28,582 research outputs found
Fermion masses in the economical 3-3-1 model
We show that, in frameworks of the economical 3-3-1 model, all fermions get
masses. At the tree level, one up-quark and two down-quarks are massless, but
the one-loop corrections give all quarks the consistent masses. This conclusion
is in contradiction to the previous analysis in which, the third scalar triplet
has been introduced. This result is based on the key properties of the model:
First, there are three quite different scales of vacuum expectation values:
\om \sim {\cal O}(1) \mathrm{TeV}, v \approx 246 \mathrm{GeV} and . Second, there exist two types of Yukawa couplings
with different strengths: the lepton-number conserving couplings 's and the
lepton-number violating ones 's satisfying the condition in which the second
are much smaller than the first ones: .
With the acceptable set of parameters, numerical evaluation shows that in
this model, masses of the exotic quarks also have different scales, namely, the
exotic quark () gains mass GeV, while the
D_\al exotic quarks (q_{D_\al} = -1/3) have masses in the TeV scale:
m_{D_\al} \in 10 \div 80 TeV.Comment: 20 pages, 8 figure
Sertraline and Phenytoin Drug Interaction in a Geriatric Patient
This report presents the case of a 78-year-old man residing in a nursing home who presented with a 2-month history of increasing lethargy and confusion. These symptoms coincided with the initiation of sertraline in the patient. Among other medications, he was also taking phenytoin. The medical team concluded that the cause of the patientâs lethargy and confusion was a drug interaction between sertraline and phenytoin. Phenytoin was held, while the sertraline was slowly tapered to discontinuation. The patientâs symptoms resolved soon thereafter. Future research is needed to better guide clinicians in appropriate selection, dosing, and monitoring of selective serotonin reuptake inhibitors with concomitant phenytoin use.Key words: phenytoin, sertraline, SSRIs, drug interactio
The Effect of wake Turbulence Intensity on Transition in a Compressor Cascade
Direct numerical simulations of separating flow along a section at midspan of a low-pressure V103 compressor cascade with periodically incoming wakes were performed. By varying the strength of the wake, its influence on both boundary layer separation and bypass transition were examined. Due to the presence of small-scale three-dimensional fluctuations in the wakes, the flow along the pressure surface undergoes bypass transition. Only in the weak-wake case, the boundary layer reaches a nearly-separated state between impinging wakes. In all simulations, the flow along the suction surface was found to separate. In the simulation with the strong wakes, separation is intermittently suppressed as the periodically passing wakes managed to trigger turbulent spots upstream of the location of separation. As these turbulent spots convect downstream, they locally suppress separation. © 2014 Springer Science+Business Media Dordrecht
Neutrino masses in the economical 3-3-1 model
We show that, in frameworks of the economical 3-3-1 model, the suitable
pattern of neutrino masses arises from the three quite different sources - the
lepton-number conserving, the spontaneous lepton-number breaking and the
explicit lepton-number violating, widely ranging over the mass scales including
the GUT one: , , \om\sim
O(1) \mathrm{TeV} and . At
the tree-level, the model contains three Dirac neutrinos: one massless, two
large with degenerate masses in the order of the electron mass. At the one-loop
level, the left-handed and right-handed neutrinos obtain Majorana masses
in orders of and degenerate in
, while the Dirac masses get a large reduction down to
scale through a finite mass renormalization. In this model, the contributions
of new physics are strongly signified, the degenerations in the masses and the
last hierarchy between the Majorana and Dirac masses can be completely removed
by heavy particles. All the neutrinos get mass and can fit the data.Comment: 15 pages, 8 figure
Magneto-transport properties of monolayer borophene in perpendicular magnetic field: influence of electron-phonon interaction
The magneto-transport properties of a borophene monolayer in a perpendicular magnetic field B are studied via calculating the conductivity tensor and resistance under electron-optical phonon interaction by using the linear response theory. Numerical results are obtained and discussed for some specific parameters. The magnetic field-dependent longitudinal conductivity shows the magneto-phonon resonance effect that describes the transition of electrons between Landau levels by absorbing/emitting an optical phonon. The Hall conductivity increases first and then decreases with the magnetic field strength. Also, the longitudinal resistance increases significantly with increasing temperature, which shows the metal behaviour of the material. Practically, the observed magneto-phonon resonance can be applied to experimentally determine some material parameters, such as the distance between Landau levels and the optical phonon energy
Volcanic ash supply to the surface ocean â remote sensing of biological responses and their wider biogeochemical significance
Transient micronutrient enrichment of the surface ocean can enhance phytoplankton growth rates and alter microbial community structure with an ensuing spectrum of biogeochemical feedbacks. Strong phytoplankton responses to micronutrients supplied by volcanic ash have been reported recently. Here we: (i) synthesize findings from these recent studies; (ii) report the results of a new remote sensing study of ash fertilization; and (iii) calculate theoretical bounds of ash-fertilized carbon export. Our synthesis highlights that phytoplankton responses to ash do not always simply mimic that of iron amendment; the exact mechanisms for this are likely biogeochemically important but are not yet well understood. Inherent optical properties of ash-loaded seawater suggest rhyolitic ash biases routine satellite chlorophyll-a estimation upwards by more than an order of magnitude for waters with 0.5 mg chlorophyll-a m-3. For this reason post-ash-deposition chlorophyll-a changes in oligotrophic waters detected via standard Case 1 (open ocean) algorithms should be interpreted with caution. Remote sensing analysis of historic events with a bias less than a factor of 2 provided limited stand-alone evidence for ash-fertilization. Confounding factors were poor coverage, incoherent ash dispersal, and ambiguity ascribing biomass changes to ash supply over other potential drivers. Using current estimates of iron release and carbon export efficiencies, uncertainty bounds of ash-fertilized carbon export for 3 events are presented. Patagonian iron supply to the Southern Ocean from volcanic eruptions is less than that of windblown dust on thousand year timescales but can dominate supply at shorter timescales. Reducing uncertainties in remote sensing of phytoplankton response and nutrient release from ash are avenues for enabling assessment of the oceanic response to large-scale transient nutrient enrichment
Multimodal Hippocampal Subfield Grading For Alzheimerâs Disease Classification
Numerous studies have proposed biomarkers based on magnetic resonance imaging (MRI) to detect and predict the risk of evolution toward Alzheimerâs disease (AD). Most of these methods have focused on the hippocampus, which is known to be one of the earliest structures impacted by the disease. To date, patch-based grading approaches provide among the best biomarkers based on the hippocampus. However, this structure is complex and is divided into different subfields, not equally impacted by AD. Former in-vivo imaging studies mainly investigated structural alterations of these subfields using volumetric measurements and microstructural modifications with mean diffusivity measurements. The aim of our work is to improve the current classification performances based on the hippocampus with a new multimodal patch-based framework combining structural and diffusivity MRI. The combination of these two MRI modalities enables the capture of subtle structural and microstructural alterations. Moreover, we propose to study the efficiency of this new framework applied to the hippocampal subfields. To this end, we compare the classification accuracy provided by the different hippocampal subfields using volume, mean diffusivity, and our novel multimodal patch-based grading framework combining structural and diffusion MRI. The experiments conducted in this work show that our new multimodal patch-based method applied to the whole hippocampus provides the most discriminating biomarker for advanced AD detection while our new framework applied into subiculum obtains the best results for AD prediction, improving by two percentage points the accuracy compared to the whole hippocampus
A bremsstrahlung gamma-ray source based on stable ionization injection of electrons into a laser wakefield accelerator
Laser wakefield acceleration permits the generation of ultra-short,
high-brightness relativistic electron beams on a millimeter scale. While those
features are of interest for many applications, the source remains constraint
by the poor stability of the electron injection process. Here we present
results on injection and acceleration of electrons in pure nitrogen and argon.
We observe stable, continuous ionization-induced injection of electrons into
the wakefield for laser powers exceeding a threshold of 7 TW. The beam charge
scales approximately linear with the laser energy and is limited by beam
loading. For 40 TW laser pulses we measure a maximum charge of almost 1 nC per
shot, originating mostly from electrons of less than 10 MeV energy. The
relatively low energy, the high charge and its stability make this source
well-suited for applications such as non-destructive testing. Hence, we
demonstrate the production of energetic radiation via bremsstrahlung conversion
at 1 Hz repetition rate. In accordance with Geant4 Monte-Carlo simulations, we
measure a gamma-ray source size of less than 100 microns for a 0.5 mm tantalum
converter placed at 2 mm from the accelerator exit. Furthermore we present
radiographs of image quality indicators
Local spin and charge properties of beta-Ag0.33V2O5 studied by 51V NMR
Local spin and charge properties were studied on beta-Ag0.33V2O5, a
pressure-induced superconductor, at ambient pressure using 51V-NMR and
zero-field-resonance (ZFR) techniques. Three inequivalent Vi sites (i=1, 2, and
3) were identified from 51V-NMR spectra and the principal axes of the
electric-field-gradient (EFG) tensor were determined in a metallic phase and
the following charge-ordering phase. We found from the EFG analysis that the V1
sites are in a similar local environment to the V3 sites. This was also
observed in ZFR spectra as pairs of signals closely located with each other.
These results are well explained by a charge-sharing model where a 3d1 electron
is shared within a rung in both V1-V3 and V2-V2 two-leg ladders.Comment: 12pages, 16figure
Far-red emitting fluorescent dyes for optical nanoscopy: Fluorinated siliconârhodamines (SiRF dyes) and phosphorylated oxazines.
Far-red emitting fluorescent dyes for optical microscopy, stimulated emission depletion (STED), and ground-state depletion (GSDIM) super-resolution microscopy are presented. Fluorinated siliconârhodamines (SiRF dyes) and phosphorylated oxazines have absorption and emission maxima at about λâ660 and 680â
nm, respectively, possess high photostability, and large fluorescence quantum yields in water. A high-yielding synthetic path to introduce three aromatic fluorine atoms and unconventional conjugation/solubilization spacers into the scaffold of a siliconârhodamine is described. The bathochromic shift in SiRF dyes is achieved without additional fused rings or double bonds. As a result, the molecular size and molecular mass stay quite small (<600â
Da). The use of the λ=800â
nm STED beam instead of the commonly used one at λ=750â775â
nm provides excellent imaging performance and suppresses re-excitation of SiRF and the oxazine dyes. The photophysical properties and immunofluorescence imaging performance of these new far-red emitting dyes (photobleaching, optical resolution, and switch-off behavior) are discussed in detail and compared with those of some well-established fluorophores with similar spectral properties
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