Buffer Time Research Articles

Factors Affecting the Growth of Pseudokirchneriella subcapitata in Single‐Species Tests: Lessons for the Experimental Design and the Reproducibility of a Multitrophic Laboratory Microcosm

The need for an integrated risk assessment at an ecologically relevant scale (e.g., at the population/community levels) has been acknowledged. Multispecies systems with increased ecological complexity, however, are difficult if not impossible to reproduce. The laboratory-scale microcosm TriCosm (Pseudokirchneriella subcapitata, Ceriodaphnia dubia, Hydra viridissima) of intermediate complexity was developed for the reproducible assessment of chemical effects at the population/community levels. The system dynamics were repeatable in the short term, but interexperimental variation of algal dynamics in the long term triggered knock-on effects on grazer and predator populations. We present 20 experiments to assess the effects of 12 factors (test medium, vessel type/condition, shaking speed, light intensity/regime, inoculation density, medium preparation components, metal concentration/composition, buffering salt type/concentration) on algal growth in the TriCosm enclosure. Growth rates varied between ≤ 0 and 1.40 (± 0.21) and generally were greatest with increased shaking speed, light exposure, medium buffer, or aeration time. Treatments conducted in dishes with aseptically prepared, lightly buffered, and/or hardly aerated medium resulted in low growth rates. We found that inter-experimental variation of algal dynamics in the TriCosm was caused by a modification of medium preparation (omission of medium aeration) with the aim of reducing microbial contamination. Our findings highlight the facts that consistency in experimental procedures and in-depth understanding of system components are indispensable to achieve repeatability. Environ Toxicol Chem 2019;00:1-13. © 2019 SETAC.

An optical H2S biosensor based on the chemoselective Hb-I protein tethered to a transparent, high surface area nanocolumnar electrode

Sensitive and selective detection of analytes in complex biological fluids can be an extremely challenging issue. The constructive association of biomolecules and transparent mesoporous electrodes is of interest in this area, as it can lead to innovative biosensors combining optical and electrochemical detection modes. This concept, however, requires the development of appropriate surface functionalization methodologies that are robust enough for long-term operation in physiological environments. In the present work, the high-surface area of 3D transparent mesoporous indium-tin oxide (ITO) electrodes (prepared by glancing angle deposition or GLAD) has been chemically functionalized with recombinant hemoglobin I from Lucina pectinata according to a versatile 2-step process. First, 4-diazoniumbenzoic acid salt is covalently electrografted onto the ITO surface, followed by amide coupling of the protein. The resulting electrodes were quantitatively characterized by cyclic voltammetry and UV–vis absorption spectroscopy, demonstrating high surface coverages (up to 45% of a closed-packed monolayer for Hemoglobin-I) and homogeneous distribution across the entire thickness of the GLAD mesoporous structure. Good stability is also observed when the modified electrodes are immersed for prolonged times in a high ionic strength saline buffer. We also show that the hemoglobin I-modified electrode can be used as an optical biosensor for the selective, reversible, and fast detection of H2S in aqueous solutions over a ∼two-decade concentration range (i.e. up to 10 μM) and with a limit of detection of 0.35 μM. Good analytical performance was also achieved in human plasma without significant interference from the biological matrix.

A closed form railway line delay propagation model

Railway service quality can be measured by the aggregate delay over a time horizon due to an event that delays a given train. Timetables for railway services may dampen delay propagations to subsequent trains by adding either supplement time or buffer time to the timetable. The evaluation of these variables is often performed by time consuming analysis with simulation software, or other complex, time-consuming calculations. This paper proposes instead an analytical closed form formulation of aggregate delay, which offers theoretical insights into railway delays and managerial insight into the properties of timetables at an aggregate level, and which may function as a fast sub-algorithm for timetable evaluations in larger optimization and transport models. Analysis of the function recommends a restraint in the utilization of timetable supplement and buffer, as their delay-damping effect decreases with their magnitude. Further, the effect of different threshold values in delay measurement is demonstrated, giving information valuable to the design of service contracts. Numerical analysis of a common suburban railway line shows that the polynomial function provides guidance and insight even when theoretical assumptions are violated.

Quantum repeater architecture with hierarchically optimized memory buffer times

We propose a quantum repeater protocol and architecture that mitigates decoherence of the entangled states by optimizing the quantum memory buffer time. The protocol maximizes the rate of distillable entanglement in the average accessed state at all nesting levels. The achievable rate is higher by orders of magnitude in comparison to a canonical protocol that does not optimize the buffer time. The advantage of the proposed design is observed for all nesting levels of the repeater for technologically feasible memory quality, entanglement generation and swapping success probabilities.

Recoverable robustness in weekly berth and quay crane planning

The performance of a container terminal heavily relies on how efficiently the quayside resources, which are mainly berth and quay cranes, are used. The quayside related planning problems face uncertainty in various parameters, and this makes the efficient planning of these operations even more complicated. This study aims at developing a recoverable robust optimization approach for the weekly berth and quay crane planning problem. In order to build systematic recoverable robustness, a proactive baseline schedule with reactive recovery costs has been suggested. The uncertainty of vessel arrivals and the fluctuation in the container handling rate of quay cranes are considered. The baseline schedule includes berthing positions, times and quay crane assignments for all vessels along with vessel-specific buffer times and buffer quay cranes. The problem also introduces recovery plans for each scenario. The objective is to minimize the cost of baseline schedule, the recovery costs from the baseline schedule and the cost of scenario solutions for different realizations of uncertain parameters. A mathematical model and an adaptive large neighborhood based heuristic framework are presented to solve the novel problem. Computational results point out the strength of the solution methods and practical relevance for container terminals.

Novel Oligo-Guanidyl-PEG Carrier Forming Rod-Shaped Polyplexes.

A novel unconventional supramolecular oligo-cationic structure (Agm6-M-PEG-OCH3) has been synthesized to yield high efficiency therapeutic oligonucleotide (ON) delivery. Agm6-M-PEG-OCH3 was obtained by a multistep protocol that included the conjugation of agmatine (Agm) moieties to maltotriose (M), which was further derivatized with one poly(ethylene glycol) (PEG) chain. Gel electrophoresis analysis showed that the 19 base pairs dsDNA model ON completely associates with Agm6-M-PEG-OCH3 at 3 N/P molar ratio, which is in agreement with the in silico molecular predictions. Isothermal titration calorimetry (ITC) analyses showed that the Agm6-M-PEG-OCH3/ON association occurs through a combination of mechanisms depending on the N/P ratios resulting in different nanostructures. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) revealed that the Agm6-M-PEG-OCH3/ON polyplexes have rod-shape structure with a mean diameter of 50-75 nm and aspect ratio depending on the N/P ratio. The polyplexes were stable over time in buffer, while a slight size increase was observed in the presence of serum proteins. Cell culture studies showed that neither Agm6-M-PEG-OCH3 nor polyplexes displayed cytotoxic effects. Cellular uptake depended on the cell line and polyplex composition: cellular internalization was higher in the case of MCF-7 and KB cells compared to MC3T3-E1 cells and polyplexes with smaller aspect ratio were taken-up by cells more efficiently than polyplexes with higher aspect ratio. Finally, preliminary studies showed that our novel carrier efficiently delivered ONs into cells providing gene silencing.

Simultaneous Optimization of Speed and Buffer Times with an Application to Liner Shipping

Transport companies often have a published timetable. To maintain timetable reliability despite delays, companies include buffer times during timetable development and adjust the traveling speed during timetable execution. We develop an approach that integrates timetable development and execution. We model execution of the timetable as a stochastic dynamic program (SDP). An SDP is a natural framework to model random events causing (additional) delay, propagation of delays, and real-time optimal speed adjustments. However, SDPs alone cannot incorporate the buffer allocation during timetable development, as buffer allocation requires choosing the same action in different states of the SDP. Motivated by the practical need for timetables that operate well during timetable execution, our model seeks the buffer allocation that yields the SDP that has minimal long-run average costs. We derive several analytical insights into the model. We prove that costs are joint convex in the buffer times, and we develop theory to compute subgradients. Our fast and exact algorithm for buffer time allocation is based on these results. Our case study considers container vessels sailing a round tour consisting of 14 ports based on Maersk data. The algorithm finds the optimal timetable in roughly 70 seconds for realistic problem instances. The optimal timetable yields cost reductions of about four to 10 million U.S. dollars per route per year in comparison with the current timetable. Finally, we show the robustness of our solution approach for different parameter settings using a sensitivity analysis. The online appendices are available at https://doi.org/10.1287/trsc.2018.0842 .

Evaluation of Train Crews Schedule in Terms of Robustness

Abstract The evaluation of team work schedules in complex rail transport conditions is related to the robustness of individual solutions. In rail systems there are many aims that are important for users. One of the most important aims is to find a feasible solution. It is characterized by the non-conflicting schedule with another train, minimizing the travel time of the trainset and taking into account the priority of train. The problem of responding to delays in terms of reorganisation of work, prevention of delay propagation and real-time schedule changes is important. Schedules are built in a way that ensures the best use of work time. This has a negative impact on critical situations. The study analysed the changes of the conductor’s team to another train depending on the buffer time provided in work plan, real time needed for change and train delays.

Speech motor planning in the context of phonetically similar words: Evidence from apraxia of speech and aphasia

The purpose of this study was to test two competing hypotheses about the nature of the impairment in apraxia of speech (AOS). The Reduced Buffer Capacity Hypothesis argues that people with AOS can hold only one syllable at a time in the speech motor planning buffer. The Program Retrieval Deficit Hypothesis, states that people with AOS have difficulty accessing the intended motor program in the context where several motor programs are activated simultaneously. The participants included eight speakers with AOS, most of whom also had aphasia, nine speakers with aphasia without AOS, and 25 age-matched control speakers. The experimental paradigm prompted single word production following three types of primes. In most trials, prime and target were the same (e.g., bill-bill). On some trials, the initial consonant differed in one phonetic feature (e.g., bill-dill; Similar) or in all phonetic features (fill-bill; Different). The dependent measures were accuracy and reaction time. The results revealed a switch cost – longer reaction times in trials where the prime and target differed compared to trials where they were the same words – in all groups; however, the switch cost was significantly larger in the AOS group compared to the other two groups. These findings are in line with the prediction of the Program Retrieval Deficit Hypothesis and suggest that speakers with AOS have difficulty with selecting one program over another when several programs compete for selection.

Passenger Travel Time Reliability for Multimodal Public Transport Journeys

Urban transit networks typically consist of multiple modes and the journeys may involve a transfer within or across modes. Therefore, the passenger experience of travel time reliability is based on the whole journey experience including the transfers. Although the impact of transfers on reliability has been highlighted in the literature, the existing indicators either focus on unimodal transfers only or fail to include all components of travel time in reliability measurement. This study extends the existing “reliability buffer time” metric to transit journeys with multimodal transfers and develops a methodology to calculate it using a combination of smartcard and automatic vehicle location data. The developed methodology is applied to a real-life case study for the Amsterdam transit network consisting of bus, metro, and tram lines. By using a consistent method for all journeys in the network, reliability can be compared between different transit modes or between multiple routes for the same origin–destination pair. The developed metric can be used to study the reliability impacts of policies affecting multiple transit modes. It can also be used as an input to behavioral models such as mode, route, or departure time choice models.

Arbuscular mycorrhizal (Glomus fasciculatum) fungi as a plant immunity booster against fungal pathogen

Reactive Oxygen Species (ROS) mediated immune response in tomato (Solanum lycopersicum) plants inoculated with arbuscular mycorrhizal fungi (AMF) Glomus fasciculatum (GF) was studied in the presence of plant pathogenic fungi Fusarium oxysporum f. sp. lycopersici (FOL). Our aim was to assess how symbiosis of AMF potentiates ROS immune response system to deal pathogen mediated biotic stress. Tomato plant was inoculated with GF, FOL and GF + FOL in separate experimental sets to examine its effect on plants ROS machinery and the time taken to alleviate biotic stress. The antioxidant response was evaluated and correlated with the time provided by GF treated plants against FOL to initiate their second line of defenses as compared to only FOL treated ones. The establishment of symbiosis and development showed a positive effect on plant ROS response system and subsequently its growth. No significant difference was seen in the root mass of only GF, FOL and GF + FOL. The increase in activities of superoxide dismutase, catalase and peroxidase was similar in all the control and treated plants however; reduction in activities of these ROS scavengers was much faster in GF supplemented plants. Similar trend was also observed for ROS radicals possibly due to the involvement of antioxidant enzymes. LC-MS analysis of FOL was performed to co-relate the effect of some dominant compounds with its pathogenicity. Therefore, our results showcase AMF-GF’s ability to alleviate the oxidative damage generated by biotic stress and highlights on the buffer time taken by plants defense machinery to immunize itself at various levels.

Buffering Time for Wireless Full-Duplex Systems Under Random Arrival

Full-duplex wireless communication has the potential to double the capacity of wireless networks by reducing the band occupancy of transmissions. However, a full-duplex capability cannot always reduce the band occupancy because the real traffic is not fully buffered. Buffering time while waiting for a packet to arrive at an opposite node is expected to reduce the band occupancy. In this study, we provide the first theoretical analysis of band occupancy and the mean waiting time for full-duplex communication with and without buffering time under traffic that is not fully buffered based on queueing theory, as well as the closed-form results. We also present the results of simulations of band occupancy and the mean waiting time. The basic analysis provided in this study shows how the mean waiting time and band occupancy are affected by the buffering time. When the buffering time is half the packet length, the band occupancy is reduced by approximately 15 %. In addition, under asymmetrical traffic, the results suggest that the buffering time should not be set at the node who has a higher traffic intensity compared with another node. These results support the design of a full-duplex medium access control protocol and devices.

DesCom: Routing Decision using Estimation Time in VDTN

VDTN was proposed as a disrupting network which is established on the paradigm of the delay-tolerant network. VDTN uses vehicular nodes to convey messages as, it permits sparse opportunistic network connectivity, which is considered by the low node density where the vehicular traffic is sporadic, and no end-to-end paths exist between nodes. The message bundle is directed from the sender to the receiver node based on the routing protocol decision. While Routing protocols take decisions based on different metrics like Time to live, Location, Remaining Buffer Size, meeting probability, etc. In this paper, a routing protocol named DesCom is proposed for Vehicular Delay-Tolerant Network under a highly suppressed and sparse environment. DesCom takes the decision based on Message TTL, Transmission rate, and Estimation time. Estimation time is calculated in our previous work. The protocol defines whether to direct the message to the requested node or search the other more suitable node to carry that data bundles. After compiling multiple simulations with different numbers of vehicles and comparing DesCom with other routing protocols it is concluded that DesCom has the least buffer time with low latency along with good delivery probability.

Tiankeng: an ideal place for climate warming research on forest ecosystems

In order to better understand the response of terrestrial ecosystems’ structure and function to climate warming, various field methods need to be explored. Among a series of existing methods, the active open top chamber (OTC) was the only method that has been used in the entire forest ecosystem. However, this method needs rethinking because its high cost and long buffer time during experimental implementation limit its use. A tiankeng, a large steep-walled sinkhole, which has evolved by roof collapse over a large cave chamber, is a natural OTC surrounded by rocks. Tiankengs are uniquely distributed in fragile ecosystems of karst regions, and are ideal study sites for climate warming research on forest ecosystems. Although their inaccessibility and monitoring difficulties are the main drawbacks, unmanned aerial vehicles containing micro robots could help and carry out relevant research tasks in the future.

Developing a train timetable according to track maintenance plans: A stochastic optimization of buffer time schedules

Abstract The scheduling of maintenance operations in railway is a major concern for both maintenance planners and train dispatchers since it requires the track to be blocked and the rail traffic to be disrupted. This paper provides a mathematical programming model aimed at adjusting the timetable of trains in a single track according to maintenance operations. The uncertainty of the maintenance activities might cause delays in the initial maintenance plan which is further overlapped with pre-determined train scheduling. This study addresses the uncertainty in maintenance activities through including buffer time to the modified scheduling. We also addressed the operational constraints such as speed limit due to maintenance operations in the adjusted scheduling. The result of the model provides railway planners with a modified timetable which includes both maintenance plan and train operations schedules.

Travel time variability analysis based on level of service: a case study of mixed traffic urban arterial corridors

Since the Indian urban traffic is characterised by heterogeneity with the dominance of two-wheelers (2Ws), three-wheelers (3Ws) and precarious traffic impedance, travel time is often highly unstable and varies significantly which entails additional cost due to delays. Travel time variation not only leads to wasting of productive time but also increase the stress level of the commuters. In addition, variable travel time leads to the reduction in satisfaction level which influences commuters' travel decision such as route and departure choice etc. With this in the background, an attempt has been made to study the travel time variability of urban arterial corridors focusing on level of service (LoS) as the criteria for reference of travel time. The study probes into various attributes of traffic, composition, road side friction and intersection for their impact on travel time by employing multiple-linear regression (MLR) technique. The proposed travel time variability index (TTVI) based on LoS speed suggested as better reliability indicator against buffer time index (BTI) or planning time index (PTI).

Design, implementation and analysis of routing based attack model for delay tolerant networks for prophet routing protocol

Delay tolerant network (DTN) is an evolution of mobile adhoc network (MANET). In computing, network security is the main issue as the attacks by malicious and selfish nodes are increasing on the network day by day. This paper defines an attack model in which malicious nodes (in DTN with Prophet Routing Protocol) receive the data from genuine nodes. It is done by falsifying their routing information (Delivery Predictability). Later malicious nodes spoof their identity and receive messages as destination nodes. The Legitimate messages are deleted by malicious nodes and also from the source node buffer as the source node treats the message being delivered to the final destination. Delivery Probability, Overhead Ratio, Average Latency and Average Buffer time metrics are evaluated using ONE simulator. In simulated network, 126 nodes are considered and by making only 3% nodes malicious, performance of the network is decreased by approximately 40-50%.

Travel time variability analysis based on level of service: a case study of mixed traffic urban arterial corridors

Since the Indian urban traffic is characterised by heterogeneity with the dominance of two-wheelers (2Ws), three-wheelers (3Ws) and precarious traffic impedance, travel time is often highly unstable and varies significantly which entails additional cost due to delays. Travel time variation not only leads to wasting of productive time but also increase the stress level of the commuters. In addition, variable travel time leads to the reduction in satisfaction level which influences commuters' travel decision such as route and departure choice etc. With this in the background, an attempt has been made to study the travel time variability of urban arterial corridors focusing on level of service (LoS) as the criteria for reference of travel time. The study probes into various attributes of traffic, composition, road side friction and intersection for their impact on travel time by employing multiple-linear regression (MLR) technique. The proposed travel time variability index (TTVI) based on LoS speed suggested as better reliability indicator against buffer time index (BTI) or planning time index (PTI).

Factors that affect students' intention and use of technology: an assessment of UTAUT2 in the context of YouTube video forwarding behaviour

This study aims to understand the students' behaviour on forwarding content through YouTube by applying UTAUT2 model. Though forwarding content to other users in a network exhibits an implicit consent and adds credibility to the message, the factors that affect a user's decision to accept YouTube and forward the content have received limited consideration. The study reveals that YouTube is largely perceived as a technology for consumption of content that influenced by automaticity, ease of use and hedonic factors. The finding suggest that developers must reduce the buffer time and facilitate easy download, must target informative content rather than entertaining and provide an interface of friends list for quick forwards. The system designers must look into the ease of navigating between other SNS's friends list that must appear on the user's login accounts which will be compelling for the user to browse and share quality informative content.

Load and energy management for factories through multi-stage production planning and optimization

The production phase has a major influence on the embodied energy of many products and, thus, their overall environmental performance. As a result, manufacturing enterprises are prompted to raise their energy efficiency and flexibility to improve their products’ sustainability. The simultaneous integration of renewable energy sources and decentral storages is a feasible option in this but also require consistent solutions for appropriately planning and controlling the operation of the entire factory system. This paper proposes an iterative multi-stage heuristic optimization for intelligent load and energy management. A load profile of the production plan, based on the minimized overall makespan, is checked against the available energy supply to identify demands and opportunities to shift single jobs based on calculated buffer times. Whenever infeasibility is determined, the process returns to the previous production planning stage for further alterations. This cycle is initiated regularly (e.g. weekly) or following certain events (e.g. long-lasting machine failure) and terminates once all restrictions are observed or if a termination threshold (e.g. calculation time) is reached. The experimental setup used for developing and validating this approach to energy-aware factory operation makes use of a probabilistic material flow simulation model. It provides information on tasks to be scheduled and executes production plans to evaluate the performance of the proposed solution. This new approach to energy-aware factory operation also provides opportunity to integrate additional ecologic criteria to improve the sustainability of manufactured products.