The catalytic systems NiBr
2
(DPP-DAB) + 20 MAO and NiBr
2
(DPP-BIAN) + 20 MAO (DPP-BIAN = bis(2,6-diisopropylphenyl)-bis(imino)-acenaphtene, MAO = methylaluminoxane), as well as a number of model ...systems, are studied under conditions of their activation and functioning. There are paramagnetic nickel complexes and radical-anion aluminum complexes in the systems under real conditions of activation and functioning. The highest activity is observed when the Ni(I) signal intensity in the ESR spectrum is maximal. A mechanism of paramagnetic species formation is proposed.
Molecular envelope around the HII region RCW 120 Kirsanova, M S; Pavlyuchenkov, Ya N; Wiebe, D S ...
Monthly Notices of the Royal Astronomical Society,
10/2019, Letnik:
488, Številka:
4
Journal Article
Recenzirano
Odprti dostop
ABSTRACT
The H ii region RCW 120 is a well-known object, which is often considered as a target to verify theoretical models of gas and dust dynamics in the interstellar medium. However, the exact ...geometry of RCW 120 is still a matter of debate. In this work, we analyse observational data on molecular emission in RCW 120 and show that 13CO(2–1) and C18O(2–1) lines are fitted by a 2D model representing a ring-like face-on structure. The changing of the C18O(3–2) line profile from double-peaked to single-peaked from the dense molecular Condensation 1 might be a signature of stalled expansion in this direction. In order to explain a self-absorption dip of the 13CO(2–1) and 13CO(3–2) lines, we suggest that RCW 120 is surrounded by a diffuse molecular cloud, and find confirmation of this cloud on a map of interstellar extinction. Optically thick 13CO(2–1) emission and the infrared 8 $\mu$m PAH band form a neutral envelope of the H ii region resembling a ring, while the envelope breaks into separate clumps on images made with optically thin C18O(2–1) line and far-infrared dust emission.
ABSTRACT We report the results of our observations of the S255IR area with the Submillimeter Array (SMA) at 1.3 mm in the very extended configuration and at 0.8 mm in the compact configuration as ...well as with the IRAM 30 m at 0.8 mm. The best achieved angular resolution is about 0.4 arcsec. The dust continuum emission and several tens of molecular spectral lines are observed. The majority of the lines is detected only toward the S255IR-SMA1 clump, which represents a rotating structure (probably a disk) around the young massive star. The achieved angular resolution is still insufficient to make any conclusions about the Keplerian or non-Keplerian character of the rotation. The temperature of the molecular gas reaches 130-180 K. The size of the clump is about 500 AU. The clump is strongly fragmented as follows from the low beam-filling factor. The mass of the hot gas is significantly lower than the mass of the central star. A strong DCN emission near the center of the hot core most probably indicates a presence of a relatively cold ( 80 K) and rather massive clump there. High-velocity emission is observed in the CO line as well as in lines of high-density tracers HCN, HCO+, CS and other molecules. The outflow morphology obtained from a combination of the SMA and IRAM 30 m data is significantly different from that derived from the SMA data alone. The CO emission detected with the SMA traces only one boundary of the outflow. The outflow is most probably driven by jet bow shocks created by episodic ejections from the center. We detected a dense high velocity clump associated apparently with one of the bow shocks. The outflow strongly affects the chemical composition of the surrounding medium.
The effect of positioning of the In
0.8
Ga
0.2
As quantum dots (QDs) array in the
i
-region of the solar cell (SC) on its photogenerated current and dark saturation currents, which determine the ...device operating voltage, have been investigated. It was found out that the indicated photoelectric characteristics depend on the location of the QD array relative to the electric field of the
p–n
junction. The displacement of the QD array to the boundary of the weakly doped base leads to a decrease in the photogenerated current. But at the same time, the voltage drop effect, which is well-known for nanoheterostructural SC, is minimal.
Photovoltaic converters of high-power (λ = 800–860 nm, ELR = 150–550 W/cm2) laser radiation (PhotoVoltaic Laser Power Converters – PVLPCs) based on AlGaAs/GaAs heterostructures grown by metalorganic ...vapor-phase epitaxy have been developed. To increase the output voltage, the space charge region of p-GaAs/n-AlхGa1-хAs heterojunction was shifted to the n-AlхGa1-хAs wide-gap layer with a gradual “x”. The technology for embedding a rear reflector based on TiOx/SiO2/Ag into the photovoltaic converter structure by “transferring” the heterostructure to a supporting substrate and the method of bonding to form a monolithic structure of the PVLPC has been elaborated. To operate the heterostructures at an increased power density of laser radiation, they have been designed to eliminate possible potential barriers at the heterointerfaces and the frontal contact topology with a high density of the metal grid (50 μm and 125 μm contact pitch are under consideration) has been employed. PVLPCs with efficiency of 62% were obtained at the power density of monochromatic radiation (λ = 850 nm) ELR = 170 W/cm2. The finger pitch of 50 μm allows keeping efficiency more than 56% even with a fivefold increase in laser radiation (up to ELR = 500 W/cm2).
•AlGaAs/GaAs photovoltaic converters of high-power laser radiation were grown by MOVPE.•p-GaAs/n-AlGaAs heterojunction is used for decreasing injection current.•Carrier lifetime is increased with rear reflector for "inverted" heterostructure.•Optimal front contact pitch for both high laser power and for high SR is developed.•PVLPC efficiency doesn't fall below 56% for laser power up to 0.5 kW/cm2 (62% max.eff).
For the first time, differential inclusive-jet cross sections have been measured in neutral current deep inelastic ep scattering using the anti-kT and SIScone algorithms. The measurements were made ...for boson virtualities Q2>125 GeV2 with the ZEUS detector at HERA using an integrated luminosity of 82 pb−1 and the jets were identified in the Breit frame. The performance and suitability of the jet algorithms for their use in hadron-like reactions were investigated by comparing the measurements to those performed with the kT algorithm. Next-to-leading-order QCD calculations give a good description of the measurements. Measurements of the ratios of cross sections using different jet algorithms are also presented; the measured ratios are well described by calculations including up to O(αs3) terms. Values of αs(MZ) were extracted from the data; the results are compatible with and have similar precision to the value extracted from the kT analysis.
An option for the structural design of the metamorphic InGaAs photovoltaic converter is presented. The peculiarity of the proposed device is the ability to operate efficiently with the high-power ...1064 nm laser radiation at the elevated up to +125°C temperatures. The temperature dependencies of the output photovoltaic parameters for two types of InxGa1-xAs laser-power converters are presented in regard to In content: with x = 0.23 and x = 0.18 and with an efficiency of ∼50% and ∼40% (25 °C), respectively. For In0.18Ga0.82As device, an increase in efficiency of up to 50% is recorded upon transition to a temperature range of 50÷60 °C with maintaining efficiency at a level of more than 45% at elevated to 100 °C operating temperatures. In comparison, the "standard" In0.23Ga0.77As device performs a negative efficiency trend within a whole temperature range with absolute values below 45% in practically important operating modes of +75÷100 °C.
The current–voltage characteristics of In
x
Ga
1 –
x
As/GaAs metamorphic photovoltaic converters with built-in
n
-InGaAs/InAlAs Bragg reflectors are studied at an indium content of
x
= 0
.
025–0
.
...24. The series resistance of the heterostructures is measured in the temperature range from 90 to 400 K. It is found that a sharp rise in the resistance of silicon-doped reflectors with an increasing fraction of In is due to weak activation of the donor impurity in InAlAs–
n
:Si layers. As a result, the energy barriers for majority carriers are formed in the latter, with a height of 0
.
32–0
.
36 eV and a substantial width. To suppress this effect, the technology of the Te doping of
n
-InGaAs/InAlAs Bragg reflectors is developed, which reduces the series resistance by five orders of magnitude. This makes it possible to keep the fill factor of the current–voltage characteristic above 80% up to current densities of 2 A/cm
2
. Values exceeding 85%, achieved for the quantum efficiency, indicate that the “memory” and tellurium segregation effects characteristic of this kind of impurity are suppressed.
Abstract
In the work, the effect of In
0.8
Ga
0.2
As quantum dots position in the i-region of a GaAs solar cell on its spectral and photoelectric characteristics has been investigated. Three solar ...cell structures were obtained by metal-organic vapor-phase epitaxy, in which layers of quantum dots were placed in the middle of the i-region and also have been shifted to the base and the emitter. As a result, it has been shown that the solar cell with a quantum dot array shifted to the base demonstrates the smallest open-circuit voltage drop and, accordingly, a higher efficiency value.
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