497 research outputs found
Selenium in wastewater: fast analysis method development and advanced oxidation treatment applications.
Abstract
Selenium, a ubiquitous non-metal in nature, is potentially toxic to natural ecosystems due to its bioaccumulation potential. Due to increased monitoring and enforcement of selenium regulations, the need to be able to measure and treat selenium efficiently has taken on an increased importance. The principal aqueous forms of inorganic selenium are selenite (Se(IV)) and selenate (Se(VI)). Selenate, due to its high mobility and lack of affinity to conventional adsorbents, is typically much more difficult to treat and remove. To address both measurement and removal, an analytical method is reported for quantification of selenium in wastewater (WW) using UV-Vis spectrophotometer followed by removal studies using advanced oxidation processes (AOPs). Malachite green and azure blue were selected for colorimetric analysis using UV-Vis. Malachite green indicator showed the best results for analysis. The reported UV-Vis method was applied to establish the effect of AOPs on selenium removal. It was noted that all of the AOP treated samples showed removal of selenium and it was established that the UV-Vis method has a lower limit of detection at 2 mg/L. Further, through this study, it was found that the chemical cavitation yield and selenium removal efficiency peaked at low frequency ultrasound of 40 kHz
A Minimal See-Saw Model for Hierarchical Neutrino Masses with Large Mixing
The atmospheric and solar neutrino oscillation data suggest hierarchical
neutrino masses with at least one large mixing. The simplest see-saw models for
reconciling the two features are U(1) extensions of the SM with flavour
dependent gauge charges. I discuss a minimal model of this type containing two
heavy right-handed neutrinos, which have normal Dirac couplings to
and but suppressed ones to . It can naturally account for the
large (small) mixing solutions to the atmospheric (solar) neutrino oscillation
data.Comment: 6 pages, Latex, Invited Talk at the 6th San Miniato Topical Seminar
on `Neutrino and Astroparticle Physics', to appear in Nuclear Physics B
(Proc. Suppl.
Heavy Triplet Leptons and New Gauge Boson
A heavy triplet of leptons per family is
proposed as the possible anchor of a small seesaw neutrino mass. A new U(1)
gauge symmetry is then also possible, and the associated gauge boson may be
discovered at or below the TeV scale. We discuss the phenomenology of this
proposal, with and without possible constraints from the NuTeV and atomic
parity violation experiments, which appear to show small discrepancies from the
predictions of the standard model.Comment: 20 pages including 4 figure
Limits on Associated Production of Visibly and Invisibly Decaying Higgs Bosons from Z Decays
Many extensions of the standard electroweak model Higgs sector suggest that
the main Higgs decay channel is "invisible", for example, where
denotes the majoron, a weakly interacting pseudoscalar Goldstone boson
associated to the spontaneous violation of lepton number. In many of these
models the Higgs boson may also be produced in association to a massive
pseudoscalar boson (HA), in addition to the standard Bjorken mechanism (HZ). We
describe a general strategy to determine limits from LEP data on the masses and
couplings of such Higgs bosons, using the existing data on acoplanar dijet
events as well as data on four and six jet event topologies. For the sake
of illustration, we present constraints that can be obtained for the ALEPH
data.Comment: FTUV/94-36, IFIC/94-31 TIFR/TH/94--25, 12 pages + 4 figures (included
as ps files at the end
Transient domain walls and lepton asymmetry in the Left-Right symmetric model
It is shown that the dynamics of domain walls in Left-Right symmetric models,
separating respective regions of unbroken SU(2)_L and SU(2)_R in the early
universe, can give rise to baryogenesis via leptogenesis. Neutrinos have a
spatially varying complex mass matrix due to CP-violating scalar condensates in
the domain wall. The motion of the wall through the plasma generates a flux of
lepton number across the wall which is converted to a lepton asymmetry by
helicity-flipping scatterings. Subsequent processing of the lepton excess by
sphalerons results in the observed baryon asymmetry, for a range of parameters
in Left-Right symmetric models.Comment: v2 version accepted for publication in Phys. Rev. D. Discussion in
Introduction and Conclusion sharpened. Equation (12) corrected. 16 pages, 3
figure files, RevTeX4 styl
Search for the Lepton Flavor Violation Processes and
The lepton flavor violation processes and are
searched for using a sample of 5.8 events collected with
the BESII detector. Zero and one candidate events, consistent with the
estimated background, are observed in and
decays, respectively. Upper limits on the branching ratios are determined to be
and at the 90% confidence level (C.L.).Comment: 9 pages, 2 figure
Search for Doubly-Charged Higgs Boson Production at HERA
A search for the single production of doubly-charged Higgs bosons H^{\pm \pm}
in ep collisions is presented. The signal is searched for via the Higgs decays
into a high mass pair of same charge leptons, one of them being an electron.
The analysis uses up to 118 pb^{-1} of ep data collected by the H1 experiment
at HERA. No evidence for doubly-charged Higgs production is observed and mass
dependent upper limits are derived on the Yukawa couplings h_{el} of the Higgs
boson to an electron-lepton pair. Assuming that the doubly-charged Higgs only
decays into an electron and a muon via a coupling of electromagnetic strength
h_{e \mu} = \sqrt{4 \pi \alpha_{em}} = 0.3, a lower limit of 141 GeV on the
H^{\pm\pm} mass is obtained at the 95% confidence level. For a doubly-charged
Higgs decaying only into an electron and a tau and a coupling h_{e\tau} = 0.3,
masses below 112 GeV are ruled out.Comment: 15 pages, 3 figures, 1 tabl
Search for Doubly-Charged Higgs Bosons at LEP
Doubly-charged Higgs bosons are searched for in e^+e^- collision data
collected with the L3 detector at LEP at centre-of-mass energies up to 209 GeV.
Final states with four leptons are analysed to tag the pair-production of
doubly charged Higgs bosons. No significant excess is found and lower limits at
95% confidence level on the doubly-charged Higgs boson mass are derived. They
vary from 95.5 GeV to 100.2 GeV, depending on the decay mode. Doubly-charged
Higgs bosons which couple to electrons would modify the cross section and
forward-backward asymmetry of the e^+e^- -> e^+e^- process. The measurements of
these quantities do not deviate from the Standard Model expectations and
doubly-charged Higgs bosons with masses up to the order of a TeV are excluded
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV
A search for a Higgs boson decaying into two photons is described. The
analysis is performed using a dataset recorded by the CMS experiment at the LHC
from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an
integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross
section of the standard model Higgs boson decaying to two photons. The expected
exclusion limit at 95% confidence level is between 1.4 and 2.4 times the
standard model cross section in the mass range between 110 and 150 GeV. The
analysis of the data excludes, at 95% confidence level, the standard model
Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The
largest excess of events above the expected standard model background is
observed for a Higgs boson mass hypothesis of 124 GeV with a local significance
of 3.1 sigma. The global significance of observing an excess with a local
significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is
estimated to be 1.8 sigma. More data are required to ascertain the origin of
this excess.Comment: Submitted to Physics Letters
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