Vacuum-ultraviolet (VUV) irradiation (kexc: 172 ± 12 nm) of polystyrene films in the presence of oxygen
produced not only oxidatively functionalized surfaces, but generated also morphological changes.
Whereas OH- and C=O-functionalized surfaces might be used for e.g. secondary functionalization,
enhanced aggregation or printing, processes leading to morphological changes open new possibilities of
microstructurization. Series of experiments made under different experimental conditions brought
evidence of two different reaction pathways: introduction of OH- and C=O-groups at the polystyrene
pathways is mainly due to the reaction of reactive oxygen species (hydroxyl radicals, atomic oxygen,
ozone) produced in the gas phase between the VUV-radiation source and the substrate. However,
oxidative fragmentation leading to morphological changes, oxidation products of low molecular weight
and eventually to mineralization of the organic substrate is initiated by electronic excitation of the
polymer leading to C–C-bond homolysis and to a complex oxidation manifold after trapping of the
C-centred radicals by molecular oxygen. The pathways of oxidative functionalization or fragmentation
could be differentiated by FTIR-ATR analysis of irradiated polystyrene surfaces before and after
washing with acetonitrile and microscopic fluorescence analysis of the surfaces secondarily
functionalized with the N,N,N-tridodecyl-triaza-triangulenium (TATA) cation. Ozonization of the
polystyrene leads to oxidative functionalization of the polymer surface but cannot initiate the
fragmentation of the polymer backbone. Oxidative fragmentation is initiated by electronic excitation of
the polymer (contact-mode AFM analysis), and evidence of the generation of intermediate C-centred
radicals is given e.g. by experiments in the absence of oxygen leading to cross-linking (solubility effects,
optical microscopy, friction-mode AFM) and disproportionation (fluorescence).
Vanadia/ceria catalysts (2–10 wt% of V2O5) were prepared by wet impregnation of ammonium metavanadate in oxalic acid solution. Structural characterization was done with energy dispersive X-ray analysis (EDX), powder X-ray diffraction (XRD), BET surface area measurements, FT-IR spectroscopy and nuclear magnetic spectral analysis (51V MASNMR). XRD and 51V MASNMR results show highly dispersed vanadia species at lower loadings and the formation of CeVO4 phase at higher V2O5 loading. The catalytic activity of catalysts was conducted in liquid phase oxidation of ethylbenzene with H2O2 as oxidant. The oxidation activity is increased with loading up to 8 wt% V2O5 and then decreased with further increase in V2O5 content to 10 wt%. Different vanadia species evidenced by various techniques were found to be selective towards ethylbenzene oxidation. The CeVO4 formation associated with increased concentration of vanadia on ceria results the production of acetophenone along with 2-hydroxyacetophenone.
Hyunkieu,Yang; Sangseol,Lee(Microwave and Optical Technology Letters, December 5, 2001)
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Abstract:
The cutoff wavenumbers of higher order modes in circular
eccentric guides are computed with the variational analysis combined
with a conformal mapping. A conformal mapping is applied to the
variational formulation, and the variational equation is solved by the
finite-element method. Numerical results for TE and TM cutoff
wavenumbers are presented for different distances between the centers
and ratio of the radii. Comparisons with numerical results found in the
literature validate the presented method
Madhusoodana Kurup, B; Thomas, Joice V; Sreedevi, C(Indian Journal of Marine Sciences, September , 2006)
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Abstract:
Variations of the infaunal polychates populations due to bottom trawling were studied during December 2000 to November 2002 at depth ranging from 0-50 m along Cochin-Munambam area (Kerala, long. 76degree10'94" to 75degree 56' and lat.9degree58' to 10degree10'), in the southwest coast of India.Infaunal polychaetes from the sediment samples were collected both before and after experimental trawling in order to assess the variations on their abundance (no.m-2),biomass(g.m-2) and diversity due to bottom trawling .Highest variations in polychaetes were recorded at station 9 in May 2002 where polychaete abundance increased to 20710 no.m-2 after trawling from 2787 no.m-2 before trawling.Biomass showed highest variations at station 3 in December 2000 where biomass increased from 7.16g.m-2 recorded before trawling to 34.53 g.m-2 in the samples collected after trawling .Multivariate community analysis carried out based on both species abundance and biomass of plychaetes also confirm the wide variations in the similarities of the stations comparing both before and after trawling
V P N Nampoori; Litty, Irimpan; Radhakrishnan, P(Journal of Applied Physics, American Institute of Physics,, 2008)
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Abstract:
We describe the structure of luminescence spectrum in the visible region in nano-ZnO in colloidal
and thin film forms under weak confinement regime by modeling the transition from excited state
energy levels of excitons to their ground state. Measurements on nanocrystallites indicate the
presence of luminescence due to excitonic emissions when excited with 255 nm. The relevant
energy levels showing the transitions corresponding to the observed peaks in the emission spectrum
of ZnO of particle size 18 nm are identified.
Manju, Kurian; Sugunan, S(Elsevier, January , 2006)
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Abstract:
Wet peroxide oxidation (WPO) of phenol is an effective means for the production of diphenols, which are of great industrial importance. An added advantage of this method is the removal of phenol from wastewater effluents. Hydroxylation of phenol occurs efficiently over mixed iron aluminium pillared montmorillonites. An initial induction period is noticed in all cases. A thorough study on the reaction variables suggests free radical mechanism for the reaction.
Manjusha,M; Bright Singh,I S(School of Environmental Studies,Faculty of Marine Sciences, 2003)
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Abstract:
The present study is the first comprehensive approach towards histopathology of White Spot Syndrome Virus (WSSV) in Penaeus indicus. WSSV could be demonstrated in the nuclei of all tissues, except those of midgut, subjected of electron microscopic observation. They were the nuclei of gill, foregut, heart, hepatopancreatic connective tissue, hindgut, nerve and dorsal aorta. A comparison was made between the electron microscopic and histopathological observations and a greater degree of correlation between the two in depicting the severity of the infection of the infection was unraveled. The study also illustrated variations in response and susceptibility of various tissues to WSSV infection. Accordingly, out of the tissues investigated, gill, foregut, hindgut and dorsal aorta exhibited advanced viral multiplication than the other tissues such as heart, midgut, nerve and hepatopancreas. Even though hepatocytes were not infected the connective tissue nuclei were packed with virions.
Lethakumari,B; Sreedevi,Menon K; Priya,Francis; Aanandan,C K; Mohanan,P(Microwave and Optical Technology Letters, January 20, 2005)
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Abstract:
In this paper, we introduce a novel feeding technique for
bandwidth enhancement of a rectangular microstrip antenna This antenna
offers an impedance bandwidth of 22% without degrading the effciencv.
The effect of the feed parameters upon patch characteristics
such as resonant frequency, impedance bandwidth, and radiation pattern are studied in detail. The experimental results are verified using the
FDTD results
Sreedevi,Menon K; Lethakumary,B; Mohanan,P; Bijumon,P V; Sebastian,M T(Microwave and Optical Technology Letters, August 20, 2004)
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Abstract:
A broadband cylindrical dielectric resonator antenna
(DRA) energized with an L-strip feed is presented The novel exciting
technique achieves a 2:1 VSWR bandwidth of 18%. The variation of
bandwidth for different feed parameters is also studied
The design and development of an L-band printed dipole antenna.
optimized for wide-band applications near first resonance, is reported.
This design has achieved more than 48% impedance bandwidth
(VSWR 2:1), without degrading its overall radiation efficiency
Sarin, V P; Nisha, Nassar; Deepu, V; Aanandan, C K; Mohanan, P; Vasudevan, K(Antennas and Wireless Propagation Letters, IEEE, 2009)
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Abstract:
A simple electromagnetically coupled wideband printed microstrip antenna having a 2:1 VSWR bandwidth of 38% covering the 5.2/5.8-GHz WLAN, HIPERLAN2, and HiSWANa communication bands is presented. The large bandwidth is obtained by adding a rectangular metal strip on a slotted square microstrip antenna. The antenna occupies an overall dimension of 42 times 55 times 3.2 mm3 when printed on a substrate of dielectric constant 4. It exhibits good radiation characteristics and moderate gain in the entire operating band. Details of the design along with experimental and simulation results are presented and discussed.