Preliminary Results for LP VPE X-Ray Detectors

Thick epitaxial layers have been grown using Low Pressure Vapour Phase Epitaxy techniques with low free carrier concentrations . This type of material is attractive as a medium for X-ray detection, because of its high conversion efficiency for X-rays in the medically interesting energy range.Comment: 4 pages. PS file only - original in WORD. Also available at http://ppewww.ph.gla.ac.uk/preprints/97/07

Development of radiographic classification criteria for hand osteoarthritis: a methodological report (Phase 2)

ObjectivesIn Phase 1 of developing new hand osteoarthritis (OA) classification criteria, features associated with hand OA were identified in a population with hand complaints. Radiographic findings could better discriminate patients with hand OA and controls than clinical examination findings. The objective of Phase 2 was to achieve consensus on the features and their weights to be included in three radiographic criteria sets of overall hand OA, interphalangeal OA and thumb base OA.MethodsMultidisciplinary, international expert panels were convened. Patient vignettes were used to identify important features consistent with hand OA. A consensus-based decision analysis approach implemented using 1000minds software was applied to identify the most important features and their relative importance influencing the likelihood of symptoms being due to hand OA. Analyses were repeated for interphalangeal and thumb base OA. The reliability and validity of the proposed criteria sets were tested.ResultsThe experts agreed that the criteria sets should be applied in a population with pain, aching or stiffness in hand joint(s) not explained by another disease or acute injury. In this setting, five additional criteria were considered important: age, morning stiffness, radiographic osteophytes, radiographic joint space narrowing and concordance between symptoms and radiographic findings. The reliability and validity were very good.ConclusionRadiographic features were considered critical when determining whether a patient had symptoms due to hand OA. The consensus-based decision analysis approach in Phase 2 complemented the data-driven results from Phase 1, which will form the basis of the final classification criteria set

Continental-scale patterns of pathogen prevalence: a case study on the corncrake

Pathogen infections can represent a substantial threat to wild populations, especially those already limited in size. To determine how much variation in the pathogens observed among fragmented populations is caused by ecological factors, one needs to examine systems where host genetic diversity is consistent among the populations, thus controlling for any potentially confounding genetic effects. Here, we report geographic variation in haemosporidian infection among European populations of corncrake. This species now occurs in fragmented populations, but there is little genetic structure and equally high levels of genetic diversity among these populations. We observed a longitudinal gradient of prevalence from western to Eastern Europe negatively correlated with national agricultural yield, but positively correlated with corncrake census population sizes when only the most widespread lineage is considered. This likely reveals a possible impact of local agriculture intensity, which reduced host population densities in Western Europe and, potentially, insect vector abundance, thus reducing the transmission of pathogens. We conclude that in the corncrake system, where metapopulation dynamics resulted in variations in local census population sizes, but not in the genetic impoverishment of these populations, anthropogenic activity has led to a reduction in host populations and pathogen prevalence

European wildcat populations are subdivided into five main biogeographic groups: consequences of Pleistocene climate changes or recent anthropogenic fragmentation?

Extant populations of the European wildcat are fragmented across the continent, the likely consequence of recent extirpations due to habitat loss and over-hunting. However, their underlying phylogeographic history has never been reconstructed. For testing the hypothesis that the European wildcat survived the Ice Age fragmented in Mediterranean refuges, we assayed the genetic variation at 31 microsatellites in 668 presumptive European wildcats sampled in 15 European countries. Moreover, to evaluate the extent of subspecies/population divergence and identify eventual wild × domestic cat hybrids, we genotyped 26 African wildcats from Sardinia and North Africa and 294 random-bred domestic cats. Results of multivariate analyses and Bayesian clustering confirmed that the European wild and the domestic cats (plus the African wildcats) belong to two well-differentiated clusters (average Ф ST = 0.159, r st = 0.392, P > 0.001; Analysis of molecular variance [AMOVA]). We identified from c. 5% to 10% cryptic hybrids in southern and central European populations. In contrast, wild-living cats in Hungary and Scotland showed deep signatures of genetic admixture and introgression with domestic cats. The European wildcats are subdivided into five main genetic clusters (average Ф ST = 0.103, r st = 0.143, P > 0.001; AMOVA) corresponding to five biogeographic groups, respectively, distributed in the Iberian Peninsula, central Europe, central Germany, Italian Peninsula and the island of Sicily, and in north-eastern Italy and northern Balkan regions (Dinaric Alps). Approximate Bayesian Computation simulations supported late Pleistocene-early Holocene population splittings (from c. 60 k to 10 k years ago), contemporary to the last Ice Age climatic changes. These results provide evidences for wildcat Mediterranean refuges in southwestern Europe, but the evolution history of eastern wildcat populations remains to be clarified. Historical genetic subdivisions suggest conservation strategies aimed at enhancing gene flow through the restoration of ecological corridors within each biogeographic units. Concomitantly, the risk of hybridization with free-ranging domestic cats along corridor edges should be carefully monitored

Inferring introduction routes of invasive species using approximate Bayesian computation on microsatellite data

Determining the routes of introduction provides not only information about the history of an invasion process, but also information about the origin and construction of the genetic composition of the invading population. It remains difficult, however, to infer introduction routes from molecular data because of a lack of appropriate methods. We evaluate here the use of an approximate Bayesian computation (ABC) method for estimating the probabilities of introduction routes of invasive populations based on microsatellite data. We considered the crucial case of a single source population from which two invasive populations originated either serially from a single introduction event or from two independent introduction events. Using simulated datasets, we found that the method gave correct inferences and was robust to many erroneous beliefs. The method was also more efficient than traditional methods based on raw values of statistics such as assignment likelihood or pairwise F(ST). We illustrate some of the features of our ABC method, using real microsatellite datasets obtained for invasive populations of the western corn rootworm, Diabrotica virgifera virgifera. Most computations were performed with the DIYABC program (http://www1.montpellier.inra.fr/CBGP/diyabc/)

Quality check of cardiac MRI exams for Fallot patients: Interest of a simple formula to detect invalid exams

PurposeCardiac MRI (CMR) is the key exam for Fallot patients but remains tricky. The CMR report should at least mention left and right ventricle end-diastole volumes (Vl and Vr), ejection fraction (EFl and EFr) and pulmonary regurgitation (PR). Obviously, these variables are linked together by basic physiology rules and indeed Vl×EFl=Vr×EFr×(1-PR). We investigated the interest of using such formula as quality check during Fallot CMR exams in our center.Methods98 consecutive CMR examinations for Fallot (or Fallot-like) cardiopathy between 2010 and 2014 were retrospectively included. The exams failing to pass the formula (with a 10% tolerance) constituted the Invalid-group and a control group of the same size was also constituted. CMR of both groups were randomly submitted to a blinded senior observer. The inter-observer limits of agreements were compared for the different variables within both groups.Results(Fig. 1) 12 CMR (12%) failed to pass the validation formula. From the 24 reanalyzed CMR, only 4 failed to pass the formula (all from the Invalid-group). Two had persistent defect (VSD or ASD) which were not mentioned to the radiologist and not detected during the CMR. Two had significant artefacts in the aorta or pulmonary trunk due to sterna wires. The inter-observer disagreements for the 8 other CMR of the Invalid-group concerned the Right ventricle end-diastole volume (P<0.05).ConclusionThe use of a simple formula as quality check of CMR examinations for Fallot patients was useful to detect a total of 12% of CMR with issues. 8% of the CMR corresponded to uncertain right ventricle contours, 2% to persistent septal defects that should have been noticed during the examination and 2% to unreliable aortic or pulmonary flow due to artifacts. The formula could have permitted either to detect the anomalies or at least to conclude that the quality of the exams was impaired

Evidence for Suzuki–Miyaura cross-couplings catalyzed by ligated Pd3-clusters: from cradle to grave

Pdn clusters offer unique selectivity and exploitable reactivity in catalysis. Understanding the behavior of Pdn clusters is thus critical for catalysis, applied synthetic organic chemistry and greener outcomes for precious Pd. The Pd3 cluster, [Pd3(μ-Cl)(μ-PPh2)2(PPh3)3][Cl] (denoted as Pd3Cl2), which exhibits distinctive reactivity, was synthesized and immobilized on a phosphine-functionalized polystyrene resin (denoted as immob-Pd3Cl2). The resultant material served as a tool to study closely the role of Pd3 clusters in a prototypical Suzuki–Miyaura cross-coupling of 4-fluoro-1-bromobenzene and 4-methoxyphenyl boronic acid at varying low Pd ppm concentrations (24, 45, and 68 ppm). Advanced heterogeneity tests such as Hg poisoning and the three-phase test showed that leached mononuclear or nanoparticulate Pd are unlikely to be the major active catalyst species under the reaction conditions tested. EXAFS/XANES analysis from (pre)catalyst and filtered catalysts during and after catalysis has shown the intactness of the triangular structure of the Pd3X2 cluster, with exchange of chloride (X) by bromide during catalytic turnover of bromoarene substrate. This finding is further corroborated by treatment of immob-Pd3Cl2 after catalyzing the Suzuki–Miyaura reaction with excess PPh3, which releases the cluster from the polymer support and so permits direct observation of [Pd3(μ-Br)(μ-PPh2)2(PPh3)3]+ ions by ESI-MS. No evidence is seen for a proposed intermediate in which the bridging halogen on the Pd3 motif is replaced by an aryl group from the organoboronic acid, i.e. formed by a transmetallation-first process. Our findings taken together indicate that the ‘Pd3X2’ motif is an active catalyst species, which is stabilized by being immobilized, providing a more robust Pd3 cluster catalyst system. Non-immobilized Pd3Cl2 is less stable, as is followed by stepwise XAFS of the non-immobilized Pd3Cl2, which gradually changes to a species consistent with ‘Pdx(PPh3)y’ type material. Our findings have far-reaching future implications for Pd3 cluster involvement in catalysis, showing that immobilization of Pd3 cluster species offers advantages for rigorous mechanistic examination and applied chemistries

Phenol is its own selectivity promoter in low-temperature liquid-phase hydrogenation

Phenol hydrogenation is widely studied for selective production of the chemical intermediate cyclohexanone. A plethora of studies in the literature have reported catalysts aiming to achieve high selectivity compared to Pd/C. However, we demonstrate that selective and high-yielding reactions are inherent features of liquid-phase phenol hydrogenation using conventional Pd/C catalysts. We also show there is a very strong dependance of selectivity upon conversion, with high selectivity being maintained until near complete consumption of the phenol, after which subsequent reaction to the unwanted, fully hydrogenated cyclohexanol occurs rapidly. Furthermore, through competitive reactions with other aromatic molecules it is demonstrated that the phenol molecule effectively self-poisons the onwards reaction of weakly bound cyclohexanone, likely by virtue of its relative adsorption strength, and this is the source of the intrinsic selectivity. The implications of this to the reaction mechanism, and in turn to the rational design of catalysts, especially for obtaining chemicals from phenolic bio-oils, are discussed

Catalytic pyrolysis of plastic waste using metal-incorporated activated carbons for monomer recovery and carbon nanotube synthesis

As the global plastic waste crisis intensifies, innovative and sustainable solutions are urgently needed. This study evaluated waste-derived metal-incorporated activated carbon (AC) catalysts for the pyrolysis of mixed plastic waste to generate value-added products, focusing on product yield distribution, composition, hydrogen, and carbon nanotube (CNT) formation. Pyrolysis-catalysis experiments were conducted using a two-stage fixed-bed reactor, wherein the temperature was maintained at 500 °C in first stage (pyrolysis) and varied (500, 600, and 700 °C) in the second stage (catalysis). The tested ACs were incorporated with nickel (Ni-AC), iron (Fe-AC), and zinc (Zn-AC) to assess the impact of metal particles distributed on the carbonaceous support in the second stage. The results from the ACs were compared to those obtained using zeolite (H-ZSM-5), Raw-AC, and non-catalytic runs. The Ni-AC and Fe-AC demonstrated superior catalytic activity, with Ni-AC being more efficient in producing hydrogen (4.24wt%) and CNTs (34.5wt%) with diameters of approximately 30nm, and Fe-AC leading to higher gas yields (68.8wt%) and CNTs (12.4wt%) of around 60nm. In contrast, Zn-AC and Raw-AC presented limited effectiveness, although Raw-AC moderately outperformed Zn-AC with enhanced gas yields and reduced oil/wax yields. The zeolite H-ZSM-5 exhibited the highest gas yields (78wt%), converting heavy fractions into lighter molecules, notably the monomers ethylene and propylene. These findings provide valuable insights into catalyst selection and optimization for plastic waste pyrolysis processes, with H-ZSM-5 being the most effective catalyst for monomer recovery, and Ni-AC and Fe-AC demonstrating promising results