bluuebunny/crossref_metadata_2025 huggingface dataset:
Antibiotic Resistance in
Haemophilus influenzae
Decreased, except for β-Lactamase-Negative Amoxicillin-Resistant Isolates, in Parallel with Community Antibiotic Consumption in Spain from 1997 to 2007
Authors: García-Cobos Silvia , Campos José , Cercenado Emilia , Román Federico , Lázaro Edurne , Pérez-Vázquez María , de Abajo Francisco , Oteo Jesús
Published: May 2008

The susceptibility to 14 antimicrobial agents and the mechanisms of aminopenicillin resistance were studied in 197 clinical isolates of
Haemophilus influenzae
—109 isolated in 2007 (study group) and 88 isolated in 1997 (control group). Community antibiotic consumption trends were also examined.
H. influenzae
strains were consecutively isolated from the same geographic area, mostly from respiratory specimens from children and adults. Overall, amoxicillin resistance decreased by 8.4% (from 38.6 to 30.2%). β-Lactamase production decreased by 15.6% (from 33 to 17.4%,
P
= 0.01), but amoxicillin resistance without β-lactamase production increased by 7.1% (from 5.7 to 12.8%). All β-lactamase-positive isolates were TEM-1, but five different promoter regions were identified, with Pdel being the most prevalent in both years, and Prpt being associated with the highest amoxicillin resistance. A new promoter consisting of a double repeat of 54 bp was detected. Community consumption of most antibiotics decreased, as did the geometric means of their MICs, but amoxicillin-clavulanic acid and azithromycin consumption increased by ca. 60%. For amoxicillin-clavulanic acid, a 14.2% increase in the population with an MIC of 2 to 4 μg/ml (
P
= 0.02) was observed; for azithromycin, a 21.2% increase in the population with an MIC of 2 to 8 μg/ml (
P
= 0.0005) was observed. In both periods, the most common gBLNAR (i.e.,
H. influenzae
isolates with mutations in the
ftsI
gene as previously defined) patterns were IIc and IIb. Community consumption of trimethoprim-sulfamethoxazole decreased by 54%, while resistance decreased from 50 to 34.9% (
P
= 0.04). Antibiotic resistance in
H. influenzae
decreased in Spain from 1997 to 2007, but surveillance should be maintained since new forms of resistances may be developing.
Oral Vaccination against Bubonic Plague Using a Live AvirulentYersinia pseudotuberculosisStrain
Authors: Blisnick Thierry , Ave Patrick , Huerre Michel , Carniel Elisabeth , Demeure Christian E.
Published: May 2008

We evaluated the possibility of usingYersinia pseudotuberculosisas a live vaccine against plague because it shares high genetic identity withY. pestiswhile being much less virulent, genetically much more stable, and deliverable orally. A total of 41Y. pseudotuberculosisstrains were screened by PCR for the absence of the high pathogenicity island, the superantigens YPM, and the type IV pilus and the presence of the pYV virulence plasmid. One strain (IP32680) fulfilled these criteria. This strain was avirulent in mice upon intragastric or subcutaneous inoculation and persisted for 2 months in the mouse intestine without clinical signs of disease. IP32680 reached the mesenteric lymph nodes, spleen, and liver without causing major histological lesions and was cleared after 13 days. The antibodies produced in vaccinated animals recognized bothY. pseudotuberculosisandY. pestisantigens efficiently. After a subcutaneous challenge withY. pestisCO92, bacteria were found in low amounts in the organs and rarely in the blood of vaccinated animals. One oral IP32680 inoculation protected 75% of the mice, and two inoculations induced much higher antibody titers and protected 88% of the mice. Our results thus validate the concept that an attenuatedY. pseudotuberculosisstrain can be an efficient, inexpensive, safe, and easy-to-produce live vaccine for oral immunization against bubonic plague.
Hypercholesterolemia Impairs Immunity to Tuberculosis
Authors: Martens Gregory W. , Arikan Meltem Cevik , Lee Jinhee , Ren Fucheng , Vallerskog Therese , Kornfeld Hardy
Published: May 2008

We demonstrate that apolipoprotein E -deficient (
ApoE
−/
−
) mice are highly susceptible to tuberculosis and that their susceptibility depends on the severity of hypercholesterolemia. Wild-type (WT) mice and
ApoE
−/
−
mice fed a low-cholesterol (LC) or high-cholesterol (HC) diet were infected with ∼50 CFU
Mycobacterium tuberculosis
Erdman by aerosol.
ApoE
−/
−
LC mice were modestly more susceptible to tuberculosis than WT LC mice. In contrast,
ApoE
−/
−
HC mice were extremely susceptible, as evidenced by 100% mortality after 4 weeks with tuberculosis. The lung pathology of
ApoE
−/
−
HC mice was remarkable for giant abscess-like lesions, massive infiltration by granulocytes, elevated inflammatory cytokine production, and a mean bacterial load ∼2 log units higher than that of WT HC mice. Compared to WT HC mice, the gamma interferon response of splenocytes restimulated ex vivo with
M. tuberculosis
culture filtrate protein was delayed in
ApoE
−/
−
HC mice, and they failed to control
M. tuberculosis
growth in the lung. OT-II cells adoptively transferred into uninfected
ApoE
−/
−
HC mice had a weak proliferative response to their antigen, indicating impaired priming of the adaptive immune response. Our studies show that
ApoE
−/
−
deficiency is associated with delayed expression of adaptive immunity to tuberculosis caused by defective priming of the adaptive immune response and that elevated serum cholesterol is responsible for this effect.
The Terminal Sialic Acid of Glycoconjugates on the Surface of Intestinal Epithelial Cells Activates Excystation of
Cryptosporidium parvum
Authors: Choudhry Naheed , Bajaj-Elliott Mona , McDonald Vincent
Published: May 2008

The apicomplexan
Cryptosporidium parvum
reproduces in the intestinal epithelial cells of many mammalian species and is an agent of the important diarrheal disease cryptosporidiosis. Infection is transmitted fecal-orally by oocysts that pass through the stomach and excystation occurs in the intestine, releasing four invasive sporozoites. Some factors involved in inducing excystation have been identified, but the role of the enterocyte is not known. The present study showed that excystation was accelerated in the presence of the three enterocyte cell lines Caco2, HCT8, and CMT93. Epithelial cell lines derived from other organs, including the stomach, had no effect on excystation. No evidence was obtained that factors secreted from enterocytes induced excystation, but an enterocyte membrane preparation promoted sporozoite release. In addition, modification of the enterocyte surface by trypsin digestion or paraformaldehyde fixation abrogated the ability to enhance excystation. Importantly, the level of excystation in the presence of enterocytes decreased after treatment with either sialidase/neuraminidase to deplete surface terminal sialic acid or with lectins that specifically bind to sialic acid. Furthermore, the addition of sialic acid to oocysts in the absence of cells increased the level of excystation. These results suggest that sialic acid on the surface of enterocytes may provide an important local signal for the excystation of
C. parvum
sporozoites.
Effect of Discharge Rate on Biotic and Abiotic Chemical Flux in an Acidified Stream
Authors: Hall Ronald J. , Likens Gene E.
Published: May 2008

Acidity of Norris Brook, a mountain stream in the Hubbard Brook Experimental Forest, New Hampshire, was manipulated to estimate the effects on biotic and abiotic chemical flux during high (spring) and low (summer) discharge periods. Sulfuric acid was added to maintain the pH near 4.0 from April to September 1977. Al, Ca, Mg, and K were mobilized into streamwater with concentrations progressively increasing downstream, as a result of increased H+concentration. Concentrations of Na and NO3were not affected by the acidification. Dissolved organic carbon concentrations decreased downstream during periods of high discharge but did not change significantly during low flow. During storms, Al, Ca, Mg, and K increased in concentration below the acid addition as well as in the reference reach of the stream. Net flux of dissolved Al in streamwater was significant during both high- and low-discharge periods. Net flux of Al in invertebrate biomass was significantly increased only during high flow but was insignificant when compared with the amount in the dissolved form. Net flux of N was significant only in biomass of invertebrates at high discharge. Significance of flux of N in biota was totally overshadowed by transport (flux) of dissolved N (as NO3and NH4) during storms.
Multivariate Morphometric Variability in Pacific Salmon: Technical Demonstration
Authors: Winans Gary A.
Published: May 2008

A computer oriented approach to the collection and analysis of morphometric characteristics in juvenile chinook salmon (Oncorhynchus tshawytscha) is described. A three-step data collection and storage method is used whereby X–Y coordinate data for relevant morphological features on a body form are collected with a digitizing pad and used to calculate morphometric characters. To test this method, I calculated two morphometric data sets, a conventional and a truss network, and compared them by multivariate analysis in a preliminary study of growth and development in one hatchery stock of fish, and in a survey of population differences in three naturally occurring populations of chinook salmon. Technical advantages of using a digitizing pad for collecting morphometric data are demonstrated. Hatchery-reared chinook salmon showed marked changes in body shape during the period of spring smoltification when marked changes in condition factor occurred. Multivariate differences were discerned among the three Oregon coastal stocks. Truss data provided more specific information concerning shape changes in the study of early development and produced greater between-group differences in the geographic survey. The results of these preliminary analyses can be applied to problems of identifying smolt status in hatchery fish and stock origin in mixed-stock fisheries.
Insights from the Markets for Limited Entry Permits in Alaska
Authors: Karpoff Jonathan M.
Published: May 2008

Under Alaska's entry limitation program, transferable permits convey fishing rights. Information from permit markets is used to study several key issues regarding the behavior of fishermen and the effects of fishery management policy. I conclude that (1) expectations of future fishing incomes are the primary determinants of permit prices, (2) Alaska Department of Fish and Game forecasts of fish recruitment are capitalized in permit values, (3) a state program that provides low-interest loan money to some purchasers of permits has coincided with a significant increase in permit prices, (4) the "average memory" of fishermen in projecting future incomes is about 2.5 yr, and (5) it is possible to infer the rate at which the markets discount future fishing income flows.
Sites of Uptake of Geosmin, a Cause of Earthy-Flavor, in Rainbow Trout (Salmo gairdneri)
Authors: From Jon , Hørlyck Viggo
Published: May 2008

To identify absorption sites of earthy-flavor in rainbow trout (Salmo gairdneri), we placed the geosmin-producing algae Symploca muscorum on four locations. We showed that the most rapid absorption occurred in the gills (6 min), followed by the skin (1.5 h), small intestine (4 h), and stomach (7 h). In trout farming, if ingestion of algae is reduced, then the most significant route of uptake of geosmin will be through the gills and skin.
Selective Predation for Vertebral Number of Young Sticklebacks, Gasterosteus aculeatus
Authors: Swain D. P. , Lindsey C. C.
Published: May 2008

Young laboratory-reared threespine sticklebacks, Gasterosteus aculeatus, were exposed to predation by pumpkinseed sunfish, Lepomis gibbosus, until 50–65% of the initial number were eaten; vertebral counts of survivors were compared with those of unexposed controls. Experiments were conducted on prey of two different mean sizes and at two temperatures. With smaller prey (average initial length 8.2 mm), selective predation for vertebral number was striking; survival rate was from 1.3 to 1.7 times greater for fish with 31 vertebrae than for those with 32. With larger prey (average initial length 8.9 mm), experimental and control fish did not differ significantly in vertebral number. Selection did not vary significantly with water temperature; each prey length was tested at 15 °C and 17 or 20 °C. Selectivity of predation with respect to vertebral number was not attributable to selection with respect to body size of prey.
Forecasting Yields of Two-Sea-Winter Atlantic Salmon (Salmo salar) from Icelandic Rivers
Authors: Scarnecchia Dennis L.
Published: May 2008

To forecast yields of two-sea-winter Atlantic salmon (Salmo salar) from 15 Icelandic rivers, I developed predictive regression equations based on yields of grilse of the same smolt class harvested in the previous year. The relationships were positive and significant (P < 0.05) for all rivers. The logarithm of grilse catch explained 25–85% of the variation in logarithm of two-sea-winter salmon catch the following year. Inasmuch as statistical tests for linearity between the variables were difficult to interpret and showed conflicting conclusions, I consider them inadequate for assessing whether density dependence occurs between grilse and two-sea-winter salmon. Linear or near linear relationships, which imply no density dependence, appear to occur between log grilse and log two-sea-winter salmon yields. The critical period determining run size from a given escapement thus occurs either during the freshwater rearing phase or during the first year the salmon are at sea.
Growth Rates of Five Freshwater Algae in Well-Buffered Acidic Media
Authors: Gensemer Robert W. , Kilham Susan Soltau
Published: May 2008

Growth rates for five freshwater algae, Asterionella formosa, Stephanodiscus hantzschii, Scenedesmus sp., Cryptomonas ozolini, and Anabaena flos-aquae, in media ranging in pH from 5.0 to 7.5 using three zwitterionic buffers, MES, PIPES, and TES, were determined. These buffers supported similar growth rates when compared with each other in treatment groups of similar pH. For pH values below 6.0 no growth occurred or growth rates were significantly reduced in some treatment groups for all species except Cryptomonas. In some cases, these lowered growth rates were partially or completely restored by reducing trace metals in the media by one or two orders of magnitude. We suggest that these buffers could provide a useful technique for investigating the physiological responses of phytoplankton in lakes undergoing acidification.
Size Selectivity of Passive Fishing Gear: A Correction for Encounter Probability Applied to Gill Nets
Authors: Rudstam Lars G. , Magnuson John J. , Tonn William M.
Published: May 2008

The probability of catching a fish in a gill net may be separated into two components: (1) the probability of the fish encountering the net and (2) the probability of the fish being caught and retained in the net. We consider the probability of encounter to be directly proportional to the distance travelled by the fish during the sampling period. This distance will increase with fish size if different-sized fish swim for the same amount of time because swimming speed increases with fish size. Routine swimming speed measured in the laboratory for three size-classes of bloater (Coregonus hoyi) increased with length to the 0.8 power. Corrections for encounter probability were incorporated in gill net selectivity calculations for samples of cisco (Coregonus artedii), a species closely related to bloater. These corrections can significantly increase the proportional estimates of smaller relative to larger animals in the estimated population structure. The approach should also be applicable to other passive fishing gear, such as longlines and set nets.
Significance of Egg and Larval Size to Recruitment Variability of Temperate Marine Fish
Authors: Pepin Pierre , Myers Ransom A.
Published: May 2008

Recruitment variability is commonly associated with fluctuations in abundance of marine fish populations. Previous studies have focussed on stock-specific correlative or mechanistic models or on comparisons of recruitment variations of several stocks or species. The purpose of this study is to determine whether recruitment variability of commercial marine fish populations is associated with either size or the duration of early life history stages. The analysis was performed with data from 86 stocks representing 21 species of commercial marine fish. Univariate analysis shows that neither egg size nor the length at hatch is significantly correlated with recruitment variability. The change in length during the larval phase, which is representative of the duration of the stage, is significantly positively correlated with recruitment variability. Multivariate analysis shows that recruitment variability increases with increasing length at metamorphosis but that recruitment variability is poorly associated with length at hatch. The degree of serial correlation is related to the relative duration of egg and larval stages. The results clearly indicate that recruitment variability is linked to characteristics of early life history stages.
Longevity, Body Size, and Growth in Anadromous Brown Trout (Salmo trutta)
Authors: Jonsson Bror , L'Abée-Lund Jan Henning , Heggberget Tor G. , Jensen Arne J. , Johnsen Bjørn O. , Næsje Tor F. , Sættem Leif M.
Published: May 2008

Longevity in 25 populations of anadromous brown trout (Salmo trutta) showed a significant trend with increasing life span at latitudes of 58–70°N in Norway, with the largest change from 58 to 60°N. Moreover, longevity was negatively correlated with temperature and growth rate in freshwater and at sea. Body size was negatively correlated with water temperature and growth rate in freshwater, but not with latitude or water temperature and growth rate at sea. Thus, conditions influencing development and metabolic rates in fresh water seem more important than conditions in the sea in determining variation in longevity and body size of anadromous brown trout. Our results support the hypothesis that interpopulation variation in longevity and body size is influenced by rate of metabolism, chiefly influenced by ambient water temperature.
Interpretation of Otolith Microstructure in Juvenile Winter Flounder (Pseudopleuronectes americanus): Ontogenetic Development, Daily Increment Validation, and Somatic Growth Relationships
Authors: Sogard Susan M.
Published: May 2008

In winter flounder (Pseudopleuronectes americanus), sagittae developed secondary origins of calcium carbonate deposition during metamorphosis just prior to completion of eye migration. Sagittae and lapilli of larvae were bilaterally symmetrical, but those of postmetamorphic individuals showed increasing morphological asymmetry between the left and right side. In juveniles marked with oxytetracycline and maintained in field enclosures for 10 d, increment deposition on sagittae was daily if somatic growth following marking was good (> 0.25 mm∙d−1), but less than daily in individuals with poor or negative somatic growth (< 0.25 mm∙d−1). Narrowly spaced increments or divergence of otolith growth from the main rostral–postrostral growth axis, where counts were made, may have limited detection of daily deposition. Lack of detectable daily increments occurred primarily in larger juveniles (> 50 mm total length), which had lower absolute growth rates than newly settled juveniles. In oxytetracycline-marked fish there was a significant correspondence between otolith growth and somatic growth in both length and weight. The strength of this relationship, which varied with the specific radius used, was highest (r = 0.854) for the rostral radius of the left sagitta; increment widths along this radius are reliable estimators of prior somatic growth rates.
Changes in Catchability in a Bottom-Trawl Fishery for Cape Hake (Merluccius capensis)
Authors: Gordoa Ana , Hightower Joseph E.
Published: May 2008

Management of the Cape hake (Merluccius capensis) stock off the coasts of Angola and Namibia has been based on surplus production modeling, which incorporates an assumption of constant catchability. Results of least-squares catch-at-age analysis and virtual population analysis were used to estimate catchability from 1968 to 1986. Estimated catchability was either relatively constant or gradually increasing from 1968 to 1978, but fluctuated considerably between about 1979 and 1983. The fluctuations may have been due to an inverse relationship between catchability and abundance or to environmental factors affecting fish distribution. The period of highest estimated catchability corresponded to the period of lowest estimated abundance and below-average water temperatures. If management is based on the assumption of constant catchability but catchability is inversely related to abundance, the risk of overfishing will be greatest when the stock is at the lowest levels. Future assessments should place increased reliance on survey data or incorporate an appropriate model of catchability changes.
Drift Responses of Benthic Invertebrates to Experimental Streamflow Variation in a Hydrologically Stable Stream
Authors: Poff N. LeRoy , Ward J. V.
Published: May 2008

Field experiments were conducted in the regulated upper Colorado River to assess drift responses of lotic macroinvertebrates to streamflow manipulations. In each of three seasons, drift was collected in one control and two experimental riffles. On the first day, no flow manipulations occurred. Six hours before sunset on the second day, streamflow was simultaneously reduced and elevated in two experimental riffles with instream diversion structures. Following flow elevation, both mean daily drift density and drift rate generally increased for 13 taxa across all seasons. Flow reductions generally induced elevated drift densities for most taxa, but drift rates declined for some taxa. Patterns of diel drift periodicity were less frequently modified by flow manipulations. Taxa with typical nocturnal peaks in drift activity (Baetis spp., Epeorus longimanus, Triznaka signata) generally maintained this pattern despite some increases in diurnal drift. For a few taxa, modification of diel drift patterns occurred, either as nocturnal decreases following reduced flow (Paraleptophlebia heteronea, Ephemerella infrequens) or as diurnal drift increases in response to either elevated flow (Lepidostoma ormea, Chironomidae larvae) or reduced flow (Simuliidae). With some exceptions, observed drift responses could be used to suggest active versus passive processes of drift entry.
Effects of Time of Day, Water Temperature, and Water Velocity on Swimming by Postlarvae of the American Lobster,Homarus americanus
Authors: Rooney Patricia , Cobb J. Stanley
Published: May 2008

Swimming speeds and swimming behavior of laboratory-reared and wild postlarvae (larval stage IV) of the American lobster, Homarus americanus, were observed in tanks of still water and in a linear flume. Mean swimming speeds ranged from about 7 cm∙s−1in the "claws-apart" swimming mode to 13.2 cm∙s−1in the streamlined, "claws-together" mode. In the flume, the total time spent swimming during a 30-min test period decreased as water velocity increased from 8 to 14 cm∙s−1. The time spent swimming was greater during the day than at either dusk or night. Postlarvae spent very little time swimming at 15 °C but significantly more at 21 °C. Wild postlarvae were larger, heavier, and swam more rapidly than laboratory-reared postlarvae. Rapid, directional swimming by postlarval lobsters may play a role in determination of distribution and recruitment to benthic populations.
Effect of Sampling Protocol on Estimates of Phosphorus and Chlorophyll Concentrations in Lakes of Low to Moderate Trophic Status
Authors: Hanna Micheline , Peters Robert Henry
Published: May 2008

Methods of sampling lake phosphorus and chlorophyll concentrations were assessed by comparing mean values for 16 lake basins in southern Quebec. Integrating tube and discrete-depth samples were analyzed to yield six different subsurface, depth-integrated, and volume-weighted average values representing epilimnetic, euphotic, and trophogenic zones. The different protocols were found to be similarly precise. Epilimnetic samples yield low values, while trophogenic samples yield high ones; however, the differences in protocol accounted for less than 50%. Analysis of variance associated most of the uncertainty in these estimates with lake and sampling date and showed that sampling site rarely had a significant effect. Year had only a minor effect, but interannual variation is probably underestimated, since these data represent only two years. These patterns suggest that representative sampling for a given lake requires only a single sample per visit but several visits within a season. Since chlorophyll varied more spatially than phosphorus, sampling protocol affects its estimates to a greater extent. Phosphorus–chlorophyll regressions based on data collected in different ways were very similar, so differences in protocol and sampling depth seem unlikely to contribute to the high uncertainty in existing phosphorus response models.
Limit equilibrium slope stability analysis using rigid finite elements
Authors: Stolle Dieter , Guo Peijun
Published: June 2008

This paper revisits the interslice force assumptions associated with the method-of-slices approach to slope stability analysis. A brief review is presented on analysis procedures for this class of problem and a comparison is made between the factor of safety equations derived by Fellenius and a modified form of Bishop’s equation. A simplified rigid finite element method that takes into account progressive yielding through a sliding law is proposed, eliminating the need to provide constraint equations for the variation of interslice forces required by more advanced procedures, such as that developed by Morgenstern and Price. An example is given to demonstrate the proposed procedure and to investigate the sensitivity of the global and local factors of safety to the interslice and basal shear forces. It is demonstrated that the global factor of safety tends not to be sensitive to interslice shear forces when dealing with circular slip. For the slip circles that were analyzed, the Morgenstern and Price procedure yielded slice forces that were similar to those predicted by the proposed method, which takes into account the deformation and failure characteristics of the material comprising the slope.
Capillary-induced tensile strength in unsaturated sands
Authors: Kim Tae-Hyung , Sture Stein
Published: June 2008

While a majority of the studies related to unsaturated soils have focused on volume change, flow, and shear strength behavior, investigations of tensile strength of unsaturated soils, especially granular soils, have not received much attention except for those on cemented and clayey soils. This paper focuses on fundamental studies of tensile strength properties of granular soils in the unsaturated state, which were examined experimentally and theoretically. Experimental studies have shown that it is possible to accurately measure the tensile strength of sands at water contents in the range of 0.5%–17% by means of simple techniques. The method of specimen preparation has proved important, and the use of relatively large specimens has made development of homogeneous specimens and measurements relatively straightforward. The magnitude of the tensile strength of moist and relatively clean sands varies with water content, density, and soil type. The experimental data are also compared with mechanics-based models developed for monosized spheres, and their application for a real granular soil with a variety of particles is discussed in the unsaturated state, which includes the pendular, funicular, and capillary regions.
Chloroplast DNA phylogeography in long-lived Huon pine, a Tasmanian rain forest conifer
Authors: Clark Catherine M. , Carbone Ignazio
Published: June 2008

Genealogy based methods were used to estimate phylogeographic history for a Tasmanian endemic conifer, Huon pine ( Lagarostrobos franklinii (Hook. f.) Quinn). DNA from trees in eight populations was sequenced using three chloroplast primers (trnS–trnT, trnD–trnT, and psbC–trnS). Mean nucleotide diversity was low (π = 0.000 93 ± 0.000 06) from 892 base pairs of sequence, but varied in stands from 0.0 to 0.001 15. Two of the five haplotypes were widely distributed, but the most frequently occurring haplotype was found only in the western portion of the range. Population structure was highly significant among populations overall (GST= 0.261, where GSTis the coefficient of gene differentiation, and p ≤ 0.0001), and there were indications of significant isolation by distance (p ≤ 0.022). Populations exhibited the highest levels of differentiation between the southeastern and northwestern watersheds. Estimates of migration between populations obtained using both parametric and nonparametric methods indicated levels of gene flow consistent with an isolation by distance model. Nested clade analysis demonstrated a pattern of genetic diversity in Huon pine that is consistent with a history of range expansion. The exceptionally low level of nucleotide diversity, haplotype distribution, and paleoecological data are congruent with a history of long-term range reduction, population bottlenecks, and subsequent colonization events from refugial areas.
Variation in soil microbial communities across a boreal spruce forest landscape
Authors: Bach Lisbet Holm , Frostegård Åsa , Ohlson Mikael
Published: June 2008

We investigated soil microbial community structure by phospholipid fatty acid (PLFA) analysis in a mature boreal spruce forest landscape in southern Norway, with low diversity of vascular plants. We investigated the spatial variation in PLFAs and the importance of environmental variables in 10 plots (each 13 samples) in a study area of 1 km × 1 km. The scales investigated were 15 cm to 10 m within study plots and 100 m to 1 km between study plots. Soil microbial biomass varied 10-fold and we found a large variation in microbial community structure, even at distances of 15 cm. Samples aggregated into plots when PLFAs were subjected to a principal components analysis. Plot identity explained 36.3% of the variation in the PLFAs and geostatistical analysis showed that the microbial community structure displayed spatial dependence at within-plot distances. Environmental variables differed significantly between all plots but explained only minor parts of the variation in the overall PLFA pattern. The vegetation variables were, however, the best at explaining the PLFA pattern, and up to 60% of within-plot variation in individual plots, respectively, could be explained by vegetation variables, pH, and soil depth.
Latitudinal variation in tree-ring and wood cell characteristics of Picea mariana across the continuous boreal forest in Quebec
Authors: St-Germain Jean-Luc , Krause Cornelia
Published: June 2008

Wood anatomical features measured in tree-rings are useful indicators of environmental change and wood quality. The effect of latitude on the wood anatomy of mature black spruce ( Picea mariana (Mill.) BSP) was investigated along a 500 km transect from 47°N to 52°N across the continuous boreal forest in Quebec, Canada. Total tree-ring width, earlywood width, latewood width, latewood proportion, cell numbers, tracheid length, radial diameter, lumen diameter, and cell wall thickness were measured using image analysis on samples from 15 mature stands. Our results suggest that tree-ring, earlywood, and latewood widths, cell numbers, latewood radial cell diameter, and cell wall thickness decrease with latitude. No significant trend was observed for latewood proportion, despite a slight increase with latitude (p = 0.0856). However, the high variability in radial growth seen along the gradient might explain the absence of a significant relationship. Latitude and the associated growth rate reduction had no effect on tracheid length. The existence of a latitudinal pattern of variation in black spruce wood anatomy may be the result of tree adaptation to differing environmental conditions along the gradient.
CHARACTERISATION AND LUMINESCENCE INVESTIGATIONS OF Mn DOPED CaAl2O4 PHOSPHOR PREPARED BY COMBUSTION
Authors: SINGH VIJAY , NATARAJAN V. , KIM DONG-KUK
Published: May 2008

Manganese-doped calcium aluminate powder was prepared at furnace temperatures as low as 500°C using the combustion route without further calcining treatment. Powder X-ray diffraction, thermogravimetric analysis and scanning electron microscopy measurements were used to characterize the as-prepared combustion products, while the optical properties were studied using photoluminescence. Photoluminescence studies of Mn doped CaAl 2 O 4 showed green emission from Mn 2+ ions. EPR investigations also indicated the presence of Mn 2+ ions in the prepared material.
INTERACTION OF THE DIOXYGEN MOLECULE WITH THE C96H24 POLYAROMATIC HYDROCARBON CLUSTER: A QUANTUM CHEMICAL INSIGHT
Authors: KHAVRYUCHENKO VOLODYMYR D. , TARASENKO YURIJ A. , STRELKO VOLODYMYR V. , KHAVRYUCHENKO OLEKSIY V. , LISNYAK VLADYSLAV V.
Published: May 2008

Interaction of the previously described [V. D. Khavryuchenko, Y. A. Tarasenko, V. V. Strelko, O. V. Khavryuchenko and V. V. Lisnyak, Quantum chemical study of polyaromatic hydrocarbons in high multiplicity states, Int. J. Modern. Phys. B21, 4507 (2007), in press] polyaromatic hydrocarbon (PAH) C 96 H 24 with dioxygen molecule and KO2 have been quantum chemically examined. The probability of existence of the oxygen superoxide ion-radical O 2 adsorbed on the surface of the PAH is critically discussed.
EVOLVING SCALE-FREE NETWORK MODEL
Authors: QIN QIONG , WANG ZHIPING , ZHANG FANG , XU PENGYUAN
Published: May 2008

The Barabási–Albert (BA) model is extended here to include the concept of modifying the preferential attachment and combining the global preferential attachment with local preferential attachment. Our preferential attachment makes the nodes with higher degree increase less rapidly than the BA model after a long time. The maximum degree is introduced. We compare the time-evolution of the degree of the BA model and our model to illustrate that our model can control the degree of some nodes increasing dramatically with increasing time. Using the continuum theory and the rate equation method, we obtain the analytical expressions of the time-evolution of the degree and the power-law degree distribution.
QUANTUM ELECTRON CONDUCTANCE OF FOUR-TERMINAL JUNCTIONS
Authors: LU JIAN-DUO , HOU YANG-LAI , DAI HOU-MEI , HOU TING-PING , LIN YI
Published: May 2008

With the help of the scattering-matrix method, the quantum states of ballistic electrons and conductance, as well as resistance are studied in a four-terminal junction of narrow wire with various widths. We find that these observable quantities are highly sensitive to the geometries of junctions and differ from the conventional structure with the same width. In particular, the predicted quantization conductance phenomena are striking and are also in self-consistency with calculated scattering probabilities, relating to electronic subbands and transmission states.
INSIGHTS ON THE BOUND STATES IN THE STRAINED CdSe–ZnSe SINGLE-QUANTUM WELLS
Authors: TIT NACIR , OBAIDAT IHAB M.
Published: May 2008

The bound states in the (CdSe) Nw– ZnSe (001) single quantum well are investigated versus the well width (Nw monolayers) and the valence-band offset (VBO). The calculation, based on the sp3s* tight-binding method which includes the spin-orbit interactions, is employed to calculate the band-gap energy (Eg), quantum-confinement energy (EQ), and band structures. It is found that the studied systems possess a vanishing valence-band offset ( VBO ≃ 0) in consistency with the common-anion rule, and a large conduction band offset of about ( CBO ≃ 1 eV ); both of which made the electronic confinement become predominant. The bi-axial strain, on the other hand, remains to control the hole states. Namely, the two highest (spin-degenerate) hole states are found to localize at the two interfaces due to the formation of two similar strain-induced potential dips at these interfaces, each of depth equal to the strain energy ~35 meV. More importantly, the ultrathin CdSe wells (with Nw ≤ 4 monolayers) are found to contain only a single (spin-degenerate) bound state; but by increasing the well width further, a new (spin-degenerate) bound state falls into the well every time Nw hits a multiple of 4 monolayers (more specifically, for 4n+1 ≤ Nw ≤ 4 (n+1), the number of bound states is (n+1), where n is an integer). The rule governing the variation of the quantum-confinement energy EQ versus the well width Nw has been derived. Our theoretical results are in excellent agreement with the available experimental photoluminescence data.
EFFECT OF Pr DOPING ON FERROELECTRIC BEHAVIORS OF Pb(Zr0.65Ti0.35)O3
Authors: YUAN F. , GAO F. , WANG K. F. , DONG S. , WANG Y. , LIU J.-M.
Published: May 2008

Pr -doped Pb ( Zr 0.65 Ti 0.35) O 3 ( Pb 1-x Pr x( Zr 0.65 Ti 0.35)1-x/4 O 3, PPZT) ceramic samples are prepared using conventional solid-state sintering method, and their structural, dielectric, ferroelectric, and piezoelectric properties are investigated, focusing on the effects of Pr -doping. Upon increasing Pr doping level x, a transition of the crystallographic structure from rhombohedral symmetry to tetrahedral and finally to pseudocubic symmetry is observed at x ~ 0.08. The detailed dielectric measurements present a clear indication of relaxor-like behaviors at x = 0.08, while the samples at x < 0.08 offer slightly improved ferroelectric properties compared with pure Pb ( Zr 0.65 Ti 0.35) O 3. In spite of the dielectric relaxor behaviors induced by Pr -doping, both the ferroelectric and piezoelectric properties of PPZT are degraded at x = 0.08. The physics underlying the Pr -doping induced relaxor behaviors is then discussed.
SYNTHESIS AND CHARACTERIZATION OF POTASSIUM SODIUM NIOBATE PHASES
Authors: BOUTAOUI N. , BENABBES A. , RAMDANE K.
Published: May 2008

Potassium niobate KNbO 3 and some compounds of ( K 1-x Na x) NbO 3 (x = 0.3, 0.4, 0.6, 0.7) ceramics powders were successfully prepared by the solid-state reaction method using a non-stoichiometric mixture of starting materials. A possible formation of these phases was proposed based on the experimental results. All of the prepared compounds were characterized using the X-ray diffraction method, and grain size has been calculated using SEM images, and their stoichiometry was obtained from the EDAX results.
IDENTIFICATION OF IMPACT FORCE ON THE GAS PIPE BASED ON ANALYSIS OF THE ACOUSTIC WAVE
Authors: KIM MIN-SOO , LEE SANG-KWON , KIM SUNG-JONG
Published: June 2008

An acoustic wave signal measured on the gas pipe due to impact force is transfer to the far distance through the medium inside of duct. This signal is very complex since it includes the acoustic wave and solid wave. Acoustic wave is affected by the cavity mode inside of duct. The analysis of this acoustic wave gives information about the impact force. For the analysis of this signal, the correlation technique has been used for a long time. This method has a limitation for the application since the waves have dispersive and cavity mode characteristics for the flexible wave. In this paper, we present the time-frequency method for the identification of impact force and the location of impact on the gas pipe. The results give the useful information for the impact force and are applied to the analysis of leakage location of the gas pipe.
EFFECT OF MICROSTRUCTURES ON THE DYNAMIC DEFORMATION BEHAVIOR OF Ti-6Al-4V ALLOY
Authors: KIM JIN-YOUNG , SHIM IN-OK , HONG SOON-HYUNG
Published: June 2008

The effects of microstructures of Ti -6 Al -4 V alloy on the flow stresses and fracture behaviors at quasi-static and dynamic deformation conditions were investigated. Specimens of different sizes and fractions of α globules in equiaxed and bimodal structures were compressed at the strain rate of 2×10−3/ s and 3×103/ s using hydraulic testing machine and split Hopkinson pressure bar, respectively. The a globule size in equiaxed structure changed the level of flow stresses, but did not affect the strain hardening characteristics. Meanwhile, the volume fraction of α globule (or lamellar phase) in bimodal structures influenced both the flow stress and strain hardening exponent at quasi-static and dynamic deformation conditions. Bimodal structure of 50% lamellar fraction is considered to be more favorable in dynamic deformation condition at strain rate regime of 3×103/ s than equiaxed or bimodal one having higher lamellar fraction.
MODIFIED INTEGRATION ALGORITHM IN THE STRAIN SPACE FOR RATE AND TEMPERATURE DEPENDENT ELASTO-PLASTIC CONSTITUTIVE MODEL
Authors: CHO SANG-SOON , HUH HOON
Published: June 2008

This paper is concerned with modified integration algorithm in the strain space for rate and temperature dependent elasto-plastic constitutive relations in order to obtain more accurate results in numerical implementation. The proposed algorithm adopts both the 2-stage Lobatto IIIA with second-order accuracy and the iteration procedure using the Newton–Raphson method to enfoce consistency at the end of the step. The algorithm enables to consider the convective stress rates on the yield surface in the strain space in the numerical integration of the constitutive model. Accuracy assessment using the isoerror maps and FEM analysis of the adiabatic shear band is carried out in order to demonstrate the accuracy of the proposed algorithm.
SENSITIVITY OF THE FLOW STRESS OF NYLON 6 AND NYLON 66 TO STRAIN-RATE
Authors: BENACEUR ISSAM , OTHMAN RAMZI , GUEGAN PIERRICK , DHIEB ABDERRAZEK , DAMEK FAKHREDDINE
Published: June 2008

The sensitivity of the flow stress of polymers to strain-rate is one of the major concerns in mechanics of materials since polymers and polymer matrix composites are widely used in many engineering applications. In this paper, we present tests on Nylon 6 and Nylon 66 on wide range of strain-rates (0.001-5000 s −1). Specifically, we used INSTRON machine for low strain-rates. The high strain-rate measurements were inferred from the Hopkinson bar tests. Only the compressive behaviour was investigated. To eliminate any interference with temperature and humidity effects, test samples were conditioned at 20°C and 50% of hygrometry. Moreover, the effects of the specimen geometry were considered. The current study results are also compared to values found in literature.
HISTORICAL REVIEW OF RESEARCH AND DEVELOPMENT OF THE SHPB METHOD IN JAPAN
Authors: OGAWA KINYA
Published: June 2008

Historical review of research and development of the SHPB method in Japan is outlined. After introduction of the SHPB in early 1960s, various kinds of compression, tension, torsion and bending tests have been performed in Japan and are presently shown together with special techniques such as the strain rate change test and the ramped wave method. Applications of the SHPB method to characterize dynamic response of materials from various points of view are also described in connection with its flexibility and simplicity. Current activities related to the SHPB method are briefly explained.
ON THE MECHANISMS FOR DEFEATING AP PROJECTILES
Authors: ROSENBERG Z. , DEKEL E. , ASHUACH Y. , YESHURUN Y.
Published: June 2008

The important mechanisms for defeating armor piercing (AP) projectiles are reviewed in this paper. These mechanisms are based on the compressive strength of the target material (its inherent resistance to penetration) and on the asymmetrical forces which it exerts on the threat, through proper geometrical arrangements. We discuss the basic features of the resistance to penetration, starting with the classical analysis of the cavity expansion process in elasto-plastic solids. This property of the target is responsible for the deceleration of hard cored projectiles and for the erosion of long rods, under normal impact conditions. We then discuss the asymmetrical interaction of AP projectiles with inclined plates (metals and polymers) and with ceramic spheres. These asymmetric forces are responsible for their deflection and breakup. Our work combines experimental observations with numerical simulations and engineering models, which enhance the understanding of the various phenomena encountered in these complex situations. This understanding is necessary for optimizing the performance of any armor design against a given threat.
THE OBLIQUE PENETRATION AND PERFORATION OF A RIGID PROJECTILE INTO A THICK METALLIC TARGET: ANALYTICAL MODEL
Authors: MOHAMMADI AMIR HOSSEIN MOUSAVI , LIAGHAT GHOLAM HOSSEIN , KHODARAHMI HOSSEIN
Published: June 2008

In this paper, the oblique penetration and perforation process has been analyzed in three stages.

In the first and second stages, the entering of projectile nose into the target and the tunneling process have been considered, respectively. The calculation of force in these stages is based on spherical cavity expansion method. In both of these stages, the friction coefficient has been considered to vary with velocity changes during the process. At the end of each time step, the velocity components are readily determined by solving the equations of motion. The plug formation is modeled in the third stage, where the residual velocity is calculated by the application of energy balance.

In summary, a new approach has been developed to determine the residual velocity, the exit angle, and the depth of penetration of projectiles with spherical nose into the targets, for both cases of oblique and normal striking. The predicted results from this analytical model are in good agreement with experimental and analytical results from other researchers.
AN EXPERIMENTAL AND PRELIMINARY ANALYTICAL STUDY ON THE IMPULSE RESPONSE OF METALLIC SANDWICH PANELS
Authors: ZHU FENG , ZHAO LONGMAO , LU GUOXING , WANG ZHIHUA
Published: June 2008

To investigate the structural response of sandwich panels loaded by impulsive loads, a systematic investigation has been conducted, and some experimental results are reported and discussed in this paper. Quantitative results were obtained based on the measurement in the tests by a pendulum with corresponding sensors, and then the deformation/failure patterns of front face and core were classified and analyzed systematically. Finally, an empirical equation is proposed to predict the back face deflection of the panels.
IMPACT FORCE RESPONSE OF SHORT CONCRETE FILLED STEEL TUBULAR COLUMNS UNDER AXIAL LOAD
Authors: REN GOUPING , LI ZHU
Published: June 2008

The impact test on short concrete filled steel tubular column was conducted through DHR-9401 dropped hammer tester. Based on analysis on recorded time-history curve of impact force, the relations of impact force with respect to confining effect coefficient and impact speed are obtained. So are done that of the impact duration. By use of ANSYS/LS-DYNA, values of impact peak force in relation with those of impact speed were computed in the case of unitary material model and composite material model respectively. The simulation results show that peak force-speed curve of unitary model has better description of test data than that of composite one. Critical energy is found to increase linearly with the steel ratio when steel tube and concrete remain unchanged.