bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance enhanced headgear: a scientific approach to the development of protective headgear
Authors: McIntosh A , McCrory P , Finch C F 
Published: January 2004

Background:There is a continuing debate about the performance of protective headgear in rugby union, rugby league, and Australian rules football.Objectives:To examine the impact energy attenuation performance of foam that could be incorporated into headgear and examine the performance of prototypes of modified headgear.Methods:Impact tests were conducted on polyethylene foams and protective headgear. Free fall drop tests with a rigid headform on to a flat rigid anvil were conducted. Resultant headform acceleration was measured. Means of the headform acceleration maxima for repeat tests were calculated.Results:Tests on polyethylene foam indicated that an increase in thickness from 10 mm to 16 mm would improve headgear performance. These modifications were incorporated in part into two headgear models: the Albion Headpro and the Canterbury brand Body Armour honeycomb headgear. The headgear tests show that significant reductions in headform acceleration were achieved by increasing the foam density and thickness. Mean headform acceleration maxima for the 16 mm thick modified rugby headgear was about 25% of that of standard headgear for lateral impact 0.3 and 0.4 m drop heights and 27% for the centre front 0.3 m drop tests. At these impacts, the headform acceleration for the modified rugby headgear was below 200g.Conclusions:Significant improvements in impact energy attenuation performance are possible with small design changes. Whether these are sufficient to reduce the rate or severity of concussion in rugby and Australian rules football can only be shown by formal prospective studies on the field.
Effect of tai chi exercise on proprioception of ankle and knee joints in old people
Authors: Xu D , Hong Y , Li J , Chan K 
Published: January 2004

Objectives:To assess if tai chi, a traditional Chinese form of exercise, could improve proprioception in old people and if the effects of tai chi on proprioception are more evident than other exercise forms in the elderly.Methods:By detecting the threshold of passive movement, ankle and knee joint kinaesthesis was measured in 21 elderly long term tai chi practitioners (TC group), 20 elderly long term swimmers/runners (S/R group), and 27 elderly sedentary controls (control group).Results:Ankle joint kinaesthesis differed significantly among the three groups (p  =  0.001). Subjects in the TC group could detect a significantly smaller amount of motion than those in the S/R group (p  =  0.022) and control group (p  =  0.001). No significant difference was found between the S/R group and the control group (p  =  0.701). The threshold for detection of passive motion was significantly different in knee extension and flexion. For knee flexion, the TC group showed a significantly lower mean threshold for detection of passive motion than the control group (p  =  0.026). There were no significant differences between the S/R group and control group (p  =  0.312), or between the TC group and S/R group (p  =  0.533). For knee extension, no significant difference was noted among the three groups (p  =  0.597).Conclusions:The elderly people who regularly practiced tai chi not only showed better proprioception at the ankle and knee joints than sedentary controls, but also better ankle kinaesthesis than swimmers/runners. The large benefits of tai chi exercise on proprioception may result in the maintenance of balance control in older people.
Prevalence of temporomandibular dysfunction in a group of scuba divers
Authors: Aldridge R D , Fenlon M R 
Published: January 2004

Background:Temporomandibular dysfunction (TMD) has been reported to be a common problem in divers, with a prevalence of up to 68%. No evidence for this is available.Objective:To investigate the prevalence of TMD in divers.Method:Sixty three subjects were asked to retrospectively complete a questionnaire on symptoms of TMD after diving in warm and cold water areas and in daily life.Results:The prevalence of TMD was greater in female divers. The prevalence of TMD while diving was about 26%, comparable to that experienced in daily life.Conclusion:Improvements in mouthpiece design and lighter demand valves mean that TMD is now probably exacerbated by diving rather than caused by it.
Effect of physiotherapy attendance on outcome after anterior cruciate ligament reconstruction: a pilot study
Authors: Feller J A , Webster K E , Taylor N F , Payne R , Pizzari T 
Published: January 2004

Background:In many centres patients are routinely referred for physiotherapy after anterior cruciate ligament (ACL) reconstruction. However, to date the role and amount of supervised physiotherapy required has not been clearly established.Objective:To establish whether there was any difference in outcome between a group of patients who attended physiotherapy regularly after ACL reconstruction and a group who attended only infrequently.Methods:Ten patients who had attended physiotherapy infrequently (mean 1.9 visits) during the first six months after ACL reconstructive surgery were matched for age, sex, graft type, and activity level and occupation before injury with 10 patients who had attended physiotherapy regularly (mean 26.5 visits). Outcome was assessed at 12 months using the Cincinnati knee rating system and the IKDC form.Results:Compared with the regular physiotherapy group, patients in the minimal physiotherapy group had fewer symptoms (mean Cincinnati symptom score 46.2v43.4, p  =  0.045). There was alsoatrend towards higher overall Cincinnati knee scores in the minimal physiotherapy group (mean 93.7v87.3, p  =  0.06) but no difference in IKDC ratings.Conclusion:These preliminary results indicate that some patients who choose to attend physiotherapy on a very limited basis after ACL reconstruction can achieve satisfactory, if not better, outcomes than patients who attend physiotherapy regularly.
Raised concentrations of C reactive protein in anabolic steroid using bodybuilders: Table 1
Authors: Grace F M , Davies B 
Published: January 2004

Objective:To examine levels of C reactive protein in users of anabolic androgenic steroids (AAS) compared with age matched control groups consisting of AAS using (but abstinent)/resistance trained and non-drug using/sedentary controls.Method:Subjects included AAS using bodybuilders (n  =  10); bodybuilders who denied AAS use (n  =  10); sedentary controls (n  =  8). Venous blood was sampled, from which serum concentrations of C reactive protein, male sex hormones, and cardiac troponin T were determined.Results:A significantly altered hormonal profile in the AAS using group provided indirect confirmation of AAS use. C reactive protein concentrations were significantly (p<0.05) higher in the AAS using bodybuilders. There was no relation between C reactive protein and cardiac troponin T.Conclusion:AAS using bodybuilders had significantly higher C reactive protein concentrations, indicating a greater propensity to develop peripheral arterial disease.
MATHEMATICAL MODELING OF CARDIAC ELECTRO-MECHANICS: FROM PROTEIN TO ORGAN
Authors: SACHSE FRANK B. , SEEMANN GUNNAR , MOHR MATTHIAS B. , HOLDEN ARUN V. 
Published: January 2004

Mathematical models of cardiac anatomy and physics provide information, which help to understand structure and behavior of the heart. Miscellaneous cardiac phenomena can only be adequately described by combination of models representing different aspects or levels of detail. Coupling of these models necessitates the definition of appropriate interfaces. Adequateness and efficiency of interfaces is crucial for efficient application of the combined models.In this work an integrated model is presented consisting of several models interconnected by interfaces. The integrated model allows the reconstruction of macroscopic electro-mechanical processes in the heart. The model comprises a three-dimensional are of left ventricular anatomy represented as truncated ellipsoid. The integrated model includes electrophysiological, tension development and elastomechanical models of myocardium at levels of single cell, proteins, and tissue patches, respectively.The model is exemplified by simulations of extracorporated left ventricle of small mammals. These simulations yield temporal distributions of electrophysiological parameters as well as descriptions of electrical propagation and mechanical deformation. The simulations show characteristic macroscopic ventricular function resulting from the interplay between cellular electrophysiology, electrical excitation propagation, tension development, and mechanical deformation.
MECHANICAL INTERACTION OF HETEROGENEOUS CARDIAC MUSCLE SEGMENTSIN SILICO: EFFECTS ONCa2+HANDLING AND ACTION POTENTIAL
Authors: SOLOVYOVA O. , VIKULOVA N. , KATSNELSON L. B. , MARKHASIN V. S. , NOBLE P. J. , GARNY A. , KOHL P. , NOBLE D. 
Published: January 2004

Effects of cardiac mechanical heterogeneity on the electrical function of the heart are difficult to assess experimentally, yet they pose a serious (patho-)physiological challenge. Here, we present an in silico study of the effects of mechanical heterogeneity on action potential duration (APD) in mechanically interacting muscle regions and consequent effects on the dispersion of repolarization, a well-established determinant of cardiac arrhythmogenesis.Using a novel mathematical description of ventricular electromechanical activity (virtual muscle), we first assessed how differences in intrinsic contractile properties affect the electrical behavior of cardiac muscle representations. In spite of identical electrophysiological model descriptions in virtual muscle samples, faster muscle models show shorter APD than their slower counterparts. This is a consequence of Ca2+-mediated feedback from mechanical to electrical activity in the individual muscle models.This mechano-electric feedback (MEF) is, of course, significantly more complex in native cardiac tissue, as the heterogeneous muscle elements interact both mechanically and electrically. Cardiac mechanical heterogeneity, in its most reduced form, can be represented by a duplex consisting of two mechanically interacting muscle segments. Our in silico model of heterogeneous myocardium therefore consists of two individual virtual muscles that are mechanically interconnected in-series to form a virtual heterogeneous duplex. During isometric contraction of the duplex (i.e. at constant external length), internal mechanical interactions affect Ca2+handling and APD of muscle elements, resulting in an increased dispersion of repolarization beyond the intrinsic APD differences.Duplex electromechanical activity is strongly affected by the activation sequence of its elements. Late activation of the faster (subepicardial type) duplex element, postponed by time-lags that correspond to normal transmural activation delays, optimizes duplex contractility and smoothes out intrinsic APD differences, thereby reducing dispersion in repolarization. This smoothing effect is not observed upon delayed activation of the slower (subendocardial type) duplex element. In both settings, changes in repolarization timing follow a nonlinear dependence of APD on activation delay. Furthermore, asynchronous activation of identical elements in a homogeneous duplex causes an impairment of contractile function and increases dispersion of repolarization. This suggests that the normal electrical activation sequence in the heart requires matching mechanical and electrical heterogeneity for optimal cardiac performance.On the subcellular level, our results suggest that mechanical modulation of Ca2+handling is a key mechanism of MEF in heterogeneous myocardium, which contributes to the matching of local mechanical and/or electrical activity to global hemodynamic demand.
Functional Study of the [Ca<sup>2+</sup>]<sub>i</sub> Signaling Pathway in Aortas of <i>L</i>-NAME-Hypertensive Rats
Authors: de Campos Grifoni Samira , Maria Bendhack Lusiane 
Published: January 2004

A variety of mechanisms has been proposed to suggest that nitric oxide participates in the regulation of smooth muscle free [Ca<sup>2+</sup>]<sub>c</sub> (the primary determinant of contractile tone), including inhibition of Ca<sup>2+</sup> influx across the plasma membrane and inhibition of intracellular Ca<sup>2+</sup> release. In view of such considerations, the aim of this study was to investigate the possible alterations in contractile responses induced by drugs that mobilize Ca<sup>2+</sup> from different sources in aortae from N<sup>G</sup>-nitro-<i>L</i>-arginine methyl ester (<i>L</i>-NAME) hypertensive rats (LHR). Treatment with <i>L</i>-NAME did not alter the contractile response induced by phenylephrine; however, indomethacin increased the contraction to phenylephrine only in LHR aortae (1.36 ± 0.08 g, n = 6, vs. 1.97 ± 0.09 g, n = 7). Both phenylephrine and caffeine evoked rapid and phasic contractions in intact or denuded aortic rings in Ca<sup>2+</sup>-free solution containing EGTA. Phenylephrine-elicited phasic contractions were lower in normotensive rats (NR; 0.41 ± 0.05 g, n = 9) than in LHR (0.57 ± 0.06 g, n = 6) and were increased by endothelium removal only in the NR group (0.64 ± 0.05 g, n = 6). Conversely, neither with treatment with <i>L</i>-NAME nor endothelium removal altered the phasic contractile responses induced by caffeine. The Ca<sup>2+</sup> influx stimulated with phenylephrine was greater in NR (1.95 ± 0.08 g; pD<sub>2</sub> 6.06 ± 0.69; n = 8) than in the LHR denuded aorta (1.63 ± 0.11 g; pD<sub>2</sub> 3.52 ± 0.06; n = 6). Similarly, contractions stimulated with phorbol ester in denuded arteries were greater in NR (1.76 ± 0.08 g, n = 7) than in LHR (1.11 ± 0.11 g, n = 7). In the same manner, indomethacin failed to alter the contraction stimulated with phorbol ester in NR arteries (2.01 ± 0.21 g, n = 7), although it completely blocked the inhibitory effect of chronic treatment with <i>L</i>-NAME on this contractile response (1.94 ± 0.24 g; n = 9). Indomethacin did not change the contractile responses stimulated by increasing concentrations of extracellular Ca<sup>2+</sup> in either NR aortas (1.44 ± 0.26 g; pD<sub>2</sub> 4.74 ± 0.79; n = 6) or LHR aorta (1.99 ± 0.19 g; pD<sub>2</sub> 4.10 ± 0.47; n = 8). However, in the presence of indomethacin, the Ca<sup>2+</sup> influx was similar in NR and LHR aortae. Taken together, these results suggest that, in this model of hypertension, the increase in agonist-induced release of Ca<sup>2+</sup> from intracellular stores may be partly compensated by inhibition of Ca<sup>2+</sup> influx and that this effect is due to the increased production of the relaxant prostanoid in vascular smooth muscle cells.
Relationship of Pregnancy-Associated Plasma Protein-A to Renal Function and Dialysis Modalities
Authors: Fialová L. , Kalousová M. , Soukupová J. , Sulková S. , Merta M. , Jelínková E. , Hořejší M. , Šrámek P. , Malbohan I. , Mikulíková L. , Tesař V. , Zima T. 
Published: January 2004

<i>Background:</i> The aim of the study was to determine pregnancy-associated plasma protein-A (PAPP-A), which was recently described as a new marker of cardiovascular events, in patients with chronic renal insufficiency/failure and to find out its relationship to renal function and to prominent markers of oxidative stress (advanced oxidation protein products – AOPP) and inflammation (C-reactive protein – CRP). <i>Methods:</i> The studied group consisted of 36 chronic hemodialysis patients (HD), 10 patients treated with continuous ambulatory peritoneal dialysis (CAPD) and 38 patients with chronic renal insufficiency (CHRI) not yet dialyzed. PAPP-A was measured by Time Resolved Amplified Cryptate Emission technology. Determination of AOPP is based on a spectrophotometric method. <i>Results:</i> PAPP-A levels are statistically significantly elevated in the both groups of dialyzed patients in comparison with healthy subjects (27.0 ± 16.5 mIU/l in HD and 14.07 ± 6.73 mIU/l in CAPD vs. 8.22 ± 2.7 mIU/l in the control group, p < 0.0001 and p < 0.001, respectively, p < 0.05 HD vs. CAPD). The mean serum PAPP-A levels in the CHRI patients not yet dialyzed were not significantly higher in comparison with the control group (9.72 ±4.44 vs. 8.22 ± 2.7 mIU/l, n.s.). In the CHRI not dialyzed patients, we found a significant positive correlation between serum creatinine and PAPP-A levels (r = 0.68, p < 0.05). In comparison with controls, AOPP and CRP levels were significantly higher in HD patients [AOPP 155.0 ± 37.9 µmol/l, p < 0.0001 vs. controls, CRP 10.0 (4.6– 26.9) mg/l (median, interquartile range), p < 0.0001 vs. controls], CAPD patients [AOPP 118.5 ± 25.8 µmol/l, p < 0.0001 vs. controls, CRP 7.7 (2.0–18.8) mg/l, p < 0.01 vs. controls] and AOPP levels in chronic renal failure patients not yet dialyzed (98.5 ± 43.24 µmol/l, p < 0.01 vs. controls). The correlations between PAPP-A and AOPP (r = 0.49, p < 0.05) and PAPP-A and CRP (r = 0.48, p < 0.05) serum concentration were statistically significant in HD patients. In CAPD patients, neither a correlation between PAPP-A and AOPP nor a correlation between PAPP-A and CRP were found. <i>Conclusion:</i> We can conclude that serum PAPP-A levels sensitively reflect the changes in renal function, depend on dialysis modality, and may represent a novel marker associated with inflammation and oxidative stress in chronic renal failure patients.
The effect of local distortions on time‐domain electromagnetic measurements
Authors: Hördt Andreas , Scholl Carsten 
Published: January 2004

Based on the time‐domain integral equation, we derive expressions for the effect of an anomalous body close to the receiver or close to the transmitter on transient electromagnetic measurements. Similar to magnetotellurics, the distortion of electric fields at late times can be described by a constant distortion tensor relating the secondary electric field to the primary field components that would be obtained in the absence of the body. The distortion of a single electric field transient is a static shift only for particular configurations over a layered half‐space. In the general case, the perturbation is time dependent because the direction of the total electric field vector varies with time. The theory nicely explains spatial variations in electric field transients measured during a high‐redundancy long‐offset transient electromagnetics (LOTEM) survey over an underground gas storage site. An inversion example with synthetic data illustrates how distortion can be corrected. The elements of the distortion tensor are determined simultaneously with the model parameters. Ambiguity is reduced by a regularization of the distortion parameters. In the example, the background model is recovered well, even for the difficult case where only one transmitter is used. The distortion of the magnetic field time derivatives caused by bodies close to the receiver is proportional to the time derivative of the primary electric step response. The distortion is generally not limited to early times and cannot be neglected in general. Transmitter overprint effects resulting in static shifts of vertical magnetic field time derivatives may also be understood from the theory.
Elastic impedance inversion of multichannel seismic data from unconsolidated sediments containing gas hydrate and free gas
Authors: Lu Shaoming , McMechan George A. 
Published: January 2004

The elastic properties of hydrated sediments are not well‐known, which leads to inaccuracy in the evaluation of the amount of gas hydrate worldwide. Elastic impedance inversion is useful in estimating the elastic properties of sediments containing gas hydrate, or free gas trapped beneath the gas hydrate, from angle‐dependent P‐wave reflections.We reprocess the multichannel U.S. Geological Survey seismic line BT‐1 from the Blake Ridge off the east coast of North America to obtain migrated common‐angle aperture data sets, which are then inverted for elastic impedance. Two new algorithms to estimate P‐impedance and S‐impedance from the elastic impedance are developed and evaluated using well‐log data from Ocean Drilling Program (ODP) Leg 164; these new algorithms are stable, even in the presence of modest noise in the data.The Vs/Vpratio, Poisson's ratio, and Lamé parameter terms λρ and λ/μ are estimated from the P‐impedance and S‐impedance. The hydrated sediments have high elastic impedance, high P‐impedance, high S‐impedance, high λρ, slightly higher Vs/Vpratio, slightly lower Poisson's ratio, and slightly lower λ/μ values compared to those of the surrounding unhydrated sediments. The sediments containing free gas have low elastic impedance, low P‐impedance, nonanomalous background S‐impedance, high Vs/Vpratio, low Poisson's ratio, low λρ, and low λ/μ values. We conclude that some parameters such as Vs/Vpratio, Poisson's ratio, and λ/μ, although they help identify the free‐gas charged layers, cannot differentiate between the hydrated sediments and nonhydrated sediments when gas hydrate concentration is low, and cannot differentiate between the hydrated sediments and free‐gas charged sediments when the gas hydrate concentration is high.Three distinct layers of gas hydrate are interpreted as being caused by gas hydrates with gas of different molecular weights, with correspondingly different stability zones in depth. Free gas appears to be present below the two deeper gas‐hydrate layers, but not below the shallowest one because the lack of a trapping structure. The gas hydrate has an average concentration of ∼3–5.5% by volume, and is highest (9%) at the base of the lower gas hydrate stability zone. The free‐gas concentration ranges from 1 to 8% by volume, and is most developed beneath the local topographic high of the ocean bottom.
Genetic‐algorithm/neural‐network approach to seismic attribute selection for well‐log prediction
Authors: Dorrington Kevin P. , Link Curtis A. 
Published: January 2004

Neural‐network prediction of well‐log data using seismic attributes is an important reservoir characterization technique because it allows extrapolation of log properties throughout a seismic volume. The strength of neural‐networks in the area of pattern recognition is key in its success for delineating the complex nonlinear relationship between seismic attributes and log properties. We have found that good neural‐network generalization of well‐log properties can be accomplished using a small number of seismic attributes. This study presents a new method for seismic attribute selection using a genetic‐algorithm approach. The genetic algorithm attribute selection uses neural‐network training results to choose the optimal number and type of seismic attributes for porosity prediction.We apply the genetic‐algorithm attribute‐selection method to the C38 reservoir in the Stratton field 3D seismic data set. Eleven wells with porosity logs are used to train a neural network using genetic‐algorithm selected‐attribute combinations. A histogram of 50 genetic‐algorithm attribute selection runs indicates that amplitude‐based attributes are the best porosity predictors for this data set. On average, the genetic algorithm selected four attributes for optimal porosity log prediction, although the number of attributes chosen ranged from one to nine. A predicted porosity volume was generated using the best genetic‐algorithm attribute combination based on an average cross‐validation correlation coefficient. This volume suggested a network of channel sands within the C38 reservoir.