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排序方式: 共有681条查询结果,搜索用时 31 毫秒
661.
Ant?nio C. H. Barreto Vivian R. Santiago Rafael M. Freire Selma E. Mazzetto Juliano C. Denardin Giuseppe Mele Igor M. Cavalcante Maria E. N. P. Ribeiro Nágila M. P. S. Ricardo Tamara Gon?alves Luigi Carbone Telma L. G. Lemos Otília D. L. Pessoa Pierre B. A. Fechine 《International journal of molecular sciences》2013,14(9):18269-18283
This paper describes the investigation and development of a novel magnetic drug delivery nanosystem (labeled as MO-20) for cancer therapy. The drug employed was oncocalyxone A (onco A), which was isolated from Auxemma oncocalyx, an endemic Brazilian plant. It has a series of pharmacological properties: antioxidant, cytotoxic, analgesic, anti-inflammatory, antitumor and antiplatelet. Onco A was associated with magnetite nanoparticles in order to obtain magnetic properties. The components of MO-20 were characterized by XRD, FTIR, TGA, TEM and Magnetization curves. The MO-20 presented a size of about 30 nm and globular morphology. In addition, drug releasing experiments were performed, where it was observed the presence of the anomalous transport. The results found in this work showed the potential of onco A for future applications of the MO-20 as a new magnetic drug release nanosystem for cancer treatment. 相似文献
662.
Gregory B. Kharas Emi Hanawa Aida B. Agpasa Tamara O. Fedczyna Bridget M. Flaherty Jennifer L. Fernandes Magdaline Liosatos Michael E. Lukowski Kathrine G. Skinner Regan N. Theiler 《Polymer Bulletin》2013,70(2):707-714
Novel electrophilic trisubstituted ethylene monomers, alkyl ring-substituted 2-cyano-3-phenyl-2-propenamides, RC6H4CH=C(CN)CONH2 (where R is 2-methyl, 3-methyl, 4-methyl, 4-ethyl, 4-i-propyl, 4-i-butyl, and 4-t-butyl), were synthesized by potassium hydroxide catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and cyanoacetamide, and characterized by CHN elemental analysis, IR, 1H- and 13C-NMR. Novel copolymers of the ethylenes and styrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator, AIBN at 70 °C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, 1H- and 13C-NMR, GPC, DSC, and TGA. High T g of the copolymers in comparison with that of polystyrene indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200–500 °C range with residue (5–7 wt%), which then decomposed in the 500–800 °C range. 相似文献
663.
Yang Wang Guangjie Zheng Steven R. Spielman Tamara Pinterich Susanne V. Hering Jian Wang 《Aerosol science and technology》2013,47(9):1092-1106
Hygroscopicity describes the tendency of aerosol particle to uptake water and is among the key parameters in determining the impact of atmospheric aerosols on global radiation and climate. A hygroscopicity tandem differential mobility analyzer (HTDMA) system is the most widely used instrument for determining the aerosol hygroscopic growth. Because of the time needed to scan the classifying voltage of the DMA, HTDMA measurement often requires a minimum of 30?min to characterize the particle hygroscopic growth at a single relative humidity for five to six different sizes. This slow speed is often inadequate for measurements onboard mobile platforms or when aerosols evolve rapidly. Recently, a humidity-controlled fast integrated mobility spectrometer (HFIMS) was developed for measuring the hygroscopic growth of particles. The measurement speed of the HFIMS is about one order of magnitude faster than that of the conventional HTDMA. In this work, a data inversion routine is developed to retrieve the growth factor probability density function (GF-PDF) of particles measured by the HFIMS. The inversion routine considers the transfer functions of the upstream DMA and the downstream water-based fast integrated mobility spectrometer (FIMS), and derives the GF-PDF that reproduces the measured responses of the HFIMS. The performance of the inversion routine is examined using ambient measurements with different assumptions for the spectral shape of the particle GF-PDF (multimodal lognormal or piecewise linear). The influences of the data inversion parameters and counting statistics on the inverted GF-PDFs were further investigated, and an approach to determine the optimized inversion parameters is presented.Copyright © 2019 American Association for Aerosol Research 相似文献
664.
Binding of pyrene to hydrophobic fractions of dissolved organic matter: effect of polyvalent metal complexation 总被引:2,自引:0,他引:2
The effects of polyvalent metal cations on pyrene binding to hydrophobic acid and neutral fractions (HoA and HoN, respectively) of dissolved organic matter (DOM) were elucidated. The DOM was isolated from sewage sludge; pyrene binding was estimated from fluorescence measurements. Isotherms of pyrene binding to both fractions were nonlinear. Pyrene binding was higher for HoN due to the combined effect of greater hydrophobicity, aromaticity and the large molecular size of this fraction relative to HoA. The complexation of HoA with Cu2+, Al3+, and Fe3+ increased the binding of pyrene only when the HoA was equilibrated with polyvalent cations before pyrene was added. The maximal increase in pyrene binding to HoA was 56%, 64%, and 118% when pre-equilibrated with Cu2+, Fe3+, and Al3+, respectively. Pyrene binding to HoN was not affected by the presence of metal cations. HoA complexation with metal cations increased the apparent molecular size of this fraction. We suggest that the presence of metal cations induces the formation of pseudomicelles, which are more efficient in binding pyrene than the low-molecular-weight components. Our results demonstrate that HoA and HoN components can significantly affect the transport of organic contaminants in soils irrigated with treated wastewater or amended with sewage sludge. 相似文献
665.
Tamara G. Oberti Martín J. Lavecchia M. Susana Cortizo 《Journal of Polymer Research》2011,18(6):1293-1299
p-Nitrobenzyl acrylate was polymerized under microwave irradiation initiated by benzoyl peroxide. The effect of the reaction
conditions on the conversion, average molecular weights and the polydispersity index (Mw/Mn) were investigated. The polymers were characterized by IR, 1H and 13C-NMR spectroscopies and molecular weights were analyzed with size exclusion chromatography (SEC). Optical properties in seven
solvents were studied. The most outstanding characteristics of this monomer were slow kinetics of polymerization and low average
molecular weight (Mw ~ 3000) as result of the chain transfer reaction to monomer, as it was demonstrated by experimental test and theoretical
calculations. Solvatochromic effect of polymer solutions by changing the solvent polarity was quantitatively expressed by
means of the linear solvation energy relationship using the empirical Kamlet-Taft solvents parameters set. The analyses demonstrated
that the solute-solvent dipolar interactions were mainly responsible of the observed shift of νmax and attributed to the para-nitrobenzyl group of the monomer, which enhanced the optical properties of the polymer. 相似文献
666.
Radoslava Pravilović Tamara Janković Milica Veljković Branislav Todić Milica Simović Dejan Bezbradica Nikola Nikačević 《American Institute of Chemical Engineers》2023,69(9):e18122
A new micro-kinetic model of the enzyme-catalyzed synthesis of fructo-oligosaccharides (FOS) was developed. A commercial enzyme mixture Pectinex® Ultra SP-L derived from Aspergillus aculeatus was used. A variety of initial enzyme concentrations (1–5 vol%) and sucrose concentrations (400–600 g/L) were experimentally investigated and included in kinetic modeling. Several variations of kinetic mechanisms and corresponding models have been examined. A hybrid genetic algorithm was used to predict the kinetic parameters simultaneously for all experimental data. The best fitting model has been adopted, and with an average error of 13.34%, it describes the experimental data very well. The influence of initial concentrations on the conversion of sucrose and production of FOS is being carefully investigated. It was shown that the initial sucrose concentration significantly affects the highest level of FOS concentration, but the enzyme concentration controls the time at which maximum is reached as well as the rate of FOS decomposition. 相似文献
667.
The gastropod Littorina littorea (common periwinkle) is an abundant and widespread North Atlantic species. The characteristic development of Intersex in L. littorea has been widely applied as a biomarker for tributyltin (TBT) contamination. Here, we assess the potential of L. littorea as a novel sentinel species for evaluating the sublethal effects in wild populations of widely distributed contaminants. We collected animals from six sites across the South coast of England. Tissue concentrations of polycyclic aromatic hydrocarbons (PAHs), organotin compounds (OTCs), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs) were measured and compared with biomarkers of damage to DNA (Comet assay), lysosomal stability (NRR assay), and endocrine disruption (Intersex development). There was a strong correlation between DNA damage and PAH bioaccumulation (n=6, r=0.84, p<0.05), as well as that between Intersex development and OTC pollution (n=6, r=0.91, p<0.05). The relationship between PAH bioaccumulation and DNA strand breaks was nonlinear, highlighting the need to consider the role of adaptive mechanisms in the interpretation of field results. These results illustrate the potential use of periwinkles for monitoring a wide range of priority pollutants. 相似文献
668.
Mechanical lightweight structures often tend to unwanted vibrations due to disturbances. Passive methods for increasing the structural damping are often inadequate for the vibration suppression, since they include additional mass in the form of damping materials, additional stiffening designs or mass damper. In this paper the concept of an active vibration control for piezoelectric light weight structures is introduced and presented through several subsequent steps: model identification, controller design, simulation, experimental verification and implementation on a particular object??piezoelectric smart cantilever beam. Special attention is paid to experimental testing and verification of the results obtained through simulations. The efficiency of the modeling procedure through the subspace-based system identification along with the efficiency of the designed optimal controller are proven based on the experimental verification, which results in vibration suppression to a very high extent not only in comparison with the uncontrolled case, but also in comparison with previously achieved results. The experimental work demonstrates a very good agreement between simulations and experimental results. 相似文献
669.
Sorption and desorption hysteresis of widely applied triazine and phenylurea herbicides were studied for river sediments. Organic carbon normalized sorption coefficient (KOC) values for all herbicides were significantly higher for the sediment from the downstream region of the river vs. the upstream sediment. On the basis of the measured KOC values, the triazine herbicides can be arranged in the following order: terbutryn>terbuthylazine>ametryn>atrazine. Among the phenylurea herbicides, chlorotoluron exhibited higher sorption than isoproturon (KOC values of 137 vs. 60 and 228 vs. 125 L/kg for the upstream and downstream sediments, respectively). Moreover, chlorotoluron exhibited lower desorption potential as compared with isoproturon (apparent hysteresis index values were 0.2–0.3 for chlorotoluron vs. 0.6–0.9 for isoproturon, measured with the upstream sediment). High sorption affinity of chlorotoluron to the sediments is probably due to stronger H-bonding interactions of the herbicide molecules with the sorbents. For both phenylurea herbicides, desorption hysteresis increased with decrease in sorbed amount. This behavior was opposite to the hysteresis trend observed for the triazines. The Cl-triazines (atrazine and terbuthylazine) exhibited higher desorption hysteresis than the S-triazines (ametryn and terbutryn). Therefore, the apparent hysteresis index values calculated for the Cl-triazines were lower than the values of S-triazines (about 0.4 and 0.7, respectively). Based on the relative strength of H-bonding interactions of Cl- and S-triazines with formate anion and on the desorption hysteresis data we suggest a gradient-derived hole-filling sorption mechanism for the triazine herbicides with the river sediments. 相似文献
670.
Tamara Bakuradze Roman Lang Thomas Hofmann Herbert Stiebitz Gerhard Bytof Ingo Lantz Matthias Baum Gerhard Eisenbrand Christine Janzowski 《Molecular nutrition & food research》2010,54(12):1734-1743
Scope: Epidemiological studies suggest that coffee can reduce the risk of degenerative diseases such as diabetes type 2, cardiovascular disease and cancer. These beneficial effects have partly been attributed to the antioxidant activity of coffee. We determined composition and antioxidant potential of differentially roasted coffee extracts and investigated the impact of selected original constituents and roast products. Methods and results: Parameters studied were direct antioxidant activity (trolox equivalent antioxidant capacity/oxygen radical absorbing capacity), cellular reactive oxygen species (ROS) level, DNA damage and protein expression of NAD(P)H: quinone oxidoreductase, γ‐glutamylcysteine ligase and glutathione reductase in HT‐29/Caco‐2 cells at 24‐h incubation. All extracts showed distinct direct antioxidant activity: medium roasts>light roast AB1 (caffeoylquinic acid (CQA)‐rich Arabica Brazil extract); dark roast AB2 (N‐methylpyridinium (NMP)‐rich Arabica Brazil extract), and diminished t‐butylhydroperoxide‐induced ROS level in HT‐29 cells (AB2>medium roasts>AB1). NAD(P)H:quinone oxidoreductase 1 expression and γ‐glutamylcysteine ligase expression were distinctly induced by AB1 and 5‐CQA, but not by AB2 and NMP. 5‐CQA and caffeic acid exhibited highest trolox equivalent antioxidant capacity/oxygen radical absorbing capacity values (5‐CQA: 1.3/3.5 mM and caffeic acid: 1.3/3.9 mM trolox); ROS level was distinctly diminished by 5‐CQA (≥3 μM), catechol (30 μM) and trigonelline (≥30 μM), whereas menadione‐induced DNA damage in Caco‐2 cells was reduced by NMP compounds (1–30 μM). Conclusion: The results emphasize that both original constituents and roast products contribute to the cellular antioxidant effectiveness of coffee. 相似文献