Microcantilever deflection induced to hybridization of monomolecular DNA films: lower immobilization densities lead to larger deflections?

Experimental results show that specific binding between a ligand and surface immobilized receptor such as hybridization of single-stranded DNA (ssDNA) immobilized on a microcantilever surface leads to cantilever deflection. The binding induced deflection may be used as a method for detection of biomolecules, such as pathogens and biohazards. Mechanical deformation induced because of hybridization of surface immobilized DNA strands is a commonly used system to demonstrate the efficacy of microcantilever sensors; therefore, hybridization induced cantilever deflection has been reported for range of parameters that chain distributions – ssDNA immobilization densities, hybridization efficiencies, and ssDNA conformation [1–7]. However, it has been hard to draw general conclusions on the DNA hybridization induced deflections because a large range of deflections has been reported for similar density of hybridized DNA strands on the cantilever. To understand the mechanism underlying the cantilever deflections, a theoretical model that incorporates the influence of ligand/receptor complex surface distribution, conformation, configuration, and empirical interchain potential is developed to predict the binding induced deflections. The cantilever bending induced because of hybridization of DNA strands is predicted for different receptor immobilization densities, hybridization efficiencies, receptor configuration, and spatial arrangements. Predicted deflections are compared with experimental reports to validate the modeling assumptions and identify the influence of various components on mechanical deformation. Comparison of numerical predictions and experimental results suggest that initial immobilization density of receptors is a primary factor that determines the conformation and distribution of hybridized DNA strands and in turn, the cantilever deflection associated with DNA hybridization. Contrary to our expectations, the cantilever deflections are found to be larger for smaller receptor immobilization densities. For high immobilization densities, hybridization-induced mechanical deformation is determined primarily by immobilization density and hybridization efficiency as the hybridized DNA strands are restricted to be in standing-up conformation, whereas at lower immobilization densities, different conformations and spatial arrangement of hybridized chains need to be considered in determining the cantilever deflection. In addition, for similar immobilization densities, changing the immobilized receptor configuration from one end-tethered to both end-tethered leads to larger cantilever deflection on hybridization. Comparison of numerical predictions and experimental results highlights the importance of immobilized receptor configurations, immobilization density, and spatial disorder imposed during immobilization and hybridization on the hybridization induced cantilever bending

Picosecond Laser based Additive Manufacturing of Hydroxyapatite Coatings on Cobalt Chromium Surfaces

We report high repetition rate picosecond laser based additive manufacturing process to coat nanoscale rough hydroxyapatite (HA) on cobalt chromium plates (CoCr). Nanoscale rough coatings of hydroxyapatite are desirable as they mimic the naturally formed hydroxyapatite and in addition provide very high surface area and surface roughness, which leads to better cell adhesion and cell-matrix interaction. Nanoscale HA powders are synthesized using sol-gel procedure and ball milling. Ball-milled powders are suspended in volatile solvents and coated on the CoCr surface using picosecond laser irradiation. The chemical composition and morphology of the coated material was characterized using electron microscopy. The laser-assisted fusion process results in HA coatings that have hierarchical surface roughness down to nanometer scale which may enhance the biocompatibility of the CoCr implants

Adversarial Sign-Corrupted Isotonic Regression

Classical univariate isotonic regression involves nonparametric estimation under a monotonicity constraint of the true signal. We consider a variation of this generating process, which we term adversarial sign-corrupted isotonic (\texttt{ASCI}) regression. Under this \texttt{ASCI} setting, the adversary has full access to the true isotonic responses, and is free to sign-corrupt them. Estimating the true monotonic signal given these sign-corrupted responses is a highly challenging task. Notably, the sign-corruptions are designed to violate monotonicity, and possibly induce heavy dependence between the corrupted response terms. In this sense, \texttt{ASCI} regression may be viewed as an adversarial stress test for isotonic regression. Our motivation is driven by understanding whether efficient robust estimation of the monotone signal is feasible under this adversarial setting. We develop \texttt{ASCIFIT}, a three-step estimation procedure under the \texttt{ASCI} setting. The \texttt{ASCIFIT} procedure is conceptually simple, easy to implement with existing software, and consists of applying the \texttt{PAVA} with crucial pre- and post-processing corrections. We formalize this procedure, and demonstrate its theoretical guarantees in the form of sharp high probability upper bounds and minimax lower bounds. We illustrate our findings with detailed simulations.Comment: Total paper (52 pages, 2 figures): Main paper (13 pages, 2 figures) + Appendix (39 pages

Ultrahard Polycrystalline Cubic Boron Nitride Composite through Hybrid Laser/Waterjet Heat (LWH) Treatment

Ultra-hard materials that are chemically inert and thermally stable at high temperatures are desirable for enhancing machining and wear performance in demanding chemical and thermal environments. Single and polycrystalline diamonds are the hardest tool materials; however, at high temperatures, diamond reacts with ferrous alloys, losing its chemical inertness and thermal stability. In contrast, cubic boron nitride (cBN) has exceptional chemical and thermal stability but has much lower hardness (35-45 GPa). Increasing the hardness of BN is expected to fill the property gap in state-of-the-art tool materials as shown and to generate huge industrial interest for meeting the stringent design requirements such as machining optical surfaces and reducing the cost and time for machining ferrous materials. A novel laser/waterjet heat treatment (LWH) process is investigated to enhance the surface hardness of a dual phase boron nitride (BN) material composed of 50% cubic and 50% wurtzite phases. Results indicate that experimentally measured hardness increase is dependent on the processing parameter such as laser fluence and overlap between heat treatment passes. Statistical analysis is carried out to identify the processing parameter that result in maximum hardness increase

Revisiting Le Cam's Equation: Exact Minimax Rates over Convex Density Classes

We study the classical problem of deriving minimax rates for density estimation over convex density classes. Building on the pioneering work of Le Cam (1973), Birge (1983, 1986), Wong and Shen (1995), Yang and Barron (1999), we determine the exact (up to constants) minimax rate over any convex density class. This work thus extends these known results by demonstrating that the local metric entropy of the density class always captures the minimax optimal rates under such settings. Our bounds provide a unifying perspective across both parametric and nonparametric convex density classes, under weaker assumptions on the richness of the density class than previously considered. Our proposed `multistage sieve' MLE applies to any such convex density class. We further demonstrate that this estimator is also adaptive to the true underlying density of interest. We apply our risk bounds to rederive known minimax rates including bounded total variation, and Holder density classes. We further illustrate the utility of the result by deriving upper bounds for less studied classes, e.g., convex mixture of densities.Comment: Total paper (46 pages, 2 figures): Main paper (17 pages, 2 figures) + Appendix (29 pages). Updated to include proof of adaptivity of estimato

Mechanical load assisted dissolution response of biomedical cobalt–chromium and titanium metallic alloys: influence of in-plane stress and chemical environment

Mechanical load-assisted dissolution is identified as one of the key mechanisms governing material removal in fretting and crevice corrosion of biomedical implants. In the current study, material removal on a stressed surface of cobalt–chromium–molybdenum (CoCrMo) and titanium (Ti64) alloys subjected to single asperity contact is investigated to identify the influence of contact loads and in-plane stress state on surface damage mechanisms. The experiments were conducted in three different aqueous environments—phosphate-buffered saline (PBS) at pH 7.4, PBS at pH 4.1, and high chloride solutions at pH 2.0. The tip of an atomic force microscope is used as a well-characterized “asperity” to apply controlled contact forces and mechanically stimulate the loaded specimen surface in different aqueous environments from passivating to corroding. The volume of the material removed is measured to determine the influence of contact loads, in-plane stresses, and the environment on the material dissolution rate. Experimental results indicate that surface damage is initiated at all the contact loads studied and as expected in a wear situation, removal rate increases with increase in contact loads. For both alloys, removal rates display a complex dependence on residual stresses and the environment. In a passivating environment, the material removal rate is linearly dependent on the stress state such that surface damage is accelerated under compressive stresses and suppressed under tensile stresses. In a corrosive environment, the dissolution rate demonstrates a quadratic dependence on stress, with both compressive and tensile stresses accelerating material dissolution. The material removal rates are found to be consistently larger for CoCrMo in comparison to Ti64 surfaces under the same mechanical and electrochemical stimuli, despite the higher hardness of CoCrMo surfaces. A surface damage mechanism based on stress-assisted dissolution is proposed to elucidate the experimental observations

Asynchronous Message Transmission Technique for Latency Requirements in Time Critical Ship-borne System

A solution to data ageing requirements in time critical ship system like fire control system is presented. In an operational sea borne platform, navigation requirements for the onboard systems are fulfilled by ring laser gyro-based inertial navigation system. For critical systems like fire control system, navigational data must be delivered in real time without any delay. However due to delay occurring in processing of raw information and transmission of data on interface bus some latency is introduced. Algorithm for an asynchronous message transmission technique from inertial navigation system to user system to meet its latency requirements is discussed. Latency requirement is achieved by sending a separate message with the time stamp for the instance the first byte of 100 Hz attitude data is received at the processing computer of navigation system.

Police System in Gwalior Division of Madhya Pradesh: An Analytical Study

For the security of the country, it is necessary that the link between internal and external security of the country should be strong. If the internal and external links of a country are insecure, then that country becomes a victim of terrorism and crimes, sometimes it has to work under foreign power. The security of any country is very important, whether it is internal security or external security, both hold an important place in their place. Now the question is what is external security? So in external security, three types of forces work in our country, Army, the Navy, Air Force, and other forces, which are approved by the government, and they also work secretly. The forces work mostly for external security, prevent external aggression and protect the country's border. Similarly, the work of the police is also to maintain the internal security of the country and prevent armed rebellion and internal rebellion. Through this research paper, necessary suggestions have to be discussed by doing an analytical study regarding the functioning of the efforts being made by the researcher for the security of the country and the state