On the design and development of a miniature ceramic gimbal bearing

A review is made of a program to develop ceramic gimbal bearings for a miniaturized missile guidance system requiring nonmagnetic properties and higher load capacity than possible with conventional AISI 440C stainless steel bearings. A new gimbal design concept is described which utilizes the compressive strength and nonmagnetic properties of silicon nitride (Si3N4) ceramics for the gimbal bearing. Considerable manufacturing development has occurred in the last 5 years making ceramic bearings a viable option in the gimbal design phase. A preliminary study into the feasibility of the proposed design is summarized. Finite element analysis of the brittle ceramic bearing components under thermal stress and high acceleration loading were conducted to ensure the components will not fail catastrophically in service. Finite element analysis was also used to optimize the adhesive joint design. Bearing torque tests run at various axial loads indicate that the average running torque of ceramic bearings varies with load similarly to that of conventional steel bearings

Between resistance and resilience: a study of flood risk management in the Don catchment area (UK)

The river Don catchment area in Sheffield and Rotherham offers a good place for a case study of flood risk management, given the impact of a flooding event in 2007 and the way in which local events have become entwined with national and international policy shifts. To interpret local policy, a combination of systems-based and socio-cultural theory is used. Both the theories and the case study serve to disentangle the multiple meanings of resilience. Understood in opposition to flood resistance, resilience has only limited applicability in an area such as the case study where engineering works protect employment and infrastructure. Resilience as a policy discourse also lacks political transparency and a recognition of socio-cultural influences. Underlying the shift towards resilient styles of management is an appreciation of the importance of capacity, to learn and to act. The case study identifies blockages to the realisation of that capacity

Spectral Characteristics of Schwa in Czech Accented English

The English central mid lax vowel (i.e., schwa) often contributes considerably to the sound differences between native and non-native speech. Many foreign speakers of English fail to reduce certain underlying vowels to schwa, which, on the suprasegmental level of description, affects the perceived rhythm of their speech. However, the problem of capturing quantitatively the differences between native and non-native schwa poses difficulties that, to this day, have been tackled only partially. We offer a technique of measurement in the acoustic domain that has not been probed properly as yet: the distribution of acoustic energy in the vowel spectrum. Our results show that spectral slope features measured in weak vowels discriminate between Czech and British speakers of English quite reliably. Moreover, the measurements of formant bandwidths turned out to be useful for the same task, albeit less direc

Ex-ante assessment of demand for improved forage seed and planting materials among Ethiopian smallholder farmers: A contingent valuation analysis

United States Agency for International Developmen

Ex-ante assessment of demand for improved forage seed and planting materials among smallholder farmers in Ethiopia: A contingent valuation analysis

United States Agency for International Developmen

Ex-ante assessment of potential market demands and commercial viabilities for private forage seeds production in Ethiopia

United States Agency for International Developmen

Engineered gp120 immunogens that elicit VRC01-like antibodies by vaccination

Background: One of the great challenges for an HIV vaccine is to elicit broadly neutralizing antibodies specific for conserved epitopes from which the virus cannot easily escape. The CD4 binding site is one such epitope against which several antibodies (e.g. b12, VRC01) have been isolated. In macaques infected with SHIV, passive immunization with these CD4-directed neutralizing antibodies fails to control the virus, but prophylactic administration is highly protective. Similarly, patients who generate neutralizing antibodies over the course of an HIV infection derive no clinical benefit from them, but eliciting such antibodies prophylactically by vaccination may prevent the virus from establishing its lethal foothold

Value chains, markets and economics: Africa RISING Science, Innovations and Technologies with Scaling Potential from the Ethiopian Highlands

United States Agency for International Developmen

Carbon and oxygen depletion and extinction in the translucent cloud toward HD 24534 (X Persei)

Recent studies of the gas-phase abundances of carbon and oxygen in diffuse clouds have suggested that the depletions of both elements are invariant and independent of extinction curve properties. We show, however, that in the line of sight toward HD 24534 (X Persei), the depletion of carbon is at least a factor of 3 greater than in the diffuse clouds previously surveyed. For HD 24534, the interstellar gas-phase C/H ratio is lower than the mean of diffuse sight lines by a factor of about 3.5. We conclude that the carbon depletion may be enhanced in translucent molecular clouds and also that carbon begins to show an enhanced level of depletion at lower extinctions than oxygen, which is also discussed. We argue that it is imperative to measure abundances and depletions in translucent and denser clouds in order to understand the interaction between gas and dust as the thicknesses and densities of clouds increase

Rapid Conformational Epitope Mapping of Anti-gp120 Antibodies with a Designed Mutant Panel Displayed on Yeast

gp120 is a substrate for protein engineering both for human immunodeficiency virus (HIV) immunogen design and as a bait for isolating anti-HIV antibodies from patient samples. In this work, we describe the display of a stripped core gp120 on the yeast cell surface. Validation against a panel of neutralizing antibodies confirms that yeast-displayed gp120 presents the CD4 binding site in the correct conformation. We map the epitope of the broadly neutralizing anti-gp120 antibody VRC01 using both a random mutagenesis library and a defined mutant panel and find that the resultant epitope maps are consistent with one another and with the crystallographically identified contact residues. Mapping the VRC01-competitive antibodies b12 and b13 reveals energetic differences in their epitopes that are not obvious from existing crystal structures. These data suggest mutation sets that abrogate binding to broadly neutralizing antibodies with greater specificity than the canonical mutation D368R, useful in rapidly assessing the nature of a vaccine response.Ragon Institute of MGH, MIT and Harvar