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Hops
Selected AbstractsLOW-INCOME HOMEOWNERSHIP: DOES IT NECESSARILY MEAN SACRIFICING NEIGHBORHOOD QUALITY TO BUY A HOME?JOURNAL OF URBAN AFFAIRS, Issue 2 2010ANNA M. SANTIAGO ABSTRACT:,Questions have been raised about the wisdom of low-income homeownership policies for many reasons. One potential reason to be skeptical: low-income homebuyers perhaps may be constrained to purchase homes in disadvantaged neighborhoods. This is a potential problem because home purchases in such neighborhoods: (1) may limit appreciation; (2) may reduce quality of life for adults; and (3) may militate against reputed advantages of homeownership for children. Our study examines the neighborhood conditions of a group of 126 low-income homebuyers who purchased their first home with assistance from the Home Ownership Program (HOP) operated by the Denver Housing Authority. Our approach is distinguished by its use of a comprehensive set of objective and subjective indicators measuring the neighborhood quality of pre-move and post-move neighborhoods. Do low-income homebuyers sacrifice neighborhood quality to buy their homes? Our results suggest that the answer to this question is more complex than it might at first appear. On the one hand, HOP homebuyers purchased in a wide variety of city and suburban neighborhoods. Nonetheless, a variety of neighborhood quality indicators suggest that these neighborhoods, on average, were indeed inferior to those of Denver homeowners overall and to those in the same ethnic group. However, our analyses also revealed that their post-move neighborhoods were superior to the ones they lived in prior to homeownership. Moreover, very few HOP destination neighborhoods evinced severe physical, environmental, infrastructural, or socioeconomic problems, as measured by a wide variety of objective indicators or by the homebuyers' own perceptions. Indeed, only 10% of HOP homebuyers perceived that their new neighborhoods were worse than their prior ones, and only 8% held pessimistic expectations about their new neighborhoods' quality of life. Finally, we found that Black homebuyers fared less well than their Latino counterparts, on average, in both objective and subjective measures. [source] Mutational Analysis and Functional Correlation With Phenotype in German Patients With Childhood-Type HypophosphatasiaJOURNAL OF BONE AND MINERAL RESEARCH, Issue 12 2001Hideo Orimo Abstract The tissue-nonspecific alkaline phosphatase (TNSALP) gene from five German family members with childhood-type hypophosphatasia (HOPS) was analyzed using the polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP)-direct sequencing method. Four novel missense mutations (T51M, R54S, L258P, and R374H) and two that had been described previously (A160T and R206W) were detected in the respective patients. Mutation A160T was detected in 3 distinct patients, and a polymorphism V505A that had been described previously was detected in the same allele as L258P mutation in 1 patient and in 2 fathers whose V505A alleles were not transmitted to the probands. No other mutations were found in 2 patients. Transient expression of the mutant proteins in COS-1 cells showed that the four novel mutations and R206W were severe alleles, whereas A160T was a moderate allele. Analysis of its enzymatic activity and genetic transmission patterns confirmed that V505A was a polymorphism. Immunoprecipitation of the transiently expressed proteins showed that levels of the 80-kDa mature form of the enzyme were diminished or absent with the severe alleles; instead, levels of high-molecular mass disulfide-linked aggregates were increased. These results suggest that in compound heterozygotes, the combination of severe and moderate alleles may combine to cause the mild phenotype seen in childhood-type HOPS. [source] On-line monitoring and fingerprint technology: new tools for the development of new catalysts and polyolefin materialsMACROMOLECULAR SYMPOSIA, Issue 1 2004Arno Tuchbreiter Abstract The High-Output Polymer Screening (HOPS) combines process-relevant automated reactor systems and rapid polymer characterization with on-line polymerization monitoring and automated data acquisition ("electronic notebook") in order to make effective use of advanced data mining tools. This has led to the development of fingerprint technology based upon correlations between spectroscopic data and polymerization process conditions, catalyst compositions, as well as polymer end-use properties. Infrared spectroscopic fingerprints proved to be very useful for accelerating polymer analyses including characterization of polymer molecular architectures as well as non-destructive testing of the mechanical, thermal and other end-use polymer properties. Such spectroscopic fingerprints represent important components of effective on-line quality control systems. With ATR-FT-IR probes on-line monitoring of catalytic olefin copolymerization was performed in solution to measure in real time copolymerization kinetics, catalyst productivities, catalyst deactivation as well as copolymerization parameters and copolymer sequence distributions. Monomer consumption and comonomer incorporation were monitored simultaneously. Advanced fingerprint technology can reduce significantly the need for time- and money consuming polymer testing and can also stimulate the search for new catalyst systems and polymeric materials. [source] (W)rapped Space: The Architecture of Hip HopJOURNAL OF ARCHITECTURAL EDUCATION, Issue 1 2000Craig L. Wilkins My research work is broadly framed around the confluence of contemporary and historical-spatial-theoretical understandings, architecture, the progressive self-defining energy of African-American culture, and the historical legacy of urban spaces in current society. A preeminent principle of this confluence focuses on questions of identity. "(W)rapped Space: The Architecture of Hip Hop" theorizes the development of an African-American spatial paradigm that at once recalls, creates, and deploys a new space of diasporian origin that is predicated on a response to spaces that represent an erasure of identity and, concomitantly, the presence of repressive power. [source] Arabic Hip Hop: Claims of Authenticity and Identity of a New GenreJOURNAL OF POPULAR MUSIC STUDIES, Issue 4 2007Usama Kahf [source] Isolation and characterization of polymorphic microsatellites for assessment of genetic variation of hops (Humulus lupulus L.)MOLECULAR ECOLOGY RESOURCES, Issue 2 2004A. M. Hadonou Abstract Hop (Humulus lupulus L.) cultivars are vegetatively propagated and it is difficult to differentiate them during the process of propagation. Fingerprinting with molecular markers based on DNA could be a useful means of identifying different cultivars. Simple sequence repeats, or microsatellite markers, are the most suitable marker for genetic fingerprinting because they are multi-allelic and co-dominant. For this purpose, we have developed primers for 10 new polymorphic microsatellite loci that are suitable for genetic fingerprinting in hop. [source] D. Q. Liu, C. E. C. A. Hop, M. G. Beconi, A. Mao, S.-H.RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 3 200315(19), 1832-183, Use of on-line hydrogen/deuterium exchange to facilitate metabolite identification' Rapid Communications in Mass Spectrometry No abstract is available for this article. [source] How to kill a mocking bug?CELLULAR MICROBIOLOGY, Issue 4 2006Vitor B. Pinheiro Summary All metazoans have evolved means to protect themselves from threats present in the environment: injuries, viruses, fungi, bacteria and other parasites. Insect protection includes innate physical barriers and both cellular and humoral responses. The insect innate immune response, best characterized in Drosophila melanogaster, is a rapid broad response, triggered by pathogen-associated molecular patterns (PAMPs) recognition, which produces a limited range of effectors that does not alter upon continued pathogen exposure and lacks immunological memory. The Drosophila response, particularly its humoral response, has been investigated by both low and high-throughput methods. Three signalling pathways conserved between insects and mammals have been implicated in this response: Toll (equivalent to mammalian TLR), Imd (equivalent to TNF,) and Hop (equivalent to JAK/STAT). This review provides an entry point to the insect immune system literature outlining the main themes in D. melanogaster bacterial pathogen detection and humoral and cellular immune responses. The Drosophila immune response is compared with other insects and the mammalian immune system. [source] Arabidopsis proteins important for modulating defense responses to Pseudomonas syringae that secrete HopW1-1THE PLANT JOURNAL, Issue 3 2008Min Woo Lee Summary Plant infection responses result from the interaction of pathogen-derived molecules with host components. For the bacterial pathogen Pseudomonas syringae, these molecules are often effector proteins (Hops) that are injected into plant cells. P. syringae carrying hopW1-1 have restricted host range on some Arabidopsis thaliana accessions. At least two Arabidopsis genomic regions are important for the natural variation that conditions resistance to P. syringae/hopW1-1. HopW1-1 elicits a resistance response, and consequently the accumulation of the signal molecule salicylic acid (SA) and transcripts of HWI1 (HopW1-1-Induced Gene1). This work identified three HopW1-1-interacting (WIN) plant proteins: a putative acetylornithine transaminase (WIN1), a protein phosphatase (WIN2) and a firefly luciferase superfamily protein (WIN3). Importantly, WIN2 and WIN3 are partially required for HopW1-1-induced disease resistance, SA production and HWI1 expression. The requirement for WIN2 is specific for HopW1-1-induced resistance, whereas WIN3 is important for responses to several effectors. Overexpression of WIN2 or WIN3 confers resistance to virulent P. syringae, which is consistent with these proteins being defense components. Several known genes important for SA production or signaling are also partially (EDS1, NIM1/NPR1, ACD6 and ALD1) or strongly (PAD4) required for the robust resistance induced by HopW1-1, suggesting a key role for SA in the HopW1-1-induced resistance response. Finally, WIN1 is an essential protein, the overexpression of which over-rides the resistance response to HopW1-1 (and several other defense-inducing effectors), and delays SA and HWI1 induction. Thus, the WIN proteins have different roles in modulating plant defense. [source] Verticillium albo-atrum and V. dahliae on hopEPPO BULLETIN, Issue 3 2007Article first published online: 7 DEC 200 First page of article [source] Expedited forwarding end-to-end delay and jitter in DiffServINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 8 2008Hamada Alshaer Abstract The scheduling disciplines and active buffer management represent the main components employed in the differentiated services (DiffServ) data plane, which provide qualitative per-hop behaviors corresponding to the QoS required by supported traffic classes. In the first part of this paper, we compute the per-hop delay bound that should be guaranteed by the different multiservice scheduling disciplines, so that the end-to-end (e2e) delay required by expedited forwarding (EF) traffic can be guaranteed. Consequently, we derive the e2e delay bound of EF traffic served by priority queuing,weighted fair queuing (PQ,WFQ) at every hop along its routing path. Although real-time flows are principally offered EF service class, some simulations on DiffServ-enabled network show that these flows suffer from delay jitter and they are negatively impacted by lower priority traffic. In the second part of this paper, we clarify the passive impact of delay jitter on EF traffic, where EF flows are represented by renewal periodic ON,OFF flows, and the background (BG) flows are characterized by the Poisson process. We analyze through different scenarios the jitter effects of these BG flows on EF flow patterns when they are served by a single class scheduling discipline, such as first-input first-output, and a multiclass or multiservice scheduling discipline, such as static priority service discipline. As a result, we have found out that the EF per-hop behaviors (PHBs) configuration according to RFCs 2598 and 3246 (IETF RFC 2598, June 1999; RFC 3246, IETF, March 2002) cannot stand alone in guaranteeing the delay jitter required by EF flows. Therefore, playout buffers must be added to DiffServ-enabled networks for handling delay jitter problem that suffers from EF flows. Copyright © 2008 John Wiley & Sons, Ltd. [source] Blocking performance of fixed-paths least-congestion routing in multifibre WDM networksINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 2-3 2002Ling Li Abstract Wavelength-routed all-optical networks have been receiving significant attention for high-capacity transport applications. Good routing and wavelength assignment (RWA) algorithms are critically important in order to improve the performance of wavelength-routed WDM networks. Multifibre WDM networks, in which each link consists of multiple fibres and each fibre carries information on multiple wavelengths, offer the advantage of reducing the effect of the wavelength continuity constraint without using wavelength converters. A wavelength that cannot continue on the next hop on the same fibre can be switched to another fibre using an optical cross-connect (OXC) if the same wavelength is free on one of the other fibres. However, the cost of a multifibre network is likely to be higher than a single-fibre network with the same capacity, because more amplifiers and multiplexers/demultiplexers may be required. The design goal of a multifibre network is to achieve a high network performance with the minimum number of fibres. In this paper, we study the blocking performance of fixed-paths least-congestion (FPLC) routing in multifibre WDM networks. A new analytical model with the consideration of link-load correlation is developed to evaluate the blocking performance of the FPLC routing. The analytical model is a generalized model that can be used in both regular (e.g. mesh-torus) and irregular (e.g. NSFnet) networks. It is shown that the analytical results closely match the simulation results, which indicate that the model is adequate in analytically predicting the performance of the FPLC routing in different networks. Two FPLC routing algorithms, wavelength trunk (WT)-based FPLC and lightpath (LP)-based FPLC, are developed and studied. Our analytical and simulation results show that the LP-based FPLC routing algorithm can use multiple fibres more efficiently than the WT-based FPLC and the alternate path routing. In both the mesh-torus and NSFnet networks, limited number of fibres is sufficient to guarantee high network performance. Copyright © 2002 John Wiley & Sons, Ltd. [source] Enhancing multimedia streaming over existing wireless LAN technology using the Unified Link Layer APIINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 5 2007Tim Farnham This paper examines how multimedia streaming scenarios can be enhanced by cross-layer interaction, and in particular link performance information and configuration options provided by the recently developed Unified Link Layer API (ULLA). It provides results of an experimental implementation developed for this purpose in a wireless LAN (WLAN) environment. Multimedia streaming is an application that is gaining in popularity for mobile devices and in particular mobile Internet-based content broadcasting is rapidly emerging as a key feature on mobile devices. In these scenarios, the wireless link (last hop) is normally the performance bottleneck due to the dynamic and limited capacity of the wireless medium. The use of ULLA in this context can provide the ability to tailor the video transmission to the wireless link performance and also to configure the links in response to performance problems or environmental changes. For this purpose the focus of multimedia streaming has been on WLAN link technology and dynamic adaptation (i.e., dynamic channel selection and video transcoding) using a dynamic resource reservation overlay protocol. Copyright © 2007 John Wiley & Sons, Ltd. [source] An optimum design of deep-space downlinks affected by tropospheric attenuation,INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 6 2009Emilio Matricciani Abstract In the paper, we propose an optimum design of deep-space downlinks made with 2 hops, at Ka band and above, in which each hop should be designed for providing half of the total noise-to-signal power ratio. We have derived this result from maximizing the ratio between the tropospheric attenuation in the 2-hop downlink and that in the 1-hop downlink. The design of the 1st hop (free-space) of the 2-hop downlink can reduce the spacecraft power, for the same antennas physical size, by increasing the carrier frequency from Ka band (32,GHz) to W band (80,GHz). This choice is not available in 1-hop downlink design because of the huge Earth tropospheric attenuation expected in the W frequency band. To show a practical design, we have applied the theory to compare 1-hop downlink design at 32,GHz to 2-hop downlink design that adopts 32 or 80,GHz in the 1st hop. The calculations refer to spacecrafts located at two astronomical units (300×106,km, about planet Mars) and to NASA and ESA receiving stations located in Goldstone (California), Cebreros (Madrid, Spain), Canberra and New Norcia (Australia). At 0.1% outage probability, in an average year or in the worst month, 1-hop downlinks show performance critical or close to fail, because of the large tropospheric attenuation (except at Goldstone), while 2-hop downlinks always work. Copyright © 2009 John Wiley & Sons, Ltd. [source] Genetic structure and gene flow in French populations of two Ostrinia taxa: host races or sibling species?MOLECULAR ECOLOGY, Issue 20 2007T. MALAUSA Abstract Most models of ecological speciation concern phytophagous insects in which speciation is thought to be driven by host shifts and subsequent adaptations of populations. Despite the ever-increasing number of studies, the current evolutionary status of most models remains incompletely resolved, as estimates of gene flow between taxa remain extremely rare. We studied the population genetics of two taxa of the Ostrinia genus , one feeding mainly on maize and the other on mugwort and hop , occurring in sympatry throughout France. The actual level of divergence of these taxa was unknown because the genetic structure of populations had been investigated over a limited geographical area and the magnitude of gene flow between populations had not been estimated. We used 11 microsatellite markers to investigate the genetic structure of populations throughout France and the extent of gene flow between the two Ostrinia taxa at several sites at which they are sympatric. We observed clear genetic differentiation between most populations collected on the typical respective hosts of each taxon. However, populations displaying intermediate allelic frequencies were found on hop plants in southern France. Individual assignments revealed that this result could be accounted for by the presence of both taxa on the same host. Gene flow, estimated by determining the proportion of hybrids detected, was low: probably < 1% per generation, regardless of site. This indicates that the two Ostrinia taxa have reached a high level of genetic divergence and should be considered sibling species rather than host races. [source] Isolation and characterization of polymorphic microsatellites for assessment of genetic variation of hops (Humulus lupulus L.)MOLECULAR ECOLOGY RESOURCES, Issue 2 2004A. M. Hadonou Abstract Hop (Humulus lupulus L.) cultivars are vegetatively propagated and it is difficult to differentiate them during the process of propagation. Fingerprinting with molecular markers based on DNA could be a useful means of identifying different cultivars. Simple sequence repeats, or microsatellite markers, are the most suitable marker for genetic fingerprinting because they are multi-allelic and co-dominant. For this purpose, we have developed primers for 10 new polymorphic microsatellite loci that are suitable for genetic fingerprinting in hop. [source] Eleven new microsatellites for hop (Humulus lupulus L.)MOLECULAR ECOLOGY RESOURCES, Issue 4 2002J. Jak Abstract We present a new set of 11 polymorphic microsatellite primer sequences for use with Humulus lupulus. Microsatellite-enriched libraries for GAn and GTn types of repeats were produced. Sequencing of 72 clones revealed 42 unique inserts containing microsatellites, out of which 19 primer pairs were designed and microsatellite amplification was tested on 39 wild hops and cultivars. Eleven primer pairs showed single locus amplification with 2,13 alleles, average 7.2, of which 17 unique alleles were discovered. One primer pair amplified too strong stutter bands, one locus was monomorphic and multilocus amplification was obtained with the remaining six primer pairs. [source] Old school crossings: Hip hop in teacher education and beyondNEW DIRECTIONS FOR ADULT & CONTINUING EDUCATION, Issue 115 2007Mary Stone Hanley This chapter discusses how to draw on hip hop as a culturally relevant tool for teaching educators and adult learners to read the word, the world, and the media. [source] The effectiveness of a pre-operative home-based physiotherapy programme for chronic anterior cruciate ligament deficiencyPHYSIOTHERAPY RESEARCH INTERNATIONAL, Issue 4 2006SL Keays Abstract Background and Purpose.,Little evidence supports the prescription of pre-operative rehabilitation in the treatment of chronic anterior cruciate ligament-deficient (ACLD) subjects. The aim of the present study was to assess the effectiveness of a specific six-week pre-operative exercise programme on ACLD knees.,Method.,A single, masked, controlled study was designed. This comprised two matched groups of 12 chronically ACLD patients awaiting reconstruction and a group of 12 matched uninjured control subjects. Only one ACLD group received a home-based exercise and educational programme. Assessment before and after the exercise intervention included: knee joint stability (clinical and KT1000 evaluation); muscle strength (Cybex II); standing balance and functional performance (agility, hop and subjective tests).,Results.,At the time of initial assessment there were no statistically significant differences in any measures for the two ACLD groups but both ACLD groups were significantly different from the uninjured control group as regards quadriceps strength and function. Measures taken after six weeks showed no significant improvement in the untreated ACLD group or in the uninjured control group The treated ACLD group showed significant improvement in the following measures: quadriceps strength measured at 60° and 120° per second (p < 0.001); single leg standing balance with eyes closed (p < 0.001); instrumented passive stability at 20,lb (89N) force (p = 0.003); agility and subjective performance (p < 0.001). The incidence of unstable episodes had decreased in the treated ACLD group, reducing further damage to the joint.,Conclusion.,This study leaves little doubt that pre-operative physiotherapy had a positive effect on motor function in ACLD subjects and should be prescribed routinely to maximize muscle stabilizing potential prior to reconstruction. Patients report improved stability and, in certain cases, may avoid surgery. The finding that exercise increased the passive stability of the joint was unexpected and requires further investigation. Copyright © 2006 John Wiley & Sons, Ltd. [source] Occurrence of Cercospora cantuariensis on hop in Austria and SloveniaPLANT PATHOLOGY, Issue 2 2009S. Radisek No abstract is available for this article. [source] First report of Phoma exigua as a pathogen of hop in SloveniaPLANT PATHOLOGY, Issue 2 2008S. Radisek No abstract is available for this article. [source] Basic forms of supramolecular self-assembly organized by parallel and antiparallel hydrogen bonds in the racemic crystal structures of six disubstituted and trisubstituted cyclopentane derivativesACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2001Alajos Kálmán A selection of stereoisomeric 2-hydroxy-1-cyclopentanecarboxamides, a 4- tert -butyl derivative and three tert -butyl derivatives of the respective carboxylic acid were subjected to X-ray crystallography. The optically active molecules (I),(VI) form racemic crystals. Each racemic structure is basically determined by two intermolecular hydrogen bonds of O,H,O=C,XH and O=C,X,H,OH types (X = O, NH). The partially similar patterns of close packing observed reflect five basic forms of supramolecular self-assembly. In the racemic crystals of chiral molecules, there are homo- and heterochiral chains of molecules formed by the principal (O,H,O=C) hydrogen bonds. These chains assemble either in a parallel or antiparallel mode. The parallel homochiral chains (hop) observed in structure (II), (1R*,2R*)-2-hydroxy-1-cyclopentanecarboxamide, demand the polar space group Pca21, while the parallel heterochiral chains (hep) are organized in antiparallel layers with space group P21/n in structure (VI), (1R*,2S*,5R*-5- tert -butyl-2-hydroxy-1-cyclopentanecarboxylic acid). Heterochiral chains in an antiparallel array (hea) are found in (I), (1R*,2S*)-2-hydroxy-1-cyclopentanecarboxamide, and (V) [(1R*,2S*4S*)-4- tert -butyl-2-hydroxy-1-cyclopentanecarboxylic acid, space group P21/c]. Structures (IV), (1R*,2S*,4R*)-4- tert -butyl-2-hydroxy-1-cyclopentanecarboxylic acid, and (III), (1R*,2R*,4S*)-4- tert -butyl-2-hydroxy-1-cyclopentanecarboxamide, reveal that homochiral chains in an antiparallel array (hoa; cross-linked by heterochiral dimers held together by the second hydrogen bonds) can be formed by either translation (space group P) or a screw axis (space group P21/c). These alternatives are denoted hoa1 and hoa2. Similarly, within each pattern (hea, hep and hop) two slightly different alternatives can be expected. The partial similarities in the identified five patterns of hydrogen bonding are described by graph-set notations. Structures (I), (IV) and (V) can be characterized by a common supramolecular synthon, while the highest degree of similarity is shown by the isostructurality of (I) and (V). [source] Flight activity of the damson,hop aphid, Phorodon humuli.ANNALS OF APPLIED BIOLOGY, Issue 1 2005C.A.M. Campbell Abstract Flight activity of Phorodon humuli was monitored using suction traps, laboratory studies and mark and recapture experiments. Emigrants were trapped as they flew from a Myrobalan (Prunus cerasifera) hedge and among dwarf hops (Humulus lupulus). Daily flight curves were bimodal with 69% and 38% of emigrants caught in the morning peak near Myrobalan and among hops, respectively. The median period of flight activity was from 2 h after sunrise until 30 min before sunset. The lower temperature for flight was 13.5°C in the field and 14.9°C for take off in the laboratory. Variations in wind speed had little effect on flight activity explaining <2.5% of the total variance among insect counts. The percentage of emigrants on hop declined exponentially with time. The relationship, y= 10.9(±2.0) + 64.3(±2.3) × 0.92(±0.01)t where t = daylight hours (standard error in parentheses), explained 98.3% of the variance. Hence, 62% of new arrivals flew within 1 day of arrival and 79% within 2 days. Similar numbers arrived as departed at 08:30, 10:30 and 12:30 h, but at 14:30 h twice as many arrived than departed and at 16:30 h, the accumulation was threefold. Daily flight curves of return migrants and males leaving hop were bimodal with 70% and 80%, respectively, trapped in the earlier peak. In the field, the median lower temperature for flight was 13.2°C for return migrants and a nonsignificantly different 12.8°C for males. The mean temperature for take off by return migrants was 15.7°C in the laboratory. [source] Distributed end-host multicast algorithms for the Knowledge GridCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 15 2007Wanqing Tu Abstract The Knowledge Grid built on top of the peer-to-peer (P2P) network has been studied to implement scalable, available and sematic-based querying. In order to improve the efficiency and scalability of querying, this paper studies the problem of multicasting queries in the Knowledge Grid. An m -dimensional irregular mesh is a popular overlay topology of P2P networks. We present a set of novel distributed algorithms on top of an m -dimensional irregular mesh overlay for the short delay and low network resource consumption end-host multicast services. Our end-host multicast fully utilizes the advantages of an m -dimensional mesh to construct a two-layer architecture. Compared to previous approaches, the novelty and contribution here are: (1) cluster formation that partitions the group members into clusters in the lower layer where cluster consists of a small number of members; (2) cluster core selection that searches a core with the minimum sum of overlay hops to all other cluster members for each cluster; (3) weighted shortest path tree construction that guarantees the minimum number of shortest paths to be occupied by the multicast traffic; (4) distributed multicast routing that directs the multicast messages to be efficiently distributed along the two-layer multicast architecture in parallel, without a global control; the routing scheme enables the packets to be transmitted to the remote end hosts within short delays through some common shortest paths; and (5) multicast path maintenance that restores the normal communication once the membership alteration appears. Simulation results show that our end-host multicast can distributively achieve a shorter delay and lower network resource consumption multicast services as compared with some well-known end-host multicast systems. Copyright © 2006 John Wiley & Sons, Ltd. [source] Determination of xanthohumol in hops (Humulus lupulus L.) by nonaqueous CEELECTROPHORESIS, Issue 6 2007Javor Kac Dr. Abstract Xanthohumol (XN) is a prenylated chalcone with antimutagenic and anticancer activity from hops. A nonaqueous reverse polarity capillary electrophoretic method for the determination of XN in hop extract was developed and validated. The optimal parameters were a 64.5,cm long fused-silica capillary with 50,,m id at 25°C; 30,kV negative voltage (anode at detector side of the capillary); nonaqueous buffer with 75,mM NaOH and 50,mM boric acid in methanol; hydrodynamical injection with 10,mbar for 40,s; and detection at 440,nm. XN, isoxanthohumol (IX), colupulone, adlupulone, and n -lupulone were well resolved on the electropherogram. The LOD for XN was 0.05,mg/L and RSD for peak area was below 3%. The amount of XN in different samples of hop pellets varied from 0.14 to 0.42%. [source] A new distributed approximation algorithm for constructing minimum connected dominating set in wireless ad hoc networksINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 8 2005Bo Gao Abstract In recent years, constructing a virtual backbone by nodes in a connected dominating set (CDS) has been proposed to improve the performance of ad hoc wireless networks. In general, a dominating set satisfies that every vertex in the graph is either in the set or adjacent to a vertex in the set. A CDS is a dominating set that also induces a connected sub-graph. However, finding the minimum connected dominating set (MCDS) is a well-known NP-hard problem in graph theory. Approximation algorithms for MCDS have been proposed in the literature. Most of these algorithms suffer from a poor approximation ratio, and from high time complexity and message complexity. In this paper, we present a new distributed approximation algorithm that constructs a MCDS for wireless ad hoc networks based on a maximal independent set (MIS). Our algorithm, which is fully localized, has a constant approximation ratio, and O(n) time and O(n) message complexity. In this algorithm, each node only requires the knowledge of its one-hop neighbours and there is only one shortest path connecting two dominators that are at most three hops away. We not only give theoretical performance analysis for our algorithm, but also conduct extensive simulation to compare our algorithm with other algorithms in the literature. Simulation results and theoretical analysis show that our algorithm has better efficiency and performance than others. Copyright © 2005 John Wiley & Sons, Ltd. [source] A unifying co-operative web caching architectureINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 6 2002Abdullah Abonamah Abstract Network caching of objects has become a standard way of reducing network traffic and latency in the web. However, web caches exhibit poor performance with a hit rate of about 30%. A solution to improve this hit rate is to have a group of proxies form co-operation where objects can be cached for later retrieval. A co-operative cache system includes protocols for hierarchical and transversal caching. The drawback of such a system lies in the resulting network load due to the number of messages that need to be exchanged to locate an object. This paper proposes a new co-operative web caching architecture, which unifies previous methods of web caching. Performance results shows that the architecture achieve up to 70% co-operative hit rate and accesses the cached object in at most two hops. Moreover, the architecture is scalable with low traffic and database overhead. Copyright © 2002 John Wiley & Sons, Ltd. [source] Unfairness of measurement-based admission controls in a heterogeneous environmentINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 9 2001Yuan-Cheng Lai Abstract Admission controls are required to determine whether new connections should be admitted to networks. These controls ensure the quality of service (QoS) for data transmission. This paper introduces three measurement-based admission control algorithms called Measured Sum, Hoeffding Bound, and Adaptive Weight Factor. The unfairness of these algorithms in a heterogeneous environment is investigated. Simulation results indicate that the fairness of the Measured Sum exceeds that of the other methods. Admission of connections with large peak rates or travelling many hops can be difficult. Copyright © 2001 John Wiley & Sons, Ltd. [source] Autonomic self-organization architecture for wireless sensor communicationsINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 3 2007Jiann-Liang Chen Wireless sensor nodes may be spread over large areas and long distances, and require multi-hop communications between nodes, making direct management numerous wireless sensor nodes inefficient. Hierarchical management can be adopted to control several nodes. Effectively controlling the top-level nodes can decrease the costs of managing nodes and of the communication among them. The lower-level nodes are controlled and organized with the higher-level nodes. This study presents an algorithm for self-organization mechanism of higher-level nodes, contesting member nodes by multi-hop to form hierarchical clusters, and applying the ,20/80 rule' to determine the ratio of headers to member nodes. Furthermore, the broadcast tree is constructed with the minimum number of hops. Simulation results indicate that the mechanism has a 6,22% lower cover loss than other approaches. The average delay of the minimum hop count approach is 0.22,1.57ms less than that of free hop count approach. The simulation also reveals the influence of 20/80 rule on cluster formation between sensor nodes. Copyright © 2006 John Wiley & Sons, Ltd. [source] An optimum design of deep-space downlinks affected by tropospheric attenuation,INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 6 2009Emilio Matricciani Abstract In the paper, we propose an optimum design of deep-space downlinks made with 2 hops, at Ka band and above, in which each hop should be designed for providing half of the total noise-to-signal power ratio. We have derived this result from maximizing the ratio between the tropospheric attenuation in the 2-hop downlink and that in the 1-hop downlink. The design of the 1st hop (free-space) of the 2-hop downlink can reduce the spacecraft power, for the same antennas physical size, by increasing the carrier frequency from Ka band (32,GHz) to W band (80,GHz). This choice is not available in 1-hop downlink design because of the huge Earth tropospheric attenuation expected in the W frequency band. To show a practical design, we have applied the theory to compare 1-hop downlink design at 32,GHz to 2-hop downlink design that adopts 32 or 80,GHz in the 1st hop. The calculations refer to spacecrafts located at two astronomical units (300×106,km, about planet Mars) and to NASA and ESA receiving stations located in Goldstone (California), Cebreros (Madrid, Spain), Canberra and New Norcia (Australia). At 0.1% outage probability, in an average year or in the worst month, 1-hop downlinks show performance critical or close to fail, because of the large tropospheric attenuation (except at Goldstone), while 2-hop downlinks always work. Copyright © 2009 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||||||||||||||||||||