Hydrogen bonding as a clustering agent in protic ionic liquids: like-charge vs opposite-charge dimer formation

The local structure of a series of homologous protic ionic liquids (PILs) is investigated using ab initio computations and ab initio-based molecular dynamics. The purpose of this work is to show that in PILs the network of hydrogen bonds may promote like-charge clustering between anionic species. We correlate the theoretical evidence of this possibility with viscosity experimental data. The homologous series of liquids is obtained by coupling choline with amino acid anions and varying the side chain. We find that the frictional properties of the liquids are clearly connected to the ability of the side chain to establish additional hydrogen bonds (other than the trivial cation–anion interaction). We also show that the large variation of bulk properties along the series of compounds can be explained by assuming that one of the sources of friction in the bulk liquid is the like-charge interaction between anions

A Note on the Estimation of the Hölder Constant

In this article, we develop a nonparametric estimator for the Hölder constant of a density function. We consider a simulation study to evaluate the performance of the proposal and construct smooth bootstrap confidence intervals. Also, we give a brief review over the impossibility to decide whether a density function is Hölder.Fil: Henry, Guillermo Sebastian. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rodriguez, Daniela Andrea. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Sued, Raquel Mariela. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Ecological life history of Crangonyx pseudogracilis Bousfield (Crustacea: Amphipoda) in the Green Bottom Wildlife Management Area, Cabell County, West Virginia

Although the genus Crangonyx has been studied in the Appalachian area, most of this work has concentrated on subterranean species. A Crangonyx pseudogracilis population from the Green Bottom Wildlife Management Area (GBWMA), Cabell County, West Virginia was sampled weekly from March 1995 through July 1996 to investigate the ecological life history of the amphipod. A total of 1508 amphipods were collected. Amphipods were present in the study sites from November through July, at which time they migrated to deeper waters. Crangonyx pseudogracilis had a one year life cycle and bred from November to May. Adult amphipods began to die off in May and were gone by June. Males averaged 5.88 mm and females averaged 8.73 mm in length. There was no significant seasonal variation in sex ratio. Females produced several broods per year and ovigerous females were found from November 2 until May 8. They carried an average of 53.55 eggs and there was a low correlation between fecundity and length. The median tolerance limit (TLm) for low pH was 4.06, and a 96 hour laboratory test at this value produced a 65 percent survival rate. Plant detritus was the preferred food year round and comprised between 47 and 62 percent of the diet

Endogenous Financial Constraints and Innovation

We investigate which indicators of a firm’s innovation activities are associated with financial constraints and analyse the nature and direction of causal links between innovation and financial constraints. By estimating simultaneous bivariate probit models on data from the UK Innovation Surveys, we show that among innovation inputs, R&D activity increases the likelihood that firms face financial constraints while innovation outputs in the form of new-to-market products seem to generate financial constraints. Reverse effects on innovation appear limited to external R&D

Robust estimators in partly linear regression models on Riemannian manifolds

Under a partly linear model we study a family of robust estimates for the regression parameter and the regression function when some of the predictors take values on a Riemannian manifold. We obtain the consistency and the asymptotic normality of the proposed estimators. Simulations and an application to a real dataset show the good performance of our proposal under small samples and contamination.Fil: Henry, Guillermo Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santalo". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Matemáticas "Luis A. Santalo"; ArgentinaFil: Rodriguez, Daniela Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santalo". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Matemáticas "Luis A. Santalo"; Argentin

Tercerización de servicios en la Argentina: empleo y gestión de RRHH en los call centers

En la actualidad un número cada vez mayor de países se ve alcanzado por el cambio en la dimensión geográfica de las actividades económicas que representa la tercerización de la producción. En este contexto, las grandes firmas optan por deslocalizar funciones administrativas recurriendo a proveedores especializados en gestionar -a distancia- operaciones empresariales. En nuestro país contamos con un ejemplo elocuente a partir del crecimiento explosivo de la actividad de los call centers tercerizados y en la conformación de un dinámico sector de Empresas Tercerizadoras de Call Centers (ETCC).En nuestro estudio, dirigimos la atención al sector de ETCC y a su interior, nos interesamos por las empresas tercerizadoras con participación en el mercado de exportación de servicios que -desde plataformas ubicadas en Argentina- proveen servicios a empresas subcontratantes que operan en el extranjero (CC offshore). Nos preguntamos por la vinculación que existe entre las ETCC y las firmas que las subcontratan, por el posicionamiento de estas empresas proveedoras de servicios en el mercado doméstico y en el de exportación, y por los factores que orientan sus estrategias de crecimiento y de localización. El objetivo nuestras exploraciones es analizar las implicancias de estas cuestiones sobre la gestión de la fuerza de trabajo y sobre las características que adoptan los recursos humanos del sector.Fil: del Bono, Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Centro de Estudios e Investigaciones Laborales; ArgentinaFil: Henry, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Centro de Estudios e Investigaciones Laborales; Argentin

Hypoxic Incubation Chamber

In developing a model to test anti-tumor drugs, Dr. Christopher Heylman’s lab requires the ability to culture cells in a hypoxic environment. The purpose of this project was to make this possible. Funding for this project comes from the Biomedical Engineering Department, the Hannah-Forbes Fund, and Dr. Heylman’s lab. The chamber must be able to reach a user-defined oxygen concentration and hold that concentration for 48 hours while creating an environment conducive to cell culture. Importantly, the chamber must also be sterilizable and cleanable for repeated use. While several products exist to create hypoxic environments for cell culture, they are either too expensive or too simple. The timeline of this project has been largely dictated by the BMED senior project class and its deadlines, culminating in the Final Report and Presentation given on March 9th. Several different ideas were generated to meet the customer requirements in various ways. The final design of the chamber is a rectangular box with a detachable door that is held onto the chamber by 3 latches. The door uses a rubber gasket with neoprene to prevent air from escaping or entering the chamber. Gas is allowed into the chamber through two different tubes- one supplying oxygen as an “up” control and one supplying a nitrogen and carbon dioxide mixture as a “down” control of the oxygen concentration. Flow through the tubes is regulated by two needle valves. A check valve on the side of the chamber allows excess gas to exit if the pressure passes 0.5 psi. An oxygen sensor sits in the top of the chamber that gives a continuous oxygen reading to a connected computer through an Arduino Uno. The only manufacturing required was that of the chamber, but because the chamber is a pressure vessel, the manufacturing had to be quite precise. Tests were to be conducted on the sealability of the chamber, the accuracy of setting the O2 level, the oxygen sensor itself and more. Due to time constraints, the only test that was able to be carried out to any significant extent was a Modified Maintain Oxygen Level test which determined what the best method of sealing the chamber was to maximize the amount of time the chamber was able to hold a given oxygen concentration. More work needs to be done for this project to be useful in a research setting. The chamber needs a way to be heated and held at a temperature conducive to cell proliferation. Additionally, active control of the valves will need to be introduced to hold the oxygen concentration within spec for 48 hours