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901.
N. Lago J. L. Legido M. I. Paz Andrade I. Arias L. M. Casás 《Journal of Thermal Analysis and Calorimetry》2011,105(2):651-655
Microcalorimetry is an experimental technique which allows us to precisely measure the energy released as a consequence of
any transformation process. All organisms produce heat as a consequence of metabolism. The rate of heat production is an adequate
measurement of metabolic activity of organisms and their constituent parts, cells and sub-cellular levels. Microorganisms
produce small amounts of heat, in the order of 1–3 pW per cell. Despite the low quantity of heat produced by bacteria, their
exponential replication in culture medium allows their detection using microcalorimetry. This study is a microcalorimetric
study of the growth and metabolism of the bacterium Pseudomonas aeruginosa, using the heat liberated as a consequence of bacterial metabolism. With this aim, we used a Calvet microcalorimeter, inside
which two Teflon screw-capped stainless steel cells were located (sample and reference). Experiments were carried out at final
concentrations of 106, 105, 103 and 10 CFU/mL, and a constant temperature of 309.65 K was maintained within the microcalorimeter. Recording the difference
in calorific potential over time we obtained P. aeruginosa’s growth curves. The shape of these curves is characteristic and has a single phase. Thus, the heat flow curves were mathematically
studied to calculate the growth constant and generation time of this bacterium. 相似文献
902.
dos Santos DP Andrade GF Brolo AG Temperini ML 《Chemical communications (Cambridge, England)》2011,47(25):7158-7160
Stokes and anti-Stokes SERRS intensity fluctuations were observed from a roughened silver electrode immersed in diluted solutions of Brilliant Green (BG), a behaviour linked to single-molecule events. The distributions of the anti-Stokes to Stokes ratios were obtained and their shape showed a strong dependence on the applied potential. 相似文献
903.
Nogueira Kde O Araújo VA Rodrigues Sartori SS Neves CA 《Micron (Oxford, England : 1993)》2011,42(5):377-380
Hemidactylus mabouia is an Africa oviparous lizard that is now distributed on other continents and has been introduced to Brazil. In the majority of reptiles, the females have the ability to store spermatozoa in specialized regions of the genital tract. Considering that in H. mabouia the storage of spermatozoa is restricted to the region of the uterine tube, in this study we utilized optical and transmission electron microscopy to investigate the processes related to the large number of spermatozoa in the vagina. Although it was possible to visualize spermatozoa in the vagina, an ultrastructural analysis of the region revealed that significant phagocytosis occurs, which is mediated by the epithelial cells. Such a process indicates that the anterior portion of the vagina is related to the elimination of supernumerary or deficient spermatozoa and not storage. 相似文献
904.
Orlando D. H. Santos Jacqueline M. Morais Fernanda F. Andrade Tatiana A. Aguiar Pedro A. Rocha Filho 《Journal of Dispersion Science and Technology》2013,34(3):433-438
Emulsions containing vegetable oils and anisotropic phases have especially attractive properties in pharmaceutical technology. They are use as vehicle for different kind of drugs, especially those of topical application. Apart from that, many vegetable oil have pharmacological activity, increasing the necessity for the development of new delivery systems for them. We developed emulsions with vegetable oils at a fixed surfactant ratio and observed the formation of liquid crystalline phases. Nine vegetable oils: Andiroba, Apricot, Avocado, Brazil Nut, Buriti, Cupuassu, Marigold, Passion Fruit and Pequi and mineral oil were tested. Surfactant system was consisted by Steareth-2 and Ceteareth-5. Emulsions were prepared by the emulsion phase inversion (EPI) method, presenting high stability independent on the HLB value. Results indicate that this method could be employed to attain stable emulsions, even if the required HLB value is not known. 相似文献
905.
Patricia Leme Goto José Mario Carneiro Vilela Margareth Spangler Andrade 《Journal of Dispersion Science and Technology》2013,34(2):228-233
Polymeric nanoparticles constitute an important drug delivery system with controlled release profile. This article describes a new way to produce polymeric nanocapsules using a vegetable oil nanoemulsion as template. The process occurs in two steps: First, a nanoemulsion was obtained with a low-energy method based on phase inversion emulsification, using 2-ethylhexyl acrylate as lipophilic monomer. The in situ polymerization of the nanoemulsion droplets is induced by the addition of polymerization catalyzers. The mean size of the polymeric nanoparticles was evaluated by photon correlation spectroscopy and atomic force microscopy. Both techniques showed the formation of polymeric nanocapsules with a mean particle size less than 300 nm. 相似文献
906.
Ana Paula Dias Ribeiro Mariana Carvalho Andrade Julhiany de Fátima da Silva Janaina Habib Jorge Fernando Lucas Primo Antonio Cláudio Tedesco Ana Cláudia Pavarina 《Photochemistry and photobiology》2013,89(1):111-119
New drug delivery systems, such as nanoemulsions (NE), have been developed to allow the use of hydrophobic drugs on the antimicrobial photodynamic therapy. This study evaluated the photodynamic potential of aluminum‐chloride‐phthalocyanine (ClAlPc) entrapped in cationic and anionic NE to inactivate Candida albicans planktonic cultures and biofilm compared with free ClAlPc. Fungal suspensions were treated with different delivery systems containing ClAlPc and light emitting diode. For planktonic suspensions, colonies were counted and cell metabolism was evaluated by XTT assay. Flow cytometry evaluated cell membrane damage. For biofilms, the metabolic activity was evaluated by XTT and ClAlPc distribution through biofilms was analyzed by confocal laser scanning microscopy (CLSM). Fungal viability was dependent on the delivery system, superficial charge and light dose. Free ClAlPc caused photokilling of the yeast when combined with 100 J cm?2. Cationic NE‐ClAlPc reduced significantly both colony counts and cell metabolism (P < 0.05). In addition, cationic NE‐ClAlPc and free ClAlPc caused significant damage to the cell membrane (P < 0.05). For the biofilms, cationic NE‐ClAlPc reduced cell metabolism by 70%. Anionic NE‐ClAlPc did not present antifungal activity. CLSM showed different accumulation on biofilms between the delivery systems. Although NE system showed a lower activity for planktonic culture, cationic NE‐ClAlPc showed better results for Candida biofilms. 相似文献
907.
Roberto Luiz Andrade HaidukeAuthor Vitae Ubirajara Pereira Rodrigues-FilhoAuthor Vitae 《Polyhedron》2011,30(8):1396-1403
We employed the Density Functional Theory along with small basis sets, B3LYP/LANL2DZ, for the study of FeTIM complexes with different pairs of axial ligands (CO, H2O, NH3, imidazole and CH3CN). These calculations did not result in relevant changes of molecular quantities as bond lengths, vibrational frequencies and electronic populations supporting any significant back-donation to the carbonyl or acetonitrile axial ligands. Moreover, a back-donation mechanism to the macrocycle cannot be used to explain the observed changes in molecular properties along these complexes with CO or CH3CN. This work also indicates that complexes with CO show smaller binding energies and are less stable than complexes with CH3CN. Further, the electronic band with the largest intensity in the visible region (or close to this region) is associated to the transition from an occupied 3d orbital on iron to an empty π∗ orbital located at the macrocycle. The energy of this Metal-to-Ligand Charge Transfer (MLCT) transition shows a linear relation to the total charge of the macrocycle in these complexes as given by Mulliken or Natural Population Analysis (NPA) formalisms. Finally, the macrocycle total charge seems to be influenced by the field induced by the axial ligands. 相似文献
908.
Velvadapu V Paul T Wagh B Glassford I DeBrosse C Andrade RB 《The Journal of organic chemistry》2011,76(18):7516-7527
Novel sources of antibiotics are required to address the serious problem of antibiotic resistance. Telithromycin (2) is a third-generation macrolide antibiotic prepared from erythromycin (1) and used clinically since 2004. Herein we report the details of our efforts that ultimately led to the total synthesis of (-)-4,8,10-tridesmethyl telithromycin (3) wherein methyl groups have been replaced with hydrogens. The synthesis of desmethyl macrolides has emerged as a novel strategy for preparing bioactive antibiotics. 相似文献
909.
Tôrres AR Lyra Wda S de Andrade SI Andrade RA da Silva EC Araújo MC Gaião Eda N 《Talanta》2011,84(3):601-606
This work proposes the use of digital image-based method for determination of total acidity in red wines by means of acid-base titration without using an external indicator or any pre-treatment of the sample. Digital images present the colour of the emergent radiation which is complementary to the radiation absorbed by anthocyanines present in wines. Anthocyanines change colour depending on the pH of the medium, and from the variation of colour in the images obtained during titration, the end point can be localized with accuracy and precision. RGB-based values were employed to build titration curves, and end points were localized by second derivative curves. The official method recommends potentiometric titration with a NaOH standard solution, and sample dilution until the pH reaches 8.2-8.4. In order to illustrate the feasibility of the proposed method, titrations of ten red wines were carried out. Results were compared with the reference method, and no statistically significant difference was observed between the results by applying the paired t-test at the 95% confidence level. The proposed method yielded more precise results than the official method. This is due to the trivariate nature of the measurements (RGB), associated with digital images. 相似文献
910.
The Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence has been used in many applications of magnetic resonance imaging (MRI) and low-resolution NMR (LRNMR) spectroscopy. Recently, CPMG was used in online LRNMR measurements that use long RF pulse trains, causing an increase in probe temperature and, therefore, tuning and matching maladjustments. To minimize this problem, the use of a low-power CPMG sequence based on low refocusing pulse flip angles (LRFA) was studied experimentally and theoretically. This approach has been used in several MRI protocols to reduce incident RF power and meet the specific absorption rate. The results for CPMG with LRFA of 3π/4 (CPMG135), π/2 (CPMG90) and π/4 (CPMG45) were compared with conventional CPMG with refocusing π pulses. For a homogeneous field, with linewidth equal to Δυ = 15 Hz, the refocusing flip angles can be as low as π/4 to obtain the transverse relaxation time (T2) value with errors below 5%. For a less homogeneous magnetic field, Δυ = 100 Hz, the choice of the LRFA has to take into account the reduction in the intensity of the CPMG signal and the increase in the time constant of the CPMG decay that also becomes dependent on longitudinal relaxation time (T1). We have compared the T2 values measured by conventional CPMG and CPMG90 for 30 oilseed species, and a good correlation coefficient, r = 0.98, was obtained. Therefore, for oilseeds, the T2 measurements performed with π/2 refocusing pulses (CPMG90), with the same pulse width of conventional CPMG, use only 25% of the RF power. This reduces the heating problem in the probe and reduces the power deposition in the samples. 相似文献