FE modeling of Lamb mode diffraction by defects in anisotropic viscoelastic plates

A Finite Element code is used in a stationary mode to compute, at a single frequency, the stress and displacement fields in plates made of anisotropic, viscoelastic materials. An appropriated spatial load at one boundary of the plate is applied to generate a guided mode. This step is included in a frequency loop for which the number of iterations (≈ usually less than 50) is defined by the frequency spectrum of a temporal excitation. Then the temporal response at any location in the plate can be reconstructed with inverse Fourier transform. The phase velocity, attenuation and nature of one or several propagating modes can be identified in the classical frequency/wave number representation. The first example concerns the interaction of the symmetric Lamb mode S₀ with an opening notch in a Perspex plate. The proportion of S₀ and converted antisymmetric A₀ mode, transmitted past the notch is evaluated by the FE method and validated by a comparison with measurements made on a real system using an air coupled transducer. The second example shows the effect of the viscoelasticity on the propagation of the symmetric Lamb mode S₀ in a cross-ply, carbon-epoxy material plate. Focus is made on some difficulties that the attenuation causes on the detection of a delamination between plies.     

Long-term functional outcome following transient middle cerebral artery occlusion in the rat: Correlation between brain damage and behavioral impairment.

The assessment of both histological and functional long-term outcomes after cerebral ischemia is increasingly recommended for preclinical studies. Whereas correlations between behavioral impairments and primary ischemic lesion are documented, little is known about their relationships with remote nonischemic regions that undergo secondary degeneration, such as the thalamus. Anesthetized rats were subjected to mild (30 min) or severe (60 min) occlusion of the middle cerebral artery. Two months after ischemia, sensorimotor behavior was assessed according to the neurological score, limb-placing, adhesive-removal, and staircase tests; the final histological lesion was measured after this assessment. Cortical damage was correlated to all transient and long-lasting sensorimotor deficits, whereas striatal lesion was more consistently reflected by the forelimb-placing reflexes and adhesive-removal motor deficits. By contrast, the thalamic atrophy was not correlated to early neurological impairment, but rather to the late sensory deficit at the adhesive-removal test and to the skilled forepaw reaching alteration at the staircase test. This suggests that thalamus contributes, albeit moderately, to the ischemia-induced long-lasting sensorimotor deficits, some of which represent relevant targets for therapeutic interventions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Presence of a gene encoding choline sulfatase in Sinorhizobium meliloti bet operon: choline-O-sulfate is metabolized into glycine betaine

Glycine betaine is a potent osmoprotectant accumulated by Sinorhizobium meliloti to cope with osmotic stress. The biosynthesis of glycine betaine from choline is encoded by an operon of four genes, betICBA, as determined by sequence and mutant analysis. The betI and betC genes are separated by an intergenic region containing a 130-bp mosaic element that also is present between the betB and betA genes. In addition to the genes encoding a presumed regulatory protein (betI), the betaine aldehyde dehydrogenase (betB), and the choline dehydrogenase (betA) enzymes also found in Escherichia coli, a new gene (betC) was identified as encoding a choline sulfatase catalyzing the conversion of choline-O-sulfate and, at a lower rate, phosphorylcholine, into choline. Choline sulfatase activity was absent from betC but not from betB mutants and was shown to be induced indifferently by choline or choline-O-sulfate as were the other enzymes of the pathway. Unlike what has been shown in other bacteria and plants, choline-O-sulfate is not used as an osmoprotectant per se in S. meliloti, but is metabolized into glycine betaine. S. meliloti also can use this compound as the sole carbon, nitrogen, and sulfur source for growth and that depends on a functional bet locus. In conclusion, choline-O-sulfate and phosphorylcholine, which are found in higher plants and fungi, appear to be substrates for glycine betaine biosynthesis in S. meliloti.     

Differential diagnosis between exudate and transudate in pleural effusion

We determined the relative contributions of endogenous gastrin, histamine and cholinergic tone to basal acid secretion in chronic fistula rats. Results were compared with those for acid secretion in pylorus-ligated rats. In chronic fistula rats, YM022 ?(R)-1-[2,3-dihydro-1-(2'-methylphenacyl)-2-oxo-5-phenyl-1 H-1,4-benzodiazepin-3-yl]-3-(3-methylphenyl)urea? dose-dependently inhibited pentagastrin-stimulated acid secretion and abolished this secretion at 1 mumol/kg, s.c., but did not affect histamine- and carbachol-induced acid secretion even at 10 mumol/kg. In contrast, famotidine at 1 mumol/kg completely inhibited not only the acid secretion induced by histamine but also those by pentagastrin and carbachol. Furthermore, atropine abolished carbachol- and pentagastrin-stimulated acid secretion and significantly suppressed histamine-stimulated acid secretion at 0.1 mumol/kg. YM022 dose-dependently inhibited basal acid secretion. The YM022 dosage required to inhibit basal acid secretion is consistent with that required to suppress pentagastrin-induced acid secretion. Famotidine (1 mumol/kg) and atropine (0.1 mumol/kg) also abolished basal acid secretion. In pylorus-ligated rats, YM022 inhibited acid secretion in a dose-dependent manner; the inhibition at 1 mumol/kg, i.v. was 65%. No additional effect was observed when rats were dosed at 30 mumol/kg. Famotidine partially inhibited acid secretion in these rats, whereas atropine abolished this secretion. These results indicate that the major part of basal acid secretion in rats is attributable to endogenous gastrin via histamine- and cholinergic tone-dependent pathways. Moreover, pylorus ligation reduces the relative contribution of gastrin to acid secretion due to the activation of cholinergic tone.     

Mechanical Barkhausen noise during fatigue of iron

In this paper, the potentiality for using the mechanical Barkhausen noise (BN) to monitor fatigue tests of ferrous materials is investigated. The fatigue tests are carried out on iron specimens subjected to rotational bending on a standard fatigue bench. The mechanical BN is detected using an encircling coil. The mechanical BN exhibits three main stages during the fatigue life: it increases at the beginning of the test, then a plateau is reached and finally it decreases before rupture. These successive stages can be associated to the classical stages of the fatigue life of metals and alloys: crystalline microstructure changes, a saturation stage, and microcrack nucleation and growth leading to rupture. An early indicator of damage is derived from the results.     

Cyclic Testing of Concrete-Filled Circular Steel Bridge Piers having Encased Fixed-Based Detail

To investigate their adequacy as energy dissipating elements during earthquakes, this paper reports on cyclic inelastic tests executed to determine the maximum strength and ductility of four concrete-filled circular steel piers joined to a foundation detail proposed to develop the full composite strength at the base of these columns. Column diameters considered were 324 and 406 mm, with D/t ratios ranging from 34 to 64. The ductility of all tested columns was found to be good, all columns being able to reach drifts of 7% before a significant loss in moment capacity occurred as a result of cracks opening on the local buckles, suggesting that concrete-filled steel tubes can be effective as bridge piers in seismic regions of North America.     

Thrombus formation on a calcific and severely stenotic bicuspid aortic valve

We report on a case of thrombus formation on a native bicuspid aortic valve, which was found during an elective operation for aortic valve replacement. Although no apparent predisposing cause of thrombosis could be ascertained, severe calcific stenosis of the bicuspid valve and cardiac catheterization may have played a role. The patient is in excellent condition 9 months after the operation.     

Chitosan supported palladium catalyst. VI. Nitroaniline degradation

A chitosan‐supported palladium catalyst was prepared by immobilization of palladium on glutaraldehyde crosslinked chitosan followed by in situ chemical reduction. This catalyst was successfully used for the degradation of 4‐nitroaniline (4‐NA) in the presence of sodium formate, used as the hydrogen donor. The reaction product was 1,4‐phenylenediamine. The degradation was favored by acidic pH. A 10 to 15 excess of formate (compared to 4‐NA) is required to achieve complete degradation of the substrate. The reaction appears to be limited to the external layers of the catalyst: small particle size is required to optimize the degradation kinetics. Alternatively, an increase of catalyst dosage is required to increase kinetic rates but at the expense of palladium consumption. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1634–1642, 2004     

Paracoccidioidoma: case record and review

The ulcer resulting from snake-bite injury was characterized by deep and wide tissue necrosis and secondary infection. The patient was at high risk of loss of function of his extremity. From 1989 to 1996, 16 cases with deep ulcer of the upper extremity resulting from snake-bite injury were treated with different types of axial thoraco-abdominal skin flaps, depending on the location of the ulcer. Thoraco-umbilical skin flap was used in 2 cases, lateral thoracoabdominal skin flap in 1 case, iliolumbar skin flaps in 5 cases, lower abdominal skin flaps in 6 cases, lower abdominal divided foliated skin flap in 1 case and Y-shaped hypogastric skin flap in 1 case. Reparative operation was carried out within 3 weeks after injury and primary repair were undertaken in 6 of them. The pedicles were divided in 17 to 24 days after operation. Twelve flaps survived. Three of the 6 flaps had mild signs of inflammation which disappeared after administration of antibiotics. One had necrosis of the distal part of the flap, and was healed with split skin graft. This type of skin flap was an ideal method for the treatment of snake-bite injury of the upper extremity.