Gaussian content as a laser beam quality parameter

We propose the Gaussian content (GC) as an optional quality parameter for the characterization of laser beams. It is defined as the overlap integral of a given field with an optimally defined Gaussian. The definition is especially suited for applications where coherence properties are targeted. Mathematical definitions and basic calculation procedures are given along with results for basic beam profiles. The coherent combination of an array of laser beams and the optimal coupling between a diode laser and a single-mode fiber are elaborated as application examples. The measurement of the GC and its conservation upon propagation are experimentally confirmed.     

A qualitative approach to the evaluation of psychosocial interventions for persons with severe mental illness.

This article describes the development and assessment of a qualitative interview for comprehensively assessing both the process and the outcome of interventions for persons with severe mental illness (SMI). A open-ended 16-question Narrative Evaluation of Intervention Interview (NEII) was developed. The NEII contains questions that ask the participants to evaluate and describe both process and outcome of interventions for persons with SMI. Research participants were 64 persons with SMI attending rehabilitation programs in the community. Analysis of participants' responses to the NEII, using the open step of the grounded theory approach, produced a comprehensive set of themes. Interrater reliabilities for these themes ranged from moderate to high, and these themes differentiated between the three psychosocial interventions. Ways of modifying the NEII so as to make it more sensitive to participants' expectations and experiences are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

High‐resolution measurements of water permeability and solubility in microelectronic‐casing made of a hydrophobic polymeric composite

Exposing the composite polymeric casing of integrated circuits (ICs) to water results in miniscule water absorption, followed by its permeation throughout the packaging, and component damage. Studying water penetration and solubility mechanisms in the IC casing is crucial for understanding water‐related damage mechanisms and protection against them. The main analytical challenge, hereafter, stems from the need to study miniscule water amounts (<0.5 wt %) capable of penetrating the casing, despite its hydrophobic nature. In this article, a TGA has been employed to study the water uptake kinetics in the casing, and to decipher the related water penetration mechanisms. High‐resolution measurements of water adsorption and desorption profiles were performed, followed by calculations of the related activation energies and solubility enthalpies. These data were correlated with a relatively new model that assigned the primary locales of the adsorbed water to the compatible filler–polymer interface. Thus, water permeability is related to molecules hopping between these sites. Finally, we have shown that for the IC casing in our study, the activation energy of water permeation is related to the binding energy of H₂O onto the Si? O? Si groups at the fused‐silica‐filler surface, where they desorb, hop, and reabsorb. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4523–4527, 2006     

Surface-Enhanced Raman Scattering (SERS) of Microorganisms

Normal Raman (NR) spectra and surface-enhanced Raman scattering (SERS) spectra were obtained for the bacterium Escherichia coli and were compared with those of two other microorganisms, Haloferax volcanii and Thiobacillus neapolitanus. It was found that at 514 nm the SERS of E. coli was similar to that of flavin adenine dinucleotide (FAD). Upon increasing the excitation wavelength, contributions from other cell components became evident, and they were attributed to nicotinamide adenine dinucleotide (NAD) or other adenine-containing molecules in the bacterium. A comprehensive study of FAD, riboflavin (RF), NAD, and adenine under various experimental conditions was thus performed to shed light on the features in the SERS obtained for E. coli. Comparison of NR and SERS measurements of the various samples enabled a better understanding of the SERS spectra and their sensitivity to the specific experimental conditions (excess metal ion concentration and laser excitation wavelengths and intensity). It was concluded that SERS is a highly sensitive technique and that careful examination of the spectra can provide important chemical information.     

Fading channels: how perfect need "perfect side information" be?

The analysis of flat-fading channels is often performed under the assumption that the additive noise is white and Gaussian, and that the receiver has precise knowledge of the realization of the fading process. These assumptions imply the optimality of Gaussian codebooks and of scaled nearest-neighbor decoding. Here we study the robustness of this communication scheme with respect to errors in the estimation of the fading process. We quantify the degradation in performance that results from such estimation errors, and demonstrate the lack of robustness of this scheme. For some situations we suggest the rule of thumb that, in order to avoid degradation, the estimation error should be negligible compared to the reciprocal of the signal-to-noise ratio (SNR)     

Pulmonary function threshold for distinguishing ventilatory- and nonventilatory-limited patients with airflow obstruction

Patients with chronic obstructive pulmonary disease (COPD) may demonstrate great variability between results on the pulmonary function test (PFT) compared to those on the cardiopulmonary exercise test (CPXT). The purpose of this study was to correlate PFT and CPXT indices and to identify PFT threshold values for predicting exercise capacity in patients with airflow limitation. Fifty-seven patients (48 men and 9 women) of mean age 66.4 +/- 4.8 years with COPD and 40 age-matched control patients underwent PFT and CPXT. Based on the CPXT results, the patients were divided into ventilatory-limited (VL) and nonventilatory-limited (NVL), and the findings were correlated with the PFT indices. Linear regression analysis was used to determine the relationship between dyspnea index (VEmax/MVV) and forced expiratory volume in one second (FEV1). The cutoff value for VL was FEV1 < 38% and for NVL FEV1 > 68%. The prominent limiting symptom (61%) in the VL group was dyspnea sensation, with leg discomfort presenting in only 14%; corresponding rates in the NVL group were 38% and 31%. We conclude that the FEV1 is a reliable index for distinguishing VL from NVL COPD patients during CPXT at two extremes: below 38% of the predicted value (VL) and above 68% of the predicted value (NVL).     

A glass liquid helium cryostat for Mössbauer spectroscopy

The combination of a metal extension sealed to a glass cryostat enables the use of indium sealed mylar or beryllium windows, resulting in an improved solid angle when the source is immersed in liquid helium. The low cost, low helium consumption, the versatility in tails and interchangeability are the main features of this cryostat.     

A method for call admission control in ATM networks with heterogeneous sources

We present a procedure for call admission control for ATM networks. The procedure can be applied to deciding if an additional Virtual Channel (user, source) can be assigned to an end-to-end Virtual Path, or if a link connecting two ATM switches can carry an additional VC. Each source is characterized by its peak rate, mean rate, and cycle length. The objective is to admit as many sources as possible, while meeting a desirable level of cell loss probability. We adapt an effective bandwidth technique to the case where sources do not have to belong to a small number of classes. We do this by suggesting an upper bound for the cell-loss-probability for the case of heterogeneous Markovian on-off sources, and by showing that its computation can be performed in real time by the sending switch, with a reasonable amount of computational and storage resources. We show by simulation that the proposed procedure is effective even for highly bursty source mixes, where it achieves more than 80% of the theoretically possible multiplexing gain.     

Information rates for a discrete-time Gaussian channel withintersymbol interference and stationary inputs

Bounds are presented on I_i.i.d.-the achievable information rate for a discrete Gaussian Channel with intersymbol interference (ISI) present and i.i.d. channel input symbols governed by an arbitrary predetermined distribution p_x(x). The lower and upper bounds on I _i.i.d. and I are formulated. The bounds on I_i.i.d. are calculated for independent equiprobably binary channel symbols and for causal channels with ISI memory of degree one and two. The bounds on I_i.i.d. are compared to the approximated (by Monte Carlo methods) known value of I_i.i.d. and their tightness is considered. An application of the new lower bound on I_i.i.d. yields an improvement on previously reported lower bounds for the capacity of the continuous-time strictly bandlimited (or bandpass) Gaussian channel with either peak or simultaneously peak power and bandlimiting constraints imposed on the channel's input waveform