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111.
Abul K. Mallik Kaori Shingo Usha Ghimire Gautam Tsuyoshi Sawada Makoto Takafuji Hirotaka Ihara 《Analytical and bioanalytical chemistry》2010,397(2):623-629
Poly(2-N-carbazolylethyl acrylate) with terminal trimethoxysilyl groups was prepared as an organic phase and immobilized onto silica.
The retention behavior of the column packed with this carbazole-based polymer-immobilized silica (Sil-CEA) was investigated
by using various estrogenic steroids and corticoids in both reversed-phase and normal-phase liquid chromatography. As a result,
complete separation was confirmed for eight kinds of steroids with Sil-CEA. The most specific separation with Sil-CEA can
be emphasized by the high separation factor (e.g., α = 1.39 in methanol–water (7:3, v/v) at 35 °C) for 17α and 17β-estradiols, one of the most difficult pairs of isomers in chromatographic separation, whereas
for two kinds of commercially available polymeric ODS columns as references α = 1.01, only, under the same conditions. Because the excellent separation and retention order with Sil-CEA was maintained
even in a normal-phase mobile phase such as a hexane–2-propanol, it is estimated that the CEA phase has multiple interaction
mechanisms through stronger interactions such as dipole–dipole, carbonyl–π, and hydrogen bonding interactions than the hydrophobic
effect expected with ODS. 相似文献
112.
Paul S Russakow D Nahire R Nandy T Ambre AH Katti K Mallik S Sarkar K 《Ultrasonics》2012,52(7):962-969
Echogenic liposomes (ELIP) are an excellent candidate for concurrent imaging and drug delivery applications. They combine the advantages of liposomes-biocompatibility and ability to encapsulate both hydrophobic and hydrophilic drugs-with strong reflections of ultrasound. The objective of this study is to perform a detailed in vitro acoustic characterization - including nonlinear scattering that has not been studied before - along with an investigation of the primary mechanism of echogenicity. Both components are critical for developing viable clinical applications of ELIP. Mannitol, a cryoprotectant, added during the preparation of ELIP is commonly believed to be critical in making them echogenic. Accordingly, here ELIP prepared with varying amount of mannitol concentration are investigated for their pressure dependent linear and non-linear scattered responses. The average diameter of these liposomes is measured to be 125-185 nm. But they have a broad size distribution including liposomes with diameters over a micro-meter as observed by TEM and AFM. These larger liposomes are critical for the overall echogenicity. Attenuation through liposomal solution is measured with four different transducers (central frequencies 2.25, 3.5, 5, 10 MHz). Measured attenuation increases linearly with liposome concentration indicating absence of acoustic interactions between liposomes. Due to the broad size distribution, the attenuation shows a flat response without a distinct peak in the range of frequencies (1-12 MHz) investigated. A 15-20 dB enhancement with 1.67 μg/ml of lipids is observed both for the scattered fundamental and the second harmonic responses at 3.5 MHz excitation frequency and 50-800 kPa amplitude. It demonstrates the efficacy of ELIP for fundamental as well as harmonic ultrasound imaging. The scattered response however does not show any distinct subharmonic peak for the acoustic excitation parameters studied. Small amount of mannitol proves critical for echogenicity. However, mannitol concentration above 100 mM shows no effect. 相似文献
113.
Rudrakshula Madhavachary Rosy Mallik Dhevalapally B. Ramachary 《Molecules (Basel, Switzerland)》2021,26(14)
Biologically important, chiral natural products of butenolides, (−)-blastmycinolactol, (+)-blastmycinone, (−)-NFX-2, (+)-antimycinone, lipid metabolites, (+)-ancepsenolide, (+)-homoancepsenolide, mosquito larvicidal butenolide and their analogues were synthesized in very good yields in a sequential one-pot manner by using an organocatalytic reductive coupling and palladium-mediated reductive deoxygenation or organocatalytic reductive coupling and silica-mediated reductive deamination as the key steps. 相似文献
114.
Mallik S Dash SS Parida KM Mohapatra BK 《Journal of colloid and interface science》2006,300(1):237-243
A series of ecofriendly solid acid catalyst was synthesized by phosphomolybdic acid impregnated on hydrous zirconia (ZPMA) by an incipient wetness impregnation technique. The support and the resulting catalysts were characterized by X-ray diffraction, FTIR, EPMA, BET surface area, acid sites, etc. These studies indicate that the phosphomolybdic acid keeps its Keggin-type structure unaltered up to 500 degrees C. Catalytic activities of the material were evaluated for the esterification of acetic acid reaction. The 12 wt% of phosphomolybdic acid supported on hydrous zirconia shows highest surface area, acid sites and gives about 86% conversion with 100% selectivity of n-butyl acetate. 相似文献
115.
Abul K. Mallik Wee Keat Cheah Kaori Shingo Aika Ejzaki Makoto Takafuji Hirotaka Ihara 《Analytical and bioanalytical chemistry》2014,406(19):4585-4593
A new hydrophilic and nonionic poly(2-vinyloxazoline)-grafted silica (Sil-VOX n ) phase was synthesized and applied for the separation of nucleosides and nucleobases in hydrophilic interaction chromatography (HILIC). Polymerization and immobilization onto silica were confirmed by using characterization techniques including 1H NMR spectroscopy, elemental analysis, and diffuse reflectance infrared Fourier transform spectroscopy. The hydrophilicity or wettability of Sil-VOX n was observed by measuring the contact angle (59.9°). The chromatographic results were compared with those obtained with a conventional HILIC silica column. The Sil-VOX n phase showed much better separation of polar test analytes than the silica column, and the elution order was different. Differences in selectivity between these two columns indicate that the stationary phase cannot function merely as an inert support for a water layer into which the solutes are partitioned from the bulk mobile phase. To elucidate the interaction mechanism, the separation of dihydroxybenzene isomers was performed on both columns in normal-phase liquid chromatography. Sil-VOX n was very sensitive to the dipole moments of the positional isomers of polycyclic aromatic compounds in normal-phase liquid chromatography. The interaction mechanism for Sil-VOX n in HILIC separation is also described. Figure
Separation of nucleosides and nucleobases with Sil-VOXn (bottom) and a commercial silica column (top). Mobile phase of acetonitrile and 20 mM ammonium acetate (9:1, v/v). Flow rate 1 ml min-1, column temperature 25 °C. The analytes were as follows 5-iodouracil (1), thymine (2), uracil (3), 4,6-diaminopyrimidine (4), uridine (5), adenosine 2 (6), cytosine (7), cytidine (8), and guanosine (9) 相似文献
116.
Daniel Santhanaraj Maria P. Ruiz Mallik R. Komarneni Tu Pham Gengnan Li Daniel E. Resasco Jimmy Faria 《Angewandte Chemie (International ed. in English)》2020,59(19):7456-7460
We report a reaction platform for the synthesis of three different high‐value specialty chemical building blocks starting from bio‐ethanol, which might have an important impact in the implementation of biorefineries. First, oxidative dehydrogenation of ethanol to acetaldehyde generates an aldehyde‐containing stream active for the production of C4 aldehydes via base‐catalyzed aldol‐condensation. Then, the resulting C4 adduct is selectively converted into crotonic acid via catalytic aerobic oxidation (62 % yield). Using a sequential epoxidation and hydrogenation of crotonic acid leads to 29 % yield of β‐hydroxy acid (3‐hydroxybutanoic acid). By controlling the pH of the reaction media, it is possible to hydrolyze the oxirane moiety leading to 21 % yield of α,β‐dihydroxy acid (2,3‐dihydroxybutanoic acid). Crotonic acid, 3‐hydroxybutanoic acid, and 2,3‐dihydroxybutanoic acid are archetypal specialty chemicals used in the synthesis of polyvinyl‐co‐unsaturated acids resins, pharmaceutics, and bio‐degradable/ ‐compatible polymers, respectively. 相似文献
117.
The changes in the electronic absorption spectra (UV-Vis) (after photoexcitations) of poly(methyl methacrylate) (PMMA) thin films doped with a ferrocene derivative and containing chloroform molecules as impurities, have been studied as a function of photoexcitation wavelength (210–750 nm), photoexcitation time (duration), amount of ferrocene derivative in the film and amount of chloroform molecules present in the film. Occurrence of photoinduced charge-transfer between some ferrocene derivatives and chloroform molecules confined in the PMMA thin films has been observed. The effects of the substitution group (attached to the ferrocene unit) on the photoinduced changes are discussed. 相似文献
118.
S. Mallik 《The European Physical Journal C - Particles and Fields》2006,45(3):777-782
The vector and the axial-vector meson couplings with the vector and the axial-vector currents respectively at finite temperature
were obtained by calculating all the relevant one-loop Feynman graphs with vertices obtained from the effective chiral Lagrangian.
On the other hand, the same couplings were also derived by applying the method of current algebras and the hypothesis of partial
conservation of axial-vector currents. The latter method appears to miss certain terms; in the case of the vector meson coupling
with the vector current, for example, a term containing the ρωπ coupling is missed. A similar situation would also appear
for the nucleon coupling with the nucleon current. In this note we resolve these differences. 相似文献
119.
C.V. Ramana Rosy Mallik Rajesh G. Gonnade Mukund K. Gurjar 《Tetrahedron letters》2006,47(22):3649-3652
Functionalized bicyclic enol-ethers and spiroketals are prepared by Pd catalyzed cycloisomerization of 3-C-alkynylfuranosyl derivatives. Cycloisomerization of differently substituted alkyne derivatives revealed a preference for 6-endo-dig cyclization over 5-exo-dig if the substituent is not sufficiently electron withdrawing. The scope of these cycloisomerizations has been further extended by integrating with conjugate addition. 相似文献
120.
研究热源和体力作用下的横观各向同性厚板的二维问题,板的上表面无应力作用,但有规定的表面温度作用;板的下表面置于刚性基础之上,并处于绝热状态.采用Green和Naghdi提出的广义热弹性理论,通过Laplace和Fourier双重变换,在Laplace-Fourier变换域中,得到位移和温度场的控制方程.数值求解双重变换的逆变换,采用一个基于Fourier级数展开的方法,数值地求解Laplace变换的逆变换.对材料镁(Mg)进行数值计算,并用图形表示其结果.推演出各向同性材料铜(Cu)的数值结果,并用图形与横观各向同性材料镁进行比较.同时研究了体力的影响. 相似文献