Two-pass Mode Research Articles

A multi-omics framework reveals strawberry flavor genes and their regulatory elements.

Flavor is essential to consumer preference of foods and is an increasing focus of plant breeding programs. In fruit crops, identifying genes underlying volatile organic compounds has great promise to accelerate flavor improvement, but polyploidy and heterozygosity in many species have slowed progress. Here we use octoploid cultivated strawberry to demonstrate how genomic heterozygosity, transcriptomic intricacy and fruit metabolomic diversity can be treated as strengths and leveraged to uncover fruit flavor genes and their regulatory elements. Multi-omics datasets were generated including an expression quantitative trait loci map with 196 diverse breeding lines, haplotype-phased genomes of a highly-flavored breeding selection, a genome-wide structural variant map using five haplotypes, and volatile genome-wide association study (GWAS) with > 300 individuals. Overlaying regulatory elements, structural variants and GWAS-linked allele-specific expression of numerous genes to variation in volatile compounds important to flavor. In one example, the functional role of anthranilate synthase alpha subunit 1 in methyl anthranilate biosynthesis was supported via fruit transient gene expression assays. These results demonstrate a framework for flavor gene discovery in fruit crops and a pathway to molecular breeding of cultivars with complex and desirable flavor.

A New Single-Pass SAR Interferometry Technique with a Single-Antenna for Terrain Height Measurements

One of the prospective research topics in radar remote sensing technology is the methodology for designing an optimal radar system for high-precision two-dimensional and three-dimensional image acquisition of the Earth’s surface with minimal hardware requirements. In this study, we propose a single-pass interferometric synthetic aperture radar (SAR) imaging technique with only a single antenna for the estimation of the terrain height. This technique enabled us to obtain terrain height information in one flight of the carrier, on which only one receiving antenna was mounted. This single-antenna single-pass interferometry required a squint angle look geometry and additional image synthesis processing. The limiting accuracy of the terrain height measurement was approximately 1.5 times lower than that of the conventional two-pass mode and required a longer baseline than two-pass interferometry to have an equivalent accuracy performance. This imaging method could overcome the temporal decorrelation problem of two-pass interferometry due to a short time gap in the radar echo acquisitions during two sub-aperture intervals. We compared the accuracy performance of the terrain height measurements of our method with the conventional two-pass interferometry. This comparison was carried out at various spectral bandwidths, degrees of surface roughness, and baseline lengths. We validated our idea with numerical simulations of a digital elevation map, and showed real extracted data of the terrain heights in the Astrakhan and Volga regions of the Russian Federation, obtained from airborne SAR with our single-antenna single-pass interferometry technique.

Study on Multi-Frequency Method for Electrostatic Force Microscopy in Air

A detailed study of multi-frequency electrostatic force microscopy (MF-EFM) in air is presented. In the MF-EFM, the first eigenmode of the cantilever vibration is used for topographic imaging, while the second one is resonantly excited for the measurement of electrostatic force. Possible interferences between the two information channels are eliminated by using the lift mode and the two-pass mode. The lateral resolution of the microscopy is corroborated to be improved. The capabilities of the MF-EFM are demonstrated by characterizing a silicon wafer sample and by determining its local contact potential difference.

Resonant multi-frequency method for Kelvin probe force microscopy in air

The multi-frequency method, recently introduced in atomic force microscopy (AFM), has shown remarkable enhancement of sensitivity and resolution of microscopy with a variety of heterogeneous materials. Under ambient conditions, Kelvin probe force microscopy (KPFM) is commonly carried out using only the first flexural eigenmode of the micro-cantilever probe. Here we report a resonant multi-frequency method for KPFM in air. To implement this method, the first eigenmode of the cantilever probe is used for topography imaging, whereas the second one is used to measure the local contact potential difference in the two-pass mode with the tip lifted. By introducing an additional feedback controller, a multi-frequency KPFM (MF-KPFM) is developed upon a commercial AFM. The performance of MF-KPFM, including the feedback controller, sensitivity and noise, lift height of the cantilever and lateral resolution, is evaluated and optimized. The capabilities of MF-KPFM are demonstrated by characterizing a charge pattern on a polymer electret. The results show that the lateral resolution of KPFM in air can be improved by the resonant multi-frequency method.

Coherent data alignment and baseline calibration for improved two-pass interferometric synthetic aperture radar

Currently, two principal operation modes are utilized by interferometric synthetic aperture radar (IFSAR) systems for data collection. The first mode is a one-antenna, two-pass IFSAR operation mode, where the aircraft platform possesses a single antenna and flies by the scene of interest twice collecting data. The two-antenna, one-pass IFSAR operation mode is the second mode, in which the aircraft platform possesses two antennas and flies by the scene of interest once while collecting data. Each one of these IFSAR operation modes possesses certain strengths and weaknesses. The one-antenna, two-pass mode allows for large baselines but suffers from imprecise knowledge of the baseline length, and consequently does not possess accurate target height scaling. Alternatively, the two-antenna, one-pass mode allows for precise knowledge of baseline length, but often at the expense of a limited baseline length, and consequently suffers from increased height noise. We describe an innovative IFSAR operation mode for overcoming these weaknesses by combining the two current IFSAR operation modes into a new two-antenna, two-pass IFSAR operation mode. By accurately estimating the antenna baseline between the two flight passes from the data itself, target height scaling accuracies are improved to the equivalent of a two-antenna, one-pass IFSAR system with the height-noise performance commensurate with the larger baseline. This, in turn, allows for more accurate information about target ground position locations and heights.

A set covering approach to metallurgical grade assignment

Early in 1986 Bethlehem Steel Corporation installed two continuous slab caster machines to modernize the steelmaking facilities at two of its major plants. The installation of this equipment, at a total cost of about half a billion dollars, required accompanying production planning and control systems (PPC) in order to function efficiently. The PPC module responsible for assigning metallurgical grades to customer orders uses a minimum cardinality set covering approach which not only minimizes the number of metallurgical grades required to satisfy a given collection of customer orders, but also is able to ‘show preference’ to priority orders. The algorithm, Optsol is used in a two-pass mode to quickly generate very good solutions to these large scale (up to 1000 zero-one variables and 2500 constraints) problems. When compared to the traditional method of grade assignment, this approach has the potential to significantly improve caster productivity and to reduce semi-finished inventory.

The Thermal Performance of the Two-Pass, Two-Glass-Cover Solar Air Heater

Analytic models are developed for the performance prediction of a two-glass-cover solar air heater operated in both the single-pass and two-pass modes. It is shown that the two-pass mode of operation is superior to the single-pass mode of operation over the range of collector inlet temperatures considered. This is seen to be mainly due to the fact that, in the two-pass mode of operation, the outer glass cover is cooled by the working fluid, thereby reducing the top losses. It is also shown that the performance in the two-pass mode of operation is independent of length, over the range of collector lengths considered, and that a critical plate spacing, dependent on the temperature level of operation of the collector, is indicated. Predicted values of performance are in good agreement with experimental results.

Heat withdrawal from multi-layer thermal trap collectors

The single-pass as well as the two-pass mode of heat withdrawal from a two-layer Thermal Trap Collector with slabs of variable thermal and optical properties are modelled mathematically. The working fluid is assumed to be transparent. Results are computed for slabs of methylmethacrylate plastic and “ideal” glass with air as the working fluid and these are compared with the air-heater experimental results due to Satcunanathan and Deonarine[1] and the novel collector theoretical results due to Caouris et al.[2]. From such a comparison the important features which increase the efficiency of a two-pass two-layer Thermal Trap Collector are identified.

Thermal performance study of two-pass solar air heaters

The operation of a conventional solar air heater with two covers in a two-pass mode offers an inexpensive method of improving the collector efficiency by about 10–15 per cent. Heat transfer models are developed for two such two-pass flow arrangements and are compared with the performance of the single pass design. The computer models are validated by comparing with the experimental data from a series of collector testing experiments. The collector performance is examined over a wide range of design and operating conditions and the two-pass designs are found to perform better than the single pass system. For closed-loop systems with air recirculation the two-pass designs have some limitations in performance. Design curves for two-pass systems over a range of variables are presented.

A two-pass solar air heater

The performance of a solar heater depends on the losses from the collector surfaces. The losses through the bottom and sides of the heater may be reduced or almost eliminated by the use of adequate insulation. In an attempt to reduce the losses from the glass cover of the simple two-glass cover air heater, a unit was constructed in which provision was made for the air to pass between the glass panes before passing through the blackened metal collector (two pass). It was found that the outer glass cover temperatures under these conditions were significantly lower (4–10°F over the day) and much nearer atmospheric temperatures compared to those when the collector was operated in the conventional single-pass manner. Consequently, efficiencies of the order of 10–15 per cent higher, were obtained. It was also found that smaller separations between the two glass panes yielded better results with the two-pass mode of operation.