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Electron diffraction study on the preceding states of martensitic phase transition in AgCd shows that small β 2 phase domains are formed as embryos of the martensites. Their formation process depends strongly on the surrounding stress field. Each domain contains various degrees of the shear, which are introduced in order to release the stress field. Anomalous diffraction phenomena of the β 2 phase regions are observed and they are explained by a model of the sheared β 2 lattice.

A simple generalization of the Anomalous Diffraction light scattering approximation is proposed which enables linear birefringence and linear dichroism to be calculated for dispersions of colloidal particles. The case is considered of completely orientated, intrinsically anisotropic, spherical particles. The Anomalous Diffraction approximation shows that the relation between the optical properties of the dispersion, and the optical properties of its constituent particles, is much more complicated than for particles of molecular size, i.e., Rayleigh scatters. The empirical Zocher's Rule, which states that the linear dichroism is a maximum when the linear birefringence is zero, is shown to follow from the Anomalous Diffraction approximation.

Single intrinsic stacking faults in f.c.c. crystals are observed to give rise to diffraction spots in h.c.p. positions and anomalous diffraction spots in twin positions. This, together with similar observations in diffraction patterns from overlapping faults, are discussed in relation to the problem of determining the extent to which overlapping faults generated by plastic deformation constitute nuclei of h.c.p. or twinned material. The results suggest that nuclei of twin or h.c.p. material develop by the filling in of a disordered array of faults rather than by the operation of polar mechanisms.

New methods were recently developed for calculating the differential and total scattering cross sections of ellipsoids of revolution. In one, the extended boundary condition method numerically solves Maxwell's equations exactly for this and other particle shapes. In the other, postulates of the Rayleigh-Gans-Debye and anomalous diffraction approximations and the Lorenz-Mie equations are used to obtain improved approximate methods for ellipsoids. In this paper, these methods are used to calculate differential and total scattering cross sections and the corresponding scattering efficiencies of prolate and oblate ellipsoids. Comparisons of the results provide an independent check of each method. They also supply a basis for assessing the roles of the various mechanisms of the wave-particle interaction.

A computer analysis is made on a six-beam diffraction on (220), (242), (044), (224), and (202) of Ge and the anomalous diffraction which is observed near the intersection points of anomalous transmission lines is interpreted. When an incident X-ray satisfies the condition of simultaneous diffraction, several excited waves have very small absorption coefficients and the same direction of propagation, but they propagate towards various directions in the crystal according to the shape of the dispersion surface, if the incident X-ray deviates only a little from the six-beam condition. The observed anomalous diffraction is regarded as the traces of the survived waves in the crystal which are excited by the incident X-rays nearly satisfying the six-beam condition and describes one part of the dispersion surface. Eine Sechsstrahlinterferenz auf (220)-, (242)-, (044)-, (224)- und (202)-Flachen des Germaniums wird mittels Computer analysiert und die anomale Beugung interpretiert, die man in der Nahe des Schnittpunktes der anomalen Durchdringungslinien beobachtet. Wenn ein einfallender Rontgenstrahl die Sechsstrahlinterferenz erzeugt, haben einige angeregte Wellen sehr kleine Absorptionskoeffizienten und die gleiche Fortpflanzungsrichtung, pflanzen sich jedoch in unterschiedlicher Richtung im Kristall entsprechend der Form der Dispersionsflache fort, wenn der Einfallsstrahl von der Richtung der Sechsstrahlinterferenz auch nur ein wenig abweicht. Die beobachtete anomale Beugung wird als geometrischer Ort der im Kristall uberlebenden, angeregten Wellen angesehen und entspricht einem Teil der Dispersionsflache.

The Synchrotron Resource of the Howard Hughes Medical Institute will be dedicated to structural analyses of biological macromolecules, primarily through crystallography. This facility is under construction at the X4 port of the National Synchrotron Light Source at Brookhaven National Laboratory, and it will comprise three beamlines. The first line to be built has been devised to apply the multiwavelength anomalous diffraction method which provides direct estimates for the phases of reflections. The second line will be devoted to rapid and essentially routine diffraction measurements, mainly through the rotation method. These two experimental stations are contained within refrigerated radiation enclosures that will maintain clean environments, narrowly defined constant temperatures, and protection against biohazard at biosafety level BL‐2. At the same time as the second line will be developed, the swath center is planned to first serve as a monitor of the white x‐ray beam vertical stability. This project w...

This communication reports the occurrence of anomalous paired diffraction spots and image fringes from thin gold films on graphite substrates. The observations are considered with regard to their possible origin.

InAlAs crystals grown on (001) InP substrates by molecular beam epitaxy have been structurally investigated for the first time by transmission electron microscopy. Modulated structures lying in two equivalent directions of 〈100〉 and 〈010〉 are found in crystals grown at 500–560°C. In the crystals grown at temperature below 500°C, anomalous diffraction contrast elongating in the 〈110〉 direction is present. Ordered strutures of CuPt-type are also found in these crystals. Only two of the four equivalent variants are observed in the (110) cross-section. The super-spots are observed only in the crystals grown at 435–505°C and their intensity is weaker than in MOCVD-grown InGaP. These results suggest that the ordering is not perfect and that ordered regions are likely to be microdomains.

STEM microdiffraction is used to study the structure of polycrystalline thin gold films grown at room temperature on a NaCl substrate. Individual grains were diffracted in regions having a lateral resolution of 120-400 A.The patterns show anomalous spots which can be indexed in terms of a hexagonal net. A number of zone axes of the hexagonal structure are shown. Several possibilities for explaining the forbidden intensities are discussed.

The influence of substrate temperature between 200 and 700 °C on the growth process of iron which was sublimed onto (111) gold platelets was investigated. Between 400 and 500 °C the morphology of the iron overgrowth changed dramatically from a random island growth mode to needle-like rods with well-defined crystallographic boundaries along the 〈110〉 directions on the subtrate. This change in morphology is attributed to a higher surface mobility as revealed by the decreasing angle φ of misorientation with temperature. Anomalous diffraction spots from iron samples prepared at substrate temperatures between 300 and 400 °C were observed.

Premelting phenomena have been searched for in pure, perfect gallium crystals by using anomalous X-ray transmission. The temperature dependence of the integrated intensity under the Bragg peak does not reveal any deviations from its normal behaviour, i.e. an essentially linear increase of the mean square vibrational amplitude of the lattice atoms as a function of temperature between 10 °C and a temperature at least 10−4 °C close to the melting temperatureT m =29.75 °C. The temperature dependence of the integrated intensity of the 020-reflection can be described by a Debye temperatureΘ (020)=189±6 K. Premelting effects could not be detected.

The anomalous diffraction approximation has been used in an attempt to account for the low-angle scattering from composite spheres. These are used as models for biological cells. Solutions have been obtained for both thinly and thickly coated spheres.

In anamolous transmission patterns of germanium {220}{220}/{422} type of simultaneous reflections cause a kind of anomalous diffraction in the vicinity of the cross point of the corresponding {220} lines. The anomaly has a doublet structure and the amount of the anomaly depends on the wavelength of X-ray and the thickness of the specimen. Considering a simple model of the anomaly, the doublet structure is attributed to the spectral doublet of the X-ray. The wavelength and specimen thickness dependency of the anomaly can be explained by considering the path of X-ray energy flow in the crystal. In anomalen Durchdringungsfiguren von Germanium erzeugt ein gleichzeitiger Reflex des {220}{220}/{422} Typus irgendeine anomale Raumgitterinterferenz in der Nahe des Kreuzungspunktes der {220} Linien. Die Anomalie hat eine Dublett-Struktur und die Quantitat der Anomalie ist abhangig von der Wellenlange der Rontgenstrahlen und von der Probendicke. Aus einem einfachen Modell der Anomalie kann man folgern, das die doppelten Strukturen von den Rontgenstrahlen-Dubletts herruhren. Die Abhangigkeiten der Anomalien von der Wellenlange und von der Probendicke konnen mit dem Lauf des Energieflusses der Rontgenstrahlen im Kristall erklart werden.

SUMMARY: Application of the anomalous diffraction theory of van de Hulst to turbidity measurements of Gram-positive bacteria is discussed. It is shown that this method is capable of detecting characteristic morphological changes during growth. Comparison with the cell mass method and direct observations of Micrococcus freudenreichii suggest that these changes are primarily related to cluster size. Initial application of the method in the study of osmotic change in Bacillus megaterium is described.

The annealing textures of cold-drawn molybdenum, iron, and an iron base alloy containing 14 pet Al were investigated as a function of annealing temperature by using neutron diffraction techniques. Upon recrystallization, the [110] deformation texture was retained in all cases, and the texture became progressively sharper with increasing annealing temperature. At high temperatures, however, in the case of molybdenum, a new texture appeared. An anomalous diffraction effect was observed for iron; certain (110) plane orientations yielded more integrated intensity than others. Consideration of the problem showed a magnetostrictive effect to be improbable, and a hypothesis concerning the preferred distribution of grains deviating from the ideal [110] orientation is proposed.

Mitomycin C (MC) is a potent anticancer agent. Streptomyces lavendulae, which produces MC, protects itself from the lethal effects of the drug by expressing several resistance proteins. One of them (MRD) binds MC and functions as a drug exporter. We report the crystal structure of MRD and its complex with an MC metabolite, 1,2-cis-1-hydroxy-2,7-diaminomitosene, at 1.5 Å resolution. The drug is sandwiched by π-stacking interactions of His-38 and Trp-108. MRD is a dimer. The βαβββ fold of the MRD molecule is reminiscent of methylmalonyl-CoA epimerase, bleomycin resistance proteins, glyoxalase I, and extradiol dioxygenases. The location of the binding site is identical to the ones in evolutionarily related enzymes, suggesting that the protein may have been recruited from a different metabolic pathway.

Extinction curves in the eikonal approximation and the anomalous diffraction approximation have been compared with exact extinction curves for homogeneous spheres of various refractive indices. Our results show the anomalous diffraction approximation to be more suitable for extinction calculations.

The problem of multiple scattering of light by dense particle fields in a light scattering measurement technique is resolved. A mathematical model for this phenomenon is developed which predicts the light energy distribution produced by any given size distribution at any obscuration. The mathematical analysis is carried out for Fraunhofer and the anomalous diffraction theories. A systematic procedure is established to correct for the effect of multiple scattering. Excellent agreement with experimental results is obtained. The study therefore enables the application of the measurement technique to very dense particle fields.

The crystalline structure of small gold particles in the size range between 50–200 Å is studied using STEM in microdiffraction.It is found that some single-crystalline particles showed an anomalous diffraction pattern. In some cases these pattern be indexed as an hexagonal lattice with a ratio c/a= 2.46. A number of models to explain the hexagonal diffraction are discussed. In some other cases the patterns correspond to fcc structures but with a large splitting effect. The results reveal the strong dynamical character of the diffraction by small gold particles.

Small-angle laser light diffraction has been used to measure the size distribution and relative concentration of solid particles in liquids. The technique has been extended from spherical to non-spherical convex particles, to the determination of absolute concentration and, finally, to systems where the values of refractive index of solid and liquid are close together.

Single-wavelength anomalous diffraction (SAD) phasing from multiple crystals can be especially challenging in samples with weak anomalous signals and/or strong non-isomorphism. Here, advantage is taken of the combinatorial diversity possible in such experiments to study the relationship between merging statistics and downstream metrics of phasing signals. It is furthermore shown that a genetic algorithm (GA) can be used to optimize the grouping of data sets to enhance weak anomalous signals based on these merging statistics.

We report on the first experimental demonstration of anomalous diffraction, negative refraction and image transmission via coherent-destructive-tunneling in optically-induced three-dimensional photonic lattices, in good agreement with our theoretical predictions.

X-ray anomalous diffraction in different geometries and X-ray resonant magnetic scattering have been used to investigate Fe x Mn 1− x /Ir(001) superlattices. The influence of the alloy stoichiometry on the structural and magnetic properties has been studied and compared with the bulk alloy properties. The structural results are compared with the magnetic results in order to understand the outstanding properties of these systems.

We demonstrate coherent destruction of tunneling (CDT) in optically induced three-dimensional photonic lattices. By fine-tuning the lattice modulation, we show unusual behavior of beam propagation, including light tunneling inhibition, anomalous diffraction, and negative refraction mediated by zero or negative coupling in the waveguide arrays. Image transmission based on CDT is also proposed and demonstrated. Our experimental results are in good agreement with our theoretical analyses.

The available diffraction-corona theory for the interpretation of the cloud iridescence phenomenon is reviewed and applied to photographic observations of an iridescent contrail. It is concluded that the simple-diffraction theory qualitatively explains the occurrence of corona and iridescence under the cloud microphysical conditions with which these phenomena are typically associated, and that the theoretical predictions of cloud droplet diameters of 1–3 μm during initial contrail formation appear to be reasonable for a highly supersaturated environment. However, additional Mie theory simulations utilizing narrow droplet size distributions should be performed to assess the impact of anomalous diffraction in realistic cloud compositions in order that iridescence observations may be more precisely interpreted for cloud microphysical studies.

For the eleven pairs of enantiomorphous space groups there are special sums of triple-product phases (identities), the values of which depend on the space group. By means of anomalous diffraction that sum of phases can be estimated without a priori determination of the structure |Kroon, Spek & Krabbendam (1977). Acta Cryst. A33, 382-385]. It is shown that, as a consequence of this, a priori space-group determination (and enantiomorph determination) can be effected for this class of space groups.

The Peterlin and Stuart formulation of the optical anisotropy parameter (ga–gb) is discussed in the case of large rigid macromolecules or colloidal particles in dilute solutions or dispersions. Whereas the Peterlin and Stuart expressions indicate that (ga–gb) is independent of particle size for a given particle in a given continuous medium, this has not been found experimentally. Another formulation of (ga–gb) is proposed, based on the anomalous diffraction theory of light scattering by large particles. In contrast to the Peterlin and Stuart expressions, this anomalous diffraction expression predicts a strong particle size dependence for wavelength-sized colloidal particles. The particle size dependence of (ga–gb) found recently in kaolinite clay dispersions receives a satisfactory explanation in terms of the anomalous diffraction theory. The relevance of the anomalous diffraction theory to the theories of all induced birefringences is discussed, as these now appear to be in error for large particles. Similarly, particle sizing methods which assume that (ga–gb) is particle size independent appear to be invalid for large particles.