The effect of soot on the storage-reduction performances of a PtBa/Al₂O₃ catalyst is investigated in this work. It is found that the presence of soot reduces the NOₓ storage capacity of the catalyst, ...evaluated in presence of water and CO₂ in the feed stream in the range 200–350°C and with different values of the NO inlet concentration. Besides the presence of soot favors the decomposition and the reduction of the stored nitrates, while soot is being oxidized. A direct reaction between the stored nitrates and soot is suggested, that has been explained on the basis of the surface mobility of the adsorbed nitrates. This soot oxidation pathway involves surface species and parallels the NO₂-soot oxidation that occurs in the presence of gas-phase NO₂. Finally, the presence of soot does not influence appreciably the behavior of the PtBa/Al₂O₃ catalyst in the reduction by H₂ of the stored nitrates: in all cases N₂ is the main reaction product and ammonia is observed in minor amounts.
In this study, Ce/Zr-based materials without noble metals in their formulation have been prepared, characterized and tested in NO
x
adsorption at different temperatures. In particular, the effect of ...the presence of Ba and Cu in the catalytic formulation has been investigated. The catalyst characterization shows that the redox properties of the catalysts are enhanced by Cu and inhibited by Ba. Upon interaction with NO/O
2
, it is found that NO
x
are stored at low temperatures (150 °C) in the form of nitrites, without any relevant NO oxidation activity. This suggests a direct NO uptake. At higher temperatures (300 °C) a significant NO oxidation activity is observed, that is enhanced by Cu and depressed by Ba. In this case, NO
x
are stored in the form of nitrates; the samples containing both Ba and Cu exhibits the better performances in terms of NO
x
adsorption capacity.
In this paper mechanistic aspects on the formation of N
2
O over a model Pt–Ba/Al
2
O
3
NO
x
storage and reduction catalyst are investigated. The data indicate that N
2
O formation involves the ...coupling of N-adspecies with undissociated NO molecules: accordingly this requires the presence of partially reduced Pt sites, to catalyse the NO dissociation into N- and O-adspecies on one side and to prevent complete NO dissociation on the other side. In fact N
2
O formation is observed at temperatures where the reductant leads to a partial reduction of the Pt sites, at increasing temperatures in the order CO > NH
3
> H
2
.
Lipid droplets (LDs) and mitochondria in the ooplasm are essential for energy production required for maturation, fertilization and embryo development. This study investigates the correlations ...between cytoplasmic LDs polar aggregation and: (1) nuclear maturation (Experiment 1); (2) mitochondrial (mt) distribution pattern and localization (Experiment 2); (3) fertilization and embryonic development after intracytoplasmic sperm injection (ICSI; Experiment 3) in equine oocytes recovered from slaughtered mares and matured in vitro. Morphologically normal oocytes were selected after culture and categorized as having polar (P) aggregation or uniform (U) distribution of LDs. In Experiment 1, the maturation rate was significantly higher in P compared with U oocytes (69%, 40/58 vs. 32%, 13/41;
P
<
0.001). In Experiment 2, it was observed that P and U oocytes showed heterogeneous mt distribution at comparable rates (68%, 25/37 vs. 50%, 2/4 for P and U respectively; NS). Moreover, only in 8/25 (32%) of P oocytes, LDs overlapped with mt aggregates in the area containing meiotic spindle. In Experiment 3, normal fertilization (51%, 19/37 vs. 60%, 6/10, for P and U) and cleavage rates (83%, 20/24 vs. 67%, 4/6, for P and U) did not differ between groups, also in oocytes with LDs located nearby the polar body. Overall, P aggregation of LDs was related to cumulus expansion at collection. In conclusion, in equine matured oocytes, P aggregation of LDs is related with cumulus expansion and nuclear maturation. However, it is not related with heterogeneous mt distribution and cannot be considered a predictive indicator for normal fertilization and embryo development.
Flexor Tendon Rehabilitation Matarrese, Marissa R., MD; Hammert, Warren C., MD
The Journal of hand surgery (American ed.),
11/2012, Letnik:
37, Številka:
11
Journal Article
In this study the selective catalytic reduction (SCR) of NO has been investigated over H-ZSM-5 with three different reducing agents. Comparison of the reaction mechanisms using propane, ammonia and ...isopropylamine has been performed using in situ DRIFTS step-response experiments. The same type of surface NH species, likely organic amines, is formed in the presence of either propane or isopropylamine as reducing agent. For NH
3, on the other hand, NH
+
4 is the dominating NH surface species during reaction. Furthermore, in the case of propane, the nature of the NO
x
-source, i.e. NO or NO
2, is crucial for the reaction. With NO
2, the reaction likely proceeds fast via direct reduction, while for NO, oxidation to NO
2 is required initially. In either case NH species play a vital role in the SCR reaction and organic amines are possible key-intermediates in the SCR with saturated hydrocarbons over H-ZSM-5.
The results of an experimental study on the photo electrochemical behavior of nanotubular TiO
2
structures are presented in this work. TiO
2
samples were prepared by electrochemical anodization of Ti ...foils and submitted to thermal annealing. The influence of the current transient during the anodization, and of the annealing temperature on the photochemical response of the samples at different wavelengths was studied. Different behavior of the samples was observed, which may be attributed to the distributions of defects and to their different sensitivity to the temperature. The analysis of the performance of the samples in absence or in the presence of glycerol, used as hole scavenger, provided more information on the photo-catalytic properties of these structures.
Chronic ischemia in the upper extremity is a challenging condition for both patients and surgeons. When ischemia reaches a critical level, tissue loss ensues, which results in necrosis of fingers at ...various levels. Amputation of necrotic digits, without addressing the etiology of the necrosis, often results in wound-healing problems and more proximal amputations. The purpose of this report was to describe a surgical technique that improves vascular supply to the hand and allows for healing of the amputation sites and relief of pain through arterialization of the venous system.
The Catalytic Activity of "Naked" Gold Particles Comotti, Massimiliano; Della Pina, Cristina; Matarrese, Roberto ...
Angewandte Chemie (International ed.),
November 5, 2004, Letnik:
43, Številka:
43
Journal Article
Recenzirano
Reducing size helps to oxidize: Unsupported gold particles behave as an efficient catalyst for the aerobic oxidation of glucose, showing a similar activity to enzymatic systems. The catalytic ...activity is inversely proportional to the particle diameter (d, see graph). With carbon‐supported gold, no gold–support interaction is found; however, the use of a support avoids particle aggregation thus preserving the original activity for longer.
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