Publicacions de projectes de recerca del Plan Nacional
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- ItemRestrictedA Time-Domain Method for the Analysis of Thermal Impedance Response Preserving the Convolution Form(Institute of Electrical and Electronics Engineers, 1999) Carmona, Manuel; Marco, Santiago; Palacín Roca, Jordi; Samitier, JosepThe study of the thermal behavior of complex packages as multichip modules (MCM’s) is usually carried out by measuring the so-called thermal impedance response, that is: the transient temperature after a power step. From the analysis of this signal, the thermal frequency response can be estimated, and consequently, compact thermal models may be extracted. We present a method to obtain an estimate of the time constant distribution underlying the observed transient. The method is based on an iterative deconvolution that produces an approximation to the time constant spectrum while preserving a convenient convolution form. This method is applied to the obtained thermal response of a microstructure as analyzed by finite element method as well as to the measured thermal response of a transistor array integrated circuit (IC) in a SMD package.
- ItemRestrictedExploiting Knowledge of Temporal Behaviour in Parallel Programs for Improving Distributed Mapping(Springer Verlag, 2000) Roig Mateu, Concepció; Ripoll, A.; Senar, M.A.; Guirado Fernández, Fernando; Luque, EmilioIn the distributed processing area, mapping and scheduling are very important issues in order to exploit the gain from parallelization. The generation of efficient static mapping techniques implies a previous modelling phase of the parallel application as a task graph, which properly reflects its temporal behaviour. In this paper we use a new model, the Temporal Task Interaction Graph (TTIG), which explicitly captures the temporal behaviour of program tasks; and we evaluate the advantages that derive from the use of the TTIG model in task allocation. Experimentation was performed in a current PVM environment, for a set of synthetic graphs which exhibit different ratios of computation/ communication cost (coarse-grain, medium-grain). The execution times when these programs were mapped using the information contained in the TTIG model, were compared with the times obtained using the two following mapping alternatives: (a) PVM default scheme and, (b) mapping strategy based on the classical model TIG (Task Interaction Graph). The results confirm that with the TTIG model, better assignments are obtained, providing improvements of up to 49% compared with the PVM assignments and up to 30% compared with TIG assignments.
- ItemRestrictedMonito: A Communication Monitoring Tool for a PVM-Linux Environment(Springer Verlag, 2000) Solsona Tehàs, Francesc; Giné, Francesc; Lérida Monsó, Josep Lluís; Hernandez, Porfidio; Luque, EmilioIn this paper a new tool for monitoring the different queues of messages in a PVM environment is presented. The main aim of implementing this facility is to provide a means of capturing the bottlenecks and overheads of the communication system in a PVM-Linux cluster. Also, it will allow to know the communication pattern of a distributed application. Its good behaviour has been proved experimentally.
- ItemRestrictedCombined use of the green and yellow fluorescent proteins and fluorescence-activated cell sorting to select populations of transiently transfected PC12 cells(Elsevier, 2000) Espinet Mestre, Carme; Gómez Arbonés, Javier; Egea Navarro, Joaquim; Comella i Carnicé, Joan XavierOne of the more time-consuming procedures in the study of exogenously expressed proteins in cell lines is the selection of individual transfected clones. In recent years, green fluorescent protein variants with excitation/emission spectra matching the typical flow cytometer configurations have been generated and are in common use. We employed PC12 cells transfected with vectors encoding fluorescent proteins and a fluorescence selection procedure using a fluorescence-activated cell-sorter. In order to select the optimal co-electroporation and sorting conditions, we used the simultaneous detection of two variants of the green fluorescent protein, that possess separable emission peaks when excited at 488 nm. Using these variants and the adequate combination of band-pass filters, we were able to analyze and establish the conditions for identifying and sorting cells transfected with enhanced green fluorescent protein, that simultaneously express another plasmid of interest. Using this procedure, the cells sorted that express both plasmids exceeded 90%. The whole procedure did not alter the physiological responsiveness of the transfected cells to growth factors, and has been successfully applied to the constitutive activation of the mitogen-activated protein kinase pathway, resulting in the spontaneous differentiation of PC12 cells. Also, this procedure has been used with other set of expression vectors encoding proteins that protect PC12 cells from apoptosis caused by different stimuli. The method that we present here provides an easy and fast procedure to obtain a high proportion of positively transfected populations of PC12 cells.
- ItemRestrictedImplementing Explicit and Implicit Coscheduling in a PVM Environment(Springer Verlag, 2000) Solsona Tehàs, Francesc; Giné, Francesc; Hernandez, Porfidio; Luque, EmilioOur efforts are directed towards the understanding of the coscheduling mechanism in a NOW system when a parallel job is executed with local workloads, balancing parallel efficiency against the local interactive response. Explicit and implicit coscheduling techniques in a PVM-Linux NOW (or cluster) has been implemented. Their performance and overheads executing local tasks and representative distributed benchmarks have been analyzed and compared.
- ItemRestrictedMemTo: A Memory Monitoring Tool for a Linux Cluster(Springer Verlag, 2001) Giné, Francesc; Solsona Tehàs, Francesc; Navarro, Xavi; Hernandez, Porfidio; Luque, EmilioStudies dealing with tuning, performance debugging and diagnosis in cluster environments largely benefit from in-depth knowledge of memory system information. In this paper a tool (called MemTo) for monitoring the behavior of the memory system through a Linux cluster is presented. MemTo has been designed to have as low intrusiveness as possible while keeping a high detail of monitoring data. The good behavior and usefulness of this tool are proved experimentally.
- ItemRestrictedSuboptimal Filtering and Nonlinear Time Scale Transformation for the Analysis of Multiexponential Decays(IEEE, 2001) Palacín Roca, Jordi; Marco, Santiago; Samitier, JosepMultiexponential decays may contain time-constants differing in several orders of magnitudes. In such cases, uniform sampling results in very long records featuring a high degree of oversampling at the final part of the transient. Here, we analyze a nonlinear time scale transformation to reduce the total number of samples with minimum signal distortion, achieving an important reduction of the computational cost of subsequent analyses. We propose a time-varying filter whose length is optimized for minimum mean square error.
- ItemRestrictedCoscheduling under Memory Constraints in a NOW(Springer Verlag, 2001) Giné, Francesc; Solsona Tehàs, Francesc; Hernández Budé, Porfidio; Luque, EmilioNetworks of Workstations (NOW) have become important and cost-effective parallel platforms for scientific computations. In practice, a NOW system is heterogeneous and non-dedicated. These two unique factors make scheduling policies on multiprocessor/multicomputer systems unsuitable for NOWs. However, the coscheduling principle is still an important basis for parallel process scheduling in these environments. We propose a new coscheduling algorithm for reducing the number of page faults across a non-dedicated cluster by increasing the execution priority of parallel tasks with lower page fault rate. Our method is based on knowledge of events obtained during execution, as communication activity and memory size of every task. The performance of our proposal has been analyzed and compared with other coscheduling implementations by means of simulation.
- ItemRestrictedThe Absence of Oligonucleosomal DNA Fragmentation during Apoptosis of IMR-5 Neuroblastoma Cells(American Society for Biochemistry and Molecular Biology, 2001) Yuste Mateos, Víctor J. (Víctor José); Bayascas Ramírez, José Ramón; Llecha Cano, Núria; Sánchez-López, Isabel; Boix Torras, Jacint; Comella i Carnicé, Joan XavierCaspase-activated DNase is responsible for the oligonucleosomal DNA degradation during apoptosis. DNA degradation is thought to be important for multicellular organisms to prevent oncogenic transformation or as a mechanism of viral defense. It has been reported that certain cells, including some neuroblastoma cell lines such as IMR-5, enter apoptosis without digesting DNA in such a way. We have analyzed the causes for the absence of DNA laddering in staurosporine-treated IMR-5 cells, and we have found that most of the molecular mechanisms controlling apoptosis are well preserved in this cell line. These include degradation of substrates for caspases, blockade of cell death by antiapoptotic genes such as Bcl-2 or Bcl-XL, or normal levels and adequate activation of caspase-3. Moreover, these cells display normal levels of caspase-activated DNase and its inhibitory protein, inhibitor of caspase-activated DNase, and their cDNA sequences are identical to those reported previously. Nevertheless, IMR-5 cells lose caspase-activated DNase during apoptosis and recover their ability to degrade DNA when human recombinant caspase-activated DNase is overexpressed. Our results lead to the conclusion that caspase-activated DNase is processed during apoptosis of IMR-5 cells, making these cells a good model to study the relevance of this endonuclease in physiological or pathological conditions.
- ItemRestrictedTowards an Automated Deduction System for First-Order Possibilistic Logic Programming with Fuzzy Constants(Wiley, 2002) Alsinet, Teresa; Godo i Lacasa, LluísIn this article, we present a first-order logic programming language for fuzzy reasoning under possibilistic uncertainty and poorly known information. Formulas are represented by a pair (ϕ, α), in which ϕ is a first-order Horn clause or a query with fuzzy constants and regular predicates, and α ∈ [0, 1] is a lower bound on the belief on ϕ in terms of necessity measures. Since fuzzy constants can occur in the logic component of formulas, the truth value of formulas is many-valued instead of Boolean. Moreover, since we have to reason about the possibilistic uncertainty of formulas with fuzzy constants, belief states are modeled by normalized possibility distributions on a set of many-valued interpretations. In this framework, (1) we define a syntax and a semantics of the underlying logic; (2) we give a sound modus ponens-style calculus by derivation based on a semantic unification pattern of fuzzy constants; (3) we develop a directional fuzzy unification algorithm based on the distinction between general and specific object constants; and (4) we describe a backward first-order proof procedure oriented to queries that is based on the calculus of the language and the computation of the unification degree between fuzzy constants in terms of a necessity measure for fuzzy events.
- ItemRestrictedAdjusting Time Slices to Apply Coscheduling Techniques in a non-dedicated NOW(Springer Verlag, 2002) Giné, Francesc; Solsona Tehàs, Francesc; Hernandez, Porfidio; Luque, EmilioOur research is focussed on keeping both local and parallel jobs together in a time-sharing NOW and efficiently scheduling them by means of coscheduling mechanisms. In such systems, the proper length of the time slice still remains an open question. In this paper, an algorithm is presented to adjust the length of the quantum dynamically to the necessity of the distributed tasks while keeping good response time for interactive processes. It is implemented and evaluated in a Linux cluster.
- ItemRestrictedAdjusting the Lengths of Time Slices when Scheduling PVM Jobs with High Memory Requirements(Springer Verlag, 2002) Giné, Francesc; Solsona Tehàs, Francesc; Hernandez, Porfidio; Luque, EmilioOur research is focussed on keeping both local and parallel jobs together in a non-dedicated cluster and scheduling them efficiently. In such systems, the overflow of the physical memory into the virtual memory usually causes a severe performance penalty for distributed jobs. This impact can be reduced by means of giving more time slice length to parallel tasks in order better to exploit their memory reference locality. Thus, an algorithm is presented to adjust the length of the time slice dynamically to the necessity of the distributed and local tasks. It is implemented in a Linux cluster and evaluated with PVM jobs.
- ItemRestrictedTillage effects on water storage during fallow, and on barley root growth and yield in two contrasting soils of the semi-arid Segarra region in Spain(Elsevier, 2002) Lampurlanés Castel, Jorge; Angás Pueyo, Pedro; Cantero-Martínez, CarlosIn semi-arid areas under rainfed agriculture water is the most limiting factor of crop production. To investigate the best way to perform fallow and its effect on soil water content (SWC) and root growth in a barley (Hordeum vulgare L.) crop after fallow, an experiment was conducted on two soils in La Segarra, a semi-arid area in the Ebro Valley (Spain). Fallow was a traditional system used in these areas to capture out-of-season rainfall to supplement that of the growing period, usually lasting 16 months, from July to October of the next year. Soil A was a loamy fine Fluventic Xerochrept (Haplic Calcisol, FAO) of 120 cm depth and Soil B was a loamy Lithic Xeric Torriorthent (Calcaric Regosol, FAO) of only 30 cm depth. The experiment was continued for four fallow-crop cycles in Soil A and for two in Soil B. In Soil A, three tillage systems were compared: subsoil tillage (ST), minimum tillage (MT) and no-tillage (NT). In Soil B, only MT and NT were compared. In the fields cropped to barley, SWC and root length density (LV) were measured at important developmental stages during the season, lasting from October to June. In the fallow fields SWC was also monitored. Here, evaporation (EV), water storage (WS) and water storage efficiency (WSE) were calculated using a simplified balance approach. The fallow period was split in two 8-month sub-periods: July–February (infiltration) and March–October evaporation (EV). In Soil A, values of WSE were in the range 10–18% in 1992–1993, 1993–1994 and 1994–1995 fallow, but fell to 3% in 1995–1996. Among tillage systems, NT showed significantly greater WSE in the July–February sub-period of 1992–1993 and 1993–1994 fallow, but significantly lower WSE in the March–October sub-period, due to greater EV under NT. Consequently, no differences in total WSE were found between tillage systems. In Soil B, WSE was low, about 3–7%, and there were no difference between tillage systems. During the crop period, the differences in SWC and LV between tillage systems were small. Regarding yields, the best tillage system depended on the year. NT is potentially the best system for executing fallow, but residues of the preceding crop must be left spread over the soil.
- ItemOpen AccessAssessment of Recycling Tunnel Sprayers in Mediterranean Vineyards and Apple Orchards(Elsevier, 2002) Planas de Martí, Santiago; Solanelles Batlle, Francesc; Fillat, A.The use of air-assisted recycling tunnel sprayers in Mediterranean fruit orchards and vineyards was assessed by comparing the performance of two tunnel sprayer prototypes with an air-assisted axial flow sprayer. Field trials comprised measurements of spray deposit on the canopy, off-target spray losses and the biological efficacy of chemical applications. According to the results, no spray drift was measured during the applications with tunnel sprayers. Spray losses on the ground were localized mainly under the crop rows. However, the uniformity of the spray deposition on the canopy was worse than that obtained with the axial flow sprayer. It seems that this can be attributed to poor adjustment of the tunnel dimensions in relation to the crop size or to inadequate air-jet design. Tunnel sprayers may be an option to meet future environmental requirements for spray applications, so long as crop training systems change to smaller-size orchards and wall-shaped trellis vineyards.
- ItemOpen AccessDouble P-Tree: A Distributed Architecture for Large-Scale Video-on-Demand(Springer Verlag, 2002) Cores Prado, Fernando; Ripoll, A.; Luque, EmilioIn order to ensure a more widespread implementation of video-ondemand (VoD) services, it is essential that the design of cost-effective largescale VoD (LVoD) architectures be able to support hundreds of thousands of concurrent users. The main keys for the designing of such architectures are high streaming capacity, low costs, scalability, fault tolerance, load balance, low complexity and resource sharing among user requests. To achieve these objectives, we propose a distributed architecture, called double P-Tree, which is based on a tree topology of independent local networks with proxies. The proxy functionality has been modified in such a way that it works at the same time as cache for the most-watched videos, and as a distributed mirror for the remaining videos. In this way, we manage to distribute main server functionality (as a repository of all system videos, server of proxy-misses and system manager) among all local proxies. The evaluation of this new architecture, through an analytical model, shows that double P-Tree architecture is a good approach for the building of scalable and fault-tolerant LVoD systems. Experimental results show that this architecture achieves a good tradeoff between effective bandwidth and storage requirements.
- ItemOpen AccessNew approaches to the study of Antarctic lithobiontic microrganisms and their inorganic traces, and their application in the detection of life in Martian rocks(Springer Verlag, 2002) Ascaso, C.; Wierzchos, JacekMicrobial life in the harsh conditions of Antarctica’s cold desert may be considered an analogue of potential life on early Mars. In order to explore the development and survival of this epilithic and endolithic form of microbial life, our most sophisticated, state-ofthe- art visualization technologies have to be used to their full potential. The study of any ecosystem requires a knowledge of its components and the processes that take place within it. If we are to understand the structure and function of each component of the microecosystems that inhabit lithic substrates, we need to be able to quantify and identify the microorganisms present in each lithobiontic ecological niche and to accurately characterize the mineralogical features of these hidden microhabitats. Once we have established the techniques that will allow us to observe and identify these microorganisms and mineral substrates in situ, and have confirmed the presence of water, the following questions can be addressed: How are the microorganisms organized in the fissures or cavities? Which microorganisms are present and how many are there? Additional questions that logically follow include: What are the existing water relationships in the microhabitat and what effects do the microorganisms have on the mineral composition? Mechanical and chemical changes in minerals and mineralization of microbial cells can give rise to physical and/or chemical traces (biomarkers) and to microbial fossil formation. In this report, we describe the detection of chains of magnetite within the Martian meteorite ALH84001, as an example of the potential use of SEM-SEMBSE in the search for plausible traces of life on early Mars.
- ItemRestrictedSoil bulk density and penetration resistance under different tillage and crop management systems and their relationship with barley root growth(American Society of Agronomy, 2003) Lampurlanés Castel, Jorge; Cantero-Martínez, CarlosTo study the effects of fallow and tillage on soil physical properties and barley (Hordeum vulgare L.) root growth, an experiment was conducted for several years on two soils of contrasting depth: deep, a Fluventic Xerochrept of 120-cm depth, and shallow, a Lithic Xeric Torriorthent of 30-cm depth. Subsoil tillage (ST), minimum tillage (MT), and no-tillage (NT) were compared in the deep soil and MT and NT in the shallow soil. Bulk density (BD), penetration resistance, gravimetric water content, gravel content, and root length density were determined at several times during the year. In the deep soil, BD was lower in the fallow and crop-after-fallow plots (1.26 Mg m−3) than in the continuous-crop plots (1.32 Mg m−3). In this soil, NT showed the largest bulk densities (mean of 1.34 Mg m−3), followed by MT (mean of 1.27 Mg m−3) and ST (mean of 1.22 Mg m−3). Larger penetration resistance was found in NT than in ST and MT in both soils soon after tillage operations. However, root length density profiles sometimes showed greater values for NT than for the other tillage systems, revealing a good soil condition for root growth under NT. Therefore, an increase in soil strength is observed under NT in the first years after its introduction that does not greatly affect root growth in well-structured soils. Fallow reduces soil strength due to the effect of tillage and natural loosening factors like drying and wetting cycles or fauna activity. This effect extends to the following crop.
- ItemRestrictedMultiprogramming Level of PVM Jobs in a Non-dedicated Linux NOW(Springer Verlag, 2003) Giné, Francesc; Solsona Tehàs, Francesc; Barrientos, Jesus; Hernandez, Porfidio; Hanzich, Mauricio; Luque, EmilioOur research is focussed on keeping both local and PVM jobs together in a time-sharing Network Of Workstations (NOW) and efficiently scheduling them by means of dynamic coscheduling mechanisms. In this framework, we study the sensitivity of PVM jobs to multiprogramming. According to the results obtained, we propose a new extension of the dynamic coscheduling technique, named Cooperating Coscheduling. Its feasibility is shown experimentally in a PVM-Linux cluster.
- ItemOpen AccessFixed versus variable bulk canopy resistance for reference evapotranspiration estimation using the Penman-Monteith equation under semiarid conditions(Elsevier, 2003) Lecina Brau, Sergio; Martínez-Cob, Antonio; Pérez García, Pedro J.; Villalobos, F. J.; Baselga, J. J.
- ItemRestrictedGrowth, yield and water productivity of barley (Hordeum vulgare L.) affected by tillage and N fertilization in Mediterranean semiarid, rainfed conditions of Spain(Elsevier, 2003) Cantero-Martínez, Carlos; Angás Pueyo, Pedro; Lampurlanés Castel, JorgeIn dryland agricultural systems of the Mediterranean area, the amount and variability of the rainfall are the main constraints to crop yield. Soil management through tillage and rational use of N fertilization can improve the performance of crops through improved use of available water and increased use efficiency. Field experiments were carried out at three locations differing in degree of aridity (Guissona, Agramunt and Candasnos) in the Ebro Valley in Northeast Spain during three growing seasons. Yield and water-use efficiency (WUE) of barley, the predominant crop in the area, were examined under three levels of N fertilization (zero, medium and high) and three soil management systems (no tillage (NT), minimum or reduced (MT) and conventional tillage (CT)). Soil water content, total crop dry matter, leaf area, yield and yield components were measured during consecutive crop cycles. In general, both levels of added nitrogen, increased the yield to about 30% above zero nitrogen. Grain number increased with N fertilization and determined the level of yield response. At two locations (Guissona and Agramunt), a positive effect of MTor NTwas observed under dry conditions. Yield (up to 60%) and WUE (up to 50%) were reduced by tillage. In the driest location of Candasnos, where a better response to reduced tillage (MT and NT) was expected, the WUEs for grain yield were low for all treatments (between 2.4 and 6.5 kg ha 1 mm 1 ) and the best crop performance was obtained in tilled treatments. Negative effects on yield were caused by the pests Mayetiola mimeuri Mesnil and Tetramesa tritici (Fitch), when stubble residues remained without tillage management. The use of conservation tillage in this specific Northeast area of the Ebro Valley improved the yield of barley and its WUE. Nitrogen fertilization in this area could be reduced to levels lower that those currently used by farmers. This reduction could be greater with increased tillage intensity. No additional N fertilizer was needed when under conservation tillage.