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At least 289 records · Page 16Linked to original sources
PubMed2007

A comparison of denominator degrees of freedom methods for multiple observer ROC analysis.

There are several methods available for analysing multireader ROC studies that generalize results to both the reader and case populations. Two of these methods--the Dorfman-Berbaum-Metz (DBM) method and the Obuchowki-Rockette (OR) method--appear to be quite different in their original formulations. However, recently it has been shown that the DBM and OR procedures yield the same test statistic when based on the same accuracy measure and covariance estimation method, but inferences can vary depending on which denominator degrees of freedom (ddf) method, DBM or OR, is used. I show in simulations that there are problems with both ddf methods: OR is ultraconservative with significance levels considerably below the nominal level, and DBM can result in extremely wide confidence intervals because the ddf can be close to zero. I propose a new ddf method that overcomes both of these problems and can be used with either the OR or DBM procedure.

Aortic Aneurysm, Thoracic↗
PubMed1991

A one degree of freedom nominal association model for testing independence in two-way contingency tables.

In testing the independence of the row and column variables in a two-way contingency table, the standard Pearson and likelihood ratio chi-square statistics often have low power, especially as the dimensions of the table increase. In this paper, one degree of freedom tests of independence based on likelihood ratio and score statistics from an association model for tables with nominal row and column classifications are described. The score statistic is especially easy to use, since it can be expressed in closed form, is simple to compute, and has size and power properties which are only slightly inferior to those of the more complicated likelihood ratio statistic.

Brain Neoplasms↗
PubMed1981

Is the failure of (-)deprenyl, a selective monoamine oxidase B inhibitor, to alleviate depression related to freedom from the cheese effect?

The selective monoamine oxidase (MAO) B inhibitor (-)deprenyl failed to produce any greater benefit than placebo in a limited double-blind trial conducted in depressive patients. Its relative freedom from the so-called cheese effect was confirmed, however, in drug-treated patients challenged IV with tyramine. There is evidence to suggest that this cheese effect, a facilitated tyramine-induced hypertensive response, is pharmacologically distinct from MAO inhibition proper. Thus, it is conceivable that its central counterpart, an enhanced noradrenaline release due to the access of traces of tyramine to the CNS, is a prerequisite for any therapeutic benefit obtainable with the MAO-inhibitory drugs in general.

Blood Pressure↗
PubMed1990

[Freedom in research and responsibilities of scientists].

The future of the modern world, which in its structure is a Leonardo world, depends on the future of science. Science solves problems but it creates problems, too. Hence, the conflict over scientific (and technological) progress is normal and talk about a crisis of acceptance is misleading. Freedom of research--within the scientific triangle formed by pure basic research, application-oriented basic research, and applied research for product development--finds its limits in the responsibility of the scientist. The scientific imperative, without which a Leonardo world cannot survive, must be supplemented by an ethical imperative, without which it cannot steer a reasonable course.

Civil Rights↗
PubMed1984

[Law and freedom in medical decisions from the viewpoint of the law].

Modern medicine has given doctors more and more possibilities for "manipulative" intervention in natural processes. However, even in the context of daily medical routine of beginning, continuing or terminating treatment, the doctor is repeatedly faced with the dilemma of whether to make use of the opportunities open to him. Contrary to the widely-held view that such decisions are of a purely empirico-medical nature, it becomes apparent with reference, for example, to the definition of death and the discontinuation of treatment that these decisions also have a normative-evaluative character. In relation to the postulate of the widest possible "medical discretion" emphasis is attached to the necessity for a legal framework for four functions of the law as regards the relationship between doctor and patient: protection--avoidance of abuse--presentation of guidelines--stabilisation of confidence. In conclusion the question of medical freedom in relation to active euthanasia is considered.

Decision Making↗
PubMed1998

Common principles underlying the control of rapid, single degree-of-freedom movements at different joints.

Studies of rapid, single degree-of-freedom movements have shown different changes in electromyographic patterns for movement tasks that appear very similar (e.g., movements over different ranges of distance). However, it is not clear whether these differences are a result of joint-specific control schemes or whether they are instead due to the limited range of task parameters studied relative to the mechanical constraints of each joint (e.g., short compared with long movements relative to the range of motion of a particular joint). In this study, we measured and compared the kinematic trajectories and electromyograms recorded during various movement tasks at the wrist, elbow, and ankle. Subjects performed movements over a wide range of distances "as fast as possible," "at a comfortable speed," and against two inertial loads (at the elbow only), and they performed movements over a fixed distance at three different speeds at the wrist and ankle. For fast movements we show that, in spite of some joint-specific differences, the basic pattern of electromyographic (EMG) modulation is similar at all three joints; for example, the agonist EMG burst transitions from a fixed duration to an increasing duration with increasing movement distance at all three joints. Moreover, the distance at which this transition occurs in one joint relative to the distance at which this transition occurs in the other two joints is consistent across subjects. The transition occurs at the shortest distance at the ankle and the longest distance at the wrist. In general we suggest that the data are consistent with a single set of control rules applied at all three joints, with the biomechanical constraints at each joint accounting for the differences in the EMG and kinematic patterns observed across joints.

Adult↗
PubMed1999

Recruitment and sequencing of different degrees of freedom during pointing movements involving the trunk in healthy and hemiparetic subjects.

Previous studies have shown that in neurologically normal subjects the addition of trunk motion during a reaching task does not affect the trajectory of the arm endpoint. Typically, the trunk begins to move before the onset and continues to move after the offset of the arm endpoint displacement. This observation shows that the potential contribution of the trunk to the motion of the arm endpoint toward a target is neutralized by appropriate compensatory movements of the shoulder and elbow. We tested the hypothesis that cortical and subcortical brain lesions may disrupt the timing of trunk and arm endpoint motion in hemiparetic subjects. Eight hemiparetic and six age-matched healthy subjects were seated on a stool with the right (dominant) arm in front of them on a table. The tip of the index finger (the arm endpoint) was initially at a distance of 20 cm from the midline of the chest. Wrist, elbow, and upper body positions as well as the coordinates of the arm endpoint were recorded with a three-dimensional motion analysis system (Optotrak) by infrared light-emitting diodes placed on the tip of the finger, the styloid process of the ulna, the lateral epicondyle of the humerus, the acromion processes bilaterally, and the sternal notch. In response to a preparatory signal, subjects lifted their arm 1-2 cm above the table and in response to a "go" signal moved their endpoint as fast as possible from a near to a far target located at a distance of 35 cm and at a 45 degrees angle to the right or left of the sagittal midline of the trunk. After a pause (200-500 ms) they moved the endpoint back to the near target. Pointing movements were made without trunk motion (control trials) or with a sagittal motion of the trunk produced by means of a hip flexion or extension (test trials). In one set of test trials, subjects were required to move the trunk forward while moving the arm to the target ("in-phase movements"). In the other set, subjects were required to move the trunk backward when the arm moved to the far target ("out-of-phase movements"). Compared with healthy subjects, movements in hemiparetic subjects were segmented, slower, and characterized by a greater variability and by deflection of the trajectory from a straight line. In addition, there was a moderate increase in the errors in movement direction and extent. These deficits were similar in magnitude whether or not the trunk was involved. Although hemiparetic subjects were able to compensate the influence of the trunk motion on the movement of the arm endpoint, they accomplished this by making more segmented movements than healthy subjects. In addition, they were unable to stabilize the sequence of trunk and arm endpoint movements in a set of trials. It is concluded that recruitment and sequencing of different degrees of freedom may be impaired in this population of patients. This inability may partly be responsible for other deficits observed in hemiparetic subjects, including an increase in movement segmentation and duration. The lack of stereotypic movement sequencing may imply that these subjects had deficits in learning associated with short-term memory.

Adult↗
PubMed2005

Bacterial species diversity in cigarettes linked to an investigation of severe pneumonitis in U.S. Military personnel deployed in operation iraqi freedom.

This report presents results from a study on the bacterial diversity of cigarette brands collected from military personnel during the U.S. Army's investigation of a series of cases of acute eosinophilic pneumonitis in military personnel deployed in Operation Iraqi Freedom. Eight species of Bacillus, including five new species, and one new species of Kurthia were isolated from the cigarettes. Some of these species have been identified elsewhere as causes of hypersensitivity pneumonitis and other respiratory syndromes. All of the isolates were facultative anaerobes, and many displayed mucoid growth under anaerobic conditions. In addition, many isolates also displayed the ability to form surface biofilms under liquid culture. Although biofilm formation and mucoid growth were not correlated, the former was found to be much more pronounced under anaerobic conditions as opposed to aerobic ones. The implications of these findings are discussed.

Acute Disease↗
PubMed1999

Muscle activity in rapid multi-degree-of-freedom elbow movements: solutions from a musculoskeletal model.

The activity of certain muscles that cross the elbow joint complex (EJC) are affected by forearm position and forearm movement during elbow flexion/extension. To investigate whether these changes are based on the musculoskeletal geometry of the joint, a three-dimensional musculotendinoskeletal computer model of the EJC was used to estimate individual muscle activity in multi-degree-of-freedom (df) rapid (ballistic) elbow movements. It is hypothesized that this model could reproduce the major features of elbow muscle activity during multi-df elbow movements using dynamic optimal control theory, given a minimum-time performance criterion. Results from the model are presented and verified with experimental kinematic and electromyographic data from movements that involved both one-df elbow flexion/extension and two-df flexion/extension with forearm pronation/supination. The model demonstrated how the activity of particular muscles is affected by both forearm position and movement, as measured in these experiments and as previously reported by others. These changes were most evident in the flexor muscles and least evident in the extensor muscles. The model also indicated that, for specific one- and two-df movements, activating a muscle that is antagonistic or noncontributory to the movement could reduce the movement time. The major features of muscle activity in multi-df elbow movements appear to be highly dependent on the joint's musculoskeletal geometry and are not strictly based on neural influences or neuroanatomical substrates.

Computational Biology↗
PubMed2006

Upper extremity vascular injury: a current in-theater wartime report from Operation Iraqi Freedom.

Past wartime experience and recent civilian reports indicate upper extremity (UE) vascular injury occurs less often and with less limb loss than lower extremity (LE) injury. Given advances in critical care, damage control techniques, and military armor technology, the objective of this evaluation was to define contemporary patterns of UE injury and effectiveness of vascular surgical management in UE vascular injury during Operation Iraqi Freedom (OIF). From 1 September 2004 through 31 August 2005, 2,473 combat-related injuries were treated at the central echelon III surgical facility in Iraq. Patients with UE vascular injuries upon arrival were reviewed. Vessels injured were delineated. Therapeutic interventions, early limb viability, and complication rates following vascular repair were recorded. Of casualties treated during the study period, 43 (1.7%) UE and 83 (3.3%) LE vascular injuries were identified. Of the UE injuries, 11 (26%) had been operated on at forward locations and six (14%) had temporary shunts in place upon arrival at our facility. Injury levels included 10 (23%) subclavian-axillary, 25 (58%) brachial, and 10 (23%) distal to the brachial bifurcation. Two patients had multilevel injury. Twenty-eight grafts were placed, and 10 vessel repairs and eight ligations were performed. Two (4.7%) brachial interposition grafts required removal due to infection. Four (9.3%) subacute brachial graft thromboses occurred. Four (9.3%) patients underwent early UE amputation. In this most recent U.S. military evaluation of wartime UE vascular injury, UE injury appears rare, with LE injury twice as frequent. Yet, UE limb loss appears more substantial than noted previously. These findings are likely related to significant tissue destruction occurring with the combined mechanisms of injury sustained in OIF.

Amputation, Surgical↗
PubMed2006

The President's New Freedom Commission: capitalizing on opportunities to advance school-based mental health services.

The report from President George W. Bush's New Freedom Commission on Mental Health (NFC), Achieving the Promise: Transforming Mental Health Care in America(2003), proposes goals and recommendations for improving mental health services. This report has significant implications for the delivery of mental health services through the schools. A focused discussion of the potential opportunities and challenges of implementing NFC recommendations related to school-based mental health is presented. Strategies for addressing five key areas at the intersection of school mental health and the Commission's recommendations include: stigma reduction, suicide prevention, expansion and improvement of school mental health, and screening and treatment of co-occurring mental health and substance abuse disorders.

Advisory Committees↗
PubMed2006

Evaluation of the cumulative evidence for freedom from BSE in birth cohorts.

Substantial resources are used for surveillance of bovine spongiform encephalopathy (BSE) despite an extremely low detection rate, especially in healthy slaughtered cattle. We have developed a method based on the geometric waiting time distribution to establish and update the statistical evidence for BSE-freedom for defined birth cohorts using continued surveillance data. The results suggest that currently (data included till September 2004) a birth cohort of Danish cattle born after March 1999 is free from BSE with probability (power) of 0.8746 or 0.8509, depending on the choice of a model for the diagnostic sensitivity. These results apply to an assumed design prevalence of 1 in 10,000 and account for prevalence heterogeneity. The age-dependent, diagnostic sensitivity for the detection of BSE has been identified as major determinant of the power. The incorporation of heterogeneity was deemed adequate on scientific grounds and led to improved power values. We propose our model as a decision tool for possible future modification of the BSE surveillance and discuss public health and international trade implications.

Animals↗
PubMed1994

Translational and rotational joint power terms in a six degree-of-freedom model of the normal ankle complex.

We hypothesized that defining joint power (JP) merely on the basis of joint rotations ignores important translational power terms, and may not adequately represent the energy flow profile for a given muscle group. A novel six degree-of-freedom (6 DOF) model of the ankle complex was implemented, accounting for previously ignored joint translations as well as traditional rotations. Foot and shank kinematic and kinetic data were collected over a stride cycle on five male and five female adults, walking five trials each at 0.69 statures s-1. During intra-subject analyses, ensemble averages were calculated (n = 5) for JP associated with each DOF, and for related velocity and force/moment data. Translational joint velocities typically peaked below 10% of the mean walking velocity. The largest peak in JP occurred for the rotational DOF associated with dorsi/plantar flexion (360 W). The next largest peak in JP was for the vertical translational DOF, and was nearly 10% of the predominant peak. Positive work during push-off was significantly less p < or = 0.05) for the 6 DOF model (27.9 J) than for either 1 or 3 DOF rotational models (30.3 and 29.9 J, respectively). Negative work during early stance was significantly less for the 6 DOF model (-10.3 J) than for either the 1 or 3 DOF models (-13.1 and -12.6 J, respectively). Inter-subject analyses (n = 50) were conducted for JP data only, with similar results. We conclude that translational JP terms are of practical importance in mechanical energy studies, and may be of particular concern when evaluating energy storing prostheses, when summing total power at several joints, and when studying pathologies that disturb joint geometry.

Adult↗
PubMed1994

A six-degree-of-freedom transducer for in vitro measurement of patellofemoral contact forces.

A satisfactory design of the patellar component used in total knee arthroplasty and a general understanding of the effects of orthopedic procedures require, in part, an accurate description of patellofemoral contact forces. Experimental determination of the contact stress distribution requires integration to estimate the contact forces. Due to complex patellar geometry, the determination of the components of the resultant load is difficult. Current techniques for the direct measurement of contact loads either report a single load component or require sequential experiments to fully describe the contact force. The present study describes the development of a six-degree-of-freedom patellofemoral force transducer. This transducer allows the simultaneous determination of the three components of the contact force with an increase in accuracy over available devices. The contact forces components are accurate to 1% of full scale (900 N anterior-posterior, +/- 200 N medial-lateral and inferior-superior). The location on the patella where the resultant force acts is determined to within 1 mm. Relative movement of this point as a function of either normal change in knee flexion angle or as a result of a typical orthopedic procedure is determined to within 0.1 mm. A protocol is presented that allows the contact forces to be determined for either the anatomically normal patella or a patella following total knee arthroplasty.

Calibration↗
PubMed1996

A six-degrees-of-freedom instrumented linkage for measuring the flexibility characteristics of the ankle joint complex.

Diagnosis of ligament injuries to the ankle joint complex is a difficult clinical problem which relies primarily on manual physical examination and on radiographic evaluations. In an attempt to develop a reliable, quantitative diagnostic tool for such injuries we developed a six-degrees-of-freedom instrumented linkage (Ankle Flexibility Tester-AFT) capable of measuring the flexibility characteristics of the ankle joint complex in vivo. The unique non-serial structure of this linkage was such that these characteristics were recorded directly in an ]anatomical coordinate system which enhanced clinical interpretation. The goal of the present study was to develop this linkage and to test its accuracy and its test-retest reliability. The positional accuracy of the AFT was measured and was found to be better than 0.5 mm for translation and 1.2 degrees for rotations. The results obtained from a study conducted on two cadaveric specimens indicate negligible effect of loading rate on the flexibility characteristics within the range of possible manually applied loads. Finally, the reliability of the AFT was examined from test-retest studies conducted on a total of thirteen young healthy volunteers. The intraclass correlation coefficient (ICC), calculated from the test-retest data, indicated a reliability higher than 0.85. It was concluded that the high reliability and accuracy of the AFT, its simplicity of operation, the easy alignment procedure, the on-line load-displacement results, and the elimination of complex data processing render this device suitable for use in the clinic as well as in the research laboratory.

Ankle Injuries↗
PubMed1995

Optimal control for an above-knee prosthesis with two degrees of freedom.

Our previous research and clinical tests of a self-contained powered above-knee prosthesis (AKP) showed that a knee joint with one degree of freedom (DOF) increases the energy cost of walking with respect to able-bodied subjects. Better symmetry of the gait can improve performance, so we suggest here the integration of a second powered DOF into the knee joint mechanism to control the internal-external rotation of the shank-foot complex. The control for the AKP with two DOFs is based on a method of optimal tracking. The data used for analysis were collected in able-bodied subjects braced with an ankle splint to experimentally duplicate a gait like that of amputees using a two-DOF prosthesis. The simulation showed the following: (1) the technique of optimal programming can be used for simulation of the artificial leg during locomotion; (2) the optimal tracking method is an efficient tool for selection of actuators for the above-knee prosthesis, ensuring that the tracking remains within limits. Limitation of joint torque is desirable in order to reduce the size of the motor, but beyond a certain point limiting maximal torques lead to tracking errors that are associated with higher energy costs and hence the need for a larger power source. The errors are also associated with higher forces at the interface between the socket and the prosthesis. The optimal tracking method allows the optimization of tracking with constraints on the size of the motor used and its energy cost.

Adult↗
PubMed1986

Smoking intervention: combination therapy using nicotine chewing gum and the American Lung Association's "Freedom from Smoking" manuals.

The smoking cessation efficacy of a two-session group program using the American Lung Association's "Freedom from Smoking" self-help manuals, nicotine gum, and brief, repeated professional supervision was estimated in an uncontrolled clinical trial. Of the 39 participants, 12 (31%) remained cigarette free for 1 year, and 4 others (10%) had not smoked during the 3 months prior to the 1-year follow-up. Claims of cessation were verified by expired-air carbon monoxide measurement. Nearly all successful abstainers were able to achieve 48-hr cessation during their first week using the gum. This finding suggests that nicotine gum is best used to help the smoker quit abruptly, rather than as an aid in a tapering-off strategy. This study's smoking intervention program appears to provide a relatively low-cost method of improving the success rates among smokers who wish to quit.

Adolescent↗
PubMed1990

Space Station Freedom crew training.

The nature of the Space Station Freedom Program presents an array of new and enhanced challenges which need to be addressed en route to developing an effective and affordable infrastructure for crew training. Such an infrastructure is essential for the safety and success of the program. The three major challenges that affect crew training are the long lifetime of the program (thirty years), the interdependence of successive increments, and the participation of the three International Partners (Canada, European Space Agency, and Japan) and a myriad of experimenters. This paper addresses these major challenges as they drive the development of a crew training capability and the actual conduct of crew training.

Astronauts↗