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91.
Kenzo Shinkai 《偏微分方程通讯》2013,38(4-5):667-682
92.
Lee Chuin Chen Zhan Yu Hiroko Furuya Yutaka Hashimoto Kenichi Takekawa Hiroaki Suzuki Osamu Ariyada Kenzo Hiraoka 《Journal of mass spectrometry : JMS》2010,45(8):861-869
The development of a new configuration of chemical ionization (CI)‐based ion source is presented. The ambient air containing the gaseous sample is sniffed into an enclosed ionization chamber which is of sub‐ambient pressure, and is subsequently mixed with metastable species in front of the ion inlet of the mass spectrometer. Metastable helium atoms (He*) are used in this study as the primary ionizing agents and are generated from a dielectric barrier discharge (DBD) source. The DBD is powered by an AC high‐voltage supply and the configuration of the electrodes is in such a way that the generated plasma is confined within the discharge tube and is not extended into the ionization chamber. The construction of the ion source is simple, and volatile compounds released from the bulky sample can also be analyzed directly by approaching the sample to the sampling nozzle. When combined with heated nitrogen or other desorption methods, its application can also be extended to non‐volatile compounds, and the consumption for helium can be kept minimum solely for maintaining the stable discharge and gas phase ionization. Applications to non‐proximate sample analysis, direct determination of active ingredients in drug tablets and the detection of trace explosive such as hexamethylene triperoxide diamine are demonstrated. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
93.
94.
The measuring system of two-dimensional birefringence distribution with a polarization modulator and a rotating analyzer using
a rotating analyzer method is presented. The system simply consists of a laser diode, two polarizers, two quarter wave plates
and a CCD camera. Thanks to an imaging system, the mechanism to scan a sample is unnecessary and two-dimensional measurement
is possible and easy. The birefringence of retardation and orientation of the optic axis can be determined by the azimuth
angle of an elliptically polarized light passing through a sample. The azimuth angle is obtained by applying the phase shifting
algorithm to measure the polarization properties; by improving the calculation algorithm, wide range measurement is accomplished.
The measurement procedure and a number of results are described. 相似文献
95.
Kentaro Yoshimura Lee Chuin Chen Daiki Asakawa Kenzo Hiraoka Sen Takeda 《Journal of mass spectrometry : JMS》2009,44(6):978-985
Probe electrospray ionization (PESI) is a recently developed technique that uses a fine solid needle as a probe for sampling biological materials. In this study, we quantified the volume of liquid sample picked up by the solid needle with the tip diameter of ~700 nm and the apex angle of ~60°. The amounts of low‐viscosity samples (rat urine) loaded on the tip of the needle by a single stroke were 0.35 ± 0.09 pl. Interestingly, the amount of liquid adhered to the tip did not significantly depend on the protein concentration, but viscosity and surface tension of the sample. Under these conditions, we successfully obtained mass spectra for each biological sample. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
96.
We found new plasticizers with high molecular weight and low mobility for poly(lactic acid) (PLA). The new plasticizers are polyester-diols (PED) with nominal molecular weight 2000. Temperature dependence of oscillatory tensile moduli of PLA/PED blends in solid states was measured and miscible pairs of the blends were found. The miscible pairs are PLA/poly(ethylene adipate) and PLA/poly(diethylene adipate). Observation by scanning electron microscope and results of differential scanning calorimetry also indicate that these blends are miscible with PLA at weight ratio of PED less than or equal to 20%. In these blends, glass transition temperature is significantly lower than that of PLA. On the other hand, poly(butylene adipate) and poly(hexamethylene adipate) are partially miscible with PLA at weight ratio of PED 20%. The difference of the miscibility is discussed in terms of solubility parameter, which is calculated using the method by Small and configurational entropy. 相似文献
97.
The stress relaxation under large step equibiaxial elongation for low‐density polyethylene with long‐chain branches revealed that the time‐strain separability holds in relaxation modulus GB(t, εB), and damping function hB(εB) exhibits weaker equibiaxial elongational strain εB dependence than that predicted by the Doi–Edwards theory without the independent alignment approximation. Dependencies of damping function h(γ) for step shear deformation and hB(εB) on stretch ratio α of polymer contour length and orientation of a polymer chain in direction of the maximum orientation were evaluated, and it was found that the α dependencies of h(γ) and hB(εB) are different, whereas dependencies of h(γ) and hB(εB) on the orientation coincide fairly well. These results indicate that the damping is dominated by the chain orientation rather than α. This implies that withdrawal of long‐chain branches into tube of a backbone chain occurs when the orientation of the long‐chain branches is large and friction force against the branch point withdrawal is small. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1275–1284, 2009 相似文献
98.
Lee Chuin Chen Md. Matiur Rahman Kenzo Hiraoka 《Journal of mass spectrometry : JMS》2013,48(3):392-398
Super‐atmospheric pressure chemical ionization (APCI) mass spectrometry was performed using a commercial mass spectrometer by pressurizing the ion source with compressed air up to 7 atm. Similar to typical APCI source, reactant ions in the experiment were generated with corona discharge using a needle electrode. Although a higher needle potential was necessary to initiate the corona discharge, discharge current and detected ion signal were stable at all tested pressures. A Roots booster pump with variable pumping speed was installed between the evacuation port of the mass spectrometer and the original rough pumps to maintain a same pressure in the first pumping stage of the mass spectrometer regardless of ion source pressure. Measurement of gaseous methamphetamine and research department explosive showed an increase in ion intensity with the ion source pressure until an optimum pressure at around 4–5 atm. Beyond 5 atm, the ion intensity decreased with further increase of pressure, likely due to greater ion losses inside the ion transport capillary. For benzene, it was found that besides molecular ion and protonated species, ion due to [M + 2H]+ which was not so common in APCI, was also observed with high ion abundance under super‐atmospheric pressure condition. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
99.
Dr. Jun Nakamura Hidenori Yamashiro Hiroto Miya Dr. Kenzo Nishiguchi Dr. Hideki Maki Prof. Dr. Hirokazu Arimoto 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(36):12104-12112
Vancomycin‐resistant Staphylococcus aureus (S. aureus) (VRSA) uses depsipeptide‐containing modified cell‐wall precursors for the biosynthesis of peptidoglycan. Transglycosylase is responsible for the polymerization of the peptidoglycan, and the penicillin‐binding protein 2 (PBP2) plays a major role in the polymerization among several transglycosylases of wild‐type S. aureus. However, it is unclear whether VRSA processes the depsipeptide‐containing peptidoglycan precursor by using PBP2. Here, we describe the total synthesis of depsi‐lipid I, a cell‐wall precursor of VRSA. By using this chemistry, we prepared a depsi‐lipid II analogue as substrate for a cell‐free transglycosylation system. The reconstituted system revealed that the PBP2 of S. aureus is able to process a depsi‐lipid II intermediate as efficiently as its normal substrate. Moreover, the system was successfully used to demonstrate the difference in the mode of action of the two antibiotics moenomycin and vancomycin. 相似文献
100.
Atmospheric pressure chemical ionization of explosives using alternating current corona discharge ion source 下载免费PDF全文
Dilshadbek Tursunbaevich Usmanov Lee Chuin Chen Zhan Yu Shinichi Yamabe Shigeyoshi Sakaki Kenzo Hiraoka 《Journal of mass spectrometry : JMS》2015,50(4):ii-ii
The high‐sensitive detection of explosives is of great importance for social security and safety. In this work, the ion source for atmospheric pressure chemical ionization/mass spectrometry using alternating current corona discharge was newly designed for the analysis of explosives. An electromolded fine capillary with 115 µm inner diameter and 12 mm long was used for the inlet of the mass spectrometer. The flow rate of air through this capillary was 41 ml/min. Stable corona discharge could be maintained with the position of the discharge needle tip as close as 1 mm to the inlet capillary without causing the arc discharge. Explosives dissolved in 0.5 µl methanol were injected to the ion source. The limits of detection for five explosives with 50 pg or lower were achieved. In the ion/molecule reactions of trinitrotoluene (TNT), the discharge products of NOx? (x = 2,3), O3 and HNO3 originating from plasma‐excited air were suggested to contribute to the formation of [TNT ? H]? (m/z 226), [TNT ? NO]? (m/z 197) and [TNT ? NO + HNO3]? (m/z 260), respectively. Formation processes of these ions were traced by density functional theory calculations. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献