162 research outputs found
Different aprotinin applications influencing hemostatic chances in orthotopic liver transplantation
The effect of different aprotinin applications on hemmtatic changes and blood product requirements in orthotopic liver transplantation was investigated in a prospective, open, and randomized study.
From November 1989 to June 1990, 13 patients received aprotinin as a bolus of 0.5 Mill, kallikrein inac-tivator units (KIU) on three occasions in the course of an OLT, whereas 10 other patients were treated with continuous aprotinin infusion of 0.1-0.4 Mill. KIU/hr. Before and after reperfusion of the graft liver, signs of hyperfibrinolysis, measured by thrombelastography, were significantly lower in the infusion group. Tissue-type plasminogen activator (t-PA) activity increased during the anhepatic phase but to a significantly lesser extent in the infusion group. Blood product requirements during OLT were tendentiously higher in the bolus group but not significantly so. However, the use of packed red blood cells was significantly lower in the postoperative period, whereas there was no significant difference in fresh frozen plasma requirements between the two groups.
All 23 patients have survived, and only one woman of each group required retransplantation due to severe host-versus-graft reactions.
Furthermore, we investigated the perfusate of the graft liver in both groups and detected signs of a decreased t-PA release in the infusion group.
Our results demonstrate an advantage of aprotinin given as continuous infusion over bolus application in OLT
Dry Friction due to Adsorbed Molecules
Using an adiabatic approximation method, which searches for Tomlinson
model-like instabilities for a simple but still realistic model for two
crystalline surfaces in the extremely light contact limit, with mobile
molecules present at the interface, sliding relative to each other, we are able
to account for the virtually universal occurrence of "dry friction." The model
makes important predictions for the dependence of friction on the strength of
the interaction of each surface with the mobile molecules.Comment: four pages of latex, figure provide
Static Friction between Elastic Solids due to Random Asperities
Several workers have established that the Larkin domains for two three
dimensional nonmetallic elastic solids in contact with each other at a
disordered interface are enormously large. This implies that there should be
negligible static friction per unit area in the macroscopic solid limit.
The present work argues that the fluctuations in the heights of the random
asperities at the interface that occur in the Greenwood-Williamson model can
account for static friction.Comment: Contains some improvements in the treatment of the subjec
Static and Dry Friction due to Multiscale Surface Roughness
It is shown on the basis of scaling arguments that a disordered interface
between two elastic solids will quite generally exhibit static and "dry
friction" (i.e., kinetic friction which does not vanish as the sliding velocity
approaches zero), because of Tomlinson model instabilities that occur for small
length scale asperities. This provides a possible explanation for why static
and "dry" friction are virtually always observed, and superlubricity almost
never occurs
Diagnosis and treatment of idiopathic premature ventricular contractions: A stepwise approach based on the site of origin
Premature ventricular contractions in the absence of structural heart disease are among the most common arrhythmias in clinical practice, with well-defined sites of origin in the right and left ventricle. In this review, starting from the electrocardiographic localization of premature ventricular contractions, we investigated the mechanisms, prevalence in the general population, diagnostic work-up, prognosis and treatment of premature ventricular contractions, according to current scientific evidence
Distal Reoperations after Repair of Acute Type A Aortic DissectionâIncidence, Causes and Outcomes
Background and Aim of the Study: In patients with acute type A aortic dissection (A-AAD) whether initial repair should include also aortic arch replacement is still debated. We aimed to assess if extensive aortic repair prevents from reoperations patients with A-AAD. Methods: Outcomes after distal reoperation following repair of A-AAD (n = 285; 1977 to 2018) were analysed in 22 of 226 who underwent ascending aorta/hemiarch replacement (Group 1R) and 7 of 59 who had ascending aorta/arch replacement (Group 2R). Results: Distal reoperation was more common in Group 1R (n = 22) than in Group 2R (n = 0) (p < 0.001) while thoracic endovascular stenting was more frequent in Group 2R (7 vs 3, p < 0.001). Indications for reoperation were pseudoaneurysm at distal anastomosis (n = 4, 18%) and progression of aortic dissection (n = 18, 82%) in Group 1R. Indication for thoracic endovascular stenting was progressive aortic dissection in 3 patients of Group 1R and in 6 of Group 2R. Second reoperation was required in 2 patients from Group 1R (2%) during a mean follow-up of 5 years. Median follow-up was 4 years in Group 1R and 7 years in Group 2R (p = 0.36). Hospital mortality was 14% in Group 1R and 0% in Group 2R (p = 0.3). Actuarial survival is 68 ± 10%, and 62 ± 11% for Group 1R and 100% for Group 2R at 5 and 10 years (p = 0.076). Conclusions: Distal reoperations after A-AAD repair have an acceptable mortality. An extensive initial repair has lower rate of reoperation and better mid-term survival and should be indicated especially for young patients in experienced centers
Under-reporting bicycle accidents to police in the COST TU1101 international survey: Cross-country comparisons and associated factors
Police crash reports are often the main source for official data in many countries. However, with the exception of fatal crashes, crashes are often underreported in a biased manner. Consequently, the countermeasures adopted according to them may be inefficient. In the case of bicycle crashes, this bias is most acute and it probably varies across countries, with some of them being more prone to reporting accidents to police than others. Assessing if this bias occurs and the size of it can be of great importance for evaluating the risks associated with bicycling. This study utilized data collected in the COST TU1101 action âTowards safer bicycling through optimization of bicycle helmets and usageâ. The data came from an online survey that included questions related to bicyclists' attitudes, behaviour, cycling habits, accidents, and patterns of use of helmets. The survey was filled by 8655 bicyclists from 30 different countries. After applying various exclusion factors, 7015 questionnaires filled by adult cyclists from 17 countries, each with at least 100 valid responses, remained in our sample. The results showed that across all countries, an average of only 10% of all crashes were reported to the police, with a wide range among countries: from a minimum of 0.0% (Israel) and 2.6% (Croatia) to a maximum of a 35.0% (Germany). Some factors associated with the reporting levels were type of crash, type of vehicle involved, and injury severity. No relation was found between the likelihood of reporting and the cyclist's gender, age, educational level, marital status, being a parent, use of helmet, and type of bicycle. The significant under-reporting â including injury crashes that do not lead to hospitalization â justifies the use of self-report survey data for assessment of bicycling crash patterns as they relate to (1) crash risk issues such as location, infrastructure, cyclists' characteristics, and use of helmet and (2) strategic approaches to bicycle crash prevention and injury reduction.Fil: Shinar, D.. Ben Gurion University of the Negev; IsraelFil: Valero Mora, Pedro. Universidad de Valencia; EspañaFil: van Strijp Houtenbos, M.. Institute For Road Safety Research; PaĂses BajosFil: Haworth, N.. Queensland University of Technology; AustraliaFil: Schramm, A.. Queensland University of Technology; AustraliaFil: de Bruyne, G.. Universiteit Antwerp; BĂ©lgicaFil: Cavallo, V.. No especifĂca;Fil: Chliaoutakis, J.. No especifĂca;Fil: Pereira Dias, Joao. Instituto Superior Tecnico; PortugalFil: Ferraro, Ottavia Eleonora. Universita Degli Studi Di Pavia; ItaliaFil: Fyhri, Aslak. No especifĂca;Fil: Sajatovic, Anika Hursa. No especifĂca;Fil: Kuklane, Kalev. Lund University; SueciaFil: Ledesma, Ruben Daniel. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Mar del Plata. Instituto de PsicologĂa BĂĄsica, Aplicada y TecnologĂa. Universidad Nacional de Mar del Plata. Facultad de PsicologĂa. Instituto de PsicologĂa BĂĄsica, Aplicada y TecnologĂa.; ArgentinaFil: CalvĂ© Mascarell, Oscar. Ben Gurion University of the Negev; IsraelFil: Morandi, A.. Universita Degli Studi Di Pavia; ItaliaFil: Muser, Markus. No especifĂca;Fil: Otte, Diettmar. No especifĂca;Fil: Papadakaki, M.. No especifĂca;Fil: SanmartĂn, J.. Universidad de Valencia; EspañaFil: Dulf, D.. No especifĂca;Fil: Saplioglu, M.. No especifĂca;Fil: Tzamalouka, Georgia. No especifĂca
Crack-Like Processes Governing the Onset of Frictional Slip
We perform real-time measurements of the net contact area between two blocks
of like material at the onset of frictional slip. We show that the process of
interface detachment, which immediately precedes the inception of frictional
sliding, is governed by three different types of detachment fronts. These
crack-like detachment fronts differ by both their propagation velocities and by
the amount of net contact surface reduction caused by their passage. The most
rapid fronts propagate at intersonic velocities but generate a negligible
reduction in contact area across the interface. Sub-Rayleigh fronts are
crack-like modes which propagate at velocities up to the Rayleigh wave speed,
VR, and give rise to an approximate 10% reduction in net contact area. The most
efficient contact area reduction (~20%) is precipitated by the passage of slow
detachment fronts. These fronts propagate at anomalously slow velocities, which
are over an order of magnitude lower than VR yet orders of magnitude higher
than other characteristic velocity scales such as either slip or loading
velocities. Slow fronts are generated, in conjunction with intersonic fronts,
by the sudden arrest of sub-Rayleigh fronts. No overall sliding of the
interface occurs until either of the slower two fronts traverses the entire
interface, and motion at the leading edge of the interface is initiated. Slip
at the trailing edge of the interface accompanies the motion of both the slow
and sub-Rayleigh fronts. We might expect these modes to be important in both
fault nucleation and earthquake dynamics.Comment: 19 page, 5 figures, to appear in International Journal of Fractur
How do field of view and resolution affect the information content of panoramic scenes for visual navigation? A computational investigation
The visual systems of animals have to provide information to guide behaviour and the informational requirements of an animalâs behavioural repertoire are often reflected in its sensory system. For insects, this is often evident in the optical array of the compound eye. One behaviour that insects share with many animals is the use of learnt visual information for navigation. As ants are expert visual navigators it may be that their vision is optimised for navigation. Here we take a computational approach in asking how the details of the optical array influence the informational content of scenes used in simple view matching strategies for orientation. We find that robust orientation is best achieved with low-resolution visual information and a large field of view, similar to the optical properties seen for many ant species. A lower resolution allows for a trade-off between specificity and generalisation for stored views. Additionally, our simulations show that orientation performance increases if different portions of the visual field are considered as discrete visual sensors, each giving an independent directional estimate. This suggests that ants might benefit by processing information from their two eyes independently
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