5,076 research outputs found

### Non-catalytic bromination of benzene: a combined computational and experimental study

The non-catalytic bromination of benzene is shown experimentally to require high 5-14M concentrations of bromine in order to proceed at ambient temperatures to form predominantly bromobenzene, along with detectable (The non-catalytic bromination of benzene is shown experimentally to require high 5-14M concentrations of bromine in order to proceed at ambient temperatures to form predominantly bromobenzene, along with detectable (The non-catalytic bromination of benzene is shown experimentally to require high 5-14M concentrations of bromine in order to proceed at ambient temperatures to form predominantly bromobenzene, along with detectable

### Angular distributions in $J/\psi\to p\bar{p}\pi^{0}(\eta)$ decays

The differential decay rates of the processes $J/\psi\to p\bar{p}\pi^{0}$ and
$J/\psi\to p\bar{p}\eta$ close to the $p\bar{p}$ threshold are calculated with
the help of the $N\bar{N}$ optical potential. The same calculations are made
for the decays of $\psi(2S)$. We use the potential which has been suggested to
fit the cross sections of $N\bar{N}$ scattering together with $N\bar{N}$ and
six pion production in $e^{+}e^{-}$ annihilation close to the $p\bar{p}$
threshold. The $p\bar{p}$ invariant mass spectra is in agreement with the
available experimental data. The anisotropy of the angular distributions, which
appears due to the tensor forces in the $N\bar{N}$ interaction, is predicted
close to the $p\bar{p}$ threshold. This anisotropy is large enough to be
investigated experimentally. Such measurements would allow one to check the
accuracy of the model of $N\bar{N}$ interaction.Comment: 10 pages, 8 figure

### Исследование работы стеклопластиковых крепежных элементов в стеновых конструкциях

The article is devoted to the study of pull-out tests of fiberglass plastic dowels installed in the walls made of lightweight concrete. The authors have undertaken experimental tests of anchors in use on the construction site and conducted analysis of test results.Работа посвящена исследованию характеристик сцепления композитных стеклопластиковых дюбелей с легким бетоном. Авторами проведены экспериментальные испытания анкеров в натурных условияx на строительной площадке и выполнен анализ результатов испытаний

### Natural explanation of recent results on $e^{+}e^{-}\to\Lambda\bar{\Lambda}$

We show that the recent experimental data on the cross section of the process
$e^{+}e^{-}\to\Lambda\bar{\Lambda}$ near the threshold can be perfectly
explained by the final-state interaction of $\Lambda$ and $\bar{\Lambda}$. The
enhancement of the cross section is related to the existence of low-energy real
or virtual state in the corresponding potential. We present a simple analytical
formula that fits the experimental data very well.Comment: 2 pages, 1 figur

### Harmonic oscillators in the Nos\'e - Hoover thermostat

We study the dynamics of an ensemble of non-interacting harmonic oscillators
in a nonlinear dissipative environment described by the Nos\'e - Hoover model.
Using numerical simulation we find the histogram for total energy, which agrees
with the analysis of the Nos\'e - Hoover equations effected with the method of
averaging. The histogram does not correspond to Gibbs' canonical distribution.
We have found oscillations at frequency proportional to $\sqrt{\alpha/m}$,
$\alpha$ the dissipative parameter of thermostat and $m$ the characteristic
mass of particle, about the stationary state corresponding to equilibrium. The
oscillations could have an important bearing upon the analysis of simulating
molecular dynamics in the Nos\'e - Hoover thermostat.Comment: 7 pages, 4 figure

### 2d Gauge Theories and Generalized Geometry

We show that in the context of two-dimensional sigma models minimal coupling
of an ordinary rigid symmetry Lie algebra $\mathfrak{g}$ leads naturally to the
appearance of the "generalized tangent bundle" $\mathbb{T}M \equiv TM \oplus
T^*M$ by means of composite fields. Gauge transformations of the composite
fields follow the Courant bracket, closing upon the choice of a Dirac structure
$D \subset \mathbb{T}M$ (or, more generally, the choide of a "small
Dirac-Rinehart sheaf" $\cal{D}$), in which the fields as well as the symmetry
parameters are to take values. In these new variables, the gauge theory takes
the form of a (non-topological) Dirac sigma model, which is applicable in a
more general context and proves to be universal in two space-time dimensions: A
gauging of $\mathfrak{g}$ of a standard sigma model with Wess-Zumino term
exists, \emph{iff} there is a prolongation of the rigid symmetry to a Lie
algebroid morphism from the action Lie algebroid $M \times \mathfrak{g}\to M$
into $D\to M$ (or the algebraic analogue of the morphism in the case of
$\cal{D}$). The gauged sigma model results from a pullback by this morphism
from the Dirac sigma model, which proves to be universal in two-spacetime
dimensions in this sense.Comment: 22 pages, 2 figures; To appear in Journal of High Energy Physic

### Energy loss for heavy quarks in relation to light partons; is radiative energy loss for heavy quarks anomalous?

The scaling properties of jet suppression measurements are compared for
non-photonic electrons ($e^{\pm}$) and neutral pions ($\pi^0$) in Au + Au
collisions at $\sqrt{s_{NN}}=200$ GeV. For a broad range of transverse momenta
and collision centralities, the comparison is consistent with jet quenching
dominated by radiative energy loss for both heavy and light partons. Less
quenching is indicated for heavy quarks via $e^{\pm}$; this gives an
independent estimate of the transport coefficient $\hat{q}$ that agrees with
its magnitude obtained from quenching of light partons via $\pi^0$'s.Comment: Published versio

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