The relationship between activation energy and precipitate size for precipitate agglomeration

Superalloys are used in aggressive atmospheres in aero-engines and land-base gas turbines. IN738LC is an important superalloy used in gas turbines. Strengthening Ni₃(Al,Ti,Nb) type precipitate phase in this superalloy goes through size and morphological changes with time and temperature. Experimental observations suggest precipitate motion as a whole in the matrix leading to agglomeration of nearby precipitates for coarsening, which is in contrast to the traditional Ostwald ripening. Likewise, contrary to the conventionally accepted view of constant activation energy, experimental data in this study indicate varying activation energy, which causes coalescence and relates to the precipitate size in the form of an increasing polynomial.     

Intracellular pH distribution as a cell health indicator in Saccharomyces cerevisiae

Internal pH regulation is vital for many cell functions, including transport mechanisms and metabolic enzyme activity. More specifically, transport mechanisms are to a wide degree governed by internal pH distributions. We introduce the term standard deviation of the intracellular pH (s.d.(pH_int)) to describe the internal pH distributions. The cellular pH distributional response to external stress such as heat has not previously been determined. In this study, the intracellular pH (pH_i) and the s.d.(pH_int) of Saccharomyces cerevisiae cells exposed to supralethal temperatures were measured using fluorescence ratio imaging microscopy (FRIM). An exponential decline in pH_i was observed after an initial small decline. For the first time, we report the use of FRIM for determining in vivo plasma membrane proton permeability coefficients in yeast. Furthermore, the exponential decay of pH_i and the rupture of the cell plasma membrane, as measured by propidium iodide staining, at 70°C were not simultaneous but were separated by a significant temporal difference. Finally, a nonlinear relationship between the pH_i and s.d.(pH_int) was found; i.e. the s.d.(pH_int) was significantly more sensitive to supralethal temperatures than pH_i. s.d.(pH_int) is therefore proposed as an early health/vitality indicator in S. cerevisiae cells exposed to heat stress.     

BaTiO_3压电陶瓷的断裂韧性与晶粒尺寸及分布的研究

以压电陶瓷的自增韧作用机理为出发点,综合考虑微裂纹和气孔的双重因素影响,建立了一个断裂韧性与晶粒尺寸及分布的模型。理论分析了Ba-TiO3压电陶瓷的断裂韧性与晶粒尺寸及分布的关系;并进一步分析了大颗粒加入量对断裂韧性的影响。运用该模型得出的计算结果和实验结果具有很好的一致性。     

Antimicrobial Activity of Natural Agents against Saccharomyces cerevisiae

The antimicrobial (AM) activity of starch‐based films coated with linalool, carvacrol or thymol against Saccharomyces cerevisiae in vitro and/or inoculated on the surface of Cheddar cheese was investigated. In solid medium using the agar diffusion method and in experiments involving the inoculation of the microorganism on the surface of Cheddar cheese, all the films containing these AM agents in coatings demonstrated an inhibitory effect against S. cerevisiae. The results suggest that the overall inhibitory effect of linalool, carvacrol or thymol increased significantly (p ≤ 0.05) with the concentration of each of the AM agents in the film coating and that the response is linear in the concentration range of 1 to 5% (w/w) of the AM agent. Thymol had the highest AM efficacy followed by carvacrol, whereas linalool had the lowest efficacy amongst the three systems. The zones of inhibition in the agar diffusion test method at 25°C for S. cerevisiae were found to be 7.6, 7.1 and 6.1 mm for thymol, carvacrol and linalool at 1% (w/w) loading and 13.2, 12.2 and 11.2 mm at 5% (w/w) loading of the AM agents, respectively. The death rates of S. cerevisiae on Cheddar cheese wrapped in films coated with thymol, carvacrol and linalool and stored for up to 28 days at 15°C were found to be 0.044, 0.043 and 0.038 per day at 1% (w/w) loading and 0.077, 0.073 and 0.063 per day at 5% (w/w) loading of the AM agents, respectively. Copyright © 2011 John Wiley & Sons, Ltd.     

The relationship between extrusion die line roughness and high cycle fatigue life of an AA6082 alloy

The effect of surface finish on the fatigue life of hollow extruded AA6082 was studied by comparing results from specimens with as-extruded surfaces to results from specimens with polished surfaces. Extrusion die lines are the main contributor to surface roughening, and since die lines are parallel to the extrusion direction, distinct variations exist between fatigue lives of as-extruded specimens taken longitudinal and transverse to the extrusion direction [Nanninga N, White C, Furu T, Anderson O, Dickson R. Effect of orientation and extrusion welds on the fatigue life of an Al–Mg–Si–Mn alloy. Int J Fatigue 2008;30(9):1569–78]. Polishing specimen surfaces eliminated much of the variation between specimen orientations. Fatigue lives of polished specimens containing extrusion seam welds transverse to the loading direction were also studied. The seam weld did not appear to significantly affect the fatigue life. Die lines were modeled as notches and finite element analysis (FEA) was used to estimate a linear-elastic stress concentration factor for approximating fatigue run-out values for specimens with as-extruded surfaces loaded transverse to the die lines. The predicted run-out stress values based on the FEA match well with those obtained experimentally.     

Unusual relationship between impact toughness and grain size in a high-manganese steel

The high-manganese steels are important structural materials,owing to their excellent toughness at low temperatures.However,the microstructural causes for their...     

Theoretical relationship between maximum pore size and toughness in experimental inflammatory arthritis

Rheumatoid arthritis increases the risk of fracture. In an animal model of inflammatory arthritis, femoral diaphysis had a decreased toughness as well as increased cortical porosity, when compared to normal bone. Based on the hypothesis that stress concentration from the large porous defects reduces the ability of the cortical bone to resist failure, this work determined if the changes observed in porosity could explain the changes observed in toughness. Using theoretical relationships of the stress concentration and stress states, a model of the observed conditions was considered. A relationship was developed that indicated the relative difference in toughness between normal and arthritic specimens as a function of pore size. Results indicated that the increase in cortical pore size could theoretically reduce toughness by 55%. This decrease compares with the experimentally observed drop in toughness of 61%. Furthermore, the critical parameter for fracture in this situation is the ratio of pore diameter to cortical thickness. Efforts to reduce cortical porosity seen in inflammatory arthritis would be effective in enhancing the toughness of bone and may reduce morbidity in a human population. ©2000 Kluwer Academic Publishers     

The relationship between advisors and students

Considering the influence of graduation courses on the scientific productivity in Brazil, fifty productive Brazilian scientists working in life sciences were interviewed about their relationship with their advisors and their own experience with their students. Admired by freedom and intellectual qualities, by their love and dedication for science, advisors seem to have had a deep influence on their students. This bond is not free from either an idealized frame or from some complaints and conflicts. Interviewed scientists see in themselves lesser qualities and faults but the same respect for freedom. Some students are thought to be specially important to the interviewed's productivity. Eldest and most productive scientists seem to be intellectually more impressed by their advisors than the other groups. The emotional and sometimes strong and idealized bond between advisor and students lead us to believe that the stated frequencies of conflicts might be underestimated.     

Adhesion-dependent rupturing of Saccharomyces cerevisiae on biological antimicrobial nanostructured surfaces

Recent studies have shown that some nanostructured surfaces (NSS), many of which are derived from surfaces found on insect cuticles, rupture and kill adhered prokaryotic microbes. Most important, the nanoscale topography is directly responsible for this effect. Although parameters such as cell adhesion and cell wall rigidity have been suggested to play significant roles in this process, there is little experimental evidence regarding the underlying mechanisms involving NSS-induced microbial rupture. In this work, we report the NSS-induced rupturing of a eukaryotic microorganism, Saccharomyces cerevisiae. We show that the amount of NSS-induced rupture of S. cerevisiae is dependent on both the adhesive qualities of the yeast cell and the nanostructure geometry of the NSS. Thus, we are providing the first empirical evidence that these parameters play a direct role in the rupturing of microbes on NSS. Our observations of this phenomenon with S. cerevisiae, particularly the morphological changes, are strikingly similar to that reported for bacteria despite the differences in the yeast cell wall structure. Consequently, NSS provide a novel approach for the control of microbial growth and development of broad-spectrum microbicidal surfaces.     

Application of TOF-SIMS with chemometrics to discriminate between four different yeast strains from the species Candida glabrata and Saccharomyces cerevisiae

We present a TOF-SIMS analysis of the cell surface differences between four yeast strains from two species, Candida glabrata and Saccharomyces cerevisiae (haploid strains BY4742 and BY4741 and the derived diploid BY4743). The study assesses the suitability of TOF-SIMS analysis in combination with statistical methods (principal component analysis, Fisher's discriminant analysis, and cluster analysis) for the discrimination between the four yeast strains. We demonstrate that a combination of these statistical methods identifies 34 ions, from a total data set of 1200, which can be used to distinguish between the four yeasts. The study discusses the assignments of surface cell membrane phospholipids for the identified ions and the resulting differences in the phospholipid pattern between the four yeasts, particularly in relation to ploidy and budding pattern. The method shows that fatty acids, phosphatidylglycerols, phosphatidylethanolamines, phosphatidylserines, and phosphatidylcholines, as well as cardiolipins, are of diagnostic importance.     

Theoretical analysis on the relationship between left ventricular energetic efficiency and acute infarct size

Energetic efficiency is an important indicator of cardiac function in acute myocardial infarction. However, the relationship between cardiac energetic efficiency and infarct size is not perfectly elucidated. In this study, the relationship is analysed by means of simulation using a theoretical model of the guinea pig left ventricle. In simulation with varied ratios of infarct area, pressure–volume area (PVA), which is an index of total mechanical energy by ventricular contraction, and myocardial oxygen consumption (MVO₂) are calculated for each infarct ratio. Then, change of PVA when MVO₂ alters (PVA/MVO₂) as a well‐known index of energy conversion efficiency is evaluated. In addition, PVA/VO₂, which represents a ratio of PVA change to alteration of mean oxygen consumption of myocytes except for infarct myocytes, is introduced as an index for real energetic efficiency. In simulation results, PVA/MVO₂ increases but PVA/VO₂ decreases as infarct area expands, because with expansion of infarct area PVA decreases but VO₂ remains almost unchanged because of larger shortening of myocytes. This implies that the enlargement of shortening of noninfarcted myocyte to compensate for depression of cardiac output is a potential cause of myocardial remodelling.Inspec keywords: blood vessels, cardiology, cellular biophysics, haemodynamics, muscle, oxygen, physiological modelsOther keywords: theoretical analysis, left ventricular energetic efficiency, acute infarct size, cardiac function, acute myocardial infarction, cardiac energetic efficiency, guinea pig left ventricle, pressure‐volume area, total mechanical energy, ventricular contraction, myocardial oxygen consumption, energy conversion efficiency, myocyte mean oxygen consumption, infarct myocytes, energetic efficiency index, noninfarcted myocyte shortening enlargement, cardiac output, myocardial remodellingInspec keywords: blood vessels, cardiology, cellular biophysics, haemodynamics, muscle, oxygen, physiological modelsOther keywords: theoretical analysis, left ventricular energetic efficiency, acute infarct size, cardiac function, acute myocardial infarction, cardiac energetic efficiency, guinea pig left ventricle, pressure‐volume area, total mechanical energy, ventricular contraction, myocardial oxygen consumption, energy conversion efficiency, myocyte mean oxygen consumption, infarct myocytes, energetic efficiency index, noninfarcted myocyte shortening enlargement, cardiac output, myocardial remodelling     

高分子量PAN的粒径分布与均匀度关系的考察

对高性能碳纤维原丝性能有重要影响的聚合物粒径均匀度问题目前尚未有人研究过。本研究率先采用沉淀聚合合成高分子量PAN,根据其微观形貌,应用第四统计力学群子统计参数理论研究了聚合物的粒径分布与粒径均匀度的关系,表明粒径均匀度与混合溶剂无关,而与混合溶剂的配比有关,DMSO含量越少,粒径分布越均匀。     

The effect of cycle lanes on the proximity between motor traffic and cycle traffic

An experiment collected proximity data of motor traffic overtaking cycle traffic on roads with and without cycle lanes using an instrumented bicycle. The work enhances previous research which has considered the riding position of the cyclist and whether or not the cyclist was helmeted, while controlling for vehicle type.The analysis shows that significantly wider passing distances are adopted by motorists in the condition without a 1.45 m cycle lane, with posted speed limits of 40 mph and 50 mph with a 9.5 m wide carriageway. These findings were not replicated for a similar width road with a posted speed limit of 30 mph and a 1.3 m cycle lane.The results suggest that in the presence of a cycle lane, drivers may be driving within the confines of their own marked lane with less recognition being given to the need to provide a comfortable passing distance to cycle traffic in the adjacent cycle lane.     

The relationship between microsystem technology and metrology

Microsystem technology (MST) has enabled silicon sensors to evolve from simple transduction elements to microsystems (micro-instruments) that include readout circuits, self-test, and auto-zeroing facilities. This paper discusses the impact of MST in the instrumentation and measurement (I&M) field. In metrology, in particular, the development of electrical reference standards by using microtechnology has opened a wide variety of potential applications, such as the Josephson junction array (DC voltage reference) and thin-film multijunction thermal converters (AC voltage and AC current reference). It is shown that MST has even more to offer to the I&M field. Two devices that have highly benefited from MST. thermal and capacitive RMS-to-DC converters are discussed in historical perspective., Subsequently, a recently developed microdevice, the pull-in voltage reference, which may have a huge impact in I&M applications, is outlined. Finally, it is demonstrated that recent developments in electrical and nonelectrical metrology system concepts offer special opportunities for on-chip cointegrated silicon microsystem realizations     

FLP介导的酿酒酵母rDNA多拷贝定点整合

构建了一个带有ＦＲＴ位点以及启动子缺陷的ＵＲＡ３ｄ选择标记的环状质粒,并通过位点特异性重组将其整合到酵母染色体ｒＤＮＡ中放置的一个ＦＲＩ位点上。Ｓｏｕｔｈｅｒｎ杂交分析表明若处于很强的选择压力下,该质粒的拷贝数会发生有效的扩增。为了证明该质粒能够作为表达载体,将乙肝融合表面抗原ＳＡ－２８基因的表达单元插入该质粒后整合到ｒＤＮＡ位点。与ｒＤＮＡ位点整合了单个表达单元的菌株相比,ＳＡ－２８蛋白的表达量     

Adhesion and internalization of functionalized polystyrene latex nanoparticles toward the yeast Saccharomyces cerevisiae

The toxicity and the internalization, adhesion, and dispersion behavior of manufactured polystyrene latex (PSL) nanoparticles (nominal diameter: 50 nm) with various functional groups toward the yeast Saccharomyces cerevisiae (which was applied as a model eukaryote) were examined using the colony count method, and microscopic observations. The colony count tests suggested that PSL nanoparticles with a negative surface charge showed little or no toxicity toward the yeast. In contrast, PSL nanoparticles with an amine functional group and a positive surface charge (p-Amine) displayed a high toxicity in 5 mM NaCl. However, the yeast cells were mostly unharmed by the p-Amine in 154 mM NaCl, results that were quite different from the toxicological effects observed when Escherichia coli was used as a model prokaryote. Confocal and atomic force microscopies indicated that in 5 mM NaCl, the p-Amine nanoparticles entirely covered the surface of the yeast, and cell death occurred; in contrast, in 154 mM NaCl, the p-Amine nanoparticles were internalized via endocytosis, and cell death did not occur.     

企业标准化与环境管理的关系

本文从分析企业的环境现状，提出控制产品生命周期过程的现实和潜在环境影响因素的方法，导出企业标准化与环境管理的成功发展关系，为企业实施可持续发展奠定基础。