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PubMed2003

Six degrees-of-freedom kinematics of ACL deficient knees during locomotion-compensatory mechanism.

The purpose of the study was to investigate six degrees-of-freedom (DOF) kinematic changes in anterior cruciate ligament ACL-deficient knees during locomotion and the possible compensatory mechanism involved. Compared with healthy subjects, ACL-deficient patients walked with increased tibial external rotation throughout most of the stride and increased tibial abduction at the heel contact, and the tibia was more anterior during swing phase (P<0.05). Considering tibial external rotation and abduction unload the ACL, the kinematic changes indicated compensatory mechanism developed by patients to avoid unstable knee positions due to the loss of the ACL or to avoid stretching a partially torn ACL.

Adaptation, Physiological↗

PubMed2000

Single centre experience on primary correction of common arterial trunk: overall survival and freedom from reoperation after more than 15 years.

OBJECTIVE: To identify predictors of early and late outcomes of common arterial trunk (CAT) after primary surgical correction, such as clinical state prior to surgery, age and weight at presentation, implications of truncal valve abnormalities and associated anomalies of this complex congenital malformation. METHODS: A consecutive series of 106 patients, operated between 1976 and 1998, were reviewed retrospectively. Using the 'Van Praagh' classification, 59 patients presented as A1, 33 as A2, six as A3, and eight as A4. The mean age at operation was 8.6 months (range, 14 days-8.9 years; median, 4.4 months), and the mean weight was 5.2 kg (range, 2.5-30.8 kg; median, 4.4 kg). At the time of operation, 32 patients had congestive heart failure, five were on ventilator support for less than 1 week, and 21 for more than 1 week. RESULTS: Between 1976 and 1989, the early mortality was 21%, and between 1990 and 1998, it dropped to 13%. After 1, 10 and 15 years, the overall survival was 66, 61 and 59%. The 1, 5, 10 and 15 year freedom from reoperation was 82, 60, 22 and 10%, respectively. Clinical condition prior to intervention, truncal valvar dysfunction, and coronary anomalies were significantly associated with poor surgical outcome, whereas weight and age at presentation in our series were not. CONCLUSIONS: In the current era of paediatric cardiac surgery, primary surgical repair of CAT can be carried out with reasonable early and late mortality. However, our data suggest that a high incidence of reoperation, mainly due to the outgrowth and failure of the conduit, has to be expected. The patient's clinical state after diagnosis is decisive for the timing of intervention.

Child↗

PubMed2003

A heuristic for the degrees of freedom of statistics based on multiple variance parameters.

In neuroimaging, data are often modeled using general linear models. Here, we focus on GLMs with error covariances which are modeled as a linear combination of multiple variance/covariance components. Each of these components is weighted by one variance parameter. In many analyses variance parameters are estimated using restricted maximum likelihood (ReML). Most classical approaches assume the error covariance matrix can be factorized into a single variance parameter and a nonspherical correlation matrix. In this context, the F test based on a single variance parameter, with a suitable correction to the degrees of freedom, is the standard inference tool. This correction can also be adapted to models with multiple variance parameters. However, this extension overlooks the uncertainty about the variance parameter estimates and P values tend to be underestimated. Here, we show how one can overcome this problem to render the F test more exact. This issue is important, because serial correlations in fMRI time series are generally modeled using multiple variance parameters. Another application is to hierarchical linear models, which are used for modeling multisubject data. To illustrate our approach, we apply it to some typical modeling scenarios in fMRI data analysis.

Algorithms↗

PubMed2002

Estimating the effective degrees of freedom in univariate multiple regression analysis.

The general linear model provides the most widely applied statistical framework for analyzing functional MRI (fMRI) data. With the increasing temporal resolution of recent scanning protocols, and more elaborate data preprocessing schemes, data independency is no longer a valid assumption. In this paper, we revise the statistical background of the general linear model in the presence of temporal autocorrelations. First, when detecting the activation signal, we explicitly account for the temporal autocorrelation structure, which yields a generalized F-test and the associated corrected (or effective) degrees of freedom (DOF). The proposed approach is data driven and thus independent of any specific preprocessing method. Then, for event-related protocols, we propose a new model for the temporal autocorrelations ("damped oscillator" model) and compare this model to another, previously used in the field (first-order autoregressive model, or AR(1) model). In the case of long fMRI time series, an efficient approximation for the number of effective DOF is provided for both models. Finally, the validity of our approach is assessed using simulated and real fMRI data and is compared with more conventional methods.

Analysis of Variance↗

PubMed2007

Ball catching in children with developmental coordination disorder: control of degrees of freedom.

This study investigated two-handed catching in eight children (four males, four females) aged 7 to 8 years (mean 7y 4mo [SD 3mo]) with developmental coordination disorder (DCD) and their age-matched controls (AMCs). Kinematic data were collected to examine Bernstein's (1967) notion of freezing and releasing degrees of freedom (DF). Participants were asked to catch a ball 30 times, delivered in three blocks of 10 trials. Video analysis showed that children with DCD caught significantly fewer balls than their AMCs (p< or =0.001) counterparts. Kinematic analyses showed that children with DCD exhibited smaller ranges of motion and less variable angular excursions of the elbow joints than their AMCs, and that their elbows are more rigidly coupled (p< or =0.001). These data suggest that children with DCD rigidly fix and couple their limbs to reduce the number of DF actively involved in the task.

Biomechanical Phenomena↗

PubMedDate not supplied

Ab initio stochastic optimization of conformational and many-body degrees of freedom.

Moderate to large size molecules in solution have complex energy surfaces due to intramolecular (conformational) and intermolecular (many-body) interactions. The first principles Monte Carlo (FPMC) method, previously shown to effectively locate minimum-energy structures for systems with only many-body complexity, has been extended to address conformational flexibility by adding three new Monte Carlo move types. The primary advantage of the FPMC method is the ability to efficiently locate minimum energy structures of molecules with conformational flexibility in the presence of explicit solvent molecules using highly accurate quantum chemical calculations. The additions to FPMC were validated by studying conformers of glycerol, glyceraldehyde, and a large humic acid monomer unit. The structure of glyceraldehyde in the presence of one and two water molecules was also explored to demonstrate the power of FPMC to study systems with both conformational and many-body degrees of freedom.

Journal Article↗

PubMed1975

Analogs of bradykinin with restricted conformational freedom.

Three analogs of bradykinin have been synthesized which bear an alpha-methyl group in the place of an alpha proton at position, 4, 5, or 8. Such analogs possess restricted conformational freedom and are of interest for three reasons. (1) They may provide information about the receptor-bound conformation of the peptide. (2) They may provide a route to antagonists of the native peptide. (3) They may be degraded slowly by proteolytic enzymes. None of the analogs described here antagonized the action of bradykinin, but one exhibited tissue specificity and decreased pulmonary inactivation in the rat.

Amino Acid Sequence↗

PubMed2006

Peierls transitions in ionic organic charge-transfer crystals with spin and charge degrees of freedom.

The quasi-one-dimensional electronic structure of organic charge-transfer (CT) salts rationalizes Peierls transitions in mixed or segregated stacks of pi-electron donors (D) and acceptors (A). A microscopic Peierls-Hubbard model, HCT, is presented for CT salts with mixed stacks (Drho+Arho-)n and ionicity rho > 0.7. Dimerization opens a Peierls gap that, due to electron correlation, is the singlet-triplet gap, EST. In contrast to spin-Peierls systems, such as Heisenberg spin chains with rho = 1 and TSP < 20 K, Peierls transitions in CT salts with rho < 1 occur at higher TP and involve both spin and charge degrees of freedom. Linear electron-phonon coupling and an adiabatic approximation for a harmonic lattice are used to model the dimerization amplitude deltaT for T < TP, the magnetic (spin) susceptibility chiT, and the relative infrared intensity of totally symmetric molecular modes. Exact thermodynamics of HCT for stacks up to N = 12 sites are applied to two CT salts with TP approximately 50 and 120 K whose magnetism and infrared have not been modeled previously and to CT salts with inaccessibly high TP > 350 K whose description has been difficult. Ionic CT salts are correlated Peierls systems with a degenerate ground state (GS) at T = 0 whose elementary excitations are spin solitons, while dimerized ion-radical stacks that support triplet-spin excitons have nondegenerate GS. In less ionic CT salts, modulation of HCT parameters on cooling or under pressure leads to Peierls and/or neutral-ionic transitions of the GS, without appreciable thermal population of excited states. Correlations change the gap equation that relates EST at T = 0 to TP compared to free electrons, and size convergence is fast in stacks with large delta0 and high TP.

Journal Article↗

PubMed2000

The legislative tenets of client's right to treatment in the least restrictive environment and freedom from harm: implications for community providers.

For over four decades, national legislation has supported efforts to move persons with severe and persistent mental illness out of restrictive hospital settings and into community based services. Within institutional walls, numerous duties of state have been established to help ensure humane and effective treatment. However, the legal protections afforded hospitalized residents have not appeared to follow these individuals into the community. This article analyzes relevant case law and attempts to establish similarities between the state hospital's duty to protect its residents and the responsibility of community mental health centers to do the same for the persons they serve. The authors argue that the client's right to freedom-from-harm must receive increased attention and community based service providers will have to enhance their capacity to deliver more effective risk management services if mental health reform is to become a successful social policy.

Community Mental Health Services↗

PubMed2001

Foetal images: the power of visual technology in antenatal care and the implications for women's reproductive freedom.

Continuing medico-technical progress has led to an increasing medicalisation of pregnancy and childbirth. One of the most common technologies in this context is ultrasound. Based on some identified 'pro-technology feminist theories', notably the postmodernist feminist discourse, the technology of ultrasound is analysed focusing mainly on social and political rather than clinical issues. As empirical research suggests, ultrasound is welcomed by the majority of women. The analysis, however, shows that attitudes and decisions of women are influenced by broader social aspects. Furthermore, it demonstrates how the visual technology of ultrasound, in addition to other reproductive technology in maternity care, is linked to the 'personification' of the foetus and has therefore contributed to a new image of the foetus. The exploration of these issues challenges some arguments of feminist discourse. It draws attention to possible adverse implications of the technology for women's reproductive freedom and indicates the importance of the topic for political discussions.

Abortion, Induced↗

PubMed2000

Recruitment of degrees of freedom stabilizes coordination.

By showing that transitions may be obviated by recruiting degrees of freedom in the coupled pendulum paradigm, the authors reveal a novel mechanism for coordinative flexibility. In Experiment 1, participants swung pairs of unconstrained pendulums in 2 planes of motion (sagittal and frontal) at 8 movement frequencies starting from either an in-phase or antiphase mode. Few transitions were observed. Measures of spatial trajectory showed recruitment effects tied to the stability of the initial coordinative pattern. When the motion of the pendulums was physically restricted to a single plane in Experiment 2, transitions were more common, indicating that recruitment delays--or even eliminates--transitions. Such recruitment complements transitions as a source of coordinative flexibility and is incorporated in a simple extension of the Haken-Kelso-Bunz (1985) model.

Adult↗

PubMed2003

Task goals and change in dynamical degrees of freedom with motor learning.

In this article, the authors examined the hypothesis that the direction of the change (increase or decrease) in the dynamical degrees of freedom (dimension) regulated as a function of motor learning is task-dependent. Adult participants learned 1 of 2 isometric force-production tasks (Experiment 1: constant force output; Experiment 2: sinusoidal force output) over 5 days of practice and a 6th day with augmented information withdrawal. The results showed that over practice, the task goal induced either an increase (Experiment 1) or a decrease (Experiment 2) in the dimension of force output as performance error was reduced. These findings support the proposition that the observed increase or decrease in dimension with learning is dependent on both the intrinsic dynamics of the system and the short-term change required to realize the task goal.

Adaptation, Physiological↗

PubMed1999

Human nature and clinical freedom, barriers to evidence-based practice?

The perceived threat to clinical freedom offered by evidence-based practice is neither logical nor surprising. Resistance to change and to authority is part of human nature. When we make decisions based upon good quality information we are inconsistent and biased. Human nature offers many challenges to evidence-based practice. Can we do a better job of promoting evidence-based practice? And even if we find and use the evidence, will we make consistent unbiased decisions?

Attitude of Health Personnel↗

PubMed2001

Elderly persons' experiences of living with venous leg ulcer: living in a dialectal relationship between freedom and imprisonment.

The aim was to illuminate elderly persons' experiences of living with venous leg ulcer. Fifteen persons 74-89 years of age with active leg ulcer were interviewed. Data were analysed utilizing a phenomenological-hermeneutic approach inspired by Ricoeur. The analysis includes dialectic movement between understanding and explanation of the text as a whole and its parts. In the structural analysis four themes were identified: emotional consequences of altered body image, living a restricted life, achievement of well-being in connection with a painful wound and bandage, and struggle between hope and despair with regard to a lengthy healing process. The comprehensive understanding indicated that the meaning of living with venous leg ulcer can be understood as a dialectal relationship between, on the one hand the feeling of being imprisoned in the body, the bandage and the home, and on the other hand, hope of freedom from a burdensome body. The results indicate that the concept, body of image, is vitally relevant to the caring of elderly people with venous leg ulcer. The study shows the importance of recognizing the persons' perceptions of their leg ulcers and the impact of these perceptions on well-being. Nurses can thereby anticipate problems and provide more sensitive care.

Adaptation, Psychological↗

PubMed2001

Patients' aims for epilepsy surgery: desires beyond seizure freedom.

PURPOSE: To evaluate prospectively patient's aims for epilepsy surgery as previously outlined theoretically by Taylor et al. (Epilepsia 1997;3:625-30). METHODS: Ninety-three consecutive patients were interviewed by a psychiatrist as part of their evaluation for epilepsy surgery. Open-ended questions about the patient were asked, and carers' aims or ambitions for change as a result of putative relief of seizures were elicited. The interviewer aimed to obtain a maximum of five aims for later follow-up purposes. These questions were part of an extensive psychiatric interview that is described. RESULTS: The aims of 69 patients or carers were analyzed. The 204 statements of aims were grouped into 59 categories initially. The five most frequently cited constituted 50% of all the aims listed. These aims were desire for work, driving of motor vehicles, independence, socializing, and freedom from drugs. The patients rarely identified a desire for improvement in cognitive functioning as an aim for epilepsy surgery. A final analysis into six categories showed that changes in social process predominated, even over changes in personal behavior. CONCLUSIONS: The social and personal aims to accompany relief of epilepsy identified by patients are consistent with the literature on psychosocial adjustment to epilepsy.

Adaptation, Psychological↗

PubMed2001

Australia's campaign to eradicate bovine tuberculosis: the battle for freedom and beyond.

In 1970, voluntary State-based TB control programs in Australia were replaced by a coordinated national campaign to eliminate both brucellosis and tuberculosis from the cattle population. The campaign was funded and managed under tripartite agreement by State/Territory and Commonwealth governments and Industry. The tuberculosis component of the campaign relied on test and slaughter with surveillance for the disease in abattoirs and trace-back to property of origin an essential component. Because of the moderate sensitivity of the skin test ( approximately 70%), testing was repeated at prescribed intervals over a number of years. In the more hostile environment of northern Australia, novel strategies were developed to maximize musters and remove 'at risk' animals. Australia is fortunate it did not have a feral host for M. bovis (apart from buffalo, which were included in the campaign) to complicate eradication. A national granuloma submission program was implemented in 1992 to increase the intensity of abattoir monitoring. Selective or total depopulation was used in some herds to achieve the requirements of the national Standard Definitions and Rules of the Campaign and achieve the status of 'TB Free Area' in December 1997. Monitoring for tuberculosis has continued under the 5-year Tuberculosis Freedom Assurance Program and measures to further reduce the risk of new cases have been implemented.

Abattoirs↗

PubMed1994

Normal values of isokinetic maximum strength, the strength/velocity curve, and the angle at peak torque of all degrees of freedom in the shoulder.

Many acute and chronic complaints in the shoulder joint are due to a reduced active stabilization capacity. Procedures to measure isokinetic strength are used to objectify the muscle deficits and imbalances of various muscle groups. In this study, standard values and reference ranges were determined for peak torque (PT), strength/velocity curve, and range of motion (ROM) at peak torque in the shoulder in 19 untrained women and 32 men. Differentiation was made by the individual degrees of freedom of the shoulder joint and the various types of work (concentric, isometric, eccentric). Moreover, the influence of height, body weight, and body mass index on isokinetic maximum strength development was investigated. It was found that it is necessary to distinguish between the various movements and types of work in development of peak torque. A decrease in maximum strength is observed in the sequence extension, adduction/flexion, abduction/internal rotation, external rotation. The maximum strength of men was determined to be higher than that in women. ROM shows a wide fluctuation and does not possess high validity. Height, as well as body weight and body mass index have only slight influence on the isokinetic maximum strength in the shoulder of untrained men and women.

Adult↗

PubMed2002

Degenerate resonances in Hamiltonian systems with 3/2 degrees of freedom.

Hamiltonian systems with 3/2 degrees of freedom close to autonomous systems are considered. Special attention is focused on the case of degenerate resonances. In this case, an averaged system in the first approximation reduces to an area-preserving mapping of a cylinder whose rotation number is a nonmonotonic function of the action variable. Behavior of the trajectories of such a map is similar to that of the trajectories of a Poincare map. Three regions: B(+/-) in the upper and lower parts of the cylinder and an additional region A which contains separatrices of fixed points for the corresponding resonance are distinguished on the cylinder. It is shown that there is a nonempty set of initial points corresponding to walking trajectories in B(+/-) and, hence, there are no closed invariant curves that are homotopically nontrivial on the cylinder. Cells limited by a "stochastic network" can exist in region A. The number of cells is the greater the higher the order of degeneration of the resonance. Possible types of orbit behavior in region A are described. (c) 2002 American Institute of Physics.

Journal Article↗