Universal fieldable assay with unassisted visual detection

NASA Technical Reports Server (NTRS)

Chelyapov, Nicolas (Inventor)

2012-01-01

A universal detection system based on allosteric aptamers, signal amplification cascade, and eye-detectable phrase transition. A broadly applicable homogeneous detection system is provided. It utilizes components of the blood coagulation cascade in the presence of polystyrene microspheres (MS) as a signal amplifier. Russell's viper venom factor X activator (RVV-X) triggers the cascade, which results in an eye-visible phase transition--precipitation of MS bound to clotted fibrin. An allosteric RNA aptamer, RNA132, with affinity for RVV-X and human vascular endothelial growth factor (VEGF.sub.165) was created. RNA132 inhibits enzymatic activity of RVV-X. The effector molecule, VEGF.sub.165, reverses the inhibitory activity of RNA132 on RVV-X and restores its enzymatic activity, thus triggering the cascade and enabling the phase transition. Similar results were obtained for another allosteric aptamer modulated by a protein tyrosine phosphatase. The assay is instrumentation-free for both processing and readout.

Multistage WDM access architecture employing cascaded AWGs

NASA Astrophysics Data System (ADS)

El-Nahal, F. I.; Mears, R. J.

2009-03-01

Here we propose passive/active arrayed waveguide gratings (AWGs) with enhanced performance for system applications mainly in novel access architectures employing cascaded AWG technology. Two technologies were considered to achieve space wavelength switching in these networks. Firstly, a passive AWG with semiconductor optical amplifiers array, and secondly, an active AWG. Active AWG is an AWG with an array of phase modulators on its arrayed-waveguides section, where a programmable linear phase-profile or a phase hologram is applied across the arrayed-waveguide section. This results in a wavelength shift at the output section of the AWG. These architectures can address up to 6912 customers employing only 24 wavelengths, coarsely separated by 1.6 nm. Simulation results obtained here demonstrate that cascaded AWGs access architectures have a great potential in future local area networks. Furthermore, they indicate for the first time that active AWGs architectures are more efficient in routing signals to the destination optical network units than passive AWG architectures.

Pulsed laser-based optical frequency comb generator for high capacity wavelength division multiplexed passive optical network supporting 1.2 Tbps

NASA Astrophysics Data System (ADS)

Ullah, Rahat; Liu, Bo; Zhang, Qi; Saad Khan, Muhammad; Ahmad, Ibrar; Ali, Amjad; Khan, Razaullah; Tian, Qinghua; Yan, Cheng; Xin, Xiangjun

2016-09-01

An architecture for flattened and broad spectrum multicarriers is presented by generating 60 comb lines from pulsed laser driven by user-defined bit stream in cascade with three modulators. The proposed scheme is a cost-effective architecture for optical line terminal (OLT) in wavelength division multiplexed passive optical network (WDM-PON) system. The optical frequency comb generator consists of a pulsed laser in cascade with a phase modulator and two Mach-Zehnder modulators driven by an RF source incorporating no phase shifter, filter, or electrical amplifier. Optical frequency comb generation is deployed in the simulation environment at OLT in WDM-PON system supports 1.2-Tbps data rate. With 10-GHz frequency spacing, each frequency tone carries data signal of 20 Gbps-based differential quadrature phase shift keying (DQPSK) in downlink transmission. We adopt DQPSK-based modulation technique in the downlink transmission because it supports 2 bits per symbol, which increases the data rate in WDM-PON system. Furthermore, DQPSK format is tolerant to different types of dispersions and has a high spectral efficiency with less complex configurations. Part of the downlink power is utilized in the uplink transmission; the uplink transmission is based on intensity modulated on-off keying. Minimum power penalties have been observed with excellent eye diagrams and other transmission performances at specified bit error rates.

Surface emitting ring quantum cascade lasers for chemical sensing

NASA Astrophysics Data System (ADS)

Szedlak, Rolf; Hayden, Jakob; Martín-Mateos, Pedro; Holzbauer, Martin; Harrer, Andreas; Schwarz, Benedikt; Hinkov, Borislav; MacFarland, Donald; Zederbauer, Tobias; Detz, Hermann; Andrews, Aaron Maxwell; Schrenk, Werner; Acedo, Pablo; Lendl, Bernhard; Strasser, Gottfried

2018-01-01

We review recent advances in chemical sensing applications based on surface emitting ring quantum cascade lasers (QCLs). Such lasers can be implemented in monolithically integrated on-chip laser/detector devices forming compact gas sensors, which are based on direct absorption spectroscopy according to the Beer-Lambert law. Furthermore, we present experimental results on radio frequency modulation up to 150 MHz of surface emitting ring QCLs. This technique provides detailed insight into the modulation characteristics of such lasers. The gained knowledge facilitates the utilization of ring QCLs in combination with spectroscopic techniques, such as heterodyne phase-sensitive dispersion spectroscopy for gas detection and analysis.

Optical wave turbulence and the condensation of light

NASA Astrophysics Data System (ADS)

Bortolozzo, Umberto; Laurie, Jason; Nazarenko, Sergey; Residori, Stefania

2009-11-01

In an optical experiment, we report a wave turbulence regime that, starting with weakly nonlinear waves with randomized phases, shows an inverse cascade of photons towards the lowest wavenumbers. We show that the cascade is induced by a six-wave resonant interaction process and is characterized by increasing nonlinearity. At low wavenumbers the nonlinearity becomes strong and leads to modulational instability developing into solitons, whose number is decreasing further along the beam.

Interferometric modulation of quantum cascade interactions

NASA Astrophysics Data System (ADS)

Cusumano, Stefano; Mari, Andrea; Giovannetti, Vittorio

2018-05-01

We consider many-body quantum systems dissipatively coupled by a cascade network, i.e., a setup in which interactions are mediated by unidirectional environmental modes propagating through a linear optical interferometer. In particular we are interested in the possibility of inducing different effective interactions by properly engineering an external dissipative network of beam splitters and phase shifters. In this work we first derive the general structure of the master equation for a symmetric class of translation-invariant cascade networks. Then we show how, by tuning the parameters of the interferometer, one can exploit interference effects to tailor a large variety of many-body interactions.

Dynamic optical arbitrary waveform shaping based on cascaded optical modulators of single FBG.

PubMed

Chen, Jingyuan; Li, Peili

2015-08-10

A dynamic optical arbitrary waveform generation (O-AWG) with amplitude and phase independently controlled in optical modulators of single fiber Bragg Grating (FBG) has been proposed. This novel scheme consists of several optical modulators. In the optical modulator (O-MOD), a uniform FBG is used to filter spectral component of the input signal. The amplitude is controlled by fiber stretcher (FS) in Mach-Zehnder interference (MZI) structure through interference of two MZI arms. The phase is manipulated via the second FS in the optical modulator. This scheme is investigated by simulation. Consequently, optical pulse trains with different waveforms as well as pulse trains with nonuniform pulse intensity, pulse spacing and pulse width within each period are obtained through FSs adjustment to alter the phase shifts of signal in each O-MOD.

A photonic chip based frequency discriminator for a high performance microwave photonic link.

PubMed

Marpaung, David; Roeloffzen, Chris; Leinse, Arne; Hoekman, Marcel

2010-12-20

We report a high performance phase modulation direct detection microwave photonic link employing a photonic chip as a frequency discriminator. The photonic chip consists of five optical ring resonators (ORRs) which are fully programmable using thermo-optical tuning. In this discriminator a drop-port response of an ORR is cascaded with a through response of another ORR to yield a linear phase modulation (PM) to intensity modulation (IM) conversion. The balanced photonic link employing the PM to IM conversion exhibits high second-order and third-order input intercept points of + 46 dBm and + 36 dBm, respectively, which are simultaneously achieved at one bias point.

Applications of Optical Coherent Transient Technology to Pulse Shaping, Spectral Filtering Arbitrary Waveform Generation and RF Beamforming

DTIC Science & Technology

2006-04-14

the EOPM (~1 mW) was amplified by injection locking of a high power diode laser and further amplified to ~300 mW with a semiconductor optical ...The spectra of 8 GHz CW phase modulated signals in cascaded injection locking system from (a) master laser ; (b) the first slave, and (c) the second...cascaded injection locked amplifiers at 793nm, and frequency chirped lasers at 793nm. 15. SUBJECT TERMS Optical Coherent Transients, Spatial

Simulation of novel intensity modulated cascaded coated LPFG sensor based on PMTP

NASA Astrophysics Data System (ADS)

Feng, Wenbin; Gu, Zhengtian; Lin, Qiang; Sang, Jiangang

2017-12-01

This paper presents a novel intensity modulated cascaded long-period fiber grating (CLPFG) sensor which is cascaded by two same coated long-period fiber gratings (LPFGs) operating at the phase-matching turning point (PMTP). The sensor combines the high sensitivity of LPFG operating at PMTP and the narrow bandwidth of interference attenuation band of CLPFG, so a higher response to small change of the surrounding refractive index (SRI) can be obtained by intensity modulation. Based on the coupled-mode theory, the grating parameters of the PMTP of a middle odd order cladding mode of a single LPFG are calculated. Then this two same LPFGs are cascaded into a CLPFG, and the optical transmission spectrum of the CLPFG is calculated by transfer matrix method. A resonant wavelength of a special interference attenuation band whose intensity has the highest response to SRI, is selected form CLPFG’s spectrum, and setting the resonant wavelength as the operating wavelength of the sensor. Furthermore, the simulation results show that the resolution of SRI of this CLPFG is available to 1.97 × 10-9 by optimizing the film optical parameters, which is about three orders of magnitude higher than coated dual-peak LPFG and cascaded LPFG sensors. It is noteworthy that the sensor is also sensitive to the refractive index of coat, so that the sensor is expected to be applied to detections of gas, PH value, humidity and so on, in the future.

A Cascaded Approach for Correcting Ionospheric Contamination with Large Amplitude in HF Skywave Radars

PubMed Central

Wei, Yinsheng; Guo, Rujiang; Xu, Rongqing; Tang, Xiudong

2014-01-01

Ionospheric phase perturbation with large amplitude causes broadening sea clutter's Bragg peaks to overlap each other; the performance of traditional decontamination methods about filtering Bragg peak is poor, which greatly limits the detection performance of HF skywave radars. In view of the ionospheric phase perturbation with large amplitude, this paper proposes a cascaded approach based on improved S-method to correct the ionospheric phase contamination. This approach consists of two correction steps. At the first step, a time-frequency distribution method based on improved S-method is adopted and an optimal detection method is designed to obtain a coarse ionospheric modulation estimation from the time-frequency distribution. At the second correction step, based on the phase gradient algorithm (PGA) is exploited to eliminate the residual contamination. Finally, use the measured data to verify the effectiveness of the method. Simulation results show the time-frequency resolution of this method is high and is not affected by the interference of the cross term; ionospheric phase perturbation with large amplitude can be corrected in low signal-to-noise (SNR); such a cascade correction method has a good effect. PMID:24578656

Mid-IR femtosecond frequency conversion by soliton-probe collision in phase-mismatched quadratic nonlinear crystals.

PubMed

Liu, Xing; Zhou, Binbin; Guo, Hairun; Bache, Morten

2015-08-15

We show numerically that ultrashort self-defocusing temporal solitons colliding with a weak pulsed probe in the near-IR can convert the probe to the mid-IR. A near-perfect conversion efficiency is possible for a high effective soliton order. The near-IR self-defocusing soliton can form in a quadratic nonlinear crystal (beta-barium borate) in the normal dispersion regime due to cascaded (phase-mismatched) second-harmonic generation, and the mid-IR converted wave is formed in the anomalous dispersion regime between λ=2.2-2.4  μm as a resonant dispersive wave. This process relies on nondegenerate four-wave mixing mediated by an effective negative cross-phase modulation term caused by cascaded soliton-probe sum-frequency generation.

Purely wavelength- and amplitude-modulated quartz-enhanced photoacoustic spectroscopy.

PubMed

Patimisco, Pietro; Sampaolo, Angelo; Bidaux, Yves; Bismuto, Alfredo; Scott, Marshall; Jiang, James; Muller, Antoine; Faist, Jerome; Tittel, Frank K; Spagnolo, Vincenzo

2016-11-14

We report here on a quartz-enhanced photoacoustic (QEPAS) sensor employing a quantum cascade laser (QCL) structure capable of operating in a pure amplitude or wavelength modulation configuration. The QCL structure is composed of three electrically independent sections: Gain, Phase (PS) and Master Oscillator (MO). Selective current pumping of these three sections allows obtaining laser wavelength tuning without changes in the optical power, and power modulation without emission wavelength shifts. A pure QEPAS amplitude modulation condition is obtained by modulating the PS current, while pure wavelength modulation is achieved by modulating simultaneously the MO and PS QCL sections and slowly scanning the DC current level injected in the PS section.

A simultaneous all-optical half/full-subtraction strategy using cascaded highly nonlinear fibers

NASA Astrophysics Data System (ADS)

Singh, Karamdeep; Kaur, Gurmeet; Singh, Maninder Lal

2018-02-01

Using non-linear effects such as cross-gain modulation (XGM) and cross-phase modulation (XPM) inside two highly non-linear fibres (HNLF) arranged in cascaded configuration, a simultaneous half/full-subtracter is proposed. The proposed simultaneous half/full-subtracter design is attractive due to several features such as input data pattern independence and usage of minimal number of non-linear elements i.e. HNLFs. Proof of concept simulations have been conducted at 100 Gbps rate, indicating fine performance, as extinction ratio (dB) > 6.28 dB and eye opening factors (EO) > 77.1072% are recorded for each implemented output. The proposed simultaneous half/full-subtracter can be used as a key component in all-optical information processing circuits.

Limitations to THz generation by optical rectification using tilted pulse fronts.

PubMed

Ravi, Koustuban; Huang, W Ronny; Carbajo, Sergio; Wu, Xiaojun; Kärtner, Franz

2014-08-25

Terahertz (THz) generation by optical rectification (OR) using tilted-pulse-fronts is studied. A one-dimensional (1-D) model which simultaneously accounts for (i) the nonlinear coupled interaction of the THz and optical radiation, (ii) angular and material dispersion, (iii) absorption, iv) self-phase modulation and (v) stimulated Raman scattering is presented. We numerically show that the large experimentally observed cascaded frequency down-shift and spectral broadening (cascading effects) of the optical pump pulse is a direct consequence of THz generation. In the presence of this large spectral broadening, the large angular dispersion associated with tilted-pulse-fronts which is ~15-times larger than material dispersion, accentuates phase mismatch and degrades THz generation. Consequently, this cascading effect in conjunction with angular dispersion is shown to be the strongest limitation to THz generation in lithium niobate for pumping at 1 µm. It is seen that the exclusion of these cascading effects in modeling OR, leads to a significant overestimation of the optical-to-THz conversion efficiency. The results are verified with calculations based on a 2-D spatial model. The simulation results are supported by experiments.

Integrated optical modulator for signal up-conversion over radio-on-fiber link.

PubMed

Kim, Woo-Kyung; Kwon, Soon-Woo; Jeong, Woo-Jin; Son, Geun-Sik; Lee, Kwang-Hyun; Choi, Woo-Young; Yang, Woo-Seok; Lee, Hyung-Man; Lee, Han-Young

2009-02-16

An integrated optical modulator, which consists of a dual-sideband suppressed carrier (DSB-SC) modulator cascaded with a single-sideband (SSB) modulator, is proposed for signal up-conversion over Radio-on-Fiber. Utilizing a single-drive domain inverted structure in both modulators, balanced modulations were obtained without complicated radio frequency (RF) driving circuits and delicate RF phase adjustments. Intermediate frequency (IF) band signal was up-conversed to 60GHz band by using the fabricated device and was transmitted over optical fiber. Experiment results show that the proposed device enables millimeter wave generation and signal transmission without any power penalty caused by chromatic dispersion.

Physics of frequency-modulated comb generation in quantum-well diode lasers

NASA Astrophysics Data System (ADS)

Dong, Mark; Cundiff, Steven T.; Winful, Herbert G.

2018-05-01

We investigate the physical origin of frequency-modulated combs generated from single-section semiconductor diode lasers based on quantum wells, isolating the essential physics necessary for comb generation. We find that the two effects necessary for comb generation—spatial hole burning (leading to multimode operation) and four-wave mixing (leading to phase locking)—are indeed present in some quantum-well systems. The physics of comb generation in quantum wells is similar to that in quantum dot and quantum cascade lasers. We discuss the nature of the spectral phase and some important material parameters of these diode lasers.

Gas Phase Photoacoustic Sensor at 8.41 mu m Using Quartz Tuning Forks and Amplitude Modulated Quantum Cascade Lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wojcik, Michael D.; Phillips, Mark C.; Cannon, Bret D.

2006-10-01

We demonstrate the performance of a novel long-wave infrared photoacoustic laser absorbance spectrometer for gas-phase species using an amplitude modulated (AM) quantum cascade (QC) laser and a quartz tuning fork microphone. Photoacoustic signal was generated by focusing the output of a Fabry-Perot QC laser operating at 8.41 ?m between the legs of a quartz tuning fork which served as a transducer for the transient acoustic pressure wave. The QC laser was modulated at the resonant frequency of the tuning fork (32.8 kHz) and delivered a modest 5.3 mW at the tuning fork. This spectrometer was calibrated using the infrared absorbermore » Freon-134a by performing a simultaneous absorption measurement using a 35 cm absorption cell. The NEAS of this instrument was determined to be 2 x 10{sup -8} W cm-1 Hz{sup -1/2}. A corresponding theoretical analysis of the instrument sensitivity is presented and is capable of quantitatively reproducing the experimental NEAS, indicating that the fundamental sensitivity of this technique is limited by the noise floor of the tuning fork itself.« less

Vortex algebra by multiply cascaded four-wave mixing of femtosecond optical beams.

PubMed

Hansinger, Peter; Maleshkov, Georgi; Garanovich, Ivan L; Skryabin, Dmitry V; Neshev, Dragomir N; Dreischuh, Alexander; Paulus, Gerhard G

2014-05-05

Experiments performed with different vortex pump beams show for the first time the algebra of the vortex topological charge cascade, that evolves in the process of nonlinear wave mixing of optical vortex beams in Kerr media due to competition of four-wave mixing with self-and cross-phase modulation. This leads to the coherent generation of complex singular beams within a spectral bandwidth larger than 200nm. Our experimental results are in good agreement with frequency-domain numerical calculations that describe the newly generated spectral satellites.

Multi-tap complex-coefficient incoherent microwave photonic filters based on optical single-sideband modulation and narrow band optical filtering.

PubMed

Sagues, Mikel; García Olcina, Raimundo; Loayssa, Alayn; Sales, Salvador; Capmany, José

2008-01-07

We propose a novel scheme to implement tunable multi-tap complex coefficient filters based on optical single sideband modulation and narrow band optical filtering. A four tap filter is experimentally demonstrated to highlight the enhanced tuning performance provided by complex coefficients. Optical processing is performed by the use of a cascade of four phase-shifted fiber Bragg gratings specifically fabricated for this purpose.

Active mode-locking of mid-infrared quantum cascade lasers with short gain recovery time.

PubMed

Wang, Yongrui; Belyanin, Alexey

2015-02-23

We investigate the dynamics of actively modulated mid-infrared quantum cascade lasers (QCLs) using space- and time-domain simulations of coupled density matrix and Maxwell equations with resonant tunneling current taken into account. We show that it is possible to achieve active mode locking and stable generation of picosecond pulses in high performance QCLs with a vertical laser transition and a short gain recovery time by bias modulation of a short section of a monolithic Fabry-Perot cavity. In fact, active mode locking in QCLs with a short gain recovery time turns out to be more robust to the variation of parameters as compared to previously studied lasers with a long gain recovery time. We investigate the effects of spatial hole burning and phase locking on the laser output.

Mid infrared quantum cascade laser operating in pure amplitude modulation for background-free trace gas spectroscopy.

PubMed

Bidaux, Yves; Bismuto, Alfredo; Patimisco, Pietro; Sampaolo, Angelo; Gresch, Tobias; Strubi, Gregory; Blaser, Stéphane; Tittel, Frank K; Spagnolo, Vincenzo; Muller, Antoine; Faist, Jérôme

2016-11-14

We present a single mode multi-section quantum cascade laser source composed of three different sections: master oscillator, gain and phase section. Non-uniform pumping of the QCL's gain reveals that the various laser sections are strongly coupled. Simulations of the electronic and optical properties of the laser (based on the density matrix and scattering matrix formalisms, respectively) were performed and a good agreement with measurements is obtained. In particular, a pure modulation of the laser output power can be achieved. This capability of the device is applied in tunable-laser spectroscopy of N₂O where background-free quartz enhanced photo acoustic spectral scans with nearly perfect Voigt line shapes for the selected absorption line are obtained.

Asymmetric multiple-image encryption based on the cascaded fractional Fourier transform

NASA Astrophysics Data System (ADS)

Li, Yanbin; Zhang, Feng; Li, Yuanchao; Tao, Ran

2015-09-01

A multiple-image cryptosystem is proposed based on the cascaded fractional Fourier transform. During an encryption procedure, each of the original images is directly separated into two phase masks. A portion of the masks is subsequently modulated into an interim mask, which is encrypted into the ciphertext image; the others are used as the encryption keys. Using phase truncation in the fractional Fourier domain, one can use an asymmetric cryptosystem to produce a real-valued noise-like ciphertext, while a legal user can reconstruct all of the original images using a different group of phase masks. The encryption key is an indivisible part of the corresponding original image and is still useful during decryption. The proposed system has high resistance to various potential attacks, including the chosen-plaintext attack. Numerical simulations also demonstrate the security and feasibility of the proposed scheme.

Cascade photonic integrated circuit architecture for electro-optic in-phase quadrature/single sideband modulation or frequency conversion.

PubMed

Hasan, Mehedi; Hall, Trevor

2015-11-01

A photonic integrated circuit architecture for implementing frequency upconversion is proposed. The circuit consists of a 1×2 splitter and 2×1 combiner interconnected by two stages of differentially driven phase modulators having 2×2 multimode interference coupler between the stages. A transfer matrix approach is used to model the operation of the architecture. The predictions of the model are validated by simulations performed using an industry standard software tool. The intrinsic conversion efficiency of the proposed design is improved by 6 dB over the alternative functionally equivalent circuit based on dual parallel Mach-Zehnder modulators known in the prior art. A two-tone analysis is presented to study the linearity of the proposed circuit, and a comparison is provided over the alternative. The proposed circuit is suitable for integration in any platform that offers linear electro-optic phase modulation such as LiNbO(3), silicon, III-V, or hybrid technology.

High-Power X-Band Semiconductor RF Switch for Pulse Compression Systems of Future Colliders

NASA Astrophysics Data System (ADS)

Tantawi, Sami G.; Tamura, Fumihiko

2000-04-01

We describe the potential of semiconductor X-band RF switch arrays as a means of developing high power RF pulse compression systems for future linear colliders. The switch systems described here have two designs. Both designs consist of two 3dB hybrids and active modules. In the first design the module is composed of a cascaded active phase shifter. In the second design the module uses arrays of SPST (Single Pole Single Throw) switches. Each cascaded element of the phase shifter and the SPST switch has similar design. The active element consists of symmetrical three-port tee-junctions and an active waveguide window in the symmetrical arm of the tee-junction. The design methodology of the elements and the architecture of the whole switch system are presented. We describe the scaling law that governs the relation between power handling capability and number of elements. The design of the active waveguide window is presented. The waveguide window is a silicon wafer with an array of four hundred PIN/NIP diodes covering the surface of the window. This waveguide window is located in an over-moded TE01 circular waveguide. The results of high power RF measurements of the active waveguide window are presented. The experiment is performed at power levels of tens of megawatts at X-band.

Harnessing rogue wave for supercontinuum generation in cascaded photonic crystal fiber.

PubMed

Zhao, Saili; Yang, Hua; Zhao, Chujun; Xiao, Yuzhe

2017-04-03

Based on induced modulation instability, we present a numerical study on harnessing rogue wave for supercontinuum generation in cascaded photonic crystal fibers. By selecting optimum modulation frequency, we achieve supercontinuum with a great improvement on spectrum stability when long-pulse is used as the pump. In this case, rogue wave can be obtained in the first segmented photonic crystal fiber with one zero dispersion wavelength in a controllable manner. Numerical simulations show that spectral range and flatness can be regulated in an extensive range by cascading a photonic crystal fiber with two zero dispersion wavelengths. Some novel phenomena are observed in the second segmented photonic crystal fiber. When the second zero dispersion wavelength is close to the first one, rogue wave is directly translated into dispersion waves, which is conducive to the generation of smoother supercontinuum. When the second zero dispersion wavelength is far away from the first one, rogue wave is translated into the form of fundamental soliton steadily propagating in the vicinity of the second zero dispersion wavelength. Meanwhile, the corresponding red-shifted dispersion wave is generated when the phase matching condition is met, which is beneficial to the generation of wider supercontinuum. The results presented in this work provide a better application of optical rogue wave to generate flat and broadband supercontinuum in cascaded photonic crystal fibers.

Mode-locking of a terahertz laser by direct phase synchronization.

PubMed

Maysonnave, J; Maussang, K; Freeman, J R; Jukam, N; Madéo, J; Cavalié, P; Rungsawang, R; Khanna, S P; Linfield, E H; Davies, A G; Beere, H E; Ritchie, D A; Dhillon, S S; Tignon, J

2012-09-10

A novel scheme to achieve mode-locking of a multimode laser is demonstrated. Traditional methods to produce ultrashort laser pulses are based on modulating the cavity gain or losses at the cavity roundtrip frequency, favoring the pulsed emission. Here, we rather directly act on the phases of the modes, resulting in constructive interference for the appropriated phase relationship. This was performed on a terahertz quantum cascade laser by multimode injection seeding with an external terahertz pulse, resulting in phase mode-locked terahertz laser pulses of 9 ps duration, characterized unambiguously in the time domain.

Filterless frequency-octupling mm-wave generation by cascading Sagnac loop and DPMZM

NASA Astrophysics Data System (ADS)

Zhang, Wu; Wen, Aijun; Gao, Yongsheng; Shang, Shuo; Zheng, Hanxiao; He, Hongye

2017-12-01

In this paper, a filterless photonic frequency-octupling scheme is presented. It is implemented by cascading a Sagnac loop with an intensity modulator (IM) in it and a dual-parallel Mach-Zehnder modulator (DPMZM) in series. The Sagnac loop is used to get the ±2nd-order sidebands of LO signal. The following DPMZM is utilized to obtain the ±4th-order sidebands. By photo-detecting the ±4th-order sidebands, mm-wave signal with the eightfold frequency of LO signal can be obtained. The scheme is verified by experiments, and a 32-GHz mm-wave signal is produced with the assistance of a 4-GHz LO signal. A 20-dB optical sideband suppression ratio (OSSR) and a 17-dB electrical spurious suppression ratio (ESSR) are realized, and no extra deterioration of phase noise is observed. Besides, the verification of the frequency tunability is implemented in the experiment.

A simple system for 160GHz optical terahertz wave generation and data modulation

NASA Astrophysics Data System (ADS)

Li, Yihan; He, Jingsuo; Sun, Xueming; Shi, Zexia; Wang, Ruike; Cui, Hailin; Su, Bo; Zhang, Cunlin

2018-01-01

A simple system based on two cascaded Mach-Zehnder modulators, which can generate 160GHz optical terahertz waves from 40GHz microwave sources, is simulated and tested in this paper. Fiber grating filter is used in the system to filter out optical carrier. By properly adjusting the modulator DC bias voltages and the signal voltages and phases, 4-tupling optical terahertz wave can be generated with fiber grating. This notch fiber grating filter is greatly suitable for terahertz over fiber (TOF) communication system. This scheme greatly reduces the cost of long-distance terahertz communication. Furthermore, 10Gbps digital signal is modulated in the 160GHz optical terahertz wave.

Modulation response characteristics of optical injection-locked cascaded microring laser

NASA Astrophysics Data System (ADS)

Yu, Shaowei; Pei, Li; Liu, Chao; Wang, Yiqun; Weng, Sijun

2014-09-01

Modulation bandwidth and frequency chirping of the optical injection-locked (OIL) microring laser (MRL) in the cascaded configuration are investigated. The unidirectional operation of the MRL under strong injection allows simple and cost-saving monolithic integration of the OIL system on one chip as it does not need the use of isolators between the master and slave lasers. Two cascading schemes are discussed in detail by focusing on the tailorable modulation response. The chip-to-power ratio of the cascaded optical injection-locked configuration has decreased by up to two orders of magnitude, compared with the single optical injection-locked configuration.

Sub-μrad laser beam tracking

NASA Astrophysics Data System (ADS)

Buske, Ivo; Riede, Wolfgang

2006-09-01

We compare active optical elements based on different technologies to accomplish the requirements of a 2-dim. fine tracking control system. A cascaded optically and electrically addressable spatial light modulator (OASLM) based on liquid crystals (LC) is used for refractive beam steering. Spatial light modulators provide a controllable phase wedge to generate a beam deflection. Additionally, a tip/tilt mirror approach operating with piezo-electric actuators is investigated. A digital PID controller is implemented for closed-loop control. Beam tracking with a root-mean-squared accuracy of Δα=30 nrad has been laboratory-confirmed.

Experimental implementation of phase locking in a nonlinear interferometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hailong; Jing, Jietai, E-mail: jtjing@phy.ecnu.edu.cn; Marino, A. M.

2015-09-21

Based upon two cascade four-wave mixing processes in two identical hot rubidium vapor cells, a nonlinear interferometer has been experimentally realized [Jing et al., Appl. Phys. Lett. 99, 011110 (2011); Hudelist et al., Nat. Commun. 5, 3049 (2014)]. It has a higher degree of phase sensitivity than a traditional linear interferometer and has many potential applications in quantum metrology. Phase locking of the nonlinear interferometer is needed before it can find its way into applications. In this letter, we investigate the experimental implementation of phase locking of the relative phase between the three beams at different frequencies involved in suchmore » a nonlinear interferometer. We have utilized two different methods, namely, beat note locking and coherent modulation locking. We find that coherent modulation locking can achieve much better phase stability than beat note locking in our system. Our results pave the way for real applications of a nonlinear interferometer in precision measurement and quantum manipulation, for example, phase control in phase-sensitive N-wave mixing process, N-port nonlinear interferometer and quantum-enhanced real-time phase tracking.« less

GHz Modulation of GaAs-Based Bipolar Cascade VCSELs (Preprint)

DTIC Science & Technology

2006-11-01

VCSELs were grown on n+ GaAs substrates by molecular beam epitaxy . The laser cavities consist of 1-, 2-, or 3-stage 52λ microcavi- ties, each containing...AFRL-SN-WP-TP-2006-128 GHz MODULATION OF GaAs-BASED BIPOLAR CASCADE VCSELs (PREPRINT) W.J. Siskaninetz, R.G. Bedford, T.R. Nelson, Jr., J.E...TITLE AND SUBTITLE GHz MODULATION OF GaAs-BASED BIPOLAR CASCADE VCSELs (PREPRINT) 5c. PROGRAM ELEMENT NUMBER 69199F 5d. PROJECT NUMBER 2002 5e

Adaptive Selective Harmonic Minimization Based on ANNs for Cascade Multilevel Inverters With Varying DC Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Filho, Faete; Maia, Helder Z; Mateus, Tiago Henrique D

2013-01-01

A new approach for modulation of an 11-level cascade multilevel inverter using selective harmonic elimination is presented in this paper. The dc sources feeding the multilevel inverter are considered to be varying in time, and the switching angles are adapted to the dc source variation. This method uses genetic algorithms to obtain switching angles offline for different dc source values. Then, artificial neural networks are used to determine the switching angles that correspond to the real-time values of the dc sources for each phase. This implies that each one of the dc sources of this topology can have different valuesmore » at any time, but the output fundamental voltage will stay constant and the harmonic content will still meet the specifications. The modulating switching angles are updated at each cycle of the output fundamental voltage. This paper gives details on the method in addition to simulation and experimental results.« less

Linear models of activation cascades: analytical solutions and coarse-graining of delayed signal transduction

PubMed Central

Desikan, Radhika

2016-01-01

Cellular signal transduction usually involves activation cascades, the sequential activation of a series of proteins following the reception of an input signal. Here, we study the classic model of weakly activated cascades and obtain analytical solutions for a variety of inputs. We show that in the special but important case of optimal gain cascades (i.e. when the deactivation rates are identical) the downstream output of the cascade can be represented exactly as a lumped nonlinear module containing an incomplete gamma function with real parameters that depend on the rates and length of the cascade, as well as parameters of the input signal. The expressions obtained can be applied to the non-identical case when the deactivation rates are random to capture the variability in the cascade outputs. We also show that cascades can be rearranged so that blocks with similar rates can be lumped and represented through our nonlinear modules. Our results can be used both to represent cascades in computational models of differential equations and to fit data efficiently, by reducing the number of equations and parameters involved. In particular, the length of the cascade appears as a real-valued parameter and can thus be fitted in the same manner as Hill coefficients. Finally, we show how the obtained nonlinear modules can be used instead of delay differential equations to model delays in signal transduction. PMID:27581482

Homogeneous spectral broadening of pulsed terahertz quantum cascade lasers by radio frequency modulation.

PubMed

Wan, W J; Li, H; Cao, J C

2018-01-22

The authors present an experimental investigation of radio frequency modulation on pulsed terahertz quantum cascade lasers (QCLs) emitting around 4.3 THz. The QCL chip used in this work is based on a resonant phonon design which is able to generate a 1.2 W peak power at 10 K from a 400-µm-wide and 4-mm-long laser with a single plasmon waveguide. To enhance the radio frequency modulation efficiency and significantly broaden the terahertz spectra, the QCLs are also processed into a double-metal waveguide geometry with a Silicon lens out-coupler to improve the far-field beam quality. The measured beam patterns of the double-metal QCL show a record low divergence of 2.6° in vertical direction and 2.4° in horizontal direction. Finally we perform the inter-mode beat note and terahertz spectra measurements for both single plasmon and double-metal QCLs working in pulsed mode. Since the double-metal waveguide is more suitable for microwave signal transmission, the radio frequency modulation shows stronger effects on the spectral broadening for the double-metal QCL. Although we are not able to achieve comb operation in this work for the pulsed lasers due to the large phase noise, the homogeneous spectral broadening resulted from the radio frequency modulation can be potentially used for spectroscopic applications.

Optical single side-band Nyquist PAM-4 transmission using dual-drive MZM modulation and direct detection.

PubMed

Zhu, Mingyue; Zhang, Jing; Yi, Xingwen; Ying, Hao; Li, Xiang; Luo, Ming; Song, Yingxiong; Huang, Xiatao; Qiu, Kun

2018-03-19

We present the design and optimization of the optical single side-band (SSB) Nyquist four-level pulse amplitude modulation (PAM-4) transmission using dual-drive Mach-Zehnder modulator (DDMZM)modulation and direct detection (DD), aiming at the C-band cost-effective, high-speed and long-distance transmission. At the transmitter, the laser line width should be small to avoid the phase noise to amplitude noise conversion and equalization-enhanced phase noise due to the large chromatic dispersion (CD). The optical SSB signal is generated after optimizing the optical modulation index (OMI) and hence the minimum phase condition which is required by the Kramers-Kronig (KK) receiver can also be satisfied. At the receiver, a simple AC-coupled photodiode (PD) is used and a virtual carrier is added for the KK operation to alleviate the signal-to-signal beating interference (SSBI).A Volterra filter (VF) is cascaded for remaining nonlinearities mitigation. When the fiber nonlinearity becomes significant, we elect to use an optical band-pass filter with offset filtering. It can suppress the simulated Brillouin scattering and the conjugated distortion by filtering out the imaging frequency components. With our design and optimization, we achieve single-channel, single polarization 102.4-Gb/s Nyquist PAM-4 over 800-km standard single-mode fiber (SSMF).

Filterless frequency 12-tupling optical millimeter-wave generation using two cascaded dual-parallel Mach-Zehnder modulators.

PubMed

Zhu, Zihang; Zhao, Shanghong; Zheng, Wanze; Wang, Wei; Lin, Baoqin

2015-11-10

A novel frequency 12-tupling optical millimeter-wave (mm-wave) generation using two cascaded dual-parallel Mach-Zehnder modulators (DP-MZMs) without an optical filter is proposed and demonstrated by computer simulation. By properly adjusting the amplitude and phase of radio frequency (RF) driving signal and the direct current (DC) bias points of two DP-MZMs, a 120 GHz mm-wave with an optical sideband suppression ratio (OSSR) of 25.1 dB and a radio frequency spurious suppression ratio (RFSSR) of 19.1 dB is shown to be generated from a 10 GHz RF driving signal, which largely reduces the response frequency of electronic devices. Furthermore, it is also proved to be valid that even if the phase difference of RF driving signals, the RF driving voltage, and the DC bias voltage deviate from the ideal values to a certain degree, the performance is still acceptable. Since no optical filter is employed to suppress the undesired optical sidebands, a high-spectral-purity mm-wave signal tunable from 48 to 216 GHz can be obtained theoretically when a RF driving signal from 4 to 18 GHz is applied to the DP-MZMs, and the system can be readily implemented in wavelength-division-multiplexing upconversion systems to provide high-quality optical local oscillator signal.

High speed ultra-broadband amplitude modulators with ultrahigh extinction >65 dB.

PubMed

Liu, S; Cai, H; DeRose, C T; Davids, P; Pomerene, A; Starbuck, A L; Trotter, D C; Camacho, R; Urayama, J; Lentine, A

2017-05-15

We experimentally demonstrate ultrahigh extinction ratio (>65 dB) amplitude modulators (AMs) that can be electrically tuned to operate across a broad spectral range of 160 nm from 1480 - 1640 nm and 95 nm from 1280 - 1375 nm. Our on-chip AMs employ one extra coupler compared with conventional Mach-Zehnder interferometers (MZI), thus form a cascaded MZI (CMZI) structure. Either directional or adiabatic couplers are used to compose the CMZI AMs and experimental comparisons are made between these two different structures. We investigate the performance of CMZI AMs under extreme conditions such as using 95:5 split ratio couplers and unbalanced waveguide losses. Electro-optic phase shifters are also integrated in the CMZI AMs for high-speed operation. Finally, we investigate the output optical phase when the amplitude is modulated, which provides us valuable information when both amplitude and phase are to be controlled. Our demonstration not only paves the road to applications such as quantum information processing that requires high extinction ratio AMs but also significantly alleviates the tight fabrication tolerance needed for large-scale integrated photonics.

Signaling cascades modulate the speed of signal propagation through space.

PubMed

Govern, Christopher C; Chakraborty, Arup K

2009-01-01

Cells are not mixed bags of signaling molecules. As a consequence, signals must travel from their origin to distal locations. Much is understood about the purely diffusive propagation of signals through space. Many signals, however, propagate via signaling cascades. Here, we show that, depending on their kinetics, cascades speed up or slow down the propagation of signals through space, relative to pure diffusion. We modeled simple cascades operating under different limits of Michaelis-Menten kinetics using deterministic reaction-diffusion equations. Cascades operating far from enzyme saturation speed up signal propagation; the second mobile species moves more quickly than the first through space, on average. The enhanced speed is due to more efficient serial activation of a downstream signaling module (by the signaling molecule immediately upstream in the cascade) at points distal from the signaling origin, compared to locations closer to the source. Conversely, cascades operating under saturated kinetics, which exhibit zero-order ultrasensitivity, can slow down signals, ultimately localizing them to regions around the origin. Signal speed modulation may be a fundamental function of cascades, affecting the ability of signals to penetrate within a cell, to cross-react with other signals, and to activate distant targets. In particular, enhanced speeds provide a way to increase signal penetration into a cell without needing to flood the cell with large numbers of active signaling molecules; conversely, diminished speeds in zero-order ultrasensitive cascades facilitate strong, but localized, signaling.

Investigation of oscillating cascade aerodynamics by an experimental influence coefficient technique

NASA Technical Reports Server (NTRS)

Buffum, Daniel H.; Fleeter, Sanford

1988-01-01

Fundamental experiments are performed in the NASA Lewis Transonic Oscillating Cascade Facility to investigate the torsion mode unsteady aerodynamics of a biconvex airfoil cascade at realistic values of the reduced frequency for all interblade phase angles at a specified mean flow condition. In particular, an unsteady aerodynamic influence coefficient technique is developed and utilized in which only one airfoil in the cascade is oscillated at a time and the resulting airfoil surface unsteady pressure distribution measured on one dynamically instrumented airfoil. The unsteady aerodynamics of an equivalent cascade with all airfoils oscillating at a specified interblade phase angle are then determined through a vector summation of these data. These influence coefficient determined oscillation cascade data are correlated with data obtained in this cascade with all airfoils oscillating at several interblade phase angle values. The influence coefficients are then utilized to determine the unsteady aerodynamics of the cascade for all interblade phase angles, with these unique data subsequently correlated with predictions from a linearized unsteady cascade model.

Self-starting harmonic frequency comb generation in a quantum cascade laser

NASA Astrophysics Data System (ADS)

Kazakov, Dmitry; Piccardo, Marco; Wang, Yongrui; Chevalier, Paul; Mansuripur, Tobias S.; Xie, Feng; Zah, Chung-en; Lascola, Kevin; Belyanin, Alexey; Capasso, Federico

2017-12-01

Optical frequency combs1,2 establish a rigid phase-coherent link between microwave and optical domains and are emerging as high-precision tools in an increasing number of applications3. Frequency combs with large intermodal spacing are employed in the field of microwave photonics for radiofrequency arbitrary waveform synthesis4,5 and for the generation of terahertz tones of high spectral purity in future wireless communication networks6,7. Here, we demonstrate self-starting harmonic frequency comb generation with a terahertz repetition rate in a quantum cascade laser. The large intermodal spacing caused by the suppression of tens of adjacent cavity modes originates from a parametric contribution to the gain due to temporal modulations of population inversion in the laser8,9. Using multiheterodyne self-detection, the mode spacing of the harmonic comb is shown to be uniform to within 5 × 10-12 parts of the central frequency. This new harmonic comb state extends the range of applications of quantum cascade laser frequency combs10-13.

Switching circuit to improve the frequency modulation difference-intensity THz quantum cascade laser imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saat, N. K.; Dean, P.; Khanna, S. P.

2015-04-24

We demonstrate new switching circuit for difference-intensity THz quantum cascade laser (QCL) imaging by amplitude modulation and lock in detection. The switching circuit is designed to improve the frequency modulation so that it can stably lock the amplitude modulation of the QCL and the detector output. The combination of a voltage divider and a buffer in switching circuit to quickly switch the amplitude of the QCL biases of 15.8 V and 17.2 V is successfully to increase the frequency modulation up to ∼100 Hz.

A grid-connected single-phase photovoltaic micro inverter

NASA Astrophysics Data System (ADS)

Wen, X. Y.; Lin, P. J.; Chen, Z. C.; Wu, L. J.; Cheng, S. Y.

2017-11-01

In this paper, the topology of a single-phase grid-connected photovoltaic (PV) micro-inverter is proposed. The PV micro-inverter consists of DC-DC stage with high voltage gain boost and DC-AC conversion stage. In the first stage, we apply the active clamp circuit and two voltage multipliers to achieve soft switching technology and high voltage gain. In addition, the flower pollination algorithm (FPA) is employed for the maximum power point tracking (MPPT) in the PV module in this stage. The second stage cascades a H-bridge inverter and LCL filter. To feed high quality sinusoidal power into the grid, the software phase lock, outer voltage loop and inner current loop control method are adopted as the control strategy. The performance of the proposed topology is tested by Matlab/Simulink. A PV module with maximum power 300W and maximum power point voltage 40V is applied as the input source. The simulation results indicate that the proposed topology and the control strategy are feasible.

Chirped laser dispersion spectroscopy using a directly modulated quantum cascade laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hangauer, Andreas, E-mail: hangauer@princeton.edu; Nikodem, Michal; Wysocki, Gerard, E-mail: gwysocki@princeton.edu

2013-11-04

Chirped laser dispersion spectroscopy (CLaDS) utilizing direct modulation of a quantum cascade laser (QCL) is presented. By controlling the laser bias nearly single- and dual-sideband CLaDS operation can be realized in an extremely simplified optical setup with no external optical modulators. Capability of direct single-sideband modulation is a unique feature of QCLs that exhibit a low linewidth enhancement factor. The developed analytical model shows excellent agreement with the experimental, directly modulated CLaDS spectra. This method overcomes major technical limitations of mid-infrared CLaDS systems by allowing significantly higher modulation frequencies and eliminating optical fringes introduced by external modulators.

Analyses of conversion efficiency in high-speed clock recovery based on Mach-Zehnder modulator

NASA Astrophysics Data System (ADS)

Dong, H.; Sun, H.; Zhu, G.; Dutta, N. K.

2006-09-01

In this paper, detailed analyses of the conversion efficiency in high-speed clock recovery based on Mach-Zehnder (MZ) modulator has been carried out. The theoretical results show the conversion efficiency changes with RF driving power and the mixing order. For high order clock recovery, the cascaded MZ modulator provides higher conversion efficiency. A study of clock recovery at 160 Gb/s using the cascaded MZ modulator has been carried out. The experimental results agree with the results of the analysis.

Purified frequency modulation of a quantum cascade laser with an all-optical approach.

PubMed

Peng, Chen; Zhou, Haijun; Zhu, Liguo; Chen, Tao; Liu, Qiao; Wang, Detian; Li, Jiang; Peng, Qixian; Chen, Gang; Li, Zeren

2017-11-01

Purified frequency modulation (FM) is demonstrated in a standard middle-infrared quantum cascade laser by illuminating its front facet with two near-infrared (NIR) lasers. A 2 mW laser at 1550 nm is utilized to modulate the amplitude and frequency of a quantum cascade laser, and the associated amplitude modulation (AM) is suppressed by a 1.85 mW laser at 850 nm. Due to the hot carrier effect and the increment of electron temperature, the AM has been decreased. In addition, the free carrier concentration increases in the active region due to the two NIR illuminations, which enhance the FM. Purified FM is beneficial in improving the signal fidelity for free-space optical communication and high-speed FM spectroscopy.

An Efficient Modulation Strategy for Cascaded Photovoltaic Systems Suffering From Module Mismatch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Cheng; Zhang, Kai; Xiong, Jian

Modular multilevel cascaded converter (MMCC) is a promising technique for medium/high-voltage high-power photovoltaic systems due to its modularity, scalability, and capability of distributed maximum power point tracking (MPPT) etc. However, distributed MPPT under module-mismatch might polarize the distribution of ac output voltages as well as the dc-link voltages among the modules, distort grid currents, and even cause system instability. For the better acceptance in practical applications, such issues need to be well addressed. Based on mismatch degree that is defined to consider both active power distribution and maximum modulation index, this paper presents an efficient modulation strategy for a cascaded-H-bridge-basedmore » MMCC under module mismatch. It can operate in loss-reducing mode or range-extending mode. By properly switching between the two modes, performance indices such as system efficiency, grid current quality, and balance of dc voltages, can be well coordinated. In this way, the MMCC system can maintain high-performance over a wide range of operating conditions. As a result, effectiveness of the proposed modulation strategy is proved with experiments.« less

An Efficient Modulation Strategy for Cascaded Photovoltaic Systems Suffering From Module Mismatch

DOE PAGES

Wang, Cheng; Zhang, Kai; Xiong, Jian; ...

2017-09-26

Modular multilevel cascaded converter (MMCC) is a promising technique for medium/high-voltage high-power photovoltaic systems due to its modularity, scalability, and capability of distributed maximum power point tracking (MPPT) etc. However, distributed MPPT under module-mismatch might polarize the distribution of ac output voltages as well as the dc-link voltages among the modules, distort grid currents, and even cause system instability. For the better acceptance in practical applications, such issues need to be well addressed. Based on mismatch degree that is defined to consider both active power distribution and maximum modulation index, this paper presents an efficient modulation strategy for a cascaded-H-bridge-basedmore » MMCC under module mismatch. It can operate in loss-reducing mode or range-extending mode. By properly switching between the two modes, performance indices such as system efficiency, grid current quality, and balance of dc voltages, can be well coordinated. In this way, the MMCC system can maintain high-performance over a wide range of operating conditions. As a result, effectiveness of the proposed modulation strategy is proved with experiments.« less

Cascaded Bragg scattering in fiber optics.

PubMed

Xu, Y Q; Erkintalo, M; Genty, G; Murdoch, S G

2013-01-15

We report on a theoretical and experimental study of cascaded Bragg scattering in fiber optics. We show that the usual energy-momentum conservation of Bragg scattering can be considerably relaxed via cascade-induced phase-matching. Experimentally we demonstrate frequency translation over six- and 11-fold cascades, in excellent agreement with derived phase-matching conditions.

Environmental solid particle effects on compressor cascade performance

NASA Technical Reports Server (NTRS)

Tabakoff, W.; Balan, C.

1982-01-01

The effect of suspended solid particles on the performance of the compressor cascade was investigated experimentally in a specially built cascade tunnel, using quartz sand particles. The cascades were made of NACA 65(10)10 airfoils. Three cascades were tested, one accelerating cascade and two diffusing cascades. The theoretical analysis assumes inviscid and incompressible two dimensional flow. The momentum exchange between the fluid and the particle is accounted for by the interphase force terms in the fluid momentum equation. The modified fluid phase momentum equations and the continuity equation are reduced to the conventional stream function vorticity formulation. The method treats the fluid phase in the Eulerian system and the particle phase in Lagrangian system. The experimental results indicate a small increase in the blade surface static pressures, while the theoretical results indicate a small decrease. The theoretical analysis, also predicts the loss in total pressure associated with the particulate flow through the cascade.

High speed ultra-broadband amplitude modulators with ultrahigh extinction >65 dB

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, S.; Cai, H.; DeRose, C. T.

Here, we experimentally demonstrate ultrahigh extinction ratio (>65 dB) amplitude modulators (AMs) that can be electrically tuned to operate across a broad spectral range of 160 nm from 1480 – 1640 nm and 95 nm from 1280 – 1375 nm. Our on-chip AMs employ one extra coupler compared with conventional Mach-Zehnder interferometers (MZI), thus form a cascaded MZI (CMZI) structure. Either directional or adiabatic couplers are used to compose the CMZI AMs and experimental comparisons are made between these two different structures. Furthermore, we investigate the performance of CMZI AMs under extreme conditions such as using 95:5 split ratio couplersmore » and unbalanced waveguide losses. Electro-optic phase shifters are also integrated in the CMZI AMs for high-speed operation. Finally, we investigate the output optical phase when the amplitude is modulated, which provides us valuable information when both amplitude and phase are to be controlled. This demonstration not only paves the road to applications such as quantum information processing that requires high extinction ratio AMs but also significantly alleviates the tight fabrication tolerance needed for large-scale integrated photonics.« less

High speed ultra-broadband amplitude modulators with ultrahigh extinction >65 dB

DOE PAGES

Liu, S.; Cai, H.; DeRose, C. T.; ...

2017-05-04

Here, we experimentally demonstrate ultrahigh extinction ratio (>65 dB) amplitude modulators (AMs) that can be electrically tuned to operate across a broad spectral range of 160 nm from 1480 – 1640 nm and 95 nm from 1280 – 1375 nm. Our on-chip AMs employ one extra coupler compared with conventional Mach-Zehnder interferometers (MZI), thus form a cascaded MZI (CMZI) structure. Either directional or adiabatic couplers are used to compose the CMZI AMs and experimental comparisons are made between these two different structures. Furthermore, we investigate the performance of CMZI AMs under extreme conditions such as using 95:5 split ratio couplersmore » and unbalanced waveguide losses. Electro-optic phase shifters are also integrated in the CMZI AMs for high-speed operation. Finally, we investigate the output optical phase when the amplitude is modulated, which provides us valuable information when both amplitude and phase are to be controlled. This demonstration not only paves the road to applications such as quantum information processing that requires high extinction ratio AMs but also significantly alleviates the tight fabrication tolerance needed for large-scale integrated photonics.« less

Regular and irregular patterns of self-localized excitation in arrays of coupled phase oscillators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolfrum, Matthias; Omel'chenko, Oleh E.; Sieber, Jan

We study a system of phase oscillators with nonlocal coupling in a ring that supports self-organized patterns of coherence and incoherence, called chimera states. Introducing a global feedback loop, connecting the phase lag to the order parameter, we can observe chimera states also for systems with a small number of oscillators. Numerical simulations show a huge variety of regular and irregular patterns composed of localized phase slipping events of single oscillators. Using methods of classical finite dimensional chaos and bifurcation theory, we can identify the emergence of chaotic chimera states as a result of transitions to chaos via period doublingmore » cascades, torus breakup, and intermittency. We can explain the observed phenomena by a mechanism of self-modulated excitability in a discrete excitable medium.« less

Improved multistage wide band laser frequency stabilization

NASA Astrophysics Data System (ADS)

Kawamura, Seiji; Abramovici, Alex; Zucker, Michael E.

1997-01-01

Suppression of laser frequency fluctuations is an essential technology for planned interferometric detectors for astrophysical gravitational waves. Because of the low degree of residual frequency noise which is ultimately required, control topologies comprising two or more cascaded loops are favored. One such topology, used in the Laser Interferometer Gravitational-Wave Observatory 40 m interferometer, relied on electro-optic Pockels cell phase correction as a fast actuator for the final stage. This actuation method proved susceptible to spurious amplitude modulation effects, which provided an unintended parasitic feedback path. An alternate arrangement, which achieves comparably effective frequency stabilization without using a phase correcting Pockels cell, was introduced and successfully tested.

Modulation properties of optically injection-locked quantum cascade lasers.

PubMed

Wang, Cheng; Grillot, Fédéric; Kovanis, Vassilios I; Bodyfelt, Joshua D; Even, Jacky

2013-06-01

A rate equation analysis on the modulation response of an optical injection-locked quantum cascade laser is outlined. It is found that the bifurcation diagram exhibits both bistable and unstable locked regions. In addition, the stable locked regime widens as the linewidth enhancement factor increases. It is also shown that both positive and negative optical detunings as well as strong injection strength enhance the 3 dB modulation bandwidth by as much as 30 GHz. Finally, the peak in the modulation response is significantly influenced by the optical frequency detuning.

New Challenges in Computational Thermal Hydraulics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yadigaroglu, George; Lakehal, Djamel

New needs and opportunities drive the development of novel computational methods for the design and safety analysis of light water reactors (LWRs). Some new methods are likely to be three dimensional. Coupling is expected between system codes, computational fluid dynamics (CFD) modules, and cascades of computations at scales ranging from the macro- or system scale to the micro- or turbulence scales, with the various levels continuously exchanging information back and forth. The ISP-42/PANDA and the international SETH project provide opportunities for testing applications of single-phase CFD methods to LWR safety problems. Although industrial single-phase CFD applications are commonplace, computational multifluidmore » dynamics is still under development. However, first applications are appearing; the state of the art and its potential uses are discussed. The case study of condensation of steam/air mixtures injected from a downward-facing vent into a pool of water is a perfect illustration of a simulation cascade: At the top of the hierarchy of scales, system behavior can be modeled with a system code; at the central level, the volume-of-fluid method can be applied to predict large-scale bubbling behavior; at the bottom of the cascade, direct-contact condensation can be treated with direct numerical simulation, in which turbulent flow (in both the gas and the liquid), interfacial dynamics, and heat/mass transfer are directly simulated without resorting to models.« less

High frequency modulation and injection locking of terahertz quantum cascade lasers

NASA Astrophysics Data System (ADS)

Gu, L.; Wan, W. J.; Zhu, Y. H.; Fu, Z. L.; Li, H.; Cao, J. C.

2017-06-01

Due to intersubband transitions, the quantum cascade laser (QCL) is free of relaxations and able to work under fast modulations. In this work, the authors investigate the fast modulation properties of a continuous wave (cw) terahertz QCL emitting around 3 THz (˜100 μm). Both simulation and experimental results show that the 3 dB modulation bandwidth for the device can reach 11.5 GHz and the modulation response curve is relatively flat upto ˜16 GHz. The radio frequency (RF) injection measurements verify that around the laser threshold the inter-mode beat note interacts strongly with the RF signal and the laser can be modulated at the round trip frequency of 15.5 GHz.

Trophic cascades, invasive species and body-size hierarchies interactively modulate climate change responses of ecotonal temperate-boreal forest.

PubMed

Frelich, Lee E; Peterson, Rolf O; Dovčiak, Martin; Reich, Peter B; Vucetich, John A; Eisenhauer, Nico

2012-11-05

As the climate warms, boreal tree species are expected to be gradually replaced by temperate species within the southern boreal forest. Warming will be accompanied by changes in above- and below-ground consumers: large moose (Alces alces) replaced by smaller deer (Odocoileus virginianus) above-ground, and small detritivores replaced by larger exotic earthworms below-ground. These shifts may induce a cascade of ecological impacts across trophic levels that could alter the boreal to temperate forest transition. Deer are more likely to browse saplings of temperate tree species, and European earthworms favour seedlings of boreal tree species more than temperate species, potentially hindering the ability of temperate tree species to expand northwards. We hypothesize that warming-induced changes in consumers will lead to novel plant communities by changing the filter on plant species success, and that above- and below-ground cascades of trophic interactions will allow boreal tree species to persist during early phases of warming, leading to an abrupt change at a later time. The synthesis of evidence suggests that consumers can modify the climate change-induced transition of ecosystems.

Ultrasensitivity in signaling cascades revisited: Linking local and global ultrasensitivity estimations.

PubMed

Altszyler, Edgar; Ventura, Alejandra C; Colman-Lerner, Alejandro; Chernomoretz, Ariel

2017-01-01

Ultrasensitive response motifs, capable of converting graded stimuli into binary responses, are well-conserved in signal transduction networks. Although it has been shown that a cascade arrangement of multiple ultrasensitive modules can enhance the system's ultrasensitivity, how a given combination of layers affects a cascade's ultrasensitivity remains an open question for the general case. Here, we introduce a methodology that allows us to determine the presence of sequestration effects and to quantify the relative contribution of each module to the overall cascade's ultrasensitivity. The proposed analysis framework provides a natural link between global and local ultrasensitivity descriptors and it is particularly well-suited to characterize and understand mathematical models used to study real biological systems. As a case study, we have considered three mathematical models introduced by O'Shaughnessy et al. to study a tunable synthetic MAPK cascade, and we show how our methodology can help modelers better understand alternative models.

Generation of Optical Millimeter Wave Using Two Cascaded Polarization Modulators Based on Frequency Octupling Without Filtering

NASA Astrophysics Data System (ADS)

Yang, Yang; Ma, Jianxin; Zhang, Ruijiao; Xin, Xiangjun; Zhang, Junyi

2015-11-01

An approach to generate an optical millimeter wave is introduced with frequency octupling using two cascaded polarization modulators followed by polarizers, respectively. By adjusting the modulation indexes of polarization modulators, only the ±4th-order sidebands are generated with a pure spectrum. Since no filter is needed, the proposed technique can be used to generate a frequency-tunable millimeter wave with a large frequency-tunable range. To prove the feasibility of the proposed approach, a simulation is conducted to generate an 80-GHz millimeter wave, and then its transmission performance is checked.

Pseudorandom dynamics of frequency combs in free-running quantum cascade lasers

NASA Astrophysics Data System (ADS)

Henry, Nathan; Burghoff, David; Yang, Yang; Hu, Qing; Khurgin, Jacob B.

2018-01-01

Recent research has shown that free-running quantum cascade lasers are capable of producing frequency combs in midinfrared and THz regions of the spectrum. Unlike familiar frequency combs originating from mode-locked lasers, these do not require any additional optical elements inside the cavity and have temporal characteristics that are dramatically different from the periodic pulse train of conventional combs. Frequency combs from quantum cascade lasers are characterized by the absence of sharp pulses and strong frequency modulation, periodic with the cavity round trip time but lacking any periodicity within that period. To explicate for this seemingly perplexing behavior, we develop a model of the gain medium using optical Bloch equations that account for hole burning in spectral, spatial, and temporal domains. With this model, we confirm that the most efficient mode of operation of a free-running quantum cascade laser is indeed a pseudorandom frequency-modulated field with nearly constant intensity. We show that the optimum modulation period is commensurate with the gain recovery time of the laser medium and the optimum modulation amplitude is comparable to the gain bandwidth, behavior that has been observed in the experiments.

All-optical phase modulation in a cavity-polariton Mach–Zehnder interferometer

PubMed Central

Sturm, C.; Tanese, D.; Nguyen, H.S.; Flayac, H.; Galopin, E.; Lemaître, A.; Sagnes, I.; Solnyshkov, D.; Amo, A.; Malpuech, G.; Bloch, J.

2014-01-01

Quantum fluids based on light is a highly developing research field, since they provide a nonlinear platform for developing optical functionalities and quantum simulators. An important issue in this context is the ability to coherently control the properties of the fluid. Here we propose an all-optical approach for controlling the phase of a flow of cavity-polaritons, making use of their strong interactions with localized excitons. Here we illustrate the potential of this method by implementing a compact exciton–polariton interferometer, which output intensity and polarization can be optically controlled. This interferometer is cascadable with already reported polariton devices and is promising for future polaritonic quantum optic experiments. Complex phase patterns could be also engineered using this optical method, providing a key tool to build photonic artificial gauge fields. PMID:24513781

Dual Phase-space Cascades in 3D Hybrid-Vlasov–Maxwell Turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cerri, S. S.; Kunz, M. W.; Califano, F.

To explain energy dissipation via turbulence in collisionless, magnetized plasmas, the existence of a dual real- and velocity-space cascade of ion-entropy fluctuations below the ion gyroradius has been proposed. Such a dual cascade, predicted by the gyrokinetic theory, has previously been observed in gyrokinetic simulations of two-dimensional, electrostatic turbulence. For the first time we show evidence for a dual phase-space cascade of ion-entropy fluctuations in a three-dimensional simulation of hybrid-kinetic, electromagnetic turbulence. Some of the scalings observed in the energy spectra are consistent with a generalized theory for the cascade that accounts for the spectral anisotropy of critically balanced, intermittent,more » sub-ion-Larmor-scale fluctuations. Also, the observed velocity-space cascade is anisotropic with respect to the magnetic-field direction, with linear phase mixing along magnetic-field lines proceeding mainly at spatial scales above the ion gyroradius and nonlinear phase mixing across magnetic-field lines proceeding at perpendicular scales below the ion gyroradius. Such phase-space anisotropy could be sought in heliospheric and magnetospheric data of solar-wind turbulence and has far-reaching implications for the dissipation of turbulence in weakly collisional astrophysical plasmas.« less

Dual Phase-space Cascades in 3D Hybrid-Vlasov–Maxwell Turbulence

DOE PAGES

Cerri, S. S.; Kunz, M. W.; Califano, F.

2018-03-23

To explain energy dissipation via turbulence in collisionless, magnetized plasmas, the existence of a dual real- and velocity-space cascade of ion-entropy fluctuations below the ion gyroradius has been proposed. Such a dual cascade, predicted by the gyrokinetic theory, has previously been observed in gyrokinetic simulations of two-dimensional, electrostatic turbulence. For the first time we show evidence for a dual phase-space cascade of ion-entropy fluctuations in a three-dimensional simulation of hybrid-kinetic, electromagnetic turbulence. Some of the scalings observed in the energy spectra are consistent with a generalized theory for the cascade that accounts for the spectral anisotropy of critically balanced, intermittent,more » sub-ion-Larmor-scale fluctuations. Also, the observed velocity-space cascade is anisotropic with respect to the magnetic-field direction, with linear phase mixing along magnetic-field lines proceeding mainly at spatial scales above the ion gyroradius and nonlinear phase mixing across magnetic-field lines proceeding at perpendicular scales below the ion gyroradius. Such phase-space anisotropy could be sought in heliospheric and magnetospheric data of solar-wind turbulence and has far-reaching implications for the dissipation of turbulence in weakly collisional astrophysical plasmas.« less

Dual Phase-space Cascades in 3D Hybrid-Vlasov–Maxwell Turbulence

NASA Astrophysics Data System (ADS)

Cerri, S. S.; Kunz, M. W.; Califano, F.

2018-03-01

To explain energy dissipation via turbulence in collisionless, magnetized plasmas, the existence of a dual real- and velocity-space cascade of ion-entropy fluctuations below the ion gyroradius has been proposed. Such a dual cascade, predicted by the gyrokinetic theory, has previously been observed in gyrokinetic simulations of two-dimensional, electrostatic turbulence. For the first time, we show evidence for a dual phase-space cascade of ion-entropy fluctuations in a three-dimensional simulation of hybrid-kinetic, electromagnetic turbulence. Some of the scalings observed in the energy spectra are consistent with a generalized theory for the cascade that accounts for the spectral anisotropy of critically balanced, intermittent, sub-ion-Larmor-scale fluctuations. The observed velocity-space cascade is also anisotropic with respect to the magnetic-field direction, with linear phase mixing along magnetic-field lines proceeding mainly at spatial scales above the ion gyroradius and nonlinear phase mixing across magnetic-field lines proceeding at perpendicular scales below the ion gyroradius. Such phase-space anisotropy could be sought in heliospheric and magnetospheric data of solar-wind turbulence and has far-reaching implications for the dissipation of turbulence in weakly collisional astrophysical plasmas.

A simplified filterless photonic frequency octupling scheme based on cascaded modulators

NASA Astrophysics Data System (ADS)

Zhang, Wu; Wen, Aijun; Gao, Yongsheng; Zheng, Hanxiao; Chen, Wei; He, Hongye

2017-04-01

A simplified filterless frequency octupling scheme by connecting an intensity modulator (IM) with a dual-parallel Mach-Zehnder (DPMZM) in series is proposed in this paper. The LO signal is distributed into two parts, and one part is used to drive the IM and the other part is applied to drive the DPMZM's upper sub-modulator, both at the peak point. The lower sub-modulator is only driven by dc bias, and the parent modulator works at null point. By properly adjusting dc bias of the lower sub-modulator, only ±4th-order optical sidebands dominate at the output of the DPMZM. The approach is verified by experiments, and 32-GHz and 40-GHz millimetre waves (mm-waves) are generated using 4-GHz and 5-GHz LO signals, respectively. We acquire a 15-dB electrical spurious suppression ratio (ESSR) and a relatively good phase noise of the signal. Compared with other schemes, the scheme is simple in configuration because only an IM and a DPMZM are needed. What's more, the scheme is tunable in frequency as no filter is used.

Modulation of enzyme catalytic properties and biosensor calibration parameters with chlorides: studies with glucose oxidase.

PubMed

Kagan, Margarita; Kivirand, Kairi; Rinken, Toonika

2013-09-10

We studied the modulation of calibration parameters of biosensors, in which glucose oxidase was used for bio-recognition, in the presence of different chlorides by following the transient phase dynamics of oxygen concentration with an oxygen optrode. The mechanism of modulation was characterized with the changes of the glucose oxidase catalytic constant and oxygen diffusion constant. The modulation of two biosensor calibration parameters were studied: the maximum calculated signal change was amplified for about 20% in the presence of sodium and magnesium chlorides; the value of the kinetic parameter decreased along with the addition of salts and increased only at sodium chloride concentrations over 0.5 mM. Besides glucose bioassay, the amplification of calibration parameters was also studied in cascaded two-enzyme lactose biosensor, where the initial step of lactose bio-recognition, the β-galactosidase - catalyzed lactose hydrolysis, was additionally accelerated by magnesium ions. Copyright © 2013 Elsevier Inc. All rights reserved.

Frequency modulation spectroscopy with a THz quantum-cascade laser.

PubMed

Eichholz, R; Richter, H; Wienold, M; Schrottke, L; Hey, R; Grahn, H T; Hübers, H-W

2013-12-30

We report on a terahertz spectrometer for high-resolution molecular spectroscopy based on a quantum-cascade laser. High-frequency modulation (up to 50 MHz) of the laser driving current produces a simultaneous modulation of the frequency and amplitude of the laser output. The modulation generates sidebands, which are symmetrically positioned with respect to the laser carrier frequency. The molecular transition is probed by scanning the sidebands across it. In this way, the absorption and the dispersion caused by the molecular transition are measured. The signals are modeled by taking into account the simultaneous modulation of the frequency and amplitude of the laser emission. This allows for the determination of the strength of the frequency as well as amplitude modulation of the laser and of molecular parameters such as pressure broadening.

Conveying endogenous and exogenous signals: MAPK cascades in plant growth and defense.

PubMed

Zhang, Mengmeng; Su, Jianbin; Zhang, Yan; Xu, Juan; Zhang, Shuqun

2018-05-09

Mitogen-activated protein kinase (MAPK) cascades are key signaling modules downstream of receptors/sensors that perceive endogenous and exogenous stimuli such as hormones, peptide ligands, and pathogen-derived patterns/effectors. In this review, we summarize recent advances in the establishment of MAPK cascades as unified signaling modules downstream of receptor-like kinases (RLKs) and receptor-like proteins (RLPs) in plant growth and defense, the identification of components connecting the RLK/RLP receptor complexes to the MAPK cascades, and the interactions between MAPK and hormone signaling pathways. We also propose a set of criteria for defining the physiological substrates of plant MAPKs. With only a limited number of MAPK components, multiple functional pathways often share the same MAPK cascade. As a result, understanding the signaling specificity, which requires detailed information about the spatiotemporal expression of the components involved, their complex formation, and the consequence of substrate phosphorylation, is central to our study of MAPK functions. Copyright © 2018 Elsevier Ltd. All rights reserved.

Tunable signal processing in synthetic MAP kinase cascades.

PubMed

O'Shaughnessy, Ellen C; Palani, Santhosh; Collins, James J; Sarkar, Casim A

2011-01-07

The flexibility of MAPK cascade responses enables regulation of a vast array of cell fate decisions, but elucidating the mechanisms underlying this plasticity is difficult in endogenous signaling networks. We constructed insulated mammalian MAPK cascades in yeast to explore how intrinsic and extrinsic perturbations affect the flexibility of these synthetic signaling modules. Contrary to biphasic dependence on scaffold concentration, we observe monotonic decreases in signal strength as scaffold concentration increases. We find that augmenting the concentration of sequential kinases can enhance ultrasensitivity and lower the activation threshold. Further, integrating negative regulation and concentration variation can decouple ultrasensitivity and threshold from the strength of the response. Computational analyses show that cascading can generate ultrasensitivity and that natural cascades with different kinase concentrations are innately biased toward their distinct activation profiles. This work demonstrates that tunable signal processing is inherent to minimal MAPK modules and elucidates principles for rational design of synthetic signaling systems. Copyright © 2011 Elsevier Inc. All rights reserved.

Discriminating cascading processes in nonlinear optics: A QED analysis based on their molecular and geometric origin

NASA Astrophysics Data System (ADS)

Bennett, Kochise; Chernyak, Vladimir Y.; Mukamel, Shaul

2017-03-01

The nonlinear optical response of a system of molecules often contains contributions whereby the products of lower-order processes in two separate molecules give signals that appear on top of a genuine direct higher-order process with a single molecule. These many-body contributions are known as cascading and complicate the interpretation of multidimensional stimulated Raman and other nonlinear signals. In a quantum electrodynamic treatment, these cascading processes arise from second-order expansion in the molecular coupling to vacuum modes of the radiation field, i.e., single-photon exchange between molecules, which also gives rise to other collective effects. We predict the relative phase of the direct and cascading nonlinear signals and its dependence on the microscopic dynamics as well as the sample geometry. This phase may be used to identify experimental conditions for distinguishing the direct and cascading signals by their phase. Higher-order cascading processes involving the exchange of several photons between more than two molecules are discussed.

Cascade pulse-tube cryocooler using a displacer for efficient work recovery

NASA Astrophysics Data System (ADS)

Xu, Jingyuan; Hu, Jianying; Hu, Jiangfeng; Luo, Ercang; Zhang, Limin; Gao, Bo

2017-09-01

Expansion work is generally wasted as heat in a pulse-tube cryocooler and thus represents an obstacle to obtaining higher Carnot efficiency. Recovery of this dissipated power is crucial to improvement of these cooling systems, particularly when the cooling temperature is not very low. In this paper, an efficient cascade cryocooler that is capable of recovering acoustic power is introduced. The cryocooler is composed of two coolers and a displacer unit. The displacer, which fulfills both phase modulation and power transmission roles, is sandwiched in the structure by the two coolers. This means that the expansion work from the first stage cooler can then be used by the second stage cooler. The expansion work of the second stage cooler is much lower than the total input work and it is thus not necessary to recover it. Analyses and experiments were conducted to verify the proposed configuration. At an input power of 1249 W, the cascade cryocooler achieved its highest overall relative Carnot efficiency of 37.2% and a cooling power of 371 W at 130 K. When compared with the performance of a traditional pulse-tube cryocooler, the cooling efficiency was improved by 32%.

Trophic cascades, invasive species and body-size hierarchies interactively modulate climate change responses of ecotonal temperate–boreal forest

PubMed Central

Frelich, Lee E.; Peterson, Rolf O.; Dovčiak, Martin; Reich, Peter B.; Vucetich, John A.; Eisenhauer, Nico

2012-01-01

As the climate warms, boreal tree species are expected to be gradually replaced by temperate species within the southern boreal forest. Warming will be accompanied by changes in above- and below-ground consumers: large moose (Alces alces) replaced by smaller deer (Odocoileus virginianus) above-ground, and small detritivores replaced by larger exotic earthworms below-ground. These shifts may induce a cascade of ecological impacts across trophic levels that could alter the boreal to temperate forest transition. Deer are more likely to browse saplings of temperate tree species, and European earthworms favour seedlings of boreal tree species more than temperate species, potentially hindering the ability of temperate tree species to expand northwards. We hypothesize that warming-induced changes in consumers will lead to novel plant communities by changing the filter on plant species success, and that above- and below-ground cascades of trophic interactions will allow boreal tree species to persist during early phases of warming, leading to an abrupt change at a later time. The synthesis of evidence suggests that consumers can modify the climate change-induced transition of ecosystems. PMID:23007083

Broadband optical frequency comb generator based on driving N-cascaded modulators by Gaussian-shaped waveform

NASA Astrophysics Data System (ADS)

Hmood, Jassim K.; Harun, Sulaiman W.

2018-05-01

A new approach for realizing a wideband optical frequency comb (OFC) generator based on driving cascaded modulators by a Gaussian-shaped waveform, is proposed and numerically demonstrated. The setup includes N-cascaded MZMs, a single Gaussian-shaped waveform generator, and N-1 electrical time delayer. The first MZM is driven directly by a Gaussian-shaped waveform, while delayed replicas of the Gaussian-shaped waveform drive the other MZMs. An analytical model that describes the proposed OFC generator is provided to study the effect of number and chirp factor of cascaded MZM as well as pulse width on output spectrum. Optical frequency combs at frequency spacing of 1 GHz are generated by applying Gaussian-shaped waveform at pulse widths ranging from 200 to 400 ps. Our results reveal that, the number of comb lines is inversely proportional to the pulse width and directly proportional to both number and chirp factor of cascaded MZMs. At pulse width of 200 ps and chirp factor of 4, 67 frequency lines can be measured at output spectrum of two-cascaded MZMs setup. Whereas, increasing the number of cascaded stages to 3, 4, and 5, the optical spectra counts 89, 109 and 123 frequency lines; respectively. When the delay time is optimized, 61 comb lines can be achieved with power fluctuations of less than 1 dB for five-cascaded MZMs setup.

Tunable optical frequency comb enabled scalable and cost-effective multiuser orthogonal frequency-division multiple access passive optical network with source-free optical network units.

PubMed

Chen, Chen; Zhang, Chongfu; Liu, Deming; Qiu, Kun; Liu, Shuang

2012-10-01

We propose and experimentally demonstrate a multiuser orthogonal frequency-division multiple access passive optical network (OFDMA-PON) with source-free optical network units (ONUs), enabled by tunable optical frequency comb generation technology. By cascading a phase modulator (PM) and an intensity modulator and dynamically controlling the peak-to-peak voltage of a PM driven signal, a tunable optical frequency comb source can be generated. It is utilized to assist the configuration of a multiple source-free ONUs enhanced OFDMA-PON where simultaneous and interference-free multiuser upstream transmission over a single wavelength can be efficiently supported. The proposed multiuser OFDMA-PON is scalable and cost effective, and its feasibility is successfully verified by experiment.

Slowdown of group velocity of light in dual-frequency laser-pumped cascade structure of Er3+-doped optical fiber at room temperature

NASA Astrophysics Data System (ADS)

Qiu, Wei; Yang, Yujing; Gao, Yuan; Liu, Jianjun; Lv, Pin; Jiang, Qiuli

2018-04-01

Slow light is demonstrated in the cascade structure of an erbium-doped fiber with two forward propagation pumps. The results of the numerical simulation of the time delay and the optimum modulation frequency complement each other. The time delay and the optimum modulation frequency depend on the pump ratio G (G  =  {{P}1480}:{{P}980} ). The discussion results of this paper show that a larger time delay of slow light propagation can be obtained in the cascade structure of Er3+-doped optical fibers with dual-frequency laser pumping. Compared to previous research methods, the dual-frequency laser-pumped cascade structure of an Er3+-doped optical fiber is more controllable. Based on our discussion the pump ratio G should be selected in order to obtain a more appropriate time delay and the slowdown of group velocity.

External amplitude and frequency modulation of a terahertz quantum cascade laser using metamaterial/graphene devices.

PubMed

Kindness, S J; Jessop, D S; Wei, B; Wallis, R; Kamboj, V S; Xiao, L; Ren, Y; Braeuninger-Weimer, P; Aria, A I; Hofmann, S; Beere, H E; Ritchie, D A; Degl'Innocenti, R

2017-08-09

Active control of the amplitude and frequency of terahertz sources is an essential prerequisite for exploiting a myriad of terahertz applications in imaging, spectroscopy, and communications. Here we present a optoelectronic, external modulation technique applied to a terahertz quantum cascade laser which holds the promise of addressing a number of important challenges in this research area. A hybrid metamaterial/graphene device is implemented into an external cavity set-up allowing for optoelectronic tuning of feedback into a quantum cascade laser. We demonstrate powerful, all-electronic, control over the amplitude and frequency of the laser output. Full laser switching is performed by electrostatic gating of the metamaterial/graphene device, demonstrating a modulation depth of 100%. External control of the emission spectrum is also achieved, highlighting the flexibility of this feedback method. By taking advantage of the frequency dispersive reflectivity of the metamaterial array, different modes of the QCL output are selectively suppressed using lithographic tuning and single mode operation of the multi-mode laser is enforced. Side mode suppression is electrically modulated from ~6 dB to ~21 dB, demonstrating active, optoelectronic modulation of the laser frequency content between multi-mode and single mode operation.

Femtosecond measurements of near-infrared pulse induced mid-infrared transmission modulation of quantum cascade lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai, Hong; Liu, Sheng; Center for Advanced Studied in Photonics Research

2014-05-26

We temporally resolved the ultrafast mid-infrared transmission modulation of quantum cascade lasers (QCLs) using a near-infrared pump/mid-infrared probe technique at room temperature. Two different femtosecond wavelength pumps were used with photon energy above and below the quantum well (QW) bandgap. The shorter wavelength pump modulates the mid-infrared probe transmission through interband transition assisted mechanisms, resulting in a high transmission modulation depth and several nanoseconds recovery lifetime. In contrast, pumping with a photon energy below the QW bandgap induces a smaller transmission modulation depth but much faster (several picoseconds) recovery lifetime, attributed to intersubband transition assisted mechanisms. The latter ultrafast modulationmore » (>60 GHz) could provide a potential way to realize fast QCL based free space optical communication.« less

Dynamic Reweighting of Auditory Modulation Filters.

PubMed

Joosten, Eva R M; Shamma, Shihab A; Lorenzi, Christian; Neri, Peter

2016-07-01

Sound waveforms convey information largely via amplitude modulations (AM). A large body of experimental evidence has provided support for a modulation (bandpass) filterbank. Details of this model have varied over time partly reflecting different experimental conditions and diverse datasets from distinct task strategies, contributing uncertainty to the bandwidth measurements and leaving important issues unresolved. We adopt here a solely data-driven measurement approach in which we first demonstrate how different models can be subsumed within a common 'cascade' framework, and then proceed to characterize the cascade via system identification analysis using a single stimulus/task specification and hence stable task rules largely unconstrained by any model or parameters. Observers were required to detect a brief change in level superimposed onto random level changes that served as AM noise; the relationship between trial-by-trial noisy fluctuations and corresponding human responses enables targeted identification of distinct cascade elements. The resulting measurements exhibit a dynamic complex picture in which human perception of auditory modulations appears adaptive in nature, evolving from an initial lowpass to bandpass modes (with broad tuning, Q∼1) following repeated stimulus exposure.

Reconfigurable generation and measurement of mutually unbiased bases for time-bin qudits

NASA Astrophysics Data System (ADS)

Lukens, Joseph M.; Islam, Nurul T.; Lim, Charles Ci Wen; Gauthier, Daniel J.

2018-03-01

We propose a method for implementing mutually unbiased generation and measurement of time-bin qudits using a cascade of electro-optic phase modulator-coded fiber Bragg grating pairs. Our approach requires only a single spatial mode and can switch rapidly between basis choices. We obtain explicit solutions for dimensions d = 2, 3, and 4 that realize all d + 1 possible mutually unbiased bases and analyze the performance of our approach in quantum key distribution. Given its practicality and compatibility with current technology, our approach provides a promising springboard for scalable processing of high-dimensional time-bin states.

Mitogen-Activated Protein Kinase Cascade MKK7-MPK6 Plays Important Roles in Plant Development and Regulates Shoot Branching by Phosphorylating PIN1 in Arabidopsis

PubMed Central

Liang, Yan; Wu, Xiaowei; Cai, Yueyue; Zhang, Yuanya; Wang, Yingchun; Li, Jiayang; Wang, Yonghong

2016-01-01

Emerging evidences exhibit that mitogen-activated protein kinase (MAPK/MPK) signaling pathways are connected with many aspects of plant development. The complexity of MAPK cascades raises challenges not only to identify the MAPK module in planta but also to define the specific role of an individual module. So far, our knowledge of MAPK signaling has been largely restricted to a small subset of MAPK cascades. Our previous study has characterized an Arabidopsis bushy and dwarf1 (bud1) mutant, in which the MAP Kinase Kinase 7 (MKK7) was constitutively activated, resulting in multiple phenotypic alterations. In this study, we found that MPK3 and MPK6 are the substrates for phosphorylation by MKK7 in planta. Genetic analysis showed that MKK7-MPK6 cascade is specifically responsible for the regulation of shoot branching, hypocotyl gravitropism, filament elongation, and lateral root formation, while MKK7-MPK3 cascade is mainly involved in leaf morphology. We further demonstrated that the MKK7-MPK6 cascade controls shoot branching by phosphorylating Ser 337 on PIN1, which affects the basal localization of PIN1 in xylem parenchyma cells and polar auxin transport in the primary stem. Our results not only specify the functions of the MKK7-MPK6 cascade but also reveal a novel mechanism for PIN1 phosphorylation, establishing a molecular link between the MAPK cascade and auxin-regulated plant development. PMID:27618482

Quantum cascade laser combs: effects of modulation and dispersion.

PubMed

Villares, Gustavo; Faist, Jérôme

2015-01-26

Frequency comb formation in quantum cascade lasers is studied theoretically using a Maxwell-Bloch formalism based on a modal decomposition, where dispersion is considered. In the mid-infrared, comb formation persists in the presence of weak cavity dispersion (500 fs² mm^-1) but disappears when much larger values are used (30'000 fs² mm^-1). Active modulation at the round-trip frequency is found to induce mode-locking in THz devices, where the upper state lifetime is in the tens of picoseconds. Our results show that mode-locking based on four-wave mixing in broadband gain, low dispersion cavities is the most promising way of achieving broadband quantum cascade laser frequency combs.

Quantum Cascade Laser Tuning by Digital Micromirror Array-controlled External Cavity

DTIC Science & Technology

2014-01-01

P. Vujkovic-Cvijin, B. Gregor, A. C. Samuels, E. S. Roese, Quantum cascade laser tuning by digital micromirror array-controlled external cavity...REPORT TYPE 3. DATES COVERED 00-00-2014 to 00-00-2014 4. TITLE AND SUBTITLE Quantum cascade laser tuning by digital micromirror array-controlled...dimensional digital micromirror array (DMA) is described. The laser is tuned by modulating the reflectivity of DMA micromirror pixels under computer

Signal transduction in a covalent post-assembly modification cascade

NASA Astrophysics Data System (ADS)

Pilgrim, Ben S.; Roberts, Derrick A.; Lohr, Thorsten G.; Ronson, Tanya K.; Nitschke, Jonathan R.

2017-12-01

Natural reaction cascades control the movement of biomolecules between cellular compartments. Inspired by these systems, we report a synthetic reaction cascade employing post-assembly modification reactions to direct the partitioning of supramolecular complexes between phases. The system is composed of a self-assembled tetrazine-edged FeII8L12 cube and a maleimide-functionalized FeII4L6 tetrahedron. Norbornadiene (NBD) functions as the stimulus that triggers the cascade, beginning with the inverse-electron-demand Diels-Alder reaction of NBD with the tetrazine moieties of the cube. This reaction generates cyclopentadiene as a transient by-product, acting as a relay signal that subsequently undergoes a Diels-Alder reaction with the maleimide-functionalized tetrahedron. Cyclooctyne can selectively inhibit the cascade by outcompeting NBD as the initial trigger. Initiating the cascade with 2-octadecyl NBD leads to selective alkylation of the tetrahedron upon cascade completion. The increased lipophilicity of the C18-tagged tetrahedron drives this complex into a non-polar phase, allowing its isolation from the initially inseparable mixture of complexes.

Cascading Failures as Continuous Phase-Space Transitions

DOE PAGES

Yang, Yang; Motter, Adilson E.

2017-12-14

In network systems, a local perturbation can amplify as it propagates, potentially leading to a large-scale cascading failure. We derive a continuous model to advance our understanding of cascading failures in power-grid networks. The model accounts for both the failure of transmission lines and the desynchronization of power generators and incorporates the transient dynamics between successive steps of the cascade. In this framework, we show that a cascade event is a phase-space transition from an equilibrium state with high energy to an equilibrium state with lower energy, which can be suitably described in a closed form using a global Hamiltonian-likemore » function. From this function, we show that a perturbed system cannot always reach the equilibrium state predicted by quasi-steady-state cascade models, which would correspond to a reduced number of failures, and may instead undergo a larger cascade. We also show that, in the presence of two or more perturbations, the outcome depends strongly on the order and timing of the individual perturbations. These results offer new insights into the current understanding of cascading dynamics, with potential implications for control interventions.« less

Cascading Failures as Continuous Phase-Space Transitions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Yang; Motter, Adilson E.

In network systems, a local perturbation can amplify as it propagates, potentially leading to a large-scale cascading failure. We derive a continuous model to advance our understanding of cascading failures in power-grid networks. The model accounts for both the failure of transmission lines and the desynchronization of power generators and incorporates the transient dynamics between successive steps of the cascade. In this framework, we show that a cascade event is a phase-space transition from an equilibrium state with high energy to an equilibrium state with lower energy, which can be suitably described in a closed form using a global Hamiltonian-likemore » function. From this function, we show that a perturbed system cannot always reach the equilibrium state predicted by quasi-steady-state cascade models, which would correspond to a reduced number of failures, and may instead undergo a larger cascade. We also show that, in the presence of two or more perturbations, the outcome depends strongly on the order and timing of the individual perturbations. These results offer new insights into the current understanding of cascading dynamics, with potential implications for control interventions.« less

Three-phase multilevel solar inverter for motor drive system

NASA Astrophysics Data System (ADS)

Bhasagare, Mayuresh P.

This thesis deals with three phase inverters and the different control strategies that can be associated with an inverter being used together. The first part of this thesis discusses the present research in the fields of PV panels, motor drive systems and three phase inverters along with their control. This control includes various strategies like MPPT, Volts-Hertz and modulation index compensation. Incorporating these techniques together is the goal of this thesis. A new topology for operating an open end motor drive system has also been discusses, where a boost converter and a flyback converter have been used in cascade to run a three phase motor. The main advantage of this is increasing the number of levels and improving the quality of the output voltage, not to mention a few other benefits of having the proposed circuit. A new algorithm has also been designed for starting and stopping the motor, which controls the current drawn from the power source during starting.

Solid-state transformer-based new traction drive system and control

NASA Astrophysics Data System (ADS)

Feng, Jianghua; Shang, Jing; Zhang, Zhixue; Liu, Huadong; Huang, Zihao

2017-11-01

A new type of traction drive system consisting of solid-state traction transformer (SSTT), inverter unit, auxiliary inverter, traction motor and other key components is built in order to suit the demand of developing the next-generation electric traction system which will be efficient and lightweight, with high power density. For the purpose of reducing system volume and weight and improving efficiency and grid-side power quality, an efficient SSTT optimized topology combining high-voltage cascaded rectifiers with high-power high-frequency LLC resonant converter is proposed. On this basis, an integrated control strategy built upon synchronous rotating reference frame is presented to achieve unified control over fundamental active, reactive and harmonic components. The carrier-interleaving phase shift modulation strategy is proposed to improve the harmonic performance of cascaded rectifiers. In view of the secondary pulsating existing in a single-phase system, the mathematical model of secondary power transfer is built, and the mechanism of pulsating voltage resulting in beat frequency of LLC resonant converter is revealed, so as to design optimum matching of system parameters. Simulation and experimental results have verified that the traction system and control scheme mentioned in this paper are reasonable and superior and that they meet the future application requirements for rail transit.

Optical modulation of quantum cascade laser with optimized excitation wavelength.

PubMed

Yang, Tao; Chen, Gang; Tian, Chao; Martini, Rainer

2013-04-15

The excitation wavelength for all-optical modulation of a 10.6 μm mid-infrared (MIR) quantum cascade laser (QCL) was varied in order to obtain maximum modulation depth. Both amplitude and wavelength modulation experiments were conducted at 820 nm and 1550 nm excitation respectively, whereby the latter matches the interband transition in the QCL active region. Experimental results show that for continuous-wave mode-operated QCL, the efficiency of free carrier generation is doubled under 1550 nm excitation compared with 820 nm excitation, resulting in an increase of the amplitude modulation index from 19% to 36%. At the same time, the maximum wavelength shift is more than doubled from 1.05 nm to 2.80 nm. Furthermore, for the first time to our knowledge, we demonstrated the optical switching of a QCL operated in pulse mode by simple variation of the excitation wavelength.

Ras regulates assembly of mitogenic signalling complexes through the effector protein IMP.

PubMed

Matheny, Sharon A; Chen, Chiyuan; Kortum, Robert L; Razidlo, Gina L; Lewis, Robert E; White, Michael A

2004-01-15

The signal transduction cascade comprising Raf, mitogen-activated protein (MAP) kinase kinase (MEK) and MAP kinase is a Ras effector pathway that mediates diverse cellular responses to environmental cues and contributes to Ras-dependent oncogenic transformation. Here we report that the Ras effector protein Impedes Mitogenic signal Propagation (IMP) modulates sensitivity of the MAP kinase cascade to stimulus-dependent activation by limiting functional assembly of the core enzymatic components through the inactivation of KSR, a scaffold/adaptor protein that couples activated Raf to its substrate MEK. IMP is a Ras-responsive E3 ubiquitin ligase that, on activation of Ras, is modified by auto-polyubiquitination, which releases the inhibition of Raf-MEK complex formation. Thus, Ras activates the MAP kinase cascade through simultaneous dual effector interactions: induction of Raf kinase activity and derepression of Raf-MEK complex formation. IMP depletion results in increased stimulus-dependent MEK activation without alterations in the timing or duration of the response. These observations suggest that IMP functions as a threshold modulator, controlling sensitivity of the cascade to stimulus and providing a mechanism to allow adaptive behaviour of the cascade in chronic or complex signalling environments.

Phase-synchronization, energy cascade, and intermittency in solar-wind turbulence.

PubMed

Perri, S; Carbone, V; Vecchio, A; Bruno, R; Korth, H; Zurbuchen, T H; Sorriso-Valvo, L

2012-12-14

The energy cascade in solar wind magnetic turbulence is investigated using MESSENGER data in the inner heliosphere. The decomposition of magnetic field time series in intrinsic functions, each characterized by a typical time scale, reveals phase reorganization. This allows for the identification of structures of all sizes generated by the nonlinear turbulent cascade, covering both the inertial and the dispersive ranges of the turbulent magnetic power spectrum. We find that the correlation (or anticorrelation) of phases occurs between pairs of neighboring time scales, whenever localized peaks of magnetic energy are present at both scales, consistent with the local character of the energy transfer process.

Nonlinear THz absorption and cyclotron resonance in InSb

NASA Astrophysics Data System (ADS)

Heffernan, Kate; Yu, Shukai; Talbayev, Diyar

The emergence of coherent high-field terahertz (THz) sources in the past decade has allowed the exploration of nonlinear light-matter interaction at THz frequencies. Nonlinear THz response of free electrons in semiconductors has received a great deal of attention. Such nonlinear phenomena as saturable absorption and self-phase modulation have been reported. InSb is a narrow-gap (bandgap 0.17 eV) semiconductor with a very low electron effective mass and high electron mobility. Previous high-field THz work on InSb reported the observation of ultrafast electron cascades via impact ionization. We study the transmission of an intense THz electric field pulse by an InSb wafer at different incident THz amplitudes and 10 K temperature. Contrary to previous reports, we observe an increased transmission at higher THz field. Our observation appears similar to the saturable THz absorption reported in other semiconductors. Along with the increased absorption, we observe a strong modulation of the THz phase at high incident fields, most likely due to the self-phase modulation of the THz pulse. We also study the dependence of the cyclotron resonance on the incident THz field amplitude. The cyclotron resonance exhibits a lower strength and frequency at the higher incident THz field. The work at Tulane was supported by the Louisiana Board of Regents through the Board of Regents Support Fund Contract No. LEQSF(2012-15)-RD-A-23 and through the Pilot Funding for New Research (PFund) Contract No. LEQSF-EPS(2014)-PFUND-378.

Evaluating the coherence and time-domain profile of quantum cascade laser frequency combs

DOE PAGES

Burghoff, David; Yang, Yang; Hayton, Darren J.; ...

2015-01-01

Recently, much attention has been focused on the generation of optical frequency combs from quantum cascade lasers. We discuss how fast detectors can be used to demonstrate the mutual coherence of such combs, and present an inequality that can be used to quantitatively evaluate their performance. We discuss several technical issues related to shifted wave interference Fourier Transform spectroscopy (SWIFTS), and show how such measurements can be used to elucidate the time-domain properties of such combs, showing that they can possess signatures of both frequency-modulation and amplitude-modulation.

Bilayer avalanche spin-diode logic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Friedman, Joseph S., E-mail: joseph.friedman@u-psud.fr; Querlioz, Damien; Fadel, Eric R.

2015-11-15

A novel spintronic computing paradigm is proposed and analyzed in which InSb p-n bilayer avalanche spin-diodes are cascaded to efficiently perform complex logic operations. This spin-diode logic family uses control wires to generate magnetic fields that modulate the resistance of the spin-diodes, and currents through these devices control the resistance of cascaded devices. Electromagnetic simulations are performed to demonstrate the cascading mechanism, and guidelines are provided for the development of this innovative computing technology. This cascading scheme permits compact logic circuits with switching speeds determined by electromagnetic wave propagation rather than electron motion, enabling high-performance spintronic computing.

miR-302b inhibits tumorigenesis by targeting EphA2 via Wnt/ β-catenin/EMT signaling cascade in gastric cancer.

PubMed

Huang, Jin; He, Yijing; Mcleod, Howard L; Xie, Yanchun; Xiao, Desheng; Hu, Huabin; Chen, Pan; Shen, Liangfang; Zeng, Shan; Yin, Xianli; Ge, Jie; Li, Li; Tang, Lanhua; Ma, Jian; Chen, Zihua

2017-12-22

EphA2 is a crucial oncogene in gastric cancer (GC) development and metastasis, this study aims to identify microRNAs that target it and serve as key regulators of gastric carcinogenesis. We identified several potential microRNAs targeting EphA2 by bioinformatics websites and then analyzed the role of miR-302b in modulating EphA2 in vitro and in vivo of GC, and it's mechanism. Our analysis identified miR-302b, a novel regulator of EphA2, as one of the most significantly downregulated microRNA (miRNA) in GC tissues. Overexpression of miR-302b impaired GC cell migratory and invasive properties robustly and suppressed cell proliferation by arresting cells at G0-G1 phase in vitro. miR-302b exhibited anti-tumor activity by reversing EphA2 regulation, which relayed a signaling transduction cascade that attenuated the functions of N-cadherin, β-catenin, and Snail (markers of Wnt/β-catenin and epithelial-mesenchymal transition, EMT). This modulation of EphA2 also had distinct effects on cell proliferation and migration in GC in vivo. miR-302b serves as a critical suppressor of GC cell tumorigenesis and metastasis by targeting the EphA2/Wnt/β-catenin/EMT pathway.

Musa paradisiaca inflorescence induces human colon cancer cell death by modulating cascades of transcriptional events.

PubMed

K B, Arun; Madhavan, Aravind; T R, Reshmitha; Thomas, Sithara; Nisha, P

2018-01-24

Colorectal cancer (CRC) is one of the leading causes of cancer death, and diet plays an important role in the etiology of CRC. Traditional medical practitioners in many South Asian countries use plantain inflorescence to treat various gastro-intestinal ailments. The aim of the present study was to investigate the anticancer effects of extracts of inflorescence of Musa paradisiaca against HT29 human colon cancer cells and elucidate the mechanism of these effects by studying the modulation of cascades of transcriptional events. In vitro assays depicted that methanol extract of Musa paradisiaca inflorescence (PIMET) was cytotoxic to HT29 cells. PIMET induced DNA damage and arrested the cell cycle at the G2/M phase. Expression studies showed that PIMET pretreatment upregulates pro-apoptotic Bcl2 and downregulates anti-apoptotic Bax proteins. Different assays showed that the deregulation of pro/antiapoptotic proteins reduces the mitochondrial membrane potential and ATP production; moreover, it enhances cytochrome c release, which triggers the apoptotic pathway, and further cleaves caspase 3 and PARP proteins, resulting in apoptosis. Changes in the protein expression profile of HT29 cells after PIMET treatment were analyzed using mass-spectrometry-based proteomics. PIMET treatment significantly altered the expression of HT29 protein; interestingly, X-linked inhibitor of apoptosis protein was also downregulated. Alteration in the expression of this protein has significant effects, leading to HT29 cell death.

A real-time and closed-loop control algorithm for cascaded multilevel inverter based on artificial neural network.

PubMed

Wang, Libing; Mao, Chengxiong; Wang, Dan; Lu, Jiming; Zhang, Junfeng; Chen, Xun

2014-01-01

In order to control the cascaded H-bridges (CHB) converter with staircase modulation strategy in a real-time manner, a real-time and closed-loop control algorithm based on artificial neural network (ANN) for three-phase CHB converter is proposed in this paper. It costs little computation time and memory. It has two steps. In the first step, hierarchical particle swarm optimizer with time-varying acceleration coefficient (HPSO-TVAC) algorithm is employed to minimize the total harmonic distortion (THD) and generate the optimal switching angles offline. In the second step, part of optimal switching angles are used to train an ANN and the well-designed ANN can generate optimal switching angles in a real-time manner. Compared with previous real-time algorithm, the proposed algorithm is suitable for a wider range of modulation index and results in a smaller THD and a lower calculation time. Furthermore, the well-designed ANN is embedded into a closed-loop control algorithm for CHB converter with variable direct voltage (DC) sources. Simulation results demonstrate that the proposed closed-loop control algorithm is able to quickly stabilize load voltage and minimize the line current's THD (<5%) when subjecting the DC sources disturbance or load disturbance. In real design stage, a switching angle pulse generation scheme is proposed and experiment results verify its correctness.

Polarization switch of four-wave mixing in a lawtunable fiber optical parametric oscillator.

PubMed

Yang, Kangwen; Ye, Pengbo; Zheng, Shikai; Jiang, Jieshi; Huang, Kun; Hao, Qiang; Zeng, Heping

2018-02-05

We reported the simultaneous generation and selective manipulation of scalar and cross-phase modulation instabilities in a fiber optical parametric oscillator. Numerical and experimental results show independent control of parametric gain by changing the input pump polarization state. The resonant cavity enables power enhancement of 45 dB for the spontaneous sidebands, generating laser pulses tunable from 783 to 791 nm and 896 to 1005 nm due to the combination of four-wave mixing, cascaded Raman scattering and other nonlinear effects. This gain controlled, wavelength tunable, fiber-based laser source may find applications in the fields of nonlinear biomedical imaging and stimulated Raman spectroscopy.

Characterization Of Improved Binary Phase-Only Filters In A Real-Time Coherent Optical Correlation System

NASA Astrophysics Data System (ADS)

Flannery, D.; Keller, P.; Cartwright, S.; Loomis, J.

1987-06-01

Attractive correlation system performance potential is possible using magneto-optic spatial light modulators (SLM) to implement binary phase-only reference filters at high rates, provided the correlation performance of such reduced-information-content filters is adequate for the application. In the case studied here, the desired filter impulse response is a rectangular shape, which cannot be achieved with the usual binary phase-only filter formulation. The correlation application problem is described and techniques for synthesizing improved filter impulse response are considered. A compromise solution involves the cascading of a fixed amplitude-only weighting mask with the binary phase-only SLM. Based on simulations presented, this approach provides improved impulse responses and good correlation performance, while retaining the critical feature of real-time variations of the size, shape, and orientation of the rectangle by electronic programming of the phase pattern in the SLM. Simulations indicate that, for at least one very challenging input scene clutter situation, these filters provide higher correlation signal-to-noise than does "ideal" correlation, i.e. using a perfect rectangle filter response.

Wind tunnel wall effects in a linear oscillating cascade

NASA Technical Reports Server (NTRS)

Buffum, Daniel H.; Fleeter, Sanford

1991-01-01

Experiments in a linear oscillating cascade reveal that the wind tunnel walls enclosing the airfoils have, in some cases, a detrimental effect on the oscillating cascade aerodynamics. In a subsonic flow field, biconvex airfoils are driven simultaneously in harmonic, torsion-mode oscillations for a range of interblade phase angle values. It is found that the cascade dynamic periodicity - the airfoil to airfoil variation in unsteady surface pressure - is good for some values of interblade phase angle but poor for others. Correlation of the unsteady pressure data with oscillating flat plate cascade predictions is generally good for conditions where the periodicity is good and poor where the periodicity is poor. Calculations based upon linearized unsteady aerodynamic theory indicate that pressure waves reflected from the wind tunnel walls are responsible for the cases where there is poor periodicity and poor correlation with the predictions.

Joint compensation scheme of polarization crosstalk, intersymbol interference, frequency offset, and phase noise based on cascaded Kalman filter

NASA Astrophysics Data System (ADS)

Zhang, Qun; Yang, Yanfu; Xiang, Qian; Zhou, Zhongqing; Yao, Yong

2018-02-01

A joint compensation scheme based on cascaded Kalman filter is proposed, which can implement polarization tracking, channel equalization, frequency offset, and phase noise compensation simultaneously. The experimental results show that the proposed algorithm can not only compensate multiple channel impairments simultaneously but also improve the polarization tracking capacity and accelerate the convergence speed. The scheme has up to eight times faster convergence speed compared with radius-directed equalizer (RDE) + Max-FFT (maximum fast Fourier transform) + BPS (blind phase search) and can track up polarization rotation 60 times and 15 times faster than that of RDE + Max-FFT + BPS and CMMA (cascaded multimodulus algorithm) + Max-FFT + BPS, respectively.

Design of a 0.13-μm CMOS cascade expandable ΣΔ modulator for multi-standard RF telecom systems

NASA Astrophysics Data System (ADS)

Morgado, Alonso; del Río, Rocío; de la Rosa, José M.

2007-05-01

This paper reports a 130-nm CMOS programmable cascade ΣΔ modulator for multi-standard wireless terminals, capable of operating on three standards: GSM, Bluetooth and UMTS. The modulator is reconfigured at both architecture- and circuit- level in order to adapt its performance to the different standards specifications with optimized power consumption. The design of the building blocks is based upon a top-down CAD methodology that combines simulation and statistical optimization at different levels of the system hierarchy. Transistor-level simulations show correct operation for all standards, featuring 13-bit, 11.3-bit and 9-bit effective resolution within 200-kHz, 1-MHz and 4-MHz bandwidth, respectively.

Two-dimensional profiling of carriers in terahertz quantum cascade lasers using calibrated scanning spreading resistance microscopy and scanning capacitance microscopy.

PubMed

Dhar, R S; Ban, D

2013-07-01

The distribution of charge carriers inside the active region of a terahertz (THz) quantum cascade laser (QCL) has been measured with scanning spreading resistance microscopy (SSRM) and scanning capacitance microscopy (SCM). Individual quantum well-barrier modules with a 35.7-nm single module thickness in the active region of the device have been resolved for the first time using high-resolution SSRM and SCM techniques at room temperature. SSRM and SCM measurements on the quantum well-barrier structure were calibrated utilizing known GaAs dopant staircase samples. Doping concentrations derived from SSRM and SCM measurements were found to be in quantitative agreement with the designed average doping values of the n-type active region in the terahertz quantum cascade laser. The secondary ion mass spectroscopy provides a partial picture of internal device parameters, and we have demonstrated with our results the efficacy of uniting calibrated SSRM and SCM to delineate quantitatively the transverse cross-sectional structure of complex two-dimensional terahertz quantum cascade laser devices. © 2013 The Authors Journal of Microscopy © 2013 Royal Microscopical Society.

High-power, fixed, and tunable wavelength, grating-free cascaded Raman fiber lasers

NASA Astrophysics Data System (ADS)

Balaswamy, V.; Arun, S.; Aparanji, Santosh; Choudhury, Vishal; Supradeepa, V. R.

2018-04-01

Cascaded Raman lasers enable high powers at various wavelength bands inaccessible with conventional rare-earth doped lasers. The input and output wavelengths of conventional implementations are fixed by the constituent fiber gratings necessary for cascaded Raman conversion. We demonstrate here, a simple architecture for high power, fixed and wavelength tunable, grating-free, cascaded Raman conversion between different wavelength bands. The architecture is based on the recently proposed distributed feedback Raman lasers. Here, we implement a module which converts the Ytterbium band to the eye-safe 1.5micron region. We demonstrate pump-limited output powers of over 30W in fixed and continuously wavelength tunable configurations.

High-Speed Operation of Interband Cascade Lasers

NASA Technical Reports Server (NTRS)

Soibel, Alexander; Hill, Cory J.; Keo, Sam A.; Wright, Malcom W.; Farr, William H.; Yang, Rui Q.; Liu, H. C.

2010-01-01

Optical sources operating in the atmospheric window of 3-5 microns are of particular interest for the development of free-space optical communication link. It is more advantageous to operate the free-space optical communication link in 3-5-microns atmospheric transmission window than at the telecom wavelength of 1.5 m due to lower optical scattering, scintillation, and background radiation. However, the realization of optical communications at the longer wavelength has encountered significant difficulties due to lack of adequate optical sources and detectors operating in the desirable wavelength regions. Interband Cascade (IC) lasers are novel semiconductor lasers that have a great potential for the realization of high-power, room-temperature optical sources in the 3-5-microns wavelength region, yet no experimental work, until this one, was done on high-speed direct modulation of IC lasers. Here, highspeed interband cascade laser, operating at wavelength 3.0 m, has been developed and the first direct measurement of the laser modulation bandwidth has been performed using a unique, highspeed quantum well infrared photodetector (QWIP). The developed laser has modulation bandwidth exceeding 3 GHz. This constitutes a significant increase of the IC laser modulation bandwidth over currently existing devices. This result has demonstrated suitability of IC lasers as a mid-IR light source for multi-GHz free-space optical communications links

Compact high-power red-green-blue laser light source generation from a single lithium tantalate with cascaded domain modulation.

PubMed

Xu, P; Zhao, L N; Lv, X J; Lu, J; Yuan, Y; Zhao, G; Zhu, S N

2009-06-08

1W quasi-white-light source has been generated from a single lithium tantalate with cascaded domain modulation. The quasi-white-light is combined by proper proportion of the red, green and blue laser light. The red and the blue result from a compact self-sum frequency optical parametric oscillation when pumped by a single green laser. The efficiency of quasi-white-light from the green pump reaches 27%. This compact design can be employed not only as a stable and powerful RGB light source but also an effective blue laser generator.

Continuous wave operation of quantum cascade lasers with frequency-shifted feedback

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lyakh, A., E-mail: arkadiy.lyakh@ucf.edu; NanoScience Technology Center, University of Central Florida, 12424 Research Pkwy, Orlando, FL 32826; College of Optics and Photonics, University of Central Florida, 304 Scorpius St, Orlando, FL 32826

2016-01-15

Operation of continuous wave quantum cascade lasers with a frequency-shifted feedback provided by an acousto-optic modulator is reported. Measured linewidth of 1.7 cm{sup −1} for these devices, under CW operating conditions, was in a good agreement with predictions of a model based on frequency-shifted feedback seeded by spontaneous emission. Linewidth broadening was observed for short sweep times, consistent with sound wave grating period variation across the illuminated area on the acousto-optic modulator. Standoff detection capability of the AOM-based QCL setup was demonstrated for several solid materials.

Coherent frequency combs produced by self frequency modulation in quantum cascade lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khurgin, J. B.; Dikmelik, Y.; Hugi, A.

2014-02-24

One salient characteristic of Quantum Cascade Laser (QCL) is its very short τ ∼ 1 ps gain recovery time that so far thwarted the attempts to achieve self-mode locking of the device into a train of single pulses. We show theoretically that four wave mixing, combined with the short gain recovery time causes QCL to operate in the self-frequency-modulated regime characterized by a constant power in time domain and stable coherent comb in the frequency domain. Coherent frequency comb may enable many potential applications of QCL's in sensing and measurement.

Multidimensional phase space methods for mass measurements and decay topology determination

NASA Astrophysics Data System (ADS)

Altunkaynak, Baris; Kilic, Can; Klimek, Matthew D.

2017-02-01

Collider events with multi-stage cascade decays fill out the kinematically allowed region in phase space with a density that is enhanced at the boundary. The boundary encodes all available information as regards the spectrum and is well populated even with moderate signal statistics due to this enhancement. In previous work, the improvement in the precision of mass measurements for cascade decays with three visible and one invisible particles was demonstrated when the full boundary information is used instead of endpoints of one-dimensional projections. We extend these results to cascade decays with four visible and one invisible particles. We also comment on how the topology of the cascade decay can be determined from the differential distribution of events in these scenarios.

Methodology of Blade Unsteady Pressure Measurement in the NASA Transonic Flutter Cascade

NASA Technical Reports Server (NTRS)

Lepicovsky, J.; McFarland, E. R.; Capece, V. R.; Jett, T. A.; Senyitko, R. G.

2002-01-01

In this report the methodology adopted to measure unsteady pressures on blade surfaces in the NASA Transonic Flutter Cascade under conditions of simulated blade flutter is described. The previous work done in this cascade reported that the oscillating cascade produced waves, which for some interblade phase angles reflected off the wind tunnel walls back into the cascade, interfered with the cascade unsteady aerodynamics, and contaminated the acquired data. To alleviate the problems with data contamination due to the back wall interference, a method of influence coefficients was selected for the future unsteady work in this cascade. In this approach only one blade in the cascade is oscillated at a time. The majority of the report is concerned with the experimental technique used and the experimental data generated in the facility. The report presents a list of all test conditions for the small amplitude of blade oscillations, and shows examples of some of the results achieved. The report does not discuss data analysis procedures like ensemble averaging, frequency analysis, and unsteady blade loading diagrams reconstructed using the influence coefficient method. Finally, the report presents the lessons learned from this phase of the experimental effort, and suggests the improvements and directions of the experimental work for tests to be carried out for large oscillation amplitudes.

Natural product-inspired cascade synthesis yields modulators of centrosome integrity.

PubMed

Dückert, Heiko; Pries, Verena; Khedkar, Vivek; Menninger, Sascha; Bruss, Hanna; Bird, Alexander W; Maliga, Zoltan; Brockmeyer, Andreas; Janning, Petra; Hyman, Anthony; Grimme, Stefan; Schürmann, Markus; Preut, Hans; Hübel, Katja; Ziegler, Slava; Kumar, Kamal; Waldmann, Herbert

2011-12-25

In biology-oriented synthesis, the scaffolds of biologically relevant compound classes inspire the synthesis of focused compound collections enriched in bioactivity. This criterion is, in particular, met by the scaffolds of natural products selected in evolution. The synthesis of natural product-inspired compound collections calls for efficient reaction sequences that preferably combine multiple individual transformations in one operation. Here we report the development of a one-pot, twelve-step cascade reaction sequence that includes nine different reactions and two opposing kinds of organocatalysis. The cascade sequence proceeds within 10-30 min and transforms readily available substrates into complex indoloquinolizines that resemble the core tetracyclic scaffold of numerous polycyclic indole alkaloids. Biological investigation of a corresponding focused compound collection revealed modulators of centrosome integrity, termed centrocountins, which caused fragmented and supernumerary centrosomes, chromosome congression defects, multipolar mitotic spindles, acentrosomal spindle poles and multipolar cell division by targeting the centrosome-associated proteins nucleophosmin and Crm1.

Generation of ultra-wide and flat optical frequency comb based on electro absorption modulator

NASA Astrophysics Data System (ADS)

Ujjwal; Thangaraj, Jaisingh

2018-05-01

A novel technique is proposed for the generation of ultra-wide and flat optical frequency comb (OFC) based on serially cascading three stages of electro absorption modulators (EAMs) through sinusoidal radio frequency (RF) signals by setting frequencies at f GHz, f/2 GHz and f/4 GHz. Here, the first stage acts as subcarrier generator, the second stage acts as subcarrier doubler, and the third stage acts as subcarrier quadrupler. In addition, a higher number of subcarriers can easily be generated by adjusting the driving sinusoidal RF signal. In this paper, cascading three stages of EAMs driven by 50 GHz, 25 GHz and 12.5 GHz clock sources, we obtain 272 subcarriers with spacing of 2.5 GHz and power deviation within 1 dB. Theoretical analysis of serially cascaded EAMs for subcarrier generation is also investigated. Principal analysis and simulation of this technique are demonstrated.

Ultrasensitivity in signaling cascades revisited: Linking local and global ultrasensitivity estimations

PubMed Central

Altszyler, Edgar; Ventura, Alejandra C.; Colman-Lerner, Alejandro; Chernomoretz, Ariel

2017-01-01

Ultrasensitive response motifs, capable of converting graded stimuli into binary responses, are well-conserved in signal transduction networks. Although it has been shown that a cascade arrangement of multiple ultrasensitive modules can enhance the system’s ultrasensitivity, how a given combination of layers affects a cascade’s ultrasensitivity remains an open question for the general case. Here, we introduce a methodology that allows us to determine the presence of sequestration effects and to quantify the relative contribution of each module to the overall cascade’s ultrasensitivity. The proposed analysis framework provides a natural link between global and local ultrasensitivity descriptors and it is particularly well-suited to characterize and understand mathematical models used to study real biological systems. As a case study, we have considered three mathematical models introduced by O’Shaughnessy et al. to study a tunable synthetic MAPK cascade, and we show how our methodology can help modelers better understand alternative models. PMID:28662096

Dynamics of a broad-band quantum cascade laser: from chaos to coherent dynamics and mode-locking

NASA Astrophysics Data System (ADS)

Columbo, L. L.; Barbieri, S.; Sirtori, C.; Brambilla, M.

2018-02-01

The dynamics of a multimode Quantum Cascade Laser, is studied in a model based on effective semiconductor Maxwell-Bloch equations, encompassing key features for the radiationmedium interaction such as an asymmetric, frequency dependent, gain and refractive index as well as the phase-amplitude coupling provided by the Henry factor. By considering the role of the free spectral range and Henry factor, we develop criteria suitable to identify the conditions which allow to destabilize, close to threshold, the traveling wave emitted by the laser and lead to chaotic or regular multimode dynamics. In the latter case our simulations show that the field oscillations are associated to self-confined structures which travel along the laser cavity, bridging mode-locking and solitary wave propagation. In addition, we show how a RF modulation of the bias current leads to active mode-locking yielding high-contrast, picosecond pulses. Our results compare well with recent experiments on broad-band THz-QCLs and may help understanding the conditions for the generation of ultrashort pulses and comb operation in Mid-IR and THz spectral regions

Investigation of giant Kerr nonlinearity in quantum cascade lasers using mid-infrared femtosecond pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai, Hong; Liu, Sheng; Department of Physics, University of Maryland, Baltimore County

2015-02-02

We study the Kerr nonlinearity of quantum cascade lasers (QCLs) by coupling resonant and off-resonant mid-infrared (mid-IR) femtosecond (fs) pulses into an active QCL waveguide. We observe an increase in the spectral width of the transmitted fs pulses as the coupled mid-infrared (mid-IR) pulse power increases. This is explained by the self-phase modulation effect due to the large Kerr nonlinearity of QCL waveguides. We further confirm this effect by observing the intensity dependent far-field profile of the transmitted mid-IR pulses, showing the pulses undergo self-focusing as they propagate through the active QCL due to the intensity dependent refractive index. Wemore » experimentally estimate the nonlinear refractive index n{sub 2} of a QCL to be ∼8 × 10{sup −9 }cm{sup 2}/W using the far-field beam profile of the transmitted pulses. The finite-difference time-domain simulations of QCL waveguides with Kerr nonlinearity incorporated show similar behavior to the experimental results.« less

β-Adrenergic Receptors Regulate the Acquisition and Consolidation Phases of Aversive Memory Formation Through Distinct, Temporally Regulated Signaling Pathways

PubMed Central

Schiff, Hillary C; Johansen, Joshua P; Hou, Mian; Bush, David E A; Smith, Emily K; Klein, JoAnna E; LeDoux, Joseph E; Sears, Robert M

2017-01-01

Memory formation requires the temporal coordination of molecular events and cellular processes following a learned event. During Pavlovian threat (fear) conditioning (PTC), sensory and neuromodulatory inputs converge on post-synaptic neurons within the lateral nucleus of the amygdala (LA). By activating an intracellular cascade of signaling molecules, these G-protein-coupled neuromodulatory receptors are capable of recruiting a diverse profile of plasticity-related proteins. Here we report that norepinephrine, through its actions on β-adrenergic receptors (βARs), modulates aversive memory formation following PTC through two molecularly and temporally distinct signaling mechanisms. Specifically, using behavioral pharmacology and biochemistry in adult rats, we determined that βAR activity during, but not after PTC training initiates the activation of two plasticity-related targets: AMPA receptors (AMPARs) for memory acquisition and short-term memory and extracellular regulated kinase (ERK) for consolidating the learned association into a long-term memory. These findings reveal that βAR activity during, but not following PTC sets in motion cascading molecular events for the acquisition (AMPARs) and subsequent consolidation (ERK) of learned associations. PMID:27762270

β-Adrenergic Receptors Regulate the Acquisition and Consolidation Phases of Aversive Memory Formation Through Distinct, Temporally Regulated Signaling Pathways.

PubMed

Schiff, Hillary C; Johansen, Joshua P; Hou, Mian; Bush, David E A; Smith, Emily K; Klein, JoAnna E; LeDoux, Joseph E; Sears, Robert M

2017-03-01

Memory formation requires the temporal coordination of molecular events and cellular processes following a learned event. During Pavlovian threat (fear) conditioning (PTC), sensory and neuromodulatory inputs converge on post-synaptic neurons within the lateral nucleus of the amygdala (LA). By activating an intracellular cascade of signaling molecules, these G-protein-coupled neuromodulatory receptors are capable of recruiting a diverse profile of plasticity-related proteins. Here we report that norepinephrine, through its actions on β-adrenergic receptors (βARs), modulates aversive memory formation following PTC through two molecularly and temporally distinct signaling mechanisms. Specifically, using behavioral pharmacology and biochemistry in adult rats, we determined that βAR activity during, but not after PTC training initiates the activation of two plasticity-related targets: AMPA receptors (AMPARs) for memory acquisition and short-term memory and extracellular regulated kinase (ERK) for consolidating the learned association into a long-term memory. These findings reveal that βAR activity during, but not following PTC sets in motion cascading molecular events for the acquisition (AMPARs) and subsequent consolidation (ERK) of learned associations.

Optical frequency comb generation with high tone-to-noise ratio for large-capacity wavelength division multiplexed passive optical network

NASA Astrophysics Data System (ADS)

Ullah, Rahat; Liu, Bo; Zhang, Qi; Tian, Qinghua; Tian, Feng; Qu, Zhaowei; Yan, Cheng; Khan, Muhammad Saad; Ahmad, Ibrar; Xin, Xiangjun

2015-11-01

We propose a technique for the generation of optical frequency comb from a single source, which reduces the costs of optical access networks. Two Mach-Zehnder modulators are cascaded with one phase modulator driven by radiofrequency signals. With 10-GHz frequency spacing, the generated 40 optical multicarriers have good tone-to-noise ratio with least excursions in their comb lines. The laser array at the optical line terminal of the conventional wavelength division multiplexed passive optical network (WDM-PON) system has been replaced with optical frequency comb generator (OFCG), which may result in cost-effective optical line terminal (OLT) supporting a large-capacity WDM-PON system. Of 40 carriers generated, each carrier carries 10 Gbps data based on differential phase-shift keying. Four hundred Gbps multiplexed data from all channels are successfully transmitted through a fiber span of 25 km with negligible power penalties. Part of the downlink signal is used in uplink transmission at optical network unit where intensity-modulated on-off keying is deployed for remodulation. Theoretical analysis of the proposed WDM-PON system based on OFCG are in good agreement with simulation results. The metrics considered for the analysis of the proposed OFCG in a WDM-PON system are power penalties of the full-duplex transmission, eye diagrams, and bit error rate.

Isothiocyanates Are Promising Compounds against Oxidative Stress, Neuroinflammation and Cell Death that May Benefit Neurodegeneration in Parkinson’s Disease

PubMed Central

Sita, Giulia; Hrelia, Patrizia; Tarozzi, Andrea; Morroni, Fabiana

2016-01-01

Parkinson’s disease (PD) is recognized as the second most common neurodegenerative disorder and is characterized by a slow and progressive degeneration of dopaminergic neurons in the substantia nigra. Despite intensive research, the mechanisms involved in neuronal loss are not completely understood yet; however, misfolded proteins, oxidative stress, excitotoxicity and inflammation play a pivotal role in the progression of the pathology. Neuroinflammation may have a greater function in PD pathogenesis than initially believed, taking part in the cascade of events that leads to neuronal death. To date, no efficient therapy, able to arrest or slow down PD, is available. In this context, the need to find novel strategies to counteract neurodegenerative progression by influencing diseases’ pathogenesis is becoming increasingly clear. Isothiocyanates (ITCs) have already shown interesting properties in detoxification, inflammation, apoptosis and cell cycle regulation through the induction of phase I and phase II enzyme systems. Moreover, ITCs may be able to modulate several key points in oxidative and inflammatory evolution. In view of these considerations, the aim of the present review is to describe ITCs as pleiotropic compounds capable of preventing and modulating the evolution of PD. PMID:27598127

Theoretical investigation of injection-locked high modulation bandwidth quantum cascade lasers.

PubMed

Meng, Bo; Wang, Qi Jie

2012-01-16

In this study, we report for the first time to our knowledge theoretical investigation of modulation responses of injection-locked mid-infrared quantum cascade lasers (QCLs) at wavelengths of 4.6 μm and 9 μm, respectively. It is shown through a three-level rate equations model that the direct intensity modulation of QCLs gives the maximum modulation bandwidths of ~7 GHz at 4.6 μm and ~20 GHz at 9 μm. By applying the injection locking scheme, we find that the modulation bandwidths of up to ~30 GHz and ~70 GHz can be achieved for QCLs at 4.6 μm and 9 μm, respectively, with an injection ratio of 5 dB. The result also shows that an ultrawide modulation bandwidth of more than 200 GHz is possible with a 10 dB injection ratio for QCLs at 9 μm. An important characteristic of injection-locked QCLs is the nonexistence of unstable locking region in the locking map, in contrast to their diode laser counterparts. We attribute this to the ultra-short upper laser state lifetimes of QCLs.

On the investigation of cascade and turbomachinery rotor wake characteristics

NASA Technical Reports Server (NTRS)

Raj, R.; Lakshminarayana, B.

1975-01-01

The objective of the investigation reported in this thesis is to study the characteristics of a turbomachinery rotor wake, both analytically and experimentally. The constitutive equations for the rotor wake are developed using generalized tensors and a non-inertial frame of reference. Analytical and experimental investigation is carried out in two phases; the first phase involved the study of a cascade wake in the absence of rotation and three dimensionality. In the second phase the wake of a rotor is studied. Simplified two- and three-dimensional models are developed for the prediction of the mean velocity profile of the cascade and the rotor wake, respectively, using the principle of self-similarity. The effect of various major parameters of the rotor and the flow geometry is studied on the development of a rotor wake. Laws governing the decay of the wake velocity defect in a cascade and rotor wake as a function of downstream distance from the trailing edge, pressure gradient and other parameters are derived.

Purinergic signaling modulates the cerebral inflammatory response in experimentally infected fish with Streptococcus agalactiae: an attempt to improve the immune response.

PubMed

Souza, Carine F; Baldissera, Matheus D; Bottari, Nathiele B; Moreira, Karen L S; da Rocha, Maria Izabel U M; da Veiga, Marcelo L; Santos, Roberto C V; Baldisserotto, Bernardo

2018-06-01

Appropriate control of the immune response is a critical determinant of fish health, and the purinergic cascade has an important role in the immune and inflammatory responses. This cascade regulates the levels of adenosine triphosphate (ATP), adenosine diphosphate, adenosine monophosphate and adenosine (Ado), molecules involved in physiological or pathological events as inflammatory and anti-inflammatory mediators. Thus, the aim of this study was to evaluate whether purinergic signaling, through the activities of nucleoside triphosphate diphosphohydrolase (NTPDase), 5'-nucleotidase, and adenosine deaminase (ADA), is capable of modulating the cerebral immune and inflammatory responses in silver catfish that is experimentally infected with Streptococcus agalactiae. Cerebral NTPDase (with ATP as substrate) and 5'-nucleotidase activities increased, while ADA activity decreased in silver catfish that is experimentally infected with S. agalactiae, compared to the control group. Moreover, the cerebral levels of ATP and Ado increased in infected animals compared to the uninfected control group. Brain histopathology in infected animals revealed inflammatory demyelination (the presence of occasional bubbly collections), increased cellular density in the area near to pia-mater and intercellular edema. Based on this evidence, the modulation of the purinergic cascade by the enzymes NTPDase, 5'-nucleotidase, and ADA exerts an anti-inflammatory profile due to the regulation of ATP and Ado levels. This suggests involvement of purinergic enzymes on streptococcosis pathogenesis, through regulating cerebral ATP and Ado levels, molecules known to participate in physiological or pathological events as inflammatory and anti-inflammatory mediators, respectively. In summary, the modulation of the cerebral purinergic cascade exerts an anti-inflammatory profile in an attempt to reduce inflammatory damage.

Wavelength-preserving polarization-insensitive all-optical 3R regenerator based on self- and cross-phase modulation and offset filtering utilizing Raman amplification

NASA Astrophysics Data System (ADS)

Chung, Sung Han

Optical regeneration has the potential to significantly increase the reach of long-haul transmission systems. In this thesis, wavelength-preserving polarization-insensitive all-optical 3R regeneration is investigated and demonstrated for 10 and 40 Gb/s signals. The all-optical regenerator utilizes a self-pulsating laser for clock recovery, cross-phase modulation (XPM) based spectral broadening in a highly nonlinear fiber (HNLF) and offset filtering for retiming, and self-phase modulation based spectral broadening in a HNLF and offset filtering for reshaping. Raman amplification is used to increase the XPM-based spectral broadening and thus allow a design that meets the tradeoffs involved in simultaneously achieving good retiming and reshaping performance. The regenerator is shown to reduce amplitude noise and timing jitter while not causing a BER penalty. To fully validate the regeneration scheme, the cascadability is demonstrated using a recirculating loop. For a 10 Gb/s signal, with a regenerator spacing of 240 km, a return-to-zero, on-off-keyed (RZ-OOK) signal was transmitted over 18,000 km (75 loops) with a power penalty of 1.6 dB at a BER of 10 -9 compared to the back-to-back case. For a 40 Gb/s signal, with a regenerator spacing of 80 km, a RZ-OOK signal was transmitted over 8,000 km (100 loops) with a power penalty of 1.2 dB. In addition, all-optical 3R regeneration is demonstrated using a multimode quantum-dot Fabry Perot laser with ultra-low timing jitter.

Phase-locking of a 2.5 THz quantum cascade laser to a frequency comb using a GaAs photomixer.

PubMed

Ravaro, M; Manquest, C; Sirtori, C; Barbieri, S; Santarelli, G; Blary, K; Lampin, J-F; Khanna, S P; Linfield, E H

2011-10-15

We report the heterodyne detection and phase locking of a 2.5 THz quantum cascade laser (QCL) using a terahertz frequency comb generated in a GaAs photomixer using a femtosecond fiber laser. With 10 mW emitted by the QCL, the phase-locked signal at the intermediate frequency yields 80 dB of signal-to-noise ratio in a bandwidth of 1 Hz.

Optical Wave Turbulence and Wave Condensation in a Nonlinear Optical Experiment

NASA Astrophysics Data System (ADS)

Laurie, Jason; Bortolozzo, Umberto; Nazarenko, Sergey; Residori, Stefania

We present theory, numerical simulations and experimental observations of a 1D optical wave system. We show that this system is of a dual cascade type, namely, the energy cascading directly to small scales, and the photons or wave action cascading to large scales. In the optical context the inverse cascade is particularly interesting because it means the condensation of photons. We show that the cascades are induced by a six-wave resonant interaction process described by weak turbulence theory. We show that by starting with weakly nonlinear randomized waves as an initial condition, there exists an inverse cascade of photons towards the lowest wavenumbers. During the cascade nonlinearity becomes strong at low wavenumbers and, due to the focusing nature of the nonlinearity, it leads to modulational instability resulting in the formation of solitons. Further interaction of the solitons among themselves and with incoherent waves leads to the final condensate state dominated by a single strong soliton. In addition, we show the existence of the direct energy cascade numerically and that it agrees with the wave turbulence prediction.

Quantum critical point underlying the pseudogap state in underdoped cuprate superconductors

NASA Astrophysics Data System (ADS)

Pepin, Catherine

2014-03-01

Cuprate superconductors rank among the most complex materials that are known in the universe. Faced with this complexity, scientists have adopted two types of approaches. In a bottom up approach, one considers that strong correlations occur at a high energy scale of roughly 1 eV upon very strong Coulomb interactions. In the top down approach one considers that one universal singularity at very low temperatures is responsible for complexity of the phase diagram. In this talk we will argue that the strong quantum fluctuations experienced at the proximity to a anti-ferromagnetic Quantum Critical Point (QCP) is responsible for a cascade of phase transitions in the charge and superconducting channels. We will discuss in this context the emergence of the pseudo-gap and charge order modulations. Symmetries and relations to experimental observations will be addressed. Work done in collaboration with K.B. Efetov (Bochum) and H. Meier (Yale).

Cascaded Microinverter PV System for Reduced Cost

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bellus, Daniel R.; Ely, Jeffrey A.

2013-04-29

In this project, a team led by Delphi will develop and demonstrate a novel cascaded photovoltaic (PV) inverter architecture using advanced components. This approach will reduce the cost and improve the performance of medium and large-sized PV systems. The overall project objective is to develop, build, and test a modular 11-level cascaded three-phase inverter building block for photovoltaic applications and to develop and analyze the associated commercialization plan. The system will be designed to utilize photovoltaic panels and will supply power to the electric grid at 208 VAC, 60 Hz 3-phase. With the proposed topology, three inverters, each with anmore » embedded controller, will monitor and control each of the cascade sections, reducing costs associated with extra control boards. This report details the final disposition on this project.« less

High-power, fixed, and tunable wavelength, grating-free cascaded Raman fiber lasers.

PubMed

Balaswamy, V; Arun, S; Aparanji, Santosh; Choudhury, Vishal; Supradeepa, V R

2018-04-01

Cascaded Raman lasers enable high powers at various wavelength bands inaccessible with conventional rare-earth-doped lasers. The input and output wavelengths of conventional implementations are fixed by the constituent fiber gratings necessary for cascaded Raman conversion. We demonstrate here a simple architecture for high-power, fixed, and wavelength tunable, grating-free, cascaded Raman conversion between different wavelength bands. The architecture is based on the recently proposed distributed feedback Raman lasers. Here, we implement a module which converts the ytterbium band to the eye-safe 1.5 μm region. We demonstrate pump-limited output powers of over 30 W in fixed and continuously wavelength tunable configurations.

Simulation of Cascaded Longitudinal-Space-Charge Amplifier at the Fermilab Accelerator Science & Technology (Fast) Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halavanau, A.; Piot, P.

2015-12-01

Cascaded Longitudinal Space Charge Amplifiers (LSCA) have been proposed as a mechanism to generate density modulation over a board spectral range. The scheme has been recently demonstrated in the optical regime and has confirmed the production of broadband optical radiation. In this paper we investigate, via numerical simulations, the performance of a cascaded LSCA beamline at the Fermilab Accelerator Science & Technology (FAST) facility to produce broadband ultraviolet radiation. Our studies are carried out using elegant with included tree-based grid-less space charge algorithm.

Gain and losses in THz quantum cascade laser with metal-metal waveguide.

PubMed

Martl, Michael; Darmo, Juraj; Deutsch, Christoph; Brandstetter, Martin; Andrews, Aaron Maxwell; Klang, Pavel; Strasser, Gottfried; Unterrainer, Karl

2011-01-17

Coupling of broadband terahertz pulses into metal-metal terahertz quantum cascade lasers is presented. Mode matched terahertz transients are generated on the quantum cascade laser facet of subwavelength dimension. This method provides a full overlap of optical mode and active laser medium. A longitudinal optical-phonon depletion based active region design is investigated in a coupled cavity configuration. Modulation experiments reveal spectral gain and (broadband) losses. The observed gain shows high dynamic behavior when switching from loss to gain around threshold and is clamped at total laser losses.

Phase-I monitoring of standard deviations in multistage linear profiles

NASA Astrophysics Data System (ADS)

Kalaei, Mahdiyeh; Soleimani, Paria; Niaki, Seyed Taghi Akhavan; Atashgar, Karim

2018-03-01

In most modern manufacturing systems, products are often the output of some multistage processes. In these processes, the stages are dependent on each other, where the output quality of each stage depends also on the output quality of the previous stages. This property is called the cascade property. Although there are many studies in multistage process monitoring, there are fewer works on profile monitoring in multistage processes, especially on the variability monitoring of a multistage profile in Phase-I for which no research is found in the literature. In this paper, a new methodology is proposed to monitor the standard deviation involved in a simple linear profile designed in Phase I to monitor multistage processes with the cascade property. To this aim, an autoregressive correlation model between the stages is considered first. Then, the effect of the cascade property on the performances of three types of T 2 control charts in Phase I with shifts in standard deviation is investigated. As we show that this effect is significant, a U statistic is next used to remove the cascade effect, based on which the investigated control charts are modified. Simulation studies reveal good performances of the modified control charts.

Cytotoxic Effect of Nano-SiO2 in Human Breast Cancer Cells via Modulation of EGFR Signaling Cascades.

PubMed

Jeon, Donghwan; Kim, Hyungjoo; Nam, Keesoo; Oh, Sunhwa; Son, Seog-Ho; Shin, Incheol

2017-11-01

Silica nanoparticles (nano-SiO 2 ) are widely used in many industrial areas and there is much controversy surrounding cytotoxic effects of such nanoparticles. In order to determine the toxicity and possible molecular mechanisms involved, we conducted several tests with two breast cancer cell lines, MDA-MB-231 and Hs578T. After exposure to nano-SiO 2 , growth, apoptosis, motility of breast cancer cells were monitored. In addition, modulation of signal transduction induced by nano-SiO 2 was detected through western blot analysis. Treatment of nano-SiO 2 repressed the growth of breast cancer cell lines. It also increased apoptosis and reduced cell motility. Moreover, exposure to nano-SiO 2 significantly disturbed the dimerization of epidermal growth factor receptor (EGFR), followed by down-regulation of its downstream cellular sarcoma kinase (c-SRC) and signal transducer and activator of transcription 3 (STAT3) signaling cascades. Nano-SiO 2 has a cytotoxic effect on MDA-MB-231 and Hs578T breast cancer cells via modulation of EGFR signaling cascades. Copyright© 2017, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.

Fragmentation of displacement cascades into subcascades: A molecular dynamics study

DOE PAGES

Antoshchenkova, E.; Luneville, L.; Simeone, D.; ...

2014-12-12

The fragmentation of displacement cascades into subcascades in copper and iron has been investigated through the molecular dynamics technique. A two-point density correlation function has been used to analyze the cascades as a function of the primary knock-on (PKA) energy. This approach is used as a tool for detecting subcascade formation. The fragmentation can already be identified at the end of the ballistic phase. Its resulting evolution in the peak damage state discriminates between unconnected and connected subcascades. The damage zone at the end of the ballistic phase is the precursor of the extended regions that contain the surviving defects.more » A fractal analysis of the cascade exhibits a dependence on both the stage of the cascade development and the PKA energy. This type of analysis enables the minimum and maximum displacement spike energies together with the subcascade formation threshold energy to be determined. (C) 2014 Elsevier B.V. All rights reserved.« less

Fragmentation of displacement cascades into subcascades: A molecular dynamics study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Antoshchenkova, E.; Luneville, L.; Simeone, D.

The fragmentation of displacement cascades into subcascades in copper and iron has been investigated through the molecular dynamics technique. A two-point density correlation function has been used to analyze the cascades as a function of the primary knock-on (PKA) energy. This approach is used as a tool for detecting subcascade formation. The fragmentation can already be identified at the end of the ballistic phase. Its resulting evolution in the peak damage state discriminates between unconnected and connected subcascades. The damage zone at the end of the ballistic phase is the precursor of the extended regions that contain the surviving defects.more » A fractal analysis of the cascade exhibits a dependence on both the stage of the cascade development and the PKA energy. This type of analysis enables the minimum and maximum displacement spike energies together with the subcascade formation threshold energy to be determined. (C) 2014 Elsevier B.V. All rights reserved.« less

Mitogen-activated protein kinase cascades in signaling plant growth and development.

PubMed

Xu, Juan; Zhang, Shuqun

2015-01-01

Mitogen-activated protein kinase (MAPK) cascades are ubiquitous signaling modules in eukaryotes. Early research of plant MAPKs has been focused on their functions in immunity and stress responses. Recent studies reveal that they also play essential roles in plant growth and development downstream of receptor-like protein kinases (RLKs). With only a limited number of MAPK components, multiple functional pathways initiated from different receptors often share the same MAPK components or even a complete MAPK cascade. In this review, we discuss how MAPK cascades function as molecular switches in response to spatiotemporal-specific ligand-receptor interactions and the availability of downstream substrates. In addition, we discuss other possible mechanisms governing the functional specificity of plant MAPK cascades, a question central to our understanding of MAPK functions. Copyright © 2014 Elsevier Ltd. All rights reserved.

The importance of sensory integration processes for action cascading

PubMed Central

Gohil, Krutika; Stock, Ann-Kathrin; Beste, Christian

2015-01-01

Dual tasking or action cascading is essential in everyday life and often investigated using tasks presenting stimuli in different sensory modalities. Findings obtained with multimodal tasks are often broadly generalized, but until today, it has remained unclear whether multimodal integration affects performance in action cascading or the underlying neurophysiology. To bridge this gap, we asked healthy young adults to complete a stop-change paradigm which presented different stimuli in either one or two modalities while recording behavioral and neurophysiological data. Bimodal stimulus presentation prolonged response times and affected bottom-up and top-down guided attentional processes as reflected by the P1 and N1, respectively. However, the most important effect was the modulation of response selection processes reflected by the P3 suggesting that a potentially different way of forming task goals operates during action cascading in bimodal vs. unimodal tasks. When two modalities are involved, separate task goals need to be formed while a conjoint task goal may be generated when all stimuli are presented in the same modality. On a systems level, these processes seem to be related to the modulation of activity in fronto-polar regions (BA10) as well as Broca's area (BA44). PMID:25820681

Simulation studies of a XUV/soft X-ray harmonic-cascade FEL for the proposed LBNL recirculating linac*

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fawley, W.M.; Barletta, W.A.; Corlett, J.N.

Presently there is significant interest at LBNL in designing and building a facility for ultrafast (i.e. femtosecond time scale) x-ray science based upon a superconducting, recirculating RF linac (see Corlett et al. for more details). In addition to producing synchrotron radiation pulses in the 1-15 keV energy range, we are also considering adding one or more free-electron laser (FEL) beamlines using a harmonic cascade approach to produce coherent XUV soft X-ray emission beginning with a strong input seed at {approx}200 nm wavelength obtained from a ''conventional'' laser. Each cascade is composed of a radiator together with a modulator section, separatedmore » by a magnetic chicane. The chicane temporally delays the electron beam pulse in order that a ''virgin'' pulse region (with undegraded energy spread) be brought into synchronism with the radiation pulse, which together then undergo FEL action in the modulator. We present various results obtained with the GINGER simulation code examining final output sensitivity to initial electron beam parameters. We also discuss the effects of spontaneous emission and shot noise upon this particular cascade approach which can limit the final output coherence.« less

Gigabit free-space multi-level signal transmission with a mid-infrared quantum cascade laser operating at room temperature.

PubMed

Pang, Xiaodan; Ozolins, Oskars; Schatz, Richard; Storck, Joakim; Udalcovs, Aleksejs; Navarro, Jaime Rodrigo; Kakkar, Aditya; Maisons, Gregory; Carras, Mathieu; Jacobsen, Gunnar; Popov, Sergei; Lourdudoss, Sebastian

2017-09-15

Gigabit free-space transmissions are experimentally demonstrated with a quantum cascaded laser (QCL) emitting at mid-wavelength infrared of 4.65 μm, and a commercial infrared photovoltaic detector. The QCL operating at room temperature is directly modulated using on-off keying and, for the first time, to the best of our knowledge, four- and eight-level pulse amplitude modulations (PAM-4, PAM-8). By applying pre- and post-digital equalizations, we achieve up to 3  Gbit/s line data rate in all three modulation configurations with a bit error rate performance of below the 7% overhead hard decision forward error correction limit of 3.8×10 -3 . The proposed transmission link also shows a stable operational performance in the lab environment.

Opiates Modulate Noxious Chemical Nociception through a Complex Monoaminergic/Peptidergic Cascade

PubMed Central

Mills, Holly; Ortega, Amanda; Law, Wenjing; Hapiak, Vera; Summers, Philip; Clark, Tobias

2016-01-01

The ability to detect noxious stimuli, process the nociceptive signal, and elicit an appropriate behavioral response is essential for survival. In Caenorhabditis elegans, opioid receptor agonists, such as morphine, mimic serotonin, and suppress the overall withdrawal from noxious stimuli through a pathway requiring the opioid-like receptor, NPR-17. This serotonin- or morphine-dependent modulation can be rescued in npr-17-null animals by the expression of npr-17 or a human κ opioid receptor in the two ASI sensory neurons, with ASI opioid signaling selectively inhibiting ASI neuropeptide release. Serotonergic modulation requires peptides encoded by both nlp-3 and nlp-24, and either nlp-3 or nlp-24 overexpression mimics morphine and suppresses withdrawal. Peptides encoded by nlp-3 act differentially, with only NLP-3.3 mimicking morphine, whereas other nlp-3 peptides antagonize NLP-3.3 modulation. Together, these results demonstrate that opiates modulate nociception in Caenorhabditis elegans through a complex monoaminergic/peptidergic cascade, and suggest that this model may be useful for dissecting opiate signaling in mammals. SIGNIFICANCE STATEMENT Opiates are used extensively to treat chronic pain. In Caenorhabditis elegans, opioid receptor agonists suppress the overall withdrawal from noxious chemical stimuli through a pathway requiring an opioid-like receptor and two distinct neuropeptide-encoding genes, with individual peptides from the same gene functioning antagonistically to modulate nociception. Endogenous opioid signaling functions as part of a complex, monoaminergic/peptidergic signaling cascade and appears to selectively inhibit neuropeptide release, mediated by a α-adrenergic-like receptor, from two sensory neurons. Importantly, receptor null animals can be rescued by the expression of the human κ opioid receptor, and injection of human opioid receptor ligands mimics exogenous opiates, highlighting the utility of this model for dissecting opiate signaling in mammals. PMID:27194330

Phase locking of 2.324 and 2.959 terahertz quantum cascade lasers using a Schottky diode harmonic mixer.

PubMed

Danylov, Andriy; Erickson, Neal; Light, Alexander; Waldman, Jerry

2015-11-01

The 23rd and 31st harmonics of a microwave signal generated in a novel THz balanced Schottky diode mixer were used as a frequency stable reference source to phase lock solid-nitrogen-cooled 2.324 and 2.959 THz quantum cascade lasers. Hertz-level frequency stability was achieved, which was maintained for several hours.

Experimental investigation of polarization insensitivity and cascadability with semiconductor optical amplifier-based differential phase-shift keyed wavelength converter

NASA Astrophysics Data System (ADS)

Mao, Yaya; Wu, Chongqing; Liu, Bo; Ullah, Rahat; Tian, Feng

2017-12-01

We experimentally investigate the polarization insensitivity and cascadability of an all-optical wavelength converter for differential phase-shift keyed (DPSK) signals for the first time. The proposed wavelength converter is composed of a one-bit delay interferometer demodulation stage followed by a single semiconductor optical amplifier. The impact of input DPSK signal polarization fluctuation on receiver sensitivity for the converted signal is carried out. It is found that this scheme is almost insensitive to the state of polarization of the input DPSK signal. Furthermore, the cascadability of the converter is demonstrated in a two-path recirculating loop. Error-free transmission is achieved with 20 stage cascaded wavelength conversions over 2800 km, where the power penalty is <3.4 dB at bit error rate of 10-9.

Cascaded Amplitude Modulations in Sound Texture Perception

PubMed Central

McWalter, Richard; Dau, Torsten

2017-01-01

Sound textures, such as crackling fire or chirping crickets, represent a broad class of sounds defined by their homogeneous temporal structure. It has been suggested that the perception of texture is mediated by time-averaged summary statistics measured from early auditory representations. In this study, we investigated the perception of sound textures that contain rhythmic structure, specifically second-order amplitude modulations that arise from the interaction of different modulation rates, previously described as “beating” in the envelope-frequency domain. We developed an auditory texture model that utilizes a cascade of modulation filterbanks that capture the structure of simple rhythmic patterns. The model was examined in a series of psychophysical listening experiments using synthetic sound textures—stimuli generated using time-averaged statistics measured from real-world textures. In a texture identification task, our results indicated that second-order amplitude modulation sensitivity enhanced recognition. Next, we examined the contribution of the second-order modulation analysis in a preference task, where the proposed auditory texture model was preferred over a range of model deviants that lacked second-order modulation rate sensitivity. Lastly, the discriminability of textures that included second-order amplitude modulations appeared to be perceived using a time-averaging process. Overall, our results demonstrate that the inclusion of second-order modulation analysis generates improvements in the perceived quality of synthetic textures compared to the first-order modulation analysis considered in previous approaches. PMID:28955191

Cascaded Amplitude Modulations in Sound Texture Perception.

PubMed

McWalter, Richard; Dau, Torsten

2017-01-01

Sound textures, such as crackling fire or chirping crickets, represent a broad class of sounds defined by their homogeneous temporal structure. It has been suggested that the perception of texture is mediated by time-averaged summary statistics measured from early auditory representations. In this study, we investigated the perception of sound textures that contain rhythmic structure, specifically second-order amplitude modulations that arise from the interaction of different modulation rates, previously described as "beating" in the envelope-frequency domain. We developed an auditory texture model that utilizes a cascade of modulation filterbanks that capture the structure of simple rhythmic patterns. The model was examined in a series of psychophysical listening experiments using synthetic sound textures-stimuli generated using time-averaged statistics measured from real-world textures. In a texture identification task, our results indicated that second-order amplitude modulation sensitivity enhanced recognition. Next, we examined the contribution of the second-order modulation analysis in a preference task, where the proposed auditory texture model was preferred over a range of model deviants that lacked second-order modulation rate sensitivity. Lastly, the discriminability of textures that included second-order amplitude modulations appeared to be perceived using a time-averaging process. Overall, our results demonstrate that the inclusion of second-order modulation analysis generates improvements in the perceived quality of synthetic textures compared to the first-order modulation analysis considered in previous approaches.

The effects of self-interstitial clusters on cascade defect evolution beyond the primary damage state

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heinisch, H.L.

1997-04-01

The intracascade evolution of the defect distributions of cascades in copper is investigated using stochastic annealing simulations applied to cascades generated with molecular dynamics (MD). The temperature and energy dependencies of annihilation, clustering and free defect production are determined for individual cascades. The annealing simulation results illustrate the strong influence on intracascade evolution of the defect configuration existing in the primary damage state. Another factor significantly affecting the evolution of the defect distribution is the rapid one-dimensional diffusion of small, glissile interstitial loops produced directly in cascades. This phenomenon introduces a cascade energy dependence of defect evolution that is apparentmore » only beyond the primary damage state, amplifying the need for further study of the annealing phase of cascade evolution and for performing many more MD cascade simulations at higher energies.« less

Frequency Stabilization of a Single Mode Terahertz Quantum Cascade Laser to the Kilohertz Level

DTIC Science & Technology

2009-04-27

analog locking circuit was shown to stabilize the beat signal between a 2.408 THz quantum cascade laser and a CH2DOH THz CO2 optically pumped...codes: (140.5965) Semiconductor lasers , quantum cascade; (140.3425) Laser stabilization; (300.3700) Linewidth; (040.2840) Heterodyne . References...Reno, “Frequency and phase - lock control of a 3 THz quantum cascade laser ,” Opt. Lett. 30, 1837-1839 (2005). 10. D. Rabanus, U. U. Graf, M. Philipp

6.2-GHz modulated terahertz light detection using fast terahertz quantum well photodetectors.

PubMed

Li, Hua; Wan, Wen-Jian; Tan, Zhi-Yong; Fu, Zhang-Long; Wang, Hai-Xia; Zhou, Tao; Li, Zi-Ping; Wang, Chang; Guo, Xu-Guang; Cao, Jun-Cheng

2017-06-14

The fast detection of terahertz radiation is of great importance for various applications such as fast imaging, high speed communications, and spectroscopy. Most commercial products capable of sensitively responding the terahertz radiation are thermal detectors, i.e., pyroelectric sensors and bolometers. This class of terahertz detectors is normally characterized by low modulation frequency (dozens or hundreds of Hz). Here we demonstrate the first fast semiconductor-based terahertz quantum well photodetectors by carefully designing the device structure and microwave transmission line for high frequency signal extraction. Modulation response bandwidth of gigahertz level is obtained. As an example, the 6.2-GHz modulated terahertz light emitted from a Fabry-Pérot terahertz quantum cascade laser is successfully detected using the fast terahertz quantum well photodetector. In addition to the fast terahertz detection, the technique presented in this work can also be used for optically characterizing the frequency stability of terahertz quantum cascade lasers, heterodyne detections and photomixing applications.

Modulation of learning and memory by cytokines: signaling mechanisms and long term consequences.

PubMed

Donzis, Elissa J; Tronson, Natalie C

2014-11-01

This review describes the role of cytokines and their downstream signaling cascades on the modulation of learning and memory. Immune proteins are required for many key neural processes and dysregulation of these functions by systemic inflammation can result in impairments of memory that persist long after the resolution of inflammation. Recent research has demonstrated that manipulations of individual cytokines can modulate learning, memory, and synaptic plasticity. The many conflicting findings, however, have prevented a clear understanding of the precise role of cytokines in memory. Given the complexity of inflammatory signaling, understanding its modulatory role requires a shift in focus from single cytokines to a network of cytokine interactions and elucidation of the cytokine-dependent intracellular signaling cascades. Finally, we propose that whereas signal transduction and transcription may mediate short-term modulation of memory, long-lasting cellular and molecular mechanisms such as epigenetic modifications and altered neurogenesis may be required for the long lasting impact of inflammation on memory and cognition. Copyright © 2014 Elsevier Inc. All rights reserved.

Digital redesign of anti-wind-up controller for cascaded analog system.

PubMed

Chen, Y S; Tsai, J S H; Shieh, L S; Moussighi, M M

2003-01-01

The cascaded conventional anti-wind-up (CAW) design method for integral controller is discussed. Then, the prediction-based digital redesign methodology is utilized to find the new pulse amplitude modulated (PAM) digital controller for effective digital control of the analog plant with input saturation constraint. The desired digital controller is determined from existing or pre-designed CAW analog controller. The proposed method provides a novel methodology for indirect digital design of a continuous-time unity output-feedback system with a cascaded analog controller as in the case of PID controllers for industrial control processes with the presence of actuator saturations. It enables us to implement an existing or pre-designed cascaded CAW analog controller via a digital controller effectively.

One-Pot Evolution of Ageladine A through a Bio-Inspired Cascade towards Selective Modulators of Neuronal Differentiation.

PubMed

Iwata, Takayuki; Otsuka, Satoshi; Tsubokura, Kazuki; Kurbangalieva, Almira; Arai, Daisuke; Fukase, Koichi; Nakao, Yoichi; Tanaka, Katsunori

2016-10-04

A bio-inspired cascade reaction has been developed for the construction of the marine natural product ageladine A and a de novo array of its N1-substituted derivatives. This cascade features a 2-aminoimidazole formation that is modeled after an arginine post-translational modification and an aza-electrocyclization. It can be effectively carried out in a one-pot procedure from simple anilines or guanidines, leading to structural analogues of ageladine A that had been otherwise synthetically inaccessible. We found that some compounds out of this structurally novel library show a significant activity in modulating the neural differentiation. Namely, these compounds selectively activate or inhibit the differentiation of neural stem cells to neurons, while being negligible in the differentiation to astrocytes. This study represents a successful case in which the native biofunction of a natural product could be altered by structural modifications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microwave assisted reconstruction of optical interferograms for distributed fiber optic sensing.

PubMed

Huang, Jie; Hua, Lei; Lan, Xinwei; Wei, Tao; Xiao, Hai

2013-07-29

This paper reports a distributed fiber optic sensing technique through microwave assisted separation and reconstruction of optical interferograms in spectrum domain. The approach involves sending a microwave-modulated optical signal through cascaded fiber optic interferometers. The microwave signal was used to resolve the position and reflectivity of each sensor along the optical fiber. By sweeping the optical wavelength and detecting the modulation signal, the optical spectrum of each sensor can be reconstructed. Three cascaded fiber optic extrinsic Fabry-Perot interferometric sensors were used to prove the concept. Their microwave-reconstructed interferogram matched well with those recorded individually using an optical spectrum analyzer. The application in distributed strain measurement has also been demonstrated.

Pulse sequences for efficient multi-cycle terahertz generation in periodically poled lithium niobate.

PubMed

Ravi, Koustuban; Schimpf, Damian N; Kärtner, Franz X

2016-10-31

The use of laser pulse sequences to drive the cascaded difference frequency generation of high energy, high peak-power and multi-cycle terahertz pulses in cryogenically cooled (100 K) periodically poled Lithium Niobate is proposed and studied. Detailed simulations considering the coupled nonlinear interaction of terahertz and optical waves (or pump depletion), show that unprecedented optical-to-terahertz energy conversion efficiencies > 5%, peak electric fields of hundred(s) of mega volts/meter at terahertz pulse durations of hundred(s) of picoseconds can be achieved. The proposed methods are shown to circumvent laser induced damage limitations at Joule-level pumping by 1µm lasers to enable multi-cycle terahertz sources with pulse energies > 10 milli-joules. Various pulse sequence formats are proposed and analyzed. Numerical calculations for periodically poled structures accounting for cascaded difference frequency generation, self-phase-modulation, cascaded second harmonic generation and laser induced damage are introduced. The physics governing terahertz generation using pulse sequences in this high conversion efficiency regime, limitations and practical considerations are discussed. It is shown that varying the poling period along the crystal length and further reduction of absorption can lead to even higher energy conversion efficiencies >10%. In addition to numerical calculations, an analytic formulation valid for arbitrary pulse formats and closed-form expressions for important cases are presented. Parameters optimizing conversion efficiency in the 0.1-1 THz range, the corresponding peak electric fields, crystal lengths and terahertz pulse properties are furnished.

Unsteady aerodynamics of an oscillating cascade in a compressible flow field

NASA Technical Reports Server (NTRS)

Buffum, Daniel H.; Boldman, Donald R.; Fleeter, Sanford

1987-01-01

Fundamental experiments were performed in the NASA Lewis Transonic Oscillating Cascade Facility to investigate and quantify the unsteady aerodynamics of a cascade of biconvex airfoils executing torsion-mode oscillations at realistic reduced frequencies. Flush-mounted, high-response miniature pressure transducers were used to measure the unsteady airfoil surface pressures. The pressures were measured for three interblade phase angles at two inlet Mach numbers, 0.65 and 0.80, and two incidence angles, 0 and 7 deg. The time-variant pressures were analyzed by means of discrete Fourier transform techniques, and these unique data were then compared with predictions from a linearized unsteady cascade model. The experimental results indicate that the interblade phase angle had a major effect on the chordwise distributions of the airfoil surface unsteady pressure, and that reduced frequency, incidence angle, and Mach number had a somewhat less significant effect.

Simulation of a cascaded longitudinal space charge amplifier for coherent radiation generation

DOE PAGES

Halavanau, A.; Piot, P.

2016-03-03

Longitudinal space charge (LSC) effects are generally considered as harmful in free-electron lasers as they can seed unfavorable energy modulations that can result in density modulations with associated emittance dilution. It was pointed out, however, that such \\micro-bunching instabilities" could be potentially useful to support the generation of broadband coherent radiation. Therefore there has been an increasing interest in devising accelerator beam lines capable of controlling LSC induced density modulations. In the present paper we augment these previous investigations by combining a grid-less space charge algorithm with the popular particle-tracking program elegant. This high-fidelity model of the space charge ismore » used to benchmark conventional LSC models. We then employ the developed model to optimize the performance of a cascaded longitudinal space charge amplifier using beam parameters comparable to the ones achievable at Fermilab Accelerator Science & Technology (FAST) facility currently under commissioning at Fermilab.« less

Dual quantum cascade laser-based sensor for simultaneous NO and NO2 detection using a wavelength modulation-division multiplexing technique

NASA Astrophysics Data System (ADS)

Yu, Yajun; Sanchez, Nancy P.; Yi, Fan; Zheng, Chuantao; Ye, Weilin; Wu, Hongpeng; Griffin, Robert J.; Tittel, Frank K.

2017-05-01

A sensor system capable of simultaneous measurements of NO and NO2 was developed using a wavelength modulation-division multiplexing (WMDM) scheme and multi-pass absorption spectroscopy. A continuous wave (CW), distributed-feedback (DFB) quantum cascade laser (QCL) and a CW external-cavity (EC) QCL were employed for targeting a NO absorption doublet at 1900.075 cm-1 and a NO2 absorption line at 1630.33 cm-1, respectively. Simultaneous detection was realized by modulating both QCLs independently at different frequencies and demodulating the detector signals with LabView-programmed lock-in amplifiers. The sensor operated at a reduced pressure of 40 Torr and a data sampling rate of 1 Hz. An Allan-Werle deviation analysis indicated that the minimum detection limits of NO and NO2 can reach sub-ppbv concentration levels with averaging times of 100 and 200 s, respectively.

Modulation transfer function cascade model for a sampled IR imaging system.

PubMed

de Luca, L; Cardone, G

1991-05-01

The performance of the infrared scanning radiometer (IRSR) is strongly stressed in convective heat transfer applications where high spatial frequencies in the signal that describes the thermal image are present. The need to characterize more deeply the system spatial resolution has led to the formulation of a cascade model for the evaluation of the actual modulation transfer function of a sampled IR imaging system. The model can yield both the aliasing band and the averaged modulation response for a general sampling subsystem. For a line scan imaging system, which is the case of a typical IRSR, a rule of thumb that states whether the combined sampling-imaging system is either imaging-dependent or sampling-dependent is proposed. The model is tested by comparing it with other noncascade models as well as by ad hoc measurements performed on a commercial digitized IRSR.

Active polarisation control of a quantum cascade laser using tuneable birefringence in waveguides.

PubMed

Dhirhe, D; Slight, T J; Holmes, B M; Ironside, C N

2013-10-07

We discuss the design, modelling, fabrication and characterisation of an integrated tuneable birefringent waveguide for quantum cascade lasers. We have fabricated quantum cascade lasers operating at wavelengths around 4450 nm that include polarisation mode converters and a differential phase shift section. We employed below laser threshold electroluminescence to investigate the single pass operation of the integrated device. We use a theory based on the electro-optic properties of birefringence in quantum cascade laser waveguides combined with a Jones matrix based description to gain an understanding of the electroluminescence results. With the quantum cascade lasers operating above threshold we demonstrated polarisation control of the output.

A Memory-Based Programmable Logic Device Using Look-Up Table Cascade with Synchronous Static Random Access Memories

NASA Astrophysics Data System (ADS)

Nakamura, Kazuyuki; Sasao, Tsutomu; Matsuura, Munehiro; Tanaka, Katsumasa; Yoshizumi, Kenichi; Nakahara, Hiroki; Iguchi, Yukihiro

2006-04-01

A large-scale memory-technology-based programmable logic device (PLD) using a look-up table (LUT) cascade is developed in the 0.35-μm standard complementary metal oxide semiconductor (CMOS) logic process. Eight 64 K-bit synchronous SRAMs are connected to form an LUT cascade with a few additional circuits. The features of the LUT cascade include: 1) a flexible cascade connection structure, 2) multi phase pseudo asynchronous operations with synchronous static random access memory (SRAM) cores, and 3) LUT-bypass redundancy. This chip operates at 33 MHz in 8-LUT cascades at 122 mW. Benchmark results show that it achieves a comparable performance to field programmable gate array (FPGAs).

Phase-locked, high power, mid-infrared quantum cascade laser arrays

NASA Astrophysics Data System (ADS)

Zhou, W.; Slivken, S.; Razeghi, M.

2018-04-01

We demonstrate phase-locked, high power quantum cascade laser arrays, which are combined using a monolithic, tree array multimode interferometer, with emission wavelengths around 4.8 μm. A maximum output power of 15 W was achieved from an eight-element laser array, which has only a slightly higher threshold current density and a similar slope efficiency compared to a Fabry-Perot laser of the same length. Calculated multimode interferometer splitting loss is on the order of 0.27 dB for the in-phase supermode. In-phase supermode operation with nearly ideal behavior is demonstrated over the working current range of the array.

Controlling light by light with an optical event horizon.

PubMed

Demircan, A; Amiranashvili, Sh; Steinmeyer, G

2011-04-22

A novel concept for an all-optical transistor is proposed and verified numerically. This concept relies on cross-phase modulation between a signal and a control pulse. Other than previous approaches, the interaction length is extended by temporally locking control and the signal pulse in an optical event horizon, enabling continuous modification of the central wavelength, energy, and duration of a signal pulse by an up to sevenfold weaker control pulse. Moreover, if the signal pulse is a soliton it may maintain its solitonic properties during the switching process. The proposed all-optical switching concept fulfills all criteria for a useful optical transistor in [Nat. Photon. 4, 3 (2010)], in particular, fan-out and cascadability, which have previously proven as the most difficult to meet.

Comparison of Theoretical and Experimental Unsteady Aerodynamics of Linear Oscillating Cascade With Supersonic Leading-Edge Locus

NASA Technical Reports Server (NTRS)

Ramsey, John K.; Erwin, Dan

2004-01-01

An experimental influence coefficient technique was used to obtain unsteady aerodynamic influence coefficients and, consequently, unsteady pressures for a cascade of symmetric airfoils oscillating in pitch about mid-chord. Stagger angles of 0 deg and 10 deg were investigated for a cascade with a gap-to-chord ratio of 0.417 operating at an axial Mach number of 1.9, resulting in a supersonic leading-edge locus. Reduced frequencies ranged from 0.056 to 0.2. The influence coefficients obtained determine the unsteady pressures for any interblade phase angle. The unsteady pressures were compared with those predicted by several algorithms for interblade phase angles of 0 deg and 180 deg.

Cascading failures mechanism based on betweenness-degree ratio distribution with different connecting preferences

NASA Astrophysics Data System (ADS)

Wang, Xiao Juan; Guo, Shi Ze; Jin, Lei; Chen, Mo

We study the structural robustness of the scale free network against the cascading failure induced by overload. In this paper, a failure mechanism based on betweenness-degree ratio distribution is proposed. In the cascading failure model we built the initial load of an edge which is proportional to the node betweenness of its ends. During the edge random deletion, we find a phase transition. Then based on the phase transition, we divide the process of the cascading failure into two parts: the robust area and the vulnerable area, and define the corresponding indicator to measure the performance of the networks in both areas. From derivation, we find that the vulnerability of the network is determined by the distribution of betweenness-degree ratio. After that we use the connection between the node ability coefficient and distribution of betweenness-degree ratio to explain the cascading failure mechanism. In simulations, we verify the correctness of our derivations. By changing connecting preferences, we find scale free networks with a slight assortativity, which performs better both in robust area and vulnerable area.

Aerodynamics of a linear oscillating cascade

NASA Technical Reports Server (NTRS)

Buffum, Daniel H.; Fleeter, Sanford

1990-01-01

The steady and unsteady aerodynamics of a linear oscillating cascade are investigated using experimental and computational methods. Experiments are performed to quantify the torsion mode oscillating cascade aerodynamics of the NASA Lewis Transonic Oscillating Cascade for subsonic inlet flowfields using two methods: simultaneous oscillation of all the cascaded airfoils at various values of interblade phase angle, and the unsteady aerodynamic influence coefficient technique. Analysis of these data and correlation with classical linearized unsteady aerodynamic analysis predictions indicate that the wind tunnel walls enclosing the cascade have, in some cases, a detrimental effect on the cascade unsteady aerodynamics. An Euler code for oscillating cascade aerodynamics is modified to incorporate improved upstream and downstream boundary conditions and also the unsteady aerodynamic influence coefficient technique. The new boundary conditions are shown to improve the unsteady aerodynamic influence coefficient technique. The new boundary conditions are shown to improve the unsteady aerodynamic predictions of the code, and the computational unsteady aerodynamic influence coefficient technique is shown to be a viable alternative for calculation of oscillating cascade aerodynamics.

Novel monolithic integration scheme for high-speed electroabsorption modulators and semiconductor optical amplifiers using cascaded structure.

PubMed

Lin, Fang-Zheng; Wu, Tsu-Hsiu; Chiu, Yi-Jen

2009-06-08

A new monolithic integration scheme, namely cascaded-integration (CI), for improving high-speed optical modulation is proposed and demonstrated. High-speed electroabsorption modulators (EAMs) and semiconductor optical amplifiers (SOAs) are taken as the integrated elements of CI. This structure is based on an optical waveguide defined by cascading segmented EAMs with segmented SOAs, while high-impedance transmission lines (HITLs) are used for periodically interconnecting EAMs, forming a distributive optical re-amplification and re-modulation. Therefore, not only the optical modulation can be beneficial from SOA gain, but also high electrical reflection due to EAM low characteristic impedance can be greatly reduced. Two integration schemes, CI and conventional single-section (SS), with same total EAM- and SOA- lengths are fabricated and compared to examine the concept. Same modulation-depth against with EAM bias (up to 5V) as well as SOA injection current (up to 60mA) is found in both structures. In comparison with SS, a < 1dB extra optical-propagation loss in CI is measured due to multi-sections of electrical-isolation regions between EAMs and SOAs, suggesting no significant deterioration in CI on DC optical modulation efficiency. Lower than -12dB of electrical reflection from D.C. to 30GHz is observed in CI, better than -5dB reflection in SS for frequency of above 5GHz. Superior high-speed electrical properties in CI structure can thus lead to higher speed of electrical-to-optical (EO) response, where -3dB bandwidths are >30GHz and 13GHz for CI and SS respectively. Simulation results on electrical and EO response are quite consistent with measurement, confirming that CI can lower the driving power at high-speed regime, while the optical loss is still kept the same level. Taking such distributive advantage (CI) with optical gain, not only higher-speed modulation with high output optical power can be attained, but also the trade-off issue due to impedance mismatch can be released to reduce the driving power of modulator. Such kind of monolithic integration scheme also has potential for the applications of other high-speed optoelectronics devices.

Nonlinear tunneling of optical soliton in 3 coupled NLS equation with symbolic computation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mani Rajan, M.S., E-mail: senthilmanirajanofc@gmail.com; Mahalingam, A.; Uthayakumar, A.

We investigated the soliton solution for N coupled nonlinear Schrödinger (CNLS) equations. These equations are coupled due to the cross-phase-modulation (CPM). Lax pair of this system is obtained via the Ablowitz–Kaup–Newell–Segur (AKNS) scheme and the corresponding Darboux transformation is constructed to derive the soliton solution. One and two soliton solutions are generated. Using two soliton solutions of 3 CNLS equation, nonlinear tunneling of soliton for both with and without exponential background has been discussed. Finally cascade compression of optical soliton through multi-nonlinear barrier has been discussed. The obtained results may have promising applications in all-optical devices based on optical solitons,more » study of soliton propagation in birefringence fiber systems and optical soliton with distributed dispersion and nonlinearity management. -- Highlights: •We consider the nonlinear tunneling of soliton in birefringence fiber. •3-coupled NLS (CNLS) equation with variable coefficients is considered. •Two soliton solutions are obtained via Darboux transformation using constructed Lax pair. •Soliton tunneling through dispersion barrier and well are investigated. •Finally, cascade compression of soliton has been achieved.« less

Dynamics of a broad-band quantum cascade laser: from chaos to coherent dynamics and mode-locking.

PubMed

Columbo, L L; Barbieri, S; Sirtori, C; Brambilla, M

2018-02-05

The dynamics of a multimode quantum cascade laser, are studied in a model based on effective semiconductor Maxwell-Bloch equations, encompassing key features for the radiation-medium interaction such as an asymmetric frequency dependent gain and refractive index as well as the phase-amplitude coupling provided by the linewidth enhancement factor. By considering its role and that of the free spectral range, we find the conditions in which the traveling wave emitted by the laser at the threshold can be destabilized by adjacent modes, thus leading the laser emission towards chaotic or regular multimode dynamics. In the latter case our simulations show that the field oscillations are associated to self-confined structures which travel along the laser cavity, bridging mode-locking and solitary wave propagation. In addition, we show how a RF modulation of the bias current leads to active mode-locking yielding high-contrast, picosecond pulses. Our results compare well with recent experiments on broad-band THz-QCLs and may help in the understanding of the conditions for the generation of ultrashort pulses and comb operation in mid-IR and THz spectral regions.

Developmental emergence of different forms of neuromodulation in Aplysia sensory neurons.

PubMed

Marcus, E A; Carew, T J

1998-04-14

The capacity for neuromodulation and biophysical plasticity is a defining feature of most mature neuronal cell types. In several cases, modulation at the level of the individual neuron has been causally linked to changes in the functional output of a neuronal circuit and subsequent adaptive changes in the organism's behavioral responses. Understanding how such capacity for neuromodulation develops therefore may provide insights into the mechanisms both of neuronal development and learning and memory. We have examined the development of multiple forms of neuromodulation triggered by a common neurotransmitter, serotonin, in the pleural sensory neurons of Aplysia californica. We have found that multiple signaling cascades within a single neuron develop sequentially, with some being expressed only very late in development. In addition, our data suggest a model in which, within a single neuromodulatory pathway, the elements of the signaling cascade are developmentally expressed in a "retrograde" manner with the ionic channel that is modulated appearing early in development, functional elements in the second messenger cascade appearing later, and finally, coupling of the second messenger cascade to the serotonin receptor appearing quite late. These studies provide the characterization of the development of neuromodulation at the level of an identified cell type and offer insights into the potential roles of neuromodulatory processes in development and adult plasticity.

Thermal management of quantum cascade lasers in an individually addressable monolithic array architecture

NASA Astrophysics Data System (ADS)

Missaggia, Leo; Wang, Christine; Connors, Michael; Saar, Brian; Sanchez-Rubio, Antonio; Creedon, Kevin; Turner, George; Herzog, William

2016-03-01

There are a number of military and commercial applications for high-power laser systems in the mid-to-long-infrared wavelength range. By virtue of their demonstrated watt-level performance and wavelength diversity, quantum cascade laser (QCL) and amplifier devices are an excellent choice of emitter for those applications. To realize the power levels of interest, beam combining of arrays of these emitters is required and as a result, array technology must be developed. With this in mind, packaging and thermal management strategies were developed to facilitate the demonstration of a monolithic QCL array operating under CW conditions. Thermal models were constructed and simulations performed to determine the effect of parameters such as array-element ridge width and pitch on gain region temperature rise. The results of the simulations were considered in determining an appropriate QCL array configuration. State-of-the-art micro-impingement cooling along with an electrical distribution scheme comprised of AlN multi-layer technology were integrated into the design. The design of the module allows for individual electrical addressability of the array elements, a method of phase control demonstrated previously for coherent beam combining of diode arrays, along with access to both front and rear facets. Hence, both laser and single-pass amplifier arrays can be accommodated. A module was realized containing a 5 mm cavity length monolithic QCL array comprised of 7 elements on 450 m pitch. An output power of 3.16 W was demonstrated under CW conditions at an emission wavelength of 9μm.

Multilevel cascade voltage source inverter with seperate DC sources

DOEpatents

Peng, Fang Zheng; Lai, Jih-Sheng

1997-01-01

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

Multilevel cascade voltage source inverter with seperate DC sources

DOEpatents

Peng, Fang Zheng; Lai, Jih-Sheng

2002-01-01

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

Multilevel cascade voltage source inverter with seperate DC sources

DOEpatents

Peng, Fang Zheng; Lai, Jih-Sheng

2001-04-03

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

Multilevel cascade voltage source inverter with separate DC sources

DOEpatents

Peng, F.Z.; Lai, J.S.

1997-06-24

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations. 15 figs.

Prostate Cancer Stem Cells: Viewing Signaling Cascades at a Finer Resolution.

PubMed

Lin, Xiukun; Farooqi, Ammad Ahmad; Qureshi, Muhammad Zahid; Romero, Mirna Azalea; Tabassum, Sobia; Ismail, Muhammad

2016-06-01

It is becoming characteristically more understandable that within tumor cells, there lies a sub-population of tumor cells with "stem cell" like properties and remarkable ability of self-renewal. Many features of these self-renewing cells are comparable with normal stem cells and are termed as "cancer stem cells". Accumulating experimentally verified data has started to scratch the surface of spatio-temporally dysregulated intracellular signaling cascades in the biology of prostate cancer stem cells. We partition this multicomponent review into how different signaling cascades operate in cancer stem cells and how bioactive ingredients isolated from natural sources may modulate signaling network.

The Impact of Electromagnetic Cascades of Very-high Energy Gamma Rays on the Extragalactic Gamma-ray Background

NASA Technical Reports Server (NTRS)

Venters, Tonia

2012-01-01

As very high energy (VHE) photons propagate through the extragalactic background light (EBL), they interact with the soft photons of the EBL and initiate electromagnetic cascades of photons and electrons. The collective intensity of a cosmological population emitting at VHEs (such as blazars) will be attenuated at the highest energies through interactions with the EBL and enhanced at lower energies by the resulting cascade. As such, depending on the space density and spectra of the sources and the model of the EBL, cascade radiation can provide a significant contribution to the extragalactic gamma-ray background (EGB). Through deflections of the charged particles of the cascade, an intergalactic magnetic field (IGMF) may leave an imprint on the anisotropy properties of the EGB. The impact of a strong IGMF is to isotropize lower energy cascade photons, inducing a modulation in the anisotropy energy spectrum of the EGB. We discuss the implications of cascade radiation for the origins of the EGB and the nature of the IGMF, as well as insight that will be provided by data from the Fermi Large Area Telescope in the upcoming years.

Euler flow predictions for an oscillating cascade using a high resolution wave-split scheme

NASA Technical Reports Server (NTRS)

Huff, Dennis L.; Swafford, Timothy W.; Reddy, T. S. R.

1991-01-01

A compressible flow code that can predict the nonlinear unsteady aerodynamics associated with transonic flows over oscillating cascades is developed and validated. The code solves the two dimensional, unsteady Euler equations using a time-marching, flux-difference splitting scheme. The unsteady pressures and forces can be determined for arbitrary input motions, although only harmonic pitching and plunging motions are addressed. The code solves the flow equations on a H-grid which is allowed to deform with the airfoil motion. Predictions are presented for both flat plate cascades and loaded airfoil cascades. Results are compared to flat plate theory and experimental data. Predictions are also presented for several oscillating cascades with strong normal shocks where the pitching amplitudes, cascade geometry and interblade phase angles are varied to investigate nonlinear behavior.

160-Gb/s all-optical phase-transparent wavelength conversion through cascaded SFG-DFG in a broadband linear-chirped PPLN waveguide.

PubMed

Lu, Guo-Wei; Shinada, Satoshi; Furukawa, Hideaki; Wada, Naoya; Miyazaki, Tetsuya; Ito, Hiromasa

2010-03-15

We experimentally demonstrated ultra-fast phase-transparent wavelength conversion using cascaded sum- and difference-frequency generation (cSFG-DFG) in linear-chirped periodically poled lithium niobate (PPLN). Error-free wavelength conversion of a 160-Gb/s return-to-zero differential phase-shift keying (RZ-DPSK) signal was successfully achieved. Thanks to the enhanced conversion bandwidth in the PPLN with linear-chirped periods, no optical equalizer was required to compensate the spectrum distortion after conversion, unlike a previous demonstration of 160-Gb/s RZ on-off keying (OOK) using fixed-period PPLN.

Terahertz lasers and amplifiers based on resonant optical phonon scattering to achieve population inversion

NASA Technical Reports Server (NTRS)

Hu, Qing (Inventor); Williams, Benjamin S. (Inventor)

2007-01-01

The present invention provides quantum cascade lasers and amplifier that operate in a frequency range of about 1 Terahertz to about 10 Terahertz. In one aspect, a quantum cascade laser of the invention includes a semiconductor heterostructure that provides a plurality of lasing modules connected in series. Each lasing module includes a plurality of quantum well structure that collectively generate at least an upper lasing state, a lower lasing state, and a relaxation state such that the upper and the lower lasing states are separated by an energy corresponding to an optical frequency in a range of about 1 to about 10 Terahertz. The lower lasing state is selectively depopulated via resonant LO-phonon scattering of electrons into the relaxation state.

Terahertz lasers and amplifiers based on resonant optical phonon scattering to achieve population inversion

NASA Technical Reports Server (NTRS)

Williams, Benjamin S. (Inventor); Hu, Qing (Inventor)

2009-01-01

The present invention provides quantum cascade lasers and amplifier that operate in a frequency range of about 1 Terahertz to about 10 Terahertz. In one aspect, a quantum cascade laser of the invention includes a semiconductor heterostructure that provides a plurality of lasing modules connected in series. Each lasing module includes a plurality of quantum well structure that collectively generate at least an upper lasing state, a lower lasing state, and a relaxation state such that the upper and the lower lasing states are separated by an energy corresponding to an optical frequency in a range of about 1 to about 10 Terahertz. The lower lasing state is selectively depopulated via resonant LO-phonon scattering of electrons into the relaxation state.

Phase noise in RF and microwave amplifiers.

PubMed

Boudot, Rodolphe; Rubiola, Enrico

2012-12-01

Understanding amplifier phase noise is a critical issue in many fields of engineering and physics, such as oscillators, frequency synthesis, telecommunication, radar, and spectroscopy; in the emerging domain of microwave photonics; and in exotic fields, such as radio astronomy, particle accelerators, etc. Focusing on the two main types of base noise in amplifiers, white and flicker, the power spectral density of the random phase φ(t) is Sφ(f) = b(0) + b(-1)/f. White phase noise results from adding white noise to the RF spectrum in the carrier region. For a given RF noise level, b(0) is proportional to the reciprocal of the carrier power P(0). By contrast, flicker results from a near-dc 1/f noise-present in all electronic devices-which modulates the carrier through some parametric effect in the semiconductor. Thus, b(-1) is a parameter of the amplifier, constant in a wide range of P(0). The consequences are the following: Connecting m equal amplifiers in parallel, b(-1) is 1/m times that of one device. Cascading m equal amplifiers, b(-1) is m times that of one amplifier. Recirculating the signal in an amplifier so that the gain increases by a power of m (a factor of m in decibels) as a result of positive feedback (regeneration), we find that b(-1) is m(2) times that of the amplifier alone. The feedforward amplifier exhibits extremely low b(-1) because the carrier is ideally nulled at the input of its internal error amplifier. Starting with an extensive review of the literature, this article introduces a system-oriented model which describes the phase flickering. Several amplifier architectures (cascaded, parallel, etc.) are analyzed systematically, deriving the phase noise from the general model. There follow numerous measurements of amplifiers using different technologies, including some old samples, and in a wide frequency range (HF to microwaves), which validate the theory. In turn, theory and results provide design guidelines and give suggestions for CAD and simulation. To conclude, this article is intended as a tutorial, a review, and a systematic treatise on the subject, supported by extensive experiments.

High-power phase-locked quantum cascade laser array emitting at λ ∼ 4.6 μm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Fang-Liang; Zhang, Jin-Chuan, E-mail: zhangjinchuan@semi.ac.cn, E-mail: fqliu@semi.ac.cn; Jia, Zhi-Wei

2016-03-15

A phase-locked quantum cascade laser (QCL) array consisting of one hundred elements that were integrated in parallel was achieved at λ ∼ 4.6 μm. The proposed Fraunhofer’s multiple slits diffraction model predicted and explained the far-field pattern of the phase-locked laser array. A single-lobed far-field pattern, attributed to the emission of an in-phase-like supermode, is obtained near the threshold (I{sub th}). Even at 1.5 I{sub th}, greater than 73.3% of the laser output power is concentrated in a low-divergence beam with an optical power of up to 40 W.

Phase locking of a 2.7 THz quantum cascade laser to a microwave reference.

PubMed

Khosropanah, P; Baryshev, A; Zhang, W; Jellema, W; Hovenier, J N; Gao, J R; Klapwijk, T M; Paveliev, D G; Williams, B S; Kumar, S; Hu, Q; Reno, J L; Klein, B; Hesler, J L

2009-10-01

We demonstrate the phase locking of a 2.7 THz metal-metal waveguide quantum cascade laser (QCL) to an external microwave signal. The reference is the 15th harmonic, generated by a semiconductor superlattice nonlinear device, of a signal at 182 GHz, which itself is generated by a multiplier chain (x12) from a microwave synthesizer at approximately 15 GHz. Both laser and reference radiations are coupled into a bolometer mixer, resulting in a beat signal, which is fed into a phase-lock loop. The spectral analysis of the beat signal confirms that the QCL is phase locked. This result opens the possibility to extend heterodyne interferometers into the far-infrared range.

Common mode frequency instability in internally phase-locked terahertz quantum cascade lasers.

PubMed

Wanke, M C; Grine, A D; Fuller, C T; Nordquist, C D; Cich, M J; Reno, J L; Lee, Mark

2011-11-21

Feedback from a diode mixer integrated into a 2.8 THz quantum cascade laser (QCL) was used to phase lock the difference frequencies (DFs) among the Fabry-Perot (F-P) longitudinal modes of a QCL. Approximately 40% of the DF power was phase locked, consistent with feedback loop bandwidth of 10 kHz and phase noise bandwidth ~0.5 MHz. While the locked DF signal has ≤ 1 Hz linewidth and negligible drift over ~30 min, mixing measurements between two QCLs and between a QCL and molecular gas laser show that the common mode frequency stability is no better than a free-running QCL. © 2011 Optical Society of America

Phase Locking of a 2.7 THz Quantum Cascade Laser to a Microwave Reference

NASA Technical Reports Server (NTRS)

Khosropanah, P.; Baryshev, A.; Zhang, W.; Jellema, W.; Hovenier, J. N.; Gao, J. R.; Klapwijk, T. M.; Paveliev, D. G.; Williams, B. S.; Hu, Q.;

Phase seeding of a terahertz quantum cascade laser

PubMed Central

Oustinov, Dimitri; Jukam, Nathan; Rungsawang, Rakchanok; Madéo, Julien; Barbieri, Stefano; Filloux, Pascal; Sirtori, Carlo; Marcadet, Xavier; Tignon, Jérôme; Dhillon, Sukhdeep

2010-01-01

The amplification of spontaneous emission is used to initiate laser action. As the phase of spontaneous emission is random, the phase of the coherent laser emission (the carrier phase) will also be random each time laser action begins. This prevents phase-resolved detection of the laser field. Here, we demonstrate how the carrier phase can be fixed in a semiconductor laser: a quantum cascade laser (QCL). This is performed by injection seeding a QCL with coherent terahertz pulses, which forces laser action to start on a fixed phase. This permits the emitted laser field to be synchronously sampled with a femtosecond laser beam, and measured in the time domain. We observe the phase-resolved buildup of the laser field, which can give insights into the laser dynamics. In addition, as the electric field oscillations are directly measured in the time domain, QCLs can now be used as sources for time-domain spectroscopy. PMID:20842195

Optically Tunable Long Wavelength Infrared Quantum Cascade Laser Operated at Room Temperature

DTIC Science & Technology

2013-01-09

optics (Figure 2(d)). QCL emission spectra were obtained using a FTIR spectrometer with resolution of 0.125 cm1 and a photovoltaic MCT detector . A...frequency modulation (FM) optical data links,1 which can have orders of magnitude higher signal-to- noise ratio compared to the amplitude-modulation (AM

Electrical modulation of the complex refractive index in mid-infrared quantum cascade lasers.

PubMed

Teissier, J; Laurent, S; Manquest, C; Sirtori, C; Bousseksou, A; Coudevylle, J R; Colombelli, R; Beaudoin, G; Sagnes, I

2012-01-16

We have demonstrated an integrated three terminal device for the modulation of the complex refractive index of a distributed feedback quantum cascade laser (QCL). The device comprises an active region to produce optical gain vertically stacked with a control region made of asymmetric coupled quantum wells (ACQW). The optical mode, centered on the gain region, has a small overlap also with the control region. Owing to the three terminals an electrical bias can be applied independently on both regions: on the laser for producing optical gain and on the ACQW for tuning the energy of the intersubband transition. This allows the control of the optical losses at the laser frequency as the absorption peak associated to the intersubband transition can be electrically brought in and out the laser transition. By using this function a laser modulation depth of about 400 mW can be achieved by injecting less than 1 mW in the control region. This is four orders of magnitude less than the electrical power needed using direct current modulation and set the basis for the realisation of electrical to optical transducers.

The kinetics of inactivation of the rod phototransduction cascade with constant Ca2+i

PubMed Central

1996-01-01

A rich variety of mechanisms govern the inactivation of the rod phototransduction cascade. These include rhodopsin phosphorylation and subsequent binding of arrestin; modulation of rhodopsin kinase by S- modulin (recoverin); regulation of G-protein and phosphodiesterase inactivation by GTPase-activating factors; and modulation of guanylyl cyclase by a high-affinity Ca(2+)-binding protein. The dependence of several of the inactivation mechanisms on Ca2+i makes it difficult to assess the contributions of these mechanisms to the recovery kinetics in situ, where Ca2+i is dynamically modulated during the photoresponse. We recorded the circulating currents of salamander rods, the inner segments of which are held in suction electrodes in Ringer's solution. We characterized the response kinetics to flashes under two conditions: when the outer segments are in Ringer's solution, and when they are in low-Ca2+ choline solutions, which we show clamp Ca2+i very near its resting level. At T = 20-22 degrees C, the recovery phases of responses to saturating flashes producing 10(2.5)-10(4.5) photoisomerizations under both conditions are characterized by a dominant time constant, tau c = 2.4 +/- 0.4 s, the value of which is not dependent on the solution bathing the outer segment and therefore not dependent on Ca2+i. We extended a successful model of activation by incorporating into it a first-order inactivation of R*, and a first-order, simultaneous inactivation of G-protein (G*) and phosphodiesterase (PDE*). We demonstrated that the inactivation kinetics of families of responses obtained with Ca2+i clamped to rest are well characterized by this model, having one of the two inactivation time constants (tau r* or tau PDE*) equal to tau c, and the other time constant equal to 0.4 +/- 0.06 s. PMID:8741728

Blind I/Q imbalance and nonlinear ISI mitigation in Nyquist-SCM direct detection system with cascaded widely linear and Volterra equalizer

NASA Astrophysics Data System (ADS)

Liu, Na; Ju, Cheng

2018-02-01

Nyquist-SCM signal after fiber transmission, direct detection (DD), and analog down-conversion suffers from linear ISI, nonlinear ISI, and I/Q imbalance, simultaneously. Theoretical analysis based on widely linear (WL) and Volterra series is given to explain the relationship and interaction of these three interferences. A blind equalization algorithm, cascaded WL and Volterra equalizer, is designed to mitigate these three interferences. Furthermore, the feasibility of the proposed cascaded algorithm is experimentally demonstrated based on a 40-Gbps data rate 16-quadrature amplitude modulation (QAM) virtual single sideband (VSSB) Nyquist-SCM DD system over 100-km standard single mode fiber (SSMF) transmission. In addition, the performances of conventional strictly linear equalizer, WL equalizer, Volterra equalizer, and cascaded WL and Volterra equalizer are experimentally evaluated, respectively.

Implementation of cascade logic gates and majority logic gate on a simple and universal molecular platform.

PubMed

Gao, Jinting; Liu, Yaqing; Lin, Xiaodong; Deng, Jiankang; Yin, Jinjin; Wang, Shuo

2017-10-25

Wiring a series of simple logic gates to process complex data is significantly important and a large challenge for untraditional molecular computing systems. The programmable property of DNA endows its powerful application in molecular computing. In our investigation, it was found that DNA exhibits excellent peroxidase-like activity in a colorimetric system of TMB/H 2 O 2 /Hemin (TMB, 3,3', 5,5'-Tetramethylbenzidine) in the presence of K + and Cu 2+ , which is significantly inhibited by the addition of an antioxidant. According to the modulated catalytic activity of this DNA-based catalyst, three cascade logic gates including AND-OR-INH (INHIBIT), AND-INH and OR-INH were successfully constructed. Interestingly, by only modulating the concentration of Cu 2+ , a majority logic gate with a single-vote veto function was realized following the same threshold value as that of the cascade logic gates. The strategy is quite straightforward and versatile and provides an instructive method for constructing multiple logic gates on a simple platform to implement complex molecular computing.

Curcumin on the "flying carpets" to modulate different signal transduction cascades in cancers: Next-generation approach to bridge translational gaps.

PubMed

Celik, Hulya; Aydin, Tuba; Solak, Kubra; Khalid, Sumbul; Farooqi, Ammad A

2018-06-01

Curcumin, a bioactive and pharmacologically efficient component isolated from Curcuma longa has attracted considerable attention because of its ability to modulate diverse cellular and physiological pathways. WNT, TGF/SMAD, NOTCH, and SHH are fundamentally different signaling cascades, but their choreographed activation is strongly associated with cancer development and progression. In this review we have attempted to set spotlight on regulation of different cell signaling pathways by curcumin in different cancers. We partition this multi-component review into in-depth biological understanding of various signal transduction cascades and how curcumin targets intracellular signal transducers of deregulated pathways to inhibit cancer development and progression. Rapidly broadening landscape of both established and candidate oncogenic driver mutations identified in different cancers is a major stumbling block in the standardization of drugs having significant clinical outcome. Intra and inter-tumor heterogeneity had leveraged the complexity of therapeutic challenges to another level. Multi-pronged approach and molecularly guided treatments will be helpful in improving the clinical outcome. © 2018 Wiley Periodicals, Inc.

A developmental cascade perspective of paediatric obesity: a conceptual model and scoping review.

PubMed

Smith, Justin D; Egan, Kaitlyn N; Montaño, Zorash; Dawson-McClure, Spring; Jake-Schoffman, Danielle E; Larson, Madeline; St George, Sara M

2018-04-05

Considering the immense challenge of preventing obesity, the time has come to reconceptualise the way we study the obesity development in childhood. The developmental cascade model offers a longitudinal framework to elucidate the way cumulative consequences and spreading effects of risk and protective factors, across and within biopsychosocial spheres and phases of development, can propel individuals towards obesity. In this article, we use a theory-driven model-building approach and a scoping review that included 310 published studies to propose a developmental cascade model of paediatric obesity. The proposed model provides a basis for testing hypothesised cascades with multiple intervening variables and complex longitudinal processes. Moreover, the model informs future research by resolving seemingly contradictory findings on pathways to obesity previously thought to be distinct (low self-esteem, consuming sugary foods, and poor sleep cause obesity) that are actually processes working together over time (low self-esteem causes consumption of sugary foods which disrupts sleep quality and contributes to obesity). The findings of such inquiries can aid in identifying the timing and specific targets of preventive interventions across and within developmental phases. The implications of such a cascade model of paediatric obesity for health psychology and developmental and prevention sciences are discussed.

Effect of acute alarm odor exposure and biological sex on generalized avoidance and glutamatergic signaling in the hippocampus of Wistar rats.

PubMed

Homiack, Damek; O'Cinneide, Emma; Hajmurad, Sema; Dohanich, Gary P; Schrader, Laura A

2018-06-19

Post-traumatic stress disorder (PTSD) is characterized by the development of paradoxical memory disturbances including intrusive memories and amnesia for specific details of the traumatic experience. Despite evidence that women are at higher risk to develop PTSD, most animal research has focused on the processes by which male rodents develop adaptive fear memory. As such, the mechanisms contributing to sex differences in the development of PTSD-like memory disturbances are poorly understood. In this investigation, we exposed adult male and female Wistar rats to the synthetic alarm odor 2,4,5-trimethylthiazole (TMT) to assess development of generalized fear behavior and rapid modulation of glutamate uptake and signaling cascades associated with hippocampus-dependent long-term memory. We report that female Wistar rats exposed to alarm odor exhibit context discrimination impairments relative to TMT-exposed male rats, suggesting the intriguing possibility that females are at greater risk in developing generalized fear memories. Mechanistically, alarm odor exposure rapidly modulated signaling cascades consistent with activation of the CREB shut-off cascade in the male, but not the female hippocampus. Moreover, TMT exposure dampened glutamate uptake and affected expression of the glutamate transporter, GLT-1 in the hippocampus. Taken together, these results provide evidence for rapid sex-dependent modulation of CREB signaling in the hippocampus by alarm odor exposure which may contribute to the development of generalized fear.

Robustness of 40 Gb/s ASK modulation formats in the practical system infrastructure

NASA Astrophysics Data System (ADS)

Pincemin, Erwan; Tan, Antoine; Bezard, Aude; Tonello, Alessandro; Wabnitz, Stefano; Ania-Castañòn, Juan-Diego; Turitsyn, Sergei

2006-12-01

In this work, we theoretically and experimentally analyzed the resilience of 40 Gb/s amplitude shift keying modulation formats to transmission impairments in standard single-mode fiber lines as well as to optical filtering introduced by the optical add/drop multiplexer cascade. Our study is a pre-requisite to assess the implementation of cost-effective 40 Gb/s modulation technology in next generation high bit-rate robust optical transport networks.

Ideal-observer detectability in photon-counting differential phase-contrast imaging using a linear-systems approach

PubMed Central

Fredenberg, Erik; Danielsson, Mats; Stayman, J. Webster; Siewerdsen, Jeffrey H.; Åslund, Magnus

2012-01-01

Purpose: To provide a cascaded-systems framework based on the noise-power spectrum (NPS), modulation transfer function (MTF), and noise-equivalent number of quanta (NEQ) for quantitative evaluation of differential phase-contrast imaging (Talbot interferometry) in relation to conventional absorption contrast under equal-dose, equal-geometry, and, to some extent, equal-photon-economy constraints. The focus is a geometry for photon-counting mammography. Methods: Phase-contrast imaging is a promising technology that may emerge as an alternative or adjunct to conventional absorption contrast. In particular, phase contrast may increase the signal-difference-to-noise ratio compared to absorption contrast because the difference in phase shift between soft-tissue structures is often substantially larger than the absorption difference. We have developed a comprehensive cascaded-systems framework to investigate Talbot interferometry, which is a technique for differential phase-contrast imaging. Analytical expressions for the MTF and NPS were derived to calculate the NEQ and a task-specific ideal-observer detectability index under assumptions of linearity and shift invariance. Talbot interferometry was compared to absorption contrast at equal dose, and using either a plane wave or a spherical wave in a conceivable mammography geometry. The impact of source size and spectrum bandwidth was included in the framework, and the trade-off with photon economy was investigated in some detail. Wave-propagation simulations were used to verify the analytical expressions and to generate example images. Results: Talbot interferometry inherently detects the differential of the phase, which led to a maximum in NEQ at high spatial frequencies, whereas the absorption-contrast NEQ decreased monotonically with frequency. Further, phase contrast detects differences in density rather than atomic number, and the optimal imaging energy was found to be a factor of 1.7 higher than for absorption contrast. Talbot interferometry with a plane wave increased detectability for 0.1-mm tumor and glandular structures by a factor of 3–4 at equal dose, whereas absorption contrast was the preferred method for structures larger than ∼0.5 mm. Microcalcifications are small, but differ from soft tissue in atomic number more than density, which is favored by absorption contrast, and Talbot interferometry was barely beneficial at all within the resolution limit of the system. Further, Talbot interferometry favored detection of “sharp” as opposed to “smooth” structures, and discrimination tasks by about 50% compared to detection tasks. The technique was relatively insensitive to spectrum bandwidth, whereas the projected source size was more important. If equal photon economy was added as a restriction, phase-contrast efficiency was reduced so that the benefit for detection tasks almost vanished compared to absorption contrast, but discrimination tasks were still improved close to a factor of 2 at the resolution limit. Conclusions: Cascaded-systems analysis enables comprehensive and intuitive evaluation of phase-contrast efficiency in relation to absorption contrast under requirements of equal dose, equal geometry, and equal photon economy. The benefit of Talbot interferometry was highly dependent on task, in particular detection versus discrimination tasks, and target size, shape, and material. Requiring equal photon economy weakened the benefit of Talbot interferometry in mammography. PMID:22957600

Isorhynchophylline, a Potent Plant Alkaloid, Induces Apoptotic and Anti-Metastatic Effects in Human Hepatocellular Carcinoma Cells through the Modulation of Diverse Cell Signaling Cascades

PubMed Central

Lee, Hanwool; Baek, Seung Ho; Lee, Jong Hyun; Kim, Chulwon; Ko, Jeong-Hyeon; Lee, Seok-Geun; Chinnathambi, Arunachalam; Alharbi, Sulaiman Ali; Yang, Woong Mo; Um, Jae-Young; Sethi, Gautam; Ahn, Kwang Seok

2017-01-01

Isorhynchophylline (Rhy) is an active pharmacological component of Uncaria rhynchophylla that has been reported previously to exert significant antihypertensive and neuroprotective effects. However, very little is known about its potential anti-cancer activities. This study was carried out to evaluate the anticancer effects of Rhy against various human carcinoma cell lines. We found that Rhy exhibited substantial cytotoxic effect against human hepatocellular carcinoma HepG2 cells when compared with other human carcinoma cell lines including those of lung, pancreas, prostate, head and neck, breast, multiple myeloma, brain and renal cell carcinoma. Rhy induced apoptosis as characterized by accumulation of cells in sub G1 phase; positive Annexin V binding; activation of caspase-8, -9, and -3; and cleavage of PARP (poly-ADP ribose polymerase). This effect of Rhy correlated with the down-regulation of various proteins that mediated cell proliferation, cell survival, metastasis, and angiogenesis. Moreover, cell proliferation, migration, and constitutive CXCR4 (C-X-C chemokine receptor type 4), MMP-9 (Matrix metallopeptidase-9), and MMP-2 expression were inhibited upon Rhy treatment. We further investigated the effect of Rhy on the oncogenic cell signaling cascades through phospho-kinase array profiling assay. Rhy was found to abrogate phospho-p38, ERK, JNK, CREB, c-Jun, Akt, and STAT3 signals, but interestingly enhanced phospho-p53 signal. Overall, our results indicate, for the first time, that Rhy could exert anticancer and anti-metastatic effects through regulation of multiple signaling cascades in hepatocellular carcinoma cells. PMID:28534824

Isorhynchophylline, a Potent Plant Alkaloid, Induces Apoptotic and Anti-Metastatic Effects in Human Hepatocellular Carcinoma Cells through the Modulation of Diverse Cell Signaling Cascades.

PubMed

Lee, Hanwool; Baek, Seung Ho; Lee, Jong Hyun; Kim, Chulwon; Ko, Jeong-Hyeon; Lee, Seok-Geun; Chinnathambi, Arunachalam; Alharbi, Sulaiman Ali; Yang, Woong Mo; Um, Jae-Young; Sethi, Gautam; Ahn, Kwang Seok

2017-05-19

Isorhynchophylline (Rhy) is an active pharmacological component of Uncaria rhynchophylla that has been reported previously to exert significant antihypertensive and neuroprotective effects. However, very little is known about its potential anti-cancer activities. This study was carried out to evaluate the anticancer effects of Rhy against various human carcinoma cell lines. We found that Rhy exhibited substantial cytotoxic effect against human hepatocellular carcinoma HepG2 cells when compared with other human carcinoma cell lines including those of lung, pancreas, prostate, head and neck, breast, multiple myeloma, brain and renal cell carcinoma. Rhy induced apoptosis as characterized by accumulation of cells in sub G1 phase; positive Annexin V binding; activation of caspase-8, -9, and -3; and cleavage of PARP (poly-ADP ribose polymerase). This effect of Rhy correlated with the down-regulation of various proteins that mediated cell proliferation, cell survival, metastasis, and angiogenesis. Moreover, cell proliferation, migration, and constitutive CXCR4 (C-X-C chemokine receptor type 4), MMP-9 (Matrix metallopeptidase-9), and MMP-2 expression were inhibited upon Rhy treatment. We further investigated the effect of Rhy on the oncogenic cell signaling cascades through phospho-kinase array profiling assay. Rhy was found to abrogate phospho-p38, ERK, JNK, CREB, c-Jun, Akt, and STAT3 signals, but interestingly enhanced phospho-p53 signal. Overall, our results indicate, for the first time, that Rhy could exert anticancer and anti-metastatic effects through regulation of multiple signaling cascades in hepatocellular carcinoma cells.

Terahertz Sideband-tuned Quantum Cascade Laser Radiation

DTIC Science & Technology

2008-03-31

resolution of 2 MHz in CW regime was observed. ©2008 Optical Society of America OCIS codes: (140.5965) Semiconductor lasers , quantum cascade...diode,” Opt. Lett. 29, 1632 (2004). 6. A. Baryshev, et.al., “ Phase locking and spectral linewidth of a two-mode terahertz quantum cascade laser ,” Appl... optically pumped gas laser . With further improvements in power and spatial mode quality, it should be possible to lock a TQCL to the harmonic of an ultra

Volterra series based blind equalization for nonlinear distortions in short reach optical CAP system

NASA Astrophysics Data System (ADS)

Tao, Li; Tan, Hui; Fang, Chonghua; Chi, Nan

2016-12-01

In this paper, we propose a blind Volterra series based nonlinear equalization (VNLE) with low complexity for the nonlinear distortion mitigation in short reach optical carrierless amplitude and phase (CAP) modulation system. The principle of the blind VNLE is presented and the performance of its blind adaptive algorithms including the modified cascaded multi-mode algorithm (MCMMA) and direct detection LMS (DD-LMS) are investigated experimentally. Compared to the conventional VNLE using training symbols before demodulation, it is performed after matched filtering and downsampling, so shorter memory length is required but similar performance improvement is observed. About 1 dB improvement is observed at BER of 3.8×10-3 for 40 Gb/s CAP32 signal over 40 km standard single mode fiber.

Demonstration of reconfigurable joint orbital angular momentum mode and space switching

PubMed Central

Liu, Jun; Wang, Jian

2016-01-01

We propose and demonstrate space-selective switch functions employing orbital angular momentum (OAM) modes in the space domain for switching network. One is the switching among different OAM modes having different spatial phase structures, called OAM mode switching. The other is the switching among different space locations, called space switching. The switching operation mechanism relies on linear optics. Reconfigurable 4 × 4 OAM mode switching, space switching, and joint OAM mode and space switching fabric using a single spatial light modulator (SLM) are all demonstrated in the experiment. In addition, the presented OAM-incorporated space-selective switch might be further extended to N × N joint OAM mode and space switching with fast response, scalability, cascading ability and compability to facilitate robust switching applications. PMID:27869133

Demonstration of reconfigurable joint orbital angular momentum mode and space switching

NASA Astrophysics Data System (ADS)

Liu, Jun; Wang, Jian

2016-11-01

We propose and demonstrate space-selective switch functions employing orbital angular momentum (OAM) modes in the space domain for switching network. One is the switching among different OAM modes having different spatial phase structures, called OAM mode switching. The other is the switching among different space locations, called space switching. The switching operation mechanism relies on linear optics. Reconfigurable 4 × 4 OAM mode switching, space switching, and joint OAM mode and space switching fabric using a single spatial light modulator (SLM) are all demonstrated in the experiment. In addition, the presented OAM-incorporated space-selective switch might be further extended to N × N joint OAM mode and space switching with fast response, scalability, cascading ability and compability to facilitate robust switching applications.

Demonstration of reconfigurable joint orbital angular momentum mode and space switching.

PubMed

Liu, Jun; Wang, Jian

2016-11-21

We propose and demonstrate space-selective switch functions employing orbital angular momentum (OAM) modes in the space domain for switching network. One is the switching among different OAM modes having different spatial phase structures, called OAM mode switching. The other is the switching among different space locations, called space switching. The switching operation mechanism relies on linear optics. Reconfigurable 4 × 4 OAM mode switching, space switching, and joint OAM mode and space switching fabric using a single spatial light modulator (SLM) are all demonstrated in the experiment. In addition, the presented OAM-incorporated space-selective switch might be further extended to N × N joint OAM mode and space switching with fast response, scalability, cascading ability and compability to facilitate robust switching applications.

Hydrogen sulphide in cardiovascular system: A cascade from interaction between sulphur atoms and signalling molecules.

PubMed

Wang, Ming-Jie; Cai, Wen-Jie; Zhu, Yi-Chun

2016-05-15

As a gasotransmitter, hydrogen sulphide exerts its extensive physiological and pathophysiological effects in mammals. The interaction between sulphur atoms and signalling molecules forms a cascade that modulates cellular functions and homeostasis. In this review, we focus on the signalling mechanism underlying the effect of hydrogen sulphide in the cardiovascular system and metabolism as well as the biological relevance to human diseases. Copyright © 2016 Elsevier Inc. All rights reserved.

Rapid screening and identification of illicit drugs by IR absorption spectroscopy and gas chromatography

NASA Astrophysics Data System (ADS)

Mengali, Sandro; Liberatore, Nicola; Luciani, Domenico; Viola, Roberto; Cardinali, Gian Carlo; Elmi, Ivan; Poggi, Antonella; Zampolli, Stefano; Biavardi, Elisa; Dalcanale, Enrico; Bonadio, Federica; Delemont, Olivier; Esseiva, Pierre; Romolo, Francesco S.

2013-01-01

Analytical instruments based on InfraRed Absorption Spectroscopy (IRAS) and Gas Chromatography (GC) are today available only as bench-top instrumentation for forensic labs and bulk analysis. Within the 'DIRAC' project funded by the European Commission, we are developing an advanced portable sensor, that combines miniaturized GC as its key chemical separation tool, and IRAS in a Hollow Fiber (HF) as its key analytical tool, to detect and recognize illicit drugs and key precursors, as bulk and as traces. The HF-IRAS module essentially consists of a broadly tunable External Cavity (EC) Quantum Cascade Laser (QCL), thermo-electrically cooled MCT detectors, and an infrared hollow fiber at controlled temperature. The hollow fiber works as a miniaturized gas cell, that can be connected to the output of the GC column with minimal dead volumes. Indeed, the module has been coupled to GC columns of different internal diameter and stationary phase, and with a Vapour Phase Pre-concentrator (VPC) that selectively traps target chemicals from the air. The presentation will report the results of tests made with amphetamines and precursors, as pure substances, mixtures, and solutions. It will show that the sensor is capable of analyzing all the chemicals of interest, with limits of detection ranging from a few nanograms to about 100-200 ng. Furthermore, it is suitable to deal with vapours directly trapped from the headspace of a vessel, and with salts treated in a basic solution. When coupled to FAST GC columns, the module can analyze multi-components mixes in less than 5 minutes.

Phase-locking to a free-space terahertz comb for metrological-grade terahertz lasers.

PubMed

Consolino, L; Taschin, A; Bartolini, P; Bartalini, S; Cancio, P; Tredicucci, A; Beere, H E; Ritchie, D A; Torre, R; Vitiello, M S; De Natale, P

2012-01-01

Optical frequency comb synthesizers have represented a revolutionary approach to frequency metrology, providing a grid of frequency references for any laser emitting within their spectral coverage. Extending the metrological features of optical frequency comb synthesizers to the terahertz domain would be a major breakthrough, due to the widespread range of accessible strategic applications and the availability of stable, high-power and widely tunable sources such as quantum cascade lasers. Here we demonstrate phase-locking of a 2.5 THz quantum cascade laser to a free-space comb, generated in a LiNbO(3) waveguide and covering the 0.1-6 THz frequency range. We show that even a small fraction (<100 nW) of the radiation emitted from the quantum cascade laser is sufficient to generate a beat note suitable for phase-locking to the comb, paving the way to novel metrological-grade terahertz applications, including high-resolution spectroscopy, manipulation of cold molecules, astronomy and telecommunications.

Tuning and performance evaluation of PID controller for superheater steam temperature control of 200 MW boiler using gain phase assignment algorithm

NASA Astrophysics Data System (ADS)

Begum, A. Yasmine; Gireesh, N.

2018-04-01

In superheater, steam temperature is controlled in a cascade control loop. The cascade control loop consists of PI and PID controllers. To improve the superheater steam temperature control the controller's gains in a cascade control loop has to be tuned efficiently. The mathematical model of the superheater is derived by sets of nonlinear partial differential equations. The tuning methods taken for study here are designed for delay plus first order transfer function model. Hence from the dynamical model of the superheater, a FOPTD model is derived using frequency response method. Then by using Chien-Hrones-Reswick Tuning Algorithm and Gain-Phase Assignment Algorithm optimum controller gains has been found out based on the least value of integral time weighted absolute error.

Phase-locking of a 2.7-THz Quantum Cascade Laser to a Microwave Reference

NASA Astrophysics Data System (ADS)

Baryshev, A. M.; Khosropanah, P.; Zhang, W.; Jellema, W.; Hovenier, J. N.; Gao, J. R.; Klapwijk, T. M.; Paveliev, D. G.; William, B. S.; Kumar, S.; Hu, Q.; Reno, J. L.; Klein, B.; Hesler, J. L.

2009-04-01

We demonstrate phase-locking of a 2.7-THz metal-metal waveguide quantum cascade laser (QCL) to an external microwave signal. The reference is the 15th harmonic, generated by a semiconductor superlattice nonlinear device, of a signal at 182 GHz, which itself is generated by a multiplier-chain (x2x3x2) from a microwave synthesizer at 15 GHz. Both laser and reference radiations are coupled into a hot electron bolometer mixer, resulting in a beat signal, which is fed into a phase-lock loop. Spectral analysis of the beat signal (see fig. 1) confirms that the QCL is phase locked. This result opens the possibility to extend heterodyne interferometers into the far-infrared range.

Integrated all-optical infrared switchable plasmonic quantum cascade laser.

PubMed

Kohoutek, John; Bonakdar, Alireza; Gelfand, Ryan; Dey, Dibyendu; Nia, Iman Hassani; Fathipour, Vala; Memis, Omer Gokalp; Mohseni, Hooman

2012-05-09

We report a type of infrared switchable plasmonic quantum cascade laser, in which far field light in the midwave infrared (MWIR, 6.1 μm) is modulated by a near field interaction of light in the telecommunications wavelength (1.55 μm). To achieve this all-optical switch, we used cross-polarized bowtie antennas and a centrally located germanium nanoslab. The bowtie antenna squeezes the short wavelength light into the gap region, where the germanium is placed. The perturbation of refractive index of the germanium due to the free carrier absorption produced by short wavelength light changes the optical response of the antenna and the entire laser intensity at 6.1 μm significantly. This device shows a viable method to modulate the far field of a laser through a near field interaction.

Feeling safe in the plane: neural mechanisms underlying superior action control in airplane pilot trainees--a combined EEG/MRS study.

PubMed

Yildiz, Ali; Quetscher, Clara; Dharmadhikari, Shalmali; Chmielewski, Witold; Glaubitz, Benjamin; Schmidt-Wilcke, Tobias; Edden, Richard; Dydak, Ulrike; Beste, Christian

2014-10-01

In day-to-day life, we need to apply strategies to cascade different actions for efficient unfolding of behavior. While deficits in action cascading are examined extensively, almost nothing is known about the neuronal mechanisms mediating superior performance above the normal level. To examine this question, we investigate action control in airplane pilot trainees. We use a stop-change paradigm that is able to estimate the efficiency of action cascading on the basis of mathematical constraints. Behavioral and EEG data is analyzed along these constraints and integrated with neurochemical data obtained using Magnetic Resonance Spectroscopy (MRS) from the striatal gamma-aminobutyric acid (GABA) -ergic system. We show that high performance in action cascading, as exemplified in airplane pilot trainees, can be driven by intensified attentional processes, circumventing response selection processes. The results indicate that the efficiency of action cascading and hence the speed of responding as well as attentional gating functions are modulated by striatal GABA and Glutamate + Glutamine concentrations. In superior performance in action cascading similar increases in the concentrations of GABA and Glutamate + Glutamine lead to stronger neurophysiological and behavioral effects as compared to subjects with normal performance in action cascading. Copyright © 2014 Wiley Periodicals, Inc.

Fiber-based coherent polarization beam combining with cascaded phase-locking and polarization-transforming controls

NASA Astrophysics Data System (ADS)

Yang, Yan; Geng, Chao; Li, Feng; Huang, Guan; Li, Xinyang

2018-05-01

In this paper, the fiber-based coherent polarization beam combining (CPBC) with cascaded phase-locking (PL) and polarization-transforming (PT) controls was proposed to combine imbalanced input beams where the number of the input beams is not binary, in which the PL control was performed using the piezoelectric-ring fiber-optic phase compensator, and the PT control was realized by the dynamic polarization controller, simultaneously. The principle of the proposed CPBC was introduced. The performance of the proposed CPBC was analyzed in comparison with the CPBC based on PL control and the CPBC based on PT control. The basic experiment of CPBC of three laser beams was carried out to validate the feasibility of the proposed CPBC, where cascaded controls of PL and PT were implemented based on stochastic parallel gradient descent algorithm. Simulation and experimental results show that the proposed CPBC incorporates the advantages of the two previous CPBC schemes and performs well in the closed loop. Moreover, the expansibility and the application of the proposed CPBC were validated by scaling the CPBC to combine seven laser beams. We believe that the proposed fiber-based CPBC with cascaded PL and PT controls has great potential in free space optical communications employing the multi-aperture receiver with asymmetric structure.

Electron and Ion Reactions in Molecular Solids: from water ice to DNA

NASA Astrophysics Data System (ADS)

Huels, Michael A.

2002-05-01

Wherever ionizing radiation interacts with matter, it initiates reaction cascades involving non-thermal ions, radicals, and ballistic secondary electrons, which in turn may lead to substantial physical and chemical modifications of a medium. The detailed study of the fundamental reaction mechanisms which occur on a molecular level aids our general understanding of radiation induced processes in a variety of contexts, ranging from radiobiology to astrochemistry. Here I present measurements of electron (1 - 80 eV) and some ion (1 - 8 eV) mediated reactions in molecular films that resemble biological model systems. These consist of cryogenic films (pure or mixed) of rare gases, oxygen, water, methane, or aromatic hydrocarbons of increasing complexity, including bases, sugars, single and double stranded DNA. Although the basic nature of the electron or ion reaction mechanisms are found to be similar to those in the gas phase, they are often modulated by the physico-chemical characteristics of the medium. Depending on the latter, some reaction channels may be strongly enhanced, some may be quenched, and new reaction pathways, unavailable in the gas phase, may open. Thus, a given reaction cascade may lead to different end-points even in the same target. Although the goal of these studies is to unravel some of the nascent secondary-electron and reactive-ion induced events that contribute to radiation damage in living tissue, the basic observed reactions relate to other areas of application which will be briefly discussed. This research is supported by the Canadian Institutes of Health Research (CIHR), the National Cancer Institutes of Canada, the Natural Science and Engineering Research Council, and NATO.

Presynaptic Dopamine D2 Receptors Modulate [3H]GABA Release at StriatoPallidal Terminals via Activation of PLC → IP3 → Calcineurin and Inhibition of AC → cAMP → PKA Signaling Cascades.

PubMed

Jijón-Lorenzo, Rafael; Caballero-Florán, Isaac Hiram; Recillas-Morales, Sergio; Cortés, Hernán; Avalos-Fuentes, José Arturo; Paz-Bermúdez, Francisco Javier; Erlij, David; Florán, Benjamín

2018-02-21

Striatal dopamine D2 receptors activate the PLC → IP3 → Calcineurin-signaling pathway to modulate the neural excitability of En+ Medium-sized Spiny GABAergic neurons (MSN) through the regulation of L-type Ca 2+ channels. Presynaptic dopaminergic D2 receptors modulate GABA release at striatopallidal terminals through L-type Ca 2+ channels as well, but their signaling pathway is still undetermined. Since D2 receptors are Gi/o-coupled and negatively modulate adenylyl cyclase (AC), we investigated whether presynaptic D2 receptors modulate GABA release through the same signaling cascade that controls excitability in the striatum or by the inhibition of AC and decreased PKA activity. Activation of D2 receptors stimulated formation of [ 3 H]IP 1 and decreased Forskolin-stimulated [ 3 H]cAMP accumulation in synaptosomes from rat Globus Pallidus. D2 receptor activation with Quinpirole in the presence of L 745,870 decreased, in a dose-dependent manner, K + -induced [ 3 H]GABA release in pallidal slices. The effect was prevented by the pharmacological blockade of Gi/o βγ subunit effects with Gallein, PLC with U 73122, IP3 receptor activation with 4-APB, Calcineurin with FK506. In addition, when release was stimulated with Forskolin to activate AC, D2 receptors also decreased K + -induced [ 3 H]GABA release, an effect occluded with the effect of the blockade of PKA with H89 or stimulation of release with the cAMP analog 8-Br-cAMP. These data indicate that D2 receptors modulate [ 3 H]GABA release at striatopallidal terminals by activating the PLC → IP3 → Calcineurin-signaling cascade, the same one that modulates excitability in soma. Additionally, D2 receptors inhibit release when AC is active. Both mechanisms appear to converge to regulate the activity of presynaptic L-type Ca 2+ channels. Copyright © 2018 IBRO. Published by Elsevier Ltd. All rights reserved.

Probing the Intergalactic Magnetic Field with the Anisotropy of the Extragalactic Gamma-Ray Background

NASA Technical Reports Server (NTRS)

Venters, T. M.; Pavlidou, V.

2012-01-01

The intergalactic magnetic field (IGMF) may leave an imprint on the anisotropy properties of the extragalactic gamma-ray background, through its effect on electromagnetic cascades triggered by interactions between very high energy photons and the extragalactic background light. A strong IGMF will deflect secondary particles produced in these cascades and will thus tend to isotropize lower energy cascade photons, thus inducing a modulation in the anisotropy energy spectrum of the gamma-ray background. Here we present a simple, proof-of-concept calculation of the magnitude of this effect and demonstrate that the two extreme cases (zero IGMF and IGMF strong enough to completely isotropize cascade photons) would be separable by ten years of Fermi observations and reasonable model parameters for the gamma-ray background. The anisotropy energy spectrum of the Fermi gamma-ray background could thus be used as a probe of the IGMF strength.

Cascade generalized predictive control strategy for boiler drum level.

PubMed

Xu, Min; Li, Shaoyuan; Cai, Wenjian

2005-07-01

This paper proposes a cascade model predictive control scheme for boiler drum level control. By employing generalized predictive control structures for both inner and outer loops, measured and unmeasured disturbances can be effectively rejected, and drum level at constant load is maintained. In addition, nonminimum phase characteristic and system constraints in both loops can be handled effectively by generalized predictive control algorithms. Simulation results are provided to show that cascade generalized predictive control results in better performance than that of well tuned cascade proportional integral differential controllers. The algorithm has also been implemented to control a 75-MW boiler plant, and the results show an improvement over conventional control schemes.

Laminar Module Cascade from Layer 5 to 6 Implementing Cue-to-Target Conversion for Object Memory Retrieval in the Primate Temporal Cortex.

PubMed

Koyano, Kenji W; Takeda, Masaki; Matsui, Teppei; Hirabayashi, Toshiyuki; Ohashi, Yohei; Miyashita, Yasushi

2016-10-19

The cerebral cortex computes through the canonical microcircuit that connects six stacked layers; however, how cortical processing streams operate in vivo, particularly in the higher association cortex, remains elusive. By developing a novel MRI-assisted procedure that reliably localizes recorded single neurons at resolution of six individual layers in monkey temporal cortex, we show that transformation of representations from a cued object to a to-be-recalled object occurs at the infragranular layer in a visual cued-recall task. This cue-to-target conversion started in layer 5 and was followed by layer 6. Finally, a subset of layer 6 neurons exclusively encoding the sought target became phase-locked to surrounding field potentials at theta frequency, suggesting that this coordinated cell assembly implements cortical long-distance outputs of the recalled target. Thus, this study proposes a link from local computation spanning laminar modules of the temporal cortex to the brain-wide network for memory retrieval in primates. Copyright © 2016 Elsevier Inc. All rights reserved.

DC-DC Type High-Frequency Link DC for Improved Power Quality of Cascaded Multilevel Inverter

NASA Astrophysics Data System (ADS)

Sadikin, Muhammad; Senjyu, Tomonobu; Yona, Atsushi

2013-06-01

Multilevel inverters are emerging as a new breed of power converter options for power system applications. Recent advances in power switching devices enabled the suitability of multilevel inverters for high voltage and high power applications because they are connecting several devices in series without the need of component matching. Usually, a transformerless battery energy storage system, based on a cascaded multilevel inverter, is used as a measure for voltage and frequency deviations. System can be reduced in size, weight, and cost of energy storage system. High-frequency link circuit topology is advantageous in realizing compact and light-weight power converters for uninterruptible power supply systems, new energy systems using photovoltaic-cells, fuel-cells and so on. This paper presents a DC-DC type high-frequency link DC (HFLDC) cascaded multilevel inverter. Each converter cell is implemented a control strategy for two H-bridge inverters that are controlled with the same multicarrier pulse width modulation (PWM) technique. The proposed cascaded multilevel inverter generates lower voltage total harmonic distortion (THD) in comparison with conventional cascaded multilevel inverter. Digital simulations are carried out using PSCAD/EMTDC to validate the performance of the proposed cascaded multilevel inverter.

Purification of complex samples: Implementation of a modular and reconfigurable droplet-based microfluidic platform with cascaded deterministic lateral displacement separation modules

PubMed Central

Pudda, Catherine; Boizot, François; Verplanck, Nicolas; Revol-Cavalier, Frédéric; Berthier, Jean; Thuaire, Aurélie

2018-01-01

Particle separation in microfluidic devices is a common problematic for sample preparation in biology. Deterministic lateral displacement (DLD) is efficiently implemented as a size-based fractionation technique to separate two populations of particles around a specific size. However, real biological samples contain components of many different sizes and a single DLD separation step is not sufficient to purify these complex samples. When connecting several DLD modules in series, pressure balancing at the DLD outlets of each step becomes critical to ensure an optimal separation efficiency. A generic microfluidic platform is presented in this paper to optimize pressure balancing, when DLD separation is connected either to another DLD module or to a different microfluidic function. This is made possible by generating droplets at T-junctions connected to the DLD outlets. Droplets act as pressure controllers, which perform at the same time the encapsulation of DLD sorted particles and the balance of output pressures. The optimized pressures to apply on DLD modules and on T-junctions are determined by a general model that ensures the equilibrium of the entire platform. The proposed separation platform is completely modular and reconfigurable since the same predictive model applies to any cascaded DLD modules of the droplet-based cartridge. PMID:29768490

The EAL domain protein YciR acts as a trigger enzyme in a c-di-GMP signalling cascade in E. coli biofilm control

PubMed Central

Lindenberg, Sandra; Klauck, Gisela; Pesavento, Christina; Klauck, Eberhard; Hengge, Regine

2013-01-01

C-di-GMP—which is produced by diguanylate cyclases (DGC) and degraded by specific phosphodiesterases (PDEs)—is a ubiquitous second messenger in bacterial biofilm formation. In Escherichia coli, several DGCs (YegE, YdaM) and PDEs (YhjH, YciR) and the MerR-like transcription factor MlrA regulate the transcription of csgD, which encodes a biofilm regulator essential for producing amyloid curli fibres of the biofilm matrix. Here, we demonstrate that this system operates as a signalling cascade, in which c-di-GMP controlled by the DGC/PDE pair YegE/YhjH (module I) regulates the activity of the YdaM/YciR pair (module II). Via multiple direct interactions, the two module II proteins form a signalling complex with MlrA. YciR acts as a connector between modules I and II and functions as a trigger enzyme: its direct inhibition of the DGC YdaM is relieved when it binds and degrades c-di-GMP generated by module I. As a consequence, YdaM then generates c-di-GMP and—by direct and specific interaction—activates MlrA to stimulate csgD transcription. Trigger enzymes may represent a general principle in local c-di-GMP signalling. PMID:23708798

Spectrally resolved modal characteristics of leaky-wave-coupled quantum cascade phase-locked laser arrays

NASA Astrophysics Data System (ADS)

Sigler, Chris; Gibson, Ricky; Boyle, Colin; Kirch, Jeremy D.; Lindberg, Donald; Earles, Thomas; Botez, Dan; Mawst, Luke J.; Bedford, Robert

2018-01-01

The modal characteristics of nonresonant five-element phase-locked arrays of 4.7-μm emitting quantum cascade lasers (QCLs) have been studied using spectrally resolved near- and far-field measurements and correlated with results of device simulation. Devices are fabricated by a two-step metal-organic chemical vapor deposition process and operate predominantly in an in-phase array mode near threshold, although become multimode at higher drive levels. The wide spectral bandwidth of the QCL's core region is found to be a factor in promoting multispatial-mode operation at high drive levels above threshold. An optimized resonant-array design is identified to allow sole in-phase array-mode operation to high drive levels above threshold, and indicates that for phase-locked laser arrays full spatial coherence to high output powers does not require full temporal coherence.

Molecular and functional characterization of caspase-8 from the big-belly seahorse (Hippocampus abdominalis).

PubMed

Oh, Minyoung; Elvitigala, Don Anushka Sandaruwan; Bathige, S D N K; Lee, Seongdo; Kim, Myoung-Jin; Lee, Jehee

2016-11-01

Apoptosis is a physiological process that can also participate in host immune defense mechanisms, including tumor growth suppression along with homeostasis and maturation of immune cells. Caspases are known to be involved in cellular apoptotic signaling; among them, caspase-8 plays an important role in the initiation phase of the apoptotic death cascade. In the current study, we molecularly characterized a caspase-8 homolog (designated as HaCasp-8) from Hippocampus abdominalis. The HaCasp-8 gene harbors a 1476 bp open reading frame (ORF) that codes for a protein of 492 amino acids (aa) with a predicted molecular mass of 55 kDa. HaCasp-8 houses the typical domain architecture of known initiator caspases, including the death effector domain and the carboxyl-terminal catalytic domain. As expected, phylogenetic analysis reflected a closer evolutionary relationship of HaCasp-8 with its teleostean similitudes. The results of our qPCR assays confirmed the ubiquitous expression of HaCasp-8 in physiologically important tissues examined, with pronounced expression levels in ovary tissues, followed by blood cells. HaCasp-8 expression at the mRNA level was found to be significantly modulated by lipopolysaccharide, polyinosinic:polycytidylic acid, Streptococcus iniae, and Edwardsiella tarda injection. Overexpression of HaCasp-8 could trigger a significant level of cell death in HEK293T cells, suggesting its putative role in cell death. Taken together, our findings suggest that HaCasp-8 is an important component in the caspase cascade, and its expression can be significantly modulated under pathogen stress conditions in the big-belly seahorse. Copyright © 2016 Elsevier Ltd. All rights reserved.

Electrically controllable photonic molecule laser.

PubMed

Fasching, G; Deutsch, Ch; Benz, A; Andrews, A M; Klang, P; Zobl, R; Schrenk, W; Strasser, G; Ragulis, P; Tamosiūnas, V; Unterrainer, K

2009-10-26

We have studied the coherent intercavity coupling of the evanescent fields of two microdisk terahertz quantum-cascade lasers. The electrically controllable optical coupling of the single-mode operating lasers has been observed for cavity spacings up to 30 mum. The strongest coupled photonic molecule with 2 mum intercavity spacing allows to conditionally switch the optical emission by the electrical modulation of only one microdisk. The lasing threshold characteristics demonstrate the linear dependence of the gain of a quantum-cascade laser on the applied electric field.

Molecular dispersion spectroscopy based on Fabry-Perot quantum cascade lasers.

PubMed

Sterczewski, Lukasz A; Westberg, Jonas; Wysocki, Gerard

2017-01-15

Two Fabry-Perot quantum cascade lasers are used in a differential dual comb configuration to perform rapidly swept dispersion spectroscopy of low-pressure nitrous oxide with <1  ms acquisition time. Active feedback control of the laser injection current enables simultaneous wavelength modulation of both lasers at kilohertz rates. The system demonstrates similar performance in both absorption and dispersion spectroscopy modes and achieves a noise-equivalent absorption figure of merit in the low 10^-4/Hz range.

Mitochondrial and Chloroplast Stress Responses Are Modulated in Distinct Touch and Chemical Inhibition Phases1[OPEN

PubMed Central

Ivanova, Aneta; Millar, A. Harvey; Whelan, James

2016-01-01

Previous studies have identified a range of transcription factors that modulate retrograde regulation of mitochondrial and chloroplast functions in Arabidopsis (Arabidopsis thaliana). However, the relative importance of these regulators and whether they act downstream of separate or overlapping signaling cascades is still unclear. Here, we demonstrate that multiple stress-related signaling pathways, with distinct kinetic signatures, converge on overlapping gene sets involved in energy organelle function. The transcription factor ANAC017 is almost solely responsible for transcript induction of marker genes around 3 to 6 h after chemical inhibition of organelle function and is a key regulator of mitochondrial and specific types of chloroplast retrograde signaling. However, an independent and highly transient gene expression phase, initiated within 10 to 30 min after treatment, also targets energy organelle functions, and is related to touch and wounding responses. Metabolite analysis demonstrates that this early response is concurrent with rapid changes in tricarboxylic acid cycle intermediates and large changes in transcript abundance of genes encoding mitochondrial dicarboxylate carrier proteins. It was further demonstrated that transcription factors AtWRKY15 and AtWRKY40 have repressive regulatory roles in this touch-responsive gene expression. Together, our results show that several regulatory systems can independently affect energy organelle function in response to stress, providing different means to exert operational control. PMID:27208304

Quantum structures for recombination control in the light-emitting transistor

NASA Astrophysics Data System (ADS)

Chen, Kanuo; Hsiao, Fu-Chen; Joy, Brittany; Dallesasse, John M.

2017-02-01

Recombination of carriers in the direct-bandgap base of a transistor-injected quantum cascade laser (TI-QCL) is shown to be controllable through the field applied across the quantum cascade region located in the transistor's base-collector junction. The influence of the electric field on the quantum states in the cascade region's superlattice allows free flow of electrons out of the transistor base only for field values near the design field that provides optimal QCL gain. Quantum modulation of base recombination in the light-emitting transistor is therefore observed. In a GaAs-based light-emitting transistor, a periodic superlattice is grown between the p-type base and the n-type collector. Under different base-collector biasing conditions the distribution of quantum states, and as a consequence transition probabilities through the wells and barriers forming the cascade region, leads to strong field-dependent mobility for electrons in transit through the base-collector junction. The radiative base recombination, which is influenced by minority carrier transition lifetime, can be modulated through the quantum states alignment in the superlattice. A GaAs-based transistor-injected quantum cascade laser with AlGaAs/GaAs superlattice is designed and fabricated. Radiative base recombination is measured under both common-emitter and common-base configuration. In both configurations the optical output from the base is proportional to the emitter injection. When the quantum states in the superlattice are aligned the optical output in the base is reduced as electrons encounter less impedance entering the collector; when the quantum states are misaligned electrons have longer lifetime in the base and the radiative base recombination process is enhanced.

PAM4 silicon photonic microring resonator-based transceiver circuits

NASA Astrophysics Data System (ADS)

Palermo, Samuel; Yu, Kunzhi; Roshan-Zamir, Ashkan; Wang, Binhao; Li, Cheng; Seyedi, M. Ashkan; Fiorentino, Marco; Beausoleil, Raymond

2017-02-01

Increased data rates have motivated the investigation of advanced modulation schemes, such as four-level pulseamplitude modulation (PAM4), in optical interconnect systems in order to enable longer transmission distances and operation with reduced circuit bandwidth relative to non-return-to-zero (NRZ) modulation. Employing this modulation scheme in interconnect architectures based on high-Q silicon photonic microring resonator devices, which occupy small area and allow for inherent wavelength-division multiplexing (WDM), offers a promising solution to address the dramatic increase in datacenter and high-performance computing system I/O bandwidth demands. Two ring modulator device structures are proposed for PAM4 modulation, including a single phase shifter segment device driven with a multi-level PAM4 transmitter and a two-segment device driven by two simple NRZ (MSB/LSB) transmitters. Transmitter circuits which utilize segmented pulsed-cascode high swing output stages are presented for both device structures. Output stage segmentation is utilized in the single-segment device design for PAM4 voltage level control, while in the two-segment design it is used for both independent MSB/LSB voltage levels and impedance control for output eye skew compensation. The 65nm CMOS transmitters supply a 4.4Vppd output swing for 40Gb/s operation when driving depletion-mode microring modulators implemented in a 130nm SOI process, with the single- and two-segment designs achieving 3.04 and 4.38mW/Gb/s, respectively. A PAM4 optical receiver front-end is also described which employs a large input-stage feedback resistor transimpedance amplifier (TIA) cascaded with an adaptively-tuned continuous-time linear equalizer (CTLE) for improved sensitivity. Receiver linearity, critical in PAM4 systems, is achieved with a peak-detector-based automatic gain control (AGC) loop.

Oscillatory bursting of gel fuel droplets in a reacting environment.

PubMed

Miglani, Ankur; Nandagopalan, Purushothaman; John, Jerin; Baek, Seung Wook

2017-06-12

Understanding the combustion behavior of gel fuel droplets is pivotal for enhancing burn rates, lowering ignition delay and improving the operational performance of next-generation propulsion systems. Vapor jetting in burning gel fuel droplets is a crucial process that enables an effective transport (convectively) of unreacted fuel from the droplet domain to the flame zone and accelerates the gas-phase mixing process. Here, first we show that the combusting ethanol gel droplets (organic gellant laden) exhibit a new oscillatory jetting mode due to aperiodic bursting of the droplet shell. Second, we show how the initial gellant loading rate (GLR) leads to a distinct shell formation which self-tunes temporally to burst the droplet at different frequencies. Particularly, a weak-flexible shell is formed at low GLR that undergoes successive rupture cascades occurring in same region of the droplet. This region weakens due to repeated ruptures and causes droplet bursting at progressively higher frequencies. Contrarily, high GLRs facilitate a strong-rigid shell formation where consecutive cascades occur at scattered locations across the droplet surface. This leads to droplet bursting at random frequencies. This method of modulating jetting frequency would enable an effective control of droplet trajectory and local fuel-oxidizer ratio in any gel-spray based energy formulation.

Full quaternion based finite-time cascade attitude control approach via pulse modulation synthesis for a spacecraft.

PubMed

Mazinan, A H; Pasand, M; Soltani, B

2015-09-01

In the aspect of further development of investigations in the area of spacecraft modeling and analysis of the control scheme, a new hybrid finite-time robust three-axis cascade attitude control approach is proposed via pulse modulation synthesis. The full quaternion based control approach proposed here is organized in association with both the inner and the outer closed loops. It is shown that the inner closed loop, which consists of the sliding mode finite-time control approach, the pulse width pulse frequency modulator, the control allocation and finally the dynamics of the spacecraft is realized to track the three-axis referenced commands of the angular velocities. The pulse width pulse frequency modulators are in fact employed in the inner closed loop to accommodate the control signals to a number of on-off thrusters, while the control allocation algorithm provides the commanded firing times for the reaction control thrusters in the overactuated spacecraft. Hereinafter, the outer closed loop, which consists of the proportional linear control approach and the kinematics of the spacecraft is correspondingly designed to deal with the attitude angles that are presented by quaternion vector. It should be noted that the main motivation of the present research is to realize a hybrid control method by using linear and nonlinear terms and to provide a reliable and robust control structure, which is able to track time varying three-axis referenced commands. Subsequently, a stability analysis is presented to verify the performance of the overall proposed cascade attitude control approach. To prove the effectiveness of the presented approach, a thorough investigation is presented compared to a number of recent corresponding benchmarks. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Optoelectronic properties of type I indium gallium arsenide quantum cascade lasers with applications to optical modulation

NASA Astrophysics Data System (ADS)

Murawski, Robert K.

Quantum Cascade Lasers (QCL) are unique unipolar conduction band devices designed to emit in the mid infrared region (MIR). They have been employed very successfully in spectroscopy and sensing applications. Motivated by predictions of modulation bandwidths above 100 GHz, communication links based on QCLs were recently demonstrated. However, the intrinsic device circuitry of the QCL limits its bandwidth. In this thesis a new All-Optical Modulation of the QCL is presented and investigated both theoretically and experimentally. This method of modulation allows for full access to the bandwidth as well as unique optical control of the MIR laser emission. For this purpose, conduction and valence band wave functions for the complex QCL structure are presented allowing for the first time calculations of their interband energy resonances. Based on this knowledge, a novel optical modulation scheme is developed utilizing interband transition for laser modulation. Using laser rate equations, more accurate predictions for the response function can be derived. Optical modulation is shown to be superior to direct modulation. In addition to this theoretical framework, first experiments are presented on the effects of illuminating a QCL with additional lasers at or above the interband gap. The first demonstration of All-Optical Modulation was achieved using time varying near infrared illumination and the complimentary signature in the MIR QCL emission was observed. In addition to extending the knowledge base of QCL research by a first calculation of its valence band structure, this work opens new possibilities in modulation and control of the QCL's MIR emission by interband transition. Application of this technique range from fundamental physics research (e.g. electron coherence) to ultrafast communication (e.g. free-space links) and high-resolution spectroscopy.

Microwave phase shifter with controllable power response based on slow- and fast-light effects in semiconductor optical amplifiers.

PubMed

Xue, Weiqi; Sales, Salvador; Capmany, José; Mørk, Jesper

2009-04-01

We suggest and experimentally demonstrate a method for increasing the tunable rf phase shift of semiconductor waveguides while at the same time enabling control of the rf power. This method is based on the use of slow- and fast-light effects in a cascade of semiconductor optical amplifiers combined with the use of spectral filtering to enhance the role of refractive index dynamics. A continuously tunable phase shift of approximately 240 degrees at a microwave frequency of 19 GHz is demonstrated in a cascade of two semiconductor optical amplifiers, while maintaining an rf power change of less than 1.6 dB. The technique is scalable to more amplifiers and should allow realization of an rf phase shift of 360 degrees.

Numerical Investigation of a Cascaded Longitudinal Space-Charge Amplifier at the Fermilab's Advanced Superconducting Test Accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halavanau, A.; Piot, P.

2015-06-01

In a cascaded longitudinal space-charge amplifier (LSCA), initial density noise in a relativistic e-beam is amplified via the interplay of longitudinal space charge forces and properly located dispersive sections. This type of amplification process was shown to potentially result in large final density modulations [1] compatible with the production of broadband electromagnetic radiation. The technique was recently demonstrated in the optical domain [2]. In this paper we investigate, via numerical simulations, the performances of a cascaded LSCA beamline at the Fermilab’s Advanced Superconducting Test Accelerator (ASTA). We especially explore the properties of the produced broadband radiation. Our studies have beenmore » conducted with a grid-less three-dimensional space-charge algorithm.« less

Cascade flutter analysis with transient response aerodynamics

NASA Technical Reports Server (NTRS)

Bakhle, Milind A.; Mahajan, Aparajit J.; Keith, Theo G., Jr.; Stefko, George L.

1991-01-01

Two methods for calculating linear frequency domain aerodynamic coefficients from a time marching Full Potential cascade solver are developed and verified. In the first method, the Influence Coefficient, solutions to elemental problems are superposed to obtain the solutions for a cascade in which all blades are vibrating with a constant interblade phase angle. The elemental problem consists of a single blade in the cascade oscillating while the other blades remain stationary. In the second method, the Pulse Response, the response to the transient motion of a blade is used to calculate influence coefficients. This is done by calculating the Fourier Transforms of the blade motion and the response. Both methods are validated by comparison with the Harmonic Oscillation method and give accurate results. The aerodynamic coefficients obtained from these methods are used for frequency domain flutter calculations involving a typical section blade structural model. An eigenvalue problem is solved for each interblade phase angle mode and the eigenvalues are used to determine aeroelastic stability. Flutter calculations are performed for two examples over a range of subsonic Mach numbers.

Pathway and network-based analysis of genome-wide association studies and RT-PCR validation in polycystic ovary syndrome

PubMed Central

Shen, Haoran; Liang, Zhou; Zheng, Saihua; Li, Xuelian

2017-01-01

The purpose of this study was to identify promising candidate genes and pathways in polycystic ovary syndrome (PCOS). Microarray dataset GSE345269 obtained from the Gene Expression Omnibus database includes 7 granulosa cell samples from PCOS patients, and 3 normal granulosa cell samples. Differentially expressed genes (DEGs) were screened between PCOS and normal samples. Pathway enrichment analysis was conducted for DEGs using ClueGO and CluePedia plugin of Cytoscape. A Reactome functional interaction (FI) network of the DEGs was built using ReactomeFIViz, and then network modules were extracted, followed by pathway enrichment analysis for the modules. Expression of DEGs in granulosa cell samples was measured using quantitative RT-PCR. A total of 674 DEGs were retained, which were significantly enriched with inflammation and immune-related pathways. Eight modules were extracted from the Reactome FI network. Pathway enrichment analysis revealed significant pathways of each module: module 0, Regulation of RhoA activity and Signaling by Rho GTPases pathways shared ARHGAP4 and ARHGAP9; module 2, GlycoProtein VI-mediated activation cascade pathway was enriched with RHOG; module 3, Thromboxane A2 receptor signaling, Chemokine signaling pathway, CXCR4-mediated signaling events pathways were enriched with LYN, the hub gene of module 3. Results of RT-PCR confirmed the finding of the bioinformatic analysis that ARHGAP4, ARHGAP9, RHOG and LYN were significantly upregulated in PCOS. RhoA-related pathways, GlycoProtein VI-mediated activation cascade pathway, ARHGAP4, ARHGAP9, RHOG and LYN may be involved in the pathogenesis of PCOS. PMID:28949383

iss031e140701

NASA Image and Video Library

2012-06-23

ISS031-E-140701 (23 June 2012) --- Russian cosmonaut Sergei Revin, Expedition 31 flight engineer, works on the BTKh-26 KASKAD (Cascade) experiment in the Rassvet Mini-Research Module 1 (MRM-1) of the International Space Station.

iss031e140699

NASA Image and Video Library

2012-06-23

ISS031-E-140699 (23 June 2012) --- Russian cosmonaut Sergei Revin, Expedition 31 flight engineer, works on the BTKh-26 KASKAD (Cascade) experiment in the Rassvet Mini-Research Module 1 (MRM-1) of the International Space Station.

The frequencies of calcium oscillations are optimized for efficient calcium-mediated activation of Ras and the ERK/MAPK cascade.

PubMed

Kupzig, Sabine; Walker, Simon A; Cullen, Peter J

2005-05-24

Ras proteins are binary switches that, by cycling through inactive GDP- and active GTP-bound conformations, regulate multiple cellular signaling pathways, including those that control growth and differentiation. For some time, it has been known that receptor-mediated increases in the concentration of intracellular free calcium ([Ca(2+)](i)) can modulate Ras activation. Increases in [Ca(2+)](i) often occur as repetitive Ca(2+) spikes or oscillations. Induced by electrical or receptor stimuli, these repetitive Ca(2+) oscillations increase in frequency with the amplitude of receptor stimuli, a phenomenon critical for the induction of selective cellular functions. Here, we show that Ca(2+) oscillations are optimized for Ca(2+)-mediated activation of Ras and signaling through the extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK) cascade. We present additional evidence that Ca(2+) oscillations reduce the effective Ca(2+) threshold for the activation of Ras and that the oscillatory frequency is optimized for activation of Ras and the ERK/MAPK pathway. Our results describe a hitherto unrecognized link between complex Ca(2+) signals and the modulation of the Ras/ERK/MAPK signaling cascade.

Antithrombin, an Important Inhibitor in Blood Clots.

PubMed

Zhu, Ying; Cong, Qing-Wei; Liu, Yue; Wan, Chun-Ling; Yu, Tao; He, Guang; He, Lin; Cai, Lei; Chou, Kuo-Chen

2016-01-01

Blood coagulation is healthy and lifesaving because it can stop bleeding. It can, however, be a troublemaker as well, causing serious medical problems including heart attack and stroke. Body has complex blood coagulation cascade to modulate the blood clots. In the environment of plasma, the blood coagulation cascade is regulated by antithrombin, which is deemed one of the most important serine protease inhibitors. It inhibits thrombin; it can inhibit factors IXa and Xa as well. Interestingly, its inhibitory ability will be significantly increased with the existence of heparin. In this minireview paper, we are to summarize the structural features of antithrombin, as well as its heparin binding modes and anti-coagulation mechanisms, in hopes that the discussion and analysis presented in this paper can stimulate new strategies to find more effective approaches or compounds to modulate the antithrombin.

Critical behavior in the inverse to forward energy transition in two-dimensional magnetohydrodynamic flow.

PubMed

Seshasayanan, Kannabiran; Alexakis, Alexandros

2016-01-01

We investigate the critical transition from an inverse cascade of energy to a forward energy cascade in a two-dimensional magnetohydrodynamic flow as the ratio of magnetic to mechanical forcing amplitude is varied. It is found that the critical transition is the result of two competing processes. The first process is due to hydrodynamic interactions and cascades the energy to the large scales. The second process couples small-scale magnetic fields to large-scale flows, transferring the energy back to the small scales via a nonlocal mechanism. At marginality the two cascades are both present and cancel each other. The phase space diagram of the transition is sketched.

A Mechanism for Bulk Energization in the Impulsive Phase of Solar Flares: MHD Turbulent Cascade

NASA Technical Reports Server (NTRS)

LaRosa, T. N.; Moore, R. L.

1993-01-01

We propose that the large production rate (approximately 10(exp 36)/s) of energetic electrons (greater than or approximately equal to 25 keV) required to account for the impulsive-phase hard X-ray burst in large flares is achieved through MHD turbulent cascade of the bulk kinetic energy of the outflows from many separate reconnection events. Focusing on large two- ribbon eruptive flares as representative of most large flares, we envision the reconnection events to be the driven reconnection of oppositely directed elementary flux tubes pressing into the flare-length current-sheet interface that forms in the wake of the eruption of the sheared core of the preflare bipolar field configuration. We point out that, because the outflows from these driven reconnection events have speeds of order the Alfven speed and because the magnetic field reduces the shear viscosity of the plasma, it is reasonable that the outflows are unstable and turbulent, so that the kinetic energy of an outflow is rapidly dissipated through turbulent cascade. If the largest eddies in the turbulence have diameters of order the expected widths of the outflows (10(exp 7)-10(exp 8)cm), then the cascade dissipation of each of these eddies could produce approximately 10(exp 26) erg burst of energized electrons (approximately 3 x (10(exp 33) 25 keV electrons) in approximately 0.3 s, which agrees well with hard X-ray and radio sub-bursts commonly observed during the impulsive phase. Of order 10(exp 2) simultaneous reconnection events with turbulent outflow would produce the observed rate of impulsive-phase plasma energization in the most powerful flares (approximately 10(exp 36) 25 keV electrons/ s); this number of reconnection sites can easily fit within the estimated 3 x 10(exp 9) cm span of the overall current-sheet dissipation region formed in these large flares. We therefore conclude that MHD turbulent cascade is a promising mechanism for the plasma energization observed in the impulsive phase of solar flares.

The Anti-inflammatory Drug Indomethacin Alters Nanoclustering in Synthetic and Cell Plasma Membranes*

PubMed Central

Zhou, Yong; Plowman, Sarah J.; Lichtenberger, Lenard M.; Hancock, John F.

2010-01-01

The nonsteroidal anti-inflammatory drug indomethacin exhibits diverse biological effects, many of which have no clear molecular mechanism. Membrane-bound receptors and enzymes are sensitive to their phospholipid microenvironment. Amphipathic indomethacin could therefore potentially modulate cell signaling by changing membrane properties. Here we examined the effect of indomethacin on membrane lateral heterogeneity. Fluorescence lifetime imaging of cells expressing lipid-anchored probes revealed that treatment of BHK cells with therapeutic levels of indomethacin enhances cholesterol-dependent nanoclustering, but not cholesterol-independent nanoclustering. Immuno-electron microscopy and quantitative spatial mapping of intact plasma membrane sheets similarly showed a selective effect of indomethacin on promoting cholesterol-dependent, but not cholesterol-independent, nanoclustering. To further evaluate the biophysical effects of indomethacin, we measured fluorescence polarization of the phase-sensitive probe Laurdan and FRET between phase-partitioning probes in model bilayers. Therapeutic levels of indomethacin enhanced phase seperation in DPPC/DOPC/Chol (1:1:1) and DPPC/Chol membranes in a temperature-dependent manner, but had minimal effect on the phase behavior of pure DOPC at any temperature. Taken together, the imaging results on intact epithelial cells and the biophysical assays of model membranes suggest that indomethacin can enhance phase separation and stabilize cholesterol-dependent nanoclusters in biological membranes. These effects on membrane lateral heterogeneity may have significant consequences for cell signaling cascades that are assembled on the plasma membrane. PMID:20826816

Phase-locked array of quantum cascade lasers with an integrated Talbot cavity.

PubMed

Wang, Lei; Zhang, Jinchuan; Jia, Zhiwei; Zhao, Yue; Liu, Chuanwei; Liu, Yinghui; Zhai, Shenqiang; Ning, Zhuo; Xu, Xiangang; Liu, Fengqi

2016-12-26

We show a phase-locked array of three quantum cascade lasers with an integrated Talbot cavity at one side of the laser array. The coupling scheme is called diffraction coupling. By controlling the length of Talbot to be a quarter of Talbot distance (Z_t/4), in-phase mode operation can be selected. The in-phase operation shows great modal stability under different injection currents, from the threshold current to the full power current. The far-field radiation pattern of the in-phase operation contains three lobes, one central maximum lobe and two side lobes. The interval between adjacent lobes is about 10.5°. The output power is about 1.5 times that of a single-ridge laser. Further studies should be taken to achieve better beam performance and reduce optical losses brought by the integrated Talbot cavity.

Differentially expressed regulatory genes in honey bee caste development

NASA Astrophysics Data System (ADS)

Hepperle, C.; Hartfelder, K.

2001-03-01

In the honey bee, an eminently fertile queen with up to 200 ovarioles per ovary monopolizes colony level reproduction. In contrast, worker bees have only few ovarioles and are essentially sterile. This phenotype divergence is a result of caste-specifically modulated juvenile hormone and ecdysteroid titers in larval development. In this study we employed a differential-display reverse transcription (DDRT)-PCR protocol to detect ecdysteroid-regulated gene expression during a critical phase of caste development. We identified a Ftz-F1 homolog and a Cut-like transcript. Ftz-F1 could be a putative element of the metamorphic ecdysone response cascade of bees, whereas Cut-like proteins are described as transcription factors involved in maintaining cellular differentiation states. The downregulation of both factors can be interpreted as steps in the metamorphic degradation of ovarioles in worker-bee ovaries.

Multiwavelength self-pulsating fibre laser based on cascaded SPM spectral broadening and filtering

NASA Astrophysics Data System (ADS)

Rochette, Martin; Sun, Kai; Hernández-Cordero, Juan; Chen, Lawrence R.

2008-06-01

We experimentally demonstrate the operation of a laser based on self-phase modulation followed by offset spectral filtering. This laser has three operation modes: a continuous-wave mode, a self-pulsating mode where the laser self ignites and produces pulses, and a pulse-buffering mode where no new pulse is formed from spontaneous emission noise but only pulses already propagating or pulses injected in the laser cavity can be sustained. In the self-pulsating and pulse-buffering modes, the laser is multi-wavelength and continuously tunable over the entire gain band of the amplifiers. The output pulse width is quasi transform-limited with respect to the spectral-width of the filters used in the cavity. Overall, this device provides a simple alternative to pulsed laser source and also represents a promising approach for signal buffering.

Interferon Lambda: Modulating Immunity in Infectious Diseases.

PubMed

Syedbasha, Mohammedyaseen; Egli, Adrian

2017-01-01

Interferon lambdas (IFN-λs; IFNL1-4) modulate immunity in the context of infections and autoimmune diseases, through a network of induced genes. IFN-λs act by binding to the heterodimeric IFN-λ receptor (IFNLR), activating a STAT phosphorylation-dependent signaling cascade. Thereby hundreds of IFN-stimulated genes are induced, which modulate various immune functions via complex forward and feedback loops. When compared to the well-characterized IFN-α signaling cascade, three important differences have been discovered. First, the IFNLR is not ubiquitously expressed: in particular, immune cells show significant variation in the expression levels of and susceptibilities to IFN-λs. Second, the binding affinities of individual IFN-λs to the IFNLR varies greatly and are generally lower compared to the binding affinities of IFN-α to its receptor. Finally, genetic variation in the form of a series of single-nucleotide polymorphisms (SNPs) linked to genes involved in the IFN-λ signaling cascade has been described and associated with the clinical course and treatment outcomes of hepatitis B and C virus infection. The clinical impact of IFN-λ signaling and the SNP variations may, however, reach far beyond viral hepatitis. Recent publications show important roles for IFN-λs in a broad range of viral infections such as human T-cell leukemia type-1 virus, rotaviruses, and influenza virus. IFN-λ also potentially modulates the course of bacterial colonization and infections as shown for Staphylococcus aureus and Mycobacterium tuberculosis . Although the immunological processes involved in controlling viral and bacterial infections are distinct, IFN-λs may interfere at various levels: as an innate immune cytokine with direct antiviral effects; or as a modulator of IFN-α-induced signaling via the suppressor of cytokine signaling 1 and the ubiquitin-specific peptidase 18 inhibitory feedback loops. In addition, the modulation of adaptive immune functions via macrophage and dendritic cell polarization, and subsequent priming, activation, and proliferation of pathogen-specific T- and B-cells may also be important elements associated with infectious disease outcomes. This review summarizes the emerging details of the IFN-λ immunobiology in the context of the host immune response and viral and bacterial infections.

Regulatory effect of the AMPK-COX-2 signaling pathway in curcumin-induced apoptosis in HT-29 colon cancer cells.

PubMed

Lee, Yun-Kyoung; Park, Song Yi; Kim, Young-Min; Park, Ock Jin

2009-08-01

AMP-activated protein kinase (AMPK), a highly conserved protein in eukaryotes, functions as a major metabolic switch to maintain energy homeostasis. It also intrinsically regulates the mammalian cell cycle. Moreover, the AMPK cascade has emerged as an important pathway implicated in cancer control. In this study we investigated the effects of curcumin on apoptosis and the regulatory effect of the AMPK-cyclooxygenase-2 (COX-2) pathway in curcumin-induced apoptosis. Curcumin has shown promise as a chemopreventive agent because of its in vivo regression of various animal-model colon cancers. This study focused on exploiting curcumin to apply antitumorigenic effects through modulation of the AMPK-COX-2 cascade. Curcumin exhibited a potent apoptotic effect on HT-29 colon cancer cells at concentrations of 50 micromol/L and above. These apoptotic effects were correlated with the decrease in pAkt and COX-2, as well as the increase in p-AMPK. Cell cycle analysis showed that curcumin induced G(1)-phase arrest. Further study with AMPK synthetic inhibitor Compound C has shown that increased concentrations of Compound C would abolish AMPK expression, accompanied by a marked increase in COX-2 as well as pAkt expression in curcumin-treated HT-29 cells. By inhibiting AMPK with Compound C, we found that curcumin-treated colon cancer cells were no longer undergoing apoptosis; rather, they were proliferative. These results indicate that AMPK is crucial in apoptosis induced by curcumin and further that the pAkt-AMPK-COX-2 cascade or AMPK-pAkt-COX-2 pathway is important in cell proliferation and apoptosis in colon cancer cells.

A versatile, C-band spanning, high repetition rate, cascaded four wave mixing based multi-wavelength source

NASA Astrophysics Data System (ADS)

Vikram, B. S.; Prakash, Roopa; K. P., Nagarjun; Selvaraja, Shankar Kumar; Supradeepa, V. R.

2018-02-01

Demand for bandwidth in optical communications necessitates the development of scalable transceivers that cater to these needs. For this, in DWDM systems with/without Superchannels, the optical source needs to provide a large number of optical carriers. The conventional method of utilizing separate lasers makes the system bulky and inefficient. A multi-wavelength source which spans the entire C-band with sufficient power is needed to replace individual lasers. In addition, multi-wavelength sources at high repetition rates are necessary in various applications such as spectroscopy, astronomical spectrograph calibration, microwave photonics and arbitrary waveform generation. Here, we demonstrate a novel technique for equalized, multi-wavelength source generation which generates over 160 lines at 25GHz repetition rate, spanning the entire C-band with total power >700mW. A 25GHz Comb with 16 lines is generated around 1550nm starting with two individual lasers using a system of directly driven, cascaded intensity and phase modulators. This is then amplified to >1W using an optimized, Erbium-Ytterbium co-doped fiber amplifier. Subsequently, they are passed through Highly NonLinear Fiber at its zero-dispersion wavelength. Through cascaded Four Wave Mixing, a ten-fold increase in the number of lines is demonstrated. A bandwidth of 4.32 THz (174 lines, SNR>15 dB), covering the entire C-band is generated. Enhanced spectral broadening is enabled by two key aspects - Dual laser input provides the optimal temporal profile for spectral broadening while the comb generation prior to amplification enables greater power scaling by suppression of Brillouin scattering. The multi-wavelength source is extremely agile with tunable center frequency and repetition rate.

Harmonic cascade FEL designs for LUX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Penn, G.; Reinsch, M.; Wurtele, J.

LUX is a design concept for an ultrafast X-ray science facility, based on an electron beam accelerated to GeV energies in are circulating linac. Included in the design are short duration (200 fs or shorter FWHM) light sources using multiple stages of higher harmonic generation, seeded by a 200-250 nm laser of similar duration. This laser modulates the energy of a group of electrons within the electron bunch; this section of the electron bunch then produces radiation at a higher harmonic after entering a second, differently tuned undulator. Repeated stages in a cascade yield increasing photon energies up to 1more » keV. Most of the undulators in the cascade operate in the low-gain FEL regime. Harmonic cascades have been designed for each pass of the recirculating linac up to a final electron beam energy of 3.1 GeV. For a given cascade, the photon energy can be selected over a wide range by varying the seed laser frequency and the field strength in the undulators. We present simulation results using the codes GENESIS and GINGER, as well as the results of analytical models which predict FEL performance. We discuss lattice considerations pertinent for harmonic cascade FELs, as well as sensitivity studies and requirements on the electron beam.« less

A period-doubling cascade precedes chaos for planar maps.

PubMed

Sander, Evelyn; Yorke, James A

2013-09-01

A period-doubling cascade is often seen in numerical studies of those smooth (one-parameter families of) maps for which as the parameter is varied, the map transitions from one without chaos to one with chaos. Our emphasis in this paper is on establishing the existence of such a cascade for many maps with phase space dimension 2. We use continuation methods to show the following: under certain general assumptions, if at one parameter there are only finitely many periodic orbits, and at another parameter value there is chaos, then between those two parameter values there must be a cascade. We investigate only families that are generic in the sense that all periodic orbit bifurcations are generic. Our method of proof in showing there is one cascade is to show there must be infinitely many cascades. We discuss in detail two-dimensional families like those which arise as a time-2π maps for the Duffing equation and the forced damped pendulum equation.

Homogeneous spectral spanning of terahertz semiconductor lasers with radio frequency modulation.

PubMed

Wan, W J; Li, H; Zhou, T; Cao, J C

2017-03-08

Homogeneous broadband and electrically pumped semiconductor radiation sources emitting in the terahertz regime are highly desirable for various applications, including spectroscopy, chemical sensing, and gas identification. In the frequency range between 1 and 5 THz, unipolar quantum cascade lasers employing electron inter-subband transitions in multiple-quantum-well structures are the most powerful semiconductor light sources. However, these devices are normally characterized by either a narrow emission spectrum due to the narrow gain bandwidth of the inter-subband optical transitions or an inhomogeneous broad terahertz spectrum from lasers with heterogeneous stacks of active regions. Here, we report the demonstration of homogeneous spectral spanning of long-cavity terahertz semiconductor quantum cascade lasers based on a bound-to-continuum and resonant phonon design under radio frequency modulation. At a single drive current, the terahertz spectrum under radio frequency modulation continuously spans 330 GHz (~8% of the central frequency), which is the record for single plasmon waveguide terahertz lasers with a bound-to-continuum design. The homogeneous broadband terahertz sources can be used for spectroscopic applications, i.e., GaAs etalon transmission measurement and ammonia gas identification.

Homogeneous spectral spanning of terahertz semiconductor lasers with radio frequency modulation

PubMed Central

Wan, W. J.; Li, H.; Zhou, T.; Cao, J. C.

2017-01-01

Homogeneous broadband and electrically pumped semiconductor radiation sources emitting in the terahertz regime are highly desirable for various applications, including spectroscopy, chemical sensing, and gas identification. In the frequency range between 1 and 5 THz, unipolar quantum cascade lasers employing electron inter-subband transitions in multiple-quantum-well structures are the most powerful semiconductor light sources. However, these devices are normally characterized by either a narrow emission spectrum due to the narrow gain bandwidth of the inter-subband optical transitions or an inhomogeneous broad terahertz spectrum from lasers with heterogeneous stacks of active regions. Here, we report the demonstration of homogeneous spectral spanning of long-cavity terahertz semiconductor quantum cascade lasers based on a bound-to-continuum and resonant phonon design under radio frequency modulation. At a single drive current, the terahertz spectrum under radio frequency modulation continuously spans 330 GHz (~8% of the central frequency), which is the record for single plasmon waveguide terahertz lasers with a bound-to-continuum design. The homogeneous broadband terahertz sources can be used for spectroscopic applications, i.e., GaAs etalon transmission measurement and ammonia gas identification. PMID:28272492

Process Intensification of Enzymatic Fatty Acid Butyl Ester Synthesis Using a Continuous Centrifugal Contactor Separator.

PubMed

Ilmi, Miftahul; Abduh, Muhammad Y; Hommes, Arne; Winkelman, Jozef G M; Hidayat, Chusnul; Heeres, Hero J

2018-01-17

Fatty acid butyl esters were synthesized from sunflower oil with 1-butanol using a homogeneous Rhizomucor miehei lipase in a biphasic organic (triglyceride, 1-butanol, hexane)- water (with enzyme) system in a continuous setup consisting of a cascade of a stirred tank reactor and a continuous centrifugal contactor separator (CCCS), the latter being used for integrated reaction and liquid-liquid separation. A fatty acid butyl ester yield up to 93% was obtained in the cascade when operated in a once-through mode. The cascade was run for 8 h without operational issues. Enzyme recycling was studied by reintroduction of the water phase from the CCCS outlet to the stirred tank reactor. Product yield decreased over time to an average of 50% of the initial value, likely due to accumulation of 1-butanol in water phase, loss of enzyme due to agglomeration, and the formation of a separate enzyme layer.

Process Intensification of Enzymatic Fatty Acid Butyl Ester Synthesis Using a Continuous Centrifugal Contactor Separator

PubMed Central

2017-01-01

Fatty acid butyl esters were synthesized from sunflower oil with 1-butanol using a homogeneous Rhizomucor miehei lipase in a biphasic organic (triglyceride, 1-butanol, hexane)– water (with enzyme) system in a continuous setup consisting of a cascade of a stirred tank reactor and a continuous centrifugal contactor separator (CCCS), the latter being used for integrated reaction and liquid–liquid separation. A fatty acid butyl ester yield up to 93% was obtained in the cascade when operated in a once-through mode. The cascade was run for 8 h without operational issues. Enzyme recycling was studied by reintroduction of the water phase from the CCCS outlet to the stirred tank reactor. Product yield decreased over time to an average of 50% of the initial value, likely due to accumulation of 1-butanol in water phase, loss of enzyme due to agglomeration, and the formation of a separate enzyme layer. PMID:29398779

Engineering quadratic nonlinear photonic crystals for frequency conversion of lasers

NASA Astrophysics Data System (ADS)

Chen, Baoqin; Hong, Lihong; Hu, Chenyang; Zhang, Chao; Liu, Rongjuan; Li, Zhiyuan

2018-03-01

Nonlinear frequency conversion offers an effective way to extend the laser wavelength range. Quadratic nonlinear photonic crystals (NPCs) are artificial materials composed of domain-inversion structures whose sign of nonlinear coefficients are modulated with desire to implement quasi-phase matching (QPM) required for nonlinear frequency conversion. These structures can offer various reciprocal lattice vectors (RLVs) to compensate the phase-mismatching during the quadratic nonlinear optical processes, including second-harmonic generation (SHG), sum-frequency generation and the cascaded third-harmonic generation (THG). The modulation pattern of the nonlinear coefficients is flexible, which can be one-dimensional or two-dimensional (2D), be periodic, quasi-periodic, aperiodic, chirped, or super-periodic. As a result, these NPCs offer very flexible QPM scheme to satisfy various nonlinear optics and laser frequency conversion problems via design of the modulation patterns and RLV spectra. In particular, we introduce the electric poling technique for fabricating QPM structures, a simple effective nonlinear coefficient model for efficiently and precisely evaluating the performance of QPM structures, the concept of super-QPM and super-periodically poled lithium niobate for finely tuning nonlinear optical interactions, the design of 2D ellipse QPM NPC structures enabling continuous tunability of SHG in a broad bandwidth by simply changing the transport direction of pump light, and chirped QPM structures that exhibit broadband RLVs and allow for simultaneous radiation of broadband SHG, THG, HHG and thus coherent white laser from a single crystal. All these technical, theoretical, and physical studies on QPM NPCs can help to gain a deeper insight on the mechanisms, approaches, and routes for flexibly controlling the interaction of lasers with various QPM NPCs for high-efficiency frequency conversion and creation of novel lasers.

Multiple-image authentication with a cascaded multilevel architecture based on amplitude field random sampling and phase information multiplexing.

PubMed

Fan, Desheng; Meng, Xiangfeng; Wang, Yurong; Yang, Xiulun; Pan, Xuemei; Peng, Xiang; He, Wenqi; Dong, Guoyan; Chen, Hongyi

2015-04-10

A multiple-image authentication method with a cascaded multilevel architecture in the Fresnel domain is proposed, in which a synthetic encoded complex amplitude is first fabricated, and its real amplitude component is generated by iterative amplitude encoding, random sampling, and space multiplexing for the low-level certification images, while the phase component of the synthetic encoded complex amplitude is constructed by iterative phase information encoding and multiplexing for the high-level certification images. Then the synthetic encoded complex amplitude is iteratively encoded into two phase-type ciphertexts located in two different transform planes. During high-level authentication, when the two phase-type ciphertexts and the high-level decryption key are presented to the system and then the Fresnel transform is carried out, a meaningful image with good quality and a high correlation coefficient with the original certification image can be recovered in the output plane. Similar to the procedure of high-level authentication, in the case of low-level authentication with the aid of a low-level decryption key, no significant or meaningful information is retrieved, but it can result in a remarkable peak output in the nonlinear correlation coefficient of the output image and the corresponding original certification image. Therefore, the method realizes different levels of accessibility to the original certification image for different authority levels with the same cascaded multilevel architecture.

Impact of predator dormancy on prey-predator dynamics

NASA Astrophysics Data System (ADS)

Freire, Joana G.; Gallas, Marcia R.; Gallas, Jason A. C.

2018-05-01

The impact of predator dormancy on the population dynamics of phytoplankton-zooplankton in freshwater ecosystems is investigated using a simple model including dormancy, a strategy to avoid extinction. In addition to recently reported chaos-mediated mixed-mode oscillations, as the carrying capacity grows, we find surprisingly wide phases of nonchaos-mediated mixed-mode oscillations to be present well before the onset of chaos in the system. Nonchaos-mediated cascades display spike-adding sequences, while chaos-mediated cascades show spike-doubling. A host of braided periodic phases with exotic shapes is found embedded in a region of control parameters dominated by chaotic oscillations. We describe the organization of these complicated phases and show how they are interconnected and how their complexity unfolds as control parameters change. The novel nonchaos-mediated phases are found to be large and stable, even for low carrying capacity.

Multichannel, Active Low-Pass Filters

NASA Technical Reports Server (NTRS)

Lev, James J.

1989-01-01

Multichannel integrated circuits cascaded to obtain matched characteristics. Gain and phase characteristics of channels of multichannel, multistage, active, low-pass filter matched by making filter of cascaded multichannel integrated-circuit operational amplifiers. Concept takes advantage of inherent equality of electrical characteristics of nominally-identical circuit elements made on same integrated-circuit chip. Characteristics of channels vary identically with changes in temperature. If additional matched channels needed, chips containing more than two operational amplifiers apiece (e.g., commercial quad operational amplifliers) used. Concept applicable to variety of equipment requiring matched gain and phase in multiple channels - radar, test instruments, communication circuits, and equipment for electronic countermeasures.

Cascaded Raman shifting of high-peak-power nanosecond pulses in As₂S₃ and As₂Se₃ optical fibers.

PubMed

White, Richard T; Monro, Tanya M

2011-06-15

We report efficient cascaded Raman scattering of near-IR nanosecond pulses in large-core (65 μm diameter) As₂S₃ and As₂Se₃ optical fibers. Raman scattering dominates other spectral broadening mechanisms, such as four-wave mixing, modulation instability, and soliton dynamics, because the fibers have large normal group-velocity dispersion in the spectral range of interest. With ~2 ns pump pulses at a wavelength of 1.9 μm, four Stokes peaks, all with peak powers greater than 1 kW, have been measured.

Investigation of advanced pre- and post-equalization schemes in high-order CAP modulation based high-speed indoor VLC transmission system

NASA Astrophysics Data System (ADS)

Wang, Yiguang; Chi, Nan

2016-10-01

Light emitting diodes (LEDs) based visible light communication (VLC) has been considered as a promising technology for indoor high-speed wireless access, due to its unique advantages, such as low cost, license free and high security. To achieve high-speed VLC transmission, carrierless amplitude and phase (CAP) modulation has been utilized for its lower complexity and high spectral efficiency. Moreover, to compensate the linear and nonlinear distortions such as frequency attenuation, sampling time offset, LED nonlinearity etc., series of pre- and post-equalization schemes should be employed in high-speed VLC systems. In this paper, we make an investigation on several advanced pre- and postequalization schemes for high-order CAP modulation based VLC systems. We propose to use a weighted preequalization technique to compensate the LED frequency attenuation. In post-equalization, a hybrid post equalizer is proposed, which consists of a linear equalizer, a Volterra series based nonlinear equalizer, and a decision-directed least mean square (DD-LMS) equalizer. Modified cascaded multi-modulus algorithm (M-CMMA) is employed to update the weights of the linear and the nonlinear equalizer, while DD-LMS can further improve the performance after the preconvergence. Based on high-order CAP modulation and these equalization schemes, we have experimentally demonstrated a 1.35-Gb/s, a 4.5-Gb/s and a 8-Gb/s high-speed indoor VLC transmission systems. The results show the benefit and feasibility of the proposed equalization schemes for high-speed VLC systems.

A bacterial genetic selection system for ubiquitylation cascade discovery.

PubMed

Levin-Kravets, Olga; Tanner, Neta; Shohat, Noa; Attali, Ilan; Keren-Kaplan, Tal; Shusterman, Anna; Artzi, Shay; Varvak, Alexander; Reshef, Yael; Shi, Xiaojing; Zucker, Ori; Baram, Tamir; Katina, Corine; Pilzer, Inbar; Ben-Aroya, Shay; Prag, Gali

2016-11-01

About one-third of the eukaryotic proteome undergoes ubiquitylation, but the enzymatic cascades leading to substrate modification are largely unknown. We present a genetic selection tool that utilizes Escherichia coli, which lack deubiquitylases, to identify interactions along ubiquitylation cascades. Coexpression of split antibiotic resistance protein tethered to ubiquitin and ubiquitylation target together with a functional ubiquitylation apparatus results in a covalent assembly of the resistance protein, giving rise to bacterial growth on selective media. We applied the selection system to uncover an E3 ligase from the pathogenic bacteria EHEC and to identify the epsin ENTH domain as an ultraweak ubiquitin-binding domain. The latter was complemented with a structure-function analysis of the ENTH-ubiquitin interface. We also constructed and screened a yeast fusion library, discovering Sem1 as a novel ubiquitylation substrate of Rsp5 E3 ligase. Collectively, our selection system provides a robust high-throughput approach for genetic studies of ubiquitylation cascades and for small-molecule modulator screening.

Mode stabilization in quantum cascade lasers via an intra-cavity cascaded nonlinearity.

PubMed

St-Jean, M Renaudat; Amanti, M I; Bismuto, A; Beck, M; Faist, J; Sirtori, C

2017-02-06

We present self-stabilization of the inter-mode separation of a quantum cascade laser (QCL) emitting at 9 μm via cascaded second order nonlinearity. This effect has been observed in lasers that have the optical cavity embedded into a microwave strip-line. The intermodal beat note spectra narrow with increasing laser output power, up to less than 100 kHz. A flat frequency response to direct modulation up to 14 GHz is reported for these microstrip QCLs. The laser inter-mode spacing can be locked to an external RF signal and tuned by more than 1 MHz from the free-running spacing. A parallel study on the same laser material in a non-microstrip line waveguide shows superior performances of the microstrip QCL in terms of the intermodal spectral locking and stability. Finally by analyzing our results with the theory of the injection locking of coupled oscillators, we deduce that the microwave power injected in the microstrip QCL is 2 orders of magnitude higher than in the reference laser.

AKAP-Lbc enhances cyclic AMP control of the ERK1/2 cascade.

PubMed

Smith, F Donelson; Langeberg, Lorene K; Cellurale, Cristina; Pawson, Tony; Morrison, Deborah K; Davis, Roger J; Scott, John D

2010-12-01

Mitogen-activated protein kinase (MAPK) cascades propagate a variety of cellular activities. Processive relay of signals through RAF-MEK-ERK modulates cell growth and proliferation. Signalling through this ERK cascade is frequently amplified in cancers, and drugs such as sorafenib (which is prescribed to treat renal and hepatic carcinomas) and PLX4720 (which targets melanomas) inhibit RAF kinases. Natural factors that influence ERK1/2 signalling include the second messenger cyclic AMP. However, the mechanisms underlying this cascade have been difficult to elucidate. We demonstrate that the A-kinase-anchoring protein AKAP-Lbc and the scaffolding protein kinase suppressor of Ras (KSR-1) form the core of a signalling network that efficiently relay signals from RAF, through MEK, and on to ERK1/2. AKAP-Lbc functions as an enhancer of ERK signalling by securing RAF in the vicinity of MEK1 and synchronizing protein kinase A (PKA)-mediated phosphorylation of Ser 838 on KSR-1. This offers mechanistic insight into cAMP-responsive control of ERK signalling events.

Multiple roles of the coagulation protease cascade during virus infection.

PubMed

Antoniak, Silvio; Mackman, Nigel

2014-04-24

The coagulation cascade is activated during viral infections. This response may be part of the host defense system to limit spread of the pathogen. However, excessive activation of the coagulation cascade can be deleterious. In fact, inhibition of the tissue factor/factor VIIa complex reduced mortality in a monkey model of Ebola hemorrhagic fever. Other studies showed that incorporation of tissue factor into the envelope of herpes simplex virus increases infection of endothelial cells and mice. Furthermore, binding of factor X to adenovirus serotype 5 enhances infection of hepatocytes but also increases the activation of the innate immune response to the virus. Coagulation proteases activate protease-activated receptors (PARs). Interestingly, we and others found that PAR1 and PAR2 modulate the immune response to viral infection. For instance, PAR1 positively regulates TLR3-dependent expression of the antiviral protein interferon β, whereas PAR2 negatively regulates expression during coxsackievirus group B infection. These studies indicate that the coagulation cascade plays multiple roles during viral infections.

Probing the Intergalactic Magnetic Field with the Anisotropy of the Extragalactic Gamma-ray Background

NASA Technical Reports Server (NTRS)

Venters, T. M.; Pavlidou, V.

2013-01-01

The intergalactic magnetic field (IGMF) may leave an imprint on the angular anisotropy of the extragalactic gamma-ray background through its effect on electromagnetic cascades triggered by interactions between very high energy photons and the extragalactic background light. A strong IGMF will deflect secondary particles produced in these cascades and will thus tend to isotropize lower energy cascade photons, thereby inducing a modulation in the anisotropy energy spectrum of the gamma-ray background. Here we present a simple, proof-of-concept calculation of the magnitude of this effect and demonstrate that current Fermi data already seem to prefer nonnegligible IGMF values. The anisotropy energy spectrum of the Fermi gamma-ray background could thus be used as a probe of the IGMF strength.

High-power lightweight external-cavity quantum cascade lasers

NASA Astrophysics Data System (ADS)

Day, Timothy; Takeuchi, Eric B.; Weida, Miles; Arnone, David; Pushkarsky, Michael; Boyden, David; Caffey, David

2009-05-01

Commercially available quantum cascade gain media has been integrated with advanced coating and die attach technologies, mid-IR micro-optics and telecom-style assembly and packaging to yield cutting edge performance. When combined into Daylight's external-cavity quantum cascade laser (ECqcL) platform, multi-Watt output power has been obtained. Daylight will describe their most recent results obtained from this platform, including high cw power from compact hermetically sealed packages and narrow spectral linewidth devices. Fiber-coupling and direct amplitude modulation from such multi-Watt lasers will also be described. In addition, Daylight will present the most recent results from their compact, portable, battery-operated "thermal laser pointers" that are being used for illumination and aiming applications. When combined with thermal imaging technology, such devices provide significant benefits in contrast and identification.

Generation and Amplification of Tunable Multicolored Femtosecond Laser Pulses by Using Cascaded Four-Wave Mixing in Transparent Bulk Media

PubMed Central

Liu, Jun; Kobayashi, Takayoshi

2010-01-01

We have reviewed the generation and amplification of wavelength-tunable multicolored femtosecond laser pulses using cascaded four-wave mixing (CFWM) in transparent bulk media, mainly concentrating on our recent work. Theoretical analysis and calculations based on the phase-matching condition could explain well the process semi-quantitatively. The experimental studies showed: (1) as many as fifteen spectral up-shifted and two spectral down-shifted sidebands were obtained simultaneously with spectral bandwidth broader than 1.8 octaves from near ultraviolet (360 nm) to near infrared (1.2 μm); (2) the obtained sidebands were spatially separated well and had extremely high beam quality with M2 factor better than 1.1; (3) the wavelengths of the generated multicolor sidebands could be conveniently tuned by changing the crossing angle or simply replacing with different media; (4) as short as 15-fs negatively chirped or nearly transform limited 20-fs multicolored femtosecond pulses were obtained when one of the two input beams was negatively chirped and the other was positively chirped; (5) the pulse energy of the sideband can reach a μJ level with power stability better than 1% RMS; (6) broadband two-dimensional (2-D) multicolored arrays with more than ten periodic columns and more than ten rows were generated in a sapphire plate; (7) the obtained sidebands could be simultaneously spectra broadened and power amplified in another bulk medium by using cross-phase modulation (XPM) in conjunction with four-wave optical parametric amplification (FOPA). The characterization showed that this is interesting and the CFWM sidebands generated by this novel method have good enough qualities in terms of power stability, beam quality, and temporal features suited to various experiments such as ultrafast multicolor time-resolved spectroscopy and multicolor-excitation nonlinear microscopy. PMID:22399882

Cascading second-order nonlinear processes in a lithium niobate-on-insulator microdisk.

PubMed

Liu, Shijie; Zheng, Yuanlin; Chen, Xianfeng

2017-09-15

Whispering-gallery-mode (WGM) microcavities are very important in both fundamental science and practical applications, among which on-chip second-order nonlinear microresonators play an important role in integrated photonic functionalities. Here we demonstrate resonant second-harmonic generation (SHG) and cascaded third-harmonic generation (THG) in a lithium niobate-on-insulator (LNOI) microdisk resonator. Efficient SHG in the visible range was obtained with only several mW input powers at telecom wavelengths. THG was also observed through a cascading process, which reveals simultaneous phase matching and strong mode coupling in the resonator. Cascading of second-order nonlinear processes gives rise to an effectively large third-order nonlinearity, which makes on-chip second-order nonlinear microresonators a promising frequency converter for integrated nonlinear photonics.

Intensity autocorrelation measurements of frequency combs in the terahertz range

NASA Astrophysics Data System (ADS)

Benea-Chelmus, Ileana-Cristina; Rösch, Markus; Scalari, Giacomo; Beck, Mattias; Faist, Jérôme

2017-09-01

We report on direct measurements of the emission character of quantum cascade laser based frequency combs, using intensity autocorrelation. Our implementation is based on fast electro-optic sampling, with a detection spectral bandwidth matching the emission bandwidth of the comb laser, around 2.5 THz. We find the output of these frequency combs to be continuous even in the locked regime, but accompanied by a strong intensity modulation. Moreover, with our record temporal resolution of only few hundreds of femtoseconds, we can resolve correlated intensity modulation occurring on time scales as short as the gain recovery time, about 4 ps. By direct comparison with pulsed terahertz light originating from a photoconductive emitter, we demonstrate the peculiar emission pattern of these lasers. The measurement technique is self-referenced and ultrafast, and requires no reconstruction. It will be of significant importance in future measurements of ultrashort pulses from quantum cascade lasers.

Efficient generation of 1.9  W yellow light by cascaded frequency doubling of a distributed Bragg reflector tapered diode.

PubMed

Hansen, A K; Christensen, M; Noordegraaf, D; Heist, P; Papastathopoulos, E; Loyo-Maldonado, V; Jensen, O B; Skovgaard, P M W

2016-11-10

Watt-level yellow emitting lasers are interesting for medical applications, due to their high hemoglobin absorption, and for efficient detection of certain fluorophores. In this paper, we demonstrate a compact and robust diode-based laser system in the yellow spectral range. The system generates 1.9 W of single-frequency light at 562.4 nm by cascaded single-pass frequency doubling of the 1124.8 nm emission from a distributed Bragg reflector (DBR) tapered laser diode. The absence of a free-space cavity makes the system stable over a base-plate temperature range of 30 K. At the same time, the use of a laser diode enables the modulation of the pump wavelength by controlling the drive current. This is utilized to achieve a power modulation depth above 90% for the second harmonic light, with a rise time below 40  μs.

Pathway and network-based analysis of genome-wide association studies and RT-PCR validation in polycystic ovary syndrome.

PubMed

Shen, Haoran; Liang, Zhou; Zheng, Saihua; Li, Xuelian

2017-11-01

The purpose of this study was to identify promising candidate genes and pathways in polycystic ovary syndrome (PCOS). Microarray dataset GSE345269 obtained from the Gene Expression Omnibus database includes 7 granulosa cell samples from PCOS patients, and 3 normal granulosa cell samples. Differentially expressed genes (DEGs) were screened between PCOS and normal samples. Pathway enrichment analysis was conducted for DEGs using ClueGO and CluePedia plugin of Cytoscape. A Reactome functional interaction (FI) network of the DEGs was built using ReactomeFIViz, and then network modules were extracted, followed by pathway enrichment analysis for the modules. Expression of DEGs in granulosa cell samples was measured using quantitative RT-PCR. A total of 674 DEGs were retained, which were significantly enriched with inflammation and immune-related pathways. Eight modules were extracted from the Reactome FI network. Pathway enrichment analysis revealed significant pathways of each module: module 0, Regulation of RhoA activity and Signaling by Rho GTPases pathways shared ARHGAP4 and ARHGAP9; module 2, GlycoProtein VI-mediated activation cascade pathway was enriched with RHOG; module 3, Thromboxane A2 receptor signaling, Chemokine signaling pathway, CXCR4-mediated signaling events pathways were enriched with LYN, the hub gene of module 3. Results of RT-PCR confirmed the finding of the bioinformatic analysis that ARHGAP4, ARHGAP9, RHOG and LYN were significantly upregulated in PCOS. RhoA-related pathways, GlycoProtein VI-mediated activation cascade pathway, ARHGAP4, ARHGAP9, RHOG and LYN may be involved in the pathogenesis of PCOS.

Frequency and amplitude modulation of ultra-compact terahertz quantum cascade lasers using an integrated avalanche diode oscillator.

PubMed

Castellano, Fabrizio; Li, Lianhe; Linfield, Edmund H; Davies, A Giles; Vitiello, Miriam S

2016-03-15

Mode-locked comb sources operating at optical frequencies underpin applications ranging from spectroscopy and ultrafast physics, through to absolute frequency measurements and atomic clocks. Extending their operation into the terahertz frequency range would greatly benefit from the availability of compact semiconductor-based sources. However, the development of any compact mode-locked THz laser, which itself is inherently a frequency comb, has yet to be achieved without the use of an external stimulus. High-power, electrically pumped quantum cascade lasers (QCLs) have recently emerged as a promising solution, owing to their octave spanning bandwidths, the ability to achieve group-velocity dispersion compensation and the possibility of obtaining active mode-locking. Here, we propose an unprecedented compact architecture to induce both frequency and amplitude self-modulation in a THz QCL. By engineering a microwave avalanche oscillator into the laser cavity, which provides a 10 GHz self-modulation of the bias current and output power, we demonstrate multimode laser emission centered around 3 THz, with distinct multiple sidebands. The resulting microwave amplitude and frequency self-modulation of THz QCLs opens up intriguing perspectives, for engineering integrated self-mode-locked THz lasers, with impact in fields such as nano- and ultrafast photonics and optical metrology.

Calibration-free wavelength modulation spectroscopy for gas concentration measurements using a quantum cascade laser

NASA Astrophysics Data System (ADS)

Wei, Min; Kan, RuiFeng; Chen, Bing; Xu, ZhenYu; Yang, ChenGuang; Chen, Xiang; Xia, HuiHui; Hu, Mai; He, Yabai; Liu, JianGuo; Fan, XueLi; Wang, Wei

2017-05-01

We report the development of an accurate calibration-free wavelength-scanned wavelength modulation spectroscopy system based on the temporal wavelength response of a current-modulated quantum cascade laser (QCL) for gas concentration detections. Accurate measurements and determination of the QCL output intensity and wavelength response to current modulation enabled calculations of 1f-normalized 2f signal to obtain spectroscopic information with and without gas absorption in the beam path. The gas concentration was retrieved by fitting a simulation spectrum based on spectral line parameters to the background-subtracted 1f-normalized 2f signal based on measurements. In this paper, we demonstrate the performance of the developed system for the CH4 detection by applying an infrared QCL (at 7.84 µm or 1275 cm-1) to probe its two infrared transition lines at 1275.042 cm-1 and 1275.387 cm-1. The experimental results indicated very good agreements between measurements and modeling, for integrated absorbance ranging from 0.0057 cm-1 to 0.11 cm-1 (or absorbance ranging from 0.029 to 0.57). The extracted integrated absorbance was highly linear ( R = 0.99996) to the gas sample concentration. Deviations between the nominal sample gas concentrations and the extracted gas concentrations calculated based on HITRAN spectroscopic parameters were within 3.5%.

Frequency and amplitude modulation of ultra-compact terahertz quantum cascade lasers using an integrated avalanche diode oscillator

PubMed Central

Castellano, Fabrizio; Li, Lianhe; Linfield, Edmund H.; Davies, A. Giles; Vitiello, Miriam S.

2016-01-01

Mode-locked comb sources operating at optical frequencies underpin applications ranging from spectroscopy and ultrafast physics, through to absolute frequency measurements and atomic clocks. Extending their operation into the terahertz frequency range would greatly benefit from the availability of compact semiconductor-based sources. However, the development of any compact mode-locked THz laser, which itself is inherently a frequency comb, has yet to be achieved without the use of an external stimulus. High-power, electrically pumped quantum cascade lasers (QCLs) have recently emerged as a promising solution, owing to their octave spanning bandwidths, the ability to achieve group-velocity dispersion compensation and the possibility of obtaining active mode-locking. Here, we propose an unprecedented compact architecture to induce both frequency and amplitude self-modulation in a THz QCL. By engineering a microwave avalanche oscillator into the laser cavity, which provides a 10 GHz self-modulation of the bias current and output power, we demonstrate multimode laser emission centered around 3 THz, with distinct multiple sidebands. The resulting microwave amplitude and frequency self-modulation of THz QCLs opens up intriguing perspectives, for engineering integrated self-mode-locked THz lasers, with impact in fields such as nano- and ultrafast photonics and optical metrology. PMID:26976199

Impact of temporal, spatial and cascaded effects on the pulse formation in ultra-broadband parametric amplifiers.

PubMed

Lang, T; Harth, A; Matyschok, J; Binhammer, T; Schultze, M; Morgner, U

2013-01-14

A 2 + 1 dimensional nonlinear pulse propagation model is presented, illustrating the weighting of different effects for the parametric amplification of ultra-broadband spectra in different regimes of energy scaling. Typical features in the distribution of intensity and phase of state-of-the-art OPA-systems can be understood by cascaded spatial and temporal effects.

Mitogen-activated protein kinase cascades in Vitis vinifera

PubMed Central

Çakır, Birsen; Kılıçkaya, Ozan

2015-01-01

Protein phosphorylation is one of the most important mechanisms to control cellular functions in response to external and endogenous signals. Mitogen-activated protein kinases (MAPK) are universal signaling molecules in eukaryotes that mediate the intracellular transmission of extracellular signals resulting in the induction of appropriate cellular responses. MAPK cascades are composed of four protein kinase modules: MAPKKK kinases (MAPKKKKs), MAPKK kinases (MAPKKKs), MAPK kinases (MAPKKs), and MAPKs. In plants, MAPKs are activated in response to abiotic stresses, wounding, and hormones, and during plant pathogen interactions and cell division. In this report, we performed a complete inventory of MAPK cascades genes in Vitis vinifera, the whole genome of which has been sequenced. By comparison with MAPK, MAPK kinases, MAPK kinase kinases and MAPK kinase kinase kinase kinase members of Arabidopsis thaliana, we revealed the existence of 14 MAPKs, 5 MAPKKs, 62 MAPKKKs, and 7 MAPKKKKs in Vitis vinifera. We identified orthologs of V. vinifera putative MAPKs in different species, and ESTs corresponding to members of MAPK cascades in various tissues. This work represents the first complete inventory of MAPK cascades in V. vinifera and could help elucidate the biological and physiological functions of these proteins in V. vinifera. PMID:26257761

Neural correlates of informational cascades: brain mechanisms of social influence on belief updating

PubMed Central

Klucharev, Vasily; Rieskamp, Jörg

2015-01-01

Informational cascades can occur when rationally acting individuals decide independently of their private information and follow the decisions of preceding decision-makers. In the process of updating beliefs, differences in the weighting of private and publicly available social information may modulate the probability that a cascade starts in a decisive way. By using functional magnetic resonance imaging, we examined neural activity while participants updated their beliefs based on the decisions of two fictitious stock market traders and their own private information, which led to a final decision of buying one of two stocks. Computational modeling of the behavioral data showed that a majority of participants overweighted private information. Overweighting was negatively correlated with the probability of starting an informational cascade in trials especially prone to conformity. Belief updating by private information was related to activity in the inferior frontal gyrus/anterior insula, the dorsolateral prefrontal cortex and the parietal cortex; the more a participant overweighted private information, the higher the activity in the inferior frontal gyrus/anterior insula and the lower in the parietal-temporal cortex. This study explores the neural correlates of overweighting of private information, which underlies the tendency to start an informational cascade. PMID:24974396

Tunable microwave photonic filter free from baseband and carrier suppression effect not requiring single sideband modulation using a Mach-Zenhder configuration.

PubMed

Mora, José; Ortigosa-Blanch, Arturo; Pastor, Daniel; Capmany, José

2006-08-21

We present a full theoretical and experimental analysis of a novel all-optical microwave photonic filter combining a mode-locked fiber laser and a Mach-Zenhder structure in cascade to a 2x1 electro-optic modulator. The filter is free from the carrier suppression effect and thus it does not require single sideband modulation. Positive and negative coefficients are obtained inherently in the system and the tunability is achieved by controlling the optical path difference of the Mach-Zenhder structure.

Finite-Size Scaling Analysis of Binary Stochastic Processes and Universality Classes of Information Cascade Phase Transition

NASA Astrophysics Data System (ADS)

Mori, Shintaro; Hisakado, Masato

2015-05-01

We propose a finite-size scaling analysis method for binary stochastic processes X(t) in { 0,1} based on the second moment correlation length ξ for the autocorrelation function C(t). The purpose is to clarify the critical properties and provide a new data analysis method for information cascades. As a simple model to represent the different behaviors of subjects in information cascade experiments, we assume that X(t) is a mixture of an independent random variable that takes 1 with probability q and a random variable that depends on the ratio z of the variables taking 1 among recent r variables. We consider two types of the probability f(z) that the latter takes 1: (i) analog [f(z) = z] and (ii) digital [f(z) = θ(z - 1/2)]. We study the universal functions of scaling for ξ and the integrated correlation time τ. For finite r, C(t) decays exponentially as a function of t, and there is only one stable renormalization group (RG) fixed point. In the limit r to ∞ , where X(t) depends on all the previous variables, C(t) in model (i) obeys a power law, and the system becomes scale invariant. In model (ii) with q ≠ 1/2, there are two stable RG fixed points, which correspond to the ordered and disordered phases of the information cascade phase transition with the critical exponents β = 1 and ν|| = 2.

PLZT Electrooptic Ceramic Photonic Devices for Surface-Normal Operation in Trenches Cut Across Arrays of Optical Fiber

NASA Astrophysics Data System (ADS)

Hirabayashi, Katsuhiko

2005-03-01

Simple Pb_1-x La_x(Zr_y Ti_z)_1-x/4 O3 (PLZT) electrooptic ceramic photonic device arrays for surface-normal operation have been developed for application to polarization-controller arrays and Fabry-Pérot tunable filter arrays. These arrays are inserted in trenches cut across fiber arrays. Each element of the arrayed structure corresponds to one optical beam and takes the form of a cell. Each sidewall of the cell (width: 50-80 μm) is coated to form an electrode. The arrays have 16 elements at a pitch of 250 μm. The phase modulator has about 1 dB of loss and a half-wavelength voltage of 120 V. A cascade of two PLZT phase modulators (thickness: 300 μm), with each attached to a polyimide lambda/2 plate (thickness:15 μm), is capable of converting an arbitrary polarization to the transverse-electric (TE) or transverse-magnetic (TM) polarization. The response time is 1 μs. The Fabry-Pérot tunable filters have a thickness of 50 μm . The front and back surfaces of each cell are coated by 99%-reflective mirror. The free spectral range (FSR) of the filters is about 10 nm, tunable range is about 10 nm, loss is 2.2 dB, and finesse is 150. The tuning speed of these devices is high, taking only 1 μs.

A Discrete Dynamical System Approach to Pathway Activation Profiles of Signaling Cascades.

PubMed

Catozzi, S; Sepulchre, J-A

2017-08-01

In living organisms, cascades of covalent modification cycles are one of the major intracellular signaling mechanisms, allowing to transduce physical or chemical stimuli of the external world into variations of activated biochemical species within the cell. In this paper, we develop a novel method to study the stimulus-response of signaling cascades and overall the concept of pathway activation profile which is, for a given stimulus, the sequence of activated proteins at each tier of the cascade. Our approach is based on a correspondence that we establish between the stationary states of a cascade and pieces of orbits of a 2D discrete dynamical system. The study of its possible phase portraits in function of the biochemical parameters, and in particular of the contraction/expansion properties around the fixed points of this discrete map, as well as their bifurcations, yields a classification of the cascade tiers into three main types, whose biological impact within a signaling network is examined. In particular, our approach enables to discuss quantitatively the notion of cascade amplification/attenuation from this new perspective. The method allows also to study the interplay between forward and "retroactive" signaling, i.e., the upstream influence of an inhibiting drug bound to the last tier of the cascade.

Polarization entangled cluster state generation in a lithium niobate chip

NASA Astrophysics Data System (ADS)

Szep, Attila; Kim, Richard; Shin, Eunsung; Fanto, Michael L.; Osman, Joseph; Alsing, Paul M.

2016-10-01

We present a design of a quantum information processing C-phase (Controlled-phase) gate applicable for generating cluster states that has a form of integrated photonic circuits assembled with cascaded directional couplers on a Ti in-diffused Lithium Niobate (Ti-LN) platform where directional couplers as the integrated optical analogue of bulk beam splitters are used as fundamental building blocks. Based on experimentally optimized fabrication parameters of Ti-LN optical waveguides operating at an 810nm wavelength, an integrated Ti-LN quantum C-phase gate is designed and simulated. Our proposed C-phase gate consists of three tunable directional couplers cascaded together with having different weighted switching ratios for providing a tool of routing vertically- and horizontally-polarized photons independently. Its operation mechanism relies on selectively controlling the optical coupling of orthogonally polarized modes via the change in the index of refraction, and its operation is confirmed by the BPM simulation.

Centrifugal contactor modified for end stage operation in a multistage system

DOEpatents

Jubin, Robert T.

1990-01-01

A cascade formed of a plurality of centrifugal contactors useful for countercurrent solvent extraction processes such as utilizable for the reprocessing of nuclear reactor fuels is modified to permit operation in the event one or both end stages of the cascade become inoperative. Weir assemblies are connected to each of the two end stages by suitable conduits for separating liquids discharged from an inoperative end stage based upon the weight of the liquid phases uses in the solvent extraction process. The weir assembly at one end stage is constructed to separate and discharge the heaviest liquid phase while the weir assembly at the other end stage is constructed to separate and discharge the lightest liquid phase. These weir assemblies function to keep the liquid discharge from an inoperative end stages on the same weight phase a would occur from an operating end stage.

Vedolizumab: A New Opponent in the Battle Against Crohn's Disease and Ulcerative Colitis.

PubMed

Poulakos, Mara; Machin, Jade D; Pauly, Julienne; Grace, Yasmin

2016-10-01

Inflammatory bowel diseases (IBDs) are chronic inflammatory disorders affecting the gastrointestinal (GI) tract that encompass Crohn's disease (CD) and ulcerative colitis (UC). In these disease states, epithelial damage of the intestinal mucosa is evident due to increased lymphocyte trafficking to the area, which affects the normal intestinal barrier function. Currently available pharmacotherapy can be limited in terms of efficacy and associated toxicities. Newer agents have emerged, including the monoclonal antibody natalizumab, which antagonizes integrin, an important component within the inflammation cascade. Natalizumab works by modulating both the GI and brain biologic responses and as a result there is risk of the opportunistic infection known as progressive multifocal leukoencephalopathy (PML), putting patients at risk for severe disability and death. Vedolizumab, another integrin inhibitor, is selective for modulating the gut biologic response but not the brain, consequently decreasing the risk for PML. To generate information regarding the role of vedolizumab in the treatment of IBD, a literature search was conducted, yielding 7 phase I to III clinical trials. This article serves as a summary of efficacy, safety, and other relevant information from clinical studies to explore the role of vedolizumab in the treatment of CD and UC. © The Author(s) 2015.

Full-duplex radio-over-fiber system with tunable millimeter-wave signal generation and wavelength reuse for upstream signal.

PubMed

Wang, Yiqun; Pei, Li; Li, Jing; Li, Yueqin

2017-06-10

A full-duplex radio-over-fiber system is proposed, which provides both the generation of a millimeter-wave (mm-wave) signal with tunable frequency multiplication factors (FMFs) and wavelength reuse for uplink data. A dual-driving Mach-Zehnder modulator and a phase modulator are cascaded to form an optical frequency comb. An acousto-optic tunable filter based on a uniform fiber Bragg grating (FBG-AOTF) is employed to select three target optical sidebands. Two symmetrical sidebands are chosen to generate mm waves with tunable FMFs up to 16, which can be adjusted by changing the frequency of the applied acoustic wave. The optical carrier is reused at the base station for uplink connection. FBG-AOTFs driven by two acoustic wave signals are experimentally fabricated and further applied in the proposed scheme. Results of the research indicate that the 2-Gbit/s data can be successfully transmitted over a 25-km single-mode fiber for bidirectional full-duplex channels with power penalty of less than 2.6 dB. The feasibility of the proposed scheme is verified by detailed simulations and partial experiments.

A photothermal Mach-Zehnder interferometer for measuring caffeine and proteins in aqueous solutions using external cavity quantum cascade lasers

NASA Astrophysics Data System (ADS)

Kristament, Christian; Schwaighofer, Andreas; Montemurro, Milagros; Lendl, Bernhard

2018-02-01

One of the advantages of mid-IR spectroscopy in biomedical research lies in its capability to provide direct information on the secondary structure of proteins in their natural, often aqueous, environment. One impediment of direct absorption measurements in the correspondent spectral region is the strong absorbance of the native solvent (H2O). In this regard, the advent of broadly-tunable external cavity quantum cascade lasers (EC-QCL) allowed to significantly increasing the optical path length employed in transmission measurements due to their high spectral power densities. Low measured S/N ratios were improved by elaborated data analysis protocols that corrected mechanical flaws in the tuning mechanism of ECQCLs and allow for S/N ratios comparable to research grade FTIR spectrometers. Recent development of new optical set-ups outpacing direct absorption measurements led to further advancements. We present a dedicated Mach-Zehnder interferometer for photothermal measurements in balanced detection mode. In this highly sensitive design, the interferometer is illuminated by a HeNe laser to detect the refractive index change induced by the heat insertion of the EC-QCL. Here, we present photothermal phase shift interferometry measurements of caffeine in ethanol as well as casein in water. Further, the dependency of the signal amplitude on varying modulation frequencies was investigated for different liquids.

A Modular Multilevel Converter with Power Mismatch Control for Grid-Connected Photovoltaic Systems

DOE PAGES

Duman, Turgay; Marti, Shilpa; Moonem, M. A.; ...

2017-05-17

A modular multilevel power converter configuration for grid connected photovoltaic (PV) systems is proposed. The converter configuration replaces the conventional bulky line frequency transformer with several high frequency transformers, potentially reducing the balance of systems cost of PV systems. The front-end converter for each port is a neutral-point diode clamped (NPC) multi-level dc-dc dual-active bridge (ML-DAB) which allows maximum power point tracking (MPPT). The integrated high frequency transformer provides the galvanic isolation between the PV and grid side and also steps up the low dc voltage from PV source. Following the ML-DAB stage, in each port, is a NPC inverter.more » N number of NPC inverters’ outputs are cascaded to attain the per-phase line-to-neutral voltage to connect directly to the distribution grid (i.e., 13.8 kV). The cascaded NPC (CNPC) inverters have the inherent advantage of using lower rated devices, smaller filters and low total harmonic distortion required for PV grid interconnection. The proposed converter system is modular, scalable, and serviceable with zero downtime with lower foot print and lower overall cost. A novel voltage balance control at each module based on power mismatch among N-ports, have been presented and verified in simulation. Analysis and simulation results are presented for the N-port converter. The converter performance has also been verified on a hardware prototype.« less

A Modular Multilevel Converter with Power Mismatch Control for Grid-Connected Photovoltaic Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duman, Turgay; Marti, Shilpa; Moonem, M. A.

A modular multilevel power converter configuration for grid connected photovoltaic (PV) systems is proposed. The converter configuration replaces the conventional bulky line frequency transformer with several high frequency transformers, potentially reducing the balance of systems cost of PV systems. The front-end converter for each port is a neutral-point diode clamped (NPC) multi-level dc-dc dual-active bridge (ML-DAB) which allows maximum power point tracking (MPPT). The integrated high frequency transformer provides the galvanic isolation between the PV and grid side and also steps up the low dc voltage from PV source. Following the ML-DAB stage, in each port, is a NPC inverter.more » N number of NPC inverters’ outputs are cascaded to attain the per-phase line-to-neutral voltage to connect directly to the distribution grid (i.e., 13.8 kV). The cascaded NPC (CNPC) inverters have the inherent advantage of using lower rated devices, smaller filters and low total harmonic distortion required for PV grid interconnection. The proposed converter system is modular, scalable, and serviceable with zero downtime with lower foot print and lower overall cost. A novel voltage balance control at each module based on power mismatch among N-ports, have been presented and verified in simulation. Analysis and simulation results are presented for the N-port converter. The converter performance has also been verified on a hardware prototype.« less

Continuous pressure letdown system

DOEpatents

Sprouse, Kenneth M.; Matthews, David R.; Langowski, Terry

2010-06-08

A continuous pressure letdown system connected to a hopper decreases a pressure of a 2-phase (gas and solid) dusty gas stream flowing through the system. The system includes a discharge line for receiving the dusty gas from the hopper, a valve, a cascade nozzle assembly positioned downstream of the discharge line, a purge ring, an inert gas supply connected to the purge ring, an inert gas throttle, and a filter. The valve connects the hopper to the discharge line and controls introduction of the dusty gas stream into the discharge line. The purge ring is connected between the discharge line and the cascade nozzle assembly. The inert gas throttle controls a flow rate of an inert gas into the cascade nozzle assembly. The filter is connected downstream of the cascade nozzle assembly.

Odd harmonics-enhanced supercontinuum in bulk solid-state dielectric medium.

PubMed

Garejev, N; Jukna, V; Tamošauskas, G; Veličkė, M; Šuminas, R; Couairon, A; Dubietis, A

2016-07-25

We report on generation of ultrabroadband, more than 4 octave spanning supercontinuum in thin CaF₂ crystal, as pumped by intense mid-infrared laser pulses with central wavelength of 2.4 μm. The supercontinuum spectrum covers wavelength range from the ultraviolet to the mid-infrared and its short wavelength side is strongly enhanced by cascaded generation of third, fifth and seventh harmonics. Our results capture the transition from Kerr-dominated to plasma-dominated filamentation regime and uncover that in the latter the spectral superbroadening originates from dramatic plasma-induced compression of the driving pulse, which in turn induces broadening of the harmonics spectra due to cross-phase modulation effects. The experimental measurements are backed up by the numerical simulations based on a nonparaxial unidirectional propagation equation for the electric field of the pulse, which accounts for the cubic nonlinearity-induced effects, and which reproduce the experimental data in great detail.

External cavity quantum cascade lasers with ultra rapid acousto-optic tuning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lyakh, A., E-mail: alyakh@pranalytica.com; Barron-Jimenez, R.; Dunayevskiy, I.

2015-04-06

We report operation of tunable external cavity quantum cascade lasers with emission wavelength controlled by an acousto-optic modulator (AOM). A long-wave infrared quantum cascade laser wavelength tuned from ∼8.5 μm to ∼9.8 μm when the AOM frequency was changed from ∼41MHz to ∼49 MHz. The laser delivered over 350 mW of average power at the center of the tuning curve in a linewidth of ∼4.7 cm{sup −1}. Measured wavelength switching time between any two wavelengths within the tuning range of the QCL was less than 1 μs. Spectral measurements of infrared absorption features of Freon demonstrated a capability of obtaining complete spectral data in less thanmore » 20 μs.« less

An experimental investigation of gapwise periodicity and unsteady aerodynamic response in an oscillating cascade. 1: Experimental and theoretical results. [turbine blades

NASA Technical Reports Server (NTRS)

Carta, F. O.

1982-01-01

Tests were conducted on a linear cascade of airfoils oscillating in pitch to measure the unsteady pressure response on selected blades along the leading edge plane of the cascade, over the chord of the center blade, and on the sidewall in the plane of the leading edge. The pressure data were reduced to Fourier coefficient form for direct comparison, and were also processed to yield integrated loads and, particularly, the aerodynamic damping coefficient. Results from the unsteady Verdon/Caspar theory for cascaded blades with nonzero thickness and camber were compared with the experimental measurements. The three primary results are: (1) from the leading edge plane blade data, the cascade was judged to be periodic in unsteady flow over the range of parameters tested; (2) the interblade phase angle was found to be the single most important parameter affecting the stability of the oscillating cascade blades; and (3) the real blade theory and the experiment were in excellent agreement for the several cases chosen for comparison.

Cascading training the trainers in ophthalmology across Eastern, Central and Southern Africa.

PubMed

Corbett, Melanie C; Mathenge, Wanjiku; Zondervan, Marcia; Astbury, Nick

2017-07-10

The Royal College of Ophthalmologists (RCOphth) and the College of Ophthalmology of Eastern Central and Southern Africa (COECSA) are collaborating to cascade a Training the Trainers (TTT) Programme across the COECSA Region. Within the VISION 2020 Links Programme, it aims to develop a skilled motivated workforce who can deliver high quality eye care. It will train a lead, faculty member and facilitator in 8 countries, who can cascade the programme to local trainers. In phase 1 (2013/14) two 3-day courses were run for 16/17 selected delegates, by 3 UK Faculty. In phase 2 (2015/16) 1 UK Faculty Member ran 3 shorter courses, associated with COECSA events (Congress and Examination). A COECSA Lead was appointed after the first course, and selected delegates were promoted as Facilitators then Faculty Members on successive courses. They were given appropriate materials, preparation, training and mentoring. In 4 years the programme has trained 87 delegates, including 1 COECSA Lead, 4 Faculty Members and 7 Facilitators. Delegate feedback on the course was very good and Faculty were impressed with the progress made by delegates. A questionnaire completed by delegates after 6-42 months demonstrated how successfully they were implementing new skills in teaching and supervision. The impact was assessed using the number of eye-care workers that delegates had trained, and the number of patients seen by those workers each year. The figures suggested that approaching 1 million patients per year were treated by eye-care workers who had benefited from training delivered by those who had been on the courses. Development of the Programme in Africa initially followed the UK model, but the need to address more extensive challenges overseas, stimulated new ideas for the UK courses. The Programme has developed a pyramid of trainers capable of cascading knowledge, skills and teaching in training with RCOphth support. The third phase will extend the number of facilitators and faculty, develop on-line preparatory and teaching materials, and design training processes and tools for its assessment. The final phase will see local cascade of the TTT Programme in all 8 countries, and sustainability as UK support is withdrawn.

Developments in photonic and mm-wave component technology for fiber radio

NASA Astrophysics Data System (ADS)

Iezekiel, Stavros

2013-01-01

A review of photonic component technology for fiber radio applications at 60 GHz will be given. We will focus on two architectures: (i) baseband-over-fiber and (ii) RF-over-fiber. In the first approach, up-conversion to 60 GHz is performed at the picocell base stations, with data being transported over fiber, while in the second both the data and rum­ wave carrier are transported over fiber. For the baseband-over-fiber scheme, we examine techniques to improve the modulation efficiency of directly­ modulated fiber links. These are based on traveling-wave structures applied to series cascades of lasers. This approach combines the improvement in differential quantum efficiency with the ability to tailor impedance matching as required. In addition, we report on various base station transceiver architectures based on optically-controlled :tvfMIC self­ oscillating mixers, and their application to 60 GHz fiber radio. This approach allows low cost optoelectronic transceivers to be used for the baseband fiber link, whilst minimizing the impact of dispersion. For the RF-over-fiber scheme, we report on schemes for optical generation of 100 GHz. These use modulation of a Mach-Zehnder modulator at Vπ bias in cascade with a Mach-Zehnder driven by 1.25 Gb/s data. One of the issues in RF-over-fiber is dispersion, while reduced modulation efficiency due to the presence of the optical carrier is also problematic. We examine the use of silicon nitride micro-ring resonators for the production of optical single sideband modulation in order to combat dispersion, and for the reduction of optical carrier power in order to improve link modulation efficiency.

Quantum cascade laser-based analyzer for hydrogen sulfide detection at sub-parts-per-million levels

NASA Astrophysics Data System (ADS)

Nikodem, Michal; Krzempek, Karol; Stachowiak, Dorota; Wysocki, Gerard

2018-01-01

Due to its high toxicity, monitoring of hydrogen sulfide (H2S) concentration is essential in many industrial sites (such as natural gas extraction sites, petroleum refineries, geothermal power plants, or waste water treatment facilities), which require sub-parts-per-million sensitivities. We report on a quantum cascade laser-based spectroscopic system for detection of H2S in the midinfrared at ˜7.2 μm. We present a sensor design utilizing Herriott multipass cell and a wavelength modulation spectroscopy to achieve a detection limit of 140 parts per billion for 1-s integration time.

Information cascade on networks

NASA Astrophysics Data System (ADS)

Hisakado, Masato; Mori, Shintaro

2016-05-01

In this paper, we discuss a voting model by considering three different kinds of networks: a random graph, the Barabási-Albert (BA) model, and a fitness model. A voting model represents the way in which public perceptions are conveyed to voters. Our voting model is constructed by using two types of voters-herders and independents-and two candidates. Independents conduct voting based on their fundamental values; on the other hand, herders base their voting on the number of previous votes. Hence, herders vote for the majority candidates and obtain information relating to previous votes from their networks. We discuss the difference between the phases on which the networks depend. Two kinds of phase transitions, an information cascade transition and a super-normal transition, were identified. The first of these is a transition between a state in which most voters make the correct choices and a state in which most of them are wrong. The second is a transition of convergence speed. The information cascade transition prevails when herder effects are stronger than the super-normal transition. In the BA and fitness models, the critical point of the information cascade transition is the same as that of the random network model. However, the critical point of the super-normal transition disappears when these two models are used. In conclusion, the influence of networks is shown to only affect the convergence speed and not the information cascade transition. We are therefore able to conclude that the influence of hubs on voters' perceptions is limited.

A Low Power Linear Phase Programmable Long Delay Circuit.

PubMed

Rodriguez-Villegas, Esther; Logesparan, Lojini; Casson, Alexander J

2014-06-01

A novel linear phase programmable delay is being proposed and implemented in a 0.35 μm CMOS process. The delay line consists of N cascaded cells, each of which delays the input signal by Td/N, where Td is the total line delay. The delay generated by each cell is programmable by changing a clock frequency and is also fully independent of the frequency of the input signal. The total delay hence depends only on the chosen clock frequency and the total number of cascaded cells. The minimum clock frequency is limited by the maximum time a voltage signal can effectively be held by an individual cell. The maximum number of cascaded cells will be limited by the effects of accumulated offset due to transistor mismatch, which eventually will affect the operating mode of the individual transistors in a cell. This latter limitation has however been dealt with in the topology by having an offset compensation mechanism that makes possible having a large number of cascaded cells and hence a long resulting delay. The delay line has been designed for scalp-based neural activity analysis that is predominantly in the sub-100 Hz frequency range. For these signals, the delay generated by a 31-cell cascade has been demonstrated to be programmable from 30 ms to 3 s. Measurement results demonstrate a 31 stage, 50 Hz bandwidth, 0.3 s delay that operates from a 1.1 V supply with power consumption of 270 nW.

Pro-Resolving lipid mediators and Mechanisms in the resolution of acute inflammation

PubMed Central

Buckley, Christopher D.; Gilroy, Derek W.; Serhan, Charles N.

2014-01-01

SUMMARY Inflammatory responses, like all biological cascades, are shaped by a delicate balance between positive and negative feedback loops. It is now clear that in addition to positive and negative checkpoints, the inflammatory cascade rather unexpectedly boasts an additional checkpoint, a family of chemicals that actively promote resolution and tissue repair without compromising host defence. Indeed the resolution phase of inflammation is just as actively orchestrated and carefully choreographed as its induction and inhibition. In this review we explore the immunological consequences of these omega-3-derived specialized pro-resolving mediators (SPMs) and discuss their place within what is currently understood of the role of the arachidonic acid-derived prostaglandins, lipoxins and their natural C15-epimers. We propose that treatment of inflammation should not be restricted to the use of inhibitors of the acute cascade (antagonism) but broadened to take account of the enormous therapeutic potential of inducers (agonists) of the resolution phase of inflammation. PMID:24656045

Statistical analysis of cascading failures in power grids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chertkov, Michael; Pfitzner, Rene; Turitsyn, Konstantin

2010-12-01

We introduce a new microscopic model of cascading failures in transmission power grids. This model accounts for automatic response of the grid to load fluctuations that take place on the scale of minutes, when optimum power flow adjustments and load shedding controls are unavailable. We describe extreme events, caused by load fluctuations, which cause cascading failures of loads, generators and lines. Our model is quasi-static in the causal, discrete time and sequential resolution of individual failures. The model, in its simplest realization based on the Directed Current description of the power flow problem, is tested on three standard IEEE systemsmore » consisting of 30, 39 and 118 buses. Our statistical analysis suggests a straightforward classification of cascading and islanding phases in terms of the ratios between average number of removed loads, generators and links. The analysis also demonstrates sensitivity to variations in line capacities. Future research challenges in modeling and control of cascading outages over real-world power networks are discussed.« less

Gabapentin’s minimal action on markers of rat brain arachidonic acid metabolism agrees with its inefficacy against bipolar disorder

PubMed Central

Reese, Edmund A.; Cheon, Yewon; Ramadan, Epolia; Kim, Hyung-Wook; Chang, Lisa; Rao, Jagadeesh S.; Rapoport, Stanley I.; Taha, Ameer Y.

2012-01-01

In rats, FDA-approved mood stabilizers used for treating bipolar disorder (BD) selectively downregulate brain markers of the arachidonic acid (AA) cascade, which are upregulated in postmortem BD brain. Phase III clinical trials show that gabapentin (GBP) is ineffective in treating BD. We hypothesized that GBP would not alter the rat brain AA cascade. Chronic GBP (10 mg/kg body weight, injected i.p. for 30 days) compared to saline vehicle did not significantly alter brain expression or activity of AA-selective cytosolic phospholipase A2 (cPLA2) IVA or secretory (s) PLA2 IIA, activity of cyclooxygenase-2, or prostaglandin or thromboxane concentrations. Plasma AA concentration was unaffected. These results, taken with evidence of an upregulated AA cascade in the BD brain and that approved mood stabilizers downregulate rat brain AA cascade, support the hypothesis that effective anti-BD drugs act by targeting the AA cascade, and suggest that the rat model might be used for drug screening PMID:22841517

Regimes of external optical feedback in 5.6 μm distributed feedback mid-infrared quantum cascade lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jumpertz, L., E-mail: louise.jumpertz@telecom-paristech.fr; Alcatel Thales III-V Lab, Campus de Polytechnique, 1 avenue Augustin Fresnel, 91767 Palaiseau; Carras, M.

2014-09-29

External optical feedback is studied experimentally in mid-infrared quantum cascade lasers. These structures exhibit a dynamical response close to that observed in interband lasers, with threshold reduction and optical power enhancement when increasing the feedback ratio. The study of the optical spectrum proves that the laser undergoes five distinct regimes depending on the phase and amplitude of the reinjected field. These regimes are mapped in the plane of external cavity length and feedback strength, revealing unstable behavior only for a very narrow range of operation, making quantum cascade lasers much more stable than their interband counterparts.

Identification and Analysis of Mitogen-Activated Protein Kinase (MAPK) Cascades in Fragaria vesca.

PubMed

Zhou, Heying; Ren, Suyue; Han, Yuanfang; Zhang, Qing; Qin, Ling; Xing, Yu

2017-08-13

Mitogen-activated protein kinase (MAPK) cascades are highly conserved signaling modules in eukaryotes, including yeasts, plants and animals. MAPK cascades are responsible for protein phosphorylation during signal transduction events, and typically consist of three protein kinases: MAPK, MAPK kinase, and MAPK kinase kinase. In this current study, we identified a total of 12 FvMAPK , 7 FvMAPKK , 73 FvMAPKKK , and one FvMAPKKKK genes in the recently published Fragaria vesca genome sequence. This work reported the classification, annotation and phylogenetic evaluation of these genes and an assessment of conserved motifs and the expression profiling of members of the gene family were also analyzed here. The expression profiles of the MAPK and MAPKK genes in different organs and fruit developmental stages were further investigated using quantitative real-time reverse transcription PCR (qRT-PCR). Finally, the MAPK and MAPKK expression patterns in response to hormone and abiotic stresses (salt, drought, and high and low temperature) were investigated in fruit and leaves of F. vesca . The results provide a platform for further characterization of the physiological and biochemical functions of MAPK cascades in strawberry.

Upstream paths for Hippo signaling in Drosophila organ development.

PubMed

Choi, Kwang-Wook

2018-03-01

Organ growth is fundamental to animal development. One of major mechanisms for growth control is mediated by the conserved Hippo signaling pathway initially identified in Drosophila. The core of this pathway in Drosophila consists of a cascade of protein kinases Hippo and Warts that negatively regulate transcriptional coactivator Yorkie (Yki). Activation of Yki promotes cell survival and proliferation to induce organ growth. A key issue in Hippo signaling is to understand how core kinase cascade is activated. Activation of Hippo kinase cascade is regulated in the upstream by at least two transmembrane proteins Crumbs and Fat that act in parallel. These membrane proteins interact with additional factors such as FERM-domain proteins Expanded and Merlin to modulate subcellular localization and function of the Hippo kinase cascade. Hippo signaling is also influenced by cytoskeletal networks and cell tension in epithelia of developing organs. These upstream events in the regulation of Hippo signaling are only partially understood. This review focuses on our current understanding of some upstream processes involved in Hippo signaling in developing Drosophila organs. [BMB Reports 2018; 51(3): 134-142].

[Renin-angiotensin-aldosterone system (RAAS) and its pharmacologic modulation].

PubMed

Giestas, Anabela; Palma, Isabel; Ramos, Maria Helena

2010-01-01

The renin-angiotensin-aldosterone system (RAAS) is a neuroendocrine complex system that regulates the modulation of salt and water homeostasis, and regulation of blood pressure. Through its multiple interactions it protects the endothelium, heart, brain and kidney. In addition, the RAAS regulates the vascular response to injury and inflammation. Chronic activation/dysregulation of the RAAS leads to hypertension and perpetuates a cascade of proinflammatory, prothrombotic and atherogenic effects associated with endorgan damage (heart, brain, kidney, endothelium). Consequently, the RAAS is an important therapeutic target in these situations. This article presents an overview of physiology, pathophysiology and pharmacologic modulation of the RAAS.

The neural speed of familiar face recognition.

PubMed

Barragan-Jason, G; Cauchoix, M; Barbeau, E J

2015-08-01

Rapidly recognizing familiar people from their faces appears critical for social interactions (e.g., to differentiate friend from foe). However, the actual speed at which the human brain can distinguish familiar from unknown faces still remains debated. In particular, it is not clear whether familiarity can be extracted from rapid face individualization or if it requires additional time consuming processing. We recorded scalp EEG activity in 28 subjects performing a go/no-go, famous/non-famous, unrepeated, face recognition task. Speed constraints were used to encourage subjects to use the earliest familiarity information available. Event related potential (ERP) analyses show that both the N170 and the N250 components were modulated by familiarity. The N170 modulation was related to behaviour: subjects presenting the strongest N170 modulation were also faster but less accurate than those who only showed weak N170 modulation. A complementary Multi-Variate Pattern Analysis (MVPA) confirmed ERP results and provided some more insights into the dynamics of face recognition as the N170 differential effect appeared to be related to a first transitory phase (transitory bump of decoding power) starting at around 140 ms, which returned to baseline afterwards. This bump of activity was henceforth followed by an increase of decoding power starting around 200 ms after stimulus onset. Overall, our results suggest that rather than a simple single-process, familiarity for faces may rely on a cascade of neural processes, including a coarse and fast stage starting at 140 ms and a more refined but slower stage occurring after 200 ms. Copyright © 2015 Elsevier Ltd. All rights reserved.

Potassium titanyl arsenate based cascaded optical parametric oscillator emit at 2.5 µm derived by neodymium-doped yttrium lithium fluoride laser

NASA Astrophysics Data System (ADS)

Duan, Yanmin; Zhang, Jing; Guo, Junhong; Zhu, Haiyong; Zhang, Yongchang; Xu, Changwen; Wang, Hongyan; Zhang, Yaoju

2018-04-01

We reported a potassium titanyl arsenate (KTA) based cascaded optical parametric oscillator (OPO). The secondary OPO signal light at 2.5 µm was obtained with two OPO processes in one non-critical phase matching cut KTA crystal. This cascaded OPO was driven by a Q-switched neodymium-doped yttrium lithium fluoride (Nd:YLF) laser at 1047 nm. Making full use of the negative thermal lens effect and long upper level fluorescence lifetime of Nd:YLF, signal power of 605 mW at 2503 nm was achieved with a pulse repetition frequency of 15 kHz and an incident diode pump power of 9.7 W. Therefore, the cascaded OPO derived by Q-switched Nd:YLF laser could provide high peak power pulsed laser emission in mid-infrared band.

The Potential of a Cascaded TEG System for Waste Heat Usage in Railway Vehicles

NASA Astrophysics Data System (ADS)

Wilbrecht, Sebastian; Beitelschmidt, Michael

2018-02-01

This work focuses on the conceptual design and optimization of a near series prototype of a high-power thermoelectric generator system (TEG system) for diesel-electric locomotives. The replacement of the silencer in the exhaust line enables integration with already existing vehicles. However, compliance with the technical and legal frameworks and the assembly space requirements is just as important as the limited exhaust back pressure, the high power density and the low life cycle costs. A special emphasis is given to the comparison of cascaded two-stage Bi2Te3 and Mg2Si0.4Sn0.6/MnSi1.81 modules with single-stage Bi2Te3 modules, both manufactured in lead-frame technology. In addition to the numerous, partly competing boundary conditions for the use in rail vehicles, the additional degree of freedom from the cascaded thermoelectric modules (TEM) is considered. The problem is investigated by coupling one-dimensional multi-domain simulations with an optimization framework using a genetic algorithm. The achievable electrical power of the single-stage system is significantly higher, at 3.2 kW, than the performance of the two-stage system (2.5 kW). Although the efficiency of the two-stage system is 44.2% higher than the single-stage system, the overall power output is 22.8% lower. This is because the lower power density and the lower number of TEM more than compensates the better efficiency. Hence, the available installation space, and thus the power density, is a critical constraint for the design of TEG systems. Furthermore, for applications recovering exhaust gas enthalpy, the large temperature drop across the heat exchanger is characteristic and must be considered carefully within the design process.

The Potential of a Cascaded TEG System for Waste Heat Usage in Railway Vehicles

NASA Astrophysics Data System (ADS)

Wilbrecht, Sebastian; Beitelschmidt, Michael

2018-06-01

This work focuses on the conceptual design and optimization of a near series prototype of a high-power thermoelectric generator system (TEG system) for diesel-electric locomotives. The replacement of the silencer in the exhaust line enables integration with already existing vehicles. However, compliance with the technical and legal frameworks and the assembly space requirements is just as important as the limited exhaust back pressure, the high power density and the low life cycle costs. A special emphasis is given to the comparison of cascaded two-stage Bi2Te3 and Mg2Si0.4Sn0.6/MnSi1.81 modules with single-stage Bi2Te3 modules, both manufactured in lead-frame technology. In addition to the numerous, partly competing boundary conditions for the use in rail vehicles, the additional degree of freedom from the cascaded thermoelectric modules (TEM) is considered. The problem is investigated by coupling one-dimensional multi-domain simulations with an optimization framework using a genetic algorithm. The achievable electrical power of the single-stage system is significantly higher, at 3.2 kW, than the performance of the two-stage system (2.5 kW). Although the efficiency of the two-stage system is 44.2% higher than the single-stage system, the overall power output is 22.8% lower. This is because the lower power density and the lower number of TEM more than compensates the better efficiency. Hence, the available installation space, and thus the power density, is a critical constraint for the design of TEG systems. Furthermore, for applications recovering exhaust gas enthalpy, the large temperature drop across the heat exchanger is characteristic and must be considered carefully within the design process.

Identification of key candidate genes and pathways in hepatitis B virus-associated acute liver failure by bioinformatical analysis

PubMed Central

Lin, Huapeng; Zhang, Qian; Li, Xiaocheng; Wu, Yushen; Liu, Ye; Hu, Yingchun

2018-01-01

Abstract Hepatitis B virus-associated acute liver failure (HBV-ALF) is a rare but life-threatening syndrome that carried a high morbidity and mortality. Our study aimed to explore the possible molecular mechanisms of HBV-ALF by means of bioinformatics analysis. In this study, genes expression microarray datasets of HBV-ALF from Gene Expression Omnibus were collected, and then we identified differentially expressed genes (DEGs) by the limma package in R. After functional enrichment analysis, we constructed the protein–protein interaction (PPI) network by the Search Tool for the Retrieval of Interacting Genes online database and weighted genes coexpression network by the WGCNA package in R. Subsequently, we picked out the hub genes among the DEGs. A total of 423 DEGs with 198 upregulated genes and 225 downregulated genes were identified between HBV-ALF and normal samples. The upregulated genes were mainly enriched in immune response, and the downregulated genes were mainly enriched in complement and coagulation cascades. Orosomucoid 1 (ORM1), orosomucoid 2 (ORM2), plasminogen (PLG), and aldehyde oxidase 1 (AOX1) were picked out as the hub genes that with a high degree in both PPI network and weighted genes coexpression network. The weighted genes coexpression network analysis found out 3 of the 5 modules that upregulated genes enriched in were closely related to immune system. The downregulated genes enriched in only one module, and the genes in this module majorly enriched in the complement and coagulation cascades pathway. In conclusion, 4 genes (ORM1, ORM2, PLG, and AOX1) with immune response and the complement and coagulation cascades pathway may take part in the pathogenesis of HBV-ALF, and these candidate genes and pathways could be therapeutic targets for HBV-ALF. PMID:29384847

Stable long-term indigo production by overexpression of dioxygenase genes using a chromosomal integrated cascade expression circuit.

PubMed

Royo, Jose Luis; Moreno-Ruiz, Emilia; Cebolla, Angel; Santero, Eduardo

2005-03-16

In our laboratory we have analyzed different factors to maximize the yield in heterologous protein expression for long-term cultivation, by combination of an efficient cascade expression system and stable integration in the bacterial chromosome. In this work, we have explored this system for the production of indigo dye as a model for biotechnological production, by expressing in Escherichia coli the thnA1A2A3A4 genes from Sphingomonas macrogolitabida strain TFA, which encode the components of a tetralin dioxygenase activity. We compared Ptac, and the Pm-based cascade expression circuit in a multicopy plasmid and stably integrated into the bacterial chromosome. Plasmid-based expression systems resulted in instability of indigo production when serially diluted batch experiments were performed without a selective pressure. This problem was solved by integrating the expression module in the chromosome. Despite the gene dosage reduction, the synergic effect of the cascade expression system produced comparable expression to the dioxygenase activity in the plasmid configuration but could be stably maintained for at least 5 days. Here, we show that the cascade amplification circuit integrated in the chromosome could be an excellent system for tight control and stable production of recombinant products.

Optimal information transfer in enzymatic networks: A field theoretic formulation

NASA Astrophysics Data System (ADS)

Samanta, Himadri S.; Hinczewski, Michael; Thirumalai, D.

2017-07-01

Signaling in enzymatic networks is typically triggered by environmental fluctuations, resulting in a series of stochastic chemical reactions, leading to corruption of the signal by noise. For example, information flow is initiated by binding of extracellular ligands to receptors, which is transmitted through a cascade involving kinase-phosphatase stochastic chemical reactions. For a class of such networks, we develop a general field-theoretic approach to calculate the error in signal transmission as a function of an appropriate control variable. Application of the theory to a simple push-pull network, a module in the kinase-phosphatase cascade, recovers the exact results for error in signal transmission previously obtained using umbral calculus [Hinczewski and Thirumalai, Phys. Rev. X 4, 041017 (2014), 10.1103/PhysRevX.4.041017]. We illustrate the generality of the theory by studying the minimal errors in noise reduction in a reaction cascade with two connected push-pull modules. Such a cascade behaves as an effective three-species network with a pseudointermediate. In this case, optimal information transfer, resulting in the smallest square of the error between the input and output, occurs with a time delay, which is given by the inverse of the decay rate of the pseudointermediate. Surprisingly, in these examples the minimum error computed using simulations that take nonlinearities and discrete nature of molecules into account coincides with the predictions of a linear theory. In contrast, there are substantial deviations between simulations and predictions of the linear theory in error in signal propagation in an enzymatic push-pull network for a certain range of parameters. Inclusion of second-order perturbative corrections shows that differences between simulations and theoretical predictions are minimized. Our study establishes that a field theoretic formulation of stochastic biological signaling offers a systematic way to understand error propagation in networks of arbitrary complexity.

A cascading failure analysis tool for post processing TRANSCARE simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

This is a MATLAB-based tool to post process simulation results in the EPRI software TRANSCARE, for massive cascading failure analysis following severe disturbances. There are a few key modules available in this tool, including: 1. automatically creating a contingency list to run TRANSCARE simulations, including substation outages above a certain kV threshold, N-k (1, 2 or 3) generator outages and branche outages; 2. read in and analyze a CKO file of PCG definition, an initiating event list, and a CDN file; 3. post process all the simulation results saved in a CDN file and perform critical event corridor analysis; 4.more » provide a summary of TRANSCARE simulations; 5. Identify the most frequently occurring event corridors in the system; and 6. Rank the contingencies using a user defined security index to quantify consequences in terms of total load loss, total number of cascades, etc.« less

Phenotypic and evolutionary implications of modulating the ERK-MAPK cascade using the dentition as a model

NASA Astrophysics Data System (ADS)

Marangoni, Pauline; Charles, Cyril; Tafforeau, Paul; Laugel-Haushalter, Virginie; Joo, Adriane; Bloch-Zupan, Agnès; Klein, Ophir D.; Viriot, Laurent

2015-06-01

The question of phenotypic convergence across a signalling pathway has important implications for both developmental and evolutionary biology. The ERK-MAPK cascade is known to play a central role in dental development, but the relative roles of its components remain unknown. Here we investigate the diversity of dental phenotypes in Spry2-/-, Spry4-/-, and Rsk2-/Y mice, including the incidence of extra teeth, which were lost in the mouse lineage 45 million years ago (Ma). In addition, Sprouty-specific anomalies mimic a phenotype that is absent in extant mice but present in mouse ancestors prior to 9 Ma. Although the mutant lines studied display convergent phenotypes, each gene has a specific role in tooth number determination and crown patterning. The similarities found between teeth in fossils and mutants highlight the pivotal role of the ERK-MAPK cascade during the evolution of the dentition in rodents.

Coupled ridge waveguide distributed feedback quantum cascade laser arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Ying-Hui; Zhang, Jin-Chuan, E-mail: zhangjinchuan@semi.ac.cn; Yan, Fang-Liang

2015-04-06

A coupled ridge waveguide quantum cascade laser (QCL) array consisting of fifteen elements with parallel integration was presented. In-phase fundamental mode operation in each element is secured by both the index-guided nature of the ridge and delicate loss management by properly designed geometries of the ridges and interspaces. Single-lobe lateral far-field with a nearly diffraction limited beam pattern was obtained. By incorporating a one-dimensional buried distributed feedback grating, the in-phase-operating coupled ridge waveguide QCL design provides an efficient solution to obtaining high output power and stable single longitudinal mode emission. The simplicity of this structure and fabrication process makes thismore » approach attractive to many practical applications.« less

A widely tunable 10-μm quantum cascade laser phase-locked to a state-of-the-art mid-infrared reference for precision molecular spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sow, P. L. T.; Mejri, S.; Tokunaga, S. K.

2014-06-30

We report the coherent phase-locking of a quantum cascade laser (QCL) at 10-μm to the secondary frequency standard of this spectral region, a CO{sub 2} laser stabilized on a saturated absorption line of OsO{sub 4}. The stability and accuracy of the standard are transferred to the QCL resulting in a line width of the order of 10 Hz, and leading to the narrowest QCL to date. The locked QCL is then used to perform absorption spectroscopy spanning 6 GHz of NH{sub 3} and methyltrioxorhenium, two species of interest for applications in precision measurements.

The PPAR-Platelet Connection: Modulators of Inflammation and Potential Cardiovascular Effects

PubMed Central

Spinelli, S. L.; O'Brien, J. J.; Bancos, S.; Lehmann, G. M.; Springer, D. L.; Blumberg, N.; Francis, C. W.; Taubman, M. B.; Phipps, R. P.

2008-01-01

Historically, platelets were viewed as simple anucleate cells responsible for initiating thrombosis and maintaining hemostasis, but clearly they are also key mediators of inflammation and immune cell activation. An emerging body of evidence links platelet function and thrombosis to vascular inflammation. peroxisome proliferator-activated receptors (PPARs) play a major role in modulating inflammation and, interestingly, PPARs (PPARβ/δ and PPARγ) were recently identified in platelets. Additionally, PPAR agonists attenuate platelet activation; an important discovery for two reasons. First, activated platelets are formidable antagonists that initiate and prolong a cascade of events that contribute to cardiovascular disease (CVD) progression. Dampening platelet release of proinflammatory mediators, including CD40 ligand (CD40L, CD154), is essential to hinder this cascade. Second, understanding the biologic importance of platelet PPARs and the mechanism(s) by which PPARs regulate platelet activation will be imperative in designing therapeutic strategies lacking the deleterious or unwanted side effects of current treatment options. PMID:18288284

Raf kinase inhibitory protein: a signal transduction modulator and metastasis suppressor.

PubMed

Granovsky, Alexey E; Rosner, Marsha Rich

2008-04-01

Cells have a multitude of controls to maintain their integrity and prevent random switching from one biological state to another. Raf Kinase Inhibitory Protein (RKIP), a member of the phosphatidylethanolamine binding protein (PEBP) family, is representative of a new class of modulators of signaling cascades that function to maintain the "yin yang" or balance of biological systems. RKIP inhibits MAP kinase (Raf-MEK-ERK), G protein-coupled receptor (GPCR) kinase and NFkappaB signaling cascades. Because RKIP targets different kinases dependent upon its state of phosphorylation, RKIP also acts to integrate crosstalk initiated by multiple environmental stimuli. Loss or depletion of RKIP results in disruption of the normal cellular stasis and can lead to chromosomal abnormalities and disease states such as cancer. Since RKIP and the PEBP family have been reviewed previously, the goal of this analysis is to provide an update and highlight some of the unique features of RKIP that make it a critical player in the regulation of cellular signaling processes.

Model for a pulsed terahertz quantum cascade laser under optical feedback.

PubMed

Agnew, Gary; Grier, Andrew; Taimre, Thomas; Lim, Yah Leng; Bertling, Karl; Ikonić, Zoran; Valavanis, Alexander; Dean, Paul; Cooper, Jonathan; Khanna, Suraj P; Lachab, Mohammad; Linfield, Edmund H; Davies, A Giles; Harrison, Paul; Indjin, Dragan; Rakić, Aleksandar D

2016-09-05

Optical feedback effects in lasers may be useful or problematic, depending on the type of application. When semiconductor lasers are operated using pulsed-mode excitation, their behavior under optical feedback depends on the electronic and thermal characteristics of the laser, as well as the nature of the external cavity. Predicting the behavior of a laser under both optical feedback and pulsed operation therefore requires a detailed model that includes laser-specific thermal and electronic characteristics. In this paper we introduce such a model for an exemplar bound-to-continuum terahertz frequency quantum cascade laser (QCL), illustrating its use in a selection of pulsed operation scenarios. Our results demonstrate significant interplay between electro-optical, thermal, and feedback phenomena, and that this interplay is key to understanding QCL behavior in pulsed applications. Further, our results suggest that for many types of QCL in interferometric applications, thermal modulation via low duty cycle pulsed operation would be an alternative to commonly used adiabatic modulation.

Blood coagulation factor XII drives adaptive immunity during neuroinflammation via CD87-mediated modulation of dendritic cells

PubMed Central

Göbel, Kerstin; Pankratz, Susann; Asaridou, Chloi-Magdalini; Herrmann, Alexander M.; Bittner, Stefan; Merker, Monika; Ruck, Tobias; Glumm, Sarah; Langhauser, Friederike; Kraft, Peter; Krug, Thorsten F.; Breuer, Johanna; Herold, Martin; Gross, Catharina C.; Beckmann, Denise; Korb-Pap, Adelheid; Schuhmann, Michael K.; Kuerten, Stefanie; Mitroulis, Ioannis; Ruppert, Clemens; Nolte, Marc W.; Panousis, Con; Klotz, Luisa; Kehrel, Beate; Korn, Thomas; Langer, Harald F.; Pap, Thomas; Nieswandt, Bernhard; Wiendl, Heinz; Chavakis, Triantafyllos; Kleinschnitz, Christoph; Meuth, Sven G.

2016-01-01

Aberrant immune responses represent the underlying cause of central nervous system (CNS) autoimmunity, including multiple sclerosis (MS). Recent evidence implicated the crosstalk between coagulation and immunity in CNS autoimmunity. Here we identify coagulation factor XII (FXII), the initiator of the intrinsic coagulation cascade and the kallikrein–kinin system, as a specific immune cell modulator. High levels of FXII activity are present in the plasma of MS patients during relapse. Deficiency or pharmacologic blockade of FXII renders mice less susceptible to experimental autoimmune encephalomyelitis (a model of MS) and is accompanied by reduced numbers of interleukin-17A-producing T cells. Immune activation by FXII is mediated by dendritic cells in a CD87-dependent manner and involves alterations in intracellular cyclic AMP formation. Our study demonstrates that a member of the plasmatic coagulation cascade is a key mediator of autoimmunity. FXII inhibition may provide a strategy to combat MS and other immune-related disorders. PMID:27188843

Regional turbulence patterns driven by meso- and submesoscale processes in the Caribbean Sea

NASA Astrophysics Data System (ADS)

C. Pérez, Juan G.; R. Calil, Paulo H.

2017-09-01

The surface ocean circulation in the Caribbean Sea is characterized by the interaction between anticyclonic eddies and the Caribbean Upwelling System (CUS). These interactions lead to instabilities that modulate the transfer of kinetic energy up- or down-cascade. The interaction of North Brazil Current rings with the islands leads to the formation of submesoscale vorticity filaments leeward of the Lesser Antilles, thus transferring kinetic energy from large to small scales. Within the Caribbean, the upper ocean dynamic ranges from large-scale currents to coastal upwelling filaments and allow the vertical exchange of physical properties and supply KE to larger scales. In this study, we use a regional model with different spatial resolutions (6, 3, and 1 km), focusing on the Guajira Peninsula and the Lesser Antilles in the Caribbean Sea, in order to evaluate the impact of submesoscale processes on the regional KE energy cascade. Ageostrophic velocities emerge as the Rossby number becomes O(1). As model resolution is increased submesoscale motions are more energetic, as seen by the flatter KE spectra when compared to the lower resolution run. KE injection at the large scales is greater in the Guajira region than in the others regions, being more effectively transferred to smaller scales, thus showing that submesoscale dynamics is key in modulating eddy kinetic energy and the energy cascade within the Caribbean Sea.

Modules for in vitro metabolic engineering: Pathway assembly for bio-based production of value-added chemicals.

PubMed

Taniguchi, Hironori; Okano, Kenji; Honda, Kohsuke

2017-06-01

Bio-based chemical production has drawn attention regarding the realization of a sustainable society. In vitro metabolic engineering is one of the methods used for the bio-based production of value-added chemicals. This method involves the reconstitution of natural or artificial metabolic pathways by assembling purified/semi-purified enzymes in vitro . Enzymes from distinct sources can be combined to construct desired reaction cascades with fewer biological constraints in one vessel, enabling easier pathway design with high modularity. Multiple modules have been designed, built, tested, and improved by different groups for different purpose. In this review, we focus on these in vitro metabolic engineering modules, especially focusing on the carbon metabolism, and present an overview of input modules, output modules, and other modules related to cofactor management.

A 65nm CMOS low-power MedRadio-band integer-N cascaded phase-locked loop for implantable medical systems.

PubMed

Wang, Yi-Xiao; Chen, Wei-Ming; Wu, Chung-Yu

2014-01-01

This paper presents a low-power MedRadio-band integer-N phase-locked Loop (PLL) system which is composed of two charge-pump PLLs cascade connected. The PLL provides the operation clock and local carrier signals for an implantable medical electronic system. In addition, to avoid the off-chip crystal oscillator, the 13.56 MHz Industrial, Scientific and Medical (ISM) band signal from the wireless power transmission system is adopted as the input reference signal for the PLL. Ring-based voltage controlled oscillators (VCOs) with current control units are adopted to reduce chip area and power dissipation. The proposed cascaded PLL system is designed and implemented in TSMC 65-nm CMOS technology. The measured jitter for 216.96 MHz signal is 12.23 ps and the phase noise is -65.9 dBc/Hz at 100 kHz frequency offset under 402.926 MHz carrier frequency. The measured power dissipations are 66 μW in the first PLL and 195 μW in the whole system under 1-V supply voltage. The chip area is 0.1088 mm(2) and no off-chip component is required which is suitable for the integration of the implantable medical electronic system.

Systemic risk in a unifying framework for cascading processes on networks

NASA Astrophysics Data System (ADS)

Lorenz, J.; Battiston, S.; Schweitzer, F.

2009-10-01

We introduce a general framework for models of cascade and contagion processes on networks, to identify their commonalities and differences. In particular, models of social and financial cascades, as well as the fiber bundle model, the voter model, and models of epidemic spreading are recovered as special cases. To unify their description, we define the net fragility of a node, which is the difference between its fragility and the threshold that determines its failure. Nodes fail if their net fragility grows above zero and their failure increases the fragility of neighbouring nodes, thus possibly triggering a cascade. In this framework, we identify three classes depending on the way the fragility of a node is increased by the failure of a neighbour. At the microscopic level, we illustrate with specific examples how the failure spreading pattern varies with the node triggering the cascade, depending on its position in the network and its degree. At the macroscopic level, systemic risk is measured as the final fraction of failed nodes, X*, and for each of the three classes we derive a recursive equation to compute its value. The phase diagram of X* as a function of the initial conditions, thus allows for a prediction of the systemic risk as well as a comparison of the three different model classes. We could identify which model class leads to a first-order phase transition in systemic risk, i.e. situations where small changes in the initial conditions determine a global failure. Eventually, we generalize our framework to encompass stochastic contagion models. This indicates the potential for further generalizations.

Spectral modification of the laser emission of a terahertz quantum cascade laser induced by broad-band double pulse injection seeding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Markmann, Sergej, E-mail: sergej.markmann@ruhr-uni-bochum.de; Nong, Hanond, E-mail: nong.hanond@ruhr-uni-bochum.de; Hekmat, Negar

2015-09-14

We demonstrate by injection seeding that the spectral emission of a terahertz (THz) quantum cascade laser (QCL) can be modified with broad-band THz pulses whose bandwidths are greater than the QCL bandwidth. Two broad-band THz pulses delayed in time imprint a modulation on the single THz pulse spectrum. The resulting spectrum is used to injection seed the THz QCL. By varying the time delay between the THz pulses, the amplitude distribution of the QCL longitudinal modes is modified. By applying this approach, the QCL emission is reversibly switched from multi-mode to single mode emission.

Mode switching in a multi-wavelength distributed feedback quantum cascade laser using an external micro-cavity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sidler, Meinrad; Institute for Quantum Electronics, ETH Zurich, Wolfgang-Pauli-Strasse 16, 8093 Zurich; Rauter, Patrick

2014-02-03

We demonstrate a multi-wavelength distributed feedback (DFB) quantum cascade laser (QCL) operating in a lensless external micro-cavity and achieve switchable single-mode emission at three distinct wavelengths selected by the DFB grating, each with a side-mode suppression ratio larger than 30 dB. Discrete wavelength tuning is achieved by modulating the feedback experienced by each mode of the multi-wavelength DFB QCL, resulting from a variation of the external cavity length. This method also provides a post-fabrication control of the lasing modes to correct for fabrication inhomogeneities, in particular, related to the cleaved facets position.

Cascadable all-optical inverter based on a nonlinear vertical-cavity semiconductor optical amplifier.

PubMed

Zhang, Haijiang; Wen, Pengyue; Esener, Sadik

2007-07-01

We report, for the first time to our knowledge, the operation of a cascadable, low-optical-switching-power(~10 microW) small-area (~100 microm(2)) high-speed (80 ps fall time) all-optical inverter. This inverter employs cross-gain modulation, polarization gain anisotropy, and highly nonlinear gain characteristics of an electrically pumped vertical-cavity semiconductor optical amplifier (VCSOA). The measured transfer characteristics of such an optical inverter resemble those of standard electronic metal-oxide semiconductor field-effect transistor-based inverters exhibiting high noise margin and high extinction ratio (~9.3 dB), making VCSOAs an ideal building block for all-optical logic and memory.

Wavelength-modulation-spectroscopy for real-time, in situ NO detection in combustion gases with a 5.2 μm quantum-cascade laser

NASA Astrophysics Data System (ADS)

Chao, X.; Jeffries, J. B.; Hanson, R. K.

2012-03-01

A mid-infrared absorption strategy with calibration-free wavelength-modulation-spectroscopy (WMS) has been developed and demonstrated for real-time, in situ detection of nitric oxide in particulate-laden combustion-exhaust gases up to temperatures of 700 K. An external-cavity quantum-cascade laser (ECQCL) near 5.2 μm accessed the fundamental absorption band of NO, and a wavelength-scanned, 1 f-normalized WMS with second-harmonic detection (WMS-2 f/1 f) strategy was developed. Due to the external-cavity laser architecture, large nonlinear intensity modulation (IM) was observed when the wavelength was modulated by injection-current modulation, and the IM indices were also found to be strongly wavelength-dependent as the center wavelength was scanned with piezoelectric tuning of the cavity. A quantitative model of the 1 f-normalized WMS-2 f signal was developed and validated under laboratory conditions. A sensor was subsequently designed, built and demonstrated for real-time, in situ measurements of NO across a 3 m path in the particulate-laden exhaust of a pulverized-coal-fired power plant boiler. The 1 f-normalized WMS-2 f method proved to have better noise immunity for non-absorption transmission, than wavelength-scanned direct absorption. A 0.3 ppm-m detection limit was estimated using the R15.5 transition near 1927 cm-1 with 1 s averaging. Mid-infrared QCL-based NO absorption with 1 f-normalized WMS-2 f detection shows excellent promise for practical sensing in the combustion exhaust.

Phase transition and information cascade in a voting model

NASA Astrophysics Data System (ADS)

Hisakado, M.; Mori, S.

2010-08-01

In this paper, we introduce a voting model that is similar to a Keynesian beauty contest and analyse it from a mathematical point of view. There are two types of voters—copycat and independent—and two candidates. Our voting model is a binomial distribution (independent voters) doped in a beta binomial distribution (copycat voters). We find that the phase transition in this system is at the upper limit of t, where t is the time (or the number of the votes). Our model contains three phases. If copycats constitute a majority or even half of the total voters, the voting rate converges more slowly than it would in a binomial distribution. If independents constitute the majority of voters, the voting rate converges at the same rate as it would in a binomial distribution. We also study why it is difficult to estimate the conclusion of a Keynesian beauty contest when there is an information cascade.

Optical multiple-image authentication based on cascaded phase filtering structure

NASA Astrophysics Data System (ADS)

Wang, Q.; Alfalou, A.; Brosseau, C.

2016-10-01

In this study, we report on the recent developments of optical image authentication algorithms. Compared with conventional optical encryption, optical image authentication achieves more security strength because such methods do not need to recover information of plaintext totally during the decryption period. Several recently proposed authentication systems are briefly introduced. We also propose a novel multiple-image authentication system, where multiple original images are encoded into a photon-limited encoded image by using a triple-plane based phase retrieval algorithm and photon counting imaging (PCI) technique. One can only recover a noise-like image using correct keys. To check authority of multiple images, a nonlinear fractional correlation is employed to recognize the original information hidden in the decrypted results. The proposal can be implemented optically using a cascaded phase filtering configuration. Computer simulation results are presented to evaluate the performance of this proposal and its effectiveness.

Mid-infrared frequency comb generation via cascaded quadratic nonlinearities in quasi-phase-matched waveguides

NASA Astrophysics Data System (ADS)

Kowligy, Abijith S.; Lind, Alex; Hickstein, Daniel D.; Carlson, David R.; Timmers, Henry; Nader, Nima; Cruz, Flavio C.; Ycas, Gabriel; Papp, Scott B.; Diddams, Scott A.

2018-04-01

We experimentally demonstrate a simple configuration for mid-infrared (MIR) frequency comb generation in quasi-phase-matched lithium niobate waveguides using the cascaded-$\\chi^{(2)}$ nonlinearity. With nanojoule-scale pulses from an Er:fiber laser, we observe octave-spanning supercontinuum in the near-infrared with dispersive-wave generation in the 2.5--3 $\\text{\\mu}$m region and intra-pulse difference-frequency generation in the 4--5 $\\text{\\mu}$m region. By engineering the quasi-phase-matched grating profiles, tunable, narrow-band MIR and broadband MIR spectra are both observed in this geometry. Finally, we perform numerical modeling using a nonlinear envelope equation, which shows good quantitative agreement with the experiment---and can be used to inform waveguide designs to tailor the MIR frequency combs. Our results identify a path to a simple single-branch approach to mid-infrared frequency comb generation in a compact platform using commercial Er:fiber technology.

Mid-infrared frequency comb generation via cascaded quadratic nonlinearities in quasi-phase-matched waveguides.

PubMed

Kowligy, Abijith S; Lind, Alex; Hickstein, Daniel D; Carlson, David R; Timmers, Henry; Nader, Nima; Cruz, Flavio C; Ycas, Gabriel; Papp, Scott B; Diddams, Scott A

2018-04-15

We experimentally demonstrate a simple configuration for mid-infrared (MIR) frequency comb generation in quasi-phase-matched lithium niobate waveguides using the cascaded-χ (2) nonlinearity. With nanojoule-scale pulses from an Er:fiber laser, we observe octave-spanning supercontinuum in the near-infrared with dispersive wave generation in the 2.5-3 μm region and intrapulse difference frequency generation in the 4-5 μm region. By engineering the quasi-phase-matched grating profiles, tunable, narrowband MIR and broadband MIR spectra are both observed in this geometry. Finally, we perform numerical modeling using a nonlinear envelope equation, which shows good quantitative agreement with the experiment-and can be used to inform waveguide designs to tailor the MIR frequency combs. Our results identify a path to a simple single-branch approach to mid-infrared frequency comb generation in a compact platform using commercial Er:fiber technology.

Open Cascades as Simple Solutions to Providing Ultrasensitivity and Adaptation in Cellular Signaling

PubMed Central

Srividhya, Jeyaraman; Li, Yongfeng; Pomerening, Joseph R.

2011-01-01

Cell signaling is achieved predominantly by reversible phosphorylation-dephosphorylation reaction cascades. Up until now, circuits conferring adaptation have all required the presence of a cascade with some type of closed topology: negative–feedback loop with a buffering node, or incoherent feedforward loop with a proportioner node. In this paper—using Goldbeter and Koshland-type expressions—we propose a differential equation model to describe a generic, open signaling cascade that elicits an adaptation response. This is accomplished by coupling N phosphorylation–dephosphorylation cycles unidirectionally, without any explicit feedback loops. Using this model, we show that as the length of the cascade grows, the steady states of the downstream cycles reach a limiting value. In other words, our model indicates that there are a minimum number of cycles required to achieve a maximum in sensitivity and amplitude in the response of a signaling cascade. We also describe for the first time that the phenomenon of ultrasensitivity can be further subdivided into three sub–regimes, separated by sharp stimulus threshold values: OFF, OFF-ON-OFF, and ON. In the OFF-ON-OFF regime, an interesting property emerges. In the presence of a basal amount of activity, the temporal evolution of early cycles yields damped peak responses. On the other hand, the downstream cycles switch rapidly to a higher activity state for an extended period of time, prior to settling to an OFF state (OFF-ON-OFF). This response arises from the changing dynamics between a feed–forward activation module and dephosphorylation reactions. In conclusion, our model gives the new perspective that open signaling cascades embedded in complex biochemical circuits may possess the ability to show a switch–like adaptation response, without the need for any explicit feedback circuitry. PMID:21566270

Divisive normalization and neuronal oscillations in a single hierarchical framework of selective visual attention.

PubMed

Montijn, Jorrit Steven; Klink, P Christaan; van Wezel, Richard J A

2012-01-01

Divisive normalization models of covert attention commonly use spike rate modulations as indicators of the effect of top-down attention. In addition, an increasing number of studies have shown that top-down attention increases the synchronization of neuronal oscillations as well, particularly in gamma-band frequencies (25-100 Hz). Although modulations of spike rate and synchronous oscillations are not mutually exclusive as mechanisms of attention, there has thus far been little effort to integrate these concepts into a single framework of attention. Here, we aim to provide such a unified framework by expanding the normalization model of attention with a multi-level hierarchical structure and a time dimension; allowing the simulation of a recently reported backward progression of attentional effects along the visual cortical hierarchy. A simple cascade of normalization models simulating different cortical areas is shown to cause signal degradation and a loss of stimulus discriminability over time. To negate this degradation and ensure stable neuronal stimulus representations, we incorporate a kind of oscillatory phase entrainment into our model that has previously been proposed as the "communication-through-coherence" (CTC) hypothesis. Our analysis shows that divisive normalization and oscillation models can complement each other in a unified account of the neural mechanisms of selective visual attention. The resulting hierarchical normalization and oscillation (HNO) model reproduces several additional spatial and temporal aspects of attentional modulation and predicts a latency effect on neuronal responses as a result of cued attention.

Divisive Normalization and Neuronal Oscillations in a Single Hierarchical Framework of Selective Visual Attention

PubMed Central

Montijn, Jorrit Steven; Klink, P. Christaan; van Wezel, Richard J. A.

2012-01-01

Divisive normalization models of covert attention commonly use spike rate modulations as indicators of the effect of top-down attention. In addition, an increasing number of studies have shown that top-down attention increases the synchronization of neuronal oscillations as well, particularly in gamma-band frequencies (25–100 Hz). Although modulations of spike rate and synchronous oscillations are not mutually exclusive as mechanisms of attention, there has thus far been little effort to integrate these concepts into a single framework of attention. Here, we aim to provide such a unified framework by expanding the normalization model of attention with a multi-level hierarchical structure and a time dimension; allowing the simulation of a recently reported backward progression of attentional effects along the visual cortical hierarchy. A simple cascade of normalization models simulating different cortical areas is shown to cause signal degradation and a loss of stimulus discriminability over time. To negate this degradation and ensure stable neuronal stimulus representations, we incorporate a kind of oscillatory phase entrainment into our model that has previously been proposed as the “communication-through-coherence” (CTC) hypothesis. Our analysis shows that divisive normalization and oscillation models can complement each other in a unified account of the neural mechanisms of selective visual attention. The resulting hierarchical normalization and oscillation (HNO) model reproduces several additional spatial and temporal aspects of attentional modulation and predicts a latency effect on neuronal responses as a result of cued attention. PMID:22586372

Postnatal Experience Modulates Functional Properties of Mouse Olfactory Sensory Neurons

PubMed Central

He, Jiwei; Tian, Huikai; Lee, Anderson C.; Ma, Minghong

2012-01-01

Early experience considerably modulates the organization and function of all sensory systems. In the mammalian olfactory system, deprivation of the sensory inputs via neonatal, unilateral naris closure has been shown to induce structural, molecular, and functional changes from the olfactory epithelium to the olfactory bulb and cortex. However, it remains unknown how early experience shapes functional properties of individual olfactory sensory neurons (OSNs), the primary odor detectors in the nose. To address this question, we examined odorant response properties of mouse OSNs in both the closed and open nostril after four weeks of unilateral naris closure with age-matched untreated animals as control. Using patch-clamp technique on genetically-tagged OSNs with defined odorant receptors (ORs), we found that sensory deprivation increased the sensitivity of MOR23 neurons in the closed side while overexposure caused the opposite effect in the open side. We next analyzed the response properties including rise time, decay time, and adaptation induced by repeated stimulation in MOR23 and M71 neurons. Even though these two types of neurons showed distinct properties in dynamic range and response kinetics, sensory deprivation significantly slowed down the decay phase of odorant-induced transduction events in both types. Using western blotting and antibody staining, we confirmed upregulation of several signaling proteins in the closed side as compared with the open side. This study suggests that early experience modulates functional properties of OSNs, probably via modifying the signal transduction cascade. PMID:22703547

Cross-Phase Modulation: A New Technique for Controlling the Spectral, Temporal, and Spatial Properties of Ultrashort Pulses

NASA Astrophysics Data System (ADS)

Baldeck, P. L.; Ho, P. P.; Alfano, Robert R.

Self-phase modulation (SPM) is the principal mechanism responsible for the generation of picosecond and femtosecond white-light supercontinua. When an intense ultrashort pulse progagates through a medium, it distorts the atomic configuration of the material, which changes the refractive index. The pulse phase is time modulated, which causes the generation of new frequencies. This phase modulation originates from the pulse itself (self-phase modulation). It can also be generated by a copropagating pulse (cross-phase modulation).

Laboratory hemostasis: from biology to the bench.

PubMed

Lippi, Giuseppe; Favaloro, Emmanuel J

2018-06-27

Physiological hemostasis is an intricate biological system, where procoagulant and anticoagulant forces interplay and preserves blood fluidity when blood vessels are intact, or trigger clot formation to prevent excessive bleeding when blood vessels are injured. The modern model of hemostasis is divided into two principal phases. The first, defined as primary hemostasis, involves the platelet-vessel interplay, whilst the second, defined as secondary hemostasis, mainly involves coagulation factors, damaged cells and platelet surfaces, where the so-called coagulation cascade rapidly develops. The activation and amplification of the coagulation cascade is finely modulated by the activity of several physiological inhibitors. Once bleeding has been efficiently stopped by blood clot formation, dissolution of the thrombus is essential to restore vessel permeability. This process, known as fibrinolysis, also develops through coordinate action of a vast array of proteins and enzymes. An accurate diagnosis of hemostasis disturbance entails a multifaceted approach, encompassing family and personal history of hemostatic disorders, accurate collection of clinical signs and symptoms, integrated with laboratory hemostasis testing. Regarding laboratory testing, a reasonable approach entails classifying hemostasis testing according to cost, complexity and available clinical information. Laboratory workout may hence initiate with some rapid and inexpensive "screening" tests, characterized by high negative predictive value, then followed by second- or third-line analyses, specifically aimed to clarify the nature and severity of bleeding or thrombotic phenotype. This article aims to provide a general overview of the hemostatic process, and to provide some general suggestions to optimally facilitate laboratory hemostasis testing.

Plasmodium falciparum-infected erythrocytes induce Tissue Factor expression in endothelial cells and support the assembly of multimolecular coagulation complexes

PubMed Central

Francischetti, Ivo MB; Seydel, Karl B; Monteiro, Robson Q; Whitten, Richard O; Erexson, Cindy R; Noronha, Almério LL; Ostera, Graciela R.; Kamiza, Steve B; Molyneux, Malcolm E; Ward, Jerrold M; Taylor, Terrie E

2010-01-01

Summary Background Plasmodium falciparum malaria infects 300–500 million people every year causing 1–2 million deaths annually. Evidence of a coagulation disorder, activation of endothelial cells (EC) and increase in inflammatory cytokines are often present in malaria. Objectives We have asked whether parasitized red blood cells (pRBC) interaction with EC induces Tissue Factor expression in vitro and in vivo. The potential of phosphatidylserine-containing pRBC to support the assembly of blood coagulation complexes was also investigated. Results We demonstrate that mature forms of pRBC induce functional expression of tissue factor (TF) by endothelial cells (EC) in vitro with productive assembly of the extrinsic Xnase complex and initiation of the coagulation cascade. Late stage pRBC also support the prothrombinase and intrinsic Xnase complex formation in vitro, and may function as activated platelets in the amplification phase of the blood coagulation. Notably, postmortem brain sections obtained from P. falciparum-infected children who died from Cerebral Malaria and other causes display a consistent staining for TF in the EC. Conclusions These findings place TF expression by endothelium and the amplification of the coagulation cascade by pRBC and/or activated platelets as potentially critical steps in the pathogenesis of malaria. Furthermore, it may allow investigators to test other therapeutic alternatives targeting TF or modulators of EC function in the treatment of malaria and/or its complications. PMID:17002660

Inverse regulatory coordination of motility and curli-mediated adhesion in Escherichia coli.

PubMed

Pesavento, Christina; Becker, Gisela; Sommerfeldt, Nicole; Possling, Alexandra; Tschowri, Natalia; Mehlis, Anika; Hengge, Regine

2008-09-01

During the transition from post-exponential to stationary phase, Escherichia coli changes from the motile-planktonic to the adhesive-sedentary "lifestyle." We demonstrate this transition to be controlled by mutual inhibition of the FlhDC/motility and sigma(S)/adhesion control cascades at two distinct hierarchical levels. At the top level, motility gene expression and the general stress response are inversely coordinated by sigma(70)/sigma(FliA)/sigma(S) competition for core RNA polymerase and the FlhDC-controlled FliZ protein acting as a sigma(S) inhibitor. At a lower level, the signaling molecule bis-(3'-5')-cyclic-diguanosine monophosphate (c-di-GMP) reduces flagellar activity and stimulates transcription of csgD, which encodes an essential activator of adhesive curli fimbriae expression. This c-di-GMP is antagonistically controlled by sigma(S)-regulated GGDEF proteins (mainly YegE) and YhjH, an EAL protein and c-di-GMP phosphodiesterase under FlhDC/FliA control. The switch from motility-based foraging to the general stress response and curli expression requires sigma(S)-modulated down-regulation of expression of the flagellar regulatory cascade as well as proteolysis of the flagellar master regulator FlhDC. Control of YhjH by FlhDC and of YegE by sigma(S) produces a fine-tuned checkpoint system that "unlocks" curli expression only after down-regulation of flagellar gene expression. In summary, these data reveal the logic and sequence of molecular events underlying the motile-to-adhesive "lifestyle" switch in E. coli.

Limits of Predictability of Cascading Overload Failures in Spatially-Embedded Networks with Distributed Flows.

PubMed

Moussawi, A; Derzsy, N; Lin, X; Szymanski, B K; Korniss, G

2017-09-15

Cascading failures are a critical vulnerability of complex information or infrastructure networks. Here we investigate the properties of load-based cascading failures in real and synthetic spatially-embedded network structures, and propose mitigation strategies to reduce the severity of damages caused by such failures. We introduce a stochastic method for optimal heterogeneous distribution of resources (node capacities) subject to a fixed total cost. Additionally, we design and compare the performance of networks with N-stable and (N-1)-stable network-capacity allocations by triggering cascades using various real-world node-attack and node-failure scenarios. We show that failure mitigation through increased node protection can be effectively achieved against single-node failures. However, mitigating against multiple node failures is much more difficult due to the combinatorial increase in possible sets of initially failing nodes. We analyze the robustness of the system with increasing protection, and find that a critical tolerance exists at which the system undergoes a phase transition, and above which the network almost completely survives an attack. Moreover, we show that cascade-size distributions measured in this region exhibit a power-law decay. Finally, we find a strong correlation between cascade sizes induced by individual nodes and sets of nodes. We also show that network topology alone is a weak predictor in determining the progression of cascading failures.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fernandez-Gutierrez, Sulmer, E-mail: sulmer.a.fernandez.gutierrez@intel.com; Browning, Jim; Lin, Ming-Chieh

Phase-control of a magnetron is studied via simulation using a combination of a continuous current source and a modulated current source. The addressable, modulated current source is turned ON and OFF at the magnetron operating frequency in order to control the electron injection and the spoke phase. Prior simulation work using a 2D model of a Rising Sun magnetron showed that the use of 100% modulated current controlled the magnetron phase and allowed for dynamic phase control. In this work, the minimum fraction of modulated current source needed to achieve a phase control is studied. The current fractions (modulated versusmore » continuous) were varied from 10% modulated current to 100% modulated current to study the effects on phase control. Dynamic phase-control, stability, and start up time of the device were studied for all these cases showing that with 10% modulated current and 90% continuous current, a phase shift of 180° can be achieved demonstrating dynamic phase control.« less

Few-cycle solitons and supercontinuum generation with cascaded quadratic nonlinearities in unpoled lithium niobate ridge waveguides.

PubMed

Guo, Hairun; Zeng, Xianglong; Zhou, Binbin; Bache, Morten

2014-03-01

Formation and interaction of few-cycle solitons in a lithium niobate ridge waveguide are numerically investigated. The solitons are created through a cascaded phase-mismatched second-harmonic generation process, which induces a dominant self-defocusing Kerr-like nonlinearity on the pump pulse. The inherent material self-focusing Kerr nonlinearity is overcome over a wide wavelength range, and self-defocusing solitons are supported from 1100 to 1900 nm, covering the whole communication band. Single cycle self-compressed solitons and supercontinuum generation spanning 1.3 octaves are observed when pumped with femtosecond nanojoule pulses at 1550 nm. The waveguide is not periodically poled, as quasi-phase-matching would lead to detrimental nonlinear effects impeding few-cycle soliton formation.

Broadband standoff detection of large molecules by mid-infrared active coherent laser spectrometry.

PubMed

Macleod, Neil A; Molero, Francisco; Weidmann, Damien

2015-01-26

A widely tunable active coherent laser spectrometer (ACLaS) has been demonstrated for standoff detection of broadband absorbers in the 1280 to 1318 cm^-1 spectral region using an external cavity quantum cascade laser as a mid-infrared source. The broad tuning range allows detection and quantification of vapor phase molecules, such as dichloroethane, ethylene glycol dinitrate, and tetrafluoroethane. The level of confidence in molecular mixing ratios retrieved from interfering spectral measurements is assessed in a quantitative manner. A first qualitative demonstration of condensed phase chemical detection on nitroacetanilide has also been conducted. Detection performances of the broadband ACLaS have been placed in the context of explosive detection and compared to that obtained using distributed feedback quantum cascade lasers.

Coherent emission from integrated Talbot-cavity quantum cascade lasers.

PubMed

Meng, Bo; Qiang, Bo; Rodriguez, Etienne; Hu, Xiao Nan; Liang, Guozhen; Wang, Qi Jie

2017-02-20

We report experimental realization of phase-locked quantum cascade laser (QCL) array using a monolithically integrated Talbot cavity. An array with six laser elements at a wavelength of ~4.8 μm shows a maximum peak power of ~4 W which is more than 5 times higher than that of a single ridge laser element and a slope efficiency of 1 W/A at room temperature. Operation of in-phase coherent supermode has been achieved over the whole dynamic range of the Talbot-cavity QCL. The structure was analysed using a straightforward theoretical model, showing quantitatively good agreement with the experimental results. The reduced thermal resistance makes the structure an attractive approach to achieve high beam quality continuous wave QCLs.

ß-Adrenergic Receptor Signaling and Modulation of Long-Term Potentiation in the Mammalian Hippocampus

ERIC Educational Resources Information Center

O'Dell, Thomas J.; Connor, Steven A.; Guglietta, Ryan; Nguyen, Peter V.

2015-01-01

Encoding new information in the brain requires changes in synaptic strength. Neuromodulatory transmitters can facilitate synaptic plasticity by modifying the actions and expression of specific signaling cascades, transmitter receptors and their associated signaling complexes, genes, and effector proteins. One critical neuromodulator in the…

Quantum cascade transmitters for ultrasensitive chemical agent and explosives detection

NASA Astrophysics Data System (ADS)

Schultz, John F.; Taubman, Matthew S.; Harper, Warren W.; Williams, Richard M.; Myers, Tanya L.; Cannon, Bret D.; Sheen, David M.; Anheier, Norman C., Jr.; Allen, Paul J.; Sundaram, S. K.; Johnson, Bradley R.; Aker, Pamela M.; Wu, Ming C.; Lau, Erwin K.

2003-07-01

The small size, high power, promise of access to any wavelength between 3.5 and 16 microns, substantial tuning range about a chosen center wavelength, and general robustness of quantum cascade (QC) lasers provide opportunities for new approaches to ultra-sensitive chemical detection and other applications in the mid-wave infrared. PNNL is developing novel remote and sampling chemical sensing systems based on QC lasers, using QC lasers loaned by Lucent Technologies. In recent months laboratory cavity-enhanced sensing experiments have achieved absorption sensitivities of 8.5 x 10-11 cm-1 Hz-1/2, and the PNNL team has begun monostatic and bi-static frequency modulated, differential absorption lidar (FM DIAL) experiments at ranges of up to 2.5 kilometers. In related work, PNNL and UCLA are developing miniature QC laser transmitters with the multiplexed tunable wavelengths, frequency and amplitude stability, modulation characteristics, and power levels needed for chemical sensing and other applications. Current miniaturization concepts envision coupling QC oscillators, QC amplifiers, frequency references, and detectors with miniature waveguides and waveguide-based modulators, isolators, and other devices formed from chalcogenide or other types of glass. Significant progress has been made on QC laser stabilization and amplification, and on development and characterization of high-purity chalcogenide glasses, waveguide writing techniques, and waveguide metrology.

Development a low-cost carbon monoxide sensor using homemade CW-DFB QCL and board-level electronics

NASA Astrophysics Data System (ADS)

Dang, Jingmin; Yu, Haiye; Zheng, Chuantao; Wang, Lijun; Sui, Yuanyuan; Wang, Yiding

2018-05-01

A mid-infrared sensor was demonstrated for the detection of carbon monoxide (CO) at trace level. In order to reduce cost, a homemade continuous-wave mode distributed feedback quantum cascade laser (CW-DFB QCL), a mini gas cell with 1.6-m optical length, and some self-development electronic modules were adopted as excitation source, absorption pool, and signal controlling and processing tool, respectively. Wavelength modulation spectroscopy (WMS) and phase sensitive detection (PSD) techniques as well as wavelet filtering software algorithm were used to reduce the influence of light source fluctuation and system noise and to improve measurement precision and sensitivity. Under the selected P(11) absorption line located at 2099.083 cm-1, a limit of detection (LoD) of 26 parts per billion by volume (ppbv) at atmospheric pressure was achieved with a 1-s acquisition time. Allan deviation was used to characterize the long-term performance of the CO sensor, and a measurement precision of ∼3.4 ppbv was observed with an optimal integration time of ∼114 s. As a field measurement, a continuous monitoring on indoor CO concentration for a period of 24 h was conducted, which verified the reliable and robust operation of the developed sensor.

Palytoxin: exploiting a novel skin tumor promoter to explore signal transduction and carcinogenesis.

PubMed

Wattenberg, Elizabeth V

2007-01-01

Palytoxin is a novel skin tumor promoter, which has been used to help probe the role of different types of signaling mechanisms in carcinogenesis. The multistage mouse skin model indicates that tumor promotion is an early, prolonged, and reversible phase of carcinogenesis. Understanding the molecular mechanisms underlying tumor promotion is therefore important for developing strategies to prevent and treat cancer. Naturally occurring tumor promoters that bind to specific cellular receptors have proven to be useful tools for investigating important biochemical events in multistage carcinogenesis. For example, the identification of protein kinase C as the receptor for the prototypical skin tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) (also called phorbol 12-myristate 13-acetate, PMA) provided key evidence that tumor promotion involves the aberrant modulation of signaling cascades that govern cell fate and function. The subsequent discovery that palytoxin, a marine toxin isolated from zoanthids (genus Palythoa), is a potent skin tumor promoter yet does not activate protein kinase C indicated that investigating palytoxin action could help reveal new aspects of tumor promotion. Interestingly, the putative receptor for palytoxin is the Na(+),K(+)-ATPase. This review focuses on palytoxin-stimulated signaling and how palytoxin has been used to investigate alternate biochemical mechanisms by which important targets in carcinogenesis can be modulated.

Palytoxin: Exploiting a novel skin tumor promoter to explore signal transduction and carcinogenesis

PubMed Central

Wattenberg, Elizabeth V.

2006-01-01

Palytoxin is a novel skin tumor promoter, which has been used to help probe the role of different types of signaling mechanisms in carcinogenesis. The multi-stage mouse skin model indicates that tumor promotion is an early, prolonged, and reversible phase of carcinogenesis. Understanding the molecular mechanisms underlying tumor promotion is therefore important for developing strategies to prevent and treat cancer. Naturally occurring tumor promoters that bind to specific cellular receptors have proven to be useful tools for investigating important biochemical events in multi-stage carcinogenesis. For example, the identification of protein kinase C as the receptor for the prototypical skin tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) (also called phorbol-12-myristate-13-acetate or PMA) provided key evidence that tumor promotion involves the aberrant modulation of signaling cascades that govern cell fate and function. The subsequent discovery that palytoxin, a marine toxin isolated from zoanthids (genus Palythoa), is a potent skin tumor promoter yet does not activate protein kinase C indicated that investigating palytoxin action could help reveal new aspects of tumor promotion. Interestingly, the putative receptor for palytoxin is the Na+,K+-ATPase. This review focuses on palytoxin-stimulated signaling, and how palytoxin has been used to investigate alternate biochemical mechanisms by which important targets in carcinogenesis can be modulated. PMID:16855216

CANT1 lncRNA Triggers Efficient Therapeutic Efficacy by Correcting Aberrant lncing Cascade in Malignant Uveal Melanoma.

PubMed

Xing, Yue; Wen, Xuyang; Ding, Xia; Fan, Jiayan; Chai, Peiwei; Jia, Renbing; Ge, Shengfang; Qian, Guanxiang; Zhang, He; Fan, Xianqun

2017-05-03

Uveal melanoma (UM) is an intraocular malignant tumor with a high mortality rate. Recent studies have shown the functions of long non-coding RNAs (lncRNAs) in tumorigenesis; thus, targeting tumor-specific lncRNA abnormalities has become an attractive approach for developing therapeutics to treat uveal melanoma. In this study, we identified a novel nuclear CANT1 lncRNA (CASC15-New-Transcript 1) that acts as a necessary UM suppressor. CANT1 significantly reduced tumor metastatic capacity and tumor formation, either in cell culture or in animals harboring tumor xenograft. Intriguingly, XIST lncRNA serves as a potential target of CANT1, and JPX or FTX lncRNA subsequently serves as a contextual hinge to activate a novel CANT1-JPX/FTX-XIST long non-coding (lncing) pathway in UM. Moreover, CANT1 triggers the expression of JPX and FTX by directly binding to their promoters and promoting H3K4 methylation. These observations delineate a novel lncing cascade in which lncRNAs directly build a lncing cascade without coding genes that aims to modulate UM tumorigenesis, thereby specifying a novel "lncing-cascade renewal" anti-tumor therapeutic strategy by correcting aberrant lncing cascade in uveal melanoma. Copyright © 2017 The American Society of Gene and Cell Therapy. Published by Elsevier Inc. All rights reserved.

System and method for tuning adjusting the central frequency of a laser while maintaining frequency stabilization to an external reference

NASA Technical Reports Server (NTRS)

Livas, Jeffrey (Inventor); Thorpe, James I. (Inventor); Numata, Kenji (Inventor)

2011-01-01

A method and system for stabilizing a laser to a frequency reference with an adjustable offset. The method locks a sideband signal generated by passing an incoming laser beam through the phase modulator to a frequency reference, and adjusts a carrier frequency relative to the locked sideband signal by changing a phase modulation frequency input to the phase modulator. The sideband signal can be a single sideband (SSB), dual sideband (DSB), or an electronic sideband (ESB) signal. Two separate electro-optic modulators can produce the DSB signal. The two electro-optic modulators can be a broadband modulator and a resonant modulator. With a DSB signal, the method can introduce two sinusoidal phase modulations at the phase modulator. With ESB signals, the method can further drive the optical phase modulator with an electrical signal with nominal frequency OMEGA(sub 1) that is phase modulated at a frequency OMEGA(sub 2)

Suppression of turbulent energy cascade due to phase separation in homogenous binary mixture fluid

NASA Astrophysics Data System (ADS)

Takagi, Youhei; Okamoto, Sachiya

2015-11-01

When a multi-component fluid mixture becomes themophysically unstable state by quenching from well-melting condition, phase separation due to spinodal decomposition occurs, and a self-organized structure is formed. During phase separation, free energy is consumed for the structure formation. In our previous report, the phase separation in homogenous turbulence was numerically simulated and the coarsening process of phase separation was discussed. In this study, we extended our numerical model to a high Schmidt number fluid corresponding to actual polymer solution. The governing equations were continuity, Navier-Stokes, and Chan-Hiliard equations as same as our previous report. The flow filed was an isotropic homogenous turbulence, and the dimensionless parameters in the Chan-Hilliard equation were estimated based on the thermophysical condition of binary mixture. From the numerical results, it was found that turbulent energy cascade was drastically suppressed in the inertial subrange by phase separation for the high Schmidt number flow. By using the identification of turbulent and phase separation structure, we discussed the relation between total energy balance and the structures formation processes. This study is financially supported by the Grand-in-Aid for Young Scientists (B) (No. T26820045) from the Ministry of Education, Cul-ture, Sports, Science and Technology of Japan.

Theoretical analysis of terahertz generation from a compact optical parametric oscillator based on adhesive-free-bonded periodically inverted KTiOPO4 plates

NASA Astrophysics Data System (ADS)

Li, Zhongyang; Wang, Silei; Wang, Mengtao; Yuan, Bin; Wang, Weishu

2017-10-01

Terahertz (THz) generation by difference frequency generation (DFG) processes with dual signal waves is theoretically analyzed. The dual signal waves are generated by an optical parametric oscillator (OPO) with periodically inverted KTiOPO4 (KTP) plates based on adhesive-free-bonded (AFB) technology. The phase-matching conditions in a same AFB KTP composite for the OPO generating signals and idlers and for the DFG generating THz wave can be simultaneously satisfied by selecting the thickness of each KTP plate. Moreover, 4-order cascaded DFG processes can be realized in the same AFB KTP composite. The cascaded Stokes interaction processes generating THz photons and the cascaded anti-Stokes interaction processes consuming THz photons are investigated from coupled wave equations. Take an example of 3.106 THz which locates in the vicinity of polariton resonances, THz intensities and quantum conversion efficiencies are calculated. Compared with non-cascaded DFG processes, THz intensities of 3.106 THz in 4-order cascaded DFG processes increase to 5.56 times. When the pump intensity equals 20 MW mm-2, the quantum conversion efficiency of 259% in 4-order cascaded DFG processes can be realized, which exceeds the Manley-Rowe limit.

All optical coherent receiver for self-homodyne detection of digitally phase modulated optical signals

NASA Astrophysics Data System (ADS)

Kiasaleh, Kamran

1994-02-01

A novel optical phase-locked loop (OPLL) system for the self-homodyne detection of digitally phase modulated optical signals is introduced. A Mach-Zehnder type interferometer is used to self-homodyne binary phase-modulated optical signals with an external phase modulator inserted in the control arm of the interferometer.

Phase modulation in RF tag

DOEpatents

Carrender, Curtis Lee; Gilbert, Ronald W.

2007-02-20

A radio frequency (RF) communication system employs phase-modulated backscatter signals for RF communication from an RF tag to an interrogator. The interrogator transmits a continuous wave interrogation signal to the RF tag, which based on an information code stored in a memory, phase-modulates the interrogation signal to produce a backscatter response signal that is transmitted back to the interrogator. A phase modulator structure in the RF tag may include a switch coupled between an antenna and a quarter-wavelength stub; and a driver coupled between the memory and a control terminal of the switch. The driver is structured to produce a modulating signal corresponding to the information code, the modulating signal alternately opening and closing the switch to respectively decrease and increase the transmission path taken by the interrogation signal and thereby modulate the phase of the response signal. Alternatively, the phase modulator may include a diode coupled between the antenna and driver. The modulating signal from the driver modulates the capacitance of the diode, which modulates the phase of the response signal reflected by the diode and antenna.

Tolerance of the frequency deviation of LO sources at a MIMO system

NASA Astrophysics Data System (ADS)

Xiao, Jiangnan; Li, Xingying; Zhang, Zirang; Xu, Yuming; Chen, Long; Yu, Jianjun

2015-11-01

We analyze and simulate the tolerance of frequency offset at a W-band optical-wireless transmission system. The transmission system adopts optical polarization division multiplexing (PDM), and multiple-input multiple-output (MIMO) reception. The transmission signal adopts optical quadrature phase shift keying (QPSK) modulation, and the generation of millimeter-wave is based on the optical heterodyning technique. After 20-km single-mode fiber-28 (SMF-28) transmission, tens of Gb/s millimeter-wave signal is delivered. At the receiver, two millimeter-wave signals are down-converted into electrical intermediate-frequency (IF) signals in the analog domain by mixing with two electrical local oscillators (LOs) with different frequencies. We investigate the different frequency LO effect on the 2×2 MIMO system performance for the first time, finding that the process during DSP of implementing frequency offset estimation (FOE) before cascaded multi-modulus-algorithm (CMMA) equalization can get rid of the inter-channel interference (ICI) and improve system bit-error-ratio (BER) performance in this type of transmission system.

Spectral line-by-line pulse shaping of on-chip microresonator frequency combs

NASA Astrophysics Data System (ADS)

Ferdous, Fahmida; Miao, Houxun; Leaird, Daniel E.; Srinivasan, Kartik; Wang, Jian; Chen, Lei; Varghese, Leo Tom; Weiner, Andrew M.

2011-12-01

Recently, on-chip comb generation methods based on nonlinear optical modulation in ultrahigh-quality-factor monolithic microresonators have been demonstrated, where two pump photons are transformed into sideband photons in a four-wave-mixing process mediated by Kerr nonlinearity. Here, we investigate line-by-line pulse shaping of such combs generated in silicon nitride ring resonators. We observe two distinct paths to comb formation that exhibit strikingly different time-domain behaviours. For combs formed as a cascade of sidebands spaced by a single free spectral range that spread from the pump, we are able to compress stably to nearly bandwidth-limited pulses. This indicates high coherence across the spectra and provides new data on the high passive stability of the spectral phase. For combs where the initial sidebands are spaced by multiple free spectral ranges that then fill in to give combs with single free-spectral-range spacing, the time-domain data reveal partially coherent behaviour.

A Single Phase 7-Level Cascade Inverter Topology with Reduced Number of Switches on Resistive Load by Using PWM

NASA Astrophysics Data System (ADS)

Hamzah, H. H.; Ponniran, A.; Kasiran, A. N.; Harimon, M. A.; Gendum, D. A.; Yatim, M. H.

2018-04-01

This paper discussing design principles of inverter structure with reduced number of semiconductor devices of seven levels symmetric H-bridge multilevel inverter (MLI) topology. The aim of this paper is to design an inverter circuit with reduction of semiconductor losses, converter size and development cost. The H-bridge and auxiliary structures were considered in order to achieve seven levels output voltage. The performance of design circuit is compared with conventional seven levels structure in terms of voltage output. The circuit development consists of seven switches and three diode. A basic modulation technique is used to confirm the designed circuit. The results show that the designed circuit is able to convert seven level output voltage with low total harmonics distortion (THD) in voltage fundamental output. According to the results, fundamental output voltage is increased up to 8.314%, and the THD is decreased up to 0.81% compared to the conventional seven level inverter.

Phenotypic and evolutionary implications of modulating the ERK-MAPK cascade using the dentition as a model

PubMed Central

Marangoni, Pauline; Charles, Cyril; Tafforeau, Paul; Laugel-Haushalter, Virginie; Joo, Adriane; Bloch-Zupan, Agnès; Klein, Ophir D.; Viriot, Laurent

2015-01-01

The question of phenotypic convergence across a signalling pathway has important implications for both developmental and evolutionary biology. The ERK-MAPK cascade is known to play a central role in dental development, but the relative roles of its components remain unknown. Here we investigate the diversity of dental phenotypes in Spry2−/−, Spry4−/−, and Rsk2−/Y mice, including the incidence of extra teeth, which were lost in the mouse lineage 45 million years ago (Ma). In addition, Sprouty-specific anomalies mimic a phenotype that is absent in extant mice but present in mouse ancestors prior to 9 Ma. Although the mutant lines studied display convergent phenotypes, each gene has a specific role in tooth number determination and crown patterning. The similarities found between teeth in fossils and mutants highlight the pivotal role of the ERK-MAPK cascade during the evolution of the dentition in rodents. PMID:26123406

A Shadowing Problem in the Detection of Overlapping Communities: Lifting the Resolution Limit through a Cascading Procedure

PubMed Central

Young, Jean-Gabriel; Allard, Antoine; Hébert-Dufresne, Laurent; Dubé, Louis J.

2015-01-01

Community detection is the process of assigning nodes and links in significant communities (e.g. clusters, function modules) and its development has led to a better understanding of complex networks. When applied to sizable networks, we argue that most detection algorithms correctly identify prominent communities, but fail to do so across multiple scales. As a result, a significant fraction of the network is left uncharted. We show that this problem stems from larger or denser communities overshadowing smaller or sparser ones, and that this effect accounts for most of the undetected communities and unassigned links. We propose a generic cascading approach to community detection that circumvents the problem. Using real and artificial network datasets with three widely used community detection algorithms, we show how a simple cascading procedure allows for the detection of the missing communities. This work highlights a new detection limit of community structure, and we hope that our approach can inspire better community detection algorithms. PMID:26461919

Lyapunov exponents and phase diagrams reveal multi-factorial control over TRAIL-induced apoptosis

PubMed Central

Aldridge, Bree B; Gaudet, Suzanne; Lauffenburger, Douglas A; Sorger, Peter K

2011-01-01

Receptor-mediated apoptosis proceeds via two pathways: one requiring only a cascade of initiator and effector caspases (type I behavior) and the second requiring an initiator–effector caspase cascade and mitochondrial outer membrane permeabilization (type II behavior). Here, we investigate factors controlling type I versus II phenotypes by performing Lyapunov exponent analysis of an ODE-based model of cell death. The resulting phase diagrams predict that the ratio of XIAP to pro-caspase-3 concentrations plays a key regulatory role: type I behavior predominates when the ratio is low and type II behavior when the ratio is high. Cell-to-cell variability in phenotype is observed when the ratio is close to the type I versus II boundary. By positioning multiple tumor cell lines on the phase diagram we confirm these predictions. We also extend phase space analysis to mutations affecting the rate of caspase-3 ubiquitylation by XIAP, predicting and showing that such mutations abolish all-or-none control over activation of effector caspases. Thus, phase diagrams derived from Lyapunov exponent analysis represent a means to study multi-factorial control over a complex biochemical pathway. PMID:22108795

Molecular characterization and immunological roles of avian IL-22 and its soluble receptor IL-22 binding protein

USDA-ARS?s Scientific Manuscript database

As a member of the interleukin (IL)-10 family, IL-22 is an important mediator in modulating tissue responses during inflammation. Through activation of STAT3-signaling cascades, IL-22 induces proliferative and anti-apoptotic pathways, as well as antimicrobial peptides (AMPs), that help prevent tissu...

Norepinephrine Triggers Metaplasticity of LTP by Increasing Translation of Specific mRNAs

ERIC Educational Resources Information Center

Maity, Sabyasachi; Rah, Sean; Sonenberg, Nahum; Gkogkas, Christos G.; Nguyen, Peter V.

2015-01-01

Norepinephrine (NE) is a key modulator of synaptic plasticity in the hippocampus, a brain structure crucially involved in memory formation. NE boosts synaptic plasticity mostly through initiation of signaling cascades downstream from beta (ß)-adrenergic receptors (ß-ARs). Previous studies demonstrated that a ß-adrenergic receptor agonist,…

Wavelength modulation spectroscopy coupled with an external-cavity quantum cascade laser operating between 7.5 and 8 µm

NASA Astrophysics Data System (ADS)

Maity, Abhijit; Pal, Mithun; Maithani, Sanchi; Dutta Banik, Gourab; Pradhan, Manik

2018-04-01

We demonstrate a mid-infrared detection strategy with 1f-normalized 2f-wavelength modulation spectroscopy (WMS-2f/1f) using a continuous wave (CW) external-cavity quantum cascade laser (EC-QCL) operating between 7.5 and 8 µm. The detailed performance of the WMS-2f/1f detection method was evaluated by making rotationally resolved measurements in the (ν 4  +  ν 5) combination band of acetylene (C2H2) at 1311.7600 cm-1. A noise-limited detection limit of three parts per billion (ppb) with an integration time of 110 s was achieved for C2H2 detection. The present high-resolution CW-EC-QCL system coupled with the WMS-2f/1f strategy was further validated with an extended range of C2H2 concentration of 0.1-1000 ppm, which shows excellent promise for real-life practical sensing applications. Finally, we utilized the WMS-2f/1f technique to measure the C2H2 concentration in the exhaled breath of smokers.

Ultraflat and broadband optical frequency comb generator based on cascaded two dual-electrode Mach-Zehnder modulators

NASA Astrophysics Data System (ADS)

Qu, Kun; Zhao, Shanghong; Li, Xuan; Tan, Qinggui; Zhu, Zihang

2018-04-01

A novel scheme for the generation of ultraflat and broadband optical frequency comb (OFC) is proposed based on cascaded two dual-electrode Mach-Zehnder modulators (DE-MZM). The first DE-MZM can generate a four-comb-line OFC, then the OFC is injected into the second DE-MZM as a carrier, which can increase the number of comb lines. Our modified scheme finally can generate a broadband OFC with high flatness by simply modifying the electrical power and the bias voltage of the DE-MZM. Theoretical analysis and simulation results reveal that a 16-comb-line OFC with a frequency spacing that two times the frequency of the RF signal can be obtained. The power fluctuation of the OFC lines is 0.48 dB and the unwanted-mode suppression ratio (UMSR) can reach 16.5 dB. Additionally, whether the bias drift of the DE-MZMs has little influence on the power fluctuation is also analyzed. These results demonstrate the robustness of our scheme and verify its good accuracy and high stability with perfect flatness.

Ppbv-Level Ethane Detection Using Quartz-Enhanced Photoacoustic Spectroscopy with a Continuous-Wave, Room Temperature Interband Cascade Laser

PubMed Central

Li, Chunguang; Dong, Lei; Zheng, Chuantao; Lin, Jun; Wang, Yiding

2018-01-01

A ppbv-level quartz-enhanced photoacoustic spectroscopy (QEPAS)-based ethane (C2H6) sensor was demonstrated by using a 3.3 μm continuous-wave (CW), distributed feedback (DFB) interband cascade laser (ICL). The ICL was employed for targeting a strong C2H6 absorption line located at 2996.88 cm−1 in its fundamental absorption band. Wavelength modulation spectroscopy (WMS) combined with the second harmonic (2f) detection technique was utilized to increase the signal-to-noise ratio (SNR) and simplify data acquisition and processing. Gas pressure and laser frequency modulation depth were optimized to be 100 Torr and 0.106 cm−1, respectively, for maximizing the 2f signal amplitude. Performance of the QEPAS sensor was evaluated using specially prepared C2H6 samples. A detection limit of 11 parts per billion in volume (ppbv) was obtained with a 1-s integration time based on an Allan-Werle variance analysis, and the detection precision can be further improved to ~1.5 ppbv by increasing the integration time up to 230 s. PMID:29495610

Indirectly pumped 3.7 THz InGaAs/InAlAs quantum-cascade lasers grown by metal-organic vapor-phase epitaxy.

PubMed

Fujita, Kazuue; Yamanishi, Masamichi; Furuta, Shinichi; Tanaka, Kazunori; Edamura, Tadataka; Kubis, Tillmann; Klimeck, Gerhard

2012-08-27

Device-performances of 3.7 THz indirect-pumping quantum-cascade lasers are demonstrated in an InGaAs/InAlAs material system grown by metal-organic vapor-phase epitaxy. The lasers show a low threshold-current-density of ~420 A/cm2 and a peak output power of ~8 mW at 7 K, no sign of parasitic currents with recourse to well-designed coupled-well injectors in the indirect pump scheme, and a maximum operating temperature of Tmax ~100 K. The observed roll-over of output intensities in current ranges below maximum currents and limitation of Tmax are discussed with a model for electron-gas heating in injectors. Possible ways toward elevation of Tmax are suggested.

A hierarchy of factors influence discontinuous gas exchange in the grasshopper Paracinema tricolor (Orthoptera: Acrididae).

PubMed

Groenewald, Berlizé; Chown, Steven L; Terblanche, John S

2014-10-01

The evolutionary origin and maintenance of discontinuous gas exchange (DGE) in tracheate arthropods are poorly understood and highly controversial. We investigated prioritization of abiotic factors in the gas exchange control cascade by examining oxygen, water and haemolymph pH regulation in the grasshopper Paracinema tricolor. Using a full-factorial design, grasshoppers were acclimated to hypoxic or hyperoxic (5% O2, 40% O2) gas conditions, or dehydrated or hydrated, whereafter their CO2 release was measured under a range of O2 and relative humidity (RH) conditions (5%, 21%, 40% O2 and 5%, 60%, 90% RH). DGE was significantly less common in grasshoppers acclimated to dehydrating conditions compared with the other acclimations (hypoxia, 98%; hyperoxia, 100%; hydrated, 100%; dehydrated, 67%). Acclimation to dehydrating conditions resulted in a significant decrease in haemolymph pH from 7.0±0.3 to 6.6±0.1 (mean ± s.d., P=0.018) and also significantly increased the open (O)-phase duration under 5% O2 treatment conditions (5% O2, 44.1±29.3 min; 40% O2, 15.8±8.0 min; 5% RH, 17.8±1.3 min; 60% RH, 24.0±9.7 min; 90% RH, 20.6±8.9 min). The observed acidosis could potentially explain the extension of the O-phase under low RH conditions, when it would perhaps seem more useful to reduce the O-phase to lower respiratory water loss. The results confirm that DGE occurrence and modulation are affected by multiple abiotic factors. A hierarchical framework for abiotic factors influencing DGE is proposed in which the following stressors are prioritized in decreasing order of importance: oxygen supply, CO2 excretion and pH modulation, oxidative damage protection and water savings. © 2014. Published by The Company of Biologists Ltd.

Terahertz generation by difference frequency generation from a compact optical parametric oscillator

NASA Astrophysics Data System (ADS)

Li, Zhongyang; Wang, Silei; Wang, Mengtao; Wang, Weishu

2017-11-01

Terahertz (THz) generation by difference frequency generation (DFG) processes with dual idler waves is theoretically analyzed. The dual idler waves are generated by a compact optical parametric oscillator (OPO) with periodically poled lithium niobate (PPLN). The phase-matching conditions in a same PPLN for the optical parametric oscillation generating signal and idler waves and for the DFG generating THz waves can be simultaneously satisfied by selecting the poling period of PPLN. Moreover, 3-order cascaded DFG processes generating THz waves can be realized in the same PPLN. To take an example of 8.341 THz which locates in the vicinity of polariton resonances, THz intensities and quantum conversion efficiencies are calculated. Compared with non-cascaded DFG processes, THz intensities of 8.341 THz in 3-order cascaded DFG processes increase to 2.57 times. When the pump intensity equals to 20 MW/mm2, the quantum conversion efficiency of 106% in 3-order cascaded DFG processes can be realized, which exceeds the Manley-Rowe limit.

The effect of alloying nickel with iron on the supersonic ballistic stage of high energy displacement cascades

DOE PAGES

Béland, Laurent Karim; Osetsky, Yuri N.; Stoller, Roger E.

2016-06-23

Previous experimental and theoretical studies suggest that the production of extended defect structures by collision cascades is inhibited in equiatomic NiFe, in comparison to pure Ni. It is also known that the production of such extend defect structures results from the formation of subcascades by high-energy recoils and their subsequent interaction. A detailed analysis of the ballistics of 40 keV cascades in Ni and NiFe is performed to identify the formation of such subcascades and to assess their spatial distribution. It is found that subcascades in Ni and NiFe are created with nearly identical energies and distributed similarly in space.more » This suggests that the differences in production of extended defect structures is not related to processes taking place in the ballistic phase of the collision cascade. Lastly, these results can be generalized to other, more chemically complex, concentrated alloys where the elements have similar atomic numbers, such as many high-entropy alloys.« less

Broadly tunable terahertz generation in mid-infrared quantum cascade lasers.

PubMed

Vijayraghavan, Karun; Jiang, Yifan; Jang, Min; Jiang, Aiting; Choutagunta, Karthik; Vizbaras, Augustinas; Demmerle, Frederic; Boehm, Gerhard; Amann, Markus C; Belkin, Mikhail A

2013-01-01

Room temperature, broadly tunable, electrically pumped semiconductor sources in the terahertz spectral range, similar in operation simplicity to diode lasers, are highly desired for applications. An emerging technology in this area are sources based on intracavity difference-frequency generation in dual-wavelength mid-infrared quantum cascade lasers. Here we report terahertz quantum cascade laser sources based on an optimized non-collinear Cherenkov difference-frequency generation scheme that demonstrates dramatic improvements in performance. Devices emitting at 4 THz display a mid-infrared-to-terahertz conversion efficiency in excess of 0.6 mW W(-2) and provide nearly 0.12 mW of peak power output. Devices emitting at 2 and 3 THz fabricated on the same chip display 0.09 and 0.4 mW W(-2) conversion efficiencies at room temperature, respectively. High terahertz-generation efficiency and relaxed phase-matching conditions offered by the Cherenkov scheme allowed us to demonstrate, for the first time, an external-cavity terahertz quantum cascade laser source tunable between 1.70 and 5.25 THz.

The effect of alloying nickel with iron on the supersonic ballistic stage of high energy displacement cascades

DOE Office of Scientific and Technical Information (OSTI.GOV)

Béland, Laurent Karim; Osetsky, Yuri N.; Stoller, Roger E.

Previous experimental and theoretical studies suggest that the production of extended defect structures by collision cascades is inhibited in equiatomic NiFe, in comparison to pure Ni. It is also known that the production of such extend defect structures results from the formation of subcascades by high-energy recoils and their subsequent interaction. A detailed analysis of the ballistics of 40 keV cascades in Ni and NiFe is performed to identify the formation of such subcascades and to assess their spatial distribution. It is found that subcascades in Ni and NiFe are created with nearly identical energies and distributed similarly in space.more » This suggests that the differences in production of extended defect structures is not related to processes taking place in the ballistic phase of the collision cascade. Lastly, these results can be generalized to other, more chemically complex, concentrated alloys where the elements have similar atomic numbers, such as many high-entropy alloys.« less

Phase Modulator with Terahertz Optical Bandwidth Formed by Multi-Layered Dielectric Stack

NASA Technical Reports Server (NTRS)

Keys, Andrew S. (Inventor); Fork, Richard L. (Inventor)

2005-01-01

An optical phase modulator includes a bandpass multilayer stack, formed by a plurality of dielectric layers, preferably of GaAs and AlAs, and having a transmission function related to the refractive index of the layers of the stack, for receiving an optical input signal to be phase modulated. A phase modulator device produces a nonmechanical change in the refractive index of each layer of the stack by, e.g., the injection of free carrier, to provide shifting of the transmission function so as to produce phase modulation of the optical input signal and to thereby produce a phase modulated output signal.

Impact of the phase-mismatch in the SHG crystal and consequential self-action of the fundamental wave by cascaded second-order effects on the THG efficiency of a Q-switched 1342 nm Nd:YVO₄ laser.

PubMed

Koch, Peter; Bartschke, Juergen; L'huillier, Johannes A

2015-05-18

We report on the influence of self-focusing and self-defocusing in the phase-mismatched frequency doubling crystal on the third harmonic generation (THG) efficiency in a two crystal frequency tripling scheme. By detuning the temperature of the doubling crystal, the impact of a phase-mismatch in second harmonic generation (SHG) on the subsequent sum frequency mixing process was investigated. It was found that adjusting the temperature not only affected the power ratio of the second harmonic to the fundamental but also the beam diameter of the fundamental beam in the THG crystal, which was caused by self-focusing and self-defocusing of the fundamental beam, respectively. This self-action was induced by a cascaded χ(2) : χ(2) process in the phase-mismatched SHG crystal. Self-defocusing was observable for positive detuning and self-focusing for negative detuning of the phase-matching temperature. Hence, the THG efficiency was not symmetric with respect to the point of optimum phase-matching. Optimum THG was obtained for positive detuning and the resulting self-defocusing in combination with the focusing lens in front of the THG stage was also beneficial for the beam quality of the third harmonic.

A wideband photonic microwave phase shifter with 360-degree phase tunable range based on a DP-QPSK modulator

NASA Astrophysics Data System (ADS)

Chen, Yang

2018-03-01

A novel wideband photonic microwave phase shifter with 360-degree phase tunable range is proposed based on a single dual-polarization quadrature phase shift-keying (DP-QPSK) modulator. The two dual-parallel Mach-Zehnder modulators (DP-MZMs) in the DP-QPSK modulator are properly biased to serve as a carrier-suppressed single-sideband (CS-SSB) modulator and an optical phase shifter (OPS), respectively. The microwave signal is applied to the CS-SSB modulator, while a control direct-current (DC) voltage is applied to the OPS. The first-order optical sideband generated from the CS-SSB modulator and the phase tunable optical carrier from the OPS are combined and then detected in a photodetector, where a microwave signal is generated with its phase controlled by the DC voltage applied to the OPS. The proposed technique is theoretically analyzed and experimentally demonstrated. Microwave signals with a carrier frequency from 10 to 23 GHz are continuously phase shifted over 360-degree phase range. The proposed technique features very compact configuration, easy phase tuning and wide operation bandwidth.

Dihydroartemisinin inhibits indoxyl sulfate (IS)-promoted cell cycle progression in mesangial cells by targeting COX-2/mPGES-1/PGE2 cascade.

PubMed

Mungun, Harr-Keshauve; Li, Shuzhen; Zhang, Yue; Huang, Songming; Jia, Zhanjun; Ding, Guixia; Zhang, Aihua

2018-01-01

Dihydroartemisinin (DHA) is a semisynthetic derivative of artemisinin and has been used as an antimalarial drug. Recently, roles of artemisinin and its derivatives in treating diseases besides antimalarial effect were documented. Thus, this study was undertaken to investigate the role of DHA in indoxyl sulfate (IS)-promoted cell cycle progression in glomerular mesangial cells, as well as the potential mechanisms. Under the basal condition, DHA significantly retarded the cell cycle progression as shown by decreased cell percentage in S phase and increased cell percentage in G1/G0 phases in line with reduced cell cycle proteins cyclin A2 and cyclin D1. Interestingly, DHA also inactivated the COX-2/mPGES-1/PGE 2 cascade which has been shown to play a critical role in promoting the mesangial cell cycle progression by our previous studies. Next, we investigated the role of DHA in IS-triggered cell cycle progression in this mesangial cell line. As expected, DHA treatment significantly retarded IS-induced cell cycle progression and inhibited the activation of COX-2/mPGES-1/PGE 2 cascade induced by IS. In summary, these data indicated that DHA inhibited the cell cycle progression in glomerular mesangial cells under normal condition or IS challenge possibly through the inhibition of COX-2/mPGES-1/PGE 2 cascade, suggesting a potential of DHA in treating glomerular diseases with mesangial cell proliferation.

Spectral changes induced by a phase modulator acting as a time lens

DOE Office of Scientific and Technical Information (OSTI.GOV)

Plansinis, B. W.; Donaldson, W. R.; Agrawal, G. P.

2015-07-06

We show both numerically and experimentally that a phase modulator, acting as a time lens in the Fourier-lens configuration, can induce spectral broadening, narrowing, or shifts, depending on the phase of the modulator cycle. These spectral effects depend on the maximum phase shift that can be imposed by the modulator. In our numerical simulations, pulse spectrum could be compressed by a factor of 8 for a 30 rad phase shift. Experimentally, spectral shifts over a 1.35 nm range and spectral narrowing and broadening by a factor of 2 were demonstrated using a lithium niobate phase modulator with a maximum phasemore » shift of 16 rad at a 10 GHz modulation frequency. All spectral changes were accomplished without employing optical nonlinear effects such as self- or cross-phase modulation.« less

Direct phase-locking of a 8.6-μm quantum cascade laser to a mid-IR optical frequency comb: application to precision spectroscopy of N2O.

PubMed

Gambetta, Alessio; Cassinerio, Marco; Coluccelli, Nicola; Fasci, Eugenio; Castrillo, Antonio; Gianfrani, Livio; Gatti, Davide; Marangoni, Marco; Laporta, Paolo; Galzerano, Gianluca

2015-02-01

We developed a high-precision spectroscopic system at 8.6 μm based on direct heterodyne detection and phase-locking of a room-temperature quantum-cascade-laser against an harmonic, 250-MHz mid-IR frequency comb obtained by difference-frequency generation. The ∼30  dB signal-to-noise ratio of the detected beat-note together with the achieved closed-loop locking bandwidth of ∼500  kHz allows for a residual integrated phase noise of 0.78 rad (1 Hz-5 MHz), for an ultimate resolution of ∼21  kHz, limited by the measured linewidth of the mid-IR comb. The system was used to perform absolute measurement of line-center frequencies for the rotational components of the ν2 vibrational band of N2O, with a relative precision of 3×10(-10).

Design of an ultra low power third order continuous time current mode ΣΔ modulator for WLAN applications.

PubMed

Behzadi, Kobra; Baghelani, Masoud

2014-05-01

This paper presents a third order continuous time current mode ΣΔ modulator for WLAN 802.11b standard applications. The proposed circuit utilized feedback architecture with scaled and optimized DAC coefficients. At circuit level, we propose a modified cascade current mirror integrator with reduced input impedance which results in more bandwidth and linearity and hence improves the dynamic range. Also, a very fast and precise novel dynamic latch based current comparator is introduced with low power consumption. This ultra fast comparator facilitates increasing the sampling rate toward GHz frequencies. The modulator exhibits dynamic range of more than 60 dB for 20 MHz signal bandwidth and OSR of 10 while consuming only 914 μW from 1.8 V power supply. The FoM of the modulator is calculated from two different methods, and excellent performance is achieved for proposed modulator.

Design of an ultra low power third order continuous time current mode ΣΔ modulator for WLAN applications

PubMed Central

Behzadi, Kobra; Baghelani, Masoud

2013-01-01

This paper presents a third order continuous time current mode ΣΔ modulator for WLAN 802.11b standard applications. The proposed circuit utilized feedback architecture with scaled and optimized DAC coefficients. At circuit level, we propose a modified cascade current mirror integrator with reduced input impedance which results in more bandwidth and linearity and hence improves the dynamic range. Also, a very fast and precise novel dynamic latch based current comparator is introduced with low power consumption. This ultra fast comparator facilitates increasing the sampling rate toward GHz frequencies. The modulator exhibits dynamic range of more than 60 dB for 20 MHz signal bandwidth and OSR of 10 while consuming only 914 μW from 1.8 V power supply. The FoM of the modulator is calculated from two different methods, and excellent performance is achieved for proposed modulator. PMID:25685504

Effects of particle mixing and scattering in the dusty gas flow through moving and stationary cascades of airfoils

NASA Astrophysics Data System (ADS)

Tsirkunov, Yu. M.; Romanyuk, D. A.; Panfilov, S. V.

2011-10-01

Time-dependent two-dimensional (2D) flow of dusty gas through a set of two cascades of airfoils (blades) has been studied numerically. The first cascade was assumed to move (rotor) and the second one to be immovable (stator). Such a flow can be considered, in some sense, as a flow in the inlet stage of a turbomachine, for example, in the inlet compressor of an aircraft turbojet engine. Dust particle concentration was assumed to be very low, so that the interparticle collisions and the effect of the dispersed phase on the carrier gas were negligible. Flow of the carrier gas was described by full Navier-Stokes equations. In calculations of particle motion, the particles were considered as solid spheres. The particle drag force, transverse Magnus force, and damping torque were taken into account in the model of gas-particle interaction. The impact interaction of particles with blades was considered as frictional and partly elastic. The effects of particle size distribution and particle scattering in the course of particle-blade collisions were investigated. Flow fields of the carrier gas and flow patterns of the particle phase were obtained and discussed.

High-frequency modulation of the four states of polarization of light with a single phase modulator

NASA Astrophysics Data System (ADS)

Compain, Eric; Drevillon, Bernard

1998-04-01

A method for light polarization modulation is described. It allows us to independently modulate, at a high frequency, the four components of the Stokes vector of light using a single phase modulator. It works in a double-pass configuration: the polarization of light is modulated a first time by the phase modulator, and is then modified by a coupling object before being modulated a second time by the same modulator. The coupling object consists of multiple glass plates, oriented at the Brewster angle, acting as a partial polarizer and in a right angle prism acting as a phase shifter and back reflector. Its polarimetric properties are obtained from refractive index contrast effects, which provides optimized and constant properties over a wide spectral range. The phase modulator can be either an electro-optic modulator providing a very high-frequency capability (up to 100 MHz) or a photoelastic modulator providing a wide spectral range capability. It is robust because there is no moving part and simple to implement because of the presence of one modulation. It displays a high level of sensitivity because all the components are high-frequency modulated. Two applications using this modulator in a polarimeter or in a polarization states generator are described. The four modulations, having the same fundamental frequency, are easily demodulated by numerical data processing. Optimized demodulation processing, adapted to the different kind of phase modulator is described. Its adaptation taking into account the bandwidth limitation and the variation of the sampling phase, are finally presented in the case of a photoelastic modulator.

Single-photon frequency conversion via cascaded quadratic nonlinear processes

NASA Astrophysics Data System (ADS)

Xiang, Tong; Sun, Qi-Chao; Li, Yuanhua; Zheng, Yuanlin; Chen, Xianfeng

2018-06-01

Frequency conversion of single photons is an important technology for quantum interface and quantum communication networks. Here, single-photon frequency conversion in the telecommunication band is experimentally demonstrated via cascaded quadratic nonlinear processes. Using cascaded quasi-phase-matched sum and difference frequency generation in a periodically poled lithium niobate waveguide, the signal photon of a photon pair from spontaneous down-conversion is precisely shifted to identically match its counterpart, i.e., the idler photon, in frequency to manifest a clear nonclassical dip in the Hong-Ou-Mandel interference. Moreover, quantum entanglement between the photon pair is maintained after the frequency conversion, as is proved in time-energy entanglement measurement. The scheme is used to switch single photons between dense wavelength-division multiplexing channels, which holds great promise in applications in realistic quantum networks.

Effect of wind tunnel acoustic modes on linear oscillating cascade aerodynamics

NASA Technical Reports Server (NTRS)

Buffum, Daniel H.; Fleeter, Sanford

1993-01-01

The aerodynamics of a biconvex airfoil cascade oscillating in torsion is investigated using the unsteady aerodynamic influence coefficient technique. For subsonic flow and reduced frequencies as large as 0.9, airfoil surface unsteady pressures resulting from oscillation of one of the airfoils are measured using flush-mounted high-frequency-response pressure transducers. The influence coefficient data are examined in detail and then used to predict the unsteady aerodynamics of a cascade oscillating at various interblade phase angles. These results are correlated with experimental data obtained in the traveling-wave mode of oscillation and linearized analysis predictions. It is found that the unsteady pressure disturbances created by an oscillating airfoil excite wind tunnel acoustic modes which have detrimental effects on the experimental data. Acoustic treatment is proposed to rectify this problem.

Phase modulated high density collinear holographic data storage system with phase-retrieval reference beam locking and orthogonal reference encoding.

PubMed

Liu, Jinpeng; Horimai, Hideyoshi; Lin, Xiao; Huang, Yong; Tan, Xiaodi

2018-02-19

A novel phase modulation method for holographic data storage with phase-retrieval reference beam locking is proposed and incorporated into an amplitude-encoding collinear holographic storage system. Unlike the conventional phase retrieval method, the proposed method locks the data page and the corresponding phase-retrieval interference beam together at the same location with a sequential recording process, which eliminates piezoelectric elements, phase shift arrays and extra interference beams, making the system more compact and phase retrieval easier. To evaluate our proposed phase modulation method, we recorded and then recovered data pages with multilevel phase modulation using two spatial light modulators experimentally. For 4-level, 8-level, and 16-level phase modulation, we achieved the bit error rate (BER) of 0.3%, 1.5% and 6.6% respectively. To further improve data storage density, an orthogonal reference encoding multiplexing method at the same position of medium is also proposed and validated experimentally. We increased the code rate of pure 3/16 amplitude encoding method from 0.5 up to 1.0 and 1.5 using 4-level and 8-level phase modulation respectively.

Modulation of transcription factors by curcumin.

PubMed

Shishodia, Shishir; Singh, Tulika; Chaturvedi, Madan M

2007-01-01

Curcumin is the active ingredient of turmeric that has been consumed as a dietary spice for ages. Turmeric is widely used in traditional Indian medicine to cure biliary disorders, anorexia, cough, diabetic wounds, hepatic disorders, rheumatism, and sinusitis. Extensive investigation over the last five decades has indicated that curcumin reduces blood cholesterol, prevents low-density lipoprotein oxidation, inhibits platelet aggregation, suppresses thrombosis and myocardial infarction, suppresses symptoms associated with type II diabetes, rheumatoid arthritis, multiple sclerosis, and Alzheimer's disease, inhibits HIV replication, enhances wound healing, protects from liver injury, increases bile secretion, protects from cataract formation, and protects from pulmonary toxicity and fibrosis. Evidence indicates that the divergent effects of curcumin are dependent on its pleiotropic molecular effects. These include the regulation of signal transduction pathways and direct modulation of several enzymatic activities. Most of these signaling cascades lead to the activation of transcription factors. Curcumin has been found to modulate the activity of several key transcription factors and, in turn, the cellular expression profiles. Curcumin has been shown to elicit vital cellular responses such as cell cycle arrest, apoptosis, and differentiation by activating a cascade of molecular events. In this chapter, we briefly review the effects of curcumin on transcription factors NF-KB, AP-1, Egr-1, STATs, PPAR-gamma, beta-catenin, nrf2, EpRE, p53, CBP, and androgen receptor (AR) and AR-related cofactors giving major emphasis to the molecular mechanisms of its action.

Temperature and H2O sensing in laminar premixed flames using mid-infrared heterodyne phase-sensitive dispersion spectroscopy

NASA Astrophysics Data System (ADS)

Ma, Liuhao; Wang, Zhen; Cheong, Kin-Pang; Ning, Hongbo; Ren, Wei

2018-06-01

We report the first demonstration of heterodyne phase-sensitive dispersion spectroscopy (HPSDS) for the simultaneous temperature and H2O concentration measurements in combustion environments. Two continuous-wave distributed-feedback quantum cascade lasers (DFB-QCLs) at 5.27 and 10.53 µm were used to exploit the strong H2O transitions (1897.52 and 949.53 cm-1) at high temperatures. The injection current of each QCL was modulated at sub-GHz or GHz to generate the three-tone radiation and the dispersion signal was detected by the radio-frequency down-conversion heterodyning. The peak-to-peak ratio of the two H2O dispersion spectra exhibits a monotonic relationship with temperature over the temperature range of 1000-3000 K, indicating the capability of performing two-line thermometry using laser dispersion spectroscopy. We measured the temperatures of CH4/air flames at different equivalence ratios ( Φ = 0.8-1.2), yielding a good agreement with the corresponding thermocouple measurements. In addition, one-dimensional kinetic modeling coupled with a detailed chemical kinetic mechanism (GRI 3.0) was conducted to compare with the measured H2O concentrations using HPSDS. Finally, we demonstrated HPSDS is immune to optical power fluctuations by measuring the dispersion spectra at varied incident laser powers.

Effect of Parametric Dichotomic Markov Noise on the Properties of Chaotic Transitions in Dynamical Systems

NASA Astrophysics Data System (ADS)

Gac, J. M.; Żebrowski, J. J.

A chaotic transition occurs when a continuous change of one of the parameters of the system causes a discontinuous change in the properties of the chaotic attractor of the system. Such phenomena are present in many dynamical systems, in which a chaotic behavior occurs. The best known of these transitions are: the period-doubling bifurcation cascade, intermittency and crises. The effect of dichotomous Markov noise (DMN) on the properties of systems with chaotic transitions is discussed. DMN is a very simple two-valued stochastic process, with constant transition rates between the two states. In spite of its simplicity, this kind of noise is a very powerful tool to describe various phenomena present in many physical, chemical or biological systems. Many interesting phenomena induced by DMN are known. However, there is no research on the effect of this kind of noise on intermittency or crises. We present the change of the mean laminar phase length and of laminar phase length distribution caused by DMN modulating the parameters of a system with intermittency and the modification of the mean life time on the pre-crisis attractor in the case of a boundary crisis. The results obtained analytically are compared with numerical simulations for several simple dynamical systems.

Nitric oxide in B6 mouse and nitric oxide-sensitive soluble guanylate cyclase in cat modulate acetylcholine release in pontine reticular formation.

PubMed

Lydic, Ralph; Garza-Grande, Ricardo; Struthers, Richard; Baghdoyan, Helen A

2006-05-01

ACh regulates arousal, and the present study was designed to provide insight into the neurochemical mechanisms modulating ACh release in the pontine reticular formation. Nitric oxide (NO)-releasing beads microinjected into the pontine reticular formation of C57BL/6J (B6) mice significantly (P < 0.0001) increased ACh release. Microdialysis delivery of the NO donor N-ethyl-2-(1-ethyl-2-hydroxy-2-nitrosohydrazino)-ethanamine (NOC-12) to the mouse pontine reticular formation also caused a concentration-dependent increase in ACh release (P < 0.001). These are the first neurochemical data showing that ACh release in the pontine reticular formation of the B6 mouse is modulated by NO. The signal transduction cascade through which NO modulates ACh release in the pontine reticular formation has not previously been characterized. Therefore, an additional series of studies quantified the effects of a soluble guanylate cyclase (sGC) inhibitor, 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ), on ACh release in the cat medial pontine reticular formation. During naturally occurring states of sleep and wakefulness, but not anesthesia, ODQ caused a significant (P < 0.001) decrease in ACh release. These results show for the first time that NO modulates ACh in the medial pontine reticular formation of the cat via an NO-sensitive sGC signal transduction cascade. Isoflurane and halothane anesthesia have been shown to decrease ACh release in the medial pontine reticular formation. The finding that ODQ did not alter ACh release during isoflurane or halothane anesthesia demonstrates that these anesthetics disrupt the NO-sensitive sGC-cGMP pathway. Considered together, results from the mouse and cat indicate that NO modulates ACh release in arousal-promoting regions of the pontine reticular formation via an NO-sensitive sGC-cGMP pathway.

Drive and protection circuit for converter module of cascaded H-bridge STATCOM

NASA Astrophysics Data System (ADS)

Wang, Xuan; Yuan, Hongliang; Wang, Xiaoxing; Wang, Shuai; Fu, Yongsheng

2018-04-01

Drive and protection circuit is an important part of power electronics, which is related to safe and stable operation issues in the power electronics. The drive and protection circuit is designed for the cascaded H-bridge STATCOM. This circuit can realize flexible dead-time setting, operation status self-detection, fault priority protection and detailed fault status uploading. It can help to improve the reliability of STATCOM's operation. Finally, the proposed circuit is tested and analyzed by power electronic simulation software PSPICE (Simulation Program with IC Emphasis) and a series of experiments. Further studies showed that the proposed circuit can realize drive and control of H-bridge circuit, meanwhile it also can realize fast processing faults and have advantage of high reliability.

Matrix-Dependent Perturbation of TGFβ Signaling and Disease

PubMed Central

Doyle, Jefferson J.; Gerber, Elizabeth E.; Dietz, Harry C.

2012-01-01

Transforming growth factor beta (TGFβ) is a multipotent cytokine that is sequestered in the extracellular matrix (ECM) through interactions with a number of ECM proteins. The ECM serves to concentrate latent TGFβ at sites of intended function, to influence the bioavailability and/or function of TGFβ activators, and perhaps to regulate the intrinsic performance of cell surface effectors of TGFβ signal propagation. The downstream consequences of TGFβ signaling cascades in turn provide feedback modulation of the ECM. This review covers recent examples of how genetic mutations in constituents of the ECM or TGFβ signaling cascade result in altered ECM homeostasis, cellular performance and ultimately disease, with an emphasis on emerging therapeutic strategies that seek to capitalize on this refined mechanistic understanding. PMID:22641039

Tunneling and traversal of ultracold three-level atoms through vacuum-induced potentials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Badshah, Fazal; Irfan, Muhammad; Qamar, Shahid

2011-09-15

The passage of ultracold three-level atoms through the potential induced by the vacuum cavity mode is discussed using cascade atomic configuration. We study the tunneling or traversal time of the ultracold atoms via a bimodal high-Q cavity. It is found that the phase time, which may be considered as a measure for the time required to traverse the cavity, exhibits superclassical and subclassical behaviors. Further, the dark states and interference effects in cascade atomic configuration may influence the passage time of the atom through the cavity.

Distributed-feedback Terahertz Quantum-cascade Lasers with Laterally Corrugated Metal Waveguides

NASA Technical Reports Server (NTRS)

Williams, Benjamin S.; Kumar, Sushil; Hu, Qing; Reno, John L.

2005-01-01

We report the demonstration of distributed-feedback terahertz quantum-cascade lasers based on a first-order grating fabricated via a lateral corrugation in a double-sided metal ridge waveguide. The phase of the facet reflection was precisely set by lithographically defined facets by dry etching. Single-mode emission was observed at low to moderate injection currents, although multimode emission was observed far beyond threshold owing to spatial hole burning. Finite-element simulations were used to calculate the modal and threshold characteristics for these devices, with results in good agreement with experiments.

Digital quadrature phase detection

DOEpatents

Smith, James A.; Johnson, John A.

1992-01-01

A system for detecting the phase of a frequency of phase modulated signal that includes digital quadrature sampling of the frequency or phase modulated signal at two times that are one quarter of a cycle of a reference signal apart, determination of the arctangent of the ratio of a first sampling of the frequency or phase modulated signal to the second sampling of the frequency or phase modulated signal, and a determination of quadrant in which the phase determination is increased by 2.pi. when the quadrant changes from the first quadrant to the fourth quadrant and decreased by 2.pi. when the quadrant changes from the fourth quadrant to the first quadrant whereby the absolute phase of the frequency or phase modulated signal can be determined using an arbitrary reference convention.

Digital quadrature phase detection

DOEpatents

Smith, J.A.; Johnson, J.A.

1992-05-26

A system for detecting the phase of a frequency or phase modulated signal that includes digital quadrature sampling of the frequency or phase modulated signal at two times that are one quarter of a cycle of a reference signal apart, determination of the arctangent of the ratio of a first sampling of the frequency or phase modulated signal to the second sampling of the frequency or phase modulated signal, and a determination of quadrant in which the phase determination is increased by 2[pi] when the quadrant changes from the first quadrant to the fourth quadrant and decreased by 2[pi] when the quadrant changes from the fourth quadrant to the first quadrant whereby the absolute phase of the frequency or phase modulated signal can be determined using an arbitrary reference convention. 6 figs.

Metal-organic vapor-phase epitaxy-grown ultra-low density InGaAs/GaAs quantum dots exhibiting cascaded single-photon emission at 1.3 μm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paul, Matthias, E-mail: m.paul@ihfg.uni-stuttgart.de; Kettler, Jan; Zeuner, Katharina

By metal-organic vapor-phase epitaxy, we have fabricated InGaAs quantum dots on GaAs substrate with an ultra-low lateral density (<10{sup 7} cm{sup −2}). The photoluminescence emission from the quantum dots is shifted to the telecom O-band at 1.31 μm by an InGaAs strain reducing layer. In time-resolved measurements, we find fast decay times for exciton (∼600 ps) and biexciton (∼300 ps). We demonstrate triggered single-photon emission (g{sup (2)}(0)=0.08) as well as cascaded emission from the biexciton decay. Our results suggest that these quantum dots can compete with their counterparts grown by state-of-the-art molecular beam epitaxy.

Neuroprotective Interventions: Is It Too Late?

PubMed Central

Jenkins, Dorothea; Chang, Eugene; Singh, Inderjit

2013-01-01

In most cases of neonatal hypoxic-ischemic encephalopathy, the exact timing of the hypoxic-ischemic event is unknown, and we have few reliable biomarkers to precisely identify the phase of injury or recovery in an individual patient. However, it is becoming increasingly clear that for neuroprotection in neonates to succeed, an understanding of the phase of injury is important to ascertain. In addition, in utero antecedents of chronic hypoxia, hypoxic preconditioning, intrauterine infection, and fetal gender may change the expected time course of injury. Neuroprotective interventions, such as hypothermia and N-acetylcysteine, currently have efficacy in human and animal studies only if instituted early in the inflammatory cascade. While these cascades are currently being investigated, molecular mechanisms of recovery have received little attention and may ultimately reveal a window for therapeutic intervention that is much longer than current paradigms. PMID:19745093

Nonlinear dynamics investigation in few-cycle laser seeding of quantum cascade lasers: role of permanent dipole moment

NASA Astrophysics Data System (ADS)

Wu, Erheng; Cao, Qing; You, Jun; Liu, Chengpu

2017-06-01

The ultrafast dynamics in the few-cycle laser seeding of quantum cascade laser (QCL) is numerically investigated via the exact solution of the full-wave Maxwell-Bloch equations. It is found that, with or without taking permanent dipole moment (PDM) into account, the QCL emission is quite different: beyond the fundamental frequency band, additional high and low bands occur for that with PDM, which forms an ultra-broad quasi-comb. The origin for this is closely related to the generation of second order harmonic and direct-current components as a result of PDM breaking down the parity symmetry. Moreover, the carrier-envelope-phase (CEP) of laser seed is locked to the QCL output, no matter with or without PDM, and this phase controlled QCL maybe has more wide and convenient applications in related fields.

Wave structure and flow amplitude-frequency characteristics in the turbine nozzle lattice in the presence of phase transition

NASA Astrophysics Data System (ADS)

Gribin, V. G.; Gavrilov, I. Yu.; Tishchenko, A. A.; Tishchenko, V. A.; Alekseev, R. A.

2017-05-01

This paper is devoted to the wave structure of a flow at its near- and supersonic velocities in a flat turbine cascade of profiles in the zone of phase transitions. The main task was investigation of the mechanics of interaction of the condensation jump with the adiabatic jumps of packing in a change of the initial condition of the flow. The obtained results are necessary for verification of the calculation models of the moisture-steam flow in the elements of lotic parts of the steam turbines. The experimental tests were made on a stand of the wet steam contour (WSC-2) in the Moscow Power Engineering Institute (MPEI, National Research University) at various initial states of steam in a wide range of Mach numbers. In the investigation of the wave structure, use was made of an instrument based on the Schlieren-method principle. The amplitude-frequency characteristics of the flow was found by measurement of static pressure pulsations by means of the piezo resistive sensors established on a bandage plate along the bevel cut of the cascade. It is shown that appearance of phase transitions in the bevel cut of the nozzle turbine cascade leads to a change in the wave structure of the flow. In case of condensation jump, the system of adiabatic jumps in the bevel cut of the cascade becomes nonstationary, and the amplitude-frequency characteristics of static pressure pulsations are restructured. In this, a change in the frequency pulsations of pressure and amplitude takes place. It is noted that, at near-sonic speeds of the flow and the state of saturation at the input, the low-frequency pulsations of static pressure appear that lead to periodic disappearance of the condensation jump and of the adiabatic jump. As a result, in this mode, the flow discharge variations take place.

One-dimensional optical wave turbulence: Experiment and theory

NASA Astrophysics Data System (ADS)

Laurie, Jason; Bortolozzo, Umberto; Nazarenko, Sergey; Residori, Stefania

2012-05-01

We present a review of the latest developments in one-dimensional (1D) optical wave turbulence (OWT). Based on an original experimental setup that allows for the implementation of 1D OWT, we are able to show that an inverse cascade occurs through the spontaneous evolution of the nonlinear field up to the point when modulational instability leads to soliton formation. After solitons are formed, further interaction of the solitons among themselves and with incoherent waves leads to a final condensate state dominated by a single strong soliton. Motivated by the observations, we develop a theoretical description, showing that the inverse cascade develops through six-wave interaction, and that this is the basic mechanism of nonlinear wave coupling for 1D OWT. We describe theory, numerics and experimental observations while trying to incorporate all the different aspects into a consistent context. The experimental system is described by two coupled nonlinear equations, which we explore within two wave limits allowing for the expression of the evolution of the complex amplitude in a single dynamical equation. The long-wave limit corresponds to waves with wave numbers smaller than the electrical coherence length of the liquid crystal, and the opposite limit, when wave numbers are larger. We show that both of these systems are of a dual cascade type, analogous to two-dimensional (2D) turbulence, which can be described by wave turbulence (WT) theory, and conclude that the cascades are induced by a six-wave resonant interaction process. WT theory predicts several stationary solutions (non-equilibrium and thermodynamic) to both the long- and short-wave systems, and we investigate the necessary conditions required for their realization. Interestingly, the long-wave system is close to the integrable 1D nonlinear Schrödinger equation (NLSE) (which contains exact nonlinear soliton solutions), and as a result during the inverse cascade, nonlinearity of the system at low wave numbers becomes strong. Subsequently, due to the focusing nature of the nonlinearity, this leads to modulational instability (MI) of the condensate and the formation of solitons. Finally, with the aid of the probability density function (PDF) description of WT theory, we explain the coexistence and mutual interactions between solitons and the weakly nonlinear random wave background in the form of a wave turbulence life cycle (WTLC).

A system for tracking and recognizing pedestrian faces using a network of loosely coupled cameras

NASA Astrophysics Data System (ADS)

Gagnon, L.; Laliberté, F.; Foucher, S.; Branzan Albu, A.; Laurendeau, D.

2006-05-01

A face recognition module has been developed for an intelligent multi-camera video surveillance system. The module can recognize a pedestrian face in terms of six basic emotions and the neutral state. Face and facial features detection (eyes, nasal root, nose and mouth) are first performed using cascades of boosted classifiers. These features are used to normalize the pose and dimension of the face image. Gabor filters are then sampled on a regular grid covering the face image to build a facial feature vector that feeds a nearest neighbor classifier with a cosine distance similarity measure for facial expression interpretation and face model construction. A graphical user interface allows the user to adjust the module parameters.

Simulation of reflectometry Bragg backscattering spectral responses in the absence of a cutoff layer.

PubMed

da Silva, F; da Graça, S; Heuraux, S; Conway, G D

2010-10-01

Experimental reflectometry signals obtained in the absence of a cutoff layer, with the possibility of interferometric operation excluded, show a coherent and recurrent frequency spectrum signature similar to an Alfvén cascade signature. A possible explanation resides in the modulation of a resonant Bragg backscattering response by an Alfvén mode structure located at the center of the plasma whose frequency of oscillation modulates the backscattered signal in a conformable way. This situation is modeled and simulated using an O-mode full-wave Maxwell finite-difference time-domain code and the resulting signatures are discussed.

The spurious response of microwave photonic mixer

NASA Astrophysics Data System (ADS)

Xiao, Yongchuan; Zhong, Guoshun; Qu, Pengfei; Sun, Lijun

2018-02-01

Microwave photonic mixer is a potential solution for wideband information systems due to the ultra-wide operating bandwidth, high LO-to-RF isolation, the intrinsic immunity to electromagnetic interference, and the compatibility with exsiting microwave photonic transmission systems. The spurious response of microwave photonic mixer cascading in series a pair of Mach-Zehnder interferometric intensity modulators has been simulated and analyzed in this paper. The low order spurious products caused by the nonlinearity of modulators are non-negligible, and the proper IF frequency and accurate bias-controlling are of great importance to mitigate the impact of spurious products.

Compact nanomechanical plasmonic phase modulators [Ultracompact nano-mechanical plasmonic phase modulators

DOE PAGES

Dennis, B. S.; Haftel, M. I.; Czaplewski, D. A.; ...

2015-03-30

Highly confined optical energy in plasmonic devices is advancing miniaturization in photonics. However, for mode sizes approaching ≈10 nm, the energy increasingly shifts into the metal, raising losses and hindering active phase modulation. Here, we propose a nanoelectromechanical phase-modulation principle exploiting the extraordinarily strong dependence of the phase velocity of metal–insulator–metal gap plasmons on dynamically variable gap size. We experimentally demonstrate a 23-μm-long non-resonant modulator having a 1.5π rad range, with 1.7 dB excess loss at 780 nm. Analysis shows that by simultaneously decreasing the gap, length and width, an ultracompact-footprint π rad phase modulator can be realized. This ismore » achieved without incurring the extra loss expected for plasmons confined in a decreasing gap, because the increasing phase-modulation strength from a narrowing gap offsets rising propagation losses. Here, such small, high-density electrically controllable components may find applications in optical switch fabrics and reconfigurable plasmonic optics.« less

Activation of the yeast Hippo pathway by phosphorylation-dependent assembly of signaling complexes.

PubMed

Rock, Jeremy M; Lim, Daniel; Stach, Lasse; Ogrodowicz, Roksana W; Keck, Jamie M; Jones, Michele H; Wong, Catherine C L; Yates, John R; Winey, Mark; Smerdon, Stephen J; Yaffe, Michael B; Amon, Angelika

2013-05-17

Scaffold-assisted signaling cascades guide cellular decision-making. In budding yeast, one such signal transduction pathway called the mitotic exit network (MEN) governs the transition from mitosis to the G1 phase of the cell cycle. The MEN is conserved and in metazoans is known as the Hippo tumor-suppressor pathway. We found that signaling through the MEN kinase cascade was mediated by an unusual two-step process. The MEN kinase Cdc15 first phosphorylated the scaffold Nud1. This created a phospho-docking site on Nud1, to which the effector kinase complex Dbf2-Mob1 bound through a phosphoserine-threonine binding domain, in order to be activated by Cdc15. This mechanism of pathway activation has implications for signal transmission through other kinase cascades and might represent a general principle in scaffold-assisted signaling.

Learning at different satiation levels reveals parallel functions for the cAMP-protein kinase A cascade in formation of long-term memory.

PubMed

Friedrich, Anke; Thomas, Ulf; Müller, Uli

2004-05-05

Learning and memory formation in intact animals is generally studied under defined parameters, including the control of feeding. We used associative olfactory conditioning of the proboscis extension response in honeybees to address effects of feeding status on processes of learning and memory formation. Comparing groups of animals with different but defined feeding status at the time of conditioning reveals new and characteristic features in memory formation. In animals fed 18 hr earlier, three-trial conditioning induces a stable memory that consists of different phases: a mid-term memory (MTM), translation-dependent early long-term memory (eLTM; 1-2 d), and a transcription-dependent late LTM (lLTM; > or =3 d). Additional feeding of a small amount of sucrose 4 hr before conditioning leads to a loss of all of these memory phases. Interestingly, the basal activity of the cAMP-dependent protein kinase A (PKA), a key player in LTM formation, differs in animals with different satiation levels. Pharmacological rescue of the low basal PKA activity in animals fed 4 hr before conditioning points to a specific function of cAMP-PKA cascade in mediating satiation-dependent memory formation. An increase in PKA activity during conditioning rescues only transcription-dependent lLTM; acquisition, MTM, and eLTM are still impaired. Thus, during conditioning, the cAMP-PKA cascade mediates the induction of the transcription-dependent lLTM, depending on the satiation level. This result provides the first evidence for a central and distinct function of the cAMP-PKA cascade connecting satiation level with learning.

Modulator for tone and binary signals. [phase of modulation of tone and binary signals on carrier waves in communication systems

NASA Technical Reports Server (NTRS)

Mcchesney, J. R.; Lerner, T.; Fitch, E. J. (Inventor)

1975-01-01

Tones and binary information are transmitted as phase variations on a carrier wave of constant amplitude and frequency. The carrier and tones are applied to a balanced modulator for deriving an output signal including a pair of sidebands relative to the carrier. The carrier is phase modulated by a digital signal so that it is + or - 90 deg out of phase with the predetermined phase of the carrier. The carrier is combined in an algebraic summing device with the phase modulated signal and the balanced modulator output signal. The output of the algebraic summing device is hard limited to derive a constant amplitude and frequency signal having very narrow bandwidth requirements. At a receiver, the tones and binary data are detected with a phase locked loop having a voltage controlled oscillator driving a pair of orthogonal detection channels.

Kilohertz binary phase modulator for pulsed laser sources using a digital micromirror device.

PubMed

Hoffmann, Maximilian; Papadopoulos, Ioannis N; Judkewitz, Benjamin

2018-01-01

The controlled modulation of an optical wavefront is required for aberration correction, digital phase conjugation, or patterned photostimulation. For most of these applications, it is desirable to control the wavefront modulation at the highest rates possible. The digital micromirror device (DMD) presents a cost-effective solution to achieve high-speed modulation and often exceeds the speed of the more conventional liquid crystal spatial light modulator but is inherently an amplitude modulator. Furthermore, spatial dispersion caused by DMD diffraction complicates its use with pulsed laser sources, such as those used in nonlinear microscopy. Here we introduce a DMD-based optical design that overcomes these limitations and achieves dispersion-free high-speed binary phase modulation. We show that this phase modulation can be used to switch through binary phase patterns at the rate of 20 kHz in two-photon excitation fluorescence applications.

Kilohertz binary phase modulator for pulsed laser sources using a digital micromirror device

NASA Astrophysics Data System (ADS)

Hoffmann, Maximilian; Papadopoulos, Ioannis N.; Judkewitz, Benjamin

2018-01-01

The controlled modulation of an optical wavefront is required for aberration correction, digital phase conjugation or patterned photostimulation. For most of these applications it is desirable to control the wavefront modulation at the highest rates possible. The digital micromirror device (DMD) presents a cost-effective solution to achieve high-speed modulation and often exceeds the speed of the more conventional liquid crystal spatial light modulator, but is inherently an amplitude modulator. Furthermore, spatial dispersion caused by DMD diffraction complicates its use with pulsed laser sources, such as those used in nonlinear microscopy. Here we introduce a DMD-based optical design that overcomes these limitations and achieves dispersion-free high-speed binary phase modulation. We show that this phase modulation can be used to switch through binary phase patterns at the rate of 20 kHz in two-photon excitation fluorescence applications.

Unsteady pressure measurements on a biconvex airfoil in a transonic oscillating cascade

NASA Technical Reports Server (NTRS)

Shaw, L. M.; Boldman, D. R.; Buggele, A. E.; Buffum, D. H.

1985-01-01

Flush-mounted dynamic pressure transducers were installed on the center airfoil of a transonic oscillating cascade to measure the unsteady aerodynamic response as nine airfroils were simultaneously driven to provide 1.2 deg of pitching motion about the midchord. Initial tests were performed at an incidence and angle of 0 deg and A Mach number of 0.65 in order to obtain results in a shock-free compressible flowfield. Subsequent tests were performed at an incidence angle of 7 deg and Mach number of 0.8 in order to observe the surface pressures with an oscillating shock near the leading edge of the airfoil. Results are presented for interblade phase angles of 90 and -90 deg and at blade oscillatory frequencies of 200 and 500 Hz (semi-chord reduced frequencies up to about 0.5 at a Mach number of 0.8). Results from the zero-incidence cascade are compared with a classical unsteady flat-plate analysis. Flow visualization results depicting the shock motion on the airfoils in the high-incidence cascade are discussed. The airfoil pressure data are tabulated.

Soliton compression to few-cycle pulses with a high quality factor by engineering cascaded quadratic nonlinearities.

PubMed

Zeng, Xianglong; Guo, Hairun; Zhou, Binbin; Bache, Morten

2012-11-19

We propose an efficient approach to improve few-cycle soliton compression with cascaded quadratic nonlinearities by using an engineered multi-section structure of the nonlinear crystal. By exploiting engineering of the cascaded quadratic nonlinearities, in each section soliton compression with a low effective order is realized, and high-quality few-cycle pulses with large compression factors are feasible. Each subsequent section is designed so that the compressed pulse exiting the previous section experiences an overall effective self-defocusing cubic nonlinearity corresponding to a modest soliton order, which is kept larger than unity to ensure further compression. This is done by increasing the cascaded quadratic nonlinearity in the new section with an engineered reduced residual phase mismatch. The low soliton orders in each section ensure excellent pulse quality and high efficiency. Numerical results show that compressed pulses with less than three-cycle duration can be achieved even when the compression factor is very large, and in contrast to standard soliton compression, these compressed pulses have minimal pedestal and high quality factor.

Molecular dynamics modeling of atomic displacement cascades in 3C-SiC: Comparison of interatomic potentials

NASA Astrophysics Data System (ADS)

Samolyuk, G. D.; Osetsky, Y. N.; Stoller, R. E.

2015-10-01

We used molecular dynamics modeling of atomic displacement cascades to characterize the nature of primary radiation damage in 3C-SiC. We demonstrated that the most commonly used interatomic potentials are inconsistent with ab initio calculations of defect energetics. Both the Tersoff potential used in this work and a modified embedded-atom method potential reveal a barrier to recombination of the carbon interstitial and carbon vacancy which is much higher than the density functional theory (DFT) results. The barrier obtained with a newer potential by Gao and Weber is closer to the DFT result. This difference results in significant differences in the cascade production of point defects. We have completed both 10 keV and 50 keV cascade simulations in 3C-SiC at a range of temperatures. In contrast to the Tersoff potential, the Gao-Weber potential produces almost twice as many C vacancies and interstitials at the time of maximum disorder (∼0.2 ps) but only about 25% more stable defects at the end of the simulation. Only about 20% of the carbon defects produced with the Tersoff potential recombine during the in-cascade annealing phase, while about 60% recombine with the Gao-Weber potential. The Gao-Weber potential appears to give a more realistic description of cascade dynamics in SiC, but still has some shortcomings when the defect migration barriers are compared to the ab initio results.

Nitrite in organ protection

PubMed Central

Rassaf, Tienush; Ferdinandy, Peter; Schulz, Rainer

2014-01-01

In the last decade, the nitrate-nitrite-nitric oxide pathway has emerged to therapeutical importance. Modulation of endogenous nitrate and nitrite levels with the subsequent S-nitros(yl)ation of the downstream signalling cascade open the way for novel cytoprotective strategies. In the following, we summarize the actual literature and give a short overview on the potential of nitrite in organ protection. PMID:23826831

Breast Cancer Malignant Processes are Regulated by Pax-5 Through the Disruption of FAK Signaling Pathways

PubMed Central

Benzina, Sami; Harquail, Jason; Guerrette, Roxann; O'Brien, Pierre; Jean, Stéphanie; Crapoulet, Nicolas; Robichaud, Gilles A.

2016-01-01

The study of genetic factors regulating breast cancer malignancy is a top priority to mitigate the morbidity and mortality associated with this disease. One of these factors, Pax-5, modulates cancer aggressiveness through the regulation of various components of the epithelial to mesenchymal transitioning (EMT) process. We have previously reported that Pax-5 expression profiles in cancer tissues inversely correlate with those of the Focal Adhesion Kinase (FAK), a potent activator of breast cancer malignancy. In this study, we set out to elucidate the molecular and regulatory relationship between Pax-5 and FAK in breast cancer processes. Interestingly, we found that Pax-5 mediated suppression of breast cancer cell migration is dependent of FAK activity. Our mechanistic examination revealed that Pax-5 inhibits FAK expression and activation. We also demonstrate that Pax-5 is a potent modulator of FAK repressors (p53 and miR-135b) and activator (NFκB) which results in the overall suppression of FAK-mediated signaling cascades. Altogether, our findings bring more insight to the molecular triggers regulating phenotypic transitioning process and signaling cascades leading to breast cancer progression. PMID:28070224

Plant cell surface receptor-mediated signaling - a common theme amid diversity.

PubMed

He, Yunxia; Zhou, Jinggeng; Shan, Libo; Meng, Xiangzong

2018-01-29

Sessile plants employ a diverse array of plasma membrane-bound receptors to perceive endogenous and exogenous signals for regulation of plant growth, development and immunity. These cell surface receptors include receptor-like kinases (RLKs) and receptor-like proteins (RLPs) that harbor different extracellular domains for perception of distinct ligands. Several RLK and RLP signaling pathways converge at the somatic embryogenesis receptor kinases (SERKs), which function as shared co-receptors. A repertoire of receptor-like cytoplasmic kinases (RLCKs) associate with the receptor complexes to relay intracellular signaling. Downstream of the receptor complexes, mitogen-activated protein kinase (MAPK) cascades are among the key signaling modules at which the signals converge, and these cascades regulate diverse cellular and physiological responses through phosphorylation of different downstream substrates. In this Review, we summarize the emerging common theme that underlies cell surface receptor-mediated signaling pathways in Arabidopsis thaliana : the dynamic association of RLKs and RLPs with specific co-receptors and RLCKs for signal transduction. We further discuss how signaling specificities are maintained through modules at which signals converge, with a focus on SERK-mediated receptor signaling. © 2018. Published by The Company of Biologists Ltd.

Direct nanoscale imaging of evolving electric field domains in quantum structures.

PubMed

Dhar, Rudra Sankar; Razavipour, Seyed Ghasem; Dupont, Emmanuel; Xu, Chao; Laframboise, Sylvain; Wasilewski, Zbig; Hu, Qing; Ban, Dayan

2014-11-28

The external performance of quantum optoelectronic devices is governed by the spatial profiles of electrons and potentials within the active regions of these devices. For example, in quantum cascade lasers (QCLs), the electric field domain (EFD) hypothesis posits that the potential distribution might be simultaneously spatially nonuniform and temporally unstable. Unfortunately, there exists no prior means of probing the inner potential profile directly. Here we report the nanoscale measured electric potential distribution inside operating QCLs by using scanning voltage microscopy at a cryogenic temperature. We prove that, per the EFD hypothesis, the multi-quantum-well active region is indeed divided into multiple sections having distinctly different electric fields. The electric field across these serially-stacked quantum cascade modules does not continuously increase in proportion to gradual increases in the applied device bias, but rather hops between discrete values that are related to tunneling resonances. We also report the evolution of EFDs, finding that an incremental change in device bias leads to a hopping-style shift in the EFD boundary--the higher electric field domain expands at least one module each step at the expense of the lower field domain within the active region.

Direct Nanoscale Imaging of Evolving Electric Field Domains in Quantum Structures

PubMed Central

Dhar, Rudra Sankar; Razavipour, Seyed Ghasem; Dupont, Emmanuel; Xu, Chao; Laframboise, Sylvain; Wasilewski, Zbig; Hu, Qing; Ban, Dayan

2014-01-01

The external performance of quantum optoelectronic devices is governed by the spatial profiles of electrons and potentials within the active regions of these devices. For example, in quantum cascade lasers (QCLs), the electric field domain (EFD) hypothesis posits that the potential distribution might be simultaneously spatially nonuniform and temporally unstable. Unfortunately, there exists no prior means of probing the inner potential profile directly. Here we report the nanoscale measured electric potential distribution inside operating QCLs by using scanning voltage microscopy at a cryogenic temperature. We prove that, per the EFD hypothesis, the multi-quantum-well active region is indeed divided into multiple sections having distinctly different electric fields. The electric field across these serially-stacked quantum cascade modules does not continuously increase in proportion to gradual increases in the applied device bias, but rather hops between discrete values that are related to tunneling resonances. We also report the evolution of EFDs, finding that an incremental change in device bias leads to a hopping-style shift in the EFD boundary – the higher electric field domain expands at least one module each step at the expense of the lower field domain within the active region. PMID:25431158

A Clb/Cdk1-mediated regulation of Fkh2 synchronizes CLB expression in the budding yeast cell cycle.

PubMed

Linke, Christian; Chasapi, Anastasia; González-Novo, Alberto; Al Sawad, Istabrak; Tognetti, Silvia; Klipp, Edda; Loog, Mart; Krobitsch, Sylvia; Posas, Francesc; Xenarios, Ioannis; Barberis, Matteo

2017-01-01

Precise timing of cell division is achieved by coupling waves of cyclin-dependent kinase (Cdk) activity with a transcriptional oscillator throughout cell cycle progression. Although details of transcription of cyclin genes are known, it is unclear which is the transcriptional cascade that modulates their expression in a timely fashion. Here, we demonstrate that a Clb/Cdk1-mediated regulation of the Fkh2 transcription factor synchronizes the temporal mitotic CLB expression in budding yeast. A simplified kinetic model of the cyclin/Cdk network predicts a linear cascade where a Clb/Cdk1-mediated regulation of an activator molecule drives CLB3 and CLB2 expression. Experimental validation highlights Fkh2 as modulator of CLB3 transcript levels, besides its role in regulating CLB2 expression. A Boolean model based on the minimal number of interactions needed to capture the information flow of the Clb/Cdk1 network supports the role of an activator molecule in the sequential activation, and oscillatory behavior, of mitotic Clb cyclins. This work illustrates how transcription and phosphorylation networks can be coupled by a Clb/Cdk1-mediated regulation that synchronizes them.

Direct Nanoscale Imaging of Evolving Electric Field Domains in Quantum Structures

NASA Astrophysics Data System (ADS)

Dhar, Rudra Sankar; Razavipour, Seyed Ghasem; Dupont, Emmanuel; Xu, Chao; Laframboise, Sylvain; Wasilewski, Zbig; Hu, Qing; Ban, Dayan

2014-11-01

The external performance of quantum optoelectronic devices is governed by the spatial profiles of electrons and potentials within the active regions of these devices. For example, in quantum cascade lasers (QCLs), the electric field domain (EFD) hypothesis posits that the potential distribution might be simultaneously spatially nonuniform and temporally unstable. Unfortunately, there exists no prior means of probing the inner potential profile directly. Here we report the nanoscale measured electric potential distribution inside operating QCLs by using scanning voltage microscopy at a cryogenic temperature. We prove that, per the EFD hypothesis, the multi-quantum-well active region is indeed divided into multiple sections having distinctly different electric fields. The electric field across these serially-stacked quantum cascade modules does not continuously increase in proportion to gradual increases in the applied device bias, but rather hops between discrete values that are related to tunneling resonances. We also report the evolution of EFDs, finding that an incremental change in device bias leads to a hopping-style shift in the EFD boundary - the higher electric field domain expands at least one module each step at the expense of the lower field domain within the active region.

Emerging Importance of Phytochemicals in Regulation of Stem Cells Fate via Signaling Pathways.

PubMed

Dadashpour, Mehdi; Pilehvar-Soltanahmadi, Younes; Zarghami, Nosratollah; Firouzi-Amandi, Akram; Pourhassan-Moghaddam, Mohammad; Nouri, Mohammad

2017-11-01

To reach ideal therapeutic potential of stem cells for regenerative medicine purposes, it is essential to retain their self-renewal and differentiation capacities. Currently, biological factors are extensively used for stemness maintaining and differentiation induction of stem cells. However, low stability, high cost, complicated production process, and risks associated with viral/endotoxin infection hamper the widespread use of biological factors in the stem cell biology. Moreover, regarding the modulation of several signaling cascades, which lead to a distinct fate, phytochemicals are preferable in the stem cells biology because of their efficiency. Considering the issues related to the application of biological factors and potential advantages of phytochemicals in stem cell engineering, there is a considerable increasing trend in studies associated with the application of novel alternative molecules in the stem cell biology. In support of this statement, we aimed to highlight the various effects of phytochemicals on signaling cascades involved in commitment of stem cells. Hence, in this review, the current trends in the phytochemicals-based modulation of stem cell fate have been addressed. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Electro-Optic Modulator and Method

DTIC Science & Technology

An optical intensity modulator which uses a Sagnac interferometer having an electro - optic phase modulator therein. An electric modulation signal is...modulating the optical signals by the electrical signal, the electro - optic effect in the modulator phase shifts the optical signals with respect to one another

Perturbing laser field dependent high harmonic phase modulations

NASA Astrophysics Data System (ADS)

Li, Zhengyan; Kong, Fanqi; Brown, Graham; Hammond, TJ; Ko, Dong-Hyuk; Zhang, Chunmei; Corkum, P. B.

2018-06-01

A perturbing laser pulse modulates and controls the phase of the high harmonic radiation driven by an intense fundamental pulse. Thus, a structured wave front can impress a specific spatial phase onto the generated high harmonic wave front. This modulation procedure leads to all-optical spatial light modulators for VUV or XUV radiation created by high harmonic generation. Here, through theoretical analysis and experiment, we study the correlation between the high harmonic phase modulations and the perturbing laser field amplitude and phase, providing guidelines for practical high harmonic spatial light modulators. In addition, we show that the petahertz optical oscilloscope for measuring electric fields of a perturbing beam is most robust using low order harmonics, far from the cut-off.

Long-period grating and its cascaded counterpart in photonic crystal fiber for gas phase measurement.

PubMed

Tian, Fei; Kanka, Jiri; Du, Henry

2012-09-10

Regular and cascaded long period gratings (LPG, C-LPG) of periods ranging from 460 to 590 μm were inscribed in an endlessly single mode photonic crystal fiber (PCF) using CO(2) laser for sensing measurements of helium, argon and acetylene. High index sensitivities in excess of 1700 nm/RIU were achieved in both grating schemes with a period of 460 μm. The sharp interference fringes in the transmission spectrum of C-PCF-LPG afforded not only greatly enhanced sensing resolution, but also accuracy when the phase-shift of the fringe pattern is determined through spectral processing. Comparative numerical and experimental studies indicated LP(01) to LP(03) mode coupling as the principal coupling step for both PCF-LPG and C-PCF-LPG with emergence of multi-mode coupling at shorter grating periods or longer resonance wavelengths.

The mediating role of phosphodiesterase type 4 in the dopaminergic modulation of motor impulsivity.

PubMed

Heckman, P R A; Blokland, A; Van Goethem, N P; Van Hagen, B T J; Prickaerts, J

2018-09-17

The current study investigated the mediating role of phosphodiesterase type 4 (PDE4) regulated cAMP in the dopaminergic modulation of premature responding (action restraint) in rats. Response inhibition, which includes action restraint, finds its neurobiological origin in cortico-striatal-thalamic circuitry and can be modulated by dopamine. Intracellularly, the effect of dopamine is largely mediated through the cAMP/PKA signaling cascade. Areas in the prefrontal cortex are very sensitive to their neurochemical environment, including catecholamine levels. As a result, we investigated the effects of intracellular modulation of the dopamine cascade by means of PDE4 inhibition by roflumilast on premature responding in a hypo, normal and hyper dopaminergic state of the brain. As a hypo dopaminergic model we induced a 6-OHDA lesion in the (rat) prefrontal cortex, more specifically the infralimbic cortex. For the hyper dopaminergic state we also turned to a well-established model of impaired action restraint, namely the systemic administration of d-amphetamine. In line with the notion of a U-shaped relation between dopamine and impulsive responding, we found that both increasing and decreasing dopamine levels resulted in an increase in premature responding in the choice serial reaction time task (CSRTT). The PDE4 inhibitor roflumilast increased premature responses in combination with d-amphetamine, whereas a decrease in premature responding after roflumilast treatment was found in the 6-OHDA lesioned animals. As a result, it would be interesting to test the effects of PDE4 inhibition in disorders affected by disrupted impulse control related to cortico-striatal-thalamic hypodopaminergia including attention deficit hyperactivity disorder (ADHD). Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Performance analysis of cascaded h-bridge multilevel inverter using mixed switching frequency with various dc-link voltages

NASA Astrophysics Data System (ADS)

Citarsa, I. B. F.; Satiawan, I. N. W.; Wiryajati, I. K.; Supriono

2016-01-01

Multilevel inverters have been widely used in many applications since the technology is advantageous to increase the converter capability as well as to improve the output voltage quality. According to the applied switching frequency, multilevel modulations can be subdivided into three classes, i.e: fundamental switching frequency, high switching frequency and mixed switching frequency. This paper investigates the performance of cascaded H-bridge (CHB) multilevel inverter that is modulated using mixed switching frequency (MSF) PWM with various dc-link voltage ratios. The simulation results show the nearly sinusoidal load output voltages are successfully achieved. It is revealed that there is improvement in output voltages quality in terms of THD and low-order harmonics content. The CHB inverter that is modulated using MSF PWM with equal dc-link voltage ratio (½ Vdc: ½ Vdc) produces output voltage with the lowest low-order harmonics (less than 1% of fundamental) while the CHB inverter that is modulated using MSF PWM with un-equal dc-link voltage ratio (2/3 Vdc: 1/3 Vdc) produces a 7-level output voltage with the lowest THD (16.31%) compared to the other PWM methods. Improvement of the output voltage quality here is also in line with improvement of the number of available levels provided in the output voltage. Here only 2 cells H-bridge inverter (contain 8 switches) are needed to produce a 7- level output voltage, while in the conventional CHB inverter at least 3 cells of H-bridge inverter (contain 12 switches) are needed to produce a 7-level output voltage. Hence it is valuable in term of saving number of component.

Direct-Sequence Spread Spectrum System

DTIC Science & Technology

1990-06-01

by directly modulating a conventional narrowband frequency-modulated (FM) carrier by a high rate digital code. The direct modulation is binary phase ...specification of the DSSS system will not be developed. The results of the evaluation phase of this research will be compared against theoretical...spread spectrum is called binary phase -shift keying 19 (BPSK). BPSK is a modulation in which a binary Ŕ" represents a 0-degree relative phase

Auditory sensitivity to spectral modulation phase reversal as a function of modulation depth

PubMed Central

Grose, John

2018-01-01

The present study evaluated auditory sensitivity to spectral modulation by determining the modulation depth required to detect modulation phase reversal. This approach may be preferable to spectral modulation detection with a spectrally flat standard, since listeners appear unable to perform the task based on the detection of temporal modulation. While phase reversal thresholds are often evaluated by holding modulation depth constant and adjusting modulation rate, holding rate constant and adjusting modulation depth supports rate-specific assessment of modulation processing. Stimuli were pink noise samples, filtered into seven octave-wide bands (0.125–8 kHz) and spectrally modulated in dB. Experiment 1 measured performance as a function of modulation depth to determine appropriate units for adaptive threshold estimation. Experiment 2 compared thresholds in dB for modulation detection with a flat standard and modulation phase reversal; results supported the idea that temporal cues were available at high rates for the former but not the latter. Experiment 3 evaluated spectral modulation phase reversal thresholds for modulation that was restricted to either one or two neighboring bands. Flanking bands of unmodulated noise had a larger detrimental effect on one-band than two-band targets. Thresholds for high-rate modulation improved with increasing carrier frequency up to 2 kHz, whereas low-rate modulation appeared more consistent across frequency, particularly in the two-band condition. Experiment 4 measured spectral weights for spectral modulation phase reversal detection and found higher weights for bands in the spectral center of the stimulus than for the lowest (0.125 kHz) or highest (8 kHz) band. Experiment 5 compared performance for highly practiced and relatively naïve listeners, and found weak evidence of a larger practice effect at high than low spectral modulation rates. These results provide preliminary data for a task that may provide a better estimate of sensitivity to spectral modulation than spectral modulation detection with a flat standard. PMID:29621338

Typing pictures: Linguistic processing cascades into finger movements.

PubMed

Scaltritti, Michele; Arfé, Barbara; Torrance, Mark; Peressotti, Francesca

2016-11-01

The present study investigated the effect of psycholinguistic variables on measures of response latency and mean interkeystroke interval in a typewritten picture naming task, with the aim to outline the functional organization of the stages of cognitive processing and response execution associated with typewritten word production. Onset latencies were modulated by lexical and semantic variables traditionally linked to lexical retrieval, such as word frequency, age of acquisition, and naming agreement. Orthographic variables, both at the lexical and sublexical level, appear to influence just within-word interkeystroke intervals, suggesting that orthographic information may play a relevant role in controlling actual response execution. Lexical-semantic variables also influenced speed of execution. This points towards cascaded flow of activation between stages of lexical access and response execution. Copyright © 2016 Elsevier B.V. All rights reserved.

Hormonal control of cold stress responses in plants.

PubMed

Eremina, Marina; Rozhon, Wilfried; Poppenberger, Brigitte

2016-02-01

Cold stress responses in plants are highly sophisticated events that alter the biochemical composition of cells for protection from damage caused by low temperatures. In addition, cold stress has a profound impact on plant morphologies, causing growth repression and reduced yields. Complex signalling cascades are utilised to induce changes in cold-responsive gene expression that enable plants to withstand chilling or even freezing temperatures. These cascades are governed by the activity of plant hormones, and recent research has provided a better understanding of how cold stress responses are integrated with developmental pathways that modulate growth and initiate other events that increase cold tolerance. Information on the hormonal control of cold stress signalling is summarised to highlight the significant progress that has been made and indicate gaps that still exist in our understanding.

Modulating complex beams in amplitude and phase using fast tilt-micromirror arrays and phase masks.

PubMed

Roth, Matthias; Heber, Jörg; Janschek, Klaus

2018-06-15

The Letter proposes a system for the spatial modulation of light in amplitude and phase at kilohertz frame rates and high spatial resolution. The focus is fast spatial light modulators (SLMs) consisting of continuously tiltable micromirrors. We investigate the utilization of such SLMs in combination with a static phase mask in a 4f setup. The phase mask enables the complex beam modulation in a linear optical arrangement. Furthermore, adding so-called phase steps to the phase mask increases both the number of image pixels at constant SLM resolution and the optical efficiency. We illustrate our concept based on numerical simulations.

Cascaded Quadruple Active Bridge Structures for Multilevel DC to Three-Phase AC Conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Brian B; Achanta, Prasanta K; Maksimovic, Dragan

This paper introduces a multilevel architecture comprised of interconnected dc to three-phase ac converter units. To enable series connected operation, each converter unit contains a quadruple active bridge (QAB) converter that provides isolation between the dc side and each of the three ac sides. Since each converter unit transfers dc-side power as constant balanced three-phase power on the ac side, this implies instantaneous input-output power balance and allows elimination of bulk capacitive energy storage. In addition to minimizing required capacitance, the proposed approach simultaneously enables simplified dc-link controllers amenable to decentralized implementation, supports bidirectional power transfer, and exhibits a modularmore » structure to enhance scalability. Isolation provided by the QAB allows a wide range of electrical configurations among multiple units in various dc-ac, ac-dc or ac-ac applications. In this paper, the focus is on series connections on the ac side to emphasize multilevel operation, and the approach is experimentally validated in a dc-ac system containing two cascaded converter units.« less

Modulation of C. elegans Touch Sensitivity Is Integrated at Multiple Levels

PubMed Central

Chen, Xiaoyin

2014-01-01

Sensory systems can adapt to different environmental signals. Here we identify four conditions that modulate anterior touch sensitivity in Caenorhabditis elegans after several hours and demonstrate that such sensory modulation is integrated at multiple levels to produce a single output. Prolonged vibration involving integrin signaling directly sensitizes the touch receptor neurons (TRNs). In contrast, hypoxia, the dauer state, and high salt reduce touch sensitivity by preventing the release of long-range neuroregulators, including two insulin-like proteins. Integration of these latter inputs occurs at upstream neurohormonal cells and at the insulin signaling cascade within the TRNs. These signals and those from integrin signaling converge to modulate touch sensitivity by regulating AKT kinases and DAF-16/FOXO. Thus, activation of either the integrin or insulin pathways can compensate for defects in the other pathway. This modulatory system integrates conflicting signals from different modalities, and adapts touch sensitivity to both mechanical and non-mechanical conditions. PMID:24806678

Design of 5 V DC to 20 V DC switching regulator for power supply module

NASA Astrophysics Data System (ADS)

Azmi, N. A.; Murad, S. A. Z.; Harun, A.; Ismail, R. C.; Isa, M. N. M.; Zulkifeli, M. A.

2017-09-01

This paper presents the design of 5 V to 20 V DC switching regulator for power supply module. A voltage multiplier which consists of cascaded diode-capacitor combination is used in order to obtain a high voltage power supply. Due to power loss that has occurred in a stray of component arrangement, the proposed design employs a pulse width modulation (PWM) controller circuit with an inclusion of a capacitor, diode, and inductor components. The input supply of 5 V DC to LT1618 controller circuit has produced 20.35 V based from simulation results. Meanwhile, the measurement results of 19.36 V are obtained and the feedback signal is required for the purpose of stabilizing the output. The proposed design can reduce the components as well as the PCB size, thus minimizing the overall cost of making a switching regulator for power supply module.

Ring resonator-based on-chip modulation transformer for high-performance phase-modulated microwave photonic links.

PubMed

Zhuang, Leimeng; Taddei, Caterina; Hoekman, Marcel; Leinse, Arne; Heideman, René; van Dijk, Paulus; Roeloffzen, Chris

2013-11-04

In this paper, we propose and experimentally demonstrate a novel wideband on-chip photonic modulation transformer for phase-modulated microwave photonic links. The proposed device is able to transform phase-modulated optical signals into intensity-modulated versions (or vice versa) with nearly zero conversion of laser phase noise to intensity noise. It is constructed using waveguide-based ring resonators, which features simple architecture, stable operation, and easy reconfigurability. Beyond the stand-alone functionality, the proposed device can also be integrated with other functional building blocks of photonic integrated circuits (PICs) to create on-chip complex microwave photonic signal processors. As an application example, a PIC consisting of two such modulation transformers and a notch filter has been designed and realized in TriPleX(TM) waveguide technology. The realized device uses a 2 × 2 splitting circuit and 3 ring resonators with a free spectral range of 25 GHz, which are all equipped with continuous tuning elements. The device can perform phase-to-intensity modulation transform and carrier suppression simultaneously, which enables high-performance phase-modulated microwave photonics links (PM-MPLs). Associated with the bias-free and low-complexity advantages of the phase modulators, a single-fiber-span PM-MPL with a RF bandwidth of 12 GHz (3 dB-suppression band 6 to 18 GHz) has been demonstrated comprising the proposed PIC, where the achieved spurious-free dynamic range performance is comparable to that of Class-AB MPLs using low-biased Mach-Zehnder modulators.

Semi-actuator disk theory for compressor choke flutter

NASA Technical Reports Server (NTRS)

Micklow, J.; Jeffers, J.

1981-01-01

A mathematical anaysis predict the unsteady aerodynamic utilizing semi actuator theory environment for a cascade of airfoils harmonically oscillating in choked flow was developed. A normal shock is located in the blade passage, its position depending on the time dependent geometry, and pressure perturbations of the system. In addition to shock dynamics, the model includes the effect of compressibility, interblade phase lag, and an unsteady flow field upstream and downstream of the cascade. Calculated unsteady aerodynamics were compared with isolated airfoil wind tunnel data, and choke flutter onset boundaries were compared with data from testing of an F100 high pressure compressor stage.

Graphene based terahertz phase modulators

NASA Astrophysics Data System (ADS)

Kakenov, N.; Ergoktas, M. S.; Balci, O.; Kocabas, C.

2018-07-01

Electrical control of amplitude and phase of terahertz radiation (THz) is the key technological challenge for high resolution and noninvasive THz imaging. The lack of active materials and devices hinders the realization of these imaging systems. Here, we demonstrate an efficient terahertz phase and amplitude modulation using electrically tunable graphene devices. Our device structure consists of electrolyte-gated graphene placed at quarter wavelength distance from a reflecting metallic surface. In this geometry, graphene operates as a tunable impedance surface which yields electrically controlled reflection phase. Terahertz time domain reflection spectroscopy reveals the voltage controlled phase modulation of π and the reflection modulation of 50 dB. To show the promises of our approach, we demonstrate a multipixel phase modulator array which operates as a gradient impedance surface.

Time-dependent activation of MAPK/Erk1/2 and Akt/GSK3 cascades: modulation by agomelatine.

PubMed

Musazzi, Laura; Seguini, Mara; Mallei, Alessandra; Treccani, Giulia; Pelizzari, Mariagrazia; Tornese, Paolo; Racagni, Giorgio; Tardito, Daniela

2014-10-21

The novel antidepressant agomelatine, a melatonergic MT1/MT2 agonist combined with 5-HT2c serotonin antagonist properties, showed antidepressant action in preclinical and clinical studies. There is a general agreement that the therapeutic action of antidepressants needs the activation of slow-onset adaptations in downstream signalling pathways finally regulating neuroplasticity. In the last several years, particular attention was given to cAMP-responsive element binding protein (CREB)-related pathways, since it was shown that chronic antidepressants increase CREB phosphorylation and transcriptional activity, through the activation of calcium/calmodulin-dependent (CaM) and mitogen activated protein kinase cascades (MAPK/Erk1/2). Aim of this work was to analyse possible effects of chronic agomelatine on time-dependent changes of different intracellular signalling pathways in hippocampus and prefrontal/frontal cortex of male rats. To this end, measurements were performed 1 h or 16 h after the last agomelatine or vehicle injection. We have found that in naïve rats chronic agomelatine, contrary to traditional antidepressants, did not increase CREB phosphorylation, but modulates the time-dependent regulation of MAPK/Erk1/2 and Akt/glycogen synthase kinase-3 (GSK-3) pathways. Our results suggest that the intracellular molecular mechanisms modulated by chronic agomelatine may be partly different from those of traditional antidepressants and involve the time-dependent regulation of MAPK/Erk1/2 and Akt/GSK-3 signalling pathways. This could exert a role in the antidepressant efficacy of the drug.

Reaction Mechanisms of Energetic Materials in the Condensed Phase: Long-term Aging, Munition Safety and Condensed-Phase Processes in Propellants and Explosives

DTIC Science & Technology

2009-03-31

Journal of the American Society for Mass Spectrometry, 2002. 13(2): p. 135- 143 . 7. Delcorte, A., P. Bertrand, and B.J. Garrison, Collision cascade and...TNCHP. 49, 50 The presence of the keto group in K6 appears to promote a more direct reaction to the gaseous decomposition products. Decomposition

Electrical system for pulse-width modulated control of a power inverter using phase-shifted carrier signals and related operating methods

DOEpatents

Welchko, Brian A [Torrance, CA

2012-02-14

Systems and methods are provided for pulse-width modulated control of power inverter using phase-shifted carrier signals. An electrical system comprises an energy source and a motor. The motor has a first set of windings and a second set of windings, which are electrically isolated from each other. An inverter module is coupled between the energy source and the motor and comprises a first set of phase legs coupled to the first set of windings and a second set of phase legs coupled to the second set of windings. A controller is coupled to the inverter module and is configured to achieve a desired power flow between the energy source and the motor by modulating the first set of phase legs using a first carrier signal and modulating the second set of phase legs using a second carrier signal. The second carrier signal is phase-shifted relative to the first carrier signal.

An experimental investigation of gapwise periodicity and unsteady aerodynamic response in an oscillating cascade. Volume 2: Data report. Part 1: Text and mode 1 data

NASA Technical Reports Server (NTRS)

Carta, F. O.

1981-01-01

Tests were conducted a linear cascade of airfoils oscillating in pitch to measure the unsteady pressure response on selected blade along the leading edge plane of the cascade, over the chord of the center blade, and on the sidewall in the plane of the leading edge. The tests were conducted for all 96 combinations 2 mean camberline incidence angles 2 pitching amplitudes 3 reduced frequencies and 8 interblade phase angles. The pressure data were reduced to Fourier coefficient form for direct comparison, and were also processed to yield integrated loads and particularly, the aerodynamic damping coefficient. Data obtained during the test program, reproduced from the printout of the data reduction program are complied. A further description of the contents of this report is found in the text that follows.

Dispersion compensated mid-infrared quantum cascade laser frequency comb with high power output

NASA Astrophysics Data System (ADS)

Lu, Q. Y.; Manna, S.; Slivken, S.; Wu, D. H.; Razeghi, M.

2017-04-01

Chromatic dispersion control plays an underlying role in optoelectronics and spectroscopy owing to its enhancement to nonlinear interactions by reducing the phase mismatching. This is particularly important to optical frequency combs based on quantum cascade lasers which require negligible dispersions for efficient mode locking of the dispersed modes into equally spaced comb modes. Here, we demonstrated a dispersion compensated mid-IR quantum cascade laser frequency comb with high power output at room temperature. A low-loss dispersive mirror has been engineered to compensate the device's dispersion residue for frequency comb generation. Narrow intermode beating linewidths of 40 Hz in the comb-working currents were identified with a high power output of 460 mW and a broad spectral coverage of 80 cm-1. This dispersion compensation technique will enable fast spectroscopy and high-resolution metrology based on QCL combs with controlled dispersion and suppressed noise.

Timing of hospital admission in labour: latent versus active phase, mode of birth and intrapartum interventions. A correlational study.

PubMed

Rota, A; Antolini, L; Colciago, E; Nespoli, A; Borrelli, S E; Fumagalli, S

2017-10-17

Hospitalization of women in latent labour often leads to a cascade of unnecessary intrapartum interventions, to avoid potential disadvantages the recommendation should be to stay at home to improve women's experience and perinatal outcomes. The primary aim of this study was to investigate the association between hospital admission diagnosis (latent vs active phase) and mode of birth. The secondary aim was to explore the relationship between hospital admission diagnosis, intrapartum intervention rates and maternal/neonatal outcomes. A correlational study was conducted in a large Italian maternity hospital. Data from January 2013 to December 2014 were collected from the hospital electronic records. 1.446 records of low risk women were selected. These were dichotomized into two groups based on admission diagnosis: 'latent phase' or 'active phase' of labour. 52.7% of women were admitted in active labour and 47.3% in the latent phase. Women in the latent phase group were more likely to experience a caesarean section or an instrumental birth, artificial rupture of membranes, oxytocin augmentation and epidural analgesia. Admission in the latent phase was associated with higher intrapartum interventions, which were statistically correlated to the mode of birth. Women admitted in the latent phase were more likely to experience intrapartum interventions, which increase the probability of caesarean section. Maternity services should be organized around women and families needs, providing early labour support, to enable women to feel reassured facilitating their admission in labour to avoid the cascade of intrapartum interventions which increases the risk of caesarean section. Copyright © 2017 Australian College of Midwives. All rights reserved.

Generation of ultra-wideband triplet pulses based on four-wave mixing and phase-to-intensity modulation conversion.

PubMed

Li, Wei; Wang, Li Xian; Hofmann, Werner; Zhu, Ning Hua; Bimberg, Dieter

2012-08-27

We propose and demonstrate a novel scheme to generate ultra-wideband (UWB) triplet pulses based on four-wave mixing and phase-to-intensity modulation conversion. First a phase-modulated Gaussian doublet pulse is generated by four-wave mixing in a highly nonlinear fiber. Then an UWB triplet pulse is generated by generating the first-order derivative of the phase-modulated Gaussian doublet pulse using an optical filter serving as a frequency discriminator. By locating the optical signal at the linear slope of the optical filter, the phase modulated Gaussian doublet pulse is converted to an intensity-modulated UWB triplet pulse which well satisfies the Federal Communications Commission spectral mask requirements, even in the extremely power-restricted global positioning system band.

Cross-phase modulation spectral shifting: nonlinear phase contrast in a pump-probe microscope

PubMed Central

Wilson, Jesse W.; Samineni, Prathyush; Warren, Warren S.; Fischer, Martin C.

2012-01-01

Microscopy with nonlinear phase contrast is achieved by a simple modification to a nonlinear pump-probe microscope. The technique measures cross-phase modulation by detecting a pump-induced spectral shift in the probe pulse. Images with nonlinear phase contrast are acquired both in transparent and absorptive media. In paraffin-embedded biopsy sections, cross-phase modulation complements the chemically-specific pump-probe images with structural context. PMID:22567580

Optical modulator system

NASA Technical Reports Server (NTRS)

Brand, J.

1972-01-01

The fabrication, test, and delivery of an optical modulator system which will operate with a mode-locked Nd:YAG laser indicating at either 1.06 or 0.53 micrometers is discussed. The delivered hardware operates at data rates up to 400 Mbps and includes a 0.53 micrometer electrooptic modulator, a 1.06 micrometer electrooptic modulator with power supply and signal processing electronics with power supply. The modulators contain solid state drivers which accept digital signals with MECL logic levels, temperature controllers to maintain a stable thermal environment for the modulator crystals, and automatic electronic compensation to maximize the extinction ratio. The modulators use two lithium tantalate crystals cascaded in a double pass configuration. The signal processing electronics include encoding electronics which are capable of digitizing analog signals between the limit of + or - 0.75 volts at a maximum rate of 80 megasamples per second with 5 bit resolution. The digital samples are serialized and made available as a 400 Mbps serial NRZ data source for the modulators. A pseudorandom (PN) generator is also included in the signal processing electronics. This data source generates PN sequences with lengths between 31 bits and 32,767 bits in a serial NRZ format at rates up to 400 Mbps.

Structural and functional characterization of a novel molluskan ortholog of TRAF and TNF receptor-associated protein from disk abalone (Haliotis discus discus).

PubMed

Lee, Youngdeuk; Elvitigala, Don Anushka Sandaruwan; Whang, Ilson; Lee, Sukkyoung; Kim, Hyowon; Zoysa, Mahanama De; Oh, Chulhong; Kang, Do-Hyung; Lee, Jehee

2014-09-01

Immune signaling cascades have an indispensable role in the host defense of almost all the organisms. Tumor necrosis factor (TNF) signaling is considered as a prominent signaling pathway in vertebrate as well as invertebrate species. Within the signaling cascade, TNF receptor-associated factor (TRAF) and TNF receptor-associated protein (TTRAP) has been shown to have a crucial role in the modulation of immune signaling in animals. Here, we attempted to characterize a novel molluskan ortholog of TTRAP (AbTTRAP) from disk abalone (Haliotis discus discus) and analyzed its expression levels under pathogenic stress. The complete coding sequence of AbTTRAP consisted of 1071 nucleotides, coding for a 357 amino acid peptide, with a predicted molecular mass of 40 kDa. According to our in-silico analysis, AbTTRAP resembled the typical TTRAP domain architecture, including a 5'-tyrosyl DNA phosphodiesterase domain. Moreover, phylogenetic analysis revealed its common ancestral invertebrate origin, where AbTTRAP was clustered with molluskan counterparts. Quantitative real time PCR showed universally distributed expression of AbTTRAP in selected tissues of abalone, from which more prominent expression was detected in hemocytes. Upon stimulation with two pathogen-derived mitogens, lipopolysaccharide (LPS) and polyinosinic:polycytidylic acid (poly I:C), transcript levels of AbTTRAP in hemocytes and gill tissues were differentially modulated with time. In addition, the recombinant protein of AbTTRAP exhibited prominent endonuclease activity against abalone genomic DNA, which was enhanced by the presence of Mg(2+) in the medium. Collectively, these results reinforce the existence of the TNF signaling cascade in mollusks like disk abalone, further implicating the putative regulatory behavior of TTRAP in invertebrate host pathology. Copyright © 2014 Elsevier Ltd. All rights reserved.

Simulation and analysis of OOK-to-BPSK format conversion based on gain-transparent SOA used as optical phase-modulator.

PubMed

Hong, Wei; Huang, Dexiu; Zhang, Xinliang; Zhu, Guangxi

2007-12-24

All-optical on-off keying (OOK) to binary phase-shift keying (BPSK) modulation format conversion based on gain-transparent semiconductor optical amplifier (GT-SOA) is simulated and analyzed, where GT-SOA is used as an all-optical phase-modulator (PM). Numerical simulation of the phase modulation effect of GT-SOA is performed using a wideband dynamic model of GT-SOA and the quality of the BPSK signal is evaluated using the differential-phase-Q factor. Performance improvement by holding light injection is analyzed and non-return-to-zero (NRZ) and return-to-zero (RZ) modulation formats of the OOK signal are considered.

Toward high fidelity spectral sensing and RF signal processing in silicon photonic and nano-opto-mechanical platforms

NASA Astrophysics Data System (ADS)

Siddiqui, Aleem; Reinke, Charles; Shin, Heedeuk; Jarecki, Robert L.; Starbuck, Andrew L.; Rakich, Peter

2017-05-01

The performance of electronic systems for radio-frequency (RF) spectrum analysis is critical for agile radar and communications systems, ISR (intelligence, surveillance, and reconnaissance) operations in challenging electromagnetic (EM) environments, and EM-environment situational awareness. While considerable progress has been made in size, weight, and power (SWaP) and performance metrics in conventional RF technology platforms, fundamental limits make continued improvements increasingly difficult. Alternatively, we propose employing cascaded transduction processes in a chip-scale nano-optomechanical system (NOMS) to achieve a spectral sensor with exceptional signal-linearity, high dynamic range, narrow spectral resolution and ultra-fast sweep times. By leveraging the optimal capabilities of photons and phonons, the system we pursue in this work has performance metrics scalable well beyond the fundamental limitations inherent to all electronic systems. In our device architecture, information processing is performed on wide-bandwidth RF-modulated optical signals by photon-mediated phononic transduction of the modulation to the acoustical-domain for narrow-band filtering, and then back to the optical-domain by phonon-mediated phase modulation (the reverse process). Here, we rely on photonics to efficiently distribute signals for parallel processing, and on phononics for effective and flexible RF-frequency manipulation. This technology is used to create RF-filters that are insensitive to the optical wavelength, with wide center frequency bandwidth selectivity (1-100GHz), ultra-narrow filter bandwidth (1-100MHz), and high dynamic range (70dB), which we will present. Additionally, using this filter as a building block, we will discuss current results and progress toward demonstrating a multichannel-filter with a bandwidth of < 10MHz per channel, while minimizing cumulative optical/acoustic/optical transduced insertion-loss to ideally < 10dB. These proposed metric represent significant improvements over RF-platforms.

A Nonlinear Model for Transient Responses from Light-Adapted Wolf Spider Eyes

PubMed Central

DeVoe, Robert D.

1967-01-01

A quantitative model is proposed to test the hypothesis that the dynamics of nonlinearities in retinal action potentials from light-adapted wolf spider eyes may be due to delayed asymmetries in responses of the visual cells. For purposes of calculation, these delayed asymmetries are generated in an analogue by a time-variant resistance. It is first shown that for small incremental stimuli, the linear behavior of such a resistance describes peaking and low frequency phase lead in frequency responses of the eye to sinusoidal modulations of background illumination. It also describes the overshoots in linear step responses. It is next shown that the analogue accounts for nonlinear transient and short term DC responses to large positive and negative step stimuli and for the variations in these responses with changes in degree of light adaptation. Finally, a physiological model is proposed in which the delayed asymmetries in response are attributed to delayed rectification by the visual cell membrane. In this model, cascaded chemical reactions may serve to transduce visual stimuli into membrane resistance changes. PMID:6056011

Regulation of the Anaphase-promoting Complex–Separase Cascade by Transforming Growth Factor-β Modulates Mitotic Progression in Bone Marrow Stromal Cells

PubMed Central

Fujita, Takeo; Epperly, Michael W.; Zou, Hui; Greenberger, Joel S.

2008-01-01

Alteration of the tumor microenvironment by aberrant stromal cells influences many aspects of cell biology, including differentiation of stem cells and tumor metastasis. The role of transforming growth factor (TGF)-β signaling in stromal cells of the tissue microenvironment is critical to both pathways. We examined murine marrow stromal cells with deletion of Smad3 and found that they have an altered cell cycle profile, with a higher fraction of cells in G2/M phase. Deletion of Smad3 significantly abrogates TGF-β signaling and suppresses phosphorylation of CDC27–anaphase-promoting complex (APC) during mitosis, thereby resulting in elevated cyclin-dependent kinase (CDK)1 activity via increased levels of cyclin B. Enhanced CDK1 activity due to deregulation of APC leads in turn to hyperphosphorylation of separase, impeding chromatid separation. A residue Ser1126Ala mutation in separase specifically abolished separase hyperphosphorylation in Smad3-deficient cells. The present results unveil a new function for the TGF-β pathway in the regulation of APC to mediate chromatid separation during mitosis. PMID:18843049

Nonlinear photothermal Mid-Infrared Microspectroscopy with Superresolution

NASA Astrophysics Data System (ADS)

Erramilli, Shyamsunder; Mertiri, Alket; Liu, Hui; Totachawattana, Atcha; Hong, Mi; Sander, Michelle

2015-03-01

We describe a nonlinear method for breaking the diffraction limit in mid-infrared microscopy using nonlinear photothermal microspectroscopy. A Quantum Cascade Laser (QCL) tuned to an infrared active vibrational molecular normal mode is used as the pump laser. A low-phase noise Erbium-doped fiber (EDFL) laser is used as the probe. When the incident intensity of the mid-infrared pump laser is increased past a critical threshold, a nanobubble is nucleated, strongly modulating the scatter of the probe beam, in agreement with prior work. Remarkably, we have also found that the photothermal spectral signature of the mid-infrared absorption bifurcates and is strongly narrowed, consistent with an effective ``mean-field'' theory of the observed pitchfork bifurcation. This ultrasharp narrowing can be exploited to obtain mid-infrared images with a resolution that breaks the diffraction limit, without the need of mechanical scanning near-field probes. The method provides a powerful new tool for hyperspectral label-free mid-infrared imaging and characterization of biological tissues and materials science and engineering. We thank our collaborators H. Altug, L. D. Ziegler, J. Mertz, for their advice and generous loan of equipment.

CB1 Cannabinoid Receptors Couple to Focal Adhesion Kinase to Control Insulin Release*

PubMed Central

Malenczyk, Katarzyna; Jazurek, Magdalena; Keimpema, Erik; Silvestri, Cristoforo; Janikiewicz, Justyna; Mackie, Ken; Di Marzo, Vincenzo; Redowicz, Maria J.; Harkany, Tibor; Dobrzyn, Agnieszka

2013-01-01

Endocannabinoid signaling has been implicated in modulating insulin release from β cells of the endocrine pancreas. β Cells express CB1 cannabinoid receptors (CB1Rs), and the enzymatic machinery regulating anandamide and 2-arachidonoylglycerol bioavailability. However, the molecular cascade coupling agonist-induced cannabinoid receptor activation to insulin release remains unknown. By combining molecular pharmacology and genetic tools in INS-1E cells and in vivo, we show that CB1R activation by endocannabinoids (anandamide and 2-arachidonoylglycerol) or synthetic agonists acutely or after prolonged exposure induces insulin hypersecretion. In doing so, CB1Rs recruit Akt/PKB and extracellular signal-regulated kinases 1/2 to phosphorylate focal adhesion kinase (FAK). FAK activation induces the formation of focal adhesion plaques, multimolecular platforms for second-phase insulin release. Inhibition of endocannabinoid synthesis or FAK activity precluded insulin release. We conclude that FAK downstream from CB1Rs mediates endocannabinoid-induced insulin release by allowing cytoskeletal reorganization that is required for the exocytosis of secretory vesicles. These findings suggest a mechanistic link between increased circulating and tissue endocannabinoid levels and hyperinsulinemia in type 2 diabetes. PMID:24089517

Perception of the plant hormone ethylene: known-knowns and known-unknowns.

PubMed

Light, Kenneth M; Wisniewski, John A; Vinyard, W Andrew; Kieber-Emmons, Matthew T

2016-09-01

The gaseous phytohormone ethylene is implicated in virtually all phases of plant growth and development and thus has a major impact on crop production. This agronomic impact makes understanding ethylene signaling the Philosopher's Stone of the plant biotechnology world in applications including post-harvest transport of foodstuffs, consistency of foodstuff maturity pre-harvest, decorative flower freshness and longevity, and biomass production for biofuel applications. Ethylene is biosynthesized by plants in response to environmental factors and plant life-cycle events, and triggers a signaling cascade that modulates over 1000 genes. The key components in the perception of ethylene are a family of copper dependent receptors, the bioinorganic chemistry of which has been largely ignored by the chemical community. Since identification of these receptors two decades ago, there has been tremendous growth in knowledge in the biological community on the signal transduction pathways and mechanisms of ethylene signaling. In this review, we highlight these advances and key chemical voids in knowledge that are overdue for exploration, and which are required to ultimately regulate and control ethylene signaling.

All optical controlled photonic integrated circuits using azo dye functionized sol-gel material

NASA Astrophysics Data System (ADS)

Ke, Xianjun

The main focus of this dissertation is development and characterization of all-optical controllable azo dye functionized sol gel material, demonstrating a PIC fabrication technique on glass substrate using such material, and exploration and feasibility demonstration of three PIC functional devices namely optical variable attenuator, optical switches, and optical tunable filters using the material. The realization of all the devices in this dissertation are based on one material: dye functionalized sol-gel material. A photochromic sol-gel material functionalized with azo dye was synthesized and characterized. It possesses a photochromic characteristic under the control of green laser beam illumination. The material characteristics suggest the possibility of a new promising material platform candidate for the fabrication of alloptical controlled photonic integrated circuits. As the first potential application of the dye functionalized sol-gel material, an alloptical variable attenuator was designed and demonstrated. The optical variable attenuation is achieved in Mach-Zehnder interferometric configuration through all-optical modulation of sol-gel waveguide phase shifters. A 2 x 2 optical switch based on multimode interference (MMI) waveguide structure is proposed in the dissertation. The schematic configuration of the optical switch consists of a cascade of two identical MMIs with two all-optical controlled phase shifters realized by using the photochromic sol-gel material. The cross or bar switch state of the optical switch is determined by the phase difference between the two sol-gel waveguide phase shifters. An all-optical tunable filter is designed and its feasibility demonstrated by using the sol-gel photochromic material. Except for the phase change demonstrated on sol-gel waveguide phase shifters, dynamic gratings were observed on sol-gel film when exposed to two interference beams. This reveals the possibility of realizing Bragg grating-based tunable filters. The schematic configuration of proposed tunable filters consists of a single straight waveguide embedded with a sol-gel waveguide. The wavelength tuning of the tunable filters is accomplished by varying the grating period.

Analysis of phase error effects in multishot diffusion-prepared turbo spin echo imaging

PubMed Central

Cervantes, Barbara; Kooijman, Hendrik; Karampinos, Dimitrios C.

2017-01-01

Background To characterize the effect of phase errors on the magnitude and the phase of the diffusion-weighted (DW) signal acquired with diffusion-prepared turbo spin echo (dprep-TSE) sequences. Methods Motion and eddy currents were identified as the main sources of phase errors. An analytical expression for the effect of phase errors on the acquired signal was derived and verified using Bloch simulations, phantom, and in vivo experiments. Results Simulations and experiments showed that phase errors during the diffusion preparation cause both magnitude and phase modulation on the acquired data. When motion-induced phase error (MiPe) is accounted for (e.g., with motion-compensated diffusion encoding), the signal magnitude modulation due to the leftover eddy-current-induced phase error cannot be eliminated by the conventional phase cycling and sum-of-squares (SOS) method. By employing magnitude stabilizers, the phase-error-induced magnitude modulation, regardless of its cause, was removed but the phase modulation remained. The in vivo comparison between pulsed gradient and flow-compensated diffusion preparations showed that MiPe needed to be addressed in multi-shot dprep-TSE acquisitions employing magnitude stabilizers. Conclusions A comprehensive analysis of phase errors in dprep-TSE sequences showed that magnitude stabilizers are mandatory in removing the phase error induced magnitude modulation. Additionally, when multi-shot dprep-TSE is employed the inconsistent signal phase modulation across shots has to be resolved before shot-combination is performed. PMID:28516049

High power, high efficiency, continuous-wave supercontinuum generation using standard telecom fibers

NASA Astrophysics Data System (ADS)

Arun, S.; Choudhury, Vishal; Balaswamy, V.; Prakash, Roopa; Supradeepa, V. R.

2018-04-01

We demonstrate a simple module for octave spanning continuous-wave supercontinuum generation using standard telecom fiber. This module can accept any high power Ytterbium-doped fiber laser as input. The input light is transferred into the anomalous dispersion region of the telecom fiber through a cascade of Raman shifts. A recently proposed Raman laser architecture with distributed feedback efficiently performs these Raman conversions. A spectrum spanning over 1000nm(>1 octave) from 880-1900nm is demonstrated. The average power from the supercontinuum is ~34W with a high conversion efficiency of 44%. Input wavelength agility is demonstrated with similar supercontinua over a wide input wavelength range.

Effects of modulation phase on profile analysis in normal-hearing and hearing-impaired listeners

NASA Astrophysics Data System (ADS)

Rogers, Deanna; Lentz, Jennifer

2003-04-01

The ability to discriminate between sounds with different spectral shapes in the presence of amplitude modulation was measured in normal-hearing and hearing-impaired listeners. The standard stimulus was the sum of equal-amplitude modulated tones, and the signal stimulus was generated by increasing the level of half the tones (up components) and decreasing the level of half the tones (down components). The down components had the same modulation phase, and a phase shift was applied to the up components to encourage segregation from the down tones. The same phase shift was used in both standard and signal stimuli. Profile-analysis thresholds were measured as a function of the phase shift between up and down components. The phase shifts were 0, 30, 45, 60, 90, and 180 deg. As expected, thresholds were lowest when all tones had the same modulation phase and increased somewhat with increasing phase disparity. This small increase in thresholds was similar for both groups. These results suggest that hearing-impaired listeners are able to use modulation phase to group sounds in a manner similar to that of normal listeners. [Work supported by NIH (DC 05835).

High-speed microwave photonic switch for millimeter-wave ultra-wideband signal generation.

PubMed

Wang, Li Xian; Li, Wei; Zheng, Jian Yu; Wang, Hui; Liu, Jian Guo; Zhu, Ning Hua

2013-02-15

We propose a scheme for generating millimeter-wave (MMW) ultra-wideband (UWB) signal that is free from low-frequency components and a residual local oscillator. The system consists of two cascaded polarization modulators and is equivalent to a high-speed microwave photonic switch, which truncates a sinusoidal MMW into short pulses. The polarity switchability of the generated MMW-UWB pulse is also demonstrated.

Semantically Grounded Briefings

DTIC Science & Technology

2005-12-01

cascading interface, mirroring the class inheritance of the ontologies. Clicking on one of these tools, like PowerPoint’s native autoshape tools...connections are their graphic templates. This determines the appearance of an instance of that concept. Any of PowerPoint’s native autoshapes , formatted...which can be any PowerPoint autoshape , group shape, or image • Identification of a modulated component of C’s graphic template. If C’s graphic

Wide-band analog frequency modulation of optic signals using indirect techniques

NASA Technical Reports Server (NTRS)

Fitzmartin, D. J.; Balboni, E. J.; Gels, R. G.

1991-01-01

The wideband frequency modulation (FM) of an optical carrier by a radio frequency (RF) or microwave signal can be accomplished independent of laser type when indirect modulation is employed. Indirect modulators exploit the integral relation of phase to frequency so that phase modulators can be used to impress frequency modulation on an optical carrier. The use of integrated optics phase modulators, which are highly linear, enables the generation of optical wideband FM signals with very low intermodulation distortion. This modulator can be used as part of an optical wideband FM link for RF and microwave signals. Experimental results from the test of an indirect frequency modulator for an optical carrier are discussed.

5.5 W near-diffraction-limited power from resonant leaky-wave coupled phase-locked arrays of quantum cascade lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kirch, J. D.; Chang, C.-C.; Boyle, C.

2015-02-09

Five, 8.36 μm-emitting quantum-cascade lasers (QCLs) have been monolithically phase-locked in the in-phase array mode via resonant leaky-wave coupling. The structure is fabricated by etch and regrowth which provides large index steps (Δn = 0.10) between antiguided-array elements and interelement regions. Such high index contrast photonic-crystal (PC) lasers have more than an order of magnitude higher index contrast than PC-distributed feedback lasers previously used for coherent beam combining in QCLs. Absorption loss to metal layers inserted in the interelement regions provides a wide (∼1.0 μm) range in interelement width over which the resonant in-phase mode is strongly favored to lase. Room-temperature, in-phase-mode operation withmore » ∼2.2 kA/cm{sup 2} threshold-current density is obtained from 105 μm-wide aperture devices. The far-field beam pattern has lobewidths 1.65× diffraction limit (D.L.) and 82% of the light in the main lobe, up to 1.8× threshold. Peak pulsed near-D.L. power of 5.5 W is obtained, with 4.5 W emitted in the main lobe. Means of how to increase the device internal efficiency are discussed.« less

The Global Regulators GacA and ςS Form Part of a Cascade That Controls Alginate Production in Azotobacter vinelandii

PubMed Central

Castañeda, Miguel; Sánchez, Judith; Moreno, Soledad; Núñez, Cinthia; Espín, Guadalupe

2001-01-01

Transcription of the Azotobacter vinelandii algD gene, which encodes GDP-mannose dehydrogenase (the rate-limiting enzyme of alginate synthesis), starts from three sites: p1, p2, and p3. The sensor kinase GacS, a member of the two-component regulatory system, is required for transcription of algD from its three sites during the stationary phase. Here we show that algD is expressed constitutively throughout the growth cycle from the p2 and p3 sites and that transcription from p1 started at the transition between the exponential growth phase and stationary phase. We constructed A. vinelandii strains that carried mutations in gacA encoding the cognate response regulator of GacS and in rpoS coding for the stationary-phase ςS factor. The gacA mutation impaired alginate production and transcription of algD from its three promoters. Transcription of rpoS was also abolished by the gacA mutation. The rpoS mutation impaired transcription of algD from the p1 promoter and increased it from the p2 ςE promoter. The results of this study provide evidence for the predominant role of GacA in a regulatory cascade controlling alginate production and gene expression during the stationary phase in A. vinelandii. PMID:11698366

The Energy Cascade Associated with the North Atlantic Oscillation

NASA Astrophysics Data System (ADS)

Castanheira, J. M.; Marques, C. A. F.

2017-12-01

The North Atlantic Oscillation or Arctic Oscillation (NAO/AO), in a more hemispheric expression, is the dominant mode of variability of the extratropical atmospheric circulation. In the literature which analyses the association of low frequency variability of the NAO/AO with other climate variables, it is very common to find the idea of circulation and climate impacts of the NAO/AO. It is usually suggested that the NAO influences the position of North Atlantic storm tracks and the related transport of heat and moisture. However, in spite of the long time since the NAO variability mode was uncovered (Walker and Bliss, 1932), its underlying dynamical mechanisms are not well understood yet. In fact, it is not yet consensual that the NAO influences the position of the storm tracks, being possible that the relationship is in the opposite way with the storm track activity influencing de NAO. In this communication we will present an analysis of anomalies of the energy cascade associated with the NAO. A detailed version of the Lorenz energy cycle, which decomposes the energy flows into baroclinic and barotropic terms and into zonal mean and eddy components, was applied to the 6-hourly ERA-I reanalysis for the period of 1979 to 2016. The obtained results show that the positive NAO phase is preceded by an significant increase of synoptic baroclinic eddy activity. The eddy available potential energy is converted into kinetic energy and transferred to barotropic synoptic eddies. Then, the kinetic energy is transferred upscale into the barotropic planetary waves, which reproduce the NAO pattern. Therefore, we conclude that the synoptic baroclinic eddy activity forces the NAO variability. No clear signal was found for a modulating role of the NAO in the baroclinic eddy activity.

Low frequency piezoresonance defined dynamic control of terahertz wave propagation

NASA Astrophysics Data System (ADS)

Dutta, Moumita; Betal, Soutik; Peralta, Xomalin G.; Bhalla, Amar S.; Guo, Ruyan

2016-11-01

Phase modulators are one of the key components of many applications in electromagnetic and opto-electric wave propagations. Phase-shifters play an integral role in communications, imaging and in coherent material excitations. In order to realize the terahertz (THz) electromagnetic spectrum as a fully-functional bandwidth, the development of a family of efficient THz phase modulators is needed. Although there have been quite a few attempts to implement THz phase modulators based on quantum-well structures, liquid crystals, or meta-materials, significantly improved sensitivity and dynamic control for phase modulation, as we believe can be enabled by piezoelectric-resonance devices, is yet to be investigated. In this article we provide an experimental demonstration of phase modulation of THz beam by operating a ferroelectric single crystal LiNbO3 film device at the piezo-resonance. The piezo-resonance, excited by an external a.c. electric field, develops a coupling between electromagnetic and lattice-wave and this coupling governs the wave propagation of the incident THz beam by modulating its phase transfer function. We report the understanding developed in this work can facilitate the design and fabrication of a family of resonance-defined highly sensitive and extremely low energy sub-millimeter wave sensors and modulators.

Low frequency piezoresonance defined dynamic control of terahertz wave propagation.

PubMed

Dutta, Moumita; Betal, Soutik; Peralta, Xomalin G; Bhalla, Amar S; Guo, Ruyan

2016-11-30

Phase modulators are one of the key components of many applications in electromagnetic and opto-electric wave propagations. Phase-shifters play an integral role in communications, imaging and in coherent material excitations. In order to realize the terahertz (THz) electromagnetic spectrum as a fully-functional bandwidth, the development of a family of efficient THz phase modulators is needed. Although there have been quite a few attempts to implement THz phase modulators based on quantum-well structures, liquid crystals, or meta-materials, significantly improved sensitivity and dynamic control for phase modulation, as we believe can be enabled by piezoelectric-resonance devices, is yet to be investigated. In this article we provide an experimental demonstration of phase modulation of THz beam by operating a ferroelectric single crystal LiNbO 3 film device at the piezo-resonance. The piezo-resonance, excited by an external a.c. electric field, develops a coupling between electromagnetic and lattice-wave and this coupling governs the wave propagation of the incident THz beam by modulating its phase transfer function. We report the understanding developed in this work can facilitate the design and fabrication of a family of resonance-defined highly sensitive and extremely low energy sub-millimeter wave sensors and modulators.

Phase-Controlled Polarization Modulators

NASA Technical Reports Server (NTRS)

Chuss, D. T.; Wollack, E. J.; Novak, G.; Moseley, S. H.; Pisano, G.; Krejny, M.; U-Yen, K.

2012-01-01

We report technology development of millimeter/submillimeter polarization modulators that operate by introducing a a variable, controlled phase delay between two orthogonal polarization states. The variable-delay polarization modulator (VPM) operates via the introduction of a variable phase delay between two linear orthogonal polarization states, resulting in a variable mapping of a single linear polarization into a combination of that Stokes parameter and circular (Stokes V) polarization. Characterization of a prototype VPM is presented at 350 and 3000 microns. We also describe a modulator in which a variable phase delay is introduced between right- and left- circular polarization states. In this architecture, linear polarization is fully modulated. Each of these devices consists of a polarization diplexer parallel to and in front of a movable mirror. Modulation involves sub-wavelength translations of the mirror that change the magnitude of the phase delay.

Network overload due to massive attacks

NASA Astrophysics Data System (ADS)

Kornbluth, Yosef; Barach, Gilad; Tuchman, Yaakov; Kadish, Benjamin; Cwilich, Gabriel; Buldyrev, Sergey V.

2018-05-01

We study the cascading failure of networks due to overload, using the betweenness centrality of a node as the measure of its load following the Motter and Lai model. We study the fraction of survived nodes at the end of the cascade pf as a function of the strength of the initial attack, measured by the fraction of nodes p that survive the initial attack for different values of tolerance α in random regular and Erdös-Renyi graphs. We find the existence of a first-order phase-transition line pt(α ) on a p -α plane, such that if p pt , pf is large and the giant component of the network is still present. Exactly at pt, the function pf(p ) undergoes a first-order discontinuity. We find that the line pt(α ) ends at a critical point (pc,αc) , in which the cascading failures are replaced by a second-order percolation transition. We find analytically the average betweenness of nodes with different degrees before and after the initial attack, we investigate their roles in the cascading failures, and we find a lower bound for pt(α ) . We also study the difference between localized and random attacks.

Interaction of upstream flow distortions with high Mach number cascades

NASA Technical Reports Server (NTRS)

Englert, G. W.

1981-01-01

Features of the interaction of flow distortions, such as gusts and wakes with blade rows of advance type fans and compressors having high tip Mach numbers are modeled. A typical disturbance was assumed to have harmonic time dependence and was described, at a far upstream location, in three orthogonal spatial coordinates by a double Fourier series. It was convected at supersonic relative to a linear cascade described as an unrolled annulus. Conditions were selected so that the component of this velocity parallel to the axis of the turbomachine was subsonic, permitting interaction between blades through the upstream as well as downstream flow media. A strong, nearly normal shock was considered in the blade passages which was allowed curvature and displacement. The flows before and after the shock were linearized relative to uniform mean velocities in their respective regions. Solution of the descriptive equations was by adaption of the Wiener-Hopf technique, enabling a determination of distortion patterns through and downstream of the cascade as well as pressure distributions on the blade and surfaces. Details of interaction of the disturbance with the in-passage shock were discussed. Infuences of amplitude, wave length, and phase of the disturbance on lifts and moments of cascade configurations are presented. Numerical results are clarified by reference to an especially orderly pattern of upstream vertical motion in relation to the cascade parameters.

Stable Optical Phase Modulation With Micromirrors

DTIC Science & Technology

2012-01-27

Stable optical phase modulation with micromirrors Caleb Knoernschild, Taehyun Kim, Peter Maunz, Stephen G. Crain, and Jungsang Kim∗ Fitzpatrick...position stability of the micromirror is dominated by the thermal mechanical noise of the structure. With this level of stability, we utilize the... micromirror to realize an optical phase modulator by simply reflecting light off the mirror and modulating its position. The resonant frequency of the

Gap solitons in a nonlinear quadratic negative-index cavity.

PubMed

Scalora, Michael; de Ceglia, Domenico; D'Aguanno, Giuseppe; Mattiucci, Nadia; Akozbek, Neset; Centini, Marco; Bloemer, Mark J

2007-06-01

We predict the existence of gap solitons in a nonlinear, quadratic Fabry-Pérot negative index cavity. A peculiarity of a single negative index layer is that if magnetic and electric plasma frequencies are different it forms a photonic band structure similar to that of a multilayer stack composed of ordinary, positive index materials. This similarity also results in comparable field localization and enhancement properties that under appropriate conditions may be used to either dynamically shift the band edge, or for efficient energy conversion. We thus report that an intense, fundamental pump pulse is able to shift the band edge of a negative index cavity, and make it possible for a weak second harmonic pulse initially tuned inside the gap to be transmitted, giving rise to a gap soliton. The process is due to cascading, a well-known phenomenon that occurs far from phase matching conditions that limits energy conversion rates, it resembles a nonlinear third-order process, and causes pulse compression due to self-phase modulation. The symmetry of the equations of motion under the action of either an electric or a magnetic nonlinearity suggests that both nonlinear polarization and magnetization, or a combination of both, can lead to solitonlike pulses. More specifically, the antisymmetric localization properties of the electric and magnetic fields cause a nonlinear polarization to generate a dark soliton, while a nonlinear magnetization spawns a bright soliton.

Multi-Gigabit Free-Space Optical Data Communication and Network System

DTIC Science & Technology

2016-04-01

IR), Ultraviolet ( UV ), Laser Transceiver, Adaptive Beam Tracking, Electronic Attack (EA), Cyber Attack, Multipoint-to-Multipoint Network, Adaptive...FileName.pptx Free Space Optical Datalink Timeline Phase 1 Point-to-point demonstration 2012 Future Adaptive optic & Quantum Cascade Laser

DEVELOPMENT OF A SUPERSONIC TRANSPORT AIRCRAFT ENGINE - PHASE II-A.

DTIC Science & Technology

JET TRANSPORT PLANES, *SUPERSONIC AIRCRAFT ) (U) TURBOJET ENGINES , PERFORMANCE( ENGINEERING ), TURBOFAN ENGINES , AFTERBURNING, SPECIFICATIONS...COMPRESSORS, GEOMETRY, TURBOJET INLETS, COMBUSTION, TEST EQUIPMENT, TURBINE BLADES , HEAT TRANSFER, AIRFOILS , CASCADE STRUCTURES, EVAPOTRANSPIRATION, PLUG NOZZLES, ANECHOIC CHAMBERS, BEARINGS, SEALS, DESIGN, FATIGUE(MECHANICS)

Color vision predicts processing modes of goal activation during action cascading.

PubMed

Jongkees, Bryant J; Steenbergen, Laura; Colzato, Lorenza S

2017-09-01

One of the most important functions of cognitive control is action cascading: the ability to cope with multiple response options when confronted with various task goals. A recent study implicates a key role for dopamine (DA) in this process, suggesting higher D1 efficiency shifts the action cascading strategy toward a more serial processing mode, whereas higher D2 efficiency promotes a shift in the opposite direction by inducing a more parallel processing mode (Stock, Arning, Epplen, & Beste, 2014). Given that DA is found in high concentration in the retina and modulation of retinal DA release displays characteristics of D2-receptors (Peters, Schweibold, Przuntek, & Müller, 2000), color vision discrimination might serve as an index of D2 efficiency. We used color discrimination, assessed with the Lanthony Desaturated Panel D-15 test, to predict individual differences (N = 85) in a stop-change paradigm that provides a well-established measure of action cascading. In this task it is possible to calculate an individual slope value for each participant that estimates the degree of overlap in task goal activation. When the stopping process of a previous task goal has not finished at the time the change process toward a new task goal is initiated (parallel processing), the slope value becomes steeper. In case of less overlap (more serial processing), the slope value becomes flatter. As expected, participants showing better color vision were more prone to activate goals in a parallel manner as indicated by a steeper slope. Our findings suggest that color vision might represent a predictor of D2 efficiency and the predisposed processing mode of goal activation during action cascading. Copyright © 2017 Elsevier Ltd. All rights reserved.

On the power spectral density of quadrature modulated signals. [satellite communication

NASA Technical Reports Server (NTRS)

Yan, T. Y.

1981-01-01

The conventional (no-offset) quadriphase modulation technique suffers from the fact that hardlimiting will restore the frequency sidelobes removed by proper filtering. Thus, offset keyed quadriphase modulation techniques are often proposed for satellite communication with bandpass hardlimiting. A unified theory is developed which is capable of describing the power spectral density before and after the hardlimiting process. Using the in-phase and the quadrature phase channel with arbitrary pulse shaping, analytical results are established for generalized quadriphase modulation. In particular MSK, OPSK or the recently introduced overlapped raised cosine keying all fall into this general category. It is shown that for a linear communication channel, the power spectral density of the modulated signal remains unchanged regardless of the offset delay. Furthermore, if the in phase and the quadrature phase channel have identical pulse shapes without offset, the spectrum after bandpass hardlimiting will be identical to that of the conventional QPSK modulation. Numerical examples are given for various modulation techniques. A case of different pulse shapes in the in phase and the quadrature phase channel is also considered.

Dynamical phases of the Hindmarsh-Rose neuronal model: studies of the transition from bursting to spiking chaos.

PubMed

Innocenti, Giacomo; Morelli, Alice; Genesio, Roberto; Torcini, Alessandro

2007-12-01

The dynamical phases of the Hindmarsh-Rose neuronal model are analyzed in detail by varying the external current I. For increasing current values, the model exhibits a peculiar cascade of nonchaotic and chaotic period-adding bifurcations leading the system from the silent regime to a chaotic state dominated by bursting events. At higher I-values, this phase is substituted by a regime of continuous chaotic spiking and finally via an inverse period doubling cascade the system returns to silence. The analysis is focused on the transition between the two chaotic phases displayed by the model: one dominated by spiking dynamics and the other by bursts. At the transition an abrupt shrinking of the attractor size associated with a sharp peak in the maximal Lyapunov exponent is observable. However, the transition appears to be continuous and smoothed out over a finite current interval, where bursts and spikes coexist. The beginning of the transition (from the bursting side) is signaled from a structural modification in the interspike interval return map. This change in the map shape is associated with the disappearance of the family of solutions responsible for the onset of the bursting chaos. The successive passage from bursting to spiking chaos is associated with a progressive pruning of unstable long-lasting bursts.

Terahertz holography for imaging amplitude and phase objects.

PubMed

Hack, Erwin; Zolliker, Peter

2014-06-30

A non-monochromatic THz Quantum Cascade Laser and an uncooled micro-bolometer array detector with VGA resolution are used in a beam-splitter free holographic set-up to measure amplitude and phase objects in transmission. Phase maps of the diffraction pattern are retrieved using the Fourier transform carrier fringe method; while a Fresnel-Kirchhoff back propagation algorithm is used to reconstruct the complex object image. A lateral resolution of 280 µm and a relative phase sensitivity of about 0.5 rad are estimated from reconstructed images of a metallic Siemens star and a polypropylene test structure, respectively. Simulations corroborate the experimental results.

Monitoring of biological markers indicative of doping: the athlete biological passport.

PubMed

Saugy, Martial; Lundby, Carsten; Robinson, Neil

2014-05-01

The athlete biological passport (ABP) was recently implemented in anti-doping work and is based on the individual and longitudinal monitoring of haematological or urine markers. These may be influenced by illicit procedures performed by some athletes with the intent to improve exercise performance. Hence the ABP is a valuable tool in the fight against doping. Actually, the passport has been defined as an individual and longitudinal observation of markers. These markers need to belong to the biological cascade influenced by the application of forbidden hormones or more generally, affected by biological manipulations which can improve the performance of the athlete. So far, the haematological and steroid profile modules of the ABP have been implemented in major sport organisations, and a further module is under development. The individual and longitudinal monitoring of some blood and urine markers are of interest, because the intraindividual variability is lower than the corresponding interindividual variability. Among the key prerequisites for the implementation of the ABP is its prospect to resist to the legal and scientific challenges. The ABP should be implemented in the most transparent way and with the necessary independence between planning, interpretation and result management of the passport. To ensure this, the Athlete Passport Management Unit (APMU) was developed and the WADA implemented different technical documents associated to the passport. This was carried out to ensure the correct implementation of a profile which can also stand the challenge of any scientific or legal criticism. This goal can be reached only by following strictly important steps in the chain of production of the results and in the management of the interpretation of the passport. Various technical documents have been then associated to the guidelines which correspond to the requirements for passport operation. The ABP has been completed very recently by the steroid profile module. As for the haematological module, individual and longitudinal monitoring have been applied and the interpretation cascade is also managed by a specific APMU in a similar way as applied in the haematological module. Thus, after exclusion of any possible pathology, specific variation from the individual norms will be then considered as a potential misuse of hormones or other modulators to enhance performance.

All-optical phase modulation for integrated interferometric biosensors.

PubMed

Dante, Stefania; Duval, Daphné; Sepúlveda, Borja; González-Guerrero, Ana Belen; Sendra, José Ramón; Lechuga, Laura M

2012-03-26

We present the theoretical and the experimental implementation of an all-optical phase modulation system in integrated Mach-Zehnder Interferometers to solve the drawbacks related to the periodic nature of the interferometric signal. Sensor phase is tuned by modulating the emission wavelength of low-cost commercial laser diodes by changing their output power. FFT deconvolution of the signal allows for direct phase readout, immune to sensitivity variations and to light intensity fluctuations. This simple phase modulation scheme increases the signal-to-noise ratio of the measurements in one order of magnitude, rendering in a sensor with a detection limit of 1.9·10⁻⁷ RIU. The viability of the all-optical modulation approach is demonstrated with an immunoassay detection as a biosensing proof of concept.

Boon and Bane of Inflammation in Bone Tissue Regeneration and Its Link with Angiogenesis.

PubMed

Schmidt-Bleek, Katharina; Kwee, Brian J; Mooney, David J; Duda, Georg N

2015-08-01

Delayed healing or nonhealing of bone is an important clinical concern. Although bone, one of the two tissues with scar-free healing capacity, heals in most cases, healing is delayed in more than 10% of clinical cases. Treatment of such delayed healing condition is often painful, risky, time consuming, and expensive. Tissue healing is a multistage regenerative process involving complex and well-orchestrated steps, which are initiated in response to injury. At best, these steps lead to scar-free tissue formation. At the onset of healing, during the inflammatory phase, stationary and attracted macrophages and other immune cells at the fracture site release cytokines in response to injury. This initial reaction to injury is followed by the recruitment, proliferation, and differentiation of mesenchymal stromal cells, synthesis of extracellular matrix proteins, angiogenesis, and finally tissue remodeling. Failure to heal is often associated with poor revascularization. Since blood vessels mediate the transport of circulating cells, oxygen, nutrients, and waste products, they appear essential for successful healing. The strategy of endogenous regeneration in a tissue such as bone is interesting to analyze since it may represent a blueprint of successful tissue formation. This review highlights the interdependency of the time cascades of inflammation, angiogenesis, and tissue regeneration. A better understanding of these inter-relations is mandatory to early identify patients at risk as well as to overcome critical clinical conditions that limit healing. Instead of purely tolerating the inflammatory phase, modulations of inflammation (immunomodulation) might represent a valid therapeutic strategy to enhance angiogenesis and foster later phases of tissue regeneration.

Electrical 2π phase control of infrared light in a 350-nm footprint using graphene plasmons

NASA Astrophysics Data System (ADS)

Woessner, Achim; Gao, Yuanda; Torre, Iacopo; Lundeberg, Mark B.; Tan, Cheng; Watanabe, Kenji; Taniguchi, Takashi; Hillenbrand, Rainer; Hone, James; Polini, Marco; Koppens, Frank H. L.

2017-07-01

Modulating the amplitude and phase of light is at the heart of many applications such as wavefront shaping, transformation optics, phased arrays, modulators and sensors. Performing this task with high efficiency and small footprint is a formidable challenge. Metasurfaces and plasmonics are promising, but metals exhibit weak electro-optic effects. Two-dimensional materials, such as graphene, have shown great performance as modulators with small drive voltages. Here, we show a graphene plasmonic phase modulator that is capable of tuning the phase between 0 and 2π in situ. The device length of 350 nm is more than 30 times shorter than the 10.6 μm free-space wavelength. The modulation is achieved by spatially controlling the plasmon phase velocity in a device where the spatial carrier density profile is tunable. We provide a scattering theory for plasmons propagating through spatial density profiles. This work constitutes a first step towards two-dimensional transformation optics for ultracompact modulators and biosensing.

Directly Phase-Modulated Light Source

NASA Astrophysics Data System (ADS)

Yuan, Z. L.; Fröhlich, B.; Lucamarini, M.; Roberts, G. L.; Dynes, J. F.; Shields, A. J.

2016-07-01

The art of imparting information onto a light wave by optical signal modulation is fundamental to all forms of optical communication. Among many schemes, direct modulation of laser diodes stands out as a simple, robust, and cost-effective method. However, the simultaneous changes in intensity, frequency, and phase have prevented its application in the field of secure quantum communication. Here, we propose and experimentally demonstrate a directly phase-modulated light source which overcomes the main disadvantages associated with direct modulation and is suitable for diverse applications such as coherent communications and quantum cryptography. The source separates the tasks of phase preparation and pulse generation between a pair of semiconductor lasers leading to very pure phase states. Moreover, the cavity-enhanced electro-optic effect enables the first example of subvolt half-wave phase modulation at high signal rates. The source is compact, stable, and versatile, and we show its potential to become the standard transmitter for future quantum communication networks based on attenuated laser pulses.

Validity of High School Physic Module With Character Values Using Process Skill Approach In STKIP PGRI West Sumatera

NASA Astrophysics Data System (ADS)

Anaperta, M.; Helendra, H.; Zulva, R.

2018-04-01

This study aims to describe the validity of physics module with Character Oriented Values Using Process Approach Skills at Dynamic Electrical Material in high school physics / MA and SMK. The type of research is development research. The module development model uses the development model proposed by Plomp which consists of (1) preliminary research phase, (2) the prototyping phase, and (3) assessment phase. In this research is done is initial investigation phase and designing. Data collecting technique to know validation is observation and questionnaire. In the initial investigative phase, curriculum analysis, student analysis, and concept analysis were conducted. In the design phase and the realization of module design for SMA / MA and SMK subjects in dynamic electrical materials. After that, the formative evaluation which include self evaluation, prototyping (expert reviews, one-to-one, and small group. At this stage validity is performed. This research data is obtained through the module validation sheet, which then generates a valid module.

Relative sideband amplitudes versus modulation index for common functions using frequency and phase modulation. [for design and testing of communication system

NASA Technical Reports Server (NTRS)

Stocklin, F.

1973-01-01

The equations defining the amplitude of sidebands resulting from either frequency modulation or phase modulation by either square wave, sine wave, sawtooth or triangular modulating functions are presented. Spectral photographs and computer generated tables of modulation index vs. relative sideband amplitudes are also included.

Tc-99 Decontamination From Heat Treated Gaseous Diffusion Membrane -Phase I

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oji, L.; Wilmarth, B.; Restivo, M.

2017-03-13

Uranium gaseous diffusion cascades represent a significant environmental challenge to dismantle, containerize and dispose as low-level radioactive waste. Baseline technologies rely on manual manipulations involving direct access to technetium-contaminated piping and materials. There is a potential to utilize novel thermal decontamination technologies to remove the technetium and allow for on-site disposal of the very large uranium converters. Technetium entered these gaseous diffusion cascades as a hexafluoride complex in the same fashion as uranium. Technetium, as the isotope Tc-99, is an impurity that follows uranium in the first cycle of the Plutonium and Uranium Extraction (PUREX) process. The technetium speciation ormore » exact form in the gas diffusion cascades is not well defined. Several forms of Tc-99 compounds, mostly the fluorinated technetium compounds with varying degrees of volatility have been speculated by the scientific community to be present in these cascades. Therefore, there may be a possibility of using thermal desorption, which is independent of the technetium oxidation states, to perform an in situ removal of the technetium as a volatile species and trap the radionuclide on sorbent traps which could be disposed as low-level waste.« less