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排序方式: 共有886条查询结果,搜索用时 15 毫秒
81.
Rajesh Kumar Rajesh Kumar Singh Pawan Kumar Dubey Dinesh Pratap Singh Ram Manohar Yadav Radhey Shyam Tiwari 《Advanced Materials Interfaces》2015,2(15)
3D hierarchical structures are reported based on graphene–nickel encapsulated nitrogen‐rich aligned bamboo like carbon nanotubes, which show not only high‐performance supercapacitance behavior but also a great robust cyclic stability. A facile synthesis route is developed of 2D nickel oxide decorated functionalized graphene nanosheets (2D‐NiO‐f:GNSs) hybrids and 3D nitrogen doped bamboo‐shaped carbon nanotubes (NCNTs) vertically standing on the functionalized graphene nanosheets (3D‐NCNT@f:GNSs) by using a thermal decomposition method. The chemical reduction and morphology‐dependent electrochemical response are investigated. The enhanced specific capacitance of 3D‐NCNT@f:GNSs as compared to that of 2D‐NiO‐f:GNSs suggests the synergistic effects and indicates the importance of energy storage and superior long‐term cycling performance that are achieved. This 3D‐NCNT@f:GNSs hybrid shows a remarkable cycling stability with a maximum power density of 12.32 kW kg−1 and maximum energy density of 109.13 Wh kg−1 due to the good connection of NCNT and f:GNSs. This unique 3D nano network architecture enables the availability of large surface areas of NCNT, thus endowing the nanohybrids with high specific capacitance and excellent reusability. 相似文献
82.
Harish C. Upadhyay Dr. Gaurav R. Dwivedi Dr. Sudeep Roy Dr. Ashok Sharma Mahendra P. Darokar Dr. Santosh K. Srivastava 《ChemMedChem》2014,9(8):1860-1868
Phytol was chemically transformed into fifteen semi‐synthetic derivatives, which were evaluated for their antibacterial and drug resistance reversal potential in combination with nalidixic acid against E. coli strains CA8000 and DH5α. The pivaloyl ( 4 ), 3,4,5‐trimethoxybenzoyl ( 9 ), 2,3‐dichlorobenzoyl ( 10 ), cinnamoyl ( 11 ), and aldehyde ( 14 ) derivatives of phytol ((2E,7R,11R)‐3,7,11,15‐tetramethyl‐2‐hexadecen‐1‐ol) were evaluated by using another antibiotic, tetracycline, against the MDREC‐KG4 clinical isolate of E. coli. Derivative 4 decreased the maximal inhibitory concentration (MIC) of the antibiotics by 16‐fold, while derivatives 9 , 10 , 11 , and 14 reduced MIC values of the antibiotics up to eightfold against the E. coli strains. Derivatives 4 , 9 , 10 , 11 , and 14 inhibited the ATP‐dependent efflux pump; this was also supported by their in silico binding affinity and down‐regulation of the efflux pump gene yojI, which encodes the multidrug ATP‐binding cassette transporter protein. This study supports the possible use of phytol derivatives in the development of cost‐effective antibacterial combinations. 相似文献
83.
This paper represents an efficient bootstrapped analog to digital converter with augmented NMOS sleep transistors. The newly designed MOS-based bootstrapped circuit is implemented to provide controlled input supply for analog to digital converter to develop the enhancing capability of circuit. This will reduce the effective leakage of the circuit. In the second stage, the NMOS sleep transistors are augmented as pull-up and pull-down transistors. Due to augmentation of transistors, controlled power supply ( \(V_{\mathrm{DD}})\) is obtained. Because of this, current driving capability in MOS transistors is improved and minimum sub-threshold leakage current is formed. Due to this, reduction of leakage power dissipation occurs much effectively. The whole simulation has been done at 45 nm (nanometer) technology. It is realized that the leakage power is reduced till 50 % approximately and delay performance is improved. It means that speed is improved using bootstrapped circuit with augmented sleep transistors NMOS. In this paper, different consecutive designs with Analog to Digital converter are represented. 相似文献
84.
High strength aluminium alloys generally present low weldability because of the poor solidification microstructure, porosity in the fusion zone and loss in mechanical properties when welded by fusion welding processes which otherwise can be welded successfully by comparatively newly developed process called friction stir welding (FSW). This paper presents the effect of post weld heat treatment (T6) on the microstructure and mechanical properties of friction stir welded 7039 aluminium alloy. It was observed that the thermo-mechanically affected zone (TMAZ) showed coarser grains than that of nugget zone but lower than that of heat affected zone (HAZ). The decrease in yield strength of welds is more serious than decrease in ultimate tensile strength. As welded joint has highest joint efficiency (92.1%). Post weld heat treatment lowers yield strength, ultimate tensile strength but improves percentage elongation. 相似文献
85.
Biodegradation of phenylurea herbicide isoproturon was studied in soil microcosm bioaugmented with a novel bacterial strain JS-11 isolated from wheat rhizosphere. The molecular characterization based on 16SrDNA sequence homology confirmed its identity as Pseudomonas aeruginosa strain JS-11. The herbicide was completely degraded within 20 days at ambient temperature with the rate constant of 0.08 day(-1), following the first-order rate kinetics. In stationary phase, at a cell density of 6.5 × 10(9) CFU mL(-1), the bacteria produced substantially increased amounts of indole acetic acid (IAA) in the presence of tryptophan as compared with the control. Also, the bacteria exhibited a time-dependent increase in the amount of tri-calcium phosphate solubilization in Pikovskaya's medium. Further screening of the strain JS-11 for auxiliary activities revealed its remarkable capability of producing the siderophores and hydrogen cyanide (HCN), besides antifungal activity against a common phytopathogen Fusarium oxysporum. Thus, the versatile P. aeruginosa strain JS-11 with innate potential for multifarious biological activities is envisaged as a super-bioinoculant for exploitation in the integrated bioremediation, plant growth and disease management (IBPDM) in contaminated agricultural soils. 相似文献
86.
Transparent ceramics for high-energy laser systems 总被引:1,自引:0,他引:1
Jas Sanghera Shyam BayyaGuillermo Villalobos Woohong KimJesse Frantz Brandon ShawBryan Sadowski R. MiklosColin Baker Michael HuntIshwar Aggarwal Fred KungDavid Reicher Stan PeplinskiAl Ogloza Peter LangstonChuck Lamar Peter VarmetteMark Dubinskiy Lewis DeSandre 《Optical Materials》2011,33(3):511-518
We demonstrate that transparent magnesium aluminate spinel ceramic possesses excellent thermo-optical properties, a record low absorption loss of 6 ppm/cm, and superior ruggedness which position it as a prime candidate for an exit window aperture for high energy laser systems, especially in hostile environments. We also demonstrate lasing with an efficiency of about 45% in transparent Yb3+:Y2O3 ceramic made by hot pressing high purity submicron co-precipitated powder. This paves the way forward for high power solid state lasers exploiting hosts with higher thermal conductivity than YAG. 相似文献
87.
Pathak P Kapil U Yajnik CS Kapoor SK Dwivedi SN Singh R 《Food and nutrition bulletin》2007,28(4):435-438
BACKGROUND: Iron, folate, and vitamin B12 deficiencies have adverse effects on pregnancy outcome. In India, data on the concomitant prevalence of these deficiencies among pregnant women are meager. OBJECTIVE: We conducted a community-based study to assess the prevalence of deficiencies of iron, folate, and vitamin B12 among pregnant women in a rural block of Haryana State. METHODS: The study was approved by the ethics committee of the All India Institute of Medical Sciences, New Delhi. A total of 283 pregnant women were enrolled in the study. After oral informed consent had been obtained from the women, blood was drawn from the antecubital vein for estimation of the levels of serum ferritin by enzyme-linked immunosorbent assay (levels < 12 ng/ mL were considered as indicative of poor iron stores); serum folate was determined by radioimmunoassay (levels <3 ng/mL were considered as indicative of poor folate stores); and serum vitamin B12 was estimated by the microbiologic method (levels < 200 pg/mL were considered as indicative of poor vitamin B12 stores). RESULTS: The results indicated that 67.7%, 26.3%, and 74.1% of the women had poor iron, folate, and vitamin B12 stores, respectively. Concomitant deficiencies of iron, folate, and vitamin B12 occurred in 16.2% of the women. We found that 59.9% of the women were consuming less than 75% of the recommended daily caloric allowance (2175 kcal), indicating an overall poor food intake. This could be one of the predominant reasons for poor iron, folate, and vitamin B12 stores among the women. CONCLUSIONS: Our findings suggest that apart from iron and folate, vitamin B12 deficiencies may play an important role in causing anemia. 相似文献
88.
J. N. Srivastava K. K. Awasthi C. D. Dwivedi Hansraj G. N. Mathur 《Fullerenes, Nanotubes and Carbon Nanostructures》2002,10(2):107-116
Fullerene production by arc-discharge method using graphite electrodes has been studied with respect to influence of different design and operational parameters on fullerene yield in a constant arc fullerene reactor. The design parameters like reactor length, diameter, heat transfer area and operational parameters like voltage, current, pressure, coolant flow rate, graphite evaporation rate and electrode diameter etc. have been experimentally studied in detail to establish a relationship between these parameters and fullerene yield. All the parameters affecting the yield have been correlated by dimensional analysis and an equation to calculate the fullerene yield is derived. It was observed experimentally as well as by dimensional analysis that many favorable parameters for getting good yield are linked with other parameters which also get changed if the favorable parameters are changed and thus it is difficult to make a substantial change in the yield of fullerenes. The relationship established between the yield and parameters is however useful in optimising fullerene yield in a reactor and also helpful in designing a futuristic fullerene reactor of improved yield and productivity. The fullerene yield from different designs of reactors is obtained in the range of 4% to 20%. 相似文献
89.
The differences in the bioavailability of different drug products are most frequently caused by differences in the dissolution rates of the active ingredient. In case of magnesium oxide the drug release can be directly determined by reaction kinetics method based on acid neutralization.
For a more precise study of the factors influencing the kinetical characteristics of the neutralization rates it is advisable to use homogeneous granule fractions. Before the granulation the substance was pretreated with silicone oil. The granulation of the obtained grains having hydrophobe surface was carried out in an AEROMATIC STREA-I type laboratory fluidization equipment with Eudragit polymer solved in isopropyl alcohol.
For determining the acid neutralization kinetics of the granules the “constant pH” method and the Rossett-Rice test were used.
As a result of the granulation the neutralization rate decreased. The granules can be considered as an Eudragit matrix which contains the pretreated magnesium oxide in embedded form. During the chemical reaction the resulted salt (magnesium chloride) leaves the surface of the unreacted magnesium oxide unless having a chemical reaction with the polymer. Meanwhile the residual matrix forms a mesh which increases the viscosity of the solution and the thickness of the diffusion layer. The dissolution rate decreases in both cases.
Under the same conditions the kinetic values of the neutralization change by several magnitudes depending on the utilized methods. In this way different systems of medicine, which alter their reaction capacity according to the expected physiological purposes, can be created. 相似文献
For a more precise study of the factors influencing the kinetical characteristics of the neutralization rates it is advisable to use homogeneous granule fractions. Before the granulation the substance was pretreated with silicone oil. The granulation of the obtained grains having hydrophobe surface was carried out in an AEROMATIC STREA-I type laboratory fluidization equipment with Eudragit polymer solved in isopropyl alcohol.
For determining the acid neutralization kinetics of the granules the “constant pH” method and the Rossett-Rice test were used.
As a result of the granulation the neutralization rate decreased. The granules can be considered as an Eudragit matrix which contains the pretreated magnesium oxide in embedded form. During the chemical reaction the resulted salt (magnesium chloride) leaves the surface of the unreacted magnesium oxide unless having a chemical reaction with the polymer. Meanwhile the residual matrix forms a mesh which increases the viscosity of the solution and the thickness of the diffusion layer. The dissolution rate decreases in both cases.
Under the same conditions the kinetic values of the neutralization change by several magnitudes depending on the utilized methods. In this way different systems of medicine, which alter their reaction capacity according to the expected physiological purposes, can be created. 相似文献
90.
Juan C. Juarez Anurag Dwivedi A. Roger Hammons Steven D. Jones Vijitha Weerackody Robert A. Nichols 《Communications Magazine, IEEE》2006,44(11):46-51
There is a continuing need for increased capacity for military applications, especially in network-centric operational concepts that promote the use of information as fundamental for gaining superiority on the battlefield. As an example, the access to, and distribution of, sensor data is a major tenet of network-centric warfare and yet radio frequency (RF) links will struggle to provide the needed capacity. Free-space optical communications (FSOC) has the potential to meet these emerging military needs by offering dramatic increases in capacity. However, there are many technical challenges al multiple layers of the communications protocol stack. This article describes these challenges and discusses some mitigation approaches to provide a path to realizing this capability on the battlefield 相似文献