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Selected AbstractsA new biodegradation prediction model specific to petroleum hydrocarbonsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2005Philip Howard Abstract A new predictive model for determining quantitative primary biodegradation half-lives of individual petroleum hydrocarbons has been developed. This model uses a fragment-based approach similar to that of several other biodegradation models, such as those within the Biodegradation Probability Program (BIOWIN) estimation program. In the present study, a half-life in days is estimated using multiple linear regression against counts of 31 distinct molecular fragments. The model was developed using a data set consisting of 175 compounds with environmentally relevant experimental data that was divided into training and validation sets. The original fragments from the Ministry of International Trade and Industry BIOWIN model were used initially as structural descriptors and additional fragments were then added to better describe the ring systems found in petroleum hydrocarbons and to adjust for nonlinearity within the experimental data. The training and validation sets had r2 values of 0.91 and 0.81, respectively. [source] Predicting ready biodegradability in the Japanese ministry of international trade and industry testENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2000Jay Tunkel Abstract Two new predictive models for assessing a chemical's biodegradability in the Japanese Ministry of International Trade and Industry (MITI) ready biodegradation test have been developed. The new methods use an approach similar to that in the existing BIOWIN© program, in which the probability of rapid biodegradation is estimated by means of multiple linear or nonlinear regression against counts of 36 chemical substructures (molecular fragments) plus molecular weight (mol wt). The data set used to develop the new models consisted of results (pass/no pass) from the MITI test for 884 discrete organic chemicals. This data set was first divided into randomly selected training and validation sets, and new coefficients were derived for the training set using the BIOWIN fragment library and mol wt as independent variables. Based on these results, the fragment library was then modified by deleting some fragments and adding or refining others, and the new set of independent variables (42 substructures and mol wt) was fit to the MITI data. The resulting linear and nonlinear regression models accurately classified 81% of the chemicals in an independent validation set. Like the established BIOWIN models, the MITI models are intended for use in chemical screening and in setting priorities for further review. [source] Use of dispersal,vicariance analysis in biogeography , a critiqueJOURNAL OF BIOGEOGRAPHY, Issue 1 2010Ullasa Kodandaramaiah Abstract Aim, Analytical methods are commonly used to identify historical processes of vicariance and dispersal in the evolution of taxa. Currently, dispersal,vicariance analysis implemented in the software diva is the most widely used method. Despite some recognized shortcomings of the method, it has been treated as error-free in many cases and used extensively as the sole method to reconstruct histories of taxa. In light of this, an evaluation of the limitations of the method is needed, especially in relation to several newer alternatives. Methods, In an approach similar to simulation studies in phylogenetics, I use hypothetical taxa evolving in specific geological scenarios and test how well diva reconstructs their histories. Results,diva reconstructs histories accurately when evolution has been simple; that is, where speciation is driven mainly by vicariance. Ancestral areas are wrongly identified under several conditions, including complex patterns of dispersals and within-area speciation events. Several potentially serious drawbacks in using diva for inferences in biogeography are discussed. These include the inability to distinguish between contiguous range expansions and across-barrier dispersals, a low probability of invoking extinctions, incorrect constraints set on the maximum number of areas by the user, and analysing the ingroup taxa without sister groups. Main conclusions, Most problems with inferences based on diva are linked to the inflexibility and simplicity of the assumptions used in the method. These are frequently invalid, resulting in spurious reconstructions. I argue that it might be dangerous to rely solely on diva optimization to infer the history of a group. I also argue that diva is not ideally suited to distinguishing between dispersal and vicariance because it cannot a priori take into account the age of divergences relative to the timing of barrier formation. I suggest that other alternative methods can be used to corroborate the findings in diva, increasing the robustness of biogeographic hypotheses. I compare some important alternatives and conclude that model-based approaches are promising. [source] TRAM flap delay: an extraperitoneal laparoscopic techniqueANZ JOURNAL OF SURGERY, Issue 10 2005Ardalan Ebrahimi Although the transverse rectus abdominis musculocutaneous (TRAM) flap is the gold standard in autogenous breast reconstruction, it is less reliable in patients at high risk of ischaemic compromise. A preliminary delay procedure involving ligation of the deep inferior epigastric vessels has been shown to augment flap vascularity and improve outcome in those high risk patients undergoing unipedicled TRAM flap reconstruction. Despite previous description of a transperitoneal laparoscopic technique, surgical delay generally continues to be performed as an open procedure. This may reflect apprehension over the transperitoneal approach with its attendant risk of injury to intra-abdominal organs and vessels as well as adhesion formation. In this paper we describe an extraperitoneal laparoscopic technique for TRAM flap delay. Access to the deep inferior epigastric vessels is obtained using an extraperitoneal approach similar to that used for total extraperitoneal laparoscopic inguinal hernia repair and the vessels are easily identified and ligated using a single working port. While further study is required to evaluate the safety and efficacy of this technique, we report this as an alternative to the known open procedure which may be particularly useful for bilateral TRAM flap delay with the potential for reduced operative time, postoperative pain and scarring by avoiding bilateral inguinal incisions. [source] Imaging auditory hallucinations in schizophreniaACTA NEUROPSYCHIATRICA, Issue 2 2006D. K. Tracy It is increasingly recognized that there are a heterogeneous range of symptoms within the syndrome of schizophrenia and that some of these also occur frequently within other psychiatric conditions. An approach similar to that in neuropsychology, where cases are grouped based on a discrete deficit, or in this case a discrete symptom, rather than a cause or diagnosis, may be useful in exploring the neural correlates of psychotic symptomatology. Functional neuroimaging provides an excellent tool for investigating the in vivo cortical function of patients with schizophrenia. Auditory verbal hallucinations are one of the most commonly occurring psychotic symptoms in schizophrenia; and this paper examines the progress that has been made in utilizing neuroimaging techniques to investigate auditory hallucinations in schizophrenia and review potential implications for treatment and future directions for research. [source] Comparison of two plant functional approaches to evaluate natural restoration along an old-field , deciduous forest chronosequenceJOURNAL OF VEGETATION SCIENCE, Issue 2 2009Isabelle Aubin Abstract Question: Are direct and indirect trait-based approaches similar in their usefulness to synthesize species responses to successional stages? Location: Northern hardwood forests, Québec, Canada (45°01,,45°08,N; 73°58,,74°21,W). Methods: Two different trait-based approaches were used to relate plant functional traits to succession on an old-field , deciduous forest chronosequence: (i) a frequently used approach based on co-occurrence of traits (emergent groups), and (ii) a new version of a direct functional approach at the trait level (the fourth-corner method). Additionally, we selected two different cut-off levels for the herb subset of the emergent group classification in order to test its robustness and ecological relevance. Results: Clear patterns of trait associations with stand developmental stages emerged from both the emergent group and the direct approach at the trait level. However, the emergent group classification was found to hide some trait-level differences such as a shift in seed size, light requirement and plant form along the chronosequence. Contrasting results were obtained for the seven or nine group classification of the herbaceous subset, illustrating how critical is the number of groups for emergent group classification. Conclusion: The simultaneous use of two different trait-based approaches provided a robust and comprehensive characterization of vegetation responses in the old-field , deciduous forest chronosequence. It also underlines the different goals as well as the limitations and benefits of these two approaches. Both approaches indicated that abandoned pastures of the northern hardwood biome have good potential for natural recovery. Conversion of these lands to other functions may lead to irremediable loss of biodiversity. [source] | ||||||||||