Fine Time Resolution Research Articles

Multiplexed Nanoplasmonic Temporal Profiling of T-Cell Response under Immunomodulatory Agent Exposure.

Immunomodulatory drugs—agents regulating the immune response—are commonly used for treating immune system disorders and minimizing graft versus host disease in persons receiving organ transplants. At the cellular level, immunosuppressant drugs are used to inhibit pro-inflammatory or tissue-damaging responses of cells. However, few studies have so far precisely characterized the cellular-level effect of immunomodulatory treatment. The primary challenge arises due to the rapid and transient nature of T-cell immune responses to such treatment. T-cell responses involve a highly interactive network of different types of cytokines, which makes precise monitoring of drug-modulated T-cell response difficult. Here, we present a nanoplasmonic biosensing approach to quantitatively characterize cytokine secretion behaviors of T cells with a fine time-resolution (every 10 min) that are altered by an immunosuppressive drug used in the treatment of T-cell-mediated diseases. With a microfluidic platform integrating antibody-conjugated gold nanorod (AuNR) arrays, the technique enables simultaneous multi-time-point measurements of pro-inflammatory (IL-2, IFN-γ, and TNF-α) and anti-inflammatory (IL-10) cytokines secreted by T cells. The integrated nanoplasmonic biosensors achieve precise measurements with low operating sample volume (1 μL), short assay time (∼30 min), heightened sensitivity (∼20–30 pg/mL), and negligible sensor crosstalk. Data obtained from the multicytokine secretion profiles with high practicality resulting from all of these sensing capabilities provide a comprehensive picture of the time-varying cellular functional state during pharmacologic immunosuppression. The capability to monitor cellular functional response demonstrated in this study has great potential to ultimately permit personalized immunomodulatory treatment.

Reconstruction of Historical Inflows into and Water Supply from Shasta Dam by Coupling Physically Based Hydroclimate Model with Reservoir Operation Model

AbstractLong-term water supply data are important for the current practice of water resources management at a target region. However, long-term water outflow data from reservoirs are typically limited at fine time resolution (hourly). In this study, the historical data on water supply from the Shasta Dam were reconstructed by a reservoir operation model with reconstructed reservoir inflow data. Before embarking on this exercise, first the inflow data were reconstructed by means of a watershed environmental hydrology hydroclimate model, with its input provided from historical atmospheric reanalysis data. The reanalysis data used in this study are from the National Center for Atmospheric Research and the National Center for Environmental Prediction (NCAR–NCEP) at spatial resolution of 2.5° (210 km at the modeled region). The NCAR–NCEP reanalysis data were dynamically downscaled to 3-km spatial grid resolution at hourly intervals by means of the regional atmospheric component of the hydroclimate model. The d...

Performance of the second MEMS space telescope for observation of extreme lightning from space

A small space-telescope equipped with a micro-electro-mechanical system (MEMS) micro-mirror is applied to space missions for observing random, rare and temporal events like transient luminous events (TLEs). The measurement of TLEs with fine time resolution will show the different temporal profiles predicted by the various models for sprites, blue jets, elves and halos. The proposed space-telescope consists of three components: two sub-telescopes with different focal lengths and a spectrometer. The trigger telescope with a short focal length surveys a wide field of view. The zoom-in telescope with a long focal length looks into a small field of view area that is part of the trigger telescope’s wide field of view. Upon identifying a candidate TLE, the trigger telescope determines the location of the event and provides the location to the MEMS micro-mirror. Then, the micro-mirror, which is placed as a pinhole in front of the zoom-in telescope, rotates its mirror plane by such an angle that the zoom-in telescope will watch the small field of view around the center of the event. In this manner, the zoom-in telescope achieves the zoom-in designed by its long focal length. The first such small-space telescope, the MEMS Telescope for Extreme Lightning (MTEL), was launched into space in 2009 and identified a few candidates sprites. However a power failure (over-charge of the solar battery) of the main satellite occurred, and the MTEL was not able to continue space operation to acquire sizable statistics for TLE events. We developed and constructed the second small-space telescope, called MTEL-II, to continue to observe TLE events in space. In this paper, we present the performance of MTEL-II based on ground tests.

Evaluating the solution performance of IP and CP for berth allocation with time-varying water depth

This paper considers the berth allocation problem (BAP) with time-varying water depth at a tidal river port. Both integer programming (IP) and constraint programming (CP) models are developed. Numerical experiments find that CP tends to be superior to IP when the feasible domain is small (e.g. dynamic vessel arrivals), when the restriction of the objective towards decision variables is loose (e.g. makespan, departure delay), or when the size of IP models is too large due to fine time resolution. Meanwhile, CP’s incapability of proving optimality can be compensated by post-optimization with IP, by using a simple CP/IP hybrid procedure.

Time-to-Digital Converter With 2.1-ps RMS Single-Shot Precision and Subpicosecond Long-Term and Temperature Stability

This paper presents the design and performance measurement results of a prototype time-to-digital converter (TDC) implemented using commercially available components. The TDC is based on an interpolation principle. In this principle, the time interval is first roughly digitized by a coarse counter driven by a high-stability reference clock, and the fractions between the clock periods are measured by two high-resolution interpolators based on the time-to-amplitude conversion method. This principle ensures theoretically unlimited measurement range with fine time resolution. The TDC achieves 2.1-ps rms time interval measurement precision with a resolution of 0.17 ps and the maximum measurement rate of 200 Hz. The estimated single-channel precision is 1.5-ps rms. A unique circuit structure was developed to allow individual channel calibration after each event. During the calibration, a value corresponding to one reference clock period is obtained. This gives the TDC an outstanding long-term stability of 110 fs peak–peak and a long-term drift of 0.2 fs/h over a 24-h interval. The calibration also helps to obtain a high temperature stability of 0.2 ps/°C. The power consumption is 10 W. The circuit structure allows for programmable customization of the TDC to satisfy many potential applications in time-of-flight systems, such as laser range finding or event counting.

The geological cycle of plastics and their use as a stratigraphic indicator of the Anthropocene

The rise of plastics since the mid-20th century, both as a material element of modern life and as a growing environmental pollutant, has been widely described. Their distribution in both the terrestrial and marine realms suggests that they are a key geological indicator of the Anthropocene, as a distinctive stratal component. Most immediately evident in terrestrial deposits, they are clearly becoming widespread in marine sedimentary deposits in both shallow- and deep-water settings. They are abundant and widespread as macroscopic fragments and virtually ubiquitous as microplastic particles; these are dispersed by both physical and biological processes, not least via the food chain and the ‘faecal express’ route from surface to sea floor. Plastics are already widely dispersed in sedimentary deposits, and their amount seems likely to grow several-fold over the next few decades. They will continue to be input into the sedimentary cycle over coming millennia as temporary stores – landfill sites – are eroded. Plastics already enable fine time resolution within Anthropocene deposits via the development of their different types and via the artefacts (‘technofossils’) they are moulded into, and many of these may have long-term preservation potential when buried in strata.

Multiple Time Resolution Stochastic Scheduling for Systems with High Renewable Penetration

This paper presents a stochastic unified unit commitment and economic dispatch model for short-term operations scheduling of power systems with high renewable penetration. The model is a unique stochastic real-time tool that performs economic dispatch with up to 36-hour look-ahead capability, providing dispatch instructions for the first time interval and advisory commitment and dispatch schedules for the remaining scheduling horizon. Variable time resolution is used to contain computational requirements, i.e., finer time resolution is used during the first hours and coarser time resolution during the last hours of the scheduling horizon. The mathematical formulation comprises a MILP problem and it is presented as a two-stage scenario-based stochastic, multiple time resolution unit commitment model. The proposed stochastic model is tested against its deterministic counterpart via an annual simulation of Greek power system short-term operations using real 2013 data. Performance indices concerning dispatch costs, energy balances, and unit cycling are calculated and discussed.

Independent Component Analysis of Gait-Related Movement Artifact Recorded using EEG Electrodes during Treadmill Walking.

There has been a recent surge in the use of electroencephalography (EEG) as a tool for mobile brain imaging due to its portability and fine time resolution. When EEG is combined with independent component analysis (ICA) and source localization techniques, it can model electrocortical activity as arising from temporally independent signals located in spatially distinct cortical areas. However, for mobile tasks, it is not clear how movement artifacts influence ICA and source localization. We devised a novel method to collect pure movement artifact data (devoid of any electrophysiological signals) with a 256-channel EEG system. We first blocked true electrocortical activity using a silicone swim cap. Over the silicone layer, we placed a simulated scalp with electrical properties similar to real human scalp. We collected EEG movement artifact signals from ten healthy, young subjects wearing this setup as they walked on a treadmill at speeds from 0.4–1.6 m/s. We performed ICA and dipole fitting on the EEG movement artifact data to quantify how accurately these methods would identify the artifact signals as non-neural. ICA and dipole fitting accurately localized 99% of the independent components in non-neural locations or lacked dipolar characteristics. The remaining 1% of sources had locations within the brain volume and low residual variances, but had topographical maps, power spectra, time courses, and event related spectral perturbations typical of non-neural sources. Caution should be exercised when interpreting ICA for data that includes semi-periodic artifacts including artifact arising from human walking. Alternative methods are needed for the identification and separation of movement artifact in mobile EEG signals, especially methods that can be performed in real time. Separating true brain signals from motion artifact could clear the way for EEG brain computer interfaces for assistance during mobile activities, such as walking.

Localization error modeling of hybrid fingerprint-based techniques for indoor ultra-wideband systems

Acquiring an accurate estimate of a device's indoor position can lead to the development of various services, such as disaster recovery, content delivery and efficient point-to-point communications. To this end, different positioning techniques have been developed aiming to minimize the localization error. UWB signals are well-suited to communication and tracking systems, as they provide increased tolerance to localization errors due to the fine time resolution of the transmitted pulses and their large bandwidth. This work presents two indoor Ultra-Wideband (UWB) positioning schemes based on the hybrid combination of Fingerprinting with temporal or angular data. The proposed schemes are evaluated using five different propagation models and different numbers of Anchor Nodes (AN) that emit omnidirectional UWB signals. Then, measures are gathered for these parameters and results are presented in terms of localization and angular error. Also, results are provided for the basic statistics, cumulative distribution function and the boxplot of the positioning error, thus providing probabilistic modeling for the localization error. The performance evaluation shows that the two proposed hybrid UWB schemes provide accurate indoor positioning independently of the type of data used during the localization procedure and optimum placement along with the optimum number of the ANs is provided.

An advanced process-based distributed model for the investigation of rainfall-induced landslides: The effect of process representation and boundary conditions

Extreme rainfall events are the major driver of shallow landslide occurrences in mountainous and steep terrain regions around the world. Subsurface hydrology has a dominant role on the initiation of rainfall-induced shallow landslides, since changes in the soil water content affect significantly the soil shear strength. Rainfall infiltration produces an increase of soil water potential, which is followed by a rapid drop in apparent cohesion. Especially on steep slopes of shallow soils, this loss of shear strength can lead to failure even in unsaturated conditions before positive water pressures are developed. We present HYDROlisthisis, a process-based model, fully distributed in space with fine time resolution, in order to investigate the interactions between surface and subsurface hydrology and shallow landslides initiation. Fundamental elements of the approach are the dependence of shear strength on the three-dimensional (3-D) field of soil water potential, as well as the temporal evolution of soil water potential during the wetting and drying phases. Specifically, 3-D variably saturated flow conditions, including soil hydraulic hysteresis and preferential flow phenomena, are simulated for the subsurface flow, coupled with a surface runoff routine based on the kinematic wave approximation. The geotechnical component of the model is based on a multidimensional limit equilibrium analysis, which takes into account the basic principles of unsaturated soil mechanics. A series of numerical simulations were carried out with various boundary conditions and using different hydrological and geotechnical components. Boundary conditions in terms of distributed soil depth were generated using both empirical and process-based models. The effect of including preferential flow and soil hydraulic hysteresis was tested together with the replacement of the infinite slope assumption with the multidimensional limit equilibrium analysis. The results show that boundary conditions play a crucial role in the model performance and that the introduced hydrological (preferential flow and soil hydraulic hysteresis) and geotechnical components (multidimensional limit equilibrium analysis) significantly improve predictive capabilities in the presented case study.

Investigation of Nanoparticle Adsorption During Transport in Porous Media

Summary Nanoparticles (diameter of approximately 5 to 50 nm) easily pass through typical pore throats in reservoirs, but physicochemical attraction between nanoparticles and pore walls may still lead to significant retention. We conducted an extensive series of nanoparticle-transport experiments in core plugs and in columns packed with crushed sedimentary rock, systematically varying flow rate, type of nanoparticle, injection-dispersion concentration, and porous-medium properties. Effluent-nanoparticle-concentration histories were measured with fine resolution in time, enabling the evaluation of nanoparticle adsorption in the columns during slug injection and post-flushes. We also applied this analysis to nanoparticle-transport experiments reported in the literature. Our analysis suggests that nanoparticles undergo both reversible and irreversible adsorption. Effluent-nanoparticle concentration reaches the injection concentration during slug injection, indicating the existence of an adsorption capacity. Experiments with a variety of nanoparticles and porous media yield a wide range of adsorption capacities (from 10–5 to 101 mg/g for nanoparticles and rock, respectively) and also a wide range of proportions of reversible and irreversible adsorption. Reversible- and irreversible-adsorption sites are distinct and interact with nanoparticles independently. The adsorption capacities are typically much smaller than monolayer coverage. Their values depend not only on the type of nanoparticle and porous media, but also on the operating conditions, such as injection concentration and flow rate.

ARIES, Nainital:A Strategically Important Location for Climate Change Studies in the Central Gangetic Himalayan Region

ARIES, acronym for Aryabhatta Research Institute of Observational Sciences, located in the Central Gangetic Himalayan (CGH) region is emerging as one of the unique sites for climate change studies. The long-term, in situ, precise measurements of aerosols and trace gases obtained from this region provide valuable inputs for climate studies. Atmospheric scientists from ARIES are actively involved in nearsurface measurements for meteorology, aerosols and trace gases as well as vertical profiling. The Institute is also providing the observational infrastructure and research support to three major projects of the Indian Space Research Organization, Geosphere Biosphere Programme, which basically deals with the measurement of aerosols, trace gases and boundary-layer experiments. The upcoming stratosphere-troposphere radar and high-power micro-pulse lidar observational facilities will be utilized for the continuous vertical profiling of winds, aerosol and cloud properties at a very fine resolution in time and space. Apart from this, atmospheric scientists of ARIES also have active national and international research collaborations. The important results obtained from these research activities are highlighted and upcoming major observational facilities in the field of atmospheric sciences are discussed. They clearly demonstrate the importance of the unique geographical location of ARIES for climate change studies in the CGH region. These measurements and routine meteorological observations provide the necessary atmospheric corrections to the astrophysical observations taken using optical telescopes located at the site.

Time-resolved imaging of the microbunching instability and energy spread at the Linac Coherent Light Source

The microbunching instability (MBI) is a well-known problem for high brightness electron beams and has been observed at accelerator facilities around the world. Free-electron lasers (FELs) are particularly susceptible to MBI, which can distort the longitudinal phase space and increase the beam’s slice energy spread (SES). Past studies of MBI at the Linac Coherent Light Source (LCLS) relied on optical transition radiation to infer the existence of microbunching. With the development of the x-band transverse deflecting cavity (XTCAV), we can for the first time directly image the longitudinal phase space at the end of the accelerator and complete a comprehensive study of MBI, revealing both detailed MBI behavior as well as insights into mitigation schemes. The fine time resolution of the XTCAV also provides the first LCLS measurements of the final SES, a critical parameter for many advanced FEL schemes. Detailed MBI and SES measurements can aid in understanding MBI mechanisms, benchmarking simulation codes, and designing future high-brightness accelerators.

Spectral dynamics of a diffusive random laser under two photon pumping

The spectral dynamics of a diffusive random laser under two photon excitation is investigated by using an experimental set-up which allows for fine mode discrimination and time resolution. The diffusive scattering system consists of a di-ureasil hybrid matrix powder doped with Rhodamine B. The anti-Stokes random laser emission obtained by pumping at 1064 nm shows a larger output pulse duration, build-up time, and threshold than the one produced under one photon pumping at 532 nm using the same experimental conditions. The time resolved analysis of the single shot emission pulse demonstrates the inherent stochastic nature of its lasing modes as well as the existence of modal relaxation oscillations. The outcome of our experiments also suggests that mode saturation appears with the increase of pump power.

High Performance Integrated Circuits for Biomedical Imaging Applications

Biomedical imaging modalities, such as time-of-flight (ToF) positron emission tomography (PET) and fluorescence-lifetime imaging microscopy (FLIM) have been primarily employed for molecular and cellular imaging in medical diagnosis and the health care fields [1]. In particular, ToF-PET plays a critical role in cancer detection at an early stage due to its noninvasive, in-vivo characteristics. To obtain high precision, high temporal resolution and high contrast medical images, state-of-the-art electronics with high sensitivity, high counting rates and fine time resolution are needed. To meet these requirements, single photon avalanche diodes (SPAD) are employed as extremely sensitive photo-detectors. SPADs have compact size and can be designed and manufactured in a standard low-cost CMOS technology [2-4]. Figure 1a shows a schematic diagram of our SPAD-based bioimaging system. As the time intervals between two coincidence pulses from ToF-PET detectors have a direct relationship with the spatial resolution of the final reconstructed PET images, our principal work is to design a time-to-digital converter (TDC) which has sub-gate time resolution, small area and low-power consumption, and is integrated with the SPADs in the same CMOS technology. A Vernier-gated ring oscillator TDC is used. Figure 1b shows the block diagram of the proposed TDC. The TDC proposed employs Vernier technique to achieve fine time resolution. Two delay lines are arranged in a ring format such that pulses can propagate continuously (more than once) inside the rings. The dynamic range is increased by utilizing digital counters. Using this ring configuration in Vernier mode, fine resolution and large dynamic range are easily achieved simultaneously with short delay chains, and hence requires less silicon area occupation. The proposed TDC has its intrinsic first-order tolerance towards common mode noises, because the delay-cells are configured in the differential method. Additional common mode noise tolerance is provided by the Vernier operation behavior. The TDC is implemented in a commercial, mainstream 0.13μm CMOS technology. With the proposed Vernier-gated ring oscillator TDC, less than 10ps time resolution is achieved. This will greatly help improve the spatial resolution of the final reconstructed images, making an early detection of cancers and/or small size cancers possible. Future work will aim to integrate the proposed TDC with SPADs for digital silicon photomultiplier (SiPM).

Investigating the Effect of Channel Width and Surface Wettability on Liquid Water Content in PEMFCs Using Synchrotron Radiography

Polymer electrolyte membrane (PEM) fuel cells show promise as electrochemical energy conversion devices for transport, stationary, and portable applications. Despite their potential for high efficiencies, the widespread adoption of PEM fuel cells has been hindered by their current durability and cost. These obstacles are related to a lack of fundamental understanding of the water transport mechanisms in the gas diffusion layers (GDLs) [1]. Another aspect in the improvement of fuel cell performance requires an understanding of the effects of flow channel geometry and wettability on water management in the PEM fuel cells. For instance, liquid water transferred from the GDL to the flow channel may be constrained by water slugs in the channel, which may result in increased saturation inside the GDL [2,3]. Moreover, liquid water flux from the GDL can be influenced by the rib/channel geometry due to reaction distribution, heat transport, and water transport [2,3].In this study, a PEM fuel cell, with an active area of 0.48 cm2, was designed for synchrotron imaging to acquire through-plane radiographs of the cell. Using Toray GDLs coated with an MPL (TGP-H-60), each fuel cell experiment was performed at specified operating conditions controlled with a Scribner 850e test station. Two different channel geometries were studied: one with a channel width of 0.6 mm; the other, 0.2 mm. In addition, the effect of channel wettability was also investigated. For each channel geometry, two sets of bipolar plates were prepared; they were either coated with a hydrophilic or hydrophobic coating.Visualizations of the dynamic liquid water content in operating fuel cells were performed at the Biomedical Imaging and Therapy – Bending Magnet (05B1-1) beamline at the Canadian Light Source Inc. (Saskatoon, Canada) using conventional absorption imaging. A monochromatic X-ray beam set to an energy level of 18 keV was used to acquire two- dimensional radiographs. By applying the principles of the Beer-Lambert law, the raw radiographs were processed to isolate the water content, in the form of a water thickness distribution.The results of the current study aim to improve the understanding of how the channel surface wettability and channel dimensions influence the water management of PEM fuel cells. This is important as the channel water morphology can have an effect on the GDL water distribution, which is linked to the overall fuel cell performance. As the interface between the liquid water in the GDL and the liquid water in the channel is not fully understood, this study will shed light on interface effect by taking advantage of the fine spatial and time resolutions of the synchrotron X-ray radiography.

Comparison of mean radiant temperature from field experiment and modelling: a case study in Freiburg, Germany

Mean radiant temperature (T mrt) based on two measurement methods and outputs from three models are compared in this study. They are the six direction radiation method, globe thermometer method, RayMan model, ENVI-met model and SOLWEIG model. The comparison shows that globe thermometer method may overestimate the T mrt since wind velocity is a key variable in the estimation based on this method. For better estimation, T mrt measured by the globe-thermometer method be corrected by the imported wind speed (stable, low and assuming wind speed) and validated by the six-direction radiation method. The comparison of models shows that the RayMan model’s evaluation of T mrt involving global radiation with fine time resolution was better than the corresponding evaluations under the other two models (ENVI-met and SOLWEIG) in this case. However, the RayMan model can only assess T mrt for a one-point one-time context, whereas the other two models can evaluate two-dimensional T mrt. For two-dimensional evaluations of T mrt, SOLWEIG have a better prediction of T mrt than ENVI-met, and ENVI-met can simulate several different variables, which are wind field, particle distribution, CO2 distribution and the other thermal parameters (T a, surface temperature and radiation fluxes), that SOLWEIG cannot.

Multiple Time Resolution Unit Commitment for Short-Term Operations Scheduling Under High Renewable Penetration

This paper introduces the idea of unified unit commitment and economic dispatch modeling within a unique tool that performs economic dispatch with up to 24-hour look-ahead capability. The tool provides financially binding dispatch and ex-ante locational marginal prices (LMPs) for the next 5-min interval and advisory commitment, dispatch schedule and prices for the remaining scheduling horizon. Variable time resolution and variable modeling complexity are used in order to reduce computational requirements. A finer time resolution and detailed modeling are used during the first hours of the scheduling horizon while coarser time resolution and simplified modeling during the last ones. The viability of the method for medium-sized systems is demonstrated through its application to the Greek power system.

A multichannel time-to-digital converter ASIC with better than 3 ps RMS time resolution

The development of a new multichannel, fine-time resolution time-to-digital converter (TDC) ASIC is currently under development at CERN. A prototype TDC has been designed, fabricated and successfully verified with demonstrated time resolutions of better than 3 ps-rms. Least-significant-bit (LSB) sizes as small as 5 ps with a differential-non-linearity (DNL) of better than ±0.9 LSB and integral-non-linearity (INL) of better than ±1.3 LSB respectively have been achieved. The contribution describes the implemented architecture and presents measurement results of a prototype ASIC implemented in a commercial 130 nm technology.

A model for optimal scheduling of hydro thermal systems including pumped‐storage and wind power

This study describes a model for optimal scheduling of hydro thermal systems with multiple hydro reservoirs. Inflow to hydropower reservoirs, wind power and exogenously given prices are treated as stochastic variables. Power flow constraints are included through a linearised power flow model. A linearised representation of start-up costs for generating units and pumps is provided. The model is well suited for medium- and long-term hydro thermal generation scheduling and has the capability of capturing detailed system constraints by using a fine time resolution. The presented model is tested on a realistic representation of the Icelandic power system, considering some potential future system extensions.