Activatable tiles for compact robust programmable molecular assembly and other applications

Algorithmic DNA self-assembly is capable of forming complex patterns and shapes, that have been shown theoretically, and experimentally. Its experimental demonstrations, although improving over recent years, have been limited by significant assembly errors. Since 2003 there have been several designs of error-resilient tile sets but all of these existing error-resilient tile systems assumed directional growth of the tiling assembly. This is a very strong assumption because experiments show that tile self-assembly does not necessarily behave in such a fashion, since they may also grow in the reverse of the intended direction. The assumption of directional growth of the tiling assembly also underlies the growth model in theoretical assembly models such as the TAM. What is needed is a means for enforce this directionality constraint, which will allow us to reduce assembly errors. In this paper we describe a protection/deprotection strategy to strictly enforce the direction of tiling assembly growth so that the assembly process is robust against errors. Initially, we start with (1) a single “activated” tile with output pads that can bind with other tiles, along with (2) a set of “deactivated” tiles, meaning that the tile’s output pads are protected and cannot bind with other tiles. After other tiles bind to a “deactivated” tile’s input pads, the tile transitions to an active state and its output pads are exposed, allowing further growth. When these are activated in a desired order, we can enforce a directional assembly at the same scale as the original one. Such a system can be built with minimal modifications of existing DNA tile nanostructures. We propose a new type of tiles called activatable tiles and its role in compact proofreading. Activatable tiles can be thought of as a particular case of the more recent signal tile assembly model, where signals transmit binding/unbinding instructions across tiles on binding to one or more input sites. We describe abstract and kinetic models of activatable tile assembly and show that the error rate can be decreased significantly with respect to Winfree’s original kinetic tile assembly model without considerable decrease in assembly growth speed. We prove that an activatable tile set is an instance of a compact, error-resilient and self-healing tile-set. We describe a DNA design of activatable tiles and a mechanism of deprotection using DNA polymerization and strand displacement. We also perform detailed stepwise simulations using a DNA Tile simulator Xgrow, and show that the activatable tiles mechanism can reduce error rates in self assembly. We conclude with a brief discussion on some applications of activatable tiles beyond computational tiling, both as (1) a novel system for concentration of molecules, and (2) a catalyst in sequentially triggered chemical reactions.     

Treatment of arsenic contaminated water in a batch reactor by using Ralstonia eutropha MTCC 2487 and granular activated carbon

This paper presents the observations on the bio-removal of arsenic from contaminated water by using Ralstonia eutropha MTCC 2487 and activated carbon in a batch reactor. The effects of agitation time, pH, type of granular activated carbon (GAC) and initial arsenic concentration (As(o)) on the % removal of arsenic have been discussed. Under the experimental conditions, optimum removal was obtained at the pH of 6-7 with agitation time of 100 h. The % removal of As(T) increased initially with the increase in As(o) and after attaining the maximum removal (~86%) at the As(o) value of around 15 ppm, it started to decrease. Simultaneous adsorption bioaccumulation (SABA) was observed, when fresh GAC was used as supporting media for bacterial immobilization. In case of SABA, the % removal of As(III) was almost similar (only ~1% more) to the additive values of individual removal of As(III) obtained by only adsorption and only bio-adsorption. However, for As(V) the % removal was less (~8%) than the additive value of the individual % removals obtained by only adsorption and bio-adsorption. Percentage removal of Fe, Mn, Cu and Zn were 65.17%, 72.76%, 98.6% and 99.31%, respectively. Maximum regeneration (~99.4%) of the used bio-adsorbent was achieved by the treatment with 5NH(2)SO(4) followed by 1N NaOH and 30% H(2)O(2) in HNO(3). The fitness of the isotherms to predict the specific uptake for bio-adsorption/accumulation process has been found to decrease in the following order: Temkin isotherm>Langmuir isotherm>Freundlich isotherm. For the adsorption process with fresh GAC the corresponding order is Freundlich isotherm>Langmuir isotherm>Temkin isotherm for As(V) and As(T). However, for As(III) it was Langmuir>Temkin>Freundlich.     

Thermal stability of Ti/Mo and Ti/MoN nanostructures for barrier applications in Cu interconnects

This work focuses on the barrier capabilities of sputter deposited Ti/Mo and Ti/MoN nanofilms against diffusion of Cu into Si substrates. The thermal stability of the corresponding bi-layer barrier structures is investigated after annealing Cu/barrier layer/Si samples at different temperatures in N(2) for 5?min. The drastic increase in sheet resistance of Cu and the probing of Cu(3)Si with x-ray diffraction after high temperature annealing indicate the failure of these barrier structures. The formation of Cu(3)Si at the barrier breakdown temperature is also confirmed by scanning electron microscopy and energy dispersive x-ray spectroscopy. Cu?diffusion barrier performance analyses show that a Ti(5?nm)/MoN(5?nm) bi-layer nanostructure fails only after annealing at 800?°C; on the other hand, a Ti(5?nm)/Mo(5?nm) barrier stack is found to break down at 700?°C.     

Error propagation of the track model and track fitting strategy for the Iron CALorimeter detector in India-based neutrino observatory

A Kalman filter package has been developed for reconstructing muon (μ^±)$\left({\mu }^{\pm }\right)$ tracks (coming from the neutrino interactions) in ICAL detector. Here, we describe the algorithm of muon track fitting, with emphasis on the error propagation of the elements of Kalman state vector along the muon trajectory through dense materials and inhomogeneous magnetic field. The higher order correction terms are included for reconstructing muon tracks at large zenith angle θ$\theta$ (measured from the perpendicular to the detector planes). The performances of this algorithm and its limitations are discussed.     

磁性隧道结器件的建模与验证

描述了一个简单的磁性隧道结器件的模型.利用基于运算放大器的反向放大器通过仿真和实验研究并验证了该模型的隧道磁致电阻效应.实验结果证实了仿真和理论的正确性.     

A distribution free newsvendor model with consignment policy and retailer’s royalty reduction

Reducing the system cost and achieving significant profit are the key factors for every successful business sector. A consignment contract under distribution-free approach may be a fruitful combination to achieve a profitable business. This model deals with a single-period newsvendor problem with a consignment policy. The consignment policy is an agreement between any two parties, named as the consignor and the consignee. Under Stackelberg approach, firms act as leader and follower. Both parties carry some parts of the holding cost instead of one. A new policy for paying the fixed fee to the consignee is introduced. This paper considers no specific probability distribution for customer’s demand except a known mean and standard deviation. An efficient approach is proposed to reduce the retailer’s cost and building a sustainable consignment contract. The solution of this model is obtained using distribution free approach. A comparison between the traditional supply chain policy and the consignment policy is established. The price-sensitivity on demand is analysed. Some numerical examples and graphical representations are given for both traditional and consignment policy. Result proves that consignment policy is dominating over the traditional policy and a significant reduction of retailer’s royalty is found.     

A New Groundwater Management Model by Coupling Analytic Element Method and Reverse Particle Tracking with Cat Swarm Optimization

The performance of groundwater management models mostly depends upon the methodology employed to simulate flow and transport processes and the efficiency of optimization algorithms. The present study examines the effectiveness of cat swarm optimization (CSO) for groundwater management problems, by coupling it with the analytic element method (AEM) and reverse particle tracking (RPT). In this study, we propose two coupled simulation-optimization models, viz. AEM-CSO and AEM-RPT-CSO by combining AEM with RPT and CSO. Both the models utilize the added advantages of AEM, such as precise estimation of hydraulic head at pumping location and generation of continuous velocity throughout the domain. The AEM-CSO model is applied to a hypothetical unconfined aquifer considering two different objectives, i.e., maximization of the total pumping of groundwater from the aquifer and minimization of the total pumping costs. The model performance reflects the superiority of CSO in comparison with other optimization algorithms. Further, the AEM-RPT-CSO model is successfully applied to a hypothetical confined aquifer to minimize the total number of contaminant sources, within the time related capture zone of the wells, while maintaining the required water demand. In this model, RPT gets continuous velocity information directly from the AEM model. The performance evaluation of the proposed methodology, illustrates its ability to solve groundwater management problems.     

An efficient circuit-level power reduction technique for ultralow power applications

Microsystem Technologies - This research work explores various circuit-level design techniques to identify the best technique suitable for low power circuit design. To establish a proper...     

Internal fluid motion and particle transport in externally heated sessile droplets

Experiments and numerical simulations were carried out for an evaporating sessile droplet. The droplet was confined in the narrow gap between two glass plates, making it a “Hele‐Shaw” droplet and particle image velocimetry technique was used. In case of the evaporating droplet with pinned contact line and exposed to ambient condition, two symmetric but counterrotating convection cells were observed. After complete evaporation, the particles deposited on the substrate near the contact line. The direction of the flow was reversed for a droplet placed on uniformly heated substrate, and the final deposition pattern was a large spot at the center with a thin line at the periphery. For asymmetrically heated substrate a single convection cell appeared, and the final deposition was also asymmetric. When the liquid was subjected to localized heating, the contact line no longer remains pinned and a relatively uniform deposition was obtained after complete drying. © 2015 American Institute of Chemical Engineers AIChE J, 62: 1308–1321, 2016     

Precursor dependent tailoring of morphology and bandgap of zinc oxide nanostructures

Zinc oxide (ZnO) nanoparticles have been synthesized by wet chemical processing from four different zinc precursor materials at room temperature. Synthesis of phase pure material with four different morphologies and orientations have been confirmed through different characterization techniques like, X-ray diffraction, field emission SEM, fourier transformed IR etc. The band gap energies of the synthesized materials were within specific semiconductor limits and the same have been determined from UV–Visible and photoluminescence spectra of the synthesized nanostructured ZnO materials. Thus it is possible to control ZnO nanostructures and morphologies through facile room temperature synthesis and tailor their band gaps for different application purposes.