Due to its breakthrough the electro-optical time response limitation for picosecond dynamics of processes, many research
groups around the world operating in different fields from physics and chemistry to biology, medicine and material science,
utilize laser setups capable of providing subpicosecond pulses and femtosecond-level time delay lines. However
the signal amount of Femto-picosecond Dynamics is about at an altitude of 1%, but the fluctuation of femtosecond probe
pulse at its best can only reach about 5%. Real-time correct the probe pulse is the only effective way to realize
subpicosecond time-resolved detection precision of transient absorption spectroscopy. So in this paper, reference pulse
was drawn into the measurement equipment through different methods to dispel the fluctuation of probe pulse. Firstly, in
the case of Subpicosecond time-resolved transient absorption spectroscopy, probe and reference beams have the same
spectral distribution and derived from the same source to measure the variation of transmittance in the excited volume.
Secondly probe pulse is spatially and temporally overlapped to the excitation pulse, reference pulse spatially overlapped
but temporally anticipated in respect to the excitation pulse. Finally reference pulse passes through the sample in a
different position. The detector can be a CCD camera or a double photodiode. The results shown that when reference
pulse passes through the sample in a different position and detected by CCD, the correction results can reach to 1%.
Which meet the femto-picosecond dynamics precise requirement.
Q-switched Short pulse laser has been widely applied in many fields, such as optical ranging, remote sensing,
communications, nonlinear optics and spectroscopy etc. Q-switched Nd3+: YAG laser, with its high thermal conductivity
and resistance to damage threshold, longer energy levels were generally used especially. Second harmonics generation
was usually obtained through optical nonlinear effects in crystal. To the frequency doubling technology, poor conversion
efficiency and multi-output frequency are the main problems. Researchers focus more on phase and group velocity
matching induced by nonlinear effects, but pays less attention on theoretical modeling and numerical calculation of
factors affecting frequency doubling of pulsed laser. In this article, nonlinear effects of double frequency crystals in
Q-switched Nd3+: YAG laser was first analyzed in theory, then we deduced the relation expressions between factors
affecting the efficiency of frequency doubling( thickness of frequency doubling crystal, cross section area of incident
beam, power of the fundamental field, phase matching of incidence light)and double frequency efficiency. Secondly,
taken KTP Crystal for example; numerical results and theirs' corresponding curves on these relation expressions was
calculated and drawn with MATLAB software. These findings can be used for processing the specific requests of
frequency doubling crystal. Finally, Theory modeling and numerical calculation were tested in experiment. The
experiment results are in good agreement with those obtained in theory.
One of the popular methods for measurement of intracellular free calcium ([Ca2+]i) is ratiometric fluorescence technique.
Rmax and Rmin play an important role in the calibration of [Ca2+]i measurement. The purpose of this study was to analyze
influencing factors in the [Ca2+]i measurement. Rmax and Rmin deduced from theory had a hyperbolic relation with the
ratio of Cf and Cb (Cf: free indicator concentration; Cb: Ca2+-bound indicator concentration). In experiments, using
radiometric fluorescence imaging system, they were measured separately in two types of cell lines in concentration
gradient (2×105cells/ml, 5×105cells/ml, 1×106cells/ml and 2×106cells/ml). By Triton method, Rmax and Rmin of K562 cells
were 1.21 and 0.20, respectively, and that of Hepa1-6 cells were 2.02 and 1. These results indicated that Rmax and Rmin
were not influenced by concentration gradient in a certain range of cell concentration, but they were different in various
types of cell lines.
Hepa1-6 cells were irradiated with UV and incubated for varying periods of time. [Ca2+]i (intracellular calcium
concentration) of UV-irradiated cell was measured by ratio fluorescence imaging system. The comet assay was used to
determine DNA damage. During the UVB-irradiation, [Ca2+]i had an ascending tendency from 0.88 J/m2 to 92.4J/m2.
Comet assay instant test indicated that when the irradiation dosage was above 0.88J/m2, DNA damage was observed.
Even after approximate 2 h of incubation, DNA damage was still not detected by 0.88J/m2 of UVB irradiation. During
UVA-irradiation, the elevation of [Ca2+]i was not dose-dependent in a range of 1200 J/m2-6000J/m2 and DNA damage
was not observed by comet assay. These results suggested that several intracellular UV receptors might induce [Ca2+]i
rising by absorption of the UV energy. Just [Ca2+]i rising can't induce DNA damage certainly, it is very likely that the
breakdown of calcium steady state induces DNA damage.u
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