Materials Literature
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The structure of RP 71955, a new tricyclic 21 amino acid peptide active against human immunodeficiency virus 1, was determined. Its amino acid composition was inferred from the results of fast atom bombardment mass spectrometry, nuclear magnetic resonance, Raman spectroscopy, and amino acid analysis. Its sequence coul…
Abstract In the present study, the dose‐rate effects of γ‐irradiation in air on two isotactic polypropylene grades of different molecular weight distribution, used for medical devices, were investigated. The thermal, mechanical, rheological, and photometric properties of these materials were examined using DSC, stress…
This paper deals with the application of simulated annealing to rock magnetism. The implementation of the algorithm is discussed in detail. It is shown that the technique can be used to determine stable micromagnetic structures by finding very low energy states which are not easily found using other optimization techn…
Abstract This article presents crystallization kinetics studies on a cocrystallizing polymer highdensity polyethylene (HDPE)/linear lowd‐ensity polyethylene (LLDPE) blend. The nonisothermal crystallization exotherms obtained by differential scanning calorimetry (DSC) were analyzed to investigate the effect of cocrysta…
The electrical characteristics of chemically vapor deposited (CVD) diamond films were measured as a function of film thickness. The samples studied were polycrystalline with the average grain size increasing from approximately 1 μm on the substrate side to approximately 30 μm on the growth surface for the thickest sam…
We report on a novel technique for synthesizing large quantities of single-shell carbon nanotubes in a dc arc with a composite anode of graphite and copper. Based on systematic studies involving a varying diameter and distribution of copper rods inside the graphite anode, we have correlated the presence of copper to t…
Abstract Polycondensation of dimethylolurea leads to the formation of a gel or a film according to the experimental conditions. Both forms of the polymer would be characterized by a specific chemical structure, i.e., dimethylene ether or diaminomethylene, respectively. We studied both forms of dimethylolurea polymer b…
We report on a small angle neutron scattering study of the flux-line lattice in single crystal 2H-${\mathrm{NbSe}}_{2}$. As the magnetic field is tilted away from the crystalline c axis, we find distortions in the flux lattice as would be expected for a mass anisotropy \ensuremath{\Gamma}=10.1\ifmmode\pm\else\textpm\f…
The itinerant electron ferromagnetism in La 1-x Sr x CoO 3 (0.1<or=x<or=0.5) has been reinvestigated. AC magnetic susceptibility studies on these systems have been carried out for the first time. The nature of the susceptibility indicates the freezing of superparamagnetic clusters at low values of x (<0.3) and long-ra…
Samples of FeCu, FeCuMn, FeCuNi, and FeCuCr alloys containing 1.5 wt% of each solute have been electron irradiated around 290 degrees C or thermally aged at 500 degrees C for various times. It is known that such treatments induce Cu precipitation; the Cu depletion of the matrix is measured by the resistivity decrease…
We study phonon transport in random 3D lattices when the mean free path l becomes comparable to the lattice spacing a. Through numerical simulation, it is shown that in contrast to the electronic case, here the Ioffe-Regel criterion is inaccurate in the prediction of phonon localization. By using the Thouless criterio…
The low-temprature heat capacity and ac and dc magnetic properties of (Dy0.5Er0.5)Al2 have been studied as a function of magnetic fields up to ∼10 T. The magnetocaloric effect in (Dy0.5Er0.5)Al2 is 30% larger than that of the prototype material, GdPd. Magnetic measurements show that there is no measurable magnetic hys…
Abstract The effect of viscosity ratio and processing conditions on LCP/PP blend morphology was studied. The viscosity ratio (η LCP /η PP ) was varied from 0.1 to 3.6 by using five different polypropylene grades as the matrix and two LCPs as the dispersed phase (20 wt %). The most spontaneous fiber formation was achie…
New ENDOR measurements on the single substitutional nitrogen centre in diamond are reported. The CW-ENDOR mechanism utilizes cross relaxation, and measurements have been made on both 14 N and 15 N, as well as the first detailed 13 C ENDOR study on the isotope at the natural abundance of 1.1%. The change in EPR intensi…
Abstract Cellulose fibers have been surface‐modified by selected cold, microwave plasma treatments. Inverse gas chromatographic (IGC), XPS, and SEM analyses showed surface treatment to be incomplete, but, nevertheless, effective in controllably altering the acid/base interaction balance of fiber surfaces. Surface‐modi…
The visible luminescence of porous Si is known to contain at least two spectrally distinct emission bands with widely different response times. The orange-red luminescence component (1.5–1.9 eV) decays in times being of the order of 10 μs at room temperature. The blue-green band (2.3–2.6 eV) is very much faster with r…
Porous silicon carbide has been fabricated using single crystal 6H-SiC that has a wider indirect band gap than silicon crystal. Intense blue-green luminescence has been observed at room temperature. The peak wavelength is around 460 nm, below the band gap of crystalline SiC. The luminescence intensity is about 100 tim…
We report here our discovery of bulk superconductivity at rather high ${\mathit{T}}_{\mathit{c}}$ in samples having nominal compositions ${\mathrm{YNi}}_{4}$${\mathrm{BO}}_{0.2}$ (${\mathit{T}}_{\mathit{c}}$\ensuremath{\approxeq}12.5 K) and ${\mathrm{YNi}}_{2}$${\mathrm{B}}_{3}$${\mathrm{O}}_{0.2}$ (${\mathit{T}}_{\ma…
Abstract To obtain poly(lactic acid) (PLA) complex fibers, spinning was performed by wet and dry methods from 5–10 g/dL chloroform solutions of poly(D‐lactic acid) (PDLA) and poly(L‐lactic), both with a viscosity‐average molecular weight of 3 × 10 5 . The dope was extruded from a monohole nozzle into coagulation baths…
Laser radiation (XeCl laser, 308-nanometer wavelength) focused into a cell containing Mo(CO)(6) vapor produced ultrafine particles in the extended waist of the laser beam. Negative ion mass spectrometry revealed molybdenum carbide cluster ions with a stoichiometry MonC4n (n = 1 to 4). The MonC4n(-) (n = 2 to 4) ions a…