Limited sensitivity analysis of ARAIM availability for LPV-200 over Australia using real data

Current availability of Advanced Receiver Autonomous Integrity Monitoring (ARAIM) for LPV-200 in aviation is experimentally investigated using real navigation data and GPS measurements collected at 60 stations across Australia. ARAIM algorithm and fault probabilities were first discussed. Availability sensitivity analysis due to changes in the elevation mask angle and the error model parameters URA, URE, and nominal biases for integrity and accuracy used for computation of the protection level is presented. It is shown that incorporation of other GNSS constellation with GPS in ARAIM is needed to achieve LPV-200 Australia wide. The inclusion of BeiDou with GPS at two tests sites in Western and Eastern Australia demonstrates the promising potential of achieving this goal

The Raman optical activity of β-D-xylose: where experiment and theory meet

Besides its applications in bioenergy and biosynthesis, β-D-xylose is a very simple monosaccharide that exhibits relatively high rigidity. As such, it provides the best basis to study the impact of different solvation shell radii on the computation of its Raman optical activity (ROA) spectrum. Indeed, this chiroptical spectroscopic technique provides exquisite sensitivity to stereochemistry, and benefits much from theoretical support for interpretation. Our simulation approach combines density functional theory (DFT) and molecular dynamics (MD) in order to efficiently account for the crucial hydration effects in the simulation of carbohydrates and their spectroscopic response predictions. Excellent agreement between the simulated spectrum and the experiment was obtained with a solvation radius of 10 Å. Vibrational bands have been resolved from the computed ROA data, and compared with previous results on different monosaccharides in order to identify specific structure–spectrum relationships and to investigate the effect of the solvation environment on the conformational dynamics of small sugars. From the comparison with ROA analytical results, a shortcoming of the classical force field used for the MD simulations has been identified and overcome, again highlighting the complementary role of experiment and theory in the structural characterisation of complex biomolecules. Indeed, due to unphysical puckering, a spurious ring conformation initially led to erroneous conformer ratios, which are used as weights for the averaging of the spectral average, and only by removing this contribution was near perfect comparison between theory and experiment achieved

Distinguishing epimers through raman optical activity

The Raman optical activity spectra of the epimers β-d-glucose and β-d-galactose, two monosaccharides of biological importance, have been calculated using molecular dynamics combined with a quantum mechanics/molecular mechanics approach. Good agreement between theoretical and experimental spectra is observed for both monosaccharides. Full band assignments have been carried out, which has not previously been possible for carbohydrate epimers. For the regions where the spectral features are opposite in sign, the differences in the vibrational modes have been noted and ascribed to the band sign changes

Estudio transversal sobre conductas sexuales asociadas a la transmisión del VIH entre hombres homosexuales de Cataluña

ResumenEn 1993, se realizó un estudio transversal sobre los comportamientos sexuales de una muestra de hombres homosexuales reclutados en saunas, sex-shops y una organización comunitaria de base gay de Cataluña. Un total de 551 hombres de 34 años de edad media y alto nivel educativo devolvieron por correo un cuestionario anónimo. En los últimos seis meses, la mediana de parejas sexuales masculinas fue de seis y la de parejas con penetración de tres. En el último mes, el 94% habían realizado sexo oro-genital (22% con eyaculación) y el 76% sexo ano-genital (38% sin preservativo y 21% con eyaculación). El 51 % declaraba consumir alcohol durante las relaciones sexuales; el 34%, nitritos inhalados; el 20%, haschis y el 10%, cocaína. El 61% se había realizado la prueba de detección de anticuerpos anti-VIH, notificando una prevalencia de infección del 21 %. El 86% declaró conocer alguna persona infectada por el VIH o con SIDA. El alto porcentaje de hombres que practican el sexo ano-genital sin preservativo y la alta seroprevalencia auto-declarada de infección por VIH ponen de manifiesto la necesidad de aumentar los esfuerzos de prevención y la investigación en este colectivo. La monitorización de conductas relacionadas con la transmisión del VIH proporciona indicadores de utilidad, para el seguimiento de la evolución de la epidemia y para el diseño y evaluación de las intervenciones preventivas.SummaryIn 1993, a cross sectional study was carried out on the sexual behaviour of a sample of homosexual men recruited in saunas, sex shops and a gay community-beased organisation of Catalonia. A total of 551 men with an average age of 34 years and a high educational level sent in an anonymous questionnaire. In the previous 6 months the mean number of male sexual partners was 6 and for penetrative partners 3. In the previous month, 94% had had oral sex (22% with ejaculation) and 76% anal intercourse (38% without a condom and 21% with ejaculation). During sex, 51% used alcohol, 34% nitrite inhalants, 20% hashish and 10% cocaine. 61% had had the HIV test, with a self-reported HIV prevalence of 21%. 86% stated that they knew of one or more people infected by HIV or with AIDS. The high percentage of men who had unprotected anal intercourse and the high self-reported HIV prevalence highlights the need to increase efforts in AIDS prevention and research in this group. Monitoring HIV associated sexual behaviours provides valuable indicators of the evolution of the epidemic, useful for designing and evaluating preventive interventions

MULTI OPTICAL TRANSITION RADIATION SYSTEM FOR ATF2 ∗

In this paper we describe the design, installation and first calibration tests of a Multi Optical Transition Radiation System in the beam diagnostic section of the Extraction (EXT) line of ATF2, close to the multi wire scanner system. This system will be a valuable tool for measuring beam sizes and emittances coming from the ATF Damping Ring. With an optical resolution of about 2μm an original OTR design (OTR1X) located after the septum at the entrance of the EXT line demonstrated the ability to measure a5.5μm beam size in one beam pulse and to take many fast measurements. This gives the OTR the ability to measure the beam emittance with high statistics, giving a low error and a good understanding of emittance jitter. Furthermore the nearby wire scanners will be a definitive test of the OTR as a beam emittance diagnostic device. The multi-OTR system design proposed here is based on the existing OTR1X

Solution structure of Mannobioses unravelled by means of Raman optical activity

Structural analysis of carbohydrates is a complicated endeavour, due to the complexity and diversity of the samples at hand. Herein, we apply a combined computational and experimental approach, employing molecular dynamics (MD) and density functional theory (DFT) calculations together with NMR and Raman optical activity (ROA) measurements, in the structural study of three mannobiose disaccharides, consisting of two mannoses with varying glycosidic linkages. The disaccharide structures make up the scaffold of high mannose glycans and are therefore important targets for structural analysis. Based on the MD population analysis and NMR, the major conformers of each mannobiose were identified and used as input for DFT analysis. By systematically varying the solvent models used to describe water interacting with the molecules and applying overlap integral analysis to the resulting calculational ROA spectra, we found that a full quantum mechanical/molecular mechanical approach is required for an optimal calculation of the ROA parameters. Subsequent normal mode analysis of the predicted vibrational modes was attempted in order to identify possible marker bands for glycosidic linkages. However, the normal mode vibrations of the mannobioses are completely delocalised, presumably due to conformational flexibility in these compounds, rendering the identification of isolated marker bands unfeasible