With the explosive growth of World Wide Web, it is becoming increasingly difficult for users to collect and analyze Web pages that are relevant to a particular subject. In this paper, a subject-oriented Web information classification system (WICS) is presented, by which Web pages can be efficiently collected and classified into several subjects, and the search results are provided to users. Based on analyzing the ordinary search engines, Web text mining is introduced and applied to the WICS. The text preprocessing, index, inverted files and vector space distance algorithm (vector space model, VSM) are brought forward in the prototype. The initial experiments show that classify Web information by the prototype makes convenience for users to inquire information; the relevancy and precision are improved.

The recent status of the SPring-8 Taiwan Contract Beamline BL12132 is reported. The beamline was designed to provide multiple applications for materials and biological researches. It is equipped with four end stations, including an EXAFS station, a Huber 6-circle diffractometer for X-ray scattering, a curved image plate for the studies of powder diffraction, and a station for the protein crystallography. The beamline construction was completed in 2000 and it has been in full speed operation since September 2001. To enhance the focusing capacity, the beamline optics has been modified in 2002 and a gain of factor of 10 in photon flux was consequently obtained at protein crystallography station.

A challenge in neutron diffraction experiments is growing large (greater than 1 cubic millimeter) macromolecule crystals.In taking up this challenge we have used statistical experiment design techniques to quickly identify crystallization conditions under which the largest crystals grow.These techniques provide the maximum information for minimal experimental effort, allowing optimal screening of crystallization variables in a simple experimental matrix, using the minimum amount of sample.Analysis of the results quickly tells the investigator what conditions are the most important for the crystallization.These can then be used to maximize the crystallization results in terms of reducing crystal numbers and providing large crystals of suitable habit.We have used these techniques to grow large crystals of glucose isomerase.Glucose isomerase is an industrial enzyme used extensively in the food industry for the conversion of glucose to fructose.The aim of this study is the elucidation of the enzymatic mechanism at the molecular level.The accurate determination of hydrogen positions, which is critical for this, is a requirement that neutron diffraction is uniquely suited for.Preliminary neutron diffraction experiments with these crystals conducted at the Institute Laue-Langevin (Grenoble, France) reveal diffraction to beyond 2.5 Ǻ. Macromolecular crystal growth is a process involving many parameters, and statistical experimental design is naturally suited to this field.These techniques are sample independent and provide an experimental strategy to maximize crystal volume and habit for neutron diffraction studies.

A challenge in neutron diffraction experiments is growing large (greater than 1 cubic millimeter) macromolecule crystals.In taking up this challenge we have used statistical experiment design techniques to quickly identify crystallization conditions under which the largest crystals grow.These techniques provide the maximum information for minimal experimental effort, allowing optimal screening of crystallization variables in a simple experimental matrix, using the minimum amount of sample.Analysis of the results quickly tells the investigator what conditions are the most important for the crystallization.These can then be used to maximize the crystallization results in terms of reducing crystal numbers and providing large crystals of suitable habit.We have used these techniques to grow large crystals of glucose isomerase.Glucose isomerase is an industrial enzyme used extensively in the food industry for the conversion of glucose to fructose.The aim of this study is the elucidation of the enzymatic mechanism at the molecular level.The accurate determination of hydrogen positions, which is critical for this, is a requirement that neutron diffraction is uniquely suited for.Preliminary neutron diffraction experiments with these crystals conducted at the Institute Laue-Langevin (Grenoble, France) reveal diffraction to beyond 2.5 Ǻ. Macromolecular crystal growth is a process involving many parameters, and statistical experimental design is naturally suited to this field.These techniques are sample independent and provide an experimental strategy to maximize crystal volume and habit for neutron diffraction studies.

The effects of anomalous dispersion (resonance) on multiple reflection of x rays and their interference in crystals at atomic absorption edges are studied. Intensity ratios of two inversion-symmetry-related multiple diffractions at or near absorption edges exhibit highly phase-sensitive profiles with strong asymmetric characteristics, unlike those far from the edges. A new resonance perturbation Bethe approach is developed to explain this behavior. This leads to direct determination of the phase change for x-ray reflections at resonance.

The polarization suppression of the interfering components in X-ray multiple-wave interaction is observed for the first time by using a polarization analyzer with an arbitrary inclination of the diffraction plane with respect to that of the investigated crystal. The condition for total suppression of the multiple-wave interaction outside the investigated crystals by a polarization analyzer is derived theoretically from the modified Born approximation. By means of the partial suppression of the strong interfering component, the increase in the visibility of multiple-wave interference is experimentally and theoretically demonstrated. The proposed experimental polarization-resolved technique provides an operational way to enhance the visibility of X-ray multiple-wave interaction outside the investigated crystals for direct phase determination.

A detailed analysis of multiple diffraction data collected by the stereoscopic multibeam imaging technique from a tetragonal lysozyme crystal is reported. Calculations based on the dynamical theory are employed to account for diffraction profiles obtained with Bragg-angle scan in stereoscopic imaging and the conventional azimuthal scan in Renninger arrangement. The formation of a multibeam intensity profile and the relationship and mutual influence between the two scans are investigated. A simple practical method of quantitative estimation of the reflection phases of structure-factor multiplets from the experimental data obtained with two inversion-symmetry-related diffractions is proposed. The procedures for data handling and for distinguishing "partial" diffraction images from "full" diffraction images are also developed considering multibeam diffraction geometry and experimental conditions. These procedures thus provide a practical way of reconstructing diffraction profiles for experimental phase determination for macromolecular crystals.

An ultra-high vacuum soft X-ray diffractometer has been constructed and commissioned at the Synchotron Radiation Research Center (SRRC) to investigate materials structures in mesoscale. The diffractometer, housed in a UHV tank, consists of a 6-circle goniometer, together with the systems for beam-collimation, signal detection, vacuum, and control panels. The κ–ϕ–ψ goniostat is adopted for the sample orientation. Crystal samples can be rotated along a given reciprocal lattice vector by using ψ scan. Two orthogonal axes, γ (or 2θ) and δ, are used to move the detector. The detector is a semiconductor pin diode, which can be used in UHV ambient. This 6-circle goniometer allows for sample scanning of a wide range in the momentum space. The motors used for goniometer rotation and slit selection are UHV compatible. The UHV tank is placed on an XYZ table capable of positioning the center of the goniometer onto the incident beam. Test experiments have been carried on the 1–9keV double-crystal monochromator (DCM) beamline to commission the diffractometer. These include powder diffraction of standard quartz crystals, θ–2θ scans of zeolite thin films, specular reflectivity of Ti2O5/SiO2/Zerdur multilayers, soft X-ray multiple diffraction of silicon single crystals, and the polarization effects on three-beam diffraction. The obtained experimental results demonstrate the excellent capability of the diffractometer in characterizing both mososcopic and microscopic structures of matter.

Conventional x-ray diffraction patterns were recorded and used for peak identification and phase determination of MBE multilayer Pt/FePt/Pt thin films on MgO single-crystal substrates. Results showed that both the FePt and the Pt layers were either epitaxially grown or strongly textured with the (110) planes parallel to the surfaces of the MgO (110) substrates. The FePt layer was ordered to the Ll, (AuCu I) phase. An extra strong peak at 30" was identified to be the W2 peak of CuKa for the MgO (220) reflection. The h/2 peak was greatly reduced using a scintillation counter with a narrow PHA window. To eliminate the ?J2 peak completely, a Xe proportional counter with a high energy resolution of 28% was used. Intermetallic alloy thin films of FePt have recently been found to show promising characteristics for high density recording application.' Magnetic and magneto-optical properties of the films were found to correlate with film structure. 2,3,4 The ordered FePt phase with its c- axis in plane showed large magnetic anisotropy. The higher the order, the larger the anisotropy. In our laboratory, we used X-ray diffraction techniques to determine the structure of FePt films. Crystalline phases presented in the films was first identified using the conventional

A quasi-universal function describing the intensity distribution of three-wave X-ray interaction in single crystals is derived for the first time from X-ray dynamical theory under the Bethe approximation for inversion-symmetry related reflections. The intensity distributions of three-wave interference can be scaled down to this dimensionless universal function with proper scaling factors. A newly derived intensity-ratio formula provides a new way of analyzing three-wave diffraction data for direct quantitative determination of X-ray reflection phases of complex systems involving macromolecules.

Three-wave resonance grazing incidence x-ray diffraction is realized for the first time by tuning the x-ray photon energy to match the incident wave vector with the coplanar momentum transfers of crystal surface in-plane reflections. Near the resonance energy, the observed specularly diffracted intensities decreasing at lower energies and increasing at higher energies or vice versa reveal the effects of reflection phases due to the coherent interaction of x-ray surface waves. This experiment thus provides a new way of direct phase determination for surface in-plane reflections.

Census data on migration within and between the 25 largest U.S. metropolitan areas-containing more than 113 million people-permit construction of a probability-of-contact matrix corresponding to a particular Markov process dominated by the nation's largest cities, a hierarchical structure. Regression models based on vectors associated with that process find the large-scale diffusion of AIDS in the U.S.A. depends strongly on national patterns of contact with the original AIDS outbreaks in New York City and San Francisco as modulated by the violent crime rate, a local index of social disintegration resulting from the marginalization of minority ethnic urban communities. Violent crime is itself undergoing a recognizably similar hierarchical diffusion from the largest U.S. cities into smaller metropolitan regions. Further analysis suggests that continuation of public policies of "benign neglect" and "planned shrinkage" directed against marginalized urban populations may trigger a strong stochastic resonance which can significantly degrade public health and public order for much of the three-quarters of the U.S. population living in or near cities, in effect reversing the mortality transition of the last century.