scholarly journals A ‘NanoSuit’ surface shield successfully protects organisms in high vacuum: observations on living organisms in an FE-SEM

2015 ◽  
Vol 282 (1802) ◽  
pp. 20142857 ◽  
Author(s):  
Yasuharu Takaku ◽  
Hiroshi Suzuki ◽  
Isao Ohta ◽  
Takami Tsutsui ◽  
Haruko Matsumoto ◽  
...  
Keyword(s):  
High Vacuum ◽  
Tween 20 ◽  
Electrically Conducting ◽  
Observation Methods ◽  
Conducting Materials ◽  
Wide Range ◽  
Electrostatic Charging ◽  
Increase Survival Time ◽  
Living Organisms ◽  
Electrical Conductors

Although extremely useful for a wide range of investigations, the field emission scanning electron microscope (FE-SEM) has not allowed researchers to observe living organisms. However, we have recently reported that a simple surface modification consisting of a thin extra layer, termed ‘NanoSuit’, can keep organisms alive in the high vacuum (10 −5 to 10 −7 Pa) of the SEM. This paper further explores the protective properties of the NanoSuit surface-shield. We found that a NanoSuit formed with the optimum concentration of Tween 20 faithfully preserves the integrity of an organism's surface without interfering with SEM imaging. We also found that electrostatic charging was absent as long as the organisms were alive, even if they had not been coated with electrically conducting materials. This result suggests that living organisms possess their own electrical conductors and/or rely on certain properties of the surface to inhibit charging. The NanoSuit seems to prolong the charge-free condition and increase survival time under vacuum. These findings should encourage the development of more sophisticated observation methods for studying living organisms in an FE-SEM.

Direct STEM ADF imaging of gold on silicon (111)

1989 ◽  
Vol 47 ◽  
pp. 472-473
Author(s):  
P. Xu ◽  
E. J. Kirkland ◽  
J. Silcox
Keyword(s):  
Film Growth ◽  
Heavy Atom ◽  
High Vacuum ◽  
Dark Field ◽  
Thin Metal Film ◽  
Base Pressure ◽  
Ultra High Vacuum ◽  
Specimen Preparation ◽  
Dark Field Imaging ◽  
Wide Range

Many studies of thin metal film growth and the formation of metal-semiconductor contacts have been performed using a wide range of experimental methods. STEM annular dark field imaging could be an important complement since it may allow direct imaging of a single heavy atom on a thin silicon substrate. This would enable studies of the local atomic arrangements and defects in the initial stage of metal silicide formation.Preliminary experiments were performed in an ultra-high vacuum VG HB501A STEM with a base pressure of 1 × 10-10 mbar. An antechamber directly attached to the microscope for specimen preparation has a base pressure of 2×l0-10 mbar. A thin single crystal membrane was fabricated by anodic etching and subsequent reactive etching. The specimen was cleaned by the Shiraki method and had a very thin oxide layer left on the surface. 5 Å of gold was deposited on the specimen at room temperature from a tungsten filament coil monitored by a quartz crystal monitor.

scholarly journals The Growth of Semiconductor Thin Films Studied by RHEED

1990 ◽  
Vol 43 (5) ◽  
pp. 583
Author(s):  
GL Price
Keyword(s):  
Thin Films ◽  
Surface Science ◽  
High Vacuum ◽  
High Energy ◽  
Ultra High Vacuum ◽  
Large Area ◽  
Growth Modes ◽  
Semiconductor Thin Films ◽  
Wide Range ◽  
Recent Developments

Recent developments in the growth of semiconductor thin films are reviewed. The emphasis is on growth by molecular beam epitaxy (MBE). Results obtained by reflection high energy electron diffraction (RHEED) are employed to describe the different kinds of growth processes and the types of materials which can be constructed. MBE is routinely capable of heterostructure growth to atomic precision with a wide range of materials including III-V, IV, II-VI semiconductors, metals, ceramics such as high Tc materials and organics. As the growth proceeds in ultra high vacuum, MBE can take advantage of surface science techniques such as Auger, RHEED and SIMS. RHEED is the essential in-situ probe since the final crystal quality is strongly dependent on the surface reconstruction during growth. RHEED can also be used to calibrate the growth rate, monitor growth kinetics, and distinguish between various growth modes. A major new area is lattice mismatched growth where attempts are being made to construct heterostructures between materials of different lattice constants such as GaAs on Si. Also described are the new techniques of migration enhanced epitaxy and tilted superlattice growth. Finally some comments are given On the means of preparing large area, thin samples for analysis by other techniques from MBE grown films using capping, etching and liftoff.

scholarly journals Effective Doping of Single-Walled Carbon Nanotubes with Polyethyleneimine

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 65
Author(s):  
Monika Rdest ◽  
Dawid Janas
Keyword(s):  
Carbon Nanotubes ◽  
Technological Progress ◽  
Single Walled Carbon Nanotubes ◽  
Performance Limits ◽  
Operational Parameters ◽  
Single Walled Carbon ◽  
Electrically Conducting ◽  
Conducting Materials ◽  
Walled Carbon Nanotubes ◽  
Synthesis Stage

More and more electrically conducting materials are required to sustain the technological progress of civilization. Faced with the performance limits of classical materials, the R&D community has put efforts into developing nanomaterials, which can offer sufficiently high operational parameters. In this work, single-walled carbon nanotubes (SWCNTs) were doped with polyethyleneimine (PEI) to create such material. The results show that it is most fruitful to combine these components at the synthesis stage of an SWCNT network from their dispersion. In this case, the electrical conductivity of the material is boosted from 249 ± 21 S/cm to 1301 ± 56 S/cm straightforwardly and effectively.

scholarly journals Electrical percolation in extrinsically conducting, poly(ε-decalactone) composite neural interface materials

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Katarzyna Krukiewicz ◽  
James Britton ◽  
Daria Więcławska ◽  
Małgorzata Skorupa ◽  
Jorge Fernandez ◽  
...  
Keyword(s):  
Silver Nanowires ◽  
Electrochemical Characteristics ◽  
Electrical Percolation ◽  
Electrically Conducting ◽  
Biomedical Device ◽  
Conducting Materials ◽  
Bidirectional Communication ◽  
Polyester Matrix ◽  
Electrical Percolation Threshold

AbstractBy providing a bidirectional communication channel between neural tissues and a biomedical device, it is envisaged that neural interfaces will be fundamental in the future diagnosis and treatment of neurological disorders. Due to the mechanical mismatch between neural tissue and metallic neural electrodes, soft electrically conducting materials are of great benefit in promoting chronic device functionality. In this study, carbon nanotubes (CNT), silver nanowires (AgNW) and poly(hydroxymethyl 3,4-ethylenedioxythiophene) microspheres (MSP) were employed as conducting fillers within a poly(ε-decalactone) (EDL) matrix, to form a soft and electrically conducting composite. The effect of a filler type on the electrical percolation threshold, and composite biocompatibility was investigated in vitro. EDL-based composites exhibited favourable electrochemical characteristics: EDL/CNT—the lowest film resistance (1.2 ± 0.3 kΩ), EDL/AgNW—the highest charge storage capacity (10.7 ± 0.3 mC cm− 2), and EDL/MSP—the highest interphase capacitance (1478.4 ± 92.4 µF cm−2). All investigated composite surfaces were found to be biocompatible, and to reduce the presence of reactive astrocytes relative to control electrodes. The results of this work clearly demonstrated the ability of high aspect ratio structures to form an extended percolation network within a polyester matrix, resulting in the formulation of composites with advantageous mechanical, electrochemical and biocompatibility properties.

scholarly journals Graphene Oxide-Based Nanofiltration for Hg Removal from Wastewater: A Mini Review

Membranes ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 269
Author(s):  
Megawati Zunita
Keyword(s):  
Graphene Oxide ◽  
Negative Impact ◽  
Treatment Area ◽  
Functionalized Graphene Oxide ◽  
Flexible Membrane ◽  
High Mechanical Strength ◽  
Wide Range ◽  
Living Organisms ◽  
Filtration Properties ◽  
High Chemical Stability

Mercury (Hg) is one of heavy metals with the highest toxicity and negative impact on the biological functions of living organisms. Therefore, many studies are devoted to solving the problem of Hg separation from wastewater. Membrane-based separation techniques have become more preferable in wastewater treatment area due to their ease of operation, mild conditions and also more resistant to toxic pollutants. This technique is also flexible and has a wide range of possibilities to be integrated with other techniques. Graphene oxide (GO) and derivatives are materials which have a nanostructure can be used as a thin and flexible membrane sheet with high chemical stability and high mechanical strength. In addition, GO-based membrane was used as a barrier for Hg vapor due to its nano-channels and nanopores. The nano-channels of GO membranes were also used to provide ion mobility and molecule filtration properties. Nowadays, this technology especially nanofiltration for Hg removal is massively explored. The aim of the review paper is to investigate Hg removal using functionalized graphene oxide nanofiltration. The main focus is the effectiveness of the Hg separation process.

A Parallel HOFD Scheme for Direct Numerical Simulation of Turbulent Magnetically Driven Flows

2001 ◽  
Author(s):  
X. Ai ◽  
B. Q. Li
Keyword(s):  
Numerical Simulation ◽  
Finite Difference ◽  
Direct Numerical Simulation ◽  
Turbulent Flows ◽  
Parallel Machines ◽  
Higher Order ◽  
Electrically Conducting ◽  
Wide Range ◽  
Order Scheme ◽  
Higher Order Scheme

Abstract Turbulent magnetically flows occur in a wide range of material processing systems involving electrically conducting melts. This paper presents a parallel higher order scheme for the direct numerical simulation of turbulent magnetically driven flows in induction channels. The numerical method is based on the higher order finite difference algorithm, which enjoys the spectral accuracy while minimizing the computational intensity. This, coupled with the parallel computing strategy, provides a very useful means to simulate turbulent flows. The higher order finite difference formulation of magnetically driven flow problems is described in this paper. The details of the parallel algorithm and its implementation for the simulations on parallel machines are discussed. The accuracy and numerical performance of the higher order finite difference scheme are assessed in comparison with the spectral method. The examples of turbulent magnetically driven flows in induction channels and pressure gradient driven flows in regular channels are given, and the computed results are compared with experimental measurements wherever possible.

scholarly journals Defect detection in conducting materials using eddy current testing techniques

2014 ◽  
Vol 11 (4) ◽  
pp. 535-549 ◽  
Author(s):  
Hartmut Brauer ◽  
Marek Ziolkowski ◽  
Hannes Toepfer
Keyword(s):  
Eddy Current ◽  
Eddy Current Testing ◽  
Internal Defects ◽  
Testing Technique ◽  
Defect Identification ◽  
Testing Conditions ◽  
Current Testing ◽  
Conducting Materials ◽  
Testing Techniques ◽  
Electrical Conductors

Lorentz force eddy current testing (LET) is a novel nondestructive testing technique which can be applied preferably to the identification of internal defects in nonmagnetic moving conductors. The LET is compared (similar testing conditions) with the classical eddy current testing (ECT). Numerical FEM simulations have been performed to analyze the measurements as well as the identification of internal defects in nonmagnetic conductors. The results are compared with measurements to test the feasibility of defect identification. Finally, the use of LET measurements to estimate of the electrical conductors under test are described as well.

scholarly journals Characterization of an Insoluble and Soluble Form of Melanin Produced by Streptomyces cavourensis SV 21, a Sea Cucumber Associated Bacterium

Marine Drugs ◽  
2022 ◽  
Vol 20 (1) ◽  
pp. 54
Author(s):  
Joko Tri Wibowo ◽  
Matthias Y. Kellermann ◽  
Lars-Erik Petersen ◽  
Yustian R. Alfiansah ◽  
Colleen Lattyak ◽  
...  
Keyword(s):  
Biological Properties ◽  
Water Soluble ◽  
Soluble Form ◽  
Wide Range ◽  
Biological Form ◽  
Insoluble Form ◽  
New Perspective ◽  
Living Organisms ◽  
Purification Protocol

Melanin is a widely distributed and striking dark-colored pigment produced by countless living organisms. Although a wide range of bioactivities have been recognized, there are still major constraints in using melanin for biotechnological applications such as its fragmentary known chemical structure and its insolubility in inorganic and organic solvents. In this study, a bacterial culture of Streptomyces cavourensis SV 21 produced two distinct forms of melanin: (1) a particulate, insoluble form as well as (2) a rarely observed water-soluble form. The here presented novel, acid-free purification protocol of purified particulate melanin (PPM) and purified dissolved melanin (PDM) represents the basis for an in-depth comparison of their physicochemical and biological properties, which were compared to the traditional acid-based precipitation of melanin (AM) and to a synthetic melanin standard (SM). Our data show that the differences in solubility between PDM and PPM in aqueous solutions may be a result of different adjoining cation species, since the soluble PDM polymer is largely composed of Mg2+ ions and the insoluble PPM is dominated by Ca2+ ions. Furthermore, AM shared most properties with SM, which is likely attributed to a similar, acid-based production protocol. The here presented gentler approach of purifying melanin facilitates a new perspective of an intact form of soluble and insoluble melanin that is less chemical altered and thus closer to its original biological form.

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