Materials Literature
按标题、摘要、年份、主题和来源检索公开元数据。结果保留作者、摘要、分类与原始来源链接。
The role of pH, temperature, salt type, and salt concentration on the three possible transformations involving the crystalline, dispersed helical, and randomly coiled forms of collagen has been investigated. The results are given in terms of pseudo phase diagrams where the field of stability of each form is delimited…
Abstract The kinetics of alkaline degradation of cotton hydrocellulose were determined in 5% NaOH at various temperatures. An activation energy of 24 kcal./mole was found for the endwise degradation reaction, while that of termination to a stable m ‐saccharinic acid endunit is 32 kcal./mole. Consequently, the DP n of…
The fluorescence of Eu3+-activated lanthanide oxyhalides LnOX (Ln=Y, La, Gd, and X=Cl, Br) is reported. Although all host lattices under consideration are isomorphous, the spectral energy distribution of the Eu3+ emission depends strongly on the choice of X and to a lesser extent on that of Ln. This variation is accou…
No abstract available.
Proceedings of the National Academy of Sciences (PNAS), a peer reviewed journal of the National Academy of Sciences (NAS) - an authoritative source of high-impact, original research that broadly spans the biological, physical, and social sciences.
The glass-transition temperatures of 34 liquids have been measured by differential thermal analysis, and the results compared with the values predicted from viscosity measurements by the equation lnη = A″+B″/(T—T0). In those liquids which have two non-Arrhenius viscosity regions, there is good agreement between observ…
A survey is made of all published data on self-diffusion in liquid metals and an examination is carried out on the temperature-dependence of D for studies covering a wide range of temperatures. Log D versus 1/T and D versus T represent the best data equally well, while D versus T 1/2 and D versus T 2 do not. The prope…
Experiments on the vacuum flashover of dielectric frusta subjected to 35 and 75 nsec pulses show the strong influence of cone angle on insulation strength. A theory is presented to explain the formative process leading to flashover for one polarity. It is proposed that positive surface charge grows by emission of hot…
The molybdates of Sm, Eu, Tb, and Dy are isotypic with ferroelectric Gd2(MoO4)3. Other compositions of this structure occur in the pseudoternary system Gd–La–Y-molybdate and in the pseudobinary system Gd2(MoO4)3–Gd2(WO4)3. A representative number of these compositions were grown as single crystals and tested for ferro…
Abstract Calcium carbonate samples containing known amounts of additives and impurities have been calcined in air at a series of temperatures for different lengths of time. Changes in specific surface and average crystallite size show the effect of the additives and impurities (accessory minerals in limestones and cha…
Rates of tail regeneration in the Madeira wall lizard (Lacerta dugesii) and the slow-worm (Anguis fragilis) were studied. L. dugesii regenerates very rapidly, the new tail sometimes attaining a maximum rate of growth of 2'6 mm a day during the fifth week after autotomy. By the twelfth week 90% of the original tail len…
The vaporization behavior of the titanium—oxygen system has been established by experimental measurements of the change in composition of the solid residue accompanying vaporization as determined by x-ray diffraction, chemical analysis, and color of sample. The solid phases studied were Ti2O, TiO, Ti2O3, Ti3O5, Ti4O7,…
The fluorescence quenching of the two phosphors Ba2Gd1−xEuxMe5+O6 (Me5+=Nb5+ or Ta5+) and Gd1−xEuxAl3B4O12 is reported. The shortest distance between the rare-earth sites in these materials is large and nearly equal, viz., 6.0 and 5.9 Å, respectively. The quenching behavior is different: In the materials Ba2Gd1−xEuxMe…
Observations on thermophilic algal communities during a three‐year period at Mount Rainier National Park and during January 1965 and 1966 in Yellowstone National Park have been analyzed to evaluate the distribution of species in thermal streams relative to temperature and competitive interaction. Although temperature…
Abstract A T‐x‐section of the phase diagram is proposed for the system CuMnO in air between 750 and 1,400°C. From X‐ray and chemical analyses on quenched samples and from high‐temperature X‐ray diffraction studies the occurrence of the following phases is deduced: a cubic phase α‐Mn 2 O 3 , a phase Cu x Mn 3−x O 4+γ…
A plot of the initial spreading pressures (F sub ba) or initial spreading coefficients (S sub ba) against the surface tensions of a homologous series of organic liquids b can be used to determine the critical surface tension for spreading on a second substrate liquid phase a. Straight-line relations are found for vari…
Abstract Activation energy E , pre‐exponential factor k 0 , and reaction order n for the pyrolysis of α‐cellulose and cellulose modified with dihydrogen ammonium phosphate were determined by means of TGA and DTA. The results obtained are E = 53.5 kcal./mole, k 0 = 10 18.8 min. −1 , n = 1 for α‐cellulose and E = 32 kca…
Growth of Escherichia coli in medium containing glucose, at a concentration insufficient to support full growth, and containing lactose, is diauxic. A mutation in the gene, CR, which determines catabolite repression specific to the lac operon, was found to relieve glucose-lactose but not glucose-maltose diauxie. Furth…
Certain general features of the second-order reduced density matrix, or 2 matrix, for configuration-interaction (CI) wavefunctions are reviewed, with special reference to the simplifying features of spin singlet states. A restricted form of CI in which all spatial orbitals are doubly occupied (DOCI) is proposed for si…
Phase relations for the systems ZrO 2 –WO 2 –WO 3 and HfO 2 –WO 2 –WO 3 from 1000° to 1700° C were determined by the quenching technique using sealed sample containers. In the system ZrO 2 –WO 3 , 1:2 compound, ZrW 2 O 8 forms, having a cubic structure with a = 9.159 A. The ZrW 2 O 8 melts incongruently at 1257°± 3°C…