8,917 research outputs found
Multilateralism and Democracy: A Dissent Regarding Keohane, Macedo, and Moravcsik
In an article printed last year in International Organization, Keohane, Macedo, and Moravcsik argued that multilateral organizations (MLO) could actually be good for democracy. We argue that KMM discount the prospect that MLO influence can be detrimental to democracies not because MLOs are “distant, elitist, and technocratic” but precisely because MLOs are highly political. International organizations have much to offer in improving the welfare of citizens and facilitating coordinations among states. They are not likely to improve procedural functions of democracies without a cost that itself is problematic for democracy
Membrane fusion of secretory vesicles and liposomes Two different types of fusion
Secretory vesicles isolated from adrenal medulla were found to fuse in vitro in response to incubation with Ca2+. Intervesicular fusion was detected by electron microscopy and was indicated by the appearance of twinned vesicles in freeze-fractured suspensions of vesicles and in thin-sectioned pellet. Two types of fusion could be distinguished: Type I, occurring between 10−7 M and 10−4 M Ca2+, was specific for Ca2+, was inhibited by other divalent cations and was abolished by pretreatment of vesicles with glutaraldehyde, neuraminidase or trypsin. Fusion type I was linear with temperature. A second type of intervesicular fusion was elicited by Ca2+ in concentrations higher than 2.5 mM and was morphologically characterized by multiple fusions of secretory vesicles. This type of fusion was found to be similar to fusion of liposomes prepared from the membrane lipids of adrenal medullary secretory vesicles: Ca2+ could be replaced by other divalent cations, the effect of different divalent cations was additive and pretreatments attacking membrane proteins were ineffective. Fusion type II of intact secretory vesicles as well as liposome fusion was discontinuous with temperature. Liposome fusion could be detected within 35 ms and persisted for 180 min. Using liposomes containing defined Ca2+ concentrations we have not found a major influence of Ca2+ asymmetry on fusion. Incorporation of the ganglioside GM3, which is present in the membranes of intact adrenal medullary secretory vesicles did not change the properties of liposomes fusion. Using a Ca2+-selective electrode we have identified in secretory vesicle membranes both high affinity binding sites for Ca2+ (Kd = 1.6 · 10−6M) and low affinity sites (Kd = 1.2 · 10−4M)
Several types of types in programming languages
Types are an important part of any modern programming language, but we often
forget that the concept of type we understand nowadays is not the same it was
perceived in the sixties. Moreover, we conflate the concept of "type" in
programming languages with the concept of the same name in mathematical logic,
an identification that is only the result of the convergence of two different
paths, which started apart with different aims. The paper will present several
remarks (some historical, some of more conceptual character) on the subject, as
a basis for a further investigation. The thesis we will argue is that there are
three different characters at play in programming languages, all of them now
called types: the technical concept used in language design to guide
implementation; the general abstraction mechanism used as a modelling tool; the
classifying tool inherited from mathematical logic. We will suggest three
possible dates ad quem for their presence in the programming language
literature, suggesting that the emergence of the concept of type in computer
science is relatively independent from the logical tradition, until the
Curry-Howard isomorphism will make an explicit bridge between them.Comment: History and Philosophy of Computing, HAPOC 2015. To appear in LNC
Fusion of isolated myoblast plasma membranes
Fusion of plasma membranes isolated from myoblasts grown in culture has been investigated.
1. 1. Membrane fusion was specifically dependent on Ca2+ at physiological concentrations. However, at higher concentrations of cations, fusion could be triggered not only by Ca2+, but by Mg2+ and Sr2+ as well.
2. 2. The amount of fusion was directly proportional to temperature.
3. 3. Fusion was found to depend on the state of maturation of the myoblast membranes.
4. 4. Experiments with chemically and enzymatically modified membranes and with membranes derived from myoblasts grown in the presence of inhibitors of protein biosynthesis suggest the participation of proteinaceous membrane components in the fusion mechanism
The Aqueous Phase Yield Of Alkyl Nitrates From Roo+No: Implications For Photochemical Production In Seawater
Alkyl nitrates have been observed in remote oceanic regions of the troposphere and in the surface ocean. The mechanism for their production in the oceans is not known. A likely source is the reaction of ROO + NO (where R is an alkyl group). Steady-state laboratory experiments show that alkyl nitrates are produced in the aqueous phase via this reaction, with branching ratios of 0.23 +/- 0.04, 0.67 +/- 0.03, and 0.71 +/- 0.04 for methyl, ethyl, and propyl nitrate respectively. The branching ratios in aqueous solution are significantly higher than in the gas phase. Irradiation of surface seawaters yield rates of alkyl nitrate production on the order of 10(-18) mol cm(-3) s(-1), suggesting that the reaction of ROO and NO is an important source of alkyl nitrates in seawater
Guiding 3D U-nets with signed distance fields for creating 3D models from images
Morphological analysis of the left atrial appendage is an important tool to
assess risk of ischemic stroke. Most deep learning approaches for 3D
segmentation is guided by binary labelmaps, which results in voxelized
segmentations unsuitable for morphological analysis. We propose to use signed
distance fields to guide a deep network towards morphologically consistent 3D
models. The proposed strategy is evaluated on a synthetic dataset of simple
geometries, as well as a set of cardiac computed tomography images containing
the left atrial appendage. The proposed method produces smooth surfaces with a
closer resemblance to the true surface in terms of segmentation overlap and
surface distance.Comment: MIDL 2019 [arXiv:1907.08612
Mapping the Wigner distribution function of the Morse oscillator into a semi-classical distribution function
The mapping of the Wigner distribution function (WDF) for a given bound-state
onto a semiclassical distribution function (SDF) satisfying the Liouville
equation introduced previously by us is applied to the ground state of the
Morse oscillator. Here we give results showing that the SDF gets closer to the
corresponding WDF as the number of levels of the Morse oscillator increases. We
find that for a Morse oscillator with one level only, the agreement between the
WDF and the mapped SDF is very poor but for a Morse oscillator of ten levels it
becomes satisfactory.Comment: Revtex, 27 pages including 13 eps figure
Occurrence and diversity of Xanthomonas campestris pv. campestris in vegetable brassica fields in Nepal
Black rot caused by Xanthomonas campestris pv. campestris was found in 28 sampled cabbage fields in five major cabbage-growing districts in Nepal in 2001 and in four cauliflower fields in two districts and a leaf mustard seed bed in 2003. Pathogenic X. campestris pv. campestris strains were obtained from 39 cabbage plants, 4 cauliflower plants, and 1 leaf mustard plant with typical lesions. Repetitive DNA polymerase chain reaction-based fingerprinting (rep-PCR) using repetitive extragenic palindromic, enterobacterial repetitive intergenic consensus, and BOX primers was used to assess the genetic diversity. Strains were also race typed using a differential series of Brassica spp. Cabbage strains belonged to five races (races 1, 4, 5, 6, and 7), with races 4, 1, and 6 the most common. All cauliflower strains were race 4 and the leaf mustard strain was race 6. A dendrogram derived from the combined rep-PCR profiles showed that the Nepalese X. campestris pv. campestris strains clustered separately from other Xanthomonas spp. and pathovars. Race 1 strains clustered together and strains of races 4, 5, and 6 were each split into at least two clusters. The presence of different races and the genetic variability of the pathogen should be considered when resistant cultivars are bred and introduced into regions in Nepal to control black rot of brassicas
Formal solutions of stargenvalue equations
The formal solution of a general stargenvalue equation is presented, its
properties studied and a geometrical interpretation given in terms of
star-hypersurfaces in quantum phase space. Our approach deals with discrete and
continuous spectra in a unified fashion and includes a systematic treatment of
non-diagonal stargenfunctions. The formalism is used to obtain a complete
formal solution of Wigner quantum mechanics in the Heisenberg picture and to
write a general formula for the stargenfunctions of Hamiltonians quadratic in
the phase space variables in arbitrary dimension. A variety of systems is then
used to illustrate the former results.Comment: 29 pages. Revised version, to appear in Annals of Physic
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