Use of software to search for higher symmetry: space group C2

From a search of the October 2000 release of the Cambridge Structural Database we find coordinate data for approximately 1500 entries under space group No. 5: C2 or, occasionally, A2, I2 or B112. Software designed to detect cases of missed higher symmetry identified 144 entries for detailed inspection. Of these, 50 should, we believe, be revised to space groups of higher symmetry. The most common revision is to space group C2/m, which entails adding a center of inversion and usually results in important changes in bond lengths and angles

Crystal structure of the yellow 1:2 molecular complex lumiflavin–bisnaphthalene-2,3-diol

In the first molecular complex of the physiologically active neutral form of isoalloxazine studied, lumiflavin–bisnaphthalene-2,3-diol, each flavin is sandwiched between two naphthalenediol molecules with extensive overlap but a moderately large (3·44 Å) spacing, indicating at most weak charge-transfer interaction and in agreement with the yellow colour of the complex, nearly the same as that of the parent lumiflavin

Seasonality in the Surface Energy Balance of Tundra in the Lower Mackenzie River Basin

This study details seasonal characteristics in the annual surface energy balance of upland and lowland tundra during the 1998–99 water year (Y2). It contrasts the results with the 1997–98 water year (Y1) and relates the findings to the climatic normals for the lower Mackenzie River basin region. Both years were much warmer than the long-term average, with Y1 being both warmer and wetter than Y2. Six seasons are defined as early winter, midwinter, late winter, spring, summer, and fall. The most rapid changes in the surface energy balance occur in spring, fall, and late winter. Of these, spring is the most dynamic, and there is distinct asymmetry between rates of change in spring and those in fall. Rates of change of potential insolation (extraterrestrial solar radiation) in late winter, spring, and fall are within 10% of one another, being highest in late winter and smallest in spring. Rates of change in air temperature and ground temperature are twice as large in spring as in fall and late winter, when they are about the same. Rates of change in components of the energy balance in spring are twice and 4 times as large as in fall and late winter, respectively. The timing of snowpack ripening and snowmelt is the major agent determining the magnitude of asymmetry between fall and spring. This timing is a result of interaction between the solar cycle, air temperature, and snowpack longevity. Based on evidence from this study, potential surface responses to a 18C increase in air temperature are small to moderate in most seasons, but are large in spring when increases range from 7% to 10% of average surface energy fluxes

Structure of an anti-Aldol Addition Product of Benzaldehyde and a Pseudoephedrine-Derived O-Silyl Ketene N,O-Acetal

[4S-(4R*,5R*,8R*,9S*)]-2,2,5,6,8-Penta- methyl-4,9-diphenyl- 1,3-dioxa-6-aza-2-silacyclono-nan-7-one, CE2H29NO3Si, Mr = 383.56, monoclinic, P21, a = 6.550 (3), b = 17.318 (6), c = 20.129 (6) A, /3=98.83(3)° , V =2256.2(14) A 3, Z=4, Dx= 1.13 gcm -3, A(Mo Ka) = 0.71073 A,/z = 1.18 cm -1, F(000) = 824, room temperature, R on F = 0.039 for 4305 reflections with Fo 2 > 3cr(Fo2). The two independent molecules in this structure have nearly the same configuration and geometry. The Si atoms are tetrahedrally coordinated, with average Si--C bond distances of 1.842(3)/~ and average Si---O bond distances of 1.636 (7)A; angles at Si differ from 109.5 ° by an average of 3.5 °. The nine-membered rings are fully extended and the planes of the phenyl groups are approximately perpendicular to the nine- membered ring.Chemistry and Chemical Biolog

Use of software to search for higher symmetry: space group C2

From a search of the October 2000 release of the Cambridge Structural Database we find coordinate data for approximately 1500 entries under space group No. 5: C2 or, occasionally, A2, I2 or B112. Software designed to detect cases of missed higher symmetry identified 144 entries for detailed inspection. Of these, 50 should, we believe, be revised to space groups of higher symmetry. The most common revision is to space group C2/m, which entails adding a center of inversion and usually results in important changes in bond lengths and angles

Neural Correlates of Attentional and Mnemonic Processing in Event-Based Prospective Memory

Prospective memory (PM), or memory for realizing delayed intentions, was examined with an event-based paradigm while simultaneously measuring neural activity with high-density EEG recordings. Specifically, the neural substrates of monitoring for an event-based cue were examined, as well as those perhaps associated with the cognitive processes supporting detection of cues and fulfillment of intentions. Participants engaged in a baseline lexical decision task (LDT), followed by a LDT with an embedded PM component. Event-based cues were constituted by color and lexicality (red words). Behavioral data provided evidence that monitoring, or preparatory attentional processes, were used to detect cues. Analysis of the event-related potentials (ERP) revealed visual attentional modulations at 140 and 220 ms post-stimulus associated with preparatory attentional processes. In addition, ERP components at 220, 350, and 400 ms post-stimulus were enhanced for intention-related items. Our results suggest preparatory attention may operate by selectively modulating processing of features related to a previously formed event-based intention, as well as provide further evidence for the proposal that dissociable component processes support the fulfillment of delayed intentions