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Abstract: numerical simulation of hydrocyclones aiming at investigating the separation of microorganisms and mammalian cells was performed using computational fluid dynamics (cfd). the turbulence model used in the 2daxisymmetric calculations was the reynolds stress model (rsm), in order to take into account the high swirl effects that occur in this type of equipment, which induce anisotropic turbulence. the volume of fluid model (vof) was used to account for the gas/liquid interface. in all calculations, a cylindrical air core, running the whole length of the cyclone, appeared naturally as a consequence of a low pressure region that developed along the central axis. the separation of escherichia coli, saccharomyces cerevisiae and mammalian cells (bhk-21) using bradley hydrocyclones was studied. according to the present work, bradley hydrocyclones with diameters down to 10 mm cannot efficiently separate microorganisms, but the separation of mammalian cells with predicted efficiencies as high as 90% can be achieved.

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Numerical simulation of hydrocyclones for cell separation
R. A. Medronho,J. Schuetze,W.-D. Deckwer
Latin American applied research , 2005,

Abstract: Numerical simulation of hydrocyclones aiming at investigating the separation of microorganisms and mammalian cells was performed using Computational Fluid Dynamics (CFD). The turbulence model used in the 2daxisymmetric calculations was the Reynolds Stress Model (RSM), in order to take into account the high swirl effects that occur in this type of equipment, which induce anisotropic turbulence. The Volume of Fluid Model (VOF) was used to account for the gas/liquid interface. In all calculations, a cylindrical air core, running the whole length of the cyclone, appeared naturally as a consequence of a low pressure region that developed along the central axis. The separation of Escherichia coli, Saccharomyces cerevisiae and mammalian cells (BHK-21) using Bradley hydrocyclones was studied. According to the present work, Bradley hydrocyclones with diameters down to 10 mm cannot efficiently separate microorganisms, but the separation of mammalian cells with predicted efficiencies as high as 90% can be achieved.

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Subsurface low pH and carbonate saturation state of aragonite on China side of the North Yellow Sea: combined effects of global atmospheric CO2 increase, regional environmental changes, and local biogeochemical processes
W.-D. Zhai,N. Zheng,C. Huo,Y. Xu
Biogeosciences Discussions , 2013, DOI: 10.5194/bgd-10-3079-2013

Abstract: Based upon seven field surveys conducted between May 2011 and January 2012, we investigated pH, carbonate saturation state of aragonite (Ωarag), and ancillary parameters on the Chinese side of the North Yellow Sea, a western North Pacific continental margin of major economic importance. Subsurface waters were nearly in equilibrium with air in May and June. From July to October, the fugacity of CO2 (fCO2) of bottom water gradually increased to 697 ± 103 μatm and pH decreased to 7.83 ± 0.07 due to respiration/remineralization processes of primary production induced biogenic particles. In November and January, bottom water fCO2 decreased and pH gradually returned to an air-equilibrated level due to cooling enhanced vertical mixing. The corresponding bottom water Ωarag was 1.74 ± 0.17 (May), 1.77 ± 0.26 (June), 1.70 ± 0.26 (July), 1.72 ± 0.33 (August), 1.32 ± 0.31 (October), 1.50 ± 0.28 (November), and 1.41 ± 0.12 (January). Critically low Ωarag values of 1.0 to 1.2 were mainly observed in subsurface waters in a salinity range of 31.5–32.5 psu in October and November, accounting for ~ 10% of the North Yellow Sea area. Water mass derived from the adjacent Bohai Sea had a typical water salinity of 30.5–31.5 psu, and bottom water Ωarag values ranged mostly between 1.6 and 2.4. This study showed that the carbonate system in the North Yellow Sea was substantially influenced by global atmospheric CO2 increase. The community respiration/remineralization rates in typical North Yellow Sea bottom water mass were estimated at 0.55–1.0 μmol O2 kg 1 d 1 in warm seasons, leading to seasonal drops in subsurface pH and Ωarag. Outflow of the Bohai Sea water mass counteracted the subsurface Ωarag reduction in the North Yellow Sea.

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Bioactive Components of the Traditionally used Mushroom Podaxis pistillaris
M. A. A. Al-Fatimi,W.-D. Jülich,R. Jansen,U. Lindequist
Evidence-Based Complementary and Alternative Medicine , 2006, DOI: 10.1093/ecam/nek008

Abstract: In the course of an ethnobotanical study on fungi used in Yemeni ethnomedicine the fungus Podaxis pistillaris (Podaxales, Podaxaceae, Basidiomycetes) was found to exhibit antibacterial activity against Staphylococcus aureus, Micrococcus flavus, Bacillus subtilis, Proteus mirabilis, Serratia marcescens and Escherichia coli. In the culture medium of P. pistillaris three epidithiodiketopiperazines were identified by activity-guided isolation. Based on spectral data (NMR, ESI-MS and DCI-MS) their identity was established as epicorazine A (1), epicorazine B (2) and epicorazine C (3, antibiotic F 3822), which have not been reported as constituents of P. pistillaris previously. It is assumed that the identified compounds contribute to the antibacterial activity of the extract.

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Seasonal variations of air-sea CO2 fluxes in the largest tropical marginal sea (South China Sea) based on multiple-year underway measurements
W.-D. Zhai,M.-H. Dai,B.-S. Chen,X.-H. Guo
Biogeosciences Discussions , 2013, DOI: 10.5194/bgd-10-7031-2013

Abstract: Based upon fourteen field surveys conducted between 2003 and 2008, we showed that the seasonal pattern of sea surface partial pressure of CO2 (pCO2) and air–sea CO2 fluxes differed among four different physical-biogeochemical domains in the South China Sea (SCS) proper. The four domains were located between 4 and 23° N and 109 and 121° E, covering ~ 38% of the surface area of the entire SCS. In the area off the Pearl River Estuary, relatively low pCO2 values of 320 to 390 μatm were observed in all four seasons and both the biological productivity and CO2 uptake were enhanced in summer in the Pearl River plume waters. In the northern SCS slope/basin area, a typical seasonal cycle of relatively high pCO2 in the warmer seasons and relatively low pCO2 in the cold seasons was revealed. In the central/southern SCS area, moderately high sea surface pCO2 values of 360 to 425 μatm were observed throughout the year. In the area west of the Luzon Strait, a major exchange pathway between the SCS and the Pacific Ocean, pCO2 was particularly dynamic in winter, when northeast monsoon induced upwelling events and strong outgassing of CO2. These episodic events might have dominated the annual air–sea CO2 flux in this particular area. The estimate of annual sea–air CO2 fluxes showed that, most areas of the SCS proper served as weak sources to the atmospheric CO2, with sea–air CO2 flux values of 0.46 ± 0.43 mol m 2 yr 1 in the northern SCS slope/basin, 1.37 ± 0.55 mol m 2 yr 1 in the central/southern SCS, and 1.21 ± 1.47 mol m 2 yr 1 in the area west of the Luzon Strait. However, the annual sea–air CO2 exchange was nearly in equilibrium ( 0.44 ± 0.65 mol m 2 yr 1) in the area off the Pearl River Estuary. Overall the four domains released (18 ± 10) × 1012 g C yr 1 into the atmosphere. The CO2 release rate of the South China Sea essentially exceeded the average CO2 emission level of most tropical oceans.

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Large magnetoresistance effect due to spin-injection into a non-magnetic semiconductor
G. Schmidt,G. Richter,P. Grabs,C. Gould,D. Ferrand,L. W. Molenkamp
Physics , 2001, DOI: 10.1103/PhysRevLett.87.227203

Abstract: A novel magnetoresistance effect, due to the injection of a spin-polarized electron current from a dilute magnetic into a non-magnetic semiconductor, is presented. The effect results from the suppression of a spin channel in the non-magnetic semiconductor and can theoretically yield a positive magnetoresistance of 100%, when the spin flip length in the non-magnetic semiconductor is sufficiently large. Experimentally, our devices exhibit up to 25% magnetoresistance.

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The FUSE Spectrum of PG0804+761: A Study of Atomic and MolecularGas in the Lower Galactic Halo and Beyond
P. Richter,B. D. Savage,B. P. Wakker,K. R. Sembach,P. M. W. Kalberla
Physics , 2000, DOI: 10.1086/319070

Abstract: We present an analysis of interstellar and intergalactic absorption lines in the FUSE spectrum of the low-redshift quasar PG0804+761 (z=0.100) at intermediate resolution (FWHM=25 km/s) in the direction l=138.3, b=31.0. With a good signal-to-noise ratio and the presence of several interesting Galactic and extragalactic absorption components along the sight line, this spectrum provides a good opportunity to demonstrate the ability of FUSE to do both interstellar and extragalactic science. Although the spectrum of PG0804+761 is dominated by strong absorption from local Galactic gas, we concentrate our study on absorption by molecular hydrogen and neutral neutral and ionized metals related to an intermediate-velocity cloud in the lower Galactic halo at -55 km/s, and on absorption from OVI extended to negative velocities. In the IVC, weak molecular hydrogen absorption is found in 5 lines for rotational levels 0 and 1, leading to a total H_2 column density of log N = 14.71(+-0.30). We derive an OI gas-phase abundance for the IVC of 1.03(+0.71-0.42) solar. Absorption by OVI is found at velocities as negative as -110 km/s, but no absorption from any species is found at velocities of -180 km/ where absorption from the nearby high-velocity Complex A would be expected. We suggest that the extended OVI absorption traces hot gas above the Perseus spiral arm. Finally, we find intergalactic absorption by an intervening HI Ly betax absorber at z=0.019 and absorption by HI, CIII and OVI in an associated system at z=0.102. No intervening OVI absorbers are seen in the spectrum of PG0804+761.

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The nature of molecular cloud boundary layers from SOFIA [O？I] observations
E. T. Chambers,H. Richter,J. L. Pineda,K. Jacobs,P. F. Goldsmith,W. D. Langer
- , 2018, DOI: 10.1051/0004-6361/201832691

Abstract: Context. Dense highly ionized boundary layers (IBLs) outside of the neutral Photon Dominated Regions (PDRs) have recently been detected via the 122 and 205 μm transitions of ionized nitrogen. These layers have higher densities than in the Warm Ionized Medium (WIM) but less than typically found in H？II regions. Observations of [C？II] emission, which is produced in both the PDR and IBL, do not fully define the characteristics of these sources. Observations of additional probes which just trace the PDRs, such as the fine structure lines of atomic oxygen, are needed derive their properties and distinguish among different models for [C？II] and [N？II] emissison.Aims. We derive the properties of the PDRs adjacent to dense highly ionized boundary layers of molecular clouds.Methods. We combine high-spectral resolution observations of the 63 μm [O？I] fine structure line taken with the upGREAT HFA-band instrument on SOFIA with [C？II] observations to constrain the physical conditions in the PDRs. The observations consist of samples along four lines of sight (LOS) towards the inner Galaxy containing several dense molecular clouds. We interpret the conditions in the PDRs using radiative transfer models for [C？II] and [O？I].Results. We have a 3.5-σ detection of [O？I] toward one source but only upper limits towards the others. We use the [O？I] to [C？II] ratio, or their upper limits, and the column density of C^{+^{to estimate the thermal pressure, P_{th_{, in these PDRs. In two LOS the thermal pressure is likely in the range 2–5 × 10^{5^{in units of K cm^{？3^{, with kinetic temperatures of order 75–100 K and H_{2_{densities, n(H_{2_{) ~ 2–4 × 10^{3^{cm^{？3^{. For the other two sources, where the upper limits on [O？I] to [C？II] are larger, P_{th_{？10^{5^{(K cm^{？3^{). We have also used PDR models that predict the [O？I] to [C？II] ratio, along with our observations of this ratio, to limit the intensity of the Far UV radiation field.Conclusions. The [C？II] and [N？II] emission with either weak, or without any, evidence of [O？I] indicates that the source of dense highly ionized gas traced by [N？II] most likely arises from the ionized boundary layers of clouds rather than from H？II regions}}}}}}}}}}}}}}}}}}}}}}

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Quantum kagome antiferromagnet in a magnetic field: Low-lying non-magnetic excitations versus valence-bond crystal order
D. C. Cabra,M. D. Grynberg,P. C. W. Holdsworth,A. Honecker,P. Pujol,J. Richter,D. Schmalfuss,J. Schulenburg
Physics , 2004, DOI: 10.1103/PhysRevB.71.144420

Abstract: We study the ground state properties of a quantum antiferromagnet on the kagome lattice in the presence of a magnetic field, paying particular attention to the stability of the plateau at magnetization 1/3 of saturation and the nature of its ground state. We discuss fluctuations around classical ground states and argue that quantum and classical calculations at the harmonic level do not lead to the same result in contrast to the zero-field case. For spin S=1/2 we find a magnetic gap below which an exponential number of non-magnetic excitations are present. Moreover, such non-magnetic excitations also have a (much smaller) gap above the three-fold degenerate ground state. We provide evidence that the ground state has long-range order of valence-bond crystal type with nine spins in the unit cell.

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