1,008 research outputs found
Nanostructure and properties of a Cu-Cr composite processed by severe plastic deformation
A Cu-Cr composite was processed by severe plastic deformation to investigate
the role of interphase boundaries on the grain size reduction mechanisms. The
as-deformed material exhibits a grain size of only 20nm. This gives rise to a
dramatic increase of the hardness. Some deformation induced Cu super saturated
solid solutions were clearly exhibited and it is shown that they decrease the
hardness. The formation of such supersaturated solid solution and their
influence on the mechanical properties are discussed
Spin-orbit coupling effects in O(2) activation by cofactor-independent 2,4-dioxygenase
The O2 (dioxygen) is paramagnetic molecule with two non-paired electron spins and triplet ground state (S = 1) while majority of organic molecules are diamagnetic species; they have all electron spins paired and the singlet ground state with the total spin S = 0. Oxygenases catalyze a concerted insertion of the triplet dioxygen into organic (diamagnetic) molecules in a strictly spin-forbidden process and this puzzle is not solved so far in modern enzymology. Many oxidases and oxygenases utilize the π-conjugated organic cofactor (like flavins, pterins) in a singlet ground state and reaction of cofactor with O2 is still spin-forbidden. It is clear that the protein environment in the enzyme active-site “helps” in some way to overcome spin prohibition, but this environment is definitely diamagnetic and the spin-puzzle still exists. Some oxidases and oxygenases use paramagnetic metal ions as a cofactor; in this case the spin prohibition is formally reduced. In recent years, a numbers of oxidative enzymes are discovered which do not contain any cofactor. In the present work, we considered a rather popular cofactor-free bacterial 2,4-dioxygenase and its oxygenolytic reactions with 2-n-alkyl-3-hydroxy-4(1H)-quinolones (AHQ’s). We presented results of quantum-chemical calculations of intermediate diradical proposed recently for direct reaction of dioxygen with AHQ substrate and made conclusion about the mechanism of spin-catalysis
Aromaticity of the doubly charged [8]circulenes
Magnetically induced current densities and current pathways have been calculated for a series of fully annelated dicationic and dianionic tetraphenylenes, which are also named [8]circulenes. The gauge including magnetically induced current (GIMIC) method has been employed for calculating the current density susceptibilities. The aromatic character and current pathways are deduced from the calculated current density susceptibilities showing that the neutral [8]circulenes have two concentric pathways with aromatic and antiaromatic character, respectively. The inner octatetraene core (the hub) is found to sustain a paratropic (antiaromatic) ring current, whereas the ring current along the outer part of the macrocycle (the rim) is diatropic (aromatic). The neutral [8]circulenes can be considered nonaromatic, because the sum of the ring-current strengths of the hub and the rim almost vanishes. The aromatic character of the doubly charged [8]circulenes is completely different: the dianionic [8]circulenes and the OC-, CH-, CH2-, SiH-, GeH-, SiH2-, and GeH2-containing dicationic species sustain net diatropic ring currents i.e., they are aromatic, whereas the O-, S-, Se-, NH-, PH- and AsH-containing dicationic [8]circulenes are strongly antiaromatic. The present study also shows that GIMIC calculations on the [8]circulenes provide more accurate information about the aromatic character than that obtained using local indices such as nuclear-independent chemical shifts (NICSs) and H-1 NMR chemical shifts.Peer reviewe
Integration of global ring currents using the Ampere-Maxwell law
Magnetically induced ring currents are calculated from the magnetic shielding tensor by employing the Ampere-Maxwell law. The feasibility of the method is demonstrated by integrating the zz component of the shielding tensor along the symmetry axis of highly symmetric ring-shaped aromatic, antiaromatic and nonaromatic molecules. The calculated ring-current strengths agree perfectly with the ones obtained by integrating the current-density flux passing through a plane cutting half the molecular ring. The method can be used in combination with all electronic structure codes capable of calculating nuclear magnetic resonance (NMR) shielding tensors in general points in space. We also show that nucleus independent chemical shifts (NICS) along the symmetry axis are related to the spatial derivative of the strength of the global ring-current along the z axis.Peer reviewe
Photon recycling in Fabry-Perot micro-cavities based on SiN waveguides
We present a numerical analysis and preliminary experimental results on
one-dimensional Fabry-Perot micro-cavities in SiN waveguides. The
Fabry-Perot micro-cavities are formed by two distributed Bragg reflectors
separated by a straight portion of waveguide. The Bragg reflectors are composed
by a few air slits produced within the SiN waveguides. In order to
increase the quality factor of the micro-cavities, we have minimized, with a
multiparametric optimization tool, the insertion loss of the reflectors by
varying the length of their first periods (those facing the cavity). To explain
the simulation results the coupling of the fundamental waveguide mode with
radiative modes in the Fabry-Perot micro-cavities is needed. This effect is
described as a recycling of radiative modes in the waveguide. To support the
modelling, preliminary experimental results of micro-cavities in SiN
waveguides realized with Focused Ion Beam technique are reported.Comment: 5 pages, 5 figure
Polarized fluorescent emission in uniaxial liquid crystals. The effect of intramolecular energy transfer and rotational Brownian motion on measurements of the orientational distribution function
ASPIRATING DRAINAGE OF THE CAVITY OF THE LESSER PELVIS AS A WAY OF CONSERVATIVE TREATMENT OF LOW-LYING COLORECTAL ANASTOMOTIC LEAK
Aim. Examination of efficacy of the double-lumen “pipe in pipe” drainage set mounted in the cavity of the lesser pelvis by the method developed by the authors for conservative treatment of colorectal anastomotic leak.Material and methods. Data have been analyzed for 124 patients operated in two surgeries of the base No.2 of the Republican Clinical Onco- logic Dispensary of the Ministry of Health of the Republic of Tatarstan, whose surgery was completed with formation of colorectal anastomo- sis; aspirating drainage of the cavity of the lesser pelvis was performed with double-lumen drainage of the authors’ design, mounted in the retroperitoneal part of the cavity of the lesser pelvis through a puncture in the anterior abdominal wall. No patient was applied a preventive intestinal stoma.Results. 4 (3.2 %) out of 124 patients died after surgeries. 21 (16.9 %) patients experienced colorectal anastomotic leak, which was resolved in a conservative manner in all patients.Conclusion. Our data allow us to speak about the efficacy of this technique of drainage of the cavity of the lesser pelvis in colorectal anastomotic leak
The influence of energy-information impact on an electric vehicle
The main results of studying the energy-informational impact on the driver of an electric vehicle. The parameters of electrical and magnetic fields recorded in the vehicle exhibit fairly complex patterns. A significant influence on the level of electromagnetic radiation comes from the electronic devices for onboard diagnostics and control, passive and active noise and vibration protection means, navigation systems, immediate access to information, climate control devices, air purification, and security systems. Moreover, during the movement of the electric vehicle, there is a change in electromagnetic radiation due to the presence of external fields from power lines, telecommunication towers, radio transmitting stations, and others. The loads arising from the operation of an electric vehicle inevitably affect the elements of its structure, resulting in their alteration. Apart from regular operational faults, which are unavoidable, sudden malfunctions can always occur due to changes in the technical condition of the vehicle and road conditions, which are of an incidental nature
Fast Pre-Trigger Electronics of T0/Centrality MCP-Based Start Detector for ALICE
This work describes an alternative to the current ALICE baseline solution for a TO detector, still under development. The proposed system consists of two MCP-based T0/Centrality Start Detectors (backward-forward isochronous disks) equipped with programmable, TTC synchronized front-end electronic cards (FEECs) which would be positioned along the LHC colliding beam line on both sides of the ALICE interaction region. The purpose of this arrangement, providing both precise timing and fast multiplicity selection, is to give a pre-trigger signal at the earliest possible time after a central event. This pre-trigger can be produced within 25 ns. It can be delivered within 100 ns directly to the Transition Radiation Detector and would be the earliest L0 input coming to the ALICE Central Trigger Processor. A noise-free passive multichannel summator of 2ns signals is used to provide a determination of the collision time with a potential accuracy better than 10 ps in the case of Pb-Pb collisions, the limit coming from the electronics. Results from in-beam tests confirm the functionality of the main elements. Further development plans are presented
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