Void formation in zirconium under irradiation in the high-voltage electron microscope

NUCLEAR TRACKS IN SOLIDS PRINCIPLES AND APPLICATIONS, by Robert L Fleischer, P. Buford Price and Robert M. Walker. University of California Press 1975. 605 pages, £20.50.

NEW USES OF ION ACCELERATORS, J. F. Ziegler, ed. Plenum Publishing Corporation, $33.60.

ATOMIC COLLISIONS IN SOUDS, Volumes 1 and 2, Edited by S. Datz, B. R. Appleton and C. D. Moak. Plenum Publishing Corporation, New York, $90.00.

HYPERFINE INTERACTIONS, Journal devoted to research in the border region of solid state, atomic and nuclear physics. Editors: B. I. Deutch and H. de Waard. North-Holland, Amsterdam, $46.95 per year.

ATOMIC ENERGY LEVELS AND GROTRIAN DIAGRAMS, VOL. 1, HYDROGEN I-PHOSPHORUS XV, by S. Bashkin and J. 0. Stoner, Jr., North-Holland Publishing Co., Amsterdam 1975. 615 pp., $59.95, Dfl. 150.00.

THE DYNAMICS OF SPECTROSCOPIC TRANSITIONS, by James D. Macomber. John Wiley and Sons, New York, 1976, $23.00, £1.50. 332 pages, 93 figures, 67 bibliographical references, 37 problems, a general index and a key to symbols.     

Phase transitions in lysozyme solutions characterized by differential scanning calorimetry

The detailed understanding of the structure of biological macromolecules reveals their functions and is thus important in the design of new medicines and for engineering molecules with improved properties for industrial applications. However, obtaining high-quality crystals of proteins for determining structures is still quite difficult in general, and successful protein crystallization remains largely empirical and operator-dependent. In this work, a microcalorimetric technique has been utilized to investigate liquid-liquid phase separation through measuring the cloud-point temperature T^cloud for high supersaturated lysozyme solution, and the structure formation of lysozyme solution at low concentration. Pronounced heat-flow curves dependent on solution conditions during cooling process have been obtained and analyzed. The implications of calorimetric results are (i) as to lysozyme solution at low concentration, aggregates form and grow into clusters with the increase of supersaturation in the absence of glycerol, while three-dimensional network instead of aggregates maybe form in the presence of glycerol; (ii) with respect to concentrated lysozyme solution, the cloud-point temperature increases monotonically with the concentration of sodium chloride, and is decresed when glycerol is added as additive.     

Review of pulsed neutron techniques for the study of amorphous solids

This paper presents some of the advantages of neutrons and pulsed neutron methods for study of amorphous materials. It compares the kinematic constraints on neutron and other spectroscopies, and describes the main features of pulsed neutron beams. The report discusses time-of-flight wide- and small-angle neutron diffractometers, chopper and inverse-geometry spectrometers, and illustrates a method of millisecond-scale time-resolved neutron diffraction.     

Mixing of phases in non-crystalline materials: Application to carbon

The atomic structure of non-crystalline solids is described by the correlation function. When more than one phase is present, the simple addition of the correlation functions for the various phases in proportion to their concentrations within the system is not valid, except in the case of the completely phase-separated system. The overall correlation function must reflect the boundaries between the various phases within the system. The cross correlation functions between the phases have a dependence both on the degree of mixing of the phases and also on the sizes of the domains of the phases. The correlation function for a non-crystalline solid with more than one phase has been derived in a general way. Particular application has been made to non-crystalline carbon for which the correlation function given previously did not have the correct limits because of absence of the cross correlation terms.     

Quantitative model for prediction of hydrodynamic size of nonionic reverse micelles

The sizes of nonionic reverse micelles were investigated as a function of the molecular structure of the surfactant, the type of oil, the total concentration of surfactant [NP], the ratio of surfactant to total surfactant (r), the water to surfactant molar ratio (omega), temperature, salt concentration, and polar phase. The basis of our investigation was a mixture of nonylphenol polyethoxylates--NP4 and NP7, various polar phases, and several oils. Micelle sizes were determined using dynamic light scattering (DLS). A central composite experimental design was used to quantitatively model micelle size as a function of omega, surfactant concentration, and r. The model has demonstrated the capability of predicting the mean diameter of micelles from 4 to 13 with a precision of +/-2 nm as measured by DLS. This quantitative correlation between the size of reverse micelles and the synthetic variables provides the foundation for choosing experimental conditions to control reverse micelle size. In turn, this allows control of the size of nanoparticles synthesized within them.     

A study of rotationally invariant and symmetric indices of diffusion anisotropy.

This study investigated the properties of a class of rotationally invariant and symmetric (relative to the principal diffusivities) indices of the anisotropy of water self-diffusion, namely fractional anisotropy (FA), relative anisotropy (RA), and volume ratio (VR), with particular emphasis to their measurement in brain tissues. A simplified theoretical analysis predicted significant differences in the sensitivities of the anisotropy indices (AI) over the distribution of the principal diffusivities. Computer simulations were used to investigate the effects on AI image quality of three magnetic resonance (MR) diffusion tensor imaging (DTI) acquisition schemes, one being novel: the schemes were simulated on cerebral model fibres varying in shape and spatial orientation. The theoretical predictions and the results of the simulations were corroborated by experimentally determined spatial maps of the AI in a normal feline brain in vivo. We found that FA mapped diffusion anisotropy with the greatest detail and SNR whereas VR provided the strongest contrast between low- and high-anisotropy areas at the expense of increased noise contamination and decreased resolution in anisotropic regions. RA proved intermediate in quality. By sampling the space of the effective diffusion ellipsoid more densely and uniformly and requiring the same total imaging time as the published schemes, the novel DTI scheme achieved greater rotational invariance than the published schemes, with improved noise characteristics, resulting in improved image quality of the AI examined. Our findings suggest that significant improvements in diffusion anisotropy mapping are possible and provide criteria for the selection of the most appropriate AI for a particular application.     

Dynamic Behavior of Organic Reactive Intermediates

An unexpected yes is the answer the author gives to the following questions: If a reactive intermediate was faced with two equally high energy barriers to product formation, could the kinetic product ratio ever be anything other than 1:1? If the two barriers were of unequal height, could there ever be a preference to form the product that corresponds to the higher barrier pathway? The basis for this yes are the results from molecular dynamics simulations and experiments that suggest that the interpretation of reaction mechanisms by statistical models is not always correct.