On the existence and evaluation of Stokes phenomena in fluid mechanics

A singularly perturbed, high order KdV-type model, which describes localized travelling waves (“solitons”) is being considered. We focus on the Inner solution, and detect Stokes phenomena that are crucial as to whether we can obtain a suitable solution. We provide a simple proof that the corresponding Stokes constant is non-zero. Also, we evaluate this splitting constant numerically by using two methods that are induced by the underlying theory.

What properties of non-electrolyte solutions does a DNA molecule feel?

As early as in 1953 it was reported that at low relative humidity of the atmosphere (about 70 %) DNA films were in A-form, while at higher humidity (more than 80%) they were in B-form. Relative humidity of the atmosphere corresponds to the water activity in the system. It was found in the beginning of the 70th that DNA transfers to the A-form when non-electrolytes, such as monoatomic alcohols, dioxane, tetrahydrofurane were added to water. It was reasonable to suppose that B to A transition of DNA occurs in the non-electrolyte solutions at the same values af water activity as in the moist atmosphere. This prediction was borne out. But in water solutions of very polar non-electrolytes such as methanol and ethylene glycol B to A DNA does not occur even at very low water activity values. It was supposed that A form of DNA can arise only in the medium with sufficiently low polarity. We used hyperfine splitting constant (A) of a nitroxide spin label determined from the EPR spectra as a measure of the liquid solvent polarity. It was found that DNA transition into B form occurs when A reached a certain value. Polarity of methanol and ethylene glycol is much higher than that of the solutions in which B to A DNA transition takes place. This transition also occurs in water solutions of trifluoroethanol. But in these solutions the transition takes place at hyperfine splitting values, which are much greater than in other non-electrolyte solutions. Water activity in the zone of B-A DNA transition in trifluoroethanol solutions does not correspond water activity which was calculated for other nob-electrolyte solutions in which B-A transition is observed.

Physical and spectroscopic studies on manganese ions in lead halo borate glasses

Lead halo borate glass systems containing manganese ions have been investigated to study the role of halide ions on the physical, optical and EPR studies. The amorphous phase of the prepared glass samples [Formula: see text]PbX2–(30[Formula: see text])PbO–69.5B2O3–0.5MnO2 with X = F, Cl and Br and [Formula: see text] mol% was confirmed from their X-ray diffraction spectra. Ionic radii of the halides played an important role in the physical properties. From the optical absorption spectra, optical band gap and Urbach energy values were evaluated. The EPR spectra have shown a six-line hyperfine (HF) structure centered at [Formula: see text] and attributed to Mn[Formula: see text] centers in octahedral symmetry. The other signals at [Formula: see text] and 4.3 were attributed to the rhombic surroundings of Mn[Formula: see text] ions. The negative shift in [Formula: see text]-value revealed highly ionic environment around the Mn[Formula: see text] ion in the glass hosts. The HF splitting constant (A), number of spins (N) and susceptibility [Formula: see text] values of the prepared glasses were also reported.

EPR Study of the Nitrogen Containing Defect Center Created in Self-Assembled 6H SiC Nanostructure

Triplet center with spin state S = 1 is detected in the EPR spectrum of the self-assembled 6H SiC nanostructure obtained by non-equilibrium boron diffusion into the n-type 6H SiC epitaxial layer (EL) under conditions of the controlled injection of the silicon vacancies at the temperature of T = 900°C. From the analysis of the angular dependences of the EPR spectrum and the numerical diagonalization of the spin Hamiltonian, the value of the zero-field splitting constant D and g-factor are found to be D = 1140•10-4см-1 and gpar = 1.9700, gper = 1.9964. Based on the hyperfine (hf) structure of the defect originating from the hf interaction with one 14N nuclei, the large value of the zero-field splitting constant D and technological conditions of the boron diffusion into the n-type 6H SiC EL, the triplet center is tentatively assigned to the defect center consisting of nitrogen atom and silicon vacancy.

High-resolution Fourier transform infrared spectra of the CH3 ν3and CH2D ν4 bands

The spectrum of the ν3 band CH3 was observed in the 2800–3100 cm–1 region with a Fourier transform infrared spectrometer. The 76 observed lines were analyzed together with the previous difference frequency data to determine the molecular constants including sextic centrifugal distortion constants and the A1 – A2 splitting constant in the ground state. The ν4 band (out-of-plane vibrational mode) of CH2D was observed in the 550–700 cm–1 region by a discharge in a mixture of CH2DI and Ar. The molecular constants in both the ground and the ν4 states of this radical have been determined for the first time. PACS No.: 33.20Ea

First Synthesis of C-Phenyl N-tert-Butyl [15N]nitrone (PBN-15N) for the EPR Spin Trapping Methodology

As compared to normal PBN, about fifty percent increase of electron paramagnetic resonance (EPR) spin trapping sensitivity has been gained by using a new 100% 15N-enriched spin trap, C-phenyl N-tert-butyl[15N]nitrone (PBN-15N). PBN-15N has been prepared by a convenient four-step route using ammonium-15N chloride as the starting material. This synthetic method produces 2-methyl-2-[15N]nitropropane which is useful for the synthesis of many other PBN-15N type spin traps for the purpose of increasing spin trapping sensitivity. EPR spin trapping with PBN-15N in benzene and in phosphate buffer has been investigated. The 15N hyperfine splitting constant (15N-hfsc) is larger than 14N-hfsc by 40%. The larger 15N-hfsc gives more opportunity to identify different radical addends within the same system.

An EPR and MS Investigation of Hexa-Substituted Pyrrolidine-l-oxyl Aminoxyl Stable Radicals. Unexpectedly Large y-Hydrogen Splittings

The y-hydrogen hyperfine splitting constant (γ-H hfsc) for stable aminoxyl (nitroxide) spin labels such as 2,2,5,5-tetramethylpyrrolidine-1-oxyl and their derivatives is usually very small (<1.0 G) and not distinguished with EPR spectrometry. Surprisingly, large γ-H hfsc’s (≥2 .0 G) have been detected with EPR for the first time from ten 2-alkyl-2-phenyl-3,3,5,5- tetramethylpyrrolidine-1-oxyl stable aminoxyl radicals. It is discovered that γ-H hfsc’s are very sensitive to the size and the substitution pattern of 2-alkyl groups. When the 2-alkyl group is CH3 or CD3, γ-H hfsc’s are not resolved in the EPR spectra. But if the 2-alkyl group is C2H5, one γ-H hfsc is very large, equal to 4.72 G in C6H6. If the substituent is longer than C2H5, such as n-C3H7, n-C4H9, n-C5H11, n-C6H13 and CH2=CHCH2- substituents, the γ-H hfsc is slightly smaller, equal to 4.59 G. For secondary substituents such as sec-C4H9 and cyclo-C6H11 , the γ-H hfsc decreases to 2.00 G. Intermediate γ-H hfsc’s correspond to C6H5CH2 (3.18 G) or a tertiary alkyl group such as t-C4H9 (3.47 G). Variation of γ-H hfsc’s is based on the change of the pyrrolidine ring conformation which is a result of the 2-alkyl group influence. The structures of these aminoxyl radicals are characterized also with mass spectrometry. Possible MS fragmentation mechanisms are discussed.