Long-lived Systems Research Articles

Precipitation and Mesoscale Convective Systems: Radiative Impact of Dust over Northern Africa

Abstract The radiative effect of dust on precipitation and mesoscale convective systems (MCSs) is examined during a case of dust emission and transport from 9 to 14 June 2006 over northern Africa. The same method to identify and track different cloud types is applied to satellite observations and two convection-permitting simulations (with grid mesh of 2.5 km), with and without the radiative effect of dust, performed with the MesoNH model. The MCSs produce most of the observed total precipitation (66%), and the long-lived systems (lasting 6 h or more) are responsible for 55% of the total. Both simulations reproduce the observed distribution of precipitation between the cloud categories but differ due to the radiative effects of dust. The overall impacts of dust are a warming of the midtroposphere; a cooling of the near surface, primarily in the western parts of northern Africa; and a decrease in precipitation due to a too-low number of long-lived MCSs. The drop in their number is due to the stabilization of the lower atmosphere, which inhibits the triggering of convection. The long-lived MCSs are a little longer lived, faster, and more efficient in rainfall production when accounting for the dust–radiation interaction. This higher degree of organization is due to the larger convective available potential energy and an intensified African easterly jet. The latter is, in turn, a response to the variation in the meridional gradient of the temperature induced by the dust.

The Zambezi Channel: A new perspective on submarine channel evolution at low latitudes

Submarine channels are not stand-alone systems. They are long-lived systems modified by imperceptibly slow processes and rapid gravity flows, in some part controlled by hinterland dynamics. The submarine Zambezi Channel, within the Mozambique Channel, receives sediment from the Zambezi River catchment which has a dynamic tectonic and morphological history. Using recently collected multibeam bathymetry and PARASOUND data we discuss the geomorphology of the Zambezi Channel. Results show this system to be distinct in geomorphologic character when compared to other low-latitude submarine channels, sharing similarities with high-latitude systems. We propose a new, source-to-sink, hypothesis for the evolution of the Zambezi Channel, taking in to consideration hinterland tectonics, palaeo-lake development, river capture and rapid gravity flows. This hypothesis accounts for the unique present-day anatomy of the Zambezi Channel within the dynamic framework of the systems regional setting.

Toward Architecture Knowledge Sustainability: Extending System Longevity

Complex software systems must be maintained for years or decades, and the effort and cost to maintain them are often high, involving continuous refactoring to ensure their longevity in the face of changing requirements. In this article, we introduce the notion of architectural knowledge (AK) sustainability as a new concept to support architects dealing with the evolution of long-lived systems. Architecture sustainability refers to the ability of the architecture to endure over time with the minimum number of refactoring cycles possible. We suggest that sustainability of the AK is a function of how stable the decisions are, and we discuss a set of sustainability criteria and metrics useful to estimate the sustainability of this AK.

A link between phenotypic robustness and life expectancy in Drosophila melanogaster

Long-lived systems are expected to be stable, i. e. resistant to either external influences, or internal failures. Robustness of biological systems can be defined as a reciprocal value to their phenotypic plasticity expressed through a coefficient of variation (C.V.) for positively distributed phenotypic traits. Considering lifespan as phenotype, which integrates all functions of an organism, we showed that its phenotypic robustness correlates positively with life expectancy. We assessed lifespan parameters for a selection of inbred Drosophila melanogaster strains from Drosophila Genetic Reference Panel (DGRP) reared at 29 ºС. The robustness of lifespan phenotype (C.V.–1) correlated positively with estimated life expectancy for these strains. The same relation also holds for the lifespan of all DGRP strains reared at 25 ºС. Also, in agreement with previous observations, upon temperature change (decrease or increase) the survival curves scaled in time (stretched or shrunk respectively). In other words, the average lifespan decreased for flies reared at elevated temperature, but so did the standard deviation, and thus the coefficients of variation remained in the same range. From this we conclude that coefficients of variation correlate with life expectancies and account for the robustness of lifespan phenotype irrespective of accelerated aging caused by temperature.

A large-scale study of architectural evolution in open-source software systems

From its very inception, the study of software architecture has recognized architectural decay as a regularly occurring phenomenon in long-lived systems. Architectural decay is caused by repeated, ...

Book Review: Highly Siderophile and Strongly Chalcophile Elements in High-Temperature Geochemistry and Cosmochemistry, RIMG Volume 81, ed. by Jason Harvey and James M.D. Day

Book Review: Highly Siderophile and Strongly Chalcophile Elements in High-Temperature Geochemistry and Cosmochemistry, RIMG Volume 81. Edited by Jason Harvey, James M.D. Day (2016) Reviews in Mineralogy and Geochemistry, i–xiv + 774 p., ISBN 978-0-939950-9-73. Highly siderophile elements (HSE) have been studied in high-temperature settings for several decades. Their peculiar affinity to metal and sulfide phases provides complementary insights into geological processes compared to those gained from lithophile or atmophile elements, notably planetary accretion and differentiation. The HSE comprise the noble metals (Ru, Rh, Pd, Re, Os, Ir, Pt, Au), and include two long-lived isotope systems: the Re-Os and the Pt-Os system. The RIMG volume edited by Harvey and Day presents the current state of HSE research in 12 chapters devoted to geo- and cosmochemical applications of the HSE and their isotope systems. After a preface by Harvey and Day providing an overview about HSE geochemistry, the first chapters present experimental and analytical methods. Chapter 1 by Brenan et al. summarizes experimental studies on HSE, discussing the partitioning of HSE between …

Long-term stability of the HR 8799 planetary system without resonant lock

HR 8799 is a star accompanied by four massive planets on wide orbits. The observed planetary configuration has been shown to be unstable on a timescale much shorter than the estimated age of the system (~ 30 Myr) unless the planets are locked into mean motion resonances. This condition is characterised by small-amplitude libration of one or more resonant angles that stabilise the system by preventing close encounters. We simulate planetary systems similar to the HR 8799 planetary system, exploring the parameter space in separation between the orbits, planetary masses and distance from the Sun to the star. We find systems that look like HR 8799 and remain stable for longer than the estimated age of HR 8799. None of our systems are forced into resonances. We find, with nominal masses and in a narrow range of orbit separations, that 5 of 100 systems match the observations and lifetime. Considering a broad range of orbit separations, we find 12 of 900 similar systems. The systems survive significantly longer because of their slightly increased initial orbit separations compared to assuming circular orbits from the observed positions. A small increase in separation leads to a significant increase in survival time. The low eccentricity the orbits develop from gravitational interaction is enough for the planets to match the observations. With lower masses, but still comfortably within the estimated planet mass uncertainty, we find 18 of 100 matching and long-lived systems in a narrow orbital separation range. In the broad separation range, we find 82 of 900 matching systems. Our results imply that the planets in the HR 8799 system do not have to be in strong mean motion resonances.

Influence of biomass aerosol on precipitation over the Central Amazon: an observational study

Abstract. Understanding the influence of biomass burning aerosol on clouds and precipitation in the Amazon is key to reducing uncertainties in simulations of climate change scenarios with regard to deforestation fires. Here, we associate rainfall characteristics obtained from an S-band radar in the Amazon with in situ measurements of biomass burning aerosol for the entire year of 2009. The most important results were obtained during the dry season (July–December). The results indicate that the influence of aerosol on precipitating systems is modulated by the atmospheric degree of instability. For less unstable atmospheres, the higher the aerosol concentration is, the lower the precipitation is over the region. In contrast, for more unstable cases, higher concentrations of black carbon are associated with greater precipitation, increased ice content, and larger rain cells; this finding suggests an association with long-lived systems. The results presented are statistically significant. However, due to limitations imposed by the available data set, important features, such as the contribution of each mechanism to the rainfall suppression, need further investigation. Regional climate model simulations with aircraft and radar measurements would help clarify these questions.

Stochastic background of gravitational waves generated by eccentric neutron star binaries

Binary systems emit gravitational waves in a well-known pattern; for binaries in circular orbits, the emitted radiation has a frequency that is twice the orbital frequency. Systems in eccentric orbits, however, emit gravitational radiation in the higher harmonics too. In this paper, we are concerned with the stochastic background of gravitational waves generated by double neutron star systems of cosmological origin in eccentric orbits. We consider in particular the long-lived systems, that is, those binaries for which the time to coalescence is longer than the Hubble time ($\sim 10$Gyr). Thus, we consider double neutron stars with orbital frequencies ranging from $10^{-8}$ to $2\times 10^{-6}$Hz. Although in the literature some papers consider the spectra generated by eccentric binaries, there is still space for alternative approaches for the calculation of the backgrounds. In this paper, we use a method that consists in summing the spectra that would be generated by each harmonic separately in order to obtain the total background. This method allows us to clearly obtain the influence of each harmonic on the spectra. In addition, we consider different distribution functions for the eccentricities in order to investigate their effects on the background of gravitational waves generated. At last, we briefly discuss the detectability of this background by space-based gravitational wave antennas and pulsar timing arrays.

Producing Accurate and Complete Profile Descriptions

Producing Accurate and Complete Profile Descriptions

Multiple timescales of cyclical behaviour observed at two dome-forming eruptions

Cyclic behaviour over a range of timescales is a well-documented feature of many dome-forming volcanoes, but has not previously been identified in high resolution seismic data from Volcán de Colima (Mexico). Using daily seismic count datasets from Volcán de Colima and Soufrière Hills volcano (Montserrat), this study explores parallels in the long-term behaviour of seismicity at two long-lived systems. Datasets are examined using multiple techniques, including Fast-Fourier Transform, Detrended Fluctuation Analysis and Probabilistic Distribution Analysis, and the comparison of results from two systems reveals interesting parallels in sub-surface processes operating at both systems. Patterns of seismicity at both systems reveal complex but broadly similar long-term temporal patterns with cycles on the order of ~50- to ~200-days. These patterns are consistent with previously published spectral analyses of SO2 flux time-series at Soufrière Hills volcano, and are attributed to variations in the movement of magma in each system. Detrended Fluctuation Analysis determined that both volcanic systems showed a systematic relationship between the number of seismic events and the relative ‘roughness’ of the time-series, and explosions at Volcán de Colima showed a 1.5–2year cycle; neither observation has a clear explanatory mechanism. At Volcán de Colima, analysis of repose intervals between seismic events shows long-term behaviour that responds to changes in activity at the system. Similar patterns for both volcanic systems suggest a common process or processes driving the observed signal but it is not clear from these results alone what those processes may be. Further attempts to model conduit processes at each volcano must account for the similarities and differences in activity within each system. The identification of some commonalities in the patterns of behaviour during long-lived dome-forming eruptions at andesitic volcanoes provides a motivation for investigating further use of time-series analysis as a monitoring tool.

Progenitor delay-time distribution of short gamma-ray bursts: Constraints from observations

Context. The progenitors of short gamma-ray bursts (SGRBs) have not yet been well identified. The most popular model is the merger of compact object binaries (NS-NS/NS-BH). However, other progenitor models cannot be ruled out. The delay-time distribution of SGRB progenitors, which is an important property to constrain progenitor models, is still poorly understood. Aims. We aim to better constrain the luminosity function of SGRBs and the delay-time distribution of their progenitors with newly discovered SGRBs. Methods. We present a low-contamination sample of 16 Swift SGRBs that is better defined by a duration shorter than 0.8 s. By using this robust sample and by combining a self-consistent star formation model with various models for the distribution of time delays, the redshift distribution of SGRBs is calculated and then compared to the observational data. Results. We find that the power-law delay distribution model is disfavored and that only the lognormal delay distribution model with the typical delay tau >= 3 Gyr is consistent with the data. Comparing Swift SGRBs with T90 > 0.8 s to our robust sample (T90 < 0.8 s), we find a significant difference in the time delays between these two samples. Conclusions. Our results show that the progenitors of SGRBs are dominated by relatively long-lived systems (tau >= 3 Gyr), which contrasts the results found for Type Ia supernovae. We therefore conclude that primordial NS-NS systems are not favored as the dominant SGRB progenitors. Alternatively, dynamically formed NS-NS/BH and primordial NS-BH systems with average delays longer than 5 Gyr may contribute a significant fraction to the overall SGRB progenitors.

Crustal deformation effects on the chemical evolution of geothermal systems: the intra-arc Liquiñe–Ofqui fault system, Southern Andes

A better understanding of the chemical evolution of fluids in geothermal and hydrothermal systems requires data-based knowledge regarding the interplay between active tectonics and fluid flow. The Southern Andes volcanic zone is one of the best natural laboratories to address this issue because of the occurrence of numerous geothermal areas, recent seismic activity generated by regional fault systems, and intense volcanic activity. Geothermal systems have been understudied in this area, and limited scientific information exists about the role of local kinematic conditions on fluid flow and mineralization during the development and evolution of geothermal reservoirs. In this study, we provide data for a 1:200,000 scale geological and structural map of the Villarrica–Chihuio area as a setting in which to perform a structural analysis of active geothermal areas. This structural analysis, combined with geochemical modelling of hot spring data, allows the identification of two magmatic-tectonic-geothermal domains based on fault systems, volcanic activity, and lithologies. The Liquiñe–Ofqui fault system (LOFS) domain encompasses geothermal areas located either along the master or subsidiary faults. These are favourably orientated for shear and extension, respectively. In the LOFS domain, the geochemistry of hot spring discharges is controlled by interaction with the crystalline basement, and is characterized by low B/Cl conservative element ratios and high pH. In marked contrast, the arc-oblique long-lived fault systems (ALFS) domain includes geothermal occurrences located on the flanks of volcanoes forming WNW-trending alignments; these systems are built over faults that promote the development of crustal magma reservoirs. Unlike the first domain, the fluid chemistry of these geothermal discharges is strongly controlled by volcanic host rocks, and is typified by lower pH and higher B/Cl ratios. Reaction path modelling supports our model: chemical evolution of geothermal fluids in the Villarrica–Chihuio area is strongly dependent on structurally controlled mechanisms of heat transfer. Within this framework, heat transfer by conduction is responsible for the LOFS domain, whereas magmatically enhanced advective transport dominates heat flow in the ALFS domain. Although more studies are needed to constrain the complex interplay between tectonics and fluid flow, results from this study provide new insights towards efficient exploration strategies of geothermal resources in Southern Chile.

Comparison of multi-crystalline silicon PV modules’ performance under augmented solar irradiation

ABSTRACTIn developing photovoltaic (PV) systems with reliable lifetime performances, it is critical to have quantitative knowledge of not just initial properties and performances, but also their performance over the warrantied 25 year lifetime. In 2010, the Science for Energy Technology Workshop, convened by U.S Department of Energy (DOE) Basic Energy Science, prioritized photovoltaic module lifetime and degradation science (L&amp;DS), which serve as the basis for quantitative and mechanistic understanding of lifetime performance. In order to better understand degradation rates and mechanisms of PV systems in the real-world environment, the SDLE SunFarm at Case Western Reserve University has been created, which is a highly instrumented outdoor test facility with 148 PV modules and &gt; 8000 samples on sun for weathering and degradation studies of materials components and systems designed for long-lived energy systems. I-V and power performance of 10 multi-crystalline silicon PV modules from different manufacturers, using baseline and continuous power monitoring and comprehensive weather and solar resource monitoring, to enable time series analysis for insights into performance characteristics and initial degradation.Five modules from each manufacturer were exposed using mirror augmentation in typical (Cleveland, OH) climatic conditions. The mirror augmentation used geometric concentration factors of 1X, 1.5X and 1.9X of the nominal 1 sun. The effect of mirror augmentation on the modules' performance is reported. A Daystar multi-tracer was used to measure I-V curves of individual modules every 15 minutes while power output under maximum power point tracking was monitored continuously. Monitoring environmental factors (wind speed, wind direction, rainfall, and humidity), solar resource, and module temperatures allow for determination of the effects of these conditions on module power production. Power data was corrected to standard test condition (STC) according to climatic and solar irradiance. Changes in fill factor, short circuit current, open circuit voltage and maximum power are reported for each module. With time series analysis, a better understanding of the module's performance over time and under environmental conditions can be developed.

Isotopic constraints on the age of the Earth’s core: Mutual consistency of the Hf-W and U-Pb systems

The estimation of the time of Earth’s core formation on the basis of isotopic systems with short-lived and long-lived parent nuclides gives significantly different results. Isotopic data for the 182Hf-182W system with a 182Hf half-life of approximately 9 Myr can be interpreted in such a way that the core was formed 34 Myr after the origin of the solar system assuming complete core-mantle equilibrium. Similar estimates on the basis of the U-Pb isotopic system suggest a significantly longer mean time of core formation of approximately 120 Myr. If the Earth’s core were formed instantaneously, both isotopic systems would have shown identical values corresponding to the true age. The discrepancy between the U-Pb and Hf-W systems can be resolved assuming prolonged differentiation of prototerrestrial material into silicate and metallic phases, which occurred not simultaneously and uniformly in different parts of the mantle. This resulted in the isotopic heterogeneity of the mantle, and its subsequent isotopic homogenization occurred slowly. Under such conditions, the mean isotopic compositions of W and Pb in the mantle do not correspond to the mean time of the separation of silicate and metallic phases. This is related to the fact that the exponential function of radioactive decay is strongly nonlinear at high values of the argument, and its mean value does not correspond to the mean value of the function. There are compelling reasons to believe that the early mantle was heterogeneous with respect to W isotopic composition and was subsequently homogenized by convective mixing. This follows from the fact that the lifetime of isotopic heterogeneities in the mantle is close to 1.8 Gyr for various long-lived isotopic systems. There is also no equilibrium between the mantle and the core with respect to the contents of siderophile elements. Because of this, the mean isotopic ratios of W and Pb cannot be used for the direct computation of the time of metal-silicate differentiation in the Earth. Such estimation requires more sophisticated models accounting for the duration of the differentiation process using several isotope pairs. Given the prolonged core formation, which has probably continued up to now, the question about its age becomes ambiguous, and only the most probable growth rate of the core can be estimated. The combined use of the U-Pb and Hf-W systems constrains the time of formation of 90% of the core mass between 0.12 and 2.7 billion years. These model estimates could have been realistic under the condition of complete disequilibrium between the silicate and metallic phases, which is as improbable as the suggestion of complete equilibrium between them on the whole Earth scale.

Ground and Range Operations for a Heavy-Lift Vehicle: Preliminary Thoughts

This paper discusses the ground and range operations for a Shuttle derived Heavy-Lift Vehicle being launched from the Kennedy Space Center on the Eastern range. Comparisons will be made between the Shuttle and a heavy lift configuration (SLS-ETF MPCV April 2011) by contrasting their subsystems. The analysis will also describe a simulation configuration with the potential to be utilized for heavy lift vehicle processing/range simulation modeling and the development of decision-making systems utilized by the range. In addition, a simple simulation model is used to provide the required critical thinking foundations for this preliminary analysis.

Multiple cycles of wave-dominated estuarine deposits in low-accommodation settings, Cretaceous J sandstone, northwestern Nebraska

The J sandstone comprises less than 46 m (151 ft) of sandstone-dominated strata within the mudrock-dominated lower Upper Cretaceous succession of northwestern Nebraska. The unit is a prolific hydrocarbon producer in this region (Denver-Julesburg Basin), but its lithostratigraphic and sequence-stratigraphic framework, critical for reservoir characterization and mapping, is poorly known. We have achieved an improved understanding of depositional history and sequence stratigraphy by describing and correlating cores and wireline logs from wells within Sioux, Dawes, and Box Butte counties, Nebraska, and Niobrara and Goshen counties, Wyoming. Coals, paleosols, fluvial or inner estuarine sandstones, estuarine mudstones, fluvial conglomerate, shoreface sandstone, and reworked volcanic fallout (bentonite) lithofacies were identified. Trace fossil assemblages representing stressed expressions of the Skolithos and Cruziana ichnofacies are common. These lithofacies are arranged vertically into three erosionally based cycles, each less than 28 m (92 ft) thick, and each grade upward from fluvial or inner estuarine sandstones into estuarine mudstones and in turn into shoreface sandstones. The lateral and vertical stacking patterns of the lithofacies are complex, however, and the upper cycles appear to fill space eroded into the underlying ones. Northeast-southwest–elongate isochore trends appear in all three cycles. Lithofacies transition downdip from inner estuarine sandstones in the northeast to estuarine basin mudstones and shoreface sandstones toward the southwest. Detrital mineralogy indicates an easterly (cratonic) provenance for the entire unit. Our data suggest that the J sandstone in northwestern Nebraska accumulated in wave-dominated estuarine settings, as part of a long-lived transgressive systems tract. The unit as a whole occupies a complexly incised landscape cut during a third-order lowstand ca. 98 Ma. Coeval cycles of similar magnitude throughout the Western Interior suggest that the three cycles represent eustatic fluctuations. The highest quality reservoirs occur at the base of the unit in inner estuarine lithofacies in the central and southwestern parts of the study area.

Consensus when all processes may be Byzantine for some time

Among all classes of faults, Byzantine faults form the most general modeling of value faults. Traditionally, in the Byzantine fault model, faults are statically attributed to a set of up to t processes. This, however, implies that in this model a process at which a value fault occurs is forever “stigmatized” as being Byzantine, an assumption that might not be acceptable for long-lived systems, where processes need to be reintegrated after a fault. We thus consider a model where Byzantine processes can recover in a predefined recovery state, and show that consensus can be solved in such a model. Our model admits executions where over time every process is faulty as long as there are always enough correct processes.

Long-lived authentication protocols for process control systems

Abstract Process control systems that manage critical infrastructures have to be available continuously; they may have nodes that once deployed cannot be easily accessed; and they need to be functional over long periods of time. Since the consequences of critical infrastructure disruptions are potentially serious and since critical infrastructures are under threats ranging from extortion to terrorism, it is vital to keep the security services up to current standards over many years of deployment. The mutual authentication of process control system nodes is a fundamental building block of security. This paper describes authentication protocols for use in long-lived process control systems. The protocols address the issue of longevity by defining, as part of the protocol suites, a means for the cryptographic components of the authentication system to be replaced dynamically and securely. The correctness of the component update protocol is established using an extended version of the Burrows, Abadi and Needham (BAN) authentication logic, which incorporates primitives and rules for reasoning about the belief of the ability of cryptographic modules to maintain secrecy.

Possible Physical Mechanisms in the Galaxy to Cause Homochiral Biomaterials for Life

The origin of homochirality in life remains a mystery that some believe is essential for life, and which may result from chiral symmetry breaking interactions with galactic organic material.