Non-resonant multiphoton photoacoustic spectroscopy for noninvasive subsurface chemical diagnostics

This paper describes the development and validation of a novel noninvasive spectroscopic subsurface chemical detection technique, non-resonant multiphoton photoacoustic spectroscopy (NMPPAS). In this technique, non-resonant multiphoton excitation is used to provide subsurface excitation of chemical constituents in a sample followed by the subsequent detection of an acoustic signal using a piezoelectric transducer. Because NMPPAS relies on non-radiative relaxation of the absorbing species, it is capable of monitoring both fluorescent and non-fluorescent species. Moreover, since the majority of the energy imparted to most molecules upon the absorption of light is released through non-radiative pathways, sensitive measurements of even fluorescent molecules can be performed. In this paper, demonstration of proof-of-principle of this novel technique has been shown using test samples of common fluorescent dyes and biomarkers including rhodamine 6G, tryptophan, and NADH in solution and gelatin tissue phantoms. From these studies, it was found that detection limits of these chromophores are in the subnanomolar concentration regime. In addition, preliminary results on excised tumor and healthy tissue samples have demonstrated significant differences between the tumorous and non-tumorous tissues at 740 nm and 950 nm wavelengths. From this work, it was found that NMPPAS has a great deal of potential for subsurface chemical diagnostics in the field of biomedical research.     

Flow diagnostics in a vortex furnace by particle image velocimetry

The internal aerodynamics of a model vortex furnace for a steam generator with a horizontal axis of flow rotation and distributed input of fuel-air mixture jets has been studied. Average characteristics of the flow velocity field in various cross sections have been determined using a digital tracer imaging (particle image velocimetry) technique. Results are compared to data obtained by the method of laser Doppler anemometry.     

Laser diagnostics of welding plasma by polarization spectroscopy

The application of polarization spectroscopy (PS) to detect atomic species in an atmospheric pressure welding plasma has been demonstrated. PS spectra of Na atoms, seeded in the shielding gas flow of a gas tungsten arc welding (GTAW) plasma, are presented at different pump beam energies. The nature of the PS technique was found to be very efficient in suppressing the high background emission associated with the welding plasma. The PS spectral profiles appear to be Lorentzian and Lorentzian cubed for high and low pump beam energy, respectively. The effect of beam steering, due to the thermal gradient in the interaction plasma zone, was addressed. It was found that there is 2% unavoidable error in the detectable PS signal.     

Development of broadband cavity ring-down spectroscopy for biomedical diagnostics of liquid analytes

We present a spectrometer for sensitive absorption measurements in liquids across broad spectral bandwidths. The spectrometer combines the unique spectral properties of incoherent supercontinuum light sources with the advantages of cavity ring-down spectroscopy, which is a self-calibrating technique. A custom-built avalanche photodiode array is used for detection, permitting the simultaneous measurement of ring-down times for up to 64 different spectral components at nanosecond temporal resolution. The minimum detectable absorption coefficient was measured to be 3.2 × 10(-6) cm(-1) Hz(-1/2) at 527 nm. We show that the spectrometer is capable of recording spectral differences in trace levels of blood before and after hemolysis.     

Emission and absorption spectroscopy of magnetic materials

In recent years, optical methods have been accepted as a useful means for studying the magnetic properties in solids. In this paper it will be shown, from an introductory point of view, what kind of information optical studies can provide. The most numerous investigations have been performed with insulating materials. The observed phenomena can be divided into four types: first those where spectra can be described by a simple molecular field picture; second those where one incorporates small quantities of magnetic ions into a diamagnetic host and studies the spectra of various neighbour configurations; third those where one deals with the simultaneous excitation of states in the electronic system (excitons) and the spin system (magnons) which gives rise to the so-called magnon sidebands in absorption and emission spectra; and fourth those which deal with the exchange of energy between various magnetic sublattices by the magnetic interactions. Much less information is available on magnetic semiconductors. Yet here a very striking and perhaps technologically important effect has been observed, namely a considerable red shift of the absorption edge in going through the magnetic transition temperature, e.g., in EuO and EuS. In metals, so far only a few experiments have been performed, and only those on Ni and MnAg are mentioned here. In addition, the question of short-range correlations, which can be observed via optical spectra will be discussed. Finally, recent reviews in this field will be compiled to facilitate a deeper understanding.     

Emission spectroscopy analysis for the non-destructive evaluation of the health of thermal barrier coatings

Lithium oxide was selected as an emission spectroscopic marker in yttria stabilized zirconia (YSZ) thermal barrier coatings (TBCs). The spectral response of excited lithium atoms from dip-coated YSZ containing 5, 3, 1, and 0.3 wt.% lithium oxide and plasma-sprayed YSZ containing 1 wt% lithium oxide was examined under an oxy-acetylene flame. Results showed that the intensity of lithium emission spectrum is a function of the concentration of lithium oxide in the YSZ, the flame temperature, and the degree of TBC degradation. It indicates that an emission spectroscopy can be used to monitor the degradation of TBCs.     

Emission following laser-induced breakdown spectroscopy of organic compounds in ambient air

Laser-induced breakdown spectroscopy (LIBS) was applied to nitroaromatic (NC) and polycyclic aromatic hydrocarbon (PAH) samples in ambient air to characterize their resultant emission. Compounds covering various surface, were ablated by use of the second (532-nm) or the fourth (266-nm) harmonic of a nanosecond pulsed Nd:YAG laser. The emission consisted of spectral features related mostly to CNand C2 molecular fragments and to C, H, N, and O atomic fragments. The transitions of the molecular fragments correspond to the CN (B 2sigma+ - X 2sigma+) violet system and the C2 (d 3IIg - a 3IIu) Swan system; the intensity of the former is higher in NCs than in PAHs. The intensity ratios between C2 and CN and between O and N correlate to the molecular structure, suggesting the possibility of distinguishing one chemical class from another and in optimum cases even identifing specific compounds by use of LIBS.     

Vibrating wires for beam diagnostics

A new approach to the technique of particle beam scanning by wires has been developed. The novelty of the method is that the wire heating quantity is used as a source of information about the number of interacting particles. The wire heating measurement is performed as a change of the wire natural oscillation frequency. The excitation of wire natural oscillations is provided by interaction of a current through the wire with a permanent magnetic field. A shift in the wire natural oscillation frequency characterizes the change in the conditions of wire irradiation by the measured beam. By the rigid fixing of the wire ends on the support an unprecedented sensitivity of the frequency to the temperature and to the corresponding flux of colliding particles is obtained. The range of frequencies used (about 10 kHz) and characteristic time of heat transfer limit the speed characteristics of the proposed scanning method; however, the high sensitivity makes it a prospective one for investigation of beam halo and weak beam scanning. Traditional beam profile monitors generally focus on the beam core and loose sensitivity in the halo region where a large dynamic range of detection is necessary. The scanning by a vibrating wire can also be used in profiling and detecting of neutron and photon beams.     

Nondestructive diagnostics of nanoheterostructures with InGaN/GaN multiple quantum wells by thermal admittance spectroscopy

On the basis of the designed complex of low-temperature admittance spectroscopy, the electron spectrum of semiconductor light emitting diode (LED) heterostructures with InGaN/GaN multiple quantum wells was investigated. The features of the construction of the measuring complex, as well as the technique of measurements of semiconductor nanoheterostructures and processing of admittance spectra, are presented.     

Progress in Raman spectroscopy in the fields of tissue engineering, diagnostics and toxicological testing

This review summarises progress in Raman spectroscopy and its application in diagnostics, toxicological testing and tissue engineering. Applications of Raman spectroscopy in cell biology are in the early stages of development, however, recent publications have demonstrated its utilisation as a diagnostic and development tool with the key advantage that investigations of living cells can be performed non-invasively. Some of the research highlighted here demonstrates the ability of Raman spectroscopy to accurately characterise cancer cells and distinguish between similar cell types. Many groups have used Raman spectroscopy to study tissues, but recently increased effort has gone into single cell analysis of cell lines; the advantages being that cell lines offer ease of handling and increased reproducibility over tissue studies and primary cells. The main goals of bio-Raman spectroscopy at this stage are twofold. Firstly, the aim is to further develop the diagnostic ability of Raman spectroscopy so it can be implemented in a clinical environment, producing accurate and rapid diagnoses. Secondly, the aim is to optimise the technique as a research tool for the non-invasive real time investigation of cell/material interactions in the fields of tissue engineering and toxicology testing.     

Emission spectroscopy of a dipolar plasma source in hydrogen under low pressures

Low-temperature hydrogen plasma has been investigated under the conditions of electron cyclotron resonance by emission spectroscopy. The molecular distribution functions over the low rotational and vibrational levels of the hydrogen molecule in the d³Π_u^- triplet state have been measured. The translational, rotational, and vibrational temperatures of the ground and excited triplet states of the hydrogen molecule are determined. The obtained translational and vibrational temperatures indicate that low-temperature hydrogen plasma under the conditions of electron cyclotron resonance is a more efficient source of vibrationally excited hydrogen molecules in comparison with the other gas discharges.     

Multisensor microsystem for pulmonary function diagnostics

A multisensor microsystem for general lung diagnostics is presented. The microsystem measures peak expiratory flow, temperature, pressure, and relative humidity. Solid-state technology provides an integrated multisensor solution applying silicon MEMS technology. Prototypes implemented on two silicon chips show promising results in their application to flow measurement in a healthy volunteer. Calibration issues are briefly discussed.     

Time-of-flight neutron spectrometer for DT-plasma diagnostics

A novel technique for energy measurements of fusion neutrons from DT-plasmas has been investigated. The method is based on double interaction of neutrons in two scintillators and uses time-of-flight measurement. By using a deuterium based first detector and recording the backscattered neutrons the resolution is found to be 3.5% for 14 MeV neutrons with a flight path equal to 2 m.     

Pulsed holography for hypervelocity impact diagnostics

The development of pulsed holography has two principal objectives. The first objective is to quantify the three dimensional characteristics of hypervelocity impact events, and the second is to provide a diagnostic with the ability to capture high fidelity information for the validation of sophisticated three-dimensional hydrocodes. The holographic image-capturing subsystem uses a Q-switched, seeded, frequency-doubled Nd-YAG laser which produces 5 ns, 750 mJ, coherent pulses at 532 nm. Holographic images have been captured of the back-surface debris bubble from 4 km/s perforating impacts and crater ejecta from 2 km/s non-perforating impacts. A prototype holographic reconstruction and image analysis subsystem has been assembled that provides the ability to measure both the spatial distribution of particles and the morphology of individual particles produced in a hypervelocity impact event. The demonstrated image resolution of this system is 20 μm; however, higher resolutions are possible with magnification optics.     

二元颗粒的旋风分离效率

为了揭示二元颗粒的分离特性,以较难分离的沥青和滑石粉为母体粉料,以容易分离的煤粉和石油焦为添加粉料,两两形成4种差异二元颗粒体系,并以直径300 mm的PV型旋风分离器为模型,比较分离效率。结果表明:沥青颗粒、煤粉和石油焦的加入均能促进其分离效率,添加比例越大,效率提高越明显,且煤粉的促进作用比石油焦的更大;滑石粉、煤粉和石油焦的加入降低其分离效率,添加比例越大,分离效率降低越明显,且煤粉的抑制作用也更大;提出稳定团聚促进颗粒分离的观点,建议采用团聚相对稳定度来判断添加颗粒的促进或抑制作用,且采用团聚相对稳定度可从定性和定量两方面解释二元颗粒旋风分离的特殊现象。     

Adsorbents for capturing mercury in coal-fired boiler flue gas

This paper reviews recent advances in the research and development of sorbents used to capture mercury from coal-fired utility boiler flue gas. Mercury emissions are the source of serious health concerns. Worldwide mercury emissions from human activities are estimated to be 1000 to 6000 t/annum. Mercury emissions from coal-fired power plants are believed to be the largest source of anthropogenic mercury emissions. Mercury emissions from coal-fired utility boilers vary in total amount and speciation, depending on coal types, boiler operating conditions, and configurations of air pollution control devices (APCDs). The APCDs, such as fabric filter (FF) bag house, electrostatic precipitator (ESP), and wet flue gas desulfurization (FGD), can remove some particulate-bound and oxidized forms of mercury. Elemental mercury often escapes from these devices. Activated carbon injection upstream of a particulate control device has been shown to have the best potential to remove both elemental and oxidized mercury from the flue gas. For this paper, NORIT FGD activated carbon was extensively studied for its mercury adsorption behavior. Results from bench-, pilot- and field-scale studies, mercury adsorption by coal chars, and a case of lignite-burned mercury control were reviewed. Studies of brominated carbon, sulfur-impregnated carbon and chloride-impregnated carbon were also reviewed. Carbon substitutes, such as calcium sorbents, petroleum coke, zeolites and fly ash were analyzed for their mercury-adsorption performance. At this time, brominated activated carbon appears to be the best-performing mercury sorbent. A non-injection regenerable sorbent technology is briefly introduced herein, and the issue of mercury leachability is briefly covered. Future research directions are suggested.     

Tunable KrCI excimer-laser operation for combustion diagnostics

Operating conditions for a tunable XeCl excimer laser have been optimized for tunable narrow-band operation at 222 nm with KrCl, formed in Kr/He/Ne/HCl gas mixtures. This wavelength is interesting for detection of nitric oxide (NO) in combustion environments. The laser emission coincides with the (1, 1) and (2, 2) bands of the NO A-X system. Laser-induced-fluorescence spectra taken in a flame show specific excitation of NO with this laser.