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991.
Paola Palmero Frank KernMariangela Lombardi Rainer Gadow 《Ceramics International》2011,37(8):3547-3556
An ultra-fine alumina powder was doped with yttrium or zirconium chloride to produce Al2O3-5 vol.%ZrO2 (AZ-5) and Al2O3-5 vol.%YAG (AY-5) composite powders. Composite samples and pure alumina, used as a reference, were submitted to dilatometric analyses up to 1500-1550 °C at 2, 5 and 10 °C/min for supplying the data required for the modeling of their sintering behaviour. The best fit for the three samples was obtained by applying an Avrami-Erofeev nucleation and growth model (An) and a subsequent power law reaction (AnFn). The evolution of the activation energy with densification is given for the three samples, as well as the prediction of their best sintering conditions. Finally, densification mechanism for the immiscible (AZ-5) and miscible (AY-5) systems are hypothesized and correlated with their final microstructures. 相似文献
992.
The synthesis and characterization of carbon nanotubes grown by chemical vapor deposition using a stainless steel catalyst 总被引:3,自引:0,他引:3
Luca Camilli Manuela Scarselli Silvano Del Gobbo Paola Castrucci Francesca Nanni Eric Gautron Serge Lefrant Maurizio De Crescenzi 《Carbon》2011,(10):3307-3315
Multi wall carbon nanotubes (MWCNTs) were grown on a stainless steel (SS) sheet by chemical vapor deposition without the addition of external metal catalyst. We found that the key for highly efficient growth includes the nanoscale roughness of the SS surface, as shown by scanning tunneling microscopy, that acts as catalyst/template in the nanotube formation. Raman spectroscopy and electron microscopy were used to check the nature and quality of the synthesized nanotubes. We conclude that stainless steel favors a base-growth mechanism. Transmission electron energy loss spectroscopy performed on single metallic particles found inside the nanotubes clarified the atomic nature of the catalytic particles supplied by the steel. Only unoxidized iron was found and no traces of nickel and chromium were detected. In addition, the SS substrate has been used for a second growth process after carefully removing the synthesized CNTs, proving that a continuous production of CNTs from the same substrate is achievable. 相似文献
993.
A laboratory study was performed on the extracellular production of carbohydrates by the marine diatoms Cylindrotheca closterium, Thalassiosira pseudonana and Skeletonema costatum. The investigation was aimed at elucidating the role of P-starvation and growth status on abundance and chemical characteristics of the released non-attached polysaccharides. Inorganic phosphorus depletion determined an increase of total polysaccharides in all species examined compared to nutrient-replete (complete f/2) conditions. The highest abundance of polysaccharides per unit cell was found in T. pseudonana (28.4 micromol C 10(-6) cells), followed by C. closterium (2.56 micromol C 10(-6) cells) and S. costatum (1.18 micromol C 10(-6) cells). Maximum production rates were found at the transition between exponential and stationary growth phase. Gas-chromatographic analysis of the dissolved fraction showed glucose to be the most abundant monomer in exponentially growing, P-replete cultures (81.6%, 90% and 32% as molar percentage of total aldoses in C. closterium, T. pseudonana and S. costatum, respectively). A strong reduction in glucose was found in C. closterium, but not in T. pseudonana and S. costatum, under P-depleted conditions. Species-specific variations in the amount and aldose signatures of the released polysaccharides according to nutrient status and growth conditions can provide useful insights on the production and persistence of these organic compounds in the water column. 相似文献
994.
Natalia Quici María E. Morgada Gabriela Piperata Paola Babay Raquel T. Gettar Marta I. Litter 《Catalysis Today》2005,101(3-4):253-260
Heterogeneous photocatalysis (HP) using UV/TiO2, photo-Fenton (PF) reaction using UV/Fe/H2O2 and the combination UV/TiO2/Fe/H2O2 (HP–PF) were tested as processes to degrade oxalic acid (Ox) at relatively high concentrations (0.032 M). PF reactions were generally more efficient than HP including the reaction in the absence of H2O2. Oppositely to previous results (e.g., with EDTA), HP–PF combinations did not result, in the case of oxalate, better techniques for degradation than systems in the absence of TiO2. The kinetic behavior was not unique and two parameters were taken to evaluate the efficiency of each system: initial rates (R0) and time to 95% of total mineralization (TOC95). Addition of hydrogen peroxide improves the initial HP reaction rate and reduces TOC95. Addition of Fe3+ also affects the reaction parameters but the effect of H2O2 seems to be higher, at least under the present conditions. When both H2O2 and iron were added simultaneously, the efficiency was higher. The optimal H2O2:Ox:Fe molar ratio was established and the results indicated that, at a fixed iron concentration, H2O2 increased R0 until a limit beyond which it did not cause any effect. No intermediates were formed in the reaction, oxalate being degraded directly to CO2. Analogies and differences with the EDTA system are presented. 相似文献
995.
Often, in finite samples, the true level of the confidence intervals for natural estimators of inequality indices belonging to the Gini family differs greatly from their nominal level, which is based on the asymptotic confidence limits. This paper shows how the Gram-Charlier series can be used to obtain improved finite-sample confidence intervals. Our work focuses on the implementation in Mathematica 3.0 of computational procedures to compute the Gram-Charlier distribution for the following sampling inequality indices: R by Gini, P by Piesch and M by Mehran for the Dagum (Type I) distribution. The results of a Monte Carlo experiment confirm that, for the cases investigated, the Gram-Charlier distribution largely eliminates the problem of incorrect finite-sample level. 相似文献
996.
Monica Oldani Anna Maria Villa Marta Manzoni Pasquale Melchioretto Paolo Parenti Eugenio Monti Paola Fusi Matilde Forcella Chiara Urani 《International journal of molecular sciences》2021,22(19)
In this paper, we report the metabolic characterization of two foci, F1 and F3, obtained at the end of Cell Transformation Assay (CTA), performed by treating C3H10T1/2Cl8 mouse embryo fibroblasts with 1 μM CdCl2 for 24 h. The elucidation of the cadmium action mechanism can be useful both to improve the in vitro CTA and to yield insights into carcinogenesis. The metabolism of the two foci was investigated through Seahorse and enzyme activity assays; mitochondria were studied in confocal microscopy and reactive oxygen species were detected by flow cytometry. The results showed that F1 focus has higher glycolytic and TCA fluxes compared to F3 focus, and a more negative mitochondrial membrane potential, so that most ATP synthesis is performed through oxidative phosphorylation. Confocal microscopy showed mitochondria crowded in the perinuclear region. On the other hand, F3 focus showed lower metabolic rates, with ATP mainly produced by glycolysis and damaged mitochondria. Overall, our results showed that cadmium treatment induced lasting metabolic alterations in both foci. Triggered by the loss of the Pasteur effect in F1 focus and by mitochondrial impairment in F3 focus, these alterations lead to a loss of coordination among glycolysis, TCA and oxidative phosphorylation, which leads to malignant transformation. 相似文献
997.
Giada Amodeo Benedetta Verduci Patrizia Sartori Patrizia Procacci Vincenzo Conte Gianfranco Balboni Paola Sacerdote Silvia Franchi 《International journal of molecular sciences》2021,22(19)
The development of neuropathy and of mood alterations is frequent after chemotherapy. These complications, independent from the antitumoral mechanism, are interconnected due to an overlapping in their processing pathways and a common neuroinflammatory condition. This study aims to verify whether in mice the treatment with the proteasome inhibitor bortezomib (BTZ), at a protocol capable of inducing painful neuropathy, is associated with anxiety, depression and supraspinal neuroinflammation. We also verify if the therapeutic treatment with the antagonist of the prokineticin (PK) system PC1, which is known to contrast pain and neuroinflammation, can prevent mood alterations. Mice were treated with BTZ (0.4 mg/kg three times/week for 4 weeks); mechanical allodynia and locomotor activity were evaluated over time while anxiety (dark light and marble burying test), depression (sucrose preference and swimming test) and supraspinal neuroinflammation were checked at the end of the protocol. BTZ treated neuropathic mice develop anxiety and depression. The presence of mood alterations is related to the presence of neuroinflammation and PK system activation in prefrontal cortex, hippocampus and hypothalamus with high levels of PK2 and PKR2 receptor, IL-6 and TNF-α, TLR4 and an upregulation of glial markers. PC1 treatment, counteracting pain, prevented the development of supraspinal inflammation and depression-like behavior in BTZ mice. 相似文献
998.
Savina Apolloni Paola Fabbrizio Susanna Amadio Giulia Napoli Mattia Freschi Francesca Sironi Paolo Pevarello Paola Tarroni Chiara Liberati Caterina Bendotti Cinzia Volont 《International journal of molecular sciences》2021,22(19)
Amyotrophic lateral sclerosis (ALS) is a disease with a resilient neuroinflammatory component caused by activated microglia and infiltrated immune cells. How to successfully balance neuroprotective versus neurotoxic actions through the use of anti-inflammatory agents is still under debate. There has been a boost of awareness regarding the role of extracellular ATP and purinergic receptors in modulating the physiological and pathological mechanisms in the nervous system. Particularly in ALS, it is known that the purinergic ionotropic P2X7 receptor plays a dual role in disease progression by acting at different cellular and molecular levels. In this context, we previously demonstrated that the P2X7 receptor antagonist, brilliant blue G, reduces neuroinflammation and ameliorates some of the pathological features of ALS in the SOD1-G93A mouse model. Here, we test the novel, noncommercially available, and centrally permeant Axxam proprietary P2X7 antagonist, AXX71, in SOD1-G93A mice, by assessing some behavioral and molecular parameters, among which are disease progression, survival, gliosis, and motor neuron wealth. We demonstrate that AXX71 affects the early symptomatic phase of the disease by reducing microglia-related proinflammatory markers and autophagy without affecting the anti-inflammatory markers or motor neuron survival. Our results suggest that P2X7 modulation can be further investigated as a therapeutic strategy in preclinical studies, and exploited in ALS clinical trials. 相似文献
999.
Jesica Romina Mufari Horacio Adrián Gorostegui Patricia Paola Miranda-Villa Antonella Estefanía Bergesse Edgardo Luis Calandri 《Journal of the American Oil Chemists' Society》2020,97(1):57-66
Quinoa seeds are a source of lipids of great quality, and they highlight the content and composition of fatty acids and the presence of antioxidants such as tocopherols. Solvent extraction of quinoa oils was carried out from two matrices (wholemeal and germ flours), and in both cases, the extraction performance, physical–chemical characteristics, and oxidative stability were determined. Oxidative stability of the oil was assessed using an accelerated aging experiment under storage conditions at 60 °C for 12 days, in which the following parameters were measured: peroxide value, acid value, conjugated dienes and trienes, and scavenging radical capacity. Germ flour showed greater extraction yields (27.30 ± 0.15 g/100 g) compared to wholemeal (5.88 ± 0.02 g/100 g). Both oils presented similar physicochemical parameters, although the tocopherol content was higher in the oil extracted from germ flour (1354 vs. 735 mg/kg oil). At the same time, wholemeal oil showed a superior oxidative stability; hence, the wet milled process produces a minor impact on the compounds responsible for protection against lipid oxidation. 相似文献
1000.
In this work we present the development of a MARTINI-type coarse-graining (CG) model for poly-ε-caprolactone (PCL) dissolved in a solvent binary mixture of acetone and water. A thermodynamic/conformational procedure is adopted to build up the CG model of the system, starting from the standard MARTINI force field. The single CG bead is parametrized upon solvation free energy calculations, whereas the conformation of the whole polymer chain is optimized using the radius of gyration values calculated at different chain lengths. The model is then able to reproduce the correct thermodynamics of the system, as well as the conformation of single PCL chains, especially in pure water and acetone. The results obtained here are then used to simulate the interactions between multiple longer PCL chains in solution. The model developed here can be used in the future to achieve deeper insight into the dynamics of the polymer self-assembly. 相似文献