Free Internal Rotation Research Articles

Modification of Humeral Component Results in Increased Impingement Free Range of Motion in a Reverse Shoulder Arthroplasty Model.

Shoulder arthroplasties have been demonstrated to provide reliable pain relief as well as functional benefits. The advent of the reverse shoulder arthroplasty allowed for expanded indications for shoulder replacement. Several studies comparing the outcomes of anatomic and reverse total shoulder arthroplasties have demonstrated decreased range of motion in the reverse arthroplasty cohort, especially in internal rotation. The authors hypothesized that slight modifications to the humeral component of a reverse shoulder arthroplasty could result in increased impingement free range of motion without significant sacrifices to stability. A reverse shoulder arthroplasty model was fashioned to mimic a setting of anterior mechanical impingement after replacement. Sequential resections were taken from the anterior aspect of the polyethylene up to a resection of 10 mm. A solid modeling software was utilized to compare the experimental group to the control group with regard to impingement free motion. Finite element analysis was subsequently utilized to assess stability of the construct in comparison to the nonmodified polyethylene. Impingement free internal rotation increased minimally at 3 mm of resection but considerably at each further increase in resection. A resection of 10 mm resulted roughly 30% improvement in impingement free internal rotation. Instability in this model increased with modifications beyond 7 mm. Slight alterations to the geometry of the humeral tray and polyethene components can result in improvements in impingement-free internal rotation without substantial increased instability in this model. Further work is needed to determine in vivo implications of modifications to the humeral tray and polyethylene.

Automated reaction kinetics and network exploration (Arkane): A statistical mechanics, thermodynamics, transition state theory, and master equation software

AbstractThe open‐source statistical mechanics software described here, Arkane–Automated Reaction Kinetics and Network Exploration–facilitates computations of thermodynamic properties of chemical species, high‐pressure limit reaction rate coefficients, and pressure‐dependent rate coefficient over multi‐well molecular potential energy surfaces (PES) including the effects of collisional energy transfer on phenomenological kinetics. Arkane can use estimates to fill in information for molecules or reactions where quantum chemistry information is missing. The software solves the internal energy master equation for complex unimolecular reaction systems. Inputs to the software include converged electronic structure computations performed by the user using a variety of supported software packages (Gaussian, Molpro, Orca, TeraChem, Q‐Chem, Psi4). The software outputs high‐pressure limit rate coefficients and pressure‐dependent phenomenological rate coefficients, as well as computed thermodynamic properties (enthalpy, entropy, and constant pressure heat capacity) with added energy corrections. Some of the key features of Arkane include treatment of 1D, 2D or ND hindered internal rotation modes, treatment of free internal rotation modes, quantum tunneling effect consideration, transition state theory (TST) and Rice‐Ramsperger‐Kassel‐Marcus (RRKM) rate coefficient computations, master equation solution with four implemented methods, inverse‐Laplace transform of high‐pressure limit rate coefficients into the energy domain, energy corrections based on bond‐additivity or isodesmic reactions, automated and efficient PES exploration, and PES sensitivity analysis. The present work describes the design of Arkane, how it should be used, and refers to the theory that it employs. Arkane is distributed via the RMG‐Py software suite (https://github.com/ReactionMechanismGenerator/RMG‐Py).

Formula omitted]-type doubling in the rotational spectrum of CH[formula omitted]–He: A group theoretical explanation

In a previous paper, we reported the pure rotational spectrum of the CH3+–He ion observed in a 22-pole ion trap by IR-MW double resonance spectroscopy [Töpfer et al. (2018)]. In that work the K=1 rotational levels in the ground state of the ion were observed to be split, i.e. the K-type doubling was observed. This finding would be consistent with a slightly asymmetric rotor of Cs symmetry, although ab-initio calculations predict that the equilibrium structure of the ion is of C3v symmetry. In the present study we inspect the energy-level correlation-diagram between the semi-rigid symmetric-top (C3v), the free internal-rotor (C3v(M)), and the semi-rigid asymmetric-top models (Cs), by using group theory, especially the correlation and reverse correlation in the symmetry representations. We find that the lowest K=1 rotational levels of the CH3+–He ion can be of A1⊕A2 symmetry rather than of E symmetry, and thus they can be split depending on the nature of the C–He bending vibration.

Rovibrational jet-cooled spectroscopy of the Kr–H2O van der Waals complex in the [formula omitted] bending mode region of H2O

Five rovibrational bands of the Kr–H2O complex have been recorded in the ν2 bending region of H2O using a quantum cascade laser coupled to a pulsed slit supersonic jet. Four of them have been unambiguously assigned to the Σ and Π states in v2=1,111,110, and 212 rotational levels of the monomer based on ground state combination differences and similarities with the vibration–rotation tunneling states of Ar–H2O. One of the bands is tentatively assigned to a combination band with two quanta of intermolecular van der Waals stretching mode (νs). Due to the efficient rovibrational cooling in our pulsed supersonic expansion, all observed bands originate from the lowest lying states. Four of them are from the lowest ortho ground state Σe(101) and one of them is from the lowest para ground state Σe(000). The jet-cooled spectra have been analyzed in terms of a nearly free internal rotor model taking into account Coriolis couplings between close lying Σ and Π levels. Molecular parameters for the five upper vibrational states, band origin, rotational and centrifugal distortion constants have been accurately determined. The β parameter describing the Coriolis coupling between the Σ and Π states originating from the (212) state has also been obtained.

Symmetry-Breaking Charge Separation in Phenylene-Bridged Perylenediimide Dimers.

Perylenediimides (PDIs) are important molecular building blocks that are being investigated for their applicability in optoelectronic technologies. Covalently linking multiple PDI acceptors at the 2,5,8,11 (headland) positions adjacent to the PDI carbonyl groups is reported to yield higher power conversion efficiencies in photovoltaic cells relative to PDI acceptors linked at the 1,6,7,12 (bay) positions. While the photophysical properties of PDIs linked via the bay positions have been investigated extensively, those linked at the headland positions have received far less attention. We showed previously that symmetry-breaking charge separation (SB-CS) in PDIs hold promise as a strategy for increasing photovoltaic efficiency. Here we use transient absorption and emission spectroscopies to investigate the competition between SB-CS, fluorescence, and internal conversion in three related PDI dimers linked at the headland positions with o-, m-, and p-phenylene moieties: o-PDI2, m-PDI2, and p-PDI2, respectively. It is found that o-PDI2 supports SB-CS yielding PDI•+-PDI•-, which is in equilibrium with the o-PDI2 first excited state in a polar solvent (CH2Cl2) while m-PDI2 and p-PDI2 exhibit accelerated internal conversion due to the motion of the linker along with subnanosecond intersystem crossing (ISC). Electronic coupling and structural dynamics are shown to play a significant role, with o-PDI2 being the only member of the series that exhibits significant through-bond interchromophore coupling. The pronounced o-PDI2 steric congestion prevents the free internal rotation that leads to rapid deactivation of the excited state in the other dimers.

Ferroelectric Aspect and Phase Transitions of Solid Solution of Cadmium Acetate with Aluminium (III) Oxide

The behavior of variation of dielectric constant with temperature of solid solution of Cadmium Acetate Cd(C2H3O2)2 with Aluminium (III) Oxide Al2O3 and other dielectric parameters have been measured between the temperatures 35°C to 100°C using the capacitance bridge model ZENITH-FM89A and Q meter at the frequency of 2000 Hz. In the measurement, it have been observed that the compound has lower value of dielectric constant (ε = 1580) below 36ºC, which rises upto a value of 5600 at the moderate temperature of 45ºC. After this temperature, the dielectric constant of compound decreases upto the value of nearly 3521 at the temperature of 75ºC and a high peak at the temperature of 76°C (ε = 7000) in the heating cycle curve with some fluctuations.. When the variation of dielectric constant was studied in cooling cycle the peak was observed at 62ºC(ε = 6500), above and below this temperature dielectric constant decreases with some intermediate fluctuations and by increasing aluminium oxide content in the mother compound, its quality factor also increases with a little effect on dielectric constant. The cooling cycle curve does not follow heating curve because of the relaxor behaviour of the compound. The results have been explained on the basis of crystal structure changes and the possibility of free internal rotation of acetate groups within the crystal lattice at elevated temperature. One of the advantages of Cd(C2H3O2)2 with Al2O3 is that by varying the Aluminium Oxide content, one can control temperature coefficient of resonant frequency τf without affecting the other properties. This is important for many ferroelectric applications because τf of near about low value is not always required. A non-zero τf is often preferable to compensate for frequency variation due to the effect of temperature change on the resonator housing and dielectric support structure. Solid solution of Cadmium Acetate with Aluminium Oxide suggests for its valuable applications as dielectric material with excellent properties useful in ceramics engineering and communication system. KEY WORDS: Polarization, Quality Factor, Dielectric Constant, Phase Transition, Curie temperature, Resonant Frequency and Ceramics Engineering.

Stability limits of a red Carthamin-cellulose complex as a potential food colourant.

This study covers aspects of stability and colouration of Carthamin- a unique red chalcone extracted from Carthamus tinctorius L. Due to its fast degradation in aqueous solutions even at room temperature, Carthamin has no significant use in the food industry. Therefore, obtaining Carthamin in a stable form is of high interest. Comparing UV-Vis spectra of Carthamin solutions and RGB-data of Carthamin-cellulose complex in the wet state showed a predominant formation of stable Carthamin conformation on the cellulose phase. It was determined that the wet Carthamin-cellulose complex acquires a stable and rich magenta colour in the pH range of 1-5. In aqueous suspensions with pH >6, the Carthamin-cellulose complex gets a purple colour, which is absolutely uncharacteristic for pure Carthamin in an aqueous solution. IR spectra indicate the fixation of Carthamin molecules on the cellulose, which presumably causes hindrance of free internal rotation of Carthamin molecules in the cellulose phase. The reduction of water activity in the cellulosic phase represents an additional stabilizing factor. As a result, the Carthamin-cellulose complex withstands heating up to 70 °C for 15 min in the pH range of 2-5, showing up to 90% of stability. These conditions are typical for the preparation of a wide range of food products. High stability in a food-like environment and magenta colour make the Carthamin-cellulose complex a prospective natural food dye.

Infrared Spectrum of the Adamantane+ -Water Cation: Hydration-Induced C-H Bond Activation and Free Internal Water Rotation.

Diamondoid cations are reactive intermediates in their functionalization reactions in polar solution. Hydration is predicted to strongly activate their C−H bonds in initial proton abstraction reactions. To study the effects of microhydration on the properties of diamondoid cations, we characterize herein the prototypical monohydrated adamantane cation (C10H16 +–H2O, Ad+–W) in its ground electronic state by infrared photodissociation spectroscopy in the CH and OH stretch ranges and dispersion‐corrected density functional theory (DFT) calculations. The water (W) ligand binds to the acidic CH group of Jahn–Teller distorted Ad+ via a strong CH⋅⋅⋅O ionic H‐bond supported by charge–dipole forces. Although W further enhances the acidity of this CH group along with a proton shift toward the solvent, the proton remains with Ad+ in the monohydrate. We infer essentially free internal W rotation from rotational fine structure of the ν3 band of W, resulting from weak angular anisotropy of the Ad+–W potential.

Infrared Spectrum of the Adamantane+–Water Cation: Hydration‐Induced C−H Bond Activation and Free Internal Water Rotation

AbstractDiamondoid cations are reactive intermediates in their functionalization reactions in polar solution. Hydration is predicted to strongly activate their C−H bonds in initial proton abstraction reactions. To study the effects of microhydration on the properties of diamondoid cations, we characterize herein the prototypical monohydrated adamantane cation (C10H16+–H2O, Ad+–W) in its ground electronic state by infrared photodissociation spectroscopy in the CH and OH stretch ranges and dispersion‐corrected density functional theory (DFT) calculations. The water (W) ligand binds to the acidic CH group of Jahn–Teller distorted Ad+via a strong CH⋅⋅⋅O ionic H‐bond supported by charge–dipole forces. Although W further enhances the acidity of this CH group along with a proton shift toward the solvent, the proton remains with Ad+in the monohydrate. We infer essentially free internal W rotation from rotational fine structure of the ν3band of W, resulting from weak angular anisotropy of the Ad+–W potential.

Halogen bond and internal dynamics in the σ–complex of pyridine-chlorotrifluoromethane: A rotational study

The rotational spectrum of the 1:1 complex pyridine–chlorotrifluoromethane shows that the two moieties are held together through a CCl···N halogen bond (RCl···N = 2.909(5) Å). The quadrupolar effects of the 35Cl (or 37Cl) and 14N nuclei combined with the high density of the rotational transitions give rise to a very congested spectrum. The multidimensional large amplitude internal dynamics is reflected in a two times larger rotational constant A, on an unexpected positive values of the inertial defect of the ground state, and on a negative value of the DJ centrifugal distortion constant. This comes from a combination of a free internal rotation and of a very low energy in plane oscillation of CF3Cl with respect to pyridine. However, a coupled Hamiltonian including Coriolis interactions with an hypothetical (unobserved) v = 1 state solves the initial result of an unphysical negative value for the centrifugal distortion constant.

Coriolis Interactions in benzene-water and related molecular complexes

Rotational spectra of benzene-water and several related complexes were fit according to a free internal rotor model over the last three decades, though the model did not explain all of the excited state transitions found or yield an RMS deviation within experimental uncertainty. We use a model Hamiltonian, including Coriolis interactions that is able to explain all excited state transitions observed, giving a fit with an RMS deviation within experimental uncertainty.

Structure and Dynamics of the Methane-Propane van der Waals Complex

Microwave transitions in the region 7-26 GHz were measured for the methane-propane van der Waals complex. The nearly free internal rotation of methane within the complex gives rise to three states that do not relax even in a 5 K supersonic expansion. Eighteen lines have been assigned to the lowest state and are well fitted to a semirigid rotor model, with rotational constants A = 7553.8229 (24) MHz, B = 2483.9200 (8) MHz, and C = 2041.8692 (5) MHz, and six distortion constants. The structure has the methane positioned above the plane defined by the propane carbon atoms with a center-of-mass van der Waals bond distance of 3.98 Å. This is significantly larger than the equilibrium value of 3.71 Å found with ab initio calculations done at the CCSD(T)-F12a/aug-cc-pVTZ level of theory. Further calculations encompassing a large range of angular orientations of the methane subunit indicate that angular motion produces a large zero-point contribution to the energy, which not only lowers the effective barrier to internal rotation of the methane but also increases the radial distance between subunits. Therefore, although in the lowest energy structure the methane can get close to the propane by interdigitating the hydrogens atoms, the zero-point energy effectively flattens out the potential so that the hydrogens become less restricting.

Halogen bond in the water adduct of chloropentafluoroethane revealed by rotational spectroscopy.

The rotational spectrum of the chloropentafluoroethane-water complex has been investigated by pulsed jet Fourier transform microwave spectroscopy. Experimental rotational and quadrupole coupling constants of five isotopologues imply that the two subunits are held together by an almost linear C-Cl⋯O halogen bond. Water lies effectively in the symmetric plane of C2F5Cl and undergoes a plausible free internal rotation. The experimental structure and dissociation energies of the complex are also deduced.

Conformational effect on the almost free internal rotation in 4-hexyn-3-ol studied by microwave spectroscopy and quantum chemistry.

The microwave spectrum of 4-hexyn-3-ol, CH3-C≡C-CH(OH)-CH2CH3, was recorded in the frequency range of 2-26.5 GHz by molecular jet Fourier transform microwave spectroscopy. The conformational analysis based on quantum chemical calculations yielded nine conformers exhibiting C1 symmetry, of which three could be assigned in the experimental spectrum. The propynyl methyl group CH 3 -C≡C- experiences internal rotation with a very low barrier due to the presence of the cylindrically symmetric -C≡C- group serving as a spacer to the rest of the molecule, which is 7.161 012(7) cm-1, 4.236 5(26) cm-1, and 7.901 6(39) cm-1 for the three assigned conformers, respectively. The spectrum was analyzed with the program XIAM using the combined axis method and the program BELGI-C 1 using the rho axis method and a very flexible Hamiltonian which yields fits with root-mean-square deviations within the measurement accuracy.

Infrared Spectroscopy of Au+(CH4)n Complexes and Vibrationally-Enhanced C\u2013H Activation Reactions

A combined spectroscopic and computational study of gas-phase Au+(CH4)n (n = 3–8) complexes reveals a strongly-bound linear Au+(CH4)2 core structure to which up to four additional ligands bind in a secondary coordination shell. Infrared resonance-enhanced photodissociation spectroscopy in the region of the CH4a1 and t2 fundamental transitions reveals essentially free internal rotation of the core ligands about the H4C–Au+–CH4 axis, with sharp spectral features assigned by comparison with spectral simulations based on density functional theory. In separate experiments, vibrationally-enhanced dehydrogenation is observed when the t2 vibrational normal mode in methane is excited prior to complexation. Clear infrared-induced enhancement is observed in the mass spectrum for peaks corresponding 4u below the mass of the Au+(CH4)n=2,3 complexes corresponding, presumably, to the loss of two H2 molecules.

Collective Molecular Superrotation: A Model for Extremely Flexible Molecules Applied to Protonated Methane.

The concept of molecular structure is traditionally considered to be virtually fundamental. However, it breaks down in extremely flexible molecules, whose dynamics are governed by large-amplitude motions. For the dynamics of molecules with free internal rotations, we therefore propose a five-dimensional rigid rotor model, with states characterized by two generalized angular momentum quantum numbers and a rotational constant B. The quantum numbers characterize a 5D angular-momentum vector, super-j, which describes collective rotations that involve both the internal and the overall rotation. This model predicts the lowest energy states of the prototypical, extremely flexible molecule, CH_{5}^{+}. Both energies and symmetries compare very favorably to recent experimental results. The respective assignment to the new quantum numbers indicates the validity of our concept of collective rotations in extremely flexible molecules.

Structural and spectroscopic characterization of methyl isocyanate, methyl cyanate, methyl fulminate, and acetonitrile N-oxide using highly correlated ab initio methods

Various astrophysical relevant molecules obeying the empirical formula C2H3NO are characterized using explicitly correlated coupled cluster methods (CCSD(T)-F12). Rotational and rovibrational parameters are provided for four isomers: methyl isocyanate (CH3NCO), methyl cyanate (CH3OCN), methyl fulminate (CH3ONC), and acetonitrile N-oxide (CH3CNO). A CH3CON transition state is inspected. A variational procedure is employed to explore the far infrared region because some species present non-rigidity. Second order perturbation theory is used for the determination of anharmonic frequencies, rovibrational constants, and to predict Fermi resonances. Three species, methyl cyanate, methyl fulminate, and CH3CON, show a unique methyl torsion hindered by energy barriers. In methyl isocyanate, the methyl group barrier is so low that the internal top can be considered a free rotor. On the other hand, acetonitrile N-oxide presents a linear skeleton, C3v symmetry, and free internal rotation. Its equilibrium geometry depends strongly on electron correlation. The remaining isomers present a bend skeleton. Divergences between theoretical rotational constants and previous parameters fitted from observed lines for methyl isocyanate are discussed on the basis of the relevant rovibrational interaction and the quasi-linearity of the molecular skeleton.

The infrared spectrum of the Ar–C2D2 complex

Infrared spectra of Ar–C2D2 are observed in the region of the ν3 fundamental band (asymmetric C–D stretch, ≈2440cm−1) using a tunable optical parametric oscillator to probe a pulsed supersonic slit jet expansion from a cooled nozzle. Transitions are assigned involving K=0–2 in the ground vibrational state, and K=0–4 in the excited state. The intermolecular bending combination band is also observed, giving a bending frequency of 4.798cm−1. Despite this low bending frequency, the Ar–C2D2 spectrum qualitatively resembles that of a normal semi-rigid molecule, in contrast to He– and Ne–C2D2 which are much closer to the limit of free internal rotation.

Even the Intraoperative Knowledge of Femoral Stem Anteversion Cannot Prevent Impingement in Total Hip Arthroplasty

BackgroundIn this prospective study of 66 patients undergoing cementless total hip arthroplasty through a minimally invasive anterolateral approach, we evaluated the impact of an intraoperative hybrid combined anteversion technique on postoperative range of motion (ROM). MethodsAfter navigation of femoral stem anteversion, trial acetabular components were positioned manually, and their position recorded with navigation. Then, final components were implanted with navigation at the goals prescribed by the femur-first impingement detection algorithm. Postoperatively, three-dimensional computed tomographies were performed to determine achieved component position and model impingement-free ROM by virtual hip movement, which was compared with published values necessary for activities of daily living. This model was run a second time with the implants in the position selected by the surgeon rather than the navigation program. In addition, we researched into risk factors for ROM differences between the freehand and navigated cup position. ResultsWe found a lower flexion of 8.3° (8.8°, P < .001) and lower internal rotation of 9.2° (9.5°, P < .001) for the freehand implanted cups in contrast to a higher extension of 9.8° (11.8°, P < .001) compared with the navigation-guided technique. For activities of daily living, 58.9% (33/56) in the freehand group compared with 85.7% (48/56) in the navigation group showed free flexion (P < .001) and similarly 50.0% (28/56) compared with 76.8% (43/56) free internal rotation (P < .001). Body mass index, incision length, and cup size were identified as independent risk factors for reduced flexion and internal rotation in the freehand group. ConclusionFor implementation of a combined anteversion algorithm, intraoperative alignment guides for accurate cup positioning are required using a minimally invasive anterolateral approach. Obese patients are especially at risk of cup malpositioning.

Internal rotation, spin–orbit coupling, and low-frequency vibrations in the ground state of CH3–CC–CH+3 and CD3–CC–CD+3

Pulsed-field-ionisation zero-kinetic-energy (PFI-ZEKE) photoelectron spectra of 2-butyne (CH3–CC–CH3) and its fully deuterated isotopomer have been recorded in the region of the origin band of the ionising transition. The spectral congestion originating from the combined effects of the internal rotation of the methyl groups, the spin–orbit coupling, and the Jahn–Teller effect prevented the full resolution of the rotational structure of the photoelectron spectra. A tentative analysis of the rotational branch structure of the photoelectron spectra using rovibronic photoionisation selection rules derived in the permutation–inversion spin double group G36(M2) suggests a splitting of ∼10.5 cm−1 between the two spin–orbit components E3/2 and E1/2 of the 2 E1 ground state and an almost free internal rotation of the methyl groups in the cations. Assignments are proposed for several low-lying vibrational levels of the cations.