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  • 1
    Electronic Resource
    Electronic Resource
    Dispersion of ideal particles in a two-dimensional model of electrostatic turbulence (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 4575-4585 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dispersion of ideal test particles in electrostatic drift-wave turbulence is investigated numerically. A self-consistent model with an internal instability drive is used to obtain the turbulent two-dimensional (2D) flow-field. It is shown that nonlinear couplings lead to the formation of coherent vortical structures in the flow. The dispersion of the particles is found to be anisotropic, with the weakest dispersion in the direction of the density gradient. By distinguishing between particles trapped in structures and free particles, it is demonstrated that the trapping and subsequent displacement of particles by nonlinear vortex structures enhances the particle diffusion in the direction of the background density gradient. Conditional diffusion coefficients are obtained showing that particles trapped by the vortex structures are convected by the structures. The time a particle on the average stays trapped in the structure is closely related to the lifetime of the vortical structures. The relation between the diffusion coefficient obtained from the test particle dispersion and an effective diffusion coefficient obtained from the cross-field turbulent flux is discussed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873745
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  • 2
    Electronic Resource
    Electronic Resource
    Turbulent transport in low-β plasmas (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 1530-1544 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-frequency electrostatic fluctuations are studied experimentally in a low-β plasma, with particular attention to their importance for the anomalous plasma transport across magnetic field lines. The presence of large coherent structures in a turbulent background at the edge of the plasma column is demonstrated by a statistical analysis. The importance of these structures for the turbulent transport is investigated. The study is extended by a multichannel conditional analysis to illustrate detailed properties and parameter dependences of the turbulent transport. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872008
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  • 3
    Electronic Resource
    Electronic Resource
    Coherent structures in two-dimensional plasma turbulence (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 1609-1625 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-frequency, flute-type electrostatic fluctuations propagating across a strong, homogeneous magnetic field are studied experimentally. The fluctuations are generated by the Kelvin–Helmholtz instability. The presence of relatively long-lived vortexlike structures in a background of wide-band turbulent fluctuations is demonstrated by a conditional sampling technique. Depending on plasma parameters, the dominant structures can appear as monopole or multipole vortices, dipole vortices in particular. The importance of large structures for the turbulent plasma diffusion is discussed. A statistical analysis of the randomly varying plasma flux is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859680
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  • 4
    Electronic Resource
    Electronic Resource
    Formation and temporal evolution of the Lamb-dipole (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 9 (1997), S. 982-991 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The formation and dynamics of dipolar vortex structures in two-dimensional flows are studied. Localized initial structures possessing a finite linear momentum are found to develop into dipoles by direct numerical solutions of the two-dimensional Navier-Stokes equations. The detailed structure of the evolving dipoles depend on the initial condition. However, the gross properties of their evolution are only weakly dependent on the detailed structure and can be well-described by the so-called Lamb-dipole solution. The viscous decay of the Lamb-dipole, leading to an expansion and a decreasing velocity, is well described by an adiabatic theory. During the expansion the dipole is found to trap fluid as it evolves. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869193
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  • 5
    Electronic Resource
    Electronic Resource
    Infrared Vibrational-Rota-Tional Spectroscopy (1963)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Physical Chemistry 14 (1963), S. 359-386 
    Details
    ISSN: 0066-426X
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.pc.14.100163.002043
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  • 6
    Electronic Resource
    Electronic Resource
    Vortex merging and spectral cascade in two-dimensional flows (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 8 (1996), S. 2263-2265 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The merging of two identical vortices is studied numerically using a spectral code. It is noted that the enstrophy cascade is most active on the distorted vortex boundaries, with a Kolmogorov-like spectrum E(k)≈k−α, α≤4, developed at high wave numbers. The inverse energy cascade is completed when the vortices merge into one of larger size. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869027
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  • 7
    Electronic Resource
    Electronic Resource
    Dynamics of a nonlinear dipole vortex (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 7 (1995), S. 2220-2229 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A localized stationary dipole solution to the Euler equations with a relationship between the vorticity and streamfunction given as ω=−ψ+ψ3 is presented. By numerical integration of the Euler equations this dipole is shown to be unstable. However, the initially unstable dipole reorganizes itself into a new nonlinear dipole, which is found to be stable. This new structure has a functional relationship given as ω=αψ+βψ3−γψ5. Such dipoles are stable to head-on collisions and they are capable of creating tripolar structures when colliding off axis. The effects of increasing Newtonian viscosity on the nonlinear dipole is studied revealing that even though the nonlinearity is weakening, the dipole does not relax towards a Lamb dipole. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868470
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  • 8
    Electronic Resource
    Electronic Resource
    PRORENIN AND ACTIVE RENIN CONCENTRATIONS IN OVARIAN FOLLICULAR FLUID INCREASE AFTER THE LH PEAK IN SUPEROVULATED HEIFERS (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical and experimental pharmacology and physiology 21 (1994), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. The aim was to analyse the in vivo variations with time of prorenin and active renin and their relationship to steroid hormones in ovarian follicular fluid during follicular growth in heifers.2. Thirty one beef heifers were assigned to two groups after oestrous synchronization: an unstimulated and a follicle-stimulating hormone (FSH)-treated (superovulated) group. Within each group, animals were slaughtered at different times of the follicular phase of the oestrous cycle. Ovarian follicular fluids were aspirated and analysed for the concentrations of active renin, prorenin, oestradiol-17β (E2) and progesterone (P4).3. Prorenin and active renin concentrations in follicular fluid remained constant until the luteinizing hormone (LH) peak, after which time they increased four- and two-fold, respectively, in superovulated heifers.4. In follicular fluid, prorenin and active renin correlated negatively with oestradiol and E2/P4 ratio but positively with progesterone during follicular growth in superovulated heifers. Prorenin also correlated negatively with oestradiol and E2/P4 ratio in unstimulated heifers.5. The increase of renin concentrations in ovarian follicles after the LH peak and the correlations to steroid hormones suggest an important role of the ovarian renin-angiotensin system in bovine follicular growth and maturation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.1994.tb02565.x
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  • 9
    Electronic Resource
    Electronic Resource
    ANGIOTENSIN II RECEPTOR DENSITY IN BOVINE OVARIAN FOLLICLES RELATES TO TISSUE RENIN AND FOLLICULAR SIZE (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical and experimental pharmacology and physiology 21 (1994), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. The purpose of this study was to investigate angiotensin II (AII) receptors in isolated bovine ovarian follicles and the relationship of their density to follicular concentrations of prorenin, active renin, oestradiol and progesterone.2. Displacement of [125I]-[Sar1-Ile5-Ile8]-AII binding by the AII receptor antagonists PD 123319 and Losartan (DuP 753) confirmed that follicular AII receptors are of subtype 2 (AT2 receptor).3. The dissociation constant (Kd) for [Ile5]-AII (human AII) was 0.84 (range 0.51–1.47) nmol/ L. The receptor density varied between 90 and 5990 (mean 1640) fmol/ mg membrane protein.4. The follicular AII receptor density correlated positively with follicular diameter (Spearman's rho= 0.518; P〈0.003) and tissue weight (Spearman's rho= 0.636; P〈0.0001), and negatively with the active renin concentration in the follicular wall (Spearman's rho=-0.399; P〈0.02). The AII receptor density did not correlate with the follicular fluid concentrations of prorenin, active renin, oestradiol (E2, progesterone (P4) or the E2/P4 ratio. The follicular fluid concentrations of prorenin correlated negatively with the E2/P4 ratio (Spearman's rho= -0.716; P〈0.00001).5. The inverse relationship between AII receptor density and the high active renin concentrations in the follicular wall suggests an active regulated tissue renin-angiotensin system. A high AII receptor density is a general feature of large bovine ovarian follicles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.1994.tb02542.x
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  • 10
    Electronic Resource
    Electronic Resource
    IN VITRO INCUBATION OF BOVINE OVARIAN FOLLICLES: INDICATIONS FOR AN ACTIVE AND REGULATED RENIN-ANGIOTENSIN SYSTEM (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical and experimental pharmacology and physiology 21 (1994), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. The ovarian follicular renin—angiotensin system was investigated by using an in vitro incubation method, based on tissue incubation of individual bovine follicles.2. Very high and varying concentrations of active renin (median 18.0 GU/kg, range 2.1–107 GU/kg; n= 101) and prorenin (11.7 GU/kg, range 〈2.6–142 GU/kg; n = 101) existed in unincubated ovarian follicular tissue.3. Active renin and prorenin increased 35 and 959%, respectively, in follicular wall tissue and incubation medium during 72 h of in vitro incubation. The protein synthesis inhibitor cyclohexamide inhibited active renin and prorenin formation. No activation of prorenin occurred in incubation medium or follicular fluid in vitro. Active renin was degraded during incubation.4. Primarily prorenin but also active renin were secreted into the incubation medium. Secretion was directed both to the internal and external surface of the follicular wall.5. Follicle-stimulating hormone (FSH) slightly stimulated the synthesis and secretion of prorenin in vitro.6. The synthesis and secretion rates of active renin and prorenin varied markedly between individual follicles.7. The finding of very high and varying concentrations of active renin in follicular wall tissues together with the formation and secretion of active renin during in vitro incubation provide further evidence for an active and regulated renin-angiotensin system in ovarian follicles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.1994.tb02556.x
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