Rapid Quantification of Low-Viscosity Acetyl-Triacylglycerols Using Electrospray Ionization Mass Spectrometry

Acetyl‐triacylglycerols (acetyl‐TAG) possess an sn‐3 acetate group, which confers useful chemical and physical properties to these unusual triacylglycerols (TAG). Current methods for quantification of acetyl‐TAG are time consuming and do not provide any information on the molecular species profile. Electrospray ionization mass spectrometry (ESI–MS)‐based methods can overcome these drawbacks. However, the ESI–MS signal intensity for TAG depends on the aliphatic chain length and unsaturation index of the molecule. Therefore response factors for different molecular species need to be determined before any quantification. The effects of the chain length and the number of double‐bonds of the sn‐1/2 acyl groups on the signal intensity for the neutral loss of short chain length sn‐3 groups were quantified using a series of synthesized sn‐3 specific structured TAG. The signal intensity for the neutral loss of the sn‐3 acyl group was found to negatively correlated with the aliphatic chain length and unsaturation index of the sn‐1/2 acyl groups. The signal intensity of the neutral loss of the sn‐3 acyl group was also negatively correlated with the size of that chain. Further, the position of the group undergoing neutral loss was also important, with the signal from an sn‐2 acyl group much lower than that from one located at sn‐3. Response factors obtained from these analyses were used to develop a method for the absolute quantification of acetyl‐TAG. The increased sensitivity of this ESI–MS‐based approach allowed successful quantification of acetyl‐TAG in various biological settings, including the products of in vitro enzyme activity assays.     

Micromechanics of spatially uniform heterogeneous media: A critical review and emerging approaches

Outside of the classical microstructural detail-free estimates of effective moduli, micromechanical analyses of macroscopically uniform heterogeneous media may be grouped into two categories based on different geometric representations of material microstructure. Analysis of periodic materials is based on the repeating unit cell (RUC) concept and the associated periodic boundary conditions. This contrasts with analysis of statistically homogeneous materials based on the representative volume element (RVE) concept and the associated homogeneous boundary conditions. In this paper, using the above classification framework we provide a critical review of the various micromechanical approaches that had evolved along different paths, and outline recent emerging trends. We begin with the basic framework for the solution of micromechanics problems independent of microstructural representation, and then clarify the often confused RVE and RUC concepts. Next, we describe classical models, including the available RVE-based models, and critically examine their limitations. This is followed by discussion of models based on the concept of microstructural periodicity. In the final part, two recent unit cell-based models, which continue to evolve, are outlined. First, a homogenization technique called finite-volume direct averaging micromechanics theory is presented as a viable and easily implemented alternative to the mainstream finite-element based asymptotic homogenization of unit cells. The recent incorporation of parametric mapping into this approach has made it competitive with the finite-element method. Then, the latest work based on locally-exact solutions of unit cell problems is described. In this approach, the interior unit cell problem is solved exactly using the elasticity approach. The exterior problem is tackled with a new variational principle that successfully overcomes the non-separable nature of the overall unit cell problem.     

Application of geographic information systems in construction safety planning

Execution schedule and 2D drawings are generally used for hazards identification in the construction safety planning process. Planner visualises 2D drawings into a 3D model and mentally links its components with the respective activities defined in the schedule to understand the execution sequence in safety planning. Sequence interpretation and accordingly the hazards identification vary with the level of experience, knowledge and individual perspective of the safety planner. Therefore, researchers suggest the use of four dimensional (4D) modelling or building information modelling (BIM) to create the simulation of construction process by linking execution schedule with the 3D model. Both however lack in the features like: generation and updating of schedule, 3D components editing, topography modelling and geospatial analysis within a single platform which is now a major requirement of the construction industry. This work facilitates 4D modelling, geospatial analysis and topography modelling in the development of safe execution sequence by using geographic information systems (GIS), both 3D model along with its surrounding topography and schedule were developed and linked together within the same environment. During safety review process if planned sequence results a hazard situation, it may be corrected within the GIS itself before actual implementation. Paper also discusses the use of GIS in the development of safety database from which safety information are retrieved and linked with the activities of the schedule or components of a building model. 4D modelling along with topographical conditions and safety database in a single environment assist safety planner in examining what safety measures are required when, where and why. Developed methodology was tested on a real life project in India, lessons learned from the implementation have been discussed in the potential benefits and limitations section. At last, paper highlights major research areas for further improvements.     

Raman Study of Hi-Nicalon-Fiber-Reinforced Celsian Composites: II, Residual Stress in Fibers

Band shifts in Raman spectra were used to assess, on a microscopic scale, the residual strain existing in Hi-Nicalon silicon carbide fibers reinforcing celsian-matrix composites. Uncoated as well as p-BN/SiC-coated and p-B(Si)N/SiC-coated Hi-Nicalon fibers were used as the reinforcements. We unambiguously conclude that the fibers were in a state of compressive residual stress. Quantitative determination of the residual stress was made possible by taking into account the heating induced by laser probing and by using a reference line, of fixed wavenumber. We found fiber compressive residual stress values between 110 and 960 MPa, depending on the fiber/matrix coating in the composite. A stress relaxation-like phenomenon was observed at the surface of p-BN/SiC-coated Hi-Nicalon fibers whereas the uncoated or p-B(Si)N/SiC-coated Hi-Nicalon fibers did not show any stress relaxation in the celsian-matrix composites.     

An intelligent traffic control system using RFID

Vehicular traffic control at road crossings has always been a matter of concern for administrations in many modern cities around the world. Several attempts have been made to design efficient automated systems to solve this problem. Most of the present day systems use predetermined timing circuits to operate traffic signals, which are not very efficient because they do not operate according to the current volume of traffic at the crossing. It is often seen in today's automated traffic control systems that vehicles have to wait at a road crossing even though there is little or no traffic in the other direction. There are other problems as well, such as ambulances getting caught up by a red traffic signal and wasting valuable time. Congestion is often translated into lost time, missed opportunities, lost worker productivity, delivery delay, and a general increased cost.     

Spent fuel reprocessing: A vital link in Indian nuclear power program

The success of the three stage Indian nuclear energy program is inter-linked with the establishment of an efficient closed fuel cycle approach with recycling of both fissile and fertile components of the spent fuel to appropriate reactor systems. The Indian reprocessing journey was started way back in 1964 with the commissioning of a plant based on PUREX technology to reprocess aluminum clad natural uranium spent fuel from the research reactor CIRUS. After achieving the basic skills, a power reactor reprocessing facility was built to reprocess spent fuel from power reactors. Adequate design and operating experience was gained from these two plants for mastering the reprocessing technology. The first plant, being the maiden venture, based on indigenous technology had to undergo many modifications during its operation and finally needed refurbishment for continued operation. Decommissioning and decontamination of this plant was carried out meticulously to allow unrestricted access to the cells for fresh installation. A third plant was built for power reactor spent fuel reprocessing to serve as a design standard for future plants with the involvement of industry. Over the years, spent fuel reprocessing based on PUREX technology has reached a matured status and can be safely deployed to meet the additional reprocessing requirements to cater to the expanding nuclear energy program. Side by side with the developments in the spent natural uranium fuel reprocessing, irradiated thoria reprocessing is also perused to develop THOREX into a robust process. The additional challenges in this domain are being addressed to evolve appropriate technological solutions. Advancements in the field of science and technology are being absorbed to meet the challenges of higher recovery combined with reduced exposure and environmental discharges.     

Surface characteristics and surface behaviour of polymer carbons—II: Adsorption of water vapor

The water adsorption isotherms of polymer carbons obtained on carbonizing different precursor materials (viz. polyfurfuryl alcohol (PF), polyvinylidene chloride (PVDC), polyvinyl chloride (PVC), urea formaldehyde resin (UF) and Saran), and having different porosities and associated with varying amounts of oxygenindicate that the adsorption at lower relative vapor pressures (< 0.5) is largely governed by the amount of oxygen associated with different functional groups attached to individual carbon atoms forming the walls of the micropores. The amount of water vapor adsorbed increases with increase in the amount of associated oxygen and vice-versa. In the region of medium relative vapor pressure the steep rise in the adsorption isotherm is not due to the coalescence of discrete islands of adsorbed water but to the filling up of pores by capillary condensation at least in those samples which are porous in nature. In the case of PF, PVDC and Saran chars because of the presence of sufficiently wide pores, capillary condensation plays a significant role. The shape of the isotherms in the case of PVC and UF chars indicates that they are less porous and have pores which are too narrow for capillary condensation to occur.     

Fundamental Limits of Organic Packages and Boards and the Need for Novel Ceramic Boards for Next Generation Electronic Packaging

The system-on-a-package (SOP) paradigm proposes a package level integration of digital, RF/analog and opto-electronic functions to address future convergent microsystems. Two major components of SOP fabrication are sequential build-up of multiple layers (4–8) of conducting copper patterns with interlayer dielectrics on a board and multiple ICs flip-chip bonded on the top layer. A wide range of passives, wave-guides and other RF and opto-electronic components buried within the dielectric layers provide the multiple functions on a single microminiaturized platform.The routing of future nanoscale ICs with 10,000+ I/Os require multiple build-up layers of ultra fine board feature sizes of 10 m lines/space widths and 40 m pad diameters. Current FR4 boards cannot achieve this build-up technology because of dimensional instability during processing. These boards also undergo high warpage during the sequential build-up process which limits the fine-line lithography and also causes misalignment between the vias and their corresponding landing pads. In addition, the CTE mismatch between the silicon die and the board leads to IC-package interconnect reliability concerns, particularly in future fine-pitch assemblies where underfilling becomes complicated and expensive.This work reports experimental and analytical work comparing the performance of organic and novel ceramic boards for SOP requirements. The property requirements as deduced from these results indicate that a high stiffness and tailorable CTE from 2–4 ppm/C is required to enable SOP microminiaturized board fabrication and assembly without underfill. A novel ceramic board technology is proposed to address these requirements.