Effect of internal heating during hot compression on the stress-strain behavior of alloy 304L

The temperature change due to the conversion of mechanical deformation to internal heat and its effect on the as-measured stress-strain behavior of alloy 304L was investigated by means of initially isothermal (compression specimen, dies, and environment at same temperature at initiation of test), constant strain rate, uniaxial compression of laboratory-sized cylindrical specimens. Strain rate was varied in the range 0.01 to 1 s⁻¹, where the thermal state of the test specimen varied from nearly isothermal to nearly adiabatic, respectively. Specimens were deformed in the temperature range of 750 °C to 1150 °C to a strain of 1. The change in specimen temperature with applied strain was calculatedvia finite-element analysis (FEA) from the asmeasured stress-strain data. Selected predictions were confirmed with embedded thermocouples to verify the model employed. Temperature was found to increase monotonically with strain at a strain rate of 1 s^-1, consistent with what is theoretically expected for the adiabatic case. At the 0.1 and 0.01 s^-1 rates, the sample temperature initially increased, peaked, and then decreased as the sample thinned and the contact area between the sample and the cooler dies increased. As-measured stress was corrected for softening associated with deformational heating by interpolation between the various instantaneous stress-temperature behaviors. The resulting isothermal flow data are compared to those predicted by a conventional method that employs an empirical estimate of the heat retention efficiency of the test specimen, assumed dependent on strain rate but independent of strain, to reduce the increase in temperature calculated for the adiabatic case. Differences between the calculated isothermal stress-strain data from the two methods are discussed. Values for the apparent activation energy of deformation and the strain to the peak in the flow curve, which is associated with the onset of dynamic recrystallization, determined from isothermal stress-strain data differed significantly from those obtained from the as-measured compression test data. Formerly Senior Systems Engineer with EG&G Rocky Flats, Inc., is retired.     

A conserved sequence in tRNA and rRNA promoters of Lactococcus lactis

A tRNA operon (trnA) from Lactococcus lactis consisting of seven tRNA genes and a 5S rRNA gene was cloned and sequenced. Promoter-fusion of the trnA promoter to a promoter-less beta-galactosidase gene of Leuconostoc mesenteroides resulted in high levels of beta-galactosidase activity in L. lactis. Searching for sequences with similarity to the sequence of the promoter region revealed a consensus sequence of promoters preceeding rRNA operons and tRNA operons from Lactococcus species including a not previously described conserved sequence (AGTT).     

Clonal analysis of peripheral blood lymphocytes from three patients with advanced neuroblastoma receiving recombinant interleukin-2 and interferon alpha

Cultures of both isolated and conjugated explants from early gastrulae of Bufo arenarum were prepared for a study of the development of ventral mesoderm. Only combinations including components of the deep ventral marginal zone and the animal pole successfully differentiated into blood cells (erythrocytes). Histological studies indicated that, while prospective mesodermal cells constituted the only source of such cells, prospective ectodermal cells provided the necessary stimulus for this kind of differentiation. Differentiated cultures, in which the tracer of cell-lineage fluorescein dextran amine was used to label these components, confirmed the above conclusions. These findings are discussed in the context of current concepts about the formation of mesoderm.     

A local solution method for shock boundary-layer interaction on a swept wing

Summary The paper describes a local solution method for the calculation of the interaction between a weak shock front and a turbulent boundary layer on a swept wing. A multiple-deck approach allows the simplification of the governing equations according to the physical character of each deck. The mathematical model is based upon small-perturbation theory. The final boundary-layer solution is given by an iterative coupling of the solutions for each domain. The results are compared with experiments and with other theoretical solutions.     

Control of neuronal morphogenesis by homeoproteins: consequences for the making of neuronal networks

The authors investigated the relationship between plasma lipids and the risk for cortical infarction (61 cases) and transient ischaemic attacks (TIA) (35 cases) compared with matched controls. They observed a maximal increase of total cholesterol, of very low-density lipoprotein and low-density lipoprotein (LDL), triglycerides, total apolipoprotein (Apo), B,LDL-Apo B and Apo-A1, and small size high-density lipoprotein (HDL) and large size HDL whose separation was not possible. In contrast they observed a decrease of HDL-ApoE, a distribution of LDL in a single fraction and the presence of LDL of low weight in the group with cortical infarction with or without cardiac arrhythmias. For the first time, we describe a decrease of the HDL-ApoE/total ApoE ratio. TIA differed from the former group by a low level of HDL and the lack of abnormalities of Apo-A1, distribution of small and large size HDL, and in the distribution and the weight of LDL. These data suggest that previously demonstrated differences in LDL-cholesterol and HDL-cholesterol levels between patients with ischaemic stroke and control subjects may apply to patients with cortical infarction, and that in TIA there are changes in the distribution and the weight of LDL.     

Opiate users and the first years after treatment: outcome analysis of the proportion of follow up time spent in abstinence

This second report on a follow-up study of drug users focuses on changes that occurred on a number of variables between intake and follow-up and during the follow-up period. The length of abstinence from opiates was considered as a proportion of the total follow-up period. Overall there was a reduction in opiate use, in injecting and sharing equipment at follow-up. There had been, however, a high level of these risky activities during the follow-up period. Sustained abstinence from opiates was associated with increased employment, enhanced social stability and mental health. Intake drug use was strongly related to follow-up drug status. In particular, those who were injectors of multiple drugs at intake were far less likely to be long term opiate abstainers at follow-up than those who were not injectors at intake or injectors of opiates only.