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Oldowan sites in primary geological context are rare in the archaeological record. Here we describe the depositional environment of Oldowan occurrences at Kanjera South, Kenya, based on field descriptions and granulometric analysis. Excavations have recovered a large Oldowan artefact sample as well as the oldest substantial sample of archaeological fauna. The deposits at Kanjera South consist of 30 m of fluvial, colluvial and lacustrine sediments. Magneto- and biostratigraphy indicate the Kanjera South Member of the Kanjera Formation was deposited during 2.3–1.92 Ma, with 2.0 Ma being a likely age for the archaeological occurrences. Oldowan artefacts and associated fauna were deposited in the colluvial and alluvial silts and sands of beds KS1–3, in the margins of a lake basin. Field descriptions and granulometric analysis of the sediment fine fraction indicate that sediments from within the main archaeological horizon were emplaced as a combination of tractional and hyperconcentrated flows with limited evidence of debris-flow deposition. This style of deposition is unlikely to significantly erode or disturb the underlying surface, and therefore promotes preservation of surface archaeological accumulations. Hominins were repeatedly attracted to the site locale, and rapid sedimentation, minimal bone weathering and an absence of bone or artefact rounding further indicate that fossils and artefacts were quickly buried.
The poultry meat industry, in continual pursuit of improved efficiency, has demanded rapid growth rate. Primary breeding companies have responded to industry pressure and growth rate has increased in an almost linear fashion. Despite the obvious advantages to industry profitability, it can be argued that increased growth has placed more emphasis on the demand tissues of growth than those systems or organs that supply the substrates for rapid growth and/or are essential to support the increase in body mass. One of the consequences is that modern broilers are not as adaptable to their environments as their predecessors were. Rapid growth has also produced problems not seen in slower growing birds. Skeletal and cardiovascular disease (sudden death syndrome (SDS), ascites) are examples of growth related problems. Although it can not be said that rapid growth automatically will result in these problems, there is no doubt that the!re is a relationship.
The most important element in consumer enjoyment of meat is tenderness, closely followed by flavour, with variation in these traits having a significant impact on consumer satisfaction (Casas et al. 2006). In order to forge improvements in these traits, either through quantitative breeding or molecular genetics, it is essential that there is a reliable method of trait testing. Sensory data, as collected using a taste panel, are subject to high measurement error as well as problems associated with subjectivity. Unfortunately these sensory panels are a necessary step in the improvement of the above mentioned beef traits, as no machine can measure the range of interacting characteristics that contribute to eating quality and palatability (Warriss 2000). This study aimed to test the repeatability and reproducibility values for seven sensory beef traits assessed by a taste panel operating in a commercial setting.
A QTL (TM-QTL) identified on ovine chromosome 18 (Walling et al., 2004), which increases loin muscle depth by 4-8% in UK Texel sheep, is of interest for the sheep industry as a potential means to increase carcass value. Since the contribution of Texel genes to the UK slaughter generation is generally through use of Texel sires to produce crossbred slaughter lambs (e.g. Texel x Mule lambs), it is necessary to verify the effects of the TM-QTL on loin muscularity and other carcass traits in such crossbred progeny of Texel sires before explotiation of the TM-QTL in commercial sheep populations.
The recent dynamic behaviour of Karakoram glaciers is expected to differ from that shown by glaciers in the central and eastern Himalaya because of regional variations in precipitation and temperature trends. However, there are insufficient quantitative data to support or confute such hypotheses. We present velocity data covering the period 1993–2008 for Baltoro Glacier, one of the longest glaciers in the Karakoram. Velocity measurements were made using cross-correlation feature tracking applied to European Remote-sensing Satellite (ERS-1 and -2) and Envisat advanced synthetic aperture radar (ASAR) data, supplemented by differential global positioning system (DGPS) measurements. We find a gradual acceleration of the glacier during the early 2000s, in particular during winter months. Multi-seasonal data reveal a large difference between summer and winter flow characteristics, but only in the upper ablation zone. Summer 2005 was a particularly dynamic period following from the heavy winter snowfall of 2004, indicating the importance of basal meltwater availability for glacier flow. Transverse velocity profiles indicate that Baltoro Glacier undergoes ‘block’ flow across much of the upper ablation zone during the summer, which we interpret as evidence of widespread basal sliding. The DGPS data confirm the rapid increase in flow detected during 2005. Modelled climatic data reveal decreasing summer temperatures and increasing precipitation over the study period, helping to explain the observed dynamic variations and their differences from glaciers elsewhere in the Himalaya.
The incidence of recreational water-associated outbreaks in the United States has significantly increased, driven, at least in part, by outbreaks both caused by Cryptosporidium and associated with treated recreational water venues. Because of the parasite's extreme chlorine tolerance, transmission can occur even in well-maintained treated recreational water venues (e.g. pools) and a focal cryptosporidiosis outbreak can evolve into a community-wide outbreak associated with multiple recreational water venues and settings (e.g. childcare facilities). In August 2004 in Auglaize County, Ohio, multiple cryptosporidiosis cases were identified and anecdotally linked to pool A. Within 5 days of the first case being reported, pool A was hyperchlorinated to achieve 99·9% Cryptosporidium inactivition. A case-control study was launched to epidemiologically ascertain the outbreak source 11 days later. A total of 150 confirmed and probable cases were identified; the temporal distribution of illness onset was peaked, indicating a point-source exposure. Cryptosporidiosis was significantly associated with swimming in pool A (matched odds ratio 121·7, 95% confidence interval 27·4–∞) but not with another venue or setting. The findings of this investigation suggest that proactive implementation of control measures, when increased Cryptosporidium transmission is detected but before an outbreak source is epidemiologically ascertained, might prevent a focal cryptosporidiosis outbreak from evolving into a community-wide outbreak.
TM-QTL is a quantitative trait locus (QTL) on ovine chromosome 18 (OAR18) known to affect loin muscling in Texel sheep. Previous work suggested that its mode of inheritance is consistent with paternal polar overdominance, but this has yet to be formally demonstrated. This study used purebred Texel sheep segregating for TM-QTL to confirm its presence in the chromosomal region in which it was first reported and to determine its pattern of inheritance. To do so, this study used the first available data from a Texel flock, which included homozygote TM-QTL carriers (TM/TM; n=34) in addition to homozygote non-carriers (+/+; n=40 and, heterozygote TM-QTL-carriers inheriting TM-QTL from their sire (TM/+; n=53) or their dam (+/TM; n=17). Phenotypes included a wide range of loin muscling, carcass composition and tissue distribution traits. The presence of a QTL affecting ultrasound muscle depth on OAR18 was confirmed with a paternal QTL effect ranging from +0.54 to +2.82 mm UMD (s.e. 0.37 to 0.57 mm) across the sires segregating for TM-QTL. Loin muscle width, depth and area, loin muscle volume and dissected M. longissimus lumborum weight were significantly greater for TM/+ than +/+ lambs (+2.9% to +7.9%; P<0.05). There was significant evidence that the effect of TM-QTL on the various loin muscling traits measured was paternally polar overdominant (P<0.05). In contrast, there was an additive effect of TM-QTL on both live weight at 20 weeks and carcass weight; TM/TM animals were significantly (P<0.05) heavier than +/+ (+11.1% and +7.3%, respectively) and +/TM animals (+11.9% and +11.7%, respectively), with TM/+ intermediate. Weights of the leg, saddle and shoulder region (corrected for carcass weight) were similar in the genotypic groups. There was a tendency for lambs inheriting TM-QTL from their sire to be less fat with slightly more muscle than non-carriers. For example, carcass muscle weight measured by live animal CT-scanning was 2.8% higher in TM/TM than +/+ lambs (P<0.05), carcass muscle weight measured by carcass CT-scanning was 1.36% higher in TM/+ than +/+ lambs (P<0.05), and weight of fat trimmed from the carcass cuts was significantly lower for TM/+ than +/+ lambs (−11.2%; P<0.05). No negative effects of TM-QTL on carcass traits were found. Optimal commercial use of TM-QTL within the sheep industry would require some consideration, due to the apparently different mode of action of the two main effects of TM-QTL (on growth and muscling).
In August 2008 an outbreak of Salmonella Typhimurium DT104 occurred in South West London. Sixteen cases were identified with a particular multilocus variable number tandem repeat analysis (MLVA) pattern. In a matched case-control study 14 primary cases were included. These were defined as individuals with gastrointestinal symptoms and Salmonella Typhimurium DT104 isolated from a stool specimen, with a characteristic antibiotic resistance profile and MLVA pattern, and diagnosed in a local laboratory. Four controls per case were matched on age, gender and area of residence. Cases were 26 times more likely than controls to have eaten beef biltong, a South African speciality meat product (odds ratio 25·83, 95% confidence interval 4·92–135·59, P < 0·01). Although environmental investigation failed to identify Salmonella in the food product we conclude that beef biltong consumption led to this outbreak. This conclusion has importance in informing the ongoing risk assessment relating to uncontrolled foodstuffs.
Genetic resistance to gastrointestinal worms is a complex trait of great importance in both livestock and humans. In order to gain insights into the genetic architecture of this trait, a mixed breed population of sheep was artificially infected with Trichostrongylus colubriformis (n=3326) and then Haemonchus contortus (n=2669) to measure faecal worm egg count (WEC). The population was genotyped with the Illumina OvineSNP50 BeadChip and 48 640 single nucleotide polymorphism (SNP) markers passed the quality controls. An independent population of 316 sires of mixed breeds with accurate estimated breeding values for WEC were genotyped for the same SNP to assess the results obtained from the first population. We used principal components from the genomic relationship matrix among genotyped individuals to account for population stratification, and a novel approach to directly account for the sampling error associated with each SNP marker regression. The largest marker effects were estimated to explain an average of 0·48% (T. colubriformis) or 0·08% (H. contortus) of the phenotypic variance in WEC. These effects are small but consistent with results from other complex traits. We also demonstrated that methods which use all markers simultaneously can successfully predict genetic merit for resistance to worms, despite the small effects of individual markers. Correlations of genomic predictions with breeding values of the industry sires reached a maximum of 0·32. We estimate that effective across-breed predictions of genetic merit with multi-breed populations will require an average marker spacing of approximately 10 kbp.
Homoepitaxial films of 4H-SiC(1120) and 8° off-axis 4H-SiC(0001) have been grown and characterized. The number of domains and the range of full-width half-maxima values of the x-ray rocking curves of the -oriented wafers were smaller than the analogous values acquired from the (0001) materials. Hydrogen etching of the former surface for 5 and 30 minutes reduced the RMS roughness from 0.52 nm to 0.48 nm and to 0.28 nm, respectively; the RMS roughness for a 30 μm (1120) film was 0.52 nm. Micropipes in the substrates did not thread beyond the film-substrate interface. The separation distance between stacking faults was determined to be 10 μm by transmission electron microscopy. Hall mobilities and carrier concentrations of 12,200 cm2/Vs and 3.1×1014 cm−3 and 800 cm2/Vs and 7.4×1014 cm−3 were measured at 100°K and 300°K, respectively. Photoluminescence indicated high purity. 4H-SiC(1120) PiN devices exhibited average blocking voltages to 1344 V and a minimum average forward voltage drop of 3.94 V.
We have investigated the effect of stress upon the infrared absorption spectrum of the neutral charge state of the oxygen donor in silicon. Our results show that the central cell of the donor has C2ν, symmetry and that this anisotropy gives rise to a ground state wave function that is constructed from a single pair of conduction band valleys.
The silicon “dangling bond” defect plays a large part in controlling the electronic properties of a-Si, polycrystalline silicon, and the Si/Si0 2 interface. Jackson et al. have suggested that transitions of electrons occupying this defect produce the Urbach-like sub-gap absorption tail seen in two of these materials. We have performed optical and electron spin resonance measurements on polycrystalline silicon, plastically deformed silicon, and Si/Si02 interfaces to further examine this contention. In addition to seeing no measurable absorptance due to dangling bond interface states in the latter system, we conclude from the poor correlation of ESR signals with optical data that the Urbach tail in polycrystalline and deformed silicon is not due to transitions of dangling bond electrons.
The application of transient junction current and capacitance techniques to the study of imperfection in semiconductor materials is reviewed. An array of perturbation techniques are described which allow direct determination of electronic and atomic structure, as well as electrical and physical properties. The methods are illustrated with silicon materials studies of the divacancy using Polarized Excitation Photocapacitance, the oxygen donor using Stress and Electric Field Modulated DLTS, dislocations using spatially resolved DLTS, and iron impurities employing Charge State Control of Structure.
The role of the luminescence killer center iron in GaP has been studied by the optically detected magnetic resonance technique. Observations of strong Fe°(3d5) and O0 resonance in the (Zn,O) donor-acceptor pair (DAP) and the 0.841 eV electron capture (EC) luminescence bands show that the luminescence killing action is via (Fe,O) DAP recombination.
Two distinct but similar (Fe,O) DAP processes were detected: The (Fe0,O0) process with a slower recombination rate and (Fe0,O0*) process, with a faster effective relaxation rate, involving the oxygen excited state.
The high resolution Bitter Pattern technique has been used to reveal the structure of the array of flux lines which is present when single crystal samples of the high Tc superconductor YBa2Cu3O7 are placed in a magnetic field. At 4.2K with the magnetic field parallel to the c axis, the patterns formed are strongly reminiscent of the analogous structures in ordinary type II superconductors. The structures typically consist of flux spots with short range hexagonal correlations. We interpret the patterns to consist of singly quantized vortices. Very uniform patterns are observed in thin, flat samples cooled in a constant field. Sampling the spot density yields a vortex density consistent with a flux quantum of hc/2e.
Experiments at 77K, the only other temperature studied, showed no spatially varying magnetic structure. Recent mechanical measurements which are sensitive to the bulk modulus and dissipation within the vortex lattice show evidence for a mobility transition near 75K, which would be consistent with this observation. We believe this stems from materials properties rather than some more fundamental property of the new superconductors.
The properties of SiO2 and Si3 N4 films deposited by an ArF excimer laser, glow discharge electron beam and conventional plasma-enhanced CVD are compared. The deposition apparatus, technique, and conditions in addition to the physical, chemical and electrical properties of the films are discussed.
Both concentrated and dilute simulated solutions of saturated J13 and unsaturated UZ pore water were concentrated through distillation of the solutions under atmospheric pressure. It was observed that condensed vapors from the pH of J13 waters steadily rose during the distillations to a value of 10, while the pH of UZ waters remained steady until 90% of the volume of the solution had been distilled, after which the pH of the condensed vapors dropped precipitously, often below 1. Residual solutions analyzed when most of the solution had been distilled away were also found to be extremely acidic. The temperature of these residual solutions was around 144°C due to their high solute content causing boiling point elevation. All experiments were performed with the condenser open to ambient air at atmospheric pressure. The pH drop during the distillation of UZ water is attributed largely to the presence of large amounts of magnesium. Specimens of Alloy 22 tested in the residual solutions of at their boiling temperature (around 144°C) showed significant rates of general corrosion over a broad range, often approaching 1 mm/year. Similarly high corrosion rates were also observed in tests on Alloy 22 specimens in condensates obtained during the late stages of the distillation. These tests were performed either in situ at 75–80°C using a Soxhlet extractor, or in separate pressure vessels at temperatures between 90 and 130°C.
A monolithic quantum well infrared photodetector (QWIP) structure has been presented that is suitable for dual bands in the two atmospheric transmission windows of 3 – 5.3 μm and 7.5 – 14μm, respectively. The proposed structure employs dual stacked, strain InGaAs/AlGaAs and latticematched GaAs/AlGaAs quantum well infrared photodetector for mid wavelength and long wavelength detection. The response peak of the strain InGaAs/AlGaAs quantum well is at 4.9 μm and the lattice-matched GaAs/AlGaAs is at 10.5μm; their peak sensitivities are in the spectral regions of 3 – 5.3mu;m and 7.5 – 14μm. The peak responsivity when the dual-band QWIP is biased at 5 Volts is ∼0.065A/W at 4.9μm and ∼0.006A/W at 10.5μm; at this voltage the dual-band QWIP is more sensitive at the shorter wavelengths due to its larger impedance thus exhibiting wavelength tunability characteristics with bias. Additionally, single colored 4.9 and 10.5μm QWIPs were fabricated from the dual-band QWIP structure to study the bias-dependent behavior and also to understand the effects of growing the strain layer InGaAs/AlGaAs QWIP on top of the lattice-matched GaAs/AlGaAs QWIP. In summary, two stack dual-band QWIPs using GaAs/AlGaAs and strained InGaAs/AlGaAs multiquantum wells have been demonstrated with peak spectral sensitivities in the spectral region of 3 – 5.3μm and 7.5 – 14μm. Also, the voltage tunable dual-band detection have been realized for this kind of QWIP structure.
P-type InGaAs/InP quantum-well infrared photodetectors operated at 4.55 μm require the growth of ultra-thin (10 Å) quantum wells. We report a study of interfaces in QWIPs grown by gas-source molecular beam epitaxy in which we optimized the group V source supply sequence so that a 6 K photoluminescence linewidth as narrow as 8.4 meV was observed from a structure with 10 Å wells. Analysis of the PL suggests that interface roughness was minimized. Cross-sectional scanning tunneling microscopy, double crystal x-ray diffraction, and cross-sectional tunneling electron microscopy confirmed that high-quality interfaces and uniform layers were obtained. Using the derived structural parameters, photocurrent spectral response was theoretically predicted for these QWIPs and then experimentally verified.