Theory of band broadening during cycling temperature capillary electrophoresis

A two-state transport model is presented for cycling temperature CE. In this high-throughput method of mutation detection, the temperature oscillates in time, causing the DNA to periodically transit between an annealed state and a partially melted (denatured) state. The change in state alters the electrophoretic mobility, and the presence of a mutation changes the temperature dependence of the denaturing/annealing kinetics. Asymptotic formulae for the mean velocity and effective diffusivity (dispersivity) of the DNA are computed by a multiple-time scales scheme in the limit where the DNA have experienced many temperature cycles before reaching the detector. Explicit analytical results are presented for the case where the temperature cycle consists of one interval with irreversible annealing, followed by a second interval with an infinitely fast, irreversible denaturation. The lag in the annealing leads to a reduction in the mean velocity and an enhanced dispersion compared to the idealized case where the DNA respond instantaneously to the changes in temperature, with the dispersion scaling quadratically with the electric field. The predicted plate height scales linearly with the electric field, and the optimal separation resolution is predicted for moderate values of the cycle frequency that allow the DNA to relax during each temperature oscillation.     

A memetic algorithm for the Multi Trip Vehicle Routing Problem

We consider the Multi Trip Vehicle Routing Problem, in which a set of geographically scattered customers have to be served by a fleet of vehicles. Each vehicle can perform several trips during the working day. The objective is to minimize the total travel time while respecting temporal and capacity constraints.     

Electrical and magnetic properties of La0.67Ba0.33Mn1−x (Me) x O3 perovskite manganites: case of manganese substituted by trivalent (Me = Cr) and tetravalent (Me = Ti) elements

The effects of non-magnetic Ti⁴⁺ substitution on the structural, electrical and magnetic properties of La_0.67Ba_0.33Mn_1?x Ti _x O₃ (0≤x≤0.1) are investigated and compared to those existing in La_0.67Ba_0.33Mn_1?x Cr _x O₃ (magnetic Cr³⁺). The structural refinement by the Rietveld method revealed that Ti-doped samples crystallize in the cubic lattice with space group $\mathrm{Pm}\bar{3}\mathrm{m}$ , while samples with Cr crystallize in the hexagonal setting of the rhombohedral $\mathrm{R}\bar{3}\mathrm{C}$ space group for identical contents of dopant. The most relevant structural features are an increase of the lattice parameters, of the cell volume and of the inter-ionic distances with increasing Ti doping level. Both series of samples show a decrease of the paramagnetic–ferromagnetic transition temperature when the amount of chromium or titanium increases. Transport measurements show that when increasing the metal doping, the resistivity increases whereas the metallic behavior of the parent compound La_0.67Ba_0.33MnO₃ is destroyed. For a substitution higher than 5 at.% of Ti and 10 at.% of Cr, the samples exhibit a semiconducting behavior in the whole range of temperature, for which the electronic transport can be explained by variable range hopping and/or small polaron hopping models.     

Numerical simulation of the interface molten metal air in the shot sleeve chambre and mold cavity of a die casting machine

The objective of this study relates to the numerical simulation of the free surface during the two-dimensional flow and solidification of aluminum in the horizontal cylinder and mold cavity of the high pressure die casting HPDC machine with cold chamber. The flow is governed by the Navier–Stokes equations (the mass and the momentum conservations) and solved in the two phase’s liquid aluminum and air. The tracking of the free surface is ensured by the VOF method. The equivalent specific heat method is used to solve the phase change heat transfer problem in the solidification process. Considering the displacement of the plunger, the geometry of the problem is variable and the numerical resolution uses a dynamic grid. The study examines the influence of the plunger speed on the evolution of the interface aluminum liquid–air profile, the mass of air imprisoned and the stream function contours versus time. Filling of a mold is an essential part of HPDC process and affects significantly the heat transfer and solidification of the melt. For this reason, accurate prediction of the temperature field in the system can be achieved only by including simulation of filling in the analysis.     

Heat transfer and flow behavior around four staggered elliptic cylinders in cross flow

Experimental and numerical studies were carried out to investigate forced convection heat transfer and flow features around the downstream elliptic cylinder in four staggered cylinders in cross flow. The elliptic cylinders examined had an axis ratio (b/c) of 1:2, and they were arranged with zero angle of attack to the upstream flow. The present heat transfer measurements were obtained by heating only the downstream elliptic cylinder (test cylinder) under the condition of constant heat flux. The testing fluid was air and the Reynolds number based on the major axis length (c) was ranged from 4,000 to 45,570. The tested longitudinal spacing ratio (S_x/c) and the transversal spacing ratio (S_y/b) were in the ranges of 1.5 ≤ S_x/c ≤ 4.0 and 1.5 ≤ S_y/b ≤ 4.0, respectively. The air flow pattern and temperature fields around the four staggered elliptic cylinders were predicted by using CFD software package. Also, a flow visualization study was made to show the flow features around the elliptic cylinders. It was observed that Nu_m of the downstream elliptic cylinder in four staggered cylinders was higher than that of three in-line cylinders for all tested spacing ratios and Reynolds numbers except for Re = 4,000. It was clear that, at lower Reynolds number values (Re < 14,100), the average Nusselt number of the downstream elliptic cylinder in three staggered arrangement was higher than that of the downstream cylinder in four staggered arrangement for all tested spacing ratios. On the other hand, at Re > 14,100, the tested elliptic cylinder in four staggered arrangement had the higher values of the average Nusselt number. Moreover, in four staggered arrangement, the maximum average Nusselt number enhancement ratio (average Nusselt number of the tested downstream cylinder/average Nusselt number of a single elliptic cylinder) was found to be about 2.0, and was obtained for spacing ratios of S_x/c = 2.5, S_y/b = 2.5 and at Re = 32,000. Finally, the average Nusselt number of the tested cylinder in four staggered arrangement was correlated in terms of Reynolds number and cylinder spacing ratios.     

Linear and non-linear viscoelastic rheology of hybrid nanostructured materials from block copolymers with gold nanoparticles

A polystyrene-b-poly-4-vinypyridine (PS-b-P4VP) diblock copolymer is modified with a gold precursor to obtain an organic–inorganic (hybrid) block copolymer in bulk with gold nanoparticles selectively incorporated in the P4VP block. In the linear viscoelastic regime, temperature sweep tests over a series of these hybrid block copolymer systems revealed consistent shifts (ΔT) in the glass transition temperatures (both T _g\text-PS_{\rm g\text{-}PS} and T _g\text-P4VP_{\rm g\text{-}P4VP}) of the hybrid materials in comparison to the pristine polymers. Studying different volume fractions of the pyridine block, a level-off point was found for block copolymers with f _P4VP > 0.26, where the shifts in T _g\text-P4VP_{\rm g\text{-}P4VP} consistently increased up to ΔT = 25°C. By artificially increasing the volume fraction of the pyridine block, the nanoparticles reduce the transition regime determined in master curves. At higher volume fractions of the pyridine block, crossover frequencies were not detected after the entanglement regime, indicating that the material does not relax from topological constraints (entanglements and nanoparticles) into the terminal regime. Above a specific volume fraction of nanoparticles (Φ _P = 0.05), the flow behaviour of the hybrid materials becomes increasingly elastic, exhibiting wall-slip from the geometry at lower strain values in comparison to the pristine material. In the non-linear viscoelastic regime, Fourier-transformed rheology was used to analyse the raw signals from strain sweep experiments. It was clearly demonstrated the nanoparticle effect by following the second and third harmonic (I _2/1, I _3/1) of the stress response. Comparing the behaviour of the third and second harmonics provided an unambiguous fingerprint for the effect of the nanoparticles.     

Microwave-Assisted Conjugate Addition of Pyrrole on Electron-Deficient Nitro-Olefins

Michael addition of pyrrole to β-nitrovinyl compounds were carried out using microwave methodology. Monosubstituted pyrroles were obtained selectively in a major amount. Formation of novel product obtained during one of the reactions was explained by the double addition to nitrostyrene.     

Residually FCP extensions of commutative rings

Ricerche di Matematica - A ring extension $$R\subseteq S$$ is said to be residually FCP if, for all $$Q\in \mathrm {Spec}(S)$$, each chain of rings between $$R/(Q\cap R)$$ and...     

Analysis of a Non-hyperbolic System Modeling Two-phase Flows Part 1: The Effects of Diffusion and Relaxation

The paper considers the non-linear stability of a non-hyperbolic system of conservation laws with both relaxation and diffusion, which is commonly used for the modeling of two-phase fluid flows. Global existence in time is proved for initial data with a sufficiently small H¹ norm. This result heavily depends on the nice structure of the relaxation system, derived from the initial system by setting the relaxation variables to zero. © 1997 by B. G. Teubner Stuttgart–John Wiley & Sons Ltd.     

Recent Advances in Floating Photovoltaic Systems

In recent years, floating photovoltaic (FPV) technologies have gained more importance as a key source of clean energy, particularly in the context of providing sustainable energy to buildings. The rise of land scarcity and the need to reduce carbon emissions have made FPV systems a cost-effective solution for generating electricity. This review article aims to explore the rapidly growing trend of floating PV systems, which can be a practical solution for regions with limited land areas. The article discusses the structure of the PV modules used in FPV plants and key factors that affect site suitability choice. Moreover, the article presents various techniques for cooling and cleaning FPV to keep optimal performance and discusses feasible trends and prospects for the technology. Finally, this paper proposes the potential integration of FPV systems with other technologies to enhance energy generation efficiency and discusses other research aimed at the advancement of the technology. By examining the various features of FPV systems, this review article contributes to understanding the advantages and challenges associated with using this sustainable energy technology in different regional contexts.