Bacterial reduction of N-oxides of tobacco- specific nitrosamines (TSNA)

1 Contrary to established metabolic pattern, a recent investigation of NNK metabolism produced in rat urine higher levels of 4-(methylnitrosamino)-1-(3-pyridyl)-1- butanone (NNK) and 4-(methylnitrosamino)-1-(3-pyri dyl)-1-butanol (NNAL) than their N-oxides, suggesting that reconversion of N-oxides could occur after urine formation. 2 To verify the possible role of bacteria in the reduction of NNK-N-oxide and NNAL-N-oxide to their respective parent compounds, NNK and NNAL, in smokers with urinary tract infection (UTI), the N-oxides were isolated from the urine of rats treated with 5-3HNNK and individually incubated at 37°C with ten bacterial species in sterile human urine under different pH regimens. After incubation with the bacteria, aliquots of culture media were analyzed by high pressure liquid chromatography (HPLC) with radiochemical detection. 3 Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae and Proteus mirabilis possessed varying capacity to regenerate NNK and NNAL from their N- oxides while others showed no detectable reductive capability within 24 h. 4 This result constitutes the first experimental evidence that in tobacco users with concomitant UTI, bacterial regeneration of the procarcinogenic NNK and NNAL from their N-oxides could occur in the bladder leading to increased carcinogen burden in these individuals

Sobre el problema geomorfológico del alineamiento de las cumbres en la region del lago Buenos Aires y la determinación de las líneas tectónicas en la parte sur de la Cordillera de Los Andes

En el presente trabajo se desarrolla un método de análisis geomorfológico-estadístico aplicado a la deducción de hechos geológicos generales. Es el método estadístico de los alineamientos, que se ha empleado para determinar las direcciones tectónicas de la región cordillerana del lago Buenos Aires, valiéndose del trazado de los alineamientos de las cumbres de la región considerada. De ese modo se ha inferido la existencia de cuatro direcciones tectónicas predominantes, caracterizadas por ángulos de 27°, 55°, 100° y 175°, medidos a partir de la dirección Norte y en ei sentido del movimiento de las agujas del reloj.The purpose of this work is to develope a method of a morphologic-statistical analysis applied to the deduction of general geological fats. This is the statistical method of the alinements, which has been applied to determine the tectonic directions of the Andes región in the vecinity of the Buenos Aires lalte, by establishing the alinements of the tops of the mountains in the above mentioned región. In this way it has possible to deduce the existance of four main tectonic directions, distinguished by angles of 27°, 55°, 100° and 175°, measured from the North and moving like of the hands of a dock

Efficiency and comfort of knee braces: A parametric study based on computational modelling

International audienceKnee orthotic devices are widely proposed by physicians and medical practitioners for preventive or therapeutic objectives in relation with their effects, usually known as to stabilize joint or restrict ranges of motion. This study focuses on the understanding of force transfer mechanisms from the brace to the joint thanks to a Finite Element Model. A Design Of Experiments approach was used to characterize the stiffness and comfort of various braces in order to identify their mechanically influent characteristics. Results show conflicting behavior: influent parameters such as the brace size or textile stiffness improve performance in detriment of comfort. Thanks to this computational tool, novel brace designs can be tested and evaluated for an optimal mechanical efficiency of the devices and a better compliance of the patient to the treatment

Dynamic correlations of the Coulomb Luttinger liquid

The dynamic density response function, form-factor, and spectral function of a Luttinger liquid with Coulomb electron-electron interaction are studied with the emphasis on the short-range electron correlations. The Coulomb interaction changes dramatically the density response function as compared to the case of the short-ranged interaction. The form of the density response function is smoothing with time, and the oscillatory structure appears. However, the spectral functions remain qualitatively the same. The dynamic form-factor contains the $\delta$-peak in the long-wave region, corresponding to one-boson excitations. Besides, the multi-boson-excitations band exists in the wave-number region near to $2k_F$. The dynamic form-factor diverges at the edges of this band, while the dielectric function goes to zero there, which indicates the appearance of a soft mode. We develop a method to analyze the asymptotics of the spectral functions near to the edges of the multi-boson-excitations band.Comment: 11 pages, 3 figures, submitted to PR

Late Pleistocene yedoma in south-western Yukon (Canada): a remnant of Eastern Beringia?

Yedoma deposits developed from the syngenetic accumulation and freezing of organic-rich and ice-rich sediments during the Late Pleistocene over vast portions of Siberia, Alaska and Yukon Territory. Cryostratigraphic investigations revealed the presence of a yedoma deposit in the Beaver Creek area of south-western Yukon. The Beaver Creek area was not glaciated during the last glacial advance and the cryostratigraphic record comprises Middle Wisconsinian up to Holocene deposits covering the Mirror Creek disintegration moraine. Reworking of glacial deposits by alluvial and solifluction processes and peat accumulation in the depression of the hummocky moraine likely occurred during the Middle Wisconsinian period and was followed during the Late Wisconsinian by the yedoma build-up. A major thaw event interrupted the syngenetic permafrost aggradation which eventually resumed as attested by the upward growth of ice wedges

Efficiency of knee braces: A biomechanical approach based on computational modeling.

International audienceThe knee is the largest joint in the body and is vulnerable to injury during athletic activities or to musculoskeletal conditions such as arthrosis. Knee orthotic devices are widely used by physicians as preventive and therapeutic adjuncts for both musculoskeletal conditions and sport injuries. Their goal is to stabilize or restrict non-physiological knee ranges of motion. The efficiency of these devices has been studied both from clinical and biomechanical perspectives, leading to controversial results from questionable methods. As for now, the mechanisms of force transfer from the device to the joint bones have never been characterized and both device manufacturers and clinicians still expect a standard procedure to compare and grade the efficiency of different knee braces. The objectives of this work are: 1. to quantify the mechanical reactions of knee braces against non-physiological movements; 2. to relate these mechanical reactions to the pressure applied by the braces onto the skin. The latter is particularly important because it refers to comfort issues, which play a key role in a patient's compliance to the orthopedic treatment. A Finite Element Model of a braced human leg is developed. The model is first applied for characterizing the behavior of different kinds of knee braces, focusing on the mechanical reactions against non-physiological movements. In the model, a special attention is paid to the interfaces between knee-braces and the skin and between the skin and the muscles. The interface properties of the model are calibrated against experimental data measured by full-field measurements of 3D displacement over the surface of a patient's leg. The results show that the mechanical action of knee braces is essentially limited by skin/fabric and skin/muscles sliding. Finally, the model leads to a better understanding of the knee/brace interaction, and of the role of the brace components on the stability of the injured knee. Thanks to this computational tool, novel brace designs can be tested and evaluated for an optimal mechanical efficiency of the devices. Future work consists in considering the patient's comfort in the approach

Evaluation of the mechanical efficiency of knee braces based on computational modelling

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