Grain Boundary Responses to Heterogeneous Deformation in Tantalum Polycrystals

The evolution of heterogeneous deformation in a tantalum polycrystal was examined during a three-point bending experiment using electron backscatter pattern mapping. Slip bands formed at strains as low as 1%, and they became more intense with strain. Heterogeneous deformation was evident as intragranular orientation gradients as large as 30° were observed after a strain of about 8%. Nonmonotonic changes in the local average misorientation distribution were observed, implying that dislocation substructure developed in a complex manner. Slip bands were analyzed using plane traces computed from local orientation information. With the assumption of uniaxial stress, Schmid factors for favorable slip systems were identified for each grain and compared with observations, showing evidence for macroscopic activity on both {110} and {112} slip systems. Reconstructed boundary data were used to estimate the geometric potential for slip transfer at grain boundaries. The correlations indicated that when active slip systems were favorably oriented for slip transfer across the boundary, it was often observed in the form of continuous slip bands aligned across the boundary. In boundaries where geometrical alignment and Schmid factors were not favorable for slip transfer, there was a higher likelihood to form ledges (topographic discontinuities) along the grain boundaries. Dislocation pileups at grain boundaries were also correlated with a low potential for slip transfer.     

Biological conversion of low-grade coal discard to a humic substance-enriched soil-like material

International Journal of Coal Science & Technology - A mutualistic relationship between grasses, coal-degrading fungi, and arbuscular mycorrhizal fungi was proposed to account for the...     

Rice-like CuO nanostructures for sensitive electrochemical sensing of hydrazine

In this work, a low temperature aqueous chemical growth methodology was used for the fabrication of CuO nanostructures. The as-synthesised nanostructures were then elaborately characterised by number of analytical techniques such as scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). The obtained nanostructures were observed to possess interlaced rice-shaped structural features with the length and width of individual rice determined to be in the range of 200–300 nm and 50–100 nm respectively. The unique nanostructures when utilised as electrode material exhibited excellent electro-catalytic potential towards oxidation of hydrazine in alkaline media. The excellent conductive of CuO added by the high surface area of obtained nanorice-like structures enabled development of highly sensitive (3087 µA mM⁻¹ cm⁻²), selective and stable electrochemical sensor for hydrazine. In addition, the successfully application of the developed sensor in spiked tap, bottled and industrial water samples for the detection of hydrazine suggested its feasibility for practical environmental application.

     

Non-uniform illumination in concentrating solar cells

After a gap of more than two decades, Concentrator Photovoltaics (CPV) technology is once again under spotlight for making use of the best available solar cell technologies and improving the overall performance. CPV finds its use in a number of applications ranging from building integration to huge power generation units. Although the principles of solar concentration are well understood, many practical design, operation, control issues require further understanding and research. A particular issue for CPV technology is the non-uniformity of the incident flux which tends to cause hot spots, current mismatch and reduce the overall efficiency of the system. Understanding of this effect requires further research, and shall help to employ the most successful means of using solar concentrators. This study reviews the causes and effects of the non-uniformity in the CPV systems. It highlights the importance of this issue in solar cell design and reviews the methods for the solar cell characterization under non-uniform flux conditions. Finally, it puts forward a few methods of improving the CPV performance by reducing the non-uniformity effect on the concentrator solar cells.     

Genes without prominence: a reappraisal of the foundations of biology

The sequencing of the human genome raises two intriguing questions: why has the prediction of the inheritance of common diseases from the presence of abnormal alleles proved so unrewarding in most cases and how can some 25 000 genes generate such a rich complexity evident in the human phenotype? It is proposed that light can be shed on these questions by viewing evolution and organisms as natural processes contingent on the second law of thermodynamics, equivalent to the principle of least action in its original form. Consequently, natural selection acts on variation in any mechanism that consumes energy from the environment rather than on genetic variation. According to this tenet cellular phenotype, represented by a minimum free energy attractor state comprising active gene products, has a causal role in giving rise, by a self-similar process of cell-to-cell interaction, to morphology and functionality in organisms, which, in turn, by a self-similar process entailing Darwin''s proportional numbers are influencing their ecosystems. Thus, genes are merely a means of specifying polypeptides: those that serve free energy consumption in a given surroundings contribute to cellular phenotype as determined by the phenotype. In such natural processes, everything depends on everything else, and phenotypes are emergent properties of their systems.     

Stress among South African construction professionals: a job demand-control-support survey

Research into workplace stress in the construction industry has been dominated by studies undertaken in Hong Kong, England and Australia, with relatively little attention having been paid to African countries. A purposively selected sample of thirty-six construction professionals (comprising architects, project managers, construction managers, engineers and quantity surveyors) based in Cape Town, South Africa, were surveyed regarding their perceptions about, and experiences of, workplace stress. The purpose was to identify and rank job demand, job control and job support factors and to analyse these by gender and professional grouping, both in terms of how respondents perceived them, as well as in terms of how frequently they had experienced them. The main finding was that respondents’ perceptions about the importance of job demand, job control and job support factors were largely consistent with their own experience of these factors. Distinguishing between perceptions and experience of stressors and moderators of stress was, however, considered valuable because the fact that differences were found indicates the need for precision in the design of scales. The highest ranked factors were, respectively, ‘critical time constraints’, ‘volume of work’ and ‘adequate compensation (salary)’. Women and men ranked items differently, as did the various professional groups. The main conclusions were that the construction project environment is a time-pressured, complex, environment in which work-life balance is negatively affected, particularly for women. Control over the type, flow and volume of work were perceived to be the main moderators of stress, whilst salary and career path opportunities were perceived to be the main job support moderators of stress. The applicability of using the job demand–control–support framework was confirmed given that the main stressors, control and support moderators were found to be to be largely consistent with the findings of previous studies. Future research taking a gendered approach should anticipate issues important to female respondents and should consider the benefits of qualitative methods. The design of research focusing on construction professionals should consider using the project team as the unit of analysis to ensure that the influence of the interconnectedness of participants’ roles is taken into account.     

A Double Resonance Method for Studying Collision Rates in an Intense Laser Field

Abstract

We propose a method for studying the modification of atomic collision rates in the presence of an intense laser field. This method employs a three-level lambda-system driven by two laser pulses: one strong and the other weak. The weak laser is used to populate a particular dressed state produced by the intense laser at some time during the pulse history. We show that this point can be selected by tuning the frequency of the weak laser. The spectrum of the emission produced by the dressed state is then recorded. Measuring this spectrum, both in the presence and in the absence of collisions, enables one to deduce the dependence of the collision rates on laser intensity. The method has other advantages discussed in the text.     

Flex and Flex-Rigid PCB Technologies and Trends

Offering all of the benefit of rigid PCBs and wire harnesses combined, flex-rigid technology provides an improvement in reliability for applications in aerospace, medical, computer, telecom and auto-motive market sectors.