Analogies and differences in optical and mathematical systems and approaches

Publication in the conference proceedings of SampTA, Bremen, Germany, 201

A methodology to compute GPS slant total delays in a numerical weather model

A numerical algorithm based on Fermat's Principle was developed to simulate the propagation of Global Positioning System (GPS) radio signals in the refractivity field of a numerical weather model. The unique in the proposed algorithm is that the ray-trajectory automatically involves the location of the ground-based receiver and the satellite, i.e. the posed two-point boundary value problem is solved by an implicit finite difference scheme. This feature of the algorithm allows the fast and accurate computation of the signal travel-time delay, referred to as Slant Total Delay (STD), between a satellite and a ground-based receiver. We provide a technical description of the algorithm and estimate the uncertainty of STDs due to simplifying assumptions in the algorithm and due to the uncertainty of the refractivity field. In a first application, we compare STDs retrieved from GPS phase-observations at the German Research Centre for Geosciences Potsdam (GFZ STDs) with STDs derived from the European Center for Medium-Range Weather Forecasts analyses (ECMWF STDs). The statistical comparison for one month (August 2007) for a large and continuously operating network of ground-based receivers in Germany indicates good agreement between GFZ STDs and ECMWF STDs; the standard deviation is 0.5% and the mean deviation is 0.1%

Phase-resolved HST/STIS spectroscopy of the exposed white dwarf in the high-field polar AR UMa

Phase-resolved HST/STIS ultraviolet spectroscopy of the high-field polar AR UMa confirms that the WD photospheric Ly alpha Zeeman features are formed in a magnetic field of ~200 MG. In addition to the Ly alpha pi and sigma+ components, we detect the forbidden hydrogen 1s0->2s0 transition, which becomes ``enabled'' in the presence of both strong magnetic and electric fields. Our attempt in fitting the overall optical+UV low state spectrum with single temperature magnetic WD models remains rather unsatisfactory, indicating either a shortcoming in the present models or a new physical process acting in AR UMa. As a result, our estimate of the WD temperature remains somewhat uncertain, Twd=20000+-5000K. We detect a broad emission bump centered at ~1445A and present throughout the entire binary orbit, and a second bump near ~1650A, which appears only near the inferior conjunction of the secondary star. These are suggestive of low harmonic cyclotron emission produced by low-level (M-dot~1e-13 Msun/yr) accretion onto both magnetic poles. However, there is no evidence in the power spectrum of light variations for accretion in gas blobs. The observed Ly alpha emission line shows a strong phase dependence with maximum flux and redshift near orbital phase phi~0.3, strongly indicating an origin on the trailing hemisphere of the secondary star. An additional Ly alpha absorption feature with similar phasing as the Ly alpha emission, but a \~700km/s blueshift could tentatively be ascribed to absorption of WD emission in a moderately fast wind. We derive a column density of neutral hydrogen of NH=(1.1+-1.0)1e18 cm**-2, the lowest of any known polar.Comment: 26 pages, 10 figures, AAS TeX 5.0, accepted for publication in the Astrophysical Journa

Taxation of unprocessed sugar or sugar-added foods for reducing their consumption and preventing obesity or other adverse health outcomes:protocol

To assess the effects of taxation of unprocessed sugar or sugar-added foods in the general population on the: consumption of unprocessed sugar or sugar-added foods; prevalence and incidence of overweight and obesity; and prevalence and incidence of diet-related health conditions

Taxation of the fat content of foods for reducing their consumption and preventing obesity or other adverse health outcomes

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows: To assess the effects of taxation of fat content in food on consumption of total fat and saturated fat, energy intake, overweight, obesity, and other adverse health outcomes in the general population

Исследование актуальных проблем социальной политики России и меры повышения ее эффективности

Рассмотрена сущность социальной политики России и направления ее деятельности. Указаны основные общественные проблемы, стоящие перед государством, а также недостатки механизма функционирования социальной политики. На основании анализа полученной информации были разработаны меры, позволяющие значительно снизить уровень той или иной проблемы социальной политики. Кроме того, разработаны рекомендации по улучшению эффективности проведения социальных программ в России, путем устранения внутренних проблем самого механизма регулирования

Searching two or more databases decreased the risk of missing relevant studies: a metaresearch study

BACKGROUND AND OBJECTIVES: Assessing changes in coverage, recall, review, conclusions and references not found when searching fewer databases. METHODS: In randomly selected 60 Cochrane reviews, we checked included study publications' coverage (indexation) and recall (findability) using different search approaches with MEDLINE, Embase, and CENTRAL and related them to authors' conclusions and certainty. We assessed characteristics of unfound references. RESULTS: Overall 1989/2080 included references, were indexed in ≥1 database (coverage = 96%). In reviews where using one of our search approaches would not change conclusions and certainty (n = 44-54), median coverage and recall were highest (range 87.9%-100.0% and 78.2%-93.3%, respectively). Here, searching ≥2 databases reached >95% coverage and ≥87.9% recall. In reviews with unchanged conclusions but less certainty (n = 2-8): 63.3%-79.3% coverage and 45.0%-75.0% recall. In reviews with opposite conclusions (n = 1-3): 63.3%-96.6% and 52.1%-78.7%. In reviews where a conclusion was no longer possible (n = 3-7): 60.6%-86.0% and 20.0%-53.8%. The 265 references that were indexed but unfound were more often abstractless (30% vs. 11%) and older (28% vs. 17% published before 1991) than found references. CONCLUSION: Searching ≥2 databases improves coverage and recall and decreases the risk of missing eligible studies. If researchers suspect that relevant articles are difficult to find, supplementary search methods should be used