Optics Concept for a Pair of Undulator Beamlines for MX

We describe a concept for x-ray optics to feed a pair of macromolecular crystallography (MX) beamlines which view canted undulator radiation sources in the same storage ring straight section. It can be deployed at NSLS-II and at other low-emittance third-generation synchrotron radiation sources where canted undulators are permitted, and makes the most of these sources and beamline floor space, even when the horizontal angle between the two canted undulator emissions is as little as 1-2 mrad. The concept adopts the beam-separation principles employed at the 23-ID (GM/CA-CAT) beamlines at the Advanced Photon Source (APS), wherein tandem horizontally-deflecting mirrors separate one undulator beam from the other, following monochromatization by a double-crystal monochromator. The scheme described here would, in contrast, deliver the two tunable monochromatic undulator beams to separate endstations that address rather different and somewhat complementary purposes, with further beam conditioning imposed as required. A downstream microfocusing beamline would employ dual-stage focusing for work at the micron scale and, unique to this design, switch to single stage focusing for larger beams. On the other hand, the upstream, more highly automated beamline would only employ single stage focusing.

Small-gap insertion-device development at the National Synchrotron Light Source--performance of the new X13 mini-gap undulator

The National Synchrotron Light Source (NSLS) 2.8 GeV electron storage ring continues to set high standards in insertion-device research and development. The Chasman-Green NSLS lattice design provides for dispersion-free long straight sections in addition to a very small vertical beta function. As the electron beam size is proportional to the square root of this function, a program to exploit this feature was undertaken more than a decade ago by implementing short-period small-gap insertion devices in the NSLS storage ring. The possibility of utilizing existing moderate-energy synchrotron radiation electron storage rings to produce high-brightness photon beams into the harder X-ray region have been realised using in-vacuum undulators. In this article the operation of a 1.25 cm-period mini-gap undulator, operating down to a gap of 3.3 mm within the NSLS X13 straight section, is reported. It is the brightest source of hard X-rays in the energy range approximately 3.7-16 keV at the NSLS, and replaces an in-vacuum undulator which had a more limited tunability.

Hybridization and bond-orbital components in site-specific X-ray photoelectron spectra of rutile TiO2

We have determined the Ti and O components of the rutile TiO2 valence band using the method of site-specific x-ray photoelectron spectroscopy. Comparisons with calculations based on pseudopotentials within the local density approximation reveal the hybridization of the Ti 3d, 4s, and 4p states, and the O 2s and 2p states on each site. These chemical effects are observed due to the large differences between the angular-momentum dependent matrix elements of the photoelectron process.

Pairing interactions and Gibbs adsorption at the liquid bi-in surface: a resonant X-ray reflectivity study

Resonant x-ray reflectivity measurements from the surface of liquid Bi(22)In(78) find only a modest surface Bi enhancement, with 35 at. % Bi in the first atomic layer. This is in contrast to the Gibbs adsorption in all liquid alloys studied to date, which show surface segregation of a complete monolayer of the low surface tension component. This suggests that surface adsorption in Bi-In is dominated by attractive interactions that increase the number of Bi-In neighbors at the surface. These are the first measurements in which resonant x-ray scattering has been used to quantify compositional changes induced at a liquid alloy surface.

Mental health parity

The subject of mental health parity has been a hotly debated issue over the years. Mental health advocates and professionals consider their area a victim of discrimination in that insurance carriers and legislators have provided greater benefits for physical illness, while reducing or even excluding mental health benefits from health insurance and HMO policies. This article explores the background of the mental health parity movement and how various states and the federal government have acted to end this discrimination.

Statistical analysis of X-ray speckle at the NSLS

A statistical analysis of the static speckle produced by illuminating a disordered aerogel sample by a nominally coherent X-ray beam at wiggler beamline X25 at the National Synchrotron Light Source is reported. The results of the analysis show that the coherence delivered to the X25 hutch is within 35% of what is expected. The rate of coherent photons is approximately two times smaller than expected on the basis of the X25 wiggler source brilliance.

A client/server system for Internet access to biomedical text/image databanks

Internet access to mixed text/image databanks is finding application in the medical world. An example is a database of medical X-rays and associated data consisting of demographic, socioeconomic, physician's exam, medical laboratory and other information collected as part of a nationwide health survey conducted by the government. Another example is a collection of digitized cryosection images, CT and MR taken of cadavers as part of the National Library of Medicine's Visible Human Project. In both cases, the challenge is to provide access to both the image and the associated text for a wide end user community to create atlases, conduct epidemiological studies, to develop image-specific algorithms for compression, enhancement and other types of image processing, among many other applications. The databanks mentioned above are being created in prototype form. This paper describes the prototype system developed for the archiving of the data and the client software to enable a broad range of end users to access the archive, retrieve text and image data, display the data and manipulate the images. System design considerations include; data organization in a relational database management system with object-oriented extensions; a hierarchical organization of the image data by different resolution levels for different user classes; client design based on common hardware and software platforms incorporating SQL search capability, X Window, Motif and TAE (a development environment supporting rapid prototyping and management of graphic-oriented user interfaces); potential to include ultra high resolution display monitors as a user option; intuitive user interface paradigm for building complex queries; and contrast enhancement, magnification and mensuration tools for better viewing by the user.

Existence of a flat phase in red cell membrane skeletons

Biomolecular membranes display rich statistical mechanical behavior. They are classified as liquid in the absence of shear elasticity in the plane of the membrane and tethered (solid) when the neighboring molecules or subunits are connected and the membranes exhibit solid-like elastic behavior in the plane of the membrane. The spectrin skeleton of red blood cells was studied as a model tethered membrane. The static structure factor of the skeletons, measured by small-angle x-ray and light scattering, was fitted with a structure factor predicted with a model calculation. The model describes tethered membrane sheets with free edges in a flat phase, which is a locally rough but globally flat membrane configuration. The fit was good for large scattering vectors. The membrane roughness exponent, zeta, defined through h alpha L zeta, where h is the average amplitude of out-of-plane fluctuations and L is the linear membrane dimension, was determined to be 0.65 +/- 0.10. Computer simulations of model red blood cell skeletons also showed this flat phase. The value for the roughness exponent, which was determined from the scaling properties of membranes of different sizes, was consistent with that from the experiments.

The kidnapping of W. S. Gilbert

Gilbert's probable screen memory of having been kidnapped, along with his persistent preoccupations with babyhood, remembering and forgetting, stress the intensity of his struggle against remembering the painful experiences from his childhood. His creative efforts function as an obsessional defense; they divert his attention from the experiences themselves to a fascination with the process of remembering and forgetting, while the painful affects are reversed into playful, good-natured humor. The results are some of his most treasured anecdotes. Watson (1918) quotes Gilbert's story of the amateur burglar who badly bungled an attempted robbery and ended up being arrested and jailed under the most humiliating circumstances. For years afterward, every time he though of the incident, he felt wretchedly uncomfortable, and he tried vainly to drive the occurrence from his mind. The story concludes with a statement which, remarks Watson, only Gilbert could have written: "Gradually one detail after another slipped from my recollection, and one lovely morning last May I found to my intense delight that I had absolutely forgotten all about it" (p. 94).

Gilbert's first night anxiety

W. S. Gilbert, librettist of the Gilbert and Sullivan operas, suffered from such extreme anxiety at the opening night performance of his plays that he was unable to remain in the theater. This paper explores the dynamics behind Gilbert's first night anxiety, utilizing his literary works as well as biographical and autobiographical sources.