1,351 research outputs found

    The Plan Put into Practice: USAAF Bombing Doctrine and the Ploesti Campaign

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    This thesis is a contribution to the continuing study of the development of American daylight precision strategic bombing doctrine. Using the multiple USAAF bombing attacks on the oil targets of Ploesti, Romania, it concludes that the USAAF entered the war with preconceived, untested notions regarding the effects of bombing and, because of bureaucratic inertia, failed to adjust to German passive and active defenses. The new technology of bombardment aviation therefore did not result in the desired destruction of the industrial targets, but only inflicted damage at high costs to the attackers. Resting on extensive archival research, the study brings to light several previously unrecognized aspects of the Ploesti campaign and also calls into question the fundamental assumptions which underlay American strategic bombing missions in World War Two

    Average chemical properties and potential formation pathways of highly oxidized organic aerosol

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    Measurements of ambient organic aerosol indicate that a substantial fraction is highly oxidized and low in volatility, but this fraction is generally not reproduced well in either laboratory studies or models. Here we describe a new approach for constraining the viable precursors and formation pathways of highly oxidized organic aerosol, by starting with the oxidized product and considering the possible reverse reactions, using a set of simple chemical rules. The focus of this work is low-volatility oxidized organic aerosol (LV-OOA), determined from factor analysis of aerosol mass spectrometer data. The elemental composition and volatility of the aerosol enable the determination of its position in a three-dimensional chemical space (defined by H/C, O/C, and carbon number) and thus its average chemical formula. Consideration of possible back-reactions then defines the movement taken through this chemical space, constraining potential reaction pathways and precursors. This approach is taken for two highly oxidized aerosol types, an average of LV-OOA factors from ten field campaigns (average formula C[subscript 10.5]H[subscript 13.4]O[subscript 7.3]), and extremely oxidized LV-OOA (from Mexico City, average formula C[subscript 10]H[subscript 12.1]O[subscript 8.4]). Results suggest that potential formation pathways include functionalization reactions that add multiple functional groups per oxidation step, oligomerization of highly oxidized precursors, and, in some cases, fragmentation reactions that involve the loss of small, reduced fragments.National Science Foundation (U.S.) (Grant CHE-1012809)National Science Foundation (U.S.) (Grant AGS-1056225

    Private Enforcement of Statutory and Administrative Law in the United States (and Other Common Law Countries)

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    Our aim in this paper, which was prepared for an international conference on comparative procedural law to be held in July 2011, is to advance understanding of private enforcement of statutory and administrative law in the United States, and, to the extent supported by the information that colleagues abroad have provided, of comparable phenomena in other common law countries. Seeking to raise questions that will be useful to those who are concerned with regulatory design, we briefly discuss aspects of American culture, history, and political institutions that reasonably can be thought to have contributed to the growth and subsequent development of private enforcement in the United States. We also set forth key elements of the general legal landscape in which decisions about private enforcement play out, aspects of which should be central to the choice of an enforcement strategy and, in the case of private enforcement, are critical to the efficacy of a private enforcement regime. We then turn to the business of institutional architecture, describing the considerationsā€”both in favor of and against private enforcementā€”that should affect the choice of an enforcement strategy. We lay out choices to be made about elements of a private enforcement regime, attending to the general legal landscape in which the regime would operate, particularly court access, as well as how incentives for enforcement interact with the market for legal services, which has important implications for private enforcement activity. We situate these legislative choices about private enforcement in the context of institutions that shape them. Finally, we seek to demonstrate how general considerations play out by examining private enforcement in two policy areas: legislation proscribing discrimination in employment, and laws protecting consumers from unfair and deceptive practices. A long appendix containing our questionnaire addressed to scholars in other countries, with the respondentsā€™ answers interpolated, has been omitted but is available online

    Determining Adoption of Integrated Pest Management Practices by Grains Farmers in Virginia

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    This article describes the results of three integrated pest management (IPM) surveys of corn, soybean, and small grains farmers in the coastal plains region of Virginia. Farmers identified their weed, disease, insect, and animal pests, and the reasons they use (or do not use) IPM practices for those pests

    The aging of organic aerosol in the atmosphere : chemical transformations by heterogeneous oxidation

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    Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (p. 94-107).The immense chemical complexity of atmospheric organic particulate matter ("aerosol") has left the general field of condensed-phase atmospheric organic chemistry relatively under-developed when compared with either gas-phase chemistry or the formation of inorganic compounds. In this work, we endeavor to improve the general understanding of the narrow class of oxidation reactions that occur at the interface between the particle surface and the gas-phase. The heterogeneous oxidation of pure erythritol (C4H1 00 4 ) and levoglucosan (C6H1 00 5) particles by hydroxyl radical (OH) was studied first in order to evaluate the effects of atmospheric aging on the mass and chemical composition of atmospheric organic aerosol, particularly that resembling fresh secondary organic aerosol (SOA) and biomass-burning organic aerosol (BBOA). In contrast to what is generally observed for the heterogeneous oxidation of reduced organics, substantial volatilization is observed in both systems. As a continuation of the heterogeneous oxidation experiments, we also measure the kinetics and products of the aging of highly oxidized organic aerosol, in which submicron particles composed of model oxidized organics -- 1,2,3,4-butanetetracarboxylic acid (C8H100 8), citric acid (C6 H8 0 7), tartaric acid (C4H6 0 6 ), and Suwannee River fulvic acid -- were oxidized by gas-phase OH in the same flow reactor, and the masses and elemental composition of the particles were monitored as a function of OH exposure. In contrast to studies of the less-oxidized model systems, particle mass did not decrease significantly with heterogeneous oxidation, although substantial chemical transformations were observed and characterized. Lastly, the immense complexity inherent in the formation of SOA -- due primarily to the large number of oxidation steps and reaction pathways involved -- has limited the detailed understanding of its underlying chemistry. In order to simplify this inherent complexity, we give over the last portion of this thesis to a novel technique for the formation of SOA through the photolysis of gas-phase alkyl iodides, which generates organic peroxy radicals of known structure. In contrast to standard OH-initiated oxidation experiments, photolytically initiated oxidation forms a limited number of products via a single reactive step. The system in which the photolytic SOA is formed is also repurposed as a generator of organic aerosol for input into a secondary reaction chamber, where the organic particles undergo additional aging by the heterogeneous oxidation mechanism already discussed. Particles exiting this reactor are observed to have become more dramatically oxidized than comparable systems containing SOA formed by gas-phase alkanes undergoing "normal" photo-oxidation by OH, suggesting simultaneously the utility of gas-phase precursor photolysis as an effective experimental platform for studying directly the chemistry involved in atmospheric aerosol formation and also the possibility that heterogeneous processes may play a more significant role in the atmosphere than what is predicted from chamber experiments. Consideration is given for the application of these results to larger-scale experiments, models, and conceptual frameworks.by Sean Herbert Kessler.Ph.D

    An On-Line Survey Process for Assessing Impact of an Email-Delivered Pest Advisory

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    IPM specialists simplified the entry, collection, editing, and distribution of pest alerts by creating a new Web site, the Virginia Ag Pest Advisory. A simple on-line survey was used to assess the usefulness of the advisory. The on-line survey was low-cost and required less effort than conventional surveys. Such a system provides feedback from users, which can be used to improve Extension programs and generates results to be used in reporting impact data

    Designing and engineering evolutionary robust genetic circuits

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    <p>Abstract</p> <p>Background</p> <p>One problem with engineered genetic circuits in synthetic microbes is their stability over evolutionary time in the absence of selective pressure. Since design of a selective environment for maintaining function of a circuit will be unique to every circuit, general design principles are needed for engineering evolutionary robust circuits that permit the long-term study or applied use of synthetic circuits.</p> <p>Results</p> <p>We first measured the stability of two BioBrick-assembled genetic circuits propagated in <it>Escherichia coli </it>over multiple generations and the mutations that caused their loss-of-function. The first circuit, T9002, loses function in less than 20 generations and the mutation that repeatedly causes its loss-of-function is a deletion between two homologous transcriptional terminators. To measure the effect between transcriptional terminator homology levels and evolutionary stability, we re-engineered six versions of T9002 with a different transcriptional terminator at the end of the circuit. When there is no homology between terminators, the evolutionary half-life of this circuit is significantly improved over 2-fold and is independent of the expression level. Removing homology between terminators and decreasing expression level 4-fold increases the evolutionary half-life over 17-fold. The second circuit, I7101, loses function in less than 50 generations due to a deletion between repeated operator sequences in the promoter. This circuit was re-engineered with different promoters from a promoter library and using a kanamycin resistance gene (<it>kanR</it>) within the circuit to put a selective pressure on the promoter. The evolutionary stability dynamics and loss-of-function mutations in all these circuits are described. We also found that on average, evolutionary half-life exponentially decreases with increasing expression levels.</p> <p>Conclusions</p> <p>A wide variety of loss-of-function mutations are observed in BioBrick-assembled genetic circuits including point mutations, small insertions and deletions, large deletions, and insertion sequence (IS) element insertions that often occur in the scar sequence between parts. Promoter mutations are selected for more than any other biological part. Genetic circuits can be re-engineered to be more evolutionary robust with a few simple design principles: high expression of genetic circuits comes with the cost of low evolutionary stability, avoid repeated sequences, and the use of inducible promoters increases stability. Inclusion of an antibiotic resistance gene within the circuit does not ensure evolutionary stability.</p

    Secure Arcade: A Gamified Defense Against Cyber Attacks

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    In modernity, we continually receive increasingly intricate technologies that allow us to increase our lives convenience and efficiency. Our technology, particularly technology available over the internet, is advancing at unprecedented speed. However, this speed of advancement allows those behind malicious attacks to have an increasingly easier time taking advantage of those who know little about computer security. Unfortunately, education in the computer security field is generally limited only to tertiary education. This research addresses this problem through a gamified web-based application that drives users to reach learning goals to help them become more vigilant internet users: 1. Learn and memorize general computer security terminology, 2. Become familiar with basic cryptography concepts, 3. Learn to recognize potential phishing scams via email quickly, and 4. Learn common attacks on servers and how to deal with them
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