bluuebunny/crossref_metadata_2025 huggingface dataset:
Seed ecology in a population of Acaciaholosericea
Authors: Hellum A. K.
Published: May 2008

One population of seed from 18 trees of Acaciaholosericea A. Cunn. ex G. Don from Western Australia was studied. Seeds were weighed individually and germinated in replicates of 25 to try to describe population behaviour under constant temperatures between 17 and 40 °C. Total germination peaked at between 95 and 99% at temperatures between 17 and 35 °C and then dropped sharply to 45% at 40 °C. Temperatures between 17 and 35 °C, therefore, did not influence total germination, and all respective slope coefficients were the same over the entire temperature range. This reflects a very wide optimal temperature range for germination. In all cases, seeds slightly heavier than the mean (11.6 mg) reached the highest rate of total germination. Peak germination occurred in progressively heavier seeds as temperatures were raised from 17 to 40 °C. The germinative rate was also found to decrease as seed weight increased at temperatures between 25 and 35 °C. This was true for seeds from single trees and for pooled seed. At 20 and 40 °C, however, lighter seeds tended to lose the ability to germinate quickly. Lighter seeds also tended to germinate well without a boiling pretreatment, whereas heavier seeds needed to be boiled for 90 s before germination could proceed. Boiling tended to kill the lightest seeds. Seeds weighing between 8 and 10 mg were able to germinate more quickly initially than either lighter or heavier seeds, regardless of which trees the seeds came from.
Seasonal trends and effects of temperature and rainfall on stem electrical capacitance of spruce and fir trees
Authors: Lekas Timothy M. , MacDougall R. Glenn , MacLean David A. , Thompson Robert G.
Published: May 2008

Seasonal trends of stem capacitance were generally similar among balsam fir (Abiesbalsamea (L.) Mill.), white spruce (Piceaglauca (Moench) Voss), red spruce (Picearubens Sarg.), and black spruce (Piceamariana (Mill.) B.S.P.) trees and among plots. In 1987, stem capacitance increased following bud break until early June and then slowly declined until September 8, corresponding to an extended dry period (less than 27% of the annual rainfall of the previous 7 years). Dramatic increases in stem capacitance were observed following 55 mm of rain on September 9, 1987. During autumn of both 1987 and 1988, stem capacitance steadily declined; mean capacitance of trees in seven plots in October and November 1987 was 55–89 and 35–74% of values in June and July 1987, respectively. Diameter at breast height increment of 34 red spruce trees and 190 spruce and fir trees in permanent plots was consistently significantly (p <0.001) related to mean monthly capacitance; the strongest relationships (55–83% of the variability explained) were with mean June or July capacitance. The relationship of stem capacitance with growth of fir and spruce trees was corroborated. In addition, a stronger influence of water relations on capacitance than previously thought was demonstrated.
Response of red spruce seedlings to aluminum toxicity in nutrient solution: alterations in root anatomy
Authors: McQuattie Carolyn J. , Schier George A.
Published: May 2008

One year old red spruce (Picearubens Sarg.) were grown for 37 days in a nutrient solution containing 0, 50, 100, or 200 mg/L Al. No macroscopic evidence of Al injury was observed in the shoots of seedlings; however, Al toxicity symptoms were well developed in the roots. Aluminum reduced root length but increased root diameter and the number of cell layers in the root cap. Light and electron microscopic examination of root tips and segments 5–10 mm from the tip revealed numerous cellular changes in Al-stressed roots: premature vacuolation, accumulation of phenoliclike material, loss of cells from peripheral cell layers, formation of intercellular spaces, increased disruption of cellular membranes, and degeneration of the cytoplasm.
Growth response of Pseudotsugamenziesii to air pollution from copper smelting
Authors: Sutherland Elaine Kennedy , Martin Bjorn
Published: May 2008

We collected increment cores from Pseudotsugamenziesii trees growing 9.5 km (closest site) and 15.5 km (intermediate site) from a copper smelter producing pollutant gases (primarily SO2) and also sampled a control site 27.0 km from the smelter. Annual rings were cross-dated and measured, and the growth trend due to age and geometry was removed. All sites had similar high-frequency variance, indicating comparable climatic response. Autocorrelation was highest at the closest site and lowest at the control site, an intimation of long-term disturbance to polluted trees. Approximate climatic variation was removed from the two polluted growth series using control site growth in a subtraction technique, which produced corrected tree-ring indices. Corrected indices were regression modeled using SO2 emissions from 1940–1984. Although both models were significant, SO2 accounted for 54% of closest site nonclimatic growth variance but only 6% at the intermediate site. At highest known emission levels (during World War II), growth at the closest and intermediate sites was reduced 49% and 14%, respectively. SO2 production declined after World War II, and growth increased, perhaps from decreased stand density or from low-concentration SO2 fertilization.
Assessing components of competition indices for young boreal plantations
Authors: MacDonald Blake , Morris Dave M. , Marshall Peter L.
Published: May 2008

Important components of interspecific competition affecting apical and cambial growth in young plantations of black spruce (Piceamariana (Mill.) B.S.P.) and jack pine (Pinusbanksiana Lamb.) in northern Ontario were identified. The relative importance of competition, initial seedling status, and some soil factors was also assessed. Measures of perennial competition were calculated using hemispherical photographs, stand maps, and mensurational data from 360 seedling-centred plots (1.4 m radius) for each of the two species. Fractal geometry was used to quantify the textures of the competing canopies. Reliable competition indices should include horizontal and vertical dimensions and express the amount of competition relative to the size of the seedling. The total canopy fraction on the photographs and some simple field measurements of competition correlated significantly with seedling growth. Complex expressions of competition were unjustified, and measures of dispersion and canopy texture correlated weakly with growth. The consistently good correlations between growth and some components of competition revealed that an index applicable to all species, stock types, and growth responses could be developed.
Modelling stand growth of radiata pine thinned to varying densities
Authors: Whyte A. G. D. , Woollons R. C.
Published: May 2008

Growth trends in a radiata pine thinning experiment established 18 years ago in Kaingaroa Forest, New Zealand, are portrayed and analyzed. The six thinnings, to 200, 300, 400, 500, 600, and 700/ha, were carried out at age 7 years; four replicates of each thinning level were laid out in 0.2 ha plots in a randomized complete block design. The dbh outside bark of all trees and the heights of a sample of 12–15 trees per 0.1 ha inner plot were remeasured at least once each year up to age 20 and then at 2-year intervals thereafter. Mean top-height development after age 7 years was little affected by thinning intensity, although initial negative selection may have reduced the subsequent vigour of the most heavily thinned plots. Analysis of a Gompertz projection model for net basal area per hectare and a similar yield formulation indicated that thinning down to 300/ha progressively lowered basal-area production and the maximum attainable yield but did not impair the ability to capture fully the available growing space. The 200/ha treatment, however, was much impaired, and its asymptote was lowered to such an extent that its yield trajectory was continuing to fall away relative to the others. The analysis quantifies this reduction and could possibly allow estimates of how much production would be lost between 200 and 300/ha, so that due allowance could be made when predicting yields for routine thinning prescriptions within that range.
Carbon and nitrogen cycling in North American boreal forests. II. Biogeographic patterns
Authors: Bonan Gordon B.
Published: May 2008

A model of carbon and nitrogen cycling developed with ecological relationships from upland boreal forests in interior Alaska was tested with forest structure and forest floor data from several bioclimatic regions of the North American boreal forest. Test forests included black spruce (Piceamariana (Mill.) B.S.P.), white spruce (Piceaglauca (Moench) Voss), white birch (Betulapapyrifera Marsh.), balsam fir (Abiesbalsamea (L.) Mill.), and jack pine (Pinusbanksiana Lamb.) stands located in five different bioclimatic regions. Test comparisons of simulated and actual data included aboveground tree biomass, basal area, density, litter fall, and moss and lichen biomass as well as forest floor biomass, turnover, thickness, nitrogen concentration, and nitrogen mineralization. The model correctly simulated 60 (76%) of the 79 variables tested. Approximately 42% of the incorrectly simulated variables occurred in one forest. The major recurring errors included inaccurate moss and lichen biomass and low moss nitrogen concentrations. These tests indicated that ecological relationships from interior Alaska can be extended to other boreal forest regions and identified the factors controlling vegetation patterns in different bioclimatic regions of the North American boreal forest.
Spatial variation in black cottonwood (Populustrichocarpa) foliar nutrient concentrations at seven alluvial sites in coastal British Columbia
Authors: McLennan Donald S.
Published: May 2008

Spatial variability of 13 foliar nutrients was assessed within and between individual black cottonwood (Populustrichocarpa Torr. & Gray ex Hook.) trees at seven alluvial sites in coastal British Columbia to help in the development of foliar sampling protocol for the determination of black cottonwood nutrient status. Foliar nutrients were divided into two groups based on concentration differences in foliage samples from within black cottonwood canopies: group 1 included N, P, K, S, SO4-S, Cu, and possibly Mg and B, mostly macronutrients that are mobile in the phloem; group 2 included mostly immobile micronutrients (Mn, Zn, Ca, and possibly Fe and active Fe, although these last two might best be included in a third group). Group 1 nutrient concentrations were significantly higher in the upper canopy, while group 2 nutrient concentrations were higher in the lower canopy at the two sites studied. Numbers of samples required for several combinations of accuracy (including both α and β significance) and precision were calculated based on mean coefficient of variation estimates from the seven stands. Fifteen foliar samples collected from the most recently matured late leaves on lateral branches in the top one-third of the canopy of dominant or codominant black cottonwood trees will estimate the mean with an allowable error of 10% at an α significance level of 0.95 for most macronutrients (N, P, K, S, Mg, and Ca). Including a β significance level of 0.95 at this level of precision and α significance would increase the number of required samples to at least 20 for these nutrients. Between 21 and 56 samples would be required to estimate the mean concentrations of SO4-S, Cu, Zn, Mn, B, active Fe, and Fe at the same levels of accuracy and precision.
Diameter-based biomass regression models ignore large sapwood-related variation in Sitka spruce
Authors: Bormann B. T.
Published: May 2008

Precise estimates of biomass are needed in productivity and nutrient cycling studies, and for improved estimates of potential productivity. Improvements in prediction of foliage and branch biomass were sought by comparing multiple regression models using stem diameter, sapwood radial thickness, and tree height as independent variables in stands of Sitka spruce (Piceasitchensis (Bong.) Carr.) in southeast Alaska. Five sites were sampled by stratifying trees into four diameter and three sapwood-thickness classes. Within stands, sample trees with thick sapwood consistently had 2–3 times more foliage and branch biomass than paired trees with thin sapwood but nearly equal diameter. Inclusion of both diameter and sapwood thickness in equations increased precision of foliage and branch biomass, leaf area, and net primary productivity by 15–31% and reduced standard error by 35–48% when compared with equations containing only diameter as an independent variable. Height growth over the last 30 years of intermediate and codominant trees with thick sapwood was 12–27% greater than that of paired trees with thin sapwood but nearly equal diameter at breast height. The addition of total tree height to multiple regression models, however, had little effect on their precision. Stem biomass equations were not improved by including tree height or sapwood thickness. The use of a diameter – sapwood thickness sampling matrix for construction of biomass equations may reduce the sample size needed and result in equations with wider application.
Litter fall transfers of dry matter and nutrients in ponderosa pine stands
Authors: Klemmedson J. O. , Meier C. E. , Campbell R. E.
Published: May 2008

A 34-month study was conducted in an Arizona ponderosa pine (Pinusponderosa Laws.) forest to determine the effect of stand type and silvicultural treatment on rates and components of dry matter and nutrient (C, N, P, S, Ca, Mg, K, and Na) transfers via litter fall. Forest stand conditions (treatments) studied were dense saplings and small poles, large poles, thinned large poles, and clear-cut strips through thinned large poles. Total annual litter fall (<10% coarse woody litter fall) varied from 2795 kg•ha−1 for large-pole stands to 460 kg•ha−1 for clear-cut strips. Peak seasonal needle fall occurred in September–October, whereas the rate of non-needle litter fall was uniform across seasons but irregular in composition. Nutrient concentrations of litter fall differed significantly among treatments, but nutrient transfer was primarily a function of litter fall mass. Thus, dry matter and nutrient transfer patterns were similar. The mean nutrient concentrations of needle fall were as follows: C, 49.9%; N, 0.55%; P, 0.064%; S, 0.055%; Ca, 3133 ppm; Mg, 1349 ppm; K, 1487 ppm; and Na, 90 ppm. Needle fall had high concentrations of N, P, Mg, and K and low concentrations of Ca and Na compared with other (non-needle) fine litter fall, which was relatively high in Ca and Na and low in N. The ranking by treatments for dry matter and nutrient mass transfer was sapling and small poles = large poles > thinned large poles > clear-cut strips. The low concentration of nutrients in fine litter fall, especially N, compared with that of other cold temperate coniferous forests, suggests high N use efficiency for these stands.
Prediction of stand susceptibility to feeding damage by red squirrels in young lodgepole pine
Authors: Sullivan Thomas P. , Krebs John A. , Diggle Paul K.
Published: May 2008

This paper provides a forecast model to predict when and where significant feeding damage by red squirrels (Tamiasciurushudsonicus Erxleben) will occur in managed stands of lodgepole pine (Pinuscontorta Dougl. var. latifolia Engelm.). Information from 51 managed stands (average DBH > 6.0 cm) in the interior of British Columbia and from past squirrel population studies was used to formulate the model. Incidence of damage was significantly greater in stands originating from wildfire than from harvesting. Stands within the Montane Spruce biogeoclimatic zone had the highest levels of damage of the five zones sampled. There was no relationship between damage incidence and average stand diameter, area of managed stand, or site class. In a subset of stands where understory shrub data were available, shrub cover was positively related to incidence of damage. Major factors in the forecast model that influence stand susceptibility include (i) stand origin and proximity to mature timber; (ii) frequency of cone crops leading to squirrel population increases in juvenile pine; and (iii) shrub cover, which may provide security from predators. Additional potential factors include (iv) switching of predators from squirrels to snow-shoe hares (Lepusamericanus Erxleben) during peak years of the hare cycle and (v) fertilization. A decisionmaking profile is outlined for prespacing surveys to identify susceptible stands.
A cross-dated fire history from coast redwood near Redwood National Park, California
Authors: Brown Peter M. , Swetnam Thomas W.
Published: May 2008

Cross sections from coast redwood trees (Sequoiasempervirens (D.Don.)Endl.) in and near Redwood National Park were dendrochronologically cross-dated and used to develop a fire history from 1714 to 1985. A master chronology for the study area was first developed from old-growth trees and provided dating control for fire-scarred samples. Redwood offers a challenge for dendrochronology owing to partially absent rings (ring wedging) and uniform ring widths (complacency). Cross dating was successful in portions of 12 of 24 fire-scarred trees. Fire events were dated by noting the position of fire scars and other fire-associated ring structures (resin ducts, double latewood, growth releases, and ring separations) in the cross-dated ring series. Using only dates of fire scars, the mean fire interval (MFI) was 9.9 years from the first recorded fire in 1714 to the last in 1962. The MFI was 8.0 years for the best represented (greatest sample depth) presettlement period from 1714 to 1881. Using dates for all fire-associated ring features, the MFI from 1714 to 1962 was 7.0 years and from 1714 to 1881 was 6.0 years. Use of all fire-associated ring characteristics is argued to be a more complete representation of past fire frequency due to possible under-representation of fire-scar records from stump-top samples. Based upon scar positions within annual rings, fires occurred predominately late in the growing season or after growth ceased for the year. The mean fire intervals determined are shorter than those reported in all except one other fire history study from coast redwood and suggest that fire frequency in redwood may have been underestimated in many past studies.
Effects of plus tree selection and seed orchard environment on progenies of Piceaabies
Authors: Johnsen Øystein , Østreng Geir
Published: May 2008

Open-pollinated progenies from selected plus trees of Piceaabies (L.) Karst., and from average performing trees (controls) in each of five northern (65–66°N) natural stands in Norway, were tested for growth, timing of bud set, and autumn frost hardiness during the first growing season. The plus trees had also been grafted in a southern seed orchard, Lyngdal (58°N). Crosses were performed in the orchard, using orchard pollen from the same plus trees. All progenies were grown in a common test. There were no differences between natural stand progenies from plus tree and from control stand trees, but the plus tree progenies were different from their seed orchard half-sibs. The seed orchard progenies were slightly taller, formed terminal buds later and were more damaged by frost in a freezing test than their northern half-sibs. Except for one mother, seeds were heavier when produced in the southern seed orchard, but the heavier seeds could not explain the more southern-like performance of the seed orchard progenies. The results are discussed in relation to a hypothesis that the non-native southern seed orchard environment affects the progenies, leading to a more southern phenotypic performance than expected.
Acid rain and soils of the Adirondacks. I. Changes in pH and available calcium, 1930–1984
Authors: Johnson A.H. , Andersen S.B. , Siccama T.G.
Published: May 2008

Interest in acid rain effects led us to resample 48 Adirondack soil profiles that had been sampled by Carl C. Heimburger in 1930–1932. Changes in pH and dilute-acid-extractable Ca were detected in 1984, which differed by horizon and were dependent on initial conditions. Moderately acidic organic horizons (pH > 4.0) showed substantial decreases in pH and extractable Ca, while strongly acidic organic horizons (pH < 4.0) showed a significant reduction in extractable Ca without a reduction in pH. The E horizons appeared to lose extractable Ca, while the B and C horizons showed no evidence of acidification. A partial Ca budget for the ≥50-year interval for 16 sites in a mixed hardwood–softwood forest showed that Ca uptake was approximately equal to the loss of Ca from the soil, suggesting that this was a major cause of acidification. Acid-consuming processes apparently balanced acid additions in B and C horizons as no acidification was observed. While acid rain has increased hydrogen-ion loading and base-cation leaching, we did not find evidence of serious impacts on bulk soil chemistry in the Adirondacks through the mid-1980s.
Effect of nursery culture on morphological development of western hemlock seedlings during field establishment. II. Survival, shoot length components, and needle length
Authors: O'Reilly Conor , Owens J.N. , Arnott J.T. , Dunsworth B.G.
Published: May 2008

Western hemlock (Tsugaheterophylla (Raf.) Sarg.) seedlings grown in two different container cavities that received four different dormancy induction treatments, short (SD) or long days (LD) in combination with moisture stress (D) or no stress (W) in the greenhouse, and lifted and placed in cold storage (November, January, or March), were planted on two adjacent coastal reforestation sites in British Columbia and monitored for survival and morphological development. Survival was greatest in seedlings grown in the larger cavities in the greenhouse, in seedlings lifted in March, and in seedlings not treated to moisture stress. Seedling shoots had more stem units on the southeast than the northwest site, but the amount varied with nursery treatment. Seedlings from the LD treatments produced more stem units during free growth and lammas growth than those from the SD treatment. Nevertheless, most shoot growth was predetermined in the buds during nursery culture, accounting for a minimum of 67% of the final number of stem units. Stem unit length (SUL) was longer in seedlings on the southeast site than on the northwest site for those treated to LD in the nursery. Seedlings treated to short days showed the reverse pattern (SDW) to this, or were unaffected by site (SDD). Shoots and needles were shortest for seedlings from the SDD treatment and for those lifted in November. Shoot growth was greatest for seedlings lifted in March and for those treated with LD, mainly owing to their longer SUL. Lammas growth was most frequent in seedlings from the smaller cavities, and in those from the November and March lifts.
Development of flowering and the effect of pruning in a clonal seed orchard of lodgepole pine
Authors: Fries Anders
Published: May 2008

The development of female and male flowering among 20 clones was studied in a clonal seed orchard of lodgepole pine (Pinuscontorta var. latifolia Engelm.) in central Sweden. Flowering in relation to height, crown volume, and pruning was also studied. Twelve years after grafting (7 years after field planting), female flowering averaged 43 strobili per graft while male strobili were few. Eighteen years from grafting, the number of female and male strobuli were 143 and 142, respectively. The female effective population size was around 80% of maximum and was stable during the whole period. The male effective population size increased from 25 to 68%. Index of monoecy increased from 58 to 81% of maximum. The results indicate that at around 18 years after grafting, female and male flowering were satisfactorily distributed among the clones. There were no clonal correlations between male flowering and female flowering, while correlations between years for those traits separately were strong. Male flowering showed stronger correlation to the size of the graft than female flowering.
Age-dependent tree-ring growth responses of subarctic white spruce to climate
Authors: Szeicz Julian M. , MacDonald Glen M.
Published: May 2008

We test one of the fundamental assumptions of most dendroclimatological research, that the radial growth response of trees to climate does not vary with age once the biological growth trend has been removed. Piceaglauca (Moench) Voss from three sites in the western Northwest Territories, Canada, are disaggregated into age-classes, and their response to climate examined through response function and linear regression analyses. These data are then used in multiple regression analyses to estimate June-July temperatures at Norman Wells, N.W.T., from 1909 to 1989 using both age-dependent and standard (age-independent) models. The response function and regression analyses suggest that the response of Piceaglauca radial growth to climate differs between trees greater than 200 years old and less than 200 years old. These results suggest that the assumption of an age-invariate climate–growth function is therefore invalid at these sites. These apparent age-dependent responses are site specific and may reflect physiological changes related to aging. One possible causal factor of age dependence is that the trees are becoming increasingly moisture stressed with age owing to a reduction in the efficiency of water and nutrient translocation mechanisms. The estimation of June–July temperatures based on an age-dependent model produced improved calibration and verification statistics as compared with a reconstruction based on standard dendroclimatic modelling. If present, age-dependent climate–growth relationships may result in less accurate reconstructions of past climate, particularly during the early portions. However, age-dependent responses could also be used to increase the number of tree-ring based predictor variables for dendroclimatic reconstructions.
Effects of nitrogen fertilization on leaf area, light interception, and productivity of short-rotation Populustrichocarpa × Populusdeltoides hybrids
Authors: Heilman Paul E. , Fu-Guang Xie
Published: May 2008

Nitrogen treatment consisted of spring applications of ammonium nitrate at the rate of 167 kg N•ha−1•year−1 repeated for 3 years starting in the 2nd year after the planting of six Populus hybrids. No response to fertilizer was evident either in bole growth or leaves in year 2, but in year 3, fertilization caused a 14% increase in leaf size (upper terminal leaves), a 54% increase in leaf-fall mass, and a 58% increase in leaf area index (L, m2•m−2). Leaf and canopy responses were not as large in year four, i.e., a 32% increase in leaf-fall mass and a 31% increase in L. Biomass response to nitrogen, reported in an earlier paper, was a 24% increase in dry weight at the end of 4 years. This total was the result of a very large and significant dry weight response to nitrogen in year 3 (about 40%), and a small, nonsignificant response of about 8% in year 4. Leaf-fall means ranged from 3.3 Mg•ha−1•year−1 in year 3 on control plots to 5.8 Mg•ha−1•year−1 on fertilized plots in year 4. Means for L ranged from 3.8 on control plots in year 3 to 8.5 on fertilized plots in year 4. Plotting annual production of aboveground woody biomass versus L revealed a curvilinear relationship described by the polynomial model y = 6.92x − 0.18x2 (r2 = 0.963), where y is the current annual biomass production in Mg•ha−1•year−1 and x = L. Calculation of the extinction coefficient (k) in the Beer–Lambert equation indicated decreased efficiency of the canopies in capturing light in year 4 (k = 0.48) compared with year 3 (k = 0.63). Fertilization had no effect on k in either year. Efficiency of the leaf area in producing biomass per unit of L (E) was lower (though not significantly) on fertilized plots than on control plots (E = 5.3 vs. 5.8 Mg•ha−1•year−1•L−1, respectively). In contrast with the indications from the k-values, E appeared to increase in year 4 compared with year 3 (5.8 vs. 5.4 Mg•ha−1•year−1•L−1, respectively), a contradiction that could arise from a change in carbon allocation favoring aboveground over belowground tissues. The limited response of woody biomass to nitrogen in year 4 appears to be a consequence of the large increase in canopy density (L) on the control plots in that year compared with fertilized plots. The average for L on control plots was higher in year 4 than it was on fertilized plots in year 3. Also contributing to the limited response to nitrogen in year 4 were lower leaf area efficiencies at the high levels of L on the fertilized plots in year 4.
Metal concentrations in wood of sugar maple infected with sapstreak disease
Authors: Smith K.T. , Houston D.R.
Published: May 2008

The inoculation of sugar maple (Acersaccharum Marsh.) saplings with Ceratocystisvirescens (Davidson) C. Moreau (=Ceratocystiscoerulescens (Munch) Bakshi), the causal agent of sapstreak disease, resulted in infection and the development of extensive discoloration. A distinct column boundary layer formed between the discolored wood and sapwood in wounded saplings infected with C. virescens and in noninoculated controls. Elemental markers of discoloration and column boundary layer formation were similar for infected and noninoculated control saplings. The extensive damage caused by sapstreak disease is interpreted as resulting from the rapid spread of the pathogen prior to column boundary layer formation.
Phosphatidylinositol 4,5-bisphosphate hydrolysis mediates histamine-induced KCNQ/M current inhibition
Authors: Liu Boyi , Liang Huiling , Liu Li , Zhang Hailin
Published: May 2008

The M-type potassium channel, of which its molecular basis is constituted by KCNQ2-5 homo- or heteromultimers, plays a key role in regulating neuronal excitability and is modulated by many G protein-coupled receptors. In this study, we demonstrate that histamine inhibits KCNQ2/Q3 currents in human embryonic kidney (HEK)293 cells via phosphatidylinositol 4,5-bisphosphate (PIP2) hydrolysis mediated by stimulation of H1 receptor and phospholipase C (PLC). Histamine inhibited KCNQ2/Q3 currents in HEK293 cells coexpressing H1 receptor, and this effect was totally abolished by H1 receptor antagonist mepyramine but not altered by H2 receptor antagonist cimetidine. The inhibition of KCNQ currents was significantly attenuated by a PLC inhibitor U-73122 but not affected by depletion of internal Ca2+ stores or intracellular Ca2+ concentration ([Ca2+]i) buffering via pipette dialyzing BAPTA. Moreover, histamine also concentration dependently inhibited M current in rat superior cervical ganglion (SCG) neurons by a similar mechanism. The inhibitory effect of histamine on KCNQ2/Q3 currents was entirely reversible but became irreversible when the resynthesis of PIP2 was impaired with phosphatidylinsitol-4-kinase inhibitors. Histamine was capable of producing a reversible translocation of the PIP2 fluorescence probe PLCδ1-PH-GFP from membrane to cytosol in HEK293 cells by activation of H1 receptor and PLC. We concluded that the inhibition of KCNQ/M currents by histamine in HEK293 cells and SCG neurons is due to the consumption of membrane PIP2 by PLC.
Ubiquitination regulates the plasma membrane expression of renal UT-A urea transporters
Authors: Stewart Gavin S. , O'Brien Jennifer H. , Smith Craig P.
Published: May 2008

The renal UT-A urea transporters UT-A1, UT-A2, and UT-A3 are known to play an important role in the urinary concentrating mechanism. The control of the cellular localization of UT-A transporters is therefore vital to overall renal function. In the present study, we have investigated the effect of ubiquitination on UT-A plasma membrane expression in Madin-Darby canine kidney (MDCK) cell lines expressing each of the three renal UT-A transporters. Inhibition of the ubiquitin-proteasome pathway caused an increase in basal transepithelial urea flux across MDCK-rat (r)UT-A1 and MDCK-mouse (m)UT-A2 monolayers ( P < 0.01, n = 3, ANOVA) and also increased dimethyl urea-sensitive, arginine vasopressin-stimulated urea flux ( P < 0.05, n = 3, ANOVA). Inhibition of the ubiquitin-proteasome pathway also increased basolateral urea flux in MDCK-mUT-A3 monolayers ( P < 0.01, n = 4, ANOVA) in a concentration-dependent manner. These increases in urea flux corresponded to a significant increase in UT-A transporter expression in the plasma membrane ( P < 0.05, n = 3, ANOVA). Further analysis of the MDCK-mUT-A3 cell line confirmed that vasopressin specifically increased UT-A3 expression in the plasma membrane ( P < 0.05, n = 3, ANOVA). However, preliminary data suggested that vasopressin produces this effect through an alternative route to that of the ubiquitin-proteasome pathway. In conclusion, our study suggests that ubiquitination regulates the plasma membrane expression of all three major UT-A urea transporters, but that this is not the mechanism primarily used by vasopressin to produce its physiological effects.
Single muscle fiber adaptations to resistance training in old (>80 yr) men: evidence for limited skeletal muscle plasticity
Authors: Slivka Dustin , Raue Ulrika , Hollon Chris , Minchev Kiril , Trappe Scott
Published: May 2008

The purpose of this study was to investigate whole muscle and single muscle fiber adaptations in very old men in response to progressive resistance training (PRT). Six healthy independently living old men (82 ± 1 yr; range 80–86 yr, 74 ± 4 kg) resistance-trained the knee extensors (3 sets, 10 repetitions) at ∼70% one repetition maximum 3 days/wk for 12 wk. Whole thigh muscle cross-sectional area (CSA) was assessed before and after PRT using computed tomography (CT). Muscle biopsies were obtained from the vastus lateralis before and after the PRT program. Isolated myosin heavy chain (MHC) I and IIa single muscle fibers ( n = 267; 142 pre; 125 post) were studied for diameter, peak tension, shortening velocity, and power. An additional set of isolated single muscle fibers ( n = 2,215; 1,202 pre; 1,013 post) was used to identify MHC distribution. One repetition maximum knee extensor strength increased ( P < 0.05) 23 ± 4 kg (56 ± 4 to 79 ± 7 kg; 41%). Muscle CSA increased ( P < 0.05) 3 ± 1 cm2 (120 ± 7 to 123 ± 7 cm2; 2.5%). Single muscle fiber contractile function and MHC distribution were unaltered with PRT. These data indicate limited muscle plasticity at the single-muscle fiber level with a resistance-training program among the very old. The minor increases in whole muscle CSA coupled with the static nature of the myocellular profile indicate that the strength gains were primarily neurological. These data contrast typical muscle responses to resistance training in young (∼20 yr) and old (∼70 yr) humans and indicate that the physiological regulation of muscle remodeling is adversely modified in the oldest old.
A warmer ambient temperature increases the passage of interleukin-1β into the brains of old rats
Authors: Buchanan Jessica B. , Peloso Elizabeth , Satinoff Evelyn
Published: May 2008

We have demonstrated that after intraperitoneal lipopolysaccharide (LPS) injection, old rats mount fevers similar to those of young rats at an ambient temperature (Ta) of 31°C, but not at 21°C. The same is true for intraperitoneal or intravenous IL-1β administration. The underlying mechanism responsible for blunted fever in old rats may be a deficiency in communication between the periphery and the brain. Possibly, peripheral cytokine actions are altered in old rats, such that the signal that reaches the brain is diminished. Here, we hypothesized that at standard laboratory temperatures, not enough IL-1β is reaching the brain for fever to occur and that a warmer Ta would increase the influx of IL-1β into the brain, enabling old rats to generate fever. Young (3–5 mo) and old (23–29 mo) Long-Evans rats were maintained for 3 days at either Ta 21 or 31°C prior to intravenous injection with radiolabeled IL-1β to measure passage across the blood-brain barrier. Young rats showed similar influx of IL-1β into the brain at the two Tas, but old rats showed significant influx only at the warmer Ta. These data suggest that the lack of fever at a cool Ta may be due to a reduced influx of IL-1β into the brain.
A p38 mitogen-activated protein kinase inhibitor protects against renal damage in a non-heart-beating donor model
Authors: Doucet Carole , Milin Serge , Favreau Frederic , Desurmont Thibault , Manguy Emilie , Hébrard William , Yamamoto Yuriyo , Mauco Gérard , Eugene Michel , Papadopoulos Vassilios , Hauet Thierry , Goujon Jean Michel
Published: May 2008

Ischemia-reperfusion injury is one of the central nonimmunologic processes involved in renal allograft dysfunction. Kidneys from non-heart beating donors (NHBD) exhibit higher rates of delayed graft function (DGF) than those from other donors. Primary nonfunction and DGF are the main barriers to the use of kidneys from NHBD. Using a pig model of NHBD transplantation, we studied the effect of FR167653 (a p38 MAP kinase inhibitor) on the recovery and reparation of kidneys exposed to both warm (WI: 1 h) and cold ischemia (24 h). Our results demonstrate that the addition of FR167653 increases the kinetics of proximal tubule cell regeneration after 60 min of WI. Hypoxia-inducible factor and vascular endothelial growth factor expression was also more important in FR167653-treated kidneys compared with those in nontreated groups. Also, expression of peripheral-type benzodiazepine receptor, involved in tissue repair, was increased in the FR167653-treated groups. At 3 mo, the protective effects of FR167653 were accompanied by a reduction of long-term inflammation process and tubulointerstitial fibrosis development associated with a limitation of ischemia-induced remodeling. This study suggests that such treatment may be useful in protocols aimed at improving the quality of renal transplants from NHBD. In addition, the beneficial role of FR167653 in limiting early injury is associated with secondary reduction in development of tubular atrophy and interstitial fibrosis which are together the hallmark of failing renal transplants. The more efficient effect was observed when FR167653 was added in combination before WI, during cold storage and reperfusion.
Cochlear-Implant High Pulse Rate and Narrow Electrode Configuration Impair Transmission of Temporal Information to the Auditory Cortex
Authors: Middlebrooks John C.
Published: May 2008

In the most commonly used cochlear prosthesis systems, temporal features of sound are signaled by amplitude modulation of constant-rate pulse trains. Several convincing arguments predict that speech reception should be optimized by use of pulse rates ≳2,000 pulses per second (pps) and by use of intracochlear electrode configurations that produce restricted current spread (e.g., bipolar rather than monopolar configurations). Neither of those predictions has been borne out in consistent improvements in speech reception. Neurons in the auditory cortex of anesthetized guinea pigs phase lock to the envelope of sine-modulated electric pulse trains presented through a cochlear implant. The present study used that animal model to quantify the effects of carrier pulse rate, electrode configuration, current level, and modulator wave shape on transmission of temporal information from a cochlear implant to the auditory cortex. Modulation sensitivity was computed using a signal-detection analysis of cortical phase-locking vector strengths. Increasing carrier pulse rate in 1-octave steps from 254 to 4,069 pps resulted in systematic decreases in sensitivity. Comparison of sine- versus square-wave modulator waveforms demonstrated that some, but not all, of the loss of modulation sensitivity at high pulse rates was a result of the decreasing size of pulse-to-pulse current steps at the higher rates. Use of a narrow bipolar electrode configuration, compared with the monopolar configuration, produced a marked decrease in modulation sensitivity. Results from this animal model suggest explanations for the failure of high pulse rates and/or bipolar electrode configurations to produce hoped-for improvements in speech reception.
A Stream Tapping Protocol Involving Clients in the Distribution of Videos on Demand
Authors: Kulkarni Santosh , Pâris Jehan-François , Shah Purvi
Published: May 2008

We present a stream tapping protocol that involves clients in the video distribution process. As in conventional stream tapping, our protocol allows new clients to tap the most recent broadcast of the video they are watching. While conventional stream tapping required the server to send to these clients the part of the video they missed, our protocol delegates this task to the clients that are already watching the video, thus greatly reducing the workload of the server. Unlike previous solutions involving clients in the video distribution process, our protocol works with clients that can only upload video data at a fraction of the video consumption rate and includes a mechanism to control its network bandwidth consumption.
Apparent Enhanced Solubility of Single‐Wall Carbon Nanotubes in a Deuterated Acid Mixture
Authors: Ramanathan T. , Fisher Frank T. , Ruoff Rodney S. , Catherine Brinson L.
Published: May 2008

An apparent enhanced solubility of single‐wall carbon nanotubes (SWNTs) in the deuterated form of the standard 3 : 1 sulfuric (H2SO4) to nitric (HNO3) acid mixture treatment is reported and attributed to the stronger interaction of deuterium bonds with the single‐wall carbon nanotube surface. UV‐Visible spectroscopy was used to characterize the apparent enhanced solubility of the SWNTs treated in deuterated forms of the acid mixture in comparison to the standard acid mix, while FTIR was used to analyze the nature of the functional groups generated on the SWNTs as a result of the different acid treatments. The apparent enhanced solubility reported here is consistent with the limited number of computational and experimental results published in the literature regarding the interaction of carbon nanotubes with deuterated solvents; however, a detailed understanding of the underlying mechanism responsible for this observation is currently lacking. The apparent increased solubility observed here could potentially be utilized in many applications where carbon nanotube dispersion is required.
Efficient Terrain Triangulation and Modification Algorithms for Game Applications
Authors: Raman Sundar , Jianmin Zheng
Published: May 2008

An efficient terrain generation algorithm is developed, based on constrained
conforming Delaunay triangulation. The density of triangulation in different regions of a terrain is
determined by its flatness, as seen from a height map, and a control map. Tracks and other objects
found in a game world can be applied over the terrain using the “stenciling” and “stitching” algorithms.
Using user controlled parameters, varying levels of detail can be preserved when applying these objects
over the terrain as well. The algorithms have been incorporated into 3dsMax as plugins, and the
experimental results demonstrate the usefulness and efficiency of the developed algorithms.
Hydriding Reaction of LaNi5: Correlations between Thermodynamic States and Sorption Kinetics during Activation
Authors: Millet P. , Lebouin C. , Ngameni R. , Ranjbari A. , Guymont M.
Published: May 2008

This research work concerns the hydriding reaction of LaNi5 during the first hydriding cycles (activation process). Step-by-step sorption isotherms (Δ[H/M]≈0.03) were measured at 298 K, in the composition range 0<H/M<2.0, at the beginning (first hydriding cycle, where hysteresis is maximum) and at the end (tenth hydriding cycle, where hysteresis is minimum) of the activation process, offering the possibility to correlate thermodynamic states (pressure-composition data points) to sorption kinetics. Using pneumatochemical impedance spectroscopy (PIS), experimental impedance diagrams were obtained for each data point of the isotherms. Microscopic rate parameters such as surface resistance and hydrogen diffusion coefficient were obtained as a function of composition, by fitting appropriate model equations to experimental impedances. It is found that the high-frequency pneumatochemical resistance significantly decreases during activation. This is correlated with the surface increase of the solid-gas interface area. The hydrogen diffusion coefficient is found to be larger at the beginning of the activation process and lower on a fully activated sample.
Flow Stagnation under Single and Two-Phase Natural Circulation Conditions in the APEX-CE Test Facility
Authors: Reyes José N.
Published: May 2008

Natural circulation experiments were conducted at Oregon State University using the advanced plant experiment (APEX-CE) integral system test facility as configured to simulate a typical2×4Combustion Engineering nuclear steam supply system. This paper describes the mechanisms by which natural circulation flow was interrupted under single-phase and two-phase natural circulation conditions in APEX-CE.
Effect of Coolant Inventories and Parallel Loop Interconnections on the Natural Circulation in Various Heat Transport Systems of a Nuclear Power Plant during Station Blackout
Authors: Gaikwad Avinash J. , Vijayan P. K. , Bhartya Sharad , Iyer Kannan , Kumar Rajesh , Contractor A. D. , Lele H. G. , Vhora S. F. , Maurya A. K. , Ghosh A. K. , Kushwaha H. S.
Published: May 2008

Provision of passive means to reactor core decay heat removal enhances the nuclear power plant (NPP) safety and availability. In the earlier Indian pressurised heavy water reactors (IPHWRs), like the 220 MWe and the 540 MWe, crash cooldown from the steam generators (SGs) is resorted to mitigate consequences of station blackout (SBO). In the 700 MWe PHWR currently being designed an additional passive decay heat removal (PDHR) system is also incorporated to condense the steam generated in the boilers during a SBO. The sustainability of natural circulation in the various heat transport systems (i.e., primary heat transport (PHT), SGs, and PDHRs) under station blackout depends on the corresponding system's coolant inventories and the coolant circuit configurations (i.e., parallel paths and interconnections). On the primary side, the interconnection between the two primary loops plays an important role to sustain the natural circulation heat removal. On the secondary side, the steam lines interconnections and the initial inventory in the SGs prior to cooldown, that is, hooking up of the PDHRs are very important. This paper attempts to open up discussions on the concept and the core issues associated with passive systems which can provide continued heat sink during such accident scenarios. The discussions would include the criteria for design, and performance of such concepts already implemented and proposes schemes to be implemented in the proposed 700 MWe IPHWR. The designer feedbacks generated, and critical examination of performance analysis results for the added passive system to the existing generation II & III reactors will help ascertaining that these safety systems/inventories in fact perform in sustaining decay heat removal and augmenting safety.
ADC Production Test Technique Using Low‐Resolution Arbitrary Waveform Generator
Authors: Kerzérho V. , Cauvet P. , Bernard S. , Azaïs F. , Renovell M. , Comte M. , Chakib O.
Published: May 2008

Standard production test techniques for ADC require an ATE with an arbitrary waveform generator (AWG) with a resolution at least 2 bits higher than the ADC under test resolution. This requirement is a real issue for the new high‐performance ADCs. This paper proposes a test solution that relaxes this constraint. The technique allows the test of ADC harmonic distortions using only low‐cost ATE. The method involves two steps. The first step, called the learning phase, consists in extracting the harmonic contributions from the AWG. These characteristics are then used during the second step, called the production test, to discriminate the harmonic distortions induced by the ADC under test from the ones created by the generator. Hardware experimentations are presented to validate the proposed approach.