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Experimental Applications (experimental + application)
Selected AbstractsHigh-resolution NMR correlation experiments in a single measurement (HR-PANACEA)MAGNETIC RESONANCE IN CHEMISTRY, Issue 5 2010riks Kup Abstract Three important NMR pulse sequences, INADEQUATE, HSQC and three-dimensional HMBC have been combined into a single entity called high-resolution Parallel Acquisition NMR: an All-in-one Combination of Experimental Applications (HR-PANACEA) to provide reliable structural information about a small molecule in a single measurement. This exploits a recent instrumental development that permits simultaneous acquisition of signals from several nuclear species, using multiple receivers. Where high-precision values of the long-range heteronuclear splittings are important, selected regions of a large experimental data matrix are extracted and examined with the highest possible resolution. The J -doubling technique is then applied to derive precise values for these couplings. As proof of principle, the method is applied to the molecule of methyl salicylate, confirming the expected conformation of the COH moiety. Copyright © 2010 John Wiley & Sons, Ltd. [source] Effects of experimental acidification and alkalinization on soil and growth and health of Acer saccharum Marsh.JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 6 2008Rock Ouimet Abstract Experimental application of eight acidifying, neutral, or alkalizer compounds (range: ,16 to 16 kmol ha,1 of acid-neutralizing capacity [ANC]) was realized in two northern hardwood stands having significantly different soil base saturation (BS) (a "poor" and a "rich" site) to assess responses of soil physico-chemical properties, and nutrition, growth, and health of sugar maple (Acer saccharum Marsh.) trees in the short (3 y) and longer term (10 y). The treatments influenced the main indicators of acidity in the forest floor (soil exchangeable-Ca saturation [SCa], BS, exchangeable-acidity saturation [SH+Al], and the SCa/SH+Al ratio) at both sites, their values increasing (decreasing for SH+Al) along the ANC treatment gradient in both the short and longer term, except for pH. Base saturation of the upper 15,cm of the mineral B horizons of soils was influenced at the two sites 10 y after treatment application. Although ANC treatments affected nutrient concentrations of tree foliage in the short term, their effect was no longer detectable after 10 y at the two sites. Growth, however, was strongly related to ANC treatments after 10 y, but only at the poor site. From 1990 to 2000, the basal-area growth rate of trees at the poor site was (mean ± SE) ,0.62 ± 0.28,cm2 y,2 tree,1 for the most negative ANC treatment to +0.90 ± 0.20,cm2 y,2 tree,1 for the most positive ANC treatment. A climatic-stress episode occurring in 1995/96 appeared to accentuate the growth decline of trees subjected to the most negative ANC treatment at the poor site. The experimental results support the hypothesis that atmospheric acid deposition load can cause forest soil base-cation depletion, acidification, and predispose sugar maple to health and growth decline in the longer term in base-cation-poor soils, and that the phenomenon may be reversible by adding alkalizers. [source] Stabilization of n integrators in cascade with bounded input with experimental application to a VTOL laboratory systemINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 10 2010G. Sanahuja Abstract This paper presents a global stabilization of a chain of n integrators in cascade. The control strategy is obtained using the Lyapunov approach and separated saturation functions. Moreover, the stability analysis is obtained using the recurrence theorem. This generalized control law is designed in order to quickly implement it on a system, as choosing a degree n gives all conditions to have a stable system. Moreover, in the proposed controller the saturation function bound only one state. This allows us to easily tune the control parameters. Simulations and real-time experiments are presented for the VTOL platform represented as a chain of two and four integrators in cascade. Copyright © 2009 John Wiley & Sons, Ltd. [source] Numerical model for polymer electrolyte membrane fuel cells with experimental application and validationASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2009Javier Alonso Mora Abstract The aim of this paper is to present a simple 3D computational model of a polymer electrolyte membrane fuel cell (PEMFC) that simulates over time the heat distribution, energy, and mass balance of the reactant gas flows in the fuel cell including pressure drop, humidity, and liquid water. Although this theoretical model can be adapted to any type of PEMFC, for verification of the model and to present different analysis it has been adapted to a single cell test fixture. The model parameters were adjusted through a series of experimental tests and the model was experimentally validated for a well-defined range of operating conditions: H2/air O2 as reactants, flow rates of 0.5,1.5 SLPM, dew points and cell temperatures of 30,80 °C, currents 0,5 A and with/without water condensation. The model is especially suited for the analysis of liquid water condensation in the reactant channels. A key finding is that the critical current at which liquid water is formed is determined at different flows, temperatures, and humidity. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Baseflow and peakflow chemical responses to experimental applications of ammonium sulphate to forested watersheds in north-central West Virginia, USA,HYDROLOGICAL PROCESSES, Issue 12 2002Pamela J. Edwards Abstract Stream water was analysed to determine how induced watershed acidification changed the chemistry of peakflow and baseflow and to compare the relative timing of these changes. Two watersheds in north-central West Virginia, WS3 and WS9, were subjected to three applications of ammonium sulphate fertilizer per year to induce acidification. A third watershed, WS4, was the control. Samples were collected for 8 years from WS9 and for 9 years from WS3. Prior to analyses, concentration data were flow adjusted, and the influence of natural background changes was removed by accounting for the chemical responses measured from WS4. This yielded residual values that were evaluated using robust locally weighted regression and Mann,Kendall tests. On WS3, analyte responses during baseflow and peakflow were similar, although peakflow responses occurred soon after the first treatment whereas baseflow responses lagged 1,2 years. This lag in baseflow responses corresponded well with the mean transit time of baseflow on WS3. Anion adsorption on WS3 apparently delayed increases in SO4 leaching, but resulted in enhanced early leaching losses of Cl and NO3. Leaching of Ca and Mg was strongly tied, both by timing and stoichiometrically, to NO3 and SO4 leaching. F -factors for WS3 baseflow and peakflow indicated that the catchment was insensitive to acid neutralizing capacity reductions both before and during treatment, although NO3 played a large role in reducing the treatment period F -factor. By contrast, the addition of fertilizer to WS9 created an acid sensitive system in both baseflow and peakflow. On WS9, baseflow and peakflow responses also were similar to each other, but there was no time lag after treatment for baseflow. Changes in concentrations generally were not as great on WS9 as on WS3, and several ions showed no significant changes, particularly for peakflow. The lesser response to treatment on WS9 is attributed to the past abusive farming and site preparation before larch planting that resulted in poor soil fertility, erosion, and consequently, physical and chemical similarities between upper and lower soil layers. Even with fertilizer-induced NO3 and SO4 leaching increases, base cations were in low supplies and, therefore, unavailable to leach via charge pairing. The absence of a time lag in treatment responses for WS9 baseflow indicates that it has substantially different flow paths than WS3. The different hydrologies on these nearby watersheds illustrates the importance of understanding watershed hydrology when establishing a monitoring programme to detect ecosystem change. Published in 2002 by John Wiley & Sons, Ltd. [source] Measurement of bone blood flow using the hydrogen washout technique,part II: Validation by comparison to microsphere entrapmentJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 6 2008Mikko Larsen Abstract Accurate and reproducible measurement of bone blood flow has important clinical and experimental applications. Hydrogen washout is simple, safe, and widely used, but its use in bone tissue has not been validated. To this end, we have compared cortical bone blood flow measurements obtained by radioactive-labeled microsphere entrapment with those from hydrogen washout. Blood flow was measured in tibial cortical bone of 12 New Zealand White rabbits by radioactive microsphere entrapment and by hydrogen washout. Besides a control group (n,=,6), four animals were treated with systemic epinephrine (0.8 µg/kg/min) (group 2) and two with nitroprusside (100 µg/kg/min) (group 3). Furthermore, nine femora from seven rats were isolated on their vascular pedicles and repeated bone blood flow measurements were made at each location with the hydrogen washout method to confirm reproducibility of blood flow determinations by hydrogen washout. An average flow of 2.3,±,2.0 mL/min/100 g was obtained with the microsphere method and 2.0,±,0.5 mL/min/100 g with the hydrogen washout method. There was a significant correlation and agreement: R2,=,0.97 (p,<,0.01). No consistent flow variations were found with systemic vasoactive drug administration. Hydrogen washout provided reproducible results and showed high sensitivity to flow changes. Hydrogen washout is both sensitive and reproducible in measuring bone blood flow. Results agree well with flow values obtained by labeled microsphere entrapment. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:746,752, 2008 [source] Analog pixel array detectorsJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2006A. Ercan X-ray pixel array detectors (PADs) are generally thought of as either digital photon counters (DPADs) or X-ray analog-integrating pixel array detectors (APADs). Experiences with APADs, which are especially well suited for X-ray imaging experiments where transient or high instantaneous flux events must be recorded, are reported. The design, characterization and experimental applications of several APAD designs developed at Cornell University are discussed. The simplest design is a `flash' architecture, wherein successive integrated X-ray images, as short as several hundred nanoseconds in duration, are stored in the detector chips for later off-chip digitization. Radiography experiments using a prototype flash APAD are summarized. Another design has been implemented that combines flash capability with the ability to continuously stream X-ray images at slower (e.g. milliseconds) rates. Progress is described towards radiation-hardened APADs that can be tiled to cover a large area. A mixed-mode PAD, design by combining many of the attractive features of both APADs and DPADs, is also described. [source] Characterization of tissue structure at varying length scales using temporal diffusion spectroscopy,NMR IN BIOMEDICINE, Issue 7 2010John C. Gore Abstract The concepts, theoretical behavior and experimental applications of temporal diffusion spectroscopy are reviewed and illustrated. Temporal diffusion spectra are obtained using oscillating-gradient waveforms in diffusion-weighted measurements, and represent the manner in which various spectral components of molecular velocity correlations vary in different geometrical structures that restrict or hinder free movements. Measurements made at different gradient frequencies reveal information on the scale of restrictions or hindrances to free diffusion, and the shape of a spectrum reveals the relative contributions of spatial restrictions at different distance scales. Such spectra differ from other so-called diffusion spectra which depict spatial frequencies and are defined at a fixed diffusion time. Experimentally, oscillating gradients at moderate frequency are more feasible for exploring restrictions at very short distances which, in tissues, correspond to structures smaller than cells. We describe the underlying concepts of temporal diffusion spectra and provide analytical expressions for the behavior of the diffusion coefficient as a function of gradient frequency in simple geometries with different dimensions. Diffusion in more complex model media that mimic tissues has been simulated using numerical methods. Experimental measurements of diffusion spectra have been obtained in suspensions of particles and cells, as well as in vivo in intact animals. An observation of particular interest is the increased contrast and heterogeneity observed in tumors using oscillating gradients at moderate frequency compared with conventional pulse gradient methods, and the potential for detecting changes in tumors early in their response to treatment. Computer simulations suggest that diffusion spectral measurements may be sensitive to intracellular structures, such as nuclear size, and that changes in tissue diffusion properties may be measured before there are changes in cell density. Copyright © 2010 John Wiley & Sons, Ltd. [source] Reliability of measurement of angular movements of the pelvis and lumbar spine during treadmill walkingPHYSIOTHERAPY RESEARCH INTERNATIONAL, Issue 4 2001Nicholas Taylor Abstract Background and Purpose Angular movements of the pelvis and lumbar spine are thought to play an important role in walking. However, little is known about the amount of unpredictable variability in measurement of these movements during human walking. The aim of the present study was to determine the retest reliability of measuring the angular movements of the pelvis and lumbar spine during unimpaired familiarized treadmill walking. Method Retest reliability for 26 subjects without pathology was determined over a one-week interval. Subjects walked on a treadmill at self-selected or a slower speed while measurements of the three-dimensional angular movements were taken with a computer-based video analysis system. Results The frontal plane movements of pelvic list and lumbar lateral flexion (relative to the pelvis) could be measured with high retest reliability at both self-selected and slow walking speeds (intraclass coefficient (ICC) (2,1) , 0.81). In contrast, transverse and sagittal plane movements demonstrated moderate reliability at both speeds (0.37 , ICC (2,1) , 0.76). Averaging the measurement over six strides resulted in increased observed reliability (self-selected walking speed summary Pearson's r = 0.71, slow walking speed summary Pearson's r = 0.79) compared to taking the measurement based on a single stride (self-selected walking speed summary Pearson's r = 0.63, slow walking speed summary Pearson's r = 0.67). Unlike pelvic and lumbar movements (relative to the pelvis), the measurement of lumbar movements (relative to the global reference frame) appeared to depend on whether subjects were walking at self-selected or slow speeds. Conclusions Measurement of pelvic list and lumbar lateral flexion (relative to the pelvis) could be applied with confidence to hypothesis testing about individuals or groups. Movements in the transverse and sagittal planes are unlikely to be appropriate in hypothesis testing about individuals and hence clinical practice, but may still have experimental applications in hypothesis testing about groups. Copyright © 2001 Whurr Publishers Ltd. [source] Confined structures: basic crystallographic aspectsACTA CRYSTALLOGRAPHICA SECTION A, Issue 5 2002Liberato De Caro The concept of a confined structure is introduced. The statistical properties of the structure factors for such structures are derived and the main features of the Patterson function are described. It is shown that the structure-factor distributions for the confined structures coincide with those derived for the rational index reflections of ordinary structures. Algorithms potentially useful for protein crystal structure solution are identified and checked via experimental applications. [source] | ||||||||||||||||