Liquid-liquid phase transition in supercooled silicon

Silicon in its liquid and amorphous forms occupies a unique position among amorphous materials. Obviously important in its own right, the amorphous form is structurally close to the group of 4-4, 3-5 and 2-6 amorphous semiconductors that have been found to have interesting pressure-induced semiconductor-to-metal phase transitions. On the other hand, its liquid form has much in common, thermodynamically, with water and other 'tetrahedral network' liquids that show density maxima. Proper study of the 'liquid-amorphous transition', documented for non-crystalline silicon by both experimental and computer simulation studies, may therefore also shed light on phase behaviour in these related materials. Here, we provide detailed and unambiguous simulation evidence that the transition in supercooled liquid silicon, in the Stillinger-Weber potential, is thermodynamically of first order and indeed occurs between two liquid states, as originally predicted by Aptekar. In addition we present evidence to support the relevance of spinodal divergences near such a transition, and the prediction that the transition marks a change in the liquid dynamic character from that of a fragile liquid to that of a strong liquid.     

Dynamic range expansion applied to mass spectrometry based on data-dependent selective ion ejection in capillary liquid chromatography fourier transform ion cyclotron resonance for enhanced proteome characterization.

The characterization of cellular proteomes is important for understanding biochemical processes ranging from cell differentiation to cancer development. In one highly promising approach, whole protein extracts or fractions are digested (e.g., with trypsin) and injected into a packed capillary column for subsequent separation. The separated peptides are then introduced on-line to an electrospray ionization source of a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer for the detection of peptide accurate mass tags that serve as biomarkers for their parent proteins. In this work, we report the use of data-dependent selective external ion ejection in conjunction with FTICR and on-line capillary LC separations for the enhanced characterization of peptide mixtures and a yeast extract proteome. The number of peptides identified in an LC-FTICR analysis of a yeast proteome digest employing data-dependent rf-only dipolar ejection of the most abundant ion species prior to ion accumulation was 40% higher than that detected in a separate LC-FTICR analysis using conventional nonselective ion accumulation.     

Dehydrocyanation of cultivars of lima bean (Phaseolus lunatus L) and its effect on tryptophan content

Three cultivars (red, black and white) of lima bean were studied to determine the best medium in which to cook them in order to reduce their hydrocyanic acid content to tolerable levels. The study also investigated the effects of processing media on the trytophan content of lima beans. Samples of each cultivar were parboiled in each of three media, 0.94 M HCl, 0.47 M H₂SO₄ and distilled water, for various times. Portions of each cultivar were also parboiled in the three media after enzyme incubation. Boiled samples were dried, pulverised and analysed for cyanide and tryptophan contents. There were 96.82, 99.78 and 99.62% reductions in cyanide content of the red cultivar after boiling in water, dilute HCl and dilute H₂SO₄ respectively for 30 min. The corresponding values for the white cultivar were 96.39, 99.59 and 94.77% respectively. Dehydrocyanation was more effective in enzyme‐incubated samples when they were parboiled in dilute mineral acids. The residual cyanide content in enzyme‐incubated samples was below tolerable limits after 30 min of treatment. However, the longer the parboiling time, the higher was the trytophan loss. Therefore parboiling for 30 min in dilute HCl will produce the desired result of insignificant residual cyanide content and minimal tryptophan loss in all samples. Copyright © 2004 Society of Chemical Industry     

MR of hippocampal sclerosis: comparison of qualitative and quantitative assessments

We describe a patient with dysgerminoma who had elevated serum inhibin, tumor-associated trypsin inhibitor (TATI), and CA 125 concentrations, which increased progressively during follow-up of the advancing disease. Inhibin levels correlated closely with disease behavior. In contrast to inhibin, serum TATI and CA 125 failed to reveal the presence of silent disease.     

Oxygen modulation of guanylate cyclase-mediated retinal pericyte relaxations with 3-morpholino-sydnonimine and atrial natriuretic peptide

PURPOSE: This study explores at which level of the guanylate cyclase pathway oxygen modulates retinal pericyte relaxation induced by nitric oxide (NO). METHODS: Bovine retinal microvascular pericytes were grown on silicone. On silicone, pericyte contractile tone induces wrinkles. Drug-induced relaxation was quantified as a reduced number of wrinkles after exposure to 3-morpholino-sydnonimine (SIN-1) or atrial natriuretic peptide (ANP) in the absence or in the presence of either 0.3 microM methylene blue (MB), a guanylate cyclase inhibitor, or 10 microM hemoglobin, a NO scavenger; and under 100% oxygen (hyperoxia), ambient air (normoxia), or 100% nitrogen (hypoxia). RESULTS: Pericytes were relaxed with SIN-1 and ANP in a concentration-dependent manner (EC50: 0.1 microM and 0.01 microM, respectively). Relaxations induced by SIN-1 or ANP were inhibited (P < 0.001) by MB, whereas hemoglobin inhibited only SIN-1 relaxations (P < 0.001). Relaxations induced by SIN-1, but not by ANP were increased (P < 0.001) under hypoxia and decreased (P = 0.002) under hyperoxia. CONCLUSIONS: SIN-1 and ANP relax pericytes through the activation of guanylate cyclase (inhibited by MB), but only SIN-1 through an extracellular release of NO (inhibited by hemoglobin). That oxygen only modulates pericyte relaxations induced by SIN-1 (NO-mediated) but not those induced by ANP suggests that an interaction between oxygen and NO might participate in the capillary network's blood-flow modulation according to local tissue oxygen tension.     

In vivo and in vitro responses to poly(ethylene terephthalate-co-diethylene glycol terephthalate) and polyethylene oxide blends

Although biocompatible polymeric compounds are generally nontoxic, nonimmunogenic, and chemically inert, implants made from these materials may trigger acute and chronic inflammatory responses. These inflammatory reactions may induce degeneration of implanted biopolymer. Interactions between implanted biomaterial and inflammatory cells are mediated by many cellular events involving cellular adhesion and activation. We studied the inflammatory responses in vivo and in vitro to samples of biopolymers composed of poly(ethylene terephthalate-co-diethylene glycol terephthalate) plus 0, 5, 25% of polyethylene oxide. We observed that these biopolymers did not induce inflammatory responses when implanted in the peritoneal cavity of mice for 28 days. However we observed deposition of hyaluronic acid at the surface of implanted biomaterial, suggesting that tolerance to biomaterial occurred after surgical implantation. No significant adhesion of inflammatory cells such as mononuclear phagocytes and peripheral leukocytes were observed in vitro, when poly(ethylene terephthalate-co-diethylene glycol terephthalate) blends were used as substratum to cellular adhesion. These results suggest that blends composed of poly(ethylene terephthalate-co-diethylene glycol terephthalate) induce low inflammatory cell adhesion, since no rejection of biopolymer was observed when implanted in experimental animal models.     

Why C1 = 16–17 in the WLF equation is physical-and the fragility of polymers

From the well-recognized equivalence of the Williams-Landel-Ferry (WLF) equation and the Vogel-Tammann-Fulcher (VTF) equation, τ = τ_o exp (B/[T - T_o]), we shall show that the parameter C₁ in the former is just the number of orders of magnitude between the relaxation time at the chosen reference temperature and the pre-exponent of the VTF equation. Thus C₁^g = log(τ_g/τ_o) (a relation which is not found in the present polymer literature), measures the gap between the two characteristic time scales of the polymer liquid, microscopic and α-relaxation, at the glass transition temperature. For systems which obey these two equations over wide temperature ranges, τ_o is consistent with a quasilattice vibration period in accord with theoretical derivations of the VTF equation and also with the microscopic process of mode coupling theory. Thus for such systems, C₁^g is obliged to have the value 16–17 (depending on how T_g is defined), while C₂^g scaled by T_g will reflect the non-Arrhenius character, i.e. fragility, of the system. In fact when C₁^g has the physical value of 16–17, then (1 − C₂^g/T_g), which varies between 0 and unity, conveniently gives the ‘fragility’ of the polymer within the ‘strong/fragile’ classification scheme. This is useful because it permits prediction from the WLF parameters of other properties such as physical ageing behaviour through the now-established correlation of fragility with other canonical characteristics of glassforming behaviour. Where the best fit C₁^g is not 17 ± 2, the corresponding best fit τ_o must be unphysical, and then the range of relaxation times for which the VTF or WLF equations are valid with a single parameter set will be limited, and the predictions of other properties based on that parameter set will be unreliable. © 1997 Elsevier Science Ltd.     

Long term prognosis after hepatectomy for hepatocellular carcinoma: a survival analysis of 204 consecutive patients

BACKGROUND: Intrahepatic recurrence continues to be the main cause of late death among hepatocellular carcinoma patients after hepatic resection. The aims of the current study were to identify the prognostic factors affecting long term survival and to evaluate the clinical value of pTNM classification as a prognostic factor for these patients. The identification of significant prognostic factors plays an important role in the selection of patients for postoperative adjuvant therapy and counseling. METHODS: From January 1989 to August 1995, 204 consecutive patients underwent hepatectomy for hepatocellular carcinoma. The overall cumulative and disease free survival rates for these patients were analyzed. Univariate and multivariate analyses of 16 clinicopathologic factors, including factors associated with pTNM classification, were performed to determine the significant prognostic factors. RESULTS: The median periods of overall cumulative survival and disease free survival were 35 months and 12.4 months, respectively. By univariate analysis, all factors associated with tumor (T) classification, namely, tumor size, vascular invasion, the number of tumor nodules, and tumor localization, were correlated with survival. By Cox regression analysis, preoperative indocyanine green retention value at 15 minutes, tumor size, and number of tumor nodules were independent prognostic factors of long term survival, whereas the number of tumor nodules, tumor size, and venous permeation were the most powerful predictors of tumor recurrence. The cumulative 5-year survival rates for patients with Stages I, II, III, and IVA tumors were 72%, 55%, 34%, and 8%, respectively. Significant differences in cumulative survival curves were observed among the categories of pTNM classification. CONCLUSIONS: The results of this study showed that pTNM classification correlated well with postoperative survival. Preoperative evaluation of hepatic functional reserve with an indocyanine green clearance test plays an important role in determining the long term prognoses of patients with hepatocellular carcinoma.     

Wound botulism in heroin addiction]

Botulism is a rare disease which usually is caused by preformed botulinum toxin in food. However, this article describes a case of wound botulism in a 29-year-old male heroin addict who developed progressive diplopia, dysphagia and proximal weakness of skeletal limb muscles. He needed mechanical ventilation for two weeks. The clinical diagnosis of botulism was supported by neurophysiological tests. Assays for detection of botulinum toxin and Clostridium botulinum were negative. The patient had not eaten any contaminated food the last two weeks before symptoms appeared, but he had multiple contaminated skin wounds. After treatment with botulinum antitoxins and antibiotics he gradually recovered, and six weeks later he was discharged from hospital in good condition. To the best of our knowledge this is the first case of wound botulism reported in Norway.