734 research outputs found
Signatures of Star-planet interactions
Planets interact with their host stars through gravity, radiation and
magnetic fields, and for those giant planets that orbit their stars within
10 stellar radii (0.1 AU for a sun-like star), star-planet
interactions (SPI) are observable with a wide variety of photometric,
spectroscopic and spectropolarimetric studies. At such close distances, the
planet orbits within the sub-alfv\'enic radius of the star in which the
transfer of energy and angular momentum between the two bodies is particularly
efficient. The magnetic interactions appear as enhanced stellar activity
modulated by the planet as it orbits the star rather than only by stellar
rotation. These SPI effects are informative for the study of the internal
dynamics and atmospheric evolution of exoplanets. The nature of magnetic SPI is
modeled to be strongly affected by both the stellar and planetary magnetic
fields, possibly influencing the magnetic activity of both, as well as
affecting the irradiation and even the migration of the planet and rotational
evolution of the star. As phase-resolved observational techniques are applied
to a large statistical sample of hot Jupiter systems, extensions to other
tightly orbiting stellar systems, such as smaller planets close to M dwarfs
become possible. In these systems, star-planet separations of tens of stellar
radii begin to coincide with the radiative habitable zone where planetary
magnetic fields are likely a necessary condition for surface habitability.Comment: Accepted for publication in the handbook of exoplanet
Heavy-to-light baryonic form factors at large recoil
We analyze heavy-to-light baryonic form factors at large recoil and derive
the scaling behavior of these form factors in the heavy quark limit. It is
shown that only one universal form factor is needed to parameterize Lambda_b to
p and Lambda_b to Lambda matrix elements in the large recoil limit of light
baryons, while hadronic matrix elements of Lambda_b to Sigma transition vanish
in the large energy limit of Sigma baryon due to the space-time parity
symmetry. The scaling law of the soft form factor eta(P^{\prime} \cdot v),
P^{\prime} and v being the momentum of nucleon and the velocity of Lambda_b
baryon, responsible for Lambda_b to p transitions is also derived using the
nucleon distribution amplitudes in leading conformal spin. In particular, we
verify that this scaling behavior is in full agreement with that from
light-cone sum rule approach in the heavy-quark limit. With these form factors,
we further investigate the Lambda baryon polarization asymmetry alpha in
Lambda_b to Lambda gamma and the forward-backward asymmetry A_{FB} in Lambda_b
to Lambda l^{+} l^{-}. Both two observables (alpha and A_{FB}) are independent
of hadronic form factors in leading power of 1/m_b and in leading order of
alpha_s. We also extend the analysis of hadronic matrix elements for Omega_b to
Omega transitions to rare Omega_b to Omega gamma and Omega_b to Omega l^{+}
l^{-} decays and find that radiative Omega_b to Omega gamma decay is probably
the most promising FCNC b to s radiative baryonic decay channel. In addition,
it is interesting to notice that the zero-point of forward-backward asymmetry
of Omega_b to Omega l^{+} l^{-} is the same as the one for Lambda_b to Lambda
l^{+} l^{-} to leading order accuracy provided that the form factors
\bar{\zeta}_i (i=3, 4, 5) are numerically as small as indicated from the quark
model.Comment: 19 page
Buzz vs. Sales: Big Social Data Analytics of Style Icon Campaigns and Fashion Designer Collaborations on H&Mâs Facebook Page
This paper examines the relationship between social media engagement and financial performance of the global fast fashion company, H&M. We analyze big social data from Facebook on the seven H&M style collections that occurred during 2012 and 2013 to investigate if style icon campaigns have a larger effect on quarterly sales than designer collaborations. We find that style icons such as David Beckham generate more social buzz than designer collaborations. Social Set Analysis of the Facebook data shows that the overlap between the users H&M reach with their different style collections is fairly small. The deviations between forecasted quarterly sales and actual quarterly sales are analyzed. Our results show that that style icon campaigns have a larger impact on sales than designer collaborations and reveal that the quarters with the largest deviations coincide with the quarter in which H&M ran a style icon campaign. We discuss the implications of our findings and outline directions for future research
Comparative study on calcium, magnesium and cobalt in diabetic and non diabetic patients (males) in Punjab, Pakistan
Minerals are very important because of their important role in the maintenance of human health. Our study was aimed at assessing and comparing the levels of Ca, Mg and Co in the blood samples of diabetic and non diabetic persons (males) of five age groups between one and 75 years. For this purpose, fasting blood samples of diabetic and non diabetic males of selected age groups were collected. The blood samples were centrifuged to get serum. The mineral elements in the serum were analyzed by using atomic absorption spectrophotometer. The results depicted that the diabetic patients had higher mean concentration of Ca (141.47 ppm), Mg (18 ppm) and Co (0.057 ppm) while non diabetic persons had higher mean concentration of Ca (201.33 ppm), Mg (36.15 ppm) and Co (0.047 ppm). Statistical analysis was done by applying Studentâs T-test. It can be concluded from the study that the diabetic patients of all five age groups are deficient of Ca, Mg, whereas the concentration of Co is higher in diabetic patients. In the further study physiological parameters along with other inorganic cofactors are being taken into consideration.Key words: Diabetes mellitus, blood serum, Ca, Mg, Co
The bioprotective effects of Marigold-tea polyphenols on obesity and oxidative stress biomarkers in high-fat-sugar diet-fed rats
Background: The research is aimed at exploring the potential of marigold petal tea (MPT), rich in polyphenol contents, against oxidative stress and obesity in a rat model following a high-fat-sugar diet (HFSD). Methods: The MPT was prepared through the customary method of decoction and was subjected to analysis for its polyphenol composition using reversed-phase high-performance liquid chromatography (RP-HPLC). Two specific doses of MPT, namely, 250 and 500âmg/kg body weight (BW), were chosen for the studyâreferred to as MPT-250 and MPT-500, respectively. Result: The main phenolic acids and flavonoids identified in MPT, with concentrations exceeding 10âmg/100âmL of tea, included catechin, rutin, salicylic acid, gallic acid, sinapic acid, chlorogenic acid, cinnamic acid, and ellagic acid. The total phenolic (TP) and total flavonoid (TF) contents in MPT were measured to be 5.53 and 7.73âmg/g, respectively. Additionally, MPT demonstrated a 57.2% scavenging capacity with 2,2-diphenyl-1-picrylhydrazyl radical. Notably, the administration of a higher dose (MPT-500) showed a significant reduction in body mass index (BMI) and a 51.24% reduction in the rate of increase in BW compared to the HFSD group. The findings indicated that all the treatment groups, that is, orlistat treatment (OT), MPT-250, and MPT-500 groups, experienced reduced levels of serum total cholesterol (TC), triglyceride (TG), and markers of lipoproteins in contrast to the HFSD group. Moreover, MPT helped restore the levels of malondialdehyde (MDA), superoxide dismutase (SOD), and reduced glutathione (GSH), thereby demonstrating its potential in combating oxidative stress. The MPT-500 group also displayed decreased liver and kidney weights and an improved atherogenic index when compared to the HFSD group. Conclusion: The results clearly indicate that a high dosage of MPT showed antiobesity activity which was comparable to the same effects produced by the conventional drug orlistat
Predicting Physical Time Series Using Dynamic Ridge Polynomial Neural Networks
Forecasting naturally occurring phenomena is a common problem in many domains of science, and this has been addressed and investigated by many scientists. The importance of time series prediction stems from the fact that it has wide range of applications, including control systems, engineering processes, environmental systems and economics. From the knowledge of some aspects of the previous behaviour of the system, the aim of the prediction process is to determine or predict its future behaviour. In this paper, we consider a novel application of a higher order polynomial neural network architecture called Dynamic Ridge Polynomial Neural Network that combines the properties of higher order and recurrent neural networks for the prediction of physical time series. In this study, four types of signals have been used, which are; The Lorenz attractor, mean value of the AE index, sunspot number, and heat wave temperature. The simulation results showed good improvements in terms of the signal to noise ratio in comparison to a number of higher order and feedforward neural networks in comparison to the benchmarked techniques
Stellar Coronal and Wind Models: Impact on Exoplanets
Surface magnetism is believed to be the main driver of coronal heating and
stellar wind acceleration. Coronae are believed to be formed by plasma confined
in closed magnetic coronal loops of the stars, with winds mainly originating in
open magnetic field line regions. In this Chapter, we review some basic
properties of stellar coronae and winds and present some existing models. In
the last part of this Chapter, we discuss the effects of coronal winds on
exoplanets.Comment: Chapter published in the "Handbook of Exoplanets", Editors in Chief:
Juan Antonio Belmonte and Hans Deeg, Section Editor: Nuccio Lanza. Springer
Reference Work
Evaluation of gut modulatory and bronchodilator activities of Amaranthus spinosus Linn.
Background
The aqueous-methanolic extract of Amaranthus spinosus (A. spinosus Linn.,) whole plant, was studied for its laxative, spasmolytic and bronchodilator activities to validate some of its medicinal uses. Methods
The crude extract of A. spinosus was studied in-vivo for bronchodilator and laxative activities and in-vitro using isolated tissue preparations which were mounted in tissue baths assembly containing physiological salt solutions, maintained at 37°C and aerated with carbogen, to assess the spasmolytic effect and to find out the possible underlying mechanisms. Results
In the in-vivo experiments in mice, the administration of A. spinosus increased fecal output at doses of 100 and 300 mg/kg showing laxative activity. It also inhibited carbachol-induced bronchospasm in anesthetized rats at 1, 3, 10 and 30 mg/kg indicative of bronchodilator activity. When tested on isolated gut preparations, the plant extract showed a concentration-dependent (0.01-10.0 mg/ml) spasmogenic effect in spontaneously contracting rabbit jejunum and guinea-pig ileum. The spasmogenic effect was partially blocked in tissues pretreated with atropine (0.1 ÎŒM). When tested on K+ (80 mM)-induced sustained contractions in isolated rabbit jejunum, the plant extract caused complete relaxation and also produced a shift in the Ca++ concentration-response curves (CRCs) towards right, similar to diltiazem. In rabbit trachea, the plant extract completely inhibited K+ (80 mM) and carbachol (CCh, 1 ÎŒM)-induced contractions at 1 mg/ml but pretreatment of tissue with propranolol (1 ÎŒM), caused around 10 fold shift in the inhibitory CRCs of the plant extract constructed against CCh-induced contraction. The plant extract (up to 0.3 mg/ml) also increased both force and rate of spontaneous contractions of isolated guinea-pig atria, followed by relaxation at higher concentration (1.0-5.0 mg/ml). The cardio-stimulant effect was abolished in the presence of propranolol, similar to that of isoprenaline. Activity-directed fractionation revealed that the spasmolytic component(s) was separated in the organic fraction, whereas the spasmogenic component was concentrated in the aqueous fraction. Conclusion
These results indicate that A. spinosus possesses laxative activity partially mediated through cholinergic action. The spasmolytic effect was mediated through calcium channel blocking (CCB), while bronchodilator activity through a combination of ÎČ-adrenergic and CCB pathways, which may explain the traditional uses of A. spinosus in gut and airways disorders
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