scholarly journals Quenching an active swarm: Effects of light exposure on collective motility in swarmingSerratia marcescenscolonies

2018 ◽  
Author(s):  
Alison E Patteson ◽  
Junyi Yang ◽  
Paulo E Arratia ◽  
Arvind Gopinath
Keyword(s):  
Brownian Dynamics ◽  
Large Scale ◽  
Light Exposure ◽  
Ultra Violet ◽  
Dynamics Model ◽  
Planktonic Bacteria ◽  
Radial Extent ◽  
Active Bacteria ◽  
Macroscopic Domain ◽  
Independent Parameters

Swarming colonies of the light responsive bacteriaSerratia marcescensgrown on agar exhibit robust fluctuating large-scale collective flows that include arrayed vortices, jets, and sinuous streamers. We study the immobilization and quenching of these large-scale flows when the moving swarm is exposed to light with a substantial ultra-violet component. We map the response to light in terms of two independent parameters - the light intensity and duration of exposure and identify the conditions under which mobility is affected significantly. For small exposure times and/or low intensities, we find collective mobility to be negligibly affected. Increasing exposure times and/or intensity to higher values temporarily suppresses collective mobility. Terminating exposure allows bacteria regain motility and eventually reestablish large scale flows. For long exposure times or at high intensities, exposed bacteria become paralyzed, with macroscopic speeds eventually reducing to zero. In this process, they form highly aligned, jammed domains. Individual domains eventually coalesce into a large macroscopic domain with mean radial extent growing as the square root of exposure time. Post exposure, active bacteria dislodge exposed bacteria from these jammed configurations; initial dissolution rates are found to be strongly dependent on duration of exposure suggesting that caging effects are substantial at higher exposure times. Based on our experimental observations, we propose a minimal Brownian dynamics model to examine the escape of exposed bacteria from the region of exposure. Our results complement studies on planktonic bacteria and inform models for pattern formation in gradated illumination.

scholarly journals Quenching active swarms: effects of light exposure on collective motility in swarming Serratia marcescens

2019 ◽  
Vol 16 (156) ◽  
pp. 20180960 ◽  
Author(s):  
Junyi Yang ◽  
Paulo E. Arratia ◽  
Alison E. Patteson ◽  
Arvind Gopinath
Keyword(s):  
Serratia Marcescens ◽  
Brownian Dynamics ◽  
Large Scale ◽  
Light Exposure ◽  
Wide Spectrum ◽  
Dynamics Model ◽  
Planktonic Bacteria ◽  
Starting Point ◽  
Active Bacteria ◽  
Two Parameters

Swarming colonies of the light-responsive bacteria Serratia marcescens grown on agar exhibit robust fluctuating large-scale flows that include arrayed vortices, jets and sinuous streamers. We study the immobilization and quenching of these collective flows when the moving swarm is exposed to intense wide-spectrum light with a substantial ultraviolet component. We map the emergent response of the swarm to light in terms of two parameters—light intensity and duration of exposure—and identify the conditions under which collective motility is impacted. For small exposure times and/or low intensities, we find collective motility to be negligibly affected. Increasing exposure times and/or intensity to higher values suppresses collective motility but only temporarily. Terminating exposure allows bacteria to recover and eventually reestablish collective flows similar to that seen in unexposed swarms. For long exposure times or at high intensities, exposed bacteria become paralysed and form aligned, jammed regions where macroscopic speeds reduce to zero. The effective size of the quenched region increases with time and saturates to approximately the extent of the illuminated region. Post-exposure, active bacteria dislodge immotile bacteria; initial dissolution rates are strongly dependent on duration of exposure. Based on our experimental observations, we propose a minimal Brownian dynamics model to examine the escape of exposed bacteria from the region of exposure. Our results complement studies on planktonic bacteria, inform models of patterning in gradated illumination and provide a starting point for the study of specific wavelengths on swarming bacteria.

scholarly journals A Facile Urea-Assisted Thermal Decomposition Process of TiO2 Nanoparticles and Their Photocatalytic Activity

Coatings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 165
Author(s):  
Sandip Madhukar Deshmukh ◽  
Mohaseen S. Tamboli ◽  
Hamid Shaikh ◽  
Santosh B. Babar ◽  
Dipak P. Hiwarale ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Photocatalytic Activity ◽  
Tio2 Nanoparticles ◽  
Large Scale ◽  
Ultra Violet ◽  
Tio2 Nps ◽  
Transmission Electron ◽  
Structures And Properties ◽  
Ft Ir ◽  
Large Scale Synthesis

In the present work, we have reported a facile and large-scale synthesis of TiO2 nanoparticles (NPs) through urea-assisted thermal decomposition of titanium oxysulphate. We have successfully synthesized TiO2 NPs by using this effective route with different weight ratios of titanium oxysulphate: urea. The structures and properties of TiO2 NPs were confirmed by scanning electron microscope) (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), fourier transform infrared spectroscopy (FT-IR), ultra violet–visible spectroscopy (UV-vis), and photoluminescence (Pl) techniques. XRD demonstrated that TiO2 NPs holds of anatase crystal phase with crystallizing size 14–19 nm even after heating at 600 °C. TGA, SEM, and TEM images reveal urea’s role, which controls the size, morphology, and aggregation of TiO2 NPs during the thermal decomposition. These TiO2 NPs were employed for photodegradation of Methyl Orange (MO) in the presence of ultraviolet (UV) radiation. An interesting find was that the TiO2 NPs exhibited better photocatalytic activity and excellent recycling stability over several photodegradation cycles. Furthermore, the present method has a great perspective to be used as an efficient method for large-scale synthesis of TiO2 NPs.

scholarly journals Characterization of Pharmaceutical Tablets Using UV Hyperspectral Imaging as a Rapid Line to Line Analysis Tool

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4436
Author(s):  
Mohammad Al Ktash ◽  
Mona Stefanakis ◽  
Barbara Boldrini ◽  
Edwin Ostertag ◽  
Marc Brecht
Keyword(s):  
Hyperspectral Imaging ◽  
Large Scale ◽  
Solid Phase ◽  
Ultra Violet ◽  
Principal Component ◽  
Ccd Camera ◽  
Conveyor Belt ◽  
Hyperspectral Data ◽  
Analysis Tool ◽  
Sample Set

A laboratory prototype for hyperspectral imaging in ultra-violet (UV) region from 225 to 400 nm was developed and used to rapidly characterize active pharmaceutical ingredients (API) in tablets. The APIs are ibuprofen (IBU), acetylsalicylic acid (ASA) and paracetamol (PAR). Two sample sets were used for a comparison purpose. Sample set one comprises tablets of 100% API and sample set two consists of commercially available painkiller tablets. Reference measurements were performed on the pure APIs in liquid solutions (transmission) and in solid phase (reflection) using a commercial UV spectrometer. The spectroscopic part of the prototype is based on a pushbroom imager that contains a spectrograph and charge-coupled device (CCD) camera. The tablets were scanned on a conveyor belt that is positioned inside a tunnel made of polytetrafluoroethylene (PTFE) in order to increase the homogeneity of illumination at the sample position. Principal component analysis (PCA) was used to differentiate the hyperspectral data of the drug samples. The first two PCs are sufficient to completely separate all samples. The rugged design of the prototype opens new possibilities for further development of this technique towards real large-scale application.

scholarly journals Potential Energy Implications of Connected and Automated Vehicles: Exploring Key Leverage Points through Scenario Screening and Analysis

2019 ◽  
Vol 2673 (5) ◽  
pp. 84-94 ◽  
Author(s):  
Brian Bush ◽  
Laura Vimmerstedt ◽  
Jeff Gonder
Keyword(s):  
Systems Engineering ◽  
Large Scale ◽  
Operating Cost ◽  
Dynamics Model ◽  
Transportation Service ◽  
Service Outcomes ◽  
Behavioral Parameters ◽  
Computationally Intensive ◽  
Different Levels ◽  
Selection Of

Connected and automated vehicle (CAV) technologies could transform the transportation system over the coming decades, but face vehicle and systems engineering challenges, as well as technological, economic, demographic, and regulatory issues. The authors have developed a system dynamics model for generating, analyzing, and screening self-consistent CAV adoption scenarios. Results can support selection of scenarios for subsequent computationally intensive study using higher-resolution models. The potential for and barriers to large-scale adoption of CAVs have been analyzed using preliminary quantitative data and qualitative understandings of system relationships among stakeholders across the breadth of these issues. Although they are based on preliminary data, the results map possibilities for achieving different levels of CAV adoption and system-wide fuel use and demonstrate the interplay of behavioral parameters such as how consumers value their time versus financial parameters such as operating cost. By identifying the range of possibilities, estimating the associated energy and transportation service outcomes, and facilitating screening of scenarios for more detailed analysis, this work could inform transportation planners, researchers, and regulators.

Molecular Dynamics Modeling the Nano-Identation of Titanium

2021 ◽  
Author(s):  
Peiqiang Yang ◽  
Xueping Zhang ◽  
Zhenqiang Yao ◽  
Rajiv Shivpuri
Keyword(s):  
Molecular Dynamics ◽  
Plastic Deformation ◽  
Titanium Alloys ◽  
Large Scale ◽  
Mechanical Response ◽  
Pure Titanium ◽  
Dynamics Modeling ◽  
Dynamics Model ◽  
Nano Indentation ◽  
Molecular Dynamics Modeling

Abstract Titanium alloys’ excellent mechanical and physical properties make it the most popular material widely used in aerospace, medical, nuclear and other significant industries. The study of titanium alloys mainly focused on the macroscopic mechanical mechanism. However, very few researches addressed the nanostructure of titanium alloys and its mechanical response in Nano-machining due to the difficulty to perform and characterize nano-machining experiment. Compared with nano-machining, nano-indentation is easier to characterize the microscopic plasticity of titanium alloys. This research presents a nano-indentation molecular dynamics model in titanium to address its microstructure alteration, plastic deformation and other mechanical response at the atomistic scale. Based on the molecular dynamics model, a complete nano-indentation cycle, including the loading and unloading stages, is performed by applying Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). The plastic deformation mechanism of nano-indentation of titanium with a rigid diamond ball tip was studied under different indentation velocities. At the same time, the influence of different environment temperatures on the nano-plastic deformation of titanium is analyzed under the condition of constant indentation velocity. The simulation results show that the Young’s modulus of pure titanium calculated based on nano-indentation is about 110GPa, which is very close to the experimental results. The results also show that the mechanical behavior of titanium can be divided into three stages: elastic stage, yield stage and plastic stage during the nano-indentation process. In addition, indentation speed has influence on phase transitions and nucleation of dislocations in the range of 0.1–1.0 Å/ps.

Orientation of chain molecules in ionotropic gels: a Brownian dynamics model

2003 ◽  
Vol 293 (3) ◽  
pp. 323-340 ◽  
Author(s):  
Stefan Woelki ◽  
Hans-Helmut Kohler
Keyword(s):  
Brownian Dynamics ◽  
Dynamics Model ◽  
Chain Molecules

Effects Of Ultra Violet Light Exposure on Gated Sillicon Field Emitter Arrays

2021 ◽  
Author(s):  
Ranajoy Bhattacharya ◽  
Mason Canon ◽  
Nedeljko Karaulac ◽  
Girish Rughoobur ◽  
Winston Chern ◽  
...  
Keyword(s):  
Light Exposure ◽  
Ultra Violet ◽  
Field Emitter ◽  
Ultra Violet Light ◽  
Violet Light ◽  
Field Emitter Arrays

Confinement Of Myosin Motor Activity On Trimethylchlorosilane Surface By Ultra Violet Light Exposure For Nano-Technology Applications

2008 ◽  
Vol 40 (Supplement) ◽  
pp. S297
Author(s):  
Madhukar B. Kolli ◽  
Hideyo Takatsuki ◽  
Devashish Desai ◽  
Kevin M. Rice ◽  
Sunil Kakarla ◽  
...  
Keyword(s):  
Motor Activity ◽  
Light Exposure ◽  
Ultra Violet ◽  
Nano Technology ◽  
Ultra Violet Light ◽  
Myosin Motor ◽  
Violet Light ◽  
Technology Applications

scholarly journals Ephemeral protein binding to DNA shapes stable nuclear bodies and chromatin domains

2016 ◽  
Author(s):  
C. A. Brackley ◽  
B. Liebchen ◽  
D. Michieletto ◽  
F. Mouvet ◽  
P. R. Cook ◽  
...  
Keyword(s):  
Dna Binding ◽  
Self Assembly ◽  
Brownian Dynamics ◽  
Large Scale ◽  
Nuclear Bodies ◽  
Underlying Structure ◽  
Post Translational Modification ◽  
Equilibrium Process ◽  
Dynamics Simulations ◽  
Brownian Dynamics Simulations

AbstractFluorescence microscopy reveals that the contents of many (membrane-free) nuclear “bodies” exchange rapidly with the soluble pool whilst the underlying structure persists; such observations await a satisfactory biophysical explanation. To shed light on this, we perform large-scale Brownian dynamics simulations of a chromatin fiber interacting with an ensemble of (multivalent) DNA-binding proteins; these proteins switch between two states – active (binding) and inactive (non-binding). This system provides a model for any DNA-binding protein that can be modified post-translationally to change its affinity for DNA (e.g., like the phosphorylation of a transcription factor). Due to this out-of-equilibrium process, proteins spontaneously assemble into clusters of self-limiting size, as individual proteins in a cluster exchange with the soluble pool with kinetics like those seen in photo-bleaching experiments. This behavior contrasts sharply with that exhibited by “equilibrium”, or non-switching, proteins that exist only in the binding state; when these bind to DNA non-specifically, they form clusters that grow indefinitely in size. Our results point to post-translational modification of chromatin-bridging proteins as a generic mechanism driving the self-assembly of highly dynamic, non-equilibrium, protein clusters with the properties of nuclear bodies. Such active modification also reshapes intra-chromatin contacts to give networks resembling those seen in topologically-associating domains, as switching markedly favors local (short-range) contacts over distant ones.

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