A comparative study of multiple attribute tree and inverted file structures for large bibliographic files

A variety of data structures such as inverted file, multi-lists, quad tree, k-d tree, range tree, polygon tree, quintary tree, multidimensional tries, segment tree, doubly chained tree, the grid file, d-fold tree. super B-tree, Multiple Attribute Tree (MAT), etc. have been studied for multidimensional searching and related problems. Physical data base organization, which is an important application of multidimensional searching, is traditionally and mostly handled by employing inverted file. This study proposes MAT data structure for bibliographic file systems, by illustrating the superiority of MAT data structure over inverted file. Both the methods are compared in terms of preprocessing, storage and query costs. Worst-case complexity analysis of both the methods, for a partial match query, is carried out in two cases: (a) when directory resides in main memory, (b) when directory resides in secondary memory. In both cases, MAT data structure is shown to be more efficient than the inverted file method. Arguments are given to illustrate the superiority of MAT data structure in an average case also. An efficient adaptation of MAT data structure, that exploits the special features of MAT structure and bibliographic files, is proposed for bibliographic file systems. In this adaptation, suitable techniques for fixing and ranking of the attributes for MAT data structure are proposed. Conclusions and proposals for future research are presented.

A comparative study of side-band Fresnel holograms recorded with self-imaging and general objects

This paper deals with new results obtained in regard to the reconstruction properties of side-band Fresnel holograms (SBFH) of self-imaging type objects (for example, gratings) as compared with those of general objects. The major finding is that a distribution I2, which appears on the real-image plane along with the conventional real-image I1, remains a 2Z distribution (where 2Z is the axial distance between the object and its self-imaging plane) under a variety of situations, while its nature and focusing properties differ from one situation to another. It is demonstrated that the two distributions I1 and I2 can be used in the development of a novel technique for image subtraction.

Electronic-structures of h2o.bf3 and related n-v addition-compounds - a combined eels-ups study in vapor-phase

The detailed electronic structure of the n-v addition compound H2O·BF3 has been investigated for the first time by a combined use of electron energy loss spectroscopy (EELS) and UV photoelectron spectroscopy (UPS) augmented by MO calculations. The calculated molecular orbital energies of H2O·BF3 agree well with the UPS results and have been used to assign the electronic transitions obtained from EELS and to construct an orbital correlation diagram. The Journal of Chemical Physics is copyrighted by The American Institute of Physics.

On the direct parallel solution of systems of linear equations: New algorithms and systolic structures

The paper presents two new algorithms for the direct parallel solution of systems of linear equations. The algorithms employ a novel recursive doubling technique to obtain solutions to an nth-order system in n steps with no more than 2n(n −1) processors. Comparing their performance with the Gaussian elimination algorithm (GE), we show that they are almost 100% faster than the latter. This speedup is achieved by dispensing with all the computation involved in the back-substitution phase of GE. It is also shown that the new algorithms exhibit error characteristics which are superior to GE. An n(n + 1) systolic array structure is proposed for the implementation of the new algorithms. We show that complete solutions can be obtained, through these single-phase solution methods, in 5n−log2n−4 computational steps, without the need for intermediate I/O operations.

Push-pull ethylenes: the structures of 3-(2-imidazolidinylidene)-2,4-pentanedione (I), C8H12N2O2, and 3-(1,3-dimethyl-2-imidazolidinylidene)-2,4-pentanedione trihydrate (II), C10H16N2O2.3H2O

(I): Mr= 168, triclinic, P1, Z=2, a= 5.596 (2), b = 6.938 (3), c = 10.852 (4) A, ~t= 75.64 (3), fl= 93.44 (3), ),= 95.47 (3) °, V= 406.0A 3, Din= 1.35 (by flotation using carbon tetrachloride and n-hexane), D x= 1.374 Mg m -3, g(Mo Kct, 2 = 0.7107 A) = 1.08 cm -l, _F(000) = 180, T= 293 K. (II): Mr= 250, triclinic, P1, Z= 2, a = 7.731(2), b=8.580(2), c=11.033(3)A, a= 97-66 (2), fl= 98.86 (2), y= 101.78 (2) °, V= 697.5 A 3, D m = 1.18 (by flotation using KI solution), Dx= 1.190Mgm -3, g(MoKa, 2=0.7107A)= 1.02 cm -1, F(000) = 272, T= 293 K. Both structures were solved by direct methods and refined to R = 4.4% for 901 reflexions for (I) and 5.7% for 2001 reflexions for (II). The C=C bond distances are 1.451 (3) A in (I) and 1.468 (3)A in (II), quite significantly longer than the C=C bond in ethylene [1.336 (2).~; Bartell, Roth, Hollowell, Kuchitsu & Young (1965). J. Chem. Phys. 42, 2683-2686]. The twist angle about the C=C bond in (II) is 72.9 (5) ° but molecule (I) is essentially planar, the twist angle being only 4.9 (5) ° .

The structures of the ammonium halides

A comparison with the alkali halides suggests that all the ammonium halides should occur in the NaCl centre-of-mass structure. Experimentally, at room temperature and atmospheric pressure, only NH4I crystallizes in this structure, while NH4F is found in the ZnO structure, and NH4C1 and NH4Br occur in the CsCl structure. We show that a distributed charge on the NH4+ ion can explain these structures. Taking charges of + 0.2e on each of the five atoms in NH4+, as suggested by other studies, we have recomputed the Madelung energy in the cases of interest. A full ionic theory including electrostatic, van der Waals and repulsive interactions then explains the centre-of-mass structures of all the four ammonium halides. The thermal and pressure transitions are also explained reasonably well. The calculated phase diagram of NH4F compares well with experiment. Barring the poorly understood NH4F(II) phase, which is beyond the scope of this work, the other features are in qualitative agreement. In particular, the theory correctly predicts a pressure transition at room temperature from the ZnO structure directly to the CsCl structure without an intermediate NaCl phase. A feature of our approach is that we do not need to invoke hydrogen bonding in NH4F.

Theoretical description of time-resolved pump/probe photoemission in TaS2: a single-band DFT+DMFT(NRG) study within the quasiequilibrium approximation

In this work, we theoretically examine recent pump/probe photoemission experiments on the strongly correlated charge-density-wave insulator TaS2.We describe the general nonequilibrium many-body formulation of time-resolved photoemission in the sudden approximation, and then solve the problem using dynamical mean-field theory with the numerical renormalization group and a bare density of states calculated from density functional theory including the charge-density-wave distortion of the ion cores and spin-orbit coupling. We find a number of interesting results: (i) the bare band structure actually has more dispersion in the perpendicular direction than in the two-dimensional planes; (ii) the DMFT approach can produce upper and lower Hubbard bands that resemble those in the experiment, but the upper bands will overlap in energy with other higher energy bands; (iii) the effect of the finite width of the probe pulse is minimal on the shape of the photoemission spectra; and (iv) the quasiequilibrium approximation does not fully describe the behavior in this system.

Chemical bond approach to determining conductivity band gaps in amorphous chalcogenides and pnictides

The minimum energy required for the formation of conjugate pair of charged defects is found to be approximately equal to the experimental activation energy for d.c. conductivity in a number of amorphous chalcoganides and pnictides. This observation implies that the defect pair formation energy represents an intrinsic gap for transport in amorphous chalcogenides.

X-ray Studies on Crystalline Complexes Involving Amino Acids and Peptides. XIII. Effect of Chirality on Molecular Aggregation: The Crystal Structures of L-Arginine D-Aspartate and L-Arginine D-Glutamate Trihydrate

The crystal structures of (1) L-arginine D-asparate, C6HIsN40~.C4H6NO4 [triclinic, P1, a=5.239(1), b=9.544(1), c=14.064(2)A, a=85"58(1), /3=88.73 (1), ~/=84.35 (1) °, Z=2] and (2) L-arginine D-glutamate trihydrate, C6H15N40~-.CsHsNO4.3H20 [monoclinic, P2~, a=9.968(2), b=4.652(1), c=19.930 (2) A, fl = 101.20 (1) °, Z = 2] have been determined using direct methods. They have been refined to R =0.042 and 0.048 for 2829 and 2035 unique reflections respectively [I>2cr(I)]. The conformations of the two arginine molecules in the aspartate complex are different from those observed so far in the crystal structures of arginine, its salts and complexes. In both complexes, the molecules are organized into double layers stacked along the longest axis. The core of each double layer consists of two parallel sheets made up of main-chain atoms, each involving both types of molecules. The hydrogen bonds within each sheet and those that interconnect the two sheets give rise to EL-, DD- and DE-type head-to-tail sequences. Adjacent double layers in (1) are held together by side-chain-side-chain interactions whereas those in (2) are interconnected through an extensive network of water molecules which interact with sidechain guanidyl and carboxylate groups. The aggregation pattern observed in the two LD complexes is fundamentally different from that found in the corresponding EL complexes.

Conformations Of Peptides Containing 1-Aminocyclohexane-Carboxylic Acid (Acc6) - Crystal-Structures Of 2 Model Peptides

The crystal structures of two peptides containing 1-aminocyclohexanecarboxylic acid (Acc6) are described. Boc-Aib-Acc6-NHMe · H2O adopts a β-turn conformation in the solid state, stabilized by an intramolecular 4 → 1 hydrogen bond between the Boc CO and methylamide NH groups. The backbone conformational angles (φAib = – 50.3°, ψAib = – 45.8°; φAcc6 = – 68.4°, ψAcc6 = – 15°) lie in between the values expected for ideal Type I or III β-turns. In Boc-Aib-Acc6-OMe, the Aib residue adopts a partially extended conformation (φAib = – 62.2°, ψAib = 143°) while the Acc6residue maintains a helical conformation (φAcc6 = 48°, ψAcc6= 42.6°). 1H n.m.r. studies in CDCl3 and (CD3)2SO suggest that Boc-Aib-Acc6-NHMe maintains the β-turn conformation in solution.

Large cryptic internal sequence repeats in protein structures from Homo sapiens

Amino acid sequences are known to constantly mutate and diverge unless there is a limiting condition that makes such a change deleterious. However, closer examination of the sequence and structure reveals that a few large, cryptic repeats are nevertheless sequentially conserved. This leads to the question of why only certain repeats are conserved at the sequence level. It would be interesting to find out if these sequences maintain their conservation at the three-dimensional structure level. They can play an active role in protein and nucleotide stability, thus not only ensring proper functioning but also potentiating malfunction and disease. Therefore, insights into any aspect of the repeats - be it structure, function or evolution - would prove to be of some importance. This study aims to address the relationship between protein sequence and its three-dimensional structure, by examining if large cryptic sequence repeats have the same structure.

Thermally Induced Acyl Migration in Salicylamides. 1. Structures of the Reactants, O-Acetylsalicylamide and O-Benzoylsalicylamide

O-Acetylsalicylamide (Ia), C9H9NO3, M r =179.18, monoclinic, P2Jc, a=8.155(5), b=8.571 (2), c= 13.092 (3)A, fl=99.54 (5) ° , V= 902.4(6)A 3, Z=4, Dm=l.31, Dx=l.319gcm -3, 2(Mo Ka) = 0.71069 A,/~ = 1.08 cm -1, F(000) = 376, T = 295 K, R = 0.076 for 1604 reflections. O-Benzoylsalicylamide (Ib), C14HtlNO 3, M,=241.2, monoclinic, P2t/e, a=9.423(1), b=5.116(1), e= 26.424 (2) A, fl= 103.97 (1)% V= 1236.2 (3)/~3, Z= 4, D~ = 1.28, D x = 1.296 gcm -3, ,;L(Cu Ks) = 1.5418 A, p = 7.71 cm-', F(000) = 504, T= 295 K, R =0.050 for 2115 reflections. The dihedral angles between the amide group and the benzene ring are 39.9 ° (Ia) and 37.9 ° (Ib), whereas between the acyl group and the benzene ring they are 78.1 ° (Ia) and 93.4 ° (Ib). The differences in the packing of the two structures are brought out in terms of the observed hydrogen-bonding patterns. Based on the crystallographic results, an intramolecular mechanism for the migration of the acyl group from the O to the N position is suggested in both compounds.

X-ray absorption spectra of niobium dichalcogenides and their first-row transition-metal intercalates

X-ra!. K-absorption spectra of niobium in niobium dichalcogenides. namely NbS, and NbSe, and their first-row transition-metal intercalates Mi P 3N bSz (M = Cr. Mn. Fe. Co. Ni) and Ml#,NbSe2 (M = Fe. CO). have been measured together with those in niobium metal. The spectra of these materials are \er? similar to one another. They reflect the transitions to the partially filled niobium d band with some p character. A bariety of x-ray absorption nearedge structures (XASES) associated with the K edges of intercalated atoms are also presented and discussed.

Non-linear resonance in strings under narrow band random excitation, part I: Planar response and stability

Non-linear planar response of a string to planar narrow band random excitation is investigated in this paper. A response equation for the mean square deflection σ2 is obtained under a single mode approximation by using the equivalent linearization technique. It is shown that the response is triple valued, as in the case of harmonic excitation, if the centre frequency of excitation Ω lies in a certain specified range. The triple valued response occurs only if the excitation bandwidth β is smaller than a critical value βcrit which is a monotonically increasing function of the intensity of excitation. An approximate method of investigating the almost sure asymptotic stability of the solution is presented and regions of instability in the Ω-σ2 plane have been charted. It is shown that planar response can become unstable either due to an unbounded growth of the in-plane component of motion or due to a spontaneous appearance of an out-of-plane component.