Molecular dynamics simulation and crystal field calculations of the Eu2O3-PbO-SiO2 glassy system submitted to long annealing time

The Eu2O3-PbO-SiO2 glassy system submitted to a long annealing time (100 ps) has been obtained by molecular dynamics calculations. The average of 87/86 sites of the Eu3 + ion with six/seven nearest neighbours are used to discuss the number of lines and the local symmetry of the luminescent site through the crystal field parameters, using the simple overlap model in the frame of the method of equivalent nearest neighbours. The magnitude of the [View the MathML source] Bq2(q = 0, 1, 2) and the non-negligible [View the MathML source] B44 and [View the MathML source] B46( [View the MathML source] B34, [View the MathML source] B36 and [View the MathML source] B66) lead to the indication of distorted C4h and C3i site symmetries of the six and seven nearest neighbours, respectively. We have then compared very satisfactorily our 7F1 sublevels calculations with those observed in the emission spectra of an Eu-borate glass annealed for 30 min and 17 h. This comparison is justified because the emission behaviour of europium ions in different glassy systems are honestly very similar. Further, the decrease observed in the 5D0→7F2/5D0→7F1 transition intensity ratio is a clear indication that the Eu3 + ion are nucleating a crystalline phase. Such satisfactory comparisons indicate that we have obtained a transparent glass-ceramics

Improved Transfer-Matrix Schemes of Phenomenological Renormalization

Different phenomenological RG transformations based on scaling relations for the derivatives of the inverse correlation length and singular part of the free-energy density are considered. These transformations are tested on the 2D square Ising and Potts models as well as on the 3D simple-cubic Ising model. Variants of RG equations yielding more accurate results than Nightingale's RG scheme are obtained. In the 2D case the finite-size equations which give the {\it exact} values of the critical point or the critical exponent are found.Comment: LATTICE99(spin), 3 pages, no figures; to be published in Nucl. Phys. B (Proc. Suppl.

Spatio-temporal variations of Anopheles coluzzii and An. gambiae and their Plasmodium infectivity rates in Lobito, Angola

From 2003 to 2007, entomological surveys were conducted in Lobito town (Benguela Province, Angola) to determine which Anopheles species were present and to identify the vectors responsible for malaria transmission in areas where workers of the Sonamet Company live. Two types of surveys were conducted: (1) time and space surveys in the low and upper parts of Lobito during the rainy and dry periods; (2) a two-year longitudinal study in Sonamet workers' houses provided with long-lasting insecticide-treated nets (LLIN), "PermaNet," along with the neighboring community. Both species, An. coluzzii (M molecular form) and An. gambiae (S molecular form), were collected. Anopheles coluzzii was predominant during the dry season in the low part of Lobito where larvae develop in natural ponds and temporary pools. However, during the rainy season, An. gambiae was found in higher proportions in the upper part of the town where larvae were collected in domestic water tanks built near houses. Anopheles melas and An. listeri were captured in higher numbers during the dry season and in the low part of Lobito where larvae develop in stagnant brackish water pools. The infectivity rates of An. gambiae s.l. varied from 0.90% to 3.41%

Preinvex functions and weak efficient solutions for some vectorial optimization problem in Banach spaces

AbstractIn this work, we introduce the notion of preinvex function for functions between Banach spaces. By using these functions, we obtain necessary and sufficient conditions of optimality for vectorial problems with restrictions of inequalities. Moreover, we will show that this class of problems has the property that each local optimal solution is in fact global

Molecular dynamics simulation of silver nanoparticles in a europium doped sodosilicate glass

Molecular dynamics simulation is applied to an europium doped sodosilicate glass containing silver [(Na–Ag)2O–SiO2–Eu2O3]. The silver is implanted in substitution of Na, simulating an ionic exchange. For ionic interactions a modified Born–Mayer–Huggins potential was employed. For the Ag–Ag interaction, a Lennard-Jones (LJ) potential is applied, while for the Eu–Ag interaction, a modified LJ potential is introduced. The particle size increases with the annealing treatment and follows a lognormal law. After 75 ps the average particle size reaches 5.8 atoms (4.8 for Ag and 1.0 for Eu), and it is found that the europium is preferentially situated on these nanoclusters

Indicadores das condições nutricionais na região do polonoroeste: IV. Inquérito alimentar em famílias de seis cidades da região do Polonoroeste, Mato Grosso, Brasil, 1983

O trabalho se refere aos dados coletados em inquérito alimentar recordatório de 24h no Inquérito Nutricional da Pesquisa Diagnóstico em Saúde no Polonoroeste em 1983 em 6 cidades da região do Polonoroeste/MT. Como uma primeira aproximação da problemática alimentar da região, o estudo revela os alimentos mais referidos nas entrevistas que são alimentos básicos, fontes de energia, semi-industrializados e de custo mais baixo.This work refers to collected data in a 24 h - oral - recall method, from the Nutritional Inquiry of Health Diagnostic Survey in Polonoroeste area in 1983, within six cities from this area. As a first approach of the Nutritional problematic of the area, the study shows the most referred foods in the interviews, which are non industrialized basic foods, source of energy and of lower cost

Theoretical investigation of the 7F1 level splitting in a series of Eu3+ doped oxides matrixes

The point charge electrostatic model (PCEM) and the simple overlap model (SOM) are applied to a series of oxide crystals (Gd2O3, Y2O3, Lu2O3, In2O3 and Sc2O3) and a silicate glass (Al2O3–SiO2) doped with the Eu3+ ion. The SOM factor ρ(2β)k+1 is input as the shielding factor for all B q k expressions, which enters in the calculations of the crystal-field strength parameter, NV. The maximum splitting ΔE of the 7F1 manifold of the Eu3+ ion is then obtained as a function of NV. It has been developed another way to calculate alpha, which is an expansion factor in the ΔE expression. For the glass, as the mean metal-ligating ions distances are larger than for the crystals, NV and ΔE are smaller, as expected. The prediction of the PCEM shows a linear dependence between ΔE and NV, even though the known mismatch in respect to the experimental splitting is kept. In the case of the SOM, two situations have been analyzed: firstly the charge factor varies in order to reproduce the experimental splitting (a phenomenological procedure); secondly the charge factor is the valence of the oxygen ions. The agreement between the experimental results and theoretical predictions for all investigated systems is very satisfactory in respect to both the linearity between ΔE and NV and the ΔE splitting

Is it possible to photoperiod manipulate spawning time in planktivorous fish ? A long-term experiment on Atlantic herring

The oocyte development (vitellogenesis) of individual fish is highly dependent upon their physiology which is influenced by both intrinsic and extrinsic factors. Thus, if individuals encounter poor biophysical conditions, they will likely be unable to reproduce. The photoperiod is an external factor that is constant between years but with increasing intra-annual (seasonal) variation polewards. In high-latitude marine environments, several ecological processes are strongly photic entrained, e.g., the planktonic spring bloom. However, it is still unclear whether day length or planktonic peaks (feeding opportunity) is the main timer or regulator behind gametogenesis not only for teleost piscivores but also for planktivores living in these waters. Hence, we experimentally investigated the role of photoperiod steering vitellogenesis in the planktivorous Atlantic herring (Clupea harengus), rearing larvae up to the mature adult stage. We imposed a natural and 6-month offset photoperiod hypothesising that vitellogenesis is entrained by this photic zeitgeber. The results of our experiment clearly demonstrated that herring have a strong photic zeitgeber acting upon vitellogenesis according to the experienced photoperiod. Thus, the Offset Group showed a displacement in vitellogenesis of 6 months. The second hypothesis that feeding opportunities play a clear role in assisting this photic zeitgeber in Atlantic herring could be rejected. This clarification supports that the survival potential of the larvae is the main selection pressure in operation in these respects, i.e., rather than the extent of feeding opportunities of the adults.publishedVersio