bluuebunny/crossref_metadata_2025 huggingface dataset:
A Sensitivity-Based Method for Direct Stochastic Analysis of Nonlinear Forced Response for Bladed Disks With Friction Interfaces
Authors: Petrov E. P.
Published: March 2008

An efficient method is developed to calculate stochastic and uncertainty characteristics of forced response for nonlinear vibrations of bladed disks with friction and gap contact interfaces. Uncertainty ranges, statistical characteristics, and probability density functions for forced response levels are determined directly without any sampling procedure. The method uses approximations of the forced response level based on derived analytically and calculated extremely fast and accurately sensitivity coefficients of forced response with respect to friction contact interface parameters. The method effectiveness allows analysis of strongly nonlinear vibration of bladed disks using realistic large-scale finite element models. The method is implemented in a program code developed at Imperial College and numerical examples of application of the method for stochastic analysis of a realistic blisc with underplatform dampers are provided.
Performance Assessment of Turbocharged Pem Fuel Cell Systems for Civil Aircraft Onboard Power Production
Authors: Campanari Stefano , Manzolini Giampaolo , Beretti Andrea , Wollrab Uwe
Published: March 2008

In recent years, civil aircraft projects are showing a continuous increase in the demand of onboard electrical power, both for the partial substitution of hydraulic or pneumatic controls and drives with electrical ones, and for the consumption of new auxiliary systems developed in response to flight safety and environmental control issues. Aiming to generate onboard power with low emissions and better efficiency, several manufacturers and research groups are considering the possibility to produce a relevant fraction of the electrical power required by the aircraft by a fuel cell system. The first step would be to replace the conventional auxiliary power unit (based on a small gas turbine) with a polymer electrolyte membrane (PEM) fuel cell type, which today is favored with respect to other fuel cell types; thanks to its higher power density and faster startup. The PEM fuel cell can be fed with a hydrogen rich gas coming from a fuel reformer, operating with the same jet fuel used by the aircraft, or relying on a dedicated hydrogen storage onboard. The cell requires also an air compression unit, where the temperature, pressure, and humidity of the air stream feeding the PEM unit during land and in-flight operation strongly influence the performance and the physical integrity of the fuel cell. In this work we consider different system architectures, where the air compression system may exploit an electrically driven compressor or a turbocharger unit. The compressor type and the system pressure level are optimized according to a fuel cell simulation model, which calculates the cell voltage and efficiency as a function of temperature and pressure, calibrated over the performances of real PEM cell components. The system performances are discussed under different operating conditions, covering ground operation, and intermediate and high altitude cruise conditions. The optimized configuration is selected, presenting energy balances and a complete thermodynamic analysis.
A Hybrid Prognostic Model Formulation and Health Estimation of Auxiliary Power Units
Authors: Shetty Pradeep , Mylaraswamy Dinkar , Ekambaram Thirumaran
Published: March 2008

Prognostic health monitoring is an important element of condition-based maintenance and logistics support. The accuracy of prediction and the associated confidence in prediction greatly influence overall performance and subsequent actions either for maintenance or logistics support. Accuracy of prognosis is directly dependent on how closely one can capture the system and component interactions. Traditionally, such models assume a constant and univariate prognostic formulation—that is, components degrade at a constant rate and are independent of each other. Our objective in this paper is to model the degrading system as a collection of prognostic states (health vectors) that evolve continuously over time. The proposed model includes an age dependent deterioration distribution, component interactions, as well as effects of discrete events arising from line maintenance actions and/or abrupt faults. Mathematically, the proposed model can be summarized as a continuously evolving dynamic model, driven by non-Gaussian input and switches according to the discrete events in the system. We develop this model for aircraft auxiliary power units, but it can be generalized to other progressive deteriorating systems. The system identification and recursive state estimation scheme for the developed non-Gaussian model under a partially specified distribution framework has been deduced. The diagnostic/prognostic capabilities of our model and algorithms have been demonstrated using simulated and field data.
An Optimal Maintenance Policy for Compressor of a Gas Turbine Power Plant
Authors: Rao P. Naga Srinivasa , Naikan V. N. Achutha
Published: March 2008

This paper proposes a condition based maintenance policy for compressors of industrial gas turbine. Compressor blade fouling contributes a major performance loss in the operation of gas turbine. Water washing is usually done for recovery of the blade fouling problem. There exist two different washing methods, namely, online and offline washings. Many researchers suggested that performing a combined program of regular online washing plus periodic offline washing would give fruitful results with respect to economy. However, such studies are of empirical nature or have considered only deterministic treatment. Considering the rate of fouling as discrete state random process, we propose a condition based maintenance policy with periodic online washing and inspection directed offline washing. According to this policy, the compressor undergoes regular online washes for every 1∕λm operating hours, and also undergoes inspections at constant rate λI. If the observed condition at an inspection is worse than threshold deterioration state, then perform offline washing. Otherwise, continue with online washing. The proposed algorithm gives optimum schedules for both online washing and inspections considering minimization of total cost per operating hour as objective. It also gives optimum threshold deterioration level for performing offline washing. A comparison of the results for a hypothetical gas turbine compressor is presented as illustration.
Hydrogen-Enhanced Gasoline Stratified Combustion in SI-DI Engines
Authors: Conte Enrico , Boulouchos Konstantinos
Published: March 2008

Experimental investigations were carried out to assess the use of hydrogen in a gasoline direct injection (GDI) engine. Injection of small amounts of hydrogen (up to 27% on energy basis) in the intake port creates a reactive homogeneous background for the direct injection of gasoline in the cylinder. In this way, it is possible to operate the engine with high exhaust gas recirculation (EGR) rates and, in certain conditions, to delay the ignition timing as compared to standard GDI operation, in order to reduce NOx and HC emissions to very low levels and possibly soot emissions. The results confirmed that high EGR rates can be achieved and NOx and HC emissions reduced, showed significant advantage in terms of combustion efficiency and gave unexpected results relative to the delaying of ignition, which only partly confirmed the expected behavior. A realistic application would make use of hydrogen-containing reformer gas produced on board the vehicle, but safety restrictions did not allow using carbon monoxide in the test facility. Thus, pure hydrogen was used for a best-case investigation. The expected difference in the use of the two gases is briefly discussed.
Moonlighting Proteins in Yeasts
Authors: Gancedo Carlos , Flores Carmen-Lisset
Published: March 2008

Proteins able to participate in unrelated biological processes have been grouped under the generic name of moonlighting proteins. Work with different yeast species has uncovered a great number of moonlighting proteins and shown their importance for adequate functioning of the yeast cell. Moonlighting activities in yeasts include such diverse functions as control of gene expression, organelle assembly, and modification of the activity of metabolic pathways. In this review, we consider several well-studied moonlighting proteins in different yeast species, paying attention to the experimental approaches used to identify them and the evidence that supports their participation in the unexpected function. Usually, moonlighting activities have been uncovered unexpectedly, and up to now, no satisfactory way to predict moonlighting activities has been found. Among the well-characterized moonlighting proteins in yeasts, enzymes from the glycolytic pathway appear to be prominent. For some cases, it is shown that despite close phylogenetic relationships, moonlighting activities are not necessarily conserved among yeast species. Organisms may utilize moonlighting to add a new layer of regulation to conventional regulatory networks. The existence of this type of proteins in yeasts should be taken into account when designing mutant screens or in attempts to model or modify yeast metabolism.
Comparison of Bulk, Wet-Only, and Wet-plus-Dry Deposition Measurements at the Turkey Lakes Watershed
Authors: Vet Robert J. , Sirois Alain , Jeffries Dean S. , Semkin R. G. , Foster N. W. , Hazlett P. , Chan C. H.
Published: March 2008

Four different types of atmospheric deposition measurements were made at the Turkey Lakes Watershed from 1981 to 1984. They included weekly and variable period bulk deposition measurements. The resulting annual and seasonal deposition estimates from the four methods were compared for numerical and statistical differences. Several results unexpected from the theory of the measurement methods appeared in the comparison: (1) one of the bulk deposition measurements produced lower deposition of acid-related ions than the two wet-only measurements and (2) the monthly wet-only measurements produced higher deposition of sulphate than the two bulk deposition data sets (by 6 and 19%). Several results were consistent with the theory of the measurements: (1) the daily wet-only measurements produced deposition values lower than the weekly bulk deposition measurements and (2) the wet-plus-dry deposition measurements produced higher estimates of sulphate and nitrate deposition than the two bulk data sets (15 – 35% higher). Laboratory biases appeared to be partially responsible for some of the differences found in the comparison.
Modelling Stream Chemistry for the Turkey Lakes Watershed: Comparison with 1981–84 Data
Authors: Lam D. C. L. , Bobba A. G. , Jeffries D. S. , Craig D.
Published: March 2008

Simulation results obtained from interfacing a hydrological model with a hydrogeochemical model are used to explain the increase of Ca2+ + Mg2+, alkalinity, and pH in a progressively buffered stream system in the Turkey Lakes Watershed, Ontario. Results from the model, which were calibrated with observed data for 1981, were confirmed with those from 1982, 1983, and 1984. The results further supported the hypothesis that the increases of the groundwater input of Ca into the lower streams contributed to the increase of alkalinity and pH in the downstream lakes which appeared to have caused a corresponding increase in the biological primary productivity in these lakes.
Water and Chemical Budgets for Terrestrial Basins at the Turkey Lakes Watershed
Authors: Nicolson J. A.
Published: March 2008

Twenty terrestrial basins ranging in area from 2.3 to 62.7 ha were monitored in the 1050-ha Turkey Lakes Watershed (TLW) to measure discharge and ion loss from the terrestrial ecosystem and to estimate terrestrial contributions to the main aquatic system. These basins span 400 m of elevation, beginning at 60 m above Lake Superior (183 m a.s.l.). Annual streamflow represented 28–63% of precipitation; 30–60% of the total occurred during springmelt. Water, H+, and NH4+ output of the small basins increased with basin elevation; conductivity, alkalinity, Ca2+, and NO3− decreased. Losses of Mg2+, K+, Na+, SO42−, and Cl− were not related to basin elevation. Input–output values indicate a net loss of Ca2+, Mg2+, K+, and Na+; Cl− slowly accumulated, N was strongly retained, and SO42− was generally in balance. Alkalinity values indicate that HCO3− was important in balancing cation losses in low-elevation basins but that SO42− dominated in high-elevation basins. Output of H+ was substantially lower than its input through precipitation at ail elevations; however, H+ removal by the terrestrial system was greater in low-elevation than in high-elevation basins within the main watershed. Precipitation quantity and SO42− and NO3− input were measured at the Atmospheric Environment Service APN station southeast of the TLW; other chemical parameters were measured on samples collected near the main outlet on the west side of the TLW.
Acid Deposition and Nutrient Leaching from Deciduous Vegetation and Podzolic Soils at the Turkey Lakes Watershed
Authors: Foster N. W. , Nicolson J. A.
Published: March 2008

Mean annual ion concentrations and ion fluxes in precipitation induced by contact with a maple–birch forest and soil were determined for 1981–85 at the Turkey Lakes Watershed (47°03′N, 84°15′W). Neutralization of atmospherically deposited H+ was effected by the canopy and mineral soil. Sulphate was an important counter-ion for K+ leached from the vegetation. Acid deposition had a minor impact on the quality of stemflow and forest floor percolate, which were enriched in K+ and Ca2+ mobilized in association with organic anions. Calcium and Mg2+ were leached from the mineral soil in association with SO42− and NO3−. Sulphate was derived largely from acid deposition, and NO3− from both precipitation and nitrification of native soil N.
Zoobenthic Distribution and Biomass in the Turkey Lakes
Authors: Dermott R. M.
Published: March 2008

The composition of the benthic fauna in the four oligotrophic lakes of the Turkey Lakes Watershed was dependent on the absence offish, depth, and hypolimnetic oxygen concentrations, rather than the chemical gradient in the watershed. Biomass in the littoral zone was greatest in the fishless upper lake of the watershed (0.35 g∙m−2), dominated by amphipods and predatory insects, which replaced fish as top predators in the lake. The shallowest lake (Wishart) had the lowest lakewide biomass (199 g∙ha−1) and estimated production of the four lakes, in spite of having the greatest algal and fish production in the watershed. The biomass present below 2 m was greater in the lower two lakes, dominated by the Chironomidae. Little Turkey Lake had the greatest area weighted lakewide biomass (843 g∙ha−1) and estimated production, as a result of a large population of Chironomus spp. in the hypolimnion. Batchawana Lake, the upper lake in the watershed, had the lowest benthic populations due to severe oxygen depletion in the hypolimnion.
Young-of-the-Year Fish Community in Nine Lakes, Varying in pH, on the Canadian Shield
Authors: Kelso J. R. M. , Lipsit J. H.
Published: March 2008

In nine Canadian Shield lakes, seven with resident fish populations, the young-of-the-year (yoy) were first captured some 4 wk and more following the major spring depressions in pH. Since spawning of many resident species followed the spring freshet, yellow perch (Perca flavescens), darters, and many cyprinids sensitive to low pH would hatch and develop folowing the most serious spring changes in chemistry. Within a lake, the period of peak abundance occurred within a period of 2–9 wk during the 3 yr of study. Abundance of yoy was not strongly linked to lake pH or alkalinity. Diversity of yoy was strongly related to lake pH (r = 0.87) and alkalinity (r = 0.89). Monitoring the larval fish community appears to provide a responsive, reproducible measure of change for some of the fish communities sensitive to effects of acidic deposition and can be carried out with only moderate expenditure of time and resources.
Fossil Midge Associations in Relation to Trophic and Acidic State of the Turkey Lakes
Authors: Johnson M. G. , McNeil O. C.
Published: March 2008

Most changes in profiles of relative abundance of Chironomus, Sergentia, Procladius, Heterotrissocladius, Micropsectra, Tanytarsus, and other taxa in dated sediment cores suggested a trend to more oligotrophy conditions at present in four dimictic lakes, but not in the single polymictic lake in which species composition was least variable temporally. Decreased numbers of chironomids and chaoborids toward the present indicated declining productivity in all five lakes. Total phosphorus concentrations in sediments declined through these periods of inferred greater oligotrophy. Most of these trends were probably not caused by anthropogenic acidification because they began up to 130 yr B.P. and they were sometimes duplicated even deeper in sediment cores. Furthermore, taxa common in acidified lakes elsewhere did not increase in these lakes. Recent acidification may have affected taxonomic composition and diversity of chironomids in the headwater lake, the only lake which showed a near-surface reduction in members of the tribe Tanytarsini, and the ratio of taxa to individuals. Chaoborus americanus occurred at high densities throughout the cores from the two upper lakes, indicating that these lakes probably never had fish communities.
Sediment pH in Profundal Core Samples from the Turkey Lakes (Algoma, Ontario)
Authors: Morris J. R. , Kwain W.
Published: March 2008

Vertical pH profiles were recorded in sediment cores from four of the Turkey Lakes in the Algoma region of northern Ontario. In the three upper lakes of the chain, median down-core pH, which should be correlated with historic lake water pH, was below the median down-core pH for other lakes in northeastern Ontario. The Turkey lakes had probably been relatively acidic, therefore, since pre-industrial times. Down-core pH tended to be lower in upstream lakes. While a pH minimum was typically observed at the sediment–water interface, the surficial sediments were not acidified relative to down-core sediments.
Effect of Acid Precipitation on Microbial Decomposition Processes in Sediment From Streams in the Turkey Lakes Watershed
Authors: Jensen M. J. , Kaushik N. K. , Wong P. T. S. , Robinson J. B.
Published: March 2008

The effect of simulated acid precipitation (pHs between 3.5 and 5.9) on the breakdown of organic matter in streams was examined under laboratory conditions using two different sediment types from streams. Decomposition processes were measured using 14C-labelled glucose, leaf leachate, and leached leaf material. The data indicated that penetration of acid into settled sediment is small. Therefore, little effect of pH on organic matter breakdown could be perceived. During suspended conditions, however, a marked decrease in breakdown rates was noted. It appeared that under these conditions a slight stimulation in decomposition rates caused by the sulphate and nitrate present in the acid precipitation occurred. The effect of pH on the rate of organic matter breakdown depended on the type of substrate used in the experiment. Glucose decomposition was least inhibited by pH, followed by leaf leachate, and leached leaf material breakdown was the most inhibited. Sediment with higher organic matter was more sensitive under conditions of suspension, but less sensitive than the sediment with less organic matter under settled conditions. This appeared to be a result of the lower penetration of acid in the settled organic sediment.
Effet de la propagation non linéaire des débits sur le contrôle en temps réel des débordements de réseaux unitaires
Authors: Wilson Lucie , Isabel Denis , Villeneuve Jean-Pierre
Published: March 2008

A number of reports on simulations of real-time control of combined sewer system runoff have been published. Most of the control strategies suggested use linear models to calculate discharge routing. We used a nonlinear model for discharge routing and some of our findings differ from those obtained in earlier studies. In particular, it appears that the prediction horizon used for control optimization could be favourably shorter than the time of system flow-through. Key words: combined sewer system overflow, real-time control, nonlinear programming, discharge propagation. [Journal translation]
Mechanical properties and freezing and thawing durability of concrete incorporating a ground granulated blast-furnace slag
Authors: Malhotra V. M.
Published: March 2008

This paper gives the results of laboratory invstigations to determine the mechanical properties and freezing and thawing durability of concrete incorporating a granulated blast-furnace slag from a Canadian source. A series of fifteen 0.06 m3 concrete mixtures were made with water-to-(cement + slag) ratios (W/(C + S)) ranging from 0.70 to 0.45. The percentage of slag used as a partial replacement for normal portland cement ranged from 0 to 100% by weight. All mixtures were air entrained. A number of test cylinders and prisms were cast for determining the mechanical properties and freezing and thawing resistance of concrete.The test results indicate that the ground granulated blast-furnace slag can be used with advantage as a partial replacement for portland cement in concrete at 50% or lower replacement levels, especially at W/(C + S) of the order of 0.55 or lower. At 28 days, irrespective of the W/(C + S) and regardless of the percentage replacement of the cement by the slag investigated, the compressive strength of the concrete incorporating slag is comparable with that of the concrete made with normal portland cement. At all W/(C + S) and at all percentages of replacement, the flexural strength of the slag concrete is comparable with or greater than the corresponding strength of the control concrete. Durability of air-entrained slag concrete exposed to repeated cycles of freezing and thawing is satisfactory as evidenced by the high durability factors achieved. Key words: granulated slag, bleeding, time of setting, concrete, strength, freezing and thawing, shrinkage, creep, abrasion.
Nonlinear wave forces on a circular cylinder
Authors: Isaacson Michael , Zuo Qi-Hua
Published: March 2008

Nonlinear wave forces on a surface-piercing vertical circular cylinder are considered using a time-stepping method previously developed which is based on Green's theorem. Possible improvements in the efficiency, accuracy, and stability of the method are considered. Results based on this method are compared with those obtained previously using perturbation methods as well as with experimental results. It is found that the time-stepping method adopted here is quite reasonable. Wave force coefficients are given as functions of the governing parameters of the problem and the importance of nonlinear wave effects on the forces is assessed. Key words: hydrodynamics, ocean engineering, offshore structures, waves, wave forces.
Factor substitution and economies of scale in the Alberta sawmill industry
Authors: Banskota Kamal , Phillips William , Williamson Timothy
Published: March 2008

An analysis of cross-sectional data reveals that a nonhomothetic transcendental logarithmic cost function provides an appropriate representation of the structure of the Alberta sawmill industry. While the econometric approach used is well established, its application to forestry using cross-sectional data is rare. In this study, mill lumber output was specified as a function of the input prices for labour, capital, wood, and energy. All own-price elasticities are significant and negative as expected. There are significant degrees of factor substitution among the inputs in the sawmills in response to changes in factor prices. Virtually all mills have positive scale economies. There is a positive association between larger sawmills and significant scale economies. These results have important implications regarding long-term timber supply and economic efficiency.
A fossil pollen based reconstruction of the late Quaternary history of lodgepole pine (Pinuscontorta ssp. latifolia) in the western interior of Canada
Authors: MacDonald Glen M. , Cwynar Les C.
Published: March 2008

Previous reconstructions of the late Quaternary biogeographical history of lodgepole pine (Pinuscontorta Dougl.) have been based upon inferences from the modern geographical distribution of morphological and genetic variation. These studies have led to the widely accepted conclusion that relict populations of the Rocky Mountain subspecies of lodgepole pine (ssp. latifolia Engelm.) persisted in glacial refugia located in northwestern Canada. New fossil pollen evidence of the late Pleistocene and Holocene distribution of lodgepole pine in the western interior of Canada contradicts this view. Pinuscontorta ssp. latifolia migrated northward into Canada from refugia located south of the continental glacial limits and did not reach its northern range limits in the southern Yukon until the late Holocene.
The effect of top pruning, girdling, and gibberellin A4/7 application on the production and distribution of pollen and seed cones in Sitka spruce
Authors: Philipson J. J.
Published: March 2008

In intact grafted Piceasitchensis (Bong.) Carr., which had about 10 whorls of main branches, the seed cones were largely confined to the upper 4 whorls; pollen cones were broadly distributed throughout the tree, though they were most numerous in the same region as the seed cones. Girdling plus gibberellin A4/7 application to the stem did not greatly alter the distribution of seed cones, but the zone of densest pollen cones occurred lower down. When the treatments were applied directly to branches in the lower crown, very few seed cones were produced on the treated branches but the number of pollen cones was enhanced. The lower crown of intact trees thus appears to be a zone that does not normally produce seed cones. However, when trees were top pruned (decapitated at whorl 6) and treated at the stem, numerous seed cones were produced on whorls previously in the nonproducing zone in the lower crown. Top-pruned trees became bushier and, in a good flowering year, 3 years after pruning, they produced as many seed cones as intact trees. Top pruning thus greatly improved the accessibility of seed cones and appears to be a practical management technique for Sitka spruce breeding programmes and seed orchards.
Sampling and genetic variation of foliar nitrogen in black cottonwood and its hybrids in short rotation
Authors: Heilman Paul E.
Published: March 2008

Concentrations of N in foliage of black cottonwood (Populustrichocarpa Torr. & Gray) and three of its hybrids varied significantly for all factors studied (crown position, sampling date, years, populations, and clones) and was not correlated with productivity of populations or clones. Significant interactions occurred for black cottonwood between populations and years and between clones and years. Six-year mean nitrogen concentration varied relatively little among the 10 black cottonwood populations (2.73–2.91%), but the 50 individual clones varied from 2.47 to 3.08% N. Concentrations of N were significantly higher in leaves from three positions in the upper crown than from low in the crown. No significant differences were evident among the three upper crown positions. A significant decline in nitrogen concentration occurred in most clones over the period from August 15 to October 17. The effect of years was due to an average decline from a mean of 3.03% N in the 1st year to 2.65% N in the 6th year. Estimates of the number of trees to be included in sampling to determine 1st-year mean foliar N for individual clones within ±10% at P ≥ 0.05 ranged from 23 to 55, depending upon the clonal variability. If the 1st year is avoided, the number of trees required would be 6–37. Somewhat more trees would need to be sampled to estimate population means.
A comparison of four methods for determining leaf area index in successional hardwood forests
Authors: Jurik Thomas W. , Briggs George M. , Gates David M.
Published: March 2008

Four methods of determining leaf area index of three successional hardwood forests in northern lower Michigan were compared. Direct harvests gave values for leaf area index ranging from 1.4 to 3.6. Estimates of leaf area index derived from litter fall data were consistently higher than the harvest values and were highly dependent on the ratio of leaf area to leaf mass, which had to be estimated. A visual method using sightings through a tube gave values consistently lower (by 27–42%) than the harvest values. Calculations of leaf area index based on regressions of leaf mass versus tree diameter gave results very close to the harvest values for each site as a whole; calculations for smaller plots were more variable. The harvest method allowed measurement of the vertical distribution of leaf area; the other methods could not do so.
Propagation of Abiesfraseri by softwood stem cuttings
Authors: Wise Farrell C. , Blazich Frank A. , Hinesley L. Eric
Published: March 2008

Effects of collection date, crown position, and indole-3-butyric acid concentration on rooting and subsequent vegetative growth of softwood cuttings taken from 14-year-old Fraser fir (Abiesfraseri (Pursh) Poir.) Christmas trees were studied. Indole-3-butyric acid levels producing maximum rooting (approximately 50%) varied with crown position and date of severance. Abaxial bending during rooting was greatest for cuttings from the first collection (June 23). Increasing indole-3-butyric acid concentrations decreased abaxial bending of cuttings from the first two severance dates. One year after rooting, plagiotropism was still most pronounced on cuttings collected the first date as a result of active bending of the original cutting segment. Terminal shoot growth was greatest for cuttings from the first and third collections. Lateral budbreak was superior on cuttings collected on the first date. When all factors are taken into consideration, the best combination of rooting and vegetative growth was obtained from upper-crown cuttings which were collected just prior to lignification, wounded, and treated with 1500 ppm indole-3-butyric acid. After one season (one growth flush), rooted softwood cuttings were comparable to 2-year-old plants (two flushes) propagated by hardwood cuttings. The temporal separation of rooting from shoot extension may have been responsible for improving initial vegetative growth.
A method of forcing additivity of biomass tables when using nonlinear models
Authors: Reed David D. , Green Edwin J.
Published: March 2008

A procedure is presented for estimating the coefficients of allometric models for predicting tree component biomass. The resulting equations force the sum of the component estimates to be equal to the estimate of total biomass. An illustration of the procedure is given using published biomass data and the relationship of this procedure to previously published procedures is discussed.
The Canadian Forest Fire Weather Index System as a predictor of total soil moisture content as estimated by the Thornthwaite water balance
Authors: McAlpine Robert S. , Eiber Thomas G.
Published: March 2008

Weather data from Upsala and Atikokan, Ontario, were used to determine the Canadian Forest Fire Weather Index System values and to calculate the soil moisture for two soil types using the Thornthwaite water balance. The Duff Moisture Code and the Drought Code were found to give excellent correlations with the total soil moisture content under most weather patterns.
POSITIVE MASS THEOREMS FOR ASYMPTOTICALLY ADS SPACETIMES WITH ARBITRARY COSMOLOGICAL CONSTANT
Authors: XIE NAQING , ZHANG XIAO
Published: March 2008

We formulate and prove the Lorentzian version of the positive mass theorems with arbitrary negative cosmological constant for asymptotically AdS spacetimes. This work is the continuation of the second author's recent work on the positive mass theorem on asymptotically hyperbolic 3-manifolds.
Exercise-induced alterations in intramyocellular lipids and insulin resistance: the athlete's paradox revisited
Authors: Dubé John J. , Amati Francesca , Stefanovic-Racic Maja , Toledo Frederico G. S. , Sauers Sarah E. , Goodpaster Bret H.
Published: March 2008

We previously reported an “athlete's paradox” in which endurance-trained athletes, who possess a high oxidative capacity and enhanced insulin sensitivity, also have higher intramyocellular lipid (IMCL) content. The purpose of this study was to determine whether moderate exercise training would increase IMCL, oxidative capacity of muscle, and insulin sensitivity in previously sedentary overweight to obese, insulin-resistant, older subjects. Twenty-five older (66.4 ± 0.8 yr) obese (BMI = 30.3 ± 0.7 kg/m2) men ( n = 9) and women ( n = 16) completed a 16-wk moderate but progressive exercise training program. Body weight and fat mass modestly but significantly ( P < 0.01) decreased. Insulin sensitivity, measured using the euglycemic hyperinsulinemic clamp, was increased (21%, P = 0.02), with modest improvements (7%, P = 0.04) in aerobic fitness (V̇o2peak). Histochemical analyses of IMCL (Oil Red O staining), oxidative capacity [succinate dehydrogenase activity (SDH)], glycogen content, capillary density, and fiber type were performed on skeletal muscle biopsies. Exercise training increased IMCL by 21%. In contrast, diacylglycerol and ceramide, measured by mass spectroscopy, were decreased ( n = 13; −29% and −24%, respectively, P < 0.05) with exercise training. SDH (19%), glycogen content (15%), capillary density (7%), and the percentage of type I slow oxidative fibers (from 50.8 to 55.7%), all P ≤ 0.05, were increased after exercise. In summary, these results extend the athlete's paradox by demonstrating that chronic exercise in overweight to obese older adults improves insulin sensitivity in conjunction with favorable alterations in lipid partitioning and an enhanced oxidative capacity within muscle. Therefore, several key deleterious effects of aging and/or obesity on the metabolic profile of skeletal muscle can be reversed with only moderate increases in physical activity.
Calcium- and Calmodulin-Dependent Inactivation of Calcium Channels in Inner Hair Cells of the Rat Cochlea
Authors: Grant Lisa , Fuchs Paul
Published: March 2008

Modulation of voltage-gated calcium channels was studied in inner hair cells (IHCs) in an ex vivo preparation of the apical turn of the rat organ of Corti. Whole cell voltage clamp in the presence of potassium channel blockers showed inward calcium currents with millisecond activation and deactivation kinetics. When temperature was raised from 22 to 37°C, the calcium currents of immature IHCs [<12 days postnatal (P12)] increased threefold in amplitude, and developed more pronounced inactivation. This was determined to be calcium-dependent inactivation (CDI) on the basis of its reliance on external calcium (substitution with barium), sensitivity to internal calcium-buffering, and voltage dependence (reflecting the calcium driving force). After the onset of hearing at P12, IHC calcium current amplitude and the extent of inactivation were greatly reduced. Although smaller than in prehearing IHCs, CDI remained significant in the mature IHC near the resting membrane potential. CDI in mature IHCs was enhanced by application of the endoplasmic calcium pump blocker, benzo-hydroquinone. Conversely, CDI in immature IHCs was reduced by calmodulin inhibitors. Thus voltage-gated calcium channels in mammalian IHCs are subject to a calmodulin-mediated process of CDI. The extent of CDI depends on the balance of calcium buffering mechanisms and may be regulated by calmodulin-specific processes. CDI provides a means for the rate of spontaneous transmitter release to be adjusted to variations in hair cell resting potential and steady state calcium influx.
Targeted drug delivery to mesothelioma cells using functionally selected internalizing human single-chain antibodies
Authors: An Feng , Drummond Daryl C. , Wilson Shannon , Kirpotin Dmitri B. , Nishimura Stephen L. , Broaddus V. Courtney , Liu Bin
Published: March 2008

Mesothelioma is a malignancy of the mesothelium and current treatments are generally ineffective. One promising area of anticancer drug development is to explore tumor susceptibility to targeted therapy. To achieve efficient, targeted intracellular delivery of therapeutic agents to mesothelioma cells, we selected a naive human single-chain (scFv) phage antibody display library directly on the surface of live mesothelioma cells to identify internalizing antibodies that target mesothelioma-associated cell surface antigens. We have identified a panel of internalizing scFvs that bind to mesothelioma cell lines derived from both epithelioid (M28) and sarcomatous (VAMT-1) types of this disease. Most importantly, these antibodies stain mesothelioma cells in situ and therefore define a panel of clinically represented tumor antigens. We have further exploited the internalizing function of these scFvs to achieve targeted intracellular drug delivery to mesothelioma cells. We showed that scFv-targeted immunoliposomes were efficiently and specifically taken up by both epithelioid and sarcomatous mesothelioma cells, but not control cells, and immunoliposomes encapsulating the small-molecule drug topotecan caused targeted killing of both types of mesothelioma cells in vitro. [Mol Cancer Ther 2008;7(3):569–78]
Basic Research on Dopamine in Parkinson’s Disease and the Discovery of the Nigrostriatal Dopamine Pathway: The View of an Eyewitness
Authors: Hornykiewicz Oleh
Published: March 2008

The article recapitulates some of the historical facts that led up to the recognition of dopamine (DA) as a biologically active substance in the brain and its crucial role in Parkinson’s disease (PD). Three events to which the writer has been an eyewitness are specially highlighted and placed in their proper historical perspective: (1) the discovery of the striatal DA deficit in the PD brain; (2) the development of the DA replacement treatment with L-dopa, and (3) the ‘birth’ of the nigrostriatal DA pathway. The opposition to the new observations and their unexpected and far-reaching consequences will be illustrated by briefly discussing the strongly negative opinions expressed by some famous brain scientists of the day about the relationship between the substantia nigra, PD, and the DA-containing nigrostriatal fiber connection.
Early Detection of Parkinson’s Disease: Unmet Needs
Authors: Gerlach Manfred , Hendrich Albrecht , Hueber Roland , Jost Wolfgang , Winkler Jürgen , Woitalla Dirk , Riederer Peter
Published: March 2008

A biomarker (biological marker) is a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenetic processes or pharmacological responses to a therapeutic intervention. Expectations are high for the development of biomarkers since they make it possible to achieve a significant improvement in the diagnosis and classification of diseases like Parkinson’s disease. As a surrogate marker for clinical studies, a biomarker can also be used to determine the efficacy of novel therapeutic interventions, such as neuroprotective strategies, and for monitoring the progress of the disease. Imaging techniques (18F-DOPA PET, 123I-β-CIT SPECT, MIBG scintigraphy, functional imaging), clinical tests (e.g. hyposmia, micrography, hyperechogenicity, apomorphine test), biochemical markers (e.g. α-synuclein and neuromelanin antibodies, oxidative and mitochondrial markers) and genetic tests for hereditary forms (PARK1 to PARK11) are evaluated for their suitability.
Activation of the Amyloid Cascade by Intracerebroventricular Injection of the Protease Inhibitor Phosphoramidon
Authors: Nisemblat Yotam , Belinson Haim , Dolev Iftach , Michaelson Daniel M.
Published: March 2008

We presently investigated the pathological effects of prolonged inhibition of brain β-amyloid (Aβ) degradation in vivo. The results obtained revealed that intracerebroventricular injection of the protease inhibitor phosphoramidon into wild-type mice for up to a month elevated the soluble and deposited brain Aβ levels and concomitantly induced the neurodegeneration of distinct hippocampal neurons as well as neuroinflammation. These findings reproduce pathological effects associated with the initial stages of the amyloid cascade and provide a novel model system for studying their underlying mechanisms.
Influence of Pharmacogenetic Factors on Alzheimer’s Disease Therapeutics
Authors: Cacabelos Ramón
Published: March 2008

Alzheimer’s disease (AD) is the result of the phenotypic expression of more than 200 genes which are potentially involved in neurodegeneration. Structural and functional genomics studies demonstrate that genomic factors, probably induced by environmental factors, cerebrovascular dysfunction, and epigenetic phenomena, might be responsible for AD pathogenesis leading to premature neuronal death. Drug metabolism, pharmacokinetics and pharmacodynamics are genetically regulated complex traits in which hundreds of genes may participate. Pharmacogenetics studies show that the therapeutic response in AD is genotype specific, with APOE-4/4 carriers as the worst responders to conventional treatments. In addition, about 10–20% of Caucasians are carriers of defective CYP2D6 polymorphic variants that alter the metabolism and effects of AD drugs and many psychotropic agents currently administered to patients with dementia. With multifactorial therapies, combining different drugs, it is possible to slow down cognitive deterioration in parallel with improvement in noncognitive symptoms; however, the association of the APOE-4 allele with specific genetic variants of other genes negatively modulates the therapeutic response to multifactorial treatments affecting cognition, mood and behavior. Pharmacogenetic factors may account for 60–90% of drug variability in drug disposition and pharmacodynamics. The incorporation of pharmacogenetic protocols into AD research and clinical practice can foster therapeutics optimization by improving drug efficacy and safety.
Investigating Convergent Actions of Genes Linked to Familial Parkinson’s Disease
Authors: Wolozin Benjamin , Saha Shamol , Guillily Maria , Ferree Andrew , Riley Misha
Published: March 2008

Background: Mutations in LRRK2 are among the most frequent genetic changes identified in Parkinson’s disease (PD), but how LRRK2 contributes to the pathophysiology of PD is not known. Objectives: To investigate how expressing wild-type or G2019S LRRK2 modifies cellular responses to rotenone, a mitochondrial toxin. Methods: We investigated the vulnerability to mitochondrial toxins in Caenorhabditis elegans expressing wild-type or G2019S LRRK2. Results: We observed a powerful role for LRRK2 in mitochondrial biology. Overexpressing LRRK2 strongly protects C. elegans against rotenone toxicity. The G2019S LRRK2 construct also protected LRRK2 against rotenone, but to a lesser degree than wild-type LRRK2. Knockdown of lrk-1 potentiated rotenone toxicity. Conclusions: These data suggest that LRRK1/2 regulate mitochondrial physiology.
Progress in the Active Immunotherapeutic Approach to Alzheimer’s Disease: Clinical Investigations into AN1792-Associated Meningoencephalitis
Authors: Pride Michael , Seubert Peter , Grundman Michael , Hagen Michael , Eldridge John , Black Ronald S.
Published: March 2008

Background: In a phase 2a clinical trial of AN1792 (Study 201), a potential immunotherapeutic agent for use in Alzheimer’s disease (AD), approximately 6% of the treated AD patients (18/300) developed meningoencephalitis (ME). Objective: To elucidate potential immune mechanisms of treatment-induced ME. Methods: Peripheral blood mononuclear cells obtained from patients who received AN1792 were stimulated in vitro either with β-amyloid (Aβ) or various overlapping peptides of Aβ1–42, followed by quantification of cytokine-secreting cells by enzyme-linked immunosorbent spot assay. Results: A significant difference in the quality of the T-cell responses between patients in Study 201 and those in earlier studies of AN1792 was noted. T-cell responses specific to the carboxy terminus of Aβ elicited from patients’ peripheral blood mononuclear cells in an earlier multiple dose study (Study 102) were Th2 biased, while those from Study 201 were biased toward a proinflammatory Th1 response. Antibody responses in both studies were quantitatively and qualitatively similar (as determined by epitope mapping). The addition of polysorbate 80 to the formulation used in Study 201 is the most likely explanation for the difference in the T-cell response. Conclusion: ME following injection of AN1792 may be related to immune response differences driven by a formulation change. To address this, a novel peptide-carrier protein conjugate using an amino-terminal fragment of Aβ (ACC-001) has been developed to avoid potentially harmful T-cell responses, while maintaining a similar antibody response to that of AN1792. Immunotherapeutic trials using this treatment approach in AD patients are in progress.
Engineered Heparins: Novel β-Secretase Inhibitors as Potential Alzheimer’s Disease Therapeutics
Authors: Patey S.J. , Edwards E.A. , Yates E.A. , Turnbull J.E.
Published: March 2008

Background: Cleavage of β-amyloid precursor protein (APP) by the protease β-secretase (BACE1) is a key step in β-amyloid peptide processing. We have described a novel role for heparan sulphate polysaccharides in Alzheimer’s disease pathology as naturally occurring inhibitors of β-secretase, suggesting new avenues for discovery of novel drugs for Alzheimer’s disease based on heparins. Objective: To evaluate engineered heparin analogues as novel β-secretase inhibitors in vitro, including modifications to increase bioavailability. Methods: We tested a number of selectively desulphated and chemically modified heparins for their ability to inhibit BACE1 and other proteases in vitro using APP fluorescent resonance energy transfer peptide substrates Results: Several lead compounds have been identified that are effective β-secretase inhibitors, but have negligible activity as anticoagulants or as inhibitors of other aspartyl proteases structurally related to β-secretase. In addition, the compounds studied also give some insight into the structural interaction between β-secretase and heparin, indicating that the structure of the polysaccharide is much more important than charge. Conclusion: We have demonstrated that modifications to increase bioavailability of chemically modified heparins have little effect on their efficacy as β-secretase inhibitors. Therefore, these heparins show promise for development as a novel class of pharmaceuticals that target the underlying pathology of Alzheimer’s disease. We have also found further evidence that it is the structure of the polysaccharide that is important for the interaction with β-secretase, not simply the level of sulphation or charge.
Regulation of proBACE1 by Glycosaminoglycans
Authors: Small David H. , Klaver David W. , Beckman Marie
Published: March 2008

The β-secretase (BACE1) is initially synthesized as a partially active zymogen containing a prodomain which can be further activated through proteolytic cleavage of the prodomain by a furin-like protease. The active site of BACE1 is large and although a number of high-affinity active-site inhibitors of BACE1 have been described, most of these compounds are large, polar and do not cross the blood-brain barrier. However, it may be possible to target other regions of the protein which regulate BACE1 allosterically. We have found that proBACE1 can be stimulated by relatively low concentrations (e.g. 1 µg/ml) of heparin. Heparin initially increases proBACE1 activity, probably by binding to the prodomain, which decreases steric inhibition at the active site. However, the heparin-activated zymogen also undergoes autocatalysis, which ultimately leads to a loss of enzyme activity. We speculate that proBACE1 can be regulated by endogenous heparan sulfate proteoglycans and that drugs which target this interaction may have value in the treatment of Alzheimer’s disease.