Reaction mechanism of direct episulfidation of caryophyllene and humulene

Direct episulfidations of caryophyllene or humulene with elemental sulfur were examined by means of gas chromatography. Caryophyllene-6,7-episulfide was formed at an early stage in a reaction of the caryophyllene and elemental sulfur at 120 degrees C. Caryophyllene-3,6-sulfide and polymer compounds were formed after the episulfidation. Formations of the these compounds were related to the disappearance of the caryophyllene-6,7-episulfide. Isomerization from the caryophyllene to isocaryophyllene was also observed during the reaction. In the reaction of humulene with elemental sulfur, humulene-6,7-episulfide was initially produced and then converted to humulene-9,10-episulfide. It was assumed that the polymer compound in the reaction of humulene with sulfur was related to the disappearance of the both humulene episulfides.     

Determination of aluminum in large volume parenteral drug products used in total parenteral nutrition therapy by ICP-MS with a dynamic reaction cell

The proposed method was developed for the determination of aluminum (Al) in large volume parenteral (LVP) drug products used in total parenteral nutrition (TPN) therapy. The determination of Al in LVP drug products was performed by an inductively coupled plasma mass spectrometer equipped with a dynamic reaction cell (DRC-ICP-MS). DRC-ICP-MS conditions for the analysis of Al were studied to obtain the best signal to background (S/N) ratios. The interfering polyatomic ions at mass 27 (Al) were reduced by using NH(3) as a reaction gas. The detection limit of Al in a 1% (v/v) HNO(3) aqueous solution was 2 ng/l. The Al contents in LVP drug products obtained by this method were in the range of 1.16-4.33 microg/l and were less than 25 microg/l, that is, the regulation value of Food and Drug Administration (FDA). In order to trace the origin of Al in LVP drug products, each part of the LVP drug product, which is composed of three chambers, was investigated. However, a clear difference of the Al contents in each chamber was not observed. Furthermore, the Al contents in injection bags were quantified. Although the Al contents in injection bags were relatively high (in the range of 27.5-33.6 microg/g), dissolution of Al from the injection bags was not observed in the stability testing. From all of these results, it was concluded that the Al contents in the LVP drug products investigated originated in the amount of the Al in each raw material.     

New C(28) steroidal glycosides from Tubocapsicum anomalum

Two new C(28) steroidal glycosides, tuboanosides A (1) and B (2), were isolated from the fruit of Tubocapsicum anomalum MAKINO. Their chemical structures were elucidated on the basis of spectroscopic and X-ray diffraction analysis of the p-bromobenzoyl derivative (4) of tuboanosigenin (3), the sapogenol derivative of these two glycosides. Tuboanosides have the structural peculiarity of an unusual side chain carrying an unusual linkage with a C-21 bound to C-25 on the lactone ring.     

In situ observation of thermal relaxation of interstitial-vacancy pair defects in a graphite gap

Direct observation of individual defects during formation and annihilation in the interlayer gap of double-wall carbon nanotubes (DWNT) is demonstrated by high-resolution transmission electron microscopy. The interlayer defects that bridge two adjacent graphen layers in DWNT are stable for a macroscopic time at the temperature below 450 K. These defects are assigned to a cluster of one or two interstitial-vacancy pairs (I-V pairs) and often disappear just after their formation at higher temperatures due to an instantaneous recombination of the interstitial atom with vacancy. Systematic observations performed at the elevated temperatures find a threshold for the defect annihilation at 450-500 K, which, indeed, corresponds to the known temperature for the Wigner energy release.     

Parametrization of nuclear parton distributions

Optimum nuclear parton distributions are obtained by analysing available experimental data on electron and muon deep inelastic scattering (DIS). The distributions are given at Q ²=1 GeV² with a number of parameters, which are determined by a X ² analysis of the data. Valencequark distributions are relatively well determined at medium x, but they are slightly dependent on the assumed parametrization form particularly at small x. Although antiquark distributions are shadowed at small x, their behavior is not obvious at medium x from the F ₂ data. The gluon distributions could not be restricted well by the inclusive DIS data; however, the analysis tends to support the gluon shadowing at small x. We provide analytical expressions and computer subroutines for calculating the nuclear parton distributions, so that other researchers could use them for applications to other high-energy nuclear reactions.     

Bias voltage dependence of tunneling magnetoresistance in granular C60–Co films with current-perpendicular-to-plane geometry

Voltage-dependence of the tunneling magnetoresistance effect in the granular C₆₀–Co films has been investigated for the samples with the current-perpendicular-to-plane geometry. The transport measurements under this geometry demonstrate that the granular C₆₀–Co films show an unusual exponential bias voltage dependence of the magnetoresistance ratio down to zero voltage. Small characteristic energies of less than 10's meV are derived from the temperature dependences of the characteristic voltage in the exponential relationship. Considering the magnitudes of the voltage drop between Co nanoparticles and also the effect of cotunneling on the energy values, the characteristic energies for the voltage-induced degradation of the spin polarization are found to show a satisfactory agreement with that for the thermally-induced one. It can be reasonably expected that the onset of magnetic disorder to the localized d-electron spins at the interface region of the C₆₀-based matrix (C₆₀–Co compound) with Co nanoparticles leading to the unusual voltage and temperature dependence of the magnetoresistance ratio and the spin polarization at low temperatures.     

Characterization of Benzo[a]naphtho[2,3-f]pentalene: Interrelation between Open-shell and Antiaromatic Characters Governed by Mode of the Quinoidal Subunit and Molecular Symmetry

The singlet open-shell character and antiaromaticity are intriguing features in π-conjugated carbocycles. These two exhibit similar chemical and physical properties. However, they rarely coexist in the same molecule. Understanding the interrelation between the open-shell and antiaromatic characteristics in the same molecule is crucial to control the electronic properties. Herein we describe the synthesis and characterization of a new member of diareno[a,f]pentalene, benzo[a]naphtho[2,3-f]pentalene 6 . Unlike its isomer 5 with a closed-shell ground state, 6 exhibits an appreciable open-shell character and a moderate antiaromatic feature. The behaviors of the open-shell index (y₀) against the difference of the proton chemical signal (Δδ(H¹)) between pentalenide dianions/neutral pentalenes for our reported pentalenes 1 , 4 , 5 , and 6 give a thought-provoking conclusion about the interrelation between open-shell and antiaromatic characteristics in this series. The mode of the incorporated quinoidal moiety and the formal molecular symmetry are critical to balance these two characteristics.     

Improved Synthesis of ortho-Phenylene-bridged Cyclic Tetrapyrroles and Oxidative Fusion Reactions Toward Substituted Tetraaza[8]circulenes

Hetero[8]circulenes have emerged as novel functionalized heteronanographenes that show various promising functions such as bright fluorescence, charge transporting, and redox reactivities. One of the effective synthetic strategy is the fold-in type oxidative fusion reaction of ortho-phenylene-bridged cyclic tetrapyrroles, whose construction, however, is not well-sophisticated in terms of reproducibility and possibility for versatile derivatization. In this paper, a “reverse” coupling strategy has been developed, which enabled synthesis of opp-type low symmetric analogues of cyclic tetrapyrroles. Oxidative fusion reaction conditions to afford tetraaza[8]circulenes have also been reinvestigated and improved. Substituent effects of cyclic tetrapyrroles and tetrabenzotetraaza[8]circulenes are studied for solid-state structures and packing structures, redox potentials, and optical properties.