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1.
Giuseppina Castronuovo Vittorio Elia Filomena Velleca 《Journal of solution chemistry》1995,24(12):1209-1217
Calorimetric measurements were carried out at 25°C on binary and ternary aqueous solutions containing L and D forms fo the following -aminoacids: tryptophan, cysteine, methionine, phenylalanine, histidine, threonine, and citrulline, which contain both hydrophilic and hydrophobic domains. Differences were found between the values of the homochiral and heterochiral pairwise enthalpic interaction coefficients for tryptophan, cysteine, and methionine. To the contrary, chiral recognition was not detected for phenylalanine, histidine, citrulline, and threonine. The data were interpreted in terms of a preferential configuration model. Chiral recognition is detected only when the interactions of the side chains in the homo- and heterochiral configurations are different. Chiral recognition disappears when a competition exists between zwitterion-zwitterion interactions and side chain-side chain interactions. In some cases, such as for citrulline, compensation effects can occur due to thermal contributions from different domains which mask chiral recognition. 相似文献
2.
The data clustering problem consists in dividing a data set into prescribed groups of homogeneous data. This is an NP-hard problem that can be relaxed in the spectral graph theory, where the optimal cuts of a graph are related to the eigenvalues of graph 1-Laplacian. In this paper, we first give new notations to describe the paths, among critical eigenvectors of the graph 1-Laplacian, realizing sets with prescribed genus. We introduce the pseudo-orthogonality to characterize m3(G), a special eigenvalue for the graph 1-Laplacian. Furthermore, we use it to give an upper bound for the third graph Cheeger constant h3(G), that is, h3(G) 6 m3(G). This is a first step for proving that the k-th Cheeger constant is the minimum of the 1-Laplacian Raylegh quotient among vectors that are pseudo-orthogonal to the vectors realizing the previous k - 1 Cheeger constants. Eventually, we apply these results to give a method and a numerical algorithm to compute m3(G), based on a generalized inverse power method. 相似文献
3.
Giuseppina Castronuovo Vittorio Elia Marcella Niccoli Filomena Velleca 《Thermochimica Acta》1998,320(1-2):13-22
The thermodynamics of dissolution in water of a set of substances has been studied calorimetrically. The examined substances were: potassium chloride, (glycyl-glycyl)diketopiperazine, (alanyl-alanyl)diketopiperazine, (leucyl-glycyl)diketopiperazine. They were chosen on the basis of their solubilities, going from a highly soluble electrolyte to the sparingly soluble diketopiperazines. It is shown that, using a commercially available calorimeter, it is possible to perform in a single calorimetric experiment the simultaneous determination of all thermodynamic parameters characterizing dissolution of a substance in a given solvent, i.e. solubility, dissolution enthalpy and dilution enthalpy. The solubility values in water obtained through the proposed method are in good agreement with those reported in the literature and obtained by other techniques. 相似文献
4.
Beaumont Jonathan S. Lee Tae Hoon Mayorov Mikhail Tintori Carlo Rogo Francesco Angelucci Bruno Corbo Matteo 《Journal of Radioanalytical and Nuclear Chemistry》2017,314(2):803-812
Journal of Radioanalytical and Nuclear Chemistry - The IAEA has developed a liquid scintillator-based system for the non-destructive assay of 235U in fresh fuel assemblies. The fast neutron... 相似文献
5.
Francesca Guerriero Filomena Olivito 《Journal of Mathematical Modelling and Algorithms》2014,13(3):247-282
In this paper, we consider the application of revenue management techniques in the context of the car rental industry. In particular, the paper presents a dynamic programming formulation for the problem of assigning cars of several categories to different segments of customers, with rental requests arising dynamically and randomly with time. Customers make a rental request for a given type of car, for a given number of days at a given pickup time. The rental firm can satisfy the demand for a given product with either the product requested or with a car of at most one category superior to that initially required, in this case an “upgrade” can take place. The one-way rental scenario, which allows the possibility of the rental starting and ending at different locations, is also addressed. In the framework considered, the logistic operator has to decide whether to accept or reject a rental request. Since the proposed dynamic programming formulations are impractical due to the curse of dimensionality, linear programming approximations are used to derive revenue management decision policies for the operator. Indeed, primal and dual acceptance policies are developed (i.e. booking limits, bid prices) and their effectiveness is assessed on the basis of an extensive computational phase. 相似文献
6.
The effect of the quenching rate on the phase separation of partially miscible liquid mixtures is studied, showing that it may influence the growth rate of single-phase domains. In particular, the phase separation of metastable binary mixtures in the presence of strong emulsifiers appears to be heavily retarded. These effects constitute an important limitation to the phase transition extraction process introduced by the authors in previous works, which is based on the fact that phase separation of unstable mixtures is rapid, even in the presence of surface active compounds. 相似文献
7.
Ana Salomé Pires João Batista Dina Murtinho Célia Nogueira Anna Karamysheva M. Luísa Ramos Bruce F. Milne Nuno Tiago Tavares José Gonçalves Ana Cristina Gonçalves Ana Margarida Abrantes Rui Soares Teresa Gonçalves Maria Filomena Botelho M. Elisa Silva Serra 《应用有机金属化学》2020,34(5):e5569
Platinum metal complexes are the most common chemotherapeutics currently used in cancer treatment. However, the frequent adverse effects, as well as acquired resistance by tumor cells, urge the development of effective alternatives. In the recent past, copper complexes with Schiff base ligands have emerged as good alternatives, showing interesting results. Accordingly, and in continuation of previous studies in this area, three new camphoric acid-derived halogenated salen ligands and their corresponding Cu (II) complexes were synthesized and their antitumor activity was evaluated in order to determine the influence of the type and number of halogens present (Br, Cl). The in vitro cytotoxic activity was screened against colorectal WiDr and LS1034 and against breast MCF-7 and HCC1806 cancer cell lines. The results proved the halogenated complexes to be very efficient, the tetrachlorinated Cu (II) complex being the most promising, presenting IC50 of 0.63–1.09 μM for the cell lines studied. The complex also shows selectivity to colorectal cancer cells compared to non-tumor colon cells. It is worth highlighting that the tetrachlorinated Cu (II) complex, our most efficient complex, shows a significantly more powerful antitumor effect than the reference drugs currently used in conventional chemotherapy. The halogenated salen and corresponding complexes were also screened for their antimicrobial activity against four bacterial species-Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa-and four fungal species-Candida albicans, Candida glabrata, Aspergillus fumigatus and Alternaria alternata. The compounds were found to exhibit moderate to strong antibacterial activity against the bacterial strains studied. NMR studies and theoretical calculations provided some insight into the structure of the ligands and copper complexes. Considering the results presented herein, our work validates the potential use of copper-based chemotherapeutics as alternatives for cancer treatment. 相似文献
8.
Migliardini F. Di Palma T. M. Gaele M. F. Corbo P. 《Journal of Solid State Electrochemistry》2018,22(9):2901-2916
Journal of Solid State Electrochemistry - This paper presents first investigations on solid and strongly acid electrolytes for Al-air batteries. These electrolytes are prepared starting from a... 相似文献
9.
Marina Russo Filomena Cichello Carla Ragonese Paola Donato Francesco Cacciola Paola Dugo Luigi Mondello 《Analytical and bioanalytical chemistry》2013,405(13):4617-4626
In this work, a high-performance liquid chromatography with evaporative light scattering detection method has been developed and applied for quantification of the polar content of the lipid fraction in milk samples of different origin. From a chromatographic stand-point, a 4.6-mm I.D. hydrophilic interaction liquid chromatography column was employed to attain a baseline separation of major phospholipid classes contained in the various milk samples tested. Quantitative analysis was performed by the external calibration method using reference material solutions in the 5–100 mg/L concentration range. Analytical recoveries ranging from 57 to 100 %, and repeatability data lower than 8.04 % were obtained on a skimmed cow’s milk sample. The crude cow milk was the most abundant (0.04 %) in phospholipids and donkey milk was the poorest (0.004 %). Quantitative differences were determined in the phospholipid content of the milk samples tested. Finally, characterization of phospholipid profile and fatty acid composition of the different samples was carried out by an ion trap-time of flight mass spectrometer and gas chromatography coupled to flame ionization and mass spectrometry detection. A thorough screening of the polar lipid composition of milk samples of different origin is here outlined, for the first time. 相似文献
10.
Dell’Accio Francesco Di Tommaso Filomena Siar Najoua Vianello Marco 《BIT Numerical Mathematics》2022,62(3):773-801
BIT Numerical Mathematics - We discuss a pointwise numerical differentiation formula on multivariate scattered data, based on the coefficients of local polynomial interpolation at Discrete Leja... 相似文献