Resolution Ones Research Articles

Performance of a coupled atmosphere-streamflow prediction system at the Pyungchang River IHP basin

A coupled atmosphere-streamflow model has been developed for the Pyungchang River basin in Korea to improve operational rainfall and streamflow forecasts. Here, the authors examine how the modeling system performs for different domain sizes and spatial resolutions from a set of 72-h simulations over the 10-day-period from 00 UTC 24 June to 12 UTC 4 July, 1998. The larger and smaller domains cover East Asia and the Korean Peninsula at spatial resolutions of 60 and 12 km, respectively. For both domains, the simulated rainfall and streamflow show reasonable agreement with observations during the first 48-h-periods. A correlation of 0.89 is obtained between the simulated and observed streamflow for the first 12-h-period. Agreements between the simulated and observed rainfall appear to be highest during the period of 12–24 h from initialization for the smaller domain, and 24–36 h for the larger domain. The results suggest that a larger domain with a coarser resolution requires longer spin-up period than a smaller domain with a fine resolution. The transfer trends from the simulated rainfall to streamflow show a 12-h lag for the Pyungchang River basin, which implies that the streamflow model takes additional spin-up time to respond to the rainfall forcing. The fine resolution simulations generally outperform the coarse resolution ones, perhaps due to better representation of orographic effects in local precipitation and shorter spin-up period.

Core shell excitation of furan at the O1s and C1s edges: An experimental and ab initio study

The K-shell spectra of gaseous furan have been measured using the inner-shell electron energy loss spectroscopy (ISEELS) method at the carbon and oxygen thresholds. Large-scale ab initio configuration interaction calculations have been carried out in order to help in the assignments of the observed bands. The spectra are close to previous low resolution ones obtained using ISEELS in the gas phase and photoabsorption with the synchrotron radiation in gaseous and condensed phases. The presence of a new feature located at 287.3 eV in the C1s spectrum and recently detected by photoabsorption with synchrotron radiation is confirmed. At both edges, the calculations confirm the assignments proposed in earlier experimental works, with the exception of several C1s pre-edge features for which a new interpretation is given.

Efficient Computational Algorithms for Docking and for Generating and Matching a Library of Functional Epitopes I. Rigid and Flexible Hinge-Bending Docking Algorithms

In this, and the next review article (1), we present highly efficient, computer-vision and robotics based algorithms for docking and for the generation and matching of epitopes on molecular surfaces. We start with descriptions of molecular surfaces, and proceed to utilize these in both rigid-body and flexible matching routines. These algorithms originate in the computer vision and robotics disciplines. Frequently used approaches, both in searches for molecular similarity and for docking, i.e., molecular complementarity, strive to obtain highly accurate correspondence of respective molecular surfaces. However, owing to molecular surface variability in solution, to mutational events, and to the need to use modeled structures in addition to high resolution ones, utilization of epitopes might prove to be a judicious approach to follow. Furthermore, through the deployment of libraries of epitopes which represent recurring features, or motifs in a given family of receptors or of enzymes, in principle we a priori focus on the more critical groups of atoms, or amino acids, essential for the binding of the two molecules. Utilization of recurring motifs may prove more robust than single molecule matchings. In addition, via utilization of epitopes one can make use of information derived from evolutionary related molecules. All of the above combine to represent an approach which may be highly advantageous. Combinatorial approaches have proven their immense utility in the wet laboratory. The combination of efficient computational approaches and the utilization of such libraries may well be particularly profitable. Our highly efficient techniques are amenable to such a task. In this review we focus on rigid and flexible docking algorithms. In the second review (1) we address the generation of epitopes in families of molecules. These may be used by the docking algorithms to identify the more likely bound interfaces.

Polysilanes fonctionnels, 3. Synthèse d'α,ω‐bis(triméthylsilyl)oligo(méthylphénylsilane)s précurseurs des α,ω‐bis(triméthylsilyl)oligo(chlorométhyl‐silane)s. Charactérisation des heptaméthyl phényl‐2 trisilane et octaméthyl diphényl‐2,3 tétrasilane

AbstractLow‐molecular‐weight organosilane polymers were prepared by sodium coupling of dichloro‐methylphenylsilane (1) with chlorotrimethylsilane (2). Gel permeation chromatography (GPC), IR and NMR (1H, 13C and 29Si) analysis of the crude product (3) were performed and compared with those of the isolated first oligomers, trisilane (3a) and tetrasilane (3b). The GPC characteristics, especially high resolution ones, in accordance with the α,ω‐bis(trimethylsilyl)‐oligo(methylphenylsilane) structure are compared with those of hydrocarbon polymers. The relations of the NMR characteristics of the methylphenylsilanediyl unit with the position along the chain and the configuration of the diads are approached. Some spectroscopic indications of the secondary structure are discussed.

Radio constraints on the nature of BL Lacertae objects and their parent population

The Very Large Array has been used at 5 GHz to make images of 17 BL Lacertae objects, 13 of which are members of the "1 Jy sample" defined by Stickel et al. (ApJ, 374,431(1991)]. Sixteen sources were observed with the D array and 11 with the B array. All but one of the higher resolution images, and some of the lower resolution ones, show extended radio features. In at least four cases the sensitivity is sufficient to show linear polarization features in the extended emission. Of the ten sources that exhibit extended emission and have measured redshifts, at least three appear to be in the Fanaroff-Riley class II (FR II), from both their morphology and polarization properties, in addition to the luminosity of their extended emission. Three other sources are clearly in the FRI class, and four sources near the luminosity division between FR I and FR II sources are difficult to classify morphologically. At milliarcsecond resolution, however, none of these BL Lacertae objects show the polarization properties expected of a FR II nucleus. The characteristic "BL Lacertae-like" polarization on parsec scales is distinct from that of quasars, and is exhibited by both broad-line and narrow-line BL Lacertae objects. This suggests that the broad-line BL Lacertae objects are not simply an extension of the quasar/OVV population, and it also argues against the proposal that most BL Lacertae objects are gravitationally microlensed images of distant quasars. We present several arguments suggesting that not every FR I radio galaxy would appear as a radio-selected BL Lacertae object if viewed at a small angle to the jet direction. It seems likely that only those FR I radio galaxies with intrinsically-stronger cores would do so, while x-ray selected BL Lacertae objects may be found among the weaker cored and less favorably oriented FIR I radio galaxies. This alleviates some of the problems with the current unification schemes. The data for the radio- selected BL Lacertae objects are then consistent with typical jet Lorentz factors of {GAMMA} ~5, thus accounting straightforwardly with the modest superluminal speeds that have been measured so far in these objects.