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991.
In this contribution, chemical sensor for the detection of aqueous ammonia has been fabricated using UV-curable polyurethane acrylate (PU) and nanohybrids (NH-1, NH-3 and NH-5). PU has been prepared by reacting polycaprolactone triol (PCLT) and isophorone diisocyanate (IPDI) while the nanohybrids, NH-1, NH-3, and NH-5 have been synthesized by solution blending method using PU with 1, 3, and 5 wt% loading levels of C-20B. PU and their nanohybrids showed higher sensitivity investigated by I-V technique using aqueous ammonia as a target chemical. All the nanohybrids showed higher sensitivity as compared to neat PU. The sensitivity increased with increase in clay content and the nanohybrid containing 5 wt% of clay showed the highest sensitivity (8.5254 μA cm−2 mM−1) with the limit of detection (LOD) of 0.0175 ± 0.001 μM, being 7.8 times higher than pure PU. The calibration plot for all the sensors was linear over the large range of 0.05 μM to 0.05 M. The response time of the fabricated sensor was <10.0 s. Therefore, one can fabricate efficient aqueous ammonia sensor by utilization of nanohybrid as an efficient electron mediator. 相似文献
992.
M. M. Rahman 《Meccanica》2011,46(5):1127-1143
This paper presents heat transfer process in a two-dimensional steady hydromagnetic convective flow of an electrically conducting
fluid over a flat plate with partial slip at the surface of the boundary subjected to the convective surface heat flux at
the boundary. The analysis accounts for both temperature-dependent viscosity and temperature dependent thermal conductivity.
The local similarity equations are derived and solved numerically using the Nachtsheim-Swigert iteration procedure. Results
for the dimensionless velocity, temperature and ambient Prandtl number within the boundary layer are displayed graphically
delineating the effect of various parameters characterizing the flow. The results show that momentum boundary layer thickness
significantly depends on the surface convection parameter, Hartmann number and on the sign of the variable viscosity parameter.
The results also show that plate surface temperature is higher when there is no slip at the plate compared to its presence.
For both slip and no-slip cases surface temperature of the plate can be controlled by controlling the strength of the applied
magnetic field. In modelling the thermal boundary layer flow with variable viscosity and variable thermal conductivity, the
Prandtl number must be treated as a variable irrespective of flow conditions whether there is slip or no-slip at the boundary
to obtain realistic results. 相似文献
993.
This paper considers the analysis of transient heating of a hemispherical solid plate of finite thickness during impingement
of a free liquid jet. A constant heat flux was imposed at the inner surface of the hemispherical plate at t = 0 and heat transfer was monitored for the entire duration of the transient until a steady state condition was reached.
Calculations were done for Reynolds number (Re) ranging from 500 to 1,500 and dimensionless plate thicknesses to nozzle diameter ratio (b/d
n) from 0.083 to 1.5. Results are presented for local and average Nusselt number using water as the coolant and various solid
materials such as silicon, constantan, and copper. It was detected that increasing the Reynolds number decreases the time
for the plate to achieve the steady-state condition. Also, a higher Reynolds number increases the Nusselt number. Hemispherical
plate materials with higher thermal conductivity maintain lower temperature non-uniformity at the solid–fluid interface. Increasing
the plate thickness decreases the maximum temperature in the solid and increases the time to reach the steady-state condition. 相似文献
994.
Ghalib Al-Saidi Mohammad Shafiur Rahman Ahmed Al-Alawi Nejib Guizani 《Journal of Thermal Analysis and Calorimetry》2011,104(2):593-603
Gelatin extraction yield increased with the increase of acetic acid concentration and temperature. Gelatin extracted from
shaari skin using 0.1 N acid solutions and temperatures of 323 and 353 K gave highest protein content comparable to that of
commercial bovine and porcine gelatins. In general, gelatin extracted from shaari gelatin showed lower onset of glass transition
temperature than mammalian gelatins. For shaari skin gelatin, the onset of glass transition temperature decreased with the
increase of extraction temperature up to 323 K and then remained nearly constant. The decrease in glass transition was more
pronounced for gelatin extracted at 0.01 N compared to the 0.1 and 1.0 N samples. Unfolding temperature decreased exponentially
with the increase of extraction temperature. The unfolding temperature shifted to lower temperature, and the decrease was
more pronounced in the case of higher (1.0 N) concentrated samples. The extraction concentration and temperature did not show
significant effect on the onset solids-melting temperature. 相似文献
995.
Teresa L. Augustin Roxanna Hajbabaie Matthew T. Harper Taufiq Rahman 《Molecules (Basel, Switzerland)》2020,25(23)
The ongoing pandemic caused by the novel coronavirus has been the greatest global health crisis since the Spanish flu pandemic of 1918. Thus far, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in over 1 million deaths, and there is no cure or vaccine to date. The recently solved crystal structure of the SARS-CoV-2 main protease has been a major focus for drug-discovery efforts. Here, we present a fragment-guided approach using ZINCPharmer, where 17 active fragments known to bind to the catalytic centre of the SARS-CoV-2 main protease (SARS-CoV-2 Mpro) were used as pharmacophore queries to search the ZINC databases of natural compounds and natural derivatives. This search yielded 134 hits that were then subjected to multiple rounds of in silico analyses, including blind and focused docking against the 3D structure of the main protease. We scrutinised the poses, scores, and protein–ligand interactions of 15 hits and selected 7. The scaffolds of the seven hits were structurally distinct from known inhibitor scaffolds, thus indicating scaffold novelty. Our work presents several novel scaffolds as potential candidates for experimental validation against SARS-CoV-2 Mpro. 相似文献
996.
Aromaticity and Chemical Bonding of Chalcogen-Bonded Capsules Featuring Enhanced Magnetic Anisotropy
Prof. Demeter Tzeli Dr. Ioannis D. Petsalakis Dr. Giannoula Theodorakopoulos Dr. Faiz-Ur Rahman Prof. Pablo Ballester Prof. Julius Rebek Jr. Prof. Yang Yu 《Chemphyschem》2020,21(19):2187-2195
We present a theoretical study of chalcogen bonded container capsules ( AX+AX ) where X=O, S, Se, and Te, and their encapsulation complexes with n-C9H20 (n-C9H20@ AX+AX ). Both Se and Te encapsulation complexes have significant experimental and computed binding energies, analogous to the hydrogen bonded counterparts, while the S and O capsules and their encapsulation complexes show only weak binding energies, which are attributed to different types of bonding: chalcogen S⋅⋅⋅N bonds for S-capsules and π–π stacking and weak hydrogen bonds for the O case. All AX+AX and C9H20@ AX+AX present unusually high magnetic anisotropies in their interiors. The 1H NMR spectra of the encapsulation complexes display the proton signals of the encapsulated n-nonane highly upfield shifted, in agreement with the available experimental data for the Se capsule. We found that different factors contribute to the observed magnetic anisotropy of the capsule's interior: for the Te capsule the most important factor is Te's large polarizability; for the O analogue the inductive effects produced by the electronegative nature of the O and N heteroatoms; and for the S and Se capsules, the polarizability of the heteroatoms combines with electric field effects. 相似文献
997.
M. W. Rahman M. M. Hossain M. J. Alam N. C. Dafader M. E. Haque 《International Journal of Polymer Analysis and Characterization》2013,18(7):479-487
The effect of transition metals as a promoter of physico-mechanical properties of radiation-vulcanized natural rubber latex (RVNRL) films was investigated. RVNRL films were prepared by the addition of transition metals (Fe, Mn, etc.) of different concentrations (0–30 ppm) in natural rubber (NR) latex and irradiated with various radiation doses (0–20 kGy). The concentrations of metal ions and radiation doses were optimized and found to be 20 ppm and 12 kGy, respectively. Tensile strength, tear strength, and cross-linking density of the irradiated rubber films were increased with increasing concentration of metal ions as well as radiation doses. The mechanical properties of the films were enhanced by approximately 20% at the optimum conditions. In contrast, elongation at break, permanent set, and swelling ratio of the films were decreased under the same conditions. The comparative effect of metal ions can be explained by Fajan's rules, reported in this article. 相似文献
998.
Abstract Cellulose ethers were prepared by the reaction of sodium cellulosate with 1-chloromethylnaphthalene, 2-bromomethyl-pyridine, 2-chloropyridine, crotyl bromide, propargyl chloride, and 1-naphthyl glycidyl ether and their complexation ability was investigated. No π-complex formation with picric acid or 2,4,6-trinitrobenzene took place. Results were attributed to steric hindrance from the cellulosic backbone. Complexation of some metal salts by the crotyl and propargyl ethers was investigated. Good results were obtained with mercuric chloride, aluminum chloride, and silver nitrate when propargyl cellulose was used. 相似文献
999.
Md. Mijanur Rahman 《Optik》2011,122(8):660-665
A novel approach for representing logic states in the quantum nodes and transferring the states from one node to another is proposed. Both transmit and receive nodes consist of a rubidium atom (87Rb) placed at the center of a two-mode cavity. Representation of logic states by two subspaces of the space of 87Rb atom hyperfine states eliminates the need for the transmitting node to change logic state during logic transfer through Raman process. The atom is excited by simultaneous application of two laser beams - one for each subspace. Based on the logic state, the atom emits a photon of appropriate frequency and polarization through Raman process within the corresponding subspace. The emitted photon leaks out of the cavity, reaches the receiving node, and initiates logic dependent transitions there. A simulation platform is developed through the system Hamiltonians for transmit and receive nodes followed by the formulation of the time evolution of the density matrices for the nodes. The efficacy of the simulation approach is emphasized. 相似文献
1000.
Md. Mijanur Rahman 《Optik》2011,122(1):84-88
A novel approach for transferring logic states from one quantum node to other is proposed. Logic states ‘0’ and ‘1’ are represented by two subspaces of the hyperfine states space of rubidium atom (87Rb). The atom, placed at the center of a two-mode cavity, is excited by simultaneous application of two laser beams, one for each subspace. Based on the logic state of the atom, it makes a transition to a higher energy level within the corresponding subspace. When the atom relaxes back to a lower state within the subspace, a left- or right-circularly polarized photon is emitted depending on whether the initial state was logic ‘0’ or logic ‘1’. The polarized photon leaks out of the cavity, reaches the receive node and gets detected therein. Simulation results show the efficacy of the approach. 相似文献