Comparative study of the effect of nutrients on motility and chemotaxis of Escherichia coli strains

This thesis evaluates two strains of Escherichia coli MG1655 and MDS42 for their motility in different nutrient conditions in M9 minimal medium in 2 parts. It evaluates the effect of genome deletion in the motility and also observes the heterogeneity despite sharing the same genetically encoded machinery. The first part investigates Escherichia coli strains’ motility in 5 different medium compositions and the second part explores the chemotactic response of MG1655 to the linear gradients of different concentrations of Glucose using a single-layer membrane-based microfluidic device. In Part 1, we study the motility of MG1655 and MDS42 in different concentrations of glucose and casamino acids in M9 minimal medium. The motility experiments conducted as a part of this study observed the average cell velocities in the range of 2.9 ± 0.5 μm/s, which are significantly less than the values recorded in literature, for the strain MG1655. The lowest motility occurs in the medium (without casamino acids) with 0M glucose, followed by 10mM Glucose and then 10μM glucose concentration. The same trend is visible in the case of both the strains MG1655 and MDS42. The presence of casamino acids did not significantly affect the motility of MG1655 in the presence or absence of Glucose. Whereas, in the case of MDS42, the casamino acids lower the motility in the presence of Glucose but tend to have no significant effect in the absence of Glucose. The two strains, however, showed no significant difference in average velocity under the same medium conditions. In Part 2, we record and evaluate the chemotaxis of the MG1655 strain, using a single-layer membrane-based microfluidic device. The device generates a linear gradient of 10μM and 10mM glucose, to observe the chemotaxis of the MG1655 strain. The average of mean velocities for the 10μM gradient was higher than those observed in the 10mM gradient, but the difference was not significant. The higher fraction of cells (~67%) under the 10mM gradient showed almost a straight-line trajectory, unlike the cells under 10μM gradient. The cells that followed a nearly straight line path did all the more so in the case of the 10mM glucose gradient

Quantum limits on phase-preserving linear amplifiers

The purpose of a phase-preserving linear amplifier is to make a small signal larger, regardless of its phase, so that it can be perceived by instruments incapable of resolving the original signal, while sacrificing as little as possible in signal-to-noise. Quantum mechanics limits how well this can be done: a high-gain linear amplifier must degrade the signal-to-noise; the noise added by the amplifier, when referred to the input, must be at least half a quantum at the operating frequency. This well-known quantum limit only constrains the second moments of the added noise. Here we derive the quantum constraints on the entire distribution of added noise: we show that any phase-preserving linear amplifier is equivalent to a parametric amplifier with a physical state for the ancillary mode; the noise added to the amplified field mode is distributed according to the Wigner function of the ancilla state.Comment: 37 pages, 6 figure

Understanding the Modus Operandi of Class II KNOX Transcription Factors in Secondary Cell Wall Biosynthesis

Lignocellulosic biomass from the secondary cell walls of plants has a veritable potential to provide some of the most appropriate raw materials for producing second-generation biofuels. Therefore, we must first understand how plants synthesize these complex secondary cell walls that consist of cellulose, hemicellulose, and lignin in order to deconstruct them later on into simple sugars to produce bioethanol via fermentation. Knotted-like homeobox (KNOX) genes encode homeodomain-containing transcription factors (TFs) that modulate various important developmental processes in plants. While Class I KNOX TF genes are mainly expressed in the shoot apical meristems of both monocot and eudicot plants and are involved in meristem maintenance and/or formation, Class II KNOX TF genes exhibit diverse expression patterns and their precise functions have mostly remained unknown, until recently. The expression patterns of Class II KNOX TF genes in Arabidopsis, namely KNAT3, KNAT4, KNAT5, and KNAT7, suggest that TFs encoded by at least some of these genes, such as KNAT7 and KNAT3, may play a significant role in secondary cell wall formation. Specifically, the expression of the KNAT7 gene is regulated by upstream TFs, such as SND1 and MYB46, while KNAT7 interacts with other cell wall proteins, such as KNAT3, MYB75, OFPs, and BLHs, to regulate secondary cell wall formation. Moreover, KNAT7 directly regulates the expression of some xylan synthesis genes. In this review, we summarize the current mechanistic understanding of the roles of Class II KNOX TFs in secondary cell wall formation. Recent success with the genetic manipulation of Class II KNOX TFs suggests that this may be one of the biotechnological strategies to improve plant feedstocks for bioethanol production

Contact Charge Electrophoresis: Cooperative dynamics of particle dispersions

In 1745 a Scotch Benedictine monk Andrew Gordon discovered Contact Charge Electrophoresis (CCEP) which remained in dormant state for centuries until gaining renewed prominence in the field of particle manipulation and actuation. Contact Charge Electrophoresis (CCEP) refers to the continuous to and fro motion of a conductive object between two electrodes subject to an applied voltage. The continuous motion of the conductive particle and the low power requirement provide an attractive alternative to traditional methods for particle manipulation techniques such as dielectrophoresis. Recent efforts to understand and apply CCEP have focused on the motion of single particles and we present dynamics of multiple conductive particles dispersed in non-conducting media that utilize CCEP to perform tasks like pumping and cargo transport operations as well as multiparticle clusters capable of tailored trajectories. Chapters 1 provides motivation for this work and background on CCEP. Providing brief details on development of microfluidic devices and modeling that are covered in more details in subsequent chapters. It also focuses on the historical aspect of CCEP, relevant background, mechanism, physics, application strategies in literature, strategies developed for single particle systems and possible extension to multiparticle systems. Chapters 2 and 3 talk about the dynamics and modeling of multiple conductive particles both in dispersion and aggregates/clusters powered by CCEP. In Chapter 2, we propose a new hybrid approach based on image-based method proposed earlier by Bonnecaze[18] for modeling CCEP. It covers challenges to modeling a multiple particle system in confinement, dynamics of chain formation and dynamics of cluster comprising conductive and non-conductive particles between two electrodes. While Chapter 3 focuses on details of methods and techniques used in development of the simulation for dispersion of conductive particles in confinement. Here we also illustrate variation of conductivity for complete range of electrode separation with varying volume fraction. Chapter 4 expands on multiple particle CCEP and shows that when we physically constrain particle trajectories to parallel tracks between the electrodes, the traveling waves of mechanical actuation can be realized in linear arrays of electromechanical oscillators that move and interact via electrostatic forces. Conductive spheres oscillate between biased electrodes through cycles of contact charging and electrostatic actuation. The combination of repulsive interactions among the particles and spatial gradients in their natural frequencies lead to phase locked states characterized by gradients in the oscillation phase. The frequency and wavelength of these traveling waves can be specified independently by varying the applied voltage and the electrode separation. We demonstrate how traveling wave synchronization can enable the directed transport of material cargo. Our results suggests that simple energy inputs can power complex patterns of mechanical actuation with potential opportunities for soft robotics and colloidal machines. Chapter 5 systematically investigate the dynamics of cluster comprising multiple spherical conductive particles driven via contact charge electrophoresis (CCEP). We are specifically interested in understanding dynamics of closed packed cluster of particles with both conductive and non-conductive particles in three dimensions(3D). Finally, Chapter 6 summarizes new ideas and proposes possible applications for multiple particle Contact charge electrophoresis motivated by this dissertation

An exothermal energy release layer for microchip transience

pre-printA single layer nanothermite spin coated gel has been utilized as a solid-state exothermic energy release layer for triggered microchip transience. A proportional combination of self-assembled CuO/Al nanothermite and Napalm-B as gelling agent has been used to develop for the first time a spinable nanothermite film onto the surface of a micro-chip. This layer when ignited instantaneously releases enough heat energy to melt the surface of the underlying substrate and any surface-bound microdevices, electronic feature or any surface deposited component. We observe the effect of thermite enabled destruction prior and post ignition through microscopic imaging and electrical measurements on surface bound components

Antioxidant mediated protective effect of Parthenium hysterophorus against oxidative damage using in vitro models

BACKGROUND: Parthenium hysterophorus L. (Asteraceae) is a common weed occurring throughout the globe. In traditional medicine its decoction has been used for treatment of many infectious and degenerative diseases. This work was therefore designed to assess the phytochemical constitution of P. hysterophorus flower and root extracts and to evaluate their reducing power, radical scavenging activity as well as protective efficacy against membrane lipid damage. METHODS: Dried flower and root samples were sequentially extracted with non-polar and polar solvents using Soxhlet apparatus. The phytochemical screening was done using standard chemical methods and thin layer chromatography. Total phenolic content was determined spectrophotometrically. Reducing power and hydroxyl radical scavenging activity assays were used to measure antioxidant activity. Protection against membrane damage was evaluated by inhibition of lipid peroxidation (TBARS assay) in rat kidney homogenate. RESULTS: Flavonoids, terpenoids, alkaloids and cardiac glycosides were present in all the extract. The total phenol contents in flower and root extracts were found to be in the range 86.69-320.17 mg propyl gallate equivalent (PGE)/g and 55.47-253.84 mg PGE/g, respectively. Comparatively better reducing power was observed in hexane fractions of flower (0.405) and root (0.282). Benzene extract of flower and ethyl acetate fraction of root accounted for appreciable hydroxyl radical scavenging activity (75-77%). Maximum protection against membrane lipid peroxidative damage among flower and root extracts was provided by ethanol (55.26%) and ethyl acetate (48.95%) fractions, respectively. Total phenolic content showed positive correlations with reducing power and lipid peroxidation inhibition (LPOI) % in floral extracts as well as with hydroxyl radical scavenging activity and LPOI % in root extracts. CONCLUSION: Study established that phytochemicals present in P. hysterophorus extracts have considerable antioxidant potential as well as lipo-protective activity against membrane damage

Interfacing of High Temperature Z-meter Setup Using Python

In this work, we interface high temperature Z-meter setup to automize the whole measurement process. A program is built on open source programming language Python which convert the manual measurement process into fully automated process without any cost addition. Using this program, simultaneous measurement of Seebeck coefficient, thermal conductivity and electrical resistivity are performed and using all three, figure-of-merit (ZT) is calculated. Developed program is verified by performing measurement over p-type Bi0.36Sb1.45Te3 sample and the data obtained are found to be in good agreement with the reported data.Comment: 3 pages, 4 figures, Accepted for publication in AIP Conference Proceeding

Future evolution due to backreaction in a Universe with multiple inhomogeneous domains

We formulate a model of spacetime with inhomogeneous matter distribution in multiple domains. In the context of the backreaction framework using Buchert's averaging procedure, we evaluate the effect of backreaction due to the inhomogeneities on the late time global evolution of the Universe. Examining the future evolution of this universe, we find that it can transit from the presently accelerating phase to undergo future deceleration. The future deceleration is governed by our model parameters. We constrain the model parameters using observational analysis of the Union 2.1 supernova Ia data employing the Markov Chain Monte Carlo method.Comment: 12 pages, 7 figure