On the contact detection for contact-impact analysis in multibody systems

One of the most important and complex parts of the simulation of multibody systems with contact-impact involves the detection of the precise instant of impact. In general, the periods of contact are very small and, therefore, the selection of the time step for the integration of the time derivatives of the state variables plays a crucial role in the dynamics of multibody systems. The conservative approach is to use very small time steps throughout the analysis. However, this solution is not efficient from the computational view point. When variable time step integration algorithms are used and the pre-impact dynamics does not involve high-frequencies the integration algorithms may use larger time steps and the contact between two surfaces may start with initial penetrations that are artificially high. This fact leads either to a stall of the integration algorithm or to contact forces that are physically impossible which, in turn, lead to post-impact dynamics that is unrelated to the physical problem. The main purpose of this work is to present a general and comprehensive approach to automatically adjust the time step, in variable time step integration algorithms, in the vicinity of contact of multibody systems. The proposed methodology ensures that for any impact in a multibody system the time step of the integration is such that any initial penetration is below any prescribed threshold. In the case of the start of contact, and after a time step is complete, the numerical error control of the selected integration algorithm is forced to handle the physical criteria to accept/reject time steps in equal terms with the numerical error control that it normally uses. The main features of this approach are the simplicity of its computational implementation, its good computational efficiency and its ability to deal with the transitions between non contact and contact situations in multibody dynamics. A demonstration case provides the results that support the discussion and show the validity of the proposed methodology.Fundação para a Ciência e a Tecnologia (FCT

PRINCIPLES AND PRACTICE OF GAMMA KNIFE RADIOSURGERY: A REVIEW

Objectives: To determine the physics, biology, outcomes and risks of gamma knife radiosurgery (GKRS) in treating brain tumours, arteriovenous malformations (AVMs), pain and movement disorders.Data sources: A retrospective MEDLINE search was used to find all gamma knife radiosurgery studies published from 1967 to 12th March 2005 and strict inclusion criteria were applied.Study selection: Limited to the review articles in the human study with the key word of gamma knife radiosurgery.Data extraction: In each subject, both authors reviewed related articles separately.Data synthesis: Adding up data and compare the results.Conclusions: The GKRS represents one of the most advanced means available to treat brain tumours, arteriovenous malformations (AVMs), pain and movement disorders safely and effectively. At present, the long-term results after GKRS procedures remain to be documented. The physics, biology, current indications and expected outcomes after GKRS are discussed

Stereotactic radiosurgery for intractable cluster headache: an initial report from the North American Gamma Knife Consortium.

The MME workshop is a well established and recognized European event in the field of Micromachining, Microengineering and Technology for the realization of micro-sensors and -actuators. At the MME workshop scientists and people from industry interested in the field gather annually. The goals are stimulation and improvement of know-how in the field, as well as the establishment of cooperation and friendship between all delegates. Thus MME is arranged so that people can meet in a friendly and informal atmosphere. Therefore the accent lies on mutual discussions around poster presentations rather than on formal oral presentations

Cloning, expression, and purification of an anti‐desipramine single chain antibody in NS/0 myeloma cells

Drug‐specific monoclonal antibodies and their antigen‐binding Fab fragments reverse acute desipramine toxicity in a rat experimental model by inducing a redistribution of drug from cardiac tissue into serum and extracellular fluid. In order to investigate the use of smaller recombinant antibody fragments such as single chain Fv (sFv) as an antidote, an efficient murine NS/0 myeloma expression system was developed. The variable light (V) and variable heavy (V) domains of a murine anti‐desipramine monoclonal antibody were cloned and sequenced. A 270 amino acid V‐(GlySer)‐V sFv was prepared by overlapping polymerase chain reaction (PCR) amplification of V with heavy chain leader peptide, V, and the linker. This construct was subcloned into a mammalian expression vector which utilizes the SRα promoter, a hybrid promoter consisting of the SV40 early promoter with portions of the human T‐cell leukemia virus type I long terminal repeat and also containing the Escherichia coli xanthine–guanine phosphoribo‐syltransferase gene for selection. NS/0 myeloma cells were transfected by electroporation. Stable recombinant NS/0 clones were screened for expression of sFv using reverse transcriptase‐PCR to detect mRNA and an enzyme‐linked immunosorbent assay (ELISA) to detect sFv. Secreted sFv from clones capable of growth to a cell density of 2–4 × 10 viable cells/mL was purified in a single step using a desipramine affinity column resulting in 12–39 mg/L of purified sFv. Affinity‐purified sFv had comparable desipramine binding activity to Fab when evaluated by competitive ELISA. Copyrigh