3,917 research outputs found
Sessile ciliates on artificial substrata submerged in a polluted estuary (Santos, SP, Brazil)
Primary growth was analysed on artificial substrata submerged at three sites of the Santos estuary (State of São Paulo, Brazil). Research on sessile ciliates was emphasized because they were the most conspicuous organisms of the primary growth developed along this estuary. Zoothamnium commune, dominated near the headwaters of the estuary, where the greatest amount of suspended matter in the water was found. Ephelota gemmipara dominated downstream. Although short time variability was observed in the colonization of substrata submerged on subsequent days, seasonal patterns could be determined. These patterns were characterized by a greater number of rare species of sessile ciliates, and a higher density of the most frequent ones, during spring and summer
Current and voltage shaping method via modified d–q transformation for the torque ripple compensation in PMSMs
This study deals with a novel control strategy for permanent magnet synchronous machines (PMSMs) to incorporate disturbance compensation features in the existing current controller maintaining at the same time the integrity of the reference tracking performances. The torque produced by a PMSM arises from the interaction of stator currents and rotor magnetic flux, therefore an intrinsic disturbance is propagated to the output, in case the flux is not perfectly sinusoidal. In particular, the authors focus is to propose the effective correction of undesired harmonic effects generated on the torque from the non-ideal machine rotor. With the knowledge of the back electromagnetic force waveform, it is possible to determine the current waveforms necessary to produce a smooth torque in normal operation and through model-base considerations, the required voltage harmonic waveforms are also computed. The method is also extended to the flux weakening operation of the machine. The analytical solutions found are used in place of the classical αβ/dq transformations, without modifying the field-oriented control performance of the main controller. The effectiveness of the proposed control scheme is verified by means of test-bench measurement
Development of an Automated Method for Selected Aromas of Red Wines from Cold-Hardy Grapes Using Solid-Phase Microextraction and Gas Chromatography-Mass Spectrometry-Olfactometry
The aroma profile of red wine is complex and research focusing on aroma compounds and their links to viticultural and enological practices is needed. Current research is limited to wines made from cold-hardy cultivars (interspecific hybrids of vinifera and native N. American grapes). The objective of this research was to develop a fully automated solid phase microextraction (SPME) method, using tandem gas chromatography-mass spectrometry (GC-MS)-olfactometry for the simultaneous chemical and sensory analysis of volatile/semi-volatile compounds and aroma in cold-hardy red wines. Specifically, the effects of SPME coating selection, extraction time, extraction temperature, incubation time, sample volume, desorption time, and salt addition were studied. The developed method was used to determine the aroma profiles of seven selected red wines originating from four different cold-hardy grape cultivars. Thirty-six aroma compounds were identified from Maréchal Foch, St. Croix, Frontenac, Vincent, and a Maréchal Foch/Frontenac blend. Among these 36 aroma compounds, isoamyl alcohol, ethyl caproate, benzeneethanol, ethyl decanoate, and ethyl caproate are the top five most abundant aroma compounds. Olfactometry helps to identify compounds not identified by MS. The presented method can be useful for grape growers and wine makers for the screening of aroma compounds in a wide variety of wines and can be used to balance desired wine aroma characteristics
Large mass dilepton production from jet-dilepton conversion in the quark-gluon plasma
We calculate the production of large mass dileptons from the passage of jets
passing through the quark-gluon plasma. Using the relativistic kinetic theory,
we rigorously derive the production rate for the jet-dilepton conversion in the
hot medium. The jet-dilepton conversion is compared with the thermal dilepton
emission and the Drell-Yan process. The contribution of the jet-dilepton
conversion is not prominent for all values of the invariant mass , and the
Drell-Yan process is found to dominate over the thermal dilepton emission and
the jet-dilepton conversion for 2.5 GeV at RHIC. The jet-dilepton
conversion is the dominant source of large mass dileptons in the range of 4 GeV
10 GeV at LHC.Comment: 2 figure
Instanton interactions in dense-matter QCD
A Coulomb gas representation of dense-matter QCD is derived from a dual
transformation of the low-energy effective Lagrangian. The point-like charges
Q=+1,-1 of the gas are identified with the instantons and anti-instantons of
such topological charges. An instanton repels another instanton with the same
force as it attracts an anti-instanton, in contrast to the semiclassical
interaction.Comment: 8 pages, Revtex (a typo fixed
QCD in Extreme Environments
I review present challenges that QCD in extreme environments presents to
lattice gauge theory. Recent data and impressions from RHIC are emphasized.
Physical pictures of heavy ion wavefunctions, collisions and the generation of
the Quark Gluon Plasma are discussed, with an eye toward engaging the lattice
and its numerical methods in more interaction with the experimental and
phenomenological developments. Controversial, but stimulating scenarios which
can be confirmed or dismissed by lattice methods are covered. In the second
half of the talk, several promising developments presented at the conference
Lattice 2002 are reviewed.Comment: Lattice2002(plenary), 12 pages, 3 figure
Dynamics and Hadronization at intermediate transverse momentum at RHIC
The ultra-relativistic heavy-ion program at RHIC has shown that at
intermediate transverse momenta (-6 GeV) standard (independent)
parton fragmentation can neither describe the observed baryon-to-meson ratios
nor the empirical scaling of the hadronic elliptic flow () according to
the number of valence quarks. Both aspects find instead a natural explanation
in a coalescence plus fragmentation approach to hadronization. After a brief
review of the main results for light quarks, we focus on heavy quarks showing
that a combined fragmentation and quark-coalescence framework is relevant also
here. Moreover, within relativistic Langevin simulations we find evidence for
the importance of heavy-light resonances in the Quark-Gluon Plasma (QGP) to
explain the strong energy loss and collective flow of heavy-quark spectra as
inferred from non-photonic electron observables. Such heavy-light resonances
can pave the way to a unified understanding of the microscopic structure of the
QGP and its subsequent hadronization by coalescence.Comment: Proceedings of the International Workshop on QCD - Martina Franca
(Italy), June 2007. To be published in AIP. 6 pages, 6 figure
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