scholarly journals In situ experiments on the effect of low pH on the ultrastructure of the seagrasses Cymodocea nodosa and Posidonia oceanica

2021 ◽  
Author(s):  
MARIA KOUTALIANOU ◽  
MARIA CRISTINA BUIA ◽  
CHRISTOS KATSAROS
Keyword(s):  
Cell Structure ◽  
Posidonia Oceanica ◽  
Control Area ◽  
Low Ph ◽  
Cymodocea Nodosa ◽  
Transmission Electron ◽  
In Situ Experiments ◽  
Young Leaves ◽  
Tubulin Immunofluorescence

The present study investigates the impacts of low pH on the cell structure of the seagrasses Posidonia oceanica (L.) Delile and Cymodocea nodosa (Ucria) Ascherson. The study was applied with in situ experiments at the Castello Aragonese of Ischia (Naples, Italy), where shallow submarine vents, lowering the pH, can be used as natural laboratories. Shoots of the seagrasses were transferred from the control area (pH 8.1) to the two venting areas (pH 7.8 and 6.8) for different times. Epidermal cells of young leaves were examined using transmission electron microscopy (TEM) and tubulin immunofluorescence. After one week at pH 7.8, the cell structure of Posidonia oceanica was normal, while in Cymodocea nodosa microtubule (MT) network and cell structure were affected. In addition, in C. nodosa, ultrastructural analysis revealed a gradual degradation of the nuclei, a disorganization of the chloroplasts, and an increase in the number of mitochondria and dictyosomes. The exposure of both plants for 3 weeks at pH 6.8 resulted in the aggregation and finally in the dilation of the endoplasmic reticulum (ER) membranes. Tubulin immunofluorescence revealed that after three weeks, the MT cytoskeleton of both plants was severely affected. All these alterations can be considered as indications of an apoptotic like programmed cell death (AL-PCD) which may be executed in order to regulate stress response.

A computer-control program for TEM in situ fatigue experiments

1989 ◽  
Vol 47 ◽  
pp. 620-621
Author(s):  
Kenneth S. Vecchio ◽  
John A. Hunt
Keyword(s):  
Slow Crack Growth ◽  
Computer Control ◽  
Control Program ◽  
Video Tape ◽  
Computer Control System ◽  
Transmission Electron ◽  
In Situ Experiments ◽  
Tremendous Amount ◽  
And Control

In-situ experiments conducted within a transmission electron microscope provide the operator a unique opportunity to directly observe microstructural phenomena, such as phase transformations and dislocation-precipitate interactions, “as they happen”. However, in-situ experiments usually require a tremendous amount of experimental preparation beforehand, as well as, during the actual experiment. In most cases the researcher must operate and control several pieces of equipment simultaneously. For example, in in-situ deformation experiments, the researcher may have to not only operate the TEM, but also control the straining holder and possibly some recording system such as a video tape machine. When it comes to in-situ fatigue deformation, the experiments became even more complicated with having to control numerous loading cycles while following the slow crack growth. In this paper we will describe a new method for conducting in-situ fatigue experiments using a camputer-controlled tensile straining holder.The tensile straining holder used with computer-control system was manufactured by Philips for the Philips 300 series microscopes. It was necessary to modify the specimen stage area of this holder to work in the Philips 400 series microscopes because the distance between the optic axis and holder airlock is different than in the Philips 300 series microscopes. However, the program and interfacing can easily be modified to work with any goniometer type straining holder which uses a penrmanent magnet motor.

In-Situ Annealing of Metal Thin Films on Silicon

1981 ◽  
Vol 39 ◽  
pp. 164-165
Author(s):  
L. J. Chen ◽  
J. W. Mayer
Keyword(s):  
Thin Films ◽  
Device Fabrication ◽  
Electron Gun ◽  
Specimen Thickness ◽  
Metal Thin Films ◽  
Thin Foils ◽  
Transmission Electron ◽  
In Situ Experiments ◽  
Annealing Study

In-situ dynamical experiments in the transmission electron microscope (TEM) have long interested electron microscopists. In designing and performing the experiments, it is important to minimize the influences of the factors, which include the specimen thickness, electron beam heating, electron irradiation and specimen environments that may affect the validity of in-situ experiments. Comparisons of the results with those of other experiments are also very desirable.In microelectronic device fabrication process, it has become increasingly common to react a few hundred Å in thickness metal films with silicon substrate to form silicide contacts. Ni thin films on silicon have been chosen for in-situ annealing study since this system has been extensively investigated by Rutherford backscattering and glancing angle x-ray experiments. In-situ annealing of Co, Mo, Ti, Pd and W thin films on silicon have also been performed.Ni films, 300 and 400 Å thick, were electron gun deposited on (001) n-type silicon. Thin foils for TEM examination were chemically polished from silicon side. A JEOL 100B microscope equipped with a side entry, single tilt hot stage was used for TEM study.

Grimsel Test Site - Phase VI: Review of Accomplishments and Next Generation of In-Situ Experiments Under Repository Relevant Boundary Conditions

2008 ◽  
Vol 1107 ◽  
Author(s):  
Ingo Blechschmidt ◽  
Stratis Vomvoris ◽  
Joerg Rueedi ◽  
Andrew James Martin
Keyword(s):  
Near Field ◽  
Planning Horizon ◽  
Test Site ◽  
Low Ph ◽  
Swiss Alps ◽  
In Situ Experiments ◽  
Grimsel Test Site ◽  
And Migration

AbstractThe Grimsel Test Site owned and operated by Nagra is located in the Swiss Alps (www.grimsel.com). The Sixth Phase of investigations was started in 2003 with a ten-year planning horizon. With the investigations and projects of Phase VI the focus has shifted more towards projects assessing perturbation effects of repository implementation and projects evaluating and demonstrating engineering and operational aspects of the repository system. More than 17 international partners participate in the various projects, which form the basic organisational “elements” of Phase VI. Scientific and engineering interaction among the different projects is ensured via an annual meeting and several experimental team meetings throughout the year. On-going projects include: evaluation of full-scale engineered systems under simulated heat production and long-term natural saturation (NF-Pro/FEBEX), gas migration through engineered barrier systems (GMT, finished this year), emplacement of a shotcrete low-pH plug (ESDRED/Module IV), testing and evaluation of standard monitoring techniques (TEM).Numerous in-situ experiments with inactive tracers and radionuclides were successfully carried out over the past few years at the Grimsel Test Site (GTS). For the GTS Phase VI, three major projects have been initiated to simulate the long-term behaviour of contamination plumes in the repository near-field and the surrounding host rock:•The CFM (Colloid Formation and Migration) project, which focuses on colloid generation and migration from a bentonite source doped with radionuclides•The LCS (Long-Term Cement Studies) project, which aims at improving the understanding of low-pH cement interaction effects in water conducting features•The LTD (Long-Term Diffusion) project, which aims at in-situ verification of long-term diffusion concepts for radionuclidesAs Phase VI approaches its mid-term point, what are the next steps planned? The accomplishments assessed to date and the opportunities with the on-going projects as well as new projects – currently under discussion – are presented herein

Possibility of an integrated transmission electron microscope: enabling complex in-situ experiments

2021 ◽  
Vol 56 (9) ◽  
pp. 5309-5320
Author(s):  
Khalid Hattar ◽  
Katherine L. Jungjohann
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Extreme Environments ◽  
Structure Property ◽  
Multispectral Data ◽  
Transmission Electron ◽  
Holistic Understanding ◽  
In Situ Experiments ◽  
Scanning Transmission

Abstract Multimodal in-situ experiments are the wave of the future, as this approach will permit multispectral data collection and analysis during real-time nanoscale observation. In contrast, the evolution of technique development in the electron microscopy field has generally trended toward specialization and subsequent bifurcation into more and more niche instruments, creating a challenge for reintegration and backward compatibility for in-situ experiments on state-of-the-art microscopes. We do not believe this to be a requirement in the field; therefore, we propose an adaptive instrument that is designed to allow nearly simultaneous collection of data from aberration-corrected transmission electron microscopy (TEM), probe-corrected scanning transmission electron microscopy, ultrafast TEM, and dynamic TEM with a flexible in-situ testing chamber, where the entire instrument can be modified as future technologies are developed. The value would be to obtain a holistic understanding of the underlying physics and chemistry of the process-structure–property relationships in materials exposed to controlled extreme environments. Such a tool would permit the ability to explore, in-situ, the active reaction mechanisms in a controlled manner emulating those of real-world applications with nanometer and nanosecond resolution. If such a powerful tool is developed, it has the potential to revolutionize our materials understanding of nanoscale mechanisms and transients. Graphical Abstract

scholarly journals In situ straining experiments in the Transmission Electron Microscope

1990 ◽  
Vol 48 (4) ◽  
pp. 518-519
Author(s):  
Ulrich Messerschmidt
Keyword(s):  
Effective Stress ◽  
Line Tension ◽  
Prismatic Slip ◽  
Water Cooling ◽  
Transmission Electron ◽  
In Situ Experiments ◽  
Ordered Alloys ◽  
Kinematic Behaviour

Recently a number of in situ straining experiments have been carried out at temperatures between about 80 K and 1200 K. A new HVEM straining stage was constructed for temperatures above 1300 K. Its design features are: top entry double tilting stage, thermal expansion drive of high stiffness, heating by electron bombardment, and water cooling to quickly reach a steady state.The following deformation phenomena have successfully been treated by in situ experiments:Determination of the effective stress from the curvature of bowed-out dislocation segments: As shown by in situ experiments on MgO crystals, the line tension of dislocations may differ from its theoretical value. Nevertheless, the anomalous temperature dependence of the effective stress in ordered alloys as well as for prismatic slip in Be has been determined in accordance with macroscopic experiments. Measurement of velocities and kinematic behaviour of dislocations: In situ experiments allow the coordination of the motion of individual dislocation segments with their geometrical configuration.

In situ Transmission Electron Microscope observations of mesotaxial silicide formation in the CoSi2/Si system

1989 ◽  
Vol 47 ◽  
pp. 452-453
Author(s):  
R. Hull ◽  
A.E. White ◽  
K.T. Short ◽  
S.M. Yalisove ◽  
D. Loretto
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Ex Situ ◽  
Metal Silicide ◽  
Silicide Formation ◽  
Plan View ◽  
Silicide Layer ◽  
Transmission Electron ◽  
In Situ Experiments

A new technique for synthesis of buried epitaxial metal silicide layers in Si (“mesotaxy”) by high-dose implantation of Co and Ni into Si surfaces has been developed. Subsequent to implantation at energies in the few hundred keV range and doses in the 1017Cm−2 regime, thermal annealing at temperatures up to 1000°C results in the formation of well-defined and relatively high quality Si/metal disilicide/Si structures.The exact implantation and processing conditions are crucial in determining the structure and quality of the buried silicide layer. In this work, we describe transmission electron microscope experiments which illuminate the silicide formation process both by static studies of as-implanted and annealed structures, and dynamical in-situ experiments where as-implanted structures are annealed inside the microscope to mimic the ex-situ annealing conditions. The structure geometry in these materials turns out to be close to ideal for such in-situ experimentation: typical implantation conditions for formation of a contiguous silicide layer result in tlqe metal layers being of the order a few hundred to a thousand Å and buried about 600-1000 Å below the Si surface. In-situ annealing in the plan-view geometry inhibits surface diffusion across the interfaces, which would be expected in the cross-sectional geometry (5). The typical penetration depths attainable in Si with 200 keV electrons, say ~ 1 micron, allow a significant thickness, hsubthin of Si substrate below the metal layer, thickness hm, to be retained during the in-situ experiment such that hm ≪hsubthin. This is important, as it ensures that the film stress condition (which arises because of the difference in bulk lattice parameters between the Si and metal silicide layers) is reasonably representative of the stress conditions relevant for the case of annealing on the unthinned substrate.

scholarly journals Probing microwave fields and enabling in-situ experiments in a transmission electron microscope

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
F. J. T. Goncalves ◽  
G. W. Paterson ◽  
D. McGrouther ◽  
T. Drysdale ◽  
Y. Togawa ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Transmission Electron ◽  
In Situ Experiments

A TEM Study of Dynamic Continuous Recrystallization in a Superplastic AL-4MG-0.3SC Alloy

1999 ◽  
Vol 601 ◽  
Author(s):  
L.M. Dougherty ◽  
I.M. Robertson ◽  
J.S. Vetrano
Keyword(s):  
True Strain ◽  
Orientation Imaging Microscopy ◽  
Superplastic Forming ◽  
Orientation Imaging ◽  
Transmission Electron ◽  
In Situ Experiments ◽  
Continuous Recrystallization ◽  
Cold Rolled ◽  
Nominal Temperature

AbstractAn Al-4Mg-0.3Sc alloy, aged at 280°C for 8 hours and cold rolled to a 70% reduction, exhibited dynamic recrystallization during superplastic forming at 460°C and at a strain rate of 10−3sec−1. To understand the progression of recrystallization during forming, specimens were deformed under these same conditions to 0.1, 0.2, 0.4 and 0.8 true strain and studied postmortem using optical microscopy, transmission electron microscopy and orientation imaging microscopy. The microstructural evolution that occurred between each strain state was directly observed during deformation experiments at a nominal temperature of 460°C in the transmission electron microscope. These in-situ experiments showed the migration, coalescence, disintegration and annihilation of subboundaries. This combination of post-mortem analysis of specimens strained in bulk with real time observations made during these in-situ experiments allows the mechanisms operating during dynamic continuous recrystallization to be ascertained.

In Situ Transmission Electron Microscope Studies of Ion Irradiation-Induced and Irradiation-Enhanced Phase Changes

1991 ◽  
Vol 235 ◽  
Author(s):  
Charles W. Allen
Keyword(s):  
Materials Science ◽  
Ion Irradiation ◽  
Ion Beam ◽  
Phase Changes ◽  
In Situ Tem ◽  
Irradiation Effects ◽  
Transmission Electron ◽  
In Situ Experiments ◽  
Electron Microscopes

ABSTRACTMotivated at least initially by materials needs for nuclear reactor development, extensive irradiation effects studies employing transmission electron microscopes (TEM) have been performed for several decades, involving irradiation-induced and irradiation-enhanced microstructural changes, including phase transformations such as precipitation, dissolution, crystallization, amorphization, and order-disorder phenomena. From the introduction of commercial high voltage electron microscopes (HVEM) in the mid-1960s, studies of electron irradiation effects have constituted a major aspect of HVEM application in materials science. For irradiation effects studies two additional developments have had particularly significant impact; (1) the development of TEM specimen holders in which specimen temperature can be controlled in the range 10–2200 K and (2) the interfacing of ion accelerators which allows in situ TEM studies of irradiation effects and the ion beam modification of materials within this broad temperature range. This paper treats several aspects of in situ studies of electron and ion beam-induced and enhanced phase changes and presents two case studies involving in situ experiments performed in an HVEM to illustrate the strategies of such an approach of the materials research of irradiation effects.

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