bluuebunny/crossref_metadata_2025 huggingface dataset:
Meteorological and Hydrographic Regulation of Year-Class Strength in Capelin (Mallotus villosus)
Authors: Leggett W. C. , Frank K. T. , Carscadden J. E.
Published: May 2008

Year-class strength (YCS) in eastern Newfoundland stocks of capelin (Mallotus villosus), a beach spawning osmerid, during the interval 1966–78 was strongly influenced by onshore wind frequency during the period immediately following hatching (WIND) and water temperatures experienced during the subsequent period of larval drift (TEMPSUM). The exact form of the relationship was ln YCS = 16.10 − 0.19WIND + 0.19TEMPSUM, R2 = 0.58. Wind conditions subsequent to hatching are known to influence both the timing of larval emergence from the beach spawning beds and the physical condition of larvae at emergence. Our analysis suggests that the influence of wind on early larval survival is also strong. The role of water temperatures during drift may be indirect, operating via its influence on food production. This could operate by altering mortality rates due to starvation or by altering growth rates which would influence swimming performance, predator avoidance, and time to metamorphosis. The strong influence of these abiotic variables, independent of parent stock size, adds further support to the hypothesis that abiotic factors operating at critical periods in larval development may be more important than spawning stock biomass as regulators of year-class size. Our findings also suggest that these critical periods must be identified and quantified at time scales relevant to individual larvae if reliable forecasting of year-class strength is to be achieved. On the other hand, the large spatial scale of the effects suggests that the space scale of individual larvae is of lesser importance in such analyses.
Environmental Controls of Marine Food Webs: Food Habits of Seabirds in the Eastern Chukchi Sea
Authors: Springer Alan M. , Roseneau David G. , Murphy Edward C. , Springer Martha I.
Published: May 2008

Food habits of thick-billed murres (Uria lomvia), common murres (U. aalge), and black-legged kittiwakes (Rissa tridactyla) were examined at two breeding colonies in the eastern Chukchi Sea between 1976 and 1980. Cods (Gadidae), sculpins (Cottidae), sand lance (Ammodytes hexapterus), and capelin (Mallotus villosus) were the dominant (biomass) prey of thick-billed murres. Cods, sand lance, and capelin were the dominant prey of common murres and kittiwakes. Annual changes in the consumption of fishes by murres and kittiwakes suggest that available fish biomass in the eastern Chukchi Sea was low in 1976 and 1977, but increased each year through 1979 and 1980. The average size of several taxa of fishes eaten by the birds increased also between most years. Invertebrates were less important than fishes in all years, were eaten most frequently by thick-billed murres, and were eaten more frequently in 1976–77 than in 1978–79. A pattern of climatic cooling in the early 1970's followed by warming in the second half of the decade caused annual differences in the extent and duration of sea ice, and apparently in the spacial and temporal development of Alaskan Coastal Water, a major oceanographic feature of the Bering–Chukchi shelf. Fluctuations in the physical environment could have led to changes in fish populations through direct physiological and behavioral effects, or indirectly by altering the abundance of important zooplankton prey populations. Variability in the reproductive success of murres and kittiwakes in the northern Bering Sea and eastern Chukchi Sea corresponded with the apparent changes in fish stocks: reproductive success was very low in 1976 but improved in successive years. Short-term responses of seabirds to environmental fluctuation and its proposed effect on supporting food webs suggest that the stability of regional seabird populations could also be affected by long-term changes in weather and climate.
Effects of Fluctuations in Hydrographic Conditions on Year-Class Strength of American Shad (Alosa sapidissima) in the Connecticut River
Authors: Crecco Victor A. , Savoy Thomas F.
Published: May 2008

We evaluated a parent–progeny relationship for Connecticut River shad, Alosa sapidissima, with population data from 1966 through 1982. The hypothesis that shad year-class strength is established during larval development mainly by abiotic factors was assessed by correlation analysis between environmental variables, year-class strength, weekly zooplankton densities, hydrographic conditions, and larval feeding success among the 1979 through 1982 year-classes. No significant parent–progeny relationship was found for American shad even after recruitment variations due to river flow and water temperatures were removed. All three environmental variables (mean river discharge, water temperatures, and total monthly precipitation) were significantly correlated with shad year-class strength for the month of June, the period when most American shad larvae emerge.
Method of Solving for Natural Mortality Rate for Stock Components with Different Schedules of Growth and Mortality
Authors: Caddy J. F.
Published: May 2008

A method is proposed for solving the natural mortality rates, MA and MB, for two stock components with different von Bertalanffy growth rates (KA and KB), where total mortality rates ZA and ZB are available for a series of years, and where the assumption of a constant M/K ratio can reasonably be made. The method has obvious applications for populations where the two sexes have different growth and mortality schedules, but have a constant relative availability to fishing.
An In Situ Substratum Fertilization Technique: Diatom Colonization on Nutrient-Enriched, Sand Substrata
Authors: Pringle Catherine M. , Bowers James A.
Published: May 2008

Using an in situ substratum enrichment method, we assessed the effects of nutrient release from sand substrata on the community structure of attached diatoms in a sand-bottomed, northern Michigan stream. Sand from the stream bottom was washed, sterilized, and then consolidated into small plastic petri dishes with agar solutions enriched with various concentrations of NaNO3and KH2PO4. Laboratory estimates of nutrient release rates were performed over a 144-h period with uncolonized substrata having different agar and nutrient concentrations. Release rates decreased 10-fold in an exponential fashion with no significant differences between replicates. Agar concentrations had no significant effect on release rates, although the rates were proportional to nutrient concentrations in the substratum. Racks of substrata were installed parallel to the stream current flow and retrieved after a 6-wk colonization period. Using multiple comparisons of treatment means for both nutrients and algal taxa, we found no differences between control and NO3enrichments; significant differences were found, however, between PO4and NO3 + PO4(N:P = 25:1) treatment means relative to each other and the control. Diatom biovolume was two times as great on PO4treatments and four times greater on NO3 + PO4treatments. Effects of PO4and NO3enrichment appear to be taxa specific, with PO4and NO3 + PO4treatments favoring Navicula and Nitzschia spp. Control and NO3treatments were dominated by Cocconeis placentula Ehr. and Achnanthes minutissima Kutz.
Ecological Effects of Acid Deposition Upon Peatlands: A Neglected Field in "Acid-Rain" Research
Authors: Gorham Eville , Bayley Suzanne E. , Schindler David W.
Published: May 2008

Certain types of peatlands are probably highly susceptible to anthropogenic acidification, yet very little research is being done on the vulnerability of bogs and fens to acid deposition. We have documented the need for such research and for studies of the role of acidification — natural and anthropogenic — in determining nutrient availability, metal mobilization, and biogeochemical cycling by fauna and microflora. Possible effects of hydrological changes, and of drainage from acid peatlands to lakes and streams, are noted. We provide an outline of possible responses of plants and animals to acidification; these should be investigated at species, community, and ecosystem levels. Studies of peatlands as possible sources of the gaseous precursors of acid deposition are needed. Different approaches to examining the responses of peatlands to acid deposition include geographical surveys, experimental studies, short-term, long-term, and paleoecological investigations, and analysis of biogeochemical mass-balances. Finally, we emphasize the need for inclusive studies of peatlands in relation to surrounding uplands and to the streams and lakes that receive their drainage.
Crustacean Zooplankton Food Web Structure in Lakes of Varying Acidity
Authors: Havens Karl E.
Published: May 2008

Crustacean zooplankton food web models were constructed for 25 softwater United States lakes of varying pH (4.7–7.2). Eight lakes on the North Mountain Plateau of Pennsylvania were sampled in 1987, and data from 17 Adirondack Mountain, NY, and White Mountain, NH, lakes were taken from Confer et al. (1983. Can. J. Fish. Aquat. Sci. 40: 36–42). In the most acidic lakes, the zooplankton food webs were simplified, with only two or three crustacean species; the highest pH lakes contained 6–10 species. Positive relationships were found between lake water pH and species richness, total number of predator–prey interactions, average number of interactions per species, and average generalization of predators. Inverse relationships were found between pH and both the degree of omnivory and cannibalism in the webs, perhaps reflecting the adaptiveness of those feeding strategies under circumstances where energy flow from adjacent trophic levels is reduced. Reduced energy flow may limit the number of trophic levels in the most acidic lakes. Lakes of pH < 5 had only two or three modal trophic levels, while lakes of pH > 5 had three, four, or five levels.
Efficiency of a Brush Sampler to Measure Periphyton in Streams and Lakes
Authors: Cattaneo Antonella , Roberge Guy
Published: May 2008

Natural periphytic communities are usually sampled by scraping all the algae from a small area. Such a protocol seems more likely to sample loosely attached forms than those which grow tightly attached to the substratum, but this bias has never been quantified. To this end, chlorophyll estimates were obtained by sampling periphyton on cobbles with a brushing syringe sampler in a series of streams and lakes in southern Québec and compared with estimates obtained by immersing the cobble in extractant solvent. In streams, the syringe sampler underestimated chlorophyll concentration, and the severity of this underestimation increased with the current speed. In lakes, the situation was reversed: the brushing syringe gave higher values than those obtained by immersion. These results likely reflect the relative proportions of loosely and tightly attached subcommunities within the periphyton. The latter fraction, which cannot be quantitatively removed by brushing, appears especially important in fast-flowing streams. Ineffective sampling of this fraction may invalidate comparisons obtained with different methods.
Biases Associated with Four Stream Substrate Samplers
Authors: Young Michael K. , Hubert Wayne A. , Wesche Thomas A.
Published: May 2008

We compared samples collected from 10 substrates of various compositions with a single-probe freeze-core sampler, a triple-probe freeze-core sampler, a McNeil sampler, and a shovel. The accuracy with which these devices sampled particles larger than 50 mm in diameter varied; they were oversampled by the freeze-core devices, sampled in proportion to their availability by a shovel, and sampled inconsistently by the McNeil sampler. The geometric mean particle size and variance of single-probe freeze-core samples consistently exceeded those of samples collected with the other devices. Most sample means also exceeded the test substrate means. By excluding the proportions of particles larger than 50 mm in diameter in our analyses, we found that proportions of several particles sizes in samples collected by different methods differed significantly from the actual proportions in test substrates. There were few differences between the single- and triple-probe freeze-core samples or between McNeil and shovel samples. All four samplers were biased, but the McNeil sampler most frequently produced samples that approximated the true substrate composition.
Ontogeny of Feeding Behavior of First-Feeding Atlantic Salmon (Salmo salar)
Authors: Coughlin David J.
Published: May 2008

Feeding strikes of Atlantic salmon (Salmo salar) alevins preying upon Daphnia are described using videorecording of synchronous lateral and antero-ventral views. Based on examination of characteristics such as aiming inaccuracy and capture distance, it is demonstrated that feeding behavior significantly improves during the first 2 wk after initiation of exogenous feeding. With increasing experience, young salmon tend to capture prey more quickly and with greater accuracy. First-feeding alevins use a body-ram feeding mode, relying on their swimming motion to overtake and capture prey. After 7–10 d of feeding, the fish change to a suction feeding mode that effectively uses suction generated by expansion of the orobranchial chamber to pull in prey from a distance. Also, feeding behavior of alevins raised on a commercial salmon feed lags developmentally behind the behavior offish raised on live food. This lag time is short (2–3 d), indicating that despite reports to the contrary, hatchery-raised fish do not require a Song time to learn to capture prey effectively in the wild.
Use of the Morphoedaphic Index to Predict Nutrient Status and Algal Biomass in Some Canadian Lakes
Authors: Chow-Fraser Patricia
Published: May 2008

The underlying assumptions of the morphoedaphic index (MEI; total dissolved solids (TDS)/mean depth), which has been used to predict fish yields in lakes, and its power for predicting biomass at lower trophic levels were examined using published data. The assumptions included the relationship between mean depth of lakes and various hydrologic characteristics (flushing rate and stratification regime), water transparency characteristics (water color and turbidity), and the stoichiometric relationship among ions (expressed as a proportion between TDS and the concentration of primary nutrients, total phosphorus (TP) and total nitrogen (TN)). Although these basic assumptions could be supported empirically, the predictive power of the MEI became progressively weakened with increasing trophic level. MEI accounted for up to 85% of the variation in TP and TN, less than 50% of the variation in [Chl a], and none of the variation in the biomass of herbivorous zooplankton. The functions relating TDS to both TP and TN were fundamentally different: as lakes increased in salinity, the TN:TP ratio decreased dramatically so that TP almost exceeded TN concentrations in extremely saline lakes. This necessitated the development of separate MEI–nutrient relationships for saline (TDS > 1000 mg/L) and nonsaline lakes.
Gape Limitation and Prey Selection in Larval Yellow Perch (Perca flavescens), Freshwater Drum (Aplodinotus grunniens), and Black Crappie (Pomoxis nigromaculatus)
Authors: Schael Denise M. , Rudstam Lars G. , Post John R.
Published: May 2008

We compared prey selection of larval yellow perch (Perca flavescens), freshwater drum (Aplodinotus grunniens), and black crappie (Pomoxis nigromaculatus) in Lake Mendota, Wisconsin. All three species had a diet dominated by copepods and selected progressively larger prey as fish length increased. For a given fish length, freshwater drum selected larger prey and black crappie selected smaller prey than yellow perch. These differences in prey selectivity were partly explainable from differences in gape to length relationships. Freshwater drum did have the largest gape for a given length of the three species, but gape size for black crappie and yellow perch were similar. Gape size predicted 67% of the variability in mean prey size ingested by yellow perch but only 15% for freshwater drum and 8% for black crappie. Although gape size did predict the upper limit of ingestible prey sizes and explained some of the differences in prey selectivity among the three species, both the degree to which the different fishes can ingest prey close to their gape limit and the degree to which gape predicted mean size of ingested prey varied among the three fish species.
A Statistically Valid Model of the Morphoedaphic Index
Authors: Rempel Robert S. , Colby Peter J.
Published: May 2008

The morphoedaphic index (MEI) has been criticized because of the use of ratio variables in linear regression. Computationally simple, the continued use of the index is questionable given the widespread access fisheries biologists now have to computerized statistical packages. We present a statistically valid analogue to the MEI, the morphoedaphic model (MEM), that utilizes multiple regression to characterize the morphometric and fertility properties of lakes to predict annual fish yield. Surface area, lake volume, and total dissolved solids (TDS) are used to predict annual fish yield for the lake and to derive associated confidence limits. Predicted yield of the newly derived model was compared with predictions from the original MEI Comparisons were also made based on models derived from Ontario sport and commercial fisheries data sets. The MEM derived from these partitioned data sets more accurately modelled the observed long-term yields for these lakes. Analysis of the remaining outliers suggests that several additional variables and stratification may be required to further develop the precision of the statistical model.
Interactive Effects of Nutrient Reduction and Herbivory on Biomass, Taxonomic Structure, and P Uptake in Lotic Periphyton Communities
Authors: Steinman Alan D. , Mulholland Patrick J. , Kirschtel David B.
Published: May 2008

Four treatments were imposed on eight laboratory streams in a factorial design to examine the roles of nutrient reduction and herbivory on periphyton communities. Treatments included two flow regimes (once-through flow or 90% recirculated water) and two levels of grazer density (1000 or 0∙m−2, using the snail Elimia clavaeformis). Periphyton biomass was significantly greater in streams without snails than in those with them, but water supply had no overall significant effect on biomass, even though inorganic P and N concentrations were significantly lower in recirculated than in once-through streams. Areal-specific P uptake rates (measured with 33P) were significantly greater on two dates in no-snail streams compared with snail streams, presumably because of the greater biomass levels in the former systems. Differences in biomass-specific P uptake rates were not significantly affected by either grazer density or water supply. Relative abundances of most algal species were unaffected by the water supply treatment, although percent biovolume of two Epithemia species was greater in no-snail, recirculated than in no-snail, once-through streams. Grazing activity dramatically reduced the percent biovolume of species with upright growth forms, resulting in dominance by species with prostrate growth forms.
Acclimation to Sublethal Aluminum: Modifications of Metal – Gill Surface Interactions of Juvenile Rainbow Trout (Oncorhynchus mykiss)
Authors: Reid Scott D. , McDonald D. G. , Rhem R. R.
Published: May 2008

Juvenile rainbow trout (Oncorhynchus mykiss) were exposed for 21 d to one of three concentrations of H+and Al. Exposure to 27 μg Al∙L−1at pH 5.2 resulted in a significant internal physiological disturbance associated with the accumulation of Al at the gill, both of which declined with continued exposure. Increased resistance to an acutely lethal Al concentration (118 μg∙L−1, pH 5.2) was demonstrated by a reduction in both rate of mortality and in the magnitude of the internal physiological disturbance relative to controls at pH 6.5 or 5.2 and 0 μg Al∙L−1Both Al and H+were strong Ca2+antagonists causing modifications in the ability of the gill microenvironment to bind Ca2+during the acclimation exposures (saturation binding and competitive inhibition techniques used). The Al resistance was associated with a significant reduction in both the binding affinity of the gill surface for Al and the ability of Al to inhibit gill Ca2+binding. This reduction in the surface activity of Al in the fish with prior Al exposure suggested that increased Al resistance involved modifications in the chemical characteristics of the anionic groups present in the gill microenvironment, resulting in the reestablishment of membrane stability and electrolyte permeability.
Nature and Time Course of Acclimation to Aluminum in Juvenile Brook Trout (Salvelinus fontinalis). I. Physiology
Authors: McDonald D. G. , Wood C. M. , Rhem R. G. , Mueller M. E. , Mount D. R. , Bergman H. L.
Published: May 2008

Chronic exposure (up to 42 d) of juvenile brook trout (Salvelinus fontinalis) to sublethal aluminum at pH 5.2 resulted in a damage/repair acclimation phenomenon. The damage developed rapidly (within 24 h), was centered at the gills, and was characterized by substantial accumulation of Al, a corresponding reduction of gill sialic acid content (a measure of gill mucus), and inhibition of branchial Na+ transport. The corresponding internal effects of this initial damage were losses of electrolytes, hemoconcentration, and impaired tissue O2 delivery (as indicated by elevated lactate). Repair was characterized by progressive reduction of gill Al, restoration of sialic acid content, recovery of Na+ transport, and reduction in hemoconcentration and lactate levels. Accompanying the recovery was progressive development (by day 10 onwards) of increased resistance (i.e. acclimation) to acutely lethal Al. This acclimation was characterized by a reduction in both the rate of mortality and in the magnitude of physiological disturbances relative to control (i.e. Al naive) fish. The increased short-term resistance translated to greatly improved survivorship and correspondingly diminished physiological impact in the face of chronically elevated Al levels (2 wk at < 300 μg Al/L). The acclimation process clearly resulted from specific changes at the gills.
Shortening of Branchial Tight Junction Acid-Exposed Rainbow Trout (Oncorhynchus mykiss)
Authors: Freda J. , Sanchez D. A. , Bergman H. L.
Published: May 2008

The objective of this study was to investigate possible sites for Na+loss in fish exposed to low environmental pH. In rainbow trout (Oncorhynchus mykiss) exposed to pH 4.0 for 1 h, a net loss of Na+was stimulated, and changes in gill structure occurred. In addition to epithelial lifting and necrosis in the gills of acid-exposed fish, tight junctions between pavement epithelial cells and chloride cells decreased in length by 25% whereas tight junctions between adjacent pavement cells did not significantly change. In a second experiment where fish were moved from pH 4.0 or 3.5 water to pH 6.5 water, we observed that Na+loss declined immediately and approached control levels. The reversible nature of the stimulation of Na+loss indicates that the site of Na+loss in the fish gill can be reversibly opened and closed, which is consistent with the known properties of tight junctions. We hypothesize that the opening of tight junctions contributes to the loss of plasma electrolytes at low environmental pH. However, the relative magnitude of electrolyte loss through the tight junctions remains unknown.
CRITICAL STATE MODELS FOR GRANULAR MAGNETIC SUPERCONDUCTOR RuSr2GdCu2O8
Authors: AWAYSA G. M. , SALEH A. M. , ABU-SAMREH M. M. , KITANEH R. M.-L.
Published: May 2008

A systematic investigation of the ac susceptibility of polycrystalline RuSr 2 GdCu 2 O 8 was carried out with different field amplitudes and various frequencies. The study covered a wide range of frequencies between 0.020 to 12.5 kHz and temperatures from 7 to 50 K. The first derivative of susceptibility curves indicated the presence of a superconducting intragranular transition coupled by weak links distribution of intergranular transitions. The intragranular-, χg, and intergranular-, χi contribution to susceptibility were estimated and found to be consistent with the prediction of the critical state model. Variation of the peak temperature of the imaginary part with frequency was employed to determine the vortex activation energy. The derived low activation energy values provide clear evidence of the thermally activated flux creep process in the superconducting state. Qualitative analysis of the χ′′ - χ′ parametric relation was carried out.
SIMULATION FOR RAMIFIED AGGREGATES ON NONLATTICE SUBSTRATES WITH IMPURITIES
Authors: GAO GUOLIANG , QIAN CHANGJI , LI HONG , HUANG XIAOHONG , GU WENJING
Published: May 2008

A growth mechanism of ramified aggregates on nonlattice substrates with fixed impurities is studied systematically. Based on the experimental observations of Au atomic aggregates on molten glass surfaces, an Improved Restricted Cluster-Cluster Aggregation (IRCCA) model is established. In this model, fixed impurities are distributed randomly on a nonlattice substrate, and all the aggregates with different sizes are allowed to diffuse and rotate. The influence of the liquid substrate and impurity on the structure of the ramified aggregates is studied systematically. The simulation results are in good agreement with the experimental findings.
SLIDING MODE CONTROL OF LORENZ SYSTEM WITH MULTIPLE INPUTS CONTAINING SECTOR NONLINEARITIES AND DEAD ZONE
Authors: WANG XINGYUAN , LIU MING , WANG MINGJUN , HE YIJIE
Published: May 2008

This paper designs the controller for uncertain Lorenz system with multiple inputs containing sector nonlinearities and dead zone, and theoretically demonstrates the effectiveness of this controller. By this controller, the controlled Lorenz system can asymptotically drive the system orbits to arbitrarily objective trajectories even with uncertainties and sector nonlinearities and dead zone in the inputs, and thus has strong robustness. Finally, through the emulation studies of controlled Lorenz systems, it demonstrates the effectiveness of this controller.
PROBABILISTIC TELEPORTATION OF A TWO-ATOM ENTANGLED STATE IN CAVITY QED
Authors: LIU JIN-MING , WANG YI-CAI , XIAO XIAO-QI
Published: May 2008

We present two schemes for probabilistically teleporting a two-atom entangled state using a three-atom partially entangled state as the quantum channel in cavity QED with the help of separate atomic measurements. The first scheme is only based on the interaction between two driven atoms and a quantized cavity mode in the large detuning limit, so the effects of both cavity decay and the thermal field are eliminated. In the second scheme, it is necessary to introduce an additional resonant cavity besides the thermal cavity to realize the teleportation, and the corresponding success probability is improved.
KIDNEY-BOOJUM-LIKE SOLUTIONS AND EXACT SHAPE EQUATION OF LIPID MONOLAYER DOMAINS
Authors: IWAMOTO MITSUMASA , LIU FEI , OU-YANG ZHONG-CAN
Published: May 2008

The shape of the solid lipid monolayer domain surrounded by a fluid phase is of considerable interest from both physical and mathematical points of view. Here, we report two new results about this topic. First, we find an exact analytical solution to an approximated shape equation that we derived recently. This solution can well-describe the kidney- and boojum-like domains that abound in lipid monolayer. Second, we derive an exact domain shape equation by a direct variation of domain energy without any artificial cutoff. We find no continuous solutions that satisfy this shape equation due to the divergence of its coefficients, which is rooted in the continuous description of electrostatic dipoles.
COMMENTS ON "NTH-ORDER SQUEEZING OF THE FIELD AMPLITUDE IN RAMAN PROCESS AS A GENERALIZATION OF THE HIGHER-ORDER SQUEEZING"
Authors: SEN BISWAJIT , MANDAL SWAPAN
Published: May 2008

In a recent paper, Giri and Gupta [Int. J. Mod. Phys. B19, 1943 (2005)] discussed the possibility of obtaining nth-order squeezing of the field amplitude of the fundamental mode in spontaneous Raman processes. These investigations are based on the earlier works of Kumar and Gupta [Quantum & Semiclassical Opt.7, 835 (1995)] and Giri and Gupta [J. Mod. Opt.51, 1705 (2004)]. As a consequence of our re-investigation on the same model, we found that the calculations and hence the conclusion of Giri and Gupta [Int. J. Mod. Phys. B19, 1943 (2005) and J. Mod. Opt.51, 1705 (2004)] and Kumar and Gupta are entirely baseless and misleading. There will be no squeezing of the fundamental mode in stimulated and/or in spontaneous Raman processes.
FIRST-PRINCIPLES STUDY OF GAMMA-Si3N4 WITH GENERALIZED GRADIENT APPROXIMATION AND LOCAL DENSITY APPROXIMATION
Authors: DING YINGCHUN , ZHOU HAIPING , XU MING , SHEN YIBING , CHEN QINGYUN , ZHU WEN-JUN , HE HONGLIANG
Published: May 2008

The electronic structure, and optical and mechanical properties of gamma- Si 3 N 4 are calculated by means of the plane-wave pseudo-potential method (PWP) with generalized gradient approximation (GGA) and local density approximation (LDA). The calculated values are in good agreement with experimental results. A comparative investigation reveals that the band gap calculated by GGA agrees better with the experimental value than by the other methods, while the calculated bulk modulus by LDA is comparable with that by the method of orthogonalized linear combinations of atomic orbitals (OLCAO). Our results indicate that a satisfactory calculation of the structures and properties of gamma- Si 3 N 4 could be achieved by combining GGA and LDA methods.
So-Grid
Authors: Forestiero Agostino , Mastroianni Carlo , Spezzano Giandomenico
Published: May 2008

This article presents So-Grid, a set of bio-inspired algorithms tailored to the decentralized construction of a
Grid
information system that features adaptive and self-organization characteristics. Such algorithms exploit the properties of
swarm
systems, in which a number of entities/agents perform simple operations at the local level, but together engender an advanced form of
swarm intelligence
at the global level. In particular, So-Grid provides two main functionalities: logical reorganization of resources, inspired by the behavior of some species of ants and termites that move and collect items within their environment, and resource discovery, inspired by the mechanisms through which ants searching for food sources are able to follow the pheromone traces left by other ants. These functionalities are correlated, since an intelligent dissemination can facilitate discovery. In the Grid environment, a number of ant-like agents autonomously travel the Grid through P2P interconnections and use biased probability functions to: (i) replicate resource descriptors in order to favor resource discovery; (ii) collect resource descriptors with similar characteristics in nearby Grid hosts; (iii) foster the dissemination of descriptors corresponding to
fresh
(recently updated) resources and to resources having high quality of service (QoS) characteristics. Simulation analysis shows that the So-Grid replication algorithm is capable of reducing the entropy of the system and efficiently disseminating content. Moreover, as descriptors are progressively reorganized and replicated, the So-Grid discovery algorithm allows users to reach Grid hosts that store information about a larger number of useful resources in a shorter amount of time. The proposed approach features characteristics, including self-organization, scalability and adaptivity, which make it useful for a dynamic and partially unreliable distributed system.
A control theoretical approach to self-optimizing block transfer in Web service grids
Authors: Gounaris Anastasios , Yfoulis Christos , Sakellariou Rizos , Dikaiakos Marios D.
Published: May 2008

Nowadays, Web Services (WS) play an important role in the dissemination and distributed processing of large amounts of data that become available on the Web. In many cases, it is essential to retrieve and process such data in blocks, in order to benefit from pipelined parallelism and reduced communication costs. This article deals with the problem of minimizing at runtime, in a self-managing way, the total response time of a call to a database exposed to a volatile environment, like the Grid, as a WS. Typically, in this scenario, response time exhibits a concave, nonlinear behavior depending on the client-controlled size of the individual requests comprising a fixed size task. In addition, no accurate profiling or internal state information is available, and the optimum point is volatile. This situation is encountered in several systems, such as WS Management Systems (WSMS) for DBMS-like data management over wide area service-based networks, and the widely spread OGSA-DAI WS for accessing and integrating traditional DBMS. The main challenges in this problem apart from the unavailability of a model, include the presence of noise, which incurs local minima, the volatility of the environment, which results in moving optimum operating point, and the requirements for fast convergence to the optimal size of the request from the side of the client rather than of the server, and for low overshooting. Two solutions are presented in this work, which fall into the broader areas of runtime optimization and switching extremum control. They incorporate heuristics to avoid local optimal points, and address all the aforementioned challenges. The effectiveness of the solutions is verified via both empirical evaluation in real cases and simulations, which show that significant performance benefits can be provided rendering obsolete the need for detailed profiling of the WS.
Agent clustering based on semantic negotiation
Authors: Garruzzo Salvatore , Rosaci Domenico
Published: May 2008

Forming groups of agents is an important task in many agent-based applications, for example when determining a coalition of buyers in an e-commerce community or organizing different Web services in a Web services' composition. A key issue in this context is that of generating groups of agents such that the communication among agents of the same group is not subjected to comprehension problems. To this purpose, several approaches have been proposed in the past in order to form groups of agents based on some similarity measures among agents. Such similarity measures are mainly based on lexical and/or structural similarities among agent ontologies. However, the necessity of taking into account a semantic component of the similarity value arises, for example by considering the context in which a term is used in an agent ontology. Therefore we propose a clustering technique based on the HISENE semantic negotiation protocol, using a similarity value that has lexical, structural and semantic components. Moreover, we introduce a suitable multiagent architecture that allows computing agent similarities by means of an efficient distributed approach.
A new intra-disk redundancy scheme for high-reliability RAID storage systems in the presence of unrecoverable errors
Authors: Dholakia Ajay , Eleftheriou Evangelos , Hu Xiao-Yu , Iliadis Ilias , Menon Jai , Rao K.K.
Published: May 2008

Today's data storage systems are increasingly adopting low-cost disk drives that have higher capacity but lower reliability, leading to more frequent rebuilds and to a higher risk of unrecoverable media errors. We propose an efficient intradisk redundancy scheme to enhance the reliability of RAID systems. This scheme introduces an additional level of redundancy inside each disk, on top of the RAID redundancy across multiple disks. The RAID parity provides protection against disk failures, whereas the proposed scheme aims to protect against media-related unrecoverable errors. In particular, we consider an intradisk redundancy architecture that is based on an interleaved parity-check coding scheme, which incurs only negligible I/O performance degradation. A comparison between this coding scheme and schemes based on traditional Reed--Solomon codes and single-parity-check codes is conducted by analytical means. A new model is developed to capture the effect of correlated unrecoverable sector errors. The probability of an unrecoverable failure associated with these schemes is derived for the new correlated model, as well as for the simpler independent error model. We also derive closed-form expressions for the mean time to data loss of RAID-5 and RAID-6 systems in the presence of unrecoverable errors and disk failures. We then combine these results to characterize the reliability of RAID systems that incorporate the intradisk redundancy scheme. Our results show that in the practical case of correlated errors, the interleaved parity-check scheme provides the same reliability as the optimum, albeit more complex, Reed--Solomon coding scheme. Finally, the I/O and throughput performances are evaluated by means of analysis and event-driven simulation.
Process-oriented abstraction of the complex evolvable systems
Authors: Bastani Behzad
Published: May 2008

Architectural design and lifecycle management of complex Evolvable Systems encounter contexts and environments in which ambiguity and volatility are of essence. Ambiguity relates to the content of the information the architect has available at the time of the design and maps to the aspects, dimensions and boundaries of the system. Volatility represents constant changes of vision, knowledge and information due to the advances in science or techniques of handling and demands the architect to redesign the system to match the new realities of the time. As a result, the nature of the complex Evolvable Systems introduces serious challenges to the conventional Software Architecture and Software Engineering. This paper presents a new method called Nuclear-Process Oriented Analysis and Modeling (NPOAM), for the design of complex Open Evolvable Systems [1], and focuses on its implementation within the scope of the Problem Model construction [2] for a Cardiac Arrhythmia Management model. Our Problem Model construction develops its conceptualization on the premises of the complexities and requirements of scientific domains. Yet its applicability is not exclusive to scientific domains but since it is designed for more complex scientific environments, it is perfectly applicable to business domains as well. One of the critical contributions of NPOAM is providing the capability of random process modeling and design. The paper concludes with addressing the model analysis and verification issues.
Definition and modeling of process using object orientation
Authors: Borsoi Beatriz Terezinha , Becerra Jorge Luis Risco
Published: May 2008

Software development processes can be represented as objects because they and the elements that compose them have attributes and operations, can be linked by relationships and have behavior and states. Therefore, this paper proposes a way to represent processes and their elements as objects. This proposal can be used to represent process models benefiting from the object orientation properties and to define tools to automate processes.
An experimental evaluation of SEC+, an enhanced search engine for component-based software development
Authors: Khemakhem Sofien , Drira Khalil , Khemakhem Emna , Jmaiel Mohamed
Published: May 2008

Current approaches for service discovery are inherently restricted to the exact querying. This may provide incomplete answers since queries are often overspecified and may lead to low precision and recall. To alleviate these problems, we achieved an experimental evaluation that uses of the enhanced search engine, SEC+. This engine is based on the subsumption mechanism and a function that calculates the semantic distance. Both the used rate and the non-functional features are considered to filter the selection. We show that such a solution can improve the quality of the search and can enhance both the recall and the precision.
Slicing UML architectural models
Authors: Lallchandani Jaiprakash T , Mall R
Published: May 2008

We propose a technique for static and dynamic slicing of UML models. For a software architecture specified using UML, we first transform the systems' architectural model into an intermediate representation which we have named Model Dependency Graph(MDG). MDG combines information available in various sequence diagrams along with the relevant information available in class diagrams into an integrated UML model. For a given slicing criterion, our slicing algorithm traverses the constructed MDG to identify the relevant model elements. Our algorithm's novelty lies in its computing a slice based on an integrated UML model as against independently processing separate UML diagrams, and determining the implicit interdependencies among the different model elements distributed across various UML diagrams.
Debugging debugged, a metaphysical manifesto of systems integration
Authors: Schaefer Robert
Published: May 2008

Systems designers will most often design to the N-1 criterion whether the designers know they are doing so or not. Systems designed to the N-1 criterion detect, isolate and (possibly) recover from at most one fault at a time. In contrast to the N-1 criterion, systems integrators must fault isolate in the presence of multiple simultaneous faults and in the absence of user guides. The purpose of this paper is to debug the debugging process used by systems integrators. To that end this paper describes the systems integration environment, identifies factors that drive the efficiency of that effort and provides a critique of the historical roots of architectural firewalls. (If there were
no
firewalls everything could theoretically interfere with everything else as only the stricture of time would prevent everything from happening at once. Yet a
perfect
firewall would be an impossibility; a Maxwell's demon of information.) This paper penultimately provides philosophical musings, a self-reflection on meanings uncovered. As this paper has strong non-linear content an attempt has been made for textual constraint by theme:

I. The Systems Integration Environment

II. An Efficient Systems Integration Efficiency Metric

III. Architectural Investigations

IV. the Problem Behind the Problem (tPBtP)
Software test effort estimation
Authors: Kushwaha Dharmender Singh , Misra A. K.
Published: May 2008

Software Testing is an important process of software development that is performed to support and enhance reliability and quality of the software. It consist of estimating testing effort, selecting suitable test team, designing test cases, executing the software with those test cases and examining the results produced by those executions. Studies indicate that more than fifty percent of the cost of software development is devoted to testing, with the percentage for testing critical software being even higher. Unless we can predict the testing effort and find efficient ways to perform effective testing, the percentage of development costs devoted to testing will increase significantly coupled with mismatch in project costing and development schedule. In order to estimate the testing effort, this paper makes an attempt to establish Cognitive Information Complexity Measure (CICM) as an appropriate estimation tool.
A framework for service-oriented computing with C and C++ Web service components
Authors: Engelen Robert A. Van
Published: May 2008

Service-oriented architectures use loosely coupled software
services to support the requirements of business processes and
software users. Several software engineering challenges have to be
overcome to expose legacy C and C++ applications and specialized
system resources as XML-based software services. It is critical to
devise effective bindings between XML and C/C++ data to efficiently
interoperate with other XML-based services. Binding application
data to XML has many software solutions, ranging from generic
document object models to idiosyncratic type mappings. A safe
binding must conform to XML validation constraints, guarantee type
safety, and should preserve the structural integrity of
communicated application data. However, tight XML bindings impose
mapping constraints that can hamper interoperability between
services. This paper presents a framework for constructing loosely
coupled C/C++ services based on a programming model that integrates
XML bindings into the C and C++ syntax. The concepts behind the
bindings are generic, which makes the approach applicable to other
programming languages.
Conformance checking of service behavior
Authors: Aalst Wil M. P. van der , Dumas Marlon , Ouyang Chun , Rozinat Anne , Verbeek Eric
Published: May 2008

A service-oriented system is composed of independent software units, namely services, that interact with one another exclusively through message exchanges. The proper functioning of such system depends on whether or not each individual service behaves as the other services expect it to behave. Since services may be developed and operated independently, it is unrealistic to assume that this is always the case. This article addresses the problem of checking and quantifying how much the actual behavior of a service, as recorded in message logs, conforms to the expected behavior as specified in a process model. We consider the case where the expected behavior is defined using the BPEL industry standard (Business Process Execution Language for Web Services). BPEL process definitions are translated into Petri nets and Petri net-based conformance checking techniques are applied to derive two complementary indicators of conformance:
fitness
and
appropriateness
. The approach has been implemented in a toolset for business process analysis and mining, namely ProM, and has been tested in an environment comprising multiple Oracle BPEL servers.
Adapting Support Vector Machines for F-term-based Classification of Patents
Authors: Li Yaoyong , Bontcheva Kalina
Published: May 2008

Support Vector Machines (SVM) have obtained state-of-the-art results on many applications including document classification. However, previous works on applying SVMs to the F-term patent classification task did not obtain as good results as other learning algorithms such as kNN. This is due to the fact that F-term patent classification is different from conventional document classification in several aspects, mainly because it is a multiclass, multilabel classification problem with semi-structured documents and multi-faceted hierarchical categories.

This article describes our SVM-based system and several techniques we developed successfully to adapt SVM for the specific features of the F-term patent classification task. We evaluate the techniques using the NTCIR-6 F-term classification terms assigned to Japanese patents. Moreover, our system participated in the NTCIR-6 patent classification evaluation and obtained the best results according to two of the three metrics used for task performance evaluation. Following the NTCIR-6 participation, we developed two new techniques, which achieved even better scores using all three NTCIR-6 metrics, effectively outperforming all participating systems. This article presents this new work and the experimental results that demonstrate the benefits of the latest approach.
Intel® Turbo Memory
Authors: Matthews Jeanna , Trika Sanjeev , Hensgen Debra , Coulson Rick , Grimsrud Knut
Published: May 2008

Hard-disk drives are a significant bottleneck to system performance and are also responsible for a significant fraction of total system power consumption. Intel Turbo Memory addresses these problems by adding a new layer to the storage hierarchy: a platform-based and nonvolatile, disk cache. In this article, we describe the hardware and software elements of the Intel Turbo Memory architecture. We show how it supports the new ReadyBoost and ReadyDrive features in Microsoft Vista and describe its key caching algorithms. We present performance, power savings, and wear-leveling results achieved by Intel Turbo Memory.