Dimethylacetals of ketones; cyclohexanone, acetophenone,
and benzophenone have been prepared by reacting
ketones with methanol under mild reaction conditions.
Large pore zeolites (H-Y and its rare earth metal, Ce3+, La3+,
and RE3+ modified forms), and mesoporous clay (K-10
montmorillonite and its cerium exchanged counterpart) with
regular pore structure, silica and silica-alumina have been
used as catalysts. Clay catalysts are found to be much more
active than zeolites, thanks to slightly bigger pore size. The
nature of the pores of the solid acid catalysts determine acetalization
efficiency of a particular catalyst. As evidenced
by the reaction time studies, the catalyst decay is greater
over the zeolites than over the clays. Carrying out the reaction
with ketones of different molecular sizes it is shown
that K-10 clays and rare earth exchanged H-Y zeolites are
promising environmentally friendly catalysts for their use in
the production fine chemicals.
Three enzymes, α-amylase, glucoamylase and invertase, were immobilized on acid activated montmorillonite K 10 via two independent techniques, adsorption and covalent binding. The immobilized enzymes were characterized by XRD, N2 adsorption measurements and 27Al MAS-NMR spectroscopy. The XRD patterns showed that all enzymes were intercalated into the clay inter-layer space. The entire protein backbone was situated at the periphery of the clay matrix. Intercalation occurred through the side chains of the amino acid residues. A decrease in surface area and pore volume upon immobilization supported this observation. The extent of intercalation was greater for the covalently bound systems. NMR data showed that tetrahedral Al species were involved during enzyme adsorption whereas octahedral Al was involved during covalent binding. The immobilized enzymes demonstrated enhanced storage stability. While the free enzymes lost all activity within a period of 10 days, the immobilized forms retained appreciable activity even after 30 days of storage. Reusability also improved upon immobilization. Here again, covalently bound enzymes exhibited better characteristics than their adsorbed counterparts. The immobilized enzymes could be successfully used continuously in the packed bed reactor for about 96 hours without much loss in activity. Immobilized glucoamylase demonstrated the best results.
Sugunan, S; Anto, Paul(Indian Journal of Chemistry, December , 1997)
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Abstract:
The surface acidity and basicity of mixed oxides of Zr and Y
and their mixed oxides have been determined by titration method
using Hammett indicators. The acid base properties are evaluated
on a common scale of acid strength. Liquid phase reduction of
cyclohexanone has been selected as a model reaction to correlate
catalytic activity.
Sugunan, S; Rani, G D; Unnikrishnan, P A(J. Mater. Sci. Technol., 1994)
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Abstract:
The electron donor properties of Pr6O11 activated at 300. 500 and 800°C are reported from the studies
on adsorption of electron acceptors of various electron affinity (7. 7, 8, 8-tetracyanoquinodimethane.
2, 3. 5, 6-tetrachloro-l, 4-benzoquin one. p-dinitrobenzene. and
m-dinitrobenzene) in three solvents (acetonitrile, 1,4-dioxan and ethyl acetate). The extent of electron
transfer during adsorption is understood from magnetic measurements and ESR spectral data. The corresponding
data on mixed oxides of Pr and Al are reported for various compositions, The acid / base
properties of these oxides are determined using a set of Hammett indicators.
Sugunan, S; Chemparathy, G V; Anto, Paul(Indian Journal of Engineering & Materials Sciences, 1996)
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Abstract:
The surface acidity and basicity of binary oxides of Zr with Ce and La are determined using a series of Hammet indicators and Ho,,max values are reported. The generation of new acid sites habe been ascribed to the charge imbalance of M1-O-M2 bonds, where M1 and M2 are metal atoms. Both Bronsted and Lewis acid sites contribute to the acidity of the oxides
Sugunan, S; Devika Rani, G(Journal of Materials Science Letters, 1993)
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Abstract:
The electron donor properties of Nd2O3 activated at 300, 500 and 800°C were investigated
through studies on the adsorption of electron acceptors of various electron affinities - 7, 7, 8,8-tetracyanoquinodimethane (2.84 eV). 2, 3, 5, 6-tetrachloro-l , 4-benzoquinone (2.40 eV).
p-dinitrobenzene (1.77 eV), and m-dinitrobenzene (1.26 eV) in solvents acetonitrile and
1, 4-dioxan. The extent of electron transfer during adsorption has been found from magnetic
measurements and electronic spectral data. The corresponding data on mixed oxides of
neodymium and aluminium are reported for various. compositions. The acid-base properties of
catalysts were also determined using a set of Hammett indicators.
Sugunan, S; Nisha, K; Rekha, R; Rahna, K S; Suja, H; Deepa, C S(Indian Journal of Chemistry, July , 2000)
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Abstract:
The pillared montmorillonite has been prepared by exchanging
Na+ in the interlayer of montmorillonite with Al hydroxy cation followed
by calcination. Pillared clays are also prepared after exchanging
Na' ions with Ce, La, Sm-ions and then pillarcd with aluminium
oxides, The surface characterisation of the prepared catalysts has been
done using XRD and surface area measurements. To probe the acidic
property of the system, temperature programmed desorption (TPD)
of NH, has been done. Toluene alkylation by benzyl chloride has
been carried out for the evaluation of catalytic activity. The most
active system is found to be mixed Al/Zr pillarcd montrnorillonite.
Sugunan, S; Bindhu, Jacob(Indian Journal of Chemistry, October , 1999)
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Abstract:
The acidity of the various rare-earth exchanged zeolite-Y
catalysts has been examined by titration method using Hammett
indicators and is correlated with the catalytic activity of the
samples in the benzylation of 0-xylene.
Surface acidity/Basicity of mixed oxides of La and Zn activated at three different temperatures were determined. The data have been correlated with the catalytic activity for liquid phase reduction of cyclohexanone in isopropanol.
Sugunan, S; Seena, C R K(Indian Journal of Chemistry, September , 1999)
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Abstract:
The surface acidity/ basicity of TiO2 (rutile) and its sulphate modified
form have been determined by titration method using Hammett
indicators after activation at different temperatures. The electron
donating properties of these oxides are also studied from the adsorption
of electron acceptors of different electron affinity values. The
data have been correlated with the catalytic activity of these oxides
towards esterification of acetic acid using n-butanol, reduction of
cyclohexanone in isopropanol and oxidation of cyclohexanol in benzophenone.
Catalytic activity for esterification and oxidation reaction
parallels the acidity while that for reduction reaction parallels
the basicity of these oxides.
Sugunan, S; Seena, C R Kumaree(Indian Journal of Chemistry, November , 1999)
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Abstract:
The changes in surface acidity/basicity and catalytic activity of cerium oxide due to surface modification by sulphate ion have been
investigated. Electron donor properties of both the modified and unmodified oxides have been studied using electron acceptors of
various electron affinity values, viz. 7,7,8,8-tetracyanoquinodimethane, 2,3,5,6-tetrachloro--l, 4-benzoquinone. p-dinitrobenzene and
m-dinitrobenzene in order to find out whether the increase in acidity on suphation is due to the generation of new acidic sites or they are
formed at the expense of some of the basic sites. The surface acidity/basicity has been determined using a set of Hammett indicators.
The data have been correlated with the catalytic activity of the oxides for esterification of acetic acid using l-butanol, reduction of
cyclohexanone with 2- propanol and oxidation of cyclohexanol using benzophenone.
Sugunan, S; Kumaree Seena, C R(Indian Journal of Chemistry, August , 1998)
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Abstract:
The surface electron donor properties of sulphate modified stannic oxide have been determined from the
adsorption of electron acceptors of various electron affinities on the oxide surface. The acid base properties of
stannic oxide have been determined by titration method using Hammett indicators. Catalytic activities of the
oxide for esterification of acetic acid using n-butanol.reduction of cyclohexanone in 2-propanol and oxidation of
cyclohexanol with benzophenone have been studied. The data have been correlated with the surface electron
donor properties of these oxides. The activity for reduction and oxidation decreases and that for esterification
reaction increases on modification with sulphate ion. It has heen found that electron donating capacity decreased
when stannic oxide was modified with sulphate ion.
Description:
Note:Indian Journal of Chemistry
Vol. 37A, August 1998, pp. 669 - 673
Sunil K Narayanankutty(John Wiley & Sons. Inc., June 21, 2001)
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Abstract:
The effect of diphenylmethane diisocyanate
(MDI) -polyethyleneglycol (PEG) resin on the cure characteristics and mechanical
properties of nitrile rubber/whole tyre eclaim-short nylon fiber
composite-was studied. At a constant loading of 5 phr, the resin composition
was varied. The minimum torque .,id (maximum - minimum) torque increased
with isocyanate concentration. Scorch time and cure time showed a reduction on
introduction of bonding agent. Properties like tensile strength, tear strength, and
abrasion resistance increased with increase in MDI/PEG ratio, and these
properties are higher in the longitudinal direction of fiber orientation.
Compression set increased with isocyanate concentration and the resilience
remain unchanged.
Deepu, V; Sujith, R; Mridula, S; Aanandan, C K; Vasudevan, K; Mohanan, P(Wiley InterScience, August , 2009)
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Abstract:
An asymmetric coplanar strip (ACS) fed dual band F-shaped antenna covering the 2.4/5.2 GHz WLAN bands is presented. The optimized dimensions of the proposed uniplanar antenna are 21 mm × 19 mm when printed on a substrate of dielectric constant 4.4 and height 1.6 mm. The dual band nature of the antenna is brought about by the various current paths in the F-shaped structure and the ground plane. The antenna exhibits nearly omnidirectional radiation characteristics and moderate gain in both the operating bands. Details of the antenna design, simulation, and experimental results are presented and discussed.
Virinder,Moudgil; Vera,Kruczak; Thomas,Eessalu; Paulose,C S; Michael,Taylor; Jeffrey,Hansen(Department of Biotechnology, May 14, 1981)
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Abstract:
Progesterone-receptor complex from freshly prepared hen oviduct cytosol acquired the ability to bind to
isolated nuclei, DNA-cellulose and ATP-Sepharose when incubated with 5-10 mM ATP at 4°C. The extent of
this ATP-dependent activation was higher when compared with heat-activation achieved by warming the progesterone-
receptor complex at 23 °C. The transformation of progesterone-receptor complex which occurred in a
time-dependent manner was only partially dependent on hormone presence. The ATP effect was selective in
causing this transformation whereas ADP, AMP and cAMP failed to show any such effect. The non-hydrolizable
analogs of ATP, adenosine 5'-[a,/3-methylene]triphosphate and adenosine 5-[/l,y-imido]triphosphate were also
found to be ineffective. Presence of 10 mM sodium molybdate blocked both the ATP and the heat-activation of
progesterone-receptor complex. Mn" or Mg` had no detectable effect on the receptor activation but the presence
of Ca" increased the extent of ATP-activation slightly. EDTA presence (> 5 mM) decreased the extent of
receptor activation by about 40 % and was, therefore, not included in the buffers used for activation studies.
Divalent cations were also ineffective when tested in the presence of 1- 5 mM EDTA. The
properties of progesterone-receptor complex remained intact under the above conditions when analyzed for
steroid-binding specificity and Scatchard analysis. However, the ATP-activated progesterone-receptor complex
lost the ability to aggregate when tested on low-salt sucrose gradients. ATP was equally effective in activating
the rat-uterine estradiol-receptor complex at 4 "C and influenced the transformation of 4-S receptor form into
a 5-S form when analyzed on sucrose gradients containing 0.3 M KCI. The presence of ATP also increased the
rate of activation of progesterone-receptor complex at 23 °C. These findings suggest a role for ATP in receptor
function and offer a convenient method of studying the process of receptor activation at low temperature and
mild assay conditions.
Bindu, G; Anil, Lonappan; Vinu, Thomas; Anandan, C K; Mathew, K T(Progress In Electromagnetics Research, 2006)
[+]
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Abstract:
Active microwave imaging is explored as an imaging
modality for early detection of breast cancer. When exposed to
microwaves, breast tumor exhibits electrical properties that are
significantly different from that of healthy breast tissues. The
two approaches of active microwave imaging — confocal microwave
technique with measured reflected signals and microwave tomographic
imaging with measured scattered signals are addressed here. Normal
and malignant breast tissue samples of same person are subjected to
study within 30 minutes of mastectomy. Corn syrup is used as coupling
medium, as its dielectric parameters show good match with that of
the normal breast tissue samples. As bandwidth of the transmitter is
an important aspect in the time domain confocal microwave imaging
approach, wideband bowtie antenna having 2:1 VSWR bandwidth
of 46% is designed for the transmission and reception of microwave
signals. Same antenna is used for microwave tomographic imaging too
at the frequency of 3000 MHz. Experimentally obtained time domain
results are substantiated by finite difference time domain (FDTD)
analysis. 2-D tomographic images are reconstructed with the collected
scattered data using distorted Born iterative method. Variations of
dielectric permittivity in breast samples are distinguishable from the
obtained permittivity profiles.
Indrapal Singh,N; Shrivastaw,K P; Paulose,C S; Subba Rao,K(Department of Biotechnology, November 13, 1981)
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Abstract:
Acid and alkaline DNase activities in partially purified preparations from young and old chick brain were measured. The
specific activity of acid DNase from old brain was lower by about 50% than that of enzyme from young brain , whereas alkaline
DNase exhibited only marginal difference in activity of the two preparations . Study of various properties, viz. heat-stability
and effect of exogenous compounds like Mg=', Hgl', Zn=', PHM B , on these enzymes revealed that while acid DNase in old
brain is more susceptible to heat and heavy metal ion inhibition , alkaline DNase is devoid of any age-dependent variation in
its properties.
Paulose, C S; Kanungo, M S(Department of Biotecnology, April 21, 1982)
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Abstract:
The binding of (-)[ 3H ]dihydroalprenolol , an antagonist of norepinephrine , to $-adrenergic receptors
in different regions of the brain of male and female rats of various ages was measured . The binding to the
synaptosomal fraction of corpus striatum , hypothalamus, cerebral cortex, cerebellum and the brainstems
shows a significant decrease in the binding in old rats of both sexes . Only in the female corpus striatal
region, the binding in the adult and the old is the same . In the case of females, the highest binding is seen
in the young. In the male, an increase in binding occurs up to adulthood , after which it declines,
suggesting a definite sex-related difference in the Q-adrenergic receptor.
Botha, E C; Odendaal, J W; Geggus, K M(Microwave and Optical Technology Letters, February 20, 1998)
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Abstract:
Compact-range radar backscatter measurements are taken
of aircraft scale models. In addition, computer software is used to predict
the RCS of the aircraft. Synthetic down-range profiles formed from the
two sources of backscatter data are compared and visualized in an
innovative manner. Similar discrimination rates between the two aircraft
are obtained on data from both source