630 research outputs found
Nanocrystalline Cerium Oxide Films for Microelectronic Biosensor Transducers
The physical properties of thin nanocrystalline cerium oxide films have been studied with the purpose
of their application as a functional material of different microelectronic transducers for biosensors: highperformance
photoresistors and photodiodes for bioluminescence registration, ion-selective field-effect
transistors (ISFET) and MOS-varactors indicating the pH changes as a result of biochemical processes.
The effect of technological factors on the photoelectrical, optical, temperature and electrophysical properties
of cerium oxide films has been studied. We established the technological conditions which allow to obtain
СеОх-films with desired functional characteristics. On the basis of the synthesized nanocrystalline
СеОх-films obtained by the "explosive evaporation" method we developed new types of photodetectors for
registration of bioluminescent signal (photoresistors and photodiodes) with enhanced photosensitivity (310-
330 mA/lm∙V) in the visible range. Application of cerium oxide based photoresistors in the bioluminometers
instead of photomultiplier tubes and avalanche photodiodes allows to significantly reduce the cost of bioluminometer
and increase its sensitivity when measuring at alternating signal.
On the basis of nanocrystalline СеОх-films obtained by the "metallic mirrors oxidation" method we developed
potentiometric biosensory transducers (ion-selective field-effect transistors and MOS-varactors)
with CeOx as gate dielectric. It yields higher sensitivity and stability as compared to the use of the SiO2
and Si3N4 films.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3496
Optically Detected Effect of Size on the Oxygen Vacancies Concentration in Cerium Oxide Nanocrystals
In this work effect of the size on the oxygen vacancies concentration in cerium oxide nanocrystals have been investigated by means of luminescence spectroscopy techniques. For determination of changes of oxygen stoichiometry intensity of 5d-4f luminescence of Ce3+ ions were used. It was shown that for CeO2 nanocrystals decrease of the size from 50 nm to 2 nm manifests itself in 8 times increase of the band intensity associated with vacancy-stabilized Ce3+ ions. The same effects have been observed at atmosphere variation from oxidizing to reducing and are connected with significant increase of concentration of oxygen vacancies. Obtained results allow to determine that decrease of the size stimulate formation of oxygen vacancies in cerium oxide nanocrystals
Spectroscopically Detected Formation of Oxygen Vacancies in Nano-Crystalline CeO2 – x
In this work the peculiarities of oxygen vacancies formation in cerium oxide nanoparticles for different external influences have been investigated by spectroscopic methods. The features of oxygen vacancies and therefore non-stoichiometric cerium oxide formation in CeO2 nanocrystals depending on the atmosphere of high temperature treatment were investigated. Stimulation of oxygen vacancies formation in reducing and neutral atmospheres was revealed. Occurrence of two different luminescence centers (viz. the charge-transfer complexes formed by Ce4 + and O2 – ions, and Ce3 + ions stabilized by vacancies) after cerium oxide nanoparticles annealing in a neutral atmosphere has been observed.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3094
About the new version of ISO/IEC 17025
This article outlines the general concept of ISO/IEC 17025 that can help laboratories demonstrate their ability to provide reliable results. The most significant changes in 17025: 2017 are reviewed
Formation of Luminescence Centers in Oxygen-Deficient Cerium Oxide Nanocrystals
In this work the peculiarities of oxygen vacancies formation in cerium oxide nanoparticles for different
external influences have been investigated by spectroscopic methods.
The features of oxygen vacancies and therefore non-stoichiometric cerium oxide formation in CeO2
nanocrystals depending on the atmosphere of high temperature treatment were investigated. Stimulation
of oxygen vacancies formation in reducing and neutral atmospheres was revealed. Occurrence of two different
luminescence centers (viz. the charge-transfer complexes formed by Ce4+ and O2- ions, and Ce3+ ions
stabilized by vacancies) after cerium oxide nanoparticles annealing in a neutral atmosphere has been observed.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3544
Relativistic spherical plasma waves
Tightly focused laser pulses as they diverge or converge in underdense plasma
can generate wake waves, having local structures that are spherical waves. Here
we report on theoretical study of relativistic spherical wake waves and their
properties, including wave breaking. These waves may be suitable as particle
injectors or as flying mirrors that both reflect and focus radiation, enabling
unique X-ray sources and nonlinear QED phenomena.Comment: 6 pages; 4 figure
Laser acceleration of protons from near critical density targets for application to radiation therapy
Laser accelerated protons can be a complimentary source for treatment of
oncological diseases to the existing hadron therapy facilities. We demonstrate
how the protons, accelerated from near-critical density plasmas by laser pulses
having relatively small power, reach energies which may be of interest for
medical applications. When an intense laser pulse interacts with near-critical
density plasma it makes a channel both in the electron and then in the ion
density. The propagation of a laser pulse through such a self-generated channel
is connected with the acceleration of electrons in the wake of a laser pulse
and generation of strong moving electric and magnetic fields in the propagation
channel. Upon exiting the plasma the magnetic field generates a quasi-static
electric field that accelerates and collimates ions from a thin filament formed
in the propagation channel. Two-dimensional Particle-in-Cell simulations show
that a 100 TW laser pulse tightly focused on a near-critical density target is
able to accelerate protons up to energy of 250 MeV. Scaling laws and optimal
conditions for proton acceleration are established considering the energy
depletion of the laser pulse.Comment: 25 pages, 8 figure
Acceleration of electrons in a self-modulated laser wakefield
Acceleration of electrons in a self-modulated laser-wakefield is investigated. The generated electron beam is oberved to have a multi-component beam profile and its energy distribution undergoes discrete transitions as the conditions are varied. These features can be explained by simple simulations of electron propagation in a 3-D plasma wave. © 1999 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87719/2/333_1.pd
Electron acceleration by self-modulated laser wakefield in a relativistically self-guided channel
The relativistic self-focusing of an intense laser pulse (I ∼ 4×1018 W/cm2,I∼4×1018W/cm2, λ = 1 μm,λ=1μm, τ = 400 fsτ=400fs) in a gas jet 750 μm in length was observed using sidescattering imaging. A self-modulated laser wakefield was generated to accelerate self-trapped electrons. The energy distribution and transverse emittance of the electron beam changed due to the onset of the relativistic self-guiding. © 1997 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87563/2/408_1.pd
High Flux Femtosecond X-ray Emission from the Electron-Hose Instability in Laser Wakefield Accelerators
Bright and ultrashort duration X-ray pulses can be produced by through
betatron oscillations of electrons during Laser Wakefield Acceleration (LWFA).
Our experimental measurements using the \textsc{Hercules} laser system
demonstrate a dramatic increase in X-ray flux for interaction distances beyond
the depletion/dephasing lengths, where the initial electron bunch injected into
the first wake bucket catches up with the laser pulse front and the laser pulse
depletes. A transition from an LWFA regime to a beam-driven plasma wakefield
acceleration (PWFA) regime consequently occurs. The drive electron bunch is
susceptible to the electron-hose instability and rapidly develops large
amplitude oscillations in its tail, which leads to greatly enhanced X-ray
radiation emission. We measure the X-ray flux as a function of acceleration
length using a variable length gas cell. 3D particle-in-cell (PIC) simulations
using a Monte Carlo synchrotron X-ray emission algorithm elucidate the
time-dependent variations in the radiation emission processes.Comment: 6 pages, 4 figures, accepted for publication in Phys. Rev. Accel.
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