NMR and magnetic studies on 7 K anomaly in Tl3H(SO4)2

Measurements of the spin-lattice relaxation time, NMR absorption line and magnetization have been carried out on the Tl₃H(SO₄)₂ crystal below 50 K. The anomaly at around 7 K was: (1) the spin-lattice relaxation times of ¹H and ²⁰⁵Tl nuclei increase steeply with decreasing temperature below 7 K, (2) the NMR absorption lines below 7 K shift to the high-magnetic field side in comparison with that above 7 K, and (3) the ¹H NMR line width exhibits a drastic increase of the line width with decreasing temperature below 7 K. These results indicate that the magnetic dipole fluctuation of the proton changes at 7 K. On the other hand, there are no remarkable anomalies of magnetic susceptibility at around 7 K. From these results it is deduced that the anomaly at around 7 K is caused by the change in quantum mechanical process of the proton from proton tunneling to zero-point vibration of hydrogen in the hydrogen bond with the decrease of temperature.     

Synthesis of Zinc Chlorophyll Homo/Hetero‐Dyads and their Folded Conformers with Porphyrin,Chlorin, and Bacteriochlorin π‐Systems

Zinc complex of pyropheophorbide‐b, a derivative of chlorophyll‐b, was covalently dimerized through ethylene glycol diester. The synthetic homo‐dyad was axially ligated with two methanol molecules from the β‐face and both the diastereomerically coordinating methanol species were hydrogen bonded with the keto‐carbonyl groups of the neighboring chlorin in a complex. The resulting folded conformer in a solution was confirmed by visible, ¹H NMR and IR spectra. All the synthetic zinc chlorin homo‐ and hetero‐dyads consisting of pyropheophorbides‐a, b and/or d took the above methanol‐locked and π–π stacked supramolecules in 1% (v/v) methanol and benzene to give redmost (Qy) electronic absorption band(s) at longer wavelengths than those of the corresponding monomeric chlorin composites. The other zinc chlorin and bacteriochlorin homo‐dyads completely formed similar folded conformers in the same solution, while zinc inverse chlorin and porphyrin homo‐dyads partially took such supramolecules. The J‐type aggregation to folded conformers and the redshift values of composite Qy bands were dependent on the electronic and steric factors of porphyrinoid moieties in dyads.     

Differential scanning calorimetry analysis of crystal structure transformation in spray-dried particles consisting of ammonium nitrate,potassium nitrate,and a polymer

Ammonium nitrate (AN) is an affordable oxidant; however, it undergoes crystal structure transformations accompanied by a change in volume at comparatively low temperatures (approx. 30, 80, and 125 °C) and exhibits high hygroscopicity. Both these properties are particularly problematic for the industrial application of AN. In a previous study, we prepared spray-dried particles comprising three components: AN, potassium nitrate (PN) as a phase stabilizer, and a polymer (e.g., polyvinyl alcohol, carboxymethylcellulose salt, and styrene-butadiene latex), which was confirmed to provide effective moisture proofing. In the present study, the crystal transformation behavior of AN/PN/Polymer particles is investigated by observing their thermal behavior by differential scanning calorimetry. The results reveal that phase-stabilized AN can be successfully prepared by the addition of PN. In addition, an intriguing possibility was identified in that carboxymethylcellulose ammonium salt and polyvinyl alcohol, which were both added as polymer components for moisture proofing, also acted as phase stabilizers for AN crystal transformation.     

Remarks on the Cauchy problem for first order hyperbolic systems with constant coefficient principal part

Abstract In this article we shall introduce the results obtained in [16], i.e., we shall give a necessary and sufficient condition that the Cauchy problem for first order hyperbolic systems with constant coefficient principal part is C^∞ well-posed under the maximal rank condition (see the condition (R) below). We shall also give a simple sufficient condition without any assumptions on the rank. Keywords: Hyperbolic system, Cauchy problem, Constant coefficient principal part     

Synthesis of Oxygen‐Containing Spirobipyrrolidinium Salts for High Conductivity Room Temperature Ionic Liquids

Synthesis of ionic liquids (IL) based on oxygen‐containing spirobipyrrolidinium salts with BF₄, BF₃C₂F₅, and NTf₂ as counterions was undertaken. Their physical and electrochemical properties were evaluated for suitability for Room Temperature Ionic Liquids (RTIL) application. Reduction in melting point occurred upon exchange of C(2) by an O‐atom of spirobipyrrolidinium, without sacrificing the electrochemical stability; while introduction of alkyl groups between the N‐ and O‐atoms led to incorporation of asymmetry, and hence reduced the melting points, and viscosity.     

Magnetoresistance in the magnetization reversal process of micropatterned Co wires

We measured the magnetoresistance (MR) and magnetization of Co wires of various widths in the range from 0.3 to 200 μm. The observed width dependence of some characteristics of MR is attributed to the change of the domain structure. As the width decreased below 1 μm, an abrupt jump appeared in the longitudinal MR. This can be interpreted as due to an abrupt reversal of the overall magnetization. The measured longitudinal MR was compared with the calculation in the Stoner–Wohlfarth model.     

Efficient charge generation and collection in organic solar cells based on low band gap dyad molecules

Low band gap dyad molecules were prepared that have absorption spectra matched well with the solar spectrum, and the construction of efficient charge transport pathways was observed. Under AM 1.5 illumination, the devices have achieved the highest J(SC) (4.79 mA cm(2)) and FF (0.46) in dyad-based organic solar cells to date.     

Alignment-retainable nitrogenation of cylindrical carbon nanotubes by thermal reaction with ammonia following UV oxidation: chemical alteration effects on electrical conductivity

Cylindrical carbon nanotubes (CNTs) pretreated by UV irradiation were able to react with NH(3) to give nitrogen-containing CNTs without destroying their vertically aligned morphology. This process provided incorporation of nitrogen mostly at pyridinic and pyrrolic sites and promoted disordering, which was correlated with decreased electrical conductivity of CNT yarns.     

A combined quantum mechanical and molecular mechanical method using modified generalized hybrid orbitals: implementation for electronic excited states

The generalized hybrid orbital (GHO) method is implemented at the second-order approximate coupled cluster singles and doubles (CC2) level for quantum mechanical (QM)/molecular mechanical (MM) electronic excited state calculations. The linear response function of CC2 in the GHO scheme is derived and implemented. The new implementation is applied to the first singlet excited states of three aromatic amino acids, phenylalanine, tyrosine, and tryptophan, and also bacteriorhodopsin for assessment. The results obtained for aromatic amino acids agreed well with the full QM CC2 calculations, while the calculated excitation energies of bacteriorhodopsin and its chromophore, all-trans retinal, reproduced the environmental shift of the experimental data. For the bacteriorhodopsin case, the environmental shift of GHO also showed good agreements with the experimental data. The contribution of the quantum effect of certain moieties in the excited states is elucidated by changing the partitioning of QM and MM regions.