Determination of nerve conduction velocity distribution fromsampled compound action potential signals

The sampled compound action potential (CAP) data sequence was expressed as the circular convolution of the delay sequence and the sampled single fiber action potential (SFAP) data sequence. An algorithm, based on Hirose's method (1986) was then developed to separate the delay sequence from the sampled CAP data sequence, and the nerve conduction velocity distribution (NCVD) was consequently calculated from the delay sequence. The NCVD was found to be the product of the amplitude of the SFAP and the number of fibers. Simulations show that the estimated results were in good agreement with the calculated results. Experiments were performed on ten sciatic nerves from five bullfrogs (Rana pipens) using two independent variables: interelectrode distance and stimulus current strength. The results estimated from CAP's recorded under each condition reflect the corresponding feature of NCVD of the condition. The advantage of the technique is to provide detailed information about both slow and fast conducting fibers. This technique also offers the possibility to directly calculate the nerve fiber diameter distribution from the sampled CAP data sequences     

Sprint start instrumentation

A prototype instrument has been developed to measure the forces generated on the starting blocks and the speed of a sprinter at the start of a sprint event. The starting block forces can be resolved into horizontal and vertical components for each foot, or the various combinations of these four forces can be calculated and displayed along with the resultant angle. The speed of the sprinter is measured by means of a Doppler microwave technique (radar gun). Both static and dynamic tests have been used to calibrate the force transducers and to verify their functional bandwidth. The speed measurement technique has been validated by four independent procedures: measurement of a constant velocity object; measurement of an object undergoing constant acceleration; determination of distance travelled by an athlete; and comparison with high-speed cinematography. Both the force and speed profiles can be displayed immediately on the screen of a microcomputer for feedback to the coach and athlete during training sessions     

100 Jahre Margarine — vom Ersatzprodukt zum Grundnahrungsmittel

100 Years of Margarine — From a Substitute to a Basic Food-Stuff Inspite of the outdated and discriminating regulations that were obstructive, margarine, since the patent application in 1869 by Mège-Mouriés, has turned out to be an important foodstuff. In countries with high standard of living and progressive thinking in nutritional matters like USA, Sweden and Holland as well as in the Federal Republic of Germany the consumption of margarine as spread and cooking fat is higher than butter. Margarine as an independent food-stuff has the advantage that its composition and structure can be varied to meet the demands of the housewife, thereby taking the nutritional aspects into consideration as well. Owing to the modern technology and packaging involved in its production margarine is an extremely hygienic food-stuff with fully acceptable taste. In view of expanding population and high acrage yield of vegetable oils, margarine has a great future as a cheap and economically purposeful food-stuff.     

Multigrid interpretations of the parareal algorithm leading to an overlapping variant and MGRIT

Computing and Visualization in Science - The parareal algorithm is by construction a two level method, and there are several ways to interpret the parareal algorithm to obtain multilevel versions....     

International water law and supporting water management principles in the development of a model transboundary agreement between riparians in international river basins

A set of water management principles are analyzed and form the basis for a template for a model transboundary agreement for international river basins. The tenets of international water law, which support the selection of the principles, are analyzed. The principles include equitable and reasonable utilization and the obligation to not cause significant harm as the interrelated and overarching principles of international watercourse management. The development of a template is undertaken because ratification of the 1997 UN watercourses convention is at hand and a template consistent with this convention may facilitate the protection of shared water resources.     

Physico-chemical and antigenic properties of tetanus and diphtheria toxoids and steps towards improved stability

Physico-chemical, antigenic and immunogenic properties may be altered during microencapsulation of antigens and their release from poly(lactic acid) and poly(lactic-co-glycolic acid) microspheres. Here, the physico-chemical, conformational and antigenic stability of tetanus and diphtheria toxoids was studied in aqueous solutions stressed by elevated temperature and the presence of lactic and glycolic acids. Further, the stabilising effect of albumin was investigated. The analytical tools used were fluorimetry, circular dichroism spectroscopy, turbidimetry, electrophoresis and ELISA. Elevated temperatures altered the physico-chemical and antigenic properties of the toxoids to a greater extent than the acids (50 mM) did. Substantial unfolding and chemical changes of tryptophan were observed upon 1-4 weeks of incubation at 60 degreesC. At 4 degreesC, only minor conformational changes were observed, even in the presence of the acids. Furthermore, 40% of the tetanus toxoid antigenicity was lost after 7 days at 37 degreesC. This loss increased in the presence of the acids. At 60 degreesC, the antigenicity had completely vanished. Very importantly, 0.5% albumin preserved the tetanus antigenicity over 6 weeks' incubation at 37 degreesC, regardless of the presence of glycolic acid. This qualifies albumin as potential stabilising additive for toxoid loaded poly(lactic acid) and poly(lactic-co-glycolic acid) microspheres.     

Crosslinked Poloxamers as a Versatile Monolithic Drug Delivery System

There is growing interest in the development of homogeneous monolithic drug release systems for various routes of administration. One very attractive type of such dosage forms is based on hydrophilic water-swellable polymers which generally exhibit high biocompatibility. On contact with an aqueous liquid (dissolution medium or gastrointestinal fluid) the polymer swells. Liquid penetrates into the system and drug is released by counter-current diffusion. Depending on the physical characteristics of the polymer, different thermodynamic transitions such as glass-to-rubber transition of the amorphous zones or melting out of crystallites may occur during liquid penetration. These thermodynamic reactions might be responsible for the drug release kinetics not showing square-root-of-time dependance^1-5.     

Kinetics of 1,1,1-trichloroethane transformation by iron sulfide and a methanogenic consortium

To evaluate the effect of potential interactions between methanogenic bacteria and iron sulfide minerals during transformation of 1,1,1-trichloroethane (1,1,1-TCA), we measured the kinetics of 1,1,1-TCA transformation by mackinawite (FeS(1 - x), but abbreviated as FeS) and a methanogenic consortium enriched on lactate (termed LEC). Results from batch kinetic experiments show that 1,1,1-TCA transformation by FeS and resting LEC can be described by second-order rate expressions, with rates depending on 1,1,1-TCA concentration (M), FeS surface area concentration (m2 L(-1)), and LEC concentration (as measured by mg L(-1) volatile suspended solids (VSS)). In reactors containing FeS alone, 1,1-dichloroethane (1,1-DCA) and 2-butyne were identified as products, but only accounted for 6% of the 1,1,1-TCA transformed. In reactors containing LEC alone, the only identified product was 1,1-DCA, which accounted for 46 +/- 8% of the 1,1,1-TCA transformed. Supernatant from LEC-alone reactors also transformed 1,1,1-TCA, suggesting that 1,1,1-TCA may be transformed by some non-cell component (such as a extracellular compound excreted by the organisms) that either reacts directly with 1,1,1-TCA or with the abiotic media to form a reactive species. Comparison of 1,1,1-TCA transformation rates from experiments with combinations of FeS (varying surface area concentrations) and LEC (varying VSS concentrations) to those with just FeS alone or LEC alone suggests some synergism occurs between the two reactive species. Observed enhancements took the form of faster 1,1,1-TCA transformation and faster 1,1-DCA appearance but less production of 1,1-DCA per unit of 1,1,1-TCA transformed. These observations suggest that the faster 1,1,1-TCA transformation in the combined systems (compared to the FeS-alone and LEC-alone experiments) is due to increased reactivity of both FeS and LEC, possibly due to production of soluble microbial products that make the FeS more reactive or less inhibition of LEC by 1,1,1-TCA due to FeS transformation of 1,1,1-TCA.