Optical binding in nanoparticle assembly: Potential energy landscapes

Optical binding is an optomechanical effect exhibited by systems of micro- and nanoparticles, suitably irradiated with off-resonance laser light. Physically distinct from standing-wave and other forms of holographic optical traps, the phenomenon arises as a result of an interparticle coupling with individual radiation modes, leading to optically induced modifications to Casmir-Polder interactions. To better understand how this mechanism leads to the observed assemblies and formation of patterns in nanoparticles, we develop a theory in terms of optically induced energy landscapes exhibiting the three-dimensional form of the potential energy field. It is shown in detail that the positioning and magnitude of local energy maxima and minima depend on the configuration of each particle pair, with regards to the polarization and wave vector of the laser light. The analysis reveals how the positioning of local minima determines the energetically most favorable locations for the addition of a third particle to each equilibrium pair. It is also demonstrated how the result of such an addition subtly modifies the energy landscape that will, in turn, determine the optimum location for further particle additions. As such, this development represents a rigorous and general formulation of the theory, paving the way toward full comprehension of nanoparticle assembly based on optical binding

An analysis of the fluctuation potential in the modified Poisson-Boltzmann theory for restricted primitive model electrolytes

An approximate analytical solution to the fluctuation potential problem in the modified Poisson-Boltzmann theory of electrolyte solutions in the restricted primitive model is presented. The solution is valid for all inter-ionic distances, including contact values. The fluctuation potential solution is implemented in the theory to describe the structure of the electrolyte in terms of the radial distribution functions, and to calculate some aspects of thermodynamics, viz., configurational reduced energies, and osmotic coefficients. The calculations have been made for symmetric valence 1:1 systems at the physical parameters of ionic diameter $4.25 \times 10^{-10}$ m, relative permittivity 78.5, absolute temperature 298 K, and molar concentrations 0.1038, 0.425, 1.00, and 1.968. Radial distribution functions are compared with the corresponding results from the symmetric Poisson-Boltzmann, and the conventional and modified Poisson-Boltzmann theories. Comparisons have also been done for the contact values of the radial distributions, reduced configurational energies, and osmotic coefficients as functions of electrolyte concentration. Some Monte Carlo simulation data from the literature are also included in the assessment of the thermodynamic predictions. Results show a very good agreement with the Monte Carlo results and some improvement for osmotic coefficients and radial distribution functions contact values relative to these theories. The reduced energy curve shows excellent agreement with Monte Carlo data for molarities up to 1 mol/dm$^{3}$.Comment: 16 pages, 8 figures, 3 table

C1,αC^{1,\alpha} regularity of solutions of degenerate fully non-linear elliptic equations

In the present paper, a class of fully non-linear elliptic equations are considered, which are degenerate as the gradient becomes small. H\"older estimates obtained by the first author (2011) are combined with new Lipschitz estimates obtained through the Ishii-Lions method in order to get $C^{1,\alpha}$ estimates for solutions of these equations.Comment: Submitte

A retarded coupling approach to intermolecular interactions

A wide range of physical phenomena such as optical binding and resonance energy transfer involve electronic coupling between adjacent molecules. A quantum electrodynamical description of these intermolecular interactions reveals the presence of retardation effects. The clarity of the procedure associated with the construction of the quantum amplitudes and the precision of the ensuing results for observable energies and rates are widely acknowledged. However, the length and complexity of the derivations involved in such quantum electrodynamical descriptions increase rapidly with the order of the process under study. Whether through the use of time-ordering approaches, or the more expedient state-sequence method, time-consuming calculations cannot usually be bypassed. A simple and succinct method is now presented, which provides for a direct and still entirely rigorous determination of the quantum electrodynamical amplitudes for processes of arbitrarily high order. Using the approach, new results for optical binding in two- and three-particle systems are secured and discussed

Germanene: a novel two-dimensional Germanium allotrope akin to Graphene and Silicene

Using a gold (111) surface as a substrate we have grown in situ by molecular beam epitaxy an atom-thin, ordered, two-dimensional multi-phase film. Its growth bears strong similarity with the formation of silicene layers on silver (111) templates. One of the phases, forming large domains, as observed in Scanning Tunneling Microscopy, shows a clear, nearly flat, honeycomb structure. Thanks to thorough synchrotron radiation core-level spectroscopy measurements and advanced Density Functional Theory calculations we can identify it to a $\sqrt{3}$x$\sqrt{3}$R(30{\deg}) germanene layer in coincidence with a $\sqrt{7}$x$\sqrt{7}$R(19.1{\deg}) Au(111) supercell, thence, presenting the first compelling evidence of the birth of a novel synthetic germanium-based cousin of graphene.Comment: 16 pages, 4 figures, 1 tabl

El empresariado colombiano (1850-2010) ¿microcosmos del empresariado latinoamericano? Una aproximación a sus características

In this article the origins and basis of Colombian entrepreneurship since 1850 are examined and a number of their main features are outlined within the framework of Latin American entrepreneurship. The article draws on Colombian business historiography which, as in the case of Latin America as a whole, shows an increase in output and quality since early 1990s. An overview of its evolution is portrayed. The features of Colombian entrepreneurship dealt with are: its regional basis in this, a «country of regions» with natural resources, social and cultural differentiation; a pattern of high business and investment diversification; the role of land as a means of accumulation; and the important entrepreneurial performance of immigrants in this «non-immigrants land». These traits constitute a legacy whose positive and negative aspects may be critically scrutinized through theoretically oriented business history research. In this perspective, some useful theoretical inputs are outlined.En este artículo se examinan el origen y las bases del empresariado colombiano desde mediados del siglo XIX y se delinean algunos de sus rasgos en el marco del empresariado latinoamericano del que forma parte. El trabajo está basado en la historiografía empresarial que en Colombia, como en Latinoamérica en conjunto, muestra un notorio crecimiento en volumen y calidad desde comienzos de la década de 1990 y cuya evolución se esboza. Los rasgos del empresariado que se tratan son: su base regional en un «país de regiones», en las cuales la dotación de recursos, estructura social y cultura son diferenciadas; el patrón de alta diversificación de sus negocios e inversiones; la posesión de la tierra como base de acumulación; y el destacado papel empresarial de los escasos inmigrantes que se aventuraron en esta non-immigrants land. La conjunción de estas características le ha dejado al empresariado actual un legado que contiene tanto elementos positivos como negativos que pueden analizarse de manera crítica mediante la investigación en historia empresarial, anclada en avances teóricos de diferentes disciplinas que contribuyen a ella y que se delinean en el artículo

Circular dichroism of cholesteric polymers and the orbital angular momentum of light

We explore experimentally if the light's orbital angular momentum (OAM) interacts with chiral nematic polymer films. Specifically, we measure the circular dichroism of such a material using light beams with different OAM. We investigate the case of strongly focussed, non-paraxial light beams, where the spatial and polarization degrees of freedom are coupled. Within the experimental accuracy, we cannot find any influence of the OAM on the circular dichroism of the cholesteric polymer.Comment: 3 pages, 4 figure

Raman scattering mediated by neighboring molecules

Raman scattering is most commonly associated with a change in vibrational state within individual molecules, the corresponding frequency shift in the scattered light affording a key way of identifying material structures. In theories where both matter and light are treated quantum mechanically, the fundamental scattering process is represented as the concurrent annihilation of a photon from one radiation mode and creation of another in a different mode. Developing this quantum electrodynamical formulation, the focus of the present work is on the spectroscopic consequences of electrodynamic coupling between neighboring molecules or other kinds of optical center. To encompass these nanoscale interactions, through which the molecular states evolve under the dual influence of the input light and local fields, this work identifies and determines two major mechanisms for each of which different selection rules apply. The constituent optical centers are considered to be chemically different and held in a fixed orientation with respect to each other, either as two components of a larger molecule or a molecular assembly that can undergo free rotation in a fluid medium or as parts of a larger, solid material. The two centers are considered to be separated beyond wavefunction overlap but close enough together to fall within an optical near-field limit, which leads to high inverse power dependences on their local separation. In this investigation, individual centers undergo a Stokes transition, whilst each neighbor of a different species remains in its original electronic and vibrational state. Analogous principles are applicable for the anti-Stokes case. The analysis concludes by considering the experimental consequences of applying this spectroscopic interpretation to fluid media; explicitly, the selection rules and the impact of pressure on the radiant intensity of this process

Evaluation of the criteria for the interpretation of the oral glucose tolerance test in the National Mother-Child Teaching Hospital ‘‘San Bartolome’’

Diabetes mellitus (DM) is a metabolic disorder that causes chronic hyperglycemia with disturbances in the metabolism of carbohydrates, fats and proteins, and alterations in microcirculation. We evaluate the criteria for the interpretation of the oral glucose tolerance test (OGTT) in the Hospital Nacional Docente Madre-Ni˜no ‘‘San Bartolomé’’ in Lima, Peru, and determine the percentages of pre-diabetic patients, diabetics that should not be included in the test, and those with alterations in their glucose curve during the biochemical determinations. To this purpose, a non-experimental, prospective cross-sectional analytic study was performed in 1271 patients, included in the study to comply with the guidelines and recommendations of the ADA and the CLSI POCT12-A3 guide, which were processed in the Biochemical Autoanalyzer Biosystems A25. Data analysis was performed using SPSS version 20.0 statistical analyzer, and respecting ethical diabetics. The main results are 1.97% diabetic and 13.85% pre-diabetic. The LJ phenomenon occurred with 6.45% (alteration in glucose curve after oral load decreases plasma glucose concentration determination after 60 min and returns at relatively higher than the basal concentration levels at 180 min) and 5.19% were poorly studied, including a >110 mg/dl baseline (p = <0.05). We determined a high rate of pre-diabetic patients and a reduced rate of diabetes coincident with Qiao et al. We highlight the usefulness of the OGTT, which must be rigorously evaluated, and reaffirm the importance of the LJ phenomenon as it may interfere with the final results of unsolved events, and evidence the importance of interindividual biological variability