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71.
A combination of light and focused ultrasound waves provides a unique way to obtain directly three-dimensional absorption data in a turbid medium. We present the combination of an ultrasound wave and light in which both the input and the output optodes are on the same side of the sample (reflectance geometry). This technique permits local detection in depth of the presence of a purely absorbing object, without further mathematical processing. It is a promising technique for medical imaging and monitoring of tissues. 相似文献
72.
H. Keskinen J. M. Mäkelä M. Aromaa J. Ristimäki T. Kanerva E. Levänen T. Mäntylä J. Keskinen 《Journal of nanoparticle research》2007,9(4):569-588
In this study, liquid flame spray (LFS) was used to produce titania, silver and silver–titania deposits of nanoparticles.
Titanium(IV)ethoxide (TEOT) and silver nitrate in ethanol solutions were used as precursors and sprayed into turbulent hydrogen–oxygen
flame. Production rates of 1.5–40 mg/min of titania were used with silver additions of 1, 2, 4, and 8 wt% compared to titania.
Nanoparticle deposits were collected by thermophoretic sampling at six different axial distances from the flame torch head:
3, 5, 10, 12, 15, and 20 cm, of which the all but the last one occurred inside the flame. The deposit samples were analysed
by TEM and SAED analysis. The powder samples of the particles were also collected by electric precipitator to XPS and specific
surface area analysis. Particle size and effective density after the flame in the aerosol were analysed with SMPS and ELPI.
The results from the previous studies i.e. controlling the particle size by setting the production rates of the particles
were seen to apply also for this binary system. Characterisation of the deposits showed that when the substrate is inserted
into the flame, in the beginning of the flame the deposit is formed by gas phase deposition whereas further down the flame
the particles are first formed in the gas phase and then deposited. The location of the transition from gas phase deposition
to gas phase nucleation prior to deposition depends on chemical/physical properties (e.g. thermodynamics and gas phase interactions)
of the precursor, precursor concentration in the flame and also flame temperature profile. Therefore, the deposit collection
distance from the burner also affected the collected particle size and degree of agglomeration. The two component deposits
were produced in two different ways: one-step method mixing both precursors in the same solute, and two-step method spraying
each precursor separately. The particle morphology differs between these two cases. In one-step method the primary (d
TEM) and agglomerate particle size (d
SMPS) decreased with the amount of silver addition, verifying the fact that when present, the silver has a clear effect on the
titania nanoparticle formation and growth. 相似文献
73.
We have synthesized bulk RuSr2RECu2O8 (RE=Eu, Gd and Ho) compounds using the ammonium nitrate melt technique. The phase purity of the samples decreases as the ionic radii of the RE element decreases. For RE=Ho, magnetic Sr2HoRuO6 and CuO were formed instead of the 1212 phase. The magnetization vs. temperature curves of the samples are similar to those of the samples prepared using the solid-state reaction method. The magnetic anomalies observed in M-T curves are discussed. 相似文献
74.
75.
76.
Bis(trifluoroalkylsulfonylimino)trifluoromethanesulfonic acid has demonstrated remarkable catalytic ability in the electrophilic acylation of aromatic substrates. Various perfluoroalkyl substituted aroyl chlorides are employed in Friedel-Crafts acylation typically using 1 mol % of catalyst. 相似文献
77.
Let Abe a finite set of integers. Assuming that R⊆A×Ais “not too large”, we give a lower-bound estimate for the cardinality of the restricted sumset A+ R A:= {a1 + a2 : a1; a2 ∈A;(a1; a2) ∉R}in terms of the cardinality and the length of A. 相似文献
78.
Let be a prime. We show that the space of weight one Eisenstein series defines an embedding into ${\mathbb P}^{(p-3)/2}X_1(p)$ for the congruence group that is scheme-theoretically cut out by explicit quadratic equations.
Received: 8 November 2000 / Published online: 17 August 2001 相似文献
79.
A facile synthetic route to N-polyfluoro(trimethylsilyl)ethyl azole derivatives was developed starting from N-bromo(chloro)polyfluoroethyl-substituted azoles. The silanes thus obtained were reacted with various electrophiles in the presence of the fluoride ion to yield the corresponding fluorinated carbinols, ketones, carboxylic acids, and methyl dithiocarboxylates as well as N-pentafluoroethylbenzimidazole. 相似文献