Search

Gamma-ray bursts are known to display various features on top of their canonical behavior. In this short review, we will describe and discuss two of them: the ultra-long gamma-ray bursts, which are defined by an extreme duration of their prompt phase, and the plateau phase, which is defined by a steady phase of large duration at the start of the afterglow. We will review the main properties of those two phenomena, and will discuss their possible origin, in light of the standard fireball model of gamma-ray bursts. A final section will discuss the future missions, which could bring new evidence to the study of those objects.

In the manuscript, effects of tidal disruption events (TDEs) are estimated on long-term AGN variability, to provide interesting clues to detect probable hidden TDEs in normal broad line AGN with apparent intrinsic variability which overwhelm the TDEs expected variability features, after considering the unique TDEs expected variability patterns. Based on theoretical TDEs expected variability plus AGN intrinsic variability randomly simulated by Continuous AutoRegressive process, long-term variability properties with and without TDEs contributions are well analysed in AGN. Then, interesting effects of TDEs can be determined on long-term observed variability of AGN. First, more massive BHs, especially masses larger than |$10^7\, {\rm M_\odot }$|⁠ , can lead to more sensitive and positive dependence of τ TN on RTN , with τ TN as variability time-scale ratio of light curves with TDEs contributions to intrinsic light curves without TDEs contributions, and RTN as ratio of peak intensity of TDEs expected variability to the mean intensity of intrinsic AGN variability without TDEs contributions. Secondly, stronger TDEs contributions RTN can lead to τ TN quite larger than 5. Thirdly, for intrinsic AGN variability having longer variability time-scales, TDEs contributions will lead τ TN to be increased more slowly. The results actually provide an interesting forward-looking method to detect probable hidden TDEs in normal broad-line AGN, due to quite different variability properties, especially different DRW/CAR process expected variability time-scales, in different epochs, especially in normal broad line AGN with shorter intrinsic variability time-scales and with BH masses larger than |$10^7\, {\rm M_\odot }$|⁠. [ABSTRACT FROM AUTHOR]

This paper is an extension of the study by Khamitov et al. (2022) with regard to the catalog and the astrophysical interpretation of the imitation of significant proper motions in active galactic nuclei (AGNs) and quasars based on data from the Gaia space observatory. We present a sample of SRG/eROSITA X-ray sources in the eastern Galactic hemisphere () having significant proper motions in the Gaia EDR3 measurements with the confirmed extragalactic nature of the objects. The catalog consists of 248 extragalactic sources with spectroscopically measured redshifts. The catalog includes all of the objects available in the SIMBAD database and coincident with the identified optical counterpart within 0.5 arcsec. Eighteen sources with spectroscopically measured redshifts from observations with the Russian–Turkish 1.5-m telescope RTT-150 (Khamitov et al. 2022) have been additionally included in the catalog. The sources in the catalog are AGNs of various types (Sy1, Sy2, LINER), quasars, radio galaxies, and star-forming galaxies. The imitation of significant proper motions can be explained (by the VIM effect previously known in astrometry) by the presence of transient events on the line of sight in the vicinity of AGNs and quasars (within the Gaia optical resolution element). Among such astrophysical events are supernova outbursts, tidal disruption events in binary AGNs, the variability of high-mass supergiants, the presence of OB associations against the background of AGNs with a variable brightness, etc. The model of outbursts with a fast rise–exponential decay profile allows the variable positional parameters of most sources observed in Gaia to be described. This approach can be used as an independent way of detecting transient events in the vicinity of AGNs (on scales of several hundred parsecs in the plane of the sky) based on data from the SRG/eROSITA catalogs of X-ray sources and the optical Gaia catalog. [ABSTRACT FROM AUTHOR]

Over the past decades, the achievements in astronomical instrumentation have given rise to a number of novel advanced studies related to the analysis of large arrays of observational data. One of the most famous of these studies is a study of transient events in the near and far space and a search for exoplanets. The main requirements for such kinds of projects are a simultaneous coverage of the largest possible field of view with the highest possible detection limits and temporal resolution. In this study, we present a similar project aimed at creating an extensive, continuously updated survey of transient events and exoplanets. To date, the core of the project incorporates several 0.07–2.5 m optical telescopes and the 6-m BTA telescope of the Special Astrophysical Observatory of RAS (Russia), a number of other Russian observatories and the Bonhyunsan observatory of the Korea Astronomy and Space Science Institute (South Korea). Our attention is mainly focused on the description of two groups of small, wide-angle optical telescopes for primary detection. All the telescopes are originally designed for the goals of the project and may be of interest to the scientific community. A description is also given for a new, high-precision optical spectrograph for the Doppler studies of transient and exoplanet events detected within the project. We present here the philosophy, expectations and first results obtained during the first year of running the project. [ABSTRACT FROM AUTHOR]

MICROSCOPE’s space test of the weak equivalence principle (WEP) is based on the minute measurement of the difference of accelerations experienced by two test masses as they orbit the Earth. A detection of a violation of the WEP would appear at a well-known frequency f EP depending on the satellite’s orbital and spinning frequencies. Consequently, the experiment was optimised to minimise systematic errors at f EP. Glitches are short-lived events visible in the test masses’ measured acceleration, most likely originating in cracks of the satellite’s coating. In this paper, we characterise their shape and time distribution. Although intrinsically random, their time of arrival distribution is modulated by the orbital and spinning periods. They have an impact on the WEP test that must be quantified. However, the data available prevents us from unequivocally tackling this task. We show that glitches affect the test of the WEP, up to an a priori unknown level. Discarding the perturbed data is thus the best way to reduce their effect. [ABSTRACT FROM AUTHOR]

Vibrations and shocks are found among mechanical phenomena undergone by packaging systems. In order to verify the behaviour of packaging systems under shocks, test protocols advocate the execution of drop tests, inclined plane tests, forklift handling courses and so on in laboratories. Nevertheless, even if these protocols are efficient, they do not replicate the wide variety of transient events occurring during transportation. That is why there is a need in developing a method capable of replicating actual transient events in a reproductive way in laboratories. This work concerns the comparison of the responses of a packaging system subjected to two different simulations of the same transient event with the aim to forward develop specifications. The definition and elaboration of shock response spectra (SRS) are reviewed in the first part of this work. Afterwards, a data acquisition enables the recording of classical transient events generated by a forklift. Then the calculation of the SRS of one of those transient events enables the generation of a time signal different from the transient event recorded. Finally, a comparison between the response of a packaging system subjected to the time transient event as it is recorded and the response to the time transient event calculated from the SRS is carried out. The first results based on the study of autocorrelation functions, intercorrelation functions, energy spectral densities (ESDs) and damage calculation conclude towards an equivalence between a real‐time replication and an SRS simulation in the case of one transient event and one packaging system. [ABSTRACT FROM AUTHOR]

Two techniques for analyzing human extracranial neurophysiological signals, namely the periodic/aperiodic parameterization of neural power spectra and the transient events framework of oscillatory activity, have recently emerged in the scientific literature. In this work, we integrate these two analysis perspectives to analyze extracranial neurophysiological signals as a series of transient rhythmic events disambiguated from the background aperiodic activity. We call this novel technique the periodic/aperiodic parametrization of transient oscillations (PAPTO). We demonstrate PAPTO by investigating resting-state sensorimotor magnetoencephalography recordings from the Cambridge Center for Ageing and Neuroscience cross-sectional study on healthy ageing (n = 600, ages 18–88). We show that PAPTO is more sensitive to neocortical transient beta rhythms compared to more conventional transient event detection algorithms and captures more variance in the resting-state occurrence rate of beta events across participants. The improved sensitivity of PAPTO reveals that the beta occurrence rate almost doubles over the adult lifespan which we discuss in terms of thalamocortical beta generation in the somatosensory cortex and the age-related decline of sensory perception.

The High Energy Modular Ensemble of Satellites (HERMES) project intends to build an all-sky monitor operating from keV to MeV for the detection and localisation of transient events, like gamma ray bursts. HERMES is a modular observatory composed by detectors on-board of nanosatellites. HERMES aims to revolutionise the world of multi-messenger astrophysics thanks to the innovative concept of a modular instrument based on small satellites and characterised by reduced design and development times and low costs, in the face of high technological content and scientific profile of the mission. A first part of the project, HERMES Technological Pathfinder, composed of three CubeSats, aims to demonstrate the feasibility of detecting transient phenomena in high energy with small satellites. The next phase of the project, HERMES Scientific Pathfinder, will expand the constellation up to six satellites, allowing routinely accurate triangulation measurements. This paper presents an analysis that aims to be propaedeutic for the design of the final HERMES Full Constellation, which will be an all-sky monitor made up of tens/hundreds of nanosatellites in Low Earth Orbit with a total effective area of ∼ m 2. An adequate number of nanosatellites, simultaneously detecting a transient, provides a source localisation accuracy of the order of magnitude of few arcmin and large effective area. The objective of this work is to define possible strategies of injection in orbit of the complete constellation. In this first analysis we used only the number of triangulable Gamma Ray Bursts (simultaneously detected by at least three nanosatellites) as discriminating factor in order to maximise the constellation performance. By achieving the goal of at least a mean number of 20 Gamma Ray Bursts triangulated per nanosatellite over the two years life-time, optimal configurations for the complete constellation, consisting of seven to fourteen CubeSats, have been identified. • High Energy Modular Ensemble of Satellites (HERMES) mission. • Propaedeutic analysis for the design of the final Full Constellation. • Nanosatellites constellation for fast detection and positioning of Gamma Ray Bursts. • All-sky coverage constellation based on small satellites in Low Earth Orbit. • Maximisation of Gamma Ray Bursts triangulable during the lifetime by each satellite. • Robustness analysis: atmospheric drag, solar radiation pressure and early failures. [ABSTRACT FROM AUTHOR]

The aim of data science is to catch up with the data-intensive life style as well as the demand for decision support, which becomes common in various domains such as medical, education and other smart solutions. As such, high quality of data analysis is greatly desired for accurate and effective downstreaming exploitations. This is also true for the domain of astronomical survey like GOTO (Gravitational-wave Optical Transient Observer), where large amount of raw data has been collected daily. This is one of recognised projects that search for transient events with the new breed of optical survey telescopes that can detect the sky faster and deeper. This is accomplished by comparing the night-specific data with the reference such that new bright sources are obtained for further study. However, the huge size of data makes it difficult to sift by naked eyes, thus requiring an automated system. Yet, many conventional machine-learning models have been sub-optimal for this task, as true positives can hardly be recognised due to the nature of imbalance data. This motivates the exploration of convolutional neural networks or CNN for this binary classification problem. Based on existing technologies, the paper reports the original application of basic CNN model to a representative data, which has been designed and generated within the GOTO project. In addition to the improvement over those previous works, this empirical study also includes details of parameter analysis, which will be useful for practice and further investigation. [ABSTRACT FROM AUTHOR]

Over the past decades, the achievements in astronomical instrumentation have given rise to a number of novel advanced studies related to the analysis of large arrays of observational data. One of the most famous of these studies is a study of transient events in the near and far space and a search for exoplanets. The main requirements for such kinds of projects are a simultaneous coverage of the largest possible field of view with the highest possible detection limits and temporal resolution. In this study, we present a similar project aimed at creating an extensive, continuously updated survey of transient events and exoplanets. To date, the core of the project incorporates several 0.07–2.5 m optical telescopes and the 6-m BTA telescope of the Special Astrophysical Observatory of RAS (Russia), a number of other Russian observatories and the Bonhyunsan observatory of the Korea Astronomy and Space Science Institute (South Korea). Our attention is mainly focused on the description of two groups of small, wide-angle optical telescopes for primary detection. All the telescopes are originally designed for the goals of the project and may be of interest to the scientific community. A description is also given for a new, high-precision optical spectrograph for the Doppler studies of transient and exoplanet events detected within the project. We present here the philosophy, expectations and first results obtained during the first year of running the project.

Even in response to simple tasks such as hand movement, human brain activity shows remarkable inter-subject variability. Recently, it has been shown that individual spatial variability in fMRI task responses can be predicted from measurements collected at rest; suggesting that the spatial variability is a stable feature, inherent to the individual’s brain. However, it is not clear if this is also true for individual variability in the spatio-spectral content of oscillatory brain activity. Here, we show using MEG (N ​= ​89) that we can predict the spatial and spectral content of an individual’s task response using features estimated from the individual’s resting MEG data. This works by learning when transient spectral ‘bursts’ or events in the resting state tend to reoccur in the task responses. We applied our method to motor, working memory and language comprehension tasks. All task conditions were predicted significantly above chance. Finally, we found a systematic relationship between genetic similarity (e.g. unrelated subjects vs. twins) and predictability. Our approach can predict individual differences in brain activity and suggests a link between transient spectral events in task and rest that can be captured at the level of individuals.

Networked and interconnected microgrids can improve resilience of critical end-use loads during extreme events. However, the frequency deviations in microgrids during transient events are significantly larger than those typically seen in bulk transmission systems. The larger frequency deviations can cause a loss of inverter-connected assets, resulting in a loss of power to critical end-use loads. Grid Friendly Appliance^TM (GFA) controllers can mitigate the transient event effects by engaging end-use loads. This paper presents a method to select set-points for end-use loads equipped with GFA controllers, while minimizing the interruptions to end-use customers. An online (i.e. real-time), device-level algorithm adjusts individual GFA controller frequency setpoints based on the operational characteristics of each end-use load and on the changing grid dynamic characteristics to selectively engage the load for mitigating the switching transients. The adaptive gradient-descent-based algorithm does not require control or coordination amongst end-use devices for adapting frequency set-points. The method is validated using dynamic simulations on a modified version of the IEEE 123-node test system with three microgrids using the GridLAB-D^TM simulation environment. The improved dynamic stability achieved through the engagement of GFAs support the switching operations necessary for networked microgrid operations.

As the distributed energy resources penetration level increases, the distribution system operator faces a challenging task of unintentional islanding detection. Besides islanding detection schemes are affected due to the presence of different types of distributed generation systems and smart inverters. The presence of these devices hinders the capability of islanding detection schemes. To mitigate these issues, this study proposes a practical methodology of variational mode decomposition‐based energy index for islanding detection. It decomposes the sampled voltage signal at the point of common coupling into four modes/intrinsic mode functions (IMFs). Among these modes/IMFs, the energy index of mode two has been utilised to detect the islanding. It is an entirely intrinsic, adaptive, and variational method. The five bus and practical distribution systems have been modelled using PSCAD/EMTDC software while considering various components' practical aspects. The technique has been tested for the mixed type of distributed generation and various transient events. The test results reveal that the proposed method is capable of discriminating the islanding event from other disturbances. [ABSTRACT FROM AUTHOR]

The world-wide application of photovoltaic (PV) plants is a promising solution to the energy crisis. However, PV plants usually suffer from transient instability due to weakness in dynamical adaptability. This study, based on the transient stability mechanism, devises an adaptive control scheme to achieve transient stability enhancement for PV plants. The transient stability mechanism shows that the active droop factor is negatively associated with the transient stability whereas the reactive droop factor is positively associated. The transient stability enhancement is implemented by increasing the reactive droop factor and reducing the active droop factor to raise the power angle curve. The proposed control scheme adjusts the droop factors dynamically during the transient events by detecting the real-time electrical quantities. The control scheme advances in a designed activation module which is able to judge if there exist transient events. A series of simulation cases demonstrate the effectiveness of the control scheme in different transient events. Simulation results show that the control scheme adjusts droop factors adaptively and possesses better transient stability than the normal droop control. [ABSTRACT FROM AUTHOR]

A systematic search for cosmic gamma-ray bursts (GRBs) and other short hard X-ray events in the archival data from the IBIS/ISGRI telescope of the INTEGRAL observatory over 2003–2018 has been carried out. Seven previously unknown GRBs have been recorded in the telescope field of view; all of them have been localized with an accuracy ≤2 arcmin. These events were not revealed by the INTEGRAL burst alert system (IBAS) designed for an automatic GRB search and alert. Four more such localized events missed by IBAS, but known previously, i.e., observed in other experiments, have been found. Eight hundred and eighty six GRBs outside the field of view that arrived at large angles to the IBIS/ISGRI axis have also been recorded. All of them were previously recorded in other experiments, primarily by the anticoincidence shield (ACS) of the SPI gamma-ray spectrometer onboard the INTEGRAL observatory, the PICsIT detector of the IBIS gamma-ray telescope, and the KONUS/WIND monitor. An order of magnitude more events without any confirmations in other experiments have been recorded. Both GRBs and solar flares or magnetospheric transient events can be among them. Catalogs with the basic parameters of confirmed and previously unknown cosmic GRBs recorded by the IBIS/ISGRI telescope have been compiled. The statistical distributions of bursts in various parameters have been constructed and investigated. [ABSTRACT FROM AUTHOR]

Highlights • Poloidal current induced in the vacuum vessel wall during transient events in tokamaks. • Explicit dependence of the diamagnetic signal on the wall current. • Sensitivity of the diamagnetic signal to the loop position with respect to the wall. • Sensitivity of the diamagnetic signal to the resistive wall time. • Complete analytical derivations and estimates. Abstract Effect of the poloidal current induced in the tokamak vessel wall during transient events is explicitly incorporated into the formulas for the diamagnetic signal. The analysis is based on the equation linking this current to two drivers, the evolving plasma inside and the varying toroidal field produced by currents outside. The wall itself is considered resistive and serves as a damper. The main part of the described analytical approach is applicable to any situation of interest, but the emphasis is put on the case with diamagnetic loop placed on the inner side of the wall, as it is planned in ITER [R. Fresa, et al., Fusion Eng. Des. 100, 133 (2015)]. Such a loop will actually measure the voltage equal to the poloidal current induced in the wall multiplied by the wall poloidal resistivity. With this current as a main detectable quantity, a refined algorithm is needed for determining the plasma energy from the magnetic measurements. Theory-based recommendations are given to improve the diagnostics, especially for the rapid events like thermal quenches and ELM (edge localized mode) crashes. [ABSTRACT FROM AUTHOR]

In this study, the values of chaoticity and dynamical complexity parameters for some selected storm periods in the year 2011 and 2012 have been computed. This was done using detrended TEC data sets measured from Birnin-Kebbi, Torro and Enugu global positioning system (GPS) receiver stations in Nigeria. It was observed that the significance of difference (SD) values were mostly greater than 1.96 but surprisingly lower than 1.96 in September 29, 2011. The values of the computed SD were also found to be reduced in most cases just after the geomagnetic storm with immediate recovery a day after the main phase of the storm while the values of Lyapunov exponent and Tsallis entropy remains reduced due to the influence of geomagnetic storms. It was also observed that the value of Lyapunov exponent and Tsallis entropy reveals similar variation pattern during storm period in most cases. Also recorded surprisingly were lower values of these dynamical quantifiers during the solar flare event of August 8th and 9th of the year 2011. The possible mechanisms responsible for these observations were further discussed in this work. However, our observations show that the ionospheric effects of some other possible transient events other than geomagnetic storms can also be revealed by the variation of chaoticity and dynamical complexity. [ABSTRACT FROM AUTHOR]

In this paper, the thermal-mechanical responses of the first wall (FW) composed of pure tungsten (W) and China Low Activation Martensitic steel in China Fusion Engineering Test Reactor are predicted under the normal state and the transient events, i.e., major disruption (MD), vertical displacement events (VDEs) and edge localized modes (ELMs), using finite element method (FEM). The temperature distribution in the armor material and structural material is predicted and analyzed, and the temperature induced thermal stress is obtained through a fully coupled thermal-stress analysis module. The comparative simulation results reveal that the short duration time of MD and ELMs have less thermal/mechanical effects on the FW than that of the long deposition time of VDEs. [ABSTRACT FROM AUTHOR]

Wind turbine gearbox bearings (WTGBs) are the most reliability critical component in wind turbine gearboxes because of their high failure rate and long downtime‐per‐failure. Current design methods predict bearing failure‐by‐fatigue life models. However, premature WTGB failures have been observed by many other modes. This study presents the development of a multibody dynamic gearbox model, used to determine maximum bearing contact stresses from laboratory measured shaft torque data during normal operation and shutdown conditions. The model was validated by comparing its results to other models of the 750 kW National Renewable Energy Laboratory test drive train by the Gearbox Reliability Collaborative. During normal operation, the maximum contact stress experienced by the planetary stage bearings exceeded recommended levels by 1% and during shutdown by 15%. High‐speed shaft bearings also exceeded recommended levels during shutdown by 18%. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes a methodology for the extrapolation of a single measured non-stationary time series to an expected long-term service history. Within the context of limited data availability, stochastic simulation is used to generate an ensemble of surrogate realizations from which expected long-term service histories can be derived. Two non-stationary stochastic simulation algorithms are implemented. Both simulation algorithms are compared using the transient response measured on hydroelectric turbine blades during startup. In both algorithms, an independent random phase shift is introduced in the analytic signal given by the Hilbert transform of each time series subcomponent. The subcomponents are obtained either by Empirical Mode Decomposition (EMD) or by Stationary Wavelet Decomposition (SWD). The simulated realizations will invariably include some inherent variations arising from the process itself, combined with epistemic uncertainty due to the assumptions made during modeling. To ensure the quality of the simulated realizations, the following quantitative criteria are used to compare the simulated ensemble to the reference data: cumulative energy, extreme value distribution and rainflow amplitude spectra. [Copyright &y& Elsevier]

Copyright of Computer Science (1407-7493) is the property of RTU Publishing House and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Two transient pollution events were monitored in a pastoral stream in southwestern Kenya to evaluate their relative contribution to diffuse pollution. Peak loads of pollutants during storm-induced transients were within 3-4 orders of magnitude higher than the short-lived (30-60 minutes) diurnal episodes provoked by in-stream activities of people and livestock. Transient yields were striking during storm-induced events; 778,000, 8,400, 550 and 100 kg day-1 for suspended solids, BOD5, total P and total N, respectively, compared to wet weather base flow (150, 30, 0.8 and 1.4 kg day-1, for the same parameters, respectively). Two forms of concentration-discharge relationships were observed: increases in concentration for turbidity, suspended solids, BOD5, total P and the faecal indicator bacteria at the peak of the stream hydrograph, and concurrent decreases in concentration for conductivity and total N. Following each storm-induced transient event, a marked improvement in water quality was observed within 48-72 hrs of the receding limb of the stream hydrograph before the next base low was established. It was concluded that storm-induced transients are exceedingly important for the mobilization of pollutants from diffuse sources but both transient events affect stream-channel processes, especially water quality, with the possibility of attendant consequences on the health of riparian inhabitants. [ABSTRACT FROM AUTHOR]

Abstract: Numerical simulations of wind loads and their effects are critical in the design of structures to ensure their safety under winds. The simulations range from generation of time histories of wind velocity, pressure and force fluctuations to structural response and assessment of attendant functionality and safety under service and design loads, respectively. Typically these schemes employ Monte Carlo-based approaches that encompass model-based simulations or information derived from observed data. The scope of simulations spans uni-variate to multi-variate processes; uni-dimensional to multi-dimensional fields; Gaussian to non-Gaussian; stationary to non-stationary; conditional and unconditional cases. In order to accomplish these tasks, methods based on the time, frequency, or time–frequency domains are employed. This paper summarizes a historical perspective, recent developments and future challenges. Also included in the discussion are computational tools employed for data analysis, response analysis and its management, and prediction. Examples are presented to illustrate some of the topics discussed. [Copyright &y& Elsevier]

The work presented here had two main aims: first, it investigated the relationship between in-cylinder combustion performance and particulate size distribution and number count; second, it examined the possibility of reconstructing transient events using steady state test data relating to particulate size distribution and number count. It identified a strong correlation between the geometric mean diameter (GMD) of the engine-out particulate matter and the rate of burning during the early stage of combustion. In addition, it identified correlations between the coefficient of variance for 50 per cent mass fraction burned and the coefficient of variance for particulate GMD. The tests relating to transient events identified that steady state data can be used to reconstruct acceleration events, but not deceleration events. The methodology followed to obtain these findings is detailed in this paper. [ABSTRACT FROM AUTHOR]

The passage of a flood wave over sandy stream sediments can cause changes in the discharge of groundwater to the stream that range from a transient reduction in the discharge rate to a reversal of flow and temporary storage of stream water in the stream sediments. These phenomena were examined in laboratory studies with an intact core and by numerical modeling to assess the effect of both physical and biological processes on the nitrate flux from nitrate-contaminated groundwater to a stream. The balance between the rates of groundwater flow through organic-rich sediments and of denitrification ultimately determines the efflux of nitrate to the stream. The transient impact on nitrate loading suggested by results from the numerical model indicates that high flood stage and low-sediment hydraulic diffusivity can result in excess nitrate loading to surface water following storm events, whereas large-sediment hydraulic diffusivity, regardless of the size of stream stage changes, facilitates greater removal of NO3− by denitrification by allowing for a longer residence time of water in the subsurface. [ABSTRACT FROM AUTHOR]

In an article on the role of temporal information in life-cycle assessment in this journal, Field and colleagues argued that frequently it is not the single product but the "fleet" (or cohort) of products that "is the appropriate unit of analysis," and that in focusing on the fleet one "explicitly introduces the notion of time as a critical element of comparative life-cycle assessments. . . . " Major transitions, such as replacement of one fleet of products by an alternative fleet, correspond to a system in a transient rather than steady state, and explicit consideration of time is central to transient analysis. One tool increasingly used as part of life-cycle assessment, economic input-output (EIO) analysis, at best deals with time in an implicit fashion. This article illustrates how the sequential interindustry model (SIM), a formulation of the EIO model that explicitly represents time, might be utilized in life-cycle assessment. SIM introduces this temporal component by explicitly accounting for the time required by production activities and the resulting sequencing of the inputs. This can be thought of as engineering rather than accounting information. The data demands of such a model are not likely to be met at present or at any time in the near future. Even so, simulation methods and the use of so-called synthetic data have a history of productive use in a number of fields, including the social sciences. SIM also utilizes the contribution of Joshi on the application of the EIO model to environmental impact and the inclusion of the use as well as the production phases of a product in EIO analysis. The possibility of accounting for discounting of future events, with its impact on decision making, is also briefly discussed. [ABSTRACT FROM AUTHOR]

We review recent plasma and magnetic field results stemming from Voyager 1 and 2 observations of the solar wind in the outer heliosphere. The solar wind speed profiles in 2002 are dominated by shock-related speed increases followed by long ramps of decreasing speed. Significant variability in the density and temperature are seen on all time scales. Transient events near solar maxima drive the formation of MIRs which are increasingly important at large radial distances. Both the density and magnetic field magnitude are consistent with the predictions of Parker''s solar wind model. The solar wind pressure changes at all latitudes over the solar cycle, resulting in an oscillation of the heliospheric boundary positions. As the Voyagers move farther out, the effect of the interstellar medium on the solar wind increases. Observed speeds at Voyager 2 are about 60 km/s lower than those in the inner heliosphere due to interaction with the interstellar neutrals. [Copyright &y& Elsevier]

The mechanism of interaction between subcellular pigment microparticles and short pulse laser radiation was investigated with nanosecond time-resolved microscopy and fluorescence microscopy. Stroboscopic illumination was used to capture images of transient events induced in cells by laser pulses. Fluorescence microscopy enabled assessment of cell damage using fluorescent probes. Short-lived intracellular cavitation bubbles were directly visualized within nanoseconds after laser irradiation. Microbubble expansion and implosion took place on the timescale of 0.1-1 μs and were confined entirely within pigmented cells with remarkable selectivity. Cells containing particles underwent cavitation and rapidly lost viability, while adjacent cells without particles remained viable. Nonpigmented cells can be targeted by labeling them with absorbing particles. Laser-pumped microparticles provide an efficient means of selective cell targeting [ABSTRACT FROM PUBLISHER]