Metastable lattice stabilities for the elements

Lattice stabilities for the metastable FCC (Al), BCC (A2) and CPH (A3) allotropes of 43 elements have been evaluated. The results are based on (1) Assessed stable phase data; (2) Phase boundary extrapolations from binary alloy, and elemental pressure-temperature, phase diagrams; (3) A relationship between the entropy of fusion, crystal structure and melting point; (4) Stacking fault energies; (5) Periodic and group trends and (6) First principle electronic energy calculations. Qualitative trends proposed by previous thermochemical evaluations for the transition metals are to a large extent confirmed. However, the evaluated energy differences between the different crystal allotropes are substantially higher and can be closer in magnitude to those predicted by ab-initio electron energy calculations, although particular discrepancies, for example concerning Cr(FCC), still remain. Many of the changes proposed here arise from the reassessment of stable phase data, particularly with respect to recently measured heats of fusion of the high melting point elements.     

Radiation-curable carbon fiber prepreg composites

Radiation processing is the utilization of ionizing radiation, usually photons or electron beams, to produce useful physical and chemical changes in a material. A potential application for electron beam processing for composite manufacturing is for curing carbon fiber prepregs. These prepregs, carbon fibers or fabrics preimpregnated with liquid polymer resin, are commonly used in the aircraft industry. Their use, however, can be time consuming and labor intensive. The advantages of radiation curing over thermal or chemical curing methods include improved rate control, reduced curing times, and curing at ambient temperature. There is no need for chemical initiators. A radiation-curable prepreg has been designed to meet the mechanical and physical property specifications of a leading aircraft manufacturing company. The resin is a mixture of an expoxy diacrylate, polybutadiene diacrylate, and a multifunctional monomer. This resin was used to impregnate a plain weave carbon fabric, at a loading of 35 percent (by mass), using a solvent process. Preliminary characterization studies show that the cured polymer produced by irradiation in air to a dose of 40 kGy is amorphous with a maximum gel fraction of 85 percent. The softening point of the polymer varied from 228°C (30-kGy sample) to 237°C (50-kGy sample). The linear thermal expansion coefficient of the polymer was 1.7 × 10⁻⁴ m/m°C from 25°C to 150°C and was unaffected by varying the applied dose from 30 to 50 kGy.     

Phage‐mediated transfer of virulence genes

Bacteriophages as accessory genetic elements play a crucial role in the dissemination of genes and the promotion of genetic diversity within bacterial populations. Such horizontal transfer of DNA is critical in the emergence of new pathogenic organisms, through the dissemination of genes encoding virulence factors such as toxins, adhesins and agressins. Phages can transfer genes that are not necessary for bacteriophage persistence and are generally recognised by their ability to convert their host bacteria to new phenotypes. This phenomenon is known as phage conversion. If such converting genes encode for virulence factors, the consequences of phage infection may include increased virulence of the host bacteria, and the conversion of a non‐pathogenic strain to a potentially dangerous pathogen. A number of virulence factors in bacteria causing diseases in plants, animals and humans are encoded by converting phages, the vast majority of which are temperate as opposed to lytic in nature. © 2001 Society of Chemical Industry     

High frequency testing of rubber mounts

Rubber and fluid-filled rubber engine mounts are commonly used in automotive and aerospace applications to provide reduced cabin noise and vibration, and/or motion accommodations. In certain applications, the rubber mount may operate at frequencies as high as 5000 Hz. Therefore, dynamic stiffness of the mount needs to be known in this frequency range. Commercial high frequency test machines are practically nonexistent, and the best high frequency test machine on the market is only capable of frequencies as high as 1000 Hz. In this paper, a high frequency test machine is described that allows test engineers to study the high frequency performance of rubber mounts at frequencies up to 5000 Hz.     

Social capital from carbon property: creating equity for indigenous people

New incentives for protection and in situ use of forests and the services they provide raise hopes for the reversal of tropical and temperate deforestation. Past management of forests appropriated the rights of forest communities, providing incentives to convert natural forest into financial capital through logging, while destroying the underlying physical property. Carbon trading aims to provide a means to convert the forest property into financial capital, while protecting the physical property of forests, thereby providing new incentives for in situ forest management. The potential for carbon-emission trading as a contributor to these new incentives is tempered by concerns that it is another tool for capitalists to exploit the indigenous communities of the developing world. Estimates of annual emission trading amounting to US $200 billion raise alarm bells about the effect of such trade in the developing world. People are right to be concerned, as the history of exploitation of indigenous people, the appropriation of their rights, the loss of forests and their benefits is well documented. This exploitation resulted in the exclusion of forest communities from the basic tenets for development created by the wealth generated by traded property. However, one virtue of trade is that it can be made subject to constraints. Through international treaties and agreements, trade can be constrained and national governments obliged to observe the rules of trade. The value of tradable carbon credits will be discounted or invalid if they do not meet these criteria, providing all parties with strong incentives to achieve the necessary performance standards relating to both processes and contracts. For carbon trading to develop social capital from natural capital requires the admission of forest communities into the polity and management of forest resources. In this paper we argue for responsible carbon-emission trading based on the clear and appropriate definition of carbon entitlements, with the proviso that trading respects the rights and needs of indigenous people. We adopt this position as emissions trading now seems inevitable and there should be proper rules to control this trade where it affects forests and their inhabitants. It is imperative that the poor and indigenous people are not excluded from these systems. Trading systems and the property systems they depend on need to be more accountable, transparent and inclusive of those features which we propose.     

Sperm phospholipase Czeta from humans and cynomolgus monkeys triggers Ca2+ oscillations,activation and development of mouse oocytes

Fusion with a fertilizing spermatozoon induces the mammalian oocyte to undergo a remarkable series of oscillations in cytosolic Ca(2+), leading to oocyte activation and development of the embryo. The exact molecular mechanism for generating Ca(2+) oscillations has not been established. A sperm-specific zeta isoform of phospholipase C (PLCzeta) has been identified in mice. Mouse PLCzeta triggers Ca(2+) oscillations in mouse oocytes and exhibits properties synonymous with the 'sperm factor' that has been proposed to diffuse into the oocyte after gamete fusion. The present study isolated the PLCzeta homologue from human and cynomolgus monkey testes. Comparison with mouse and monkey PLCzeta protein sequences indicates a shorter X-Y linker region in human PLCzeta and predicts a distinctly different isoelectric point. Microinjection of complementary RNA for both human and cynomolgus monkey PLCzeta elicits Ca(2+) oscillations in mouse oocytes equivalent to those seen during fertilization in mice. Moreover, human PLCzeta elicits mouse egg activation and early embryonic development up to the blastocyst stage, and exhibits greater potency than PLCzeta from monkeys and mice. These results are consistent with the proposal that sperm PLCzeta is the molecular trigger for egg activation during fertilization and that the role and activity of PLCzeta is highly conserved across mammalian species.     

Loss of emotional experience after traumatic brain injury: Findings with the startle probe procedure.

The authors used affective modulation of the eyeblink startle response to examine the impact of traumatic brain injury (TBI) on emotional reactions to pictures. Participants were 13 individuals with severe TBI and 24 controls. Participants were presented with pictures that differed in affective valence (e.g., mutilated bodies, erotic couples, and household objects) while the eyeblink startle response to an acoustic probe was measured. Startle amplitude was used to assess valence of emotional response, and startle latency was used to index interest in the pictures. Subjective ratings of the affect and arousal elicited by the various pictures were also obtained. TBI impaired startle potentiation to unpleasant pictures but not startle attenuation to pleasant pictures. Further, subjective ratings indicated that TBI participants found unpleasant pictures less arousing than did controls. The results are consistent with recent evidence of differential impairment in negative versus positive emotions after TBI and are discussed in relation to 2 competing explanations of startle modulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Simulated Bacterially-Inspired Problem Solving – The Behavioural Domain

Bacterial populations meet the challenges of dynamic spatially heterogeneous environments with fluctuating biotic and abiotic factors in a number of ways. The motivation for the work presented here has been to transfer ideas from bacterial adaptability and evolvability to computational problem solving. Following a brief comment on some examples of the ways bacteria solve problems, a bacterially-inspired computational architecture for simulating aspects of problem solving is described. We then examine three case studies. The first, a study of the mutational impact of a remediation to toxic (fitness-reducing) material, highlights how a sufficiently pre-engineered adaptive system can solve a difficult problem quite easily. The second study looks at why it is difficult to evolve complex problem solving behaviours and how artificial selection mechanisms coupled with pre-engineering the system can help. Specifically, this refers to quorum sensing and tactic behaviours. A further study looked at ways in which a quorum sensing analogue could help computational agents find multiple peaks in a landscape. The paper concludes with a discussion of an investigation of bacteria that had both quorum sensing and tactic capabilities.