Overcharging: The Crucial Role of Excluded Volume

In this Letter we investigate the mechanism for overcharging of a single spherical colloid in the presence of aqueous salts within the framework of the primitive model by molecular dynamics (MD) simulations as well as integral-equation theory. We find that the occurrence and strength of overcharging strongly depends on the salt-ion size, and the available volume in the fluid. To understand the role of the excluded volume of the microions, we first consider an uncharged system. For a fixed bulk concentration we find that upon increasing the fluid particle size one strongly increases the local concentration nearby the colloidal surface and that the particles become laterally ordered. For a charged system the first surface layer is built up predominantly by strongly correlated counterions. We argue that this a key mechanism to produce overcharging with a low electrostatic coupling, and as a more practical consequence, to account for charge inversion with monovalent aqueous salt ions.Comment: 7 pages, 3 figs (4 EPS files). To appear in Europhysics Letter

The electrical double layer for a fully asymmetric electrolyte around a spherical colloid: an integral equation study

The hypernetted chain/mean spherical approximation (HNC/MSA) integral equation is obtained and solved numerically for a totally asymmetric primitive model electrolyte around a spherical macroparticle. The ensuing radial distribution functions show a very good agreement when compared to our Monte Carlo and molecular dynamics simulations for spherical geometry and with respect to previous anisotropic reference HNC calculations in the planar limit. We report an analysis of the potential vs charge relationship, radial distribution functions, mean electrostatic potential and cumulative reduced charge for representative cases of 1:1 and 2:2 salts with a size asymmetry ratio of 2. Our results are collated with those of the Modified Gouy-Chapman (MGC) and unequal radius Modified Gouy-Chapman (URMGC) theories and with those of HNC/MSA in the restricted primitive model (RPM) to assess the importance of size asymmetry effects. One of the most striking characteristics found is that,\textit{contrary to the general belief}, away from the point of zero charge the properties of an asymmetric electrical double layer (EDL) are not those corresponding to a symmetric electrolyte with the size and charge of the counterion, i.e. \textit{counterions do not always dominate}. This behavior suggests the existence of a new phenomenology in the EDL that genuinely belongs to a more realistic size-asymmetric model where steric correlations are taken into account consistently. Such novel features can not be described by traditional mean field theories like MGC, URMGC or even by enhanced formalisms, like HNC/MSA, if they are based on the RPM.Comment: 29 pages, 13 figure

Foreign Direct Investment For Developing Financing: Teaching Market-Related Aspects Through Cases

This article presents two cases that have been used to supplement the teaching of how market-related aspects impact decisions, policies and tasks associated with attracting foreign direct investment into emerging markets and developing economies. The authors share their experiences in workshops and in the classroom and provide discussion strategies and teaching notes for each case

Acceptability of yacon flakes (Smallanthus sonchifolia) for dietary use with inulin

"This study aimed to elaborate on yacon flakes and determine the proximal composition of fresh yacon and final flakes, made at different temperatures (120°C, 150°C and 180°C) for 20 mins. We measured the acceptability of the sensory attributes: taste, texture, odour and colour and the global acceptability at the laboratory level, using semi-trained panellists and an unstructured hedonic scale. The acceptability of the flakes was measured at different temperatures. Our results indicate that the flakes made at 180°C had the highest acceptance (87%), and the flakes made at 120°C had 80% of unacceptability. Our data were analysed according to the analysis of variance (ANOVA) and Tukey's test. We found significant differences between the averages of the taste scores (T0:7.1; T1:7.6; T2:6.7; T3:4.6), p<0.05; texture (T0:7.1; T1:7.2; T2:5.7; T3:4.5), p<0.05; and odour (T0:7.2; T1:7.6; T2:5.1; T3:3.3), p<0.05. The amount of fructooligosaccharides on a fresh basis was Ⱦ±SD (31.60±0.650) and on a dry basis (37.44±1DS). Microbiological analysis shows that the flakes are fit for human consumption. It is concluded that yacon flakes contain significant amounts of inulin, being a good substitute alternative for the preparation of snack-type dietetic products

Quantum simulation of the Anderson Hamiltonian with an array of coupled nanoresonators: delocalization and thermalization effects

The possibility of using nanoelectromechanical systems as a simulation tool for quantum many-body effects is explored. It is demonstrated that an array of electrostatically coupled nanoresonators can effectively simulate the Bose-Hubbard model without interactions, corresponding in the single-phonon regime to the Anderson tight-binding model. Employing a density matrix formalism for the system coupled to a bosonic thermal bath, we study the interplay between disorder and thermalization, focusing on the delocalization process. It is found that the phonon population remains localized for a long time at low enough temperatures; with increasing temperatures the localization is rapidly lost due to thermal pumping of excitations into the array, producing in the equilibrium a fully thermalized system. Finally, we consider a possible experimental design to measure the phonon population in the array by means of a superconducting transmon qubit coupled to individual nanoresonators. We also consider the possibility of using the proposed quantum simulator for realizing continuous-time quantum walks.Comment: Replaced with new improved version. To appear in EPJ Q

Central Composite Design to Optimizate the Derivatization Procedure for Analysis of Biogenic Amines by HPLC-UV

A simple benzoylation procedure was optimized for the biogenic amines derivatization prior to high-performance liquid chromatography determination. The significant factors affecting biogenic amine benzoylation yield were optimized by central composite design (CCD). The obtained optimal conditions resulted in a chromatographic peaks area increase with fewer interferences. Moreover, the efficiency parameters for chromatographic separation of putrescine, histamine and tyramine were determined under optimum operating conditions, which included: capacity factors or retention (k’) = 2.5-4.2, selectivity factors (α) > 1 and resolution values (Rs) > 1.5, indicating that the column provided good separation of the analytes. The optimized method was applied in spiked fish samples with standard solutions of putrescine, histamine and tyramine at concentrations of 50, 80 and 50 mg L-1, respectively, to achieve recovery rates in a range from 90.89 to 96.65% for putrescine; 93.36 to 95.87% for histamine; 86.57 to 93.33% for tyramine, with the relative standard deviation (RSD) less than 4%

Solidarity (Solidarność) at Forty: Memories and Influences on Contemporary Poland - Does Solidarity Still Matter?

This paper is dedicated to the memory of Brother Leo V. Ryan, C.S.V., who passed away in 2016. Abstract Part I of the paper is a retrospective on the origins of the Solidarity Movement in Poland and the economic program it introduced after its assumption of power in 1989. Part II outlines various challenges faced by Polish society in light of current political configurations and discusses Solidarity’s contemporary relevance on the political and economic calculus of Poland. This retrospective is based on more than thirty-five years of research and analysis on the Polish economic and political scenes. Keywords: Poland, Polish Economy, Solidarity Movement, JUST REMEMBER: STALIN HIMSELF WAS REPORTED TO HAVE STATED THAT “SOCIALISM WOULD FIT POLAND LIKE A SADDLE WOULD FIT A COW.” DOI: 10.7176/EJBM/11-23-12 Publication date: August 31st 201

Estructura de la propiedad y poblamiento en Milpa Alta 1917-1960

Proyecto Terminal (Licenciatura en Sociología) -- Universidad Autónoma Metropolitana, Unidad Azcapotzalco, División de Ciencias Sociales y Humanidades, Departamento de Sociología, 2006. UAMADCSHDS 1 archivo PDF (95 páginas

Insulator phases of Bose-Fermi mixtures induced by next-neighbor interactions between fermions

We study a one-dimensional mixture of two-color fermions and scalar bosons at the hard-core limit, focusing on the effect that the next-neighbor interaction between fermions has on the zero-temperature ground state of the system for different fillings of each carrier. Exploring the parameters of the problem, we observed that the non-local interaction modifies the well-known mixed and spin-selective Mott insulators, and we also found the emergence of three unusual insulating states with peculiar charge density wave orderings, a fully out-of-phase density of carriers for bosonic half-filling, an insulator with the same bosonic and fermionic fillings, and a different spin-selective insulator where the bosonic filling matches the density of one kind of fermion. Modern cold-atom setups correspond to the ideal experimental setting where these incommensurable insulators can be observed.Comment: 11 pages, 9 figures. Comments are welcom