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, α λ T (in deg dm-1 [g/mL]-1 ), extracted for ambient vapor-phase samples of R-MBA [-11.031(98) and -2.29 (11)] and R-DMBA [-9.434 (72) and -1.350 (48)] at 355 and 633 nm were best reproduced by counterintuitive solvents of high polarity (yet low polarizability) like acetonitrile and methanol. Attempts to interpret observed spectral signatures quantitatively relied on the linear-response frameworks of density-functional theory (B3LYP, cam-B3LYP, and dispersion-corrected analogs) and coupled-cluster theory (CCSD), with variants of the polarizable continuum model (PCM) deployed to account for the effects of implicit solvation. Building on the identification of several low-lying equilibrium geometries (nine for R-MBA and three for R-DMBA), ensemble-averaged ORD profiles were calculated at T = 300 K by means of the independent-conformer ansatz, which enabled response properties predicted for the optimized structure of each isomer to be combined through Boltzmann-weighted population fractions derived from corresponding relative internal-energy or free-energy values, the latter of which stemmed from composite CBS-APNO and G4 analyses. Although reasonable accord between theory and experiment was realized for the isolated (vapor-phase) species, the solution-phase results were less satisfactory and tended to degrade progressively as the solvent polarity increased. These trends were attributed to solvent-mediated changes in structural parameters and energy metrics for the transition states that separate and putatively isolate the equilibrium conformations supported by the ground electronic potential-energy surface, with the resulting displacement of barrier locations and/or decrease of barrier heights compromising the underlying premise of the independent-conformer ansatz.

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 ab initio 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 ab initio instanton analysis reveal that the tunneling path does not pass through the instantaneous transition-state geometry. Instead, the tunneling process involves a multidimensional reaction coordinate with concerted reorganization of the heavy-atom skeletal framework to substantially reduce the donor-acceptor distance and drive the ensuing intramolecular proton-transfer event. The predicted tunneling-induced splittings for HFF isotopologues are in good agreement with experimental findings, leading to percentage deviations of only 20-40%. Our full-dimensional results allow us to characterize vibrational contributions along the tunneling path, highlighting the intrinsically multidimensional nature of the attendant hydron-migration dynamics.

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). In group 2, patients underwent serial debridement and placement of antibiotic beads until culture-negative wounds were achieved. Significantly more patients underwent muscle flap coverage in group 2 (27/31) compared with group 1 (7/22; P < 0.001). Data collected included demographics, comorbidities, intraoperative details, and outcomes, including patency, limb salvage, mortality, and number of procedures. Continuous variables were examined with Student's t-test, and dichotomous variables were examined with chi-squared test. Linear and logistic regressions were used to analyze factors associated with outcomes, in addition to Kaplan-Meier analysis with log rank for actuarial analysis. RESULTS: Both groups were similar with respect to demographics. The overall Kaplan-Meier 1- and 3-year survival rates were 66.2% and 34.1%, with no statistically significant difference between groups. The Kaplan-Meier 1- and 3-year limb salvage rates were 68.8% and 36.6% for group 1 vs. 58.5% and 38.7% for group 2 (P = not significant [NS]). The 1- and 3-year primary patency rates were 71% and 71% in traditional group 1 vs. 72% and 56% in group 2 (P = NS). One-year and 3-year secondary patency rates in traditional group 1 were 83% and 71% vs. 85% and 61% in group 2 (P = NS). Patients in group 1 underwent fewer total procedures when compared with group 2 (2.3 ± 0.2 vs. 5.1 ± 0.7, P = 0.03). The late reinfection rate was significantly less in group 1 (4.5%) compared with group 2 (26%; P = 0.04). Freedom from reinfection at 1 and 3 years were 94% and 94% in traditional group 1 vs. 74% and 62% in group 2 (P = 0.03). Multivariable analysis showed a higher incidence of amputation in patients who suffered reinfection (n = 13, P = 0.049). There was a higher mortality in patients with septic shock (n = 10, P = 0.007) and reinfection (n = 13, P = 0.036). Reinfection was associated with the highest mortality (P = 0.03). CONCLUSIONS: Conventional graft excision with extra-anatomic bypass resulted in similar mortality when compared with aggressive attempts at graft preservation and trended toward improved limb salvage and patency. However, attempts at graft preservation with antibiotic beads resulted in a significantly higher reinfection rate and greater number of procedures, and therefore, this approach should be used very selectively.

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. Materials and Methods Between August 2013 and March 2019, 72 participants with AAA and 56 healthy participants were enrolled in this prospective study. MRE examinations were performed to estimate AAA stiffness and the stiffness ratio between AAA and its adjacent remote normal aorta. Two Cox proportional hazards models were used to assess AAA stiffness and stiffness ratio for predicting aneurysmal events (subsequent repair, rupture, or diameter >5.0 cm). Log-rank tests were performed to determine a critical stiffness ratio suggesting high-risk AAAs. Baseline AAA stiffness and stiffness ratio were studied using Wilcoxon rank-sum tests between participants with and without aneurysmal events. Spearman correlation was used to investigate the relationship between stiffness and other potential imaging markers. Results Seventy-two participants with AAA (mean age, 71 years ± 9 [SD]; 56 men and 16 women) and 56 healthy participants (mean age, 42 years ± 16; 27 men and 29 women) were evaluated. In healthy participants, aortic stiffness positively correlated with age (ρ = 0.44; P < .001). AAA stiffness (event group [n = 21], 50.3 kPa ± 26.5 [SD]; no-event group [n = 21], 86.9 kPa ± 52.6; P = .01) and the stiffness ratio (event group, 0.7 ± 0.4; no-event group, 2.0 ± 1.4; P < .001) were lower in the event group than the no-event group at a mean follow-up of 449 days. AAA stiffness did not correlate with diameter in the event group (ρ = -0.06; P = .68) or the no-event group (ρ = -0.13; P = .32). AAA stiffness was inversely correlated with intraluminal thrombus area (ρ = -0.50; P = .01). Conclusion Lower abdominal aortic aneurysm stiffness and stiffness ratio measured with use of MR elastography was associated with aneurysmal events at a 15-month follow-up. © RSNA, 2022 See also the editorial by Sakuma in this issue.

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. METHODS: PR for the following 5 VS procedures and 4 VL studies were obtained from our billing department: CPT 34803 (Endovascular aortic repair, EVAR), 35301 (carotid endarterectomy, CEA), 35656 (lower extremity bypass, LEB), 36010 (introduction of catheter into vena cava, ICVC), 36200 first, 93922 (ankle brachial index, ABI), 93925 (lower extremity arterial duplex, LEA duplex), 93970 (lower extremity venous duplex, LEV Duplex), and 93990 (hemodialysis duplex). The data was organized by payer: Medicare, Medicaid, Commercial Insurers (CI), and Other. PR was studied pre-ACA (January 2008 through December 2009) and post-ACA (January 2015 through December 2016). The post-ACA PR and inflation adjusted reimbursement (IAR) in 2016 dollars using the consumer price index (CPI) were calculated and compared using one-sample t-test. The percent difference between the post-ACA PR and IAR was also compared. RESULTS: PR for 1,637 VS procedures and 16,333 VL studies was analyzed. The post-ACA PR was significantly lower than the IAR for most Medicare and Medicaid procedures. For EVAR, post-ACA reimbursement was overall on par with the IAR but significantly lower for Medicare. For CEA, post-ACA reimbursement was overall lower than IAR. For LEB, overall average PR was lower than IAR, with statistically significant lower Medicare and Medicaid (P < 0.001) payments. For ICAo, overall PR was significantly lower than the IAR and this was true across all insurance types. In contrast, for ICV, the post-ACA reimbursement was higher than IAR for all payers but did not reach statistical significance (P = 0.25). The post-ACA PR was significantly higher than the IAR for most VL studies, except for Medicare PR. The percent change for VS procedures were mostly negative for the Medicaid and Medicare groups. This results in potential annual shortcomings of $2, 862 and $20,923 respectively. CONCLUSION: When comparing reimbursement before and after ACA implementation, Medicare and Medicaid PR for most VS procedures has not kept up with inflation. However, for most VL procedures, PR has exceeded inflation. Further efforts are needed to support Vascular Surgery reimbursement including higher valuation of the Medicare Conversion factor.

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. Clinical features that distinguish PAES from other causes of leg pain include a sensation of coolness of the posterior leg during exercise and associated paresthesia of the plantar aspect of the foot. Physical examination often reveals decreased intensity of the posterior tibial or dorsalis pedis pulses with passive dorsiflexion or active plantarflexion of the ankle. Diagnostic tests that confirm the presence of PAES include lower extremity angiography during active resisted plantarflexion or maximal passive dorsiflexion, and magnetic resonance angiography done after exercise provocation. Nonsurgical treatment with physical therapy and stretching of the gastrocnemius complex should be done as the first line of treatment. When conservative treatments are ineffective, referral to a vascular specialist for surgical intervention with a muscular band excision or transection, vascular bypass, or arterial reconstruction is necessary.

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, (R)-2-methylpyrrolidine (R-2MPY) and (S)-2-methylpiperidine (S-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. Chiroptical signatures predicted for these species were combined through an independent-conformer ansatz to simulate the ensemble-averaged response, with a polarizable continuum model (PCM) being used to treat implicit solute-solvent interactions. The intrinsic behavior observed for isolated (gaseous) R-2MPY and S-2MPI was reproduced best by merging coupled-cluster (CCSD) estimates of rotatory powers with thermal population fractions deduced from complete basis set (CBS-APNO) free-energy calculations. Although prior claims of sizable chiroptical contributions arising from helically twisted (chiral) heterocyclic frameworks could be discounted, less satisfactory agreement between experiment and theory was realized for solution phases. Response properties sustained modest isomer-dependent changes in the presence of PCM solvation, but the corresponding energy metrics showed systematic trends, whereby structures having larger electric-dipole moments were stabilized preferentially in media of high polarity. Despite the fact that R-2MPY conformations were predicted to undergo a progressive reordering of their relative energies across the six solvents of interest, S-2MPI was found to exhibit more pronounced solvent-induced perturbations at long wavelengths (viz., in regions far removed from electronic resonances). Experimental results are discussed in terms of the distinct ring-puckering mechanisms for R-2MPY and S-2MPI, which are expected to be dominated by hindered pseudorotation among envelope/twist motifs and semi-inversion between chairlike antipodes, respectively.

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). • In-person evaluation and treatment for neurogenic TOS (interventional or surgical) are generally postponed during all pandemic phases, with telephone/telemedicine visits and at-home physical therapy exercises recommended when feasible. • Venous TOS presenting with acute upper extremity deep venous thrombosis (Paget-Schroetter syndrome) is managed primarily with anticoagulation, with percutaneous interventions for venous TOS (thrombolysis) considered in early phases (I and II) and surgical treatment delayed until pandemic conditions resolve. Catheter-based interventions may also be considered for selected patients with central subclavian vein obstruction and threatened hemodialysis access in all pandemic phases, with definitive surgical treatment postponed. • Evaluation and surgical treatment for arterial TOS should be reserved for limb-threatening situations, such as acute upper extremity ischemia or acute digital embolization, in all phases of pandemic response. In late pandemic phases, surgery should be restricted to thrombolysis or brachial artery thromboembolectomy, with more definitive treatment delayed until pandemic conditions resolve.

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. After a process improvement strategy, we chose to review progress in our vascular laboratory related to time to interpretation (TI), patient check-in to study completion (study time), wait time for first available outpatient venous duplex scan (wait time), technologist productivity, and critical results reporting. METHODS: Data from our hospital-based vascular laboratory were collected from 2010 to 2016. TI was collected through our reporting software VascuPro (Consensus Medical), and study time and wait time were obtained from electronic medical records (EMR) (Epic). Technologist productivity was calculated by commercially available productivity tools, and compliance with critical results reporting was calculated quarterly as per our quality assurance program. Appropriateness of carotid duplex scan testing was performed by expert review of International Classification of Disease codes used to request the test. RESULTS: TI analysis comprised 91,352 studies with a mean of 3.3 hr between test completion and final interpretation. The TI improved from 5.0 to 2.1 hr on weekdays and was longer on weekends (4.9 hr; P < 0.001). The study time improved from 29.8 to 27.2 min and was 14.9 min shorter on the weekends (P < 0.001). The wait time ranged from a mean of 1-2.08 days. Technologist productivity improved from 90.7% to 93.6%. Critical results reporting quarterly audits showed a 100% compliance rate. On expert review, the International Classification of Disease code on carotid duplex scan requests in the EMR was deemed inaccurate in 17.4% of cases. CONCLUSIONS: TI and study time improved; wait time and critical results reporting remained steady. Most of the data are readily available in a vascular laboratory standard EMR. The plan-do-study-act (PDSA or Shewhart Cycle) principle is critical to process improvement and needed as we transition from traditional accreditation mostly based on test accuracy to one demanding efficiency, timeliness, patient satisfaction, productivity, accountability, and appropriateness of testing. Process improvement studies will improve patient care and satisfaction, increase efficiency and throughput, while satisfying changing IAC standards and preparing for upcoming regulatory requirements of the MACRA.

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. Although older or less active people may tolerate the lower volume flow of a long segment extra-anatomic bypass, there is growing evidence that a subset of patients will be symptomatic from reduced flow volumes. Here we present 3 patients in whom symptomatic relief was achieved with the addition of a contralateral axillary femoral bypass and ligation of the previous femorofemoral component.

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 Ã1B2-X̃1A1 (π* ← π) absorption system of 6-hydroxy-2-formylfulvene (HFF) and its monodeuterated isotopolog (HFF-d) 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 X̃1A1 and Ã1B2 manifolds, yet a radical alteration in the nature of the reaction coordinate, whereby the planar (C2v) transition-state configuration of the former is supplanted by a notably aplanar (C2) 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 X̃1A1 potential surface, the present measurements have revealed surprisingly regular patterns of Ã1B2 vibronic structure which are devoid of obvious band shifts/splittings that would be indicative of efficient proton-transfer processes. Detailed analyses enabled a total of 41 (6) and 28 (5) excited-state vibrational levels (fundamentals) to be assigned for HFF and HFF-d, with extensive activity found for modes involving displacement of the seven-membered chelate ring that harbors the O-H···O reaction center. Quantitative simulations of partially resolved rotational contours for the HFF origin band showed the transition dipole moment to possess hybrid type-a/b character, thereby allowing the tunneling-induced bifurcation of the vibrationless Ã1B2 level to be extracted, Δ0à = 0.119(11) cm-1. This represents an enormous (>1000-fold) decrease over the analogous ground-state metric and implies a pronounced quenching of excited-state hydron migration, in keeping with the kinematic penalties that would be exacted by requisite heavy-atom motion along a putatively aplanar reaction coordinate.

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. This led to optical rotatory dispersion profiles that reproduced the overall shape of observations but failed to achieve uniform agreement with measured specific-rotation values even when anharmonic vibrational corrections were applied. A mixed QM/FQ paradigm, whereby quantum-mechanical (QM) calculations of optical activity were combined with classical molecular dynamics simulations of explicit solvation that included mutual-polarization effects by means of fluctuating charges (FQ), was enlisted to elucidate the microsolvation environment and gauge its impact upon conformer distributions and response properties. Although quantitative accord with experiments remained elusive, this approach revealed strong variations in the magnitude and sign of rotatory powers for R-GME as the configuration of surrounding water molecules evolved, thereby highlighting the inherently dynamical nature of the solvated chiroptical response, calling into question the validity of "static" descriptions based on the presumption of distinct energy minima, and giving insight into the inherent complexity posed by the modeling of such properties for solvated systems.

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-1). Quantitative analyses yield unusual deuterium kinetic isotope effects that straddle limiting values attributed to above-barrier vibration and below-barrier tunneling of the proton adjoining donor/acceptor sites. Our findings provide compelling experimental evidence for ultrafast hydron-migration events commensurate with the onset of low-barrier hydrogen bonding and afford a trenchant glimpse of molecular phenomena taking place at the "tipping point" between disparate dynamical regimes.

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). Across the various theoretical methods surveyed, CCSD with the modified velocity gauge provided the best overall performance for both isolated and solvated conditions. Zero-point vibrational corrections to equilibrium calculations of chiroptical response tended to improve agreement with gas-phase experiments, but the quality of performance realized for solutions varied markedly. Direct comparison of measured and predicted specific-rotation suggests that PCM, in general, is not able to reproduce attendant solvent shifts (neither between gas and solution phases nor among solvents) and fares better in estimating actual medium-dependent values of this property (although the error is rather system dependent). Thus, more elaborate solvation models seem necessary for a proper theoretical description of solvation in dispersive optical activity.

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. Thus, we sought to investigate the use of thrombolysis versus anticoagulation alone, timing of FRR following thrombolysis, post-FRR venous intervention, and FRR for McCleery syndrome (MCS) and their impact on patient symptoms and return to function. All patients undergoing FRR for VTOS at our institution from 4 April 2000 through 31 December 2013 were reviewed. Demographics, symptoms, diagnostic and treatment details, and outcomes were collected. Per "Reporting Standards of the Society for Vascular Surgery for Thoracic Outlet Syndrome", symptoms were described as swelling/discoloration/heaviness, collaterals, concomitant neurogenic symptoms, and functional impairment. Patient-reported response to treatment was defined as complete (no residual symptoms and return to function), partial (any residual symptoms present but no functional impairment), temporary (initial improvement but subsequent recurrence of any symptoms or functional impairment), or none (persistent symptoms or functional impairment). Sixty FRR were performed on 59 patients. 54.2% were female with a mean age of 34.3 years. Swelling/discoloration/heaviness was present in all but one patient, deep vein thrombosis in 80%, and visible collaterals in 41.7%. Four patients had pulmonary embolus while 65% had concomitant neurogenic symptoms. In addition, 74.6% of patients were anticoagulated and 44.1% also underwent thrombolysis prior to FRR. Complete or partial response occurred in 93.4%. Of the four patients with temporary or no response, further diagnostics revealed residual venous disease in two and occult alternative diagnoses in two. Use of thrombolysis was not related to FRR outcomes (p = 0.600). Performance of FRR less than or greater than six weeks after the initiation of anticoagulation or treatment with thrombolysis was not related to FRR outcomes (p = 1). Whether patients had DVT or MCS was not related to FRR outcomes (p = 1). No patient had recurrent DVT. From a patient-centered, patient-reported standpoint, VTOS is equally effectively treated with FRR regardless of preoperative thrombolysis or timing of surgery after thrombolysis. A conservative approach to venous interrogation and intervention after FRR is safe and effective for symptom control and return to function. Additionally, patients with MCS are effectively treated with FRR.

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 ± 5.5 and 390.4 ± 3.7 deg dm-1 (g/mL)-1) were found to be factors of 3.9 and 2.1 smaller in magnitude than analogous quantities obtained for the kindred enone, (R)-norbornenone (R-NBO), reflecting, in part, the loss of prominent magnetic-dipole contributions from the C═O moiety and the exclusion of electron delocalization from the oxygen lone pairs. The wavelength-resolved rotatory powers of R-MNB were enhanced dramatically (by ∼40% on average) upon dissolution in any of the four common solvents targeted by the present study (acetonitrile, di-n-butylether, cyclohexane, and chloroform), yet displayed only a slight dependence on the exact nature of the surrounding liquid (±2.7% variation from the mean at 589.3 nm). Quantum-chemical calculations built upon the linear-response frameworks of density-functional theory and coupled-cluster theory were enlisted to interpret experimental results, with the substantial effects incurred by nonspecific solvation phenomena being explored through use of polarizable continuum models and bulk property-response relationships. Aside from enumerating the varied quality of agreement attained between computational predictions and polarimetric measurements, these efforts have found that refractive-index correlations, akin to those embodied in the venerable (albeit often discounted) Lorentz local-field correction, afford a viable means of linking the chiroptical behavior of R-MNB across phases.

Vibrational self-consistent field theory using optimized curvilinear coordinates.

A vibrational SCF model is presented in which the functions forming the single-mode functions in the product wavefunction are expressed in terms of internal coordinates and the coordinates used for each mode are optimized variationally. This model involves no approximations to the kinetic energy operator and does not require a Taylor-series expansion of the potential. The non-linear optimization of coordinates is found to give much better product wavefunctions than the limited variations considered in most previous applications of SCF methods to vibrational problems. The approach is tested using published potential energy surfaces for water, ammonia, and formaldehyde. Variational flexibility allowed in the current ansätze results in excellent zero-point energies expressed through single-product states and accurate fundamental transition frequencies realized by short configuration-interaction expansions. Fully variational optimization of single-product states for excited vibrational levels also is discussed. The highlighted methodology constitutes an excellent starting point for more sophisticated treatments, as the bulk characteristics of many-mode coupling are accounted for efficiently in terms of compact wavefunctions (as evident from the accurate prediction of transition frequencies).