Mass generation in the aether: Neutrino oscillations and massive gauge fields

Neutrino mixing is studied in an absolute spacetime conception based on a dispersive aether. The effect of the frequency-dependent permeability of the aether on the interference phase of neutrino mass eigenstates is analyzed. Neutrinos are treated as massless Dirac spinors, and mass eigenstates are due to the neutrino permeability of spacetime. The aether can also generate effective gauge masses, resulting in massive dispersion relations preserving the gauge symmetry. The propagators of gauge and spinor fields are derived, illustrating mass generation by isotropic permeability tensors in the aether frame, the rest frame of the cosmic background radiation.     

H NMR relaxation in urea

Proton NMR spin–lattice relaxation times T₁ were measured for urea as a function of temperature. An activation energy of 46.3 ± 4.7 kJ/mol was extracted and compared with the range of 38–65 kJ/mol previously reported in the literature as measured by different magnetic resonance techniques. In addition, proton NMR spin–lattice relaxation times in the rotating frame T_1ρ were measured as a function of temperature. These measurements provide acquisition conditions for the ¹³C and ¹⁵N CP/MAS spectra of pure urea in the crystalline phase.     

Variable temperature CP/MAS13C NMR study of cyclodextrin complexes of benzaldehyde

Fully hydrated as well as dried benzaldehyde complexes of - and -cyclodextrins were studied by using CP/MAS¹³C NMR techniques. Variable temperature studies have shown that below 200 K the guest is rigidly held in the complex, whereas at 328 K, only the aromatic ring performs rapid two-fold flips about the C₁–C₄ axis. In the -Cd complex the benzaldehyde performs more general reorientation. Removal of water causes marked changes in both guest and host spectra, generally consistent with a loss of short-range order and increase in guest motional rate.NRCC No. 27826.     

A 1H, 13C and 15N NMR study in solution and in the solid state of six N-substituted pyrazoles and indazoles

Three N-substituted pyrazoles and three N-substituted indazoles [1-(4-nitrophenyl)-3,5-dimethylpyrazole (1), 1-(2,4-dinitrophenyl)-3,5-dimethylpyrazole (2), 1-tosyl-pyrazole (3), 1-p-chlorobenzoylindazole (4), 1-tosylinda-zole (5) and 2-(2-hydroxy-2-phenylethyl)-indazole (6)] have been studied by NMR spectroscopy in solution (1H, 13C, 15N) and in the solid state (13C, 15N). The chemical shifts have been compared with GIAO/DFT calculated absolute shieldings. Some discrepancies have been analyzed.     

Examination of the structure in solid state of amino analogs of 4,4′-[1,5-pentanediylbis(oxy)]bisbenzonitrile by means of X-ray diffraction, C CP/MAS NMR, and theoretical calculations

A single crystal of X-ray diffraction structures is presented for 4,4′-[1,5-(3-oxapentanediylbis(amino))]bisbenzonitrile 2 and 4,4′-[1,5-(N-methyl-3-azapentane-diylbis(oxy))]bisbenzonitrile 3. The molecular structures of these derivatives differ especially in conformations of the central linker: in 2 this linker adopts a trans/gauche conformation, whereas in 3 – a fully extended conformation. The N atoms in various positions of the aliphatic linker change dramatically the molecular packing mode of both bisnitriles. But in both cases the nitrile groups take part in intermolecular hydrogen bonds: a type of NH···N in 2 and of CH···N in 3. Various conformations of both molecules were reflected in ¹³C CP/MAS NMR spectra in solid state as single and double resonance patterns for 2 and 3, respectively. A preliminary anticancer assay against 60 cell lines of 3 reveals strong growth inhibition of leukemia, melanoma, and renal cancer cells.     

Spectral assignments for 1H, 13C and 15N solution and solid-state NMR spectra of s-tetrazine and dihydro-s-tetrazine derivatives

Tetrazine-based organic species are interesting intermediates for organic synthesis and represent a source of new materials bearing specific properties with potential applications in biology and material science. 1H, 13C, 15N NMR measurements carried out in solution and in the solid-state have been used to characterize a series of 3,6-disubstituted 1,2,4,5-tetrazine/dihydrotetrazine new derivatives. Experimental results presented here provide data for the assignment of 15N chemical shifts including new organic small molecules; two polymers having the tetrazine ring in the main chain and several previously published compounds. We report apparently for the first time 15N experimental chemical shift data for tetrazine systems in the solid state.     

High‐resolution 15N solid‐state NMR investigations on borazine‐based precursors

Reference compounds based on borazine units and polyborylborazines have been characterized by ¹⁵N solid‐state NMR. The various nitrogen sites (B₃N, B₂NH, B₂NX (X = H, Me, ⁱPr), BN(H)X and BNX₂ (X = Me, ⁱPr) have been discriminated according to their cross‐polarization behaviour and chemical shift values, which range from ?265 to ?350 ppm. This has permitted the elucidation of the polymerization mechanism associated with the polycondensation of two borazine‐based derivatives. In particular, this technique appears to be a powerful investigation tool for finding whether the B₃N₃ rings are linked through three‐atom N? B? N aminoboryl bridges or connected by direct B? N bonds. Copyright © 2004 John Wiley & Sons, Ltd.     

QCD因子化方法下_s→π~ π~-中湮没强度的探索

利用QCD因子化方法,并采用具有质量的有效胶子传播子来消除端点发散,计算了纯湮没衰变 Bs→π π-过程的CP平均分支比并对该过程的CP破坏进行了具体研究．结果表明:该过程的CP平均分支比为1．24×10-7,同时企鹅图对该过程起着主要贡献;Bs→π π-过程中直接CP破坏参数Cππ估算为-0．05,混合CP破坏参数Sππ比较大,可达到0．18．该过程在未来的LHC-b物理实验上是完全有可能被测量到的,通过对该过程的研究能够使我们更好地了解B介子无璨衰变的动力学机制和胶子的性质．     

Solid‐state cross‐polarization magic angle spinning 13C and 15N NMR characterization of Sepia melanin,Sepia melanin free acid and Human hair melanin in comparison with several model compounds

This paper presents the high‐resolution ¹³C and ¹⁵N cross‐polarization magic angle spinning (CP/MAS) NMR spectra of three natural melanin solids: Sepia officinalis melanin, Sepia officinalis melanin free acid (MFA) and Human hair melanin. The functional group characterization of Human hair melanin by NMR is the first to date and the ¹³C CP/MAS NMR spectra reported here show improved resolution of chemically inequivalent sites. The observed spectral regions of the solid melanin samples can be assigned to the postulated structural unit of the polymer chain of Sepia MFA derived from solution‐state NMR studies. To assist in the assignment of functional groups in the spectra, the solid‐state CP/MAS NMR spectra are compared with high‐resolution ¹³C and ¹⁵N CP/MAS spectra of four model compounds, L ‐dopa, dopamine, 2‐methoxycarbonyl‐3‐ethoxycarbonyl‐4‐methylpyrrole and ethyl 5,6‐dimethoxyindole‐2‐carboxylate. To aid further in the assignment of protonated and non‐protonated carbon atoms, CP contact time dependence and non‐quaternary carbon suppression (NQS) experiments were performed on the melanin samples. The ¹⁵N CP/MAS spectra of the melanin samples confirm the presence of indole and pyrrole units in the melanin polymer chain. The NMR peaks observed in all of the melanin samples are relatively broad, presumably owing to the presence of free radicals. Electron spin resonance (ESR) data shows that all three melanin samples contain localized free radicals (g = 2.007), with the Sepia melanin containing a 10‐fold higher free radical density than Human hair melanin. Copyright © 2003 John Wiley & Sons, Ltd.