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101.
102.
A systematic computational investigation on protonated and nonprotonated boron-containing zeolites (boralites), performed by using different periodic density functional theory approximations, is presented. Both minimum energy structures and finite temperature behavior of model boron sodalites were analyzed. All of the adopted computational schemes agree in predicting an acid site composed of a silanol Si-OH group loosely linked to a planar BO(3) structure in the protonated system and a BO(4) tetrahedral site in the sodium-containing zeolite. Calculated structural and vibrational properties are in line with experimental data. Comparisons of the protonated boralite site with Al and Ga zeolitic acid sites are discussed as well. Results indicate that this class of mild acid catalysts is characterized by significant framework flexibility and pronounced thermal effects due to the loosely bound acid site. 相似文献
103.
A new NIR method based on multivariate calibration for determination of ethanol in industrially packed wholemeal bread was developed and validated. GC-FID was used as reference method for the determination of actual ethanol concentration of different samples of wholemeal bread with proper content of added ethanol, ranging from 0 to 3.5% (w/w). Stepwise discriminant analysis was carried out on the NIR dataset, in order to reduce the number of original variables by selecting those that were able to discriminate between the samples of different ethanol concentrations. With the so selected variables a multivariate calibration model was then obtained by multiple linear regression. The prediction power of the linear model was optimized by a new “leave one out” method, so that the number of original variables resulted further reduced. 相似文献
104.
Citrus aurantium (bitter orange) is a plant belonging to the family Rutaceae, whose fruit extracts have been used recently for the treatment of obesity. The most important biologically active constituents of the C. aurantium fruits are phenethylamine alkaloids (i.e. octopamine, synephrine, tyramine, N-methyltyramine and hordenine). Synephrine is a primary synthesis compound with pharmacological activities such as vasoconstriction, elevation of blood pressure and relaxation of bronchial muscle. Synephrine is present in the peel and the edible part of Citrus fruit. Of the adrenergic amines of natural origin, synephrine has been found to be the main constituent of C. aurantium fruits and extracts; the other alkaloids are either absent or present in only low concentrations. It is known that synephrine and the other amines found in C. aurantium have adverse effects on the cardiovascular system, owing to adrenergic stimulation. In light of the great commercial proliferation of C. aurantium herbal medicines in recent years, this review provides an overview of various extraction, separation and detection techniques employed for the qualitative and quantitative determination of the alkaloids in C. aurantium and related species. The application of chromatographic and electrophoretic methods for the separation and determination of these active components in C. aurantium plant material and derivatives are described. Since synephrine is a chiral compound, enantioselective chromatographic and electrophoretic techniques for the analysis of synephrine enantiomers in natural products are presented. Furthermore, examples of identification of these active compounds in complex matrices by hyphenated methods, such as gas chromatography-mass spectrometry and high-performance liquid chromatography-mass spectrometry, are described. The advantages and limitations of these separation and identification methods are assessed and discussed. 相似文献
105.
The adsorption of NO, NO/O2 mixtures and NO2 on pure ZrO2 and on two series of catalysts supported on ZrO2, one containing vanadia and the other molybdena (ZV and ZMo, respectively), has been investigated. The V and Mo surface contents
of the latter were ≤3 atoms nm−2 and ≤5 atoms nm−2, respectively. All samples had been previously submitted to a standard oxidation treatment.
On all samples, only extremely minor amounts of NOx surface species are formed by NO interaction at room temperature (RT). NOx surface species are formed in greater amounts on pure ZrO2 when NO and O2 are coadsorbed at RT; they are mainly nitrites, small amounts of nitrates, and small amounts of (O2NO−H)δ− species; when ZrO2 is warmed to 623 K in the NO/O2 mixture, nitrites decrease, nitrates and (O2NO−H)δ− species increase. The same NOx species as on the ZrO2 surface free from V (or Mo) are formed on ZV (or ZMo) samples with surface V (or Mo) density <1.5 atoms nm−2; however, they occur in decreased amount with increasing V (or Mo) coverage. On ZV samples with a surface V density of 1.5–3
atoms nm−2 (or ZMo samples with a surface Mo density of 1.5–5 atoms nm−2) when NO and O2 are coadsorbed at RT, there is formation of small amounts of nitrites, nitrates (both on ZrO2 surface free from V (or Mo) and at the edges of V- or Mo-polyoxoanions) and NO2
δ+ species, associated with V5+ (or Mo6+) of very strong Lewis acidity; when samples are warmed up 623 K in the NO/O2 mixture, nitrites disappear, nitrates increase, NO2
δ+ species remain constant or slightly decrease. When NO2 is allowed into contact at RT with oxidized samples, surface situations almost identical to those obtained for each sample
warmed to 623 K in NO/O2 mixture is reached. The NOx surface species stable at 623 K, the temperature at which catalysts show the best performance in the selective catalytic
reduction (SCR) of NO by NH3, are nitrates, both on ZrO2 and on polyvanadates or polymolybdates at high nuclearity. On the contrary, nitrites and NO2
δ+ species are unstable at 623 K. 相似文献
106.
Vera L. Covolan Roberta Di Ponzio Federica Chiellini Elizabeth Grillo Fernandes Roberto Solaro Emo Chiellini 《Macromolecular Symposia》2004,218(1):273-282
Polyurethanes (PUs) composed by hard and soft segments have been extensively used in the manufacturing of biocompatible prosthesis and medical devices. A broad variety of PUs can be obtained by modifying the balance between both segments. In the present work, different basically-flexible PUs have been prepared by employing different combinations of aliphatic hexamethylene diisocyanate, poly(ethylene glycol) (Mw 400 Da), poly(ϵ-caprolactone) diol (Mw 530 Da), and 1,4-butanediol. Thermal analysis of the synthesized PUs demonstrated high thermal stability and the assumption of glassy state well below room temperature, in agreement with their marked flexibility. Morphological characterization of PUs films indicated that films prepared by spin coating were smoother and more homogeneous than those obtained by casting. Biological assays performed by using 3T3/BALB-C mouse embryo fibroblast cell line confirmed the absence of toxicity and hence the biocompatibility of PU-films. 相似文献
107.
Ivana Generali Mekini Martina agalj Giulia Tabanelli Chiara Montanari Federica Barbieri Danijela Skroza Vida imat 《Molecules (Basel, Switzerland)》2021,26(21)
Marine macroalgae are well known to release a wide spectrum of volatile organic components, the release of which is affected by environmental factors. This paper aimed to identify the essential oil (EO) compounds of the brown algae Cystoseira compressa collected in the Adriatic Sea monthly, from May until August. EOs were isolated by hydrodistillation using a Clavenger-type apparatus and analyzed by gas chromatography coupled with mass spectrometry (GC–MS). One hundred four compounds were identified in the volatile fraction of C. compressa, accounting for 84.37–89.43% of the total oil. Samples from May, June, and July were characterized by a high share of fatty acids (56, 69, and 34% respectively) with palmitic acid being the dominant one, while in the August sample, a high content of alcohols (mainly phytol and oleyl alcohol) was found. Changes in the other minor components, which could be important for the overall aroma and biological activities of the algal samples, have also been noted during the vegetation periods. The results of this paper contribute to studies of algal EOs and present the first report on C. compressa EOs. 相似文献
108.
Giuliana Pavone Lucia Motta Federica Martorana Gianmarco Motta Paolo Vigneri 《Molecules (Basel, Switzerland)》2021,26(23)
Human trophoblast cell-surface antigen-2 (Trop-2) is a membrane glycoprotein involved in cell proliferation and motility, frequently overexpressed in epithelial tumors. Thus, it represents an attractive target for anticancer therapies. Sacituzumab govitecan (SG) is a third-generation antibody-drug conjugate, consisting of an anti-Trop-2 monoclonal antibody (hRS7), a hydrolyzable linker, and a cytotoxin (SN38), which inhibits topoisomerase 1. Specific pharmacological features, such as the high antibody to payload ratio, the ultra-toxic nature of SN38, and the capacity to kill surrounding tumor cells (the bystander effect), make SG a very promising drug for cancer treatment. Indeed, unprecedented results have been observed with SG in patients with heavily pretreated advanced triple-negative breast cancer and urothelial carcinomas, and the drug has already received approval for these indications. These results are coupled with a manageable toxicity profile, with neutropenia and diarrhea as the most frequent adverse events, mainly of grades 1–2. While several trials are exploring SG activity in different tumor types and settings, potential biomarkers of response are under investigation. Among these, Trop-2 overexpression and the presence of BRCA1/2 mutations seem to be the most promising. We review the available literature concerning SG, with a focus on its toxicity spectrum and possible biomarkers of its response. 相似文献
109.
Due to its crucial role in pathophysiology, erythrocyte deformability represents a subject of intense experimental and modeling research. Here a computational approach to electro-deformation for erythrocyte mechanical characterization is presented. Strong points of the proposed strategy are: (1) an accurate computation of the mechanical actions induced on the cell by the electric field, (2) a microstructurally-based continuum model of the erythrocyte mechanical behavior, (3) an original rotation-free shell finite element, especially suited to the application in hand. As proved by the numerical results, the developed tool is effective and sound, and can foster the role of electro-deformation in single-cell mechanical phenotyping. 相似文献
110.