A Scheme for Performance Evaluations of UV–Visible Spectrophotometer by Standard Procedures Including Certified Reference Materials for the Analysis of Geological Samples

UV–Visible spectrophotometers have been used as a tool for chemical analysis over last few decades. The simplicity and ease of operation makes the instrument more reliable and convenient to use, and therefore, they find important application in many fields. In the present case, the performance evaluations of a UV–Visible spectrophotometer has been made for wavelength accuracy, stray light, resolution, photometric accuracy and photometric repeatability using Certified Reference Materials and other complimentary calibrators. The strategy adopted for the performance evaluation/calibration of the spectrophotometer were based on extensive use of different geo-standards of diverse matrices including the candidate geo-standards like Nephelinite, NKT-1, Syenite, CG-2, Limestone, ML-2 and River sediment, sdAR-1 studied recently as a part of 29th, 30th, 30Ath and 31st round of international geo-standards programmes held recently in addition to, employing a set practice of calibration being followed internationally.     

Effect of sulfonic acid-functionalized polysilsesquioxane on new semifluorinated sulfonated polytriazole composites and investigation of proton exchange membrane properties

A new semifluorinated sulfonated copolytriazole is synthesized, maintaining a particular degree of sulfonation of 80% following the click reaction of two terminal azides 1,4-bis-[{2′-trifluromethyl 4′-(4″-azidophenyl)phenoxy}]phenyl, and 4,4′-diazido-2,2′-stilbenedisulfonic acid disodium salt with equal molar amounts of two dialkyne monomers namely, 1,3-diethynylbenzene and 3,5-bis(prop-2-ynyloxy)benzoic acid and designated as PTEHCSH-80. Further, the copolytriazole is used to prepare polymer composites employing the sol-gel reaction of the starting precursor sol 3-(trihydroxylsilyl) propane-1-sulfonic acid. The weight percentage (wt%) of the filler is varied from 0 to 10 wt%, and a series of polymer composite films are prepared and abbreviated as PTEHCSH-80/X (where X is wt% of the filler, X = 0. 2.5, 5.0, 7.5, 10.0). All the polymer composites are characterized through FTIR spectroscopic techniques. The composite films revealed various desirable properties such as high thermochemical and dimensional and mechanical stabilities in their corresponding acid form. Moreover, the composites exhibited proton conductivities ranging from 62 to 98, 117 to 182, and 131 to 195 mS/cm at three different temperatures 30°C, 80°C, and 90°C, respectively, in a hydrated state.     

Electrical and mechanical properties of acrylonitrile‐butadiene‐styrene/multiwall carbon nanotube nanocomposites prepared by melt‐blending

The electrical properties in polymer/carbon nanotube (CNT) nanocomposites are governed not only by the degree of dispersion but also to a greater extent on the aspect ratio of the CNTs in the final composites. Melt‐mixing of polymer and CNTs at high shear rate usually breaks the CNTS that lowers the aspect ratio of the nanotubes. Thus, homogeneous dispersion of CNTs while retaining the aspect ratio is a major challenge in melt‐mixing. Here, we demonstrate a novel method that involves melt‐blending of acrylonitrile‐butadiene‐styrene (ABS) and in situ polymerized polystyrene (PS)/multiwalled CNT (MWCNT) nanocomposites, to prepare electrically conducting ABS/MWCNT nanocomposites with very low CNT loading than reported. The rationale behind choosing PS/MWCNT as blending component was that ABS is reported to form miscible blend with the PS. Thus, (80/20 w/w) ABS/(PS/MWCNT) nanocomposites obtained by melt‐blending showed electrical conductivity value ≈1.27 × 10^?6 S cm^?1 at MWCNT loading close to 0.64 wt %, which is quite lower than previously reported value for ABS/MWCNT system prepared via solution blending. Scanning electron microscopy and differential scanning calorimetry analysis indicated the formation of homogenous and miscible blend of ABS and PS. The high temperature (100°C) storage modulus of ABS (1298 MPa) in the nanocomposites was increased to 1696 MPa in presence of 0.64 wt % of the MWCNT. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Polyimides 6: Synthesis,characterization, and comparison of properties of novel fluorinated poly(ether imides)

Five new poly(ether imides) have been prepared on reaction with oxydiphthalic anhydride (ODA) with five different diamines: 1,4‐bis(p‐aminophenoxy‐2′‐trifluoromethyl benzyl) benzene, 4,4′‐bis(p‐aminophenoxy‐2′‐trifluoromethyl benzyl) benzene, 1,3‐bis(p‐aminophenoxy‐2′‐trifluoromethyl benzyl) benzene, 2,6‐bis(p‐aminophenoxy‐2′‐trifluoromethyl benzyl) pyridine, and 2,5‐bis(p‐aminophenoxy‐2′‐trifluoromethyl benzyl) thiophene. Synthesized polymers showed good solubility in different organic solvents. The polyimide films have low water absorption of 0.3–0.7%, low dielectric constants of 2.82–3.19 at 1 MHz, and high optical transparency at 500 nm (>73%). These polyimides showed very high thermal stability with decomposition temperatures (5% weight loss) up to 531°C in air and good isothermal stability; only 0.4% weight loss occurred at 315°C after 5 h. Transparent thin films of these polyimides exhibited tensile strength up to 147 MPa, a modulus of elasticity up to 2.51 GPa and elongation at break up to 30% depending upon the repeating unit structure. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 821–832, 2004     

Experimental and numerical investigation of capillary flow in SU8 and PDMS microchannels with integrated pillars

Microfluidic channels with integrated pillars are fabricated on SU8 and PDMS substrates to understand the capillary flow. Microscope in conjunction with high-speed camera is used to capture the meniscus front movement through these channels for ethanol and isopropyl alcohol, respectively. In parallel, numerical simulations are conducted, using volume of fluid method, to predict the capillary flow through the microchannels with different pillar diameter to height ratio, ranging from 2.19 to 8.75 and pillar diameter to pitch ratio, ranging from 1.44 to 2.6. The pillar size (diameter, pitch and height) and the physical properties of the fluid (surface tension and viscosity) are found to have significant influence on the capillary phenomena in the microchannel. The meniscus displacement is non-uniform due to the presence of pillars and the non-uniformity in meniscus displacement is observed to increase with decrease in pitch to diameter ratio. The surface area to volume ratio is observed to play major roles in the velocity of the capillary meniscus of the devices. The filling speed is observed to change more dramatically under different pillar heights upto 120 μm and the change is slow with further increase in the pillar height. The details pertaining to the fluid distribution (meniscus front shapes) are obtained from the numerical results as well as from experiments. Numerical predictions for meniscus front shapes agree well with the experimental observations for both SU8 and PDMS microchannels. It is observed that the filling time obtained experimentally matches very well with the simulated filling time. The presence of pillars creates uniform meniscus front in the microchannel for both ethanol and isopropyl alcohol. Generalized plots in terms of dimensionless variables are also presented to predict the performance parameters for the design of these microfluidic devices. The flow is observed to have a very low Capillary number, which signifies the relative importance of surface tension to viscous effects in the present study.     

Power and cost aware localized routing with guaranteed delivery in unit graph based ad hoc networks

In a localized routing algorithm, each node currently holding a message makes forwarding decision solely based on the position information about itself, its neighbors and destination. In a unit graph, two nodes can communicate if and only if the distance between them is no more than the transmission radius, which is the same for each node. This paper proposes localized routing algorithms, aimed at minimizing total power for routing a message or maximizing the total number of routing tasks that a network can perform before a partition. The algorithms are combinations of known greedy power and/or cost aware localized routing algorithms and an algorithm that guarantees delivery. A shortcut procedure is introduced in later algorithm to enhance its performance. Another improvement is to restrict the routing to nodes in a dominating set. These improvements require two‐hop knowledge at each node. The efficiency of proposed algorithms is verified experimentally by comparing their power savings, and the number of routing tasks a network can perform before a node loses all its energy, with the corresponding shortest weighted path algorithms and localized algorithms that use fixed transmission power at each node. Significant energy savings are obtained, and feasibility of applying power and cost‐aware localized schemes is demonstrated. Copyright © 2004 John Wiley & Sons, Ltd.     

In vivo comparison of atherosclerotic plaque progression with vessel wall strain and blood flow velocity in apoE−/− mice with MR microscopy at 17.6 T

Object  At present, in vivo plaque characterization in mice by MRI is typically limited to the visualization of vascular lesions with no accompanying analysis of vessel wall function. The aim of this study was to analyze the influence of atherosclerotic plaque development on the morphological and mechanical characteristics of the aortic vessel wall in a pre-clinical murine model of atherosclerosis. Materials and methods  Groups of apolipoprotein E-deficient (apoE^−/−) and C57BL/6J control mice fed a high-fat diet were monitored over a 12-week time period by high-field MRI. Multi-Slice-Multi-Spin-Echo and Phase-Contrast MRI sequences were employed to track changes to aortic vessel wall area, blood flow velocity and distensibility. Results  After 6- and 12-weeks, significant changes in vessel wall area and circumferential strain were detected in the apoE^−/− mice relative to the control animals. Blood flow velocity and intravascular lumen remained unchanged in both groups, findings that are in agreement with the theory of positive remodeling of the ascending aorta during plaque progression. Conclusion  This study has demonstrated the application of high-field MRI for characterizing the temporal progression of morphological and mechanical changes to murine aortic vasculature associated with atherosclerotic lesion development.     

Modeling product-mix planning for batches of melt under multiple objectives in a small scale iron foundry

Product-mix of castings of different types/sizes can be produced in a heat (batch of melt) if all these castings require similar raw material composition. However, inappropriate product-mix may lead to under utilization of furnace capacity or failure in timely delivery or overproduction of castings or may call for deployment of excess resources for packing of molds to enable starting of the pouring operation in time. Some objectives, again, can be conflicting in nature. This paper presents a weighted integer goal programming model for the product-mix planning, developed in the context of a small scale iron foundry. Implementation of the model is illustrated using real life data from an Indian foundry.