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AirSWOT is an airborne Ka-band synthetic aperture radar, capable of mapping water surface elevation (WSE) and water surface slope (WSS) using single-pass interferometry. AirSWOT was designed as a calibration and validation instrument for the forthcoming Surface Water and Ocean Topography (SWOT) mission, an international spaceborne synthetic aperture radar mission planned for launch in 2022 which will enable global mapping of WSE and WSS. As an airborne instrument, capable of quickly repeating overflights, AirSWOT enables measurement of high frequency and fine scale hydrological processes encountered in coastal regions. In this paper, we use data collected by AirSWOT in the Mississippi River Delta and surrounding wetlands of coastal Louisiana, USA, to investigate the capabilities of Ka-band interferometry for mapping WSE and WSS in coastal marsh environments. We introduce a data-driven method to estimate the time-varying interferometric phase drift resulting from radar hardware response to environmental conditions. A system of linear equations based on AirSWOT measurements is solved for elevation bias and time-varying phase calibration parameters using weighted least squares. We observed AirSWOT WSE uncertainty of 12 cm RMS compared to in situ water level measurements when averaged over an area of 0.5 km 2 at incidence angles below 15 ∘ . At higher incidence angles, the observed AirSWOT elevation bias is possibly due to residual phase calibration errors or radar backscatter from vegetation. Elevation profiles along the Wax Lake Outlet river channel indicate AirSWOT can measure WSS over a 24 km distance with uncertainty below 0.3 cm/km, 8% of the true water surface slope as measured by in situ data. The data analysis and results presented in this paper demonstrate the potential of AirSWOT to measure water surface elevation and slope within highly dynamic and spatially complex coastal environments.

Active-layer thickness (ALT) is an important parameter for studying surface energy balance, ecosystems, and hydrologic processes in cold regions. We measured ALT along 10 routes with lengths ranging from 0.7 to 6.9 km located on the Alaska North Slope near Toolik Lake and the Happy Valley airstrip (between 68.475° and 69.150°N, and [Formula: see text] and [Formula: see text]). Using a ground-penetrating radar (GPR) system in a common-offset configuration, we measured the two-way traveltimes from the surface to the bottom of the active layer at the end of summer, when the thaw depth was greatest. We used 500 and 800 MHz antennas; the 500 MHz antenna provided suitable vertical resolution, while producing more unambiguous active-layer reflections in the presence of nonideal antenna coupling and active layer inhomogeneity. We derived ALT measurements and their uncertainties from GPR two-way traveltimes, with mechanical probing for velocity calibration. Using an empirical relationship between the wave velocity and soil volumetric water content (VWC), we found that the velocities were consistent with soil VWCs ranging from 0.46 to 0.63. In 31% of traces, the permafrost table horizon was identifiable, resulting in ALT measurements with uncertainties of generally less than 25%. The average ALT was 48.1 cm, with a standard deviation of 16.1 cm. We found distinct patterns of ALT spatial variability at different sites and different length scales. At some sites, the ALT at one point was effectively uncorrelated with ALT at other points separated by lag distances as small as tens of meters; for other sites, there was correlation at lag distances up to approximately 400 m. The ALT statistics were similar to nearby long-term in situ ALT measurements from the Circumpolar Active Layer Monitoring Network, through which yearly ALT measurements have been made since 1990.

AirSWOT is an experimental airborne Ka-band radar interferometer developed by NASA-JPL as a validation instrument for the forthcoming NASA Surface Water and Ocean Topography (SWOT) satellite mission. In 2017, AirSWOT was deployed as part of the NASA Arctic Boreal Vulnerability Experiment (ABoVE) to map surface water elevations across Alaska and western Canada. The result is the most extensive known collection of near-nadir airborne Ka-band interferometric synthetic aperture radar (InSAR) data and derivative high-resolution (3.6 m pixel) digital elevation models to produce water surface elevation (WSE) maps. This research provides a synoptic assessment of the 2017 AirSWOT ABoVE dataset to quantify regional WSE errors relative to coincident in situ field surveys and LiDAR data acquired from the NASA Land, Vegetation, and Ice Sensor (LVIS) airborne platform. Results show that AirSWOT WSE data can penetrate cloud cover and have nearly twice the swath-width of LVIS as flown for ABoVE (3.2 km vs. 1.8 km nominal swath-width). Despite noise and biases, spatially averaged AirSWOT WSEs can be used to estimate sub-seasonal hydrologic variability, as confirmed with field GPS surveys and in situ pressure transducers. This analysis informs AirSWOT ABoVE data users of known sources of measurement error in the WSEs as influenced by radar parameters including incidence angle, magnitude, coherence, and elevation uncertainty. The analysis also provides recommended best practices for extracting information from the dataset by using filters for these four parameters. Improvements to data handing would significantly increase the accuracy and spatial coverage of future AirSWOT WSE data collections, aiding scientific surface water studies, and improving the platform’s capability as an airborne validation instrument for SWOT.

Active layer thickness (ALT) is a critical parameter for monitoring the status of permafrost that is typically measured at specific locations using probing, in situ temperature sensors, or other ground-based observations. Here we evaluated the Remotely Sensed Active Layer Thickness (ReSALT) product that uses the Interferometric Synthetic Aperture Radar technique to measure seasonal surface subsidence and infer ALT around Barrow, Alaska. We compared ReSALT with ground-based ALT obtained using probing and calibrated, 500 MHz Ground Penetrating Radar at multiple sites around Barrow. ReSALT accurately reproduced observed ALT within uncertainty of the GPR and probing data in ~76% of the study area. However, ReSALT was less than observed ALT in ~22% of the study area with well-drained soils and in ~1% of the area where soils contained gravel. ReSALT was greater than observed ALT in some drained thermokarst lake basins representing ~1% of the area. These results indicate remote sensing techniques based on InSAR could be an effective way to measure and monitor ALT over large areas on the Arctic coastal plain.

SummaryHow transcription factors (TFs) reprogram one cell lineage to another remains unclear. Here, we define chromatin accessibility changes induced by the proneural TF Ascl1 throughout conversion of fibroblasts into induced neuronal (iN) cells. Thousands of genomic loci are affected as early as 12 hr after Ascl1 induction. Surprisingly, over 80% of the accessibility changes occur between days 2 and 5 of the 3-week reprogramming process. This chromatin switch coincides with robust activation of endogenous neuronal TFs and nucleosome phasing of neuronal promoters and enhancers. Subsequent morphological and functional maturation of iN cells is accomplished with relatively little chromatin reconfiguration. By integrating chromatin accessibility and transcriptome changes, we built a network model of dynamic TF regulation during iN cell reprogramming and identified Zfp238, Sox8, and Dlx3 as key TFs downstream of Ascl1. These results reveal a singular, coordinated epigenomic switch during direct reprogramming, in contrast to stepwise cell fate transitions in development.

Interferometric synthetic aperture radar (InSAR) is a valuable tool for the study of geophysical phenomena such as crustal deformation, ice motion and structure, and vegetation canopy depths, but it is adversely affected by uncharacterized inhomogeneities in ionospheric propagation delay. Ionospheric disturbances distort both InSAR phase and correlation maps. Here, we present a method to compensate ionospheric propagation variations using accurate image coregistration. This significantly improves both the interferometric coherence and phase accuracy. An azimuth gradient in the total electron content (TEC) from a spatially variable ionosphere results in a range-dependent azimuth phase gradient being added to the phase histories of the pixels being imaged. These phase gradients are equivalent to Doppler shifts, and thus they cause azimuth offsets between the actual and imaged positions of the pixels. Measuring these offsets accurately permits estimation of the gradient and correction of the interferograms for much of the phase distortion, resulting in more accurate estimates of coherence. We show an example over Greenland where the TEC variation causes the correlation to drop from about 0.7 to about 0.2 in one region if spatially varying offsets are not accounted for; it also adds an estimated 4.4 radians of interferometric phase over an 80 km InSAR scene. After applying our algorithm, we find that the correlation in regions affected by the ionospheric inhomogeneity becomes comparable to correlation in the rest of the image. In a more challenging example over Iceland, we show that our method improves the correlation from 0.15 to 0.25 in some areas.

Ground penetrating radar (GPR) has emerged as an effective tool for estimating active layer thickness (ALT) and volumetric water content (VWC) within the active layer. In August 2013, we conducted a series of GPR and probing surveys using a 500 MHz antenna and metallic probe around Barrow, Alaska. We collected about 15 km of GPR data and 1.5 km of probing data. Here, we describe the GPR data processing workflow from raw GPR data to the estimated ALT and VWC. We include the corresponding uncertainties for each measured and estimated parameter. The estimated average GPR-derived ALT was 41 cm, with a standard deviation of 9 cm. The average probed ALT was 40 cm, with a standard deviation of 12 cm. The average GPR-derived VWC was 0.65, with a standard deviation of 0.14.

Cholesteric liquid crystal displays (Ch-LCDs) have potential as screens in portable readers. In the present study, it is demonstrated that a Ch-LCD can be driven by a thermal process at a temperature of 90 °C. At a suitable temperature, the texture of the cholesteric liquid crystal will be transfrred from planar to focal conic. The experimental results show that the reflectance of a Ch-LCD is influenced by texture after the thermal process. After thermal treatment at 90 °C, the periodicity was reduced from 63 nm to 55 nm. A chain tilting angle of ∼29° was estimated.

Man-made land or islands that are reclaimed from the sea are suitable for building airports, harbors, and industry parks for material transportation because of their broad air and land spaces. However, the reclaimed foundation settlement process is of public concern, including the continuous impact of ocean processes on its stability. The majority of the buildings and facilities of Hong Kong International Airport (HKIA) are built on a reclaimed foundation. The reclaimed foundation has been in residual settlement since completion of the filling project in 1994. In this study, we use persistent scatterer interferometry (PSI) and ENVISAT (European Satellite) advanced synthetic aperture radar (ASAR) data to detect the residual settlement rates from 19 April 2006 to 9 January 2008. We use ground truth data to develop empirical correction models for correcting systematic biases in the ASAR PSI-detected settlement rates. The corrected data follow the Lorentz distribution well, implying that the residual settlement process is dominated by two modes or categories of settlement rates. The first category represents a relatively stable state and the second category represents a continuous settlement state. A ground settlement rate map of HKIA shows that an area of the Passenger Terminal Building and an area of the Southern Runway are two relatively stable areas. There are two major continuous settlement areas. One covers the airport Midfield. Another is along the coastline, implying that attention should be paid to impacts of ocean processes on the stability of airport foundations.

In this paper, we present the development of an even-mode matching network for a Marchand balun to achieve 50-? match and high isolation at the balanced ports. A very wide matching bandwidth can be accomplished with the novel addition of an open-circuit stub to the network. Experimental results demonstrate that the even-mode matched balun achieves return losses that are greater than 15 dB at the balanced ports from 6 to 17 GHz. The measured isolation between the balanced ports is greater than 15 dB from 4 to 19 GHz. For the unbalanced port, the return loss is greater than 15 dB from 4 to 19 GHz. The measured insertion loss is less than 1 dB, and amplitude and phase imbalances are ±0.5 dB and ±5° from 4 to 18 GHz, respectively.

In this paper, we present the design and fabrication of ultra-wideband (UWB) baluns embedded in multilayer liquid crystal polymer (LCP) flex. Fabrication techniques are demonstrated for processing these commercially available LCP thin-films by standard PCB equipments. Variations in the LCP thin-film thickness are characterized and compared before and after lamination. Results show good dimensional stability of the material, a critical factor in controlling the line impedances and performance of the balun. Electrical results of these baluns show bandwidths exceeding 3.1-10.6 GHz with less than 1 dB insertion loss, and amplitude and phase imbalance less than 1.2 dB and 2deg, respectively. These baluns are ideal for applications in UWB communication systems specified by the IEEE 802.15.3a standard.

In order to discover new subsets (clusters) of a data set, researchers often use algorithms that perform unsupervised clustering, namely, the algorithmic separation of a dataset into some number of distinct clusters. Deciding whether a particular separation (or number of clusters, K) is correct is a sort of ‘dark art’, with multiple techniques available for assessing the validity of unsupervised clustering algorithms. Here, we present a new technique for unsupervised clustering that uses multiple clustering algorithms, multiple validity metrics and progressively bigger subsets of the data to produce an intuitive 3D map of cluster stability that can help determine the optimal number of clusters in a data set, a technique we call COmbined Mapping of Multiple clUsteriNg ALgorithms (COMMUNAL). COMMUNAL locally optimizes algorithms and validity measures for the data being used. We show its application to simulated data with a known K and then apply this technique to several well-known cancer gene expression datasets, showing that COMMUNAL provides new insights into clustering behavior and stability in all tested cases. COMMUNAL is shown to be a useful tool for determining K in complex biological datasets and is freely available as a package for R.

This paper presents the design and development of a low-loss and wide-band width multilayered Marchand balun. The balun has been implemented using printed circuit board materials with integrated multilayered organic thin films. We have designed the top layer transmission lines on twin-thickness organic thin films to achieve low loss and wide bandwidth for the balun. The experimental results demonstrate that the balun achieves less than 0.5-0.7 dB insertion loss throughout the 4-20-GHz operation bandwidth. The phase and amplitude imbalances are less than 5/spl deg/ and 0.5 dB, respectively. Time-domain measurement results demonstrate that the balun has negligible dispersion.

A parallel-execution model that can concurrently exploit AND and OR parallelism in logic programs is presented. This model employs a combination of techniques in an approach to executing logic problems in parallel, making tradeoffs among number of processes, degree of parallelism, and combination bandwidth. For interpreting a nondeterministic logic program, this model (1) performs frame inheritance for newly created goals, (2) creates data-dependency graphs (DDGs) that represent relationships among the goals, and (3) constructs appropriate process structures based on the DDGs. (1) The use of frame inheritance serves to increase modularity. In contrast to most previous parallel models that have a large single process structure, frame inheritance facilitates the dynamic construction of multiple independent process structures, and thus permits further manipulation of each process structure. (2) The dynamic determination of data dependency serves to reduce computational complexity. In comparison to models that exploit brute-force parallelism and models that have fixed execution sequences, this model can reduce the number of unification and/or merging steps substantially. In comparison to models that exploit only AND parallelism, this model can selectively exploit demand-driven computation, according to the binding of the query and optional annotations. (3) The construction of appropriate process structures serves to reduce communication complexity. Unlike other methods that map DDGs directly onto process structures, this model can significantly reduce the number of data sent to a process and/or the number of communication channels connected to a process. >

We present the development of a microwave push-pull power amplifier (PA) module that achieves both high output power and wide bandwidth 2nd-order harmonic cancellation from 6 GHz to 18 GHz. Measured PldB output power for the push-pull PA is 31 dBm, while its 2nd-order harmonic distortion is reduced by a minimum 20 dB throughout the 6-18 GHz passband compared to a single PA. The 2nd-harmonic output of the push-pull PA was also measured to be lower than -40 dBc all the way up to 36 GHz. The PA module was integrated into a liquid crystal polymer (LCP) substrate that enables the design of wide bandwidth baluns with less than 0.5 dB and 6deg amplitude and phase imbalances, respectively.

We present the development of molded liquid crystal polymer (LCP) surface mount packages for millimeter wave applications. We show that a coplanar waveguide transmission line on a molded liquid crystal polymer has a measured insertion loss of less than 0.16 dB/mm. The LCP quad flat no-lead (QFN) has demonstrated a return loss of less than -16dB and insertion loss of less than -1.2 dB at 25 GHz.

In this paper, we present the design and development of two low loss, ultra-wide band, planar Marchand baluns (1). The baluns were implemented in a multi-layered liquid crystal polymer (LCP) flex, and in a LCP film laminated on an organic substrate. The best performing balun achieved a bandwidth exceeding 3.1-10.6 GHz with a less than 0.6 dB insertion loss. The amplitude and phase imbalance was measured to be less than 1.2 dB and 2°. The baluns are highly applicable to ultra-wide band communication systems specified by the IEEE 802.15.3a standard. To the best of our knowledge, this is the first reported multi-octave bandwidth balun capable of being implemented in organic substrates using standard printed circuit technologies.

We present the development of a multilayered Marchand balun that operates over a 4-20 GHz bandwidth. The balun achieves a measured insertion loss of less than 0.5 dB from 4 to 17 GHz, and less than 0.7 dB from 17 to 20 GHz. Measured amplitude and phase imbalances are less than 0.5 dB and 5°, respectively within 4-20 GHz. The balun design employs a novel twin dielectric thin-film thickness structure to achieve a low insertion loss and a wide bandwidth.

The cellular industry has been very successful in providing voice services to consumers and business. The next big opportunity for wireless networks will be differentiation based on data and multimedia services. Wireless service providers face ever-increasing pressure to offer innovative services, new capabilities, and make more efficient use of spectrum. In order to meet these needs, existing wireless networks have evolved with new technology both in the air interface and the core network. Specifically, the wireless mobile data communication technologies have evolved from the circuit switched second-generation (2G) networks to 2.5G and then to the third generation (3G) networks and beyond. The paper describes how the revolution of wireless communications, the wireless mobile data industry, evolution of wireless mobile data communication technologies, the wireless mobile data market and the failing barriers to wireless data proliferation.

The authors explore methodologies for effective realization of recursive procedures in logic programs. The effectiveness is achieved by reducing the number of context frames and interframe relations, through several related schemes. During programming or preprocessing, a subset of recursive procedures are transformed into ones that ensure the application of last call optimizations; the procedures can then be transformed into ones that allow multiple use, when desirable. During parallel interpretation, structured data are manipulated by a scheme that dynamically applies structure sharing or copying with little overhead. A communication scheme can then be used to realize transformed doubly recursive procedures. With these schemes the process structures of the transformed procedures coincide with the data structures of the procedures, and the transformed procedures achieve efficiencies up to an order of magnitude in time, space, and interprocess communication over the untransformed ones. >

Over the past decade, paging, cellular and personal communications have become the fastest growing segments of the telecommunications services. The demand for wireless technologies has been absolutely exploding. In the 1980s, many analog cellular networks were implemented. These networks are already reaching capacity limits in some service areas. Several digital technologies were introduced to increase spectral efficiency and enhance wireless communications by adding features and services such as facsimile and data transmission and new call handling features. In other words, wireless communication technology has evolved from first generation analog systems for business applications to second generation digital systems with rich features and services for residential and business applications. As the turn of the century approaches, a new vision of ubiquitous personal communication systems starts to emerge. For the new century, many new wireless communication services and capabilities using the wideband CDMA technology are being defined by the industry worldwide. Specifically, the specifications for the future global wireless access system, the International Mobile Telecommunications-2000 (IMT-2000) are currently being developed within the International Telecommunication Union (ITU). With the higher data transmission speed and the new services such as simultaneous voice and data, multimedia and location services, applications of the new wireless technologies to the biomedical field become practical in the near future. The paper describes several such potential applications.

Paging, cellular and personal communications have become the fast growing segments of the communications services in the past decade. The demand for wireless technology has been exploding. Several competing digital wireless access technologies including CT-2, DECT/CT-3, GSM, TDMA, and IS-95 CDMA have been used for providing the low tier and high-tier wireless services. This presentation focuses on the code division multiple access (CDMA) technology. Specifically it describes the following aspects of the CDMA technology: (a) background and fundamentals; (b) personal communication services and growth; (c) CDMA concepts and reception; (d) CDMA channel structures; (e) IS-95 radio link processes and signaling; (f) typical CDMA based system architecture and operations including call setup, call handoffs, call terminations and dynamic power control; and (g) roles of wideband CDMA technology in the third generation digital wireless communications and its applications in voice, data, and multimedia communications.

The author discusses the background and general issues of wireless communication access technologies. The author then discusses wireless multiple access techniques, existing and proposed air interfaces and their comparisons, wireless data and microcell technologies.

The first current injection lasing action in AlGaInP/Ga0.65In0.35P heterostructures grown on commercially available GaAs0.6P0.4 substrates is reported. At 77 K, laser diodes exhibited threshold current densities of 900 A/cm2 with yellow stimulated emission near 5735 A. This is the shortest current injection lasing wavelength ever achieved in a III-V compound semiconductor.

The effect of space charge reduction in an electrohydrodynamic (EHD) generator via fluidic switching was studied. An electrofluidic generator was shown to embody a significant advantage of space charge reduction via fluidic switching. At a certain range of frequency of fluidic switching, a substantial increase in output voltage beyond a steady flow EHD generator was obtained. A small model generator EFD-II and a scaled-up generator EFD-III were built to study the effect of space charge reduction. Experiments were performed on EFD-II and EFD-III generators at various operating conditions. For similar flow and particle charge, EFD-III gave at a switching frequency of 4 cycles per second an open circuit voltage of 220 kV compared with 180 kV at steady flow.

1. 1. No female specific proteins were found in the stable fly hemolymph by polyacrylamide gel electrophoresis. 2. 2. Six major yolk polypeptides (YP1, YP2, YP3, YP4, YP5 and YP6) have been identified in the stable fly. Their mol. wt as determined by SDS-polyacrylamide gel electrophoresis are 41,100, 42,600, 44,100, 46,600, 48,900 and 50,600, respectively. 3. 3. YP3 was purified and antibody made against it. By using the antibody and in vitro organ culture the stable fly yolk polypeptides were shown to be synthesized exclusively by the ovaries and not the fat body. 4. 4. The stable fly yolk polypeptides are immunologically similar to yolk proteins of other related flies.

Five putative chitin synthesis inhibitors (CSI) were tested to determine if they inhibited nucleoside incorporation into acid precipitable material in a cell line from Manduca sexta (L.). The results varied. Diflubenzuron (DFB) (100 micron) inhibited cytidine incorporation by 38%; EL-494 (100 micron) inhibited adenosine incorporation by 43%; Bay Sir 8514 (100 micron) inhibited uridine incorporation by 24%. Superdiflubenzuron (100 micron) was the worst inhibitor overall (18-22%) for the benzoylphenyl urea CSI. The triazine CSI, CGA 19255, was the best inhibitor tested with 60% inhibition for cytidine and 49% for adenosine incorporation into DNA and RNA. Examination of cells incubated with diflubenzuron by scanning electron microscopy revealed distinct external morphological changes. Transmission electron microscopy showed that crystalline structures accumulated in the cytoplasm of cells treated with DFB. The crystalline structures were assumed to be diflubenzuron and they persisted even after diflubenzuron was removed from the medium.

The effect of 80 min of low frequency (2 Hz) electric acupuncture stimulation at facial sites on the perception of induced dental pain was evaluated using both pain threshold and sensory decision theory (SDT) procedures. The demonstration of a 187% increase in threshold over a 20 min period of acupunctural stimulation replicated earlier work by Swedish investigators. SDT analyses indicated that the threshold increase reflected a relatively pure sensory change with no significant modification of response bias. However, subjects were able to perceive some of the stimuli presented below threshold level following acupuncture, thus indicating that the threshold concept has been an inadequate description of the phenomenon. This study demonstrated that intrasegmental analgesic stimulation is more efficacious than the extrasegmental meridian point stimulation used in our earlier studies. Possible mechanisms for the observed effect were discussed.