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PubMed1994

Periodontal conditions after facial root tipping and palatal root torque of incisors.

UNLABELLED: The maxilla of a deceased 19-year-old young woman who had been treated with a fixed appliance was removed during autopsy. The sagittal movements of the incisors could be reconstructed by using the treatment records, which were also at our disposal. The anterior segment of the specimen was prepared histologically in the sagittal plane and stained with toluidine blue. RESULTS: The tooth movements were executed in two phases: an uncontrolled tipping (root movement to vestibular) was followed by palatinal root torque. The histologic changes, induced by the palatinal root torque were (1) root resorption with apical slope from facioapical to orocoronal, and (2) pronounced subperiosteal bone apposition (palatinal) with partial protrusion of the cortical plate thinning toward coronal. No osseous perforations occurred. The extent and the localization of root resorptions were not verified in the orthoradial x-ray film of the specimen.

Adult↗
PubMed2000

Criterion validation of surface EMG variables as fatigue indicators using peak torque: a study of repetitive maximum isokinetic knee extensions.

A number of studies have been published that have used variables of the electromyogram (EMG) power spectrum during dynamic exercise. Despite these studies there is a shortage of studies of the validity of surface EMG registrations during repetitive dynamic contractions with respect to fatigue. The aim of this study was to investigate if the surface EMG variables mean frequency (MNF [Hz]) and the signal amplitude (RMS [microV]) are valid indicators of muscular fatigue (defined as "any exercise-induced reduction in the capacity to generate force or power output") during maximum repeated isokinetic knee extensions (i.e. criterion validity using peak torque). Twenty-one healthy volunteers performed 100 isokinetic knee extensions at 90 degrees s(-1). EMG signals were recorded from the vastus lateralis, the rectus femoris and the vastus medialis of the right thigh by surface electrodes. MNF and RMS of the EMG together with peak torque (PT [Nm]) were determined for each contraction. MNF showed consequently higher correlation coefficients with PT than RMS did. Positive correlations generally existed between MNF and PT. The majority of the subjects had positive correlations between RMS and PT (i.e. decreases both in PT and in RMS). In conclusion, at the individual level MNF generally - in contrast to RMS - showed good criterion validity with respect to biomechanical fatigue during dynamic maximum contractions.

Adult↗
PubMed2000

The effects of torque control spurs in twin-block appliances.

The study compared the effects of torque control spurs on upper incisor retroclination and extrusion with two designs of a twin-block functional appliance in Class II/1 cases. The two designs were also compared with respect to anchorage loss in the lower arch and for patient compliance rates. Consecutively started cases were chosen - 90 patients with a design incorporating a labial bow (CTB group) and 110 with upper incisor 'torquing' spurs (STB group) and used to calculate failure rates. Thirty consecutive patients with satisfactory records from each group were analysed cephalometrically. The STB group experienced substantially less upper incisor retroclination, reduced upper incisor extrusion and slightly more favourable mandibular growth. The labial movement of lower incisors and the patient compliance were not significantly different in the two groups. Overall, 82.5% of patients fully reduced their overjet with 9% failing to reduce the overjet below 6 mm.Fig. 1f

Journal Article↗
PubMed2003

The vector alignments of asteroid spins by thermal torques.

Collisions have been thought to be the dominant process altering asteroid rotations, but recent observations of the Koronis family of asteroids suggest that this may be incorrect. This group of asteroids was formed in a catastrophic collision several billion years ago; in the intervening period their rotational axes should have become nearly random because of subsequent collisions, with spin rates that follow a maxwellian distribution. What is seen, however, is that the observed family members with prograde spins have nearly identical periods (7.5-9.5 h) and obliquities between 42 and 50 degrees, while those with retrograde spins have obliquities between 154 and 169 degrees with periods either <5 h or >13 h. Here we show that these non-random orientations and spin rates can be explained by 'thermal torques' (arising from differential solar heating), which modify the spin states over time. In some cases, the asteroids become trapped in spin-orbit resonances. Our results suggest that thermal torques may be more important than collisions in changing the spin states (and possibly shapes) of asteroids with diameters <40 km.

Journal Article↗
PubMed2005

Mutual phase-locking of microwave spin torque nano-oscillators.

The spin torque effect that occurs in nanometre-scale magnetic multilayer devices can be used to generate steady-state microwave signals in response to a d.c. electrical current. This establishes a new functionality for magneto-electronic structures that are more commonly used as magnetic field sensors and magnetic memory elements. The microwave power emitted from a single spin torque nano-oscillator (STNO) is at present typically less than 1 nW. To achieve a more useful power level (on the order of microwatts), a device could consist of an array of phase coherent STNOs, in a manner analogous to arrays of Josephson junctions and larger semiconductor oscillators. Here we show that two STNOs in close proximity mutually phase-lock-that is, they synchronize, which is a general tendency of interacting nonlinear oscillator systems. The phase-locked state is distinct, characterized by a sudden narrowing of signal linewidth and an increase in power due to the coherence of the individual oscillators. Arrays of phase-locked STNOs could be used as nanometre-scale reference oscillators. Furthermore, phase control of array elements (phased array) could lead to nanometre-scale directional transmitters and receivers for wireless communications.

Journal Article↗
PubMed1989

Aligning, leveling, and torque control--a pilot study.

Aligning, leveling, and anterior torque control of teeth from the onset of treatment is suggested with thermal ni-ti rectangular low stiffness wires. Before and after superimpositions show the degree that torque control was achieved on four clinical patients.

Adolescent↗
PubMed2003

Influence of scale on electrostatic forces and torques in AC particulate electrokinetics.

Dielectrophoretic forces and torques move and manipulate biological cells, typically of the order of 10 mum ( approximately 10(-5) m) in diameter and ordinarily suspended in aqueous liquids, using electrodes with dimensions around 100 mum ( approximately 10(-4) m). The ability to exploit these same electromechanical effects for particles below 1 mum, that is, <10(-6) m, creates opportunities for remote manipulation and handling of subcellular components, biological macromolecules, and DNA. In this paper, Trimmer's bracket notation is adapted for systematic examination of the scaling laws governing electrokinetic behaviour. The purpose is to shed light on how critical performance measures relevant to the laboratory on a chip are affected by reducing particle sizes and electrode dimensions into the nanometre range. The scaling methodology facilitates consideration of the effect of electrode structure and particle size reduction on voltage, electric field, heating, and response time. Particles with induced moments, dipolar and quadrupolar, as well as permanent dipoles are examined. Separate consideration is given to electrical torque and its application in electrorotation and particle alignment. An eventual goal of these scaling studies is to identify the lower limit on the size of particles that can be manipulated effectively using electrokinetic phenomena.

Journal Article↗
PubMedDate not supplied

[Macerated human hip bone preparation as a substitute for fresh frozen preparations for testing the primary stability and frictional torques of cementless hip cups].

AIM: The aim of the study was to validate macerated human acetabuli as replacement for fresh frozen preparations for testing primary stability and the screwing in moments of cementless threaded hip cups. METHOD: Three fresh frozen human pelvis were tested. One half of each pelvis was macerated whereas the other half was preserved as fresh frozen preparation. In the side of every pelvis the moments of screwing-in, the micromotions, the maximum expressing force and the maximum pull-out torque were determined. RESULTS: The screwing in moments, the maximum expressing forces and the maximum pull-out torques did not change. The micromotions were reduced to half. CONCLUSION: Considering the reduction of the micromotions, macerated human acetabuli are valid replacements for fresh frozen preparations for testing the primary stability and the screwing-in behaviour of screwed pans.

Cementation↗
PubMed1994

[Time-torque diagrams of self-cutting osteosynthesis screws of various lengths in fracture tests in aluminum].

Tapping screws of the Medicon system were checked for their mechanical strength by a time-torque curve and a new measurement system. To simulate a real situation three types of screws were applied. The predrill was 80% of the kernel diameter. The percentage of demolition was significantly higher with longer screws because there was a typical tilting of screws in aluminium. All tested screws had double the minimum fracture moment of 43 Ncm. Fracture of the screws occurred at about triple the torque of the maximal moment in the bones.

Aluminum↗
PubMed2005

Free energy profile along a discretized reaction path via the hyperplane constraint force and torque.

By employing mechanical work analogies, we derive a convenient computational approach for evaluation of the free energy profile (FEP) along some discretized path defined as a sequence of hyperplanes. A hyperplane is fully specified by any of its point and a tangent vector. The FEP is obtained as an integral of two components. The translational component of the free energy is computed by integrating the hyperplane constraint force. The rotational component is evaluated via the hyperplane torque. Both ingredients--the constraint force and the hyperplane torque-are evaluated on each hyperplane independently. The integration procedure utilizes a set of reference points defining a point of rotation on each hyperplane, and these points can be chosen before or after the sampling takes place. A shift in the reference points redistributes the FEP contributions between the translational and rotational components. For systems where the FEP is dominated by the potential energy differences, reference points residing on the minimum energy path present a natural choice. We demonstrate the validity of our approach on two examples, a simple two-dimensional (2D) potential, and a seven-atom Lennard-Jones cluster. In each case, we compare the numerical FEP with the harmonic approximation estimates. Our results for the 2D potential are also verified by the data available in the literature. In both cases, the rotational component of the FEP represents a sizable contribution to the total FEP, so ignoring it would yield clearly incorrect results.

Journal Article↗
PubMed2001

ATP synthase F(1) sector rotation. Defective torque generation in the beta subunit Ser-174 to Phe mutant and its suppression by second mutations.

Subunit gamma of the ATP synthase F(1) sector is located at the center of the alpha(3)beta(3) hexamer and rotates unidirectionally during ATP hydrolysis, generating the rotational torque of approximately 45 pN.nm. A mutant F(1) with the betaSer-174 to Phe substitution (betaS174F) in the beta subunit generated lower torque ( approximately 17 pN.nm), indicating that betaS174F is mechanically defective, the first such mutant reported. The defective rotation of betaS174F was suppressed by a second-site mutation, betaGly-149 to Ala, betaIle-163 to Ala, or betaIle-166 to Ala in the same subunit, but not by betaLeu-238 to Ala. These results suggest that the region between betaGly-149 and betaSer-174 plays an important role in the coupling between ATP hydrolysis and mechanical work.

Actins↗
PubMed1978

Laser microbeam study of a rotary motor in termite flagellates. Evidence that the axostyle complex generates torque.

A rotary motor in a termite flagellate continually turns the anterior part of the cell (head) in a clockwise direction. Previous descriptive observations implicated the noncontractile axostyle, which runs through the cell like a drive shaft, in the motile mechanism. This study demonstrates directly that the axostyle complex generates torque, and describes serval of its dynamic properties. By laser microbeam irradiation, the axostyle is broken into an anterior segment attached to the cell's head, and a posterior segment which projects caudally as a thin spike, or axostylar projection. Before lasing, both head and axostylar projection rotate at the same speed. After breaking the axostyle, the rotation velocity of the head decreases, depending on the length of the anterior segment. Head speed is not a linear function of axostyle length, however. In contrast, the rotation velocity of the axostylar projection always increases about 1.5 times after lasing, regardless of the length of the posterior segment. Turning the head is thus a load on the axostylar rotary motor, but the speed of the posterior segment represents the free-running motor. A third, middle segment of the axostyle, not connected to the head or axostylar projection, can also rotate independently. No ultrastructural differences were found along the length of the axostyle complex, except at the very anterior end; lenth-velocity data suggest that this region may not be able to generate torque. An electric model of the axostylar rotary motor is presented to help understand the length-velocity data.

Animals↗
PubMed2006

Computational model of a primate arm: from hand position to joint angles, joint torques and muscle forces.

Three-dimensional reaching by non-human primates is an important behavioral paradigm for investigating representations existing in motor control areas of the brain. Most studies to date have correlated neural activity to a few of the many arm motion parameters including: global hand position or velocity, joint angles, joint angular velocities, joint torques or muscle activations. So far, no single study has been able to incorporate all these parameters in a meaningful way that would allow separation of these often highly correlated variables. This paper introduces a three-dimensional, seven degree-of-freedom computational musculoskeletal model of the macaque arm that translates the coordinates of eight tracking markers placed on the arm into joint angles, joint torques, musculotendon lengths and finally into an optimized prediction of muscle forces. This paper uses this model to illustrate how the classic center-out reaching task used by many researchers over the last 20 years is not optimal in separating out intrinsic, extrinsic, kinematic and kinetic variables. However, by using the musculoskeletal model to design and test novel behavioral movement tasks, a priori, it is possible to disassociate the myriad of movement parameters in motor neurophysiological reaching studies.

Algorithms↗
PubMed2006

"Torque-like" action of remedies and diseases on the vital force and their consequences for homeopathic treatment.

INTRODUCTION: Within the developing theoretical context of quantum macroentanglement, a mathematical model of the Vital Force (Vf) has recently been formulated. It describes the Vf in terms of a hypothetical gyroscope with quantized angular momentum. This enables the Vf's state of health to be represented in terms of a "wave function" derived solely from secondary symptom observables produced in response to disease or homeopathic remedies. So far, this approach has illustrated the biphasal action of remedies, resonance phenomena arising out of homeopathic provings, and aspects of the therapeutic encounter. METHOD: In this paper, the effects of a therapeutic remedy and disease states on the gyroscopic angular momentum characteristics of the Vf were investigated by mathematical manipulation the Vf "wave function." RESULTS: The formulation of the Vf in terms of a quantized gyroscope permits disease to be represented as a braking "torque" decreasing the Vf's angular momentum, causing it to "precess" (i.e., express symptoms). The therapeutic remedy, however, provides an accelerating "torque," increasing the Vf's angular momentum and decreasing precession (i.e., reducing symptom expression). CONCLUSIONS: According to this model, symptom expression corresponds to precession of the Vf "gyroscope." Conversely, complete removal of symptoms is equivalent to cessation of Vf "precession." However, if overprescribed or given in unsuitable potency, the curative remedy (which may also be formulated as a wave function but this time derived solely from changes in Vf secondary symptom observables) may cause the Vf to express proving symptoms. Thus, with only observation of symptoms and changes in them to indicate, indirectly, the state of a patient's Vf, the safest treatment strategy might be for the practitioner to proceed via gradual removal of the symptoms. This is congruent with Hahnemann's later development and use of the LM potencies, as described in his final 6th edition of The organon.

Empiricism↗
PubMed1984

Alterations in ankle dorsiflexion torque as a result of continuous ultrasound to the anterior tibial compartment.

Although considerable documentation of the physiologic effects of ultrasound (US) exists, little information is available concerning direct effects of US on muscle, particularly when the US is applied immediately before muscle performance. The purpose of this study was to determine the effect of continuous US to the anterior tibial muscle compartment on ankle dorsiflexion torque assessed immediately posttreatment, at 30 minutes, and at 60 minutes posttreatment. Seventeen healthy subjects were tested performing isometric contractions at dynamometer velocities of 60 and 180 degrees/sec. Subjects first received either a placebo or a 1.5 W/cm2 15-minute US treatment. One week later, the protocol was repeated with the administration of a second treatment. Analysis of variance showed no significant interactions for time and treatment for any contraction; time, for isometric contraction, was the only significant main effect. Follow-up analyses were all nonsignificant for comparisons of pretreatment to posttreatment and posttreatment to 30- and 60-minute intervals within treatment groups. The study concludes that in spite of known physiologic effects, one treatment of US does not have an immediate or latent effect on peak torque.

Adult↗
PubMed1992

Reliability of lumbar isometric torque in patients with chronic low back pain.

In this study, the test-retest reliability of lumbar isometric strength testing in patients with chronic low back pain (CLBP) was assessed. Isometric torque measurements were obtained from 89 patients with CLBP at seven different angles of lumbar flexion. Because previous studies have demonstrated significant strength differences between male and female subjects, separate data analyses were performed for each gender. Results indicated moderate to high reliability for patients with CLBP when tested at individually determined angles of flexion within their idiosyncratic range of motion (ROM) (female subjects: r = .59-.96, P less than .05, SEE = 12.0-24.2 N.m; male subjects: r = .71-.93, P less than .05, SEE = 25.1-62.1 N.m). For comparison with previously published data on asymptomatic controls, an additional set of analyses was conducted for subjects with full lumbar ROM. Similar reliability was demonstrated for this subsample (female subjects: r = .57-.93, P less than .05, SEE = 12.4-27.9 N.m; male subjects: r = .63-.93, P less than .05, SEE = 34.2-44.2 N.m). The authors concluded that isometric lumbar extension torque could be reliably measured in patients with CLBP at multiple positions within the full ROM, although reliability decreased at the most extended positions. The demonstrated reliability will allow researchers to assess treatment effects and group differences without undue concern for artifact attributable to measurement error.

Back Pain↗
PubMedDate not supplied

Computerized analysis of isokinetic torque curves for muscle strengthening.

Isokinetic exercise measurements are widely used in rehabilitation medicine for evaluation and treatment planning. Computerized peak torque, work, and power measurements in isokinetic exercise can be obtained reliably when testing muscles that cross the knee and elbow joints. Important technical considerations in torque curve analysis are axis alignment, instrument calibration, and damp and gravity correction factors. The usefulness of these measurements has been limited by the small number of accurate scientific studies providing valid normative data on healthy individuals.

Biomechanical Phenomena↗