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two photon

Jens Neumann, Sophie Henneberg, Susanne von Kenne, Niklas Nolte, Andreas J Müller, Burkhart Schraven, Michael W Görtler, Klaus G Reymann, Matthias Gunzer, Monika Riek-Burchardt
Inflammation plays an important role in the pathogenesis of ischemic stroke including an acute and prolonged inflammatory process. The role of neutrophil granulocytes as first driver of the immune reaction from the blood site is under debate due to controversial findings. In bone marrow chimeric mice we were able to study the dynamics of tdTomato-expressing neutrophils and GFP-expressing microglia after photothrombosis using intravital two-photon microscopy. We demonstrate the infiltration of neutrophils into the brain parenchyma and confirm a long-lasting contact between neutrophils and microglia as well as an uptake of neutrophils by microglia clearing the brain from peripheral immune cells...
2018: PloS One
Yuly Vesga, Carlos Diaz, Jeanne Crassous, Florencio E Hernandez
Herein, we report on the theoretical-experimental analysis of the two photon absorption and circular dichroism spectra of 1-(2-pyridyl)-4-methoxy-carbo[6]helicene derivative (P6). The primary outcomes of our investigation on this particular helicene derivative with a donor-acceptor motif on one end led to two important conclusions: 1) The lengthening of the π-electron delocalization within the helical core of P6 predominantly increases the contribution of the magnetic transition dipole moment to the TPCD signal; 2) The electric transition quadrupole moment contribution to the TPCD signal is enhanced by the intramolecular charge transfer (ICT) produced by the donor-acceptor combination on one end of the molecule...
March 15, 2018: Journal of Physical Chemistry. A
S F Cooper, Z Burkley, A D Brandt, C Rasor, D C Yost
We demonstrate a 650 mW 243 nm continuous-wave laser coupled to a linear optical enhancement cavity. The enhancement cavity can maintain >30  W of intracavity power for 1 h of continuous operation without degradation. This system has sufficient power for a demonstration of two-photon laser cooling of hydrogen and may be useful for experiments on other simple two-body atomic systems.
March 15, 2018: Optics Letters
Xiaolong Liu, Yuan Yu, Haitao Tang, Lu Xu, Jianji Dong, Xinliang Zhang
We propose and demonstrate a silicon-on-insulator (SOI)-based widely tunable microwave photonic filter (MPF), which is implemented by using an under-coupled microring resonator (MRR) assisted by two cascaded tunable Mach-Zehnder interferometers. In the experiment, the MPF achieves an ultrahigh peak rejection exceeding 60 dB, a full width at half-maximum bandwidth of 780 MHz, and a frequency tuning range of 0-40 GHz, even when the propagation loss of the MRR is 1.65 dB/cm. To the best of our knowledge, this MPF demonstrates ultrahigh peak rejection and narrow bandwidth simultaneously in SOI for the first time with MRR of such propagation loss and avoids using external electrical devices to improve the rejection...
March 15, 2018: Optics Letters
L Ortiz-Gutiérrez, L F Muñoz-Martínez, D F Barros, J E O Morales, R S N Moreira, N D Alves, A F G Tieco, P L Saldanha, D Felinto
Superradiance in an ensemble of atoms leads to the collective enhancement of radiation in a particular mode shared by the atoms in their spontaneous decay from an excited state. The quantum aspects of this phenomenon are highlighted when such collective enhancement is observed in the emission of a single quantum of light. Here we report a further step in exploring experimentally the nonclassical features of superradiance by implementing the process not only with single excitations, but also in a two-excitation state...
February 23, 2018: Physical Review Letters
Ting Cao, Meng Wu, Steven G Louie
We show that band topology can dramatically change the photophysics of two-dimensional semiconductors. For systems in which states near the band extrema are of multicomponent character, the spinors describing these components (pseudospins) can pick up nonzero winding numbers around the extremal k point. In these systems, we find that the strength and required light polarization of an excitonic optical transition are dictated by the optical matrix element winding number, a unique and heretofore unrecognized topological characteristic...
February 23, 2018: Physical Review Letters
Jin-Wen Liu, Yu-Min Wang, Chong-Hua Zhang, Lu-Ying Duan, Zheng Li, Ru-Qin Yu, Jian-Hui Jiang
Unique physicochemical characteristics of graphitic carbon nitride (g-CN) nanosheets suit them a useful tool for two-photon fluorescence bioimaging. Current g-CN nanosheets based imaging probes typically use the "always-on" design strategies, which may suffer from increased fluorescence background and limited contrast. To advance corresponding applications, g-CN nanosheets based activatable two-photon fluorescence probes remain to be explored. For the first time, we developed an activatable two-photon fluorescence probe, constructed from a nanoassembly of g-CN nanosheets and hyaluronic acid (HA)-gold nanoparticles (HA-AuNPs), for detection and imaging of hyaluronidase (HAase) in cancer cells...
March 15, 2018: Analytical Chemistry
Shulian Wu, Yudian Huang, Qinggong Tang, Zhifang Li, Hannah Horng, Jiatian Li, Zaihua Wu, Yu Chen, Hui Li
Preoperative neoadjuvant treatment in locally advanced breast cancer is recognized as an effective adjuvant therapy, as it improves treatment outcomes. However, the potential complications remain a threat, so there is an urgent clinical need to assess both the tumor response and changes in its microenvironment using non-invasive and precise identification techniques. Here, two-photon microscopy was employed to detect morphological alterations in breast cancer progression and recession throughout chemotherapy...
March 1, 2018: Biomedical Optics Express
Koshonna Brown, Ted Thurn, Lun Xin, William Liu, Remon Bazak, Si Chen, Barry Lai, Stefan Vogt, Chris Jacobsen, Tatjana Paunesku, Gayle E Woloschak
Titanium dioxide (TiO2 ) nanoparticles are produced for many different purposes, including development of therapeutic and diagnostic nanoparticles for cancer detection and treatment, drug delivery, induction of DNA double-strand breaks, and imaging of specific cells and subcellular structures. Currently, the use of optical microscopy, an imaging technique most accessible to biology and medical pathology, to detect TiO2 nanoparticles in cells and tissues ex vivo is limited with low detection limits, while more sensitive imaging methods (transmission electron microscopy, X-ray fluorescence microscopy, etc...
January 2018: Nano Research
Jiang-Hao Ding, Sai-Nan Huai, Hou Ian, Yu-Xi Liu
We study the absorption spectrum of a probe field by a Λ-type three-level system, which is coupled to a quantized control field through the two upper energy levels. The probe field is applied to the ground and the second excited states. When the quantized control field is in vacuum, we derive a threshold condition to discern vacuum induced transparency (VIT) and vacuum induced Autler-Townes splitting (ATS). We also find that the parameter changing from VIT to vacuum induced ATS is very similar to that from broken PT symmetry to PT symmetry...
March 14, 2018: Scientific Reports
Angelo Forli, Dania Vecchia, Noemi Binini, Francesca Succol, Serena Bovetti, Claudio Moretti, Francesco Nespoli, Mathias Mahn, Christopher A Baker, McLean M Bolton, Ofer Yizhar, Tommaso Fellin
Sensory information is encoded within the brain in distributed spatiotemporal patterns of neuronal activity. Understanding how these patterns influence behavior requires a method to measure and to bidirectionally perturb with high spatial resolution the activity of the multiple neuronal cell types engaged in sensory processing. Here, we combined two-photon holography to stimulate neurons expressing blue light-sensitive opsins (ChR2 and GtACR2) with two-photon imaging of the red-shifted indicator jRCaMP1a in the mouse neocortex in vivo...
March 13, 2018: Cell Reports
Krzysztof Kucharz, Martin Lauritzen
Cortical spreading depolarization waves, the cause underlying migraine aura, are also the markers and mechanism of pathology in the acutely injured human brain. Propagation of spreading depolarization wave uniquely depends on the interaction between presynaptic and postsynaptic glutamate N-methyl-d-aspartate receptors (NMDARs). In the normally perfused brain, even a single wave causes a massive depolarization of neurons and glia, which results in transient loss of neuronal function and depression of the ongoing electrocorticographic activity...
March 12, 2018: Brain: a Journal of Neurology
Jitendra B Maurya, Alexandre François, Yogendra K Prajapati
One-dimensional photonic crystal (1DPC) sensors have emerged as contenders for traditional surface plasmon resonance sensors, owing to their potential for the detection of bigger molecules and particles due to their higher interaction volume in the sensing medium. Two-dimensional layered nanomaterials, most notably graphene and dichalcogenides (e.g., MoS₂, MoSe₂, WS₂, and WSe₂), have shown higher refractive index sensitivity because of their absorption as well as adsorption property. The proposed configuration of 1DPC presented consists of alternate layers of the aforementioned nanomaterials and silicon...
March 14, 2018: Sensors
Katsuyuki Taguchi, Karl Stierstorfer, Christoph Polster, Okkyun Lee, Steffen Kappler
PURPOSE: The inter-pixel cross-talk of energy-sensitive photon counting x-ray detectors (PCDs) has been studied and an analytical model (version 2.1) has been developed for double-counting between neighboring pixels due to charge sharing and K-shell fluorescence x-ray emission followed by its re-absorption [Taguchi K, et al., Medical Physics 2016;43(12):6386-6404]. While the model version 2.1 simulated the spectral degradation well, it had the following problems that has been found to be significant recently: (1) The spectrum is inaccurate with smaller pixel sizes; (2) the charge cloud size must be smaller than the pixel size; (3) the model underestimates the spectrum/counts for 10-40 keV; and (4) the model version 2...
March 14, 2018: Medical Physics
Fang Zhang, W Mx, Zhengping Wang, Kezhen Han, Xiaojuan Liu, Xinguang Xu
As the cousins of graphene, i.e. same group IVA element, the nonlinear absorption properties of silicene nanosheets were rarely studied. In this paper, we successfully exfoliated the two-dimensional silicene nanosheets from bulk silicon crystal using liquid phase exfoliation method. The nonlinear absorption properties of silicene nanosheets were systemically investigated for the first time, as we have known. Silicene performed exciting saturable absorption and two photon absorption behavior. The lower saturable intensity and larger two photon absorption coefficient at 532 nm excitation indicates that silicene has potential application in ultrafast lasers and optical limiting devices, especially in visible waveband...
March 14, 2018: Nanotechnology
Julian M M Rogasch, Holger Amthauer, Christian Furth, Patrick Hundsdoerfer, Florian Wedel, Imke Schatka
AIM: According to German guidelines, I-123-MIBG scintigraphy in neuroblastoma (NB) is preferably performed as early (about 4 h p.i.) and late (24 h p.i.) planar imaging and single- photon emission computed tomography (SPECT) or SPECT/CT 24 h p.i. This study evaluated if the work-up could be reduced to a single timepoint. METHODS: Retrospective analysis of 37 examinations in 26 patients (f:8; m:18; age, 0.5-23.5a) with NB (initial, 15; restaging, 22). All 74 (early + late) pairs of ventral/dorsal planar whole-body images were reviewed by 3 independent readers in random order blinded to clinical data (1, certainly physiological; 2, likely physiological; 3, likely malignant; 4, certainly malignant)...
February 2018: Nuklearmedizin. Nuclear Medicine
Zhiyi Liu, Dimitra Pouli, Carlo A Alonzo, Antonio Varone, Sevasti Karaliota, Kyle P Quinn, Karl Münger, Katia P Karalis, Irene Georgakoudi
Monitoring subcellular functional and structural changes associated with metabolism is essential for understanding healthy tissue development and the progression of numerous diseases, including cancer, diabetes, and cardiovascular and neurodegenerative disorders. Unfortunately, established methods for this purpose either are destructive or require the use of exogenous agents. Recent work has highlighted the potential of endogenous two-photon excited fluorescence (TPEF) as a method to monitor subtle metabolic changes; however, mechanistic understanding of the connections between the detected optical signal and the underlying metabolic pathways has been lacking...
March 2018: Science Advances
Hadi Keivan, Daryoush Shahbazi-Gahrouei, Ahmad Shanei, Alireza Amouheidari
Background: Dosimetric accuracy in intensity-modulated radiation therapy (IMRT) is the main part of quality assurance program. Improper beam modeling of small fields by treatment planning system (TPS) can lead to inaccuracy in treatment delivery. This study aimed to evaluate of the dose delivery accuracy at small segments of IMRT technique using two-dimensional (2D) array as well as evaluate the capability of two TPSs algorithm in modeling of small fields. Methods: Irradiation were performed using 6 MV photon beam of Siemens Artiste linear accelerator...
January 2018: Journal of Medical Signals and Sensors
Keyvan Jabbari, Fakhereh Pashaei, Mohammad R Ay, Alireza Amouheidari, Mohammad B Tavakoli
Background: MapCHECK2 is a two-dimensional diode arrays planar dosimetry verification system. Dosimetric results are evaluated with gamma index. This study aims to provide comprehensive information on the impact of various factors on the gamma index values of MapCHECK2, which is mostly used for IMRT dose verification. Methods: Seven fields were planned for 6 and 18 MV photons. The azimuthal angle is defined as any rotation of collimators or the MapCHECK2 around the central axis, which was varied from 5 to -5°...
January 2018: Journal of Medical Signals and Sensors
Jue Hou, Joshua Williams, Elliot Botvinick, Eric Potma, Bruce J Tromberg
Label-free non-linear optical microscopy (NLOM) based on two-photon excited fluorescence (TPEF) from cofactors Nicotinamide Adenine Dinucleotide (NADH) and Flavin Adenine Dinucleotide (FAD+) is widely used for high-resolution cellular redox imaging. In this work, we combined three, label-free NLOM imaging methods to quantitatively characterize breast cancer cells and their relative invasive potential: 1) TPEF optical redox ratio (ORR = FAD+/NADH + FAD+), 2) coherent Raman scattering (CRS) of cellular lipids, and 3) second harmonic generation (SHG) of extracellular matrix (ECM) collagen...
March 13, 2018: Cancer Research
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