Physical Sciences and Mathematics Commons^™

A Magnetic, Neutron Diffraction, And Mössbauer Spectral Study Of The Nd₂Fe₁₇₋ₓalₓ Solid Solutions, Gary J. Long, Gaya Kanishka Marasinghe, Sanjay R. Mishra, Oran Allan Pringle, Zhongbo Hu, William B. Yelon, D. P. Middleton, K. H. J. Buschow, Fernande Grandjean

Chemistry Faculty Research & Creative Works

The magnetic properties of a series of Nd₂Fe_17-xAl_x solid solutions, with x equal to 2.04, 4.01, 5.97, 7.94, and 9.06, have been studied by magnetic measurements, neutron diffraction, and Mössbauer spectroscopy. Magnetization studies indicate that the Curie temperature increases from 330 K in Nd₂Fe₁₇ to a maximum of ~470 K at an x of 3.5. The compounds crystallize in the Th₂Zn₁₇ structure with lattice parameters and unit cell volumes which increase linearly with increasing aluminum content. The neutron diffraction results indicate that aluminum atoms are excluded from the 9d …

Neutron Diffraction And Mössbauer Effect Study Of Several Nd₂Fe₁₇₋ₓalₓ Solid Solutions, William B. Yelon, H. Xie, Gary J. Long, Oran Allan Pringle, Fernande Grandjean, K. H. J. Buschow

Physics Faculty Research & Creative Works

Aluminum-substituted Nd₂Fe_17-xAl_x solid solutions with x=2.30, 4.44, 6.13, 8.00, and 9.40 have been studied by neutron diffraction and Mössbauer spectroscopy. A Rietveld analysis of the neutron scattering indicates that the aluminum atoms have a high initial affinity for the 18h site, show a high affinity for the 6c site at high aluminum concentrations, and are absent from the 9d site at all aluminum concentrations. The Mössbauer spectra show a maximum in both the maximum and weighted average hyperfine field for x≅2. This indicates that the lattice expansion which occurs with aluminum substitution is sufficient, at …

Neutron-Diffraction And Mössbauer Effect Study Of The Tb₂Fe₁₇₋ₓalₓ Solid Solutions, Gaya Kanishka Marasinghe, Sanjay R. Mishra, Oran Allan Pringle, Gary J. Long, Zhong Bo Hu, William B. Yelon, Fernande Grandjean, D. P. Middleton, K. H. J. Buschow

Physics Faculty Research & Creative Works

The magnetic properties of a series of Tb₂Fe_17-xAl_x solid solutions, with nominal x compositions of 0, 2, 3, 4, 5, 6, 7, and 8, have been studied by neutron diffraction and Mössbauer spectroscopy. Neutron-diffraction data indicate that the compounds all crystallize with the Th₂Zn₁₇ structure and that the aluminum atoms are excluded from the 9d site and show a distinct preference for the 6c site only for an aluminum content greater than 6. The unit-cell volume increases by approximately 1% per aluminum atom substituted in the formula unit. The magnetic moment per …

A Magnetic, Neutron Diffraction, And Mössbauer Spectral Study Of Nd₂Fe₁₅Ga₂ And The Tb₂Fe₁₇₋ₓgaₓ Solid Solutions, Zhong Bo Hu, William B. Yelon, Sanjay R. Mishra, Gary J. Long, Oran Allan Pringle, D. P. Middleton, K. H. J. Buschow, Fernande Grandjean

Physics Faculty Research & Creative Works

An x-ray diffraction study of the substitution of gallium in Tb ₂Fe₁₇ to form the Tb₂Fe_17-xGa_x solid solutions indicates that the compounds adopt the rhombohedral Th₂Zn₁₇ structure. The unit cell volume and the a-axis lattice parameter increase linearly with increasing gallium content. The c-axis lattice parameter increases linearly from x=0 to 6 and then decreases between x=7 and 8. Magnetic studies show the Curie temperature increases by ~150° above that of Tb₂Fe₁₇ to reach a maximum between x=3 and 4, and then decreases with further increases in …

Comparative Mössbauer Effect Study Of Several R₂Fe₁₇ And R₂Fe₁₇Nₓ Compounds, Gary J. Long, Sanjay R. Mishra, Oran Allan Pringle, Fernande Grandjean, K. H. Buschow

Chemistry Faculty Research & Creative Works

The Mössbauer spectra of Sm₂Fe₁₇ and Ho ₂Fe₁₇ and their nitrides have been measured between 295 and 85 K and analyzed with a model which is consistent with our earlier work on R₂Fe₁₇ and R₂Fe₁₇N_x compounds, where R is Pr, Nd, and Th. This model is completely consistent throughout these rare-earth compounds and is in agreement with the crystallographic changes occurring upon nitrogenation and with the prediction of band structure calculations. The dramatic increase in Curie temperature in the nitrides results from the expansion of the crystallographic …

The Synthesis And Characterization Of Poly (1,1'-Divinyl-2,2’-Biimidazole), Timothy S. Evenson

Opportunities for Undergraduate Research Experience Program (OURE)

The monomer 1,1 ,-divinyl-2,2’-biimidazole was prepared using a previously published procedure (1). The new divinyl biimidazole polymer was then synthesized from this monomer. The polymer was characterized by infrared and ultraviolet-visible spectroscopy. Nuclear magnetic resonance confirms the structure of the polymer. Also, gel permeation chromatography was used to determine molecular weight, while differential scanning calorimetry was used to determine the glass transition temperature and crystalline melting point of the polymer.

Macrocyclic Antibiotics As A New Class Of Chiral Selectors For Liquid Chromatography, Christine Bagwill

Opportunities for Undergraduate Research Experience Program (OURE)

In the field of chromatographic separations, the need for new chiral stationary phases is always in demand. Many stationary phases already exist, some of the more popular being cyclodextrin or protein based phases. During this research, a new class of chiral selectors were discovered and evaluated for chiral recognition. Vancomycin, thiostrepton, and rifamycin B all belong to the macrocyclic antibiotic family. Not only can this new class of chiral selectors be used to resolve compounds that cannot be separated on any other column, but it is also more stable and has much greater capacity than protein based columns.

Modified Recycled Glass As An Additive In Coatings Applications, Garth D. Brown

Opportunities for Undergraduate Research Experience Program (OURE)

The feasibility of using chemically modified, finely pulverized recycled glass as an additive in coatings was investigated. The ground glass was added as partial replacement for the conventional pigment titanium dioxide (TiO₂). The loss of TiO₂ pigment was compensated with an optical brightening agent (OB agents). OB agents can help contribute to a coating’s hiding capacity by absorbing light in the UV range, releasing light of a lower energy in the visible spectrum. Glass supplemented coatings were formulated and common paint tests were performed. The glass changed the optical and physical properties of the coating formulations. The …

Synthesis Evaluation Of New High Performance Polymer Systems Involving Tetrachlorohydroquinone, Jason A. Giles

Opportunities for Undergraduate Research Experience Program (OURE)

New high performance transparent polymers are in demand in the aerospace and automotive industries to replace current glass and composite systems. Tetrachlorohydroquinone (TCHQ) was used as the base monomer for various copolymer formulations. Different acid chloride monomers lead to polyester formation with TCHQ. Polycarbonates were formed with triphosgene and diethyl carbonate. This base monomer added rigidity, transparency, and high temperature resistance, however, resulting polymers were brittle and difficult to process. Polymers were characterized by IR and DSC.

Development Of A Recycled Glass Corrosion Inhibitor For Surface Coatings And Concrete Applications, Theresa Pierce

Opportunities for Undergraduate Research Experience Program (OURE)

This research was performed to study the possibility of attaching a metal corrosion inhibitor to recycled glass powder. Such a material would be useful as a corrosion inhibitor component for metal substrate coatings. The major experiments performed were first to produce a metal corrosion inhibitor (Irgacor 153)/silane coupling agent (3-(chloropropyl)trimethoxysilane) adduct and secondly to attach this corrosion inhibitor/silane adduct onto the surface of glass. To test feasibility, qualitative corrosion tests were performed using steel wool as the corroding metal and a number of product samples.

A Mössbauer Effect Study Of The Microscopic Magnetic Properties Of Th₂Fe₁₇ And Its Nitride, Th₂Fe₁₇N₂.₆, Gary J. Long, Oran Allan Pringle, Fernande Grandjean, T. H. Jacobs, K. H. Buschow

Chemistry Faculty Research & Creative Works

The Mössbauer spectra of Th₂Fe₁₇ and Th₂Fe₁₇N_2.6 have been measured at various temperatures between 85 and 295 K and analyzed with a model that is based on the Wigner-Seitz cell environment of each iron site, the orientation of the magnetization, and the magnetic moments as determined from either neutron-diffraction measurements or band-structure calculations. Upon nitrogenation of Th₂Fe₁₇, the 85 K weighted average isomer shift increases from 0.037 to 0.156 mm/s and further the isomer shifts of the four crystallographically distinct sites increase in agreement with the increase observed …

A Prospective Community-Based Study Of Stroke In Warsaw, Poland, Anna Czlonkowska, Danuta Ryglewicz, Thomas Weissbein, Maria Baranska-Gieruszczak, Daniel B. Hier

Chemistry Faculty Research & Creative Works

Background and Purpose Poland is a Country with High Morbidity and Mortality Rates from Cardiovascular Diseases. No Recent Studies Have Evaluated the Contribution of Cerebrovascular Diseases to This Morbidity and Mortality. Our Aim Was to Accurately Determine Stroke Incidence Rates in Warsaw, Poland. Methods a 2-Year Prospective and Population-Based Stroke Registry Was Maintained for Health Care Units 2 and 3 in Warsaw, Poland (Population, 182 285). Case Subjects Were Ascertained by Surveying Hospital Admissions, Outpatient Visits, and Death Certificates. Results during the 2 Years of the Study (1991 to 1992), 633 Cases of First-Event Strokes Were Registered, 462 of Which …

Synthesis And Characterization Of Binuclear And Unsymmetrical Phthalocyanines, Jiang Yang

Doctoral Dissertations

"The metal free planar binuclear phthalocyanines sharing a benzene or naphthalene ring have been synthesized and characterized. The position of Q band of binuclear phthalocyanine sharing a naphthalene ring is red shifted compared to binuclear phthalocyanine sharing a benzene ring. The compounds are shown to form the liquid crystal mesophases at room temperature.

The unique unsymmetrical phthalocyanines with steric hindrance tetraphenyl or “opposite” octaphenyl substitution have been synthesized with the aid of computer modeling. The compounds are characterized by UV-visible near IR absorption and NMR spectroscopy. Mesophase is observed by optical microscopy and differential scanning calorimetry.

The aggregation behavior has …

Gender And Aphasia In The Stroke Data Bank, Daniel B. Hier, William B. Yoon, J. P. Mohr, Thomas R. Price, Philip A. Wolf

Chemistry Faculty Research & Creative Works

Aphasia Was Present in 19.4% of the Men and 22.5% of the Women in the Stroke Data Bank. There Were No Gender Differences in Aphasia Incidence among the Intracerebral Hemorrhages. Aphasia Was More Frequent among Women with Infarcts (37.0%) Than Men (28.3%). When Stroke Mechanism Was Controlled For, There Was an Excess of Aphasia among the Women with Stroke Due to Cardiac Embolism. When Stroke Site Was Controlled For, There Were No Gender Differences in Aphasia Frequency. Wernicke′s, Global, and Anomic Aphasias Were More Common in Women Than Men; Broca′s Aphasia Was Somewhat More Common in Men. Although There Were …