Application of terahertz quantum-cascade lasers to semiconductor cyclotron resonance

Quantum-cascade lasers operating at 4.7, 3.5, and 2.3 THz have been used to achieve cyclotron resonance in InAs and InSb quantum wells from liquid-helium temperatures to room temperature. This represents one of the first spectroscopic applications of terahertz quantum-cascade lasers. Results show that these compact lasers are convenient and reliable sources with adequate power and stability for this type of far-infrared magneto-optical study of solids. Their compactness promises interesting future applications in solid-state spectroscopy.     

Mo:Y multilayer mirror technology utilized to image the near-field output of a Ni-like Sn laser at 11.9 nm

Although bright x-ray sources exist at shorter wavelengths, the development of sophisticated diagnostics with x-ray laser sources has been restricted to wavelengths longer than 12.5 nm because of the limitations of the widely used Mo:Si multilayer mirrors. With the novel Mo:Y multilayer mirrors that we present, many x-ray laser applications can be extended to the 7-12-nm range. We demonstrate this new capability by imaging the near-field output of the Ni-like Sn laser at 11.9 nm.     

Use of functional microgels with vinyl groups to accelerate photopolymerization reaction

Three types of functional microgels with vinyl groups on their surface were prepared. For the first type, the counter anion from clorin was exchanged with β-methacryloylethyl sulfonic acid, styrene sulfonic acid or allyl sulfonic acid in a microgel with ammonium anions. For the second and third types, a quaternization with N,N-dimethylaminoethyl methacrylate of 3-chloro-2-hydroxypropyl methacrylate in the presence of microgel particles was prepared by emulsion copolymerization of styrene, chloromethylstyrene or N,N-dimethylamino-methylbenzene, and divinylbenzene. The resulting samples show good dispersibility in organic solvents without an emulsifier. A functional microgel-based photopolymer combined with an acrylate monomer and ultraviolet (UV) or visible (VIS) light-absorbing photoinitiators provides oleophilic images when exposed to UV or VIS light and developed in tap water. This photopolymer has a higher sensitivity than those of photopolymers based on microgels with an analogous composition but without vinyl groups. Photopolymers pepared by using functional microgels with a methacryloyl group exhibited a higher rate of polymerization (R_p) than that of photopolymers based on microgels without a vinyl group. The R_p of photopolymers prepared by using a functional microgel with either an allyl group or vinylphenyl group was nearly equal to that of photopolymers based on microgels with ammonium ions. Their high sensitivities are attributed to the rapid photopolymerization in the methacryloyl group. To determine how the photoreaction mechanism enhances sensitivity, the photoreaction products were investigated using a model photopolymerization system. It was found that the gelation reactions enhancing sensitivity are predominantly the polymerization and crosslinking ones when a microgel with the methacryloyl group is used, and the graft copolymerization with acrylate monomers when a microgel with either the allyl group or vinylphenyl group is used.     

Levels of tritium concentration in the environmental samples around JAERI TOKAI

By the operation of research reactors, tritium-handling facilities, nuclear power plants, and a reprocessing facility around JAERI TOKAI, tritium is released into the environment in compliance with the regulatory standards.To investigate the levels of tritium concentration in environmental samples around JAERI, rain, air (vapor and hydrogen gas), and tissue-free water of pine needles were measured and analyzed from 1984 to 1993. Sampling locations were determined by taking into consideration wind direction, distance from nuclear facilities, and population distribution. The NAKA site (about 6 km west-northwest from the TOKAI site) was also selected as a reference point.Rain and tissue-free water of pine needles were sampled monthly. For air samples, sampling was carried out for two weeks by using the continuous tritium sampler. After the pretreatment of samples, tritium concentrations were measured by a low background liquid scintillation counter (detection limit is 0.8 Bq/l).Annual mean tritium concentrations in rain observed at six points for 10 years was 0.8 to 8.9 Bq/l, which decreased with distance from the nuclear facilities. Tritium concentrations in rain obtained at Chiba City were around 0.8 Bq/l (1987–1988) and those at the NAKA site were 0.8 to 3.8 Bq/l.Annual mean HTO concentrations in air at three points for 10 years were 9.2×10^–2 to 1.1 Bq/m³, although HT concentrations in air, ranging from 1.7×10^–2 to 5.8×10^–2 Bq/m³, were not influenced by the operation of the nuclear facilities.Annual mean tritium concentrations in tissue-free water of pine needles at four points for 10 years were 1.4 to 31 Bq/l. Those at the NAKA site ranging from 1.4 to 6.2 Bq/l were in good agreement with the reported value by Takashima of 0.78 to 3.0 Bq/l at twenty-one locations in Japan.Monthly mean HTO concentrations in air for 10 years showed a good correlation with absolute humidity, while other samples showed no seasonal variation.Higher level tritium concentrations in rain, in air (vapor), and in tissue-free water of pine needles at the TOKAI site were caused by the tritium released from the nuclear facilities.The committed effective dose equivalent to the member of general public, estimated using the maximum tritium concentration in air (1.1 Bq/m³), was 0.23 Sv, which was about 1/4000 of dose limit for general public.     

Wide mass range trapping using a 7-T internal source matrix-assisted laser desorption/ionization Fourier transform mass spectrometer

A wide mass range trapping experiment using internal source matrix-assisted laser desorption–Fourier transform mass spectrometry (MALDI–FTMS) was evaluated. In this method, the front trap plate potential is ramped up and the rear trap plate potential is simultaneously decreased using a cubic cell to trap ions over a wide range of mass-to-charge ratios. To apply this to MS/MS experiments, a second ion ejection procedure would remove unwanted ions, with the selected remaining ions then fragmented by collision-induced dissociation. In measurements using a 7.2-T unshielded magnet presented here, an approximately equimolar mixture of a set of poly(ethylene glycol) (PEG) species for the ramped measurements had peak areas of 1.0:1.0:1.0:1.0, as did the previously described integral method which gave peak areas of 1.0:1.1:1.0:1.0, in good agreement with the known composition of the samples deposited on the MALDI probe tip. Comparative MALDI–TOF in reflectron mode results were of similar quality for the equimolar mixture, giving a ratio of 1.0:1.0:1.2:0.9. All methods failed to varying degrees when individual PEG compositions of the trial mixture were changed. However, the previously described integral method showed relatively better results for all but the PEG 8000 doubled mixture.     

Pyrene aromatic arrays on RNA duplexes as helical templates

RNA oligomers having multiple (2 to 4) pyrenylmethyl substituents at the 2'-O-sugar residues were synthesized. UV-melting studies showed that the pyrene-modified RNAs could form duplexes with complementary RNA sequences without loss of thermal stability. Absorption, fluorescence, and circular dichroism (CD) spectra revealed that the incorporated pyrenes projected toward the outside of A-form RNA duplexes and assembled in helical aromatic arrays along the minor grooves of the RNA duplexes. Results of computer simulations agreed with the assembled structures of the pyrenes. The helical pyrene arrays exhibited remarkably strong excimer fluorescence, which was dependent on the sequence contexts of RNA duplexes.     

Separation of plant viral satellite double-stranded RNA using high-performance liquid chromatography

High-performance liquid chromatography was developed for further separation of double-stranded (ds) RNAs obtained by CF-11 cellulose chromatography from plants infected with satellite associated cucumber mosaic virus. Fractions separated by monolithic polymer column, especially applicable for nucleic acid analyses, were identified electrophoretically and confirmed with a polymerase chain reaction test. Once standardized, the method has revealed clear evidence of satellite presence without precipitation and electrophoresis. According to demonstrated sensitivity, its application in the preliminary diagnostics of field samples is also predictable. Principally, it can be used as a powerful preparative approach resulting in highly pure satellite dsRNA for further analyses.