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71.
Elliptic fourier analysis of cell and nuclear shapes 总被引:1,自引:0,他引:1
72.
Pujol M.C. Massons J. Aguilo M. Diaz F. Rico M. Zaldo C. 《Quantum Electronics, IEEE Journal of》2002,38(1):93-100
The spectroscopic properties of Ho3+ laser channels in KGd(WO4)2 crystals have been investigated using optical absorption, photoluminescence, and lifetime measurements. The radiative lifetimes of Ho3+ have been calculated through a Judd-Ofelt (JO) formalism using 300-K optical absorption results. The JO parameters obtained were Ω2=15.35×10-20 cm2, Ω 4=3.79×10-20 cm2, Ω6 =1.69×10-20 cm2. The 7-300-K lifetimes obtained in diluted (8·1018 cm-3) KGW:0.1% Ho samples are: τ(5F3)≈0.9 μs, τ( 5S2)=19-3.6 μs, and τ(5F5 )≈1.1 μs. For Ho concentrations below 1.5×1020 cm-3, multiphonon emission is the main source of non radiative losses, and the temperature independent multiphonon probability in KGW is found to follow the energy gap law τph -1(0)=βexp(-αΔE), where β=1.4×10-7 s-1, and α=1.4×103 cm. Above this holmium concentration, energy transfer between Ho impurities also contributes to the losses. The spectral distributions of the Ho3+ emission cross section σEM for several laser channels are calculated in σ- and π-polarized configurations. The peak a σEM values achieved for transitions to the 5I8 level are ≈2×10-20 cm2 in the σ-polarized configuration, and three main lasing peaks at 2.02, 2.05, and 2.07 μm are envisaged inside the 5I7→5I8 channel 相似文献
73.
L. Bolanos M. Boscardin A.E. Cabal M. Diaz P. Grybos P. Maj F. Prino L. Ramello R. Szczygiel 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2009,608(3):410-416
We present the energy resolution and imaging performance of a digital X-ray imaging system based on a 512-strip silicon strip detector (SSD) working in the edge-on configuration. The SSDs tested in the system are 300 μm thick with 1 or 2-cm-long strips and 100 μm pitch. To ensure a very small dead area of the SSD working in edge-on configuration, the detector is cut perpendicular to the strips at a distance of only 20 μm from the end of the strips. The 512-strip silicon detector is read out by eight 64-channel integrated circuits called DEDIX [Grybos et al., IEEE Trans. Nucl. Sci. NS-54 (2007) 1207]. The DEDIX IC operates in a single photon counting mode with two independent amplitude discriminators per channel. The readout electronic channel connected to a detector with effective input capacitance of about 2 pF has an average equivalent noise charge (ENC) of about 163 el. rms and is able to count 1 Mcps of average rate of input pulses. The system consisting of 512 channels has an excellent channel-to-channel uniformity—the effective threshold spread calculated to the charge-sensitive amplifier inputs is 12 el. rms (at one sigma level). With this system a few test images of a phantom have been taken in the 10–30 keV energy range. 相似文献
74.
S. García‐Hernández G. Solorio‐Diaz J. A. Ramos‐Banderas J. de J. Barreto R. D. Morales 《国际钢铁研究》2009,80(4):256-263
A mathematical model was developed to study the significance of the fluid dynamics of vortex formation in tundish operations. The aim is to contribute to the fundamental understanding of vortex formation and related phenomena. For this purpose a typical slab tundish was employed; the mathematical model was solved using FLUENT® commercial software capable to simulate highly turbulent flows. The well known k‐? turbulence model was applied to compute this effect in the process. The mathematical simulations confirmed the results from a water analogue model. The vortex formation is directly related to the highly turbulent flows present in the reactor. Great changes in velocity fields during short times and large distances between the upper edge of the dam and the free surface of the bath enhance the formation of vortex flows. 相似文献
75.
Jordan A. Doumanov Christina Zeitz Paloma Dominguez Gimenez Isabelle Audo Abhay Krishna Giovanna Alfano Maria Luz Bellido Diaz Veselina Moskova-Doumanova Marie-Elise Lancelot José-Alain Sahel Emeline F. Nandrot Shomi S. Bhattacharya 《International journal of molecular sciences》2013,14(7):15121-15140
76.
We address restoration of eutrophic lakes and reservoirs through the formulation of dynamic optimization problems subject to complex PDAE systems representing biogeochemical processes in the water bodies. The model includes phytoplankton, zooplankton, fish, nutrients, DO, particulate and dissolved carbon dynamics. The PDAE has been transformed into an ordinary differential algebraic equation system by spatial discretization into two water layers. An optimal control problem for the implementation of three different restoration techniques and their combinations has been formulated within a control vector parameterization approach. Numerical results for the different problems provide optimal profiles for tributary deviation flowrate through a nearby wetland, aeration rates and fish removal rates, as restoration strategies. 相似文献
77.
Using the measures of initial reaction rate, a kinetic-photometric method is developed that uses the reaction of Diquat with H2O2 in basic medium. The reaction rate is very high and therefore the stopped-flow mixing technique is required in order to make kinetic measurements. The reaction rate is obtained in 20 s after the reactants are mixed and it allows the simple application of the method proposed to the routine analyses. The sensitivity of the method is very high being the detection limit 0.44 microgmL(-1) and the application range between 1 and 16 microgmL(-1). The time of measure per sample is 90s. The proposed kinetic-photometric method has been applied to the direct determination of this compound in river water, in the water of laundry of the olives, and in a commercial product. The results are very acceptable. 相似文献
78.
Shepard CL Burghard BJ Friesel MA Hildebrand BP Xang M Diaz AA Enderlin CW 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1999,46(3):536-548
The continuing need for in-situ measurements of physical properties of wastes contained within many high level radioactive waste tanks within the Hanford Site has initiated experimental and theoretical investigations of candidate measurement methods. This paper describes experiments performed with acoustic waveguide sensors. This technology has potential application at the Hanford Site for in-situ measurements of density, viscosity, and temperature of liquid wastes. Waveguides of both circular and rectangular geometry were used in these studies for determination of the densities and viscosities of various fluids. The flight time of a torsional pulse through the sensing region of the waveguide forms the measured quantity. The flight time depends on the velocity of the wave through the sensing region of the waveguide, and this velocity in turn depends upon the properties of the fluid in contact with the waveguide. We performed experiments with 15 different fluids, most of which were single-phase Newtonian fluids. However, three of the fluids were particle-liquid mixtures, and one of these Newtonian in behavior. Most of the wastes held in Hanford tanks contain high solids content. The results of our experiments showed that acoustic waveguides were well suited for measurements in most Newtonian fluids, in agreement with earlier research presented in the literature. However, results for two-phase Newtonian fluids containing particles indicate that, in our case, the waveguides responded primarily to the background fluid rather than the mixture. Very poor results were obtained with the non-Newtonian fluid. In addition, there was a class of fluids, which serve the community as viscosity standards, for which viscosities determined with torsional waveguides were in disagreement with viscosities obtained with standard viscometers. 相似文献
79.
BACKGROUND: To examine the seasonality of suicides in Australia and New Zealand during the period 1981 to 1993. METHODS: A chi-square test and a harmonic analysis were used to detect the seasonality of the suicide data. RESULTS: The reduced amplitude and a smaller proportion of variance accounted for by seasonality suggested the seasonal effect on suicide is greatly diminished. The absence of biseasonal distribution of female suicides was also consistently found in the two countries. The finding was contrary to the reported results in seventies in many Western countries. CONCLUSIONS: The change in living condition, roles of males and females and communication pattern resulted in the reduction of climatic and environment effect in the seasonality of suicides were suggested. LIMITATIONS: The results would be better if a longer series of suicide date were available. 相似文献
80.
Eleven viruses isolated between 1993 and 1997 from outbreaks of classical swine fever in the neighbouring countries of Slovakia, The Czech Republic and Austria were compared after partial sequencing of the NS5B and E2 genes. Viruses collected from South-Central and West Slovakia were indistinguishable during a period of four years, even when associated with outbreaks of variable severity. Outbreaks that occurred in the Czech Republic in 1996 involved two types of virus, one of which was related to the Slovakian outbreaks, and the other to Austrian outbreaks. The results show that the molecular-genetic approach can reveal epizootiological relationships between outbreaks that would not otherwise be apparent. Furthermore, the relative genetic stability of the classical swine fever virus in the field, means that quite small sequence differences can have epizootiological significance. 相似文献