5,226 research outputs found

    Atmospheric Chemistry for Astrophysicists: A Self-consistent Formalism and Analytical Solutions for Arbitrary C/O

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    We present a self-consistent formalism for computing and understanding the atmospheric chemistry of exoplanets from the viewpoint of an astrophysicist. Starting from the first law of thermodynamics, we demonstrate that the van't Hoff equation (which describes the equilibrium constant), Arrhenius equation (which describes the rate coefficients) and procedures associated with the Gibbs free energy (minimisation, rescaling) have a common physical and mathematical origin. We address an ambiguity associated with the equilibrium constant, which is used to relate the forward and reverse rate coefficients, and restate its two definitions. By necessity, one of the equilibrium constants must be dimensionless and equate to an exponential function involving the Gibbs free energy, while the other is a ratio of rate coefficients and must therefore possess physical units. We demonstrate that the Arrhenius equation takes on a functional form that is more general than previously stated without recourse to tagging on ad hoc functional forms. Finally, we derive analytical models of chemical systems, in equilibrium, with carbon, hydrogen and oxygen. We include acetylene and are able to reproduce several key trends, versus temperature and carbon-to-oxygen ratio, published in the literature. The rich variety of behavior that mixing ratios exhibit as a function of the carbon-to-oxygen ratio is merely the outcome of stoichiometric book-keeping and not the direct consequence of temperature or pressure variations.Comment: Accepted by ApJ. 9 pages, 4 figure

    23(B)(2) Class Certification: Choosing an Approach for Certifying Civil Rights Discrimination Class Action Suits

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    The passage of the 1991 amendments to the Civil Rights Act granted injunctive as well as monetary damages for impermissible discrimination in the workplace. The Act also created a tension with the last revision of the Federal Rules of Civil Procedure in 1966. This revision prohibits the certification of a class under Rule 23(b)(2) if the damages sought are predominantly monetary in nature. On one end of this resulting tension is the desire to protect individuals rights to “opt-out” of a class action suit and maintain future individual actions. On the other end is the desire for judicial economy and the possibility to have sweeping remedies in the form of injunctive or declaratory relief. This tension is not reconcilable at the present and has fueled the growth of a three-way circuit split over what standard should be used to decide the certification of a class action civil rights discrimination suit. I argue that the circuit split has presented some courts to provide a higher burden to alleged victims of civil rights discrimination, in direct frustration of Congress’ legislative intent to compensate victims and give a punitive remedy against large companies that commit civil rights violations. I propose a burden-shifting solution to the circuit split that takes into account the interests of the parties in a class action suit as well as the effects of racial politics. I however advocate an appropriate and ultimate solution that revises the Federal Rule that clearly expresses an approach taking into account this tension

    International Justice and Shifting Paradigms: Foreward

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    A Comparison of Water Potential and Mechanical Strength of Tip and Base Leaves in Heteromeles arbutifolia

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    Heteromeles arbutifolia, commonly known as, Hollywood, is a plant that is extremely common in the California Chaparral ecosystem. It was observed that with Hollywood, the leaves grow on the tips of the branches predominantly. However, there are leaves that grow on the base of the branches that appear to be equally as healthy. The purpose of this investigation was to determine whether the leaves that grow at the tips of the branches or at the base of the branches were better suited to benefit the rest of the plant. Our hypothesis was that the leaves at the tips of the branches would be better suited to benefit the rest of the plant due to their better access to sunlight, as the rest of the plant does not overshadow them. We determined which leaves would be better suited to benefit the plant by measuring the water potential and mechanical strength of leaves at the tip and bases of branches on Heteromeles arbutifolia plants across the street from the Pepperdine cross. Samples were collected from Heteromeles arbutifolia specimens that were both in the sun and in the shade. After the results were compared, the plants in the sun showed that leaves at the base were mechanically stronger than those at the tip, while plants in the shade showed leaves at the tip were mechanically stronger. As for water potential, base leaves had higher water potential across the board

    Unanticipated differences between α- and γ-diaminobutyric acid-linked hairpin polyamide-alkylator conjugates

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    Hairpin polyamide–chlorambucil conjugates containing an {alpha}-diaminobutyric acid ({alpha}-DABA) turn moiety are compared to their constitutional isomers containing the well-characterized {gamma}-DABA turn. Although the DNA-binding properties of unconjugated polyamides are similar, the {alpha}-DABA conjugates display increased alkylation specificity and decreased rate of reaction. Treatment of a human colon carcinoma cell line with {alpha}-DABA versus {gamma}-DABA hairpin conjugates shows only slight differences in toxicities while producing similar effects on cell morphology and G2/M stage cell cycle arrest. However, striking differences in animal toxicity between the two classes are observed. Although mice treated with an {alpha}-DABA hairpin polyamide do not differ significantly from control mice, the analogous {gamma}-DABA hairpin is lethal. This dramatic difference from a subtle structural change would not have been predicted

    When Causal Intervention Meets Adversarial Examples and Image Masking for Deep Neural Networks

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    Discovering and exploiting the causality in deep neural networks (DNNs) are crucial challenges for understanding and reasoning causal effects (CE) on an explainable visual model. "Intervention" has been widely used for recognizing a causal relation ontologically. In this paper, we propose a causal inference framework for visual reasoning via do-calculus. To study the intervention effects on pixel-level features for causal reasoning, we introduce pixel-wise masking and adversarial perturbation. In our framework, CE is calculated using features in a latent space and perturbed prediction from a DNN-based model. We further provide the first look into the characteristics of discovered CE of adversarially perturbed images generated by gradient-based methods \footnote{~~https://github.com/jjaacckkyy63/Causal-Intervention-AE-wAdvImg}. Experimental results show that CE is a competitive and robust index for understanding DNNs when compared with conventional methods such as class-activation mappings (CAMs) on the Chest X-Ray-14 dataset for human-interpretable feature(s) (e.g., symptom) reasoning. Moreover, CE holds promises for detecting adversarial examples as it possesses distinct characteristics in the presence of adversarial perturbations.Comment: Noted our camera-ready version has changed the title. "When Causal Intervention Meets Adversarial Examples and Image Masking for Deep Neural Networks" as the v3 official paper title in IEEE Proceeding. Please use it in your formal reference. Accepted at IEEE ICIP 2019. Pytorch code has released on https://github.com/jjaacckkyy63/Causal-Intervention-AE-wAdvIm
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