bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and Properties of Three Immunogens with a Spacer on the β-Side of the Steroid Skeleton and the Effect of Immunogen Structure on Specificity of the Obtained Antisera
Authors: Kasal Alexander , Hampl Richard , Putz Zdeněk , Kohout Ladislav , Stárka Luboslav
Published: June 2004

Three haptenes for the determination of Reichstein's compound S and progesterone were prepared in which hemisuccinyloxy group was attached to the β-side of the steroid skeleton (compounds VII, XIII and XV). These haptenes were bound to BSA and used for preparation of antisera. The specificity of these antisera was compared with that of antisera obtained with usual immunogens.
Purification of Penicillin Amidohydrolase, an Enzyme for Semisynthetic Procedures
Authors: Jiráček Jiří , Barth Tomislav , Velek Jiří , Bláha Ivo , Pospíšek Jan , Svoboda Ivan
Published: June 2004

Penicillin amidohydrolase (EC 3.5.1.11.) is one of the few enzymes used successfully for deprotection of primary amino groups of semisynthetic peptides. The available material is usually contamined by endo- and exopeptidases. We managed to prepare the enzyme devoid of trypsin- and chymotrypsin-like activities using affinity chromatography with specific ligands: Gly-D-Phe-Phe-Tyr-Thr-Pro-Lys-Thr (the fF peptide) and Leu-Gly-Val-D-Arg-Arg-Gly-Phe (the rR peptide). For further purification of the enzyme affinity chromatography with N-phenylacetyl-D-tert-Leu as a ligand was used.
A Novel Approach to the Study of Briggs-Rauscher Reaction
Authors: Lalitha Punchayil Velayudhan Nair , Ramaswamy Renganathan
Published: June 2004

The Briggs-Rauscher reaction with substrates containing acidic hydrogen such as malonic acid, acetonyl acetone has been studied. The employment of mixed media involving an organic solvent and water enabled the study of water-insoluble substrates. The present communication reports the oscillatory behaviour of malonic acid in the iodate system in different mixed media (5 vol.% of the organic solvent) as well as the oscillatory behaviour of seven substrates in acetonitrile-water mixed medium of which two are new substrates hitherto unreported in any of the oscillatory systems.
The Polarographic and Voltammetric Determination of 1-(3'-Carbamoylphenyl)-3,3-dimethyltriazene
Authors: Barek Jiří , Kubíčková Jana , Mejstřík Viktor , Zima Jiří
Published: June 2004

A study was made of the polarographic reduction of the title triazene, a mechanism was proposed for this process and optimal conditions were found for its analytical application using tast polarography in the range 1 . 10-4 - 2 . 10-6 mol l-1, differential pulse polarography in the range 1 . 10-4 - 2 . 10-7 mol l-1 and fast scan differential pulse voltammetry at a hanging mercury drop electrode in the range 1 . 10-4 - 2 . 10-7 mol l-1. The sensitivity of the latter technique was increased through adsorptive accumulation of the test substance on the surface of the working electrode, permitting determination in the concentration range 1 . 10-7 - 2 . 10-9 mol l-1.
The Reactivity of Different Active Forms of Sodium Carbonate with Respect to Sulfur Dioxide
Authors: Mocek Karel , Lippert Erich , Erdös Emerich
Published: June 2004

The kinetics of the reaction of solid sodium carbonate with sulfur dioxide depends on the microstructure of the solid, which in turn is affected by the way and conditions of its preparation. The active form, analogous to that obtained by thermal decomposition of NaHCO3, emerges from the dehydration of Na2CO3 . 10 H2O in a vacuum or its weathering in air at room temperature. The two active forms are porous and have approximately the same specific surface area. Partial hydration of the active Na2CO3 in air at room temperature followed by thermal dehydration does not bring about a significant decrease in reactivity. On the other hand, if the preparation of anhydrous Na2CO3 involves, partly or completely, the liquid phase, the reactivity of the product is substantially lower.
Influence of the Temperature on Calcium Sulfite Content of the Reaction of SO2 with CaO
Authors: Allal K. M. , Abbessi M. , Zerdaoui M.
Published: June 2004

The purification of the gases containing sulfur oxides such as SO2 and SO3 can be realized by reacting with dry alkaline substances like calcium oxide. At relatively low temperatures (<500 °C) calcium sulfite (CaSO3), an unstable product of the reaction can be formed and may react reversibly to give back SO2. It is therefore important that the reaction be controlled. The influence of the temperature on the amount of calcium sulfite formed has been studied experimentally by means of a thermobalance. The formation of CaSO3 can be avoided if the temperature is higher than 650 °C.
Cycloaddition Reactions of Arylmethylenemalonaldehydes with Olefins
Authors: Dvořák Dalimil , Šaman David , Arnold Zdeněk , Císařová Ivana , Petříček Václav
Published: June 2004

A series of 2,4-disubstituted 3,4-dihydro-2H-pyran-5-carboxaldehydes II-XIX was prepared by reaction of substituted arylmethylenemalonaldehydes I with 2-methylpropane, 1,1-diphenylethylene, styrene, ethyl vinyl ether, 1,1-dimethoxyethylene and 1,1-bis(methylthio)ethylene. In the case of the reaction with ethyl vinyl ether the dependence of the ratio of the arising cis- and trans- 2-ethoxy-4-aryl-3,4-dihydropyran-5-carboxaldehydes VII-XIV on the substitutent on the aromatic nucleus was studied. Information on the mechanism of this reaction was obtained and conformational equilibria of 2-ethoxy-4-aryl-3,4-dihydropyran-5-carboxaldehydes in solution were studied by 1H NMR spectroscopy. The structure of trans-2-ethoxy-4-(4-chlorophenyl)-3,4-dihydropyran-5-carboxaldehyde (trans-VIII) was confirmed by X-ray analysis of the corresponding carboxylic acid trans-XXII.
Synthesis and Reactions of Some New 3-Amino-2-substituted Thieno[2,3-b]quinolines
Authors: Bakhite Etify Abdel-Ghafar
Published: June 2004

Reaction of 3-cyano-quinolin-2(1H)-thione (II) with ω-bromoacetophenones gave 3-amino-2-aroyl-thieno[2,3-b]quinolines (IVa-IVd). Whereas, interaction of II with chloroacetanilides yielded the corresponding thioesters Va-Vc which cyclized into 3-amino-2-arylcarbamoylthiene[2,3-b]quinolines (VIa-VIc) on treatment with ethoxide. Compounds VIa-VIc were reacted with nitrous acid, triethyl orthoformate and carbon disulfide to afford the fused polycyclic compounds VIIa-VIIc, VIIIa-VIIIc and IXa-IXc, respectively. Also treatment of IXa-IXc with ethyl iodide gave 3-ethylthio derivatives Xa-Xc. Moreover, refluxing of VIa-VIc with acetic anhydride resulted in the formation of oxazinone XI which recyclized into pyrimidinones XIIIa-XIIIc upon reaction with aromatic amines.
Novel Ring Closure Carbonylation Reaction of 1,5-Cyclooctadiene in the Presence of Pd(II)-Catalysts
Authors: Anderson Curtis B. , Marković Rade
Published: June 2004

Oxidative carbonylation of 1,5-cyclooctadiene in methylene chloride-methanol mixture, catalyzed by Pd(II)-salts, gave rise to a bicyclic, bifunctional product under mild experimental conditions. The mechanism, involving multiple carbon monoxide and double bond insertions into the Pd(II)-carbon σ-bond, has been proposed, as being consistent with the outcome of this novel ring closure reaction.
Artificial Intelligence in Chemistry
Authors: Jakuš Vladimír
Published: June 2004

The definition of artificial intelligence and the associated tasks of this branch of science are discussed. The tasks include pattern recognition, adaptation and learning, problem solving by means of expert systems or neural networks, and understanding the natural language and communication with a machine in it. The principles of problem solving are analyzed. It is demonstrated how artificial intelligence-based computer programs in which chemical expertise is encoded assist in structure elucidation, in the investigation of relations between structure and biological activity or chromatographic retention, etc.; problems emerging in the synthesis planning with a retrosynthetic analysis, or in the planning of experiments and intelligent consultations are dealt with. Several models used for structure elucidation and synthesis planning are evaluated. An overview is presented of additional expert systems which, along with artificial intelligence-based robotics, are used in intelligent instrumentation. Also discussed is the role of neural networks, which begin to be successfully employed in structure elucidation, synthesis planning, in intelligent instrumentation and in the treatment of natural languages. They are expected to be an important tool in the implementation of intelligent systems for the classification of chemical databases and prediction of properties of molecules.
Xanes Investigation of Molybdate Catalysts Supported on Titania
Authors: Hippel Lukas M. J. von , Hilbrig Frank , Schmelz Helmut , Lengeler Bruno , Knözinger Helmut
Published: June 2004

Molybdenum oxide supported on titania is an important material for catalytic processes in petroleum industry as well as in air pollution control. A structure analysis by means of X-ray absorption spectroscopy (XANES) is reported for sample prepared by spreading of MoO3 in physical mixtures with the support as well as by impregnation from aqueous solution. Analysis of the XANES region of the Mo K edge indicated that the surface molybdate has a structure similar to ammonium heptamolybdate.
FEM Study of Oxidized Tungsten Surfaces
Authors: Šotola Jan , Savkin Vladimir , Knor Zlatko
Published: June 2004

Surface reconstruction of tungsten induced by oxygen chemisorption in the temperature range 300 K ≤ T ≤ 2200 K, has been investigated by means of FEM. Two types of surfaces have been used in this study: (i) hemispherical tungsten tips exposing small low index planes and stepped regions to the gas phase; (ii) polyhedral tungsten tips exposing large densely populated planes. A model for the reconstruction of a (100) plane is presented, explaining all the phenomena observed by FEM, TDS, LEED and MBS.
Application of Quantum Chemical Calculations to the Identification of Positional Isomers of Polysubstituted Alkylbenzenes
Authors: Jakuš Vladimír , Matisová Eva , Miertuš Stanislav
Published: June 2004

The problem of assignment of positional isomers of alkylbenzenes to chromatographic peaks is addressed. Probable structures are attributed based on the correlation of stabilities of the isomers, which are expressed as the total molecular energies calculated by the MINDO/3 semiempirical quantum chemical method, and the proportions of the isomers in the reaction mixture. Multicomponent alkylbenzene mixtures were prepared and separated by capillary gas chromatography, and the identity of the isomers was confirmed by the gas chromatography-mass spectrometry combination.
Development of Cobalt-Molybdenum Hydrodesulfurization Catalysts
Authors: Sporka Karel , Hanika Jiří
Published: June 2004

The Co-Mo catalysts have been prepared on laboratory scale by controlled impregnation of extruded γ-alumina with aqueous solutions of suitable active components, and their activity has been tested in the hydrodesulfurization and hydrogenation of aromatic compounds in gas oil. The kinetics of impregnation of the carrier, the effect of its nature, the order of impregnation of precursors of the individual active components, and the effect of their nature on the activity of the catalyst prepared have been studied. The samples prepared have been compared with selected commercial catalysts.
Lead Containing Zeolites as Catalysts for Oxidative Conversion of Methane
Authors: Kovacheva Pavlina Ch. , Davidova Nadka P. , Weiss Alvin H.
Published: June 2004

The oxidative conversion of methane was studied over lead containing zeolites of type X, silicalite and ALPO-5 in the temperature range 750-850 °C. An impregnation of catalysts in the range 3-7 wt.% lead was found optimum for the conversion and C2 selectivity. The 6.4 wt.% lead-containing zeolite showed the best C2 hydrocarbon yield. Higher reaction temperatures caused higher C2H4/C2H6 ratios. The catalysts did not deactivate in 10 h time-on-stream. PbO and zeolitic basic sites play role in the reaction.
Surface Redox Strength and Catalytic Activity of the CuO/ZnO System
Authors: Andreeva Donka Ch. , Kalchev Matey G. , Andreev Atanas A.
Published: June 2004

Information about the reduction properties and reactivity of surface hydroxyl groups has been obtained from the interaction of iodine with a series of CuO/ZnO samples in wide range of concentrations. The maximum capacity of iodine reduction and maximum catalytic activity in water gas shift reaction were observed with the sample containing 20 wt.% CuO. The correlation found gives evidence in favour of the associative mechanism of reaction.
Hydrogenation of Fatty Acid Esters. III. Hydrogenation of Methyl (9Z,12Z)-Octadecadienoate and Methyl (9Z,12Z,15Z)-Octadecatrienoate
Authors: Krupičková Jana , Včelák Jaroslav , Hetflejš Jiří
Published: June 2004

The title hydrogenation catalyzed by nickel(II) 2,4-pentanedionate-triethylaluminium system has been studied with the use of combination of initial rate measurements with time changes of product distribution. It was found that the hydrogenation of methyl (9Z,12Z)-octadecadienoate is first order in the octadecadienoate. Similar results were obtained also for (9Z,12Z,15Z)-octadecatrienoate. The course of both reactions has been described by models involving set of parallel and consecutive hydrogenation steps and reversible isomerizations. Computed rate constants for hydrogenation of methyl (9Z,12Z)-octadecadienoate support qualitative conclusions deduced from the product analysis.
Effect of Components of Based Catalytic System on Reductive Carbonylation of Nitrobenzene
Authors: Macho Vendelín , Vojček Loránt , Schmidtová Mária , Terlandová Jana
Published: June 2004

A three component catalytic system consisting of (i) elemental sulfur or sulfur compounds (CS2, H2S, COS), (ii) an alkali methoxide or triethylamine, and (iii) vanadium(V) compounds (V2O5, NH4VO3) has been applied as catalyst for reductive carbonylation of nitrobenzene to methyl N-phenyl carbamate with carbon monoxide and methanol at a temperature of 423 ± 2 K and an initial carbon monoxide pressure of 10-14 MPa/298 K. The efficiency of sulfur compounds increased in the sequence S:CS2:H2S:COS = 1:1.6:7.9:13.8. Hydrogen sulfide decreased however the selectivity of the reaction to the carbamate and increased that to aniline. Formation of the latter amine is increased especially in the presence of water in the reaction mixture and of hydrogen in the synthesis gas above 40 vol.%. The efficiency of the bases decreased in order CH3OK > CH3ONa = NaOH > (C2H5)3N and of vanadium compounds in the sequence NH4VO3 > V2O5. The catalyst system thus allows to effect the reductive carbonylation of aromatic nitro compounds in the absence of transition metal compounds.
Recent Application of ab initio Calculations on Calixarenes and Calixarene Complexes. A Review
Authors: Schatz Jürgen
Published: June 2004

In this short review the application of ab initio quantum chemical calculations on calixarenes and calixarene complexes is highlighted. The main focus lies on results obtained mainly during the last 2-3 years. A review with 92 references.
1,3-Alternate Calix[4]arene: the Sophisticated Conformer of Calix[4]arene. A Review
Authors: Pulpoka Buncha , Vicens Jacques
Published: June 2004

The fascinating calix[4]arene derivatives in 1,3-alternate conformation are reviewed. The review focuses on their molecular construction methodologies, sophisticated properties and applications. A review with 110 references.
Anion Complexation Properties of Thiophene-2,4- and -2,5-biscarboxamides
Authors: Gale Philip A. , Hursthouse Michael B. , Light Mark E. , Warriner Colin N.
Published: June 2004

Thiophene-2,4- and -2,5-biscarboxamides have been synthesised and shown to act as anion receptors in DMSO-d6/water solution. The crystal structure of the fluoride complex of a N,N'-diphenylthiophene-2,5-biscarboxamide derivative has been solved and reveals the involvement of the thiophene CH protons in anion complexation in the solid state.
Concave Reagents. New 2'-Substituted m-Terphenyls
Authors: Abbass Michael , Kühl Christine , Manthey Christian , Müller Anja , Lüning Ulrich
Published: June 2004

New 2'-substituted 2,2'',6,6''-tetramethyl-1,1':3',1''-terphenyls have been synthesized. Solubility of concave acids 4b-6b could be enhanced by substitution in 4 and 4'' position, allowing the study of hydrogen-bonded heterodimers. Concave acids show larger binding constants for 2-amidopyridines 7 than non-macrocyclic ones, probably due to the prevention of homodimer formation by the macrocyclic shielding. New 2,6-diarylbenzyl alcohols 1d, 8d and 9d have been synthesized and tested in protonation reactions. New functional groups were introduced into the 2' position: OH (phenols 1f and 12f) and NH2 (aniline 1j). The basicity of aniline 1j in ethanol was determined by titration and was compared to other bases. Also sulfonic acids 1l and 17l were prepared, and the corresponding methyl esters 1m and 17m were tested as methylating agents.
Design and Preparation of Mesogenic Cavitands
Authors: Pirondini Laura , Vecchi Gabriele , Negri Sara , Di Blasi Alfredo , Massera Chiara , Dalcanale Enrico
Published: June 2004

Mesogenic cavitands have been prepared for the first time. They form uniaxial disordered columnar mesophases (Dhd). The structure requirements for mesophase formation have been identified: (i) macrocyclic cores with thickness below 5 Å and (ii) four large (3,4,5-tris{[4-(dodecyloxy)benzyl]oxy}benzoyl)oxy groups at the upper rim. The orientation of the molecules within the columns is random, excluding the formation of intracolumnar cavities of molecular dimensions in the mesophase.
Variation in flower biomass among nearby populations of Impatiens textori (Balsaminaceae): effects of population plant densities
Authors: Iwaizumi Masakazu G , Sakai Satoki
Published: June 2004

Although most of the previously detected variation in flower biomass was among populations that were far apart from each other, differences in population characteristics (population size, area, and plant density) may bring the variation in flower biomass to a more local scale. To examine the variation in flower biomass among nearby populations of Impatiens textori Miq. (Balsaminaceae), field studies were conducted on six natural populations located along a stream in Japan. We also examined the dependence of flower biomass and outcrossing rate on population characteristics, as well as the differences in plant size and pollinator behavior among populations. We conducted pollination experiments with potted plants, in which plant density and flower size were independently manipulated. Mean flower mass varied among populations, being negatively dependent on plant density. One-factor ANCOVA showed that both plant size and the other population-level factor affected flower biomass variation. Experiments with potted plant arrays showed that geitonogamous pollination more likely occurred in sparse populations, but in field studies, the population outcrossing rate was not significantly dependent on plant density of the population. Thus, the variation in flower biomass cannot be fully explained by these commonly considered factors. Our results show that the flower biomass of populations may evolve locally in response to plant density or other population characteristics.Key words: variation, flower biomass, population, Impatiens textori, plant density, local scale.
Regulation of the mutualism between yuccas and yucca moths: intrinsic and extrinsic patterns of fruit set
Authors: Humphries Shelley A , Addicott John F
Published: June 2004

In plants that produce many more flowers than fruit, nonrandom patterns of fruit set arise from (1) factors intrinsic to inflorescence architecture, such as flower position or timing in the blooming sequence, and (2) factors extrinsic to the plant, such as pollinator visitation patterns. Here, we address how intrinsic and extrinsic factors drive fruit set in the interaction between Yucca kanabensis McKelvey and its pollinating moths. On inflorescences from which moths were excluded and all flowers were hand pollinated, the flowers most likely to produce fruit were (1) flowers from the first of three waves of flowering, (2) earlier opening flowers but not the earliest, and (3) flowers lower on the inflorescence but not the lowest. However, inflorescences experiencing natural levels of pollination and oviposition showed no effect of flowering wave, and flowers later in the flowering sequence and higher on the inflorescence were the ones most likely to produce fruit. The intrinsic patterns of fruit set were associated with differences among flowers, with the largest flowers being wave 1 flowers and flowers lower on the inflorescence. However, these differences among flowers did not translate into commensurate differences among fruit.Key words: mutualism, abscission, fruit, yucca, yucca moth.
Salt-induced changes in the vegetative anatomy ofProsopis strombulifera(Leguminosae)
Authors: Reinoso Herminda , Sosa Laura , Ramírez Lucía , Luna Virginia
Published: June 2004

Seedlings of Prosopis strombulifera (Lam.) Benth. were grown hydroponically in Hoagland's solution with addition of 25 mmol/L NaCl every 48 h until final salt concentrations of 250, 500, and 700 mmol/L were reached. Control plants were grown without salt. Salinity induced anatomical changes in roots (young and mature zones), hypocotyls, young stems, and leaflets. The diameters of the young zone of roots of plants grown in increasing salt concentrations were smaller than those of controls, with reduced number of cortex layers and reduced size of the vascular system. The roots from tolerant plants showed precocious suberization and (or) lignification of the endodermal cells and early activity of the pericycle. Hypocotyl diameter was reduced along with a reduction in secondary phloem. Roots and hypocotyls showed abundant phellem formation. The stem diameter of young tolerant plants was notably diminished and less tissue lignification occurred. In stems and leaflets of treated plants, NaCl stimulated the production of tannins. In the leaflets, vascular bundles were similar in size. Groups of elongated parenchyma cells with many chloro plasts surrounded the bundles. These results suggest that in the absence of secretory organs, the anatomical modifications in this species are related to metabolic adaptations, such as an early development of the endodermal barrier for ion exclusion, to allow survival in high salinity.Key words: Prosopis strombulifera, anatomical changes, hydroponics, NaCl.
Distribution and abundance of infective, soilborne Frankia and host symbionts Shepherdia, Alnus, and Myrica in a sand dune ecosystem
Authors: Batzli Janet McCray , Zimpfer Jeff F , Huguet Valérie , Smyth Charles A , Fernandez Maria , Dawson Jeffrey O
Published: June 2004

We describe presence, abundance, and distribution of three sympatric nitrogen-fixing shrubs and their symbiotic diazatroph, Frankia, in a sand dune ecosystem differing in successional stage, vegetative cover, edaphic characteristics, and topography. Distribution of actinorhizal Myrica gale L., Alnus incana (L.) Moench subsp. rugosa (Du Roi) Clausen, and Shepherdia canadensis (L.) Nutt. was analyzed among 120 sampling locations representing a gradient of successional stages in a sand dune system along Lake Michigan. In a greenhouse study, seedlings of these species were employed to bioassay the presence and abundance of infective Frankia in soils. Shepherdia-infective Frankia was detected in 80% of the plots, while Alnus- and Myrica-infective Frankia were found in 65% and 64% of the plots, respectively, with no Frankia found in 18% of the plots. Only 14% of the plots supported actinorhizal host-plant species. Infective Frankia were present in soils of young dunes prior to the establishment of any actinorhizal hosts. Shepherdia-infective Frankia were more abundant in soils from drier, earlier successional sites, while Alnus- and Myrica-infective Frankia were more abundant in moister soils of later successional communities. A previous study had revealed that nodular Frankia strains at this site were host specific for Shepherdia and largely so for Myrica and Alnus, which had only a small proportion of shared strains (Huguet et al. 2001). The likelihood of host-plant nodulation by soilborne Frankia was increased by the presence of actinorhizal plants in general, but not by the presence of their respective specific host plants. Submerged soils had no infectious capacity, whereas soils with greater in situ moisture content and soils subject to intermittent saturation tended to have lower infectious capacities overall. Our results suggest that soilborne, infective Frankia genotypes are not only host specific, but are also associated with spatially and chronologically distinct sets of ecological conditions.Key words: speckled alder, sweet gale, Canada buffalo berry, actinorhizal, nitrogen fixation, Frankia, root nodules.
SIMULATION OF MESHES WITH SEPARABLE BUSES BY MESHES WITH MULTIPLE PARTITIONED BUSES
Authors: MATSUMAE Susumu
Published: June 2004

This paper studies the simulation problem of meshes with separable buses [Formula: see text] by meshes with multiple partitioned buses [Formula: see text]. The [Formula: see text] and the [Formula: see text] are the mesh connected computers enhanced by the addition of broadcasting buses along every row and column. The broadcasting buses of the [Formula: see text], called separable buses, can be dynamically sectioned into smaller bus segments by program control, while those of the [Formula: see text], called partitioned buses, are statically partitioned in advance. In the [Formula: see text] model, each row/column has only one separable bus, while in the [Formula: see text] model, each row/column has L partitioned buses (L≥2). We consider the simulation and the scaling-simulation of the [Formula: see text] by the [Formula: see text], and show that the [Formula: see text] of size n×n can be simulated in O(n1/(2L)) steps by the [Formula: see text] of size n×n, and that the [Formula: see text] of size n×n can be simulated in [Formula: see text] steps by the [Formula: see text] of size m×m(m<n). The latter result implies that the [Formula: see text] of size n×n can be simulated time-optimally by the [Formula: see text] of size m×m when n≥m1+∊ holds where [Formula: see text].
A HIERARCHICAL MODEL FOR DISTRIBUTED COLLABORATIVE COMPUTATION IN WIRELESS SENSOR NETWORKS
Authors: Singh Mitali , Prasanna Viktor K.
Published: June 2004

In-network collaborative computation is essential for implementation of a large number of sensor applications. We approach the problem of computation in sensor networks from a parallel and distributed system's perspective. We define COSMOS, the Cluster-based, heterOgeneouSMOdel for Sensor networks. The model abstracts the key features of the class of cluster-based sensor applications. It assumes a hierarchical network architecture comprising of a large number of low cost sensors with limited computation capability, and fewer number of powerful clusterheads, uniformly distributed in a two dimensional terrain. The sensors are organized into single hop clusters, each managed by a distinct clusterhead. The clusterheads are organized in a mesh-like topology. All sensors in a cluster are time synchronized, whereas the clusterheads communicate asynchronously. The sensors are assumed to have multiple power states and a wakeup mechanism to facilitate power management. To illustrate algorithm design using our model, we discuss implementation of algorithms for sorting and summing in sensor networks.
ON HIERARCHICAL CONFIGURATION OF DISTRIBUTED SYSTEMS ON MESH AND HYPERCUBE
Authors: WANG DAJIN , CAO JIANNONG
Published: June 2004

We study hierarchical configuration of distributed systems for achieving optimized system performance. A distributed system consists of a collection of local processes which are distributed over a network of processors, and work in a cooperative manner to fulfill various tasks. A hierarchical approach is to group and organize the distributed processes into a logical hierarchy of multiple levels, so as to coordinate the local computation/control activities to improve the overall system performance. It has been proposed as an effective way to solve various problems in distributed computing, such as distributed monitoring, resource scheduling, and network routing. The optimization problem considered in this paper is concerned with finding an optimal hierarchical partition of the processors, so that the total traffic flow over the network is minimized. The problem in its general form has been known to be NP-hard. Therefore, we just focus on distributed computing jobs which require collecting and processing information from all processors. By limiting levels of the hierarchy to two, we will establish the analytically optimal hierarchical configurations for two popular interconnection networks: mesh and hypercube. Based on analytical results, partitioning algorithms are proposed to achieve minimal communication cost (network traffic flow). We will also present and discuss heuristic algorithms for multiple-level hierarchical partitions.
PROGRAM-BASED LOCALITY MEASURES FOR SCIENTIFIC COMPUTING
Authors: RAUBER THOMAS , RÜNGER GUDULA
Published: June 2004

Numerical software for sequential or parallel machines with memory hierarchies can benefit from locality optimizations which are usually achieved by program restructuring or program transformations. In this paper we introduce and discuss program-based locality measures which can be used to guide the restructuring and transformation process at program level. As example we consider a popular solution method to solve ordinary differential equations provided in many scientific libraries.
CONTENT NETWORKS: DISTRIBUTED ROUTING DECISIONS IN PRESENCE OF REPEATED QUERIES
Authors: CIGLARIČ MOJCA
Published: June 2004

Content networks are overlay networks, enabling access to distributed contents on centralized servers or individual computers. Since flooding-based routing scheme features poor scalability, we present a modification, which reduces the total network traffic while retaining the original efficiency. In choosy routing, as we call it, each node, while passing an answer, remembers which neighbor it came from. Subsequently repeated queries about the same content are forwarded only to that neighbor. This way, the network learns effective routes. The simulations on several topology types have shown the expected behavior, with up to three-fold reduction in the overall query traffic.
PHANTOM FIELD AND THE FATE OF THE UNIVERSE
Authors: SAMI M. , TOPORENSKY ALEXEY
Published: June 2004

In this paper we analyze the cosmological dynamics of phantom field in a variety of potentials unbounded from above. We demonstrate that the nature of future evolution generically depends upon the steepness of the phantom potential and discuss the fate of the universe accordingly.
A THEORETICAL ANALYSIS ON THE FERMI LEVEL IN MULTIWALLED CARBON NANOTUBES
Authors: GRADO-CAFFARO M. A. , GRADO-CAFFARO M.
Published: June 2004

The Fermi level for a multiwalled carbon nanotube is determined analytically by using the Fermi velocity obtained from the particle-in-a-box model. Fermi energy is found to be quantized so that the corresponding quantum number coincides with the wall number. In addition, the classical limit is discussed.
IRREDUCIBLE MONOMIAL LINEAR GROUPS OF DEGREE FOUR OVER FINITE FIELDS
Authors: FLANNERY D. L.
Published: June 2004

We describe an algorithm for explicitly listing the irreducible monomial subgroups of GL (n,q), given a suitable list of finite irreducible monomial subgroups of [Formula: see text], where n is 4 or a prime, and q is a prime power. Particular attention is paid to the case n=4, and the algorithm is illustrated for n=4 and q=5. Certain primitive permutation groups can be constructed from a list of irreducible monomial subgroups of GL (n,q). The paper's final section shows that the computation of automorphisms of such permutation groups reduces mainly to computation of irreducible monomial subgroups of GL (n,q), q prime.
AUTOMORPHISMS OF CERTAIN RELATIVELY FREE GROUPS AND LIE ALGEBRAS
Authors: PAPISTAS A. I.
Published: June 2004

For positive integers n and c, with n≥2, let Gn,c be a relatively free group of rank n in the variety N2A∧AN2∧Nc. It is shown that there exists an explicitly described finite subset Ω of IA-automorphisms of Gn,c such that the cardinality of Ω is independent upon n and c and the subgroup of the automorphism group Aut (Gn,c) of Gn,c generated by the tame automorphisms and Ω has finite index in Aut (Gn,c). This is a simpler result than one given in [12, Theorem 1(I)]. Let L(Gn,c) be the associated Lie ring of Gn,c and K be a field of characteristic zero. The method developed in the proof of the aforementioned result is applied in order to find an explicitly described finite subset ΩL of the IA-automorphism group of K⊗L(Gn,c) such that the automorphism group of K⊗L(Gn,c) is generated by GL (n,K) and ΩL. In particular, for n≥3, the cardinality of ΩL is independent upon n and c.
A Novel Permutation Testing Method Implicates Sixteen Nicotinic Acetylcholine Receptor Genes as Risk Factors for Smoking in Schizophrenia Families
Authors: Faraone Stephen V. , Su Jessica , Taylor Levi , Wilcox Marsha , van Eerdewegh Paul , Tsuang Ming T.
Published: June 2004

Smoking is a common correlate of schizophrenia, which leads to medical morbidity. Although twin and adoption studies have consistently implicated genes in the etiology of both smoking and schizophrenia, finding genes has been difficult. Several authors have suggested that clinical or neurobiological features associated with schizophrenia, such as smoking, might improve the ability to detect schizophrenia susceptibility genes by identifying genes related to the etiology of that feature. The objective of this study is to assess evidence for linkage of sixteen nicotinic acetylcholine receptor genes and smoking in schizophrenia families, using data from the NIMH Genetics Initiative for schizophrenia. Sixteen nicotinic acetylcholine receptor genes were selected prior to analysis. We used a multipoint sibling pair linkage analysis program, SIBPAL2, with a smoking trait in schizophrenia families. The significance of the group of candidate genes, in addition to each individual candidate gene, was assessed using permutation testing, which adjusted for multiple comparisons. The group of genes showed significant linkage to the smoking trait after adjusting for multiple comparisons through permutation testing (p = 0.039). In addition, two of the individual candidate genes were significant (CHRNA2, p = 0.044) and (CHRNB2, p = 0.015) and two genes were marginally significant (CHRNA7, p = 0.095; CHRNA1, p = 0.076). The significance of the complex hypothesis, involving sixteen genes, implicates the nicotinic system in smoking for schizophrenic families. Individual gene analysis suggests that CHRNA2 and CHRNB2 may play a particular role in this involvement. Such findings help prioritize genes for future case control studies. In addition, we provide a novel permutation method that is useful in future analyses involving a single hypothesis, with multiple candidate genes.
Class I and II HLA Genes Are Associated with Susceptibility and Age at Onset in Finnish Families with Type 1 Diabetes
Authors: Pitkäniemi Janne , Hakulinen Timo , Näsänen Jurkka , Tuomilehto-Wolf Eva , Tuomilehto Jaakko
Published: June 2004

Objectives: We explored the properties of the long-term survivor model (LTS) in the genetic association studies and studied allelic and haplotypic associations between the age at onset and partially latent susceptibility of type 1 diabetes (T1DM) and Human Leucocyte Antigen (HLA) A, B and DR loci. Methods: The authors applied the long-term survivor model (LTS) for sibships collected in a population-based registry during a calendar time period. The method uses sibs that could not become probands and includes the proband’s age at onset during the recruitment period. Association between the candidate gene and the partially latent susceptibility is modeled with logistic regression and the age at onset with a two-parameter gamma distribution, where a scale parameter depends on the candidate genotypes. We also performed a simulation study of nuclear families to compare the power of the likelihood ratio tests of the genetic association based on the LTS model with those obtained using family-based association method (FBAT) and bias of the case-pseudo control design. In addition, we analysed allele and haplotype associations between HLA A, B and DR loci (IDDM1) with T1DM, using population-based ascertainment of 705 sibships with complete HLA information. Results: A simulation study showed that the estimates of the genetic association using an ascertainment-corrected LTS model are virtually unbiased and that the relative risk estimates obtained from case-pseudo control design (TDT) are negatively biased. In the analysis of the Finnish T1DM families we found that only B62 (p < 0.05) is positively significantly associated with susceptibility after adjusting for the haplotype effects. Five alleles were significantly associated with age at onset (B8 and DR3, p < 0.01; A2, B60 and DR6, p < 0.05). No significant three-locus haplotype associations with the susceptibility were found, but A3B18DR4 (p < 0.001) haplotype was associated with older age at onset than average. Conclusions: Estimates of genetic relative risk obtained from the case-pseudo control design are negatively biased and the prospective LTS model is an appropriate choice, when there are non-susceptible subjects in the population with variable age at onset. Based on the analysis of T1DM, we conclude that there are gene(s) in the HLA region that are associated with susceptibility and/or age at onset of T1DM, and this should be taken into account in future studies.
Familial Aggregation and Genome-Wide Linkage Analysis of Carotid Artery Plaque: The NHLBI Family Heart Study
Authors: Pankow James S. , Heiss Gerardo , Evans Gregory W. , Sholinsky Phyliss , Province Michael A. , Coon Hilary , Ellison R. Curtis , Miller Michael B. , Qaqish Bahjat
Published: June 2004

Objective: To evaluate familial and genetic influences on carotid artery plaque, a qualitative marker of the systemic burden of atherosclerosis. Methods: The design was a cross-sectional study of 2,223 members of 525 randomly-ascertained families and 2,514 members of 589 high coronary heart disease (CHD) risk families from 4 U.S. communities. Results: The prevalence of plaque was 33, 36, and 47%, respectively, among probands with 0, 1, and 2 or more first-degree relatives with a history of CHD. There was evidence of sibling aggregation of plaque in random families (OR = 1.89; 95% CI: 1.44, 2.48), but associations were substantially attenuated when adjusted for major cardiovascular disease risk factors. A genome scan with 420 microsatellite markers revealed no regions of significant or suggestive linkage for plaque in 342 affected sibling pairs, although suggestive linkage (LOD score: 2.43) was found on chromosome 2p11.2 (D2S1790) in pairs aged 55 years or younger. Other markers with nominal evidence for linkage (p < 0.05) were found on chromosomes 2p25, 2q24-q32, 6q21-q23, 7p12-p21, 7q11-q21, 8q24, 12q12-q13, 18p11, 21q21 and Xp11, Xq12, and Xq24. Conclusions: There was modest familial aggregation of carotid artery plaque, but a genome-wide scan indicated no regions of significant or suggestive linkage.
A New Method for Computing the Multipoint Posterior Probability of Linkage
Authors: Logue Mark W. , Vieland Veronica J.
Published: June 2004

The posterior probability of linkage (PPL) is a Bayesian statistic which directly measures the probability of linkage between a trait locus and a marker (in the 2-point case) or a genomic region (in the multipoint case). It has several benefits, including ease of interpretation, the ability to incorporate prior genomic information, and a mathematically rigorous and robust procedure for accumulating linkage information across multiple heterogeneous datasets. To date, the majority of work on the PPL has focused on the development of the 2-point statistic, with only preliminary attempts at the development of an equivalent multipoint version. In this paper we present a new way of computing of the multipoint PPL. This new version imputes to each genomic point an estimate of the 2-point PPL we would have obtained from a fully informative marker giving similar evidence for linkage. This version, which we call the imputed PPL, is shown to be superior to previously developed versions.
Using Lod Scores to Detect Sex Differences in Male-Female Recombination Fractions
Authors: Feenstra B. , Greenberg D.A. , Hodge S.E.
Published: June 2004

Human recombination fraction (RF) can differ between males and females, but investigators do not always know which disease genes are located in genomic areas of large RF sex differences. Knowledge of RF sex differences contributes to our understanding of basic biology and can increase the power of a linkage study, improve gene localization, and provide clues to possible imprinting. One way to detect these differences is to use lod scores. In this study we focused on detecting RF sex differences and answered the following questions, in both phase-known and phase-unknown matings: (1) How large a sample size is needed to detect a RF sex difference? (2) What are ‘optimal’ proportions of paternally vs. maternally informative matings? (3) Does ascertaining nonoptimal proportions of paternally or maternally informative matings lead to ascertainment bias? Our results were as follows: (1) We calculated expected lod scores (ELODs) under two different conditions: ‘unconstrained,’ allowing sex-specific RF parameters (Θ♀, Θ♂); and ‘constrained,’ requiring Θ♀ = Θ♂. We then examined the ΔELOD (≡ difference between maximized constrained and unconstrained ELODs) and calculated minimum sample sizes required to achieve statistically significant ΔELODs. For large RF sex differences, samples as small as 10 to 20 fully informative matings can achieve statistical significance. We give general sample size guidelines for detecting RF differences in informative phase-known and phase-unknown matings. (2) We defined p as the proportion of paternally informative matings in the dataset; and the optimal proportion pcirc; as that value of p that maximizes ΔELOD. We determined that, surprisingly, pcirc; does not necessarily equal ½, although it does fall between approximately 0.4 and 0.6 in most situations. (3) We showed that if p in a sample deviates from its optimal value, no bias is introduced (asymptotically) to the maximum likelihood estimates of Θ♀ and Θ♂, even though ELOD is reduced (see point 2). This fact is important because often investigators cannot control the proportions of paternally and maternally informative families. In conclusion, it is possible to reliably detect sex differences in recombination fraction.
Intra-Aortal Therapy with 5-Fluorouracil- Polyethylene Glycol Stealth Liposomes: Does the Metabolism of 5-Fluorouracil into 5-Fluoro-2′-Deoxyuridine Depend on pH Value?
Authors: Pohlen U. , Binnenhei M. , Reszka R. , Buhr H.J. , Berger G.
Published: June 2004

Background: The application of liposome-encapsulated cytostatics results in higher concentrations in tumor tissue. This effect can be further increased by blood flow retardation with longer retention time in the tumor and by arterial administration realized in abdominal stop-flow therapy, a separate partial circulation with a defined flow under hypoxic conditions. The pH changes under stop-flow therapy may affect the further metabolism of 5-fluorouracil (5-FU), used here. Methods: The in vitro 5-fluoro-2′-deoxyuridine (5-FUrd) concentrations at increasing pH values were measured using liposomal encapsulated and free 5-FU. Subsequently, 20 chinchilla rabbits were treated intra-aortally with 5-FU or 5-FU-polyethylene glycol (PEG) liposomes. The pH value was maintained in the physiological range by continuous NaHCO3 application. After 20 min, concentrations of 5-FU and its metabolite 5-FUrd were determined in different organs, the perfusate, serum and the VX-2 tumor by HPLC. Results: The in vitro 5-FUrd concentrations, which occur only in the physiological pH range, were doubled by the use of 5-FU-PEG liposomes. In the animal trial, NaHCO3 titration doubled the 5-FUrd concentrations found in our preliminary studies. Compared to free 5-FU, 5-FU-PEG liposomes significantly increased the concentrations in the VX-2 liver tumor by 6.6-fold and in the para-aortal lymph nodes by 8.76-fold. Conclusion: The metabolism of 5-FU into its active metabolite 5-FUrd depends on the pH value and can be modulated. 5-FUrd concentrations can be approximately doubled with the intra-aortal application of 5-FU-PEG liposomes compared to free 5-FU.
Antimicrobial Susceptibility of 128 Salmonella enterica Serovar Typhi and Paratyphi A Isolates from Northern India
Authors: Safdar Amar , Kaur Harjit , Elting Linda , Rolston Kenneth V.I.
Published: June 2004

Most systemic Salmonella enterica serovar typhi and paratyphi A infections diagnosed in the United States (up to 70%) are acquired during travel to regions of high endemicity. Increasing resistance to agents commonly used for the treatment of such infections (including multidrug resistant isolates) is being reported from several areas of the world (Southeast Asia, Africa, Latin America). Since regional differences in susceptibility patterns may exist, we sought to determine the frequency of antimicrobial resistance among blood and stool isolates (n = 128) from patients in Northwestern India. Salmonella enterica serotype typhi (n = 101) isolates from 14 patients were susceptible to all agents tested. Among 55 isolates with single drug resistance, 44 (81%) were resistant to chloramphenicol. Multidrug resistant (≧3 drugs) Salmonella enterica was more common in pediatric patients (10 of 30) compared to adults (10 of 71 patients; p = 0.05). All isolates (S. enterica serovar typhi and serovar paratyphi A) were susceptible to ciprofloxacin and ceftriaxone. Travelers to Northwestern India may still receive trimethoprim-sulfamethoxazole, or ciprofloxacin for effective chemoprophylaxis if indicated. Ceftriaxone and ciprofloxacin remain favorable choices for treatment of patients with enteric fever in this region.
A Comparison of the Microbiological Characteristics of Neisseria gonorrhoeae Isolated from Male and Female Patients with Gonorrhea
Authors: Saika Takeshi , Kobayashi Intetsu , Inoue Matsuhisa
Published: June 2004

Background: A trend towards a decrease in gonorrhea in Japan was observed until the mid-1990s, but soon after that period, an increased incidence of gonorrhea was reported. Methods: Antimicrobial susceptibility, auxotype and the type of gyrA and parC mutations were compared between 200 and 132 Neisseria gonorrhoeae isolates from male and female patients with gonorrhea, respectively. Results and Conclusion: The isolation frequency of ciprofloxacin-resistant isolates from male patients was higher than that from female patients (19.5 and 13.6%, respectively). All ciprofloxacin-resistant isolates had single to triple mutations in gyrA and/or parC genes. N. gonorrhoeae isolates showed a predominance of Pro-requiring auxotypes (46.5 and 46.2% of the isolates from male and female patients, respectively). Of the Pro-requiring isolates, the incidence of ciprofloxacin-resistant isolates was higher in the isolates from male patients than in the isolates from female patients.
Moxifloxacin and Biofilm Production by Coagulase-Negative Staphylococci
Authors: Pérez-Giraldo C. , Gonzalez-Velasco C. , Sánchez-Silos R.M. , Hurtado C. , Blanco M.T. , Gómez-García A.C.
Published: June 2004

The in vitro activity of moxifloxacin against 41 strains of coagulase-negative staphylococci was determined. A relationship between the activity of moxifloxacin and biofilm formation was detected. Biofilm-producing strains were more resistant to moxifloxacin than biofilm-negative strains. Our global results obtained with six strains of Staphylococcus epidermidis showed that subinhibitory concentrations of moxifloxacin did not significantly modify biofilm formation. On the other hand, moxifloxacin concentrations of 2, 10, 50 and 100 × MIC produced a log decrease in viable count (included in a biofilm) of 0.20, 0.37, 1.10 and 1.69, respectively.