Optical encoding of microbeads for gene screening: alternatives to microarrays

Rapid access to genetic information is central to the revolution presently occurring in the pharmaceutical industry, particularly In relation to novel drug target identification and drug development. Genetic variation, gene expression, gene function and gene structure are just some of the important research areas requiring efficient methods of DNA screening. Here, we highlight state-of-the-art techniques and devices for gene screening that promise cheaper and higher-throughput yields than currently achieved with DNA microarrays. We include an overview of existing and proposed bead-based strategies designed to dramatically increase the number of probes that can be interrogated in one assay. We focus, in particular, on the issue of encoding and/or decoding (bar-coding) large bead-based libraries for HTS.

Warehouse, PNG Coffee Industry Board Office and Warehouse, Goroka

View of exterior wall to warehouse.

Downpipes, PNG Coffee Industry Board Office and Warehouse, Goroka

Detailed view of downpipes and drainage grill.

PNG Coffee Industry Board Office and Warehouse, Goroka

View past tiered amphitheatre and offices above to air strip beyond.

View along western elevation, PNG Coffee Industry Board Office and Warehouse, Goroka

View past timber blinds to balcony and timber sunscreens.

Under construction, PNG Coffee Industry Board Office and Warehouse, Goroka

View of post being hoisted into position during construction.

Warehouse, PNG Coffee Industry Board Office and Warehouse, Goroka

View of warehouse exterior.

Pole detail, PNG Coffee Industry Board Office and Warehouse, Goroka

Detailed view of poles used in construction. Poles were spliced in their length with steel bars (like 3 pin plugs) and these joints were restrained from splitting with steel strap belts. The belts were tightened with opposing wedges like the old Greene & Greene wrought iron detail.

Warehouse, PNG Coffee Industry Board Office and Warehouse, Goroka

View of warehouse exterior.

Roof structure, internal, PNG Coffee Industry Board Office and Warehouse, Goroka

View to underside of roof with steel beam and insulation.

Post and beam connection, PNG Coffee Industry Board Office and Warehouse, Goroka

Detailed view of cast iron brackets connecting beams and posts.

Front elevation, PNG Coffee Industry Board Office and Warehouse, Goroka

View of front elevation with entrance from exterior.

Post and beam connection, PNG Coffee Industry Board Office and Warehouse, Goroka

Detailed view of cast iron brackets connecting beams and posts.

A method to lower the detection limit for optical beat signals from a frequency-dithered stabilized laser

A narrow absorption feature in an atomic or molecular gas (such as iodine or methane) is used as the frequency reference in many stabilized lasers. As part of the stabilization scheme an optical frequency dither is applied to the laser. In optical heterodyne experiments, this dither is transferred to the RF beat signal, reducing the spectral power density and hence the signal to noise ratio over that in the absence of dither. We removed the dither by mixing the raw beat signal with a dithered local oscillator signal. When the dither waveform is matched to that of the reference laser the output signal from the mixer is rendered dither free. Application of this method to a Winters iodine-stabilized helium-neon laser reduced the bandwidth of the beat signal from 6 MHz to 390 kHz, thereby lowering the detection threshold from 5 pW of laser power to 3 pW. In addition, a simple signal detection model is developed which predicts similar threshold reductions.

Quantum noise in optical fibers. I. Stochastic equations

We analyze the quantum dynamics of radiation propagating in a single-mode optical fiber with dispersion, nonlinearity, and Raman coupling to thermal phonons. We start from a fundamental Hamiltonian that includes the principal known nonlinear effects and quantum-noise sources, including linear gain and loss. Both Markovian and frequency-dependent, non-Markovian reservoirs are treated. This treatment allows quantum Langevin equations, which have a classical form except for additional quantum-noise terms, to be calculated. In practical calculations, it is more useful to transform to Wigner or 1P quasi-probability operator representations. These transformations result in stochastic equations that can be analyzed by use of perturbation theory or exact numerical techniques. The results have applications to fiber-optics communications, networking, and sensor technology.