Two-phonon Raman scattering of light in argon at high temperatures

The two-phonon Raman spectra of solid argon at 60 K, 22.1 cm³/mole and at 153.5 K, 22.3 cm³/mole are calculated, with phonon frequencies obtained from a calculation in which cubic anharmonicity is included self-consistently and short-range correlations are incorporated. The results are compared with existing molecular dynamics calculations and with experimental measurements. Certain general trends, such as the presence of a two-phonon cutoff and a smoothing out of the features of the spectra, are correctly reproduced, but the calculations predict too low intensity at frequencies around 40 cm^–1, between the sum and difference bands.Supported in part by a grant from the Rutgers University Research Council.Work submitted in partial fulfillment of the requirements of the Ph.D. degree at Rutgers University.     

Remote pulsed Raman spectroscopy of inorganic and organic materials to a radial distance of 100 meters

A portable pulsed remote Raman spectroscopy system has been fabricated and tested to 100 m radial distance. The remote Raman system is based on a directly coupled f/2.2 spectrograph with a small (125 mm diameter) telescope and a frequency-doubled Nd:YAG pulsed laser (20 Hz, 532 nm, 25 mJ/pulse) used as the excitation source in a co-axial geometry. The performance of the Raman system is demonstrated by measuring the gated Raman spectra of calcite, sodium phosphate, acetone, and naphthalene. Raman spectra of these materials were recorded with the 532 nm pulsed laser excitation and accumulating the spectra with 600 laser shots (30 s integration time) at 100 m with good signal-to-background ratio. The remote pulsed Raman system can be used for remotely identifying both inorganic and organic materials during daytime or nighttime. The system will be useful for terrestrial applications such as monitoring environmental pollution and for detecting minerals and organic materials such as polycyclic aromatic hydrocarbons (PAHs) on planetary surfaces such as Mars.     

Resolving magnetic nanostructures in the 10-nm range using MFM at ambient conditions

Following the demand of the magnetic data storage industry, the magnetic structures in hard disk heads are continuously shrinking. This requires a powerful tool to investigate the magnetic properties of these elements in the range of about 10 nm. To achieve this goal, we prepared MFM tips using the electron-beam deposition (EBD) contamination technique, where carbon caps and needles are grown onto the micromachined Si cantilevers. For batch production of MFM tips, however, this technique is not suited well, so we employ the focussed ion-beam (FIB) technique to produce MFM tips with a high aspect ratio similar to those tips with carbon needles. We show that the use of these tips not only improves the lateral resolution, but also considerably reduces the disturbation effects of the weak magnetic structures due to the magnetic tips.     

Phenomenological aspects of a modified fragmentation test using small quantities of explosive

This paper describes the phenomenological aspects of a modified fragmentation test which utilizes an annulus of high explosive in contact with the inner wall of a cylinder of material under test. The shock interactions within the cylinder wall on detonation of the explosive are modelled using a one-dimensional Lagrangian computer code. Predictions of fragment velocities are made in this work. The velocities are found to be influenced by the spallation of the cylinder and this effect can be accounted for in the model by using the position of the spall surfaces which have been obtained from experimental firings of cylinders.

The fragment velocities are found to be much lower than those predicted for a conventional fragmentation test which utilizes a cylinder completely filled with high explosive and this suggests that the post-fragmentation damage of the fragments on recovery from the modified fragmentation test will be small. Experimental evidence from the steel cylinders tested in this work shows that the fragmentation mechanisms operating at the initiation of the test are similar to those reported for a conventional fragmentation test.     

Improved method on image detection at low light level using a sinusoidal-shaped-function signal

This study proposes an improved method which employs the shaped-function technology and Discrete Fourier Series Transform (DFST)-based algorithm to improve the subjective impression at low light level. A sinusoidal wave light signal which is generated in the low frequency range plays the role of a shaped-function signal. The basic procedure of the proposed method is that an LED with a time-varying (sinusoidal) beam is used to illuminate the image sensor evenly. Then, a DFST-based algorithm is employed to remove the sinusoidal wave signal from the captured images for restoring the low-light-level image signal with a low gray resolution. The main purpose of this method was to improve gray-level resolution and signal-to-noise ratio of the acquired image and process the image data in real time by sliding the window. The derivation processes and experiments verify that the improved method not only can reveal a better result than the algorithms we have proposed before, but also have a better performance on the imaging speed.     

Portable and quantitative detection of protein biomarkers and small molecular toxins using antibodies and ubiquitous personal glucose meters

Developing portable and low-cost methods for quantitative detection of large protein biomarkers and small molecular toxins can play a significant role in controlling and preventing diseases or toxins outbreaks. Despite years of research, most current methods still require laboratory-based or customized devices that are not widely available to the general public for quantitative analysis. We have previously demonstrated the use of personal glucose meters (PGMs) and functional DNAs for the detection of many nonglucose targets. However, the range of targets detectable by functional DNAs is limited at the current stage. To expand the range of targets that can be detected by PGMs, we report here the use of antibodies in combination with sandwich and competitive assays for quantitative detection of protein biomarkers (PSA, with a detection limit of 0.4 ng/mL) and small molecular toxins (Ochratoxin A, with a detection limit of 6.8 ng/mL), respectively. In both assay methods, with invertase conjugates as the link, quantitative detection is achieved via the dependence between the concentrations of the targets in the sample and the glucose measured by PGMs. Given the wide availability of antibodies for numerous targets, the methods demonstrated here can expand the range of target detection by PGMs significantly.     

Remote Raman spectra of benzene obtained from 217 meters using a single 532 nm laser pulse

This report describes a mobile Raman lidar system that has been developed for spectral measurements of samples located remotely at ranges of hundreds of meters. The performance of this system has been quantitatively verified in a lidar calibration experiment using a hard target of standardized reflectance. A new record in detection range was achieved for remote Raman systems using 532 nm laser excitation. Specifically, Raman spectra of liquid benzene were measured with an integration time corresponding to a single 532 nm laser pulse at a distance of 217 meters. The single-shot Raman spectra at 217 meters demonstrated high signal-to-noise ratio and good resolution sufficient for the unambiguous identification of the samples of interest. The transmitter consists of a 20 Hz Nd:YAG laser emitting at 532 nm and 1064 nm and a 178 mm telescope through the use of which allows the system to produce a focused beam at the target location. The receiver consists of a large custom telescope (609 mm aperture) and a Czerny-Turner monochromator equipped with two fast photomultiplier tubes.     

Two-phonon Raman scattering of light in argon at low temperatures

The two-phonon Raman spectrum of solid argon at 19 K has been calculated using the point-dipole model, with phonon frequencies derived from a model fitted to neutron scattering experiments. The positions of peaks in the calculated spectra correlate well with peaks in the measured results. In order to obtain correctly the sharpness of the peaks it is necessary to include a small linewidth in the phonon spectral functions. Some discrepancies remain, which may show the inadequacy of the point-dipole matrix element, assuming that the cor- rection of the data for background, etc. is reliable.Work submitted in partial fulfillment of the requirements of the Ph.D. degree at Rutgers University.     

An instrument for the detection of optimal working conditions in stochastic systems

Stochastic resonance (SR) is an active research topic in the area of nonlinear system theory. It has been used to explain the behavior of both natural systems and man-made produced devices. SR conditions are generally investigated by mathematical analysis of complex systems or by realizing nonlinear systems (a typical example being the Schmitt trigger) that are known to be characterized by the presence of SR and performing experimental studies on them. This paper introduces a novel instrument for the detection of SR conditions that does not require any human intervention and, hence, allows independent validation of results concerning SR.     

Ultrasensitive detection of 1,4-Bis(4-vinylpyridyl)phenylene in a small volume of low refractive index liquid by surface-enhanced Raman scattering-active light waveguide

This paper reports a novel surface-enhanced Raman scattering (SERS)-active light waveguide method for ultrasensitive detection of a sample dissolved in a small volume of low refractive index liquid. The SERS-active light waveguide demonstrated in this study was constructed via the light-guiding silica capillary. The surface of its inner wall was modified with SERS-active silver nanoparticles that can remarkably enhance Raman signals. The capillary with SERS-active modified layer was filled with the sample solution to form the SERS-active liquid core (LC) fiber. The incident laser beam travels through the waveguide in a totally reflective mode within the fiber wall and penetrates a small distance into the sample solution by the evanescent wave field. The Raman scattering of the analytes adsorbed onto the surface of the SERS-active modified layer can be excited by the laser beam and refracted into the fiber wall. Thus, a sample dissolved in low index liquid, e.g., methanol, can be quantitatively monitored by Raman spectroscopy and detection limit of its concentration is lower than 10(-9) mol/L.     

The detection of defects in materials using thermography

A three-dimensional solution of the direct problem of heat conduction for a semi-bounded isotropic body with a defect when it is heated by pulsed thermal radiation and cools due to convective heat transfer to the surroundings is presented. The results of modeling and experiment are given. __________ Translated from Izmeritel’naya Tekhnika, No. 4, pp. 49–53, April, 2008.     

Versatile new ion source for the analysis of materials in open air under ambient conditions

A new ion source has been developed for rapid, noncontact analysis of materials at ambient pressure and at ground potential. The new source, termed DART (for "Direct Analysis in Real Time"), is based on the reactions of electronic or vibronic excited-state species with reagent molecules and polar or nonpolar analytes. DART has been installed on a high-resolution time-of-flight mass spectrometer (TOFMS) that provides improved selectivity and accurate elemental composition assignment through exact mass measurements. Although DART has been applied to the analysis of gases, liquids, and solids, a unique application is the direct detection of chemicals on surfaces without requiring sample preparation, such as wiping or solvent extraction. DART has demonstrated success in sampling hundreds of chemicals, including chemical agents and their signatures, pharmaceutics, metabolites, peptides and oligosaccharides, synthetic organics, organometallics, drugs of abuse, explosives, and toxic industrial chemicals. These species were detected on various surfaces, such as concrete, asphalt, human skin, currency, airline boarding passes, business cards, fruits, vegetables, spices, beverages, body fluids, horticultural leaves, cocktail glasses, and clothing. DART employs no radioactive components and is more versatile than devices using radioisotope-based ionization. Because its response is instantaneous, DART provides real-time information, a critical requirement for screening or high throughput.     

Raman scattering of vibrational overtones in deuterium at high pressures

We report observations of the Raman-active vibrational overtone in normal deuterium at 77K and pressures up to 36.4 GPa (1 GPa = 10⁴ bar). We observed a sharp Q₂(J) line corresponding to the v=20, J=0, k=0, k=0 transition and a broad Q₁(J)+Q'₁(J) band corresponding to v,v'=10, J=0, k-k' transitions. The selection rules for the Q₁(J)+Q'₁(J) manifold allowed us to measure the joint density of states of the manifold which we compared to a theoretical density of states for the v=1 vibrational band.     

Remote Raman spectroscopic detection of minerals and organics under illuminated conditions from a distance of 10 m using a single 532 nm laser pulse

Raman spectra of several minerals and organics were obtained from a small portable instrument at a distance of 10 m in a well-illuminated laboratory with a single 532 nm laser pulse with energy of 35 mJ/pulse. Remote Raman spectra of common minerals (dolomite, calcite, marble, barite, gypsum, quartz, anatase, fluorapatite, etc.) obtained in a short period of time (1.1 mus) clearly show Raman features that can be used as fingerprints for mineral identification. Raman features of organics (benzene, cyclohexane, 2-propanol, naphthalene, etc.) and other chemicals such as oxides, silicates, sulfates, nitrates, phosphates, and carbonates were also easily detected. The ability to identify minerals from their Raman spectra obtained from a single laser pulse has promise for future space missions where power consumption is critical. Such a system could be reduced in size by minimizing the cooling requirements for the laser unit. The remote Raman system is also capable of performing time-resolved measurements. Data indicate that further improvement in the performance of the system is possible by reducing the gate width of the detector (ICCD) from 1.1 mus to approximately 20 ns, which would significantly reduce the background signal from daylight or a well-illuminated laboratory. The 1.1 mus signal gating was effective in removing nearly all background fluorescence with 532 nm excitation, indicating that the fluorescence in most minerals is probably from long-lifetime inorganic phosphorescence.     

Deformation at ambient and high temperature of in situ Laves phases-ferrite composites

The mechanical behavior of a Fe₈₀Zr₁₀Cr₁₀ alloy has been studied at ambient and high temperature. This Fe₈₀Zr₁₀Cr₁₀ alloy, whoose microstructure is formed by alternate lamellae of Laves phase and ferrite, constitutes a very simple example of an in situ CMA phase composite. The role of the Laves phase type was investigated in a previous study while the present work focuses on the influence of the microstructure length scale owing to a series of alloys cast at different cooling rates that display microstructures with Laves phase lamellae width ranging from ～50 nm to ～150 nm. Room temperature compression tests have revealed a very high strength (up to 2 GPa) combined with a very high ductility (up to 35%). Both strength and ductility increase with reduction of the lamella width. High temperature compression tests have shown that a high strength (900 MPa) is maintained up to 873 K. Microstructural study of the deformed samples suggests that the confinement of dislocations in the ferrite lamellae is responsible for strengthening at both ambient and high temperature. The microstructure scale in addition to CMA phase structural features stands then as a key parameter for optimization of mechanical properties of CMA in situ composites.     

Selective removal of lead and bromide from a hazardous industrial solid waste using Limited Acid Demand and Separation Factor at ambient conditions

A detailed methodology is described for the selective removal of lead and bromide content from an industrial toxic solid waste, containing also large quantities of iron. Limited Acid Demand (LAD) was examined in order to avoid the co-dissolution of undesirable constituents. The Separation Factor (SF), which is the concentration ratio of dissolved constituents in the resulting leaching solution after the application of extraction stage, can describe the selective release of lead against iron, according to the variation of major leaching parameters (i.e. the molarity of used acid and the liquid to solid (L/S) ratio). A general equation, describing the overall leaching process was obtained, containing a specific "inhibition constant" and indicating that when the initial stoichiometry of leaching procedure and the applied L/S ratio are known, then the removal of lead can be predicted.