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91.
Laves-phase Nb(1+c)Fe(2-c) is a rare itinerant intermetallic compound exhibiting magnetic quantum criticality at c(cr)~1.5%Nb excess; its origin, and how alloying mediates it, remains an enigma. For NbFe(2), we show that an unconventional band critical point above the Fermi level E(F) explains most observations and that chemical alloying mediates access to this unconventional band critical point by an increase in E(F) with decreasing electrons (increasing %Nb), counter to rigid-band concepts. We calculate that E(F) enters the unconventional band critical point region for c(cr) > 1.5%Nb and by 1.74%Nb there is no Nb site-occupation preference between symmetry-distinct Fe sites, i.e., no electron-hopping disorder, making resistivity near constant as observed. At larger Nb (Fe) excess, the ferromagnetic Stoner criterion is satisfied. 相似文献
92.
Shaista Bano Ayaz Mohd Aftab Aslam Parwaz Khan K. S. Siddiqi 《Journal of Analytical Chemistry》2011,66(7):603-609
Simple, accurate, rapid, and sensitive spectrofluorimetric methods for the determination of levosulpiride in pharmaceutical
formulation were developed utilizing its fluorescence reaction with Fe3+ (method A) and Al3+ (method B). The calibration curves were found to be linear in the concentration range 0.239–3.44 μg/mL and 0.310–2.730 μg/mL with limit
of detection 0.005 μg/mL and 0.0032 μg/mL, respectively, for method A and method B. The reaction conditions were studied and optimized. In addition, the complexation of Mg2+ and Ca2+ was also studied. In all cases, an enhancement in fluorescence emission of levosulpiride upon formation of complex with metal
ions was observed. A 2: 1 (drug: metal) stoichiometry for all the complexes was established. Benesi-Hildebrand method was
applied for calculation of association constant at 25 and 35°C. The thermodynamic parameters obtained in this study revealed
that the interaction process was spontaneous and mainly ΔS-driven. 相似文献
93.
Mohamed T. Ghoneim Jhonathan P. Rojas Aftab M. Hussain Muhammad M. Hussain 《固体物理学:研究快报》2014,8(2):163-166
We report the inherent increase in capacitance per unit planar area of state‐of‐the art high‐κ integrated metal/insulator/metal capacitors (MIMCAPs) fabricated on flexible silicon fabric with release‐first process. We methodically study and show that our approach to transform bulk silicon (100) into a flexible fabric adds an inherent advantage of enabling higher integration density dynamic random access memory (DRAM) on the same chip area. Our approach is to release an ultra‐thin silicon (100) fabric (25 µm thick) from the bulk silicon wafer, then build MIMCAPs using sputtered aluminium electrodes and successive atomic layer depositions (ALD) without break‐ing the vacuum of a high‐κ aluminium oxide sandwiched between two tantalum nitride layers. This result shows that we can obtain flexible electronics on silicon without sacrificing the high density integration aspects and also utilize the non‐planar geometry associated with fabrication process to obtain a higher integration density compared to bulk silicon integration due to an increased normalized capacitance per unit planar area. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
94.
Sadia Sagar Nadeem Iqbal Asghari Maqsood Umair Javaid 《Journal of Thermal Analysis and Calorimetry》2013,113(1):161-167
Pristine multiwalled carbon nanotubes (MWCNTs) were impregnated in acrylonitrile butadiene rubber (NBR) using internal dispersion kneader and two roller mixing mill to investigate the effects of various nanotubes concentrations on the thermal transport/stability of rubber nanocomposites. Thermal conductivity (λ N) and thermal impedance (R) measurement experimental setups were established according to ASTM E1225-99 and D5470-03. The 1 mass % addition of MWCNTs in the polymer matrix has enhanced R up to 44 % and reduced λ N of the rubber nanocomposite up to 40 % compare to the base composite formulation. Thermal decomposition and differential thermal analyses of the fabricated composite specimens simulate that the thermal stability and endothermic capability are augmented with increasing the nanotubes contents in the host matrix. The progressive incorporations of carbon nanotubes into the rubber matrix have efficiently influenced the composite specimens regarding glass transition, crystallization, and melting temperatures including their specific enthalpies. Scanning electron microscopy along with the energy dispersive spectroscopy was used to analyze MWCNTs dispersion in NBR matrix, compositional analysis of the nanocomposite, and impregnated nanotubes. 相似文献
95.
Hasib Khan Yongjin Li Aftab Khan Aziz Khan 《Mathematical Methods in the Applied Sciences》2019,42(9):3377-3387
In the literature, many researchers have studied Lotka‐Volterra (L‐V) models for different types of studies. In order to continue the study, we consider a fractional‐order L‐V model involving three different species in the Atangana‐Baleanu‐Caputo (ABC) sense of fractional derivative. This new model has potentials for a large number of research‐oriented studies. The first point that arises is whether the new model has a solution or not. Therefore, to answer this question, we consider the existence and uniqueness (EU) of the solutions and then Hyers‐Ulam (HU) stability for the proposed L‐V model. 相似文献
96.
Youquan Chen Yuyang Yin Dr. Xing Xing Daqi Fang Yang Zhao Yanan Zhu Muhammad Umair Ali Yuhao Shi Junwu Bai Prof. Peiheng Wu Prof. Clifton Kwang-Fu Shen Prof. Hong Meng 《Chemphyschem》2020,21(4):321-327
Solution-processable electrochromic polymers (ECPs) with high performance are urgently needed for extensive applications. Nevertheless, they suffer from slow switching speed because of low ionic conductivities. Herein, we present an effective strategy to improve the contrast and switching speed in ECPs via facile side-chain engineering. A novel electrochromic thieno[3,2-b]thiophene-based polymer (PmOTTBTD) is designed and successfully synthesized by introducing oligo(ethylene oxide) side chains with high ionic conductivity. Compared to the counterpart POTTBTD without modification by oligo(ethylene oxide) chains, PmOTTBTD demonstrates nearly double contrast (42 % vs. 24 %) with a fast oxidation switching process that just takes half of the time when detected under 400 nm, as well as much higher coloration efficiencies (e. g. 239.04 cm2 C−1 vs. 226.26 cm2 C−1 @ 400 nm and 314.04 cm2 C−1 vs. 174.00 cm2 C−1 @ 650∼700 nm). Besides, PmOTTBTD exhibits excellent stability with negligible decay after 3000 cycles. Our work suggests a facile strategy that could be adopted to realize high-performance ECPs via molecular design tuning. 相似文献
97.
98.
Mohammed M. Rahman Sher Bahadar Khan Abdullah M. Asiri Khalid A. Alamry Aftab Aslam Parwaz Khan Anish Khan Malik Abdul Rub Naved Azum 《Mikrochimica acta》2013,180(7-8):675-685
This paper describes a reliable and sensitive method for sensing dissolved acetone using doped nanomaterials. Large-scale synthesis of ZnO nanorods (NRs) doped with Co3O4 was accomplished by a solvothermal method at low temperature. The doped NRs were characterized in terms of their morphological, structural, and optical properties by using field-emission scanning electron microscopy coupled with energy-dispersive system, UV-Vis., Fourier transform IR, X-ray diffraction, and Xray photoelectron spectroscopy. The calcinated (at 400 °C) doped NRs are shown to be an attractive semiconductor nanomaterial for detecting acetone in aqueous solution using silver electrodes. The sensor exhibits excellent sensitivity, stability and reproducibility. The calibration plot is linear over a large concentration range (66.8 μM to 0.133 mM), displays high sensitivity (~3.58 μA cm?2 mM?1) and a low detection limit (~14.7?±?0.2 μM; at SNR of 3). Figure
The present study describes a simple, reliable, accurate, sensitive, and cost effective method for the detection of acetone using solvothermally prepared semiconductor co-doped nanomaterials. 相似文献
99.
Naved Azum Malik Abdul Rub Abdullah M. Asiri Aftab Aslam Parwaz Khan Anish Khan Sher Bahadar Khan Mohammad M. Rahman Abdulrahman O. Al-Youbi 《Journal of solution chemistry》2013,42(7):1532-1544
Pyrene fluorescence measurements were carried out on various binary mixtures of the antidepressant amphiphilic drug amitriptyline hydrochloride (AMT) with conventional (TTAB and CTAB) and gemini surfactants (14-4-14 and 16-4-16). In all cases mixed micellar aggregates were formed and the mixed critical micelle concentration (cmc) of various mixtures was computed from the I 1/I 3 versus total surfactant concentration plots. In the region where mixed micelles are formed, the interaction of the amphiphlic drug and four surfactants showed synergistic behavior. The results were analyzed using an interaction parameter, β, which characterize the interaction in the mixed micelle and is introduced by a regular solution theory. The β values are negative in all binary mixtures, and their magnitudes increase with increasing hydrophobicity of the amphiphile. The micellar mole fraction of AMT in the mixed micelle (x 1) and in the ideal sate (x ideal) were evaluated and their values (x 1 > x ideal) suggest that the contribution of the AMT component is greater in binary mixtures as compared to that in the ideal state. Activity coefficients (f 1 and f 2) and excess Gibbs energy (G ex) were also calculated. The values of micelle aggregation numbers (N agg) and various other parameters like the Stern–Volmer constant (K sv), micropolarity and dielectric constant of mixed systems have also been evaluated from the ratios of respective peak intensities (I 1/I 3 or I 0/I 1). 相似文献
100.
Malik Abdul Rub Abdullah M. Asiri Anish Khan Aftab Aslam Parwaz Khan Naved Azum Sher Bahadar Khan Kabir-ud-Din 《Journal of solution chemistry》2013,42(2):390-411
Micellization and phase separation of the amphiphilic drug amitriptyline hydrochloride (AMT) in the absence and presence of cationic hydrotropes (aniline hydrochloride, para-toluidine hydrochloride, and ortho-toluidine hydrochloride) have been investigated in the present study. The experimental critical micelle concentration (cmc) values are lower than cmc id values (cmc id is the cmc value at ideal mixing state), indicating attractive interactions between the two components (drug and hydrotrope) in mixed micelles. The bulk behaviors were investigated using the different theoretical models of Clint, Rubingh, Motomura, and Rodenas for comparison of the results of different binary combinations of the drug and hydrotropes. Synergistic interactions were confirmed in all binary combinations at all temperatures, which increase with increasing concentration of hydrotropes. Activity coefficients (f 1 and f 2) were found to be consistently less than unity indicating nonideality in the systems. At a fixed drug concentration (50 mmol·dm?3) and pH (6.7), the hydrotropes showed a continuous increase in the cloud point. Thermodynamic parameters were also evaluated and discussed in detail. 相似文献