Protocol and validity testing of femoroacetabular posterior translation with dynamic hip ultrasonography.

OBJECTIVE: To describe femoroacetabular posterior translation (FAPT) using dynamic hip ultrasonography (DHUS), and to determine the inter- and intra-rater reliability of hip ultrasound measurements of FAPT. MATERIALS AND METHODS: The study design was a feasibility study of 13 healthy young adults (26 hips) using test-retest analysis. The data was collected prospectively over a 2-week time period. Three DHUS measurements (posterior neutral (PN), flexion, adduction, and internal rotation (PFADIR), and stand and load (PStand) were measured by four independent raters (2 senior who divided the cohort, 1 intermediate, 1 junior) at two time points for bilateral hips of each participant. Reliability was assessed by calculating the intraclass correlation coefficient (ICC) along with 95% confidence intervals (CIs) for each rater and across all raters. RESULTS: A total of 468 US scans were completed. The mean age of the cohort was 25.7 years (SD 5.1 years) and 54% were female. The inter-rater reliability was excellent for PFADIR (ICC 0.85 95% CI 0.76-0.91), good for PN (ICC 0.69 95% CI 0.5-0.81), and good for PStand (ICC 0.72 95% CI 0.55-0.83). The intra-rater reliability for all raters was good for PFADIR (ICC 0.60 95% CI 0.44-0.73), fair for PN (ICC 0.42 95% CI 0.21-0.59), and fair for PStand (ICC 0.42 95% CI 0.22-0.59). CONCLUSION: This is the first study to present a protocol using dynamic ultrasonography to measure FAPT. DHUS measure for FAPT was shown to be reliable across raters with varying levels of ultrasound experience.

Dissociation of hydrogen peroxide in water and methanol through a biased molecular dynamics investigation.

The two dissociation channels of HOOH, namely, HOOH and HOOH, in water and methanol are investigated using umbrella-sampling ab initio molecular dynamics. Our potential of mean force calculations reveals the HOOH dissociation to be more favorable in methanol with a free energy barrier of 7.56 kcal/mol, while the HOOH dissociation possesses a free energy barrier of 11.46 kcal/mol. In water, the HOOH dissociation channel is more favorable (8.25 kcal/mol), while the HOOH dissociation process requires a higher free energy (11.28 kcal/mol). Such reaction favorability can be explained by inspecting the formation of secondary radical species during the course of multiple hydrogen donating-accepting processes in each reaction channel. The radical species, that is, H3 O• (observed in water) and CH3 OH2• (observed in methanol), are the first subordinate species upon the HOOH dissociation. For the HOOH dissociation channel in methanol, the secondary species such as water and formaldehyde can be observed, while the re-generation of HOOH in water can be spotted.

Femoral Injury Over the Site of Spontaneous Regression of an Osteochondroma in a Teenage Athlete.

ABSTRACT: The spontaneous regression of an osteochondroma is extremely rare. We report a case of medial femoral condyle impaction fracture over the site of spontaneous regression of a pedunculated osteochondroma discovered on advanced imaging after an acute injury in a 16-year-old male American football athlete. Although spontaneous regression of an osteochondroma has been described, the case presented reveals questions regarding resultant architectural changes to the bone after resorption, leaving it prone to injury. This is the first case that describes increased injury risk potential at the site of osteochondral regression.

Point-of-Care Ultrasound, the New Musculoskeletal Physical Examination.

ABSTRACT: The availability of handheld ultrasound offers physicians an opportunity to better define anatomy and pathophysiology, thus enhancing the diagnostic capabilities of a standard physical examination. The medical community increasingly embraces the potential for point-of-care ultrasound across medical specialties. The primary aim of this review was to identify and compile information on the current clinical utility of point-of-care ultrasound for musculoskeletal examination. This information will enable health care providers to understand the current utility and potential of musculoskeletal point-of-care ultrasound, thus facilitating its appropriate adoption into clinical practice.

Reaction probability and kinetics of water splitting on the penta-NiAs2 monolayer from an ab initio molecular dynamics investigation.

The reaction probability and kinetics of the water splitting process on the penta-NiAs2 monolayer are studied using ab initio molecular dynamics simulations. A total of 100 trajectories are investigated, in which a H2O molecule is set to strike the surface with a translational energy of 1 eV or 2 eV. The results show that the NiAs2 monolayer is an excellent candidate for the activation of water splitting with a reaction probability of 94% for both energy levels. Interestingly, the kinetics of two O-H dissociation stages varies greatly with respect to the inletting translational energy. Interpreting the reaction data for the 1 eV case, we conclude that O-H1 and O-H2 dissociations are first-order processes. However, such dissociation steps become pseudo-zeroth order in the 2 eV case. At the time of the dissociation, the force acting on atoms and the principal component analysis suggest that the two OH breaking stages behave like harmonic springs until reaching the dissociation.

A proton transfer mechanism along the PO4 anion chain in the [Zn(HPO4)(H2PO4)]2- coordination polymer.

In this study, we revisit the proton transfer mechanism in [Zn(HPO4)(H2PO4)]2-, a coordination polymer possessing high proton conductivity. In a previous report [N. Phattharasupakun, J. Wutthiprom, S. Kaenket, Th. Maihom, J. Limtrakul, M. Probst, S. S. Nagarkar, S. Horike and M. Sawangphruk, Chem. Commun., 2017, 53, 11786-11789], it was hypothesized that protons could move along the ImH+ chain involving phosphate anions within the polymer structure, with energy barriers >1.3 eV. Adopting M06-2X calculations to examine the reaction pathway, we observe that it is much more favorable for H+ to move along a one-dimensional channel formed by HPO42- and H2PO4- anions. Within a unit cell, the proton hopping process can be divided into three elementary steps. For the forward proton transfer direction, the maximum energy barrier is only 0.04 eV, while that of the backward direction is 0.27 eV. Even though the barriers of the backward direction seem to outreach the barriers of the forward direction, both are still low in comparison with those reported in the literature. Moreover, we also point out the involvement of PO4 rotation during the proton transfer process. Activation energies of 0.37 eV and 0.15 eV are required for single steps of rotation of the phosphate anion. Both H+ translation (hopping) and rotation steps of PO4 anions simultaneously participate in the course of proton transfer in the coordination polymer.

Correction: Penetrating probability and cross section of the Li+-C60 encapsulation process through an ab initio molecular dynamics investigation.

Correction for 'Penetrating probability and cross section of the Li+-C60 encapsulation process through an ab initio molecular dynamics investigation' by Thi H. Ho et al., Phys. Chem. Chem. Phys., 2018, 20, 7007-7013.

Penetrating probability and cross section of the Li+-C60 encapsulation process through an ab initio molecular dynamics investigation.

The endohedral complex system of Li+-C60 has been shown to possess interesting applications in photovoltaics, supramolecular chemistry, and functionalized materials. In this study, we perform a theoretical investigation of Li+ encapsulation within a C60 cage by employing an ab initio molecular dynamics approach. The Li+ cation is positioned 9 Å away from the C60 center of mass, and fired towards a randomized spot in a six-membered ring with a certain level of inletting energy, which is 7.5 eV, 9 eV, 12 eV, or 15 eV. In total, 2000 samples of MD trajectories are investigated. Our statistical results yielded a penetrating probability in the range of 0.8% to 15.6% with respect to the above inletting energy, while the cross section ranges from 0.006 Å2 to 0.123 Å2. Moreover, we observed that the penetrating probability exhibited direct proportionality to the inletting energy. Hence, we can determine that the minimum required inletting energy for reaction occurrence is 6.6 eV. Overall, it seems difficult for Li+ to penetrate through the sp2-carbon wall, because a very high inletting energy is required to open the entrance. At the same time, Li+ must approach closely to the center of a six-membered ring to enhance the penetration probability.

A Density Functional Theory Investigation of Nin , Pdn , and Ptn Clusters (n=1-4) Adsorbed on Buckminsterfullerene.

In this study, we examine the adsorptions of Ni, Pd, and Pt clusters on C60 by using a computational approach. Our calculation results show that the base structure of C60 can host Nin /Pdn /Ptn (n=1-4) clusters with good adsorption stability and the complexes establish either two or no unpaired electrons. The binding energy of Pd and Pt clusters increases as the number of metal atoms increases, implying that the coverage of C60 with Pd or Pt preferentially establishes a large-size metal cluster. A single metal atom favorably occupies the C-C bridge site. For dimer clusters, the three metals of interest share a similar binding fashion, in which two metal atoms establish direct interactions with the C-C bridge sites. For trimer adsorptions, the formation of linear and triangular structures is observed. Both Pt3 and Ni3 preferably constitute isosceles triangles on C60 , whilst Pd3 favorably establishes a linear shape. Finally, for each of the Ni4 and Pd4 adsorption cases, we observed three stable binding configurations: rhombus, tetrahedron, and Y-form. Whereas Ni4 establishes a tetrahedral form, Pd4 attains the most stable form with the Y-shape geometry on C60 . Overall, we observe that the trend of Pd binding to C60 tends to go beyond the fashion of Ni and Pt. In terms of magnetic alignment, the Pdn -C60 systems seem to be non-magnetic in most cases, unlike the Ni and Pt cases, the structures of which possess magnetic moments of 2 µB in their most stable forms.

Atomistic observation of the collision and migration of Li on MoSe2 and WS2 surfaces through ab initio molecular dynamics.

We present in this study a theoretical investigation of the collision of Li with the MX2 surface (MoSe2 or WS2) by employing the Born-Oppenheimer molecular dynamics (MD) approach. In each trajectory, atomic Li is fired toward the two-dimensional monolayer with an inletting kinetic energy of 0.2 eV or 2.0 eV and a chosen striking angle. In total, 84 MD trajectories are analyzed. We observe that Li has a high tendency to migrate on WS2 in most investigated cases (20/21 cases at 0.2 eV inletting kinetic energy and 21/21 cases at 2.0 eV inletting kinetic energy), while the migration probability on MoSe2 is much lower (only 5/21 cases with the inletting kinetic energy of 0.2 eV and 15/21 cases with the inletting kinetic energy of 2.0 eV). Interestingly, our finding shows that the migration probability does not depend on the binding energies of Li-MoSe2 (1.61 eV) and Li-WS2 (1.77 eV), but it is in good agreement with the nudged-elastic-band prediction of migration barriers. In fact, it is the intensity of elastic vibration of the transition metal dichalcogenide layer that plays a very significant role in the migration of Li. During the collision process, Li is able to absorb energy from the layer vibration to jump out from one X-X-X trap to another. Consequently, with the assistance from intensive vibration of WS2, Li would possess higher migration probability on the layer surface. Finally, electronic structure analysis on various interacting Li-MX2 configurations is performed. From Bader charge estimation, we observe that WS2 tends to establish more charge transferability with Li. Moreover, when Li approaches closer to the S/Se layer, the hybridization of Li-2s and Mo-4d (or W-5d) orbitals results in a magnetic moment (up to ∼1 µB).

Ab Initio Investigation of O-H Dissociation from the Al-OH2 Complex Using Molecular Dynamics and Neural Network Fitting.

The dissociation dynamics of the O-H bond in Al-OH2 is investigated on an approximated ab initio potential energy surface (PES). By adopting a dynamic sampling method, we obtain a database of 92 834 configurations. The potential energy for each point is calculated using MP2/6-311G (3df, 2p) calculations; then, a 60-neuron feed-forward neural network is utilized to fit the data to construct an analytic PES. The root-mean-square error (rmse) for the training set is reported as 0.0036 eV, while the rmse for the independent testing set is 0.0034 eV. Such excellent fitting accuracy indeed confirms the reliability of the constructed PES. Subsequently, quasi-classical molecular dynamics (MD) trajectories are performed on the constructed PES at various levels of vibrational excitation in the range of 1.03 to 2.23 eV to investigate the probability of O-H bond dissociation. The results indicate a linear relationship between reaction probability and internal energy, from which we can determine the minimum activation internal energy required for the dissociation as 0.62 eV. Moreover, the O-H bond rupture is shown to be highly correlated with the formation of Al-O bond.

First-principles modeling of C60-Cr-graphene nanostructures for supporting metal clusters.

We present a first-principles modeling study of a new class of nanomaterials in which buckminsterfullerene (C60) and graphene (G) are bridged by Cr via coordination bonds. Two nanostructures denoted as G(C54)-Cr-C60 and G(C150)-Cr-C60 are investigated, which share many similarities in the configuration geometries but differ in the distribution densities of Cr-C60 on the graphene surface. The binding energies between C60 and the rest of the system in these complexes are calculated to be 2.59 and 2.10 eV, respectively, indicative of their good structural stability. Additional spin-polarized calculations indicate that G(C54)-Cr-C60 is weakly ferromagnetic, which is chiefly due to the contribution from the 3d shell of Cr. We then investigate three model complexes of C60-Cr-G(C54) and a metal cluster (Ni4, Pd4, or Pt4). The binding energies of these three nanostructures are significantly large (3.57, 2.38, and 4.35 eV, respectively). Electron density analysis along the Ni-C, Pd-C, and Pt-C bonds consistently affirms that the Pt-C bond is the strongest while the Pd-C bond is the weakest. The strong Pt-C bond is attributed to the effective overlap of 5d(z(2)) (Pt) and 2p(z) (C) orbitals. Partial density of states analysis indicates that Ni4 and Pd4 substantially contribute to the strong ferromagnetism of the complexes, whereas Pt4 is observed to be non-magnetic even when the spin-orbit coupling is taken into account. H2 dissociation on the Ni4 complex is also examined, and the estimated reaction barrier is relatively low (0.76 eV).

Modified feed-forward neural network structures and combined-function-derivative approximations incorporating exchange symmetry for potential energy surface fitting.

The classical interchange (permutation) of atoms of similar identity does not have an effect on the overall potential energy. In this study, we present feed-forward neural network structures that provide permutation symmetry to the potential energy surfaces of molecules. The new feed-forward neural network structures are employed to fit the potential energy surfaces for two illustrative molecules, which are H(2)O and ClOOCl. Modifications are made to describe the symmetric interchange (permutation) of atoms of similar identity (or mathematically, the permutation of symmetric input parameters). The combined-function-derivative approximation algorithm (J. Chem. Phys. 2009, 130, 134101) is also implemented to fit the neural-network potential energy surfaces accurately. The combination of our symmetric neural networks and the function-derivative fitting effectively produces PES fits using fewer numbers of training data points. For H(2)O, only 282 configurations are employed as the training set; the testing root-mean-squared and mean-absolute energy errors are respectively reported as 0.0103 eV (0.236 kcal/mol) and 0.0078 eV (0.179 kcal/mol). In the ClOOCl case, 1693 configurations are required to construct the training set; the root-mean-squared and mean-absolute energy errors for the ClOOCl testing set are 0.0409 eV (0.943 kcal/mol) and 0.0269 eV (0.620 kcal/mol), respectively. Overall, we find good agreements between ab initio and NN prediction in term of energy and gradient errors, and conclude that the new feed-forward neural-network models advantageously describe the molecules with excellent accuracy.

Platelet rich plasma for hallux sesamoid injuries: a case series.

OBJECTIVE: Hallux sesamoid injuries are well described and can be debilitating and chronically disabling. The role of orthobiologics such as platelet-rich plasma (PRP) in sesamoid injuries has not been reported. This study describes three cases of recalcitrant hallux sesamoid injuries in teenage athletes who returned to impact activities, pain free, following one treatment of PRP. METHODS: This is a case-series study describing three teenage athletes presenting to a tertiary level pediatric sports medicine practice with chronic hallux sesamoid injuries. RESULTS: The three patients (two female, one male) described in this case series were 13-, 16-, and 17-year-old athletes. Their primary sports were ballet, basketball, and Irish step dance, respectively. All three athletes received PRP: two received unilateral treatment (one tibial sesamoid, one fibular sesamoid) and one received treatment to bilateral tibial sesamoids. The average duration of symptoms prior to PRP was 52.5 weeks (14-128 weeks). The average time out of their primary sport was 48.7 weeks (20-78 weeks). Three of the 4 sesamoids treated with PRP were tibial sesamoids. Each site of injury was treated with one treatment of leukocyte-rich PRP. All three athletes were cleared to return to impact activities such as running and jumping at 6-9 weeks following PRP, specifically 9 weeks after the final PRP injection for the patient who underwent bilateral treatments. CONCLUSION: In the three cases provided of sesamoid injuries treated with PRP, the time to return to impact activities was less than reported for athletes not treated with PRP. Acknowledging that other management factors likely contributed to return to impact activities, this case series sets the groundwork for future research investigating the role of PRP with needle fenestration in the treatment of sesamoid injuries.

Behavior of Linear and Nonlinear Dimensionality Reduction for Collective Variable Identification of Small Molecule Solution-Phase Reactions.

Identifying collective variables (CVs) for chemical reactions is essential to reduce the 3N-dimensional energy landscape into lower dimensional basins and barriers of interest. However, in condensed phase processes, the nonmeaningful motions of bulk solvent often overpower the ability of dimensionality reduction methods to identify correlated motions that underpin collective variables. Yet solvent can play important indirect or direct roles in reactivity, and much can be lost through treatments that remove or dampen solvent motion. This has been amply demonstrated within principal component analysis (PCA), although less is known about the behavior of nonlinear dimensionality reduction methods, e.g., uniform manifold approximation and projection (UMAP), that have become recently utilized. The latter presents an interesting alternative to linear methods though often at the expense of interpretability. This work presents distance-attenuated projection methods of atomic coordinates that facilitate the application of both PCA and UMAP to identify collective variables in the presence of explicit solvent and further the specific identity of solvent molecules that participate in chemical reactions. The performance of both methods is examined in detail for two reactions where the explicit solvent plays very different roles within the collective variables. When applied to raw molecular dynamics data in solution, both PCA and UMAP representations are dominated by bulk solvent motions. On the other hand, when applied to data preprocessed by our attenuated projection methods, both PCA and UMAP identify the appropriate collective variables (though varying sensitivity is observed due to the presence of explicit solvent that results from the projection method). Importantly, this approach allows identification of specific solvent molecules that are relevant to the CVs and their importance.

Exploration of glassy state in Prussian blue analogues.

Prussian blue analogues (PBAs) are archetypes of microporous coordination polymers/metal-organic frameworks whose versatile composition allows for diverse functionalities. However, developments in PBAs have centred solely on their crystalline state, and the glassy state of PBAs has not been explored. Here we describe the preparation of the glassy state of PBAs via a mechanically induced crystal-to-glass transformation and explore their properties. The preservation of short-range metal-ligand-metal connectivity is confirmed, enabling the framework-based functionality and semiconductivity in the glass. The transformation also generates unconventional CN- vacancies, followed by the reduction of metal sites. This leads to significant porosity enhancement in recrystallised PBA, enabled by further accessibility of isolated micropores. Finally, mechanical stability under stress for successful vitrification is correlated to defect contents and interstitial water. Our results demonstrate how mechanochemistry provides opportunities to explore glassy states of molecular framework materials in which the stable liquid state is absent.

Molecular dynamics investigations of ozone on an ab initio potential energy surface with the utilization of pattern-recognition neural network for accurate determination of product formation.

The singlet-triplet transformation and molecular dissociation of ozone (O(3)) gas is investigated by performing quasi-classical molecular dynamics (MD) simulations on an ab initio potential energy surface (PES) with visible and near-infrared excitations. MP4(SDQ) level of theory with the 6-311g(2d,2p) basis set is executed for three different electronic spin states (singlet, triplet, and quintet). In order to simplify the potential energy function, an approximation is adopted by ignoring the spin-orbit coupling and allowing the molecule to switch favorably and instantaneously to the spin state that is more energetically stable (lowest in energy among the three spin states). This assumption has previously been utilized to study the SiO(2) system as reported by Agrawal et al. (J. Chem. Phys. 2006, 124 (13), 134306). The use of such assumption in this study probably makes the upper limits of computed rate coefficients the true rate coefficients. The global PES for ozone is constructed by fitting 5906 ab initio data points using a 60-neuron two-layer feed-forward neural network. The mean-absolute error and root-mean-squared error of this fit are 0.0446 eV (1.03 kcal/mol) and 0.0756 eV (1.74 kcal/mol), respectively, which reveal very good fitting accuracy. The parameter coefficients of the global PES are reported in this paper. In order to identify the spin state with high confidence, we propose the use of a pattern-recognition neural network, which is trained to predict the spin state of a given configuration (with a prediction accuracy being 95.6% on a set of testing data points). To enhance the prediction effectiveness, a buffer series of five points are validated to confirm the spin state during the MD process to gain better confidence. Quasi-classical MD simulations from 1.2 to 2.4 eV of total internal energy (including zero-point energy) result in rate coefficients of singlet-triplet transformation in the range of 0.027 ps(-1) to 1.21 ps(-1). Also, we find very low dissociation probability up to 2.4 eV of internal energy during the investigating period (5 ps), which suggests that dissociation does not occur directly from the singlet ground-state, but it involves the excited triplet-state as an intermediate step and requires more reaction time to occur.

Current Recommendations on Returning to Youth Sports After COVID-19 Infection.

Children represent a small fraction of total cumulative cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. The potential health consequences related to infection for children are not inconsequential. For example, some may develop multisystem inflammatory syndrome in children, which is commonly associated with cardiovascular involvement. Nevertheless, the short- and long-term effects of SARS-CoV-2 infection remain unknown. In particular, the impact on physical health and how it affects one's ability to return to physical activity are continuously evolving. As more youth sports organizations are lifting restrictions, the volume of youth athletes will increase and the demand for providing medical clearance will grow. This article aims to provide a review of return to physical activity guidelines for young athletes post-SARS-CoV-2 infection based on expert consensus statements and professional organization recommendations. [Pediatr Ann. 2021;50(11):e461-e464.].

Ensemble effects on allylic oxidation within explicit solvation environments.

Umbrella-sampling density functional theory molecular dynamics (DFT-MD) has been employed to study the full catalytic cycle of the allylic oxidation of cyclohexene using a Cu(ii) 7-amino-6-((2-hydroxybenzylidene)amino)quinoxalin-2-ol complex in acetonitrile to create cyclohexenone and H2O as products. After the initial H-atom abstraction step, two different reaction pathways have been identified that are distinguished by the participation of alkyl hydroperoxide (referred to as the "open" cycle) versus the methanol side-product (referred to as the "closed" cycle) within the catalyst recovery process. Importantly, both pathways involve dehydrogenation and re-hydrogenation of the -NH2 group bound to the Cu-site - a feature that is revealed from the ensemble sampling of configurations of the reactive species that are stabilized within the explicit solvent environment of the simulation. Estimation of the energy span from the experimental turnover frequency yields an approximate value of 22.7 kcal mol-1 at 350 K. Whereas the closed cycle value is predicted to be 26.2 kcal mol-1, the open cycle value at 16.5 kcal mol-1. Both pathways are further consistent with the equilibrium between Cu(ii) and Cu(iii) that has previously been observed. In comparison to prior static DFT calculations, the ensemble of both solute and solvent configurations has helped to reveal a breadth of processes that underpin the full catalytic cycle yielding a more comprehensive understanding of the importance of radical reactions and catalysis recovery.

Comparison of the Limb-lead Electrocardiogram to the 12-Lead Electrocardiogram for Identifying Conditions Associated with Sudden Cardiac Death in Youth Athletes.

The optimal screening strategy to prevent sudden cardiac death (SCD) in athletes remains unknown. Pre-participation screening with electrocardiogram (ECG) remains controversial. The utility and accuracy of limb-lead (LL) ECG alone in identifying cardiac abnormalities associated with SCD has not been studied. This study was a comparative secondary data analysis, comparing the interpretation accuracy of 4 physicians evaluating publicly available ECGs of the most common cardiac conditions associated with SCD in athletes. Each physician interpreted a total of 100 ECGs: 50 normal ECGs (25 LL and 25 standard 12L) and 50 abnormal ECGs (25 LL and 25 standard 12L). The agreement between LL ECGs and 12L ECGs was assessed by Cohen's kappa coefficient and the accuracy of identifying an abnormal ECG was compared across LL and 12L ECGs using a chi-squared test. Inter-rater reliability was assessed by estimating the Fleiss's kappa coefficient. The sensitivity of LL ECG and 12L ECG was identical at 86%. The specificity of LL ECG was 75% (95% CI = 65% to 83%) and 12L ECG was 82% (95% CI = 73% to 89%). Substantial agreement was seen between LL ECG and 12L ECG interpretation across all readers (k = 0.63; 95% CI = 0.49 to 0.77). Interpretation accuracy was 81% (95% CI = 74% to 86%) and 84% (95% CI 78% to 89%) using LL ECG and 12L ECG, respectively (p = 0.43). In conclusion, the accuracy, sensitivity, and specificity were high and comparable for both LL ECG and 12L ECG in identifying cardiovascular conditions associated with SCD. Agreement between LL ECG and 12L ECG was substantial.