Scanning Operation Research Articles

Are cortical models really bound by the "binding problem"?

Are cortical models really bound by the "binding problem"?

Homogeneous Cell- and Bead-Based Assays for High Throughput Screening Using Fluorometric Microvolume Assay Technology.

High throughput drug screening has become a critical component of the drug discovery process. The screening of libraries containing hundreds of thousands of compounds has resulted in a requirement for assays and instrumentation that are amenable to nonradioactive formats and that can be miniaturized. Homogeneous assays that minimize upstream automation of the individual assays are also preferable. Fluorometric microvolume assay technology (FMAT) is a fluorescence-based platform for the development of nonradioactive cell- and bead-based assays for HTS. This technology is plate format-independent, and while it was designed specifically for homogeneous ligand binding and immunological assays, it is amenable to any assay utilizing a fluorescent cell or bead. The instrument fits on a standard laboratory bench and consists of a laser scanner that generates a 1 mm(2) digitized image of a 100-µmm deep section of the bottom of a microwell plate. The instrument is directly compatible with a Zymark Twistertrade mark (Zymark Corp., Hopkinton, MA) for robotic loading of the scanner and unattended operation in HTS mode. Fluorescent cells or beads at the bottom of the well are detected as localized areas of concentrated fluorescence using data processing. Unbound flurophore comprising the background signal is ignored, allowing for the development of a wide variety of homogeneous assays. The use of FMAT for peptide ligand binding assays, immunofluorescence, apoptosis and cytotoxicity, and bead-based immunocapture assays is described here, along with a general overview of the instrument and software.

Efficient support for interactive operations in multi-resolution video servers

In this paper, we present a placement algorithm that interleaves multi-resolution video streams on a disk array and enables a video server to efficiently support playback of these streams at different resolution levels. We then combine this placement algorithm with a scalable compression technique to efficiently support interactive scan operations (i.e., fast-forward and rewind). We present an analytical model for evaluating the impact of the scan operations on the performance of disk-array-based servers. Our experiments demonstrate that: (1) employing our placement algorithm substantially reduces seek and rotational latency overhead during playback, and (2) exploiting the characteristics of video streams and human perceptual tolerances enables a server to support interactive scan operations without any additional overhead.

Computing the medial axis transform in parallel with eight scan operations

The main result of this paper shows that the block-based digital medial axis transform can be computed in parallel by a constant number of calls to scan (parallel prefix) operations. This gives time- and/or work-optimal parallel implementations for the distance-based and the block-based medial axis transform in a wide variety of parallel architectures. Since only eight scan operations plus a dozen local operations are performed, the algorithm is very easy to program and use. The originality of our approach is the use of the notion of a derived grid and the oversampling of the image in order to reduce the computation of the block-based medial axis transform in the original grid to the much easier task of computing the distance based medial axis transform of the oversampling of the image on the derived grid.

Image composition for two-piece DRD cans

Abstract For the purpose of duplicating an original designed art work for metal printing of two-piece drawn and redrawn (DRD) cans, this paper studies image acquisition methods that can transform half-tone pictorial images into a binary output for further usage. Due to the limited resolution that can be applied to images for metal printing, to create such images in a computer one has to use a binary system device, such as a scanner, with appropriate resolution to encode the original pictorial half-tone images. Thus, some of the finer detailed data points in original images may not be recognized or may be distorted in the acquisition process. To minimize such defects, and image composition technique is proposed here, which merges two reading images obtained from using two different percentage measurements of a fixed light source illumination in the scanning operation. However, this method may cause false contours to appear in the final result. To remedy this syndrome, a smoothing technique is introduced and evaluated for its ability to duplicate an original input image.

A smart radar absorber

This paper proposes a configuration for a smart radar absorber which is capable of both self-tuning and absorb while scan operation. The discussion is complemented by modelled and measured performance data.

Broadcasting test patterns to multiple circuits

Scan designs can alleviate test difficulties of sequential circuits by replacing the memory elements with scannable registers. However, scan operations usually result in long test application time. Most classical methods to solving this problem either perform test compaction to obtain fewer test vectors or use multiple scan chain design to reduce the scan time. For a large system, test vector compaction is a time-consuming process, while multiple scan chains either require extra pin overhead or need the sharing of normal I/O and scan I/O pins. In this paper, we present a novel test methodology that not only substantially reduces the total test pattern number for multiple circuits but also allows a single input data line to support multiple scan chains. Our main idea is to explore the "sharing" property of test patterns among all circuits under test (CUT's). By appropriately connecting the inputs of all CUT's during the automatic test-pattern generation process such that the generated test patterns can be broadcast to all scan chains when the actual testing operation is executed, the above-mentioned problems can be solved effectively. Our method also provides a low-cost and high-performance method to integrate the boundary scan and scan architectures. Experimental results show that 157 test patterns are enough to detect all detectable faults in the ten ISCAS'85 combinational circuits, while 280 are enough for the ten largest ISCAS'89 scan-based sequential circuits.

Simulation of PRAMs with scan primitives by unbounded fan-in circuits

We show that PRAMs that have multiprefix (scan) operations available as primitives may be simulated by unbounded fanin circuits with gates for related operations. The complexity bounds depend on the word-size of the PRAM but not on the multiprefix operations or the instruction set of the processors.

Numerical simulation of the acoustic field of a phased-array medical ultrasound scanner

In order to evaluate the possible side effects of diagnostic medical ultrasound, and in particular the effects of nonlinear propagation of sound, it is necessary to characterize the scanners used. To this end, the acoustic field emitted by a phased-array Hitachi EUB-26 ultrasound scanner operating in a strongly focused mode was measured a small distance from the scanner head, and the velocity field at the surface of the head deduced. A finite difference model was then used to propagate the pressure field beyond the focus, taking into account nonlinear effects, attenuation and diffraction, and the result compared with observations in water, giving reasonable agreement out to the scanplane focus. The extrapolated field was then examined in detail, revealing those regions in which most power is lost to the medium, some of which are off-axis, and so might not be detected by normal calibration procedures.

New method of determining the plane deformation of paper

A description is given of a new method and a new measuring instrument for determining the plane deformation of banknotes, securities, and other commercial documents. The deformation unit models the compression of a paper specimen, while a scanner and computer operating on a specially developed program provide for measurement of strains on the order 2.0–5.0 mm with an absolute error no greater than ±10 μm.

Insertion devices for BESSY II.

The high-brilliance synchrotron radiation source BESSY II will provide space for the installation of 14 insertion devices. At the time of writing (July 1997), eight insertion devices are funded. The first light for use by scientists will be available in January 1999. The undulators are designed for a scanning operation in parallel with the monochromator. This modus requires tight tolerances concerning the drive system. The first insertion device to be installed, a U-49 undulator, has been assembled and magnetically measured. The r.m.s. phase error is 2 degrees. An endpole configuration using coils with less than 64 amp-turns makes the angular kick smaller than +/-3 micro rad over a gap range 15-50 mm.

%Nanoscale Imaging of Molecular Adsorption of Metal Complexes on the Surface of a Hydrotalcite Crystal

Atomic force microscopy (AFM) and scanning tunnel microscopy (STM) observations have been performed on the surfaces of a hydrotalcite (HT) crystal ([Mg6Al2(OH)16](CO3)1/2·Cl·2H2O) and HT crystals ion-exchanged with [Fe(CN)6]3- and [Fe(CN)6]4- (denoted by HT−[Fe(CN)6]3- and HT−[Fe(CN)6]4-, respectively). The AFM image of a HT crystal surface in contact with an aqueous solution of 0.1 M Na2SO4 shows two-dimensional periodicity with the unit lattice of a = 0.31 ± 0.02 nm, b = 0.31 ± 0.02 nm, and α = 58 ± 3°. This corresponds to the lattice made by the external hydroxyl groups on a basal plane. No ion-exchanged anion was observed by the AFM method, indicating that an external anion is so weakly bound to a surface that it is removed under the scanning operation of an AFM tip. The STM image of the same crystal under air shows a two-dimensional lattice with a = 0.75 ± 0.04 nm, b = 1.10 ± 0.03 nm, and α = 70 ± 3°. One bright spot in the image exists at every 1.1 [Mg6Al2(OH)16]2+ unit, leading to the conclusion that the spot represents a chloride ion adsorbed on a surface. The STM image of the same crystal at less negative bias voltage exhibits a different two-dimensional lattice with a = 0.62 ± 0.03 nm, b = 0.62 ± 0.03 nm, and α = 65 ± 3°. This is ascribed to the lattice made by the aluminum atoms at the octahedral sites inside a layer. The STM images of HT−[Fe(CN)6]3- and HT−[Fe(CN)6]4- crystals in contact with an aqueous solution of 0.1 M Na2SO4 show the two-dimensional lattices of a = 1.43 ± 0.06 nm, b = 1.86 ± 0.06 nm, and α = 90 ± 4° and a = 2.20 ± 0.06 nm, b = 2.20 ± 0.06 nm, and α = 75 ± 3°, respectively. These are ascribed to the molecular layers of [Fe(CN)6]3- and [Fe(CN)6]4- on a surface, respectively. The causes for the ordered molecular adsorption are discussed.

Test-point insertion: scan paths through functional logic

Conventional scan design imposes considerable area and delay overheads. To establish a scan chain in the test mode, multiplexers at the inputs of flip-flops and scan wires are added to the actual design. We propose a low-overhead scan design methodology that employs a new test-point insertion technique. Unlike the conventional test-point insertion, where test points are used directly to increase the controllability and observability of the selected signals, the test points are used here to establish scan paths through the functional logic. The proposed technique reuses the functional logic for scan operations; as a result, the design-for-testability overhead on area or timing can be minimized. We show an algorithm that uses the new test-point insertion technique to reduce the area overhead for the full-scan design. We also discuss its application to the timing-driven partial-scan design.

Mobile computed tomography in the trauma/critical care environment: Preliminary clinical experience

This study reviews the initial clinical experience using a portable computed tomographic (CT) scanner in the trauma resuscitation unit (TRU), intensive care units (ICUs), and operating rooms (ORs) of a large trauma center. Data were collected on the first 200 patients scanned within the trauma center (including 92 in the TRU, 92 in the ICUs, and 16 in the ORs) over the first 5 months of operation. Evaluation forms were completed by interpreting radiologists, CT technicians operating the system, and nurses/clinicians involved with patients being scanned. Information sought included subjective image quality, ease of use, software and hardware limitations, accessibility to and monitoring of patients during scanning, mobility, and perceived advantages or limitations compared to fixed CT. Radiation scatter also was measured to determine the safety of the scanner for portable use.CT scans of 224 body regions performed in 200 patients included: cranium (163), cervical spine (21), abdomen/pelvis (14), chest (12), face (8), thoracic/lumbar spine (4), and temporal bone (2). Image quality was judged subjectively as excellent (107), good (99), poor (6), or artifact degraded (12). Patient transfer to the scanner was judged to be easy (63) or fair/difficult (4). Patient accessibility and monitoring during scanning was assessed as easy (61) or fair/difficult (6). Access in the smaller TRU bays was more difficult than in the ICU or OR. Cited advantages over fixed CT included decreased risk and cost of transport, quicker assessment of cranial injury on admission, and more rapid postcraniotomy assessment. Limitations cited were relatively slow scan speed, slightly poorer image quality, and technical limits on scanning multiple body regions. Radiation scatter was 25% of the ALARA (as low as reasonably achievable) target for the scanner operator. Initial clinical experience with mobile CT in the TRU, ICU, and OR of a major trauma center shows application for focused admission scanning, assessment of critically ill ICU patients, and immediate postoperative assessment after craniotomy. The system has been incorporated easily into the trauma center and has been accepted enthusiastically. Further technical improvements are anticipated to extend the range of applications in this clinical setting.

Characterization of dynamic 3-D PET imaging for functional brain mapping.

Methods for optimizing the acquisition, reconstruction and analysis of positron emission tomography (PET) images for functional brain mapping have been investigated. The scatter fraction and noise-equivalent count rate characteristics were measured for the ECAT 951/31R PET scanner operating in septa-extended two-dimensional (2-D) and septa-retracted three-dimensional (3-D) modes. The 3-D mode is shown to provide higher signal-to-noise images than the 2-D mode at specific activities less than 30 kBq/ml. To enable increased temporal resolution in dynamic 3-D PET activation studies, a parallel version of the 3-D reconstruction algorithm was developed. Implementation of the reprojection algorithm on an 88 processor 1860 supercomputer resulted in a more than tenfold increase in reconstruction speed compared to a single 1860 processor system. An investigation of the optimal duration for imaging brain activations was undertaken in 12 normal subjects using repeated H2(15)O slow infusions and a visually presented lexical decision task. The significance of change in regional cerebral blood flow (CBF) was determined using statistical parametric maps for images acquired during stimulation, immediately after stimulation, and commencing 1 min after cessation of the stimulus. Regions of CBF change were detected in all three images. Dynamic 3-D, or four-dimensional (4-D), PET activation scanning is shown to be practical and likely to further improve the sensitivity of PET for detection of subtle regional CBF changes in functional brain mapping research.

Method and apparatus for generating large compound ultrasound image

An image registration method and apparatus is provided in which consecutive ultrasonic image frames are correlated in order to derive transducer motion information. Since ultrasonic images from real-time scanning operations are highly correlated from one frame to another, the individual images can be divided into several smaller sub-image regions and a very fast and robust image motion detection algorithm utilized to measure the sub-image motion. This algorithm uses a fast adaptive coarse/fine minimum-sum-absolute-difference (MSAD) search strategy to compute an initial estimation of the local motion vectors. The initial estimation is combined with two measurement parameters by use of a fuzzy logic technique to derive a final estimation of the local motion vectors. The final local motion vectors are applied to a least-squares (L-S) process in order to estimate global image motion. Finally, a fast display technique generates compound images based on the derived global image motion.

Low-temperature tunnelling-electron luminescence microscopy using tip collection

A tunnelling-electron luminescence(TL) microscope using the tip collection method has been developed for real-space characterization of the electronic and optical properties of materials and structures with nanometre-level spatial resolution. Tip collection can provide spatial resolution, luminescence collection yield, and thermal isolation better than can be obtained whenlens collection is used. The new microscope has a novel conductive transparent tip that injects tunnelling electrons into a sample and simultaneously collects tunnelling-electron luminescence. The tip is a multimode fibre that tapers to a point and is coated with a gold-on-In2O3double-layer transparent-electrode for high optical performance and stable scanning operation. The tip also has a thick coaxial metal-plating on the shaft of the fibre so that it is as reliable and easy to use as a metal tip. Effective optical coupling between the tip and an optical transmission line to a monochromator can be automatically reproduced even if the tip is changed. Photon-counting TL-image taking is synchronized with tip scanning and is free from signal distortion and mixing among pixels. This TL microscope has been used to carry out TL spectroscopy and TL microscopy in nanometre-scale regions of the cross-section of GaAs/AlAs multiple quantum wells at low temperatures. The TL microscope can distinguish individual layers and pick up subsurface information in contrast to scanning tunnelling microscopy.

A multioctave coaxially oriented beam-resonator arrangement Fourier-transform microwave spectrometer

The design, performance, and operation of a broadband (3–26.5 GHz) high resolution microwave spectrometer is described. In comparison to previously developed molecular beam Fabry–Perot resonator spectrometers the design presented here implements some significant improvements: a coaxially oriented beam resonator arrangement (COBRA) formed by a confocal pair of mirrors incorporating an electromechanical valve and employing two pairs of microwave antennas, and a multioctave Fourier-transform microwave (FTMW) instrument providing the pulsed excitation source with microwave pulse phase-inversion scheme and the low-noise receiving system employing image-rejection downconversion with superheterodyne as well as quadrature detection. The entire apparatus, fully automated for scanning operation, covers a frequency range of more than three octaves. The novel design of the FTMW instrument does not require any changes of the spectrometer hardware in order to reach all regions of its spectral range. While operated in high resolution mode the COBRA-FTMW spectrometer is achieving a linewidth (half-width at half-height, HWHH) relative to the molecular emission frequency of better than 10−7 HWHH. The sensitivity and resolution of the spectrometer is demonstrated by several examples.

Carotid duplex criteria for a 60% or greater angiographic stenosis: Variation according to equipment

The purpose of this study was to evaluate the carotid duplex criteria for a > or = 60% angiographic internal carotid artery (ICA) stenosis and the degree of variation among duplex scanners. Carotid duplex criteria for a > or = 60% angiographic stenosis were evaluated in two ICAVL-accredited vascular laboratories with different brands of duplex scanners (Siemens-Quantum and Diasonics in Laboratory A, ATL and Diasonics in Laboratory B). Analysis was performed for 360 carotid bifurcations in 180 consecutive patients who had concurrent angiographic and duplex evaluation. Blinded angiogram evaluation was performed with precision electronic calipers on magnified views, with stenosis calculated by criteria of the Asymptomatic Carotid Atherosclerosis Study and the North American Symptomatic Carotid Endarterectomy Trial. Duplex data included internal carotid artery peak systolic velocity (ICA PSV), ICA end-diastolic velocity, and the ratio of ICA PSV to common carotid artery (CCA) PSV (ICA/CCA ratio). The most accurate determination of a > or = 60% ICA stenosis was obtained with ICA/CCA ratio and ICA PSV, but the optimal threshold differed for all four scanners. The optimal ICA/CCA ratio varied from 2.6 to 3.3, and the optimal ICA PSV varied from 190 to 240 cm/sec. All four scanners produced criteria that give a positive predictive value > 90% while maintaining accuracy at > or = 90%. Logarithmic transformation of duplex variables created a linear relationship between duplex values and angiographic stenosis, allowing statistical evaluation of scanner operating characteristics by linear regression analysis and analysis of covariance. This analysis revealed that the mathematic equation relating duplex values with angiographic percent stenosis was statistically different for one of the four scanners (p < 0.05). Scanner differences did not appear to be due to technologists, because the regression lines were nearly identical for the two Diasonics scanners despite use by different technologists. Ignoring the significant difference in operating characteristics for one of the four scanners would result in a mean error for predicting a 60% stenosis of 14% to 18% (equating a 46% or 78% stenosis with a 60% stenosis). We conclude that the correlation of duplex data with angiographic percent stenosis and the duplex criteria for a > or = 60% stenosis are machine-specific. Regression analysis can determine whether apparent differences are due to chance or significant differences in scanner characteristics. Future studies should include regression analysis according to equipment type.

Tailoring a high-transmission fiber probe for photon scanning tunneling microscope

Transmission efficiency of a fiber probe used in photon scanning tunneling microscope is evaluated as a function of aperture diameter. The apertured probe has been fabricated by chemical etching technique and metal coating. By comparing two types of probes with different cone angles, we determine the most influential factor in the transmission property of the metal-cladding tapered waveguide. A long tip with high efficiency is developed by a multistep etching method so as to be suitable during actual scanning operation. Photoluminescence imaging of lateral p-n junctions on the GaAs substrate is demonstrated in the illumination-collection hybrid mode operation of photon scanning tunneling microscope.