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991.
Zhu X Santos L Howard C Sankar R Chou FC Chamon C El-Batanouny M 《Physical review letters》2012,108(18):185501
In this Letter, we report measurements of the coupling between Dirac fermion quasiparticles (DFQs) and phonons on the (001) surface of the strong topological insulator Bi2Se3. While most contemporary investigations of this coupling have involved examining the temperature dependence of the DFQ self-energy via angle-resolved photoemission spectroscopy measurements, we employ inelastic helium-atom scattering to explore, for the first time, this coupling from the phonon perspective. Using a Hilbert transform, we are able to obtain the imaginary part of the phonon self-energy associated with a dispersive surface-phonon branch identified in our previous work [Phys. Rev. Lett. 107, 186102 (2011)] as having strong interactions with the DFQs. From this imaginary part of the self-energy we obtain a branch-specific electron-phonon coupling constant of 0.43, which is stronger than the values reported from the angle-resolved photoemission spectroscopy measurements. 相似文献
992.
Vanesa Sanz Helen M. Coley S. Ravi P. Silva Johnjoe McFadden 《Journal of nanoparticle research》2012,14(2):695
An in-depth study of a novel functionalization of carbon nanotubes for their application as protein and DNA carriers is presented.
First, the optimum conditions for the dispersion of single-walled carbon nanotubes (SWCNTs) with amphiphilic polypeptides
were obtained, and the SWCNT–polypeptide complexes were characterized by different techniques (UV–Vis-NIR, CD, and AFM). Based
on the properties of the SWCNT–polypeptide complexes, a model that characterizes the adsorption of natural proteins onto SWCNT
was described for the first time. This model predicts the adsorption of natural proteins on SWCNTs based on the protein structure
and composition, and therefore, allows the design of methods for the preparation of SWCNT–protein complexes. Besides, the
use of cationic-designed amphiphilic polypeptides to disperse SWCNTs is applied for subsequent and efficient binding of DNA
to carbon nanotubes by a bilayer approach. Therefore, in this article, we develop procedures for the use of SWCNTs as protein
and DNA carriers. The systems were delivered into cells showing that the efficiency of delivery is affected by the charge
of the complexes, which has important implications in the use of SWCNT as platforms for protein and DNA binding and subsequent
use as delivery systems. 相似文献
993.
The present numerical investigation deals with the size and location effects of a single isoflux discrete heater on the buoyancy induced convection in a cylindrical annulus. A discrete heater is placed at the inner wall, while the top and bottom walls as well as the unheated portions of the inner wall are kept adiabatic, and the outer wall is maintained at a lower temperature. The influence of location and size of the discrete heater on the convective flow and the corresponding heat transfer are obtained for a wide range of physical parameters. The predicted numerical results reveal that the placement of heater near the middle portion of inner wall yields a maximum heat transfer and minimum hot spots rather than placing the heater near the top and bottom portions of the inner wall. We found that the location of heater affects the rates of flow circulation and heat transfer in a complex fashion. The rate of heat transfer is an increasing function of radii ratio of the annulus. Further, we found that the rate of heat transfer and maximum temperature in the annular cavity are significantly modified by the heater length and location. 相似文献
994.
We have predicted high pressure structural behavior and elastic properties of alkaline earth tellurides (AETe; AE = Ca, Sr,
Ba) by using two body interionic potential approach with modified ionic charge (Z
m
e). This method has been found quite satisfactory in case of the rare earth compounds. The equation of state curve, structural
phase transition pressure from NaCl (B1) to CsCl (B2) phase and associated volume collapse at transition pressure of alkaline
earth tellurides (AETe) obtained from this approach, so have been compared with experimentally measured data reveal good agreement.
We have also investigated bulk modulus, second and third order elastic constants and pressure derivatives of second order
elastic constants at ambient pressure which shows predominantly ionic nature of these compounds. First time, we have calculated
the Poisson ratio, Young and Shear modulus of these compounds.
相似文献
995.
996.
We show the equivalence of categories of model-theoretic imaginaries (of various kinds) with categories of “small” (finitely
generated, finitely presented, coherent) functors. We do this first for certain locally finitely presented categories and
then, by localising, for much more general “definable categories” (categories of models of coherent theories). We also investigate
the corresponding notion of interpretation. 相似文献
997.
The Pichia pastoris clone producing streptokinase (SK) was optimized for its nutritional requirements to improve intracellular expression using
statistical experimental designs and response surface methodology. The skc gene was ligated downstream of the native glyceraldehyde 3-phosphate dehydrogenase promoter and cloned in P. pastoris. Toxicity to the host was not observed by SK expression using YPD medium. The transformant producing SK at level of 1,120 IU/ml
was selected, and the medium composition was investigated with the aim of achieving high expression levels. The effect of
various carbon and nitrogen sources on SK production was tested by using Plackett–Burman statistical design and it was found
that dextrose and peptone are the effective carbon and nitrogen sources among all the tested. The optimum conditions of selected
production medium parameters were predicted using response surface methodology and the maximum predicted SK production of
2,136.23 IU/ml could be achieved with the production medium conditions of dextrose (x1), 2.90%; peptone (x2), 2.49%; pH, 7.2 (x3), and temperature, 30.4 (x4). Validation studies showed a 95% increase in SK production as compared to that before optimization at 2,089 IU/ml. SK produced
by constitutive expression was found to be functionally active by plasminogen activation assay and fibrin clot lysis assay.
The current recombinant expression system and medium composition may enable maximum production of recombinant streptokinase
at bioreactor level. 相似文献
998.
Venkata R. Sabbasani Kung‐Pern Wang Matthew D. Streeter David A. Spiegel 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(52):19089-19093
Here we describe a general method for the synthesis of 2,5‐diaminoimidazoles, which involves a thermal reaction between α‐aminoketones and substituted guanylhydrazines without the need for additives. As one of the few known ways to access the 2,5‐diaminoimidazole motif, our method greatly expands the number of reported diaminoimidazoles and further supports our previous observations that these compounds spontaneously adopt the non‐aromatic 4(H) tautomer. The reaction works successfully on both cyclic and acyclic amino ketone starting materials, as well as a range of substituted guanylhydrazines. Following optimization, the method was applied to the efficient synthesis of the advanced glycation end product (AGE) methylglyoxal‐derived imidazolium crosslink (MODIC). We expect that this method will enable rapid access to a variety of biologically important 2,5‐diaminoimidazole‐containing products. 相似文献
999.
Reddy Vemulapati Hanuman Kumari Avula Krishna Reddy Guda Mallikarjuna Reddy Yellala Venkata Rami Garcia Jarem Raul Zyryanov Grigory V. Reddy Nemallapudi Bakthavatchala Rammohan Aluru 《Chemistry of Heterocyclic Compounds》2019,55(1):60-65
Chemistry of Heterocyclic Compounds - Environmentally benign one-pot multicomponent synthesis of different 1,4-dihydropyridine derivatives using montmorillonite K10 has been achieved. The... 相似文献
1000.
An analytical model is developed to describe the effects of nitrogen doping on the growth of the carbon nanofibers (CNFs) and to elucidate the growth mechanism of nitrogen‐contained carbon nanofibers (N‐CNFs) on the catalyst substrate surface through the plasma‐enhanced chemical vapour deposition (PECVD) process. The analytical model accounts for the charging of CNFs, kinetics of all plasma species (electrons, ions, and neutrals) in the reactive plasma, generation of carbon species on the catalyst nanoparticle surface due to dissociation of hydrocarbons, CNF growth due to diffusion and precipitation of carbon species, and various other processes. First‐order differential equations have been solved for glow discharge plasma parameters for undoped CNFs (CNF growth in C2H2/H2 plasma) and nitrogen‐doped CNFs (N‐CNF growth in C2H2/NH3 plasma). Our investigation found that nitrogen‐doped CNFs exhibit lower tip diameters and smaller heights compared to the undoped CNFs. In addition, we have estimated that nitrogen‐doped CNFs have more enhanced field emission characteristics than the undoped CNFs. Moreover, we have also observed that N‐CNFs' growth rate increases and tip diameter decreases as the C2H2/NH3 gas ratio decreases. The theoretical results of the present investigation are consistent with the existing experimental observations. 相似文献