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<正>Two new eudesmane derivatives were isolated from the leaves and flowers of Verbesina virginica,along with the known 6-O-β-E -p-coumaroyl-4α-hydroxyeudesmane(1).Their structures were determined as 6-O-β-Z-p-coumaroyl-4α-hydroxyeudesmane(2) and 6-O-α-E-p-coumaroyl-1β-4α-dihydroxyeudesmane(3) by spectroscopic methods. 相似文献
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3+ :Ho3+:YAG laser is operated in active mirror configuration. This laser is characterised by a rather thin crystal (3 mm thickness
in our experiment) and a very short resonator (about 3.2 mm). Therefore this laser is well suited for operation in a single
longitudinal mode. Single-frequency operation is demonstrated with and without an intracavity etalon. It is further shown
that single-frequency emission is reached with a stable cw emission. With a slight detuning of the outcoupling mirror, spiking
can be achieved, resulting in an emission on different lines. The assignment of the observed laser lines to the known transitions
between Stark sublevels of the 5I7 and the 5I8 level is discussed and compared with predictions in the literature.
Received: 2 December 1997 相似文献
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CM Thaker S Rayaprol Krushna Mavani DS Rana MS Sahasrabudhe SI Patil DG Kuberkar 《Pramana》2002,58(5-6):1035-1039
The effect of simultaneous substitution of a fluctuating cation and a divalent cation in LaMnO3 perovskite modifies the properties of the material to exhibit large valence colossal magnetoresistance (CMR) effect. A good
example of these properties is (La1−2x
Pr
x
Ca
x
)MnO3 (LPCMO) type CMR material. In this communication it is reported that, with the increase in x (for x=0.1, 0.15, 0.2), the T
c varies between 100 and 120 K with improvisation in metal-insulator transition. Interestingly, resistance increases with x from few hundred ohms to few kilo ohms with corresponding decrease in the unit cell volume. The results of the studies using
X-ray diffraction (XRD), electrical resistivity, magnetoresistance and ac susceptibility measurements on LPCMO samples for
understanding the structural, transport and magnetic properties are discussed in detail. 相似文献
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John W.Grove 《数学物理学报(B辑英文版)》2010,30(2):563-594
This article describes mathematical models for phase separated mixtures of materials that are in pressure and velocity equilibrium but not necessarily temperature equilibrium. General conditions for constitutive models for such mixtures that exhibit a single mixture sound speed are discussed and specific examples are described. 相似文献
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Ratnamma Pasar Pallavi MS Harischandra Naik R Devaraj M Nandini P Bheemanna M Badariprasad P R Paramasivam M 《Journal of separation science》2022,45(11):1831-1838
This study presents the method development, validation, and simultaneous determination of dimethoate and its metabolite omethoate in curry leaf. Samples were extracted following modified quick, easy, cheap, effective, rugged, and safe extraction protocol and analyzed using liquid chromatography-tandem mass spectrometry. The limit of quantification in the matrix was 0.005 μg g−1 for dimethoate and omethoate. Extraction using acetonitrile recorded the average recoveries in the range of 82.25 to 112.97% for dimethoate and 85.57 to 107.22% for omethoate at 0.005, 0.025 and 0.050 μg g−1 fortification levels and relative standard deviation less than 5%. Similarly, the relative standard deviation values for intraday (Repeatability) and interday (Reproducibility) tests were less than 15%. Dissipation kinetics of dimethoate 30% emulsifiable concentrate at 200 and 400 g a.i h−1 recorded initial deposits of 5.20 and 10.05 μg g−1 and 0.33 and 0.48 μg g−1 for dimethoate and omethoate, respectively, and half-life of 3.07 and 3.34 days. The estimated hazard index value found more than one at a day after dimethoate application. It is not safe for consumer health to use curry leaves in the initial days after application. 相似文献
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T. Rothacher W. Lüthy H.P. Weber 《Applied Physics A: Materials Science & Processing》2001,73(2):133-136
According to UN estimations there are between 80 and 115 million activated landmines worldwide. These mines, or other unexploded
ordnance (UXO), can be triggered accidentally and kill or injure more than 2000 civilians per month. The most common explosive
in these mines is trinitrotoluene (TNT). In this paper, the potential of some of the most promising lasers for mine neutralisation
is investigated, namely an ArF laser, a KrF excimer laser and a Nd:YAG solid-state laser. We have studied the interaction
between laser beams emitting at λ=193 nm, 248 nm and 1060 nm and a bare solid sample of TNT of approximately 15 mg. Using
pulsed excimer radiation at λ=193 nm, with an energy density up to 1 J/mm2, ablation of the TNT without any deflagration has been achieved. At λ=248 nm, using the KrF excimer laser with a pulse duration
of 30 ns and a repetition rate of 5 Hz, the TNT sample started melting and burning after an irradiation of 10 s. Preliminary
results with the Nd:YAG solid-state laser operating in cw emission have shown that the irradiated sample exhibits the desired
burning behaviour even after the exposure is stopped.
Received: 14 December 2000 / Accepted: 18 December 2000 / Published online: 20 June 2001 相似文献
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Rupp J Schmidt M Münch S Cavalar M Steller U Steigert J Stumber M Dorrer C Rothacher P Zengerle R Daub M 《Lab on a chip》2012,12(7):1384-1388
We present a disposable microarray hybridization chamber with an integrated micropump to speed up diffusion based reaction kinetics by generating convective flow. The time-to-result for the hybridization reaction was reduced from 60 min (standard protocol) down to 15 min for a commercially available microarray. The integrated displacement micropump is pneumatically actuated. It includes two active microvalves and is designed for low-cost, high volume manufacturing. The setup is made out of two microstructured polymer parts realized in polycarbonate (PC) separated by a 25 μm thermoplastic elastomer (TPE) membrane. Pump rate can be controlled between 0.3 μl s(-1) and 5.7 μl s(-1) at actuation frequencies between 0.2 Hz and 8.0 Hz, respectively. 相似文献