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Hélène Fleurbaey, Sandrine Galtier, Simon Thomas, Marie Bonnaud, Lucile Julien, François Biraben, François Nez, Michel Abgrall, Jocelyne Guéna
We present a new measurement of the 1S-3S two-photon transition frequency of hydrogen, realized with a continuous-wave excitation laser at 205 nm on a room-temperature atomic beam, with a relative uncertainty of 9×10^{-13}. The proton charge radius deduced from this measurement, r_{p}=0.877(13)  fm, is in very good agreement with the current CODATA-recommended value. This result contributes to the ongoing search to solve the proton charge radius puzzle, which arose from a discrepancy between the CODATA value and a more precise determination of r_{p} from muonic hydrogen spectroscopy...
May 4, 2018: Physical Review Letters
Xiaoli Huang, Qiyang Li, Xue Xiao, Shuping Jia, Yue Li, Zhigang Duan, Lei Bai, Ze Yuan, Lin Li, Zhihua Lin, Yonggang Zhao
We present here the synthesis of one enantiomeric pair of metal-organic framework materials comprised of a unique multioriented double-helix structure from an achiral spirocenter ligand. Our study clearly shows that the chiral MOF material encompasses concurrently multiple nonlinear-optical functions in the solid state: the noncentrosymmetric structural feature brings the chiral MOF high second-harmonic-generation efficiency; the incorporation of the spirocenter ligand can efficiently produce two-photon-excited photoluminescence with a larger-action cross-sectional value...
May 18, 2018: Inorganic Chemistry
Kohei Yoshihara, Tsuyoshi Matsuda, Yuta Kohro, Hidetoshi Tozaki-Saitoh, Kazuhide Inoue, Makoto Tsuda
The role of astrocytes in the spinal dorsal horn (SDH) for sensory information processing under normal conditions is poorly understood. In this study, we investigated whether SDH astrocytes respond to noxious and innocuous stimuli to the skin of normal mice using in vivo two-photon Ca2+ imaging under anesthesia. We found that noxious stimulation evoked by intraplantar formalin injection provoked an elevation in intracellular Ca2+ levels in SDH astrocytes. By contrast, neither instantaneous noxious pinching nor innocuous stimuli (cooling or brushing) to the hindpaw elicited astrocytic Ca2+ responses...
May 3, 2018: Journal of Pharmacological Sciences
Lina Li, Xiaoying Shang, Sasa Wang, Ningning Dong, Chengmin Ji, Xueyuan Chen, Sangen Zhao, Jun Wang, Zhihua Sun, Maochun Hong, Junhua Luo
Perovskite ferroelectrics with prominent nonlinear optical absorption have attracted great attention in the field of photonics. However, they are traditionally dominated by inorganic oxides and exhibit relatively small nonlinear optical absorption coefficients which hinder their further applications. Herein, we report a new organic-inorganic hybrid bilayered perovskite ferroelectric, (C4H9NH3)2(NH2CHNH2)Pb2Br7 (1), showing an above-room-temperature Curie temperature (~322 K) and notable spontaneous polarization (~3...
May 17, 2018: Journal of the American Chemical Society
Sourav Sahoo, Sucheta Mondal, Gwilym Williams, Andrew May, Sam Ladak, Anjan Barman
Three-dimensional magnetic nanostructures are now attracting intense interest due to their potential as ultrahigh density future magnetic storage devices. Here, we report on the study of ultrafast magnetization dynamics of a complex three-dimensional magnetic nanostructure. Arrays of magnetic tetrapod structures were fabricated using a combination of two-photon lithography (TPL) and electrodeposition. All-optical time-resolved magneto-optical Kerr microscopy was exploited to probe the spin-wave modes from the junction of a single tetrapod structure...
May 17, 2018: Nanoscale
Feng Wang, Erik Bélanger, Sylvain L Côté, Patrick Desrosiers, Steven A Prescott, Daniel C Côté, Yves De Koninck
Primary afferents transduce environmental stimuli into electrical activity that is transmitted centrally to be decoded into corresponding sensations. However, it remains unknown how afferent populations encode different somatosensory inputs. To address this, we performed two-photon Ca2+ imaging from thousands of dorsal root ganglion (DRG) neurons in anesthetized mice while applying mechanical and thermal stimuli to hind paws. We found that approximately half of all neurons are polymodal and that heat and cold are encoded very differently...
May 15, 2018: Cell Reports
Genggongwo Shi, Taeseung Yoon, Seoncheol Cha, Seulgi Kim, Muhammad Yousuf, Nisar Ahmed, Doseok Kim, Hyun-Wook Kang, Kwang S Kim
Water-soluble, carbazole-based two-photon excitable fluorescent probes MPVC-I ("turn-on") and MPVC-II ("turn-off") are rationally designed and synthesized for the selective monitoring of carbon monoxide (CO). Both probes can effectively measure carboxyhemoglobin (HbCO) in the blood of the animals exposed to a CO dose as low as 100 ppm for 10 min. The palladium catalyzed azidocarbonylation reaction was optimized to improve the sensing efficiency.
May 16, 2018: ACS Sensors
Thomas Mehringer, Simon Mährlein, Joachim von Zanthier, Girish S Agarwal
Interference of light fields, first postulated by Young, is one of the fundamental pillars of physics. Dirac extended this observation to the quantum world by stating that each photon interferes only with itself. A precondition for interference to occur is that no welcher-weg information labels the paths the photon takes; otherwise, the interference vanishes. This remains true, even if two-photon interference is considered, e.g., in the Hong-Ou-Mandel-experiment. Here, the two photons interfere only if they are indistinguishable, e...
May 15, 2018: Optics Letters
Kyo Koizumi, Masatoshi Inoue, Srikanta Chowdhury, Haruhiko Bito, Akihiro Yamanaka, Toru Ishizuka, Hiromu Yawo
To investigate how the functional architecture is organized in layer 5 (L5) of the somatosensory cortex of a mouse in vivo, the input-output relationship was investigated using an all-optical approach. The neural activity in L5 was optically recorded using a Ca2+ sensor, R-CaMP2, through a microprism inserted in the cortex under two-photon microscopy, while the L5 was regionally excited using optogenetics. The excitability was spread around the blue-light irradiated region, but the horizontal propagation was limited to within a certain distance (λ < 130 μm from the center of the illumination spot)...
May 14, 2018: Journal of Physiological Sciences: JPS
Shu Wang, Huiping Du, Bingbing Lin, Chenxi Liao, Xiaoqin Zhu, Xingfu Wang, Hong Chen, Shuangmu Zhuo, Liwei Jiang, Lianhuang Li, Haohua Tu, Jianxin Chen
Ischemic stroke is a leading cause of death and permanent disability worldwide. Middle cerebral artery occlusion (MCAO) of variable duration times could be anticipated to result in varying degrees of injury that evolve spatially over time. Therefore, investigations following strokes require information concerning the spatiotemporal dimensions of the ischemic core as well as of perilesional areas. In the present study, multiphoton microscopy (MPM) based on two-photon excited fluorescence (TPEF) and second harmonic generation (SHG) was applied to image such pathophysiological events...
May 1, 2018: Biomedical Optics Express
Kriti Charan, Bo Li, Mengran Wang, Charles P Lin, Chris Xu
Deep tissue multiphoton imaging requires high peak power to enhance signal and low average power to prevent thermal damage. Both goals can be advantageously achieved through laser repetition rate tuning instead of simply adjusting the average power. We show that the ideal repetition rate for deep two-photon imaging in the mouse brain is between 1 and 10 MHz, and we present a fiber-based source with an arbitrarily tunable repetition rate within this range. The performance of the new source is compared to a mode-locked Ti:Sapphire (Ti:S) laser for in vivo imaging of mouse brain vasculature...
May 1, 2018: Biomedical Optics Express
Teppei Ebina, Yoshito Masamizu, Yasuhiro R Tanaka, Akiya Watakabe, Reiko Hirakawa, Yuka Hirayama, Riichiro Hira, Shin-Ichiro Terada, Daisuke Koketsu, Kazuo Hikosaka, Hiroaki Mizukami, Atsushi Nambu, Erika Sasaki, Tetsuo Yamamori, Masanori Matsuzaki
Two-photon imaging in behaving animals has revealed neuronal activities related to behavioral and cognitive function at single-cell resolution. However, marmosets have posed a challenge due to limited success in training on motor tasks. Here we report the development of protocols to train head-fixed common marmosets to perform upper-limb movement tasks and simultaneously perform two-photon imaging. After 2-5 months of training sessions, head-fixed marmosets can control a manipulandum to move a cursor to a target on a screen...
May 14, 2018: Nature Communications
Esther Park, Michelle Tjia, Yi Zuo, Lu Chen
Retinoic acid (RA) and its receptors (RARs) are well-established essential transcriptional regulators during embryonic development. Recent findings in cultured neurons identified an independent and critical post-transcriptional role of RA and RARα in the homeostatic regulation of excitatory and inhibitory synaptic transmission in mature neurons. However, the functional relevance of synaptic RA signaling in vivo has not been established. Here, using somatosensory cortex as a model system and the RARα conditional knockout mouse as a tool, we applied multiple genetic manipulations to delete RARα postnatally in specific populations of cortical neurons, and asked whether synaptic RA signaling observed in cultured neurons is involved in cortical information processing in vivo Indeed, conditional ablation of RARα in mice via a CaMKIIα-Cre or a layer 5-Cre driver line or via somatosensory cortex-specific viral expression of Cre-recombinase impaired whisker-dependent texture discrimination, suggesting a critical requirement of RARα expression in L5 pyramidal neurons of somatosensory cortex for normal tactile sensory processing...
May 14, 2018: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
Zhixuan Zhou, Jiangping Liu, Thomas W Rees, Heng Wang, Xiaopeng Li, Hui Chao, Peter J Stang
As an effective and noninvasive treatment of various diseases, photodynamic therapy (PTD) relies on the combination of light, a photosensitizer, and oxygen to generate cytotoxic reactive oxygen species that can damage malignant tissue. Much attention has been paid to covalent modifications of the photosensitizers to improve their photophysical properties and to optimize the pathway of the photosensitizers interacting with cells within the target tissue. Herein we report the design and synthesis of a supramolecular heterometallic Ru-Pt metallacycle via coordination-driven self-assembly...
May 14, 2018: Proceedings of the National Academy of Sciences of the United States of America
Jyun-You Liou, Hongtao Ma, Michael Wenzel, Mingrui Zhao, Eliza Baird-Daniel, Elliot H Smith, Andy Daniel, Ronald Emerson, Rafael Yuste, Theodore H Schwartz, Catherine A Schevon
Focal seizure propagation is classically thought to be spatially contiguous. However, distribution of seizures through a large-scale epileptic network has been theorized. Here, we used a multielectrode array, wide field calcium imaging, and two-photon calcium imaging to study focal seizure propagation pathways in an acute rodent neocortical 4-aminopyridine model. Although ictal neuronal bursts did not propagate beyond a 2-3-mm region, they were associated with hemisphere-wide field potential fluctuations and parvalbumin-positive interneuron activity outside the seizure focus...
May 10, 2018: Brain: a Journal of Neurology
Yuqing Cheng, Weidong Zhang, Jingyi Zhao, Te Wen, Aiqin Hu, Qihuang Gong, Guowei Lu
Scattering and absorption properties of metal nanostructures have been understood well based on classic oscillator theory. Here, we demonstrate that photoluminescence of metal nanostructures can also be explained based on classic model. The model shows that inelastic radiation of an oscillator resembles its resonance band after external excitation, that is related with the photoluminescence from metallic nanostructures. The understanding based on classic oscillator model is in agreement with that predicted by quantum electromagnetic cavity model...
May 14, 2018: Nanotechnology
Paul Shin, WooJhon Choi, JongYoon Joo, Wang-Yuhl Oh
Functional hyperemia in the rat cortex was investigated using high-speed optical coherence tomography (OCT) angiography and Doppler OCT. OCT angiography (OCTA) was performed to image the hemodynamic stimulus-response over a wide field of view. Temporal changes in vessel diameters in different vessel compartments, which were determined as the diameters of erythrocyte flows in OCT angiograms, were measured in order to monitor localized hemodynamic changes. Our results showed that the dilation of arterioles at the site of activation was accompanied by the dilation of upstream arteries...
January 1, 2018: Journal of Cerebral Blood Flow and Metabolism
J S Pedernales, M Beau, S M Pittman, I L Egusquiza, L Lamata, E Solano, A Del Campo
We introduce an exact mapping between the Dirac equation in (1+1)-dimensional curved spacetime (DCS) and a multiphoton quantum Rabi model (QRM). A background of a (1+1)-dimensional black hole requires a QRM with one- and two-photon terms that can be implemented in a trapped ion for the quantum simulation of Dirac particles in curved spacetime. We illustrate our proposal with a numerical analysis of the free fall of a Dirac particle into a (1+1)-dimensional black hole, and find that the Zitterbewegung effect, measurable via the oscillatory trajectory of the Dirac particle, persists in the presence of gravity...
April 20, 2018: Physical Review Letters
M Fabbrichesi, E Gabrielli, B Mele
We study the Z→γγ[over ¯] process in which the Z boson decays into a photon γ and a massless dark photon γ[over ¯], when the latter couples to standard-model fermions via dipole moments. This is a simple yet nontrivial example of how the Landau-Yang theorem-ruling out the decay of a massive spin-1 particle into two photons-is evaded if the final particles can be distinguished. The striking signature of this process is a resonant monochromatic single photon in the Z-boson center of mass together with missing momentum...
April 27, 2018: Physical Review Letters
Anne-Kathrin Theis, Balázs Rózsa, Gergely Katona, Dietmar Schmitz, Friedrich W Johenning
The majority of excitatory synapses are located on dendritic spines of cortical glutamatergic neurons. In spines, compartmentalized Ca2+ signals transduce electrical activity into specific long-term biochemical and structural changes. Action potentials (APs) propagate back into the dendritic tree and activate voltage gated Ca2+ channels (VGCCs). For spines, this global mode of spine Ca2+ signaling is a direct biochemical feedback of suprathreshold neuronal activity. We previously demonstrated that backpropagating action potentials (bAPs) result in long-term enhancement of spine VGCCs...
2018: Frontiers in Cellular Neuroscience
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