Metastable and transient states of chemical ordering in Fe-V nanocrystalline alloys

Chemical ordering of the disordered alloys Fe0.78V0.22, Fe0.53V0.47, Fe0.39V0.61, and Fe0.37V0.63 was performed by annealing at temperatures from 723 to 973 K. The initial state of chemical disorder was produced by high-energy ball milling, and the evolution of order was measured by neutron diffractometry and by 57Fe Mössbauer spectrometry. The hyperfine magnetic field distributions obtained from the Mössbauer spectra provided quantitative measurements of the number of antisite Fe atoms in the partially ordered alloys. The long-range order parameters in steady state after long annealing times were used as states of metastable equilibrium for a generally successful comparison with the metastable Fe-V phase diagram calculated by Sanchez et al. [Phys. Rev. B 54, 8958 (1996)]. For the metastable equilibrium state of order in Fe0.53V0.47 at low temperatures, the order parameters were smaller than expected. This corresponded to an abundance of antisite atoms, which were not removed effectively by annealing at the lower temperatures

Quantification of Cell Subpopulations, Fractions of Dead Cells and Debris in Cell Suspensions by Laser Diffractometry

Laser diffractometry was employed for size analysis in liver cell and blood cell suspensions to assess its suitability for characterizing cell populations. The method proved sensitive to detect subpopulations in liver cells (bimodal or trimodal distributions) and to quantify their volume fractions. Cell debris and aggregates of cells could also be quantified, dead cell populations recognized by their shift in the mean cell diameter. Laser diffractometry is therefore suitable for determining the quality of cell isolations (e.g. by liver perfusion) or for following alterations in cell populations during culture of cells in suspension. Analysis of human blood allowed differenciations to be made between thrombocytes and other blood cells. No peak separation was obtained for the populations of erythrocytes and granulocytes due to their similarity in size. Monocytes could not be detected due to their extremely low number in the blood indicating the limit of the metho

Recycled powder as filler admixture in cementitious systems : production and characterization

In concrete production, aggregate represents almost 75% of the materials used. The exploitation of natural sources for this purpose also causes an environmental impact, while deposition of wastes from construction industry pollutes soil and water. The feasibility of recycled coarse aggregate used as component of concrete has been amply proved. Fine recycled aggregate is a by-product derived from the processing of recycled coarse aggregate, but there are some technological difficulties for its use in concrete, because of the high water absorption and powder content. The aim of this study is to propose and analyse the alternative use of milled recycled fine aggregate as mineral admixture. For this purpose, dry recycled fine aggregate was processed in a laboratory ball mill for cement, with the aid of cylpebs. Grinding was carried out for 2:00, 2:45 and 3:30 hours, and the sampling of ground recycled fine aggregate (GRFA) was done after each period. For the three grindings periods, the characterization of GFRA was performed for assessing its suitability as mineral filler. Tests included determinations of contents of material < 45 μm and < 75 μm by wet sieving, density, particle size distribution by laser diffraction, chemical composition and Blaine specific surface. Additionally, water demand for standard consistency paste with ordinary Portland cement (OPC) was prepared as reference, and also determined for pastes with replacement of 15% and 30% of cement by GRFA for each grinding period. Also, setting times and strength were measured. Results showed limited filler effect from GRFA when incorporated in cementitious materials, with the consideration of the grinding period as an important factor. Thus, further feasibility studies are necessary in order to investigate different potential applications of this ground material

Melem (2,5,8-Triamino-tri-s-triazine), an Important Intermediate during Condensation of Melamine Rings to Graphitic Carbon Nitride: Synthesis, Structure Determination by X-ray Powder Diffractometry, Solid-State NMR, and Theoretical Studies

Single-phase melem (2,5,8-triamino-tri-s-triazine) C6N7(NH2)3 was obtained as a crystalline powder by thermal treatment of different less condensed C−N−H compounds (e.g., melamine C3N3(NH2)3, dicyandiamide H4C2N4, ammonium dicyanamide NH4[N(CN)2], or cyanamide H2CN2, respectively) at temperatures up to 450°C in sealed glass ampules. The crystal structure was determined ab initio by X-ray powder diffractometry (Cu Kα1:  P21/c (No. 14), a = 739.92(1) pm, b = 865.28(3) pm, c = 1338.16(4) pm, β = 99.912(2)°, and Z = 4). In the solid, melem consists of nearly planar C6N7(NH2)3 molecules which are arranged into parallel layers with an interplanar distance of 327 pm. Detailed 13C and 15N MAS NMR investigations were performed. The presence of the triamino form instead of other possible tautomers was confirmed by a CPPI (cross-polarization combined with polarization inversion) experiment. Furthermore, the compound was characterized using mass spectrometry, vibrational (IR, Raman), and photoluminescence spectroscopy. The structural and vibrational properties of molecular melem were theoretically studied on both the B3LYP and the MP2 level. A structural optimization in the extended state was performed employing density functional methods utilizing LDA and GGA. A good agreement was found between the observed and calculated structural parameters and also for the vibrational frequencies of melem. According to temperature-dependent X-ray powder diffractometry investigations above 560°C, melem transforms into a graphite-like C−N material

Glucosamine HCl-based solid dispersions to enhance the biopharmaceutical properties of acyclovir

The objective of the work presented here was to assess the feasibility of using glucosamine HCl as a solid-dispersion (SD) carrier to enhance the biopharmaceutical properties of a BCS class III/IV drug, acyclovir (ACV). The solid-dispersions of acyclovir and glucosamine HCl were prepared by an ethanol-based solvent evaporation method. The prepared formulations characterized by photomicroscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transforms infrared spectrophotometry (FTIR), powder x-ray diffractometry (PXRD) and drug content analysis. The functional characterization of ACV-SD was performed by aqueous solubility evaluation, dissolution studies, fasted versus fed state dissolution comparison, ex vivo permeability, and stability studies. Photomicroscopy and SEM analysis showed different surface morphologies for pure ACV, glucosamine HCl and ACV-SD. The physical-chemical characterization studies supported the formation of ACV-SD. A 12-fold enhancement in the aqueous solubility of ACV was observed in the prepared solid dispersions, compared to pure ACV. Results from in vitro dissolution demonstrated a significant increase in the rate and extent of ACV dissolution from the prepared ACV-SD formulations, compared to pure ACV. The rate and extent of ACV permeability across everted rat intestinal membrane were also found to be significantly increased in the ACV-SD formulations. Under fed conditions, the rate and extent of the in vitro dissolution of ACV from the formulation was appreciably greater compared to fasted conditions. Overall, the results from the study suggest the feasibility of utilizing glucosamine HCl as a solid dispersion carrier/excipient for enhancement of biopharmaceutical properties of acyclovir, and similar drugs with low solubility/permeability characteristics

Study of non-linear viscoelastic behavior of the human red blood cell

The non-linear behavior of human erythrocytes subjected to shear stress was analyzed using data series from the Erythrocyte Rheometer and a theoretical model was developed. Linear behavior was eliminated by means of a slot filter and a sixth order Savisky-Golay filter was applied to the resulting time series that allows the elimination of any possible white noise in the data. A fast Fourier transform was performed on the processed data, which resulted in a series of frequency dominant peaks. Results suggest the presence of a non-linear quadratic term in the Kelvin-Voigt phenomenological model. The correlation dimension studied through recurrence quantification analysis gave C2=2.58. Results suggest that the underlying dynamics is the same in each RBC sample corresponding to healthy donors

Chemical Environment Selectivity in Mössbauer Diffraction from 57Fe3Al

Mössbauer diffraction was used to measure different autocorrelation functions for 57Fe atoms in different chemical environments. The sample was polycrystalline 57Fe3Al with the ordered DO3 structure. Diffraction peaks from a fcc structure with a doubled unit cell were detected when the incident radiation was tuned to the Mössbauer resonance of the Wyckoff 4(b) Fe site, but not for tuning to the 8(c) site, thereby distinguishing the spatial arrangements of these two Fe sites

Two-phase coexistence in Fe–Ni alloys synthesized by ball milling

We used mechanical alloying with a Spex 8000 mixer/mill to synthesize a series of Fe100–xNix alloys from x=0 to x=49. The Spex mill was modified so that it could also operate at a reduced milling intensity, and we compared the alloys synthesized after long times with the normal and reduced milling intensities. X-ray diffractometry and Mössbauer spectrometry were used to measure the volume fractions of the bcc and fcc phases in the alloys, and to determine the chemical compositions of the individual phases. We found that the composition ranges of the bcc and fcc single phase regions were extended well beyond their equilibrium ranges. At the higher milling intensity, we found that the bcc phase was destabilized with respect to the fcc phase, and the two-phase region shifted to lower Ni concentrations. For those alloys with coexisting bcc and fcc phases, we present evidence that the chemical compositions of the two phases are nearly the same. We explain the destabilization of the bcc with milling intensity as originating with a higher defect density in the bcc alloys than in the fcc alloys. We argue that this defect density is not homogeneous throughout the alloy, however, and the distribution of defect enthalpies can explain the two-phase coexistence in the as-milled alloys

Chromium (III) complexes and their relationship to the glucose tolerance factor : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Chemistry at Massey University

Two forms of the dinicotinate complex Cr(nic)2(H2O)3OH were formed which were yellow and blue, respectively. For the yellow form the nicotinic acid ligands were coordinated via the pyridine ring nitrogen atom but this complex was biologically inactive, while for the blue form nicotinic acid was coordinated via the carboxylate group and this compound was biologically active. Only Cr(III) formed a stable carboxylate coordinated dinicotinate complex. No stable complexes were formed with Fe(III) and Mn(III) due to significant olation, even at acidic pH's, and the complexes of nicotinic acid with Cr(II), Mn(II), Co(II) and Ni(II) were all pyridine nitrogen atom coordinated and biologically inactive. Several chromium (III) complexes with amino acids possessed biological activity also, and these included the α -carboxylate coordinated species Cr(gly)n(H2O)3+6-nand Cr(glu)n(H2O)3+6-n, the bidentate coordinated Cr(gln)2(H2O)2+ complex, and the NH4OH- eluted complexes obtained when Cr(gly)2(H2O)2+ and Cr(glu)2(H2O) 2+, but not Cr(cys) 2(H2O) 2+, were eluted from a DOWEX 50W-X12 cation-exchange column (loss of the α-amino coordination was postulated to have occurred). The biologically active mixed ligand complex postulated as Cr2(nic) 4(gly) 2(OH) 2 was prepared and found to be stable at neutral pH as a result of coordination of the glycine ligands. The activity of the chromium (III) complexes in the yeast fermentation assay suggested that similar effects would be found in mammalian systems. The yeast assay system was found to be a simple, quick and reproducible method of determining biological activity. All of the active chromium (III) complexes prepared were found to be similar, in structure, to the diguanide compound 1,4-diguanidinobutane which is known to lower blood sugar levels in mammals. This similarity in structure suggested a similar function might be possessed by the complexes reported in this thesi