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21.
Sankaraiah Subramani Sun Jong Lee Jung Min Lee Sung Wook Choi Jung Hyun Kim 《Colloids and surfaces. A, Physicochemical and engineering aspects》2009,340(1-3):40-49
A process to prepare microparticles of narrow size distribution having a particle size in the range of approximately 1–8 μm was developed. The primary objective of this work was to study the formation and morphology of copolyester microparticles prepared using a sulfonated copolyester emulsion by an emulsion–aggregation process. Molecular weight of the copolyesters was measured by gel permeation chromatography. The glass transition temperature (Tg) of the copolyesters was found to be in the range of 40–70 °C. Aggregating agents used in this study were 1–5% (wt.%) solutions of divalent ions of zinc acetate and magnesium chloride salts. Emulsion–aggregation experiments were performed at various temperatures: 40, 50, 60, and 80 °C. Particle morphologies studied by field emission-scanning electron microscopy measurements provided an understanding of the conditions and mechanism leading to formation of microparticles by the emulsion–aggregation process. Molecular weight and Tg of the copolyester, the concentration of aggregating agent, and the temperature were determined to be the most important parameters influencing the preparation of microparticles. This process illustrates the preparation of microparticles of uniform size with morphology of controlled shape from a nanometer-sized emulsion by ionic crosslinking. 相似文献
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Claudia Shah Subramani Sellappan Datta Madamwar 《Applied biochemistry and biotechnology》1997,62(2-3):183-189
α-amylase (3.2.1.1) was solubilized in reverse micelles formed by Triton X-100 in xylene. Although the enzyme shows decrease
in specific activity in reverse micellar medium, it possesses significantly high stability in comparison to bulk aqueous medium.
Water/Surfactant ratio (Wo) was found to play a crucial role in both activity and stability of the enzyme. The optimum water/surfactant
ratio for the catalytic function of an enzyme in reverse micelles is 36, while the enzyme is stable at Wo 12 for a considerably
long period, and at Wo above 20 the enzyme gets inactivated within a day. Glycerol and CaCl2 improve the stability in both aqueous and reverse micellar medium. Thus the interior of the reverse micelles acts as a microreactor
and provides favorable environment for the enzyme activity and stability. 相似文献
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Arumugam P Patra D Samanta B Agasti SS Subramani C Rotello VM 《Journal of the American Chemical Society》2008,130(31):10046-10047
Terpyridine thiol functionalized FePt and Au NPs were self-assembled and cross-linked at the liquid-liquid interfaces using Fe(II) metal ion. Complexation of terpyridine with Fe(II) metal ion leads to NP network and affords stable membranes and colloidal shells at the liquid-liquid interfaces. 相似文献
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Fault Tolerant Sorting—Theoretical and Empirical Analyses of the Randomized QuickMergesort Algorithm
K. Subramani C. Tauras David Owen 《Journal of Mathematical Modelling and Algorithms》2008,7(3):255-276
This paper introduces a new paradigm in the design of sorting algorithms, viz., fault tolerance. Fault tolerance is an important
concept in modern day computing and design workflows must accommodate this need. In general, there are a number of avenues
for faults to occur and techniques to address the same; this paper focusses on only one source of faulty behavior, viz., process
termination. Process termination, as a cause of faulty behavior, is important from the perspective of various applications
in real-time scheduling. In order to measure the effectiveness of a fault tolerant protocol, it is necessary to define a suitable
metric and analyze the performance of the protocol with respect to that metric. We measure the “unsortedness” of an array,
as characterized by the number of inversion pairs that remain when the sorting algorithm (process) terminates. This paper
proposes a new algorithm for sorting called the Randomized QuickMergesort (RQMS) algorithm. RQMS has a higher degree of fault tolerance than either Randomized Quicksort (RQS) or Mergesort (MS), in
that fewer inversion pairs remain when it terminates. Likewise, RQMS has a lower comparison overhead than RQS and is more
space-efficient than MS. Our empirical analysis, which was conducted over a wide variety of distributions, conclusively establishes
that RQMS is the algorithm of choice, when fault tolerance is paramount in the application.
This research was supported in part by the Air Force Office of Scientific Research under Contract FA9550-06-1-0050. 相似文献
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Water-dispersible blocked polyurethane dispersions (BPUD) were synthesized by prepolymer mixing process using toluene 2,4-diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), poly(tetramethylene glycol) (PTMG), dimethylol propionic acid (DMPA), and methyl ethyl ketoxime (MEKO). The particle size, viscosity, pH and storage stability of the BPUDs were studied and compared. The aqueous dispersions were characterized by FT-IR, GPC, DSC and TGA techniques. De-blocking temperatures of the BPUDs were measured and end-capped with phenylamino propyl trimethoxysilane (PAPTMS) at different de-blocking temperatures. The thermal analysis revealed that both MDI- and TDI-based BPUDs started to de-block at about 60–85 °C. The average molecular weights of the MDI-BPUDs were higher than that of the TDI-BPUDs due to the high reactivity of MDI. It was noticed that the tensile strength increased and elongation at break decreased in the silylated BPUD compared to pure BPUDs, which confirmed that the BPUDs were de-blocked and end-capped with PAPTMS. The Tg values of the silylated BPUD were higher than the BPUD and pure PTMG as well as thermal stability. Storage stability results showed that all BPUDs containing PAPTMS were stable. Water and xylene resistance tests and gel content studies confirmed that silylated PU cross-linked well after silylation of blocked PUDs. 相似文献
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G. V. S. Ashok Kumar J. Vithya R. Kumar C. R. Venkata Subramani 《Journal of Radioanalytical and Nuclear Chemistry》2014,302(2):939-945
Carrier-free 32P was produced in KAlpakkam MINI reactor (KAMINI) via 32S (n, p) 32P using its small fast flux component. This method has established the flow-sheet for the production of 32P from sulphate targets such as magnesium sulphate and strontium sulphate which can withstand high temperatures of fast reactors unlike the conventionally used sulphur powder. The chemical processing involved (i) struvite precipitation method for magnesium sulphate and (ii) co-precipitation with ferric hydroxide method for strontium sulphate. 相似文献
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Dr. Jaume Garcia‐Amorós Subramani Swaminathan Prof. Salvatore Sortino Prof. Françisco M. Raymo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(33):10276-10284
The covalent attachment of a carbazole fluorophore to an oxazine photochrome permits the reversible activation of fluorescence under optical control. Ultraviolet irradiation with a pulsed laser opens the oxazine ring to shift bathochromically the absorption of the carbazole component. Concomitant visible illumination excites selectively the carbazole fluorophore of the photochemical product to produce fluorescence. The photogenerated and fluorescent species reverts spontaneously on a submicrosecond timescale to the initial nonemissive state of the carbazole–oxazine dyad. The photochemical and photophysical properties engineered into this particular molecular switch allow the convenient monitoring of plasmonic effects on photochemical reactions with fluorescence measurements. In close proximity to silver nanoparticles, visible illumination with a continuous‐wave laser also results in fluorescence activation. The metallic nanostructures enable the two‐photon excitation of the oxazine component to induce the photochromic transformation and then facilitate the one‐photon excitation of the photochemical product to generate fluorescence. Thus, these operating principles offer the opportunity to avoid altogether the need of pulsed ultraviolet irradiation to trigger the photochromic transformation and, instead, allow fluorescence activation with a single visible source operating at low illumination power. 相似文献
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Seung Mo Lee Wonseok Cho Subramani Sankaraiah Sun Jong Lee Jung Hyun Kim In Woo Cheong 《Colloid and polymer science》2013,291(1):33-44
Poly(alkyl methacrylate)/poly(thiophene) (PAMA/PTh) core/shell nanoparticles were synthesized using a one-pot dual initiation system. A ferric chloride/hydrogen peroxide mixture and sodium vinyl sulfonate were used as an initiator couple and a reactive surfactant, respectively. In the dual initiation, process variables such as the concentration of reactive surfactant, monomer ratio, and monomer type were adjusted to control the particle size of PAMA/PTh core/shell nanoparticles from 192 to 1,172 nm. The inner structure of the core/shell nanoparticles was confirmed in their morphological transition from spherical particles to a crumpled sheath using a solvent extraction method and field-emission scanning electron microscopy. From the spectroscopic data, it was found that the UV-adsorption and fluorescent emission intensity of PAMA/PTh latexes increased with a decrease in the average particle size. The quantum efficiency of all the samples was approximately 12 % and was unaffected by the particle size. 相似文献