Successful Extracorporeal Cardiopulmonary Resuscitation Despite Aortic Occlusion.

We present the case of a 62-year-old man with severe coronary artery disease who presented to the hospital in refractory ventricular fibrillation cardiac arrest. He showed signs of life despite prolonged resuscitation. We thus decided to initiate extracorporeal cardiopulmonary resuscitation (ECPR). The patient had a known total occlusion of his infrarenal aorta that had been surgically bypassed with a bifemoral-axillary graft. We successfully initiated ECPR via the surgical graft, establishing blood flow to the central circulation through the axillary artery in a peripheral configuration while ensuring blood flow to the left leg via the femoral-femoral graft. The patient was extubated neurologically intact the following day and subsequently underwent coronary artery bypass graft surgery while on extracorporeal membrane oxygenation (ECMO) support. He was subsequently weaned off inotropic support and decannulated from ECMO. He was discharged home neurologically intact and independent in his activities of daily living. This case demonstrates that cannulation for ECPR via a surgical vascular graft is possible and that a total occlusion of the infrarenal aorta in the presence of a surgical bypass is not an absolute contraindication to ECMO.

Venoarterial Extracorporeal Membrane Oxygenation for "Protected" Percutaneous Coronary Intervention Secondary to Refractory Polymorphic Ventricular Tachycardia and Cardiac Arrest.

ABSTRACT: We present a case of cardiogenic shock secondary to refractory polymorphic ventricular tachycardia associated with coronary ischemia resulting in cardiac arrest. Following the return of spontaneous circulation, the patient was cannulated for peripheral venoarterial extracorporeal membrane oxygenation (V-A ECMO) in anticipation of high-risk "protected" percutaneous coronary intervention (PCI). Under full V-A ECMO support, inotropes and vasopressors were weaned off, and the patient underwent uneventful PCI of left circumflex and obtuse marginal lesions. After 48 hours, the patient was decannulated and could be discharged home alive 16 days after his initial cardiac arrest.

Impact of parenteral nutrition guideline implementation on growth of very low-birth-weight infants in a neonatal intensive care unit.

BACKGROUND: In preterm neonates, parenteral nutrition (PN) is utilized to provide adequate energy and maintain the expected growth rate of a fetus. To optimize growth, our institution implemented comprehensive guidelines for prescribing PN. This study compared the effect of this change on growth outcomes of very low-birth-weight (VLBW) infants at 28 days' postnatal age (PNA). METHODS: Neonates <1250 g who received PN for >7 days were divided into preimplementation and postimplementation cohorts based on date of birth. The primary objective was to compare the average weight velocity (g/kg/day) of neonates at 28 days' PNA. Secondary objectives included identifying the average number of days to regain birth weight and comparing the percentage of infants above the 10th percentile for weight for age at 28 days with those at baseline. RESULTS: There were 204 neonates in cohort 1 (before implementation) and 176 neonates in cohort 2 (after). No difference in weight velocity was identified (12.9 ± 5.2 vs 12.1 ± 4.9 g/kg/day; P = .177). No difference was detected in days to regain birth weight (9.2 ± 4.6 vs 9.9 ± 4.7; P = .909) or in the percentage of patients above the 10th percentile for weight for age (birth: 85.3% vs 83.5% [P = .634]; 28 days: 73% vs 64.8% [P = .082]). CONCLUSION: No difference was observed in the weight velocity of VLBW neonates <1250 g at birth when using the implemented guideline for PN prescription writing at our institution.

Magnetic Exchange Couplings in Heterodinuclear Complexes Based on Differential Local Spin Rotations.

We analyze the performance of a new method for the calculation of magnetic exchange coupling parameters for the particular case of heterodinuclear transition metals complexes of Cu, Ni, and V. This method is based on a generalized perturbative approach which uses differential local spin rotations via formal Lagrange multipiers (Phillips, J. J.; Peralta, J. E. J. Chem. Phys. 2013, 138, 174115). The reliability of the calculated couplings has been assessed by comparing with results from traditional energy differences with different density functional approximations and with experimental values. Our results show that this method to calculate magnetic exchange couplings can be reliably used for heteronuclear transition metal complexes, and at the same time, that it is independent from the different mapping schemes used in energy difference methods.

Efficient Temperature-Dependent Green's Functions Methods for Realistic Systems: Compact Grids for Orthogonal Polynomial Transforms.

The Matsubara Green's function that is used to describe temperature-dependent behavior is expressed on a numerical grid. While such a grid usually has a couple of hundred points for low-energy model systems, for realistic systems with large basis sets the size of an accurate grid can be tens of thousands of points, constituting a severe computational and memory bottleneck. In this paper, we determine efficient imaginary time grids for the temperature-dependent Matsubara Green's function formalism that can be used for calculations on realistic systems. We show that, because of the use of an orthogonal polynomial transform, we can restrict the imaginary time grid to a few hundred points and reach micro-Hartree accuracy in the electronic energy evaluation. Moreover, we show that only a limited number of orthogonal polynomial expansion coefficients are necessary to preserve accuracy when working with a dual representation of the Green's function or self-energy and transforming between the imaginary time and frequency domain.

Fractional charge and spin errors in self-consistent Green's function theory.

We examine fractional charge and spin errors in self-consistent Green's function theory within a second-order approximation (GF2). For GF2, it is known that the summation of diagrams resulting from the self-consistent solution of the Dyson equation removes the divergences pathological to second-order Møller-Plesset (MP2) theory for strong correlations. In the language often used in density functional theory contexts, this means GF2 has a greatly reduced fractional spin error relative to MP2. The natural question then is what effect, if any, does the Dyson summation have on the fractional charge error in GF2? To this end, we generalize our previous implementation of GF2 to open-shell systems and analyze its fractional spin and charge errors. We find that like MP2, GF2 possesses only a very small fractional charge error, and consequently minimal many electron self-interaction error. This shows that GF2 improves on the critical failings of MP2, but without altering the positive features that make it desirable. Furthermore, we find that GF2 has both less fractional charge and fractional spin errors than typical hybrid density functionals as well as random phase approximation with exchange.

Local Hamiltonians for quantitative Green's function embedding methods.

Embedding calculations that find approximate solutions to the Schrödinger equation for large molecules and realistic solids are performed commonly in a three step procedure involving (i) construction of a model system with effective interactions approximating the low energy physics of the initial realistic system, (ii) mapping the model system onto an impurity Hamiltonian, and (iii) solving the impurity problem. We have developed a novel procedure for parametrizing the impurity Hamiltonian that avoids the mathematically uncontrolled step of constructing the low energy model system. Instead, the impurity Hamiltonian is immediately parametrized to recover the self-energy of the realistic system in the limit of high frequencies or short time. The effective interactions parametrizing the fictitious impurity Hamiltonian are local to the embedded regions, and include all the non-local interactions present in the original realistic Hamiltonian in an implicit way. We show that this impurity Hamiltonian can lead to excellent total energies and self-energies that approximate the quantities of the initial realistic system very well. Moreover, we show that as long as the effective impurity Hamiltonian parametrization is designed to recover the self-energy of the initial realistic system for high frequencies, we can expect a good total energy and self-energy. Finally, we propose two practical ways of evaluating effective integrals for parametrizing impurity models.

Communication: the description of strong correlation within self-consistent Green's function second-order perturbation theory.

We report an implementation of self-consistent Green's function many-body theory within a second-order approximation (GF2) for application with molecular systems. This is done by iterative solution of the Dyson equation expressed in matrix form in an atomic orbital basis, where the Green's function and self-energy are built on the imaginary frequency and imaginary time domain, respectively, and fast Fourier transform is used to efficiently transform these quantities as needed. We apply this method to several archetypical examples of strong correlation, such as a H32 finite lattice that displays a highly multireference electronic ground state even at equilibrium lattice spacing. In all cases, GF2 gives a physically meaningful description of the metal to insulator transition in these systems, without resorting to spin-symmetry breaking. Our results show that self-consistent Green's function many-body theory offers a viable route to describing strong correlations while remaining within a computationally tractable single-particle formalism.

Magnetic exchange couplings from noncollinear perturbation theory: dinuclear CuII complexes.

To benchmark the performance of a new method based on noncollinear coupled-perturbed density functional theory [J. Chem. Phys. 138, 174115 (2013)], we calculate the magnetic exchange couplings in a series of triply bridged ferromagnetic dinuclear Cu(II) complexes that have been recently synthesized [Phys. Chem. Chem. Phys. 15, 1966 (2013)]. We find that for any basis-set the couplings from our noncollinear coupled-perturbed methodology are practically identical to those of spin-projected energy-differences when a hybrid density functional approximation is employed. This demonstrates that our methodology properly recovers a Heisenberg description for these systems, and is robust in its predictive power of magnetic couplings. Furthermore, this indicates that the failure of density functional theory to capture the subtle variation of the exchange couplings in these complexes is not simply an artifact of broken-symmetry methods, but rather a fundamental weakness of current approximate density functionals for the description of magnetic couplings.

Towards the blackbox computation of magnetic exchange coupling parameters in polynuclear transition-metal complexes: theory, implementation, and application.

We present a method for calculating magnetic coupling parameters from a single spin-configuration via analytic derivatives of the electronic energy with respect to the local spin direction. This method does not introduce new approximations beyond those found in the Heisenberg-Dirac Hamiltonian and a standard Kohn-Sham Density Functional Theory calculation, and in the limit of an ideal Heisenberg system it reproduces the coupling as determined from spin-projected energy-differences. Our method employs a generalized perturbative approach to constrained density functional theory, where exact expressions for the energy to second order in the constraints are obtained by analytic derivatives from coupled-perturbed theory. When the relative angle between magnetization vectors of metal atoms enters as a constraint, this allows us to calculate all the magnetic exchange couplings of a system from derivatives with respect to local spin directions from the high-spin configuration. Because of the favorable computational scaling of our method with respect to the number of spin-centers, as compared to the broken-symmetry energy-differences approach, this opens the possibility for the blackbox exploration of magnetic properties in large polynuclear transition-metal complexes. In this work we outline the motivation, theory, and implementation of this method, and present results for several model systems and transition-metal complexes with a variety of density functional approximations and Hartree-Fock.

The place of solar power: an economic analysis of concentrated and distributed solar power.

BACKGROUND: This paper examines the cost and benefits, both financial and environmental, of two leading forms of solar power generation, grid-tied photovoltaic cells and Dish Stirling Systems, using conventional carbon-based fuel as a benchmark. METHODS: First we define how these solar technologies will be implemented and why. Then we delineate a model city and its characteristics, which will be used to test the two methods of solar-powered electric distribution. Then we set the constraining assumptions for each technology, which serve as parameters for our calculations. Finally, we calculate the present value of the total cost of conventional energy needed to power our model city and use this as a benchmark when analyzing both solar models' benefits and costs. RESULTS: The preeminent form of distributed electricity generation, grid-tied photovoltaic cells under net-metering, allow individual homeowners a degree of electric self-sufficiency while often turning a profit. However, substantial subsidies are required to make the investment sensible. Meanwhile, large dish Stirling engine installations have a significantly higher potential rate of return, but face a number of pragmatic limitations. CONCLUSIONS: This paper concludes that both technologies are a sensible investment for consumers, but given that the dish Stirling consumer receives 6.37 dollars per watt while the home photovoltaic system consumer receives between 0.9 and 1.70 dollars per watt, the former appears to be a superior option. Despite the large investment, this paper deduces that it is far more feasible to get few strong investors to develop a solar farm of this magnitude, than to get 150,000 households to install photovoltaic arrays in their roofs. Potential implications of the solar farm construction include an environmental impact given the size of land require for this endeavour. However, the positive aspects, which include a large CO2 emission reduction aggregated over the lifespan of the farm, outweigh any minor concerns or potential externalities.

Magnetic Exchange Couplings from Semilocal Functionals Evaluated Nonself-Consistently on Hybrid Densities: Insights on Relative Importance of Exchange, Correlation, and Delocalization.

Semilocal functionals generally yield poor magnetic exchange couplings for transition-metal complexes, typically overpredicting in magnitude the experimental values. Here we show that semilocal functionals evaluated nonself-consistently on densities from hybrid functionals can yield magnetic exchange couplings that are greatly improved with respect to their self-consistent semilocal values. Furthermore, when semilocal functionals are evaluated nonself-consistently on densities from a "half-and-half" hybrid, their errors with respect to experimental values can actually be lower than those from self-consistent calculations with standard hybrid functionals such as PBEh or TPSSh. This illustrates that despite their notoriously poor performance for exchange couplings, for many systems semilocal functionals are capable of delivering accurate relative energies for magnetic states provided that their electron delocalization error is corrected. However, while self-consistent calculations with hybrids uniformly improve results for all complexes, evaluating nonself-consistently with semilocal functionals does not give a balanced improvement for both ferro- and antiferromagnetically coupled complexes, indicating that there is more at play with the overestimation problem than simply the delocalization error. Additionally, we show that for some systems the conventional wisdom of choice of exchange functional mattering more than correlation does not hold. This combined with results from the nonself-consistent calculations provide insight on clarifying the relative roles of exchange, correlation, and delocalization in calculating magnetic exchange coupling parameters in Kohn-Sham Density Functional Theory.

Magnetic exchange couplings from constrained density functional theory: an efficient approach utilizing analytic derivatives.

We introduce a method for evaluating magnetic exchange couplings based on the constrained density functional theory (C-DFT) approach of Rudra, Wu, and Van Voorhis [J. Chem. Phys. 124, 024103 (2006)]. Our method shares the same physical principles as C-DFT but makes use of the fact that the electronic energy changes quadratically and bilinearly with respect to the constraints in the range of interest. This allows us to use coupled perturbed Kohn-Sham spin density functional theory to determine approximately the corrections to the energy of the different spin configurations and construct a priori the relevant energy-landscapes obtained by constrained spin density functional theory. We assess this methodology in a set of binuclear transition-metal complexes and show that it reproduces very closely the results of C-DFT. This demonstrates a proof-of-concept for this method as a potential tool for studying a number of other molecular phenomena. Additionally, routes to improving upon the limitations of this method are discussed.

Magnetic exchange couplings evaluated with Rung 3.5 density functionals.

Rung 3.5 exchange-correlation functionals are assessed for the calculation of magnetic exchange coupling parameters and atomic spin populations for a variety of inorganic and organic magnetic systems. Density functional theory calculations of exchange couplings sensitively depend on nonlocal contributions to the exchange-correlation functional. Semilocal functionals, Rungs 1-3 on "Jacob's Ladder" of density functional approximations, yield excessively delocalized electrons and overestimated absolute exchange couplings. Fourth-rung hybrid functionals admixing nonlocal exchange improve the results. We show that new "Rung 3.5" functionals give magnetic properties intermediate between semilocal and hybrid functionals, providing additional evidence that these functionals incorporate some desirable aspects of nonlocal exchange. Results for ferromagnetic complexes indicate areas for future improvement.

The role of range-separated Hartree-Fock exchange in the calculation of magnetic exchange couplings in transition metal complexes.

We assess the dependence of magnetic exchange couplings on the variation of Hartree-Fock exchange (HFX) admixture in global hybrid functionals and the range-separation parameter ω in range-separated hybrid functionals in a set of 12 spin-1/2 binuclear transition metal complexes. The global hybrid PBEh (hybrid Perdew-Burke-Ernzerhof) and range-separated hybrids HSE (Heyd-Scuseria-Ernzerhof) and LC-ωPBE (long-range corrected hybrid PBE) are employed for this assessment, and exchange couplings are calculated from energy differences within the framework of the spin-projected approach. It is found that these functionals perform optimally for magnetic exchange couplings with 35% HFX admixture for PBEh, ω = 0.50 a.u.(-1) for LC-ωPBE, and ω at or near 0.0 a.u.(-1) for HSE (which corresponds to PBEh). We find that in their standard respective forms, LC-ωPBE slightly outperforms PBEh, while PBEh with 35% HFX yields exchange couplings closer to experiment than those of LC-ωPBE with ω = 0.50 a.u.(-1). Additionally, we show that the profile of exchange couplings with respect to ω in HSE is appreciably flat from 0 to 0.2 a.u.(-1). This combined with the fact that HSE is computationally more tractable than global hybrids makes HSE an attractive alternative for the evaluation of exchange couplings in extended systems. These results are rationalized with respect to how varying the parameters within these functionals affects the delocalization of the magnetic orbitals, and conclusions are made regarding the relative importance of range separation versus global mixing of HFX for the calculation of exchange couplings.

Experimental in vitro arterial reactivity and tissue culture solutions alter the time-dependent stability of anthocyanins from elderberry, chokeberry, and bilberry extracts.

We examined the effect of solutions commonly used for in vitro assessment of blood vessel physiology and pharmacology on the half-lives of monomeric anthocyanins contained in extracts from elderberry, chokeberry, and bilberry. We observed that monomeric anthocyanin degradation in all extracts was accelerated when they were solubilized in an in vitro vascular physiological salt solution (PSS) compared with extracts in purified water. Degradation was accelerated further by increasing the temperature of the PSS to 37 degrees C and bubbling it with 95% oxygen/5% carbon dioxide. A common, complex, tissue culture media yielded similar results to the physiological salt solution at 37 degrees C. We also observed that the percentage polymeric color estimated by bisulfite bleaching corresponded to monomeric degradation in PSS. These results suggest that exposure of anthocyanins to physiological conditions that mimic those in the human body may stimulate the conversion of monomeric anthocyanins to their polymeric forms. Such conversion would probably contribute to the effects of anthocyanins on physiological functions in in vitro experiments and needs to be considered when evaluating effects of these compounds on physiological processes.