| 1. |
- Carlsson, F, et al.
(författare)
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Protein-polyelectrolyte cluster formation and redissolution: A Monte Carlo study
- 2003
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Ingår i: Journal of The American Ceramic Society. - : American Chemical Society (ACS). - 0002-7820 .- 1551-2916. ; 125:10, s. 3140-9
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Tidskriftsartikel (refereegranskat)abstract
- Aqueous solutions of proteins and oppositely charged polyelectrolytes were studied at different polyelectrolyte chain length, ionic strength, and protein-protein interaction potential as a function of the polyelectrolyte concentration. One of the protein models used represented lysozyme in aqueous environment. The model systems were solved by Monte Carlo simulations, and their properties were analyzed in terms of radial distribution functions, structure factors, and cluster composition probabilities. In the system with the strongest electrostatic protein-polyelectrolyte interaction the largest clusters were formed near or at equivalent amount of net protein charge and polyelectrolyte charge, whereas in excess of polyelectrolyte a redissolution appeared. Shorter polyelectrolyte chains and increased ionic strength lead to weaker cluster formation. An inclusion of nonelectrostatic protein-protein attraction promoted the protein-polyelectrolyte cluster formation.
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| 2. |
- Halthur, Tobias, et al.
(författare)
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Stability of Polypeptide Multilayers As Studied by in Situ Ellipsometry : Effects of Drying and Post-Buildup Changes in Temperature and pH
- 2004
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 126, s. 17009-17015
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Tidskriftsartikel (refereegranskat)abstract
- Polyelectrolyte multilayers (PEM) of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) with an initial layer of polyethyleneimine (PEI) were built on silica and titanium surfaces using the layer-by-layer (LbL) technique. The stability of the film during drying/rewetting, temperature cycles, and pH shifts was studied in situ by means of ellipsometry. The film thickness was found to decrease significantly (approximately 70%) upon drying, but the original film thickness was regained upon rewetting, and the buildup could be continued. The thickness in the dry state was found to be extremely sensitive to ambient humidity, needing several hours to equilibrate. Changes in temperature and pH were also found to influence the multilayer thickness, leading to swelling and deswelling of as much as 8% and 10-20% respectively. The film does not necessarily regain its original thickness as the pH is shifted back, but instead shows clear signs of hysteresis.
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| 3. |
- Tyrode, Eric, et al.
(författare)
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Adsorption of CTAB on hydrophilic silica studied by linear and nonlinear optical spectroscopy
- 2008
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Ingår i: Journal of The American Ceramic Society. - : American Chemical Society. - 0002-7820 .- 1551-2916 .- 0002-7863 .- 1520-5126. ; 130:51, s. 17434–17445-
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Tidskriftsartikel (refereegranskat)abstract
- Vibrational sum-frequency spectroscopy (SFS) and total internal reflection Raman scattering (TIR Raman) have been used to study the adsorption of hexadecyltrimethylammonium bromide (CTAB) to hydrophilic silica. These two complementary techniques permit the determination of the adsorbed amount with a sensitivity of 1% of the maximum surface coverage, changes in the average tilt of the adsorbed molecules, the presence of asymmetric aggregates in the adsorbed film, and the structure and orientation of the water molecules in the interfacial region. The TIR Raman spectra show a monotonic increase with CTAB concentration with no measurable changes in the relative intensities of the different polarization combinations probed, implying that no significant changes occur in the conformational order of the hydrocarbon chain. In the sum-frequency (SF) spectra, no detectable peaks from the surfactant headgroup and hydrophobic chain were observed at any surface coverage. Major changes are observed in the water bands of the SF spectra, as the originally negatively charged silica surface becomes positively charged with an increase in the adsorbed amount, inducing a change in the polar orientation of the water molecules near the surface. The detection limits for hydrocarbons chains in the SF spectra were estimated by comparison with the SF spectrum of a disordered octadecyltrichlorosilane monolayer. The simulations demonstrate that the asymmetry in the adsorbed CTAB layer at any concentration is less than 5% of a monolayer. The results obtained pose severe constraints on the possible structural models, in particular at concentrations below the critical micellar concentration where information is scarce. The formation of hemimicelles, monolayers and other asymmetric aggregates is ruled out, with centrosymmetric aggregates forming from early on in the adsorption process.
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| 4. |
- Tyrode, Eric, et al.
(författare)
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Hydration State of Non-ionic Surfactant Monolayers at the Liquid/Vapor Interface : Structure Determination by Vibrational Sum Frequency Spectroscopy
- 2005
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 127, s. 16848-16859
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Tidskriftsartikel (refereegranskat)abstract
- The OH stretching region of water molecules in the vicinity of nonionic surfactant monolayers has been investigated using vibrational sum frequency spectroscopy (VSFS) under the polarization combinations ssp, ppp, and sps. The surface sensitivity of the VSFS technique has allowed targeting the few water molecules present at the surface with a net orientation and, in particular, the hydration shell around alcohol, sugar, and poly(ethylene oxide) headgroups. Dramatic differences in the hydration shell of the uncharged headgroups were observed, both in comparison to each another and in comparison to the pure water surface. The water molecules around the rigid glucoside and maltoside sugar rings were found to form strong hydrogen bonds, similar to those observed in tetrahedrally coordinated water in ice. In the case of the poly(ethylene oxide) surfactant monolayer a significant ordering of both strongly and weakly hydrogen bonded water was observed. Moreover, a band common to all the surfactants studied, clearly detected at relatively high frequencies in the polarization combinations ppp and sps, was assigned to water species located in proximity to the surfactant hydrocarbon tail phase, with both hydrogen atoms free from hydrogen bonds. An orientational analysis provided additional information on the water species responsible for this band.
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| 5. |
- Ikoma, T., et al.
(författare)
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Protein adsorption on hydroxyapatite nanosensors with different crystal sizes studied in situ by a quartz crystal microbalance with the dissipation method
- 2009
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Ingår i: Journal of the American Ceramic Society. - : Wiley. - 0002-7820 .- 1551-2916. ; 92:5, s. 1125-1128
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Tidskriftsartikel (refereegranskat)abstract
- Hydroxyapatite (HAp) nanocrystals with different crystal sizes were deposited by the electrophoretic deposition method on the gold surface of a quartz crystal microbalance with a dissipation probe. The nanosensors formed this way were used to elucidate the adsorption mechanism of proteins with a similar pI value. The crystal sizes and the area of the a-plane affected only the adsorption amount of human serum albumin, but not that of bovine plasma fibrinogen. The viscoelastic property, Delta D/Delta f, of each absorbed layer on the nanosensors was almost constant. The protein adsorption mechanism can be explained as follows: the dissociated carboxyl groups (negative charge) of albumin were interacted with calcium ions and the hydrated amine groups (positive charge) at the alpha C domain of fibrinogen were with phosphate ions on the HAp surface.
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| 6. |
- Weidow, Jonathan, 1980, et al.
(författare)
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Transition Metal Solubilities in WC in Cemented Carbide Materials
- 2011
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Ingår i: Journal of the American Ceramic Society. - : Wiley. - 0002-7820 .- 1551-2916. ; 94:2, s. 605-610
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Tidskriftsartikel (refereegranskat)abstract
- Solubilities of different transition metals in WC in cemented carbides at around 1700 K were determined with atom probe tomography. Ta had the highest solubility, followed by Nb, Cr, and V, all with atom fractions in the 10−3 range. Ti and Mn showed lower, yet detectable, solubilities in the 10−6 or 10−5 range. Zr and Co solubilities were too low to be measured. The results were compared with the theoretically calculated solubilities using density functional theory. These calculations predicted that Ta, Nb, V, and Cr should have the highest solubility, all in the 10−4 or 10−3 range. Ti was predicted to have a lower solubility (10−5 range) and Co, Hf, and Zr even lower (10−8 or 10−7 range).
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| 7. |
- Ahmed, Istaq, 1972, et al.
(författare)
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Crystal structure and proton conductivity of BaZr0.9Sc0
- 2008
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Ingår i: Journal of the American Ceramic Society. - : Wiley. - 0002-7820 .- 1551-2916. ; 91:9, s. 3039-3044
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Tidskriftsartikel (refereegranskat)abstract
- Solid-state sintering has been used to prepare the perovskite BaZr0.9Sc0.1O3-delta. Analysis of X-ray powder diffraction data shows that an increase of the unit cell parameter, a, was observed after deuteration. Rietveld analysis of room-temperature neutron powder diffraction data confirmed cubic symmetry (space group Pm-3m). Dynamic thermogravimetric analysis indicates that the hydration process occurs below 335 degrees C and approximately 58% of the theoretical number of protonic defects can be filled. The presence of protons/deutrons is seen from the strong O-H/O-D stretch band in the infrared spectrum of the hydrated/deuterated samples. The proton conductivity of a prehydrated sample was investigated under dry and wet Ar atmospheres
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| 8. |
- Akhtar, Farid, et al.
(författare)
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Colloidal Processing and Thermal Treatment of Binderless Hierarchically Porous Zeolite 13X Monoliths for CO2 Capture
- 2011
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Ingår i: Journal of The American Ceramic Society. - : Wiley. - 0002-7820 .- 1551-2916. ; 94:1, s. 199-205
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Tidskriftsartikel (refereegranskat)abstract
- Adsorbents with high surface area are potential candidates forefficient postcombustion CO2 capture. Binderless zeolite 13Xmonoliths with a hierarchical porosity and high CO2 uptakehave been produced by slip casting followed by pressurelessthermal treatment. The zeolite powder displayed an isoelectricpoint at pH 4.7 and electrostatically stabilized suspensions couldbe prepared at alkaline pH. The volume fraction-dependentsteady shear viscosity could be fitted to a modified Krieger–Dougherty model with a maximum volume fraction of 0.66. Thenarrow temperature range where monoliths could be producedwithout significant loss of the microporous surface area wasidentified and related to the phase behavior of the 13X material.Slip casting of concentrated suspensions followed by thermaltreatment of the powder bodies at a temperature of 8001Cwithout holding time resulted into strong hierarchically porouszeolite 13X monolith that displayed a CO2 uptake larger than29 wt%.
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| 9. |
- Akhtar, Farid, et al.
(författare)
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Hierarchically Porous Ceramics from Diatomite Powders by Pulsed Current Processing
- 2009
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Ingår i: Journal of The American Ceramic Society. - : Wiley. - 0002-7820 .- 1551-2916. ; 92:2, s. 338-343
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Tidskriftsartikel (refereegranskat)abstract
- Hierarchically porous ceramic monoliths have been fabricated by pulsed current processing (PCP) of diatomite powders. The partial sintering behavior of the porous diatomite powders during PCP or spark plasma sintering was evaluated at temperatures between 600 degrees and 850 degrees C. Scanning electron microscopy and mercury porosimetry measurements showed that the PCP method was able to bond the diatomite powder together into relatively strong monoliths without significantly destroying the internal pores of the diatomite powder at a temperature range of 700 degrees-750 degrees C. Little fusion at the particle contact points occurred at temperatures below 650 degrees C while the powder showed partial melting and collapse of both the interparticle pores and the internal structure at temperatures above 800 degrees C.
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| 10. |
- Ali, Sharafat, 1976-, et al.
(författare)
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Glasses in the Ba–Si–O–N System
- 2011
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Ingår i: Journal of The American Ceramic Society. - : Wiley. - 0002-7820 .- 1551-2916. ; 94:9, s. 2912-2917
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Tidskriftsartikel (refereegranskat)abstract
- The preparation and properties of Ba–Si–O–N glasses arereported. These oxynitride glasses were prepared by meltingmixtures of BaH2, SiO2, and Si3N4 powders in a nitrogenatmosphere at 1550°–1700°C. The glasses were characterized by X-ray powder diffraction, differential thermal analysis, and scanning electron microscopy. Final glass compositions were calculated from analyses obtained by energy dispersive X-ray(EDX) spectroscopy and combustion analysis, for cation and anion compositions, respectively. The glasses were found to behomogenous, translucent gray to opaque black, and consists of N contents of up to 42 equiv% and Ba contents of up to 36 equiv%. Determined glass densities varied between 3.27 and 4.18 g/cm3, and calculated molar volumes varied between1 0.28 and 11.11 cm3/mol. Both density and molar volume increase with Ba content. Glass compactness (0.45–0.49), glasstransition temperature (786°–905°C), and microhardness (7.93–9.56 GPa) were found to increase linearly with N content. There fractive index increased from 1.66 to 1.91 and was found tobe strongly correlated with the amounts of Ba and N.
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