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PubMed2002

Demonstrating disease freedom-combining confidence levels.

Part of the requirements for demonstrating disease freedom usually will be that sufficient testing be done to give a specified confidence of detecting the disease if it were present at a specified level. Often, this requirement is translated into a fixed testing regime that must be followed (an inflexible approach that might not be the most economic or practical solution).A more flexible approach is to specify the capabilities of the various tests that can be used to detect the disease, and let the party hoping to demonstrate disease freedom decide upon the testing regime. The question then arises as to how to combine information that can come from a variety of sources over a period of time to give an overall level of confidence. Two methods are given. The first, an exact method based on multiplying probabilities, would be more appropriate for a survey of an area in which no disease is thought to be present. The second method (more appropriate for a herd-assurance program within an infected area) is a point-based system that takes into account the different sensitivities of the methods used to detect disease and the change in prevalence over time. It allocates points for each test done proportional to the sensitivity of the test and the prevalence at the time of testing.

Animal Diseases↗
PubMed2002

Risk-based design of repeated surveys for the documentation of freedom from non-highly contagious diseases.

The documentation of freedom from disease requires reliable information on the actual disease status in a specific animal population. The implementation of active surveillance (surveys) is an effective method to gain this information. For economical reasons, the sample size should be as small as possible but large enough to achieve the required confidence level for a targeted threshold. When conducting surveys repeatedly, various information sources about the disease status of the population can be taken into account to adjust the required level of confidence for a follow-up survey (e.g. risk assessments regarding disease introduction and results of previous surveys). As a benefit, the sample size for national surveys can be reduced considerably. We illustrate this risk-based approach using examples of national surveys conducted in Switzerland. The sample size for the documentation of freedom from enzootic bovine leucosis (EBL) and Brucella melitensis in sheep and in goats could be reduced from 2325 to 415 cattle herds, from 2325 to 838 sheep herds and from 1975 to 761 goat herds, respectively.

Animals↗
PubMed2002

A simulation study of the degrees of freedom of movement in reaching and grasping.

The question of independently controlled components in the act of reaching and grasping has attracted interest experimentally and theoretically. Data from 35 studies were recently found consistent with simulated kinematic finger and thumb trajectories optimised for minimum jerk. The present study closely reproduces those trajectories using a discrete-time model based on minimum acceleration. That model was further used to generate two-dimensional trajectories for finger and thumb to reach and grasp an elliptical object with varying position and/or orientation. Orthogonalisation of these four trajectories revealed one degree of freedom when direction of reach was constant and two degrees of freedom when direction of reach varied, irrespective of object distance and orientation. These simulations indicate that reach and grasp movements contain redundancy that is removable by formation of task-dependent synergies. As skilled movement can be planned and executed in a low dimension workspace, control of these independent components lessens central workload.

Algorithms↗
PubMed2002

Freedom from castration: an alternative end point for men with localized prostate cancer treated by external beam radiation therapy.

PURPOSE: Androgen deprivation therapy (ADT) is frequently given to men with localized prostate cancer. This study was designed to determine what proportion of men require subsequent ADT if their localized prostate cancer is first treated by radiation. METHODS AND MATERIALS: A retrospective review of the outcome of 768 men with T1-4NxM0 prostate cancer treated with external beam radiation at a single institution from 1988 to 1995. The median follow-up for the entire group was 5.8 years. The end points analyzed were biochemical failure (3 successive rises in prostate-specific antigen) and ADT (either medical or surgical castration). RESULTS: A total of 322 biochemical failure events occurred among the 768 treated patients, and 187 began ADT during the period of observation. Fifty-four percent of men starting ADT did so without rebiopsy or radiographic evidence of persistent disease. The overall freedom from biochemical failure rate at 10 years was 43.3% and the 10-year freedom from ADT rate was 56.3%. The corresponding values for the most favorable subgroup (T1-2a, Gleason sum 6, prostate-specific antigen <or=10 ng/mL) were 61.8% and 72.8%. CONCLUSIONS: Curative therapy is often given to men with prostate cancer and a life expectancy of <10 years, even when a survival gain is not expected. One new measure of its value, if any, may be its efficacy in preventing a subsequent, potentially more morbid, therapy such as ADT. The results of this study showed that most men with early-stage prostate cancer do avoid ADT in the 10 years after radiation therapy. This rate is less than that seen in the few contemporary watchful-waiting series.

Aged↗
PubMed2003

An experimental two degrees-of-freedom actuated external fixator for in vivo investigation of fracture healing.

A novel two degrees-of-freedom external fixator that can accurately control interfragmentary mechanical conditions over an ovine tibial osteotomy is presented. The device can apply either axial or torsional motion, to investigate mechano-transduction mechanisms in fracture healing. The device was bench-tested over a range of gap stiffnesses, for its ability to apply pure axial or torsional motions, control interfragmentary strain magnitudes and to measure stiffness over the gap. The experiments reveal very little cross-coupling between axial and torsional displacements, although some transverse displacement occurs for both degrees-of-freedom. The mean interfragmentary strain can also be accurately controlled, but with some variation over the gap (due to coupled transverse displacement error). Interfragmentary stiffness measurements are accurate up to gap stiffnesses corresponding to bony bridging. This characterisation study has shown that the system is adequate to control and measure the mechanical conditions in a fracture healing experiment.

Animals↗
PubMedDate not supplied

Academic freedom amidst competing demands.

Academic freedom means freedom from control in the fulfillment of the faculty roles of teaching and scholarship, but conflicts and misunderstandings regarding this right and responsibility occur, particularly during a time of rapid change. This article discusses the potential conflicts inherent in the academic setting between faculty and administration and differentiates between the role of a faculty member and the academic administrator in three areas: service, scholarship, and support.

Education, Nursing↗
PubMed2002

A review of criticisms of phylogenetic nomenclature: is taxonomic freedom the fundamental issue?

The proposal to implement a phylogenetic nomenclatural system governed by the PhyloCode), in which taxon names are defined by explicit reference to common descent, has met with strong criticism from some proponents of phylogenetic taxonomy (taxonomy based on the principle of common descent in which only clades and species are recognized). We examine these criticisms and find that some of the perceived problems with phylogenetic nomenclature are based on misconceptions, some are equally true of the current rank-based nomenclatural system, and some will be eliminated by implementation of the PhyloCode. Most of the criticisms are related to an overriding concern that, because the meanings of names are associated with phylogenetic pattern which is subject to change, the adoption of phylogenetic nomenclature will lead to increased instability in the content of taxa. This concern is associated with the fact that, despite the widespread adoption of the view that taxa are historical entities that are conceptualized based on ancestry, many taxonomists also conceptualize taxa based on their content. As a result, critics of phylogenetic nomenclature have argued that taxonomists should be free to emend the content of taxa without constraints imposed by nomenclatural decisions. However, in phylogenetic nomenclature the contents of taxa are determined, not by the taxonomist, but by the combination of the phylogenetic definition of the name and a phylogenetic hypothesis. Because the contents of taxa, once their names are defined, can no longer be freely modified by taxonomists, phylogenetic nomenclature is perceived as limiting taxonomic freedom. We argue that the form of taxonomic freedom inherent to phylogenetic nomenclature is appropriate to phylogenetic taxonomy in which taxa are considered historical entities that are discovered through phylogenetic analysis and are not human constructs.

Animals↗
PubMed1986

Depolymerization of microtubules alters membrane potential and affects the motional freedom of membrane proteins.

Two independent lines of evidence were obtained indicating that microtubule depolymerization affects the functions and the physical state of membranes in intact Chinese hamster ovary cells. The first type of evidence was obtained by using the dye dihexyloxacarbocyanine iodide to measure membrane potential before and after treatment with several microtubule active agents. Microtubule depolymerization resulted in a decrease in cell fluorescence, whereas stabilization of microtubules with taxol resulted in an increase in cell fluorescence. These effects of the drugs were due to their interactions with microtubules and not to direct effects of the drugs on the plasma membranes for the following reasons: effects were time dependent and required entry into the cells as indicated by the lack of fluorescence change in a multi-drug-resistant mutant that does not accumulate antimicrotubule drugs and a colcemid-resistant tubulin mutant did not show these effects on cell fluorescence. Evidence for altered motional freedom of membrane proteins in the plasma membrane was obtained by using electron spin resonance analysis of maleimide spin probe labeled cells. This study showed that depolymerization of microtubules results in increased motional freedom of maleimide-labeled sulfhydryl group containing proteins. Taken together, these data argue that microtubules function in mammalian cells to regulate the physical state of membranes and modulate membrane potential generated across cell membranes.

Animals↗
PubMed2005

Probing interfacial organization in surface monolayers using tethered pyrene. 2. Spectroscopy and motional freedom of the adsorbates.

We have studied the steady-state and time-resolved emission spectroscopy of the pyrene-containing monolayers reported in the previous article, where in this work we have bound the monolayers to SiO(x). We find that these monolayer structures are sensitive to the identity of the solvent overlayer, with the solvent playing a significant role in the organization of the surface-bound monolayers. We discuss our findings in the context of the known polarity dependence of the pyrene emission spectrum and find that the motional freedom of the chromophores varies with both the monolayer composition and the identity of the solvent overlayer. Our data point to the importance of neighbor-neighbor interactions within the monolayer structures in mediating the motional freedom of the tethered pyrene chromophores.

Journal Article↗
PubMed2005

Relative Gibbs energies in solution through continuum models: effect of the loss of translational degrees of freedom in bimolecular reactions on Gibbs energy barriers.

We present here a cell model for evaluating Gibbs energy barriers corresponding to bimolecular reactions (or processes of larger molecularity) in which a loss of translational degrees of freedom takes place along the reaction coordinate. With this model, we have studied the Walden inversion processes: Xa- + H3CXb --> XaCH3 + Xb- (X = F, Cl, Br, and I). In these processes, our model yields an increase of about 2.3-3.4 kcal/mol in Gibbs energy in solution corresponding to the loss of the translational degrees of freedom when passing from separate reactants to the TS in good agreement with experimental data. The corresponding value in the gas phase is about 6.7-7.1 kcal/mol. When the difference between these two figures is used to correct the results obtained by the standard UAHF implementation of the continuum model, the theoretical results are brought significantly closer to the experimental ones. This seems to indicate that for these reactions the parametrization used does not adequately introduce the increase in Gibbs energy corresponding to the constriction of the translational motion of the species along the reaction coordinate when passing from the gas phase to solution. Therefore, we believe that continuum models could perform much better if we released the parametrization process from the task of taking into account the constriction in translation motion in solution, which could be more adequately evaluated using the cell model proposed here, thus allowing it to focus on better reproducing all the remaining solvation effects.

Journal Article↗
PubMed2004

Stabilization and destabilization of perception--action patterns influence the self-organized recruitment of degrees of freedom.

The recruitment of an additional biomechanical degree of freedom in a unimanual rhythmic task was explored. Subjects were asked to synchronize adduction or abduction of their right index finger with a metronome, the frequency of which was increased systematically. In addition, haptic contact on or off the metronome beat was provided. Results showed that the pattern exhibiting the highest intrinsic stability recruited the vertical plane more than did the less stable one. Moreover, presence and location of haptic contact modulated coordination stability and therefore induced changes in the recruitment of the vertical plane. Thus, a trade-off was shown between coordination stability on the horizontal plane and recruitment of the vertical one. These findings suggest that recruitment of degrees of freedom is governed by general principles of coordination dynamics.

Adult↗
PubMed1997

An examination of the degrees of freedom of human jaw motion in speech and mastication.

The kinematics of human jaw movements were assessed in terms of the three orientation angles and three positions that characterize the motion of the jaw as a rigid body. The analysis focused on the identification of the jaw's independent movement dimensions, and was based on an examination of jaw motion paths that were plotted in various combinations of linear and angular coordinate frames. Overall, both behaviors were characterized by independent motion in four degrees of freedom. In general, when jaw movements were plotted to show orientation in the sagittal plane as a function of horizontal position, relatively straight paths were observed. In speech, the slopes and intercepts of these paths varied depending on the phonetic material. The vertical position of the jaw was observed to shift up or down so as to displace the overall form of the sagittal plane motion path of the jaw. Yaw movements were small but independent of pitch, and vertical and horizontal position. In mastication, the slope and intercept of the relationship between pitch and horizontal position were affected by the type of food and its size. However, the range of variation was less than that observed in speech. When vertical jaw position was plotted as a function of horizontal position, the basic form of the path of the jaw was maintained but could be shifted vertically. In general, larger bolus diameters were associated with lower jaw positions throughout the movement. The timing of pitch and yaw motion differed. The most common pattern involved changes in pitch angle during jaw opening followed by a phase predominated by lateral motion (yaw). Thus, in both behaviors there was evidence of independent motion in pitch, yaw, horizontal position, and vertical position. This is consistent with the idea that motions in these degrees of freedom are independently controlled.

Humans↗
PubMedDate not supplied

Operation Iraqi Freedom: the Landstuhl Regional Medical Center experience.

Landstuhl Regional Medical Center, Germany, the only American medical center in Europe, received approximately 80% of American military patients evacuated out of theater during the first 4 months of Operation Iraqi Freedom. 1236 patients arrived at Landstuhl Regional Medical Center from the beginning of Operation Iraqi Freedom until May 15, 2003, consisting of 256 battle casualties (20.7%), 510 injury patients (41.3%), and 470 disease patients (38.0%). Retrospective record reviews were done on all battle casualties, as well as all disease and injury patients with a musculoskeletal diagnosis. Of the battle casualty patients, 68.4% suffered an extremity injury--a percentage that is consistent with that from prior wars. 52.8% had a lower extremity injury and 21.5% had a foot or ankle injury. Additionally, of all disease and non-battle injury patients with a musculoskeletal diagnosis, 74.7% had an extremity complaint, 44.1% had a lower extremity diagnosis, and 23.2% had foot or ankle pathology. Of all 1236 patients evacuated during this period, 39.5% had extremity pathology, 25.8% had lower extremity pathology, and 12.4% had foot and ankle pathology in isolation or combined with other complaints. Extremity injuries, and specifically lower extremity injuries, continue to be the predominant wounding pattern found in surviving troops in modern warfare. Proper staffing and positioning of medical specialties involved in musculoskeletal trauma care is vital in ensuring proper casualty care in future conflicts.

Adolescent↗
PubMed2002

[Towards a neuropsychology of autonomy: re-presenting forgetting, subliminality and freedom].

Recent neurobiological concepts about sensomotor processes in animals exhibit that voluntary motor behavior is not due primarily to external cues but to internal activation-processes ("initial activity"). Thus questions are raised as to the role of internal "limbic" valuation-processes in relation to contexts of the past. These are not limited to the actual memorial contents but also relate to subliminal aspects of the past. The inclusion of processes of "re-presenting forgetting" means a re-evaluation of autonomy within a neuropsychological theory of freedom. Consequently, subjective freedom may be realized by intrapsychic processes of re-presentation of the past.

Animals↗
PubMed2005

Impact of implantation technique on hemodynamic results of the Pericarbon Freedom stentless valve.

BACKGROUND: The Pericarbon Freedom stentless valve has shown excellent hemodynamic results in the midterm course. However, there is no information as to whether a continuous or interrupted suture technique at the inflow site has an impact on postoperative hemodynamics. METHODS: 139 patients were enrolled in a non-randomized, prospective matched trial. An interrupted suture line technique was used in 68 patients and a continuous suture line technique was used in 71 at the inflow site. Isolated valve replacement was performed in 70.4% of the continuous and 67.6% of the interrupted suture group. Pre- and postoperative hemodynamics and one-year follow-up were obtained by echocardiography and expressed as mean and peak gradients and grade of regurgitation. RESULTS: No significant difference between continuous and interrupted suture techniques were noted with respect to mean (11.8 +/- 6.3 vs. 12.5 +/- 6.2 mm Hg, p = 0.251) and peak gradients (21.0 +/- 9.6 vs. 22.0 +/- 10.9 mm Hg, p = 0.292) as well as to the degree of regurgitation. Bypass and cross-clamping times decreased by 22.4 and 20.6 minutes, respectively, with the use of the continuous suture technique. One year follow-up showed a further, significant decrease of mean and peak gradients. CONCLUSIONS: The Pericarbon Freedom stentless valve appears to offer excellent postoperative performance. The suture line technique at the inflow site does not result in any hemodynamic differences.

Aged↗
PubMed1997

On chaotic dynamics in "pseudobilliard" Hamiltonian systems with two degrees of freedom.

A new class of Hamiltonian dynamical systems with two degrees of freedom is studied, for which the Hamiltonian function is a linear form with respect to moduli of both momenta. For different potentials such systems can be either completely integrable or behave just as normal nonintegrable Hamiltonian systems with two degrees of freedom: one observes many of the phenomena characteristic of the latter ones, such as a breakdown of invariant tori as soon as the integrability is violated; a formation of stochastic layers around destroyed separatrices; bifurcations of periodic orbits, etc. At the same time, the equations of motion are simply integrated on subsequent adjacent time intervals, as in billiard systems; i.e., all the trajectories can be calculated explicitly: Given an initial data, the state of the system is uniquely determined for any moment. This feature of systems in interest makes them very attractive models for a study of nonlinear phenomena in finite-dimensional Hamiltonian systems. A simple representative model of this class (a model with quadratic potential), whose dynamics is typical, is studied in detail. (c) 1997 American Institute of Physics.

Journal Article↗
PubMed2006

Transition rate prefactors for systems of many degrees of freedom.

When a minimum on the potential energy surface is surrounded by multiple saddle points with similar energy barriers, the transition pathways with greater prefactors are more important than those that have similar energy barriers but smaller prefactors. In this paper, we present a theoretical formulation for the prefactors, computing the probabilities for transition paths from a minimum to its surrounding saddle points. We apply this formulation to a system of 2 degrees of freedom and a system of 14 degrees of freedom. The first is Brownian motion in a two-dimensional potential whose global anharmonicities play a dominant role in determining the transition rates. The second is a Lennard-Jones (LJ) cluster of seven particles in two dimensions. Low lying transition states of the LJ cluster, which can be reached directly from a minimum without passing through another minimum, are identified without any presumption of their characteristics nor of the product states they lead to. The probabilities are computed for paths going from an equilibrium ensemble of states near a given minimum to the surrounding transition states. These probabilities are directly related to the prefactors in the rate formula. This determination of the rate prefactors includes all anharmonicities, near or far from transition states, which are pertinent in the very sophisticated energy landscape of LJ clusters and in many other complex systems.

Algorithms↗
PubMed2001

Predictors of long-term event-free survival and of freedom from restenosis after percutaneous balloon mitral commissurotomy.

BACKGROUND: Most long-term studies after balloon mitral commissurotomy (BMC) were from industrialized countries. Less is known about the long-term results of BMC from developing countries where patients are younger with fewer mitral valve deformities. METHODS: Between December 1987 and December 1998, we performed BMC in 654 patients whose mean age was 33 +/- 13 years. Baseline and postprocedural variables were evaluated to identify predictors of event-free survival (survival without repeat BMC or mitral valve replacement) and of freedom from restenosis defined as a mitral valve area (MVA) >/=1.5 cm(2) after BMC and <1.5 cm(2) at follow-up. RESULTS: The actuarial survival rates were 98%, 98%, and 97% at 5, 7, and 10 years, respectively. The 5-, 7-, and 10-year event-free survival rates were 85%, 81%, and 72%. Multivariate predictors of a higher 10-year event-free survival rate were lower echocardiographic score (79% for a score </=8, 61% for a score of 9 to 11, 62% for a score >/=12, P <.001) and cardiac sinus rhythm (P =.04) before BMC, lower mean left atrial pressure (P <.001), lower mitral valve gradient (P <.001), and less than or equal to grade 2 mitral regurgitation (P =.036) after BMC. Restenosis occurred in 16% of patients. The restenosis-free rates were 88%, 80%, and 66% at 5, 7, and 10 years, respectively. A higher freedom from restenosis at 10 years was associated with a lower score (77% for a score </=8, 45% for a score of 9-11 and 50% for a score >/=12, P =.03) and a larger MVA before BMC (P =.03), a larger MVA (P <.001), and a lower mitral valve gradient (P =.04) after BMC. CONCLUSIONS: BMC produces excellent 10-year results in patients with pliable mitral stenosis and good results in patients with semipliable or calcified mitral stenosis. BMC is the procedure of choice in patients with pliable valves and it is a reasonable treatment option in young patients with unfavorable mitral valve anatomy.

Adult↗