Transverse "resistance overshoot" in a Si/SiGe two-dimensional electron gas in the quantum Hall effect regime

We investigate the peculiarities of the "overshoot" phenomena in the transverse Hall resistance R_{xy} in Si/SiGe. Near the low magnetic field end of the quantum Hall effect plateaus, when the filling factor \nu approaches an integer i, R_{xy} overshoots the normal plateau value h/ie^2. However, if magnetic field B increases further, R_{xy} decreases to its normal value. It is shown that in the investigated sample n-Si/Si_{0.7}Ge_{0.3}, overshoots exist for almost all \nu. Existence of overshoot in R_{xy} observed in different materials and for different \nu, where splitting of the adjacent Landau bands has different character, hints at the common origin of this effect. Comparison of the experimental curves R_{xy}(\nu) for \nu = 3 and \nu = 5 with and without overshoot showed that this effect exist in the whole interval between plateaus, not only in the region where R_{xy} exceeds the normal plateau value.Comment: 3 pages, 5 EPS figure

Time-partitioning simulation models for calculation on parallel computers

A technique allowing time-staggered solution of partial differential equations is presented in this report. Using this technique, called time-partitioning, simulation execution speedup is proportional to the number of processors used because all processors operate simultaneously, with each updating of the solution grid at a different time point. The technique is limited by neither the number of processors available nor by the dimension of the solution grid. Time-partitioning was used to obtain the flow pattern through a cascade of airfoils, modeled by the Euler partial differential equations. An execution speedup factor of 1.77 was achieved using a two processor Cray X-MP/24 computer

A serological survey of ruminant livestock in Kazakhstan during post-Soviet transitions in farming and disease control

The results of a serological survey of livestock in Kazakhstan, carried out in 1997–1998, are reported. Serum samples from 958 animals (cattle, sheep and goats) were tested for antibodies to foot and mouth disease (FMD), bluetongue (BT), epizootic haemorrhagic disease (EHD), rinderpest (RP) and peste des petits ruminants (PPR) viruses, and to Brucella spp. We also investigated the vaccination status of livestock and related this to changes in veterinary provision since independence in 1991. For the 2 diseases under official surveillance (FMD and brucellosis) our results were similar to official data, although we found significantly higher brucellosis levels in 2 districts and widespread ignorance about FMD vaccination status. The seroprevalence for BT virus was 23%, and seropositive animals were widespread suggesting endemicity, despite the disease not having being previously reported. We found a few seropositives for EHDV and PPRV, which may suggest that these diseases are also present in Kazakhstan. An hierarchical model showed that seroprevalence to FMD and BT viruses were clustered at the farm/village level, rather than at a larger spatial scale. This was unexpected for FMD, which is subject to vaccination policies which vary at the raion (county) level

Causality and replication in concurrent processes

The replication operator was introduced by Milner for obtaining a simplified description of recursive processes. The standard interleaving semantics denotes the replication of a process P, written !P, a shorthand for its unbound parallel composition, operationally equivalent to the process P | P | …, with P repeated as many times as needed. Albeit the replication mechanism has become increasingly popular, investigations on its causal semantics has been scarce. In fact, the correspondence between replication and unbound parallelism makes it difficult to recover basic properties usually associated with these semantics, such as the so-called concurrency diamond. In this paper we consider the interleaving semantics for the operator proposed by Sangiorgi and Walker, and we show how to refine it in order to capture causality. Furthermore, we prove it coincident with the standard causal semantics for recursive process studied in the literature, for processes defined by means of constant invocations

Positive practices : solution-focused and narrative therapeutic techniques with children with sexually harmful behaviours

This article explores the use of solution-focused and Narrative Therapeutic approaches with a boy who had sexually harmful behaviours. The paper will highlight the practical challenges of working with someone who is 'problem-saturated' through institutionalisation and who is also subjected to powerful discourses claiming the 'truth' about him. The use of solution-focused and Narrative Therapeutic principles and approaches will be demonstrated in the work described, in a way that allows the reader to reflect on how these may differ from modernist understandings and responses to this behaviour

Manual for starch gel electrophoresis: A method for the detection of genetic variation

The procedure to conduct horizontal starch gel electrophoresis on enzymes is described in detail. Areas covered are (I) collection and storage of specimens, (2) preparation of tissues, (3) preparation of a starch gel, (4) application of enzyme extracts to a gel, (5) setting up a gel for electrophoresis, (6) slicing a gel, and (7) staining a gel. Recipes are also included for 47 enzyme stains and 3 selected gel buffers. (PDF file contains 26 pages.