Gravitational instability in suspension flow

The gravity-driven flow of non-neutrally buoyant suspensions is shown to be unstable to spanwise perturbations when the shearing motion generates a density profile that increases with height. The instability is simply due to having heavier material over light – a Rayleigh–Taylor-like instability. The wavelength of the fastest growing disturbance is on the order of the thickness of the suspension layer. The parameters important to the problem are the angle of inclination of the layer relative to gravity, the relative density difference between the particles and the fluid, the ratio of the particle size to the thickness of the layer and the bulk volume fraction of particles. The instability is illustrated for a range of these parameters and shown to be most pronounced at intermediate values thereof. This instability mechanism may play an important role in pattern formation in multiphase flows

Remittance stability, cyclicality and stabilizing impact in developing countries

That remittances are a stable source of external finance seems to have become the received wisdom. In addition, many studies have found remittances to behave counter-cyclically, increasing during crises and times of hardship for the recipient countries. Are remittances reliable macroeconomic stabilizers? To answer this question, the present study examines the stability, cyclicality, and stabilizing impact of remittances in comparison with the same three features for other foreign-exchange inflows, namely foreign direct investment and official development aid. The analysis is performed at the country and regional levels rather than at the aggregate or global level (on which much of the received wisdom rests), because policymakers are concerned with the impact of remittances in their country rather than at the global level. The main findings for 1980-2007 are that in a majority of countries: i) official development aid is more stable than remittances, and remittances are more stable than foreign direct investment; ii) official development aid is counter-cyclical, while remittances are pro-cyclical, although less so than foreign direct investment; and iii) official development aid is stabilizing and remittances are destabilizing, although less so than foreign direct investment. The paper suggests that it is necessary to examine counter-cyclicality separately from the stabilizing impact, as the former does not seem to always imply the latter.Economic Conditions and Volatility,Remittances,Debt Markets,Economic Theory&Research,Emerging Markets

Examining Various Aspects of Zika Virus Dissemination in Aedes aegypti

South Texas is one of the few locations where Zika virus has been locally transmitted in the U.S. It has a climate which is distinct to other areas with autochthonous transmission, with extremely hot, dry summers and moderate winter temperatures. Studying mosquito transmission of Zika in a range of temperatures conditions replicating where virus transmission is occurring is essential in order to have a better understanding of transmission patterns. These factors were examined by infecting mosquitoes and monitoring the dissemination status through real-time PCR analysis. To further characterize dissemination of Zika virus within south Texas mosquitoes a time series immunohistochemical analysis was conducted. In this proof of concept experiment infected mosquitoes were fixed days post infection and processed for antibody staining before being imaged with a confocal microscope. More reliable experimental methodology will result in more accurate assessment of transmission risk and prediction of transmission of Zika virus transmission

Geodesic Universal Molecules

The first phase of TreeMaker, a well-known method for origami design, decomposes a planar polygon (the “paper”) into regions. If some region is not convex, TreeMaker indicates it with an error message and stops. Otherwise, a second phases is invoked which computes a crease pattern called a “universal molecule”. In this paper we introduce and study geodesic universal molecules, which also work with non-convex polygons and thus extend the applicability of the TreeMaker method. We characterize the family of disk-like surfaces, crease patterns and folded states produced by our generalized algorithm. They include non-convex polygons drawn on the surface of an intrinsically flat piecewise-linear surface which have self-overlap when laid open flat, as well as surfaces with negative curvature at a boundary vertex

Lang’s Universal Molecule Algorithm

Robert Lang’s Universal Molecule algorithm, a landmark in modern computational origami, is the main component of his widely used Tree Maker program for origami design. It computes a crease pattern of a convex polygonal region, starting with a compatible metric tree. Although it has been informally described in several publications, neither the full power nor the inherent limitations of the method are well understood. In this paper we introduce a rigorous mathematical formalism to relate the input metric tree, the output crease pattern and the folded uniaxial origami base produced by the Universal Molecule algorithm. We characterize the family of tree-like 3D shapes that are foldable from the computed crease patterns and give a correctness proof of the algorithm

Experimental pharmacological research regarding some new quinazolin-4-ones derivatives

A series of new compounds with quinazolin-4-one structure, synthesized by the Pharmaceutical Chemistry Department of the Faculty of Pharmacy of the University of Medicine and Pharmacy “Carol Davila” Bucharest, was studied. Five of them were selected, conventionally named S1, S2, S3, S4, S5, and investigated in terms of their potential influence on the central nervous system (CNS). For this purpose, the antidepressant effect was determined using the forced swimming test; the anxiolytic/ anxiogenic effect was determined using the suspended plus-shaped maze (Ugo Basile); the effect on the motor activity was determined using the Ugo Basile activity cage; and the potential analgesic effect was investigated using the hot plate test (Ugo Basile). Compounds S3 and S5 lowered the motor activity and showed an anxiolytic effect, while S1 and S2 proved to have antidepressant and analgesic effects. A good correlation between antidepressant and analgesic effects was observed, consistent with the fact that analgesic drugs, by increasing norepinephrine and serotonin levels in the pain inhibiting descendent pathways, can be used as co-analgesics in therapy

Impact of seeing and host galaxy into the analysis of photo-polarimetric microvariability in blazars : Case study of the nearby blazars 1ES 1959+650 and HB89 2201+044

Blazars, a type of Active Galactic Nuclei, present a particular orientation of their jets close to the line of sight. Their radiation is thus relativistically beamed, giving rise to extreme behaviors, specially strong variability on very short timescales (i.e., microvariability). Here we present simultaneous photometric and polarimetric observations of two relatively nearby blazars, 1ES 1959+650 and HB89 2201+044, that were obtained using the Calar Alto Faint Object Spectrograph mounted at the 2.2 m telescope in Calar Alto, Spain. An outstanding characteristic of these two blazars is the presence of well resolved host galaxies. This particular feature allows us to produce a study of their intrinsic polarization, a measurement of the polarization state of the galactic nucleus una ected by the host galaxy. To carry out this work, we computed photometric fluxes from which we calculated the degree and orientation of the blazars polarization. Then, we analyzed the depolarizing e ect introduced by the host galaxy with the main goal to recover the intrinsic polarization of the galactic nucleus, carefully taking into consideration the spurious polarimetric variability introduced by changes in seeing along the observing nights. We find that the two blazars do not present intra-night photo-polarimetric variability, although we do detect a significant inter-night variability. Comparing polarimetric values before and after accounting for the host galaxies, we observe a significant di erence in the polarization degree of about 1% in the case of 1ES 1959+650, and 0.3% in the case of HB89 2201+044, thus evidencing the non-negligible impact introduced by the host galaxies. We note that this host galaxy e ect depends on the waveband, and varies with changing seeing conditions, so it should be particularly considered when studying frequency-dependent polarization in blazars.Facultad de Ciencias Astronómicas y Geofísicas (FCAG