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 $T_c$. 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 $T_c$, 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