Effect Of Internal Rotation Research Articles

Hydrogen abstraction reactions by NH2 radicals from C3-C6 Cycloalkanes: A theoretical study

Amino (NH2) radicals are crucial in ammonia pyrolysis and oxidation, and their reactions in NH3-dual-fuel combustion are well-recognized. We theoretically investigated the reactions of NH2 radicals with C3-C6 cycloalkanes – a component type of gasoline, using the CCSD(T)/aug-cc-pVTZ//M06-2X/aug-cc-pVTZ level of theory. Canonical transition state theory with corrections for hindered internal rotation and Eckart tunneling effects was employed to gain high-pressure limiting rate constants over 500 – 2000 K. Our calculated rate constant for NH2 with cyclohexane matches the experimental measurement, though experimental data for other reactions are limited. The Arrhenius parameters for the studied reactions are also provided.

Phase transition thermodynamics of organic semiconductors: N,N,N’,N’-tetraphenylbenzidine and 4,4′-bis(N-carbazolyl)-1,1′-biphenyl

In this work, we report a comprehensive study of the phase change thermodynamics of two compounds, N,N,N’,N’-tetraphenylbenzidine (TPB) and 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP), used in the production of organic light-emitting diodes and photovoltaics. The vapor pressures and phase transition enthalpies of these compounds have been previously studied at the elevated temperatures which may not be relevant to the conditions during fabrication and use TPB- and CBP-based materials. In this work, a combination of experimental and computational methods was employed to establish the reliable temperature dependences of the sublimation, fusion, and vaporization enthalpies of TPB and CBP in a wide temperature range. The vapor pressures of both compounds over solid and liquid phases were measured using fast scanning calorimetry. The fusion enthalpies at the melting point were determined by DSC. The isobaric heat capacities of the compounds in crystalline and liquid phases, including the supercooled liquids, were measured using scanning calorimetry. For the first time, the heat capacities of the ideal gas TPB and CBP were computed, considering internal rotation effects. The solution enthalpies in benzene at 298.15 K were measured, providing an independent estimate of the fusion enthalpy temperature dependence. Its consistency with the data on the fusion enthalpies was confirmed using Hess’s and Kirchhoff’s laws of Thermochemistry. Using the obtained results, the available literature data were critically evaluated. The obtained thermodynamic parameters may facilitate optimization of vapor deposition conditions and description of the thermodynamic and kinetic stability of the glassy state of TPB and CBP.

Influence of Internal Bond Rotation on Ultrafast IR Anisotropy Measurements and the Internal Rotational Potential.

Measurement of molecular orientation relaxation using ultrafast infrared (IR) pump-probe experiments is widely used to understand the properties of liquids and other systems. In the simplest situation, the anisotropy decay is a single exponential reflecting diffusive orientational relaxation. However, the anisotropy decay is frequently biexponential. The faster component is caused by solvent caging restricting angular sampling until constraint release permits all angles to be sampled. Here, we describe another mechanism that limits the range of sampling, i.e., sampling of a restricted range of angles via internal bond reorientation on a rotational potential surface with barriers. If the internal angular sampling occurs faster than the entire molecule's diffusive orientational relaxation, it will produce a fast component of anisotropy decay with a cone angle determined by the shape of the internal rotation potential. We studied four molecules to illustrate the effects of internal bond rotations on anisotropy decay. The molecules are p-chlorobenzonitrile, phenylselenocyanate, phenylthiocyanate, and 2-nitrophenylselenocyante in the solvent N,N-dimethylformamide. The CN stretch is used as the IR chromophore. p-Chlorobenzonitrile does not have internal rotation; its anisotropy decays as a single exponential. The other three have bent geometries and internal rotation of the moieties containing the CN occurs; the anisotropies decay as biexponentials. The faster of the two decays can be understood in terms of motions on the rotational potential surface. A method is developed for extracting the intramolecular rotational potential surface by employing a modification of the harmonic cone model, and the results are compared to density functional theory calculations.

Effective stretching position for the posterior deltoid muscle evaluated by shear wave elastography.

Deteriorated extensibility of the posterior deltoid muscle is one of the factors of posterior shoulder tightness, and improvement in its extensibility is needed. However, no study has investigated which shoulder positions effectively stretch the posterior deltoid muscle invivo. The aim of this study was to verify the effective stretching position of the posterior deltoid muscle invivo by shear wave elastography. Fifteen healthy men participated in this study. The shear modulus of the posterior deltoid was measured at resting and 13 stretching positions: 60°, 90°, and 120° shoulder flexion; maximum shoulder flexion, horizontal adductions at 60°, 90°, and 120° shoulder flexion; internal rotations at 60°, 90°, and 120° shoulder flexion; and combinations of horizontal adduction with internal rotation at 60°, 90°, and 120° shoulder flexion. The shear moduli of each stretching position were compared to those of the rest. Then, among the stretching positions for which the shear modulus was significantly different from the rest, the shear moduli were compared using a three-way analysis of variance with repeated measures of the 3 factors-flexion, horizontal adduction, and internal rotation. The shear moduli in all stretching positions were significantly higher than those of the rest, except for maximum shoulder flexion. The three-way analysis of variance with repeated measures revealed significant main effects in flexion and horizontal adduction. Comparing the flexion angles, the shear modulus was significantly higher at 90° than that at 60° and 120°. The shear modulus with horizontal adduction was significantly higher than that without horizontal adduction. Moreover, a significant two-way interaction was found only at flexion and horizontal adduction. The shear modulus with horizontal adduction was significantly higher at all angles than that without horizontal adduction at each flexion angle. Comparing the flexion angles with horizontal adduction, the shear modulus was significantly higher at 90° than that at 60° and 120°. No significant three-way interactions were found. Shoulder flexion and horizontal adduction affected the extensibility of the posterior deltoid muscle, whereas the effect of shoulder internal rotation was limited. More precisely, maximal horizontal adduction at 90° shoulder flexion was the most effective stretching position for the posterior deltoid muscle.

Tibial internal rotation in combined anterior cruciate ligament and high-grade anterolateral ligament injury and its influence on ACL length

BackgroundAssessment of combined anterolateral ligament (ALL) and anterior cruciate ligament (ACL) injury remains challenging but of high importance as the ALL is a contributing stabilizer of tibial internal rotation. The effect of preoperative static tibial internal rotation on ACL -length remains unknown. The aim of the study was analyze the effect of tibial internal rotation on ACL length in single-bundle ACL reconstructions and to quantify tibial internal rotation in combined ACL and ALL injuries.MethodsThe effect of tibial internal rotation on ACL length was computed in a three-dimensional (3D) model of 10 healthy knees with 5° increments of tibial internal rotation from 0 to 30° resulting in 70 simulations. For each step ACL length was measured. ALL injury severity was graded by a blinded musculoskeletal radiologist in a retrospective analysis of 61 patients who underwent single-bundle ACL reconstruction. Preoperative tibial internal rotation was measured in magnetic resonance imaging (MRI) and its diagnostic performance was analyzed.ResultsACL length linearly increased 0.7 ± 0.1 mm (2.1 ± 0.5% of initial length) per 5° of tibial internal rotation from 0 to 30° in each patient.Seventeen patients (27.9%) had an intact ALL (grade 0), 10 (16.4%) a grade 1, 21 (34.4%) a grade 2 and 13 (21.3%) a grade 3 injury of the ALL. Patients with a combined ACL and ALL injury grade 3 had a median static tibial internal rotation of 8.8° (interquartile range (IQR): 8.3) compared to 5.6° (IQR: 6.6) in patients with an ALL injury (grade 0–2) (p = 0.03). A cut-off > 13.3° of tibial internal rotation predicted a high-grade ALL injury with a specificity of 92%, a sensitivity of 30%; area under the curve (AUC) 0.70 (95% CI: 0.54–0.85) (p = 0.03) and an accuracy of 79%.ConclusionACL length linearly increases with tibial internal rotation from 0 to 30°. A combined ACL and high-grade ALL injury was associated with greater preoperative tibial internal rotation. This potentially contributes to unintentional graft laxity in ACL reconstructed patients, in particular with concomitant high-grade ALL tears.Study designCohort study; Level of evidence, 3.

Determination of the semiexperimental equilibrium structure of 2-acetylthiophene in the presence of methyl internal rotation and substituent effects compared to thiophene.

The microwave spectra of thiophene and 2-acetylthiophene were recorded in the frequency range from 2 to 40 GHz using two molecular jet Fourier transform microwave spectrometers. For 2-acetylthiophene, two conformers with a syn and an anti orientation of the S1-C2 and C6O bonds (with respect to the C2-C6 bond) were identified, and the syn-conformer was more stable. The spectra of the 34S- and 13C-isotopologues of syn-2-acetylthiophene were also assigned, and the semiexperimental equilibrium structure could be determined. Compared to thiophene, at the substitution position, the S1-C2 and C2C3 bond lengths both increase by about 0.007 Å, and the bond angle S1-C2C3 decreases by 0.06°, noticeably larger than the experimental uncertainties. A-E torsional splittings were observed due to internal rotation of the methyl group hindered by a barrier height of 330.187(35) and 295.957(17) cm-1 for the syn-conformer and the anti-conformer, respectively. Geometry and internal rotation parameters are compared with those of related thiophene derivatives, as well as those of furan and 2-acetylthiophene to gain a better understanding of structure determination in the presence of methyl internal rotation.

Radiography and frontal plane knee dynamics in Achondroplasia during walking and running

Gait analysis studies in patients with femoroacetabular impingement syndrome focused until today on alterations in pelvic and hip mechanics, but distal articulations in this syndrome were not explored. Viewing the inter-relationships between foot and hip mechanics and the importance of the subtalar joint in load attenuation at heel strike and during forward propulsion thereafter, alterations in hindfoot mechanics in this syndrome may have clinical significance.Three-dimensional gait kinematics were explored with emphasis on hindfoot mechanics in a group of 15 men with cam-type femoroacetabular impingement and compared to 15 healthy men.Subjects with femoroacetabular impingement had decreased pelvic internal rotation (effect size = 0.70) and hip abduction (effect size = 0.86) at heel strike, and increased sagittal pelvic range of motion during the stance (effect size = 0.81), compared to controls. At the hindfoot level, subjects with femoroacetabular impingement had inverted position at heel strike compared to neutral position in controls (effect size = 0.89), and reduced maximum hindfoot eversion during the stance (effect size = 0.72). Range of motion from heel strike to maximum eversion was not different between the groups (effect size = 0.21).Young adult men with cam-type femoroacetabular impingement syndrome present excessively inverted hindfoot at the moment of heel strike and reduction in maximum eversion during the stance phase. Viewing the deleterious effects of hindfoot malalignment on load attenuation during the stance, custom-designed insoles may be a consideration in this population and this should be investigated further.

Microwave Zeeman effect of methanol

Zeeman effect of the rotational spectrum of methanol has been measured in a magnetic field of 7.0 kG produced by rectangular bar magnets of neodymium. Thirty low J, K (J ≤ 10, K ≤ 3) rotational transitions, including those in the excited torsional states, were observed. Their Zeeman effect splittings were measured with uncertainties of about 5%, and the four diagonal elements of the rotational g tensor, including the effect of internal rotation of the methyl group, were determined. Using this g tensor, the g factors of low J, K levels can be calculated with an uncertainty of about 5%. They allow us to calculate Zeeman shifts of rotational transitions of methanol observed in interstellar space.

Foot Rotation Gait Modifications Affect Hip and Ankle, But Not Knee, Stance Phase Joint Reaction Forces During Running.

Alterations of foot rotation angles have successfully reduced external knee adduction moments during walking and running. However, reductions in knee adduction moments may not result in reductions in knee joint reaction forces. The purpose of this study was to examine the effects of internal and external foot rotation on knee, hip, and ankle joint reaction forces during running. Motion capture and force data were recorded of 19 healthy adults running at 3.35 m/s during three conditions: (1) preferred (normal) and with (2) internal and (3) external foot rotation. Musculoskeletal simulations were performed using opensim and the Rajagopal 2015 model, modified to a two degree-of-freedom knee joint. Muscle excitations were derived using static optimization, including muscle physiology parameters. Joint reaction forces (i.e., the total force acting on the joints) were computed and compared between conditions using one-way analyses of variance (ANOVAs) via statistical parametric mapping (SPM). Internal foot rotation reduced resultant hip forces (from 18% to 23% stride), while external rotation reduced resultant ankle forces (peak force at 20% stride) during the stance phase. Three-dimensional and resultant knee joint reaction forces only differed at very early and very late stance phase. The results of this study indicate, similar to previous findings, that reductions in external knee adduction moments do not mirror reductions in knee joint reaction forces.

The Effect of Lower Extremity Internal and External Rotation on the Hindfoot Alignment Moment Arm and Hindfoot Alignment Angle

Category:Ankle; HindfootIntroduction/Purpose:The hindfoot moment arm was first described by Saltzman and el-Khoury to evaluate hindfoot varus and valgus alignment and has been well described and validated in the literature. It is commonly used by surgeons for preoperative planning of various hindfoot reconstructive procedures. The hindfoot alignment angle (the angle formed by the intersection between the tibial axis and the calcaneal axis) is another metric of measuring hindfoot alignment commonly utilized by surgeons. The purpose of this study was to determine if rotation of the hindfoot alters the hindfoot alignment moment arm and hindfoot alignment angle. We hypothesize that slight changes in internal and external rotation of the foot during x-ray positioning will have a large effect on the hindfoot moment arm and hindfoot alignment angle.Methods:We prospectively enrolled 29 patients, totaling 58 lower extremities, presenting to outpatient clinic for evaluation of a foot and ankle complaint. Patients <18 years of age, unable to perform bilateral weightbearing radiographs, or presenting for postoperative visits from recent foot and ankle surgery were excluded. Bilateral Saltzman hindfoot radiographs in neutral, 10 degrees of internal rotation, and 10 degrees of external rotation were performed. Marking lines were drawn on the standing platform to standardize rotation, with patients aligning their second ray with the lines. A fellowship-trained foot and ankle orthopaedic surgeon and an orthopaedic surgery resident individually measured the hindfoot moment arms and alignment angles. Analysis of variance (ANOVA) testing was used to assess for differences in hindfoot moment arm and hindfoot alignment angle in neutral, internal, and external rotation. Intra- and inter-observer agreement (95% limits) and intra-class correlation coefficients were calculated to assess for intra- and inter-observer reliability.Results:The cohort consisted of 11 (37.9%) males and 18 (62.1%) females, with a mean age of 48.7 (SD=14.7) years and mean body mass index (BMI) of 29.9 (SD=6.6) kg/m2. The mean hindfoot moment arms were 4.6 (SD=6.7) mm, 11.3 (SD=3.4) mm, and -5.4 (SD=6.2) mm in neutral, internal, and external rotation, respectively. The mean hindfoot alignment angles were 4.5 (SD=5.6) degrees, 18.6 (SD=6.8) degrees, and -10.9 (SD=10.6) degrees in neutral, internal, and external rotation, respectively. There was a significant difference in both the hindfoot moment arm (p<0.001) and hindfoot alignment angle (p<0.001) among rotational positions. A strong positive correlation existed between the amount of rotation and both moment arm (r=0.78; p<0.001) and alignment angle (r=0.84; p<0.001).Conclusion:There appears to be significant variability in both the hindfoot moment arm and hindfoot alignment angle with respect to rotation of the patient’s lower extremity. Orthopaedic surgeons should carefully scrutinize limb rotation when making clinical decisions based on the hindfoot moment arm or alignment angle.

The structure and low-barrier methyl torsion of 3-fluorotoluene.

The rotational spectra of 3-fluorotoluene and its seven 13C isotopic species have been recorded at natural abundance in the frequency range from 4 to 26GHz using a pulsed molecular jet Fourier transform microwave spectrometer. The molecular structure comprising bond lengths and angles as well as parameters describing the methyl torsion were determined with high accuracy. Due to the very low torsional barrier of 17cm-1, the lowest torsional states of the vibrational ground state exhibited large splittings in the spectrum, which were modeled satisfactorily with a modified version of the program XIAM and the program aixPAM, both developed to treat the methyl internal rotation effects. They were also applied to refit the microwave data of 3,4-difluorotoluene to standard deviations close to measurement accuracy.

Effects Of Foot Rotation On Knee Joint Reaction Forces During Running

PURPOSE: The purpose of this study was to examine the effects of internal and external foot rotation on knee joint reaction forces during running. METHODS: Motion capture and force data were recorded on nineteen healthy adult runners (22.3±4.0 years, 67.99±10.27 kg, and 1.77±0.10 m) running at 3.5 m/s with normal and maximal comfortable external (EXT) and internal (INT) foot rotation. Musculoskeletal simulations were performed using the Rajagopal 2015 model and OpenSim (SimTK). All data were low pass filtered at 10 Hz and normalized to a full stride (stance: 0-36% & swing: 37-100% stride). Models were scaled to each subject’s anthropometric parameters. Inverse dynamics were derived by combining inverse kinematics and force data. Muscle excitations were derived using Static Optimization, including muscle physiology parameters. Joint Reaction Forces were obtained by combining inverse kinematics, force data, and muscle excitations. Within-subjects ANOVAs via Statistical Parametric Mapping were used to determine differences in resultant knee joint reaction force waveforms. RESULTS: The EXT condition decreased early stance (0-2% stride) and late swing (92-100% stride) phase forces, but increased forces during early swing (44-46%) phase compared to normal. The INT condition reduced forces during very late swing phase (92-94% stride). The EXT reduced forces during early stance (0-1% stride) and late swing (97-100% stride) compared to INT. CONCLUSIONS: Despite the known success of altered foot rotation on reducing external knee abduction moments during walking and running, knee forces were only reduced during low-loading portions of running strides. Thus, it appears altered foot rotations does not improve knee loading during running.

The role of low-lying conformers and pressure effect in kinetic modeling of hydrogen abstraction of tertiary amyl methyl ether by OH radicals

In this short communication, the kinetic discrepancy between calculation and experiment for the hydrogen abstraction reaction of t-amyl methyl ether by OH radicals is resolved by combining (i) an accurate potential energy surface, including the newly found lowest-lying structures of the reactant and transition states, explored at the CCSD(T)/CBS//M06-2X/aug-cc-pVTZ level and (ii) a rigorous master equation/Rice–Ramsperger–Kassel–Marcus (ME/RRKM) rate model, which includes the corrections of the hindered internal rotation and tunneling effects, to account for pressure and temperature effects.

The effect of internal rotation in p-methyl anisole studied by microwave spectroscopy

The Fourier transform microwave spectrum of p-methyl anisole, CH3C6H4OCH3, was measured in the frequency range from 2 to 26.5GHz under molecular jet conditions. The conformational analysis yielded only one stable conformer, in which all heavy atoms are co-planar, and which was identified after analyzing the spectrum by comparison with the results from quantum chemical calculations. The barrier of the V3 potential of the ring methyl rotor was found to be 49.6370(1) cm−1, and was compared with that found in other para-substituted toluenes as well as in o-methyl anisole. A comparison between two theoretical approaches treating internal rotations, the rho axis method (program BELGI-Cs) and combined axis method (program XIAM), was also performed.

A 3D model analysis of patellofemoral joint: effect of anterior translation and internal rotation of tibia

A 3D model analysis of patellofemoral joint: effect of anterior translation and internal rotation of tibia

Effect of Hip Flexion and Internal Rotation on the Hip Abductor Muscle Activity During Side-Lying Hip Abduction in Subjects With Gluteus Medius Weakness

Background: Many previous studies recommended the side-lying hip abduction (SHA) exercise for targeting the gluteus medius (Gmed) and gluteus maximus...

The effect of isometric internal and external rotation on the acromiohumeral distance in subjects with sub-acromial pain syndrome

The effect of isometric internal and external rotation on the acromiohumeral distance in subjects with sub-acromial pain syndrome

Alkynes as CH/π Acceptors: Microwave Spectra and Structures of the CH2F2···Propyne and CH2ClF···Propyne Dimers.

Rotational spectra of weakly bound complexes of chlorofluoromethane (CH2ClF) and difluoromethane (CH2F2) with propyne (HCCCH3) have been measured using chirped-pulse and resonant-cavity Fourier-transform microwave spectroscopy, adding to a relatively small body of high resolution spectroscopic data on propyne complexes. Both dimers contain CH/π contacts, as well as secondary contacts between one or both halogen atoms and the methyl group of propyne. A detailed structural determination for CH2F2···propyne has been made by study of the normal, one deuterated and four (13)C substituted isotopologues, with the second lowest energy configuration predicted from ab initio calculations agreeing well with the observed structure. Experimental rotational constants for the most abundant isotopologue of CH2F2···propyne are A00 = 5815.5858(15) MHz, B00 = 1341.1191(5) MHz, C00 = 1099.2040(4) MHz (uncorrected for internal rotation effects), and the dipole moment components, determined by Stark effect measurements, are μa = 1.568(2) D, μb = 0.587(2) D, and μtot = 1.674(3) D. For CH2ClF···propyne, only (35)Cl and (37)Cl isotopologues have been assigned, providing rotational constants and chlorine atom coordinates consistent with the lowest energy structure from a series of ab initio predictions. Rotational constants for the (35)Cl isotopologue are A = 3423.639(7) MHz, B = 1253.7562(20) MHz, and C = 1200.4828(15) MHz and the diagonal and two off diagonal components of the quadrupole coupling tensor have also been determined.

Gait synthesis assessment of the effect of crouch gait and hip internal rotation on ‘stiff-knee’ gait

Gait synthesis assessment of the effect of crouch gait and hip internal rotation on ‘stiff-knee’ gait

Femoroacetabular impingement syndrome is associated with alterations in hindfoot mechanics: A three-dimensional gait analysis study

BackgroundGait analysis studies in patients with femoroacetabular impingement syndrome focused until today on alterations in pelvic and hip mechanics, but distal articulations in this syndrome were not explored. Viewing the inter-relationships between foot and hip mechanics and the importance of the subtalar joint in load attenuation at heel strike and during forward propulsion thereafter, alterations in hindfoot mechanics in this syndrome may have clinical significance. MethodsThree-dimensional gait kinematics were explored with emphasis on hindfoot mechanics in a group of 15 men with cam-type femoroacetabular impingement and compared to 15 healthy men. FindingsSubjects with femoroacetabular impingement had decreased pelvic internal rotation (effect size=0.70) and hip abduction (effect size=0.86) at heel strike, and increased sagittal pelvic range of motion during the stance (effect size=0.81), compared to controls. At the hindfoot level, subjects with femoroacetabular impingement had inverted position at heel strike compared to neutral position in controls (effect size=0.89), and reduced maximum hindfoot eversion during the stance (effect size=0.72). Range of motion from heel strike to maximum eversion was not different between the groups (effect size=0.21). InterpretationYoung adult men with cam-type femoroacetabular impingement syndrome present excessively inverted hindfoot at the moment of heel strike and reduction in maximum eversion during the stance phase. Viewing the deleterious effects of hindfoot malalignment on load attenuation during the stance, custom-designed insoles may be a consideration in this population and this should be investigated further.