Application of the triisobutylaluminum-promoted reductive rearrangement to sucrose-5-enes

Carbohydrate-based vinyl acetals (5-hex-enopyranosides) undergo reductive rearrangement with triisobutylaluminum (TIBAL) to afford highly functionalized cyclohexanes in which both the aglycon and anomeric stereochemistry are retained. Here, we report the first application of this process to the rearrangement of hex-5-enopyranosides of sucrose in which the interglycosidic oxygen atom of the vinyl acetal system links the anomeric centers of both monosaccharide units. The sucrose-derived 5-hex-enopyranoside 1 undergoes smooth reductive rearrangement with TIBAL to afford the (1 → 2′) ether-linked pseudo-disaccharide 2 in 34% yield. The rearrangement is accompanied by some loss of stereochemical integrity at C-2′ due to a competitive exo-cleavage of the interglycosidic (O-C2′) bond, hence diastereomers at C-2′ are also obtained in 12% yield. The 4-O-allyl-protected sucrose-5-ene 3 is similarly transformed into the corresponding (1 → 2′) ether-linked pseudo-disaccharide 4 , illustrating the compatibility of the allyl group with the TIBAL reaction conditions.      

Between-cue associations influence searching for a hidden goal in an environment with a distinctive shape.

In Experiment 1 rats had to escape from a kite-shaped pool by swimming to a submerged escape platform in a right-angled corner. The two walls creating this corner were white and the two walls creating the opposite, incorrect, right-angled corner were black. The rats were then trained in a square pool with two white walls forming one corner and two black walls forming the opposite corner. The platform was in the white corner for a consistent group and the black corner for an inconsistent group. A test in an entirely white kite revealed a stronger preference for the correct than the incorrect corner in the consistent but not the inconsistent group. This outcome is attributed to the formation of associations between geometric cues, provided by the shape of the pool, and the color of the walls. The results were replicated in a second experiment in which the walls of the test pool were the same color as the incorrect corner during initial training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Application of high-throughput computing in bioinformatics

We describe the challenges faced when developing a Linux/PC-based cluster to apply bioinformatics algorithms to the rapidly increasing raw genomics data available. The calculations, which take around two months to complete, result in a powerful resource that can be used for data mining--most obviously for the human genome. Our current infrastructure consists of a 1314 node cluster with 1734 processors supporting both production and research. This paper highlights the problems in achieving high data throughput with such systems and shows that raw computer power is only one component of a complex problem.     

Spatial-temporal antialiasing

A framework for discussing the motion blur image generation process is formulated. Previous work is studied in the context of this framework. Due to the implicit assumptions on low temporal frequencies in most motion blur algorithms, issues involved in large screen space movements and fast illumination changes in time have not been adequately addressed so far. A new approach that does not make these assumptions is introduced to solve the spatial-temporal geometric and shading aliasing problems separately. Based on newly developed adaptive algorithms in the spatial-temporal domain, an implementation of the new approach is developed to efficiently deliver high-quality motion blurred images in general computer graphics production environments     

Word completion in chronic pain: evidence for schematic representation of pain?

Schematic representation of pain information was investigated in chronic pain patients, health professionals, and nonpatient controls. Under the guise of an English-language experiment, Ss were presented with 12 word stems to be completed with the first 2 English words that came to mind. Four of the stems could be completed with sensory pain words, 4 with effective, and 4 with words associated with pain or illness. All could be completed with at least 3 other nonpain words of equal or greater frequency. Results indicate that chronic pain Ss produced significantly more pain-related completions than control Ss and that in all 3 groups the types of pain words produced were related to the extent of personal experience of pain. The theoretical implications of these findings are discussed in relation to the organization of schema, implicit memory, and the activation of mental representations of pain (schema).     

Copolymerization of caprolactam with polyoxybutylene diamine

Nylon 6-polyoxybutylene block copolymers were prepared by reacting polyoxybutylene diamine with caprolactam in the presence of phosphoric acid. The copolymerization was carried out in a Helicone-type reactor and the effect of time, temperature, and caprolactam concentration on the properties of the products was recorded. Differential Scanning Calorimetry studies of the products suggest the presence of both the ABA and AB types of sequences, where A and B represent nylon 6 and polyether blocks, respectively. Dynamic mechanical measurements of typical copolymers revealed the presence of at least two different nylon moieties. The melt rheology data reflect a general increase in the pseudoplasticity of the copolymer with the increase of the polyether content. Increases of the polyether content in the copolymer result in an increased elongation and a decreased tensile strength and modulus.     

Propagation of terahertz pulses in random media

We describe measurements of single-cycle terahertz pulse propagation in a random medium. The unique capabilities of terahertz time-domain spectroscopy permit the characterization of a multiply scattered field with unprecedented spatial and temporal resolution. With these results, we can develop a framework for understanding the statistics of broadband laser speckle. Also, the ability to extract information on the phase of the field opens up new possibilities for characterizing multiply scattered waves. We illustrate this with a simple example, which involves computing a time-windowed temporal correlation between fields measured at different spatial locations. This enables the identification of individual scattering events, and could lead to a new method for imaging in random media.