Capturing CO2 by ceria and ceria-zirconia nanomaterials of different origin.

Ceria and ceria-zirconia nanomaterials of different origin were studied in order to elucidate the role of their structural and textural characteristics in controlling the performance towards CO2 capture. Two commercial cerias and two home-prepared samples, CeO2 and CeO2-ZrO2 (75% CeO2) mixed oxide, were investigated. The samples were characterized by a number of analytical techniques including XRD, TEM, N2-adsorption, XPS, H2-TPR, Raman and FTIR spectroscopy. Static and dynamic CO2 adsorption experiments were applied to assess the CO2 capture performance. The type of surface species formed and their thermal stability were evaluated by in situ FTIR spectroscopy and CO2-TPD analysis. The two commercial ceria samples possessed similar structural and textural characteristics, formed the same types of carbonate-like surface species upon CO2 adsorption and, consequently, demonstrated almost identical CO2 capture performance under both static and dynamic conditions. The thermal stability of the adsorbed species increased in the order bidentate (B) carbonates, hydrogen carbonates (HC) and tridentate carbonates (T-III, T-II, T-I). Reduction of CeO2 increased the relative amount of the most strongly bonded T-I tridentate carbonates. Preadsorbed water led to hydroxylation and enhanced formation of hydrogen carbonates. Although the synthesized CeO2 sample had a higher surface area (by 30%) it showed a disadvantageous long mass transfer zone in the CO2-adsorption breakthrough curves. Because of its complex pore structure, this sample probably experiences severe intraparticle CO2 diffusion resistance. Having the same surface area as the synthesized CeO2, the mixed CeO2-ZrO2 oxide exhibited the highest CO2 capture capacity of 136 µmol g-1 under dynamic conditions. This was related to the highest concentration of CO2 adsorption sites (including defects) on this sample. The CeO2-ZrO2 system showed the lowest sensitivity to the presence of water vapor in the gas stream due to the lack of dissociative water adsorption on this material.

Halo nucleus 11Be: a spectroscopic study via neutron transfer.

The best examples of halo nuclei, exotic systems with a diffuse nuclear cloud surrounding a tightly bound core, are found in the light, neutron-rich region, where the halo neutrons experience only weak binding and a weak, or no, potential barrier. Modern direct-reaction measurement techniques provide powerful probes of the structure of exotic nuclei. Despite more than four decades of these studies on the benchmark one-neutron halo nucleus 11Be, the spectroscopic factors for the two bound states remain poorly constrained. In the present work, the 10Be(d,​p) reaction has been used in inverse kinematics at four beam energies to study the structure of 11Be. The spectroscopic factors extracted using the adiabatic model were found to be consistent across the four measurements and were largely insensitive to the optical potential used. The extracted spectroscopic factor for a neutron in an nℓj=2s(1/2) state coupled to the ground state of 10Be is 0.71(5). For the first excited state at 0.32 MeV, a spectroscopic factor of 0.62(4) is found for the halo neutron in a 1p(1/2) state.

Catalytic reduction of NO with decomposed methanol on alumina-supported Mn-Ce catalysts.

A series of manganese-ceria supported on alumina catalysts with various Mn/Ce ratios are investigated in both methanol decomposition to CO and hydrogen and SCR of NO(x) with CO. The study is aimed at the potential application of both reactions in integrated devices, where NO(x) is reduced with the products of the decomposed methanol. The samples are characterized by nitrogen physisorption, XRD, TEM, XPS, UV-Vis, and TPR. It was established that manganese-ceria supported on alumina catalysts are perspective in both methanol decomposition and NO reduction at temperatures above 723 K, which are typical for exhausted gases from the vehicles and some stationary stations. The best catalytic activity and selectivity to the desired products under these conditions was found for the samples with Mn/Mn+Ce ratio of 0.5 and 0.7. This superior catalytic performance is related to the formation of mixed valence Mn(3+)/Ce(4+) and Mn(4+)/Ce(3+) active sites.

Influence of Ce addition on the catalytic behavior of alumina-supported Cu-Co catalysts in NO reduction with CO.

The effect of Ce addition to alumina-supported copper, cobalt, and copper-cobalt oxides with low loadings on the catalysts efficiency in NO reduction with CO was studied. The attention was focused on varying the impregnation procedure in the ternary-supported catalysts in order to determine the best catalyst as well as the reasons for the enhanced catalytic activity. Ternary Co-Cu-Ce and binary Co-Ce, Cu-Ce, and Cu-Co-supported alumina were prepared and characterized by ICP, XRD, TEM, adsorption studies, XPS, H(2)-TPR, and catalytic investigations. The high activity of the ternary and the binary catalysts was determined by the favorable influence of the added cerium on the dispersion of the copper and cobalt active phases. The presence of ceria contributes to the formation of appropriate active phases, resulting in catalytic sites on the surface of the samples that promote the reduction of NO with CO.

Novel application of depleted fullerene soot (DFS) as support of catalysts for low-temperature reduction of NO with CO.

Depleted fullerene soot (DFS) with fullerene residue content of about 2.2-3.2% are investigated in order to elucidate the possibility for their use as support of catalysts in low-temperature reduction of NO with CO. Bimetalic copper-cobalt and copper-manganese oxides supported on DFS are prepared. All samples are characterized by chemical analysis, XRD, SEM, IR spectroscopy, XPS, nitrogen adsorption measurements. The two DFS supported bimetallic catalysts manifest a high activity towards the reduction of NO with CO at temperatures below 150 degrees C, the CuCo/DFS being the more active one. The peculiarity of the support DFS predetermines the porous texture of the catalysts. The occurrence of a specific metal-support interaction favors the formation of the mixed oxide spinels CuCo2O4 and Cu1.5 Mn1.5 O4 that are responsible for the enhanced activity.

Fine structure of synapses in the vestibular ganglion of the cat.

The vestibular ganglion of cat contains two distinguishable cell types, the larger and myelinated of which are much more numerous. The smaller and unmyelinated are represented by two cell populations: the first population displays complete Schwann cell ensheathment. The sheath of the second population is usually discontinuous at more than one point. Few axosomatic synapses are present on either cell type and profiles with clear synaptic vesicles predominate on each. The populations of presynaptic profiles in general are one type: a large variety with round synaptic vesicles and an asymmetrical contact. This type contacts the cell soma or the axon hillock surface. Those containing myelinated cells are covered on one side by the myelin sheath of the cell soma. Potential origins for the presynaptic profiles and possible functional significance of the synapses is discussed.

Observations on the ultrastructure of the axon hillock and initial axon segments of vestibular ganglion cells in the cat.

The axon hillock and initial axon segments of the vestibular ganglion cells in the cat were studied electron microscopically. The results revealed that the two cell processes are not completely comparable from morphological point of view. One of them is larger, with a more straight course, the axoplasm of the initia segment contains mainly longitudinally arranged neurotubules. The second cell process appears smaller in size, the initial segment have a curved course.

Further observations concerning the motor innervation of the tensor tympani muscle of the cat.

The cat tensor tympani muscle presented an uncommon ultrastructural organization of neuromuscular junctions compared with those in the other striated muscles. In cross sections, individual neuromuscular junctions had very extended contact area of the nerve terminal and muscle fiber, the terminal bouton was covering as a "calyx" the postjunctional muscle fiber. Long basal lamina was interposed between them. The sarcolemma at the level of the nerve terminal had multiple infoldings along its length, or smooth postjunctional muscle membrane was found beneath endings on both fiber types.

Fine structure of the neurons of the geniculate ganglion of the cat.

The geniculate ganglion of adult cat was studied electron microscopically. The results revealed that the neuronal soma displays different cytoplasmic features and the neurons were classified into two types: light cells and dark cells. Light neurons contained individual clumps of Nissl substance distributed randomly throughout the cytoplasm, dark neurons were characterized by densely packed stacks of Nissl substance in the peripheral cytoplasm. The unipolar cell process showed several ultrastructural peculiarities which differ from multipolar nerve cell axons.

Fine structure of the neurons and synapses of the vestibular ganglion of the cat.

The vestibular ganglion of 3-month-old cat was studied electron microscopically. The results revealed that the nerve cell bodies are surrounded by thin myelin sheaths which differ in some respects from typical axonal myelin. The neuronal soma displayed different cytoplasmic features and the neurons were classified into two types: light cells and dark cells. Light neurons contained individual clumps of Nissl substance distributed randomly throughout the cytoplasm, dark neurons were characterised by densely packed stacks of Nissl substance in the peripheral cytoplasm. The dark neurons of the ganglion are the only sensory neurons so far described which receive synapses.

Ultrastructural relationships between the receptor nerve fiber and surrounding lamellae in Krause end-bulbs.

The ultrastructural relationship between the receptor nerve fiber and the surrounding lamellae in Krause end-bulbs was discussed. Many sites of specialized junctions of symmetrical or asymmetrical type along the receptor nerve fiber and the surrounding lamellae were found. In addition, in close vicinity to them, spine-like digitations of the receptor nerve fiber, filled mainly with small clear vesicles, were observed. Mitochondrion-like cholinesterase-positive structures bulging in some cytoplasmic lamellae were also found. It is suggested that a functional link might exist between the specialized junctions, digitations and mitochrondrion-like structures in the transformation of external mechanical stimuli into nerve impulses.