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Samuel Beaulieu, Antoine Comby, Baptiste Fabre, Dominique Descamps, Amélie Ferré, Gustavo Garcia, Romain Géneaux, Francois Légaré, Laurent Nahon, Stéphane Petit, Thierry Ruchon, Bernard Pons, Valérie Blanchet, Yann Mairesse
Measuring the ultrafast dynamics of chiral molecules in the gas phase has been a long standing and challenging quest of molecular physics. The main limitation to reach that goal has been the lack of highly sensitive chiroptical measurement. By enabling chiral discrimination with up to several 10% of sensitivity, photoelectron circular dichroism (PECD) offers a solution to this issue. However, tracking ultrafast processes requires measuring PECD with ultrashort light pulses. Here we compare the PECD obtained with different light sources, from the extreme ultraviolet to the mid-infrared range, leading to different ionization regimes: single-photon, resonance-enhanced multiphoton, above-threshold and tunnel ionization...
October 18, 2016: Faraday Discussions
Qian Zhao, Xueqi Chen, Yun Zhou
Alzheimer's disease (AD) is a progressive neurodegenerative disorder, causing changes in memory, thinking, and other dysfunction of brain functions. More and more people are suffering from the disease. Early neuroimaging techniques of AD are needed to develop. This review provides a preliminary summary of the various neuroimaging techniques that have been explored for in vivo imaging of AD. Recent advances in magnetic resonance (MR) techniques, such as functional MR imaging (fMRI) and diffusion MRI, give opportunities to display not only anatomy and atrophy of the medial temporal lobe, but also at microstructural alterations or perfusion disturbance within the AD lesions...
March 2016: Brain Informatics
Borja Peropadre, Gian Giacomo Guerreschi, Joonsuk Huh, Alán Aspuru-Guzik
Boson sampling, the task of sampling the probability distribution of photons at the output of a photonic network, is believed to be hard for any classical device. Unlike other models of quantum computation that require thousands of qubits to outperform classical computers, boson sampling requires only a handful of single photons. However, a scalable implementation of boson sampling is missing. Here, we show how superconducting circuits provide such platform. Our proposal differs radically from traditional quantum-optical implementations: rather than injecting photons in waveguides, making them pass through optical elements like phase shifters and beam splitters, and finally detecting their output mode, we prepare the required multiphoton input state in a superconducting resonator array, control its dynamics via tunable and dispersive interactions, and measure it with nondemolition techniques...
September 30, 2016: Physical Review Letters
Anthony G Jay, James A Hamilton
Membrane organization and fluidity research continues to expand and the understanding of membrane dynamics continues to be refined. Within this field of study, laurdan remains among the most popular, versatile, and established fluorescence probes. Fluorimetry and multiphoton microscopy techniques are standards for measuring laurdan fluorescence and continue to be refined. However, complications have arisen due to an amended membrane model, revised terms used for describing membrane phases, and wide variation in the selection of laurdan generalized polarization equation values...
October 13, 2016: Journal of Fluorescence
Pouriska B Kivanany, Kyle C Grose, W Matthew Petroll
Extracellular matrix (ECM) supplies both physical and chemical signals to keratocytes which can impact their differentiation to fibroblasts and/or myofibroblasts. It also provides a substrate through which they migrate during wound repair. We have previously shown that following transcorneal freeze injury (FI), migrating corneal fibroblasts align parallel to the stromal lamellae during wound repopulation. In this study, we compare cell and ECM patterning both within and on top of the stroma at different time points following lamellar keratectomy (LK) in the rabbit...
October 9, 2016: Experimental Eye Research
Yosuke Shimo, Tomohiro Uchimura
Multiphoton ionization time-of-flight mass spectrometry was applied to the measurement of an oil-in-water emulsion that contained toluene as a dispersed phase. Before the measurement, the sample was sufficiently creamed, and then stirred for a short period of time for dispersion. As a result, several intense spikes appeared on the time profile constructed from the peak area for toluene. In the present study, an optical microscope was used to observe the capillary column for sample introduction, and small toluene droplets along with their aggregates were found in the images of the emulsion flowing through the capillary...
2016: Analytical Sciences: the International Journal of the Japan Society for Analytical Chemistry
Kristen Zuraski, Daniel Thomas Kwasniewski, Amit Kumar Samanta, Hanna Reisler
The vibrational predissociation of the HCl-(H2O)3 tetramer, the largest HCl-(H2O)n cluster for which HCl is not predicted to be ionized, is reported. This work focuses on the predissociation pathway giving rise to H2O + HCl-(H2O)2 following IR laser excitation of the H-bonded OH stretch fundamental. H2O fragments are monitored state-selectively by 2+1 resonance enhanced multiphoton ionization (REMPI) combined with time-of-flight mass spectrometry (TOF-MS). Velocity map images of H2O in selected rotational levels are used to determine translational energy distributions from which the internal energy distributions in the pair-correlated cofragments are derived...
October 10, 2016: Journal of Physical Chemistry Letters
Pierre Çarçabal, Dominique Descamps, Stéphane Petit, Yann Mairesse, Valérie Blanchet, Raluca Cireasa
5-Fluorouracil (5FU) is a radiosensitiser molecule routinely used in combined chemo- and radio-therapies to enhance and localize cancer treatments. We have employed ultra-short XUV pulses produced by high harmonic generation (HHG) as a pump pulse to study the dynamics underlying the photo-stability and the radiation damage of this molecule. This work shows that it is possible to resolve individual dynamics even when using unselected HH. By comparing the results with those obtained in the multiphoton absorption at 400 nm, we were able to identify the frequencies of the HH comb relevant to the recorded dynamics: HH5 and HH3...
September 22, 2016: Faraday Discussions
Arnfinn Hykkerud Steindal, Maarten T P Beerepoot, Magnus Ringholm, Nanna Holmgaard List, Kenneth Ruud, Jacob Kongsted, Jógvan Magnus Haugaard Olsen
We present the theory and implementation of an open-ended framework for electric response properties at the level of Hartree-Fock and Kohn-Sham density functional theory that includes effects from the molecular environment modeled by the polarizable embedding (PE) model. With this new state-of-the-art multiscale functionality, electric response properties to any order can be calculated for molecules embedded in polarizable atomistic molecular environments ranging from solvents to complex heterogeneous macromolecules such as proteins...
October 12, 2016: Physical Chemistry Chemical Physics: PCCP
Adam D Smith, Hannah M Watts, Edward Jager, Daniel A Horke, Emma Springate, Oliver Alexander, Cephise Cacho, Richard T Chapman, Russell S Minns
The dissociation dynamics of the Ã-state of ammonia have been studied using a resonant multiphoton ionisation probe in a photoelectron spectroscopy experiment. The use of a resonant intermediate in the multiphoton ionisation process changes the ionisation propensity, allowing access to different ion states when compared with equivalent single photon ionisation experiments. Ionisation through the E' (1)A1' Rydberg intermediate means we maintain overlap with the ion state for an extended period, allowing us to monitor the excited state population for several hundred femtoseconds...
October 12, 2016: Physical Chemistry Chemical Physics: PCCP
W Strek, R Tomala, L Marciniak, M Lukaszewicz, B Cichy, M Stefanski, D Hreniak, A Kedziorski, M Krosnicki, L Seijo
The laser induced white emission (LIWE) from Sr2CeO4 nanocrystals upon irradiation with a focused IR laser beam was investigated. It was observed to be a threshold phenomenon with its intensity increasing exponentially with the excitation power density. This process was investigated under double laser beam simultaneous excitation in the UV range leading to Stokes emission in the visible range and in the IR range leading to anti-Stokes LIWE. With increasing LIWE intensity, the Stokes emission intensity strongly decreased...
October 12, 2016: Physical Chemistry Chemical Physics: PCCP
Pavle Glodic, Dimitris Zaouris, Peter C Samartzis, Arnar Hafliðason, Ágúst Kvaran
Analysis of mass resolved spectra as well as velocity map images derived from resonance enhanced multiphoton ionization (REMPI) of HBr via resonance excitations to mixed Rydberg (6pπ (3)Σ(-)(v' = 0)) and valence (ion-pair) (V (1)Σ(+)(v' = m + 17)) states allows characterization of the effect of a triplet-to-singlet state interaction on further photoexcitation and photoionization processes. The analysis makes use of rotational spectra line shifts, line intensity alterations, kinetic energy release spectra as well as angular distributions...
September 21, 2016: Physical Chemistry Chemical Physics: PCCP
Virginia Brancato, Alessandro Garziano, Filomena Gioiella, Francesco Urciuolo, Giorgia Imparato, Valeria Panzetta, Sabato Fusco, Paolo A Netti
: We fabricated three-dimensional microtissues with the aim to replicate in vitro the composition and the functionalities of the tumor microenvironment. By arranging either normal fibroblasts (NF) or cancer-activated fibroblasts (CAF) in two different three dimensional (3D) configurations, two kinds of micromodules were produced: spheroids and microtissues. Spheroids were obtained by means of the traditional cell aggregation technique resulting in a 3D model characterized by high cell density and low amount of extracellular proteins...
October 6, 2016: Acta Biomaterialia
Yu Jin Kim, Bum Chul Park, June Park, Hee-Dae Kim, Nam Hoon Kim, Yung Doug Suh, Young Keun Kim
Magnetite nanoparticles combined with polymers produce white-light emission under multiphoton laser irradiation. Understanding the photonic reaction in magnetite-polymer composites is critical for application of magnetite NPs as photothermal agents. Laser irradiated magnetite nanoparticle-poly(methyl methacrylate) (PMMA) composites exhibit fluorescence due to the carbon double-bond formation resulting from the oxidation of the PMMA.
October 6, 2016: Nanoscale
Pablo Sampedro, Bo Y Chang, Ignacio R Sola
We find a new mechanism of electronic population inversion using strong femtosecond pulses, where the transfer is mediated by vibrational motion on a light-induced potential. The process can be achieved with a single pulse tuning its frequency to the red of the Franck-Condon window. We show the determinant role that the gradient of the transition dipole moment can play on the dynamics, and extend the method to multiphoton processes with odd number of pulses. As an example, we show how the scheme can be applied to population inversion in Na2...
September 14, 2016: Physical Chemistry Chemical Physics: PCCP
Adan Li, Totaro Imasaka
To decrease health-risks to humans, non-toxic compounds were evaluated for use as internal standards for calibrating data obtained by gas chromatography/multiphoton ionization mass spectrometry (GC-MPI-MS) using an ultraviolet femtosecond laser as the ionization source. The retention time in the mass chromatogram was calibrated using a retention index, in which a series of n-alkanes was employed as internal standards for evaluating the retention times for polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs)...
September 30, 2016: Journal of Chromatography. A
Yitong Dong, David Parobek, Daniel Rossi, Dong Hee Son
The benefits of the hot electrons from semiconductor nanostructures in photocatalysis or photovoltaics result from their higher energy compared to the bandedge electrons facilitating the electron transfer process. The production of high-energy hot electrons usually requires short-wavelength UV or intense multiphoton visible excitation. Here, we show that highly energetic hot electrons capable of above-threshold ionization are produced via exciton-to-hot carrier upconversion in Mn-doped quantum dots under weak bandgap excitation (~10W/cm(2)) achievable with the concentrated solar radiation...
October 5, 2016: Nano Letters
Shimpei Shibuta, Tomoko Imasaka, Totaro Imasaka
The allergenic compounds listed in the Cosmetics Directive by the Scientific Committee for Consumer Safety were analyzed by gas chromatography combined with multiphoton ionization mass spectrometry using a femtosecond laser emitting at 200 and 267 nm as the ionization source. The limits of detection were less than 100 pg/μL for all of the compounds, permitting them to be measured in actual samples that were simply prepared by a 100-fold dilution of the original sample. The ionization process was investigated for the 26 allergens, some of which had no absorption band, even in the far-ultraviolet region...
October 4, 2016: Analytical Chemistry
Chih-Ju Lin, Feng-Chieh Li, Yu-Yang Lee, Te-Yu Tseng, Wei-Liang Chen, Vladimir Hovhannisyan, Ning Kang, Nicholas G Horton, Shu-Jen Chiang, Chris Xu, Hsuan-Shu Lee, Chen-Yuan Dong
Hepatobiliary metabolism is one of the major functions of the liver. However, little is known of the relationship between the physiological location of the hepatocytes and their metabolic potential. By the combination of time-lapse multiphoton microscopy and first order kinetic constant image analysis, the hepatocellular metabolic rate of the model compound 6-carboxyfluorescein diacetate (6-CFDA) is quantified at the single cell level. We found that the mouse liver can be divided into three zones, each with distinct metabolic rate constants...
September 1, 2016: Biomedical Optics Express
Ilyas Saytashev, Rachel Glenn, Gabrielle A Murashova, Sam Osseiran, Dana Spence, Conor L Evans, Marcos Dantus
Red blood cells (RBC) in two-photon excited fluorescence (TPEF) microscopy usually appear as dark disks because of their low fluorescent signal. Here we use 15fs 800nm pulses for TPEF, 45fs 1060nm pulses for three-photon excited fluorescence, and third harmonic generation (THG) imaging. We find sufficient fluorescent signal that we attribute to hemoglobin fluorescence after comparing time and wavelength resolved spectra of other expected RBC endogenous fluorophores: NADH, FAD, biliverdin, and bilirubin. We find that both TPEF and THG microscopy can be used to examine erythrocyte morphology non-invasively without breaching a blood storage bag...
September 1, 2016: Biomedical Optics Express
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