Levels of genetic polymorphism: marker loci versus quantitative traits

Species are the units used to measure ecological diversity and alleles are the units of genetic diversity. Genetic variation within and among species has been documented most extensively using allozyme electrophoresis. This reveals wide differences in genetic variability within, and genetic distances among, species, demonstrating that species are not equivalent units of diversity. The extent to which the pattern observed for allozymes can be used to infer patterns of genetic variation in quantitative traits depends on the forces generating and maintaining variability. Allozyme variation is probably not strictly neutral but, nevertheless, heterozygosity is expected to be influenced by population size and genetic distance will be affected by time since divergence. The same is true for quantitative traits influenced by many genes and under weak stabilizing selection. However, the limited data available suggest that allozyme variability is a poor predictor of genetic variation in quantitative traits within populations. It is a better predictor of general phenotypic divergence and of postzygotic isolation between populations or species, but is only weakly correlated with prezygotic isolation. Studies of grasshopper and planthopper mating signal variation and assortative mating illustrate how these characters evolve independently of general genetic and morphological variation. The role of such traits in prezygotic isolation, and hence speciation, means that they will contribute significantly to the diversity of levels of genetic variation within and among species

Observations of the J = 2→1 transitions of ¹²C¹⁶O and ¹²C¹⁸O towards galactic H II regions

Observations are reported of the J = 2→1 transitions of CO and 12C18O at 230 and 219 GHz respectively from a number of galactic sources. A map of the central 1/2° × 1/2° of the Orion A molecular cloud is presented. The spectra are interpreted to derive molecular densities and abundance ratios in the molecular clouds observed

NLO prescription for unintegrated parton distributions

We show how parton distributions unintegrated over the parton transverse momentum, k_t, may be generated, at NLO accuracy, from the known integrated (DGLAP-evolved) parton densities determined from global data analyses. A few numerical examples are given, which demonstrate that sufficient accuracy is obtained by keeping only the LO splitting functions together with the NLO integrated parton densities. However, it is important to keep the precise kinematics of the process, by taking the scale to be the virtuality rather than the transverse momentum, in order to be consistent with the calculation of the NLO splitting functions.Comment: 20 pages, 8 figures. v2: version to appear in Eur. Phys. J.

Sex distribution of offspring-parents obesity: Angel's hypothesis revisited

This study, which is based on two cross sectional surveys' data, aims to establish any effect of parental obesity sex distribution of offspring and to replicate the results that led to the hypothesis that obesity may be associated with sex-linked recessive lethal gene. A representative sample of 4,064 couples living in Renfrew/Paisley, Scotland was surveyed 1972-1976. A total of 2,338 offspring from 1,477 of the couples screened in 1972-1976, living in Paisley, were surveyed in 1996. In this study, males represented 47.7% among the total offspring of the couples screened in 1972-1976. In the first survey there was a higher male proportion of offspring (53%, p < 0.05) from parents who were both obese, yet this was not significant after adjustment for age of parents. Also, there were no other significant differences in sex distribution of offspring according to body mass index, age, or social class of parents. The conditions of the original 1949 study of Angel (1949) (which proposed a sex-linked lethal recessive gene) were simulated by selecting couples with at least one obese daughter. In this subset, (n = 409), obesity in fathers and mothers was associated with 26% of offspring being male compared with 19% of offspring from a non-obese father and obese mother. Finally we conclude that families with an obese father have a higher proportion of male offspring. These results do not support the long-established hypotheses of a sex-linked recessive lethal gene in the etiology of obesity

Defending Against Insider Use of Digital Steganography

The trusted insider is among the most harmful and difficult to detect threats to information security, according to the Federal Plan for Information Assurance and Cyber Security Research and Development released in April 2006. By default, employees become trusted insiders when granted the set of privileges needed to do their jobs, which typically includes access to the Internet. It is generally presumed the insiders are loyally working to achieve the organization’s goals and objectives and would not abuse the privileges given to them. However, some insiders will inevitably abuse some of their privileges. For example, a trusted insider might abuse their privilege of access to the Internet to download, install, and use an information hiding tool, such as one of the hundreds of digital steganography applications available on the Internet, to steal sensitive, classified, or proprietary information. Effective countermeasures to this threat must begin with an organizational policy prohibiting installation of information hiding tools on user workstations and must also include automated tools capable of detecting attempts to download and use digital steganography applications. This paper will describe the threat from insider use of digital steganography applications; a new approach to detecting the presence or use of these applications; and extraction of hidden information when a known signature of one of these applications is detected. The analytical approach to steganalysis involves the development and use of computer forensic tools that can detect fingerprints and signatures of digital steganography applications. These tools can be employed in both an off-line forensic-based mode as well as a real-time network surveillance mode. Detection of fingerprints or signatures in either mode may lead to the discovery and extraction of hidden information. Accordingly, this approach represents a significant improvement over traditional blind detection techniques which typically only provide a probability that information may be hidden in a given file without providing a capability to extract any hidden information. Keywords: insider, steganography, steganalysis, computer forensics, artifacts, fingerprints, hash values, signature

Digital interferometry for flow visualization

Digital holographic interferometry is a hybrid optical-digital technique for determining the phase of an interferogram. This technique improves the accuracy of interferometric measurement of fluid properties and enhances the utility of interferometric flow visualization. Displays of the interferometric phase produce excellent images of weakly refracting two-dimensional flows and can be used to produce integral projection images of three dimensional flows which differ from and complement schlieren and shadowgraph images. The technique is explained herein and examples of its use in both continuous wave and pulsed interferometry are presented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47080/1/348_2004_Article_BF00264404.pd