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Search Results: 1 - 10 of 512899 matches for " José A.; "
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Possible Magnetic Resonance Signal Due to the Movement of Counterions around a Polyelectrolyte with Rotational Symmetry  [PDF]
José A. Fornés
Advances in Nanoparticles (ANP) , 2015, DOI: 10.4236/anp.2015.41002
Abstract: Experimental, theoretical and computational studies revealed that the characteristic time scales involved in counterion dynamics in polyelectrolytes systems might span several orders of magnitude ranging from subnanosecond times to time scales corresponding to acoustic-like phonon mode frequencies, with an structural organization of counterions in charge density waves (CDWs). These facts raise the possibility of observing Magnetic Resonance (MR) signals due to the movement of counterions in polyelectrolytes. In case that this signal is detected in macroions or other biological systems, like micelles, vesicles, organeles, etc. with rotational symmetry, this method opens a new tool to measure with precission the counterions velocity.
Hydrodynamic Interactions Introduce Differences in the Behaviour of a Ratchet Dimer Brownian Motor  [PDF]
José A. Fornés
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2015, DOI: 10.4236/jbnb.2015.62008
Abstract: We use the Brownian dynamics with hydrodynamic interactions simulation in order to describe the movement of an elastically coupled dimer Brownian motor in a ratchet potential. The only external forces considered in our system were the load, the random thermal noise and an unbiased thermal fluctuation. We observe differences in the dynamic behaviour if hydrodynamic interactions are considered as compared with the case without them. In conclusion, hydrodynamic interactions influence substantially the dynamics of a ratchet dimer Brownian motor; consequently they have to be considered in any theory where the molecular motors are in a liquid medium.
Temperature Fluctuations in a Rectangular Nanochannel  [PDF]
José A. Fornés
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2015, DOI: 10.4236/jbnb.2015.63011
Abstract: We consider an incompressible fluid in a rectangular nanochannel. We solve numerically the three dimensional Fourier heat equation to get the steady solution for the temperature. Then we set and solve the Langevin equation for the temperature. We have developed equations in order to determine relaxation time of the temperature fluctuations, τT = 4.62 × 10-10s. We have performed a spectral analysis of the thermal fluctuations, with the result that temporal correlations are in the one-digit ps range, and the thermal noise excites the thermal modes in the two-digit GHz range. Also we observe long-range spatial correlation up to more than half the size of the cell, 600 nm; the wave number, q, is in the 106 m-1 range. We have also determined two thermal relaxation lengths in the z direction: l1 = 1.18 nm and l2 = 9.86 nm.
On the Asymptotics of Stochastic Restrictions  [PDF]
José A. Hernández
Theoretical Economics Letters (TEL) , 2016, DOI: 10.4236/tel.2016.64075
Abstract: This paper investigates inference methods to introduce prior information in econometric modelling through stochastic restrictions. The goal is to show that stochastic restrictions method estimator can be asymptotically more efficient than the estimator ignoring prior information and can achieve efficiency if prior information grows faster than the sample information in the asymptotics. The set up includes the nonlinear least squares and indirect inference estimators. The paper proposes a new indirect inference estimator that incorporates stochastic equality constraints on the parameters of interest. Finally, the proposed approach is applied to a macroeconomics model where high efficiency gains are shown.
Extreme Rainfall Indices in the Hydrographic Basins of Brazil  [PDF]
María C. Valverde, José A. Marengo
Open Journal of Modern Hydrology (OJMH) , 2014, DOI: 10.4236/ojmh.2014.41002
Abstract: The authors analyze climate extremes indices (CEI) of rainfall over the largest basins of the Brazilian territory: Amazon (AMA), S?o Francisco (SF), Tocantins (TO) and Paraná (PAR) rivers. The CEI represent the frequency of heavy precipitation events (R30mm and R95p) and short duration extreme rainfall (RX5day and RX1day). Droughts (CDDd) are identified based on two indicators: The longest dry period (CDD) and the annual cycle. The results demonstrate that CDDd, RX1day and RX5day occurred with more frequency and intensity in SF basin during El Ni?o events. CDDd was of greater magnitude in the TO basin during La Ni?a events, while an increase of RX1day occurred in El Ni?o. The strong El Ni?o events (1983 and 1997) caused more intense and frequent RX1day and R30mm over the PAR basin. Amazon droughts occurred in two out of the six El Ni?o events. Moreover, the relationship between the positive (negative) sea superficial temperatures anomalies in North (South) Tropical Atlantic and drought in AMA basin was corroborated. A gradual warming of SST was observed at the start of 2003 until it achieved a maximum in 2005 associated with the southwestern Amazon drought. The second highest anomaly of SST was in 2010 linked with drought that was more spatially extensive than the 2005 drought. The spatial distribution of annual trends showed a significant increase of CDD in south-eastern AMA, Upper SF, northern PAR and throughout the TO basins. R20mm, RX1day and RX5day tend to increase significantly in southwestern (northeast) PAR (AMA) and northwestern TO basins. Comparisons between CEI derived from daily precipitation data from Climate Prediction Center (CPCp) and of the ETA_HadCM3 model showed that the model overestimated RX1day, RX5day and CDD, in the four basins. Future scenarios show that dry periods will occur with greatest magnitude in all the basins until 2071-2099 time slice, while RX1day will be more intense in the TO and SF basins.
Electron Confinement Effect of Laser Dyes within Dendritic Structures  [PDF]
Francisco Márquez, María José Sabater
Journal of Encapsulation and Adsorption Sciences (JEAS) , 2011, DOI: 10.4236/jeas.2011.11001
Abstract: Dendrimers are a novel class of nanometric-size macromolecules with a regular tree-dimensional like array of branch units.1,2 Their synthetic availability in a wide range of sizes combined with their peculiar architecture makes them versatile building blocks for a wide range of potential applications.3 Some years ago, Meijer and co-workers reported that the modification of terminal amine functionalities of a fifth generation poly(propyleneimine) dendrimer (DAB-dendr-(NH2)64) with bulky substituents, (typically N-t-BOC protected phenylalanine), results in the formation of the so-called “dendritic box” (DAB-dendr-(NH-t-BOC-L-Phe)64).4 Within this macromolecular structure it is possible to encapsulate a variety of guest molecules due to the existence of internal cavities in the core. The photophysical properties of the guests can be modulated by the innovative electron confinement effect. In this respect, we wish to report that the emission frequency of organic dyes can be easily modulated by encapsulation in a dendritic box. The emission bands of dye molecules incorporated into a dendrimer can effectively be red shifted with respect to their emission in solution and contrary to other confined spaces of considerable hardness, the magnitude of this shifting can be regulated under appropriate experimental conditions. This peculiar effect could have unprecedented applications in the development of supramolecular devices relating to the frequency tuning of organic laser dyes.
Multi-TBaud Optical Coding Based on Superluminal Space-to-Time Mapping in Long Period Gratings  [PDF]
Reza Ashrafi, Ming Li, José Aza?a
Optics and Photonics Journal (OPJ) , 2013, DOI: 10.4236/opj.2013.32B031

A novel time-domain ultra-fast pulse shaping approach for multi-TBaud serial optical communication signal (e.g. QPSK and 16-QAM) generation based on the first-order Born approximation in feasible all-fiber long-period gratings is proposed and numerically demonstrated.

Response of Nitrous Oxide Flux to Addition of Anecic Earthworms to an Agricultural Field  [PDF]
José A. Amador, Edward J. Avizinis
Open Journal of Soil Science (OJSS) , 2013, DOI: 10.4236/ojss.2013.32011

The burrowing and feeding activities of earthworms may have a strong effect on the flux of N2O from agricultural soils. As such, shifts to agricultural management practices that increase the number of earthworms require an understanding of the role of earthworms in N2O dynamics. We conducted a field experiment to examine the effects of addition of anecic earthworms (Lumbricus terrestris) on N2O flux in a field previously planted with corn (Zea mays) in southern Rhode Island, USA. Plots were amended with (15NH4)2SO4 and either 0 (CTL) or 48 L. terrestris m-2 (EW). The flux of N2O, 15N2O and 15N2 was measured over 28 days between October and November 2008. The EW treatment had a significantly higher flux of N2O and 15N2O 1 - 3 days after 15NH4 addition. No treatment effects were observed on 15N2 flux. The addition of earthworms significantly increased (Day 1) and decreased (Day 12) the mole fraction of N2O relative to the CTL. Our results suggest that anecic earthworm additions can increase N2O flux from inorganic fertilizer N amendments, but the effects appear to short-lived.

Into the life and death: RecA a WISE factor working to integrate survival and evolution in Escherichia coli  [PDF]
José María Gómez Gómez
Advances in Bioscience and Biotechnology (ABB) , 2013, DOI: 10.4236/abb.2013.43A059

Escherichia coli RecA has been considered traditionally a cellular protein with multiple vital functions working to ensure the maintenance of integrity of genome in each individual bacterial cell as well as promoting swarming migration in collectivity. On the contrary, recently it has been described that RecA promotes cellular apoptotic-like death (ALD), a pathway of programmed cellular death (PCD). In fact, RecA has been dubbed as the major apoptotic executor in E. coli. From these studies, RecA emerges as a prototypical Gin/Gan protein that despite of their intrinsic vital and lethal anfi-funcionality becomes in a WISE factor: a Worker to Integrate Survival and Evolution in E. coli evolving populations living in community. Here, I provide a review of recent experimental and conceptual advances trying to understand these RecA’s antagonistic roles in appearance contradictory under a unified biological vision.

The Rise of Emerging Markets and Its Impact on Global Energy Security  [PDF]
José María Martín-Moreno
Modern Economy (ME) , 2014, DOI: 10.4236/me.2014.59089

This paper first explores the implications of the rise of emerging markets on energy and, then, on energy security. Nowadays, emerging economies are key players in the international political arena, in the global economy and, in energy markets. The new economic scenario, which favors emerging markets, produces a mirror image in the business world. The new oil and natural gas titans are now public companies from those emerging countries, while private companies from the developed world play second fiddle. This fact also affects energy security. This paper points out that oil is still the most vulnerable source of energy. Yet in this new context, the International Energy Agency must actively collaborate with China and India (to say the least) to create an efficient policy for energy security. Finally, this paper suggests that Russia is the world cornerstone of energy supply. And the OPEC continues to play the most relevant role in the oil markets as it has for the past 40 years.

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