4,886 research outputs found
The Double Charge of External Debt Servicing
The approach proposed in the paper is rather unconventional, yet very rigorous. The paper set the proof of the iniquitous double charge laid on indebted countries when paying interest on their external debt.External Debt Servicing
Diffusion and infrared properties of molecules in ice mantles
Within dense molecular clouds the formation of frozen icy mantles on interstellar dust grains is thought to be the result of various growth conditions. The molecules, which make up the ice mantles are probably completely mixed. To study the physical properties of such ice mixtures the experiments were performed on the evaporation processes and on the spectroscopic properties of CO, CO2, and CH4 in water rich ices. The decrease in concentration of volatile molecules in ice samples deposited at 10 K and subsequently heated is found to occur essentially in two steps. The first one, corresponding to an evaporation of part of the volatile molecules, starts at about 25 K for CO, 32 K for CH4, and 70 K for CO2. During the crystallization of H2O ice at temperatures greater than 120 K a second evaporation occurs leading to the complete disappearance of the volatile molecules in the solid phase. The main astrophysical implications of the diffusion and spectroscopic behaviors are presented. The possible effects of a heating source on the fraction of volatile molecules, such as CO trapped in grain mantles, are discussed
Emulsions stabilised by whey protein microgel particles: Towards food-grade Pickering emulsions
We have investigated a new class of food-grade particles, whey protein microgels, as stabilisers of triglyceride-water emulsions. The sub-micron particles stabilized oil-in-water emulsions at all pH with and without salt. All emulsions creamed but exhibited exceptional resistance to coalescence. Clear correlations exist between the properties of the microgels in aqueous dispersion and the resulting emulsion characteristics. For conditions in which the particles were uncharged, fluid emulsions with relatively large drops were stabilised, whereas emulsions stabilized by charged particles contained smaller flocculated drops. A combination of optical microscopy of the drops and spectrophotometry of the resolved aqueous phase allowed us to estimate the interfacial adsorption densities of the particles using the phenomenon of limited coalescence. We deduce two classes of particle arrangement. Complete adsorption of the particles was obtained when they were neutral or when their charges were screened by salt resulting in at least one particle monolayer at the interface. By contrast, only around 50% of the particles adsorbed when they were charged with emulsion drops being covered by less than half a monolayer. These findings were supported by direct visualization of drop interfaces using cryo-scanning electron microscopy. Uncharged particles were highly aggregated and formed a continuous 2-D network at the interface. Otherwise particles organized as individual aggregates separated by particle-free regions. In this case, we suggest that some particles spread at the interface leading to the formation of a continuous protein membrane. Charged particles displayed the ability to bridge opposing interfaces of neighbouring drops to form dense particle disks protecting drops against coalescence; this is the main reason for the flocculation and stability of emulsions containing sparsely covered drops. © 2014 the Partner Organisations
New insights in the photochemistry of grain mantles: The identification of the 4.62 and 6.87 micron bands
The mid-IR spectral region of molecular clouds is known to show the fingerprints of molecules frozen in the icy mantles of the interstellar grains. To study the complex chemical and physical interactions on the ice mantles accreted on grains in molecular clouds numerous UV irradiation and diffusion experiments were performed. The irradiation of binary ices was studied. Using isotopic labelling on NH3/CO and NH3/O2 ices numerous compounds were identified, of which OCN(-), NO2(-), NO3(-), and NH4(+) ions reveal a new type of chemical reactions. It appeared that these compounds were formed by proton transfer reactions induced by the interaction between an acid (HNCO, HNO2, HNO3) and a base (NH3) through a hydrogen bond. This mechanism was confirmed by a study of photolyzed diluted argon mixtures. The main astrophysically relevant data from the overall study are presented. The 4.62 micron band in W33A can be reproduced with NH3/CO containing irradiated ices and was identified with OCN(-). The 6.87 micron band in W33A and other photostellar objects is reproduced with NH3/O2 containing ices and is identified with NH4(+)
Characterizing contextual equivalence in calculi with passivation
AbstractWe study the problem of characterizing contextual equivalence in higher-order languages with passivation. To overcome the difficulties arising in the proof of congruence of candidate bisimilarities, we introduce a new form of labeled transition semantics together with its associated notion of bisimulation, which we call complementary semantics. Complementary semantics allows to apply the well-known Howeʼs method for proving the congruence of bisimilarities in a higher-order setting, even in the presence of an early form of bisimulation. We use complementary semantics to provide a coinductive characterization of contextual equivalence in the HOπP calculus, an extension of the higher-order π-calculus with passivation, obtaining the first result of this kind. We then study the problem of defining a more effective variant of bisimilarity that still characterizes contextual equivalence, along the lines of Sangiorgiʼs notion of normal bisimilarity. We provide partial results on this difficult problem: we show that a large class of test processes cannot be used to derive a normal bisimilarity in HOπP, but we show that a form of normal bisimilarity can be defined for HOπP without restriction
Sequestration of ethane in the cryovolcanic subsurface of Titan
Saturn's largest satellite, Titan, has a thick atmosphere dominated by
nitrogen and methane. The dense orange-brown smog hiding the satellite's
surface is produced by photochemical reactions of methane, nitrogen and their
dissociation products with solar ultraviolet, which lead primarily to the
formation of ethane and heavier hydrocarbons. In the years prior to the
exploration of Titan's surface by the Cassini-Huygens spacecraft, the
production and condensation of ethane was expected to have formed a
satellite-wide ocean one kilometer in depth, assuming that it was generated
over the Solar system's lifetime. However, Cassini-Huygens observations failed
to find any evidence of such an ocean. Here we describe the main cause of the
ethane deficiency on Titan: cryovolcanic lavas regularly cover its surface,
leading to the percolation of the liquid hydrocarbons through this porous
material and its accumulation in subsurface layers built up during successive
methane outgassing events. The liquid stored in the pores may, combined with
the ice layers, form a stable ethane-rich clathrate reservoir, potentially
isolated from the surface. Even with a low open porosity of 10% for the
subsurface layers, a cryovolcanic icy crust less than 2300 m thick is required
to bury all the liquid hydrocarbons generated over the Solar system's lifetime.Comment: accepted for publication in Astrophysical Journa
Can Conservation and Profits Co-Exist?: The Case of Lion Hunting
Resource /Energy Economics and Policy,
Biomechanical surrogate modelling using stabilized vectorial greedy kernel methods
Greedy kernel approximation algorithms are successful techniques for sparse
and accurate data-based modelling and function approximation. Based on a recent
idea of stabilization of such algorithms in the scalar output case, we here
consider the vectorial extension built on VKOGA. We introduce the so called
-restricted VKOGA, comment on analytical properties and present
numerical evaluation on data from a clinically relevant application, the
modelling of the human spine. The experiments show that the new stabilized
algorithms result in improved accuracy and stability over the non-stabilized
algorithms
Detection of Mucosal Human Papillomavirus Types 6/11 in Cutaneous Lesions from Transplant Recipients
Transplant recipients develop multiple cutaneous lesions. We have identified human papillomavirus (HPV) DNA in these lesions using three different techniques, namely polymerase chain reaction (PCR), in situ hybridization, and Southern blotting. By PCR, HPV DNA was detected in 43 of 62 samples: warts, actinic keratoses, Bowen's disease, and squamous cell carcinomas. Surprisingly, HPV 6/11, usually associated with mucosa, were frequently found in benign, premalignant, and malignant cutaneous lesions (30/43 cases). Some of these biopsies were simultaneously tested by in situ hybridization and/or Southern blotting. By in situ hybridization, HPV 6/11 were identified in two warts and one squamous cell carcinoma among 29 tissue specimens tested. Of the three samples examined by Southern blotting, HPV 6/11 were detected in one squamous cell carcinoma. In patients from a control population cutaneous biopsies did not exhibit HPV types 6/11 except in Bowen's disease; HPV types 1 or 2 were mainly found in benign warts. These findings suggest that in transplant recipients, HPV can lose their specificity towards mucosa or cutaneous epithelium. The significance of the presence of HPV 6/11 in skin lesions remains unknown
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