Materials Literature
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Growth of enteric bacteria on acetate as the sole source of carbon and energy requires operation of a particular anaplerotic pathway known as the glyoxylate bypass. In this pathway, two specific enzymes, isocitrate lyase and malate synthase, are activated to divert isocitrate from the tricarboxylic acid cycle and prev…
A new nonlinear optical (NLO) borate crystal K 2 Al 2 B 2 O 7 (Potassium Aluminum Borate, KAB) has been discovered. The structure has been established by 4-axis X-ray diffraction methods. The material crystallizes in the trigonal space group P321 with a = 8.5657(9) Å, C = 8.463(2) Å and Z = 3. KAB possesses a space ar…
The optical properties of alpha‐Al 2 O 3 have been determined by two independent methods, vacuum ultraviolet (VUV) spectroscopy and electron energy‐loss spectroscopy (EELS) over the energy range from 6 to 142 eV. For each experimental method two sets of high‐quality data have been measured and analyzed from alpha‐Al 2…
CdS/dendrimer nanocomposites that emit blue light are formed by the arrested precipitation of nanometer-scale CdS quantum dots in the presence of Starburst (poly(aminoamine)) dendrimers as the stabilizing host. The authors report a strong photoluminescence with emission maxima at about 450 nm. The optoelectronic prope…
A novel model system of hard colloidal platelets was observed to phase-separate into an isotropic and a liquid crystalline phase. Polarization microscopy revealed that the liquid crystalline phase was of nematic origin. With such orientational ordering in suspensions of platelike particles already being predicted in t…
A series of dendrimer porphyrins ((L 5 ) n P, n = 1−4), which bear different numbers ( n ) of five-layered dendron subunits (L 5 ) at the meso -positions of a porphyrin, were synthesized. Upon excitation of the dendron subunits in CH 2 Cl 2 at 20 °C, (L 5 ) n P showed an intramolecular singlet energy transfer from the…
A high-efficiency guided-mode resonance reflection filter is reported. The device consists of a surface-relief photoresist grating and an underlying HfO (2) waveguide layer deposited on a fused-silica substrate. The spectral response measured with a dye-laser beam at normal incidence exhibited a peak reflectance of 98…
A comparative analysis of quantitative infrared absorption spectra and mass selected thermal effusion transients measured for a large number of hydrogenated amorphous carbon (a-C:H) films is presented in order to establish reliable IR absorption cross sections for the different hydrogen bonding configurations in the m…
The size and shape of macromolecules such as proteins and nucleic acids play an important role in their functions. Prior efforts to quantify these properties have been based on various discretization or tessellation procedures involving analytical or numerical computations. In this article, we present an analytically…
The radial breathing mode is a promising candidate for the analysis of conformational and electronic properties of carbon nanotubes. The paper presents calculations based on the local density approximation to determine the radial breathing mode (RBM) frequency of various zigzag and armchair tubes with radii between 3.…
The addition of polyethylene glycol (PEG) and to an acid copper electrolyte inhibits the deposition reaction for cathodic overpotentials of up to about 150 mV. Adding only promotes the deposition reaction, while adding PEG alone has a relatively small effect on electrode kinetics. Frequency shifts of an electrochemica…
A diverse and entirely new class of monomer and polymer technology based on polyhedral oligomeric silsesquioxane (POSS) reagents has been developed. POSS reagents are unique in that they are physically large (approx. 15 Å diameter and 1000 amu) and are composed of a robust silicon–oxygen framework that can be easily f…
X-ray Diffraction: A Practical Approach, C. Suryanarayana and M. Grant Norton, 1998. Plenum Press, New York and London. xiii + 273 pages. (hardback, $49.50, U.S. and Canada; $59.40, elsewhere).It is the aim of this text to teach undergraduates majoring in materials science the use of powder X-ray diffraction for mater…
The 1985 discovery of the third form of ordered carbon, commonly known as the fullerenes, spurred the subsequent discovery of a number of related novel forms of carbon. The most famous among these carbons are the nanotubes, sometimes referred to as buckytubes as well. In this review, I discuss the structure, propertie…
Abstract We measured the visible to near-infrared (IR) spectra of 176 synthetic and natural samples of Fe oxides, oxyhydroxides and an oxyhydroxysulfate (here collectively called “Fe oxides”), and of 56 soil samples ranging widely in goethite/hematite and goethite/lepidocrocite ratios. The positions of the second-deri…
For patients with extensive burns, wound coverage with an autologous in vitro reconstructed skin made of both dermis and epidermis should be the best alternative to split-thickness graft. Unfortunately, various obstacles have delayed the widespread use of composite skin substitutes. Insufficient vascularization has be…
Hydrophobic dodecanethiol-capped silver nanocrystals ranging from 50 to 80 Å in diameter were synthesized using arrested growth methods. Size-selective precipitation was employed to isolate nanocrystals homogeneous in size and shape which exhibited close-packed structural order after drying on a carbon or mica substra…
Over the past decade, many efforts have been made to develop new materials exhibiting high oxide ion mobility at low temperature. In addition to the improvements of existing materials, new classes of conductors in which the structure have been shown to play an important role has been proposed. These materials are revi…
The single‐phase, cubic‐perovskite region of the LaO 1.5 ‐SrO‐Gao 1.5 ‐MgO phase diagram was determined from room‐temperature and high‐temperature X‐ray diffraction. Two impurity phases were identified, LaSrGaO 4 and aSrGa 3 O 7 . The conductivity of the oxygen‐deficient perovskite phase was shown to be essentially a…
A novel material for molecular optoelectronics consisting of a composite of carbon nanotubes and poly(m-phenylenevinylene-co-2,5-dioctoxy-p-phenylenevinylene) (PmPV) is reported. Incorporation of the nanotubes is demonstrated to increase the electrical conductivity of the polymer by up to eight orders of magnitude. Th…