In this article we show that diffraction segregates the polarization singularities according to their handedness. Polarization singularities are superpositions of left and right handed circular ...polarization vortex states. In the superposition, the component states possess different orbital angular momenta depending on the type of the singularity. A fork grating that can generate different orbital angular momentum (OAM) states in different diffraction orders is shown to segregate right and left handed polarization singularities. A V-point polarization singularity that corresponds to one combination of OAM states incident on the fork grating is found to diffract in such a way that the same OAM combination does not occur in all the nonzero diffraction orders. As a result, each of the diffraction orders will have different polarization singularities. This OAM transfer by the fork grating segregates the right and left handed polarization singularities thereby, making the diffraction helicity dependent.
Potential use of turmeric in COVID‐19 Gupta, H.; Gupta, M.; Bhargava, S.
Clinical and experimental dermatology,
October 2020, 2020-Oct, 2020-10-00, 20201001, Letnik:
45, Številka:
7
Journal Article
In this paper we present experimental studies on diffraction of V-point singularities through equilateral and isosceles right triangular apertures. When V-point index, also called Poincare-Hopf index ...(η), of the optical field is +1, the diffraction disintegrates it into two monstars/lemons. When V-point index η is -1, diffraction produces two stars. The diffraction pattern, unlike phase singularity, is insensitive to polarity of the polarization singularity and the intensity pattern remains invariant. Higher order V-point singularities are generated using Sagnac interferometer and it is observed that the diffraction disintegrates them into lower order C-points.
This review presents an insight into additive manufacturing (AM) technologies as they are applied to heterogeneous catalysis; the combination of these fields presents opportunities but also comes ...with challenges. AM enables greater design complexity, rapid prototyping, control over reactant stoichiometry and unique catalyst immobilisation options. The challenges to applying AM in heterogeneous catalysis are associated with limited material choices, quasi-stable printed materials and chemical interfacing of the catalyst system with cthese printed materials. AM printing technologies are introduced to the heterogeneous catalysis research community with a focus on the many benefits they offer in this growing field.
A review on additive manufacturing (AM) applied to heterogeneous catalysis reveals enabling power of AM and challenges to overcome in chemical interfacing and material printability.
Oil shales and coal have considerable amount of pyrite which undergoes various thermal transformations during their processing or combustion. Reactions and changes in pyrite chemistry vary ...considerably under different environmental conditions. In this paper, we report an
in situ high-temperature X-ray diffraction study of phase transformations in pyrite under variable environmental conditions (atmospheric pressure (1
atm.), low air pressure (<0.001
atm.), inert and carbon dioxide atmosphere). We observe that while heating of pyrite in air promotes the formation of hematite (α-Fe
2O
3), magnetite (Fe
3O
4) is a major product in low pressure environment. On the other hand, in the inert environments (nitrogen and argon) pyrrhotite, a non-stoichiometric iron sulphide, is the most dominant product. However, in carbon dioxide (CO
2) environment, pyrrhotite is an intermediate low temperature product which further transforms into magnetite and hematite, attributed to the dissociation of the CO
2 into O
2 and CO providing conducive conditions for the oxidation. We also propose the possible reaction pathways including self-dissociation of CO
2.
Electroreduction of CO2 (eCO2RR) is a potentially sustainable approach for carbon‐based chemical production. Despite significant progress, performing eCO2RR economically at scale is challenging. Here ...we report meeting key technoeconomic benchmarks simultaneously through electrolyte engineering and process optimization. A systematic flow electrolysis study ‐ performing eCO2RR to CO on Ag nanoparticles as a function of electrolyte composition (cations, anions), electrolyte concentration, electrolyte flow rate, cathode catalyst loading, and CO2 flow rate ‐ resulted in partial current densities of 417 and 866 mA/cm2 with faradaic efficiencies of 100 and 98 % at cell potentials of −2.5 and −3.0 V with full cell energy efficiencies of 53 and 43 %, and a conversion per pass of 17 and 36 %, respectively, when using a CsOH‐based electrolyte. The cumulative insights of this study led to the formulation of system design rules for high rate, highly selective, and highly energy efficient eCO2RR to CO.
Top performer: Revealing mechanistic insights into the role of electrolyte composition allows for optimization of key performance metrics simultaneously. Resulting generalized insights lead to system design rules for intensified electroreduction of CO2 to CO on Ag nanoparticles under ambient conditions.
The present paper discusses the powder processing techniques of mechanically alloyed Cu–Cr powder. Mechanical alloying is required to obtain a nano-scale homogeneous mixture of Cu and Cr. Two ...processes to prepare Cu–Cr contacts are proposed from the present study for obtaining compacts having better properties. While the explosive compaction of the mechanically alloyed powder forcibly fills the pores to show excellent density and electrical conductivity, application of Cu coating to the mechanical alloyed powder gives a short-circuit diffusion path during sintering and thus, shows the best combination of properties compared to the presently used Cu–Cr compacts. Both the processes show near theoretical density, exceptionally high electrical conductivity and comparable hardness. Moreover, both the processes change the sintering process of Cu–Cr compacts from liquid phase sintering to solid-state sintering, thus making the process more energy efficient.
The paper discusses two novel processes to prepare Cu–Cr contacts, suitable for contact materials. While the explosive compaction of the mechanically alloyed powder forcibly fills the pores, application of Cu coating to it gives a short-circuit diffusion path during sintering to show excellent properties. Both processes show exceptionally high density and electrical conductivity, apart from reducing sintering temperature by 300 K, thus making the process more energy efficient.
Display omitted
The field of photovoltaics is revolutionized in recent years by the development of two–dimensional (2D) type‐II heterostructures. These heterostructures are made up of two different materials with ...different electronic properties, which allows for the capture of a broader spectrum of solar energy than traditional photovoltaic devices. In this study, the potential of vanadium (V)‐doped WS2 is investigated, hereafter labeled V‐WS2, in combination with air‐stable Bi2O2Se for use in high‐performance photovoltaic devices. Various techniques are used to confirm the charge transfer of these heterostructures, including photoluminescence (PL) and Raman spectroscopy, along with Kelvin probe force microscopy (KPFM). The results show that the PL is quenched by 40%, 95%, and 97% for WS2/Bi2O2Se, 0.4 at.% V‐WS2/Bi2O2Se, and 2 at.% V‐WS2/Bi2O2Se, respectively, indicating a superior charge transfer in V‐WS2/Bi2O2Se compared to pristine WS2/Bi2O2Se. The exciton binding energies for WS2/Bi2O2Se, 0.4 at.% V‐WS2/Bi2O2Se and 2 at.% V‐WS2/Bi2O2Se heterostructures are estimated to be ≈130, 100, and 80 meV, respectively, which is much lower than that for monolayer WS2. These findings confirm that by incorporating V‐doped WS2, charge transfer in WS2/Bi2O2Se heterostructures can be tuned, providing a novel light‐harvesting technique for the development of the next generation of photovoltaic devices based on V‐doped transition metal dichalcogenides (TMDCs)/Bi2O2Se.
ABSTRACT
We implement the first blind analysis of cluster abundance data to derive cosmological constraints from the abundance and weak lensing signal of redMaPPer clusters in the Sloan Digital Sky ...Survey (SDSS). We simultaneously fit for cosmological parameters and the richness–mass relation of the clusters. For a flat Λ cold dark matter cosmological model with massive neutrinos, we find $S_8 \equiv \sigma _{8}(\Omega _\mathrm{ m}/0.3)^{0.5}=0.79^{+0.05}_{-0.04}$. This value is both consistent and competitive with that derived from cluster catalogues selected in different wavelengths. Our result is also consistent with the combined probes analyses by the Dark Energy Survey (DES), the Kilo-Degree Survey (KiDS), and with the cosmic microwave background (CMB) anisotropies as measured by Planck. We demonstrate that the cosmological posteriors are robust against variation of the richness–mass relation model and to systematics associated with the calibration of the selection function. In combination with baryon acoustic oscillation data and big bang nucleosynthesis data (Cooke et al.), we constrain the Hubble rate to be h = 0.66 ± 0.02, independent of the CMB. Future work aimed at improving our understanding of the scatter of the richness–mass relation has the potential to significantly improve the precision of our cosmological posteriors. The methods described in this work were developed for use in the forthcoming analysis of cluster abundances in the DES. Our SDSS analysis constitutes the first part of a staged-unblinding analysis of the full DES data set.
PDF
