Fast Peak Research Articles

Muscle-Power Quality: Does Sex or Race Affect Movement Velocity in Older Adults?

To determine sex and race differences in muscle power per unit of muscle contraction, knee-extensor muscle power normalized for knee-extensor muscle volume was measured in 79 middle-aged and older adults (30 men and 49 women, age range 50-85 years). Results revealed that women displayed a 38% faster peak movement velocity than men and African Americans had a 14% lower peak movement velocity than Whites of a similar age when expressed per unit of involved muscle (p < .001). As expected, men exhibited greater knee-extensor strength and peak power per unit of muscle than women, but women had a faster knee- extension movement velocity per unit of muscle than men at the same relative strength level. Moreover, African Americans had greater knee-extensor muscle volume than Whites but exhibited lower knee-extensor strength and lower movement velocity per unit of muscle when tested at the same relative strength levels.

Application of precise phase detector for density profile and fluctuation measurements using CO2 imaging heterodyne interferometer on LHD

The two-color CO2∕YAG laser imaging heterodyne interferometer was recently equipped with a precise digital phase counter (eight channels, 0.5mrad resolution, 1MHz carrier frequency and sampling rate, 500kHz bandwidth, ±250rad recording range, and a maximum data record of 8.4×106 samples/channel). This modification enables detailed measurements of plasma density dynamics during pellet ablation and, in addition, observations of density fluctuations. Examples of fast rising density peaks in pellet discharges as well as spatial and spectral characteristics of plasma density fluctuations obtained with the heterodyne interferometer are presented.

Comprehensive two‐dimensional gas chromatography/mass spectrometric analysis of pepper volatiles

The headspace compositions of 13 pepper and peppercorn samples of different species, colloquially also referred to as pepper, were analyzed, and more than 300 compounds were tentatively characterized by means of comprehensive two-dimensional gas chromatography in tandem with flame ionization detection, quadrupole mass spectrometric detection and time-of-flight mass spectrometric detection (GC x GC-FID, GC x GC/qMS and GC x GC/TOFMS, respectively). The analysis of volatile organic compounds (VOCs) was performed after solid-phase microextraction (SPME) using a 75-microm PDMS/DVB fibre. Fingerprint comparison between the three techniques permitted peaks to be assigned in the GC x GC-FID experiment based on the analogous MS analysis, taking into account retention shifts arising from method variations. When using GC x GC/TOFMS, about five times more peaks were identified than in GC x GC/qMS. Retention indices for all peaks were calculated in the bi-dimensional column set comprising of a 5% phenyl polysilphenylene-siloxane primary column and a polyethylene glycol second column. The spectra obtained by both mass detection techniques (qMS and TOFMS) give very similar results when spectral library searching was performed. The majority of the identified compounds eluted as pure components as a result of high-resolution GC x GC separations, which significantly reduces co-elution, and therefore increases the likelihood that pure spectra can be obtained. The differences between TOFMS and qMS (in fast scanning mode) spectra were generally small. Whilst spectral quality and relative ion ratios across a narrow peak (e.g. w(b) approximately 100-150 ms) do vary more for the fast peaks obtained in GC x GC/qMS operation, than with TOFMS, in general adequate spectral matching with the library can be achieved.

Detector technologies for comprehensive two‐dimensional gas chromatography

The detector is an integral and important part of any chromatographic system. The chromatographic peak profiles (i.e. peak separation) should, ideally, be unaffected by the detector--it should only provide the sensing capacity required at the end of a column separation process. The relatively new technique of comprehensive 2-D GC (GC x GC) extends the performance of GC manyfold, but comes at a price--existing GC systems may not be adequately designed with the requirements of GC x GC in mind. This is primarily the need for precise measurement of very fast peaks entering the detector (e.g. as fast as 50 ms basewidth in some instances). The capacity of the detector to closely track a rapidly changing chromatographic peak profile depends on a number of factors, such as design of flow paths and make-up gas introduction, type of detector response mechanism, and the chemistry of the response. These factors are discussed here as a means to appreciate the technical demands of detection in GC x GC. The MS detector will not be included in this review.

Factors that influence mesenteric artery blood flow velocity in newborn preterm infants

To identify demographic and clinical variables that relate to the postnatal increase in intestinal blood flow velocity in preterm infants. Fasting or preprandial peak systolic velocity (PSV) and time-averaged mean velocity (TAMV) in the superior mesenteric artery were measured once each day for the first 5 days of life. We investigated the relationship between blood flow velocity and the following variables: birth weight, gestational age, feeding volumes, number of days to reach full feeding volumes, type of feeding given, continuous positive airway pressure (CPAP) administration and hyperalimentation (HAL) administration. Twenty-five infants with a mean birth weight of 1740 g and mean gestational age of 31.8 weeks were studied. There were significant increases in PSV (P < 0.001) and TAMV (P = 0.005) from postnatal day 1 to 5. The postnatal increase in TAMV and PSV was attenuated in infants administered CPAP or HAL for > or =3 days; the results remained significant after controlling for birth weight and gestational age. There was a significant correlation (P < 0.02) between volume of enteral feedings given on 2 of 5 days for TAMV, and on 1 of 5 days for PSV. These data support previous findings of significant increases in intestinal blood flow in preterm infants during the first week of life, and of inconsistent effects of enteral feeding volumes on fasting or preprandial intestinal blood flow. The reasons for, and the clinical implications of, attenuated increases in postnatal intestinal blood flow in infants on CPAP or HAL require further investigation.

Imaging CIN3 photodissociation from 234 to 280 nm

We report Cl((2)P(3/2)) and Cl*((2)P(1/2)) fragment images following ClN(3) photolysis in the 234-280 nm region measured by velocity map imaging. Kinetic energy distributions change shape with photolysis wavelength from bimodal at 234 and 240 nm to single peak at 266 and 280 nm. Where two peaks exist, their ratio is significantly different for Cl and Cl* fragments. The single peak of 266 and 280 nm and the faster peak at 234 and 240 nm are assigned to a Cl + linear-N(3) dissociation channel, in agreement with previous work. The slow peak in the bimodal distributions is assigned to the formation of a high energy form (HEF) of N(3). Candidates for the identity of HEF-N(3) are discussed. Combining our data with photofragmentation translational spectroscopy results, we determined the threshold for the appearance of HEF-N(3) at 4.83 +/- 0.17 eV photolysis energy. This threshold behavior is similar to recently reported results on the wavelength dependence of HN(3) photolysis, where the threshold was associated with a ring closed isomer of HN(3) on the S(1) potential energy surface. We also note that the HEF-N(3) formation threshold observed for ClN(3) occurs where the energy available to the products equals the isomerization barrier from linear to cyclic-N(3).

Theoretical and Experimental Investigation of Calcium-Contraction Coupling in Airway Smooth Muscle

We investigated theoretically and experimentally the Ca2+-contraction coupling in rat tracheal smooth muscle. [Ca2+]i, isometric contraction and myosin light chain (MLC) phosphorylation were measured in response to 1 mM carbachol. Theoretical modeling consisted in coupling a model of Ca2+-dependent MLC kinase (MLCK) activation with a four-state model of smooth muscle contractile apparatus. Stimulation resulted in a short-time contraction obtained within 1 min, followed by a long-time contraction up to the maximal force obtained in 30 min. ML-7 and Wortmannin (MLCK inhibitors) abolished the contraction. Chelerythrine (PKC inhibitor) did not change the short-time, but reduced the long-time contraction. [Ca2+]i responses of isolated myocytes recorded during the first 90 s consisted in a fast peak, followed by a plateau phase and, in 28% of the cells, superimposed Ca2+ oscillations. MLC phosphorylation was maximal at 5 s and then decreased, whereas isometric contraction followed a Hill-shaped curve. The model properly predicts the time course of MLC phosphorylation and force of the short-time response. With oscillating Ca2+ signal, the predicted force does not oscillate. According to the model, the amplitude of the plateau and the frequency of oscillations encode for the amplitude of force, whereas the peak encodes for force velocity. The long-time phase of the contraction, associated with a second increase in MLC phosphorylation, may be explained, at least partially, by MLC phosphatase (MLCP) inhibition, possibly via PKC inhibition.

Dynamic light scattering of semidilute hydrophobically modified alkali‐soluble emulsion solutions with different lengths of poly(ethylene oxide) spacer chain

AbstractSemidilute solutions of hydrophobically modified alkali‐soluble emulsion (HASE) were examined by dynamic light scattering and rheological techniques. For the model polymer without associative macromonomer, two q2 dependent diffusional modes were detected in the decay time distributions. With increasing hydrophobicity of the associative macromonomer, the narrow fast peak was substituted by a shallow broad peak and only one q2 dependent slow mode could be accurately detected, which indicated that the heterogeneity of these associated clusters increases with increasing carbon number. The bulk steady‐shear viscosity exhibits similar results to the diffusion coefficients of the aggregate observed from light scattering measurements. The length of poly(ethylene oxide) (PEO) spacer chain alters the solution properties as well as the associative cluster structure. With increasing length of PEO spacer chain, intramolecular association was substituted by intermolecular association. For EO segment larger than 32 units, intramolecular association dominates, where the formation of HASE aggregates is controlled by the balance of electrostatic repulsion and hydrophobic attraction. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3288–3298, 2005

Deposition of Corticosteroid Aerosol in the Human Lung by Respimat® Soft Mist™ Inhaler Compared to Deposition by Metered Dose Inhaler or by Turbuhaler® Dry Powder Inhaler

Fourteen mild-to-moderate asthmatic patients completed a randomized four-way crossover scintigraphic study to determine the lung deposition of 200 microg budesonide inhaled from a Respimat Soft Mist Inhaler (Respimat SMI), 200 microg budesonide inhaled from a Turbuhaler dry powder inhaler (Turbuhaler DPI, used with fast and slow peak inhaled flow rates), and 250 microg beclomethasone dipropionate inhaled from a pressurized metered dose inhaler (Becloforte pMDI). Mean (range) whole lung deposition of drug from the Respimat SMI (51.6 [46-57]% of the metered dose) was significantly (p < 0.001) greater than that from the Turbuhaler DPI used with both fast and slow inhaled flow rates (28.5 [24-33]% and 17.8 [14-22]%, respectively) or from the Becloforte pMDI (8.9 [6-12]%). The deposition pattern within the lungs was more peripheral for Respimat SMI than for Turbuhaler DPI. The results of this study showed that Respimat SMI deposited corticosteroid more efficiently in the lungs than either of two widely used inhaler devices, Turbuhaler DPI or Becloforte pMDI.

Long-Term Plasticity Mediated by mGluR1 at a Retinal Reciprocal Synapse

The flow of information across the retina is controlled by reciprocal synapses between bipolar cell terminals and amacrine cells. However, the synaptic delays and properties of plasticity at these synapses are not known. Here we report that glutamate release from goldfish Mb-type bipolar cell terminals can trigger fast (delay of 2-3 ms) and transient GABA(A) IPSCs and a much slower and more sustained GABA(C) feedback. Synaptically released glutamate activated mGluR1 receptors on amacrine cells and, depending on the strength of presynaptic activity, potentiated subsequent feedback. This poststimulus enhancement of GABAergic feedback lasted for up to 10 min. This form of mGluR1-mediated long-term synaptic plasticity may provide retinal reciprocal synapses with adaptive capabilities.

Regulation of the Ca2+ Sensitivity of the Nonselective Cation Channel TRPM4

TRPM4, a Ca(2+)-activated cation channel of the transient receptor potential superfamily, undergoes a fast desensitization to Ca(2+). The mechanisms underlying the alterations in Ca(2+) sensitivity are unknown. Here we show that cytoplasmic ATP reversed Ca(2+) sensitivity after desensitization, whereas mutations to putative ATP binding sites resulted in faster and more complete desensitization. Phorbol ester-induced activation of protein kinase C (PKC) increased the Ca(2+) sensitivity of wild-type TRPM4 but not of two mutants mutated at putative PKC phosphorylation sites. Overexpression of a calmodulin mutant unable to bind Ca(2+) dramatically reduced TRPM4 activation. We identified five Ca(2+)-calmodulin binding sites in TRPM4 and showed that deletion of any of the three C-terminal sites strongly impaired current activation by reducing Ca(2+) sensitivity and shifting the voltage dependence of activation to very positive potentials. Thus, the Ca(2+) sensitivity of TRPM4 is regulated by ATP, PKC-dependent phosphorylation, and calmodulin binding at the C terminus.

Absorption kinetics and pharmacodynamics of two oral dosage forms of flecainide in patients with an episode of paroxysmal atrial fibrillation

The objectives were to study the absorption kinetics and pharmacodynamics of two oral formulations of flecainide in patients with atrial fibrillation (AF) and to assess the relationship between pharmacokinetic parameters and the efficacy in restoring sinus rhythm. The data of 54 patients included in a randomised, open, parallel-group study were used. Patients received an oral solution containing 300 mg flecainide and 20 mg cisapride or three tablets each containing 100 mg flecainide. The pharmacokinetic profile of flecainide was fitted using a one-compartment model with lag-time and first-order absorption. The tablets gave a maximum concentration (C (max\ fit)) of 0.43+/-0.14 mg/l at 2.37+/-1.20 h. The oral solution resulted in a much faster peak concentration at 1.05+/-0.71 h (P<0.0001). The C (max\ fit) of the oral solution of 0.60+/-0.17 mg/l was higher (P=0.0002) than that of the tablets, and interindividual variabilities of C (max\ fit) were 28% and 33%, respectively. The absorption rate constant (ka) of the oral solution was twofold larger (P<0.0001). A higher ka (P=0.04) and a duration of AF less than 24 h (P=0.006) increased the probability of cardioversion. If atrial fibrillation lasted less than 24 h, only ka (P=0.016) was obtained as a significant variable in multivariate analysis. The linear models of QRS interval changes versus flecainide concentrations of both formulations had similar slopes with similar interindividual variabilities. The probability of cardioversion after an oral loading dose of flecainide in patients with AF is dependent on ka. Rapid loading of the effect compartment, i.e. the atria, appears to be critical to reach cardioversion. Higher flecainide serum concentrations and a more rapid absorption does not increase interindividual variability of pharmacokinetics and pharmacodynamics, which is important when safety is considered.

Lipid emulsions reduce NMDA-evoked currents

Membrane currents conducted by the NMDA receptor channels were investigated in cultured cortical neurons and TsA cells transfected with NR1-1a/NR2A subunits of the NMDA receptor. The whole-cell recording technique was used. Current transients evoked by bath application of NMDA for 5 s were characterized by a fast peak and a slow decay to 46.1±15.5% of the peak level at the end. When NMDA was applied in combination with various lipid emulsions (Intralipid ®, ClinOleic ®, Lipofundin ® or Abbolipid ®), the NMDA-induced currents were reduced, although this reduction did not affect the fast peak, it did affect the decay phase. The amount of reduction depended on the concentration of the lipids (in the case of Abbolipid ® diluted at 1:40, the current at the end of the 5-s drug application was approximately 2/3 of control). When Abbolipid ® was applied 40 s before NMDA, peak and late current were reduced to approximately 2/3. The effect of current reduction was the same at either of the two chosen membrane potentials (−80 and +40 mV) which indicates that the effect was not mediated by contamination of the emulsions with Mg 2+. The current reduction produced by Abbolipid ® was about the same in native neuronal cells and in TsA cells expressing the NR1-1a/NR2A subunits. The current-reducing effect of the lipid emulsions may add to the anesthetic, analgesic and neuroprotective effects seen with hypnotics administered by way of lipid carriers.

The velocity distribution of droplets ejected from Fe and Si targets by pulsed laser ablation in a vacuum and their elimination using a vane-type velocity filter

Droplet deposition has been a serious problem for film preparation by pulsed laser deposition. In this study, for metallic Fe and semiconducting Si targets, whose droplet ejections are remarkable, the droplets could be eliminated using a vane-type velocity filter. The velocity distribution for the droplets sizes was investigated. It was found that the velocity distribution of the Fe droplet had two peaks, while on the other hand, that of Si had only faster peak. The slower one is less than 10 m/s and the faster one ranges between 20 and 50 m/s. The droplet velocity is not significantly dependent on their size and the maximum is at most 50 m/s.

Multiple Tracing Experiments in Unsaturated Fractured Clayey Till

Current monitoring and sampling techniques in unsaturated fractured clay often fail to characterize fast preferential flow. To circumvent these problems, an isolated block (3.5 by 3.5 by 3.3 m) of unsaturated fractured clayey till was used for multiple tracing experiments. The setup allowed full control of the water balance in the block. Experiments at three different steady‐state flow rates were performed. Multiple tracers with different diffusion coefficients were applied in each experiment to evaluate the influence of diffusive exchange between fractures and the matrix. The tracers included two halogen anions (Cl− and Br−), two fluorobenzoic acids (FBA) (2,3‐DFBA and 2,6‐DFBA), two fluorescent dyes (uranine and sulforhodamine B), and one colloidal tracer (0.5‐μm latex particles). At high flow rates, the obtained tracer breakthrough showed a traditional asymmetrical behavior where a fast peak was followed by a long tailing period. At low flow rates, two of the applied tracers revealed a double peak breakthrough curve, whereas the tracer with the lowest molecular diffusion coefficient showed only one peak. The separation of the tracers was hypothesized to be influenced by extensive diffusion into stagnant areas by the tracers with the high diffusion coefficients. This was supported by the breakthrough curve obtained for the colloidal tracer, which showed earlier breakthrough and only one tracer peak.

Multiple Tracing Experiments in Unsaturated Fractured Clayey Till

Current monitoring and sampling techniques in unsaturated fractured clay often fail to characterize fast preferential flow. To circumvent these problems, an isolated block (3.5 by 3.5 by 3.3 m) of unsaturated fractured clayey till was used for multiple tracing experiments. The setup allowed full control of the water balance in the block. Experiments at three different steady-state flow rates were performed. Multiple tracers with different diffusion coefficients were applied in each experiment to evaluate the influence of diffusive exchange between fractures and the matrix. The tracers included two halogen anions (Cl − and Br − ), two fluorobenzoic acids (FBA) (2,3-DFBA and 2,6-DFBA), two fluorescent dyes (uranine and sulforhodamine B), and one colloidal tracer (0.5-μm latex particles). At high flow rates, the obtained tracer breakthrough showed a traditional asymmetrical behavior where a fast peak was followed by a long tailing period. At low flow rates, two of the applied tracers revealed a double peak breakthrough curve, whereas the tracer with the lowest molecular diffusion coefficient showed only one peak. The separation of the tracers was hypothesized to be influenced by extensive diffusion into stagnant areas by the tracers with the high diffusion coefficients. This was supported by the breakthrough curve obtained for the colloidal tracer, which showed earlier breakthrough and only one tracer peak.

Dynamic light scattering studies of irradiated kappa carrageenan

Investigation of the dynamic behavior of irradiated kappa carrageenan (in KCl) as a function of irradiation dose and temperature was done by dynamic light scattering (DLS). The intensity correlation function (ICF) shifted towards shorter relaxation times with increasing radiation dose as a result of radiolysis. The characteristic decay time distribution function, G ( Γ ), indicates the presence of fast and slow mode peaks respectively at around 0.1–10 ms and 100–1000 ms. A peak broadening of the fast mode peak in G ( Γ ) appeared with decreasing temperature, indicating that coil-to-helical conformational transition took place. The conformation transition temperature (CTT) decreased with increasing radiation dose. No transition was observed for κ-carrageenan irradiated at 200 kGy. A new faster relaxation mode appeared at around 0.1–1 ms at temperatures below the CTT. This peak is found in κ-carrageenan irradiated at doses exclusively between 75 and 175 kGy. The peak height of this mode is largest at 100 kGy which corresponds to the optimum biologic activity of κ-carrageenan reported previously.

Dynamic light scattering studies of irradiated kappa carrageenan

Investigation of the dynamic behavior of irradiated kappa carrageenan (in KCl) as a function of irradiation dose and temperature was done by dynamic light scattering (DLS). The intensity correlation function (ICF) shifted towards shorter relaxation times with increasing radiation dose as a result of radiolysis. The characteristic decay time distribution function, G( Γ), indicates the presence of fast and slow mode peaks respectively at around 0.1–10 ms and 100–1000 ms. A peak broadening of the fast mode peak in G( Γ) appeared with decreasing temperature, indicating that coil-to-helical conformational transition took place. The conformation transition temperature (CTT) decreased with increasing radiation dose. No transition was observed for κ-carrageenan irradiated at 200 kGy. A new faster relaxation mode appeared at around 0.1–1 ms at temperatures below the CTT. This peak is found in κ-carrageenan irradiated at doses exclusively between 75 and 175 kGy. The peak height of this mode is largest at 100 kGy which corresponds to the optimum biologic activity of κ-carrageenan reported previously.

Electrochemical detection of trace insulin at carbon-nanotube-modified electrodes

Carbon-nanotube (CNT)-modified glassy-carbon electrodes dramatically accelerate the electrooxidation of insulin to offer an attractive amperometric detection of this important hormone. Hydrodynamic voltammograms indicate a substantial lowering of the detection potential, with oxidation starting above +0.5 V (versus Ag/AgCl) and leveling off of the response above +0.7 V. The flow-injection amperometric response (at pH 7.4) is highly linear (to at least 1000 nM), reproducible (RSD=4.8%; n=30), and fast (peak width of 45 s). The high sensitivity (48 nA/μM) and moderate detection potential (+0.8 V) lead to a low detection limit of 14 nM. Such performance characteristics compare favorably with those of previously reported metal-oxide-modified electrodes for insulin, and indicate great promise for in vivo measurements of insulin release and for monitoring this hormone in chromatographic effluents.

The velocity distribution of droplets ejected from Fe and Si targets by pulsed laser ablation in a vacuum and their elimination using a vane-type velocity filter

Droplet deposition has been a serious problem for film preparation by pulsed laser deposition. In this study, for metallic Fe and semiconducting Si targets, whose droplet ejections are remarkable, the droplets could be eliminated using a vane-type velocity filter. The velocity distribution for the droplets sizes was investigated. It was found that the velocity distribution of the Fe droplet had two peaks, while on the other hand, that of Si had only faster peak. The slower one is less than 10 m/s and the faster one ranges between 20 and 50 m/s. The droplet velocity is not significantly dependent on their size and the maximum is at most 50 m/s.