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Time resolved detection and analysis of single nanoparticle electrocatalytic impacts

Time resolved detection and analysis of single nanoparticle electrocatalytic impacts

ing a peak, the current shows a decay with time over a few ms. This difference in behavior between the experiment and model simulation can be seen in Figures 4C and D which each show the occupancy extracted from single example simulation runs plotted with current-time profiles obtained experimentally, as the average of 10 transients (C) and 5 tran- sients (D). The experimental transients and example simula- tion plots were grouped by the rise time, with the rise time centered about 330  s (C) and 500  s (D). The difference between experiment (colored traces) and the model (black traces) indicates that the hydrodynamic trapping is ultimate- ly overcome, and this can reasonably be attributed to the propulsion of the NP due to the release of oxygen as part of H 2 O 2 electro-oxidation, as seen at larger “swimmer particles”
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Quantitative, time-resolved detection of CH 4 concentrations in flows for injection analysis in CNG engines using IR absorption

Quantitative, time-resolved detection of CH 4 concentrations in flows for injection analysis in CNG engines using IR absorption

The crank angle resolved results for predefined λ = 4.06 and λ = 1 mixtures are shown in Fig. 12. The green line in- dicates the nominal value of the premixed gas used. For both measurement series, we find small periodic and reproducible fluctuations which likely result from engine vibrations influ- encing the optical system of the probe. It was not possible to completely eliminate these fluctuations through the sig- nal correction procedure. We speculate that the fluctuations influence the coupling of light into the detection fibre that might result in wavelength dependent signal variations. A reference channel at a different wavelength cannot correct such wavelength dependent fluctuations. However, the fluc- tuations are rather small, with 0.3 % (0.4 %) in λ-values for λ = 1.0 (4.06) for the range − 90–360 ◦ CA.
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Polarised stimulated emission depletion studies of two-photon excited states

Polarised stimulated emission depletion studies of two-photon excited states

Stimulated emission depletion (STED) of excited states has proved to be both a valuable tool in high resolution molecular spectroscopy 1 , in time resolved spectroscopy as a means of orientational photoselection 2 and in the study of ultrafast vibrational relaxation within electronic ground states 3 . There has been considerable interest in the use of single- photon STED in fluorescence microscopy 4 where sub-wavelength image resolution has been recently demonstrated 5 . Recent work in our laboratory 6,7 has demonstrated the feasibility of performing STED in two-photon excited states. In this work femtosecond two-photon 800nm excitation (PUMP) of the widely used fluorescent probe fluorescein was followed by picosecond stimulated emission depletion (DUMP) of the excited state at 580nm. Time resolved detection was employed to determine changes in excited state population and alignment following STED together with the measurement of stimulated emission cross-sections and ground state vibrational relaxation times. In this paper stimulated emission cross-sections and ground state relaxation times for rhodamine 6G in ethylene glycol are determined from the (DUMP) energy dependence of the excited state depletion using a 90° excitation-detection geometry. We also investigate the polarisation dependence of two-photon STED using both parallel and orthogonal PUMP and DUMP polarisations and demonstrate excited state re-polarisation using a collinear excitation-detection geometry. Time resolved STED measurements can circumvent the constraints imposed by the selection rules for single-photon emission in that higher degrees of excited state order and correlation functions for molecular motion can be determined, measurements of hexadecapole alignment dynamics in rhodamine 6G are presented.
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A compact electron gun for time-resolved electron diffraction

A compact electron gun for time-resolved electron diffraction

A number of studies have been performed using TRED to look at order-disorder transitions such as the melting of aluminum, 21,24,25 as well as order-order transitions in cyclohexadiene, 26 silicon, 27 graphite, 28 bismuth, 29 diarylethene, 30 and EDO-TTF. 4 The application of TRED in reflection mode (rather than transmission mode) also allows time- resolved studies of surfaces to be performed. 31,32 The majority of studies using TRED have involved crystalline and polycrystalline samples, with relatively few studies published for gas-phase samples beyond the early work of Zewail. 33 One notable exception is the work of Centurion, 34 who recently showed that it is possible to use electron pulses to obtain non- circularly-symmetric gas-phase diffraction patterns, by temporarily aligning molecules non- adiabatically with ultrafast laser pulses. Upon resolving these patterns using holographic methods, an increase in the amount of data collected is observed compared to experiments using randomly oriented samples of molecules. 34
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Time resolved spectroscopy of the pulsating CV GW Lib

Time resolved spectroscopy of the pulsating CV GW Lib

All other data sets were reduced in the following way. The average bias and flat-field correction was carried out using the figaro package from starlink and nightly average bias and tungsten frames. Pamela was used for the optimal ex- traction of the spectra (Marsh 1989). Regular CuAr arc lamp exposures allowed us to establish an accurate wavelength scale for each spectrum through interpolation between the nearest arcs in time. Each arc frame has been fitted with a 5th order polynomial to 10-40 lines to give a typical RMS of 0.1 pixel. The individual spectra were normalised to the continuum level using a spline fit to selected continuum re- gions.
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Time resolved fluoroimmunoassay: a new test for rubella antibodies

Time resolved fluoroimmunoassay: a new test for rubella antibodies

TR-FIA was also found to be suitable for the diagnosis of acute infections, as significant increases of antibody level were detected in all 30 paired serum specimens tested from patients[r]

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Capturing Protein Dynamics with Time Resolved Luminescence Spectroscopy

Capturing Protein Dynamics with Time Resolved Luminescence Spectroscopy

Protein folding is triggered by a change from conditions that disfavor folding, e.g., high temperature, acidic pH, or denaturants, to conditions that favor folding. Chemical denaturants, including guanidine hydrochloride (Gdn) and urea, are proposed to denature proteins by interacting with and disrupting the hydrogen bonding of the protein backbone and/or altering the intermolecular bonding of water [22, 23]. To trigger folding, denatured protein is mixed rapidly with buffer to decrease the denaturant concentration. In stopped flow mixing, the two solutions are mixed into a cell with high pressure. The ”dead time,” or time needed for complete sample mixing, of these instruments (∼ 1–3 ms [24]) does not allow for resolution of fast folding processes. Newer models with smaller volumes and pneumatic drives reach dead times of 0.5–1 ms.
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Fast time-resolved aerosol collector: proof of concept

Fast time-resolved aerosol collector: proof of concept

Several groups have used scanning or imaging techniques to observe particles while they are being collected. Semleit et al. (1996) experimentally and theoretically analyzed real- time particle detection while particles were deposited onto a far side of a glass plate, as a possible way to examine am- bient particles in clean rooms. They concluded that they should be able to detect down to 0.2 micron particles. They were limited by what is considered the “random” scattering of the glass surface, which was at about the 10 −5 to 10 −6 of the incident light. They also concluded that the best ratio of particle signal to substrate scattering involved light scat- tered at large angles. Mienders et al. (1992) looked at real- time colloid deposition of sub-micron particles with a long- range optical microscope objective. Li et al. (1998) examined micron-sized biological particles sticking to membranes with real-time optical microscopy. Many papers related to these two studies have evolved over time developing “microsieves” and “nanosieves”, with goals of using lithography-produced grids for chemical and biological separations. Some have in- volved real-time observation of particle deposition with au- tomated video analysis (Lin et al., 2009). Another example involves a laser scanner examining particles being deposited over 25 cm squares, with sensitivity down to at least 0.3 mi- cron particles (Tsuchiya and Takami, 1998).
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Time Resolved Transposon Insertion Sequencing Reveals Genome Wide Fitness Dynamics during Infection

Time Resolved Transposon Insertion Sequencing Reveals Genome Wide Fitness Dynamics during Infection

TIS analyses that calculate fitness costs per generation (4, 5) presume that growth can be modeled as a linear process across an experiment, and for many mutants, the calculated fitness has been confirmed to be very near their actual growth rate (4, 5, 29, 30). Our analyses support the idea that growth of most mutants can be effectively modeled with either no change or a fairly consistent difference in growth rate (zero- order and first-order equations, respectively) from that of the population average. However, PACE also allowed us to identify a biologically significant subset of genes whose growth was best described using more complex equations, indicative of fitness that varied across the duration of the experiment. For example, fitness profiles of genes modeled by higher-order functions tended to show decreased slopes late in infection, perhaps reflecting infection-related changes in the host, such as (for example) the onset of an adaptive host response. Ultimately, detection of such variance, as well as clustering of genes based upon their fitness profiles, may facilitate insight into the biological roles filled by their products.
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Spectral Intensity Bioaerosol Sensor (SIBS): an instrument for spectrally resolved fluorescence detection of single particles in real time

Spectral Intensity Bioaerosol Sensor (SIBS): an instrument for spectrally resolved fluorescence detection of single particles in real time

The PMT used in the SIBS shows a wavelength-dependent sensitivity distribution along all 16 detection channels. To compensate for this characteristic and to be able to use the broadest possible fluorescence emission range, the measured emission spectra were corrected with respect to reference spectra acquired from deuterium and halogen lamps. A spec- tral correction over a broad emission range also introduces drawbacks, however, that LIF-instrument users should keep in mind while interpreting derived fluorescence information. In particular, the first two (UV) and the last two (near-IR) detection channels should be treated with care because they require larger correction factors compared to adjacent chan- nels. Ultimately, the correction factor and amplification volt- ages applied to the detector will be experiment specific and will need to be investigated with respect to individual experi- mental aims. To this extent, possible differences between in- struments and important calibrations complicate the concept of the instrument being commercially available. Individual users may desire to purchase the SIBS as a “plug-and-play” detector, but using it without a critical understanding of these complexities would not be appropriate at this time and could lead to inadvertent misinterpretation of the data.
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Airborne measurements of particulate organic matter by  proton-transfer-reaction mass  spectrometry (PTR-MS): a pilot study

Airborne measurements of particulate organic matter by proton-transfer-reaction mass spectrometry (PTR-MS): a pilot study

Abstract. Herein we report on the first successful airborne deployment of the CHemical Analysis of AeRosol ONline (CHARON) particle inlet which allowed us to measure the chemical composition of atmospheric submicrometer par- ticles in real time using a state-of-the-art proton-transfer- reaction time-of-flight mass spectrometry (PTR-ToF-MS) analyzer. The data were collected aboard the NASA DC-8 Airborne Science Laboratory on 26 June 2018 over Cali- fornia in the frame of NASA’s Student Airborne Research Program (SARP). We show exemplary data collected when the airplane (i) shortly encountered a fresh ( < 1 h old) smoke plume that had emanated from the Lions Fire in the Sierra Nevada, (ii) intercepted a particle plume emit- ted from an amine gas treating unit of a petroleum re- finery close to Bakersfield, (iii) carried out a spatial sur- vey in the boundary layer over the San Joaquin Valley and (iv) performed a vertical profile measurement over the greater Bakersfield area. The most important finding from this pilot study is that the CHARON PTR-ToF-MS system measures fast enough to be deployed on a jet research air- craft. The data collected during 3 to 15 s long plume en- counters demonstrate the feasibility of airborne point or small area emission measurements. Further improvements are, however, warranted to eliminate or reduce the observed signal tailing (1/e decay time between 6 and 20 s). The fast time response of the analyzer allowed us to generate highly spatially resolved maps (1–2 km in the horizontal, 100 m in the vertical) of atmospheric particle chemical con- stituents. The chemical information that was extracted from
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Time resolved infrared imaging and spectroscopy for engine diagnostics

Time resolved infrared imaging and spectroscopy for engine diagnostics

Molecular emissions in the infrared spectral region can provi- de access to a range of quantities that are of interest in inter- nal-combustion engine research and development. Molecu- les; such as water, carbon dioxide, carbon monoxide, and hydrocarbons; provide the strongest signals in the range from 1.0 to 5.5 µm. We describe several imaging experiments that employed high-frame-rate infrared cameras to capture spec- trally resolved and spectrally integrated signals from both op- tical and production engines. Spectrally resolved infrared emis- sions that were recorded at kHz rates (i.e., crank-angle steps) in an optically accessible, propane-fueled, single-cylinder en- gine are used to guide the development and validation of a radiative-emission model that is integrated into large-eddy si- mulations (not discussed in this paper). The emissions were dispersed with a spectrometer, and the spectra were recorded with an InSb camera. Clear spectral signatures from water and carbon dioxide were recorded, and the spectra reveal the evo- lution of combustion through each of 100 consecutive cycles for each engine run. Furthermore, at any wavelength of these spectra, cycle-to-cycle variation can be extracted readily. Cy- cle-to-cycle variation was of particular interest in a study of a production heavy-duty engine fueled by natural gas.The ad- dition of two borescopes outfitted with high-frame-rate In- GaAs cameras enabled spectrally integrated measurements from 1.0-1.7 µm. The images allow cycle-resolved observations of ignition and flame growth. The intent of this work was to identify and quantify the impact of a range of ignition systems on lean and/or dilute operation limits from a combustion de- velopment and stability point of view.
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The development and application of time resolved PIV at the University of Strathclyde

The development and application of time resolved PIV at the University of Strathclyde

In early 2000 a Photron Fastcam super 10KC was acquired. The Fastcam is a high speed digital video capable of capturing up to 10k images per second It has a higher resolution that the original Motioncorder and can digitally down load directly to a PC via a SCSI 2 link in .bmp format. Illumination was still provided by a 5W Spectra Physics Argon Ion laser and analysis was by cross correlation using VidPIV V2.41 from Optical Flow Systems of Edinburgh. The time from acquisition to production of a single vector map had now reduced to just ten minutes.

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Picosecond time-resolved infrared spectroscopy of rhodium and iridium azides

Picosecond time-resolved infrared spectroscopy of rhodium and iridium azides

citation of complex 1 at 400 nm in any of the studied solvents is reversible and the quantum yield for the generation of any reactive intermediate is negligible (Fig. 3). While the excitation of complex 1 in MeCN and THF at higher photon energy (266 nm, see Fig. 3 top left and top right) leads to similar spectral transient features, these are, however, extended much further to lower wavenumbers in the period up to 10 ps after excitation. On the contrary, the TRIR spectra at late time delays, after the cooling process of the electronic excited states is complete, are nearly identical for both excitation energies. This indicates that the excited state detected in TRIR experiments is formed considerably hotter vibrationally if populated with a 266 nm pulse, which in principle could be expected. Importantly, close inspection of the TRIR spectra of 1 (  exc = 266 nm) reveals residual parent bleach bands which persist at late time indicating irreversible photochemical
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Localized and time resolved measurements of pulsatile flow in a rectangular channel

Localized and time resolved measurements of pulsatile flow in a rectangular channel

To determine the analytical profiles, a sine wave is fitted to the cross-sectional flow rates of the experimental measure- ments. Any deviation from the fitted sine wave is largely as a result of timing errors in the imaging system. Slight corrections are made to instantaneous phases to ensure that the flow rate of the analytical velocity profile matches that of experiment. The solid lines of Figure 4, plotting the analytical distributions, indicate that the local time-resolved behaviour of inertia-dominated pulsating flow is well captured by theory. Pulsating velocity profiles that are universally positive have a maximum deviation of 16.6%, which occurs near the channel wall. The 20.2% maximum error of velocity profiles that experience flow reversal is calculated at locations 0.8 mm further than the point of zero velocity, which introduces large percentage errors. The discrepancy reduces in the bulk of the fluid with the majority (y > 5mm) of all phase-averaged profiles within about 8% of theory. The oscillating velocity profiles typically have less absolute deviation from theory since some experimental error is removed upon subtraction of the mean from the pulsating profiles; however, the lower velocities result in relative errors of similar magnitude.
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Intracranial Time Resolved Contrast Enhanced MR Angiography at 3T

Intracranial Time Resolved Contrast Enhanced MR Angiography at 3T

S everal approaches to MR angiography (MRA), using dif- ferent contrast mechanisms, have been developed, includ- ing time-of-flight (TOF), phase contrast (PC), T2-prepara- tion, 1 and contrast-enhanced (CE) MRA. Of these techniques, all can produce high-quality static images, but only first-pass multiphase CE-MRA is capable of capturing the dynamic fill- ing of vessels, similar to conventional radiographic digital sub- traction angiography (DSA). Although CE-MRA cannot yet match the spatial and temporal resolutions of conventional radiographic DSA (⬃0.1 ⫻ 0.1 mm and as many as ⬃10 frames/s), CE-MRA is noninvasive, does not involve ionizing radiation, has no risk of iatrogenic stroke, and provides a true 3D dataset. Time-resolved MRA techniques have been applied to various anatomic regions with success. 2-5 Previously, how- ever, the primary goal of time-resolved MRA was to eliminate error associated with timing the arrival of contrast. As hard- ware and software continue to improve, noninvasive evalua- tion of certain pathologies where the order, direction, and rapidity of vessel filling are of clinical significance—such as
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Investigating DNA-Mediated Charge Transport by Time-Resolved Spectroscopy

Investigating DNA-Mediated Charge Transport by Time-Resolved Spectroscopy

of life depends mainly on the quality of those interactions. I am fortunate to have been part of a supportive, creative, and at times eccentric lab group throughout my time in grad school. Of course I appreciate the help and advice they have given me in the lab, but I am more thankful for the personal memories. I will never forget Eddie’s enthusiasm during summer softball and how he convinced every single person in the lab to play that first year; Brian’s ability to make Pumpkinpalooza and Lablympics come to life and his even more impressive ability to convince us all that we wanted to participate; Paul’s cat suit, paper cutouts, clay sculptures, skull stickers, suicide bunnies, and secret messages; physics discussions with Joey; 4th of July at the Rose Bowl; spending ages in the laser lab with Ben; the vacation cottage at ACS; Yosemite and King’s Canyon, talent shows, long car rides, Whiskey Rock, fire breathing, and Christine’s camp cooking; the cake-baking committee; the lunch train; late night trips to Pinkberry and Papa George’s; karaoke and balls; Curtis’s brews; crossword puzzles; flag football; beer and cheese pairings; and so much more. Thanks everyone.
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Steady State and Time Resolved Fluorescence Studies of Anthrylacrylic Ester

Steady State and Time Resolved Fluorescence Studies of Anthrylacrylic Ester

ties of Anthrylacrylic ester were investigated to explore its photophysical properties in various conditions using steady-state absorption and time-resolved fluorescence measurements. The ground and excited state geometric isomers (i.e., structural change of Trans to Cis forms) of this molecule is shown in Figure 1. Orientation of the es- ter group with respect to double bond is different, it can be S-Cis or it can be S-Trans. Cis-Trans isomers are due to rotation around double bond. The energy difference between Cis and Trans-isomers is much higher at room temperature and only the more stable Trans isomers pre- dominate. If dynamic equilibrium between Trans and Cis- isomers is of prime importance in describing the photo- physical behaviour of Anthrylacrylic ester, this should be reflected in the decay parameters. Such studies were not reported in previous work and we have thus performed the experiments in various solvents to confirm the kinetic behaviour of Anthrylacrylic ester in various conditions. Fluorescence decays monitored over each emission maxima showed bi-exponential behavior, and yielded two lifetime components and are in favor of the existence of different isomers having two excited electronic sates. Bi-expo- nential behavior might also be interpreted in terms of ag- gregates, S 2 emission twisted intramolecular charge trans-
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Extrasolar planet detection through spatially resolved observations

Extrasolar planet detection through spatially resolved observations

The direct detection of planets provides a unique opportunity to study exoplan- ets in the context of their formation and evolution. It complements the underlying semi-major axis exoplanet distribution from RV surveys (from 100 AU down to a few AUs) and enables the characterization of the planet itself with an exam- ination of its emergent flux as a function of wavelength. The detection of the planets HR8799 bcde (Marois et al. 2008), Fomalhaut b (Kalas et al. 2008), β Pic b (Lagrange et al. 2009), 2MASS1207 (Chauvin et al. 2004), 1RXS J1609–2105 b (Lafreni` ere et al. 2008), HD 95086 b (Rameau et al. 2013b), KOI-94 (Takahashi et al. 2013) as well as discoveries of protoplanetary candidates LkCa 15 b (Kraus & Ireland 2012) and HD100546 b (Quanz et al. 2013), demonstrate the potential breakthroughs of the technique. However, thus far, most dedicated high contrast imaging surveys have yielded null results (e.g., Rameau et al. 2013a; Vigan et al. 2012; Chauvin et al. 2010; Biller et al. 2007; Heinze et al. 2008). These null results are due to the lack of contrast at small orbital separations, where most planets are expected to be found. Since planets are concluded to be rare at large orbital separations (Chauvin et al. 2010; Lafreni` ere et al. 2007), high contrast imaging must probe close to the parent star to detect a planet.
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Jugular Anomalies in Multiple Sclerosis Are Associated with Increased Collateral Venous Flow

Jugular Anomalies in Multiple Sclerosis Are Associated with Increased Collateral Venous Flow

of increased collaterals in MS by using TOF and time-resolved imaging of con- trast kinetics. Their method for evaluat- ing collaterals was ordinal: any collater- als that were ⬎ 5 mm in diameter (or 7 mm for the segment of the inferior seg- ment of the external jugular vein) were noted as prominent. This shows that anatomic assessment alone is not enough to show differences between patients with MS and HCs and may provide an incomplete picture of the cerebral hemodynamics.

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