Isolated and solvated chiroptical behavior in conformationally flexible butanamines.

The nonresonant optical activity of two highly flexible aliphatic amines, (2R)-3-methyl-2-butanamine (R-MBA) and (2R)-(3,3)-dimethyl-2-butanamine (R-DMBA), has been probed under isolated and solvated conditions to examine the roles of conformational isomerism and to explore the influence of extrinsic perturbations. The optical rotatory dispersion (ORD) measured in six solvents presented uniformly negative rotatory powers over the 320-590 nm region, with the long-wavelength magnitude of chiroptical response growing nearly monotonically as the dielectric constant of the surroundings diminished. The intrinsic specific optical rotation, (in deg dm [g/mL] ), extracted for ambient vapor-phase samples of R-MBA [-11.

Proton-Tunneling Dynamics along Low-Barrier Hydrogen Bonds: A Full-Dimensional Instanton Study of 6-Hydroxy-2-formylfulvene.

Understanding the dynamics of proton transfer along low-barrier hydrogen bonds remains an outstanding challenge of great fundamental and practical interest, reflecting the central role of quantum effects in reactions of chemical and biological importance. Here, we combine calculations with the semiclassical ring-polymer instanton method to investigate tunneling processes on the ground electronic state of 6-hydroxy-2-formylfulvene (HFF), a prototypical neutral molecule supporting low-barrier hydrogen-bonding. The results emerging from a full-dimensional instanton analysis reveal that the tunneling path does not pass through the instantaneous transition-state geometry.

Extra-Anatomic Bypass and Excision is Superior to Graft Salvage Attempts with Antibiotic Beads to Treat Vascular Graft Infections in the Groin.

Background: This study aimed to determine if conventional extra-anatomic bypass and graft removal versus aggressive attempts at graft preservation have better survival and limb salvage in patients with localized groin wound infections of vascular grafts.

Methods: We conducted a retrospective review of 53 consecutive patients with vascular graft infections presenting in the groin. Treatment groups consisted of group 1 (extra-anatomic bypass and graft excision, n = 22) and group 2 (initial graft preservation attempts with utilization of antibiotic beads, n = 31).

MR Elastography of Abdominal Aortic Aneurysms: Relationship to Aneurysm Events.

Background Abdominal aortic aneurysm (AAA) diameter remains the standard clinical parameter to predict growth and rupture. Studies suggest that using solely AAA diameter for risk stratification is insufficient. Purpose To evaluate the use of aortic MR elastography (MRE)-derived AAA stiffness and stiffness ratio at baseline to identify the potential for future aneurysm rupture or need for surgical repair.

Physician Reimbursement for Vascular Surgery Procedures and Vascular Laboratory Studies Before and After the Affordable Care Act.

Objectives: The Patient Protection and Affordable Care Act (ACA), fully implemented by 2015, has significantly increased the number of Americans with health insurance. However, its impact on physician reimbursement (PR) is not well studied. Our objective was to determine the ACA's impact on the professional component of PR for selected vascular surgery (VS) procedures and vascular laboratory (VL) studies at our institution.

Cardiac resynchronization therapy defibrillators in patients with permanent atrial fibrillation.

Aims: There are conflicting data on the benefit of cardiac resynchronization therapy (CRT) in heart failure (HF) patients with permanent atrial fibrillation (AF). We aimed to compare patient outcomes according to the presence or absence of permanent AF at device implantation.

Methods And Results: We retrospectively analysed remote monitoring data from 1141 CRT defibrillators.

Optical Activity in Saturated Cyclic Amines: Untangling the Roles of Nitrogen-Inversion and Ring-Puckering Dynamics.

The dispersive optical activity of two saturated cyclic amines, ()-2-methylpyrrolidine (-2MPY) and ()-2-methylpiperidine (-2MPI), has been interrogated under isolated and solvated conditions to elucidate the roles of large-amplitude motion associated with nitrogen-center inversion and ring-puckering dynamics. Experimental optical rotatory dispersion profiles were almost mirror images of one another and displayed parallel solvent dependencies. Quantum-chemical analyses built on density-functional and coupled-cluster methods revealed four low-lying conformers for each molecule, which are distinguished by axial/equatorial orientations of their amino hydrogens and methyl substituents.

Popliteal Artery Entrapment Syndrome: A Diagnostic and Treatment Enigma for Orthopaedic Surgeons.

Popliteal artery entrapment syndrome (PAES) is an uncommon condition that causes recurrent posterior leg pain and foot paresthesia in running athletes. This condition occurs most commonly due to an accessory or abnormal implant of the medial head of the gastrocnemius muscle. It may mimic or coincide with other chronic conditions of the lower extremity including chronic exertional compartment syndrome but is most consistent with vascular claudication.

Evaluation and treatment of thoracic outlet syndrome during the global pandemic due to SARS-CoV-2 and COVID-19.

The global SARS-CoV-2/COVID-19 pandemic has required a reduction in nonemergency treatment for a variety of disorders. This report summarizes conclusions of an international multidisciplinary consensus group assembled to address evaluation and treatment of patients with thoracic outlet syndrome (TOS), a group of conditions characterized by extrinsic compression of the neurovascular structures serving the upper extremity. The following recommendations were developed in relation to the three defined types of TOS (neurogenic, venous, and arterial) and three phases of pandemic response (preparatory, urgent with limited resources, and emergency with complete diversion of resources).

Addition of Efficiency Measures to Current Accuracy Measures in the Vascular Laboratory Can Be Used for Future Accreditation and Payment Models.

Background: The Medicare Access and CHIP Reauthorization Act (MACRA) brings with it increased regulatory requirements not traditionally addressed by standard vascular laboratory accreditation, which is based on accuracy. The new quality improvement project of the Intersocietal Accreditation Commission (IAC) may satisfy an improvement activity (IA) of the MACRA. We hypothesize that other IAs in the MACRA such as timeliness of test results or patient care quality performance requirements can be met by analyzing data already being collected by the vascular laboratory.

Approaches to the Salvage of Axillary Bilateral Femoral Bypass in Patients with Claudication due to Demand Ischemia.

The axillary bilateral femoral bypass is often utilized as an alternative to in-line aortic reconstruction in patients with multiple medical comorbidities, who would be unable to tolerate open abdominal surgery with an aortic clamp, or patients with mycotic aneurysms, or infected grafts. Idealized fluid mechanics suggest that there would be equal flow in an axillary bilateral femoral bypass when compared to in-line reconstruction. However, in a non-idealized state, friction results in kinetic energy loss and decreased volume flow to the lower extremities in the longer, smaller diameter graft.

Hydrogen-Bonding Motifs and Proton-Transfer Dynamics in Electronically Excited 6-Hydroxy-2-formylfulvene.

To elucidate low-barrier hydrogen-bonding (LBHBing) motifs and their ramifications for hydron-migration dynamics, the B-A (π* ← π) absorption system of 6-hydroxy-2-formylfulvene (HFF) and its monodeuterated isotopolog (HFF-) has been probed under free-jet expansion conditions through synergistic application of fluorescence-based laser spectroscopy and quantum-chemical calculations. Neither the donor-acceptor distance nor the proton-transfer barrier is predicted to change markedly between the A and B manifolds, yet a radical alteration in the nature of the reaction coordinate, whereby the planar () transition-state configuration of the former is supplanted by a notably aplanar () form in the latter, is suggested to take place following π* ← π electron promotion (owing, in part, to attendant rearrangements of π-electron conjugation about the molecular framework). In contrast to the strongly perturbed vibrational landscape (commensurate with LBHBing) reported for the A potential surface, the present measurements have revealed surprisingly regular patterns of B vibronic structure which are devoid of obvious band shifts/splittings that would be indicative of efficient proton-transfer processes.

A combined experimental and theoretical study of optical rotatory dispersion for (R)-glycidyl methyl ether in aqueous solution.

The dispersive optical activity for aqueous solutions of non-rigid (R)-glycidyl methyl ether (R-GME) has been explored synergistically from experimental and theoretical perspectives. Density functional theory analyses performed with the polarizable continuum model for implicit solvation identified nine low-lying stable conformers that are interconverted by rotation about two large-amplitude torsional coordinates. The antagonistic chiroptical signatures predicted for these structural isomers were averaged under a Boltzmann-weighting ansatz to estimate the behavior expected for a thermally equilibrated ensemble.

Spectral Signatures of Proton-Transfer Dynamics at the Cusp of Low-Barrier Hydrogen Bonding.

Despite their importance in diverse chemical and biochemical processes, low-barrier hydrogen bonds remain elusive targets to classify and interpret spectroscopically. Here the correlated nature of hydrogen bonding and proton transfer in the low-barrier regime has been probed for the ground and excited electronic states of 6-hydroxy-2-formylfulvene by acquiring jet-cooled fluorescence spectra of the parent and monodeuterated isotopologs. While excited-state profiles reveal regular vibronic patterns devoid of obvious dynamical signatures, their ground-state counterparts display a radically altered energy landscape characterized by spectral bifurcations comparable in magnitude to typical vibrational spacings (>100 cm).

Fixed-Node, Importance-Sampling Diffusion Monte Carlo for Vibrational Structure with Accurate and Compact Trial States.

We present a new approach to importance sampling in diffusion Monte-Carlo (DMC) simulations of vibrational excited states whereby the trial wave functions for low-energy states are incorporated into the diffusion equations so as to enforce their orthogonality. For the model systems examined here, simple variational wave functions based on the vibrational self-consistent field (VSCF) and the simplest vibrational configuration interaction (VCI) are effective in importance sampling provided that internal coordinates used in the underlying one-particle functions have been variationally optimized. The resulting model yields results comparable in accuracy to the best unguided DMC calculations without requiring an a priori choice of coordinates to specify nodal hyperplanes.

Comparison of measured and predicted specific optical rotation in gas and solution phases: A test for the polarizable continuum model of solvation.

A comparative theoretical and experimental study of dispersive optical activity is presented for a set of small, rigid organic molecules in gas and solution phases. Target species were chosen to facilitate wavelength-resolved measurements of specific rotation in rarefied vapors and in organic solvents having different polarities, while avoiding complications due to conformational flexibility. Calculations were performed with two density functionals (B3LYP and CAM-B3LYP) and with the coupled-cluster singles and doubles (CCSD) ansatz, and solvent effects were included through use of the polarizable continuum model (PCM).

A Patient-Centered Approach to Guide Follow-Up and Adjunctive Testing and Treatment after First Rib Resection for Venous Thoracic Outlet Syndrome Is Safe and Effective.

Controversies in the treatment of venous thoracic outlet syndrome (VTOS) have been discussed for decades, but still persist. Calls for more objective reporting standards have pushed practice towards comprehensive venous evaluations and interventions after first rib resection (FRR) for all patients. In our practice, we have relied on patient-centered, patient-reported outcomes to guide adjunctive treatment and measure success.

Thermal transport in epitaxial Si Ge alloy nanowires with varying composition and morphology.

We report on structural, compositional, and thermal characterization of self-assembled in-plane epitaxial Si Ge alloy nanowires grown by molecular beam epitaxy on Si (001) substrates. The thermal properties were studied by means of scanning thermal microscopy (SThM), while the microstructural characteristics, the spatial distribution of the elemental composition of the alloy nanowires and the sample surface were investigated by transmission electron microscopy and energy dispersive x-ray microanalysis. We provide new insights regarding the morphology of the in-plane nanostructures, their size-dependent gradient chemical composition, and the formation of a 5 nm thick wetting layer on the Si substrate surface.

Dispersive Optical Activity of (R)-Methylene Norbornene: Intrinsic Response and Solvation Effects.

The dispersive optical activity of a homoconjugated bicyclic diene, (R)-methylene norbornene (R-MNB), was interrogated under complementary vapor-phase and solution-phase conditions to elucidate the structural/electronic provenance of its unusual chiroptical signatures and to explore the marked influence of environmental perturbations. The intrinsic (isolated-molecule) values of specific rotation measured at 355 and 633 nm (1623.5 ± 5.

Ultrasound-Guided Thrombin Injection Is a Safe and Effective Treatment for Femoral Artery Pseudoaneurysm in the Morbidly Obese.

Introduction: Ultrasound-guided thrombin injection (UGTI) is a well-established practice for the treatment of femoral artery pseudoaneurysm. This procedure is highly successful but dependent on appropriate pseudoaneurysm anatomy and adequate ultrasound visualization. Morbid obesity can present a significant technical challenge due to increased groin adiposity, resulting in poor visualization of critical structures needed to safely perform the procedure.