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At least 1,207 records · Page 67Linked to original sources
PubMed2006

Selective erasure of speckle-multiplexed holograms by use of a double Mach-Zehnder interferometric arrangement.

A novel method to selectively erase and update speckle-multiplexed holograms in photorefractive crystals by use of a double Mach-Zehnder (DMZ) interferometric arrangement is presented. The DMZ arrangement automatically produces a pair of pi-phase-shifted interference patterns used for holographic recording, erasure, and update operations with a fairly simple optical configuration that consists of a commonly used dielectric multilayer beam splitter and two mirrors. The recording and the erasure conditions required for erasing a photorefractive hologram quickly and completely are discussed by calculating the temporal property of the hologram buildup and decay using the time-dependent coupled-wave equations. An experiment is also performed, in which arbitrary holograms in speckle-multiplexed holograms are selectively erased and updated with the simple DMZ optical configuration.

Journal Article↗
PubMed2005

Low through channel loss wavelength multiplexer using multiple transmission volume Bragg gratings.

We describe a wavelength multiplexer design that employs multiple transmission volume Bragg gratings written in the same region of a photosensitive glass having a through channel loss of < 0.5 dB. A two-channel multiplexer for wavelengths of lambda = 1310 and 1550 nm is demonstrated to test our design methods and assumptions. Agreement between simulation and experiment is within 0.2 dB at the peak diffraction efficiency. Grating apodization is used to reduce the interchannel cross talk from (13.5 +/- 0.5) to (41.5 +/- 8.5) dB, with an experimental through channel loss of (0.6 +/- 0.2) dB. Effects of angular dispersion on diffraction efficiency and grating spectral shape due to the finite diameter of the incident reading beam are also analyzed.

Journal Article↗
PubMed2003

Spectrally scanned, repetitively pulsed erbium-doped fiber laser for spectral and temporal multiplexing of fiber Bragg grating sensors.

An erbium-doped fiber laser that emits a series of spectrally scanned pulses is used to monitor an array of fiber Bragg grating (FBG) sensors. The cavity for this Fabry-Perot laser is formed by two spectrally selective reflectors: a rotating mirror-grating combination for scanning the reflectance peak wavelength and a fiber Fabry-Perot interferometer (FFPI) with a periodic reflectance spectrum. During a scan of the rotating mirror, the laser produces a set of Q-switched pulses over the 1522-1568-nm spectral range at each of the FFPI reflectance peak wavelengths. This laser is used to simultaneously demonstrate wavelength-division multiplexing of FBGs with reflectance peaks in different spectral regimes and time-division multiplexing of FBGs with overlapping spectra. The spectral location of the FBG peaks was determined to an accuracy of 1.4 pm.

Journal Article↗
PubMed2004

Holographic simultaneous readout polarization multiplexing based on photoinduced anisotropy in bacteriorhodopsin.

Bacteriorhodopsin (bR) is a reversible photochromic protein that can be used as a holographic medium. The dichroic absorption of the bR molecule is polarization dependent, thereby allowing for the recording of polarization holograms. The properties of polarization holograms can be used to multiplex two independent images in a single bR film. A new technique and associated polarization-multiplexing scheme are demonstrated that allow for simultaneous readout of two orthogonally polarized images while achieving a high normalized diffraction efficiency for each of the individual images.

Journal Article↗
PubMed2004

Cross talk between holograms of finite contrast in a phase-code multiplexing system.

The cross talk between holograms recorded in a phase-code multiplexing system is analyzed. The signal-to-noise ratio (SNR) is derived for the original image of a finite contrast ratio in the presence of a phase-shift error of the reference beam. It is shown that one particular code in the Walsh-Hadamard code set can be the dominant cross-talk noise source. We experimentally measured the SNR of the holograms recorded in an 8-bit phase-code multiplexing system by varying the contrast ratio of the original image. We show good agreement between experiment and theory. The existence of one bad code is also shown experimentally.

Journal Article↗
PubMed2004

Polytopic multiplexing.

Polytopic multiplexing is a new method of overlapping holograms that, when combined with other multiplexing techniques, can increase the capacity of a volume holographic data storage system by more than a factor of 10. This is because the method makes possible the effective utilization of thick media. An experimental demonstration of this technique is also presented.

Journal Article↗
PubMed2005

Shift multiplexing by planar waveguide referencing.

We present a new method with which to implement shift multiplexing by planar waveguide referencing. In this method, a planar waveguide is used to steer the reference beam, and we implement shift multiplexing by shifting the recording medium. A spatial selectivity as high as 1.1 microm is obtained. By using waveguide referencing we can make a compact and simple holographic system.

Journal Article↗
PubMed2006

White light micrograting multiplexing for high density data storage.

Recording of multiplexed microholographic gratings with improved recording volume for high density optical data storage is proposed and demonstrated. By using a hybrid diffractive-refractive objective lens with extended depth of focus, we have achieved a recording beam size of approximately 1 microm and a focal depth of 20 microm. Multiple gratings corresponding to spectral lines within the 400-650 nm spectral band have been successfully multiplexed in a single recording spot or pit of size 1.25 microm on a DuPont photopolymer film using a white light source along with narrowband filters or dispersion elements, thus demonstrating the storage of multiple bits in a single pit. Simultaneous readout of multiple bits in a single storage pit is accomplished with a microspectrometer-type readout head using a white light source.

Journal Article↗
PubMed2003

Potential for using a digital micromirror device as a signal multiplexer in visible spectroscopy.

A digital micromirror device (DMD) was tested to demonstrate its potential as a multiplexing device for the simultaneous detection of visible electromagnetic radiation. Using a Visual Basic program, four sections of the DMD were illuminated by a light source and each region of mirrors was modulated at different low frequencies (14.92, 20.00, 25.00, and 34.48 Hz). A time-domain, multiplexed signal was collected from the sectors and a Fourier transform was performed on these data. The resulting frequency-domain spectrum showed that signal intensities correlated well with what was expected. Three different times were used to establish the best frequency resolution. Using this calculated frequency resolution, a 16 s scan could allow simultaneous detection of up to 240 emission/absorption wavelengths. Data collected also shows the selectivity of micromirror regions and the ability to choose specific regions of the micromirror plane, which could be valuable for a number of spectroscopic techniques.

Equipment Design↗
PubMed2004

High-level multiplex genotyping of polymorphisms involved in folate or homocysteine metabolism by matrix-assisted laser desorption/ionization mass spectrometry.

BACKGROUND: Increased plasma total homocysteine (tHcy), a risk factor for cardiovascular disease, is related to genetic, environmental, and nutritional factors, in particular folate status. Future large epidemiologic studies of the genetic basis of hyperhomocysteinemia will require high-throughput assays for polymorphisms of genes related to folate and Hcy metabolism. METHOD: We developed a high-level multiplex genotyping method based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for the detection of 12 polymorphisms in 8 genes involved in folate or Hcy metabolism. The assay includes methylenetetrahydrofolate reductase (MTHFR) 677C>T and 1298A>C, methionine synthase (MTR) 2756A>G, methionine synthase reductase (MTRR) 66A>G, cystathionine beta-synthase (CBS) 844ins68 and 699C>T, transcobalamin II (TCII) 776C>G and 67A>G, reduced folate carrier-1 (RFC1) 80G>A, paraoxonase-1 (PON1) 575A>G and 163T>A, and betaine homocysteine methyltransferase (BHMT) 742G>A. RESULTS: The failure rate of the assay was < or = 1.7% and was attributable to unsuccessful DNA purification, nanoliter dispensing, and spectrum calibration. Most errors were related to identification of heterozygotes as homozygotes. The mean error rate was 0.26%, and error rates differed for the various single-nucleotide polymorphisms. Identification of CBS 844ins68 was carried out by a semiquantitative approach. The throughput of the MALDI-TOF MS assay was 1152 genotypes within 20 min. CONCLUSIONS: This high-level multiplex method is able to genotype 12 polymorphisms involved in folate or Hcy metabolism. The method is rapid and reproducible and could facilitate large-scale studies of the genetic basis of hyperhomocysteinemia and associated pathologies.

Folic Acid↗
PubMed2004

Multiplexed genetic analysis using an expanded genetic alphabet.

BACKGROUND: All states require some kind of testing for newborns, but the policies are far from standardized. In some states, newborn screening may include genetic tests for a wide range of targets, but the costs and complexities of the newer genetic tests inhibit expansion of newborn screening. We describe the development and technical evaluation of a multiplex platform that may foster increased newborn genetic screening. METHODS: MultiCode PLx involves three major steps: PCR, target-specific extension, and liquid chip decoding. Each step is performed in the same reaction vessel, and the test is completed in approximately 3 h. For site-specific labeling and room-temperature decoding, we use an additional base pair constructed from isoguanosine and isocytidine. We used the method to test for mutations within the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The developed test was performed manually and by automated liquid handling. Initially, 225 samples with a range of genotypes were tested retrospectively with the method. A prospective study used samples from >400 newborns. RESULTS: In the retrospective study, 99.1% of samples were correctly genotyped with no incorrect calls made. In the perspective study, 95% of the samples were correctly genotyped for all targets, and there were no incorrect calls. CONCLUSIONS: The unique genetic multiplexing platform was successfully able to test for 31 targets within the CFTR gene and provides accurate genotype assignments in a clinical setting.

Autoanalysis↗
PubMed2006

Development and validation of a multiplex add-on assay for sepsis biomarkers using xMAP technology.

BACKGROUND: Sepsis is a common and often fatal disease. Because sepsis can be caused by many different organisms, biomarkers that can aid in diagnosing sepsis and monitoring treatment efficacy are highly warranted. New sepsis markers may provide additional information to complement the currently used markers. METHODS: We used a combination of in-house and commercially available multiplex immunoassays based on Luminex xMAP technology to assay biomarkers of potential interest in EDTA-plasma samples. RESULTS: A 3-plex assay for soluble urokinase plasminogen activator receptor (suPAR), soluble triggering receptor expressed on myeloid cells-1 (sTREM-1), and macrophage migration inhibiting factor (MIF) was developed and validated in-house. This 3-plex assay was added to a commercially available interleukin-1beta (IL-1beta), IL-6, IL-8, granulocyte/macrophage colony-stimulating factor, and tumor necrosis factor-alpha human cytokine panel. No cross-reactivity was observed when the assays were combined. Correlation between values obtained with the 8-plex, the 5-cytokine panel, the 3 in-house 1-plex assays, and a suPAR ELISA ranged from 0.86 to 0.99. Mean within- and between-run CVs were 8.0% and 11%, respectively. Recoveries of suPAR, sTREM-1, and MIF calibrators were 108%, 88%, and 51%, respectively. In plasma collected from 10 patients with bacterial sepsis confirmed by blood culture, the assay detected significantly increased concentrations of all 8 analytes compared with healthy controls. CONCLUSIONS: A commercially available xMAP panel can be expanded with markers of interest. The combined multiplex assay can measure the 8 analytes with high reproducibility. The xMAP technology is an appealing tool for assaying conventional cytokines in combination with new markers.

Biomarkers↗
PubMed2006

MALDI-TOF mass spectrometry for multiplex genotyping of CYP2B6 single-nucleotide polymorphisms.

BACKGROUND: CYP2B6 is a highly variable and polymorphic cytochrome P450 (CYP) enzyme involved in the biotransformation of an increasing number of drugs, including cyclophosphamide, bupropion, and the nonnucleosidic reverse transcriptase inhibitor efavirenz. Several nonsynonymous and promoter single-nucleotide polymorphisms (SNPs) in the CYP2B6 gene are associated with altered hepatic expression and function, which affect drug plasma concentrations. METHODS: We used multiplex PCR to amplify relevant gene fragments while avoiding amplification of the CYP2B7P1 pseudogene. Polymorphic sites were analyzed by allele-specific primer extension followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Method evaluation was performed on a panel of 287 genomic DNA samples previously genotyped by other methods. RESULTS: Five multiplex assays were developed, comprising the following 15 SNPs: -82T --> C (*22); 86G --> C (R29T, *17); 136A --> G (M46V, *11); 296G --> A (G99E, *12); 415A --> G (K139E, *8, *13); 419G --> A (R140Q, *14); 516G --> T (Q172H, *6, *7, *9, *13, *19, *20), 547G --> A (V183I); 769G --> A (D257N); 785A --> G (K262R, *4, *6, *7, *13, *16, *19, *20); 983T-->C (I328T, *16, *18); 1006C --> T (R336C, *19); 1172T --> A (I391N, *15); 1282C --> A (P428T, *21); 1459C --> T (R487C, *5, *7). In 9 DNA samples showing discrepant genotypes, correctness of the MALDI-TOF MS result was confirmed by direct sequencing. CONCLUSIONS: This genotyping method enabled sensitive, specific, accurate, and comprehensive determination of 15 relevant SNPs of CYP2B6. The assay design allows analysis of SNP subsets, incorporation of additional SNPs, and performance of high-throughput genotyping.

Aryl Hydrocarbon Hydroxylases↗
PubMed2005

Constructing STR multiplex assays.

Multiplex polymerase chain reaction (PCR) refers to the simultaneous amplification of multiple regions of deoxyribonucleic acid (DNA) using PCR. Commercial short tandem repeat (STR) assays that can coamplify as many as 16 different loci have become widely used in forensic DNA typing. This chapter will focus on some of the aspects of constructing robust STR multiplex assays, including careful design and quality control of PCR primers. Examples from the development of a cat STR 12plex and a human Y chromosome STR 20plex are used to illustrate the importance of various parts of the protocol. Primer design parameters and Internet-accessible resources are discussed, as are solutions to problems with residual dye artifacts that result from impure primers.

Chromosomes, Human, Y↗
PubMed2005

Sensitive detection of SARS coronavirus RNA by a novel asymmetric multiplex nested RT-PCR amplification coupled with oligonucleotide microarray hybridization.

We have developed a sensitive method for the detection of specific genes simultaneously. First, DNA was amplified by a novel asymmetric multiplex PCR with universal primer(s). Second, the 6-carboxytetramethylrhodamine (TAMRA)-labeled PCR products were hybridized specifically with oligonucleotide microarrays. Finally, matched duplexes were detected by using a laser-induced fluorescence scanner. The usefulness of this method was illustrated by analyzing severe acute respiratory syndrome (SARS) coronavirus RNA. The detection limit was 10(0) copies/microL. The results of the asymmetric multiplex nested reverse transcription-PCR were in agreement with the results of the microarray hybridization; no hybridization signal was lost as happened with applicons from symmetric amplifications. This reliable method can be used to the identification of other microorganisms, screening of genetic diseases, and other applications.

Oligonucleotide Array Sequence Analysis↗
PubMed2006

Frequency division multiplexed multichannel high-speed fluorescence confocal microscope.

In this article, we report a new type of fluorescence confocal microscope: frequency division multiplexed multichannel fluorescence confocal microscope, in which we encode the spatial location information into the frequency domain. In this microscope, the exciting laser beam is first split into multiple beams and each beam is modulated at a different frequency. These multiple beams are focused at different locations of the target to form multiple focal points, which further generate multiple fluorescent emission spots. The fluorescent emissions from different focal points are also modulated at different frequencies, because the exciting beams are modulated at different frequencies (or difference carrier frequency). Then, all the fluorescent emissions (modulated at different frequencies) are collected together and detected by a highly sensitive, large-dynamic-range photomultiplier tube. By demodulating the detected signal (i.e., via the Fourier transform), we can distinguish the fluorescent light emitted from the different locations by the corresponding carrier frequencies. The major advantage of this unique fluorescence confocal microscope is that it not only has a high sensitivity because of the use of photomultiplier tube but also can get multiple-point data simultaneously, which is crucial to study the dynamic behavior of many biological process. As an initial step, to verify the feasibility of the proposed multichannel confocal microscope, we have developed a two-channel confocal fluorescence microscope and applied it to study the dynamic behavior of the changes of the calcium ion concentration during the single cardiac myocyte contraction. Our preliminary experimental results demonstrated that we could indeed realize multichannel confocal fluorescence microscopy by utilizing the frequency division multiplexed microscope, which could become an effective tool to study the dynamic behavior of many biological processes.

Animals↗
PubMed2000

Comparative analysis of follistatin-, activin beta A- and activin beta B-mRNA steady-state levels in diverse porcine tissues by multiplex S1 nuclease analysis.

OBJECTIVE: The relation of activins (dimers of the beta-subunits of inhibin) and follistatin (FS) (their binding protein) affect the growth and differentiation of many cell types. Activin- and FS-mRNAs show a widespread co-expression throughout the organism, indicating an essential role for the FS/activin system in diverse physiological processes. The present study was performed to investigate FS-, activin betaA-, and activin beta B-mRNA expression in porcine tissues and to compare the relative mRNA tissue distribution by a newly developed multiplex S1 nuclease protection assay. METHODS: Twenty micrograms total RNA from different porcine tissues were subjected to multiplex S1 analysis. Specific mRNA expression was determined by measurements of optical densities on autoradiographs. RESULTS: Activin beta A-mRNA expression was abundant in the ovary, adrenal gland, fat, vein, artery and uterus, activin beta B-mRNA was highly expressed in the ovary, pituitary, uterus, placenta, aorta and cerebellum. FS-mRNA showed a widespread expression with high levels in ovary, uterus, cerebellum, placenta and fat. The comparison of relative activin beta A-, activin beta B- and FS-mRNA expression within a certain tissue showed a predominance of activin beta A-mRNA in the adrenal gland, fat, artery, spinal cord, cerebrum and colon and of activin beta B-m RNA in pituitary, testis and placenta, while FS-mRNA levels exceeded those of activin subunits in epididymis, liver, lymphoid tissue, muscle, intestine, cerebellum, ovary and uterus. CONCLUSIONS: The presented data provide an overview of FS-, activin beta A-, and activin beta B-mRNA steady state levels in porcine tissues.

Activins↗
PubMed2006

A universal array-based multiplexed test for cystic fibrosis carrier screening.

Cystic fibrosis is a multisystem autosomal recessive disorder with high carrier frequencies in caucasians and significant, but lower, carrier frequencies in other ethnicities. Based on technology that allows high detection of mutations in caucasians and significant detection in other ethnic groups, the American College of Medical Genetics (ACMG) and American College of Obstetricians and Gynecologists (ACOG) have recommended pan-ethnic cystic fibrosis carrier screening for all reproductive couples. This paper discusses carrier screening using the Tag-It multiplex mutation platform and the Cystic Fibrosis Mutation Detection Kit. The Tag-It cystic fibrosis assay is a multiplexed genotyping assay that detects a panel of 40 cystic fibrosis transmembrane conductance regulator mutations including the 23 mutations recommended by the ACMG and ACOG for population screening. A total of 16 additional mutations detected by the Tag-It cystic fibrosis assay may also be common. The assay method is described in detail, and its performance in a genetics reference laboratory performing high-volume cystic fibrosis carrier screening is assessed.

Cell Membrane↗