Si nanocolumns as novel nanostructured supports for enzyme immobilization

Silicon nanocolumns have been used as novel supports for the high-density immobilization of enzymes. Silicon nanocolumns with diameters of ca. 50-100 nm and a height of 1 micron were constructed using glancing angle deposition. The surfaces were successively treated with 3-aminopropyltriethoxysilane (APTES) and then with an amine reactive polymer, poly(ethylene-alt-maleic anhydride), to attach soybean peroxidase (SBP) to the support. Optimal coverage of APTES, polymer, and SBP was obtained for incorporation of enzyme onto the sidewalls of the nanocolumns. SBP immobilized on the silicon nanocolumns demonstrated an enhancement in biocatalytic activity of 160% over that of the enzyme immobilized on flat silicon wafers with the same projected area. The enzymatic activity decreased with progressive washes for both supports. This decrease in the activity of enzyme was found to be primarily due to the intrinsic deactivation of immobilized enzyme on the silicon surface. Designing nanocolumns with optimal dimensions, spacing, and surface chemistry may lead to the development of high-density arrays of proteins for applications in biotechnology.     

Three dimensional reconstruction of coronary arteries from two views

Geometric representation and measurements of localized lumen stenosis of coronary arteries are important considerations in the diagnosis of cardiovascular diseases. This discrete narrowing of the arteries typically impairs blood flow in regions of the heart, and can be present along the entire length of the artery. Three-dimensional (3-D) reconstruction of coronary arterial tree allows clinician to visualize vascular geometry. Three-dimensional representation of tree topology facilitates calculation of hemodynamic measurements to study myocardial infarction and stenosis. The 3-D arterial tree, computed from two views, can provide more information about the tree geometry than individual views. In this paper, a 3-step algorithm for 3-D reconstruction of arterial tree using two standard views is presented. The first step is a multi-resolution segmentation of the coronary vessels followed by medial-axis detection along the entire arterial tree for both views. In the second step, arterial trees from the two views are registered using medial-axis representation at the coarsest resolution level to obtain an initial 3-D reconstruction. This initial reconstruction at the coarsest level is then modified using 3-D geometrical a priori information. In the third step, the modified reconstruction is projected on the next higher-resolution segmented medial-axis representation and an updated reconstruction is obtained at the higher resolution. The process is iterated until the final 3-D reconstruction is obtained at the finest resolution level. Linear programming based constrained optimization method is used for registering two views at the coarse resolution. This is followed by a Tree-Search method for registering detailed branches at higher resolutions. The automated 3-D reconstruction method was evaluated on computer-simulated as well as human angiogram data. Results show that the automated 3-D reconstruction method provided good registration of computer-simulated data. On human angiogram data, the computed 3-D reconstruction matched well with manual registration.     

Towards a verifiable real-time, autonomic, fault mitigation framework for large scale real-time systems

Designing autonomic fault responses is difficult, particularly in large-scale systems, as there is no single ‘perfect’ fault mitigation response to a given failure. The design of appropriate mitigation actions depend upon the goals and state of the application and environment. Strict time deadlines in real-time systems further exacerbate this problem. Any autonomic behavior in such systems must not only be functionally correct but should also conform to properties of liveness, safety and bounded time responsiveness. This paper details a real-time fault-tolerant framework, which uses a reflex and healing architecture to provide fault mitigation capabilities for large-scale real-time systems. At the heart of this architecture is a real-time reflex engine, which has a state-based failure management logic that can respond to both event- and time-based triggers. We also present a semantic domain for verifying properties of systems, which use this framework of real-time reflex engines. Lastly, a case study, which examines the details of such an approach, is presented.     

Study of air oxidation of amorphous Zr<Subscript>65</Subscript>Cu<Subscript>17.5</Subscript>Ni<Subscript>10</Subscript>Al<Subscript>7.5</Subscript> by X-ray photoelectron spectroscopy (XPS)

The oxidation of the bulk amorphous alloy Zr₆₅Cu_17.5Ni₁₀Al_7.5 in air in its amorphous and the supercooled liquid states was studied in the temperature range 573–663 K using X-ray photoelectron spectroscopy (XPS). The oxide film mainly consisted of the oxides of Zr (as ZrO₂) and Al (as Al₂O₃). No Cu or Ni was found in the oxide film formed on the amorphous state of the alloy while significant Cu (as CuO) was present in the oxide film formed on the alloy in its supercooled liquid state. The role of the various alloying elements during oxidation at high temperatures in air is discussed in the paper. The XPS data from oxide film support the previously suggested mechanism for oxidation of this alloy, i.e. the rate controlling process during oxidation of the alloy at low temperatures (in the amorphous state) is the back-diffusion of Ni and Cu, while the oxidation at high temperatures (in the supercooled liquid state) is dominated by the inward diffusion of oxygen.     

A Process of Notch Wavy Rolling for Strengthening Metal Sheets

Wavy roll design was employed for strengthening 1 mm thin austenitic stainless steel coil sheet by cold rolling without further reduction in thickness. This steel possesses high corrosion resistance and high ductility. Initially, the sheets were rolled into sine wave shape (wave amplitude <2 mm) and then flattened using conventional cold rolling mill. Such a process cycle was repeated for four times successfully and the mechanical properties were measured after each cycle. The yield strength increased from 255 to 931 MPa with corresponding decrease in elongation from 45% to only 17% after the fourth cycle of severe cold working. Tensile strength and hardness values increased from 753 MPa and 185 HV to 973 MPa and 371 HV, respectively. The micro-to-nano-scale resolution structures, obtained by optical and atomic force microscope (AFM), were used to explain the variation in properties during this manufacturing process and to propose schematically the deformation mechanism.     

Rotary Ultrasonic Machining: A Review

Rotary ultrasonic machining (RUM) is a mechanical type of nontraditional hybrid machining process that has been utilized potentially to machine a wide range of latest and difficult-to-machine materials, including ductile, hard and brittle, ceramics, composites, etc. In RUM, the basic material removal phenomenon of ultrasonic machining (USM) and conventional diamond grinding amalgamates together and results in higher material removal rate (MRR), improved hole accuracy with superior surface finish. In the current article, several investigations carried out in the domain of RUM for enormous materials have been critically reviewed and reported. It also highlights several experimental and theoretical ensues of RUM to improve the process outcomes and it is reported that process performance can be substantially improved by making the right selection of machine, diamond tooling, material and operating parameters. In recent years, various investigators have explored umpteen ways to enhance the RUM process performance by probing the different factors that influence the quality attributes. Among the various accessible modifications in RUM as employed in industries, rotary ultrasonic drilling is more strongly established compared to other versions such as rotary ultrasonic side milling, face milling, grinding, surface texturing, etc. The micro machining applications of RUM have also been discussed briefly. The final section of this paper discusses RUM developments and outlines the aspects for future research.     

Neotectonic study of Ganga and Yamuna tear faults,NW Himalaya,using remote sensing and GIS

The Ganga and Yamuna rivers emerge from the Himalayas along two major faults known as the Ganga and Yamuna Tear Faults respectively. The two major strike-slip faults transverse to the Siwalik range are clearly seen in satellite imagery of the Dehradun area. Earthquake records, landslide and recent changes in geomorphological features indicate that the area between the Main Boundary Thrust and the Main Frontal Thrust is tectonically active. An effort has been made to study the tectonic evolution and neotectonism of the Ganga and Yamuna tear faults. Spectral and spatial enhancement techniques have been employed to the digital data of IRS-1B LISS-I to delineate the lineaments and major faults of the area. Based on Mohr's theory, failure criteria and statistical analysis of remotely sensed lineament data, horizontal compressive stress values (S_Hmax) have been estimated at various sites of the study area. These data are found to be consistent with the published S_Hmax orientation determined from earthquake focal mechanism solutions. Active faults and lineaments have been extracted from the remotely sensed lineament data. Past earthquake data and depth to basement contour data have been used in an integrated approach with available Geographic Information System (GIS) techniques to reconstruct a present-day regional geodynamic model. Attempts have been made to investigate the genesis of Ganga and Yamuna Tear Faults and possible causes of recent tectonic activities of the area with the help of the proposed geodynamic model.     

The impact of assimilation of AMSU data for the prediction of a tropical cyclone over India using a mesoscale model

Tropical cyclones form over the seas: a typical data‐sparse region for conventional observations. Therefore, satellites, especially with microwave sensors, are ideal for cyclone studies. The advanced microwave sounding unit (AMSU) , in addition to providing very valuable data over non‐precipitating cloudy regions, can provide very high horizontal resolution of the temperature and humidity soundings. Such high‐resolution microwave data can improve the poorly analysed cyclone. The objective of this study is to investigate the impact of ingesting and assimilating the AMSU data together with conventional upper air and surface meteorological observations over India on the prediction of a tropical cyclone which formed over the Arabian Sea during November 2003 using analysis nudging. The impact of assimilating the AMSU‐derived temperature and humidity vertical profiles in a mesoscale model has not been tested yet over the Indian region. Such studies are important as most weather systems over India form over the seas. The present study is unique in the sense that it addresses the impact of ingesting and assimilating microwave sounding data (together with conventional India Meteorological Department data) on the prediction of a tropical cyclone, which formed over the Arabian Sea during November 2003 using analysis nudging. Two sets of numerical experiments are designed in this study. While the first set utilizes the National Center for Environmental Prediction (NCEP) reanalysis (for the initial and lateral boundary conditions) only in the fifth‐generation mesoscale model simulation, the second set utilized the AMSU satellite and conventional meteorological upper air and surface data to provide an improved analysis through analysis nudging. The results of the two sets of model simulations are compared with one another as well as with the NCEP reanalysis and the observations.

The results of the study indicated that the impact of ingesting and assimilating microwave sounding data and the conventional meteorological data through nudging resulted in an improvement in the simulation of wind asymmetries and the warm temperature anomalies. The with‐assimilation run simulated stronger wind speeds and stronger vertical velocity motion as compared with the without‐assimilation run. The time series of the minimum sea level pressure (SLP) and maximum wind speed for the simulations with the microwave sounding data and conventional meteorological data show better agreement with the observations than the simulations without the assimilation. The central minimum pressure of the simulations with the modified analysis are lower by 7 hPa as compared with the simulations without the assimilations. Even though there is not much of a difference in the maximum wind speed between the two simulations at the initial forecast time, the results indicate that the simulations with microwave sounding data and conventional meteorological data reveal a marked (9 m/s) increase in the maximum wind speed over the simulations without the assimilation. While the lowest central pressure estimated from the satellite image is 988 hPa, the simulations with microwave sounding data and conventional meteorological data show a value of 999.5 hPa for the lowest central minimum pressure. One reason for the inability of the simulation with improved analysis to achieve the observed lowest SLP is that the NCEP reanalysis had manifested an extremely weak system in the first place and, despite assimilation with microwave sounding data and conventional meteorological data, only a moderate improvement in the lowest SLP could be achieved. A proper appreciation of the impact of the microwave sounding data can be obtained by comparing with the lowest SLP obtained from the simulation without assimilation which showed a value of 1007 hPa. The initial mis‐representation in the location of the centre of the cyclone in the NCEP reanalysis with respect to the observed location has led to marked errors in the track prediction of both the model simulations. The assimilation of microwave satellite data is yet to be implemented in the current operational regional model over India and hence the results of this study may be relevant to the operational tropical cyclone forecasting community.     

Design and Fabrication of Fiber-Optic Nanoprobes for Optical Sensing

This paper describes the design and fabrication of fiber-optic nanoprobes developed for optical detection in single living cells. It is critical to fabricate probes with well-controlled nanoapertures for optimized spatial resolution and optical transmission. The detection sensitivity of fiber-optic nanoprobe depends mainly on the extremely small excitation volume that is determined by the aperture sizes and penetration depths. We investigate the angle dependence of the aperture in shadow evaporation of the metal coating onto the tip wall. It was found that nanoaperture diameters of approximately 50 nm can be achieved using a 25° tilt angle. On the other hand, the aperture size is sensitive to the subtle change of the metal evaporation angle and could be blocked by irregular metal grains. Through focused ion beam (FIB) milling, optical nanoprobes with well-defined aperture size as small as 200 nm can be obtained. Finally, we illustrate the use of the nanoprobes by detecting a fluorescent species, benzo[a]pyrene tetrol (BPT), in single living cells. A quantitative estimation of the numbers of BPT molecules detected using fiber-optic nanoprobes for BPT solutions shows that the limit of detection was approximately 100 molecules.