16,856 research outputs found
Liquid bridging of cylindrical colloids in near-critical solvents
Within mean field theory, we investigate the bridging transition between a
pair of parallel cylindrical colloids immersed in a binary liquid mixture as a
solvent which is close to its critical consolute point . We determine the
universal scaling functions of the effective potential and of the force between
the colloids. For a solvent which is at the critical concentration and close to
, we find that the critical Casimir force is the dominant interaction at
close separations. This agrees very well with the corresponding Derjaguin
approximation for the effective interaction between the two cylinders, while
capillary forces originating from the extension of the liquid bridge turn out
to be more important at large separations. In addition, we are able to infer
from the wetting characteristics of the individual colloids the first-order
transition of the liquid bridge connecting two colloidal particles to the
ruptured state. While specific to cylindrical colloids, the results presented
here provide also an outline for identifying critical Casimir forces acting on
bridged colloidal particles as such, and for analyzing the bridging transition
between them.Comment: 23 pages, 12 figure
Dimensionality of Local Minimizers of the Interaction Energy
In this work we consider local minimizers (in the topology of transport
distances) of the interaction energy associated to a repulsive-attractive
potential. We show how the imensionality of the support of local minimizers is
related to the repulsive strength of the potential at the origin.Comment: 27 page
Nonlocal interactions by repulsive-attractive potentials: radial ins/stability
In this paper, we investigate nonlocal interaction equations with
repulsive-attractive radial potentials. Such equations describe the evolution
of a continuum density of particles in which they repulse each other in the
short range and attract each other in the long range. We prove that under some
conditions on the potential, radially symmetric solutions converge
exponentially fast in some transport distance toward a spherical shell
stationary state. Otherwise we prove that it is not possible for a radially
symmetric solution to converge weakly toward the spherical shell stationary
state. We also investigate under which condition it is possible for a
non-radially symmetric solution to converge toward a singular stationary state
supported on a general hypersurface. Finally we provide a detailed analysis of
the specific case of the repulsive-attractive power law potential as well as
numerical results. We point out the the conditions of radial ins/stability are
sharp.Comment: 42 pages, 7 figure
Performance Assessment of Six Public Health Programs in Katsina State, Nigeria
This research aimed to evaluate the performance of six ongoing public health programs through core performance indicators in Katsina State, Nigeria. The healthcare delivery in Africa is mostly program-based. This requires that such programs need to be evaluated which may in turn help to identify any existing gaps towards the improvement of patients' access and coverage to their given service. We identified all active health facilities where our programs on malaria, Routine Immunization (RI), Family Planning (FP), Tuberculosis and Leprosy (TBL), HIV/AIDS, and Free Medicare (FMC) were being carried out. After that, a representative sample was derived to obtain data regarding five key performance indicators by using a Logistics Indicators Assessment Tool. Of 1,718 facilities, a total of 983 (57.22%) were visited, In other words, by assuming a normal distribution; each facility expectedly covers only 3,371 individuals. All programs provided different and diverse results on each indicator; however, the most obvious challenge was in the stock-out and demand vs. receipt of required medications. These are particularly for malaria, FMC, FP, and HIV. For instance, the stock-out lasted 222 days for malaria and 135 days for FP. Despite this, none of the programs had a lower than gold-standard near-term availability of required products. Program-based healthcare delivery is inadequate and ineffective unless the local system gets simultaneously developed. If required medications are not becoming available, optimal access, coverage, and benefits cannot be expected to be obtained. Clearly, Nigeria experiences a push system of meeting term supplies. Nigeria needs to strengthen its pharmaceutical system
Hidden Convexity in Partially Separable Optimization
The paper identifies classes of nonconvex optimization problems whose convex relaxations have optimal solutions which at the same time are global optimal solutions of the original nonconvex problems. Such a hidden convexity property was so far limited to quadratically constrained quadratic problems with one or two constraints. We extend it here to problems with some partial separable structure. Among other things, the new hidden convexity results open up the possibility to solve multi-stage robust optimization problems using certain nonlinear decision rules.convex relaxation of nonconvex problems;hidden convexity;partially separable functions;robust optimization
Modelling the exposure to Cronobacter sakazakii by consumption of a cocoa-milk-based beverage processed by pulsed electric fields
peer-reviewedM.C. Pina-Pérez is grateful to CSIC for providing a DOCTOR contract linked to the INNPACTO project IPT-2011-1724-060000. This study was carried out with funds from BISOSTAD project PSE-060000-2009-003, Generalitat Valenciana I+D+I emergent research groups GV/2010/064 and CYCIT project AGL2010-22206-C02-01.Infants’ exposure (Nf ) to Cronobacter sakazakii via the consumption of infant-rich-inpolyphenols
cocoa-milk-based beverages (CCX-M) treated with high-intensity pulsed
electric fields (PEF) was evaluated. Monte Carlo simulation enabled the prediction
of the variability in C. sakazakii load in beverages at the time of consumption to be
estimated. Different scenarios (initial contamination levels; PEF treatment conditions;
and time-temperature combinations of CCX-M beverages storage after treatment) were
simulated. Cocoa addition and PEF treatment resulted in the most influential input
factors to control bacterial final load. Cronobacter spp. exposure risk was reduced by
a maximum of 100 times at 95% of iterations due to addition of cocoa at 5 g/100 mL,
corresponding to scenario 3 (PEF: 15 kV/cm–3,000 μs; storage 120 h at 8 °C). Moreover,
the probability of illness for a healthy population was reduced from 2.15 × 10-8,
in the baseline scenario, to 4.78 × 10-10 due to cocoa addition and application of
15 kV/cm–3,000 μs PEF treatment.BISOSTAD projec
A Study of the Formation of Single- and Double-Walled Carbon Nanotubes by a CVD Method
The reduction in H2/CH4 atmosphere of aluminum-iron oxides produces metal particles small enough to catalyze the formation of single-walled carbon nanotubes. Several experiments have been made using the same temperature profile and changing only the maximum temperature (800-1070 °C). Characterizations of the catalyst materials are performed using notably 57Fe Mo¨ssbauer spectroscopy. Electron microscopy and a macroscopical method are used to characterize the nanotubes. The nature of the iron species (Fe3+, R-Fe, ç-Fe-C, Fe3C) is correlated to their location in the material. The nature of the particles responsible for the high-temperature formation of the nanotubes is probably an Fe-C alloy which is, however, found as Fe3C by postreaction analysis. Increasing the reduction temperature increases the reduction yield and thus favors the formation of surface-metal particles, thus producing more nanotubes. The obtained carbon nanotubes are mostly single-walled and double-walled with an average diameter close to 2.5 nm. Several formation mechanisms are thought to be active. In particular, it is shown that the second wall can grow inside the first one but that subsequent ones are formed outside. It is also possible that under given experimental conditions, the smallest (<2 nm) catalyst particles preferentially produce double-walled rather than single-walled carbon nanotubes
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