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Symmetry lowering in crystalline solid solutions: A study of cinnamamide-thienylacrylamide by x-ray and neutron diffraction and solid-state photochemistry

Description: Principles are outlined for symmetry lowering of a mixed crystal. A survey is given of methods used to detect reduced symmetry: changes in crystal morphology, detection of enantiomeric segregation of chiral additives in centrosymmetric'' crystals, generation of second harmonic optical signals, optical birefringence, asymmetric photoreactions in the crystalline state and X-ray and neutron diffraction. The last two methods are applied to mixed crystals of cinnamamide host and thienylacrylamide. Diffraction demonstrated that the mixed crystals are composed of six sectors of reduced symmetry, from monoclinic centrosymmetric P2[sub 1]/c to triclinic P1 in four sectors and possibly Pc in the remaining two. The X-ray diffraction data were not sufficiently accurate for assigning the absolute structures of the PI sectors of anomalous X-ray scattering. Thus, by this method one could not ascertain the absolute orientation of the guest molecules on the surface sites through which they were selectively occluded. This ambiguity was resolved by assignment of the absolute configuration of the chiral heterophotodimers, between host and guest, in enantiomeric excess in the PI sectors, after irradiation with UV light. This leads to the conclusion that the selective occlusion of thienylacrylamide arises from replacement of attractive C-H[pi] (electron) interactions between host molecules by a repulsive sulfur (lone pair electron)[pi](electron) interactions between guest and host at the crystal surfaces.
Date: January 1, 1993
Creator: Shimon, L.J.W.; Weissinger-Lewin, Y.; McMullan, R.K. (Brookhaven National Lab., Upton, NY (United States)); Vaida, M.; Frolow, F.; Lahav, M. et al.
Partner: UNT Libraries Government Documents Department

The effect of porous support composition and operating parameters on the performance of supported liquid membranes

Description: Factors, such as porous support composition and operating parameters, that influence the performance of supported liquid membranes (SLMs) were investigated. SLMs of varying porous support compositions and structures were studied for the transport of metal ions. A microporous polybenzimidazole support was synthesized and prepared in the form of an SLM. This SLM containing the selective extractant di-(2-ethylhexyl)phosphoric acid was evaluated for the transport of copper and neodymium. Dramatically improved performance over that of commercially available membranes was found in tests for removing the metal ions from solution. Metal ion transport reaches near completion in less than 3 hours, whereas Celgard-polypropylene and Nuclepore-polycarbonate reaches only 50% completion even after 15 hours. The transport driving force for acidic extractants is a pH gradient between the feed and strip solutions. Polybenzimidazole, an acid- and radiation-resistant polymer, has two protonatable tertiary nitrogens per repeat unit that may help sustain the pH driving force. Another factor may be the ability of the polybenzimidazole to hydrogen bond with the extractant. Transport through the flat-sheet SLMs were tested using a unique cell design. Countercurrent flow of the feed and strip solutions was established through machined channels in half-cell faceplates that are in a spiral, mirror-image pattern with respect to each other, with the flat-sheet SLM interposed between the two channeled solutions. 7 refs., 14 figs.
Date: February 1, 1991
Creator: Takigawa, D.Y.
Partner: UNT Libraries Government Documents Department

Molecular-orbital calculations for polynitropolyhedranes

Description: Various synthetic pathways to polyhedranes are being evaluated by using theoretical calculations. The results indicate that the synthesis of tetranitrotetrahedrane from tetralithiotetrahedrane is not a promising route. Alternatively, sequential base-promoted nitrations of cubanes seem a much more promising route for obtaining polynitrocubanes.
Date: January 1, 1982
Creator: Ritchie, J.P.
Partner: UNT Libraries Government Documents Department

Study of new materials for gun propellant formulations

Description: We are searching for new energetic materials to improve gun- propellant formulations. Theoretical calculations indicate that certain types of high nitrogen compounds produce lower average- molecular-weight gases than those with more carbon, and low average-molecular-weight by-products contribute to higher impetus. Therefore, our target compounds were chosen to contain only the elements C, H, N, and O, with a high percentage of nitrogen, be thermally stable and moderately insensitive to impact. The chemical preparations, impetus, flame temperatures, and heats of formation for the compounds are described.
Date: January 1, 1989
Creator: Lee, Kien-Yin & Stinecipher, M.M. (Los Alamos National Lab., NM (USA))
Partner: UNT Libraries Government Documents Department

Spectroscopy of the amide-I modes of acetanilide

Description: Raman measurements were made on acetanilide (N-phenyl-acetamide). Data are presented of the integrated intensity of the 1650 cm/sup /minus/1/ band as a function of temperature. The experimental procedures and data reduction were highly rigorous and are believed to be to most reliable data available. A concise theory of polaron states is presented and used to interpret the data. 22 refs., 4 figs., 1 tab.
Date: January 1, 1989
Creator: Bigio, I.J.; Scott, A.C. & Johnston, C.T.
Partner: UNT Libraries Government Documents Department

Uniform aluminum deposits on large nonplanar and planar polyimide substrates by physical vapor deposition

Description: The capability to deposit 10- to 12-..mu..m-thick aluminum films with less than 2 percent thickness uniformity (defined as standard deviation/average thickness) on large nonplanar and planar polyimide substrates has been developed using physical vapor deposition (PVD). A technique called shadow masking was developed to provide this consistent deposit uniformity over the entire substrate surfaces (greater than 2000 cm/sup 2/). The specific dimensions of a shadow mask for each substrate are generated from a computer-reduced plot of beta-backscatter thickness measurements of a previous deposit. With this developed method, initial thickness uniformities of 9.7 and 24.7 percent obtained for the nonplanar and planar deposits were improved to 1.07 and 1.80 percent, respectively.
Date: July 1, 1980
Creator: Hale, G.J.
Partner: UNT Libraries Government Documents Department

Stress relaxation of cellular silicone material

Description: Stress relaxation information for cellular silicone materials formed with urea leachable filler is being gathered. Two types of polymers are used in the test: equilibrium type (random copolymer) and condensation type (block copolymer). Each of these was compounded to provide finished materials with nominal apparent densities of 0.34 and 0.52 g/cm/sup 3/. Three sample variations of 1.17, 1.52, and 2.54 mm nominal thickness were prepared from the lower density product, and two sample variations higher density product. Each of the material/thickness combinations was compressed to nominal compressions of 20 and 40% with nine replicates at each condition. A compression fixture for aging is used to maintain a specific compression on the cellular sample at room temperature, and a test machine is used to acquire the load data. The load was recorded at initial assembly and at selected times thereafter. A total of 180 specimens are in test, 90 equilibrium type material samples that have been stored 4 years and 90 condensation type material samples that have been stored for 3 years. Each condition for each material type has nine replicates. Of these nine samples, two are 3 year controls, two more are 10 year controls, and five are tested regularly. Current data supports the statement that the time dependent loss of load bearing properties is approximately log-linear, with the major differences found to be between the material types and the two densities of each material type. Extrapolation indicates that at the end of the planned 10-year study, the load retention of all samples will be between 58 and 68% of original; the condensation type material is expected to be superior.
Date: May 1, 1980
Creator: Schneider, J.W.
Partner: UNT Libraries Government Documents Department

Capacitance of edge plane of pyrolytic graphite in acetonitrile solutions

Description: The capacitance of the edge plane of pyrolytic graphite electrodes, in acetonitrile solutions, is measured by recording the current response to an applied triangular voltage sweep; TVS, and then fitting the current response with an appropriate function, (via a set of adjustable parameters). The pretreatment of the electrodes, the supporting electrolyte concentration used, and the frequency of the input TVS, were all found to affect the measured capacitance. In these experiments, a background current was also seen and the shape of the current output for the TVS; the charging/discharging curve, is shown to correlate with the magnitude of this background current. In addition, the size of the background current was found to have some dependence on the type of electrode pretreatment procedure used. 60 refs., 49 figs., 3 tabs.
Date: May 1, 1991
Creator: Minick, S.K. & Ishida, Takanobu.
Partner: UNT Libraries Government Documents Department

Non-ammonium reduced nitrogen species in atmospheric aerosol particles

Description: The traditional belief that ambient aerosol particles contain nitrogen predominantly in the form of inorganic ionic species such as NH/sub 4//sup +/ and NO/sub 3//sup -/ was challenged about 10 years ago by results from x-ray photoelectron spectroscopic analysis (ESCA) of California aerosol particles. A significant fraction (approx. 50%) of the reduced nitrogen was observed to have an oxidation state more reduced than ammonium, characteristic of organic nitrogen species. We have used a recently developed thermal evolved gas analysis method (NO/sub x/) in conjunction with ESCA to confirm the existence of these species in aerosol particles collected in both the United States and Europe. The agreement of EGA and ESCA analyses indicates that these species are found not only on the surface but also throughout the particles. 9 references, 6 figures.
Date: August 1, 1983
Creator: Dod, R.L.; Gundel, L.A.; Benner, W.H. & Novakov, T.
Partner: UNT Libraries Government Documents Department

Visualization of drug-nucleic acid interactions at atomic resolution. IV. Structure of an aminoacridine/dinucleoside monophosphate crystalline complex, 9-aminoacridine: 5-iodocytidylyl(3'-5')guanosine

Description: 9-Aminoacridine forms a crystalline complex with the dinucleoside monophosphate, 5-iodocytidylyl(3'-5')guanosine (iodoCpG). These crystals are monoclinic, space group P2/sub 1/, with a = 13.98 A, b = 30.58 A, c = 22.47 A and ..beta.. = 113.9. The structure has been solved to atomic resolution by Patterson and Fourier methods, and refined by a combination of Fourier and sum function Fourier methods. The asymmetric unit contains four 9-aminoacridine molecules, four iodoCpG molecules and 21 water molecules, a total of 245 atoms. 9-Aminoacridine demonstrates two different intercalative binding modes and, along with these, two slightly different intercalative geometries in this model system. The first of these is very nearly symmetric, the 9-amino- group lying in the narrow groove of the intercalated base-paired nucleotide structure. The second shows grossly asymmetric binding to the dinucleotide, the 9-amino- group lying in the wide groove of the structure. Associated with these two different intercalative binding modes is a difference in geometries in the structures. Although both structures demonstrate C3' endo (3'-5') C2' endo mixed sugar puckering patterns, with corresponding twist angles between base-pairs of about 10/sup 0/, they differ in the magnitude of the helical screw axis dislocation accompanying intercalation. In the pseudosymmetric intercalative structure, this value is about +0.5 A, whereas in the asymmetric intercalative structure this value is about +2.7 A. These conformational differences can be best described as a sliding of base-pairs on the intercalated acridine molecule.
Date: January 1, 1979
Creator: Sakore, T.D.; Reddy, B.S. & Sobell, H.M.
Partner: UNT Libraries Government Documents Department

Visualization of drug-nucleic acid interactions at atomic resolution. VI. Structure of two drug/ dinucleoside monophosphate crystalline complexes, ellipticine: 5-iodocytidylyl(3'-5')guanosine and 3,5,6,8-tetramethyl-n-methyl phenanthrolinium: 5-iodocytidylyl(3'-5')guanosine

Description: Ellipticine and 3,5,6,8-tetramethyl-N-methyl phenanthrolinium (TMP) form complexes with the dinucleoside monophosphate, 5-iodocytidylyl(3'-5')guanosine (iodoCpG). These crystals are isomorphous: ellipticine-iodoCpG crystals are monoclinic, space group P2/sub 1/, with a = 13.88 A, b = 19.11 A, c = 21.42 A, ..beta.. = 105.4; TMP-iodoCpG crystals are monoclinic, space group P2/sub 1/, with a = 13.99 A, b = 19.12 A, c = 21.31 A, ..beta.. = 104.9. Both structures have been solved to atomic resolution by Patterson and Fourier methods, and refined by full matrix least squares. The asymmetric unit in the ellipticine-iodoCpG structure contains two ellipticine molecules, two iodoCpG molecules, 16 water molecules and 2 methanol molecules, a total of 140 atoms, whereas, in the tetramethyl-N-methyl phenanthrolinium-iodoCpG complex, the asymmetric unit contains two TMP molecules, two iodoCpG molecules, 17 water molecules and 2 methanol molecules, a total of 141 atoms. In both structures, the two iodoCpG molecules are hydrogen bonded together by guanine-cytosine Watson--Crick base-pairing. Adjacent base-pairs within this paired iodoCpG structure are separated by about 6.7 A; this separation results from intercalative binding by one ellipticine (of TMP) molecule and stacking by the other ellipticine (or TMP) molecule above or below the base-pairs. Base-pairs within the paired nucleotide units are related by a twist of 10 to 12/sup 0/. The stereochemistry observed in these model drug-nucleic acid intercalative complexes is almost identical to that observed in the ethidium-iodoUpA and iodoCpG complexesdetermined previously. This stereochemistry is also very similar to that observed in the 9-amino-acridine-iodoCpG and acridine orange-iodoCpG complexes.
Date: January 1, 1979
Creator: Jain, S.C.; Bhandary, K.K. & Sobell, H.M.
Partner: UNT Libraries Government Documents Department

Development of electrolysis-cell separator for 125/sup 0/C operation. Advanced alkaline electrolysis cell development. Final report

Description: This report contains the findings of a seven-month contracted effort. The major technical task involved a 125/sup 0/C operating temperature test of the 20 v/o polybenzimidazole (PBI) - 80 v/o potassium titanate (K/sub 2/TiO/sub 3/) separator in combination with the nickel-molybdenum cathode electrocatalyst system dubbed the C-AN cathode using the ARIES test system which was developed previously. The test of the PBI-K/sub 2/TiO/sub 3/ separator was only partially successful. The anticipated 1.85 (75/sup 0/C) and 1.75 volt per cell (100/sup 0/C) input requirement at 550 ma/cm/sup 2/ were surpassed slightly. The test module operated stably for about 550 hr. Although there were some mechanical difficulties with the ARIES test unit, testing at 125/sup 0/C proceeded from 745 hr on test until the test was terminated at 2318 operating hours to allow diagnostic disassembly. The input voltage degraded to a value of 1.82 volt per cell at 125/sup 0/C which is unacceptable. Diagnostic disassembly showed the PBI portion of the separator was no longer present. PBI had been shown to be stable in 123/sup 0/C, 45 w/o KOH solutions in a 1000-hr test. The attack is suggested to be attributable to a peroxide or perchlorate type oxidizer which would be unique to the electrolysis mode and probably not present in alkaline fuel cell applications. Recommendations for further testing include an evaluation of the chemical compatibility of PBI with alkaline/oxidizer solutions and endurance testing the C-AN cathode with new improved anode structures at 125/sup 0/C using asbestos separators in combination with a silicate saturated KOH electrolyte. Demonstration of the stability of this 1.65 volt per cell (90% voltage efficiency) technology at 500 ma/cm/sup 2/ will document an inexpensive and intelligent hydrogen production process which will satisfy the needs of the United States in the 1990s.
Date: March 1, 1983
Creator: Murray, J N
Partner: UNT Libraries Government Documents Department

Improved synthesis and properties of 3,6-diamino-1,2,4,5-tetrazine and 3,6-dihydrazino-1,2,4,5-tetrazine

Description: The chemical preparation of: (a) 3,6-diamino-1,2,4,5-tetrazine and (b) 3,6-dihydrazino-1,2,4,5-tetrazine is described. The explosive performance of the compounds was calculated with the BKW code. 3 refs., 2 tabs.
Date: January 1, 1989
Creator: Coburn, M.D.; Ott, D.G.; Stine, J.R. & Stinecipher, M.M. (Los Alamos National Lab., NM (USA))
Partner: UNT Libraries Government Documents Department

Oxidation of heterocyclic nitrogen yields to nitroheterocycles. [Nitrofurazans]

Description: In the process of finding new routes to synthesize nitrofurazans the investigators compared the oxidation of a sulfilimide and a phosphine imine derived from 3-amino-4-(chlorophenyl)furazan (1). The sulfilimine, 3-(4-chlorophenyl)-4-dimethyl-sulfiliminofurazan (2), was prepared by treating 1 with dimethyl sulfide ditriflate. Oxidation of 1 with peroxytrifluoroacetic acid (ptfa) in dichloromethane gave a mixture that was chromatographed to give 3-(4-chlorophenyl)-4- nitro-furazan (5) in 11% yield and azoxy(4-chlorophenylfurazan) (6) in 32% yield. Under the same conditions, 2 gave a 96% yield of 5 with no trace of 6. Oxidation of diaminofurazan (7) with ptfa gives 3-amino-4-nitrofurazan (8), which was converted to the sulfilimine. Treatment of the sulfilimine with anhydrous ptfa in dichloromethane gave a solution that contained dimethyl sulfone according to /sup 13/C-NMR analysis, but no nitrocarbon could be detected. However, the /sup 14/N-NMR spectrum contained a very sharp singlet with a width at half-height of 19 Hz and a chemical shift almost identical to that of 5. Thus, it appears that we may have formed dinitrofurazan in solution, but we have not been able to isolate it in pure form as yet. 10 refs., 4 figs.
Date: January 1, 1985
Creator: Coburn, M.D.
Partner: UNT Libraries Government Documents Department

In-situ study of the chemically driven flow fields in initiating homogeneous and heterogeneous nitromethane explosives

Description: Electromagnetic gauging has been used to make in-situ measurements of particle velocity and impulse at five Lagrangian positions in nitromethane (NM) during gas-gun-driven, shock-to-detonation experiments. Homogeneous initiation experiments were conducted using NM that was chemically sensitized (using an organic base) and heterogeneous initiation experiments were done with physically sensitized NM (using silica particles). In the homogeneous initiation experiments, some of the features we observed are consistent with the classical homogeneous initiation model, however, our measurements show that the superdetonation does not form immediately after an induction time. Considerably behind the initial shock, reaction causes a wave to build up over a discernible length and this wave evolves into a superdetonation which catches the initial shock. In the heterogeneous initiation experiments, the waveforms indicated that wave growth occurs primarily in the shock front, similar to earlier observations in other heterogeneous explosives. 21 refs., 8 figs., 3 tabs.
Date: January 1, 1989
Creator: Sheffield, S.A.; Engelke, R. & Alcon, R.R.
Partner: UNT Libraries Government Documents Department

Sensitivity relationships in energetic materials

Description: In searching for new explosives one is most concerned with performance (detonation velocity and pressure), thermal properties, and sensitivity. Whether a new candidate explosive is ultimately widely used may well be determined by other factors, such as cost, toxicity, melting point, etc., but the initial research effort is guided by the trinity of performance, thermal stability, and sensitivity. This presents a difficult multifactoral problem in assessing the various molecular properties that contribute to each of these principal selection criteria. For instance, detonation velocity is affected by density, elemental composition, and heat of formation. These factors must be varied together in such a way as to maximize the combined effect on performance. We have shown a relationship between impact and shock sensitivity and illustrated how a sensitivity index based on oxygen balance can be used to estimate sensitivity in closely related series of molecules. It is shown that the critical temperature of an explosive calculated by the Frank-Kamenetskii equation correlated fairly well with the shock sensitivity of the material. This supports the idea that the shock or impact initiation of an explosive is primarily a thermal event and not dominated by pressure driven chemistry. The concept of the ''trigger linkage'' in explosives is discussed and it is pointed out that insensitive explosives will require early chemistry that is thermomechanically neutral or endothermic and leads to the build-up of later strongly exothermic chemistry.
Date: January 1, 1989
Creator: Storm, C.B.; Stine, J.R. & Kramer, J.F.
Partner: UNT Libraries Government Documents Department

Vibrational spectroscopic investigations of shock-compressed liquid nitrogen and shock-compressed liquid nitromethane

Description: Vibrational spectra of liquid nitrogen and liquid nitromethane shock compressed to several high pressure/high temperature states were recorded using single-pulse multiplex coherent anti-Stokes Raman scattering. Vibrational frequencies were extracted from the data by computer spectral simulation techniques. Vibrational frequencies of liquid nitrogen were found to increase monotonically up to /approx/17.5 GPa single shock and /approx/30 GPa double shock and then to decrease with further increases in pressure. The consequence of the decrease in vibrational frequency on the Grueneisen mode gamma and its effect on the N/sub 2/ equation-of-state is discussed. A model is developed that includes the thermally-excited vibrational state transitions in the synthesized spectral fits of the nitromethane CARS data. The adequacy of the model for interpretation of CARS spectra in both ambient and shock-compressed nitromethane is discussed. 42 refs., 5 figs., 1 tab.
Date: January 1, 1989
Creator: Moore, D.S. & Schmidt, S.C.
Partner: UNT Libraries Government Documents Department

Heat of detonation, the cylinder test, and performance munitions

Description: Heats of detonation of CHNO explosives correlate well with copper cylinder test expansion data. The detonation products/calorimetry data can be used to estimate performance in the cylinder test, in munitions, and for new molecules or mixtures of explosives before these are made. Confidence in the accuracy of the performance estimates is presently limited by large deviations of a few materials from the regression predictions; but these same deviations, as in the insensitive explosive DINGU and the low carbon systems, appear to be sources of information useful for detonation and explosives research. The performance correlations are functions more of the detonation products and thermochemical energy than they are of the familiar parameters of detonation pressure and velocity, and the predictions are closer to a regression line on average than are those provided by CJ calculations. The prediction computations are simple but the measurements (detonation calorimetry/products and cylinder experiments) are not. 17 refs., 5 tabs.
Date: January 1, 1989
Creator: Akst, I.B.
Partner: UNT Libraries Government Documents Department

Electrophilic metal alkyl chemistry in new ligand environments

Description: Methods have been worked out for efficient synthesis of various N[sub 4][sup 2[minus]] macrocyclic ligands, neutral group 4 metal (e.g., Zr) (N[sub 4])MR[sub 2] complexes, and cationic mono-alkyl (N[sub 4])M(R)[sup +] species. Intital indications are that the latter will be highly reactive in base-free form. Objective is to develop new types of electrophilic metal alkyl complexes for study of olefin polymerization and C-H activation catalysis.
Date: January 1, 1992
Creator: Jordan, R.F.
Partner: UNT Libraries Government Documents Department