Theoretical Characterization of the Interface in a Nonequilibrium Lattice System

The influence of nonequilibrium bulk conditions on the properties of the interfaces exhibited by a kinetic Ising--like model system with nonequilibrium steady states is studied. The system is maintained out of equilibrium by perturbing the familiar spin--flip dynamics at temperature T with completely--random flips; one may interpret these as ideally simulating some (dynamic) impurities. We find evidence that, in the present case, the nonequilibrium mechanism adds to the basic thermal one resulting on a renormalization of microscopic parameters such as the probability of interfacial broken bonds. On this assumption, we develop theory for the nonequilibrium "surface tension", which happens to show a non--monotonous behavior with a maximum at some finite T. It ensues, in full agreement with Monte Carlo simulations, that interface fluctuations differ qualitatively from the equilibrium case, e.g., the interface remains rough at zero--T. We discuss on some consequences of these facts for nucleation theory, and make some explicit predictions concerning the nonequilibrium droplet structure.Comment: 10 pages, 7 figures, submitted to Phys. Re

The Puzzling Stability of Monatomic Gold Wires

We have examined theoretically the spontaneous thinning process of tip-suspended nanowires, and subsequently studied the structure and stability of the monatomic gold wires recently observed by Transmission Electron Microscopy (TEM). The methods used include thermodynamics, classical many-body force simulations, Local Density (LDA) and Generalized Gradient (GGA) electronic structure calculations as well as ab-initio simulations including the two tips. The wire thinning is well explained in terms of a thermodynamic tip suction driving migration of surface atoms from the wire to the tips. For the same reason the monatomic wire becomes progressively stretched. Surprisingly, however, all calculations so far indicate that the stretched monatomic gold wire should be unstable against breaking, contrary to the apparent experimental stability. The possible reasons for the observed stability are discussed.Comment: 4 figure

Evolución del perfil comunicacional de los médicos residentes de medicina de familia

ObjetivoConocer cómo evolucionan en los residentes de medicina de familia las habilidades de relación con los pacientes, al comienzo y al final de su tercer año de residencia, cuando atienden a problemas de salud comunes en su especialidad.DiseñoEstudio cuasi-experimental (antesdespués), multicéntrico, de ámbito nacional. Un total de 193 médicos residentes de tercer año de medicina familiar de 8 unidades docentes, que realizaron su residencia entre 1996–1999. Durante este período los residentes realizaron las actividades formativas y asistenciales habituales que marca el Programa Nacional de la Especialidad. Se valoraron 6 escenarios clínicos videograbados con pacientes estandarizados (3 al inicio del tercer año y 3 al finalizar) mediante el cuestionario GATHA-RES. Análisis estadístico descriptivo, bivariado y multivariante.ResultadosSe evaluó un total de 1.024 entrevistas. El tiempo empleado con cada paciente disminuye significativamente al finalizar la residencia; se observa una relación directamente proporcional entre el tiempo de consulta y las puntuaciones obtenidas (p < 0,05). Se detectan mejorías en los aspectos formales y organizativos de la consulta. Por el contrario, las habilidades relacionadas con la exploración de los aspectos personales y contextuales de la dolencia, así como las habilidades negociadoras, empeoran al finalizar el estudio. Las variables que mejor predicen el perfil comunicacional de los residentes fueron: edad (inversamente), duración de la entrevista, formación del tutor en entrevista clínica y unidad docente.ConclusionesLos residentes aprenden a acortar el tiempo de consulta en detrimento de habilidades de comunicación básicas para la realización de una correcta asistencia a los problemas de salud de sus pacientes. Estos resultados sugieren la necesidad de cambios sustanciales en la formación de los médicos residentes de medicina de familia en España.AimsTo study the development of patient relation skills, as used during interviews with patients for health problems that are common within their specialty, in family medicine residents during the third year of their residency program.MethodsQuasi-experimental (before-after), national-level, multicenter study. The participants were 193 third-year residents in family medicine at 8 training units who were trained between 1996 and 1999. During this period all residents participated in the usual training and clinical activities included in the National Plan for this specialty. The GATHA-RES questionnaire was used to evaluated six clinical scenarios in video recordings of encounters with standardized patients (3 at the start of the third year and 3 at the end of the third year). Descriptive, bivariate and multivariate statistical analyses were used.ResultsA total of 1,024 interviews were analyzed. The time spent with each patient decreased significantly at the end of the residency program; the duration of the visit was directly proportional to the score on the GATHA-RES questionnaire (p < 0.05). Improvements were seen in formal and organizational aspects of the interview. In contrast, skills related with the exploration of personal and contextual aspects of the problem, and negotiating skills, were worse at the end of the study. The variables that best predicted residents’ communicational profile were age (inverse relation), duration of the interview, training of the tutor in clinical interviewing, and teaching unit.ConclusionsResidents learn to shorten the duration of the visit to the detriment of communication skills that are basic to appropriate care for their patients’ health problems. These results suggest the need for substantial changes in the training of family medicine residents in Spain

Interaction between a laser beam and semiconductor nanowires: application to the raman spectrum of Si nanowires

One presents in this work the study of the interaction between a focused laser beam and Si nanowires (NWs). The NWs heating induced by the laser beam is studied by solving the heat transfer equation by finite element methods (FEM). This analysis permits to establish the temperature distribution inside the NW when it is excited by the laser beam. The overheating is dependent on the dimensions of the NW, both the diameter and the length. When performing optical characterisation of NWs using focused laser beams, one has to consider the temperature increase introduced by the laser beam. An important issue concerns the fact that the NW's diameter has subwavelength dimensions, and is also smaller than the focused laser beam. The analysis of the thermal behaviour of the NWs under the excitation with the laser beam permits the interpretation of the Raman spectrum of Si NWs. It is demonstrated that the temperature increase induced by the laser beam plays a major role in shaping the Raman spectrum of Si NWs

Platelet and Fibrin Deposition at the Damaged Vessel Wall: Cooperative Substrates for Neutrophil Adhesion Under Flow Conditions

At sites of vessel wall damage, the primary hemostatic reac- tion involves platelet and fibrin deposition. At these sites, circulating leukocytes marginate and become activated. Ad- hered platelets can support leukocyte localization; however, the role of fibrin in this respect is not known. We studied the adhesion of human neutrophils (polymorphonuclear leukocytes [PMNs]) to endothelial extracellular matrix (ECM)- bound fibrin and platelets under flow conditions. ECM alone did not show PMN adhesion. ECM-coated cover slips were perfused with plasma to form a surface-bound fibrin network, and/or with whole blood to allow platelet adhesion. Unstimulated PMNs adhered to fibrin at moderate shear stress (20 to 200 mPa). ECM-bound platelets induced rolling adhesion and allowed more PMNs to adhere at higher shear (320 mPa). ECM coated with both platelets and fibrin induced more static and shear-resistant PMN adhesion. PMN adhesion to fibrin alone but not to platelet/fibrin surfaces was inhibited by soluble fibrinogen. Adhesion to fibrin alone was inhibited by CD11b and CD18 blocking antibodies. Furthermore, fibrin formed under flow conditions showed up to threefold higher PMN adhesion compared with fibrin formed under static conditions, due to structural differences. These results indicate that circulating PMNs adhere to fibrin in an integrin-dependent manner at moderate shear stresses. However, at higher shear rates (Û200 mPa), additional mechanisms (ie, activated platelets) are necessary for an interac- tion of PMNs with a fibrin network

Residual stresses and stress corrosion cracking in pipe fittings

Residual stresses can play a key role in the SCC performance of susceptible materials in PWR primary water applications. Residual stresses are stresses stored within the metal that develop during deformation and persist in the absence of external forces or temperature gradients. Sources of residual stresses in pipe fittings include fabrication processes, installation and welding. There are a number of methods to characterize the magnitude and orientation of residual stresses. These include numerical analysis, chemical cracking tests, and measurement (e.g., X-ray diffraction, neutron diffraction, strain gage/hole drilling, strain gage/trepanning, strain gage/section and layer removal, and acoustics). This paper presents 400 C steam SCC test results demonstrating that residual stresses in as-fabricated Alloy 600 pipe fittings are sufficient to induce SCC. Residual stresses present in as-fabricated pipe fittings are characterized by chemical cracking tests (stainless steel fittings tested in boiling magnesium chloride solution) and by the sectioning and layer removal (SLR) technique