Influence of surface states and size effects on the Seebeck coefficient and electrical resistance of Bi1-xSbx nanowire arrays.

The Seebeck coefficient and electrical resistance of Bi1-xSbx nanowire arrays electrodeposited in etched ion-track membranes have been investigated as a function of wire diameter (40-750 nm) and composition (0 ≤ x ≤ 1). The experimental data reveal a non-monotonic dependence between thermopower and wire diameter for three different compositions. Thus, the thermopower values decrease with decreasing wire diameter, exhibiting a minimum around ∼60 nm. This non-monotonic dependence of the Seebeck coefficient is attributed to the interplay of surface and bulk states. On the one hand, the metallic properties of the surface states can contribute to decreasing the thermopower of the nanostructure with increasing surface-to-volume ratio. On the other hand, for wires thinner than ∼60 nm, the relative increase of the thermopower can be tentatively attributed to the presence of quantum-size effects on both surface and bulk states. These measurements contribute to a better understanding of the interplay between bulk and surface states in nanostructures, and indicate that the decrease of Seebeck coefficient with decreasing diameter caused by the presence of surfaces states can possibly be overcome for even thinner nanowires.

Entrevista motivacional: ¿cuál es su efectividad en problemas prevalentes de la atención primaria? / Motivational interviews: what are their effectiveness in prevalent primary care problems?

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Determination of airborne isocyanate exposure: considerations in method selection.

To assess worker isocyanate exposures in a variety of processes involving the manufacture and use of surface coatings, polyurethane foams, adhesives, resins, elastomers, binders, and sealants, it is important to be able to measure airborne reactive isocyanate-containing compounds. Choosing the correct methodology can be difficult. Isocyanate species, including monomers, prepolymers, oligomers, and polyisocyanates, are capable of producing irritation to the skin, eyes, mucous membranes, and respiratory tract. The most common adverse health effect is respiratory sensitization, and to a lesser extent dermal sensitization and hypersensitivity pneumonitis. Furthermore, isocyanate species formed during polyurethane production or thermal degradation may also produce adverse health effects. Isocyanate measurement is complicated by the fact that isocyanates may be in the form of vapors or aerosols of various particle size; the species of interest are reactive and therefore unstable; few pure analytical standards exist; and high analytical sensitivity is needed. There are numerous points in the sampling and analytical procedures at which errors can be introduced. The factors to be considered for selecting the most appropriate methodology for a given workplace include collection, derivatization, sample preparation, separation, identification, and quantification. This article discusses these factors in detail and presents a summary of method selection criteria based on the isocyanate species, its physical state, particle size, cure rate, and other factors.

Delayed repair of an acquired posterior septal defect through a right atrial approach.

A patient with chronic postinfarction ventricular septal defect located posteriorly is described. The right atrial approach is suggested for these defects and the operative differences between chronic and acute defects are discussed.

Laboratory evaluation of silica gel sorbent tubes for sampling hydrogen fluoride.

The NIOSH sampling and analytical method for inorganic acids employs a silica gel sorbent tube for the collection of five common inorganic acids with simultaneous determination of these acids in a single sample by ion chromatography. When the method was extended to the determination of hydrogen fluoride (HF) the sampled HF reacted with the silica gel and glass fiber of the sampler, but the reaction products remained trapped on the sorbent. Silica gel samplers were evaluated for the collection of HF from laboratory generated atmospheres. Factors tested included capacity, storage stability, humidity, accuracy and precision. Based on comparison with impinger collection, the mean recovery of HF from silica gel tube samples was 100.7% with a precision of 0.144.

Performance of sulfur dioxide passive monitors.

The following four commercial sulfur dioxide passive monitors were tested for performance and realiability: DuPont Pro-Tek C-20 air monitoring badges; MSA Vaporgard Dosimeter tubes; REAL BioBadges; and 3M Sulfur Dioxide Nutshell monitors. The experiments conducted were designed to test factors critical to the operation of passive samplers: accuracy and precision; capacity; stability; analytical recovery; and the effects of exposure time, concentration, humidity, face velocity, orientation, chemical interference, and temperature. The DuPont Pro-Tek badges performed satisfactorily for all the factors tested, and the REAL BioBadges performed satisfactorily except for the instability of the SO2/tetrachloromercurate complex when stored. An alternate monitoring system, REAL BioBadges containing deionized water absorbent had a limited capacity. Only the MSA dosimeters exhibited unsatisfactory performance. The 3M Nutshell monitor was withdrawn by the manufacturer after only partial evaluation.

[Our experience with fundoplication according to Nissen in the treatment of hiatal hernia]. / Nostra esperienza con la fundusplicatio secondo Nissen nel trattamento dell'ernia iatale.

The authors illustrate their experience with the fundoplication according to Nissen in the treatment of hiatal hernia and gastroesophageal reflux, and appraise its effectiveness in the light of the most modern diagnostical methods, among which chiefly the monitored pH-metry of distal oesophagus.

Fistula coronaria pulmonar.Tratamiento quirurgico. / Coronary pulmonary fistula. Surgical treatment

Se describe un caso de fistula de arteria coronaria derecha a tronco de arteria pulmonar, en un paciente de 59 anos con historia de angor estable que se hace progresivo de lesiones coronarias, tratado en el Instituto Nacional de Cirugia Cardiaca. Se discute brevemente la frecuencia de manifestaciones clinicas y de variedades anatomicas de esta patologia, finalmente se detallan los criterios aceptados hoy dia para el tratamiento de esta anomalia, concluyendo, en base a revision de la literatura que: 1 - La fistula debe ser obliterada una vez realizado el diagnostico debido a sus posibles complicaciones: 2 - La reparacion se rige por la forma anatomica de presentacion; 3 - El cierre intracavitario del ostium fistuloso es la forma de asegurar una obliteracion completa; 4 - El uso de CEC para esto ultimo y para aquellas de dificil asceso, debe tenerse en cuenta

Mortalidad operatoria en cirugia de revascularizacion miocardica. / Operative mortality in myocardial revascularization surgery

Se analiza la experiencia en el Instituto Nacional de Cirugia Cardiaca en cirugia de revascularizacion miocardica en el periodo de un ano - agosto de 1980 a julio de 1981 Se evaluan los resultados en relacion a la mortalidad operatoria - es decir, la mortalidad en el periodo de treinta dias del postoperatorio. La mortalidad operatoria registrada en dicho periodo fue del 2,85%.3 muertes en 105 pacientes - lo que resulta compatible con los resultados internacionalmente aceptados en 1981. Se analizan los distintos factores considerados predictores de mortalidad operatoria en cirugia coronaria