Scaling factor in continuous spin detonation of syngas–air mixtures

Multiwave regimes of continuous spin detonation in syngas–air mixtures in a flow-type annular cylindrical combustor 503 mm in diameter are obtained. Experiments are performed for mixtures of carbon oxide and hydrogen with the ratio of the components equal to 1/3, 1/2, or 1/1. The varied parameters are the flow rates of air and syngas, the ratio of these flow rates, and the combustor length. Scalability of the continuous spin detonation process is demonstrated: at identical values of the specific flow rate of air and the combustor expansion ratio, the number of transverse detonation waves increases with increasing combustor diameter. In the examined ranges of combustor lengths and specific flow rates of air, the frequency of these waves is independent of the combustor length, except for narrow regions where the number of waves (and, correspondingly, the flow regime) changes. The structures of transverse detonation waves in regular regimes are almost identical for all examined syngas compositions. It is shown that detonation can be initiated by a jet of combustion products. The minimum diameters of the detonation chamber for different flow rates of the mixture are estimated.     

Continuous spin detonation of a heterogeneous kerosene–air mixture with addition of hydrogen

Regimes of continuous spin detonation of two-phase kerosene–air mixtures with small addition of hydrogen are obtained for the first time in a flow-type annular cylindrical combustor 503 mm in diameter.     

Towards β-phase formation probability in spin coated PVDF thin films

This work aimed towards the study on variations in the percentage of β-phase in Poly vinylidene fluoride (PVDF) thin films deposited by spin coating technique. PVDF is a semi-crystalline polymer which exhibits α, β, γ and δ polymorphs. Among these polymorphs, generally it crystallizes in a non-polar α-phase, which is of little importance as far as its applications are concerned. However, the β-phase, which exhibits spontaneous polarity created tremendous interest and showed a path towards the devices based on its pyro- and piezoelectric properties. Fourier Transform Infrared (FTIR) spectroscopy and XRD techniques were used to study the percentage of formation of β-phase in spin coated PVDF thin films at different processing conditions viz. spin rotation speed (rpm), solution concentration and annealing temperature. We identified the β-phase percentage in PVDF thin films, which are (i) Deposited with different rotation speeds ranging from 1000 to 9000 rpm, (ii) Annealed at different temperatures viz.; room temperature to 100C, and (iii) Deposited at various solution concentrations. It is identified that percentage of formation of β-phase is high in the films deposited with 15(w/v)% solution concentration which is annealed at 100C. The films deposited at higher rpm is showing low enhancement in the β-phase with annealing temperature.     

Modulation of magnetoelectric coupling through systematically engineered spin canting in nickel–zinc ferrite

A nickel–zinc ferrite system, which is one of the well-known versatile soft-ferromagnetic oxides, was investigated in terms of magnetoelectric (ME) coupling at room temperature. Herein, we demonstrated that spin canting is manipulated through a composition-induced structural transition from an inverse to a normal spinel structure, leading to modulation in the ME coupling. The ME coefficient was maximized at 60 at.% Zn substitution with a value of 0.1 mV/(Oe·cm), denoting ∼70% enhancement compared to that of the pure nickel ferrite. It was revealed that the interspin angle is enhanced along the octahedral site at up to ∼60 at.% Zn substitution, consistent with the composition level at the culmination of the ME coupling, evidenced by X-ray diffraction profiles and magnetic hysteresis loops combined with density functional theory calculations. Given that this approach is based on a tractable fabrication method, this study is expected to be widely used in modulation of the ME coupling in spinel-structured oxides.     

Corrosion protection by zirconia-based thin films deposited by a sol–gel spin coating method

This paper focuses on the structure and corrosion behavior of 316L stainless steel coated by inorganic ZrO₂, hybrid ZrO₂–PMMA, and combined inorganic–hybrid films. The coatings were deposited by a particulate sol–gel spin-coating route, using carboxymethyl cellulose as a nanoparticle dispersant. The electrochemical evaluations were conducted in a simulated body fluid, via potentiodynamic polarization and impedance spectroscopic experiments. According to the results, the hybrid coating presented a better corrosion protection compared to the inorganic coating, due to a lesser density of structural defects. However, the best corrosion resistance was found for a combined coating which consists of an inorganic bottom layer and a hybrid top layer, due to a desirable compromise of good adhesion and low defect density.     

1H n.m.r. spin—lattice relaxation study in bituminous coal

¹H n.m.r. studies of spin-lattice relaxation of a bituminous coal were performed at temperatures between 128 and 308 K. The relaxation function was observed to be two-component over the whole temperature range. The component with the shorter relaxation time was assumed to be the molecular phase in coal and the component with the longer relaxation time to be the macromolecular phase. Mechanisms of spin-lattice relaxation through spin diffusion to paramagnetic centres and through modulation of dipolar interactions by molecular motions are suggested.     

Fabrication of inverted zinc oxide photonic crystal using sol–gel solution by spin coating method

Inverted zinc oxide photonic crystal structures were fabricated from polystyrene sphere (PSS) template using the sol–gel solution of ZnO by spin-coating method. It is easily able to control and fabricate the photonic crystal structures using the self-organized PSS with a size of 193 nm. The inverted ZnO photonic crystal structures observed show the (111) tendency of the hexagonal compact arrangement formation. The resulting structures possess the photonic band gaps in the near-ultraviolet range and exhibit an enhanced photoluminescence spectrum. The technology can effectively increase the light output intensity or efficiency for the applications of optoelectronic devices.     

Optical spin polarization in the di-〈001〉-split interstitial (R1) centre in diamond

Irradiating diamond with electrons or neutrons produces the electron paramagnetic resonance (EPR) R1 centre which has been shown to be a di-〈001〉-split interstitial. We report that on cooling below a certain threshold temperature and illuminating with unpolarized light of energy greater than 1.7(1) eV, spin polarization within the S=1 multiplet of the ground state of the R1 centre is observed. The threshold temperature to observe this effect depends on the concentration of the defect in the diamond. For a type IIa stone irradiated to a dose of 7×10¹⁷ 2 MeV e⁻cm⁻² with an R1 concentration of 0.056(15) ppm the temperature is 67(2) K. The results of this study are consistent with a spin-selective, orientation-dependent optical transition, which changes the populations of the spin manifold and results in emissive EPR transitions. The spin polarization arises by selective excitation/repopulation of the ³B_u ground state of R1 mediated by spin–orbit coupling with a higher ¹B_u state. Optical activity in the EPR system has yielded information about the electronic energy levels, and provides a bridge between optical and magnetic resonance spectroscopy. This system might have use as a light-pumped microwave or millimetre-wave maser material.     

Effect of N3 modifications on the affinity of spin label ç for abasic sites in duplex DNA

Noncovalent site‐directed spin labeling (NC‐SDSL) of abasic sites in duplex DNAs with the spin label ç , a cytosine analogue, is a promising approach for spin‐labeling nucleic acids for EPR spectroscopy. In an attempt to increase the affinity of ç for abasic sites, several N3 derivatives were prepared, and their binding affinities were determined by EPR spectroscopy. Most of the N3 substituents had a detrimental effect on binding. The triazole‐linked polyethylene‐glycol derivative ( 12 a ) showed a 15‐fold decrease in affinity, whereas the binding affinities of ethyl azido ( 8 b ) and hydroxyl ( 8 c ) derivatives were five‐ to sixfold lower. The spin‐labeled nucleoside Ç showed only a twofold decrease, thus binding better than 8 c , even though it contains the larger 2′‐deoxyribose substituent at N3 instead of a 2‐hydroxyethyl group. N3 derivatives that contained the basic ethyl amino ( 9 ) or ethyl guanidino ( 10 ) substituents had both higher binding affinity and solubility, attributed to their cationic charge at neutral pH. Compounds 9 and 10 are promising candidates for NC‐SDSL of nucleic acids, for distance measurements by pulsed EPR spectroscopy.     

Interplay of spin–orbit coupling and Zeeman effect probed by Kondo resonance in a carbon nanotube quantum dot

The spin orbit interaction in a carbon nanotube is probed by Kondo resonance. Spin orbit interaction lifts level degeneracy and leads to additional satellite current peaks along with the zero-bias Kondo resonance peak. From the positions of satellite peaks, the spin–orbit interaction energy Δ_so is determined to be 0.38 meV. In the presence of a parallel magnetic field, the satellite peaks split into two; one follows spin-Zeeman dependence with a g-factor of 1.91 and the other one follows orbital-Zeeman dependence with a 2μ_orb value of 170 μeV/T. The zero-bias Kondo resonance peak also displays a spin-Zeeman dependence but has an offset in magnetic field of 2.25 T, consistent with the value of Δ_so/2μ_orb obtained independently.     

Selectivity control in electron spin inversion processes: regio- and stereochemistry of Paternò-Büchi photocycloadditions as a powerful tool for mapping intersystem crossing processes

Regio- and stereoselectivity in ene-carbonyl photocycloadditions depend on the spin multiplicity of the excited carbonyl state, although both singlet and triplet states produce the cycloadducts with comparable chemoselectivity. The correlation between selectivity and spin state was evaluated by concentration, temperature, and solvent viscosity studies. The higher selectivity observed for triplet reactions is rationalized by the optimal conformations of the intermediate 2-oxabutane-1,4-diyls for intersystem crossing (ISC) to the singlet manifold, controlled preferentially by spin-orbit coupling. This weak interaction connected with ISC can lead to substantial control of regio- and stereoselectivity. The role of hyperfine coupling is demonstrated by magnetic isotope effects.     

The Chemistry of Detonations. IX. Some observations regarding a computer based parametric study of detonation characteristics of C?H?N?O explosives

Swaminathan and Rajagopalan (S and R) have recently published a parameter study describing the dependence of important detonation characteristics of C H N O explosives on their densities and enthalpies of formation which is seriously inconsistent with earlier highly reliable calculations by Mader using the same equation of state and presumably the same input information. S and R's computer-based conclusions are also not in accord with parametric relationships established over a decade ago by Johansson and Persson and Kamlet and Jacobs. S and R's calculated detonation pressures are significantly lower at high loading densities and higher at lower loading densities than Mader's corresponding calculations. Also out of line on the high side (compared with Mader's calculations or experimentally observed values) are S and R's calculated detonation velocities. The differences between S and R's parametric relationships and those of the other workers can have important and misleading implications to the planning of future explosives chemistry research. It is suggested to those interested in such parametric studies that the simplified method for detonation property calculation be used, since the input information is explicit and easily checked and the results are at least as reliable as those from complex computer programs.