Control valves usually are sized by picking a valve with a flow coefficient (Cv) that produces the desired pressure drop. Though these are not the only considerations because cavitation can sometimes ...occur, resulting in noise and rapid deterioration of the valve trim. Gaining knowledge on how to design to prevent cavitation and what to do when it occurs is a possible solution to such problems.
The dominant interannual El Niño–Southern Oscillation (ENSO) phenomenon and the short length of climate observation records make it difficult to study long-term climate variations in the ...spatiotemporal domain. Based on the fact that the ENSO signal spreads to remote regions and induces delayed climate variation through atmospheric teleconnections, an ENSO-removal method is developed through which the ENSO signal can be approximately removed at the grid box level from the spatiotemporal field of a climate parameter. After this signal is removed, long-term climate variations are isolated at mid- and low latitudes in the climate parameter fields from observed and reanalysis datasets. This paper addresses the long-term global warming trend (GW); a companion paper concentrates on Pacific pan-decadal variability (PDV).
The warming that occurs in the Pacific basin (approximately 0.4 K in the twentieth century) is much weaker than in surrounding regions and the other two ocean basins (approximately 0.8 K). The modest warming in the Pacific basin is likely due to its dynamic nature on the interannual and decadal time scales and/or the leakage of upper ocean water through the Indonesian Throughflow.
Based on the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) and the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40), a comprehensive atmospheric structure associated with the GW trend is given. Significant discrepancies exist between the two datasets, especially in the tightly coupled dynamics and water vapor fields. The dynamics fields based on NCEP–NCAR, which show a change in the Walker Circulation, are consistent with the GW change in the surface temperature field. However, intensification in the Hadley Circulation is associated with GW trend in ERA-40 instead.
The spatiotemporal structure of Pacific pan-decadal variability (PDV) is isolated in global long-term surface temperature (ST) datasets and reanalysis atmospheric parameter fields from which El ...Niño–Southern Oscillation (ENSO) effects have been removed. Empirical orthogonal function (EOF) and combined EOF analysis of the resulting time series identify PDV as one of two primary modes of long-term variability, the other being a global warming (GW) trend, which is addressed in a companion paper (Part I).
In this study, it is shown that one of several PDV interdecadal regime shifts occurred during the 1990s. This significant change in the Pacific basin is comparable but antiphase to the well-known 1976 climate regime shift and is consistent with the observed changes in biosystems and ocean circulation. A comprehensive picture of PDV as manifested in the troposphere and at the surface is described. In general, the PDV spatial patterns in different parameter fields share some similarities with the patterns associated with ENSO, but important differences exist. First, the PDV circulation pattern is shifted westward by about 20° and is less zonally extended than that for ENSO. The westward shift of the PDV wave train produces a different North American teleconnection pattern that is more west–east oriented. The lack of a strong PDV surface temperature (ST) signal in the west equatorial Pacific and the relatively strong ST signal in the subtropical regions are consistent with an atmospheric overturning circulation response that differs from the one associated with ENSO. The analysis also suggests that PDV is a combination of decadal and/or interdecadal oscillations interacting through teleconnections.
Staged pyrolysis and combustion of waste tire chips was investigated as a technique to minimize emissions of pollutants. Fixed quantities of chips were introduced to a furnace under pyrolytic ...conditions (in nitrogen) and devolatilized at furnace temperatures in the range 500-1000°C. The pyrolyzate gases were then mixed with additional streams of either nitrogen or oxygen in a venturi mixer, placed in-side the furnace. In the oxygen case, a nominally premixed flame occurred at the exit of the venturi, still inside the furnace. The effluent of either case was channeled to a secondary furnace for further treatment at 1000°C for a duration of 0.6 s. Sampling for combustion emissions, including products of incomplete combustion (PIC), took place at the exits of both furnaces. Sampled species included CO
2
, CO, polynuclear aromatic hydrocarbons (PAHs), particulates, as well as nitrogen and sulfur oxides. Results showed that under inert conditions in both furnaces (pyrolysis-pyrolysis case) the emissions of PAHs and particulates from the primary furnace were high and drastically increased by the secondary furnace treatment. To the contrary, in the pyrolysis-oxidation case, when the pyrolyzates ignited and formed a flame at the exit of the venturi, the particulate and PAH emissions were low at the exit of the primary furnace. PIC were further reduced in the secondary furnace as oxidative conditions prevailed therein. As these experiments measured the PAH and soot amounts in the tire pyrolyzates before and after the flame, they illustrated the effectiveness of a nominally premixed flame for oxidizing such species. They also illustrated that a sequential pyrolysis-oxidation approach has the potential for low emissions in waste tire-to-energy plants.
A laboratory investigation was performed on the emissions from the batch combustion of waste tire chips in fixed beds. Techniques and conditions that minimize toxic emissions were identified. ...Tire-derived fuel (TDF), in the form of waste tire chips (1 cm in size), was burned in a two-stage combustor. Batches of tire chips were introduced to the primary furnace, where gasification and combustion occurred. The gaseous effluent of this furnace was mixed with streams of additional preheated air in a mixing venturi, and it was then passed through a silicon carbide (SiC) honeycomb wall-flow filter that had been placed inside this furnace. Subsequently, it was channeled into a secondary furnace (afterburner), where further oxidation occurred. The arrangement of the two furnaces in series allowed for independent temperature control; varying the temperature in the primary furnace influenced the type and the flux of pyrolysates. The hot-flue-gas filtering section, ahead of the exit of the primary furnace, allowed the retention and further oxidation of most of the generated particulates and, thus, prevented them from entering the afterburner. Results showed that the combination of the high-temperature ceramic filter with the afterburner treatment was successful in reducing the emissions from the combustion of waste tires. Depending on the temperature of the primary furnace, the final emissions of CO were reduced by factors of 2−6, NO x emissions were reduced by factors of 2−3, particulate emissions were reduced by 2 orders of magnitude (both PM2.5 and PM10), and most individual polycyclic aromatic hydrocarbon (PAH) species emissions were reduced by more than 1 order of magnitude, with the exception of naphthalene, whose reduction was less drastic. The overall combustion effectiveness was enhanced, as evidenced by higher CO2 yields.
The feasibility of utilizing rainbow trout,
Oncorhynchus mykiss, as an alternative model for studying the inhibition of aromatase (CYP 19) was investigated. The suppression of estrogen-dependent ...tumors by aromatase inhibitors has been important in the treatment of breast cancer. Estrogens, estrogen precursors and xenoestrogens have been found to promote liver cancer in the trout model. A steroid, 4-hydroxy-4-androstene-3,17-dione (4-OHA), and non-steroids, aminoglutethimide (AG) and Letrozole (CGS 20267), all of which are known aromatase inhibitors in rats and humans, were examined in vitro for activity in trout ovarian microsomes. Aromatase activity was quantified as the release of
3H
2O from the conversion of
3H-4-androstene-3,17-dione to 17β-estradiol and estrone. Trout ovarian microsomes exhibited activity between 39–60 fmol mg
−1 min
−1 with a calculated
V
max of 71.1 fmol mg
−1 min
−1 when incubated at 25°C with 200 nM 4-androstene-3,17-dione (
K
M=435 nM). Significant inhibition by 4-OHA up to 80% was seen at 1.5 μM. At 2000 μM, AG decreased aromatase activity by up to 82%. Letrozole reduced aromatase activity a maximum of 90% in a dose-dependent manner, but the
K
i (2.3 μM) was 1000-fold higher than reported in human trials. Indole-3-carbinol and some of its derivatives, two DDE isomers and four flavones (except α-naphthoflavone) at 1000 μM did not significantly inhibit aromatase in vitro. Letrozole and clotrimazole, fed to juvenile rainbow trout at doses up to 1000 ppm for 2 weeks, were not effective in suppressing dehydroepiandrosterone (DHEA) induced increases in vitellogenin and 17β-estradiol levels. These results document that trout aromatase is sensitive to inhibition in vitro by known inhibitors of the mammalian enzyme. The mechanism(s) for lack of inhibition in vivo is currently unknown and must be further investigated in order to develop a trout model for studying the role of aromatase in carcinogenesis.
Glacier forefields have long provided ecologists with a model to study patterns of plant succession following glacier retreat. While plant-survey-based approaches applied along chronosequences ...provide invaluable information on plant communities, the “space-for-time” approach assumes
environmental uniformity and equal ecological potential across sites and does not account for spatial variability in initial site conditions. Remote
sensing provides a promising avenue for assessing plant colonization dynamics using a so-called “real-time” approach. Here, we combined 36 years
of Landsat imagery with extensive field sampling along chronosequences of deglaciation for eight glacier forefields in the southwestern European
Alps to investigate the heterogeneity of early plant succession dynamics. Based on the two complementary and independent approaches, we found strong
variability in the time lag between deglaciation and colonization by plants and in subsequent growth rates and in the composition of early plant
succession. All three parameters were highly dependent on the local environmental context, i.e., neighboring vegetation cover and energy
availability linked to temperature and snowmelt gradients. Potential geomorphological disturbance did not emerge as a strong predictor of succession
parameters, which is perhaps due to insufficient spatial resolution of predictor variables. Notably, the identity of pioneer plant species was highly
variable, and initial plant community composition had a much stronger influence on plant assemblages than elapsed time since deglaciation. Overall,
both approaches converged towards the conclusion that early plant succession is not stochastic as previous authors have suggested but rather
determined by local ecological context. We discuss the importance of scale in deciphering the complexity of plant succession in glacier forefields
and provide recommendations for improving botanical field surveys and using Landsat time series in glacier forefield systems. Our work demonstrates
complementarity between remote sensing and field-based approaches for both understanding and predicting future patterns of plant succession in
glacier forefields.
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