257 research outputs found
Universal Holographic Chiral Dynamics in an External Magnetic Field
In this work we further extend the investigation of holographic gauge
theories in external magnetic fields, continuing earlier work. We study the
phenomenon of magnetic catalysis of mass generation in 1+3 and 1+2 dimensions,
using D3/D7- and D3/D5-brane systems, respectively. We obtain the low energy
effective actions of the corresponding pseudo Goldstone bosons and study their
dispersion relations. The D3/D7 system exhibits the usual
Gell-Mann--Oakes--Renner (GMOR) relation and a relativistic dispersion
relation, while the D3/D5 system exhibits a quadratic non-relativistic
dispersion relation and a modified linear GMOR relation. The low energy
effective action of the D3/D5 system is related to that describing magnon
excitations in a ferromagnet. We also study properties of general Dp/Dq systems
in an external magnetic field and verify the universality of the magnetic
catalysis of dynamical symmetry breaking.Comment: 41 pages, 11 figures, references adde
Changes in the middle and upper atmosphere parameters during the January 2013 sudden stratospheric warming
We present the results of complex obser-vations of various parameters of the middle and upper atmosphere over Siberia in December 2012 – January 2013, during a major sudden stratospheric warming (SSW) event. We analyze variations in ozone concentration from microwave measurements, in stratosphere and lower mesosphere temperatures from lidar and satellite measurements, in the F2-layer critical frequency (foF2), in the total electron content (TEC), as well as in the ratio of concentrations of atomic oxygen to molecular nitrogen (O/N2) in the thermosphere. To interpret the observed disturbances in the upper atmosphere, the experimental measurements are compared with the results of model calculations obtained with the Global Self-consistent Model of Thermosphere—Ionosphere—Protonosphere (GSM TIP). The response of the upper atmosphere to the SSW event is shown to be a decrease in foF2 and TEC during the evolution of the warming event and a prolonged increase in O/N2, foF2, and TEC after the SSW maximum. For the first time, we observe the relation between the increase in stratospheric ozone, thermospheric O/N2, and ionospheric electron density for a fairly long time (up to 20 days) after the SSW maximum at midlatitudes
Influence of the High-Temperature Annealing on the Structure and Mechanical Properties of Vacuum–Arc Coatings from Mo/(Ti + 6 wt % Si)N
Scanning electron microscopy with energy dispersive element microanalysis, X-ray structural
analysis, and microindentation were used to study the effect of the deposition conditions in a reactive
nitrogen atmosphere on the growth morphology, phase composition, structure, and microhardness of vacuum–arc multilayer coatings produced by the evaporation of cathodes from Mo and (Ti + 6 wt % Si) both
after their deposition and after high?temperature annealing. It has been established that the use of the
composite cathode of Ti and Si allows the formation of the structure state inclined to ordering to form a
two-phase compound from TiN and Ti5Si3 at high-temperature annealing. In this case the coating hard?
ness increases to a value higher than 45 GPa
Cavitation erosion of Ti-6Al-4V alloy with vacuum-arc TiN and CrN coatings
The distilled-water cavitation erosion resistance of Ti-6Al-4V alloy with vacuum-arc TiN and CrN coatings is
investigated. The results show that the coatings having high mechanical properties are capable to reduce appreciably
the cavitation erosion of the alloy by prolonging the incubation period of fracture and by decreasing the mass loss.
Preliminary ion-plasma nitriding of the alloy leads to the formation under the coating of a solid transition layer
which enhances the coating alloy adhesion and so increases the alloy resistance to the cavitation erosion.Досліджено стійкість до кавітації в дистильованій воді сплаву Ti-6Al-4V з вакуумно-дуговими
покриттями TiN і CrN. Показано, що покриття, які мають високі механічні властивості, істотно знижують
кавітаційний знос сплаву, подовжуючи інкубаційний період руйнування і знижуючи втрату маси. Попереднє
іонно-плазмове азотування сплаву призводить до формування під покриттям твердого перехідного шару,
який покращує адгезію покриття до металу і тим самим збільшує його стійкість до кавітаційного
руйнування.Исследована стойкость к кавитации в дистиллированной воде сплава Ti-6Al-4V с вакуумно-дуговыми
покрытиями TiN и CrN. Показано, что покрытия, обладающие высокими механическими свойствами,
существенно снижают кавитационный износ сплава, продлевая инкубационный период разрушения и
снижая потерю массы. Предварительное ионно-плазменное азотирование сплава приводит к формированию
под покрытием твердого переходного слоя, который улучшает адгезию покрытия к сплаву и тем самым
увеличивает его стойкость к кавитационному разрушению
Deposition of TiN-based coatings using vacuum arc plasma in increased negative substrate bias voltage
The paper presents the results of the study on the influence of a high substrate bias voltage from 300 up to 1300 V on the titanium nitride coating deposition under nitrogen pressure of 2 Pa. The deposition rate, phase and chemical composition, adhesion and mechanical properties of coatings, macroparticle number and size distribution were investigated.Представлені результати дослідження впливу високої напруги зсуву підкладки від 300 до 1300 В на осадження покриттів нітриду титану при тиску азоту 2 Па. Вивчені швидкість осадження, фазовий і хімічний склад, адгезія і механічні властивості покриттів, кількість і розподіл за розмірами макрочасток.Представлены результаты исследования влияния высокого напряжения смещения подложки от 300 до 1300 В на осаждение покрытий нитрида титана при давлении азота 2 Па. Изучены скорость осаждения, фазовый и химический составы, адгезия и механические свойства покрытий, количество и распределение по размерам макрочастиц
High Precision Mass Measurements in and Families Revisited
High precision mass measurements in and families performed
in 1980-1984 at the VEPP-4 collider with OLYA and MD-1 detectors are revisited.
The corrections for the new value of the electron mass are presented. The
effect of the updated radiative corrections has been calculated for the
and mass measurements.Comment: 5 pages, 1 table, submitted to Phys. Lett.
Complete measurement of three-body photodisintegration of 3He for photon energies between 0.35 and 1.55 GeV
The three-body photodisintegration of 3He has been measured with the CLAS
detector at Jefferson Lab, using tagged photons of energies between 0.35 GeV
and 1.55 GeV. The large acceptance of the spectrometer allowed us for the first
time to cover a wide momentum and angular range for the two outgoing protons.
Three kinematic regions dominated by either two- or three-body contributions
have been distinguished and analyzed. The measured cross sections have been
compared with results of a theoretical model, which, in certain kinematic
ranges, have been found to be in reasonable agreement with the data.Comment: 22 pages, 25 eps figures, 2 tables, submitted to PRC. Modifications:
removed 2 figures, improvements on others, a few minor modifications to the
tex
A Kinematically Complete Measurement of the Proton Structure Function F2 in the Resonance Region and Evaluation of Its Moments
We measured the inclusive electron-proton cross section in the nucleon
resonance region (W < 2.5 GeV) at momentum transfers Q**2 below 4.5 (GeV/c)**2
with the CLAS detector. The large acceptance of CLAS allowed for the first time
the measurement of the cross section in a large, contiguous two-dimensional
range of Q**2 and x, making it possible to perform an integration of the data
at fixed Q**2 over the whole significant x-interval. From these data we
extracted the structure function F2 and, by including other world data, we
studied the Q**2 evolution of its moments, Mn(Q**2), in order to estimate
higher twist contributions. The small statistical and systematic uncertainties
of the CLAS data allow a precise extraction of the higher twists and demand
significant improvements in theoretical predictions for a meaningful comparison
with new experimental results.Comment: revtex4 18 pp., 12 figure
Measurement of the Deuteron Structure Function F2 in the Resonance Region and Evaluation of Its Moments
Inclusive electron scattering off the deuteron has been measured to extract
the deuteron structure function F2 with the CEBAF Large Acceptance Spectrometer
(CLAS) at the Thomas Jefferson National Accelerator Facility. The measurement
covers the entire resonance region from the quasi-elastic peak up to the
invariant mass of the final-state hadronic system W~2.7 GeV with four-momentum
transfers Q2 from 0.4 to 6 (GeV/c)^2. These data are complementary to previous
measurements of the proton structure function F2 and cover a similar
two-dimensional region of Q2 and Bjorken variable x. Determination of the
deuteron F2 over a large x interval including the quasi-elastic peak as a
function of Q2, together with the other world data, permit a direct evaluation
of the structure function moments for the first time. By fitting the Q2
evolution of these moments with an OPE-based twist expansion we have obtained a
separation of the leading twist and higher twist terms. The observed Q2
behaviour of the higher twist contribution suggests a partial cancellation of
different higher twists entering into the expansion with opposite signs. This
cancellation, found also in the proton moments, is a manifestation of the
"duality" phenomenon in the F2 structure function
eta-prime photoproduction on the proton for photon energies from 1.527 to 2.227 GeV
Differential cross sections for the reaction gamma p -> eta-prime p have been
measured with the CLAS spectrometer and a tagged photon beam with energies from
1.527 to 2.227 GeV. The results reported here possess much greater accuracy
than previous measurements. Analyses of these data indicate for the first time
the coupling of the etaprime N channel to both the S_11(1535) and P_11(1710)
resonances, known to couple strongly to the eta N channel in photoproduction on
the proton, and the importance of j=3/2 resonances in the process.Comment: 6 pages, 3 figure
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