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571.
Polycrystalline BaCo1/2W1/2O3 (BCW) is prepared by the solid-state reaction technique. The X-ray diffraction study of the compound at room temperature reveals the monoclinic phase. The field dependence of the dielectric constant and the conductivity are measured in the frequency range from 50 Hz to1 MHz and in the temperature range from 300 to 413 K. An analysis of the real and imaginary parts of the dielectric permittivity with frequency is performed. The frequency-dependent maxima in the imaginary impedance are found to obey an Arrhenius law with an activation energy=0.86 eV. The frequency-dependent electrical data are also analysed in the framework of the conductivity and modulus formalisms. 相似文献
572.
P. Gupta B.C. Choudhary S. Chatterji S. Bhattacharya 《The European Physical Journal C - Particles and Fields》2008,53(1):49-58
We present simulation results of γ+jet analysis using CMS (compact muon solenoid) object-oriented software at the large hadron
collider (LHC) center of mass energy = 14 TeV. The study of direct photon production helps in validating the perturbative quantum chromodynamics (pQCD) and providing
information on the gluon distribution in the nucleons. Direct photon processes also constitute a major background to several
other standard model (SM) processes and signals of new physics. Thus these processes need to be understood precisely in the
new energy regime. In this work, we have done a detailed study of the GEANT4 simulated γ+jet events generated with Pythia,
and the related background processes. Isolation cuts have been optimized for direct photon which improves the signal over
background ratio by ∼25% as compared to previous studies done in CMS. The inclusion of a large Δφ cut between the photon and
the leading jet at 40° in the analysis leads to a further increase of ∼15% in S/B, thus giving an overall gain of ∼42% in
S/B ratio. 相似文献
573.
Dinesh Varshney A. Yogi K.K. Choudhary 《Physica C: Superconductivity and its Applications》2010,470(22):2016-2022
In this paper, we undertake a quantitative analysis of observed temperature-dependent in-plane normal state electrical resistivity of single crystal YBa2Cu4O8. The analysis is within the framework of classical electron–phonon i.e., Bloch-Gruneisen model of resistivity. It is based on the inherent acoustic (low frequency) phonons (ωac) as well as high frequency optical phonons (ωop), the contributions to the phonon resistivity were first estimated. The optical phonons of the oxygen breathing mode yields a relatively larger contribution to the resistivity compared to the contribution of acoustic phonons. Estimated contribution to in-plane electrical resistivity by considering both phonons i.e., ωac and ωop, along with the zero-limited resistivity, when subtracted from single crystal data infers a quadratic temperature dependence over most of the temperature range [80 ? T ? 300]. Quadratic temperature dependence of ρdiff. = [ρexp − {ρ0 + ρe−ph (=ρac + ρop)}] is understood in terms of electron–electron inelastic scattering. The relevant energy gap expressions within the Nambu-Eliashberg approach are solved imposing experimental constraints on their solution (critical temperature Tc). It is found that the indirect-exchange formalism provides a unique set of electronic parameters [electron–phonon (λph), electron-charge fluctuations (λpl), electron–electron (μ) and Coulomb screening parameter (μ*)] which, in particular, reproduce the reported value of Tc. 相似文献
574.
Aaminat Qureshi Louise A. Ouattara Naglaa Salem El-Sayed Amita Verma Gustavo F. Doncel Muhammad Iqbal Choudhary Hina Siddiqui Keykavous Parang 《Molecules (Basel, Switzerland)》2022,27(14)
The activity of nucleoside and nucleotide analogs as antiviral agents requires phosphorylation by endogenous enzymes. Phosphate-substituted analogs have low bioavailability due to the presence of ionizable negatively-charged groups. To circumvent these limitations, several prodrug approaches have been proposed. Herein, we hypothesized that the conjugation or combination of the lipophilic amide bond with nucleotide-based tenofovir (TFV) (1) could improve the anti-HIV activity. During the current study, the hydroxyl group of phosphonates in TFV was conjugated with the amino group of L-alanine, L-leucine, L-valine, and glycine amino acids and other long fatty ester hydrocarbon chains to synthesize 43 derivatives. Several classes of derivatives were synthesized. The synthesized compounds were characterized by 1H NMR, IR, UV, and mass spectrometry. In addition, several of the synthesized compounds were evaluated as racemic mixtures for anti-HIV activity in vitro in a single round infection assay using TZM-bl cells at 100 ng/mL. TFV (1) was used as a positive control and inhibited HIV infection by 35%. Among all the evaluated compounds, the disubstituted heptanolyl ester alanine phosphonamidate with naphthol oleate (69), pentanolyl ester alanine phosphonamidate with phenol oleate (62), and butanolyl ester alanine phosphonamidate with naphthol oleate (87) ester conjugates of TFV were more potent than parent drug TFV with 79.0%, 76.5%, 71.5% inhibition, respectively, at 100 ng/mL. Furthermore, two fatty acyl amide conjugates of tenofovir alafenamide (TAF) were synthesized and evaluated for comparative studies with TAF and TFV conjugates. Tetradecanoyl TAF conjugate 95 inhibited HIV infection by 99.6% at 100 ng/mL and showed comparable activity to TAF (97–99% inhibition) at 10–100 ng/mL but was more potent than TAF when compared at molar concentration. 相似文献
575.
The paper describes the sulphonation of commercially available poly(ether ether ketone) PEEK (GATONETM, Gharda Chemicals Limited, India and VICTREX®, ICI Limited, UK) by using concentrated sulphuric acid. The concentration of GATONE in conc. H2SO4 was varied from 4-10% (w/v) whereas in VICTREX® the concentration was 4% (w/v). The temperature was varied from 35-55°C and the duration of reaction was 3-7 h. Structural characterisation of sulphonated polymers was done by elemental analysis, FT-IR and 1H-NMR spectroscopy. On the basis of elemental analysis, the extent of sulphonation of GATONE was found to be 57-75%. The extent of sulphonation as determined by 1H-NMR in case of GATONE was in the range of 53-80% and for VICTREX 58-87%. Thermal analysis, proton conductivity and water uptake of these samples were also studied. Proton conductivity of the films was comparable to the perflourinated polymer (Nafion). 相似文献
576.
Ghulam Murtaza Majid Khan Saba Farooq M. Iqbal Choudhary Sammer Yousuf 《Acta Crystallographica. Section C, Structural Chemistry》2023,79(6):237-248
Many heterocycles have been developed as drugs due to their capacity to interact productively with biological systems. The present study aimed to synthesize cocrystals of the heterocyclic antitubercular agent pyrazinamide ( PYZ , 1 , BCS III) and the commercially available anticonvulsant drug carbamazepine ( CBZ , 2 , BCS class II) to study the effect of cocrystallization on the stability and biological activities of these drugs. Two new cocrystals, namely, pyrazinamide–homophthalic acid (1/1) ( PYZ:HMA , 3 ) and carbamazepine–5-chlorosalicylic acid (1/1) ( CBZ:5-SA , 4 ), were synthesized. The single-crystal X-ray diffraction-based structure of carbamazepine–trans-cinnamic acid (1/1) ( CBZ:TCA , 5 ) was also studied for the first time, along with the known cocrystal carbamazepine–nicotinamide (1/1) ( CBZ:NA , 6 ). From a combination drug perspective, these are interesting pharmaceutical cocrystals to overcome the known side effects of PYZ ( 1 ) therapy, and the poor biopharmaceutical properties of CBZ ( 2 ). The purity and homogeneity of all the synthesized cocrystals were confirmed by single-crystal X-ray diffraction, powder X-ray diffraction and FT–IR analysis, followed by thermal stability studies based on differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Detailed intermolecular interactions and the role of hydrogen bonding towards crystal stability were evaluated quantitatively via Hirshfeld surface analysis. The solubility of CBZ at pH 6.8 and 7.4 in 0.1 N HCl and H2O were compared with the values of cocrystal CBZ:5-SA ( 4 ). The solubility of CBZ:5-SA was found to be significantly improved at pH 6.8 and 7.4 in H2O. All the synthesized cocrystals 3 – 6 exhibited a potent urease inhibition (IC50 values range from 17.32 ± 0.89 to 12.3 ± 0.8 µM), several times more potent than standard acetohydroxamic acid (IC50 = 20.34 ± 0.43 µM). PYZ:HMA ( 3 ) also exhibited potent larvicidal activity against Aedes aegypti. Among the synthesized cocrystals, PYZ:HMA ( 3 ) and CBZ:TCA ( 5 ) were found to possess antileishmanial activity against the miltefosine-induced resistant strain of Leishmania major, with IC50 values of 111.98 ± 0.99 and 111.90 ± 1.44 µM, respectively, in comparison with miltefosine (IC50 = 169.55 ± 0.20 µM). 相似文献
577.
Deepshikha Yadav Shilpi Verma Jyoti Choudhary Harleen Kaur Pratibha Tiwari Sandeep Singh Pallavi Kushwaha Premshankar K. Dubey Pranjal Chandra Surinder P. Singh 《Electroanalysis》2023,35(4):e202200286
Folic acid (FA) deficiency is associated with several clinical conditions such as megaloblastic anemia, neuropsychiatric, and pregnancy-related syndromes, this makes FA an important metabolite to be monitored. We have fabricated an electrochemical biosensor based on gold nanoparticles decorated molybdenum disulfide nanosheets (AuNPs−MoS2NSs) nanocomposite as a transducer matrix for specific and rapid electrochemical detection of FA. Differential pulse voltammetry (DPV) studies displayed a rapid analytical response of the fabricated AuNPs−MoS2NSs/GCE sensor probe towards FA in a wide concentration range of 0.001–100 μM with a very low detection limit of 0.72±0.03 nM. The selectivity of the fabricated sensor probe has been examined in the presence of interferents such as dopamine, uric acid, ascorbic acid, glucose, and urea. The clinical potential of the fabricated biosensor was established by monitoring FA in human serum samples. The developed AuNPs−MoS2NSs/GCE sensor probe showed high reproducibility and stability, indicating its promise for FA detection in clinical settings. 相似文献
578.