排序方式: 共有53条查询结果,搜索用时 686 毫秒
21.
Mikulskiene B Gruodis A Sablinskas V Nelander B 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(4):733-741
The temperature dependencies of the intensities of the HCl stretching bands of the hydrogen chloride complexes with acetylene and ethylene have been used to obtain estimates of the dissociation enthalpies of the two complexes. Quantum chemical calculations on the Hartree Fock and DFT/B3LYP levels of theory have been combined with experimental data to give estimates of the intensities of the HCl stretching vibration in the two complexes. 相似文献
22.
Niels Meiser Kai Seger Valdas Pasiskevicius Hoon Jang Edik Rafailov Igor Krestnikov 《Applied physics. B, Lasers and optics》2013,110(3):327-333
Fundamental mode-locking is achieved in a 1.036 GHz cavity using a semiconductor quantum dot saturable absorber mirror with a fast relaxation time component of down to 550 fs. The dispersive cavity delivers 1.7 ps wide pulses with spectra supporting sub-picosecond pulse durations and an M² of 1.3. An average output power of up to 339 mW at wavelengths around 1,032 nm is achieved and the saturable absorber’s damage threshold is identified as a limitation for further power scaling. 相似文献
23.
Steiner G Mackenroth L Geiger KD Stelling A Pinzer T Uckermann O Sablinskas V Schackert G Koch E Kirsch M 《Analytical and bioanalytical chemistry》2012,403(3):727-735
Fourier transform infrared (FT-IR) spectroscopic imaging has been used to characterize different types of pituitary gland
tumors and normal pituitary tissue. Freshly resected tumor tissue from surgery was prepared as thin cryosections and examined
by FT-IR spectroscopic imaging. Tissue types were discriminated via k-means cluster analysis and a supervised classification algorithm based on linear discriminant analysis. Spectral classification
allowed us to discriminate between tumor and non-tumor cells, as well as between tumor cells that produce human growth hormone
(hGH+) and tumor cells that do not produce that hormone (hGH−).The spectral classification was compared and contrasted with
a histological PAS and orange G stained image. It was further shown that hGH+ pituitary tumor cells show stronger amide bands
than tumor cells that do not produce hGH. This study demonstrates that FT-IR spectroscopic imaging can not only potentially
serve as a fast and objective approach for discriminating pituitary gland tumors from normal tissue, but that it can also
detect hGH-producing tumor cells. 相似文献
24.
Simona Strazdaite Ruta Bariseviciute Justinas Ceponkus Valdas Sablinskas 《Central European Journal of Chemistry》2012,10(5):1647-1656
Theoretical calculations of structures, stability and vibrational spectra of 1-butene secondary ozonide (SOZ) conformers were performed using DFT method B3LYP with a 6-311++G(3df, 3pd) basis set. The calculations predict six staggered structures of 1-butene SOZ. The FTIR spectra of 1-butene SOZ isolated in Ar, N2 and Xe matrices were recorded. It was found that nitrogen is the best suited for the matrix isolation of 1-butene SOZ. The bandwidth of the spectral bands of the ozonide isolated in nitrogen was as narrow as 2 cm−1. For the first time the existence of five conformers of 1-butene SOZ were confirmed experimentally by means of matrix isolation infrared absorption spectroscopy. The equatorial gauche (∠OCCC=−66.1°) conformer was proved theoretically and experimentally to be the most stable. It was found that due to high potential barriers of the conformational transitions annealing of the matrix is useless for the assignment of spectral bands to various conformers of 1-butene SOZ. Using the hot nozzle technique the van’t Hoff experimental plots were made for three additional conformers of 1-butene SOZ and experimental ΔH values for these additional conformers were established. The crystallization problems of 1-butene SOZ are discussed which accounts for the rich conformational diversity of the ozonide as well as high conformational barriers for axial-equatorial transitions. 相似文献
25.
Mindaugas Marksa Jolita Radušienė Valdas Jakštas Liudas Ivanauskas Rūta Marksienė 《Natural product research》2016,30(5):536-543
The aim of this work was to modify and validate the post-column high-performance liquid chromatography (HPLC)-ABTS and DPPH methods for evaluating the antioxidant activity of the methanolic extracts of Solidago canadensis (Canadian goldenrod) leaves and flowers. Separation of the analytes was performed via the HPLC-PDA method on a YMC analytical column using a gradient elution program. Three compounds with antioxidant properties – chlorogenic acid, rutin and isoquercitrin – and two unidentified antioxidants were established. The research showed that the coil temperature regimes and loop length combinations influence the optimised post-column assay method for detecting the antioxidant activity of goldenrod radical scavengers. Investigations established that the temperature in the reaction coil was a substantial factor contributing to the signal strength of the analytes after reacting with the DPPH and ABTS radicals. 相似文献
26.
Mantas Puida Feliksas Ivanauskas Valdas Laurinavičius 《Journal of mathematical chemistry》2010,47(1):191-200
Electrochemical biosensor containing flat semi-permeable membrane covering enzyme-containing layer has been investigated.
Mathematical modeling of the action modes of electrochemical biosensors with outer diffusion membrane was performed. Operation
of the biosensor under the conditions when the permeability of the membrane and the activity of the biocatalytic layer depend
on the parameters of the probe has been examined. The pH and temperature were selected as the main parameters which often
affect the action of biosensors. A set of parameters was selected when the biosensor operates in kinetic and diffusion modes
of action. The response time of the biosensor was shown to be sensitive to the mode of the biosensor action especially in
the boundary region of the biosensor action. The linearity of the biosensor (the linear dependence of the biosensor response
on the substrate concentration) in the deep diffusion mode can be increased by several magnitudes, whereas the response time
increases only several times. 相似文献
27.
Georgi Marchev Paolo Dallocchio Federico Pirzio Antonio Agnesi Giancarlo Reali Valentin Petrov Aleksey Tyazhev Valdas Pasiskevicius Nicky Thilmann Fredrik Laurell 《Applied physics. B, Lasers and optics》2012,109(2):211-214
We employed a 9-mm long periodically poled KTiOPO4 (PPKTP) crystal in an optical parametric oscillator (OPO) to generate sub-nanosecond idler pulses around 2.8???m. With a 1-cm long OPO cavity in a singly resonant configuration and double pass pumping by 1-ns pulses at 1,064?nm, the maximum idler energy reached 110???J at 1?kHz. Pumping with 500?ps pulses at 1?C10?kHz, resulted in an idler energy of ~50???J and the shortest pulse duration of ~250?ps, ever reported for an OPO. The corresponding quantum conversion efficiencies were 32.5 and 34.9?%, respectively. 相似文献
28.
Levenius M Conforti M Baronio F Pasiskevicius V Laurell F De Angelis C Gallo K 《Optics letters》2012,37(10):1727-1729
We theoretically and experimentally investigate multistep parametric processes in broadband optical parametric generators (OPGs) based on periodically poled 1 mol. % MgO-doped stoichiometric LiTaO3. We demonstrate that parametric collateral processes may deplete or enhance spectral portions of the OPG output, depending on pump pulse duration. 相似文献
29.
V. Nagirnyi G. Geoffroy R. Grigonis S. Guizard M. Kirm A. Kotlov L.L. Nagornaya M. Nikl V. Sirutkaitis S. Vielhauer 《Radiation measurements》2010,45(3-6):262-264
The relaxation of electronic excitations in CdWO4 and CaWO4 crystals was studied using the method of time-resolved interferometry with 100-fs temporal resolution at temperatures 15–295 K. The electronic system was excited in the one-photon and two-photon regime within the excitonic band in CaWO4 and in the electron-hole continuum in CdWO4. Immediate trapping of charge carriers was detected under pumping in the excitonic band of CaWO4. This result is in agreement with decay kinetics measurements with nanosecond time resolution under direct creation of excitons by 100-fs laser pulses. Fast relaxation of charge carriers followed by formation of excitons was observed in CdWO4. The comparison with previous work allows suggesting the formation of bulk excitons and surface-perturbed excitons in the multi-photon and one-photon regime. The corresponding models of self-trapped exciton creation in tungstate crystals are discussed. 相似文献
30.
Gender determination of fertilized unincubated chicken eggs by infrared spectroscopic imaging 总被引:2,自引:0,他引:2
Steiner G Bartels T Stelling A Krautwald-Junghanns ME Fuhrmann H Sablinskas V Koch E 《Analytical and bioanalytical chemistry》2011,400(9):2775-2782
Each year, billions of day-old layer chicks are produced in the world. Since only female chicks are reared for egg production,
the chicks must be sexed and the unwanted male layer chicks are culled. The culling of male chicks is a serious problem, both
in terms of animal welfare and waste disposal. The germinal disc in fertilized but unincubated eggs contains already several
thousands of blastoderm cells. The cellular DNA in birds is different for male and female chicks. The difference in DNA content
between male and female chicks is around 2% and is measurable by Fourier transform infrared (FT-IR) spectroscopy. In this
study, small amounts of blastoderm cells from 22 chicken eggs were characterized by attenuated total reflection FT-IR spectroscopic
imaging and classified by linear discriminant analysis. Polymerase chain reaction (PCR) was used as a reference method to
determine the gender. The spectroscopic results demonstrate that male blastoderm cells exhibit a higher content of DNA than
cells from female blastoderm. The spectroscopic-based gender determination led to the same result as the PCR analysis. FT-IR
spectroscopic imaging allows the gender determination of unincubated eggs within a few seconds based on the accurate determination
of the different DNA contents in blastoderm cells of both sexes. 相似文献