Single Line Source Research Articles

Shear-wave focusing with a laser-ultrasound phased-array

Pulsed laser arrays have been used to improve the beam parameters of laser generated ultrasound. The focusing and steering of shear-acoustic-wave beams generated by an array of thermoelastic sources has been investigated. A modeling of the impulse diffraction response of a single line source was derived from the point source model (Surface Center Of Expansion) of the thermoelastic source. The acoustic field launched by an array of point- or line-sources has been computed. Experimentally, the impulse response of a line source has been measured by using a heterodyne interferometer. It was shown with a 16-beam YAG laser, that shear-acoustic-wave beams can be focused and steered inside a duraluminum sample with a great efficiency.

Proliferation measurements with flow cytometry T pot in cancer of the uterine cervix: Correlation between two laboratories and preliminary clinical results

Purpose : To assess the prognostic value of the pretreament potential doubling time (T pot) in carcinoma of the uterine cervix, relative to other established clinical factors.' Methods and Materials : Fifty-two patients with cervical cancer were studied prospectively from March 1991 to October 1993. Pretrement evaluation included examination under anesthesia and tumor biopsy 6 h following the intravenous administration of bromodeoxyuridine (2000 mg). T pot was determined by deriving the labeling index (LI) and S-phase synthesis time (T s) using flow cytometry. Six patients were not evaluable and excluded. The remaining 46 patients (average age 55 years) were treated uniformly with radical radiation therapy. There were 39 squamous carcinomas and 7 adenocarcinomas. Fédération Internale de Gynécologie et d'Obstérique (FIGO) stages were: Ib and IIa, 12 patients; IIb, 18 patients; III and IV, 16 patients. The median external beam dose was 50 Gy (range. 25.5–40 Gy) delivered with a single line source to a point 2 cm lateral of the midline, with a mean dose rate of 0.71 Gy/h. The median overall treatment time was 45 days (range, 34–73 days). As of July 31, 1994, 12 patients had died of disease, and the average follow-up for alive patients was 1.4 years (range, 0.5–3.3 years). Results : There were 27 tumors with diploid deoxyribonucleic acid (DNA) content and 19 tumors were aneuploid. The median and mean T pot for the 46 patients were 5.5 and 6.6 days, respectively [range, 2.0–35.6 days; coefficient of variation (CV) 74%]. For 25 patients where T pot measurements were performed at two separate laboratories, there was a fair correlation ( r = 0.74), but systematic differences were detected suggesting that the lack of agreement was not simply due to intratumoral variation. To date, 30 patients remained disease free, while 8 patients had pelvic failure and 9 patients developed distant metastases as the first failure site (1 patient developed both at the same time). In univariate analysis, the only significant prognostic factor for disease-free survival was tumor size ( p = 0.004). A short T pot (or high LI) and long overall treatment time (OTT) were weakly associated with poorer disease-free survival, although not statistically significant (1/T pot, p = 0.14; LI, p = 0.23; OTT, p = 0.04). Age, FIGO stage, hemoglobin level, S-phase fraction, DNA ploidy, and T s were not associated with disease-free survival. Multiple regression analysis was not performed because of the relatively small number of patients and short follow-up. Conclusions : T pot values determined with current techniques by different laboratories cannot be used interchangeably for the purpose of therapy decisions. Vigorous quality assurance and standardization of the laboratory procedures and analysis methods are important to reduce interlaboratory variation. In this uniformly treated group of patients with cancer of the uterine cervix, traditional clinical prognostic factors remain the most important. Preliminary data suggest that the flow cytometry-determined T pot and labeling index predict for disease-free survival, although a larger number of patients with longer follow-up is required to assess the true prognostic significance of these assays and to determine if their effect is independent of other clinical factors.

Fast SPECT simulation including object shape dependent scatter

A fast simulator of SPECT projection data taking into account attenuation, distance dependent detector response, and scatter has been developed, based on an analytical point spread function model. The parameters of the scatter response are obtained from a single line source measurement with a triangular phantom. The simulator is able to include effects of object curvature on the scatter response to a high accuracy. The simulator has been evaluated for homogeneous media by measurements of (99m)Tc point sources placed at different locations in a water-filled cylinder at energy windows of 15% and 20%. The asymmetrical shapes of measured projections of point sources are In excellent agreement with simulations for both energy windows. Scatter-to-primary ratio (SPR) calculations of point sources at different positions in a cylindrical phantom differ not more than a few percent from measurements. The simulator uses just a few megabytes of memory for storing the tables representing the forward model; furthermore, simulation of 60 SPECT projections from a three-dimensional digital brain phantom with 6-mm cubic voxels takes only ten minutes on a standard workstation. Therefore, the simulator could serve as a projector in iterative true 3-D SPECT reconstruction.

Simulation of the effect of drought stress on the rate of photosynthesis in cotton

The purpose of this study was to use field experimental data to evaluate the quantitative effects of drought stress on the rate of photosynthesis of cotton plants. Measurements were made on plants growing at various distances from a single line source. Relationships between daily sums of photosynthetic rates and noon values of leaf water potential (LWP), and between LWP and a drought stress factor computed in the model have been evaluated. The derived equation for the effect of drought stress on the rate of photosynthesis was used in a modified model, and it significantly improved the simulation results. The modified model was tested with data from four treatments of a drip irrigation experiment, which represent extreme soil moisture conditions during two irrigation periods. The simulation results also agreed closely with the experimental data.

Laser generation of narrow-band surface waves

Tone-burst-like narrow-band surface waves are generated in the thermoelastic regime by illuminating the surface of a solid with an array of laser-generated line sources. The laser line array is formed by a system of lenses and an optical diffraction grating that provide for flexible and easy control of the line-array parameters. It is shown experimentally, consistent with theory, that the generation of narrow-band surface waves can be controlled by adjusting the line-array parameters such as the number of line sources in the array, the width of each line source, and the separation distance between them. Certain optimum generation conditions are experimentally determined whereby the amplitude of the narrow-band surface waves can be increased by a factor of N (the effective number of lines in the array) over the corresponding broadband signals that would be generated using only a single line source. A laser-interferometric system is used to detect the generated surface waves. By suitably bandpass filtering the detected signal, the greater part of the white noise in the system can be eliminated, leading to a significant improvement in the signal-to-noise ratio and hence the sensitivity of the whole laser ultrasonic system.

Laser generation of narrow-band and directed ultrasound

An aluminium hemicylindrical sample has been irradiated with an array of laser lines, with each line acting as a source of acoustic waves. Detection of the generated ultrasonic waves was performed using both a wide-band stabilized Michelson interferometer and a 20 MHz piezoelectric transducer. Experimental and theoretical results are presented which reveal that the use of a spatially modulated laser source produces significant narrow-banding of the detected ultrasound, compared with a single point or single line source case. Additionally, for a given line spacing, ultrasound of a particular frequency can be directed. Owing to the nature of the acoustic signals generated by each individual array element, superposition of several signals does not result in any energy directivity similar to that encountered in phase electromagnetic array antennas. While time or frequency feature enhancement may be obtained in a desired direction, in most cases the far field energy directivity pattern is simply the incoherent sum of the energy directivity of each array element.

On the Monte Carlo simulation program “RESIS” for electron exposure of resists

Some of the results of the simulation program “RESIS” for modeling the electron exposure of resist PMMA are presented. As an example, the electron energy dissipation distribution at different depths in 0.8 μm resist on silicon substrate is given for a 20 keV single electron line source. The resist profiles in near-micron line patterns before and after proximity exposure compensation are simulated using the energy threshold criterion and the time dependent development process. The proposed proximity exposure compensation scheme based on dose correction technique leads to the ideal compensation of proximity exposure in electron beam lithography. Finally the comparison of resist edge slope and line width variation before and after proximity exposure compensation is made.

Numerical simulation of transport from an infinite line source: Error analysis

State-of-the-art numerical techniques for solving partial differential equations utilize adaptive grid techniques. In these methods, the mesh is refined based on a posteriori error estimates. However, these techniques have not been used for air pollution simulations since software is available only for certain limiting forms of equations. The aim of this study is to identify parameters that affect the accuracy of numerical solutions of the transport equations involving point sources. Based on these, a grid can be chosen a priori and used for the entire simulation. A two-dimensional finite element model using bilinear elements is presented for the advection-diffusion problem with an infinite line source. This paper is restricted to two spatial directions, with advection dominating in the x-direction and turbulent diffusion dominating in the z-direction. Numerical results for an inert plume emanating from a single infinite line source show that the ratio of the advection time scale to the turbulent diffusion time scale, K zΔx uΔz 2 , should be equal to or greater than one for the most accurate solutions. In addition, comparisons between the volume-averaged representation of a point source and the use of an irregular grid for point source representation demonstrate that, near the source, improved results can be obtained by placing a node at the source location.

Line Source Irrigation to Assess Maize Inbred Line Stability1

Stability of inbred lines over a range of environments is variable. The objective of this research was to evaluate field response of inbred lines grown under line source irrigation as a predictor of yield stability of inbred lines over environments. Stability regression analyses were computed on yield data of five widely used inbred lines from a single line source experiment and from an interregional study grown at seven locations. Stability response slopes of inbred line performance under a line source irrigation system and in interregional testing were in perfect agreement when compared by rank order correlation. Line source irrigation experiments could serve as a time and moneysaving alternative to testing at numerous locations in a program of selecting for inbred line performance stability.

Tuber yield and tuber quality of several potato cultivars as affected by seasonal high temperatures and by water deficit in a semi-arid environment

The effects of high temperatures and water deficit on potatoes were investigated under field conditions. Nine cultivars and one un-named seedling were grown in the spring and in the summer under high temperatures. In both seasons the cultivars were grown under 3 water regimes: adequate water supply, moderate water deficit, and severe water deficit that were achieved by a modification of the single line source sprinkler irrigation system. Severe drought reduced tuber yields in both seasons. Moderate tolerance to a moderate water deficit in the spring season was exhibited by Draga, Desiree, and Monalisa. Late and intermediate cultivars produced high tuber yields in the spring season, and early cultivars had relatively smaller yield losses in the summer. The extent of tuber disorders, sprouting, rotting and malformation, varied considerably. High temperatures enhanced sprouting, rotting and malformation and drought may enhance sprouting and malformation.

57Co doped oxides as57Fe Mössbauer single line sources

The preparation of several57Fe Mossbauer single line sources is reported. It is also discussed the mechanisms involved in the appearance of anomalous charge states for the57Fe daughter. The57CoO:Li, MgO:57Co and Ti57CoO3 appear to be very good candidates to be used as strong sources.

Mössbauer effect study of the 105.3 keV transition in 155Gd

Mossbauer effect studies on the 105.3 keV transition of 155Gd using the single line source and absorber combination of SmPd3 and GdCo2 have shown that the previously reported narrowing in the linewidth is due to the formation of antipeaks on the spectrum. These antipeaks occur on the 105.3 keV spectrum at positions which correspond to maximum resonant absorption of the 86.5 keV radiation in 155Gd. They are observed at a very low amplifier output count rate of 6 kHz which corresponds to a multichannel analyzer recording rate of 200 counts per channel per minute for the 105.3 keV spectrum. The antipeaks were not present on the 105.3 keV spectrum after attenuating the 86.5 keV radiation with a thallium acetate filter. The resultant linewidth of the 105.3 keV transition, after correcting for finite source and absorber thickness, was found to be Γ0=1.129 mms−1 in comparison with the theoretical value of 1.112 mms−1 calculated from the lifetime of the 105.3 keV energy level.

The interference of thermal fields from line sources in grid turbulence

The interference of passive thermal fields produced by two (and more) line sources in decaying grid turbulence is studied by using the inference method described by Warhaft (1981) to determine the cross-correlation coefficient ρ between the temperature fluctuations produced by the sources. The evolution of ρ as a function of downstream distance, for 0.075 <d/l< 10, wheredis the wire spacing andlis the integral lengthscale of the turbulence, is determined for a pair of sources located at various distances from the grid. It is found that ρ may be positive or negative (thereby enhancing or diminishing the total temperature variance) depending on the line-source spacing, their location from the grid and the position of measurement. It is also shown that the effects of a mandoline (Warhaft & Lumley 1978) may be idealized as the interference of thermal fields produced by a number of line sources. Thus new light is shed on the rate of decay of scalar-variance dissipation. The thermal field of a single line source is also examined in detail, and these results are compared with other recent measurements.

Theory for cross coupling in ultrasonic transducer arrays

Ultrasonic transducer arrays suffer from the effects of acoustic cross coupling. The beam pattern and temporal response are degraded. The mechanism for acoustic cross coupling has been postulated to be surface wave propagation along the array. Our theory has shown that surface waves are indeed responsible, and that they may propagate in either the backing or load medium. The new theory is based on an extension to periodic systems of the theory for excitation of a uniform semi-infinite substrate by a single line source. It provides a quantitative model for cross coupling, as well as physical insight into its mechanism.

R-separable solutions of Einstein's field equations

R-separable coordinate systems are introduced as a new class of systems in which the equations of general relativity may be solved. The static, axially symmetric vacuum and electrovac Einstein field equations are solved for two such systems, tangent spheres and bispherical. The bispherical is found to be more versatile than any previously used coordinate system in that its eigensolutions can represent the exteriors of single point, double point and line sources. The tangent sphere eigensolutions are found to be generalisations of the Curzon solution. The relatively simple nature of the individual bispherical eigensolutions allows explicit integration of the field equations for a completely general, static, two-body source. The bodies are then charged, according to the Weyl formalism, and the conditions for balance obtained. Finally, it is shown that all vacuum Weyl solutions are either type I or type D.

Earthquake mechanisms and tsunami generation: The Kurile Islands event of 13 October 1963

abstract Investigations of tsunamigenesis on a spherically symmetric and elastic Earth using normal mode summations and moment tensor line sources are extended to include general double-couple mechanisms so that computed tsunami waveforms can be compared with specific observations. Amplitudes of 19 tide gauge records of the Kurile Islands sea wave of 13 October 1963 are reproduced within a factor of 2 by either a single line source 250 km in length or by a triplet of parallel line sources separated by 42 km. Both models predict a strong beaming of tsunami strength with wave heights toward the northwest and southeast three to eight times larger than those in the northeast and southwest. For faults over 150 km in length, 2 of the 6 moment tensor components dominate tsunami production. This fact motivated the coining of a new parameter, tsunami moment Mt. By cataloging tsunami fields produced by suites of fault mechanisms, I find that Mt is approximately proportional to the tsunamigenic potential of earthquakes. Despite the critical role of fault mechanism in tsunami generation, many sources have nearly equal tsunami moment and nearly equal ability for sea wave excitation. Estimates of shallow source strength from measurements of elastic surface waves have questionable integrity at both long (>100 sec) and short (>30 sec) periods. Amplitudes of high-frequency waves suffer from saturation due to source size and duration, while low-frequency amplitudes are unstable with respect to small perturbations in fault mechanism because of the influence of the Earth's surface. Many tsunami earthquakes may be artifacts of underestimated source strength resulting from the inefficiency of shallow, nearly vertical dip-slip faults to produce long-period surface waves.

Recognition and Location of Pinchout Boundaries by Pressure Transient Analysis

JPT Forum articles are limited to 1,500 words (including 250 per table or figure) or a maximum of two pages. Forum articles may present preliminary results or conclusions from continuing investigations preliminary results or conclusions from continuing investigations or may impart general technical information that does not require publication as a full-length paper. Forum articles are subject to publication as a full-length paper. Forum articles are subject to approval by an editorial committee. Letters to the editor are published as Dialog and may cover technical or nontechnical topics. SPE reserves the right to edit letters for style and content. In the analysis of well pressure transient tests, only two types of boundaries are recognized currently-i.e., impermeable and constant pressure. Furthermore, from a sectional viewpoint, boundaries of either type frequently are considered vertical. However (to the best of our knowledge) there is no consideration of a reservoir boundary that results from a tapering of the reservoir to an eventual pinch out boundary. In such a case, the boundary is clearly impermeable, and yet would not behave in the same manner as a perpendicular sealing boundary. Since many oil and gas reservoirs are supposed to contain pinch out boundaries, there appears to be a need to determine the effect of such boundaries on the reservoir pressure performance and, if possible, to determine their pressure performance and, if possible, to determine their properties and position. Both proved possible in this properties and position. Both proved possible in this investigation. In the case of a well fully penetrating the formation, the pinch out configuration is illustrated in Fig. 1, where the upper and lower confining beds meet at an angle, theta, at the pinch out. The reservoir is semi-infinite in the direction away from the pinch out (i.e., other boundaries of the system are too distant to influence the solution), and the reservoir is infinite in the dimension out of the plane of Fig. 1. plane of Fig. 1. Solution to the problem hinges on accomplishing representation of the unusual wedge-shaped boundaries. Superposition may be performed in the usual manner, so that "image" wells form a polygon of line source segments. The superposition is complex in all cases except where theta is an integral division of 180 deg. -i.e., except when n is an even integer, where(1) Ref. 1 gives details of the derivation of the solution. Briefly stated, the total dimensionless pressure drop, P (with usual definition), caused by superposition of the pressure drops due to all the single line source segments pressure drops due to all the single line source segments is given as a function of dimensionless time, t (with usual definition), by (2) This equation holds for either isotropic or non isotropic cases. The only difference lies in the definition of the non dimensional variables (Ref. 1). Here, r and z are the dimensionless radius and distance, respectively, from the lower end of the i th image (nondimensionalized using the wellbore radius, r ). These radii and distances may be calculated recursively from (3) and(4) by using simple geometry, where h = h/r and h is the formation thickness. The integrals in Eq. 2 were calculated with a small computer program using Simpson's rule with 16 time divisions per log cycle. The short-time behavior follows the line-source solution. P. 517

Mössbauer study of Co and Fe spinels acting as sources and absorbents

Mössbauer spectra and X-ray powder diagrams of synthetic 57Co and 57Fe oxides having the two lattice-site spinel structure have been obtained. The distribution of iron and cobalt atoms between the octahedral and tetrahedral lattice sites has been determined by means of isomer shift and quadrupole splitting measurements. A new mechanism is proposed in order to explain the distribution of 57Fe as well as its charge state when it enters the lattice as an impurity. At high temperature a mixed valence structure of Co 3O 4 was found. It is argued that the charge state of the daughter iron depends on the vacancy concentration in the environment of those sites where the corresponding decay takes place. Single line sources are obtained under well determined conditions.

Sound source in the presence of wall shear layers

Numerical solution techniques for evaluating the acoustic field generated by a single line source located inside or outside a wall shear layer of an infinitely long lined rectangular duct are presented. A formula for calculating wave attenuation due to an acoustic lining is given.

Californium-252 line sources: experimental verification of depth dose data using NTA films and dosage tables based on Paterson and Parker rules

Californium-252 promises to be an effective radium substitute in brachy-therapy. In certain situations, such as cancer of the uterus, the dose rate near a linear source may be of interest. Paterson and Parker (see Meredith, 'Radium Dosage-the Manchester System', p.23, 1967), have tabulated the number of milligram hours for various active lengths of radium sources to give 1000 rad at different distances from the centre of the source. Similar results for Cf-252 (microgram hours to give 1000 rad neutron dose) and the results of experimental measurements of neutron depth dose distributions for both single line sources and arrays are reported. Kodak NTA films and a phantom were used. The experimental results are found to agree well with the theoretically predicted results.