Mechanical modeling of macroscopic behavior for anisotropic and heterogeneous metal alloys

The present investigative work was focused on modeling the effect of through-thickness texture gradients on the global mechanical behavior of a rolled ferritic stainless steel sheet. The material was experimentally characterized according to the needs of the analysis. First, a homogeneous rolled sheet was analytically described, based on Hill’s formalism of generalized materials. Then, a heterogeneous sheet was analyzed through two analytic approaches. The predictive capability of the resulting approaches was also proven in relation to the choice of the pseudo-anisotropic coefficients selected from fictitious materials. Finally, the application of a simple method, called continuum mechanics of textured polycrystals, taking into account crystallographic considerations, was adopted. As a result, this method was found to be an effective way to model the mechanical behavior of an anisotropic and heterogeneous sheet, replicating the evolution of experimental yield stress and plastic strain ratio either in terms of evolution or in those of level values. An attempt to estimate the impact of low-texture gradients on the heterogeneity of any industrial metal sheet is also made.     

Assessment of neutron dosemeters around standard sources and nuclear fissile objects

In order to evaluate the neutron doses around nuclear fissile objects, a comparative study has been made on several neutron dosemeters: bubble dosemeters, etched-track detectors (CR-39) and 3He-filled proportional counters used as dose-rate meters. The measurements were made on the ambient and the personal dose equivalents H*(10) and Hp(10). Results showed that several bubble dosemeters should have been used due to a low reproducibility in the measurements. A strong correlation with the neutron energy was also found, with about a 30% underestimation of Hp(10) for neutrons from the PuBe source, and about a 9% overestimation for neutrons from the 252Cf source. Measurements of the nuclear fissile objects were made using the CR-39 and the dose-rate meters. The CR-39 led to an underestimation of 30% with respect to the neutron dose-rate meter measurements. In addition, the MCNP calculation code was used in the different configurations.     

Application of ultrafiltration to the preparation of defined hydrolysates of bovine haemoglobin

Many uses of protein hydrolysates have been developed and applied to areas such as nutritional therapy, culture media, and the isolation of biologically active peptides. All these applications need carefully controlled and characterized hydrolysates. In order to produce such a type of hydrolysate, it is possible to use haemoglobin which is a very well defined and constant protein source. Enzymic hydrolysis of haemoglobin by pepsin was carried out at pilot-plant scale in an ultrafiltration reactor with mineral membranes. The object was to obtain a reproducible, decolorized, salt-free enzymic hydrolysate. Two types of membranes were tested having 10000 dalton (M5 type) and 20000 dalton (M4 type) cut-offs. Little significant difference was observed in the final products when both types of membranes were used. Reproducibility of hydrolysates was verified by amino acid analysis and gel filtration chromatography. The haemoglobin hydrolysates produced contained more than 90% protein and are especially suitable for fine applications.     

Effect of protein concentration, pH, lactose content and pasteurization on thermal gelation of acid caprine whey protein concentrates

The influence of pH (4.5-6.5), sodium chloride content (125-375 mM), calcium chloride content (10-30 mM), protein concentration (70-90 g/l) and lactose content on the gel hardness of goat whey protein concentrate (GWPC) in relation to the origin of the acid whey (raw or pasteurized milk) was studied using a factorial design. Gels were obtained after heat treatment (90 degrees C, 30 min). Gel hardness was measured using texture analyser. Only protein concentration and pH were found to have a statistically significant effect on the gel hardness. An increase in the protein concentration resulted in an increase in the gel hardness. GWPC containing 800g/kg protein formed gels with a hardness maximum at the pHi, whereas GWPC containing 300 g/kg protein did not form true gels. Whey from pasteurized milk formed softer gels than whey from raw milk. A high lactose content (approximately 360 g/kg) also reduced the gelation performance of GWPC.     

Hot plane strain compression testing of aluminum alloys by channel-die compression

A thoroughly tested, high-temperature channel-die compression (CDC) rig is described for simulating hot plane strain compression of metallic alloys up to 500 °C. The equipment is currently used to characterize the flow stress and microstructure evolution in hot-rolled Al alloys. It has been validated by several tests involving (1) metallographic analysis of deformed samples; (2) flow stress comparisons with the same, or similar alloys deformed in conventional uniaxial or plane strain compression; and (3) microstructure and texture measurements. The use of modern lubricants enables one to obtain accurate flow stresses and true plane strain deformations that are homogeneous over 80 pct of the sample. The equipment also features rapid heating and cooling systems to minimize thermally-induced microstructure changes. Some results on high-temperature slip systems, hot deformation textures, and microstructures, and the behavior of constituent particles are outlined to illustrate the advantages of the technique.     

A randomized double-blind trial comparing cibenzoline and disopyramide in the prevention of recurrences of atrial tachyarrhythmia

The aim of this multicenter, randomised, double-blind trial was to compare the efficacy and tolerance of oral disopyramide (D: 250 mg slow release twice daily) compared with cibenzoline (C: 130 mg twice daily) in the prevention of recurrences of atrial arrhythmias over a 6 month period. Sixty patients (mean age: 62 +/- 14 years; 37 men, 23 women; cardiac disease in 60% of cases) were randomised to two groups: C (N = 31) and D (N = 29). The commonest arrhythmia was atrial fibrillation (83%). The arrhythmia was recent (< 3 months) in 41% of patients and present for more than one year in 38% of patients. Sixteen patients of Group C (52%) and 11 of Group D (38%) had recurrences after an average of 79 +/- 58 days for Group C and 58 +/- 40 days for Group D (p = NS). The probability of absence of recurrence at 6 months was 36 +/- 11% in Group C and 55 +/- 10% in Group D (p = NS). Four patients in Group C (13%) and 13 patients in Group D (45%) had at least one unwanted side-effect (p = 0.009). Treatment was stopped because of side-effects in 2 patients in group C (6%) and 6 patients in Group D (21%). These results show that cibenzoline has a comparable efficacy for the prevention of recurrence of atrial tachyarrhythmia and is significantly better tolerated than disopyramide. This differences is mainly related to the marked anticholinergic effects of disopyramide.     

Hemorphins inhibit angiotensin IV binding and interact with aminopeptidase N

[125I]-Ang IV binding to rabbit collecting duct cell membranes was inhibited by hemorphins (H), a class of endogenous peptides obtained by hydrolysis of the beta chain of hemoglobin. The most potent competitors were those with a valine in their N-terminal part such as LVV-H7 and VV-H7 (IC50 = 1.3 nM) followed by VV-H8 and K6VV-H7 (5.1 nM). The same H, like Ang IV, interacted with aminopeptidase N (APN) as shown by their inhibitory effect (28-36%) on APN activity. HPLC analysis showed that only H with a N-terminal valine or leucine were hydrolyzed. Since H are detected in the body fluids, they are likely to act as endogenous competitors of Ang IV.     

Transient global amnesia: implicit/explicit memory dissociation and PET assessment of brain perfusion and oxygen metabolism in the acute stage

OBJECTIVES: To assess explicit memory and two components of implicit memory--that is, perceptual-verbal skill learning and lexical-semantic priming effects--as well as resting cerebral blood flow (CBF) and oxygen metabolism (CMRO2) during the acute phase of transient global amnesia. METHODS: In a 59 year old woman, whose amnestic episode fulfilled all current criteria for transient global amnesia, a neuropsychological protocol was administered, including word learning, story recall, categorical fluency, mirror reading, and word stem completion tasks. PET was performed using the (15)O steady state inhalation method, while the patient still exhibited severe anterograde amnesia and was interleaved with the cognitive tests. RESULTS: There was a clear cut dissociation between impaired long term episodic memory and preserved implicit memory for its two components. Categorical fluency was significantly altered, suggesting word retrieval strategy--rather than semantic memory--impairment. The PET study disclosed a reduced CMRO2 with relatively or fully preserved CBF in the left prefrontotemporal cortex and lentiform nucleus, and the reverse pattern over the left occipital cortex. CONCLUSIONS: The PET alterations with patchy CBF-CMRO2 uncoupling would be compatible with a migraine-like phenomenon and indicate that the isolated assessment of perfusion in transient global amnesia may be misleading. The pattern of metabolic depression, with sparing of the hippocampal area, is one among the distinct patterns of brain dysfunction that underlie the (apparently) uniform clinical presentation of transient global amnesia. The finding of a left prefrontal hypometabolism in the face of impaired episodic memory and altered verbal fluency would fit present day concepts from PET activation studies about the role of this area in episodic and semantic memory encoding/retrieval. Likewise, the changes affecting the lenticular nucleus but sparing the caudate would be consistent with the normal performance in perceptual-verbal skill learning. Finally, unaltered lexical-semantic priming effects, despite left temporal cortex hypometabolism, suggest that these processes are subserved by a more distributed neocortical network.     

DEHYDRATION BY DESORPTION AND BY SPRAY DRYING OF DAIRY PROTEINS: INFLUENCE OF THE MINERAL ENVIRONMENT

A drying method by desorption in a water activity meter was used to simulate the conditions of spray drying and to determine the water transfer inside dairy concentrates towards the surface and from the surface to the drying air. The concentrates were also spray dried and solubility index of powders were determined during reconstitution. Whey protein concentrates (WPC) and native phosphocaseinate suspensions (NPCS) were used to study the effect of NaCl (420 mM), CaCl₂ (222 raM), sodium phosphate (173 mM) and sodium citrate (238 mM) on the water transfers. The decrease in water transfer during drying was explained by the high hygroscopicity of added mineral salts to WPC. NaCl addition to NPCS decreased the water transfer during drying, but increased the solubility index. Citrate and phosphate addition to NPCS increased the water transfer during drying and reconstitution. CaCl₂ increased the water transfer during drying but the solubility index was always low. Results are discussed as a function of the aqueous environment, of the nature of mineral salts, of the structure of dairy proteins and of protein solvation.