Break of JC for Dec holidays

Dear all,

It is almost the end of the year and thanks for the good efforts of participating in this journal club in the past few months. Let's take a break and resume next year!

Cheers,
Shan

An interesting paper about -ive refractive index

Lately, we have been discussing about the so called negative refractive index materials (Meta Materials!), an example of which is a super-lens. I found this paper in the Arxiv web site, that negates the whole idea of -ive refraction. Some of you might find it interesting.
Cheers
Shakil

http://arxiv.org/abs/0712.0605v1

"Correct Definition of the Poynting Vector in Electrically and Magnetically Polarizable Medium Reveals that Negative Refraction is Impossible"

Author: V. A. Markel

journal club 29 Nov 2007

Hi all,

For our journal club this thursday (29/11 10.30am pantry),
let's have a discussion on the attached paper, which is related to the other paper I chose the last time.

Thanks,
Wai Teng

Journal club on 22 Nov 2007

Hi all,

It is a new cycle of Journal club again – this week I will be presenting on work that I did during Perth attachment.

“Exploring Fourier Holography for Phase Imaging Applications”


Date: 22 Nov
Time: 10.30am
Venue: pantry area

The location is tentative, maybe I can book the little discussion room in division office but not sure now, and will email again if there is an update.

Regards,
Shan

Journal club - Nov 15 2007

Title: Polarizatio-sensitive full-field optical coherence tomography
Gael Moneron,1 Albert-Claude Boccara,1 and Arnaud Dubois2,*

citation: OPTICS LETTERS / Vol. 32, No. 14 / July 15, 2007
Abstract: We present a polarization-sensitive full-field optical coherence tomography system that can produce highresolution images of the linear retardance and reflectivity properties of biological media. En face images can be delivered at a frame rate of 3.5 Hz by combination of interferometric images acquired by two CCD cameras in an interference microscope illuminated with a tungsten halogen lamp. Isotropic spatial resolution of 1.0
um achieved. The technique is demonstrated on ex vivo muscle tissues.
Date: Nov 15 2007
Venue: Division pantry area

Journal Club - Mapping polymer birefringence in three-dimensions using a polarizing microscope with oblique illumination

Dear All,

I am going to discuss following interesting paper that talks about measuring 3D distribution of birefringence in the sample. It is interesting in its own right as a basic technique and seems to be a good method of visualizing microtubules during mitosis without any label .

Mapping polymer birefringence in three-dimensions using a polarizing microscope with oblique illumination
Michael Shribak and Rudolf Oldenbourg
Marine Biological Laboratory, Woods Hole, MA 02543, USA

ABSTRACT

We have been developing a polarized light microscope with liquid crystal universal compensator and circular polarizer (the LC-PolScope) for recording images, which are independent of the orientation of birefringent objects. Separate images show the retardance and the slow axis azimuth distributions of the in-plane birefringence of the focused region in the specimen. However the measured (apparent) retardance still depends on the angle between the crystal optic axis and the axis of the illuminating beam of light. If the illuminating beam is close to parallel to the optic axis the measured retardance value decreases dramatically and becomes zero when the two axes are parallel. The description of birefringent objects oriented in 3-dimensional space requires the introduction of two additional parameters: the principal retardance and the inclination angle. Together with the azimuth angle they completely characterize the birefringence properties of a specimen, assuming the specimen has a uniaxial optical indicatrix. We devised a new technique for measuring the three birefringence parameters without moving the specimen. For exploring the out-of-plane birefringence the new instrument which is based on the LC-PolScope technique contains an additional spatial light modulator, implemented here as a liquid crystal mask. The mask is located in the aperture plane of the condenser lens. Partial occlusion of the condenser aperture changes the direction of the central ray of the cone of light converging on the specimen. So we can obtain the retardance and azimuth images using different sets of illumination rays. For experimental verification we used a biological object called an aster. An aster consists of nearly parallel arrays of microtubules, a stiff biopolymer, radiating from a common organizing center called a centrosome. The object is spherically symmetric, and its 3 dimensional distribution of birefringence orientation can be predicted. Experimental results have shown the developed polarizing microscope can successfully be used for imaging and measuring three-dimensional orientation of birefringent objects.

Date: November 07, 2007 (Wednesday)
Time: 10.30 am
Venue: E3A, Level-7 Pantry area.

A molecular ruler based on plasmon coupling of single gold and silver nanoparticles

Carsten Sönnichsen1, 3, Björn M Reinhard2, 3, Jan Liphardt2 & A Paul Alivisatos1

1 Department of Chemistry, University of California, Berkeley and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
2 Department of Physics, University of California, Berkeley and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.

Förster Resonance Energy Transfer has served as a molecular ruler that reports conformational changes and intramolecular distances of single biomolecules. However, such rulers suffer from low and fluctuating signal intensities, limited observation time due to photobleaching, and an upper distance limit of approx10 nm. Noble metal nanoparticles have plasmon resonances in the visible range and do not blink or bleach. They have been employed as alternative probes to overcome the limitations of organic fluorophores, and the coupling of plasmons in nearby particles has been exploited to detect particle aggregation by a distinct color change in bulk experiments. Here we demonstrate that plasmon coupling can be used to monitor distances between single pairs of gold and silver nanoparticles. We followed the directed assembly of gold and silver nanoparticle dimers in real time and studied the kinetics of single DNA hybridization events. These 'plasmon rulers' allowed us to continuously monitor separations of up to 70 nm for >3,000 s.


This a more application based work but quite interesting. A very simple application of a complex phenomenon.

Date : 1st Nov '07
Time: 10:30 am - 11:30 am
Venue: E3A, 7th Floor Lounge

Comsol User Conference 2007

Please find sign-up info for following workshop info of Comsol Physics by clicking above.

The workshop is held on 15 Nov 2007

Microscopy at 29 nm optical resolution

Dear Bioimaging People
Hello

Here is an interesting paper to discuss that I believe may generate some ideas. It is about Stimulated Emission Depletion (STED) fluorescence microscopy, invented by Stefen Hell's group in Germany, and has apparently removed the barriers of classical diffraction limit in optical resolution. In this paper they are claiming a resolution of 29 nm ( who needs near-field microscopy like NSOM or other scanning probe techniques now!). Anyway, let's talk about it on 25th.

Cheers

Shakil

Citation: "STED microscopy with continuous wave beams", Katrin I. Willig, Benjamin Harke, Rebecca Medda and Stefan W. Hell, Nature Methods 21 October, 2007.
Published online at http://www.nature.com/naturemethods

http://www.nature.com.libproxy1.nus.edu.sg/nmeth/journal/vaop/ncurrent/pdf/nmeth1108.pdf

Journal Club Oct 17 10.30am

Sub–Diffraction-Limited Optical Imaging with a Silver Superlens
Nicholas Fang, Hyesog Lee, Cheng Sun, Xiang Zhang

Science, Vol. 308, 534-537 (2005)

Recent theory has predicted a superlens that is capable of producing sub–
diffraction-limited images. This superlens would allow the recovery of evanescent
waves in an image via the excitation of surface plasmons. Using silver as a natural
optical superlens, we demonstrated sub–diffraction-limited imaging with 60-
nanometer half-pitch resolution, or one-sixth of the illumination wavelength. By
proper design of the working wavelength and the thickness of silver that allows
access to a broad spectrum of subwavelength features, we also showed that
arbitrary nanostructures can be imaged with good fidelity. The optical superlens
promises exciting avenues to nanoscale optical imaging and ultrasmall optoelectronic
devices.

WITec Workshop at NTU.

Hi friends,
Sorry i am a bit late in posting this announcement. There is an optics related workshop being held in NTU on 18th Oct. The details are as follows:

Combining Confocal Raman, High Resolution Optical and Scanning Probe Microscopy.

With application in the field of material science, pharmaceutics, life science, semiconductors and nanotechnology.

On the 18^th of October 2007 at NTU School of Material Science and Engineering, Polymer Lab.

Further details is in the flyer attached to this email.

Limited places is available so if you are interested, please register early to avoid disappointment.

Best regards,

Shawn

Extrad Instrumentation

371 Beach Road, #02-32 Keypoint

Singapore 199597

Tel: +65 6296 6908 Fax: +65 6296 6906

Hp: 9026 5667

Journal club schedule

Journal Club Oct 11 07 10.30am

Paper Details:

Nat Methods. 2007 Sep;4(9):717-9. Epub 2007 Aug 12.

Tomographic phase microscopy.

Choi W, Fang-Yen C, Badizadegan K, Oh S, Lue N, Dasari RR, Feld MS.

G.R. Harrison Spectroscopy Laboratory, 77 Massachusetts Avenue 6-014, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.

We report a technique for quantitative three-dimensional (3D) mapping of refractive index in live cells and tissues using a phase-shifting laser interferometric microscope with variable illumination angle. We demonstrate tomographic imaging of cells and multicellular organisms, and time-dependent changes in cell structure. Our results will permit quantitative characterization of specimen-induced aberrations in high-resolution microscopy and have multiple applications in tissue light scattering.

Discussion leader: Shan
Time: Oct 11 10.30am
Venue: Div pantry area

first to post

Hi welcome all! Hope this will be an enriching place for all of us.