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At least 199 records · Page 11Linked to original sources
PubMed2001

Simulating the impact during human jumping by means of a 4-degrees-of-freedom model with time-dependent properties.

The authors simulated the vertical movements of a jumper and the force time courses by means of a 4-degrees-of-freedom model consisting of 4 masses, springs, and dampers. Of the motions simulated, only that of the mass imitating the trunk corresponded to the measured data. The best fit to the measured force curves were obtained in the simulation in which time-dependent model parameters were used. From the results, the authors concluded that at the beginning of the landing, a jumper behaves like a 2-mass model in which the leg segments (thighs, shanks, and feet) effectively combine into 1 mass. After approximately 60 ms, the connections between the leg segments become more compliant and the jumper behaves like a 4-mass model with a soft coupling between the leg segments. The process is equivalent to an increase of the degrees of freedom of the movements. At the end of the ground contact phase during hopping, the jumper has to contract the muscles in order to reach the envisaged jump height. In the model, that contraction could not be satisfactorily simulated.

Biomechanical Phenomena↗
PubMed1992

Information feedback and the learning multiple-degree-of-freedom activities.

The influence of information feedback on the learning of a multiple-degree-of-freedom activity, the overhand throw, was investigated. During learning, feedback was presented in the form of knowledge of results, knowledge of performance, knowledge of performance with attention-focusing cues, or knowledge of performance with error-correcting transitional information. Across 12 practice sessions, performance was assessed with respect to both throwing distance and throwing form. Subjects provided with knowledge of performance along with transitional information demonstrated significant gains in throwing distance, compared with subjects receiving knowledge of performance or knowledge of results alone. Movement form ratings followed the same trend. Providing learners with cues to focus their attention on the relevant aspects of knowledge of performance or directly providing transitional information was a better aid to the acquisition of throwing form than providing knowledge of results or knowledge of performance alone. These results support the hypothesis that knowledge of results may not be the most potent form of feedback in multiple-degree-of-freedom activities and that knowledge of performance, when combined with additional information, can lead to significant gains in skill acquisition.

Journal Article↗
PubMed2006

Freedom-costs of canonical individualism: enforced euthanasia tolerance in Belgium and the problem of European liberalism.

Belgium's policy of not permitting Catholic hospitals to refuse euthanasia services rests on ethical presuppositions concerning the secular justification of political power which reveal the paradoxical character of European liberalism: In endorsing freedom as a value (rather than as a side constraint), liberalism prioritizes first-order intentions, thus discouraging lasting moral commitments and the authority of moral communities in supporting such commitments. The state itself is thus transformed into a moral community of its own. Alternative policies (such as an explicit moral diversification of public healthcare or the greater tolerance for Christian institutions in the Netherlands) are shown to be incompatible with Europe's liberal concern with securing social and material freedom resources, as well as the concern with equality of opportunity, as embodied in the European Union's anti-discrimination labor law. The essay's argument for the preferability of a libertarian solution closes with the challenge that only if the provision of public healthcare can be shown to be rationally indispensable for a morally justified polity, could the exposed incoherence of modern European liberalism be generously discounted.

Belgium↗
PubMed1999

Polytomies and phylogenetically independent contrasts: examination of the bounded degrees of freedom approach.

We examined the effect of soft polytomies on the performance (Type I error rate and bias) of Felsenstein's (1985; Am. Nat. 125:1-15) method of phylogenetically independent contrasts for estimating a bivariate correlation. We specifically tested the adequacy of bounding degrees of freedom, as suggested by Purvis and Garland (1993; Syst. Biol. 42:569-575). We simulated bivariate character evolution under Brownian motion (assumed by independent contrasts) and eight other models on five phylogenetic trees. For non-Brownian motion simulations, the adequacy of branch-length standardization was checked with a simple diagnostic (Garland et al., 1992; Syst. Biol. 41:18-32), and transformations were applied as indicated. Surprisingly, soft polytomies tended to have negligible effects on Type I error rates when models other than Brownian motion were used. Overall, and irrespective of evolutionary model, degrees of freedom were appropriately bounded for hypothesis testing, and unbiased estimates of the correlation coefficient were obtained. Our results, along with those of previous simulation studies, suggest that independent contrasts can reliably be applied to real data, even with phylogenetic uncertainty.

Models, Genetic↗
PubMed1994

Should clinical freedom be constrained in the name of self-sufficiency?

Clinical freedom should enable a physician to decide in a free and unbiased manner which is the most appropriate therapy to use for a particular patient. In order to implement the four aims of the German Haemophilia Society an average of 4-4.5 units of Factor VIII per capita of the general population per year is needed. At present European countries do not produce this amount, but to reduce the consumption of F VIII in therapy lowers treatment levels. Until plasma collection services in Europe can be expanded it is necessary that the additional, imported, sources of plasma are available, otherwise clinical freedom will be curtailed.

Adult↗
PubMedDate not supplied

Freedom of acetabular fragment rotation following three surgical techniques for correction of congenital deformities of the hip.

Femoral head coverage achieved with an acetabular osteotomy for hip dysplasia is achieved by acetabular rotation that can be restricted by osteotomy orientation and soft tissue attachments to the acetabular fragment. Procedures that allow excess rotation or motion in an undesirable direction (especially external rotation) may have undesirable consequences. Rotational aspects of these procedures have not been well described and are not well appreciated radiographically. This study examined the angular motion related to three operative techniques for redirectional acetabular osteotomies. The freedom of motion allowed for the Ganz periacetabular, Carlioz triple, and Tonnis triple osteotomies was quantified using three-dimensional motion measurement. The Ganz osteotomy allowed the greatest amount of motion. The Carlioz osteotomy allowed statistically less motion and depicted the "coupled motion" phenomenon in which a maximal angular rotation in one plane (abduction) is associated with a predicted angular change in another plane (external rotation). The Tonnis osteotomy allowed freedom of motion similar to the Ganz osteotomy without coupled motion.

Acetabulum↗
PubMedDate not supplied

Correcting scaling errors in tomographic images using a nine degree of freedom registration algorithm.

PURPOSE: Clinical imaging systems, especially MR scanners, frequently have errors of a few percent in their voxel dimensions. We evaluate a nine degree of freedom registration algorithm that maximizes mutual information for determining scaling errors. We evaluate it by registering MR and CT images for each of five patients (patient scaling) and by registering MR images of a phantom to a computer model of the phantom (phantom scaling). METHOD: Each scaling method was validated using bone-implanted markers localized in the patient images and also intraoperatively. The root mean square residual in the alignment of the fiducial markers [fiducial registration error (FRE)] was determined without scale correction, with patient scaling, and with phantom scaling. RESULTS: Each scaling method significantly reduced the average FRE (p < 0.05) for MR to CT registration and for MR to physical space registration, indicating that voxel scaling errors were reduced. The greater reduction in scaling errors was achieved using the phantom scaling method. CONCLUSION: We have demonstrated that a nine degree of freedom registration algorithm that maximizes mutual information can significantly reduce scaling errors in MR.

Algorithms↗
PubMed1975

Editorial: The right to know. On the freedom of medical information.

Information about health and disease has high social value and is, thus, subject to a variety of controls. These influence the freedom of investigators to generate it; of editors and publishers to transmit it; and of professionals and the public to have access to it. Unconstrained research may threaten the social order and evoke legal or political limit setting. Prominent in the present era are the possibilities of dangerous ethical and biological consequences of new knowledge or, perhaps more important, of procedures for obtaining it. Medical information is transmitted through both the mass media and professional journals. Access to both by potential authors is limited by institutionalized mechanisms of social control and the academic-research subculture. An emerging factor is the editor's possible ethical responsibility for material which he accepts for publication. Access to information is determined by what finally is published, as well as membership in informal communication networks. It is also influenced by dependence, due to cost, time limitation and information overload, on prepackaged material presented in texts, anthologies, busy clinician-oriented journals, or commercial, e.g., pharmaceutical firms. The possibility that governments will, in time, become the major distributors as well as generators of medical information raises new questions as to its eventual freedom and control.

Biomedical Research↗
PubMedDate not supplied

Evaluation of orthopaedic injuries in Operation Enduring Freedom.

Orthopaedic injuries constitute a majority of the combat casualties in recent U.S. military conflicts. Orthopaedic injuries sustained in Operation Enduring Freedom from December 2001 to January 2003 that were treated in forward-deployed military medical facilities and evacuated to a U.S. army medical center were reviewed. The spectrum of injuries included open fractures, amputations, neurovascular, and soft-tissue injuries. Forty-four patients (85%) received treatment beyond local wound care prior to arrival at a military medical center. Debridement and irrigation was the most commonly performed procedure due to the contaminated nature of these combat injuries. There were no infections among patients with open fractures, and no patients with external fixators had pin tract infections. None of the open fracture patients underwent primary internal fixation or primary wound closure. The average time from injury to wound coverage of the open fracture wounds was 12 days. Two amputations were infected and were treated with revision and delayed wound closure. There were no primary amputations done at our institution due to infection or ischemia. All arterial injuries underwent urgent revascularization in a field hospital. None of the arterial repairs required revision after evacuation to a medical center. Operation Enduring Freedom has been an excellent example of how early and aggressive intervention in a forward-deployed area has a significant effect on rehabilitative and reconstructive efforts at a rear echelon tertiary care center.

Adult↗
PubMed2004

Evaluation of orthopaedic injuries in Operation Enduring Freedom.

Orthopaedic injuries constitute a majority of the combat casualties in recent U.S. military conflicts. Orthopaedic injuries sustained in Operation Enduring Freedom from December 2001 to January 2003 that were treated in forward-deployed military medial facilities and evacuated to a U.S. army medical center were reviewed. The spectrum of injuries included open fractures, amputations, neurovascular, and soft-tissue injuries. Forty-four patients (85%) received treatment beyond local wound care prior to arrival at a military medical center. Debridement and irrigation was the most commonly performed procedure due to the contaminated nature of these combat injuries. There were no infections among patients with open fractures, and no patients with external fixators had pin tract infections. None of the open fracture patients underwent primary internal fixation or primary wound closure. The average time from injury to wound coverage of the open fracture wounds was 12 days. Two amputations were infected and were treated with revision and delayed wound closure. There were no primary amputations done at our institution due to infection or ischemia. All arterial injuries underwent urgent revascularization in a field hospital. None of the arterial repairs required revision after evacuation to a medical center. Operation Enduring Freedom has been an excellent example of how early and aggressive intervention in a forward-deployed area has a significant effect on rehabilitative and reconstructive efforts at a rear echelon tertiary care center.

Adult↗
PubMed2003

Improved freedom from rejection after a loading dose of sirolimus.

BACKGROUND: Sirolimus (SIR) in combination with cyclosporine reduces the incidence of acute rejection in renal transplant recipients. Limited data are available regarding SIR in combination with tacrolimus (TAC). METHODS: A single-center, retrospective review of renal transplant recipients receiving SIR, TAC, and corticosteroids postoperatively was conducted. A total of 118 consecutive renal transplant recipients were included on the basis of availability of day 1 SIR dose information. Seventy-seven patients received an SIR loading dose (SIR-LD) immediately posttransplantation, and 41 patients did not (SIR no loading dose [SIR-NLD]). RESULTS: The two groups showed similar demographic and transplant characteristics. SIR doses and trough levels were significantly higher in the SIR-LD patients at 1 and 7 days posttransplantation; however, no differences occurred beyond day 7. Patients receiving an SIR-LD experienced significantly better freedom from rejection at 1, 3, and 6 months posttransplantation (P<0.05). This rejection benefit in the SIR-LD group was independent of donor source and use of antibody induction. SIR-LD patients experienced fewer serious infections (12% SIR-LD vs. 27% SIR-NLD, P=0.04) and a lower incidence of delayed graft function (21% SIR-LD vs. 39% SIR-NLD, P<0.05). No significant differences in serum creatinine, hemoglobin, and platelet counts occurred in the first 180 days posttransplantation, but the patients in the SIR-NLD group experienced lower hemoglobin levels at day 30 than those in the SIR-LD group (10.8 g/dL SIR-LD vs. 9.7 g/dL SIR-NLD, P=0.03). CONCLUSION: SIR-LD significantly improves early posttransplantation freedom from rejection in renal transplant recipients without increasing other complications.

Adult↗
PubMed2007

Speech understanding in background noise with the two-microphone adaptive beamformer BEAM in the Nucleus Freedom Cochlear Implant System.

OBJECTIVE: This paper evaluates the benefit of the two-microphone adaptive beamformer BEAM in the Nucleus Freedom cochlear implant (CI) system for speech understanding in background noise by CI users. DESIGN: A double-blind evaluation of the two-microphone adaptive beamformer BEAM and a hardware directional microphone was carried out with five adult Nucleus CI users. The test procedure consisted of a pre- and post-test in the lab and a 2-wk trial period at home. In the pre- and post-test, the speech reception threshold (SRT) with sentences and the percentage correct phoneme scores for CVC words were measured in quiet and background noise at different signal-to-noise ratios. Performance was assessed for two different noise configurations (with a single noise source and with three noise sources) and two different noise materials (stationary speech-weighted noise and multitalker babble). During the 2-wk trial period at home, the CI users evaluated the noise reduction performance in different listening conditions by means of the SSQ questionnaire. In addition to the perceptual evaluation, the noise reduction performance of the beamformer was measured physically as a function of the direction of the noise source. RESULTS: Significant improvements of both the SRT in noise (average improvement of 5-16 dB) and the percentage correct phoneme scores (average improvement of 10-41%) were observed with BEAM compared to the standard hardware directional microphone. In addition, the SSQ questionnaire and subjective evaluation in controlled and real-life scenarios suggested a possible preference for the beamformer in noisy environments. CONCLUSIONS: The evaluation demonstrates that the adaptive noise reduction algorithm BEAM in the Nucleus Freedom CI-system may significantly increase the speech perception by cochlear implantees in noisy listening conditions. This is the first monolateral (adaptive) noise reduction strategy actually implemented in a mainstream commercial CI.

Adult↗
PubMed2004

A U.S. Army Forward Surgical Team's experience in Operation Iraqi Freedom.

BACKGROUND: The Forward Army Surgical Team (FST) was designed to provide surgical capability far forward on the battlefield to stabilize and resuscitate those soldiers with life and limb threatening injuries. Operation Iraqi Freedom represents the largest military operation in which the FST concept of health care delivery has been employed. The purpose of our review is to describe the experience of the 555FST during the assault phase of Operation Iraqi Freedom. METHODS: During the 23 days beginning 21 March 2003, data on all patients seen by the 555 FST were recorded. These data included combatant status, injuries according to anatomic location, and operative procedures performed. RESULTS: During the twenty-three day period, the 555 FST evaluated 154 patients. There were 52 EPWs, 79 U.S. soldiers, and 23 Iraqi civilians treated. Injuries to the lower extremity and chest (48% and 25%) were the most common in the EPW group. Upper extremity and lower extremity injuries were the most common in the civilian (57% and 39%) and U.S. soldier groups (32% and 30%). The number of injured regions per patient were 1.14 for U.S. soldiers, 1.33 for EPWs, and 1.52 for Iraqi civilians (p < 0.003). EPWs had proportionately more thoracic and abdominal injuries than the other groups (p < 0.05). CONCLUSIONS: Majority of the life threatening injuries evaluated involved EPWs. A combination of body armor and armored vehicles used by U.S. soldiers limited the number of torso injuries presenting to the FST. Early resuscitation and stabilization of U.S. soldiers, EPWs, and civilians can be successfully accomplished at the front lines by FSTs. Further modification of the FST's equipment will be needed to improve its ability in providing far forward surgical care.

Causality↗
PubMed2002

Dephasing due to the interaction with chaotic degrees of freedom.

We consider the motion of a particle, taking into account its interaction with environmental degrees of freedom. The dephasing time is determined by the nature of the environment and depends on the particle velocity. Our interest is in the case where the environment consists of few chaotic degrees of freedom. We obtain results for the dephasing time and compare them with those of the effective-bath approach. The latter approach is based on the conjecture that the environment can be modeled as a collection of infinitely many harmonic oscillators. The work is related to studies of driven systems, quantum irreversibility, and fidelity. The specific model that we consider requires the solution of the problem of a particle in a box with a moving wall, whose one-dimensional version is related to the Fermi acceleration problem.

Journal Article↗
PubMed2003

Rejection-free Monte Carlo algorithms for models with continuous degrees of freedom.

We construct a rejection-free Monte Carlo algorithm for a system with continuous degrees of freedom. We illustrate the algorithm by applying it to the classical three-dimensional Heisenberg model with canonical Metropolis dynamics. We obtain the lifetime of the metastable state following a reversal of the external magnetic field. Our rejection-free algorithm obtains results in agreement with a direct implementation of the Metropolis dynamic and requires orders of magnitude less computational time at low temperatures. The treatment is general and can be extended to other dynamics and other systems with continuous degrees of freedom.

Journal Article↗
PubMed2003

Two-degree-of-freedom Hamiltonian for the time-symmetric two-body problem of the relativistic action-at-a-distance electrodynamics.

We find a two-degree-of-freedom Hamiltonian for the time-symmetric problem of straight line motion of two electrons in direct relativistic interaction. This time-symmetric dynamical system appeared 100 years ago and it was popularized in the 1940s by the work of Wheeler and Feynman in electrodynamics, which was left incomplete due to the lack of a Hamiltonian description. The form of our Hamiltonian is such that the action of a Lorentz transformation is explicitly described by a canonical transformation (with rescaling of the evolution parameter). The method is closed and defines the Hamitonian in implicit form without power expansions. We outline the method with an emphasis on the physics of this complex conservative dynamical system. The Hamiltonian orbits are calculated numerically at low energies using a self-consistent steepest-descent method (a stable numerical method that chooses only the nonrunaway solution). The two-degree-of-freedom Hamiltonian suggests a simple prescription for the canonical quantization of the relativistic two-body problem.

Journal Article↗
PubMed2006

Coincidence and total photoelectron spectra and their differences induced by internal degrees of freedom.

Recent progress in experimental techniques have made it possible to measure photoelectron spectra in coincidence with particles emitted during the decay of the photoionized species. In this work it will be shown that, contrary to intuition, these coincident photoelectron spectra can be qualitatively different from the photoelectron spectra resulting when all photoelectrons are detected. In particular they carry information on the decay mechanism following photoionization as soon as the decay is influenced by internal degrees of freedom of the photoionized system. This is shown explicitly for the case of vibrational degrees of freedom of molecules and demonstrated with a model study.

Journal Article↗
PubMed2003

Fast rotational matching of rigid bodies by fast Fourier transform acceleration of five degrees of freedom.

The 'fast rotational matching' method (an approach to find the three rotational degrees of freedom in matching problems using just one three-dimensional FFT) is extended to the full six-dimensional (rotation and translation) matching scenario between two three-dimensional objects. By recasting this problem into a formulation involving five angles and just one translational parameter, it was possible to accelerate, by means of fast Fourier transforms, five of the six degrees of freedom of the problem. This method was successfully applied to the docking of atomic structures of components into three-dimensional low-resolution density maps. Timing comparisons performed with our method and with 'fast translational matching' (the standard way to accelerate the translational parameters utilizing fast Fourier transforms) demonstrates that the performance gain can reach several orders of magnitude, especially for large map sizes. This gain can be particularly advantageous for spherical- and toroidal-shaped maps, since the scanning range of the translational parameter would be significantly constrained in these cases. The method can also be harnessed to the complementary surface (or 'exterior docking') problem and to pattern recognition in image processing.

Fourier Analysis↗