When does the inverse have the same sign pattern as the transpose?

By a sign pattern (matrix) we mean an array whose entries are from the set {+, –, 0}. The sign patterns A for which every real matrix with sign pattern A has the property that its inverse has sign pattern A ^T are characterized. Sign patterns A for which some real matrix with sign pattern A has that property are investigated. Some fundamental results as well as constructions concerning such sign pattern matrices are provided. The relation between these sign patterns and the sign patterns of orthogonal matrices is examined.     

Functional and tuneable amino acid polymers prepared by RAFT polymerization

We report the application of reversible addition‐fragmentation chain transfer polymerization using a novel chain transfer agent toward the synthesis of a variety of copolymers containing proline‐derived monomeric units. This methodology enables ready access to a number of polymeric species with narrow molecular weight distributions, reliable functional unit incorporations, and high conversions. The methodology is also a facile approach to novel copolymeric species incorporating amino acids, which possess unique material properties and the potential for further organocatalytic application. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009     

Expression of Potato virus Y cytoplasmic inclusion protein in tobacco results in disorganization of parenchyma cells, distortion of epidermal cells, and induces mitochondrial and chloroplast abnormalities, formation of membrane whorls and atypical lipid accumulation

Infection of plant cells by potyviruses induces the formation of cytoplasmic inclusions ranging in size from 200 to 1000 nm. To determine if the ability to form these ordered, insoluble structures is intrinsic to the potyviral cytoplasmic inclusion protein, we have expressed the cytoplasmic inclusion protein from Potato virus Y in tobacco under the control of the chrysanthemum ribulose-1,5-bisphosphate carboxylase small subunit promoter, a highly active, green tissue promoter. No cytoplasmic inclusions were observed in the leaves of transgenic tobacco using transmission electron microscopy, despite being able to clearly visualize these inclusions in Potato virus Y infected tobacco leaves under the same conditions. However, we did observe a wide range of tissue and sub-cellular abnormalities associated with the expression of the Potato virus Y cytoplasmic inclusion protein. These changes included the disruption of normal cell morphology and organization in leaves, mitochondrial and chloroplast internal reorganization, and the formation of atypical lipid accumulations. Despite these significant structural changes, however, transgenic tobacco plants were viable and the results are discussed in the context of potyviral cytoplasmic inclusion protein function.     

The Relationship Between Chronic Cough and Paradoxical Vocal Fold Movement: A Review of the Literature

SUMMARY: Chronic cough (CC) and paradoxical vocal fold movement (PVFM) are debilitating conditions. PVFM has been given many labels, including vocal cord dysfunction, Munchausen's stridor, functional inspiratory stridor, nonorganic functional or psychogenic upper airway obstruction, factitious asthma, psychogenic stridor, emotional laryngeal wheezing, and episodic laryngeal dyskinesia. Although CC and PVFM have been considered separate entities in many reports, there is preliminary support for the notion that there may be an underlying link between these two conditions. Speech pathologists have become increasingly involved in the treatment of these patients and therefore need to understand the theoretical background of these disorders, the pathophysiological links between the two, and the impact of voice disorders on these populations. The aim of this article is to review the current literature on CC and PVFM from a speech pathology perspective to provide a model for defining and conceptualizing the disorders and to provide a framework for management and future research.     

Studies on the manganese-mediated isomerization of alkynyl carbonyls to allenyl carbonyls

[reaction: see text] A study of the role of base in the isomerization of manganese-coordinated conjugated alkynyl carbonyls to the corresponding allenyl carbonyls is described. The use of phosphine additives indicates that manganese requires a ligand prior to isomerization with amine bases. A series of amine bases were also examined for their efficacy in this isomerization reaction revealing a strong dependence on pK(a). By contrast, potassium tert-butoxide led to rapid isomerization in the absence of added manganese ligand.     

Evaluation of two procedures to determine acid and neutral detergent fibers in ruminant feeds of the temperate region of Argentina

The objective of this work was to compare the traditional Van Soest's procedure to analyze neutral detergent fibers (NDF) and acid detergent fibers (ADF) using filtering crucibles (VS) with a semiautomatic method which uses filter bags in an ANKOM Technology Corp. instrument (ANK). Nine ruminant feeds widely used in the temperate region of Argentina were analyzed: soybean meal expeller, alfalfa, pasture silage, ryegrass, corn silage, weeping lovegrass, tall wheatgrass, guinea grass, and barley grass. Four runs were done for each technique and feed. The comparison of ADF and NDF means by the means test for paired samples showed no significant differences between techniques (alpha = 0.01). The variability among runs was greater with the VS method than the ANK, both for NDF, standard deviation (SD) = 0.71 vs 0.39, and for ADF, SD = 0.83 vs 0.56, but the differences were not significant. The linear regressions were VS = 1.43 + 0.95 ANK; R2 = 0.99, and VS = 0.53 + 0.98 ANK; R2 = 0.99 for NDF and ADF, respectively, which indicated a strong linear relationship among the results of both procedures. It was concluded that the ANK procedure gave results comparable to those of the VS method when ruminant feeds from the temperate region of Argentina were analyzed.     

Enhancing vapor sensor discrimination by mimicking a canine nasal cavity flow environment

This paper discusses the use of flow dynamics in a model nasal cavity as a novel way to expand the information available from a fiber optic vapor sensor. Nasal cavities are known to play an important role in vertebrate olfaction; however, they have not previously been incorporated into gas-phase sensor technology. By exposing identical sensors to different flow environments, we found that measurements of the combined sensor responses provided increased discrimination of a series of alcohols as compared to measurements obtained from a single sensor at the anterior of the cavity. This methodology is potentially useful for improving the discriminatory power of sensors employed in "artificial noses" and could be used to model the effects of flow dynamics in vertebrate olfaction.     

A frequency-modulated quantum-cascade laser for spectroscopy of CH4 and N2O isotopomers

We report the development of a novel laser spectrometer for high-sensitivity detection of methane and nitrous oxide. The system relies on a quantum-cascade laser source emitting wavelength of around 8.06 microm, where strong fundamental absorption bands occur for the considered species and their isotopomers. The detection technique is based on audio-frequency and radio-frequency modulation of laser radiation. First experimental tests have been performed to estimate the achievable detection limits and the signal reproducibility levels in view of possible measurements of (13)C/(12)C, (18)O/(16)O, (17)O/(16)O and (15)N/(14)N isotope ratios.