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Simultaneous Measurement (simultaneous + measurement)
Selected AbstractsSimultaneous Measurement of Particle Size and Particle Velocity by the Spatial Filtering Technique,PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 6 2002Dieter Petrak Abstract The objective of this study was to compare the measuring results of a fiber-optical probe based on a modified spatial filtering technique with given size distributions of different test powders and also with particle velocity values of laser Doppler measurements. Fiber-optical spatial filtering velocimetry was modified by fiber-optical spot scanning in order to determine simultaneously the size and the velocity of particles. The fiber-optical probe system can be used as an in-line measuring device for sizing of particles in different technical applications. Spherical test particles were narrow-sized glass beads in the range 30,100,,m and irregularly shaped test particles were limestone particles in the range 10,600,,m. Particles were dispersed by a brush disperser and the measurements were carried out at a fixed position in a free particle-laden air stream. Owing to the measurement of chord lengths and to the influence of diffraction and divergent angle, the probe results show differences from the given test particle sizes. Owing to the particle-probe collisions, the mean velocity determined by the probe is smaller than the laser Doppler mean velocity. [source] Simultaneous Measurements of Ion Temperature by Segmented Tunnel and Katsumata ProbeCONTRIBUTIONS TO PLASMA PHYSICS, Issue 5-7 2008J. Adámek Abstract Simultaneous measurements of the ion temperature by the segmented tunnel and Katsumata probe in the CASTOR tokamak are reported. The segmented tunnel probe measures two ion saturation currents Iseg 1, Iseg 2 towards two segments of the tunnel. The axis of the tunnel is aligned with the total magnetic field. The value of the ratio of these two currents combined with the results of the PIC modeling provides the ion temperature. Design and experimental arrangement of the Katsumata probe enable us to measure the pure ion current by sweeping the applied voltage. The ion temperature is then estimated from the exponential part of the measured I , V characteristic. Simultaneous measurements of the ion temperature by the segmented tunnel and Katsumata probe agree within a few eV. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Structural Phase Transitions of Aliphatic Nylons Viewed from the Simultaneous Measurements of WAXD and SAXSMACROMOLECULAR SYMPOSIA, Issue 1 2006Kohji Tashiro Abstract Structural changes occurring in the high temperature region of doubly-oriented nylon 10/10 sample have been investigated through the temperature-dependent simultaneous measurements of wide-angle and small-angle X-ray scatterings, and the results were compared with the infrared spectral data as well as the molecular dynamics simulation results. In the Brill transition region of 150,180,°C the methylene segments are conformationally disordered with keeping the intermolecular hydrogen bonds. During this phase transition the stacked lamellar structure did not change very much: the lamellae are tilted by ca. 34° from the draw axis and the long period is almost 160 Ĺ. In the temperature region immediately below the melting point the molecular chains were found to be contracted by ca. 10% the original repeating period and the intermolecular hydrogen bonds were almost broken, causing the violent rotational and translational motions of the chains around the chain axis. At the same time the long period increased remarkably from 160 Ĺ to 410 Ĺ and the originally tilted lamellae stood up in parallel to the draw axis. [source] Structural Study on Water-induced Phase Transitions of Poly(ethylene imine) as Viewed from the Simultaneous Measurements of Wide-Angle X-ray Diffractions and DSC ThermogramsMACROMOLECULAR SYMPOSIA, Issue 1 2006Tomoko Hashida Abstract Thermal behavior of poly(ethylene imine) [PEI] has been studied using simultaneous WAXD/DSC measurement system. PEI exhibits water-induced and thermally-induced phase transitions among four kinds of crystalline hydrates: anhydrate (EI/water,=,1/0), hemihydrate (1/0.5), sesquihydrate (1/1.5), and dihydrate (1/2). The chain conformation changes from a double helix in the anhydrate to a planar zigzag form in the three hydrates. The anhydrate melts at 60,°C while the hydrates melt differently in the temperature region of 70,110,°C. By means of the simultaneous WAXD/DSC measurements, complex DSC thermograms of PEI hydrates were characterized on the basis of X-ray diffractions obtained concurrently. [source] Multiple-point electrochemical detection for a dual-channel hybrid PDMS-glass microchip electrophoresis deviceELECTROPHORESIS, Issue 19 2009Mario Castańo-Álvarez Abstract A new PDMS-based dual-channel MCE with multiple-point amperometric detection has been evaluated. Electrophoresis has been optimised in a single-channel device. Pretreatment with 0.1,M NaOH is very important for increasing and stabilising the EOF. The precision is adequate for a day's work in terms of both peak current and migration time. The RSD of the peak current for five successive signals was 1.9, 2.4 and 3.1% for dopamine, p- aminophenol and hydroquinone. RSD for the migration time was always less than 1.3%, which demonstrates the stability of the EOF and the possibility of running multiple experiments in the same microchip. The adequate inter-microchip precision as well as the rapid and simple manufacturing procedure indicates the disposable nature of the PDMS microchips. A dual-channel device with very simple multiple-point amperometric detection is proposed here. Elasticity of the PDMS allows removing the polymer slightly and aligning gold wires working electrodes. Injection can be performed from each of the sample reservoirs or from both simultaneously. The distance between the separation channels is critical for obtaining adequate signals as well as the introduction of a high-voltage electrode in the buffer reservoir. Simultaneous measurement of the same analytes in both channels is possible by applying the same potential. Moreover, since no cross-separation is produced, different analytes or samples can be simultaneously measured. [source] Simultaneous measurement of resistance and viscoelastic responses of carbon black-filled high-density polyethylene subjected to dynamic torsionJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Jianfeng Zhou Abstract The conduction and viscoelastic responses to temperature are measured simultaneously for carbon black (CB) filled high-density polyethylene (HDPE) subjected to dynamic torsion. PTC/NTC transition was correlated with the loss tangent peak and the quasi modulus plateau, which was ascribed to the filler network. The bond-bending model of elastic percolation networks was used to reveal the structural mechanisms for the cyclic resistance changes at different temperatures. The resistance changes at lower temperatures depended on the deformation of the polymer matrix, while the changes in melting state were mainly attributed to the rearrangement of the CB network. A simple scaling law is derived to relate resistance and dynamic storage modulus in the melting region. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] High-resolution real-time recording with microelectrode biosensors reveals novel aspects of adenosine release during hypoxia in rat hippocampal slicesJOURNAL OF NEUROCHEMISTRY, Issue 6 2003B. G. Frenguelli Abstract We have used improved miniaturized adenosine biosensors to measure adenosine release during hypoxia from within the CA1 region of rat hippocampal slices. These microelectrode biosensors record from the extracellular space in the vicinity of active synapses as they detect the synaptic field potentials evoked in area CA1 by stimulation of the afferent Schaffer collateral-commissural fibre pathway. Our new measurements demonstrate the rapid production of adenosine during hypoxia that precedes and accompanies depression of excitatory transmission within area CA1. Simultaneous measurement of adenosine release and synaptic transmission gives an estimated IC50 for adenosine on transmission in the low micromolar range. However, on reoxygenation, synaptic transmission recovers in the face of elevated extracellular adenosine and despite a post-hypoxic surge of adenosine release. This may indicate the occurrence of apparent adenosine A1 receptor desensitization during metabolic stress. In addition, adenosine release is unaffected by pharmacological blockade of glutamate receptors and shows depletion on repeated exposure to hypoxia. Our results thus suggest that adenosine release is not a consequence of excitotoxic glutamate release. The potential for adenosine A1 receptor desensitization during metabolic stress implies that its prevention may be beneficial in extending adenosine-mediated neuroprotection in a variety of clinically relevant conditions. [source] Simultaneous measurement of serotonin and melatonin from the intestine of old mice: the effects of daily melatonin supplementationJOURNAL OF PINEAL RESEARCH, Issue 1 2010P. P. Bertrand Abstract:, Ageing is associated with important changes in gastrointestinal function and in the levels of intestinal hormones secreted. Enterochromaffin (EC) cells containing serotonin (5-HT) and melatonin may play a major role in maintaining gut function during ageing. Our aim was to characterise the mucosal availability of 5-HT and melatonin in the ileum and colon of a mouse model of ageing. Female young mice (2,5 month; n = 6), aged mice (22,24 months; n = 6) and aged mice treated with melatonin (n = 6; 10 mg/kg/day) were examined. Electrochemical methods were used to measure 5-HT and melatonin concentrations near the mucosal surface of ileum and distal colon. Amperometry studies showed that steady state levels of 5-HT from ileum and colon were decreased in aged mice treated with melatonin when compared to aged mice, while compression-evoked 5-HT release was unchanged. Differential pulse voltammetry studies showed that young mice had concentrations of 5-HT of 4.8 ± 0.8 ,m in the ileum and 4.9 ± 1.0 ,m in the colon. Concentrations of melatonin were 5.7 ± 1.4 ,m in the ileum and 5.6 ± 1.9 ,m in the colon. Compared to young mice, the levels of 5-HT and melatonin were increased in aged mice (combined ileum and colon: 5-HT = 130% and melatonin = 126% of young mice) and decreased in melatonin-treated mice (5-HT = 94% and melatonin = 82%). In conclusion, our data show that the availability of gut 5-HT and melatonin is increased in aged mice and melatonin treatment suppresses natural gastrointestinal production of 5-HT and melatonin in the aged mouse intestine. [source] A Critical Evaluation of Influence of Ethanol and Diet on Salsolinol Enantiomers in Humans and RatsALCOHOLISM, Issue 2 2010Jeongrim Lee Background:, (R/S)-Salsolinol (SAL), a condensation product of dopamine (DA) with acetaldehyde, has been speculated to have a role in the etiology of alcoholism. Earlier studies have shown the presence of SAL in biological fluids and postmortem brains from both alcoholics and nonalcoholics. However, the involvement of SAL in alcoholism has been controversial over several decades, since the reported SAL levels and their changes after ethanol exposure were not consistent, possibly due to inadequate analytical procedures and confounding factors such as diet and genetic predisposition. Using a newly developed mass spectrometric method to analyze SAL stereoisomers, we evaluated the contribution of ethanol, diet, and genetic background to SAL levels as well as its enantiomeric distribution. Methods:, Simultaneous measurement of SAL enantiomers and DA were achieved by high performance liquid chromatography-tandem mass spectrometry (HPLC/MS/MS). Plasma samples were collected from human subjects before and after banana (a food rich in SAL) intake, and during ethanol infusion. Rat plasma and brain samples were collected at various time points after the administration of SAL or banana by gavage. The brain parts including nucleus accumbens (NAC) and striatum (STR) were obtained from alcohol-non-preferring (NP) or alcohol-preferring (P) rats as well as P-rats which had a free access to ethanol (P-EtOH). Results:, Plasma SAL levels were increased significantly after banana intake in humans. Consistently, administration of banana to rats also resulted in a drastic increase of plasma SAL levels, whereas brain SAL levels remained unaltered. Acute ethanol infusion did not change SAL levels or R/S ratio in plasma from healthy humans. The levels of both SAL isomers and DA were significantly lower in the NAC of P rats in comparison to NP rats. The SAL levels in NAC of P rats remained unchanged after chronic free-choice ethanol drinking. There were decreasing trends of SAL in STR and DA in both brain regions. No changes in enantiomeric ratio were observed after acute or chronic ethanol exposure. Conclusions:, SAL from dietary sources is the major contributor to plasma SAL levels. No significant changes of SAL plasma levels or enantiomeric distribution after acute or chronic ethanol exposure suggest that SAL may not be a biomarker for ethanol drinking. Significantly lower SAL and DA levels observed in NAC of P rats may be associated with innate alcohol preference. [source] Simultaneous measurement of temperature and strain based on ARC-induced long-period fiber gratings.MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2008A case study Abstract We present a potential sensor head for the simultaneous measurement of temperature and strain based on the concatenation of two long-period fiber gratings arc-induced in different fibers. Despite being the temperature and strain sensitivities of the individual gratings well defined, we demonstrate that the sensor cannot perform the simultaneous measurement of those physical parameters. This fact, results from the uncertainty in finding the determinant of the inverse matrix. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2472,2474, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23644 [source] Simultaneous measurement of water flow velocity and solute transport in xylem and phloem of adult plants of Ricinus communis over a daily time course by nuclear magnetic resonance spectrometryPLANT CELL & ENVIRONMENT, Issue 5 2001A. D. Peuke ABSTRACT A new method for simultaneously quantifying rates of flow in xylem and phloem using the FLASH imaging capabilities of nuclear magnetic resonance (NMR) spectrometry was applied in this study. The method has a time resolution of up to 4 min (for the xylem) and was used to measure the velocity of flows in phloem and xylem for periods of several hours to days. For the first time, diurnal time course measurements of flow velocities and apparent volume flows in phloem and xylem in the hypocotyl of 40-d-old Ricinus communis L were obtained. Additional data on gas exchange and the chemical composition of leaves, xylem and phloem sap were used to assess the role of leaves as sinks for xylem sap and sources for phloem. The velocity in the phloem (0·250 ± 0·004 mm s,1) was constant over a full day and not notably affected by the light/dark cycle. Sucrose was loaded into the phloem and transported at night, owing to degradation of starch accumulated during the day. Concentrations of solutes in the phloem were generally less during the night than during the day but varied little within either the day or night. In contrast to the phloem, flow velocities in the xylem were about 1·6-fold higher in the light (0·401 ± 0·004 mm s,1) than in the dark (0·255 ± 0·003 mm s,1) and volume flow varied commensurately. Larger delays were observed in changes to xylem flow velocity with variation in light than in gas exchange. The relative rates of solute transport during day and night were estimated on the basis of relative flow and solute concentrations in xylem and phloem. In general, changes in relative flow rates were compensated for by changes in solute concentration during the daily light/dark cycle. However, the major solutes (K+, NO3,) varied appreciably in relative concentrations. Hence the regulation of loading into transport systems seems to be more important to the overall process of solute transport than do changes in mass flow. Due to transport behaviour, the chemical composition of leaves varied during the day only with regard to starch and soluble carbohydrates. [source] Simultaneous measurement of 13C- and 15N-isotopic enrichments of threonine by mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2009Jean-Philippe Godin Under conditions of high isotopic dilution, e.g. in a tracer study, the ability to determine accurately and quantitatively small variations in isotopic enrichments of differently labelled chemical compounds (e.g. 13C and 15N in threonine) in a single run by gas chromatography/mass spectrometry (GC/MS) is desirable but remains a technological challenge. Here, we report a new, rapid and simple GC/MS method for simultaneously measuring the isotopic enrichments of doubly labelled threonine ([U13C] and 15N) with isotopic enrichment lower than 1.5 Molar Percent Excess (MPE). The long-term reproducibility measured was around 0.09 MPE for both tracers (throughout a 6 week period). The intra-day repeatability was lower than 0.05 and 0.06 MPE for [U13C]-Thr and 15N-Thr, respectively. To calculate both isotopic enrichments, two modes of calculations were used: one based on work by Rosenblatt et al. in 1992 and the other one using a matrix approach. Both methods gave similar results (ANOVA, P >0.05) with close precision for each mode of calculation. The GC/MS method was then used to investigate the differential utilization of threonine in different organs according to its route of administration in minipigs after administration of both tracers. In plasma samples, the lowest isotopic enrichment measured between two successive time points was at 0.01 and 0.02 MPE for [U13C]-Thr and 15N-Thr, respectively. Moreover, the accuracy of GC/MS 13C-isotopic enrichment measured was validated by analyzing the same plasma samples by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). Statistical analysis showed that both techniques gave the same results (ANOVA, P >0.05). This new GC/MS method offers the possibility to measure 13C- and 15N-isotopic enrichments with higher throughput, and using a lower amount of sample, than using GC/C/IRMS. Copyright © 2009 John Wiley & Sons, Ltd. [source] The effect of fundal pressure manoeuvre on intrauterine pressure in the second stage of labourBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 5 2002Catalin S. Buhimschi Objective To investigate the relationship between intrauterine pressure and the application of a standardised fundal pressure manoeuvre, and to determine the maternal, fetal and labour characteristics that modulate the relationship. Design Prospective measurement of intrauterine pressure during the second stage of labour. Setting North American university hospital. Population Forty full-term women in spontaneous labour were studied during the second stage. Each woman acted as her own control. All women laboured with requested epidural analgesia. Methods A fundal pressure manoeuvre was performed so as to standardise the level of force and the surface area of application. Intrauterine pressure was measured using a sensor,tip catheter. Five interventions were analysed: 1. valsalva during a uterine contraction; 2. fundal pressure and valsalva during a contraction; 3. fundal pressure during a contraction without valsalva; 4. fundal pressure in the absence of uterine contractions; and 5. valsalva in the absence of uterine contractions. Results Women in the second stage of labour transiently increased their expulsive force (as reflected by intrauterine pressure) by 86% of their baseline contraction using valsalva and fundal pressure simultaneously. The efficiency by which both contraction-enhancing manoeuvres increased intrauterine pressure was directly related to gestational age and inversely related to myometrial thickness. Conclusion Fundal pressure applied under controlled conditions significantly increases intrauterine pressure in some, but not all women. Simultaneous measurement of intrauterine pressure, to maintain feedback during application will create a ,controlled environment' for the obstetrician and reassurance that this manoeuvre can be applied in a controlled fashion. Future delineation of the group of women that could benefit from fundal pressure, as well as the group that is refractory is essential to avoid unnecessary or delayed operative interventions. [source] Simultaneous Measurements of Ion Temperature by Segmented Tunnel and Katsumata ProbeCONTRIBUTIONS TO PLASMA PHYSICS, Issue 5-7 2008J. Adámek Abstract Simultaneous measurements of the ion temperature by the segmented tunnel and Katsumata probe in the CASTOR tokamak are reported. The segmented tunnel probe measures two ion saturation currents Iseg 1, Iseg 2 towards two segments of the tunnel. The axis of the tunnel is aligned with the total magnetic field. The value of the ratio of these two currents combined with the results of the PIC modeling provides the ion temperature. Design and experimental arrangement of the Katsumata probe enable us to measure the pure ion current by sweeping the applied voltage. The ion temperature is then estimated from the exponential part of the measured I , V characteristic. Simultaneous measurements of the ion temperature by the segmented tunnel and Katsumata probe agree within a few eV. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Non-invasive monitoring of muscle blood perfusion by photoplethysmography: evaluation of a new applicationACTA PHYSIOLOGICA, Issue 4 2005M. Sandberg Abstract Aim:, To evaluate a specially developed photoplethysmographic (PPG) technique, using green and near-infrared light sources, for simultaneous non-invasive monitoring of skin and muscle perfusion. Methods:, Evaluation was based on assessments of changes in blood perfusion to various provocations, such as post-exercise hyperaemia and hyperaemia following the application of liniment. The deep penetrating feature of PPG was investigated by measurement of optical radiation inside the muscle. Simultaneous measurements using ultrasound Doppler and the new PPG application were performed to elucidate differences between the two methods. Specific problems related to the influence of skin temperature on blood flow were highlightened, as well. Results:, Following static and dynamic contractions an immediate increase in muscle perfusion was shown, without increase in skin perfusion. Liniment application to the skin induced a rapid increase in skin perfusion, but not in muscle. Both similarities and differences in blood flow measured by Ultrasound Doppler and PPG were demonstrated. The radiant power measured inside the muscle, by use of an optical fibre, showed that the near-infrared light penetrates down to the vascular depth inside the muscle. Conclusions:, The results of this study indicate the potentiality of the method for non-invasive measurement of local muscle perfusion, although some considerations still have to be accounted for, such as influence of temperature on blood perfusion. [source] Processes controlling rapid temperature variations on rock surfaces,EARTH SURFACE PROCESSES AND LANDFORMS, Issue 5 2010Jamie L. Molaro Abstract In arid environments, thermal oscillations are an important source of rock weathering. Measurements of temperature have been made on the surface of rocks in a desert environment at a sampling interval of 0·375,s, with simultaneous measurements of wind speed, air temperature, and incoming shortwave radiation. Over timescales of hours, the temperature of the rock surface was determined primarily by shortwave radiation and air temperature, while rapid temperature variations, high dT/dt, at intervals of seconds or less, were determined by wind speed. The maximum values of temperature change and time spent above 2°C,min,1 increased at high measurement rates and were much higher than previously reported. The maximum recorded value of dT/dt was 137°C,min,1 and the average percentage time spent above 2°C,min,1 was ,70 ± 13%. Maximum values of dT/dt did not correlate with the maximum values of time spent above 2°C,min,1. Simultaneous measurements of two thermocouples 5·5,cm apart on a single rock surface had similar temperature and dT/dt values, but were not correlated at sampling intervals of less than 10,s. It is suggested that this is resulting from rapid fluctuations due to small spatial and timescale wind effects that are averaged out when data is taken at longer sampling intervals, ,10,s or greater. Published in 2010 by John Wiley & Sons, Ltd. [source] Separating host-tree and environmental determinants of honeydew production by Ultracoelostoma scale insects in a Nothofagus forestECOLOGICAL ENTOMOLOGY, Issue 4 2007ROGER J. DUNGAN Abstract 1.,Sugar-rich honeydew excreted (,produced') by insects feeding on phloem sap is a key energy flow in a range of temperate and tropical ecosystems. The present study measured honeydew produced by Ultracoelostoma sp. (Homoptera: Coelostomidiidae) scale insects feeding on Nothofagus solandri var. solandri (Hook f.) Oerst. trees in a temperate evergreen forest in New Zealand. Simultaneous measurements of environmental variables and canopy photosynthesis were conducted to allow separation of host-tree and environmental determinants of honeydew production. These relationships were further examined in experiments where canopy photosynthesis was manipulated by shading or plant nitrogen levels increased by foliar spray. 2.,Rates of honeydew production varied nine-fold from a maximum (± 1 SE) of 64.4 ± 15.2 mg dry mass m,2 bark h,1 in early summer (December) to a minimum of 7.4 ± 4.2 mg m,2 h,1 in winter (August). Rates of production measured 1.4 m from the base of the trees' stems varied significantly with stem diameter, and were higher on medium-sized (18 cm diameter) than small or large stems. 3.,Rates of production were significantly related to environmental conditions over the hours preceding measurement (air temperature and air saturation deficit averaged over the preceding 24 and 12 h respectively). There was no evidence that rates of production were directly related to short-term changes in the supply of carbohydrates from the canopy (either when compared with measurements of unmanipulated photosynthetic rate, or after sugar levels were manipulated by shading 80% of host-trees' leaf area), or to changes in phloem nitrogen content. 4.,The results show that there is no clear effect of host-tree carbon supply on honeydew production; if production is related to photosynthesis, the effect of this is much less important that the large and significant direct effect of environmental conditions on honeydew production. [source] Simultaneous measurements of cerebral oxygenation changes during brain activation by near-infrared spectroscopy and functional magnetic resonance imaging in healthy young and elderly subjectsHUMAN BRAIN MAPPING, Issue 1 2002D. Jannet Mehagnoul-Schipper Abstract Near infrared spectroscopy (NIRS) and functional magnetic resonance imaging (fMRI) both allow non-invasive monitoring of cerebral cortical oxygenation responses to various stimuli. To compare these methods in elderly subjects and to determine the effect of age on cortical oxygenation responses, we determined motor-task-related changes in deoxyhemoglobin concentration ([HHb]) over the left motor cortex in six healthy young subjects (age 35 ± 9 years, mean ± SD) and five healthy elderly subjects (age 73 ± 3 years) by NIRS and blood-oxygen-level-dependent (BOLD) fMRI simultaneously. The motor-task consisted of seven cycles of 20-sec periods of contralateral finger-tapping at a rate as fast as possible alternated with 40-sec periods of rest. Time-locked averages over the seven cycles were used for further analysis. Task-related decreases in [HHb] over the motor cortex were measured by NIRS, with maximum changes of ,0.83 ± 0.38 ,mol/L (P < 0.01) for the young and ,0.32 ± 0.17 ,mol/L (P < 0.05) for the elderly subjects. The BOLD-fMRI signal increased over the cortex volume under investigation with NIRS, with maximum changes of 2.11 ± 0.72% (P < 0.01) for the young and 1.75 ± 0.71% (P < 0.01) for the elderly subjects. NIRS and BOLD-fMRI measurements showed good correlation in the young (r = ,0.70, r2 = 0.48, P < 0.001) and elderly subjects (r = ,0.82, r2 = 0.67, P < 0.001). Additionally, NIRS measurements demonstrated age-dependent decreases in task-related cerebral oxygenation responses (P < 0.05), whereas fMRI measurements demonstrated smaller areas of cortical activation in the elderly subjects (P < 0.05). These findings demonstrate that NIRS and fMRI similarly assess cortical oxygenation changes in young subjects and also in elderly subjects. In addition, cortical oxygenation responses to brain activation alter with aging. Hum. Brain Mapping 16:14,23, 2002. © 2002 Wiley-Liss, Inc. [source] Some Parameters of Correlated Current and Radiated Field Pulses from Lightning to the Gaisberg TowerIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 1 2010Hannes Pichler Non-member Abstract Simultaneous measurements of lightning current and associated radiated electromagnetic field are of fundamental interest for various applications in lightning research. These data can be used for the evaluation of return stroke (RS) models or to investigate the so-called tower effect when lightning hits an elevated object. In this paper, we show the results of simultaneous measurements of current pulses from lightning strikes on the instrumented Gaisberg tower (Austria) and the correlated vertical E-field components at a distance of 78.8 and 108.7 km, respectively. We have analyzed some main lightning current parameters (peak current Ip, 30,90% rise time TI_30-90, and full width at half maximum TI_FWHM and the time-correlated field waveform parameters (Ep, 30,90% rise time TE_30-90, TE_FWHM, and the peak-to-zero time TE_PTZ. With a geometric mean of TI_FWHM = 19 ,s and Ip = 9.6 kA (N = 73) of the RS current pulses used in this study, those strokes are very similar to the strokes in triggered lightning in Florida and Alabama1. With a TE_PTZ of about 10 µs, the zero-crossing time of the radiated E-fields from the tower strokes are significantly shorter than the typical values of 30 , 40 µs (e.g.2). Correlation between the current and field parameters TI_FWHM versus TE_FWHM and TE_PTZ, respectively, is low (R2 = 0.29 and 0.14). We assume that the relatively short lightning channel in the case of the RSs in object-triggered upward flashes is the main reason for the observed short zero-crossing time. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] The effects of partial and total interosseous membrane transection on load sharing in the cadaver forearmJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2001Michael F. Shepard This study was performed to examine the effects of partial and total transection of the interosseous membrane (IOM) on load transfer in the forearm. Twenty fresh frozen forearms were instrumented with custom designed load cells placed in the proximal radius and distal ulna. Simultaneous measurements of load cell forces, radial head displacement relative to the capitellum, and local tension within the central band of the IOM were made as the wrist was loaded to 134 N with the forearm at 90° of elbow flexion and in neutral pronation supination. For valgus elbow alignment (radial head contacting the capitellum), mean force carried by the distal ulna was 7.1% of the applied wrist force and mean force transferred from radius to ulna through the IOM was 4.4%. For varus elbow alignment (mean 2.0 mm gap between the radial head and capitellum), mean distal ulna force was 28% and mean IOM force was 51%. Section of the proximal and distal one-thirds of the IOM had no significant effect upon mean distal ulnar force or mean IOM force. Total IOM section significantly increased mean distal ulnar force for varus elbow alignment in all wrist positions tested. The mean level of applied wrist force necessary to close the varus gap (89 N) decreased significantly after both partial IOM section (71 N) and total IOM section (25 N). The IOM became loaded only when the radius displaced proximally relative to the ulna, closing the gap between the radius and capitellum. As the radius displaced proximally, the wrist becomes increasingly ulnar positive, which in turn leads to direct loading of the distal ulna. This shift of force to the distal ulna could present clinically as ulnar sided wrist pain or as ulnar impaction after IOM injury. © 2001 Orthopaedic Research Society. Punlished by Elsevier Science Ltd. All rights reserved. [source] Direction sensitive sensor probe for the evaluation of voluntary and reflex pelvic floor contractions,NEUROUROLOGY AND URODYNAMICS, Issue 3 2007Christos E. Constantinou Abstract Aims The development of a vaginal probe for the evaluation of the dynamics of pelvic floor function is described. Fundamental criteria in the design of this probe involves the incorporation of a means of assessing whether the isotonic forces closing the vagina are equally distributed or whether they are greater in some directions than others. The aim of this study is to present the design of directionally sensitive multi-sensor probe, having circumferential spatial resolution, constructed to identify the distribution of anisotropic forces acting on the vagina following voluntary and reflex pelvic floor contractions. Materials and Methods Probe system consists of four pairs of force/displacement sensors mounted on leaf springs enabling isotonic measurements of voluntary and reflex contractions. Assembly is retractable to 23 mm for insertion, and expandable to 60 mm for measurement. Simultaneous measurements were made of force and displacement with the sensors oriented in the anterior/posterior and left/right orientation of the vagina. Using this probe, measurements were carried out to identify the temporal and spatial characteristic response of the vaginal wall. Data were analyzed with respect to voluntary pelvic floor and cough-induced contractions of nine subjects having a mean age of 64 years. Results A robust probe system was developed and measurements were successfully made. Initial results show that the maximum force and displacement occurs during reflex contractions in the anterior aspect of the vagina validating the anisotropic nature of the forces acting on the vaginal wall. The data also show that both the force and displacement produced by the cough-induced has a higher magnitude than voluntary pelvic floor contraction. Conclusions A directional multi-sensor vaginal probe has been developed to evaluate the force and displacement produced during isotonic pelvic floor contractions. Analysis of the results provided new biomechanical data demonstrating the anisotropic nature of vaginal closure as a consequence of pelvic floor contractions. Neurourol. Urodynam. 26:386,391, 2007. © 2007 Wiley-Liss, Inc. [source] Cross-site comparison of herbivore impact on nitrogen availability in grasslands: the role of plant nitrogen concentrationOIKOS, Issue 11 2009E. S. Bakker Herbivores may influence the nitrogen (N) recycling rates and consequently increase or decrease the productivity of grasslands. Plant N concentration emerged as a critical parameter to explain herbivore effects from several conceptual models, which predict that herbivores decrease soil N availability when plant N concentration is low whereas they increase it when plant N concentration is high (Hobbs 1996, Ritchie et al. 1998, Pastor et al. 2006). However, a broader cross-site comparison among published studies to test these predictions is hampered by the different methodologies used to measure soil N availability or a proxy thereof, and a lack of measurements of plant N concentration. Therefore it remains unclear whether these model predictions are generally valid across a range of grasslands. We tested whether there is a relationship between plant N concentration and herbivore impact on soil N availability (measured with resin bags) with a study of replicate 6,8,year old exclosures (with an unfenced control) of vertebrate herbivores (>1,kg) established at each of seven grassland sites in North America and Europe. Contrary to model predictions, we found a negative relationship between the effect of herbivores on resin bag soil N availability and plant N concentration. Our study confirms the importance of plant N concentration as a predictor of herbivore effect on soil N availability across grasslands, but contradicts the models. A possible explanation may be that the results represent a transient situation as the exclosures were relatively young whereas the models may refer to an equilibrium state. Simultaneous measurements of both plant N concentration and herbivore effect on soil N availability from more grassland sites, preferably with contrasting plant N concentrations and including exclosures of different ages, should resolve the contrast between model predictions and our field measurements. [source] Antagonism of calcium currents and neurotransmitter release by barium ions at frog motor nerve endingsBRITISH JOURNAL OF PHARMACOLOGY, Issue 2 2000Eugene M Silinsky The effects of Ba2+ (0.1,2 mM) on the component of the perineural voltage change associated with nerve terminal calcium currents (prejunctional Ca2+ currents) were compared with the effects of this ion to antagonize calcium-dependent acetylcholine (ACh) release. These experiments were made on isolated neuromuscular junctions of the frog. In the presence of sufficient concentrations of K+ channel blockers to eliminate measurable prejunctional K+ currents, low concentrations of Ba2+ selectively antagonized prejunctional Ca2+ currents in normal Ca2+ solutions. Higher concentrations of Ba2+ also substantially reduced the Na+ component of the perineural waveform. Ba2+ inhibited the prolonged prejunctional Ca2+ currents that developed in the presence of higher concentrations of K+ channel blockers. Simultaneous measurements of the prejunctional Ca2+ currents and the electrophysiological correlates of ACh release (i.e. end-plate potentials, EPPs) were made under conditions of modest K+ channel blockade. Under these conditions, Ba2+ generally produced simultaneous decreases in both Ca2+ currents and EPP amplitudes. In some instances, a prolongation of prejunctional Ca2+ currents and a transient increase in EPP amplitudes preceded the decreases in both electrophysiological events. These results suggest that Ba2+ ions can antagonize the entry of calcium into motor nerve endings and this effect is likely to be responsible for the inhibitory effects of Ba2+ on evoked ACh release. British Journal of Pharmacology (2000) 129, 360,366; doi:10.1038/sj.bjp.0703036 [source] Presence of Biventricular Dysfunction in Patients With Type II Diabetes MellitusCONGESTIVE HEART FAILURE, Issue 2 2007Mohammad-Reza Movahed MD Diabetes mellitus (DM) has been found to be associated with depressed left ventricular (LV) function. Right ventricular (RV) function in DM patients, however, has not been well studied. The goal of this study was to evaluate the occurrence of LV and RV dysfunction in patients with DM. A series of 157 patients underwent simultaneous measurement of LV ejection fraction (LVEF) and RV ejection fraction (RVEF). Four of 26 DM patients had RVEF <30% (15.4%) vs 4 of 126 controls (3.2%) (P=.01). Eleven of 27 (40.7%) patients with DM had LVEF <30% vs 9 of 128 controls (7%) (P<.0001). Using multivariate analysis, DM remained independently associated with severely decreased biventricular function (RVEF <30%; odds ratio, 5.7; confidence interval, 1.3,25.4 [P=.02] and LVEF <30%; odds ratio, 12.9; confidence interval, 3.8,43.7 [P<.0001]). These results suggest that diabetic cardiomyopathy involves both ventricles as an independent pathologic process. [source] When fish meet fish as determined by physiological sensorsECOLOGY OF FRESHWATER FISH, Issue 4 2009O. Slavík Abstract,,, Electromyogram (EMG) biotelemetry allows a description of the spatial distribution of fish together with a simultaneous measurement of individual energy consumption. Using this technique, we observed behaviour of the largest European freshwater predator, Silurus glanis, in the Elbe River, Central Europe. In total, 52 diurnal cycles and 1248 individual fish positions were recorded with 12,480 EMG records during the period from March to May 2006; 1013 fish positions with 10,130 EMG records were further used for statistical analyses. Energy consumption increased with decreasing mutual distance between specimens, an effect that occurred predominantly when both of them were simultaneously in overlapping preferred areas [core areas (CAs)] appointed within their home ranges (HRs). Furthermore, with increasing energy consumption individual's movement range in longitudinal and lateral profiles decreased; i.e., the fish were positioned within a small area. When the CAs of tested individuals did not overlap, no relationship between EMG signals and mutual distance of conspecifics was found. Our results indicate that movement activity and also social behaviour can be determined with physiological sensors. [source] Simultaneous and Direct Determination of Tryptophan and Tyrosine at Boron-Doped Diamond ElectrodeELECTROANALYSIS, Issue 8 2006Guohua Zhao Abstract A facile method for the simultaneous measurement of tryptophan (Trp) and tyrosine (Tyr) was firstly exploited at unmodified boron-doped diamond (BDD) electrode. The experimental results indicated that by using differential pulse voltammetry, the oxidative peaks of these two kinds of amino acids could be completely separated at BDD electrode. The peak separation of Trp and Tyr was developed to be 0.64,V when Na2PO4/NaOH buffer solution with the optimized pH,11.2 was employed. The detection limit of Trp was obtained to be 1×10,5,M, while that of Tyr was achieved to be 1×10,6,M. The present method was also evidenced to be available to the determination of real samples of amino acids. [source] Electromigration diffusivity spectrometry: A way for simultaneous determination of diffusion coefficients from mixed samplesELECTROPHORESIS, Issue 17 2010Suhua Yang Abstract A novel method was proposed for simultaneous measurement of diffusion coefficients, (D), from mixed samples by electrophoresis and termed electromigration-based diffusivity spectrometry. After theoretical treatment, D- equation for practical use has been deduced. With a modified CE system built in laboratory, electromigration-based diffusivity spectrometry has been realized and validated to suit for fast and accurate determination of diffusivities of mixed aromatic amino acids, phenols and aromatic organic acid, giving diffusivity spectra by peak area versus D, much similar to mass spectra. The precision of the measurement was found to critically depend on pH value of running buffer, which should be so selected that the analytes and internal standards could be charged at above 0.5e. The standards have to be selected at an electric flux far from each other and from analytes. In these cases, sample and running buffer concentrations, voltage and system temperature were found to have only negligible impact on the determination. In our test, the obtained measuring precision was generally kept within 1% for five runs, and the measured values of D agreed well with those from literature, with a deviation of less than 2.2% after the right use of calibration standards. [source] Tuning Nanotubes: Beam to String Transition of Vibrating Carbon Nanotubes Under Axial Tension (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Mater. On page 1753, the vibration properties of carbon nanotubes (CNTs) under axial tension are quantificationally studied by X. L. Wei et al. through a novel in situ method for precise and simultaneous measurement of the resonance frequency, the axial tension applied to individual CNTs, and the tube geometry. A gradual beam-to-string transition from multiwalled CNTs to singlewalled CNTs is observed; the CNTs can be tuned like a zither! [source] Beam to String Transition of Vibrating Carbon Nanotubes Under Axial TensionADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Xianlong Wei Abstract State-of-the-art nanoelectromechanical systems have been demonstrated in recent years using carbon nanotube (CNT) based devices, where the vibration of CNTs is tuned by tension induced through external electrical fields. However, the vibration properties of CNTs under axial tension have not been quantitatively determined in experiments. Here, a novel in situ method for precise and simultaneous measurement of the resonance frequency, the axial tension applied to individual CNTs and the tube geometry is demonstrated. A gradual beam-to-string transition from multi-walled CNTs to single-walled CNTs is observed with the crossover from bending rigidity dominant regime to extensional rigidity dominant regime occur much larger than that expected by previous theoretical work. Both the tube resonance frequency under tension and transition of vibration behavior from beam to string are surprisingly well fitted by the continuum beam theory. In the limit of a string, the vibration of a CNT is independent of its own stiffness, and a force sensitivity as large as 0.25,MHz (pN),1 is demonstrated using a 2.2,nm diameter single-walled CNT. These results will allow for the designs of CNT resonators with tailored properties. [source] Indoor/outdoor concentrations and elemental composition of PM10/PM2.5 in urban/industrial areas of Kocaeli City, TurkeyINDOOR AIR, Issue 2 2010B. Pekey Abstract, This study presents indoor/outdoor PM2.5 and PM10 concentrations measured during winter and summer in 15 homes in Kocaeli, which is one of the most industrialized areas in Turkey. Indoor and outdoor PM2.5 and PM10 mass concentrations and elemental composition were determined using an X-ray fluorescence spectrometer. Quantitative information was obtained on mass concentrations and other characteristics such as seasonal variation, indoor/outdoor (I/O) ratio, PM2.5/PM10 ratio, correlations and sources. Average indoor and outdoor PM2.5 concentrations were 29.8 and 23.5 ,g/m3 for the summer period, and 24.4 and 21.8 ,g/m3 for the winter period, respectively. Average indoor and outdoor PM10 concentrations were 45.5 and 59.9 ,g/m3 for the summer period, and 56.9 and 102.3 ,g/m3 for the winter period, respectively. A varimax rotated factor analysis (FA) was performed separately on indoor and outdoor datasets in an effort to identify possible heavy metal sources of PM2.5 and PM10 particle fractions. FA of outdoor data produced source categories comprising polluted soil, industry, motor vehicles, and fossil fuel combustion for both PM fractions, while source categories determined for indoor data for both PM2.5 and PM10 comprised industry, polluted soil, motor vehicles, and smoking, with an additional source category of cooking activities detected for the PM2.5 fraction. Practical Implications In buildings close to industrial areas or traffic arteries, outdoor sources may have an important effect on indoor air pollution. Therefore, indoor and outdoor investigations should be conducted simultaneously to assess the relationship between indoor and outdoor pollution. This study presents the simultaneous measurement of PM fractions (PM2.5 and PM10) and their elemental compositions to determine the sources of respirable PM and the heavy metals bound to these particles in indoor air. Factor analysis of indoor data indicated that the contribution of outdoor pollutant sources to indoor pollution was about 70%, making these sources the most significant for indoor heavy metal pollution, wheras other sources of indoor pollution included smoking and cooking activities. [source] | ||||||||||||||||||||||||||||