The modern photographic emulsion is an extremely sensitive detector of light quanta. In fact, high speed black-and-white film (which consists mainly of microcrystalline grains of AgBr or AgBrI suspended in gelatin on an inert base) ranks with the photomultiplier tube as capable of detecting a very few individual light quanta. Exposure times can vary from minute fractions of a second to hours. Unlike the multiplier tube, the photographic emulsion also responds well to relatively high light flux, that is, film can have wide exposure latitude. In many respects such as sensitivity, latitude, resolution, etc., film sets the pace as new multiplier tubes and charge-coupled devices are developed.Of course, the high sensitivity of film comes about because light absorbed within an emulsion grain causes a latent image to be formed (usually on the surface), which then renders the entire grain developable. The tabular grains of a modern high speed emulsion are largely triangular or hexagonal single-crystal platelets approximately 10 ü across and 0.1 ü thick. Such a grain will contain about 109 silver atoms, and it can be sensitized by a few molecules of gold sulfide or other additives adsorbed on its surface.In the concentration speck theory of the latent image, light is absorbed throughout the grain, but this energy is transported by the motion of electrons to a sensitivity center usually on the surface where the latent image is formed.

BACKGROUND Unfractionated heparin and the low molecular weight heparin, dalteparin, are used for prophylaxis against venous thromboembolism in patients undergoing craniotomy. These drugs were compared in a randomized, prospective pilot study comparing intermittent pneumatic compression devices plus dalteparin to intermittent pneumatic compression devices plus heparin.METHODS One hundred patients undergoing craniotomy were randomly allocated to receive perioperative prophylaxis with subcutaneous (SC heparin, 5000 units every 12 hours, or dalteparin, 2,500 units once a day, begun at induction of anesthesia and continued for 7 days or until the patient was ambulating. Entry criteria were age over 18 years, no deep vein thrombosis (DVT) preoperatively as judged by lower limb duplex ultrasound and no clinical evidence of pulmonary embolism preoperatively. Patients with hypersensitivity to heparin, penetrating head injury or who refused informed consent were excluded. Patients underwent a duplex study 1 week after surgery and 1 month clinical follow-up. All patients were treated with lower limb intermittent pneumatic compression devices.RESULTS There were no differences between groups in age, gender, and risk factors for venous thromboembolism. There were no differences between groups in intraoperative blood loss, transfusion requirements or postoperative platelet counts. Two patients receiving dalteparin developed DVT (one symptomatic and one asymptomatic). No patient treated with heparin developed DVT and no patient in either group developed pulmonary embolism. There were two hemorrhages that did not require repeat craniotomy in patients receiving dalteparin and one that did require surgical evacuation in a patient treated with heparin. Drug was stopped in two patients treated with dalteparin because of thrombocytopenia. None of these differences were statistically significant.CONCLUSION There was no significant difference in postoperative hemorrhage, venous thromboembolism or thrombocytopenia between heparin and dalteparin. The results suggest that, given the small sample size of this trial, both drugs appear to be safe and the incidence of venous thromboembolism by postoperative screening duplex ultrasound appears to be low when these agents are used in combination with intermittent pneumatic compression devices. (C) 2003 Elsevier Inc. All rights reserved.

ABSTRACT This article studies the searching behavior of four frequent Northern Light searchers and four frequent Yahoo searchers. Participants, who were Library and Information Science students at the University of Washington, were observed as they searched in their regular search service for the answers to library reference-type questions. All participants received the same questions. Users' search styles were found to mirror the differing behind-the-scenes rules that the two search services apply to search strings. Northern Light searchers were more likely to use Boolean operators than were Yahoo users. Northern Light users were more likely to use upper-case letters. Finally, they tended to employ truncating symbols more frequently. However, these users had trouble stating explicitly the rules of their search service, even though these rules clearly influenced their searching.

The Pacific Northwest Consortium CAT is developing tapered glass capillaries using fiber optics techniques for fabrication. Previous calculations showed that, under ideal conditions and using Undulator A as a source, glass capillaries can produce higher intensity gains than those of mirrors for an output diameter of 5 micrometer or less. Recently, we fabricated several capillaries with approximately linear tapers and tested three of them with outlet diameters of 1.3, 1.4, and 12.4 micrometers and lengths of about 35–90 cm. We obtained intensity gains over a pin hole of about 270, 240, and 30, respectively. They are about half of the calculated values expected from a perfectly linear profile. Also the angular spread of the output beam was much larger than the calculated value. We measured the profile of one capillary in detail and calculated the intensity for the capillary with the measured profile and still found significant differences. We also made calculations assuming several types of misalignment and found that they are important factors in understanding the larger angular divergence and reduced intensity. These results suggest improvements in the fabrication of the capillaries and in ways to support them during experiments.

Capillary concentrators condense x-rays by multiple reflections down a gradually tapering capillary. They can provide sub-micron beam spots, and are promising candidates for use in the next generation x-ray microprobe beamlines. The weak energy dependence of their properties make them especially useful for energy scanning applications such as micro-XAFS. This paper examines the potential performance of capillary optics for an x-ray microprobe, as well as some practical issues such as fabrication and alignment. Best performance at third generation sources requires long capillaries, and we have been using fiber optics techniques to fabricate capillaries up to one meter in length. The performance of shorter (less than about 0.5 m) capillaries has often been found to agree well with theoretical calculations, indicating the inner surface is a high quality x-ray reflector. These capillaries have been tested at the NSLS for imaging and micro-XAFS down to 2.6 mu m resolution with excellent results. On an unfocused bend magnet line flux density approaching 10(6) ph/sec/mu m(2) has been achieved. While nearly optimum profiles have been achieved for longer capillaries, the results have been disappointing, and alignment problems are suspected. The dramatic improvement in performance possible at third generation synchrotrons such as the APS is discussed along with improvements possible by using the capillaries in conjunction with coupling optics.

We report the use of multi-bounce ray tracing to model single capillaries of various profiles coupled to an Advanced Photon Source insertion-device beamline containing an X-ray monochromator and a toroidal or ellipsoidal focussing mirror. Examples are given for parabolic as well as linear profiles placed at the focussed output of the insertion device beamline for the Pacific Northwest Consortium Collaborative Access Team at the Advanced Photon Source. The implementation of single and multiple capillary simulation is discussed.

The valence-band photoemission of silver bromide and silver iodobromide has been measured with use of synchrotron radiation in the region of the Ag 4d Cooper minimum. The large change in ionization cross section in this region permits the determination of the individual halogen p and silver 4d partial densities of states (PDOS). The energy-distribution curves (EDC's) were recorded at liquid-nitrogen temperatures to prevent photolysis and take advantage of the significant line narrowing which occurs in the silver halides at low temperatures. The results are in good agreement with experiments using rare-gas resonance lines and with previously calculated energy-band structures. Changes in the halogen PDOS with the addition of iodide indicate that the narrowing of the band gap is due to the broadening of the uppermost antibonding halogen bands. The PDOS were calculated for pure AgBr using a nonrelativistic, self-consistent, Hartree-Fock theory and show good agreement with the experimental results.

A bibliography of papers on high energy spectroscopic studies of the new superconductors is given, together with some selected work on related oxides. Tables are given to allow quick tracing of works on particular topics. The results of some of the more important areas of investigation are discussed.

Using polarized synchrotron radiation, angle-resolved photoemission data were obtained on randomly oriented polycrystalline AgBr and on thick films of metallic silver. Asymmetry parameters as well as relative cross sections were determined for the valence bands of both systems from 55 eV through the Ag 4d Cooper minimum at 140 eV. Comparison of asymmetry parameters with atomic data indicates that the valence bands derived from Ag 4d levels in these systems are remarkably atomiclike. In AgBr only the uppermost valence bands show a greatly reduced excursion of the \ensuremath{\beta} value through the Cooper minimum.

Thin films of hydrogenated and unhydrogenated titanium carbide, known to be amorphous from x-ray and electron diffraction studies, nevertheless exhibit short-range order at the level of the first-nearest-neighbor shell when studied by extended x-ray-absorption fine structure and extended electron-energy-loss fine structure. This short-range order appears to consist of the same octahedrally coordinated units present in crystalline titanium carbide (NaCl structure), where a titanium atom is surrounded by an octahedron of six carbon atoms and vice versa. The persistence of this basic structural unit is attributed to the difference in atomic radii between C and Ti and to the strong nature of the Ti-C bond. A slight relaxation in interatomic distance relative to the crystalline state, which increases upon hydrogenation, is also observed. The atomic positions in the first coordination shell in amorphous titanium carbide are slightly displaced relative to the crystalline form. Yet, upon hydrogenation, this displacement decreases in the first shell, made of carbon atoms and vacancies, surrounding a Ti atom by 40% for the 4.5 at. % H and 60% for the 6 at. % H relative to the unhydrogenated amorphous ${\mathrm{TiC}}_{\mathrm{x}}$ films. By contrast, the structural disorder in the first shell of Ti atoms surrounding a C atom is practically unaffected by the addition of hydrogen. These results imply that the hydrogen atoms, instead of occupying tetrahedral vacancies, fill carbon vacancies in the amorphous phase as they do in crystalline ${\mathrm{TiC}}_{\mathrm{x}}$, in agreement with our previous findings from static secondary-ion mass spectroscopy and x-ray photoelectron spectroscopy.

The local atomic structure and the stability of amorphous titanium diboride (TiB2) thin films, prepared by electron beam vaporization (EBV) of the crystalline compound onto liquid‐nitrogen‐cooled substrates, are studied using extended X‐ray absorption fine structure (EXAFS) and extended energy‐loss fine structure (EXELFS). From a comparison of the extended fine structure spectra of the amorphous films with corresponding spectra of crystalline TiB2, accurate information is derived on the nature of local structure, or short‐range order, and on the type and degree of nanostructural atomic disorder σ2 in amorphous TiB2. Subsequent controlled heating experiments and observation and imaging by transmission electron microscopy to determine the crystallization temperature of the amorphous phase show that the crystallization temperature and, thus, the stability of the amorphous phase are strongly dependent on σ2. It is shown that minimizing σ2 is crucial in enhancing the amorphicity. Finally, EXAFS and EXELFS are employed to examine in detail the structural changes induced in amorphous TiB2 by variations in the EBV deposition parameters.

First operation of a new extended range monochromator on the 1 GeV storage ring Aladdin is described. Curves are given of output flux as a function of photon energy for the 2 m and for the 5 m gratings as measured with an NBS diode. Relatively low background and flux up to 1500 eV is obtained using a 1200 line/mm 5 m holographic grating. Highly reproducible scans were obtained of the transmission of thin films including the carbon K and titanium L edges. This reproducibility and high throughput is in large part due to the small beam size and excellent stability of Aladdin.

The formation of $F$ centers by monochromatic soft x-ray radiation was studied in the range of photon energies 50 to 1500 eV by use of a sensitive laser-induced luminescence technique. Production efficiencies of the order of $\frac{1 \mathrm{keV}}{(F \mathrm{center})}$ are obtained throughout the upper end of the above energy range in KCl and KBr at 77 K. Saturation densities of about ${10}^{18}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ occur, with the total number of centers depending upon the depth of penetration of the radiation. Reduced efficiency is noted at the lowest energies and highest absorption coefficients, and is possibly related to the observed photodesorption of neutral and ion species from the surface.

X-ray-absorption and -photoemission studies were carried out on the manganese-doped Chevrel-phase compound ${\mathrm{Mn}}_{\mathrm{x}}$${\mathrm{Sn}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Mo}}_{6}$${\mathrm{S}}_{8}$ for x=0.1, where a maximum superconducting transition temperature ${T}_{c}$ occurs. With use of synchrotron radiation and x-ray fluorescence, near-edge-absorption and extended x-ray-absorption fine-structure (EXAFS) spectra were obtained at the K edge of Mn in the doped compound. The results indicate that each manganese atom, surrounded by eight sulfur atoms, substitutes for tin at the center of a large cavity in ${\mathrm{SnMo}}_{6}$${\mathrm{S}}_{8}$. The manganese-sulfur nearest-neighbor distance is found to be 2.02\ifmmode\pm\else\textpm\fi{}0.05 A\r{}, somewhat less than 2.26 A\r{} for Sn in ${\mathrm{SnMo}}_{6}$${\mathrm{S}}_{8}$. The probable charge of manganese is found to be 4+ and, considering the valence-electron-charge model of charge transfer, this explains the observed maximum in ${T}_{c}$. The photoemission experiments yield an energy distribution curve for the valence band which is in good agreement with band theory.

The spectral dependence of the F-center production efficiency was observed in the hard-x-ray region at the K edge of bromine in KBr and in the near-ultraviolet part of the spectrum corresponding to the exciton region of several alkali halides. Evidence of a definite increase at the core threshold was observed as well as a significant wavelength dependence of the F-center production efficiency in the near-uv region. These studies were made possible by the development of an extremely sensitive method of detecting F centers in ultralow concentrations, which utilizes the luminescent properties of these centers.

We report on high-resolution total-yield measurements of the Cu ${L}_{2,3}$ absorption edge in ${\mathrm{Cu}}_{2}$O using the JUMBO monochromator at the Stanford Synchrotron Radiation Laboratory. Care was taken to prepare the surface of a well-characterized single crystal, rather than use oxidized copper. A comparison was also made with electron-energy-loss spectra (transmission of a thin ${\mathrm{Cu}}_{2}$O crystal). Prominent white lines or core excitons appear at the spin-orbit-split Cu ${L}_{3}$ (931 eV) and ${L}_{2}$ (951 eV) thresholds. These edge features are like those observed in CuO (even though the Cu $d$ states are filled in ${\mathrm{Cu}}_{2}$O) but are asymmetrically broadened on the high-energy side, probably due to more than one component. The core binding energy is measured by photoemission, and local states are compared with transitions to the continuum. We believe that the strong edge features in ${\mathrm{Cu}}_{2}$O can be understood in part as transitions to antibonding molecular-orbital states of the linear O-Cu-O molecular cluster peculiar to copper in the ${\mathrm{Cu}}_{2}$O crystal structure.

A compact high resolution monochromator for undulator radiation in the 20–1000 eV energy range is described. The instrument can be programmed to operate in either the on-blaze mode of Kunz, Haensel and Sonntag or the virtual-source mode of Petersen et al., as used in the SX 700. High transmission is achieved by using only two plane and one ellipsoidal reflecting surface. A relatively small plane grating is employed. Silicon carbide mirrors, cold baffles and temperature control are definite possibilities to handle heat load and carbon buildup. The design has been facilitated by ray tracing with a Monte Carlo source distribution, which simulates the characteristics and depth of an undulator.

This paper was withdrawn after the proceedings had been assembled in its final form. In order to keep to a rapid publication schedule the succeeding pages have not been renumbered; pages 62 and 63 are therefore missing