Changes in lipids of pigeon “milk” in the first week of its secretion

Pigeon “milk” (PM) collected from the crop of 1- to 5-day-old squabs was analyzed to examine whether there were changes in lipid composition during the first week of secretion. The high PM fat content (9–11%) remained fairly constant in the first 5 days of secretion. The mean percentage of neutral lipids, glycolipids and phospholipids was 80, 12 and 8%, respectively. Unlike the content of neutral lipids, glycolipid and phospholipid levels increased significantly between day 1 and day 5 of secretion. Triglycerides, the major neutral lipids, decreased by 24% between day 1 and day 5, while free sterols, monoglycerides and hydrocarbons increased by 8%, 11% and 2.5%, respectively, during the same period; diglycerides and sterol esters, however, remained unchanged. The ratio of saturated to unsaturated fatty acids was 0.27 and it remained unchanged. Medium-chain (C₁₀, C₁₂ and C₁₄) and oddchain (C₁₅ and C₁₇) fatty acid contents were low. Fatty acids longer than C₂₀ were absent. Palmitic acid, the major saturated fatty acid, increased by 42% from day 1 to day 5, whereas stearic acid decreased by 48% during the same period. Oleic acid, the predominant unsaturated fatty acid, also decreased from 51 to 45% between the first and fifth day of PM secretion. Polyunsaturated acids (18∶2, 18∶3 and 20∶4) accounted for 26% and 30% of the total fatty acids on day 1 and day 5, respectively. Although lipid changes in the crop of squabs prior to collection of samples cannot totally be ruled out, the nature of lipid changes is likely to reflect cellular breakdown that precedes PM secretion by parent pigeons.     

Critical Stresses for Extension of Filament-Bridged Matrix Cracks in Ceramic-Matrix Composites: An Assessment with a Model Composite with Tailored Interfaces

Matrix cracking was studied in a model unidirectional composite of SiC filaments in an epoxy-bonded alumina matrix. The residual clamping stress on the filaments due to the shrinkage of the epoxy was moderated with the addition of the alumina filler, and the filament surface was coated with a releasing agent to produce unbonded frictional interfaces. Uniaxial tension specimens with controlled through-cracks with bridging filaments were fabricated by a two-step casting technique. Critical stresses for extension of the filament-bridged cracks of various lengths were measured in uniaxial tension using a high-sensitivity extensometer. The measured crack-length dependence of the critical stress was in good agreement with the prediction of a stress-intensity analysis that employed a new force-displacement law for the bridging filaments. The analysis required independent experimental evaluation of the matrix fracture toughness, the interfacial sliding friction stress, and the residual tension in the matrix. The matrix-cracking stress for the test specimens without the deliberately introduced cracks was significantly higher than the steady-state cracking stress measured for the long, filament-bridged cracks.     

Fatigue Crack Propagation in Ceria-Partially-Stabilized Zirconia (Ce-TZP)-Alumina Composites

Fatigue crack propagation rates in tension-tension load cycling were measured in ZrO₂-12 mol% CeO₂-10 wt% Al₂O₃ ceramics using precracked and annealed compact tension specimens. The fatigue crack growth behavior was examined for Ce-TZPs of different transformation yield stresses obtained by sintering for 2 h at temperatures of 1500°C (type A), 1475°C (type B), 1450°C (type C), and 1425°C (type D). The threshold stress-intensity range, ΔK_th, for initiation of fatigue crack propagation increased systematically with decreasing transformation yield stress obtained with increasing sintering temperature. However, the critical stress-intensity range for fast fracture, ΔK_c, as well as the stress-intensity exponent in a power-law correlation (log (da/d N ) vs log ΔK) were relatively insensitive to the transformation yield stress. The fatigue crack growth behavior was also strongly influenced by the history of crack shielding via the development of the crack-tip transformation zones. In particular, the threshold stess-intensity range, Δ K _th, increased with increasing size of the transformation zone formed in prior quasi-static loading. Crack growth rates under sustained peak loads were also measured and found to be significantly lower and occurred at higher peak stress intensities as compared to the fatigue crack growth rates. Calculations of crack shielding from the transformation zones indicated that the enhanced crack growth susceptibility of Ce-TZP ceramics in fatigue is not due to reduced zone shielding. Alternate mechanisms that can lead to reduced crack shielding in tension-tension cyclic loading and result in higher crack-growth rates are explored.     

Modification of epoxy resin by addition of bismaleimide and diallyl phthalate

Epoxy resins are a very versatile class of compounds. They have excellent mechanical properties and are easily processable; however, their major drawback is their brittleness. An attempt was made to improve the impact strength of the epoxy without decreasing its other properties. In the present study a commonly used epoxy resin, diglycidyl ether of Bisphenol‐A, was modified by the addition of bismaleimide (BMI) and diallyl phthalate (DAP) and was cured with diaminodiphenylmethane and benzoyl peroxide. The composition incorporating 5 phr BMI showed maximum heat deflection temperature (HDT) and flexural strength with impact properties remaining almost unaffected. Further addition of BMI reduced the HDT and flexural properties but increased the impact strength. For epoxy‐DAP systems the maximum HDT and flexural strength were observed on addition of 5 phr DAP. Further addition of DAP lead to a decrease in all properties except impact strength, which was observed to increase. Incorporation of both BMI and DAP, simultaneously, into the epoxy resin resulted in improvement in mechanical properties for most of the compositions. However, the HDT was found to be less than that for unmodified epoxy. POLYM. ENG. SCI., 47:1881–1888, 2007. © 2007 Society of Plastics Engineers     

The role of hyperarousal in the manifestation of posttraumatic psychological distress following injury.

The authors examined the temporal relation among posttraumatic stress disorder symptom clusters, using data derived from a longitudinal study of survivors of orofacial injury (N = 264). They conducted cross-lagged panel analyses, with self-reported symptom data collected at 1, 6, and 12 months postinjury. Results demonstrate that hyperarousal was a potent predictor of subsequent symptoms of reexperiencing and avoidance as well as hyperarousal. By contrast, neither reexperiencing nor avoidance was significantly related to other symptom clusters other than themselves over time. These findings underscore the distinctive nature of hyperarousal in the manifestation of posttraumatic psychological distress over time. Implications for theory, clinical intervention, and future research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

葡萄糖异构化酶对果糖生产的影响

对果葡糖浆的生产现状进行了评述,阐述了各种酶制剂,特别是葡萄糖异构化酶对果糖生产的影响,包括葡萄糖异构化酶对生产率的影响、反应器的设计及其操作影响因素.     

Optimization of dressing infeed of alumina wheel for grinding Ti-6Al-4V

In the present experiment study, dressing infeed values of 5, 10, 15, 20, and 25?µm are conceived on alumina wheel using 0.75 carat identical diamond dressers. The surface topologies of the dressed wheels are observed under scanning electron microscope. Differently dressed wheels are subsequently, employed for up-grinding Ti-6Al-4V in dry environment for 20 passes while the grinding infeed is kept constant at 10?µm during each pass. The grinding ratio is evaluated and the typical surface roughness parameters are measured using a mechanical type stylus. Tangential and normal force components are accurately measured with the help of dynamometer while the quality of ground substrate is observed under high resolution microscope. The performances of the differently dressed wheels are evaluated and subsequently, the dressing parameters are optimized based on the results obtained herein.     

Impact of dressing infeed on SiC wheel for grinding Ti-6Al-4V

Present experimental investigation is directed toward the optimization of dressing infeed for silicon carbide (SiC) wheel to be employed for grinding difficult-to-machine super alloy Ti-6Al-4V. Grinding wheels are dressed using separate, however, identical 0.75 carat single point diamond dressers at 5, 10, 15, 20 and 25 µm infeed values. Differently dressed wheels are consequently, applied for grinding Ti-6Al-4V under different infeed values of 5, 10 and 15 µm. All the operations have been performed at a constant velocity of 1810 m/min. The performances of the differently dressed SiC wheels are evaluated based on the variations of grinding force components, average surface roughness values, grinding ratio, chip forms and based on the analyses of the micrographs of wheel topologies and also of the ground surfaces, obtained using scanning electron microscope. Following the performance evaluation, the optimized dressing infeed has been found to be 20 µm for the operation range considered herein.     

Biofabrication of silver nanoparticles using bacteria from mangrove swamp

The last decade has observed a rapid advancement in utilising biological system towards bioremediation of metal ions in the form of respective metal nanostructures or microstructures. The process may also be adopted for respective metal nanoparticle biofabrication. Among different biological methods, bacteria‐mediated method is gaining great attention for nanoparticle fabrication due to their eco‐friendly and cost‐effective process. In the present study, silver nanoparticle (AgNP) was synthesised via continuous biofabrication using Aeromonas veronii, isolated from swamp wetland of Sunderban, West Bengal, India. The biofabricated AgNP was further purified to remove non‐conjugated biomolecules using size exclusion chromatography, and the purified AgNPs were characterised using UV–visible spectroscopy, X‐ray diffraction, field emission scanning electron microscopy and transmission electron microscopy (TEM). Additionally, the presence of proteins as capping and stabilising agents was confirmed by the amide‐I and amide‐II peaks in the spectra obtained using attenuated total reflection Fourier transform infrared spectroscopy. The size of biofabricated AgNP was 10–20 nm, as observed using TEM. Additionally, biofabricated AgNP shows significant antibacterial potential against E. coli and S. aureus. Hence, biofabricated AgNP using Aeromonas veronii, which found resistant to a significant concentration of Ag ion, showed enhanced antimicrobial activity compared to commercially available AgNP.Inspec keywords: silver, nanoparticles, microorganisms, nanofabrication, purification, chromatography, ultraviolet spectra, visible spectra, X‐ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, proteins, molecular biophysics, biochemistry, molecular configurations, attenuated total reflection, Fourier transform infrared spectra, particle size, antibacterial activity, biomedical materials, nanomedicineOther keywords: capping agents, stabilising agents, amide‐I peaks, amide‐II peaks, attenuated total reflection Fourier transform infrared spectroscopy, antibacterial potential, E. coli, S. aureus, Aeromonas veronii, antimicrobial activity, size 10 nm to 20 nm, Ag, proteins, TEM, transmission electron microscopy, field emission scanning electron microscopy, X‐ray diffraction, UV‐visible spectroscopy, size exclusion chromatography, nonconjugated biomolecules, purification, swamp wetland, Aeromonas veronii, cost‐effective process, eco‐friendly, bacteria‐mediated method, biological methods, metal nanoparticle biofabrication, microstructures, metal nanostructures, metal ions, bioremediation, biological system, mangrove swamp, bacteria, silver nanoparticles     

Review of the systems biology of the immune system using agent‐based models

The immune system is an inherent protection system in vertebrate animals including human beings that exhibit properties such as self‐organisation, self‐adaptation, learning, and recognition. It interacts with the other allied systems such as the gut and lymph nodes. There is a need for immune system modelling to know about its complex internal mechanism, to understand how it maintains the homoeostasis, and how it interacts with the other systems. There are two types of modelling techniques used for the simulation of features of the immune system: equation‐based modelling (EBM) and agent‐based modelling. Owing to certain shortcomings of the EBM, agent‐based modelling techniques are being widely used. This technique provides various predictions for disease causes and treatments; it also helps in hypothesis verification. This study presents a review of agent‐based modelling of the immune system and its interactions with the gut and lymph nodes. The authors also review the modelling of immune system interactions during tuberculosis and cancer. In addition, they also outline the future research directions for the immune system simulation through agent‐based techniques such as the effects of stress on the immune system, evolution of the immune system, and identification of the parameters for a healthy immune system.Inspec keywords: reviews, cancerOther keywords: review, system biology, agent‐based models, immune system, vertebrate animals, human beings, disease, gut nodes, lymph nodes, tuberculosis, cancer