994 resultados para soft-commutation technique


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ABSTRACT Cassava (Manihot esculenta Crantz) is a highly mycotrophic crop, and prior soil cover may affect the density of arbuscular mycorrhizal fungi (AMFs), as well as the composition of the AMFs community in the soil. The aim of this study was to evaluate the occurrence and the structure of AMFs communities in cassava grown after different cover crops, and the effect of the cover crop on mineral nutrition and cassava yield under an organic farming system. The occurrence and structure of the AMFs community was evaluated through polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE). A randomized block experimental design was used with four replications. Six different cover crop management systems before cassava were evaluated: black oats, vetch, oilseed radish, intercropped oats + vetch, intercropped oats + vetch + oilseed radish, plus a control (fallow) treatment mowed every 15 days. Oats as a single crop or oats intercropped with vetch or with oilseed radish increased AMFs inoculum potential in soil with a low number of propagules, thus benefiting mycorrhizal colonization of cassava root. The treatments did not affect the structure of AMFs communities in the soil since the AMFs communities were similar in cassava roots in succession to different cover crops. AMFs colonization was high despite high P availability in the soil. The cassava crop yield was above the regional average, and P levels in the leaves were adequate, regardless of which cover crop treatments were used. One cover crop cycle prior to the cassava crop was not enough to observe a significant response in variables, P in plant tissue, crop yield, and occurrence and structure of AMFs communities in the soil. In the cassava roots in succession, the plant developmental stage affected the groupings of the structure of the AMF community.

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INTRODUCTION: The arteries of bifurcation aneurysms are sometimes so angulated or tortuous that an exchange maneuver is necessary to catheterize them with a balloon or stent delivery catheter. Because of the risk of distal wire perforation associated with exchange maneuvers, we sought to find an alternative technique. METHODS: Our experience shows that a microcatheter tends to preferentially follow a previously placed microcatheter, even if the initial catheterization might be challenging. Accessing an artery with two microcatheters simultaneously may thus be an alternative to an exchange maneuver. Because of this tendency for catheters to behave like sheep following one another, we named this method the sheeping technique (ST). The ST consists of (a) first placing a 1.7 French microcatheter into the division branch requiring balloon or stent protection to straighten the course of the arteries in order to facilitate and (b) positioning in the same artery of a larger and stiffer balloon or stent microcatheter. Once the second balloon or stent microcatheter is in place, the first microcatheter can be pulled back and used to coil the aneurysm. RESULTS: Between January 2009 and December 2012, The ST was successfully used in 208/246 procedures (85 %). Conversion to an exchange maneuver was necessary in 38/246 (15 %). There were no arterial perforations or ischemic events related to the handling of both microcatheters. CONCLUSION: The sheeping technique may improve safety by replacing the need for an exchange maneuver during difficult balloon- or stent-assisted coiling.

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PURPOSE: To objectively characterize different heart tissues from functional and viability images provided by composite-strain-encoding (C-SENC) MRI. MATERIALS AND METHODS: C-SENC is a new MRI technique for simultaneously acquiring cardiac functional and viability images. In this work, an unsupervised multi-stage fuzzy clustering method is proposed to identify different heart tissues in the C-SENC images. The method is based on sequential application of the fuzzy c-means (FCM) and iterative self-organizing data (ISODATA) clustering algorithms. The proposed method is tested on simulated heart images and on images from nine patients with and without myocardial infarction (MI). The resulting clustered images are compared with MRI delayed-enhancement (DE) viability images for determining MI. Also, Bland-Altman analysis is conducted between the two methods. RESULTS: Normal myocardium, infarcted myocardium, and blood are correctly identified using the proposed method. The clustered images correctly identified 90 +/- 4% of the pixels defined as infarct in the DE images. In addition, 89 +/- 5% of the pixels defined as infarct in the clustered images were also defined as infarct in DE images. The Bland-Altman results show no bias between the two methods in identifying MI. CONCLUSION: The proposed technique allows for objectively identifying divergent heart tissues, which would be potentially important for clinical decision-making in patients with MI.

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Investigation of violent death, especially cases of sharp trauma and gunshot, is an important part of medico-legal investigations. Beside the execution of a conventional autopsy, the performance of a post-mortem Multi-Detector Computed Tomography (MDCT)-scan has become a highly appreciated tool. In order to investigate also the vascular system, post-mortem CT-angiography has been introduced. The most studied and widespread technique is the Multi-phase post-mortem CT-angiography (MPMCTA). Its sensitivity to detect vascular lesions is even superior to conventional autopsy. The application of MPMCTA for cases of gunshot and sharp-trauma is therefore an obvious choice, as vascular lesions are common in such victims. In most cases of sharp trauma and in several cases of gunshots, death can be attributed to exsanguinations. MPMCTA is able to detect the exact source of bleeding and also to visualize trajectories, which are of most importance in these cases. The reconstructed images allow to clearly visualizing the trajectory in a way that is easily comprehensible for not medically trained legal professionals. The sensitivity of MPMCTA for soft tissue and organ lesions approximately matches the sensitivity of conventional autopsy. However, special care, experience and effective use of the imaging software is necessary for performing the reconstructions of the trajectory. Large volume consuming haemorrhages and shift of inner organs are sources of errors and misinterpretations. This presentation shall give an overview about the advantages and limitations of the use of MPMCTA for investigating cases of gunshot and sharp-trauma.

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Superior vena cava (SVC) clamping can be required during thoracic surgery for SVC replacement or repair. In such cases, bypass techniques can be necessary to avoid hemodynamic instability, cerebral venous hypertension and hypoperfusion. Here, we report a novel and simple SVC bypass technique which does not require full systemic heparinization, specialized cannulation techniques or pumping devices and which can be applied percutaneously in the preoperative phase or intraoperatively. The preoperative shunt consisted in two Swan-Ganz catheters inserted in the jugular and femoral veins and connected by perfusion tubing with a three way stopcock. The intraoperative shunt consisted of a Pruitt(®)-catheter inserted in the left innominate vein and connected to a femoral Swan-Ganz catheter by perfusion tubing. We validated our system in seven patients undergoing SVC reconstruction. We monitored the systemic arterial blood pressures, the heart rate and vasoactive peptide requirements throughout the procedure. We also determined the neurological status and the in-hospital morbidity and mortality for each patient. Using this bypass, SVC clamping caused no hemodynamic instability, no neurological impairments and no in-hospital complications or deaths. This simple temporary SVC bypass procedure is safe and avoids hemodynamic instability and cerebral venous hypertension.

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We have developed a digital holographic microscope (DHM), in a transmission mode, especially dedicated to the quantitative visualization of phase objects such as living cells. The method is based on an original numerical algorithm presented in detail elsewhere [Cuche et al., Appl. Opt. 38, 6994 (1999)]. DHM images of living cells in culture are shown for what is to our knowledge the first time. They represent the distribution of the optical path length over the cell, which has been measured with subwavelength accuracy. These DHM images are compared with those obtained by use of the widely used phase contrast and Nomarski differential interference contrast techniques.

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Any transportation infrastructure system is inherently concerned with durability and performance issues. The proportioning and uniformity control of concrete mixtures are critical factors that directly affect the longevity and performance of the portland cement concrete pavement systems. At present, the only means available to monitor mix proportions of any given batch are to track batch tickets created at the batch plant. However, this does not take into account potential errors in loading materials into storage silos, calibration errors, and addition of water after dispatch. Therefore, there is a need for a rapid, cost-effective, and reliable field test that estimates the proportions of as-delivered concrete mixtures. In addition, performance based specifications will be more easily implemented if there is a way to readily demonstrate whether any given batch is similar to the proportions already accepted based on laboratory performance testing. The goal of the present research project is to investigate the potential use of a portable x-ray fluorescence (XRF) technique to assess the proportions of concrete mixtures as they are delivered. Tests were conducted on the raw materials, paste and mortar samples using a portable XRF device. There is a reasonable correlation between the actual and calculated mix proportions of the paste samples, but data on mortar samples was less reliable.

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OBJECTIVE: The purpose of this article is to assess the effect of the adaptive statistical iterative reconstruction (ASIR) technique on image quality in hip MDCT arthrography and to evaluate its potential for reducing radiation dose. SUBJECTS AND METHODS: Thirty-seven patients examined with hip MDCT arthrography were prospectively randomized into three different protocols: one with a regular dose (volume CT dose index [CTDIvol], 38.4 mGy) and two with a reduced dose (CTDIvol, 24.6 or 15.4 mGy). Images were reconstructed using filtered back projection (FBP) and four increasing percentages of ASIR (30%, 50%, 70%, and 90%). Image noise and contrast-to-noise ratio (CNR) were measured. Two musculoskeletal radiologists independently evaluated several anatomic structures and image quality parameters using a 4-point scale. They also jointly assessed acetabular labrum tears and articular cartilage lesions. RESULTS: With decreasing radiation dose level, image noise statistically significantly increased (p=0.0009) and CNR statistically significantly decreased (p=0.001). We also found a statistically significant reduction in noise (p=0.0001) and increase in CNR (p≤0.003) with increasing percentage of ASIR; in addition, we noted statistically significant increases in image quality scores for the labrum and cartilage, subchondral bone, overall diagnostic quality (up to 50% ASIR), and subjective noise (p≤0.04), and statistically significant reductions for the trabecular bone and muscles (p≤0.03). Regardless of the radiation dose level, there were no statistically significant differences in the detection and characterization of labral tears (n=24; p=1) and cartilage lesions (n=40; p≥0.89) depending on the ASIR percentage. CONCLUSION: The use of up to 50% ASIR in hip MDCT arthrography helps to reduce radiation dose by approximately 35-60%, while maintaining diagnostic image quality comparable to that of a regular-dose protocol using FBP.

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Background And Objectives: Isolated limb perfusion with TNF-alpha and melphalan (TM-ILP) is a limb salvage therapy for non-resectable soft tissue sarcomas (STS) of the extremities. It is indicated for patients for whom amputation or debilitating surgery is the only alternative. It can be used either as an exclusive therapy (in palliation) or as a neo-adjuvant treatment, followed by marginal resection of tumor remnants with minimal functional impairment. Methods: Between February 1992 and March 2006, 57 TM-ILPs were performed on 51 patients with 88% high grade and 84% advanced stage tumors. Results: Mean follow-up is 38.9 months (4-159, median 22 months). Twenty-one percent patients had significant early complications, with 3 major re-operations, and 23% suffered long-lasting complications. Complete response was observed in 25%, partial response in 42%, stable disease in 14% and progressive disease in 14%. Resection of the tumor remnants was possible in 65%. A complementary treatment was necessary in 31%, mostly radiation therapy. A local recurrence was observed in 35%, after a mean of 20.3 months (2-78), and distant relapse was seen in 45%, after a mean of 13.4 months (5-196). Mean Disease-free survival was 14.9 months, and overall 5-year-survival 43.5%. Amputation rate at 5 years was 24%. Conclusions: TM-ILP is a conservative treatment with a high complications rate, but it can be successful even for the most severe STS of extremities. As a consequence the limb can be spared from amputation or debilitating surgery on the long term in about 75% of patients