Inelastic electron scattering from 31P

Form factors for the electroexcitation of the $\text{3}\text{2}$⁺ (1.27 MeV), $\text{5}\text{2}$⁺ (2.23 MeV), and $\text{3}\text{2}$⁺ (3.51 MeV) states in ³¹P have been measured for momentum transfers from 0.36 to 0.80 fm^?1 at the NBS electron scattering facility. In addition, form factors for the 2.23 MeV state in the momentum transfer range 0.74 to 1.78 fm^?1 have been extracted from data obtained in a previous experiment. Using the DUELS distorted-wave code the B(E2, ω) ↓ were found to be 6.0 ± 0.9, 6.9 ± 0.3, and 2.7 ± 0.3 W.u. for the 1.27, 2.23, and 3.51 MeV states, respectively. The form factors for these states, calculated using wave functions derived in an intermediate-coupling vibrational calculation, are compared with the data.     

Reactions of epoxy-1,1,2-trichloroethane with nudeophiles

Epoxy-1,1,2-triehloroethane (1) was synthesized by the autuoxidation of trichloroethylene and was characterized. It was shown to react readily with 2-mercaptobenzirnidazole (2), 1 -melhyl-2-mercaptoimidazole ( 3 ), p-nitrolhiophenol ( 4 ), and 3,4-dichlorolhiophenol ( 5 ) forming 2-chloro-2-(benzirnidazole-2-thio)acelie acid ( 6 ), 2-ehloro-2-(1-methylirnidazole-2-thio)aeetic acid (characterized as methyl ester ( 8 )), 2-chloro-2-(4-nitrolhiothiophenoxy)-4-nilrophenylthioaeetate (9), and 2-chloro-2-(3,4-dichlorothiophenoxy)-3,4-dichlorophenylthioaeetale ( 10 ), respectively. Base hydrolysis of 9 yielded 2,2-di(4-nilrothiophenoxy)acetie acid ( 11 ). Adducl 9 decomposed on silica gel yielding p-nitrophcnyldisulfide ( 12 ).     

Specific volume studies of γ-irradiated polytetrafluoroethylene from 40 to 150°C

The effect of γ-irradiation and post-irradiation heat treatment on the specific volume versus temperature relationships of polytetrafluoroethylene (PTFE) samples (1/2-in. diameter rods) have been studied over the 40–150°C. temperature range for radiation doses up to 8.9 X 10⁸ rad. At low doses the specific volume at any temperature decreased with dose, but above about 10⁸ rad it increased with dose. Similarly, the rate of volumetric expansion initially decreased with dose, while, at very high doses (8.9 X 10⁸ rad) the rate of expansion at temperatures above 100°C. exceeded that of the unirradiated PTFE. Heating at 150°C. for 100 hr. produced a substantial decrease in the specific volume and a decrease in the rate of expansion for the irradiated samples. Irradiation effects in PTFE are considered to be a result of such factors as radiation-induced chain scission, increased crystallinity, and increased void content. Changes resulting from post-irradiation heat treatment can be attributed to increased crystallinity, decreased void content, and weight loss.     

Advancing the computational methodology of rigid rod and semiflexible polymer systems: A new solution to the wormlike chain model with rod‐coil copolymer calculations

A wormlike chain model for rod type blocks in a rod‐coil diblock copolymer is implemented in the self‐consistent field theory (SCFT) formalism. A pseudo‐spectral method is used to solve for the single‐chain partition function of this copolymer system. Orientation degrees of freedom are discretized using Lebedev sphere rules such that orientation integrations are carried out through a Lebedev quadrature, an approach not used previously in tandem with the pseudo‐spectral method. Phase behavior in the rigid‐rod limit as a function of rod segment volume fraction, Flory–Huggins interaction parameter χ , degree of polymerization N , and rod contour length ratio β are examined in detail in one and two dimensions. Examples extending to three dimensions are included. Semiflexible behavior via the rod bending rigidity κ is explored. An approximation is used for rigid‐rods that do not need spherical harmonics leading to increased speed in finding equilibrium morphologies. The results show that standing vertical structures may be more easily produced with rigid‐rod blocks compared to coil‐coil lamellae, an important feature in nanolithographic applications. Suggestions are made for using the model in future molecular orientation studies where the model can be used with inverse search methods to measure the values of the model parameters for the real systems. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 29–39     

Spatial energy estimates in dynamical problems for a semi-infinite piezoelectric beam

The behaviour of the total energy for a semi-infinite piezoelectricbeam, with uniform or variable cross-section, in dynamical conditionsis investigated. Precisely, we obtain some estimates in termsof the data for the energy of the portion of the body at distancegreater than z from the base and for its norm in L¹(0,t) (wheret is an arbitrary positive time). We obtain some estimates whichdepend on the initial data if t z/V (where V is a computablepositive material constant); if t > z/V, by using also theKorn inequality, we show that the bounds depend on all the data.Under mild hypotheses on the initial data we derive the asymptoticbehaviour of the energy as z +. All possible combinations ofboundary conditions are examined and the kind of the estimateis formally the same for all the problems whether the beam isa cylinder or not.     

Angstrom-to-millimeter characterization of sedimentary rock microstructure

Backscatter SEM imaging and small-angle neutron scattering (SANS) data are combined within a statistical framework to quantify the microstructure of a porous solid in terms of a continuous pore-size distribution spanning over five orders of magnitude of length scale, from 10 A to 500 microm. The method is demonstrated on a sample of natural sandstone and the results are tested against mercury porosimetry (MP) and nuclear magnetic resonance (NMR) relaxation data. The rock microstructure is fractal (D=2.47) in the pore-size range 10 A-50 microm and Euclidean for larger length scales. The pore-size distribution is consistent with that determined by MP. The NMR data show a bimodal distribution of proton T(2) relaxation times, which is interpreted quantitatively using a model of relaxation in fractal pores. Pore-length scales derived from the NMR data are consistent with the geometrical parameters derived from both the SEM/SANS and MP data. The combined SANS/BSEM method furnishes new microstructural information that should facilitate the study of capillary phenomena in hydrocarbon reservoir rocks and other porous solids exhibiting broad pore-size distributions.