bluuebunny/crossref_metadata_2025 huggingface dataset:
Flow Regime Study of a Light Material in an Industrial Scale Cold Flow Circulating Fluidized Bed
Authors: Mei Joseph S. , Monazam Esmail R. , Shadle Lawrence J.
Published: June 2006

A series of experiments was conducted in the 0.3meter diameter circulating fluidized bed test facility at the National Energy Technology Laboratory (NETL) of the U. S. Department of Energy. The particle used in this study was a coarse, light material, cork, which has a particle density of 189kg∕m3 and a mean diameter of 812μm. Fluidizing this material in ambient air approximates the same gas-solids density ratio as coal and coal char in a pressurized gasifier. The purpose of this study is twofold. First, this study is to provide a better understanding on the fundamentals of flow regimes and their transitions. The second purpose of this study is to generate reliable data to validate the mathematical models, which are currently under development at NETL. Utilization of such coarse, light material can greatly facilitate the computation of these mathematical models. Furthermore, the ratio of density of cork to air under ambient conditions is similar to the density ratio of coal to gas at the gasification and pressurized fluidized bed combustion environment. This paper presents and discusses the data, which covered operating flow regime from dilute phase, fast fluidization, and to dense phase transport by varying the solid flux, Gs at a constant gas velocity, Ug. Data are presented by mapping the flow regime for coarse cork particles in a ΔP∕ΔL‐Gs‐Ug plot. The coarse cork particles exhibited different behavior than the published literature measurements on heavier materials such as alumina, sand, FCC, silica gel, etc. A stable operation can be obtained at a fixed riser gas velocity higher than the transport velocity, e.g., at Ug=3.2m∕s, even though the riser is operated within the fast fluidization flow regime. Depending upon the solids influx, the riser can also be operated at dilute phase or dense phase flow regimes. Experimental data were compared to empirical correlations in published literature for flow regime boundaries as well as solids fractions in the upper dilute and the lower dense regions for fast fluidization flow regime. Comparisons of measured data with these empirical correlations show rather poor agreements. These discrepancies, however, are not surprising since the correlations for these transitions were derived from experimental data of comparative heavier materials such as sands, FCC, iron ore, alumina, etc.
Polo-Like Kinase Cdc5 Controls the Local Activation of Rho1 to Promote Cytokinesis
Authors: Yoshida Satoshi , Kono Keiko , Lowery Drew M. , Bartolini Sara , Yaffe Michael B. , Ohya Yoshikazu , Pellman David
Published: June 2006

The links between the cell cycle machinery and the cytoskeletal proteins controlling cytokinesis are poorly understood. The small guanine nucleotide triphosphate (GTP)–binding protein RhoA stimulates type II myosin contractility and formin-dependent assembly of the cytokinetic actin contractile ring. We found that budding yeast Polo-like kinase Cdc5 controls the targeting and activation of Rho1 (RhoA) at the division site via Rho1 guanine nucleotide exchange factors. This role of Cdc5 (Polo-like kinase) in regulating Rho1 is likely to be relevant to cytokinesis and asymmetric cell division in other organisms.
Selective Silencing of Foreign DNA with Low GC Content by the H-NS Protein in
Salmonella
Authors: Navarre William Wiley , Porwollik Steffen , Wang Yipeng , McClelland Michael , Rosen Henry , Libby Stephen J. , Fang Ferric C.
Published: June 2006

Horizontal gene transfer plays a major role in microbial evolution. However, newly acquired sequences can decrease fitness unless integrated into preexisting regulatory networks. We found that the histone-like nucleoid structuring protein (H-NS) selectively silences horizontally acquired genes by targeting sequences with GC content lower than the resident genome. Mutations in
hns
are lethal in
Salmonella
unless accompanied by compensatory mutations in other regulatory loci. Thus, H-NS provides a previously unrecognized mechanism of bacterial defense against foreign DNA, enabling the acquisition of DNA from exogenous sources while avoiding detrimental consequences from unregulated expression of newly acquired genes. Characteristic GC/AT ratios of bacterial genomes may facilitate discrimination between a cell's own DNA and foreign DNA.
Evidence for involvement of jasmonic acid in the induction of leaf senescence by potassium deficiency in Arabidopsis
Authors: Cao Shuqing , Su Liang , Fang Yuanjing
Published: June 2006

Potassium (K+) deficiency induces leaf senescence, and jasmonic acid (JA) plays a role in the regulation of leaf senescence; however, there is no direct evidence that JA has a role in the induction of leaf senescence by K+ deficiency. Here, we determined that JA is involved in the induction of leaf senescence by K+ deficiency. Leaf senescence was induced by K+ deficiency, as indicated by both the induction of expression of two senescence-associated genes, SAG12 and SAG13, and a decline in chlorophyll concentration; whereas inhibitors of JA biosynthesis, aspirin and salicylate, abolished the induction of leaf senescence by K+ deficiency. The JA concentration was threefold higher in the leaves of plants with K+ deficiency than it was in the leaves of control plants. In addition, transcript levels of two JA-responsive genes, PDF1.2 and Thi2.1, were higher in the leaves of plants with K+ deficiency than in the leaves of control plants. Our studies provide evidence that K+ deficiency induces leaf senescence, at least in part, via a JA-dependent pathway.
Cenozoic ichthyolith biostratigraphy: Tofino Basin, British Columbia
Authors: Johns Marjorie J , Barnes Christopher R , Narayan Y Roshni
Published: June 2006

Five new late Eocene  Pliocene ichthyolith zones are defined based on indigenous faunal occurrences in strata that outcrop along western Vancouver Island and samples from six offshore Tofino Basin wells. Five new interval zones are each defined based on distinct transported ichthyolith assemblages. Results are correlated within the framework of established Cenozoic west coast and Arctic foraminifer zones and ichthyolith occurrences in deep-sea core samples and Cretaceous Queen Charlotte Group and Nanaimo Group strata of coastal British Columbia. The use of multiple data sets was important to interpret complex active tectonic margin sedimentation and structures. The integrated ichthyolith and foraminifer biostratigraphy allowed an interpretation of well log data and lithology reports. Also, we reassessed previous offshore seismic data, evaluated fossil preservation and thermal alteration, and distinguished transported from indigenous ichthyolith occurrences. These data allowed a reinterpretation of tectonic segments and associated strata of the Pacific Rim and Crescent terranes and the Cascadia Accretionary Complex onshore and offshore Vancouver Island. Tectonically active phases during the Eocene and Oligocene  early Miocene resulted in transport of Cretaceous to Eocene ichthyoliths from structural highs to lows, indicating proximity of the Pluto I-87 and Zeus D-14 wells to the Tofino Fault between the Pacific Rim and Crescent terranes and suggesting derivation with coeval Hesquiat Peninsula strata. An unconformity above the Eocene Crescent Formation volcanics in Prometheus H-68 and Zeus D-14 wells is correlated with the Pluto I-87 and Apollo J-14 well stratigraphy. An upper Miocene unconformable surface coincides with accretion and uplift of the Cascadia Accretionary Complex.
Age, growth, and latitudinal patterns of two Rajidae species in the northwestern Atlantic: little skate (Leucoraja erinacea) and winter skate (Leucoraja ocellata)
Authors: Frisk Michael G , Miller Thomas J
Published: June 2006

Vertebral samples of little skate (Leucoraja erinacea) and winter skate (Leucoraja ocellata) were collected from Cape Hatteras, USA, to Canadian waters to estimate age, growth, and length at weight relationships for both species throughout this range. Maximum observed age was 12.5 and 20.5 years for little skate and winter skate, respectively. Significant length at weight relationships were found for both species. von Bertalanffy growth curves for the northwestern Atlantic were estimated for little skate (k = 0.19, L∞ = 56.1 cm, t0 = 1.17, p < 0.0001, n = 236) and winter skate (k = 0.07, L∞ = 122.1 cm, t0 = 2.07, p < 0.0001, n = 229). Additionally, latitudinal patterns in size and growth were observed in little skate, with individuals in northern regions growing slower and reaching a larger asymptotic size: von Bertalanffy growth estimates (mid-Atlantic, k = 0.22, L∞ = 53.26 cm, t0 = 1.04, p < 0.0001; southern New England  Georges Bank, k = 0.20, L∞ = 54.34 cm, t0 = 1.22, p < 0.0001; Gulf of Maine, k = 0.18, L∞ = 59.31 cm, t0 = 1.15, p < 0.0001). Although differences were observed for sex-specific growth curves for both species, only winter skate curves were significantly different.
Energy expenditure during hatching in rainbow trout (Oncorhynchus mykiss) embryos
Authors: Ninness Marcie M , Stevens E Don , Wright Patricia A
Published: June 2006

The objective of our study was to estimate the overall (aerobic and anaerobic) energy expenditure involved in hatching in rainbow trout (Oncorhynchus mykiss) embryos. During hatching, there were significant increases (50% and 19%, respectively) in movement and oxygen consumption. There were no differences in tissue indicators of anaerobic metabolism (adenosine triphosphate (ATP), adenosine monophosphate (AMP) deaminase, ammonia) between embryos that hatched naturally (chorionated) compared with embryos in which the chorion had been manually removed and therefore did not hatch (dechorionated). Furthermore, phosphocreatine (PCr), ATP, and lactate were unaltered immediately after hatching compared with embryos at rest before hatch. The anaerobic capacity of just hatched larvae was further evaluated by forced exercise and hypoxic exposure. PCr and ATP were unaltered following a 2 min manual chase, whereas lactate concentration was significantly increased (30%). Hypoxia (5 mg O2·L1, 5 days) resulted in a 2.7-fold elevation of tissue lactate concentration. Our results reveal that the increase in activity during hatch may be involved in escaping the egg capsule, but the metabolic cost of this increased movement is relatively small. Moreover, the anaerobic capacity of newly hatched rainbow trout is low relative to juvenile or adult fish.
Significant positive correlation between the recombination rate and GC content in the human pseudoautosomal region
Authors: Chen Jin-Feng , Lu Fei , Chen Su-Shing , Tao Shi-Heng
Published: June 2006

This paper establishes that recombination drives the evolution of GC content in a significant way. Because the human P-arm pseudoautosomal region (PAR1) has been shown to have a high recombination rate, at least 20-fold more frequent than the genomic average of ~1 cM/Mb, this region provides an ideal system to study the role of recombination in the evolution of base composition. Nine non-coding regions of PAR1 are analyzed in this study. We have observed a highly significant positive correlation between the recombination rate and GC content (ρ = 0.837, p ≤ 0.005). Five regions that lie in the distal part of PAR1 are shown to be significantly higher than genomic average divergence. By comparing the intra- and inter-specific AT→GC – GC→AT ratios, we have detected no fixation bias toward GC alleles except for L254915, which has excessive AT→GC changes in the human lineage. Thus, we conclude that the high GC content of the PAR1 genes better fits the biased gene conversion (BGC) model.Key words: pseudoautosomal region, GC content, base composition, evolution, recombination.
Unstable inheritance of maize B-type chromosomes that lack centric heterochromatin
Authors: Carlson Wayne R
Published: June 2006

The B chromosome of maize undergoes frequent non-disjunction at the second pollen mitosis. In B–A translocations, the B–A chromosome retains the capacity for non-disjunction. We have collected deletion-derivative TB-9Sb stocks. One derivative, the "type 1 telocentric", has a B–9 chromosome that lacks centric heterochromatin. It produces few recessive (non-disjunctional) phenotypes in pollen parent testcrosses of the translocation heterozygote, 9 9–B telo B–9. The finding helped demonstrate the role of centric heterochromatin in non-disjunction. An isochromo some derivative of the type 1 telocentric was also recovered. It was tested in the 9–B 9–B iso B–9 constitution. This is equivalent to 9 9–B telo B–9 in terms of chromosome 9 dosage. Surprisingly, crosses with the isochromosome gave significant levels of recessive phenotypes. In addition, high levels of variegated phenotypes were found. Recently, a circumstance was found that makes inheritance of the type 1 telocentric chromosome somewhat similar to that of the isochromosome. Crosses with hypoploid 9–B 9–B telo B–9 plants showed significant levels of recessive and variegated phenotypes. These crosses were investigated to help explain the source(s) of the phenotypes. Cytological and genetic studies were performed. Centric misdivision was found to account for the variegated phenotypes. A mixture of conventional B non-disjunction and centric misdivision produced the recessive phenotypes. The significance of conventional non-disjunction in the absence of centric heterochromatin is discussed.Key words: cytogenetics, B chromosome, centromere, maize.
Isolation and characterization of SSR sequences from the genome and TAC clones of common wheat using the PCR technique
Authors: Koike Michiya , Kawaura Kanako , Ogihara Yasunari , Torada Atsushi
Published: June 2006

We have developed the 2-step PCR method, a kind of suppression PCR procedure, to isolate simple sequence repeats (SSRs) from common wheat (Triticum aestivum L.) in a more convenient manner. This system requires neither genomic library screening nor the SSR-enrichment procedure. As a result, we designed 131 primer pairs based on isolated SSRs from not only genomic DNA, but also transformation-competent artificial chromosome (TAC) clones. It has been demonstrated that 34 of the 131 SSR markers developed were polymorphic among 8 wheat lines. Four of 34 polymorphic SSR markers were derived from TAC clones, indicating that this method could be applied to the targeted development of unique SSR markers in large genomic DNA libraries such as those composed of bacterial artificial chromosomes (BACs). A considerable number of isolated SSR clones had similarities with part of several long terminal repeats of retrotransposons (LTR-RTs) identified in various Triticeae genome sequences. Most of those SSRs showed smear amplification profiles, suggesting that a considerable number of dysfunctional SSRs originating from repetitive DNA components, especially LTR-RTs, might exist in the common wheat genome.Key words: common wheat, simple sequence repeat (SSR), PCR screening, LTR-retrotransposon, TAC clone.
Genetic mapping of hop (Humulus lupulusL.) applied to the detection of QTLs for alpha-acid content
Authors: Cerenak Andreja , Satovic Zlatko , Javornik Branka
Published: June 2006

The map locations and effects of quantitative trait loci (QTLs) were estimated for alpha-acid content in hop (Humulus lupulus L.) using amplified fragment length polymorphism (AFLP) and microsatellite marker (simple sequence repeat (SSR)) genetic linkage maps constructed from a double pseudotestcross. The mapping population consisted of 111 progeny from a cross between the German hop cultivar 'Magnum', which exhibits high levels of alpha-acids, and a wild Slovene male hop, 2/1. The progeny segregated quantitatively for alpha-acid content determined in 2002, 2003, and 2004. The maternal map consisted of 96 markers mapped on 14 linkage groups defining 661.90 cM of total map distance. The paternal map included 70 markers assigned to 12 linkage groups covering 445.90 cM of hop genome. QTL analysis indicated 4 putative QTLs (alpha1, alpha2, alpha3, and alpha4) on linkage groups (LGs) 03, 01, 09, and 03 of the female map, respectively. QTLs explained 11.9%–24.8% of the phenotypic variance. The most promising QTL to be used in marker-assisted selection is alpha2, the peak of which colocated exactly with the AFLP marker. Three chalcone synthase-like genes (chs2, chs3, and chs4) involved in hop bitter acid synthesis mapped together on LG04 of the female map. Saturation of the maps, particularly the putative QTL regions, will be carried out using SSR markers, and the stability of the QTLs will be tested in the coming years.Key words: Humulus lupulus L., genetic maps, alpha-acid content, QTLs.
Cytological evidence for assortment mitosis leading to loss of heterozygosity in rice
Authors: Wang Richard R.-C , Li Xiaomei , Chatterton N Jerry
Published: June 2006

In the root meristem cells of the rice line AMR, which causes loss of heterozygosity in its hybrids, both normal and assortment mitoses were observed. During normal mitosis, chromosomes did not form homologous pairs at metaphase; all chromosomes lined up at the equatorial plate and 2 chromatids of each chromosome disjoined at the centromere and moved toward opposite poles. During assortment mitosis, varying numbers of paired homologues were observed at mitotic metaphase. Two groups of 12 chromosomes separated and moved towards the opposite poles of daughter cells with few chromosomes having their chromatids separated at anaphase. These observations support the proposed mechanism that is responsible for early genotype fixation in rice hybrids involving AMR.Key words: mitosis, homologous chromosome, genotype fixation, loss of heterozygosity, rice.
Compressive strength of solid round steel members strengthened with rods or angles
Authors: Kumalasari Cindy , Ding Yongcong , Madugula Murty K.S , Ghrib Faouzi
Published: June 2006

Results of an experimental investigation of the compressive strength of solid round steel bracing members of lattice communication towers strengthened with rods or angles are presented in this paper. The reinforcing rods or angles were connected to the bracing members with clamps or U-bolts. The sizes of reinforcing members were in accordance with industry practice. Finite element models that used a modified static Riks method were built to compute the compressive strength of the members. The results from finite element analysis agree closely with the experimental failure loads. On the basis of the test results and the finite element analysis, a simplified design procedure is proposed to determine the compressive strength of solid round bracing members strengthened with rods or angles.Key words: angles, compressive strength, lattice tower, reinforcement, rods, bracing member, strengthening.
Thermophilic anaerobic acid digestion of biosolids: hydrolysis, acidification, and optimization of retention time of acid digestion
Authors: Puchajda Bartek , Oleszkiewicz Jan
Published: June 2006

The objective of the study was the optimization of the retention time in a thermophilic acid digestion system. To achieve this optimization, acidification index defined as the ratio between acidification rate and hydrolysis rate was used. First-order reaction model developed by Eastman and Ferguson (1981) was used to describe hydrolysis of particulate matter in sludge. The first-order hydrolysis rate constant was found to be 2.36 d–1, and the initial concentration of degradable particulate COD was found to be 10.4 g/L. A model of acid digestion was proposed that included acidogenic biomass growth and decay. The total acidogenic population was estimated and kinetic parameters of acidogenic population were specific growth rate 0.78 d–1, net specific growth rate 0.25 d–1, decay coefficient 0.52 d–1, and observed yield 0.05 mg biomass / mg COD consumed. Based on the acidification index, the optimum retention time in a thermophilic acid digester was 3–3.5 d. Key words: wastewater sludge, biosolids, anaerobic digestion, hydrolysis, acidification, kinetics.
A habitat suitability index model to assess moose habitat selection at multiple spatial scales
Authors: Dussault Christian , Courtois Réhaume , Ouellet Jean-Pierre
Published: June 2006

We developed a habitat suitability index (HSI) model for moose (Alces alces) in the boreal forest. The model used two components: a suitability index for food (SIfood) and another for the interspersion between cover and food (SIedge). We used forest maps as the input data source, and the value of each stand type in terms of cover and food was based on field surveys. To validate the model, the habitat preference of moose equipped with global positioning system telemetry collars was assessed at both landscape and home-range scales. We expected the habitat-preference index to correlate with suitability indices determined using the global model and each of its two components. Habitat suitability was assessed in evaluation plots of 500, 100, and 10 ha. Unexpectedly, the habitat-preference index correlated better with SIfood and SIedge than with the global model. The suitability indices also performed better when assessed in large plots. Selection of 500 ha plots related mostly to SIedge, but SIfood was more important when smaller evaluation plots were used, especially for males. Females preferred plots with intermediate SIfood values. At the fine scale, SIedge was not as attractive to moose as was previously observed, presumably because snow conditions prevailing in our study area were relatively moderate. We recommend utilizing the model with SIedge in large plots (ca. 500 ha) and SIfood in smaller plots. Our model could be adapted and applied to other areas by using empirical data to adjust the relative value of stand types in terms of cover and food.
The effects of soil compaction and fertilizer application on the establishment and growth of Pinus radiata
Authors: Simcock R C , Parfitt R L , Skinner M F , Dando J , Graham J D
Published: June 2006

Ground-based harvest operations in planted forests can adversely affect the soil and subsequently the productivity of the plantation. This study examined the effects of compaction, site preparation, and fertilization on soil physical and chemical properties and tree growth in a trial established at a second-rotation harvest on an imperfectly drained clay loam located in the North Island, New Zealand. Treatments were installed following harvest of Pinus radiata D. Don. There were four physical treatments: no treatment, compaction in rows by skidder, site preparation (rip and disk), and compaction followed by site preparation; the three nutrient treatments included no fertilizer, nitrogen (N), and N plus phosphorus (P). Response of P. radiata was studied for the first 4 years of growth. Compaction reduced survival of P. radiata at planting and during the first year of growth as the result of an increased oxygen deficit, caused by a reduction in macropore volume, and a shallower depth to the perched water table. Site preparation improved both survival of the seedlings and growth over 4 years. There was an initial growth response to N, but fertilizer did not increase survival of the seedlings. After 4 years, both site preparation and N plus P treatments gave approximately 10% extra growth, suggesting that N plus P may have been as effective as site preparation for improved growth of the trees that survived the first 2 years. However, since survival of seedlings is important to the economics of plantations, especially where planting densities are low, site preparation of soils with low macropore volume should be considered as a management tool.
Risk factors affecting escape behaviour by Puerto RicanAnolislizards
Authors: Cooper W.E.
Published: June 2006

Approach distance (flight initiation distance) and escape methods depend on predation risk. I studied escape methods and effects of risk factors (temperature, perch height and orientation, conspicuousness) on approach distance in seven Puerto Rican anoles. Approach distance increased as temperature decreased in Anolis gundlachi Peters, 1876, presumably because of decreasing running speed, but not in other species (probably because of narrow temperature range). Perch height and approach distance varied inversely in four arboreal species that escape upward, positively in two grass–bush species that are more conspicuous when higher and flee downward, and were unrelated in cryptic Anolis stratulus Cope, 1861. Approach distance was shortest in cryptic A. stratulus and shorter intraspecifically in three species for partially concealed lizards and at sites providing more cover in two species. Approach distance was shorter for A. gundlachi on vertical than nonvertical perches, suggesting that ease of escape upward affects assessed risk. Escape behaviours have been proposed to vary among anole ecomorphs. Grass–bush species fled downward as proposed, or horizontally near ground level. Contrary to predictions of escape downward by trunk–ground and upward by trunk–crown anoles, all arboreal species escaped upward. Only trunk anoles were proposed to use squirreling, but species from four ecomorphs did as well.
Space use by Eurasian lynx in relation to reindeer migration
Authors: Danell Anna C. , Andrén Henrik , Segerström Peter , Franzén Robert
Published: June 2006

Semi-domesticated reindeer ( Rangifer tarandus tarandus (L., 1758)) is the primary prey of Eurasian lynx ( Lynx lynx (L., 1758)) in northern Sweden. The reindeer migrate between winter range in the forest and summer range in the mountains, a distance of 100–150 km. We studied space use by Eurasian lynx in relation to seasonal fluctuations of their primary prey in northern Sweden. The seasonal activity range sizes for males and single females were not significantly different between the three periods of the year (December–April, May–July, and August–November). The activity range size for family groups (i.e., female with kittens) was significantly smaller during summer than during autumn and winter. The mean distance between the centre of an individual lynx's activity range in one season to the centre of the activity range in the season immediately following did not differ significantly between seasons; mean distances were 6.6 km for males, 7.3 km for single females, and 8.4 km for family groups. This is about one order of magnitude shorter than the distance between summer and winter ranges for reindeer (100–150 km). The grand mean overlap between a lynx's activity range in one season and the next season was more than 40%. Hence, Eurasian lynx in northern Sweden do not appear to move with the migrating semi-domesticated reindeer.
The role of latent inhibition in acquired predator recognition by fathead minnows
Authors: Ferrari Maud C.O. , Chivers Douglas P.
Published: June 2006

The ability of prey animals to recognize and respond to potential predators has important survival consequences. In many predator–prey systems, prey need to learn which species are potential predators. Consequently, selection should favour efficient learning mechanisms. For aquatic organisms, a very effective way to learn to identify potential predators is by associating cues of injured conspecifics with cues of an unknown predator. To our knowledge, no studies of fishes have failed to show successful acquisition of predator recognition using this learning method. The goal of our study was to begin to address the limits of this learning paradigm. Specifically, we tested whether pre-exposure to a novel predator would prevent the associative learning from occurring. In the first treatment, we pre-exposed minnows to distilled water for 1 h on 5 consecutive days and then conditioned them with conspecific skin extract paired with charr odour. In the second treatment, minnows were pre-exposed to charr odour and conditioned with conspecific skin extract paired with charr odour. In the last treatment, minnows were pre-exposed to charr odour but “conditioned” with distilled water paired with charr odour. When tested for recognition of the charr odour alone, only the fish that were not pre-exposed to charr odour showed responses to the predators. We conclude that latent inhibition affects the efficiency of associative learning of the predator.
AN ANALYTICAL APPROACH TO RELIABILITY ESTIMATION OF MOBILE AGENT-BASED SYSTEMS
Authors: MAHMOUD QUSAY H. , DAOUD MOSAAB
Published: June 2006

Reliability estimation of mobile agent-based systems remains a difficult task due to the characteristics of mobile agents that include distributed and asynchronous execution, autonomy, and mobility. In this paper we present an analytical approach to estimate the reliability of mobile agent-based systems. We define the reliability of a mobile agent in terms of the processor execution time required to perform agent's tasks at each processing node and the transmission or communication time needed to transfer the agent from one processing node to another via a network to complete its mission. The failure of entire components causes failure of the agent. Simulation experiments have been conducted using stochastic Petri Nets modeling. We investigate the effect of different component reliability and availability models (processors and links) on the system throughput. The results we have obtained demonstrate the impact of different reliability and availability models on the system throughput.
AN ANALYSIS OF PROCEDURES AND OBJECTIVE FUNCTIONS FOR HEURISTICS TO PERFORM DATA STAGING IN DISTRIBUTED SYSTEMS
Authors: THEYS MITCHELL D. , BECK NOAH B. , SIEGEL HOWARD JAY , JURCZYK MICHAEL
Published: June 2006

The data staging problem involves positioning data within a distributed heterogeneous computing environment such that programs can access the requested data faster. This problem exists because applications constantly need up-to-date information to enable users to make decisions. In addition, these requests for information are normally occurring in an oversubscribed network. In such a heterogeneous distributed computing environment, each data storage location and intermediate node may have different data available, storage limitations, and communication links available. Sites in the heterogeneous network request data items and each request has an associated deadline and priority. This work extends the research presented in [ThT00] where a basic version of the data staging problem with static information was presented. This work introduces three new cost criteria and two new bounds on performance that were designed taking into account results from [ThT00]. A subset of the possible procedure/cost criterion combinations are evaluated in simulation studies considering a different priority weighting scheme, different average number of links used to satisfy each data request, and different network loadings, than was considered in [ThT00]. This paper also introduces a variable time, variable accuracy approach for using data items with "more desirable" and "less desirable" versions.
Cardiac baroreflex facilitation evoked by hypothalamus and prefrontal cortex stimulation: role of the nucleus tractus solitarius 5-HT2Areceptors
Authors: Sévoz-Couche C. , Comet M. A. , Bernard J. F. , Hamon M. , Laguzzi R.
Published: June 2006

We previously showed that serotonin (5-HT2) receptor activation in the nucleus of the tractus solitarius (NTS) produced hypotension, bradycardia, and facilitation of the baroreflex bradycardia. Activation of the preoptic area (POA) of the hypothalamus, which is involved in shock-evoked passive behaviors, induces similar modifications. In addition, previous studies showed that blockade of the infralimbic (IL) part of the medial prefrontal cortex, which sends projections to POA, produced an inhibitory influence on the baroreflex cardiac response. Thus, to assess the possible implication of NTS 5-HT2receptors in passive cardiovascular responses, we analyzed in anesthetized rats the effects of NTS inhibition and NTS 5-HT2receptor blockade on the cardiovascular modifications induced by chemical (0.3 M d,l-homocysteic acid) and electrical (50 Hz, 150–200 μA) stimulation of IL or POA. Intra-NTS microinjections of muscimol, a GABAAreceptor agonist, prevented the decreases in blood pressure and heart rate normally evoked by IL or POA activation. In addition, we found that intra-NTS microinjection of R(+)-α-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenylethyl)]-4-piperidine-methanol, a specific 5-HT2Areceptor antagonist, did not affect the decreases in cardiovascular baseline parameters induced by IL or POA stimulation but prevented the facilitation of the aortic baroreflex bradycardia normally observed during IL (+65 and +60%) or POA (+70 and +69%) electrical and chemical stimulation, respectively. These results show that NTS 5-HT2Areceptors play a key role in the enhancement of the cardiac response of the baroreflex but not in the changes in basal heart rate and blood pressure induced by IL or POA stimulation.
Differential effects of endothelin on activation of renal mechanosensory nerves: stimulatory in high-sodium diet and inhibitory in low-sodium diet
Authors: Kopp Ulla C. , Cicha Michael Z. , Smith Lori A.
Published: June 2006

Activation of renal mechanosensory nerves is enhanced by high and suppressed by low sodium dietary intake. Afferent renal denervation results in salt-sensitive hypertension, suggesting that activation of the afferent renal nerves contributes to water and sodium balance. Another model of salt-sensitive hypertension is the endothelin B receptor (ETBR)-deficient rat. ET and its receptors are present in sensory nerves. Therefore, we examined whether ET receptor blockade altered the responsiveness of the renal sensory nerves. In anesthetized rats fed high-sodium diet, renal pelvic administration of the ETBR antagonist BQ-788 reduced the afferent renal nerve activity (ARNA) response to increasing renal pelvic pressure 7.5 mmHg from 26 ± 3 to 9 ± 3% and the PGE2-mediated renal pelvic release of substance P from 9 ± 1 to 3 ± 1 pg/min. Conversely, in rats fed low-sodium diet, renal pelvic administration of the ETAR antagonist BQ-123 enhanced the ARNA response to increased renal pelvic pressure from 9 ± 2 to 23 ± 6% and the PGE2-mediated renal pelvic release of substance P from 0 ± 0 to 6 ± 1 pg/min. Adding the ETAR antagonist to ETBR-blocked renal pelvises restored the responsiveness of renal sensory nerves in rats fed a high-sodium diet. Adding the ETBR antagonist to ETAR-blocked pelvises suppressed the responsiveness of the renal sensory nerves in rats fed a low-sodium diet. In conclusion, activation of ETBR and ETAR contributes to the enhanced and suppressed responsiveness of renal sensory nerves in conditions of high- and low-sodium dietary intake, respectively. Impaired renorenal reflexes may contribute to the salt-sensitive hypertension in the ETBR-deficient rat.
Lumbar and cervical erector spinae fatigue elicit compensatory postural responses to assist in maintaining head stability during walking
Authors: Kavanagh Justin J. , Morrison Steven , Barrett Rod S.
Published: June 2006

The purpose of this study was to examine how inducing fatigue of the 1) lumbar erector spinae and 2) cervical erector spinae (CES) muscles affected the ability to maintain head stability during walking. Triaxial accelerometers were attached to the head, upper trunk, and lower trunk to measure accelerations in the vertical, anterior-posterior, and mediolateral directions during walking. Using three accelerometers enabled two adjacent upper body segments to be defined: the neck segment and trunk segment. A transfer function was applied to root mean square acceleration, peak power, and harmonic data derived from spectral analysis of accelerations to quantify segmental gain. The structure of upper body accelerations were examined using measures of signal regularity and smoothness. The main findings were that head stability was only affected in the anterior-posterior direction, as accelerations of the head were less regular following CES fatigue. Furthermore, following CES fatigue, the central nervous system altered the attenuation properties of the trunk segment in the anterior-posterior direction, presumably to enhance head stability. Following lumbar erector spinae fatigue, the trunk segment had greater gain and increased regularity and smoothness of accelerations in the mediolateral direction. Overall, the results of this study suggest that erector spinae fatigue differentially altered segmental attenuation during walking, according to the level of the upper body that was fatigued and the direction that oscillations were attenuated. A compensatory postural response was not only elicited in the sagittal plane, where greater segmental attenuation occurred, but also in the frontal plane, where greater segmental gain occurred.
Slow diffusion of K+ in the T tubules of rat cardiomyocytes
Authors: Swift Fredrik , Strømme Tævje A. , Amundsen Bjørn , Sejersted Ole M. , Sjaastad Ivar
Published: June 2006

Cardiomyocyte contractility is regulated by the extracellular K+ concentration ([K+]o). Potassium dynamics in the T tubules during the excitation-contraction cycle depends on the diffusion rate of K+, but this rate is not known. Detubulation of rat cardiomyocytes was induced by osmotic shock using formamide, which separated the surface membrane from the T tubules. Changes in current and membrane potential in voltage-clamped (−80 mV) and current-clamped control and detubulated cardiomyocytes were compared during rapid switches between 5.4 and 8.1 mM [K+]o, and the results were simulated in a mathematical model. In the voltage-clamp experiments, the current changed significantly slower in control than in detubulated cardiomyocytes during the switch from 5.4 to 8.1 mM [K+]o, as indicated by the times to achieve 25, 50, 90, and 95% of the new steady-state current [control (ms) t25 = 98 ± 12, t50 = 206 ± 20, t90 = 570 ± 72, t95 = 666 ± 92; detubulated t25 = 61 ± 11, t50 = 142 ± 17, t90 = 352 ± 52, t95 = 420 ± 69]. These time points were not significantly different either during the 8.1 to 5.4 mM [K+]o switch or in current-clamped cardiomyocytes switching from 5.4 to 8.1 mM [K+]o. Mathematical simulation of the difference current between control and detubulated cardiomyocytes gave a t-tubular diffusion rate for K+ of ∼85 μm2/s. We conclude that the diffusion of K+ in the T tubules is so slow that they constitute a functional compartment. This might play a key role in local regulation of the action potential, and thus in the regulation of cardiomyocyte contractility.
Reproduction of MIGET retention and excretion data using a simple mathematical model of gas exchange in lung damage caused by oleic acid infusion
Authors: Rees S. E. , Kjærgaard S. , Andreassen S. , Hedenstierna G.
Published: June 2006

The multiple inert-gas elimination technique (MIGET) is a complex mathematical model and experimental technique for understanding pulmonary gas exchange. Simpler mathematical models have been proposed that have a limited view compared with MIGET but may be applicable for use in clinical practice. This study examined the use of a simple model of gas exchange to describe MIGET retention and excretion data in seven pigs before and following lung damage caused by oleic acid infusion and subsequently at different levels of positive end-expiratory pressure. The simple model was found to give, on average, a good description of MIGET data, as evaluated by a χ2 test on the weighted residual sum of squares resulting from the model fit ( P > 0.2). Values of the simple model's parameters (dead-space volume, shunt, and the fraction of alveolar ventilation going to compartment 2) compared well with the similar MIGET parameters (dead-space volume, shunt, log of the standard deviation of the perfusion, log of the standard deveation of the ventilation), giving values of bias and standard deviation on the differences between dead-space volume and shunt of 0.002 ± 0.002 liter and 7.3 ± 2.1% (% of shunt value), respectively. Values of the fraction of alveolar ventilation going to compartment 2 correlated well with log of the standard deviation of the perfusion ( r2 = 0.86) and log of the standard deviation of the ventilation ( r2 = 0.92). These results indicate that this simple model provides a good description of lung pathology following oleic acid infusion. It remains to be seen whether physiologically valid values of the simple model parameters can be obtained from clinical experiments varying inspired oxygen fraction. If so, this may indicate a role for simple models in the clinical interpretation of gas exchange.
Acute exercise and GLUT4 expression in human skeletal muscle: influence of exercise intensity
Authors: Kraniou Giorgos N. , Cameron-Smith David , Hargreaves Mark
Published: June 2006

To examine the influence of exercise intensity on the increases in vastus lateralis GLUT4 mRNA and protein after exercise, six untrained men exercised for 60 min at 39 ± 3% peak oxygen consumption (V̇o2 peak) (Lo) or 27 ± 2 min at 83 ± 2% V̇o2 peak(Hi) in counterbalanced order. Preexercise muscle glycogen levels were not different between trials (Lo: 408 ± 35 mmol/kg dry mass; Hi: 420 ± 43 mmol/kg dry mass); however, postexercise levels were lower ( P < 0.05) in Hi (169 ± 18 mmol/kg dry mass) compared with Lo (262 ± 35 mmol/kg dry mass). Thus calculated muscle glycogen utilization was greater ( P < 0.05) in Hi (251 ± 24 mmol/kg) than in Lo (146 ± 34). Exercise resulted in similar increases in GLUT4 gene expression in both trials. GLUT4 mRNA was increased immediately at the end of exercise (∼2-fold; P < 0.05) and remained elevated after 3 h of postexercise recovery. When measured 3 h after exercise, total crude membrane GLUT4 protein levels were 106% higher in Lo (3.3 ± 0.7 vs. 1.6 ± 0.3 arbitrary units) and 61% higher in Hi (2.9 ± 0.5 vs. 1.8 ± 0.5 arbitrary units) relative to preexercise levels. A main effect for exercise was observed, with no significant differences between trials. In conclusion, exercise at ∼40 and ∼80% V̇o2 peak, with total work equal, increased GLUT4 mRNA and GLUT4 protein in human skeletal muscle to a similar extent, despite differences in exercise intensity and duration.
Changes in the Approach for Invasive Prenatal Diagnosis in 35,127 Cases at a Single Center from 1977 to 2004
Authors: Monni Giovanni , Zoppi Maria A. , Axiana Carolina , Ibba Rosa M.
Published: June 2006

Objectives: To evaluate the changes in the approaches used for invasive prenatal diagnosis for β-thalassemia and karyotyping at a single center from 1977 to 2004. Methods: For β-thalassemia, in 1977 placentacentesis, in 1982 amniocentesis, in 1983 fetoscopy and cordocentesis, in 1983 trancervical chorionic villi sampling (TC-CVS), in 1984 cardiocentesis, in 1986 transabdominal CVS, and in 2002 preimplantation genetic diagnosis (PGD) were introduced. For karyotyping, in 1977 amniocentesis, in 1983 cordocentesis and cardiocentesis and TC-CVS, in 1986 TA-CVS and in 1991 hepatic vein sampling were introduced. Rates of approaches used were retrospectively considered, for 5 different groups (1977–1981; 1982–1985; 1986–1993; 1994–1999; 2000–2004). Results: 35,127 invasive prenatal diagnoses were considered, and 42 PGD included. For β-thalassemia 6,547 diagnoses were performed and 42 PGD. Since 1986–1993, TA-CVS was the only approach used except for 42 PGD in the 2000–2004 group. For karyotyping 28,538 diagnoses were performed. Amniocentesis and TA-CVS have been the most frequently used in the last years, while cordocentesis and hepatic vein sampling have shown a decline after their introduction. Conclusion: TA-CVS is now the only technique used for β-thalassemia. For karyotype, amniocentesis and TA-CVS are the most frequently used procedures. Obstetrical and laboratory experience, the availability of screening, and other individual factors, have influenced the choice, towards an earlier approach in pregnancy.
Screening for Fetal Chromosomal Abnormalities with Nuchal Translucency Measurement in the First Trimester
Authors: Has Recep , Kalelioglu İbrahim , Ermis Hayri , Ibrahimoglu Lemi , Yuksel Atil , Yildirim Alkan , Basaran Seher
Published: June 2006

Objective: To describe the detection rate of first-trimester chromosomal abnormality screening with nuchal translucency (NT) measurement and maternal age in our population. Methods: We have screened the fetuses between 11 to 14 weeks’ gestation according to the Fetal Medicine Foundation’s (London) instructions and used the FMF’s software to assess the risk based on maternal age, crown-rump length (CRL) and NT. Fetal karyotyping was offered when screening for Down syndrome identified a risk greater than 1 in 300. Sensitivity and false-positive rates were calculated for different cut-offs. Results: Pregnancy outcome was obtained from 4,598 babies of 4,365 mothers. The median maternal age of the 4,365 women was 28.2 ± 5.3 (range 15–47) years, and the median fetal CRL was 65.4 ± 9.4 (range 45–81) mm. There was risk estimate of ≧1 in 300 in 214 fetuses (4.7%). Chromosomal abnormalities were identified in 32 fetuses, including 19 cases of trisomy 21, and 13 cases of other abnormalities. The sensitivity using NT and maternal age in detecting trisomy 21 with a cut-off 1 in 300 was 73.6% (14/19) with a false-positive rate of 4.7%. At a false-positive rate of 3%, with a cut-off level 1 in 210, the detection rate was 73.6%. The detection rate for all chromosomal abnormalities with a cut-off level 1 in 300 was 68.8% (22/32) at a false-positive rate of 4.7%. Conclusion: The first-trimester screening for chromosomal anomalies with NT measurement, when carried out according to the accepted standards of quality, is useful.
Prenatal Two- and Three-Dimensional Ultrasound Diagnosis of Limb Reduction Defects Associated with Homozygous α-Thalassemia
Authors: Chen Chih-Ping , Chang Tung-Yao , Su Yi-Ning , Hsu Chin-Yuan , Wang Wayseen
Published: June 2006

Objectives: We present the prenatal two-dimensional (2D-) and three-dimensional ultrasound (3D-US) diagnosis of limb reduction defects associated with homozygous α-thalassemia and a review of the literature. Methods: At 17 weeks’ gestation, amniocentesis was performed for cytogenetic and molecular studies, and 2D- and 3D-US examinations were made for evaluation of the fetal malformations. Results: Amniocentesis revealed a 46,XY karyotype and molecular analysis of the amniocytes showed that the fetus was homozygous for the Southeast Asian deletion (– –SEA/– –SEA). 2D-US examination revealed bilateral ventriculomegaly, brachycephaly, pleural effusion, digital deficiency and hypoplasia of the right foot, and digital deficiency of the left foot. 3D-US confirmed the distal limb reduction defects. Conclusions: When the fetus is at risk for homozygous α-thalassemia, 2D- and 3D-US examinations are useful for prenatal detection of the associated limb reduction defects. Prenatal identification of the possible association with limb reduction defects is important for parental counseling and decision-making when intrauterine fetal therapy is an option.
Expression and Function of Toll-Like Receptors in Human Basophils
Authors: Komiya Akiko , Nagase Hiroyuki , Okugawa Shu , Ota Yasuo , Suzukawa Maho , Kawakami Ayako , Sekiya Takashi , Matsushima Kouji , Ohta Ken , Hirai Koichi , Yamamoto Kazuhiko , Yamaguchi Masao
Published: June 2006

We investigated the expression and function of a panel of Toll-like receptors (TLRs) in human basophils. Basophil preparations constitutively expressed TLR2, TLR4, TLR9 and TLR10 mRNAs (TLR4 > TLR2 >> TLR9, TLR10). Although TLR mRNA expression in basophils was generally less prominent compared with those in neutrophils and monocytes, basophils expressed significantly higher levels of TLR2 and TLR4 mRNA than eosinophils. Various TLR ligands (Pam3Cys-Ser-Lys4, poly I:C, lipopolysaccharide, R-848, CpG DNA) were tested, but none affected the expression level of adhesion molecule CD11b or the viability of freshly purified basophils. On the other hand, when basophils were pretreated with interferon-γ before stimulation with TLR ligands, only the TLR4 ligand, lipopolysaccharide, upregulated CD11b expression. However, the surface levels of TLR2 and TLR4 on the interferon-γ-treated basophils showed no obvious changes. These results suggest that TLR4 on basophils may be involved in the pathogenesis of infection-induced exacerbation of allergic inflammation by modulating basophil functions.