Article
Refine
Year of publication
- 2024 (15)
- 2023 (24)
- 2022 (34)
- 2021 (39)
- 2020 (44)
- 2019 (52)
- 2018 (47)
- 2017 (45)
- 2016 (32)
- 2015 (43)
- 2014 (42)
- 2013 (49)
- 2012 (41)
- 2011 (69)
- 2010 (61)
- 2009 (76)
- 2008 (51)
- 2007 (48)
- 2006 (32)
- 2005 (40)
- 2004 (75)
- 2003 (39)
- 2002 (45)
- 2001 (49)
- 2000 (53)
- 1999 (31)
- 1998 (32)
- 1997 (29)
- 1996 (27)
- 1995 (18)
- 1994 (9)
- 1993 (18)
- 1992 (11)
- 1991 (11)
- 1990 (15)
- 1989 (17)
- 1988 (20)
- 1987 (19)
- 1986 (6)
- 1985 (8)
- 1984 (7)
- 1983 (5)
- 1982 (20)
- 1981 (15)
- 1980 (29)
- 1979 (20)
- 1978 (25)
- 1977 (13)
- 1976 (16)
- 1975 (12)
- 1974 (4)
- 1973 (2)
- 1972 (6)
- 1968 (2)
- 1967 (1)
Institute
- Fachbereich Medizintechnik und Technomathematik (1593) (remove)
Document Type
- Article (1593) (remove)
Keywords
- Einspielen <Werkstoff> (7)
- FEM (4)
- Finite-Elemente-Methode (4)
- LAPS (4)
- CellDrum (3)
- Label-free detection (3)
- biosensors (3)
- hydrogen peroxide (3)
- impedance spectroscopy (3)
- shakedown analysis (3)
The impact of surgical staplers on tissues has been studied mostly in an empirical manner. In this paper, finite element method was used to clarify the mechanics of tissue stapling and associated phenomena. Various stapling modalities and several designs of circular staplers were investigated to evaluate the impact of the device on tissues and mechanical performance of the end-to-end colorectal anastomosis. Numerical simulations demonstrated that a single row of staples is not adequate to resist leakage due to non-linear buckling and opening of the tissue layers between two adjacent staples. Compared to the single staple row configuration, significant increase in stress experienced by the tissue at the inner staple rows was observed in two and three rows designs. On the other hand, adding second and/or third staple row had no effect on strain in the tissue inside the staples. Variable height design with higher staples in outer rows significantly reduced the stresses and strains in outer rows when compared to the same configuration with flat cartridge.
Temperature-dependent ranges of coexistence in a model of a two-prey-one-predator microbial food web
(2012)
The objective of our study was to analyze the effects of temperature on the population dynamics of a three-species food web consisting of two prey bacteria (Pedobacter sp. and Acinetobacter johnsonii) and a protozoan predator (Tetrahymena pyriformis) as model organisms. We assessed the effects of temperature on the growth rates of all three species with the objective of developing a model with four differential equations based on the experimental data. The following hypotheses were tested at a theoretical level: Firstly, temperature changes can affect the dynamic behavior of a system by temperature-dependent parameters and interactions and secondly, food web response to temperature cannot be derived from the single species temperature response. The main outcome of the study is that temperature changes affect the parameter range where coexistence is possible within all three species. This has significant consequences on our ideas regarding the evaluation of effects of global warming.
This paper presents a novel numerical procedure for computing limit and shakedown loads of structures using a node-based smoothed FEM in combination with a primal–dual algorithm. An associated primal–dual form based on the von Mises yield criterion is adopted. The primal-dual algorithm together with a Newton-like iteration are then used to solve this associated primal–dual form to determine simultaneously both approximate upper and quasi-lower bounds of the plastic collapse limit and the shakedown limit. The present formulation uses only linear approximations and its implementation into finite element programs is quite simple. Several numerical examples are given to show the reliability, accuracy, and generality of the present formulation compared with other available methods.
Influence of a freeze–thaw cycle on the stress–stretch curves of tissues of porcine abdominal organs
(2012)
The paper investigates both fresh porcine spleen and liver and the possible decomposition of these organs under a freeze–thaw cycle. The effect of tissue preservation condition is an important factor which should be taken into account for protracted biomechanical tests. In this work, tension tests were conducted for a large number of tissue specimens from twenty pigs divided into two groups of 10. Concretely, the first group was tested in fresh state; the other one was tested after a freeze-thaw cycle which simulates the conservation conditions before biomechanical experiments. A modified Fung model for isotropic behavior was adopted for the curve fitting of each kind of tissues. Experimental results show strong effects of the realistic freeze–thaw cycle on the capsule of elastin-rich spleen but negligible effects on the liver which virtually contains no elastin. This different behavior could be explained by the autolysis of elastin by elastolytic enzymes during the warmer period after thawing. Realistic biomechanical properties of elastin-rich organs can only be expected if really fresh tissue is tested. The observations are supported by tests of intestines.
We investigate the suitability of selected measures of complexity based on recurrence quantification analysis and recurrence networks for an identification of pre-seizure states in multi-day, multi-channel, invasive electroencephalographic recordings from five epilepsy patients. We employ several statistical techniques to avoid spurious findings due to various influencing factors and due to multiple comparisons and observe precursory structures in three patients. Our findings indicate a high congruence among measures in identifying seizure precursors and emphasize the current notion of seizure generation in large-scale epileptic networks. A final judgment of the suitability for field studies, however, requires evaluation on a larger database.
Aneurysmal subarachnoid hemorrhage (aSAH) is associated with early and delayed brain injury due to several underlying and interrelated processes, which include inflammation, oxidative stress, endothelial, and neuronal apoptosis. Treatment with melatonin, a cytoprotective neurohormone with anti-inflammatory, anti-oxidant and anti-apoptotic effects, has been shown to attenuate early brain injury (EBI) and to prevent delayed cerebral vasospasm in experimental aSAH models. Less is known about the role of endogenous melatonin for aSAH outcome and how its production is altered by the pathophysiological cascades initiated during EBI. In the present observational study, we analyzed changes in melatonin levels during the first three weeks after aSAH.
In-beam study of ¹⁴³ Eu
(1988)
Yrast states up to spin 18 have been identified in ¹³²Ce. The energies and spins of the levels suggest the existence of two fairly well-behaved collective bands. The results are compared with those obtained in the rare-earth deformed region.
High spin states in ¹⁸⁸ Au
(1982)
Side-bands in ¹⁸⁰ Os
(1981)
Band structure in ¹⁹⁴ Au
(1979)
High-spin states in ¹⁸⁰ Os
(1979)
Isomeric state in ¹³⁴ La
(1981)
Isomeric state in ¹³⁶ La
(1981)
High-spin states in ¹³³ La
(1980)
Isomeric states in ¹³⁴ Ba
(1980)
Isomeric states in ¹³⁴ Ba
(1980)
High-spin states in ¹³³ La
(1982)
In-beam study of ¹⁴⁴ Gd
(1978)
In-beam study of ¹⁴⁴ Gd
(1978)
In-beam study of ¹⁴⁴ Gd
(1977)