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排序方式: 共有180条查询结果,搜索用时 15 毫秒
101.
Annamaria Montanari 《Journal of Differential Equations》2004,202(2):306-331
We introduce a new class of curvature PDOs describing relevant properties of real hypersurfaces of . In our setting, the pseudoconvexity and the Levi form play the same role as the convexity and the real Hessian matrix play in the real Euclidean one. Our curvature operators are second-order fully nonlinear PDOs not elliptic at any point. However, when computed on generalized s-pseudoconvex functions, we shall show that their characteristic form is nonnegative definite with kernel of dimension one. Moreover, we shall show that the missing ellipticity direction can be recovered by taking into account the CR structure of the hypersurfaces. These properties allow us to prove a strong comparison principle, leading to symmetry theorems for domains with constant curvatures and to identification results for domains with comparable curvatures. 相似文献
102.
Annamaria?Montanari Daniele?MorbidelliEmail author 《Calculus of Variations and Partial Differential Equations》2017,56(2):36
We characterize the subRiemannian cut locus of the origin in the free Carnot group of step two with three generators, giving a new, independent proof of a result by Myasnichenko (J Dyn Control Syst 8(4):573-597, 2002). We also calculate explicitly the cut time of any extremal path and the distance from the origin of all points of the cut locus. Furthermore, by using the Hamiltonian approach, we show that the cut time of strictly normal extremal paths is a smooth explicit function of the initial velocity covector. Finally, using our previous results, we show that at any cut point the distance has a corner-like singularity. 相似文献
103.
Clarissa Coccia Dr. Marta Morana Dr. Arup Mahata Dr. Waldemar Kaiser Dr. Marco Moroni Dr. Benedetta Albini Prof. Pietro Galinetto Dr. Giulia Folpini Prof. Chiara Milanese Prof. Alessio Porta Dr. Edoardo Mosconi Dr. Annamaria Petrozza Prof. Filippo De Angelis Prof. Lorenzo Malavasi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(10):e202318557
Chiral perovskites possess a huge applicative potential in several areas of optoelectronics and spintronics. The development of novel lead-free perovskites with tunable properties is a key topic of current research. Herein, we report a novel lead-free chiral perovskite, namely (R/S−)ClMBA2SnI4 (ClMBA=1-(4-chlorophenyl)ethanamine) and the corresponding racemic system. ClMBA2SnI4 samples exhibit a low band gap (2.12 eV) together with broad emission extending in the red region of the spectrum (∼1.7 eV). Chirality transfer from the organic ligand induces chiroptical activity in the 465–530 nm range. Density functional theory calculations show a Rashba type band splitting for the chiral samples and no band splitting for the racemic isomer. Self-trapped exciton formation is at the origin of the large Stokes shift in the emission. Careful correlation with analogous lead and lead-free 2D chiral perovskites confirms the role of the symmetry-breaking distortions in the inorganic layers associated with the ligands as the source of the observed chiroptical properties providing also preliminary structure-property correlation in 2D chiral perovskites. 相似文献
104.
A comparison of the extraction of clove buds with supercritical carbon dioxide and superheated water 总被引:1,自引:0,他引:1
A. A. Clifford Annamaria Basile Salim H. R. Al-Saidi 《Analytical and bioanalytical chemistry》1999,364(7):635-637
Supercritical carbon dioxide and superheated water (subcritical water above 100 °C under pressure) have both been used to
extract the buds of cloves (Syzygium aromaticum). The yields of eugenol and eugenyl acetate obtained by these methods and also by steam distillation and liquid solvent (Soxhlet)
extraction are similar, but the yields of caryophyllene were lower for the methods using water.
Received: 23 December 1998 / Revised: 26 March 1999 / Accepted: 31 March 1999 相似文献
105.
The explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) is of particular interest due to its extreme insensitivity to impact, shock and heat, while providing a good detonation velocity. To determine its fate under environmental conditions, TATB powder was irradiated with simulated sunlight and, in water, under UV light at 254 nm. The hydrolysis of particles submerged in neutral and alkaline solutions was also examined. We found that, by changing experimental conditions (e.g., light source, and mass and physical state of TATB), the intermediates and final products were slightly different. Mono-benzofurazan was the major transformation product in both irradiation systems. Two minor transformation products, the aci-nitro form of TATB and 3,5-diamino-2,4,6-trinitrophenol, were detected under solar light, while 1,3,5-triamino-2-nitroso-4,6-dinitrobenzene, 1,3,5-triamino-2,4-dinitrobenzene and mono-benzofuroxan were produced under UV light. The product identified as 3,5-diamino-2,4,6-trinitrophenol was identical to the one formed in the dark under alkaline conditions (pH 13) and in water incubated at either 50 °C or aged at ambient conditions. Interestingly, when only a few milligrams of TATB were irradiated with simulated sunlight, the aci-isomer and mono-benzofurazan derivative were detected; however, the hydrolysis product 3,5-diamino-2,4,6-trinitrophenol formed only much later in the absence of light. This suggests that the water released from TATB to form mono-benzofurazan was trapped in the interstitial space between the TATB layers and slowly hydrolyzed the relatively stable aci-nitro intermediate to 3,5-diamino-2,4,6-trinitrophenol. This environmentally relevant discovery provides data on the fate of TATB in surface environments exposed to sunlight, which can transform the insoluble substrate into more soluble and corrosive derivatives, such as 3,5-diamino-2,4,6-trinitrophenol, and that some hydrolytic transformation can continue even without light. 相似文献
106.
Dr. Annamaria Panniello Dr. Mariachiara Trapani Dr. Massimiliano Cordaro Carlo Nazareno Dibenedetto Prof. Raffaele Tommasi Dr. Chiara Ingrosso Prof. Elisabetta Fanizza Dr. Roberto Grisorio Prof. Elisabetta Collini Prof. Angela Agostiano Prof. Maria Lucia Curri Dr. Maria Angela Castriciano Dr. Marinella Striccoli 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(7):2371-2380
Efficient FRET systems are developed combining colloidal CdSe quantum dots (QDs) donors and BODIPY acceptors. To promote effective energy transfer in FRET architectures, the distance between the organic fluorophore and the QDs needs to be optimized by a careful system engineering. In this context, BODIPY dyes bearing amino-terminated functionalities are used in virtue of the high affinity of amine groups in coordinating the QD surface. A preliminary QD surface treatment with a short amine ligand is performed to favor the interaction with the organic fluorophores in solution. The successful coordination of the dye to the QD surface, accomplishing a short donor–acceptor distance, provides effective energy transfer already in solution, with efficiency of 76 %. The efficiency further increases in the solid state where the QDs and the dye are deposited as single coordinated units from solution, with a distance between the fluorophores down to 2.2 nm, demonstrating the effectiveness of the coupling strategy. 相似文献
107.
Laura Musazzi Annamaria Cattaneo Daniela Tardito Alessandro Barbon Massimo Gennarelli Sergio Barlati Giorgio Racagni Maurizio Popoli 《BMC neuroscience》2009,10(1):48-7
Background
The neurotrophin BDNF has been implicated in the regulation of neuroplasticity, gene expression, and synaptic function in the adult brain, as well as in the pathophysiology of neuropsychiatric disorders and the mechanism of action of antidepressants. Antidepressant treatments have been shown to increase the expression of BDNF mRNA, although the changes measured were found to be different depending on various factors. A few studies only have measured levels of BDNF protein after antidepressant treatments, and poor correlation was found between mRNA and protein changes. We studied the time course of expression of BDNF mRNA and protein during drug treatments, in order to elucidate the temporal profile of regulation of this effector and whether mRNA and protein levels correlate. Rat groups were treated for 1, 2 or 3 weeks with fluoxetine or reboxetine; in additional groups drug treatment was followed by a washout week (3+1). Total BDNF mRNA was measured by Real Time PCR, pro- and mature BDNF proteins were measured by Western blot. 相似文献108.
Annamaria Barbagallo Paolo Mauro 《Journal of Optimization Theory and Applications》2012,155(1):288-314
The paper is devoted to generalize a previous model of the dynamic oligopolistic market equilibrium problem allowing the presence of production excesses and assuming, in a more reasonable way that the total amounts of commodity shipments from a firm to all the demand markets be upper bounded. First, we give equilibrium conditions in terms of the well-known dynamic Cournot–Nash equilibrium principle. Then we show that such conditions can be expressed in terms of Lagrange multipliers; namely, by means of an utility function, prove that both equilibrium conditions can be equivalently expressed by a variational inequality. The variational formulation allows us to provide existence theorems and qualitative properties for equilibrium solutions. At last, a numerical example illustrates the results obtained. 相似文献
109.
A new S-band erbium-doped fiber amplifier module with a double-pass configuration based on two circulators has been designed and constructed. The bending losses of a depressed-cladding doped fiber have been exploited to suppress the amplified spontaneous emission in the C band. The experimental characterization of the double-pass amplifier has shown that significant advantages can be obtained with respect to the single-pass configuration. 相似文献
110.
Maria Vittoria Ciampolillo Annamaria Zaltron Marco Bazzan Nicola Argiolas Cinzia Sada Sabrina Mignoni Marc Fontana 《Applied Physics A: Materials Science & Processing》2011,104(1):453-460
Thermal diffusion from thin film is one of the most widespread approaches to prepare iron doped regions in lithium niobate
with limited size for photorefractive applications. In this work, we investigate the doping process with the aim of determining
the best process conditions giving a doped region with the characteristics required for photorefractive applications. Six
samples were prepared by changing the atmosphere employed in the diffusion treatment in order to obtain different combination
of diffusion profiles and reduction degrees and also to check the effect of employing a wet atmosphere. The compositional,
optical, and structural properties are then extensively characterized by combining Secondary ion Mass Spectrometry, UV, visible
and IR spectrophotometry, High Resolution X-Rays Diffraction, and Micro-Raman Spectroscopy. Moreover, the sample topography
was checked by Atomic Force Microscopy. An analysis of all our data shows that the best results are obtained performing a
double step process, i.e. diffusion in oxidizing atmosphere and subsequent reduction at lower temperature in an hydrogen-containing
atmosphere. 相似文献