The science process for selecting the landing site for the 2020 Mars rover

The process of identifying the landing site for NASA's Mars 2020 rover began in 2013 by defining threshold mission science criteria related to seeking signs of ancient habitable conditions, searching for biosignatures of past microbial life, assembling a returnable cache of samples for possible future return to Earth, and collecting data for planning eventual human missions to the surface of Mars. Mission engineering constraints on elevation and latitude were used to identify candidate landing sites that addressed the scientific objectives of the mission. However, for the first time these constraints did not have a major influence on the viability of candidate sites and, with the new entry, descent, and landing capabilities included in the baseline mission, the vast majority of sites were evaluated and down-selected on the basis of science merit. More than 30 candidate sites with likely acceptable surface and atmospheric conditions were considered at a series of open workshops in the years leading up to the launch. During that period, iteration between engineering constraints and the evolving relative science potential of candidate sites led to the identification of three final candidate sites: Jezero crater (18.4386°N, 77.5031°E), northeast (NE) Syrtis (17.8899°N,77.1599°E) and Columbia Hills (14.5478°S, 175.6255°E). The final landing site will be selected by NASA's Associate Administrator for the Science Mission Directorate. This paper serves as a record of landing site selection activities related primarily to science, an inventory of the number and variety of sites proposed, and a summary of the science potential of the highest-ranking sites

Phylogeography of Scaled Quail

Scaled quail (Callipepla squamata) are distributed over much of the Chihuahuan Desert in the United States and south into central Mexico. Four subspecies have been described based on slight variations in coloration and body size, but the distinctiveness of the subspecies is unknown. We conducted a range-wide phylogeographic analysis of scaled quail based on the mitochondrial control region (D-loop). Our objectives were to: (1) ascertain the overall genetic diversity, (2) examine the phylogeographic structure of the scaled quail, and (3) examine the genetic distinctiveness of its 4 subspecies. We obtained D-loop sequences from 190 hunter-harvested wings and 38 museum specimens. Haplotype diversity (Hd 1⁄4 0.386) and nucleotide diversity (p 1⁄4 0.002) were relatively low. We found 16 D- loop haplotypes, 5 of which were shared by 2 or more subspecies. Haplotype A (carried by 178 individuals) was most widespread and occurred in nearly every population. Analysis of molecular variance revealed that most of the genetic variation in scaled quail occurred within populations rather than among subspecies. The low levels of genetic diversity probably reflect a historically restricted distribution within the Chihuahuan Desert, and wide geographic distribution of some haplotypes implies expansion from a single refugium. Our data indicate the scaled quail subspecies probably do not represent historically independent units. Phenotypic-based subspecies should not be used as proxies for management units if preserving genetic diversity and evolutionary potential is a goal of management, unless molecular data demonstrate the subspecies represent genetically distinct entities. Our data support viewing the entire species as a single management unit

Phylogeography of Bobwhites

Bobwhites (Colinus spp.) are a widely distributed genus of New World quails. Four species are recognized with a geographic range spanning the eastern United States to northern South America. The northern bobwhite (C. virginianus) historically occurred throughout much of the eastern United States and eastern Mexico with disjunct populations in Sonora and Cuba. The Yucata ́n bobwhite (C. nigrogularis) occurs in allopatric populations in Nicaragua and Honduras, and on the Yucata ́n Peninsula. The spot-bellied and crested bobwhites (C. leucopogon and C. cristatus) constitute a species complex with the spot-bellied bobwhite distributed from Guatemala to Costa Rica, and the crested bobwhite from Panama to northern Brazil. The 4 species exhibit substantial intraspecific variation, and up to 56 subspecies are recognized among Colinus largely on the basis of geographic distribution and male plumage coloration. However, relationships within and among species have not been studied in detail. We sampled museum study skins and obtained DNA sequences from mitochondrial control region and ND2 genes. We used concatenated sequences of control region and ND2 to investigate relationships among the bobwhite species, and the control region to assess the geographic distribution of genetic variation within each species. Maximum likelihood analysis of bobwhite phylogeny revealed Colinus is composed of two deeply divergent lineages, one clade of northern and Yucata ́n bobwhites and another of spot-bellied and crested bobwhites. The Yucata ́n bobwhite was genetically distinct from the northern bobwhite. The Yucata ́n bobwhite was composed of 2 distinct subclades, one confined to the Yucata ́n Peninsula and another occurring in Nicaragua. The genetic data showed the spot-bellied bobwhite is closely related to the crested bobwhite, but did not reveal clear support for 2 distinct species. The crested bobwhite was composed of 3 distinct lineages: a western clade that occurs in Panama and west of the northern Andes in Venezuela and Colombia, an eastern clade concentrated in Venezuela (east of the Andes), and a clade restricted to northern Brazil. We found 58 control region haplotypes, of which 29 were shared among 2 northern bobwhite subspecies and 5 haplotypes were especially geographically widespread. We found 16 haplotypes in the Yucata ́n bobwhite with 4 restricted to the Yucata ́n Peninsula and shared among the 3 subspecies found there, and 3 other haplotypes restricted to the Nicaraguan subspecies. The spot-bellied bobwhite did not share haplotypes with any of the 3 crested bobwhite subclades. We found little phylogeographic structure within the spot-bellied bobwhite, and 2 of the 5 haplotypes occurred across much of the species’ range and were shared among the 6 subspecies. The crested bobwhite exhibited strong phylogeographic structure and a lack of shared haplotypes among subspecies. The 20 haplotypes of the crested bobwhite were distributed unevenly among its 3 clades: 2 haplotypes in the Brazilian clade, 6 in the eastern clade, and 12 in the western clade. The weak phylogeographic structure and geographically widespread haplotypes of the northern bobwhite suggests large effective population size and gene flow among subspecies. The deep phylogeographic breaks within the Yucata ́n bobwhite and the spot-bellied bobwhite-crested bobwhite complex may be due to changes in the availability of suitable habitat and geological events during the Pleistocene. The lack of geographically distinct groups within the northern bobwhite implies that many subspecies may not provide good management units. Our data support the continued recognition of the Yucata ́n bobwhite as a distinct species. The 2 intraspecific groups identified in the Yucata ́n and the 4 groups within the spot- bellied/crested bobwhite complex may each represent discrete management units. Further assessment of the phylogenetic relationships and the phylogeography of the bobwhite species is warranted to clarify the phylogeny of Colinus

Structure of anhydrotetracycline-bound Tet(X6) reveals the mechanism for inhibition of type 1 tetracycline destructases

Inactivation of tetracycline antibiotics by tetracycline destructases (TDases) remains a clinical and agricultural threat. TDases can be classified as type 1 Tet(X)-like TDases and type 2 soil-derived TDases. Type 1 TDases are widely identified in clinical pathogens. A combination therapy of tetracycline and a TDase inhibitor is much needed to rescue the clinical efficacy of tetracyclines. Anhydrotetracycline is a pan-TDase inhibitor that inhibits both type 1 and type 2 TDases. Here, we present structural, biochemical, and phenotypic evidence that anhydrotetracycline binds in a substrate-like orientation and competitively inhibits the type 1 TDase Tet(X6) to rescue tetracycline antibiotic activity as a sacrificial substrate. Anhydrotetracycline interacting residues of Tet(X6) are conserved within type 1 TDases, indicating a conserved binding mode and mechanism of inhibition. This mode of binding and inhibition is distinct from anhydrotetracycline\u27s inhibition of type 2 TDases. This study forms the framework for development of next-generation therapies to counteract enzymatic tetracycline resistance

Effects of the KiVa Anti-bullying Program on Adolescents' Depression, Anxiety, and Perception of Peers

The present study investigated the effects of the KiVa antibullying program on students&#39; anxiety, depression, and perception of peers in Grades 4-6. Furthermore, it was investigated whether reductions in peer-reported victimization predicted changes in these outcome variables. The study participants included 7,741 students from 78 schools who were randomly assigned to either intervention or control condition, and the program effects were tested with structural equation modeling. A cross-lagged panel model suggested that the KiVa program is effective for reducing students&#39; internalizing problems and improving their peer-group perceptions. Finally, changes in anxiety, depression, and positive peer perceptions were found to be predicted by reductions in victimization. Implications of the findings and future directions for research are discussed.</p

Can screening for genetic markers improve peripheral artery bypass patency?

AbstractObjective: Three genetic mutations have been associated with an increased risk of thromboembolic events: factor V Leiden R506Q, prothrombin G20210A, and methylenetetrahydrofolate reductase C677T (MTHFR) mutations. The aim of this study was to determine the effect of these mutations on patency of peripheral bypass procedures and preoperative and postoperative thromboembolic events. Methods: Two hundred forty-four randomly selected volunteers participating in the Veterans Affairs Cooperative Study #362 were tested for factor V Leiden, prothrombin, or MTHFR mutations with polymerase chain reaction. Patients enrolled in the study were randomized to receive aspirin therapy or aspirin and warfarin therapy after a peripheral bypass procedure. The frequencies of preoperative and postoperative thromboembolic events and primary patency (PP), assisted primary patency (APP), and secondary patency (SP) rates were compared among carriers of the various mutations. Results: Fourteen patients (5.7%) were heterozygous for the factor V Leiden mutation, seven (2.9%) were heterozygous for the prothrombin mutation, and 108 (44.6%) were heterozygous and 15 (6.2%) homozygous for the MTHFR mutation. After surgery, patients homozygous for the MTHFR gene mutation had increased graft thrombosis, compared with patients who were heterozygous (33.3% versus 11.1%; P = .01), and lower PP, APP and SP rates (P < .05). Furthermore, patients heterozygous for the MTHFR mutation had fewer graft thromboses (11.1% versus 24.4%; P = .01), fewer below-knee amputations (0.9% versus 7.6%; P = .02), and higher PP, APP, and SP rates (PP, 79.6%; APP, 88.9%; SP, 90.7%; P < .05) compared with wild-type control subjects (PP, 63%; APP, 75.6%; SP, 76.5%; P < .05). Conclusion: Patients with either factor V Leiden or prothrombin mutations were not at an increased risk for postoperative graft occlusion or thromboembolic events. Patients heterozygous for MTHFR mutation had a lower risk of graft thrombosis and higher graft patency rates compared with both homozygous and wild-type control subjects. Patients homozygous for the MTHFR mutation had lower graft patency rates compared with patients who were heterozygous, and a trend was seen toward lower patency rates compared with wild-type control subjects. Therefore, screening for the MTHFR gene mutation before surgery may identify patients at an increased risk of graft thrombosis. (J Vasc Surg 2002;36:1198-206.

Application of Metapopulation Theory to Northern Bobwhite Conservation

Northern bobwhite (Colinus virginianus) populations have declined throughout the majority of the species’ range, and have experienced the largest declines in fragmented habitats, suggesting landscape scale processes may be responsible for this decline. We used the results from a stochastic population dynamics model of South Texas bobwhites as conceptual justification for use of metapopulation theory in bobwhite management. Annual quasi-extinction probabilities for isolated bobwhite populations were 0.003 (95% CI: 0.001 0.006), 0.105 (95% CI: 0.083 0.126), and 0.773 (95% CI: 0.750 0.796) for simulated populations harvested at 20, 30, and 40% annually. The probability of regional persistence at 30% harvest increased to ~ 100% in scenarios where we modeled 5 occupied hypothetical 800-ha habitat patches; however, at 40% harvest rates, probability of regional metapopulation persistence did not reach 95% until 12 habitat patches were occupied. This suggests bobwhites probably require somewhere from 800 to 9,600 ha of available habitat space to maintain 95% probability of regional metapopulation persistence as harvest varies from 0 to 40% annually. Our results have strong implications for bobwhite harvest management given the high probability of quasi-extinction of isolated populations at rates of harvest 25%. Multiple patches of habitat (where individual patch size is 800 ha) must be available to ensure bobwhite metapopulation persistence

Effects of Heat Exposure on Body Water Assessed using Single-Frequency Bioelectrical Impedance Analysis and Bioimpedance Spectroscopy

International Journal of Exercise Science 10(7): 1085-1093, 2017. The purpose of this study was to determine if heat exposure alters the measures of total body water (TBW), extracellular water (ECW), and intracellular water (ICW) in both single-frequency bioelectrical impedance analysis (BIA) and bioimpedance spectroscopy (BIS). Additionally, we sought to determine if any differences exist between the BIA and BIS techniques before and after brief exposure to heat. Body water was evaluated for twenty men (age=24±4 years) in a thermoneutral environment (22°C) before (PRE) and immediately after (POST) 15 min of passive heating (35°C) in an environmental chamber. The mean difference and 95% limits of agreement at PRE demonstrated that BIS yielded significantly higher body water values than BIA (all p0.05; 0.2±1.5kg). Additionally, the ES of the mean differences at POST were trivial to small and the r-values were high (r≥0.96). When analyzing the changes in body water before and after heat exposure, POST values for BIS were significantly higher than PRE (all