bluuebunny/crossref_metadata_2025 huggingface dataset:
Observations on the development of pore-water stresses during piezocone penetration in clays
Authors: Mayne Paul W. , Kulhawy Fred H. , Kay J. Neil
Published: July 2008

Piezocone data from 83 clay sites are reviewed to investigate first-order trends between measured penetration pore-water stresses (ut and ubt) and corrected cone-tip resistance (qT). It is shown that the presence of fissures in clay deposits and of fissured crusts significantly affects the pore water stress response. Commercially available piezocones primarily favor the location of the porous element either (1) on the cone tip or face (ut) or (2) just behind the tip (ubt). The former (ut) provides optimal profiling while the latter (ubt) is required for correcting measured cone-tip resistances for pore-water stress effects acting on unequal areas of the cone. The available data indicate that qT predominantly reflects penetration pore-water stresses (ut) with measured ratios of ut/qT on the cone face averaging in the order of 0.73 for most intact clays, 0.64 specifically for Leda clays, and 0.46 for fissured clays. Behind the cone tip, the ratio of ubt/qT averages about 0.53 for intact clays, 0.58 specifically for Leda clays, and near zero or slightly negative for heavily overconsolidated fissured clays. Key words: clays, cone penetrometers, field tests, fissuring, in situ tests, penetration tests, piezocones, pore-water stresses.
The effects of plugging on pile performance and design
Authors: Paikowsky Samuel G. , Whitman Robert V.
Published: July 2008

During installation of open-pipe piles, soil enters the pile until the inner-soil cylinder develops sufficient resistance to prevent further soil intrusion and the pile becomes "plugged." In spite of its frequent occurrence, only limited attention has thus far been given to this phenomenon and its consequences. The effects of plugging on pile performance and design are examined in reference to the following aspects: ultimate static capacity, time-dependent pile capacity, and dynamic behavior. Pile plugging is shown to have the following effects: marked contribution to the capacity of piles driven in sand; delay in capacity gain with time for piles driven in clay; and change in behavior of piles during installation, causing it to differ from that described by the models commonly used to predict and analyze pile driving. Key words: pipe piles, pile plugging, open-ended piles, static capacity, time-dependent capacity, dynamic analysis, pile driving, pile performance.
Simulation of downhole and crosshole seismic tests on sand using the hydraulic gradient similitude method
Authors: Yan Li , Byrne Peter M.
Published: July 2008

A method of simulating downhole and crosshole seismic shear-wave tests in a model under controlled stress conditionsis described. The downhole and shear wave in horizontal plane (SH) crosshole shear waves are generated and received along the principal stress axes using piezoceramic bender elements. The K0in situ stress conditions, including loading and unloading stress paths, are simulated by the hydraulic gradient similitude method, which allows high stresses simulating field conditions to be obtained. The horizontal stress during the tests is directly measured by a lateral total-stress transducer. The test data are used to evaluate various published empirical equations that relate shear-wave velocity and soil stress state. It is found that although the various empirical equations can predict the in situ shear-wave velocity profile reasonably well, only the equation that relates the shear-wave velocity to the individual principal stresses in the directions of wave propagation and particle motion can predict the variation of the velocity ratio between the downhole and SH crosshole tests. It was also found that the stress ratio has some effects on the downhole (or shear wave in vertical plane (SV) crosshole) shear-wave velocity, but not on the SH crosshole shear-wave velocity. This indicates that it is only the stress ratio in the plane of wave propagation that is important to the shear-wave velocity. Comparison between the downhole and SH crosshole shows that structure anisotropy is in the order of 10%. In addjtion, K0 values are predicted from shear-wave measurement and compared with measured ones. The difficulties in obtaining K0 values from shear-wave measurement are also discussed. Key words: hydraulic gradient, model tests, downhole and crosshole shear-wave tests, sand.
Compressive strength behavior of fine-grained frozen soils
Authors: Wijeweera Harsha , Joshi Ramesh C.
Published: July 2008

Constant strain-rate (0.01/s) uniaxial compression-strength tests were conducted on more than 200 saturated samples of six fine-grained frozen soils at temperatures between −5 and −17 °C. Saturated soil samples containing total water contents between 15% and 105% were prepared using a consolidation apparatus specially designed for this purpose. The effect of dry unit weight, total water content, temperature, and soil type on the behavior of peak compressive strength was studied. Test results indicate the peak compressive strength of fine-grained soils is sensitive to changes in the dry unit weight and the total water content. The temperature dependence of the peak compressive strength is represented by a simple power law. An empirical formula has been developed to predict the peak compressive strength of fine-grained frozen soils at a particular temperature using index properties, specific surface area, particle-size distribution, and dry unit weight. A linear relationship exists between the peak compressive stress and the yield stress. Key words: peak compressive strength, yield stress, frozen soils, fine-grained soils, dry unit weight, failure strain, temperature, total water content, slurry consolidation.
Contaminant migration through fractured till into an underlying aquifer
Authors: Rowe R. Kerry , Booker John R.
Published: July 2008

This paper examines the potential impact on groundwater quality of contaminant migration from a landfill site, through a fractured till, and into an underlying aquifer. The paper describes a simple, semi-analytic technique for modelling contaminant transport through the fractured till, including consideration of diffusion of contaminants from the fractures into the till matrix, sorption, and radioactive decay. The model also considers the finite mass of contaminant and dilution due to the flow of groundwater in the aquifer. The model can be readily implemented on a microcomputer. The model allows examination of variations in fracture spacing, fracture opening size, thickness of the fractured zone, diffusion coefficient, dispersivity, effective porosity of the matrix, radioactive decay, Darcy velocity, thickness of the aquifer, distribution coefficient, and mass of contaminant. The paper describes the results of a limited parametric study that, inter alia, examines the effects of uncertainty in fracture spacing, the thickness of the fractured till, and the effective porosity of the till matrix. Some of the practical implications are discussed. Key words: contaminant migration, fractures, till, groundwater, pollution, landfill, waste disposal.
Differential shear movements at soil-geotextile interfaces
Authors: Eigenbrod K. D. , Burak J. P. , Locker J. G.
Published: July 2008

The shear deformation behaviour along soil–geotextile interfaces has been investigated and is compared with that of the respective soils. Six soils (two sands, two clays, and two peats) in combination with eight different geotextiles (woven and nonwoven) were tested at various conditions in direct shear. It was found that the stiffnesses during shearing for the sand-geotextile interfaces were less than those for the actual sand, by a factor that was largely independent of the normal stress level. The same behaviour was found for the clays and for one of the peats in contact with non-woven geotextiles. For woven geotextile interfaces in contact with the clays and the peats, the load deformation behaviour was generally stiffer than for the actual soils. Key words: geotextiles, differential shear, soil–geotextile interfaces, load transfer during shear.
Release and dispersal of pollen from dwarf mistletoe on jack pine in Manitoba in relation to microclimate
Authors: Gilbert Jeannie , Punter David
Published: July 2008

The release and dispersal of pollen of Arceuthobiumamericanum Nutt. ex Engelm. parasitizing Pinusbanksiana Lamb. were examined in relation to microclimate in southern Manitoba. Time-lapse photography revealed that once open, the long-lived staminate flowers remain open. The anthers, however, open in response to rising temperatures and falling relative humidities and close under the reverse conditions. Small Diptera (Sciaridae) appeared on the photographs on 25 occasions during the wet spring of 1986. Nectar was scarce on pistillate flowers, but accumulated on the central cushions of staminate flowers when relative humidities were high. In the dry spring of 1987, nectar was rarely seen on the staminate flowers and one small dipteran was photographed just once. Large beads of concentrated nectar (50–65% sugar), however, formed on the stigmas in 1987. Large Diptera were rarely seen in 1986, but were numerous in 1987. Visits to staminate flowers were more frequent than to pistillate (2.7:1.0), but individual insects spent more time on pistillate flowers than staminate (9.6:1.0 s). Pollen grains, trapped on a continuously recording volumetric spore trap, increased in number during warm periods and fluctuated when weather alternated between rainy and dry. Pollination is effected by unspecialized insect visitors and wind. Like other diclinous species, A. americanum represents a compromise between entomophily and anemophily.
Early family selection in jack pine
Authors: Carter K. K. , Adams G. W. , Greenwood M. S. , Nitschke P.
Published: July 2008

Twenty open-pollinated families of jack pine (Pinusbanksiana Lamb.) were grown for 16 to 21 months in two different greenhouse regimes, one providing an extended growing season with natural photoperiod and one employing control of temperature and photoperiod to accelerate growth cycles. Height measurements during and at the end of greenhouse growth were compared with height of 7-year-old seedlings of the same families growing in field tests. For both greenhouse regimes, height at the end of the second growth cycle was positively correlated with 7-year field height. Greenhouse measurements correctly classified the majority of families into upper and lower groups based on field heights. Early family selection in jack pine appears to have applications in long-term breeding strategies.
Comparison of white, Sitka, and Lutz spruce as hosts of the spruce beetle in Alaska
Authors: Holsten Edward H. , Werner Richard A.
Published: July 2008

When white spruce is infested with spruce beetle broods, Dendroctonusrufipennis (Kirby), more beetles are produced than when Lutz and Sitka spruce are infested. In spite of host suitability differences, outbreaks of the spruce beetle have been more frequent and severe in stands of Lutz spruce than in white or Sitka spruce. Host suitability may be as important as host susceptibility and weather conditions in the development of spruce beetle outbreaks in south central Alaska. Cool summer temperatures and high precipitation limit the rate of development and growth of beetles in maritime Sitka spruce stands of southeast Alaska, but in white spruce stands of interior Alaska, cold winter temperatures usually help to maintain endemic levels. When these environmental factors are ameliorated, however, spruce beetle populations increase rapidly to epidemic levels.
Diversity of Washoe pine and comparisons with allozymes of ponderosa pine races
Authors: Niebling Charles R. , Conkle M. Thompson
Published: July 2008

Washoe pine (Pinuswashoensis Mason and Stockwell), a narrow endemic native to mountains on the western rim of the Great Basin in northeastern California and northwestern Nevada, may be on the verge of extinction. Lowered genetic diversity and increased interpopulation differentiation are expected evolutionary consequences for small, isolated populations like those of Washoe pine. But the species has levels of allozyme variation (estimated average heterozygosity for 26 loci equals 0.148) similar to those for widespread geographic races of ponderosa pine (Pinusponderosa Laws.), which are likely to be its closest extant relatives. Heterozygosity in ponderosa pine was 0.144 in the Pacific race, 0.178 in the North Plateau race, and 0.164 in the Rocky Mountain race. Electrophoretic analysis of trees in the three well-documented populations of Washoe pine revealed only minor and nonsignificant population to population differentiation (98.4% of allozyme variation was among samples within populations). Pair-wise genetic distances between the Washoe populations and the three northern races of ponderosa pine indicated that its closest similarity was with the North Plateau race (Nei's unbiased genetic distance averaged 0.004); the next closest similarity was with samples of the Pacific race (genetic distance 0.013). Washoe pine and the Pacific and North Plateau races of ponderosa pine were all strongly differentiated from the Rocky Mountain race of ponderosa pine (genetic distances were 0.066, 0.082, and 0.060, respectively. The few remaining populations of Washoe pine may be a potentially valuable gene source for the yellow pines of North America.
Response of northern red oak (Quercusrubra) seedlings to soil solution aluminum
Authors: DeWald L. E. , Sucoff E. I. , Ohno T. , Buschena C. A.
Published: July 2008

The sensitivity of northern red oak (Quercusrubra L.) to soil solution Al was experimentally examined on germinants grown for 10 weeks in a soil sample from the B2/C horizons of a Typic Fragiorthod. Adding AlCl3 raised the solution Al in the saturated paste extract from about 50 to 825 μM in study I and to 392 μM in study II. Phosphorus (KH2PO4) was added in study II. Forty percent of the variation in root growth was related to solution Al, even in study I where severe P deficiency dampened the expression of Al toxicity. Shoot growth was less sensitive to Al. In study II, total root weight was significantly reduced (36%) at 115 μM Al. This is the lowest concentration of Al reported to significantly reduce seedling growth of oak. The Ca and Mg concentrations in leaves and roots were first reduced at 115 μM Al. Higher solution Al further reduced these to levels associated with deficiency in other dicotyledonous trees. Tissue Al concentrations were not closely correlated with growth.
Sulfur fractions and retention mechanisms in forest soils
Authors: Autry Andrew R. , Fitzgerald John W. , Caldwell Penny R.
Published: July 2008

The relevance of organosulfur formation and sulfate adsorption as S retention mechanisms in forest soils based upon the sulfur status of samples collected by horizon was investigated. Several forests of varying elevation, vegetation, location, and soil type were considered. Organic S was found to constitute over 78% of total S in the uppermost mineral (0–20 cm; A,E) horizons. This trend was also observed for both intermediate (20–40 cm; primarily A/B) and deeper (40+ cm; B,C) horizons, where organic S exceeded 65% of total S in all but one site examined. Adsorbed sulfate generally constituted only a minor component of the S pool in the uppermost mineral horizons (<13% of total S in all sites examined). This trend was also observed with increasing depth, although in the lowermost horizons adsorbed sulfate increased on a percentage basis. In almost all cases, the adsorbed anion constituted substantially less of the total S than did organic S, irrespective of depth. Carbon-bonded S was the most prevalent form of organic S for most sites at all depths examined. Adsorbed ester sulfate, recovered by extraction with basic phosphate, generally constituted a substantial portion of the adsorbed S pool for both O1 and O2 components of the forest floor and for the uppermost mineral horizon of most sites examined. This trend did not hold true with increasing depth. Because organic S was the dominant form of S, irrespective of horizon, the data suggest that organosulfur formation, not sulfate adsorption, may represent the primary mechanism for S retention in forest soil.
Growth response of unthinned and thinned Douglas-fir stands to single and multiple applications of nitrogen
Authors: Stegemoeller K. A. , Chappell H. N.
Published: July 2008

Basal area and volume growth response of unthinned and thinned Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stands to single and multiple applications of nitrogen fertilizer were estimated for eight 2-year periods. Response estimates, as differences between growth rates on fertilized and control plots after adjusting for initial volume (or basal area), and trends were analyzed on a regional scale. Average responses to the initial fertilization and to both the second and third fertilizer applications, 8 and 12 years later, were statistically significant (p < 0.05). In thinned stands, average duration of response to the initial treatment was approximately 8 years; unthinned stands continued to show significant volume growth response through 14 years, although basal area growth response decreased to nonsignificant levels between years 10 and 12. In both cases, the response to refertilization, while significant, was smaller than the response to the initial fertilization. Nitrogen applied after the 8th year, and a refertilization after the 12th, on one initially untreated plot at each installation also produced significant average growth responses.
Forest fire history of Desolation Peak, Washington
Authors: Agee James K. , Finney Mark , Gouvenain Roland De
Published: July 2008

Forests in the vicinity of Desolation Peak, Washington, are of special ecological interest because of their transitional nature between coastal and interior forest types. The area is west of the Cascade Mountain crest but in the rainshadow of mountains farther to the west. Fire return intervals were hypothesized to be shorter than typical for coastal forest types, such as those dominated by western hemlock and Pacific silver fir, and longer than typical for interior forest types, such as ponderosa pine, owing to the close juxtaposition of these types at Desolation Peak. Seven forest community types were defined, and a 400-year fire history was developed for this 3500-ha area. The average natural fire rotation was 100 years; this varied by a factor of two by century and by topographic aspect. Forest types typical of coastal regions, such as Douglas-fir, – western hemlock and mountain hemlock – Pacific silver fir, had mean fire return intervals (108–137 years) much lower than in other western Washington areas. The most interior forest type, ponderosa pine – Douglas-fir, had a higher mean fire return interval (52 years) than reported for similar forest types east of the Cascades. Historically, fire has created structural and landscape diversity on Desolation Peak and may be an important process in the maintenance of such diversity into the future.
Estimating Douglas-fir wood production from soil and climate data
Authors: Robertson E. O. , Jozsa L. A. , Spittlehouse D. L.
Published: July 2008

The relationships between annual tree-ring growth and growing season climate were explored, studying 70-year-old coastal Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees in three sites of different moisture microclimates within productive forest lands. Climate data were augmented via a water balance model to calculate soil moisture deficits. Eleven ring variable components were derived via X-ray densitometry for each ring from two cores for each of 10 trees per site. First principal component scores of each ring variable were linked to climate variables (from 1951 to 1985) via multiple regression. Annual water deficit was found to account for 51% of the annual variations in ring weight. Earlywood width showed little direct climate response, and earlywood density was the least variable ring component. Latewood width was related to annual water deficit (r2 = 0.47). Latewood density showed different relationships to climate variables at the different sites. Percent latewood is increased by spring rainfall and depressed by high August temperatures. The ranges between minimum to maximum and earlywood to latewood densities were comparable for all sites, indicating that there is little density variation due to site differences.
Growth and development of eastern white pine rooted cuttings compared with seedlings through 8 years of age
Authors: Struve Daniel K. , McKeand Steven E.
Published: July 2008

Container-grown rooted stem cuttings from 13 eastern white pine (Pinusstrobus L.) clones were paired with open-pollinated bare-root seedlings to compare growth through age 8 years of the two stock types. Before planting, measures of root system quality (number of roots per cutting, root distribution, and weighted root score) were recorded for each ramet to relate growth to initial root system quality. Rooted cuttings had higher survival than seedlings through year 8, 78 vs. 68%, respectively, but the difference was not statistically significant. Rooted cuttings were significantly shorter than seedlings after age 4 years, with differences between stock types increasing in magnitude through year 8. Measures of root system quality of rooted cuttings were not significantly correlated with survival or growth at any age.
Influence of vegetation type and madrone soil inoculum on associative nitrogen fixation in Douglas-fir rhizospheres
Authors: Amaranthus M. P. , Li C. Y. , Perry D. A.
Published: July 2008

Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) seedlings grown on a site cleared of whiteleaf manzanita (Arctostaphylosviscida Parry) and an adjacent, cleared, annual grass meadow were either inoculated with 100–120 mL per seedling of pasteurized or unpasteurized soil from a nearby Pacific madrone (Arbutusmenziesii Pursh) stand or left uninoculated. After one growing season, Douglas-fir seedling whole-plant soil systems were assayed for nitrogenase activity by the acetylene reduction method. The rate of acetylene reduction in rhizospheres of uninoculated seedlings from the manzanita site (1.40 ± 0.44 nmol•h−1) was significantly higher than that of uninoculated seedlings from the meadow site (0.67 ± 0.15 nmol•h−1). Unpasteurized madrone soil increased the rate of acetylene reduction over 500% for inoculated seedlings grown on the manzanita site, but decreased it by 80% for those grown on the meadow site. The madrone soil influence was apparently biotic: pasteurized, madrone soil did not have a significant effect. No acetylene was reduced in soil without seedlings. Azospirillum sp., a microaerophilic nitrogen (N2) fixing bacterium, was isolated from within the mycorrhizae of inoculated seedlings harvested from the manzanita site. These results suggest that early successional ectomycorrhizal shrubs and hardwood trees may be important in maintaining mycorrhizal fungi and associated N2 fixers after severe disturbance.
Fatty acid synthesis and generation of glycerol-3-phosphate in brown adipose tissue from rats fed a cafeteria diet
Authors: Chaves Valéria E. , Frasson Danúbia , Martins-Santos Maria E.S. , Navegantes Luiz C.C. , Galban Victor D. , Garófalo Maria A.R. , Kettelhut Isis C. , Migliorini Renato H.
Published: July 2008

In vivo fatty acid synthesis and the pathways of glycerol-3-phosphate (G3P) production were investigated in brown adipose tissue (BAT) from rats fed a cafeteria diet for 3 weeks. In spite of BAT activation, the diet promoted an increase in the carcass fatty acid content. Plasma insulin levels were markedly increased in cafeteria diet-fed rats. Two insulin-sensitive processes, in vivo fatty acid synthesis and in vivo glucose uptake (which was used to evaluate G3P generation via glycolysis) were increased in BAT from rats fed the cafeteria diet. Direct glycerol phosphorylation, evaluated by glycerokinase (GyK) activity and incorporation of [U-14C]glycerol into triacylglycerol (TAG)–glycerol, was also markedly increased in BAT from these rats. In contrast, the cafeteria diet induced a marked reduction of BAT glyceroneogenesis, evaluated by phosphoenolpyruvate carboxykinase-C activity and incorporation of [1-14C]pyruvate into TAG–glycerol. BAT denervation resulted in an approximately 50% reduction of GyK activity, but did not significantly affect BAT in vivo fatty acid synthesis, in vivo glucose uptake, or glyceroneogenesis. The data suggest that the supply of G3P for BAT TAG synthesis can be adjusted independently from the sympathetic nervous system and solely by reciprocal changes in the generation of G3P via glycolysis and via glyceroneogenesis, with no participation of direct phosphorylation of glycerol by GyK.
Interactions of multiple signaling pathways in neuropeptide Y-mediated bimodal vascular smooth muscle cell growth
Authors: Pons Jennifer , Kitlinska Joanna , Jacques Danielle , Perreault Claudine , Nader Moni , Everhart Lindsay , Zhang Ying , Zukowska Zofia
Published: July 2008

Neuropeptide Y (NPY), a sympathetic cotransmitter, acts via G protein-coupled receptors to stimulate constriction and vascular smooth muscle cell (VSMC) proliferation through interactions with its Y1 receptors. However, VSMC proliferation appears bimodal, with high- and low-affinity peaks differentially blocked by antagonists of both Y1 and Y5 receptors. Here, we sought to determine the signaling mechanisms of NPY-mediated bimodal mitogenesis. In rat aortic VSMCs, NPY’s mitogenic effect at all concentrations was blocked by pertussis toxin and was associated with decreased forskolin-stimulated cAMP levels. NPY also increased intracellular calcium levels; in contrast to mitogenesis, this effect was dose dependent. The rise in intracellular Ca2+depended on extracellular Ca2+and was mediated via activation of Y1 receptors, but not Y5 receptors. Despite differences in calcium, the signaling pathways activated at low and high NPY concentrations were similar. The mitogenic effect of the peptide at all doses was completely blocked by inhibitors of calcium/calmodulin-dependent kinase II (CaMKII), protein kinase C (PKC), and mitogen-activated protein kinase kinase, MEK1/2. Thus, in VSMCs, NPY-mediated mitogenesis signals primarily via Y1 receptors activating 2 Ca2+-dependent, growth-promoting pathways — PKC and CaMKII. At the high-affinity peak, these 2 pathways are amplified by Y5 receptor-mediated, calcium-independent inhibition of the adenylyl cyclase – protein kinase A (PKA) pathway. All 3 mechanisms converge to the extracellular signal-regulated kinases (ERK1/2) signaling cascade and lead to VSMC proliferation.
Characterization of osteoblastic properties of 7F2 and UMR-106 cultures after acclimation to reduced levels of fetal bovine serum
Authors: Ganguly S. , Ashley L.A. , Pendleton C.M. , Grey R.D. , Howard G.C. , Castle L.D. , Peyton D.K. , Fultz M.E. , DeMoss D.L.
Published: July 2008

Estrogen plays an important role in skeletal physiology by maintaining a remodeling balance between the activity of osteoblasts and osteoclasts. In an attempt to decipher the mechanism through which estrogen elicits its action on osteoblasts, experimentation necessitated the development of a culturing environment reduced in estrogenic compounds. The selected medium (OPTI-MEM) is enriched to sustain cultures under reduced fetal bovine serum (FBS) conditions and is devoid of the pH indicator phenol red, a suspected estrogenic agent. This protocol reduced the concentration of FBS supplementation to 0% through successive 24 h incubations with diminishing amounts of total FBS (1%, 0.1%, and 0%). The protocol does not appear to alter the viability, cell morphology, or osteoblast-like phenotype of 7F2 and UMR-106 cell lines when compared with control cells grown in various concentrations of FBS. Although the rate of mitotic divisions declined, the 7F2 and UMR-106 cultures continued to express osteoblast-specific markers and exhibited estrogen responsiveness. These experimental findings demonstrate that the culture protocol developed did not alter the osteoblast nature of the cell lines and provides a model system to study estrogen’s antiresorptive role on skeletal turnover.
Pravastatin increases the expression of the tissue inhibitor of matrix metalloproteinase-1 and the oncogeneBaxin human aortic abdominal aneurysms
Authors: Mateos-Cáceres Petra J. , López-Farré Antonio J. , Morata Pilar C. , Ramos-Mozo Priscila , Macaya Carlos , Serrano Francisco J. , Moñux Guillermo
Published: July 2008

The effect of pravastatin on matrix metalloproteinase-9 (MMP-9) and the level of tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 was studied in explants of human abdominal aortic aneurysm (AAA) obtained from 13 patients. The effect of pravastatin on the apoptotic status of human AAA explants was also examined. Total MMP-9 content did not differ in human AAA explants incubated in vitro in the presence or absence of pravastatin (10−6mol/L) for 48 h. TIMP-1 levels were significantly increased in pravastatin-incubated AAA explants, but TIMP-2 production was not modified by pravastatin. Western blot experiments showed that, whereas Bax expression was increased in pravastatin-incubated AAA explants, the expression of Bcl-2 was not modified. On the other hand, the ratio of the expression of Bax to Bcl-2, an apoptotic index, was not modified by pravastatin. In the human AAA explants, the increase in Bax expression, but not the increase in TIMP-1 expression elicited by pravastatin, was reversed by l-mevalonate, a downstream HMG-CoA reductase metabolite, suggesting that the expression of Bax and TIMP-1 followed HMG-CoA reductase-dependent and -independent pathways, respectively. In conclusion, pravastatin increases both TIMP-1 and Bax expression in human AAA explants without changes in either MMP-9 activity or the apoptotic status.
DETERMINATION OF EFFECTIVE DISTRIBUTION COEFFICIENT OF IMPURITIES DURING ZONE REFINING OF TELLURIUM
Authors: PRASAD D. S. , MUNIRATHNAM N. R. , RAO J. V. , PRAKASH T. L.
Published: July 2008

Knowledge of distribution coefficient values is essential in estimating the refining efficiency, and plays an important role during the purification process, typically zone refining. The effective distribution coefficient "K eff " of impurities Se , Fe , Cr and Pb in tellurium was determined in the present study and found to be 0.48, 0.05, 0.25 and 0.19, respectively. The results are validated by comparing with the available published data, and we observed a difference of less than one order, which was reasonably comparable. The influence of "K eff " on zone refining efficiency was examined and it was noticed that the effective distribution coefficient increases with respect to the translation rate, which is minimum at an optimum lower translation rate (= 30 mm/h ). The relative solute concentration C/C0 is determined experimentally, which shows the best fit of experimental values with Pfann's equation. The impurity profile along the length of the zone refined ingot is also discussed.
ON THE RELATIONSHIP BETWEEN EFFECTIVE ELECTRON MOBILITY AND KINK EFFECT FOR SHORT-CHANNEL PD SOI NMOS DEVICES
Authors: SARAJLIĆ MILIJA , RAMOVIĆ RIFAT
Published: July 2008

Here, a new approach for calculating the triggering drain bias at the onset of the kink effect, kink voltage, V kink , for PD SOI NMOS devices utilizing electron drift properties in the channel is given. This approach directly relates electron mobility in the channel to the kink effect and enables one to determine kink voltage knowing the device technology. It also gives the possibility for calculating mobility from the kink voltage. Theory is compared to the previously published experimental results and based on this match, the behavior of the kink voltage for PD SOI NMOS components for various technology parameters is predicted. Explanation for the appearance of the kink in the volt regime below the band gap of silicon is also given. From this consideration, design rules for PD SOI NMOS devices are derived in order to soothe the kink effect.
NONCLASSIC SOLITONIC STRUCTURES IN DNA's VIBRATIONAL DYNAMICS
Authors: AGÜERO MAXIMO A. , DE LOURDES NAJERA MA. , CARRILLO MAURICIO
Published: July 2008

We study nonclassic solitonic structures on the modified oscillator — chain proposed by Peyrard and Bishop to model DNA. The two DNA's strands are linked together by hydrogen bonds that are modeled by the Morse potential. This Peyrard–Bishop model with inharmonic potential in the optical part of the Hamiltonian gives rise to several nonclassical solutions, i.e., compact-cusp and anti-peak or crowd like soliton solutions. These structures could represent not only local openings of base pairs, but also the inverse process that heals the formation of broken hydrogen bonds.
ORBITAL CORRELATIONS IN SPINLESS HUBBARD CHAIN
Authors: SRINITIWARAWONG C. , PUNPET P.
Published: July 2008

We have calculated the orbital correlation of the spinless two orbitals Hubbard chain in the limit of a very strong on-site Coulomb interaction and half-filling. The Hamiltonian is written in the form of pseudospin operators, and the Hilbert space is restricted to those states with only one electron per lattice site. The ground state wave function has been calculated using the density matrix renormalization group method. It has been found that the orbital correlations occur in the chain along the x-, y-, and z-axis and these are in antiferro-orbital states.
POSSIBLE ZERO-FLUX TRANSPORT INDUCED BY DENSITY WAVES IN A SUPERSOLID TUBE
Authors: CHU KWANG-HUA W.
Published: July 2008

Macroscopic derivation of the entrainment in a supersolid cylinder induced by a surface elastic wave (of small amplitude) propagating along the flexible interface is conducted by considering the nonlinear coupling between the interface and the rarefaction effect. We obtain the critical bounds for zero-volume-flow-rate states corresponding to specific rarefaction measure and wave number which is relevant to the rather small critical velocity or disappearance of supersolid flows reported by Kim and Chan or Rittner and Reppy.
WEAK SOLUTIONS OF QUASILINEAR BIHARMONIC PROBLEMS WITH POSITIVE, INCREASING AND CONVEX NONLINEARITIES
Authors: ABID I. , JLELI M. , TRABELSI N.
Published: July 2008

We study the existence of positive weak solutions to a fourth-order semilinear elliptic equation with Navier boundary conditions and a positive, increasing and convex source term. We also prove the uniqueness of extremal solutions. In particular, we generalize results of Mironescu and Rădulescu for the bi-Laplacian operator.
BLOCKING STRATEGIES FOR A FIRE CONTROL PROBLEM
Authors: BRESSAN ALBERTO , BURAGO MARIA , FRIEND ARTHUR , JOU JESSICA
Published: July 2008

In this paper, we analyze different strategies, in a problem of optimal confinement of a forest fire. The area burned by the fire at time t > 0 is modeled as the reachable set for a differential inclusion ẋ ∈ F(x), starting from an initial set R0. To encircle the fire, a wall can be constructed progressively in time, at a given speed. We examine the minimum construction speed which is needed to completely encircle the fire, by means of one single wall. Different strategies are then compared, by a theoretical analysis and by numerical experiments, to determine which one minimizes the total burned area. We consider first the isotropic case, where the fire propagates uniformly in all directions, and then a more general case, where the wind blows the fire in one preferred direction.
ASYMPTOTIC EXPANSIONS FOR RIEMANN–HILBERT PROBLEMS
Authors: QIU W.-Y. , WONG R.
Published: July 2008

Let Γ be a piecewise smooth contour in ℂ, which could be unbounded and may have points of self-intersection. Let V(z, N) be a 2 × 2 matrix-valued function defined on Γ, which depends on a parameter N. Consider a Riemann–Hilbert problem for a matrix-valued analytic function R(z, N) that satisfies a jump condition on the contour Γ with the jump matrix V(z, N). Assume that V(z, N) has an asymptotic expansion, as N → ∞, on Γ. An elementary proof is given for the existence of a similar type of asymptotic expansion for the matrix solution R(z, N), as n → ∞, for z ∈ ℂ\Γ. Our method makes use of only complex analysis.
Functional size measurement revisited
Authors: Gencel Cigdem , Demirors Onur
Published: July 2008

There are various approaches to software size measurement. Among these, the metrics and methods based on measuring the functionality attribute have become widely used since the original method was introduced in 1979. Although functional size measurement methods have gone a long way, they still provide challenges for software managers. This article identifies improvement opportunities based on empirical studies we performed on ongoing projects. We also compare our findings with the extended dataset provided by the International Software Benchmarking Standards Group (ISBSG).
An upper bound on software testing effectiveness
Authors: Chen Tsong Yueh , Merkel Robert
Published: July 2008

Failure patterns describe typical ways in which inputs revealing program failure are distributed across the input domain—in many cases, clustered together in contiguous regions. Based on these observations several debug testing methods have been developed. We examine the upper bound of debug testing effectiveness improvements possible through making assumptions about the shape, size and orientation of failure patterns. We consider the bounds for testing strategies with respect to minimizing the F-measure, maximizing the P-measure, and maximizing the E-measure. Surprisingly, we find that the empirically measured effectiveness of some existing methods that are not based on these assumptions is close to the theoretical upper bound of these strategies. The assumptions made to obtain the upper bound, and its further implications, are also examined.
Metric space similarity joins
Authors: Jacox Edwin H. , Samet Hanan
Published: July 2008

Similarity join algorithms find pairs of objects that lie within a certain distance ϵ of each other. Algorithms that are adapted from spatial join techniques are designed primarily for data in a vector space and often employ some form of a multidimensional index. For these algorithms, when the data lies in a metric space, the usual solution is to embed the data in vector space and then make use of a multidimensional index. Such an approach has a number of drawbacks when the data is high dimensional as we must eventually find the most discriminating dimensions, which is not trivial. In addition, although the maximum distance between objects increases with dimension, the ability to discriminate between objects in each dimension does not. These drawbacks are overcome via the introduction of a new method called
Quickjoin
that does not require a multidimensional index and instead adapts techniques used in distance-based indexing for use in a method that is conceptually similar to the Quicksort algorithm. A formal analysis is provided of the Quickjoin method. Experiments show that the Quickjoin method significantly outperforms two existing techniques.
Cache-oblivious databases
Authors: He Bingsheng , Luo Qiong
Published: July 2008

Cache-oblivious techniques, proposed in the theory community, have optimal asymptotic bounds on the amount of data transferred between any two adjacent levels of an arbitrary memory hierarchy. Moreover, this optimal performance is achieved without any hardware platform specific tuning. These properties are highly attractive to autonomous databases, especially because the hardware architectures are becoming increasingly complex and diverse.

In this article, we present our design, implementation, and evaluation of the first cache-oblivious in-memory query processor, EaseDB. Moreover, we discuss the inherent limitations of the cache-oblivious approach as well as the opportunities given by the upcoming hardware architectures. Specifically, a cache-oblivious technique usually requires sophisticated algorithm design to achieve a comparable performance to its cache-conscious counterpart. Nevertheless, this development-time effort is compensated by the automaticity of performance achievement and the reduced ownership cost. Furthermore, this automaticity enables cache-oblivious techniques to outperform their cache-conscious counterparts in multi-threading processors.
Quasi-inverses of schema mappings
Authors: Fagin Ronald , Kolaitis Phokion G. , Popa Lucian , Tan Wang-Chiew
Published: July 2008

Schema mappings are high-level specifications that describe the relationship between two database schemas. Two operators on schema mappings, namely the composition operator and the inverse operator, are regarded as especially important. Progress on the study of the inverse operator was not made until very recently, as even finding the exact semantics of this operator turned out to be a fairly delicate task. Furthermore, this notion is rather restrictive, since it is rare that a schema mapping possesses an inverse.

In this article, we introduce and study the notion of a quasi-inverse of a schema mapping. This notion is a principled relaxation of the notion of an inverse of a schema mapping; intuitively, it is obtained from the notion of an inverse by not differentiating between instances that are equivalent for data-exchange purposes. For schema mappings specified by source-to-target tuple-generating dependencies (s-t tgds), we give a necessary and sufficient combinatorial condition for the existence of a quasi-inverse, and then use this condition to obtain both positive and negative results about the existence of quasi-inverses. In particular, we show that every LAV (local-as-view) schema mapping has a quasi-inverse, but that there are schema mappings specified by full s-t tgds that have no quasi-inverse. After this, we study the language needed to express quasi-inverses of schema mappings specified by s-t tgds, and we obtain a complete characterization. We also characterize the language needed to express inverses of schema mappings, and thereby solve a problem left open in the earlier study of the inverse operator. Finally, we show that quasi-inverses can be used in many cases to recover the data that was exported by the original schema mapping when performing data exchange.
Average-case lower bounds for the plurality problem
Authors: Alonso Laurent , Reingold Edward M.
Published: July 2008

Given a set of
n
elements, each of which is colored one of
c
≥ 2 colors, we have to determine an element of the plurality (most frequently occurring) color by pairwise equal/unequal color comparisons of elements. We derive lower bounds for the expected number of color comparisons when the

c
n

colorings are equally probable. We prove a general lower bound of
c
/3
n
−
O
(√
n
) for
c
≥ 2; we prove the stronger particular bounds of 7/6
n
−
O
(√
n
) for
c
= 3, 54/35
n
−
O
(√
n
) for
c
= 4, 607/315
n
−
O
(√
n
) for
c
= 5, 1592/693
n
−
O
(√
n
) for
c
= 6, 7985/3003
n
−
O
(√
n
) for
c
= 7, and 19402/6435
n
−
O
(√
n
) for
c
= 8.
Balanced parentheses strike back
Authors: Lu Hsueh-I , Yeh Chia-Chi
Published: July 2008

An
ordinal tree
is an arbitrary rooted tree where the children of each node are ordered. Succinct representations for ordinal trees with efficient query support have been extensively studied. The best previously known result is due to Geary et al. [2004b, pages 1--10]. The number of bits required by their representation for an
n
-node ordinal tree
T
is 2
n
+
o
(
n
), whose first-order term is information-theoretically optimal. Their representation supports a large set of
O
(1)-time queries on
T
. Based upon a balanced string of 2
n
parentheses, we give an improved 2
n
+
o
(
n
)-bit representation for
T
. Our improvement is two-fold: First, the set of
O
(1)-time queries supported by our representation is a proper superset of that supported by the representation of Geary, Raman, and Raman. Second, it is also much easier for our representation to support new queries by simply adding new auxiliary strings.
Roundtrip spanners and roundtrip routing in directed graphs
Authors: Roditty Iam , Thorup Mikkel , Zwick Uri
Published: July 2008

We introduce the notion of
roundtrip-spanners
of weighted
directed
graphs and describe efficient algorithms for their construction. We show that for every integer
k
≥ 1 and any ϵ > 0, any directed graph on
n
vertices with edge weights in the range [1,
W
] has a (2
k
+ ϵ)-roundtrip-spanner with
O
(min{(
k
2
/ϵ)
n

1 + 1/
k

(log(
nW
), (
k
/ϵ)
2
n

1 + 1/
k

,(log
n
)

2−1/
k

}) edges. We then extend these constructions and obtain compact roundtrip routing schemes. For every integer
k
≥ 1 and every ϵ > 0, we describe a roundtrip routing scheme that has stretch 4
k
+ ϵ, and uses at each vertex a routing table of size
Õ
((
k
2
/ϵ)
n

1/
k

log(
nW
)). We also show that any weighted directed graph with
arbitrary/
positive edge weights has a 3-roundtrip-spanner with
O
(
n
3/2
) edges. This result is optimal. Finally, we present a stretch 3 roundtrip routing scheme that uses local routing tables of size
Õ
(
n
1/2
). This routing scheme is essentially optimal. The roundtrip-spanner constructions and the roundtrip routing schemes for directed graphs that we describe are only slightly worse than the best available spanners and routing schemes for undirected graphs. Our roundtrip routing schemes substantially improve previous results of Cowen and Wagner. Our results are obtained by combining ideas of Cohen, Cowen and Wagner, Thorup and Zwick, with some new ideas.
Writing-all deterministically and optimally using a nontrivial number of asynchronous processors
Authors: Kowalski Dariusz R. , Shvartsman Alexander A.
Published: July 2008

The problem of performing
n
tasks on
p
asynchronous or undependable processors is a basic problem in distributed computing. This article considers an abstraction of this problem called
Write-All: using p processors write 1's into all locations of an array of size n
. In this problem writing 1 abstracts the notion of performing a simple task. Despite substantial research, there is a dearth of efficient deterministic asynchronous algorithms for
Write-All/
. Efficiency of algorithms is measured in terms of
work
that accounts for all local steps performed by the processors in solving the problem. Thus, an optimal algorithm would have work Θ(
n
), however it is known that optimality cannot be achieved when
p
= Ω(
n
). The quest then is to obtain work-optimal solutions for this problem using a nontrivial, compared to
n
, number of processors
p
. The algorithm presented in this article has work complexity of
O
(
n
+
p
2 + ϵ
), and it achieves work optimality for
p
=
O
(
n
1/(2 + ε)
) for any ε > 0, while the previous best result achieved optimality for
p
≤4√
n
/log
n
. Additionally, the new result uses
only
the atomic read/write memory, without resorting to using the test-and-set primitive that was necessary in the previous solution.