The enthalpy change (303 K) for the standard state solid phase complexation reaction is derived using conventional solution calorimetric techniques (ΔH°R=?82.7±2.0 kJ mol?1. Knowlege of ΔH°R is a necessary pre-requisite for the future derivation of the FeS thermochemical bond energy. 相似文献
Acrylic-based asymmetric and variable couplers have been developed using a single structured Y-branch design with a high-index-contrast
waveguide taper and a void structure for fiber attenuation using the lateral displacement of two fibers. Device fabrication
is performed by producing the device structure on an acrylic block using a computer numerical control (CNC) machine tool.
The fabricated device has an excess loss of 5.85 dB, while the coupling ratios are 56.86 and 43.14% when the device is operated
as a 3 dB coupler. In the asymmetric coupler mode, the coupling ratio ranges from 44.84 to 8.01% for port 1 and 55.16 to 91.99%
for port 2. The excess loss of this device varies from 5.42 to 7.64 dB. In the variable coupler mode, the coupling ratio ranges
from 10.09 to 32.88% for port 1 and from 89.91 to 67.12% for port 2. The excess loss of the device varies from 5.85 to 8.49
dB. 相似文献
We proposed a simple low-cost acrylic and metal-based Y-branch plastic optical fiber (POF) splitter which utilizes a low cost
optical polymer glue NOA63 as the main waveguiding medium at the waveguide taper region. The device is composed of three sections:
an input POF waveguide, a middle waveguide taper region and output POF waveguides. A desktop high speed CNC engraver is utilized
to produce the mold inserts used for the optical devices. Short POF fibers are inserted into the engraved slots at the input
and output ports. UV curable optical polymer glue NOA63 is injected into the waveguide taper region and cured. The assembling
is completed when the top plate is positioned to enclose the device structure and connecting screws are secured. Both POF
splitters have an average insertion loss of 7.8 dB, coupling ratio of 55: 45 and 57: 43 for the acrylic and metal-based splitters
respectively. The devices have excess loss of 4.82 and 4.73 dB for the acrylic and metal-based splitters respectively. 相似文献
Four different lipases were compared for ultrasound-mediated synthesis of the biodegradable copolymer poly-4-hydroxybutyrate-co-6-hydroxyhexanoate. The copolymerization was carried out in chloroform. Of the enzymes tested, Novozym 435 exhibited the highest copolymerization rate, in fact the reaction rate was observed to increase with about 26-fold from 30 to 50 °C (7.9 × 10?3 M s?1), sonic power intensity of 2.6 × 103 W m?2 and dissipated energy of 130.4 J ml?1. Copolymerization rates with the Candida antarctica lipase A, Candida rugosa lipase, and Lecitase Ultra? were lower at 2.4 × 10?4, 1.3 × 10?4 and 3.5 × 10?4 M s?1, respectively. The catalytic efficiency depended on the enzyme. The efficiency ranged from 4.15 × 10?3 s?1 M?1 for Novozym 435–1.48 × 10?3 s?1 M?1 for C. rugosa lipase. Depending on the enzyme and sonication intensity, the monomer conversion ranged from 8.2% to 48.5%. The sonication power, time and temperature were found to affect the rate of copolymerization. Increasing sonication power intensity from 1.9 × 103 to 4.5 × 103 W m?2 resulted in an increased in acoustic pressure (Pa) from 3.7 × 108 to 5.7 × 108 N m?2 almost 2.4–3.7 times greater than the acoustic pressure (1.5 × 108 N m?2) that is required to cause cavitation in water. A corresponding acoustic particle acceleration (a) of 9.6 × 103–1.5 × 104 m s?2 was calculated i.e. approximately 984–1500 times greater than under the action of gravity. 相似文献
Thermoanalytical data (TG/DTA) have been obtained for bis-monoethanoldithiocarbamato nickel(II) and bis-diethanoldithiocarbamato nickel(II) and copper(II) complexes. A thermal decomposition mechanism is proposed for bis-monoethanoldithiocarbamato nickel(II). 相似文献
An acrylic-based Y-branch plastic optical fiber (POF) with a middle suspended waveguide taper has been developed. The suspended
high index contrast waveguide taper structure has been designed in such a way that it is surrounded by air-cladding. Non-sequential
ray tracing has been performed on the device giving an insertion loss of 4.68 dB and coupling ratio of 50: 50. The middle
waveguide taper is constructed on the acrylic block itself without using any additional optical waveguiding medium injected
into the engraved taper region. Fabrication of the devices is done by producing the device structures on an acrylic block
using high speed computer numerical control (CNC) machining tool. Input and output POF fibers are inserted into this device
structure in such a way that they are passively aligned to the middle waveguide taper structure. The device shows an insertion
loss of 5.9 dB, excess loss of 2.9 dB and a splitting ratio of 50: 50. 相似文献
Medium-chain-length poly(3-hydoxyalkanoates) (mcl-PHA), comprising six to fourteen carbon-chain-length monomers, are natural thermoplastic polyesters synthesized by fluorescent pseudomonades. In this study, mcl-PHA was produced by Pseudomonas putida from oleic acid in aerobic shake flask fermentation. Thermal degradation of mcl-PHA was performed at temperatures in the range of 160-180 °C. Thermodynamic parameters of mcl-PHA thermal degradation were determined where degradation activation energy, Ed and pre-exponential factor, A equal to 85.3 kJ mol−1 and 6.07 × 105 s−1, respectively; and exhibited a negative activation entropy (?S) of −139.4 J K−1 mol−1. Titration was carried out to determine the carboxylic terminal concentration and used to correlate number-average molecular weight (Mn) of the polymers. Thermally-degraded PHA contained higher amount of carboxylic terminals and lower Mn compared to the initial PHA and these results coincide with the decreased Mn in GPC analysis. Thermal properties of initial and degraded mcl-PHA were characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The thermal decomposition mechanism was investigated following the analyses of the degradation products using 400-MHz 1H NMR, FTIR spectroscopy and GC analysis. The overall decomposition reaction is the hydrolysis of ester linkages to produce hydroxyl and carboxylic terminals. A small proportion of unsaturated side chain fragments would undergo oxidative cleavage at CC linkages, producing minor amount of low-molecular weight esters and acids. At higher temperatures, the hydroxyl terminal can undergo dehydration to form an alkenyl terminal. 相似文献
Ultrasonic irradiation greatly improved the Candida antarctica lipase B mediated ring opening polymerization of ε-caprolactone to poly-6-hydroxyhexanoate in the ionic liquid 1-ethyl-3-methylimidazolium tetraflouroborate. Compared to the conventional nonsonicated reaction, sonication improved the monomer conversion by 63% and afforded a polymer product of a narrower molecular weight distribution and a higher degree of crystallinity. Under sonication, the polydispersity index of the product was ∼1.44 compared to a value of ∼2.55 for the product of the conventional reaction. With sonication, nearly 75% of the monomer was converted to product, but the conversion was only ∼16% for the reaction carried out conventionally. Compared to conventional operation, sonication enhanced the rate of polymer propagation by >2-fold and the turnover number of the lipase by >3-fold. 相似文献
Polymeric nanoparticles gain a widespread interest in food and pharmaceutical industries as delivery systems that encapsulate, protect, and release lipophilic compounds such as omega-3 fatty acids, fat-soluble vitamins, carotenoids, carvedilol, cyclosporine, and ketoprofen. In this study, medium-chain-length poly-3-hydroxyalkanoate (mcl-PHA)-incorporated nanoparticle was developed via facile organic solvent-free nanoemulsion templating technique. The water content (W/surfactant-to-oil (S/O)), S/O, and Cremophor EL-to-Span 80 (Cremo/Sp80) ratios were first optimized using response surface methodology (RSM) to obtain nanoemulsion template prior to incorporation of mcl-PHA. Their effects on nanoemulsion formation were investigated. The mcl-PHA-incorporated nanoparticle system showed a good preservation capability of β-carotene and extended storage stability. 相似文献
We proposed a simple low-cost acrylic and metal-based Y-branch plastic optical fiber (POF) splitter which utilizes a low cost optical polymer glue NOA63 as the main waveguiding medium at the waveguide taper region. The device is composed of three sections: an input POF waveguide, a middle waveguide taper region and output POF waveguides. A desktop high speed CNC engraver is utilized to produce the mold inserts used for the optical devices. Short POF fibers are inserted into the engraved slots at the input and output ports. UV curable optical polymer glue NOA63 is injected into the waveguide taper region and cured. The assembling is completed when the top plate is positioned to enclose the device structure and connecting screws are secured. Both POF splitters have an average insertion loss of 7.8 dB, coupling ratio of 55: 45 and 57: 43 for the acrylic and metal-based splitters respectively. The devices have excess loss of 4.82 and 4.73 dB for the acrylic and metal-based splitters respectively. 相似文献