96 research outputs found
Quartic Anomalous Couplings in Colliders
We study the constraints on the vertices ,
, and that can be obtained from
triple-gauge-boson production at the next generation of linear
colliders operating in the mode. We analyze the processes
(, or ) and show that these reactions
increase the potential of machines to search for anomalous
four-gauge-boson interactions.Comment: 15 pages, Latex file using ReVteX, 4 uufiled figures include
Probing Anomalous Quartic Couplings in e-gamma and gamma-gamma Colliders
We analyze the potential of the e+e- Linear Colliders, operating in the
e-gamma and gamma-gamma modes, to probe anomalous quartic vector--boson
interactions through the multiple production of W's and Z's. We examine all
chiral operators of order p^4 that lead to new
four--gauge--boson interactions but do not alter trilinear vertices. We show
that the e-gamma and gamma-gamma modes are able not only to establish the
existence of a strongly interacting symmetry breaking sector but also to probe
for anomalous quartic couplings of the order of 10^{-2} at 90% CL. Moreover,
the information gathered in the e-gamma mode can be used to reduced the
ambiguities of the e+e- mode.Comment: Revtex, 18 pages, 6 figure
Triple Electroweak Gauge-Boson Production at Fermilab Tevatron Energies
We calculate the three gauge-boson production in the Standard Model at
Fermilab Tevatron energies. At TeV in collisions, the
cross sections for the triple gauge-boson production are typically of order 10
femtobarns (fb). For the pure leptonic final states from the gauge-boson decays
and with some minimal cuts on final state photons, the cross sections for and
processes are of order a few fb, resulting in a few dozen clean leptonic events
for an integrated luminosity of 10 fb. The pure leptonic modes from
other gauge-boson channels give significantly smaller rate. Especially, the
trilepton modes from and
yield a cross section of order 0.1 fb if there is no significant Higgs boson
contribution. For a Higgs boson with , the triple
massive-gauge-boson production rate could be enhanced by a factor of .Comment: RevTeX 3.0; 14 pages plus 7 figures; ps files available via anonymous
ftp at ftp://ucdhep.ucdavis.edu/han/vvv/vvv.ps,fig*_vvv.p
The regulatory mechanisms of NG2/CSPG4 expression
Neuron-glial antigen 2 (NG2), also known as chondroitin sulphate proteoglycan 4 (CSPG4), is a surface type I transmembrane core proteoglycan that is crucially involved in cell survival, migration and angiogenesis. NG2 is frequently used as a marker for the identification and characterization of certain cell types, but little is known about the mechanisms regulating its expression. In this review, we provide evidence that the regulation of NG2 expression underlies inflammation and hypoxia and is mediated by methyltransferases, transcription factors, including Sp1, paired box (Pax) 3 and Egr-1, and the microRNA miR129-2. These regulatory factors crucially determine NG2-mediated cellular processes such as glial scar formation in the central nervous system (CNS) or tumor growth and metastasis. Therefore, they are potential targets for the establishment of novel NG2-based therapeutic strategies in the treatment of CNS injuries, cancer and other conditions of these types
Metal-Substituted Microporous Aluminophosphates
This chapter aims to present the zeotypes aluminophosphates (AlPOs) as a complementary alternative to zeolites in the isomorphic incorporation of metal ions within all-inorganic microporous frameworks as well as to discuss didactically the catalytic consequences derived from the distinctive features of both frameworks. It does not intend to be a compilation of either all or the most significant publications involving metal-substituted microporous aluminophosphates. Families of AlPOs and zeolites, which include metal ion-substituted variants, are the dominant microporous materials. Both these systems are widely used as catalysts, in particular through aliovalent metal ions substitution. Here, some general description of the synthesis procedures and characterization techniques of the MeAPOs (metal-contained aluminophosphates) is given along with catalytic properties. Next, some illustrative examples of the catalytic possibilities of MeAPOs as catalysts in the transformation of the organic molecules are given. The oxidation of the hardly activated hydrocarbons has probably been the most successful use of AlPOs doped with the divalent transition metal ions Co2+, Mn2+, and Fe2+, whose incorporation in zeolites is disfavoured. The catalytic role of these MeAPOs is rationalized based on the knowledge acquired from a combination of the most advanced characterization techniques. Finally, the importance of the high specificity of the structure-directing agents employed in the preparation of MeAPOs is discussed taking N,N-methyldicyclohexylamine in the synthesis of AFI-structured materials as a driving force. It is shown how such a high specificity could be predicted and how it can open great possibilities in the control of parameters as critical in catalysis as crystal size, inter-and intracrystalline mesoporosity, acidity, redox properties, incorporation of a great variety of heteroatom ions or final environment of the metal site (surrounding it by either P or Al)
Experimental evaluation of flow turbulence in bottom outlet control gate of dams based on Kolmogorov theory
In this study the fluctuating loads of the control gate in the experimental model of the bottom outlet of a dam was evaluated. The production, transportation, and dissipation of turbulent flow eddies based on Kolmogorov theory were investigated by image processing of the flow under the control gate, time series of velocity and static pressure fluctuations. According to the results: 1- the flow turbulence at 10% opening of the control gate can be related to large eddies of middle and lower half streamlines of the upstream conduit. 2- The flow turbulence at 30% opening of the control gate can be related to large eddies of lower half streamlines of the upstream conduit. 3- The flow turned turbulent at 50% and 70% opening of the control gate can be related to large eddies of upper half streamlines of the upstream conduit. It can be concluded that the middle and lower streamlines of the upstream conduit play a major role in eddies production and flow turbulence at smaller openings of the control gate. In contrast, the upper streamlines of the upstream conduit play a major role in eddies production and flow turbulence at larger openings of the control gate. Large eddies are produced by shear layers created by velocity gradient at the guide slots of gate. The large eddies are transported by side guide slots toward the gate create strong secondary flows. After the collision of strong secondary flows with the main flow, the resulting turbulence leads to fluctuating static pressures. These fluctuations lead to the fluctuating loads on the control gate. Wavelet analysis of the time series provides the magnitude and frequency of pressure waves. Then, wavelet analysis and imaging of the gate flow reveal the causes of the turbulent flow formation process. The size and frequency of these large eddies range from 7.5 mm to 25 mm and 0.1 Hz to 2 Hz, respectively
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