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81.
Using a scanning electron microscope, we make real-time movies of gold nanowires during the process of electromigration. We confirm the importance of using a small series resistance when employing electromigration to make controlled nanometer-scale gaps suitable for molecular-electronics studies. We are also able to estimate the effective temperature experienced by molecular adsorbates on the nanowire during the electromigration process. 相似文献
82.
Yury V. Malovichko Anton E. Shikov Anton A. Nizhnikov Kirill S. Antonets 《International journal of molecular sciences》2021,22(17)
In flowering plants, seeds serve as organs of both propagation and dispersal. The developing seed passes through several consecutive stages, following a conserved general outline. The overall time needed for a seed to develop, however, may vary both within and between plant species, and these temporal developmental properties remain poorly understood. In the present paper, we summarize the existing data for seed development alterations in dicot plants. For genetic mutations, the reported cases were grouped in respect of the key processes distorted in the mutant specimens. Similar phenotypes arising from the environmental influence, either biotic or abiotic, were also considered. Based on these data, we suggest several general trends of timing alterations and how respective mechanisms might add to the ecological plasticity of the families considered. We also propose that the developmental timing alterations may be perceived as an evolutionary substrate for heterochronic events. Given the current lack of plausible models describing timing control in plant seeds, the presented suggestions might provide certain insights for future studies in this field. 相似文献
83.
Tikhomirov G Hoogland S Lee PE Fischer A Sargent EH Kelley SO 《Nature nanotechnology》2011,6(8):485-490
The electronic and optical properties of colloidal quantum dots, including the wavelengths of light that they can absorb and emit, depend on the size of the quantum dots. These properties have been exploited in a number of applications including optical detection, solar energy harvesting and biological research. Here, we report the self-assembly of quantum dot complexes using cadmium telluride nanocrystals capped with specific sequences of DNA. Quantum dots with between one and five DNA-based binding sites are synthesized and then used as building blocks to create a variety of rationally designed assemblies, including cross-shaped complexes containing three different types of dots. The structure of the complexes is confirmed with transmission electron microscopy, and photophysical studies are used to quantify energy transfer among the constituent components. Through changes in pH, the conformation of the complexes can also be reversibly switched, turning on and off the transfer of energy between the constituent quantum dots. 相似文献
84.
Arapkina LV Yuryev VA Chizh KV Shevlyuga VM Storojevyh MS Krylova LA 《Nanoscale research letters》2011,6(1):218
The Si(001) surface deoxidized by short annealing at T ~ 925°C in the ultrahigh vacuum molecuar beam epitaxy chamber has been in situ investigated using high-resolution scanning
tunneling microscopy (STM)and redegreesected high-energy electron diffraction (RHEED. RHEED patterns corresponding to (2 ×
1) and (4 × 4) structures were observed during sample treatment. The (4 × 4) reconstruction arose at T ≲ 600°C after annealing. The reconstruction was observed to be reversible: the (4 × 4) structure turned into the (2 × 1)
one at T ≳ 600°C, the (4 × 4) structure appeared again at recurring cooling. The c (8 × 8) reconstruction was revealed by STM at room temperature on the same samples. A fraction of the surface area covered
by the c (8 × 8) structure decreased, as the sample cooling rate was reduced. The (2 × 1) structure was observed on the surface free
of the c (8 × 8) one. The c (8 × 8) structure has been evidenced to manifest itself as the (4 × 4) one in the RHEED patterns. A model of the c (8 × 8) structure formation has been built on the basis of the STM data. Origin of the high-order structure on the Si(001)
surface and its connection with the epinucleation phenomenon are discussed. 相似文献
85.
Kirill V Chizh Valery A Chapnin Victor P Kalinushkin Vladimir Y Resnik Mikhail S Storozhevykh Vladimir A Yuryev 《Nanoscale research letters》2013,8(1):177
Nickel silicide Schottky diodes formed on polycrystalline Si 〈P〉 films are proposed as temperature sensors of monolithic uncooled microbolometer infrared focal plane arrays. The structure and composition of nickel silicide/polycrystalline silicon films synthesized in a low-temperature process are examined by means of transmission electron microscopy. The Ni silicide is identified as a multi-phase compound composed of 20% to 40% of Ni3Si, 30% to 60% of Ni2Si, and 10% to 30% of NiSi with probable minor content of NiSi2 at the silicide/poly-Si interface. Rectification ratios of the Schottky diodes vary from about 100 to about 20 for the temperature increasing from 22℃ to 70℃; they exceed 1,000 at 80 K. A barrier of around 0.95 eV is found to control the photovoltage spectra at room temperature. A set of barriers is observed in photo-electromotive force spectra at 80 K and attributed to the Ni silicide/poly-Si interface. Absolute values of temperature coefficients of voltage and current are found to vary from 0.3%℃ to 0.6%/℃ for forward bias and around 2.5%/℃ for reverse bias of the diodes. 相似文献
86.
V. V. Berdnikov Yu. B. Gurov B. A. Dolgoshein V. V. Dmitrenko B. I. Zadneprovskii V. A. Kantserov V. V. Sosnovtsev V. O. Tikhomirov A. P. Shmeleva 《Instruments and Experimental Techniques》2013,56(2):146-150
The possibility of designing a prototype of the scintillation transition radiation detector (Sci-TRD) based on a thin (~200 μm) inorganic scintillator has been investigated. Vacuum and silicon photomultipliers have been used in the measurements with inorganic scintillator samples based on LuBO3:Ce and wavelength shifting fibers. The light collection coefficient has been measured for scintillator prototypes under exposure to X rays, and the quantity of photoelectrons has been experimentally determined by irradiating the Sci-TRD working substance with a 241Am X ray source. The electron-hadron rejection ratio of the proposed Sci-TRD is expected to be ~30. 相似文献
87.
The automotive industry promotes lightweight design to reduce the CO2-emission and enhances the passenger’s safety using high strength steel grades. One limiting factor to the accuracy of modern stamping simulation are the empirical constitutive models. In particular for high strength multiphase steels the modelling techniques like multi-scale methods are becoming more interesting. However they should meet the industrial needs. Not only the accuracy but also features like time, costs and complexity are rapidly increasing. The challenge is the development of finite element technologies and multi-scale methods in an appropriate framework for industrial projects. The crystal plasticity finite element method bridges the gap between the micro level and macroscopic mechanical properties that opens the way for more profound consideration of metal anisotropy in stamping process simulation. Nevertheless new empirical constitutive models are favourable for spring back prediction in forming simulations, even if the number of material parameters and the amount of tests for their identification increases. In this paper the application of crystal plasticity FEM within the concept of virtual material testing with a representative volume element (RVE) is demonstrated. 相似文献
88.
D. F. Zaitsev V. N. Krutikov K. Yu. Sakharov S. V. Tikhomirov 《Measurement Techniques》2010,53(7):798-808
A brief review of recent achievements in nanophotonics and the future prospects for its application in the receiving-transmitting
channels of phased antenna arrays is given. It is shown that it is necessary to use nanophotonics to solve urgent problems
of measurement techniques and metrology, including measurements of the space-time parameters of electromagnetic pulses. Some
results of research on analog nanophotonics in systems for measuring the parameters of the receiving-transmitting channels
of phased antenna arrays, carried out at the All-Russia Research Institute of Optophysical Measurements, and also an analysis
of the problems of metrological support for measurements in this area are presented. 相似文献
89.
Kirill S. Erokhin Evgeniy G. Gordeev Dmitriy E. Samoylenko Konstantin S. Rodygin Valentine P. Ananikov 《International journal of molecular sciences》2021,22(18)
The development of new drugs is accelerated by rapid access to functionalized and D-labeled molecules with improved activity and pharmacokinetic profiles. Diverse synthetic procedures often involve the usage of gaseous reagents, which can be a difficult task due to the requirement of a dedicated laboratory setup. Here, we developed a special reactor for the on-demand production of gases actively utilized in organic synthesis (C2H2, H2, C2D2, D2, and CO2) that completely eliminates the need for high-pressure equipment and allows for integrating gas generation into advanced laboratory practice. The reactor was developed by computer-aided design and manufactured using a conventional 3D printer with polypropylene and nylon filled with carbon fibers as materials. The implementation of the reactor was demonstrated in representative reactions with acetylene, such as atom-economic nucleophilic addition (conversions of 19–99%) and nickel-catalyzed S-functionalization (yields 74–99%). One of the most important advantages of the reactor is the ability to generate deuterated acetylene (C2D2) and deuterium gas (D2), which was used for highly significant, atom-economic and cost-efficient deuterium labeling of S,O-vinyl derivatives (yield 68–94%). Successful examples of their use in organic synthesis are provided to synthesize building blocks of heteroatom-functionalized and D-labeled biologically active organic molecules. 相似文献
90.
The remarkable mechanical properties of graphene, the thinnest, lightest, and strongest material in existence, are desirable in applications ranging from composite materials to sensors and actuators. Here, we demonstrate that these mechanical properties are strongly affected by the interaction with the substrate onto which graphene is deposited. By measuring the temperature-dependent deflection of graphene/substrate "bimetallic" cantilevers we determine strain, thermal expansion coefficient, and the adhesion force acting on graphene films attached to a substrate. Graphene deposited on silicon nitride (SiN(x)) is under much larger strain, ε(g) ~ 1.5 × 10(-2), compared to graphene on gold (Au), ε(g) < 10(-3). The thermal expansion coefficient α(g) of graphene attached to SiN(x) is found to be negative, in the range from (- 5... - 1) × 10(-6)K(-1) and smaller in magnitude than α(g) of suspended graphene. We also estimate the interfacial shear strength of the graphene/SiN(x) interface to be ~1 GPa at room temperature. 相似文献