A fast, preconditioned conjugate gradient Toeplitz and Toeplitz-like solvers

AbstractFor a Toeplitz or Toeplitz-like matrix T, we define a preconditioning applied to the symmetrized matrix THT, which decreases the condition number compared to the one of THT and even the one of T. This enables us to accelerate the conjugate gradient algorithm for solving Toepiltz and Toeplitz-like linear systems, thus extending the previous results of [1], restricted to the Hermitian positive definite case. The extension relies on some recent formulae of Gohberg and Olshevsky for the inverses of Toeplitz-like matrices

An Investigation of 11 previously unstudied open star clusters

The main astrophysical properties of 11 previously unstudied open star clusters are probed with JHK Near-IR (2MASS) photometry of Cutri et al. [Cutri, R., et al., 2003. The IRSA 2MASS All-sky Point Source Catalog, NASA/IPAC Infrared Science Archive] and proper motions (NOMAD) astrometry of Zacharias et al. [Zacharias, N., Monet, D., Levine, S., Urban, S., Gaume, R., Wycoff, G., 2004. American Astro. Soc. Meeting 36, 1418]. The fundamental parameters have been derived for IC (1434, 2156); King (17, 18, 20, 23, 26)}; and Dias (2, 3, 4, 7, 8)}, for which no prior parameters are available in the literature. The clusters' centers coordinates and angular diameters are re-determined, while ages, distances, and color excesses for these clusters are estimated here for the first time.Comment: 9 pages, 3 figure, the first version of this article was presented as a poster paper in the First Middle East-Africa, Regional IAU Meeting, Cairo, Egypt, April 5-10, 200

Dilution and magnification effects on image analysis applications in activated sludge characterization

The properties of activated sludge systems can be characterized using image analysis procedures. When these systems operate with high biomass content, accurate sludge characterization requires samples to be diluted. Selection of the best image acquisition magnification is directly related to the amount of biomass screened. The aim of the present study was to survey the effects of dilution and magnification on the assessment of aggregated and filamentous bacterial content and structure using image analysis procedures. Assessments of biomass content and structure were affected by dilutions. Therefore, the correct operating dilution requires careful consideration. Moreover, the acquisition methodology comprising a 100 magnification allowed data on aggregated and filamentous biomass to be determined and smaller aggregates to be identified and characterized, without affecting the accuracy of lower magnifications regarding biomass representativeness.AGERE (Empresa de Águas, Efluentes e Resíduos de Braga – EM) and AGS(Administração e Gestão de Sistemas de Salubridade, S.A.)Fundação para a Ciência e Tecnologia (FCT

A simulation toolkit for electroluminescence assessment in rare event experiments

A good understanding of electroluminescence is a prerequisite when optimising double-phase noble gas detectors for Dark Matter searches and high-pressure xenon TPCs for neutrinoless double beta decay detection. A simulation toolkit for calculating the emission of light through electron impact on neon, argon, krypton and xenon has been developed using the Magboltz and Garfield programs. Calculated excitation and electroluminescence efficiencies, electroluminescence yield and associated statistical fluctuations are presented as a function of electric field. Good agreement with experiment and with Monte Carlo simulations has been obtained

A comparison between bright field and phase-contrast image analysis techniques in activated sludge morphological characterization

Different approaches using microscopy image analysis procedures were employed for characterization of activated sludge systems. The approaches varied mainly on the type of visualization and acquisition method used for collection of data. In this context, this study focused on the comparison of the two most common acquisition methods: bright field and phase-contrast microscopy. Images were acquired from seven different wastewater treatment plants for a combined period of two years. Advantages and disadvantages of each acquisition technique and the results are discussed. Bright field microscopy proved to be more simple and inexpensive and provided the best overall results.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/32329/2006, POCI/AMB/57069/200

In situ crosslinked electrospun gelatin nanofibers for skin regeneration

Due to its intrinsic similarity to the extracellular matrix, gelatin electrospun nanofibrous meshes are promising scaffold structures for wound dressings and tissue engineering applications. However, gelatin is water soluble and presents poor mechanical properties, which generally constitute relevant limitations to its applicability. In this work, gelatin was in situ crosslinked with 1,4-butanediol diglycidyl ether (BDDGE) at different concentrations (2, 4 and 6 wt%) and incubation time-points (24, 48 and 72 h) at 37 °C. The physico-chemical and biological properties of BDDGE-crosslinked electrospun gelatin meshes were investigated. Results show that by changing the BDDGE concentration it is possible to produce nanofibers crosslinked in situ with well-defined morphology and modulate fiber size and mechanical properties. Crosslinked gelatin meshes show no toxicity towards fibroblasts, stimulating their adhesion, proliferation and synthesis of new extracellular matrix, thereby indicating the potential of this strategy for skin tissue engineering.info:eu-repo/semantics/acceptedVersio

Fenótipo De Fragilidade: Influência De Cada Item Na Determinação Da Fragilidade Em Idosos Comunitários - Rede Fibra

The phenotype of frailty is used to assess frailty among the elderly by examining the following items: weight loss; exhaustion; low level of physical activity; weakness; and slow gait speed. The aim of the study was to evaluate the contribution of each item to determine the frailty syndrome among elderly Brazilians. The analysis was done using Multinomial Logistic Regression. The total sample of 5532 randomly selected elderly people in many cities in Brazil between December 2008 and September 2009 was assessed using the phenotype of frailty. The most frequent items were level of physical activity, followed by muscular weakness and slow gait speed. Items that were more likely to develop frailty, when positive, were slow gait speed (OR = 10.50, 95%CI 8.55 - 12.90, p <0.001) and muscular weakness (OR = 7.31, 95%CI 6,02 - 8,86, p <0.001). The final model with five items explained 99.6% of frailty in the sample. These results suggested that the level of physical activity, weakness and slow gait speed were the items that most influence the determination of frailty, however the application of all items of the phenotype of frailty is the best way to assess frailty. © 2016, Associacao Brasileira de Pos - Graduacao em Saude Coletiva. All rights reserved.21113483349

The structure and dynamics of young star clusters: King 16, NGC 1931, NGC 637 and NGC 189

In this paper, using 2MASS photometry, we study the structural and dynamical properties of four young star clusters viz. King 16, NGC 1931, NGC 637 and NGC 189. For the clusters King 16, NGC 1931, NGC 637 and NGC 189, we obtain the limiting radii of 7', 12', 6' and 5' which correspond to linear radii of 3.6 pc, 8.85 pc, 3.96 pc and 2.8 pc respectively. The reddening values $E(B-V)$ obtained for the clusters are 0.85, 0.65--0.85, 0.6 and 0.53 and their true distances are 1786 pc, 3062 pc, 2270 pc and 912 pc respectively. Ages of the clusters are 6 Myr, 4 Myr, 4 Myr and 10 Myr respectively. We compare their structures, luminosity functions and mass functions ($\phi(M) = dN/dM \propto M^{-(1+\chi)}$) to the parameter $\tau = t_{age}/t_{relax}$ to study the star formation process and the dynamical evolution of these clusters. We find that, for our sample, mass seggregation is observed in clusters or their cores only when the ages of the clusters are comparable to their relaxation times ($\tau \geq 1$). These results suggest mass seggregation due to dynamical effects. The values of $\chi$, which characterise the overall mass functions for the clusters are 0.96 $\pm$ 0.11, 1.16 $\pm$ 0.18, 0.55 $\pm$ 0.14 and 0.66 $\pm$ 0.31 respectively. The change in $\chi$ as a function of radius is a good indicator of the dynamical state of clusters.Comment: Accepted for publication in Astrophysics & Space Scienc

Effect of synthesis temperature on crystallinity, morphology and cell viability of nanostructured hydroxyapatite via wet chemical precipitation method: Effect of temperature on hydroxyapatite properties

Hydroxyapatite (HA) is the main natural mineral constituent of bones and is a good alternative for biomedical applications because it is osteoconductive, non-allergenic, and non-carcinogenic, which ensures high biocompatibility. A commonly used method for obtaining hydroxyapatite is the wet route, which is simple and low-cost, produces only water as a final residue, and provides HA with a crystallinity comparable to that of bone tissue, which favors its biocompatibility. Therefore, the objective of this work is to synthesize hydroxyapatite via the wet chemical precipitation method at different temperatures (4°C, 30°C, 50°C, or 70°C) to observe the influence of temperature on crystallinity, morphology, and cytotoxicity. The results of X-ray diffraction show that all syntheses resulted in pure hydroxyapatite, while increasing the temperature led to higher crystallinity (10.6% to 56.2%) and the crystal size was slightly affected. The increase in temperature changed the particle shape from irregular to needle-like. Cell viability was tested by PicoGreen® in VERO cells for samples at concentrations of 30 and 300µg/mL, and the samples synthesized at 4°C, with lower crystallinity, caused less DNA damage to cells compared to the negative control. &nbsp