Application of equation-of-motion coupled-cluster methods to low-lying singlet and triplet electronic states of HBO and BOH

The equilibrium structures and physical properties of the X (1)sigma(+) linear electronic states, linear excited singlet and triplet electronic states of hydroboron monoxide (HBO) (A (1)sigma(-), B (1)delta, a (3)sigma(+), and b (3)delta) and boron hydroxide (BOH) (A (1)sigma(+), B (1)Pi, and b (3)Pi), and their bent counterparts (HBO a (3)A('), b (3)A("), A (1)A("), B (1)A(') and BOH X (1)A('), b (3)A('), c (3)A("), A (1)A('), B (1)A('), C (1)A(")) are investigated using excited electronic state ab initio equation-of-motion coupled-cluster (EOM-CC) methods. A new implementation of open-shell EOM-CC including iterative partial triple excitations (EOM-CC3) was tested. Coupled-cluster wave functions with single and double excitations (CCSD), single, double, and iterative partial triple excitations (CC3), and single, double, and full triple excitations (CCSDT) are employed with the correlation-consistent quadruple and quintuple zeta basis sets. The linear HBO X (1)sigma(+) state is predicted to lie 48.3 kcal mol(-1) (2.09 eV) lower in energy than the BOH X (1)sigma(+) linear stationary point at the CCSDT level of theory. The CCSDT BOH barrier to linearity is predicted to lie 3.7 kcal mol(-1) (0.16 eV). With a harmonic zero-point vibrational energy correction, the HBO X (1)sigma(+)-BOH X (1)A(') energy difference is 45.2 kcal mol(-1) (1.96 eV). The lowest triplet excited electronic state of HBO, a (3)A('), has a predicted excitation energy (T(e)) of 115 kcal mol(-1) (4.97 eV) from the HBO ground state minimum, while the lowest-bound BOH excited electronic state, b (3)A('), has a T(e) of 70.2 kcal mol(-1) (3.04 eV) with respect to BOH X (1)A('). The T(e) values predicted for the lowest singlet excited states are A (1)A(")<--X (1)sigma(+)=139 kcal mol(-1) (6.01 eV) for HBO and A (1)A(')<--X (1)A(')=102 kcal mol(-1) (4.42 eV) for BOH. Also for BOH, the triplet vertical transition energies are b (3)A(')<--X (1)A(')=71.4 kcal mol(-1) (3.10 eV) and c (3)A(")<--X (1)A(')=87.2 kcal mol(-1) (3.78 eV).     

Determination of thorium in human urine by neutron activation

A routine procedure for the determination of thorium in urine of workers has been developed by the neutron activation method. The technique suggested by Dang, et. al. has been modified in order to reduce the costs involved and the sample processing time. The samples were irradiated in the MIT (Massachusetts Institute of Technology-Boston) reactor, in a thermal neutron flux of 8×10¹²n.cm^–2.s^–1 for 31/2 hours. Thorium-232 was determined by counting²³³Pa.     

Coupled cluster methods including triple excitations for excited states of radicals

We report an extension of the coupled cluster iterative-triples model, CC3, to excited states of open-shell molecules, including radicals. We define the method for both spin-unrestricted Hartree-Fock (UHF) and spin-restricted open-shell Hartree-Fock (ROHF) reference determinants and discuss its efficient implementation in the PSI3 program package. The program is streamlined to use at most O(N(7)) computational steps and avoids storage of the triple-excitation amplitudes for both the ground- and excited-state calculations. The excitation-energy program makes use of a Lowdin projection formalism (comparable to that of earlier implementations) that allows computational reduction of the Davidson algorithm to only the single- and double-excitation space, but limits the calculation to only one excited state at a time. However, a root-following algorithm may be used to compute energies for multiple states of the same symmetry. Benchmark applications of the new methods to the lowest valence (2)B(1) state of the allyl radical, low-lying states of the CH and CO(+) diatomics, and the nitromethyl radical show substantial improvement over ROHF- and UHF-based CCSD excitation energies for states with strong double-excitation character or cases suffering from significant spin contamination. For the allyl radical, CC3 adiabatic excitation energies differ from experiment by less than 0.02 eV, while for the (2)Sigma(+) state of CH, significant errors of more than 0.4 eV remain.     

Use of a highly effective intramolecular Pauson-Khand cyclisation for the formal total synthesis of (±)-α- and β-cedrene by preparation of cedrone

The cedrene carbon skeleton was directly and efficiently assembled from a simple monocyclic precursor by the strategic use of a high yielding intramolecular Pauson-Khand cyclisation reaction. A small number of further synthetic manipulations provided a concise formal total synthesis of α- and β-cedrene. The cyclisation precursor was readily prepared, with a stereoselective ketone alkenylation selectively providing the olefin required for efficient access to the natural target.     

Immunologic relatedness of extracellular ligninases from the actinomycetesstreptomyces viridosporus t7a andstreptomyces badius 252

Four isoforms of the extracellular lignin peroxidase of the ligninolytic actinomyceteStreptomyces viridosporus T7A (ALip-P1, P2, P3, and P4) were individually purified by ultrafiltration and ammonium sulfate precipitation, followed by electro-elution using polyacrylamide gel electrophoresis. Three of the purified peroxidases were compared for their immunologic relatedness by Western blot analysis using a polyclonal antibody preparation produced in rabbits against pure isoform P3. The anti-P3 antibody was also tested for its reactivity towards a lignin peroxidase from the white-rot fungusPhanerochaete chrysosporium and another ligninolytic actinomyceteStreptomyces badius 252. Results showed that peroxidases ALip-P1 through ALip-P3 are immunologically related to one another. The peroxidases ofS. badius, but not the peroxidase ofP. chrysosporium, also reacted with the antibody, thus indicating that the lignin peroxidases ofS. viridosporus andS. badius are immunologically related. Based upon its specific affinity, lignin peroxidase isoform ALip-P3 ofS. viridosporus was readily purified using an anti-P3 antibody affinity column.     

The direct determination of organic oxygen in coals

Summary A method is described for the determination of the organic oxygen content of coals,Interfering mineral matter is removed by treatment with dilute hydrochloric acid under specified conditions, after which the resulting extracted sample is dried under controlled non-oxidising conditions.From this prepared sample, a weighed portion is introduced into a specially designed apparatus in which it is pyrolysed under rigidly controlled conditions of heating in the presence of an inert carrier gas, The oxygenated products of pyrolysis are then, with the carrier gas, passed over a platinised carbon catalyst by means of which the oxygen compounds are reduced to carbon monoxide.Finally, the carbon monoxide produced is allowed to react with heated iodine pentoxide, and the resulting iodine is determined by the Leipert titration procedure. The oxygen content of the original sample is calculated after certain corrections have been applied.

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Zusammenfassung Eine Methode zur Bestimmung des organisch gebundenen Sauerstoffs in Kohle wurde beschrieben.Störendes anorganisches Material wird durch Behandlung mit verd. Salzsäure unter besonderen Bedingungen entfernt. Die extrahierte Probe wird dann unter Ausschluß oxydierender Einflüsse getrocknet.Eine Einwaage davon wird in einer eigens dafür bestimmten Apparatur bei streng eingehaltener Temperatur in Gegenwart eines inerten Trägergases pyrolysiert. Die sauerstoffhältigen Pyrolyseprodukte gelangen mit dem Trägergas über platinierte Kohle, wo sie zu Kohlenmonoxyd reduziert werden. Dieses reagiert schließlich mit erhitztem Jodpentoxyd. Das freigesetzte Jod wird nachLeipert titriert. Bei Berechnung des Sauerstoffgehaltes der ursprünglichen Probe sind bestimmte Korrekturen anzubringen.

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Résumé On décrit une méthode de dosage de l'oxygène organique contenu dans les charbons.On élimine la matière minérale gênante par traitement à l'acide chlorhydrique dilué dans des conditions données, après quoi l'on sèche l'échantillon extrait sous des conditions contrôlées non oxydantes.On introduit un poids donné de cet échantillon dans un appareil construit spécialement dans lequel on le soumet à une pyrolyse sous des conditions strictement contrôlées de chauffage en présence d'un gaz inerte entraîneur. On fait alors passer les produits oxygénés de la pyrolyse, avec le gaz entraîneur, sur un catalyseur au charbon platinisé, grâce auquel les composés oxygénés sont réduits en oxyde de carbone.Finalement, on fait réagir l'oxyde de carbone produit, avec l'anhydride iodique chauffé et l'on dose l'iode résultant suivant le procédé de titrage deLeipert. On calcule la teneur en oxygène de l'échantillon original après avoir appliqué certaines corrections.