Ideal Approach (ideal + approach)

Distribution by Scientific Domains

Selected Abstracts

Comparison of Single Crystal Simple Shear Deformation Experiments with Crystal Plasticity Finite Element Simulations,

F. Roters
The crystal plasticity finite element method is an ideal approach to simulate the mechanics, texture, and elastic-plastic anisotropy of materials. Experimental validation of such simulations requires to measure these quantities without the disturbing influence of friction known for instance from channel-die experiments. This work presents results obtained form simple shear deformation experiments of aluminium single crystals together with corresponding crystal plasticity finite element simulations. [source]

Complement and its implications in cardiac ischemia/reperfusion: strategies to inhibit complement

Tiphaine Monsinjon
Although reperfusion of the ischemic myocardium is an absolute necessity to salvage tissue from eventual death, it is also associated with pathologic changes that represent either an acceleration of processes initiated during ischemia or new pathophysiological changes that were initiated after reperfusion. This so-called ,reperfusion injury' is accompanied by a marked inflammatory reaction, which contributes to tissue injury. In addition to the well known role of oxygen free radicals and white blood cells, activation of the complement system probably represents one of the major contributors of the inflammatory reaction upon reperfusion. The complement may be activated through three different pathways: the classical, the alternative, and the lectin pathway. During reperfusion, complement may be activated by exposure to intracellular components such as mitochondrial membranes or intermediate filaments. Two elements of the activated complement contribute directly or indirectly to damages: anaphylatoxins (C3a and C5a) and the membrane attack complex (MAC). C5a, the most potent chemotactic anaphylatoxin, may attract neutrophils to the site of inflammation, leading to superoxide production, while MAC is deposited over endothelial cells and smooth vessel cells, leading to cell injury. Experimental evidence suggests that tissue salvage may be achieved by inhibition of the complement pathway. As the complement is composed of a cascade of proteins, it provides numerous sites for pharmacological interventions during acute myocardial infarction. Although various strategies aimed at modulating the complement system have been tested, the ideal approach probably consists of maintaining the activity of C3 (a central protein of the complement cascade) and inhibiting the later events implicated in ischemia/reperfusion and also in targeting inhibition in a tissue-specific manner. [source]

A comparison of Granger causality and coherency in fMRI-based analysis of the motor system

Andrew S. Kayser
Abstract The ability of functional MRI to acquire data from multiple brain areas has spurred developments not only in voxel-by-voxel analyses, but also in multivariate techniques critical to quantifying the interactions between brain areas. As the number of multivariate techniques multiplies, however, few studies in any modality have directly compared different connectivity measures, and fewer still have done so in the context of well-characterized neural systems. To focus specifically on the temporal dimension of interactions between brain regions, we compared Granger causality and coherency (Sun et al., 2004, 2005: Neuroimage 21:647,658, Neuroimage 28:227,237) in a well-studied motor system (1) to gain further insight into the convergent and divergent results expected from each technique, and (2) to investigate the leading and lagging influences between motor areas as subjects performed a motor task in which they produced different learned series of eight button presses. We found that these analyses gave convergent but not identical results: both techniques, for example, suggested an anterior-to-posterior temporal gradient of activity from supplemental motor area through premotor and motor cortices to the posterior parietal cortex, but the techniques were differentially sensitive to the coupling strength between areas. We also found practical reasons that might argue for the use of one technique over another in different experimental situations. Ultimately, the ideal approach to fMRI data analysis is likely to involve a complementary combination of methods, possibly including both Granger causality and coherency. Hum Brain Mapp, 2009. 2009 Wiley-Liss, Inc. [source]

Replacement versus repair of defective restorations in adults: resin composite

MO Sharif
Background:, Composite filling materials have been increasingly used for the restoration of posterior teeth in recent years as a tooth coloured alternative to amalgam. As with any filling material composites have a finite life-span. Traditionally, replacement was the ideal approach to treat defective composite restorations, however, repairing composites offers an alternative more conservative approach where restorations are partly still serviceable. Repairing the restoration has the potential of taking less time and may sometimes be performed without the use of local anaesthesia hence it may be less distressing for a patient when compared with replacement. Objectives:, To evaluate the effectiveness of replacement (with resin composite) versus repair (with resin composite) in the management of defective resin composite dental restorations in permanent molar and premolar teeth. Search strategy:, For the identification of studies relevant to this review we searched the Cochrane Oral Health Group Trials Register (to 23rd September 2009); CENTRAL (The Cochrane Library 2009, Issue 4); MEDLINE (1950 to 23rd September 2009); EMBASE (1980 to 23rd September 2009); ISI Web of Science (SCIE, SSCI) (1981 to 22nd December 2009); ISI Web of Science Conference Proceedings (1990 to 22nd December 2009); BIOSIS (1985 to 22nd December 2009); and OpenSIGLE (1980 to 2005). Researchers, experts and organizations known to be involved in this field were contacted in order to trace unpublished or ongoing studies. There were no language limitations. Selection criteria:, Trials were selected if they met the following criteria: randomized or quasi-randomized controlled trial, involving replacement and repair of resin composite restorations. Data collection and analysis:, Two review authors independently assessed titles and abstracts for each article identified by the searches in order to decide whether the article was likely to be relevant. Full papers were obtained for relevant articles and both review authors studied these. The Cochrane Collaboration statistical guidelines were to be followed for data synthesis. Main results:, The search strategy retrieved 279 potentially eligible studies, after de-duplication and examination of the titles and abstracts all but four studies were deemed irrelevant. After further analysis of the full texts of the four studies identified, none of the retrieved studies met the inclusion criteria and all were excluded from this review. Authors' conclusions:, There are no published randomised controlled clinical trials relevant to this review question. There is therefore a need for methodologically sound randomised controlled clinical trials that are reported according to the Consolidated Standards of Reporting Trials (CONSORT) statement ( Further research also needs to explore qualitatively the views of patients on repairing versus replacement and investigate themes around pain, anxiety and distress, time and costs. [source]

Characteristics and management of splenic artery aneurysms in adult living donor liver transplant recipients

Deok-Bog Moon
Splenic artery aneurysms (SAAs), occurring in 7% to 17% of patients with cirrhosis, often result in catastrophic rupture after liver transplantation. We had experienced 3 cases of ruptured SAAs after adult living donor liver transplantation (LDLT), and we then performed this study to find risk factors for coexisting SAAs in liver transplant candidates with cirrhosis and to propose ideal approaches for them. Preoperative and postoperative computed tomography angiograms and axial views were reviewed for 310 adult LDLT recipients who had cirrhosis from January 2004 to August 2005. The recorded variables were the preoperative diagnosis, the presence of SAA and its characteristics, the splenic artery (SA) diameter, and the presence and size of portosystemic collaterals. Devastating SAA rupture accompanied by hypovolemic shock occurred on postoperative days 6, 82, and 8, respectively, and it was treated emergently by embolization in cases 1 and 2 and by splenectomy in case 3. Cases 1 and 3 recovered well, but case 2 died of an unrelated cause with a long hospital stay. The incidence of SAA during the study period was 14.2% (44/310), and the size was 16.6 5.7 mm. Most SAAs were single (70.6%, 31/44) and were located in the distal one-third of the SA (82.4%, 36/44). Large portosystemic collaterals demonstrating longstanding severe portal hypertension were significantly correlated with the occurrence of SAAs. Nine patients with SAAs were preventively treated by proximal ligation (n = 4) intraoperatively and by embolization (n = 5) 1 day before or after LDLT. No patient showed severe postembolization syndrome. In conclusion, a careful preoperative evaluation of SAAs by high-resolution 3-dimensional computed tomography in liver transplant candidates, especially in those showing large portosystemic collaterals, is merited. Preventive treatment should be encouraged regardless of the size in order to avoid severe morbidity and mortality related to SAA rupture, and methods such as radiological and surgical interventions need to be individualized according to the location and number of SAAs. Liver Transpl 15:1535,1541, 2009. 2009 AASLD. [source]