Correlating work hardening with co-activation of stacking fault strengthening and transformation in a high entropy alloy using in-situ neutron diffraction.

Transformation induced plasticity (TRIP) leads to enhancements in ductility in low stacking fault energy (SFE) alloys, however to achieve an unconventional increase in strength simultaneously, there must be barriers to dislocation motion. While stacking faults (SFs) contribute to strengthening by impeding dislocation motion, the contribution of SF strengthening to work hardening during deformation is not well understood; as compared to dislocation slip, twinning induced plasticity (TWIP) and TRIP. Thus, we used in-situ neutron diffraction to correlate SF strengthening to work hardening behavior in a low SFE Fe40Mn20Cr15Co20Si5 (at%) high entropy alloy, SFE ~ 6.31 mJ m-2. Cooperative activation of multiple mechanisms was indicated by increases in SF strengthening and γ-f.c.c. → ε-h.c.p. transformation leading to a simultaneous increase in strength and ductility. The present study demonstrates the application of in-situ, neutron or X-ray, diffraction techniques to correlating SF strengthening to work hardening.

Nanoindentation behavior of high entropy alloys with transformation-induced plasticity.

Nanoindentation of three metastable dual-phase high entropy alloys (HEAs) was performed to obtain their inherent elastoplastic deformation responses. Excellent combination of hardness and elastic modulus in as-cast condition confirmed that, their inherently higher strength compared to other HEAs reported in literature, can be attributed to alloy chemistry induced phase stability. Further, hardness of 8.28 GPa combined with modulus of 221.8 GPa was obtained in Fe-Mn-Co-Cr-Si-Cu HEA by annealing the as-cast material, which is the best hardness-modulus combination obtained to date in HEAs from nanoindentation. On the other hand, although Fe-Mn-Co-Cr-Si HEA showed lower hardness and modulus than Fe-Mn-Co-Cr-Si-Al and Fe-Mn-Co-Cr-Si-Cu HEAs, the former alloy exhibited the highest strain rate sensitivity, as determined from tests performed at five different strain rates. The three alloys also had subtle differences in incipient plasticity and elastoplastic behavior, while retaining similar levels of hardness; and nanoindentation response showed microstructural dependence in friction stir processed, annealed and tensile-deformed specimens. Thus, the study highlighted that while higher strength was achieved by designing a class of HEAs with similar composition, any of the individual alloys can be tuned to obtain enhanced properties.

Identification of patients with recent-onset psychosis in KwaZulu Natal, South Africa: a pilot study with traditional health practitioners and diagnostic instruments.

PURPOSE: There is considerable variation in epidemiology and clinical course of psychotic disorders across social and geographical contexts. To date, very little data are available from low- and middle-income countries. In sub-Saharan Africa, most people with psychoses remain undetected and untreated, partly due to lack of formal health care services. This study in rural South Africa aimed to investigate if it is possible to identify individuals with recent-onset psychosis in collaboration with traditional health practitioners (THPs). METHODS: We developed a strategy to engage with THPs. Fifty THPs agreed to collaborate and were asked to refer help-seeking clients with recent-onset psychosis to the study. At referral, the THPs rated probability of psychosis ("maybe disturbed" or "disturbed"). A two-step diagnostic procedure was conducted, including the self-report Community Assessment of Psychic Experiences (CAPE) as screening instrument, and a semi-structured interview using the Schedules for Clinical Assessment in Neuropsychiatry (SCAN). Accuracy of THP referrals, and test characteristics of the THP rating and the CAPE were calculated. RESULTS: 149 help-seeking clients were referred by THPs, of which 44 (29.5%) received a SCAN DSM-IV diagnosis of psychotic disorder. The positive predictive value of a THP "disturbed" rating was 53.8%. Test characteristics of the CAPE were poor. CONCLUSION: THPs were open to identifying and referring individuals with possible psychosis. They recognized "being disturbed" as a condition for which collaboration with formal psychiatric services might be beneficial. By contrast, the CAPE performed poorly as a screening instrument. Collaboration with THPs is a promising approach to improve detection of individuals with recent-onset psychosis in rural South Africa.

Extremely high strength and work hardening ability in a metastable high entropy alloy.

Design of multi-phase high entropy alloys uses metastability of phases to tune the strain accommodation by favoring transformation and/or twinning during deformation. Inspired by this, here we present Si containing dual phase Fe42Mn28Co10Cr15Si5 high entropy alloy (DP-5Si-HEA) exhibiting very high strength (1.15 GPa) and work hardening (WH) ability. The addition of Si in DP-5Si-HEA decreased the stability of f.c.c. (γ) matrix thereby promoting pronounced transformation induced plastic deformation in both as-cast and grain refined DP-5Si-HEAs. Higher yet sustained WH ability in fine grained DP-5Si-HEA is associated with the uniform strain partitioning among the metastable γ phase and resultant h.c.p. (ε) phase thereby resulting in total elongation of 12%. Hence, design of dual phase HEAs for improved strength and work hardenability can be attained by tuning the metastability of γ matrix through proper choice of alloy chemistry from the abundant compositional space of HEAs.

Enhanced strength and ductility in a friction stir processing engineered dual phase high entropy alloy.

The potential of high-entropy alloys (HEAs) to exhibit an extraordinary combination of properties by shifting the compositional regime from the corners towards the centers of phase diagrams has led to worldwide attention by material scientists. Here we present a strong and ductile non-equiatomic HEA obtained after friction stir processing (FSP). A transformation-induced plasticity (TRIP) assisted HEA with composition Fe50Mn30Co10Cr10 (at.%) was severely deformed by FSP and evaluated for its microstructure-mechanical property relationship. The FSP-engineered microstructure of the TRIP HEA exhibited a substantially smaller grain size, and optimized fractions of face-centered cubic (f.c.c., γ) and hexagonal close-packed (h.c.p., ε) phases, as compared to the as-homogenized reference material. This results in synergistic strengthening via TRIP, grain boundary strengthening, and effective strain partitioning between the γ and ε phases during deformation, thus leading to enhanced strength and ductility of the TRIP-assisted dual-phase HEA engineered via FSP.

Simple and efficient enzymatic transglycosylation of stevioside by beta-cyclodextrin glucanotransferase from Bacillus firmus.

Stevioside was subjected to 1,4-intermolecular transglycosylation using beta-cyclodextrin glucanotransferase (beta-CGtase) produced from an alkalophilic strain of Bacillus firmus. The reaction was carried out by traditional, ultrasound-assisted and microwave-assisted techniques. Reaction under microwave conditions was faster and was completed in 1 min yielding two 1,4 transglycosylated products, 4'-O-alpha-D: -glycosyl stevioside (I) and 4''-O-alpha-D: -maltosyl stevioside (II) in 66% and 24%, respectively. The optimum transglycosylation occurred by using stevioside (1.24 mmol), beta-CD (1.76 mmol) and beta-CGtase (2 U/g) under microwave assisted reaction (MAR) in 5 ml sodium phosphate buffer (pH 7) at 50 degrees C and 80 W power. MAR is therefore potentially a useful and economical method for faster transglycosylation of stevioside.

Single-Step purification and immobilization of penicillin acylase using hydrophobic ligands.

Five different hydrophobic ligands immobilized on 4% (4XL) and 6% (6XL) crosslinked agarose were used to study the single-step purification of penicillin acylase from cell lysate. The 4XL gels showed relatively higher specific activity and recovery than the 6XL gels. In single-step purification, highly active enzyme (42 U/mg) was obtained using moderately hydrophobic ligand (octyl). The crude enzyme immobilized on octyl gel by adsorption showed significant operational stability over a period of 30 d at room temperature. Reactor studies demonstrated the feasibility of hydrophobic ligands as a medium for immobilization.

Optimization of single-step purification of alkaline protease using different hydrophobic ligands.

The adsorption and desorption pattern of alkaline protease was studied using different aliphatic and aromatic hydrophobic ligands. Overall, higher adsorption was obtained on ligands coupled to 6% cross-linked gel than the 4% gel. The highest adsorption was obtained on butyl (94%) and phenyl (98.4%) of 6% cross-linked gel. The adsorption was dependent on concentration and nature of the ligand. In a single-step operation, almost 20-fold purification with 40% yield of the enzyme was obtained using all the optimized experimental parameters.

The effects of thrombus, thrombectomy and thrombolysis on endothelial function.

OBJECTIVE: this study was undertaken to examine and compare the effects of thrombus, thrombectomy, and thrombolysis on endothelial function as measured by endothelium-dependent vasorelaxation (EDR). METHODS: adult, male New Zealand white rabbits underwent ligation of the left common iliac to femoral artery to induce thrombosis and were then randomly assigned to one of five groups, n=6 in each. Group A consisted of ligation and thrombosis for 4 h. Group B underwent similar ligation for 4 h, but without intraluminal thrombus present. Following 4 h of ligation and thrombosis, Group C underwent thrombectomy while group D was treated with urokinase (UK), 4000 U/min for 30 min. Group E underwent UK infusion alone. The right external iliac artery served as control vessel in each group. All arteries were removed and endothelial function was determined by measuring EDR. RESULTS: the presence of thrombus reduced EDR by 50% (group A) compared to control. Vessels with interrupted flow, but not exposed to thrombus, retained normal EDR (group B). Thrombectomy decreased EDR significantly (group C) compared to thrombolysis (group D) and control. UK did not significantly alter EDR (groups D, E). CONCLUSIONS: exposure of endothelium to thrombus significantly decreases EDR. EDR was not affected by interruption of blood flow in the absence of thrombus. Thrombectomy appeared to cause a further additive insult to the endothelium. In contrast, thrombolysis with UK preserved residual endothelial function. These data suggest that it is important to differentiate the effects of thrombus on endothelium from effects due to thrombectomy or thrombolysis when evaluating treatment modalities for arterial thrombosis.

Exposure to thrombus diminishes endothelial derived relaxation in the rabbit carotid artery.

PURPOSE: Thrombus is believed to be deleterious to intimal function. However, few studies have directly examined this effect. This study examines the effect of thrombus on endothelial-dependent and -independent vasorelaxation in the rabbit carotid artery. METHODS: Twelve male New Zealand white rabbits (3.5-4.5 kg) were divided into two groups of six. Thrombosis was induced in group I by segmental right carotid artery ligation. Group II underwent segmental right carotid ligation immediately followed by removal of thrombus with normal saline flush through an arteriotomy. The left carotid arteries were exposed in both groups and served as internal controls. After 4 h, left and right carotid arteries were harvested, sectioned into 6-mm rings, and mounted on isometric force transducers in a physiologic bath. Thrombus was removed from the arteries in group I during the ring preparation process. Neither group I nor group II had thrombus in contact with endothelium during ex vivo testing. The arterial rings were constricted with norepinephrine (1 x 10(-4) M). Endothelium-dependent and -independent vasorelaxation to acetylcholine (Ach) and s-nitrosoacetylpenicillamine, respectively, were measured in a dose-response manner. Results were expressed as a percentage of vasorelaxation. Statistical analysis was performed using an analysis of variance. RESULTS: Endothelial-dependent vasorelaxation, which tests for endothelial cell function, was decreased in the thrombus and endothelial ischemia group (I) compared to control as noted by vasorelaxations of 22% vs 34% at 1 x 10(-4) molar concentration Ach, and 33% vs 48% at 1 x 10(-3) molar concentration Ach, respectively (P = 0.05). By comparison, there was no difference in the endothelial-dependent vasorelaxation of the endothelial ischemia group (II) versus control. Endothelial-independent vasorelaxation, which tests for smooth muscle function, was not affected by either the thrombus and endothelial ischemia group (I) or the endothelial ischemia group (II) compared to the control group. The controls in group I and group II were slightly different. When this difference was removed, the resulting comparison of treatments in group I and group II approached significance at molar concentrations of 1 x 10(-4), 1 x 10(-5), and 1 x 10(-6) (P = 0.07, 0.06, 0.06). CONCLUSIONS: The presence of thrombus within the rabbit carotid artery for a period of 4 h decreases endothelial-dependent relaxation. Four hours of endothelial ischemia without thrombus did not change endothelial-dependent vasorelaxation. Neither thrombus nor ischemia alone had any effect on the endothelium-independent vasorelaxation. We conclude that thrombus is deleterious to endothelial function independent of smooth muscle function in the acute setting as measured by endothelial-dependent vasorelaxation.

Purification and properties of a novel raw starch degrading cyclomaltodextrin glucanotransferase from Bacillus firmus.

A novel raw starch degrading cyclomaltodextrin glucanotransferase (CGTase; E.C. 2.4.1.19), produced by Bacillus firmus, was purified to homogeneity by ultrafiltration, affinity and gel filtration chromatography. The molecular weight of the pure protein was estimated to be 78,000 and 82,000 Da, by SDS-PAGE and gel filtration, respectively. The pure enzyme had a pH optimum in the range 5.5-8.5. It was stable over the pH range 7-11 at 10 degrees C, and at pH 7.0 at 60 degrees C. The optimum temperature for enzyme activity was 65 degrees C. In the absence of substrate, the enzyme rapidly lost its activity above 30 degrees C. K(m) and kcat for the pure enzyme were 1.21 mg/ml and 145.17 microM/mg per minute respectively, with soluble starch as the substrate. For cyclodextrin production, tapioca starch was the best substrate used when gelatinized, while wheat starch was the best substrate used when raw. This CGTase could degrade raw wheat starch very efficiently; up to 50% conversion to cyclodextrins was obtained from 150 g/l starch without using any additives. The enzyme produced alpha-, beta- and gamma-cyclodextrins in the ratio of 0.2:9.2:0.6 and 0.2:8.6:1.2 from gelatinized tapioca starch and raw wheat starch with 150 g/l concentration respectively, after 18 h incubation.

The role of patch angioplasty in prevention of early recurrent carotid stenosis.

The aim of this study was to determine the effect of primary closure versus patch angioplasty on the incidence of early recurrent stenosis after carotid endarterectomy in the hands of a single surgeon, and to analyze the risk factors associated with early recurrent stenosis after carotid endarterectomy. A retrospective review was performed of 178 consecutive patients who underwent 200 carotid endarterectomies-100 done consecutively with primary closure and 100 done consecutively with patch angioplasty. Of these patients, 126 qualified for analysis by having had at least 18 months of follow-up by serial duplex scanning. Of this group, the first 65 patients underwent 75 routine primary closures, while the last 61 underwent 67 routine patch angioplasties. All patients underwent a completion angiogram at the end of the case. Recurrent stenosis was defined as luminal diameter narrowing >60% on duplex scan. A multifactorial analysis was performed to analyze the effect of age, sex, tobacco use, diabetes, hypertension, peripheral vascular disease, coronary artery disease, and contralateral stenosis on recurrent stenosis. The results of this study showed that in a single surgeon's experience with carotid endarterectomy, varying only the method of closure between primary closure versus patch angioplasty, there is no statistically significant difference in the rate of early restenosis. No difference was noted in the perioperative morbidity and mortality between groups.

Cigarette smoking increases endothelial-derived vasorelaxation in the rat carotid artery in a dose-dependent manner.

While there is clear-cut epidemiologic, morphologic, and functional evidence to suggest that cigarette smoking is deleterious to the cardiovascular system and endothelium, previous experiments with regard to the effect of cigarette smoking on endothelial-derived vasorelaxation are not conclusive. This study examines the effect of cigarette smoking on endothelium-derived vasorelaxation and its relationship to serum nitric oxide concentrations. Fourteen Sprague-Dawley rats (350-500 g) were divided into two groups (N = 7). The experimental group was exposed to six cigarettes (Kentucky 1R4F) per day for 50 days using a Griffith snout exposure method. The two groups were sacrificed and the carotid arteries were mounted on isometric force transducers in a physiologic bath. The arteries were constricted with norepinephrine (1 x 10(-4) M). Vasorelaxation to acetylcholine (Ach) was measured in a dose response manner. Vasorelaxation to nitroglycerin was measured at 10(-4) M. After the rats were sacrificed, blood samples from each rat were examined for total nitrate/nitrite concentration with serum chemiluminescence on a vanadium column. The results were analyzed with ANOVA and the Student's t test. Vasorelaxation to nitroglycerin was 17.42% +/- 0. 44 versus 16.25% +/- 0.42 in the control and smoke exposure groups, respectively (P = 0.19). This experiment counterintuitively demonstrates that cigarette smoking augments endothelial-derived vasorelaxation. No effect was noted in the endothelium-independent vasorelaxation to nitroglycerin. Alternative mechanisms including the presence of hypoxia and exogenous nitric oxide, which lead to endothelial-dependent and -independent vasorelaxation secondary to cigarette smoking, may serve to explain the apparent augmentation of endothelial-derived vasorelaxation. Further experiments with isolated components of smoke will need to be done to resolve the debate.

Rupture of the perivisceral aorta: atherosclerotic versus mycotic aneurysm.

Twelve patients with rupture of the perivisceral abdominal aorta were admitted to the UCLA Medical Center between 1984 and 1996. Six patients had atherosclerotic thoracoabdominal aneurysms (TAA) which ruptured in the visceral segment of the aorta. The remaining 6 patients proved to have ruptured mycotic aneurysm (MA). Clinical presentation was different in the two groups. Whereas all 6 patients with TAA and < 24 hr history of abdominal, chest, or back pain, patients with MA had these symptoms for 2-5 weeks (mean 3.4 weeks). History of sepsis was present in 4/6 MA and in 0/6 TAA patients. No difference in risk factors for atherosclerosis were seen between these two groups. Clinical outcomes were also different. Operation consisted of in situ vascular grafting in all patients. Operative mortality for TAA was 33% (2/6), whereas all patients with MA survived repair with no operative mortality. Two patients had cardiac arrest prior to surgery. One of these had a TAA and died 5 days after surgery, whereas the other survived repair of an MA. Follow-up ranges from 1-84 months (mean 48 months). Four survivors in the TAA group are alive at 6, 8, 14, and 84 months, with the latter having a pseudoaneurysm of the visceral patch-graft anastomosis. All 6 patients with MA are alive at 1-73 months (mean 39 months) without evidence of graft sepsis or recurrent aneurysm. We conclude that rupture of the visceral portion of the aorta is often associated with a mycotic process, with important differences noted in clinical presentation when compared to atherosclerotic TAA. Surgical intervention is effective in both MA and TAA. Operative mortality, however, is significantly higher in patients with ruptured TAA. In situ prosthetic replacement for ruptured MA is associated with low mortality and excellent long-term results.

Chemoenzymatic synthesis of D(-)phenylglycine using hydantoinase of Pseudomonas desmolyticum resting cells.

We screened 125 Pseudomonas strains from our culture collection for the production of hydantoinase activity using DL-phenylhydantoin as a substrate. Pseudomonas desmolyticum NCIM 2112 was found to be the best hydantoinase (dihydropyrimidinase E.C. 3.5.2.2) producer. The enzymatic reactions were carried out using 18-20-h grown cells in nutrient broth and 5-phenylhydantoin as the substrate. Optimization studies for the biotransformation reaction were performed to increase product yield. The optimum pH and temperature for D(-)N-carbamoylphenylglycine production were 9.5 and 30 degrees C, respectively. Biotransformation under these alkaline conditions allowed the complete conversion of 27.0 g l-1 of DL-phenylhydantoin to 26.5 g l-1 of N-carbamoylphenylglycine within 24 h, with a molar yield of 90%. The hydantoinase involved in this biotransformation process was strictly D-stereospecific, because the product isolated was pure D(-)N-carbamoylphenylglycine. This pure product was further chemically converted to D(-)phenylglycine using nitrous acid with an 80% chemical yield. Thus, the overall conversion efficiency of DL-5-phenylhydantoin to D(-)phenylglycine was found to be 65-68%.

Effect of tumor size on the prognosis of carcinoma of the uterine cervix treated with irradiation alone.

The authors conducted a retrospective analysis of 1178 patients with histologically proven invasive carcinoma of the uterine cervix treated with irradiation alone. The minimum follow-up time was 3 years. The 10-year actuarial pelvic failure rate in Stage IB was 6% for tumors less than 3 cm, 15% for tumors 3 to 5 cm, and 30% for tumors more than 5 cm (P = 0.0018). The 10-year actuarial pelvic failure rate in Stage IIA was 10% for tumors less than 3 cm, 28% for tumors 3 to 5 cm, and 20% for tumors more than 5 cm (P = 0.09). Stage IIB unilateral nonbulky tumors (less than 5 cm) had a 20% pelvic failure rate compared with 28% for bilateral lesions and 35% for unilateral bulky tumors (more than 5 cm) (P = 0.35). In Stage IIB, pelvic failures were greater when disease extended into the lateral parametrium (30%) compared with medial parametrial involvement only (17%) (P = 0.01). In Stage III unilateral nonbulky tumors, the pelvic failure rate was 28% compared with 45% to 50% for unilateral bulky lesions (P = 0.002). Bilateral parametrial disease in Stage IIB did not increase the pelvic failure rate (21% in both subgroups) (P = 0.83), whereas in Stage III, bilateral parametrial involvement was associated with a 48% pelvic failure rate versus 28% for unilateral extension (P less than or equal to 0.01). Five-year disease-free survival (DFS) rates for IB tumors less than or equal to 3 cm was 90% versus 67% for tumors more than 3 cm (P = 0.01). In Stage IIA tumors less than or equal to 3 cm, 5-year DFS was 70% versus 45% for tumors more than 3 cm. Patients with Stage IIB nonbulky tumors (less than or equal to 5 cm in diameter) had better 10-year DFS (65% to 70%) compared with those with bilateral bulky tumors (45% to 55%) (P = 0.10). Stage III patients with unilateral nonbulky tumors had a 55% 10-year DFS compared with 35% to 40% for bulky tumors or bilateral parametrial involvement (P = 0.002). The authors concluded that clinical stage and size of tumor are critical factors in the prognosis, therapy selection, and evaluation of results in carcinoma of the uterine cervix.

Multiparametric evaluation of retinoic acid-induced terminal differentiation of blastoid cells from acute non-lymphocytic leukemia patients in vitro.

Recent findings that retinoic acid (RA) induces terminal granulocytic differentiation of the human promyelocytic leukemia cell line HL-60 in vitro and blast cell maturation in patients suffering from acute non-lymphocytic leukemia (ANLL) prompted an investigation on the ability of this agent to induce terminal maturation in blast cells from ANLL patients in vitro. We tested the ability of RA at 3 x 10(-6) M, 3 x 10(-7) M and 3 x 10(8-) M concentrations to induce differentiation in blastoid cells from 16 patients with ANLL using cytochemical and cytologic parameters, in addition to cytofluorometric methods. Leukemic cells in primary culture from all the patients underwent cytochemical and biochemical changes after treatment with RA. However, the extent of differentiation-positive cell clones (D+ clones) varied from patient to patient. Morphologic maturation was observed in a significant number of bone marrow samples. Leukocyte alkaline phosphatase and NBT reduction ability of cells, which are biochemical markers of granulocytic differentiation, were also significantly increased with a simultaneous decrease in DNA and RNA synthesis (which was estimated using a Phywe ICP-11 impulse flow cytometer).