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•n-Pentane cracking studied over MFI in a wide range of acid site concentrations.•Tetrahedrally coordinated EFAl in proximity to BAS is responsible for higher rates.•Equal turnover ...frequency per BAS was found for samples free of EFAl.•Post-synthetic chemical modification enables tuning of catalytic activity.
The impact of the zeolite Brønsted and Lewis acid site concentration on the catalytic cracking of alkanes was explored using n-pentane and H-ZSM-5 as examples. Rates normalized to strong Brønsted acid sites (i.e., the turnover frequencies, TOF) showed that the two samples with the highest Al content had much higher TOF than all other samples. This difference has been unequivocally linked to the presence of extra-lattice alumina. Post-treatment of the zeolites with ammonium hexafluorosilicate and static calcination was used to vary the concentration of extra-lattice alumina. After extraction of extra-lattice alumina from the samples with high TOF, all TOFs were identical. IR spectra of adsorbed pyridine and NH3, coupled with 27Al MAS NMR, showed that the overall enhanced activity is associated with tetrahedrally coordinated extra-lattice alumina in close proximity to strong Brønsted acid sites. The TOF of these sites is approximately 40-times higher than the TOF on normal Brønsted acid sites.
We have measured the temperature-dependent thermal conductivity kappa(T) of individual multiwall boron nitride nanotubes using a microfabricated test fixture that allows direct transmission electron ...microscopy characterization of the tube being measured. kappa(T) is exceptionally sensitive to isotopic substitution, with a 50% enhancement in kappa(T) resulting for boron nitride nanotubes with 99.5% 11B. For isotopically pure boron nitride nanotubes, kappa rivals that of carbon nanotubes of similar diameter.
The surface of boron nitride nanotubes (BNNTs) has been functionalized with amine groups via ammonia plasma irradiation. The functionalized tubes were characterized by Fourier transform infrared ...spectroscopy and electron energy loss spectroscopy. Amine-functionalized BNNTs were found to be highly dispersible in chloroform, and are predicted to form the basis of a new class of chemically reactive nanostructures.
OBJECTIVES
We herein report on development of a composite (synthetic and biological) tracheal scaffold with vascularized autologous connective tissue in the omentum, followed by in situ tissue ...engineering of the composite scaffold with the pedicled omentum. In this preliminary report, we focus on development and evaluation of the vascularized autologous connective tissue in the omentum.
METHODS
In animal experiment 1, a polypropylene framework as a synthetic component was placed in the omental sac for 3 weeks and another was placed in the pouch of Douglas as a control in five beagle dogs. In animal experiment 2, a polypropylene framework placed in the omental sac for 3 weeks was compared with a polypropylene framework coated with porcine atelocollagen, which was also placed in the omental sac in another five dogs, to investigate whether the coating of porcine atelocollagen contributes to development of more vascularized connective tissue. Macroscopic, radiological and histological evaluations were performed for developed autologous connective tissue on the frameworks, with a focus on its thickness and capillary vessels.
RESULTS
In animal experiment 1, the polypropylene framework in the omentum developed a composite tracheal scaffold with homogeneous and significantly thicker (2.6 ± 0.5 vs 1.2 ± 0.4 mm, P <0.0001) connective tissue in which more capillary vessels per 10-power field of view (3.5 ± 2.2 vs 0 ± 0, P = 0.015) were identified, compared with the control in the pouch of Douglas. In animal experiment 2, the omentum developed significantly thicker connective tissue on the polypropylene framework coated with porcine atelocollagen (3.6 ± 0.7 vs 2.2 ± 0.4 mm, P <0.0001) in which not significantly more capillary vessels were identified (3.5 ± 2.2 vs 5.0 ± 2.7, P = 0.12), compared with the framework that was not coated.
CONCLUSIONS
Placement of the polypropylene framework in the omental sac resulted in development of homogeneous and vascularized autologous connective tissue on the polypropylene framework for a composite tracheal scaffold. The framework coated with porcine atelocollagen did not show an additional benefit in inducing vascularization. This preliminary report will be followed by the long-term evaluations of in situ tissue engineering of the composite tracheal scaffold.
We have performed a near-edge x-ray absorption fine-structure (NEXAFS) investigation of multi-walled boron nitride nanotubes (BNNTs). We show that the one-dimensionality of BNNTs is clearly evident ...in the B K edge spectrum, while the N K edge spectrum is similar to that of layered hexagonal BN (h-BN). We observe a sharp feature at the σ* onset of the B K edge, which we ascribe to a core exciton state. We also report a comparison with spectra taken after an ammonia plasma treatment, showing that the B K edge becomes indistinguishable from that of h-BN, due to the breaking of the tubular order and the formation of small h-BN clusters.
Left ventricular pseudoaneurysm is a rare complication of myocardial infarction. However, the risk of rupture and heart failure are high, especially in a case of rapidly expanding aneurysm. As for ...left ventricular pseudoaneurysm, the risk of operation is high, and the long-term results are not good. We experienced 2 cases The 1st case was lost due to methicillin-resistant Staphylococcus aureus (MRSA) pneumonia The 2nd case is alive and has been free from heart failure for 3 years. The early diagnosis and surgery is necessary for a pseudoaneurysm.
Randomly oriented carbon nanotubes (CNTs) were synthesized directly on SiO2 substrates by thermal chemical vapor deposition (CVD) with C2H4 gas as a carbon source. To control the diameters of the ...carbon nanotubes, Fe--Ni thin films with different thickness from 80 to 320 nm were deposited as catalysts on SiO2 substrates by magnetron sputtering. The diameter of the resultant carbon nanotubes was dependent on the size of the catalyst particles. Moreover, a small catalyst particle permitted carbon nanotube growth. The resultant randomly oriented carbon nanotubes exhibited good field emission properties.
Carbon nanofiber (CNF) films have been successfully grown on Pd-Se, Fe-Ni, and Ni-Cu alloy catalysts at low temperatures by a thermal chemical vapor deposition method. Among these alloy catalysts, ...Ni-Cu alloy catalyst was found to be most suitable for low temperature growth of CNF (400°C). Using Pd-Se and Fe-Ni alloy catalysts, CNFs were grown at the lowest temperature of 500°C. The CNFs grown using Pd-Se catalyst were found to have more defective structure than that obtained with the other catalysts, and exhibited excellent field emission property (threshold field is estimated about 1.1V/mm). It is likely that defects play a role as electron emission sites.
We investigated the mechanism underlying Chiari malformation type I (CM-I) and classified it according to the morphometric analyses of posterior cranial fossa (PCF) and craniocervical junction (CCJ). ...Three independent subtypes of CM-I were confirmed (CM-I types A, B, and C) for 484 cases and 150 normal volunteers by multiple analyses. CM-I type A had normal volume of PCF (VPCF) and occipital bone size. Type B had normal VPCF and small volume of the area surrounding the foramen magnum (VAFM) and occipital bone size. Type C had small VPCF, VAFM, and occipital bone size. Morphometric analyses during craniocervical traction test demonstrated instability of CCJ. Foramen magnum decompression (FMD) was performed in 302 cases. Expansive suboccipital cranioplasty (ESCP) was performed in 102 cases. Craniocervical posterolateral fixation (CCF) was performed for CCJ instability in 70 cases. Both ESCP and FMD showed a high improvement rate of neurological symptoms and signs (84.4%) and a high recovery rate of the Japanese Orthopaedic Association (JOA) score (58.5%). CCF also showed a high recovery rate of the JOA score (69.7%), with successful joint stabilization (84.3%). CM-I type A was associated with other mechanisms that caused ptosis of the brainstem and cerebellum (CCJ instability and traction and pressure dissociation between the intracranial cavity and spinal canal cavity), whereas CM-I types B and C demonstrated underdevelopment of the occipital bone. For CM-I types B and C, PCF decompression should be performed, whereas for small VPCF, ESCP should be performed. CCF for CCJ instability (including CM-I type A) was safe and effective.
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