bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of the copepod Cardiodectes medusaeus on the laternfish Stenobrachius leucopsarus with notes on hypercastration by the hydroid Hydrichthys sp.
Authors: Moser Mike , Taylor Sam
Published: August 2008

Of the laternfish Stenobrachius leucopsarus collected, 2.7% were infected with the copepod Cardiodectes medusaeus. Coincidentally, 2.7% of the copepods were hyperparasitized by a hydroid, Hydrichthys sp. Copepod infection rates increase from Santa Barbara to San Diego, California. This increase may be due to a corresponding increase in the intermediate hosts. A comparison between the size classes of infected and uninfected fish suggests parasite-induced mortality. No relationship between the number of copepods per fish and host length was evident. Copepods were found in multiple infections up to five per host. A gregarious distribution of larval copepods and a nonspecific fibrotic response by the host is suggested. The copepod castrates its host. Multiple infection did not have an additive effect on host egg size nor did the presence of larval nematodes. A comparison of the total caloric content of copepods, infected and uninfected hosts, suggests that the copepod's energy demands on the host are negligible. The copepod appears to promote somatic growth of both female and male hosts.
Spatial relationships and social organization of adult Richardson's ground squirrels
Authors: Michener Gail R.
Published: August 2008

The spacing patterns among a group of adult Spermophilus richardsonii were studied in 1975 and 1976. Major features of the social structure were as follows: relatively uniform dispersion of the Squirrels, overlap of ranges with overlap reaching a maximum after weaning of young and before hibernation, and dominance within the core area (defined as the area in which a squirrel concentrated 50% of its aboveground time). Although there was greater proximity among kin than among nonkin, each adult maintained a separate core area. Adult males played no role in assisting females to rear young, and males were dominant to females only when within their own core areas. Throughout the active season the size of the core area remained relatively constant at about 225 m2 and the average distance between a squirrel and its nearest neighbor remained at about 20–25 m. The core area differed from the usual concept of a territory in that it was characterized by reduced submission rather than increased aggression by the resident toward intruders.
A sexual pheromone in the guppy, Poecilia reticulata (Peters)
Authors: Crow R. T. , Liley N. R.
Published: August 2008

Male guppies, Poecilia reticulata, were attracted to water which had previously held con-specific females and not to control water or water in which males or ovariectomized females had been maintained. Males expressed a preference for water which had held females in the first few days of their gestation cycles over water which held midcycle (gravid) or ovariectomized females. When males were placed with an unresponsive ovariectomized female, addition of water which had contained intact females resulted in a marked increase in courtship directed towards the ovariectomized female. It is hypothesized that the female guppy releases a sexual pheromone which attracts males and stimulates increased male courtship activity. The pheromone appears to be produced in the ovary and secreted by the female at the period of maximum receptivity following parturition.
Demography of a population of Peromyscus leucopus
Authors: Harland Richard M. , Blancher Peter J. , Millar John S.
Published: August 2008

Livetrapping and removal trapping were used to monitor a population of Peromyscus leucopus. Breeding adult arid young of the year females averaged 2.0 and 1.1 litters per year, respectively. Nest mortality was 12–31%, while 58% of the juveniles disappeared within 2 weeks after weaning. The rate of disappearance of juvenile males (77%) was higher than that of juvenile females (44%); the greater loss of males was attributed to mortality. Loss of subadult and adult mice within 2 weeks after initial capture averaged 45 and 51%, respectively, and did not differ between the sexes. However, more males than females were recorded as entering the trapping grids, indicating that males tend to explore new areas more than females. Among resident mice, adult males had the highest rate of disappearance (0.31/week) while adult females had the lowest (0.05/week).
On the life cycle of Lymnaea stagnalis (Pulmonata: Gastropoda) in southwestern Alberta
Authors: Boag D. A. , Pearlstone P. S. M.
Published: August 2008

The life cycle of Lymnaea stagnalis, occupying shallow ponds in southwestern Alberta, was studied from 1973 through 1978. Contrary to most published studies, L. stagnalis does not display an annual life cycle in this habitat. Individual snails did not begin ovipositing until their second or third summer and continued for one or more summers thereafter. Oviposition began in late May, peaked in June, and fell to low levels by August. Hatching occurred in late June through August with young snails attaining a median length of 8 mm by the end of their first summer. Surviving individuals grew rapidly during the early part of their second summer but few individuals reached a size at which they could potentially oviposit (> 30 mm) by the end of the summer. In subsequent summers, snails grew more slowly but oviposited at rates of 5–19 eggs per snail per 48 h as long as they survived. Maximum recorded length was 59 mm in this population, a snail estimated to be entering its seventh summer. Egg production, partly a function of size (age) of mature snails, varied significantly between years with maximum rates in the field being only about half those recorded in a laboratory study where conditions were assumed to be optimal. Survival rates from year to year in the field appeared to be low but cause(s) of death remain essentially unknown.
Jamming bat echolocation: the clicks of arctiid moths
Authors: Fullard James H. , Fenton M. Brock , Simmons James A.
Published: August 2008

Analysis of the clicks produced by some arctiid moths shows that their acoustic characteristics (power spectra and frequency–time structures) are remarkably similar to those of frequency-modulated echolocation calls produced by many bats as they close with their prey. We suspect that the clicks are initially processed as echoes by the auditory systems of these bats and function by interfering with information processing by the bat.
Photic sensitivity of the rhinophore in Aplysia
Authors: Chase Ronald
Published: August 2008

A response to the onset of light was recorded electrophysiologically from the rhinophore nerve of Aplysia californica. Except for the optic nerves, no other peripheral nerve is known to carry photic information to the central nervous system. The result suggests a peripheral location for the extraocular photoreceptors which are known to be capable of controlling the circadian rhythm of locomotor activity.
Satellite species among the holarctic lampreys (Petromyzonidae)
Authors: Vladykov Vadim D. , Kott Edward
Published: August 2008

The new term 'satellite species' is used to replace the less accurate and by now obsolete term 'paired species.' Among lamprey genera a complex of species is usually found: one parasitic or 'stem' species and one or several nonparasitic or 'satellite' species probably derived from it. Among eight genera of holarctic lampreys the interrelation between the number of parasitic (p) and satellite (s) species is as follows: Caspiomyzon, 1p and no s; Petromyzon, 1p and no s; Ichthyomyzon, 3p and 3s; Tetrapleurodon, 1p and 1s; Entosphenus, 3p and 3s; Lampetra in Europe, 1p and 2s, in North America, 1p and 3s; Eudontomyzon in Europe, 1p and 3s, in Asia, 1p and no s; Lethenteron, 1p and 5s. Thus among the six polyspecific genera of the holarctic lampreys, 12 parasitic and 20 satellite species are presently known.
Narcotics in hooded seals (Cystophora cristata): a preliminary report
Authors: Haigh J. C. , Stewart R. E. A.
Published: August 2008

Immobilizing darts containing either of the narcotics fentanyl or etorphine were used on 15 adult hooded seals (Cystophora cristata Erxleben). Of these seals, 13 were successfully tagged. The narcotic antagonist naloxone was administered to all seals. No deaths were recorded and seals which were observed up to 2.5 h after darting behaved normally. Based on visual estimates of weight a satisfactory dose of fentanyl for female hooded seals varied from 0.3 to 0.6 mg/kg.
Indirect body fat manipulation and its effect on hibernation cycles in Citellus lateralis
Authors: Phillips John A.
Published: August 2008

Observations of 92 laboratory born and raised golden-mantled ground squirrels (Citellus lateralis) revealed different growth rates and hibernation cycles between individuals with normal and maloccluded incisors. Weaned maloccluded infants fed at depressed rates and did not accumulate sufficient fat reserves for torpor to occur during their initial overwintering period. These same squirrels, after having had their incisors periodically cut during the following spring, fed at higher rates which led to both an increased peak autumn body fat content and a normalization of hibernation patterns during the second winter. The results suggest that even though the external conditions (photoperiod, temperature, food availability) may be consistent with those required for hibernation, the internal (endogenous) cycling cannot be initiated until sufficient fat levels have been attained.
Distribution and systematic relationships of long-eared Myotis in western Canada
Authors: Jong C. G. van Zyll de
Published: August 2008

Cranial, dental, and external characters of three long-eared bats (Myotis evotis (H. Allen), M. keenii keenii (Merriam), and M. k. septentrionalis (Trouessart)) are analyzed to elucidate their relationship, and an up-to-date summary of their distribution in western Canada is given. Although univariate comparisons showed varying degrees of overlap between any two of the three forms, discriminant function analysis demonstrates the existence of three phenetically distinct forms in western Canada. Further analyses using a ratio diagram and Gower's general similarity coefficient suggest that the eastern long-eared bat represents a distinct species, Myotis septentrionalis (Trouessart).
The Brindley's glands of Rhodnius prolixus. II. Development of the glands during the fifth instar
Authors: Millen B. F. , Barrett F. M. , Lai-Fook J.
Published: August 2008

The histology of the developing Brindley's gland of adult Rhodnius is described. The presumptive epithelium from which the gland will develop is distinguishable on the 4th day after feeding the fifth instar by its intense stainability. The epithelium thickens and lengthens through rapid mitosis resulting in a hollow, thick-walled sac with a short duct. The duct cells become distinguishable first, then glandular epithelium and the saccules and eventually the secretory apparatus of the secretory cells. Mitosis continues, at a decreasing rate, until the 20th day after feeding, somewhat later than it would occur in the surrounding integument. Just prior to ecdysis the type A glandular units are indistinguishable from those of the adult; however, the type B units appear somewhat less completely developed.
A new species of Psammonyx (Crustacea, Amphipoda, Lysianassidae) from the Northwestern Atlantic
Authors: Steele D. H.
Published: August 2008

Psammonyx terranovae n.sp., distinguished from P. nobilis in the lack of ventral setae on the anterior coxal plates, is described and figured in detail. A diagnosis of the genus Psammonyx is presented. Psammonyx terranovae has been found in the intertidal in eastern Newfoundland and in the subtidal, south to the Nova Scotia banks. Its distribution is discussed in relation to its temperature tolerances and its possible past history.
Alarm reaction of Iowa and johnny darters (Etheostoma, Percidae, Pisces) to chemicals from injured conspecifics
Authors: Smith R. J. F.
Published: August 2008

Two species of darter show reduced activity when they detect chemical stimuli from an injured conspecific. This is an appropriate response to a predator warning signal in bottom dwelling fish such as darters. Predation on darters by northern pike releases sufficient chemical stimuli to elicit the reduced activity response. Skin extract is more active than muscle extract in releasing the response. Darter skin contains large, nonmucous secretory cells that may contain the alarm substance. This alarm system in percid fishes appears to be analogous to the better known alarm substance (Schreckstoff) system in ostariophysian fishes.
A method for determining predation rates of macrozooplankton
Authors: Lasenby D. C.
Published: August 2008

A simple method for determining the predation rates of aquatic organisms using a fluorescent dye is outlined. Using Mysis relicta as a predator feeding on macrozooplankton, predation rates ranged from 0.15 to 1.35 animals per hour per mysid for mysids feeding on Diaptomus ashlandi in Kootenay Lake, B.C., to 3.2 animals per hour for mysids feeding on Limnocalanus macrurus from Stony Lake in southern Ontario.
Reduced skin mass: an adaptation for acceleration in some teleost fishes
Authors: Webb P. W. , Skadsen J. M.
Published: August 2008

The hypothesis is presented that skin mass is reduced in fish to improve acceleration performance when fast-starts have a key role in normal activity. The hypothesis was evaluated by measuring skin area, skin mass per unit area, and total skin mass of eight centrarchid species in which the importance of accleration would vary with piscivorous feeding habits. Observations were compared to a reference, taking into account effects of body size and shape. Variation in body area was fairly small. Skin mass per unit area varied by a factor of 2.5. Skin mass, expressed as a percentage of total mass, varied by a factor of 2.4. The more piscivorous species had a lighter skin, which would represent a saving in acceleration resistance of about 5%. Other reductions in mass, usually explained in terms of buoyancy control, will also improve acceleration performance. The variation in skin mass could not be attributed to skin flexibility.
Geographic variation in the effects of temperature and photoperiod on dormancy induction, development time, and predation in the tree-hole mosquito, Toxorhynchites rutilus septentrionalis (Diptera: Culicidae)
Authors: Trimble R. M. , Smith Stephen M.
Published: August 2008

Critical daylength for dormancy induction was similar for laboratory colonies of a northern (Delaware) and a southern (Louisiana) population of Toxorhynchites rutilus septentrionalis. The threshold daylength for dormancy induction was greater in the northern population and the photoperiodic response of the northern population was less affected by high temperature.Although photoperiod did not affect the duration of preadult development in the southern population, the duration of preadult development of the northern population varied in a nonlinear fashion with photoperiod at 27 °C and increased with decreasing daylength at 19 °C.The duration of the third instar was consistently longer in dormant than in active larvae of both populations.The pattern of prey consumption during larval development was similar in dormant and active larvae. Prey consumption terminated 24 h prior to pupation in active larvae; dormant larvae continued to feed at a low rate. Similar numbers of prey were consumed during development by active and dormant larvae.The differences in the biologies of the two populations are discussed in relation to climatological differences in the environments from which each population was derived.
Feeding ecology of a population of nesting yellow warblers
Authors: Busby Daniel G. , Sealy Spencer G.
Published: August 2008

The feeding ecology of a population of nesting yellow warblers (Dendroica petechia) was studied on the Delta Beach Ridge, Manitoba, during the breeding seasons of 1975 and 1976. The total numbers and taxonomic composition of the arthropods available to yellow warblers fluctuated irregularly throughout both breeding seasons. Major changes in the arthropod fauna were due mainly to emergences of adult chironomids. Chironomidae was the most abundant group during both breeding seasons and comprised more than half of the available prey. Arthropods were more numerous in the lower vegetation (0.3–3.0 m) than in the upper vegetation (7.0–9.0 m).Adult chironomids were the chief prey, comprising 58 and 56% of the diet in 1975 and 1976, respectively. The diets of males and females were similar throughout the breeding seasons. The prey consumed by yellow warblers varied temporally and spatially according to the arthropods available; prey was taken in proportion to its availability.Foraging males and females partitioned the habitat with respect to tree species, foraging height, tree section, height of tree selected, foraging methods, and length of movements between foraging bouts.
The ultrastructure of Entamoeba sp. (Laredo isolate). Observations on thin sections and freeze-fracture preparations
Authors: Injeyan Hampik S. , Huebner Erwin
Published: August 2008

The ultrastructure of Entamoeba sp. (Laredo isolate), seen in thin section and in freeze-fracture preparation, indicates that numerous structural features are common to both this E. histolytica-like amoeba and "regular" strains. In addition, heavy meromyosin (HMM)-binding, actin-like microfilaments and intranuclear microtubules and microfilaments are demonstrated for the first time in Entamoeba. Cytoplasmic microtubules were not detected using two different fixation procedures. Replicas of freeze-fractured membrane surfaces revealed particle size and distribution to be heterogeneous on both fracture faces P and E and suggested a similar structural complexity to that previously described for the HK9 strain of E. histolytica. Particle density was determined in plasma and phagosome membranes, and an enrichment of 4.5-fold and 1.6-fold was estimated for the P and E faces, respectively, of phagosome membranes.Nuclear-pore distribution was heterogenous and pore density was highly variable in log-phase cells probably reflecting different cell-cycle stages. Possible differences in nuclear-pore density and distribution relative to published accounts on "regular" strains of E. histolytica are considered.
The karyology of Procerodes lobata (Turbellaria, Tricladida, Maricola)
Authors: Ball Ian R.
Published: August 2008

The diploid complement of the marine planarian Procerodes lobata, collected from the type locality, Corfu, consists of 14 metacentric chromosomes. The karyotype is virtually identical with that of P. littoralis, the only other member of the genus for which detailed karyometric data are available, but it differs from British populations of P. lobata. Early records of P. lobata in North America probably refer to Uteriporus vulgaris, a species whose occurrence in eastern Canada has recently been established. The two species are almost indistinguishable in life but they may be separated karyologically, even when immature.
Onset and rate of drinking in rainbow trout (Salmo gairdneri) following transfer to dilute seawater
Authors: Evans Roger M.
Published: August 2008

Seawater-adapted teleosts drink to offset water loss by osmosis. A direct method of monitoring drinking by implanting a fistula to drain the stomach indicated that rainbow trout began drinking from about 9 to 12 (range 1 to 22) h after being placed in 15‰ sea water. Unlike the Japanese eel (Anguilla japonica). in which the onset of drinking has been shown to be immediate and reflex-like, the onset of drinking in trout appears to occur only after appreciable water has been lost to the medium. The trout resembles the eel in that the capacity to shallow water in the absence of postingestional negative feedback exceeds the rate of drinking required to maintain normal water balance.
Distribution of winter-developing Simuliidae (Diptera), in Eastern Newfoundland
Authors: Colbo M. H.
Published: August 2008

The distribution of larval Prosimulium mixtum, Stegopterna mutata, Cnephia ornithophilia, and Simulium vittatum are discussed in relation to temperature, pH, stream order, stream origin, current velocity, and time. The influence of microcurrents and larval density on P. mixtum and St. mutata are discussed. The distribution along the stream bed changed with time. The data suggested that with these two species the spacing of the larvae and changes in microcurrent preferences displaced the population downstream as development proceeded, although other factors may play a role in the displacement. The distribution of the other two species was closely tied to the oviposition sites at lake outlets and showed little displacement with time. It is also suggested that competition between simuliids occurs although further research will be required.
Bird communities and the structure of urban habitats
Authors: Lancaster Richard K. , Rees William E.
Published: August 2008

We examine relationships between bird communities and habitat structure along a gradient of urban habitats in Vancouver, B.C. Bird species diversity, evenness of species abundances, and numbers of species increase with foliage height diversity and total vegetation as they do in "natural" habitats. Few ecological niches for birds are enhanced by man-made features of the urban environment. Bird species diversity is actually inversely related to the apparent increase in habitat diversity contributed by elements of the built environment. While limited to a few niches, food provided by man has a major effect on density and distribution of birds in urban areas. Therefore, despite declining natural productivity and species diversity, total bird density does not decline across the Vancouver urban gradient. Overall, available habitat and food in highly urbanized environments strongly favour the few cavity-nesting, ground-feeding graminivorous or omnivorous bird species that have already come to dominate.
Distribution and feeding records of the caddisflies (Trichoptera) of the Matamek River region, Quebec
Authors: Williams Nancy E. , Williams D. Dudley
Published: August 2008

Records of immature and mature stages of caddisflies found in lentic and lotic habitats or the Matamek River region of Quebec are presented. The species are related to their typical habitats and feeding preferences in this part of the boreal forest biome. Net-spinning families dominated the caddisfly fauna of the Matamek River and their populations were sustained primarily by plankton drifting out of Matamek Lake. Net spinners were rarer in the other two large rivers sampled and this is attributed to the lack of head water lakes together with low levels of suspended detritus. The small streams of the area are categorized into Neophylax, Chyranda, and Limnephilus types based on genera restricted to each: the members of these communities were primarily bottom foragers. Phryganeids dominated the four lakes studied, while the ponds contained only limnephilids.
Reproduction of the female red-backed vole, Clethrionomys gapperi (Vigors), in the laboratory
Authors: Langford P. E. , Clulow F. V.
Published: August 2008

Female red-backed voles, Clethrionomys gapperi (Vigors), bred from wild stock trapped near Sudbury, Ontario, and maintained at 22 ± 2 °C and 18 h light and 6 h dark in the laboratory, showed no cyclic changes in their vaginal smear patterns. Copulation was followed by the development of corpora lutea in the ovaries, and it is concluded that the animal is an induced ovulator under the conditions of the experiment. The females released 5.1 ± 0.5 ova per ovulation, the gestation period was 18.5 ± 0.5 days, and litter size was 4.6 ± 0.2 pups in the laboratory.
A lateral plate dine, sexual dimorphism, and phenotypic variation in the black-spotted stickleback, Gasterosteus wheatlandi
Authors: Sargent R. Craig , Bell Michael A. , Krueger William H. , Baumgartner Jeffrey V.
Published: August 2008

We examined samples of Gasterosteus wheatlandi collected in coastal marine waters from northern Maine to southern New York. Gasterosteus wheatlandi exhibited remarkable variation in lateral plate number, including phenotypes similar to the low, partial, and complete morphs described in Gasterosteus aculeatus. Partials and completes, however, seemed to represent a continuum, thus we could only recognize two discreet phenotypes, low and partial–complete. The low phenotype predominated strongly north of Cape Cod and was rare or absent south of it. Within both phenotypes mean plate number increased toward the southern end of the range; thus, both lateral plate number and lateral plate phenotype exhibited a pronounced step-cline. We found significant sexual dimorphism among localities for total lateral plates and for a suite of other morphological characters. Both sexes had higher mean vertebral counts north of Cape Cod, a trend which ran counter to the cline in lateral plates. The pervasive sexual dimorphism in G. wheatlandi, and the fact that latitudinal variation in lateral plates ran counter to the trend in G. aculeatus, suggest that different processes may be responsible for maintaining the geographical variation in these two species.
The foraging behavior of a generalist feeder, the central mudminnow (Umbra limi)
Authors: Paszkowski Cynthia A.
Published: August 2008

The natural diet and habitat use patterns of the central mudminnow suggest that it is a generalist feeder capable of using a variety of foraging sites. Laboratory experiments were performed to measure the efficiency of this species as it foraged from four sites: open bottom substrate, the water column, submerged macrophytes, and the water's surface. Midwater, macrophyte, and surface foraging rates did not differ significantly from each other, whereas bottom rates were somewhat lower. Foraging success was also unaffected by small changes in the experimental environment. Significant variation existed among the foraging patterns of individual fish. The observed versatility of the mudminnow's foraging behavior could aid this species in exploiting physically severe, variable, unproductive, and (or) species-poor environments.
Coccidians in the liver and testis of the herring Clupea harengus L.
Authors: Morrison Carol M. , Hawkins William E.
Published: August 2008

The coccidians Goussia clupearum from liver and Eimeria sardinae from testis of herring caught in waters near Nova Scotia were studied by light and electron microscopy. Unsporulated and sporulatcd oocysts were the most frequently encountered stages. Oocyst walls of both species were thin and closely apposed to the host cell. At least a part of the oocyst wall appeared to serve also as the boundary of the parasitophorous vacuole. In G. clupearum, membranes lining parasitophorous vacuoles of various stages seemed to be involved in host–parasite nutrient transfer. Wall-forming bodies were found in the sporont of E. sardinae, and presumptive wall-forming bodies were found in the sporont of G. clupearum. The sporocyst wall of G. clupearum appeared to consist of two valves. The wall had a thick transversely striated inner layer and a thin outer layer consisting of several closely apposed membranes. The lamellated membranes extended from the outer layer. The sporocyst wall of E. sardinae was thin and consisted of three loosely organized membranes. The sporocysts of neither species had a Stieda body. Goussia clupearum, which often elicited an intense host reaction, infected 85% of mature fish whereas E. sardinae infected 90–100%. Replacement of hepatic tissue by G. clupearum could stress fish and replacement of testicular tissue by E. sardinae could reduce sperm production, thus detrimentally affecting herring stocks.
JAMMING TRANSITION IN EXTENDED COOPERATIVE DRIVING LATTICE HYDRODYNAMIC MODELS INCLUDING BACKWARD-LOOKING EFFECT ON TRAFFIC FLOW
Authors: LI XINGLI , LI ZHIPENG , HAN XIANGLIN , DAI SHIQIANG
Published: August 2008

Two extended cooperative driving lattice hydrodynamic models are proposed by incorporating the intelligent transportation system and the backward-looking effect in traffic flow under certain conditions. They are the lattice versions of the hydrodynamic model of traffic: one (model A) is described by the differential-difference equation where time is a continuous variable and space is a discrete variable, and the other (model B) is the difference-difference equation in which both time and space variables are discrete. In light of the real traffic situations, the appropriate forward and backward optimal velocity functions are selected, respectively. Then the stability conditions for the two models are investigated with the linear stability theory and it is found that the new consideration leads to the improvement of the stability of traffic flow. The modified Korteweg-de Vries equations (the mKdV equation, for short) near the critical point are derived by using the nonlinear perturbation method to show that the traffic jam could be described by the kink-antikink soliton solutions for the mKdV equations. Moreover, the anisotropy of traffic flow is further discussed through examining the negative propagation velocity as the effect of following vehicle is involved.
SPECTRAL ANALYSIS OF CURRENT-NOISE DATA FOR BILAYER LIPID MEMBRANE
Authors: GHOSH DIPANKAR , DE SHARMILA , NANDY PAPIYA
Published: August 2008

We report the spectral analysis of current-noise data obtained under voltage clamp condition in bilayer lipid membrane, using Lomb Scargle Periodogram. Such spectral analysis shows evidence of crossover from an uncorrelated phenomenon towards a state of long range correlation in time and space with the increase of applied bias. Based on these observations a probable mechanism of transmembrane charge conduction has been outlined in the light of self-organized criticality.
RANDOM-WALK TYPE MODEL WITH FAT TAILS FOR FINANCIAL MARKETS
Authors: MATUTTIS HANS-GEORS
Published: August 2008

Starting from the random-walk model, practices of financial markets are included into the random-walk so that fat tail distributions like those in the high frequency data of the SP500 index are reproduced, though the individual mechanisms are modeled by normally distributed data. The incorporation of local correlation narrows the distribution for "frequent" events, whereas global correlations due to technical analysis leads to fat tails. Delay of market transactions in the trading process shifts the fat tail probabilities downwards. Such an inclusion of reactions to market fluctuations leads to mini-trends which are distributed with unit variance.
THE FORMATION OF ULTRAFINE FERRITE THROUGH STATIC TRANSFORMATION IN LOW CARBON STEELS
Authors: ADACHI Y. , WAKITA M. , BELADI H. , HODGSON P. D.
Published: August 2008

A novel approach was used to produce an ultrafine grain structure in low carbon steels with a wide range of hardenability. This included warm deformation of supercooled austenite followed by reheating in the austenite region and cooling (RHA). The ultrafine ferrite structure was independent of steel composition. However, the mechanism of ferrite refinement changed with the steel quench hardenability. In a relatively low hardenable steel, the ultrafine structure was produced through dynamic strain induced transformation, whereas the ferrite refinement was formed by static transformation in steels with high quench hardenability. The use of a model Ni -30 Fe austenitic alloy revealed that the deformation temperature has a strong effect on the nature of the intragranular defects. There was a transition temperature below which the cell dislocation structure changed to laminar microbands. It appears that the extreme refinement of ferrite is due to the formation of extensive high angle intragranular defects at these low deformation temperature that then act as sites for static transformation.
SUPERPLASTIC INDENTATION CREEP OF FINE-GRAINED Sn-1% Bi ALLOY
Authors: MAHMUDI REZA , MHJOUBI H. , MEHRARAM P.
Published: August 2008

Creep and superplasticity of the fine-grained Sn -1wt.% Bi alloy, processed by conventional rolling (CNR), cryorolling (CRR) and equal channel angular pressing (ECAP) routes, were investigated by indentation testing at room temperature (T > 0.6T m ). Based on the steady-state power law creep relationship, the stress exponents of 4.1, 2.8 and 2.5 were obtained for the CNR, CRR and ECAP routes, respectively. The corresponding strain rate sensitivity (SRS) indices of 0.24, 0.36 and 0.40, corresponding respectively to the grain sizes of 2.8, 2.1 and 1.2 μm, indicate that the materials processed by ECAP and CRR exhibit superplastic deformation behavior for which, grain boundary sliding is the possible creep mechanism.
CHARACTERIZATION OF NANOSTRUCTURED ALUMINUM SHEETS PROCESSED BY ACCUMULATIVE ROLL BONDING
Authors: PIRGAZI HADI , AKBARZADEH ABBAS
Published: August 2008

An ultrafine grained (UFG) aluminum sheet was produced using severe plastic deformation (SPD) by a process known as accumulative roll bonding (ARB). Electron Back Scattered Diffraction (EBSD) method and Transmission Electron Microscopy (TEM) were utilized for characterization of the subgrain and grain structures of the processed sheets. The results indicate that different mechanisms at different levels of strain lead to the gradual evolution of ultrafine or nanocrystalline grains. Grain fragmentation as well as the development of subgrains are the major mechanisms at the early stages of ARB. Strain induced transformation of low angle to high angle grain boundaries and formation of a thin lamellar structure occur at the medium level of strain. Finally, the progressive fragmentation of these thin lamellar structures into more equi-axed grains is the dominant mechanism at relatively high strains which results in grain size reduction to submicron scale.
WEAR PROPERTIES OF 1100 AL ALLOY PRODUCED BY ACCUMULATIVE ROLL BONDING
Authors: TALACHI A. KAZEMI , EIZADJOU M. , MANESH H. DANESH , JANGHORBAN K.
Published: August 2008

Ultra-fine grained 1100 Al alloy was successfully produced by accumulative roll bonding (ARB) process. TEM investigation and SAD patterns showed that, after eight cycles of ARB, sheets were found to contain ultra-fine grains with high angle grain boundaries. The mechanical properties of the ARB processed (ARBed) 1100 aluminum alloy increased with increasing the number of ARB cycles. The elongation dropped abruptly at the first cycles. Wear properties were investigated using a pin on disk wear machine at ambient environment. Contrary to an expectation, the wear resistance of the ARBed Al alloy was less than the non-processed Al alloy. Morphologies of worn surfaces were studied by scanning electron microscope (SEM).
THE EFFECTS OF ACCUMULATIVE ROLL BONDING PROCESS ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF IF STEEL
Authors: TAMIMI SAEED , KETABCHI MOSTAFA , PARVIN NADER
Published: August 2008

This work aims to investigate whether accumulative roll bonding (ARB) is an effective grain refinement technique for ultra-low-carbon steel strips containing 0.004% C. For this purpose, a number of ARB processes were performed at 500 °C, with 50% reduction in area of each rolling pass. It was found that both the ultimate grain size achieved, as well as the degree of bonding, depend on number of rolling pass and reduction of area as a whole. The mean grain size was obtained using AFM was about 130nm. The mechanical properties after rolling and cooling were obtained. Also, the fracture surfaces were studied by Scanning Electron Microscopy (SEM). It was concluded that metal's tensile strengths increased by 334% while the ductility dropped from a prerolled value of 50.5% to 2.6%. Effect of wire brushing on samples observed too. It increased on the wire brushed sheet for 7 HV. The rolling process was stopped when cracking of the edges became pronounced.
ULTRAFINE GRAINED 6082 ALUMINUM ALLOY FABRICATED BY FRICTION STIR PROCESSING
Authors: SHAFIEI ZARGHANI A. , KASHANI BOZORG S. F. , ZAREI-HANZAKI A.
Published: August 2008

Recently friction stir processing (FSP) has emerged as an effective tool for enhancing metal properties through microstructure modification. FSP is a solid-state process where the material within the processed zone undergoes intense plastic deformation resulting in dynamically recrystallized grain structure. This research demonstrates the use of FSP for creating ultrafine grained materials through severe plastic deformation. FSP was applied to extruded 6082-T4 aluminum alloy to produce ultrafine grained microstructure with grain sized from 0.5 to 3μm. The hardness of the FS processed 6082 aluminum alloy increased significantly with decreased tool rotation speed.
ULTRAFINE GRAINED AND NANOSTRUCTURED MATERIALS FOR ADVANCED ENERGY APPLICATIONS
Authors: POLITIS CONSTANTIN
Published: August 2008

The understanding of nanoscale interactions of nuclear materials will help to mastering the complex behavior of actinides and of fission products, and the interfacial behavior of fuel-cladding under extreme conditions. Ultrafine grained and nanostructured engineering materials are also suggested as protective armors on the plasma-facing first wall of D-T fusion power plants. We review the constitution and preparation by arc-melting and ball milling of ultrafine grained materials for the advanced nuclear reactor fuels UC, UC-W, UN, UN- Mo , and UN-W. We report also the preparation of the first wall armour materials nano-W, nano W-Y alloys, nano-graphite, and nano- B4C by high energy ball milling and their characterization by metallography, XRD, DSC and HRTEM.
DENSIFICATION AND GRAIN GROWTH OF NANOCRYSTALLINE NIAL POWDER DURING PRESSURELESS SINTERING
Authors: MASHREGHY A. , MOSHKSAR M. M.
Published: August 2008

Nanocrystalline NiAl powder was prepared by mechanical alloying. The prepared powder was cold compacted and sintered at different temperatures and times. The crystallite size of green and sintered compacts was estimated from X-Ray Diffraction peak profile analysis. Thereafter, the Generalized Parabolic Grain Growth model and Master Sintering Curve concept based on Combined Stage Sintering model were employed to investigate the grain growth and densification behavior of nanocrystalline NiAl powder during sintering, respectively. The results of modeling were in a very good agreement to that of experiment. Finally, by comparing the modeling results the sintering parameters were optimized.
MECHANOCHEMICAL SYNTHESIS OF TIAL3/AL2O3 ULTRAFINE GRAINED COMPOSITE
Authors: VERDIAN M. M. , HESHMATI-MANESH S.
Published: August 2008

The TiAl 3/ Al 2 O 3 metal-ceramic composite was synthesized using high energy ball milling, powder compaction and thermal treatment. Micron sized powders of titanium oxide ( TiO 2) and aluminum were subjected to high energy ball milling under an argon protected atmosphere. Milling of this powder mixture although reduced crystallites sizes to a nano scale, did not result in a reaction between the reactants. Further compaction of the milled powder and annealing, paved the way to a reduction reaction and led to the formation of an ultrafine grained composite structure. The reaction appeared to proceed through two-steps. Titanium oxide was first reduced to TiO and later on, TiO was reduced to Ti . The resulting Ti was alloyed with extra Al to produce TiAl 3 intermetallic in which alumina particles were dispersed. Also, mechanical activation was found to reduce the reaction temperature between Al and TiO 2. The morphology and phase composition of the milling products were evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis.
ROLE OF PROCESS CONTROL AGENT ON MECHANICAL ALLOYING OF NANO STRUCTURED TiAl-BASED ALLOY
Authors: BAHMANPOUR H. , HESHMATI-MANESH S.
Published: August 2008

High energy ball milling was performed on a mixture of titanium and aluminum elemental powders with a composition of Ti -48(at.%) Al . Stearic acid was added to this powder mixture as a process control agent (PCA) to study its effect on the microstructure evolution and crystallite size of the milled powder after various milling times. Phase compositions and morphology of the milled powders were evaluated using X-ray diffraction and scanning electron microscopy. Crystallite sizes of milled powders were determined by Cauchy-Gaussian approach using XRD profiles. It was shown that addition of 1wt.% of stearic acid not only minimizes the adhesion of milling product to the vial and balls, but also reduces its crystallite sizes. It has also a marked effect on the morphology of the final product.
AN ELECTROCHEMICAL INVESTIGATION OF NANOCRYSTALLINE Mg2Ni0.75Nb0.25 COMPOUND SYNTHESIZED BY MECHANICAL ALLOYING
Authors: MOHRI M. , KASHANI BOZORG S. F.
Published: August 2008

The effects of mechanical alloying on the microstructure of binary and ternary powder mixtures with stoichiometric compositions of Mg 2 Ni and Mg 2 Ni 0.75 Nb 0.25 were studied, respectively. Also, the electrode properties of the milled products were investigated in 6M KOH solution. X-ray diffraction and scanning electron microscopy of the milled products showed the formation of Mg 2 Ni -based nanocrystallites after 15 and 10h of milling using the initial binary and ternary mixtures, respectively. It was found that partial substitution of Nb for Ni has beneficial effect on the formation kinetic of nanocrystalline Mg 2 Ni . Longer milling times resulted in the formation of an amorphous phase. A relatively high discharge capacity of 350mAhg-1 was measured for the electrode made up of the ternary milled product after 20h. Also, the ternary milled product showed longer discharge life. This ternary electrode showed a microstructure consisting of Mg 2 Ni nanocrystallites and an amorphous phase. Nb substitution for Ni was found to be beneficial to electrode properties of the milled products.
SYNTHESIS OF NANO-STRUCTURED MULLITE BY SOL-GEL METHOD WITH INTERMEDIATE MECHANICAL ACTIVATION
Authors: MOALLEMI-NEJAD M. , HESHMATI-MANESH S. , ATAIE A.
Published: August 2008

Nano-sized mullite was synthesized by mechano-chemical, sol-gel/milling, process. Aluminum nitrate and tetraethyl ortho silicate were used as precursors to prepare the single phase gel. The prepared gel was subjected to intense mechanical activation using a planetary ball mill prior to annealing. DTA/TGA results showed that mullitization temperature significantly decreases due to mechanical activation as mullite starts to form at 1094°C in unmilled sample whereas intermediate milling for 20 hours decreases this temperature to 988°C. Also, mullite formation occurs at 1021 and 1003°C for samples milled for 5 and 10 hours, respectively. SEM results showed that the morphology of the products was altered by the intermediate mechanical activation. Calculation of the mullite crystallite sizes indicated that they were indeed in nano scale and this result was confirmed by TEM investigations which shows the mean crystallite size of 70 nm.
EFFECT OF MILLING TIME ON MECHANOCHEMICAL SYNTHESIS OF TiO2 NANOPARTICLES
Authors: SALARI MARYAM , REZAEE MASIH , MOUSAVI KOIE S. M. , MARASHI P. , ABOUTALEBI H.
Published: August 2008

Titanium dioxide nanoparticles have great potential for use in photocatalytic applications, cosmetics, white pigments and so on. In this paper, the effect of milling time on particle size, morphology and phase composition of TiO 2 nanoparticles, prepared by mechanochemical method, was investigated by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). TiO 2 nanoparticles were prepared by the use of high energy ball milling of titanyl sulphate ( TiOSO 4) and NaCl powders as the starting mixture in different milling durations. The milled powder was annealed at 700°C for 30 min. The NaCl powder, used as the diluent phase, was removed by washing the annealed powder with distilled water. It was found that with increasing milling time, decrease in the size of equiaxed spherical particles and increase in temperature of anatase to rutile transformation ( A → R ) can be observed.
FORMATION MECHANISM AND CHARACTERIZATION OF NANOCRYSTALLINE CU SYNTHESIZED BY MECHANO-CHEMICAL METHOD
Authors: SHEIBANI S. , ATAIE A. , HESHMATI-MANESH S.
Published: August 2008

Nanocrystalline Cu particles were prepared by mechanochemical reduction of cuprite ( CU 2 O ) with graphite in a high-energy ball mill. In order to gain an understanding into the possible mechanisms, the kinetic of the process was investigated using Johnson-Mehl-Avrami (JMA) model. It can be seen that theoretical calculation agrees well with experimental data. It was found that the most important effect of mechanical activation is the formation of the lattice defects and grain boundaries in addition to activated fresh surface areas during milling, which promote the reduction process. The Cu nanopowder was characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD and TEM results showed the nano-structure nature of the product processed under the synthesis conditions; the crystallite size was measured almost 30 nm in the 30 h milled powders.
ELECTROPHORETIC DEPOSITION OF TITANIUM DIOXIDE NANO-POWDERS FILMS IN ISOPROPANOL AS A SOLVENT
Authors: GHORBANI M. , AFSHAR M. ROUSHAN
Published: August 2008

In this study, titanium dioxide nano powders were electrophoretically deposited on the stainless steel in Isopropanol and Triethanolamine as a solvent and dispersant, respectively. The effects of deposition parameters including deposition voltage (5 to 20 V) and deposition time (5 to 60 s) on the microstructure and surface topography were examined by scanning electron microscope (SEM) and scanning probe microscope (SPM), respectively. In addition, the effects of these deposition parameters on packing density were investigated. This research revealed that substrate surface is fully covered with increasing deposition voltage and deposition time. Therefore packing density of deposited films is strongly dependent on the deposition parameters and reached its highest value at 20 V and 60 s. In addition, results show that surface roughness is increased by increasing the deposition voltage and deposition time.
CHARACTERISTICS OF NANOCRYSTALLINE COMPOUND LAYER OF ELECTROPLATED HARD CHROMIUM COATINGS AFTER PULSED PLASMA ELECTROLYTIC NITROCARBURIZING
Authors: MOFIDI S. H. HEDAIAT , SABOUR A. , SHAHRABI T. , KHAZRAYIE M. ALIOF
Published: August 2008

Electrolytic Plasma nitrocarburizing was carried out on the hard chromium coating deposited in SM45C mild carbon steel substrate by electroplating in two different times and voltages. The electroplated samples were connected cathodically to a high-current pulsed power supply and biased with a negative voltage of 400 V. The treatment times were 5 and 60 minutes. A 5-μm thick layer was formed on the surface of Cr coating with microhardness of about 950- 1200 HV0.1. The microstructure of the treated layers depends strongly on the treatment time length. The corrosion properties of the treated layers depend on microstructure and can be improved, especially if a thin and dense complex layer is produced at the surface.
ELECTROCHEMICAL AND PHYSICAL PROPERTIES OF NANOCRYSTALLINE COPPER DEPOSITS PRODUCED BY PULSE ELECTRODEPOSITION
Authors: SAREMI MOHSEN , ABOUIE MARYAM , VAGHAR R.
Published: August 2008

This paper reports our recent studies on nanocrystalline layer of copper produced using pulse plating method. The grain size of the copper layer was about 60 nm. Electrochemical and physical Properties of the nanocrystalline surface were investigated using Potentiostatic scanning and Impedance measurements. Microcrystalline copper deposits were also produced by direct current electrodeposition processes and compared with pulse plated ones. Effects of deposition parameters, such as the peak Density, frequency, current-on time and current-off time of the pulse current (PC), on the grain size were investigated for the purpose of process optimization. It was demonstrated that the nanocrystalline film was markedly superior to regularly grained film made by direct current (DC) plating; the nanocrystalline deposit shows higher electrochemical stability and lower electrical resistance.