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https://www.readbyqxmd.com/read/28059397/accurate-frequency-referencing-for-fieldable-dual-comb-spectroscopy
#1
Gar-Wing Truong, Eleanor M Waxman, Kevin C Cossel, Esther Baumann, Andrew Klose, Fabrizio R Giorgetta, William C Swann, Nathan R Newbury, Ian Coddington
We describe a dual-comb spectrometer that can operate independently of laboratory-based rf and optical frequency references but is nevertheless capable of ultra-high spectral resolution, high SNR, and frequency-accurate spectral measurements. The instrument is based on a "bootstrapped" frequency referencing scheme in which short-term optical phase coherence between combs is attained by referencing each to a free-running diode laser, whilst high frequency resolution and long-term accuracy is derived from a stable quartz oscillator...
December 26, 2016: Optics Express
https://www.readbyqxmd.com/read/28034638/free-breathing-whole-heart-3d-cine-mri-with-self-gated-cartesian-trajectory
#2
M Usman, B Ruijsink, M Nazir, G Cruz, C Prieto
PURPOSE: To present a method that uses a novel free-running self-gated acquisition to achieve isotropic resolution in whole heart 3D Cartesian cardiac CINE MRI. MATERIAL AND METHODS: 3D cardiac CINE MRI using navigator gating results in long acquisition times. Recently, several frameworks based on self-gated non-Cartesian trajectories have been proposed to accelerate this acquisition. However, non-Cartesian reconstructions are computationally expensive due to gridding, particularly in 3D...
December 26, 2016: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/27997028/differential-sensitivity-to-ethanol-induced-circadian-rhythm-disruption-in-adolescent-and-adult-mice
#3
Christina L Ruby, Kaitlyn N Palmer, Jiawen Zhang, Megan O Risinger, Melissa A Butkowski, H Scott Swartzwelder
BACKGROUND: Growing evidence supports a central role for the circadian system in alcohol use disorders, but few studies have examined this relationship during adolescence. In mammals, circadian rhythms are regulated by the suprachiasmatic nucleus, a biological clock whose timing is synchronized (reset) to the environment primarily by light (photic) input. Alcohol (ethanol [EtOH]) disrupts circadian timing in part by attenuating photic phase-resetting responses in adult rodents. However, circadian rhythms change throughout life and it is not yet known whether EtOH has similar effects on circadian regulation during adolescence...
January 2017: Alcoholism, Clinical and Experimental Research
https://www.readbyqxmd.com/read/27974202/the-drosophila-clock-neuron-network-features-diverse-coupling-modes-and-requires-network-wide-coherence-for-robust-circadian-rhythms
#4
Zepeng Yao, Amelia J Bennett, Jenna L Clem, Orie T Shafer
In animals, networks of clock neurons containing molecular clocks orchestrate daily rhythms in physiology and behavior. However, how various types of clock neurons communicate and coordinate with one another to produce coherent circadian rhythms is not well understood. Here, we investigate clock neuron coupling in the brain of Drosophila and demonstrate that the fly's various groups of clock neurons display unique and complex coupling relationships to core pacemaker neurons. Furthermore, we find that coordinated free-running rhythms require molecular clock synchrony not only within the well-characterized lateral clock neuron classes but also between lateral clock neurons and dorsal clock neurons...
December 13, 2016: Cell Reports
https://www.readbyqxmd.com/read/27973517/temporal-jitter-in-free-running-ingaas-inp-single-photon-avalanche-detectors
#5
Emna Amri, Gianluca Boso, Boris Korzh, Hugo Zbinden
Negative-feedback avalanche diodes (NFADs) provide a practical solution for different single-photon counting applications requiring free-running mode operation with low afterpulsing probability. Unfortunately, the timing jitter has never been as good as for gated InGaAs/InP single-photon avalanche diodes. Here we report on the timing jitter characterization of InGaAs/InP based NFADs with particular focus on the temperature dependence and the effect of carrier transport between the absorption and multiplication regions...
December 15, 2016: Optics Letters
https://www.readbyqxmd.com/read/27973516/amplification-of-a-nanosecond-laser-pulse-chain-via-dynamic-injection-locking-of-a-laser-diode
#6
Jun He, Gang Jin, Bei Liu, Junmin Wang
We report a novel optical pulse generation method for high-speed wavelength switching of amplified nanosecond (ns) laser pulses resonant to atomic transitions. Under free-running conditions, a slave laser diode is blue-detuned with tens of GHz relative to the master laser. A nanosecond pulse chain generated by modulating the continuous-wave master laser with a fiber-pigtailed electro-optical intensity modulator is injected into the slave laser diode to fast switch the slave laser's wavelength back and forth...
December 15, 2016: Optics Letters
https://www.readbyqxmd.com/read/27910521/a-low-temperature-external-cavity-diode-laser-for-broad-wavelength-tuning
#7
William G Tobias, Jason S Rosenberg, Nicholas R Hutzler, Kang-Kuen Ni
We report on the design and characterization of a low-temperature external cavity diode laser (ECDL) system for broad wavelength tuning. The performance achieved with multiple diode models addresses the scarcity of commercial red laser diodes below 633 nm, which is a wavelength range relevant to the spectroscopy of many molecules and ions. Using a combination of multiple-stage thermoelectric cooling and water cooling, the operating temperature of a laser diode is lowered to -64 °C, more than 85 °C below the ambient temperature...
November 2016: Review of Scientific Instruments
https://www.readbyqxmd.com/read/27906312/widely-tunable-narrow-linewidth-external-cavity-gain-chip-laser-for-spectroscopy-between-1-0-1-1-%C3%A2%C2%B5m
#8
Dong K Shin, Bryce M Henson, Roman I Khakimov, Jacob A Ross, Colin J Dedman, Sean S Hodgman, Kenneth G H Baldwin, Andrew G Truscott
We have developed and characterised a stable, narrow linewidth external-cavity laser (ECL) tunable over 100 nm around 1080 nm, using a single-angled-facet gain chip. We propose the ECL as a low-cost, high-performance alternative to fibre and diode lasers in this wavelength range and demonstrate its capability through the spectroscopy of metastable helium. Within the coarse tuning range, the wavelength can be continuously tuned over 30 pm (7.8 GHz) without mode-hopping and modulated with bandwidths up to 3 kHz (piezo) and 37(3) kHz (current)...
November 28, 2016: Optics Express
https://www.readbyqxmd.com/read/27906238/microresonator-stabilized-2%C3%A2-%C3%A2-%C3%AE-m-distributed-feedback-gasb-based-diode-laser
#9
Elijah Dale, Mahmood Bagheri, Andrey B Matsko, Clifford Frez, Wei Liang, Siamak Forouhar, Lute Maleki
We report on the stabilization of a high-power distributed feedback (DFB) semiconductor laser operating at 2.05 μm wavelength, using a crystalline whispering gallery mode microresonator. The laser's frequency noise is measured to be below 100  Hz/Hz<sup>1/2</sup> at Fourier frequencies ranging from 10 Hz to 1 MHz. The instantaneous linewidth of the laser is improved by four orders of magnitude compared with the free-running DFB laser, and is measured to be 15 Hz at 0.1 ms measurement time...
December 1, 2016: Optics Letters
https://www.readbyqxmd.com/read/27869838/analytical-comparison-of-pulses-generated-by-locking-three-and-five-longitudinal-modes-in-free-running-class-b-lasers
#10
Farzane Sharafi, Jafar Jahanpanah
We consider the coherent oscillation of five longitudinal modes, which leads to the coupling of modes in the frequency domain and generation of short pulses in the time domain. The aim is to audit the mechanism of mode locking in more detail by extending the analytical solution of the Maxwell-Bloch equations of motion from three to five mode states. The characteristics of pulses including height, repetition, and duration have been calculated for a five-mode class B laser, and the changes are compared with respect to the three-mode state...
November 20, 2016: Applied Optics
https://www.readbyqxmd.com/read/27869182/the-effects-of-non-self-sustained-oscillators-on-the-en-trainment-ability-of-the-suprachiasmatic-nucleus
#11
Changgui Gu, Ming Tang, Jos H T Rohling, Huijie Yang
In mammals, the circadian rhythms of behavioral and physiological activities are regulated by an endogenous clock located in the suprachiasmatic nucleus (SCN). The SCN is composed of ~20,000 neurons, of which some are capable of self-sustained oscillations, while the others do not oscillate in a self-sustainable manner, but show arrhythmic patterns or damped oscillations. Thus far, the effects of these non-self-sustained oscillatory neurons are not fully explored. Here, we examined how the proportion of the non-self-sustained oscillators affects the free running period under constant darkness and the ability to entrain to the light-dark cycle...
November 21, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27830946/seven-day-human-biological-rhythms-an-expedition-in-search-of-their-origin-synchronization-functional-advantage-adaptive-value-and-clinical-relevance
#12
Alain E Reinberg, Laurence Dejardin, Michael H Smolensky, Yvan Touitou
This fact-finding expedition explores the perspectives and knowledge of the origin and functional relevance of the 7 d domain of the biological time structure, with special reference to human beings. These biological rhythms are displayed at various levels of organization in diverse species - from the unicellular sea algae of Acetabularia and Goniaulax to plants, insects, fish, birds and mammals, including man - under natural as well as artificial, i.e. constant, environmental conditions. Nonetheless, very little is known about their derivation, functional advantage, adaptive value, synchronization and potential clinical relevance...
November 10, 2016: Chronobiology International
https://www.readbyqxmd.com/read/27828388/time-domain-modeling-of-terahertz-quantum-cascade-lasers-for-frequency-comb-generation
#13
Petar Tzenov, David Burghoff, Qing Hu, Christian Jirauschek
The generation of frequency combs in the mid-infrared and terahertz regimes from compact and potentially cheap sources could have a strong impact on spectroscopy, as many molecules have their rotovibrational bands in this spectral range. Thus, quantum cascade lasers (QCLs) are the perfect candidates for comb generation in these portions of the electromagnetic spectrum. Here we present a theoretical model based on a full numerical solution of Maxwell-Bloch equations suitable for the simulation of such devices...
October 3, 2016: Optics Express
https://www.readbyqxmd.com/read/27828328/flexible-and-scalable-wavelength-multicast-of-coherent-optical-ofdm-with-tolerance-against-pump-phase-noise-using-reconfigurable-coherent-multi-carrier-pumping
#14
Guo-Wei Lu, Tianwai Bo, Takahide Sakamoto, Naokatsu Yamamoto, Calvin Chun-Kit Chan
Recently the ever-growing demand for dynamic and high-capacity services in optical networks has resulted in new challenges that require improved network agility and flexibility in order for network resources to become more "consumable" and dynamic, or elastic, in response to requests from higher network layers. Flexible and scalable wavelength conversion or multicast is one of the most important technologies needed for developing agility in the physical layer. This paper will investigate how, using a reconfigurable coherent multi-carrier as a pump, the multicast scalability and the flexibility in wavelength allocation of the converted signals can be effectively improved...
October 3, 2016: Optics Express
https://www.readbyqxmd.com/read/27828022/frequency-domain-phase-noise-analysis-of-dual-injection-locked-optoelectronic-oscillators
#15
Sajad Jahanbakht
Dual injection-locked optoelectronic oscillators (DIL-OEOs) have been introduced as a means to achieve very low-noise microwave oscillations while avoiding the large spurious peaks that occur in the phase noise of the conventional single-loop OEOs. In these systems, two OEOs are inter-injection locked to each other. The OEO with the longer optical fiber delay line is called the master OEO, and the other is called the slave OEO. Here, a frequency domain approach for simulating the phase noise spectrum of each of the OEOs in a DIL-OEO system and based on the conversion matrix approach is presented...
October 1, 2016: Applied Optics
https://www.readbyqxmd.com/read/27819313/circadian-rhythms-of-european-and-african-americans-after-a-large-delay-of-sleep-as-in-jet-lag-and-night-work
#16
Charmane I Eastman, Victoria A Tomaka, Stephanie J Crowley
Jet travel and night shift work produce large changes in when people sleep, work and eat; a challenge that was not encountered during most of our evolution. Successful adaptation would require the internal, master, circadian clock to make large phase shifts to reduce the circadian misalignment between circadian rhythms and the times for sleep, work and meals. We compared African-Americans and non-Hispanic European-Americans in how much their circadian clocks shifted after a 9 hour phase delay of the light/dark, sleep/wake and meal schedule, which has similarities to flying west or sleeping in the daytime after night shifts...
November 7, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27810175/altered-sleep-wake-patterns-in-blindness-a-combined-actigraphy-and-psychometric-study
#17
S Aubin, C Gacon, P Jennum, M Ptito, R Kupers
OBJECTIVE: Light plays an important role in the synchronization of the internal biological clock and the environmental day/night pattern. Thus, absence of vision is often associated with both increases in reported sleep disturbances and incidence of free-running circadian rhythms. In this study we discuss variability in the sleep-wake pattern between blind and normal-sighted individuals. METHODS: Thirty-day actigraphy recordings were collected from 11 blind individuals without residual light perception and 11 age- and sex-matched normal-sighted controls...
August 2016: Sleep Medicine
https://www.readbyqxmd.com/read/27805636/ultra-stable-high-average-power-femtosecond-laser-system-tunable-from-1-33-to-20%C3%A2-%C3%A2-%C3%AE-m
#18
Tobias Steinle, Florian Mörz, Andy Steinmann, Harald Giessen
A highly stable 350 fs laser system with a gap-free tunability from 1.33 to 2.0 μm and 2.13 to 20 μm is demonstrated. Nanojoule-level pulse energy is achieved in the mid-infrared at a 43 MHz repetition rate. The system utilizes a post-amplified fiber-feedback optical parametric oscillator followed by difference frequency generation between the signal and idler. No locking or synchronization electronics are required to achieve outstanding free-running output power and spectral stability of the whole system...
November 1, 2016: Optics Letters
https://www.readbyqxmd.com/read/27802344/independent-mobility-achieved-through-a-wireless-brain-machine-interface
#19
Camilo Libedinsky, Rosa So, Zhiming Xu, Toe K Kyar, Duncun Ho, Clement Lim, Louiza Chan, Yuanwei Chua, Lei Yao, Jia Hao Cheong, Jung Hyup Lee, Kulkarni Vinayak Vishal, Yongxin Guo, Zhi Ning Chen, Lay K Lim, Peng Li, Lei Liu, Xiaodan Zou, Kai K Ang, Yuan Gao, Wai Hoe Ng, Boon Siew Han, Keefe Chng, Cuntai Guan, Minkyu Je, Shih-Cheng Yen
Individuals with tetraplegia lack independent mobility, making them highly dependent on others to move from one place to another. Here, we describe how two macaques were able to use a wireless integrated system to control a robotic platform, over which they were sitting, to achieve independent mobility using the neuronal activity in their motor cortices. The activity of populations of single neurons was recorded using multiple electrode arrays implanted in the arm region of primary motor cortex, and decoded to achieve brain control of the platform...
2016: PloS One
https://www.readbyqxmd.com/read/27791392/impact-of-ataxin-2-knock-out-on-circadian-locomotor-behavior-and-per-immunoreaction-in-the-scn-of-mice
#20
Martina Pfeffer, Suzana Gispert, Georg Auburger, Helmut Wicht, Horst-Werner Korf
In Drosophila melanogaster, Ataxin-2 is a crucial activator of Period and is involved in the control of circadian rhythms. However, in mammals the function of Ataxin-2 is unknown despite its involvement in the inherited neurogenerative disease Spinocerebellar Ataxia type 2 in humans. Therefore, we analyzed locomotor behavior of Atxn2-deficient mice and their WT littermates under entrained- and free-running conditions as well as after experimental jet lag. Furthermore, we compared the PER1 and PER2 immunoreaction (IR) in the SCN...
October 28, 2016: Chronobiology International
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