Putting formal specifications under the magnifying glass: Model-based testing for validation

A software development process is effectively an abstract form of model transformation, starting from an end-user model of requirements, through to a system model for which code can be automatically generated. The success (or failure) of such a transformation depends substantially on obtaining a correct, well-formed initial model that captures user concerns. Model-based testing automates black box testing based on the model of the system under analysis. This paper proposes and evaluates a novel model-based testing technique that aims to reveal specification/requirement-related errors by generating test cases from a test model and exercising them on the design model. The case study outlined in the paper shows that a separate test model not only increases the level of objectivity of the requirements, but also supports the validation of the system under test through test case generation. The results obtained from the case study support the hypothesis that there may be discrepancies between the formal specification of the system modeled at developer end and the problem to be solved, and using solely formal verification methods may not be sufficient to reveal these. The approach presented in this paper aims at providing means to obtain greater confidence in the design model that is used as the basis for code generation

Association Between Air Pollution and Low Birth Weight: A Community-Based Study

The relationship between maternal exposure to air pollution during periods of pregnancy (entire and specific periods) and birth weight was investigated in a well-defined cohort. Between 1988 and 1991, all pregnant women living in four residential areas of Beijing were registered and followed from early pregnancy until delivery. Information on individual mothers and infants was collected. Daily air pollution data were obtained independently. The sample for analysis included 74,671 first-parity live births were gestational age 37-44 weeks. Multiple linear regression and logistic regression were used to estimate the effects of air pollution on birth weight and low birth weight (< 2,500 g), adjusting for gestational age, residence, year of birth, maternal age, and infant gender. There was a significant exposure-response relationship between maternal exposures to sulfur dioxide (SO2) and total suspended particles (TSP) during the third trimester of pregnancy and infant birth weight. The adjusted odds ratio for low birth weight was 1.11 (95% CI, 1.06-1.16) for each 100 micrograms/m3 increase in SO2 and 1.10 (95% CI, 1.05-1.14) for each 100 micrograms/m3 increase in TSP. The estimated reduction in birth weight was 7.3 g and 6.9 g for each 100 micrograms/m3 increase in SO2 and in TSP, respectively. The birth weight distribution of the high-exposure group was more skewed toward the left tail (i.e., with higher proportion of births < 2,500 g) than that of the low-exposure group. Although the effects of other unmeasured risk factors cannot be excluded with certainty, our data suggests that TSP and SO2, or a more complex pollution mixture associated with these pollutants, contribute to an excess risk of low birth weight in the Beijing population.National Institute of Environmental Health Sciences (ES05947, ES08337); National Institute of Child Health & Human Development (R01 HD32505); Department of Health and Human Services (MCJ-259501, HRSA 5 T32 PE10014

Comparative Study of Seed from Northern and Southern Hatcheries

Seed from Northern and Southern (hereafter called local) hatcheries was procured in May 2000. Oysters delivered by the Northern hatchery were on time and of the desired size ~3mm). Seed from the local hatchery, however, arrived several days later and were too small to go into field nursery containers and were subsequently held in upwellers and then transferred to the field nursery gear. Figure 1 shows growth as measured by mean shell height (mm) for both strains. Note that the local seed took N20 days longer to reach grow-out size (indicated by first sieve)

Population Assessment of Eastern Oysters (Crassostrea virginica) in the Seaside Coastal Bays

Declines of oyster populations and commercial harvest from the Virginia seaside coastal bays have followed similar patterns, though not as severe, as those in Chesapeake Bay. High prevalence of Dermo disease (Perkinsus marinus) and MSX disease (Haplosporidium nelsoni) coupled with over harvest and habitat destruction have dramatically reduced populations. Nevertheless, there are several promising signs that significant enhancement of the population could be achieved with well conceived restoration efforts. Oyster habitat and population distribution were examined in the coastal bay system on the seaside of the Eastern Shore of Virginia. This system is composed of barrier islands, salt marshes, broad and shallow coastal bays, intertidal mud flats, and deeper water channels. Manmade shorelines such as bulkhead and rip rap are prevalent in limited areas. This study provides the first quantitative assessment of oyster population abundance on a region wide scale in the coastal bays on the seaside of Virginia’s Eastern Shore. Our estimate of 3.2 billion oysters in this region exceeds the most recent population estimate of 1.8 billion oysters for the entire Virginia portion of Chesapeake Bay produced by the VIMS CBOPE (http://web.vims.edu/mollusc/cbope/VAPDFfiles/VABasin2006.pdf). At the time of our sampling, Dec. 2007 – June 2008, the oyster population was comprised of a wide range of sizes representing several year classes that suggest a self-sustaining population with the potential for significant expansion. The spatially-explicit oyster population GIS product developed through this work provides a valuable tool for guiding fisheries resource management and restoration activities for oysters in this region. The ultimate usefulness of this product lies in its integrative aspect as a GIS tool

On azimuthal spin correlations in Higgs plus jet events at LHC

We consider the recent proposal that the distribution of the difference between azimuthal angles of the two accompanying jets in gluon-fusion induced Higgs-plus-two-jet events at LHC reflects the CP of the Higgs boson produced. We point out that the hierarchy between the Higgs boson mass and the jet transverse energy makes this observable vulnerable to logarithmically enhanced higher-order perturbative corrections. We present an evolution equation that describes the scale variation of the azimuthal angular correlation for the two jets. The emission of extra partons leads to a significant suppression of the correlation. Using the HERWIG Monte Carlo event generator, we carry out a parton-shower analysis to confirm the findings.Comment: Published version. 11 pages, 4 figures, uses JHEP3.cl