Stability Of Orientation Research Articles

DVD Review

The Balance Evaluation Systems Test (BESTest)1 is a recently developed clinical assessment tool to identify the postural control systems responsible for deficits in functional balance. Six postural control systems (biomechanical constraints, stability limits/verticality, postural transitions, reactive postural responses, sensory orientation, and dynamic stability during gait) are examined. Each system examined has several associated test items based on both novel and known balance measures. Items are scored using a 4-point ordinal scale with 0 being the lowest score and 3 being the highest score. Percentage scores are computed and reported for each system and for the total assessment. The purpose of the BESTest training DVD is to assist clinicians in learning proper administration and scoring of this new assessment tool. The DVD is available for purchase from through the technology transfer web site of the Oregon Health & Sciences University at http://www.ohsu.edu/tech-transfer/portal/technology.php?technology_id=217191 . The training DVD is easy to load and navigate, and can be used on either PC or Mac platforms. Once loaded, the main menu screen contains icons for playing an introduction video clip, printing a copy of the BESTest, reviewing acknowledgments from the authors, and beginning the interactive tutorial for administering and scoring the test. At any time, the user can jump to a specific section or test, get help using the icons, or quit the tutorial. A video clip introduction on the theoretical background and use of the BESTest and the training DVD is provided by Dr. Fay Horak, developer of the BESTest. The interactive tutorial consists of 3 sets of video instructions: examiner, patient, and scoring. The video clips embedded in the tutorial provide a visual demonstration of an examiner performing each item with a patient. The examiner section provides an audiovisual demonstration on how to safely and consistently administer each item. Emphasis in this section is placed on examiner and patient positioning, how the test is performed, and what equipment is required to complete the test item. The patient section provides audiovisual instructions for the examiner to give to the patient for each of the test items. Emphasis is placed on verbal instructions given by the examiner. The scoring criteria section provides written descriptions of how to discriminate performance using the 0- to 3-point scoring scale. Video clips demonstrating performance for a given score can be accessed simply by clicking on the icon related to that score. Written descriptions and video clips can be viewed concurrently. This training video and downloadable written material provide a comprehensive learning experience for the clinician, researcher, or student. Directions for administration and scoring are straightforward and the video clips provide a good vantage point for the examiner to discriminate between the 0 and 3 scoring criteria. It is best to download and print a copy of the BESTest from the main menu, while reviewing the training video. These materials include a list of equipment required, administration instructions, and scoring sheets. The BESTest has reported an intraclass correlation coefficient for interrater reliability of 0.91 for the entire test with a range from 0.79 to 0.96 for the subtests in adults with balance deficits.1 Use of this training DVD should enhance examiner proficiency and reliability in administration and scoring of the tool. James Moore, PT, PhD, NCS Assistant Professor Department of Physical Therapy University of Miami Miller School of Medicine Coral Gables, Florida

Total knee arthroplasty in severe valgus knee deformity: comparison of a standard medial parapatellar approach combined with tibial tubercle osteotomy

Primary TKA in valgus knees with a deformity of more than ten degrees may prove challenging, since bone and soft tissue abnormalities make accurate axis restoration, component orientation and joint stability attainment a difficult task. The purpose of this study was to determine which approach is optimal in these patients, by comparing the standard medial parapatellar approach to a lateral parapatellar combined with a tibial tubercle osteotomy (TTO). Forty-four valgus knees--with an axis deviation ranging from 15 to 36 degrees (mean 24°)--were dealt with primary TKA and followed up for a minimum period of 7 years. Lateral parapatellar arthrotomy combined with TTO was performed in 22 individuals (Group A) and a standard medial parapatellar capsulotomy in the remaining patients (Group B). The International Knee Society System Score (IKSS) was used for clinical evaluation. Radiological assessment was performed yearly postoperatively using long films for assessment of the anatomical axis. The postoperative IKSS scores showed no significant statistical difference between groups A and B (P < 0.05). In the alignment parameter, however, residual valgus deviation occurred in 9% of patients from Group A and in 32% from Group B. No late-onset instability was displayed. Lateral parapatellar approach combined with TTO may prove highly beneficial in significant valgus deformities, as the anatomical axis is restored accurately and soft tissue release of the lateral contracted structures facilitated to an important extent.

Direct observation of the myosin Va recovery stroke that contributes to unidirectional stepping along actin.

Myosins are ATP-driven linear molecular motors that work as cellular force generators, transporters, and force sensors. These functions are driven by large-scale nucleotide-dependent conformational changes, termed “strokes”; the “power stroke” is the force-generating swinging of the myosin light chain–binding “neck” domain relative to the motor domain “head” while bound to actin; the “recovery stroke” is the necessary initial motion that primes, or “cocks,” myosin while detached from actin. Myosin Va is a processive dimer that steps unidirectionally along actin following a “hand over hand” mechanism in which the trailing head detaches and steps forward ∼72 nm. Despite large rotational Brownian motion of the detached head about a free joint adjoining the two necks, unidirectional stepping is achieved, in part by the power stroke of the attached head that moves the joint forward. However, the power stroke alone cannot fully account for preferential forward site binding since the orientation and angle stability of the detached head, which is determined by the properties of the recovery stroke, dictate actin binding site accessibility. Here, we directly observe the recovery stroke dynamics and fluctuations of myosin Va using a novel, transient caged ATP-controlling system that maintains constant ATP levels through stepwise UV-pulse sequences of varying intensity. We immobilized the neck of monomeric myosin Va on a surface and observed real time motions of bead(s) attached site-specifically to the head. ATP induces a transient swing of the neck to the post-recovery stroke conformation, where it remains for ∼40 s, until ATP hydrolysis products are released. Angle distributions indicate that the post-recovery stroke conformation is stabilized by ≥5 k B T of energy. The high kinetic and energetic stability of the post-recovery stroke conformation favors preferential binding of the detached head to a forward site 72 nm away. Thus, the recovery stroke contributes to unidirectional stepping of myosin Va.

Investigation of photosensitively bioconjugated targeted quantum dots for the labeling of Cu/Zn superoxide dismutase in fixed cells and tissue sections

This study presents the development of targeted and antibody cross-linked QDs and explores whether these bioconjugates could specifically and effectively label Cu/Zn superoxide dismutase (SOD1) on fixed cells and tissues. QD-antibody conjugation was achieved by using our previously invented AmiNoacid (monomer) Decorated and Light Underpining Conjugation Approach (ANADOLUCA) method. In this method, we have used a photosensitive aminoacid monomer having ruthenium complex which is a synthetic and inexpensive material for the preparation of bioconjugates. Its specificity was demonstrated by extracting the active enzyme from rat liver lysate by using the bioconjugate. It provided accurate antibody orientation, high specificity and mechanic stability. The protocol steps for QD-antibody conjugation and specimen preparation were described in detail. The nanobioconjugates were prepared under mild conditions (for example in day light), independent of pH and temperature, without affecting conformation and function of protein. This protocol is simple, inexpensive and can be successfully adapted to detect other targets on different cell types and tissues.

Second-Order Nonlinearity of Organic/Inorganic Hybrid Materials Doped with Organic Chromophore by All-Optical Poling

A kind of hybrid material was synthesized via sol-gel process with PMMA and TEOS as reactants, and 4’-Iodo-4-dimethylaminoazobenzene (IDMA) as nonlinear optical organic chromophore. The second order nonlinear optical properties of hybrid material in thin films were investigated by using All-optical poling technique, and the influences of films thickness, structure and poling temperature on SHG properties were discussed. The experimental results indicated that the absorption spectrum of PMMA/SiO2/IDMA film was wider than the spectrum of PMMA/IDMA film. As a consequence of the experiment, we found that different thickness films had different SHG saturation values, there was an optimum thickness for the films. In addition, the higher the sample temperature is, the smaller the SHG intensity is. We also found that the existence of SiO2 network in the film significantly improved the azo orientation stability.

A Rate-Dependent Crystal Plasticity Analysis of Orientation Stability in Biaxial Tension of Magnesium

The development of texture during plastic deformation plays an important role in determining the stretch formability of magnesium alloy sheets. In this study, the orientation stability during equibiaxial tension of magnesium was analyzed based on three dimensional lattice rotations calculated by using a rate-dependent crystal plasticity model and assuming five different combinations of slip modes. The results show that no orientations can satisfy the stability criteria with both zero rotation velocity and convergent orientation flow in all dimensions. However, relatively stable orientations with zero rotation velocity and an overall convergence are found. They are featured by characteristic alignments of specific crystallographic directions in the macroscopic axis of contraction, depending on the slip modes involved in the deformation. It is also shown that the orientation stability varies significantly with the deviation of deformation mode from equibiaxial tension. The simulation results are briefly discussed in comparison with pre-existing experiments.

A Quasi Absolute Optically Pumped Magnetometer for the Permanent Recording of the Earth's Magnetic Field Vector (OPC)

Despite the advance of technology, the fully automatic recording of absolute magnetic field vector variation at observatories remains an elusive goal. Primary difficulties are the long term stability of sensor orientation and the stable operation of the sensor system. In standard practice, definitive data are produced through the combination of continuous operation of a variometer and the occasional absolute measurements that are used for calibration of the variometer data. A single, automatic instrument that can continuously acquire absolute vector measurements with 1-second resolution is desired. We introduce a device that will fulfil these requirements. Data are acquired using Serson's method: the ambient magnetic field is modulated by superposed fields. This method has been applied, mostly in connection with Proton magnetometers, for many years. In general it requires that the applied fields have a strength on the order of the Earth's magnetic field. But the sampling rate is limited for most xisting systems. In contrast, our system only requires applied fields of about 5000nT, and the switching rate of polarities is 5Hz. This is possible because we use a fast self oscillating Cs-magnetometer. The self oscillating Cs-magnetometer is calibrated by a Cs-He cell during times without additional fields (tandem-magnetometer).

Preparation and Second-Order Nonlinearity of Organic/Inorganic Hybrid Materials Doped with Organic Chromophore

A kind of hybrid material was made through sol-gel process with the PMMA, TEOS, and 4-(N)-ethyl-N-(2-hydroxyethyl) amino-4'-nitro-azobenzene (DR1). And thefilms of sol were prepared by using the spin-coated method. Through all optical poling, it could be found that there exists an optimum thickness for film. In addition, the higher of sample temperature was, the smaller intensity of SHG was. The experiment showed that the SiO2 network was existent, and hybrid materials significantly improved orientation stability. PACS: 42.65.Ky

Relationships between early behavioural characteristics and temperament at 6 years

The aim of this study was to analyze the extent to which the relations and the stability of the neonatal behaviour and the infant behaviour at both 4 and 12 months could be used to predict the infant temperament at 6 years. Seventy-two full-term, normal-weight, healthy children were followed from 3 days postpartum to 6 years. Neonatal behaviour at 3 and 30 days was assessed using the Neonatal Behaviour Assessment Scale (NBAS), behaviour at 4 and 12 months was assessed using the Infant Behaviour Record (IBR) from the Bayley Scales for Infant Development (BSID) and temperament at 6 years was assessed using the Dimensions of Temperament Survey-Revised (DOTS-R). Negative and positive affectivity and attention were the factors extracted from the behaviours of the IBR. Our results showed a low/moderate correlation between neonatal behaviour on the one hand and behaviour at 4 and 12 months and temperament at 6 years on the other hand. The motor performance, orientation and ANS stability of the neonate at 3 and 30 days were predictors of positive and negative affectivity at 4 months. State regulation and ANS stability at 3 days were predictors of negative affectivity and attention respectively at 12 months. Negative affectivity at 12 months and endurance at 30 days were predictors of general activity and persistence/attention at 6 years. Also, an inverse relation was found between state regulation at 30 days and general activity at 6 years, and a positive relation was found between attention at 4 months and persistence/attention at 6 years. We conclude that neonatal behaviour and behaviour in the first year of life are good predictors of temperament at 6 years and that early negative affectivity has an important role on infant temperament development.

Local x-ray structure analysis of optically manipulated biological micro-objects

X-ray diffraction using micro- and nanofocused beams is well suited for nanostructure analysis at different sites of a biological micro-object. To conduct in vitro studies without mechanical contact, we developed object manipulation by optical tweezers in a microfluidic cell. Here we report x-ray microdiffraction analysis of a micro-object optically trapped in three dimensions. We revealed the nanostructure of a single starch granule at different points and investigated local radiation damage induced by repeated x-ray exposures at the same position, demonstrating high stability and full control of the granule orientation by multiple optical traps.

Time dynamics of the nematic liquid crystal director in the field of a sequence of rectangular pulses

We study theoretically and experimentally the Freedericksz transition in a sequence of rectangular pulses. We show the dependence of the accumulation effect on the pulse filling coefficient. We demonstrate that at a constant energy value in a pulse, the accumulation phenomenon substantially depends on the pulse repetition frequency. An analytical consideration of the initial stage of development of orientational instability fully confirms the conclusions of numerical analysis. The results of experiment agree well with the conclusions of theoretical analysis.

Perceived experiences of anti-bisexual prejudice: Instrument development and evaluation.

This research describes the development and psychometric evaluation of the Anti-Bisexual Experiences Scale (ABES). Items were developed on the basis of prior literature, revised on the basis of expert feedback, and submitted to psychometric evaluation. Exploratory factor analysis of data from 350 bisexual participants yielded 3 factors of reported experiences of prejudicial treatment reflecting (a) Sexual Orientation Instability, (b) Sexual Irresponsibility, and (c) Interpersonal Hostility. This structure emerged with bisexual persons' reported experiences of prejudice from heterosexual people as well as from lesbian and gay people. Confirmatory factor analysis of data from a separate sample of 349 bisexual individuals supported the stability of this 3-factor structure. The data offered evidence of acceptable reliability (i.e., Cronbach's alphas of .81 to .94), convergent validity (i.e., with stigma consciousness, r = .37 to .54; with awareness of public devaluation, r = .28 to .41), and discriminant validity (i.e., for impression management, r = -.00 to .09). Relative levels of the various types of perceived experiences of anti-bisexual prejudice and the role of such experiences within the minority stress framework were also explored. With a separate sample of 176 bisexual individuals, data on the final 17-item version of the ABES yielded 2-week test-retest reliability coefficients of .77 to .89 and Cronbach's alphas of .86 to .96 across subscales.

Building better fibrin knob mimics: an investigation of synthetic fibrin knob peptide structures in solution and their dynamic binding with fibrinogen/fibrin holes

AbstractFibrin polymerizes via noncovalent and dynamic association of thrombin-exposed “knobs” with complementary “holes.” Synthetic knob peptides have received significant interest as a means for understanding fibrin assembly mechanisms and inhibiting fibrin polymerization. Nevertheless, the inability to crystallize short peptides significantly limits our understanding of knob peptide structural features that regulate dynamic knob:hole interactions. In this study, we used molecular simulations to generate the first predicted structure(s) of synthetic knobs in solution before fibrin hole engagement. Combining surface plasmon resonance (SPR), we explored the role of structural and electrostatic properties of knob “A” mimics in regulating knob:hole binding kinetics. SPR results showed that association rates were most profoundly affected by the presence of both additional prolines as well as charged residues in the sixth to seventh positions. Importantly, analyzing the structural dynamics of the peptides through simulation indicated that the 3Arg side chain orientation and peptide backbone stability each contribute significantly to functional binding. These findings provide insights into early fibrin protofibril assembly dynamics as well as establishing essential design parameters for high-affinity knob mimics that more efficiently compete for hole occupancy, parameters realized here through a novel knob mimic displaying a 10-fold higher association rate than current mimics.

Telomeric repeat mutagenicity in human somatic cells is modulated by repeat orientation and G-quadruplex stability

Telomeres consisting of tandem guanine-rich repeats can form secondary DNA structures called G-quadruplexes that represent potential targets for DNA repair enzymes. While G-quadruplexes interfere with DNA synthesis in vitro, the impact of G-quadruplex formation on telomeric repeat replication in human cells is not clear. We investigated the mutagenicity of telomeric repeats as a function of G-quadruplex folding opportunity and thermal stability using a shuttle vector mutagenesis assay. Since single-stranded DNA during lagging strand replication increases the opportunity for G-quadruplex folding, we tested vectors with G-rich sequences on the lagging versus the leading strand. Contrary to our prediction, vectors containing human [TTAGGG] 10 repeats with a G-rich lagging strand were significantly less mutagenic than vectors with a G-rich leading strand, after replication in normal human cells. We show by UV melting experiments that G-quadruplexes from ciliates [TTGGGG] 4 and [TTTTGGGG] 4 are thermally more stable compared to human [TTAGGG] 4. Consistent with this, replication of vectors with ciliate [TTGGGG] 10 repeats yielded a 3-fold higher mutant rate compared to the human [TTAGGG] 10 vectors. Furthermore, we observed significantly more mutagenic events in the ciliate repeats compared to the human repeats. Our data demonstrate that increased G-quadruplex opportunity (repeat orientation) in human telomeric repeats decreased mutagenicity, while increased thermal stability of telomeric G-quadruplexes was associated with increased mutagenicity.

Motor-Mediated Microtubule Self-Organization in Dilute and Semi-Dilute Filament Solutions

We study molecular motor-induced microtubule self-organization in dilute and semi-dilute filament solutions. In the dilute case, we use a probabilistic model of microtubule interaction via molecular motors to investigate microtubule bundle dynamics. Microtubules are modeled as polar rods interacting through fully inelastic, binary collisions. Our model indicates that initially disordered systems of interacting rods exhibit an orientational instability resulting in spontaneous ordering. We study the existence and dynamic interaction of microtubule bundles analytically and numerically. Our results reveal a long term attraction and coalescing of bundles indicating a clear coarsening in the system; microtubule bundles concentrate into fewer orientations on a slow logarithmic time scale. In semi-dilute filament solutions, multiple motors can bind a filament to several others and, for a critical motor density, induce a transition to an ordered phase with a nonzero mean orientation. Motors attach to a pair of filaments and walk along the pair bringing them into closer alignment. We develop a spatially homogenous, mean-field theory that explicitly accounts for a force-dependent detachment rate of motors, which in turn affects the mean and the fluctuations of the net force acting on a filament. We show that the transition to the oriented state can be both continuousmore » and discontinuous when the force-dependent detachment of motors is important.« less

A Case-Oriented Approach Exploring the Relationship Between Visual and Vestibular Disturbances and Problems of Higher-Level Mobility in Persons With Traumatic Brain Injury

Dizziness and impaired balance are common complaints after traumatic brain injury as a result of injuries to many systems. Ambient visual and vestibular system impairments are strong contributors to imbalance and dizziness, often leading to problems with spatial orientation and gaze stability during movement. The purpose of this review is to provide an overview of visual-vestibular impairments common to traumatic brain injury and summarize the contribution impairments in these systems will have on higher-level mobility. Standard visual and vestibular tests and measures are described and summarized, followed by several case presentations discussing the examination and evaluation processes and interventions chosen for visual-vestibular difficulties and their relationship to higher-level mobility.

Uniaxial Magnetic Anisotropy Energy of Fe Wires Embedded in Carbon Nanotubes

In this work, we analyze the magnetic anisotropy energy (MAE) of Fe cylinders embedded within zigzag carbon nanotubes, by means of ab initio calculations. To see the influence of the confinement, we fix the Fe cylinder diameter and we follow the changes of the MAE as a function of the diameter of the nanotube, which contains the Fe cylinder. We find that the easy axis changes from parallel to perpendicular, with respect to the cylinder axis. The orientation change depends quite strongly on the confinement, which indicates a nontrivial dependence of the magnetization direction as function of the nanotube diameter. We also find that the MAE is affected by where the Fe cylinder sits with respect to the carbon nanotube, and the coupling between these two structures could also dominate the magnetic response. We analyze the thermal stability of the magnetization orientation of the Fe cylinder close to room temperature.

Hysteresis of Freedericksz transition in confined light beams

The effect of the transverse confinement of an incident light beam on the hysteresis of light-induced Freedericksz transition in a nematic liquid crystal cell is considered. The thresholds of the orientational instability of the director with an increase and decrease in the light beam’s intensity are calculated numerically in relation to its transverse size. The hysteresis loop width is shown to change nonmonotonically with an increase in the transverse dimension. In contrast to a homogeneous light beam, the hysteresis existence region is determined not only by the parameter (K3 − K1)/K3 but also by the parameter K2/K3. With an increase in the transverse beam size, the critical values of the parameter (K3 − K1)/K3 increase, while those of the parameter K2/K3 decrease.

Ferroelectric solid solutions with morphotropic boundary: Rotational instability of polarization, metastable coexistence of phases and nanodomain adaptive states

Ferroelectric solid solutions with different symmetry phases at opposite sides of the perovskite-based pseudo-binary phase diagram are considered. An analysis of the concentration dependence of polar anisotropy shows conditions under which the anisotropy changes sign, assuming zero value. The orientational stability of a polarization was investigated near this point, which is also a position of so-called morphotropic boundary (MB). The symmetry conditions resulting in the high-symmetry ferroelectric phases with finite temperature–composition stability field as well as the thermodynamic conditions providing their metastable two-phase coexistence are formulated. A loss of orientation stability around MB results in a divergence of fluctuations of polarization direction and a peak of dielectric susceptibility. The calculated energy of a 90° domain wall demonstrates that this energy is drastically reduced or even vanishes at the MB. The latter leads to a miniaturization of the domain structure to the nano-scale level and the formation of a mixed adaptive state. The miniaturization explains the observed special properties of ferroelectrics near MB that are extrinsic for the nanodomain adaptive state. It also explains the observed diffraction patterns generated by nanodomains of the mixed state. A coherent scattering generated by nanodomains mimics diffraction patterns that could be confused with a pattern generated by a homogeneous monoclinic phase.

Changing Economic Conditions and Identity Formation in Adulthood

Identity formation in political and occupational domains was examined from young to middle adulthood based on an ongoing longitudinal study. In addition to the participants’ identity status (diffused, moratorium, foreclosed, achieved), we assessed their perceived importance of politics, future orientation, and career stability four times in adulthood, at ages 27, 36, 42, and 50. The number of participants varied between analyses, from 168 to 291. Changes in the economic situation in Finland from 1986 to 2009 provided a context for the study. Data collections at ages 36 (in 1995) and 50 (in 2009) took place during economic recessions, and at age 42 (in 2001) during an economic boom. The results were discussed from both age-graded and history-graded perspectives. Developmental trends in political and occupational identity were reversed across age and changes in the economic situation. Political identity was at its lowest level and occupational identity was at its highest level at age 42 during the economic boom. Political identity progressed at a time of economic recession at age 50, whereas occupational identity regressed. In women, identity changes were associated with personal career stability. The perceived importance of politics increased concurrently with political identity achievement. During the recession when they were age 50, women tended to worry about future financial problems, while men perceived their future depending decreasingly on themselves and increasingly on the world situation. The results indicate that macro-level economic conditions may have psychological implications on people’s conceptions of themselves that are worth considering in developmental studies.