Photoacoustic Investigation of Glass Transition in AsxTe1-x Glasses

Photoacoustic (PA) technique is used to study glass transition and temperature dependence of thermal diffusivity in AsxTe1-x glasses with 0.25 0.60. PA amplitude goes through a minimum and the phase shows a maximum at glass transition temperature Tg. The variation of thermal diffusivity with temperature shows sharp decrease near Tg. The variation of thermal diffusivity with composition shows maximum at = 0.40 for all temperatures T Tg.

Compositional dependence of crystallization of As-Te glasses

Thermal crystallization studies have been carried out on bulk, semiconducting AsxTe100−x glasses of different compositions using Differential Scanning Caloritmery. AsxTe100−x glasses with x < 40, are found to exhibit one glass transition and one crystallization. On the other hand, glasses with composition 40 less-than-or-equals, slantxless-than-or-equals, slant 50 show one glass transition and two crystallization reactions. It has been found that in glasses with x greater-or-equal, slanted 40, the two crystallization reactions progressively merge with an increase in arsenic concentration. Consequently AsxTe100−x glasses with x greater-or-equal, slanted 50 show only one crystallization. The composition dependence of crystallization temperatures and activation energies for crystallization estimated by Kissinger's method, show marked deviations at a composition x = 40. These observations can be explained in terms of the changes in the local structure of the material with composition.

Effect of High Pressure on the Electrical Conductivity of TlInX2 (X = Se, Te) Layered Semiconductors

The dc electrical conductivity of TlInX2 (X = Se, Te) single crystals, parallel and perpendicular to the (001) c-axis is studied under high quasi-hydrostatic pressure up to 7.0 GPa, at room temperature. Conductivity measurements parallel to the c-axis are carried out at high pressures and down to liquid nitrogen temperatures. These materials show continuous metallization under pressure. Both compounds have almost the same pressure coefficient of the electrical activation energy parallel to the c-axis, d(ΔE∥)/dP = −2.9 × 10−10 eV/Pa, which results from the narrowing of the band gap under pressure. The results are discussed in the light of the band structure of these compounds.

Electrical switching and short-range order in As-Te glasses

The local structural order in chalcogenide network glasses is known to change markedly at two critical compositions, namely, the percolation and chemical thresholds. In the AsxTe100-x glassy system, both the thresholds coincide at the composition x = 40 (40 at. % of arsenic). It is demonstrated that the electrical switching fields of As-Te glasses exhibit a distinct change at this composition.

Vector summed sine wave tailored waveforms for dipolar excitation of ions in Paul trap mass spectrometers

A simple method to generate time domain tailored waveforms for excitation of ion axial amplitude in Paul trap mass spectrometers is described. The method is based on vector summation of sine waves followed by time domain sampling to obtain the discrete time domain data. A smoothing technique based on the time domain Kaiser window is then applied to the data so as to minimize the frequency domain Gibb's oscillations. The dynamic range of the time domain signal is controlled by phase modulation and time extension of the time domain waveform. Copyright (C) 1999 John Wiley & Sons, Ltd.

Zero-crossing approach to high-resolution reconstruction in frequency-domain optical-coherence tomography

We address the problem of high-resolution reconstruction in frequency-domain optical-coherence tomography (FDOCT). The traditional method employed uses the inverse discrete Fourier transform, which is limited in resolution due to the Heisenberg uncertainty principle. We propose a reconstruction technique based on zero-crossing (ZC) interval analysis. The motivation for our approach lies in the observation that, for a multilayered specimen, the backscattered signal may be expressed as a sum of sinusoids, and each sinusoid manifests as a peak in the FDOCT reconstruction. The successive ZC intervals of a sinusoid exhibit high consistency, with the intervals being inversely related to the frequency of the sinusoid. The statistics of the ZC intervals are used for detecting the frequencies present in the input signal. The noise robustness of the proposed technique is improved by using a cosine-modulated filter bank for separating the input into different frequency bands, and the ZC analysis is carried out on each band separately. The design of the filter bank requires the design of a prototype, which we accomplish using a Kaiser window approach. We show that the proposed method gives good results on synthesized and experimental data. The resolution is enhanced, and noise robustness is higher compared with the standard Fourier reconstruction. (c) 2012 Optical Society of America

Damage limit states of reinforced concrete beams subjected to incremental cyclic loading using relaxation ratio analysis of AE parameters

This paper presents an experimental study on damage assessment of reinforced concrete (RC) beams subjected to incremental cyclic loading. During testing acoustic emissions (AEs) were recorded. The analysis of the AE released was carried out by using parameters relaxation ratio, load ratio and calm ratio. Digital image correlation (DIC) technique and tracking with available MATLAB program were used to measure the displacement and surface strains in concrete. Earlier researchers classified the damage in RC beams using Kaiser effect, crack mouth opening displacement and proposed a standard. In general (or in practical situations), multiple cracks occur in reinforced concrete beams. In the present study damage assessment in RC beams was studied according to different limit states specified by the code of practice IS-456:2000 and AE technique. Based on the two ratios namely load ratio and calm ratio and when the deflection reached approximately 85% of the maximum allowable deflection it was observed that the RC beams were heavily damaged. The combination of AE and DIC techniques has the potential to provide the state of damage in RC structures.

Temas de historia argentina y americana, 2005, n° 7 (número completo)

Centralismo y descentralización en el Plata. Aproximaciones / Edberto Oscar Acevedo -- La Justicia letrada en la campaña bonaerense. 1853-1856 / María Angélica Corva -- La tradición indiana y la formación del derecho argentino / José María Días Couselo -- El destierro de Perón en la España franquista / Beatriz J. Figallo -- Ideología y pragmatismo: relaciones hispano-chilenas, 1964-1970 / María José Henriquez Uzal -- Los aspectos navales de las relaciones Argentino Germanas II – La época del Tercer Reich 1930-1945 / Julio M. Luqui-Lagleyze -- Las formas sociales del habitar. Derivaciones tipológicas de la vivienda hacia el Centenario de Mayo / Susana N. Tuler -- Las publicaciones producidas por el ambiente del Centenario de la Revolución de Mayo (1910) / Juan María Veniard -- Documentos -- Reseñas Bibliográficas

The role of women in marketing of frozen fish in Lagos State of Nigeria

The involvement of women in the marketing of frozen fish in Lagos State (Nigeria) was examined in this study. Two hundred questionnaires were administered to fish marketers in five markets randomly selected within the Lagos metropolis based on their storage capacities. These markets were Balogun (500 tones), Idumagbo and Idumota (250 tonnes each) Obalende and Epetedo (37.5 tonnes each). From the study results, a greater percentage of women (64.2%) are actively involved in marketing of frozen fish in the study areas. Over 56% of these traders are retailers while about 33% are wholesalers. More than 91% of the marketers were found to be literate. A high percentage of the frozen fish are imported (68%), 27% from coastal fishing and 5% from riverine fishing. The commonest fish in the markets were titus (34%), sardine (32%), hake 19%, catfish 10% and argentine 5%. Catfish has the highest profit margin. The greatest problem of these traders is the lack of modern storage facilities and where available, the erratic power supply constitutes a problem

Coastal plant growth and CO2 enrichment: Can the productivity of black needle rush keep pace with sea level rise?

The rate of sea level change has varied considerably over geological time, with rapid increases (0.25 cm yr-1) at the end of the last ice age to more modest increases over the last 4,000 years (0.04 cm yr-1; Hendry 1993). Due to anthropogenic contributions to climate change, however, the rate of sea level rise is expected to increase between 0.10 and 0.25 cm year-1 for many coastal areas (Warrick et al. 1996). Notwithstanding, it has been predicted that over the next 100 years, sea levels along the northeastern coast of North Carolina may increase by an astonishing 0.8 m (0.8 cm yr-1); through a combination of sea-level rise and coastal subsidence (Titus and Richman 2001; Parham et al. 2006). As North Carolina ranks third in the United States with land at or just above sea level, any additional sea rise may promote further deterioration of vital coastal wetland systems. (PDF contains 4 pages)

Museos, redes sociales y tecnología 2.0

Índice: - Sobre museos, redes sociales y tecnología 2.0 (Alex Ibáñez Etxeberria). - Sitios web y museos: nuevas aplicaciones para el aprendizaje informal (Mikel Asensio, Elena Asenjo y Alex Ibáñez Etxeberria). - From headphones to microphones: mobile social media in the museum as distributed network (Nancy Proctor). - Mobile learning y patrimionio: aprendiendo historia con mi teléfono, mi GPS y mi PDA (Alex Ibáñez Etxeberria, Mikel Asensio y José Miguel Correa). - Digital asset management strategies for multi-platform content delivery (Titus Bicknell). - Redes sociales y museos participativos: la irrupción de las tecnologías 2.0 en la sociedad y su aplicación en los museos a través del caso de Arazi (Juan José Aranburu).