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611.
Frank Seela Khalil Shaikh Henning Eickmeier 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(7):o489-o491
The title compound, C14H16N4O4, adopts the anti conformation at the glycosylic bond [χ−117.1 (5)°]. The sugar pucker of the 2′‐deoxyribofuranosyl moiety is C2′‐endo–C3′‐exo, 2T3 (S‐type). The orientation of the exocyclic C4′—C5′ bond is +sc (gauche). The propynyl group is linear and coplanar with the nucleobase moiety. The structure of the compound is stabilized by several hydrogen bonds (N—H⋯O and O—H⋯O), leading to the formation of a multi‐layered network. The nucleobases, as well as the propynyl groups, are stacked. This stacking might cause the extraordinary stability of DNA duplexes containing this compound. 相似文献
612.
Boron trifluoride (BF3) proportional counters are used as detectors for thermal neutrons. They are characterized by high neutron sensitivity and
good gamma discriminating properties. Most practical BF3 counters are filled with pure boron trifluoride gas enriched up to 96% 10B. But BF3 is not an ideal proportional counter gas. Worsening of plateau characteristics is observed with increasing radius due to
impurities in gas. To overcome this problem, counters are filled with BF3 with an admixture of a more suitable gas such as argon. The dilution of BF3 with argon causes a decrease in detection efficiency, but the pulse height spectrum shows sharper peaks and more stable plateau
characteristics than counters filled with pure BF3. The present investigations are undertaken to study the pulse height distribution and other important factors in BF3+Ar filled signal counters for neutron beam applications. Tests are performed with detectors with cylindrical geometry filled
with BF3 gas enriched in 10B to 90%, and high purity Ar in different proportions. By analysing pulse height spectra, a value of 6.1 ± 0.2 has been obtained
for the branching ratio of the 10B(n,α) reaction.
相似文献
613.
Superconducting Ba1−xKxBiO3−δ pellets were synthesized by solid state reaction followed by sintering. Thermo-gravimetric and differential thermo-gravimetric analysis (TG-DTA) of the mixture of nitrates was carried out to study the reactions during the phase formation. The effect of different sintering temperatures on the phase formation was studied. The X-ray diffraction data confirms the formation of superconducting Ba0.6K0.4BiO2.23 phase at 700 °C. The surface morphological studies as a function of sintering temperature were studied by SEM. It is observed that the pellets prepared by solid state reaction followed its sintering at 700°C shows the superconducting transition at 26.8 K. 相似文献
614.
Shirin Panahi Sajad Jafari Abdul Jalil M. Khalaf Karthikeyan Rajagopal Viet–Thanh Pham Fawaz E. Alsaadi 《Chinese Journal of Physics (Taipei)》2018,56(5):2254-2264
In the last decades, many studies have been done about nervous system from the mathematical and computational point of view. Many mathematical models have been proposed to describe neuron. Most of them have described the membrane potential of a neuron in terms of the leakage current and the synaptic inputs. Very recently, according to the Maxwell electromagnetic induction theorem, researchers proposed a new neuron model which considers inner magnetic fluctuation and external electromagnetic radiation as a significant missing part that can participate in neural activity. In this paper, dynamical properties of this new model, such as equilibria and its stability, phase portraits, bifurcation diagram, Lyapunov exponents, and basin of attraction, are investigated. Moreover, an implementation of electronic circuit and FPGA is also done to verify the feasibility of the theoretical model. 相似文献
615.
De P Maji S Chowdhury AD Mobin SM Mondal TK Paretzki A Lahiri GK 《Dalton transactions (Cambridge, England : 2003)》2011,40(46):12527-12539
The present article describes ruthenium nitrosyl complexes with the {RuNO}(6) and {RuNO}(7) notations in the selective molecular frameworks of [Ru(II)([9]aneS(3))(bpy)(NO(+))](3+) (4(3+)), [Ru(II)([9]aneS(3))(pap) (NO(+))](3+) (8(3+)) and [Ru(II)([9]aneS(3))(bpy)(NO˙)](2+) (4(2+)), [Ru(II)([9]aneS(3))(pap)(NO˙)](2+) (8(2+)) ([9]aneS(3) = 1,4,7-trithiacyclononane, bpy = 2,2'-bipyridine, pap = 2-phenylazopyridine), respectively. The nitrosyl complexes have been synthesized by following a stepwise synthetic procedure: {Ru(II)-Cl} → {Ru(II)-CH(3)CN} → {Ru(II)-NO(2)} → {Ru(II)-NO(+)} → {Ru(II)-NO˙}. The single-crystal X-ray structure of 4(3+) and DFT optimised structures of 4(3+), 8(3+) and 4(2+), 8(2+) establish the localised linear and bent geometries for {Ru-NO(+)} and {Ru-NO˙} complexes, respectively. The crystal structures and (1)H/(13)C NMR suggest the [333] conformation of the coordinated macrocyclic ligand ([9]aneS(3)) in the complexes. The difference in π-accepting strength of the co-ligands, bpy in 4(3+) and pap in 8(3+) (bpy < pap) has been reflected in the ν(NO) frequencies of 1945 cm(-1) (DFT: 1943 cm(-1)) and 1964 cm(-1) (DFT: 1966 cm(-1)) and E°({Ru(II)-NO(+)}/{Ru(II)-NO˙}) of 0.49 and 0.67 V versus SCE, respectively. The ν(NO) frequency of the reduced {Ru-NO˙} state in 4(2+) or 8(2+) however decreases to 1632 cm(-1) (DFT: 1637 cm(-1)) or 1634 cm(-1) (DFT: 1632 cm(-1)), respectively, with the change of the linear {Ru(II)-NO(+)} geometry in 4(3+), 8(3+) to bent {Ru(II)-NO˙} geometry in 4(2+), 8(2+). The preferential stabilisation of the eclipsed conformation of the bent NO in 4(2+) and 8(2+) has been supported by the DFT calculations. The reduced {Ru(II)-NO˙} exhibits free-radical EPR with partial metal contribution revealing the resonance formulation of {Ru(II)-NO˙}(major)?{Ru(I)-NO(+)}(minor). The electronic transitions of the complexes have been assigned based on the TD-DFT calculations on their DFT optimised structures. The estimated second-order rate constant (k, M(-1) s(-1)) of the reaction of the nucleophile, OH(-) with the electrophilic {Ru(II)-NO(+)} for the bpy derivative (4(3+)) of 1.39 × 10(-1) is half of that determined for the pap derivative (8(3+)), 2.84 × 10(-1) in CH(3)CN at 298 K. The Ru-NO bond in 4(3+) or 8(3+) undergoes facile photolytic cleavage to form the corresponding solvent species {Ru(II)-CH(3)CN}, 2(2+) or 6(2+) with widely varying rate constant values, (k(NO), s(-1)) of 1.12 × 10(-1) (t(1/2) = 6.2 s) and 7.67 × 10(-3) (t(1/2) = 90.3 s), respectively. The photo-released NO can bind to the reduced myoglobin to yield the Mb-NO adduct. 相似文献
616.
Bidhan Pandit Emad S.Goda Mahmoud H.Abu Elella Aafaq ur Rehman Sang Eun Hong Sachin R.Rondiya Pranay Barkataki Shoyebmohamad F.Shaikh Abdullah M.Al-Enizi Salah MEl-Bahy Kuk Ro Yoon 《Journal of Energy Chemistry》2022,(2):116-126
An eco-friendly, new, and controllable approach for the preparation of manganese oxide(a-MnO2) nanorods has been introduced using hydrothermal reaction for supercapacitor application. The in-depth crystal structure analysis of α-MnO2 is analyzed by X-ray Rietveld refinement by using Full Prof program with the help of pseudo-Voigt profile function. The developed a-MnO2 electrode attains a remarkable capacitance of 577.7 F/g recorded at a current density value of 1... 相似文献
617.
Banafsheh Honarvari Sara Karimifard Niyayesh Akhtari Mehrnoush Mehrarya Zahra Salehi Moghaddam Mohammad Javed Ansari Abduladheem Turki Jalil Adrin Matencio Francesco Trotta Faten Eshrati Yeganeh Bahareh Farasati Far Mandana Kazem Arki Mohammad Reza Naimi-Jamal Hassan Noorbazargan Zahra Asghari Lalami Mohsen Chiani 《Molecules (Basel, Switzerland)》2022,27(14)
As the most common cancer in women, efforts have been made to develop novel nanomedicine-based therapeutics for breast cancer. In the present study, the in silico curcumin (Cur) properties were investigated, and we found some important drawbacks of Cur. To enhance cancer therapeutics of Cur, three different nonionic surfactants (span 20, 60, and 80) were used to prepare various Cur-loaded niosomes (Nio-Cur). Then, fabricated Nio-Cur were decorated with folic acid (FA) and polyethylene glycol (PEG) for breast cancer suppression. For PEG-FA@Nio-Cur, the gene expression levels of Bax and p53 were higher compared to free drug and Nio-Cur. With PEG-FA-decorated Nio-Cur, levels of Bcl2 were lower than the free drug and Nio-Cur. When MCF7 and 4T1 cell uptake tests of PEG-FA@Nio-Cur and Nio-Cur were investigated, the results showed that the PEG-FA-modified niosomes exhibited the most preponderant endocytosis. In vitro experiments demonstrate that PEG-FA@Nio-Cur is a promising strategy for the delivery of Cur in breast cancer therapy. Breast cancer cells absorbed the prepared nanoformulations and exhibited sustained drug release characteristics. 相似文献
618.
Lohana Bhojraj Abro Kashif Ali Shaikh Abdul Wasim 《Journal of Thermal Analysis and Calorimetry》2021,144(1):155-165
Journal of Thermal Analysis and Calorimetry - This paper presents that how the characteristics of thermal radiation depend on the temperature of unsteady gravity-driven thermal convection flow of... 相似文献
619.
Romina Oliva Abdul Rajjak Shaikh Andrea Petta Anna Vangone Luigi Cavallo 《Molecules (Basel, Switzerland)》2021,26(9)
The crown of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is constituted by its spike (S) glycoprotein. S protein mediates the SARS-CoV-2 entry into the host cells. The “fusion core” of the heptad repeat 1 (HR1) on S plays a crucial role in the virus infectivity, as it is part of a key membrane fusion architecture. While SARS-CoV-2 was becoming a global threat, scientists have been accumulating data on the virus at an impressive pace, both in terms of genomic sequences and of three-dimensional structures. On 15 February 2021, from the SARS-CoV-2 genomic sequences in the GISAID resource, we collected 415,673 complete S protein sequences and identified all the mutations occurring in the HR1 fusion core. This is a 21-residue segment, which, in the post-fusion conformation of the protein, gives many strong interactions with the heptad repeat 2, bringing viral and cellular membranes in proximity for fusion. We investigated the frequency and structural effect of novel mutations accumulated over time in such a crucial region for the virus infectivity. Three mutations were quite frequent, occurring in over 0.1% of the total sequences. These were S929T, D936Y, and S949F, all in the N-terminal half of the HR1 fusion core segment and particularly spread in Europe and USA. The most frequent of them, D936Y, was present in 17% of sequences from Finland and 12% of sequences from Sweden. In the post-fusion conformation of the unmutated S protein, D936 is involved in an inter-monomer salt bridge with R1185. We investigated the effect of the D936Y mutation on the pre-fusion and post-fusion state of the protein by using molecular dynamics, showing how it especially affects the latter one. 相似文献
620.
Dr. Shaikh A. Ali Dr. Hasan A. Al-Muallem Dr. Mohammad A. J. Mazumder 《Chemical record (New York, N.Y.)》2023,23(2):e202200235
This article reviews the synthesis of polyzwitterions (PZs) (poly-carboxybetaines, -phosphonobetaines, and -sulfobetaines) having multiple pH-responsive centers. The synthesis follows the Butler cyclopolymerization protocol involving a multitude of diallylammonium salts and their copolymerization with SO2 and maleic acid. The PZs have been transformed into cationic-, anionic-polyelectrolytes, and polyampholytes under the influence of pH. Particular attention is given to the application of these polymers as antiscalants, mild steel corrosion inhibitors, components in constructing Aqueous Two-Phase Systems (ATPSs), and membrane modifiers. The ATPSs could be used to separate various biomolecules, including proteins. Many amphiphilic polymers incorporating a few mol % hydrophobic monomers have shown enhanced viscosities and could be suitable for applications in oil fields. The progress of applying Butler cyclopolymerization in reversible addition-fragmentation chain transfer (RAFT) chemistry has been discussed. Future works are expected to focus on RAFT cyclopolymerization to construct block copolymers. 相似文献