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We have performed density functional VASP calculations of a pure and of a carbon-covered (100) tungsten surface under the presence of an electric field E directed away from the surface. Our aim is to answer the question of an increased penetrability of electrons at the collector side of a nanometric tunnel diode when covered by carbon atoms, a purely quantum mechanical effect related to the value of the workfunction Φ. To obtain Φ at a non-zero electric field we have extrapolated back to the electrical surface the straight line representing the linear increase in the potential energy with distance outside the metal-vacuum interface. We have found that under the presence of E the workfunction Φ = Evac − EF of the (100) pure tungsten surface has a minor dependence on E. However, the carbon-covered tungsten (100) surface workfunction Φ(C − W) has a stronger E dependence. Φ(C − W) decreases continuously with the electric field. This decrease is ΔΦ = 0.08 eV when E = 1 V/nm. This ΔΦ is explained by our calculated changes with electric field of the electronic density of both pure and carbon-covered tungsten. The observed phenomena may be relevant to other surfaces of carbon-covered tungsten and may explain the reported collector dependence of current in Scanning Field Emission Microscopy.

We have performed density functional VASP calculations of a pure and of a carbon-covered (100) tungsten surface under the presence of an electric field E directed away from the surface. Our aim is to answer the question of an increased penetrability of electrons at the collector side of a nanometric tunnel diode when covered by carbon atoms, a purely quantum mechanical effect related to the value of the workfunction Φ. To obtain Φ at a non-zero electric field we have extrapolated back to the electrical surface the straight line representing the linear increase in the potential energy with distance outside the metal-vacuum interface. We have found that under the presence of E the workfunction Φ = Evac − EF of the (100) pure tungsten surface has a minor dependence on E. However, the carbon-covered tungsten (100) surface workfunction Φ(C − W) has a stronger E dependence. Φ(C − W) decreases continuously with the electric field. This decrease is ΔΦ = 0.08 eV when E = 1 V/nm. This ΔΦ is explained by our calculated changes with electric field of the electronic density of both pure and carbon-covered tungsten. The observed phenomena may be relevant to other surfaces of carbon-covered tungsten and may explain the reported collector dependence of current in Scanning Field Emission Microscopy. [ABSTRACT FROM AUTHOR]

Many chemical reactions occur in excited states, so, we must know their wave functions. But the excited states are saddle points in the wave function space and cannot be located by energy minimization. The reported functional, Ωn, (reducible to a self‐consistent generalized eigenvalue problem, that allows simultaneous treatment with multi‐configuration self‐consistent field ‐ MCSCF) locate the excited states/saddle points with the help of crude approximants of the lower lying states, without demanding any orthogonality to them, whatsoever. Ωn is useful for systems (mainly large) where huge wave functions expansions (that would tend to the exact values) are impracticable, and rather small truncated (but comprehensible) wave functions are needed. Ωn is checked against large wave functions of small atoms and against both large and small wave functions that implement the Hylleraas‐Undheim ‐ McDonald theorem thus locate an energy minimum near, but not the saddle point itself. Various Ωn applications are given. [ABSTRACT FROM AUTHOR]

The study of excited states is already imperative especially as it concerns reactions, after activation, of stable species, like CO2 or alkanes. First principles studies can only be utilized in truncated Hilbert spaces. Unfortunately, the standard methods of computing excited states in truncated spaces, although perhaps adequate for the energy and for spectroscopy, may yield incorrect wave functions (perhaps with correct energy), misleading for desired proper excitations. Thus, a method is needed (such as the present demonstrated) to yield excited state truncated wave functions that are not veered away from the exact Hamiltonian eigenfunctions. The ability to extend the variational principle to any excited state (without knowledge of the lower-lying exact eigenfunctions) has long been proven to be an inherent property of the Hamiltonian. The excited state truncated wave function based on the standard method of the Hylleraas and Undheim/MacDonald (HUM) theorem, is in principle incorrect in a more fundamental manner than just being truncated: Its accuracy must be strictly less than the accuracy of the ground state truncated approximant. On the other hand, an energy minimization orthogonally to all lower approximants ["orthogonal optimization" (OO)] must lead to a wave function lying lower than, and veered away from, the exact. A minimization principle for excited electronic states of a non-degenerate Hamiltonian in any given symmetry type is presented, that allows their computation to any desired accuracy, independently of the accuracy of the lower-lying states of the same symmetry, therefore without demanding orthogonality to known lower approximants, and, within a given truncated wave function parameter space, can lead to a more correct than HUM or OO approximation of the excited wave function. A demonstration is presented for the first excited state of He 1S (1s2s) using variationally optimized, optionally state-specific, orbitals in Hylleraas coordinates, while the standard truncated HUM answer, despite the correct energy, has main orbitals 1s1s 'instead. It is also demonstrated that the principle can be used to identify a "flipped root" near an avoided crossing (useful to guide MCSCF). Beyond the aforementioned demonstration, some results within conventional configuration interaction based on similarly optimized Laguerre type orbitals are also exhibited and compared to relevant literature. [ABSTRACT FROM AUTHOR]

OBJECTIVE: Cardiovascular complications are important causes of morbidity and mortality in elective non-cardiac surgery. Although difficult to diagnose, perioperative myocardial infarction (MI) remains prognostically important. High-sensitivity troponin T (hs-TnT) assays allow detection of very minor damage to cardiac muscle. These assays are yet to be fully evaluated in the perioperative setting. Our aim was to determine the incidence and predictors of myocardial necrosis in patients at high cardiovascular risk undergoing elective non-cardiac surgery using hs-TnT. DESIGN: Prospective observational cohort study. PATIENTS: 352 consecutive patients undergoing elective major non-cardiac surgery prescribed antiplatelet therapy for primary or secondary cardiovascular event prevention. MAIN OUTCOME MEASURE: The incidence of elevated preoperative hs-TnT (>=14 ng/litre), hs-TnT-defined perioperative myocardial necrosis (>= 14ng/litre and 50% increase from preoperative level), and perioperative MI were determined in relation to patient and surgical factors. RESULTS: Preoperative hs-TnT was elevated in 31% and postoperative myocardial necrosis occurred in 22% of patients. Predictors of elevated baseline hs-TnT included age (OR 1.10, p<0.001), male gender (OR 2.91, p<0.001), diabetes requiring insulin therapy (OR 4.85, p=0.004) and chronic kidney disease (OR 3.60, p<0.001). Independent predictors of perioperative myocardial necrosis were age (OR 1.07, p<0.001), intraoperative hypotension (OR 3.67, p=0.001) and orthopaedic surgery (OR 2.46, p=0.005). Only 2% of patients suffered clinically apparent MI. Elevated preoperative hs-TnT did not predict perioperative myocardial necrosis or MI. CONCLUSIONS: Perioperative myocardial damage occurs frequently in patients undergoing elective non-cardiac surgery, although the majority of events are clinically undetected. Age and intraoperative hypotension are independent predictors of myocardial necrosis in this setting. [ABSTRACT FROM AUTHOR]

Anaerobically treated sludge from a wastewater treatment plant (Psittalia) was found to contain significant amounts of metals (Cr, Cu, Fe, Ni, Pb and Zn). The sludge samples were subjected to thermal drying at 105°C and acid treatment was applied before and after thermal drying. Different acid concentrations and contact times were used in order to find the combination that caused the highest metal removal. The metal distribution in raw sewage and in thermally dried sludge as well as the chemical forms of the remaining metal load after acid treatment were determined by the application of a sequential chemical extraction procedure. It was found that thermal drying causes a shift of the metal content to more stable phases. A sufficient metal amount was removed by acid treatment and the remaining metal content was further stabilized. [ABSTRACT FROM PUBLISHER]

In order to understand the catalytic activity of small metal clusters as a function of their size, we have studied the interaction of CH4 with Al4 and Al5 neutral and charged clusters, as well as neutral thermally expanded clusters in the two lowest lying spin states, using density functional theory. These calculations, via extended search, are used to determine the stable positions of H and CH3 near the cluster, and the transition state to break the H─CH3 bond. In order to understand the factors underlying the reactivity of the clusters, we have analyzed the electronic structure at the transition state. By an analysis of the change of the electronic density of states close to the transition state, we identify the orbitals involved in the bond breaking process. In conjunction with our previous studies of Al2 and Al3 clusters, we find that the small Al clusters, except for Al5, lower the CH3─H dissociation barrier with respect to the gas‐phase value, although Al lacks occupied d‐orbitals. Still, Al5 does not catalyze methane bond breaking, which is attributed to the required interaction with low‐lying Al sp‐states. Furthermore, in all cases where stable methyl‐aluminum‐hydrides are possible, the recombinative desorption of methane is studied by vibrational analysis and application of transition state theory. [ABSTRACT FROM AUTHOR]

Anaerobically treated sludge from a wastewater treatment plant (Psittalia) was found to contain significant amounts of metals (Cr Cu, Fe,Ni, Pb and Zn). The sludge samples were subjected to thermal drying at 105 deg. C and acid treatment was applied before and after thermaldrying. Different acid concentrations and contact times were used inorder to find the combination that caused the highest metal removal.The metal distribution in raw sewage and in thermally dried sludge as well as the chemical forms of the remaining metal load after acid treatment were determined by the application of a sequential chemical extraction procedure. It was found that thermal drying causes a shiftof the metal content to more stable phases. A sufficient metal amount was removed by acid treatment and the remaining metal content was further stabilized. [ABSTRACT FROM AUTHOR]