Plastic deformation of delta-ferritic iron at intermediate strain rates

The plastic deformation of delta-ferritic iron, represented by an electrolytic iron and Fe-0.028 C, Fe-0.044 C and Fe-3.0 Si alloys, has been measured for the temperature range 1200 to 1525‡C and the strain rate range 2.8 x 10^-5 to 2.3 x 10^-2 s^-1. For the bamboo-like tension specimens the plastic flow behavior is approximately nonlinear viscous. Delta-ferrite is more than four times weaker than austenite, and does not exhibit dynamic recrystallization. At the melting point of iron the extrapolated steady-state flow stress increases from 0.31 to 1.86 MN/m² (45 to 370 psi) over the range of strain rate examined.      

An American application of Eysenck's short neuroticism and extraversion scales.

"Eysenck's short neuroticism and extraversion scales were used in interviews with 180 American housewives. The scales proved to be uncorrelated with each other, even though both were significantly correlated with a measure of agreeing response set. The reliability of the neuroticism scale was .72; and of the extraversion scale, .41. Some differences between the present results and Eysenck's results were discussed." From Psyc Abstracts 36:04:4HF71W. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tensile failure of austenitic iron at intermediate strain rates

The basic failure behavior of austenitic iron has been established for the temperature range 950 to 1350°C and the strain-rate range 2.8 x 10^-5 to 2.3 x 1(10^-2 s^-1. Failure in zone-refined iron is determined solely by plastic deformation, leading first to multiple necking, continuing by the exclusive growth of a single neck, and concluding by separation at a point within that neck. With the increasing impurity content of electrolytic iron, Fe-0.05 C and Fe-5.2 Mn, this failure process is interrupted at the lower temperatures by fracture at either second-phase particles or grain boundaries. The regimes of these two fracture modes have been determined as functions of strain rate, deformation temperature, and annealing temperature. Recrystallization is prevalent during the plastic deformation of austenitic iron and influences the necking process to some extent. Recrystallization is more influential as a means of stabilizing arrays of intergranular cracks, thereby allowing the cracks to undergo appreciable plastic deformation during the final stage of failure. The concept of failure diagrams is introduced as a simple means of representing the complex interposition of plastic instability, recrystallization, and fracture during the failure process.     

Retractions in Science

Scientometrics - Retractions are rare in science, but there is growing concern about the impact retracted papers have. We present data on the retractions in the journal Science, between 1983 and...     

Arrayed Hollow Channels in Silk‐Based Scaffolds Provide Functional Outcomes for Engineering Critically Sized Tissue Constructs

In the field of regenerative medicine there is a need for scaffolds that support large, critically‐sized tissue formation. Major limitations in reaching this goal are the delivery of oxygen and nutrients throughout the bulk of the engineered tissue as well as host tissue integration and vascularization upon implantation. To address these limitations, the development of a porous scaffold platform made from biodegradable silk protein that contains an array of vascular‐like structures that extend through the bulk of the scaffold was previously reported. Here, the hollow channels play a pivotal role in enhancing cell infiltration, delivering oxygen and nutrients to the scaffold bulk, and promoting in vivo host tissue integration and vascularization. The unique features of this protein biomaterial system, including the vascular structures and tunable material properties, render this scaffold a robust and versatile tool for implementation in a variety of tissue engineering, regenerative medicine, and disease modeling applications.     

High temperature plastic-flow behavior of mixtures of austenite,cementite, ferrite,and pearlite in plain-carbon steels

The plastic-flow behavior of ferrite + pearlite, pearlite + cementite, and austenite + cementite mixtures in plain carbon steels has been examined over the temperature range 500 to 1050 °C, strain-rate range 6 x l0⁻⁶ to 2 x l0⁻² s⁻¹, and carbon range 0.005C to 1.89C. Up to the eutectoid temperature the strength of the ferrite + pearlite mixture more than doubles as the carbon content increases from 0.005C to 0.7C, so that whereas in low-carbon steels the ferrite is weaker than the higher temperature austenite phase, in eutectoid steels the fully pearlitic structure is stronger than the fully austenitic structure. Manganese and silicon strengthen ferrite more effectively than they do austenite. A 0.17 pct phosphorus addition strengthens the ferrite + pearlite mixture across the range of microstructures from fully ferritic to fully pearlitic. Beyond the eutectoid composition, the amount of proeutectoid cementite does not significantly affect the strength of the pearlite, but above the eutectoid temperature it appreciably strengthens the austenite and cementite mixture at the strain rate of 2 X 10^-2 s^-1.     

Uterine bacterial flora and uterine lesions in bitches with cystic endometrial hyperplasia (pyometra)

Thirty-eight complete genital tracts were obtained fresh from local veterinary practices after bitches had been ovariohysterectomised for the treatment of cystic endometrial hyperplasia (pyometra). The aerobic and anaerobic culture of swabs obtained aseptically from the uterine lumen demonstrated the presence of Escherichia coli in 28 of the 29 cases from which bacteria were isolated and, from 25, a pure culture was obtained. Sixteen different serotypes were identified from 24 genital tracts; 032K+ CNF+ was isolated from four of 16 cases and 04K-; from three of 16 cases. Cytotoxin necrotising factors (CNFs) were identified in seven of the 16 serotypes; they included 02, 04, 06, 022, 025, 045 and 075, which except for 06 and 045 were haemolytic. Strains 04K- and 07K+ completely destroyed the integrity of the endometrial epithelium whereas 088K+ and 088K- had the least effect. The scores for the reduction in the integrity of the endometrial epithelium and the degree of infiltration of inflammatory cells were greater in the presence of CNF 1.     

The effects of changing intracellular pH on calcium and potassium currents in smooth muscle cells from the guinea-pig ureter

Effect of weight training exercise and treadmill exercise on postexercise oxygen consumption. Med. Sci. Sports Exerc., Vol. 30, No. 4, pp. 518-522, 1998. To compare the effect of weight training (WT) and treadmill (TM) exercise on postexercise oxygen consumption (VO2), 15 males (mean +/- SD) age = 22.7 +/- 1.6 yr; height = 175.0 +/- 6.2 cm; mass = 82.0 +/- 14.3 kg) performed a 27-min bout of WT and a 27-min bout of TM exercise at matched rates of VO2. WT consisted of performing two circuits of eight exercises at 60% of each subject's one repetition maximum with a work/rest ratio of 45 s/60 s. Approximately 5 d after WT each subject walked or jogged on the TM at a pace that elicited an average VO2 matched with his mean value during WT. VO2 was measured continuously during exercise and the first 30 min into recovery and at 60 and 90 min into recovery. VO2 during WT (1.58 L.min-1) and TM exercise (1.55 L.min-1) were not significantly (P > 0.05) different; thus the two activities were matched for VO2. Total oxygen consumption during the first 30 min of recovery was significantly higher (P < 0.05) as a result of WT (19.0 L) compared with that during TM exercise (12.7 L). However, VO2 values at 60 (0.32 vs 0.29 L.min-1), and 90 min (0.33 vs 0.30 L.min-1) were not significantly different (P > 0.05) between WT and TM exercise, respectively. The results suggest that, during the first 30 min following exercise. WT elicits a greater elevated postexercise VO2 than TM exercise when the two activities are performed at matched VO2 and equal durations. Therefore, total energy expenditure as a consequence of WT will be underestimated if based on exercise VO2 only.     

GABA inhibits migration of luteinizing hormone-releasing hormone neurons in embryonic olfactory explants

During development, a subpopulation of olfactory neurons transiently expresses GABA. The spatiotemporal pattern of GABAergic expression coincides with migration of luteinizing hormone-releasing hormone (LHRH) neurons from the olfactory pit to the CNS. In this investigation, we evaluated the role of GABAergic input on LHRH neuronal migration using olfactory explants, previously shown to exhibit outgrowth of olfactory axons, migration of LHRH neurons in association with a subset of these axons, and the presence of the olfactory-derived GABAergic neuronal population. GABAA receptor antagonists bicuculline (10(-5) M) or picrotoxin (10(-4) M) had no effect on the length of peripherin-immunoreactive olfactory fibers or LHRH cell number. However, LHRH cell migration, as determined by the distance immunopositive cells migrated from olfactory pits, was significantly increased by these perturbations. Addition of tetrodotoxin (10(-6) M), to inhibit Na+-transduced electrical activity, also significantly enhanced LHRH migration. The most robust effect observed was dramatic inhibition of LHRH cell migration in explants cultured in the presence of the GABAA receptor agonist muscimol (10(-4) M). This study demonstrates that GABAergic activity in nasal regions can have profound effects on migration of LHRH neurons and suggests that GABA participates in appropriate timing of LHRH neuronal migration into the developing brain.     

Effect of carbon content on the plastic flow of plain carbon steels at elevated temperatures

The elevated-temperature plastic-flow behavior of plain carbon steels with a base composition of 0.8 Mn and 0.25 Si was examined as a function of carbon content in the range 0.005 to 1.54 wt pct at strain rates from 6 x 10^-6 to 2 x 10^-2 sec^-1. Beyond 0.05 C the flow stress at a strain of 0.1 decreased with increasing carbon content at the rate of 13 MPa per pct carbon. However, the degree of softening depended on the strain level at which the flow stress was measured, because the increasing carbon content also decreased the rate of work hardening. The inferred increase in recovery processes with increasing carbon content is in agreement with the effects of carbon on diffusivity, elastic modulus, and lattice spacing, as well as the observed increase in grain growth with increasing carbon content. In the range 850 to 1300 °C (1562 to 2372 °F), the temperature dependence of the flow stress can be represented by σ= A exp (-BT) whereA depends on carbon content and strain, andB depends primarily on strain rate. Extrapolation to higher temperatures yields the carbon-content dependence of the flow stress at the austenite solidus.