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  • 1
    Electronic Resource
    Electronic Resource
    High-performance discharges in the Small Tight Aspect Ratio Tokamak (START) : The 39th annual meeting of division of plasma physics of APS (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 1775-1783 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Small Tight Aspect Ratio Tokamak (START) [A. Sykes et al., Nucl. Fusion 32, 769 (1994)] spherical tokamak has recently achieved the record value of toroidal β∼30% in a tokamak-like configuration. The improvements that have made these results possible are presented along with a description of the global equilibrium parameters of the discharges. The ideal magnetohydrodynamic (MHD) stability of these discharges is analyzed, and they are found to be in close proximity to both the ballooning limit and the external current driven kink limit, but they are found to be far from the pressure driven external kink limit. Disruptivity for a range of shots is not correlated with the normalized β limit, but does correlate well with the empirical high-li disruption limit. The transport properties of these high-β equilibria are analyzed and compared to conventional tokamak scaling laws and transport models. The global transport is at least as good as that predicted by the ITER97-ELMy (edge-localized) scaling law. The local ion transport is in good agreement with that predicted by neoclassical models. The electron transport is anomalous, showing rough agreement with the Lackner–Gottardi transport model. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872819
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  • 2
    Electronic Resource
    Electronic Resource
    Energetic particle orbits in the National Spherical Tokamak Experiment (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 3667-3675 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The trajectories of neutral beam injected energetic ions in spherical tokamaks are examined. The large poloidal magnetic field in the outboard region of spherical tokamaks causes neutral beam injected ions to be born on trapped orbits even with cotangential injection. Numerical solutions to the equations for particle motion and for guiding center drifts are compared in several magnetic equilibria for a range of particle initial conditions. Even when rL/a∼1/4 the guiding center orbits closely resemble the path of the instantaneous center of gyration of the particle motion; exceptions occur primarily for orbits near the trapped/passing boundary. Finite Larmor radius effects are included in guiding center simulations of prompt orbit loss in the National Spherical Tokamak Experiment (NSTX) [J. Spitzer et al., Fusion Technol. 30, 1337 (1996)]. Orbit loss in the NSTX is caused primarily by collisions with the close fitting conducting shell, and severe losses would be expected with counter directed injection. While most orbits are similar to those found in conventional tokamaks, additional orbit types are possible in spherical tokamaks. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872263
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  • 3
    Electronic Resource
    Electronic Resource
    Magneto-hydro-dynamic limits in spherical tokamaks : The 40th annual meeting of the division of plasma physics of the american physical society (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 1958-1968 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The operational limits observed in spherical tokamaks, notably the small tight aspect ratio tokamak (START) device [A. Sykes et al., Nucl. Fusion 32, 694 (1992)], are consistent with those found in conventional aspect ratio tokamaks. In particular the highest β achieved (∼40%) is consistent with an ideal magneto-hydro-dynamic (MHD) Troyon type limit, the upper limit on density is well described by the Greenwald density (πa2n¯e/Ip∼1) and the normalized current (Ip/aBt) is limited such that q95(approximately-greater-than)2. Stability calculations indicate scope for increasing both normalized β and normalized current beyond the values so far achieved, although wall stabilization is generally needed for low-n modes. In double null configurations current terminating disruptions occur at each of the operational boundaries, though the current quench tends to be slow at the density limit and disruptions at high β may be due to the low q. In early limiter START discharges, before the divertor coils were installed, disruptions rarely occurred. Instead internal reconnection events which have all the characteristics of a disruption except the current quench occurred. These various disruptive behaviors are explained in terms of a model in which helicity is conserved during the disruption. Due to the low toroidal field beam ions in START, and α particles in a ST power plant, are super-Alfvénic. This gives the possibility for toroidal Alfvén eigenmodes (TAEs) to occur and such modes are frequently observed in START neutral beam injection (NBI) discharges, but seem to be benign. The features of these observed TAEs are shown to be in agreement with MHD calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873493
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  • 4
    Electronic Resource
    Electronic Resource
    Response of American cockroach (Periplaneta americana) olfactory receptors to selected alcohol odorants and their binary combinations (1997)
    Springer
    Journal of comparative physiology 180 (1997), S. 701-709 
    Details
    ISSN: 1432-1351
    Keywords: Key words Olfaction  ;  Odor discrimination  ; Mixture perception
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The cockroach is known to possess several morphologically distinct types of sensilla on its antenna, each of which contain a couple or a few receptor cells that respond to an array of compounds. We recorded the response of cells exclusively from one type of sensillum to evaluate the variation in the response of the cells in these sensilla to three closely related alcohols and their binary mixtures. Our results indicate that cells within the class of those responsive to aliphatic alcohols are otherwise variable in their response to particular aliphatic alcohols and not easily classifiable into subclasses. They also indicate that patterns of responses among cells are not robust with respect to concentration. Finally, a considerable level of inhibition is indicated in the response of the receptor cells to binary mixtures compared with the response to pure odorants. The data suggest that discrimination of alcohols (and other odorants of general but not special significance) by the cockroach cannot be understood simply in terms of labeled lines or linear filters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003590050084
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  • 5
    Electronic Resource
    Electronic Resource
    Regulation of Mammary Gland Growth and Morphogenesis by the Mammary Fat Pad: A Species Comparison (1999)
    Springer
    Journal of mammary gland biology and neoplasia 4 (1999), S. 53-68 
    Details
    ISSN: 1573-7039
    Keywords: MAMMARY FAT PAD ; MORPHOGENESIS ; PARACRINE ; EPITHELIAL-STROMAL INTERACTION ; HORMONE RECEPTORS ; GROWTH FACTORS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The growth and morphogenesis of mammaryparenchyma varies substantially between species and isregulated by an array of systemic and local factors.Central to this regulation is the mammary fat pad, amatrix of adipose and connective tissue capable ofmediating hormone action and synthesizing an array ofgrowth regulatory molecules. In this article wehighlight differences between the morphologicaldevelopment of the mammary parenchyma in rodents, humans,and ruminant dairy animals, placing emphasis ondifferences in the cellular composition and structure ofthe mammary fat pad. While a great deal remains to be understood about the ability of stroma tolocally regulate mammary development, the significanceof its contribution is becoming increasingly apparent.The actions of several steroid and peptide hormones appear to be mediated by an array of growthfactors, proteases and extracellular matrix componentssynthesized by constituents of the mammary fat pad.Further, mammary adipose tissue represents a significant store of lipid which, by itself and through itsderivatives, could influence the growth of mammaryepithelium in diverse ways. This review describes theintegral role of the mammary fat pad duringmammogenesis, emphasizing the point that species differencesmust be addressed if local growth and morphogenicmechanisms within the mammary gland are to beresolved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018704603426
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  • 6
    Electronic Resource
    Electronic Resource
    Mammary Involution in Dairy Animals (1999)
    Springer
    Journal of mammary gland biology and neoplasia 4 (1999), S. 137-144 
    Details
    ISSN: 1573-7039
    Keywords: MAMMARY INVOLUTION ; CELL TURNOVER ; APOPTOSIS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Lifetime milk production is maximized when dairycows are pregnant during approximately 70% of eachlactation. Between lactations, a nonlactating period isnecessary for optimal milk production in the succeeding lactation. With cessation of milking, alveolarstructure is largely maintained and little or no loss ofcells occurs. However, increased apoptosis and cellproliferation, relative to that in lactating glands during the same stage of gestation, suggestthat a nonlactating period serves to promote cellturnover prior to the next lactation. Even in theabsence of pregnancy, mammary involution in dairyanimals occurs at a slower rate than in rodents;alveolar structure is maintained for several weeks andlactation can be reinitiated after four weeks or more ofinvolution. Although apoptosis appears to be initiated within a similar time frame to that in rodents,the maximum proportion of apoptotic epithelial cellsappears to be lower than in rodents, and apoptosis maybe accompanied by an initial increase in cell proliferation. The ability to manipulateapoptosis and cell proliferation during the nonlactatingperiod and during lactation is expected to provideenormous benefits to the dairy industry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018769022990
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  • 7
    Electronic Resource
    Electronic Resource
    Measurement of $$\Gamma (Z^0 \to b\bar b)/\Gamma (Z^0 \to hadrons)$$ using a double tagging method (1995)
    Springer
    The European physical journal 65 (1995), S. 17-30 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The fraction of $$Z^0 \to b\bar b$$ ; events in hadronicZ 0 decays has been measured using the data collected by OPAL in 1992 and 1993. The presence of electrons or muons from semileptonic decays of bottom hadrons and the detection of bottom hadron decay vertices were used together to obtain an event sample enriched in $$Z^0 \to b\bar b$$ decays. To reduce the systematic error on the measurement of the $$Z^0 \to b\bar b$$ fraction, the efficiency of the $$b\bar b$$ event tagging was obtained from the data by comparing the numbers of events having a bottom signature in either one or both thrust hemispheres. A value of $$\frac{{\Gamma (Z^0 \to b\bar b)}}{{\Gamma (Z^0 \to hadrons)}} = 0.2171 \pm 0.0021 \pm 0.0021$$ was obtained, where the first error is statistical and the second systematic. The uncertainty on the decay width $$\Gamma (Z^0 \to c\bar c)$$ is not included in these errors. A fractional variation of this width by ±8% about its Standard Model prediction would result in a variation of the measured $$Z^0 \to b\bar b$$ fraction of ±0.0015.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01571301
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  • 8
    Electronic Resource
    Electronic Resource
    Observations of π-B charge-flavor correlations and resonant Bπ and BK production (1995)
    Springer
    The European physical journal 66 (1995), S. 19-29 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Evidence is presented for kinematic and charge correlations of B mesons with charged pions and kaons. Using a new technique, a sample of over 80 000 partially reconstructed B mesons is obtained in 3.5·106 hadronic Z0 decays recorded using the OPAL detector at LEP. The invariant mass distributions of B+π− and B+K− combinations show enhancements consistent with the decays of P-wave resonances of a b antiquark and a light quark. We observe an excess of 1738±195 B+π− pairs with invariant masses in the range 5.60-5.85 GeV and an excess of 149±31 B+K− pairs with invariant masses in the range 5.80–6.00 GeV. Labeling the observed enhancements generically as B** we find $$\begin{gathered} \frac{{BR(Z^0 \to \bar b \to B^{**0} \to B^{(*) + } \pi ^ - )}}{{BR(Z^0 \to \bar b \to B^ + )}} = 0.18 \pm 0.04, \hfill \\ \frac{{BR(Z^0 \to \bar b \to B_s^{**0} \to B^{(*) + } K^ - )}}{{BR(Z^0 \to \bar b \to B^ + )}} = 0.026 \pm 0.008, \hfill \\ \end{gathered} $$ where B(*)+ indicates the sum of B+ and B*+ and the errors include statistical and systematic contributions. From a study of π-B charge-flavor correlations we conclude that the production flavor of a B meson can be tagged with the charge of a pion in an appropriately chosen kinematic region, and that the performance of this flavor tag compares favorably in the $$Z^0 \to q\bar q$$ environment with lepton-based tags.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01496577
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  • 9
    Electronic Resource
    Electronic Resource
    A measurement of the production of D*± mesons on the Z0 resonance (1995)
    Springer
    The European physical journal 67 (1995), S. 27-44 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have studied the production of D*± mesons in a sample of 1.25 million multihadronic decays of the Z0, in which 1969 candidates have been identified. We have determined the total multiplicity of charged D* mesons in multihadronic Z0 decays to be
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01564819
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  • 10
    Electronic Resource
    Electronic Resource
    Search for heavy charged particles and for particles with anomalous charge in e+e− collisions at LEP (1995)
    Springer
    The European physical journal 67 (1995), S. 203-211 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using the OPAL data accumulated in 1991–1993 amounting to 74 pb−1 of integrated luminosity, corresponding to 1.64×106 selected multi-hadronic events, a search has been performed for charged particles with unusual mass or unusual charge. The mass was determined from a combination of momentum and ionization energy loss measurements. No isolation criteria were applied to the tracks examined, so that both isolated particles and particles produced in jets were valid candidates. For particles with chargeQ/e=−1, one candidate with a mass of approximately 4.2 GeV/c2 was found, which is compatible with the background rate expected according to a Monte Carlo simulation. The implications of this search for the mass limits of a conjectured stable or quasi-stable charged gluino composite $$(\tilde gq\bar q')^ \pm $$ are discussed. Limits are also presented for the production of fractionally-charged particles withQ/e=±2/3 and ±4/3 as well as for particles withQ/e=±2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01571281
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