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surface curvature

Kara Elizabeth Ranaghan, William G Morris, Laura Masgrau, Kittusamy Senthilkumar, Linus O Johannissen, Nigel S Scrutton, Jeremy N Harvey, Frederick R Manby, Adrian J Mulholland
Aromatic amine dehydrogenase (AADH) and related enzymes are at the heart of debates on the roles of quantum tunnelling and protein dynamics in catalysis. The reaction of tryptamine in AADH involves significant quantum tunnelling in the rate-limiting proton transfer step, shown e.g. by large H/D primary kinetic isotope effects (KIEs), with unusual temperature dependence. We apply correlated ab initio combined quantum mechanics/molecular mechanics (QM/MM) methods, at levels up to local coupled cluster theory (LCCSD(T)/(aug)-cc-pVTZ), to calculate accurate potential energy surfaces for this reaction, which are necessary for quantitative analysis of tunnelling contributions and reaction dynamics...
September 20, 2017: Journal of Physical Chemistry. B
Ziqian Wu, Jie Wang, Ze Zhao, Yunru Yu, Luoran Shang, Yuanjin Zhao
Graphene materials have a demonstrated value in water treatment. Efforts to promote these materials are focused on the generation of functional graphene adsorbents for effectively removing contaminants from water. Here, inspired by the conformation of spider silks, we present a novel graphene microfiber material with spindle-knotted microstructures by using a microfluidic emulsification and spinning collaborative technology. The size and spacing of the spindle-knots were highly controllable by adjusting the flow rates of microfluidics during the generation process of the microfibers...
September 20, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Erik J Folkerts, Tamzin A Blewett, Yuhe He, Greg G Goss
Hydraulic fracturing to extract oil and natural gas reserves is an increasing practice in many international energy sectors. Hydraulic fracturing flowback and produced water (FPW) is a hyper saline wastewater returned to the surface from a fractured well containing chemical species present in the initial fracturing fluid, geogenic contaminants, and potentially newly synthesized chemicals formed in the fracturing well environment. However, information on FPW toxicological mechanisms of action remain largely unknown...
September 16, 2017: Environmental Pollution
Mahfujur Rahaman, Raul D Rodriguez, Gerd Plechinger, Stefan Moras, Christian Schüller, Tobias Korn, Dietrich R T Zahn
Tip-enhanced Raman spectroscopy (TERS) has been rapidly improved over the last decade and opened up opportunities to study phonon properties of materials at the nanometer scale. In this contribution we report on tip-enhanced Raman spectroscopy (TERS) of an ultra-thin MoS2 flake on a nanostructured Au on silicon surface forming a two-dimensional (2D) crystal/plasmonic heterostructure. Au nanostructures (shaped in triangles) are prepared by nanosphere lithography and then MoS2 is mechanically exfoliated on top of them...
September 19, 2017: Nano Letters
Douglas G Hayes, Ran Ye, Rachel N Dunlap, Matthew J Cuneo, Sai Venkatesh Pingali, Hugh M O'Neill, Volker S Urban
Bicontinuous microemulsions (BμEs), consisting of water and oil nanodomains separated by surfactant monolayers of near-zero curvature, are potentially valuable systems for purification and delivery of biomolecules, for hosting multiphasic biochemical reactions, and as templating media for preparing nanomaterials. We formed Winsor-III systems by mixing aqueous protein and sodium dodecyl sulfate (SDS) solutions with dodecane and 1-pentanol (cosurfactant) to efficiently extract proteins into the middle (BμE) phase...
September 7, 2017: Colloids and Surfaces. B, Biointerfaces
Gabriel Paiva Fonseca, Michiel R van den Bosch, Robert Voncken, Mark Podesta, Frank Verhaegen
A novel system was developed to improve commissioning and quality assurance of brachytherapy applicators used in High Dose Rate (HDR). It employs an imaging panel to create reference images and to measure dwell times and dwell positions. As an example: two ring applicators of the same model were evaluated. An applicator was placed on the surface of an imaging panel and a HDR 192Ir source was positioned in an imaging channel above the panel to generate an image of the applicator, using the gamma photons of the brachytherapy source...
September 15, 2017: Physics in Medicine and Biology
Zhongwei Zhang, Jie Chen, Baowen Li
From the mathematic category of surface Gaussian curvature, carbon allotropes can be classified into three types: zero curvature, positive curvature, and negative curvature. By performing Green-Kubo equilibrium molecular dynamics simulations, we found that surface curvature has a significant impact on the phonon vibration and thermal conductivity (κ) of carbon crystals. When curving from zero curvature to negative or positive curvature structures, κ is reduced by several orders of magnitude. Interestingly, we found that κ of negatively curved carbon crystals exhibits a monotonic dependence on curvature...
September 15, 2017: Nanoscale
Kazem Amanzadeh, Roghiyeh Elham, Ebrahim Jafarzadepur
PURPOSE: To assess the changes in visual acuity and topographic indices after implantation of single-segment Intacs. METHODS: Forty-two keratoconic eyes received Femtosecond-assisted single-segment Intacs. Uncorrected distance visual acuity (UDVA) and best spectacle corrected visual acuity (BSCVA), refractive error, keratometry (K1, K2, Km, and KMax.), and seven Pentacam measured topographical indices; index of surface variance (ISV), index of vertical asymmetry (IVA), keratoconus index (KI), central keratoconus index (CKI), index of height asymmetry (IHA), index of height decentration (IHD), and minimum radius of curvature (R Min) were assessed 4 months after surgery...
September 2017: Journal of Current Ophthalmology
Baharan Ali Doosti, Weria Pezeshkian, Dennis Skjøth Bruhn, John Hjort Ipsen, Himanshu Khandelia, Gavin D M Jeffries, Tatsiana Lobovkina
Experimental and theoretical studies on ion-lipid interactions, predict that binding of calcium ions to cell membranes leads to macroscopic mechanical effects and membrane remodeling. Herein, we provide experimental evidence that a point-source of Ca2+ acting upon a negatively charged membrane, generates spontaneous curvature and triggers the formation of tubular protrusions that point away from the ion source. This behavior is rationalized by strong binding of the divalent cations to the surface of the charged bilayer which effectively neutralizes the surface charge density of outer leaflet of the bilayer...
September 14, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
J Cartailler, Z Schuss, D Holcman
Voltage and charge distributions in cellular microdomains regulate communications, excitability, and signal transduction. We report here new electrical laws in a biological cell, which follow from a nonlinear electro-diffusion model. These newly discovered laws derive from the geometrical cell-membrane properties, such as membrane curvature, volume, and surface area. The electro-diffusion laws can now be used to predict and interpret voltage distribution in cellular microdomains such as synapses, dendritic spine, cilia and more...
September 12, 2017: Scientific Reports
Joseph P Vanderburgh, Shanik J Fernando, Alyssa R Merkel, Julie A Sterling, Scott A Guelcher
3D printing enables the creation of scaffolds with precisely controlled morphometric properties for multiple tissue types, including musculoskeletal tissues such as cartilage and bone. Computed tomography (CT) imaging has been combined with 3D printing to fabricate anatomically scaled patient-specific scaffolds for bone regeneration. However, anatomically scaled scaffolds typically lack sufficient resolution to recapitulate the <100 micrometer-scale trabecular architecture essential for investigating the cellular response to the morphometric properties of bone...
September 11, 2017: Advanced Healthcare Materials
Philipp Mühlhäuser, Parvesh Wadhwani, Erik Strandberg, Jochen Bürck, Anne S Ulrich
SSL-25 (SSLLEKGLDGAKKAVGGLGKLGKDA) is one of the shortest peptides present in human sweat and is produced after the proteolytic processing of the parent peptide dermcidin. Both peptides are reported to have antimicrobial function. To determine the structure of SSL-25 in lipid bilayers, a series of (19)F-labeled SSL-25 analogs were synthesized. Circular dichroism (CD) analysis showed that SSL-25 and all of its analogs formed α-helices in the presence of lipid vesicles, thus allowing a detailed analysis via oriented CD and solid-state NMR...
September 6, 2017: Biochimica et Biophysica Acta
Guillaume Gueguen, Nicolas Destainville, Manoel Manghi
It has been known for long that the fluctuation surface tension of membranes r, computed from the height fluctuation spectrum, is not equal to the bare surface tension σ, which is introduced in the theory either as a Lagrange multiplier to conserve the total membrane area or as an external constraint. In this work we relate these two surface tensions both analytically and numerically. They are also compared to the Laplace tension γ, and the mechanical frame tension τ. Using the Helfrich model and one-loop renormalisation calculations, we obtain, in addition to the effective bending modulus κeff, a new expression for the effective surface tension σeff = σ - εkBT/(2ap) where kBT is the thermal energy, ap the projected cut-off area, and ε = 3 or 1 according to the allowed configurations that keep either the projected area or the total area constant...
September 20, 2017: Soft Matter
Hanbyul Jin, Sungchul Jung, Junhyung Kim, Sanghyun Heo, Jaeik Lim, Wonsang Park, Hye Yong Chu, Franklin Bien, Kibog Park
We introduce a new type of multi-functional capacitive sensor that can sense several different external stimuli. It is fabricated only with polydimethylsiloxane (PDMS) films and silver nanowire electrodes by using selective oxygen plasma treatment method without photolithography and etching processes. Differently from the conventional single-capacitor multi-functional sensors, our new multi-functional sensor is composed of two vertically-stacked capacitors (dual-capacitor). The unique dual-capacitor structure can detect the type and strength of external stimuli including curvature, pressure, strain, and touch with clear distinction, and it can also detect the surface-normal directionality of curvature, pressure, and touch...
September 7, 2017: Scientific Reports
Jong-Woo Kim, Yoann Porte, Kyung Yong Ko, Hyungjun Kim, Jae-Min Myoung
Micropatternable double-faced (DF) zinc oxide (ZnO) nanoflowers (NFs) for flexible gas sensors have been successfully fabricated on a polyimide (PI) substrate with single-walled carbon nanotubes (SWCNTs) as electrode. The fabricated sensor comprises ZnO nanoshells laid out on a PI substrate at regular intervals, on which ZnO nanorods (NRs) were grown in- and outside the shells to maximize the surface area and form a connected network. This three-dimensional network structure possesses multiple gas diffusion channels and the micropatterned island structure allows the stability of the flexible devices to be enhanced by dispersing the strain into the empty spaces of the substrate...
September 15, 2017: ACS Applied Materials & Interfaces
Takeru Matsuda, Yasuo Sumi, Kimihiro Yamashita, Hiroshi Hasegawa, Masashi Yamamoto, Yoshiko Matsuda, Shingo Kanaji, Taro Oshikiri, Tetsu Nakamura, Satoshi Suzuki, Yoshihiro Kakeji
BACKGROUND: To treat colon cancer via complete mesocolic excision (CME) with central vascular ligation (CVL), dissection along the embryologic fusion planes is required. However, this surgery is difficult, especially for right-sided colon cancer, because the anatomy and embryology of the transverse mesocolon are not familiar to gastrointestinal surgeons. METHODS: In this video article, the anatomic details of the transverse mesocolon based on embryology are illustrated with a focus on the venous anatomy...
September 5, 2017: Annals of Surgical Oncology
Bo-Wei Du, Shao-Ying Hu, Ranjodh Singh, Tsung-Tso Tsai, Ching-Chang Lin, Fu-Hsiang Ko
The waste from semiconductor manufacturing processes causes serious pollution to the environment. In this work, a non-toxic material was developed under room temperature conditions for the fabrication of green electronics. Flexible organic thin-film transistors (OTFTs) on plastic substrates are increasingly in demand due to their high visible transmission and small size for use as displays and wearable devices. This work investigates and analyzes the structured formation of aqueous solutions of the non-toxic and biodegradable biopolymer, chitosan, blended with high-k-value, non-toxic, and biocompatible Y₂O₃ nanoparticles...
September 3, 2017: Materials
Chonghang Zhao, Takeshi Wada, Vincent De Andrade, Garth J Williams, Jeff Gelb, Li Li, Juergen Thieme, Hidemi Kato, Yu-Chen Karen Chen-Wiegart
Nanoporous materials, especially those fabricated by liquid metal dealloying processes, possess great potential in a wide range of applications due to their high surface area, bi-continuous structure-with both open pores for transport and solid phase for conductivity or support-and economical materials cost. Here we used x-ray nano-tomography and x-ray fluorescence microscopy to reveal the three-dimensional (3D) morphology and elemental distribution within materials. Focusing on nanoporous stainless steel, we evaluated the 3D morphology of the dealloying-front and established a quantitative processing-structure-property relationship at a later stage of dealloying...
September 4, 2017: ACS Applied Materials & Interfaces
Zhenwei Yao
Understanding geometric frustration of ordered phases in two-dimensional condensed matter on curved surfaces is closely related to a host of scientific problems in condensed matter physics and materials science. Here, we show how two-dimensional Lennard-Jones crystal clusters confined on a sphere resolve geometric frustration and form pentagonal vacancy structures. These vacancies, originating from the combination of curvature and physical interaction, are found to be topological defects and they can be further classified into dislocational and disclinational types...
September 4, 2017: Soft Matter
M Mert Terzi, Markus Deserno
On mesoscopic scales, lipid membranes are well described by continuum theories whose main ingredients are the curvature of a membrane's reference surface and the tilt of its lipid constituents. In particular, Hamm and Kozlov [Eur. Phys. J. E 3, 323 (2000)] have shown how to systematically derive such a tilt-curvature Hamiltonian based on the elementary assumption of a thin fluid elastic sheet experiencing internal lateral pre-stress. Performing a dimensional reduction, they not only derive the basic form of the effective surface Hamiltonian but also express its emergent elastic couplings as trans-membrane moments of lower-level material parameters...
August 28, 2017: Journal of Chemical Physics
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