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51.
Reactivity of Hydroxamate Ions in Cationic Vesicular Media for the Cleavage of Carboxylate Esters
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Neha Kandpal Hitesh K. Dewangan Rekha Nagwanshi Sandeep K. Vaishanav Kallol K. Ghosh Manmohan L. Satnami 《Journal of surfactants and detergents》2017,20(2):331-340
The hydrolysis of carboxylate esters viz. p‐nitrophenyl acetate (PNPA), p‐nitrophenyl butyrate (PNPB) and p‐nitrophenyl octanoate (PNPO) in the presence of cationic vesicles of the surfactant dioctadecyldimethylammonium bromide (DODAC) by different hydroxamate ions i.e. acetohydroxamate (AHA?), benzohydroxamate (BHA?) and salicylhydroxamate (SHA?) were studied. The kinetic data was supported by spectrophotometric measurements. The effects of vesicular size on the reaction have been discussed. The differential reactivity under endo‐ and exovesicular conditions has also been evaluated. Critical vesicle concentrations (CVC) of cationic vesicular surfactants were determined from conductometric and fluorimetric measurements at 300 K. Fluorescence probe pyrene and pyrene‐1‐carboxaldehyde have been used for determination of CVC. Further, thermodynamic parameters viz. Standard Gibb's energy (?G°), enthalpy (?H°), and entropy (?S°) of vesicles has also been evaluated within a temperature range of 303.15–328.15 K. 相似文献
52.
Stearic Acid Modified Stearyl Alcohol Oleogel: Analysis of the Thermal,Mechanical and Drug Release Properties
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Indu?Yadav Uvanesh?Kasiviswanathan Chandan?Soni Suprio?R.?Paul Suraj?K.?Nayak Sai?S.?Sagiri Arfat?Anis Kunal?PalEmail author 《Journal of surfactants and detergents》2017,20(4):851-861
The present study delineates the effect of stearic acid on the properties of stearyl alcohol oleogel. Herein, a series of oleogels were prepared by mixing different proportions of fatty alcohol (Stearyl alcohol; gelator) and fatty acid (stearic acid; co‐gelator). The characterization of the oleogels was done by thermal, macro‐scale stress relaxation, drug release, and antimicrobial studies. The oleogels were formed by the self‐assembly of stearyl alcohol/stearic acid. Thermal studies indicated that the stearic acid alters the crystal morphology, polymorphic transition and rate of crystallization of stearyl alcohol. The firmness of the oleogels with higher stearic proportion was better, which was due to the formation of a rigid network structure of stearyl alcohol in the presence of stearic acid. The release of ciprofloxacin hydrochloride, model drug, from the oleogels was better from the oleogels with higher stearic acid content. The release of the drug from the oleogels was Fickian diffusion‐mediated; except the oleogel with the highest stearic acid proportion. The antimicrobial study showed that the drug loaded oleogels were able to resist the growth of Escherichia coli, model microbe. 相似文献
53.
In Vivo Delivery and Activation of Masked Fluorogenic Hydrolase Substrates by Endogenous Hydrolases in C. elegans
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Shataakshi Dube Hitesh Dube Nicole B. Green Erik M. Larsen Alex White R. Jeremy Johnson Jennifer R. Kowalski 《Chembiochem : a European journal of chemical biology》2017,18(18):1807-1813
Protein expression and localization are often studied in vivo by tagging molecules with green fluorescent protein (GFP), yet subtle changes in protein levels are not easily detected. To develop a sensitive in vivo method to amplify fluorescence signals and allow cell‐specific quantification of protein abundance changes, we sought to apply an enzyme‐activated cellular fluorescence system in vivo by delivering ester‐masked fluorophores to Caenorhabditis elegans neurons expressing porcine liver esterase (PLE). To aid uptake into sensory neuron membranes, we synthesized two novel fluorogenic hydrolase substrates with long hydrocarbon tails. Recombinant PLE activated these fluorophores in vitro. In vivo activation occurred in sensory neurons, along with potent activation in intestinal lysosomes quantifiable by imaging and microplate and partially attributable to gut esterase 1 (GES‐1) activity. These data demonstrate the promise of biorthogonal hydrolases and their fluorogenic substrates as in vivo neuronal imaging tools and for characterizing endogenous C. elegans hydrolase substrate specificities. 相似文献
54.
Tripathi S Brajpuriya R Sharma A Soni A Okram GS Chaudhari SM Shripathi T 《Journal of nanoscience and nanotechnology》2008,8(6):2955-2963
In the present paper, we have investigated structural, optical as well as electronic properties of electron beam evaporated Ge thin films having layer thicknesses ranging from ultra-thin (5 nm) to thick (200 nm). The Raman spectra show that all peaks are shifted towards lower wave number as compared to their bulk counterparts and are considered as a signature of nanostructure formation and quantum confinement effect. The Raman line exhibits transformation from nanocrystalline to microcrystalline phase with a reduction in blue shift of peak position with increase in Ge film thickness (>5 nm). Similarly, the optical absorption spectra corresponding to these films also show reduction in blue shift effect, although Ge 5 nm film shows the absorption behaviour quite different from higher thickness films. The corresponding band gap values obtained from absorption measurements are much larger than bulk Ge and are mainly attributed to the effect of quantum confinement as expected for small size particles calculated from GIXRD patterns. AFM data in each case are correlated and discussed with structural as well as optical results to support the effect of growth morphology on the above-mentioned observations. The results are further supported by photoelectron spectroscopy (PES), photoluminescence (PL) and resistivity measurements and are interpreted in terms of crystallinity and quantum confinement effect. 相似文献
55.
Advanced bearing materials for future military and commercial gas turbines are required to operate at high speeds, high temperature, and higher thrust loads. At elevated operating conditions, the bearing and gear materials must be able to operate with ultrathin oil films without suffering detrimental effects of adhesive wear. The development of materials with rolling-element fatigue and corrosion resistance properties without deterioration in adhesive wear attributes is a significant challenge. To meet those performance requirements, the forerunner, martensitic stainless steel Pyrowear 675 (AMS 5930), has been in development for aerospace bearing and gear applications. This article addresses the adhesive wear performance of three variants of Pyrowear 675 with silicon nitride ball material simulating a hybrid bearing evaluated using a WAM8 machine. Baseline testing was conducted using conventional bearing steel AISI M-50. Adhesive wear testing was conducted at a temperature of 200°C and at different contact slips (15, 30, 50, and 70%) and entraining velocities (1.3 to 10.2 m/s). Posttest specimens were analyzed by scanning electron microscopy (SEM) and auger electron spectroscopy (AES). All the hybrid material pairs demonstrated very good adhesive wear performance compared to the baseline AISI M-50–AISI M-50 pair. 相似文献
56.
In the past few years the telecommunications industry has undergone significant changes. We are rapidly evolving to a state where audio/visual and data traffic is all provided on the same networks. Telecommunication companies are investing billions of dollars in the design and maintenance of telecommunication networks to provide the users with the better quality of service that they have begun to expect. Due to their high capacity, fiber optic cables have become the medium of choice in the deployment of such new networks worldwide. Such high capacities encourage telecommunication providers to create networks that are substantially more sparse than previous copper based networks. Unfortunately, with sparsity comes vulnerability to failure. Given the dependence on the varied services offered by the modern networks, the magnitudes of the investments involved and the costs of disasters it is only logical that researchers look at problems in survivable network design as an interesting research question. There have been a number of papers that have addressed these and other related issues. In this paper we try to classify the area of survivable network design and provide a classification scheme for the same. 相似文献
57.
S. Haig Zeronian Maria K. Inglesby Ning Pan David Lin Genevieve Sun Bhavna Soni Kenneth W. Alger John D. Gibbon 《应用聚合物科学杂志》1999,71(7):1163-1173
The application of alkaline hydrolysis to study the change in the fine structure of bicomponent polyester fibers as their surface is removed progressively was explored. The samples were prepared with a poly(butylene terephthalate) (PBT) sheath and a poly(ethylene terephthalate) (PET) core. The reagent used to hydrolyze the PBT was 1M NaOH in 75/25 methanol to water since it appeared to react topochemically with the fiber. The solution reacted more rapidly with PET than with PBT. Thus, when necessary to retard the weight loss of the bicomponent fibers, after a 2‐h hydrolysis with this reagent to remove PBT, it was replaced with aqueous 1M NaOH solution containing 0.1% cetrimmonium bromide. Unlike homofil PET or PBT fibers, where alkaline attack appeared to be confined to the surface and left the residue relatively smooth, the bicomponent fiber was attacked unevenly, and penetration to the PET core occurred before all the PBT at the surface was removed. Nevertheless, most of the reaction was confined initially to the PBT sheath. The tenacity and extension at break of the PBT–PET fiber passed through a maximum as hydrolysis progressed. The fall in tenacity at high weight losses is ascribed to increasing surface defects in the fiber surface. After removal of the PBT by the hydrolysis, the birefringence of the residue became progressively higher. The synergistic effect of the PBT sheath on the properties of the PET core and the possible causes of the nonuniform hydrolysis at the PBT surface are discussed. An equation is proposed that includes an interaction parameter, which can be utilized to determine which property is affected most by the hydrolysis of a bicomponent fiber. In this instance, it appears from the parameters that the order is strength > extension at break ≈ birefringence. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1163–1173, 1999 相似文献
58.
Helen H. Lou Daniel Chen Christopher B. Martin Xianchang Li Kyuen Li Hitesh Vaid Anjan Tula Kumar Kanwar Devesh Singh 《Clean Technologies and Environmental Policy》2012,14(4):737-748
Due to the tremendous costs and difficulties associated with flare measurements, computational fluid dynamics (CFD) simulation could be a viable approach to predict the combustion efficiency as well as VOC/NO x emissions from industrial flaring activities. However, consisting of a large number of reactions and species, most of the detailed kinetic mechanisms for the speciation study of flaring events are too complicated to use in the CFD simulation of industrial-scale flares. A reduced combustion mechanism will lead to improved computational efficiency; however, its fidelity must be validated. This study uses 2D CFD simulations and 1D Chemkin simulations to validate a reduced mechanism developed for the combustion of light hydrocarbons up to C1–C3. This mechanism, consisting of 50 species and 337 reactions, is applicable to C1–C3 hydrocarbons and can be used to predict the combustion efficiency and fate of pollutants released from industrial flares composed of C1–C3 waste gases. In this article, experimental data reported in the literatures have been used to validate the reduced mechanism. The key performance indicators used for comparison are laminar burner-stabilized flames, laminar flame speeds, adiabatic flame temperatures, ignition delay tests, and temperature and concentration profiles of the critical species. The software package CHEMKIN 4.1.1 was used to verify the computational results of laminar flame speeds, adiabatic flame temperatures, and ignition delays. The axial profiles of various critical species are simulated using the commercial CFD software package FLUENT. It is demonstrated that simulation results using this reduced mechanism are in good agreement with reported experimental results. 相似文献
59.
Chirag Nagda Narendra Prabhudas Chotai Upendra Patel Sandip Patel Tejal Soni Prateek Patel 《Drug development and industrial pharmacy》2013,39(10):1155-1166
Objective: Microencapsulation of the anti-inflammatory drug aceclofenac (ACE) was investigated as a means of controlling drug release and minimizing or eliminating local side effects. Method: Microspheres were prepared by a spray-drying technique using solutions of ACE and three polymers, namely, carbopol, chitosan, and polycarbophil, in different weight ratios. Results: The spray-dried mucoadhesive microspheres were characterized in terms of shape (scanning electron microscope), size (6.60–8.40 μm), production yield (34.10–55.62%), and encapsulation efficiency (58.14–90.57%). In vitro release studies were performed in phosphate buffer (pH 6.8) up to 10 hours. The spray-drying process of solutions of ACE with polymeric blends can give prolonged drug release. The in vitro release data were well fit into Higuchi and Korsmeyer–Peppas model and followed Fickian diffusion mechanism. In vivo data showed that the administration of ACE in polymeric microspheres prevented the gastric side effects. Conclusion: The formulations here described can be proposed for the oral administration of nonsteroidal anti-inflammatory drugs with minimal side effects on gastric mucosa. 相似文献
60.
M.J. Singh M. Bandyopadhyay C. Rotti N.P. Singh Sejal Shah G. Bansal A. Gahlaut J. Soni H. Lakdawala Harshad Waghela I. Ahmed G. Roopesh U.K. Baruah A.K. Chakraborty 《Fusion Engineering and Design》2011,86(6-8):732-735
The diagnostic neutral beam (DNB) line shall be used to diagnose the He ash content in the D–T phase of the ITER machine using the charge exchange recombination spectroscopy (CXRS). Implementation of a successful DNB at ITER requires several challenges related to the production, neutralization and transport of the neutral beam over path lengths of 20.665 m, to be overcome. The delivery is aided if the above effects are tested prior to onsite commissioning. As DNB is a procurement package for INDIA, an ITER approved Indian test facility, INTF, is under construction at Institute for Plasma Research (IPR), India and is envisaged to be operational in 2015. The timeline for this facility is synchronized with the RADI, ELISE (IPP, Garching), SPIDER (RFX, Padova) in a manner that best utilization of configurational inputs available from them are incorporated in the design. This paper describes the facility in detail and discusses the experiments planned to optimise the beam transmission and testing of the beam line components using various diagnostics. 相似文献