Two-channel Detection Research Articles

Re‐evaluating acridine orange for rapid flow cytometric enumeration of parasitemia in malaria‐infected rodents

Methods facilitating research in malaria are of pivotal relevance. Flow cytometry offers the possibility of rapid enumeration of parasitemia. It relies on staining the parasite DNA to distinguish between infected and non-infected red blood cell (RBC) populations. Unfortunately, in rodents abundant reticulocyte RNA interferes with the application of the method. This results in time-consuming sample preparation protocols that offer no clear advantage over microscopic counting. We re-evaluated the use of the DNA/RNA discriminating vital fluorochrome acridine orange (AO) for rapid flow cytometric enumeration of parasitemia in rodents. Whole blood from rodents infected with Plasmodium berghei and Plasmodium yoelii was stained with AO and analyzed by flow cytometer. A newly developed two-channel (FL1/FL3) detection method was compared with conventional one-channel (FL1) detection and microscopic counting. The new AO two-channel detection method clearly discriminated between infected and non-infected RBC populations. It showed to be linear above parasitemias of 0.3%. Sample processing time amounted to approximately 5 min. It is shown that AO can be used for rapid, precise, and accurate enumeration of parasitemia in rodents. Due to its ease of handling the method might find widespread application in malaria research.

Duty Cycle and Modulation Efficiency of Two-Channel Hadamard Transform Time-of-Flight Mass Spectrometry

Hadamard transform time-of-flight mass spectrometry (HT-TOFMS) is based on the pseudorandom gating of ion packets into a time-of-flight mass-to-charge analyzer. In its typical implementation, the technique is able to monitor continuous ion sources with a 50% duty cycle, independent of all other figures of merit. Recently, we have demonstrated that the duty cycle can be extended to 100% using patterned, two-channel detection. Two-channel HT-TOFMS involves the simultaneous optimization of paired one-channel experiments and imposes more stringent conditions to achieve high-quality spectra. An ion modulation device, known as Bradbury-Nielson Gate (BNG), is central to HT-TOFMS. It is an ideal deflection plate, capable of transmitting or deflecting an ion beam according to a known binary sequence without changing the times-of-flight of the ions. Analytical equations are derived that accurately describe the ion modulation process of the BNG as confirmed by good agreement with SimIon simulations and ion beam imaging experiments. From these expressions, the duty cycle and ion modulation efficiency were calculated for various BNG parameters, ion beam characteristics, and detector dimensions, which permit the optimum conditions to be chosen for the two-channel experiment. We conclude that the outer detector should be three times the maximum deflection angle to detect all deflected ions (100% duty cycle) and that the difference between the modulated ion counts in the sequence elements 0 and 1 should be maximized to achieve high modulation efficiency. This condition is best achieved by tight focusing of the ion beam in the center of the inner detector. When both channels are optimized, the two-channel advantage can be exploited to achieve a further improvement over a single-channel experiment.

The problem of self-calibration of fluorescence signal in microscale sensor systems

Most recent developments in fluorescent molecular sensor devices are based on "ON-OFF" switching, which is an operation with a single measurable parameter, commonly the quenching of total intensity. In the meantime, with this approach self-calibration on the molecular level is not achievable. This calibration is strongly needed in all kinds of microscale applications, including microarrays, microfluidic systems and living cell imaging. Different possibilities are discussed for overcoming this difficulty and an "OR-OR" switching concept is suggested that involves the two-channel detection as a promising solution. For achieving the desired efficiency specific conditions are needed: it should be a single reporter dye exhibiting rapid reversible excited-state reaction and providing two-band wavelength ratiometric response.

Continuous Two‐Channel Time‐of‐Flight Mass Spectrometric Detection of Electrosprayed Ions

Flying to new destinations: Instrument modifications, which give three detection areas (see scheme) in a two-channel detection scheme, extend the achievable duty cycle of a Hadamard transform time-of-flight mass spectrometer (HT-TOFMS) to 100 % and effectively converts TOFMS into a continuous detection technique. Beyond the improved signal-to-noise ratio, this advance gives an increase in the data-acquisition rate leading to a higher detection speed.

Transversal phase resolved polarization sensitive optical coherence tomography

We present a novel optical coherence tomography (OCT) method to measure backscattered intensity and birefringence properties (retardation and fast axis orientation) and apply it to imaging of human ocular tissue. The method is based on a Mach Zehnder interferometer, on transversal scanning, and on a polarization sensitive two-channel detection. A highly stable carrier frequency is generated by acousto-optic modulators (AOMs). This allows a phase sensitive demodulation by the lock-in technique. Since the recording of individual interference fringes is avoided by this method the amount of data to be recorded and processed is considerably reduced. We demonstrate this method on human cornea and anterior chamber angle and present, to the best of our knowledge, the first OCT images of retardation and fast axis orientation of the anterior chamber angle region in vivo.

A Rapid Separation of Ten Carotenoids, Three Retinoids, Alpha-Tocopherol and d-Alpha-Tocopherol Acetate by High Performance Liquid Chromatography and its Application to Serum and Vegetable Samples

Abstract The methods described herein were developed for the quantitative analysis of 10 carotenoids (lutein, zeaxanthin, canthaxanthin, beta-apo-8′carotenal, beta-cryptoxanthin, echinenone, lycopene, gamma-carotene, alpha-carotene, beta-carotene/15-cis-beta-carotene), 3 retinoids (retinol, retinyl acetate, retinyl palmitate) and alpha-tocopherol and d-alpha-tocopherol acetate with two-channel detection and a single sample preparation. Two fast and simple methods are described using a Spheri-5-RP-18 column, with two different mobile phases-acetonitrile:dichloromethane:methanol (70:20:10) in 10 minutes and acetonitrile:methanol (85:15) in 25 minutes. These methods would be beneficial to food scientists, cancer researchers and epidemiologists for the accurate estimation of vitamin A activity and the antioxidant capability of different compounds present in the human diet and the levels of these compounds in human serum.

Erratum: Two-channel direct-bit detection receiver for 16-PSK modulated signals

Erratum: Two-channel direct-bit detection receiver for 16-PSK modulated signals

Two-channel direct-bit detection receiver for 16-psk modulated signals

Two-channel direct-bit detection receiver for 16-psk modulated signals

Acetylene Measurements in Flames byCoherent Anti-Stokes Raman Scattering

Abstract Wehave performed coherent anti-Stokes Raman scattering (CARS)measurements of acetylene in a laminarCH4/C2H2/air flame. The acetyleneconcentration was determined from the ratio of the resonant acetyleneCARS signal to the nonresonant background CARS signal. The resonantand nonresonant signals were detected separately on each laser shotusing polarization analysis and a two-channel detection system. Theflame temperature profile was determined from fits of nitrogen CARSspectra. Experimental acetylene CARS spectra are compared with theoretical spectra.

Analysis of anabolic steroids in body fluids by capillary gas chromatography with a two-channel detection system and a computer

A method is described for analysis of multi-component mixtures of steroid metabolites in biological fluids by means of capillary gas chromatography with glass and fused-silica columns and simultaneous detection of methoxylamine—trimethyl-silyl derivatives with universal flame-ionization and selective nitrogen alkali flame-ionization detectors. A data system was applied to the on-line treatment of the results. Computer programs were designed for precise calculation of Kováts retention indices from the known values for selected natural urinary steroids. The programs allow the selection of nitrogen-containing components, normalized chromatogram plotting for both detection channels and qualitative and quantitative analysis. Results are presented on the detection of metabolites of methandrostenolone, 17α-methyltestosterone, 19-nortestosterone and fluoxymesterone.

Attentional factors in simultaneous two-channel auditory signal detection

This study investigated attentional factors involved in two-channel auditory signal detection. The brief 50 msec sinusoidal signals, masked by binaurally uncorrelated, band-limited noise, were presented simultaneously to two separate earphone channels each with an independent probability of 0.5. The two-channel detection tasks required observers to monitor one (selective attention condition) or both (divided attention condition) of the earphone channels. Compared to the single channel condition, observers showed a slight (1–3 dB), but consistent, decrement in detection performance in both the selective and divided attention conditions with signals separated in frequency by less than one critical band (Δf=65 Hz). With signals separated in frequency by more than one critical band (Δf=1565 Hz), observers again showed a slight performance decrement when dividing their attention between two earphone channels, but could effectively monitor one channel while attempting to ignore the other. [This work was supported by a grant from NINDS.]

Fluctuating Target Detection in Clutter Using Sidelobe Blanking Logic

In an earlier paper, Maisel [6] considered two-channel detection systems using a sidelobe blanking logic when a nonfluctuating target was present. This paper is an extension of the earlier work to include fluctuating targets. The Swerling I, II, III, and IV models are considered when single-pulse detection is of interest. An adaptive threshold procedure is also briefly discussed whereby the probability of false alarm at any given resolution cell is maintained constant, even though the input clutter level may vary from cell to cell or from beam position to beam position. Useful data are presented for detection probabilities in the range 0.5 to 0.9, for false alarm probabilities in the range 104 to 10-8, and for a false detection probability of 0.1 for a sidelobe target yielding an apparent signal to total noise power density ratio of 13.0 dB in the main beam receiver.

Age and the matching of signal frequency in a two-channel detection task.

Age and the matching of signal frequency in a two-channel detection task.