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51.
Saulo Carneiro 《General Relativity and Gravitation》2018,50(9):114
In a previous paper it was shown that a minimally coupled scalar field of mass \(M \sim H_0\) can describe both components of the dark sector in a unified way. In the solution found, the dark energy component decays linearly with the Hubble parameter, with a homogeneous creation of dark matter. In the present note we show that a \(\Lambda \)CDM dark sector can also be modeled by such a single field. More generally, we show that the system of Klein–Gordon and Einstein equations admits a uniparametric family of solutions that is equivalent to a non-adiabatic (with zero sound speed) generalised Chaplygin gas. 相似文献
52.
Sara Pacelli de Sousa Marcial Guilherme Carneiro Elaine A. Leite 《Journal of nanoparticle research》2017,19(10):340
Paclitaxel (PTX) is a well-known antitumor drug, widely utilized in the treatment of breast, ovarian, head, and neck tumors, among others. The low aqueous solubility (< 1.0 μg/mL; log P = 3.96) limits its use by intravenous route, and alternatives found for the marketed products are associated with high toxicity. Incorporation of PTX into lipid nanocarriers has been considered an interesting nontoxic alternative for this route, but drug loading is usually low. This study aimed to analyze the influence of the lipid composition and three different lipid nanosystems—solid lipid nanoparticles, nanostructured lipid carriers (NLCs), and nanoemulsion—in PTX encapsulation and its biological response. The three proposed systems were prepared by hot melt homogenization followed by ultrasonication. Among the blank formulations first prepared, NLC had the smallest size (74 ± 1 nm), with negative zeta potential (? 11.4 ± 0.1 mV). The incorporation of 0.10 mg/mL PTX into this NLC formulation yielded high and stable encapsulation (0.089 ± 0.003 mg/mL), also supported by polarized light microscopy and differential scanning calorimetry curves. NLC-PTX was very effective against MCF-7 (IC50 25.33 ± 3.17 nM) and MDA-MB-231 breast cancer cell lines (IC50 2.13 ± 0.21 nM), compared to free PTX (IC50 > 500 nM). In addition, no significant cytotoxicity was found against fibroblast cells. Taken together, these results demonstrated that PTX was successfully incorporated into NLC with appropriate physicochemical characteristics for intravenous administration, suggesting that the use of NLC as vehicle to incorporate PTX may be a promising strategy in the treatment of breast cancer. 相似文献
53.
J.S. Alcaniz H.A. Borges S. Carneiro J.C. Fabris C. Pigozzo W. Zimdahl 《Physics letters. [Part B]》2012
We demonstrate that creation of dark-matter particles at a constant rate implies the existence of a cosmological term that decays linearly with the Hubble rate. We discuss the cosmological model that arises in this context and test it against observations of the first acoustic peak in the cosmic microwave background (CMB) anisotropy spectrum, the Hubble diagram for supernovas of type Ia (SNIa), the distance scale of baryonic acoustic oscillations (BAO) and the distribution of large scale structures (LSS). We show that a good concordance is obtained, albeit with a higher value of the present matter abundance than in the ΛCDM model. We also comment on general features of the CMB anisotropy spectrum and on the cosmic coincidence problem. 相似文献
54.
Brustein VP Cavalcanti CL de Melo-Junior MR Correia MT Beltrão EI Carvalho LB 《Applied biochemistry and biotechnology》2012,166(2):268-275
Nowadays, there is an increase of investigations into the fibroadenoma, mainly because some studies have shown that the occurrence
of fibroadenoma is linked to an increased risk of developing breast carcinoma. Currently, the chemiluminescence biomarkers
are applied for validation methods and screening. Here, a lectin chemiluminescence is proposed as new histochemistry method
to identify carbohydrates in mammary tumoral tissues. The lectins concanavalin A (Con A) and peanut agglutinin (PNA) conjugated
to acridinium ester were used to characterize the glycocode of breast tissues: normal, fibroadenoma, and invasive duct carcinoma
(IDC). The lectin chemiluminescence expressed in relative light units (RLU) was higher in fibroadenoma and IDC than in normal
tissue for both lectins tested. The relationship RLU emission versus tissue area described a linear and hyperbolic curve for
IDC and fibroadenoma, respectively, using Con A whereas hyperbolic curves for both transformed tissues using PNA. RLU was
abolished by inhibiting the interaction between tissues and lectins using their specific carbohydrates: methyl-α-d-mannoside (Con A) and galactose (PNA). The intrinsic fluorescence emission did not change with combination of the lectins
(Con A/PNA) to the acridinium ester for hydrophobic residues. These results represent the lectin chemiluminescence as an alternative
of histochemistry method for tumoral diagnosis in the breast. 相似文献
55.
de Vasconcelos MA Cunha CO Arruda FV Carneiro VA Mercante FM do Nascimento Neto LG de Sousa GS Rocha BA Teixeira EH Cavada BS dos Santos RP 《Molecules (Basel, Switzerland)》2012,17(5):5244-5254
To study the interactions between a Rhizobium tropici strain and lectins isolated from the seeds of Canavalia ensiformis (ConA) and Canavalia brasiliensis (ConBr), a lectin fluorescence assay was performed. In addition, an experiment was designed to evaluate the effect of the two lectins on bacterial growth. Both lectins were found to bind to R. tropici cells, but the interactions were inhibited by D-mannose. Interestingly, only ConBr stimulated bacterial growth in proportion to the concentrations used (15.6-500 μg/mL), and the bacterial growth stimulation was inhibited by D-mannose as well. Structure/Function analyses by bioinformatics were carried out to evaluate the volume and carbohydrate recognition domain (CRD) configuration of ConA and ConBr. The difference of spatial arrangement and volume of CRD may indicate the variation between biological activities of both lectins. The results suggest that ConBr could be a promising tool for studies focusing on the interactions between rhizobia and host plants. 相似文献
56.
de Oliveira EC Monteiro MI Pontes FV de Almeida MD Carneiro MC da Silva LI Alcover Neto A 《Journal of AOAC International》2012,95(2):560-566
Chemical analysts use analytical blanks in their analyses, but seldom is this source of uncertainty evaluated. Generally, there is great confusion. Although the numerical value of the blank, in some situations, can be negligible, its source of uncertainty cannot be. This article discusses the uncertainty contribution of the analytical blank using a numerical example of the copper content in waters by flame atomic absorption spectrometry. The results indicate that the uncertainties of the analytical blank can contribute up to 50% when the blank sample is considered in this analysis, confirming its high impact. This effect can be primarily observed where the analyte concentration approaches the lower range of the analytical curve. Even so, the blank is not always computed. Therefore, the relevance of the analytical blank can be confirmed by uncertainty evaluation. 相似文献
57.
Lucas H. Martorano Jordana T. Brito Ana Carolina F. de Albuquerque Carlos Magno Rocha Ribeiro Rodolfo Goetze Fiorot José Walkimar de Mesquita Carneiro Fabio Luiz Paranhos Costa Alessandra L. Valverde Fernando Martins dos Santos Junior 《Magnetic resonance in chemistry : MRC》2022,60(4):434-441
Recently, structural elucidation of natural products has undergone a revolution. The combined use of different modern spectroscopic methods has allowed obtaining a complete structural assignment of natural products using small amounts of sample. However, despite the extraordinary ongoing advances in spectroscopy, the mischaracterization of natural products has been and remains a recurrent problem, especially when the substance presents several stereogenic centers. The misinterpretation of nuclear magnetic resonance (NMR) data has resulted in frequent reports addressing structural reassignment. In this context, a great effort has been devoted to developing quantum chemical calculations that simulate NMR parameters accurately, allowing to achieve a more precise spectral interpretation. In this work, we employed a protocol for theoretical calculations of 1H NMR chemical shifts and coupling constants using density functional theory (DFT), followed by the application of the DP4+ method to revisit the structure of Heliannuol L, a member of the Heliannuol class, isolated from Helianthus annuus. Our results indicate that the originally proposed structure of Heliannuol L needs a stereochemical reassignment, placing the hydroxyl bonded to C10 in the opposite side of the methyl and hydroxyl groups bonded to C7 and C8, respectively. 相似文献
58.
Malucelli L. C. Carneiro J. Vasconcelos E. C. Magalhães W. L. E. Murakami F. S. Carvalho Filho M. A. S. 《Journal of Thermal Analysis and Calorimetry》2020,141(3):1149-1155
Journal of Thermal Analysis and Calorimetry - The use of biomass has been a recent trend as a potential feedstock for char generation with improved energetic value. In this work, agricultural... 相似文献
59.
60.
We present electron spin resonance results on three different conducting phases of the organic conductor based on the planar molecule BEDT-TTF (bis(ethylenedithio)tetrathiafulvalene) and the anion ReO4 in different stoichiometries. Both the paramagnetic susceptibility χ as well as the ESR-linewidth ΔHpp may be used to classify the magnetic behaviour in terms of known behaviour of other organic metals. They indicate that the 2:1 phase, which under pressure becomes superconducting, has an anion-ordering assisted metal-insulator transition near 80 K and that the 3:2 phase has a Peierls transition at 88 K, below which two ESR lines are resolved. A third phase, which includes solvent in the crystal lattice, shows no evidence of a transition. 相似文献