A Fiber Optic Probe for the Detection of Cataracts

A compact fiber optic probe developed for on-orbit science experiments was used to detect the onset of cataracts, a capability that could eliminate physicians' guesswork and result in new drugs to 'dissolve' or slow down the cataract formation before surgery is necessary. The probe is based upon dynamic light scattering (DLS) principles. It has no moving parts, no apertures, and requires no optical alignment. It is flexible and easy to use. Results are presented for excised but intact human eye lenses. In a clinical setting, the device can be easily incorporated into a slit-lamp apparatus (ophthalmoscope) for complete eye diagnostics. In this set-up, the integrated fiber optic probe, the size of a pencil, delivers a low power cone of laser light into the eye of a patient and guides the light which is backscattered by the protein molecules of the lens through a receiving optical fiber to a photo detector. The non-invasive DLS measurements provide rapid determination of protein crystalline size and its size distribution in the eye lens

Method and apparatus for determining the physical properties of materials using dynamic light scattering techniques

A system for determining the physical properties of materials through the use of dynamic light scattering is disclosed. The system includes a probe, a laser source for directing a laser beam into the probe, and a photodetector for converting scattered light detected by the probe into electrical signals. The probe includes at least one optical fiber connected to the laser source and a second optical fiber connected to the photodetector. Each of the fibers may adjoin a gradient index microlens which is capable of providing a collimated laser beam into a scattering medium. The position of the second optical fiber with respect to the optical axis of the probe determines whether homodyne or self-beating detection is provided. Self-beating detection may be provided without a gradient index microlens. This allows a very small probe to be constructed which is insertable through a hypodermic needle or the like into a droplet extending from such a needle. A method of detecting scattered light through the use of a collimated, Gaussian laser beam is also provided. A method for controlling the waist and divergence of the optical field emanating from the free end of an optical fiber is also provided

Simultaneous Optical Measurements of Axial and Tangential Steady-State Blade Deflections

Currently, the majority of fiber-optic blade instrumentation is being designed and manufactured by aircraft-engine companies for their own use. The most commonly employed probe for optical blade deflection measurements is the spot probe. One of its characteristics is that the incident spot on a blade is not fixed relative to the blade, but changes depending on the blade deformation associated with centrifugal and aerodynamic loading. While there are geometrically more complicated optical probe designs in use by different engine companies, this paper offers an alternate solution derived from a probe-mount design feature that allows one to change the probe axial position until the incident spot contacts either a leading or a trailing edge. By tracing the axial position of either blade edge one is essentially extending the deflection measurement to two dimensions, axial and tangential. The blade deflection measurements were obtained during a wind tunnel test of a fan prototype

Microemulsion Characterization by the Use of a Noninvasive Backscatter Fiber Optic Probe

This paper demonstrates the utility of a noninvasive backscatter fiber optic probe for dynamic light-scattering characterization of a microemulsion comprising sodium dodecyl sulfate/1-butanol/brine/heptane. The fiber probe, comprising two optical fibers precisely positioned in a stainless steel body, is a miniaturized and efficient self-beating dynamic light-scattering system. Accuracy of particle size estimation is better than +/- 2%

Flocculation and aggregation in a microgravity environment (FAME)

An experiment to study flocculation phenomena in the constrained microgravity environment of a space shuttle or space station is described. The small size and light weight experiment easily fits in a Spacelab Glovebox. Using an integrated fiber optic dynamic light scattering (DLS) system we obtain high precision particle size measurements from dispersions of colloidal particles within seconds, needs no onboard optical alignment, no index matching fluid, and offers sample mixing and shear melting capabilities to study aggregation (flocculation and coagulation) phenomena under both quiescent and controlled agitation conditions. The experimental system can easily be adapted for other microgravity experiments requiring the use of DLS. Preliminary results of ground-based study are reported

STUDY OF 1-DIMNESIONAL MOVEMENT OF LAMBDA DNA IN NANOCHANNELS

Master'sMASTER OF SCIENC

System Developed for Real-Time Blade-Flutter Monitoring in the Wind Tunnel

A real-time system has been developed to monitor flutter vibrations in turbomachinery. The system is designed for continuous processing of blade tip timing data at a rate of 10 MB/sec. A USB 2.0 interface provides uninterrupted real-time processing of the data, and the blade-tip arrival times are measured with a 50-MHz oscillator and a 24-bit pipelined architecture counter. The input stage includes a glitch catcher, which reduces the probability of detecting a ghost blade to negligible levels. A graphical user interface provides online interrogation of any blade tip from any light probe sensor. Alternatively, data from all blades and all sensors can be superimposed into a single composite scatter plot displaying the vibration amplitude of each blade

Identification and characterisation of stripe rust resistance genes Yr66 and Yr67 in wheat cultivar VL Gehun 892

Wheat cultivar VL Gehun 892 has shown a high level of resistance against Australian Puccinia striiformis f. sp. tritici (Pst) pathotypes. In this study, it was crossed with Westonia, a susceptible wheat cultivar, and digenic segregation was observed in the derived population against Pst pathotype 134 E16A+Yr17+Yr27+. Single-gene recombinant inbred line (RIL) populations were developed from F3 families (VL Gehun 892/Westonia#1 and VLGehun 892/Westonia#4) that showed monogenic segregations with two distinct phenotypes. Single-gene segregation against Pst pathotype 134 E16A+Yr17+Yr27+ was confirmed in both F6 RIL populations. Bulked segregant analysis using a 90K Infinium SNP array placed YrVL1 in the short arm of chromosome 3D and YrVL2 in the long arm of chromosome 7B. Kompetitive allele specific polymerase chain reaction (KASP) assays were developed for the SNPs linked with YrVL1 and YrVL2 and were mapped onto the respective populations. KASP_48179 (0.6 cM proximal) and KASP_18087 (2.1 cM distal) flanked YrVL1, whereas YrVL2 was mapped between KASP_37096 (1.2 cM proximal) and KASP_2239 (3.6 cM distal). Based on their pathotypic specificities, map locations, and stages of expression, YrVL1 and YrVL2 were demonstrated to be unique loci and named Yr66 and Yr67, respectively. Markers linked with these genes showed more than 85% polymorphism when tested on a set of 89 Australian cultivars and hence could be used for the marker-assisted selection of these genes in wheat breeding programs, following checks of parental polymorphisms

Development of IRAP- and REMAP-derived SCAR markers for marker-assisted selection of the strip rust resistance gene Yr15 derived from wild emmer wheat

Stripe rust (Pucinia striformis f.sp. tritici) is one of the most important fungal diseases of wheat, found on all continents and in over 60 countries. Wild emmer wheat, Triticum dicoccoides, which is the tetraploid progenitor of durum wheat, is a valuable source of novel stripe rust resistance genes for wheat breeding. T. dicoccoides G25 accession carries Yr15, a gene on chromosome arm 1BS. Yr15 confers resistance to all known stripe rust isolates; it is also effective in introgressed durum and bread wheat. Retrotransposons generate polymorphic insertions, which can be scored as Mendelian markers with techniques including REMAP and IRAP. Six REMAP and IRAP-derived SCAR markers were developed using 1256 F2 plants derived from crosses of the susceptible T. durum accession D447 with its resistant BC3F9 and BC3F10 (B9 and B10) near isogenic lines, which carried Yr15 introgressed from G25. The nearest markers segregated 0.1 cM proximally and 1.1 cM distally to Yr15. These markers were also mapped and validated at the same position in another independent 500 F2 plants derived from crosses of B9 and B10 with the susceptible cultivar Langdon. SCAR270 and SCAR790, surrounding Yr15 at an interval of 1.2 cM, were found to be reliable and robust co-dominant markers in a wide range of wheat lines and cultivars with and without Yr15. These markers are useful tags in marker-assisted wheat breeding programs aiming to incorporate Yr15 into elite wheat lines and cultivars for durable and broad-spectrum resistance against stripe rust.Peer reviewe

A haplotype map of allohexaploid wheat reveals distinct patterns of selection on homoeologous genomes

BACKGROUND: Bread wheat is an allopolyploid species with a large, highly repetitive genome. To investigate the impact of selection on variants distributed among homoeologous wheat genomes and to build a foundation for understanding genotype-phenotype relationships, we performed population-scale re-sequencing of a diverse panel of wheat lines. RESULTS: A sample of 62 diverse lines was re-sequenced using the whole exome capture and genotyping-by-sequencing approaches. We describe the allele frequency, functional significance, and chromosomal distribution of 1.57 million single nucleotide polymorphisms and 161,719 small indels. Our results suggest that duplicated homoeologous genes are under purifying selection. We find contrasting patterns of variation and inter-variant associations among wheat genomes; this, in addition to demographic factors, could be explained by differences in the effect of directional selection on duplicated homoeologs. Only a small fraction of the homoeologous regions harboring selected variants overlapped among the wheat genomes in any given wheat line. These selected regions are enriched for loci associated with agronomic traits detected in genome-wide association studies. CONCLUSIONS: Evidence suggests that directional selection in allopolyploids rarely acted on multiple parallel advantageous mutations across homoeologous regions, likely indicating that a fitness benefit could be obtained by a mutation at any one of the homoeologs. Additional advantageous variants in other homoelogs probably either contributed little benefit, or were unavailable in populations subjected to directional selection. We hypothesize that allopolyploidy may have increased the likelihood of beneficial allele recovery by broadening the set of possible selection targets