5,061 research outputs found
The Effect of the Water Extracting Requirement Upon the Fertilizer, Yield and Growth Response of Sweet Corn
There are a number of factors that influence crop yield, two of which are soil moisture and fertility
Dynamics of Rough Interfaces in Chemical Vapor Deposition: Experiments and a Model for Silica Films
We study the surface dynamics of silica films grown by low pressure chemical
vapor deposition. Atomic force microscopy measurements show that the surface
reaches a scale invariant stationary state compatible with the
Kardar-Parisi-Zhang (KPZ) equation in three dimensions. At intermediate times
the surface undergoes an unstable transient due to shadowing effects. By
varying growth conditions and using spectroscopic techniques, we determine the
physical origin of KPZ scaling to be a low value of the surface sticking
probability, related to the surface concentration of reactive groups. We
propose a stochastic equation that describes the qualitative behavior of our
experimental system.Comment: 5 two-column pages, Revtex, 5 figures, to appear in Phys. Rev. Let
Variety patterns in defense and health technological systems: evidence from international trade data
In recent years, a debate on the technological sources of the next long wave of growth has emerged. In this context, some authors consider that health-related industries will be more likely to generate new technological systems than defense-related industries, which have entered a stage of technological maturity (Ruttan 2006; Steinbock 2014; among others). Based on evolutionary works, in this paper we state that technological systems are characterized by a high degree of technological relatedness, which is positively associated with the possibility of a system to generate variety through the recombination of knowledge from a common base. Following this statement, this work aims to analyze technological relatedness between defense (and health) technological system(s) and other groups of products to compare their variety patterns. Based on international trade data (a panel for 60 countries and 17 years), and different measures of proximity and relatedness (e.g. sectoral competitiveness of countries), we compare defense and health technological systems regarding their potential of generating related variety through two main methods: network analysis and econometrical analysis. The main results support Ruttan’s hypothesis. The network analysis shows the potential for both systems to generate related variety, but higher centrality indicators for health products. In line with that, competitiveness in health products presents a stronger correlation with competitiveness in other groups of products, both related and high and medium technology. This suggests that an improvement in countries’ competitiveness in health sectors can generate spillovers on other related sectors, which can strengthen structural competitiveness and sustain long-term growth.Fil: Vazquez, Roberto Dario. Universidad Nacional de San MartĂn; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; Argentin
Kn 26, a New Quadrupolar Planetary Nebula
Once classified as an emission line source, the planetary nebula (PN) nature
of the source Kn 26 has been only recently recognized in digital sky surveys.
To investigate the spectral properties and spatio-kinematical structure of Kn
26, we have obtained high spatial-resolution optical and near-IR narrow-band
images, high-dispersion long-slit echelle spectra, and intermediate-resolution
spectroscopic observations. The new data reveal an hourglass morphology typical
of bipolar PNe. A detailed analysis of its morphology and kinematics discloses
the presence of a second pair of bipolar lobes, making Kn 26 a new member of
the subclass of quadrupolar PNe. The time-lap between the ejection of the two
pairs of bipolar lobes is much smaller than their dynamical ages, implying a
rapid change of the preferential direction of the central engine. The chemical
composition of Kn 26 is particularly unusual among PNe, with a low N/O ratio
(as of type II PNe) and a high helium abundance (as of type I PNe), although
not atypical among symbiotic stars. Such an anomalous chemical composition may
have resulted from the curtail of the time in the Asymptotic Giant Branch by
the evolution of the progenitor star through a common envelope phase.Comment: 9 pages, 5 figures, accepted for publication in A&
A modelling language for the resilience assessment of networked systems of systems
Systems of Systems (SoS) present challenging features and existing tools result often inadequate for their analysis, especially for heteregeneous networked infrastructures. Most accident scenarios in networked systems cannot be addressed by a simplistic black or white (i.e. functioning or failed) approach. Slow deviations from nominal operation conditions may cause degraded behaviours that suddenly end up into unexpected malfunctioning, with large portions of the network affected. In this paper,we present a language for modelling networked SoS. The language makes it possible to represent interdependencies of various natures, e.g. technical, organizational and human. The representation of interdependencies is based on control relationships that exchange physical quantities and related information. The language also makes it possible the identification of accident scenarios, by representing the propagation of failure events throughout the network. The results can be used for assessing the effectiveness of those mechanisms and measures that contribute to the overall resilience, both in qualitative and quantitative terms. The presented modelling methodology is general enough to be applied in combination with already existing system analysis techniques, such as risk assessment, dependability and performance evaluatio
Infrastructure (Resilience-oriented) Modelling Language: I®ML A proposal for modelling infrastructures and their connections
The modelling of critical infrastructures (CIs) is an important issue that needs to be properly addressed, for several reasons. It is a basic support for making decisions about operation and risk reduction. It might help in understanding high-level states at the system-of-systems layer, which are not ready evident to the organisations that manage the lower level technical systems. Moreover, it is also indispensable for setting a common reference between operator and authorities, for agreeing on the incident scenarios that might affect those infrastructures. So far, critical infrastructures have been modelled ad-hoc, on the basis of knowledge and practice derived from less complex systems. As there is no theoretical framework, most of these efforts proceed without clear guides and goals and using informally defined schemas based mostly on boxes and arrows. Different CIs (electricity grid, telecommunications networks, emergency support, etc) have been modelled using particular schemas that were not directly translatable from one CI to another. If there is a desire to build a science of CIs it is because there are some observable commonalities that different CIs share. Up until now, however, those commonalities were not adequately compiled or categorized, so building models of CIs that are rooted on such commonalities was not possible. This report explores the issue of which elements underlie every CI and how those elements can be used to develop a modelling language that will enable CI modelling and, subsequently, analysis of CI interactions, with a special focus on resilienc
Structure, composition and metagenomic profile of soil microbiomes associated to agricultural land use and tillage systems in the Argentine Pampas
Agriculture is facing a major challenge nowadays: to increase crop production for food and energy while preserving ecosystem functioning and soil quality. Argentine Pampas is one of the main world producers of crops and one of the main adopters of conservation agriculture. Changes in soil chemical and physical properties of Pampas soils due to different tillage systems have been deeply studied. Still, not much evidence has been reported on the effects of agricultural practices on Pampas soil microbiomes. The aim of our study was to investigate the effects of agricultural land use on community structure, composition and metabolic profiles on soil microbiomes of Argentine Pampas. We also compared the effects associated to conventional practices with the effects of no-tillage systems. Our results confirmed the impact on microbiome structure and composition due to agricultural practices. The phyla Verrucomicrobia, Plactomycetes, Actinobacteria, and Chloroflexi were more abundant in non cultivated soils while Gemmatimonadetes, Nitrospirae and WS3 were more abundant in cultivated soils. Effects on metabolic metagenomic profiles were also observed. The relative abundance of genes assigned to transcription, protein modification, nucleotide transport and metabolism, wall and membrane biogenesis and intracellular trafficking and secretion were higher in cultivated fertilized soils than in non cultivated soils. We also observed significant differences in microbiome structure and taxonomic composition between soils under conventional and no- tillage systems. Overall, our results suggest that agronomical land use and the type of tillage system have induced microbiomes to shift their life-history strategies. Microbiomes of cultivated fertilized soils (i.e. higher nutrient amendment) presented tendencies to copiotrophy while microbiomes of non cultivated homogenous soils appeared to have a more oligotrophic life-style. Additionally, we propose that conventional tillage systems may promote copiotrophy more than no-tillage systems by decreasing soil organic matter stability and therefore increasing nutrient availability.Fil: Carbonetto, MarĂa BelĂ©n. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Rosario. Instituto de AgrobiotecnologĂa de Rosario; ArgentinaFil: Rascovan, Nicolas. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Rosario. Instituto de AgrobiotecnologĂa de Rosario; ArgentinaFil: Alvarez, Roberto. Universidad de Buenos Aires. Facultad de AgronomĂa; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Mentaberry, Alejandro Nestor. Universidad de Buenos Aires. Facultad de AgronomĂa; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de FisiologĂa, BiologĂa Molecular y Celular; ArgentinaFil: Vazquez, Martin Pablo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Rosario. Instituto de AgrobiotecnologĂa de Rosario; Argentin
Resilience analysis of networked systems-of-systems based on structural and dynamic interdependencies
Critical infrastructures support everyday activities in modern societies, facilitating the exchange of services and quantities of various nature. Their functioning is the result of the integration of diverse technologies, systems and organizations into a complex network of interconnections. Benefits from networking are accompanied by new threats and risks. In particular, because of the increased interdependency, disturbances and failures may propagate and render unstable the whole infrastructure network. This paper presents a methodology of resilience analysis of networked systems of systems. Resilience generalizes the concept of stability of a system around a state of equilibrium, with respect to a disturbance and its ability of preventing, resisting and recovery. The methodology provides a tool for the analysis of off-equilibrium conditions that may occur in a single system and propagate through the network of dependencies. The analysis is conducted in two stages. The first stage of the analysis is qualitative. It identifies the resilience scenarios, i.e. the sequence of events, triggered by an initial disturbance, which include failures and the system response. The second stage is quantitative. The most critical scenarios can be simulated, for the desired parameter settings, in order to check if they are successfully handled, i.e recovered to nominal conditions, or they end into the network failure. The proposed methodology aims at providing an effective support to resilience-informed design
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