Unusual Activity Enhancement of NO Conversion over Ag/Al2O3 by Using a Mixed NH3/H2 Reductant Under Lean Conditions

Addition of H₂ to a NO/NH₃/O₂/H₂O feed for selective catalytic reduction of nitrogen oxide over Ag/Al₂O₃ catalysts causes an unusual enhancement of activity, e.g., the marginal activity (<10%) of 1 wt% Ag impregnated on γ-Al₂O₃ or mesoporous Al₂O₃ modifications is boosted to nearly 100% over a broad temperature range from 200 to 550°C at a space velocity of 30,000cm³g^?1h^?1). Contrary, silver on SiO₂ or α-Al₂O₃ shows no improvement of activity in the presence of H₂. The effect is tentatively attributed to a higher percentage of intermediary nano-sized Ag clusters on high-surface area Al₂O₃ in the presence of hydrogen. This promotes oxygen activation and hence NO oxidation to reactive intermediate nitrite species. The required dispersion of Ag cannot be stabilized on SiO₂ or α-Al₂O₃.     

Coating with artificial matrices from collagen and sulfated hyaluronan influences the osseointegration of dental implants

Dental implants are an established therapy for oral rehabilitation. High success rates are achieved in healthy bone, however, these rates decrease in compromised host bone. Coating of dental implants with components of the extracellular matrix is a promising approach to enhance osseointegration in compromised peri-implant bone. Dental titanium implants were coated with an artificial extracellular matrix (aECM) consisting of collagen type I and either one of two regioselectively low sulfated hyaluronan (sHA) derivatives (coll/sHA1Δ6s and coll/sHA1) and compared to commercial pure titanium implants (control). After extraction of the premolar teeth, 36 implants were inserted into the maxilla of 6 miniature pigs (6 implants per maxilla). The healing periods were 4 and 8 weeks, respectively. After animal sacrifice, the samples were evaluated histomorphologically and histomorphometrically. All surface states led to a sufficient implant osseointegration after 4 and 8 weeks. Inflammatory or foreign body reactions could not be observed. After 4 weeks of healing, implants coated with coll/sHA1Δ6s showed the highest bone implant contact (BIC; coll/sHA1Δ6s: 45.4 %; coll/sHA1: 42.2 %; control: 42.3 %). After 8 weeks, a decrease of BIC could be observed for coll/sHA1Δ6s and controls (coll/sHA1Δ6s: 37.3 %; control: 31.7 %). For implants coated with coll/sHA1, the bone implant contact increased (coll/sHA1: 50.8 %). Statistically significant differences could not be observed. Within the limits of the current study, aECM coatings containing low sHA increase peri-implant bone formation around dental implants in maxillary bone compared to controls in the early healing period.     

Non-isothermal NO x storage/release over manganese based traps: mechanistic considerations

Topics in Catalysis - The NO storage properties of MnO x /support materials (5–50 wt% MnO x loading) was experimentally investigated in the presence of O2 and H2O between 50 and...     

Viscosity‐molecular weight relationship for cellulose solutions in either NMMO monohydrate or cuen

The intrinsic viscosities, [η], of nine cellulose samples, with molar masses from 50 × 10³ to 1 390 × 10³ were determined in the solvents NMMO*H₂O (N‐methyl morpholin N‐oxide hydrate) at 80°C and in cuen (copper II‐ethlenediamine) at 25°C. The evaluation of these results with respect to the Kuhn–Mark–Houwink relations shows that the data for NMMO*H₂O fall on the usual straight line in the double logarithmic plots only for M ≤ 158 10³; the corresponding [η]/M relation reads log ([η]/mL g⁻¹) = –1.465 + 0.735 log M. Beyond that molar mass [η] remains almost constant up to M ≈ 10⁶ and increases again thereafter. In contrast to NMMO*H₂O the cellulose solutions in cuen behave normal and the Kuhn–Mark–Houwink relation reads log ([η]/mL g⁻¹) = −1.185 + 0.735 log M. Possible reasons for the dissimilarities of the behavior of cellulose in these two solvents are being discussed. The comparison of three different methods for the determination of [η] from viscosity measurements at different polymer concentrations, c, demonstrates the advantages of plotting the natural logarithm of the relative viscosities as a function of c. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Zeolite-mediated removal of NOx by NH3 from exhaust streams at low temperatures

NH₃ stored on zeolites in the form of NH₄⁺ ions easily reacts with NO to N₂ in the presence of O₂ at temperatures <373 K under dry conditions. Wet conditions require a modification of the catalyst system. It is shown that MnO₂ deposited on the external surface of zeolite Y by precipitation considerably enhances the NO_x conversion by zeolite fixed NH₄⁺ ions in the presence of water at 400–430 K. Particle-size analysis, temperature-programmed reduction, textural characterization, chemical analysis, ESR and XRD gave a subtle picture of the MnO₂ phase structure. The MnO₂ is a non-stoichiometric, amorphous phase that contains minor amounts of Mn²⁺ ions. It loses O₂ upon inert heating up to 873 K, but does not crystallize or sinter. The phase is reducible by H₂ in two stages via intermediate formation of Mn₃O₄. The manufacture of extrudates preserving stored NH₄⁺ ions for NO_x reduction is described. It was found that MnO₂ can oxidize NO by bulk oxygen. This enables the reduction of NO to N₂ by the zeolitic NH₄⁺ ions without gas-phase oxygen for limited time periods. The composite catalyst retains storage capacity for both, oxygen and NH₄⁺ ions despite the presence of moisture and allows short-term reduction of NO without gaseous O₂ or additional reductants. The catalyst is likewise suitable for steady-state DeNO_x operation at higher space velocities if gaseous NH₃ is permanently supplied.     

Effect of biological implant surface coatings on bone formation, applying collagen, proteoglycans, glycosaminoglycans and growth factors

Objectives The aim of the present study was to evaluate six different implant surface coatings with respect to bone formation. Being major structural components of the extracellular matrix, collagen, the non-collagenous components decorin/chondroitin sulphate (CS) and the growth factors TGF-β1/BMP-4 served in different combinations as coatings of experimental titanium implants. Materials and methods Eight miniature pigs received each six implants in the mandible. The implant design showed two circular recesses along the length axis. Three, four, five and six weeks after implant placement, the animals were sacrificed in groups of two. Bone-implant contact (BIC) was evaluated along the outer implant surface and within the recesses. Bone volume was determined by synchrotron radiation micro computed tomography (SRμCT) for one implant of each surface state, 6 weeks after placement. Results At each week of observation, collagen/CS or collagen/CS/BMP-4 coated implants showed the highest BIC of all surface states. This was statistically significant at week five (p = 0.030, p = 0.040) and six (p = 0.025, p = 0.005). SRμCT measurements determined the highest bone volume for a collagen/CS coated implant. Conclusion The results indicate that collagen/CS and collagen/CS/BMP-4 lead to a higher degree of bone formation compared to other ECM components.     

Ethyl Hydroxyethyl Cellulose—A Biocompatible Polymer Carrier in Blood

The biocompatibility of carrier nanomaterials in blood is largely hampered by their activating or inhibiting role on the clotting system, which in many cases prevents safe intravascular application. Here, we characterized an aqueous colloidal ethyl hydroxyethyl cellulose (EHEC) solution and tested its effect on ex vivo clot formation, platelet aggregation, and activation by thromboelastometry, aggregometry, and flow cytometry. We compared the impact of EHEC solution on platelet aggregation with biocompatible materials used in transfusion medicine (the plasma expanders gelatin polysuccinate and hydroxyethyl starch). We demonstrate that the EHEC solution, in contrast to commercial products exhibiting Newtonian flow behavior, resembles the shear-thinning behavior of human blood. Similar to established nanomaterials that are considered biocompatible when added to blood, the EHEC exposure of resting platelets in platelet-rich plasma does not enhance tissue thromboplastin- or ellagic acid-induced blood clotting, or platelet aggregation or activation, as measured by integrin α_IIbβ₃ activation and P-selectin exposure. Furthermore, the addition of EHEC solution to adenosine diphosphate (ADP)-stimulated platelet-rich plasma does not affect the platelet aggregation induced by this agonist. Overall, our results suggest that EHEC may be suitable as a biocompatible carrier material in blood circulation and for applications in flow-dependent diagnostics.     

Non-Isothermal NOx Storage/Release over Manganese Based Traps: Mechanistic Considerations

The NO storage properties of MnO _x /support materials (5–50 wt% MnO _x loading) was experimentally investigated in the presence of O₂ and H₂O between 50 and 700 °C applying a non-isothermal temperature-programmed method. In dependence on MnO _x loading and NO supply, the materials show an intermediate decrease of NO storage capacity between 200 and 300 °C. This effect is caused by decomposition of surface nitrites with release of NO into the gas phase as proved by in situ DRIFT measurement. The interpretation is corroborated by modelling of the underlying adsorption/desorption reaction steps, considering the different thermal stability of nitrite/nitrate surface species.     

Targeted Nanoswitchable Inhibitors of Protein–Protein Interactions Involved in Apoptosis

Progress in drug delivery is hampered by a lack of efficient strategies to target drugs with high specificity and precise spatiotemporal regulation. The remote control of nanoparticles and drugs with light allows regulation of their action site and dosage. Peptide-based drugs are highly specific, non-immunogenic, and can be designed to cross the plasma membrane. In order to combine target specificity and remote control of drug action, here we describe a versatile strategy based on a generalized template to design nanoswitchable peptides that modulate protein–protein interactions upon light activation. This approach is demonstrated to promote photomodulation of two important targets involved in apoptosis (the interactions Bcl-xL–Bak and MDM2–p53), but can be also applied to a large pool of therapeutically relevant protein–protein interactions mediated by α-helical motifs. The template can be adjusted using readily available information about hot spots (residues contributing most to the binding energy) at the protein–protein interface of interest.     

Large Scale Fractionation of Macromolecules

Summary: Access to sufficiently large amounts of material with adequate molecular and chemical uniformity from polydisperse natural products or synthetic materials has been a long‐standing challenge to polymer scientists. We have developed a broadly applicable preparative fractionation method consisting of a special kind of continuous extraction removing the easier soluble components from the initial product. It is rendered possible by the use of spinning nozzles through which a concentrated polymer solution is pressed into a liquid of tailored thermodynamic quality. The initially produced jets of the source phase disintegrate rapidly into minute droplets of typically 50 μm diameter. This efficient subdivision provides the large surfaces and short routs of transport required for successful fractionation. Thus the pronounced kinetic hindrances resulting from the high viscosities of reasonable concentrated polymer solutions can be overcome. We portray the principal features of continuous spin fractionation and present two examples of practical importance.

Functional principle of ‘continuous spin fractionation’ (CSF).