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1.
Encephale ; 45(3): 239-244, 2019 Jun.
Article in French | MEDLINE | ID: mdl-30722937

ABSTRACT

OBJECTIVES: The patient with bipolar disorder and his family are caught in a reciprocal interaction: on one hand, the pathology leads to family sufferings and on the other hand, family behavior affects the disease of the patient and its development. Therefore, it seems of core importance that the psychologist should work with the family on their perception of bipolar disorder, that is to say, on their knowledge and psychological representations of the pathology. The aim of our study is to assess whether the initial perception of bipolar disorder evolves after a therapeutic education program. METHOD: Our research was conducted at the Bipolar Expertise Centre in Bordeaux/Centre Expert Bipolaire in Bordeaux on a sample of 145 participants (78patients and 67 family caregivers). They were all interviewed before and after the therapeutic education program (12 sessions in 6months). The Brief Illness Perception Questionnaire Revised (Moss-Morris, 2002) measures the perception of bipolar disorder and the BP Quizz (Fondation Fondamental) assesses the degree of knowledge of the disorder. RESULTS: Results show that therapeutic education helps families to level up their knowledge about bipolar disorder. Furthermore, representations on bipolar disorder have globally changed so that on average, bipolar disorder is viewed as less threatening by families after 12 sessions of therapeutic education. More precisely, after the program, families have a better understanding and a better insight of the disorder, which is then perceived as being less severe. On the emotional level, anxiety and stress have decreased. So there are an increase of knowledge and a change in perception. CONCLUSION: Our study shows that the therapeutic education program enables families to change their perception of the disease, that is to say, their knowledge but also their representations of the disease, which is a fundamental element according to the models of therapeutic education. Our results point out one of the active processes of therapeutic education at work in the sessions: in the perception of the disease, which is composed of both knowledge and representations of the disease, just a change in representations constitutes a lever for therapeutic education. Therefore, working on representations should be a therapeutic target. As a conclusion, we can say that therapeutic education of families cannot be reduced to an educational dimension which would only consist of gaining knowledge. Then, the right posture of the psychologist is to hold each participant's own development and changing process of representations.


Subject(s)
Bipolar Disorder/psychology , Bipolar Disorder/therapy , Caregivers/psychology , Family Therapy/methods , Patient Education as Topic/methods , Psychotherapy/methods , Adult , Aged , Anxiety/psychology , Emotions , Female , Health Knowledge, Attitudes, Practice , Humans , Male , Middle Aged , Surveys and Questionnaires
2.
Unfallchirurg ; 121(7): 516-529, 2018 Jul.
Article in German | MEDLINE | ID: mdl-29797031

ABSTRACT

INTRODUCTION: The effectiveness of a tourniquet in the case of life-threatening hemorrhages of the extremities is well recognized and led to the recommendations on "Tourniquet" of the German Society of Anaesthesiology and Intensive Care (DGAI) in 2016. The aim of this systematic review was to re-evaluate the current medical literature in relation to the published DGAI recommendations. MATERIAL AND METHODS: Based on the analysis of all studies published from January 2015 until January 2018 in the PubMed databases, the publicized recommendations for action on "Tourniquet" of the DGAI were critically re-evaluated. For this purpose, 17 questions on 6 subjects were formulated in advance. The systematic review followed the PRISMA recommendations and is registered in PROSPERO (International prospective register of systematic reviews, Reg.-ID: CRD42018091528). RESULTS: Of the 284 studies identified with the keywords tourniquet and trauma in the period from January 2015 to January 2018 in PubMed, 50 original papers discussing the prehospital application of tourniquet for life-threatening hemorrhage of the extremities were included. The overall level of evidence is low. No article addressed any of the formulated questions with a prospective randomized interventional study. Scientific deductions could be found only in an indirect way in a descriptive manner. CONCLUSION: The 50 original articles included in this qualitative, systematic review revealed that the recommendations "Tourniquet" of the DGAI published in 2016 are mostly still up to date despite an inhomogeneous study situation. A deviation occurred in the conversion of a tourniquet but due to the short prehospital treatment time in the civilian setting this is of little importance; however, in the future a strict distinction should be made between tourniquets which were placed for tactical reasons and those placed as a medical necessity.


Subject(s)
Emergency Medical Services , Hemorrhage , Tourniquets , Extremities , Hemorrhage/therapy , Humans , Prospective Studies
3.
Scand J Trauma Resusc Emerg Med ; 24: 75, 2016 May 20.
Article in English | MEDLINE | ID: mdl-27206483

ABSTRACT

BACKGROUND: As a part of the European Union Naval Force - Mediterranean Operation Sophia (EUNAVFOR Med), the Federal Republic of Germany is contributing to avoid further loss of lives at sea by supplying two naval vessels. In the study presented here we analyse the medical requirements of such rescue missions, as well as the potential benefits of various additional monitoring devices in identifying sick/injured refugees within the primary onboard medical assessment process. METHODS: Retrospective analysis of the data collected between May - September 2015 from a German Naval Force frigate. Initial data collection focused on the primary medical assessment and treatment process of refugees rescued from distress at sea. Descriptive statistics, uni- and multivariate analysis were performed. The study has received a positive vote from the Ethics Commission of the University of Ulm, Germany (request no. 284/15) and has been registered in the German Register of Clinical Studies (no. DRKS00009535). RESULTS: A total of 2656 refugees had been rescued. 16.9 % of them were classified as "medical treatment required" within the initial onboard medical assessment process. In addition to the clinical assessment by an emergency physician, pulse rate (PR), core body temperature (CBT) and oxygen saturation (SpO2) were evaluated. Sick/injured refugees displayed a statistically significant higher PR (114/min vs. 107/min; p < .001) and CBT (37.1 °C vs. 36.7 °C; p < .001). There was no statistically significant difference in SpO2-values. The same results were found for the subgroup of patients classified as "treatment at emergency hospital required". However, a much larger difference of the mean PR and CBT (35/min resp. 1.8 °C) was found when examining the subgroups of the corresponding refugee boats. A cut-off value of clinical importance could not be found. Predominant diagnoses have been dermatological diseases (55.4), followed by internal diseases (27.7) and trauma (12.1 %). None of the refugees classified as "healthy" within the primary medical assessment process changed to "medical treatment required" during further observation. CONCLUSIONS: The initial medical assessment by an emergency physician has proved successful. PR, CBT and SpO2 didn't have any clinical impact to improve the identification of sick/injured refugees within the primary onboard assessment process.


Subject(s)
Emergency Medical Services/methods , Health Status Disparities , Mental Disorders/therapy , Refugees , Registries , Relief Work/organization & administration , Adolescent , Adult , Aged , Child , Child, Preschool , Cross-Sectional Studies , Female , Germany/epidemiology , Humans , Infant , Male , Mediterranean Sea/ethnology , Mental Disorders/ethnology , Middle Aged , Retrospective Studies , Risk Factors , Socioeconomic Factors , Triage , Young Adult
4.
Anaesthesist ; 63(5): 439-50, 2014 May.
Article in German | MEDLINE | ID: mdl-24805284

ABSTRACT

Blast injuries may result from a variety of causes but the biomechanical impact and pathophysiological consequences do not differ between domestic or industrial accidents or even terrorist attacks. However, this differentiation relevantly affects the tactical procedures of the rescue teams. Focusing on further detonations, top priority is given to the personal safety of all rescue workers. The rareness of blast injuries in a civilian setting results in a lack of experience on the one hand but on the other hand the complexity of blast injuries to the human body places high demands on the knowledge and skills of the entire rescue team for competent treatment. The purpose of this article is to explain the physicochemical principles of explosions and to convey tactical and medical knowledge to emergency medical services.


Subject(s)
Blast Injuries/therapy , Emergency Medical Services , Head Injuries, Penetrating/therapy , Humans , Mass Casualty Incidents , Terrorism
5.
Transl Psychiatry ; 2: e202, 2012 Dec 11.
Article in English | MEDLINE | ID: mdl-23233021

ABSTRACT

Gamma aminobutyric acid (GABA)-mediated synapses and the oscillations they orchestrate are altered in autism. GABA-acting benzodiazepines exert in some patients with autism paradoxical effects, raising the possibility that like in epilepsies, GABA excites neurons because of elevated intracellular concentrations of chloride. Following a successful pilot study,(1) we have now performed a double-blind clinical trial using the diuretic, chloride-importer antagonist bumetanide that reduces intracellular chloride reinforcing GABAergic inhibition. Sixty children with autism or Asperger syndrome (3-11 years old) received for 3 months placebo or bumetanide (1 mg daily), followed by 1-month wash out. Determination of the severity of autism was made with video films at day 0 (D0) and D90 by blind, independent evaluators. Bumetanide reduced significantly the Childhood Autism Rating Scale (CARS) (D90-D0; P<0.004 treated vs placebo), Clinical Global Impressions (P<0.017 treated vs placebo) and Autism Diagnostic Observation Schedule values when the most severe cases (CARS values above the mean ± s.d.; n=9) were removed (Wilcoxon test: P-value=0.031; Student's t-test: P-value=0.017). Side effects were restricted to an occasional mild hypokalaemia (3.0-3.5 mM l(-1) K(+)) that was treated with supplemental potassium. In a companion study, chronic bumetanide treatment significantly improved accuracy in facial emotional labelling, and increased brain activation in areas involved in social and emotional perception (Hadjikhani et al., submitted). Therefore, bumetanide is a promising novel therapeutic agent to treat autism. Larger trials are warranted to better determine the population best suited for this treatment.


Subject(s)
Autistic Disorder/drug therapy , Bumetanide/therapeutic use , GABA Modulators/therapeutic use , Asperger Syndrome/drug therapy , Autistic Disorder/diagnosis , Autistic Disorder/psychology , Child , Child, Preschool , Double-Blind Method , Female , Humans , Male , Severity of Illness Index , Treatment Outcome
6.
Anal Chem ; 82(18): 7542-9, 2010 Sep 15.
Article in English | MEDLINE | ID: mdl-20715842

ABSTRACT

Liquid-phase operation of resonant cantilevers vibrating in an out-of-plane flexural mode has to date been limited by the considerable fluid damping and the resulting low quality factors (Q factors). To reduce fluid damping in liquids and to improve the detection limit for liquid-phase sensing applications, resonant cantilever transducers vibrating in their in-plane rather than their out-of-plane flexural resonant mode have been fabricated and shown to have Q factors up to 67 in water (up to 4300 in air). In the present work, resonant cantilevers, thermally excited in an in-plane flexural mode, are investigated and applied as sensors for volatile organic compounds in water. The cantilevers are fabricated using a complementary metal oxide semiconductor (CMOS) compatible fabrication process based on bulk micromachining. The devices were coated with chemically sensitive polymers allowing for analyte sorption into the polymer. Poly(isobutylene) (PIB) and poly(ethylene-co-propylene) (EPCO) were investigated as sensitive layers with seven different analytes screened with PIB and 12 analytes tested with EPCO. Analyte concentrations in the range of 1-100 ppm have been measured in the present experiments, and detection limits in the parts per billion concentration range have been estimated for the polymer-coated cantilevers exposed to volatile organics in water. These results demonstrate significantly improved sensing properties in liquids and indicate the potential of cantilever-type mass-sensitive chemical sensors operating in their in-plane rather than out-of-plane flexural modes.


Subject(s)
Chemistry Techniques, Analytical/instrumentation , Organic Chemicals/analysis , Organic Chemicals/chemistry , Limit of Detection , Polymers/chemistry , Temperature , Volatilization , Water/chemistry
7.
Biosens Bioelectron ; 18(11): 1399-406, 2003 Oct 01.
Article in English | MEDLINE | ID: mdl-12896842

ABSTRACT

The aim of this work is to study the effect of operating frequency, piezoelectric substrate and waveguide layer thickness on the sensitivity of the acoustic waveguide sensor during the specific binding of an antibody by a protein. Shear horizontal (SH) wave devices consisting of (a) a LiTaO3 substrate operating at 104 MHz, (b) a quartz substrate operating at 108 MHz and (c) a quartz substrate operating at 155 MHz were coated with a photoresist polymer layer in order to produce acoustic waveguide devices supporting a Love wave. The effect of the thickness of the polymer layer on the Love wave was assessed by measuring the amplitude and phase of the wave before and after coating. The sensitivity of the above three biosensors was compared during the detection of the specific binding of different concentrations of Immunoglobulin G in the range of 0.7-667 nM to a protein A modified surface. Results indicate that the thickness of the polymer guiding layer is critical for obtaining the maximum sensitivity for a given geometry but a trade-off has to be made between the theoretically determined optimum thickness for waveguiding and the device insertion loss. It was also found that increasing the frequency of operation results in a further increase in the device sensitivity to protein detection.


Subject(s)
Acoustics/instrumentation , Biosensing Techniques/instrumentation , Equipment Failure Analysis/methods , Immunoassay/instrumentation , Immunoglobulin G/analysis , Immunoglobulin G/chemistry , Staphylococcal Protein A/chemistry , Adsorption , Biosensing Techniques/methods , Equipment Design , Immunoassay/methods , Protein Binding , Radio Waves , Reproducibility of Results , Sensitivity and Specificity
8.
Anal Chem ; 73(24): 5937-44, 2001 Dec 15.
Article in English | MEDLINE | ID: mdl-11791563

ABSTRACT

The design and performance of guided shear horizontal surface acoustic wave (guided SH-SAW) devices on LiTaO3 substrates are investigated for high-sensitivity chemical and biochemical sensors in liquids. Despite their structural similarity to Rayleigh SAW, SH-SAWs often propagate slightly deeper within the substrate, hence preventing the implementation of high-sensitivity detectors. The device sensitivity to mass and viscoelastic loading is increased using a thin guiding layer on the device surface. Because of their relatively low shear wave velocity, various polymers including poly(methyl methacrylate) (PMMA) and cyanoethyl cellulose (cured or cross-linked) are investigated as the guiding layers to trap the acoustic energy near the sensing surface. The devices have been tested in biosensing and chemical sensing experiments. Suitable design principles for these applications are discussed with regard to wave guidance, electrical passivation of the interdigital transducers from the liquid environments, acoustic loss, and sensor signal distortion. In biosensing experiments, using near-optimal PMMA thickness of approximately 2 microm, mass sensitivity greater than 1500 Hz/(ng/mm2) is demonstrated, resulting in a minimum detection limit less than 20 pg/mm2. For chemical sensor experiments, it is found that optimal waveguide thickness must be modified to account for the chemically sensitive layer which also acts to guide the SH-SAW. A detection limit of 780 (3 x peak-to-peak noise) or 180 ppb (3 x rms noise) is estimated from the present measurements for some organic compounds in water.


Subject(s)
Acoustics , Biochemistry/instrumentation , Chemistry Techniques, Analytical/instrumentation , Algorithms , Biosensing Techniques , Immunoglobulin G/analysis , Indicators and Reagents , Polymers/analysis , Reproducibility of Results , Serum Albumin, Bovine/analysis
9.
Anal Chem ; 72(20): 4888-98, 2000 Oct 15.
Article in English | MEDLINE | ID: mdl-11055705

ABSTRACT

The selection of sensitive coatings is a critical task in the design and implementation of chemical sensors using coated thickness shear mode quartz crystal resonators (QCRs) for detection in liquid environments. This design or selection is performed through a study of the sorption process in terms of the partition coefficients of the analytes in the coatings. The partition coefficient, which is controlled by the chemical and physical properties of the coating materials, determines the inherent selectivity and sensitivity toward analyte molecules. The selection of the coatings is logically determined by the interactions between coating and target analyte molecules, but can also be made through a systematic variation of the coating's properties. The determination of the partition coefficients is only accurate if all contributions to the total measured frequency shifts, deltafs, of the coated QCR can be established. While mass loading is often assumed to be the dominant factor used in determining partition coefficients, viscoelastic effects may also contribute to deltafs. Both the effect of viscoelastic properties and the effect of mass loading on the sensor responses are investigated by using a network analyzer and oscillator circuit and by characterizing the total mechanical impedance of the loaded sensor. Different types of coatings including rubbery and glassy polymers are investigated, and the targeted analytes include classes of polar compounds (methanol), nonpolar compounds (toluene, xylenes), and chlorinated hydrocarbons (trichloroethylene, tetrachloroethylene, etc). It is seen that changes in viscoelastic properties due to analyte sorption may be significant enough to place the sensor in the nongravimetric regime. However, for most applications involving the detection of relatively low concentrations of organic compounds and the use of acoustically thin films, changes in the complex shear modulus of the coatings contribute less than 5% of the total shift in the series resonant frequency, depending on the coating. In that case, the measured deltafs and, hence, the calculated approximate classification and selection of the coatings for operation in a complex solution of water/analyte molecules.

10.
Anal Chem ; 71(22): 5064-8, 1999 Nov 15.
Article in English | MEDLINE | ID: mdl-10575962

ABSTRACT

Acoustic plate modes (APM) on various quartz substrates have been investigated in order to determine their usefulness for liquid-sensing applications. The modes have been characterized in terms of their mass sensitivity, mode separation, temperature sensitivity, and reproducibility of the experimental results. Promising characteristics are found for rotated Y-cuts of quartz with the direction of acoustic mode propagation being perpendicular to the X-axis of the quartz crystal. Experiments on the detection of immunochemical reactions are performed using different quartz APM sensors, and the results are compared to similar experiments utilizing APM devices on ZX-LiNbO3.


Subject(s)
Biosensing Techniques , Animals , Horses , Immunochemistry , Immunoglobulin G/analysis , Quartz , Rabbits , Rotation , Temperature
11.
Article in English | MEDLINE | ID: mdl-18244346

ABSTRACT

Using periodic gratings etched into the surface of a piezoelectric plate, surface acoustic waves (SAW) can be converted into bulk waves and vice versa with high efficiency. If parallel grating structures are fabricated on opposite surfaces of a piezoelectric plate, a SAW also can be directed from one surface to the other. Using such structures, acoustic wave-based sensors can be designed that utilize SAW for the detection of chemical analytes on an electrode-free surface, i.e., the back surface. As a result, spurious sensor response and electrode aging that may occur when a chemical analyte comes in contact with the transducers are minimized. The design principles of these grating-based SAW sensors are explained, and the mass sensitivity is investigated using chemical vapor deposited thin polymer films, a type of material used in many practical chemical sensor applications. Experimental results are presented for the detection of nitrogen dioxide (NO(2 )) in sub-ppm concentrations.

12.
Anal Chem ; 69(16): 3321-8, 1997 Aug 15.
Article in English | MEDLINE | ID: mdl-9271071

ABSTRACT

A detailed understanding of the interaction of proteins with artificial surfaces is essential for many applications in medicine and biochemistry. The affinity of surfaces toward proteins may, for instance, remove pharmacological proteins from media or control the adherence of pathogenic bacteria to protheses. Only a few analytical techniques now exist that can be used to study the binding process in real time, using unlabeled proteins. By investigating the adsorption kinetics of fibrinogen at differently terminated self-assembled monolayers (SAMs) of alkanethiols on thin gold films, it is demonstrated that acoustic plate-mode sensors are a promising analytical tool for studying the adsorption of proteins. In agreement with previous studies for fibrinogen, it is shown in situ that hexa(ethylene glycol)-terminated SAMs (HS(CH2)11 (OCH2CH2)6OH) exhibit very low protein adsorption and that methyl-terminated SAMs (HS(CH2)11CH3) tend to absorb large amounts of protein nonspecifically. The observed adsorption kinetics deviate from classical Langmuir behavior; these kinetics are compatible with a mechanism that involves an unfolding of fibrinogen after adsorption. Film quality is controlled by IR, XPS, and contact angle measurements.


Subject(s)
Proteins/analysis , Adsorption , Biosensing Techniques , Fibrinogen/analysis , Fibrinogen/chemistry , Kinetics , Models, Chemical , Proteins/chemistry , Ribonuclease, Pancreatic/analysis , Ribonuclease, Pancreatic/chemistry , Surface Properties
13.
Anal Chem ; 68(1): 176-82, 1996 Jan 01.
Article in English | MEDLINE | ID: mdl-8779430

ABSTRACT

Previous studies of acoustic plate modes on ZX-LiNbO3 have indicated that practical mass-sensitive immunosensors can be implemented by using devices with higher frequencies of operation and/or by improving techniques for the immobilization of antibodies. However, it is also known from these studies that the viscoelastic properties of aminosilane films, used for the covalent immobilization of antibodies on the crystal surface, cannot be ignored in the sensor response. In the present work, in an attempt to study the effect of viscoelasticity of the binding film, three different films with different viscoelasticity and binding capacities, an aminosilane, a dextran, and a poly-(etherurethane)-based immunosorbent (XP-5), were prepared on the sensor surface for the immobilization of antibodies. Immunochemical reactions were monitored by the acoustic plate mode sensor at three different frequencies, thus allowing the direct observation of the frequency dependence of mass sensitivity with different films. Depending on the type of immunosorbent, the sensitivity at the third harmonic was enhanced by a factor of 2-5 with respect to the fundamental response. A third acoustic mode at a closely spaced frequency to the third harmonic yielded lower sensitivity values, which indicates that sensitivity depends not only on the frequency of device operation but also on particle displacement amplitude and components of the selected wave. Since antigen binding capacities of the different immunosorbents were determined independently by a modified ELISA test, sensor responses can also be correlated to the immunosorbent structure, and hence the viscoelastic properties. A dual delay line configuration was used which compensates for second-order effects such as temperature variations and nonspecific adsorption.


Subject(s)
Enzyme-Linked Immunosorbent Assay/methods , Immunosorbents/chemistry , Antibodies/analysis , Antibodies/isolation & purification , Enzyme-Linked Immunosorbent Assay/instrumentation , Evaluation Studies as Topic
14.
Appl Biochem Biotechnol ; 48(2): 117-23, 1994 Aug.
Article in English | MEDLINE | ID: mdl-7944350

ABSTRACT

In order to detect low levels of enzyme activity, specifically glucose oxidase, in biological samples, an immunoenzymatic assay was developed since currently available methods could not be used because of either their lack of sensitivity or the conditions prevailing in our samples: turbidity of the medium, presence of redox systems other than glucose oxidase, and high concentration of proteins. The principle of the method is to coat a polystyrene surface with a fragment Fc-specific anti-IgG, then with an antibody directed against the looked-for enzyme, which is simultaneously the antigen and the enzyme activity required for immunoenzymatic detection. We applied this concept to biological samples after glucose oxidase administration to mice. This method achieves specificity and sensitivity (20 ng/mL or 1 ng) with samples of biological origin. No marker is needed since the antigen itself possesses an enzyme activity. This method, which requires a small sample volume (50 microL, 20 microL, if necessary), can be extended easily to the many enzymes currently used as markers. It could also be applied to the native enzymes of medical interest for which antibodies and a colorimetric reaction are available.


Subject(s)
Glucose Oxidase/analysis , Immunoenzyme Techniques , Animals , Female , Glucose Oxidase/pharmacokinetics , Immunoenzyme Techniques/statistics & numerical data , Mice , Polystyrenes , Sensitivity and Specificity , Tissue Distribution
15.
Article in English | MEDLINE | ID: mdl-18263164

ABSTRACT

The temperature dependence of acoustic plate mode (APM) devices used as probes for dilute electrolytes is described. Specifically, the probe responses that consist of the frequency change and device loss were studied for dilute aqueous solutions of alkali metal ions. It is shown that by integrating the temperature dependence of the APM probe responses with pattern recognition techniques, valuable information about the solutions can be obtained that include identification and quantification. A preliminary investigation of the feasibility of identifying binary mixtures of the alkali metal ion solutions using only the temperature responses showed good results.

16.
Article in English | MEDLINE | ID: mdl-18263208

ABSTRACT

Cochlear prosthesis systems for postlingually deaf individuals (those who have become deaf due to disease or injury after having developed mature speech capability) are considered. These systems require the surgical implantation of an array of electrodes within the cochlea and are driven by processed sound signals from outside the body. A system that uses an analog signal approach for transcutaneous transfer of six processed speech data channels using frequency multiplexing is described. The system utilizes a filterbank of six narrowband surface acoustic wave (SAW) filters in the range 72-78 MHz with a 1.2-MHz channel spacing to multiplex the six carrier signals, frequency modulated, by the processed speech signals, onto a composite signal. The same SAW filters are used in the receiver filterbank for signal separation, but are housed in a miniaturized package. The system includes a portable transmitter and a receiver package which is to be implanted in the patient. The implanted circuits are supplied exclusively from power transferred from outside the body via a separate 10-MHz transcutaneous link.

17.
Article in English | MEDLINE | ID: mdl-18267664

ABSTRACT

Surface loading of a piezoelectric crystal supporting acoustic plate modes (APMs) by a dilute conductive liquid is analyzed using a perturbation theory. The formulation of the problem is such that only the electrical loading is relevant, and the mass loading and viscous entrainment caused by the solute are ignored. The perturbation in the propagation characteristics is then obtained relative to the solvent and is described in terms of the coupling coefficient, the capacitive loading, and the conductivity of the liquid. The results are compared to measurements made on Z-cut X-propagating LiNbO(3 ) APM device loaded with various conductive liquids of different concentrations. While an interpretation of the results can be given on the use of the APM device as a detector of the liquid properties, it is shown that a conductive liquid loading of the piezoelectric surface can be used as a means of assessing the electromechanical coupling coefficient of APMs.

18.
Article in English | MEDLINE | ID: mdl-18267587

ABSTRACT

A theory describing the acoustoionic interaction of shear horizontal (SH) surface waves with viscous conductive ionic liquid is presented. A Green's function formulation that accounts for the acoustoelectric interaction with ions and dipoles in the solution is obtained for the surface potential in terms of the liquid and piezoelectric crystal parameters. For dilute ionic solutions, simple closed-form expressions for the velocity change and attenuation are obtained in terms of liquid conductivity and dielectric constant and the piezoelectric coupling coefficient. It is shown that SH surface waves in particular and acoustic waves in general can be used to perform microanalysis of dilute ionic solutions, detecting conductivity, dielectric constant, and relaxation frequency. The analysis, which was done for a simple crystal class, the hexagonal (6 mm), shows results which compare very well with exact numerical computations.

19.
Article in English | MEDLINE | ID: mdl-18285053

ABSTRACT

An analytical solution for the resonance condition of a piezoelectric quartz resonator with one surface in contact with a viscous conductive liquid is presented. The characteristic equation that describes the resonance condition and accounts for all interactions including acoustoelectric interactions with ions and dipoles in the solution is obtained in terms of the crystal and liquid parameters. A simple expression for the change in the resonance frequency is obtained. For viscous nonconductive solutions, the frequency change is reduced to a relationship in terms of the liquid density and viscosity. For dilute conductive liquid, the change in frequency is derived in terms of the solution conductivity and dielectric constant. The boundary conditions for the problem are defined with and without the electrical effects of electrodes. Experiments were conducted with various viscous and conductive chemical liquids using a fabricated miniature liquid flow cell containing an AT-cut quartz crystal resonator. The results, which show good agreement with the theory, on the use of quartz crystal resonators as conductivity and/or viscosity sensors are reported.

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