), and the overall IBDQ score (5.1 ± 0.9 versus 5.4 ± 0.9, P < .007) in the 8 patients completing the study. Conclusions. Long-term treatment with GLP-2 is feasible in SBS patients, although caution must be exercised in patients with a history of abdominal pain. Although conclusions cannot be made in a noncontrolled trial, the high reported compliance might reflect a high treatment satisfaction, where the clinical benefits of GLP-2 may outweigh the discomforts of injections

Short Bowel Patients Treated for Two Years with Glucagon-Like Peptide 2: Effects on Intestinal Morphology and Absorption, Renal Function, Bone and Body Composition, and Muscle Function

Background and aims. In a short-term study, Glucagon-like peptide 2 (GLP-2) has been shown to improve intestinal absorption in short bowel syndrome (SBS) patients. This study describes longitudinal changes in relation to GLP-2 treatment for two years. Methods. GLP-2, 400 micrograms, s.c.,TID, were offered, to eleven SBS patients keeping parenteral support constant. 72-hour nutritional balance studies were performed at baseline, weeks 13, 26, 52 during two years intermitted by an 8-week washout period. In addition, mucosal morphometrics, renal function (by creatinine clearance), body composition and bone mineral density (by DEXA), biochemical markers of bone turnover (by s-CTX and osteocalcin, PTH and vitamin D), and muscle function (NMR, lungfunction, exercise test) were measured. Results. GLP-2 compliance was >93%. Three of eleven patients did not complete the study. In the remaining 8 patients, GLP-2 significantly reduced the fecal wet weight from approximately 3.0 to approximately 2.0 kg/day. This was accompanied by a decline in the oral wet weight intake, maintaining intestinal wet weight absorption and urinary weight constant. Renal function improved. No significant changes were demonstrated in energy intake or absorption, and GLP-2 did not significantly affect mucosal morphology, body composition, bone mineral density or muscle function. Conclusions. GLP-2 treatment reduces fecal weight by approximately 1000 g/d and enables SBS patients to maintain their intestinal fluid and electrolyte absorption at lower oral intakes. This was accompanied by a 28% improvement in creatinine clearance

A real-space grid implementation of the Projector Augmented Wave method

A grid-based real-space implementation of the Projector Augmented Wave (PAW) method of P. E. Blochl [Phys. Rev. B 50, 17953 (1994)] for Density Functional Theory (DFT) calculations is presented. The use of uniform 3D real-space grids for representing wave functions, densities and potentials allows for flexible boundary conditions, efficient multigrid algorithms for solving Poisson and Kohn-Sham equations, and efficient parallelization using simple real-space domain-decomposition. We use the PAW method to perform all-electron calculations in the frozen core approximation, with smooth valence wave functions that can be represented on relatively coarse grids. We demonstrate the accuracy of the method by calculating the atomization energies of twenty small molecules, and the bulk modulus and lattice constants of bulk aluminum. We show that the approach in terms of computational efficiency is comparable to standard plane-wave methods, but the memory requirements are higher.Comment: 13 pages, 3 figures, accepted for publication in Physical Review

Propagation of Light in Photonic Crystal Fibre Devices

We describe a semi-analytical approach for three-dimensional analysis of photonic crystal fibre devices. The approach relies on modal transmission-line theory. We offer two examples illustrating the utilization of this approach in photonic crystal fibres: the verification of the coupling action in a photonic crystal fibre coupler and the modal reflectivity in a photonic crystal fibre distributed Bragg reflector.Comment: 15 pages including 7 figures. Accepted for J. Opt. A: Pure Appl. Op

Intershell resistance in multiwall carbon nanotubes: A Coulomb drag study

We calculate the intershell resistance R_{21} in a multiwall carbon nanotube as a function of temperature T and Fermi level (e.g. a gate voltage), varying the chirality of the inner and outer tubes. This is done in a so-called Coulomb drag setup, where a current I_1 in one shell induces a voltage drop V_2 in another shell by the screened Coulomb interaction between the shells neglecting the intershell tunnelling. We provide benchmark results for R_{21}=V_2/I_1 within the Fermi liquid theory using Boltzmann equations. The band structure gives rise to strongly chirality dependent suppression effects for the Coulomb drag between different tubes due to selection rules combined with mismatching of wave vector and crystal angular momentum conservation near the Fermi level. This gives rise to orders of magnitude changes in R_{21} and even the sign of R_{21} can change depending on the chirality of the inner and outer tube and misalignment of inner and outer tube Fermi levels. However for any tube combination, we predict a dip (or peak) in R_{21} as a function of gate voltage, since R_{21} vanishes at the electron-hole symmetry point. As a byproduct, we classified all metallic tubes into either zigzag-like or armchair-like, which have two different non-zero crystal angular momenta m_a, m_b and only zero angular momentum, respectively.Comment: 17 pages, 10 figure

Ultra-large bandwidth hollow-core guiding in all-silica Bragg fibers with nano-supports

We demonstrate a new class of hollow-core Bragg fibers that are composed of concentric cylindrical silica rings separated by nanoscale support bridges. We theoretically predict and experimentally observe hollow-core confinement over an octave frequency range. The bandwidth of bandgap guiding in this new class of Bragg fibers exceeds that of other hollow-core fibers reported in the literature. With only three rings of silica cladding layers, these Bragg fibers achieve propagation loss of the order of 1 dB/m.Comment: 9 pages including 5 figure

Having children with multiple partners is associated with reduced risk of malignant melanoma: an observation seeking a plausible explanation

Anne V Olesen1,2,3, Erik T Parner4, Preben B Mortensen5, Cecilia H Ramlau-Hansen6, J&amp;oslash;rn Olsen71Institute of Public Health, Department of Epidemiology, University of Aarhus; 2Unit for Psychiatric Research, Aalborg Psychiatric Hospital; 3Department of Clinical Epidemiology, Aarhus University Hospital; 4Institute of Public Health, Department of Biostatistics; 5National Centre for Register-based Research; 6Department of Occupational Medicine, Aarhus University Hospital, Denmark; 7Department of Epidemiology, School of Public Health, University of California, Los Angeles, USAObjective: We examined the association between the number of partners that mothers and fathers have children with and occurrence of cutaneous malignant melanoma (CMM).Methods: We conducted a complete registry-based follow-up of all Danish mothers born after 1935 from the birth of their second child until CMM, death, emigration, or end of study in 2002. We conducted a similar follow-up of the corresponding fathers. Incidence rate ratios (IRR) and confidence intervals (CI) were estimated by Poisson regression.Results: This study corroborates that women having children with three or more men are half as likely to have CMM as women who have children with one man: incidence rate ratio (IRR) = 0.51, 95% CI: 0.29, 0.91; having children by two fathers reduces risk among women by 20%: IRR = 0.80, 95% CI: 0.70, 0.91. Fathers with multiple partners tend to face a similar risk reduction.Conclusion: The similar patterns of mothers and fathers challenge us to consider and propose likely mechanisms common to both sexes. The patterns of reduced risk have now been reported in two large independent complete population-based studies in Sweden and Denmark.Keywords: malignant melanoma, epidemiology, children with multiple partner

Anomalous density of states in a metallic film in proximity with a superconductor

We investigated the local electronic density of states in superconductor-normal metal (Nb-Au) bilayers using a very low temperature (60 mK) STM. High resolution tunneling spectra measured on the normal metal (Au) surface show a clear proximity effect with an energy gap of reduced amplitude compared to the bulk superconductor (Nb) gap. Within this mini-gap, the density of states does not reach zero and shows clear sub-gap features. We show that the experimental spectra cannot be described with the well-established Usadel equations from the quasi-classical theory.Comment: 4 pages, 5 figure