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https://www.readbyqxmd.com/read/28646497/geometrical-principles-of-homomeric-%C3%AE-barrels-and-%C3%AE-helices-application-to-modelling-amyloid-protofilaments
#1
Steven Hayward, E James Milner-White
Examples of homomeric β-helices and β-barrels have recently emerged. Here we generalise the theory for the shear number in β-barrels to encompass β-helices and homomeric structures. We introduce the concept of the "β-strip", the set of parallel or antiparallel neighbouring strands, from which the whole helix can be generated giving it n-fold rotational symmetry. In this context the shear number is interpreted as the sum around the helix of the fixed register shift between neighbouring identical β-strips...
June 24, 2017: Proteins
https://www.readbyqxmd.com/read/28645851/nanotubes-connecting-b-lymphocytes-high-impact-of-differentiation-dependent-lipid-composition-on-their-growth-and-mechanics
#2
Eszter A Tóth, Ádám Oszvald, Mária Péter, Gábor Balogh, Anikó Osteikoetxea-Molnár, Tamás Bozó, Edina Szabó-Meleg, Miklós Nyitrai, Imre Derényi, Miklós Kellermayer, Toshiyuki Yamaji, Kentaro Hanada, László Vígh, János Matkó
Nanotubes (NTs) are thin, long membranous structures forming novel, yet poorly known communication pathways between various cell types. Key mechanisms controlling their growth still remained poorly understood. Since NT-forming capacity of immature and mature B cells was found largely different, we investigated how lipid composition and molecular order of the membrane affect NT-formation. Screening B cell lines with various differentiation stages revealed that NT-growth linearly correlates with membrane ganglioside levels, while it shows maximum as a function of cholesterol level...
June 20, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28645765/chitosan-surface-modified-electrospun-poly-%C3%AE%C2%B5-caprolactone-carbon-nanotube-composite-fibers-with-enhanced-mechanical-cell-proliferation-and-antibacterial-properties
#3
Siyu Wang, Yumei Li, Rui Zhao, Toufeng Jin, Li Zhang, Xiang Li
The surface modification is one of the most effective methods to improve the bioactivity and cell affinity effect of electrospun poly(ε-caprolactone) (PCL) fibers. In the present study, chitosan (CS), a cationic polysaccharide, was used to modify the surface of electrospun PCL fibers. To obtain strong interaction between CS and PCL fibers, negatively charged PCL fibers were prepared by the incorporation of acid-treated carbon nanotubes (CNTs) into the fibers. In this way, the positively charged chitosan could be immobilized onto the surface of PCL fibers tightly by the electrostatic attraction...
June 20, 2017: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/28642951/intermix-of-metal-nanoparticles-single-wall-carbon-nanotubes
#4
Feng Xu, Qin Lu, Lin Ye, S C Edman Tsang
Using physical mixtures of Pd/SWNTs (Pd nanoparticles on single-walled carbon nanotubes) and Pt/SWNTs, the composites show electro-catalytic properties comparable to the corresponding alloys: electron exchange readily occurs between the two metal nanoparticles via SWNT support at long ranges without direct atomic contact, which is responsible for the tunable alloy-like properties.
June 23, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28641554/future-of-spermatogonial-stem-cell-culture-application-of-nanofiber-scaffolds
#5
Azar Shams, Neda Eslahi, Mansoureh Movahedin, Fariborz Izadyar, Hamidreza Asgari, Morteza Koruji
The spermatogonial stem cells (SSCs) are unique in mammals because they can transmit genetic information from generation to generation and it is of significant importance. In testes, Sertoli cells, peritubular myoid cells, Leydig cells and other interstitial cells contribute to the spermatogonial stem cell "niche". So, creation of niche in in vitro condition that mimics in vivo environment is essential to maintain functional characteristic of SSCs. Nanofiber matrices mimic the architecture and size scale of the natural extracellular matrix (ECM)...
June 22, 2017: Current Stem Cell Research & Therapy
https://www.readbyqxmd.com/read/28641430/water-flow-in-carbon-nanotubes-the-effect-of-tube-flexibility-and-thermostat
#6
Alan Sam, Sridhar Kumar Kannam, Remco Hartkamp, Sarith P Sathian
Although the importance of temperature control in nonequilibrium molecular dynamics simulations is widely accepted, the consequences of the thermostatting approach in the case of strongly confined fluids are underappreciated. We show the strong influence of the thermostatting method on the water transport in carbon nanotubes (CNTs) by considering simulations in which the system temperature is controlled via the walls or via the fluid. Streaming velocities and mass flow rates are found to depend on the tube flexibility and on the thermostatting algorithm, with flow rates up to 20% larger when the walls are flexible...
June 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28641422/structure-and-mobility-of-water-confined-in-alpo4-54-nanotubes
#7
Cristina Gavazzoni, Nicolas Giovambattista, Paulo A Netz, Marcia C Barbosa
We performed molecular dynamics simulations of water confined within AlPO4-54 nanotubes. AlPO4-54 is an artificial material made of AlO4 and of PO4 in tetrahedra arranged in a periodic structure forming pores of approximately 1.3 nm in diameter. This makes AlPO4-54 an excellent candidate for practical applications, such as for water filtration and desalination. In this work, the structural and dynamical properties of the confined water are analyzed for various temperatures and water loadings. We find that the water structure is controlled by the heterogeneity of the nanopore surface with the water molecules located preferentially next to the surface of oxygens of AlPO4-54; consequently, at very low densities, water forms helicoidal structures in string-like arrangements...
June 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28641011/exploiting-one-dimensional-exciton-phonon-coupling-for-tunable-and-efficient-single-photon-generation-with-a-carbon-nanotube
#8
Adrien Jeantet, Yannick Chassagneux, Théo Claude, Philippe Roussignol, Jean-Sébastien Lauret, Jakob Reichel, Christophe Voisin
Condensed-matter emitters offer enriched cavity quantum electrodynamical effects due to the coupling to external degrees of freedom. In the case of carbon nanotubes a very peculiar coupling between localized excitons and the one-dimensional acoustic phonon modes can be achieved, which gives rise to pronounced phonon wings in the luminescence spectrum. By coupling an individual nanotube to a tunable optical micro-cavity, we show that this peculiar exciton-phonon coupling is a valuable resource to enlarge the tuning range of the single-photon source while keeping an excellent exciton-photon coupling efficiency and spectral purity...
June 22, 2017: Nano Letters
https://www.readbyqxmd.com/read/28640435/adjusting-the-chemical-bonding-of-sno2-cnt-composite-for-enhanced-conversion-reaction-kinetics
#9
Yayi Cheng, Jianfeng Huang, Hui Qi, Liyun Cao, Jun Yang, Qiao Xi, Xiaomin Luo, Kazumichi Yanagisawa, Jiayin Li
Carbon nanotubes (CNTs) with excellent electron conductivity are widely used to improve the electrochemical performance of the SnO2 anode. However, the chemical bonding between SnO2 and CNTs is not clearly elucidated despite it may affect the lithiation/delithiation behavior greatly. In this work, an SnO2 @CNT composite with SnC and SnOC bonds as a linkage bridge is reported and the influence of the SnC and SnOC bonds on the lithium storage properties is revealed. It is found that the SnC bond can act as an ultrafast electron transfer path, facilitating the reversible conversion reaction between Sn and Li2 O to form SnO2 ...
June 22, 2017: Small
https://www.readbyqxmd.com/read/28639984/impact-of-implant-surface-micropatterns-on-epithelial-cell-behavior
#10
Yiping Tong, Zhengyu Yang, Ruoxi Du, Siqian Wang, Qiaozhen Zhou, Chongyun Bao, Jianfeng Ma
PURPOSE: This study investigated the effect of topography on cell behavior by screening polydimethylsiloxane (PDMS) molds with different nanoscale micropatterns to determine the ideal surface characteristics for attachment of human epithelial cells. MATERIALS AND METHODS: A soft PDMS mold with regular dot arrays was fabricated based on an aluminum oxide template with ordered nanotube arrays and used as a substrate for cell culture. Cell proliferation, spread, and morphology, as well as features of the extracellular matrix and the actin cytoskeleton were assessed...
June 19, 2017: Implant Dentistry
https://www.readbyqxmd.com/read/28639380/bilayer-pbs-quantum-dots-for-high-performance-photodetectors
#11
Zhenwei Ren, Jiankun Sun, Hui Li, Peng Mao, Yuanzhi Wei, Xinhua Zhong, Jinsong Hu, Shiyong Yang, Jizheng Wang
Due to their wide tunable bandgaps, high absorption coefficients, easy solution processabilities, and high stabilities in air, lead sulfide (PbS) quantum dots (QDs) are increasingly regarded as promising material candidates for next-generation light, low-cost, and flexible photodetectors. Current single-layer PbS-QD photodetectors suffer from shortcomings of large dark currents, low on-off ratios, and slow light responses. Integration with metal nanoparticles, organics, and high-conducting graphene/nanotube to form hybrid PbS-QD devices are proved capable of enhancing photoresponsivity; but these approaches always bring in other problems that can severely hamper the improvement of the overall device performance...
June 22, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28639289/planar-polyolefin-nanostripes-perhydrogenated-graphene
#12
Daniel Bouša, Stepan Huber, David Sedmidubsky, Martin Pumera, Zdenek Sofer
Graphene hydrogenation gives an opportunity to introduce a band gap into the graphene electronic structure. Complete hydrogenation may lead to the graphane, a fully hydrogenated counterpart of graphene. However, pure graphane has not been successfully prepared to this day. Here we show that hydrogenation of single walled carbon nanotubes by means of Birch reduction could lead to graphane based carbon nanostripes with uniform dimensions. Such a material exhibits interesting electrocatalytic and magnetic properties as well huge potential for hydrogen storage since the weight concentration of hydrogen is 8...
June 21, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28638174/near-real-time-measurement-of-carbonaceous-aerosol-using-microplasma-spectroscopy-application-to-measurement-of-carbon-nanomaterials
#13
Lina Zheng, Pramod Kulkarni, M Eileen Birch, Gregory Deye, Dionysios D Dionysiou
A sensitive, field-portable microplasma spectroscopy method has been developed for real-time measurement of carbon nanomaterials. The method involves microconcentration of aerosol on a microelectrode tip for subsequent analysis for atomic carbon using laser-induced breakdown spectroscopy (LIBS) or spark emission spectroscopy (SES). The spark-induced microplasma was characterized by measuring the excitation temperature (15,000 - 35,000 K), electron density (1.0 × 10(17) - 2.2 × 10(17) cm(-3)), and spectral responses as functions of time and interelectrode distance...
August 18, 2016: Aerosol Science and Technology: the Journal of the American Association for Aerosol Research
https://www.readbyqxmd.com/read/28636819/superelastic-pseudocapacitors-from-freestanding-mno2-decorated-graphene-coated-carbon-nanotube-aerogels
#14
Yepin Zhao, Maxwell Patrick Li, Siyuan Liu, Mohammad F Islam
In recent years, the demand for emerging electronic devices has driven efforts to develop electrochemical capacitors with high power and energy densities that can preserve capacitance under and after recovery from mechanical deformation. We have developed superelastic pseudocapacitors using ≈ 1.5 mm thick graphene-coated single-walled carbon nanotube (SWCNT) aerogels decorated with manganese oxide (MnO2) as freestanding electrodes that retain high volumetric capacitance and electrochemical stability before, under, and after recovery from 50% compression...
June 21, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28636567/invariant-wide-bandgaps-in-honeycomb-monolayer-and-single-walled-nanotubes-of-iib-vi-semiconductors
#15
Xiaoxuan Ma, Jun Hu, Bicai Pan
Search for low-dimensional materials with unique electronic properties is important for the development of electronic devices in nano scale. Through systematic first-principles calculations, we found that the band gaps of the two-dimensional honeycomb monolayers and one-dimensional single-walled nanotubes of IIB-VI semiconductors (ZnO, CdO, ZnS and CdS) are nearly chirality-independent and weakly diameter-dependent. Based on analysis of the electronic structures, it was found that the conduction band minimum is contributed by the spherically symmetric $s$ orbitals of cations and the valence band maximum is dominated by the in-plane d<sub>xy</sub>-p<sub>y</sub> and d<sub>x<sup>2</sup>-y<sup>2</sup></sub>-p<sub>x</sub> hybridizations...
June 21, 2017: Nanotechnology
https://www.readbyqxmd.com/read/28636565/porous-carbon-nanotubes-decorated-carbon-nanofibers-with-effective-microwave-absorption-property
#16
Tao Zhang, Bo Xiao, Pengyu Zhou, Long Xia, Guangwu Wen, Haibin Zhang
Carbon nanofibers decorated with porous carbon nanotubes have been prepared by electrospinning and annealing methods. Microwave reflection loss of the products is investigated in the frequency range of 2-18 GHz. The bandwidth with a reflection loss less than -10 dB covers a wide frequency ranging from 7.0 to 14.1 GHz with the thickness of 3.0-5.5 mm, and the minimum reflection loss is -44.5 dB at 10.7 GHz with a thickness of 2.0 mm. The large reflection loss and wide reflection band reveals that the products could be a promising candidate for microwave absorption...
June 21, 2017: Nanotechnology
https://www.readbyqxmd.com/read/28636322/spirally-structured-conductive-composites-for-highly-stretchable-robust-conductors-and-sensors
#17
Xiaodong Wu, Yangyang Han, Xinxing Zhang, Canhui Lu
Flexible and stretchable electronics are highly desirable for next generation devices. However, stretchability and conductivity are fundamentally difficult to combine for conventional conductive composites, which restricts their widespread applications especially as stretchable electronics. Here, we innovatively develop a new class of highly stretchable and robust conductive composites via a simple and scalable structural approach. Briefly, carbon nanotubes are spray-coated onto a self-adhesive rubber film, followed by rolling up the film completely to create a spirally layered structure within the composites...
June 21, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28636314/giant-thermal-rectification-from-single-carbon-nanotube-graphene-junction
#18
Xueming Yang, Dapeng Yu, Bingyang Cao
We describe the influence of the geometry parameters on the thermal rectification of single carbon nanotube-graphene junction. The two-dimensional (2D) distribution of the thermal rectification with respect to the tube length and the side length of the graphene nanosheet are calculated and visualized. The maximum thermal rectification ratios of the designed single carbon nanotube-graphene junction can reach 1244.1% and 1681.6% at average temperatures of 300 K and 200 K, respectively. These values are much higher than those reported for single-material nanostructure-based thermal rectifiers...
June 21, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28636246/stretchable-electrochemical-sensor-for-inducing-and-monitoring-cell-mechanotransduction-in-real-time
#19
Yan-Ling Liu, Yu Qin, Zi-He Jin, Xue-Bo Hu, Miao-Miao Chen, Rong Liu, Christian Amatore, Wei-Hua Huang
Existing methods offer little direct and real-time information about stretch-triggered biochemical responses during cell mechanotransduction. Herein, we report a novel stretchable electrochemical sensor that takes advantage of a hierarchical percolation network of carbon nanotubes and gold nanotubes (CNTs- Au NTs). This hybrid nano-structure provides the sensor with excellent time-reproducible mechanical and electrochemical performances while granting very good cellular compatibility, making it perfectly apt to induce and monitor simultaneously transient biochemical signals...
June 21, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28636028/supramolecular-functional-assemblies-dynamic-membrane-transporters-and-peptide-nanotubular-composites
#20
Alberto Fuertes, Marisa Juanes, Juan R Granja, Javier Montenegro
The fabrication of functional molecular devices constitutes one of the most important current challenges for chemical sciences. The complex processes accomplished by living systems continuously demand the assistance of non-covalent interactions between molecular building blocks. Additionally, these building blocks (proteins, membranes, nucleotides) are also constituted by self-assembled structures. Therefore, supramolecular chemistry is the discipline required to understand the properties of the minimal self-assembled building blocks of living systems and to develop new functional smart materials...
June 21, 2017: Chemical Communications: Chem Comm
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