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11.
We present the application of time-resolved off-axis digital holography for the investigation of refractive index/transmission properties of laser-induced plasma filaments in water. Time evolution of both amplitude- and phase-contrast images of the self-focused beam in water was characterized with temporal resolution better than 50 fs. To the best of our knowledge, this is the first attempt to characterize the propagation of femtosecond laser pulse in nonlinear media using off-axis digital holography. 相似文献
12.
Romualdas Smičius Milda Malvina Burbuliene Virginija Jakubkienė Emilija Udrwėnaitė Povilas Vainilavičius 《Journal of heterocyclic chemistry》2007,44(2):279-284
Various 4‐amino‐2,3‐dihydro‐4H‐triazoles with aromatic, aliphatic and heterocyclic substituents at the C(5) position were synthesized from corresponding esters and thiocarbohydrazide. This method allows the synthesis these heterocycles in a short time and at reduced expenses. 相似文献
13.
Imidazole modification at C-5 of uridine that is part of tandem G-U wobble base pairs causes slight reduction of thermal stability (DeltaDeltaG(0)(310) < 0.4 kcal mol(-1)) and relatively small change in hydration of short RNA helices. 相似文献
14.
Povilas Vainilavicius Romualdas Smicius Virginija Jakubkiene Sigitas Tumkevicius 《Monatshefte für Chemie / Chemical Monthly》2001,132(7):825-831
Summary. In the reaction of 5-(6-methyl-2,4-dioxo-1,2,3,4-tetrahydro-3-pyrimidinyl)-methyl-1,3,4-oxadiazole-2-thione with hydrazine
hydrate, 5-(6-methyl-2,4-dioxo-1,2,3,4-tetrahydro-3-pyrimidinyl)-methyl-4-amino-1,2,4-triazole-3-thione was formed. The reactions
of the latter with ethyl bromoacetate and chloroacetonitrile in the presence of triethylamine proceeded under formation of
the corresponding S-alkylated derivatives, whereas from its reaction with ω-bromoacetophenone and ethyl 4-chloroacetoacetate
triazolothiadiazines were obtained. Treatment of the title compound with ethyl 2-chloroacetoacetate led to the formation of
5-(6-methyl-2,4-dioxo-1,2,3,4-tetrahydro-3-pyrimidinyl)-methyl-4-N-acetylamino-(3-ethoxy-carbonylmethylthio)-1,2,4-triazole.
Performing of the latter reaction without basic catalyst gave a triazolothiadiazine. Treatment of the S-alkylated derivatives
with sodium methoxide resulted in triazolothiadiazines via a cyclocondensation reaction.
Received November 20, 2000. Accepted January 15, 2001 相似文献
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16.
Sergey Markov Vitali Nagirnyi Andrey Vasil’ev Vladimir Makhov Raul Laasner Sebastian Vielhauer Marco Kirm Rimantas Grigonis Valdas Sirutkaitis 《Central European Journal of Physics》2012,10(4):1002-1008
The analytical expressions for the three-dimensional spatial distribution of excitons and luminescence decay kinetics of wide band-gap crystals were derived taking into account the saturation effect for absorption near the centre of the incident laser beam with Gaussian transversal profile. The model is verified for the excitonic emission of CdWO4 crystals under excitation by ultra-short laser pulses in the region of weak excitonic absorption. 相似文献
17.
S. Butkus E. Gaižauskas D. Paipulas Ž. Viburys D. Kaškelyė M. Barkauskas A. Alesenkov V. Sirutkaitis 《Applied Physics A: Materials Science & Processing》2014,114(1):81-90
Microfabrication of transparent materials using femtosecond laser pulses has showed good potential towards industrial application. Maintaining pulse energies exceeding the critical self-focusing threshold by more than 100-fold produced filaments that were used for micromachining purposes. This article demonstrates two different micromachining techniques using femtosecond filaments generated in different transparent media (water and glass). The stated micromachining techniques are cutting and welding of transparent samples. In addition, cutting and drilling experiments were backed by theoretical modelling giving a deeper insight into the whole process. We demonstrate cut-out holes in soda-lime glass having thickness up to 1 mm and aspect ratios close to 20, moreover, the fabrication time is of the order of tens of seconds, in addition, grooves and holes were fabricated in hardened 1.1 mm thick glass (Corning $^\circledR$ Gorilla $^\circledR$ glass). Glass welding was made possible and welded samples were achieved after several seconds of laser fabrication. 相似文献
18.
Domas Paipulas Viačeslav Kudriašov Mangirdas Malinauskas Valerijus Smilgevičius Valdas Sirutkaitis 《Applied Physics A: Materials Science & Processing》2011,104(3):769-773
We report studies of the modifications induced inside lithium niobate and KDP crystals by Yb:KGW ultrafast laser pulses, having
300-fs pulse duration and operating at 100-kHz repetition rate. By focusing the laser beam with a 0.42 numerical-aperture
objective, we have recorded homogeneous volume Bragg gratings in the bulk of the niobate crystal that showed excellent diffraction
efficiencies, reaching up to 87%, and remained permanent after thermal annealing for one hour at 150°C. The refractive index
modification level was found to be 0.002 in lithium niobate. The results show that lithium niobate is a very promising crystal
candidate for microphotonics applications. On the contrary, in the KDP crystal no smoothly modified refractive index zones
were created. 相似文献
19.
Hydrogen peroxide formation in the photooxidation of CO? NOx, ethene? NOx, and propene? NOx mixtures has been determined in the TVA 31 cubic meter smog chamber under the following conditions: [NOx] ca. 22–46 ppb; ethene = 0.22–1.1 ppm, [propene] = 0.12–0.97 ppm; [H2O] ca. 8 × 10?3 ppm. Ethene, propene, NO, NOx, PAN, HCHO, and CH3CHO were also monitored. Computer modeling was performed using the gas phase ethene and propene mechanism of the Regional Acid Deposition Model. There is good agreement between the model predicted and observed H2O2 concentrations. However, to successfully model all the propene? NOx experimental results, organic nitrate formation from the reaction of peroxy radicals with NO must be included in the mechanism. 相似文献
20.
V. Kudriašov E. Gaižauskas V. Sirutkaitis 《Applied Physics A: Materials Science & Processing》2008,93(2):571-576
We present a study of the refractive index modifications spontaneously induced by infrared femtosecond filaments propagating
in the bulk of transparent solids. It was found that extended modified refractive index channels up to several mm in length
can be formed under loose focusing conditions in fused silica. The observed birefringence zone at the beginning of these channels
is attributed to the anisotropic stress induced via nonlinear losses in the high intensity region of the filament. 相似文献