Design of TRIP Steel With High Welding and Galvanizing Performance in Light of Thermodynamics and Kinetics

 A new type of transformation induced plasticity (TRIP) steel with not only high strength and high ductility but also superior welding and galvanizing properties was designed and developed recently. Low carbon and low silicon content were preliminarily selected with the aim of meeting the requirements of superior quality in both welding and galvanizing. Phosphorus was chosen as one of the alloying elements, because it could reduce carbon activity in cementite and increase the stability of austenite. In addition, the possibility of phosphorus segregating at grain boundary was also discussed by thermodynamics as well as kinetics. Phase diagram was estimated at high temperature and the composition of the steel was then selected in the hyperperitectic range to avoid problems, which might occur in sheet steel continuous casting. Phase diagram in the inter critical temperature was estimated for the steel to obtain the starting temperature of fast cooling. For understanding the minimum rate of fast cooling, pearlite growth kinetics was calculated with self developed diffusion coefficients of elements in grain boundary. Overaging temperature was determined through the calculation of T0 temperature by both equilibrium and para equilibrium assumptions, which was different from the current determination, which is only based on an equilibrium estimation.     

PP7, a plant phosphatase representing a novel evolutionary branch of eukaryotic protein Ser/Thr phosphatases

Theoretical quantum mechanical ab initio Hartree-Fock calculations on molecular systems, modeling processes related to the specificity of thymidylate synthase inactivation are reported. We considered several steps of the methylation of the substrate dUMP and 4- or 5-mono- and 4,5-bisubstituted dUMP analogs, as well. The following reactions were modeled: the cysteine residue (Cys198 in the L.casei enzyme) nucleophilic attack on the substrate and the substrate C(5)-H proton abstraction. The substrate was modeled by the 1-methyluracil molecule and its structural analogs. The cysteine Cys198 residue was modeled by the methylmercaptane molecule. The substrate-enzyme binary complex was modeled by the 1-methyl-5,6-dihydro-6-thiomethyl-uracil (P1) molecule. The present theoretical calculations suggest that the cysteine nucleophilic attack on the substrate may result in the SH-group addition to the pyrimidine C(5)=C(6) bond in the course of a weakly exothermic reaction. The formerly presumed enolate carbanion appeared to be weakly stable or unstable and it can readily split into the thiol and pyrimidine residues. The s2-thio- (P2) and s2,4-dithio- (P3) substrate analogs should form stable thiolate anions after cysteine residue attachment to the C(6) position of the pyrimidine ring. Studies of the deformed P1 molecule interacting with a water molecule bound to the pyrimidine C(4)=O carbonyl residue allow a suggestion that this water molecule may be directly involved in the C(5)-H proton abstraction and may serve as a proton transmitter between the substrate and the proton acceptor residue, possibly located on the cofactor N10-nitrogen. Interaction of the pyrimidine C(4)=O group, or its modification, with the N5,10-methylenetetrahydrofolate N(10) nitrogen atom is suggested as an additional factor influencing the inhibition process.     

Temporal synthesis of band 3 oligomers during terminal maturation of mouse erythroblasts. Dimers and tetramers exist in the membrane as preformed stable species

Band 3, the anion transport protein of the erythrocyte membrane, exists in the membrane as a mixture of dimers (B3D) and tetramers (B3T). The dimers are not linked to the skeleton and constitute the free mobile band 3 fraction. The tetramers are linked to the skeleton by their interaction with ankyrin. In this report we have examined the temporal synthesis and assembly of band 3 oligomers into the plasma membrane during red cell maturation. The oligomeric state of newly synthesized band 3 in early and late erythroblasts was analyzed by size-exclusion high-pressure liquid chromatography of band 3 extracts derived by mild extraction of plasma membranes with the nonionic detergent C12E8 (octaethylene glycol n-dodecyl monoether). This analysis revealed that at the early erythroblast stage, the newly synthesized band 3 is present predominantly as tetramers, whereas at the late stages of erythroid maturation, it is present exclusively as dimers. To examine whether the dimers and tetramers exist in the membrane as preformed stable species or whether they are interconvertible, the fate of band 3 species synthesized during erythroblast maturation was examined by pulse-chase analysis. We showed that the newly synthesized band 3 dimers and tetramers are stable and that there is no interconversion between these species in erythroblast membranes. Pulse-chase analysis followed by cellular fractionation showed that, in early erythroblasts, the newly synthesized band 3 tetramers are initially present in the microsomal fraction and later incorporated stably into the plasma membrane fraction. In contrast, in late erythroblasts the newly synthesized band 3 dimers move rapidly to the plasma membrane fraction but then recycle between the plasma membrane and microsomal fractions. Fluorescence photobleaching recovery studies showed that significant fractions of B3T and B3D are laterally mobile in early and late erythroblast plasma membranes, respectively, suggesting that many B3T-ankyrin complexes are unattached to the membrane skeleton in early erythroblasts and that the membrane skeleton has yet to become tightly organized in late erythroblasts. We postulate that in early erythroblasts, band 3 tetramers are transported through microsomes and stably incorporated into the plasma membrane. However, when ankyrin synthesis is downregulated in late erythroblasts, it appears that B3D are rapidly transported to the plasma membrane but then recycled between the plasma membrane and microsomal compartments. These observations may suggest novel roles for membrane skeletal proteins in stabilizing integral membrane protein oligomers at the plasma membrane and in regulating the endocytosis of such proteins.     

The implications of head injury for family relationships

Many of those sustaining head injury recover to the point that they no longer require hospital care. However, the family frequently has to cope with an individual with varying degrees of disability involving physical, psychological, cognitive and social dysfunctioning. This review of the literature briefly considers the possible effects that head injury may have for the injured person before going on to discuss the consequences that such an injury may have for the family of that individual. The family's need for information and education is highlighted and it is suggested that the nurse has an important role to play in this context.     

Neurotoxic potential of gadodiamide after injection into the lateral cerebral ventricle of rats

PURPOSE: Results of a previous report showed that, if administered by intraventricular injection to access tissue normally protected by the blood-brain barrier, gadopentetate dimeglumine produced acute excitation, persistent ataxia, and widespread brain lesions in rats at 5-micromol/g brain but not at 3.8-micromol/g brain. The present study using gadodiamide was undertaken to see whether the effects were agent-specific. METHODS: Rats, surgically prepared with a lateral ventricular cannula, were administered a slow injection at 2 microL/min of gadodiamide into the lateral ventricle, and behavioral and neuropathologic changes were noted. RESULTS: Both gadodiamide and gadopentetate dimeglumine produced focal and generalized myoclonus over several hours. Gadodiamide did not produce the medium-term tremor or persistent ataxia seen after treatment with gadopentetate dimeglumine. Neuropathologic changes developed over 1 to 3 days and took three distinct forms: vacuolated thalamic lesions closely resembling those produced by gadopentetate dimeglumine; small but similar vacuolated symmetrical caudate lesions not produced by gadopentetate dimeglumine; and severe swelling and astrocytic hypertrophy and hyperplasia in the cerebellar vermis, again not produced by gadopentetate dimeglumine. Unlike gadopentetate dimeglumine, gadodiamide produced no spinal cord lesions. The cerebellar changes were seen at 1.25-micromol/g brain and above, behavioral changes at 2.5-micromol/g brain and above, and thalamic and caudate lesions at 10-micromol/g brain, the maximal dose used. Markedly reducing the rate of injecting the same volume over 28 hours prevented the acute excitation but did not reduce the severity of the morphologic effects. CONCLUSION: The acute excitatory effects of high intraventricular doses of gadopentetate dimeglumine and gadodiamide are similar and appear to be attributable to local action at the infusion site, but differences exist between the two agents in the character and topography of the distant morphologic changes. The cerebellum was the brain area most sensitive to gadodiamide in this experimental model. It is unlikely that gadodiamide would gain access to the brain at these tissue doses when used intravenously for conventional clinical imaging, but our experimental model suggested that it had some unexpectedly specific neuropathologic potential.     

Occupational exposure to HIV: experience at a tertiary care center

We examined our hospital-based occupational health clinic's experience with combination antiretroviral therapy for postexposure prophylaxis for human immunodeficiency virus (HIV). Over a 12-month period, 68 workers started postexposure prophylaxis: 23 with zidovudine and lamivudine and 45 with zidovudine, lamivudine, and indinavir. Fifty-one (75%) of the 68 workers starting postexposure prophylaxis reported one or more side effects. Side effects were more common among those taking three drugs. Many workers failed to complete the recommended 28-day regimen because of the side effects of the various treatments. The estimated mean cost for evaluations, prophylaxis, and monitoring of exposed workers was $669 per reported exposure. In our experience, major challenges in carrying out the current HIV postexposure prophylaxis guidelines include expeditious source testing, improved staff education and prevention measures, and scrupulous monitoring of workers taking combination antiretroviral drugs for postexposure prophylaxis, with consideration of alternate regimens for intolerant workers.