Abstract
The experiments carried out using two methods of TGA (thermogravimetric analysis) made it possible to determine the ignition temperatures for brown coal, hard coal and anthracite treated ...both with activator mills (VCM, disintegrator) and with a standard hammer mill (initial coal). Practically all the results of coal ignition obtained by different methods correlate with each other. They show a decrease in the ignition temperature of micromilled coals during mechanically activated grinding. The analysis of the results of experimental studies made it possible to calculate kinetic parameters such as the ignition index, the maximum burning rate, the burnout index, and the comprehensive index. The data obtained are new and prove the effectiveness of mechanical activation treatment of coal fuel.
Abstract
The 1 MW experimental stand was modernized with a scroll swirler and a crushed fuel supply system. Comparative data on combustion and gasification of coal fuel crushed in high-stress mills - ...disintegrator, vibrocentrifugal and hammer mill - at a stand with a thermal power of 1 MW were obtained. The experiments used coal of the Kuznetsk Basin, grade D, with technical characteristics: W
r
, % = 5.4; A
r
, %=22.3; V
r
, % = 32.3; Q
sr
, MJ/kg = 20.0. Elemental analysis showed that: C
r
, %=54.6; H
r
, % = 4.1; N
r
, % = 1.3; S
r
, % = 0.5; O
r
= 11.8. In experiments with grinding coal on a disintegrator mill, the value of H
2
= 4.5 vol.% and CO = 9.4 vol.%, when grinding in a vibro-centrifugal mill, the values of H
2
= 0.6 vol.% and CO = 5.8 vol.%, when grinding in a hammer mill, the values of H
2
= 0.3 vol.% and CO = 2.8 vol.%. When studying the combustion of mechanochemically treated coal samples, it was found that, all other things being equal, the gasification parameters, namely, the gas concentration and the distribution of temperature zones, depend strongly on the type of equipment used for processing. In particular, processing to approximately the same degree of fineness in mechanical mills-activators with constrained impact and in free impact mills (disintegrators) resulted in different flame parameters.
Silicon Photomultipliers (SiPM), also called Solid State Photomultipliers (SSPM), are based on Geiger mode avalanche breakdown that is limited by a strong negative feedback. An SSPM can detect and ...resolve single photons due to the high gain and ultra-low excess noise of avalanche multiplication in this mode. Crosstalk and afterpulsing processes associated with the high gain introduce specific excess noise and deteriorate the photon number resolution of the SSPM. The probabilistic features of these processes are widely studied because of its significance for the SSPM design, characterization, optimization and application, but the process modeling is mostly based on Monte Carlo simulations and numerical methods. In this study, crosstalk is considered to be a branching Poisson process, and analytical models of probability distribution and excess noise factor (ENF) of SSPM signals based on the Borel distribution as an advance on the geometric distribution models are presented and discussed. The models are found to be in a good agreement with the experimental probability distributions for dark counts and a few photon spectrums in a wide range of fired pixels number as well as with observed super-linear behavior of crosstalk ENF.
Photochemical reactions between stabilized furyl‐substituted phosphonium–iodonium ylides and terminal acetylenes led to the formation of new P‐containing heterocyclic compounds. For the ...heterocyclization of 2‐furyl‐substituted ylides, we observed an unprecedented electrophilic ipso attack onto the α position of the furan ring in a carbocationic intermediate, leading – via a spiro intermediate – to the rearranged product with a 2,3‐shift in the furan ring.
Photochemical reactions between furyl‐substituted phosphonium–iodonium ylides with different stabilizing groups and terminal alkynes provided new P‐containing heterocyclic compounds. For the reactions of 2‐furyl‐substituted ylides, we observed a rearrangement (a 2,3‐shift in the furan ring) during the heterocyclization process.
The results of the comparative quantitative study of oxygen-containing groups adsorbed on the surface of carbonized sponge scaffold (CSS), highly oriented pyrolytic graphite (HOPG), fullerite C60 and ...multi-walled carbon nanotubes (MWCNTs) introduced into a high vacuum from the atmosphere without any pre-treatment of the surface are discussed. The studied materials are first tested by XRD and Raman spectroscopy, and then quantitatively characterized by XPS and NEXAFS. The research results showed the presence of carbon oxides and water-dissociation products on the surfaces of materials. It was shown that main source of oxygen content (~2%) on the surface of HOPG, MWCNTs, and C60 powder is water condensed from the atmosphere in the form of an adsorbed water molecule and hydroxyl group. On the CSS surface, oxygen atoms are present in the forms of carbon oxides (4–5%) and adsorbed water molecules and hydroxyl groups (5–6%). The high content of adsorbed water on the CSS surface is due to the strong roughness and high porosity of the surface.
The role of the transition metal 3d states in the adsorption of h-BN on Cu(1
1
1) and Ni(1
1
1) has been studied by NEXAFS and PE spectroscopies and by work function measurements. Based on the ...analysis of drastic differences in the spectra from h-BN/Cu(1
1
1) and h-BN/Ni(1
1
1), it has been concluded that the strength of chemical bonding at the interfaces under study is determined mainly by the strength of the TM 3d–h-BN π orbital hybridization. On Ni(1
1
1) h-BN is found to be strongly chemisorbed, while on Cu(1
1
1) only weak chemisorption is observed. On Ni(1
1
1) the h-BN monolayer is probably metallic. On Cu(1
1
1) the monolayer should possibly also be considered as metallic, however its metallic properties are much less pronounced, and the situation is somewhat uncertain.
Cationic copolymers consisting of polycations linked to non-ionic polymers are evaluated as non-viral gene delivery systems. These copolymers are known to produce soluble complexes with DNA, but only ...a few studies have characterized the transfection activity of these complexes. This work reports the synthesis and characterization of a series of cationic copolymers obtained by grafting the polyethyleneimine (PEI) with non-ionic polyethers, poly (ethylene oxide) (PEO) or Pluronic 123 (P123). The PEO-PEI conjugates differ in the molecular mass of PEI (2 kDa and 25 kDa) and the degree of modification of PEI with PEO. All of these conjugates form complexes upon mixing with plasmids, which are stable in aqueous dispersion for several days. The sizes of the particles formed in these systems vary from 70 to 200 nm depending on the composition of the complex. However, transfection activity of these systems is much lower than that of PEI (25 kDa) or Superfect as assessed in in vitro transfection experiments utilizing a luciferase reporter expression in Cos-7 cells as a model system. In contrast, conjugate of P123 with PEI (2 kDa) mixed with free P123 (9:1(wt)) forms small and stable complexes with DNA (110 nm) that exhibit high transfection activity in vitro. Furthermore, gene expression is observed in spleen, heart, lungs and liver 24 h after i.v. injection of this complex in mice. Compared to 1,2-bis(oleoyloxy)-(trimethylammonio) propane:cholesterol (DOTAP:Chol) and PEI (25 kDa) transfection systems, the P123-PEI system reveals a more uniform distribution of gene expression between these organs, allowing a significant improvement of gene expression in liver.
The results of the research of a composite based on multi-walled carbon nanotubes (MWCNTs) decorated with CuO/Cu2O/Cu nanoparticles deposited by the cupric formate pyrolysis are discussed. The study ...used a complementary set of methods, including scanning and transmission electron microscopy, X-ray diffractometry, Raman, and ultrasoft X-ray spectroscopy. The investigation results show the good adhesion between the copper nanoparticles coating and the MWCNT surface through the oxygen atom bridge formation between the carbon atoms of the MWCNT outer graphene layer and the oxygen atoms of CuO and Cu2O oxides. The formation of the Cu–O–C bond between the coating layer and the outer nanotube surface is clearly confirmed by the results of the O 1s near edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy (XPS) of the Cu/MWCNTs nanocomposite. The XPS measurements were performed using a laboratory spectrometer with sample charge compensation, and the NEXAFS studies were carried out using the synchrotron radiation of the Russian–German dipole beamline at BESSY-II (Berlin, Germany) and the NanoPES station at the Kurchatov Center for Synchrotron Radiation and Nanotechnology (Moscow, Russia).
For practical electronic device applications of graphene nanoribbons (GNRs), it is essential to have abrupt and well-defined contacts between the ribbon and the adjacent metal lead. By analogy with ...graphene, these contacts can induce electron or hole doping, which may significantly affect the
I/V
characteristics of the device. Cu is among the most popular metals of choice for contact materials. In this study, we investigate the effect of
in sit
u intercalation of Cu on the electronic structure of atomically precise, spatially aligned armchair GNRs of width
N
= 7 (7-AGNRs) fabricated via a bottom-up method on the Au(788) surface. Scanning tunneling microscopy data reveal that the complete intercalation of about one monolayer of Cu under 7-AGNRs can be facilitated by gentle annealing of the sample at 80 °C. Angle-resolved photoemission spectroscopy (ARPES) data clearly reflect the one-dimensional character of the 7-AGNR band dispersion before and after intercalation. Moreover, ARPES and core-level photoemission results show that intercalation of Cu leads to significant electron injection into the nanoribbons, which causes a pronounced downshift of the valence and conduction bands of the GNR with respect to the Fermi energy (Δ
E
~ 0.5 eV). As demonstrated by ARPES and X-ray absorption spectroscopy measurements, the effect of Cu intercalation is restricted to n-doping only, without considerable modification of the band structure of the GNRs. Post-annealing of the 7-AGNRs/Cu/Au(788) system at 200 °C activates the diffusion of Cu into Au and the formation of a Cu-rich surface Au layer. Alloying of intercalated Cu leads to the recovery of the initial position of GNR-related bands with respect to the Fermi energy (
E
F
), thus, proving the tunability of the induced n-doping.
Summary
Cardiac arrest is associated with a very high rate of mortality, in part due to inadequate tissue perfusion during attempts at resuscitation. Parameters such as mean arterial pressure and ...end‐tidal carbon dioxide may not accurately reflect adequacy of tissue perfusion during cardiac resuscitation. We hypothesised that quantitative measurements of tissue oxygen tension would more accurately reflect adequacy of tissue perfusion during experimental cardiac arrest. Using oxygen‐dependent quenching of phosphorescence, we made measurements of oxygen in the microcirculation and in the interstitial space of the brain and muscle in a porcine model of ventricular fibrillation and cardiopulmonary resuscitation. Measurements were performed at baseline, during untreated ventricular fibrillation, during resuscitation and after return of spontaneous circulation. After achieving stable baseline brain tissue oxygen tension, as measured using an Oxyphor G4‐based phosphorescent microsensor, ventricular fibrillation resulted in an immediate reduction in all measured parameters. During cardiopulmonary resuscitation, brain oxygen tension remained unchanged. After the return of spontaneous circulation, all measured parameters including brain oxygen tension recovered to baseline levels. Muscle tissue oxygen tension followed a similar trend as the brain, but with slower response times. We conclude that measurements of brain tissue oxygen tension, which more accurately reflect adequacy of tissue perfusion during cardiac arrest and resuscitation, may contribute to the development of new strategies to optimise perfusion during cardiac resuscitation and improve patient outcomes after cardiac arrest.
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