755 research outputs found
Advanced Dual-purpose Electrochemical Aptamer Sensor based Microphysiological System for Cell Culture Monitoring
No full text© 2024 Yiling YangConventional drug discovery is a lengthy and costly process with a high failure rate, mainly due to the limited human pathophysiological relevance of preclinical models used to qualify agents for clinical evaluation. As an alternative, microphysiological systems (MPS) have emerged as promising platforms for preclinical drug research, offering more relevant models of human physiology. High-frequency, real-time measurements of specific metabolite concentrations in MPS could significantly enhance the understanding of cellular metabolism and improve the application of Good Laboratory Practice (GLP) standards in cell culture protocols. However, current approaches are often constrained to single-time-point, single-parameter measurements or are limited by the range of detectable analytes. Electrochemical aptamer-based (EAB) biosensors have shown utility in real-time monitoring of analytes in vivo within blood and tissues. This study adapts an electrochemical aptamer-based (EAB) sensor to provide a more versatile, potentially multiplexable method for monitoring media composition in MPS. The research involved designing, fabricating, and optimizing EAB sensors, culminating in the development of a novel dual-purpose sensor capable of tracking both phenylalanine and pH independently of the aptamer sequence’s target analyte. This sensor was integrated into MPS platforms and validated through extensive testing in various cell cultures and tissue environments. We applied the dual-purpose EAB sensor to continuous monitoring of pH and phenylalanine in multiple in vitro cell culture settings. The miniature sensor demonstrated rapid response times, stability, high repeatability, and biologically relevant sensitivity. Additionally, we developed a leak-free reference electrode to mitigate cytotoxic effects from silver ions typically released by conventional reference electrodes. Using this dual-purpose sensor, we performed hourly measurements of pH and phenylalanine concentrations in media superfusing cultured epithelial tumor cell lines (A549, MDA-MB-231) and a human fibroblast cell line (MRC-5) for up to 72 hours.
The results demonstrated that the dual-purpose sensor achieved high sensitivity, specificity, and reliability in real-time monitoring of biomarkers within MPS. The integration of the sensor into MPS showed effective tracking of biomarker fluctuations, which might enhance the predictive accuracy of these systems for drug testing and disease modeling. Our scalable technology further supports high-throughput, multiplexed monitoring of pH and multiple analytes, broadening the metabolic qualification of microphysiological systems. This advancement represents a significant step towards more robust and informative preclinical drug testing platforms
Doplor Sleep: Monitoring Hospital Soundscapes for Better Sleep Hygiene
No full textGood sleep is conducive to the recovery process of hospital patients - and yet, in many wards, sleep duration and quality can often be suboptimal, in part due to modifiable hospital-related sounds and noises. At the neurological ward of the Reinier de Graaf hospital in Delft, the Netherlands, we developed and evaluated a prototype information exchange system to raise awareness of specific sounds as disturbing patients' sleep. The system both classifies different relevant sound events and tracks sleep quality (using a Fitbit device). This information is then visualized for patients and staff to present the influence of the soundscape on patients' sleep hygiene in a friendly and comprehensive way. We discuss the design process, including a context study and various evaluations of the technology, interface, and created affordances. Our initial findings indicate that visualizing hospital soundscapes may, indeed, support both patients and staff in their efforts towards better sleep hygiene. Design AestheticsInternet of Thing
Light-induced enhancement of the minority carrier lifetime in boron-doped Czochralski silicon passivated by doped silicon nitride
No full textThis study reports a doubling of the effective minority carrier lifetime under light soaking conditions, observed in a boron-doped p-type Czochralski grown silicon wafer passivated by a phosphorus-doped silicon nitride thin film. The analysis of capacitance-voltage curves revealed that the fixed charge in this phosphorus-doped silicon nitride film was negative, which was unlike the well-known positive fixed charges observed in traditional undoped silicon nitride. The analysis results revealed that the enhancement phenomenon of minority carrier lifetime was caused by the abrupt increase in the density of negative fixed charge (from 7.2 x 10(11) to 1.2 x 10(12) cm(-2)) after light soaking. (C) 2015 Elsevier B.V. All rights reserved
Numerical Study of Track-Trailer Gap Aerodynamics
No full textAerodynamics have become an essential design process for ground vehicles in order to improve the fuel consumption by lowering the emissions along with increasing the range of vehicles using different source of power. A significant portion of the world CO2 emissions is a result of ground vehicles with a more significant portion of these contributed by trucks. The boxy nature of trucks is the desired shape to carry maximum payload. However, a box shaped geometry is not aerodynamically efficient. Several manufacturers have developed aerodynamic add on devices that are optimized to the shape of the truck, in order to achieve gains in lowering emission and improving range by deeper understanding of the flow physics around the vehicle. The thesis reports an in-depth understanding of the flow field within the gap region of a tractor trailer combination truck and how several aerodynamic add on devices reduce the overall drag of a truck. The gap region of a truck typically contributes to about 20-25% of the overall vehicle drag and hence presents an opportunity for considerable level of drag reduction.
A basic two box bluff body (2D & 3D) model was used to investigate how the flow field changes by changing the gap width between the two bluff bodies. A section of the thesis investigates the sudden increase in drag coefficient of the downstream cube around 2D tandem bluff bodies. Distinct flow patterns were observed in the gap and around the 2D tandem at different gap ratios. The sudden change in drag coefficient for the 2D downstream bluff body is well captured numerically, which is due to the wake of the upstream cube impinging onto the front face of the downstream cube. A steady increase in drag coefficient is witnessed for the 3D cubes which are consistent with previous experimental findings. The steady increase in drag coefficient is due to the vortical structures formed around the 3D cubes which are different, which consist of a smooth transition. Hence, they result in steady increase in drag coefficient. A second study was conducted on a realistic truck like test case with the simplified truck model where the leading edges of the tractor were rounded off to manipulate the flow separation. As a result of leading edge rounding off the flow separation reduced significantly resulting in a major portion of the flow remain attached to the lateral walls of the tractor. This was seen to increase the flow entering the gap region between the tractor and trailer. Finally, several add on devices which were subdivided based on tractor and trailer mounted devices were numerically assessed with several other devices within the gap region. Significant level of drag reduction was achieved for the entire truck with these add on devices. The highest drag reduction was achieved with the base bleeding technique. Overall, the research has shown that it is important to control the flow condition within the gap region and maintain an even pressure on the front face of the trailer. The base bleeding method proved to be a vital technique to further reduce drag
A Machine with Short-Term, Episodic, and Semantic Memory Systems
No full textInspired by the cognitive science theory of the explicit human memory systems, we have modeled an agent with short-term, episodic, and semantic memory systems, each of which is modeled with a knowledge graph. To evaluate this system and analyze the behavior of this agent, we designed and released our own reinforcement learning agent environment, the Room , where an agent has to learn how to encode, store, and retrieve memories to maximize its return by answering questions. We show that our deep Q-learning based agent successfully learns whether a short-term memory should be forgotten, or rather be stored in the episodic or semantic memory systems. Our experiments indicate that an agent with human-like memory systems can outperform an agent without this memory structure in the environment
Recommended from our members
Information Elicitation and Aggregation: Theory, Behavior, and Application
No full textRecent decades have witnessed a broadening application of the wisdom of crowds, ranging from forecasting geopolitical events to estimating business variables to predicting the replicability of social science studies. In these applications, information is elicited from a crowd of human participants and then aggregated to generate final judgments or informed decisions. Two central problems in this process are the information elicitation problem, i.e., how we can elicit authentic and high-quality information from selfish information holders, and the information aggregation problem, i.e., how we can aggregate the noisy or even biased information that we collect into more accurate judgments or decisions.
The challenges in solving the above two problems vary with the concrete application scenarios. At a high level, these scenarios can be divided into two categories, the with-verification setting and the without-verification setting. In the with-verification setting, the principal can access (historical) ground truth information to verify the information quality of each participant and design elicitation and aggregation mechanisms accordingly. In contrast, the principal cannot access such ground truth information in the without-verification setting. In this thesis, I explore and make progress on information elicitation and aggregation problems under several specific scenarios in both settings.
In the with-verification setting, I study the betting scenario and propose the randomized wagering mechanisms for prediction elicitation. These mechanisms overcome an impossibility result for deterministic mechanisms that four desirable properties cannot be satisfied simultaneously. In the without-verification setting, I study both the probabilistic prediction elicitation and aggregation problems. I first extend the strictly proper scoring rules, the most prevalent information elicitation solution in the with-verification setting, into the without-verification setting and derive the surrogate scoring rules. These rules not only provide strong incentives for participants to report true beliefs but also characterize their prediction accuracy. I further develop a forecast aggregation framework using the elicitation without-verification schemes such as the surrogate scoring rules to improve the aggregation accuracy consistently. This improvement is examined and verified on a diverse set of real-world human forecasting datasets.
Human behavior, involving how people understand elicitation questions, generate beliefs, and react to elicitation schemes, is overlooked in the literature on information elicitation and aggregation. This thesis also explores human behavior and its influence within this domain. In particular, I develop auction mechanisms to elicit truthful reporting of private signals when human players have bounded rationality in interdependent valuation auctions. I also conduct real-world elicitation and aggregation experiments that use laypeople to predict the replicability of social science studies. Several interesting experimental findings of laypeople's behaviors are analyzed and discussed
[[alternative]]Junior high school students' conceptions in animal reproduction
No full text[[abstract]]This research used two-tier diagnostic test and structured interview as instrument to explore junior high school students’ conceptions in animal reproduction. There were 568 students participating in two-tier diagnostic test and 18 of these students were selected to take part in structured interview. The findings showed that most students could understand the meaning and phenomenon of reproduction. Students’ common alternative conceptions in animal reproduction were as following: (1) students thought reproductive process must through fertilization, they lacked conceptions about asexual reproduction. (2). Students didn’t fully understand that homogenous chromosomes separate during meiosis and the gametes are haploid. (3). Students didn’t understand that through sexual reproduction offspring got new combinations of alleles and variations in traits which means a lot in population evolution. (4). Students didn’t know the existence of internal fertilization for evolution of land-dwelling animal. They thought nourishing offspring and hatching behavior as essential elements for animals to adapt land environment. (5). Students didn’t well understand ovoviviparity. About reproductive techniques issue, some students didn’t include artificial offspring creating in the domain of reproduction, and, others showed some alternative conceptions, such as: (1). “Test-tube baby” created by in vitro fertilization should be a kind of asexual reproduction. (2) “Test-tube baby” birth from a tube should be a kind of asexual reproduction. (3) Creating clone sheep were sexual reproduction. Concerning environmental factors that influence animal reproduction, students thought reproductive behavior would be affected if natural environment changed, but less effected if animals lived in zoo. This research revealed that students’ alternative conceptions in animal reproduction might hinder them from constructing genetic and evolutional conceptions. Even after learning reproduction, students could not successfully apply what they learned on solving reproductive technical problems. To help students achieve meaningful learning, science teachers should understand what students already knew and what alternative conceptions students might hold and, then, plan teaching programs accordingly. The findings of this research also could help teachers and textbook authors develop materials for junior high school students.
Deep characteristics analysis on travel time of emergency traffic
No full textOwing to the rapid development of emergency rescue transportation in cities and the frequent emergencies, demand for emergency rescue is increasing drastically. How to select an emergency rescue route quickly and shorten the rescue travel time under the condition of limited urban road resources is of great significance. Based on the characteristics analysis of emergency rescue, this paper classifies priority levels of different emergency traffic, moreover, the travel times are also analysed with three scenarios: 1) emergency rescue vehicles encountering no queues; 2) encountered queues but lanes available; 3) encountered queues with no available lanes. Related case study shows that model in this paper can effectively shorten travel time of emergency traffic in the route and improve its efficiency.Accepted Author ManuscriptTransport and Plannin
Doplor Sleep: Friendly feedback towards a better hospital soundscape for sleep
No full textRecently in the Netherlands, researchers have found that sleep duration and quality were suboptimal in the hospital. Evidence proved that many modifiable hospitalrelated factors negatively associate with patients' sleep (JAMA Internal Medicine, 2018). The sound factor is the most significant sleep disturbance in the hospital. In this graduation project, collaborating with Reiner de Graaf hospital and Critical Alarms lab, an information exchange system was proposed to raise awareness of sound as sleep disturbance. The system captures the sound-producing events and visualizes them with visually attractive graphics. In this system, we use the smartphone as the sound captor. The recorded sounds are processed locally on the phone and converted into information such as sound level and the category it belongs to (alarm, speech, incidental sounds, or snore). Fitbit is implemented in the system to collect sleep information. To both patients and medical staff, The Doplor sleep system presents the influence of sound on sleep in a friendly and comprehensive way. During this project, a functioning prototype was developed. We have tested its functionality and user experience with the potential users
Direct Fusion of Geostationary Meteorological Satellite Visible and Infrared Images Based on Thermal Physical Properties
No full textThis study investigated a novel method of fusing visible (VIS) and infrared (IR) images with the major objective of obtaining higher-resolution IR images. Most existing image fusion methods focus only on visual performance and many fail to consider the thermal physical properties of the IR images, leading to spectral distortion in the fused image. In this study, we use the IR thermal physical property to correct the VIS image directly. Specifically, the Stefan-Boltzmann Law is used as a strong constraint to modulate the VIS image, such that the fused result shows a similar level of regional thermal energy as the original IR image, while preserving the high-resolution structural features from the VIS image. This method is an improvement over our previous study, which required VIS-IR multi-wavelet fusion before the same correction method was applied. The results of experiments show that applying this correction to the VIS image directly without multi-resolution analysis (MRA) processing achieves similar results, but is considerably more computationally efficient, thereby providing a new perspective on VIS and IR image fusion
- …
