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Transducer
Kinds of Transducer Selected Abstracts"Hands-Free" Continuous Transthoracic Monitoring of Pericardiocentesis Using a Novel Ultrasound TransducerECHOCARDIOGRAPHY, Issue 6 2003F.R.C.P., P.A.N. Chandraratna Background: Pericardiocentesis can be monitored with a hand-held transducer. The purpose of this study was to assess the feasibility of monitoring pericardiocentesis using a novel ultrasound transducer, which can be attached to the chest wall, developed in our laboratory (CONTISON). Methods: We studied nine patients with large pericardial effusions. The 2.5-MHz transducer is spherical in its distal part and mounted in an external housing to permit steering in 360 degrees. The external housing is attached to the chest wall using an adhesive patch. The CONTISON transducer was placed at the cardiac apex and an apical four-chamber view obtained. Pericardiocentesis was performed from the subcostal position. The pericardial effusion was continuously imaged. Mitral inflow velocity signals were recorded before and after pericardiocentesis. When fluid was first obtained, 50 mL of fluid were discarded after which 5 mL of agitated saline was injected through the needle. Results: In the first patient the pericardiocentesis needle was seen in the left ventricular cavity. Saline injection produced a contrast effect in the left ventricle. The needle was gradually withdrawn until contrast was seen in the pericardial sac. A total of 1100 mL was removed without further complications. The second patient had clear fluid followed by blood stained aspirate. The echocardiogram revealed gradual appearance of granular echoes within the pericardial sac, suggestive of intrapericardial clot that was subsequently surgically evacuated. In the remaining seven patients, agitated saline produced a contrast effect in the pericardial sac indicative of proper needle position. Mitral flow velocity paradoxus was noted in five patients, and it resolved after pericardiocentesis in four patients. No adjustment of the transducer was required. Conclusion: The CONTISON transducer permitted continuous monitoring of pericardiocentesis. This technique could potentially facilitate pericardiocentesis. (ECHOCARDIOGRAPHY, Volume 20, August 2003) [source] Current-Free Deposition of Prussian Blue with Organic Polymers: Towards Improved Stability and Mass Production of the Advanced Hydrogen Peroxide TransducerELECTROANALYSIS, Issue 3-5 2009Anastasiya Abstract We report on a novel approach for open-circuit (current-free) deposition of Prussian blue. Synthesis of Prussian blue is carried out by reduction of ferric ferricyanide with organic molecules, which are known to form polymers upon oxidation. The proposed interfacial deposition is a result of the synthesis in the presence of electrode support due to preconcentration of precursors at the interface. The resulting modified electrodes displayed the dramatically improved operational stability in hydrogen peroxide continuous monitoring with no loss of either electrochemical or analytical performance characteristics compared to electrodes with electrochemically deposited Prussian blue. The shown possibility to deposit stable films with regular structure in the absence of any external voltage could open new horizons for sensor science. [source] Galvanostatic Polarization of All-Solid-State K+ -Selective Electrodes with Polypyrrole Ion-to-Electron TransducerELECTROANALYSIS, Issue 13-14 2006owski Abstract Influence of galvanostatic polarizations on potential vs. logarithm of ion activity dependences of all-solid-state ion-selective electrodes with conducting polymer ion-to-electron transducer was studied. As a model system K+ -sensor with polypyrrole solid contact and poly(vinyl chloride) based membrane containing valinomycin was chosen. The influence of the lipophilic salt included to the membrane composition was of special interest. [source] Design of A New Vibration Transducer for Implantable Middle Ear Hearing DevicesIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 5 2010Ki Woong Seong Non-member Abstract A new vibration transducer was developed for implantable middle ear hearing devices (IMEHDs). It comprises two permanent magnets positioned inside three coils. The transducer maximizes the interaction between the magnetic fields of the two magnets and the electrical current flowing through the coils. Further, the transducer is robust to external magnetic fields because the magnetic fields inside it are symmetrical. The frequency response was simulated by finite element analysis (FEA). The vibrational displacement of the proposed transducer is 6 dB greater than those of the differential floating mass transducer (DFMT) and the floating mass transducer (FMT). On the basis of these results, a prototype was fabricated and its frequency response was experimentally investigated and compared with simulation results. Finally, it is shown that the proposed transducer has a higher vibrational displacement than the older ones. © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Piezoelectric Multilayer Ceramic/Polymer Composite Transducer with 2,2 ConnectivityJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2006Chang-Bun Yoon A multilayer piezoelectric ceramic/polymer composite with 2,2 connectivity was fabricated by thermoplastic green machining after co-extrusion. The multilayer ceramic body was composed of piezoelectrically active lead zirconate titanate (PZN),lead zinc niobate (PZN)-lead zirconate titanate (PZT) layers and electrically conducting PZN,PZT/Ag layers. After co-extruding the thermoplastic body, which consisted of five piezoelectric layers interspersed with four conducting layers, it was computer numeric-controlled machined to create periodic channels within it. Following binder burnout and sintering, an 18 vol% array of 190 ,m thin PZT slabs with a channel size of 880 ,m was fabricated. The channels were filled with epoxy in order to fabricate a PZN,PZT/epoxy composite with 2,2 connectivity. The piezoelectric coefficient (effective d33) and hydrostatic figure of merit (dh×gh) of the PZN,PZT/epoxy composite were 1200 pC/N and 20 130 × 10,15 m2/N, respectively. These excellent piezoelectric characteristics as well as the relatively simple fabrication procedure will contribute in widening the application range of the piezoelectric transducers. [source] Dynamics Change of Phoborhodopsin and Transducer by Activation: Study Using D75N Mutant of the Receptor by Site-directed Solid-state 13C NMR,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2008Izuru Kawamura Pharaonis phoborhodopsin (ppR or sensory rhodopsin II) is a negative phototaxis receptor of Natronomonas pharaonis, and forms a complex, which transmits the photosignal into cytoplasm, with its cognate transducer (pHtrII). We examined a possible local dynamics change of ppR and its D75N mutant complexed with pHtrII, using solid-state 13C NMR of [3- 13C]Ala- and [1- 13C]Val-labeled preparations. We distinguished Ala C,13C signals of relatively static stem (Ala221) in the C-terminus of the receptors from those of flexible tip (Ala228, 234, 236 and 238), utilizing a mutant with truncated C-terminus. The local fluctuation frequency at the C-terminal tip was appreciably decreased when ppR was bound to pHtrII, while it was increased when D75N, that mimics the signaling state because of disrupted salt bridge between C and G helices prerequisite for the signal transfer, was bound to pHtrII. This signal change may be considered with the larger dissociation constant of the complex between pHtrII and M-state of ppR. At the same time, it turned out that fluctuation frequency of cytoplasmic portion of pHtrII is lowered when ppR is replaced by D75N in the complex with pHtrII. This means that the C-terminal tip partly participates in binding with the linker region of pHtrII in the dark, but this portion might be released at the signaling state leading to mutual association of the two transducers in the cytoplasmic regions within the ppR/pHtrII complex. [source] Interaction of the Halobacterial Transducer to a Halorhodopsin Mutant Engineered so as to Bind the Transducer: Cl, Circulation Within the Extracellular Channel,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2007Chisa Hasegawa An alkali-halophilic archaeum, Natronomonas pharaonis, contains two rhodopsins that are halorhodopsin (phR), a light-driven inward Cl, pump and phoborhodopsin (ppR), the receptor of negative phototaxis functioning by forming a signaling complex with a transducer, pHtrII (Sudo Y. et al., J. Mol. Biol. 357 [2006] 1274). Previously, we reported that the phR double mutant, P240T/F250YphR, can bind with pHtrII. This mutant itself can transport Cl,, while the net transport was stopped upon formation of the complex. The flash-photolysis data were analyzed by a scheme in which phR,P1,P2,P3,P4,phR. The P3 of the wild-type and the double mutant contained two components, X- and O-intermediates. After the complex formation, however, the P3 of the double mutant lacked the X-intermediate. These observations imply that the X-intermediate (probably the N-intermediate) is the state having Cl, in the cytoplasmic binding site and that the complex undergoes an extracellular Cl, circulation because of the inhibition of formation of the X-intermediate. [source] 1141636674 Differential serine and tyrosine phosphorylation of Signal Transducer and Activator of Transcription 3 (STAT3) in Jeg-3 choriocarcinoma cell linesAMERICAN JOURNAL OF REPRODUCTIVE IMMUNOLOGY, Issue 6 2006J Roediger Background:, Signal Transducer and Activator of Transcription 3 (STAT3) is an intracellular signalling molecule, which is used by several cytokines, including leukemia inhibitory factor (LIF), epithelial growth factor (EGF), and interleukin-6 (IL-6). It induces a variety of gene transcripts and cell functions. In trophoblast cells and in tumor cells, its tyrosine phosphorylation is directly linked to their invasiveness. The regulation and function of STAT3 serine phosphorylation is still widely unclear. Material and Methods:, Jeg-3 choriocarcinoma cells were stimulated with different concentrations of EGF, IL-6 and LIF. STAT3 serine (727) and tyrosine (705) phosphorylation were analyzed 5,60 min after stimulation by SDS-PAGE electrophoresis followed by Western blotting. Results:, Jeg-3 cells display spontaneous STAT3 serine phosphorylation. 100 ng/mL EGF induces a time-dependent reduction starting 15 min after stimulation. Tyrosine phosphorylation does not occur spontaneously, but is strongly induced by EGF at all analyzed time points. LIF induces tyrosine phosphorylation, but affects serine phosphorylation only very slightly. IL-6 did not influence neither serine phosphorylation nor tyrosine phosphorylation. Discussion:, The EGF induced STAT3 tyrosine phosphorylation may be responsible for its invasion triggering capacities. The parallel reduction of serine phosphorylation may enhance this effect. LIF was formerly shown to enhance trophoblast invasion via STAT3 tyrosine phosphorylation. IL-6 displays very little effects on STAT3 and seems to use other pathways for signalling. [source] 1141638491 Hepatocyte growth factor (HGF) stimulates mammalian target of rapamycin (mTOR) in choriocarcinoma cell lines and human trophoblast cellsAMERICAN JOURNAL OF REPRODUCTIVE IMMUNOLOGY, Issue 6 2006S Busch Introduction:, Hepatocyte growth factor (HGF), interleukin-6 (IL-6) and insulin-like growth factor-II (IGF-II) are involved in the regulation of trophoblast cell migration and invasion. Signal Transducer and Activator of Transcription 3 (STAT3) and Mammalian Target Of Rapamycin (mTOR) signalling regulate cell invasion, growth and proliferation. mTOR plays also a key role during embryogenesis. Knock-out mice embryos die after implantation and blastocysts trophoblast outgrowth is reduced. Aim:, Stimuli which might trigger such invasive behaviour through mTOR should be defined. Methods:, The human choriocarcinoma cell lines JEG-3, JAR, the human choriocarcinoma-trophoblast hybrid AC1-M59 and human term trophoblast cells were stimulated with HGF, IL-6 or IGF-II. At several time points, the phosphorylation level of mTOR and STAT3 were tested by Western blot. STAT3 DNA-binding capacity was analyzed by Electrophorectic Mobility Shift Assay (EMSA). To examine the role of mTOR for invasion and proliferation, mTOR expression was silenced by RNA interference (RNAi). Results:, HGF, IGF-II and IL-6 did neither induce tyrosine (705) phosphorylation of STAT3 nor STAT3 DNA binding capacity as assessed by EMSA. HGF led to an increase of mTOR serine (2448) phosphorylation for all cell types after 15 and 30 min while IL-6 and IGF-II did not induce mTOR phosphorylation. Simultaneously, HGF decreased STAT3 serine (727) phosphorylation. mTOR silencing in AC1-M59 correlates with reduced proliferation and invasion. STAT3 expression was not affected by mTOR knock down. Conclusion:, HGF triggers mTOR activity in trophoblast and trophoblast-like cells. mTOR is a main regulator of crucial trophoblast functions. [source] More TORC for the gluconeogenic engineBIOESSAYS, Issue 3 2006Alan Cheng Hepatic gluconeogenesis plays a key role in the maintenance of glucose homeostasis. The hormone glucagon stimulates this process, whereas insulin and adiponectin are inhibitory. In a recent report, Koo et al identify the transcriptional regulator TORC2 (Transducer of Regulated CREB activity 2) as a pivotal component of the gluconeogenic program.1 Both insulin and AMPK increase the phosphorylation of TORC2, while glucagon suppresses it. This in turn regulates the nuclear/cytoplasmic shuttling of TORC2 and its ability to transactivate gluconeogenic genes. Thus, TORC2 might serve as a gluconeogenic "molecular switch" that senses hormones and cellular energy status. BioEssays 28: 231,234, 2006. © 2006 Wiley Periodicals, Inc. [source] Insulin-like growth factor-I receptor signal transduction and the Janus Kinase/Signal Transducer and Activator of Transcription (JAK-STAT) pathwayBIOFACTORS, Issue 1 2009Eddy Himpe Abstract The insulin-like growth factor IGF-I is an important fetal and postnatal growth factor, which is also involved in tissue homeostasis via regulation of proliferation, differentiation, and cell survival. To understand the role of IGF-I in the pathophysiology of a variety of disorders, including growth disorders, cancer, and neurodegenerative diseases, a detailed knowledge of IGF-I signal transduction is required. This knowledge may also contribute to the development of new therapies directed at the IGF-I receptor or other signaling molecules. In this review, we will address IGF-I receptor signaling through the JAK/STAT pathway in IGF-I signaling and the role of cytokine-induced inhibitors of signaling (CIS) and suppressors of cytokine signaling (SOCS). It appears that, in addition to the canonical IGF-I signaling pathways through extracellular-regulated kinase (ERK) and phosphatidylinositol-3 kinase (PI3K)-Akt, IGF-I also signals through the JAK/STAT pathway. Activation of this pathway may lead to induction of SOCS molecules, well-known feedback inhibitors of the JAK/STAT pathway, which also suppress of IGF-I-induced JAK/STAT signaling. Furthermore, other IGF-I-induced signaling pathways may also be modulated by SOCS. It is conceivable that the effect of these classical inhibitors of cytokine signaling directly affect IGF-I receptor signaling, because they are able to associate to the intracellular part of the IGF-I receptor. These observations indicate that CIS and SOCS molecules are key to cross-talk between IGF-I receptor signaling and signaling through receptors belonging to the hematopoietic/cytokine receptor superfamily. Theoretically, dysregulation of CIS or SOCS may affect IGF-I-mediated effects on body growth, cell differentiation, proliferation, and cell survival. © 2009 International Union of Biochemistry and Molecular Biology, Inc. [source] Ras and Signal Transducer and Activator of Transcription (STAT) Are Essential and Sufficient Downstream Components of Janus Kinases in Cell ProliferationCANCER SCIENCE, Issue 5 2000Rumiko Mizuguchi Cytokines exert their activities in cell growth and differentiation by binding specific cell membrane receptors. Janus kinases (JAKs) are cytoplasmic protein tyrosine kinases that physically interact with intracellular domains of the cytokine receptors and they play crucial roles in transducing signals triggered by the cytokine-receptor interaction. We have previously shown that conditional activation of JAK through membrane-proximal dimerization confers cytokine-independence on interleukin-3 (IL-3)-dependent Ba/F3 lymphoid cells and that the cytokine-independent proliferation is completely inhibited by dominant negative Ras. In this work, we demonstrate that ectopic expression of a dominant negative form of Stat5, a major signal transducer and activator of transcription (STAT) expressed in Ba/F3 cells, also inhibits JAK-triggered mitogenesis. In contrast, overexpression of constitutively active Ras or conditional activation of Stat5 by chemical dimerization fails to confer cytokine-independence. However, concomitant activation of ectopic Ras and Stat5 molecules in Ba/F3 cells suffices for cell proliferation in the absence of IL-3. Our results indicate that Ras and STAT are essential and sufficient components of JAK-triggered mitogenesis. Our findings further indicate that the cytokine signal bifurcates into Ras and STAT pathways following JAK activation. [source] Molecular Approaches towards the Inhibition of the Signal Transducer and Activator of Transcription 3 (Stat3) ProteinCHEMMEDCHEM, Issue 8 2008Steven Fletcher Dr. Molecular approaches towards Stat3 inhibition: Stat3 inhibition represents an exciting new approach to the treatment of cancer. The advances in the direct molecular inhibition of Stat3 are highlighted through discussion of the various inhibitors currently under investigation, including peptide sequences, peptidomimetics, small molecules and platinum-based agents. [source] An Ultrasonic Profiling Method for the Inspection of Tubular StructuresCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 6 2007Francisco Gomez These graphs not only show the inner contour of the pipe but also integrate the intensity of the echoes employed to create the profile. The enhanced profile is generated by superimposing the peak intensity from the returning echoes at the calculated x, y, and z coordinates where it reflected from the pipe wall. The proposed method is capable of showing anomalous conditions, inside pipes filled with liquid, with dimensions smaller than the theoretical lateral and axial resolution of the transducer, in contrast to traditional methods where these kinds of defects are not disclosed. The proposed inspection method and its capabilities were validated through the realization of simulations and experiments. The presented approach was particularly developed with the aim of scanning internal sections of pipes filled with liquid using rotary ultrasonic sonars, but it is expected that this research could be expanded to the inspection of other submerged structures, such as water tanks, or pressurized vessels. [source] Cor Triatriatum Sinister with and without Left Ventricular Inflow Obstruction: Visualization of the Entire Supravalvular Membrane by Real-time Three-dimensional Echocardiography.CONGENITAL HEART DISEASE, Issue 6 2006Impact on Clinical Management of Individual Patient ABSTRACT We present 4 cases of cor triatriatum in whom the diagnosis was correctly made by 2-dimensional transthoracic echocardiography, which showed the supravalvular left atrial membrane that divides the left atrium into 2 chambers. The pulmonary veins were connected normally to the proximal left atrial chamber and the left atrial appendage was connected to the distal left atrial chamber. In 1 patient there was evidence of severe pulmonary venous obstruction to the mitral valve by Doppler examination, while in the other three, there was no venous obstruction. Patients were then examined by real-time 3-dimensional echocardiography (RT3DE, using ×4 matrix array transducer connected to Sonos 7500 echocardiographic system Phillips, Andover, Mass, USA). This showed the exact morphology of the membrane and led to cancellation of planed surgical intervention in 1 case in which the membrane was only a broad band crossing the left atrial cavity. In addition to delineating the exact morphology of the intracavitary anomaly, this novel echocardiographic imaging modality should be an additive tool to better understand the natural history of these nonobstructive left atrial membranes via longitudinal follow-up of these patients. [source] Effect of ,-trinositol on secretion induced by Escherichia coli ST-toxin in rat jejunumACTA PHYSIOLOGICA, Issue 4 2003A.-M. Lahti Abstract Aim:,d -myo-inositol-1,2,6-trisphosphate (, -trinositol, PP56), is a synthetic isomer of the intracellular second messenger, d -myo-inositol-1,4,5-trisphospahate. The pharmacological actions of , -trinositol include potent anti-inflammatory properties and inhibition of the secretion induced by cholera toxin and obstructive ileus. In the present study, we investigated whether , -trinositol was able to influence the secretion induced by heat-stable ST-toxin from Escherichia coli in the rat jejunum. Methods:, A midline abdominal incision was performed in anaesthetized male Sprague,Dawley rats and a 6,7 cm long jejunal segment was isolated with intact vascular supply and placed in a chamber suspended from a force displacement transducer connected to a Grass® polygraph. Intestinal net fluid transport was continuously monitored gravimetrically. Crystalline ST-toxin (120 mouse units) was introduced into the intestinal lumen and left there for the rest of the experiment. When a stable secretion was observed, , -trinositol (60 mg kg,1 h,1) or saline were infused during 2 h, followed by a 2-h control period. Results:, , -Trinositol induced a significant (P < 0.001) inhibition of ST-toxin secretion within 30 min, lasting until 2 h after infusion had stopped. The agent also moderately increased (P < 0.05) net fluid absorption in normal jejunum. Mean arterial pressure (P < 0.001) and heart rate (P < 0.001) were reduced by , -trinositol. Conclusion:, The inhibition by , -trinositol of ST-toxin induced intestinal secretion is primarily secondary to inhibition of secretory mechanisms and only to lesser extent due to increased absorption. The detailed mechanisms of action have not been clarified but may involve suppression of inflammation possibly by means of cellular signal transduction. [source] The primary cilium as a gravitational force transducer and a regulator of transcriptional noiseDEVELOPMENTAL DYNAMICS, Issue 8 2008Stephen J. Moorman Abstract Circumstantial evidence has suggested that the primary cilium might function as a gravity sensor. Direct evidence of its gravity-sensing function has recently been provided by studies of rohon beard neurons. These neurons showed changes in the variability of gene expression levels that are linked to the cyclic changes in the Earth's gravitational field due to the Sun and Moon. These cyclic changes also cause the tides. Rohon beard neurons, after the primary cilia have been selectively destroyed, no longer show changes in gene expression variability linked to the cyclic changes in Earth's gravitational field. After the neurons regrow their primary cilia, the link between variability in gene expression levels and the Earth's changing gravitational field returns. This suggests two new functions for the primary cilia, detecting the cyclical changes in the Earth's gravitational field and transducing those changes into changes in the variability (stochastic nature) of gene expression. Developmental Dynamics 237:1955,1959, 2008. © 2008 Wiley-Liss, Inc. [source] Normal dendrite growth in Drosophila motor neurons requires the AP-1 transcription factorDEVELOPMENTAL NEUROBIOLOGY, Issue 10 2008Cortnie L. Hartwig Abstract During learning and memory formation, information flow through networks is regulated significantly through structural alterations in neurons. Dendrites, sites of signal integration, are key targets of activity-mediated modifications. Although local mechanisms of dendritic growth ensure synapse-specific changes, global mechanisms linking neural activity to nuclear gene expression may have profound influences on neural function. Fos, being an immediate-early gene, is ideally suited to be an initial transducer of neural activity, but a precise role for the AP-1 transcription factor in dendrite growth remains to be elucidated. Here we measure changes in the dendritic fields of identified Drosophila motor neurons in vivo and in primary culture to investigate the role of the immediate-early transcription factor AP-1 in regulating endogenous and activity-induced dendrite growth. Our data indicate that (a) increased neural excitability or depolarization stimulates dendrite growth, (b) AP-1 (a Fos, Jun hetero-dimer) is required for normal motor neuron dendritic growth during development and in response to activity induction, and (c) neuronal Fos protein levels are rapidly but transiently induced in motor neurons following neural activity. Taken together, these results show that AP-1 mediated transcription is important for dendrite growth, and that neural activity influences global dendritic growth through a gene-expression dependent mechanism gated by AP-1. © 2008 Wiley Periodicals, Inc. Develop Neurobiol, 2008 [source] CLINICAL USE OF THE NEWLY DEVELOPED ELECTRONIC RADIAL ULTRASOUND ENDOSCOPEDIGESTIVE ENDOSCOPY, Issue 1 2006Masami Ogawa Background:, Endoscopic ultrasonography (EUS) is widely accepted as a diagnostic tool for bilio-pancreatic and gastrointestinal tract diseases. Recently, an ultrasound endoscope with an electronic radial scan transducer has been developed. To evaluate the clinical usefulness of this system, its image quality, advantages and disadvantages were evaluated. Materials and methods:, Ultrasound endoscope with electronic radial scan transducer and its monitor unit were used. The direction of the imaging plane was similar to that of the mechanical radial models. Color Doppler function and tissue harmonic imaging were feasible by this system. To evaluate this endoscope, we investigated the image quality and distance resolution by in-vitro study using thin papers, and 50 patients were examined by this system. Results:, Comparison with the mechanical radial endoscope GF-UM2000 revealed that the image quality was almost equivalent. However, the ultrasound penetration of the electronic radial scanner was better and more satisfactory with less echoic reduction. In addition, the blood-flow signal could be obtained by using the color Doppler function. In contrast, the diameter of the new endoscope was bigger than the advanced mechanical radial models, the monitor unit was bigger than that of the mechanical radial system, and the operation of this unit was complicated. Conclusion:, A prototype of the ultrasound endoscope with electronic radial scan showed satisfactory results regarding the image quality, ultrasound penetration, and clinical diagnosis. The blood flow could be investigated by using the color Doppler function, which is useful to diagnose lesions and detect involvement of the blood vessels in cancers. [source] Investigating the transport dynamics and the properties of bedload material with a hydro-acoustic measuring systemEARTH SURFACE PROCESSES AND LANDFORMS, Issue 1 2008Andreas Krein Abstract This article deals with the following two questions. Are acoustic measurements in running waters appropriate for a highly resolved investigation of the bedload transport? Which characterizations of the bedload regarding mass and shape are possible via the acoustic signals? The signals were recorded by means of data recorders (Tascam Inc. DAP1 Portable Data Recorder) and hydrophones (International Transducer Corp. ITC-4001 A). The ITC-4001 is a shallow water omnidirectional transducer containing a flexural disc transducer utilizing Channelite-5400 ceramics mounted in a rugged corrosion-resistant housing. These hydrophones were screwed onto the bottom side of stainless steel plates, serving as a contact surface for the bedload in motion above them. After more than 100 series of tests in the laboratory, which indicated the basic relations between the dimension, shape and weight of the bedload and the resulting signal, field tests of the measuring system were conducted. By artificially produced flood waves in the small brooks Riverisbach, Olewiger Bach and by a winter flood wave in the River Moselle, it is possible to elaborate similar structures of the signal course of the bedload movement. The highest transport rates can be observed at the beginning of the increasing limbs and behind the peaks of the waves. At the beginning of the waves, the increasing transport power of the water and the loose material can be considered as the cause for this result. The high stream velocity behind the wave peaks explains the increase in the bedload transport so that material from the channel beds is unfastened and will be mobilized. The characterization of the bedload regarding the shape and mass is still limited regarding the field measurements and could be solved only for homogeneous grain sizes and single stones under laboratory conditions. Copyright © 2007 John Wiley & Sons, Ltd. [source] Consequences of hyperconcentrated flow for process-based soil erosion modelling on the Chinese Loess PlateauEARTH SURFACE PROCESSES AND LANDFORMS, Issue 9 2006Rudi Hessel Abstract High sediment concentrations in runoff are a characteristic feature of the Chinese Loess Plateau, and are probably caused by factors such as the occurrence of erodible materials on steep slopes, the characteristics of the loess and the harsh climate that results in low plant cover. When sediment concentration increases, fluid density increases, viscosity increases and settling velocity decreases. These effects become increasingly important with increasing concentration and can result in flow behaviour that is quite different from that of clear water flow. Although the net effect of these changes on the flow is not always apparent, erosion models that deal with high sediment concentrations should consider such effects and could include corrections for some of these effects. A case study in a small catchment on the Loess Plateau indicated that sediment concentrations were considerable, and literature data suggested that for such sediment concentrations, corrections for settling velocity, fluid density and viscosity are needed. Furthermore, a number of corrections are necessary to be able to compare field measurements with results of soil erosion models: sediment volume should be subtracted from runoff volume and a density correction is needed to use data from a pressure transducer. For flumes that were used to measure discharge from smaller areas inside the catchment, the measured water level should be corrected by subtracting the sediment level in the flume from the water level, while the sediment volume should also be subtracted from the discharge. Finally, measured concentration should be corrected to give concentration expressed as grams per litre of clear water, since soil erosion models express sediment concentration in this way. Copyright © 2006 John Wiley & Sons, Ltd. [source] Rock thermal data at the grain scale: applicability to granular disintegration in cold environmentsEARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2003Kevin Hall Abstract Consideration of the mechanisms associated with the granular disintegration of rock has been limited by available data. In most instances, both the size of the transducer and the nature of the study have negated any applicability of the resulting data to the understanding of grain-to-grain separation within rock. The application of microthermocouples (,0·15 mm diameter) and high-frequency logging (20 s intervals) at a taffoni site on southern Alexander Island and from a rock outcrop on Adelaide Island (Antarctica) provide new data pertaining to the thermal conditions, at the grain scale, of the rock surface. The results show that thermal changes (,T/t) can be very high, with values of 22 °C min,1 being recorded. Although available data indicate that there can be differences in frequency and magnitude of ,uctuations as a function of aspect, all aspects experienced some large magnitude (,2 °C min,1) ,uctuations. Further, in many instances, large thermal changes in more than one direction could occur within 1 min or in subsequent minutes. These data suggest that the surface grains experience rapidly changing stress ,elds that may, with time, effect fatigue at the grain boundaries; albedo differences between grains and the resulting thermal variations are thought to exacerbate this. The available data failed to show any indication of water freezing (an exotherm) and thus it is suggested that microgelivation may not play as large a role in granular breakdown as is often postulated for cold regions, and that in this dry, Antarctic region thermal stress may play a signi,cant role. Copyright © 2003 John Wiley & Sons, Ltd. [source] Estimation of Coronary Flow Velocity Reserve Using Transthoracic Doppler Echocardiography and Cold Pressor Test Might Be Useful for Detecting of Patients with Variant AnginaECHOCARDIOGRAPHY, Issue 4 2010Hui-Jeong Hwang M.D. Purpose: The cold pressor test (CPT) has been used to detect variant angina, but its sensitivity in predicting vasospasm is low. The aim of this study was to determine whether estimates of the coronary flow velocity reserve (CFVR) in the distal left anterior descending coronary artery (dLAD) using transthoracic echocardiography (TTE) and CPT are useful tool to predict variant angina. Methods: 65 patients (mean age = 52 ± 10 years; male:female = 41:24) who had normal coronary artery on angiography and underwent acetylcholine provocation test were enrolled and divided into the spasm group (n = 31) and the no spasm group (n = 34). During CPT, the peak (PDV) and mean diastolic flow velocity (MDV) of the dLAD were estimated using TTE with a high-frequency transducer, and electrocardiography, blood pressures, heart rate, and symptoms were monitored every 30 seconds. CPT%PDV and CPT%MDV were defined as the percentage changes in PDV and MDV during CPT, respectively. Results: CPT%PDV was 4.99 ± 23.62% in the spasm group and 52.75 ± 24.78% in the no spasm group (P < 0.001). CPT%MDV was 6.83 ± 23.81% in the spasm group and 50.22 ± 27.83% in the no spasm group (P < 0.001). CPT%PDV<31.1% had a sensitivity of 93.5% and a specificity of 82.4% in predicting variant angina (95% confidence interval [CI]: 0.939,0.979, P < 0.001). CPT%MDV<30.55% had a sensitivity of 90% and a specificity of 76.5% in predicting variant angina (95% CI: 0.884,0.950, P < 0.001). Conclusion: The measurement of changes in the coronary flow velocity of the dLAD using TTE and CPT might be useful for the estimation of endothelial dysfunction in patients with variant angina. (ECHOCARDIOGRAPHY 2010;27:435-441) [source] Assessment of Carotid Compliance Using Real Time Vascular Ultrasound Image Analysis in Marfan SyndromeECHOCARDIOGRAPHY, Issue 4 2009Anatoli Kiotsekoglou M.D. Background: Fibrillin-1 deficiency, dysregulated cytokine transforming growth factor-,, and increased collagen deposition related to fibrillin-1 gene mutations could predispose to impaired carotid compliance (CC) in Marfan syndrome (MFS). We sought to detect any alterations in CC using the vascular image analysis system (VIA). Methods and Results: Thirty-two MFS patients, 20 men and 12 women (mean age 34.2 ± 12.05 years), and 29 controls matched for age, sex, and body surface area (BSA) were recruited. The entire length of each carotid system was initially scanned longitudinally using a 14 MHz linear transducer. Then, a stereotactic clamp held the transducer in contact with the carotid artery. Arterial diameter changes during the cardiac cycle were recorded for 1 minute from both right (RCCA) and left common carotid arteries (LCCA) separately using the VIA system. RCCA and LCCA compliance and distensibility measurements were significantly reduced in MFS patients when compared to controls, P < 0.05. RCCA and LCCA intima-media thickness did not differ between patients and controls, P > 0.05. MFS diagnosis and age were associated with reduced CC in both carotid arteries after adjusting for variables such as, sex, BSA, heart rate, beta-blockade, intima-media thickness, and aortic root size. Conclusions: Our findings showed a reduction in CC in adult patients with MFS. This could be attributed to fibrillin-1 deficiency resulting in structural abnormalities in the carotid arterial wall. [source] In Vitro Two-Dimensional Echocardiographic Imaging of a Stented Porcine Bioprosthetic Valve: The Bent Strut ArtifactECHOCARDIOGRAPHY, Issue 1 2009David S. Bach M.D.Article first published online: 8 OCT 200 Background: Echocardiographic imaging of a stented valve bioprosthesis can reveal apparent inward deflection of one or more struts. It could be assumed that this finding is related to actual strut distortion as opposed to an artifact of off-axis imaging. Objective: To determine whether normal (nondistorted) bioprosthetic struts can appear by artifact to be bent inward on two-dimensional echocardiographic imaging. Methods: A production-quality porcine bioprosthetic aortic valve was imaged in vitro using standard two-dimensional echocardiographic techniques. Apparent strut distortion on echocardiographic imaging was investigated relative to prosthesis orientation to the transducer. Results: The appearance of inward strut distortion was produced when two of three struts were simultaneously imaged, including imaging in an off-axis long axis orientation and from above or below the prosthesis. Conclusion: Apparent inward distortion of bioprosthetic struts can be simulated in vitro using a normal, nondistorted valve, and is common if two struts are simultaneously imaged. A finding of inward distortion of strut tips on in vivo imaging should be used with caution, since the finding may not be representative of actual strut anatomy. [source] Association of Coronary Sinus Diameter with Pulmonary HypertensionECHOCARDIOGRAPHY, Issue 9 2008Yilmaz Gunes M.D. Background: Impaired venous drainage secondary to increased right atrial pressure (RAP) may result in coronary sinus (CS) dilatation.,Methods: Two hundred fifteen patients referred for transthoracic echocardiography were included in the study. CS diameters were measured from apical four-chamber view with the transducer being slightly tilted posteriorly to the level of the dorsum of the heart. Pulmonary artery systolic pressure (PASP) is estimated by measurement of tricuspid regurgitation velocity (v) and estimate RAP based on size and collapsibility of inferior vena cava (VCI) with the formula PASP: 4v2+RAP. Patients with PASP >35 mmHg were considered to have pulmonary hypertension (PH).,Results: CS diameter was measured in 80.3% of the patients with normal PASP (8.1 ± 2.4 mm) and 93.1% of the patients having PH (12.3 ± 2.5 mm). PASP was significantly correlated with CS diameter (r = 0.647, P < 0.001), RA volume index (r = 0.631, P < 0.001), RV volume index (r = 0.475, P < 0.001), VCI diameter (r = 0.365, P < 0.001), and left ventricular ejection fraction (LVEF) (r =,0.270, P < 0.001). CS diameter was also correlated significantly with estimated RAP (r = 0.557, P < 0.001), RA volume index (r = 0.520, P < 0.001), RV volume index (r = 0.386, P < 0.001), LVEF (r =,0.327, P < 0.001), and VCI diameter (r = 0.313, P < 0.001). Multivariate analyses, testing for independent predictive information of CS size, VCI diameter, RA and RV volume indexes, and estimated RAP for the presence of PH revealed that estimated RAP (beta = 0.465, P < 0.001) and CS size (beta = 0.402, P = 0.003) were the significant predictors.,Conclusions: Coronary sinus is dilated in patients with pulmonary hypertension. Coronary sinus diameter significantly correlates with PASP, RAP, right heart chamber volumes, LVEF, and VCI diameter. [source] Role of Parasternal Data Acquisition During Contrast Enhanced Real-Time Three-Dimensional EchocardiographyECHOCARDIOGRAPHY, Issue 10 2007Attila Nemes M.D., Ph.D. Background: Recent technical developments have resulted in high-resolution real time three-dimensional echocardiography (RT3DE). The purpose of this study was to investigate the beneficial role of parasternal-acquired images in addition to apical-acquired images during contrast stress RT3DE. Methods: The study comprised 30 consecutive patients (52 ± 11 years, 18 males) with chest pain referred for routine stress testing. The contrast RT3DE images were acquired from the apical and parasternal window with a Sonos 7500 echo system attached to a X4 matrix array transducer. Results: From the apical and parasternal acquisition, 464 segments (91%) and 267 segments (52%) could be analyzed, respectively (P < 0.001). From the apical window, more basal segments were not analyzable (22 of 180, 12% vs. 24 of 330, 7%; P = 0.06). From the parasternal window, more apical segments were not analyzable (117 of 150, 78% vs. 126 of 360, 35%; P < 0.01). The mean image quality index of the 464 analyzable segments from the apical-acquired images was 2.43. Fourteen of 180 basal segments (8%), 12 of 180 midventricular segments (7%) and 2 of 150 apical segment (1%) were only available with parasternal data acquisition. In addition to these 28 segments, 79 segments (15%) already visualized from the apical window improved in quality. The overall mean image quality index, now assessed from 492 (96%) of all segments, using both the apical and parasternal acquired data, improved to 2.74 (P < 0.05). Conclusions: Addition of parasternal to apical acquisition of contrast RT3DE data can decrease the number of nonvisualized segments and improve mean image quality. [source] "Hands-Free" Continuous Transthoracic Monitoring of Pericardiocentesis Using a Novel Ultrasound TransducerECHOCARDIOGRAPHY, Issue 6 2003F.R.C.P., P.A.N. Chandraratna Background: Pericardiocentesis can be monitored with a hand-held transducer. The purpose of this study was to assess the feasibility of monitoring pericardiocentesis using a novel ultrasound transducer, which can be attached to the chest wall, developed in our laboratory (CONTISON). Methods: We studied nine patients with large pericardial effusions. The 2.5-MHz transducer is spherical in its distal part and mounted in an external housing to permit steering in 360 degrees. The external housing is attached to the chest wall using an adhesive patch. The CONTISON transducer was placed at the cardiac apex and an apical four-chamber view obtained. Pericardiocentesis was performed from the subcostal position. The pericardial effusion was continuously imaged. Mitral inflow velocity signals were recorded before and after pericardiocentesis. When fluid was first obtained, 50 mL of fluid were discarded after which 5 mL of agitated saline was injected through the needle. Results: In the first patient the pericardiocentesis needle was seen in the left ventricular cavity. Saline injection produced a contrast effect in the left ventricle. The needle was gradually withdrawn until contrast was seen in the pericardial sac. A total of 1100 mL was removed without further complications. The second patient had clear fluid followed by blood stained aspirate. The echocardiogram revealed gradual appearance of granular echoes within the pericardial sac, suggestive of intrapericardial clot that was subsequently surgically evacuated. In the remaining seven patients, agitated saline produced a contrast effect in the pericardial sac indicative of proper needle position. Mitral flow velocity paradoxus was noted in five patients, and it resolved after pericardiocentesis in four patients. No adjustment of the transducer was required. Conclusion: The CONTISON transducer permitted continuous monitoring of pericardiocentesis. This technique could potentially facilitate pericardiocentesis. (ECHOCARDIOGRAPHY, Volume 20, August 2003) [source] A Hand-Carried Personal Ultrasound Device for Rapid Evaluation of Left Ventricular Function: Use After Limited Echo TrainingECHOCARDIOGRAPHY, Issue 4 2003Kristina Lemola A hand-carried personal ultrasound device (HCPUD) may be used for rapid cardiac screening by physicians with limited echo training. Our objective was to determine the accuracy of rapid HCPUD evaluation of left ventricular (LV) size and function when used by a Cardiology Fellow. Forty-five patients underwent an HCPUD exam using a 2.4-kg device with a 2- to 4-MHz curved transducer and color power Doppler (SonoSite). The results were compared with sonographer-performed and echocardiographer-interpreted exams using conventional equipment. The HCPUD exam lasted 6 ± 2 minutes. There was 100% agreement between HCPUD and conventional echo on qualitative assessment of LV systolic function. Comparing the HCPUD and conventional linear measurements of left ventricular end-diastolic dimension (LVEDD) and of interventricular septal (IVS) thickness: LVEDD is HCPUD = 0.94 conventional ,0.2,r = 0.82, P < 0.0001; IVS is HCPUD= 0.59conventional+0.6, r = 0.69, P < 0.0001. Thus, an HCPUD can effectively be used after limited training to rapidly screen for qualitative abnormalities of LV systolic function. Quantitative measurements of smaller structures with the HCPUD are more challenging. (ECHOCARDIOGRAPHY, Volume 20, May 2003) [source] Sensitive Biomimetic Sensor Based on Molecular Imprinting at Functionalized Indium Tin Oxide ElectrodesELECTROANALYSIS, Issue 16 2007Na Gao Abstract We initially report an electrochemical sensing platform based on molecularly imprinted polymers (MIPs) at functionalized Indium Tin Oxide Electrodes (ITO). In this research, aminopropyl-derivatized organosilane aminopropyltriethoxysilane (APTES), which plays the role of functional monomers for template recognition, was firstly self-assembled on an ITO electrode and then dopamine-imprinted sol was spin-coated on the modified surface. APTES which can interact with template dopamine (DA) through hydrogen bonds brought more binding sites located closely to the surface of the ITO electrode, thus made the prepared sensor more sensitive for DA detection. Potential scanning is presented to extract DA from the modified film, thus DA can rapidly and completely leach out. The affinity and selectivity of the resulting biomimetic sensor were characterized using cyclic voltammetry (CV). It exhibited an increased affinity for DA over that of structurally related molecules, the anodic current for DA oxidation depended on the concentration of DA in the linear range from 2×10,6 M to 0.8×10,3 M with a correlation coefficient of 0.9927. In contrast, DA-templated film prepared under identical conditions on a bare ITO showed obviously lower response toward dopamine in solution. It should be noted that potential scanning is a very effective approach for DA extraction, and surface modification of the electrochemical transducer with functional monomers is responsible for the development of MIPs-based highly sensitive biomimetic sensor. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||