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Sampling Devices for the Measurement of Seed Rain and Hydrochory in Rivers
the bucket with bottom removed, and two 2-liter beverage bottles for flotation. The total cost of one pair of seed rain and hydrochore traps was less than $1.00. The seed dispersal estimates from the aquatic seed traps reflected the relative numbers of species and seeds dispersed in aquatic systems. A test of the effi…
Average widths of grain boundaries in nanophase alloys synthesized by mechanical attrition
Many binary ferrous alloys were synthesized by mechanical attrition in a high-energy ball mill. X-ray diffractometry and transmission electron microscopy were used to measure grain sizes, which were as small as a few nanometers in several alloys. The nanocrystalline alloys showed new features in their Mössbauer spectr…
Structural changes ofZrO2-CeO2solid solutions around the monoclinic-tetragonal phase boundary
High-resolution neutron-diffraction experiments have been performed to study the structural changes of ${\mathrm{ZrO}}_{2}$ induced by ${\mathrm{CeO}}_{2}$ doping. The crystal structures of monoclinic [P${2}_{1}$/c, Z=4] and tetragonal [P${4}_{2}$/nmc, Z=2] phases for ${\mathrm{ZrO}}_{2}$--X mol % ${\mathrm{CeO}}_{2}$…
Vibrational analysis of poly(L‐lactic acid)
Abstract The Raman and IR spectra of poly( L ‐lactic acid) in the amorphous and semicrystalline states were recorded from 3600 to 100 cm −1 . Complete vibrational assignments are proposed. In the Raman spectra, the splittings of the v C=O stretching and the δCCO bend are characteristic of the crystalline phase and the…
Introduction to living polymeriz. Living and/or controlled polymerization
Abstract The effects of various imperfections such as slow initiation, termination, transfer and slow exchange on kinetics, molecular weights and polydispersities in chain growth polymerizations are simulated. The simukations demonstrate that well defined polymers polymers can be prepared in systems with chain‐breakin…
Magneto-structural correlations in .mu.2-1,1-azide-bridged dicopper(II) complexes. 2. Dominant antiferromagnetic coupling with azide bridge angles exceeding 108.degree.. X-ray Structures of [Cu2(PAP)(.mu.2-N3)Br3].cntdot.CH2Cl2, [Cu2(PAP6Me)(.mu.2-N3)(.mu.2-Br)Br2].cntdot.1.68H2O, [Cu2(PAP6Me)(.mu.2-N3)(.mu.2-H2O)(NO3)2](NO3).cntdot.0.75CH3OH, [Cu2(PAN)(.mu.2-N3)(.mu.2-NO3)(NO3)2].cntdot.CH3OH.cntdot.CH3CN, and [Cu2(PPD35Me)(.mu.2-N3)Br3(CH3OH)]
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMagneto-structural correlations in .mu.2-1,1-azide-bridged dicopper(II) complexes. 2. Dominant antiferromagnetic coupling with azide bridge angles exceeding 108.degree.. X-ray Structures of [Cu2(PAP)(.mu.2-N3)Br3].cntdot.CH2Cl2, [Cu2(PAP6Me)(.mu.2-N3)(.mu.2-Br)Br2].cntdot.1.…
PHTHALOCYANINE FLUORESCENCE AT HIGH CONCENTRATION: DIMERS OR REABSORPTION EFFECT?
Abstract— For tetrasulfonated aluminum phthalocyanine (AlPcS 4 ), dimer formation is characterized in the absorption spectrum by a broadening of the Q‐band and the appearance of a new band at the red edge of the spectrum. The high concentrations required to produce dimers, however, often leads to anomalous observation…
X‐ray photoelectron spectroscopy investigation of pumice‐supported nickel catalysts
Abstract Pumice‐supported nickel catalysts, prepared by the method of slow homogeneous precipitation with urea, were analysed by x‐ray photoelectron spectroscopy (XPS). By comparison with similarly prepared silica‐ and alumina‐supported nickel catalysts, a preferential interaction of Ni 2+ with Al 3+ of the support ha…
Grain Size Dependence of Hardness in Dense Submicrometer Alumina
Pressureless sintered alumina compacts with a submicrometer microstructure exhibit a hardness that approaches or even exceeds the level of advanced hotpressed composites of Al 2 O 3 + 35 vol% TiC, whereas the strength of both ceramics is approximately the same. The combination of reduced dislocation mobility (due to t…
Homogeneous Catalysis. Mechanisms of the Catalytic Mukaiyama Aldol and Sakurai Allylation Reactions
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHomogeneous Catalysis. Mechanisms of the Catalytic Mukaiyama Aldol and Sakurai Allylation ReactionsT. Keith Hollis and B. BosnichCite this: J. Am. Chem. Soc. 1995, 117, 16, 4570–4581Publication Date (Print):April 1, 1995Publication History Published online1 May 2002Published…
Nearest-neighbor statistics for packings of hard spheres and disks
The probability of finding a nearest neighbor at some radial distance from a given particle in a system of interacting particles is of fundamental importance in a host of fields in the physical as well as biological sciences. A procedure is developed to obtain analytical expressions for nearest-neighbor probability fu…
Structural and optical properties of poly lactic acids
Fibrous and crystal structures of a helical polymer, poly-L-lactic acid (PLLA), were analyzed by using x-ray diffraction experiments. It was confirmed that the molecular residues were arranged on a nonintegral 10/3 helix as De Santis and Kovacs [Biopolymers 6, 299 (1968)] reported. The atomic positions in a monomeric…
Unprotected Peptides as Building Blocks for the Synthesis of Peptide Dendrimers with Oxime, Hydrazone, and Thiazolidine Linkages
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTUnprotected Peptides as Building Blocks for the Synthesis of Peptide Dendrimers with Oxime, Hydrazone, and Thiazolidine LinkagesJun Shao and James P. TamCite this: J. Am. Chem. Soc. 1995, 117, 14, 3893–3899Publication Date (Print):April 1, 1995Publication History Published o…
“Artificial muscle”: Electromechanical actuators using polyaniline films
Polyaniline films are found to expand and contract by electrochemical oxidation and reduction, respectively. Two polyaniline films are used as cathode and anode muscles. In this system, the proton transfer between the films are essential chemical reaction. Two types of actuators, viz., “Backbone-type” and “Shell-type”…
Present and Future of PLA Polymers
Lactic acid-based aliphatic polyesters (PLAs) are well known biocompatible bioresorbable polymers which are being increasingly used as biomaterials for temporary therapeutic applications. Because of their sensitivity to water and the formation of degradation by-products which can be easily metabolized by microorganism…
Magnetic measurements: A powerful tool in magnetic refrigerator design
Magnetic refrigeration, an emerging new technology for cooling and gas liquefaction, needs magnetic materials with specific thermomagnetic behavior. Depending on the thermodynamic cycle selected, the isothermal magnetic entropy change or the adiabatic temperature change upon field application needs to be a preselected…
Morphology and Thermodynamics of Symmetric Poly(A-block-B-block-C) Triblock Copolymers
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMorphology and Thermodynamics of Symmetric Poly(A-block-B-block-C) Triblock CopolymersReimund Stadler, Clemens Auschra, Joerg Beckmann, Udo Krappe, Ingrid Voight-Martin, and Ludwik LeiblerCite this: Macromolecules 1995, 28, 9, 3080–3097Publication Date (Print):April 1, 1995P…
The Dendritic Box: Shape-Selective Liberation of Encapsulated Guests
No abstract.
Active‐Filler‐Controlled Pyrolysis of Preceramic Polymers
Manufacturing of bulk ceramic components from materials in the system Si‐Me‐C‐N‐O (Me = Ti, Cr, V, Mo, Si, B, CrSi 2 , MoSi 2 , etc.) from preceramic organosilicon polymers ‐ such as poly(carbosilanes), poly(silazanes), or poly(siloxanes) ‐ has become possible by incorporating reactive filler particles into the liquid…