Multiphase poroelastic modeling in semi-space for deformable reservoirs

Field observations suggest that while pressure depletion is a local process that occurs dominantly in reservoirs being exploited, it triggers a redistribution of effective stress in a more extensive domain that involves not just the adjacent strata, but the entire overburden and surrounding rocks out to considerable distances. In an infinite or semi-infinite domain, a petroleum reservoir can be simulated as a displacement discontinuity, permitting use of an efficient displacement discontinuity boundary element method to calculate surrounding stress and displacement changes. A 3D poroelastic finite element method is used to account for the local reservoir model. By coupling the displacement discontinuity and finite element models, a 3D poroelastic reservoir in an infinite or semi-infinite domain is simulated. The numerical model has been verified and numerical examples are given. Results show that the relative deformation properties of surrounding strata have significant effects on pressure drawdown and reservoir deformation during production, and thus should be taken into account.     

Nicotine dependence subtypes among adolescent smokers: Examining the occurrence, development and validity of distinct symptom profiles.

To increase understanding of the etiology and epidemiology of nicotine dependence among adolescent smokers, the present study examined the occurrence and development of distinct nicotine dependence symptom profiles in a sample of adolescent smokers. A total of 25 secondary schools throughout the Netherlands participated in a 1-year longitudinal study. Multiple dimensions of nicotine dependence were assessed, at two time points, among 641 adolescents (aged 14–17 years) who were classified as smokers. Results showed 4 distinct, yet stable, nicotine dependence subtypes that could be characterized by quantitative as well as qualitative differences. The symptom profiles were similar for males and females but differentially associated with previously identified correlates of nicotine dependence, namely parental smoking, peer smoking, and depressive mood. Finally, differential links of the 4 subtypes were found with regard to smoking uptake and cessation. The finding of qualitative different subgroups of adolescent smokers may have important implications for intervention efforts regarding nicotine dependence and smoking cessation. Such efforts may need to be tailored to the specific subgroups’ needs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the Implementation and Performance of Water Rights Buyback Schemes

Governments are increasingly reliant on the reacquisition of water rights as a mechanism for recovering overexploited basins. Yet, serious concerns have recently been raised about the efficacy and operational dimensions of existing programs. Water buyback is typically implemented as the purchase of a fixed quantity of water rights from the agricultural sector at the price set by the Water Authority. This paper seeks to analyze whether the use of water buyback in its current form represents a sensible means of recovering overexploited basins. The results??which are particularly relevant to contexts characterised by poor enforcement regimes and widespread illegal water use??highlight the need for greater scrutiny of current programs and call for additional work to improve the design of reacquisition policies in the context of water resource management.     

Integrated Photoelasticity for Axisymmetric Thermal Stress Measurement Using the Stress Function

By investigating axisymmetric stress fields with integrated photoelasticity, the stress components σ_z and σ_rz can be determined directly from the experimental data. Stress components σ_r and σ_θ are usually determined using the equilibrium and compatibility equations. In this article it is shown that the stress function for an axisymmetric thermoelastic stress field can be determined on the basis of experimental data, obtained with integrated photoelasticity. Knowledge of the stress function permits one to calculate all the stress components as well as the temperature field in the test object.     

Alternative equations of magnetophotoelasticity and approximate solution of the inverse problem

In magnetophotoelasticity, photoelastic models are investigated in a magnetic field in order to initiate rotation of the plane of polarization that is due to the Faraday effect. The method has been used for the measurement of stress distributions that are in equilibrium on the wave normal and therefore cannot be measured with the traditional photoelastic technique. In this category belong bending stresses in plates and shells and residual stresses in glass plates. Two new systems of equations of magnetophotoelasticity are derived. One of them describes evolution of the polarization of light in a magnetophotoelastic medium in terms of eigenvectors, the other in terms of distinctive parameters. For the latter system, an approximate closed-form solution has been found. The integral Wertheim law has been generalized for the case of stress states in equilibrium when rotation of the plane of polarization is present.     

Identification of cross-linked peptides for protein interaction studies using mass spectrometry and 18O labeling

A new method is presented to screen proteolytic mass maps of cross-linked protein complexes for the presence of cross-linked peptides and for the verification of proposed structures. On the basis of the incorporation of 18O from isotopically enriched water into the C-termini of proteolytic peptides, cross-linked peptides are readily distinguished in mass spectra by a characteristic 8 amu shift. This is due to the incorporation of two 18O atoms in each C-terminus, so that normal and surface-labeled peptides shift 4 amu and cross-linked peptides containing two C-termini will shift 8 amu compared with their unlabeled counterparts. The method is fast, sensitive, and reliable and can be combined with any available cross-linking reagent and a wide range of proteolytic agents. As proof of principle, we successfully applied the method to a complex of two DNA repair proteins (Rad18-Rad6) and identified the interaction domain.     

A proposal to define a core of a scientific subject: A definition using concentration and fuzzy sets

Determining the core of a field"s literature, i.e. its "most important" sources, has been and still is an important problem in bibliometrics. In this article an exact definition of a core of a bibliography or a conglomerate is presented. The main ingredients for this definition are: fuzzy set theory, Lorenz curves and concentration measures. If one prefers a strict delineation, the fuzzy core can easily be defuzzified. The method we propose does not depend on the subjective notion of "importance". It is, moreover, completely reproducible. The method and the resulting core is also independent of the mathematical function (Lotka, Zipf, Bradford, etc.) that may be used to describe the relation between the set of sources and that of items.     

Process standardization for optimal virus recovery and removal of substrate DNA and bovine serum proteins in Vero cell-derived rabies vaccine

Purification of a rabies vaccine by a single zonal centrifugation run was replaced by two runs with optimal standardization of the sucrose density gradient. As a result, significant reductions in the levels of substrate DNA and bovine serum protein in the Vero cell-derived human rabies vaccine were achieved. Following many trials, for the first run, loading of the 3.2-l capacity K-3 rotor with 1800 ml of 60% sucrose solution and 1400 ml of vaccine PBS buffer solution gave a satisfactory linear gradient. However, after the first run, the substrate DNA and bovine serum contents exceeded the required levels. After protamine sulphate and Tween-80 treatment of the concentrated inactivated material, a second run using the same procedure as in the first run was tried. However, these purification procedures resulted in low virus recovery. To achieve optimal virus recovery, and removal of substrate DNA and bovine serum protein, the peak fractions from the first run as indicated by the haemagglutination, sucrose concentration, and optical density values were pooled and the sucrose concentration of the pooled fractions was increased to 60%. A second (flotation) run was then carried out. Using this method, the virus recovery rate was more than 95% that of the first run, and the levels of cellular DNA and bovine serum protein were well within the acceptable limits of less than 100 pg/dose and one part per million, respectively. The substrate DNA was quantified by both radioactive labeling and non-radioactive biotin labeling methods. For the quantification of calf serum protein, a counter-immunoelectrophoresis method was developed and effectively applied. A potency assay was performed using the National Institutes of Health (NIH) and well-standardized in vitro single radial immuno diffusion (SRD) methods. Finally, an immunogenicity study was conducted with human volunteers and the results were confirmed by a rapid fluorescent focus inhibition test (RFFIT).     

Biochemical markers of bone formation and resorption around parturition and during lactation in dairy cows with high and low standard milk yields

Substantial changes occur in skeletal metabolism during lactation. These dynamic changes are monitored with biochemical bone markers. The goal of the present study was to follow these changes in lactating cows and to investigate whether cows with a higher milk yield have a higher mobilization rate of calcium from bone. Hydroxyproline, deoxypyridinoline, pyridinoline, and the carboxyterminal telopeptide of type I collagen (ICTP) were chosen as markers for bone resorption, whereas osteocalcin was used as a bone formation marker. Urine and blood samples were collected from cows with a mean standard milk yield of 4900 and 6500 kg, respectively, 14 d before, and 14 d, 1 mo, 1.5 mo, and monthly after parturition. Urinary hydroxyproline, deoxypyridinoline, and pyridinoline concentrations increased with time, but no differences between the two groups were evident. Concentrations of 1,25-dihydroxy vitamin D and ICTP of the two groups showed an increase 14 d after parturition. Furthermore, using multivariate regression models with age and milk yield as covariates, ICTP concentrations were higher in the group with a higher milk yield. In contrast, osteocalcin concentrations decreased 14 d after parturition and returned to prepartum values 1 mo after parturition. The increase of ICTP concentrations in both groups indicates that bone was substantially resorbed. At the same time, probably less Ca was embedded in bone, as indicated by the decrease of the osteocalcin concentrations. In conclusion, cows showed increased bone resorption around parturition, and cows with higher milk yield mobilize calcium more actively from bone than cows with lower milk yield.     

Clinical mastitis in primiparous Holsteins: comparisons of bovine leukocyte adhesion deficiency carriers and noncarriers

The objective of this study was to determine the impact of bovine leukocyte adhesion deficiency on clinical mastitis incidence, severity, and duration in Holstein cows. Genomic DNA from milk of 847 Holstein cows in six Pennsylvania herds was used to determine bovine leukocyte adhesion deficiency genotypes (82 or 9.7% carriers). Data on clinical mastitis incidence, severity, duration, and pathogen involved were collected during first lactation for the project cows. One hundred ninety-four cows had one or more clinical mastitis episodes; milk samples from each quarter with clinical mastitis were collected at discovery of the episode and were cultured following National Mastitis Council recommendations. The overall incidence of clinical mastitis was significantly affected by sire and herd-year-season of calving. In addition, incidence of clinical mastitis tended to increase with age at first calving. Severity and duration of clinical mastitis were impacted by the pathogen involved. Incidence of clinical mastitis from all pathogens, from coagulase-negative staphylococci, and from coliform bacteria was not significantly related to bovine leukocyte adhesion deficiency status. Carriers tended to have lower rates of mastitis from streptococci other than Streptococcus agalactiae when compared with noncarriers, but this result should be interpreted with caution because of the low frequency of mastitis from the streptococci. Bovine leukocyte adhesion deficiency status was unrelated to severity or duration of clinical episodes. Bovine leukocyte adhesion deficiency carriers are probably similar to noncarriers in resistance to clinical mastitis.