Uniform WKB approximation of Coulomb wave functions for arbitrary partial wave

Coulomb wave functions are difficult to compute numerically for extremely low energies, even with direct numerical integration. Hence, it is more convenient to use asymptotic formulas in this region. It is the object of this paper to derive analytical asymptotic formulas valid for arbitrary energies and partial waves. Moreover, it is possible to extend these formulas for complex values of parameters.Comment: 5 pages, 2 figure

Scalable Parallel Numerical Constraint Solver Using Global Load Balancing

We present a scalable parallel solver for numerical constraint satisfaction problems (NCSPs). Our parallelization scheme consists of homogeneous worker solvers, each of which runs on an available core and communicates with others via the global load balancing (GLB) method. The parallel solver is implemented with X10 that provides an implementation of GLB as a library. In experiments, several NCSPs from the literature were solved and attained up to 516-fold speedup using 600 cores of the TSUBAME2.5 supercomputer.Comment: To be presented at X10'15 Worksho

LINVIEW: Incremental View Maintenance for Complex Analytical Queries

Many analytics tasks and machine learning problems can be naturally expressed by iterative linear algebra programs. In this paper, we study the incremental view maintenance problem for such complex analytical queries. We develop a framework, called LINVIEW, for capturing deltas of linear algebra programs and understanding their computational cost. Linear algebra operations tend to cause an avalanche effect where even very local changes to the input matrices spread out and infect all of the intermediate results and the final view, causing incremental view maintenance to lose its performance benefit over re-evaluation. We develop techniques based on matrix factorizations to contain such epidemics of change. As a consequence, our techniques make incremental view maintenance of linear algebra practical and usually substantially cheaper than re-evaluation. We show, both analytically and experimentally, the usefulness of these techniques when applied to standard analytics tasks. Our evaluation demonstrates the efficiency of LINVIEW in generating parallel incremental programs that outperform re-evaluation techniques by more than an order of magnitude.Comment: 14 pages, SIGMO

Tractography in the presence of multiple sclerosis lesions

Accurate anatomical localisation of specific white matter tracts and the quantification of their tract-specific microstructural damage in conditions such as multiple sclerosis (MS) can contribute to a better understanding of symptomatology, disease evolution and intervention effects. Diffusion MRI-based tractography is being used increasingly to segment white matter tracts as regions-of-interest for subsequent quantitative analysis. Since MS lesions can interrupt the tractography algorithm’s tract reconstruction, clinical studies frequently resort to atlas-based approaches, which are convenient but ignorant to individual variability in tract size and shape. Here, we revisit the problem of individual tractography in MS, comparing tractography algorithms using: (i) The diffusion tensor framework; (ii) constrained spherical deconvolution (CSD); and (iii) damped Richardson-Lucy (dRL) deconvolution. Firstly, using simulated and in vivo data from 29 MS patients and 19 healthy controls, we show that the three tracking algorithms respond differentially to MS pathology. While the tensor-based approach is unable to deal with crossing fibres, CSD produces spurious streamlines, in particular in tissue with high fibre loss and low diffusion anisotropy. With dRL, streamlines are increasingly interrupted in pathological tissue. Secondly, we demonstrate that despite the effects of lesions on the fibre orientation reconstruction algorithms, fibre tracking algorithms are still able to segment tracts that pass through areas with a high prevalence of lesions. Combining dRL-based tractography with an automated tract segmentation tool on data from 131 MS patients, the cortico-spinal tracts and arcuate fasciculi could be reconstructed in more than 90% of individuals. Comparing tract-specific microstructural parameters (fractional anisotropy, radial diffusivity and magnetisation transfer ratio) in individually segmented tracts to those from a tract probability map, we show that there is no systematic disease-related bias in the individually reconstructed tracts, suggesting that lesions and otherwise damaged parts are not systematically omitted during tractography. Thirdly, we demonstrate modest anatomical correspondence between the individual and tract probability-based approach, with a spatial overlap between 35 and 55%. Correlations between tract-averaged microstructural parameters in individually segmented tracts and the probability-map approach ranged between r=.53 ( p<.001 ) for radial diffusivity in the right cortico-spinal tract and r=.97 ( p<.001 ) for magnetisation transfer ratio in the arcuate fasciculi. Our results show that MS white matter lesions impact fibre orientation reconstructions but this does not appear to hinder the ability to anatomically reconstruct white matter tracts in MS. Individual tract segmentation in MS is feasible on a large scale and could prove a powerful tool for investigating diagnostic and prognostic markers

Splenectomy through the laparoscopic approach and how I do it

Scopul lucrării. Studierea cazurilor de splenectomie prin abord laparoscopic și clasic în vederea stabilirii cauzalității tip procedurăincidente perioperatorii și demonstrării superiorității abordului laparoscopic. Materiale și metode. Au fost selectate cazurile de splenectomie efectuate prin abord clasic și laparoscopic în Clinica de Chirurgie Colțea, perioada 01.01.2019-31.12.2022. Am revăzut filmările intraoperatorii, am evaluat factorii generali și locali asociați abordului chirurgical preferat. Rezultate. Au fost selectate 29 de cazuri, vârsta medie 54.8 ani, 72.4% femei, 27.6% barbati, 55.2% (16) cu multiple comorbidități: antecedente chirurgicale majore, insuficiența cardiacă, asmul bronșic sever etc. Cazurile au fost împărțite în 2 grupe: Gr. I- cu abord laparoscopic 34.5% (10), Gr. II- cu abord clasic 65.5% (19). Incidența comorbidităților a fost de 10% (1) în Gr.I, cu dimensiunea medie a splinei de 13.2 cm (min 8.5 cm, max 21 cm) și 84.2 % (16) în Gr.II cu dimensiunea medie a splinei de 20.4 cm (min 10 cm, max 34 cm). Doar în Gr.II au fost înregistrate sângerări intraoperatorii în 78.9% (15), iar in 15.8% (3) au fost complicații postoperatorii. Pacienții din Gr.I au avut o perioadă de spitalizare postoperatorie medie de 4 zile, iar cei din Gr. II de 7 zile și au fost externați cu o evoluție postoperatorie favorabilă. Concluzie. Abordul laparoscopic are aceleași indicații ca abordul clasic conform EAES, cu avantajul complicațiilor perioperatorii mult reduse și o spitalizare postoperatorie mai mică comparativ cu abordul clasic, iar în cazul echipelor experimentate este posibil abordul laparoscopic inclusiv la pacienții cu splenomegalii masive (>20cm), care poate fi asistat manual.Aim of study. Study of cases of splenectomy by laparoscopic and classic approach in order to establish causality type procedureperioperative incidents and demonstrate the superiority of the laparoscopic approach. Materials and methods. The cases of splenectomy performed by classical and laparoscopic approach in the Colțea Surgery Clinic, period 01.01.2019-31.12.2022, were selected. We reviewed intraoperative films, assessed general and local factors associated with the preferred surgical approach. Results. 29 cases were selected, average age 54.8 years, 72.4% women, 27.6% men, 55.2% (16) with multiple comorbidities: major surgical antecedents, heart failure, severe bronchial asthma, etc. The cases were divided into 2 groups: Gr. I- with laparoscopic approach 34.5% (10), Gr. II- with classic approach 65.5% (19). The incidence of comorbidities was 10% (1) in Gr.I, with mean spleen size of 13.2 cm (min 8.5 cm, max 21 cm) and 84.2% (16) in Gr.II with mean spleen size of 20.4 cm (min 10 cm, max 34 cm). Only in Gr.II, intraoperative bleeding was recorded in 78.9% (15), and in 15.8% (3) there were postoperative complications. The patients in Gr. I had an average postoperative hospitalization period of 4 days, and those in Gr. II of 7 days, and were discharged with a favorable postoperative evolution. Conclusions. The laparoscopic approach has the same indications as the classic one according to EAES, with the advantage of reduced perioperative complications and a shorter postoperative hospitalization, and in the case of experienced teams, the laparoscopic approach is possible, including patients with massive splenomegaly (>20cm), being manually assisted

Asymptotic equivalence of discretely observed diffusion processes and their Euler scheme: small variance case

This paper establishes the global asymptotic equivalence, in the sense of the Le Cam $\Delta$-distance, between scalar diffusion models with unknown drift function and small variance on the one side, and nonparametric autoregressive models on the other side. The time horizon $T$ is kept fixed and both the cases of discrete and continuous observation of the path are treated. We allow non constant diffusion coefficient, bounded but possibly tending to zero. The asymptotic equivalences are established by constructing explicit equivalence mappings.Comment: 21 page