The targeted synthesis of single site vanadyl species on the surface and in the framework of silicate building block materials

A new synthetic methodology for the targeted preparation of single site, atomically dispersed vanadyl groups in silicate matrices is described. This methodology requires functionalized silicate building blocks Si₈O₂₀(OSnMe₃)₈ that become linked together through vanadyl (≡VO) groups in the matrix. A sequential addition strategy is illustrated which allows the targeting of specific connectivities for the vanadyl group to the silicate building block matrix (i.e. the number of V–O–Si bonds linking the vanadyl unit). Silicate matrices containing exclusively 3-connected (OV(OSi_cube)₃), 2-connected (OV(OR)(OSi_cube)₂) or 1-connected (OVCl₂(OSi_cube)) vanadyl sites are described and characterized via a wide variety spectroscopic and physical techniques (gravimetric analysis, EXAFS, AA and solid state NMR (⁵¹V, ²⁹Si, and ¹⁷O)). We demonstrate how the combination of gravimetric, solid state NMR (SSNMR) and EXAFS data can be used to uniquely define the vanadyl sites in these matrices. Furthermore, the use of ¹⁷O SSNMR (1D and MQMAS) is illustrated as an indirect spectroscopic probe to follow changes in the ligands bound to vanadium atom within the vanadyl groups in these matrices.     

Rectangular scale-similar etch pits in monocrystalline diamond

Etching of monocrystalline diamond in oxygen and water vapor at 1100 °C through small pores in a silicon nitride film produced smooth-walled rectangular cavities. The cavities were imaged by electron microscopy and measured by interferometric microscopy. The observed cavities ranged in width from approximately 1 μm up to 72 μm, in each case exhibiting smooth, vertical sidewalls, a flat bottom, and a depth equal to half its width. Cavity boundaries were determined to lie along slow-etching {100} crystallographic planes, suggesting the possibility of a powerful class of techniques for high-aspect-ratio bulk micromachining of diamond.     

Anaerobic biodegradation of the microbial copolymer poly(3-hydroxybutyrate-co-3-hydroxyhexanoate): Effects of comonomer content, processing history, and semi-crystalline morphology

Films of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB-co-3HHx) containing 3.8-10 mol% of 3-hydroxyhexanoate (3HHx) comonomer were subjected to anaerobic biodegradation to explore the effects of copolymer composition, crystallinity, and morphology on biodegradation. As biodegradation proceeded, samples with higher HHx fraction tended to have faster weight loss; on Day 7 of the degradation experiment, P3HB-co-10 mol%-3HHx lost 80% of its original weight, while P3HB-co-3.8 mol%-3HHx lost only 28%. Scanning electron microscopy (SEM) images revealed that the anaerobic biodegradation proceeded at the surface of the samples, with preferential erosion of the amorphous regions, exposing the crystalline spherulites formed inside the copolymer films. It was observed that copolymers with higher HHx fraction had smaller diameter spherulites, ranging from roughly 40 μm for P3HB-co-3.8 mol%-3HHx to 10 μm for P3HB-co-10 mol%-3HHx. A banded spherulite morphology was observed for P3HB-co-6.9 mol%-3HHx and P3HB-co-10 mol%-3HHx, with much wider band spacing (2 μm) for the former than the latter (0.3 μm). Different thermal history seemed to affect the morphological properties and, thus, the biodegradability of the P3HB-co-3HHx samples as well. When comparing copolymers with the same copolymer composition, P3HB-co-3HHx annealed at 70 °C had 5-30% more weight loss after the same duration of incubation in active sludge compared to the quenched samples. We suggest that annealing of P3HB-co-3HHx likely induces void formation in the semi-crystalline structure, facilitating the movement of water or perhaps enzymes to a higher degree of penetration into the sample and subsequently enhancing microbial degradation.     

Proteus: A reconfigurable computational network for computer vision

The Proteus architecture is a highly parallel, multiple instruction, multiple data machine (MIMD) optimized for large granularity tasks such as machine vision and image processing. The system can achieve 20 gigaflops (80 gigaflops peak). It accepts data via multiple serial links at a rate of up to 640 MB/S. The system employs a hierarchical reconfigurable interconnection network with the highest level being a circuit-switchedenhanced hypercube, serial interconnection network for internal data transfers. The system is designed to use 256 to 1024 RISC processors. The processors use 1-MB externalread/write allocating caches for reduced multiprocessor contention. The system detects, locates, and replaces faulty subsystems using redundant hardware to facilitatefault tolerance. The parallelism is directly controllable through an advanced software system for partitioning, scheduling, and development. System software includes a translator for the INSIGHT language, a parallel debugger, lowand high-level simulators, and a message-passing system for all control needs. Image-processing application software includes a variety of point operators, neighborhood operators, convolution, and the mathematical morphology operations of binary and gray-scale dilation, erosion, opening, and closing.     

Simple method for risk assessment of nuclear power plant refueling outages

This paper discusses the method used for probabilistic risk assessment (PRA) studies of the Monticello Nuclear Power Plant's 1993 and 1994 refueling outages. The method made full use of work already completed as part of the United States Nuclear Regulatory Commission's request for at-power risk studies known as Individual Plant Examinations (IPEs) and therefore required less resources than many other techniques for shut-down risk management. The four plant models used to examine various plant outage states are described and discussed. The models are (1) reactor during manual shut-down, (2) reactor in cold shut-down with head installed, (3) reactor with head off and (4) fuel storage pool.These models were manipulated before the refueling outage began using the computer programs and to simulate different decay heat levels and various components out of service during time segments of the outage. This was used to identify higher risk periods during the outage and to sensitize operators and other personnel to the important equipment and activities during the daily briefings during the outage.Several techniques are discussed in this paper, including (1) methods to modify an existing PRA model for lower decay heat conditions, (2) editing existing cutsets to simulate various equipment availability states and (3) the use of assumptions to simplify the analysis.     

Distributed Computing and Simulation in a Traffic Research Test Bed

This article describes the laboratory backbone of the California Advanced Research Testbed (CART), which is integrated with an actual urban traffic network. The research laboratory is based at the University of California at Irvine (UCI) and has real-time communication capabilities with several traffic-control centers in Orange County, California. We discuss a simulation and optimization environment that provides the capabilities to study various components of Advanced Traveler Information Systems (ATIS) and Advanced Traffic Management Systems (ATMS) in conjunction with the available real-world connections. The platform accommodates system components such as communications, computing, modeling, prediction, optimization, and control with sufficient flexibility that different candidate system designs can be studied. The article focuses on distributed computing issues and implementation of the hybrid simulation framework that includes integrated microscopic and macroscopic simulation models.     

Cellular pathology and histopathology of hypo-salinity exposure on the coral Stylophora pistillata

Coral reefs can experience extreme salinity changes, particularly hypo-salinity, as a result of storms, heavy rainy seasons (e.g., monsoons), and coastal runoff. Field and laboratory observations have documented that corals exposed to hypo-saline conditions can undergo extensive bleaching and mortality. There is controversy in the literature as to whether hypo-saline conditions induce a pathological response in corals, and if there is a relationship between decreasing salinity treatment and pathological responses. To test the hypothesis that hypo-salinity exposure does not have a pathological effect on coral, we used histological and cellular diagnostic methods to characterize the pathology in hypo-salinity-exposed corals. Colonies of Stylophora pistillata were exposed to five salinity concentrations [39 parts per thousand (ppt), 32 ppt, 28 ppt, 24 ppt, and 20 ppt] that may realistically occur on a reef. Histological examination indicated an increasing severity of pathomorphologies associated with decreasing salinity, including increased tissue swelling, degradation and loss of zooxanthellae, and tissue necrosis. Pulse-amplitude modulated chlorophyll fluorimetry kinetics demonstrated a decreasing photosynthetic efficiency with decreasing salinity conditions. Cytochrome P450 levels were affected by even slight changes in salinity concentration suggesting that detoxification pathways, as well as several endocrine pathways, may be adversely affected. Finally, these studies demonstrated that hypo-saline conditions can induce an oxidative-stress response in both the host and in its algal symbiont, and in so doing, may synergistically increase oxidative-stress burdens. As with other types of environmental stresses, exposure to hypo-saline conditions may have long-term consequences on coral physiology.     

Behavioral Limits of Auditory Temporal Resolution in the Rat: Amplitude Modulation and Duration Discrimination.

Thresholds for detecting the presence of amplitude modulation in a noise carrier were determined for rats using conditioned avoidance procedures. There was a progressive increase in threshold with modulation rates between 5 Hz and 2 kHz. Further tests were conducted to determine difference thresholds for detecting an increase in modulation rate for standard rates of 10, 50, and 100 Hz. The size of the difference threshold increased progressively as the standard rate increased. In addition, thresholds for detecting an increase in the duration of a noise burst were determined for various standard durations. The difference thresholds were constant for values between 10 and 50 ms but increased progressively, with standard durations between 0.1 and 1.0 s. (PsycINFO Database Record (c) 2010 APA, all rights reserved)