Cluster molecular orbitals and an orbital symmetry view of solid phase transitions in perovskites

The molecular orbitals, normalization constants and energies of the M₈(O_h), M₄(T_d) and M₆(O_h) clusters are derived and tabulated through the d-atomic orbitals. A vector method, adapted to computer application, is devised to compute s, p and d overlap between variously oriented orbitals at atoms that do not have co-directional local axes. Mixing of σ, π and δ orbitals to give the same irreducible representation is also included. As illustrations, the orbitals of Sr₈, La₈, TiO₆ and AlO₆ clusters are computed by the Mulliken—Wolfsberg and Helmholz approximations. During solid phase transitions in the perovskite structures of SrTiO₃ and LaAlO₃, the TiO₆ octahedron rotates about the C₄ axis whereas the AlO₆ octahedron rotates about the C₃ axis. This difference is explained qualitatively in terms of the relative symmetries of the cluster HOMOs and LUMOs using the second-order Jahn—Teller effect. Allusions are made to the application of this cluster symmetry approach to other systems.     

Biohydrogen Production from Mushroom Cultivation Waste by Anaerobic Solid‐state Fermentation

Mushroom cultivation waste (MCW) is a polypropylene bag stuffed with wood flour and nutrients for growing mushroom, which is a feasible feedstock for anaerobic biohydrogen production owing to its abundant availability, high organic and nutrient content. This study optimized the seed inoculum from various waste sludges (sewage sludge, cow dung and pig slurry), nutrient addition and operation conditions (moisture content and MCW powder particle size) for maximal biohydrogen production by solid‐state fermentation (SSF). SSF batch test was operated at a MCW 3 g total volatile solid (TVS)/L, temperature 55 °C and rotation speed of 15 rpm with a vertical rotative shaker. The peak hydrogen production performance of hydrogen production rate (HPR) 9.50 mol H₂/kg‐d and hydrogen yield (HY) 0.29 mmol H₂/g TVS) are obtained using sewage sludge 2 seed inoculum, nutrients addition, moisture content 70 % and particle size of 1.190～0.590 mm. The results show that the MCW has the potential for hydrogen production by anaerobic mixed microflora using solid‐state fermentation. The bioenergy of 1842 kWh while using SSF to conver MCW to produce biohydrogen and it could reduce CO₂ emission of 114–178 kg per year comparing using fossil fuel such as coal, fuel oil and natural gas.     

D3R grand challenge 2015: Evaluation of protein–ligand pose and affinity predictions

The Drug Design Data Resource (D3R) ran Grand Challenge 2015 between September 2015 and February 2016. Two targets served as the framework to test community docking and scoring methods: (1) HSP90, donated by AbbVie and the Community Structure Activity Resource (CSAR), and (2) MAP4K4, donated by Genentech. The challenges for both target datasets were conducted in two stages, with the first stage testing pose predictions and the capacity to rank compounds by affinity with minimal structural data; and the second stage testing methods for ranking compounds with knowledge of at least a subset of the ligand–protein poses. An additional sub-challenge provided small groups of chemically similar HSP90 compounds amenable to alchemical calculations of relative binding free energy. Unlike previous blinded Challenges, we did not provide cognate receptors or receptors prepared with hydrogens and likewise did not require a specified crystal structure to be used for pose or affinity prediction in Stage 1. Given the freedom to select from over 200 crystal structures of HSP90 in the PDB, participants employed workflows that tested not only core docking and scoring technologies, but also methods for addressing water-mediated ligand–protein interactions, binding pocket flexibility, and the optimal selection of protein structures for use in docking calculations. Nearly 40 participating groups submitted over 350 prediction sets for Grand Challenge 2015. This overview describes the datasets and the organization of the challenge components, summarizes the results across all submitted predictions, and considers broad conclusions that may be drawn from this collaborative community endeavor.     

A Simple Method for Determining the Critical Micellar Concentration of a Surfactant

This paper will present a simple method for critical micellar concentration (cmc) determination based on light scattering using a turbidimeter. The method does not require the optical clarification of the surfactant solution. The surfactant solutions were prepared from distilled water after boiling. Distinct cmc values were observed for polyoxyethylene mono n-dodecylether, sodium taurodeoxycholate and sodium dodecyl sulfate. The cmc values obtained using the turbidity method were compared with cmc values obtained by the surface tension method and with data given in the literature. Values obtained by our simple method have comparable accuracy with data obtained from more elaborate experiments.     

Young operator methods for fermion systems

Summary Alternative methods to the standard Young technique for the construction of Fermion wave functions in the spin orbital formalism are presented and shown to be equivalent to the standard technique. To develop these methods: (i) the starting or primitive function is factored into spin and spatial parts, (ii) the conjugacy feature required to satisfy the antisymmetry principle is exploited, (iii) the necessary commutation relations with the Fermion antisymmetrizer are shown to hold and (iv) the one-to-one correspondence between the independent picture of the Young tableaux and the independent Slater determinants is used. This last feature has the advantage of reducing all three methods to rapid efficient graphical procedures. Each method is analyzed to consider the amount of labor involved to carry it out. Several examples of the methods are given for constructing both electronic wave functions and spin functions.     

On the closed form of Wigner rotation matrix elements

The closed forms of some rotation matrix elementsd _{m m} ^j (/2) are presented. The closed forms of summation involved two binomials and some special hypergeometric functions are also obtained. The MAPLE V program which calculates d _{m m} ^j (), dm,. (/2) and the help file are given in appendix.Supported in part by the Chiu Feng-Chia research Fund. Thanks are due to the Board of Trustees Chairman Dr. Ying-Ming Liao as well as the Trustee Dr. Charles Chiu-Hsiong Huang and President Dr. Ted C. Yang of Feng-Chia University, Taichung, Taiwan, ROC.     

Radiochenical determination of technetium-99 in LLW by chelation with sodium diethyl dithiocarbamate (NaDDC) and extraction with chloroform

A radiochemical method has been developed for the determination of⁹⁹Tc in low-level radioactive, waste from nuclear facilities, using^99mTc as an internal tracer. Radioactive contaminants were removed by carrier hydroxide precipitation and chelating extraction with NaDDC/CHCl₃ system at pH 4. The final technetium was chelated with NaDDC in 3N HCl solution and extracted selectively into chloroform. The average of radiochemical recovery for various types of LLW sample is about 90%. The decontamination factors for most radioactive nuclides are higher than 10⁵. The detection limit for⁹⁹Tc in a sample of about 10 g is 0.17 pCi/g (6.5 Bq·kg^–1) for a 100-minute count.     

Time-reversal symmetry in molecular rovibronic states and in second-order processes

A unified treatment of time-reversal symmetry is given for molecular systems. The treatment allows for interconversion of electronic, rotational, and vibrational angular momenta on equal footing because of a coherent phase choice. It also allows for correlation from a continuous group (of spherical or cylindrical symmetry) to lower point groups (such as C₃, C₄, C₆, S₄, S_g, T, etc.). General, many-electron molecular states that form time-reversal degenerate components are constructed. Attention is called to the Kramers' doublets as the special odd-electron case of such double degeneracy. Specific examples of a spiropentane and a 5-azoniaspiro(4.4) nonane with S₄ symmetry and possible time-reversal degeneracy are given. The optical rotation due to a time-odd polarizability tensor in one of the two time-degenerate components is shown to be of an opposite sign to that in the other component. The above result is from a second-order matrix element (over the polarizability tensor) and is proved to be independent of even- or odd-number of electron spins. It is shown to hold also for Kramers' doubly degenerate components. This result is contrasted with that of a first-order Jahn-Teller effect which depends on the number of electron spins.     

Mindo/3 study of the addition of hydrogen to vinylidene

The addition of hydrogen to vinylidene is studied using the MINDO/3 method. The results obtained are then compared with those for the addition of hydrogen to methylene applying ab initio and other semi-empirical methods. As expected, the pathways of these two reactions are qualitatively similar. The insertion is a non-least-motion process in which two phases can be easily distinguished: (i) an electrophilic step in which the empty orbital of the carbene interacts with the bonding orbital of H₂, forming a three-center bond in the process, (ii) a nucleophilic step in which the lone pair orbital of the carbene interacts with the antibonding orbital of H₂. The quantitative differences between the two reactions are also discussed.