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Internal Rotation (internal + rotation)
Selected AbstractsConformational Analysis of Molecular Machines: Internal Rotation and Enantiomerization in Triptycyl[3]heliceneCHEMPHYSCHEM, Issue 8 2008Miquel Llunell Dr. No independent rotation: Detailed analysis of the PES for triptycyl[3]helicene (see figure) shows that rotation around the helicene,triptycyl bond cannot be considered independently from other degrees of freedom when analyzing its stereodynamic behavior. The possibility of enantiomerization of the helicene pawl results in more complex dynamics than previously expected. [source] Orthopaedic issues in the musculoskeletal care of adults with cerebral palsyDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 2009HELEN M HORSTMANN MD Aims, Orthopaedic care of adults with cerebral palsy (CP) has not been well documented in orthopaedic literature. This paper focuses on some of the common problems which present themselves when adults with CP seek orthopaedic intervention. In particular, we review the most common orthopaedic issues which present to the Penn Neuro-Orthopaedics Program. Method, A formal review of consecutive surgeries performed by the senior author on adults with CP was previously conducted. This paper focuses on the health delivery care for the adult with orthopaedic problems related to cerebral palsy. Ninety-two percent of these patients required lower extremity surgery. Forty percent had procedures performed on the upper extremities. Results, The majority of problems seen in the Penn Neuro-Orthopaedics Program are associated with the residuals of childhood issues, particularly deformities associated with contractures. Patients are also referred for treatment of acquired musculoskeletal problems such as degenerative arthritis of the hip or knee. A combination of problems contribute most frequently to foot deformities and pain with weight-bearing, shoewear or both, most often due to equinovarus. The surgical correction of this is most often facilitated through a split anterior tibial tendon transfer. Posterior tibial transfers are rarely indicated. Residual equinus deformities contribute to a pes planus deformity. The split anterior tibial tendon transfer is usually combined with gastrocnemius-soleus recession and plantar release. Transfer of the flexor digitorum longus to the os calcis is done to augment the plantar flexor power. Rigid pes planus deformity is treated with a triple arthrodesis. Resolution of deformity allows for a good base for standing, improved ability to tolerate shoewear, and/or braces. Other recurrent or unresolved issues involve hip and knee contractures. Issues of lever arm dysfunction create problems with mechanical inefficiency. Upper extremity intervention is principally to correct contractures. Internal rotation and adductor tightness at the shoulder makes for difficult underarm hygiene and predispose a patient to a spiral fracture of the humerus. A tight flexor, pronation pattern is frequently noted through the elbow and forearm with further flexion contractures through the wrist and fingers. Lengthenings are more frequently performed than tendon transfers in the upper extremity. Arthrodesis of the wrist or on rare occasions of the metacarpal-phalangeal joints supplement the lengthenings when needed. Conclusions, The Penn Neuro-Orthopaedics Program has successfully treated adults with both residual and acquired musculoskeletal deformities. These deformities become more critical when combined with degenerative changes, a relative increase in body mass, fatigue, and weakness associated with the aging process. [source] Torsional Motion in (tert -Butyl)ammonium Hemispheraplexes: Rotational Barriers and Energy of BindingHELVETICA CHIMICA ACTA, Issue 5 2003Emily The ADPs (ADPs=atomic anisotropic displacement parameters) from the single-crystal X-ray studies of nine related TBA+ (TBA+=(tert -butyl)ammonium) hemispheraplexes are analyzed, and the results compared to the free energy of binding of this guest by the nine hosts. The lipophilic hosts (Fig.,1) were synthesized over a number of years, with increasing pre-organization for and specificity of binding. Structural studies for six of the complexes have been published, but the remaining three structures, including those of the strongest binders of TBA+, are disordered and have only now been completed. New area-detector data has been analyzed for the TBA+ClO complexes of 5 and of 8 at two temperatures, while the original data for 9,TBA+SCN, has been treated with a disorder model. In addition, improved models are presented for the complexes of 6 and 7. Methods for assessing the precision of the ADP analyses are discussed. Although most of the structures are imprecise, the TBA+ groups do demonstrate some of the characteristics of independent motion. The general trend in calculated libration amplitudes for the TBA+ group suggests that the guests with the greatest free energy of binding, and the shortest distances from N+ to the ligand plane, are those with the highest barriers to internal rotation. [source] Efficient calculation of configurational entropy from molecular simulations by combining the mutual-information expansion and nearest-neighbor methods,,JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 10 2008Vladimir Hnizdo Abstract Changes in the configurational entropies of molecules make important contributions to the free energies of reaction for processes such as protein-folding, noncovalent association, and conformational change. However, obtaining entropy from molecular simulations represents a long-standing computational challenge. Here, two recently introduced approaches, the nearest-neighbor (NN) method and the mutual-information expansion (MIE), are combined to furnish an efficient and accurate method of extracting the configurational entropy from a molecular simulation to a given order of correlations among the internal degrees of freedom. The resulting method takes advantage of the strengths of each approach. The NN method is entirely nonparametric (i.e., it makes no assumptions about the underlying probability distribution), its estimates are asymptotically unbiased and consistent, and it makes optimum use of a limited number of available data samples. The MIE, a systematic expansion of entropy in mutual information terms of increasing order, provides a well-characterized approximation for lowering the dimensionality of the numerical problem of calculating the entropy of a high-dimensional system. The combination of these two methods enables obtaining well-converged estimations of the configurational entropy that capture many-body correlations of higher order than is possible with the simple histogramming that was used in the MIE method originally. The combined method is tested here on two simple systems: an idealized system represented by an analytical distribution of six circular variables, where the full joint entropy and all the MIE terms are exactly known, and the R,S stereoisomer of tartaric acid, a molecule with seven internal-rotation degrees of freedom for which the full entropy of internal rotation has been already estimated by the NN method. For these two systems, all the expansion terms of the full MIE of the entropy are estimated by the NN method and, for comparison, the MIE approximations up to third order are also estimated by simple histogramming. The results indicate that the truncation of the MIE at the two-body level can be an accurate, computationally nondemanding approximation to the configurational entropy of anharmonic internal degrees of freedom. If needed, higher-order correlations can be estimated reliably by the NN method without excessive demands on the molecular-simulation sample size and computing time. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008 [source] Identification and thermodynamic treatment of several types of large-amplitude motionsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 14 2005Gernot Katzer Abstract We present a partially automated method for the thermodynamic treatment of large-amplitude motions. Starting from the molecular geometry and the Hessian matrix, we evaluate anharmonic partition functions for selected vibrational degrees of freedom. Supported anharmonic vibration types are internal rotation and inversion (oscillation in a double-well potential). By heuristic algorithms, we identify internal rotations in most cases automatically from the Hessian eigenvectors, and we also estimate the parameters of anharmonic partition functions (e.g., potential barrier, periodicity, and symmetry number) with thermodynamically sufficient precision. We demonstrate the validity of our schemes by comparison to pointwise calculated ab initio potential curves. © 2005 Wiley Periodicals, Inc. J Comput Chem 14: 1438,1451, 2005 [source] Estimation of the absolute internal-rotation entropy of molecules with two torsional degrees of freedom from stochastic simulationsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 7 2005Eva Darian Abstract A method of statistical estimation is applied to the problem of evaluating the absolute entropy of internal rotation in a molecule with two torsional degrees of freedom. The configurational part of the entropy is obtained as that of the joint probability density of an arbitrary form represented by a two-dimensional Fourier series, the coefficients of which are statistically estimated using a sample of the torsional angles of the molecule obtained by a stochastic simulation. The internal rotors in the molecule are assumed to be attached to a common frame, and their reduced moments of inertia are initially calculated as functions of the two torsional angles, but averaged over all the remaining internal degrees of freedom using the stochastic-simulation sample of the atomic configurations of the molecule. The torsional-angle dependence of the reduced moments of inertia can be also averaged out, and the absolute internal-rotation entropy of the molecule is obtained in a good approximation as the sum of the configurational entropy and a kinetic contribution fully determined by the averaged reduced moments of inertia. The method is illustrated using Monte Carlo simulations of isomers of stilbene and halogenated derivatives of propane. The two torsional angles in cis -stilbene are found to be much more strongly correlated than those in trans -stilbene, while the degree of the angular correlation in propane increases strongly on substitution of hydrogen atoms with chlorine. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 651,660, 2005 [source] Statistical thermodynamics of internal rotation in a hindering potential of mean force obtained from computer simulationsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 10 2003Vladimir Hnizdo Abstract A method of statistical estimation is applied to the problem of one-dimensional internal rotation in a hindering potential of mean force. The hindering potential, which may have a completely general shape, is expanded in a Fourier series, the coefficients of which are estimated by fitting an appropriate statistical,mechanical distribution to the random variable of internal rotation angle. The function of reduced moment of inertia of an internal rotation is averaged over the thermodynamic ensemble of atomic configurations of the molecule obtained in stochastic simulations. When quantum effects are not important, an accurate estimate of the absolute internal rotation entropy of a molecule with a single rotatable bond is obtained. When there is more than one rotatable bond, the "marginal" statistical,mechanical properties corresponding to a given internal rotational degree of freedom are educed. The method is illustrated using Monte Carlo simulations of two public health relevant halocarbon molecules, each having a single internal-rotation degree of freedom, and a molecular dynamics simulation of an immunologically relevant polypeptide, in which several dihedral angles are analyzed. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1172,1183, 2003 [source] Molecular mechanics (MM4) calculations on carbonyl compounds part I: aldehydesJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2001Charles H. Langley Abstract Aliphatic aldehydes have been studied with the aid of the MM4 force field. The structures, moments of inertia, vibrational spectra, conformational energies, barriers to internal rotation, and dipole moments have been examined for six compounds (nine conformations). MM4 parameters have been developed to fit the indicated quantities to the wide variety of experimental data. Ab initio (MP2) and density functional theory (B3LYP) calculations have been used to augment and/or replace experimental data, as appropriate. Because more, and to some extent, better, data have become available since MM3 was developed, it was anticipated that the overall accuracy of the information calculated with MM4 would be better than with MM3. The best single measure of the overall accuracy of a force field is the accuracy to which the moments of inertia of a set of compounds (from microwave spectroscopy) can be reproduced. For all of the 20 moments (seven conformations) experimentally known for the aldehyde compounds, the MM4 rms error is 0.30%, while with MM3, the most accurate force field presently available, the rms error over the same set is 1.01%. The calculation of the vibrational spectra was also improved overall. For the four aldehydes that were fully analyzed (over a total of 78 frequencies), the rms errors with MM4 and MM3 are 18 and 38 cm,1, respectively. These improvements came from several sources, but the major ones were separate parameters involving the carbonyl carbon for formaldehyde, the alkyl aldehydes and the ketones, and new crossterms featured in the MM4 force field that are not present in the MM3 version. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1396,1425, 2001 [source] Knee kinematics in medial osteoarthritis during in vivo weight-bearing activitiesJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 12 2009Satoshi Hamai Abstract Dynamic knee kinematics were analyzed for medial osteoarthritic (OA) knees in three activities, including two types of maximum knee flexion. Continuous x-ray images of kneeling, squatting, and stair climbing motions were taken using a large flat panel detector. CT-derived bone models were used for the model registration-based 3D kinematic measurements. Three-dimensional joint kinematics and contact locations were determined using two methods: bone-fixed coordinate systems and by interrogation of CT-based bone model surfaces. The femur exhibited gradual external rotation with knee flexion for kneeling and squatting activities, and gradual internal rotation with knee extension for stair climbing. From 100° to 120° flexion, contact locations showed a medial pivot pattern similar to normal knees. However, knees with medial OA displayed a femoral internal rotation bias and less posterior translation when compared with normal knees. A classic screw-home movement was not observed in OA knees near extension. Decreased variability with both activities and methods of calculation were demonstrated for all three activities. In conclusion, the weight-bearing kinematics of patients with medial OA differs from normal knees. Pathological changes of the articulating surfaces and the ligaments correspond to observed abnormalities in knee kinematics. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1555,1561, 2009 [source] Intact fibula improves fracture healing in a rat tibia osteotomy modelJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 2 2005Sandra J. Shefelbine Abstract Rat tibia fractures are often used in fracture healing studies. Usually the fracture is stabilized with an intramedullary pin, which provides bending stiffness, but little torsional stiffness. The objective of this research was to determine the in vitro torsional rigidity of an osteotomized tibia with and without the fibula, and to determine if this difference influences the healing process in vivo. In vitro eleven rat tibias received an osteotomy, were stabilized with an intramedullary pin, and were tested in internal rotation to determine the torsional rigidity. The fibula was then manually broken and the torsional rigidity measured again. In vivo 18 rats received a tibial osteotomy, eight of which had an additional fractured fibula. After three weeks, the rats were sacrificed and the tibias were analyzed. Bone density in the fracture callus was measured with qCT. Bending rigidity and maximum breaking moment were determined in three-point bending. In vitro testing demonstrated that the torsional rigidity with an intact fibula was nearly two times higher than when the fibula was fractured. Though the torsional rigidity was still small in comparison with an intact bone, it resulted in a significantly different healing process in vivo. Rats with intact fibulas had significantly higher bone mineral density, bending rigidity, and maximum breaking moment compared to rats with a fractured fibula. These results indicate that torsional stability considerably affects the healing process. In a fracture model, it is critical to characterize the mechanical environment of the fracture. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source] Effects of rotation on measurement of lower limb alignment for knee osteotomyJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 6 2004Hideo Kawakami Abstract The purposes of this study were to clarify the effects of rotation on two-dimensional measurement of lower limb alignment for knee osteotomy using a three-dimensional method and to determine whether this 3-D simulation method could help with planning of knee osteotomy. We developed computer software to calculate femorotibial angle (FTA) and hip,knee,ankle angle (HKA) and simulate knee osteotomy from a CT-based 3-D bone model of the lower limb. Lower limb rotation on anteroposterior long-standing radiographs was measured by superimposing the 3-D bone models. Changes in alignment with limb rotation were calculated using the software. FTA after virtual closed-wedged osteotomy was measured for a hypothetical case of a rotation error of the osteotomy plane in reattaching the proximal cutting surface to the distal cutting surface. For 31 varus knees in 20 patients with medial compartment arthritis, the mean rotation angle, relative to the epicondylar axis, with variable limb position was 7.4 ± 3.9° of internal rotation (mean ± SD), ranging from 8° of external rotation to 14° of internal rotation; the mean changes in FTA and HKA were 3.5 ± 2.2° (range, 0.4,8.6) and 1.6 ± 1.3° (range, 0.2,4.9), respectively. The FTA "flexion angle" (lateral view alignment from neutral AP) and the absolute HKA "flexion angle" correlated with the change in FTA and HKA with limb rotation, respectively (FTA, R = 0.999; HKA, R = 0.993). The mean change in FTA after virtual closed-wedged osteotomy was 3.2° for internal and external 10° rotation errors in reattaching the osteotomy plane. Rotation may affect measurement of lower limb alignment for knee osteotomy, and 3-D methods are preferable for surgical planning. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source] Intra- versus intermolecular hydrogen bonding equilibrium in 2-hydroxy- N,N -diethylbenzamide,JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 2 2009P. Majewska Abstract Complex studies of the intramolecular versus intermolecular hydrogen bond equilibrium and internal rotation of the N,N -diethylamine group in 2-hydroxy- N,N -diethylbenzamide were conducted. The intramolecular versus intermolecular process in 2-hydroxy- N,N -diethylbenzamide was studied by UV,Vis, NMR, IR and Vapour Pressure Osmometric (VPO) methods as a function of temperature and concentration in non-polar, basic and protic solvents. The unequal positions of the ethyl groups were analysed and the energy barrier to the re-orientation was defined by the NMR method. This paper presents a study into a complicated nature of competitive interaction 2-hydroxy- N,N -diethylbenzamide with the environment by means of the aforesaid methods. Copyright © 2008 John Wiley & Sons, Ltd. [source] Characterisation of indomethacin and nifedipine using variable-temperature solid-state NMRMAGNETIC RESONANCE IN CHEMISTRY, Issue 11 2005David C. Apperley Abstract We have characterised the stable polymorphic forms of two drug molecules, indomethacin (1) and nifedipine (2) by 13C CPMAS NMR and the resonances have been assigned. The signal for the CCl carbon of indomethacin has been studied as a function of applied magnetic field, and the observed bandshapes have been simulated. Variable-temperature 1H relaxation measurements of static samples have revealed a T1, minimum for indomethacin at 17.8 °C. The associated activation energy is 38 kJ mol,1. The relevant motion is probably an internal rotation and it is suggested that this involves the COCH3 group. Since the two drug compounds are potential candidates for formulation in the amorphous state, we have examined quench-cooled melts in detail by variable-temperature 13C and 1H NMR. There is a change in slope for and at the glass transition temperature (Tg) for indomethacin, but this occurs a few degrees below Tg for nifedipine, which is perhaps relevant to the lower real-time stability of the amorphous form for the latter compound. Comparison of relaxation time data for the crystalline and amorphous forms of each compound reveals a greater difference for nifedipine than for indomethacin, which again probably relates to real-time stabilities. Recrystallisation of the two drugs has been followed by proton bandshape measurements at higher temperatures. It is shown that, under the conditions of the experiments, recrystallisation of nifedipine can be detected already at 70 °C, whereas this does not occur until 110 °C for indomethacin. The effect of crushing the amorphous samples has been studied by 13C NMR; nifedipine recrystallises but indomethacin does not. The results were supported by DSC, powder XRD, FTIR and solution-state NMR measurements. Copyright © 2005 John Wiley & Sons, Ltd. [source] Developing a New Class of Axial Chiral Phosphorus Ligands: Preparation and Characterization of Enantiopure Atropisomeric PhosphininesCHEMISTRY - A EUROPEAN JOURNAL, Issue 16 2008Christian Müller Dr. Abstract Both enantiomers of the first atropisomeric phosphinine (1) have been isolated by using analytical HPLC on a chiral stationary phase. The enrichment of one enantiomer and a subsequent investigation into its racemization kinetics revealed a barrier for internal rotation of ,=(109.5±0.5),kJ,mol,1, which is in excellent agreement with the theoretically predicted value of ,=116,kJ,mol,1. Further analysis with UV and circular dichroism spectroscopies and density functional theory calculations led to the determination and assignment of the absolute configurations of both enantiomers. These results are the basis for future investigations into this new class of axially chiral phosphinine-based ligands and their possible applications in asymmetric homogeneous catalysis. [source] Understanding High-Resolution Spectra of Nonrigid Molecules Using Group TheoryCHEMPHYSCHEM, Issue 4 2010Melanie Schnell Dr. Abstract Permutation-inversion group theory has developed to become an important tool in the high-resolution spectroscopy of nonrigid molecules. This large class of molecules is very intriguing to study. Small molecules such as ammonia or Na3 are known to be nonrigid. With increasing size, however, several large-amplitude motions are possible in a molecule, and can even interact with each other. The high-resolution spectra of nonrigid molecules are known to be quite complicated and very rich in information. Details about the molecule and its internal dynamics can be extracted, such as the molecular structure, the character of the chemical bonds, and the barrier heights to internal rotation and their dependence on the chemical bonds. However, due to the nonrigidity of the molecule and the complexity of such spectra, their analysis is usually quite challenging. Theoretical methods are needed for their prediction and analysis. This Review concentrates on permutation-inversion group theory and its usefulness for the analysis of high-resolution spectra of nonrigid molecules, which is examined in more detail using different examples. In a separate section, a special aspect of molecular symmetry is discussed: the breakdown of symmetry principles. Special emphasis is placed on the breakdown of space inversion symmetry (parity violation) in chiral molecules and its possible implications in high-resolution spectroscopy. [source] Motor performance in very preterm infants before and after implementation of the newborn individualized developmental care and assessment programme in a neonatal intensive care unitACTA PAEDIATRICA, Issue 6 2009Anna Ullenhag Abstract Aim: To compare motor performance in supine position at the age of 4-months corrected age (CA) in very preterm (VPT) infants cared for in a neonatal intensive care unit (NICU) before and after the implementation of the Newborn Individualized Developmental Care and Assessment Program (NIDCAP). Methods: Assessments of motor performance in supine position according to level of motor development and quality of motor performance were made, using the Structured Observation of Motor Performance in Infants (SOMP-I). Subjects: VPT infants cared for in a NICU at a Swedish university hospital before, Group A (n = 68), and after, Group B (n = 58), the implementation of developmentally supportive care based on NIDCAP. Results: The infants who were treated after the introduction of NIDCAP showed higher level of motor development in the arms/hands and trunk. No significant group differences were noted in total deviation score for the respective limbs, but lower frequency of lateral flexion in head movements, extension,external rotation,abduction, extension,internal rotation,adduction and varus and valgus position in the feet was found in the NIDCAP group, compared with those treated before the introduction. Conclusion: The infants who were treated after NIDCAP care had been implemented showed a higher level of motor development in arms/hand and trunk and fewer deviations in head, legs and feet at 4-months CA than infants treated before NIDCAP implementation. The observed changes may be due to NIDCAP and/or improved perinatal and neonatal care during the studied time period. [source] A numerical study of flexural buckling of foliated rock slopesINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 9 2001D. P. Adhikary Abstract The occurrence of foliated rock masses is common in mining environment. Methods employing continuum approximation in describing the deformation of such rock masses possess a clear advantage over methods where each rock layer and each inter-layer interface (joint) is explicitly modelled. In devising such a continuum model it is imperative that moment (couple) stresses and internal rotations associated with the bending of the rock layers be properly incorporated in the model formulation. Such an approach will lead to a Cosserat-type theory. In the present model, the behaviour of the intact rock layer is assumed to be linearly elastic and the joints are assumed to be elastic,perfectly plastic. Condition of slip at the interfaces are determined by a Mohr,Coulomb criterion with tension cut off at zero normal stress. The theory is valid for large deformations. The model is incorporated into the finite element program AFENA and validated against an analytical solution of elementary buckling problems of a layered medium under gravity loading. A design chart suitable for assessing the stability of slopes in foliated rock masses against flexural buckling failure has been developed. The design chart is easy to use and provides a quick estimate of critical loading factors for slopes in foliated rock masses. It is shown that the model based on Euler's buckling theory as proposed by Cavers (Rock Mechanics and Rock Engineering 1981; 14:87,104) substantially overestimates the critical heights for a vertical slope and underestimates the same for sub-vertical slopes. Copyright © 2001 John Wiley & Sons, Ltd. [source] Identification and thermodynamic treatment of several types of large-amplitude motionsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 14 2005Gernot Katzer Abstract We present a partially automated method for the thermodynamic treatment of large-amplitude motions. Starting from the molecular geometry and the Hessian matrix, we evaluate anharmonic partition functions for selected vibrational degrees of freedom. Supported anharmonic vibration types are internal rotation and inversion (oscillation in a double-well potential). By heuristic algorithms, we identify internal rotations in most cases automatically from the Hessian eigenvectors, and we also estimate the parameters of anharmonic partition functions (e.g., potential barrier, periodicity, and symmetry number) with thermodynamically sufficient precision. We demonstrate the validity of our schemes by comparison to pointwise calculated ab initio potential curves. © 2005 Wiley Periodicals, Inc. J Comput Chem 14: 1438,1451, 2005 [source] Locomotor skills and balance strategies in children with internal rotations of the lower limbsJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 1 2008Sophie Mallau Abstract The purpose of this study was to investigate the functional effects of a structural deformation, internal rotations (IR) of the lower limbs, on upper body balance strategies used during locomotion in 5,6 year-old and 7,10 year-old children. Balance control was examined in terms of rotation around the longitudinal axis in horizontal plane (yaw) and around the sagittal axis in a frontal plane (roll). Kinematics of foot, pelvis, shoulder, and head rotations were measured with an automatic optical TV image processor and used to calculate angular dispersions and segmental stabilizations. Older children with IR showed a lower gait velocity, particularly in difficult balance conditions than typically developing (TD) children. In younger children, the effect of the local biomechanical deficit remained limited to the lower limbs and did not affect upper body coordination. By contrast, in older children with IR, the development of head stabilization in space was affected. This was demonstrated by an "en bloc" instead of an articulated mode of head-trunk unit systematically adopted by the control group. As pelvic stabilization remains the main reference frame to organize balance control in older children with IR, we conclude that the structural deformity of the legs affect and possibly delay the acquisition of the head stabilization in space strategy. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:117,125, 2008 [source] Space-demanding intramolecular isomerizations in the solid stateJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 3 2002G. Kaupp Abstract The thermal isomerizations of meso - and rac -3,4-dibromo-1,6-diphenyl-1,6-bis(p -tolyl)-1,2,4,5-hexatetraene (1) to give stereospecifically the 3,4-bis(phenyl- p -tolylmethylene)-1,2-dibromocyclobutenes 3 and 5,+,6 were studied in the solid state using atomic force microscopy (AFM) and interpreted on the basis of known crystal structural data. These isomerizations run to completion in the bulk and include highly space-demanding internal rotations around the central bond. Far-reaching anisotropic molecular movements are detected on the major faces that align the surface features along cleavage planes in the initial phase rebuilding stage. Only one of three identified cleavage planes of meso - 1 is successful, owing to closer interactions of the bromine substituents in the non-used cleavage planes. Thus, very fine details can be correlated and predicted for the occurrence of internal rotations and molecular movements in the crystal lattice. The second stage in these intramolecular isomerizations, the phase transformation, produces very high features up to 100,nm and still parallel to the preferred cleavage plane of meso - 1 but in the,µm range without relation to the initial crystal structure in the case of rac - 1. Copyright © 2002 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||