Investigating hyper-inflated M dwarfs in eclipsing binary systems

We study two eclipsing binary systems (EBs), each containing an M dwarf which published literature claims has a radius far larger than expected physical limitations. In order to test these claims of “hyper-inflation,” we look to Modules for Experiments in Stellar Astrophysics (MESA) stellar models and a new data analysis based on light curves from the Wide Angle Search for Planets (WASP). We also analyze new radial velocity data points from the Immersion Grating Infrared Spectrograph (IGRINS) and compare the results with published values. MESA models cast doubt on the hypothesis that each EB is a young, still-collapsing proto-stellar system, and a literature review rules out the possibility that convection-inhibiting magnetic activity is the cause. Our new data analysis reveals that neither M dwarf is hyper-inflated, and that the likely cause of the initial results is the use of Hydrogen-α spectroscopy.2018-06-0

Relationships of drought and biotic interactions to crayfish assemblage structure in Gulf coastal headwater streams

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references (leaves 55-62).Issued also on microfiche from Lange Micrographics.Relationships between environmental variability and natural communities have been extensively studied. However the relative strengths of abiotic and biotic factors in structuring stream communities continues to be debated. Although North American crayfish are taxonomically diverse, occur across a variety of habitats, and are important components of stream ecosystems, when compared to other invertebrates or fish, factors influencing their distribution are poorly studied. Crayfishes may respond differently to disturbance and predators or competitors. In intermittent streams of East Texas, fishes that may influence the distribution of crayfish are rare or absent, so crayfish assemblages may differ between hydrologically variable and stable streams. In order to understand abiotic and biotic factors structuring native crayfish assemblages, environmental variables and densities of fishes and crayfishes were quantified simultaneously in 16 East Texas streams during June and October 1999, and February and April 2000. Three crayfish species, Procambarus clarkii, Orconectes palmeri, and Procambarus kensleyi, and several fishes were collected. Although fish and crayfish assemblages were similar in all streams during June before drought occurred, relative densities varied across intermittent and perennial streams following drought. After flow resumed in intermittent streams, densities of juvenile P. kensleyi were higher, but predatory fishes and adult O. palmeri were reduced, whereas in perennial streams, the opposite pattern occurred. These results suggest that P. kensleyi could tolerate abiotic stress, exploit resources, and maintain higher densities in intermittent streams where predators were reduced, but its smaller size may have facilitated higher predation by fish in perennial streams. Assemblages in perennial streams suggested interactions among crayfishes and fishes favored O. palmeri and P. clarkii, which appeared to be superior competitors and resistant to predators. Procambarus clarkii was not strongly correlated with either abiotic or biotic factors measured in this study, including stressful conditions associated with drought. These results are consistent with life history trade-offs among stress tolerance, resistance to disturbance and predation, and competitive ability. The occurrence of both perennial and intermittent streams within a drainage provides a range of habitats that maintains more crayfish species from among those in the regional species pool than would either habitat alone

Efficacy of Conservation Actions for Imperiled Colorado River Fishes in the Grand Canyon, Arizona

Many fishes are critically imperiled, particularly in their native rivers, due to human water use and dam construction, which can dramatically alter habitats and block fish migratory routes. The introduction of invasive sport-fishes that prey on native fish further threatens native species that maybe restricted to only a single river basin (i.e., “endemic”). To preserve native fishes in river systems with degraded habitats, managers need to understand the effects of conservation actions to ensure limited resources are applied effectively. Two commonly applied native fish conservation actions include removal of invasive fishes, and translocations of native fish from one place into another with suitable habitat to establish new populations.My primary research goals were 1) to assess the population-level native fish responses to invasive fish removal, 2) understand what factors lead to successful establishment of new endangered humpback chub populations through translocations of juveniles, and 3) to investigate alternative strategies for reducing invasive brown trout using angling, disturbance of eggs, and electrofishing, in multiple connected populations (i.e., trout move between them)experiencing different levels of warming and climate change. My research was conducted using data collected over 10 years in the Colorado River and its tributaries in Grand Canyon National Park. I found native fish populations increased by about 480% when invasive trout populations were reduced by 60% or more. Increases in native fish were also greatest in warmer areas in years when spring flooding occurred. Translocated humpback chub populations were limited when numbers of introduced rainbow trout were higher and when floods washed ash from a fire into one stream in 2014. However, I found flooding was generally beneficial to humpback chub, which was probably because additional food was washed into their habitats. Finally, while future declines in Colorado River reservoir storage and warming of streamflow may reduce brown trout, successful Grand Canyon-wide reductions would require increasing trout removals throughout the river system particularly in tributary climate change refuges. In summary, translocations can contribute toward native fish conservation, but continued invasive fish removal and protection of natural river flow are also critical to meeting conservation goals

Non-Parametric Extraction of Implied Asset Price Distributions

Extracting the risk neutral density (RND) function from option prices is well defined in principle, but is very sensitive to errors in practice. For risk management, knowledge of the entire RND provides more information for Value-at-Risk (VaR) calculations than implied volatility alone [1]. Typically, RNDs are deduced from option prices by making a distributional assumption, or relying on implied volatility [2]. We present a fully non-parametric method for extracting RNDs from observed option prices. The aim is to obtain a continuous, smooth, monotonic, and convex pricing function that is twice differentiable. Thus, irregularities such as negative probabilities that afflict many existing RND estimation techniques are reduced. Our method employs neural networks to obtain a smoothed pricing function, and a central finite difference approximation to the second derivative to extract the required gradients. This novel technique was successfully applied to a large set of FTSE 100 daily European exercise (ESX) put options data and as an Ansatz to the corresponding set of American exercise (SEI) put options. The results of paired t-tests showed significant differences between RNDs extracted from ESX and SEI option data, reflecting the distorting impact of early exercise possibility for the latter. In particular, the results for skewness and kurtosis suggested different shapes for the RNDs implied by the two types of put options. However, both ESX and SEI data gave an unbiased estimate of the realised FTSE 100 closing prices on the options' expiration date. We confirmed that estimates of volatility from the RNDs of both types of option were biased estimates of the realised volatility at expiration, but less so than the LIFFE tabulated at-the-money implied volatility.Comment: Paper based on Application of Physics in Financial Analysis,APFA5, Conference Presentation, Torino, Italy. 11.5 Page

Magnetic inflation and stellar mass. III. revised parameters for the component stars of NSVS 07394765

We perform a new analysis of the M-dwarf–M-dwarf eclipsing binary system NSVS 07394765 in order to investigate the reported hyper-inflated radius of one of the component stars. Our analysis is based on archival photometry from the Wide Angle Search for Planets, new photometry from the 32 cm Command Module Observatory telescope in Arizona and the 70 cm telescope at Thacher Observatory in California, and new high-resolution infrared spectra obtained with the Immersion Grating Infrared Spectrograph on the Discovery Channel Telescope. The masses and radii we measure for each component star disagree with previously reported measurements. We show that both stars are early M-type main-sequence stars without evidence for youth or hyper-inflation ( = - ☉ M M + 1 0.661 0.036 0.008 , = - ☉ M M + 2 0.608 0.028 0.003 , = - ☉ + R1 0.599 0.019 R 0.032 , = - ☉ + R2 0.625 0.027 R 0.012 ), and we update the orbital period and eclipse ephemerides for the system. We suggest that the likely cause of the initial hyper-inflated result is the use of moderate-resolution spectroscopy for precise radial velocity measurements.Published versio

The case for cloud service trustmarks and assurance-as-a-service

Cloud computing represents a significant economic opportunity for Europe. However, this growth is threatened by adoption barriers largely related to trust. This position paper examines trust and confidence issues in cloud computing and advances a case for addressing them through the implementation of a novel trustmark scheme for cloud service providers. The proposed trustmark would be both active and dynamic featuring multi-modal information about the performance of the underlying cloud service. The trustmarks would be informed by live performance data from the cloud service provider, or ideally an independent third-party accountability and assurance service that would communicate up-to-date information relating to service performance and dependability. By combining assurance measures with a remediation scheme, cloud service providers could both signal dependability to customers and the wider marketplace and provide customers, auditors and regulators with a mechanism for determining accountability in the event of failure or non-compliance. As a result, the trustmarks would convey to consumers of cloud services and other stakeholders that strong assurance and accountability measures are in place for the service in question and thereby address trust and confidence issues in cloud computing

Intensive Mutagenesis of the Nisin Hinge Leads to the Rational Design of Enhanced Derivatives

peer-reviewedNisin A is the most extensively studied lantibiotic and has been used as a preservative by the food industry since 1953. This 34 amino acid peptide contains three dehydrated amino acids and five thioether rings. These rings, resulting from one lanthionine and four methyllanthionine bridges, confer the peptide with its unique structure. Nisin A has two mechanisms of action, with the N-terminal domain of the peptide inhibiting cell wall synthesis through lipid II binding and the C-terminal domain responsible for pore-formation. The focus of this study is the three amino acid ‘hinge’ region (N 20, M 21 and K 22) which separates these two domains and allows for conformational flexibility. As all lantibiotics are gene encoded, novel variants can be generated through manipulation of the corresponding gene. A number of derivatives in which the hinge region was altered have previously been shown to possess enhanced antimicrobial activity. Here we take this approach further by employing simultaneous, indiscriminate site-saturation mutagenesis of all three hinge residues to create a novel bank of nisin derivative producers. Screening of this bank revealed that producers of peptides with hinge regions consisting of AAK, NAI and SLS displayed enhanced bioactivity against a variety of targets. These and other results suggested a preference for small, chiral amino acids within the hinge region, leading to the design and creation of producers of peptides with hinges consisting of AAA and SAA. These producers, and the corresponding peptides, exhibited enhanced bioactivity against Lactococcus lactis HP, Streptococcus agalactiae ATCC 13813, Mycobacterium smegmatis MC2155 and Staphylococcus aureus RF122 and thus represent the first example of nisin derivatives that possess enhanced activity as a consequence of rational design.This work was financed by a grant from the Irish Department of Agriculture, Food and the Marine through the Food Institutional Research Measure (08/RD/C/691) and with Science Foundation Investigator award (10/IN.1/B3027)

Bioengineering of nisin to enhance functionality against dairy pathogens

The bacteriocin class of antimicrobial peptides have emerged as a viable alternative to at least partially fill the void created by the end of the golden age of antibiotic discovery. Along with this potential use in a clinical setting, bacteriocins also play an important role as bio-preservatives in the food industry. This thesis focuses on a specific bacteriocin group, the lantibiotics (Lanthionine-containing antibiotics). Their numerous methods of appliance in a food setting and how their gene-encoded nature can be modified to improve on overall bioactivity and functionality are explored here. The use of a lantibiotic (lacticin 3147) producing starter culture to control the Crohn’s disease-linked pathogen Mycobacterium paratuberculosis was assessed in a raw milk cheese. Although lacticin 3147 production did not effectively control the pathogen, the study provided an impetus to employ a variety of PCR-based mutagenesis techniques with a view to the creation of enhanced lantibiotic derivatives. Through the use of these techniques, a number of enhanced derivatives were generated from the ‘hinge’ region of the nisin peptide. Furthermore, a derivative in which the three hinge amino acids were replaced with three alanines represents the first enhanced derivative of nisin to have been designed through a rational process. This derivative also formed the backbone for the creation of an active, trypsin resistant, variant. Through the employment of further mutagenesis methods a derivative was created with potential use as an oral anti-bacterial in the future. Finally a number of lead nisin derivatives were investigated to assess their anti- Streptococcus agalactiae ability, a mastitis associated pathogen. Also a system was developed to facilitate the large scale production of these candidates, or other nisin derivatives, from dairy substrates