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Search Results: 1 - 10 of 7663 matches for " Perez Fernandez Palha "
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The influence of centrifugation on Zymomonas mobilis aggregation
Perez Fernandez Palha,María de los Angeles; Edison Lopes,Carlos; Gomes de Andrade Lima,Maria Alice; Pereira Junior,Nei;
Electronic Journal of Biotechnology , 2002,
Abstract: flocculent zymomonas mobilis breaks down in smaller flocs and individual cells when centrifuged. the main consequence of it is an increase in the dispersion of the sample, suggesting that the influence of the centrifugal force on the aggregation of cells is worth to study. the experiments showed that the degree of dispersion varied between 30% and 100% when the centrifugal acceleration changed from 25 g to 2500 g. observation under the electronic microscope showed that a slimy material covered the cells recovered by gentle gravitational settling and, that the centrifuged cells presented a bare cell wall.
Sucrose hydrolysis catalyzed by auto-immobilized invertase into intact cells of Cladosporium cladosporioides
Santana de Almeida,Ana Cláudia; Costa de Araújo,Luciares; Mendes Costa,Andressa; Moraes de Abreu,César Augusto; Gomes de Andrade Lima,Maria Alice; Perez Fernandez Palha,Maria de Los Angeles;
Electronic Journal of Biotechnology , 2005,
Abstract: the enzyme known as invertase (e.c. 3.2.1.26 - β-d-fructofuranosidase) catalyzes the sucrose hydrolysis producing an equimolar mixture of glucose and fructose named inverted sugar. the fungus cladosporium cladosporioides has invertase as its constituent. hence, its use as a natural immobilized support for the invertase produces interesting results for the enzyme. the present work has the objective of determining the optimum operational conditions of auto-immobilized invertase, as well as its kinetic parameters (km and vmax). a complete 23 factorial planning was done for the evaluation of such parameters. temperature, ph and agitation level were the studied variables. the hydrolysis percentage was the monitored result. batch tests in optimum conditions were done to determine the kinetic parameters. temperature of 70oc, ph 6 and agitation of 170 rpm were the established conditions for the hydrolysis process. the auto-immobilized invertase presented a km of 447 mm and vmax of 2,805 mmol/min.
An Analysis of the Spatial Colonization of Scrubland Intrusive Species in the Itabo and Guanabo Watershed, Cuba
Jose Damian Ruiz Sinoga,Ricardo Remond Noa,Danai Fernandez Perez
Remote Sensing , 2010, DOI: 10.3390/rs2030740
Abstract: During the last twenty years, numerous agricultural and farming areas of Cuba have seen a marked increase in invading plants; among the most common species found is the Marabú (Dychrostachys cinerea) and the Aroma (Acacia farnesiana). In the present study, an analysis was carried out of the expansion of these species over the last two decades, in the river basin of the Guanabo (17 km north-east of Havana). This was done by digital processing of satellite images and an analysis of the spatial and statistical data of the Geographical Information System (GIS). The zones most affected by this scrubland were mapped and a study of how natural factors may have influenced land use and the tendency of these species to increase was carried out.
Post-thoracentesis trapped lung
Khan H,Fernandez-Perez E,Caples S
Journal of Postgraduate Medicine , 2007,
Abstract:
Dimensioning Method for Conversational Video Applications in Wireless Convergent Networks
Alfonso Fernandez-Duran,Raquel Perez Leal,José I. Alonso
EURASIP Journal on Wireless Communications and Networking , 2007, DOI: 10.1155/2008/328089
Abstract: New convergent services are becoming possible, thanks to the expansion of IP networks based on the availability of innovative advanced coding formats such as H.264, which reduce network bandwidth requirements providing good video quality, and the rapid growth in the supply of dual-mode WiFi cellular terminals. This paper provides, first, a comprehensive subject overview as several technologies are involved, such as medium access protocol in IEEE802.11, H.264 advanced video coding standards, and conversational application characterization and recommendations. Second, the paper presents a new and simple dimensioning model of conversational video over wireless LAN. WLAN is addressed under the optimal network throughput and the perspective of video quality. The maximum number of simultaneous users resulting from throughput is limited by the collisions taking place in the shared medium with the statistical contention protocol. The video quality is conditioned by the packet loss in the contention protocol. Both approaches are analyzed within the scope of the advanced video codecs used in conversational video over IP, to conclude that conversational video dimensioning based on network throughput is not enough to ensure a satisfactory user experience, and video quality has to be taken also into account. Finally, the proposed model has been applied to a real-office scenario.
A Method to Estimate the Horizontal Handover Decision Effect on Indoor Wireless Conversational Video Quality
Alfonso Fernandez Duran,Raquel Perez Leal,Jose I. Alonso
EURASIP Journal on Advances in Signal Processing , 2008, DOI: 10.1155/2008/370524
Abstract: One of the most interesting and valuable services considered in fixed mobile convergence is video telephony. The success of this conversational video service will depend on the conversational video quality achieved in the multicell wireless indoor scenarios. One of the essential elements in the quality is the effect of the horizontal handovers in the conversational video. This paper analyzes the handover decision based on the probability calculation of handover events in the case of relative signal strength with hysteresis threshold (RSSHT) approach, and it proposes a new handover decision mechanism, variable hysteresis, to avoid unnecessary handovers. The paper presents the impact of the number of handovers and their duration time on the video's effective frame rate. Moreover, the effect of video stream modification during a short handover is also analyzed. Probability and handover duration approaches are combined and a new simple method for video quality evaluation is caused by the handovers in multicell indoor WLAN scenarios. Finally, the model proposed has been applied to a real office scenario.
Dimensioning Method for Conversational Video Applications in Wireless Convergent Networks
Fernandez-Duran Alfonso,Perez Leal Raquel,Alonso JoséI
EURASIP Journal on Wireless Communications and Networking , 2008,
Abstract: New convergent services are becoming possible, thanks to the expansion of IP networks based on the availability of innovative advanced coding formats such as H.264, which reduce network bandwidth requirements providing good video quality, and the rapid growth in the supply of dual-mode WiFi cellular terminals. This paper provides, first, a comprehensive subject overview as several technologies are involved, such as medium access protocol in IEEE802.11, H.264 advanced video coding standards, and conversational application characterization and recommendations. Second, the paper presents a new and simple dimensioning model of conversational video over wireless LAN. WLAN is addressed under the optimal network throughput and the perspective of video quality. The maximum number of simultaneous users resulting from throughput is limited by the collisions taking place in the shared medium with the statistical contention protocol. The video quality is conditioned by the packet loss in the contention protocol. Both approaches are analyzed within the scope of the advanced video codecs used in conversational video over IP, to conclude that conversational video dimensioning based on network throughput is not enough to ensure a satisfactory user experience, and video quality has to be taken also into account. Finally, the proposed model has been applied to a real-office scenario.
Measurements incompatible in Quantum Theory cannot be measured jointly in any other local theory
Michael M. Wolf,David Perez-Garcia,Carlos Fernandez
Physics , 2009, DOI: 10.1103/PhysRevLett.103.230402
Abstract: It is well known that jointly measurable observables cannot lead to a violation of any Bell inequality - independent of the state and the measurements chosen at the other site. In this letter we prove the converse: every pair of incompatible quantum observables enables the violation of a Bell inequality and therefore must remain incompatible within any other no-signaling theory. While in the case of von Neumann measurements it is sufficient to use the same pair of observables at both sites, general measurements can require different choices. The main result is obtained by showing that for arbitrary dimension the CHSH inequality provides the Lagrangian dual of the characterization of joint measurability. This leads to a simple criterion for joint measurability beyond the known qubit case.
Krall--type Orthogonal Polynomials in several variables
Lidia Fernandez,Teresa E. Perez,Miguel A. Pinar,Yuan Xu
Mathematics , 2007,
Abstract: For a bilinear form obtained by adding a Dirac mass to a positive definite moment functional in several variables, explicit formulas of orthogonal polynomials are derived from the orthogonal polynomials associated with the moment functional. Explicit formula for the reproducing kernel is also derived and used to establish certain inequalities for classical orthogonal polynomials.
New encoding schemes for quantum authentication
Priscila Garcia-Fernandez,Enrique Fernandez-Martinez,Esther Perez,David J. Santos
Physics , 2003,
Abstract: We study the potential of general quantum operations, Trace-Preserving Completely-Positive Maps (TPCPs), as encoding and decoding mechanisms in quantum authentication protocols. The study shows that these general operations do not offer significant advantage over unitary encodings. We also propose a practical authentication protocol based on the use of two successive unitary encodings.
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