Equivalent Resolution Research Articles

Color Dissociation Artifacts in Double Maddox Rod Cyclodeviation Testing

The double Maddox rod test, based on a red Maddox rod in front of one eye and a clear Maddox rod in front of the other, is used to measure cyclodeviation, typically in patients with superior oblique muscle pareses. Discrepant results between the double Maddox rod test and other torsion measures, and reports of "paradoxic" cyclodeviation in the normal eye of some patients with superior oblique paresis, suggest the two-color format of the double Maddox rod test may produce artifactual torsion measures. Forty patients with superior oblique paresis were tested twice using the double Maddox rod test, reversing the red and white Maddox rods between eyes for the second test, and 18 were tested further with same-color red or clear Maddox rods in front of both eyes. With the standard double Maddox rod test, 33 (83%) of 40 patients localized their cyclodeviation to the eye viewing through the red Maddox rod, irrespective of laterality of the paresis or fixation preference. In all 33 patients, laterality of the perceived torsion changed between eyes when testing was repeated with red and white Maddox rods interchanged between eyes. With same-color Maddox rods before both eyes, 17 (94%) of 18 patients localized extorsion to the paretic eye. There was 7.6:1 ratio of luminance transmission and a 1.6:1 ratio of grating spatial frequency bandpass in the plano meridian between the clear and red Maddox rods, which appear to be responsible for the double Maddox rod test artifact. The traditional double Maddox rod test may produce artifactual cyclodeviation measurements. An alternative version of the test, based on same-color Maddox rods in front of both eyes, is proposed. The relatively high spatial frequency bandpass characteristics of the plano meridian of the Maddox rod (as high as 20/25 Snellen equivalent resolution through the clear Maddox rod) also suggests double Maddox rod testing should be conducted in a dark room to avoid biases from visual environment cues.

4.3 terahertz four-wave mixing spectroscopy of InGaAsP semiconductor amplfiers

A four-wave mixing experiment in a bulk InGaAsP traveling-wave semiconductor amplifier is reported. The maximum pump-probe detuning is 4.3 THz. The equivalent time resolution of 37 fs is high enough to measure with good accuracy the time constant of spectral-hole burning (100 fs in our case). The simultaneous presence of spectral-hole burning and of an instantaneous, within our time resolution, saturation process is clearly displayed.

Reduced phase encoding in spectroscopic imaging

The effect of different spatial-encoding (k-space) sampling distributions are evaluated for magnetic resonance spectroscopic imaging (MRSI) using Fourier reconstruction. Previously, most MRSI studies have used square or cubic k-space functions, symmetrically distributed. These studies examine the conventional k-space distribution with spherical distribution, and 1/2 k-space acquisition, using computer simulation studies of the MRSI acquisition for three spatial dimensions and experimental results. Results compare the spatial response function, Gibbs ringing effects, and signal contamination for different spatial-encoding distribution functions. Results indicate that spherical encoding, in comparison with cubic encoding, results in a modest improvement of the response function with approximately equivalent spatial resolution for the same acquisition time. For spin-echo acquired data, reduced acquisition times can readily be obtained using 1/2 k-space methods, with a concomitant reduction in signal to noise ratio.

From adapted and computerized thermomechanical equipments to modelling and the time-evolution behaviour in Cu−Zn−Al shape memory alloys

Using two similar high resolution computer controlled stress-strain-temperature set-up of equivalent resolution (1 mN, 0.1 μm, 5 mK) the detailed study of the martensitic transformation in single crystals of the Cu−Zn−Al shape memory alloys is realized. The devices can obtain 20 or 150 N in applied force, 2 or 4 mm in length and can be operated near room temperature (between 280 and 360 K). The analysis of the hysteresis domain in single crystals clearly visualises the intrinsic characteristics of the material (pseudoelasticity, nucleation, interface friction) and enables the obtenton of parameters for physical models of the hysteretic behaviour in force—lengthening—temperature and, eventually, time-dependent processes. The observation of time evolution shows the ‘recoverable martensite creep’ associated to a microstabilization process.

The Cardiofocal collimator: a variable-focus collimator for cardiac SPECT

Investigators in nuclear medicine have long been in search of a practical method to increase the number of detected events in cardiac SPECT. A clinically practical method requires a simple data acquisition protocol, clinically acceptable reconstruction times, artifact levels near or below visual threshold, and the use of currently available cameras and computers. Towards this end, the authors have developed the Cardiofocal collimator, a variable-focus collimator for cardiac SPECT that increases the number of detected events from the heart by more than a factor of two compared to that of a parallel-hole collimator with equivalent resolution. In both the transverse and axial dimensions, the focusing is strongest at the centre of the collimator, and gradually relaxes to nearly parallel-hole collimation at the edge of the collimator. The variable-focus concept provides an increase in the number of counts from organs imaged near the centre of the collimator, where the heart will spend most of the time during a cardiac SPECT study, while adequately sampling enough of the background activity distribution to prevent truncation artifacts in the reconstructed images. Images are reconstructed in clinically acceptable times using a filtered backprojection reconstruction algorithm. The algorithm supports both full-scan (360 degrees ) and short-scan (180 degrees plus the fan angle) acquisitions. The results of simulations and phantom studies are included to demonstrate the performance of the Cardiofocal collimator.

Multifrequency Variability of AGN's: Continuum Variations from the Near IR to the X-rays

Because they emit copiously over more than 10 decades in frequency, Active Galactic Nuclei (AGN) cannot be understood without the help of multiwavelength observations. On the other hand, variability monitoring has also proven to be invaluable in understanding the continuum and line emission process as well as the geometry of the innermost regions in these objects. Indeed, at the heart of AGN's lies an object which is so compact that the only way to probe its structure is the study of the temporal evolution of its spectrum. The equivalent resolution which can be achieved in this way is of the order of 10 microarcsecs, far beyond the capability of any UV or optical telescope.

On the performance of adaptive mesh refinement computation

A finite difference scheme for the unsteady Euler equations using an adaptive mesh refinement (AMR) algorithm was applied to the time-dependent flowfield of shock diffraction problems. The effectiveness of the AMR algorithm was evaluated against a uniform mesh algorithm. Computational results showed that to obtain solutions with equivalent resolution, the AMR algorithm requires much less processing time, when compared with a uniform mesh algorithm.

Sequence Analysis of Cysteine and Cystine Containing Peptides and Proteins by a Gas-Phase Sequencer with Isocratic Separation of PTH-Amino Acids

Abstract A facile method for routine sequence analysis of cysteine and cystine containing peptides or proteins is described. An automated gas-phase protein sequencer, Shimadzu PSQ-1 System, consisting of an Edman-reaction unit and an isocratic separation mode for the phenylthiohydantoin amino acid analysis with equivalent sensitivity and resolution to that of the current gradient mode, allows easy determination of the intact second half cystine, of which phenylthiohydantoin derivatives appear as a dithiothreitol adduct of dehydroalanine, cysteine and S- pyridylethylated cysteine. The optimal sequencing protocol for in situ pyridylethylation was established. This protocol gives an N-terminal amino acid sequence with half cystines, which are automatically converted to the S-pyridylcthyl derivative in the sequencer. Sequence analyses both intact and S-pyridyiethylated cysteine can identify a disulfide form if only one disulfide linkage exists in the sample. Sequence analysis of synthetic peptides containing ...

Digital input filters for measurement, control and protection of electric power systems

Power system control and protection equipment has required higher sensitivity and operational reliability than conventional one. Studies of digital signal processing suitable for electric power systems fulfill this objective using fast sampling and digital filtering by a 32-bit floating point DSP (Digital Signal Processor). The sampling rate of 3 kHz is carefully selected in order to separate the power spectrums of the A-D conversion output errors from the signal bandwidth. The new 12-bit A-D conversion unit equipped with a recursive-type digital filter achieved the equivalent high resolution of 14-bit conversion. This paper describes the design concept and the characteristics showing applications to current differential relays, distance relays and power system controllers.

特集 画像処理―アルゴリズムとシステム ２台のカメラを用いる超高精細画像取得法の提案とその理論的解析

The method of image aquisition is one of the principal problems for handling super high definition pictures. This paper proposes a new method for acquiring high resolution pictures by processing two images taken with two different cameras. The method integrates two images into a higher resolution image. Compared to an imaging device with equivalent resolution, it will be less sensitive to the shot noise which becomes more dominant at the pixel size is reduced. Our theoretical analysis clearly shows the improvement in the high frequencies and details. The aperture effect determines the upper bound in the performance using this method. When the aperture ratio is 100%, the resolution improvement is limited to twice the original sampling frequency. Additionally, using more than two cameras, SNR of the reconstructed image improves even in the case of 100% aperture ratio. This means that the pixel size can be further reduced when extra cameras are used.

Accuracy of using point targets for SAR calibration

The peak and integral methods for radiometric calibration of a synthetic aperture radar (SAR) using reference point targets are analyzed. Both calibration methods are shown to be unbiased, but the peak method requires knowledge of the equivalent rectangle system resolution which is sensitive to system focus. Exact expressions for the RMS errors of both methods are derived. It is shown that the RMS error resulting from the peak method is always smaller than or equal to that from the integral method for a well-focused system. However, for robust radiometric calibration of SAR, or when nonlinear phase errors are present, the integral method is recommended, because it does not require detailed knowledge of the impulse response and the resulting RMS error is not dependent on system focus.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Force to frequency conversion by intracavity photoelastic modulation

Force to frequency conversion (FFC) using the photoelastic effect inside a laser cavity is described. Analytic expressions are derived for scale factor, measurement errors, and laser dependent nonlinearity of appropriate instrument transducers. The influence of the laser pushing and pulling effects on linearity is calculated on the basis of the third-order saturation model. Our experiments with a modular test setup (633 nm) demonstrate FFC to be proportional to a high degree over almost 6 decades of input signal range. From 2 x 10(-4) up to 80 N we observed the noise equivalent resolution of 10(-4) N. The frequency response of our test setup was established from dc up to some kilohertz. FFC measurement range and resolution can be extended to 10(-6) N or smaller values by applying improved laser stabilization and miniaturizing the cavity length and size of photoelastic material.

Precise force measurement over 6 decades applying the resonator-internal photoelastic effect

Mechanical forces can be measured over a range of 6 decades by applying the photoelastic effect inside the laser cavity. Our experiments with a modular test setup (633nm) demonstrate proportional force-to-frequency conversion from 1·10−4N up to 80N with the noise equivalent resolution of 3·10−5N. The frequency response of our test setup was established from dc up to some kilohertz. Measurement range and resolution can be extended to 10−6N or smaller values by applying improved laser stabilization and miniaturizing cavity length and size of photoelastic material. The upper limit of the scale factor is calculated to be of the order of 25MHz/N.

The spherical drift chamber used at LURE for protein crystallography; last developments, performances, and results (invited) (abstract)

We have developed at LURE a multiwire proportional chamber with a spherical drift space. The wire chamber consists of two cathode planes, comprising 512 wires with a spacing of 1 mm, set on both sides of the anodic plane. The drift space, a gas filled region bounded by two spherically curved electrodes 144 mm apart, offers several advantages: high quantum efficiency, no parallax effect, equivalent spatial resolution in both directions, and smoothing of the pulsed structure of the synchrotron radiation. The gaseous mixture of argon-xenon (58%), ethane (40%), and ethyl alcohol (2%) is circulated in a closed circuit and is continuously purified. Ethyl alcohol, which avoids electrical discharges and sparks, is essential to operate the instrument at high counting rates (&amp;gt;300 000 events/s). The signal processing, which makes use of one amplifier per cathode wire and of fast priority encoders, determines both coordinates with a resolution of 1 mm and a dead time of 240 ns. Each encoded event is stored into a 512×512 16 bit CAMAC histogramming memory. The experiment is controlled by a PDP11/34 linked to a VAX by a direct memory access channel. A complete set of programs, which performs the data collection and an off line data reduction, is operational. The adaptation of madnes, a general software package which performs an on line data reduction, is under way. Data, collected on a lysozyme crystal to 3.4-Å resolution, give a reliability factor based on intensities of equivalent reflections of 4.7% without absorption corrections; the variation of the detector efficiency is &amp;lt;2.7%. A new version of the instrument is under realization. The position encoder, which uses flash ADCs and signal processors, has a resolution of 0.5 mm. Data are stored into a 1024×1024 16 bit VME histogramming memory linked to a micro VAX.

Chebyshev pseudospectral method of viscous flows with corner singularities

Chebyshev pseudospectral solutions of the biharmonic equation governing two-dimensional Stokes flow within a driven cavity converge poorly in the presence of corner singularities. Subtracting the strongest corner singularity greatly improves the rate of convergence. Compared to the usual stream function/ vorticity formulation, the single fourth-order equation for stream function used here has half the number of coefficients for equivalent spatial resolution and uses a simpler treatment of the boundary conditions. We extend these techniques to small and moderate Reynolds numbers.

On the resolution of a double determinant

AbstractThe resolution of a double determinant into a sum of spin‐free orthogonal spin eigenfunctions is presented; its equivalent resolution of a spin function product θM0 is also given. Furthermore, a more general resolution of a Slater determinant into all spin eigenfunctions with S ≥ M is also obtained. Present work has also provided a method to calculate the linear coefficients in the expression of the primitive θMi in terms of the linear combination of spin eigenfunctions X̃ (S, M).

Optimized conditions for pulsed field gel electrophoretic separations of DNA

Quantitative measurement of DNA migration in gel electrophoresis requires precisely controlled homogeneous electric fields. A new electrophoresis system has allowed us to explore several parameters governing DNA migration during homogeneous field pulsed field gel (PFG) electrophoresis. Migration was measured at different switch times, temperatures, agarose concentrations, and voltage gradients. Conditions which increase DNA velocities permit separation over a wider size range, but reduce resolution. We have also varied the angle between the alternating electric fields. Reorientation angles between 105 degrees and 165 degrees give equivalent resolution, despite significant differences in DNA velocity. Separation of DNA fragments from 50 to greater than 7000 kilobases (Kb) can easily be optimized for speed and resolution based on conditions we describe.

Study of the high‐frequency spectrum of the anomalous gravity potential

The analysis of the high‐frequency spectrum of the anomalous gravity potential is important for a number of current and emerging technologies in geodesy and geophysics. Among them is the precise determination of deflections of the vertical by inertial techniques, the development of data processing methods in airborne gradiometry, and the signal extraction methods for airborne gravimetry. The spectral information required can be obtained by analyzing dense gravity data by fast Fourier transform techniques. An attempt has been made to use available data files in Canada for this purpose. The data consisted of a rather uniform set of (5 arc min × 5 arc min) point anomalies in most of the continental areas of Canada and four sets of point gravity anomalies with an average data spacing of about 1 km in areas of limited extent. The analysis showed that the gravity spectrum has to be resolved to about degree and order 7000, i.e., to a point spacing of about 3 km, to resolve the gravity anomalies to 1 mGal. Thus a similar data spacing would be required in airborne gradiometry and gravimetry in order to get an equivalent resolution. The derived spectrum was used to determine suitable degree variance models and covariance functions for the above applications. The spectrum estimated from the 5 arc min × 5 arc min gravity anomalies covering the nonmountainous areas of Canada indicates that the degree variances of the anomalous potential decay as ℓ−3.6. This means that a number of currently used covariance models do not agree with the results of this analysis. A discussion on the choice of a more adequate model concludes the paper.

Binary-coded decimal to binary digital input modification of a popular digital delay module

A simple modification is described for converting the digital program code format of an Evans Associates model 4145 programmable time delay module from binary-coded decimal to binary. The modification results in a delay module which is more easily interfaced to a computer, has a greater programmable delay range with equivalent temporal resolution, and requires less power. Similar modifications are expected to have the same results on the models 4145-1 and 4146 modules.

Countercurrent Chromatography Using a Toroidal Coil Planet-Centrifuge: A Comparative Study of the Separation of Organelles Using Aqueous Two-Phase Partition

Abstract A toroidal coil planet centrifuge is described and compared with other countercurrent chromatography (CCC) and countercurrent distribution (CCD) techniques. The basis of separation is partition in aqueous two-phase polymer systems, with each method assessed by fractionating rat liver organelles. The size and ease of operation of the toroidal coil planet centrifuge gave significant advantages over conventional CCD systems achieving equivalent resolution in a fraction of the time.