Non-empirical calculations of chlorine quadrupole coupling parameters in chloromethanes and chlorosilanes

Non-empirical calculations of the field gradient tensor at the chlorine nucleus are resorted for chloromethane, trichloromethane, chlorosilane and trichlorosilane. The calculations agree quite well with the experimental quadrupole coupling constants. The calculated asymmetry parameters in trichloromethane and trichlorosilane are low and the principal z axis of the field gradient tensor is found nearly to coincide with the CCl and SiCl bond directions.     

Treatment with lignin residue

Acid hydrolysis of lignocellulose to hydrolysates intended for production of fuel ethanol results in the formation of byproducts in addition to fermentable sugars. Some of the byproducts, such as phenolic compounds and furan aldehydes, are inhibitory to the fermenting microorganism. Detoxification of the hydrolysates may be necessary for production of ethanol at a satisfactory rate and yield. The lignin residue obtained after hydrolysis is a material with hydrophobic properties that is produced in large amounts as a byproduct within an ethanol production process based on lignocellulosic raw materials. We have explored the possibility of using this lignin residue for detoxification of spruce dilute-acid hydrolysates prior to fermentation with Saccharomyces cerevisiae. Three dilute-acid hydrolysates of spruce were treated with lignin residue, which in all cases resulted in improved fermentability in terms of productivity and yield of ethanol. The effect was improved by washing the lignin before treatment, by using larger amounts of lignin in the treatment, and by performing the treatment at low temperature. Treatment with the lignin residue removed up to 53% of the phenolic compounds and up to 68% of the furan aldehydes in a spruce dilute-acid hydrolysate. A larger fraction of furfural was removed compared to the less hydrophobic 5-hydroxymethylfurfural.     

Calculation of the 4S?4P0 spectrum of lithiumlike ions by the Hylleraas method

The energies of the five lowest ⁴S and ⁴P⁰ states for three-electron ions for 3?Z?10 have been calculated by the Hylleraas method. The largest basis set used contained 97 terms with odd as well as even powers of r_ij. The change of scale r′ = Zr was applied to the Hamiltonian so that the same basis sets could be used for all the three-electron ions leading to great savings in computing time.     

Dissociative recombination of NH4+ and ND4+ ions: storage ring experiments and ab initio molecular dynamics

The dissociative recombination (DR) process of NH4+ and ND4+ molecular ions with free electrons has been studied at the heavy-ion storage ring CRYRING (Manne Siegbahn Laboratory, Stockholm University). The absolute cross sections for DR of NH4+ and ND4+ in the collision energy range 0.001-1 eV are reported, and thermal rate coefficients for the temperature interval from 10 to 2000 K are calculated from the experimental data. The absolute cross section for NH4+ agrees well with earlier work and is about a factor of 2 larger than the cross section for ND4+. The dissociative recombination of NH4+ is dominated by the product channels NH3+H (0.85+/-0.04) and NH2+2H (0.13+/-0.01), while the DR of ND4+ mainly results in ND3+D (0.94+/-0.03). Ab initio direct dynamics simulations, based on the assumption that the dissociation dynamics is governed by the neutral ground-state potential energy surface, suggest that the primary product formed in the DR process is NH3+H. The ejection of the H atom is direct and leaves the NH3 molecule highly vibrationally excited. A fraction of the excited ammonia molecules may subsequently undergo secondary fragmentation forming NH2+H. It is concluded that the model results are consistent with gross features of the experimental results, including the sensitivity of the branching ratio for the three-body channel NH2+2H to isotopic exchange.     

Multiple scattering method applied to the electronic structure and spectra of the impurity ions Cu2+, Ni2+, Co2+, Fe2+ and their tetrahedral environments in ZnO,ZnS and CdS

The multiple scattering method with local exchange and muffin-tin potentials is applied to tetrahedral clusters with Cu²⁺, Ni²⁺, Co²⁺ and Fe²⁺ as central ions and oxygen and sulphur as ligands. The calculated orbital energy differences ?(t₂^*) - ?(e^*) are compared to Δ_t values deduced from optical spectra. The agreement is fairly good.     

Synthesis and characterization of two quaternary thorium chalcophosphates: Cs4Th2P6S18 and Rb7Th2P6Se21

Two new thorium chalcophosphates have been synthesized by the reactive flux method and characterized by single-crystal X-ray diffraction, diffuse reflectance, and Raman spectroscopy: Cs4Th2P6S18 (I); Rb7Th2P6Se21 (II). Compound I crystallizes as colorless blocks in the triclinic space group P1 (No. 2) with a = 12.303(4) A, b = 12.471(4) A, c = 12.541(4) A, alpha = 114.607(8) degrees, beta = 102.547(6) degrees, gamma = 99.889(7) degrees, and Z = 2. The structure consists of (Th2P6S18)(4-) layers separated by layers of cesium cations and only contains the (P2S6)(4-) building block. Compound II crystallizes as red blocks in the triclinic space group P1 (No. 2) with a = 11.531(3) A, b = 12.359(4) A, c = 16.161(5) A, alpha = 87.289(6) degrees, beta = 75.903(6) degrees, gamma = 88.041(6) degrees, and Z = 2. The structure consists of linear chains of (Th2P6Se21)(7-) separated by rubidium cations. Compound II contains both the (PSe4)(3-) and (P2Se6)(4-) building blocks. Both structures may be derived from two known rare earth structures where a rare earth site is replaced by an alkali or actinide metal to form these novel structures. Optical band gap measurements show that compound I has a band gap of 2.8 eV and compound II has a band gap of 2.0 eV. Solid-state Raman spectroscopy of compound I shows the vibrations expected for the (P2S6)(4-) unit. Raman spectroscopy of compound II shows the vibrations expected for both (PSe4)(3-) and (P2Se6)(4-) units. Our work shows the remarkable diversity of the actinide chalcophosphate system and demonstrates the phase space is still ripe to discover new structures.     

Protein adsorption on supported phospholipid bilayers

Quartz crystal microbalance with dissipation (QCM-D) measurements were used to investigate the adsorption of human fibrinogen, human serum albumin, bovine hemoglobin, horse heart cytochrome c, human immunoglobulin (hIgG), and 10% fetal bovine serum on supported bilayers of egg-phosphatidylcholine (eggPC) lipids. For comparison the adsorption of fibrinogen and hIgG to eggPC bilayers was also studied with surface plasmon resonance (SPR). The supported bilayers were formed in situ by vesicle adhesion and spontaneous fusion onto a SiO(2) surface. The supported lipid bilayer is highly protein resistant: The irreversible adsorption measured with the QCM-D technique was below the detection level, while reversible protein adsorption was detected for all the proteins in the range 0.3-4% of the saturation coverage on a hydrophobic thiol monolayer on gold. The adsorbed amounts were slightly higher for the SPR measurements. Possible mechanisms for the protein resistance of eggPC bilayers are briefly discussed.     

The stability of rational approximations of analytic semigroups

It is shown thatA-acceptable and, more generally,A()-arational approximations of bounded analytic semigroups in Banach space are stable. The result applies, in particular, to the Crank-Nicolson method.