Detection of Coronal Mass Ejections in V471 Tauri with the Hubble Space Telescope

V471 Tauri, an eclipsing system consisting of a hot DA white dwarf (WD) and a dK2 companion in a 12.5-hour orbit, is the prototype of the pre-cataclysmic binaries. The late-type component is magnetically active, due to its being constrained to rotate synchronously with the short orbital period. During a program of UV spectroscopy of V471 Tau, carried out with the Goddard High Resolution Spectrograph (GHRS) onboard the Hubble Space Telescope, we serendipitously detected two episodes in which transient absorptions in the Si III 1206 A resonance line appeared suddenly, on a timescale of <2 min. The observations were taken in a narrow spectral region around Ly-alpha, and were all obtained near the two quadratures of the binary orbit, i.e., at maximum projected separation (~3.3 Rsun) of the WD and K star. We suggest that these transient features arise when coronal mass ejections (CME's) from the K2 dwarf pass across the line of sight to the WD. Estimates of the velocities, densities, and masses of the events in V471 Tau are generally consistent with the properties of solar CME's. Given our detection of 2 events during 6.8 hr of GHRS observing, along with a consideration of the restricted range of latitudes and longitudes on the K star's surface that can give rise to trajectories passing in front of the WD as seen from Earth, we estimate that the active V471 Tau dK star emits some 100-500 CME's per day, as compared to 1-3 per day for the Sun. The K dwarf's mass-loss rate associated with CME's is at least (5-25) x 10^{-14} Msun/yr, but it may well be orders of magnitude higher if most of the silicon is in ionization states other than Si III.Comment: 24 pages AASTeX, 4 figures. Accepted by Astrophysical Journa

Effects of laser ablated silver nanoparticles on Lemna minor

Cataloged from PDF version of article.The present study investigates and models the effect of laser ablated silver nanoparticles (AgNPs) on the development of the aquatic macrophyte Lemna minor. Toxic effects of five different AgNP concentrations (8, 16, 32, 96 and 128μgL-1) on L. minor were recorded over seven days under simulated natural conditions. Biosorption of AgNPs by L. minor was modeled using four sorption isotherms, and the sorption behavior was found to agree most closely with the Langmuir-Freundlich model (R2=0.997). While toxic effects of AgNPs could be observed in all models and concentrations, the greatest increase in toxicity was in the 8-32μgL-1 range. Dry weight- and frond number-based inhibition experiments suggest that growth inhibition does not necessarily scale with AgNP concentration, and that slight fluctuations in inhibition rates exist over certain concentration ranges. Very close fits (R2=0.999) were obtained for all removal models, suggesting that the fluctuations are not caused by experimental variation. In addition, L. minor was found to be a successful bioremediation agent for AgNPs, and displayed higher removal rates for increasing AgNP doses. FT-IR spectroscopy suggests that carbonyl groups are involved in AgNP remediation. © 2014 Elsevier Ltd

Sourcing Flexibility, Spot Trading, and Procurement Contract Structure

We analyze the structure and pricing of option contracts for an industrial good in the presence of spot trading. We combine the analysis of spot trading and buyers' disparate private valuations for different suppliers' products, and we jointly endogenize the determination of three major dimensions in contract design: (i) sales contracts versus options contracts, (ii) flat-price versus volume-dependent contracts, and (iii) volume discounts versus volume premia. We build a model in which a supplier of an industrial good transacts with a manufacturer who uses the supplier's product to produce an end good with an uncertain demand. We show that, consistent with industry observations, volume-dependent optimal sales contracts always demonstrate volume discounts (i.e., involve concave pricing). However, options are more complex agreements, and optimal option contracts can involve both volume discounts and volume premia. Three major contract structures commonly emerge in optimality. First, if the seller has a high discount rate relative to the buyer and the seller's production costs or the production capacity is low, the optimal contracts tend to be flat-price sales contracts. Second, when the seller has a relatively high discount rate compared to the buyer but production costs or production capacity are high, the optimal contracts are sales contracts with volume discounts. Third, if the buyer's discount rate is high relative to the seller's, then the optimal contracts tend to be volume-dependent options contracts and can involve both volume discounts and volume premia. However, when the seller's production capacity is sufficiently low, it is possible to observe flat-price option contracts. Furthermore, we provide links between production and spot market characteristics, contract design, and efficiency.National Science Foundation (U.S.) (contract CMMI-0758069)National Science Foundation (U.S.) (contract DMI-0245352

Is PhoR–PhoP partner fidelity strict? PhoR is required for the activation of the pho regulon in Streptomyces coelicolor

Two-component regulatory systems play a key role in the cell metabolism adaptation to changing nutritional and environmental conditions. The fidelity between the two cognate proteins of a two-component system is important since it determines whether a specific response regulator integrates the signals transmitted by different sensor kinases. Phosphate regulation in Streptomyces coelicolor is mostly mediated by the PhoR–PhoP two-component system. Previous studies elucidated the mechanisms that control phosphate regulation as well as the genes directly regulated by the response regulator PhoP (pho regulon) in this organism. However, the role of the histidine kinase PhoR in Streptomyces coelicolor had not been unveiled so far. In this work, we report the characterization of a non-polar ΔphoR deletion mutant in S. coelicolor that keeps its native promoter. Induction of the phoRP operon was dependent upon phosphorylation of PhoP, but the ΔphoR mutant expressed phoP at a basal level. RT-PCR and reporter luciferase assays demonstrated that PhoR plays a key role in the activation of the pho regulon in this organism. Our results point towards a strict cognate partner specificity in terms of the phosphorylation of PhoP by PhoR thus corroborating the tight interaction between the two-components of this system

Comparison of selected levels of serum elements / minerals in obese dogs

Obesity is the most common metabolic disorder defined as excessive adipose tissue accumulation in the body. Elements and minerals are crucial for biological metabolism. There have been limited studies based on the relationship between elements/minerals and obesity in dogs. The study was aimed to evaluate possible alterations of selected serum elements/minerals -copper (Cu), iron (Fe), zinc (Zn), selenium (Se), chromium (Cr), nickel (Ni), calcium (Ca), phosphorus (P), magnesium (Mg), boron (B), cobalt (Co) and aluminum (Al)- in obese dogs. The study groups were categorized as obese group (n:20) and controls (n:10) with different breeds and genders due to body condition scoring system cared under similar conditions fed with dry commercial food once daily. Serum elements/minerals in serum were analyzed by using inductively coupled plasma-optical emission spectrophotometer (ICP-OES). Obese dogs had statistically higher serum Fe levels compared with healthy controls. A positive correlation was found between serum levels of Cr-Ni; Cu-Mg; Cu-Se; Mg-Se; Mg-Ca; Mg-P; B-Co; B-Ca; Ni-Co; Co-Ca and Ca-P in obese dogs. It has been accepted that obesity is a pro-inflammatory process priorly initiating in adipose tissue. Higher serum Fe levels in obese dogs might be related with inflammation during the obesity process. Moreover, the strong correlations among other discussed elements/minerals even with no statistical alterations of serum levels in obese dogs should be elucidated with further studies. Elements and minerals might be evaluated as biomarkers for the determination of effects of obesity in dogs

Comparison of selected levels of serum elements/minerals in obese dogs

Obesity is the most common metabolic disorder defined as excessive adipose tissue accumulation in the body. Elements and minerals are crucial for biological metabolism. There have been limited studies based on the relationship between elements/minerals and obesity in dogs. The study was aimed to evaluate possible alterations of se-lected serum elements/minerals-copper (Cu), iron (Fe), zinc (Zn), selenium (Se), chromium (Cr), nickel (Ni), calcium (Ca), phosphorus (P), magnesium (Mg), boron (B) and cobalt (Co)-in obese dogs. The study groups were categorized as obese group (n:20) and controls (n:10) with different breeds and genders due to body condition scoring system cared under similar conditions fed with dry commercial food once daily. Serum elements/minerals in serum were analyzed by using inductively coupled plasma-optical emission spectrophotometer (ICP-OES). Obese dogs had statistically higher serum Fe levels compared with healthy controls. A positive correlation was found between serum levels of Cr-Ni; Cu-Mg; Cu-Se; Mg-Se; Mg-Ca; Mg-P; B-Co; B-Ca; Ni-Co; Co-Ca and Ca-P in obese dogs. It has been accepted that obesity is a pro-inflammatory process priorly initiating in adipose tissue. Higher serum Fe levels in obese dogs might be related with inflammation during the obesity process. Moreover, the strong correlations among other discussed elements/minerals even with no statistical alterations of serum levels in obese dogs should be elucidated with further studies. Elements and minerals might be evaluated as biomarkers for the determination of effects of obesity in dogs