Microfocal X-Ray Computed Tomography Post-Processing Operations for Optimizing Reconstruction Volumes of Stented Arteries During 3D Computational Fluid Dynamics Modeling

Restenosis caused by neointimal hyperplasia (NH) remains an important clinical problem after stent implantation. Restenosis varies with stent geometry, and idealized computational fluid dynamics (CFD) models have indicated that geometric properties of the implanted stent may differentially influence NH. However, 3D studies capturing the in vivo flow domain within stented vessels have not been conducted at a resolution sufficient to detect subtle alterations in vascular geometry caused by the stent and the subsequent temporal development of NH. We present the details and limitations of a series of post-processing operations used in conjunction with microfocal X-ray CT imaging and reconstruction to generate geometrically accurate flow domains within the localized region of a stent several weeks after implantation. Microfocal X-ray CT reconstruction volumes were subjected to an automated program to perform arterial thresholding, spatial orientation, and surface smoothing of stented and unstented rabbit iliac arteries several weeks after antegrade implantation. A transfer function was obtained for the current post-processing methodology containing reconstructed 16 mm stents implanted into rabbit iliac arteries for up to 21 days after implantation and resolved at circumferential and axial resolutions of 32 and 50 μm, respectively. The results indicate that the techniques presented are sufficient to resolve distributions of WSS with 80% accuracy in segments containing 16 surface perturbations over a 16 mm stented region. These methods will be used to test the hypothesis that reductions in normalized wall shear stress (WSS) and increases in the spatial disparity of WSS immediately after stent implantation may spatially correlate with the temporal development of NH within the stented region

Epidemiology of nontuberculous mycobacteria (NTM) amongst individuals with cystic fibrosis (CF)

AbstractBackgroundInfection by nontuberculous mycobacteria (NTM) in patients with cystic fibrosis (CF) is often associated with significant morbidity. Limited, conflicting results are published regarding risk factors for pulmonary NTM disease. We analysed factors potentially associated with NTM in a large population of European patients with CF.MethodsWe investigated associations between presence of NTM and various factors for patients registered in the European Cystic Fibrosis Society Patient Registry.Results374 (2.75%) of 13,593 patients studied had at least one positive NTM culture within the study year. Age- and FEV1-adjusted odds of NTM infection was more than 2.5 times higher (95%CI: 1.79; 3.60) in patients infected by Stenotrophomonas maltophilia than in patients not infected (p<0.0001), 2.36 times higher (95%CI: 1.80;3.08) in patients with ABPA than without (p<0.0001), 1.79 times higher (95%CI: 1.34; 2.38) in patients who use bronchodilators than in patients who don't (p<0.0001), 1.49 times higher (95%CI: 1.18; 1.89) in patients who use inhaled antibiotics than in patients who don't (p=0.001), and 1.30 times higher (95%CI: 1.02; 1.66) in patients who use rhDNase than in patients who don't (p=0.032).ConclusionsNTM-positive cultures in individuals with CF are associated with distinct clinical variables. Improved data collection identifying risk factors for NTM infection will allow more focused screening strategies, and influence therapeutic choices and infection control measures in high-risk patients

Derivatives and Credit Contagion in Interconnected Networks

The importance of adequately modeling credit risk has once again been highlighted in the recent financial crisis. Defaults tend to cluster around times of economic stress due to poor macro-economic conditions, {\em but also} by directly triggering each other through contagion. Although credit default swaps have radically altered the dynamics of contagion for more than a decade, models quantifying their impact on systemic risk are still missing. Here, we examine contagion through credit default swaps in a stylized economic network of corporates and financial institutions. We analyse such a system using a stochastic setting, which allows us to exploit limit theorems to exactly solve the contagion dynamics for the entire system. Our analysis shows that, by creating additional contagion channels, CDS can actually lead to greater instability of the entire network in times of economic stress. This is particularly pronounced when CDS are used by banks to expand their loan books (arguing that CDS would offload the additional risks from their balance sheets). Thus, even with complete hedging through CDS, a significant loan book expansion can lead to considerably enhanced probabilities for the occurrence of very large losses and very high default rates in the system. Our approach adds a new dimension to research on credit contagion, and could feed into a rational underpinning of an improved regulatory framework for credit derivatives.Comment: 26 pages, 7 multi-part figure

Rendering an Account: An Open-State Archive in Postgraduate Supervision

The paper begins with a brief account of the transformation of research degree studies under the pressures of global capitalism and neo-liberal governmentality. A parallel transformation is occurring in the conduct of research through the use of information and communication technologies. Yet the potential of ICTs to shape practices of surveillance or to produce new student-supervisor relations and enhance the processes of developing the dissertation has received almost no critical attention. As doctoral supervisor and student, we then describe the features and uses of a web-based open state archive of the student's work-in-progress, developed by the student and accessible to his supervisor. Our intention was to encourage more open conversations between data and theorising, student and supervisor, and ultimately between the student and professional community. However, we recognise that relations of accountability, as these have developed within a contemporary "audit revolution" (Power, 1994, 1997) in universities, create particular "lines of visibility" (Munro, 1996). Thus while the open-state archive may help to redefine in less managerial terms notions of quality, transparency, flexibility and accountability, it might also make possible greater supervisory surveillance. How should we think about the panoptical potential of this archive? We argue that the diverse kinds of interactional patterns and pedagogical intervention it encourages help to create shifting subjectivities. Moreover, the archive itself is multiple, in bringing together an array of diverse materials that can be read in various ways, by following multiple paths. It therefore constitutes a collage, which we identify as a mode of cognition and of accounting distinct from but related to argument and narrative. As a more "open" text (Iser, 1978) it has an indeterminacy which may render it less open to abuse for the technologies of managerial accountability

Genome-wide association study of receptive language ability of 12 year olds

Purpose: We have previously shown that individual differences in measures of receptive language ability at age 12 are highly heritable. The current study attempted to identify some of the genes responsible for the heritability of receptive language ability using a genome-wide association (GWA) approach. Method: We administered four internet-based measures of receptive language (vocabulary, semantics, syntax, and pragmatics) to a sample of 2329 12-year-olds for whom DNA and genome-wide genotyping were available. Nearly 700,000 single-nucleotide polymorphisms (SNPs) and one million imputed SNPs were included in a GWA analysis of receptive language composite scores. Results: No SNP associations met the demanding criterion of genome-wide significance that corrects for multiple testing across the genome (p < 5 ×10-8). The strongest SNP association did not replicate in an additional sample of 2639 12-year-olds. Conclusion: These results indicate that individual differences in receptive language ability in the general population do not reflect common genetic variants that account for >3% of the phenotypic variance. The search for genetic variants associated with language skill will require larger samples and additional methods to identify and functionally characterize the full spectrum of risk variants

Reactions of Rhenium and Manganese Carbonyl Complexes with 1,8-bis(diphenylphosphino)naphthalene: Ligand Chelation, C–H and C–P bond-cleavage Reactions

Reaction of [Re2(CO)8(MeCN)2] with 1,8-bis(diphenylphosphino)naphthalene (dppn) afforded three mono-rhenium complexes fac-[Re(CO)3(κ1:η1-PPh2C10H6)(PPh2H)] (1), fac-[Re(CO)3{κ1:κ1:η1-(O)PPh2C10H6(O)PPh(C6H4)}] (2) and fac-[ReCl(CO)3(κ2-PPh2C10H6PPh2)] (3). Compounds 1–3 are formed by Re–Re bond cleavage and P–C and C–H bond activation of the dppn ligand. Each of these three complexes have three CO groups arranged in facial fashion. Compound 1 contains a chelating cyclometalated diphenylnaphthylphosphine ligand and a terminally coordinated PPh2H ligand. Compound 2 consists of an orthometalated dppn-dioxide ligand coordinated in a κ1:κ1:η1-fashion via both the oxygen atoms and ortho-carbon atom of one of the phenyl rings. Compound 3 consists of an unchanged chelating dppn ligand and a terminal Cl ligand. Treatment of [Mn2(CO)8(MeCN)2] with a slight excess of dppn in refluxing toluene at 72 °C, gave the previously reported [Mn2(CO)8(μ-PPh2)2] (4), formed by cleavage of C–P bonds, and the new compound fac-[MnCl(CO)3(κ2-PPh2C10H6PPh2)] (5), which has an unaltered chelating dppn and a terminal Cl ligand. In sharp contrast, reaction of [Mn2(CO)8(MeCN)2] with slight excess of dppn at room temperature yielded the dimanganese [Mn2(CO)9{κ1-PPh2(C10H7)}] (6) in which the diphenylnaphthylphosphine ligand, formed by facile cleavage of one of the P–C bonds, is axially coordinated to one Mn atom. Compound 6 was also obtained from the reaction of [Mn2(CO)9(MeCN)] with dppn at room temperature. The XRD structures of complexes 1–3, 5, 6 are reported

Submerged in the mainstream? A case study of an immigrant learner in a New Zealand primary classroom

Immigrant children from diverse language backgrounds face not only linguistic challenges when enrolled in mainstream English-medium classrooms, but also difficulties adjusting to an unfamiliar learning community. The culture of primary school classrooms in New Zealand typically reflects conventions across three dimensions: interactional, instructional task performance and cognitive-academic development. All three dimensions are underpinned by the culturally specific discourse conventions involved in language socialisation. New learners may be helped by classmates or their teacher to understand and successfully use these conventions, but left on their own they may sink rather than swim. This is a case study of one Taiwanese 11-year old boy, 'John', who entered a New Zealand primary classroom midway through the school year. John's basic conversational ability was sound, but he did not possess the interactive classroom skills needed to operate in the new culture of learning. Selected from a wider study of the classroom, transcript data from audio-recorded excerpts of John's interactions over several months with his teacher and classmates are interpreted from perspectives derived from sociocultural and language socialisation theories. The article concludes with a brief consideration of the extent to which John constructed, or was constrained from constructing meaningful learning experiences, and suggestions for further research and reflection

Turbulence Fluctuations and New Universal Realizability Conditions in Modelling

General turbulent mean statistics are shown to be characterized by a variational principle. The variational functionals, or ``effective actions'', have experimental consequences for turbulence fluctuations and are subject to realizability conditions of positivity and convexity. An efficient Rayleigh-Ritz algorithm is available to calculate approximate effective actions within PDF closures. Examples are given for Navier-Stokes and for a 3-mode system of Lorenz. The new realizability conditions succeed at detecting {\em a priori} the poor predictions of PDF closures even when the classical 2nd-order moment realizability conditions are satisfied.Comment: 4 pages, LaTeX (Version 2.09), 3 figures, Postscript, Submitted to Phys. Rev. Let