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排序方式: 共有755条查询结果,搜索用时 109 毫秒
741.
Ramakrishna G Verma S Jose DA Kumar DK Das A Palit DK Ghosh HN 《The journal of physical chemistry. B》2006,110(18):9012-9021
Interfacial electron transfer (ET) dynamics of 5,10,15-trisphenyl-20-(3,4-dihydroxybenzene) porphyrin (TPP-cat) adsorbed on TiO2 nanoparticles has been studied by femtosecond transient absorption spectroscopy in the visible and near-IR region exciting at 400 and 800 nm. TPP-cat molecule forms a charge transfer (CT) complex with TiO2 nanoparticles through the catechol moiety with the formation of a five-membered ring. Optical absorption measurements have shown that the Q-band of TPP-cat interacts strongly with TiO2 due to chelation; however, the Soret band is affected very little. Optical absorption measurements indicate that the catechol moiety also interacts with TiO2 nanoparticles showing the characteristic band of pure catechol-TiO2 charge transfer (CT) in the visible region. Electron injection has been confirmed by monitoring the cation radical, instant bleach, and injected electron in the conduction band of TiO2 nanoparticles. Electron injection time has been measured to be < 100 fs and recombination kinetics has been best fitted with a multiexponential function, where the majority of the injected electrons come back to the parent cation radical with a time constant of approximately 800 fs for both excitation wavelengths. However, the reaction channel for the electron injection process has been found to be different for both wavelengths. Excitation at 800 nm, found to populate the CT state of the Q-band, and from the photoexcited CT state electron injection into the conduction band, takes place through diffusion. On the other hand, with excitation at 400 nm, a complicated reaction channel takes place. Excitation with 400 nm light excites both the CT band of Cat-TiO2 and also the Soret band of TPP-cat. We have discussed the reaction path in the TPP-cat/TiO2 system after exciting with both 400 and 800 nm laser light. We have also compared ET dynamics by exciting at both wavelengths. 相似文献
742.
Ganesh V Pal SK Kumar S Lakshminarayanan V 《Journal of colloid and interface science》2006,296(1):195-203
Self-assembled monolayers (SAMs) of liquid crystalline thiol-terminated alkoxycyanobiphenyl molecules with different alkyl chain lengths on Au surface have been studied for the first time using electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The barrier property of the SAM-modified surfaces was evaluated using two different redox probes, namely potassium ferro/ferri cyanide and hexaammineruthenium(III) chloride. It was found that for short-length alkyl chain thiol (C5) the electron transfer reaction of hexaammineruthenium(III) chloride takes place through tunneling mechanism. In contrast, redox reaction of potassium ferro/ferri cyanide is almost completely blocked by the SAM-modified Au surface. From the impedance data, a surface coverage value of >99.9% was calculated for all the thiol molecules. 相似文献
743.
The synthesis of ditryptophan-pyridine conjugates and their binding to mercury ions is described. Conjugate 3 shows an excellent ability to sequester mercury from solution and rescue bacterial growth in a concentration-dependent survival assay. It is proposed that such compounds, composed primarily of bioessential/biodegradable components, could be potentially used as sequestrating agents for the removal of Hg(II) ions in detoxification strategies. 相似文献
744.
Sandeep Jain N. R. Srinivasa Raghavan 《Central European Journal of Operations Research》2009,17(1):95-110
This paper presents stylized models for conducting performance analysis of the manufacturing supply chain network (SCN) in
a stochastic setting for batch ordering. We use queueing models to capture the behavior of SCN. The analysis is clubbed with
an inventory optimization model, which can be used for designing inventory policies . In the first case, we model one manufacturer
with one warehouse, which supplies to various retailers. We determine the optimal inventory level at the warehouse that minimizes
total expected cost of carrying inventory, back order cost associated with serving orders in the backlog queue, and ordering
cost. In the second model we impose service level constraint in terms of fill rate (probability an order is filled from stock
at warehouse), assuming that customers do not balk from the system. We present several numerical examples to illustrate the
model and to illustrate its various features. In the third case, we extend the model to a three-echelon inventory model which
explicitly considers the logistics process. 相似文献
745.
Fiona M. Fennessy Andriy Fedorov Sandeep N. Gupta Ehud J. Schmidt Clare M. Tempany Robert V. Mulkern 《Magnetic resonance imaging》2012
There are many challenges in developing robust imaging biomarkers that can be reliably applied in a clinical trial setting. In the case of dynamic contrast-enhanced (DCE) MRI, one such challenge is to obtain accurate precontrast T1 maps for subsequent use in two-compartment pharmacokinetic models commonly used to fit the MR enhancement time courses. In the prostate, a convenient and common approach for this task has been to use the same 3D spoiled gradient-echo sequence used to collect the DCE data, but with variable flip angles (VFAs) to collect data suitable for T1 mapping prior to contrast injection. However, inhomogeneous radiofrequency conditions within the prostate have been found to adversely affect the accuracy of this technique. Herein we demonstrate the sensitivity of DCE pharmacokinetic parameters to precontrast T1 values and examine methods to improve the accuracy of T1 mapping with flip angle-corrected VFA SPGR methods, comparing T1 maps from such methods with “gold standard” reference T1 maps generated with saturation recovery experiments performed with fast spin-echo (FSE) sequences. 相似文献
746.
Ultrafast nonlinear optical response of carbon nanotubes functionalized with water soluble porphyrin
Jyotsana Gupta C. Vijayan Sandeep Kumar Maurya D. Goswami 《Optics Communications》2012,285(7):1920-1924
A new nanocomposite is obtained by functionalizing carbon nanotubes (CNTs) with a water soluble metalloprophyrin using a simple chemical technique and characterized by optical absorption, IR, and Raman spectroscopy. Results from spectroscopic studies indicate the noncovalent nature of interaction between CNTs and porphyrin. The ultrafast nonlinear response is characterized by measuring the nonlinear absorption coefficient and refractive index by z-scan technique in the femtosecond pulse regime. The nanocomposite is found to exhibit two-photon absorption (TPA) with a reasonably large nonlinear optical coefficient, whereas pure CNTs is known to exhibit saturable absorption. Design of such water soluble nanocomposites offers scope for obtaining materials with enhanced ultrafast optical nonlinearity. 相似文献
747.
A series of benzo[b][1,8]naphthyridines has been synthesized by Friedl?nder condensation of 2-aminoquinoline-3-carbaldehyde 1 (o-aminoaldehyde) with alicyclic ketones in basic medium. Benzonaphthyridines branched with various side-chains and substituents
are prepared with the aim of being investigated as a good fluorescent material. Electronic absorption and fluorescence properties
of some representative benzonaphthyridines in organic solvents, water-dioxane, and SDS, CTAB and Triton-X-100 micelles have
been examined. The linear correlation between solvent polarity and fluorescence properties is observed. This study may provide
new directions for the development of fluorescence probes as reporters of microenvironments of organized assemblies. 相似文献
748.
Katharigatta N. Venugopala Pottathil Shinu Christophe Tratrat Pran Kishore Deb Raquel M. Gleiser Sandeep Chandrashekharappa Deepak Chopra Mahesh Attimarad Anroop B. Nair Nagaraja Sreeharsha Fawzi M. Mahomoodally Michelyne Haroun Mahmoud Kandeel Syed Mohammed Basheeruddin Asdaq Viresh Mohanlall Nizar A. Al-Shari Mohamed A. Morsy 《Molecules (Basel, Switzerland)》2022,27(9)
Alteration of insect growth regulators by the action of inhibitors is becoming an attractive strategy to combat disease-transmitting insects. In the present study, we investigated the larvicidal effect of 1,2,3-triazolyl-pyrimidinone derivatives against the larvae of the mosquito Anopheles arabiensis, a vector of malaria. All compounds demonstrated insecticidal activity against mosquito larvae in a dose-dependent fashion. A preliminary study of the structure–activity relationship indicated that the electron-withdrawing substituent in the para position of the 4-phenyl-pyrimidinone moiety enhanced the molecules’ potency. A docking study of these derivatives revealed favorable binding affinity for the sterol carrier protein-2 receptor, a protein present in the intestine of the mosquito larvae. Being effective insecticides against the malaria-transmitting Anopheles arabiensis, 1,2,3-triazole-based pyrimidinones represent a starting point to develop novel inhibitors of insect growth regulators. 相似文献
749.
Ajay Kumar Sandeep Kaur Sukhvinder Dhiman Prithvi Pal Singh Gaurav Bhatia Sharad Thakur Hardeep Singh Tuli Upendra Sharma Subodh Kumar Abdulmajeed G. Almutary Abdullah M. Alnuqaydan Arif Hussain Shafiul Haque Kuldeep Dhama Satwinderjeet Kaur 《Molecules (Basel, Switzerland)》2022,27(11)
Onosma bracteata Wall. is an important medicinal and immunity-enhancing herbs. This plant is commonly used in the preparation of traditional Ayurvedic drugs to treat numerous diseases. Inspired by the medicinal properties of this plant, the present study aimed to investigate the antiproliferative potential and the primary molecular mechanisms of the apoptotic induction against human osteosarcoma (MG-63) cells. Among all the fractions isolated from O. bracteata, ethyl acetate fraction (Obea) showed good antioxidant activity in superoxide radical scavenging assay and lipid peroxidation assay with an EC50 value of 95.12 and 80.67 µg/mL, respectively. Silica gel column chromatography of ethyl acetate (Obea) fraction of O. bracteata yielded a pure compound, which was characterized by NMR, FTIR, and HR-MS analysis and was identified as 1,2-benzene dicarboxylic acid, bis (2-methyl propyl) ester (BDCe fraction). BDCe fraction was evaluated for the antiproliferative potential against human osteosarcoma MG-63, human neuroblastoma IMR-32, and human lung carcinoma A549 cell lines by MTT assay and exhibited GI50 values of 37.53 μM, 56.05 μM, and 47.12 μM, respectively. In MG-63 cells, the BDCe fraction increased the level of ROS and simultaneously decreased the mitochondria membrane potential (MMP) potential by arresting cells at the G0/G1 phase, suggesting the initiation of apoptosis. Western blotting analysis revealed the upregulation of p53, caspase3, and caspase9 while the expressions of p-NF-κB, p-Akt and Bcl-xl were decreased. RT-qPCR studies also showed upregulation in the expression of p53 and caspase3 and downregulation in the expression of CDK2, Bcl-2 and Cyclin E genes. Molecular docking analysis displayed the interaction between BDCe fraction with p53 (−151.13 kcal/mol) and CDK1 (−133.96 kcal/mol). The results of the present work suggest that the BDCe fraction has chemopreventive properties against osteosarcoma (MG-63) cells through the induction of cell cycle arrest and apoptosis via Akt/NF-κB/p53 pathways. This study contributes to the understanding of the utilization of BDCe fraction in osteosarcoma treatment. 相似文献
750.
Satish Kumar Sandeep Kumar Sushant Kumar Tarun Yadav Pawan Singh Dhapola Pramod K. Singh 《Macromolecular Symposia》2024,413(1):2300146
Plastics are widely used synthetic materials in various industries worldwide. The abundance of plastics, which are mainly carbon-based polymers, has led to a significant accumulation of plastic waste in landfills and the environment due to their durability and affordability. Although plastic pollution of the oceans has been known for many years, there is still limited knowledge about the composition, distribution, impact, and fate of plastic waste in the environment. In this review, the focus is on environmental pollution by plastics, highlighting the source (feedstock) and degradation behavior of these materials. The goal is to provide insights for material design strategies that address the management of plastic waste at the end of its life cycle. The authors argue that the development of materials labeled marine biodegradable or universally biodegradable is not a sufficient solution on its own to address plastic pollution. Instead, it is critical to incorporate practical plans for recovery and treatment into material and product design principles. These plans should be based on existing systems or possibly developed in parallel. In summary, this article highlights the widespread pollution of the environment by plastics and emphasizes the need for comprehensive material design strategies that include not only biodegradability but also practical recovery and treatment methods. By considering the entire lifecycle of plastics, we can work to reduce the harmful impact of plastic waste on our planet. 相似文献