The Abundance of Molecular Hydrogen and its Correlation with Midplane Pressure in Galaxies: Non-Equilibrium, Turbulent, Chemical Models

Observations of spiral galaxies show a strong linear correlation between the ratio of molecular to atomic hydrogen surface density R_mol and midplane pressure. To explain this, we simulate three-dimensional, magnetized turbulence, including simplified treatments of non-equilibrium chemistry and the propagation of dissociating radiation, to follow the formation of H_2 from cold atomic gas. The formation time scale for H_2 is sufficiently long that equilibrium is not reached within the 20-30 Myr lifetimes of molecular clouds. The equilibrium balance between radiative dissociation and H_2 formation on dust grains fails to predict the time-dependent molecular fractions we find. A simple, time-dependent model of H_2 formation can reproduce the gross behavior, although turbulent density perturbations increase molecular fractions by a factor of few above it. In contradiction to equilibrium models, radiative dissociation of molecules plays little role in our model for diffuse radiation fields with strengths less than ten times that of the solar neighborhood, because of the effective self-shielding of H_2. The observed correlation of R_mol with pressure corresponds to a correlation with local gas density if the effective temperature in the cold neutral medium of galactic disks is roughly constant. We indeed find such a correlation of R_mol with density. If we examine the value of R_mol in our local models after a free-fall time at their average density, as expected for models of molecular cloud formation by large-scale gravitational instability, our models reproduce the observed correlation over more than an order of magnitude range in density.Comment: 24 pages, 4 figures, accepted for publication in Astrophys. J, changes include addition of models with higher radiation fields and substantial clarification of the narrativ

The geometry of reaction norms yields insights on classical fitness functions for Great Lakes salmon.

Life history theory examines how characteristics of organisms, such as age and size at maturity, may vary through natural selection as evolutionary responses that optimize fitness. Here we ask how predictions of age and size at maturity differ for the three classical fitness functions-intrinsic rate of natural increase r, net reproductive rate R0, and reproductive value Vx-for semelparous species. We show that different choices of fitness functions can lead to very different predictions of species behavior. In one's efforts to understand an organism's behavior and to develop effective conservation and management policies, the choice of fitness function matters. The central ingredient of our approach is the maturation reaction norm (MRN), which describes how optimal age and size at maturation vary with growth rate or mortality rate. We develop a practical geometric construction of MRNs that allows us to include different growth functions (linear growth and nonlinear von Bertalanffy growth in length) and develop two-dimensional MRNs useful for quantifying growth-mortality trade-offs. We relate our approach to Beverton-Holt life history invariants and to the Stearns-Koella categorization of MRNs. We conclude with a detailed discussion of life history parameters for Great Lakes Chinook Salmon and demonstrate that age and size at maturity are consistent with predictions using R0 (but not r or Vx) as the underlying fitness function

Nihilation of femininity in the battle of looks: a Sartrean reading of Jhumpa Lahiri’s “A temporary matter”

The panoptic gaze is vested in with a constitutive impact upon the subjectivity of individuals. Feminist scholars like Luce Irigaray have charged that the metaphor of vision is intimately connected with the construction of gender and sexual difference. By pointing to the masculine logic of Western thought, Irigaray confirms that a woman’s entry into a dominant scopic economy signifies her inevitable confinement to passivity. This essay aims to examine the sexual politics of metaphors of vision in a literary text that is controversially argued to be a voice for the subordinated Indian immigrant women in the US. As one of the most influential schools of thought in Western philosophy, the Sartrean paradigm of sexual difference is employed to investigate this allegation by identifying the latent binary system at work in the fiction of Jhumpa Lahiri, who has garnered substantial yet controversial critical attention over her representations of gender. Specifically, this essay focuses on Lahiri’s prefatory story to her Pulitzer Prize-winning short story collection, Interpreter of Maladies (2000), to unravel the manner her exercise of vision in this narrative perpetuates the dichotomies of a male subject and a female object pre-established in the traditional hierarchies of gender in the West. In this story, Lahiri (un)wittingly privileges masculinity over femininity and reduces the latter to a typically disgusting Sartrean female body of holes and slime. Hence, notwithstanding infrequent emasculated images of the male subject, it is ultimately the masculine that, in the battle of looks between male and female, nihilates the Other to the state of “being-in-itself” and enjoys supremacy over the feminine

Efficient targeted transgenesis of large donor DNA into multiple mouse genetic backgrounds using bacteriophage Bxb1 integrase.

The development of mouse models of human disease and synthetic biology research by targeted transgenesis of large DNA constructs represent a significant genetic engineering hurdle. We developed an efficient, precise, single-copy integration of large transgenes directly into zygotes using multiple mouse genetic backgrounds. We used in vivo Bxb1 mediated recombinase-mediated cassette exchange (RMCE) with a transgene landing pad composed of dual heterologous Bxb1 attachment (att) sites in cis, within the Gt(ROSA)26Sor safe harbor locus. RMCE of donor was achieved by microinjection of vector DNA carrying cognate attachment sites flanking the donor transgene with Bxb1-integrase mRNA. This approach achieves perfect vector-free integration of donor constructs at efficiencies \u3e 40% with up to ~ 43 kb transgenes. Coupled with a nanopore-based Cas9-targeted sequencing (nCATS), complete verification of precise insertion sequence was achieved. As a proof-of-concept we describe the development of C57BL/6J and NSG Krt18-ACE2 models for SARS-CoV2 research with verified heterozygous N1 animals within ~ 4 months. Additionally, we created a series of mice with diverse backgrounds carrying a single att site including FVB/NJ, PWK/PhJ, NOD/ShiLtJ, CAST/EiJ and DBA/2J allowing for rapid transgene insertion. Combined, this system enables predictable, rapid development with simplified characterization of precisely targeted transgenic animals across multiple genetic backgrounds

Ovarian cancer symptom awareness and anticipated time to help-seeking for symptoms among UK women.

OBJECTIVES: To determine levels of awareness of ovarian cancer symptoms and to identify barriers to help-seeking and predictors of a longer time to help-seeking in a UK female population-based sample. METHODS: A UK population-based sample of women [n=1000, including a subsample of women at higher risk due to their age (≥45 years, n=510)] completed the Ovarian Cancer Awareness Measure by telephone interview. Questions measured symptom awareness (using recall and recognition), barriers to medical help-seeking and anticipated time to help-seeking. Regression analyses identified predictors of a higher score on a scale of anticipated time to help-seeking. RESULTS: Most women (58% overall sample; 54% subgroup) were unable to recall any symptoms but 99% recognised at least one. Recognition was lowest for difficulty eating and persistently feeling full. In the sample overall, higher socio-economic status and higher endorsement of practical and service barriers independently predicted a longer anticipated time to help-seeking for more symptoms. White ethnicity was an additional predictor in the older subgroup. CONCLUSIONS: This study suggests awareness of ovarian cancer symptoms is low in the UK, and varies widely between symptoms. It identifies variables that may be involved in a longer time to help-seeking for possible ovarian cancer symptoms and highlights the need for more in-depth research into the factors related to time to help-seeking in real-world situations

Modeling H2 formation in the turbulent ISM: Solenoidal versus compressive turbulent forcing

We present results from high-resolution three-dimensional simulations of the turbulent interstellar medium that study the influence of the nature of the turbulence on the formation of molecular hydrogen. We have examined both solenoidal (divergence-free) and compressive (curl-free) turbulent driving, and show that compressive driving leads to faster H2 formation, owing to the higher peak densities produced in the gas. The difference in the H2 formation rate can be as much as an order of magnitude at early times, but declines at later times as the highest density regions become fully molecular and stop contributing to the total H2 formation rate. We have also used our results to test a simple prescription suggested by Gnedin et al. (2009) for modeling the influence of unresolved density fluctuations on the H2 formation rate in large-scale simulations of the ISM. We find that this approach works well when the H2 fraction is small, but breaks down once the highest density gas becomes fully molecular.Comment: 13 pages, 8 figures, accepted for publication in MNRA

Magnetorotational turbulence transports angular momentum in stratified disks with low magnetic Prandtl number but magnetic Reynolds number above a critical value

The magnetorotational instability (MRI) may dominate outward transport of angular momentum in accretion disks, allowing material to fall onto the central object. Previous work has established that the MRI can drive a mean-field dynamo, possibly leading to a self-sustaining accretion system. Recently, however, simulations of the scaling of the angular momentum transport parameter \alphaSS with the magnetic Prandtl number \Prandtl have cast doubt on the ability of the MRI to transport astrophysically relevant amounts of angular momentum in real disk systems. Here, we use simulations including explicit physical viscosity and resistivity to show that when vertical stratification is included, mean field dynamo action operates, driving the system to a configuration in which the magnetic field is not fully helical. This relaxes the constraints on the generated field provided by magnetic helicity conservation, allowing the generation of a mean field on timescales independent of the resistivity. Our models demonstrate the existence of a critical magnetic Reynolds number \Rmagc, below which transport becomes strongly \Prandtl-dependent and chaotic, but above which the transport is steady and \Prandtl-independent. Prior simulations showing \Prandtl-dependence had \Rmag < \Rmagc. We conjecture that this steady regime is possible because the mean field dynamo is not helicity-limited and thus does not depend on the details of the helicity ejection process. Scaling to realistic astrophysical parameters suggests that disks around both protostars and stellar mass black holes have \Rmag >> \Rmagc. Thus, we suggest that the strong \Prandtl dependence seen in recent simulations does not occur in real systems.Comment: 17 pages, 9 figures. as accepted to Ap

Characterizing star formation activity in infrared dark cloud MSXDC G048.65-00.29

Infrared Dark Clouds (IRDCs), condensed regions of the ISM with high column densities, low temperatures and high masses, are suspected sites of star formation. Thousands of IRDCs have already been identified. To date, it has not been resolved whether IRDCs always show star formation activity and, if so, if massive star formation (> 8 solar masses) is the rule or the exception in IRDCs. Previous analysis of sub-millimeter cores in the cloud MSXDC G048.65-00.29 (G48.65) indicates embedded star formation activity. To characterize this activity in detail, mid-infrared photometry (3-30 micron) has been obtained with the Spitzer Space Telescope. This paper analyzes the point sources seen in the 24 micron band, combined with counterparts or upper limits at shorter and longer wavelengths. Data points in wavelength bands ranging from 1 up to 850 micron are used to compare each 24 micron source to a set of Spectral Energy Distributions of Young Stellar Object (YSO) models. By assessing the models that fit the data, an attempt is made to identify YSOs as such and determine their evolutionary stages and stellar masses. A total of 17 sources are investigated, 13 of which are classified as YSOs, primarily - but not exclusively - in an early embedded phase of star formation. The modeled masses of the central stellar objects range from sub-solar to ~8 solar masses. Every YSO is at less than 1 pc projected distance from its nearest YSO neighbor. We conclude that IRDC G48.65 is a region of active star formation. We find YSOs in various evolutionary phases, indicating that the star formation in this cloud is not an instantaneous process. The inferred masses of the central objects suggest that this IRDC hosts only low to intermediate mass YSOs and none with masses exceeding ~8 solar masses.Comment: 10 pages, 6 figures; v2: minor editorial changes to match published versio

The experiences of ethnic minority MSM with NHS sexual health services in Britain

Objective: To compare the experiences of ethnic minority and white British men who have sex with men (MSM) who attend National Health Service (NHS) sexual health clinics in Britain. Methods: In 2007-2008 a national sample of MSM living in Britain was recruited through websites, in sexual health clinics, bars, clubs and other venues. Men completed an online survey which included questions about their experience of attending an NHS sexual health clinic. Results: Analysis is restricted to 363 ethnic minority MSM and 4776 white British MSM who had attended an NHS sexual health clinic in the 12 months before the survey. Compared with white British men, men from an Indian, Pakistani or Bangladeshi background were more likely to be very anxious about attending the clinic (adjusted odds ratio (aOR) 2.58, 95% confidence interval (CI) 1.63, 4.07), express concerns about being overheard at reception (aOR 1.68, 95% CI 1.10, 2.58), be uncomfortable in the waiting area (aOR 2.04, 95% CI 1.32, 3.15), or be afraid that people in their community would find out that they have sex with men (aOR 7.70, 95% CI 4.49,13.22). The adjusted odds ratios for being afraid that people in their community would find out that they have sex with men were also elevated for black Caribbean, black African, Chinese and other Asian men. Conclusion: Sexual health clinics should be aware that some ethnic minority MSM, particularly those from an Indian, Pakistani or Bangladeshi background, have heightened concerns about clinic attendance and confidentiality compared with white British MSM

The SISO CSPI PDG standard for commercial off-the-shelf simulation package interoperability reference models

For many years discrete-event simulation has been used to analyze production and logistics problems in manufactur-ing and defense. Commercial-off-the-shelf Simulation Packages (CSPs), visual interactive modelling environ-ments such as Arena, Anylogic, Flexsim, Simul8, Witness, etc., support the development, experimentation and visua-lization of simulation models. There have been various attempts to create distributed simulations with these CSPs and their tools, some with the High Level Architecture (HLA). These are complex and it is quite difficult to assess how a set of models/CSP are actually interoperating. As the first in a series of standards aimed at standardizing how the HLA is used to support CSP distributed simula-tions, the Simulation Interoperability Standards Organiza-tion’s (SISO) CSP Interoperability Product Development Group (CSPI PDG) has developed and standardized a set of Interoperability Reference Models (IRM) that are in-tended to clearly identify the interoperability capabilities of CSP distributed simulations