1,888 research outputs found

    High area-to-mass ratio hybrid propulsion Earth to Moon transfers

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    This paper examines the design of transfers that are useful to micro or nano spacecraft with high area-to-mass ratio, propelled by a simple propulsion engine (such as chemical with a specifc impulse ca. 100 to 300 s or arcjet/resistojet), and possessing relatively small solar reflective panels to provide power and a small thrust due to solar radiation pressure. This type of transfer is becoming of greater interest as advances in structures, materials, and small spacecraft design & propulsion are made. Such a hybrid design especially offers possibilities of cheaply exploring the Moon using multiple vehicles. With this small hybrid design, interior transfers in the circular restricted 3-body problem between the pair of primary and secondary masses (e.g. the Earth and Moon) are attempted using solar radiation pressure and multiple small impulses. The source of the outside solar radiation pressure is modeled using an external source rotating about – and in the plane of – the co-rotating set of primary and secondary masses. Starting from a GTO about the primary mass a basic optimization method of sequences of manoeuvres is used to achieve the transfer, where the segments are patched together using ideally small maneuvers. The spacecraft coasting arc is controlled by a number of locally optimal control laws to optimize performance while minimizing computational cost. The spacecraft hops onto a stable invariant manifold leading to the system’s Lagrange L1 point after successive small maneuvers and coasting arcs. Following connection with a manifold and subsequent arrival at a periodic orbit at L1, temporary or permanent capture around the Moon can be performed using the remaining resources at hand

    A monoclonal antibody recognizing very late activation antigen-4 inhibits eosinophil accumulation in vivo.

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    Using an in vivo test system, the role of the β1 integrin very late activation antigen-4 (VLA-4) in eosinophil accumulation in allergic and nonallergic inflammatory reactions was investigated. Eosinophil infiltration and edema formation were measured as the local accumulation of intravenously injected 111In-labeled eosinophils and 125I-human serum albumin. The inflammatory reactions investigated were a passive cutaneous anaphylaxis (PCA) reaction and responses elicited by intradermal soluble inflammatory mediators (platelet-activating factor, leukotriene B4, C5a des Arg), arachidonic acid, and zymosan particles. The in vitro pretreatment of 111In-eosinophils with the anti-VLA-4 monoclonal antibody (mAb) HP1/2, which crossreacts with guinea pig eosinophils, suppressed eosinophil accumulation in all the inflammatory reactions investigated. Eosinophil accumulation was inhibited to the same extent when mAb HP1/2 was administered intravenously. It is interesting that HP1/2 had no effect on stimulated edema formation. These results suggest a role for VLA-4 in eosinophil accumulation in vivo and indicate a dissociation between the inflammatory events of eosinophil accumulation and edema formation

    Searching for interacting QTL in related populations of an outbreeding species

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    Many important crop species are outbreeding. In outbreeding species the search for genes affecting traits is complicated by the fact that in a single cross up to four alleles may be present at each locus. This paper is concerned with the search for interacting quantitative trait loci (QTL) in populations which have been obtained by crossing a number of parents. It will be assumed that the parents are unrelated, but the methods can be extended easily to allow a pedigree structure. The approach has two goals: (1) finding QTL that are interacting with other loci and also loci which behave additively; (2) finding parents which segregate at two or more interacting QTL. Large populations obtained by crossing these parents can be used to study interactions in detail. QTL analysis is carried out by means of regression on predictions of QTL genotypes

    Wahrhaftiger Glaube

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    Plädoyer für einen kritischen Agnostizismus.\ud In dem philosophischen Essay wird versucht, von erkenntnistheoretischen Überlegungen (radikale Konstruktivisten, Popper, Descartes, Putnam u. a.) ausgehend einen Bogen zu ethischen und gesellschaftspolitischen Positionen zu spannen

    Collective Intentionality and Individual Action

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    People often do things together and form groups in order to get things done that they cannot do alone. In short they form a collectivity of some kind or a group, for short. But if we consider a group on the one hand and the persons that constitute the group on the other hand, how does it happen that these persons work together and finish a common task with a common goal? In the philosophy of action this problem is often solved by saying that there is a kind of collective intention that the group members have in mind and that guides their actions. Does such a collective intention really exist? In this article I’ll show that the answer is “no”. In order to substantiate my view I’ll discuss the approaches of Bratman, Gilbert and Searle on collective intention. I’ll put forward four kinds of criticism that undermine the idea of collective intention. They apply mainly to Bratman and Gilbert. First, it is basically difficult to mark off smaller groups from bigger unities. Second, most groups change in membership composition over time. Third, as a rule, on the one hand groups are internally structured and on the other hand they belong to a larger structure. It makes that generally it cannot be a collective intention that moves the actions of the members of a group. Fourth, conversely, most individual actions cannot be performed without the existence of a wider context of agents who support these actions and make them possible. My critique on Searle mainly involves that in his approach his idea of collective intention is superfluous and that he is not radical enough in his idea that collective action is based on coordinated individual intentions and actions. However, it is a good starting point for showing how collective action actually functions, especially when combined with Giddens’s structuration theory. Every agent in a group executes his or her own individual intentions, relying on what the group offers to this agent and asks from him or her. In this way individual actions of the members of a group are coordinated and it makes that the group can function and that its goals can be performed. And in this way the group is produced and reproduced by fitting individual actions together. An individual agent who belongs to a group only needs to know what s/he wants and what s/he has to do in the group, even if s/he has no knowledge of the intentions and commitments of the other members. Then he or she can do things together with others in a group without supposing that there is something like a collective intention

    Functional Genomics Profiling of Bladder Urothelial Carcinoma MicroRNAome as a Potential Biomarker.

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    Though bladder urothelial carcinoma is the most common form of bladder cancer, advances in its diagnosis and treatment have been modest in the past few decades. To evaluate miRNAs as putative disease markers for bladder urothelial carcinoma, this study develops a process to identify dysregulated miRNAs in cancer patients and potentially stratify patients based on the association of their microRNAome phenotype to genomic alterations. Using RNA sequencing data for 409 patients from the Cancer Genome Atlas, we examined miRNA differential expression between cancer and normal tissues and associated differentially expressed miRNAs with patient survival and clinical variables. We then correlated miRNA expressions with genomic alterations using the Wilcoxon test and REVEALER. We found a panel of six miRNAs dysregulated in bladder cancer and exhibited correlations to patient survival. We also performed differential expression analysis and clinical variable correlations to identify miRNAs associated with tobacco smoking, the most important risk factor for bladder cancer. Two miRNAs, miR-323a and miR-431, were differentially expressed in smoking patients compared to nonsmoking patients and were associated with primary tumor size. Functional studies of these miRNAs and the genomic features we identified for potential stratification may reveal underlying mechanisms of bladder cancer carcinogenesis and further diagnosis and treatment methods for urothelial bladder carcinoma

    Equity-Efficiency Optimizing Resource Allocation: The Role of Time Preferences in a Repeated Irrigation Game

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    We study repeated water allocation decisions among small scale irrigation users in Tanzania. In a treatment replicating water scarcity conditions, convexities in production make that substantial efficiency gains can be obtained by deviating from equal sharing, leading to an equity–efficiency trade-off. In a repeated game setting, it becomes possible to reconcile efficiency with equity by rotating the person who receives the largest share, but such a strategy requires a longer run perspective. Correlating experimental data from an irrigation game with individual time preference data, we find that less patient irrigators are less likely to use a rotation strategy
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