Fracture instability and limit strength condition in structures with re-entrant corners

When considering a structural element with a re-entrant corner, the experimental analysis shows how the fracture strength increases with the angle of the corner. Thus, the strength increases with a decrease of the mass of the structure, in contrast to what we are used to observe in different kind of collapses, e.g., plasticity. To predict this behaviour, a non-local theory, basically based on the Novozhilov’s hypothesis of existence of a fracture quantum, is herein presented. Theoretical predictions for the strength of finite structures (e.g., finite plates under tension or beams under bending) by varying both angle and relative depth of the corner are presented: accordingly, simple formulas, useful in the design of such structures, are provided. The theory is then compared with experimental and numerical results, showing a relevant agreement.     

Techniques for fast simulation of models of highly dependablesystems

With the ever-increasing complexity and requirements of highly dependable systems, their evaluation during design and operation is becoming more crucial. Realistic models of such systems are often not amenable to analysis using conventional analytic or numerical methods. Therefore, analysts and designers turn to simulation to evaluate these models. However, accurate estimation of dependability measures of these models requires that the simulation frequently observes system failures, which are rare events in highly dependable systems. This renders ordinary Simulation impractical for evaluating such systems. To overcome this problem, simulation techniques based on importance sampling have been developed, and are very effective in certain settings. When importance sampling works well, simulation run lengths can be reduced by several orders of magnitude when estimating transient as well as steady-state dependability measures. This paper reviews some of the importance-sampling techniques that have been developed in recent years to estimate dependability measures efficiently in Markov and nonMarkov models of highly dependable systems     

The thermal stability of Quorn™ pieces

Summary Quorn pieces were heat-treated at 90 °C, 100 °C and at various F values (equivalent time in minutes at a reference temperature of 121.1 °C) for 6.2–24 min and at different pHs (4.5–6.0). The heat-treated Quorn product was assessed for texture using a Voledkevich probe cell, weight change, and the sensory properties of tenderness, juiciness and overall acceptability. The processed and unprocessed Quorn pieces were examined by electron microscopy. Temperature and pH were found to influence sensory tenderness but not instrumental texture. pH also influenced water absorption. However, in general Quorn pieces were found to be stable to heat processing at 90 °C, 100 °C and 120 °C.     

Role of autologous bone marrow transplantation as consolidation therapy in acute promyelocytic leukemia patients in complete remission

Recent studies in the field of de novo protein design have focused on the construction of native-like structures. Here we describe the design and characterization of an isoleucine zipper peptide intended to form a parallel triple-stranded coiled coil. To obtain the native-like structural uniqueness, the hydrophobic interface of the peptide consists of beta-branched Ile residues for complementary side chain packing. The peptide forms a stable triple-stranded coiled coil, as determined by circular dichroism and sedimentation equilibrium analyses. A fluorescence quenching assay after the incorporation of acridine revealed a parallel orientation of the peptides. The structural uniqueness of the coiled coil was confirmed by proton-deuterium amide hydrogen exchange and hydrophobic dye binding. The peptide contains amide protons with hydrogen exchange rates that are approximately an order of magnitude slower than those expected if the exchange occurred via global unfolding. A hydrophobic dye does not bind to the peptide. These results strongly suggest that the peptide folds into a well-packed structure that is very similar to the native state of a natural protein. Thus, Ile residues in the hydrophobic interface can improve the side chain packing, which can impart native-like structural uniqueness to the designed coiled coil.     

Towards a luxury uptake process via microalgae - Defining the polyphosphate dynamics

Microalgae in waste stabilization ponds (WSP) have been shown to accumulate polyphosphate. This luxury uptake of phosphorus is influenced by the wastewater phosphate concentration, light intensity and temperature, but the dynamics of how these factors affect luxury uptake with respect to time are not understood. With improved understanding of the dynamics of this mechanism and how it could be manipulated, a phosphorus removal process utilizing luxury uptake by microalgae might be developed. In this work, luxury uptake was investigated by chemical extraction of the acid-soluble and acid-insoluble fractions of polyphosphate in the microalgae. The results showed that the initial accumulation and subsequent utilization of both acid-soluble polyphosphate (ASP) and acid-insoluble polyphosphate (AISP) is a function of the wastewater phosphate concentration. It was found that light intensity influenced both the accumulation and utilization of ASP. The temperature influenced the accumulation of AISP. AISP is believed to be a form of phosphorus storage and ASP is involved in metabolism however, the results of this work show that ASP can also act as a short term form of phosphorus storage. To optimize luxury uptake by microalgae a ‘luxury uptake pond’ is proposed where the conditions the microalgae are exposed to can be manipulated. This ‘luxury uptake pond’ would be designed to expose the microalgae to a high phosphate concentration and high light intensity for a short period of time in order to achieve optimal polyphosphate accumulation. Subsequent harvesting would then remove the phosphorus rich microalgae from the system.     

Recombination parameters for antimonide-based semiconductors using the radio frequency photoreflectance technique

Radio-frequency (RF) photoreflectance measurements and one-dimensional device simulations have been used to evaluate bulk and surface recombination parameters in doubly capped, 0.50–0.59-eV, p-type InGaAsSb epitaxial materials. The InGaAsSb lifetime structures with variable active-layer thicknesses are used to extract the surface recombination velocity (SRV), while samples with different active-layer doping concentrations have been used to determine the Auger and radiative recombination coefficients. The RF photoreflectance measurements and analysis are compatible with a radiative recombination coefficient (B) of approximately 3×10⁻¹¹ cm³/s, Auger coefficient (C) of 1×10⁻²⁸ cm⁶/s, and SRV of ∼10³ cm/s or lower for 0.50–0.59 eV, doubly capped, p-type InGaAsSb epitaxial layers.     

Relation between MR abnormalities and patterns of cognitive impairment in multiple sclerosis

OBJECTIVE: This study correlated the extent of abnormalities detected by different magnetic resonance imaging (MRI) techniques [proton density (PD)-weighted, T1-weighted, and magnetization transfer imaging (MTI)] with the overall cognitive, frontal lobe, and memory impairments in patients with MS. PATIENTS: There were 30 clinically definite MS patients, with different disease courses. Exclusion criteria: psychoactive/steroid treatments, mood disorders, acute relapse phase. MAIN OUTCOME MEASURES: Neuropsychological test results. Total (TLL) and frontal (FLL) lesion loads assessed from PD-weighted, T1-weighted (22 patients), and MTI (22 patients) MRI scans. Average lesion MT ratios (MTR) and analysis of the MTR histograms from brain tissue axial slabs on MTI scans. RESULTS: Patients with frontal lobe deficits (n=15) or memory impairment (n-17) had a higher TLL on PD scans (p=0.04 and p=0.01, respectively). Patients with frontal lobe deficits had higher FLL on PD scans (p=0.01) and TLL on MTI (p=0.03) scans. No significant relationships between the extent of T1-weighted lesion loads and the presence of any neuropsychological impairment. Mean MTR of both MS lesions and whole brain tissue was lower in patients with frontal lobe impairment (p=0.04). MRI lesion loads correlated significantly with some neuropsychological test scores. CONCLUSIONS: Lesion loads on PD-weighted MRI and MTI-derived measures are associated with cognitive decline in MS patients. Overall macroscopic and microscopic brain damage is more important than the corresponding regional brain disease in determining deficits of selective cognitive domains.     

Brain insulin response to feeding in the rat is both macronutrient and area specific

A spectrum of tracheo-esophageal anomalies has been described in an adriamycin-treated model with common features to the human pattern. Tracheal agenesis was part of this spectrum. It is a rare congenital anomaly that has not been described in embryos. Virgin timed-pregnant Sprague-Dawley rats were injected with adriamycin i.p. at a dose of 2 mg/Kg on days 6-9 of gestation (plug day = day 0). Fetuses were recovered at term and histologic assessment of tracheo-esophageal anomalies was made. Also, embryos were removed on different gestational days and the embryology of these defects was analysed. Two out of sixty-two fetuses and nine out of 180 embryos were identified with tracheal atresia. Type III tracheal atresia was seen in the full-term fetuses with a tracheo-esophageal fistula arising from the origin of the left main bronchus. Day 13 embryos did not show normal tracheal development; instead, the lung buds developed from the ventral aspect of the foregut which continued to the stomach as a lower esophageal segment. A blind ending pouch was seen on the ventral aspect of the upper part of the foregut. The embryogenesis of tracheal atresia was similar to that of esophageal atresia except that the blind upper foregut pouch developed ventrally rather than dorsally.     

Sexual dimorphism and species differences in HVC volumes of cowbirds.

Cowbirds exhibit extensive variation in their social, territorial, and reproductive behaviors. Nissl-stained brain sections of specimens from a previous study (J. C. Reboreda, N. S. Clayton, & A. Kacelnik, 1996) were used to study the gross anatomy of a song control nucleus in 3 South American cowbirds (bay-winged, Molothrus badius; shiny, M. bonariensis; and screaming, M. rufoaxillaris). Cowbird high vocal center (HVC) volumes were consistently higher in males than in females in all 3 species. The largest HVC size of females found in bay-winged cowbirds is consistent with observations that females of this species, but not of the other 2 species, occasionally sing. The extent of the sexual dimorphism of relative HVC size was highest for the sexually dichromatic and promiscuous shiny cowbirds and smaller for the monochromatic and monogamous bay-winged and screaming cowbirds, suggesting that selection pressures associated with morphological traits and social systems are reflected in brain architecture. (PsycINFO Database Record (c) 2010 APA, all rights reserved)