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Low-intensity pulsed laser

Allan S Johnson, Dane R Austin, David A Wood, Christian Brahms, Andrew Gregory, Konstantin B Holzner, Sebastian Jarosch, Esben W Larsen, Susan Parker, Christian S Strüber, Peng Ye, John W G Tisch, Jon P Marangos
Laser-driven high-harmonic generation provides the only demonstrated route to generating stable, tabletop attosecond x-ray pulses but has low flux compared to other x-ray technologies. We show that high-harmonic generation can produce higher photon energies and flux by using higher laser intensities than are typical, strongly ionizing the medium and creating plasma that reshapes the driving laser field. We obtain high harmonics capable of supporting attosecond pulses up to photon energies of 600 eV and a photon flux inside the water window (284 to 540 eV) 10 times higher than previous attosecond sources...
May 2018: Science Advances
Li-Xiang Hu, Tong-Pu Yu, Zheng-Ming Sheng, Jorge Vieira, De-Bin Zou, Yan Yin, Paul McKenna, Fu-Qiu Shao
Generation of attosecond bunches of energetic electrons offers significant potential from ultrafast physics to novel radiation sources. However, it is still a great challenge to stably produce such electron beams with lasers, since the typical subfemtosecond electron bunches from laser-plasma interactions either carry low beam charge, or propagate for only several tens of femtoseconds. Here we propose an all-optical scheme for generating dense attosecond electron bunches via the interaction of an intense Laguerre-Gaussian (LG) laser pulse with a nanofiber...
May 8, 2018: Scientific Reports
Xin Zhou, Jianfeng Sun, Peng Jiang, Di Liu, Qi Wang
The ranging performance for Geiger-mode avalanche photodiode (Gm-APD) laser detection and ranging (ladar) is mainly evaluated by range accuracy and precision; although Gm-APD ladar can evaluate the ranging performance of the exact position, it is not helpful to comprehensively evaluate the influence on the ranging of each parameter in the whole gate. Due to the target echo's stochastic trigger making the delay adjustment inaccurate, the position of the echo in the gate is stochastic in the actual detection process, so the theoretical calculation may not be able to make ladar ranging performance clear...
April 1, 2018: Applied Optics
W Roseker, S O Hruszkewycz, F Lehmkühler, M Walther, H Schulte-Schrepping, S Lee, T Osaka, L Strüder, R Hartmann, M Sikorski, S Song, A Robert, P H Fuoss, M Sutton, G B Stephenson, G Grübel
One of the important challenges in condensed matter science is to understand ultrafast, atomic-scale fluctuations that dictate dynamic processes in equilibrium and non-equilibrium materials. Here, we report an important step towards reaching that goal by using a state-of-the-art perfect crystal based split-and-delay system, capable of splitting individual X-ray pulses and introducing femtosecond to nanosecond time delays. We show the results of an ultrafast hard X-ray photon correlation spectroscopy experiment at LCLS where split X-ray pulses were used to measure the dynamics of gold nanoparticles suspended in hexane...
April 27, 2018: Nature Communications
M Scisciò, M Migliorati, L Palumbo, P Antici
Laser-accelerated protons, generated by irradiating a solid target with a short, energetic laser pulse at high intensity (I > 1018  W·cm-2 ), represent a complementary if not outperforming source compared to conventional accelerators, due  to their intrinsic features, such as high beam charge and short bunch duration. However, the broadband energy spectrum of these proton sources is a bottleneck that precludes their use in applications requiring a more reduced energy spread. Consequently, in recent times strong effort has been put to overcome these limits and to develop laser-driven proton beamlines with low energy spread...
April 19, 2018: Scientific Reports
Robin Jonas, Barbara Namer, Lenka Stockinger, Kim Chisholm, Mark Schnakenberg, Gunther Landmann, Mateusz Kucharczyk, Christoph Konrad, Roland Schmidt, Richard Carr, Stephen McMahon, Martin Schmelz, Roman Rukwied
OBJECTIVE: Develop and validate a low-intensity sinusoidal electrical stimulation paradigm to preferentially activate C-fibers in human skin. METHODS: Sinusoidal transcutaneous stimulation (4 Hz) was assessed psychophysically in healthy volunteers (n=14) and neuropathic pain patients (n=9). Pursuing laser Doppler imaging and single nociceptor recordings in vivo in humans (microneurography) and pigs confirmed the activation of "silent" C-nociceptors. Synchronized C-fiber compound action potentials were evoked in isolated human nerve fascicles in vitro...
April 16, 2018: Annals of Neurology
Mohammed Mahmood Jawad Alazzawi, Adam Husein, Mohammad Khursheed Alam, Rozita Hassan, Rumaizi Shaari, Ahmad Azlina, M S Salzihan
BACKGROUND: Quality bone regeneration, which leads to the improvement of bone remodeling, is essential for orthodontic treatment. In order to improve bone regeneration and increase the amount of tooth movement, different techniques have been implemented. The object of this study is to compare the effects of low-level laser therapy (LLLT), low-intensity pulsed ultrasound (LIPUS), and their combination on bone remodeling during orthodontic tooth movement. METHODS: Eighty (80) male, 6-week-old Sprague Dawley rats were grouped in to four groups, the first group was irradiated with (940 nm) diode laser, second group with LIPUS, and third group with combination of both LLLT and LIPUS...
April 16, 2018: Progress in Orthodontics
A M Koushki, R Sadighi-Bonabi, M Mohsen-Nia, E Irani
In the present work, an efficient method is theoretically investigated for extending high-order harmonics and ultrashort attosecond pulse generation in N2 and CO molecules by using the time-dependent density functional theory approach. Our results show that by utilizing chirped laser field in the presence of a low frequency field, not only is the harmonic cutoff extended remarkably but also the single short quantum trajectory is selected to contribute to the harmonic spectra. When a low frequency field is added to the two-color chirped laser field, the long quantum trajectories are suppressed and only the short quantum trajectories contribute to the higher harmonic emission mechanism...
April 14, 2018: Journal of Chemical Physics
Yasaman Ardeshirpour, Dan L Sackett, Jay R Knutson, Amir H Gandjbakhche
BACKGROUND: Assessment of the status of tumor biomarkers in individual patients would facilitate personalizing treatment strategy, and continuous monitoring of those biomarkers and their binding process to the therapeutic drugs would provide a means for early evaluation of the efficacy of therapeutic intervention. Fluorescent probes can accumulate inside the tumor region due to the leakiness of its vascularization and this can make it difficult to distinguish if the measured fluorescence intensity is from probes bound to target receptors or just accumulated unbound probes inside the tumor...
April 4, 2018: EJNMMI Research
Ravi Jain, Gerardo Moreno Arias, Pablo Naranjo, Max Murison, Jose Luis López Estebaranz, Alina Fratila, Welf Prager, Carlos Guillén Barona, Michael Weidmann, Serge Dahan, Hugues Cartier, Gerhard Sattler, Maurizio Podda
INTRODUCTION: A variety of topical anesthetic creams are available to reduce pain associated with dermatological procedures. Pliaglis is a self-occluding eutectic mixture of lidocaine and tetracaine. STUDY OBJECTIVES: To evaluate the post-marketing safety profile of Pliaglis and efficacy in terms of pain reduction, product satisfaction, and daily practice use prior to pre-defined dermatological procedures. METHODS: A prospective, non-interventional study conducted at 44 sites in four European countries; 581 patients were treated prior to dermatological procedures such as pulsed-dye laser therapy, laser-assisted hair removal, non-ablative laser resurfacing, dermal filler injections, and vascular access...
April 1, 2018: Journal of Drugs in Dermatology: JDD
Xiaowei Lu, Qunqing Hao, Mengjia Cen, Guanhua Zhang, Ju-Long Sun, Libang Mao, Tun Cao, Chuanyao Zhou, Peng Jiang, Xueming Yang, Xinhe Bao
Noble metals, like Ag and Au, are the most intensively studied plasmonic materials in the visible range. Plasmons in semiconductors, however, are usually believed to be in the infrared wavelength region due to the intrinsic low carrier concentrations. Herein, we observe the edge plasmon modes of Bi2Te3, a narrow-band gap semiconductor, in the visible spectral range using photoemission electron microscopy (PEEM). The Bi2Te3 nanoplates excited by 400 nm femtosecond laser pulses exhibit strong photoemission intensities along the edges, which follow a 〖cos〗^4 dependence on the polarization state of incident beam...
March 29, 2018: Nano Letters
Konstantinos S Daskalakis, Aaro I Väkeväinen, Jani-Petri Martikainen, Tommi K Hakala, Päivi Törmä
Nanoscale coherent light sources offer potentially ultrafast modulation speeds, which could be utilized for novel sensors and optical switches. Plasmonic periodic structures combined with organic gain materials have emerged as promising candidates for such nanolasers. Their plasmonic component provides high intensity and ultrafast nanoscale-confined electric fields, while organic gain materials offer fabrication flexibility and a low acquisition cost. Despite reports on lasing in plasmonic arrays, lasing dynamics in these structures have not been experimentally studied yet...
April 11, 2018: Nano Letters
Vyacheslav A Trofimov, Tatiana M Lysak, Evgenii M Trykin
We discuss a novel type of surface soliton-aberrated surface soliton-appearance in a nonlinear one dimensional photonic crystal and a possibility of this surface soliton formation in two dimensional photonic crystal. An aberrated surface soliton possesses a nonlinear distribution of the wavefront. We show that, in one dimensional photonic crystal, the surface soliton is formed at the photonic crystal boundary with the ambient medium. Essentially, that it occupies several layers at the photonic crystal boundary and penetrates into the ambient medium at a distance also equal to several layers, so that one can infer about light energy localization at the lateral surface of the photonic crystal...
2018: PloS One
Marija Vranic, Ondrej Klimo, Georg Korn, Stefan Weber
The new generation of laser facilities is expected to deliver short (10 fs-100 fs) laser pulses with 10-100 PW of peak power. This opens an opportunity to study matter at extreme intensities in the laboratory and provides access to new physics. Here we propose to scatter GeV-class electron beams from laser-plasma accelerators with a multi-PW laser at normal incidence. In this configuration, one can both create and accelerate electron-positron pairs. The new particles are generated in the laser focus and gain relativistic momentum in the direction of laser propagation...
March 16, 2018: Scientific Reports
Tanya Moutray, Jennifer R Evans, Noemi Lois, David J Armstrong, Tunde Peto, Augusto Azuara-Blanco
BACKGROUND: Diabetic retinopathy (DR) is a chronic progressive disease of the retinal microvasculature associated with prolonged hyperglycaemia. Proliferative DR (PDR) is a sight-threatening complication of DR and is characterised by the development of abnormal new vessels in the retina, optic nerve head or anterior segment of the eye. Argon laser photocoagulation has been the gold standard for the treatment of PDR for many years, using regimens evaluated by the Early Treatment of Diabetic Retinopathy Study (ETDRS)...
March 15, 2018: Cochrane Database of Systematic Reviews
J H Marks, T B Ward, M A Duncan
Manganese oxide cluster cations are produced by laser vaporization in a pulsed nozzle source and detected with time-of-flight mass spectrometry. The mass spectrum contains intense peaks for stoichiometries corresponding to (MnO) n + . Multiphoton photodissociation of these clusters yields smaller ions with the same stoichiometric ratio, either by sequential elimination of MnO units or by various fission processes with roughly equal efficiencies. Fragmentation of clusters containing excess oxygen also yields (MnO) n + fragments...
April 5, 2018: Journal of Physical Chemistry. A
Andreas Leonidou, Panagiotis Lepetsos, Michalis Mintzas, Eustathios Kenanidis, George Macheras, Maria Tzetis, Michael Potoupnis, Eleftherios Tsiridis
Inducible nitric oxide synthase (iNOS) is the enzyme responsible for the production of nitric oxide (NO), a major proinflammatory and destructive mediator in osteoarthritis (OA). Areas covered: This is a comprehensive review of the recent literature on the involvement of iNOS in osteoarthritis and its potential to be used as a target for OA treatment. Evidence from in vitro, in vivo and human studies was systematically collected using medical search engines. Preclinical studies have focused on the effect of direct and indirect iNOS inhibitors in both animal and human tissues...
April 2018: Expert Opinion on Therapeutic Targets
Mei-Ling Chen, Zhi-Wen Gao, Xue-Min Chen, Shu-Chao Pang, Yi Zhang
Magnetic graphene-based hybrids are being increasing recognized as an effective nanotheranostic agent in biomedicine. Conventional technologies for their synthesis have drawbacks not only from a synthetic standpoint, mainly requiring high temperatures and multi-step processes, but also from a biological perspective, chemical precursors or surfactants involved in the chemical process are toxic to cells. Herein, we report a novel approach for one-step fabricating magnetic graphene hybrid nanocomposites based on laser irradiation of an Fe target in GO-PEG aqueous solution at room temperature without using any other chemical reagent...
May 15, 2018: Talanta
Luca Fedeli, Arianna Formenti, Lorenzo Cialfi, Andrea Pazzaglia, Matteo Passoni
Near-critical plasmas irradiated at ultra-high laser intensities (I > 1018 W/cm2 ) allow to improve the performances of laser-driven particle and radiation sources and to explore scenarios of great astrophysical interest. Near-critical plasmas with controlled properties can be obtained with nanostructured low-density materials. By means of 3D Particle-In-Cell simulations, we investigate how realistic nanostructures influence the interaction of an ultra-intense laser with a plasma having a near-critical average electron density...
March 1, 2018: Scientific Reports
Mehmet Emre Coskun, Kubra Acikalin Coskun, Yusuf Tutar
OBJECTIVE: The aim of this study was to determine the optimum operating parameters (pulse duration, energy levels, and application time) to promote induction of osteoblast and fibroblast cell proliferation and to maintain cell viability treated with low-intensity pulsed ultrasound (LIPUS) and low-level laser therapy (LLLT). BACKGROUND DATA: The positive effects of LIPUS and LLLT on cellular activity have been reported in recent years. Comparisons between experimental parameters of previous studies are difficult because scientific studies reported frequencies and the duty cycles of LIPUS and wavelengths and doses of LLLT in a wide range of parameters...
May 2018: Photomedicine and Laser Surgery
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