Separate Arrays Research Articles

Synthesis of nonuniformly spaced linear array of parallel and collinear dipole with minimum standing wave ratio using evolutionary optimization techniques

In this paper, the author proposes a method based on two recent evolutionary algorithms (EAS): particle swarm optimization (PSO) and differential evolution (DE) to design nonuniformly placed linear arrays of half-wavelength long dipoles. The objective of the work is to generate pencil beam in horizontal (for parallel array) and vertical (for collinear array) plane with minimum standing wave ratio (SWR) and fixed side lobe level (SLL). Dynamic range ratio (DRR) of current amplitude distribution is kept at a fixed value. Two different examples have been presented having different array alignments. For both the configurations parallel and collinear, the excitation distribution and geometry of individual array elements are perturbed to accomplish the designing goal. Coupling effect between the elements is analyzed using induced electromotive force (EMF) method and minimized in terms of SWR. Numerical results obtained from both the algorithms are statistically compared to present a comprehensive overview. Beside this, the article also efficiently computes the trade-off curves between SLL, beam width, and number of array elements for nonuniformly spaced parallel array. It featured the average element spacing versus SWR curve for nonuniformly separated arrays. Furthermore, minimum achievable SLL performances of uniformly and nonuniformly spaced parallel arrays are compared for same average spacing in the proposed work.

Characterization of Dense Arrays of Chemiresistor Vapor Sensors with Submicrometer Features and Patterned Nanoparticle Interface Layers

The performance of arrays of small, densely integrated chemiresistor (CR) vapor sensors with electron-beam patterned interface layers of thiolate-monolayer-protected gold nanoparticles (MPNs) is explored. Each CR in the array consists of a 100-μm(2) interdigital electrode separated from adjacent devices by 4 μm. Initial studies involved four separate arrays, each containing four CRs coated with one of four different MPNs, which were calibrated with five vapors before and after MPN-film patterning. MPNs derived from n-octanethiol (C8), 4-(phenylethynyl)-benzenethiol (DPA), 6-phenoxyhexane-1-thiol (OPH), and methyl-6-mercaptohexanoate (HME) were tested. Parallel calibrations of MPN-coated thickness-shear-mode resonators (TSMR) were used to derive partition coefficients of unpatterned films and to assess transducer-dependent factors affecting responses. A 600-μm(2) 4-CR array with four different patterned MPN interface layers, in which the MPN derived from 7-hydroxy-7,7-bis(trifluoro-methyl)heptane-1-thiol (HFA) was substituted for HME, was then characterized. This is the smallest multi-MPN array yet reported. Reductions in the diversity of the collective response patterns are observed with the patterned films, but projected vapor discrimination rates remain high. The use of such arrays as ultralow-dead-volume detectors in microscale gas chromatographic analyzers is discussed.

Generating nonlinear concentration gradients in microfluidic devices for cell studies.

We describe a microfluidic device for generating nonlinear (exponential and sigmoidal) concentration gradients, coupled with a microwell array for cell storage and analysis. The device has two inputs for coflowing multiple aqueous solutions, a main coflow channel and an asymmetrical grid of fluidic channels that allows the two solutions to combine at intersection points without fully mixing. Due to this asymmetry and diffusion of the two species in the coflow channel, varying amounts of the two solutions enter each fluidic path. This induces exponential and sigmoidal concentration gradients at low and high flow rates, respectively, making the microfluidic device versatile. A key feature of this design is that it is space-saving, as it does not require multiplexing or a separate array of mixing channels. Furthermore, the gradient structure can be utilized in concert with cell experiments, to expose cells captured in microwells to various concentrations of soluble factors. We demonstrate the utility of this design to assess the viability of fibroblast cells in response to a range of hydrogen peroxide (H(2)O(2)) concentrations.

Fast Transforms for Acoustic Imaging—Part II: Applications

In Part I ["Fast Transforms for Acoustic Imaging-Part I: Theory," IEEE Transactions on Image Processing], we introduced the Kronecker array transform (KAT), a fast transform for imaging with separable arrays. Given a source distribution, the KAT produces the spectral matrix which would be measured by a separable sensor array. In Part II, we establish connections between the KAT, beamforming and 2-D convolutions, and show how these results can be used to accelerate classical and state of the art array imaging algorithms. We also propose using the KAT to accelerate general purpose regularized least-squares solvers. Using this approach, we avoid ill-conditioned deconvolution steps and obtain more accurate reconstructions than previously possible, while maintaining low computational costs. We also show how the KAT performs when imaging near-field source distributions, and illustrate the trade-off between accuracy and computational complexity. Finally, we show that separable designs can deliver accuracy competitive with multi-arm logarithmic spiral geometries, while having the computational advantages of the KAT.

Fast Transforms for Acoustic Imaging— Part I: Theory

The classical approach for acoustic imaging consists of beamforming, and produces the source distribution of interest convolved with the array point spread function. This convolution smears the image of interest, significantly reducing its effective resolution. Deconvolution methods have been proposed to enhance acoustic images and have produced significant improvements. Other proposals involve covariance fitting techniques, which avoid deconvolution altogether. However, in their traditional presentation, these enhanced reconstruction methods have very high computational costs, mostly because they have no means of efficiently transforming back and forth between a hypothetical image and the measured data. In this paper, we propose the Kronecker Array Transform (KAT), a fast separable transform for array imaging applications. Under the assumption of a separable array, it enables the acceleration of imaging techniques by several orders of magnitude with respect to the fastest previously available methods, and enables the use of state-of-the-art regularized least-squares solvers. Using the KAT, one can reconstruct images with higher resolutions than was previously possible and use more accurate reconstruction techniques, opening new and exciting possibilities for acoustic imaging.

Crust recycling in the sources of two parallel volcanic chains in Shandong, North China

Recycled crustal components have been documented for many sources of hotspot-related ocean island basalts, but they have been difficult to identify in continental basalts, because in continental settings, hotspots are often obscured and recycled crustal sources are difficult to distinguish from crustal contamination. We show major, trace element and Sr–Nd–Hf isotopic compositions for two parallel chains of Cenozoic volcanoes from Shandong Province, North China, which are free of crustal contamination and show clear evidence for recycling of mafic lower crust. Sr, Nd, and Hf isotopes in the two volcanic chains form separate binary mixing arrays, which converge on the composition of Dashan, an isolated, nephelinitic volcano with the most depleted isotopic signature. The two chains have lower CaO values and significantly diverging isotope enrichment trends from this common endmember. Both trends deviate from the normal Sr–Nd and Hf–Nd mantle array toward lower 87Sr/ 86Sr and higher ε Hf values, all features that point to a (recycled) eclogitic source. We invoke a two-stage evolution model to generate the endmembers of these two mixing trends. In the first stage, recycled mafic crust (eclogite) is depleted by earlier (late Mesozoic) melt extraction, which elevates the Lu/Hf of the residue relative to Sm/Nd due to garnet control during melting. Subsequently, these silica-deficient residues are transported to the deeper mantle. Finally, in Cenozoic time, upwelling mantle (possibly a plume) transports lenses of residual eclogites into the shallow asthenosphere. The recycled crustal components beneath the two chains differ somewhat in isotopic composition due to different degree of the earlier melting. The upwelling mantle spreads beneath the lithosphere and flows toward regions of thinned lithosphere, e.g. the Tan–Lu Fault Zone in North China, where the recycled crust undergo remelting and mix with peridotite-derived melts to produce the two mixing trends observed.

Ultra-performance liquid chromatographic assay coupled with two-dimensional separation for spectrometric determination of urinary S-phenylmercapturic acid

A gradient ultra-performance liquid chromatographic (UPLC) assay coupled with the two dimensional separation and diode array detection method was developed to determine S-phenylmercapturic acid (SPMA), a specific urinary metabolite of benzene. Gradient separation was performed on two C18 core–shell columns (2.6 and 1.7 μm, 50 × 2.1 mm i.d.) maintained at 40 and 20 °C. Among various solvents evaluated, dichloromethane which offered >85% recovery rates of both SPMA and D-benzylmercapturic acid (internal standard) was used for extraction. The yield of free-SPMA was maximized by hydrolyzing 200 μL of urine with 20 μL of 6 M HCl prior to dichloromethane extraction. The limit of detection was 1 μg L−1(s/n = 5) and the limit of quantification was 2 μg L−1. Using our method, a correlation of 0.99 was obtained with 10 specimens (range, 1.7 to 182 μg L−1) from the German External Quality Assessment Scheme. Among the 75 non-occupational exposure individuals, 61 (81%) had SPMA levels below the LOQ. Among the 26 male petroleum workers, 5 who were exposed to <0.04 ppm of benzene were found to have SPMA levels below the LOQ. The geometric means obtained from the other 15 non-smokers and 6 smokers who were exposed to <0.5 ppm of benzene were 5.05 and 6.65 μg g−1creatinine, respectively. The proposed method can be useful for occupational benzene exposure surveillance.

Patterning of Quantum Dot Bioconjugates via Particle Lithography

We present a simple technique to fabricate hexagonally ordered quantum dot bioconjugate (QDBC) dot arrays on glass coverslips. We used particle lithography to create periodic holes in a layer of methoxy-poly(ethylene glycol)-silane and then adsorbed QDBCs into the holes. To demonstrate the versatility of this technique, we made separate periodic arrays of quantum dots (QDs) conjugated to three different biologically important molecules: biotin, streptavidin, and anti-mouse IgG. The diameters of the regions where the QDBCs adsorbed were 500-600 nm and independent of the QDBC patterned. The site density of the QDBCs in the patterned holes could be varied by simply adjusting the coating concentration of the QDBC solution. We demonstrate the applicability of these substrates by designing a QDBC-based binding assay with a working concentration range of several orders of magnitude and a sub-picomolar detection limit.

Micromolded Arrays for Separation of Adherent Cells

Micromolded Arrays for Separation of Adherent Cells

TH‐D‐201C‐06: Preliminary Performance of a DTI Capillary Phantom in a Quality Assurance Experiment

Purpose: The purpose of this study was to determine the measurement stability of fractional anisotropy (FA) and the apparent diffusion coefficient (ADC) using a phantom in conjunction with a diffusion tensor imaging (DTI) sequence. Given an appropriate phantom with anisotropic structures procedures could be developed for DTI for monitoring daily quality assurance. Methods and Materials: A doped water‐filled phantom was constructed containing four separate arrays of glass capillaries of varying diameter. A cork phantom holder was constructed for proper and reproducible placement of the phantom within the GE Excite HDx 3.0T MRI scanner. MRI images of the phantom were acquired in fourteen separate scan sessions. To evaluate intra‐session reproducibility of mechanical phantom alignment and slice prescription reproducibility software was used to coregister images from each session and determine displacement. Temperature and signal‐to‐noise measurements of the phantom were made for each scan session. Data acquired from the scan sessions were used to calculate FA and ADC which were evaluated for dependency with respect to phantom temperature and SNR. Results: Mean absolute displacements in alignment were 3.45mm along the S‐I axis 0.74mm along the A‐P axis and 1.70mm along the R‐L axis. Slice prescription was determined to vary by approximately 14.3% of DTI slice volume from session to session. FA and ADC were not significantly dependent on SNR (p&gt;0.45) but were significantly dependent on temperature (p&lt;0.003). After temperature corrections FA and ADC were stable temporally to within &lt;6% and &lt;2% respectively. Conclusion: Using our anisotropic diffusion phantom we determined that daily FA and ADC variations correlate significantly with temperature but not on SNR. After correcting these biases residual FA and ADC are stable to within a few percent.

Compositional Characteristics and Spatial Distribution of Enriched Icelandic Mantle Components

We present compositional data on a suite of 18 primitive neovolcanic alkali basalts from three flank-zone regions in Iceland (Vestmannaeyjar in the south, Snaefell in the east, and Snaefellsnes in the west) that are peripheral to the main rift zones that are dominated by tholeiitic basalts. This study integrates He isotope data with radiogenic isotope data (Sr–Nd–Pb–Hf), stable isotope data (δ18O), and trace element data to characterize the compositional features of the trace element enriched components of the Icelandic mantle. We also present high-precision Pb isotope data on an additional 57 lava samples from the flank zones (including Oraefajokull in the SE) and the Northern and Eastern rift zones. Most Icelandic lavas have negative Δ207Pb (–4 to –1), with higher values (–1 to +4) found only in samples from Oraefajokull, Snaefell, and parts of the Reykjanes Peninsula. At Snaefell, this EM1-type component is characterized by a low δ18Oolivine signature (+4·1‰ to +4·6‰), moderate 206Pb/204Pb values (18·4–18·6) and mid-ocean ridge basalt (MORB)-like 3He/4He (6·9–7·5 R/RA). Samples from Vestmannaeyjar and Snaefellsnes have mantle-like δ18Oolivine (+4·9‰ to +5·0‰), and radiogenic 206Pb/204Pb values (18·9–19·3) that fall on the Northern Hemisphere Reference Line for 208Pb/204Pb (Δ208Pb –5 to +5). Compared with the Vestmannaeyjar lavas, Snaefellsnes lavas have higher La/YbN (5–11 vs 3–5), lower eNd (5·5–6·5 vs 6·8–7·6) and lower 3He/4He (6·3–8·6 R/RA vs 11·4–13·5 R/RA). Therefore, the most trace element enriched components in the Icelandic mantle are not the carriers of the high 3He/4He values (>15 R/RA) found in some lavas on Iceland and the adjacent ridges, and instead are consistent with degassed, recycled components. Even after excluding the EM1-type high Δ207Pb samples, high-precision Pb isotope data produce a kinked array on a 206Pb/204Pb vs 208Pb/204Pb plot, which is not consistent with simple binary mixing between two end-members. This requires significant lateral heterogeneity within the Icelandic mantle and the presence of more than just two compositionally distinct local mixing end-member components. Samples from each of the main axial rift zones define different trends. Despite the tectonic continuity between the Northern Volcanic Zone and the Eastern Volcanic Zone, lavas from these two rift zones define separate sub-parallel linear arrays. Lavas from the adjacent Western Volcanic Zone and the Eastern Volcanic Zone define oblique linear arrays that converge on a common local end-member that is not involved in the magmatism of the Northern Volcanic Zone. Therefore, there is a distinct NE–SW compositional heterogeneity within the Icelandic mantle.

Assessment of Protein Expression Levels After Transient Global Cerebral Ischemia Using an Antibody Microarray Analysis

An antibody microarray was used to analyze potential modifications in brain protein levels induced by ischemic reperfusion. Total brain extracts from rats subjected to 15 min of transient global ischemia followed by 3 days of reperfusion and sham control animals were compared within the same array. Separate arrays were run to analyze resistant (cortex) and vulnerable (CA1) regions to ischemia. Candidate components distinguishing the two cellular populations were selected under stringent criteria. IR significantly decreased the expression of Bcl-x, caspase 11, GADD153, Cdk4, E2F1, Retinoblastoma-P, SMAD4, AP-1/c-jun, ATF2, PCAF, MAP1b and cofilin within both regions. NGF and NMDA 2A receptors and IkappaB were specifically down-regulated in CA1, while Pyk2-P, b-NOS, and tyrosine hydroxylase were slightly up-regulated in the same region. Some of the array results were validated by western blot. Both the array and western blot results suggested a relevant IR induced activation of calpain specifically at CA1.

Rapid characterisation of large earthquakes by multiple seismic broadband arrays

Abstract. An automatic procedure is presented to retrieve rupture parameters for large earthquakes along the Sunda arc subduction zone. The method is based on standard array analysis and broadband seismograms registered within 30°–100° epicentral distance. No assumptions on source mechanism are required. By means of semblance the coherency of P waveforms is analysed at separate large-aperture arrays. Waveforms are migrated to a 10°×10° wide source region to study the spatio-temporal evolution of earthquakes at each array. The multiplication of the semblance source maps resulting at each array increases resolution. Start, duration, extent, direction, and propagation velocity are obtained and published within 25 min after the onset of the event. First preliminary results can be obtained even within 16 min. Their rapid determination may improve the mitigation of the earthquake and tsunami hazard. Real-time application will provide rupture parameters to the GITEWS project (German Indonesian Tsunami Early Warning System). The method is applied to the two M8.0 Sumatra earthquakes on 12 September 2007, to the M7.4 Java earthquake on 2 September 2009, and to major subduction earthquakes that have occurred along Sumatra and Java since 2000. Obtained rupture parameters are most robust for the largest earthquakes with magnitudes M≥8. The results indicate that almost the entire seismogenic part of the subduction zone off the coast of Sumatra has been ruptured. Only the great Sumatra event in 2004 and the M7.7 Java event on 17 July 2006 could reach to or close to the surface at the trench. Otherwise, the rupturing was apparently confined to depths below 25 km. Major seismic gaps seem to remain off the coast of Padang and the southern tip of Sumatra.

An improved woodward method for separate arrays synthesis

Based on the property of sample function, the Woodward synthesis method for separate arrays is improved. The improved method is justified theoretically, and the sample function of the flat-topping and 30 degree cosecant-squared space segment pattern on radar phased array antenna is synthesized using it. Through simulation and analysis, it can be used fewer elements to make the same synthesis effect on the pattern with the traditional Woodward method. And if the same number of elements is used, the synthesized pattern using the improved method will have better approach to the sample function, narrower beam width, and higher gain.

Socio-Cultural Dimensions of Cluster vs. Single Home Photovoltaic Solar Energy Systems in Rural Nepal

This paper analyzes the socio-cultural dimensions of obstacles facing solar photovoltaic projects in two villages in rural Nepal. The study was conducted in Humla District, Nepal, one of the most remote and impoverished regions of the country. There are no roads in the district, homes lack running water and villagers’ health suffers from high levels of indoor air pollution from open cooking/heating fires and the smoky torches traditionally burned for light. The introduction of solar energy is important to these villagers, as it removes one major source of indoor air pollution from homes and provides brighter light than the traditional torches. Solar energy is preferable in many villages in the region due to the lack of suitable streams or rivers for micro-hydroelectric projects. In the villages under study in this paper, in-home solar electricity is a novel and recent innovation, and was installed within the last three years in two different geo-spatial styles, depending upon the configuration of homes in the village. In some villages, houses are grouped together, while in others households are widely dispersed. In the former, solar photovoltaic systems were installed in a “cluster” fashion with multiple homes utilizing power from a central battery store under the control of the householder storing the battery bank. In villages with widely spaced households, a single home system was used so that each home had a separate solar photovoltaic array, wiring system and battery bank. It became clear that the cluster system was the sensible choice due to the geographic layout of certain villages, but this put people into management groups that did not always work well due to caste or other differences. This paper describes the two systems and their management and usage costs and benefits from the perspective of the villagers themselves.

Localization of sperm whales in a group using clicks received at two separated short baseline arrays

In this paper, a sperm whale click analysis scheme is proposed in order to calculate the position of individual sperm whales in a group using data received at two arrays deployed near the surface. The proposed method mainly consists of two parts: short baseline (SBL) with classification and long baseline (LBL) with class matching. In SBL with classification, a click is automatically detected, and its direction of arrival is calculated. The clicks are then classified based on their direction vectors. The class data are then sent together with direction data and matched to the other array's class data. LBL with class matching is used for localization. The classification algorithm can be used to estimate the number of whales clicking and to list potential candidates for LBL matching. As a result, the proposed method is able to localize the positions of the whales in a group. The performance of the proposed method is evaluated using data recorded off Ogasawara islands with two arrays near the surface. The three-dimensional underwater trajectories of six sperm whales are extracted to demonstrate the capability of the proposed method.

Design of a Dual-Frequency Retrodirective Array

A dual-frequency retrodirective array is proposed. By using two separated antenna arrays and double balanced passive mixers, the proposed system can achieve dual-frequency retrodirectivity in a bidirectional way. The low-frequency interrogating signal can be retransmitted at the high frequency, and it can also work in a reverse order. The proposed array has the advantages of low cost and high isolation between interrogating and retransmitting signals. The bidirectional characteristic can make it very useful in the two-way communication system. A four-element prototype is designed and fabricated. Measured results show good retrodirective performance.

Comment on “Benefits of the induced polarization geoelectric method to hydrocarbon exploration” ()

We have read Veeken et al. (2009) with interest and congratulate the authors for much careful hard work. However, we would like to bring to the authors’ attention several technical issues and point out several relevant earlier publications that they have overlooked, including five in GEOPHYSICS . The authors indicate that they used parallel streamers — separate transmitter and receiver arrays — in their sea trials. In our experience, separate parallel streamers do not move in rigid angular or spacing distance from each other, and these relative variations contribute a complex low-frequency electrical noise that lies broadly in the induced-polarization (IP) response range for pyrite described in Zonge and Wynn (1975), Pelton et al. (1978), and Veeken et al. (2009, p. B50). It is not clear to us that the authors removed or corrected for this substantial broadband noise contribution.

Micromolded arrays for separation of adherent cells

Micromolded arrays for separation of adherent cells

Micromolded arrays for separation of adherent cells.

We present an efficient, yet inexpensive, approach for isolating viable single cells or colonies from a mixed population. This cell microarray platform possesses innovations in both the array manufacture and the manner of target cell release. Arrays of microwells with bases composed of detachable concave elements, termed microrafts, were fabricated by a dip-coating process using a polydimethylsiloxane mold as the template and the array substrate. This manufacturing approach enabled the use of materials other than photoresists to create the array elements. Thus microrafts possessing low autofluorescence could be fabricated for fluorescence-based identification of cells. Cells plated on the microarray settled and attached at the center of the wells due to the microrafts' concavity. Individual microrafts were readily dislodged by the action of a needle inserted through the compliant polymer substrate. The hard polymer material (polystyrene or epoxy resin) of which the microrafts were composed protected the cells from damage by the needle. For cell analysis and isolation, cells of interest were identified using a standard inverted microscope and microrafts carrying target cells were dislodged with the needle. The released cells/microrafts could be efficiently collected, cultured and clonally expanded. During the separation and collection procedures, the cells remained adherent and provided a measure of protection during manipulation, thus providing an extremely high single-cell cloning rate (>95%). Generation of a transfected cell line based on expression of a fluorescent protein demonstrated an important application for performing on-chip cell separations.