Measurement Of Transient Changes Research Articles

Major contributors to FLASH sparing efficacy emerge from murine skin studies: dose rate, total dose per fraction, anesthesia and oxygenation

BackgroundNormal tissue sparing from radiation damage upon ultra-high dose rate irradiation, known as the FLASH effect with an equivalent tumor response, has been widely reported in murine skin models, and translation of this type of radiotherapy to humans has already begun, with skin sparing being a primary outcome expected.MethodsThis study reviews the status of the field, focusing on the proposed mechanisms and skin response assays, outlining what has become known in terms of input parameters that might control the magnitude of the FLASH effect.ResultsMurine studies have largely focused on acute damage responses, developing over 3–8 weeks, to single doses of FLASH versus conventional dose rate (CDR), suggesting that at dose rates above tens of Gray per second, with a total dose of more than 20 Gy, the FLASH effect is induced. Fractionated delivery appears to be possible, although fraction sizes >17 Gy appear to be needed for sparing efficacy. The interplay between the dose rate and total dose per fraction remains to be fully elucidated. Oxygen is a modulator of efficacy, with both hypoxia and hyperoxia diminishing the effect of FLASH. Measurement of transient changes in oxygen levels is possible and may be a marker of treatment efficacy.ConclusionTaken together, murine skin data provide important information for translational studies, despite the associated limitations. Studies of later-term sparing effects, as well as studies on pig skin, are needed to take the next step in assessing translational FLASH efficacy. The control of biological factors, such as tissue oxygenation, may be required to understand and control the response.

Time-resolved diffraction with an optimized short pulse laser plasma X-ray source.

We present a setup for time-resolved X-ray diffraction based on a short pulse, laser-driven plasma X-ray source. The employed modular design provides high flexibility to adapt the setup to the specific requirements (e.g., X-ray optics and sample environment) of particular applications. The configuration discussed here has been optimized toward high angular/momentum resolution and uses Kα-radiation (4.51 keV) from a Ti wire-target in combination with a toroidally bent crystal for collection, monochromatization, and focusing of the emitted radiation. Ti-Kα1 photons per pulse with relative bandwidth are delivered to the sample at a repetition rate of 10 Hz. This allows for the high dynamic range (104) measurements of transient changes in the rocking curves of materials as for example induced by laser-triggered strain waves.

Ozonation of aqueous phenol using high‐silica zeolite in an aerated mixing vessel

AbstractWe examined the degradation of aqueous phenol by ozonation in an aerated mixing vessel, which was combined with a fixed‐bed reactor packed with high‐silica zeolite (HSZ) pellets. Ozone‐containing oxygen gas was introduced as fine bubbles through a sparger placed in the aerated mixing vessel, whereas the aqueous phenol solution was circulated between the vessel and the reactor. Measurements of transient changes in the concentration of both phenol and total organic carbon in the treated solution revealed that the degradation of phenol or total organic carbon by ozonation was enhanced by the presence of HSZ because both phenol and ozone could adsorb on the hydrophobic micropores. As a result of quantitative analysis of the treated solution, it was found that catechol, hydroquinone, humic acid, and maleic acid were the possible reaction intermediates during ozonation of aqueous phenol employing HSZ.

Plasmonic Sensing of Heat Transport at Solid–Liquid Interfaces

We report experimental studies of interfacial heat transport for a system of Au nanodisks supported on fused silica substrates, coated by hydrophilic and hydrophobic self-assembled monolayers, and immersed in water–ethanol mixtures and solutions of a nonionic surfactant, hexyl-β-d-glucoside in water. The Au nanodisks are abruptly heated by a sub-picosecond optical pulse; time-resolved changes in the temperature of the Au nanodisk and the liquid near the nanodisk/liquid interface are monitored by measurements of transient changes in optical transmission. The interface thermal conductance G of nanodisks coated with a hydrophilic self-assembled monolayer (SAM) of sodium 3-mercapto-1-propanesulfonate varies over the range 90 < G < 190 MW m–2 K–1 as the composition of the liquid mixture is changed from pure ethanol to pure water. With increasing hexyl-β-d-glucoside concentration in water, the interface thermal conductance of hydrophilic nanodisks decreases from 190 MW m–2 K–1 to 130 MW m–2 K–1 as the concentra...

A New Device for Simultaneous Measurements of Dynamic Interfacial Tension and Electrical Potential Difference

Abstract A new device for simultaneous time-resolved measurements of electromotive force (EMF) and interfacial tension (IT) at liquid–liquid interfaces is described. Two examples of applications are presented: 1) measurement of the variations in IT during simulated EMF measurements in model membrane-based ion-selective electrodes, and 2) measurements of transient changes in EMF in a system displaying IT oscillations without any chemical reaction.

Kinetics of laser-induced photodarkening in arsenic based chalcogenide glasses

Photoinduced changes in the optical properties of chalcogenide glass thin films have been studied extensively but usually only permanent changes were recorded through measurements before and after exposure to pump light. To understand the progression of such effects, in this paper we report in situ measurement of transient changes in the optical transmission of amorphous As2Se3, As5Se5 and As4Se3 thin films during their exposure to a He–Ne laser which has photon energy close to the bandgap of the studied compositions. Mathematical expressions are established, which describe accurately both the light intensity and time dependences of photodarkening. The structural origin of the observed changes is discussed briefly.

Optical Coherence Tomography Phase Measurement of Transient Changes in Squid Giant Axons During Activity

Noncontact optical measurements reveal that transient changes in squid giant axons are associated with action potential propagation and altered under different environmental (i.e., temperature) and physiological (i.e., ionic concentrations) conditions. Using a spectral-domain optical coherence tomography system, which produces real-time cross-sectional images of the axon in a nerve chamber, axonal surfaces along a depth profile are monitored. Differential phase analyses show transient changes around the membrane on a millisecond timescale, and the response is coincident with the arrival of the action potential at the optical measurement area. Cooling the axon slows the electrical and optical responses and increases the magnitude of the transient signals. Increasing the NaCl concentration bathing the axon, whose diameter is decreased in the hypertonic solution, results in significantly larger transient signals during action potential propagation. While monophasic and biphasic behaviors are observed, biphasic behavior dominates the results. The initial phase detected was constant for a single location but alternated for different locations; therefore, these transient signals acquired around the membrane appear to have local characteristics.

Third-order optical nonlinearities of carbon nanotubes in the femtosecond regime

Femtosecond pump–probe experiments have been carried out on an ensemble of single-wall carbon nanotubes deposited on a glass substrate. Measurements of transient changes of transmission and reflection provide an estimate of the real and imaginary parts of the second-order hyperpolarizability of carbon nanotubes. These values are compared with previous measurements and are discussed in the light of a simple model of the optical nonlinearities near the optical band-gap.

Analysis of the transient increase in cytosolic Ca2+ during the action potential of higher plants with high temporal resolution: requirement of Ca2+ transients for induction of jasmonic acid biosynthesis and PINII gene expression.

Plants respond to various abiotic stimuli by activation and propagation of fast electrical signals, action potentials. To resolve the temporal increase in cytosolic Ca(2)(+) during the action potentials of higher plants, we regenerated transgenic potato plants that expressed the Ca(2)(+) photoprotein apoaequorin. These genetically engineered potato plants were used for simultaneous measurements of transient changes in the membrane potential and the Ca(2)(+) luminescence triggered by heat-induced action potentials. High temporal resolution for recording of the fast transient electrical and light signals was accomplished by a sampling rate of 1 kHz. Upon elicitation by heat the membrane potential depolarization preceded the rise of cytosolic Ca(2)(+) by 50-100 ms. Several Ca(2)(+) channel blockers were tested to inhibit the rise in cytosolic Ca(2)(+). Treatment of plants with Ruthenium Red blocked the elevation in cytosolic Ca(2)(+) that was associated with heat-stimulated action potentials. Furthermore, action potentials have been demonstrated to stimulate jasmonic acid biosynthesis and PINII gene expression. Therefore, we measured jasmonic acid and PINII gene expression levels subsequent to action potential initiation by a short heating pulse. As expected, jasmonic acid biosynthesis and PINII gene expression were induced by action potentials. Pretreatment of potato plants with Ruthenium Red inhibited induction of jasmonic acid biosynthesis and PINII gene expression that was generally triggered by heat-activated action potentials.

Transient changes in four GLUT4 compartments in rat adipocytes during the transition, insulin-stimulated to basal: implications for the GLUT4 trafficking pathway.

In rat adipocytes, insulin-induced GLUT4 recruitment to the plasma membrane (PM) is associated with characteristic changes in the GLUT4 contents of three distinct endosomal fractions, T, H, and L. The organelle-specific marker distribution pattern suggests that these endosomal GLUT4 compartments are sorting endosomes (SR), GLUT4-storage endosomes (ST), and GLUT4 exocytotic vesicules (EV), respectively, prompting us to analyze GLUT4 recycling based upon a four-compartment kinetic model. Our analysis revealed that insulin modulates GLUT4 trafficking at multiple steps, including not only the endocytotic and exocytotic rates, but also the two rate coefficients coupling the three intracellular compartments. This analysis assumes that GLUT4 cycles through PM T, H,L, and back to PM, in that order, with transitions characterized by four first-order coefficients. Values assigned to these coefficients are based upon the four steady-state GLUT4 pool sizes assessed under both basal and insulin stimulated states and the transition time courses observed in the plasma membrane GLUT4 pool. Here we present the first reported experimental measurements of transient changes in each of the four GLUT4 compartments during the insulin-stimulated to basal transition in rat adipocytes and compare these experimental results with the corresponding model simulations. The close correlation of these results offers clear support for the general validity of the assumed model structure and the assignment of the T compartment to the sorting endosome GLUT4 pool. Variations in the recycling pathway from that of an unbranched cyclic topography are also considered in the light of these experimental observations. The possibility that H is a coupled GLUT4 storage compartment lying outside the direct cyclic pathway is contraindicated by the data. Okadaic acid-induced GLUT4 recruitment is accompanied by modulation of the rate coefficients linking individual endosomal GLUT4 compartments, further demonstrating a significant role of the endosomal pathways in GLUT4 exocytosis.

A Combined Heat Clearance Method for Tissue Blood Flow Measurement

Tissue Blood Flow is measured by applying a combined procedure of two independent approaches based on heat clearance: the Pulse Decay Method and the Continuous Method. The Pulse Method allows absolute assessment of tissue BF with no need for calibration, and can be applied only if the tissue BF is steady during the period of measurement. On the other hand, the Continuous Method enables the observation of rapid changes in tissue BF, and can be applied under non steady-state conditions. Using the combined method, a continuous quantitative measurement of transient changes in tissue BF can be obtained. For this purpose, we have developed two experimental systems consisting of independent electronic units: a Pulse Unit and a Continuous Unit. A micro-computer with dedicated software controls the operation of the electronic units and calculates tissue BF on-line. In vitro measurements are performed and demonstrate the reliability of the methods. In vivo measurements in rat brain tissue are also performed and include physiological and pharmacological changes of local tissue BF. The results of the two heat clearance methods correlate well with tissue BF values measured by a third independent method, the Hydrogen Clearance Method.

Interference by DOPAC and ascorbate during attempts to measure drug-induced changes in neostriatal dopamine with Nafion-coated, carbon-fiber electrodes

The selectivity of Nafion-coated, carbon-fiber electrodes was evaluated for the voltammetric detection of dopamine in the presence of 3,4-dihydroxyphenylacetic acid (DOPAC) and ascorbate, which are interferant anions in the brain. Nafion coating was applied to both polished carbon-disk electrodes and electrochemically modified electrodes. During in vitro testing, polished disk electrodes showed the greatest selectivity for dopamine at the fastest scan rate tested (300 V s −1), but the drift in signal made slow changes in dopamine difficult to determine. Electrochemically modified electrodes already provide an ascorbate wave distinct from that for dopamine, but Nafion coating actually decreased dopamine selectivity with respect to DOPAC. In vivo testing was carried out in the neostriatum of urethane-anesthetized rats in response to drug- or stimulation-induced increases in dopamine transmission. Administration of haloperidol (0.5 mg kg −1) followed by GBR 12909 (20 mg kg −1), which is known to cause a 10-fold increase in extracellular dopamine, failed to produce a selective signal for dopamine when measured voltammetrically. Comparable results were obtained following administration of amphetamine (2.5 mg kg −1), which also increases dopamine overflow. Voltammetric detection of dopamine was possible, however, during electrical stimulation of dopaminergic afferents in the medial forebrain bundle. Thus, voltammetry with Nafion-coated electrodes is best suited to the measurement of transient changes in extracellular dopamine rather than the relatively prolonged changes in dopamine overflow produced by various drugs.

Direct coupling of intracerebral dialysis with flow injection analysis based on enzymatic/fluorescence detection of lactic acid

Rapid, specific measurement of the lactic acid content of the extracellular fluid of a conscious, freely-moving rat can be accomplished by direct combination of intracerebral dialysis and flow injection analysis with enzymatic/fluorescence detection. Basal levels of lactic acid, the end product of anaerobic glycolysis, can be measured by using lactate dehydrogenase to convert lactate to pyruvate with consequent generation of NADH, which is monitored fluorimetrically. The rapid response time of this system, 40 s, allows real-time measurement of transient changes in anaerobic metabolism in the striatum of the rat, as illustrated after electrically-induced seizures.

New type of rapid scanning circular dichroism spectropolarimeter using an acoustic optical filter

A new circular dichroism (CD) and magnetic circular dichroism (MCD) system with narrow bandwidth and high scanning rate has been developed. The versatility of the system for the measurements of transient changes in CD and MCD has been also described. This new CD and MCD system is composed of an acoustic optical (AO) filter of TeO2 as a monochromator, a stress modulator, and a photomultiplier together with their operating devices and a computer system. The linearly polarized light from the AO filter is modulated to left- and right-circularly polarized light by a stress modulator operated at 50 kHz. The absorbance difference of the left- and right-circularly polarized light is detected by a photomultiplier, after passing through the sample. The whole optical system and detector system are matched in time by the same computer system. A rapid scanning was performed successfully at the rate of 50 nm range/10 ms, with better spectral resolution and higher signal-to-noise ratio than other commercially available CD spectropolarimeters. Finally, we showed several applications of the new CD and MCD system for the observations of CD and MCD spectral changes in biological molecules.

The measurement of transient changes in rotor angle of a microsynchronous alternator

Describes an instrument for accurate measurement of transient changes without the machine having to be synchronised. The instrument has been designed for laboratory use but the principle could be applied to practical machines.

High-Resolution Measurements of Transient Changes in the Growth Rate of Intact Lupin Seedlings

Measurements of the growth rate of intact lupin seedlings were made under steady-state conditions and as the environment was altered. Although the growth rate frequently changed smoothly with the new condition, there were several cases where periodicity or oscillations in the growth rate were observed. These cases included growth oscillations induced by: the solution in which the roots were immersed being changed back from a mannitol solution to water; the replacement of anaerobic conditions by air or oxygen; the tension being increased on the hypocotyl; and, under some condi- tions, the addition or removal of high CO2 concentrations. The observed periodicity is more complex than is accounted for by a simple relationship of the minimum yield stress increasing or decreasing with the growth rate, but more information is needed to develop a better model.

Measurement of Transient Changes in Liquid Holdup in Packed Beds

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMeasurement of Transient Changes in Liquid Holdup in Packed BedsNicholas StandishCite this: Ind. Eng. Chem. Fundamen. 1968, 7, 2, 312–314Publication Date (Print):May 1, 1968Publication History Published online1 May 2002Published inissue 1 May 1968https://doi.org/10.1021/i160026a021RIGHTS & PERMISSIONSArticle Views34Altmetric-Citations5LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (309 KB) Get e-Alerts

Ventilatory oxygen drive in acute and chronic hypoxia

Ventilatory oxygen drive has been investigated in four groups of subjects by measurement of transient changes of ventilation occurring after inhalation of two or three breaths of pure oxygen or nitrogen: 1) acutely hypoxic normal subjects, 2) lowlanders acclimatized to 3660 and 5200 m, 3) highlanders native to the same altitudes, and 4) highlanders apparently affected by chronic altitude sickness. Ventilatory oxygen drive was strong in groups one and two, slight in native highlanders and non-existent in the patients. Alveolar gases were analyzed at four altitudes, 2700, 3660, 4200 and 5200 m; at each, highlanders were significantly more hypoxic and hypercapnic than lowlanders acclimatized to the same altitude. That a third curve for highland natives can be drawn on the O 2-C0 2 Rahn and Otis diagram and is explained by the weak Ventilatory oxygen drive of highlanders.