Accelerated expansion from a non-minimal gravitational coupling to matter

It is shown that a non-minimal coupling between the scalar curvature and the matter Lagrangian density may account for the accelerated expansion of the Universe and provide, through mimicking, for a viable unification of dark energy and dark matter. An analytical exploration is first performed, and a numerical study is then used to validate the obtained results. The encountered scenario allows for a better grasp of the proposed mechanism, and sets up the discussion for improvements that can lead to a complete agreement with the observational data.Comment: Latex file, 10 pages, 6 figure

Aspectos econômicos em sistemas de produção com culturas alimentares para agricultores de baixa renda na Microrregião Bragantina, Pará.

bitstream/item/28816/1/CPATU-BP6.pd

The influence of age, sex and visual dysfunction on reading ability in school-children

t. Binocular and accommodative dysfunctions affect the efficiency and coordination of the eyes, and this may impair reading performance. Reading can be evaluated using accuracy and speed measures. In this study, we searched for evidence that dysfunctions of accommodation (i.e. accommodation insufficiency, IA) and binocular vision (i.e. convergence insufficiency, CI) and also hyperopia have impact on reading ability. A sample of 292 children read a text following vision screening. The sample was composed of control children and children with the conditions: AI; CI and hyperopia. Multilinear regression analysis was used to evaluate the influence of variables sex, age and visual condition (control, AI, CI and hyperopia) on reading accuracy and speed. The results showed that ~7% of the variation in reading accuracy was explained by a model where age (p=0.001), and presence of AI (p<0.001) and hyperopia (p=0.019) were statistically significant. On the other hand, ~38% of the variation in the index of speed was explained by age alone (p<0.001). These results confirm the importance of age on children’s ability to read, and suggests that AI and hyperopia, but not CI may affect reading accuracy. Reading speed does not appear to be affected by the presence of binocular or accommodative dysfunction.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013

Multimode Interference In Tapered Single Mode-multimode-single Mode Fiber Structures For Strain Sensing Applications

Tapering single mode-multimode-single mode structures to enhance sensitivity is proposed and experimentally demonstrated. 50 mm-long coreless MMF sections are spliced between SMFs and tapered. They are characterized in strain and an increase in strain sensitivity is obtained with taper diameter reduction. Sensitivities as high as -23.69 pm/με for the 15 μm taper are attained. A combination of an untapered and tapered SMS is proposed as a sensing system for the simultaneous measurement of strain and temperature. © 2012 SPIE.8421Soldano, L., Pennings, E., Optical multi-mode interference devices based on self-imaging: Principles and applications (1995) Lightwave Technology, Journal of, 13, pp. 615-627. , AprilKumar, A., Varshney, R.K., Sharma, P., Transmission characteristics of sms fiber optic sensor structures (2003) Optics Communications, 219, pp. 215-219Wang, Q., Farrell, G., Yan, W., Investigation on single-mode-multimode-single-mode fiber structure (2008) J. Lightwave Technol., 26, pp. 512-519. , MarMehta, A., Mohammed, W., Johnson, E., Multimode interference-based fiber-optic displacement sensor (2003) Photonics Technology Letters, IEEE, 15, pp. 1129-1131. , augMohammed, W., Mehta, A., Johnson, E., Wavelength tunable fiber lens based on multimode interference (2004) Lightwave Technology, Journal of, 22, pp. 469-477. , febFrazão, O., Silva, S.O., Viegas, J., Ferreira, L.A., Araújo, F.M., Santos, J.L., Optical fiber refractometry based on multimode interference (2011) Appl. Opt., 50, pp. E184-E188. , SepMohammed, W.S., Smith, P.W.E., Gu, X., All-fiber multimode interference bandpass filter (2006) Opt. Lett., 31, pp. 2547-2549. , SepWang, Q., Farrell, G., Multimode-fiber-based edge filter for optical wavelength measurement application and its design (2006) Microwave and Optical Technology Letters, 48 (5), pp. 900-902Wang, P., Brambilla, G., Ding, M., Semenova, Y., Wu, Q., Farrell, G., High-sensitivity, evanescent field refractometric sensor based on a tapered, multimode fiber interference (2011) Opt. Lett., 36, pp. 2233-2235. , JunFrazão, O., Silva, S.F.O., Guerreiro, A., Santos, J.L., Ferreira, L.A., Araújo, F.M., Strain sensitivity control of fiber bragg grating structures with fused tapers (2007) Appl. Opt., 46 (36), pp. 8578-8582Biazoli, C.R., André, R.M., Frazão, O., Cordeiro, C.M.B., Tapering down optical fiber to ultra-high strain sensitivity (2012) Photonics Technology Letters, IEEE, , Submitte

Magnetic Field Sensor With Terfenol-d Thin-film Coated Fbg

In this work a magnetic field sensor based on an FBG coated with a thin film of Terfenol-D is presented. The sensor was tested with two optical interrogation systems: one, a scanning laser system with a 1 pm resolution, and the other a differential white light interferometer (WLI). The results obtained in the magnetic field range of 20 mT to 100 mT, show the possibility of increasing the magnetic field measurement resolution, with temperature fluctuations invariance, by a factor of 4.5 when using the WLI system. © 2012 SPIE.8421Mora, J., Diez, A., Cruz, J.L., A magnetostrictive sensor interrogated by fiber gratings for DC-Current and temperature discrimination (2000) Ieee Photonic Tech L, 12 (12), pp. 1680-1682Satpathi, D., Moore, J.A., Ennis, M.G., Design of a terfenol-D based fiber-optic current transducer (2005) Ieee Sens J, 5 (5), pp. 1057-1065Li, M.F., Giant Magnetostrictive Magnetic Fields Sensor Based on Dual Fiber Bragg Gratings, pp. 490-495Mora, J., Martinez-Leon, L., Diez, A., Simultaneous temperature and ac-current measurements for high voltagelines using fiber Bragg gratings (2006) Sensor Actuat A-Phys, 125 (2), pp. 313-316Reilly, D., Willshire, A.J., Fusiek, G., A fiber-Bragg-grating-based sensor for simultaneous AC current and temperature measurement (2006) Ieee Sens J, 6 (6), pp. 1539-1542Davino, D., Visone, C., Ambrosino, C., Compensation of hysteresis in magnetic field sensors employing Fiber Bragg Grating and magneto-elastic materials (2008) Sensor Actuat A-Phys, 147 (1), pp. 127-136Yang, M.H., Dai, J.X., Zhou, C.M., Optical fiber magnetic field sensors with TbDyFe magnetostrictive thin films as sensing materials (2009) Opt Express, 17 (23), pp. 20777-20782Quintero, S.M.M., Braga, A.M.B., Weber, H.I., A magnetostrictive composite-fiber Bragg grating sensor (2010) Sensors-Basel, 10 (9), pp. 8119-8128Smith, G.N., Characterisation and performance of a Terfenol-D coated femtosecond laser inscribed optical fibre Bragg sensor with a laser ablated microslot for the detection of static magnetic fields (2011) Opt Express, 19 (1), pp. 363-370Quintero, S.M.M., Martelli, C., Braga, A., Magnetic field measurements based on terfenol coated photonic crystal fibers (2011) Sensors-Basel, 11 (12), pp. 11103-1111

Superhydrophobic asphalt pavements: surface improvement

The most adverse weather condition for road safety happens when there is water, snow, or ice on the road surface because their presence highly decreases friction. Therefore, it is essential to drain or repel them quickly. If the water drops are repelled from the surface or the ice/snow formation is avoided with the application of superhydrophobic coatings, roads become safer. In order to functionalize the asphalt mixtures used in road pavements, nano/micromaterials, such as Polytetrafluoroethylene (PTFE), TiO2, and SiO2, among others have been applied by spraying coating. The mixes are usually characterized by the water contact angle, and the surface roughness is typically assessed by optical and electron analysis. This research work aims to present a brief overview of superhydrophobic asphalt mixtures

Processing of the Escherichia coli leuX tRNA transcript, encoding tRNALeu5, requires either the 3′→5′ exoribonuclease polynucleotide phosphorylase or RNase P to remove the Rho-independent transcription terminator

Here we report a unique processing pathway in Escherichia coli for tRNALeu5 in which the exoribonuclease polynucleotide phosphorylase (PNPase) removes the Rho-independent transcription terminator from the leuX transcript without requiring the RhlB RNA helicase. Our data demonstrate for the first time that PNPase can efficiently degrade an RNA substrate containing secondary structures in vivo. Furthermore, RNase P, an endoribonuclease that normally generates the mature 5′-ends of tRNAs, removes the leuX terminator inefficiently independent of PNPase activity. RNase P cleaves 4–7 nt downstream of the CCA determinant generating a substrate for RNase II, which removes an additional 3–4 nt. Subsequently, RNase T completes the 3′ maturation process by removing the remaining 1–3 nt downstream of the CCA determinant. RNase E, G and Z are not involved in terminator removal. These results provide further evidence that the E. coli tRNA processing machinery is far more diverse than previously envisioned