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two photon

Shoko Saji, Srinivas Bathula, Akihiro Kubo, Masanori Tamaoki, Mitsuko Aono, Tomoharu Sano, Kazuo Tobe, Stefan Timm, Hermann Bauwe, Nobuyoshi Nakajima, Hikaru Saji
An ozone-sensitive mutant was isolated from T-DNA-tagged lines of Arabidopsis thaliana. The T-DNA was inserted at a locus on chromosome 3, where two genes encoding glycolate oxidases, GOX1 and GOX2, peroxisomal enzymes involved in photorespiration, reside contiguously. The amounts of the mutant's foliar transcripts for these genes were reduced, and glycolate oxidase activity was approximately 60% of that of the wild-type plants. No difference in growth and appearance was observed between the mutant and the wild-type plants under normal conditions with ambient air under a light intensity of 100 µmol photons m-2 s-1...
February 21, 2017: Plant & Cell Physiology
Kunio Kaneta, Hye-Sung Lee, Seokhoon Yun
The dark photon and the axion (or axionlike particle) are popular light particles of the hidden sector. Each of them has been actively searched for through the couplings called the vector portal and the axion portal. We introduce a new portal connecting the dark photon and the axion (axion-photon-dark photon, axion-dark photon-dark photon), which emerges in the presence of the two particles. This dark axion portal is genuinely new couplings, not just from a product of the vector portal and the axion portal, because of the internal structure of these couplings...
March 10, 2017: Physical Review Letters
M Milićević, T Ozawa, G Montambaux, I Carusotto, E Galopin, A Lemaître, L Le Gratiet, I Sagnes, J Bloch, A Amo
We experimentally reveal the emergence of edge states in a photonic lattice with orbital bands. We use a two-dimensional honeycomb lattice of coupled micropillars whose bulk spectrum shows four gapless bands arising from the coupling of p-like photonic orbitals. We observe zero-energy edge states whose topological origin is similar to that of conventional edge states in graphene. Additionally, we report novel dispersive edge states in zigzag and armchair edges. The observations are reproduced by tight-binding and analytical calculations, which we extend to bearded edges...
March 10, 2017: Physical Review Letters
Nicholas R Monahan, Dezheng Sun, Hiroyuki Tamura, Kristopher W Williams, Bolei Xu, Yu Zhong, Bharat Kumar, Colin Nuckolls, Avetik R Harutyunyan, Gugang Chen, Hai-Lung Dai, David Beljonne, Yi Rao, X-Y Zhu
The absorption of a photon usually creates a singlet exciton (S1) in molecular systems, but in some cases S1 may split into two triplets (2×T1) in a process called singlet fission. Singlet fission is believed to proceed through the correlated triplet-pair (1)(TT) state. Here, we probe the (1)(TT) state in crystalline hexacene using time-resolved photoemission and transient absorption spectroscopies. We find a distinctive (1)(TT) state, which decays to 2×T1 with a time constant of 270 fs. However, the decay of S1 and the formation of (1)(TT) occur on different timescales of 180 fs and <50 fs, respectively...
April 2017: Nature Chemistry
Jennifer Vogel, Liyong Lin, Charles B Simone, Abigail T Berman
BACKGROUND: While often managed with surgery alone, patients with thymic malignancies with high-risk features may benefit from adjuvant radiation therapy but are at risk for late toxicities. Previously, the risk of major cardiac events (MCEs) was reported to increase by 7% per one Gray (Gy) to the heart. In this study, we compare dose to organs at risk (OARs) with intensity-modulated (IMRT) versus proton beam therapy (PBT). We hypothesize a decrease risk of predicted MCEs with PBT. MATERIAL AND METHODS: Patients requiring adjuvant therapy for thymic malignancies were treated with double scattered proton beam therapy (DS-PBT)...
March 24, 2017: Acta Oncologica
Liang Guo, Jiechao Ge, Qian Liu, Qingyan Jia, Hongyan Zhang, Weimin Liu, Guangle Niu, Sha Liu, Jianru Gong, Steffen Hackbarth, Pengfei Wang
Clinical applications of current photodynamic therapy (PDT) photosensitizers (PSs) are often limited by their absorption in the UV-vis range that possesses limited tissue penetration ability, leading to ineffective therapeutic response for deep-seated tumors. Alternatively, two-photon excited PS (TPE-PS) using NIR light triggered is one the most promising candidates for PDT improvement. Herein, multimodal polymer nanoparticles (PNPs) from polythiophene derivative as two-photon fluorescence imaging as well as two-photon-excited PDT agent are developed...
March 24, 2017: Advanced Healthcare Materials
Xinglong Yang, Nuoxin Wang, Lingmin Zhang, Luru Dai, Huawu Shao, Xingyu Jiang
Multi-photon excitation and versatile fluorescent probes are in high need for biological imaging, since one probe can satisfy many needs as a biosensor. Herein we synthesize a series of two-photon excited probes based on tetraphenylethene (TPE) structures (TPE-Acr, TPE-Py, and TPE-Quino), which can image both mammalian cells and bacteria based on aggregation-induced emission (AIE) without washing them. Because of cationic moieties, the fluorescent molecules can aggregate into nanoscale fluorescent organic nanoscale dots to image mitochondria and bacteria with tunable emissions using both one-photon and two-photon excitation...
March 24, 2017: Nanoscale
Jarmo Teuho, Virva Saunavaara, Tuula Tolvanen, Terhi Tuokkola, Antti Karlsson, Jouni Tuisku, Mika Teräs
In positron emission tomography (PET), corrections for photon scatter and attenuation are essential for visual and quantitative consistency. Magnetic resonance attenuation correction (MRAC) is generally conducted by image segmentation and assignment of discrete attenuation coefficients, which offers limited accuracy compared to computed tomography attenuation correction (CTAC). Potential inaccuracies in MRAC may affect scatter correction, as the attenuation image (µ-map) is used in single scatter simulation (SSS) to calculate the scatter estimate...
March 23, 2017: Journal of Nuclear Medicine: Official Publication, Society of Nuclear Medicine
Denghua Li, Yibing Wang, Huiwen Du, Shiwei Xu, Zhemin Li, Yanlian Yang, Chen Wang
Purple membranes (PM) of the bacteria Halobacterium salinarum are a unique natural membrane where bacteriorhodopsin (BR) can convert photon energy and pump protons. Elucidating the electronic properties of biomembranes is critical for revealing biological mechanisms and developing new devices. We report here the electric properties of PMs studied by using multi-functional electric force microscopy (EFM) at the nanoscale. The topography, surface potential, and dielectric capacity of PMs were imaged and quantitatively measured in parallel...
November 2, 2016: Nanomaterials
Pingping Qiu, Weibin Qiu, Zhili Lin, Houbo Chen, Yixin Tang, Jia-Xian Wang, Qiang Kan, Jiao-Qing Pan
In this paper, one-dimensional (1D) and two-dimensional (2D) graphene-based plasmonic photonic crystals (PhCs) are proposed. The band structures and density of states (DOS) have been numerically investigated. Photonic band gaps (PBGs) are found in both 1D and 2D PhCs. Meanwhile, graphene-based plasmonic PhC nanocavity with resonant frequency around 175 THz, is realized by introducing point defect, where the chemical potential is from 0.085 to 0.25 eV, in a 2D PhC. Also, the bending wvaguide and the beam splitter are realized by introducing the line defect into the 2D PhC...
September 9, 2016: Nanomaterials
Fabienne Michelini, Adeline Crépieux, Katawoura Beltako
We discuss some thermodynamic aspects of energy conversion in electronic nanosystems able to convert light energy into electrical or/and thermal energy using the non-equilibrium Green's function formalism. In a first part, we derive the photon energy and particle currents inside a nanosystem interacting with light and in contact with two electron reservoirs at different temperatures. Energy conservation is verified, and radiation laws are discussed from electron non-equilibrium Green's functions. We further use the photon currents to formulate the rate of entropy production for steady-state nanosystems, and we recast this rate in terms of efficiency for specific photovoltaic-thermoelectric nanodevices...
March 23, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Kojiro Fuku, Yuta Miyase, Yugo Miseki, Takashi Funaki, Takahiro Gunji, Kazuhiro Sayama
The photoelectrochemical production and degradation properties of hydrogen peroxide (H2O2) were investigated on a WO3/BiVO4 photoanode in an aqueous electrolyte of hydrogen carbonate (HCO3-). Highly-concentration of HCO3- species rather than CO32- species inhibited the oxidative degradation of H2O2 on the WO3/BiVO4 photoanode, resulting in achieving effectively oxidative H2O2 generation and accumulation from water (H2O). Moreover, the Au cathode facilitated two-electron reduction of O2, resulting in reductive H2O2 production with high current efficiency...
March 23, 2017: Chemistry, An Asian Journal
Adam P Harrison, Ziyue Xu, David A Bluemke, Amir Pourmorteza, Daniel J Mollura
PURPOSE: We present a denoising algorithm designed for a whole-body prototype photon-counting computed tomography (PCCT) scanner with up to 4 energy thresholds and associated energy-binned images. METHODS: Spectral PCCT images can exhibit low signal to noise ratios (SNRs) due to the limited photon counts in each simultaneously-acquired energy bin. To help address this, our denoising method exploits the correlation and exact alignment between energy bins, adapting the highly-effective block-matching 3D (BM3D) denoising algorithm for PCCT...
March 23, 2017: Medical Physics
Bahaa Ghammraoui, Stephen J Glick
PURPOSE: A dual-energy material decomposition method using photon-counting spectral mammography was investigated as a non-invasive diagnostic approach to differentiate between Type I calcifications, consisting of calcium oxalate dihydrate or weddellite compounds that are more often associated with benign lesions, and Type II calcifications containing hydroxyapatite that are predominantly associated with malignant tumors. METHODS: The study was carried out by numerical simulation to assess the feasibility of the proposed approach...
March 22, 2017: Medical Physics
Andrew E Sifain, Loza F Tadesse, Josiah A Bjorgaard, David E Chavez, Oleg V Prezhdo, R Jason Scharff, Sergei Tretiak
Conjugated energetic molecules (CEMs) are a class of explosives with high nitrogen content that posses both enhanced safety and energetic performance properties and are ideal for direct optical initiation. As isolated molecules, they absorb within the range of conventional lasers. Crystalline CEMs are used in practice, however, and their properties can differ due to intermolecular interaction. Herein, time-dependent density functional theory was used to investigate one-photon absorption (OPA) and two-photon absorption (TPA) of monomers and dimers obtained from experimentally determined crystal structures of CEMs...
March 21, 2017: Journal of Chemical Physics
Hong-Wen Liu, Yongchao Liu, Peng Wang, Xiao-Bing Zhang
During the past two decades, two-photon microscopy (TPM), which utilizes two near-infrared photons as the excitation source, has emerged as a novel, attractive imaging tool for biological research. Compared with one-photon microscopy, TPM offers several advantages, such as lowering background fluorescence in living cells and tissues, reducing photodamage to biosamples, and a photobleaching phenomenon, offering better 3D spatial localization, and increasing penetration depth. Small-molecule-based two-photon fluorescent probes have been well developed for the detection and imaging of various analytes in biological systems...
March 22, 2017: Methods and Applications in Fluorescence
Dong Jiang, Yuanyuan Chen, Xuemei Gu, Ling Xie, Lijun Chen
Deterministic secure quantum communication (DSQC) can transmit secret messages between two parties without first generating a shared secret key. Compared with quantum key distribution (QKD), DSQC avoids the waste of qubits arising from basis reconciliation and thus reaches higher efficiency. In this paper, based on data block transmission and order rearrangement technologies, we propose a DSQC protocol. It utilizes a set of single d-level systems as message carriers, which are used to directly encode the secret message in one communication process...
March 22, 2017: Scientific Reports
Jarkko Tapio Niemelä, Mari Partanen, Jarkko Ojala, Petri Sipilae, Mikko Björkqvist, Mika Kapanen, Jani Keyriläinen
In small-beam radiation therapy (RT) the measurement of beam quality parameter i.e. tissue-phantom ratio or TPR<sub>20,10</sub> with conventional point detector is a challenge. To obtain reliable results, one has to consider potential sources of error, including volume averaging and adjustment of the point detector into the narrow beam. To overcome these challenges, a different type of possible beam quality parameter in small beams was studied, namely the dose-area product ratio or DAPR<sub>20,10</sub>...
March 22, 2017: Physics in Medicine and Biology
Stephen E Derenzo
This paper demonstrates through Monte Carlo simulations that a practical positron emission tomograph with (1) deep scintillators for efficient detection, (2) double-ended readout for depth-of-interaction information, (3) fixed-level analog triggering, and (4) accurate calibration and timing data corrections can achieve a coincidence resolving time (CRT) that is not far above the statistical lower bound. One Monte Carlo algorithm simulates a calibration procedure that uses data from a positron point source. Annihilation events with an interaction near the entrance surface of one scintillator are selected, and data from the two photodetectors on the other scintillator provide depth-dependent timing corrections...
March 22, 2017: Physics in Medicine and Biology
Erinke van Grinsven, Chloé Prunier, Nienke Vrisekoop, Laila Ritsma
Two-photon intravital microscopy (2P-IVM) is an advanced imaging platform that allows the visualization of dynamic processes at subcellular resolution in vivo. Dynamic processes like cell migration, cell proliferation, cell-cell interactions, and cell signaling have an interactive character and occur in complex environments. Hence, it is of pivotal importance to study these processes in living animals, using for example 2P-IVM. 2P-IVM can be performed on a variety of tissues, from the skin of the animal to internal organs, and a variety of methods can be utilized to perform 2P-IVM on these tissues...
2017: Methods in Molecular Biology
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