A model for optimal processing of multisensory information in the system for maintaining body orientation in the human

Considered is the optimal processing of multisensory information to maintain body orientation in the human. It is supposed that the orientation is performed by a system of angular stabilization with only small deviations from the equilibrium believed to be coincided with the local vertical. The linear transformation is determined which minimizes the square loss function for the stabilization error. This transformation comprises two successive steps. One of them is the averaging procedure on the the sensory inputs and the other is the optimal Kalman filtering in time domain. It is shown that the presence of two interacting channels for angular position and angular velocity in the structure of the optimal filter ensures sufficient accuracy of stabilization in both channels for the stabilization system as a whole in spite of the substantial unreliability in transmission in the channel of the angular position.     

Characterization of Thigh and Shank Segment Angular Velocity During Jump Landing Tasks Commonly Used to Evaluate Risk for ACL Injury

The dynamic movements associated with anterior cruciate ligament (ACL) injury during jump landing suggest that limb segment angular velocity can provide important information for understanding the conditions that lead to an injury. Angular velocity measures could provide a quick and simple method of assessing injury risk without the constraints of a laboratory. The objective of this study was to assess the inter-subject variations and the sensitivity of the thigh and shank segment angular velocity in order to determine if these measures could be used to characterize jump landing mechanisms. Additionally, this study tested the correlation between angular velocity and the knee abduction moment. Thirty-six healthy participants (18 male) performed drop jumps with bilateral and unilateral landing. Thigh and shank angular velocities were measured by a wearable inertial-based system, and external knee moments were measured using a marker-based system. Discrete parameters were extracted from the data and compared between systems. For both jumping tasks, the angular velocity curves were well defined movement patterns with high inter-subject similarity in the sagittal plane and moderate to good similarity in the coronal and transverse planes. The angular velocity parameters were also able to detect differences between the two jumping tasks that were consistent across subjects. Furthermore, the coronal angular velocities were significantly correlated with the knee abduction moment (R of 0.28-0.51), which is a strong indicator of ACL injury risk. This study suggested that the thigh and shank angular velocities, which describe the angular dynamics of the movement, should be considered in future studies about ACL injury mechanisms.     

Development of outcome measures according to dystrophic phenotypes in canine X-linked muscular dystrophy in Japan

Duchenne muscular dystrophy (DMD) is an X-linked lethal muscle disorder characterized by primary muscle degeneration. Therapeutic strategies for DMD have been extensively explored, and some are in the stage of human clinical trials. Along with the development of new therapies, sensitive outcome measures are needed to monitor the effects of new treatments. Therefore, we investigated outcome measures such as biomarkers and motor function evaluation in a dystrophic model of beagle dogs, canine X-linked muscular dystrophy in Japan (CXMD_J). Osteopontin (OPN), a myogenic inflammatory cytokine, was explored as a potential biomarker in dystrophic dogs over the disease course. The serum OPN levels of CXMD_J dystrophic dogs were elevated, even in the early disease phase, and this could be related to the presence of regenerating muscle fibers; as such, OPN would be a promising biomarker for muscle regeneration. Next, accelerometry, which is an efficient method to quantify performance in validated tasks, was used to evaluate motor function longitudinally in dystrophic dogs. We measured three-axis acceleration and angular velocity with wireless hybrid sensors during gait evaluations. Multiple parameters of acceleration and angular velocity showed notedly lower values in dystrophic dogs compared with wild-type dogs, even at the onset of muscle weakness. These parameters accordingly decreased with exacerbation of clinical manifestations along with the disease course. Multiple parameters also indicated gait abnormalities in dystrophic dogs, such as a waddling gait. These outcome measures could be applicable in clinical trials of patients with DMD or other muscle disorders.     

The simulation of aerial movement--III. The determination of the angular momentum of the human body

A method is presented for determining the angular momentum of the human body about its mass centre for general three-dimensional movements. The body is modelled as an 11 segment link system with 17 rotational degrees of freedom and the angular momentum of the body is derived as a sum of 12 terms, each of which is a vector function of just one angular velocity. This partitioning of the angular momentum vector gives the contribution due to the relative segmental movement at each joint rather than the usual contribution of each segment. A method of normalizing the angular momentum is introduced to enable the comparison of rotational movements which have different flight times and are performed by athletes with differing inertia parameters. Angular momentum estimates were calculated during the flight phases of nine twisting somersaults performed on trampoline. Errors in film digitization made large contributions to the angular momentum error estimates. For individual angular momentum estimates the relative error is estimated to be about 10% whereas for mean angular momentum estimates the relative error is estimated to be about 1%.     

The pathways of the stabilization of the amplitude of postsynaptic potentials in the interneuronal synapses of vertebrates]

The influence of various factors on the degree of stabilization of postsynaptic potential amplitude has been studied by mathematical modelling. Increasing of transmitter release probability in single boutons, spatial non-uniformity of these probabilities, interaction of release sites, non-linear summation of potentials lead to amplitude stabilization. Temporal fluctuations of the release probability, failures of responses from contact groups and activation of a variable number of the fibers have the opposite influence. Comparison of synaptic transmission parameters in sensorimotor synapses of Cyclostomata, amphibians and mammals showed that during evolution of these synapses two different pathways of amplitude stabilization had been realized. Formation of highly effective chemical contacts is probably the most progressive pathway among them.     

Garden dormouse (Eliomys quercinus, Linnaeus 1766) without fenestration in angular process

One of the skull traits that separates the Leithiinae subfamily from other subfamilies of Gliridae family is a prominent fenestration in the angular process of the mandible. There is no reference in the literature of dormice from Leithiinae subfamily without this fenestration. However, some garden dormice (Eliomys quercinus) have been found without this fenestration in Spain. This lack of perforation may be due to an ossification of the angular process related to bone growth. Garden dormice skulls from different parts of Spain kept in two mammal collections were revised in order to detect animals without fenestration and to take measures that differ between young and adult dormice. The measures recorded did not differ between dormice with and without fenestration, and so, the entire angular process is not the result of an ossification process. Thus, the discovery of specimens without fenestration in the angular process should be taken into account in studies which need the identification of this species and other species from Leithiinae subfamily based on skull and mandibles traits.     

Myosin cross-bridge orientation in rigor and in the presence of nucleotide studied by electron spin resonance.

The tilt series electron spin resonance (ESR) spectrum from muscle fibers decorated with spin labeled myosin subfragment 1 (S1) was measured from fibers in rigor and in the presence of MgADP. ESR spectra were measured at low amplitude modulation of the static magnetic field to insure that a minimum of spectral lineshape distortion occurs. Ten tilt series ESR data sets were fitted simultaneously by the model-independent methodology described in the accompanying paper (Burghardt, T. P., and A. R. French, 1989. Biophys. J. 56:525-534). By this method the average and standard error in the mean of order parameters for the probe angular distribution were calculated for the two states of the fiber investigated. The average order parameters were used to reconstruct the probe angular distribution in two dimensions, one angular dimension corresponding to a polar angle measured relative to the fiber axis, and the other a torsional angular degree of freedom of the probe. We find that the probe angular distributions for the rigor and MgADP states of the fiber differ such that the rigor distribution is broader and shifted relative to the distribution in the presence of MgADP. The shape of the rigor distribution suggests the presence of two probe orientations, one similar to that in the presence of MgADP, and another at a different orientation. The shape of the distribution in the presence of MgADP suggests that the binding of the nucleotide to the rigor cross-bridge shifts the spin population into a more homogeneous one by causing a cross-bridge rotation.     

The functional form of angular forces around transition metal ions in biomolecules.

A method for generating angular forces around sigma-bonded transition metal ions is generalized to treat pi-bonded configurations. The theoretical approach is based on an analysis of ligand-field and small-cluster Hamiltonians based on the moments of the electron state distribution. The functional forms that are obtained involve a modification of the usual expression of the binding energy as a sum of ligand-ligand interactions, which, however, requires very little increase in CPU time. The angular interactions have simple forms involving sin and cos functions, whose relative weights depend on whether the ligands are sigma- or pi-bonded. They describe the ligand-field stabilization energy to an accuracy of about 10%, and the interaction energy of covalently bonded systems to an accuracy of better than 4%. The resulting functional forms for the force field are used to model the structure of small clusters, including fragments of the copper blue protein structure. Large deviations from the typical square copper coordination are found when pi-bonded ligands are present.     

In vitro spontaneous reorganization of Haloferax volcanii envelope material into geometrical forms

High concentrations of NaCl and divalent cations were required for the stabilization of Haloferax volcanii envelopes. When the divalent cation concentration was lowered, the envelopes lost their angular shape and rouded up and the S-layer detached. When the combination of salts was just below the minimum enabling the envelope stabilization, partial rounding up and loss of the S-layer were observed. After a few days, a spontaneous and continuous reorganization of the envelope material occurred leading to the formation of geometrical envelope-like structures. This process could be stopped by either lowering the divalent cation concentration or by cooling the preparation, and resumed by restoring the initial conditions.Deceased 1990     

A new method for the simultaneous measurement of the movement of inertia, the damping coefficient and the location of the centre of mass of a body segment in situ.

A new method which permits, in a single measurement, the determination of the moment of inertia, the angular damping coefficient of the joint and the location of the centre of mass of a body segment in situ is presented. The underlying principle is the theory of small, damped oscillations of a system about its equilibrium position. The fact that the oscillogram contains information about certain parameters of the oscillating system is used to find these parameters. The application of the method is simple and does not require highly sophisticated instrumentation. The results are very reproducable and immediately available.     

Contribution of individual structural components to stabilization of the secondary structure of double-helical polynucleotides

Contributions of individual structural components of the double-helical polynucleotide to the stabilization of its secondary structure have been studied. The energy of intramolecular interactions was calculated by the method of atom-atom potentials. Sections of the energy function were constructed according to the parameters determining mutual location of base pairs with the optimal conformation of ribose-phosphate backbone in the points close to A- and B-forms of DNA. A complicated nature of the contribution of different structural components of the polynucleotide to its stabilization was revealed by means of different parameters. Relationships between the change of conformational parameters corresponding to optimal values of energy for A- and B-families of nucleic acids were found.     

Observations on the Etiology and Therapy of “Brittle” Diabetes

Salient aspects of prolonged metabolic studies on seven excessively labile diabetic patients and a review of the literature concerning causation and therapy of brittle diabetes are presented. Brittleness is redefined as “a syndrome of excessive insulin-sensitivity and ketosis-proneness manifested by extreme and unexplainable short-term and long-term fluctuations in the parameters of the disease”. Evidence on the causation of hyperlability points to dysfunction of plasma-protein transport and of hepatic and peripheral tissue metabolism of insulin. No objectively demonstrable complete and lasting stabilization was possible by means of any antidiabetic or adjunctive therapeutic measures. However, achievement of quantitative improvement in the accuracy of regulation of diabetes and moderation in deviations from the acceptable range of parameters were feasible. To this end, therapy recommended for everyday use incorporates the following principles found to be most helpful in following the oscillations of the disease on the research ward: flexibility in the plan of therapy; accuracy, especially in timing of therapeutic events; and employment of an insulin program best suited to the patient''s needs and comfort.     

Dependence of the Parameters of Visual Evoked Potentials on the Parameters of a Complex Visual Stimulus (Tests on Humans)

We recorded visual evoked potentials, VEP, elicited by presentation of a reversal chess pattern; 35 healthy persons were examined. A recording electrode was in point Oz, according to the 10-20 system; dimensions of the chess pattern square fields and their contrast varied from 1.8 to 120 and from 2 to 100%, respectively. Peak latencies, PL, of the N75 component depended on the contrast of stimulus elements in a U-like manner with the minimum within a 20-25% range. The PL of the P100 component monotonically increased with a decrease in the contrast, while the dependence of the PL of N145 was complex: a trend toward a decrease with a decrease in contrast to 30%, a local maximum in about 25%, a decrease and stabilization within a 15-4% range, and a sharp increase at the minimum contrast. The amplitude of N75 decreased with decrease in contrast down to 20-25% and then stabilized; the amplitude of P100 decreased in an S-like mode, with a plateau within 25-4%. The dependence of the N145 amplitude was complex, with a plateau-like maximum at 30-15% contrast. The amplitudes of the negative VEP components, N75 and N145, increased with an increase in the square dimensions to 7.5 and then decreased. Changes in the P100 amplitude included two phases, with a local minimum within an angular dimension range of 30-15^O. The PL of all analyzed components in general increased with a decrease in the angular dimension of the pattern components. The above data are discussed considering concepts on the genesis of different VEP components and on the existence of specialized channels in the visual system, which are responsible for detection of different parameters of a visual object. The complex dynamics of the PL of the analyzed VEP components and of the P100 amplitude related to variation of the contrast and angular dimensions of the elements of a complex stimulus are considered to be determined by a module principle of the organization of the elements constituting different levels of the visual system and by transformations of the receptive fields of these elements on the level of cortical modules, which are related to changes in the stimulus parameters.     

On the theory of Cherenkov emission from a short laser pulse in a magnetized plasma

Cherenkov emission from a short laser pulse propagating in an underdense plasma along a constant magnetic field is considered. The spectral, angular, energy, and spatiotemporal parameters of the emitted radiation are investigated. It is shown that the spectral content of the radiation and its directionality depend sensitively on the plasma and laser-pulse parameters. For instance, the most intense backward radiation at the upper hybrid frequency is generated by a tightly focused laser pulse.     

Angular Circulation Speed of Tablets in a Vibratory Tablet Coating Pan

In this work, a single tablet model and a discrete element method (DEM) computer simulation are developed to obtain the angular circulation speed of tablets in a vibratory tablet coating pan for range of vibration frequencies and amplitudes. The models identify three important dimensionless parameters that influence the speed of the tablets: the dimensionless amplitude ratio (a/R), the Froude number (aω ²/g), and the tablet–wall friction coefficient, where a is the peak vibration amplitude at the drum center, ω is the vibration angular frequency, R is the drum radius, and g is the acceleration due to gravity. The models predict that the angular circulation speed of tablets increases with an increase in each of these parameters. The rate of increase in the angular circulation speed is observed to decrease for larger values of a/R. The angular circulation speed reaches an asymptote beyond a tablet–wall friction coefficient value of about 0.4. Furthermore, it is found that the Froude number should be greater than one for the tablets to start circulating. The angular circulation speed increases as Froude number increases but then does not change significantly at larger values of the Froude number. Period doubling, where the motion of the bed is repeated every two cycles, occurs at a Froude number larger than five. The single tablet model, although much simpler than the DEM model, is able to predict the maximum circulation speed (the limiting case for a large value of tablet–wall friction coefficient) as well as the transition to period doubling.     

Quantitative measures for fracture healing: an in-vitro biomechanical study

A method is presented to assess the functional capabilities of plated osteotomized canine femora as load bearing structures and to quantify their healing status. In this method the osteotomized bones and their intact contralateral controls are tested in nondestructive bending, in twenty-four planes of loading at 15 degree angular increments. Flexural rigidity (EI), in each of the planes, is determined by using classical beam theory. It has been found that the EI values have the expected elliptical distribution. The 24 EI values, obtained for each bone, are curve fitted by regression analysis and the characteristics of each bone are described by the three parameters defining its ellipse. The parameters of the ellipses of the osteotomized bone and of its contralateral control are used to define four new parameters that may serve as measures for the healing efficiency. One of these serves as an indicator for the fragility of the healed bone and the other three add quantitative information on its mechanical state.     

Characterizing the mechanical contribution of fiber angular distribution in connective tissue: comparison of two modeling approaches

Modeling of connective tissues often includes collagen fibers explicitly as one of the components. These fibers can be oriented in many directions; therefore, several studies have considered statistical distributions to describe the fiber arrangement. One approach to formulate a constitutive framework for distributed fibers is to express the mechanical parameters, such as strain energy and stresses, in terms of angular integrals. These integrals represent the addition of the contribution of infinitesimal fractions of fibers oriented in a given direction. This approach leads to accurate results; however, it requires lengthy calculations. Recently, the use of generalized structure tensors has been proposed to represent the angular distribution in the constitutive equations of the fibers. Although this formulation is much simpler and fewer calculations are required, such structure tensors can only be used when all the fibers are in tension and the angular distribution is small. However, the amount of error introduced in these cases of non-tensile fiber loading and large angular distributions have not been quantified. Therefore, the objective of this study is to determine the range of values of angular distribution for which acceptable differences (less than 10%) between these two formulations are obtained. It was found, analytically and numerically, that both formulations are equivalent for planar distributions under equal-biaxial stretch. The comparison also showed, for other loading conditions, that the differences decrease when the fiber distribution is very small. Differences of less than 10% were usually obtained when the fiber distribution was very low (κ ≈ 0.03; κ ranges between 0 and 1/3, for aligned and isotropic distributed fibers, respectively). This range of angular distribution greatly limits the types of tissue that can be accurately analyzed using generalized structure tensors. It is expected that the results from this study guide the selection of a proper approach to analyze a particular tissue under a particular loading condition.     

A kinematic analysis of the formation of precise instrumental movements in cats

Kinematic parameters of cats local manipulating movements have been studied in the process of formation and stabilization of precise habit of moving and holding the lever in the zone of "working" space signalled by sound. It is shown that change of activity of the motor control system in the course of training is connected with the transfer from current correction of performed reaction to optimization of controlled parameters of pre-paired movements. It has been established that the formed precise coordination is realized owing to rapid movements with monomodal asymmetric profile of speed. During habit stabilization time to peak velocity significantly dropped from 274.6 +/- 84.7 to 211.0 +/- 22.9 ms and its value increased from 119.5 +/- 27.8 to 182.2 +/- 44.4 degrees/s. The stabilized habit is provided by uniform movements of ballistic type and characterized by independence from sound indication of final position, its reaching time becoming a function of amplitude-temporal values of speed maximum. It has been found that in the process of motor learning the relation of the duration of acceleration growth to the beginning of movement inhibition becomes an invariant parameter of the central program of precise reactions.     

Reconstruction of the probe angular distribution from a series of electron spin resonance spectra of tilted oriented samples.

Model-independent methods for the reconstruction of the nitroxide spin probe angular distribution of labeled oriented biological assemblies from electron spin resonance (ESR) spectra were investigated. We found that accurate probe angular distribution information could be obtained from the simultaneous consideration of a series of ESR spectra originating from a sample at differing tilt angles relative to the Zeeman magnetic field. Using simulated tilt series data sets, we developed a consistent criteria for judging the reliability of the simulated fit to the data as a function of the free spectral parameters and thereby have increased the significance of the model-independent reconstruction of the probe angular distribution derived from the fit. We have also enhanced the angular resolution measurable with the model-independent methodology by increasing the rank of the order parameters that we can reliably deduce from a spectrum. This enhancement allows us to accurately deduce higher resolution features of the spin probe distribution. Finally we investigated the usefulness of fitting the tilt series data in multiple data sets such that tilt series data from many identical sample preparations are fitted simultaneously. This method proved to be useful in rapidly reducing a large amount of data by eliminating any redundant computations in the application of the enhanced model-independent analysis to identical sets of tilt series data. We applied the methodology developed here to ESR spectra from probe labeled muscle fibers to study the orientation of myosin cross-bridges in fibers. This application is described in the accompanying paper.