1,027 research outputs found
Thermodynamics of Delta resonances
The thermodynamic potential of a system of pions and nucleons is computed
including the piN interactions in the P33 channel. A consistent treatment of
the width of the resonance in this channel, the Delta(1232) resonance, is
explored in detail. In the low-density limit we recover the leading term of the
virial expansion for the thermodynamic potential. An instructive diagrammatic
interpretation of the contributions to the total baryon number is presented.
Furthermore, we examine within a fireball model the consequences for the pion
spectra in heavy-ion collisions at intermediate energies, including the effect
of collective flow. A consistent treatment of the Delta width leads to a
substantial enhancement of the pion yield at low momenta.Comment: 12 pages, 3 Postscript figures, LaTeX, elsart, epsfig, minor changes,
references added, to be published in Physics Letters
Imaging of trapped ions with a microfabricated optic for quantum information processing
Trapped ions are a leading system for realizing quantum information processing (QIP). Most of the technologies required for implementing large-scale trapped-ion QIP have been demonstrated, with one key exception: a massively parallel ion-photon interconnect. Arrays of microfabricated phase Fresnel lenses (PFL) are a promising interconnect solution that is readily integrated with ion trap arrays for large-scale QIP. Here we show the first imaging of trapped ions with a microfabricated in-vacuum PFL, demonstrating performance suitable for scalable QIP. A single ion fluorescence collection efficiency of 4.2±1.5% was observed. The depth of focus for the imaging system was 19.4±2.4μm and the field of view was 140±20μm. Our approach also provides an integrated solution for high-efficiency optical coupling in neutral atom and solid-state QIP architectures
Production of resonances in a thermal model: invariant-mass spectra and balance functions
We present a calculation of the pi+ pi- invariant-mass correlations and the
pion balance functions in the single-freeze-out model. A satisfactory agreement
with the data for Au+Au collisions is found.Comment: Contribution to QM 2004 (4 pages, 2 figures
A concept of an automated function control for ambient aerosol measurements using mobility particle size spectrometers
An automated function control unit was developed to regularly check the
ambient particle number concentration derived from a mobility particle size
spectrometer as well as its zero-point behaviour. The function control allows
unattended quality assurance experiments at remote air quality monitoring or
research stations under field conditions. The automated function control also
has the advantage of being able to get a faster system stability response
than the recommended on-site comparisons with reference instruments. The
method is based on a comparison of the total particle number concentration
measured by a mobility particle size spectrometer and a condensation particle
counter while removing diffusive particles smaller than 20 nm in diameter.
In practice, the small particles are removed by a set of diffusion screens,
as traditionally used in a diffusion battery. Another feature of the
automated function control is to check the zero-point behaviour of the
ambient aerosol passing through a high-efficiency particulate air (HEPA)
filter.
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The performance of the function control is illustrated with the aid of a
1-year data set recorded at Annaberg-Buchholz, a station in the Saxon air
quality monitoring network. During the period of concern, the total particle
number concentration derived from the mobility particle size spectrometer
slightly overestimated the particle number concentration recorded by the
condensation particle counter by 2 % (grand average). Based on our first
year of experience with the function control, we developed tolerance criteria
that allow a performance evaluation of a tested mobility particle size
spectrometer with respect to the total particle number concentration. We
conclude that the automated function control enhances the quality and
reliability of unattended long-term particle number size distribution
measurements. This will have beneficial effects for intercomparison studies
involving different measurement sites, and help provide a higher data
accuracy for cohort health and climate research studies
Thermal analysis of production of resonances in relativistic heavy-ion collisions
Production of resonances is considered in the framework of the
single-freeze-out model of ultra-relativistic heavy ion collisions. The
formalism involves the virial expansion, where the probability to form a
resonance in a two-body channel is proportional to the derivative of the
phase-shift with respect to the invariant mass. The thermal model incorporates
longitudinal and transverse flow, as well as kinematic cuts of the STAR
experiment at RHIC. We find that the shape of the pi+ pi- spectral line
qualitatively reproduces the preliminary experimental data when the position of
the rho peak is lowered. This confirms the need to include the medium effects
in the description of the RHIC data. We also analyze the transverse-momentum
spectra of rho, K*(892), and f_0(980), and find that the slopes agree with the
observed values. Predictions are made for eta, eta', omega, phi, Lambda(1520),
and Sigma(1385).Comment: minor modifications, a reference adde
Seasonal and diurnal variations of particulate nitrate and organic matter at the IfT research station Melpitz
Ammonium nitrate and several organic compounds such as dicarboxylic acids (e.g. succinic acid, glutaric acid), some Polycyclic Aromatic Hydrocarbon (PAHs) or some n-alkanes are semi-volatile. The transition of these compounds between the gas and particulate phase may significantly change the aerosol particles radiative properties, the heterogeneous chemical properties, and, naturally, the total particulate mass concentration. To better assess these time-dependent effects, three intensive field experiments were conducted in 2008–2009 at the Central European EMEP research station Melpitz (Germany) using an Aerodyne Aerosol Mass Spectrometer (AMS). Data from all seasons highlight organic matter as being the most important particulate fraction of PM1 in summer (59%) while in winter, the nitrate fraction was more prevalent (34.4%). The diurnal variation of nitrate always showed the lowest concentration during the day while its concentration increased during the night. This night increase of nitrate concentration was higher in winter (ΔNO3− = 3.6 μg m−3) than in summer (ΔNO3− = 0.7 μg m−3). The variation in particulate nitrate was inherently linked to the gas-to-particle-phase equilibrium of ammonium nitrate and the dynamics of the atmosphere during day. The results of this study suggest that during summer nights, the condensation of HNO3 and NH3 on pre-existing particles represents the most prevalent source of nitrate, whereas during winter, nighttime chemistry is the predominant source of nitrate. During the summer 2008's campaign, a clear diurnal evolution in the oxidation state of the organic matter became evident (Organic Mass to Organic Carbon ratio (OM/OC) ranging from 1.65 during night to 1.80 during day and carbon oxidation state (OSc) from −0.66 to −0.4), which could be correlated to hydroxyl radical (OH) and ozone concentrations, indicating a photochemical transformation process. In summer, the organic particulate matter seemed to be heavily influenced by regional secondary formation and transformation processes, facilitated by photochemical production processes as well as a diurnal cycling of the substances between the gas and particulate phase. In winter, these processes were obviously less pronounced (OM/OC ranging from 1.60 to 1.67 and OSc from −0.8 to −0.7), so that organic matter apparently originated mainly from aged particles and long range transport
Dirac cones in two-dimensional borane
We introduce two-dimensional borane, a single-layered material of BH
stoichiometry, with promising electronic properties. We show that, according to
Density Functional Theory calculations, two-dimensional borane is semimetallic,
with two symmetry-related Dirac cones meeting right at the Fermi energy .
The curvature of the cones is lower than in graphene, thus closer to the ideal
linear dispersion. Its structure, formed by a puckered trigonal boron network
with hydrogen atoms connected to each boron atom, can be understood as
distorted, hydrogenated borophene (Science \textbf{350}, 1513 (2015)). Chemical
bonding analysis reveals the boron layer in the network being bound by
delocalized four-center two-electron bonds. Finally, we suggest
high-pressure could be a feasible route to synthesise two-dimensional borane.Comment: 5 pages, 3 figures, 1 tabl
Thermodynamical Metrics and Black Hole Phase Transitions
An important phase transition in black hole thermodynamics is associated with
the divergence of the specific heat with fixed charge and angular momenta, yet
one can demonstrate that neither Ruppeiner's entropy metric nor Weinhold's
energy metric reveals this phase transition. In this paper, we introduce a new
thermodynamical metric based on the Hessian matrix of several free energy. We
demonstrate, by studying various charged and rotating black holes, that the
divergence of the specific heat corresponds to the curvature singularity of
this new metric. We further investigate metrics on all thermodynamical
potentials generated by Legendre transformations and study correspondences
between curvature singularities and phase transition signals. We show in
general that for a system with n-pairs of intensive/extensive variables, all
thermodynamical potential metrics can be embedded into a flat (n,n)-dimensional
space. We also generalize the Ruppeiner metrics and they are all conformal to
the metrics constructed from the relevant thermodynamical potentials.Comment: Latex, 25 pages, reference added, typos corrected, English polished
and the Hawking-Page phase transition clarified; to appear in JHE
Разработка программы мероприятий по внедрению наилучших доступных технологий на примере теплоэнергетики
В связи с изменениями экологического законодательства в РФ обязательным требованием будет являться переход предприятий на НДТ с 2020 года. В работе будут предложены мероприятия для уменьшения воздействия теплоэнергетических предприятий на атмосферный воздух путем перехода на НДТ.In connection with the change in environmental legislation in the Russian Federation, the mandatory requirement will be the transition to BAT since 2020. The work will propose measures to reduce the impact of heat power plants on atmospheric air by switching to BAT
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