THE SENSITIVITY OF TRAVEL COST ESTIMATES OF RECREATION DEMAND TO THE FUNCTIONAL FORM AND DEFINITION OF ORIGIN ZONES

The travel-cost of estimating a recreation demand function requires specifying the functional form of the first-stage demand curve and defining the width of the concentric origin zones. A Monte Carlo approach is used to determine the sensitivity of demand and valuation estimates to alternative choices about these two issues. Demand and valuation estimates are shown to be sensitive to the definition of the origin zone and to the use of a semilog versus a double log first-stage demand curve. The proper choice or origin zones is unclear, but a semilog form is more appropriate than a double log form.Resource /Energy Economics and Policy,

Studies in the perinaphthene series

The thesis comprises three parts, A, B and C. Each part is divided into a number of principle sections which are prefixed by Roman numerals. Most sections are divided into subsections prefixed by Roman numerals. Part A commences with a brief survey of aromaticity and aromatic reactivity in non-benzenoid aromatic compounds. This is followed by a detailed review of the chemistry of perinaphthene and its derivatives. Part B is a discussion of the results achieved in the course of investigations on the perinaphthane nucleus. Part C is the complement to part B, being a description of experimental details

Human Infections with Plasmodium knowlesi, the Philippines.

Five human cases of infection with the simian malaria parasite Plasmodium knowlesi from Palawan, the Philippines, were confirmed by nested PCR. This study suggests that this zoonotic infection is found across a relatively wide area in Palawan and documents autochthonous cases in the country

Immunoglobulin κ Chain Allotypes (KM) in Onchocerciasis

GM and KM allotypes, powerful tools for genetic characterization of human populations, have been shown to play an important role in genetic predisposition to some infectious diseases. Two diverse racial groups-Afro-Ecuadorians and Amerindians-living in a single restricted geographical area of Ecuador, appear to have different risk factors for acquisition and clinical expression of onchocerciasis, a disease caused by the filarial parasite Onchocerca volvulus. In this study, GM and KM allotypes were determined in 25 Afro-Ecuadorians and 24 Amerindians infected with Onchocerca volvulus (INF) and in putative immune individuals (PI). In Afro-Ecuadorians, the frequency of the homozygous KM 3 phenotype was significantly decreased in INF as compared with the PI group (20 vs. 68%; P = 0.0012), while the frequency of the heterozygous KM 1,3 phenotype was increased in INF as compared with the PI subjects (48 vs 9%; P = 0.0044). These results suggest that in Afro- Ecuadorians KM 3 is associated with a lower relative risk (resistance), whereas KM 1,3 is associated with an increased risk (susceptibility) of onchocerciasis

Sociological and Human Developmental Explanations of Crime: Conflict or Consensus

This paper examines multidisciplinary correlates of delinquency in an attempt to integrate sociological and environmental theories of crime with human developmental and biological explanations of crime. Structural equation models are applied to assess links among biological, psychological, and environmental variables collected prospectively from birth through age 17 on a sample of 800 black children at high risk for learning and behavioral disorders. Results show that for both males and females, aggression and disciplinary problems in school during adolescence are the strongest predictors of repeat offense behavior. Whereas school achievement and family income and stability are also significant predictors of delinquency for males, early physical development is the next strongest predictor for females. Results indicate that some effects on delinquency also vary during different ages. It is suggested that behavioral and learning disorders have both sociological and developmental correlates and that adequate educational resources are necessary to ensure channels of legitimate opportunities for high-risk youths

Architecture of the Vibrio cholerae toxin-coregulated pilus machine revealed by electron cryotomography

Type IV pili (T4P) are filamentous appendages found on many Bacteria and Archaea. They are helical fibres of pilin proteins assembled by a multi-component macromolecular machine we call the basal body. Based on pilin features, T4P are classified into type IVa pili (T4aP) and type IVb pili (T4bP). T4aP are more widespread and are involved in cell motility, DNA transfer, host predation and electron transfer. T4bP are less prevalent and are mainly found in enteropathogenic bacteria, where they play key roles in host colonization. Following similar work on T4aP machines, here we use electron cryotomography to reveal the three-dimensional in situ structure of a T4bP machine in its piliated and non-piliated states. The specific machine we analyse is the Vibrio cholerae toxin-coregulated pilus machine (TCPM). Although only about half of the components of the TCPM show sequence homology to components of the previously analysed Myxococcus xanthus T4aP machine (T4aPM), we find that their structures are nevertheless remarkably similar. Based on homologies with components of the M. xanthus T4aPM and additional reconstructions of TCPM mutants in which the non-homologous proteins are individually deleted, we propose locations for all eight TCPM components within the complex. Non-homologous proteins in the T4aPM and TCPM are found to form similar structures, suggesting new hypotheses for their functions and evolutionary histories

The Returns to Criminal Capital

Human capital theory (Becker 1962; Mincer 1958; Schultz 1960; 1961) posits that individuals can increase their labor market returns through investments in education and training. This concept has been studied extensively across several disciplines. An analog concept of criminal capital, while the focus of speculation and limited empirical study, remains considerably less developed theoretically and methodologically. This paper offers a formal theoretical model of criminal capital indicators and tests for greater illegal wage returns using a sample of serious adolescent offenders, many of whom participate in illegal income-generating activities. Our results reveal that, consistent with human capital theory, there are important illegal wage premiums associated with investments in criminal capital, notably an increasing but declining marginal return to experience and a premium for specialization. Further, as in studies of legal labor markets, we find strong evidence that, if left unaccounted for, non-random sample selection causes severe bias in models of illegal wages. Theoretical and practical implications of these results, along with directions for future research, are discussed