Infrared upconversion for astronomical applications

The performance of an upconversion system is examined for observation of astronomical sources in the low to middle infrared spectral range. Theoretical values for the performance parameters of an upconversion system for astronomical observations are evaluated in view of the conversion efficiencies, spectral resolution, field of view, minimum detectable source brightness and source flux. Experimental results of blackbody measurements and molecular absorption spectrum measurements using a lithium niobate upconverter with an argon-ion laser as the pump are presented. Estimates of the expected optimum sensitivity of an upconversion device which may be built with the presently available components are given

Effects of Electromagnetic Field on Gravitational Collapse

In this paper, the effect of electromagnetic field has been investigated on the spherically symmetric collapse with the perfect fluid in the presence of positive cosmological constant. Junction conditions between the static exterior and non-static interior spherically symmetric spacetimes are discussed. We study the apparent horizons and their physical significance. It is found that electromagnetic field reduces the bound of cosmological constant by reducing the pressure and hence collapsing process is faster as compared to the perfect fluid case. This work gives the generalization of the perfect fluid case to the charged perfect fluid. Results for the perfect fluid case are recovered.Comment: 17 pages, accepted for publication in Mod. Phys. Lett

Design, fabrication, characterization and aging studies of solar selective absorber surfaces

Tese de Doutoramento - Programa Doutoral em Física (MAP- fis)Esta tese tem como objetivo o desenvolvimento de revestimentos para absorção seletiva da radiação solar, que tenham um elevado coeficiente de absorção solar (α) (> 95%), baixa emissividade (ε) (<12% a 400 ºC), e com elevada estabilidade térmica, acima de 400 ° C ao ar e acima de 600 ºC em vácuo, de modo a que possa ser usado em sistemas de concentração da radiação solar (CSP) que utilizem temperaturas elevadas. Os revestimentos são multicamadas, que têm quatro a cinco camadas, sendo as duas primeiras, uma barreira de difusão e um refletor de radiação infravermelha, tungsténio. As restantes são constituídas por uma estrutura de dupla camada para absorção da radiação solar e uma camada antirefletora. Para a configuração das camadas de absorção, foram utilizadas três soluções diferentes. As duas primeiras soluções baseiam-se em camadas de nitreto / oxinitreto de metais de transição, nomeadamente a partir de crómio (CrAlSiNx/CrAlSiNxOy) e tungsténio (WsiAlNx/WSiAlNxOy). A terceira solução é baseada em compósitos cerâmico-metal de AlSiOx:W. Camadas individuais das diferentes soluções foram depositadas em substratos de vidro, aço inoxidável (SS) e silício (Si) para estudar a composição química, estrutura, propriedades ópticas e mecânicas. Os espectros de transmitância e reflectância das camadas individuais, depositados em substratos de vidro, foram simulados com o software SCOUT, de modo a calcular a respetiva função dielétrica, as constantes ópticas espectrais e espessuras. As multicamadas foram desenhadas utilizando as constantes ópticas das camadas individuais, utilizando também o software SCOUT. Utilizando os resultados das simulações, as multicamadas foram depositadas em substratos de aço inoxidável utilizando a técnica de pulverização catódica por magnetrão e o desempenho dos revestimentos foi verificado por meio da sua absorção solar, da emissividade e do seu comportamento quando sujeitos a tratamentos térmicos ao ar e em vácuo. Diversas técnicas de caracterização foram utilizadas para estudar os revestimentos, nomeadamente por microscopia eletrónica de varrimento (SEM), espectrometria de retrodispersão de Rutherford (RBS), difração de raios X (DRX), espectroscopia de infravermelho com transformada de Fourier (FTIR), espectroscopia de fotoeletrões de raios-X (XPS), espectroscopia de raios-X por dispersão em energia (EDS), análise de detecção de recuo elástico por tempo de voo (TOF-ERDA), espectroscopia Raman e espectroscopia UV-VIS-NIR. Os revestimentos multicamada apresentados nesta tese mostraram boa estabilidade térmica e resistência à oxidação após o tratamento térmico em vácuo a 600 ºC ou 580 ºC e tratamento térmico ao ar a 400 ºC ou 450 ºC. A solução baseada na estrutura WSiAlNx/WSiAlOyNx apresentou os melhores resultados, em termos de estabilidade térmica, resistência à oxidação e coeficiente de absorção solar, enquanto a baseada em CrAlSiNx/CrAlSiNxOy apresentou os valores mais baixos de emissividade à temperatura de 400 ºC. As alterações no coeficiente de absorção solar (αsol) e na emissividade (ε) são insignificantes na maioria dos casos. Em alguns casos, só foram reveladas pequenas mudanças nas curvas de refletância após o primeiro passo de tratamento térmico, não aparecendo alterações nos passos subsequentes. No caso dos revestimentos baseados em CrAlSiNx / CrAlSiNxOy, após o tratamento térmico em vácuo a 600 ºC, verificou-se que ocorreu a difusão de átomos de tungsténio da camada de W para o substrato de aço inoxidável. Assim, foi introduzida uma camada de barreira de CrAlSiNx entre a camada de tungsténio e o substrato de aço e fetuado o respetivo estudo, tendo-se verificado a não ocorrência da difusão do W.This thesis has the objective to develop solar selective absorber coatings having simultaneously high solar absorptance (α) (>95%) and low emissivity (ε) (<12% at 400 ºC) together with high thermal stability above 400°C in air and above 600 ºC in vacuum, which could be used in the concentrated solar power (CSP) or in other high temperature applications. The coatings are multilayer stacks, that have four to five layers, being the first two, a barrier layer and a back-reflector tungsten layer. The remaining layers comprise a double film structure for phase interference finished by an antireflection layer. For the double absorption layer configuration, three different approaches have been used. The first two are based on transition metal nitride/oxynitride layers, namely from chromium as (CrAlSiNx/CrAlSiNxOy) and from tungsten as (WSiAlNx/WSiAlNxOy). Whereas, the third one is based on (AlSiOx:W) cermets. The single layers of each approach were deposited on glass, stainless-steel (SS) and silicon (Si) substrates to study their chemical composition, structure, optical and mechanical properties. The transmittance (T) and the reflectance (R) spectra of single thin layers, deposited on glass substrates, were modelled with the help of SCOUT software and the spectral optical constants and thicknesses were calculated. The multilayer designs were performed using the optical constants of the single layers and conducted with SCOUT software. The final multilayer stacks were deposited on stainless-steel substrates using DC magnetron sputtering technique and the functionality of the absorbers optical stacks was verified through solar absorptance, emissivity and accelerated thermal ageing treatments. All tandems and their individual layers were characterized by Scanning Electron Microscopy (SEM), Rutherford Backscattering Spectrometry (RBS), X-ray diffraction (XRD), Fourier-transform Infrared Spectroscopy (FTIR), X-Ray Photoelectron Spectroscopy (XPS), Energy Dispersive X-ray Spectroscopy (EDS), Time of flight Elastic Recoil Detection Analysis (TOF-ERDA), Raman spectroscopy and UV–VIS–IR spectroscopy. The absorber tandems presented in this thesis showed good thermal stability and oxidation resistance after vacuum annealing at 600 ºC or 580 ºC and air annealing at 400 ºC or 450 ºC. The approach based on WSiAlNx/WSiAlOyNx tandem showed the best thermal stability, oxidation resistance and it has higher solar absorbance, αsol, while the CrAlSiNx/ CrAlSiNxOy shows the lowest thermal emittance at the temperature (400 ºC). The variations in the solar absorptance (αsol) and the thermal emittance (ε) are negligible in most cases. In some cases, small variations in the reflectance curves after the first step of annealing were observed. After the annealing in vacuum at 600 ºC, tungsten diffusion from the back-reflection layer towards the stainless-steel substrate was found in the tandem based on CrAlSiNx/ CrAlSiNxOy. Thus, a CrAlSiNx barrier layer with higher nitrogen N content was included between the stainlesssteel substrate and tungsten. The influence of that barrier layer upon the W diffusion was also studied.Financial support of FCT, POCI and PORL operational programs through the project POCI- 01-0145-FEDER-016907 (PTDC/CTM-ENE/2882/2014), co-financed by European community fund FEDER

Costs analysis of a population level rabies control programme in Tamil Nadu, India

The study aimed to determine costs to the state government of implementing different interventions for controlling rabies among the entire human and animal populations of Tamil Nadu. This built upon an earlier assessment of Tamil Nadu’s efforts to control rabies. Anti-rabies vaccines were made available at all health facilities. Costs were estimated for five different combinations of animal and human interventions using an activity-based costing approach from the provider perspective. Disease and population data were sourced from the state surveillance data, human census and livestock census. Program costs were extrapolated from official documents. All capital costs were depreciated to estimate annualized costs. All costs were inflated to 2012 Rupees. Sensitivity analysis was conducted across all major cost centres to assess their relative impact on program costs. It was found that the annual costs of providing Anti-rabies vaccine alone and in combination with Immunoglobulins was \$0.7 million (Rs 36 million) and \$2.2 million (Rs 119 million), respectively. For animal sector interventions, the annualised costs of rolling out surgical sterilisation-immunization, injectable immunization and oral immunizations were estimated to be \$ 44 million (Rs 2,350 million), \$23 million (Rs 1,230 million) and \$ 11 million (Rs 590 million), respectively. Dog bite incidence, health systems coverage and cost of rabies biologicals were found to be important drivers of costs for human interventions. For the animal sector interventions, the size of dog catching team, dog population and vaccine costs were found to be driving the costs. Rabies control in Tamil Nadu seems a costly proposition the way it is currently structured. Policy makers in Tamil Nadu and other similar settings should consider the long-term financial sustainability before embarking upon a state or nation-wide rabies control programme

The Linear Optical Properties of Rhodamin110 Organic Dye Doped with Metal Nanoparticles

Background: Laser dyes are unsaturated hydrocarbon compounds that have the advantage of having double or triple bonds coupled with carbon atom chains. This system benefits from light absorption in the visible range (200–700 nm) and the transmission spectrum of absorption in the visible range Materials and Methods: This research has focused on the effect of Adding ethanol solution to rhodamine110 dye with different concentrations, the linear properties (permeability, absorbance) of Rhodamine110 dye were studied as it was dissolved in ethanol to prepare solutions with concentrations (0. 01, 0.03, 0.05) and at room temperature Results: The absorbance A of Rhodamine110 dye with ethanol was calculated for the above concentrations, respectively, as well as and the transmittance T was calculated for the above concentrations, respectively, to obtain curves and rhodamine110 dyes were mixed with nanomaterials to improve the properties of the dyes Conclusion: In this study, According to Beer-Lambert's rule, increasing the dye concentration will increase absorbance, which will raise the linear optical coefficients (refractive index and coefficient of absorption) for all produced samples. The probability of electronic transitions will definitely be affected by the type of solvent., and this has an impact on linear optical characteristics, particularly the positions and width of the absorption spectra. And the addition of nanomaterials added better improvements to the dye. The results showed that the highest linear properties appeared when the silver nanomaterials with rhodamine110 dy

Calibration and accuracy assessment of Leica ScanStation C10 terrestrial laser scanner

Requirement of high accuracy data in surveying applications has made calibration procedure a standard routine for all surveying instruments. This is due to the assumption that all observed data are impaired with errors. Thus, this routine is also applicable to terrestrial laser scanner (TLS) to make it available for surveying purposes. There are two calibration approaches: (1) component, and (2) system calibration. With the intention to specifically identify the errors and accuracy of the Leica ScanStation C10 scanner, this study investigates component calibration. Three components of calibration were performed to identify the constant, scale error, accuracy of angular measurement and the effect of angular resolution for distance measurement. The first calibration has been processed using closed least square solutions and has yielded the values of constant (1.2 mm) and scale error (1.000008879). Using variance ratio test (F-Test), angles observation (horizontal and vertical) for Leica C10 scanner and Leica TM5100A theodolite have shown significance difference. This is because the accuracy of both sensors are not similar and these differences are 0.01 and 0.0075º for horizontal and vertical measurements, respectively. Investigation on the resolution setting for Leica C10 scanner has highlighted the drawback of the tilt-and-turn target. Using the highest resolution, Leica Cyclone software only able to recognize the tilt-and-turn target up to 10 m distance compare to 200 m for the black and white target

The 43GHz SiO maser in the circumstellar envelope of the AGB star R Cassiopeiae

We present multi-epoch, total intensity, high-resolution images of 43GHz, v=1, J=1-0 SiO maser emission toward the Mira variable R Cas. In total we have 23 epochs of data for R Cas at approximate monthly intervals over an optical pulsation phase range from 0.158 to 1.78. These maps show a ring-like distribution of the maser features in a shell, which is assumed to be centred on the star at a radius of 1.6 to 2.3 times the stellar radii. It is clear from these images that the maser emission is significantly extended around the star. At some epochs a faint outer arc can be seen at 2.2 stellar radii. The intensity of the emission waxes and wanes during the stellar phase. Some maser features are seen infalling as well as outflowing. We have made initial comparisons of our data with models by Gray et. al. (2009).Comment: 12 pages, 14 figure

Horizon area bound and MOTS stability in locally rotationally symmetric solutions

In this paper, we study the stability of marginally outer trapped surfaces (MOTS), foliating horizons of the form $r=X(\tau)$, embedded in locally rotationally symmetric class II perfect fluid spacetimes. An upper bound on the area of stable MOTS is obtained. It is shown that any stable MOTS of the types considered in these spacetimes must be strictly stably outermost, that is, there are no MOTS ``outside" of and homologous to $\mathcal{S}$. Aspects of the topology of the MOTS, as well as the case when an extension is made to imperfect fluids, are discussed. Some non-existence results are also obtained. Finally, the ``growth" of certain matter and curvature quantities on certain unstable MOTS are provided under specified conditions.Comment: 21 pages, Submitted to CQG, comments are welcom