Institution
Leibniz University of Hanover
Education•Hanover, Niedersachsen, Germany•
About: Leibniz University of Hanover is a education organization based out in Hanover, Niedersachsen, Germany. It is known for research contribution in the topics: Finite element method & Population. The organization has 14283 authors who have published 29845 publications receiving 682152 citations.
Topics: Finite element method, Population, Laser, Gravitational wave, Membrane
Papers published on a yearly basis
Papers
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TL;DR: The data suggest that a complete rehardening of the softened enamel in vitro is reached after a remineralisation time of 6 h, which is of clinical relevance to tooth wear.
Abstract: The aim of this in vitro study was to determine the influence of remineralisation time on rehardening of surface-softened enamel after citric acid erosion. Seven groups of 13 samples of human enamel were eroded in 0.3% citric acid at pH 3.2 for 2 h followed by profilometric measurements. Individual groups of specimens were placed in artificial saliva for 1, 2, 4, 6, 9 or 24 h. A control group was placed in isotonic saline for 24 h. After new profilometric measurements samples were ultrasonicated stepwise up to 480 s with profilometric measurements performed at 5, 30, 120, 240 and 480 s to measure the depth of surface softening. The control group had a softened surface layer of mean thickness 2.9 microm. Mineral deposition was seen at all remineralisation times by scanning electron microscopy. Exposure to artificial saliva for 1, 2 or 4 h produced a partial rehardening of the softened enamel; the additional surface losses produced by ultrasonication were lower and time delayed compared to the control group. Specimens remineralised for 6, 9 and 24 h showed little evidence of surface loss after ultrasonication. The data suggest that a complete rehardening of the softened enamel in vitro is reached after a remineralisation time of 6 h. These data are of clinical relevance to tooth wear. However, there is a need for studies in situ of enamel demineralisation and remineralisation.
164 citations
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01 Jan 2007TL;DR: This article analyzes the open corpus problem in a popular arena: adaptive hypermedia systems with an emphasis on education, and discusses how solution strategies can be successfully employed in the future, enabling adaptive hyper media techniques within open, dynamic information spaces, such as the Semantic Web.
Abstract: Despite the fact that adaptive hypermedia techniques have proven their ability to provide user guidance and orientation in hyperspace, we do not currently see the widespread adoption of these techniques. A couple of reasons may explain this phenomenon. One of them is the current lack of reusability and interoperability between adaptive techniques/systems, which - to some degree - originates in the so-called "open corpus problem" found in adaptive hypermedia. In this article, we analyze this problem in a popular arena: adaptive hypermedia systems with an emphasis on education. The origins and effects of the open corpus problem are discussed, and recent approaches are demonstrated that have - in one way or the other - developed as strategies for solving the open corpus problem. We summarize these findings and discuss how solution strategies can be successfully employed in the future, enabling adaptive hypermedia techniques within open, dynamic information spaces, such as the Semantic Web.
164 citations
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TL;DR: The leachate treatment plant of the landfill in Mechernich including biological pretreatment, reverse osmosis and evaporation and drying of the concentrate has been in operation since the beginning of 1994 as mentioned in this paper.
164 citations
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TL;DR: Cardiac production of NO by NOS II attenuates the positive inotropic effects of beta-adrenergic stimulation and hastens relaxation in failing human hearts.
164 citations
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TL;DR: In this paper, the authors investigated the dynamics of contact angle due to variation of the water potential and found that the contact angle increased as water potential increased to a specific level, and then decreased again when water potential reached a certain level.
Abstract: Soil wettability affects hydrological processes like infiltration, percolation, preferential flow, and surface runoff. Wettability is related to the soil-water contact angle, which in turn depends on the solid surface free energy. Little is known, however, about contact angles and their dependence on soil water potential. The main objective of this study was therefore to investigate the dynamics of contact angle due to variation of the water potential. Aggregate fractions of 2- to 4-, 1- to 2-, and <1-mm diameter and corresponding homogenized material of a subcritical water repellent Orthic Luvisol were studied at water potentials of -1000, -154, -30, and -0.14 MPa. Wettability was assessed in terms of the advandng contact angle by the capillary rise method (CRM). Additionally, we calculated the surface free energy. Results showed, that the contact angle increased as water potential increased to a specific level. It was found for several soil samples, that above this water potential level, the contact angle decreased again. The change of contact angle due to variation of water potential reached nearly 90° for one sample. Contact angles of homogenized fractions were slightly larger than those measured for the aggregate surfaces. Surface free energy was consistently between 55 and 65 mJ m -2 with relative contributions of the dispersion and polar components to surface free energy of approximately 1/3 and 2/3, respectively. We conclude, that the assessment and physical description of the specific water potential for which a surface becomes wettable is a key factor for a better understanding of soil wetting.
163 citations
Authors
Showing all 14621 results
Name | H-index | Papers | Citations |
---|---|---|---|
Hyun-Chul Kim | 176 | 4076 | 183227 |
Peter Zoller | 134 | 734 | 76093 |
J. R. Smith | 134 | 1335 | 107641 |
Chao Zhang | 127 | 3119 | 84711 |
Benjamin William Allen | 124 | 807 | 87750 |
J. F. J. van den Brand | 123 | 777 | 93070 |
J. H. Hough | 117 | 904 | 89697 |
Hans-Peter Seidel | 112 | 1213 | 51080 |
Karsten Danzmann | 112 | 754 | 80032 |
Bruce D. Hammock | 111 | 1409 | 57401 |
Benno Willke | 109 | 508 | 74673 |
Roman Schnabel | 108 | 589 | 71938 |
Jan Harms | 108 | 447 | 76132 |
Hartmut Grote | 108 | 434 | 72781 |
Ik Siong Heng | 107 | 423 | 71830 |