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91.
Electrical conductivity in a novel nonconjugated conductive polymer, poly(β‐pinene), has been measured as a function of molar concentration of iodine. The conductivity increases about 10 orders of magnitude to a maximum value ?8 × 10?3 S/cm. The molar concentration of iodine, corresponding to saturation, is ?0.85. The optical absorption measurements after light doping have shown two peaks: one at 4.0 eV and the other at 3.1 eV. The first peak is due to the radical cation, and the second due to the charge‐transfer between the double bond and the dopant. As observed in other nonconjugated conductive polymers, the second peak becomes broader and undergoes a red shift, upon higher doping. The FTIR spectroscopic studies have shown that the C?C stretching vibration at 1610 cm?1 and the ?C? H bending vibration band at 728 cm?1 decrease upon doping, because of decrease of double bonds. Photoluminescence studies of poly(β‐pinene) show a maximum value at 360 nm for excitation at 280 nm. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3695–3698, 2005 相似文献
92.
U. Reus W. Westmeier R. A. Esterlund A. Rox M. Rajagopalan P. Patzelt 《Zeitschrift für Physik A Hadrons and Nuclei》1981,302(4):363-364
The pronounced isotope shift of87Sr versus87Sr observed recently in 5sns1S0 Rydberg states reflects the singlet-triplet mixing solely caused by magnetic hyperfine interaction. Using semiempirical estimates for the hyperfine coupling constant a5 s and the singlet-triplet splitting ΔEST (n) excellent agreement between experimental and calculated values is obtained. 相似文献
93.
Gitanjali Pagare Vipul Srivastava Sankar P. Sanyal M. Rajagopalan 《Physica B: Condensed Matter》2011,406(3):449-455
The ground state electronic structure and thermal properties of B2-type intermetallic compounds AlRE (RE: Pm, Sm, Eu, Tb, Gd and Dy) have been studied using a self-consistent tight-binding linear muffin-tin orbital (TB-LMTO) method at ambient as well as at high pressure. These compounds show metallic behavior under ambient condition. The band structure, total energy, density of states and ground state properties like lattice parameter, bulk modulus are calculated in the present work. The Debye-Grüneisen model is used to calculate the Debye temperature and the Grüneisen constant. The calculated results are in good agreement with the reported experimental and other theoretical results. The variation in the Debye temperature with pressure has also been reported. We present a detailed analysis of the role of f electrons of RE in the AlRE system. 相似文献
94.
Arunjunai Raj Mahendran Günter Wuzella Andreas Kandelbauer Nicolai Aust 《Journal of Thermal Analysis and Calorimetry》2012,107(3):989-998
The thermal cure kinetics of an epoxidized linseed oil with methyl nadic anhydride as curing agent and 1-methyl imidazole
as catalyst was studied by differential scanning calorimetry (DSC). The curing process was evaluated by non-isothermal DSC
measurements; three iso-conversional methods for kinetic analysis of the original thermo-chemical data were applied to calculate
the changes in apparent activation energy in dependence of conversion during the cross-linking reaction. All three iso-conversional
methods provided consistent activation energy versus time profiles for the complex curing process. The accuracy and predictive
power of the kinetic methods were evaluated by isothermal DSC measurements performed at temperatures above the glass transition
temperature of the completely cured mixture (T
g∞
). It was found that the predictions obtained from the iso-conversional method by Vyazovkin yielded the best agreement with
the experimental values. The corresponding activation energy (E
a) regime showed an increase in E
a at the beginning of the curing which was followed by a continuous decrease as the cross-linking proceeded. This decrease
in E
a is explained by a diffusion controlled reaction kinetics which is caused by two phenomena, gelation and vitrification. Gelation
during curing of the epoxidized linseed/methyl nadic anhydride system was characterized by rheological measurements using
a plate/plate rheometer and vitrification of the system was confirmed experimentally by detecting a significant decrease in
complex heat capacity using alternating differential scanning calorimetry (ADSC) measurements. 相似文献
95.
Thermal degradation of pentaerythritol phosphate alcohol 总被引:1,自引:0,他引:1
Nagarajan David Mathan Mahendran Arunjunairaj Thangamani Rajkumar Durairaj Ponraju Chinnaswamy Thangavel Vijayakumar 《Journal of Thermal Analysis and Calorimetry》2012,110(3):1133-1141
Intumescent material, 2,6,7-trioxa-1-phosphabicyclo-[2,2,2]-octane-4-methanol phosphate (PEPA), is synthesized and characterized using FTIR, 1HNMR and 13CNMR. The degradation properties of PEPA are studied by employing TG and TG?CMS technique. The activation energies for the degradation process of PEPA are calculated by using TG curves obtained from multiple heating rates (Friedman, Kissinger?CAkahira?CSunose and Flynn?CWall?COzawa methods). The degradation that is occurring in the temperature region 307?C366?°C has the highest activation energy. Eventhough the calculated activation energies for the degradation differ depending on the approximation method employed, the trend in variation of activation energy for degradation is similar. Single ion monitoring technique proved the evolution of H2O, CO/C2H4, HCHO, C2H5OH/HCOOH and trace amounts of C2H7O3P and C4H9O4P from the degrading PEPA. The thermal conductivity and stability of the char formed during the TG analysis are also discussed. 相似文献
96.
Kurniawan NA Enemark S Rajagopalan R 《Journal of the American Chemical Society》2012,134(24):10200-10208
Crowded environments inside cells exert significant effects on protein structure, stability, and function, but their effects on (pre)folding dynamics and kinetics, especially at molecular levels, remain ill-understood. Here, we examine the latter for, as an initial candidate, a small de novo β-hairpin using extensive all-atom molecular dynamics simulations for crowder volume fractions φ up to 40%. We find that crowding does not introduce new folding intermediates or misfolded structures, although, as expected, it promotes compact structures and reduces the accessible conformational space. Furthermore, while hydrophobic-collapse-mediated folding is slightly enhanced, the turn-directed zipper mechanism (dominant in crowder-free situations) increases many-fold, becoming even more dominant. Interestingly, φ influences the stability of the folding intermediates (FI(1) and FI(2)) in an apparently counterintuitive manner, which can be understood only by considering specific intrachain interactions and intermediate (and hierarchical) structural transitions. For φ values <20%, native-turn formation is enhanced, and FI(1), characterized by a hairpin structure but slightly mismatched hydrophobic contacts, increases in frequency, thus enhancing eventual folding. However, higher φ values impede native-turn formation, and FI(2), which lacks native turns, re-emerges and increasingly acts as a kinetic trap. The change in the stability of these intermediates with φ strongly correlates with the hierarchical folding stages and their kinetics. The results show that crowding assists intermediate structural changes more by impeding backward transitions than by promoting forward transitions and that a delicate competition between reduction in configuration space and introduction of kinetic traps along the folding route is key to understanding folding kinetics under crowded conditions. 相似文献
97.
The structure of statistical state spaces in the classical and quantum theories are compared in an interesting and novel manner.
Quantum state spaces and maps on them have rich convex structures arising from the superposition principle and consequent
entanglement. Communication channels (physical processes) in the quantum scheme of things are in one-to-one correspondence
with completely positive maps. Positive maps which are not completely positive do not correspond to physical processes. Nevertheless
they prove to be invaluable mathematical tools in establishing or witnessing entanglement of mixed states. We consider some
of the recent developments in our understanding of the convex structure of states and maps in quantum theory, particularly
in the context of quantum information theory. 相似文献
98.
Y.-C. Lai K. Park L. Rajagopalan 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(1):65-70
We investigate a class of nonlinear wave equations subject to
periodic forcing and noise, and address the issue of energy optimization.
Numerically, we use a pseudo-spectral method to solve the nonlinear stochastic
partial differential equation and compute the energy of the system as a
function of the driving amplitude in the presence of noise.
In the fairly general setting where the system possesses two coexisting
states, one with low and another with high energy, noise can induce
intermittent switchings between the two states. A striking finding is that,
for fixed noise, the system energy can be optimized by the driving in a
form of resonance. The phenomenon can be explained by the Langevin dynamics
of particle motion in a double-well potential system with symmetry breaking.
The finding can have applications to small-size devices such as
microelectromechanical resonators and to waves in fluid and plasma. 相似文献
99.
Of the Rh3Y, Rh3La, Ir3Y and Ir3La inter-metallic compounds, the compound Rh3Y exists in hexagonal structure, Ir3Y and Ir3La exist in rhombohedral structure, whereas the compound Rh3La exists in both hexagonal and rhombohedral structures. Based on our tight binding-linear muffin tin orbital (TB-LMTO) study of other rhodium and iridium-based Rh3X and Ir3X (where X=Ti, Zr, Hf, V, Nb, Ta and Sc) inter-metallic compounds of AuCu3 type cubic structure, an attempt is made to examine whether the compounds Rh3Y, Rh3La, Ir3Y and Ir3La will undergo a structural phase transition to cubic structure from their experimentally reported structures. From our study, it is observed that the compounds Rh3Y and Rh3La undergo a structural phase transition to cubic phase at 4.5 and 10.1 GPa, respectively, from their experimentally reported hexagonal and rhombohedral phases. Further it is predicted that both the compounds Ir3Y and Ir3La can exist in the cubic phase itself at ambient condition, in contrary to the experimental observation. From the band structure outputs that have been plotted for the compounds under compression, it is observed that the compounds Rh3La, Ir3Y and Ir3La undergo the Lifshitz type of transition which may change the Fermi surface topology and hence the physical properties of these compounds. 相似文献
100.
Farrah Syazana Khattulanuar Mahendran Sekar Shivkanya Fuloria Siew Hua Gan Nur Najihah Izzati Mat Rani Subban Ravi Kumarappan Chidambaram M. Yasmin Begum Abul Kalam Azad Srikanth Jeyabalan Arulmozhi Dhiravidamani Lakshmi Thangavelu Pei Teng Lum Vetriselvan Subramaniyan Yuan Seng Wu Kathiresan V. Sathasivam Neeraj Kumar Fuloria 《Molecules (Basel, Switzerland)》2022,27(3)
Cardiovascular disorders (CVDs) are the leading risk factor for death worldwide, and research into the processes and treatment regimens has received a lot of attention. Tilianin is a flavonoid glycoside that can be found in a wide range of medicinal plants and is most commonly obtained from Dracocephalum moldavica. Due to its extensive range of biological actions, it has become a well-known molecule in recent years. In particular, numerous studies have shown that tilianin has cardioprotective properties against CVDs. Hence, this review summarises tilianin’s preclinical research in CVDs, as well as its mechanism of action and opportunities in future drug development. The physicochemical and drug-likeness properties, as well as the toxicity profile, were also highlighted. Tilianin can be a natural lead molecule in the therapy of CVDs such as coronary heart disease, angina pectoris, hypertension, and myocardial ischemia, according to scientific evidence. Free radical scavenging, inflammation control, mitochondrial function regulation, and related signalling pathways are all thought to play a role in tilianin’s cardioprotective actions. Finally, we discuss tilianin-derived compounds, as well as the limitations and opportunities of using tilianin as a lead molecule in drug development for CVDs. Overall, the scientific evidence presented in this review supports that tilianin and its derivatives could be used as a lead molecule in CVD drug development initiatives. 相似文献