High pressure organic chemistry; XV. Non-catalyzed cleavage reaction of ethers with acyl halides

Abstract

A variety of cyclic and acyclic ethers are efficiently reacted with acyl chlorides or acyl bromides to afford the ether-cleaved compounds of ω-chloro-or ω-bromoesters under high pressure conditions. The reactivity of ethers is found to be roughly depend on the basicity of the ether oxygen atom.     

Free vibration characteristics of double-walled carbon nanotubes embedded in an elastic medium

In this Letter, a theoretical analysis of the resonant vibration of double-walled carbon nanotubes (DWCNTs) and the DWCNTs embedded in an elastic medium is presented based on Euler-Bernoulli beam model and Winkler spring model. The vibration modes of DWCNTs are quite different from those of single-walled carbon nanotubes (SWCNTs). The resonant vibrations of DWCNTs are found to have in-phase and anti-phase modes, in which the deflections of the inner and outer nanotubes occur in the same and opposite directions, respectively. For the vibration of DWCNTs with the same harmonic numbers, the resonant frequencies of anti-phase mode are larger than the ones of in-phase mode. Moreover, influence of the surrounding medium on the resonant vibrations is investigated using the Winkler spring model. The results show that surrounding medium makes a strong impact on the vibration frequencies of in-phase mode, but little on those of anti-phase mode.     

Emission Mössbauer spectroscopic studies of57Fe atoms produced in57Co-labelled trinuclear cobalt-iron halogenoacetate complexes

Mixed-valence states of⁵⁷Fe atoms produced after EC-decay of⁵⁷Co in a series of trinuclear cobalt-iron halogenoacetate complexes, [Co^IIFe ₂ ^III O(CH_3?nX_nCO₂)₆(H₂O)₃] (0≤n≤3, X=Cl, Br, and I), were studied by comparing the results obtained by emission Mössbauer spectroscopy with those observed in absorption Mössbauer spectra of analogous trinuclear iron complexes, [Fe^IIFe ₂ ^III O(CH_3?nX_nCO₂)₆(H₂O)₃]. Some of the emission Mössbauer spectra show a temperature-dependent mixed-valence state as found in the absorption Mössbauer spectra. Others show a somewhat different temperature dependence compared with the absorption Mössbauer spectra. The results were interpreted in terms of after-effects of the EC-decay.     

10-Gbit/s optical receiver using ICs with low-capacitance HBT technology

A 10-Gbit/s optical receiver is developed using low-capacitance HBT IC technology. The HBT allows a cutoff frequency of 45 GHz and a maximum oscillation frequency of 70 GHz. The receiver contains an automatic gain-control amplifier IC with a gain of 16 dB, a bandwidth of 10.7 GHz, and a decision-circuit IC with an ambiguity of 66 mVp-p at a data rate of 10 Gbit/s. The sensitivity of this receiver is -26.5 dBm at a bit error rate of 10^-9. Transmission over a 140-km fiber was achieved successfully.     

Radiator design for detecting high-energy neutrons with a nuclear track detector

Subsequent to the proposal of a two-layer structured radiator for more efficient detection of high-energy neutrons with a plastic nuclear track detector (PNTD), its availability has been investigated both experimentally and theoretically. An inner deuterized hydrocarbon (CD₂) layer adjacent to PNTD should play the role of both a radiator of deuterons recoiled there and a degrader for energetic protons recoiled in the outer layer of a CH₂ material. It was found that the energy dependence of the efficiency was changed sensitively by the thickness of the CD₂ layer. A best combination of CH₂ and CD₂ thickness was estimated under a condition of a constant total thickness. For example, the sensitivity could be flattened within 20% between about 5 and 70 MeV by using -CD₂ and -CH₂.     

Development and test of SEOP neutron spin filter in Japan

We have begun the development of an in-situ spin-exchange optical pumping (SEOP) system aiming to use it as a neutron spin filter for incident beam polarization at the Japan Proton Accelerator Research Complex (J-PARC). To use it, it is recommended that the optics be adjusted easily, have high stability, and have a small size. In this paper we improved our previous SEOP system aiming to use it in J-PARC and performed a neutron beam test at the JRR-3 NOP beamline to see the performance of the neutron spin filter (NSF). The polarization of the ³He gas reached 73%. This paper gives the present status of the development of in-situ SEOP system in J-PARC.     

Measurement of the g-Factor of the 27− High-Spin Isomer State of 152Dy

The g-factor of the 27⁻ isomer state of ¹⁵²Dy has been measured using the Time-Integral Perturbed Angular Distribution (TIPAD) method. The high-spin states of ¹⁵²Dy have been populated by ¹⁴¹Pr(¹⁶O,p4n)¹⁵²Dy reaction at E = 115 MeV from the AVF cyclotron at CYRIC. The paramagnetic correction factor of Dy ions in Pr has been determined to be 4.2(5) by the Time-Differential Perturbed Angular Distribution (TDPAD) measurement of the 21⁻ state of ¹⁵²Dy. As a result, the g-factor of the 27⁻ isomer state of ¹⁵²Dy has been obtained to be +0.09(5). This shows the smaller value than the expected one of +0.39 deduced from a fully aligned configuration of π(h _11/2 ²) ⊗ ν(f _7/2 ² h _9/2 i _13/2).     

Endoscopic Observation of Tissue by Narrowband Illumination

We propose a new illumination method for a medical endoscope: narrow band imaging (NBI), in which the spectral bandwidth of the filtered light is narrowed. To confirm how the spectral specifications of the filtered light influence a reproduced image, an experiment was conducted observing the endoscopic images of the back mucosa of a human tongue. In addition, the effect of NBI on endoscopic images was investigated through preliminary clinical tests in colonoscopy and upper gastrointestinal endoscopy. It has been shown that NBI can enhance the capillary pattern and the crypt pattern on the mucosa. These patterns are useful features for diagnosing an early cancer.     

Monitoring the brain metabolites of children with acute encephalopathy caused by the H1N1 virus responsible for the 2009 influenza pandemic: a quantitative in vivo H MR spectroscopy study

Background and Purpose

Influenza viral infection, which results in central nervous system dysfunction, is a major cause of acute encephalopathy (AE). The purpose of this study was to investigate the changes in the concentrations of brain metabolites in children with AE using single-voxel magnetic resonance spectroscopy (MRS) and to provide diagnostic information about the relationship between the symptoms of AE and metabolite concentrations.

Materials and Methods

The subjects were 10 children (mean age: 6.2 years; range: 1–13) with AE caused by the novel influenza A virus responsible for the 2009 influenza pandemic. The serial MRS data (TE/TR=30/5000 ms, 3 T) acquired from the basal ganglia (BG) and centrum semiovale (CS) of each patient were categorized into three periods: (1) initial neurological symptom presentation and the start of treatment (n= 10), (2) short-term follow-up (n= 9) and (3) long-term follow-up (n= 3). As controls, the magnetic resonance (MR) spectra of eight age-matched children were also investigated.

Results

In both regions, the concentrations of the major metabolites (N-acetylaspartate, creatine, choline, myo-inositol, glutamate/glutamine complex and glutamate) only showed minor fluctuations between the three periods. On the other hand, higher levels of taurine (Tau) were observed in the BG during the second period (P=.005), and increased levels of glucose were observed in the CS during the first (P=.005) and second (P=.036) periods.

Conclusions

Serial monitoring of brain metabolite changes was carried out with a clinical MR system. The concentrations of major metabolites only displayed very minor fluctuations in response to mild H1N1-related AE. However, a higher Tau concentration was found to be associated with neurological symptoms. Further studies are required to improve our understanding of the detailed activity of Tau in AE.     

Kinetic investigation on carbamate formation from the reaction of carbon dioxide with amino acids in homogeneous aqueous solution

The kinetics of carbamate formation from the reaction of carbon dioxide with α‐amino acids in D₂O was first investigated by means of nuclear magnetic resonance spectroscopy. Potassium carbonate was used as the CO₂ source. For each amino acid, the maximum carbamate yield, the apparent rate constant for the carbamate formation k_app, and the rate constants for the formation k₁ and the breakdown k_?1 of the carbamate were estimated. Plots of log k₁ or log k_?1 versus pK_a of amino acids indicated that the formation rate k₁ increased with the basicity (pK_a) of amino acid, while the decomposition rate k_?1 decreased. A Br?nsted β value of 0.39 was obtained from the former plot, being in good agreement with the previously reported ones (0.26–0.43). The observed negative pK_a dependence of log k_?1 (Br?nsted α = 0.34) is reasonable, because the carbamate decomposition is acid‐catalyzed and the steady‐state concentration of H⁺ should be higher for weaker basic amines. The charge (σ) and the lone‐pair energy (E_N) at the nitrogen atom of the amino group were calculated. Although log k₁ correlated with σ and E_N, log k_?1 was unrelated with both of these parameters. Considering that the carbamate formation (k₁) is not only base‐catalyzed but should also be promoted by the nucleophilicity of the amino nitrogen, its correlation with σ and E_N in addition to pK_a is rational. The irrelevance of log k_?1 to σ and E_N is not surprising, because σ and E_N are not a direct measure of [H⁺] of the solution. Copyright © 2011 John Wiley & Sons, Ltd.