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Victor V Kotlyar, Alexey A Kovalev, Alexey P Porfirev
We show that an elliptic Gaussian beam, focused by a cylindrical lens, can be represented as a linear combination of a countable number of only even angular harmonics with both positive and negative topological charge. For the orbital angular momentum (OAM) of the astigmatic Gaussian beam, an exact expression is obtained in a form of a converging series of the Legendre functions of the second kind. It is shown that at some conditions only the terms with the positive or negative topological charge are remained in this series...
January 8, 2018: Optics Express
Zhengyu Feng, Ken Ishikawa
We demonstrate a novel phase-only modulation mode based on the pre-transitional effect of the antiferroelectric liquid crystal. 2π phase modulation without changing the polarization state of the incident light is achieved with a low field (1.8 V/μm). This phase modulation mode also shows an ultrafast response time (less than 300 μs) and a uniform optical texture with an easy fabrication process. This phase modulator can be applied to laser beam steering, virtual reality, and holograms, etc., in the future...
January 15, 2018: Optics Letters
V T Tenner, M J A de Dood, M P van Exter
We demonstrate surface-plasmon lasing in hexagonal metal hole arrays with a semiconductor gain medium. The device can be tuned between two laser modes, with distinct wavelengths, spatial distributions, and polarization patterns, by changing the size of the optically pumped area. One of the modes exhibits a six-fold polarization pattern, while the mode observed for larger pump spots has a rotationally symmetric polarization pattern. We explain the mode tuning by the differences of in-plane and radiative out-of-plane losses of the modes...
January 15, 2018: Optics Letters
O Kosareva, M Esaulkov, N Panov, V Andreeva, D Shipilo, P Solyankin, A Demircan, I Babushkin, V Makarov, U Morgner, A Shkurinov, A Savel'ev
We individually control polarizations of 800 and 400 nm beams, which form a two-color femtosecond plasma filament in air irradiating a linear-to-elliptical THz signal. We detected a threshold-like appearance of THz ellipticity at the angle of ∼85° between the fundamental and second-harmonic field polarization directions. The simulations confirm the abrupt change of THz polarization and reveal that the weak ellipticity of the second harmonic is sufficient to generate essentially elliptical THz radiation.
January 1, 2018: Optics Letters
Yejin Zhang, Yanmei Su, Yu Bi, Jiaoqing Pan, Hongyan Yu, Yang Zhang, Jie Sun, Xiuyan Sun, Ming Chong
In this Letter, a new type of single-mode slotted laser used for an on-chip light source in photonic integrated circuits is proposed. An inclined light beam with a low vertical divergence angle can be directly coupled into the surface grating of the silicon to form an integrated light source. Experimentally, a III-V laser with a 54.6° inclined angle and a vertical divergence angle of 1.7° is achieved by introducing a kind of specially distributed microstructure. The side mode suppression ratio is better than 45 dB, and the continuous wave output power reaches 6...
January 1, 2018: Optics Letters
A V Volyar, Yu A Egorov
We consider optical properties of hypergeometric-Gaussian beam compositions with spiral-like intensity and phase distributions called spiroid beams. Their orbital angular momentum as a function of a fractional-order topological charge has a chain of super-pulses (bursts and dips). The form of the super-pulses can be controlled by the spiral parameters. Such a phenomenon can be used in optical switches and triggers for optical devices and communication systems.
January 1, 2018: Optics Letters
Yana V Izdebskaya, Vladlen G Shvedov, Pawel S Jung, Wieslaw Krolikowski
We report on the first experimental observation of stable vortex solitons in nematic liquid crystals with nonlocal nonlinear reorientational response. We show how these nonlinear vortex beams can be formed and confined in extraordinary optical waves by employing the cell with no lateral boundary conditions and the application of an external magnetic field that effectively controls the molecular direction and propagation of the self-trapped beams. We also find that these vortex solitons can be generated in certain ranges of the input beam power...
January 1, 2018: Optics Letters
G Mellado-Villaseñor, D Aguirre-Olivas, U Ruiz, V Arrizon
We report the design and optimization of a diffractive phase element whose phase modulation is derived from the Jacobi-Anger relation, which allows the simultaneous generation of multiple scalar Bessel beams of different integer orders. In addition, by the appropriate treatment of a couple of such Bessel beams, we generate a vector Bessel beam of arbitrary order m. This beam is constructed by the collinear superposition of the scalar Bessel beam modes of orders m-1 and m+1, with circular orthogonal polarizations...
January 1, 2018: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
M Bailly-Grandvaux, J J Santos, C Bellei, P Forestier-Colleoni, S Fujioka, L Giuffrida, J J Honrubia, D Batani, R Bouillaud, M Chevrot, J E Cross, R Crowston, S Dorard, J-L Dubois, M Ehret, G Gregori, S Hulin, S Kojima, E Loyez, J-R Marquès, A Morace, Ph Nicolaï, M Roth, S Sakata, G Schaumann, F Serres, J Servel, V T Tikhonchuk, N Woolsey, Z Zhang
Intense lasers interacting with dense targets accelerate relativistic electron beams, which transport part of the laser energy into the target depth. However, the overall laser-to-target energy coupling efficiency is impaired by the large divergence of the electron beam, intrinsic to the laser-plasma interaction. Here we demonstrate that an efficient guiding of MeV electrons with about 30 MA current in solid matter is obtained by imposing a laser-driven longitudinal magnetostatic field of 600 T. In the magnetized conditions the transported energy density and the peak background electron temperature at the 60-μm-thick target's rear surface rise by about a factor of five, as unfolded from benchmarked simulations...
January 9, 2018: Nature Communications
Saurav Bhowmick, Veera D'Mello, Nizmi Ponery, P M Abdul-Muneer
Traumatic brain injury (TBI) can result in persistent sensorimotor and cognitive deficits, which occur through a cascade of deleterious pathophysiological events over time. In this study, we investigated the hypothesis that neurodegeneration caused by TBI leads to impairments in sensorimotor function. TBI induces the activation of the caspase-3 enzyme, which triggers cell apoptosis in an in vivo model of fluid percussion injury (FPI). We analyzed caspase-3 mediated apoptosis by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining and poly (ADP-ribose) polymerase (PARP) and annexin V western blotting...
January 6, 2018: Brain Sciences
Tianchen Hu, Philip V Bayly
It remains unclear how flagella generate propulsive, oscillatory waveforms. While it is well known that dynein motors, in combination with passive cytoskeletal elements, drive the bending of the axoneme by applying shearing forces and bending moments to microtubule doublets, the origin of rhythmicity is still mysterious. Most conceptual models of flagellar oscillation involve dynein regulation or switching, so that dynein activity first on one side of the axoneme, then the other, drives bending. In contrast, a "viscoelastic flutter" mechanism has recently been proposed, based on a dynamic structural instability...
January 5, 2018: Cytoskeleton
Deepu George, Harriet Lloyd, Ronald H Silverman, Parag V Chitnis
A frequency-domain, non-contact approach to photoacoustic microscopy (PAM) that employs amplitude-modulated (0.1-1 MHz) laser for excitation (638-nm pump) in conjunction with a two-wave mixing interferometer (532-nm probe) for non-contact detection of photoacoustic waves at the specimen surface is presented. A lock-in amplifier is employed to detect the photoacoustic signal. Illustrative images of tissue-mimicking phantoms, red-blood cells, and retinal vasculature are presented. Single-frequency modulation of the pump beam directly provides an image that is equivalent to the two-dimensional projection of the image volume...
January 5, 2018: Journal of Biophotonics
Vladimir A Gritsenko, Timofey V Perevalov, Vitaliy A Voronkovskii, Andrei A Gismatulin, Vladimir N Kruchinin, Vladimir Sh Aliev, Vladimir A Pustovarov, Igor P Prosvirin, Yakov Roizin
Optical and transport properties of nonstoichiometric tantalum oxide thin films grown by ion beam sputtering were investigated in order to understand the dominant charge transport mechanisms and reveal the nature of traps. The TaOx films content was analyzed by X-ray photoelectron spectroscopy and by quantum-chemistry simulation. From the optical absorption and photoluminescence measurements and density functional theory simulations, it was concluded that the 2.75 eV blue luminescence excited in a TaOx by 4...
January 8, 2018: ACS Applied Materials & Interfaces
V Protopopov
A prototype of a combined visible-infrared spectrometer with a vertical probe beam is designed and tested. The combined spectral range is 0.4-20 μ with spatial resolution 1 mm. Basic features include the ability to measure both visibly transparent and opaque substances, as well as buried structures, such as in semiconductor industry; horizontal orientation of a sample, including semiconductor wafers; and reflection mode of operation, delivering twice the sensitivity compared to the transmission mode.
December 2017: Review of Scientific Instruments
I Tanarro, B Alemán, P de Vicente, J D Gallego, J R Pardo, G Santoro, K Lauwaet, F Tercero, A Díaz-Pulido, E Moreno, M Agúndez, J R Goicoechea, J M Sobrado, J A López, L Martínez, J L Doménech, V J Herrero, J M Hernández, R J Peláez, J A López-Pérez, J Gómez-González, J L Alonso, E Jiménez, D Teyssier, K Makasheva, M Castellanos, C Joblin, J A Martín-Gago, J Cernicharo
We present a proof of concept on the coupling of radio astronomical receivers and spectrometers with chemical reactors and the performances of the resulting setup for spectroscopy and chemical simulations in laboratory astrophysics. Several experiments including cold plasma generation and UV photochemistry were performed in a 40 cm long gas cell placed in the beam path of the Aries 40 m radio telescope receivers operating in the 41-49 GHz frequency range interfaced with fast Fourier transform spectrometers providing 2 GHz bandwidth and 38 kHz resolution...
January 2018: Astronomy and Astrophysics
Martin T King, Ming-Hui Chen, Brian J Moran, Michelle H Braccioforte, Ivan Buzurovic, Vinayak Muralidhar, David D Yang, Kent W Mouw, Phillip M Devlin, Anthony V D'Amico, Paul L Nguyen, Peter F Orio
PURPOSE/OBJECTIVE(S): Brachytherapy (BT) monotherapy is a well-established treatment modality for favorable intermediate risk (FIR) prostate cancer. However, patients with unfavorable intermediate risk (UIR) disease are often recommended trimodality therapy involving BT, androgen deprivation therapy (ADT), and external beam radiation therapy (EBRT). We sought to investigate the relative benefit of supplemental therapies (ADT and/or EBRT) for FIR and UIR prostate cancer in a large dataset...
December 21, 2017: Urologic Oncology
Nikola Cihoric, Alexandros Tsikkinis, Eugenia Vlaskou Badra, Markus Glatzer, Urban Novak, Amina Scherz, Mohamed Shelan, Ivan Soldatovic, Chittazhathu Kurian Kuruvilla Yojena, Daniel M Aebersold, Kristina Lössl
BACKGROUND: Cisplatin and gemcitabine combined with conventional radiation therapy in the treatment of cervical cancer patients results in a favorable outcome but with excess toxicity. The purpose of this study was to evaluate the toxicity profile of dual chemotherapy and highly conformal external beam radiotherapy with image guided adaptive brachytherapy. METHODS: Seventeen patients with cervical carcinoma FIGO stage IB2-IIIB were treated with curative intent between 2011 and 2015...
December 22, 2017: Radiation Oncology
Kh M Diab, A Yu Vasilyev, V N Sokolova
The objective of the present work was to overview the currently available literature publications dealing with the radiodiagnostic techniques applied to evaluate the position of the electrode array used for the purpose of cochlear implantation surgery including both the conventional methods and the recently proposed approaches. It is shown that the intraoperative control guarantees the timely identification of the possible complications and should meet both the safety criteria and the requirements for obtaining high-quality images and intraoperative usability of the surgical instruments being employed...
2017: Vestnik Otorinolaringologii
B Bhavya, Mohammed Sadique, Elsy P Simon, S V Ravi, Sandeep Lal
Aims: The aim of this study was to evaluate the specific chromatic alterations in tooth crowns induced by two different endodontic restorative materials. Settings and Design: This in vitro study was conducted at the Department of Conservative Dentistry, KMCT Dental College, Kozhikode, Kerala. Subjects and Methods: Forty-five freshly extracted, fully developed, single-rooted teeth were prepared and randomly assigned to two experimental groups (n = 15 each) and one negative control group (n = 15)...
July 2017: Journal of Conservative Dentistry: JCD
Yutaka Shiraishi, Penny Fang, Cai Xu, Juhee Song, Sunil Krishnan, Eugene J Koay, Reza J Mehran, Wayne L Hofstetter, Mariela Blum-Murphy, Jaffer A Ajani, Ritsuko Komaki, Bruce Minsky, Radhe Mohan, Charles C Hsu, Brian P Hobbs, Steven H Lin
BACKGROUND AND PURPOSE: Circulating lymphocytes are exquisitely sensitive to radiation exposure, even to low scattered doses which can vary drastically between radiation modalities. We compared the relative risk of radiation-induced lymphopenia between intensity modulated radiation therapy (IMRT) or proton beam therapy (PBT) in esophageal cancer (EC) patients undergoing neoadjuvant chemoradiation therapy (nCRT). MATERIAL AND METHODS: EC patients treated with IMRT and PBT were propensity matched based on key clinical variables...
December 13, 2017: Radiotherapy and Oncology: Journal of the European Society for Therapeutic Radiology and Oncology
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