906 research outputs found
An example of a non-Borel locally-connected finite-dimensional topological group
Answering a question posed by S.Maillot in MathOverFlow, for every
we construct a locally connected subgroup of dimension , which is not locally compact.Comment: 2 page
Evidence for strong extragalactic magnetic fields from Fermi observations of TeV blazars
Magnetic fields in galaxies are produced via the amplification of seed
magnetic fields of unknown nature. The seed fields, which might exist in their
initial form in the intergalactic medium, were never detected. We report a
lower bound ~gauss on the strength of intergalactic
magnetic fields, which stems from the nonobservation of GeV gamma-ray emission
from electromagnetic cascade initiated by tera-electron volt gamma-ray in
intergalactic medium. The bound improves as if magnetic
field correlation length, , is much smaller than a megaparsec. This
lower bound constrains models for the origin of cosmic magnetic fields.Comment: 14 pages, 3 figure
In-Situ Vibrational Spectroscopic Studies on Model Catalyst Surfaces at Elevated Pressures
Cataloged from PDF version of article.Elucidation of complex heterogeneous catalytic mechanisms at the molecular level is a challenging task due to the complex electronic structure and the topology of catalyst surfaces. Heterogeneous catalyst surfaces are often quite dynamic and readily undergo significant alterations under working conditions. Thus, monitoring the surface chemistry of heterogeneous catalysts under industrially relevant conditions such as elevated temperatures and pressures requires dedicated in situ spectroscopy methods. Due to their photons-in, photons-out nature, vibrational spectroscopic techniques offer a very powerful and a versatile experimental tool box, allowing real-time investigation of working catalyst surfaces at elevated pressures. Infrared reflection absorption spectroscopy (IRAS or IRRAS), polarization modulation-IRAS and sum frequency generation techniques reveal valuable surface chemical information at the molecular level, particularly when they are applied to atomically well-defined planar model catalyst surfaces such as single crystals or ultrathin films. In this review article, recent state of the art applications of in situ surface vibrational spectroscopy will be presented with a particular focus on elevated pressure adsorption of probe molecules (e.g. CO, NO, O-2, H-2, CH3OH) on monometallic and bimetallic transition metal surfaces (e.g. Pt, Pd, Rh, Ru, Au, Co, PdZn, AuPd, CuPt, etc.). Furthermore, case studies involving elevated pressure carbon monoxide oxidation, CO hydrogenation, Fischer-Tropsch, methanol decomposition/partial oxidation and methanol steam reforming reactions on single crystal platinum group metal surfaces will be provided. These examples will be exploited in order to demonstrate the capabilities, opportunities and the existing challenges associated with the in situ vibrational spectroscopic analysis of heterogeneous catalytic reactions on model catalyst surfaces at elevated pressures
The Beginning of Plast Publishing. Plast Publications, 1911–1922
Розглянуто перші роки пластової видавничої діяльності, проаналізовано основні видання, які побачили світ у перше десятиліття існування організації. Визначено основні ідеї, погляди та положення, викладені у виданнях, їхнє змістове наповнення, цільове та читацьке призначення. The first years of plast publishing activity were considered, the basic editions, published in the first decade of the organization were analyzed. The main ideas, views and conditions, as well as the content, target designation, and readers of the publications were identified
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