Physical Sciences and Mathematics Commons^™

Cerium Liii-Edge X-Ray Absorption Study Of The Ceₓfe4-YCoYSb₁₂ Skutterudites, Fernande Grandjean, Gary J. Long, Robert Cortès, Donald T. Morelli, Gregory P. Meisner

Chemistry Faculty Research & Creative Works

The cerium L_III-edge x-ray absorption near-edge spectra of the Ce_xFe_4-yCo_ySb₁₂ compounds have been obtained at 295 K and unambiguously indicate that cerium is in the 4f¹ electronic ground state for all values of 0.22≤x≤0.98 and 0.0≤y≤3.5. This stable trivalent state of cerium is in agreement with the proposed (CeFe₄Sb₁₂) _1-α(Co₄Sb₁₂)α, solid solution structure, in which the cerium atoms are always surrounded by twelve antimony first neighbors and six iron second neighbors, the observed magnetic properties of CeFe₄Sb₁₂ and …

Mössbauer Spectral Study Of The Magnetic Properties Of Ce₂Fe₁₇Hₓ (X=0, 1, 2, 3, 4, And 5), Dimitri Hautot, Gary J. Long, Fernande Grandjean, Olivier Isnard

Chemistry Faculty Research & Creative Works

The Mössbauer spectra of Ce₂Fe₁₇H_x, where x=0, 1, 2, 3, 4, and 5, have been measured and analyzed between 4.2 and 295 K. Because Ce₂Fe₁₇ exhibits a helical magnetic order between 225 and 90 K and a fan magnetic order below 90 K, its Mössbauer spectra were fit with a distribution of hyperfine fields and θ angles for four of the eight magnetically inequivalent sites. Because the hydrides exhibit a magnetization within the basal plane of the hexagonal cell, their Mössbauer spectra were fit with seven sextets. The four isomer shifts …

Second-Harmonic And Sum-Frequency Imaging Of Organic Nanocrystals With Photon Scanning Tunneling Microscope, Yuzhen Shen, Jacek Swiatkiewicz, Jeffrey G. Winiarz, Przemyslaw P. Markowicz, Paras N. Prasad

Chemistry Faculty Research & Creative Works

Second-harmonic generation and sum-frequency generation with photon scanning tunneling microscopy and shear-force detection are used to map the nonlinear optical response and the surface topograph of N-(4-nitrophenyl)-(L)-prolinol crystals with a subdiffraction-limited resolution. The domain-size dependence of the spatial feature is obtained, which shows the local orientational distribution of the optical near field radiated by nonlinear nanocrystals and reveals the difference between nanoscopic and macroscopic second-order optical nonlinearities of molecular crystals.

Detection Of Solid Pigment In Dermatoscopy Images Using Texture Analysis, Murali Anantha, William V. Stoecker, Randy Hays Moss

Chemistry Faculty Research & Creative Works

Background/aims: Epiluminescence microscopy (ELM), also known as dermoscopy or dermatoscopy, is a non-invasive, in vivo technique, that permits visualization of features of pigmented melanocytic neoplasms that are not discernable by examination with the naked eye. ELM offers a completely new range of visual features. One such feature is the solid pigment, also called the blotchy pigment or dark structureless area. Our goal was to automatically detect this feature and determine whether its presence is useful in distinguishing benign from malignant pigmented lesions.

Methods: Here, a texture-based algorithm is developed for the detection of solid pigment. The factors d and a …

Reply To "Comment On 'Mössbauer Effect Study Of Filled Antimonide Skutterudites'", Gary J. Long, Gary J. Long, Dimitri Hautot, Fernande Grandjean, Donald T. Morelli, Gregory P. Meisner

Chemistry Faculty Research & Creative Works

The temperature dependence of the isomer shift of α-iron between 4.2 and 990 K and of Dy₃Fe₅O₁₂ between 4.2 and 550 K has been analyzed in terms of the Debye model for the second-order Doppler shift, a model in which an additional parameter, the effective vibrating mass, is included. This mass is found equal to 57 g/mol in the ionic compound, Dy₃Fe₅O₁₂, and equal to 60 g/mol in metallic α-iron. The deviation of this mass from 57 g/mol is a measure of the covalency of the metallic bonding in …

Observation Of Stratospheric Ozone Depletion Associated With Delta Ii Rocket Emissions, Martin N. Ross, Darin W. Toohey, W. T. Rawlins, E. C. Richard, K. K. Kelly, A. F. Tuck, M. H. Proffitt, Donald E. Hagen, Alfred R. Hopkins, Philip D. Whitefield, J. R. Benbrook, W. R. Sheldon

Physics Faculty Research & Creative Works

Ozone, chlorine monoxide, methane, and submicron particulate concentrations were measured in the stratospheric plume wake of a Delta II rocket powered by a combination of solid (NH₄ClO₄/Al) and liquid (LOX/kerosene) propulsion systems. We apply a simple kinetics model describing the main features of gas-phase chlorine reactions in solid propellant exhaust plumes to derive the abundance of total reactive chlorine in the plume and estimate the associated cumulative ozone loss. Measured ozone loss during two plume encounters (12 and 39 minutes after launch) exceeded the estimate by about a factor of about two. Insofar as only the …

The Atomic And Magnetic Structure Of Ndmn(₆₋ₓ)Feₓge₆ Solid Solutions, J. Han, G. K. Marasinghe, William Joseph James, Muguo Chen, William B. Yelon, I. Dubenko, Naushad Ali

Chemistry Faculty Research & Creative Works

The magnetic and crystallographic properties of induction-melted NdMn_(6-x)Fe_xGe₆ intermetallics (x = 0, 1.0, and 1.5) in the temperature range of 30-475 K have been studied by x-ray and neutron diffraction techniques and SQUID measurements. All of the samples crystallized in the YCo₆Ge₆-type structure (P6/mmm). A small amount ( < 5 mol%) of Nd(MnFe)₂Ge₂ is present as an impurity. As expected, iron replaces manganese at the 3g site. The unit cell volume decreases slightly with increasing iron content at an average rate of 1.3% per substituted atom. Lattice parameters a and c contract at …

A Magnetic And Crystallographic Study Of (Sm/Gd)₂(Fe/Si)₁₇CZ Solid Solutions, Peter C. Ezekwenna, G. K. Marasinghe, J. H. Nam, William Joseph James, William B. Yelon, M. Ellouze, Ph. I'Héritier

Chemistry Faculty Research & Creative Works

The crystallographic and magnetic properties of Sm_yGd_2-yFe_17-xSi_x (0 ≤ x ≤ 3 and y = 1 and 1.5) solid solutions and their interstitial carbides have been investigated using x-ray diffraction and magnetic measurements. The Sm_yGd_2-yFe_17-xSi_x samples crystallized in the rhombohedral Th₂Zn₁₇ structure with less than 5 mol % of impurities. The unit cells of the mixed rare-earth (R) samples are smaller than those of Sm₂Fe₁₇ and Gd₂Fe₁₇. The carbided samples contain up to a total of …

Solid-State Deuterium Nuclear Magnetic Resonance Of The Methyl Dynamics Of Poly(Alpha-Methylstyrene) And Polymethylphenylsilane, Robert D. O'Connor, Eric J. Ginsburg, Frank D. Blum

Chemistry Faculty Research & Creative Works

The methyl-d3 dynamics of two relatively similar polymers, poly(alpha-methylstyrene) (PAMS-d3) and polymethylphenylsilane (PMPS-d3), are investigated via deuterium NMR relaxation experiments. Our analysis of the relaxation data uses the entire solid-echo spectra to maximize the precision of the experiments with regard to the information available on the methyl dynamics. The analysis is novel in that it does not use M[infinity] or M0 to fit the relaxation data. Additionally, the three-site symmetric jump model is shown to not have an observable azimuthal angular dependence for T1 relaxation. The methyl dynamics are quantified with taum, sigma, and f which are the log-average correlation …

4-Chloroacetophenone [1-(4-Methoxyphenyl)Ethylidene]Hydrazone, Michael A. Lewis, Charles Leslie Barnes, Rainer Glaser

Chemistry Faculty Research & Creative Works

The crystal structure of the title mixed azine, C₁₇H₁₇CIN₂O, contains four independent molecules, A-D, and molecule B is disordered. All four molecules have an N-N gauche conformation, with C-N-N-C torsion angles of 136.5 (4), 137.0 (4), -134.7 (4) and -134.7 (4)°, respectively. The phenyl rings are also somewhat twisted with respect to the plane defined by C_ipso and the imine bond. On average, the combined effect of these twists results in an angle of 64.7° between the best planes of the two phenyl rings. Arene-arene double T-contacts are the dominant intermolecular interaction. The …

Conceptual Problems With Remote Element Synthesis, Oliver Manuel

Chemistry Faculty Research & Creative Works

The notion of remote element synthesis has recently been modified to explain the presence of nucleogenetic isotopic anomalies and decay products of short-lived nuclides by injection of a small amount of exotic nucleogenetic material. Even with this modification, remote element synthesis seems inconsistent with the following observations: Evidence of coupled variations in the chemical and isotopic compositions of the source material for meteorites. Residual coupling of chemical and isotopic heterogeneities across planetary distances in the solar system today. The mass-fractionation relationship seen across isotopes of elements in the planetary system, in the solar wind, and in solar flares. Linkage of …

Observations Of Particulates Within The North Atlantic Flight Corridor: Polinat 2, September-October 1997, J. D. Paladino, Donald E. Hagen, Philip D. Whitefield, Alfred Raymond Hopkins, Otmar Schmid, M. R. Wilson, Hans Schlager, Peter Schulte

Physics Faculty Research & Creative Works

This paper discusses particulate concentration and size distribution data gathered using the University of Missouri-Rolla Mobile Aerosol Sampling System (UMR-MASS), and used to investigate the southern extent of the eastern end of the North Atlantic Flight Corridor (NAFC) during project Pollution From Aircraft Emissions in the North Atlantic Flight Corridor/Subsonic Assessment (SASS) Ozone and Nitrogen Oxide Experiment (POLINAT 2/SONEX) from September 19 to October 23, 1997. The analysis presented in this paper focuses on "the corridor effect," or enhancement of pollutants by jet aircraft combustion events. To investigate the phenomena, both vertical and horizontal profiles of the corridor, and regions …

Chemical Oxidation Of Mtbe Under O2-Rich And O2-Limited Environments Coupled With Biological Degradation Of Oxidation Byproducts, J. Sutherland, B. Panka, Craig D. Adams, Joel Gerard Burken

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

The H2O2/UV Advanced Oxidation Process (AOP) Was Investigated to Determine Byproduct Formation under Different Experimental Conditions (PH, Alkalinity, and H2O2/UV Dose). a Key Factor in the Efficiency of the AOP Was the Dissolved Oxygen Concentration. Gas Chromatography/mass Spectrometry (GC/MS) Analysis Was Used to Identify Byproducts Resulting from Oxidation under Oxygen-Rich and Oxygen-Limited Conditions. Resultant Oxidation Byproducts Were Analyzed for their Susceptibility to Biological Degradation. Biodegradation Rate Constants Were Determined and Modeled for the Primary Byproducts of the Advanced Oxidation Process. Inhibition Resulting from the Presence of Multiple Byproducts in a Biological System Was Investigated as Well. Effects of Process Parameters …

Computerised Evaluation Of Cognitive And Motor Function, B. Kisačanin, G. C. Agarwal, J. Taber, D. (Daniel) Hier

Chemistry Faculty Research & Creative Works

In This Paper, We Present a Clinical Study of Computerized Tracking in the Evaluation of Cognitive and Motor Function. We Investigate its Use in the Assessment of Effectiveness of Antiepileptic Drugs (AEDs) as Well as in the Process of Following the Progress of Alzheimer's Disease (AD). to Simplify the Experiments, We Introduce Real-Time Adaptation of the Target Speed. in the Study with Epileptic Patients, Three Result Groups Are Compared: Blood Levels of AEDs, Scores on Standard Neuropsychological Tests, and Scores on Computerized Tracking and Reaction Time Tests. It is Found that the Computerized Tests Are Repeatable, Reliable and Sensitive and …

Application Of Electron-Attachment Reactions To Enhance Selectivity Of Electron-Capture Detector For Nitroaromatic Explosives, Mark Gehrke, Shubhender Kapila, V. J. Flanigan

Chemistry Faculty Research & Creative Works

The differences in the extent of electron-attachment reactions between thermal electrons and selected classes of organic molecules with high electron affinities were investigated. the investigations showed that interactions of thermal electrons with nitroaromatic compounds lead to the formation of neutral products with very low electron affinities. by contrast, a number of other analytes with high electron affinities such as polyhalogenated organic compounds, lead to products with high electron affinities. This difference was exploited to differentiate between nitroaromatic and polychlorinated organic compounds with a tandem arrangement consisting of two electron-capture detectors connected in series with an electron-attachment reactor.

The Effects Of Substituting Iron For Manganese In Smmn₆Ge₆: Magnetic And Crystallographic Properties, J. Han, William B. Yelon, Naushad Ali, I. Dubenko, G. K. Marasinghe, Ph. I'Héritier, William Joseph James

Physics Faculty Research & Creative Works

No abstract provided.

Crystal And Magnetic Structures Of Lani₅₋ₓmnₓ, Chiu-Ying Tai, G. K. Marasinghe, Oran Allan Pringle, William Joseph James, Muguo Chen, William B. Yelon, I. Dubenko, Naushad Ali, Ph. I'Héritier

Physics Faculty Research & Creative Works

The crystallographic and magnetic properties of LaN_5-xMn_x with x = 1, 1.5, and 2, have been investigated using x-ray and neutron diffraction, vibrating sample magnetometer and superconducting quantum interference device measurements. All the samples crystallize in the hexagonal CaCu₅-type (P6/mmm) structure. Manganese atoms preferentially occupy the 3 g site in the LaNi₅ structure. The bulk magnetization of the LaNi_5-xMn_x powder samples decreases rapidly as nickel is replaced by manganese. A ferrimagnetic model is applied to describe the magnetic structure of the LaNi_5-xMn_x samples for x = 1.5 and …

Dynamics Of Interfacial Polymers In Composites, Frank D. Blum, Wuu-Yung Lin

Chemistry Faculty Research & Creative Works

Much experimental and theoretical work has been done on the behavior of adsorbed polymers. However, not much work has focused on the dynamics, especially segmental dynamics, of the adsorbed polymers. This is especially true of filled polymer or composite systems as the interfacial layers in these systems are difficult to study with most techniques. NMR is not restricted to use in optically clear samples and its use in the characterization in the surface polymers has been reviewed. In our laboratory, we have found that deuterium NMR could be used to probe the segmental dynamics of adsorbed polymers. The position of …