Small Mesh Size Hydrogel for Functional Photocontrol of Encapsulated Enzymes and Small Probe Molecules

2012 ◽  
Vol 84 (3) ◽  
pp. 1374-1379 ◽  
Author(s):  
Shuhei Murayama ◽  
Fumi Ishizuka ◽  
Kaihei Takagi ◽  
Hirotaka Inoda ◽  
Akira Sano ◽  
...  
Keyword(s):  
Mesh Size ◽  
Probe Molecules ◽  
Small Probe

Understanding the Diffusion of Dextrans in ‘Click' PNIPAAm Hydrogels

2014 ◽  
Vol 67 (1) ◽  
pp. 85
Author(s):  
Huey Wen Ooi ◽  
Hui Peng ◽  
Kevin S. Jack ◽  
Andrew K. Whittaker
Keyword(s):  
Drug Delivery ◽  
Drug Delivery Systems ◽  
Mesh Size ◽  
Controlled Drug Delivery ◽  
Molecular Size ◽  
Delivery Systems ◽  
Restricted Diffusion ◽  
Probe Molecules ◽  
Network Studies

Arguably the most important property of a hydrogel is the ability to allow the diffusion of solutes through the crosslinked network. Studies of the diffusion in hydrogels are important for providing information on the rate and extent of the passage of the solute and on the details of the microstructure of the hydrogel. Such knowledge is directly relevant for applications such as controlled drug delivery systems. The structure of novel poly(N-isopropylacrylamide) (PNIPAAm) hydrogels can be revealed by the restricted diffusion of appropriate probe molecules. Dextran molecules, labelled with fluorescent moieties, were incorporated into well-defined PNIPAAm hydrogels to investigate the effects of hydrogel mesh size and dextran molecular size on the diffusivities of solute molecules.

Analysis of Beta Amyloid Peptides Employing the Small Probe Molecules

2013 ◽  
Vol 9 (6) ◽  
pp. 1088-1091 ◽  
Author(s):  
Hyo-Bong Hong ◽  
In-Hyun Nam ◽  
Sung-Won Sohn ◽  
Ki-Bong Song
Keyword(s):  
Beta Amyloid ◽  
Probe Molecules ◽  
Amyloid Peptides ◽  
Small Probe

Improvements in the electron probe forming capabilities and x-ray hole counts in the Philips TEM

1983 ◽  
Vol 41 ◽  
pp. 376-377
Author(s):  
Richard L. McConville
Keyword(s):  
Field Strength ◽  
Electron Probe ◽  
Spherical Aberration ◽  
Focal Length ◽  
Objective Lens ◽  
Parallel Beam ◽  
Tilt Axis ◽  
X Ray ◽  
Small Probe ◽  
Specimen Height

A second generation twin lens has been developed. This symmetrical lens with a wider bore, yet superior values of chromatic and spherical aberration for a given focal length, retains both eucentric ± 60° tilt movement and 20°x ray detector take-off angle at 90° to the tilt axis. Adjust able tilt axis height, as well as specimen height, now ensures almost invariant objective lens strengths for both TEM (parallel beam conditions) and STEM or nano probe (focused small probe) modes.These modes are selected through use of an auxiliary lens situ ated above the objective. When this lens is on the specimen is illuminated with a parallel beam of electrons, and when it is off the specimen is illuminated with a focused probe of dimensions governed by the excitation of the condenser 1 lens. Thus TEM/STEM operation is controlled by a lens which is independent of the objective lens field strength.

SEM at Low Beam Voltage

1984 ◽  
Vol 42 ◽  
pp. 440-443
Author(s):  
James Pawley
Keyword(s):  
Low Voltage ◽  
Probe Diameter ◽  
Small Probe ◽  
Beam Voltage ◽  
Practical Constraints

Operation of the SEM with V0 = l-3kV (LVSEM) was early recognized to reduce charging artefacts and increase topographic contrast. This early promise was not pursued because several theoretical and practical considerations made it difficult to produce a small probe diameter (d0) at low voltage. Recently, the necessity of using low V0 to image uncoated semiconductors without damaging them has prompted a re-evaluation of LVSEM. This re-evaluation has taken the form of efforts to eliminate the practical constraints and to alleviate the theoretical ones. In the process, some heretofore neglected theoretical advantages of LVSEM have emerged. These problems and possibilities will now be discussed in more detail.

Energy Dispersive X-Ray Measurements of thin Metal Foils

1976 ◽  
Vol 34 ◽  
pp. 426-427
Author(s):  
J. Bentley ◽  
E. A. Kenik
Keyword(s):  
Materials Science ◽  
Energy Dispersive Spectrometer ◽  
Thin Foil ◽  
Thin Metal ◽  
Energy Dispersive ◽  
Thin Specimen ◽  
X Ray ◽  
Metal Foils ◽  
Small Probe ◽  
Scanning Transmission

Instruments combining a 100 kV transmission electron microscope (TEM) with scanning transmission (STEM), secondary electron (SEM) and x-ray energy dispersive spectrometer (EDS) attachments to give analytical capabilities are becoming increasingly available and useful. Some typical applications in the field of materials science which make use of the small probe size and thin specimen geometry are the chemical analysis of small precipitates contained within a thin foil and the measurement of chemical concentration profiles near microstructural features such as grain boundaries, point defect clusters, dislocations, or precipitates. Quantitative x-ray analysis of bulk samples using EDS on a conventional SEM is reasonably well established, but much less work has been performed on thin metal foils using the higher accelerating voltages available in TEM based instruments.

Convergent-beam electron diffraction at high spatial resolution

1992 ◽  
Vol 50 (2) ◽  
pp. 1152-1153 ◽  
Author(s):  
J W Steeds
Keyword(s):  
Electron Diffraction ◽  
High Temperature Superconductors ◽  
Bloch Wave ◽  
Convergent Beam Electron Diffraction ◽  
Beam Electron ◽  
Energy Filtering ◽  
Small Probe ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
Convergent Beam

That the techniques of convergent beam electron diffraction (CBED) are now widely practised is evident, both from the way in which they feature in the sale of new transmission electron microscopes (TEMs) and from the frequency with which the results appear in the literature: new phases of high temperature superconductors is a case in point. The arrival of a new generation of TEMs operating with coherent sources at 200-300kV opens up a number of new possibilities.First, there is the possibility of quantitative work of very high accuracy. The small probe will essentially eliminate thickness or orientation averaging and this, together with efficient energy filtering by a doubly-dispersive electron energy loss spectrometer, will yield results of unsurpassed quality. The Bloch wave formulation of electron diffraction has proved itself an effective and efficient method of interpreting the data. The treatment of absorption in these calculations has recently been improved with the result that <100> HOLZ polarity determinations can now be performed on III-V and II-VI semiconductors.

Simulation of high-resolution annular dark field STEM images

1995 ◽  
Vol 53 ◽  
pp. 40-41
Author(s):  
E. J. Kirkland
Keyword(s):  
Electron Beam ◽  
Atomic Layer ◽  
Fresnel Diffraction ◽  
Dark Field ◽  
Objective Lens ◽  
Image Simulation ◽  
Small Probe ◽  
Annular Dark Field ◽  
Stem Image ◽  
Uniform Plane

In a STEM an electron beam is focused into a small probe on the specimen. This probe is raster scanned across the specimen to form an image from the electrons transmitted through the specimen. The objective lens is positioned before the specimen instead of after the specimen as in a CTEM. Because the probe is focused and scanned before the specimen, accurate annular dark field (ADF) STEM image simulation is more difficult than CTEM simulation. Instead of an incident uniform plane wave, ADF-STEM simulation starts with a probe wavefunction focused at a specified position on the specimen. The wavefunction is then propagated through the specimen one atomic layer (or slice) at a time with Fresnel diffraction between slices using the multislice method. After passing through the specimen the wavefunction is diffracted onto the detector. The ADF signal for one position of the probe is formed by integrating all electrons scattered outside of an inner angle large compared with the objective aperture.

Performance and applications of a field-emission gun TEM/STEM

1992 ◽  
Vol 50 (2) ◽  
pp. 942-943
Author(s):  
Judith M. Brock ◽  
Max T. Otten ◽  
Marc. J.C. de Jong
Keyword(s):  
Field Emission ◽  
High Resolution Imaging ◽  
High Quality ◽  
Small Energy ◽  
High Brightness ◽  
Small Probe ◽  
Resolution Imaging ◽  
Convergent Beam ◽  
Beam Patterns ◽  
Beam Diffraction

A Field Emission Gun (FEG) on a TEM/STEM instrument provides a major improvement in performance relative to one equipped with a LaB6 emitter. The improvement is particularly notable for small-probe techniques: EDX and EELS microanalysis, convergent beam diffraction and scanning. The high brightness of the FEG (108 to 109 A/cm2srad), compared with that of LaB6 (∼106), makes it possible to achieve high probe currents (∼1 nA) in probes of about 1 nm, whilst the currents for similar probes with LaB6 are about 100 to 500x lower. Accordingly the small, high-intensity FEG probes make it possible, e.g., to analyse precipitates and monolayer amounts of segregation on grain boundaries in metals or ceramics (Fig. 1); obtain high-quality convergent beam patterns from heavily dislocated materials; reliably detect 1 nm immuno-gold labels in biological specimens; and perform EDX mapping at nm-scale resolution even in difficult specimens like biological tissue.The high brightness and small energy spread of the FEG also bring an advantage in high-resolution imaging by significantly improving both spatial and temporal coherence.

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