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Pressure Sensor (pressure + sensor)

Distribution by Scientific Domains

Medical Sciences	43%
Engineering	25%
Polymers and Materials Science	17%
Physics and Astronomy	5%
2 Other Domains	10%

Selected Abstracts

A Wet/Wet Differential Pressure Sensor for Measuring Vertical Hydraulic Gradient

GROUND WATER, Issue 1 2010
Brad G. Fritz
Vertical hydraulic gradient is commonly measured in rivers, lakes, and streams for studies of groundwater,surface water interaction. While a number of methods with subtle differences have been applied, these methods can generally be separated into two categories; measuring surface water elevation and pressure in the subsurface separately or making direct measurements of the head difference with a manometer. Making separate head measurements allows for the use of electronic pressure sensors, providing large datasets that are particularly useful when the vertical hydraulic gradient fluctuates over time. On the other hand, using a manometer-based method provides an easier and more rapid measurement with a simpler computation to calculate the vertical hydraulic gradient. In this study, we evaluated a wet/wet differential pressure sensor for use in measuring vertical hydraulic gradient. This approach combines the advantage of high-temporal frequency measurements obtained with instrumented piezometers with the simplicity and reduced potential for human-induced error obtained with a manometer board method. Our results showed that the wet/wet differential pressure sensor provided results comparable to more traditional methods, making it an acceptable method for future use. [source]

Feasibility Study of a Thick-Film PZT Resonant Pressure Sensor Made on a PreFired 3D LTCC Structure

INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2009
Marina Santo Zarnik
This paper discusses the feasibility of a piezoelectric resonant pressure sensor made of lead,zirconate,titanate (PZT) thick films on a preprocessed 3D low-temperature co-fired ceramic structure with a deformable diaphragm. Numerical and experimental analyses were carried out. Two different thick-film PZT compositions were characterized. Using experimentally evaluated material properties, a finite-element analysis showed the trends and facilitated the decisions in the design phase of the sensor. [source]

A Blood Pressure Sensor for Long-Term Implantation

ARTIFICIAL ORGANS, Issue 5 2001
Edward Bullister
Abstract: An implantable flow-through blood pressure sensor prototype has been developed for use with an implantable left ventricular assist device (LVAD). This sensor incorporates a flat pressure-sensing diaphragm that is designed to be integral with the wall of a titanium tube that may be placed in the inlet or the outlet flow path of any LVAD. The interior tube flow geometry is transitioned from a round to a D-shape such that flow separation is eliminated. Bench testing of 3 sensors was performed to characterize the sensor. The worst-case results showed a maximum nonlinearity of 0.64 mm Hg, a maximum hysteresis of 0.87 mm Hg, and a maximum nonrepeatability of 0.87 mm Hg. Long-term drift studies of 2 sensors at 193 days and 112 days resulted in a projected annual drift rate of 1.4 and 2.0 mm Hg, respectively. The APEX pressure sensors were evaluated in 5 ventricular assist acute calf experiments in which the sensor outputs were compared with Millar pressure catheter sensors. Pressure output comparisons showed similar pressure tracings. No visible evidence of thrombus formation was found on the APEX sensor compared with thrombus formation found on the Millar catheter at the entrance to the flow path. Tests demonstrated that the blood pressure sensor can accurately measure blood pressure and indicate that it has long-term stability. [source]

A Customizable Instrument for Measuring the Mechanical Properties of Thin Biomedical Membranes

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2005
Gracián Triviño
Abstract Summary: A customized instrument has been developed as part of multidisciplinary research work relating to the development of a biodegradable vascular scaffold. This instrument aims to measure the mechanical properties of elastic and viscoelastic thin membranes with tissue engineering applications. Uniform and omni-directional pressure is applied on the whole membrane which is uniformly clamped and submerged into a liquid medium. The mechanical testing described in this study is focused on the stress-strain curves of polycaprolactone (PCL) films after different treatments. The influence of Dulbecco's modified Eagle's culture medium, L929 fibroblast culture, NaOH treatment and film thickness on the mechanical properties of PCL films was evaluated after different times. These studies show that the PCL degradation process is influenced by immersion in the culture medium, inducing an increment in the slope of the pressure-dilation curve which is indicative of an increase in the polymer stiffness. On the other hand, long NaOH treatments make PCL films have more flexible behavior. A computerized version of the instrument: (1) Electrical compressor; (2) Filter; (3) Voltage-pressure converter; (5) Pressure sensor; (6) Differential pressure sensor; (7,8) Main and auxiliary pipettes; (9) Printed circuit board; (10) Personal computer. [source]

Superimposed Elastic Stockings: Pressure Measurements

DERMATOLOGIC SURGERY, Issue 3 2007
ANDRÉ CORNU-THENARD MD
BACKGROUND High-compression stockings over 40 mmHg are often difficult or even impossible to apply. A specific technique is frequently used to overcome this problem: a high-compression stocking is replaced by two or even three lower compression stockings that are applied on top of each other, thereby reducing the effort of application. To our knowledge, however, no study concerning therapeutic stockings has demonstrated that the forces exerted by two or three superimposed stockings are additive. OBJECTIVE The objective was to evaluate if the pressures exerted by two or three superimposed elastic stockings are additive. MATERIAL AND METHODS A series of measurements was performed in vitro using an apparatus fitted with a pressure sensor on four different premade elastic stockings applied separately and then superimposed. The actual pressure measurement obtained with superimposed stockings was compared to arithmetic sum of the pressures produced by each of the stockings used. RESULTS The pressures produced by superimposed stockings are adequately predicted from the pressure given by each of the stockings used in the superposition, with correlation coefficients higher than 0.9. CONCLUSION Under our experimental conditions, the superimposed elastic stocking pressures additivity hypothesis is confirmed. In vivo studies should be conducted to confirm those results. [source]

Ultra-miniature optical fiber pressure sensor with a sleeve for catheter insertion

ELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 8 2009
Masato Shimada
Abstract A diaphragm-type optical fiber pressure sensor, which has a sleeve for fiber insertion, is proposed, and the fundamental characteristics of this sensor are demonstrated. The sleeve structure is fabricated by DRIE (Deep Reactive Ion Etching). The diaphragm with a sleeve is suitable for highly reliable and easy bonding between the sleeve and the optical fiber. The light intensity change detection by the Fabry,Perot interferometer based on the pressure is increased by the improved DRIE method. The mass production method of the developed diaphragm will be useful for creating a low-cost pressure sensor. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(8): 36,42, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10044 [source]

Arterial stiffening and cardiac hypertrophy in a new rat model of type 2 diabetes

EUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 1 2006
K.-C. Chang
Abstract Background, We determined the effects of NIDDM on haemodynamic parameters describing arterial wall elasticity and cardiac hypertrophy in rats administered streptozotocin (STZ) and nicotinamide (NA), using the aortic impedance analysis. Methods, Male Wistar rats at 2 months were administered intraperitoneally 180 mg kg,1 of NA, 30 min before an intravenous injection of 50 mg kg,1 STZ, to induce type 2 diabetes. The STZ-NA rats were divided into two groups, 4 weeks and 8 weeks after induction of diabetes, and compared with untreated age-matched controls. Pulsatile aortic pressure and flow signals were measured by a high-fidelity pressure sensor and electromagnetic flow probe, respectively, and were then subjected to Fourier transformation for the analysis of aortic input impedance. Results, In each diabetic group, the experimental syndrome was characterized by a moderate and stable hyperglycaemia and a relative deficiency of insulin secretion. However, the 8-week but not the 4-week STZ-NA diabetic rats showed a decrease in cardiac output in the absence of any significant changes in mean aortic pressure, having increased total peripheral resistance. The diabetic syndrome at 8 weeks also contributed to an increase in aortic characteristic impedance, from 1·49 ± 0·33 (mean ± SD) to 1·95 ± 0·28 mmHg s mL,1 (P < 0·05), suggesting a detriment to the aortic distensibility in NIDDM. Meanwhile, the STZ-NA diabetic animals after 8 weeks had an increased wave reflection factor (0·46 ± 0·09 vs. 0·61 ± 0·13, P < 0·05) and decreased wave transit time (25·8 ± 3·8 vs. 20·6 ± 2·8 ms, P < 0·05). Ratio of the left ventricular weight to body weight was also enhanced in the 8-week STZ-NA diabetic rats. Conclusion, The heavy intensity with early return of the pulse wave reflection may augment systolic load of the left ventricle coupled to the arterial system, leading to cardiac hypertrophy in the rats at 8 weeks after following STZ and NA administration. [source]

A Wet/Wet Differential Pressure Sensor for Measuring Vertical Hydraulic Gradient

Thin Films: One Nanometer Thin Carbon Nanosheets with Tunable Conductivity and Stiffness (Adv. Mater.

ADVANCED MATERIALS, Issue 12 2009
12/2009)
Andrey Turchanin and co-workers report on page 1233 on the fabrication and characterization of atomically thin (,1 nm) carbon films and membranes with tunable conductivity and stiffness, arbitrary size and shape. These carbon nanosheets are produced using self-assembled monolayers of aromatic molecules, which are cross-linked by electrons, detached from the surfaces, and subsequently pyrolized. The technical applicability of these novel materials is demonstrated by incorporating them into a microscopic pressure sensor. The optical microscopy image shows a folded nanosheet transferred onto an oxidized silicon wafer. [source]

One Nanometer Thin Carbon Nanosheets with Tunable Conductivity and Stiffness

ADVANCED MATERIALS, Issue 12 2009
Andrey Turchanin
Atomically thin (,1,nm) carbon films and membranes whose electrical behavior can be tuned from insulating to conducting are fabricated by a novel route. These films present arbitrary size and shape based on molecular self-assembly, electron irradiation, and pyrolysis, and their technical applicability is demonstrated by their incorporation into a microscopic pressure sensor. [source]

Feasibility Study of a Thick-Film PZT Resonant Pressure Sensor Made on a PreFired 3D LTCC Structure

The relationship between caudal differential pressure and activity of Atlantic cod: a potential method to predict oxygen consumption of free-swimming fish

JOURNAL OF FISH BIOLOGY, Issue 4 2007
M. F. Steinhausen
This study reports the first results on telemetry of caudal differential pressure during spontaneous swimming activity in cod Gadus morhua and demonstrates that tail-beat pressure may be used as a predictor of activity and swimming costs of free-swimming cod. Tail-beat pressure was monitored using a differential pressure sensor on the caudal peduncle of cod and spontaneous swimming activity was quantified using a customized video-computer tracking programme. Tail-beat pressure was found to correlate with (1) swimming speed (U) and oxygen consumption during forced swimming and (2) mean U during spontaneous activity. Based on the relationship between and the integrated pressure performed by the tail during forced swimming, it should be possible to predict during spontaneous activity. To gain precise measures of activity and thus predictions of for free-swimming fish, however, individual calibrations are necessary. [source]

Investigation of the factors related to the formation of the buccal mucosa ridging

JOURNAL OF ORAL REHABILITATION, Issue 6 2003
I. Takagi
summary, The aim of this study was to clarify the factors related to the formation of the buccal mucosa ridging, which has been mentioned to be a clinical sign of clenching. Twenty-one individuals were investigated and divided into three groups: (i) those without buccal mucosa ridging, (ii) the buccal mucosa ridging located in all the posterior teeth region, and (iii) the buccal mucosa ridging corresponding only to the molar teeth region. A pressure sensor was used and placed at two points: first upper premolar and second upper molar. The recording tasks were: (i) silent reading at rest, (ii) light voluntary clenching, (iii) maximum voluntary clenching, (iv) holding the cheeks tightly against the teeth while light voluntary clenching, (v) holding the cheeks tightly against the teeth without tooth contact, (vi) pulling angle of mouth laterally while light voluntary clenching, (vii) pulling angle of mouth laterally without tooth contact and (viii) swallowing. No significant differences were found between groups in all the recording tasks except for the swallowing, at which significant difference (P < 0·05) was found between the groups of individuals having buccal mucosa ridging and without it. Based on these results it became clear that the buccal mucosa pressure exerted on the buccal aspect of teeth during swallowing plays an important role in the formation of buccal mucosa ridging. [source]

Diamond as pressure sensor in high-pressure Raman spectroscopy using sapphire and other gem anvil cells

JOURNAL OF RAMAN SPECTROSCOPY, Issue 4 2003
Valentín García Baonza
Abstract We propose a new Raman pressure scale based on the shift with pressure of the fundamental Raman band of micrometer-sized diamonds. First, we confirmed that the pressure slope of the triply degenerate diamond phonon behaves in a similar fashion to that of the bulk. Our measurements were calibrated Raman against the Sm:YAG fluorescence pressure scale up to 5 GPa using a gasketed sapphire anvil cell. The most relevant features regarding the design of the anvil cell are briefly outlined. Measurements were performed under hydrostatic conditions using 4 : 1 methanol,ethanol as pressure-transmitting medium. The calibration pressures according to the relationship p(GPa) = 0.356[,(cm,1) , 1332.3] are considered to be accurate within about 0.1 GPa. The convenience of using micrometer-sized diamonds as pressure sensors in Raman studies using gem anvil devices is demonstrated with several examples. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Appling the abdominal aortic-balloon occluding combine with blood pressure sensor of dorsal artery of foot to control bleeding during the pelvic and sacrum tumors surgery

JOURNAL OF SURGICAL ONCOLOGY, Issue 7 2008
Liu Yang MD
Abstract Background and Objectives To investigate the feasibilities of reducing intraoperative hemorrhage and improving the safety of pelvic and sacrum tumor surgery using sizing balloon occluding abdominal aorta. Method From May 2001 to May 2007, 18 patients were diagnosed as sacrum or pelvic tumor and underwent surgery in our institution. Balloon catheters were placed via femoral artery to occlude the abdominal aorta of pelvic tumor and sacrum region undergoing the sacrum resection or half pelvis resection and replacement operation in 12 patients. A sizing balloon was used to occlude the abdominal aorta for 60 min in assisting with resection of pelvic and sacral tumors. Results After the abdominal aorta was occluded, much less intraoperative hemorrhage was found, and the average blood loss was only 280 ml (range 200,600 ml). This procedure assisted the surgeon in identifying clearly the surgical margin and neurovascular structure surrounded by the tumors. The blood pressure remained stable during the operation. And the function of the kidney, the pelvis organs and the lower extremities were normal. Conclusion Intraoperative abdominal aorta occluding may effectively control intraoperative hemorrhage, thus assisting the surgeon in the complete and safe resection of pelvic and sacrum tumors. J. Surg. Oncol. 2008;97:626,628. © 2008 Wiley-Liss, Inc. [source]

A Customizable Instrument for Measuring the Mechanical Properties of Thin Biomedical Membranes

Four-channel fiber loop ring-down pressure sensor with temperature compensation based on neural networks

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 8 2010
Yang Gao
Abstract A four-channel fiber loop ring-down pressure sensor with temperature compensation based on neural networks is described. This fiber ring-down pressure sensor makes use of the principle of time division multiplexing, which consists of series and parallel fiber loops. The laser pulses from four-channels can be acquired by only one detector and the four pressure values are measured synchronously in our experiment. Taking mode dispersion in multimode fiber into consideration, the maximum multiplexing number is discussed. In addition, temperature compensation based on neural networks has been successfully used in our experiment, to eliminate the disturbance of environmental temperature. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1796,1799, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25326 [source]

Multimode fiber ring-down pressure sensor

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2007
Huiye Qiu
Abstract A fiber-loop ring-down spectroscopy based on multimode fiber is proposed for pressure measurement. It has been found that the multimode fiber-loop ring-down pressure sensor has higher sensitivity and larger dynamic range up to 6.2 × 107 Pa compared to the single mode counterpart. Good stability and repeatability of the sensor are also demonstrated. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1698,1700, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22553 [source]

Optimal Pressure Regulation of the Pneumatic Ventricular Assist Device With Bellows-Type Driver

ARTIFICIAL ORGANS, Issue 8 2009
Jung Joo Lee
Abstract The bellows-type pneumatic ventricular assist device (VAD) generates pneumatic pressure with compression of bellows instead of using an air compressor. This VAD driver has a small volume that is suitable for portable devices. However, improper pneumatic pressure setup can not only cause a lack of adequate flow generation, but also cause durability problems. In this study, a pneumatic pressure regulation system for optimal operation of the bellows-type VAD has been developed. The optimal pneumatic pressure conditions according to various afterload conditions aiming for optimal flow rates were investigated, and an afterload estimation algorithm was developed. The developed regulation system, which consists of a pressure sensor and a two-way solenoid valve, estimates the current afterload and regulates the pneumatic pressure to the optimal point for the current afterload condition. Experiments were performed in a mock circulation system. The afterload estimation algorithm showed sufficient performance with the standard deviation of error, 8.8 mm Hg. The flow rate could be stably regulated with a developed system under various afterload conditions. The shortcoming of a bellows-type VAD could be handled with this simple pressure regulation system. [source]

Physiological Control of Blood Pumps Using Intrinsic Pump Parameters: A Computer Simulation Study

ARTIFICIAL ORGANS, Issue 4 2006
Guruprasad A. Giridharan
Abstract:, Implantable flow and pressure sensors, used to control rotary blood pumps, are unreliable in the long term. It is, therefore, desirable to develop a physiological control system that depends only on readily available measurements of the intrinsic pump parameters, such as measurements of the pump current, voltage, and speed (in revolutions per minute). A previously proposed ,P control method of ventricular assist devices (VADs) requires the implantation of two pressure sensors to measure the pressure difference between the left ventricle and aorta. In this article, we propose a model-based method for estimating ,P, which eliminates the need for implantable pressure sensors. The developed estimator consists of the extended Kalman filter in conjunction with the Golay,Savitzky filter. The performance of the combined estimator,VAD controller system was evaluated in computer simulations for a broad range of physical activities and varying cardiac conditions. The results show that there was no appreciable performance degradation of the estimator,controller system compared to the case when ,P is measured directly. The proposed approach effectively utilizes a VAD as both a pump and a differential pressure sensor, thus eliminating the need for dedicated implantable pressure and flow sensors. The simulation results show that different pump designs may not be equally effective at playing a dual role of a flow actuator and ,P sensor. [source]

A Blood Pressure Sensor for Long-Term Implantation

A porcine model of bladder outlet obstruction incorporating radio-telemetered cystometry

BJU INTERNATIONAL, Issue 1 2007
Matthew B. Shaw
OBJECTIVE To present a novel porcine model of bladder outlet obstruction (BOO) with a standardized bladder outlet resistance and real-time ambulatory radio-telemetered cystometry, as BOO is a common condition with many causes in both adults and children, with significant morbidity and occasional mortality, but attempts to model this condition in many animal models have the fundamental problem of standardising the degree of outlet resistance. MATERIALS AND METHODS BOO was created in nine castrated male pigs by dividing the mid-urethra; outflow was allowed through an implanted bladder drainage catheter containing a resistance valve, allowing urine to flow across the valve only when a set pressure differential was generated across the valve. An implantable radio-telemetered pressure sensor monitored the pressure within the bladder and abdominal cavity, and relayed this information to a remote computer. Four control pigs had an occluded bladder drainage catheter and pressure sensor placed, but were allowed to void normally through the native urethra. Intra-vesical pressure was monitored by telemetry, while the resistance valve was increased weekly, beginning with 2 cmH2O and ultimately reaching 10 cmH2O. The pigs were assessed using conventional cystometry under anaesthesia before death, and samples conserved in formalin for haematoxylin and eosin staining. RESULTS The pigs had radio-telemetered cystometry for a median of 26 days. All telemetry implants functioned well for the duration of the experiment, but one pig developed a urethral fistula and was excluded from the study. With BOO the bladder mass index (bladder mass/body mass × 10 000) increased from 9.7 to 20 (P = 0.004), with a significant degree of hypertrophy of the detrusor smooth muscle bundles. Obstructed bladders were significantly less compliant than control bladders (8.3 vs 22.1 mL/cmH2O, P = 0.03). Telemetric cystometry showed that there was no statistically significance difference in mean bladder pressure between obstructed and control pigs (4.8 vs 6.7 cmH2O, P = 0.7), but that each void was longer in the pigs with BOO. CONCLUSION This new model of BOO provides a method of reliably and precisely defining the bladder outlet resistance; it induces the changes classically seen with BOO, including increased bladder mass, increased smooth muscle bundle size and decreased compliance. [source]

Patient-adjusted intermittent electrostimulation for treating stress and urge urinary incontinence

BJU INTERNATIONAL, Issue 1 2004
Israel Nissenkorn
OBJECTIVE To assess the safety and efficacy of pelvic floor muscle electrostimulation (ES) in women with stress urinary incontinence (SUI) or mixed UI (MUI, urge and interstitial cystitis), using a new portable electrostimulator (Miniaturo, Biocontrol Medical Inc., Yehud, Israel) which delivers different forms of stimulation for treating these two conditions. PATIENTS AND METHODS For SUI the stimulator is activated on demand only by a sudden increase in intra-abdominal pressure; for frequency and urgency a milder, continuous ES is used. The intensity of ES can be adjusted according to the patient's sensation. Women were enrolled into the study after satisfying inclusion criteria and pad testing; 23 participated in two study groups, i.e. 16 with SUI and seven with MUI (severe frequency, urgency and urge, and mild SUI). The pelvic floor muscles were stimulated through an electrode inserted paraurethrally, positioned similarly in all patients. In patients with SUI and MUI a pressure sensor was also inserted into the rectum, to record intra-abdominal pressure. Stimulation was applied for 1,4 h in patients with SUI and for 6 h in those with MUI. The evaluation was based on urinary symptoms (frequency, urgency, leaking episodes), quality-of-life questionnaires and pad tests at baseline and during stimulation. RESULTS All patients in both groups improved significantly; of the 16 patients with SUI, nine were completely dry during ES, and the remaining seven had a reduced mean pad weight, from 23 to 6 g (74%). There was no significant reduction in pad weight after sham ES (17 g before vs 24.2 g after). In four patients with SUI who continued ES for 4 h the mean cumulative stimulation time (calculated from the stimulator memory) was 3 min (1.3% of 4 h). In the MUI group there were no leakage episodes during ES and significant reductions in voiding variables (Student's t -test) in all. The mean (Sd) voiding frequency, urinary urgency and leaking episodes decreased from 8.1 (4.2) to 1.9 (1.5), 6.4 (2.3) to 0.7 (1.3) and 2.1 (0.7) to 0.7 (0.5) (all P < 0.001), respectively. CONCLUSIONS The concept of this ES system for treating UI is promising; this study supports the efficacy of this form of ES but no conclusions about clinical efficacy are possible at this stage, and thus a trial to evaluate the safety and efficacy of this implantable device is ongoing. [source]

Factors affecting ocular rigidity in normal human eyes

ACTA OPHTHALMOLOGICA, Issue 2009
AI DASTIRIDOU
Purpose To measure the ocular rigidity coefficient and evaluate its relation with axial length (AL), age and mean systemic blood pressure (SBP). Methods Sixty three patients (63 eyes) undergoing cataract surgery, with different refractive errors and no ocular or systemic pathology were enrolled in this study. An invasive, computer controlled device comprising a microdosimetric pump and a pressure sensor, is connected to the anterior chamber under topical anaesthesia with drops. The system is used to raise the intraocular pressure (IOP) from 15 to 40mmHg, by infusing the eye with a saline solution. After each 4 ul infusion step, the IOP is continuously recorded for 2 seconds. From an initial level of 40mmHg an IOP decay curve of 1 minute is obtained. SBP and pulse rate are measured during the procedure. The rigidity coefficient is calculated by an exponential fit to the pressure volume data after correction for outflow. The study was approved by the Institutional Board and performed under the patient's informed consent. Results Mean AL was 24.8 (range 21.2-32.5). Mean age and SBP was 59 (12) years and 93.7 (10.5) mmHg respectively. The mean ocular rigidity coefficient was 0.021 (0.005) ul-1. Increasing axial length is associated with a decrease in the rigidity coefficient (r=-0.61, p<0.01). A positive correlation between the rigidity coefficient and age of the patients is found (r=0.31, p=0.01), whereas similar findings were not observed for SBP (p>0.05). Conclusion This manonetric approach of measuring ocular rigidity provides a normative database of this parameter in living human eyes. Axial length and age influence ocular rigidity. These results may have implications on tonography and ocular pulse studies. [source]

A Wet/Wet Differential Pressure Sensor for Measuring Vertical Hydraulic Gradient

Evaluation of ferromagnetic shape-memory alloys by the extended Hückel method

IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 3 2007
Kei Ehara Student Member
Abstract Ferromagnetic shape-memory alloy (SMA) are powerful candidates as actuators, pressure sensors, magnetic sensors, etc. Magnetic-field-induced strain has been observed in many ferromagnetic SMA. The magnetic-field-induced strain is a reversible transformation in the martensite phase with the magnetic field. We have investigated the property of the ferromagnetic shape-memory materials by the extended Hückel method, and estimated the ferromagnetic shape-memory of Fe,Pt and Fe,Pd alloys at high temperatures. We used two physical quantities, i.e. cohesive energy and energy fluctuation, to measure the stability of the materials. On the basis of the cohesive energy and energy fluctuation, we discuss the characteristics of ferromagnetic SMA, in which the energy fluctuation is a measure of thermal stability of the metals and/or alloys. The martensite structure is unstable, which means that the energy fluctuation has to be controlled to a small value to keep the martensite phase. Furthermore, it is estimated that the energy fluctuation is associated with the Curie temperature. The Curie temperature is an essential parameter for ferromagnetic materials. From the discussion presented above, we can propose the following: (i) Alloys possessing a low cohesive energy are associated with a high mobility of atoms and are suitable for ferromagnetic shape-memory materials; (ii) Alloys showing a low energy fluctuation show ferromagnetic shape-memory and are favored for use as memory devices. We found that I (iodine) is the best dopant for Fe,Pt ferromagnetic SMA, and Tc (technetium) is the best dopant for Fe,Pd ferromagnetic SMA. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]

Continuous monitoring of interface pressure distribution in intensive care patients for pressure ulcer prevention

JOURNAL OF ADVANCED NURSING, Issue 4 2009
Kozue Sakai
Abstract Title.,Continuous monitoring of interface pressure distribution in intensive care patients for pressure ulcer prevention. Aim., This paper is a report of a study conducted to examine whether continuous interface pressure monitoring of postoperative patients in an intensive care unit is feasible in clinical practice. Background., The interface pressure between skin and surfaces is generally evaluated for pressure ulcer prevention. However, the intensity and duration of interface pressure necessary for pressure ulcer development remains unclear because the conventional interface pressure sensors are unsuitable for continuous monitoring in clinical settings. Methods., A total of 30 postoperative patients in an intensive care unit participated in this study in 2006,2007. A sensor was built into a thermoelastic polymer mattress. The whole-body interface pressure was recorded for up to 48 hours. Pressure ulcer development was observed during the morning bed-bath. For analysis, the intensity and duration of the maximal interface pressure was evaluated. Findings., The mean age of the study group was 62·0 ± 15·4 years. Two participants developed stage I pressure ulcer and blanchable redness at the sacrum. The longest duration of pressures greater than 100 mmHg were 487·0, 273·5 and 275·7 minutes in the pressure ulcer, blanchable redness and no redness groups respectively. Conclusion., Continuous monitoring of the intensity and duration of whole-body interface pressure using the KINOTEX sensor is feasible in intensive care patients. [source]

Effect of viscoelastic properties of resilient denture liners on pressures under dentures

JOURNAL OF ORAL REHABILITATION, Issue 11 2001
N. Taguchi
In order to evaluate the influence of viscoelastic properties of resilient denture liners on the pressures under dentures, a series of creep and stress relaxation tests were carried out using a simplified mandibular edentulous model and denture model. Two diaphragm pressure sensors were attached to the edentulous model so that they contacted the residual ridge and the buccal slope. The results may be summarized as follows: (i) The use of resilient denture liners is effective for stress relief under dentures. (ii) The thickness increase of each denture liners causes the effect of stress relaxation. (iii) The material exhibited viscoelastic behaviour after applying the stress and has the ability to distribute stress or stress relaxation. It is important to understand the viscoelastic behaviours of each resilient denture liner and choose the material according to the clinical situation. The information obtained should be useful to clinicians when they select materials for their patients. [source]

Diamond as pressure sensor in high-pressure Raman spectroscopy using sapphire and other gem anvil cells

Baseline abdominal pressure and valsalva leak point pressures-correlation with clinical and urodynamic data

NEUROUROLOGY AND URODYNAMICS, Issue 1 2003
Shahar Madjar
Abstract Aims: To characterize the factors contributing to changes in baseline abdominal pressure (Pabd) and the correlation between ,VLPP, VLPPtot, and other clinical and urodynamic variables. Methods: Two hundred sixty-four female patients who had undergone an anti-incontinence procedure between February 1994 and October 1999 were retrospectively reviewed. The urodynamics performed for each patient included abdominal and vesical pressures measured in a standardized manner with the patient sitting upright and the pressure sensors maintained at the level of the symphysis pubis. VLPP was determined at bladder volumes of 200 mL during a gradually increasing Valsalva maneuver. Results: Baseline Pabd varied between 10 and 55 cm H2O (mean, 32.7,±,8.8) and were significantly correlated with patient weight (P<0.001) and with patient body mass index (P<0.001). Baseline Pabd was not found to be correlated with patient age, Baden and Walker Classification of the grading of pelvic floor prolapse, degree of incontinence (determined by the number of pads used per day), or prior surgical procedures for stress incontinence. Higher baseline Pabd were significantly correlated with the peak abdominal pressure reached during the Valsalva maneuver (P<0.0001) and with VLPPtot (P<0.0001) but not with ,VLPP. Higher VLPPtot significantly correlated with decreased age (P=0.004), less severe incontinence (P=0.004), higher peak Valsalva pressure (P<0.0001), and the ability to increase abdominal pressure for a longer period of time (time to peak Pabd during Valsalva). VLPPtot and ,VLPP had similar statistical correlation with all the clinical variables examined and neither could predict the outcome of any anti-incontinence surgery. By using a VLPP of 60 cm H2O as a cutoff to differentiate severe ISD from GSUI, 211 (67.4%) of the patients would be categorized as having ISD according to their ,VLPP compared with only 106 (40.1%) by using the VLPPtot. Conclusions: Baseline Pabd varies considerably among patients, is correlated with patient weight and habitus. In addition, it varies with both the ability to be increased for longer periods of time and with VLPPtot. Looking at VLPPtot and ,VLPP will result in a different categorization of the type of incontinence in at least 25% of patients and, thus, affect the physician's selection of an anti-incontinence procedure for an individual patient. Neurourol. Urodynam. 22:2,6, 2003. © 2003 Wiley-Liss, Inc. [source]