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Environmental sensing in dynamic quorum responses [article]

Eric K Chu, Alex Groisman, Andre Levchenko
2019 bioRxiv   pre-print
Cell communication and coordinated cell behavior are hallmarks of multicellular behavior of living systems. However, in many cases, including the ancient and archetypal example of bacterial quorum sensing, the meaning of the communicated information remains a subject of debate. It is commonly assumed that quorum sensing encodes the information on the current state of the colony, including cell density and physical colony confinement. Here, we show that quorum sensing can also be exquisitely
more » ... itive to dynamic changes in the environment, including fluctuations of the prevailing nutrient source. We propose a new signaling mechanism accounting for this sensory capability. This mechanism combines regulation by the commonly studied lux operon-encoded network with the environmentally determined balance of protein synthesis and dilution rates, dependent on the rate of cell proliferation. This regulatory mechanism accounts for observed complex spatial distribution of quorum responses, and emergence of sophisticated processing of dynamic inputs, including temporal thresholds and persistent partial induction following a transient change in the environmental conditions. We further show that, in this context, cell communication in quorum sensing acquires a new meaning: education of cells within a population about the past history of transient exposure to adverse conditions by a subset of induced cells. In combination, these signaling and communication features may endow a cell population with increased fitness in diverse fluctuating environments.
doi:10.1101/745091 fatcat:2jstoxrvh5aotlzpainsyto3aq

Epitome for Automatic Image Colorization [article]

Yingzhen Yang, Xinqi Chu, Tian-Tsong Ng, Alex Yong-Sang Chia, Shuicheng Yan, Thomas S. Huang
2012 arXiv   pre-print
Image colorization adds color to grayscale images. It not only increases the visual appeal of grayscale images, but also enriches the information contained in scientific images that lack color information. Most existing methods of colorization require laborious user interaction for scribbles or image segmentation. To eliminate the need for human labor, we develop an automatic image colorization method using epitome. Built upon a generative graphical model, epitome is a condensed image
more » ... and shape model which also proves to be an effective summary of color information for the colorization task. We train the epitome from the reference images and perform inference in the epitome to colorize grayscale images, rendering better colorization results than previous method in our experiments.
arXiv:1210.4481v1 fatcat:sf4jqau775bg3g2revoz3ahele

Southeast Asia: Sources of Regime Support

Alex Chang, Yun-han Chu, Bridget Welsh
2013 Journal of Democracy  
doi:10.1353/jod.2013.0025 fatcat:rghumgp7w5cyhfxsvfd7tgza44

The impact of foreign fighters on civil conflict outcomes

Tiffany S. Chu, Alex Braithwaite
2017 Research & Politics  
academic, policy, and popular commentary communities have increasingly voiced concerns regarding the threat posed by foreign fighters entering and exiting civil conflicts around the globe (Braithwaite and Chu  ...  there may be an uptick in domestic terrorist attacks abroad, because there is now a surplus of well-trained foreign fighters that are not tied geographically to the conflict country (Braithwaite and Chu  ... 
doi:10.1177/2053168017722059 fatcat:tlj7gzhyujff7dwyo4xeu7yqfe

Detecting leaks in plastic pipes

Osama Hunaidi, Wing Chu, Alex Wang, Wei Guan
2000 Journal - American Water Works Association  
npsi/ctrl?lang=en http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?lang=fr Access and use of this website and the material on it are subject to the Terms and Conditions set forth at Commercial leak-noise correlators were generally able to locate leaks in plastic pipe, but modifications could increases their effectiveness.
doi:10.1002/j.1551-8833.2000.tb08819.x fatcat:l26bfehipvh47jadct5ia5v76u

COVID-19's U.S. Temperature Response Profile [article]

Richard T. Carson, Samuel L. Carson, Thayne Keegan Dye, Samuel A. Mayfield, Daniel C. Moyer, Chu A. (Alex) Yu
2020 medRxiv   pre-print
AbstractWe estimate the U.S. temperature response curve for COVID-19 and show transmission is quite sensitive to temperature variation. This is despite summer outbreaks widely assumed to show otherwise. By largely replacing the death counts states report daily, with counts based on death certificate date, we build a week-ahead statistical forecasting model that explains most of the daily variation (R2 = 0.97) and isolates COVID-19's temperature response profile (p < 0.001). These counts
more » ... ed at 31°C (U.S. mid-summer average) scale up nearly 160% at 5°C. Positive cases are more temperature sensitive; scaling up by almost 400% between 31°C and 5°C. Dynamic feedback amplifies these effects. There is a short window to get COVID-19 under control before cooler weather makes the task substantially more challenging.Significance StatementCOVID-19 transmission, in the form of daily state-level death counts and positive cases, ramps up and down with changes in maximum daily temperature. This relationship, known as COVID-19's temperature response profile, is reliably estimated by assembling a new dataset that largely repairs the sizable divergence between when COVID-19 deaths occur and when they are reported. Over time this effect is can be quite large and, as such, important to efforts to forecast and manage COVID-19.
doi:10.1101/2020.11.03.20225581 fatcat:w4or7mjg7jbojnxq6jlgq7i46a

Stability of SARS-CoV-2 in different environmental conditions [article]

Alex Chin, Julie Chu, Mahen Perera, Kenrie Hui, Hui-Ling Yen, Michael Chan, Malik Peiris, Leo Poon
2020 medRxiv   pre-print
Stability of SARS-CoV-2 in different environmental conditions.
doi:10.1101/2020.03.15.20036673 fatcat:5ohqh2o7obaihlrl4wv6andbga

A proposal for epitaxial thin film growth in outer space

Alex Ignatiev, C. W. Chu
1988 Metallurgical Transactions A  
A new concept for materials processing in space exploits the ultra vacuum component of space for thin film epitaxial growth. The unique low earth orbit space environment is expected to yield 10~14 torr or better pressures, semi-infinite pumping speeds and large ultra vacuum volume (~100 m3) without walls. These space ultra vacuum properties promise major improvement in the quality, unique nature, and the throughput of epitaxially grown materials especially in the area of semiconductors for
more » ... electronics use. For such thin film materials there is expected a very large value added from space ultra vacuum processing, and as a result the application of the epitaxial thin film growth technology to space could lead to major commercial efforts in space.
doi:10.1007/bf02645795 fatcat:e2esykqmu5hdpag254hgpltnsy

Effect of Simulated Visual Impairment on Nighttime Driving Performance

Joanne Wood, Alex Chaparro, Trent Carberry, Byoung Sun Chu
2010 Optometry and Vision Science  
Purpose: This study investigated the effects of simulated visual impairment on nighttime driving performance and pedestrian recognition under real road conditions. Methods: Closed road night-time driving performance was measured for 20 young visually normal participants (M=27.5 6.1 yrs) under three visual conditions: normal vision, simulated cataracts and refractive blur that were incorporated in modified goggles. The visual acuity levels for the cataract and blur conditions were matched for
more » ... h participant. Driving measures included sign recognition, avoidance of low contrast road hazards, time to complete the course and lane keeping. Pedestrian recognition was measured for pedestrians wearing either black clothing or black clothing with retroreflective markings on the moveable joints to create the perception of biological motion ("biomotion"). Results: Simulated visual impairment significantly reduced participants" ability to recognise road signs, avoid road hazards and increased the time taken to complete the driving course (p<0.05); the effect was greatest for the cataract condition, even though the cataract and blur conditions were matched for visual acuity. While visual impairment also significantly reduced the ability to recognise the pedestrian wearing black clothing, the pedestrian wearing "biomotion" was seen 80% of the time. Conclusions: Driving performance under night-time conditions was significantly degraded by modest visual impairment; these effects were greatest for the cataract condition. Pedestrian recognition was greatly enhanced by marking limb-joints in the pattern of "biomotion" which was relatively robust to the effects of visual impairment.
doi:10.1097/opx.0b013e3181d95b0d pmid:20386352 fatcat:io5cngrxorbdffmp7aalz5oray

A collaborative sensor grids framework

Geoffrey Fox, Alex Ho, Rui Wang, Edward Chu, Isaac Kwan
2008 2008 International Symposium on Collaborative Technologies and Systems  
Integrating sensors and grid computing provides a way to gather, process and model real-time information from the environment for informed decision-support and timely actions, proactive or reactive, to events. We create a collaborative sensor grid framework to support the integration of a sensor grid with collaboration and other grids. The framework includes a grid builder tool for discovering and managing grid services and remote, distributed sensors. It provides a real-time collaborative
more » ... t to enable distributed stakeholders to have a consistent view of displayed sensor streams. We illustrate the versatility of the framework by constructing a robotbased customizable application for shared situational awareness.
doi:10.1109/cts.2008.4543909 dblp:conf/cts/FoxHWCK08 fatcat:kbnuxdgixjb63pl7iwqehhztda

Progress on In Situ and Operando X-ray Imaging of Solidification Processes

Shyamprasad Karagadde, Chu Lun Alex Leung, Peter D. Lee
2021 Materials  
In this review, we present an overview of significant developments in the field of in situ and operando (ISO) X-ray imaging of solidification processes. The objective of this review is to emphasize the key challenges in developing and performing in situ X-ray imaging of solidification processes, as well as to highlight important contributions that have significantly advanced the understanding of various mechanisms pertaining to microstructural evolution, defects, and semi-solid deformation of
more » ... tallic alloy systems. Likewise, some of the process modifications such as electromagnetic and ultra-sound melt treatments have also been described. Finally, a discussion on the recent breakthroughs in the emerging technology of additive manufacturing, and the challenges thereof, are presented.
doi:10.3390/ma14092374 pmid:34063314 fatcat:sve5xfahvrhxtngscs4g2kjxky

A solid approach to biopharmaceutical stabilisation [article]

Aswin Doekhie, Rajeev Dattani, Yun-Chu Chen, Yi Yang, Andrew Smith, Alex P. Silve, Francoise Koumanov, Karen J. Edler, Kevin J. Marchbank, Jean van den Elsen, Asel Sartbaeva
2018 arXiv   pre-print
Ensilication is a technology we developed that can physically stabilise proteins in silica without use of a pre-formed particle matrix. Stabilisation is done by tailor fitting individual proteins with a silica coat using a modified sol-gel process. Biopharmaceuticals, for example, liquid-formulated vaccines with adjuvants, have poor thermal stability. Heating or freezing impairs their potency. As a result, there is an increase in the prevalence of vaccine-preventable diseases in low-income
more » ... ries even when there are means to combat them. One of the root causes lies in the problematic vaccine cold-chain distribution. We believe that ensilication can improve vaccine availability by enabling transportation without refrigeration. Here, we show that ensilication stabilises tetanus toxoid C fragment (TTCF) and demonstrate that this material can be stored and transported at ambient temperature without compromising the immunogenic properties of TTCF in vivo. TTCF is a component of the diphtheria, tetanus and pertussis (DTP) vaccine. To further our understanding of the ensilication process, and its protective effect on proteins we have studied the formation of TTCF-silica nanoparticles via time-resolved Small Angle X-ray Scattering (SAXS). Our results reveal ensilication to be a staged diffusion-limited cluster aggregation (DLCA) type reaction, induced by the presence of TTCF protein at neutral pH. Analysis of scattering data indicates tailor fitting of TTCF protein. The experimental in vivo immunisation data confirms the retention of immunogenicity after release from silica. Our results suggest that we could utilise this technology for multicomponent vaccines, therapeutics or other biopharmaceuticals that are not compatible with lyophilisation.
arXiv:1811.12291v1 fatcat:wkowxkubcvd5pnppgmuzxabe7q

Discrete Huygens' Metasurface: Realizing Anomalous Reflection and Diffraction Mode Circulation with a Robust, Broadband and Simple Design [article]

Chu Qi, Alex M. H. Wong
2022 arXiv   pre-print
Metasurfaces composed of subwavelength unit cells usually require a large number of unit cells which leads to complicated design and optimization. Aggressive discretization in a metasurface can significantly reduce the number of unit cells within a period, resulting in lower requirement for phase and/or surface impedance coverage. Additionally, the enlarged unit cells will encounter negligible mutual couplings when combined together, hence making straightforward the process of metasurface
more » ... . These advantages combine to allow the design of a novel class of metasurfaces which support the high efficiency redirection of electromagnetic (EM) waves over a wide bandwidth and operation angle. Moreover, an aggressively discretized metasurface may realize functionalities such as diffraction mode circulation, which are unsupported in its continuous counterparts. In this paper we propose a simple transmissive metasurface which can realize diffraction mode circulation by refracting plane waves with incident angles of -45, 0, 45 degrees to plane waves with refraction angles of 0, 45, -45 degrees respectively. The power efficiency of each anomalous refraction is more than 80% at the design frequency of 28 GHz, and the 3-dB power efficiency bandwidth is 11%. We fabricated and measured the metasurface, the experiment results agree well with simulation results.
arXiv:2201.04290v1 fatcat:scfuopkqnnc2hhn5dhcvv56wlq

Interpreting Poisson Regression Models in Dental Caries Studies

Alex Man Him Chau, Edward Chin Man Lo, May Chun Mei Wong, Chun Hung Chu
2018 Caries Research  
Oral epidemiology involves studying and investigating the distribution and determinants of dental-related diseases in a specified population group to inform decisions in the management of health problems. In oral epidemiology studies, the hypothesis is typically followed by a cogent study design and data collection. Appropriate statistical analysis is essential to demonstrate the scientific association between the independent factors and the target variable. Analysis also helps to develop and
more » ... ild a statistical model. Poisson regression and its extensions have gained more attention in caries epidemiology than other working models such as logistic regression. This review discusses the fundamental principles and basic knowledge of Poisson regression models. It also introduces the use of a robust variance estimator with a focus on the "robust" interpretation of the model. In addition, extensions of regression models, including the zero-inflated model, hurdle model, and negative binomial model, and their interpretation in caries studies are reviewed. Principles of model fitting, including goodness-of-fit measures, are also discussed. Clinicians and researchers should pay attention to the statistical context of the models used and interpret the models to improve the oral and general health of the communities in which they live.
doi:10.1159/000486970 pmid:29478049 fatcat:wfs4erzobnh3rm36bieitjacuu

Switching kinetics in epitaxial BiFeO3 thin films

Daniel Pantel, Ying-Hao Chu, Lane W. Martin, Ramamoorthy Ramesh, Dietrich Hesse, Marin Alexe
2010 Journal of Applied Physics  
The switching kinetics in epitaxial ͑001͒-, ͑110͒-, and ͑111͒-oriented BiFeO 3 thin films were investigated as a function of applied field and time. It was found that the ferroelectric switching behavior obeys the Kolmogorov-Avrami-Ishibashi theory only in the high field range. The detailed behavior depends on the film orientation. A comparison with standard systems, such as epitaxial Pb͑Zr 0.2 Ti 0.8 ͒O 3 films, reveals some similarities as well as some differences. For instance, the presence
more » ... f 109°and 71°ferroelastic domain walls might be ruled out as the source of the decrease in switched polarization at low applied fields, in contrast to what is the case for a/c domain walls in tetragonal Pb͑Zr 0.2 Ti 0.8 ͒O 3 .
doi:10.1063/1.3392884 fatcat:flbxrraj6rfipgnhiwjeyill2i
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