NIMBUS SPACECRAFT DEVELOPMENT

Nimbus meteorological satellite system for data on worldwide atmospheric processes - real-time weather forecasting and researc

Chemical Raman Enhancement of Organic Adsorbates on Metal Surfaces

Using a combination of first-principles theory and experiments, we provide a quantitative explanation for chemical contributions to surface-enhanced Raman spectroscopy for a well-studied organic molecule, benzene thiol, chemisorbed on planar Au(111) surfaces. With density functional theory calculations of the static Raman tensor, we demonstrate and quantify a strong mode-dependent modification of benzene thiol Raman spectra by Au substrates. Raman active modes with the largest enhancements result from stronger contributions from Au to their electron-vibron coupling, as quantified through a deformation potential, a well-defined property of each vibrational mode. A straightforward and general analysis is introduced that allows extraction of chemical enhancement from experiments for specific vibrational modes; measured values are in excellent agreement with our calculations.Comment: 5 pages, 4 figures and Supplementary material included as ancillary fil

The apparent roughness of a sand surface blown by wind from an analytical model of saltation

We present an analytical model of aeolian sand transport. The model quantifies the momentum transfer from the wind to the transported sand by providing expressions for the thickness of the saltation layer and the apparent surface roughness. These expressions are derived from basic physical principles and a small number of assumptions. The model further predicts the sand transport rate (mass flux) and the impact threshold (the smallest value of the wind shear velocity at which saltation can be sustained). We show that, in contrast to previous studies, the present model's predictions are in very good agreement with a range of experiments, as well as with numerical simulations of aeolian saltation. Because of its physical basis, we anticipate that our model will find application in studies of aeolian sand transport on both Earth and Mars

Scalloped margin domes: What are the processes responsible and how do they operate?

Studies of scalloped margin domes (SMD) indicate the scallops are the result of slope failure. SMD's have similar but smaller average diameters (26.5 km) to unmodified domes (29.8 km), and the majority plot at altitudes ranging from 0.5-4.7 km, relative to the mean planetary diameter. A range of morphological types exist from those least modified to those that show heavy modification. Of the 200 SMD's examined, 33 have clearly discernible debris aprons. Examination and comparison of debris aprons with mass movement features on the Moon, Mars, and in sub-aerial and submarine environments on Earth using H/L against area (km(sup 2)), suggests there are three main types of failure; debris avalanche, slumps, and debris flow. The five examples representing the morphological range within the SMD's, show the different modified forms and the different types of slope failures that have occurred

Sexual health promotion and contraceptive services in local authorities: a systematic review of economic evaluations 2010-2015

Background Since 2013, health commissioners in England’s local authorities have been responsible for sexual health services, including contraception, HIV testing, STI testing and treatment, health education and specialist sexual health services. Effective commissioning requires information to indicate which interventions may, or may not, be cost-effective. However, current UK guidance and recent research on the cost-effectiveness of sexual health services provides patchy and fragmented evidence. This study aims systematically to review the evidence available on the cost-effectiveness of OECD-based interventions relevant to UK local authority-commissioned sexual health services. Methods Key informants, bibliographic database searches and reference lists of guidance documents and included studies were searched for potentially relevant research. Guided by key stakeholders, we sought economic evaluations of sexual health interventions within the responsibility of local authorities, and focused in the UK, on contraception and on health promotion, published between 2010 and 2015 in English. Eligible studies were full economic evaluations based in an OECD country. Studies were classified using a specifically developed tool and assessed for methodological risk of bias using one of three design-specific assessment tools. Descriptive frequencies of codes were analysed to provide a ‘map’ of research that informed stakeholder discussions to focus the subsequent synthesis. The characteristics of studies, quality ratings and cost outcomes from each included study were extracted into tables and findings summarised narratively. Studies were assessed for their relative cost-saving or cost-effectiveness according to NICE guidance. Results In total, 17,705 references were screened; of these, 29 met our inclusion criteria and were included in the synthesis. Nine studies were undertaken in the UK; the remainder were US based. Fifteen studies examined the economics of contraception and 14 evaluated health promotion. Overall, studies were of medium methodological quality. In general, economic evaluations of contraception reported cost-effectiveness or cost savings for ulipristal acetate (UPA) as emergency contraception, long-acting reversible contraceptives (LARCs) for regular, post-natal and post-abortion contraception, and targeting to high risk groups; none, however, reported costs per quality-adjusted life year (QALY) within NICE thresholds. Economic evaluations of sexual health promotion interventions indicated more mixed results. Only three interventions were found to be cost-effective according to the NICE thresholds for HIV or sexually transmitted infection (STI) outcomes: nurse-led rapid testing and tailored counselling; condom negotiations skills training for female sex workers; and a teacher-led STI prevention and skills training intervention. UK studies focused on health promotion and contraception, and supported the above findings. In general, there has been a reasonable amount of economic research into sexual health interventions since 2010, and these support current NICE sexual health guidance. Abstract Sexual health promotion and contraceptive services in local authorities: a systematic review of economic evaluations 2010-2015 vi Conclusions The broad nature of the research question posed in this systematic review resulted in the inclusion of a dataset very diverse in terms of populations, interventions, outcomes and types of economic evaluation designs. In considering the cost-effectiveness of these strategies in relation to their own commissioning climate, policy and decision makers should consider carefully the fit between their context and that of individual studies. Use of longer-term outcomes in trials used in economic evaluations would strengthen estimates of effects such as QALYs, as would the routine use of longitudinal cohort data

Mode-coupling theory for multiple-time correlation functions of tagged particle densities and dynamical filters designed for glassy systems

The theoretical framework for higher-order correlation functions involving multiple times and multiple points in a classical, many-body system developed by Van Zon and Schofield [Phys. Rev. E 65, 011106 (2002)] is extended here to include tagged particle densities. Such densities have found an intriguing application as proposed measures of dynamical heterogeneities in structural glasses. The theoretical formalism is based upon projection operator techniques which are used to isolate the slow time evolution of dynamical variables by expanding the slowly-evolving component of arbitrary variables in an infinite basis composed of the products of slow variables of the system. The resulting formally exact mode-coupling expressions for multiple-point and multiple-time correlation functions are made tractable by applying the so-called N-ordering method. This theory is used to derive for moderate densities the leading mode coupling expressions for indicators of relaxation type and domain relaxation, which use dynamical filters that lead to multiple-time correlations of a tagged particle density. The mode coupling expressions for higher order correlation functions are also succesfully tested against simulations of a hard sphere fluid at relatively low density.Comment: 15 pages, 2 figure

Synchronization in a System of Globally Coupled Oscillators with Time Delay

We study the synchronization phenomena in a system of globally coupled oscillators with time delay in the coupling. The self-consistency equations for the order parameter are derived, which depend explicitly on the amount of delay. Analysis of these equations reveals that the system in general exhibits discontinuous transitions in addition to the usual continuous transition, between the incoherent state and a multitude of coherent states with different synchronization frequencies. In particular, the phase diagram is obtained on the plane of the coupling strength and the delay time, and ubiquity of multistability as well as suppression of the synchronization frequency is manifested. Numerical simulations are also performed to give consistent results