[Show abstract][Hide abstract] ABSTRACT: The plasmonic behavior of nanostructured materials has ignited intense research for the fundamental physics of plasmonic structures and their cutting-edge applications concerning the fields of nanoscience and biosensing. The optical response of plasmonic metals is generally well-described by classical Maxwell’s Equations (ME). Thus, the understanding of plasmons and the design of plasmonic nanostructures can therefore directly benefit from lastest advances achieved in classic research areas such as computational electromagnetics. In this context, this paper is devoted to review the most recent advances in nanoplasmonic modeling, related with the latest breakthroughs in surface integral equation (SIE) formulations derived from ME. These works have extended the scope of application of Maxwell’s Equations, from microwave/milimeter waves to infrared and optical frequency bands, in the emerging fields of nanoscience and medical biosensing.
Preview · Article · Jan 2015 · Progress In Electromagnetics Research
[Show abstract][Hide abstract] ABSTRACT: Cork oak (Quercus suber L.) is a research priority in the Mediterranean area and because of cork oaks’ distribution these stands are experiencing daily stress. Based on projections of intensifying climate change and considering the key role of exploring the recovery abilities, cork oak seedlings were subjected to a cumulative temperature increase from 25 °C to 55 °C and subsequent recovery. CO2 assimilation rate, chlorophyll fluorescence, anthocyanins, proline and lipid peroxidation were used to evaluate plant performance, while the relative abundance of seven genes encoding for proteins of cork oak with a putative role in thermal/stress regulation (POX1, POX2, HSP10.4, HSP17a.22, CHS, MTL and RBC) was analyzed by qPCR (quantitative Polymerase Chain Reaction). A temperature change to 35 °C showed abundance alterations in the tested genes; at 45 °C, the molecular changes were associated with an antioxidant response, possibly modulated by anthocyanins. At 55 °C, HSP17a.22, MTL and proline accumulation were evident. After recovery, physiological balance was restored, whereas POX1, HSP10.4 and MTL abundances were suggested to be involved in increased thermotolerance. The data presented here are expected to pinpoint some pathways changes occurring during such stress and further recovery in this particular Mediterranean species.
Full-text · Article · Mar 2014 · Journal of plant physiology
[Show abstract][Hide abstract] ABSTRACT: It has been proposed that disk-like micelles may be precursors to the formation of lamellar liquid crystals. The possibility of obtaining n-decane phosphonic acid (DPA) disk-like micelles in aqueous solution without the addition of a second ionic surfactant led us to study in detail the low-concentration range of this system by both a battery of experimental techniques and molecular dynamics (MD) simulations. The experimental results indicate that premicelles with some capacity to solubilize dyes are formed at 0.05 mM. The critical micelle concentration (cmc) was found to be (0.260 ± 0.023) mM, much lower than that previously reported in the literature. Spherical micelles, which immediately grow leading to disk-like micelles, are probably formed at this concentration. At (0.454 ± 0.066) mM disk-like micelles become unstable giving rise to the formation of an emulsion of lamellar mesophase that dominates the system beyond (0.670 ± 0.045) mM. These experimental results were corroborated by MD simulations which, additionally, allow describing the structure of the obtained micelles at atomic level. The analysis of the MD trajectories revealed the presence of strong intermolecular hydrogen bonds between the surfactant headgroups producing a compact polar layer with low water content. The formation of such H-bond network could explain the ability of this surfactant to form disk-like micelles at concentrations close to the cmc.
No preview · Article · Apr 2013 · The Journal of Physical Chemistry B
[Show abstract][Hide abstract] ABSTRACT: An efficient parallel implementation of the multilevel fast multipole algorithm-fast Fourier transform (MLFMA-FFT) has been successfully used to solve an electromagnetic problem involving one billion of unknowns, which indeed becomes the largest problem solved with the surface integral-equation approach up to now. In this paper, we present a deep review of this challenging execution, focusing on the details of the parallel implementation step by step, with the aim of describing the different stages of the parallel algorithm and analyzing its overall parallel performance.
Full-text · Article · Feb 2013 · Proceedings of the IEEE
[Show abstract][Hide abstract] ABSTRACT: Trees necessarily experience changes in temperature, requiring efficient short-term strategies that become crucial in environmental change adaptability. DNA methylation and histone posttranslational modifications have been shown to play a key role in both epigenetic control and plant functional status under stress by controlling the functional state of chromatin and gene expression. Cork oak (Quercus suber L.) is a key stone of the Mediterranean region, growing at temperatures of 45°C. This species was subjected to a cumulative temperature increase from 25°C to 55°C under laboratory conditions in order to test the hypothesis that epigenetic code is related to heat stress tolerance. Electrolyte leakage increased after 35°C, but all plants survived to 55°C. DNA methylation and acetylated histone H3 (AcH3) levels were monitored by HPCE (high performance capillary electrophoresis), MS-RAPD (methylation-sensitive random-amplified polymorphic DNA) and Protein Gel Blot analysis and the spatial distribution of the modifications was assessed using a confocal microscope. DNA methylation analysed by HPCE revealed an increase at 55°C, while MS-RAPD results pointed to dynamic methylation-demethylation patterns over stress. Protein Gel Blot showed the abundance index of AcH3 decreasing from 25°C to 45°C. The immunohistochemical detection of 5-mC (5-methyl-2'-deoxycytidine) and AcH3 came upon the previous results. These results indicate that epigenetic mechanisms such as DNA methylation and histone H3 acetylation have opposite and particular dynamics that can be crucial for the stepwise establishment of this species into such high stress (55°C), allowing its acclimation and survival. This is the first report that assesses epigenetic regulation in order to investigate heat tolerance in forest trees.
[Show abstract][Hide abstract] ABSTRACT: A computational modeling (in gas phase) to study the disposition of the homologous surfactants in a bidimensional simple model of mixed and homogeneous micelles was performed for the case of R-trimethylammonium bromide surfactants with different linear R lengths from R = C(5) to C(17). First, the bidimensional homogeneous (one component) micelle was modeled, and as a second step, heterogeneous (two components) bidimensional micelles were modeled. The difference in the number of carbon atoms between hydrocarbon chains of the surfactants in the heterogeneous micelles, Δn(C), ranged from 2 to 8. Results were contrasted with experimental data obtained at our own laboratory. The exothermic values of the steric energy changes showed strong attraction between components of homologous surfactants mixture, especially when one of the surfactants has a long chain. It may be argued that the inclusion of a shorter surfactant in the mixture and the twisting of the longer surfactant makes the bidimensional arrangement formation more exothermic. All predictions were in agreement with previous experimental results.
No preview · Article · Oct 2010 · The Journal of Physical Chemistry B
[Show abstract][Hide abstract] ABSTRACT: An efficient hybrid MPI/OpenMP parallel implementation of an innovative approach that combines the Fast Fourier Transform (FFT) and the Multilevel Fast Multipole Algorithm (MLFMA) has been successfully used to solve an electromagnetic problem involving 620 millions of unknowns. The MLFMA-FFT method can deal with extremely large problems due to its high scalability and its reduced computational complexity. The former is provided by the use of the FFT in distributed calculations and the latter by the application of the MLFMA in shared computation.
Full-text · Article · Jan 2010 · Progress In Electromagnetics Research
[Show abstract][Hide abstract] ABSTRACT: It is a prove infact that The Fast Fourier Transform (FFT) extension of the conventional Fast Multipole Method (FMM) reduces the matrix vector product (MVP) complexity and preserves the propensity for parallel scalling of the single level FMM. In this paper, an efficient parallel strategy of a nested variation of the FMM-FFT algorithm that reduces the memory requirements is presented. The solution provided by this parallel implementation for a challenging problem with more than 0.5 billion unknowns has constituted the world record in computational electromagnetics (CEM) at the beginning of 2009.
Full-text · Article · Jan 2010 · Progress In Electromagnetics Research
[Show abstract][Hide abstract] ABSTRACT: The evaporation behavior of solutions of an amphiphilic polymer, phosphonated polybutadiene in toluene and in water was studied by means of vapor pressure and evaporation rate measurements. The polymer reduces the vapor pressure and evaporation rate of toluene, while the opposite effect was observed in aqueous solutions. The effects were explained on the basis of the Flory-Huggins theory in the toluene solutions and the structure breaking effect in the aqueous solutions.
No preview · Article · Dec 2009 · Colloids and Surfaces A Physicochemical and Engineering Aspects
[Show abstract][Hide abstract] ABSTRACT: a b s t r a c t The critical micelle concentration (CMC) of tridecane, tetradecane and hexadecane phosphonic acids and their mono-and disodium salts were determined with a battery of methods. The CMC values for all the studied species follow the general trend of those of the lower homologos of the series. The values of the Gibbs free energy of micellisation are interpreted on the basis of the micelle structure in salts and acids. The monolater formed by acids at the air/water interface at the CMC is compact, which may be explained by the union among the polar head groups by hydrogen bonds. Monsodium salts show premicellar formation of acid soap-like compounds. The micellisation of disodium salts is accompanied by strong hydrolisis.
Full-text · Article · Sep 2009 · Colloids and Surfaces A Physicochemical and Engineering Aspects
[Show abstract][Hide abstract] ABSTRACT: An innovative preconditioner has been developed in this work. It significantly improves the convergence of the iterative solvers applied to electromagnetic radiation problems by a renormalization of the matrix equation. The preconditioner balances the disparities in terms of magnitude and units caused by the strong self-coupling of the antennas, the non-uniformity of the meshes and also by the coexistence of wire and surface basis functions. It can be easily integrated into different electromagnetic solvers with a negligible impact on the computational cost on account of its simple implementation.
Full-text · Article · Jan 2009 · Progress In Electromagnetics Research
[Show abstract][Hide abstract] ABSTRACT: The authors present a new matrix compression algorithm to improve the efficiency of the fast multipole method (FMM). The method is based on the application of the singular value decomposition (SVD) to the plane wave FMM aggregation matrices. These matrices are low-ranked, which is exploited to provide alternative sets of orthonormal singular basis functions, obtained as linear combinations of the original basis. By choosing only the most relevant singular functions, a much more compact representation is obtained to accurately handle the interactions between the FMM groups. The new formulation provides a reduction close to one order of magnitude both in computational cost and memory requirements, with a moderate impact on the accuracy of the solution.
No preview · Article · Sep 2008 · IEEE Transactions on Antennas and Propagation
[Show abstract][Hide abstract] ABSTRACT: The aqueous mixed system decyltrimethylammonium bromide (C(10)TAB)-hexadecyltrimethylammonium bromide (C(16)TAB) was studied by conductivity. ion-selective electrodes, surface tension, and fluorescence spectroscopy techniques. The mixture critical micelle concentration, M cmc*. aggregation number, N*, and micelle molar conductivity, Lambda(cmc)(M), showed that the system aggregation is strongly nonideal. Both cmc* and N* results were analyzed with two different procedures: (i) the regular solution theory on mixed micelles or Rubingh's theory, and (ii) by the determination of the partial critical micelle concentration of the amphiphile component i in the presence of a constant concentration of the other amphiphile component. cmc(i)*. The Rubingh procedure gives micelles richer in C(16)TAB than the overall mixtures, while procedure (ii) gives micelles having the same composition as in the complete surfactant mixture (alpha C(10)TAB). Mixed micelles are larger than pure surfactant ones, with nonspherical shape. Using a literature model, the cause of the synergistic effect seems to be a reduction of the hydrocarbon/water contact at the micelle surface when mixed micelles form. Conductivity and ion-selective electrodes indicate that highly ionized premicelles form immediately before the cmc*. The air/solution interface is strongly nonideal and much richer in C(16)TAB than the composition in the bulk. When micelles form there is a strong desorption from the air/solution interface because micelles are energetically favored when compared with the monolayer.
No preview · Article · Oct 2007 · Journal of Colloid and Interface Science
[Show abstract][Hide abstract] ABSTRACT: Genes constitute only a small portion of the total genome and precisely controlling their expression represents a substantial
problem for their regulation. Furthermore, non-coding DNA, that contains introns repetitive elements and active transposable
elements, demands effective mechanisms to silence it long-term. Cell differentiation and development are controlled through
temporal and spatial activation and silencing of specific genes. These patterns of gene expression must remain stable for
many cell generations and last or change when inductive developmental signals have disappeared or new ones induce new programmes.
What turns genes on and off? Among others, gene regulation is controlled by epigenetic mechanisms, defined as any gene-regulating
activity that does not also involve changes in the DNA code and is capable of persisting. It has become apparent that epigenetic
control of transcription is mediated through specific states of the chromatin structure. Associations of specific chromosomal
proteins, posttranslational histone modifications and DNA methylation are some of the epigenetic mechanisms that are involved
in controlling chromatin states. DNA methylation research can be approached from several standpoints, since there is a wide
range of techniques available to study the occurrence and localisation of methyldeoxycytosine in the genome. Several studies
dealing with DNA methylation in relation to tree development, microproprogation and somaclonal variation will be presented,
with the final aim of demonstrating that DNA methylation levels are hallmarks for growing seasonal periods and are related
to open windows of competence in plants.
Full-text · Article · Apr 2007 · Plant Cell Tissue and Organ Culture
[Show abstract][Hide abstract] ABSTRACT: A real-coded genetic algorithm was successfully applied to the matching network problem. Our approach reduces the search across different network topologies by the means of a generalized network description, in which the algorithm "decides" whether a reactive element is inductive or capacitive. Compared to previous analytical and semianalytical techniques that do not require a priori information about the network topology, this method is considerably simpler and its application is straightforward, regardless of the network complexity. Our approach accounts for constrained lossy elements, tolerances, and network on-site tuning. The results for a canonical load show the effectiveness of this method in comparison with other known methods. Finally, for HF broadband antennas, which involve network complexity limits and component value restrictions, it will be shown that the use of lossy networks may help to fulfil system requirements, with only a moderate impact on system efficiency
No preview · Article · Apr 2007 · IEEE Transactions on Antennas and Propagation