214 research outputs found

    Holomorphic symmetric differentials and a birational characterization of Abelian Varieties

    Full text link
    A generically generated vector bundle on a smooth projective variety yields a rational map to a Grassmannian, called Kodaira map. We answer a previous question, raised by the asymptotic behaviour of such maps, giving rise to a birational characterization of abelian varieties. In particular we prove that, under the conjectures of the Minimal Model Program, a smooth projective variety is birational to an abelian variety if and only if it has Kodaira dimension 0 and some symmetric power of its cotangent sheaf is generically generated by its global sections.Comment: UPDATED: more details added on main proo

    Comparison of ERBS orbit determination accuracy using batch least-squares and sequential methods

    Get PDF
    The Flight Dynamics Div. (FDD) at NASA-Goddard commissioned a study to develop the Real Time Orbit Determination/Enhanced (RTOD/E) system as a prototype system for sequential orbit determination of spacecraft on a DOS based personal computer (PC). An overview is presented of RTOD/E capabilities and the results are presented of a study to compare the orbit determination accuracy for a Tracking and Data Relay Satellite System (TDRSS) user spacecraft obtained using RTOS/E on a PC with the accuracy of an established batch least squares system, the Goddard Trajectory Determination System (GTDS), operating on a mainframe computer. RTOD/E was used to perform sequential orbit determination for the Earth Radiation Budget Satellite (ERBS), and the Goddard Trajectory Determination System (GTDS) was used to perform the batch least squares orbit determination. The estimated ERBS ephemerides were obtained for the Aug. 16 to 22, 1989, timeframe, during which intensive TDRSS tracking data for ERBS were available. Independent assessments were made to examine the consistencies of results obtained by the batch and sequential methods. Comparisons were made between the forward filtered RTOD/E orbit solutions and definitive GTDS orbit solutions for ERBS; the solution differences were less than 40 meters after the filter had reached steady state

    Improved solution accuracy for Landsat-4 (TDRSS-user) orbit determination

    Get PDF
    This paper presents the results of a study to compare the orbit determination accuracy for a Tracking and Data Relay Satellite System (TDRSS) user spacecraft, Landsat-4, obtained using a Prototype Filter Smoother (PFS), with the accuracy of an established batch-least-squares system, the Goddard Trajectory Determination System (GTDS). The results of Landsat-4 orbit determination will provide useful experience for the Earth Observing System (EOS) series of satellites. The Landsat-4 ephemerides were estimated for the January 17-23, 1991, timeframe, during which intensive TDRSS tracking data for Landsat-4 were available. Independent assessments were made of the consistencies (overlap comparisons for the batch case and convariances for the sequential case) of solutions produced by the batch and sequential methods. The filtered and smoothed PFS orbit solutions were compared with the definitive GTDS orbit solutions for Landsat-4; the solution differences were generally less than 15 meters

    PHIL photoinjector test line

    Full text link
    LAL is now equiped with its own platform for photoinjectors tests and Research and Developement, named PHIL (PHotoInjectors at LAL). This facility has two main purposes: push the limits of the photoinjectors performances working on both the design and the associated technology and provide a low energy (MeV) short pulses (ps) electron beam for the interested users. Another very important goal of this machine will be to provide an opportunity to form accelerator physics students, working in a high technology environment. To achieve this goal a test line was realised equipped with an RF source, magnets and beam diagnostics. In this article we will desrcibe the PHIL beamline and its characteristics together with the description of the first two photoinjector realised in LAL and tested: the ALPHAX and the PHIN RF Guns

    Improved solution accuracy for TDRSS-based TOPEX/Poseidon orbit determination

    Get PDF
    Orbit determination results are obtained by the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) using a batch-least-squares estimator available in the Goddard Trajectory Determination System (GTDS) and an extended Kalman filter estimation system to process Tracking and Data Relay Satellite (TDRS) System (TDRSS) measurements. GTDS is the operational orbit determination system used by the FDD in support of the Ocean Topography Experiment (TOPEX)/Poseidon spacecraft navigation and health and safety operations. The extended Kalman filter was implemented in an orbit determination analysis prototype system, closely related to the Real-Time Orbit Determination System/Enhanced (RTOD/E) system. In addition, the Precision Orbit Determination (POD) team within the GSFC Space Geodesy Branch generated an independent set of high-accuracy trajectories to support the TOPEX/Poseidon scientific data. These latter solutions use the geodynamics (GEODYN) orbit determination system with laser ranging and Doppler Orbitography and Radiopositioning integrated by satellite (DORIS) tracking measurements. The TOPEX/Poseidon trajectories were estimated for November 7 through November 11, 1992, the timeframe under study. Independent assessments were made of the consistencies of solutions produced by the batch and sequential methods. The batch-least-squares solutions were assessed based on the solution residuals, while the sequential solutions were assessed based on primarily the estimated covariances. The batch-least-squares and sequential orbit solutions were compared with the definitive POD orbit solutions. The solution differences were generally less than 2 meters for the batch-least-squares and less than 13 meters for the sequential estimation solutions. After the sequential estimation solutions were processed with a smoother algorithm, position differences with POD orbit solutions of less than 7 meters were obtained. The differences among the POD, GTDS, and filter/smoother solutions can be traced to differences in modeling and tracking data types, which are being analyzed in detail

    Safety and feasibility of thullium laser transurethral resection of prostate for the treatment of benign prostatic enlargement in overweight patients

    Get PDF
    Objective: We aimed to determine safety and feasibility of thulium laser transurethral vapoenucleation of prostate (ThuVEP) for treatment of obese patients affected by benign prostatic hyperplasia (BPH). Methods: We retrospectively analysed data of 452 patients with BPH who underwent ThuVEP from February 2012 to March 2016 in a single center. Patients were divided into three groups according to body mass index (BMI, kg/m2): Normal weight (18.5 64 BMI < 25; Group A), overweight (25 64 BMI < 30; Group B) and obese (BMI 65 30; Group C), for a total of 412 patients evaluable for this study. Preoperative total serum prostate-specific antigen (PSA), digital rectal examination of the prostate, transrectal ultrasound (TRUS), renal ultrasound, urine culture, uroflowmetry, International Prostate Symptoms Score (IPSS), and Quality of Life (QoL) score were analyzed. Post-operative complications, hospital stay and days of catheterization, questionnaires and uroflowmetry at 1 and 3 months after surgery were evaluated. Preoperative data, surgical outcomes, complication rate and clinical outcomes were compared between groups. Results: The median age of patients was 69 years (Interquartile Range [IQR 10]). The preoperative median IPSS among groups was 19 (IQR 8.75), 20 (IQR 10), and 18 (IQR 10) respectively. At 1 and 3 months of follow-up, this value was 8 (IQR 7), 8 (IQR 4), 7 (IQR 5) and 5 (IQR 6.25), 5 (IQR 6), 6 (IQR 5), respectively (all p between groups > 0.05). There was no statistically significant difference among three groups as for hospital stay and days of catheterization (p > 0.05). Conclusion: Our results showed that ThuVEP was safe and feasible even in overweight patients with substantially enlarged prostate

    Metabolic syndrome predicts worse perioperative outcomes in patients treated with partial nephrectomy for renal cell carcinoma

    Get PDF
    OBJECTIVE: To test the association between metabolic syndrome (MetS) and its components (high blood pressure, body mass index [BMI] 65 30, altered fasting glucose, low high-density lipoprotein cholesterol and high triglycerides) on perioperative outcomes after partial nephrectomy (PN). METHODS: Within the National Inpatient Sample database (2000-2015) we identified all PN patients. First, temporal trends of MetS were reported. Second, the effect of MetS components was tested in multivariable logistic regression models predicting overall and specific perioperative complications. Third, we tested for dose-response from the concomitant effect of multiple MetS components. All models were weighted and adjusted for clustering, as well as all available patient and hospital characteristics. RESULTS: Of 25,875 patients: (1) 59.3% had high blood pressure, (2) 14.7% had BMI 65 30, (3) 21.7% had altered fasting glucose, (4) 20.2% had high triglycerides, and (5) <0.01% had low high-density lipoprotein cholesterol. One vs 2 vs 3 vs 4 MetS components were recorded in 34.9% vs 22.9% vs 8.9% vs 2.2% patients. Of all, 11.1% exhibited 65 3 components and qualified for MetS. The rates of MetS increased over time (estimated annual percentage changes: +12.0%;P <.001). The 4 tested MetS components (high blood pressure, BMI 65 30, altered fasting glucose, and high triglycerides) achieved independent predictor status in multivariable models predicting overall, cardiac, miscellaneous medical, vascular, and respiratory complications, as well as transfusions. Moreover, a statistically significant dose-response was confirmed for the same endpoints. CONCLUSION: MetS and its components consistently and strongly predict perioperative complications after PN. Moreover, the strength of the effect was directly proportional to the number of MetS components exhibited by each individual patient, even if formal MetS diagnosis of 65 3 components has not been m

    Posterior musculofascial reconstruction after radical prostatectomy: an updated systematic review and a meta-analysis

    Get PDF
    To evaluate the influence of posterior musculofascial plate reconstruction (PR) on early return of continence after radical prostatectomy (RP); an updated systematic review of the literature. A systematic review of the literature was performed in June 2015, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and searching Medline, Embase, Scopus and Web of Science databases. We searched the terms posterior reconstruction prostatectomy, double layer anastomosis prostatectomy across the 'Title' and 'Abstract' fields of the records, with the following limits: humans, gender (male), and language (English). The authors reviewed the records to identify studies comparing cohorts of patients who underwent RP with or without restoration of the posterior aspect of the rhabdosphincter. A meta-analysis of the risk ratios estimated using data from the selected studies was performed. In all, 21 studies were identified, including three randomised controlled trials. The overall analysis of comparative studies showed that PR improved early continence recovery at 3-7, 30, and 90 days after catheter removal, while the continence rate at 180 days was statistically but not clinically affected. Statistically significantly lower anastomotic leakage rates were described after PR. There were no significant differences for positive surgical margins rates or for complications such as acute urinary retention and bladder neck stricture. The analysis confirms the benefits at 30 days after catheter removal already discussed in the review published in 2012, but also shows a significant advantage in terms of urinary continence recovery in the first 90 days. A multicentre prospective randomised controlled trial is currently being conducted in several institutions around the world to better assess the effectiveness of PR in facilitating an earlier recovery of postoperative urinary continence

    Caracterización energética de vinazas de caña de azúcar como posible biocombustible para calderas de vapor bagaceras

    Get PDF
    La vinaza es un líquido derivado de la destilación del vino resultante de la fermentación de jugos o mieles de caña de azúcar; posee un pH ácido con alto contenido de materia orgánica que si no se trata adecuadamente puede ser contaminante. El objetivo de este trabajo es mostrar nuevos resultados de las características energéticas de vinazas de nuestra región para diferentes grados de concentración: 30, 40, 50 y 60 ºBrix, con el objetivo de aprovechar este efluente como posible biocombustible para calderas de vapor de la industria azucarera. Los resultados promedio obtenidos fueron: 36,80 % de cenizas (b.s.); 1,02 a 1,26 g/cm3 de densidad; 0,91 a 224,84 cp de viscosidad; punto de fusión de 850 a 900ºC y poder calorífico superior (PCS) entre 1.008 a 3.356 kcal/kg. Este estudio sirve de base para el diseño de nuevos sistemas de transporte y de combustión de este posible fluido combustible.The vinasse is a liquid derived from the distillation of wine resulting from the fermentation of juice or sugar cane molasses. It has an acid pH, with high in organic matter, which if it is not well treated it could be contaminant. The aim of this paper is to show new results of the energy characteristics of vinasse in our region, for different degrees of concentration: 30, 40, 50, and 60ºBrix, with the object of making this effluent as possible biofuel for steam boilers of the sugar industry. The average results were: 36.80% ash (d.b.); 1.02 to 1.26 g/cm3 density; viscosity 0.932 to 224.84 cp; melting point 850 to 900°C and higher calorific value (PCS) between 1008 to 3356 kcal/kg. This study results can be used as a base for the design of new transport systems and combustion for this possible combustible fluid.Tema 6: Energía eólica, geotermia, biomasa y otras energías no convencionales.Facultad de Arquitectura y Urbanism

    Caracterización energética de vinazas de caña de azúcar como posible biocombustible para calderas de vapor bagaceras

    Get PDF
    La vinaza es un líquido derivado de la destilación del vino resultante de la fermentación de jugos o mieles de caña de azúcar; posee un pH ácido con alto contenido de materia orgánica que si no se trata adecuadamente puede ser contaminante. El objetivo de este trabajo es mostrar nuevos resultados de las características energéticas de vinazas de nuestra región para diferentes grados de concentración: 30, 40, 50 y 60 ºBrix, con el objetivo de aprovechar este efluente como posible biocombustible para calderas de vapor de la industria azucarera. Los resultados promedio obtenidos fueron: 36,80 % de cenizas (b.s.); 1,02 a 1,26 g/cm3 de densidad; 0,91 a 224,84 cp de viscosidad; punto de fusión de 850 a 900ºC y poder calorífico superior (PCS) entre 1.008 a 3.356 kcal/kg. Este estudio sirve de base para el diseño de nuevos sistemas de transporte y de combustión de este posible fluido combustible.The vinasse is a liquid derived from the distillation of wine resulting from the fermentation of juice or sugar cane molasses. It has an acid pH, with high in organic matter, which if it is not well treated it could be contaminant. The aim of this paper is to show new results of the energy characteristics of vinasse in our region, for different degrees of concentration: 30, 40, 50, and 60ºBrix, with the object of making this effluent as possible biofuel for steam boilers of the sugar industry. The average results were: 36.80% ash (d.b.); 1.02 to 1.26 g/cm3 density; viscosity 0.932 to 224.84 cp; melting point 850 to 900°C and higher calorific value (PCS) between 1008 to 3356 kcal/kg. This study results can be used as a base for the design of new transport systems and combustion for this possible combustible fluid.Tema 6: Energía eólica, geotermia, biomasa y otras energías no convencionales.Facultad de Arquitectura y Urbanism
    corecore