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At least 19 recordsLinked to original sources
PubMed1978

Comparative pressure measurements in the oesophagus by means of in situ tip-transducers and external transducer systems.

Basal gastro-oesophageal sphincter pressures and peak peristaltic pressure amplitudes in the oesophageal body 5 and 15 cm proximal to the gastro-oesophageal sphincter were measured with three different set ups in six healthy volunteers. The in situ tip-transducer measurements were compared to two different external pressure transducers in a perfused catheter system and to an external pressure transducer in a non-perfused catheter system. The in situ tip-transducer recorded higher sphincter pressures and peristaltic amplitudes than those recorded by the perfused and non-perfused systems (P less than 0.01). There was no difference between the pressures recorded by perfused systems in conjunction with the different external transducers. The perfused systems recorded sphincter pressures higher than those recorded by the non-perfused systems (P less than 0.02 and P less than 0.01), whereas the non-perfused system recorded higher peristaltic pressure amplitudes than those recorded by the perfused systems (P less 0.01 and P less than 0.01). The importance of the bend of the in situ tip-transducer was shown experimentally. It is concluded that the ideal system for recording oesophageal pressures is a perfused catheter set-up with minimal compliance. The probe with three side holes at the same level ensures registrations of the lowest occlusion pressure at the measuring point.

Adult↗
PubMedDate not supplied

Comparative study of a 15-MHz focused ultrasonic transducer and a 15-MHz unfocused ultrasonic transducer for clinical in-vivo skin-thickness measurements in human subjects.

A commercial focused 15-MHz immersion ultrasonic transducer and a commercial unfocused 15-MHz thickness-gaging ultrasonic transducer were evaluated for invivo skin-thickness measurements in humans. The unfocused transducer produced thicker skin measurements than did the focused transducer but both measurements were generally within previously reported ranges. The differences in the determined thicknesses may have been a result of the uneven nature of the dermissubcutaneous tissue interface and the ability of the focused transducer to better follow this interface.

Arm↗
PubMed1975

Appearance of transducing particles and the fate of host DNA after infection of Salmonella typhimurium with P22-mutants with increased transducing ability (HT-mutants).

The kinetics of production of transducing particles for different bacterial markers were followed by premature lysis of Salmonella typhimurium cells infected with P22 phages. The were compared for cells infected with wild type phage or with HT-mutants which show increased transduction frequencies. Measuring the sedimentation velocity of bacterial DNA of cells infected with wild type or HT-phages, it was shown that: a) there is no cutting of DNA at random; b) original fragments necessary for packaging host DNA into transducing particles cannot be smaller than 10 phage-genome lengths; c) cutting of transducing fragments leads immediately to the right length; d) there is no loss of precipitable DNA due to phage infection.

DNA, Bacterial↗
PubMed1975

The properties of bird feathers as converse piezoelectric transducers and as receptors of microwave radiation. I. Bird feathers as converse piezoelectric transducers.

An investigation was made of the properties of bird feathers as piezoelectric transducers in the audiofrequency range and as dielectric receptors of electromagnetic radiation in the microwave region. In the first case, cartridges of the ceramic and magnetic type and an electromagnetic transducer probe were used as detecting devices. Results show piezoelectric resonances in the 1 to 20-kHz region for the calami of feathers.

Animals↗
PubMed1976

Isolation and characterization of the specialized transducing bacteriophages phi80dargF and lambdah80cI857 dargF: specific cleavage of arginine transducing deoxyribonucleic acid by the endonucleases EcoRI and SmaR.

The directed transposition of argF to the tonB locus of the Escherichia coli chromosome and the subsequent isolation of the specialized transducing phage phi80dargF is described. The structure of this phage has been has been determined. A hybrid lambdah80cI857dargF phage has been constructed. Deoxyribonucleic acid isolated from these and their parent bacteriophages has been specifically cleaved by the endonucleases EcoRI and SmaR; the unique deoxyribonucleic acid fragments thus obtained have been resolved and analyzed by electrophoresis in agarose gel.

Arginine↗
PubMed1992

Genetic correction of cultured T cells from an adenosine deaminase-deficient patient: characteristics of non-transduced and transduced T cells.

T lymphocytes derived from peripheral blood of a patient with adenosine deaminase (ADA) deficiency were expanded in vitro. The human ADA (hADA) gene was introduced into these replicating ADA- T cells with the use of an amphotropic recombinant retrovirus carrying the hADA gene. Subsequently, infected T cells were selected on the basis of their ADA expression, by exposure to a combination of the toxic agent xylofuranosyl-adenine and the specific ADA inhibitor 2'-deoxycoformycin. CD4+ and CD8+ T cells could be infected and selected with equal efficiencies. The genetically modified T cells were shown to contain intact copies of the provirus and to express normal levels of hADA. As expected, uninfected T cells from the ADA-deficient patient displayed an increased sensitivity to 2'-deoxyadenosine. Following genetic modification, however, this sensitivity was restored to normal levels in both CD4+ and CD8+ T cells. The introduction of the hADA gene into the genome of the in vitro expanded T cells did not alter their phenotype, proliferative capacity or cytotoxic potential. These characteristics were identical to those of T cells derived from healthy individuals. These findings are of critical importance for the clinical application of hADA gene-transducted T cells.

Adenosine Deaminase↗
PubMed1991

Pulse-echo imaging using a nondiffracting beam transducer.

Conventional ultrasonic transducers generate beams that diffract as they travel. This phenomenon causes images produced in B-mode to be degraded in the far-field of the transducers. Focused transducers are used to improve image quality. Unfortunately, focused transducers have short depth of field. Although multiple pulse transmissions focused at several depths are used to increase the effective depth of field, imaging frame rate is reduced dramatically leading to blurred images of moving objects such as the heart. We present a family of transducers that produce nondiffracting beams of large depth of field. Therefore, uniformly high resolution throughout the imaging area can be obtained without sacrificing the imaging frame rate. In addition, the nondiffracting property of these beams makes the correction for beam diffraction negligible in tissue characterization. This paper reports the results of computer simulations as well as in vitro and in vivo pulse-echo imaging experiments with a nondiffracting transducer. Images are compared to those obtained by conventional focused Gaussian shaded beam transducers and a commercial ACUSON 128 B-scanner. The new transducer has much longer depth of field with higher sidelobes than conventional transducers of the same aperture. Sidelobes can be reduced using the new transducer to transmit and the dynamically focused transducer to receive.

Calibration↗
PubMed1978

Bacteriophage P22-mediated specialized transduction in Salmonella typhimurium: identification of different types of specialized transducing particles.

The temperate bacteriophage P22 mediates both generalized and specialized transduction in Salmonella typhimurium. Specialized transduction by phage P22 is different from, and less restricted than, the well characterized specialized transduction by phage lambda, due to differences in the phage DNA packaging mechanism. Phage lysates produced by induction of lysogenic strains contain very high frequencies of supQ newD- and proA,B-specialized transducing particles (10(-2)/PFU and 10(-3)/PFU, respectively), most of which are produced by independent aberrant excision events of various types. In a model, 12 different modes of transduction mechanisms were characterized by: (i) the structure of the specialized transducing genomes after injection into a new host cell, i.e., linear or circular, and (ii) the requirements for the transduction process, i.e., host recombination functions, phage integration functions, or presence of a prophage. By using different recipient strains and phage helper strains, it was possible to show that most specialized transducing particles (ca. 99%) contain linear genomes that cannot circularize upon injection into a new host cell and that require the presence of an integrated prophage as a site for a recombinational event to give rise to a transductant. Only 0.1% of all specialized transducing particles were shown to transduce by integration, suggesting that transducing genomes containing terminally redundant ends represent only a minor fraction of all transducing particles that are produced. However, it should be pointed out that the frequency (approximately 10(-5)/PFU) of these specialized transducing genomes that can circularize upon injection into a new host cell is as high as or even higher than the frequency of specialized transducing particles of phage lambda. The remaining approximately 1% of all specialized transducing particles can transduce by any one of the other mechanisms described.

Adsorption↗
PubMed1991

Recording and processing of fetal movements and sounds obtained with the Inpho inductive transducer.

A recently developed transducer based on an inductive principle allows recording of fetal displacement signals on the maternal abdominal wall. The transducer is a relatively passive device, in contrast to commonly applied ultrasound transducers. This permits long-term observation of fetal movements and sounds. The bandwidth of the system is DC-200 Hz (+/- 3 dB), and signal-to-noise ratios of more than 96 dB have been measured in a laboratory setup, whereas in the practical situation a signal-to-noise ratio of 78 dB has been established. The transducer has been applied to study fetal respiratory sinus arrhythmia, which means that fetal breathing movements have to be extracted from the transducer's output. This proved possible by digital filtering of the displacement signal as detected by the transducer. The transducer has also been applied in a study where the signal-to-noise ratio of fetal heart sounds as a function of location of the fetus and position of the transducer on the maternal abdominal wall has been studied. It proved possible to adequately record fetal heart sounds for measurement of fetal heart rate. Also uterine activity could be recorded using the sensor's DC output.

Female↗
PubMed1992

Electromagnetic midsagittal articulometer systems for transducing speech articulatory movements.

This paper describes two electromagnetic midsagittal articulometer (EMMA) systems that were developed for transducing articulatory movements during speech production. Alternating magnetic fields are generated by transmitter coils that are mounted in an assembly that fits on the head of a speaker. The fields induce alternating voltages in a number of small transducer coils that are attached to articulators in the midline plane, inside and outside the vocal tract. The transducers are connected by fine lead wires to receiver electronics whose output voltages are processed to yield measures of transducer locations as a function of time. Measurement error can arise with this method, because as the articulators move and change shape, the transducers can undergo a varying amount of rotational misalignment with respect to the transmitter axes; both systems are designed to correct for transducer misalignment. For this purpose, one system uses two transmitters and biaxial transducers; the other uses three transmitters and single-axis transducers. The systems have been compared with one another in terms of their performance, human subjects compatibility, and ease of use. Both systems can produce useful midsagittal-plane data on articular movement, and each one has a specific set of advantages and limitations. (Two commercially available systems are also described briefly for comparison purposes). If appropriate experimental controls are used, the three-transmitter system is preferable for practical reasons.

Biomechanical Phenomena↗
PubMed1990

Percutaneous vs. transcutaneous transducers for hearing by direct bone conduction.

There is a substantial need for improvement of the hearing situation for patients, with chronic middle ear or ear canal disorders. To improve hearing for these patients, two different bone conduction hearing systems have been developed. The Nobelpharma Auditory System HC 200-the bone-anchored hearing aid we present here-uses a percutaneous transducer; whereas the Audiant device, developed by Dr. Jack Hough, uses a transcutaneous transducer. In percutaneous transmission, the transducer is directly coupled to the bone by means of a permanent skin penetration, whereas in transcutaneous transmission one part of the transducer is implanted and the other part is kept outside the intact skin and soft tissue. Comprehensive audiologic assessments indicate great differences in performance between the two systems. These differences probably originate in differences in length of gap and in different suspension properties of the two transducer systems. This article will demonstrate that large gaps, such as in the transcutaneous transducer, can be devastating for power consumption, maximum output capability, and second harmonic distortion. Since the properties of the suspension in the transcutaneous transducer are not under adequate control and the complication risk of permanent skin penetration is low, we continue to concentrate our efforts on percutaneous transducer systems.

Bone Conduction↗
PubMed1991

Detection of renal stones with real-time sonography: effect of transducers and scanning parameters.

Three experiments with a variety of transducers and scanning parameters were designed to investigate if renal stones could be detected with greater certainty by using particular transducers or scanning parameters. First, the lateral resolution, derived from the -6-dB size of the beam profile, was measured at various depths for five transducers commonly used for renal sonography. Second, an in vitro test object was constructed from bovine liver, porcine kidneys, and two renal calculi to access gray-scale map effects on shadow visibility before and after storage in the digital scan converter. The third experiment combined 15 lithotripsy patients with known renal stones with 16 patients in whom the results of renal sonography and other radiographic procedures suggested renal calculi. The group of 15 patients was scanned several times with the transducers and gray-scale maps studied earlier, and the group of 16 patients was scanned only with one transducer and one gray-scale map. On radiographs, 12 of the 16 patients did not have renal calculi. Sonograms of the test object showed that low-contrast images were best for detection of posterior shadows. Three radiologists interpreted the 31 sonograms with a sensitivity of 81% and a specificity of 86% for detecting renal stones. For the 15 cases of renal stones scanned with a variety of transducers, the three radiologists found that annular-array transducers depicted stone shadowing with less ambiguity than mechanical sector transducers did 81% of the time.

Animals↗
PubMed1979

Effects of gas density on the frequency response of gas-filled pressure transducers.

The effects of gas density on the frequency responses of four pressure transducers were determined at gas densities from 1.2 to 25.0 g/l. Transducers tested included three sensitive differential types used with pneumotachographs to measure respiratory flow (Validyne DP-45 and DP-103; Medistor P-11) and a transducer commonly used to measure esophageal pressure (Statham P23Dd). Three different responses were obtained. The Validyne DP-103 was overdamped and its response was essentially independent of gas density. The frequency response of this transducer is adequate for use with quiet breathing only. The Validyne DP-45 and Medistor P-11 responses were underdamped. The resonant peaks of these transducers decreased markedly in frequency as the gas density increased. The Statham P23Dd was also underdamped; however, its resonant frequency increased as gas density increased. An esophageal balloon did not alter the frequency response characteristics of this tubing-transducer system. Both increases in length and decreases in diameter of connecting tubing reduced the frequency of resonant peaks of underdamped pressure transducers.

Atmospheric Pressure↗
PubMed1976

Effect of transducer placement on echocardiographic mitral valve systolic motion.

The influence of transducer position and angulation upon the mitral systolic echo was studied in 100 presumably healthy females. Echocardiographic studies were performed from the second, third, fourth and fifth intercostal spaces (ICS). The role of the sound beam's path relative to cardiac motion was assessed by analyzing the recorded mitral valve pattern as a function of transducer orientation, independent of the absolute ICS used. With the transducer directed caudally when both mitral leaflets and left atrium were recorded, holosystolic or midsystolic posterior motion of the mitral valve leaflet echo was seen in 59% of the subjects. These patterns, recorded this way, were not related to phonocardiographic signs suggesting mitral valve prolapse. Best correlation with phonocardiographic findings was obtained when the echocardiographic examination was performed with the transducer either perpendicular to the chest in the sagittal plane, or pointing slightly cephalad ('perpendicular' position). With the transducer in 'perpendicular' position, both holosystolic and midsystolic posterior motion of the mitral systolic echo, deviating more than 2 mm from a line joining the C and D points, were highly related statistically to phonocardiographic findings suggesting mitral valve prolapse. This study demonstrates that transducer position and angulation on the chest wall are important determinants of echocardiographic appearance of mitral valve during systole. Only the 'perpendicular' transducer position should be used when analyzing echocardiograms for the presence of mitral valve prolapse.

Echocardiography↗
PubMed1991

The actions of calcium on the mechano-electrical transducer current of turtle hair cells.

1. Mechano-electrical transducer currents evoked by deflections of the hair bundle were recorded in turtle isolated hair cells under whole-cell voltage clamp. The outcome of perfusing with solutions of reduced Ca2+ concentration was investigated. 2. The transducer current was roughly doubled by lowering the concentration of divalent cations from normal (2.2 mM-Mg2+, 2.8 mM-Ca2+) to 0 Mg2+, 0.5 mM-Ca2+. No significant effects on the current's kinetics or reversal potential, or on the current-displacement relationship, were noted. 3. If the Ca2+ concentration was lowered to 50 microM (with no Mg2+), there was about a threefold increase in the maximum current but other changes, including loss of adaptation and a decreased slope and negative shift in the current-displacement relationship, were also observed. As a result, more than half the peak transducer current became activated at the resting position of the hair bundle compared to about a tenth in the control solution. 4. The extra changes manifest during perfusion with 50 microM-Ca2+ had also been seen when the cell was held at positive potentials near the Ca2+ equilibrium potential. This supports the view that some consequences of reduced external Ca2+ stem from a decline in its intracellular concentration. 5. With 20 microM-Ca2+, a standing inward current developed and the cell became unresponsive to mechanical stimuli, which may be explained by the transducer channels being fully activated at the resting position of the bundle. 6. The results are interpreted in terms of a dual action of Ca2+: an external block of the transducer channel which reduces the maximum current, and an intracellular effect on the position and slope of the current-displacement relationship; the latter effect can be modelled by internal Ca2+ stabilizing one of the closed states of the channel. 7. During perfusion with 1 microM-Ca2+, the holding current transiently increased but then returned to near its control level. There was a concomitant irreversible loss of sensitivity to hair bundle displacements which we suggest is due to rupture of the mechanical linkages to the transducer channel. 8. Following treatment with 1 microM-Ca2+, single-channel currents with an amplitude of -9 pA at -85 mV were sometimes visible in the whole-cell recording. The probability of such channels being open could be modulated by small deflections of the hair bundle which indicates that they may be the mechano-electrical transducer channels or conductance about 100 pS. 9. Open- and closed-time distributions for the channel were fitted by single exponentials, the mean open time at rest being approximately 1 ms. The mean open time was increased and the mean closed time decreased for movements of the hair bundle towards the kinocilium.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

[Effects of depth on the display of color Doppler flow imaging with transesophageal and transthoracic transducers: an experimental study].

Transesophageal color Doppler flow imaging has proved to provide an accurate and sensitive information for diagnosis of valvular regurgitation. However, it is necessary to understand the difference in the display of color Doppler image between transesophageal and conventional transthoracic transducers for quantitative assessment of valvular regurgitation. In this study, the effects of the depth between transducer and jet flow on color Doppler flow imaging were evaluated with the transesophageal (3.75 MHz) and conventional (2.5 MHz) transducers by using a flow phantom. A flow circuit was filled with saline in which nylon corpuscles (average diameter; 5 microns) were suspended to enhance the Doppler effects. A turbulent jet with constant flow velocity (Reynolds number; 3500) stimulating valvular regurgitant flow was produced in a water bath through a small orifice (2 mm) by constant driving pressure (100 mmHg). Color jet imaging in the long- and short-axis views were observed at each depth with both transducers. The measurement was made every 1 cm in depth from 3 to 12 cm. The color gain setting was fixed at the optimal point so as to get the maximal flow image with the minimal static background noise. We obtained larger image of the color jet signal with the conventional than the transesophageal transducer. Although a mosaic pattern was displayed more distinctly with the transesophageal transducer compared with that of the conventional transducer, the transesophageal image tended to become indistinct in the depth deeper than 8 cm. On the other hand, the transthoracic image was maintained relatively constant at any depth.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗