A Nyström method for a class of integral equations on the real line with applications to scattering by diffraction gratings and rough surfaces

We propose a Nystr¨om/product integration method for a class of second kind integral equations on the real line which arise in problems of two-dimensional scalar and elastic wave scattering by unbounded surfaces. Stability and convergence of the method is established with convergence rates dependent on the smoothness of components of the kernel. The method is applied to the problem of acoustic scattering by a sound soft one-dimensional surface which is the graph of a function f, and superalgebraic convergence is established in the case when f is infinitely smooth. Numerical results are presented illustrating this behavior for the case when f is periodic (the diffraction grating case). The Nystr¨om method for this problem is stable and convergent uniformly with respect to the period of the grating, in contrast to standard integral equation methods for diffraction gratings which fail at a countable set of grating periods.

On the solvability of second kind integral equations on the real line

This paper considers general second kind integral equations of the form(in operator form φ − kφ = ψ), where the functions k and ψ are assumed known, with ψ ∈ Y, the space of bounded continuous functions on R, and k such that the mapping s → k(s, · ), from R to L1(R), is bounded and continuous. The function φ ∈ Y is the solution to be determined. Conditions on a set W ⊂ BC(R, L1(R)) are obtained such that a generalised Fredholm alternative holds: If W satisfies these conditions and I − k is injective for all k ∈ W then I − k is also surjective for all k ∈ W and, moreover, the inverse operators (I − k) − 1 on Y are uniformly bounded for k ∈ W. The approximation of the kernel in the integral equation by a sequence (kn) converging in a weak sense to k is also considered and results on stability and convergence are obtained. These general theorems are used to establish results for two special classes of kernels: k(s, t) = κ(s − t)z(t) and k(s, t) = κ(s − t)λ(s − t, t), where κ ∈ L1(R), z ∈ L∞(R), and λ ∈ BC((R\{0}) × R). Kernels of both classes arise in problems of time harmonic wave scattering by unbounded surfaces. The general integral equation results are here applied to prove the existence of a solution for a boundary integral equation formulation of scattering by an infinite rough surface and to consider the stability and convergence of approximation of the rough surface problem by a sequence of diffraction grating problems of increasingly large period.

In optics humidity compensation in NDIR exhaust gas measurements of NO2

NDIR is proposed for monitoring of air pollutants emitted by ship engines. Careful optical filtering overcomes the challenge of optical detection of NO2 in humid exhaust gas, despite spectroscopic overlap with the water vapour band.

An alternative method to study the cooling of glasses from melt to solid phase

The aim of this preliminary work was to present a novel method, suitable to investigate the glass cooling, from melt to solid state, based on a fast, non-usual and easy microwave method. The following glass system xBaO . (100-x)B(2)O(3) (x = 0% and 40%) was selected as an example for this study. The melt was poured inside a piece of waveguide and then, its cooling was monitored by the microwave signal as a function of time. The variations in the signal can provide valuable informations about some structural changes that take place during the cooling stages, such as relaxation processes. This method can be useful to investigate the cooling and heating of other materials, opening new possibilities for investigation of dielectric behavior of materials under high temperatures. (C) 2008 Elsevier Inc. All rights reserved.

Er:YAl(3)(BO(3))(4) glassy thin films from polymeric precursor and sol-gel methods: Waveguides for integrated optics

This paper presents the characterization of single-mode waveguides for 980 and 1550 nm wavelengths. High quality planar waveguide structure was fabricated from Y(1-x)Er(x)Al(3)(BO(3))(4) multilayer thin films with x = 0.02, 0.05, 0.1, 0.3, and 0.5, prepared through the polymeric precursor and sol-gel methods using spin-coating. The propagation losses of the planar waveguides varying from 0.63 to 0.88 dB/cm were measured at 632.8 and 1550 nm. The photoluminescence spectra and radiative lifetimes of the Er(3+) (4)I(13/2) energy level were measured in waveguiding geometry. For most samples the photoluminescence decay was single exponential with lifetimes in between 640 mu s and 200 mu s, depending on the erbium concentration and synthesis method. These results indicate that Er doped YAl(3)(BO(3))(4) compounds are promising for low loss waveguides. (C) 2009 Elsevier B.V. All fights reserved.

Versatile microanalytical system with porous polypropylene capillary membrane for calibration gas generation and trace gaseous pollutants sampling applied to the analysis of formaldehyde, formic acid, acetic acid and ammonia in outdoor air

The analytical determination of atmospheric pollutants still presents challenges due to the low-level concentrations (frequently in the mu g m(-3) range) and their variations with sampling site and time In this work a capillary membrane diffusion scrubber (CMDS) was scaled down to match with capillary electrophoresis (CE) a quick separation technique that requires nothing more than some nanoliters of sample and when combined with capacitively coupled contactless conductometric detection (C(4)D) is particularly favorable for ionic species that do not absorb in the UV-vis region like the target analytes formaldehyde formic acid acetic acid and ammonium The CMDS was coaxially assembled inside a PTFE tube and fed with acceptor phase (deionized water for species with a high Henry s constant such as formaldehyde and carboxylic acids or acidic solution for ammonia sampling with equilibrium displacement to the non-volatile ammonium ion) at a low flow rate (8 3 nLs(-1)) while the sample was aspirated through the annular gap of the concentric tubes at 25 mLs(-1) A second unit in all similar to the CMDS was operated as a capillary membrane diffusion emitter (CMDE) generating a gas flow with know concentrations of ammonia for the evaluation of the CMDS The fluids of the system were driven with inexpensive aquarium air pumps and the collected samples were stored in vials cooled by a Peltier element Complete protocols were developed for the analysis in air of NH(3) CH(3)COOH HCOOH and with a derivatization setup CH(2)O by associating the CMDS collection with the determination by CE-C(4)D The ammonia concentrations obtained by electrophoresis were checked against the reference spectrophotometric method based on Berthelot s reaction Sensitivity enhancements of this reference method were achieved by using a modified Berthelot reaction solenoid micro-pumps for liquid propulsion and a long optical path cell based on a liquid core waveguide (LCW) All techniques and methods of this work are in line with the green analytical chemistry trends (C) 2010 Elsevier B V All rights reserved

Thomas-Fermi ground state of dipolar fermions in a circular storage ring

Recent developments in the field of ultracold gases has led to the production of degenerate samples of polar molecules. These have large static electric-dipole moments, which in turn causes the molecules to interact strongly. We investigate the interaction of polar particles in waveguide geometries subject to an applied polarizing field. For circular waveguides, tilting the direction of the polarizing field creates a periodic inhomogeneity of the interparticle interaction. We explore the consequences of geometry and interaction for stability of the ground state within the Thomas-Fermi model. Certain combinations of tilt angles and interaction strengths are found to preclude the existence of a stable Thomas-Fermi ground state. The system is shown to exhibit different behavior for quasi-one-dimensional and three-dimensional trapping geometries.

Ideais formativos de homem da emissora de Educação Rural de Caicó (Rio Grande do Norte, 1963-1978)

Under the aegis of the third diocese bishop of Caicó, Dom Manuel Tavares de Araújo, the Broadcasting Station of Rural Education of that city was founded, in May 1 s" 1963 with the ideal of being then an educational city, preferentially for youths and adults, rural meu and women of the arca of Seridó in Rio Grande do Norte state. In the year of its 40th birthday (2003), we began the investigation of that radio station choosing as study object its educational and formative programming, in the inc1usion of the first fifteen years of its existence (1963-1978), period that reaches the official inauguration of the Radio Station and the end of the bishopric of its fOllllder as Bishop of Caicó. Elucidating and showing Man's formative ideaIs longed by that Catholic educational broadcasting station, underlying to its radiophonic programming, such as the idealization for it reached, is the objective of this Doctorate work. It was considered pertinent to discover the guidelines that historically have permeated the Social Doçtrine of the Catholic Church addressing its aggiornamento, especially in what concerns to the employment of the modern ways of communication for the distance with the aim of evangelizing and educating. In arder to understand the ideaIs of the investigated educational Radio, we have delimited the research to the thematic Catholic Church, means of social communication and base education. In face of the study object and the aim to be reached it was appealed, methodologically, to the notion of cultural action present in Certeau (1995), and to the understanding of educational formation backgrounded fIam the modern thinkers that discuss it. Such frame references have allowed us to analyze in a wider spectrum tl)e programming broadcasted on the air by the sound wavys of that educ(itional Çatholic Radio, as well as, the very acts of cultural idealizations that has orientated it in its foundations. The thesis here defended is that. the Radio, at procJaiming itself as a broadcasting station of rural education directed preferably to the rural sertanejo countrymen, without neglecting its admitted ends, has surpassed them in its overall range. It was identified an articulate approach of its programmatic modules with the guid,elines emanateq from the Catholic Teaching about the use of the. means of social communication. At conceiving, establishin,g and executing an ec1ectic programmatic and div,ersified grating, the Rural Radio of Caicó has transcended to a strict human-Christian formation to request the development of the human, spiritual and cQrporaldimensions, jointly. With suchprogramming, it addressed to the seridoenses as real meu and women inserted in the "sertanej.o" environment with effective structural and existential problems of alI types, induding the hunger, the thirst, the syndical organization, the cQoperativism, the colIective modero work and the absence of universalizing school education. Its radiophonic transmissions, I}lled by the demands of an enlarged, open, dialogic and responsible communication, wheneIllbracing dedicated modules to religious and catechetical emissions, to the entertainment, to the radiojoumalism, to the country root culture, and to the school education of b se for the modality of the School and of the radiophonic classes, subsumed to ideaIs that longed for the formation of a multifaceted and pluridimensional sertanejo Man; of men and women that, without abjuring the Catholicism, were able to understand, to dialogued and to live together with the general demands of a society in progressive mutation, whose economical, social, cultural and educational demands it IDade themselves to be felt through the sertão potiguar of the Serido region, equal way of the intemationalized world

Signal transduction-related responses to phytohormones and environmental challenges in sugarcane

Background: Sugarcane is an increasingly economically and environmentally important C4 grass, used for the production of sugar and bioethanol, a low-carbon emission fuel. Sugarcane originated from crosses of Saccharum species and is noted for its unique capacity to accumulate high amounts of sucrose in its stems. Environmental stresses limit enormously sugarcane productivity worldwide. To investigate transcriptome changes in response to environmental inputs that alter yield we used cDNA microarrays to profile expression of 1,545 genes in plants submitted to drought, phosphate starvation, herbivory and N-2-fixing endophytic bacteria. We also investigated the response to phytohormones (abscisic acid and methyl jasmonate). The arrayed elements correspond mostly to genes involved in signal transduction, hormone biosynthesis, transcription factors, novel genes and genes corresponding to unknown proteins.Results: Adopting an outliers searching method 179 genes with strikingly different expression levels were identified as differentially expressed in at least one of the treatments analysed. Self Organizing Maps were used to cluster the expression profiles of 695 genes that showed a highly correlated expression pattern among replicates. The expression data for 22 genes was evaluated for 36 experimental data points by quantitative RT-PCR indicating a validation rate of 80.5% using three biological experimental replicates. The SUCAST Database was created that provides public access to the data described in this work, linked to tissue expression profiling and the SUCAST gene category and sequence analysis. The SUCAST database also includes a categorization of the sugarcane kinome based on a phylogenetic grouping that included 182 undefined kinases.Conclusion: An extensive study on the sugarcane transcriptome was performed. Sugarcane genes responsive to phytohormones and to challenges sugarcane commonly deals with in the field were identified. Additionally, the protein kinases were annotated based on a phylogenetic approach. The experimental design and statistical analysis applied proved robust to unravel genes associated with a diverse array of conditions attributing novel functions to previously unknown or undefined genes. The data consolidated in the SUCAST database resource can guide further studies and be useful for the development of improved sugarcane varieties.

Qualidade do serviço de informação digital :um estudo exploratório em web sites de Programas de Pós-Graduação

This dissertation of Mestrado investigated the performance and quality of web sites. The target of the research is the proposal of an integrated model of evaluation of services of digital information in web educational sites. The universe of the research was constituted by eighteen Brazilian Universities that offer after-graduation courses, in the levels of mestrado and doutorado in the area of Engineering of Production. The adopted methodology was a descriptive and exploratory research, using the technique of systematic comment and focus group, for the collection of the data, using itself changeable independent dependents and, through the application of two instruments of research. The analysis protocol was the instrument adopted for evaluation and attainment of qualitative results. E the analysis grating was applied for evaluation and attainment of the quantitative results. The qualitative results had identified to the lack of standardization of web sites, under the attributes of content, hierarchy of information, design of the colors and letters. It of accessibility for carriers of auditory and visual special necessities was observed inexistence, as well as the lack of convergence of medias and assistivas technologies. The language of the sites also was evaluated and all present Portuguese only language. The general result demonstrated in grafico and tables with classification of the Universities, predominating the Good note As for the quantitative results, analysis method ed was estatistico, in order to get the descriptive and inferencial result between the dependent and independent variaveis. How much a category of analysis of the services of the evaluated sites, was found it props up and the index generality weighed. These results had served of base for ranking of existence or inexistence the Universities, how much of the information of services in its web sites. In analysis inferencial the result of the test of correlation or association of the independent variaveis (level, concept of the CAPES and period of existence of the program) with the caracteristicas, called was gotten categories of services. For this analysis the estatisticos methods had been used: coefficient of Spearman and the Test of Fisher. But the category you discipline of the Program of Mestrado presented significance with variavel independent and concept of the CAPES. Main conclusion of this study it was ausencia of satandardization o how much to the subjective aspects, design, hierarchy of information navigability and content precision and the accessibility inexistence and convergence. How much to the quantitative aspects, the information services offered by web sites of the evaluated Universities, still they do not present a satisfactory and including quality. Absence of strategies, adoption of tools web, techniques of institucional marketing and services that become them more interactive, navigable is perceived and with aggregate value

Análise e otimização de superfícies seletivas de Frequência utilizando redes neurais artificiais e algoritmos de otimização natural

The bidimensional periodic structures called frequency selective surfaces have been well investigated because of their filtering properties. Similar to the filters that work at the traditional radiofrequency band, such structures can behave as band-stop or pass-band filters, depending on the elements of the array (patch or aperture, respectively) and can be used for a variety of applications, such as: radomes, dichroic reflectors, waveguide filters, artificial magnetic conductors, microwave absorbers etc. To provide high-performance filtering properties at microwave bands, electromagnetic engineers have investigated various types of periodic structures: reconfigurable frequency selective screens, multilayered selective filters, as well as periodic arrays printed on anisotropic dielectric substrates and composed by fractal elements. In general, there is no closed form solution directly from a given desired frequency response to a corresponding device; thus, the analysis of its scattering characteristics requires the application of rigorous full-wave techniques. Besides that, due to the computational complexity of using a full-wave simulator to evaluate the frequency selective surface scattering variables, many electromagnetic engineers still use trial-and-error process until to achieve a given design criterion. As this procedure is very laborious and human dependent, optimization techniques are required to design practical periodic structures with desired filter specifications. Some authors have been employed neural networks and natural optimization algorithms, such as the genetic algorithms and the particle swarm optimization for the frequency selective surface design and optimization. This work has as objective the accomplishment of a rigorous study about the electromagnetic behavior of the periodic structures, enabling the design of efficient devices applied to microwave band. For this, artificial neural networks are used together with natural optimization techniques, allowing the accurate and efficient investigation of various types of frequency selective surfaces, in a simple and fast manner, becoming a powerful tool for the design and optimization of such structures

Desenvolvimento de circuitos planares sobre substratos têxteis

The use of flexible materials for the development of planar circuits is one of the most desired and studied characteristics, lately, by researchers. This happens because the flexibility of the substrate can provide previously impracticable applications, due to the rigidity of the substrates normally used that makes it difficult to fit into the circuits in irregular surfaces. The constant interest in recent years for more lighter devices, increasingly more compacts, flexible and with low cost, led to a new line of research of great interest from both academic and technological views, that is the study and development of textile substrates that can be applied in the development of planar circuits, for applications in the areas of security, biomedical and telecommunications. This paper proposes the development of planar circuits, such as antennas , frequency selective surfaces (FSS) and planar filters, using textile (cotton ticking, jeans and brim santista) as the dielectric substrate and the Pure Copper Polyester Taffeta Fabric, a textile of pure copper, highly conductive, lightweight and flexible, commercially sold as a conductive material. The electrical characteristics of textiles (electric permittivity and loss tangent) were characterized using the transmission line method (rectangular waveguide) and compared with those found in the literature. The structures were analyzed using commercial software Ansoft Designer and Ansoft HFSS, both from the company Ansys and for comparison we used the Iterative Method of Waves (WCIP). For the purpose of validation were built and measured several prototypes of antennas, planar filters and FSS, being possible to confirm an excellent agreement between simulated and measured results

Pré-fabricados lingüísticos: estrutura e funcionamento de sintagmas verbais idiomatizados - por uma abordagem cognitivo-funcional em sala de aula

This work aims at under the cognitive-functional perspective describing, inside the vast domain of the linguistic prefabs, the structure and the functioning of the Idiomatic Verb Phrases (SVIs), produced by speakers of the Portuguese from Brazil, located in Natal (RN). From the functionalist presupposition that the language is used essentially to assist to communicative demands, it is observed that its morphologic-syntactic structure is conditioned to the inherent pragmatic vicissitudes to the verbal interaction of subjects, socially heterogeneous and historically established. It is focalized, in the composition of SVIs, the relationships VT + OD (transitive verb + direct object), characterizing the syntactic-semantic nature of the verb and of the respective verbal complement. Those verb combinations + complement can be interpreted as lexical structures, reflexes of the idiomaticity inherent to conventional constructions already systematized in the users' of the language cultural repertoire. It is sought, still, to glimpse the cognitive and discursive motivations pertinent to that linguistic phenomenon. In the investigative process, are analyzed exclusive data of speech collected in Corpus Discurso & Gramática a lingua falada e escrita na cidade do Natal, organized by Furtado da Cunha (1998). The adopted methodological procedures configure as methods of empiric analysis and use of the intuition, being emphasized the qualitative approach (explanatory) of the data with quantitative support of statistical indicators. It shows, finally, a grating of didactic suggestions on SVIs, for Portuguese's classes, as subsidies to the educational practice in the Medium Teaching and in the course of Letters.

The influence of visual inter-hemispheric connections on spiking, assembly and LFP activities, and their phase relationship during figure-ground stimulation

Desde os descobrimentos pioneiros de Hubel e Wiesel acumulou-se uma vasta literatura descrevendo as respostas neuronais do córtex visual primário (V1) a diferentes estímulos visuais. Estes estímulos consistem principalmente em barras em movimento, pontos ou grades, que são úteis para explorar as respostas dentro do campo receptivo clássico (CRF do inglês classical receptive field) a características básicas dos estímulos visuais como a orientação, direção de movimento, contraste, entre outras. Entretanto, nas últimas duas décadas, tornou-se cada vez mais evidente que a atividade de neurônios em V1 pode ser modulada por estímulos fora do CRF. Desta forma, áreas visuais primárias poderiam estar envolvidas em funções visuais mais complexas como, por exemplo, a separação de um objeto ou figura do seu fundo (segregação figura-fundo) e assume-se que as conexões intrínsecas de longo alcance em V1, assim como as conexões de áreas visuais superiores, estão ativamente envolvidas neste processo. Sua possível função foi inferida a partir da análise das variações das respostas induzidas por um estímulo localizado fora do CRF de neurônios individuais. Mesmo sendo muito provável que estas conexões tenham também um impacto tanto na atividade conjunta de neurônios envolvidos no processamento da figura quanto no potencial de campo, estas questões permanecem pouco estudadas. Visando examinar a modulação do contexto visual nessas atividades, coletamos potenciais de ação e potenciais de campo em paralelo de até 48 eletrodos implantados na área visual primária de gatos anestesiados. Estimulamos com grades compostas e cenas naturais, focando-nos na atividade de neurônios cujo CRF estava situado na figura. Da mesma forma, visando examinar a influência das conexões laterais, o sinal proveniente da área visual isotópica e contralateral foi removido através da desativação reversível por resfriamento. Fizemos isso devido a: i) as conexões laterais intrínsecas não podem ser facilmente manipuladas sem afetar diretamente os sinais que estão sendo medidos, ii) as conexões inter-hemisféricas compartilham as principais características anatômicas com a rede lateral intrínseca e podem ser vistas como uma continuação funcional das mesmas entre os dois hemisférios e iii) o resfriamento desativa as conexões de forma causal e reversível, silenciando temporariamente seu sinal, permitindo conclusões diretas a respeito da sua contribuição. Nossos resultados demonstram que o mecanismo de segmentação figurafundo se reflete nas taxas de disparo de neurônios individuais, assim como na potência do potencial de campo e na relação entre sua fase e os padrões de disparo produzidos pela população. Além disso, as conexões laterais inter-hemisféricas modulam estas variáveis dependendo da estimulação feita fora do CRF. Observamos também uma influência deste circuito lateral na coerência entre potenciais de campo entre eletrodos distantes. Em conclusão, nossos resultados dão suporte à ideia de um mecanismo complexo de segmentação figura-fundo atuando desde as áreas visuais primárias em diferentes escalas de frequência. Esse mecanismo parece envolver grupos de neurônios ativos sincronicamente e dependentes da fase do potencial de campo. Nossos resultados também são compatíveis com a hipótese que conexões laterais de longo alcance também fazem parte deste mecanismo

FIR laser lines from CH3OD: A review

The methanol isotopic species CH3OD has also proved to be an efficient and powerful medium to generate radiation in the far infrared (FIR) region. After the critical review of 1994, six papers have been published dealing with new FIR laser lines from this molecule. As a consequence of the use of wide tunability waveguide CO2 lasers as well as a new pulsed CO2 laser operating at hot and sequential bands, as of optical pumping sources, the total number of the FIR laser lines increased from 122 in 1994 to 227 today. In this communication we present an updated and complete catalogue of FIR laser lines generated from CH3OD. Information on wavelength, offset, relative polarization, intensity, and optimum operation pressure is generally available.