Abstract Cresols, monomethyl derivatives of phenol, are high production chemicals with potential for human exposure. The three isomeric forms of cresol are used individually or in mixtures as ...disinfectants, preservatives, and solvents or as intermediates in the production of antioxidants, fragrances, herbicides, insecticides, dyes, and explosives. Carcinogenesis studies were conducted in groups of 50 male F344/N rats and 50 female B6C3F1 mice exposed to a 60:40 mixture of m - and p -cresols ( m -/ p -cresol) in feed. Rats and mice were fed diets containing 0, 1500, 5000, or 15,000 ppm and 0, 1000, 3000, or 10,000 ppm, respectively. Survival of each exposed group was similar to that of their respective control group. Mean body weight gains were depressed in rats exposed to 15,000 ppm and in mice exposed to 3000 ppm and higher. A decrease of 25% over that of controls for the final mean body weight in mice exposed to 10,000 ppm appeared to be associated with lack of palatability of the feed. A marginally increased incidence of renal tubule adenoma was observed in the 15,000-ppm-exposed rats. The increased incidence was not statistically significant, but did exceed the range of historical controls. No increased incidence of hyperplasia of the renal tubules was observed; however, a significantly increased incidence of hyperplasia of the transitional epithelium associated with an increased incidence of nephropathy was observed at the high exposure concentration. The only significantly increased incidence of a neoplastic lesion related to cresol exposure observed in these studies was that of squamous cell papilloma in the forestomach of 10,000-ppm-exposed mice. A definitive association with irritation at the site-of-contact could not be made because of limited evidence of injury to the gastric mucosa at the time of necropsy. However, given the minimal chemical-related neoplastic response in these studies, it was concluded that there was no clear evidence of carcinogenicity in male rats or female mice exposed to the cresol mixture.
The fountain darter Etheostoma fonticola (FOD) is a federally endangered fish listed under the US Endangered Species Act. Here, we identified and characterized a novel aquareovirus isolated from wild ...fountain darters inhabiting the San Marcos River. This virus was propagated in Chinook salmon embryo (CHSE)-214, rainbow trout gonad-2 and fathead minnow cells at 15°C. The epithelioma papulosum cyprini cell line was refractory at all temperatures evaluated. High throughput sequencing technologies facilitated the complete genome sequencing of this virus utilizing ribosomal RNA-depleted RNA extracted from infected CHSE-214 cells. Conventional PCR primer sets were developed for the detection and confirmation of this virus to assist diagnostic screening methods. Phylogenetic analysis suggests this virus belongs to the Aquareovirus A genus. This research provides requisite initial data critical to support hatchery and refugia biosecurity measures for this endangered species.
This paper describes design techniques to maximize the efficiency and power density of fully integrated switched-capacitor (SC) DC-DC converters. Circuit design methods are proposed to enable ...simplified gate drivers while supporting multiple topologies (and hence output voltages). These methods are verified by a proof-of-concept converter prototype implemented in 0.374 mm 2 of a 32 nm SOI process. The 32-phase interleaved converter can be configured into three topologies to support output voltages of 0.5 V-1.2 V from a 2 V input supply, and achieves 79.76% efficiency at an output power density of 0.86 W/mm 2 .
The present study investigates the levels of Mn, Zn, Ni, and Co pyritization in mangrove sediments along distinct sedimentary zones in Enseada das Graças, a lagoon-type estuary located on the ...southeastern coast of Brazil. The coastal geology is characterized by intense interactions of trace metals, forming pyrite minerals. Specific orders of DOP (degree of pyritization) and DTMP (degree of trace-metal pyritization) are shown: supratidal flat < mangrove forest < mud flat. Distinct changes in content along the sediment profiles are noted, where a supratidal flat presented low levels of DOP and DTMP with little variance along the sedimentary depths. The mangrove forest showed relatively high values of DOP and DTMP in the lower depths, while the mud flat showed the highest levels of DOP and DTMP.
The internal phase distribution of co-current, air-water bubbly flow in a 50.3
mm i.d. horizontal pipeline has been modeled using the volume averaged multiphase flow equations. Liquid and gas ...volumetric superficial velocities varied in the range from 3.8 to 5.1
m/s and 0.2–1.0
m/s, respectively, and average gas volume fraction varied in the range from 4 to 16%. The predicted gas volume fraction and the mean liquid velocity are compared with the experimental data of Kocamustafaogullari and Wang G. Kocamustafaogullari, Z. Wang, An experimental study on local interfacial parameters in a horizontal bubbly two-phase flow, Int. J. Multiphase Flow 17 (1991) 553–572, Kocamustafaogullari and Huang G. Kocamustafaogullari, W.D. Huang, Internal structure and interfacial velocity development for bubbly two-phase flow, Nucl. Eng. Des. 151 (1994) 79–101 and Iskandrani and Kojasoy A. Iskandrani, G. Kojasoy, Local void fraction and velocity field description in horizontal bubbly flow, Nucl. Eng. Des. 204 (2001) 117–128. Good quantitative agreement with the experimental data is obtained with two different models (i.e.,
k–ɛ with constant bubble size and
k–
ɛ with population balance model). The model prediction shows better agreement with the experimental data with population balance than the constant bubble size predictions. The results indicate that the volume fraction has a maximum near the upper pipe wall, and the profiles tend to flatten with increasing liquid flow rate. It was found that increasing the gas flow rate at fixed liquid flow rate would increase the local volume fraction. The axial liquid mean velocity showed a relatively uniform distribution except near the upper pipe wall. An interesting feature of the liquid velocity distribution is that it tends to form a fully developed turbulent pipe-flow profile at the lower part of the pipe irrespective of the liquid and gas superficial velocities.
•We measured solid velocity and concentration fluctuations in a highly concentrated mixture.•Velocity and concentration fluctuations maps were obtained using electrical impedance tomography.•The ...results used to study and analyse fluid-particle interactions.•The results consistency with previous studies was investigated.
Solid velocity and concentration fluctuations were measured for concentrated sand-water mixtures (20–35% solid by volume) in horizontal pipe flow using Electrical Impedance Tomography (EIT). Narrowly sized sand (d50=100μm) was used to prepare each slurry tested in a 52mm (i.d.) horizontal pipe loop at mixture velocities (2–5m/s) that were significantly above the deposition velocity. The EIT measurements were used to obtain solid velocity and concentration fluctuation maps. Results show that the magnitude of the local solid concentration fluctuations is greater near the pipe wall and increases as the mixture velocity increases. Additionally, the concentration fluctuations are greater near the pipe invert, particularly at lower mixture velocities and/or concentrations where the solid concentration profiles are asymmetric. The Fast Fourier Transform (FFT) method was employed to study the power spectral density of these fluctuations. This analysis indicates that concentration fluctuations are produced almost entirely by particle–fluid turbulence interactions, rather than through particle–particle or particle–wall interactions. Comparison of the particle diameter with the characteristic turbulent length scales shows that the particles interact with turbulent eddies in the dissipative range, which is in accordance with the power spectral density analysis. The findings presented here are consistent with previous studies of fluidized beds and gravity-driven flows.
The design, construction, and test of an integrated flywheel energy storage system with a homopolar inductor motor/generator and high-frequency drive is presented in this paper. The work is presented ...as an integrated design of flywheel system, motor, drive, and controller. The motor design features low rotor losses, a slotless stator, construction from robust and low cost materials, and a rotor that also serves as the energy storage rotor for the flywheel system. A high-frequency six-step drive scheme is used in place of pulsewidth modulation because of the high electrical frequencies. A speed-sensorless controller that works without state estimation is also described. A prototype of the flywheel system has been demonstrated at a power level of 9.4 kW, with an average system efficiency of 83% over a 30000-60000 r/min speed range.
Ocean fertilization: a potential means of geoengineering? Lampitt, R.S; Achterberg, E.P; Anderson, T.R ...
Philosophical transactions of the Royal Society of London. Series A: Mathematical, physical, and engineering sciences,
11/2008, Letnik:
366, Številka:
1882
Journal Article
Recenzirano
Odprti dostop
The oceans sequester carbon from the atmosphere partly as a result of biological productivity. Over much of the ocean surface, this productivity is limited by essential nutrients and we discuss ...whether it is likely that sequestration can be enhanced by supplying limiting nutrients. Various methods of supply have been suggested and we discuss the efficacy of each and the potential side effects that may develop as a result. Our conclusion is that these methods have the potential to enhance sequestration but that the current level of knowledge from the observations and modelling carried out to date does not provide a sound foundation on which to make clear predictions or recommendations. For ocean fertilization to become a viable option to sequester CO2, we need more extensive and targeted fieldwork and better mathematical models of ocean biogeochemical processes. Models are needed both to interpret field observations and to make reliable predictions about the side effects of large-scale fertilization. They would also be an essential tool with which to verify that sequestration has effectively taken place. There is considerable urgency to address climate change mitigation and this demands that new fieldwork plans are developed rapidly. In contrast to previous experiments, these must focus on the specific objective which is to assess the possibilities of CO2 sequestration through fertilization.
We present the first identification of large-scale structures (LSSs) at z < 1.1 in the Cosmic Evolution Survey (COSMOS). The structures are identified from adaptive smoothing of galaxy counts in the ...pseudo-3D space ( alpha , delta , z) using the COSMOS photometric redshift catalog. The technique is tested on a simulation including galaxies distributed in model clusters and a field galaxy population--recovering structures on all scales from 1' to 20' without a priori assumptions for the structure size or density profile. The COSMOS photometric redshift catalog yields a sample of 1.5 x 10 super(3) galaxies with redshift accuracy, Delta z sub(PWUM)/(1 + z) less than or equal to 0.1 at z < 1.1 down to I sub(AB) less than or equal to 25 mag. Using this sample of galaxies, we identify 42 LSSs and clusters. Projected surface-density maps for the structures indicate multiple peaks and Internal structure in many of the most massive LSSs. The stellar masses (determined from the galactic SEDs) for the LSSs range from unk similar to 10 super(11) up to similar to 3 x 10 super(13) M unk. Five LSSs have total stellar masses exceeding 10 super(13) M unk. (Total masses including nonstellar baryons and dark matter are expected to be similar to 50-100 times greater.) The derived mass function for the LSSs is consistent (within the expected Poisson and cosmic variances) with those derived from optical and X-ray studies at lower redshift. To characterize structure evolution and for comparison with simulations, we compute a new statistic: the area filling factor as a function of the overdensity value compared to the mean at surface overdensity ( integral of sub(A) capital sigma / capital sigma (z)). The observationally determined f sub(A) has less than 1% of the surface area (in each redshift slice) with overdensities exceeding 10:1, and evolution to higher overdensities is seen at later epochs (lower z); both characteristics are in good agreement with what we find using similar processing on the Millennium Simulation. Although similar variations in the filling factors as a function of overdensity and redshift are seen in the observations and simulations, we do find that the observed distributions reach higher overdensities than the simulation, perhaps indicating overmerging in the simulation. All of the LSSs show a dramatic preference for earlier SED type galaxies in the denser regions of the structures, independent of redshift. The SED types in the central 1 and 1-5 Mpc regions of each structure average about one SED type earlier than the mean type at the same redshift, corresponding to a stellar population age difference of similar to 2-4 Gyr at z = 0.3-1. We also investigate the evolution of key galactic properties--mass, luminosity, SED, and star formation rate (SFR)--with redshift and environmental density as derived from overdensities in the full pseudo-3D cube. Both the maturity of the stellar populations and the "downsizing" of star formation in galaxies vary strongly with redshift (epoch) and environment. For a very broad mass range (10 super(10)-10 super(12) M unk), we find that galaxies in dense environments tend to be older; this is not just restricted to the most massive galaxies. And in low-density environments, the most massive galaxies appear to have also been formed very early (z > 2), compared to the lower mass galaxies there. Over the range z < 1.1, we do not see evolution in the mass of galaxies by more than a factor of similar to 2 separating active and inactive star-forming galaxy populations.
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