Nanofriction behavior of cluster-assembled carbon films

We have characterized the frictional properties of nanostructured (ns) carbon films grown by Supersonic Cluster Beam Deposition (SCBD) via an Atomic Force-Friction Force Microscope (AFM-FFM). The experimental data are discussed on the basis of a modified Amonton's law for friction, stating a linear dependence of friction on load plus an adhesive offset accounting for a finite friction force in the limit of null total applied load. Molecular Dynamics simulations of the interaction of the AFM tip with the nanostructured carbon confirm the validity of the friction model used for this system. Experimental results show that the friction coefficient is not influenced by the nanostructure of the films nor by the relative humidity. On the other hand the adhesion coefficient depends on these parameters.Comment: 22 pages, 6 figures, RevTex

Scale-dependent angle of alignment between velocity and magnetic field fluctuations in solar wind turbulence

Under certain conditions, freely decaying magnetohydrodynamic (MHD) turbulence evolves in such a way that velocity and magnetic field fluctuations delta v and delta B approach a state of alignment in which delta v proportional to delta B. This process is called dynamic alignment. Boldyrev has suggested that a similar kind of alignment process occurs as energy cascades from large to small scales through the inertial range in strong incompressible MHD turbulence. In this study, plasma and magnetic field data from the Wind spacecraft, data acquired in the ecliptic plane near 1 AU, are employed to investigate the angle theta(tau) between velocity and magnetic field fluctuations in the solar wind as a function of the time scale tau of the fluctuations and to look for the scaling relation similar to tau(1/4) predicted by Boldyrev. We find that the angle appears to scale like a power law at large inertial range scales, but then deviates from power law behavior at medium to small inertial range scales. We also find that small errors in the velocity vector measurements can lead to large errors in the angle measurements at small time scales. As a result, we cannot rule out the possibility that the observed deviations from power law behavior arise from errors in the velocity measurements. When we fit the data from 2 x 10(3) s to 2 x 10(4) s with a power law of the form proportional to tau(p), our best fit values for p are in the range 0.27-0.36

Scale dependent alignment between velocity and magnetic field fluctuations in the solar wind and comparisons to Boldyrev's phenomenological theory

(Abridged abstract) A theory of incompressible MHD turbulence recently developed by Boldyrev predicts the existence of a scale dependent angle of alignment between velocity and magnetic field fluctuations that is proportional to the lengthscale of the fluctuations to the power 1/4. In this study, plasma and magnetic field data from the Wind spacecraft are used to investigate the angle between velocity and magnetic field fluctuations in the solar wind as a function of the timescale of the fluctuations and to look for the power law scaling predicted by Boldyrev.Comment: Particle Acceleration and Transport in the Heliosphere and Beyond, 7th Annual International Astrophysics Conference, Kauai, Hawaii, G. Li, Q. Hu, O. Verkhoglyadova, G. P. Zank, R. P. Lin, J. Luhmann (eds), AIP Conference Proceedings 1039, 81-8

The role of Doppler ultrasonography in determining the proper surgical approach to the management of varicocele in children and adolescents.

Abstract: OBJECTIVE To investigate whether colour Doppler ultrasonography (CDUS) is a reliable diagnostic tool for selecting patients with varicocele to undergo either laparoscopy or open microsurgical subinguinal ligation. PATIENTS AND METHODS In a 3-year period, 42 boys affected by left varicocele were evaluated before surgery by inguinal and scrotal CDUS. Using this method it was possible to distinguish Coolsaet type-1 varicocele (due to isolated renal-internal spermatic vein reflux) and Coolsaet type-3 varicocele (due to associated renal-internal spermatic reflux and iliac-deferential reflux). Boys with Coolsaet type-1 varicocele were treated by a laparoscopic transperitoneal Palomo procedure, whereas those with Coolsaet type-3 varicoceles were treated by lymphatic-sparing microsurgical subinguinal ligation. RESULTS The varicocele was Coolsaet type-3 in six patients (14%), who had microsurgical open surgery, and the remaining 36 (86%) had Coolsaet type-1 and had laparoscopic surgery. At the follow-up there was no venous scrotal reflux. In two patients in the laparoscopic group a hydrocele developed after surgery, which resolved spontaneously. CONCLUSIONS This study showed that CDUS was a reliable diagnostic tool for assessing boys with varicocele. It clearly distinguished Coolsaet-type 1 varicoceles that can be treated laparoscopically, from Coolsaet type-3 varicoceles that should be treated with microsurgical subinguinal ligature

Improved method of porcine renal allografting for transplantation Research

This study presents a refined, reproducible, and clinically appropriate animal model of renal transplantation. A pair of kidneys are harvested from a donor pig and preserved in Euro-Collins' solution (4°C). After a set period of preservation, the allografts are transplanted to two recipient pigs. The abdomen is entered through a midline incision. The right common iliac artery and vein are dissected and bilateral native nephrectomy is performed. Each allograft is then randomly assigned and transplanted to the recipients. Three minutes before un- clamping, 100 mg offurosemide and 10 g of mannitol are given IV. Immediately after reperfusion, urine output is measured for 1 h. The allograft is biopsied and ureteroneocyslostomy is created. Cystostomy is then placed using a 16F Foley catheter. The bladder neck is ligated to secure complete diversion of urine, and the abdomen is closed in layers. This kidney transplant model allows an absolutely paired study of the kidney allograft function from the same donor and also collection of pure urine at any time postoperatively, obviating the need for metabolic cages or sedation for urinary collection. This model and its unique modifications allow various transplant studies, including organ preservation, immunosuppressive protocol, and the prevention of reperfusion injury from oxygen free radicals © 1991 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted

Multi-Wavelength Monitoring of the Changing-Look AGN NGC 2617 during State Changes

Optical and near-infrared photometry, optical spectroscopy, and soft X-ray and UV monitoring of the changing-look active galactic nucleus NGC 2617 show that it continues to have the appearance of a type-1 Seyfert galaxy. An optical light curve for 2010-2017 indicates that the change of type probably occurred between 2010 October and 2012 February and was not related to the brightening in 2013. In 2016 and 2017 NGC 2617 brightened again to a level of activity close to that in 2013 April. However, in 2017 from the end of the March to end of July 2017 it was in very low level and starting to change back to a Seyfert 1.8. We find variations in all passbands and in both the intensities and profiles of the broad Balmer lines. A new displaced emission peak has appeared in Hβ. X-ray variations are well correlated with UV-optical variability and possibly lead by ̃2-3 d. The K band lags the J band by about 21.5 ± 2.5 d and lags the combined B + J bands by ̃25 d. J lags B by about 3 d. This could be because J-band variability arises predominantly from the outer part of the accretion disc, while K-band variability is dominated by thermal re-emission by dust. We propose that spectral-type changes are a result of increasing central luminosity causing sublimation of the innermost dust in the hollow bi-conical outflow. We briefly discuss various other possible reasons that might explain the dramatic changes in NGC 2617.Fil: Oknyansky, V. L.. Sternberg Astronomical Institute; RusiaFil: Gaskell, C. M.. Department of Astronomy and Astrophysics. University of California. Santa Cruz; Estados UnidosFil: Mikailov, K. M.. Shamakhy Astrophysical Observatory, National Academy of Sciences. Pirkuli; AzerbaiyánFil: Lipunov, V. M.. Sternberg Astronomical Institute. M.V.Lomonosov Moscow State University ; RusiaFil: Shatsky, N. I.. Sternberg Astronomical Institute. M.V.Lomonosov Moscow State University; RusiaFil: Tsygankov, S. S.. Tuorla Observatory, Department of Physics and Astronomy. University of Turku.; FinlandiaFil: Gorbovskoy, E. S.. Sternberg Astronomical Institute. M.V.Lomonosov Moscow State University; RusiaFil: Tatarnikov, A. M.. Sternberg Astronomical Institute. M.V.Lomonosov Moscow State University; RusiaFil: Metlov, V. G.. Sternberg Astronomical Institute. M.V.Lomonosov Moscow State University; RusiaFil: Malanchev, K. L.. Sternberg Astronomical Institute. M.V.Lomonosov Moscow State University; RusiaFil: Brotherton, M.B.. University of Wyoming; Estados UnidosFil: Kasper, D.. University of Wyoming; Estados UnidosFil: Du, P.. Institute of High Energy Physics. Chinese Academy of Sciences; ChinaFil: Chen, X.. School of Space Science and Physics. Shandong University; ChinaFil: Burlak, M. A.. Sternberg Astronomical Institute. M.V.Lomonosov Moscow State University; RusiaFil: Buckley, D. A. H.. The South African Astronomical Observatory; SudáfricaFil: Rebolo, R.. Instituto de Astrofisica de Canarias; EspañaFil: Serra-Ricart, M.. Instituto de Astrofisica de Canarias; EspañaFil: Podestá, R.. Universidad Nacional de San Juan; ArgentinaFil: Levato, O. H.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; Argentin

New Fermi smearing approach for scattering of multi-GeV electrons by nuclei

The cross section for electron scattering by nuclei at high momentum transfers is calculated within the Fermi smearing approximation (FSA), where binding effects on the struck nucleon are introduced via the relativistic Hartree approximation (RHA). The model naturally preserves current conservation, since the response tensor for an off-shell nucleon conserves the same form that for a free one but with an effective mass. Different parameterizations for the inelastic nucleon structure function, are analyzed. The smearing at the Fermi surface is introduced through a momentum distribution obtained from a perturbative nuclear matter calculation. Recent CEBAF data on inclusive scattering of 4.05 GeV electrons on ⁵⁶Fe are well reproduced for all measured geometries for the first time, as is evident from the comparison with previous calculations.Facultad de Ciencias Exacta

What really matters about teacher education at Cathedrals Group Universities: volume 2 the case studies

The case studies show insight into the extent that there is a shared understanding between schools, students and staff members in some of England’s oldest providers of teacher education in England. Is there something particular about that provision? Could it be described as distinctively, implicitly or explicitly Christian? Is there a sense of shared thinking about the answers to these questions in the provision of teacher education and the students, university tutors and school staff members who partner with these universities to educate the next generation of teachers? This document provides five answers to those questions. The answers are snapshots of the perception of teacher education at these universities, at a time when teacher education has become a major purpose of schools, and universities have found themselves being questioned and challenged about their role in the development of new teachers