Ozonolysis of dipterocarpol and its derivatives

Oxidation of dipterocarpol and its derivatives with ozone gave compounds containing lactone, lactol, alkoxytetrahydrofuran, aldehyde, and methyl ketone fragments in the side chain, as well as 1,2,4-trioxolane fragment in the A ring. The molecular and crystalline structures of dipterocarpol were determined by X-ray analysis.     

Effects of controllable process factors on Al rear surface bumps in Si solar cells

High efficiency solar cells require good back surface field passivation and high back reflectance in the rear Al region. In module processes, wafer-based solar cell can break through stress during soldering uneven rear aluminum surfaces - a serious problem that affects throughput. This work examined rear surfaces with respect to controllable process factors such as ramping and cooling rates during rapid thermal processing, and the fineness of aluminum powder used in the screen-printed paste. A faster ramp up rate resulted in a uniform temperature gradient between the aluminum and silicon surfaces. As a results, the bumps on the aluminum surface were small and of high density. Fine aluminum metal powder in the paste for screen-printing contact points resulted in large distribution, high density bumps. Bumps formed during cooling in metallization, their sizes and densities were dependent the on uniformity of the aluminum and silicon liquid wetting of the silicon surface.     

Monolayer Co3O4 Inverse Opals as Multifunctional Sensors for Volatile Organic Compounds

Monolayers of periodic porous Co₃O₄ inverse opal (IO) thin films for gas‐sensor applications were prepared by transferring cobalt‐solution‐dipped polystyrene (PS) monolayers onto sensor substrates and subsequent removal of the PS template by heat treatment. Monolayer Co₃O₄ IO thin films having periodic pores (d≈500 nm) showed a high response of 112.9 to 5 ppm C₂H₅OH at 200 °C with low cross‐responses to other interfering gases. Moreover, the selective detection of xylene and methyl benzenes (xylene+toluene) could be achieved simply by tuning the sensor temperature to 250 and 275 °C, respectively, so that multiple gases can be detected with a single chemiresistor. Unprecedentedly high ethanol response and temperature‐modulated control of selectivity with respect to ethanol, xylene, and methyl benzenes were attributed to the highly chemiresistive IO nanoarchitecture and to the tuned catalytic promotion of different gas‐sensing reactions, respectively. These well‐ordered porous nanostructures could have potential in the field of high‐performance gas sensors based on p‐type oxide semiconductors.     

Catalytic one-pot synthesis of [5.5.5.6]fenestrane systems via a dicobalt octacarbonyl-catalyzed tandem cycloaddition of dienediynes

Catalytic one-pot synthesis of fenestrane derivatives from dienediynes was developed: fenestranes were synthesized in high yields by a dicobalt octacarbonyl-catalyzed tandem cycloaddition of dienediynes.     

Oscillation and Nonoscillation of Higher Order Self-Adjoint Differential Equations

Oscillation and nonoscillation criteria for the higher order self-adjoint differential equation (-1)ⁿ(t^alphay⁽ⁿ⁾)⁽ⁿ⁾+q(t)y = 0 (*) are established. In these criteria, equation (*) is viewed as a perturbation of the conditionally oscillatory equation (-1)ⁿ(t^alphay⁽ⁿ⁾)⁽ⁿ⁾ - µ,t^2n-y = 0, where _n, is the critical constant in conditional oscillation. Some open problems in the theory of conditionally oscillatory, even order, self-adjoint equations are also discussed.     

Charge and spin structure in of YBa(2)Cu(3)O(6.35)

Neutron scattering has been used to measure the charge and spin structure in the highly underdoped superconductor YBa(2)Cu(3)O(6.35). Incommensurate static charge ordering is found that remains at high temperatures. The magnetic pattern is complex with a resonance and incommensurate structure observed at low temperatures. The results clarify the role of striped phases in YBa(2)Cu(3)O(6+x) superconductors.     

Spektrochemische bestimmung der hauptbestandteile von Cu-Al-binärlegierungen mit der glimmentladungslampe als lichtquelle

The suitability of the glow discharge lamp for the analysis of both main components of a binary system Cu-Al has been investigated. The standard samples contained Cu and Al between 0.5 and 99.5%. Different calibration methods for these systems are discussed. Only the “method of binary ratios” yields a straight line for calibration within the entire concentration range. It is obtained if the logarithm of the intensity ratio is plotted against the logarithm of the concentration ratio of Cu and Al. Accurate and precise results are obtained if the discharge voltage and the gas pressure are kept constant for all samples. The correlation coefficient was found to be 0.99986 and the relative standard deviation for the determination of the concentration was about 0.06 · (1-w), where w is the concentration expressed as a fraction.     

Trace determination of oxygen in gold-copper alloys and in high purity gold using3He and4He activation analysis

Trace amounts of oxygen in gold-copper alloys and high purity gold have been determined by³He and⁴He activation analysis. Interferences from the matrix have been identified and the factors which can have an effect upon the precision and the accuracy of the method have been investigated. Thus a destructive technique has been choosen. The¹⁸F produced was chemically separated by steam distillation and precipitated as PbClF. The values of the oxygen concentration were found to range between 0.2 and 2 μg·g⁻¹ depending on the copper concentration and the thermal treatment applied to the samples. A possible mechanism of internal oxidation is presented.