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981.
The venom gland of queens of Apis mellifera was examined through light and transmission electron microscopy and subjected to electrophoretic analyses. Virgin queens exhibited prismatic secretory cells containing large amounts of rough endoplasmic reticulum with dilated cisternae, open secretory spaces, numerous vacuoles and granules scattered in the cytoplasm, and spherical nuclei with numerous nucleoli. The secretion produced was non-refringent under polarized light and the electrophoretic analysis of glandular extracts revealed five main protein bands. In mated queens, the venom gland exhibited a high degree of degeneration. Its secretion was refringent under polarized light and one of the main bands was absent in the electrophoretic pattern obtained. The morphological aspects observed are in agreement with the function of this gland in queens, given that virgin queens use venom in battles for the dominance of the colony, a situation that occurs as soon as they emerge, while fertilized queens rarely use venom. 相似文献
982.
983.
We show that, in general, the solutions to the initial-boundary value problem for the Navier-Stokes equations under a widely adopted Navier-type slip
boundary condition do not converge, as the viscosity goes to zero, to the solution of the Euler equations under the classical
zero-flux boundary condition, and same smooth initial data, in any arbitrarily small neighborhood of the initial time. Convergence
does not hold with respect to any space-topology which is sufficiently strong as to imply that the solution to the Euler equations
inherits the complete slip type boundary condition. In our counter-example Ω is a sphere, and the initial data may be infinitely
differentiable. The crucial point here is that the boundary is not flat. In fact (see Beir?o da Veiga et al. in J Math Anal
Appl 377:216–227, 2011) if
W = \mathbb R3+,{\,\Omega = \mathbb R^3_+,} convergence holds in
C([0,T]; Wk,p(\mathbb R3+)){C([0,T]; W^{k,p}(\mathbb R^3_+))}, for arbitrarily large k and p. For this reason, the negative answer given here was not expected. 相似文献
984.
Rafael Augusto Couceiro Correa Davi Monteiro Dantas Pedro Henrique Ribeiro da Silva Moraes Alvaro de Souza Dutra Carlos Alberto Santos de Almeida 《Annalen der Physik》2018,530(7)
This work aims to analyse the so‐called configurational entropy in the Weyl pure geometrical thick brane model. The Weyl structure plays a prominent role in the brane thickness of this model. We find a set of parameters associated to the brane width where the configurational entropy exhibits critical points. The information‐theoretical measure sets bounds into parameter of Weyl pure geometrical brane model. In addition, we also argue that a similar approach can be useful to analyze the corrections to Newtonian and Coulombian potentials in Weyl scenarios. 相似文献
985.
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
986.
Dandan?Lian Bing?Shi Rongrong?Dai Xiaohua?JiaEmail author Xiangyang?WuEmail author 《Journal of nanoparticle research》2017,19(12):401
A kind of novel ZnSnO3/SnO2 hollow urchin nanostructure was synthesized by a facile, eco-friendly two-step liquid-phase process. The structure, morphology, and composition of samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption–desorption techniques. The results revealed that many tiny needle-like SnO2 nanowires with the average diameter of 5 nm uniformly grew on the surface of the ZnSnO3 hollow microspheres and the ZnSnO3/SnO2 hollow urchin nanostructures with different SnO2 content also were successfully prepared. In order to comprehend the evolution process of the ZnSnO3/SnO2 hollow urchin nanostructures, the possible growth mechanism of samples was illustrated via several experiments in different reaction conditions. Moreover, the gas-sensing performance of as-prepared samples was investigated. The results showed that ZnSnO3/SnO2 hollow urchin nanostructures with high response to various concentration levels of acetone enhanced selectivity, satisfying repeatability, and good long-term stability for acetone detection. Specially, the 10 wt% ZnSnO3/SnO2 hollow urchin nanostructure exhibited the best gas sensitivity (17.03 for 50 ppm acetone) may be a reliable biomarker for the diabetes patients, which could be ascribed to its large specific surface area, complete pore permeability, and increase of chemisorbed oxygen due to the doping of SnO2. 相似文献
987.
Carlos E. T. Magalhães Marcio M. da Silva Ranylson M. L. Savedra 《Molecular physics》2017,115(3):357-363
Polyfluorene copolymers are attractive semiconductor materials, in particular for applications in the organic electronics field. They are versatile to be chemically modified and allow a tuning of the emission to cover the entire visible spectrum. A better understanding of the fundamental aspects of the nature of electronic structure and charge transport properties contribute to the improvement of optoelectronic properties of polymeric materials. Here, we provide a structure–property relationship for models of fluorene-PPV and fluorene-MEH-PPV copolymers, using molecular quantum mechanics modelling. The anisotropy is discussed revisiting Mulliken's transition moment theory. Accordingly, our results show that electron mobility occurs preferentially intrachain for both copolymers. Moreover, the interchain electron mobility has the most propensity to occur via π-stacking interactions. 相似文献
988.
The curvature tensor and its derivatives up to any order can be covariantly characterized by a minimal set of spinor quantities. On the other hand it might be useful, particularly in cosmology, to describe the geometry of a spacetime in a (1+3) formalism, based on an invariantly defined fluid velocity. In this work, we consider an imperfect fluid possessing both isotropic and anisotropic pressure. For these fluids, we determine the (1+3) matter terms of the curvature as well as the parts of the first order covariant derivative of the curvature (\(\nabla R\)) determined pointwise by the matter via the Bianchi identities. Explicit relations between the set of such terms obtained from the (1+3) and spinor decomposition of \(\nabla R\) are given. We show that in both sets there are 36 independent terms. 相似文献
989.
L. D. da Silva A. Ranciaro Neto J. L. L. dos Santos F. A. B. F. de Moura 《Brazilian Journal of Physics》2017,47(6):583-588
We consider the problem of a harmonic lattice in which masses’ distribution is a superposition of a random and a periodic distribution. Classical equations for the mass displacement and velocities are solved using a second-order Euler formalism. Energy flow was investigated on two distinct experiments: (i) We injected an initial wave-packet with energy E 0 and analyzed the dynamics of the resulting energy pulse; (ii) we pumped one of the sides of the lattice with a external signal and then we observed the propagation of the pulse until the other side of chain. Our calculations suggest that the diluted disordered mass distribution promotes energy dynamics at high frequency limit. 相似文献
990.
A.S. Gouveia-Neto R.F. do Nascimento E.A. da Silva E.B. da Costa 《Journal of Non》2009,355(8):488-5709
Upconversion luminescence in erbium-doped PbGeO3-PbF2-CdF2-based vitroceramic under 1540 nm infrared excitation is investigated. Luminescence signals around 410, 525, 550, 660 and 850 nm were generated and attributed to the 2H9/2, 2H11/2, 4S3/2 and 4F9/2 transitions to the 4I15/2 ground-state, and 4S3/2-4I13/2, respectively. The erbium ions excited-state emitting levels were populated through a combination of stepwise ground-state absorption, phonon-assisted excited-state absorption and cross-relaxation processes. The results also disclosed that all emission signals obtained with vitroceramic samples presented intensities three times higher when compared to the precursor glass samples. In addition, the red emission signal at 660 nm for 1540 nm pumping exhibited an expressively high intensity when compared to the green signal. 相似文献