Hot working behavior of a WE54 magnesium alloy

The plastic deformation and recrystallization behavior of the commercial magnesium alloys WE54 was analyzed using the strain rates 0.01, 0.1, 1, and 5 s^?1 in the temperature range from 400 to 550 °C. The dependence of the flow stress on the temperature and the strain rate was modeled using the Garofalo hyperbolic sine equation. Thereby, the activation energy for plastic deformation of 224 kJ mol^?1 was determined considering the flow stress at a strain of 0.5. The analysis revealed a stress exponent of 3.2. Furthermore, processing maps were generated by plotting the efficiency of power dissipation and the instability parameter considering different instability criteria as a function of the temperature and the strain rate. Depending on these parameters the extent of the recrystallization and the localization of the nucleation varied, significantly. At 400 °C, the recrystallization is very limited and was observed at grain boundaries (GB), shear bands (SB), and twin boundaries (TW). Increasing temperatures result in an increased recrystallized fraction, while lower strain rates promote grain boundary nucleation and reduce the amount of SBN and TW. The prediction of the processing map was verified by large scale extrusion trials, which proof that the evaluation of hot compression data can provide an effective tool to establish viable processing parameters.     

Neuroprotective Role of Liver Growth Factor “LGF” in an Experimental Model of Cerebellar Ataxia

Cerebellar ataxias (CA) comprise a heterogeneous group of neurodegenerative diseases characterized by a lack of motor coordination. They are caused by disturbances in the cerebellum and its associated circuitries, so the major therapeutic goal is to correct cerebellar dysfunction. Neurotrophic factors enhance the survival and differentiation of selected types of neurons. Liver growth factor (LGF) is a hepatic mitogen that shows biological activity in neuroregenerative therapies. We investigate the potential therapeutic activity of LGF in the 3-acetylpiridine (3-AP) rat model of CA. This model of CA consists in the lesion of the inferior olive-induced by 3-AP (40 mg/kg). Ataxic rats were treated with 5 µg/rat LGF or vehicle during 3 weeks, analyzing: (a) motor coordination by using the rota-rod test; and (b) the immunohistochemical and biochemical evolution of several parameters related with the olivo-cerebellar function. Motor coordination improved in 3-AP-lesioned rats that received LGF treatment. LGF up-regulated NeuN and Bcl-2 protein levels in the brainstem, and increased calbindin expression and the number of neurons receiving calbindin-positive projections in the cerebellum. LGF also reduced extracellular glutamate and GABA concentrations and microglia activation in the cerebellum. In view of these results, we propose LGF as a potential therapeutic agent in cerebellar ataxias.     

An extended shear angle model derived from in situ strain measurements during orthogonal cutting

There are numerous cutting models which describe the chip formation process. However, they are based on a number of simplifying assumptions. In order to verify these assumptions and to get a better understanding of the cutting process, the different stress states in the chip formation zone were determined by means of diffraction experiments with monochromatic high-energy synchrotron X-radiation during orthogonal, quasistatic cutting of the material C45E. The results from the experiments are compared with simulated stresses. The experimental data indicate that the assumption of a free chip flow according to the shear angle model of Opitz and Hucks is not valid. The model was therefore extended considering the normal stresses in direction of the chip flow.     

Determination of the internal morphology of poly (D,L-lactide) microspheres using stereological methods

The morphological characteristics of the internal structure of poly (D,L-lactide) microspheres have been determined by stereological methods in two different formulations of microspheres, with different internal structures, prepared by using a double emulsion method. In one formulation the internal emulsion was produced by homogenisation at 3000 rpm, whilst the other was prepared at 11000 rpm. As expected the formulation prepared at the lower speed contained larger and more broadly distributed pores than that prepared at the higher speed. The porosity, pore size distribution and total internal surface area of the microspheres were obtained by stereological methods from electron microscopic measurements of the sectioned microspheres. It was found that whilst the porosity of the microspheres was 0.6 in both formulations, the preparation method gave rise to large differences in their pore size distribution characteristics. The pore size distribution was simulated by computer modelling to validate and compare alternative stereological algorithms. It was found that the Saltykov unfolding method predicts the measured pore size distribution more accurately than the Cruz-Orive unfolding method (at significance level alpha=0.1). This finding was attributed to the violation of one of the basic assumptions of the Cruz-Orive unfolding method.     

The imprinted domain in mouse distal Chromosome 7: reagents for mutagenesis and sequencing

BACKGROUND: Right lower quadrant abdominal pain may pose a diagnostic problem in patients with cystic fibrosis. Abdominal ultrasound examination, used commonly in the diagnostic work-up, may reveal abnormalities of the appendix. However, interpretation of such findings is problematic, because the appearance of the gastrointestinal system during routine examination has not been documented in patients with cystic fibrosis. The purpose of this study was to investigate the findings during routine abdominal ultrasound scans in our cohort of patients with cystic fibrosis and in control subjects. METHODS: Abdominal ultrasound scans were performed prospectively during routine clinic visits in a cohort of patients with cystic fibrosis. RESULTS: Fifty patients aged 10+/-6 years, (range, 0.5-28 years) were examined; 45 had pancreatic insufficiency. Four patients (3 with pancreatic insufficiency) reported right lower quadrant pain at the time of the scan. According to standard ultrasound criteria, the appearance of the appendix was abnormal in 8 patients (16%), 6 had a mucoid appendix, and 2 had a pathologically thickened appendiceal wall. Only 1 of these 8 patients mentioned abdominal pain at the time of the study. Other incidental findings included gallstones (3 patients), intussusception (2 patients), and pancreatic cyst (1 patient). CONCLUSIONS: Abnormalities can be observed during routine abdominal ultrasonographic studies in cystic fibrosis. These findings may not be associated with abdominal pain; their clinical relevance needs further investigation.     

The urinary ratio of 5-hydroxytryptophol to 5-hydroxyindole-3-acetic acid in surgical patients with chronic alcohol misuse

Interactions among growth factors are important in a variety of physiological and pathological processes. The regulation of IGF-I mRNA expression by bFGF was investigated in cultured rat Müller cells and the mechanism of regulation studied. Müller cells from 1- to 3-day-old Sprague-Dawley rats were isolated and cultured with Eagle MEM+10% FCS. Cultured cells were identified by immunocytochemistry using antibodies against vimentin, carbonic anhydrase C, and glutamine synthetase. Cells of passage 1-4 were treated with bFGF, the PKC inhibitor H-7, calphostin C, the PKC activator PMA or the PKA inhibitor H-89, as well as the adenylate cyclase activator forskolin, or adenylate cyclase inhibitor SQ22536. IGF-I and bFGF expression levels were assessed by Northern blot analysis. The addition of bFGF to culture medium down-regulated IGF-I expression in a dose- and time-dependent manner. Decrease of IGF-I expression started at a bFGF concentration of 1 ng ml-1. IGF-I mRNA level declined to 44% of baseline level at 10 ng ml-1 of bFGF, and reached a trough of 40% at 50 ng ml-1. At 10 ng ml-1 of bFGF, down-regulation of IGF-I expression was observed as early as 4 hr (60%) after treatment, and reached a trough of 42% by 8 hr. The temporal and concentration dependence of IGF-I expression by addition of the PKC activator PMA, to culture medium was similar to that due to the addition of bFGF. The down-regulation of IGF-I expression by bFGF (10 ng ml-1) and PMA (0.1 microM) was blocked by the PKC inhibitors H-7 (30 microM) and calphostin C (1 microM). Forskolin (5 microM), an adenylate cyclase activator, had activator, had no effect on IGF-I expression. SQ22536 (100 microM), an adenylate cyclase inhibitor, and H-89, a PKA inhibitor, had no inhibitory effect on bFGF-induced down-regulation of IGF-I expression. These results indicate that bFGF down-regulates IGF-I expression in cultured rat M uller cells through PKC activation.     

Analysis of tool wear and residual stress of CVD diamond coated cemented carbide tools in the machining of aluminium silicon alloys

Aluminium alloys have found increasing applications in the automotive and aeronautical industries in recent years. Due to their extraordinary properties however, the machining of these alloys still poses difficulties, and requires the optimized combination of cutting tool material and geometry. The potential of CVD diamond coated carbide tools has been demonstrated in recent years, however tool wear and short tool life remain as issues to be resolved. Key to increasing the tool life of CVD diamond coated tools is the further development of the coating process to optimize the coating adhesion. An understanding of the substrate and coating residual stress profiles must be gained in order to achieve this. Compressive residual stresses in cutting tools can lead to a higher crack resistance, but also to early coating delamination and tool failure. To analyze the influence of residual stresses on the coating quality and tool life, the residual stress profiles of tungsten carbide substrates and CVD diamond coatings were measured using X-ray and synchrotron radiation. The influence of the tungsten carbide substrate type and the CVD diamond coating process on the residual stress profiles was thus determined. In order to analyze the performance of the coated tools and the influence of the residual stresses on the tool lifetime, machining tests were performed with two aluminium silicon alloys. The tool wear, tool lifetime and workpiece quality were examined. Finally, many of the commonly used wear tests used to analyze the wear resistance of tool coatings cannot be implemented for CVD diamond coatings due to their high hardness. An impact test was therefore constructed to allow the determination of the wear resistance of CVD diamond tools.     

Linkage of proximal myotonic myopathy to chromosome 3q

We performed genetic linkage analysis in nine German proximal myotonic myopathy (PROMM) families using DNA-markers D3S1541 and D3S1589 from the region of the recently discovered gene locus of myotonic dystrophy type 2 (DM2) on chromosome 3q. Two-point analysis supplied an lod score of 5.9. We conclude that a gene causing PROMM is located on chromosome 3q. PROMM and DM2 may be allelic disorders or may be caused by closely linked genes.     

Using fluorescence-based human androgen receptor gene assay to analyze the clonality of microdissected dendritic cell tumors

The AGT1 permease is a alpha-glucoside-H+ symporter responsible for the active transport of maltose, trehalose, maltotriose, alpha-methylglucoside, melezitose and sucrose. In wild-type as well as in MAL constitutive strains, alpha-methylglucoside seemed to be the best inducer of transport activity, while trehalose had no inducing effect. Based on the initial rates of transport it seems that the sugar preferentially transported by this permease is trehalose, followed by sucrose.