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Nathan Henry, David Burghoff, Qing Hu, Jacob B Khurgin
We consider here a time domain model representing the dynamics of quantum cascade lasers (QCLs) generating frequency combs (FCs) in both THz and long wave infrared (LWIR λ = 8-12µm) spectral ranges. Using common specifications for these QCLs we confirm that the free running laser enters a regime of operation yielding a pseudo-randomly frequency modulated (FM) radiation in the time domain corresponding to FCs with stable phase relations in the frequency domain. We provide an explanation for this unusual behavior as a consequence of competition for the most efficient regime of operation...
May 28, 2018: Optics Express
Martina Pfeffer, Zuzana Zimmermann, Suzana Gispert, Georg Auburger, Horst-Werner Korf, Charlotte von Gall
Parkinson's disease (PD) is characterized by distinct motor and non-motor symptoms. Sleep disorders are the most frequent and challenging non-motor symptoms in PD patients, and there is growing evidence that they are a consequence of disruptions within the circadian system. PD is characterized by a progressive degeneration of the dorsal vagal nucleus and midbrain dopaminergic neurons together with an imbalance of many other neurotransmitters. Mutations in α-synuclein (SNCA), a protein modulating SNARE complex-dependent neurotransmission, trigger dominantly inherited PD variants and sporadic cases of PD...
June 3, 2018: International Journal of Molecular Sciences
SungJin Kim, Dong-Gyu Kim, Chanho Kim, Dong Soo Lee, Behnam Samadpoor Rikan, YoungGun Pu, Sang-Sun Yoo, Minjae Lee, KeumCheol Hwang, Youngoo Yang, Kang-Yoon Lee
This paper presents a 612⁻1152 MHz Injection-Locked Frequency Multiplier (ILFM). The proposed ILFM is used to send an input signal to a receiver in only the I/Q mismatch calibration mode. Adopting a Phase-Locked Loop (PLL) to calibrate the receiver places a burden on this system because of the additional area and power consumption that is required. Instead of the PLL, to satisfy high-frequency, low-jitter and low-area requirements, a Ring Oscillator is adopted in the system. The free-running frequency of the ILFM is automatically and digitally calibrated to reflect the frequency of the injected signal from the harmonics of the reference clock...
June 1, 2018: Sensors
M Sindou, P Mercier
Primary hemifacial spasm with few exceptions is due to the vascular compression of the facial nerve that can be evidenced with high resolution MRI. Microvascular decompression is the only curative treatment for this pathology. According to literature review detailed in chapter "conflicting vessels", the compression is located at the facial Root Exit Zone (REZ) in 95% of the cases, and in 5% distally at the cisternal or the intrameatal portion of the root as the sole conflict or in addition to one at brainstem/REZ...
May 18, 2018: Neuro-Chirurgie
Angela Pirri, Guido Toci, Jiang Li, Yagang Feng, Tengfei Xie, Zhaoxiang Yang, Barbara Patrizi, Matteo Vannini
We report a comprehensive characterization of a 10 at.% Yb3+ -doped YSAG (Yb:Y₃Scx Al(5-x) O12 , x = 1.5) ceramic, including microstructural, spectroscopic and laser properties. Moreover, we illustrate and discuss the fabrication technique. Yb3+ in YSAG features a broader absorption and emission band than in traditional YAG, which is advantageous for laser applications (i.e., tunable laser sources, ultrafast pulse generation). Pumping in a quasi continuous wave regime at 936 nm, the ceramic has shown good laser performance as the maximum output power was 6...
May 18, 2018: Materials
Cristian Bonatto
It is shown that a highly randomlike behavior of light polarization states in the output of a free-running laser diode, covering the whole Poincaré sphere, arises as a result from a fully deterministic nonlinear process, which is characterized by a hyperchaotic dynamics of two polarization modes nonlinearly coupled with a semiconductor medium, inside the optical cavity. A number of statistical distributions were found to describe the deterministic data of the low-dimensional nonlinear flow, such as lognormal distribution for the light intensity, Gaussian distributions for the electric field components and electron densities, Rice and Rayleigh distributions, and Weibull and negative exponential distributions, for the modulus and intensity of the orthogonal linear components of the electric field, respectively...
April 20, 2018: Physical Review Letters
Keewon Kim, Charles Cho, Moon-Suk Bang, Hyung-Ik Shin, Ji-Hoon Phi, Seung-Ki Kim
Intraoperative monitoring (IOM) utilizes electrophysiological techniques as a surrogate test and evaluation of nervous function while a patient is under general anesthesia. They are increasingly used for procedures, both surgical and endovascular, to avoid injury during an operation, examine neurological tissue to guide the surgery, or to test electrophysiological function to allow for more complete resection or corrections. The application of IOM during pediatric brain tumor resections encompasses a unique set of technical issues...
May 2018: Journal of Korean Neurosurgical Society
Shujie Wang, Yang Yang, Qiyi Li, Jie Zhu, Jianxiong Shen, Ye Tian, Yong Hu, Zhi Li, Wei Xu, Yang Jiao, Rui Cao, Jianguo Zhang
BACKGROUND: Intraoperative neurologic monitoring (IONM) has become an essential component for decreasing the incidence of spinal cord injury during spine surgeries. Many high-risk surgical maneuvers that result in significant IONM alerts have not been reported systematically. Our objective was to thoroughly summarize some common high-risk surgical points associated with IONM alerts in various spine surgeries. METHODS: Between November 2010 and April 2017, 62 patients with true-positive IONM alerts from 3139 spine surgeries were enrolled...
May 3, 2018: World Neurosurgery
Sin Ho Kweon, Jongbin Lee, Chunghun Lim, Joonho Choe
Post-translational control is a crucial mechanism for circadian timekeeping. Evolutionarily conserved kinases and phosphatases have been implicated in circadian phosphorylation and degradation of clock-relevant proteins, which sustain high-amplitude rhythms with 24 hr periodicity in animal behaviors and physiology. Here, we report a novel clock function of the heterodimeric Ca2+ /calmodulin-dependent phosphatase calcineurin and its regulator sarah ( sra ) in Drosophila Genomic deletion of the sra locus dampened circadian locomotor activity rhythms in free-running constant dark after entrainment in light-dark cycles...
May 3, 2018: Genetics
Ruoyu Liao, Youjian Song, Wu Liu, Haosen Shi, Lu Chai, Minglie Hu
We demonstrate dual-comb spectroscopy in the vicinity of 2 µm wavelength based on a single dual-wavelength dual-comb Thulium-doped fiber laser. The shared laser cavity ensures passively maintained mutual coherence between the two combs due to common mode environmental noise rejection. In a proof-of-principle experiment, the absorption characteristics caused by the water in the optical path that composes the dual-comb spectrometer are measured. The retrieved spectral positions of the water absorption dips match with the HITRAN database...
April 16, 2018: Optics Express
Songtao Liu, Tin Komljenovic, Sudharsanan Srinivasan, Erik Norberg, Gregory Fish, John E Bowers
A fully integrated heterogeneous silicon/III-V colliding pulse mode-locked laser with tunable on-chip optical feedback operating in the O-band is extensively investigated. The 19-GHz colliding pulsed laser operates in a wide mode-locking regime with good mode locking quality. By precisely controlling the strength and phase of the on-chip optical feedback signal, the laser exhibits clear periodic pulse shortening effects. The RF 3 dB linewidth was reduced by a factor of 4.7 down to 6 kHz, as compared to the free running state...
April 16, 2018: Optics Express
Michael Fleyer, Moshe Horowitz
We demonstrate, theoretically and experimentally, a new method to measure small changes in the cavity length of oscillators. The method is based on the high sensitivity of the phase of forced delay-line oscillators to changes in their cavity length. The oscillator phase is directly detected by mixing the oscillator output with the injected signal. We describe a comprehensive theoretical model for studying the signal and the noise at the output of a general forced delay-line oscillator with an instantaneous gain saturation and an amplitude-to-phase conversion...
April 2, 2018: Optics Express
Janet Ya-An Chang, Liheng Shi, Michael L Ko, Gladys Y-P Ko
Energy expenditure and metabolism in the vertebrate retina are under circadian control, as we previously reported that the overall retinal ATP content and various signaling molecules related to metabolism display daily or circadian rhythms. Changes in the fission and fusion process of mitochondria, the major organelles producing ATP, in retinal photoreceptors are largely dependent on light exposure, but whether mitochondrial dynamics in photoreceptors and retinal neurons are under circadian control is not clear...
April 2018: Journal of Biological Rhythms
T Katherine Tamai, Yusuke Nakane, Wataru Ota, Akane Kobayashi, Masateru Ishiguro, Naoya Kadofusa, Keisuke Ikegami, Kazuhiro Yagita, Yasufumi Shigeyoshi, Masaki Sudo, Taeko Nishiwaki-Ohkawa, Ayato Sato, Takashi Yoshimura
Chronic circadian disruption due to shift work or frequent travel across time zones leads to jet-lag and an increased risk of diabetes, cardiovascular disease, and cancer. The development of new pharmaceuticals to treat circadian disorders, however, is costly and hugely time-consuming. We therefore performed a high-throughput chemical screen of existing drugs for circadian clock modulators in human U2OS cells, with the aim of repurposing known bioactive compounds. Approximately 5% of the drugs screened altered circadian period, including the period-shortening compound dehydroepiandrosterone (DHEA; also known as prasterone)...
May 2018: EMBO Molecular Medicine
Nicolas Bourbeau Hébert, David G Lancaster, Vincent Michaud-Belleau, George Y Chen, Jérôme Genest
We characterize the frequency noise performance of a free-running dual-comb source based on an erbium-doped glass chip running two adjacent mode-locked waveguide lasers. This compact laser platform, contained only in a 1.2 L volume, rejects common-mode environmental noise by 20 dB thanks to the proximity of the two laser cavities. Furthermore, it displays a remarkably low mutual frequency noise floor around 10  Hz2 /Hz, which is enabled by its large-mode-area waveguides and low Kerr nonlinearity. As a result, it reaches a free-running mutual coherence time of 1 s since mode-resolved dual-comb spectra are generated even on this time scale...
April 15, 2018: Optics Letters
Maria D L A Vazquez-Montes, Richard Stevens, Rafael Perera, Kate Saunders, John R Geddes
BACKGROUND: Recurrent mood episodes and subsyndromal mood instability cause substantial disability in patients with bipolar disorder. Early identification of mood episodes enabling timely mood stabilization is an important clinical goal. This study investigates the ability of control chart methodology to predict manic and/or depressive episodes by applying Shewhart's control rules to weekly self-reported scores from mania and depression questionnaires. METHODS: Shewhart's control rules were applied to weekly self-reported scores from the Altman Self-Rating Mania Scale (ASRM) and the Quick Inventory of Depressive Symptomatology-Self-Report (QIDS) collected from 2001 to 2012 as part of the OXTEXT programme...
April 4, 2018: International Journal of Bipolar Disorders
Hum Nath Parajuli, Haymen Shams, Luis Guerrero Gonzalez, Eszter Udvary, Cyril Renaud, John Mitchell
The filter bank multicarrier (FBMC) modulation format is considered as a potential candidate for future wireless 5G due to its feature of high suppression for out-of-band emissions, which allows combining multiple sub-bands with very narrow band-gaps, and hence increases the overall wireless transmission capacity. In this paper, we experimentally demonstrate the generation of multi sub-bands FBMC signals at millimeter-wave (mm-wave) for radio-over-fiber (RoF) systems. The designed multi sub-bands FBMC system consists of 5 sub-bands of 800 MHz with inter sub-band gaps of 781...
March 19, 2018: Optics Express
Chao Wang, Zejiang Deng, Chenglin Gu, Yang Liu, Daping Luo, Zhiwei Zhu, Wenxue Li, Heping Zeng
Herein, the method of spectrum-encoded dual-comb interferometry is introduced to measure a three-dimensional (3-D) profile with absolute distance information. By combining spectral encoding for wavelength-to-space mapping, dual-comb interferometry for decoding and optical reference for calibration, this system can obtain a 3-D profile of an object at a stand-off distance of 114 mm with a depth precision of 12 μm. With the help of the reference arm, the absolute distance, reflectivity distribution, and depth information are simultaneously measured at a 5 kHz line-scan rate with free-running carrier-envelope offset frequencies...
April 1, 2018: Optics Letters
Hermann Kahle, Kostiantyn Nechay, Jussi-Pekka Penttinen, Antti Tukiainen, Sanna Ranta, Mircea Guina
An optically pumped vertical-external-cavity surface-emitting laser (VECSEL) for direct emission in the 740-790 nm wavelength region is reported. The gain structure is based on 12 AlGaAs quantum wells. We demonstrate wavelength tuning between 747 nm and 788 nm and free-running operation with a maximum power of 4.24 W (pump power limited) for a heat sink temperature of 14°C. This laser system addresses a spectral gap not currently covered by VECSEL technology and represents the most powerful VECSEL reported within the 7XX-nm wavelength region...
April 1, 2018: Optics Letters
Xing Lu, Shuangyou Zhang, Chan-Gi Jeon, Chu-Shik Kang, Jungwon Kim, Kebin Shi
We propose and demonstrate a new method which employs time-of-flight detection of femtosecond laser pulses for precise height measurement of large steps. By using time-of-flight detection with fiber-loop optical-microwave phase detectors, precise measurement of large step height is realized. The proposed method shows uncertainties of 15 nm and 6.5 nm at sampling periods of 40 ms and 800 ms, respectively. This method employs only one free-running femtosecond mode-locked laser and requires no scanning of laser repetition rate, making it easier to operate...
April 1, 2018: Optics Letters
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