共查询到20条相似文献,搜索用时 46 毫秒
1.
Aihui Liang Yueyuan Liang Zhiliang Jiang Hesheng Jiang 《Journal of fluorescence》2009,19(6):1009-1015
The AucoreAgshell (Au@Ag) nanoparticles in size of 30 nm were prepared using 10 nm gold nanoparticles as seeds at 90°C, and were purified by
high-speed centrifugation to remove the excess trisodium citrate to obtain Au@Ag nanoprobe. In the medium of pH 4.0 acetate
buffer solution—7.2 μmol/L H2O2–67 μmol/L Fe(II), Au@Ag nanoparticles exhibited a resonance scattering (RS) peak at 538 nm. Upon addition of Catalase (Ct),
the system produced hydroxyl radical that oxidized the Au@Ag nanoprobe to form the AuAg nanoparticles with partly bare nanogold.
Those AuAg nanoparticles aggregated to large nanoclusters that led to the RS peak wavelength red-shift and its RS peak intensity
enhanced. The catalase activity (C) is linear to the enhanced RS intensity (ΔI) in the range of 6 to 2,800 U/L, with regression equation of ΔI = 0.168 C-0.2, the correlation coefficient of 0.9952, and detection limit of 2.8 U/L. This method was applied to the detection of serum
samples, and the results were agreement with that of the spectrophotometry. A new catalytic mechanism of catalase was proposed
with oxywater principle that was agreement with the results of resonance scattering spectroscopy, absorption spectrophotometry,
transmission electron microscopy and laser scattering. 相似文献
2.
Boiling occurs in a solution of oxygen and fullerenes in CCl4 upon optical pumping of C60 upon the fast appearance of incandescent fullerenes in cold solvent. Upon single-photon absorption, a spherical zone of the
critical state of CCl4 is formed within 5 ns (with a diameter of 22–25 nm, P
cr ∼ 45 atm, and T
cr ∼ 556 K). This spherical zone (gas-bubble nucleus) expands to a diameter of ∼100–400 nm for 2–5 ns. If the external pressure
(natural or artificial) is rapidly released, the bubble accelerates and emerges into a vacuum chamber within 0.7–25 μs (the
length of the passage is 0.1–5 cm depending on the construction of the singlet oxygen generator). We note that singlet oxygen
appears 50 ns after the absorption of a photon by fullerene (i.e., inside of the almost formed gas bubble that only begins
to emerge from the liquid to a low-pressure gas region). 相似文献
3.
M. Maaza B. D. Ngom S. Khamlich J. B. Kana Kana P. Sibuyi D. Hamidi S. Ekambaram 《Journal of nanoparticle research》2012,14(2):714
The possibility of synthesizing binary oxides nanoparticles in a nano-scaled form by laser liquid solid interaction using
a NdYAG “1.064 μm” as an irradiating laser source is reported. The case of MoO3−δ is emphasized. Furthermore, it is demonstrated that the Mo–O electronic valence can be controlled through the coupling effects
of oxygen enriched nature of the used coating liquid layer, namely pure H2O or H2O2 and the laser beam fluence. Dark blue hydrated molybdic pentoxide Mo2O5·xH2O and yellow molybdenum trioxide MoO3 nano-suspensions were reproducibly synthesized with hydrogen peroxide and water, respectively, at a relatively high ablation
rate. The average size of the molybdenum trioxide nanoparticles was about <ϕ>~8 nm, slightly larger than the molybdic pentoxide
ones “<ϕ>~6.2 nm”. 相似文献
4.
J.U. Andersen C. Gottrup K. Hansen P. Hvelplund M.O. Larsson 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(2):189-204
Thermionic emission from hot fullerene anions, CN
-, has been measured in an electrostatic storage ring for even N values from 36 to 96. The decay is quenched by radiative cooling and hence the observations give information on the intensity
of thermal radiation from fullerenes. The experiments are analysed by comparison with a simulation which includes the quantisation
of photon energy and the statistics of emission. Experiments with heating of the molecules with a laser beam confirm the interpretation
of the observations in terms of radiative cooling and give an independent estimate of the cooling rate for C60
-. The measured cooling rates agree in general within a factor of two with the prediction from a classical dielectric model
of a thermal radiation intensity of ∼ 300 eV/s for C60 at 1 400 K, scaling approximately with the 6th power of the temperature and with the number of atoms in the molecule.
Received 12 March 2001 and Received in final form 12 June 2001 相似文献
5.
Andre Toom 《Journal of statistical physics》1997,88(1-2):347-364
We consider space- and time-uniformd-dimensional random processes with linear local interaction, which we call harnesses and which may be used as discrete mathematical
models of random interfaces. Their components are rea random variablesa
s
t
, wheres ∈ Z
d
andt=0, 1, 2.,... At every time step two events occur: first, every component turns into a linear combination of itsN neighbors, and second, a symmetric random i.i.d. “noise”v is added to every component. For any σ ∈Z
d
+
define Δσ
a′
s
as follows. If σ=(0,...,0), σ=(0,...,0), Δσ
a
s
t
=a
s
t
. Then by induction,
wheree
i is thed-dimensional vector, whoseith component is one and other components are zeros. Denote |σ| the sum of components of σ. Call a real random variable ϕ symmetric
if it is distributed as −ϕ. For any symmetric random variable ϕpower decay or P-decay is defined as the supremum of thoser for which therth absolute moment of ϕ is finite. Convergence a.s., in probability and in law whent→∞ is examined in terms of P-decay(v): Ifd=1, σ=0 ord=2, σ=(0,0), Δσ
a
s
t
diverges. In all the other cases: If P-decay(v)<(d+2)/(d+|σ|), Δσ
a
s
t
diverges; if P-decay(v)>(d+2)/(d+|σ|), Δσ
a
s
t
, converges and P-decay(ν) For any symmetric random variable ϕexponential decay or E-decay is defined as the supremum of thoser for which the expectation of exp(|x|r) is finite. Let E-decay(v)>0. Whenever Δσ
a
s
t
converges (that is, ifd>2 or |σ|>0: Ifd>2, E-decay(lima
s
t
)=min(E-decay(v),d+2/2); if |σ|=1, E-decay (lim Δσ
a
s
t
)=min(E-decay(ν),d+2); if |σ| ⩾, E-decay (lim Δσ
a
s
t
)=E-decay(ν). 相似文献
6.
N. A. Inogamov S. I. Ashitkov V. V. Zhakhovsky V. V. Shepelev V. A. Khokhlov P. S. Komarov M. B. Agranat S. I. Anisimov V. E. Fortov 《Applied Physics A: Materials Science & Processing》2010,101(1):1-5
Ultrashort laser pulse transfers metal into a two-temperature warm dense matter state and triggers a chain of hydrodynamic
and kinetic processes—melting, expansion, stretching, creation of tensile stress and transition into metastable state. We
study the response of aluminum film deposited on a glass substrate to irradiation by a pump laser pulse transmitted through
glass. Several films with thicknesses from 350 to 1200 nm have been investigated. The smallest thickness is of the order of
the heating depth d
T∼100 nm in Al. The d
T-layer and the free rear side of the film are coupled through pressure waves propagating between them. Therefore, the processes
within d
T-layer affects the time dependent displacement Δ
x
rear(t) of the rear surface. We compare simulated and experimental dependencies Δ
x
rear(t) obtained by the pump–probe technique. It allows us to define a thickness of molten Al layer and explore the two-temperature
processes occurring inside the heated layer. 相似文献
7.
Experimental results of an investigation of the kinetics of photon generation and propagation in a scintillation layer (n-terphenyl
in polystyrene) are presented in this paper for the case of relativistic μ-meson passage through the layer. The duration of
the photon emission Δtem has been measured as a function of the scintillation layer thickness (l=0.05–0.5 m). The total duration of the photon emission
and exit from the scintillation layer Δttot measured with a side coating having diffuse light reflection coefficient ρ=0.9 and 0.95 is given. A kinetic model of the
photon generation and propagation in the scintillation layer is described. Satisfactory agreement of the expected values of
Δtem and Δttot with the exeeriment is indicated.
Ivanovo State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 73–77, June, 1999. 相似文献
8.
On page 905, the second sentence after Eq. (18) should read: “If here the surface t=0 is taken as the surface of integration and the fact that the modes R
μ=0 for z<0 and are functionally the same as the Fulling modes (3) for z>0 is taken into account, then after making the change of variables (8) it might seem that (R
μ,φ)M=(Φμ, φ)R.”
The online version of the original article can be found at 相似文献
9.
D. M. Zashchirinskii L. I. Koroleva A. S. Morozov Yu. V. Dolzhenkova 《Physics of the Solid State》2011,53(2):316-319
The magnetocaloric effect ΔT has been studied by a direct method in two samples of the manganite Sm0.55Sr0.45MnO3, namely, a single crystal (sample A) and a ceramic sample (sample C). The temperature dependences of the ΔT effect of both samples exhibit a maximum at T
max = 143.3 K for the sample A and T
max = 143 K for the sample C. In these maxima, the values of the ΔT effect are 0.8 and 0.4 K in the magnetic field H = 14.2 kOe for the samples A and C, respectively. In addition, the ΔT(T) curve of the sample A has a minimum at T
min = 120 K, in which ΔT = −0.1 K. The maximum value of the ΔT effect increases with an increase in the magnetic field H in the range of magnetic fields up to 14.2 kOe, and the rate of this increase at H > 8 kOe is higher than that at H < 8 kOe. These features of the ΔT effect are explained by the presence of ferromagnetic and antiferromagnetic A- and CE-type clusters in the samples. 相似文献
10.
Hatem Zaag 《Communications in Mathematical Physics》2002,225(3):523-549
We consider u(x,t) a solution of u
t
=Δu+|u|
p
− 1
u that blows up at time T, where u:ℝ
N
×[0, T)→ℝ, p>1, (N−2)p<N+2 and either u(0)≥ 0 or (3N−4)p<3N+8. We are concerned with the behavior of the solution near a non isolated blow-up point, as T−t→ 0. Under a non-degeneracy condition and assuming that the blow-up set is locally continuous and N−1 dimensional, we escape logarithmic scales of the variable T−t and give a sharper expansion of the solution with the much smaller error term (T−t)1, 1/2−η for any η>0. In particular, if in addition p>3, then the solution is very close to a superposition of one dimensional solutions as functions of the distance to the blow-up
set. Finally, we prove that the mere hypothesis that the blow-up set is continuous implies that it is C
1, 1/2−η for any η>0.
Received: 20 June 2001 / Accepted: 6 October 2001 相似文献
11.
G. M. Molchan 《Communications in Mathematical Physics》1999,205(1):97-111
Let b
γ (t), b
γ(0)= 0 be a fractional Brownian motion, i.e., a Gaussian process with the structure function , 0 < γ < 2. We study the logarithmic asymptotics of P
T
= P{b
γ (t) < 1,□t∈TΔ} as T→∞, where Δ is either the interval (0,1) or a bounded region that contains a vicinity of 0 for the case of multidimensional
time. It is shown that ln P
T
= - D ln T(1 + o(1)), where D is the dimension of zeroes of b
γ (t) in the former case and the dimension of time in the latter.
Received: 28 September 1998 / Accepted: 19 February 1999 相似文献
12.
The dielectric properties of solid solution ceramics (1 − x)(KBi)1/2TiO3-(x/2)(NaBi)1/2TiO3-(x/2)BiFeO3 near the morphotropic phase boundary lying near x = 0.75 and separating the compositions with the orthorhombic (x < 0.75) and rhombohedral (x > 0.75) structures have been studied. The solid solutions are shown to undergo a diffuse phase transition with the Curie
temperature T
C = 640–650 K. Based on an analysis of the frequency dependence of the imaginary component of the electric modulus in the range
T > T
C, it is concluded that the transition of the system of solid solutions near the morphotropic phase boundary (x = 0.75) to the dipole-ordered state is accompanied by the formation of heterophase microregions with different relaxation
times of the dielectric polarization. The activation energies of the relaxation of the dielectric polarization (ΔE
M
) in the aforementioned temperature range and of the dc charge carriers (ΔE
dc
) are determined. It is found that ΔE
dc
stepwise increases near 570 K in going toward higher temperatures. It is shown that the behavior of the characteristics of
the dielectric response of the solid solutions below 400 K corresponds to a relaxor ferroelectric. For the compositions 0.7
≤ x ≤ 0.8, the estimated freezing temperature of dipole clusters of the relaxation state is about 240 K, and their activation
energy decreases with increasing x. 相似文献
13.
V. Z. Mordkovich Yosuke Shiratori H. Hiraoka Yoshimasa Takeuchi 《Physics of the Solid State》2002,44(4):603-606
Multishell fullerenes are the smallest among multishell carbon clusters, such as the larger graphitic onions or multishell nanotubes. Unlike classical fullerenes, which have a cage structure and are known to have been synthesized in a variety of sizes (C60, C70, C84, C102, etc.), multishell fullerenes have a cage-inside-cage concentric structure, such as double-shell C60@C240 or triple-shell C60@C240@C560. We report on the synthesis of multishell fullerenes by laser vaporization of C60-containing composite carbon targets. Transmission electron microscopy, Raman scattering spectroscopy, and other methods were used for characterization of the product. The yield of the process reaches up to 40%, which permits production in gram amounts even in laboratory conditions. 相似文献
14.
I. V. Bodnar V. F. Gremenok I. A. Viktorov O. N. Obraztsova 《Journal of Applied Spectroscopy》1997,64(6):809-812
We obtain thin films of AgGaTe2 by laser vaporization of starting crystals. The compositions of the starting crystals and of the films obtained are determined
by x-ray spectral analysis, with their structure and the parameters of the crystal lattice being determined by the x-ray method.
The energies of interband transitions and crystalline (Δ
cr
) and spin-orbit (Δ
so
) splitting are calculated from transmission spectra in the region of the main absorption band.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 6, pp. 793–796, November–December, 1997. 相似文献
15.
Summary The spin-orbit structure ofF
A centres in KCl:Li and KCl:Na have been studied by means of the magnetic circular dichroism. Due to theirC
4V symmetry theF
A centres have two different spin-orbit parameters, Δ‖ and Δ⊥, which only in the KCl:Li case follow the relation: Δ‖ < ΔF < Δ⊥ as expected from the theory. For a close comparison we have also reported our measurement of the spin-orbit coupling ofF centre in KCl. The spin-orbit parameters of theF andF
A centres have been determined using the method of moment. 相似文献
16.
J. Lu M. Prabhu J. Song C. Li J. Xu K. Ueda A.A. Kaminskii H. Yagi T. Yanagitani 《Applied physics. B, Lasers and optics》2000,71(4):469-473
Optical absorption, emission spectra have been measured for polycrystalline Nd-doped Y3Al5O12 ceramics. Fluorescence lifetimes of 257.6 μs, 237.6 μs, 184.2 μs and 95.6 μs have been obtained for 0.6%, 1%, 2% and 4% neodymium-doped
YAG ceramics, respectively. For the first time, highly efficient laser oscillation at 1064 nm has been obtained with this
kind of ceramics. Slope efficiency of 53% has been achieved on a uncoated 4.8-mm thick 1% Nd:YAG ceramics sample. Optical
to optical conversion efficiency is 47.6%. Laser oscillation has also been obtained with a 2% Nd:YAG ceramics. The optical
properties and laser output results have been compared with that of Nd:YAG single crystal grown by the Czochralski method.
Almost identical results have been achieved including laser experiments results. But fabrication of Nd:YAG ceramics is much
easier compared to the single-crystal growth method. And also large size (now of about 400 mm diameter×5 mm is available)
and high-concentration (>1%) Nd:YAG ceramics can be fabricated. The results show that this kind of Nd:YAG ceramics is a very
good alternative to Nd:YAG single crystal.
Received: 20 April 2000 / Published online: 16 August 2000 相似文献
17.
N. L. Bashlov V. M. Milenin N. A. Timofeev A. Ya. Vul’ S. V. Kidalov S. V. Kozyrev 《JETP Letters》1996,63(9):713-717
Optical radiation of C60 fullerenes in the gas phase was observed. The observed emission line λ=258 nm is identified with an electronic transition into the ground state h
g
→h
u
in C
60.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 9, 683–687 (10 May 1996) 相似文献
18.
Proteoliposomes carrying reconstituted yeast plasma membrane H+-ATPase in their lipid membrane or plasma membrane vesicles are model systems convenient for studying basic electrochemical
processes involved in formation of the proton electrochemical gradient (ΔμH
+) across the microbial or plant cell membrane. Δψ- and pH-sensitive fluorescent probes were used to monitor the gradients
formed between inner and outer volume of the reconstituted vesicles. The Δψ-sensitive fluorescent ratiometric probe oxonol
VI is suitable for quantitative measurements of inside-positive Δψ generated by the reconstituted H+-ATPase. Its Δψ response can be calibrated by the K+/valinomycin method and ratiometric mode of fluorescence measurements reduces undesirable artefacts. In situ pH-sensitive fluorescent probe pyranine was used for quantitative measurements of pH inside the proteoliposomes. Calibration
of pH-sensitive fluorescence response of pyranine entrapped inside proteoliposomes was performed with several ionophores combined
in order to deplete the gradients passively formed across the membrane. Presented model system offers a suitable tool for
simultaneous monitoring of both components of the proton electrochemical gradient, Δψ and ΔpH. This approach should help in
further understanding how their formation is interconnected on biomembranes and even how transport of other ions is combined
to it. 相似文献
19.
H. Pummer K. Hohla F. Rebentrost 《Applied Physics A: Materials Science & Processing》1979,20(2):129-134
Collisional coupling between theB, C, andD states of KrF is measured in a discharge pumped KrF laser. Detection of the time resolved populations in the three states
via measurement of the side fluorescence in theB→X, C→A, andD→X bands is used to record the collisional relaxation from theC andD state to theB state during laser emission. The experimentally determined limits for the collisional coupling times are τB-C≦1 ns and τB-D,τC-D<20 ns at total pressures of 2 bar. Investigation of theB→X fluorescence band shows that the vibrational manifold of theB state is not thermalized during laser emission. TheV-V,T coupling time is estimated to be τV-V,T=4±2 ns. The influence of collisional coupling on energy extraction in the KrF laser is discussed. 相似文献
20.
The polarizability exaltation in molecules of endohedral complexes of C20, C24, C28, C36, C50, and C60 fullerenes with He, Ne, Ar, and Kr noble gas atoms has been revealed and studied by the density functional theory method.
It has been found that the sign of the Δα polarizability exaltation depends on the number of atoms in a fullerene molecule. 相似文献