Quasi-planar InGaAsSb p-B-n photodiodes for spectroscopic sensing.

An InGaAsSb p-B-n structure has been designed and characterized for zero bias low power detection applications. Devices were grown by molecular beam epitaxy and fabricated into quasi-planar photodiodes with a 2.25 µm cut-off wavelength. Maximum responsivity was measured to be 1.05 A/W at 2.0 µm, achieved at zero bias. D* of 9.4 × 1010 Jones was determined from room temperature spectra of noise power measurements with calculated D* remaining >1 × 1010 Jones up to 380 K. With a view to simple miniaturized detection and measurement of low concentration biomarkers, optical powers down to 40 pW were detected, without temperature stabilization or phase-sensitive detection, indicating the photodiode's potential.

I22: SAXS/WAXS beamline at Diamond Light Source - an overview of 10 years operation.

Beamline I22 at Diamond Light Source is dedicated to the study of soft-matter systems from both biological and materials science. The beamline can operate in the range 3.7 keV to 22 keV for transmission SAXS and 14 keV to 20 keV for microfocus SAXS with beam sizes of 240 µm × 60 µm [full width half-maximum (FWHM) horizontal (H) × vertical (V)] at the sample for the main beamline, and approximately 10 µm × 10 µm for the dedicated microfocusing platform. There is a versatile sample platform for accommodating a range of facilities and user-developed sample environments. The high brilliance of the insertion device source on I22 allows structural investigation of materials under extreme environments (for example, fluid flow at high pressures and temperatures). I22 provides reliable access to millisecond data acquisition timescales, essential to understanding kinetic processes such as protein folding or structural evolution in polymers and colloids.

Crossover between liquidlike and gaslike behavior in CH_{4} at 400 K.

We report experimental evidence for a crossover between a liquidlike state and a gaslike state in fluid methane (CH_{4}). This crossover is observed in all of our experiments, up to a temperature of 397 K, 2.1 times the critical temperature of methane. The crossover has been characterized with both Raman spectroscopy and x-ray diffraction in a number of separate experiments, and confirmed to be reversible. We associate this crossover with the Frenkel line-a recently hypothesized crossover in dynamic properties of fluids extending to arbitrarily high pressure and temperature, dividing the phase diagram into separate regions where the fluid possesses liquidlike and gaslike properties. On the liquidlike side the Raman-active vibration increases in frequency linearly as pressure is increased, as expected due to the repulsive interaction between adjacent molecules. On the gaslike side this competes with the attractive van der Waals potential leading the vibration frequency to decrease as pressure is increased.

Mapping socio-economic scenarios of land cover change: a GIS method to enable ecosystem service modelling.

We present a GIS method to interpret qualitatively expressed socio-economic scenarios in quantitative map-based terms. (i) We built scenarios using local stakeholders and experts to define how major land cover classes may change under different sets of drivers; (ii) we formalized these as spatially explicit rules, for example agriculture can only occur on certain soil types; (iii) we created a future land cover map which can then be used to model ecosystem services. We illustrate this for carbon storage in the Eastern Arc Mountains of Tanzania using two scenarios: the first based on sustainable development, the second based on 'business as usual' with continued forest-woodland degradation and poor protection of existing forest reserves. Between 2000 and 2025 4% of carbon stocks were lost under the first scenario compared to a loss of 41% of carbon stocks under the second scenario. Quantifying the impacts of differing future scenarios using the method we document here will be important if payments for ecosystem services are to be used to change policy in order to maintain critical ecosystem services.

RASOR: an advanced instrument for soft x-ray reflectivity and diffraction.

We report the design and construction of a novel soft x-ray diffractometer installed at Diamond Light Source. The beamline endstation RASOR is constructed for general users and designed primarily for the study of single crystal diffraction and thin film reflectivity. The instrument is comprised of a limited three circle (theta, 2theta, and chi) diffractometer with an additional removable rotation (phi) stage. It is equipped with a liquid helium cryostat, and post-scatter polarization analysis. Motorized motions are provided for the precise positioning of the sample onto the diffractometer center of rotation, and for positioning the center of rotation onto the x-ray beam. The functions of the instrument have been tested at Diamond Light Source, and initial test measurements are provided, demonstrating the potential of the instrument.

Linkage disequilibrium between the pseudoautosomal PEPB-1 locus and the sex-determining region of chinook salmon.

Allele frequency differences between sexes and an excess of heterozygotes in males had suggested that the PEPB-1 locus is sex-linked in chinook salmon (Oncorhynchus tshawytscha). We here estimate less than 1% recombination between PEPB-1 and a growth hormone pseudogene known to be in the sex-determining region (SEX) in 374 progeny from eight experimental matings. We present modified maximum likelihood methods for estimating haplotype frequencies from population samples at a sex-linked locus in which functional alleles occur on both the X and Y chromosomes (pseudoautosomal loci). We find nearly complete linkage disequilibrium between PEPB-1 and SEX in 20 population samples from the Puget Sound region of Washington and southern British Columbia. However, allele frequencies at PEPB-1 were similar in males and females in 35 population samples from the coast of Washington and the Columbia River basin. Pseudoautosomal regions have been described in a broad taxonomic array of vertebrates and invertebrates, and they are likely candidate regions to find genes associated with differences in life history, morphology, or behavior between males and females.

Cryptosporidiosis in patients at a large teaching hospital.

In 1984, all stool samples submitted to a microbiology laboratory (n = 2,197) from a predominantly hospital-based population were examined for Cryptosporidium oocysts after Ziehl-Neelsen staining, but only 0.5% were positive. We suggest that in low-incidence areas, individual laboratories examine stool samples for this organism only in immunosuppressed patients and those in whom symptoms persist.

The isolation of Moellerella wisconsensis from stool samples in the U.K.

Three strains of Moellerella wisconsensis were isolated from a total of 400 stool specimens screened for this organism by means of a new selective medium developed in this laboratory. This is the first report of the isolation of this organism in the U.K. The exact role of M. wisconsensis in causing diarrhoea remains to be elucidated.

An anti-curare effect of hexamethonium at the mammalian neuromuscular junction.

1. Experiments were performed on the isolated phrenic nerve and diaphragm preparation of the rat.2. In preparations partly blocked with (+)-tubocurarine, the twitch amplitude increased after hexamethonium. This enhancement was not seen in preparations partly blocked with Mg(++) or with gallamine. High concentrations of hexamethonium produced failure of contraction.3. Extracellular endplate potentials were recorded from blocked preparations. The administration of hexamethonium resulted in an increased amplitude of these potentials only in curarized muscle.4. Hexamethonium had no anticholinesterase activity nor did it depolarize muscle cells or increase the quantal release of transmitter.5. It is concluded that hexamethonium exerts a specific anti-curare action. Experiments on the recovery of the twitch after washing out antagonists indicate that this process is limited by diffusion. The difference in rates of diffusion of hexamethonium and (+)-tubocurarine does not account for their interaction. The basis of the anti-curare action of hexamethonium is discussed.