Monthly Archives: December 2012

Optical nanoprobe for sugar sensing

A novel optical nanoprobe for sugar sensing is reported. The assay used an electrospun polyamide mesh containing Au salts. The reaction of carbohydrates with these Au salts in alkaline media generates gold nanoparticles (AuNPs) at room temperature without the need for Au seeds.

Food rich in antioxidant such as green tea was identified by their reactions on gold-nanoparticles changing it to coloured colloidals. Reactions were probed on few nanomoles of gold salt. This was based on nylon nanofibrous substrates produced by electrospinning and doped with gold ions. The total reducing sugar content of the samples were analyzed by intensity of colour change of gold-particles that varied with the sugar. The strongest purple coloration happened with galactose, followed by glucose, then fructose, whilst the non-reducing sugar sucrose showed no change!

Scampicchio et al, Optical nanoprobes based on gold nanoparticles for sugar sensing, 2009 Nanotechnology 20 135501 doi:10.1088/0957-4484/20/13/135501

http://iopscience.iop.org/0957-4484/20/13/135501/

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December 27, 2012 · 11:26 am

Oxford comes to Toronto: Summer Doctoral Programme (SDP) 2013

oii

SDP2013 Toronto: 8 July – 19 July.

Accommodation: Victoria College, University of Toronto.

We are delighted to announce that the eleventh Oxford Internet Institute (OII) Summer Doctoral Programme (SDP) will be held at the i-Schoool, University of Toronto, from 8-19 July 2013.

The aim of the programme is to bring together advanced doctoral students engaged in dissertation research relating to the Internet and other ICTs. By sharing their work and learning from leading academics in the field, students can enhance the quality and significance of their thesis research and create a peer network of excellent young researchers.

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December 19, 2012 · 12:29 am

New Target Detection in Diagnostic Ultrasound Images

Target detection in diagnostic ultrasound: Evaluation of a method based on the CLEAN algorithm- University of Toronto, Biomaterials and Biomedical Engineering

A technique is proposed for the detection of abnormalities (targets) in ultrasound images using little or no a priori information and requiring little operator intervention. The scheme is a combination of the CLEAN algorithm, originally proposed for radio astronomy, and constant false alarm rate (CFAR) processing, as developed for use in radar systems. The CLEAN algorithm identifies areas in the ultrasound image that stand out above a threshold in relation to the background; CFAR techniques allow for an adaptive, semi-automated, selection of the threshold. Neither appears to have been previously used for target detection in ultrasound images and never together in any context.

Read the full article

http://www.ncbi.nlm.nih.gov/pubmed/22853949

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Nanotechnology Shopping

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December 17, 2012 · 7:33 pm

Spacing Model (Explaining John Hunt’s Model)

Results of a comparative experimental study are presented in Space (diffusion transport) and on Earth (convection and diffusion transport) of solute macrosegregation and directional solidification microstructure in bulk Al 1.5 wt% Ni alloys, which possess a stabilising solutal effect in directional upward solidification on ground. The growth parameters are in the cell dendrite transition so that cells (no sidebranches) and dendrites (sidebranches) are simultaneously observed, the later having larger spacing. In the benchmark microstructures solidified in microgravity, it is found for the first time that the conditions for the analogy with viscous fingering are satisfied (spacing Peclet number ≪1 and tip constitutional supercooling of order one). The experimental primary spacing is about half the numerical prediction by Lu and Hunt’s model. It is suggested that the full panorama of the symmetric and non-symmetric cellular and dendritic branches may explain the misfit. Also, the longitudinal solute macrosegregation across the mushy zone is discussed and modelled, which imposes to depart from the classical Flemings profile. Due to fluid flow driven by the radial temperature gradient, the ground samples show a large macroscopic deformation of the growth front concomitant with microstructure localisation. Cells then appear in the core and dendrites at the periphery. In addition, the measured primary spacing in the centre is smaller than in the corresponding microgravity experiments, which enables to estimate the downward component of the flow velocity in this region.
John Hunt et al, Journal of Crystal Growth, Volume 281, Issue 2-4, p. 654-668.
Keywords: Phase diagrams and microstructures developed by solidification and solid-solid phase transformations, Theory and models of crystal growth; physics of crystal growth, crystal morphology, and orientation, Solubility, segregation, and mixing; phase separation, Growth in microgravity environments, Buoyancy-driven instabilities

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Imaging Oxygen with HAADF-STEM

oxygen imaging STEM 30831f1_online

 

High-angle annular dark field scanning transmission electron microscopy (HAADFSTEM) hasbeen established as a direct and robust imaging mode for determining the location of heavy atom columns within grain boundaries [1,2]. However,light elements are usually not visible in HAADFSTEM.  Structural analysis using the observed positions of only the heavy elements as reference points to compare with candidate structure models, perhaps determined by molecular dynamics or first principles calculations, has had some success. For instance, simulations in an aAl2O3 S13  grain boundary show an oxygen terminated trial structure to be consistent with the experimental HAADF image while analuminum-terminated structure is not, even though the oxygen itself was not imaged [3].
High voltage electron microscopy [4], negative Cs imagingconventional TEM [5] and exit surface wavefunction reconstruction [6] have all been used to image oxygen within grain boundaries and defect structures. However,these approaches arenot yet routine, requiring very thin specimens and detailed  simulation for intepretation and analysis [7]. Bycontrast,forbulkcrystals,annular
brightfield (ABF) STEM imaging allows for direct image interpretation with both light and heavy atom columns simultaneously visible over a wide range of thicknesses [8–10].

[1] G.Duscher,M.F.Chisholm,U.Alber,M.R¨ uhle, Nat.Mater.3(2004)621.
[2] J.P.Buban,K.Matsunaga,J.Chen,N.Shibata,W.Y.Ching,T.Yamamoto,
Y. Ikuhara,Science311(2006)212.
[3] S.Azuma,N.Shibata,S.D.Findlay,T.Mizoguchi,T.Yamamoto,Y.Ikuhara,
Philos. Mag.Lett.90(2010)539.
[4] Z.Zhang,W.Sigle,F.Phillipp,M.R¨ uhle, Science302(2003)846.
[5] C.L.Jia,K.Urban,Science303(2004)2001.
[6] C.L.Jia,A.Thust,K.Urban,Phys.Rev.Lett.95(2005)225506.
[7] K.Urban,Nat.Mater.8(2009)260.
[8] E.Okunishi,I.Ishikawa,H.Sawada,F.Hosokawa,M.Hori,Y.Kondo,Microsc.
Microanal. 15(Suppl.2)(2009)164.
[9] S.D.Findlay,N.Shibata,H.Sawada,E.Okunishi

JEOL, 15 May 2012: http://www.materialstoday.com/download/801

Direct oxygen imaging in titania nanocrystals.

Recently, rutile nanotwins were synthesized using high temperature organic solvent methods, yielding two kinds of common high-quality rutile twinned nanocrystals, (101) and (301) twins, accompanied by minor rutile nanorods (Lu et al 2012 CrystEngComm 14 3120-4). In this report, the atomic structures of the rutile and anatase nanocrystals are directly resolved with no need for calculation or image simulation using atomic resolution STEM techniques. The locations of the oxygen rows in the rutile twins’ boundaries are directly determined from both HAADF images and ABF images. To the best of our knowledge, this is the first time oxygen columns have been distinguished in rutile twin boundaries using HAADF and BF imaging………..

source: http://www.ncbi.nlm.nih.gov/pubmed/22863879

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UK announces £20m carbon capture and storage competition winners

UK has announced winners of a £20m competition for innovative projects to reduce the cost of Carbon Capture and Storage (CCS) development.

The 13 projects, including Millennium Generation which is building a 3MWe carbon capture pilot plant in the British town of Stainforth, have been awarded from the UK’s CCS £125m research and development fund.

http://www.begbroke.ox.ac.uk/

http://www.energy-business-review.com/news/uk-announces-20m-carbon-capture-and-storage-competition-winners-221112

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Challenges for performing in situ nanoindentation TEM on nanoparticles

Nanoparticles show a conspicuous lack of dislocations, even after significant deformation. Therefore, it has been suggested that dislocations cannot exist or/do not play a role on the deformation of nanoparticles. In situ TEM nanoindentation is a critical tool for addressing this issue because it allows for the deformation to be monitored in real time. In this article, we discuss some of the experimental needs and challenges for performing in situ nanoindentation TEM experiments on nanoparticles. In addition, we show both diffraction contrast and phase contrast in situ TEM nanoindentation experiments on silver nanoparticles with diameters below 50 nm. Evidence of the presence of dislocations was observed during deformation, but upon unloading dislocations disappeared.

http://www.materialstoday.com/download/974

This paper was originally published in Micron (2012) 43, 1134-1139.

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Nanofabrication MEMS

While engineers and scientists race to shrink the size of
transistors and MEMS components through nanofabrication
to create the next generation of high-performance electronic
devices, biologists and life scientists have just begun to
employ micropatterning and, to a more limited extent,
nanopatterning techniques to build high-throughput
detection systems for genomic and proteomic studies

Opportunities and challenges
The incorporation of ‘soft-wet’ biological components into
conventional nanofabrication platforms designed and built for
‘hard-dry’ semiconductors, conductors, and dielectrics brings
both new opportunities and challenges since biomolecules
possess some unique properties:
• A wide range of biomolecules, including nucleic acids,
proteins, lipids, and oligosaccharides, react with other
biological components by molecular recognition14,15,
which is important for bottom-up nanofabrication based
on self-assembly;
• Enzymes can catalyze the synthesis and removal of both
biological and synthetic molecules16,17;
• Biomolecular reactions (biotransformations) are highly
selective and site-specific17. There are many enzymes that
cleave DNA at particular sites (restriction enzymes) and
link two pieces of DNA together (ligases)17. Proteases that
digest proteins at specific sites16,17 and enzymes that add
functional motifs to proteins18 are just a few examples of
protein-modifying enzymes;
• Biomolecular reactions are often highly efficient under
physiological conditions, so the yields of
biotransformations are substantially higher than those by
chemical syntheses19,20; and
• The use of biomolecules and biological processes is often
environmentally friendly, so treatment of the waste
products can be minimal and the by-products pose little
health risk compared to the reagents used in
semiconductor processing.
On the other hand, there are also significant constraints
associated with the use of biomolecules in
bionanofabrication. These are:
• The ultrahigh-vacuum (UHV) conditions used in
conventional nanofabrication approaches are incompatible
with biomolecules, whose function and structural integrity
in most cases are destroyed in a high-vacuum
environment;
• Even in an aqueous environment, many proteins can easily
lose their native, active conformation after deposition
because they can unfold and bind nonspecifically to a
surface; and Biological reactions, with some notable exceptions21,22,
must take place in an aqueous solution or buffer, which
limits their uses in many electronic applications.

Chow D C et al, Nanofabrication with Biomolecules, NanoToday, Elsevier, Dec 2005

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