Materials Literature
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The titanium-mediated coupling of NiII and ZnII pyrophaeophorbides results in formation of planar ethenefused bisphaeophorbides 1, M = Ni, Zn. Absorption spectroscopy indicates that the two chlorin units are highly conjugated, and the X-ray crystal structure shows the two phaeophorbide rings to be almost coplanar.
Trigonal-bipyramidal and octahedral coordination is found in transition metal complexes 1 and 2 (M = Co, Ni, Cu, Zn; X = Cl, NO3, NCS (or SCN)) with dendrimeric ethyleneimine ligands of the first (1 = H; R2 = CH2-3,4-C6H3[O(CH2)9CH3]2) and second generation (R1 = R2 = CH2CH2NHCO-3,4-C6H3[O(CH2)9CH3]2). These complexes…
Manganese( II ) nitrate, sodium azide, and 2,2′‐bipyrimidine (bpym) react to give 1 in which the azido groups function as end‐on bridging ligands and the bpym as a bis(bidentate) ligand. The structure of 1 can be described as a honeycomb sheet formed by Mn 6 hexagons. Magnetic susceptibility data reveals the existence…
The scanning tunneling microscope (STM) has been used to observe threefold symmetric electron scattering from point defects on a graphite surface. These theoretically predicted electronic perturbations could not be observed with a bare metal tip but could only be imaged when a fullerene (C 60 ) molecule was adsorbed o…
The role of aminopropyltriethoxysilane in the interaction between ISAF carbon black and carboxylated nitrile rubber was studied by measurements of bound rubber, physical and dynamic mechanical properties of the vulcanizates, and Monsanto Rheometric studies on the rubber-filler mixes. It is believed that NH2 groups o…
A link has been forged between porphyrins and annulenes by carbaporphyrins 1 (R = H and CH3), in which one nitrogen atom of the porphyrin framework is replaced by a carbon atom. These novel compounds are 18π arenes like porphyrins and have similar spectroscopic properties.
A template-directed mechanism of crystal growth is demonstrated for urea inclusion compounds (UICs). For UICs containing n -alkanone or α+1,ω−1-alkanedione guests, x-ray diffraction revealed superstructure relations between host and guest repeats along the channel axis for guests containing 8 to 14 carbons. For a favo…
In spite of the very great progress made in ceramic science, and the elegance and excitement of the research which has been performed, the real driving force for developments in ceramics remains their potential applications. The opportunity for dramatic scientific advances was certainly one reason for the "ceramic fev…
SF6 gas breakdown and spacer surface flashover volt–time characteristic curves were established for a GIS of D/d = 55/25 (15 mm gap) and D/d = 45/25 (10 mm gap) for 1.2/50, 0.5/50, 0.2/50 and osc/50 (1.64 MHz) µs impulse and disconnector induced VFT voltages. VFT volt–time curves established using actual breakdown vol…
It is believed that the polymorphism observed in calcium carbonate crystals, such as aragonite and calcite in mollusk shells, is controlled by organic matrix proteins secreted from the mantle epithelia. However, the fine structures of these proteins are still unknown, and to understand the molecular mechanisms of mine…
We present in situ scanning tunneling microscopy (STM) images with the resolution of isolated $\ensuremath{\equiv}\mathrm{Si}---\mathrm{O}X$ groups on H-Si(111) in NaOH solutions with or without isopropyl alcohol $[X=H\mathrm{or}---\mathrm{CH}(\mathrm{CH}{}_{3}{)}_{2}]$. The comparison of STM with geometric contours s…
A surface under stress is morphologically unstable. In normal step-flow growth, this is manifested as a step-bunching instability. Here it is shown that for alloy growth the resulting inhomogeneous strain drives decomposition of the alloy. At the same time, this decomposition ``screens'' the inhomogeneous strain, part…
Special features of atomic vacancies in oxides of the perovskite family have been studied within the framework of the Green function method. It has been shown that, in accordance with experiments, the oxygen vacancy has both shallow and comparatively deep levels corresponding to different charge states. The single-cha…
Ellipsometric measurements of a nematic drop spreading on a rough surface are reported. The thickness profile of the drop shows two typical lengths belonging to the microscopic and to the mesoscopic scales (a few tens and some hundreds of \AA{}, respectively). No intermediate thicknesses are observed during the spread…
In this letter we report on the growth of thick films of magnetoresistive La2/3Sr1/3MnO3 films using a spray printing technique. The as-prepared films display a room-temperature magnetoresistance of 0.0012%/Oe in the 1 kOe field region. We will show that this field sensitivity is high enough to fabricate devices which…
Fungal fimbriae are surface appendages that were first described on the haploid cells of the smut fungus, Microbotryum violaceum. They are long (1-20 microm), narrow (7 nm) flexuous structures that have been implicated in cellular functions such as mating and pathogenesis. Since the initial description, numerous fungi…
The presence of interstitial oxygen molecules in glassy ${\mathrm{SiO}}_{2}$ has been demonstrated directly by 1064.1 nm $({\ensuremath{\nu}}^{\ensuremath{'}\ensuremath{'}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0)\ensuremath{\rightarrow}({\ensuremath{\nu}}^{\ensuremath{'}}\phantom{\rule{0ex}{0ex}}=\phantom…
A recently proposed computational scheme based on local increments has been applied to the calculation of correlation contributions to the cohesive energy of the CaO crystal. Using ab-initio quantum chemical methods for evaluating individual increments, we obtain 80% of the difference between the experimental and Hart…
The optical properties of N${\mathrm{d}}_{0.7}$S${\mathrm{r}}_{0.3}$Mn${\mathrm{O}}_{3}$ thin films have been studied over a broad spectral range, at temperatures down to 15 K and magnetic fields up to 8.9 T. A large transfer of spectral weight from high energy to low energy occurs as this material is cooled into the…
InAs nanocrystal quantum dots have been prepared via colloidal chemical synthesis using the reaction of InCl3 and As[Si(CH3)3]3. Sizes ranging from 25 to 60 Å in diameter are produced and isolated with size distributions of ±10%–15% in diameter. The nanocrystals are crystalline and generally spherical with surfaces pa…