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Square Wave (square + wave)

Distribution by Scientific Domains

Medical Sciences	50%
Chemistry	30%

Terms modified by Square Wave

square wave pulse

square wave voltammetry

Selected Abstracts

Quantitative Studies of Metal Ion Adsorption on a Chemically Modified Carbon Surface: Adsorption of Cd(II) and Hg(II) on Glutathione Modified Carbon

ELECTROANALYSIS, Issue 8 2009
Poobalasingam Abiman
Abstract The adsorption behavior of model toxic metal cations namely Cd(II) and Hg(II) on carbon surfaces chemically modified by glutathione was investigated as a function of the concentration of Cd2+ and Hg2+ ions, time and the amount of modified carbon used. Square wave and linear sweep anodic stripping voltammetry was used to monitor the uptake of Cd(II) and Hg(II) ions respectively. Kinetic and adsorption isotherm studies reveal that both Cd(II) and Hg(II) ions undergo similar large adsorption with the modified glutathione carbon material (Glu-carbon). [source]

Diagnostic assay of chromium (VI) in the ex vivo fluid of the urine of a smoker using a fluorine-doped handmade sensor

JOURNAL OF CLINICAL LABORATORY ANALYSIS, Issue 2 2009
Suw Young Ly
Abstract A voltammetric diagnosis of a chromium (VI) ion was investigated using a fluorine-doped graphite pencil electrode. Square wave (SW) stripping working conditions were attained at a high range of 0.051,0.45,mg,L,1 and a microrange of 0.05,0.4,µg,L,1 in a 0.1,M NH4H2PO4 electrolyte solution, at a relative standard deviation of 1.68% (RSD, n=15), using 10.0,µg,L,1 Cr(VI). A fast experimental time was used only for the 120,sec SW accumulation time. An analytical detection-limit (DL) of 0.008,µg,L,1 was attained. DL appeared to be more sensitive than common voltammetric and spectrophotometric assays. The developed sensor was applied to tap water and the urine of a smoker. It was found that the methods can be applicable for in vivo fluid or medicinal diagnosis. J. Clin. Lab. Anal. 23:82,87, 2009. © 2009 Wiley-Liss, Inc. [source]

Peculiarities of Electrochemical Bismuth Film Formation in the Presence of Bromide and Heavy Metal Ions

ELECTROANALYSIS, Issue 15 2009
Giedr, Grincien
Abstract Bi films were deposited on glassy carbon electrode from solutions with and without KBr. The morphology of both types of the films was characterized by scanning electron microscopy (SEM), and their electrochemical behavior was studied by square wave (SWV) and cyclic voltammetry (CV). Bi films were also co-deposited with common analyte-heavy-metals in the presence of KBr and these films also were characterized by SEM, SWV and CV in order to understand the formation of the mixed metal films. All films studied had a different morphology. Bromide addition made the Bi films more compact and uniform, whereas Pb catalyzed Bi film deposition. [source]

How does the pitch and pattern of a signal affect auditory arousal thresholds?

JOURNAL OF SLEEP RESEARCH, Issue 2 2009
DOROTHY BRUCK
Summary How arousal thresholds vary with different sounds is a critical issue for emergency awakenings, especially as sleepers are dying in fires despite having a working smoke alarm. Previous research shows that the current high-pitched (3000+ Hz) smoke alarm signal is significantly less effective than an alternative signal, the 520 Hz square wave, in all populations tested. However, as the number of sounds tested has been small further research is needed. Here we measured auditory arousal thresholds (AATs) across signals with a range of characteristics to determine the most effective waking signal. Thirty-nine young adults participated over three nights. In Part A, nine signals were presented in stage 4 sleep with ascending decibel levels. Signals were short beeps in the low- to mid-frequency range with different spectral complexities: square waves, pure tones, whoops and white noise. Part B manipulated temporal patterns, inserting silences of 0, 10 and 21 s after each 12 s of beeps. It was found that the low-frequency (400 and 520 Hz) square waves yielded significantly lower AATs than the alternatives. A trend was found across the three temporal manipulations, with a 10 s intervening silence showing some advantage. These findings support earlier research indicating that the best sound for awakening from deep sleep is a low-frequency square wave. It is argued that the signal with the lowest response threshold when awake may be the same as the most arousing signal when asleep, especially where the sleeper processes the signal as meaningful. [source]

Application of novel dual wave meal bolus and its impact on glycated hemoglobin A1c level in children with type 1 diabetes

PEDIATRIC DIABETES, Issue 5 2009
Ewa Pa, kowska
Background: An insulin pump is an advanced technology offering new options of bolus , normal (N), dual wave (D-W) or square wave (S-W) bolus to deliver mealtime insulin. Objectives: To assess the impact of D-W/S-W boluses on metabolic control (glycated haemoglobin A1c, HbA1c) and to estimate the paediatric patients compliance with implementation of this system in daily practice. Methods: The cross-sectional study included 499 records of patients aged 0,18 yr. Data from the insulin pump memory provided information on the number of D-W/S-W boluses during a 2-wk period, the insulin requirement (U/kg/d) and the percentage of basal insulin. The HbA1c value (%) and the patient's weight were determined during medical examinations. Mealtime dose of insulin in D-W/S-W bolus was calculated based on the amount of carbohydrate and fat/protein products. Results: The number of applied D-W/S-W boluses was 16.6 ± 0.77/14 d (ranged 0,95), while 18.8% of patients did not program D-W/S-W boluses. The lowest HbA1c value was found in the group using two and/or more D-W/S-W boluses per day (p = 0.001) compared with the group administrating less than one D-W/S-W bolus/d. Patients with HbA1c level <7.5% had a statistically higher relevant number of D-W/S-W boluses, 19.55 (95% CI: 17.44,21.65) vs. 12.42 (95% CI: 10.22,14.61) (p < 0.001), while there was no correlation between the number of boluses and HbA1c in patients in the remission phase (<0.5 IU/kg/d) (r = 0.012, p = 0.930). Conclusions: Patients using at least one D-W/S-W bolus per day achieved a recommended level of HbA1c. Paediatric patients with type 1 diabetes mellitus were found to be able to apply D-W/S-W boluses in daily self-treatment process based on food counting. [source]

Enhanced mixing of Newtonian fluids in a stirred vessel using impeller speed modulation

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2009
Wei M. Yek
Abstract This paper reports on an experimental study of mixing intensification using speed modulation of a six-blade Rushton turbine in a stirred vessel. Mixing times were measured using a non-intrusive technique based on direct visualisation of an acid-base reaction in a Newtonian fluid. The impeller speed modulation was achieved by using two waveforms: a square wave and a sine wave. The amplitude was fixed between a maximum Reynolds number of Remax,=,60 and minimum Reynolds numbers of Remin,=,40 or 30. The wave periods were varied (10, 20, or 40,s) in order to compare the effects of unsteady stirring on mixing performance. It was observed that a square wave protocol with the shortest wave period and the larger amplitude resulted in the shortest time to destroy the observed isolated mixing regions (IMRs), which are known to exist in stirred vessels operating at low Reynolds number. However, the sine wave protocol led to a slow diffusive mechanism in which IMR structures reached an asymptotic volume and remained visible even after several hours. The results are presented and discussed using digital photographs taken at different time intervals during experimentation. Ce papier présente une étude experimentale concernant l'intensification du mélange en modulant la vitesse d'une turbine de type Rushton a six palettes dans une cuve agitée. Les temps de mélanges sont mesurés avec une technique non-intrusive basée sur la visualisation directe d'une réaction acide-base au sein d'un fluide Newtonien. La modulation de la vitesse de la turbine a été realisée en utilisant deux formes d'ondes: une onde carrée et une onde sinusoidale. L'amplitude de chaque onde a été fixée entre un nombre de Reynolds maximal de Remax,=,60 et un nombre de Reynolds minimal de Remin,=,40 ou 30. Les périodes des ondes étaient variées (10, 20 ou 40,s) dans le but de comparer les effets du mélange non-stationnaire sur les performances du systeme. Il a été observé que le protocole suivant l'onde carrée avec la periode la plus courte et l'amplitude la plus large produisait le temps le plus court necessaire pour la destruction des zones de mélanges isolées (IMRs), dont l'éxistense est connue dans les cuves a mélange opérant aux nombres de Reynolds bas. Toutefois, le protocol suivant une onde sinusoidale a conduit a un mechanisme de diffusion lent dans lequel les IMRs atteignies un volume symptotique et sont restées visibles après plusieurs heures. Les résultats sont présentés and discutés en utilisant des photographes digitales prises à des intervales de temps differents durant les éxperiences. [source]

The effect of electrical and mechanical stimulation on the regenerating rodent facial nerve,

THE LARYNGOSCOPE, Issue 6 2010
Tessa Hadlock MD
Abstract Objectives/Hypothesis: Investigators have long sought realistic methods to accelerate regeneration following nerve injury. Herein, we investigated the degree to which manual target muscle manipulation and brief electrical stimulation of the facial nerve, alone or in combination, affects recovery following rat facial nerve injury. Study Design: Prospective, randomized animal study. Methods: Sixty rats were randomized to three groups: brief electrical stimulation (BES), mechanical stimulation of the whisker pad (MEC), or both (COMBO). Animals underwent facial nerve transection and immediate microsurgical repair. In BES and COMBO groups, transection was preceded by 1-hour (3 V, 20 Hz square wave) electrical stimulation. Animals were tested weekly, with 5-minute recording sessions of whisker movement. In the MEC and COMBO groups, animals received 5 minutes of daily massage to the left whisker pad throughout the recovery period. Whisking behavior was analyzed for comparisons. Results: The BES and MEC groups demonstrated improved functional recovery in all whisking parameters compared with the COMBO group or historical controls at most time points between postoperative weeks 1 and 7. After 12 weeks, functional recovery remained superior in the BES and MEC groups compared with the COMBO and control groups, although the effect was no longer statistically significant. Conclusions: We observed an accelerative recovery effect of either electrical nerve stimulation or massage of the whisker pad on whisking behavior. The combination of both interventions had a negating effect on the acceleration of recovery. The potential clinical utility of these modalities bears consideration, and their negating interaction warrants further study. Laryngoscope, 2010 [source]

ELF magnetic fields increase amino acid uptake into Vicia faba L. Roots and Alter Ion movement across the plasma membrane

BIOELECTROMAGNETICS, Issue 5 2002
B.C. Stange
Abstract Vicia faba seedlings, subjected to a 10 µT 50 Hz square wave magnetic field for 40 min together with a radioactive pulse, showed a marked increase in amino acid uptake into intact roots. A more modest increase was observed with a 100 µT 50 Hz square wave. An increase in media conductivity at low field intensities from 10 µT 50 Hz square wave, 100 µT 50 Hz sine wave, and 100 µT 60 Hz square wave fields, indicated an alteration in the movement of ions across the plasma membrane, most likely due to an increase in net outflow of ions from the root cells. Similarly, marked elevation in media pH, indicating increased alkalinity, was observed at 10 and 100µT for both square and sine waves at both 50 and 60 Hz. Our data would indicate that low magnetic field intensities of 10 and 100 µT at 50 or 60 Hz can alter membrane transport processes in root tips. Bioelectromagnetics 23:347,354, 2002. © 2002 Wiley-Liss, Inc. [source]

Magnetic field exposure and behavioral monitoring system

BIOELECTROMAGNETICS, Issue 6 2001
A.W. Thomas
Abstract To maximize the availability and usefulness of a small magnetic field exposure laboratory, we designed a magnetic field exposure system that has been used to test human subjects, caged or confined animals, and cell cultures. The magnetic field exposure system consists of three orthogonal pairs of coils 2 m square,×,1 m separation, 1.751 m,×,0.875 m separation, and 1.5 m,×,0.75 m separation. Each coil consisted of ten turns of insulated 8 gauge stranded copper conductor. Each of the pairs were driven by a constant-current amplifier via digital to analog (D/A) converter. A 9 pole zero-gain active Bessel low-pass filter (1 kHz corner frequency) before the amplifier input attenuated the expected high frequencies generated by the D/A conversion. The magnetic field was monitored with a 3D fluxgate magnetometer (0,3 kHz, ±,1 mT) through an analog to digital converter. Behavioral monitoring utilized two monochrome video cameras (viewing the coil center vertically and horizontally), both of which could be video recorded and real-time digitally Moving Picture Experts Group (MPEG) encoded to CD-ROM. Human postural sway (standing balance) was monitored with a 3D forceplate mounted on the floor, connected to an analog to digital converter. Lighting was provided by 12 offset overhead dimmable fluorescent track lights and monitored using a digitally connected spectroradiometer. The dc resistance, inductance of each coil pair connected in series were 1.5 m coil (0.27 ,, 1.2 mH), 1.75 m coil (0.32 ,, 1.4 mH), and 2 m coil (0.38 ,, 1.6 mH). The frequency response of the 1.5 m coil set was 500 Hz at ±,463 ,T, 1 kHz at ±,232 ,T, 150 ,s rise time from ,200 ,Tpk to +,200 ,Tpk (square wave) and is limited by the maximum voltage (,±,146 V) of the amplifier (Bessel filter bypassed). Bioelectromagnetics 22:401,407, 2001. © 2001 Wiley-Liss, Inc. [source]