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991.
Most practical materials are held together by covalent bonds, which are irreversible. Materials based on noncovalent interactions can undergo reversible self-assembly, which offers advantages in terms of fabrication, processing and recyclability, but the majority of noncovalent systems are too fragile to be competitive with covalent materials for practical applications, despite significant attempts to develop robust noncovalent arrays. Here, we report nanostructured supramolecular membranes prepared from fibrous assemblies in water. The membranes are robust due to strong hydrophobic interactions, allowing their application in the size-selective separation of both metal and semiconductor nanoparticles. A thin (12 μm) membrane is used for filtration (~5 nm cutoff), and a thicker (45 μm) membrane allows for size-selective chromatography in the sub-5 nm domain. Unlike conventional membranes, our supramolecular membranes can be disassembled using organic solvent, cleaned, reassembled and reused multiple times. 相似文献
992.
Ganesan Y Peng C Lu Y Loya PE Moloney P Barrera E Yakobson BI Tour JM Ballarini R Lou J 《ACS applied materials & interfaces》2011,3(2):129-134
Traditional single-fiber pull-out type experiments were conducted on individual multiwalled carbon nanotubes (MWNT) embedded in an epoxy matrix using a novel technique. Remarkably, the results are qualitatively consistent with the predictions of continuum fracture mechanics models. Unstable interface crack propagation occurred at short MWNT embedments, which essentially exhibited a linear load-displacement response prior to peak load. Deep embedments, however, enabled stable crack extension and produced a nonlinear load-displacement response prior to peak load. The maximum pull-out forces corresponding to a wide range of embedments were used to compute the nominal interfacial shear strength and the interfacial fracture energy of the pristine MWNT-epoxy interface. 相似文献
993.
Svetoch EA Stern NJ Eruslanov BV Kovalev YN Volodina LI Perelygin VV Mitsevich EV Mitsevich IP Pokhilenko VD Borzenkov VN Levchuk VP Svetoch OE Kudriavtseva TY 《Journal of food protection》2005,68(1):11-17
We evaluated anti-Campylobacter activity among 365 Bacillus and Paenibacillus isolates from poultry production environments. One novel antagonistic Bacillus circulans and three Paenibacillus polymyxa strains were identified and further studied. Cell-free ammonium sulfate precipitate (crude antimicrobial preparation) was obtained from each candidate culture. Zones of Campylobacter growth inhibition surrounding 10 microl of this crude antimicrobial preparation were quantified using a spot test. Campylobacter growth resumed when the preparation was preincubated with selected protease enzymes, demonstrating peptide characteristics consistent with a bacteriocin. These peptides were further purified using combinations of molecular mass resolution and ion exchange chromatography. Molecular masses of the peptides were estimated at approximately 3,500 Da by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Isoelectric focusing was used to determine the pI values of the peptides. Amino acid sequences of the bacteriocins and more precise molecular masses were obtained by matrix-assisted laser desorption and ionization-time of flight (MALDI-TOF) analysis. The bacteriocin from P. polymyxa NRRL B-30507 had a pI of 4.8, that from P. polymyxa NRRL B-30509 had a pI of 7.2, that from P. polymyxa NRRL B-30508 had a pI of 4.8, and that from B. circulans NRRL B-30644 had a pI of 7.8. The amino acid sequences were consistent with those of class IIa bacteriocins. These antagonists and the corresponding bacteriocins may be useful in the control of Campylobacter infection in poultry. 相似文献
994.
Boris A. Trofimov Tatyana E. Glotova Dmitrii A. Shabalin Marina Yu. Dvorko Igor A. Ushakov Elena Yu. Schmidt Anton V. Kuzmin Al'bina I. Mikhaleva 《Advanced Synthesis \u0026amp; Catalysis》2013,355(8):1535-1539
Acetylenes undergo the [4+2] cycloaddition to 3,6‐di(pyrrol‐2‐yl)‐1,2,4,5‐tetrazine in the potassium hydroxide/dimethyl sulfoxide or potassium tert‐butoxide/dimethyl sulfoxide systems (80 °C, 2.5–4 h) to afford (after extrusion of the nitrogen molecule from the intermediate) 3,6‐di(pyrrol‐2‐yl)pyridazines in up to 73% yield, while under non‐catalytic conditions this reaction does not take place. This unusual result substantially extends the scope of synthetic application and mechanistic diversity of the Diels–Alder reaction. The step‐wise mechanisms involving the formation of [OH/tetrazine]− or [t‐BuO/tetrazine]− anionic intermediate complexes or cycloaddition of tetrazine to the acetylide anion are considered. 相似文献
995.
Boris V. Balakin Sergey Alyaev Alex C. Hoffmann Pawel Kosinski 《American Institute of Chemical Engineers》2013,59(11):4045-4057
The formation of capillary bridge formed by a liquid adsorbate is one of the main reasons for agglomeration in multiphase flows. Agglomeration takes place when the relative momentum of two colliding particles is fully consumed by the bridge. This article presents a theoretical study of the collisions of particles with adsorbed liquid taking into account the influence of capillary and viscous dissipative forces. The article proposes an approximate analytical solution for the dynamics of the bridge formed during the collision, together with a more complete numerical model, which is validated with experimental data. The restitution of the relative momentum of the colliding particles, depending on a series of dimensionless parameters characterizing the bridge, is investigated. A criterion for prediction of agglomeration, or “collision efficiency,” in a flow involving cohesive particles is given. An expression is proposed for the coefficient of restitution for the case of collision via a liquid bridge. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4045–4057, 2013 相似文献
996.
997.
Pierluigi Bruzzone Kamil Sedlak Boris Stepanov 《Fusion Engineering and Design》2013,88(9-10):1564-1568
In the assumption that DEMO will be an inductively driven tokamak, the number of load cycles will be in the range of several hundred thousands. The requirements for a new generation of Nb3Sn based high current conductors for DEMO are drafted starting from the output of system code PROCESS. The key objectives include the stability of the DC performance over the lifetime of the machine and the effective use of the Nb3Sn strand properties, for cost and reliability reasons. A preliminary layout of the winding pack and conductors for the toroidal field magnets is presented. To suppress the mechanism of reversible and irreversible degradation, i.e. to preserve in the cabled conductor the high critical current density of the strand, the thermal strain must be insignificant and no space for micro-bending under transverse load must be left in the strand bundle. The “react-and-wind” method is preferred here, with a graded, layer wound magnet, containing both Nb3Sn and NbTi layers. The implications of the conductor choice on the coil design and technology are highlighted. A roadmap is sketched for the development of a full size prototype conductor sample and demonstration of the key technologies. 相似文献
998.
Shin Dong-Joo Khlevnoy Boris B. Dai Caihong Park Seongchong Lee Dong-Hoon Solodilov Maxim V. Kolesnikova Svetlana S. Wu Zhifeng Wang Yanfei 《Measurement Techniques》2021,63(12):1004-1011
Measurement Techniques - The paper presents the assessment of equivalence of the spectral radiance scales in the wavelength range from 250 to 2500 nm, reproduced at the national metrology... 相似文献
999.
Vera B. Plakhova Dmitriy M. Samosvat Georgy G. Zegrya Valentina A. Penniyaynen Arina D. Kalinina Ma Ke Svetlana A. Podzorova Boris V. Krylov Ilya V. Rogachevskii 《International journal of molecular sciences》2022,23(18)
Several arginine-containing short peptides have been shown by the patch-clamp method to effectively modulate the NaV1.8 channel activation gating system, which makes them promising candidates for the role of a novel analgesic medicinal substance. As demonstrated by the organotypic tissue culture method, all active and inactive peptides studied do not trigger the downstream signaling cascades controlling neurite outgrowth and should not be expected to evoke adverse side effects on the tissue level upon their medicinal administration. The conformational analysis of Ac-RAR-NH2, Ac-RER-NH2, Ac-RAAR-NH2, Ac-REAR-NH2, Ac-RERR-NH2, Ac-REAAR-NH2, Ac-PRERRA-NH2, and Ac-PRARRA-NH2 has made it possible to find the structural parameter, the value of which is correlated with the target physiological effect of arginine-containing short peptides. The distances between the positively charged guanidinium groups of the arginine side chains involved in intermolecular ligand–receptor ion–ion bonds between the attacking peptide molecules and the NaV1.8 channel molecule should fall within a certain range, the lower threshold of which is estimated to be around 9 Å. The distance values have been calculated to be below 9 Å in the inactive peptide molecules, except for Ac-RER-NH2, and in the range of 9–12 Å in the active peptide molecules. 相似文献
1000.