Analysis of ankle deflection during a forward fall in snowboarding

Toward the general goal of preventing ankle injuries in snowboarding accidents, the objective of this project to develop a dynamic system model of a snowboarder and assess which model parameters, particularly those attributed to the boot, most strongly influenced ankle deflections during a forward fall. To satisfy this objective, a system model was created that included the rider, the boots, the snowboard, and the snow as components. Through dynamic simulations, peak ankle deflections were computed over realistic ranges of input parameter values for each of the model components. Defining sensitivity as the total change in peak ankle deflection over the range of a particular parameter studied, results indicated that the peak ankle deflection was most sensitive to the boot stiffness. Although lower, the sensitivity of the peak ankle deflection to the snow model parameters was still significant, being roughly half of the boot sensitivity. Increases in both snow stiffness and snow damping caused higher ankle deflections. Variations in both snowboard stiffness and anthropometric parameters had little effect. Due to the strong dependence of ankle deflection on boot stiffness, the potential exists for mitigating the ankle injury problem through judicious design of the boot.     

Validity and reliability of a new in vivo ankle stiffness measurement device

This investigation was designed to test the validity and reliability of a new measure of inversion/eversion ankle stiffness on a unique medial/lateral swaying cradle device utilizing a test/retest with comparison to a known standard. Ankle stiffness is essential to maintaining joint stability. Most ankle injuries occur via an inversion mechanism. To date, very little information is available regarding stiffness of the evertor muscles in the prevention of excessive inversion joint rotation. Transient oscillation data representing inversion/eversion stiffness was obtained in a bipedal weight-bearing stance with an upright posture. Using commercially available springs with stiffness of 4.80N/cm the measured value recorded by the cradle was 4.87N/cm. Mean active stiffness values of the ankle were 35.70Nm/cm (SD 9.45). The trial-to-trial reliability ICC (2,1) coefficient was 0.96 with an SEM of 2.05Nm/rad, and the day-to-day reliability ICC (2,k) coefficient was 0.93 and an SEM of 3.00Nm/rad. The results demonstrate that inversion/eversion ankle stiffness measures on this device are a valid, repeatable and consistent measure. This is relevant because the ability to accurately quantify inversion/eversion ankle stiffness will improve our understanding of biomechanical stability and factors that influence it. It will also enable identification of ankle injury risk factors that will lead to more efficient rehabilitation programs and injury prevention strategies.     

Prenylated proteins: demonstration of a thioether linkage to cysteine of proteins

Prenylated amino acid fragments have been isolated from prenylated proteins of Chinese hamster ovary cells. Gel-exclusion chromatography indicates that these proteins are modified by two different prenyl groups. The prenyl-amino acid fragments are labeled by 35S from cysteine, and this bond is cleaved by Raney-Ni, proving that the prenyl residue is linked to protein via a thioether to cysteine. Hydrazinolysis has been used to demonstrate that the cysteine is carboxy terminal.     

Muscle use during dynamic knee extension: implication for perfusion and metabolism

Dynamic one-legged knee extension (DKE) iscommonly used to examine physiological responses to "aerobic"exercise. Muscle blood flow during DKE is often expressed relative toquadriceps femoris muscle mass irrespective of work rate.This is contrary to the notion that increased force is achieved byrecruitment in large muscles. The purpose of this study, therefore, wasto determine muscle use during DKE. Six subjects had magnetic resonance images taken of their quadriceps femoris before and after 4 min of DKEat 20 and 40 W. Muscle use was determined by shifts in T2. Thecross-sectional area of quadriceps femoris that had an elevated T2 was16 ± 1% (mean ± SE) preexercise, and 54 ± 5 and 94 ± 4% after 20- and 40-W DKE, respectively. Volume of quadriceps femorisincreased 11.4 ± 0.2% (P = 0.006), from 2,230 ± 233 cm³before exercise to 2,473 ± 232 cm³ after 40-W DKE. Extrapolationof these data indicates that 1,301 ± 111 cm³ of quadriceps femoris wereengaged during 20-W DKE compared with 2,292 ± 154 cm³ during 40-W DKE. By usingmuscle blood flow data for submaximal DKE at 20 W [P. Andersenand B. Saltin. J. Physiol. (Lond.)366: 233-249, 1985; and L. B. Rowell, B. Saltin, B. Kiens, and N. J. Christensen. Am. J. Physiol. 251 (Heart Circ.Physiol. 20): H1038-H1044, 1986] andestimating muscle use in those studies from our data (total muscle mass × 0.54), extrapolated blood flow to active muscle (263 and 278 ml · min¹ · 100 g¹, respectively) iscomparable to that obtained during peak aerobic DKE when expressedrelative to total muscle mass (243 and 250 ml · min¹ · 100 g¹,respectively). These findings indicate that increasedpower during aerobic DKE is achieved by recruitment.Additionally, they suggest that blood flow to the active quadricepsfemoris muscle does not increase with increases in submaximal work ratebut instead is maximal to support aerobic metabolism. Thus increases inmuscle blood flow are directed to newly recruited muscle, not toincreased perfusion of muscle already engaged.

     

Surrogate phenotype definition for alcohol use disorders: a genome-wide search for linkage and association

For the identification of susceptibility loci in complex diseases the choice of the target phenotype is very important. We compared results of genome-wide searches for linkage or for association related to three phenotypes for alcohol use disorder. These are a behavioral score BQ, based on a 12-item questionnaire about drinking behavior and the subject's report of drinking-related health problems, and ERP pattern and ERP magnitude, both derived from the eyes closed resting ERP measures to quantify brain activity. Overall, we were able to identify 11 candidate regions for linkage. Only two regions were found to be related to both BQ and one of the ERP phenotypes. The genome-wide search for association using single-nucleotide polymorphisms did not yield interesting leads.     

Design and application of a new cryptic-plasmid-based shuttle vector for Magnetospirillum magneticum

A 3.7-kb cryptic plasmid designated pMGT was found in Magnetospirillum magneticum MGT-1. It was characterized and used for the development of an improved expression system in strain AMB-1 through the construction of a shuttle vector, pUMG. An electroporation method for magnetic bacteria that uses the cryptic plasmid was also developed.     

A new device for measurement of fibrin clot lysis: application to the Euglobulin Clot Lysis Time

Background  

Determination of clot lysis times on whole blood, diluted whole blood, plasma or plasma fraction has been used for many years to assess the overall activity of the fibrinolytic system. We designed a completely computerised semi-automatic 8-channel device for measurement and determination of fibrin clot lysis. The lysis time is evaluated by a mathematical analysis of the lysis curve and the results are expressed in minute (range: 5 to 9999). We have used this new device for Euglobulin Clot Lysis Time (ECLT) determination, which is the most common test used in laboratories to estimate plasma fibrinolytic capacity.     

Comparison of techniques for the measurement of skin temperature during exercise in a hot,humid environment

Exercising or working in a hot, humid environment can results in the onset of heat-related illness when an individual''s temperature is not carefully monitored. The purpose of the present study was to compare three techniques (data loggers, thermal imaging, and wired electrodes) for the measurement of peripheral (bicep) and central (abdominal) skin temperature. Young men and women (N = 30) were recruited to complete the present study. The three skin temperature measurements were made at 0 and every 10-min during 40-min (60% VO₂max) of cycling in a hot (39±2°C), humid (45±5% RH) environment. Data was statistically analyzed using the Bland-Altman method and correlation analysis. For abdominal skin temperature, the Bland-Altman limits of agreement indicated that data loggers (1.5) were a better index of wired than was thermal imaging (3.5), For the bicep skin temperature the limits of agreement was similar between data loggers (1.9) and thermal (1.9), suggesting the both were suitable measurements. We also found that when skin temperature exceeded 35°C, we observed progressively better prediction between data loggers, thermal imaging, and wired skin sensors. This report describes the potential for the use of data loggers and thermal imaging to be used as alternative measures of skin temperature in exercising, human subjects.     

Study of population dynamic for a recombinant bacterium during continuous cultures: application of data filtering and smoothing

A numerical method to process experimental data concerning plasmid stability of a recombinant bacteria during continuous cultures with nonselective media is proposed here. This method differs from previous ones in that it uses the derivatve form of the state equation of the Imanaka-Aiba model for recombinant cultures. The methodology proposed here allows one to estimate values for the two model parameters without forcing them to be constant. Until now, this could not be done using classical analytical techniques because these parameters have been considered invariable because of the integration used in the evaluation of the model. These parameters are (1) the difference in the specific growth rates between plasmid-carrying cells and plasmid-free cells (deltamu), and (2) the probability of plasmid loss by plasmid-containing cells (rho(r) mu(+)). The derivative technique used here is completed by mathematical treatments involving data filtering and smoothing. The values of the two parameters are in agreement with those already publised. The current technique does not impose preconditions and permit us to further study related phenomena.     

Development of a small-scale bioreactor: application to in vivo NMR measurement

A perfused bioreactor allowing in vivo NMR measurement was developed and validated for Eschscholtzia californica cells. The bioreactor was made of a 10-mm NMR tube. NMR measurement of the signal-to-noise ratio was optimized using a sedimented compact bed of cells that were retained in the bioreactor by a supporting filter. Liquid medium flow through the cell bed was characterized from a mass balance on oxygen and a dispersive hydrodynamic model. Cell bed oxygen demand for 4 h perfusion required a minimal medium flow rate of 0.8 mL/min. Residence time distribution assays at 0.8-2.6 mL/min suggest that the cells are subjected to a uniform nutrient environment along the cell bed. Cell integrity was maintained for all culture conditions since the release of intracellular esterases was not significant even after 4 h of perfusion. In vivo NMR was performed for (31)P NMR and the spectrum can be recorded after only 10 min of spectral accumulation (500 scans) with peaks identified as G-6P, F-6P, cytoplasmic Pi, vacuolar Pi, ATP(gamma) and ADP(beta), ATP(alpha) and ADP(alpha), NADP and NDPG, NDPG and ATP(beta). Cell viability was shown to be maintained as (31)P chemical shifts were constant with time for all the identified nuclei, thus suggesting constant intracellular pH.     

Localized dynamic light scattering: a new approach to dynamic measurements in optical microscopy.

We present a new approach to probing single-particle dynamics that uses dynamic light scattering from a localized region. By scattering a focused laser beam from a micron-size particle, we measure its spatial fluctuations via the temporal autocorrelation of the scattered intensity. We demonstrate the applicability of this approach by measuring the three-dimensional force constants of a single bead and a pair of beads trapped by laser tweezers. The scattering equations that relate the scattered intensity autocorrelation to the particle position correlation function are derived. This technique has potential applications for measurement of biomolecular force constants and probing viscoelastic properties of complex media.     

Design and demonstration of a dynamometric horseshoe for measuring ground reaction loads of horses during racing conditions

Because musculoskeletal injuries to racehorses are common, instrumentation for the study of factors (e.g. track surface), which affect the ground reaction loads in horses during racing conditions, would be useful. The objectives of the work reported by this paper were to (1) design and construct a novel dynamometric horseshoe that is capable of measuring the complete ground reaction loading during racing conditions, (2) characterize static and dynamic measurement errors, and (3) demonstrate the usefulness of the instrument by collecting example data during the walk, trot, canter, and gallop for a single subject. Using electrical resistance strain gages, a dynamometric horseshoe was designed and constructed to measure the complete ground reaction force and moment vectors and the center of pressure. To mimic the load transfer surface of the hoof, the shape of the surface contacting the ground was similar to that of the solar surface of the hoof. Following static calibration, the measurement accuracy was determined. The root mean squared errors (RMSE) were 3% of full scale for the force component normal to the hoof and 9% for force components in the plane of the hoof. The dynamic calibration determined that the natural frequency with the full weight of a typical horse was 1744 Hz. Example data were collected during walking on a ground surface and during trotting, cantering, and galloping on a treadmill. The instrument successfully measured the complete ground reaction load during all four gaits. Consequently the dynamometric horseshoe is useful for studying factors, which affect ground reaction loads during racing conditions.     

The posterior probability of linkage allowing for linkage disequilibrium and a new estimate of disequilibrium between a trait and a marker

The posterior probability of linkage (PPL) statistic has been developed as a method for the rigorous accumulation of evidence for or against linkage allowing for both intra- and inter-sample heterogeneity. To date, the method has assumed linkage equilibrium between alleles at the trait locus and the marker locus. We now generalize the PPL to allow for linkage disequilibrium (LD), by incorporating variable phase probabilities into the underlying linkage likelihood. This enables us to recover the marginal posterior density of the recombination fraction, integrating out nuisance parameters of the trait model, including the locus heterogeneity (admixture) parameter, as well as a vector of LD parameters. The marginal posterior density can then be updated across data subsets or new data as they become available, while allowing parameters of the trait model to vary between data sets. The method applies immediately to general pedigree structures and to markers with multiple alleles. In the case of SNPs, the likelihood is parameterized in terms of the standard single LD parameter D'; and it therefore affords a mechanism for estimation of D' between the marker and the trait, again, without fixing the parameters of the trait model and allowing for updating across data sets. It is even possible to allow for a different associated allele in different populations, while accumulating information regarding the strength of LD. While a computationally efficient implementation for multi-allelic markers is still in progress, we have implemented a version of this new LD-PPL for SNPs and evaluated its performance in nuclear families. Our simulations show that LD-PPLs tend to be larger than PPLs (stronger evidence in favor of linkage/LD) with increased LD level, under a variety of generating models; while in the absence of linkage and LD, LD-PPLs tend to be smaller than PPLs (stronger evidence against linkage). The estimate of D' also behaves well even in relatively small, heterogeneous samples.     

Improved method for the dynamic measurement of mass transfer coefficient for application to solid–substrate fermentation

A new method has been developed for the measurement of overall volumetric mass transfer coefficient (K_L a) in gas-liquid-solid systems. This method is based on the examination of gas phase dynamics in a three-phase contactor and consists of measuring continuously the response of the outlet gas composition to a step input change of CO₂ in the inlet gas stream. The advantages and limitations of the new method are presented and its sensitivity is discussed on the basis of model predictions. Preliminary results on the implementation of the CO₂ method are also reported. Experimental data obtained in a nonviscous electrolyte solution show that the proposed method compares favorably with the conventional dissolved oxygen technique, provided that a correction is made to take account of the difference in diffusivity of oxygen and carbon dioxide.