The Use of Piezoelectric Actuators in an Energy-Efficient Noise Reduction System

The piezoelectric effect allows for conversion between mechanical stress and electrical impulses. By utilizing this phenomenon, a novel method of sound attenuation was explored and tested in which a piezoelectric plate absorbs part of an incoming sound wave. Reversing the process allows a second plate to produce a phase-inverted wave using the absorbed energy, achieving further reduction through destructive interference

Beyond a Politics of Recrimination: Scandal, Ethics and the Rehabilitation of Violence

The practice of contemporary warfare seems to be plagued by scandal. It is often assumed that the act of bearing witness to these moments of ethical failure, in which the relationship between the martial and the ethical breaks down, plays an important role in holding powerful actors to account for their conduct. Considerable faith has been placed in the role of transparency and truth-telling as foundations for normative engagements with war. This article argues that we must be cautious about this investment. Drawing on the work of Jean Baudrillard, this article offers a method for critically reading scandals as a series of line-drawing manoeuvres. Taken together, these manoeuvres demonstrate how scandals function to enable, excuse and obscure the complex landscapes of violence that define the spectacular and mundane sites of contemporary war. Reducing critical engagements with violent practices to a logic of recrimination, scandals often function to revitalise the very principles they appear to contest. Focusing upon the socio-political implications of wartime scandals, this article demonstrates that the performative force of scandals is therefore the reproduction of a violent status quo rather than opening up new spaces for imagining less violent futures. Offering a critical reading of controversies relating to the provision of humanitarian assistance and education in Afghanistan, this article reflects on the ambiguities and anxieties of critiquing violence

JetWeb: A WWW Interface and Database for Monte Carlo Tuning and Validation

A World Wide Web interface to a Monte Carlo validation and tuning facility is described. The aim of the package is to allow rapid and reproducible comparisons to be made between detailed measurements at high-energy physics colliders and general physics simulation packages. The package includes a relational database, a Java servlet query and display facility, and clean interfaces to simulation packages and their parameters.Comment: See http://jetweb.hep.ucl.ac.uk for further informatio

A quasi-one-dimensional theory for anisotropic propagation of excitation in cardiac muscle

It has been shown that propagation of excitation in cardiac muscle is anisotropic. Compared to propagation at right angles to the long axes of the fibers, propagation along the long axis is faster, the extracellular action potential (AP) is larger in amplitude, and the intracellular AP has a lower maximum rate of depolarization, a larger time constant of the foot, and a lower peak amplitude. These observations are contrary to the predictions of classical one-dimensional (1-D) cable theory and, thus far, no satisfactory theory for them has been reported. As an alternative description of propagation in cardiac muscle, this study provides a quasi-1-D theory that includes a simplified description of the effects of action currents in extracellular space as well as resistive coupling between surface and deeper fibers in cardiac muscle. In terms of classical 1-D theory, this quasi-1-D theory reveals that the anisotropies in the wave form of the AP arise from modifications in the effective membrane ionic current and capacitance. The theory also shows that it is propagation in the longitudinal, not in the transverse direction that deviates from classical 1-D cable theory

Surveillance of respiratory viruses

Respiratory virus isolates made at the National Institute for Virology from 1982 to 1991 were studied. An active virus surveillance programme, 'viral watch', which recruits throat swab specimens from a network of monitoring centres - mainly in the Witwatersrand and Vereeniging area with one centre in Middelburg - that represent a cross-section of the population, provided 68% of the specimens and 74% of the isolates, with an isolation rate of 25,5%. This was significantly higher than that of routine specimens (17,7%). Of the 966 isolates, influenza viruses accounted for 527 (54,7%), para-influenza for 122 (12,6%), respiratory syncytial virus for 34 (3,4%) and adenovirus for 106 (11,0%). Influenza viruses showed a definite seasonal peak between June and August whereas the other viruses, although they showed a winter predominance, were isolated throughout the year. An active virus surveillance programme is particularly valuable in monitoring respiratory virus epidemiology in the population

The Non-Perturbative N=2{\cal N} = 2 SUSY Yang-Mills Theory from Semiclassical Absorption of Supergravity by Wrapped D Branes

The imaginary part of the two point functions of the superconformal anomalous currents are extracted from the cross-sections of semiclassical absorption of dilaton, RR-2 form and gravitino by the wrapped D5 branes. From the central terms of the two point functions anomalous Ward identity is established which relates the exact pre-potential of the ${\cal N}=2$ SUSY Yang-Mills theory with the vacuum expectation value of the anomaly multiplet. From the Ward identity, WDVV (Witten-Dijkgraaf-Verlinde-Verlinde) equation can be derived which is solved for the exact pre-potential.Comment: 11 pages, late

Spin Precession and Oscillations in Mesoscopic Systems

We compare and contrast magneto-transport oscillations in the fully quantum (single-electron coherent) and classical limits for a simple but illustrative model. In particular, we study the induced magnetization and spin current in a two-terminal double-barrier structure with an applied Zeeman field between the barriers and spin disequilibrium in the contacts. Classically, the spin current shows strong tunneling resonances due to spin precession in the region between the two barriers. However, these oscillations are distinguishable from those in the fully coherent case, for which a proper treatment of the electron phase is required. We explain the differences in terms of the presence or absence of coherent multiple wave reflections.Comment: 9 pages, 5 figure

Fast algorithms for min independent dominating set

We first devise a branching algorithm that computes a minimum independent dominating set on any graph with running time O*(2^0.424n) and polynomial space. This improves the O*(2^0.441n) result by (S. Gaspers and M. Liedloff, A branch-and-reduce algorithm for finding a minimum independent dominating set in graphs, Proc. WG'06). We then show that, for every r>3, it is possible to compute an r-((r-1)/r)log_2(r)-approximate solution for min independent dominating set within time O*(2^(nlog_2(r)/r))

Primary and secondary infection with human parvovirus B19 in pregnant women in South Africa

A study of human parvovirus B19 infection in 1 967 pregnant women of all races in Johannesburg revealed an overall prevalence of 24,9% for IgG antibodies and 3,3% for IgM antibodies. Of the 64 IgM-positive sera indicating active infection, 62 were resistant to urea denaturation. No differences in the prevalence of IgG antibodies between population groups were observed, but active infections, as demonstrated by IgM antibodies, were significantly more prevalent in black than in white, coloured or Asian mothers

Hepatitis B virus prevalence in two institutions for the mentally handicapped

A comparative study of the prevalence of hepatitis B virus infection in two institutions for the mentally handicapped was carried out between April and November 1989 and April and August 1991. The institutions were situated within 10 km of each other in north-eastern Johannesburg. One institution had a significantly higher prevalence of virus markers, 68% (139 of 203) compared with 23% (40 of 176), was in poorer condition and had more severely handicapped residents with more aggressive behaviour. However, the most important difference between the two institutions was that residents at the higher-prevalence institution were admitted at a considerably younger age. Younger individuals appear to be more susceptible to infection and are more likely to develop persistent infection, thus contributing to a greater pool of infection in the institution