851 research outputs found
Bayesian evidence for two companions orbiting HIP 5158
We present results of a Bayesian analysis of radial velocity (RV) data for
the star HIP 5158, confirming the presence of two companions and also
constraining their orbital parameters. Assuming Keplerian orbits, the
two-companion model is found to be e^{48} times more probable than the
one-planet model, although the orbital parameters of the second companion are
only weakly constrained. The derived orbital periods are 345.6 +/- 2.0 d and
9017.8 +/- 3180.7 d respectively, and the corresponding eccentricities are 0.54
+/- 0.04 and 0.14 +/- 0.10. The limits on planetary mass (m \sin i) and
semimajor axis are (1.44 +/- 0.14 M_{J}, 0.89 +/- 0.01 AU) and (15.04 +/- 10.55
M_{J}, 7.70 +/- 1.88 AU) respectively. Owing to large uncertainty on the mass
of the second companion, we are unable to determine whether it is a planet or a
brown dwarf. The remaining `noise' (stellar jitter) unaccounted for by the
model is 2.28 +/- 0.31 m/s. We also analysed a three-companion model, but found
it to be e^{8} times less probable than the two-companion model.Comment: 5 pages, 4 figures, 3 tables. Added a couple of figures showing the
residuals after one and two companion fits. Accepted for publication in MNRAS
Letter
Detecting extrasolar planets from stellar radial velocities using Bayesian evidence
Stellar radial velocity (RV) measurements have proven to be a very successful
method for detecting extrasolar planets. Analysing RV data to determine the
parameters of the extrasolar planets is a significant statistical challenge
owing to the presence of multiple planets and various degeneracies between
orbital parameters. Determining the number of planets favoured by the observed
data is an even more difficult task. Bayesian model selection provides a
mathematically rigorous solution to this problem by calculating marginal
posterior probabilities of models with different number of planets, but the use
of this method in extrasolar planetary searches has been hampered by the
computational cost of the evaluating Bayesian evidence. Nonetheless, Bayesian
model selection has the potential to improve the interpretation of existing
observational data and possibly detect yet undiscovered planets. We present a
new and efficient Bayesian method for determining the number of extrasolar
planets, as well as for inferring their orbital parameters, without having to
calculate directly the Bayesian evidence for models containing a large number
of planets. Instead, we work iteratively and at each iteration obtain a
conservative lower limit on the odds ratio for the inclusion of an additional
planet into the model. We apply this method to simulated data-sets containing
one and two planets and successfully recover the correct number of planets and
reliable constraints on the orbital parameters. We also apply our method to RV
measurements of HD 37124, 47 Ursae Majoris and HD 10180. For HD 37124, we
confirm that the current data strongly favour a three-planet system. We find
strong evidence for the presence of a fourth planet in 47 Ursae Majoris, but
its orbital period is suspiciously close to one year, casting doubt on its
validity. For HD 10180 we find strong evidence for a six-planet system.Comment: 12 pages, 6 figures, 12 tables. Added results obtained by applying
the method to 47 Ursae Majoris and HD 10180. Accepted for publication in
MNRA
Large scale distribution of total mass versus luminous matter from Baryon Acoustic Oscillations: First search in the SDSS-III BOSS Data Release 10
Baryon Acoustic Oscillations (BAOs) in the early Universe are predicted to
leave an as yet undetected signature on the relative clustering of total mass
versus luminous matter. A detection of this effect would provide an important
confirmation of the standard cosmological paradigm and constrain alternatives
to dark matter as well as non-standard fluctuations such as Compensated
Isocurvature Perturbations (CIPs). We conduct the first observational search
for this effect, by comparing the number-weighted and luminosity-weighted
correlation functions, using the SDSS-III BOSS Data Release 10 CMASS sample.
When including CIPs in our model, we formally obtain evidence at of
the relative clustering signature and a limit that matches the existing upper
limits on the amplitude of CIPs. However, various tests suggest that these
results are not yet robust, perhaps due to systematic biases in the data. The
method developed in this Letter, used with more accurate future data such as
that from DESI, is likely to confirm or disprove our preliminary evidence.Comment: 6 pages, 2 figures, accepted for publication in PR
Asymptomatic bacteriuria among antenatal women attending a tertiary care hospital in Kanchipuram: evaluation of screening tests and antibiotic susceptibility pattern
Background: Asymptomatic bacteriuria (ASB) occurring in pregnant women can lead onto complications like acute pyelonephritis, hypertensive disease of pregnancy, premature delivery and intrauterine growth retardation if untreated.Methods: The present study aims to estimate the occurrence of asymptomatic bacteriuria in antenatal women and to study the antibiotic susceptibility pattern of the isolates. The Gram staining, pus cell count and culture was performed for 120 urine samples. Antibiotic susceptibility testing was done by Kirby Baeur disk diffusion method. MRSA (Methicillin resistant Staphylococcus aureus) and ESBL (Extended spectrum Beta Lactamases) producers were identified by Standard guidelines. The sensitivity, specificity, negative predictive values and positive predictive values of Gram staining and pus cell count was calculated.Results: Out of the 120 samples 14 (11.66%) were positive for asymptomatic bacteriuria. The Gram staining showed specificity and negative predictive value of 95.2% and 98.1% respectively. Pus cell count showed a specificity and negative predictive value of 96.29% and 98.11% respectively. Escherichia coli were the predominant species isolated 5 (35.7%). Among the gram negative bacteria, amikacin and nitrofurantoin showed a susceptibility of 90% and 80% each. All the staphylococcus aureus isolates showed 100% sensitivity for nitrofurantoin. Two Klebsiella spp and one Escherichia coli isolate were identified as ESBL producers. Among the S. aureus isolates 3 were identified as Methicillin resistant (MRSA).Conclusions: Urine culture should be performed for all pregnant women irrespective of the symptoms and should be treated promptly to prevent the complications arising out of ASB.
Accelerated Short-Term Techniques to Evaluate Corrosion in TiC Reinforced AA6063 Composites
AA6063-TiC composites have several weight percentages up to 9 wt. % were fabricated by using stir casting route method. The effects of the weight percentage of TiC particles on the microstructures and corrosion behavior of AA6063-TiC composites were studied. The results revealed that the AA6063-TiC composites exhibited higher density than the AA6063 matrix. The accelerated corrosion tests of AA6063-TiC composites in 3.5 wt. % NaCl aqueous solution at room temperature, the AA6063-TiC composites have better corrosion resistance than the AA6063 matrix. Increasing the weight percentage of the TiC particles to reduces the corrosion rate of the AA6063-TiC composites. In this process corrosion rate of 0.4402 mm/year for AA6063 matrix, 0.3891 mm/year for 3 wt. % , 0.3568 mm/year for 6 wt. % and 0.3062 mm/year for 9 wt. % of TiC particles respectively. The poor corrosion resistance of the composites can be attributed to the galvanic effects between the AA6063 matrix and TiC reinforcement
Layer by layer - Combining Monads
We develop a method to incrementally construct programming languages. Our
approach is categorical: each layer of the language is described as a monad.
Our method either (i) concretely builds a distributive law between two monads,
i.e. layers of the language, which then provides a monad structure to the
composition of layers, or (ii) identifies precisely the algebraic obstacles to
the existence of a distributive law and gives a best approximant language. The
running example will involve three layers: a basic imperative language enriched
first by adding non-determinism and then probabilistic choice. The first
extension works seamlessly, but the second encounters an obstacle, which
results in a best approximant language structurally very similar to the
probabilistic network specification language ProbNetKAT
Résultats de trois méthodes pour la détection de la mutation précore G1896A du virus de l’hépatite B chez les donneurs de sang français : PCR temps réel, séquençage et test Inno-LIPA
AIM: To screen hepatitis B virus (HBV) genotypes and associated basal core promoter (BCP; T1762A/A1764) and precore (PC; A1896) mutations among the 100 HBV surface antigen (HBsAg) positive voluntary blood donors in France.
METHODS: HBV genotypes were determined by using direct sequence analysis. Three methods were used to detect G1896A mutation: non-commercial real-time PCR (PCRTR°, line probe assay (InnoLiPA HBV PreCore, INNOGENETICS(®)) and direct sequencing of precore gene. HBV viral load was quantified with two commercial real-time PCR (COBAS(®) AmpliPrep/COBAS(®) TaqMan(®) HBV Test/Roche and Real Time HBV/M2000/Abbott).
RESULTS: The mean age of donors was 30 (18-64). Patients were from Africa (42%), Europa (50%), and Asia (8%). HBV/D was the most predominant (37%) genotype followed by HBV/A (31%) and HBV/E (22%). PC and BCP mutants were found in 57% with Inno-LIPA HBV test and 59% with both PCRTR and sequencing methods. A significant difference in the viral load of blood donors with wild and PC mutants was observed with the Taqman Cobas real time PCR (3,19 Log(10) UI/ml versus 4,93 Log(10) UI/ml, p < 0.05). Precore phenotype determination was in agreement with the three PC mutation detection methods in 56% of cases.
CONCLUSIONS: Non-Caucasian genotype E was present in the French blood donors. PC mutation was more common than BCP mutations in this study. As HBV infected blood donors were more often asymptomatic carriers, we could speculate that the G1896A mutation may favour the asymptomatic state, supporting previous observations
Эффективность процесса сушки масличных семян во взвешенном слое
The drying process of oilseeds in a suspended layer is investigated in order to increase productivity, reduce energy consumption and improve the quality of seeds for multipurpose use. To study the process of drying seeds of agricultural oilseeds, an experimental installation for drying seeds in a suspended layer has been developed, tested, optimized and implemented. The developed plant for drying seeds in a suspended layer is simple in design and easy to use, has high productivity. It also automates the process and has demonstrated a high level of operational safety during testing. To evaluate the effectiveness of the process of drying seeds in a suspended layer using the developed installation, three types of seeds of oilseed crops were selected: flax seeds, grapes and white sea buckthorn seeds. The results of the conducted studies of the drying process using the developed installation are: increasing the speed of the drying process; reducing the processing time; reducing energy consumption; reduction of processing costs; reduction of cost of processed products; improvement of the quality of processed products by increasing the degree of uniformity of drying and ensuring the preservation of the basic properties of seeds during heat treatment, mainly by reducing the degree of oxidation of vegetable fats in their components. Due to the rationalization of the drying process of oilseeds based on processing in a suspended layer, a number of tasks currently facing enterprises engaged in the primary processing of agricultural products have been solved. Using the results of the study will increase productivity, reduce energy consumption and processing costs, reduce the degree of oxidation of vegetable fats in the composition of seeds and improve their quality for subsequent use in the food industry, medicine, cosmetology, pharmaceuticals, etc.Исследован процесс сушки масличных семян во взвешенном слое с целью повышения производительности, снижения энергозатрат и повышения качества семян для их многоцелевого использования. Для изучения процесса сушки семян сельскохозяйственных масличных культур разработана, испытана, оптимизирована и внедрена экспериментальная установка для сушки семян во взвешенном слое. Разработанная установка для сушки семян во взвешенном слое проста по конструкции и удобна в применении, имеет высокую производительность. Она также позволяет автоматизировать процесс и продемонстрировала высокий уровень эксплуатационной безопасности во время испытаний. Чтобы оценить эффективность процесса сушки семян во взвешенном слое с применением разработанной установки были отобраны три вида семян масличных сельскохозяйственных культур: семена льна, винограда и облепихи белой. Результатами проведенных исследований процесса сушки с использованием разработанной установки являются: увеличение скорости процесса сушки; сокращение времени технологической обработки; снижение энергопотребления; снижение затрат на переработку; снижение себестоимости продуктов переработки; повышение качества продуктов переработки за счет повышения степени равномерности сушки и обеспечения сохранения основных свойств семян в процессе термической обработки, главным образом при снижении степени окисления растительных жиров в их компонентах. За счет рационализации процесса сушки масличных семян, основанной на обработке во взвешенном слое, решен ряд задач, стоящих в настоящее время перед предприятиями, которые заняты первичной переработкой сельскохозяйственной продукции. Использование результатов исследования позволит повысить производительность, уменьшить потребление электроэнергии и затраты на переработку, снизить степень окисления растительных жиров в составе семян и повысить их качество для последующего применения в пищевой промышленности, медицине, косметологии, фармацевтике и т.д
Micromegas operation in high pressure xenon: charge and scintillation readout
The operational characteristics of a Micromegas operating in pure xenon at
the pressure range of 1 to 10 bar are investigated. The maximum charge gain
achieved in each pressure is approximately constant, around 4x10^2, for xenon
pressures up to 5 bar and decreasing slowly above this pressure down to values
somewhat above 10^2 at 10 bar. The MM presents the highest gains for xenon
pressures above 4 bar, when compared to other micropattern gaseous multipliers.
The lowest energy resolution obtained for X-rays of 22.1 keV exhibits a steady
increase with pressure, from 12% at 1bar to about 32% at 10 bar. The effective
scintillation yield, defined as the number of photons exiting through the MM
mesh holes per primary electron produced in the conversion region was
calculated. This yield is about 2x10^2 photons per primary electron at 1 bar,
increasing to about 6x10^2 at 5 bar and, then, decreasing again to 2x10^2 at 10
bar. The readout of this scintillation by a suitable photosensor will result in
higher gains but with increased statistical fluctuations.Comment: 22 pages, 11 figure
- …