The microbial degradation of two Venezuelan crude oils enriched in 25-norhopanes was examined after a 5-week aerobic incubation using a microbial enrichment culture. Analysis of the oils using gas chromatography±mass spectrometry revealed degradation of the C28 tricyclic terpane, the C29±C34 17a(H),21b(H)-hopanes, and the C29 17a(H),21b(H)-25-norhopane. The C35 17a(H),21b(H)-hopane and 18a(H)-o...

This paper studies models for binary outcome variables that contain a binary endogenous regressor. More specifically, we consider a nonparametric, triangular system of equations with binary dependent variables. The main assumption we impose is a weak separability condition on each equation, or, equivalently, a threshold crossing model on each equation. In this setting, we construct upper and lo...

We introduce the Multivariate Autoregressive Conditional Double Poisson model to deal with discreteness, overdispersion and both auto and cross-correlation, arising with multivariate counts. We model counts with a double Poisson and assume that conditionally on past observations the means follow a Vector Autoregression. We resort to copulas to introduce contemporaneous correlation. We apply it ...

This paper uses the model proposed by Chiappori, Levitt and Groseclose (2002) to test for mixed-strategy Nash equilibria in a game between a kicker and a goalkeeper, in a situation of a soccer penalty kick. The main contribution of this paper is to develop an alternative testing methodology, based on the use of a simultaneous-equation regression approach that directly tests the equilibrium cond...

Migrant Networks, Migrant Selection, and High School Graduation in Mexico This paper examines whether family and community migration experience affect the probability of high school graduation in Mexico once unobserved heterogeneity is accounted for. Bivariate random effects dynamic probit models for cluster data are estimated to control for the endogeneity of education and migrant network vari...

A gel shift assay that distinguishes the aminoacylated form from the deacylated form of tRNAs was used to study the requirements for aminoacylation of Escherichia coli tRNA(Asn) in vivo. tRNA(Asn) derivatives containing single base changes in their anticodons or discriminator bases were constructed, and the extent of in vivo aminoacylation was determined directly. Substitution of U35 with C35 o...

High School Types, Academic Performance and Early Labour Market Outcomes Using microdata on the 1995 cohort of Italian high school graduates, this paper studies the relationship between the type of high school attended (general versus technical; private versus public) and indicators of subsequent performance. Simultaneity issues that potentially bias this type of exercise are tackled by instrum...

This paper presents empirical evidence on firms’ decisions to cooperate in R&D and the extent to which government sponsored R&D programs increase cooperation. Using a sample of firms from the Spanish innovation survey we jointly estimate the determinants of firm participation in R&D programs and of choice of cooperation partners. We find that (i) firms participating in national and European pro...

We present a hybrid Time-Dependent Density Functional /Molecular Mechanics (TDDFT/MM) simulation study on the optical properties of aminocoumarins in gas phase and solution. As solvation is described through a molecular approach, the effects due to the inhomogeneities of the electric field of the solvent molecules are fully included. We focus on the ground state and first excited singlet state ...

In this paper we discuss tests for residual cross section dependence in nonlinear panel data models. The tests are based on average pair-wise residual correlation coefficients. In nonlinear models, the definition of the residual is ambiguous and we consider two approaches: deviations of the observed dependent variable from its expected value and generalized residuals. We show the asymptotic con...