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1.
S. Willmann A. Terenji J. Osterholz H.J. Schwarzmaier P. Hering 《Applied physics. B, Lasers and optics》2002,74(6):589-595
The aim of our studies was to develop a method to determine the absorption coefficient of a turbid medium in a reflection
geometry with small source–detector separations. Therefore, the time-integrated microscopic Beer–Lambert law (MBL) was modified
in order to obtain the absolute absorption coefficient from mean time of flight and dc-intensity measurements. The new technique
was evaluated using turbid phantoms having varying scattering (μs
′ between 0.2 and 2.2 mm-1) and absorbing properties (μa between 0.04 and 0.14 mm-1), comparable to many biological tissues at various source–detector separations between 3 and 11 mm. The measurements were
performed at a wavelength of 1064 nm. We found that this new method was able to determine the absolute absorption coefficient
of the selected phantoms with a standard error of less than 0.005 mm-1 over the range of optical properties investigated.
Received: 23 November 2001 / Revised version: 28 February 2002 / Published online: 14 May 2002 相似文献
2.
The purpose of this study was to investigate the optical properties, absorption coefficient (μ
a
) scattering coefficient (μ
s
) and refractive indices, (n) of HeLa cell line in a suspension of 2% minimum essential medium (MEM) at two different (632.8 and 532.0 nm) wave lengths
of laser light. Optical properties were determined with Kubelka Munk Model (KMM) and refractive index measurement was made
through minimum angle of deviation method (MAD). We reported μ
a
= 8.643 ± 0.187 and 2.348 ± 0.249 cm−1 and μ
s
= 5.609 ± 0.287 and 88.166 ± 2.833 cm−1 at 632.8 and 532.0 nm, respectively. Refractive index was found to be 1.332 and 1.312 at 632.8 nm and 532.0 nm, respectively.
The discussed results provide a route of information for clinical diagnosis, therapeutic application and dosimetry studies
in HeLa and other cell lines. 相似文献
3.
s , the surface diffusion coefficient, Ds
′, and the surface reaction rate coefficient, βs
′, of Cu on alumina are determined in the temperature range 1048–1198 K. Measuring simultaneously the time dependence of the
effective thickness, Heff(t), the lateral shift of the boundary, y(t) of beaded films (BF) and using vapour pressure data we concluded that the process
is controlled by surface reaction at the perimeters of beads. Supposing Arrhenius-type temperature dependence for Ds
′, βs
′ and λs the activation energies and preexponential factors have been calculated.
Received: 2 October 1996/Accepted: 27 November 1996 相似文献
4.
The aim of the current study is to simulate the laser photon through biological tissue during PDT therapy using Monte Carlo
simulation technique. The model is coded using MATLAB. Interaction of laser light with turbid medium e.g. human tissue depends
on the optical properties of the medium i.e. refractive index n, absorption coefficient μ
a
, scattering coefficient μ
s
and anisotropy factor g. Laser light transport through tissue is governed by the radiative transport equations based on absorption and scattering.
Direct sampling is used for step-size generation before interaction via absorption or scattering with the transmitting medium,
for deflection and azimuthal angle (θ and ϕ) when the scattering even occurs. The tissue medium considered is divided into
radial, axial and angular grid elements and an infinite narrow beam with normal incidence on the tissue is considered. The
laser light absorbance inside the tissue, reflectance at the top boundary of the tissue and transmittance at the bottom are
estimated and these quantities are shown varying radially and angularly. Results of reflectance, transmittance and fluence
are compared with the already published results to confirm the authenticity of our coding and these results are found to lie
at only 3–4% error. 相似文献
5.
Optical parameters of bulk animal tissue in vitro, including absorption coefficient (μa), reduced scattering coefficient (μ′s) or scattering coefficient (μs), total attenuation coefficient (μt), anisotropy factor (g) and refractive index (n) are measured at wavelength of 650 nm. Clinical Intralipid-10% is diluted in distilled water into different concentrations to use as tissue phantoms. Four types of animal tissues in vitro are studied. The relationships among the optical parameters are analyzed systemically. For animal tissues, μa, μ′s or μs and n rely on muscle fiber orientations. μs and μt range from 10 to 20 mm−1, μa from 10−2 to 10−3 mm−1 and g from 0.95 to 0.99. 相似文献
6.
W. J. Kossler X. H. Yu A. Greer H. E. Schone C. E. Stronach M. Davis R. S. Cary J. E. Crow W. F. Lankford J. Oostens 《Hyperfine Interactions》1991,63(1-4):81-86
Transverse and zero-field μSR measurements were made on YBa2(Cu1−xNix)3O7−y withx=0.1 and 0.2, and YBa2(Cu1−x
Zn
x
)3O7−y
withx=0.03, 0.06, 0.1, and 0.16, wherey≈0.1. Since doping may lead to magnetic ordering this was searched for with both zero and transverse field μSR, but no evidence
was found over the temperature range studied: 10–100 K. However, depolarization rates as functions of temperature were obtained,
and the low temperature values of these are σ=3.2 μs−1.1.6μs−1, and 1 μs−1 forx=0.01, and 0.2 Ni, respectively, and σ=0.8 μs−1, 0.75 μs−1, 0.65 μs−1, and 0.4 μs−1 forx=0.03, 0.06, 0.1, and 0.16 Zn, respectively. Estimates for the effect of decreasing electron concentration for Zn are made,
but these alone do not account for the drop in σ. Estimates for the effect of scattering on λ and hence σ are made. The reduction
in σ for Ni dopant is in surprisingly good agreement with these estimates. For Zn the order of magnitude is correct, but the
relative lack of further change in σ after the effect of the first 0.03 addition seems to imply a saturation of the effect
of scattering. 相似文献
7.
A theory of optical anisotropy and quantum-confined Pockels effect in CA/C′A′(001) quantum-well structures with different
cations and anions, i.e. for C≠C′ and A≠A′, has been developed. The theory is based on a generalized effective-mass method,
in which the boundary conditions for the envelope functions were constructed taking into account the mixing of heavy-and light-hole
states under normal incidence of the hole on the interface. It is shown that an absorption anisotropy in interband transitions
occurs for different mixing coefficients t
l−h in the boundary conditions for the right-hand (A-C′) and left-hand (A′-C) interfaces. An analysis is made of the interface
contribution to the anisotropy induced by an external electric field for coinciding and different band offsets at the interfaces.
The microscopic sp
3
s* tight-binding model is used to estimate the difference between the t
l−h(A-C′) and t
l−h(A′-C) coefficients.
Fiz. Tverd. Tela (St. Petersburg) 40, 1925–1931 (October 1998) 相似文献
8.
《The European Physical Journal C - Particles and Fields》2007,49(2):545-558
Ratios of the ψ′ over the J/ψ production cross sections in the dilepton channel for C, Ti and W targets have been measured in 920 GeV proton-nucleus
interactions with the HERA-B detector at the HERA storage ring. The ψ′ and J/ψ states were reconstructed in both the μ+μ- and the e+e- decay modes. The measurements covered the kinematic range -0.35≤xF≤0.1 with transverse momentum pT≤4.5 GeV/c. The angular dependence of the ratio has been used to measure the difference of the ψ′ and J/ψ polarization. All results for the muon and electron decay channels are in good agreement: their ratio, averaged over
all events, is Rψ′(μ)/Rψ′(e)=1.00±0.08±0.04. This result constitutes a new, direct experimental constraint on the double ratio of branching fractions,
(B′(μ)B(e))/(B(μ)B′(e)), of ψ′ and J/ψ in the two channels. The ψ′ to J/ψ production ratio is almost constant in the covered xF range and shows a slow increase with pT. 相似文献
9.
M. C. Rath S. K. Sarkar V. K. Wadhawan R. Verma I. M. L. Das R. Dąbrowski M. Tykarska R. Dhar 《Opto-Electronics Review》2008,16(4):399-403
Electron beam irradiation studies on liquid crystal material 5CB have been carried out at a temperature where the compound
exists in the isotropic liquid phase. In situ time-resolved spectroscopic characterization was carried out during the irradiation.
Three different transients were observed during the 2-μs electron pulse. After about 50 μs, only one transient species was
found to be present, which has an absorption peak at 360 nm. Radiolysed sample exhibits a broad absorption at ∼400 nm. The
dielectric measurements show that even a low level of irradiation results in a dramatic increase in the component of dielectric
permittivity normal to the long axes of the molecules ε⊥′, and a corresponding decrease in the dielectric anisotropy (Δε′=ε∥′−ε⊥′ ). These studies show that 5CB is prone to substantial radiation damage on exposure to the beam of high-energy electrons. 相似文献
10.
11.
T.J. Rinke R.B. Bergmann J.H. Werner 《Applied Physics A: Materials Science & Processing》1999,68(6):705-707
Thermal crystallization of a double layer porous Si film creates a monocrystalline Si film with a thin separation layer between
the Si film and the reusable starting wafer. The process enables transfer of thin monocrystalline Si films to foreign substrates,
whereby devices may be formed before or after separation of the film. Sub-micrometer thick films are almost compact, while
films with a thickness of several μm contain voids, and are therefore termed “quasi-monocrystalline”. Internal voids strongly
enhance optical absorption by light scattering. The hole mobility is 78 cm2 V-1 s-1 at a p-type starting wafer resistivity of 0.05 Ω cm.
Received: 24 March 1999 / Accepted: 29 March 1999 / Published online: 5 May 1999 相似文献
12.
J.R. Liu M. Itoh T. Horikawa E. Taguchi H. Mori K. Machida 《Applied Physics A: Materials Science & Processing》2006,82(3):509-513
The electromagnetic wave absorption properties of resin compacts containing 40 vol. % composite powders of α-Fe/C(a), and
Fe3C/C(a) were characterized in a frequency range of 0.05–26.5 GHz, according to a conventional reflection/transmission technique.
The real part (εr
′) and the imaginary part (εr
′′) of relative permittivity were constantly low in the 2–14 GHz (εr
′= ∼12.4 and εr
′′= ∼0.6) for α-Fe/C(a) resin composites, and in the 1–26.5 GHz (εr
′= ∼9.6 and εr
′′= ∼0.8) for Fe3C/C(a) ones. The imaginary part (μr
′′) of relative permeability exhibited wide peaks in the 1–9 GHz range for α-Fe/C(a), and in the 2–26.5 GHz range for Fe3C/C(a) owing to their different magnetocrystalline anisotropy field values. Consequently, the resin compacts with 40 vol. %
α-Fe/C(a), and Fe3C/C(a) powders provided good electromagnetic wave absorption performances (reflection loss <-20 dB) in ranges of 4.3–8.2 GHz,
and 9–26.5 GHz over absorber thicknesses of 1.8–3.3 mm, and 1.0–2.4 mm, respectively.
PACS 76.50.+g; 61.46.+w; 75.50.Bb; 75.30.Gw; 75.20.En 相似文献
13.
T. N. Mamedov V. G. Grebinnik K. I. Gritsai V. N. Duginov V. A. Zhukov V. G. Ol’shevskii A. V. Stoikov 《JETP Letters》1999,69(3):192-195
The lifetimes of a negative muon in the isotopes 132Xe and 40Ar in the solid phase are measured. The lifetime of μ
− in the 1s state of the isotope 132Xe is τ(132Xe)=101.7±1.7 ns, which corresponds to a total nuclear capture rate Λc(132Xe)=9.4±0.2 μs−1. The lifetime of μ
− in the isotope 40Ar, viz., τ (40Ar)=568±6 ns, corresponding to a capture rate Λc(40Ar)=1.31±0.01 μs−1, is obtained to several times better accuracy as compared to previously published results.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 3, 181–183 (10 February 1999) 相似文献
14.
Muneyuki Ishida Keiji Igi 《The European Physical Journal C - Particles and Fields》2007,52(2):357-362
The increase of the total cross sections at very high energies described by log2(s/s0) appears to be confirmed. In the analysis of the COMPETE collaboration in the Particle Data Group (2006), the Blog2(s/s0) was assumed to extend the universal rise of all the total hadronic cross sections to reduce the number of adjustable parameters.
We test if the assumption on the universality of B is justified, through investigation of the values of B for π±p(K±p) and p̄p,pp scatterings. We search for the simultaneous best fit to the σtot and ρ ratios, using a constraint from the FESR of the P′ type for π∓p scatterings and constraints that are free from the unphysical regions for the p̄p,pp and K±p scatterings. By including rich information of the low-energy scattering data owing to the use of FESR, the errors of the
B parameters decrease especially for πp. The resulting value of Bpp is consistent with Bπp within two standard deviations, which appears to support the universality hypothesis.
PACS 11.55.Hx; 13.85.Lg 相似文献
15.
Simultaneous calculation of the dipole moment μj and the relaxation time τj of a certain number of non-spherical rigid aliphatic polar liquid molecules (j) in non-polar solvents (i) under 9.8 GHz electric
field is possible from real ε′ij and imaginary ε″ij parts of the complex relative permittivity ε*ij. The low frequency and infinite frequency permittivities ε0ij and ε∞ij measured by Purohitet al [1,2] and Srivastava and Srivastava [3] at 25, 35 and 30°C respectively are used to obtain static μs. The ratio of the individual slopes of imaginary σ″ij and real σ′ij parts of high frequency (hf) complex conductivity σ*ij with weight fractionsw
jatw
j → 0 and the slopes of σ″ij— σ′ij curves for differentw
js [4] are employed to obtain τjs. The former method is better in comparison to the existing one as it eliminates polar-polar interaction. The hf μjs in Coulomb metre (C m) when compared with static and reported μs indicate that μs s favour the monomer formations which combine to form dimers in the hf electric field. The comparison among μs shows that
a part of the molecule is rotating under X-band electric field [5]. The theoretical μtheos from available bond angles and bond moments of the substituent polar groups attached to the parent molecules differ from
the measured μjs and μs to establish the possible existence of mesomeric, inductive and electromeric effects in polar liquid molecules. 相似文献
16.
A. G. Beda V. B. Brudanin V. G. Egorov D. V. Medvedev M. V. Shirchenko A. S. Starostin 《Physics of Particles and Nuclei Letters》2010,7(6):406-409
The result of the 3-year neutrino magnetic moment measurement at the Kalinin Nuclear Power Plant (KNPP) with the GEMMA spectrometer
is presented. Antineutrino-electron scattering is investigated. A high-purity germanium detector of 1.5 kg placed at a distance
of 13.9 m from the 3 GWth reactor core is exposed to the antineutrino flux of 2.7 × 1013 cm−2 s−1. The scattered electron spectra taken in (5184 + 6798) and (1853 + 1021) h for the reactor ON and OFF periods are compared.
The upper limit for the neutrino magnetic moment μv < 3.2 × 10−11μ
B
at 90% CL is derived from the data processing. 相似文献
17.
A study is reported of the thermoelectric and galvanomagnetic properties of n-Bi2Te3−x−y
SexSey solid solutions for 0.12⩽x⩽0.36 and 0.12⩽y⩽0.21 within the 80–300 K temperature region. The thermoelectric figure-of-merit Z has been found to correlate with the parameters of the many-valley energy-band model including anisotropic carrier scattering.
It is shown that a decrease in the constant-energy surface anisotropy and scattering anisotropy results in a growth of Z for optimum carrier concentrations in the solid solution.
Fiz. Tverd. Tela (St. Petersburg) 41, 187–192 (February 1999) 相似文献
18.
Machi I. Z. Connell S. H. Sellschop J. P. F. Bharuth-Ram K. 《Hyperfine Interactions》2001,136(3-8):727-730
We report on transverse field muon spin rotation measurements on a nitrogen-rich type Ia diamond, both before and after the
conversion of some of the aggregated nitrogen centres to nitrogen-vacancy complexes known as H2/H3-centres. The prompt fractions
f and the spin relaxation rates λ were determined for the diamagnetic (μd) and the paramagnetic (MuT) states in the temperature range 10–300 K. The production of the nitrogen-vacancy complexes had little effect on the parameters
of the MuT state for which f and λ remained unchanged at approximately 30% and 4 μs−1, respectively. For the μd state, on the other hand, the formation of the H2/H3-centres resulted in an increase of the prompt fraction from 10(2)% to
20(3)%, and (for the first time) the spin relaxation rate showed a non-zero value of 0.020(3) μs−1. These results show evidence of strong μd interactions with the nitrogen-vacancy complexes in diamond, and suggest a more complex structure for this state than a bare
μ+.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
19.
V. Dierolf A.B. Kutsenko C. Sandmann F. Tallian W. von der Osten 《Applied physics. B, Lasers and optics》1999,68(5):767-775
Detailed excited state absorption measurements under pumping at 980 nm and 1.5 μm together with conventional absorption and
emission spectroscopy is employed to investigate optical transitions of Er3+ in Ti:LiNbO3 channel-waveguides. The experimental data were evaluated using the Judd–Ofelt method giving parameters close to those in
the bulk. The good agreement between theoretical prediction and measurements allows us to calculate cross section, lifetimes,
and branching ratios. Based on these results we developed and tested a model which is able to predict the conditions for which
laser operation at 550 nm and 2.7 μm will be possible under 980 nm pumping.
Received: 9 December 1998 / Revised version: 8 January 1999 / Published online: 24 March 1999 相似文献
20.
The kinetics of the optical orientation of atoms in a helium-cesium gas-discharge plasma are considered, and kinetic equations
describing the optical orientation of atoms in the case of two simultaneously occurring processes, viz., an elastic process
(spin exchange) and an inelastic process (chemi-ionization), are derived. The rate constants of these processes are determined
experimentally: C
se=(2.8±0.8)×10−9 cm3s−1, C
ci=(1.0±0.3)×10−9 cm3s−1.
Zh. Tekh. Fiz. 69, 36–40 (September 1999) 相似文献