Fiber orientation and crimp level might control the auxetic effect of biological tissues.

We propose an analytical micromechanical model for studying the lamellar-composite-like structure of fibrous soft tissue. The tissue under consideration is made up of several lamellae, and is designed to resemble the annulus fibrosus (AF) tissue or media layer of arterial tissue, for example. The collagen fibers are arranged in parallel in each lamella and the fiber orientation differs from one lamella to its neighbors. The parallel fibers in each lamella of AF tissue, for example, have been observed to have a crimped microstructure. The proposed model incorporates this quality, considering fiber waviness as a sinusoidal shape and taking into account the fiber dispersion in different layers, where both fiber and matrix are considered as solid phases. We find that collagen-fiber waviness and layer orientation have a significant influence on Poisson's ratio. The effective Poisson's ratio predicted by the proposed model demonstrates that the crimped collagen fiber microstructure might weaken the auxetic effect of fibrous soft tissue, which might explain why, as the literature suggests, the auxetic behavior is more difficult to observe than large Poisson's ratios. As opposed to the many studies that use the well-known hyperelastic fiber-based constitutive model, in which out-of-plane expansion is often observed, the present work explains the auxetic response found in modeling and in experimental data from the perspective of collagen fiber microstructure.

Skin lesions, malaise, and heart failure in a renal transplant recipient.

A male Caucasian patient developed nodular erythematous skin lesions, malaise, and clinical signs of progressive heart failure 4 months after renal transplantation. Bronchoscopy with bronchoalveolar lavage performed for a small infiltrate seen on a computed tomography scan revealed Trypanosoma, which had at this point not been suspected as a cause. Parasitemia was present, and reactivation rather than transmission of Chagas' disease was established by performing polymerase chain reaction and serology in the donor and recipient. Treatment with benznidazole and allopurinol successfully reduced parasitemia, but the clinical course was fatal owing to progression of severe myocarditis. The patient had never lived in an endemic area, but had an extensive travel history in South America. The last visit was more than 5 years before transplantation. In non-endemic countries (United States, Europe), reactivation after transplantation has only been very rarely reported. Given the rising numbers of transplantations in patients with a migration background and extensive travel histories, specific screening procedures have to be considered.

A case study of female genital tuberculosis in a Western European setting.

We have studied five women with genital tuberculosis (TB), which is an uncommon disease in Western European countries. However, young women that have emigrated from a country with high TB-prevalence and have complaints of unexplained infertility and nonspecific abdominal or pelvic symptoms should be checked for this disease. Because genital tuberculosis frequently causes infertility, early diagnosis and treatment are crucial, necessitating rapid microscopic, histological, and microbiological (culture) testing in suspected cases.

Physician-hospital integration strategies: impact on physician involvement in hospital governance.

This study investigated the impact of three physician-hospital contractual arrangements (PHCAs)--joint ventures, management service organizations, and not-for-profit foundations--on physician involvement in hospital governance and physician-hospital relationships. Analysis of data collected from a national sample of 1,013 hospitals revealed that PHCAs generate greater physician involvement in hospital decision making and result in lower physician-hospital conflict.

Application of a trochoidal electron monochromator/mass spectrometer system to the study of environmental chemicals.

A trochoidal electron monochromator has been interfaced to a mass spectrometer to perform electron capture negative ion mass spectrometric (ECNIMS) analyses of environmentally relevant chemicals. The kinetic energy of the electron beam can be varied from 0.025 to 30 eV under computer control. No reagent gas is used to moderate the electron energies. An electron energy spread of +/- 0.1 to +/- 0.4 eV full width at half-maximum (fwhm) can readily be obtained at a transmitted current of 2 x 10(-6) A, improving to +/- 0.07 eV at 5 x 10(-7) A. Comparisons of ECNI results from the electron monochromator/mass spectrometer system with those from a standard instrument that uses a moderating gas show similar spectra for heptachlor but not for the s-triazine herbicides, as for example, atrazine. This compound shows numerous adduct ions by standard ECNIMS that are eliminated by using the electron monochromator to generate the mass spectra. Isomeric tetrachlorodibenzo-p-dioxins show distinct differences in the electron energies needed to produce the maximum amount of parent and fragment anions. Multiple resonance states resulting in stable radical anions (M.-) are easily observed for nitrobenzene and for polycyclic aromatic hydrocarbons. Ionic products of dissociative electron capture invariably occur from several resonance states.

A search for the presence of 2,3,7,8 tetrachlorodibenzo-p-dioxin in beef fat.

Specimens of fat taken from steers which had grazed on rangeland previously treated with 2,4,5-T herbicides were analyzed for the presence of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). A cleanup procedure resulting in a 500-fold concentration was followed by a gas chromatography-mass spectrometry detection technique. The limit of detection of TCDD (2.5 times peak to peak noise) was found to be in the 30-60 picogram range (3-6 ppt in beef fat using 10 gram samples). None of the sixteen samples comprising two of the three studies showed any response for TCDD. In the third study, in which the animals were confined to a fenced pasture sprayed in its entirety with a 2,4,5-T herbicide, samples from three of the seven animals gave a positive response at the extremely low level of 3 to 4 ppt TCDD, which is at the detection limit.