Period doubling and other nonlinear phenomena in volcanic earthquakes and tremor

USGS Publications Warehouse

Julian, B.R.

2000-01-01

Evidence of subharmonic period-doubling cascades has recently been recognized in seismograms of volcanic tremor from several volcanoes. This phenomenon occurs only in nonlinear systems, and is the commonest route by which such systems change from periodic to chaotic behavior. It is predicted to occur in a model of volcanic tremor excitation by flow-induced vibration, and it might well also occur in other volcano-seismic source process. If the possibility of period doubling is not taken into account in interpreting spectra of tremor and long-period earthquakes, then low-frequency "sub-harmonic" oscillations may be mis-identified as normal modes of a linear acoustic resonator, leading to errors of an order of magnitude or more in inferred magma-body dimensions. This example illustrates the importance of nonlinear phenomena in attempts to understand volcano-seismic phenomena physically. Linear systems are fundamentally incapable of causing earthquakes or exciting tremor, so nonlinearity is essential to any theory of volcano-seismic phenomena. Nonlinear processes are in many respects qualitatively different from linear ones. A few of their characteristics that might be relevant in volcanoes include the possibility: (1) that damping might increase, rather than decrease, oscillation frequencies; and (2) that these frequencies might be functions of the amplitude of oscillation, so that temporal variations in spectral peak frequencies might not be manifestations of changes of conditions within the magmatic system.

Study on a Multi-Frequency Homotopy Analysis Method for Period-Doubling Solutions of Nonlinear Systems

NASA Astrophysics Data System (ADS)

Fu, H. X.; Qian, Y. H.

In this paper, a modification of homotopy analysis method (HAM) is applied to study the two-degree-of-freedom coupled Duffing system. Firstly, the process of calculating the two-degree-of-freedom coupled Duffing system is presented. Secondly, the single periodic solutions and double periodic solutions are obtained by solving the constructed nonlinear algebraic equations. Finally, comparing the periodic solutions obtained by the multi-frequency homotopy analysis method (MFHAM) and the fourth-order Runge-Kutta method, it is found that the approximate solution agrees well with the numerical solution.

Frequency doubled high-power disk lasers in pulsed and continuous-wave operation

NASA Astrophysics Data System (ADS)

Weiler, Sascha; Hangst, Alexander; Stolzenburg, Christian; Zawischa, Ivo; Sutter, Dirk; Killi, Alexander; Kalfhues, Steffen; Kriegshaeuser, Uwe; Holzer, Marco; Havrilla, David

2012-03-01

The disk laser with multi-kW output power in infrared cw operation is widely used in today's manufacturing, primarily in the automotive industry. The disk technology combines high power (average and/or peak power), excellent beam quality, high efficiency and high reliability with low investment and operating costs. Additionally, the disk laser is ideally suited for frequency conversion due to its polarized output with negligible depolarization losses. Laser light in the green spectral range (~515 nm) can be created with a nonlinear crystal. Pulsed disk lasers with green output of well above 50 W (extracavity doubling) in the ps regime and several hundreds of Watts in the ns regime with intracavity doubling are already commercially available whereas intracavity doubled disk lasers in continuous wave operation with greater than 250 W output are in test phase. In both operating modes (pulsed and cw) the frequency doubled disk laser offers advantages in existing and new applications. Copper welding for example is said to show much higher process reliability with green laser light due to its higher absorption in comparison to the infrared. This improvement has the potential to be very beneficial for the automotive industry's move to electrical vehicles which requires reliable high-volume welding of copper as a major task for electro motors, batteries, etc.

Time vs. Money: A Quantitative Evaluation of Monitoring Frequency vs. Monitoring Duration.

PubMed

McHugh, Thomas E; Kulkarni, Poonam R; Newell, Charles J

2016-09-01

The National Research Council has estimated that over 126,000 contaminated groundwater sites are unlikely to achieve low ug/L clean-up goals in the foreseeable future. At these sites, cost-effective, long-term monitoring schemes are needed in order to understand the long-term changes in contaminant concentrations. Current monitoring optimization schemes rely on site-specific evaluations to optimize groundwater monitoring frequency. However, when using linear regression to estimate the long-term zero-order or first-order contaminant attenuation rate, the effect of monitoring frequency and monitoring duration on the accuracy and confidence for the estimated attenuation rate is not site-specific. For a fixed number of monitoring events, doubling the time between monitoring events (e.g., changing from quarterly monitoring to semi-annual monitoring) will double the accuracy of estimated attenuation rate. For a fixed monitoring frequency (e.g., semi-annual monitoring), increasing the number of monitoring events by 60% will double the accuracy of the estimated attenuation rate. Combining these two factors, doubling the time between monitoring events (e.g., quarterly monitoring to semi-annual monitoring) while decreasing the total number of monitoring events by 38% will result in no change in the accuracy of the estimated attenuation rate. However, the time required to collect this dataset will increase by 25%. Understanding that the trade-off between monitoring frequency and monitoring duration is not site-specific should simplify the process of optimizing groundwater monitoring frequency at contaminated groundwater sites. © 2016 The Authors. Groundwater published by Wiley Periodicals, Inc. on behalf of National Ground Water Association.

Low-cost, smartphone based frequency doubling technology visual field testing using virtual reality (Conference Presentation)

NASA Astrophysics Data System (ADS)

Alawa, Karam A.; Sayed, Mohamed; Arboleda, Alejandro; Durkee, Heather A.; Aguilar, Mariela C.; Lee, Richard K.

2017-02-01

Glaucoma is the leading cause of irreversible blindness worldwide. Due to its wide prevalence, effective screening tools are necessary. The purpose of this project is to design and evaluate a system that enables portable, cost effective, smartphone based visual field screening based on frequency doubling technology. The system is comprised of an Android smartphone to display frequency doubling stimuli and handle processing, a Bluetooth remote for user input, and a virtual reality headset to simulate the exam. The LG Nexus 5 smartphone and BoboVR Z3 virtual reality headset were used for their screen size and lens configuration, respectively. The system is capable of running the C-20, N-30, 24-2, and 30-2 testing patterns. Unlike the existing system, the smartphone FDT tests both eyes concurrently by showing the same background to both eyes but only displaying the stimulus to one eye at a time. Both the Humphrey Zeiss FDT and the smartphone FDT were tested on five subjects without a history of ocular disease with the C-20 testing pattern. The smartphone FDT successfully produced frequency doubling stimuli at the correct spatial and temporal frequency. Subjects could not tell which eye was being tested. All five subjects preferred the smartphone FDT to the Humphrey Zeiss FDT due to comfort and ease of use. The smartphone FDT is a low-cost, portable visual field screening device that can be used as a screening tool for glaucoma.

Bimanual tapping of a syncopated rhythm reveals hemispheric preferences for relative movement frequencies.

PubMed

Pflug, Anja; Gompf, Florian; Kell, Christian Alexander

2017-08-01

In bimanual multifrequency tapping, right-handers commonly use the right hand to tap the relatively higher rate and the left hand to tap the relatively lower rate. This could be due to hemispheric specializations for the processing of relative frequencies. An extension of the double-filtering-by-frequency theory to motor control proposes a left hemispheric specialization for the control of relatively high and a right hemispheric specialization for the control of relatively low tapping rates. We investigated timing variability and rhythmic accentuation in right handers tapping mono- and multifrequent bimanual rhythms to test the predictions of the double-filtering-by-frequency theory. Yet, hemispheric specializations for the processing of relative tapping rates could be masked by a left hemispheric dominance for the control of known sequences. Tapping was thus either performed in an overlearned quadruple meter (tap of the slow rhythm on the first auditory beat) or in a syncopated quadruple meter (tap of the slow rhythm on the fourth auditory beat). Independent of syncopation, the right hand outperformed the left hand in timing accuracy for fast tapping. A left hand timing benefit for slow tapping rates as predicted by the double-filtering-by-frequency theory was only found in the syncopated tapping group. This suggests a right hemisphere preference for the control of slow tapping rates when rhythms are not overlearned. Error rates indicate that overlearned rhythms represent hierarchically structured meters that are controlled by a single timer that could potentially reside in the left hemisphere. Copyright © 2017 Elsevier B.V. All rights reserved.

Investigation about relationships between the symmetries of ferroelectric crystal Ca{sub 0.28}Ba{sub 0.72}Nb{sub 2}O{sub 6} and second-harmonic patterns

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

Xu, Tianxiang; Yu, Haohai, E-mail: haohaiyu@sdu.edu.cn; Zhang, Huaijin, E-mail: huaijinzhang@sdu.edu.cn

2015-08-07

The broadband quasi-phase matching (QPM) process in a uniaxial ferroelectric crystal Ca{sub 0.28}Ba{sub 0.72}Nb{sub 2}O{sub 6} (CBN-28) was demonstrated with the second-harmonic wavelength range from 450 nm to 650 nm, and the relationship between the symmetries of CBN-28 and the second-harmonic patterns was experimentally and theoretically investigated based on the random anti-parallel domains in the crystal and QPM conditions. The dependences of frequency-doubled patterns on the wavelength and anisotropy of the nonlinear crystal were also studied, and the frequency-doubled photons were found to be trapped on circles. By analyzing the light-matter interacting Hamiltonians, the trapping force for second-harmonic photons was found tomore » be centripetal and tunable by the fundamental lasers, and the variation tendencies of the rotational velocity of second-harmonic generation photons could also be predicated. The results indicate that the CBN-28 ferroelectric crystal is a promising nonlinear optical material for the generation of broadband frequency-doubled waves, and the analysis on centripetal force based on the interaction Hamiltonians may provide a novel recognition for the investigation of QPM process to be further studied.« less

Generation of continuous-wave single-frequency 1.5 W 378 nm radiation by frequency doubling of a Ti:sapphire laser.

PubMed

Cha, Yong-Ho; Ko, Kwang-Hoon; Lim, Gwon; Han, Jae-Min; Park, Hyun-Min; Kim, Taek-Soo; Jeong, Do-Young

2010-03-20

We have generated continuous-wave single-frequency 1.5 W 378 nm radiation by frequency doubling a high-power Ti:sapphire laser in an external enhancement cavity. An LBO crystal that is Brewster-cut and antireflection coated on both ends is used for a long-term stable frequency doubling. By optimizing the input coupler's reflectivity, we could generate 1.5 W 378 nm radiation from a 5 W 756 nm Ti:sapphire laser. According to our knowledge, this is the highest CW frequency-doubled power of a Ti:sapphire laser.

Power SiGe Heterojunction Bipolar Transistors (HBTs) Fabricated by Fully Self-Aligned Double Mesa Technology

NASA Technical Reports Server (NTRS)

Lu, Liang-Hung; Mohammadi, Saeed; Ma, Zhen-Qiang; Ponchak, George E.; Alterovitz, Samuel A.; Strohm, Karl M.; Luy, Johann-Friedrich; Downey, Alan (Technical Monitor)

2001-01-01

Multifinger SiGe HBTs have been fabricated using a novel fully self-aligned double-mesa technology. With the novel process technology, a common-emitter 2x2x30 sq micrometer device exhibits high maximum oscillating frequency (f(sub max)) and cut-off frequency (f(sub T)) of 78 and 37 GHz, respectively. In class-A operation, a multifinger device with l0x2x30 sq micrometer emitter is expected to provide an output power of 25.6 dBm with a gain of 10 dB and a maximum power added efficiency (PAE) of 30.33% at 8 GHz.

Modernization of gas-turbine engines with high-frequency induction motors

NASA Astrophysics Data System (ADS)

Abramovich, B. N.; Sychev, Yu A.; Kuznetsov, P. A.

2018-03-01

Main tendencies of growth of electric energy consumption in general and mining industries were analyzed in the paper. A key role of electric drive in this process was designated. A review about advantages and disadvantages of unregulated gearboxes with mechanical units that are commonly used in domestically produced gas-turbine engines was made. This review allows one to propose different gas-turbine engines modernization schemes with the help of PWM-driven high-frequency induction motors. Induction motors with the double rotor winding were examined. A simulation of high-frequency induction motors with double rotor windings in Matlab-Simulink software was carried out based on equivalent circuit parameters. Obtained characteristics of new motors were compared with serially produced analogues. After the simulation, results were implemented in the real prototype.

Surface plasmon dispersion engineering via double-metallic AU/AG layers for nitride light-emitting diodes

DOEpatents

Tansu, Nelson; Zhao, Hongping; Zhang, Jing; Liu, Guangyu

2014-04-01

A double-metallic deposition process is used whereby adjacent layers of different metals are deposited on a substrate. The surface plasmon frequency of a base layer of a first metal is tuned by the surface plasmon frequency of a second layer of a second metal formed thereon. The amount of tuning is dependent upon the thickness of the metallic layers, and thus tuning can be achieved by varying the thicknesses of one or both of the metallic layers. In a preferred embodiment directed to enhanced LED technology in the green spectrum regime, a double-metallic Au/Ag layer comprising a base layer of gold (Au) followed by a second layer of silver (Ag) formed thereon is deposited on top of InGaN/GaN quantum wells (QWs) on a sapphire/GaN substrate.

Specialization of the auditory processing in harbor porpoise, characterized by brain-stem potentials

NASA Astrophysics Data System (ADS)

Bibikov, Nikolay G.

2002-05-01

Brain-stem auditory evoked potentials (BAEPs) were recorded from the head surface of the three awaked harbor porpoises (Phocoena phocoena). Silver disk placed on the skin surface above the vertex bone was used as an active electrode. The experiments were performed at the Karadag biological station (the Crimea peninsula). Clicks and tone bursts were used as stimuli. The temporal and frequency selectivity of the auditory system was estimated using the methods of simultaneous and forward masking. An evident minimum of the BAEPs thresholds was observed in the range of 125-135 kHz, where the main spectral component of species-specific echolocation signal is located. In this frequency range the tonal forward masking demonstrated a strong frequency selectivity. Off-response to such tone bursts was a typical observation. An evident BAEP could be recorded up to the frequencies 190-200 kHz, however, outside the acoustical fovea the frequency selectivity was rather poor. Temporal resolution was estimated by measuring BAER recovery functions for double clicks, double tone bursts, and double noise bursts. The half-time of BAERs recovery was in the range of 0.1-0.2 ms. The data indicate that the porpoise auditory system is strongly adapted to detect ultrasonic closely spaced sounds like species-specific locating signals and echoes.

Double emulsion formation through hierarchical flow-focusing microchannel

NASA Astrophysics Data System (ADS)

Azarmanesh, Milad; Farhadi, Mousa; Azizian, Pooya

2016-03-01

A microfluidic device is presented for creating double emulsions, controlling their sizes and also manipulating encapsulation processes. As a result of three immiscible liquids' interaction using dripping instability, double emulsions can be produced elegantly. Effects of dimensionless numbers are investigated which are Weber number of the inner phase (Wein), Capillary number of the inner droplet (Cain), and Capillary number of the outer droplet (Caout). They affect the formation process, inner and outer droplet size, and separation frequency. Direct numerical simulation of governing equations was done using volume of fluid method and adaptive mesh refinement technique. Two kinds of double emulsion formation, the two-step and the one-step, were simulated in which the thickness of the sheath of double emulsions can be adjusted. Altering each dimensionless number will change detachment location, outer droplet size and droplet formation period. Moreover, the decussate regime of the double-emulsion/empty-droplet is observed in low Wein. This phenomenon can be obtained by adjusting the Wein in which the maximum size of the sheath is discovered. Also, the results show that Cain has significant influence on the outer droplet size in the two-step process, while Caout affects the sheath in the one-step formation considerably.

Phase-sensitive, through-amplification with a double-pumped JPC

NASA Astrophysics Data System (ADS)

Sliwa, K. M.; Hatridge, M.; Frattini, N. E.; Narla, A.; Shankar, S.; Devoret, M. H.

The Josephson Parametric Converter (JPC) is now routinely used as a quantum-limited signal processing device for superconducting qubit experiments. The JPC consists of two modes, the signal and the idler, that are coupled by a ring of Josephson junctions that implements a non-degenerate, three-wave mixing process. This device is conventionally operated as either a phase-preserving parametric amplifier, or a coherent frequency converter, by pumping it at the sum or difference of the signal and idler frequencies, respectively. Here we present a novel double-pumping scheme based on theory by Metelmann and Clerk where a coherent conversion process and a gain process are simultaneously imposed between the signal and idler modes. The interference of these two processes results in a phase-sensitive amplifier with only forward gain, and which breaks the traditional gain-bandwidth limit of parametric amplification. We present results on phase-sensitive amplification with increased bandwidth, and on noise performance and dynamic range that are comparable to the traditional mode of operation. Work supported by ARO, AFOSR, NSF and YINQE.

Line Tunable Ultraviolet Laser

NASA Technical Reports Server (NTRS)

Walsh, Brian M.; Barnes, Norman P.

2004-01-01

An ultraviolet laser is demonstrated using a dual wavelength Nd:YAG oscillator, sum frequency and second harmonic process. Synchronous pulses at 1.052 and 1.319 micrometers are amplified, mixed and subsequently doubled, producing pulses at 0.293 micrometers.

Low frequency noise elimination technique for 24-bit Σ-Δ data acquisition systems.

PubMed

Qu, Shao-Bo; Robert, Olivier; Lognonné, Philippe; Zhou, Ze-Bing; Yang, Shan-Qing

2015-03-01

Low frequency 1/f noise is one of the key limiting factors of high precision measurement instruments. In this paper, digital correlated double sampling is implemented to reduce the offset and low frequency 1/f noise of a data acquisition system with 24-bit sigma delta (Σ-Δ) analog to digital converter (ADC). The input voltage is modulated by cross-coupled switches, which are synchronized to the sampling clock, and converted into digital signal by ADC. By using a proper switch frequency, the unwanted parasitic signal frequencies generated by the switches are avoided. The noise elimination processing is made through the principle of digital correlated double sampling, which is equivalent to a time shifted subtraction for the sampled voltage. The low frequency 1/f noise spectrum density of the data acquisition system is reduced to be flat down to the measurement frequency lower limit, which is about 0.0001 Hz in this paper. The noise spectrum density is eliminated by more than 60 dB at 0.0001 Hz, with a residual noise floor of (9 ± 2) nV/Hz(1/2) which is limited by the intrinsic white noise floor of the ADC above its corner frequency.

Assessment and control design for steam vent noise in an oil refinery.

PubMed

Monazzam, Mohammad Reza; Golmohammadi, Rostam; Nourollahi, Maryam; Momen Bellah Fard, Samaneh

2011-06-13

Noise is one of the most important harmful agents in work environment. Noise pollution in oil refinery industries is related to workers' health. This study aimed to determine the overall noise pollution of an oil refinery operation and its frequency analysis to determine the control plan for a vent noise in these industries. This experimental study performed in control unit of Tehran Oil Refinery in 2008. To determine the noise distributions, environmental noise measurements were carried out by lattice method according to basic information and technical process. The sound pressure level and frequency distribution was measured for each study sources subject separately was performed individually. According to the vent's specification, the measured steam noise characteristics reviewed and compared to the theoretical results of steam noise estimation. Eventually, a double expansion muffler was designed. Data analysis and graphical design were carried out using Excel software. The results of environmental noise measurements indicated that the level of sound pressure was above the national permitted level (85 dB (A)). The Mean level of sound pressure of the studied steam jet was 90.3 dB (L). The results of noise frequency analysis for the steam vents showed that the dominant frequency was 4000 Hz. To obtain 17 dB noise reductions, a double chamber aluminum muffler with 500 mm length and 200 mm diameter consisting pipe drilled was designed. The characteristics of steam vent noise were separated from other sources, a double expansion muffler was designed using a new method based on the level of steam noise, and principle sound frequency, a double expansion muffler was designed.

Frequency domain measurement systems

NASA Technical Reports Server (NTRS)

Eischer, M. C.

1978-01-01

Stable frequency sources and signal processing blocks were characterized by their noise spectra, both discrete and random, in the frequency domain. Conventional measures are outlined, and systems for performing the measurements are described. Broad coverage of system configurations which were found useful is given. Their functioning and areas of application are discussed briefly. Particular attention is given to some of the potential error sources in the measurement procedures, system configurations, double-balanced-mixer-phase-detectors, and application of measuring instruments.

Micro-Welding of Copper Plate by Frequency Doubled Diode Pumped Pulsed Nd:YAG Laser

NASA Astrophysics Data System (ADS)

Nakashiba, Shin-Ichi; Okamoto, Yasuhiro; Sakagawa, Tomokazu; Takai, Sunao; Okada, Akira

A pulsed laser of 532 nm wavelength with ms range pulse duration was newly developed by second harmonic generation of diode pumped pulsed Nd:YAG laser. High electro-optical conversion efficiency more than 13% could be achieved, and 1.5 kW peak power green laser pulse was put in optical fiber of 100 μm in diameter. In micro- welding of 1.0 mm thickness copper plate, a keyhole welding was successfully performed by 1.0 kW peak power at spot diameter less than 200 μm. The frequency doubled pulsed laser improved the processing efficiency of copper welding, and narrow and deep weld bead was stably obtained.

Numerical Comparison of Active Acoustic and Structural Noise Control in a Stiffened Double Wall Cylinder

NASA Technical Reports Server (NTRS)

Grosveld, Ferdinand W.

1996-01-01

The active acoustic and structural noise control characteristics of a double wall cylinder with and without ring stiffeners were numerically evaluated. An exterior monopole was assumed to acoustically excite the outside of the double wall cylinder at an acoustic cavity resonance frequency. Structural modal vibration properties of the inner and outer shells were analyzed by post-processing the results from a finite element analysis. A boundary element approach was used to calculate the acoustic cavity response and the coupled structural-acoustic interaction. In the frequency region of interest, below 500 Hz, all structural resonant modes were found to be acoustically slow and the nonresonant modal response to be dominant. Active sound transmission control was achieved by control forces applied to the inner or outer shell, or acoustic control monopoles placed just outside the inner or outer shell. A least mean square technique was used to minimize the interior sound pressures at the nodes of a data recovery mesh. Results showed that single acoustic control monopoles placed just outside the inner or outer shells resulted in better sound transmission control than six distributed point forces applied to either one of the shells. Adding stiffeners to the double wall structure constrained the modal vibrations of the shells, making the double wall stiffer with associated higher modal frequencies. Active noise control obtained for the stiffened double wall configurations was less than for the unstiffened cylinder. In all cases, the acoustic control monopoles controlled the sound transmission into the interior better than the structural control forces.

Independent processing of changes in auditory single features and feature conjunctions in humans as indexed by the mismatch negativity.

PubMed

Takegata, R; Paavilainen, P; Näätänen, R; Winkler, I

1999-05-07

The mismatch negativity (MMN), an event-related potential component of the EEG, is elicited by violations of auditory regularities In the present study, the stimulus blocks contained two types of standard tones, differing from each other in frequency and intensity. MMNs were recorded to three different types of deviant stimuli: (a) feature deviants, differing from standards in their perceived locus of origin; (b) conjunction deviants, having the frequency of one of the standards and the intensity of the other; (c) double deviants, differing from standards in both (a) and (b). The MMN to double deviants was similar to the sum of the MMNs to feature and conjunction deviants. This result indicates that changes in simple stimulus features and conjunction of features are processed independently by the automatic sound change detection system indexed by MMN.

Modelling of double air-bridged structured inductor implemented by a GaAs integrated passive device manufacturing process

NASA Astrophysics Data System (ADS)

Li, Yang; Yao, Zhao; Zhang, Chun-Wei; Fu, Xiao-Qian; Li, Zhi-Ming; Li, Nian-Qiang; Wang, Cong

2017-05-01

In order to provide excellent performance and show the development of a complicated structure in a module and system, this paper presents a double air-bridge-structured symmetrical differential inductor based on integrated passive device technology. Corresponding to the proposed complicated structure, a new manufacturing process fabricated on a high-resistivity GaAs substrate is described in detail. Frequency-independent physical models are presented with lump elements and the results of skin effect-based measurements. Finally, some key features of the inductor are compared; good agreement between the measurements and modeled circuit fully verifies the validity of the proposed modeling approach. Meanwhile, we also present a comparison of different coil turns for inductor performance. The proposed work can provide a good solution for the design, fabrication, modeling, and practical application of radio-frequency modules and systems.

Comparison of the results of refractometric measurements in the process of diffusion, obtained by means of the backgroundoriented schlieren method and the holographic interferometry method

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

Kraiskii, A V; Mironova, T V

2015-08-31

The results of the study of interdiffusion of two liquids, obtained using the holographic recording scheme with a nonstationary reference wave with the frequency linearly varying in space and time are compared with the results of correlation processing of digital photographs, made with a random background screen. The spatio-temporal behaviour of the signal in four basic representations ('space – temporal frequency', 'space – time', 'spatial frequency – temporal frequency' and 'spatial frequency – time') is found in the holographic experiment and calculated (in the appropriate coordinates) based on the background-oriented schlieren method. Practical coincidence of the results of the correlationmore » analysis and the holographic double-exposure interferometry is demonstrated. (interferometry)« less

A high power, continuous-wave, single-frequency fiber amplifier at 1091 nm and frequency doubling to 545.5 nm

NASA Astrophysics Data System (ADS)

Stappel, M.; Steinborn, R.; Kolbe, D.; Walz, J.

2013-07-01

We present a high power single-frequency ytterbium fiber amplifier system with an output power of 30 W at 1091 nm. The amplifier system consists of two stages, a preamplifier stage in which amplified spontaneous emission is efficiently suppressed (>40 dB) and a high power amplifier with an efficiency of 52%. Two different approaches to frequency doubling are compared. We achieve 8.6 W at 545.5 nm by single-pass frequency doubling in a MgO-doped periodically poled stoichiometric LiTaO3 crystal and up to 19.3 W at 545.5 nm by frequency doubling with a lithium-triborate crystal in an external enhancement cavity.

Local oscillator induced degradation of medium-term stability in passive atomic frequency standards

NASA Technical Reports Server (NTRS)

Dick, G. John; Prestage, John D.; Greenhall, Charles A.; Maleki, Lute

1990-01-01

As the performance of passive atomic frequency standards improves, a new limitation is encountered due to frequency fluctuations in an ancillary local oscillator (L.O.). The effect is due to time variation in the gain of the feedback which compensates L.O. frequency fluctuations. The high performance promised by new microwave and optical trapped ion standards may be severely compromised by this effect. Researchers present an analysis of this performance limitation for the case of sequentially interrogated standards. The time dependence of the sensitivity of the interrogation process to L.O. frequency fluctuations is evaluated for single-pulse and double-pulse Ramsey RF interrogation and for amplitude modulated pulses. The effect of these various time dependencies on performance of the standard is calculated for an L.O. with frequency fluctuations showing a typical 1/f spectral density. A limiting 1/sq. root gamma dependent deviation of frequency fluctuations is calculated as a function of pulse lengths, dead time, and pulse overlap. Researchers also present conceptual and hardware-oriented solutions to this problem which achieve a much more nearly constant sensitivity to L.O. fluctuations. Solutions involve use of double-pulse interrogation; alternate interrogation of multiple traps so that the dead time of one trap can be covered by operation of the other; and the use of double-pulse interrogation for two traps, so that during the time of the RF pulses, the increasing sensitivity of one trap tends to compensate for the decreasing sensitivity of the other. A solution making use of amplified-modulated pulses is also presented which shows nominally zero time variation.

Importance of double-pole CFS-PML for broad-band seismic wave simulation and optimal parameters selection

NASA Astrophysics Data System (ADS)

Feng, Haike; Zhang, Wei; Zhang, Jie; Chen, Xiaofei

2017-05-01

The perfectly matched layer (PML) is an efficient absorbing technique for numerical wave simulation. The complex frequency-shifted PML (CFS-PML) introduces two additional parameters in the stretching function to make the absorption frequency dependent. This can help to suppress converted evanescent waves from near grazing incident waves, but does not efficiently absorb low-frequency waves below the cut-off frequency. To absorb both the evanescent wave and the low-frequency wave, the double-pole CFS-PML having two poles in the coordinate stretching function was developed in computational electromagnetism. Several studies have investigated the performance of the double-pole CFS-PML for seismic wave simulations in the case of a narrowband seismic wavelet and did not find significant difference comparing to the CFS-PML. Another difficulty to apply the double-pole CFS-PML for real problems is that a practical strategy to set optimal parameter values has not been established. In this work, we study the performance of the double-pole CFS-PML for broad-band seismic wave simulation. We find that when the maximum to minimum frequency ratio is larger than 16, the CFS-PML will either fail to suppress the converted evanescent waves for grazing incident waves, or produce visible low-frequency reflection, depending on the value of α. In contrast, the double-pole CFS-PML can simultaneously suppress the converted evanescent waves and avoid low-frequency reflections with proper parameter values. We analyse the different roles of the double-pole CFS-PML parameters and propose optimal selections of these parameters. Numerical tests show that the double-pole CFS-PML with the optimal parameters can generate satisfactory results for broad-band seismic wave simulations.

Second-harmonic generation of a dual-frequency laser in a MgO:PPLN crystal.

PubMed

Kang, Ying; Yang, Suhui; Brunel, Marc; Cheng, Lijun; Zhao, Changming; Zhang, Haiyang

2017-04-10

A dual-frequency CW laser at a wavelength of 1.064 μm is frequency doubled in a MgO:PPLN nonlinear crystal. The fundamental dual-frequency laser has a tunable beat note from 125 MHz to 175 MHz. A laser-diode pumped fiber amplifier is used to amplify the dual-frequency fundamental output to a maximum power of 50 W before frequency doubling. The maximum output power of the green light is 1.75 W when the input fundamental power is 12 W, corresponding to a frequency doubling efficiency of 14.6%. After frequency doubling, green light with modulation frequencies in two bands from 125 MHz to 175 MHz and from 250 MHz to 350 MHz is achieved simultaneously. The relative intensities of the beat notes at the two bands can be adjusted by changing the relative intensities at different frequencies of the fundamental light. The spectral width and frequency stabilities of the beat notes in fundamental wave and green light are also measured, respectively. The modulated green light has potential applications in underwater ranging, communication, and imaging.

Dual-wavelength green laser with a 4.5 THz frequency difference based on self-frequency- doubling in Nd3+ -doped aperiodically poled lithium niobate.

PubMed

Maestre, H; Torregrosa, A J; Fernández-Pousa, C R; Rico, M L; Capmany, J

2008-05-01

We report a dual-wavelength continuous-wave laser at 542.4 and 546.8 nm based on an Nd(3+)-doped aperiodically poled lithium niobate crystal. Two fundamental infrared (IR) wavelengths at 1084.8 and 1093.6 nm are simultaneously oscillated and self-frequency-doubled to green. The aperiodic domain distribution patterned in the crystal allows for quasi-phase matched self-frequency-doubling of both IR fundamentals while avoiding their sum-frequency mixing.

The occurrence of double strand DNA breaks is not the sole condition for meiotic crossing over in Drosophila melanogaster.

PubMed

Portin, P; Rantanen, M

2000-01-01

Analysis of the interchromosomal effects of In(2L + 2R)Cy, In(3L + 3R)LVM and their joint effect on the frequencies of single and double crossovers in the cv-v-f region of the X chromosome as well as interference showed that both inversions, occurring separately, increased the frequency of single as well as double crossovers and the coefficient of coincidence. However, when the inversions occurred together the frequencies of single crossovers no longer increased, but the frequency of double crossovers, as well as the coefficient of coincidence did increase. These results indicate firstly that the interchromosomal effects influence some precondition of exchange, but that this precondition is not an occurrence of double strand DNA breaks. Thus, the occurrence of double strand DNA breaks is not the sole condition for crossing over in Drosophila melanogaster.

Paediatric nurses' adherence to the double-checking process during medication administration in a children's hospital: an observational study.

PubMed

Alsulami, Zayed; Choonara, Imti; Conroy, Sharon

2014-06-01

To evaluate how closely double-checking policies are followed by nurses in paediatric areas and also to identify the types, frequency and rates of medication administration errors that occur despite the double-checking process. Double-checking by two nurses is an intervention used in many UK hospitals to prevent or reduce medication administration errors. There is, however, insufficient evidence to either support or refute the practice of double-checking in terms of medication error risk reduction. Prospective observational study. This was a prospective observational study of paediatric nurses' adherence to the double-checking process for medication administration from April-July 2012. Drug dose administration events (n = 2000) were observed. Independent drug dose calculation, rate of administering intravenous bolus drugs and labelling of flush syringes were the steps with lowest adherence rates. Drug dose calculation was only double-checked independently in 591 (30%) drug administrations. There was a statistically significant difference in nurses' adherence rate to the double-checking steps between weekdays and weekends in nine of the 15 evaluated steps. Medication administration errors (n = 191) or deviations from policy were observed, at a rate of 9·6% of drug administrations. These included 64 drug doses, which were left for parents to administer without nurse observation. There was variation between paediatric nurses' adherence to double-checking steps during medication administration. The most frequent type of administration errors or deviation from policy involved the medicine being given to the parents to administer to the child when the nurse was not present. © 2013 John Wiley & Sons Ltd.

Improvement in transmission loss of aircraft double wall with resonators

NASA Astrophysics Data System (ADS)

Sun, Jincai; Shi, Liming; Ye, Xining

1991-08-01

A little volume low frequency resonator applicable to double-wall configuration of propeller-driven aircraft was designed on the basis of the principle of Helmholtz resonator. The normal incidence absorption coefficient of the various single resonator has been measured. The agreement between theoretical and experimental results is encouraging. An array of resonators whose resonant frequency at 85 Hz and 160 Hz, respectively, are installed between aircraft double-panel, and it has been shown that transmission loss of the double wall structure with resonators improve 4 dB and 6.5 dB in 1/3rd octave bandwidth at 80 Hz and 160 Hz center frequency, respectively, and 5 dB and 7 dB at resonant frequencies, compared with that of the double wall configuration without resonators.

Automatic auditory processing deficits in schizophrenia and clinical high-risk patients: forecasting psychosis risk with mismatch negativity.

PubMed

Perez, Veronica B; Woods, Scott W; Roach, Brian J; Ford, Judith M; McGlashan, Thomas H; Srihari, Vinod H; Mathalon, Daniel H

2014-03-15

Only about one third of patients at high risk for psychosis based on current clinical criteria convert to a psychotic disorder within a 2.5-year follow-up period. Targeting clinical high-risk (CHR) individuals for preventive interventions could expose many to unnecessary treatments, underscoring the need to enhance predictive accuracy with nonclinical measures. Candidate measures include event-related potential components with established sensitivity to schizophrenia. Here, we examined the mismatch negativity (MMN) component of the event-related potential elicited automatically by auditory deviance in CHR and early illness schizophrenia (ESZ) patients. We also examined whether MMN predicted subsequent conversion to psychosis in CHR patients. Mismatch negativity to auditory deviants (duration, frequency, and duration + frequency double deviant) was assessed in 44 healthy control subjects, 19 ESZ, and 38 CHR patients. Within CHR patients, 15 converters to psychosis were compared with 16 nonconverters with at least 12 months of clinical follow-up. Hierarchical Cox regression examined the ability of MMN to predict time to psychosis onset in CHR patients. Irrespective of deviant type, MMN was significantly reduced in ESZ and CHR patients relative to healthy control subjects and in CHR converters relative to nonconverters. Mismatch negativity did not significantly differentiate ESZ and CHR patients. The duration + frequency double deviant MMN, but not the single deviant MMNs, significantly predicted the time to psychosis onset in CHR patients. Neurophysiological mechanisms underlying automatic processing of auditory deviance, as reflected by the duration + frequency double deviant MMN, are compromised before psychosis onset and can enhance the prediction of psychosis risk among CHR patients. Copyright © 2014 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

Study of working principle and thermal balance process of a double longitudinal-mode He-Ne laser

NASA Astrophysics Data System (ADS)

Wang, Li-qiang

2009-07-01

A double longitudinal mode He-Ne laser with frequency stabilization is proposed. Compared with general methods, such as Lamb dip, Zeeman splitting and molecule saturation absorption method, this design has some advantages, such as no piezocrystal or magnetic field, a short frequency-stabilized time, lower cost, and higher frequency stability and reproducibility. The metal wire is uniformly wrapped on the discharge tube of the laser. When the metal wire is heated up, the resonant cavity changes with the temperature field around the discharge tube to make the frequency of the laser to be tuned. The polarizations of the two longitudinal modes from the laser must be orthogonal. The parallelly polarized light and the vertically polarized light compete with each other, i. e., the parallelly polarized light generates a larger output power, while, the vertically polarized light correspondingly generates a smaller one, but an equal value is found at the reference frequencies by automatically adjusting the length of the resonant cavity, due to change of the temperature in the discharge tube. Consequently the frequencies of the laser are stabilized. In my experiment, an intracavity He-Ne laser whose length of the resonant cavity is larger than 50mm and smaller than 300mm is selected for the double longitudinal-mode laser. Influence factors of frequency stability of this laser is only change of the length of the resonant cavity. The laser includes three stages: mode hopping, transition stage, and modes stability from startup to laser stability. When this laser is in modes stability, the waveform of heating metal wire is observed to a pulse whose duty is almost 50%, and thermal balances of the resonant cavity mainly rely on discharge tube.

Wavelength-resolved emission spectroscopy of the alkoxy and alkylthio radicals in a supersonic jet

NASA Technical Reports Server (NTRS)

Misra, Prabhakar; Zhu, Xinming; Hsueh, Ching-Yu; Kamal, Mohammed M.

1993-01-01

Wavelength-resolved emission spectra of methoxy (CH3O) and methylthio (CH3S) radicals have been obtained in a supersonic jet environment with a resolution of 0.3 nm by dispersing the total laser-induced fluorescence with a 0.6 m monochromator. A detailed analysis of the single vibronic level dispersed fluorescence spectra yields the following vibrational frequencies for CH3O in the X(2)E state; nu(sub 1 double prime) = 2953/cm, nu(sub 2 double prime) = 1375/cm, nu(sub 3 double prime) = 1062/cm, nu(sub 4 double prime) = 2869/cm, nu(sub 5 double prime) = 1528/cm and nu(sub 6 double prime) = 688/cm. A similar analysis of the wavelength-resolved emission spectra of CH3S provides the following ground state vibrational frequencies: nu(sub 2 double prime) = 1329/cm, nu(sub 3 double prime) = 739/cm and nu(sub 6 double prime) = 601/cm. An experimental uncertainty of 20/cm is estimated for the assigned frequencies.

Fabrication and analysis of radiofrequency MEMS series capacitive single-pole double-throw switch

NASA Astrophysics Data System (ADS)

Bansal, Deepak; Bajpai, Anuroop; Kumar, Prem; Kaur, Maninder; Rangra, Kamaljit

2016-10-01

A compact radiofrequency (RF) MEMS single-pole double-throw (SPDT) switch based on series capacitive configuration is proposed. The critical process parameters are analyzed to improve the fabrication process. A technique of cold-hot thermal shock for lift-off method is explored. The residual stress in the structure is quantified by lancet test structures that come out to be 51 MPa. Effect of residual stress on actuation voltage is explored, which changes its value from 24 to 22 V. Resonance frequency and switching speed of the switch are 11 kHz and 44 μs, respectively, measured using laser Doppler vibrometer. Measured bandwidth of the SPDT switch is 20 GHz (5 to 25 GHz), which is verified with finite element method simulations in high frequency structure simulator©; and an equivalent LCR circuit in advanced design system©;. Insertion loss of the switch lies in -0.1 to -0.5 dB with isolation better than -20 dB for the above-mentioned bandwidth.

Characterization of the Electric Double Layer Formation Dynamics of a Metal/Ionic Liquid/Metal Structure.

PubMed

Schmidt, Elliot; Shi, Sha; Ruden, P Paul; Frisbie, C Daniel

2016-06-15

Although ionic liquids (ILs) have been used extensively in recent years as a high-capacitance "dielectric" in electric double layer transistors, the dynamics of the double layer formation have remained relatively unexplored. Better understanding of the dynamics and relaxation processes involved in electric double layer formation will guide device optimization, particularly with regard to switching speed. In this paper, we explore the dynamical characteristics of an IL in a metal/ionic liquid/metal (M/IL/M) capacitor. In particular, we examine a Au/IL/Au structure where the IL is 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate. The experiments consist of frequency-dependent impedance measurements and time-dependent current vs voltage measurements for applied linear voltage ramps and abrupt voltage steps. The parameters of an equivalent circuit model are determined by fits to the impedance vs frequency data and subsequently verified by calculating the current vs voltage characteristics for the applied potential profiles. The data analysis indicates that the dynamics of the structure are characterized by a wide distribution of relaxation times spanning the range of less than microseconds to longer than seconds. Possible causes for these time scales are discussed.

Passive mode-locking of a diode-pumped Nd:YVO(4) laser by intracavity SHG in PPKTP.

PubMed

Iliev, Hristo; Chuchumishev, Danail; Buchvarov, Ivan; Petrov, Valentin

2010-03-15

Experimental results on passive mode-locking of a Nd:YVO(4) laser using intracavity frequency doubling in periodically poled KTP (PPKTP) crystal are reported. Both, negative cascaded chi((2)) lensing and frequency doubling nonlinear mirror (FDNLM) are exploited for the laser mode-locking. The FDNLM based on intensity dependent reflection in the laser cavity ensures self-starting and self-sustaining mode-locking while the cascaded chi((2)) lens process contributes to substantial pulse shortening. This hybrid technique enables generation of stable trains of pulses at high-average output power with several picoseconds pulse width. The pulse repetition rate of the laser is 117 MHz with average output power ranging from 0.5 to 3.1 W and pulse duration from 2.9 to 5.2 ps.

Characterizing Accreting Double White Dwarf Binaries with the Laser Interferometer Space Antenna and Gaia

NASA Astrophysics Data System (ADS)

Breivik, Katelyn; Kremer, Kyle; Bueno, Michael; Larson, Shane L.; Coughlin, Scott; Kalogera, Vassiliki

2018-02-01

We demonstrate a method to fully characterize mass-transferring double white dwarf (DWD) systems with a helium-rich (He) white dwarf (WD) donor based on the mass–radius (M–R) relationship for He WDs. Using a simulated Galactic population of DWDs, we show that donor and accretor masses can be inferred for up to ∼60 systems observed by both Laser Interferometer Space Antenna (LISA) and Gaia. Half of these systems will have mass constraints {{Δ }} {M}{{D}} ≲ 0.2 {M}ȯ and {{Δ }} {M}{{A}} ≲ 2.3 {M}ȯ . We also show how the orbital frequency evolution due to astrophysical processes and gravitational radiation can be decoupled from the total orbital frequency evolution for up to ∼50 of these systems.

Stable continuous-wave single-frequency Nd:YAG blue laser at 473 nm considering the influence of the energy-transfer upconversion.

PubMed

Wang, Yaoting; Liu, Jianli; Liu, Qin; Li, Yuanji; Zhang, Kuanshou

2010-06-07

We report a continuous-wave (cw) single frequency Nd:YAG blue laser at 473 nm end-pumped by a laser diode. A ring laser resonator was designed, the frequency doubling efficiency and the length of nonlinear crystal were optimized based on the investigation of the influence of the frequency doubling efficiency on the thermal lensing effect induced by energy-transfer upconversion. By intracavity frequency doubling with PPKTP crystal, an output power of 1 W all-solid-state cw blue laser of single-frequency operation was achieved. The stability of the blue output power was better than +/- 1.8% in the given four hours.

Phase-locked bifrequency Raman lasing in a double-Λ system

NASA Astrophysics Data System (ADS)

Alaeian, Hadiseh; Shahriar, M. S.

2018-05-01

We show that it is possible to realize simultaneous Raman lasing at two different frequencies using a double-Λ system pumped by a bifrequency field. The bifrequency Raman lasers are phase-locked to one another and the beat-frequency matches the energy difference between the two metastable ground states. Akin to a conventional Raman laser, the bifrequency Raman lasers are expected to be subluminal. As such, these are expected to be highly stable against perturbations in cavity length and have quantum noise limited linewidths that are far below that of a conventional laser. Because of these properties, the bifrequency Raman lasers may find important applications in precision metrology, including atomic interferometry and magnetometry. The phase-locked Raman laser pair also represent a manifestation of lasing without inversion, albeit in a configuration that produces a pair of nondegenerate lasers simultaneously. This feature may enable lasing without inversion in frequency regimes not accessible using previous techniques of lasing without inversion. To elucidate the behavior of this laser pair, we develop an analytical model that describes the stimulated Raman interaction in a double-Λ system using an effective two-level transition. The approximation is valid as long as the excited states adiabatically follow the ground states, as verified by numerical simulations. The effective model is used to identify the optimal operating conditions for the bifrequency Raman lasing process. This model may also prove useful in other potential applications of the double-Λ system, including generation of squeezed light and spatial solitons.

Heat pump processes induced by laser radiation

NASA Technical Reports Server (NTRS)

Garbuny, M.; Henningsen, T.

1980-01-01

A carbon dioxide laser system was constructed for the demonstration of heat pump processes induced by laser radiation. The system consisted of a frequency doubling stage, a gas reaction cell with its vacuum and high purity gas supply system, and provisions to measure the temperature changes by pressure, or alternatively, by density changes. The theoretical considerations for the choice of designs and components are dicussed.

Study of noise reduction characteristics of double-wall panels

NASA Technical Reports Server (NTRS)

Navaneethan, R.; Quayle, B.; Stevenson, S.; Graham, M.

1983-01-01

The noise reduction characteristics of general aviation type, flat, double-wall structures were investigated. The experimental study was carried out on 20-by-20 inch panels with an exposed area of 18 by 18 inches. A frequency range from 20 to 5000 Hz was covered. The experimental results, in general, follow the expected trends. At low frequencies the double-wall structures are no better than the single-wall structures. However, for depths normally used in the general aviation industry, the double-wall panels are very attractive. The graphite-spoxy skin panels have higher noise reduction at very low frequencies ( 100 Hz) than the Kevlar skin panels. But the aluminum panels have higher noise reduction in the high frequency region, due to their greater mass. Use of fiberglass insulation is not effective in the low frequency region, and at times it is even negative. But the insulation is effective in the high-frequency region. The theoretical model for predicting the transmission loss of these multilayered panels is also discussed.

Study of noise reduction characteristics of double-wall panels

NASA Astrophysics Data System (ADS)

Navaneethan, R.; Quayle, B.; Stevenson, S.; Graham, M.

1983-05-01

The noise reduction characteristics of general aviation type, flat, double-wall structures were investigated. The experimental study was carried out on 20-by-20 inch panels with an exposed area of 18 by 18 inches. A frequency range from 20 to 5000 Hz was covered. The experimental results, in general, follow the expected trends. At low frequencies the double-wall structures are no better than the single-wall structures. However, for depths normally used in the general aviation industry, the double-wall panels are very attractive. The graphite-spoxy skin panels have higher noise reduction at very low frequencies ( 100 Hz) than the Kevlar skin panels. But the aluminum panels have higher noise reduction in the high frequency region, due to their greater mass. Use of fiberglass insulation is not effective in the low frequency region, and at times it is even negative. But the insulation is effective in the high-frequency region. The theoretical model for predicting the transmission loss of these multilayered panels is also discussed.

Miniature fiber-optic multiphoton microscopy system using frequency-doubled femtosecond Er-doped fiber laser

PubMed Central

Huang, Lin; Mills, Arthur K.; Zhao, Yuan; Jones, David J.; Tang, Shuo

2016-01-01

We report on a miniature fiber-optic multiphoton microscopy (MPM) system based on a frequency-doubled femtosecond Er-doped fiber laser. The femtosecond pulses from the laser source are delivered to the miniature fiber-optic probe at 1.58 µm wavelength, where a standard single mode fiber is used for delivery without the need of free-space dispersion compensation components. The beam is frequency-doubled inside the probe by a periodically poled MgO:LiNbO3 crystal. Frequency-doubled pulses at 786 nm with a maximum power of 80 mW and a pulsewidth of 150 fs are obtained and applied to excite intrinsic signals from tissues. A MEMS scanner, a miniature objective, and a multimode collection fiber are further used to make the probe compact. The miniature fiber-optic MPM system is highly portable and robust. Ex vivo multiphoton imaging of mammalian skins demonstrates the capability of the system in imaging biological tissues. The results show that the miniature fiber-optic MPM system using frequency-doubled femtosecond fiber laser can potentially bring the MPM imaging for clinical applications. PMID:27231633

The abundance of homoeologue transcripts is disrupted by hybridization and is partially restored by genome doubling in synthetic hexaploid wheat.

PubMed

Hao, Ming; Li, Aili; Shi, Tongwei; Luo, Jiangtao; Zhang, Lianquan; Zhang, Xuechuan; Ning, Shunzong; Yuan, Zhongwei; Zeng, Deying; Kong, Xingchen; Li, Xiaolong; Zheng, Hongkun; Lan, Xiujin; Zhang, Huaigang; Zheng, Youliang; Mao, Long; Liu, Dengcai

2017-02-10

The formation of an allopolyploid is a two step process, comprising an initial wide hybridization event, which is later followed by a whole genome doubling. Both processes can affect the transcription of homoeologues. Here, RNA-Seq was used to obtain the genome-wide leaf transcriptome of two independent Triticum turgidum × Aegilops tauschii allotriploids (F1), along with their spontaneous allohexaploids (S1) and their parental lines. The resulting sequence data were then used to characterize variation in homoeologue transcript abundance. The hybridization event strongly down-regulated D-subgenome homoeologues, but this effect was in many cases reversed by whole genome doubling. The suppression of D-subgenome homoeologue transcription resulted in a marked frequency of parental transcription level dominance, especially with respect to genes encoding proteins involved in photosynthesis. Singletons (genes where no homoeologues were present) were frequently transcribed at both the allotriploid and allohexaploid plants. The implication is that whole genome doubling helps to overcome the phenotypic weakness of the allotriploid, restoring a more favourable gene dosage in genes experiencing transcription level dominance in hexaploid wheat.

Microwave photonic filter using multiwavelength Brillouin-erbium fiber laser with double-Brillouin-frequency shift

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

Loh, K. K.; Yeo, K. S.; Shee, Y. G.

2015-04-24

A microwave photonic filter based on double-Brillouin-frequency spaced multiwavelength Brillouin-erbium fiber laser (BEFL) is experimentally demonstrated. The filter selectivity can be easily adjusted by tuning and apodizing the optical taps generated from the multiwavelength BEFL. Reconfiguration of different frequency responses are demonstrated.

A double expansion method for the frequency response of finite-length beams with periodic parameters

NASA Astrophysics Data System (ADS)

Ying, Z. G.; Ni, Y. Q.

2017-03-01

A double expansion method for the frequency response of finite-length beams with periodic distribution parameters is proposed. The vibration response of the beam with spatial periodic parameters under harmonic excitations is studied. The frequency response of the periodic beam is the function of parametric period and then can be expressed by the series with the product of periodic and non-periodic functions. The procedure of the double expansion method includes the following two main steps: first, the frequency response function and periodic parameters are expanded by using identical periodic functions based on the extension of the Floquet-Bloch theorem, and the period-parametric differential equation for the frequency response is converted into a series of linear differential equations with constant coefficients; second, the solutions to the linear differential equations are expanded by using modal functions which satisfy the boundary conditions, and the linear differential equations are converted into algebraic equations according to the Galerkin method. The expansion coefficients are obtained by solving the algebraic equations and then the frequency response function is finally determined. The proposed double expansion method can uncouple the effects of the periodic expansion and modal expansion so that the expansion terms are determined respectively. The modal number considered in the second expansion can be reduced remarkably in comparison with the direct expansion method. The proposed double expansion method can be extended and applied to the other structures with periodic distribution parameters for dynamics analysis. Numerical results on the frequency response of the finite-length periodic beam with various parametric wave numbers and wave amplitude ratios are given to illustrate the effective application of the proposed method and the new frequency response characteristics, including the parameter-excited modal resonance, doubling-peak frequency response and remarkable reduction of the maximum frequency response for certain parametric wave number and wave amplitude. The results have the potential application to structural vibration control.

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.

Nanoelectronics and Plasma Processing---The Next 15 Years and Beyond

NASA Astrophysics Data System (ADS)

Lieberman, Michael A.

2006-10-01

The number of transistors per chip has doubled every 2 years since 1959, and this doubling will continue over the next 15 years as transistor sizes shrink. There has been a 25 million-fold decrease in cost for the same performance, and in 15 years a desktop computer will be hundreds of times more powerful than one today. Transistors now have 37 nm (120 atoms) gate lengths and 1.5 nm (5 atoms) gate oxide thicknesses. The smallest working transistor has a 5 nm (17 atoms) gate length, close to the limiting gate length, from simulations, of about 4 nm. Plasma discharges are used to fabricate hundreds of billions of these nano-size transistors on a silicon wafer. These discharges have evolved from a first generation of ``low density'' reactors capacitively driven by a single source, to a second generation of ``high density'' reactors (inductive and electron cyclotron resonance) having two rf power sources, in order to control independently the ion flux and ion bombarding energy to the substrate. A third generation of ``moderate density'' reactors, driven capacitively by one high and one low frequency rf source, is now widely used. Recently, triple frequency and combined dc/dual frequency discharges have been investigated, to further control processing characteristics, such as ion energy distributions, uniformity, and plasma etch selectivities. There are many interesting physics issues associated with these discharges, including stochastic heating of discharge electrons by dual frequency sheaths, nonlinear frequency interactions, powers supplied by the multi-frequency sources, and electromagnetic effects such as standing waves and skin effects. Beyond the 4 nm transistor limit lies a decade of further performance improvements for conventional nanoelectronics, and beyond that, a dimly-seen future of spintronics, single-electron transistors, cross-bar latches, and molecular electronics.

All-solid-state continuous-wave frequency doubling Nd:LuVO4/LBO laser with 2.17 W output power at 543 nm

NASA Astrophysics Data System (ADS)

Li, B.; Zhao, L.; Zhang, Y. B.; Zheng, Q.; Zhao, Y.; Yao, Y.

2013-03-01

Efficient and compact green-yellow laser output at 543 nm is generated by intracavity frequency doubling of a CW diode-pumped Nd:LuVO4 laser at 1086 nm under the condition of suppressing the higher gain transition near 1064 nm. With 16 W of diode pump power and the frequency-doubling crystal LBO, as high as 2.17 W of CW output power at 543 nm is achieved, corresponding to an optical-to-optical conversion efficiency of 13.6% and the output power stability over 8 hours is better than 2.86%. To the best of our knowledge, this is the highest watt-level laser at 543 nm generated by intracavity frequency doubling of a diode pumped Nd:LuVO4 laser at 1086 nm.

Period doubling induced by thermal noise amplification in genetic circuits

PubMed Central

Ruocco, G.; Fratalocchi, A.

2014-01-01

Rhythms of life are dictated by oscillations, which take place in a wide rage of biological scales. In bacteria, for example, oscillations have been proven to control many fundamental processes, ranging from gene expression to cell divisions. In genetic circuits, oscillations originate from elemental block such as autorepressors and toggle switches, which produce robust and noise-free cycles with well defined frequency. In some circumstances, the oscillation period of biological functions may double, thus generating bistable behaviors whose ultimate origin is at the basis of intense investigations. Motivated by brain studies, we here study an “elemental” genetic circuit, where a simple nonlinear process interacts with a noisy environment. In the proposed system, nonlinearity naturally arises from the mechanism of cooperative stability, which regulates the concentration of a protein produced during a transcription process. In this elemental model, bistability results from the coherent amplification of environmental fluctuations due to a stochastic resonance of nonlinear origin. This suggests that the period doubling observed in many biological functions might result from the intrinsic interplay between nonlinearity and thermal noise. PMID:25404210

Period doubling induced by thermal noise amplification in genetic circuits.

PubMed

Ruocco, G; Fratalocchi, A

2014-11-18

Rhythms of life are dictated by oscillations, which take place in a wide rage of biological scales. In bacteria, for example, oscillations have been proven to control many fundamental processes, ranging from gene expression to cell divisions. In genetic circuits, oscillations originate from elemental block such as autorepressors and toggle switches, which produce robust and noise-free cycles with well defined frequency. In some circumstances, the oscillation period of biological functions may double, thus generating bistable behaviors whose ultimate origin is at the basis of intense investigations. Motivated by brain studies, we here study an "elemental" genetic circuit, where a simple nonlinear process interacts with a noisy environment. In the proposed system, nonlinearity naturally arises from the mechanism of cooperative stability, which regulates the concentration of a protein produced during a transcription process. In this elemental model, bistability results from the coherent amplification of environmental fluctuations due to a stochastic resonance of nonlinear origin. This suggests that the period doubling observed in many biological functions might result from the intrinsic interplay between nonlinearity and thermal noise.

Frequency-doubled microwave waveforms generation using a dual-polarization quadrature phase shift keying modulator driven by a single frequency radio frequency signal

NASA Astrophysics Data System (ADS)

Zhu, Zihang; Zhao, Shanghong; Li, Xuan; Qu, Kun; Lin, Tao

2018-01-01

A photonic approach to generate frequency-doubled microwave waveforms using an integrated dual-polarization quadrature phase shift keying (DP-QPSK) modulator driven by a sinusoidal radio frequency (RF) signal is proposed. By adjusting the dc bias points of the DP-QPSK modulator, the obtained second-order and six-order harmonics are in phase while the fourth-order harmonics are complementary when the orthogonal polarized outputs of the modulator are photodetected. After properly setting the modulation indices of the modulator, the amplitude of the second-order harmonic is 9 times of that of the six-order harmonic, indicating a frequency-doubled triangular waveform is generated. If a broadband 90° microwave phase shifter is attached after the photodetector (PD) to introduce a 90° phase shift, a frequency-doubled square waveform can be obtained after adjusting the amplitude of the second-order harmonic 3 times of that of the six-order harmonic. The proposal is first theoretically analyzed and then validated by simulation. Simulation results show that a 10 GHz triangular and square waveform sequences are successfully generated from a 5 GHz sinusoidal RF drive signal.

Field-incidence noise transmission loss of general aviation aircraft double wall configurations

NASA Astrophysics Data System (ADS)

Grosveld, F. W.

1984-01-01

Theoretical formulations have been developed to describe the transmission of reverberant sound through an infinite, semi-infinite and a finite double panel structure. The model incorporates the fundamental resonance frequencies of each of the panels, the mass-air-mass resonances of the structure, the standing wave resonances in the cavity between the panels and finally the coincidence resonance regions, where the exciting sound pressure wave and flexural waves of each of the panels coincide. It is shown that phase cancellation effects of pressure waves reflected from the cavity boundaries back into the cavity allows the transmission loss of a finite double panel structure to be approximated by a finite double panel mounted in an infinite baffle having no cavity boundaries. Comparison of the theory with high quality transmission loss data yields good agreement in the mass-controlled frequency region. It is shown that the application of acoustic blankets to the double panel structure does not eliminate the mass-air-mass resonances if those occur at low frequencies. It is concluded that this frequency region of low noise transmission loss is a potential interior noise problem area for propeller driven aircraft having a double panel fuselage construction.

A Dual Frequency Carrier Phase Error Difference Checking Algorithm for the GNSS Compass.

PubMed

Liu, Shuo; Zhang, Lei; Li, Jian

2016-11-24

The performance of the Global Navigation Satellite System (GNSS) compass is related to the quality of carrier phase measurement. How to process the carrier phase error properly is important to improve the GNSS compass accuracy. In this work, we propose a dual frequency carrier phase error difference checking algorithm for the GNSS compass. The algorithm aims at eliminating large carrier phase error in dual frequency double differenced carrier phase measurement according to the error difference between two frequencies. The advantage of the proposed algorithm is that it does not need additional environment information and has a good performance on multiple large errors compared with previous research. The core of the proposed algorithm is removing the geographical distance from the dual frequency carrier phase measurement, then the carrier phase error is separated and detectable. We generate the Double Differenced Geometry-Free (DDGF) measurement according to the characteristic that the different frequency carrier phase measurements contain the same geometrical distance. Then, we propose the DDGF detection to detect the large carrier phase error difference between two frequencies. The theoretical performance of the proposed DDGF detection is analyzed. An open sky test, a manmade multipath test and an urban vehicle test were carried out to evaluate the performance of the proposed algorithm. The result shows that the proposed DDGF detection is able to detect large error in dual frequency carrier phase measurement by checking the error difference between two frequencies. After the DDGF detection, the accuracy of the baseline vector is improved in the GNSS compass.

All-solid-state cw frequency-doubling Nd:YLiF4/LBO blue laser with 4.33 W output power at 454 nm under in-band diode pumping at 880 nm.

PubMed

Lü, Yanfei; Zhang, Xihe; Cheng, Weibo; Xia, Jing

2010-07-20

We generated efficient blue laser output at 454 nm by intracavity frequency doubling of a continuous-wave (cw) diode-pumped Nd:YLiF(4) (Nd:YLF) laser at 908 nm based on the (4)F(3/2)-(4)I(9/2) transition. With 32.8 W of incident pump power at 880 nm and the frequency-doubling crystal LiB(3)O(5), a level as high as 4.33 W of cw output power at 454 nm is achieved, corresponding to an optical conversion efficiency of 13.2% with respect to the incident pump power. To the best of our knowledge, this is the first blue laser at 454 nm generated by intracavity frequency doubling of a diode-pumped Nd:YLF.

Frequency doubling of a tunable ytterbium-doped fibre laser in KTP crystals phase-matched in the XY and YZ planes

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

Akulov, V A; Kablukov, S I; Babin, Sergei A

2012-02-28

This paper presents an experimental study of frequency doubling of a tunable ytterbium-doped fibre laser in KTP crystals phase-matched in the XY and YZ planes. In the XY plane, we obtained continuous tuning in the range 528 - 540 nm through intracavity frequency doubling. The second-harmonic power reached 450 mW for 18 W of multimode diode pump power, which was five times higher in comparison with single-pass frequency doubling. In a single-pass configuration in the YZ plane, we obtained a wide tuning range (527 - 551 nm) in the green spectral region and a second-harmonic power of {approx}10 mW. Themore » tuning range was only limited by the mechanical performance of the fibre Bragg grating and can potentially be extended to the entire lasing range of the ytterbium-doped fibre laser.« less

Compact sub-kilohertz low-frequency quantum light source based on four-wave mixing in cesium vapor

NASA Astrophysics Data System (ADS)

Ma, Rong; Liu, Wei; Qin, Zhongzhong; Su, Xiaolong; Jia, Xiaojun; Zhang, Junxiang; Gao, Jiangrui

2018-03-01

Using a nondegenerate four-wave mixing (FWM) process based on a double-{\\Lambda} scheme in hot cesium vapor, we demonstrate a compact diode-laser-pumped quantum light source for the generation of quantum correlated twin beams with a maximum squeezing of 6.5 dB. The squeezing is observed at a Fourier frequency in the audio band down to 0.7 kHz which, to the best of our knowledge, is the first observation of sub-kilohertz intensity-difference squeezing in an atomic system so far. A phase-matching condition is also investigated in our system, which confirms the spatial-multi-mode characteristics of the FWM process. Our compact low-frequency squeezed light source may find applications in quantum imaging, quantum metrology, and the transfer of optical squeezing onto a matter wave.

Double-loop frequency selective surfaces for multi frequency division multiplexing in a dual reflector antenna

NASA Technical Reports Server (NTRS)

Wu, Te-Kao (Inventor)

1994-01-01

A multireflector antenna utilizes a frequency-selective surface (FSS) in a subreflector to allow signals in two different RF bands to be selectively reflected back into a main reflector and to allow signals in other RF bands to be transmitted through it to the main reflector for primary focus transmission. A first approach requires only one FSS at the subreflector which may be an array of double-square-loop conductive elements. A second approach uses two FSS's at the subreflector which may be an array of either double-square-loop (DSL) or double-ring (DR). In the case of DR elements, they may be advantageously arranged in a triangular array instead of the rectangular array for the DSL elements.

Remote double resonance coupling of radar energy to ionospheric irregularities

NASA Technical Reports Server (NTRS)

Kennel, C. F.

1971-01-01

Experimental results indicate that low frequency modulation of a high power radar beam, tuned to one of the critical frequencies of the ionosphere, may produce field-aligned density irregularities when the modulation frequency matches an ionospheric eigenfrequency. By choosing the radar carrier frequency and polarization, a number of interaction layers were selected. The variety of possible excitations shows that the double resonance technique may be adaptable to a number of different objectives.

Dynamics of corticospinal motor control during overground and treadmill walking in humans.

PubMed

Roeder, Luisa; Boonstra, Tjeerd Willem; Smith, Simon S; Kerr, Graham K

2018-05-30

Increasing evidence suggests cortical involvement in the control of human gait. However, the nature of corticospinal interactions remains poorly understood. We performed time-frequency analysis of electrophysiological activity acquired during treadmill and overground walking in 22 healthy, young adults. Participants walked at their preferred speed (4.2, SD 0.4 km h -1 ), which was matched across both gait conditions. Event-related power, corticomuscular coherence (CMC) and inter-trial coherence (ITC) were assessed for EEG from bilateral sensorimotor cortices and EMG from the bilateral tibialis anterior (TA) muscles. Cortical power, CMC and ITC at theta, alpha, beta and gamma frequencies (4-45 Hz) increased during the double support phase of the gait cycle for both overground and treadmill walking. High beta (21-30 Hz) CMC and ITC of EMG was significantly increased during overground compared to treadmill walking, as well as EEG power in theta band (4-7 Hz). The phase spectra revealed positive time lags at alpha, beta and gamma frequencies, indicating that the EEG response preceded the EMG response. The parallel increases in power, CMC and ITC during double support suggest evoked responses at spinal and cortical populations rather than a modulation of ongoing corticospinal oscillatory interactions. The evoked responses are not consistent with the idea of synchronization of ongoing corticospinal oscillations, but instead suggest coordinated cortical and spinal inputs during the double support phase. Frequency-band dependent differences in power, CMC and ITC between overground and treadmill walking suggest differing neural control for the two gait modalities, emphasizing the task-dependent nature of neural processes during human walking.

Observations of stimulated Raman scattering and laser-induced breakdown in millimeter-sized droplets

NASA Technical Reports Server (NTRS)

Biswas, A.; Pinnick, R. G.; Xie, J.-G.; Ruekgauer, T. E.; Armstrong, R. L.

1992-01-01

We report the first observations, to our knowledge, of nonlinear optical effects in large (millimeter-sized) droplets. Stimulated Raman scattering (SRS) and laser-induced breakdown (LIB) are simultaneously observed in acoustically levitated millimeter-sized glycerol droplets irradiated by either a frequency-doubled (532-nm) or a frequency-tripled (355-nm) Nd:YAG laser. The two processes, which occur above a nearby coincident irradiation threshold, are conjectured to arise from a common initiation mechanism: self-focusing. LIB generates vapor bubbles within the droplet, resulting in the quenching of SRS emission.

Nonlinear optimization of acoustic energy harvesting using piezoelectric devices.

PubMed

Lallart, Mickaeël; Guyomar, Daniel; Richard, Claude; Petit, Lionel

2010-11-01

In the first part of the paper, a single degree-of-freedom model of a vibrating membrane with piezoelectric inserts is introduced and is initially applied to the case when a plane wave is incident with frequency close to one of the resonance frequencies. The model is a prototype of a device which converts ambient acoustical energy to electrical energy with the use of piezoelectric devices. The paper then proposes an enhancement of the energy harvesting process using a nonlinear processing of the output voltage of piezoelectric actuators, and suggests that this improves the energy conversion and reduces the sensitivity to frequency drifts. A theoretical discussion is given for the electrical power that can be expected making use of various models. This and supporting experimental results suggest that a nonlinear optimization approach allows a gain of up to 10 in harvested energy and a doubling of the bandwidth. A model is introduced in the latter part of the paper for predicting the behavior of the energy-harvesting device with changes in acoustic frequency, this model taking into account the damping effect and the frequency changes introduced by the nonlinear processes in the device.

Control of Meiotic Crossovers: From Double-Strand Break Formation to Designation

PubMed Central

Gray, Stephen

2017-01-01

Meiosis, the mechanism of creating haploid gametes, is a complex cellular process observed across sexually reproducing organisms. Fundamental to meiosis is the process of homologous recombination, whereby DNA double-strand breaks are introduced into the genome and are subsequently repaired to generate either noncrossovers or crossovers. Although homologous recombination is essential for chromosome pairing during prophase I, the resulting crossovers are critical for maintaining homolog interactions and enabling accurate segregation at the first meiotic division. Thus, the placement, timing, and frequency of crossover formation must be exquisitely controlled. In this review, we discuss the proteins involved in crossover formation, the process of their formation and designation, and the rules governing crossovers, all within the context of the important landmarks of prophase I. We draw together crossover designation data across organisms, analyze their evolutionary divergence, and propose a universal model for crossover regulation. PMID:27648641

Double-frequency microwave ionization of Na

NASA Astrophysics Data System (ADS)

Ruff, G. A.; Dietrick, K. M.; Gallagher, T. F.

1990-11-01

We report the ionization of Na atoms by the simultaneous application of microwave fields of two different frequencies. We conclude that the salient features of double-frequency ionization can be readily understood. Both the hydrogenlike ||m||=2 states and the nonhydrogenic ||m||=0 and 1 states ionize when the sum of the field amplitudes, the peak field, reaches the field required for ionization by a single microwave frequency, E=1/9n4 and E=1/3n5, respectively.

Attentional selection of relative SF mediates global versus local processing: evidence from EEG.

PubMed

Flevaris, Anastasia V; Bentin, Shlomo; Robertson, Lynn C

2011-06-13

Previous research on functional hemispheric differences in visual processing has associated global perception with low spatial frequency (LSF) processing biases of the right hemisphere (RH) and local perception with high spatial frequency (HSF) processing biases of the left hemisphere (LH). The Double Filtering by Frequency (DFF) theory expanded this hypothesis by proposing that visual attention selects and is directed to relatively LSFs by the RH and relatively HSFs by the LH, suggesting a direct causal relationship between SF selection and global versus local perception. We tested this idea in the current experiment by comparing activity in the EEG recorded at posterior right and posterior left hemisphere sites while participants' attention was directed to global or local levels of processing after selection of relatively LSFs versus HSFs in a previous stimulus. Hemispheric asymmetry in the alpha band (8-12 Hz) during preparation for global versus local processing was modulated by the selected SF. In contrast, preparatory activity associated with selection of SF was not modulated by the previously attended level (global/local). These results support the DFF theory that top-down attentional selection of SF mediates global and local processing.

Nonlinear frequency doubling characteristics of asymmetric vortices of tunable, broad orbital angular momentum spectrum

NASA Astrophysics Data System (ADS)

Alam, Sabir Ul; Rao, A. Srinivasa; Ghosh, Anirban; Vaity, Pravin; Samanta, G. K.

2018-04-01

We report on a simple experimental scheme to generate and control the orbital angular momentum (OAM) spectrum of the asymmetric vortex beams in a nonlinear frequency conversion process. Using a spiral phase plate (SPP) and adjusting the transverse shift of the SPP with respect to the incident Gaussian beam axis, we have transformed the symmetric (intensity distribution) optical vortex of order l into an asymmetric vortex beam of measured broad spectrum of OAM modes of orders l, l - 1, l - 2, …, 0 (Gaussian mode). While the position of the SPP determines the distribution of the OAM modes, we have also observed that the modal distribution of the vortex beam changes with the shift of the SPP of all orders and finally results in a Gaussian beam (l = 0). Using single-pass frequency doubling of the asymmetric vortices, we have transferred the pump OAM spectra, l, l - 1, l - 2, …, 0, into the broad spectra of higher order OAM modes, 2l, 2l - 1, 2l - 2, …, 0 at green wavelength, owing to OAM conservation in nonlinear processes. We also observed an increase in single-pass conversion efficiency with the increase in asymmetry of the pump vortices producing a higher power vortex beam of mixed OAM modes at a new wavelength than that of the pure OAM mode.

Dielectric-spectroscopy approach to ferrofluid nanoparticle clustering induced by an external electric field.

PubMed

Rajnak, Michal; Kurimsky, Juraj; Dolnik, Bystrik; Kopcansky, Peter; Tomasovicova, Natalia; Taculescu-Moaca, Elena Alina; Timko, Milan

2014-09-01

An experimental study of magnetic colloidal particles cluster formation induced by an external electric field in a ferrofluid based on transformer oil is presented. Using frequency domain isothermal dielectric spectroscopy, we study the influence of a test cell electrode separation distance on a low-frequency relaxation process. We consider the relaxation process to be associated with an electric double layer polarization taking place on the particle surface. It has been found that the relaxation maximum considerably shifts towards lower frequencies when conducting the measurements in the test cells with greater electrode separation distances. As the electric field intensity was always kept at a constant value, we propose that the particle cluster formation induced by the external ac electric field accounts for that phenomenon. The increase in the relaxation time is in accordance with the Schwarz theory of electric double layer polarization. In addition, we analyze the influence of a static electric field generated by dc bias voltage on a similar shift in the relaxation maximum position. The variation of the dc electric field for the hysteresis measurements purpose provides understanding of the development of the particle clusters and their decay. Following our results, we emphasize the utility of dielectric spectroscopy as a simple, complementary method for detection and study of clusters of colloidal particles induced by external electric field.

Development of Simple Designs of Multitip Probe Diagnostic Systems for RF Plasma Characterization

PubMed Central

Naz, M. Y.; Shukrullah, S.; Ghaffar, A.; Rehman, N. U.

2014-01-01

Multitip probes are very useful diagnostics for analyzing and controlling the physical phenomena occurring in low temperature discharge plasmas. However, DC biased probes often fail to perform well in processing plasmas. The objective of the work was to deduce simple designs of DC biased multitip probes for parametric study of radio frequency plasmas. For this purpose, symmetric double probe, asymmetric double probe, and symmetric triple probe diagnostic systems and their driving circuits were designed and tested in an inductively coupled plasma (ICP) generated by a 13.56 MHz radio frequency (RF) source. Using I-V characteristics of these probes, electron temperature, electron number density, and ion saturation current was measured as a function of input power and filling gas pressure. An increasing trend was noticed in electron temperature and electron number density for increasing input RF power whilst a decreasing trend was evident in these parameters when measured against filling gas pressure. In addition, the electron energy probability function (EEPF) was also studied by using an asymmetric double probe. These studies confirmed the non-Maxwellian nature of the EEPF and the presence of two groups of the energetic electrons at low filling gas pressures. PMID:24683326

Sub-kilohertz excitation lasers for quantum information processing with Rydberg atoms

NASA Astrophysics Data System (ADS)

Legaie, Remy; Picken, Craig J.; Pritchard, Jonathan D.

2018-04-01

Quantum information processing using atomic qubits requires narrow linewidth lasers with long-term stability for high fidelity coherent manipulation of Rydberg states. In this paper, we report on the construction and characterization of three continuous-wave (CW) narrow linewidth lasers stabilized simultaneously to an ultra-high finesse Fabry-Perot cavity made of ultra-low expansion (ULE) glass, with a tunable offset-lock frequency. One laser operates at 852~nm while the two locked lasers at 1018~nm are frequency doubled to 509~nm for excitation of $^{133}$Cs atoms to Rydberg states. The optical beatnote at 509~nm is measured to be 260(5)~Hz. We present measurements of the offset between the atomic and cavity resonant frequencies using electromagnetically induced transparency (EIT) for high-resolution spectroscopy on a cold atom cloud. The long-term stability is determined from repeated spectra over a period of 20 days yielding a linear frequency drift of $\\sim1$~Hz/s.

Development of a Double-Gauss Lens Based Setup for Optoacoustic Applications

PubMed Central

Choi, Hojong; Ryu, Jae-Myung; Yeom, Jung-Yeol

2017-01-01

In optoacoustic (photoacoustic) systems, different echo signal intensities such as amplitudes, center frequencies, and bandwidths need to be compensated by utilizing variable gain or time-gain compensation amplifiers. However, such electronic components can increase system complexities and signal noise levels. In this paper, we introduce a double-Gauss lens to generate a large field of view with uniform light intensity due to the low chromatic aberrations of the lens, thus obtaining uniform echo signal intensities across the field of view of the optoacoustic system. In order to validate the uniformity of the echo signal intensities in the system, an in-house transducer was placed at various positions above a tissue sample and echo signals were measured and compared with each other. The custom designed double-Gauss lens demonstrated negligible light intensity variation (±1.5%) across the illumination field of view (~2 cm diameter). When the transducer was used to measure echo signal from an eye of a bigeye tuna within a range of ±1 cm, the peak-to-peak amplitude, center frequency, and their −6 dB bandwidth variations were less than 2 mV, 1 MHz, and 6%, respectively. The custom designed double-Gauss lens can provide uniform light beam across a wide area while generating insignificant echo signal variations, and thus can lower the burden of the receiving electronics or signal processing in the optoacoustic system. PMID:28273794

Design of Interactively Time-Pulsed Microfluidic Mixers in Microchips using Numerical Simulation

NASA Astrophysics Data System (ADS)

Fu, Lung-Ming; Tsai, Chien-Hsiung

2007-01-01

In this paper, we propose a novel technique in which driving voltages are applied interactively to the respective inlet fluid flows of three configurations of a microfluidic device, namely T-shaped, double-T-shaped, and double-cross-shaped configurations, to induce electroosmotic flow (EOF) velocity variations in such a way as to develop a rapid mixing effect in the microchannel. In these configurations a microfluidic mixer apply only one electrokinetic driving force, which drives the sample fluids and simultaneously produces a periodic switching frequency. It requires no other external driving force to induce perturbations to the flow field. The effects of the main applied electric field, the interactive frequency, and the pullback electric field on the mixing performance are thoroughly examined numerically. The optimal interactive frequency range for a given set of micromixer parameters is identified for each type of control mode. The numerical results confirm that micromixers operating at an optimal interactive frequency are capable of delivering a significantly enhanced mixing performance. Furthermore, it is shown that the optimal interactive frequency depends upon the magnitude of the main applied electric field. The interactively pulsed mixers developed in this study have a strong potential for use in lab-on-a-chip systems. They involve a simpler fabrication process than either passive or active on-chip mixers and require less human intervention in operation than their bulky external counterparts.

Surface Fatigue Resistance with Induction Hardening

NASA Technical Reports Server (NTRS)

Townsend, Dennis; Turza, Alan; Chapman, Mike

1996-01-01

Induction hardening has been used for some years to harden the surface and improve the strength and service life of gears and other components. Many applications that employ induction hardening require a relatively long time to finish the hardening process and controlling the hardness of the surface layer and its depth often was a problem. Other surface hardening methods, ie., carbonizing, take a very long time and tend to cause deformations of the toothing, whose elimination requires supplementary finishing work. In double-frequency induction hardening, one uses a low frequency for the preheating of the toothed wheel and a much higher frequency for the purpose of rapidly heating the surface by way of surface hardening.

Source process and tectonic implication of the January 20, 2007 Odaesan earthquake, South Korea

NASA Astrophysics Data System (ADS)

Abdel-Fattah, Ali K.; Kim, K. Y.; Fnais, M. S.; Al-Amri, A. M.

2014-04-01

The source process for the 20th of January 2007, Mw 4.5 Odaesan earthquake in South Korea is investigated in the low- and high-frequency bands, using velocity and acceleration waveform data recorded by the Korea Meteorological Administration Seismographic Network at distances less than 70 km from the epicenter. Synthetic Green functions are adopted for the low-frequency band of 0.1-0.3 Hz by using the wave-number integration technique and the one dimensional velocity model beneath the epicentral area. An iterative technique was performed by a grid search across the strike, dip, rake, and focal depth of rupture nucleation parameters to find the best-fit double-couple mechanism. To resolve the nodal plane ambiguity, the spatiotemporal slip distribution on the fault surface was recovered using a non-negative least-square algorithm for each set of the grid-searched parameters. The focal depth of 10 km was determined through the grid search for depths in the range of 6-14 km. The best-fit double-couple mechanism obtained from the finite-source model indicates a vertical strike-slip faulting mechanism. The NW faulting plane gives comparatively smaller root-mean-squares (RMS) error than its auxiliary plane. Slip pattern event provides simple source process due to the effect of Low-frequency that acted as a point source model. Three empirical Green functions are adopted to investigate the source process in the high-frequency band. A set of slip models was recovered on both nodal planes of the focal mechanism with various rupture velocities in the range of 2.0-4.0 km/s. Although there is a small difference between the RMS errors produced by the two orthogonal nodal planes, the SW dipping plane gives a smaller RMS error than its auxiliary plane. The slip distribution is relatively assessable by the oblique pattern recovered around the hypocenter in the high-frequency analysis; indicating a complex rupture scenario for such moderate-sized earthquake, similar to those reported for large earthquakes.

Frequency-doubled green picosecond laser based on K3B6O10Br nonlinear optical crystal

NASA Astrophysics Data System (ADS)

Meng, Luping; Zhang, Ling; Hou, Zhanyu; Wang, Lirong; Xu, Hui; Shi, Meng; Wang, Lingwu; Yang, Yingying; Qi, Yaoyao; He, Chaojian; Yu, Haijuan; Lin, Xuechun; Su, Fufang; Xia, Mingjun; Li, Rukang

2018-05-01

We report a frequency-doubled green picosecond (ps) laser based on K3B6O10Br (KBB) nonlinear optical crystal with cutting angle of θ = 34.7° and φ = 30°. Through intracavity frequency doubling using a type I phase-matched KBB crystal with dimensions of 4 mm × 4 mm × 13.2 mm, the average output power of 185.00 mW green ps laser was obtained with a repetition rate of 80 MHz and pulse width of 25.0 ps. In addition, we present external frequency doubling using KBB crystal. The average output power of 3.00 W green ps laser was generated with a repetition rate of 10 kHz and pulse width of 38.1 ps, which corresponds to a pulse energy of 0.30 mJ and a peak power 7.89 MW, respectively. The experimental results show that KBB crystal is a promising nonlinear optical material.

Acousto-optical modulation of light at a doubled sound frequency

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

Kotov, V M; Averin, S V; Shkerdin, G N

2016-02-28

A method of acousto-optical (AO) Bragg diffraction is proposed that provides the amplitude modulation of optical radiation at a doubled acoustic frequency. The method is based on the double transmission of the light through the AO modulator made of a gyrotropic crystal and is experimentally tested by the example of the modulation of light with a wavelength of 0.63 μm, controlled by the paratellurite AO cell. (acoustooptics)

AC electric field induced dielectrophoretic assembly behavior of gold nanoparticles in a wide frequency range

NASA Astrophysics Data System (ADS)

Liu, Weiyu; Wang, Chunhui; Ding, Haitao; Shao, Jinyou; Ding, Yucheng

2016-05-01

In this work, we focus on frequency-dependence of pearl chain formations (PCF) of gold nanoparticles driven by AC dielectrophoresis (DEP), especially in a low field-frequency range, where induced double-layer charging effect at ideally polarizable surfaces on particle DEP behavior and surrounding liquid motion need not be negligible. As field frequency varies, grown features of DEP assembly structures ranging from low-frequency non-bridged gap to high-frequency single gold nanoparticle-made nanowires bridging the electrodes are demonstrated experimentally. Specifically, at 10 kHz, a kind of novel channel-like structure with parallel opposing banks is formed at the center of interelectrode gap. In stark contrast, at 1 MHz, thin PCF with diameter of 100 nm is created along the shortest distance of the isolation spacing. Moreover, a particular conductive path of nanoparticle chains is produced at 1 MHz in a DEP device embedded with multiple floating electrodes. A theoretical framework taking into account field-induced double-layer polarization at both the particle/electrolyte and electrode/electrolyte interface is developed to correlate these experimental observations with induced-charge electrokinetic (ICEK) phenomenon. And a RC circuit model is helpful in accounting for the formation of this particular non-bridged channel-like structure induced by a low-frequency AC voltage. As compared to thin PCF formed at high field frequency that effectively short circuits the electrode pair, though it is difficult for complete PCF bridging to occur at low frequency, the non-bridged conducting microstructure has potential to further miniaturize the size of electrode gap fabricated by standard micromachining process and may find useful application in biochemical sensing.

Observation of sum-frequency-generation-induced cascaded four-wave mixing using two crossing femtosecond laser pulses in a 0.1 mm beta-barium-borate crystal.

PubMed

Liu, Weimin; Zhu, Liangdong; Fang, Chong

2012-09-15

We demonstrate the simultaneous generation of multicolor femtosecond laser pulses spanning the wavelength range from UV to near IR in a 0.1 mm Type I beta-barium borate crystal from 800 nm fundamental and weak IR super-continuum white light (SCWL) pulses. The multicolor broadband laser pulses observed are attributed to two concomitant cascaded four-wave mixing (CFWM) processes as corroborated by calculation: (1) directly from the two incident laser pulses; (2) by the sum-frequency generation (SFG) induced CFWM process (SFGFWM). The latter signal arises from the interaction between the frequency-doubled fundamental pulse (400 nm) and the SFG pulse generated in between the fundamental and IR-SCWL pulses. The versatility and simplicity of this spatially dispersed multicolor self-compressed laser pulse generation offer compact and attractive methods to conduct femtosecond stimulated Raman spectroscopy and time-resolved multicolor spectroscopy.

Concurrent visual and tactile steady-state evoked potentials index allocation of inter-modal attention: a frequency-tagging study.

PubMed

Porcu, Emanuele; Keitel, Christian; Müller, Matthias M

2013-11-27

We investigated effects of inter-modal attention on concurrent visual and tactile stimulus processing by means of stimulus-driven oscillatory brain responses, so-called steady-state evoked potentials (SSEPs). To this end, we frequency-tagged a visual (7.5Hz) and a tactile stimulus (20Hz) and participants were cued, on a trial-by-trial basis, to attend to either vision or touch to perform a detection task in the cued modality. SSEPs driven by the stimulation comprised stimulus frequency-following (i.e. fundamental frequency) as well as frequency-doubling (i.e. second harmonic) responses. We observed that inter-modal attention to vision increased amplitude and phase synchrony of the fundamental frequency component of the visual SSEP while the second harmonic component showed an increase in phase synchrony, only. In contrast, inter-modal attention to touch increased SSEP amplitude of the second harmonic but not of the fundamental frequency, while leaving phase synchrony unaffected in both responses. Our results show that inter-modal attention generally influences concurrent stimulus processing in vision and touch, thus, extending earlier audio-visual findings to a visuo-tactile stimulus situation. The pattern of results, however, suggests differences in the neural implementation of inter-modal attentional influences on visual vs. tactile stimulus processing. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

A combined intervention to reduce interruptions during medication preparation and double-checking: a pilot-study evaluating the impact of staff training and safety vests.

PubMed

Huckels-Baumgart, Saskia; Niederberger, Milena; Manser, Tanja; Meier, Christoph R; Meyer-Massetti, Carla

2017-10-01

The aim was to evaluate the impact of staff training and wearing safety vests as a combined intervention on interruptions during medication preparation and double-checking. Interruptions and errors during the medication process are common and an important issue for patient safety in the hospital setting. We performed a pre- and post-intervention pilot-study using direct structured observation of 26 nurses preparing and double-checking 431 medication doses (225 pre-intervention and 206 post-intervention) for 36 patients (21 pre-intervention and 15 post-intervention). With staff training and the introduction of safety vests, the interruption rate during medication preparation was reduced from 36.8 to 28.3 interruptions per hour and during double-checking from 27.5 to 15 interruptions per hour. This pilot-study showed that the frequency of interruptions decreased during the critical tasks of medication preparation and double-checking after the introduction of staff training and wearing safety vests as part of a quality improvement process. Nursing management should acknowledge interruptions as an important factor potentially influencing medication safety. Unnecessary interruptions can be successfully reduced by considering human and system factors and increasing both staff and nursing managers' awareness of 'interruptive communication practices' and implementing physical barriers. This is the first pilot-study specifically evaluating the impact of staff training and wearing safety vests on the reduction of interruptions during medication preparation and double-checking. © 2017 John Wiley & Sons Ltd.

Study on the high-frequency laser measurement of slot surface difference

NASA Astrophysics Data System (ADS)

Bing, Jia; Lv, Qiongying; Cao, Guohua

2017-10-01

In view of the measurement of the slot surface difference in the large-scale mechanical assembly process, Based on high frequency laser scanning technology and laser detection imaging principle, This paragraph designs a double galvanometer pulse laser scanning system. Laser probe scanning system architecture consists of three parts: laser ranging part, mechanical scanning part, data acquisition and processing part. The part of laser range uses high-frequency laser range finder to measure the distance information of the target shape and get a lot of point cloud data. Mechanical scanning part includes high-speed rotary table, high-speed transit and related structure design, in order to realize the whole system should be carried out in accordance with the design of scanning path on the target three-dimensional laser scanning. Data processing part mainly by FPGA hardware with LAbVIEW software to design a core, to process the point cloud data collected by the laser range finder at the high-speed and fitting calculation of point cloud data, to establish a three-dimensional model of the target, so laser scanning imaging is realized.

An L-band multi-wavelength Brillouin-erbium fiber laser with switchable frequency spacing

NASA Astrophysics Data System (ADS)

Zhou, Xuefang; Hu, Kongwen; Wei, Yizhen; Bi, Meihua; Yang, Guowei

2017-01-01

In this paper, a novel L-band multi-wavelength Brillouin-erbium fiber laser consisting of two ring cavities is proposed and demonstrated. The frequency spacing can be switched, corresponding to the single and double Brillouin frequency shifts, by toggling the optical switch. Under a 980 nm pump power of 600 mw, and a Brillouin pump power of 4 mW and wavelength of 1599.4 nm, up to 16 Stokes signals with a frequency spacing of 0.089 nm and 5 Stokes signals with double spacing of 0.178 nm are generated. A wavelength tunability of 15 nm (1593 nm  -  1608 nm) is realized for both frequency spacings. The fluctuation of Stokes signals for both single and double Brillouin spacing regimes in the proposed setup is less than 1.5 dB throughout a 30 min time span.

Efficient diode-end-pumped actively Q-switched Nd:YAG/SrWO4/KTP yellow laser.

PubMed

Cong, Zhenhua; Zhang, Xingyu; Wang, Qingpu; Liu, Zhaojun; Li, Shutao; Chen, Xiaohan; Zhang, Xiaolei; Fan, Shuzhen; Zhang, Huaijin; Tao, Xutang

2009-09-01

An efficient intracavity frequency-doubled Raman laser was obtained by using an SrWO(4) Raman medium, an Nd:YAG ceramic gain medium, and a KTP frequency-doubling medium. Three laser cavities, including a two-mirror cavity, a three-mirror coupled cavity, and a folded cavity, were investigated. With the coupled cavity, a 2.93 W, 590 nm laser was obtained at an incident pump power of 16.2 W and a pulse repetition frequency of 20 kHz; the corresponding conversion efficiency was 18.1%. The highest conversion efficiency of 19.2% was obtained at an incident pump power of 14.1 W and a pulse repetition frequency of 15 kHz. The obtained maximum output power and conversion efficiency were much higher than the results previously obtained with intracavity frequency-doubled solid-state Raman lasers.

Effect of frequency-doubling pulse Nd:YAG laser on microbial mutation

NASA Astrophysics Data System (ADS)

Zhao, Yansheng; Wang, Luyan; Zheng, Heng; Yin, Hongping; Chen, Xiangdong; Tan, Zheng; Wu, Wutong

1999-09-01

We are going to report the mutagenic effect of frequency-doubling pulse Nd:YAG laser (532 nm) on microbe. After irradiation with pulse laser, mutants of abscisic acid producing strains and erythromycin producing strains were obtained, one of which could produce 62.1% and 57% more products than control, respectively. In the study of mutagenization of Spirulina platensis caused by pulse laser, we selected a high photosynthetic strains, with improved productivity of protein and exocellular ploysaccharides of 12% and 246%, respectively. The experimental results indicate that frequency-doubling pulse laser (532 nm) is a potential new type of physical mutagenic factor.

Gas-Phase Reaction Pathways and Rate Coefficients for the Dichlorosilane-Hydrogen and Trichlorosilane-Hydrogen Systems

NASA Technical Reports Server (NTRS)

Dateo, Christopher E.; Walch, Stephen P.

2002-01-01

As part of NASA Ames Research Center's Integrated Process Team on Device/Process Modeling and Nanotechnology our goal is to create/contribute to a gas-phase chemical database for use in modeling microelectronics devices. In particular, we use ab initio methods to determine chemical reaction pathways and to evaluate reaction rate coefficients. Our initial studies concern reactions involved in the dichlorosilane-hydrogen (SiCl2H2--H2) and trichlorosilane-hydrogen (SiCl2H-H2) systems. Reactant, saddle point (transition state), and product geometries and their vibrational harmonic frequencies are determined using the complete-active-space self-consistent-field (CASSCF) electronic structure method with the correlation consistent polarized valence double-zeta basis set (cc-pVDZ). Reaction pathways are constructed by following the imaginary frequency mode of the saddle point to both the reactant and product. Accurate energetics are determined using the singles and doubles coupled-cluster method that includes a perturbational estimate of the effects of connected triple excitations (CCSD(T)) extrapolated to the complete basis set limit. Using the data from the electronic structure calculations, reaction rate coefficients are obtained using conventional and variational transition state and RRKM theories.

Enlightenment of Yeast Mitochondrial Homoplasmy: Diversified Roles of Gene Conversion

PubMed Central

Ling, Feng; Mikawa, Tsutomu; Shibata, Takehiko

2011-01-01

Mitochondria have their own genomic DNA. Unlike the nuclear genome, each cell contains hundreds to thousands of copies of mitochondrial DNA (mtDNA). The copies of mtDNA tend to have heterogeneous sequences, due to the high frequency of mutagenesis, but are quickly homogenized within a cell (“homoplasmy”) during vegetative cell growth or through a few sexual generations. Heteroplasmy is strongly associated with mitochondrial diseases, diabetes and aging. Recent studies revealed that the yeast cell has the machinery to homogenize mtDNA, using a common DNA processing pathway with gene conversion; i.e., both genetic events are initiated by a double-stranded break, which is processed into 3′ single-stranded tails. One of the tails is base-paired with the complementary sequence of the recipient double-stranded DNA to form a D-loop (homologous pairing), in which repair DNA synthesis is initiated to restore the sequence lost by the breakage. Gene conversion generates sequence diversity, depending on the divergence between the donor and recipient sequences, especially when it occurs among a number of copies of a DNA sequence family with some sequence variations, such as in immunoglobulin diversification in chicken. MtDNA can be regarded as a sequence family, in which the members tend to be diversified by a high frequency of spontaneous mutagenesis. Thus, it would be interesting to determine why and how double-stranded breakage and D-loop formation induce sequence homogenization in mitochondria and sequence diversification in nuclear DNA. We will review the mechanisms and roles of mtDNA homoplasmy, in contrast to nuclear gene conversion, which diversifies gene and genome sequences, to provide clues toward understanding how the common DNA processing pathway results in such divergent outcomes. PMID:24710143

Double-sideband frequency scanning interferometry for long-distance dynamic absolute measurement

NASA Astrophysics Data System (ADS)

Mo, Di; Wang, Ran; Li, Guang-zuo; Wang, Ning; Zhang, Ke-shu; Wu, Yi-rong

2017-11-01

Absolute distance measurements can be achieved by frequency scanning interferometry which uses a tunable laser. The main drawback of this method is that it is extremely sensitive to the movement of targets. In addition, since this method is limited to the linearity of frequency scanning, it is commonly used for close measurements within tens of meters. In order to solve these problems, a double-sideband frequency scanning interferometry system is presented in the paper. It generates two opposite frequency scanning signals through a fixed frequency laser and a Mach-Zehnder modulator. And the system distinguishes the two interference fringe patterns corresponding to the two signals by IQ demodulation (i.e., quadrature detection) of the echo. According to the principle of double-sideband modulation, the two signals have the same characteristics. Therefore, the error caused by the target movement can be effectively eliminated, which is similar to dual-laser frequency scanned interferometry. In addition, this method avoids the contradiction between laser frequency stability and swept performance. The system can be applied to measure the distance of the order of kilometers, which profits from the good linearity of frequency scanning. In the experiment, a precision about 3 μm was achieved for a kilometer-level distance.

One-shot and aberration-tolerable homodyne detection for holographic storage readout through double-frequency grating-based lateral shearing interferometry.

PubMed

Yu, Yeh-Wei; Xiao, Shuai; Cheng, Chih-Yuan; Sun, Ching-Cherng

2016-05-16

A simple method to decode the stored phase signal of volume holographic data storage with adequate wave aberration tolerance is highly demanded. We proposed and demonstrated a one-shot scheme to decode a binary-phase encoding signal through double-frequency-grating based shearing interferometry (DFGSI). The lateral shearing amount is dependent on the focal length of the collimated lens and the frequency difference between the gratings. Diffracted waves with phase encoding were successfully decoded through experimentation. An optical model for the DFGSI was built to analyze phase-error induction and phase-difference control by shifting the double-frequency grating longitudinally and laterally, respectively. The optical model was demonstrated experimentally. Finally, a high aberration tolerance of the DFGSI was demonstrated using the optical model.

Linearity can account for the similarity among conventional, frequency-doubling, and gabor-based perimetric tests in the glaucomatous macula.

PubMed

Sun, Hao; Dul, Mitchell W; Swanson, William H

2006-07-01

The purposes of this study are to compare macular perimetric sensitivities for conventional size III, frequency-doubling, and Gabor stimuli in terms of Weber contrast and to provide a theoretical interpretation of the results. Twenty-two patients with glaucoma performed four perimetric tests: a conventional Swedish Interactive Threshold Algorithm (SITA) 10-2 test with Goldmann size III stimuli, two frequency-doubling tests (FDT 10-2, FDT Macula) with counterphase-modulated grating stimuli, and a laboratory-designed test with Gabor stimuli. Perimetric sensitivities were converted to the reciprocal of Weber contrast and sensitivities from different tests were compared using the Bland-Altman method. Effects of ganglion cell loss on perimetric sensitivities were then simulated with a two-stage neural model. The average perimetric loss was similar for all stimuli until advanced stages of ganglion cell loss, in which perimetric loss tended to be greater for size III stimuli than for frequency-doubling and Gabor stimuli. Comparison of the experimental data and model simulation suggests that, in the macula, linear relations between ganglion cell loss and perimetric sensitivity loss hold for all three stimuli. Linear relations between perimetric loss and ganglion cell loss for all three stimuli can account for the similarity in perimetric loss until advanced stages. The results do not support the hypothesis that redundancy for frequency-doubling stimuli is lower than redundancy for size III stimuli.

Quantum beats in conductance oscillations in graphene-based asymmetric double velocity wells and electrostatic wells

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

Liu, Lei; Department of Medical Physics, Basic Medical College, Hebei Medical University, Shijiazhuang, Hebei 050017; Li, Yu-Xian

2014-01-14

The transport properties in graphene-based asymmetric double velocity well (Fermi velocity inside the well less than that outside the well) and electrostatic well structures are investigated using the transfer matrix method. The results show that quantum beats occur in the oscillations of the conductance for asymmetric double velocity wells. The beating effect can also be found in asymmetric double electrostatic wells, but only if the widths of the two wells are different. The beat frequency for the asymmetric double well is exactly equal to the frequency difference between the oscillation rates in two isolated single wells with the same structuresmore » as the individual wells in the double well structure. A qualitative interpretation is proposed based on the fact that the resonant levels depend upon the sizes of the quantum wells. The beating behavior can provide a new way to identify the symmetry of double well structures.« less

Laser Research and Development Studies for Laser Guide Star Systems

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

Pennington, D.; Beach, R.; Ebbers, C.

2000-02-23

In this paper we consider two CW solid state laser approaches to a 589 nm LGS system. Both are based on the technique of sum-frequency generation, but differ in the cavity architecture. Both technologies are very promising and are worth of further consideration. This preliminary proposal is intended to encompass both designs. A down select shall be performed early in the project execution to focus on the most promising option. The two design options consist of: (1) A dual-frequency resonator with intra-cavity doubling in LB0 offers the promise of a simple architecture and may scale more easily to high power.more » This design has been shown to be highly reliable, efficient and high power when used in frequency-doubled Nd:YAG lasers for programs at LLNL and in commercial products. The challenge in this design is the demonstration of a high power13 18 nm oscillator with adequate suppression of the 1064 nm line. (2) A MOPA based design uses commercial low power oscillators to produce both wavelengths, then amplifies the wavelengths before doubling. This design requires the demonstration of a 1318 nm amplifier, though the design is scaled from a kW CW amplifier already delivered to a customer at a different wavelength. The design must also demonstrate high power scaling of sum-frequency generation in the relatively new nonlinear material, PPLN. The first step in the process would be to further evaluate the two conceptual options for technical feasibility, cost and constructability. Then a down selection to one design would be conducted. Finally, R&D on that design would then proceed. Minimal testing should be required for this selection. The majority of the funding received would be allocated to development of the design selected.« less

Phase correlation of laser waves with arbitrary frequency spacing.

PubMed

Huss, A F; Lammegger, R; Neureiter, C; Korsunsky, E A; Windholz, L

2004-11-26

The theoretically predicted correlation of laser phase fluctuations in Lambda-type interaction schemes is experimentally demonstrated. We show that the mechanism of correlation in a Lambda scheme is restricted to high-frequency noise components, whereas in a double-Lambda scheme, due to the laser phase locking in a closed-loop interaction, it extends to all noise frequencies. In this case the correlation is weakly sensitive to coherence losses. Thus the double-Lambda scheme can be used to correlate electromagnetic fields with carrier frequency differences beyond the GHz regime.

Analysis of DE-1 PWI electric field data

NASA Technical Reports Server (NTRS)

Weimer, Daniel

1994-01-01

The measurement of low frequency electric field oscillations may be accomplished with the Plasma Wave Instrument (PWI) on DE 1. Oscillations at a frequency around 1 Hz are below the range of the conventional plasma wave receivers, but they can be detected by using a special processing of the quasi-static electric field data. With this processing it is also possible to determine if the electric field oscillations are predominately parallel or perpendicular to the ambient magnetic field. The quasi-static electric field in the DE 1 spin/orbit plane is measured with a long-wire 'double probe'. This antenna is perpendicular to the satellite spin axis, which in turn is approximately perpendicular to the geomagnetic field in the polar magnetosphere. The electric field data are digitally sampled at a frequency of 16 Hz. The measured electric field signal, which has had phase reversals introduced by the rotating antenna, is multiplied by the sine of the rotation angle between the antenna and the magnetic field. This is called the 'perpendicular' signal. The measured time series is also multiplied with the cosine of the angle to produce a separate 'parallel' signal. These two separate time series are then processed to determine the frequency power spectrum.

Frequency of Tropical Ocean Deep Convection and Global Warming

NASA Astrophysics Data System (ADS)

Aumann, H. H.; Behrangi, A.; Ruzmaikin, A.

2017-12-01

The average of 36 CMIP5 models predicts about 3K of warming and a 4.7% increase in precipitation for the tropical oceans with a doubling of the CO2 by the end of this century. For this scenario we evaluate the increase in the frequency of Deep Convective Clouds (DCC) in the tropical oceans. We select only DCC which reach or penetrate the tropopause in the 15 km AIRS footprint. The evaluation is based on Probability Distribution Functions (PDFs) of the current temperatures of the tropical oceans, those predicted by the mean of the CMIP5 models and the PDF of the DCC process. The PDF of the DCC process is derived from the Atmospheric Infrared Sounder (AIRS) between the years 2003 and 2016. During this time the variability due Enso years provided a 1 K p-p change in the mean tropical SST. The key parameter is the SST associated with the onset of the DCC process. This parameter shifts only 0.5 K for each K of warming of the oceans. As a result the frequency of DCC is expected to increases by the end of this century by about 50% above the current frequency.

Hydrodynamics of insect spermatozoa

NASA Astrophysics Data System (ADS)

Pak, On Shun; Lauga, Eric

2010-11-01

Microorganism motility plays important roles in many biological processes including reproduction. Many microorganisms propel themselves by propagating traveling waves along their flagella. Depending on the species, propagation of planar waves (e.g. Ceratium) and helical waves (e.g. Trichomonas) were observed in eukaryotic flagellar motion, and hydrodynamic models for both were proposed in the past. However, the motility of insect spermatozoa remains largely unexplored. An interesting morphological feature of such cells, first observed in Tenebrio molitor and Bacillus rossius, is the double helical deformation pattern along the flagella, which is characterized by the presence of two superimposed helical flagellar waves (one with a large amplitude and low frequency, and the other with a small amplitude and high frequency). Here we present the first hydrodynamic investigation of the locomotion of insect spermatozoa. The swimming kinematics, trajectories and hydrodynamic efficiency of the swimmer are computed based on the prescribed double helical deformation pattern. We then compare our theoretical predictions with experimental measurements, and explore the dependence of the swimming performance on the geometric and dynamical parameters.

Modulation of Polarization for Phase Extraction in Holographic Interferometry with Two References

NASA Astrophysics Data System (ADS)

Rodriguez-Zurita, G.; Vázquez-Castillo, J.-F.; Toto-Arellano, N.-I.; Meneses-Fabian, C.; Jiménez-Montero, L.-E.

2010-04-01

Heterodyne holographic interferometry allows high accuracy for phase-difference extraction between two wave fronts, especially when they are previously recorded in the same recording medium. In part, this is because the wave fronts can be affected by the recording process in a very similar way. The double reconstruction of a double-exposure hologram with two independent references results in a two-beam holographic interferometer with an arm conveying a wave modulated in frequency when using heterodyne techniques. The heterodyne frequency has been usually introduced with a plane mirror attached to a piezo-electric stack driven with a suitable variable power supply. For holographic interferometry, however, less attention has been devoted to alternative phase retrieval variants as, for example, phase-shifting with modulation of polarization or Fourier methods. In this work, we propose and demonstrate the basic capabilities of modulation of polarization performing as a phase-shifting technique for holographic interferometry with two references in a phase-stepping scheme. Experimental results are provided.

Generation of 180 W average green power from a frequency-doubled picosecond rod fiber amplifier

DOE PAGES

Zhao, Zhi; Sheehy, Brian; Minty, Michiko

2017-03-29

Here, we report on the generation of 180 W average green power from a frequency-doubled picosecond rod fiber amplifier. In an Yb-doped fiber master-oscillator-power-amplifier system, 2.3-ps 704 MHz pulses are first amplified in small-core fibers and then in large-mode-area rod fibers to produce 270 W average infrared power with a high polarization extinction ratio and diffraction-limited beam quality. By carrying out frequency doubling in a lithium triborate (LBO) crystal, 180 W average green power is generated. To the best of our knowledge, this is the highest average green power achieved in fiber-based laser systems.

Specific features of low-frequency vibrational dynamics and low-temperature heat capacity of double-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Avramenko, M. V.; Roshal, S. B.

2016-05-01

A continuous model has been constructed for low-frequency dynamics of a double-walled carbon nanotube. The formation of the low-frequency part of the phonon spectrum of a double-walled nanotube from phonon spectra of its constituent single-walled nanotubes has been considered in the framework of the proposed approach. The influence of the environment on the phonon spectrum of a single double-walled carbon nanotube has been analyzed. A combined method has been proposed for estimating the coefficients of the van der Waals interaction between the walls of the nanotube from the spectroscopic data and the known values of the elastic moduli of graphite. The low-temperature specific heat has been calculated for doublewalled carbon nanotubes, which in the field of applicability of the model ( T < 35 K) is substantially less than the sum of specific heats of two individual single-walled nanotubes forming it.

Corticomuscular transmission of tremor signals by propriospinal neurons in Parkinson's disease.

PubMed

Hao, Manzhao; He, Xin; Xiao, Qin; Alstermark, Bror; Lan, Ning

2013-01-01

Cortical oscillatory signals of single and double tremor frequencies act together to cause tremor in the peripheral limbs of patients with Parkinson's disease (PD). But the corticospinal pathway that transmits the tremor signals has not been clarified, and how alternating bursts of antagonistic muscle activations are generated from the cortical oscillatory signals is not well understood. This paper investigates the plausible role of propriospinal neurons (PN) in C3-C4 in transmitting the cortical oscillatory signals to peripheral muscles. Kinematics data and surface electromyogram (EMG) of tremor in forearm were collected from PD patients. A PN network model was constructed based on known neurophysiological connections of PN. The cortical efferent signal of double tremor frequencies were integrated at the PN network, whose outputs drove the muscles of a virtual arm (VA) model to simulate tremor behaviors. The cortical efferent signal of single tremor frequency actuated muscle spindles. By comparing tremor data of PD patients and the results of model simulation, we examined two hypotheses regarding the corticospinal transmission of oscillatory signals in Parkinsonian tremor. Hypothesis I stated that the oscillatory cortical signals were transmitted via the mono-synaptic corticospinal pathways bypassing the PN network. The alternative hypothesis II stated that they were transmitted by way of PN multi-synaptic corticospinal pathway. Simulations indicated that without the PN network, the alternating burst patterns of antagonistic muscle EMGs could not be reliably generated, rejecting the first hypothesis. However, with the PN network, the alternating burst patterns of antagonist EMGs were naturally reproduced under all conditions of cortical oscillations. The results suggest that cortical commands of single and double tremor frequencies are further processed at PN to compute the alternating burst patterns in flexor and extensor muscles, and the neuromuscular dynamics demonstrated a frequency dependent damping on tremor, which may prevent tremor above 8 Hz to occur.

Corticomuscular Transmission of Tremor Signals by Propriospinal Neurons in Parkinson's Disease

PubMed Central

Hao, Manzhao; He, Xin; Xiao, Qin; Alstermark, Bror; Lan, Ning

2013-01-01

Cortical oscillatory signals of single and double tremor frequencies act together to cause tremor in the peripheral limbs of patients with Parkinson's disease (PD). But the corticospinal pathway that transmits the tremor signals has not been clarified, and how alternating bursts of antagonistic muscle activations are generated from the cortical oscillatory signals is not well understood. This paper investigates the plausible role of propriospinal neurons (PN) in C3–C4 in transmitting the cortical oscillatory signals to peripheral muscles. Kinematics data and surface electromyogram (EMG) of tremor in forearm were collected from PD patients. A PN network model was constructed based on known neurophysiological connections of PN. The cortical efferent signal of double tremor frequencies were integrated at the PN network, whose outputs drove the muscles of a virtual arm (VA) model to simulate tremor behaviors. The cortical efferent signal of single tremor frequency actuated muscle spindles. By comparing tremor data of PD patients and the results of model simulation, we examined two hypotheses regarding the corticospinal transmission of oscillatory signals in Parkinsonian tremor. Hypothesis I stated that the oscillatory cortical signals were transmitted via the mono-synaptic corticospinal pathways bypassing the PN network. The alternative hypothesis II stated that they were transmitted by way of PN multi-synaptic corticospinal pathway. Simulations indicated that without the PN network, the alternating burst patterns of antagonistic muscle EMGs could not be reliably generated, rejecting the first hypothesis. However, with the PN network, the alternating burst patterns of antagonist EMGs were naturally reproduced under all conditions of cortical oscillations. The results suggest that cortical commands of single and double tremor frequencies are further processed at PN to compute the alternating burst patterns in flexor and extensor muscles, and the neuromuscular dynamics demonstrated a frequency dependent damping on tremor, which may prevent tremor above 8 Hz to occur. PMID:24278189

Theoretical Analysis About Quantum Noise Squeezing of Optical Fields From an Intracavity Frequency-Doubled Laser

NASA Technical Reports Server (NTRS)

Zhang, Kuanshou; Xie, Changde; Peng, Kunchi

1996-01-01

The dependence of the quantum fluctuation of the output fundamental and second-harmonic waves upon cavity configuration has been numerically calculated for the intracavity frequency-doubled laser. The results might provide a direct reference for the design of squeezing system through the second-harmonic-generation.

Double Fourier analysis for Emotion Identification in Voiced Speech

NASA Astrophysics Data System (ADS)

Sierra-Sosa, D.; Bastidas, M.; Ortiz P., D.; Quintero, O. L.

2016-04-01

We propose a novel analysis alternative, based on two Fourier Transforms for emotion recognition from speech. Fourier analysis allows for display and synthesizes different signals, in terms of power spectral density distributions. A spectrogram of the voice signal is obtained performing a short time Fourier Transform with Gaussian windows, this spectrogram portraits frequency related features, such as vocal tract resonances and quasi-periodic excitations during voiced sounds. Emotions induce such characteristics in speech, which become apparent in spectrogram time-frequency distributions. Later, the signal time-frequency representation from spectrogram is considered an image, and processed through a 2-dimensional Fourier Transform in order to perform the spatial Fourier analysis from it. Finally features related with emotions in voiced speech are extracted and presented.

Double spacing multi-wavelength Brillouin Raman fiber laser of eight-shaped structure utilizing Raman amplifier

NASA Astrophysics Data System (ADS)

Madin, M. Sya'aer; Ahmad Hambali, N. A. M.; Shahimin, M. M.; Wahid, M. H. A.; Roshidah, N.; Azaidin, M. A. M.

2017-02-01

In this paper, double frequency spacing of multi-wavelength Brillouin Raman fiber laser utilizing eight-shaped structure in conjunction with Raman amplifier is simulated and demonstrated using Optisys software. Double frequency multiwavelength Brillouin Raman fiber laser is one of the solution for single frequency spacing channel de-multiplexing from narrow single spacing in the communication systems. The eight-shaped structure has the ability to produce lower noise and double frequency spacing. The 7 km of single mode fiber acting as a nonlinear medium for the generation of Stimulated Brillouin Scattering and Stimulated Raman Scattering. As a results, the optimum results are recorded at 1450 nm of RP power at 22 dBm and 1550 nm of BP power at 20 dBm. These parameters provide a high output peak power, gain and average OSNR. The highest peak power of Stokes 1 is recorded at 90% of coupling ratio which is 29.88 dBm. It is found that the maximum gain and average OSNR of about 1.23 dB and 63.74 dB.

Frequency and zero-point vibrational energy scale factors for double-hybrid density functionals (and other selected methods): can anharmonic force fields be avoided?

PubMed

Kesharwani, Manoj K; Brauer, Brina; Martin, Jan M L

2015-03-05

We have obtained uniform frequency scaling factors λ(harm) (for harmonic frequencies), λ(fund) (for fundamentals), and λ(ZPVE) (for zero-point vibrational energies (ZPVEs)) for the Weigend-Ahlrichs and other selected basis sets for MP2, SCS-MP2, and a variety of DFT functionals including double hybrids. For selected levels of theory, we have also obtained scaling factors for true anharmonic fundamentals and ZPVEs obtained from quartic force fields. For harmonic frequencies, the double hybrids B2PLYP, B2GP-PLYP, and DSD-PBEP86 clearly yield the best performance at RMSD = 10-12 cm(-1) for def2-TZVP and larger basis sets, compared to 5 cm(-1) at the CCSD(T) basis set limit. For ZPVEs, again, the double hybrids are the best performers, reaching root-mean-square deviations (RMSDs) as low as 0.05 kcal/mol, but even mainstream functionals like B3LYP can get down to 0.10 kcal/mol. Explicitly anharmonic ZPVEs only are marginally more accurate. For fundamentals, however, simple uniform scaling is clearly inadequate.

Paraesthesia during the needle-through-needle and the double segment technique for combined spinal epidural anaesthesia.

PubMed

Ahn, H J; Choi, D H; Kim, C S

2006-07-01

Paraesthesia during regional anaesthesia is an unpleasant sensation for patients and, more importantly, in some cases it is related to neurological injury. Relatively few studies have been conducted on the frequency of paraesthesia during combined spinal epidural anaesthesia. We compared two combined spinal epidural anaesthesia techniques: the needle-through-needle technique and the double segment technique in this respect. We randomly allocated 116 parturients undergoing elective Caesarean section to receive anaesthesia using one of these techniques. Both techniques were performed using a 27G pencil point needle, an 18G Tuohy needle, and a 20G multiport epidural catheter from the same manufacturer. The overall frequency of paraesthesia was higher in the needle-through-needle technique group (56.9% vs. 31.6%, p = 0.011). The frequency of paraesthesia at spinal needle insertion was 20.7% in the needle-through-needle technique group and 8.8% in the double segment technique group; whereas the frequency of paraesthesia at epidural catheter insertion was 46.6% in the needle-through-needle technique group and 24.6% in the double segment technique group.

Single crystal growth and nonlinear optical properties of Nd3+ doped STGS crystal for self-frequency-doubling application

NASA Astrophysics Data System (ADS)

Chen, Feifei; Wang, Lijuan; Wang, Xinle; Cheng, Xiufeng; Yu, Fapeng; Wang, Zhengping; Zhao, Xian

2017-11-01

The self-frequency-doubling crystal is an important kind of multi-functional crystal materials. In this work, Nd3+ doped Sr3TaGa3Si2O14 (Nd:STGS) single crystals were successfully grown by using Czochralski pulling method, in addition, the nonlinear and laser-frequency-doubling properties of Nd:STGS crystals were studied. The continuous-wave laser at 1064 nm was demonstrated along different physical axes, where the maximum output power was obtained to be 295 mW for the Z-cut samples, much higher than the Y-cut (242 mW) and X-cut (217 mW) samples. Based on the measured refractive indexes, the phase matching directions were discussed and determined for type I (42.5°, 30°) and type II (69.5°, 0°) crystal cuts. As expected, self-frequency-doubling green laser at 529 nm was achieved with output powers being around 16 mW and 12 mW for type I and type II configurations, respectively.

A new insight on the dynamics of sodium dodecyl sulfate aqueous micellar solutions by dielectric spectroscopy.

PubMed

Lanzi, Leandro; Carlà, Marcello; Lanzi, Leonardo; Gambi, Cecilia M C

2009-02-01

Aqueous sodium dodecyl sulfate micellar solutions were investigated by a recently developed double-differential dielectric spectroscopy technique in the frequency range 100 MHz-3 GHz at 22 degrees C, in the surfactant concentration range 29.8-524 mM, explored for the first time above 104 mM. The micellar contribution to dielectric spectra was analyzed according to three models containing, respectively, a single Debye relaxation, a Cole-Cole relaxation and a double Debye relaxation. The single Debye model is not accurate enough. Both Cole-Cole and double Debye models fit well the experimental dielectric spectra. With the double Debye model, two characteristic relaxation times were identified: the slower one, in the range 400-900 ps, is due to the motion of counterions bound to the micellar surface (lateral motion); the faster one, in the range 100-130 ps, is due to interfacial bound water. Time constants and amplitudes of both processes are in fair agreement with Grosse's theoretical model, except at the largest concentration values, where interactions between micelles increase. For each sample, the volume fraction of bulk water and the effect of bound water as well as the conductivity in the low frequency limit were computed. The bound water increases as the surfactant concentration increases, in quantitative agreement with the micellar properties. The number of water molecules per surfactant molecule was also computed. The conductivity values are in agreement with Kallay's model over the whole surfactant concentration range.

Linearity Can Account for the Similarity Among Conventional, Frequency-Doubling, and Gabor-Based Perimetric Tests in the Glaucomatous Macula

PubMed Central

DUL, MITCHELL W.; SWANSON, WILLIAM H.

2006-01-01

Purposes The purposes of this study are to compare macular perimetric sensitivities for conventional size III, frequency-doubling, and Gabor stimuli in terms of Weber contrast and to provide a theoretical interpretation of the results. Methods Twenty-two patients with glaucoma performed four perimetric tests: a conventional Swedish Interactive Threshold Algorithm (SITA) 10-2 test with Goldmann size III stimuli, two frequency-doubling tests (FDT 10-2, FDT Macula) with counterphase-modulated grating stimuli, and a laboratory-designed test with Gabor stimuli. Perimetric sensitivities were converted to the reciprocal of Weber contrast and sensitivities from different tests were compared using the Bland-Altman method. Effects of ganglion cell loss on perimetric sensitivities were then simulated with a two-stage neural model. Results The average perimetric loss was similar for all stimuli until advanced stages of ganglion cell loss, in which perimetric loss tended to be greater for size III stimuli than for frequency-doubling and Gabor stimuli. Comparison of the experimental data and model simulation suggests that, in the macula, linear relations between ganglion cell loss and perimetric sensitivity loss hold for all three stimuli. Conclusions Linear relations between perimetric loss and ganglion cell loss for all three stimuli can account for the similarity in perimetric loss until advanced stages. The results do not support the hypothesis that redundancy for frequency-doubling stimuli is lower than redundancy for size III stimuli. PMID:16840860

Transport limited interfacial carrier relaxation in a double-layer device investigated by time-resolved second harmonic generation and impedance spectroscopy

NASA Astrophysics Data System (ADS)

Zhang, Le; Taguchi, Dai; Li, Jun; Manaka, Takaaki; Iwamoto, Mitsumasa

2011-02-01

The interfacial carrier relaxation in an indium tin oxide/polyimide/pentacene/Au double-layer device was studied in both time and frequency domains by using time-resolved second harmonic generation (TR-SHG) and impedance spectroscopy (IS), respectively. Although both hole and electron injection into the pentacene layer and their accumulation at the pentacene/polyimide interface were revealed in TR-SHG, it was only observed in IS under the hole injection condition. The "contradiction" between the two methods for the same carrier relaxation process was explained on the basis of a model, transport limited interfacial carrier relaxation, in which the quasistatic state governs the one-directional carrier transport.

Observation of millimeter-wave oscillations from resonant tunneling diodes and some theoretical considerations of ultimate frequency limits

NASA Technical Reports Server (NTRS)

Sollner, T. C. L. G.; Brown, E. R.; Goodhue, W. D.; Le, H. Q.

1987-01-01

Recent observations of oscillation frequencies up to 56 GHz in resonant tunneling structures are discussed in relation to calculations by several authors of the ultimate frequency limits of these devices. It is found that calculations relying on the Wentzel-Kramers-Brillouin (WKB) approximation give limits well below the observed oscillation frequencies. Two other techniques for calculating the upper frequency limit were found to give more reasonable results. One method employs the solution of the time-dependent Schroedinger equation obtained by Kundrotas and Dargys (1986); the other uses the energy width of the transmission function for electrons through the double-barrier structure. This last technique is believed to be the most accurate since it is based on general results for the lifetime of any resonant state. It gives frequency limits on the order of 1 THz for two recently fabricated structures. It appears that the primary limitation of the oscillation frequency for double-barrier resonant-tunneling diodes is imposed by intrinsic device circuit parameters and by the transit time of the depletion layer rather than by time delays encountered in the double-barrier region.

A series of compact rejection filters based on the interaction between spoof SPPs and CSRRs.

PubMed

Zhang, Qian; Zhang, Hao Chi; Yin, Jia Yuan; Pan, Bai Cao; Cui, Tie Jun

2016-06-21

We propose a method to synthesize several band-rejection filters by etching split-ring resonators (SRRs) on the transmission line for spoof surface plasmon polaritons (SPPs), which is made of double-side or single-side corrugated metal strips. From dispersion relations, the corrugated strips can support spoof SPP modes when the operating frequency is less than the cutoff frequency. The electric field component perpendicular to the strip surface of the SPP modes can excite the complementary SRRs (CSRRs), leading to resonant modes preventing the SPP propagation near the resonant frequencies. Using this principle, single-frequency rejection filters, double-frequency rejection filters, and broad band-stop filters with bandwidth of 1.5 GHz have been designed and fabricated using the single- and/or double-side corrugated strips. Both measured results and numerical simulations demonstrate the excellent filtering characteristics of all design, which are in good agreements. The isolation of all filters can be less than -20 dB, and even reach to -38 dB at rejection frequencies. The proposed rejection and stop-band filters give important potentials to develop integrated plasmonic functional devices and circuits at microwave and terahertz frequencies.

Efficient 525 nm laser generation in single or double resonant cavity

NASA Astrophysics Data System (ADS)

Liu, Shilong; Han, Zhenhai; Liu, Shikai; Li, Yinhai; Zhou, Zhiyuan; Shi, Baosen

2018-03-01

This paper reports the results of a study into highly efficient sum frequency generation from 792 and 1556 nm wavelength light to 525 nm wavelength light using either a single or double resonant ring cavity based on a periodically poled potassium titanyl phosphate crystal (PPKTP). By optimizing the cavity's parameters, the maximum power achieved for the resultant 525 nm laser was 263 and 373 mW for the single and double resonant cavity, respectively. The corresponding quantum conversion efficiencies were 8 and 77% for converting 1556 nm photons to 525 nm photons with the single and double resonant cavity, respectively. The measured intra-cavity single pass conversion efficiency for both configurations was about 5%. The performances of the sum frequency generation in these two configurations was studied and compared in detail. This work will provide guidelines for optimizing the generation of sum frequency generated laser light for a variety of configurations. The high conversion efficiency achieved in this work will help pave the way for frequency up-conversion of non-classical quantum states, such as the squeezed vacuum and single photon states. The proposed green laser source will be used in our future experiments, which includes a plan to generate two-color entangled photon pairs and achieve the frequency down-conversion of single photons carrying orbital angular momentum.

Frequency Characteristics of the MAGLEV Double-layered Propulsion Coil

NASA Astrophysics Data System (ADS)

Ema, Satoshi

The MAGLEV (magnetically levitated vehicle) is now well along in development testing at Yamanashi Test Line. The MAGLEV power source needs to supply a variable voltage and variable frequency to propulsion coils, which installed on outdoor guideway. The output voltage of the electric power converter contains many higher harmonics, which causes many troubles such as inductive interference. Accordingly, it is necessary to clarify the frequency characteristics of the propulsion coils and the power feeding circuit. In view of this situation, experiments and the theoretical analysis concerning the frequency characteristics of the propulsion coils with single-layer arrangement and the power feeding circuit at Miyazaki Test Line had been performed by the author. But the arrangement of the propulsion coils had been changed in Yamanashi Test Line from the single-layered coils to the double-layered coils for the stability of the super-conducting magnet on board. Thus, experiments and investigations concerning the frequency characteristics(resonance characteristics)of the propulsion coils with double-layer arrangement at Yamanashi Test Line have been performed but a theoretical analysis had not been done enough. A theoretical analysis was therefore done in this paper by applying the inverted L equivalent circuit with mutual inductance and capacitance to the propulsion coil, from which the positive and zero phase characteristics of the double-layered propulsion coils were analyzed.

Modeling electrical double-layer effects for microfluidic impedance spectroscopy from 100 kHz to 110 GHz.

PubMed

Little, Charles A E; Orloff, Nathan D; Hanemann, Isaac E; Long, Christian J; Bright, Victor M; Booth, James C

2017-07-25

Broadband microfluidic-based impedance spectroscopy can be used to characterize complex fluids, with applications in medical diagnostics and in chemical and pharmacological manufacturing. Many relevant fluids are ionic; during impedance measurements ions migrate to the electrodes, forming an electrical double-layer. Effects from the electrical double-layer dominate over, and reduce sensitivity to, the intrinsic impedance of the fluid below a characteristic frequency. Here we use calibrated measurements of saline solution in microfluidic coplanar waveguide devices at frequencies between 100 kHz and 110 GHz to directly measure the double-layer admittance for solutions of varying ionic conductivity. We successfully model the double-layer admittance using a combination of a Cole-Cole response with a constant phase element contribution. Our analysis yields a double-layer relaxation time that decreases linearly with solution conductivity, and allows for double-layer effects to be separated from the intrinsic fluid response and quantified for a wide range of conducting fluids.

Rb vapor-cell clock demonstration with a frequency-doubled telecom laser.

PubMed

Almat, Nil; Pellaton, Matthieu; Moreno, William; Gruet, Florian; Affolderbach, Christoph; Mileti, Gaetano

2018-06-01

We employ a recently developed laser system, based on a low-noise telecom laser emitting around 1.56 μm, to evaluate its impact on the performance of an Rb vapor-cell clock in a continuous-wave double-resonance scheme. The achieved short-term clock instability below 2.5·10 -13 ·τ -1/2 demonstrates, for the first time, the suitability of a frequency-doubled telecom laser for this specific application. We measure and study quantitatively the impact of laser amplitude and frequency noises and of the ac Stark shift, which limit the clock frequency stability on short timescales. We also report on the detailed noise budgets and demonstrate experimentally that, under certain conditions, the short-term stability of the clock operated with the low-noise telecom laser is improved by a factor of three compared to clock operation using the direct 780-nm laser.

Spin-orbit signatures in the dynamics of singlet-triplet qubits in double quantum dots

NASA Astrophysics Data System (ADS)

Rolon, Juan E.; Cota, Ernesto; Ulloa, Sergio E.

2017-05-01

We characterize numerically and analytically the signatures of the spin-orbit interaction in a two-electron GaAs double quantum dot in the presence of an external magnetic field. In particular, we obtain the return probability of the singlet state by simulating Landau-Zener voltage detuning sweeps which traverse the singlet-triplet (S -T+ ) resonance. Our results indicate that non-spin-conserving interdot tunneling processes arising from the spin-orbit interaction have well defined signatures. These allow direct access to the spin-orbit interaction scales and are characterized by a frequency shift and Fourier amplitude modulation of the Rabi flopping dynamics of the singlet-triplet qubits S -T0 and S -T+ . By applying the Bloch-Feshbach projection formalism, we demonstrate analytically that the aforementioned effects originate from the interplay between spin-orbit interaction and processes driven by the hyperfine interaction between the electron spins and those of the GaAs nuclei.

MgO:PPLN frequency doubling optical chips for green light generation: from lab research to mass production

NASA Astrophysics Data System (ADS)

Xu, Chang-Qing; Gan, Yi; Sun, Jian

2012-03-01

Laser displays require red, green and blue (RGB) laser sources each with a low-cost, a high wall-plug efficiency, and a small size. However, semiconductor chips that directly emit green light with sufficient power and efficiency are not currently available on the market. A practical solution to the "green" bottleneck is to employ diode pumped solid state laser (DPSSL) technology, in which a frequency doubling crystal is used. In this paper, recent progress of MgO doped periodically poled lithium niobate (MgO:PPLN) frequency doubling optical chips will be presented. It is shown that MgO:PPLN can satisfy all of the requirements for laser displays and is ready for mass production.

Yellow light generation by frequency doubling of a diode-pumped Nd:YAG laser

NASA Astrophysics Data System (ADS)

Jia, Fu-qiang; Zheng, Quan; Xue, Qing-hua; Bu, Yi-kun; Qian, Long-sheng

2006-03-01

We demonstrate the generation of TEM00 mode yellow light in critically type II phase-matched KTiOPO4 (KTP) with intracavity frequency doubling of a diode-pumped Nd:YAG laser at room temperature. After a 150 μm thick etalon have been inserted into the cavity, the stability and beam quality of the second harmonic generation (SHG) is enhanced. A continuous wave (CW) TEM00 mode output power of 1.67 W at 556 nm is obtained at a pump level of 16 W. The total optical to optical conversion efficiency is about 10.44%. To the best of our knowledge, this is the first Watt-level yellow light generation by frequency doubling of Nd:YAG laser.

Double-quantum homonuclear rotary resonance: Efficient dipolar recovery in magic-angle spinning nuclear magnetic resonance

NASA Astrophysics Data System (ADS)

Nielsen, N. C.; Bildsøe, H.; Jakobsen, H. J.; Levitt, M. H.

1994-08-01

We describe an efficient method for the recovery of homonuclear dipole-dipole interactions in magic-angle spinning NMR. Double-quantum homonuclear rotary resonance (2Q-HORROR) is established by fulfilling the condition ωr=2ω1, where ωr is the sample rotation frequency and ω1 is the nutation frequency around an applied resonant radio frequency (rf) field. This resonance can be used for double-quantum filtering and measurement of homonuclear dipolar interactions in the presence of magic-angle spinning. The spin dynamics depend only weakly on crystallite orientation allowing good performance for powder samples. Chemical shift effects are suppressed to zeroth order. The method is demonstrated for singly and doubly 13C labeled L-alanine.

FREQUENCY DEPENDENCE OF POLARIZATION OF ZEBRA PATTERN IN TYPE-IV SOLAR RADIO BURSTS

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

Kaneda, Kazutaka; Misawa, H.; Tsuchiya, F.

2015-08-01

We investigated the polarization characteristics of a zebra pattern (ZP) in a type-IV solar radio burst observed with AMATERAS on 2011 June 21 for the purpose of evaluating the generation processes of ZPs. Analyzing highly resolved spectral and polarization data revealed the frequency dependence of the degree of circular polarization and the delay between two polarized components for the first time. The degree of circular polarization was 50%–70% right-handed and it varied little as a function of frequency. Cross-correlation analysis determined that the left-handed circularly polarized component was delayed by 50–70 ms relative to the right-handed component over the entiremore » frequency range of the ZP and this delay increased with the frequency. We examined the obtained polarization characteristics by using pre-existing ZP models and concluded that the ZP was generated by the double-plasma-resonance process. Our results suggest that the ZP emission was originally generated in a completely polarized state in the O-mode and was partly converted into the X-mode near the source. Subsequently, the difference between the group velocities of the O-mode and X-mode caused the temporal delay.« less

High-frequency response and the possibilities of frequency-tunable narrow-band terahertz amplification in resonant tunneling nanostructures

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

Kapaev, V. V., E-mail: kapaev@sci.lebedev.ru; Kopaev, Yu. V.; Savinov, S. A.

2013-03-15

The characteristics of the high-frequency response of single- and double-well resonant tunneling structures in a dc electric field are investigated on the basis of the numerical solution of a time-dependent Schroedinger equation with open boundary conditions. The frequency dependence of the real part of high frequency conductivity (high-frequency response) in In{sub 0.53}Ga{sub 0.47}As/AlAs/InP structures is analyzed in detail for various values of the dc voltage V{sub dc} in the negative differential resistance (NDR) region. It is shown that double-well three-barrier structures are promising for the design of terahertz-band oscillators. The presence of two resonant states with close energies in suchmore » structures leads to a resonant (in frequency) response whose frequency is determined by the energy difference between these levels and can be controlled by varying the parameters of the structure. It is shown that, in principle, such structures admit narrow-band amplification, tuning of the amplification frequency, and a fine control of the amplification (oscillation) frequency in a wide range of terahertz frequencies by varying a dc electric voltage applied to the structure. Starting from a certain width of the central intermediate barrier in double-well structures, one can observe a collapse of resonances, where the structure behaves like a single-well system. This phenomenon imposes a lower limit on the oscillation frequency in three-barrier resonant tunneling structures.« less

A High Power Frequency Doubled Fiber Laser

NASA Technical Reports Server (NTRS)

Thompson, Robert J.; Tu, Meirong; Aveline, Dave; Lundblad, Nathan; Maleki, Lute

2003-01-01

This viewgraph presentation reports on the development of a high power 780 nm laser suitable for space applications of laser cooling. A possible solution is to use frequency doubling of high power 1560 nm telecom lasers. The presentation shows a diagram of the frequency conversion, and a graph of the second harmonic generation in one crystal, and the use of the cascading crystals. Graphs show the second harmonic power as a function of distance between crystals, second harmonic power vs. pump power, tunability of laser systems.

Laser radiation frequency doubling in a single-crystal fibre based on a stoichiometric LiNbO3 crystal

NASA Astrophysics Data System (ADS)

Kashin, V. V.; Nikolaev, D. A.; Rusanov, S. Ya; Tsvetkov, V. B.

2015-01-01

We demonstrate the employment of single-crystal optical fibres based on lithium niobate for doubling the laser radiation frequency. The measured characteristics of the fibre confirm its high quality and spatial homogeneity. Parameters of the frequency doublers for neodymium laser radiation (λ = 1 mm) based on fibre and bulk single crystals are compared. Single crystals are grown by the method of laser-heated pedestal growing with heating by radiation of a CO2 laser (LHPG-method).

A Robust Molecular Network Motif for Period-Doubling Devices.

PubMed

Cuba Samaniego, Christian; Franco, Elisa

2018-01-19

Life is sustained by a variety of cyclic processes such as cell division, muscle contraction, and neuron firing. The periodic signals powering these processes often direct a variety of other downstream systems, which operate at different time scales and must have the capacity to divide or multiply the period of the master clock. Period modulation is also an important challenge in synthetic molecular systems, where slow and fast components may have to be coordinated simultaneously by a single oscillator whose frequency is often difficult to tune. Circuits that can multiply the period of a clock signal (frequency dividers), such as binary counters and flip-flops, are commonly encountered in electronic systems, but design principles to obtain similar devices in biological systems are still unclear. We take inspiration from the architecture of electronic flip-flops, and we propose to build biomolecular period-doubling networks by combining a bistable switch with negative feedback modules that preprocess the circuit inputs. We identify a network motif and we show it can be "realized" using different biomolecular components; two of the realizations we propose rely on transcriptional gene networks and one on nucleic acid strand displacement systems. We examine the capacity of each realization to perform period-doubling by studying how bistability of the motif is affected by the presence of the input; for this purpose, we employ mathematical tools from algebraic geometry that provide us with valuable insights on the input/output behavior as a function of the realization parameters. We show that transcriptional network realizations operate correctly also in a stochastic regime when processing oscillations from the repressilator, a canonical synthetic in vivo oscillator. Finally, we compare the performance of different realizations in a range of realistic parameters via numerical sensitivity analysis of the period-doubling region, computed with respect to the input period and amplitude. Our mathematical and computational analysis suggests that the motif we propose is generally robust with respect to specific implementation details: functionally equivalent circuits can be built as long as the species-interaction topology is respected. This indicates that experimental construction of the circuit is possible with a variety of components within the rapidly expanding libraries available in synthetic biology.

Acoustic guided waves in cylindrical solid-fluid structures: Modeling with a sweeping frequency finite element method and experimental validation

NASA Astrophysics Data System (ADS)

Liu, Yang; D'Angelo, Ralph M.; Sinha, Bikash K.; Zeroug, Smaine

2017-02-01

Modeling and understanding the complex elastic-wave physics prevalent in solid-fluid cylindrically-layered structures is of importance in many NDE fields, and most pertinently in the domain of well integrity evaluation of cased holes in the oil and gas industry. Current sonic measurements provide viable techniques for well integrity evaluation yet their practical effectiveness is hampered by the current lack of knowledge of acoustic wave fields particularly in complicated cased-hole geometry where for instance two or more nested steel strings are present in the borehole. In this article, we propose and implement a Sweeping Frequency Finite Element Method (SFFEM) for acoustic guided waves simulation in complex geometries that include double steel strings cemented to each other and to the formation and where the strings may be non-concentric. Transient dynamic finite element models are constructed with sweeping frequency signals being applied as the excitation sources. The sources and receivers disposition simulate current sonic measurement tools deployed in the oilfield. Synthetic wavetrains are recorded and processed with modified matrix pencil method to isolate both the dispersive and non-dispersive propagating guided wave modes. Scaled experiments of fluid-filled double strings with dimensions mimicking the real ones encountered in the field have also been carried out to generate reference data. A comparison of the experimental and numerical results indicates that the SFFEM is capable of accurately reproducing the rich and intricate higher-order multiple wave fields observed experimentally in the fluid-filled double string geometries.

In trans paired nicking triggers seamless genome editing without double-stranded DNA cutting.

PubMed

Chen, Xiaoyu; Janssen, Josephine M; Liu, Jin; Maggio, Ignazio; 't Jong, Anke E J; Mikkers, Harald M M; Gonçalves, Manuel A F V

2017-09-22

Precise genome editing involves homologous recombination between donor DNA and chromosomal sequences subjected to double-stranded DNA breaks made by programmable nucleases. Ideally, genome editing should be efficient, specific, and accurate. However, besides constituting potential translocation-initiating lesions, double-stranded DNA breaks (targeted or otherwise) are mostly repaired through unpredictable and mutagenic non-homologous recombination processes. Here, we report that the coordinated formation of paired single-stranded DNA breaks, or nicks, at donor plasmids and chromosomal target sites by RNA-guided nucleases based on CRISPR-Cas9 components, triggers seamless homology-directed gene targeting of large genetic payloads in human cells, including pluripotent stem cells. Importantly, in addition to significantly reducing the mutagenicity of the genome modification procedure, this in trans paired nicking strategy achieves multiplexed, single-step, gene targeting, and yields higher frequencies of accurately edited cells when compared to the standard double-stranded DNA break-dependent approach.CRISPR-Cas9-based gene editing involves double-strand breaks at target sequences, which are often repaired by mutagenic non-homologous end-joining. Here the authors use Cas9 nickases to generate coordinated single-strand breaks in donor and target DNA for precise homology-directed gene editing.

Dispersive distortions of a radio-wave pulse in a double-resonance gaseous medium

NASA Astrophysics Data System (ADS)

Strelkov, G. M.

2017-03-01

The problem on dispersive distortions of an electromagnetic pulse in a gaseous medium with two isolated resonant frequencies is solved analytically. The solution is obtained directly in the time region and, thus, is not the result of calculations of the Fourier integral. Without introducing additional assumptions, it is possible to study the regularities and the features of the process of propagation of pulses caused by variations of both their initial characteristics and the parameters of the propagation medium. As an example, the solution is applied to describe the distortions of the two-frequency pulse of subnanosecond duration in the terrestrial atmosphere.

Time-resolved measurements of statistics for a Nd:YAG laser.

PubMed

Hubschmid, W; Bombach, R; Gerber, T

1994-08-20

Time-resolved measurements of the fluctuating intensity of a multimode frequency-doubled Nd:YAG laser have been performed. For various operating conditions the enhancement factors in nonlinear optical processes that use a fluctuating instead of a single-mode laser have been determined up to the sixth order. In the case of reduced flash-lamp excitation and a switched-off laser amplifier, the intensity fluctuations agree with the normalized Gaussian model for the fluctuations of the fundamental frequency, whereas strong deviations are found under usual operating conditions. The frequencydoubled light has in the latter case enhancement factors not so far from values of Gaussian statistics.

Measurement of efficiency in calculus removal with a frequency-doubled Alexandrite laser on pigs' jaws

NASA Astrophysics Data System (ADS)

Pilgrim, Christian G.; Rechmann, Peter; Goldin, Dan S.; Hennig, Thomas

2000-03-01

Periodontal therapy aims in a most sufficient cleaning of tooth surfaces from supra- and subgingival calculus. As a standard dental procedure teeth are treated with ultrasonic devices. The competence of the frequency doubled Alexandrite laser for a highly effective and selective removal of calculus has been repeatedly proved. Aim of the study presented here was to determine the efficiency at simulated clinical conditions of the frequency doubled Alexandrite laser (laboratory prototype, q-switched, fiber guided, wavelength 377 nm, pulse duration 1 microsecond, pulse repetition rate 70 Hz, water cooling) by quantifying it's calculus removing efficiency. The evaluated data were compared to those obtained with an ultrasonic calculus remover. In the first part of the study sample material consisted of 23 pigs' jaws. They were divided into two groups. The teeth of one group were cleaned on their buccal surfaces using an ultrasonic device (Sonosoft Lux, KaVo, Biberach, Germany; tip #9). Than hand-guided cleaning was performed until no further improvement in cleanness was visible. Cleaning time was measured. Photographic documentation was taken before and after the treatment. The teeth in the second group were cleaned engaging a frequency doubled Alexandrite laser. Treatment time was measured and photographs were taken in the same way. In the second part of the study 21 surfaces of human teeth set up in an artificial pocket model were treated with both systems again. Measurements followed the same protocol. The results strongly support the use of the frequency doubled Alexandrite laser for calculus removal.

Sound transmission through triple-panel structures lined with poroelastic materials

NASA Astrophysics Data System (ADS)

Liu, Yu

2015-03-01

In this paper, previous theories on the prediction of sound transmission loss for a double-panel structure lined with poroelastic materials are extended to address the problem of a triple-panel structure. Six typical configurations are considered for a triple-panel structure based on the method of coupling the porous layers to the facing panels which determines critically the sound insulation performance of the system. The transfer matrix method is employed to solve the system by applying appropriate types of boundary conditions for these configurations. The transmission loss of the triple-panel structures in a diffuse sound field is calculated as a function of frequency and compared with that of corresponding double-panel structures. Generally, the triple-panel structure with poroelastic linings has superior acoustic performance to the double-panel counterpart, remarkably in the mid-high frequency range and possibly at low frequencies, by selecting appropriate configurations in which those with two air gaps in the structure exhibit the best overall performance over the entire frequency range. The poroelastic lining significantly lowers the cut-on frequency above which the triple-panel structure exhibits noticeably higher transmission loss. Compared with a double-panel structure, the wider range of system parameters for a triple-panel structure due to the additional partition provides more design space for tuning the sound insulation performance. Despite the increased structural complexity, the triple-panel structure lined with poroelastic materials has the obvious advantages in sound transmission loss while without the penalties in weight and volume, and is hence a promising replacement for the widely used double-panel sandwich structure.

Ultrahigh contrast from a frequency-doubled chirped-pulse-amplification beamline.

PubMed

Hillier, David; Danson, Colin; Duffield, Stuart; Egan, David; Elsmere, Stephen; Girling, Mark; Harvey, Ewan; Hopps, Nicholas; Norman, Michael; Parker, Stefan; Treadwell, Paul; Winter, David; Bett, Thomas

2013-06-20

This paper describes frequency-doubled operation of a high-energy chirped-pulse-amplification beamline. Efficient type-I second-harmonic generation was achieved using a 3 mm thick 320 mm aperture KDP crystal. Shots were fired at a range of energies achieving more than 100 J in a subpicosecond, 527 nm laser pulse with a power contrast of 10(14).

Power and efficiency scaling of diode pumped Cr:LiSAF lasers: 770-1110 nm tuning range and frequency doubling to 387-463 nm.

PubMed

Demirbas, Umit; Baali, Ilyes

2015-10-15

We report significant average power and efficiency scaling of diode-pumped Cr:LiSAF lasers in continuous-wave (cw), cw frequency-doubled, and mode-locked regimes. Four single-emitter broad-area laser diodes around 660 nm were used as the pump source, which provided a total pump power of 7.2 W. To minimize thermal effects, a 20 mm long Cr:LiSAF sample with a relatively low Cr-concentration (0.8%) was used as the gain medium. In cw laser experiments, 2.4 W of output power, a slope efficiency of 50%, and a tuning range covering the 770-1110 nm region were achieved. Intracavity frequency doubling with beta-barium borate (BBO) crystals generated up to 1160 mW of blue power and a record tuning range in the 387-463 nm region. When mode locked with a saturable absorber mirror, the laser produced 195 fs pulses with 580 mW of average power around 820 nm at a 100.3 MHz repetition rate. The optical-to-optical conversion efficiency of the system was 33% in cw, 16% in cw frequency-doubled, and 8% in cw mode-locked regimes.

Development of a 3D finite element acoustic model to predict the sound reduction index of stud based double-leaf walls

NASA Astrophysics Data System (ADS)

Arjunan, A.; Wang, C. J.; Yahiaoui, K.; Mynors, D. J.; Morgan, T.; Nguyen, V. B.; English, M.

2014-11-01

Building standards incorporating quantitative acoustical criteria to ensure adequate sound insulation are now being implemented. Engineers are making great efforts to design acoustically efficient double-wall structures. Accordingly, efficient simulation models to predict the acoustic insulation of double-leaf wall structures are needed. This paper presents the development of a numerical tool that can predict the frequency dependent sound reduction index R of stud based double-leaf walls at one-third-octave band frequency range. A fully vibro-acoustic 3D model consisting of two rooms partitioned using a double-leaf wall, considering the structure and acoustic fluid coupling incorporating the existing fluid and structural solvers are presented. The validity of the finite element (FE) model is assessed by comparison with experimental test results carried out in a certified laboratory. Accurate representation of the structural damping matrix to effectively predict the R values are studied. The possibilities of minimising the simulation time using a frequency dependent mesh model was also investigated. The FEA model presented in this work is capable of predicting the weighted sound reduction index Rw along with A-weighted pink noise C and A-weighted urban noise Ctr within an error of 1 dB. The model developed can also be used to analyse the acoustically induced frequency dependent geometrical behaviour of the double-leaf wall components to optimise them for best acoustic performance. The FE modelling procedure reported in this paper can be extended to other building components undergoing fluid-structure interaction (FSI) to evaluate their acoustic insulation.

Linear and nonlinear mechanical properties of a series of epoxy resins

NASA Technical Reports Server (NTRS)

Curliss, D. B.; Caruthers, J. M.

1987-01-01

The linear viscoelastic properties have been measured for a series of bisphenol-A-based epoxy resins cured with the diamine DDS. The linear viscoelastic master curves were constructed via time-temperature superposition of frequency dependent G-prime and G-double-prime isotherms. The G-double-prime master curves exhibited two sub-Tg transitions. Superposition of isotherms in the glass-to-rubber transition (i.e., alpha) and the beta transition at -60 C was achieved by simple horizontal shifts in the log frequency axis; however, in the region between alpha and beta, superposition could not be effected by simple horizontal shifts along the log frequency axis. The different temperature dependency of the alpha and beta relaxation mechanisms causes a complex response of G-double-prime in the so called alpha-prime region. A novel numerical procedure has been developed to extract the complete relaxation spectra and its temperature dependence from the G-prime and G-double-prime isothermal data in the alpha-prime region.

AC and DC conductivity due to hopping mechanism in double ion doped ceramics

NASA Astrophysics Data System (ADS)

Rizwana, Mahboob, Syed; Sarah, P.

2018-04-01

Sr1-2xNaxNdxBi4Ti4O15 (x = 0.1, 0.2 and 0.4) system is prepared by sol gel method involving Pechini process of modified polymeric precursor method. Phase identification is done using X-ray diffraction. Conduction in prepared materials involves different mechanisms and is explained through detailed AC and DC conductivity studies. AC conductivity studies carried out on the samples at different frequencies and different temperatures gives more information about electrical transport. Exponents used in two term power relation helps us to understand the different hopping mechanism involved at low as well as high frequencies. Activation energies calculated from the Arrhenius plots are used to calculate activation energies at different temperatures and frequencies. Hopping frequency calculated from the measured data explains hopping of charge carriers at different temperatures. DC conductivity studies help us to know the role of oxygen vacancies in conduction.

Spectral and energy characteristics of four-photon parametric scattering in sodium vapor

NASA Astrophysics Data System (ADS)

Vaicaitis, V.; Ignatavicius, M.; Kudriashov, V. A.; Pimenov, Iu. N.; Jakyte, R.

1987-04-01

Consideration is given to processes of four-photon interaction upon two-photon resonance excitation of the 3d level of sodium by two-frequency radiation from a monopulse picosecond YAG:Nd laser with frequency doubling and an optical parametric oscillator utilizing KDP crystrals. The spatial and frequency spectra of the four-photon parametric scattering (FPS) are recorded and studied at different sodium vapor concentrations (10 to the 15th to 10 to the 17th/cu cm) and upon both collinear and noncollinear excitation. It is shown that the observed conical structure of the FPS radiation can be interpreted from an analysis of the realization of the frequency and spatial phase-matching conditions. The dependences of the FPS radiation intensity on the exciting radiation intensity, the sodium vapor concentration, and the mismatching of the exciting radiation from the two-photon resonance are obtained.

High Frequency PIN-Diode Switches for Radiometer Applications

NASA Technical Reports Server (NTRS)

Montes, Oliver; Dawson, Douglas E.; Kangaslahti, Pekka; Reising, Steven C.

2011-01-01

Internally calibrated radiometers are needed for ocean topography and other missions. Typically internal calibration is achieved with Dicke switching as one of the techniques. We have developed high frequency single-pole double-throw (SPDT) switches in the form of monolithic microwave integrated circuits (MMIC) that can be easily integrated into Dicke switched radiometers that utilize microstrip technology. In particular, the switches we developed can be used for a radiometer such as the one proposed for the Surface Water and Ocean Topography (SWOT) Satellite Mission whose three channels at 92, 130, and 166 GHz would allow for wet-tropospheric path delay correction near coastal zones and over land. This feat is not possible with the current Jason-class radiometers due to their lower frequency signal measurement and thus lower resolution. The MMIC chips were fabricated at NGST using their InP PIN diode process and measured at JPL using high frequency test equipment. Measurement and simulation results will be presented.

Frequency-doubled Alexandrite laser for use in periodontology: a scanning electron microscopic investigation

NASA Astrophysics Data System (ADS)

Rechmann, Peter; Hennig, Thomas

1996-12-01

During prior studies it could be demonstrated that engaging a frequency double Alexandrite-laser allows a fast and strictly selective ablation of supra- and subgingival calculus. Furthermore, the removal of unstained microbial plaque was observed. First conclusions were drawn following light microscopic investigations on undecalcified sections of irradiated teeth. In the present study the cementum surface after irradiation with a frequency doubled Alexandrite-laser was observed by means of a scanning electron microscope. After irradiation sections of teeth were dried in alcohol and sputtered with gold. In comparison irradiated cementum surfaces of unerupted operatively removed wisdom teeth and tooth surfaces after the selective removal of calculus were investigated. A complete removal of calculus was observed as well as a remaining smooth surface of irradiated cementum.

In-phased second harmonic wave array generation with intra-Talbot-cavity frequency-doubling.

PubMed

Hirosawa, Kenichi; Shohda, Fumio; Yanagisawa, Takayuki; Kannari, Fumihiko

2015-03-23

The Talbot cavity is one promising method to synchronize the phase of a laser array. However, it does not achieve the lowest array mode with the same phase but the highest array mode with the anti-phase between every two adjacent lasers, which is called out-phase locking. Consequently, their far-field images exhibit 2-peak profiles. We propose intra-Talbot-cavity frequency-doubling. By placing a nonlinear crystal in a Talbot cavity, the Talbot cavity generates an out-phased fundamental wave array, which is converted into an in-phase-locked second harmonic wave array at the nonlinear crystal. We demonstrate numerical calculations and experiments on intra-Talbot-cavity frequency-doubling and obtain an in-phase-locked second harmonic wave array for a Nd:YVO₄ array laser.

Scalable fabrication of self-aligned graphene transistors and circuits on glass.

PubMed

Liao, Lei; Bai, Jingwei; Cheng, Rui; Zhou, Hailong; Liu, Lixin; Liu, Yuan; Huang, Yu; Duan, Xiangfeng

2012-06-13

Graphene transistors are of considerable interest for radio frequency (rf) applications. High-frequency graphene transistors with the intrinsic cutoff frequency up to 300 GHz have been demonstrated. However, the graphene transistors reported to date only exhibit a limited extrinsic cutoff frequency up to about 10 GHz, and functional graphene circuits demonstrated so far can merely operate in the tens of megahertz regime, far from the potential the graphene transistors could offer. Here we report a scalable approach to fabricate self-aligned graphene transistors with the extrinsic cutoff frequency exceeding 50 GHz and graphene circuits that can operate in the 1-10 GHz regime. The devices are fabricated on a glass substrate through a self-aligned process by using chemical vapor deposition (CVD) grown graphene and a dielectrophoretic assembled nanowire gate array. The self-aligned process allows the achievement of unprecedented performance in CVD graphene transistors with a highest transconductance of 0.36 mS/μm. The use of an insulating substrate minimizes the parasitic capacitance and has therefore enabled graphene transistors with a record-high extrinsic cutoff frequency (> 50 GHz) achieved to date. The excellent extrinsic cutoff frequency readily allows configuring the graphene transistors into frequency doubling or mixing circuits functioning in the 1-10 GHz regime, a significant advancement over previous reports (∼20 MHz). The studies open a pathway to scalable fabrication of high-speed graphene transistors and functional circuits and represent a significant step forward to graphene based radio frequency devices.

Scattering of waves by impurities in precompressed granular chains.

PubMed

Martínez, Alejandro J; Yasuda, Hiromi; Kim, Eunho; Kevrekidis, P G; Porter, Mason A; Yang, Jinkyu

2016-05-01

We study scattering of waves by impurities in strongly precompressed granular chains. We explore the linear scattering of plane waves and identify a closed-form expression for the reflection and transmission coefficients for the scattering of the waves from both a single impurity and a double impurity. For single-impurity chains, we show that, within the transmission band of the host granular chain, high-frequency waves are strongly attenuated (such that the transmission coefficient vanishes as the wavenumber k→±π), whereas low-frequency waves are well-transmitted through the impurity. For double-impurity chains, we identify a resonance-enabling full transmission at a particular frequency-in a manner that is analogous to the Ramsauer-Townsend (RT) resonance from quantum physics. We also demonstrate that one can tune the frequency of the RT resonance to any value in the pass band of the host chain. We corroborate our theoretical predictions both numerically and experimentally, and we directly observe almost complete transmission for frequencies close to the RT resonance frequency. Finally, we show how this RT resonance can lead to the existence of reflectionless modes in granular chains (including disordered ones) with multiple double impurities.

A fully integrated neural recording amplifier with DC input stabilization.

PubMed

Mohseni, Pedram; Najafi, Khalil

2004-05-01

This paper presents a low-power low-noise fully integrated bandpass operational amplifier for a variety of biomedical neural recording applications. A standard two-stage CMOS amplifier in a closed-loop resistive feedback configuration provides a stable ac gain of 39.3 dB at 1 kHz. A subthreshold PMOS input transistor is utilized to clamp the large and random dc open circuit potentials that normally exist at the electrode-electrolyte interface. The low cutoff frequency of the amplifier is programmable up to 50 Hz, while its high cutoff frequency is measured to be 9.1 kHz. The tolerable dc input range is measured to be at least +/- 0.25 V with a dc rejection factor of at least 29 dB. The amplifier occupies 0.107 mm2 in die area, and dissipates 115 microW from a 3 V power supply. The total measured input-referred noise voltage in the frequency range of 0.1-10 kHz is 7.8 microVrms. It is fabricated using AMI 1.5 microm double-poly double-metal n-well CMOS process. This paper presents full characterization of the dc, ac, and noise performance of this amplifier through in vitro measurements in saline using two different neural recording electrodes.

Rain Reevaporation, Boundary Layer Convection Interactions, and Pacific Rainfall Patterns in an AGCM

NASA Technical Reports Server (NTRS)

Bacmeister, Julio T.; Suarez, Max J.; Robertson, Franklin R.

2004-01-01

Sensitivity experiments with an atmospheric general circulation model (AGCM) show that parameterized rain re-evaporation has a large impact on simulated precipitation patterns in the tropical Pacific, especially on the configuration of the model s intertropical convergence zone (ITCZ). Weak re-evaporation leads t o the formation of a "double ITCZ" during the northern warm season. The double ITCZ is accompanied by strong coupling between precipitation and high-frequency vertical motion in the planetary boundary layer (PBL). Strong reevaporation leads to a better overall agreement of simulated precipitation with observations. The model s double ITCZ bias is reduced. At the same time, correlation between high-frequency vertical motion in the PBL and precipitation is reduced. Experiments with modified physics suggest that evaporative cooling by rain near the PBL top weakens the coupling between precipitation and vertical motion. This may reduce the model s tendency to form double ITCZs. The strength of high-frequency vertical motions in the PBL was also reduced directly through the introduction of a diffusive cumulus momentum transport (DCMT) parameterization. The DCMT had a visible impact on simulated precipitation in the tropics, but did not reduce the model s double bias in all cases.

FLAMMABLE GAS TECHNICAL BASIS DOCUMENT

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

KRIPPS, L.J.

2005-02-18

This document describes the qualitative evaluation of frequency and consequences for double shell tank (DST) and single shell tank (SST) representative flammable gas accidents and associated hazardous conditions without controls. The evaluation indicated that safety-significant SSCs and/or TSRS were required to prevent or mitigate flammable gas accidents. Discussion on the resulting control decisions is included. This technical basis document was developed to support of the Tank Farms Documented Safety Analysis (DSA) and describes the risk binning process for the flammable gas representative accidents and associated represented hazardous conditions. The purpose of the risk binning process is to determine the needmore » for safety-significant structures, systems, and components (SSC) and technical safety requirement (TSR)-level controls for a given representative accident or represented hazardous condition based on an evaluation of the event frequency and consequence.« less

FAST TRACK COMMUNICATION: Controllable optical bistability and multistability in a double two-level atomic system

NASA Astrophysics Data System (ADS)

Wu, Jing; Lü, Xin-You; Zheng, Li-Li

2010-08-01

We theoretically investigate the behaviour of optical bistability (OB) and optical multistability (OM) in a generic double two-level atomic system driven by two orthogonally polarized fields (a π-polarized control field and a σ-polarized probe field). It is found that the behaviour of OB can be controlled by adjusting the intensity or the frequency detuning of the control field. Interestingly enough, our numerical results also show that it is easy to realize the transition from OB to OM or vice versa by adjusting the relative phase between the control and probe fields. This investigation can be used for the development of new types of devices for realizing an all-optic switching process.

The contribution of microbunching instability to solar flare emission in the GHz to THz range of frequencies

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

Klopf, J. Michael; Kaufmann, Pierre; Raulin, Jean-Pierre

2014-07-01

Recent solar flare observations in the sub-terahertz range have provided evidence of a new spectral component with fluxes increasing for larger frequencies, separated from the well-known microwave emission that maximizes in the gigahertz range. Suggested interpretations explain the terahertz spectral component but do not account for the simultaneous microwave component. We present a mechanism for producing the observed "double spectra." Based on coherent enhancement of synchrotron emission at long wavelengths in laboratory accelerators, we consider how similar processes may occur within a solar flare. The instability known as microbunching arises from perturbations that produce electron beam density modulations, giving risemore » to broadband coherent synchrotron emission at wavelengths comparable to the characteristic size of the microbunch structure. The spectral intensity of this coherent synchrotron radiation (CSR) can far exceed that of the incoherent synchrotron radiation (ISR), which peaks at a higher frequency, thus producing a double-peaked spectrum. Successful CSR simulations are shown to fit actual burst spectral observations, using typical flaring physical parameters and power-law energy distributions for the accelerated electrons. The simulations consider an energy threshold below which microbunching is not possible because of Coulomb repulsion. Only a small fraction of the radiating charges accelerated to energies above the threshold is required to produce the microwave component observed for several events. The ISR/CSR mechanism can occur together with other emission processes producing the microwave component. It may bring an important contribution to microwaves, at least for certain events where physical conditions for the occurrence of the ISR/CSR microbunching mechanism are possible.« less

Microseisms Generated by Super Typhoon Megi in the Western Pacific Ocean

NASA Astrophysics Data System (ADS)

Lin, Jianmin; Lin, Jian; Xu, Min

2017-12-01

Microseisms generated by the super typhoon Megi (13-24 October 2010) were detected on both land-based and island-based seismic stations. We applied temporal frequency spectrum analysis to investigate the temporal evolution of the microseisms. When Megi was over the deep basins of the Philippine Sea, only weak microseisms with short-period double frequency (SPDF, ˜0.20-0.40 Hz) were observed. However, after Megi traveled into the shallower waters of the South China Sea, microseisms with both long-period double frequency (LPDF, ˜0.12-0.20 Hz) and SPDF were recorded. The excitation source regions of the microseisms were analyzed using seismic waveform records and synthetic modeling in frequency domain. Results reveal that part of the LPDF microseisms were excited in coastal source regions, while the intensity of both LPDF and SPDF microseisms correlated well with the distance from seismic stations to the typhoon center. Synthetic computations of equivalent surface pressure and corresponding microseisms show that the wave-to-wave interaction induced by coastal reflection has primary effects on microseismic frequency band of ˜0.10-0.20 Hz. The coastal generation of the dispersive LPDF microseisms is also supported by the observation of ocean swells induced by Megi through the images of C-band ENVISAT-ASAR satellite during its migration process. Two source regions of the microseisms during the life span of Megi are finally distinguished: One was mainly located in the left-rear quadrant of the typhoon center that generated both LPDF and SPDF microseisms at shallow seas, while the other one was near the coasts that generated mostly LPDF microseisms.

[Research on diagnosis of gas-liquid detonation exhaust based on double optical path absortion spectroscopy technique].

PubMed

Lü, Xiao-Jing; Li, Ning; Weng, Chun-Sheng

2014-03-01

The effect detection of detonation exhaust can provide measurement data for exploring the formation mechanism of detonation, the promotion of detonation efficiency and the reduction of fuel waste. Based on tunable diode laser absorption spectroscopy technique combined with double optical path cross-correlation algorithm, the article raises the diagnosis method to realize the on-line testing of detonation exhaust velocity, temperature and H2O gas concentration. The double optical path testing system is designed and set up for the valveless pulse detonation engine with the diameter of 80 mm. By scanning H2O absorption lines of 1343nm with a high frequency of 50 kHz, the on-line detection of gas-liquid pulse detonation exhaust is realized. The results show that the optical testing system based on tunable diode laser absorption spectroscopy technique can capture the detailed characteristics of pulse detonation exhaust in the transient process of detonation. The duration of single detonation is 85 ms under laboratory conditions, among which supersonic injection time is 5.7 ms and subsonic injection time is 19.3 ms. The valveless pulse detonation engine used can work under frequency of 11 Hz. The velocity of detonation overflowing the detonation tube is 1,172 m x s(-1), the maximum temperature of detonation exhaust near the nozzle is 2 412 K. There is a transitory platform in the velocity curve as well as the temperature curve. H2O gas concentration changes between 0-7% during detonation under experimental conditions. The research can provide measurement data for the detonation process diagnosis and analysis, which is of significance to advance the detonation mechanism research and promote the research of pulse detonation engine control technology.

Resonance Frequency Tuning of a Double Ring Resonator in GaInAsP/InP: Experiment and Simulation

NASA Astrophysics Data System (ADS)

Rabus, Dominik Gerhard; Hamacher, Michael; Heidrich, Helmut

2002-02-01

A racetrack shaped double ring resonator (DRR) filter is demonstrated with radii of 200 μm. The double ring resonator contains two -3 dB multimode interference (MMI) couplers for I/O coupling and a -13 dB codirectional coupler in between the rings. A free spectral range of 50 GHz has been realized. A simulation model has been developed to describe the DRR. As fabrication tolerances do not allow the realization of two identical rings with required nm-circumference accuracy in the resonator, a frequency alignment of the resonator is indispensable. The resonance frequency tuning is performed thermally using platinum resistors which have been placed on top of the waveguides in both rings. An on-off ratio increase has been achieved of more than 3 dB, resulting in a total on-off ratio larger than 18 dB. The frequency alignment is inevitable in the case of multiple coupled micro ring resonators.

Multi-band reflector antenna with double-ring element frequency selective subreflector

NASA Technical Reports Server (NTRS)

Wu, Te-Kao; Lee, S. W.

1993-01-01

Frequency selective subreflectors (FSS) are often employed in the reflector antenna system of a communication satellite or a deep space exploration vehicle for multi-frequency operations. In the past, FSS's have been designed for diplexing two frequency bands. For example, the Voyager FSS was designed to diplex S and X bands and the TDRSS FSS was designed to diplex S and Ku bands. Recently, NASA's CASSINI project requires an FSS to multiplex four frequency (S/X/Ku/Ka) bands. Theoretical analysis and experimental verifications are presented for a multi-band flat pannel FSS with double-ring elements. Both the exact formulation and the thin-ring approximation are described for analyzing and designing this multi-ring patch element FSS. It is found that the thin-ring approximation fails to predict the electrically wide ring element FSS's performance. A single screen double-ring element FSS is demonstrated for the tri-band system that reflects the X-band signal while transmitting through the S- and Ku-band signals. In addition, a double screen FSS with non-similar double-ring elements is presented for the Cassini's four-band system which reflects the X- and Ka-band signals while passing the S- and Ku-band signals. To accurately predict the FSS effects on a dual reflector antenna's radiation pattern, the FSS subreflector's transmitted/reflected field variation as functions of the polarization and incident angles with respect to the local coordinates was taken into account. An FSS transmission/reflection coefficient table is computed for TE and TM polarizations at various incident angles based on the planar FSS model. Next, the hybrid Geometric Optics (GO) and Physical Optics (PO) technique is implemented with linearly interpolating the FSS table to efficiently determine the FSS effects in a dual reflector antenna.

Dressed Gain from the Parametrically Amplified Four-Wave Mixing Process in an Atomic Vapor.

PubMed

Zhang, Zhaoyang; Wen, Feng; Che, Junling; Zhang, Dan; Li, Changbiao; Zhang, Yanpeng; Xiao, Min

2015-10-14

With a forward cone emitting from the strong pump laser in a thermal rubidium atomic vapor, we investigate the non-degenerate parametrically amplified four-wave mixing (PA-FWM) process with dressing effects in a three-level "double-Λ" configuration both theoretically and experimentally. By seeding a weak probe field into the Stokes or anti-Stokes channel of the FWM, the gain processes are generated in the bright twin beams which are called conjugate and probe beams, respectively. However, the strong dressing effect of the pump beam will dramatically affect the gain factors both in the probe and conjugate channels, and can inevitably impose an influence on the quantum effects such as entangled degree and the quantum noise reduction between the two channels. We systematically investigate the intensity evolution of the dressed gain processes by manipulating the atomic density, the Rabi frequency and the frequency detuning. Such dressing effects are also visually evidenced by the observation of Autler-Townes splitting of the gain peaks. The investigation can contribute to the development of quantum information processing and quantum communications.

Dressed Gain from the Parametrically Amplified Four-Wave Mixing Process in an Atomic Vapor

NASA Astrophysics Data System (ADS)

Zhang, Zhaoyang; Wen, Feng; Che, Junling; Zhang, Dan; Li, Changbiao; Zhang, Yanpeng; Xiao, Min

2015-10-01

With a forward cone emitting from the strong pump laser in a thermal rubidium atomic vapor, we investigate the non-degenerate parametrically amplified four-wave mixing (PA-FWM) process with dressing effects in a three-level “double-Λ” configuration both theoretically and experimentally. By seeding a weak probe field into the Stokes or anti-Stokes channel of the FWM, the gain processes are generated in the bright twin beams which are called conjugate and probe beams, respectively. However, the strong dressing effect of the pump beam will dramatically affect the gain factors both in the probe and conjugate channels, and can inevitably impose an influence on the quantum effects such as entangled degree and the quantum noise reduction between the two channels. We systematically investigate the intensity evolution of the dressed gain processes by manipulating the atomic density, the Rabi frequency and the frequency detuning. Such dressing effects are also visually evidenced by the observation of Autler-Townes splitting of the gain peaks. The investigation can contribute to the development of quantum information processing and quantum communications.

Dielectric relaxation and electrical conduction mechanism in A2HoSbO6 (A=Ba, Sr, Ca) Double Perovskite Ceramics: An impedance spectroscopic analysis

NASA Astrophysics Data System (ADS)

Halder, Saswata; Dutta, Alo; Sinha, T. P.

2017-03-01

The AC electrical properties of polycrystalline double perovskite oxides A2HoSbO6 (A=Ba, Sr, Ca; AHS) synthesized by solid state reaction technique has been explored by using impedance spectroscopic studies. The Rietveld refinement of the room temperature X-ray diffraction data show that Ba2HoSbO6 (BHS) has cubic phase and Sr2HoSbO6 (SHS) and Ca2HoSbO6 (CHS) crystallize in monoclinic phase. The samples show significant frequency dispersion in their dielectric properties. The polydispersive nature of the relaxation mechanism is explained by the modified Cole-Cole model. The scaling behavior of dielectric loss indicate the temperature independence of the relaxation mechanism. The magnitude of the activation energy indicates that the hopping mechanism is responsible for carrier transport in AHS. The frequency dependent conductivity spectra follow the double power law. Impedance spectroscopic data presented in the Nyquist plot (Z" versus Z‧) are used to identify an equivalent circuit along with to know the grain, grain boundary and interface contributions. The constant phase element (CPE) is used to analyze the experimental response of BHS, SHS and CHS comprehending the contribution of different microstructural features to the conduction process. The temperature dependent electrical conductivity shows a semiconducting behavior.

Influence of frequency tuning and double-frequency heating on ions extracted from an electron cyclotron resonance ion source

NASA Astrophysics Data System (ADS)

Maimone, F.; Celona, L.; Lang, R.; Mäder, J.; Roßbach, J.; Spädtke, P.; Tinschert, K.

2011-12-01

The electromagnetic field within the plasma chamber of an electron cyclotron resonance ion source (ECRIS) and the properties of the plasma waves affect the plasma properties and ion beam production. We have experimentally investigated the "frequency tuning effect" and "double frequency heating" on the CAPRICE ECRIS device. A traveling wave tube amplifier, two microwave sweep generators, and a dedicated experimental set-up were used to carry out experiments in the 12.5-16.5 GHz frequency range. During the frequency sweeps the evolution of the intensity and shape of the extracted argon beam were measured together with the microwave reflection coefficient. A range of different ion source parameter settings was used. Here we describe these experiments and the resultant improved understanding of these operational modes of the ECR ion source.

Influence of frequency tuning and double-frequency heating on ions extracted from an electron cyclotron resonance ion source.

PubMed

Maimone, F; Celona, L; Lang, R; Mäder, J; Rossbach, J; Spädtke, P; Tinschert, K

2011-12-01

The electromagnetic field within the plasma chamber of an electron cyclotron resonance ion source (ECRIS) and the properties of the plasma waves affect the plasma properties and ion beam production. We have experimentally investigated the "frequency tuning effect" and "double frequency heating" on the CAPRICE ECRIS device. A traveling wave tube amplifier, two microwave sweep generators, and a dedicated experimental set-up were used to carry out experiments in the 12.5-16.5 GHz frequency range. During the frequency sweeps the evolution of the intensity and shape of the extracted argon beam were measured together with the microwave reflection coefficient. A range of different ion source parameter settings was used. Here we describe these experiments and the resultant improved understanding of these operational modes of the ECR ion source.

Low-frequency switching in a transistor amplifier.

PubMed

Carroll, T L

2003-04-01

It is known from extensive work with the diode resonator that the nonlinear properties of a P-N junction can lead to period doubling, chaos, and other complicated behaviors in a driven circuit. There has been very little work on what happens when more than one P-N junction is present. In this work, the first step towards multiple P-N junction circuits is taken by doing both experiments and simulations with a single-transistor amplifier using a bipolar transistor. Period doubling and chaos are seen when the amplifier is driven with signals between 100 kHz and 1 MHz, and they coincide with a very low frequency switching between different period doubled (or chaotic) wave forms. The switching frequencies are between 5 and 10 Hz. The switching behavior was confirmed in a simplified model of the transistor amplifier.

Transmission loss of double wall panels containing Helmholtz resonators

NASA Technical Reports Server (NTRS)

Prydz, R. A.; Kuntz, H. L.; Morrow, D. L.; Wirt, L. S.

1988-01-01

Data and an analysis are presented on the use of Helholtz resonators in double wall panels (i.e., aircraft sidewalls). Several wall materials and resonator configurations were tested, and the resonators were found to substantially increase the transmission loss of the double wall system at the tuning frequency.

Transmission loss of double wall panels containing Helmholtz resonators

NASA Astrophysics Data System (ADS)

Prydz, R. A.; Kuntz, H. L.; Morrow, D. L.; Wirt, L. S.

Data and an analysis are presented on the use of Helholtz resonators in double wall panels (i.e., aircraft sidewalls). Several wall materials and resonator configurations were tested, and the resonators were found to substantially increase the transmission loss of the double wall system at the tuning frequency.

Identification and Multiplicity of Double Vowels in Cochlear Implant Users

ERIC Educational Resources Information Center

Kwon, Bomjun J.; Perry, Trevor T.

2014-01-01

Purpose: The present study examined cochlear implant (CI) users' perception of vowels presented concurrently (i.e., "double vowels") to further our understanding of auditory grouping in electric hearing. Method: Identification of double vowels and single vowels was measured with 10 CI subjects. Fundamental frequencies (F0s) of…

A Double-function Digital Watermarking Algorithm Based on Chaotic System and LWT

NASA Astrophysics Data System (ADS)

Yuxia, Zhao; Jingbo, Fan

A double- function digital watermarking technology is studied and a double-function digital watermarking algorithm of colored image is presented based on chaotic system and the lifting wavelet transformation (LWT).The algorithm has realized the double aims of the copyright protection and the integrity authentication of image content. Making use of feature of human visual system (HVS), the watermark image is embedded into the color image's low frequency component and middle frequency components by different means. The algorithm has great security by using two kinds chaotic mappings and Arnold to scramble the watermark image at the same time. The algorithm has good efficiency by using LWT. The emulation experiment indicates the algorithm has great efficiency and security, and the effect of concealing is really good.

Compact and efficient CW 473nm blue laser with LBO intracavity frequency doubling

NASA Astrophysics Data System (ADS)

Qi, Yan; Wang, Yu; Wang, Yanwei; Zhang, Jing; Yan, Boxia

2016-10-01

With diode end pumped Nd:YAG directly and LBO intracavity frequency doubling, a compact, high efficient continuous wave blue laser at 473nm is realized. When the incident pump power reach 6.2W, 630mW maximum output power of blue laser at 473nm is achieved with 15mm long LBO, the optical-to-optical conversion efficiency is as high as 10.2%.

Surface changes of composite and compomer materials following irradiation with an Er:YAG laser and a frequency doubled alexandrite laser

NASA Astrophysics Data System (ADS)

Pilgrim, Christian G.; Rechmann, Peter; Hennig, Thomas; Goldin, Dan S.

1999-05-01

Er:YAG laser as well as the frequency doubled Alexandrite laser have been suggested for the use in periodontal therapy and so for the elimination of calculus and the treatment of infected root cement. Intended is the laser application inside the gingival pocket. In consequence, both these lasers may be used in areas close to cervical or approximal location, or even on the fillings' surfaces. Light cured composite and compomer materials are in use for these types of fillings among others. Aim of the study presented here was to compare the effect of an Er:YAG laser (wavelength 2.94 μm, pulse duration 250 μs, free running. fluence 4.5 J/cm2 and 21.4 J/cm2) on compomers and composites with the result following irradiation with a frequency doubled Alexandrite laser (wavelength 377 nm, pulse duration 200 ns, fluence 3 Jcm-2 and 6 J/cm2). The surface of standardized compomer and composite samples were irradiated with both laser wavelengths (either frequency doubled Alexandrite or Er:YAG laser) using the same standardized application protocol. Scanning electron microscopic investigation showed that irradiation with both lasers causes surface changes in composites and compomers removing calculus with these lasers.

Ion-implanted WN 0.25{mu}m gate MESFET fabricated using I-line photolithography for application to MMIC and digital IC

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

Oh, E.O.; Yang, J.W.; Park, C.S.

1995-12-31

Straightforward WN 0.25{mu}m gate MESFET process based on direct ion-implantation and i-line photolithography with double exposure process has produced high performance MESFETs. The maximum transconductance of 600mS/mm and the k-factor of 450ms/Vmm were obtained. As high as 65GHz of cut-off frequency has been realized without any deembedding of parasitic effects. The MESFET shows the minimum noise figure of 0.87 dB and the associated gain of 9.97dB at 12GHz.

Laboratory simulation of volcano seismicity.

PubMed

Benson, Philip M; Vinciguerra, Sergio; Meredith, Philip G; Young, R Paul

2008-10-10

The physical processes generating seismicity within volcanic edifices are highly complex and not fully understood. We report results from a laboratory experiment in which basalt from Mount Etna volcano (Italy) was deformed and fractured. The experiment was monitored with an array of transducers around the sample to permit full-waveform capture, location, and analysis of microseismic events. Rapid post-failure decompression of the water-filled pore volume and damage zone triggered many low-frequency events, analogous to volcanic long-period seismicity. The low frequencies were associated with pore fluid decompression and were located in the damage zone in the fractured sample; these events exhibited a weak component of shear (double-couple) slip, consistent with fluid-driven events occurring beneath active volcanoes.

The detection of gravitational waves using electrodynamic system of Earth

NASA Astrophysics Data System (ADS)

Grunskaya, Lubov; Isakevich, Valiriy

There is studied the interconnection of tide processes of geophysical and astrophysical origin with the Earth electromagnetic fields. There has been developed a programme-analytical system (PAS) to investigate signal structures in spectral and time series, caused by geophysical and astrophysical processes based on the method of eigen vectors. There were discovered frequencies in the electrical and geomagnetical field of ELF range with PAS, which coincide with the frequency of gravitational -wave radiation of a number of double stellar systems. In the electrical and geomagnetic field there was discovered a specific axion frequency VA=0.5*10-5 Hz belonging to the ELF range which was predicted by the theory. The problem of the anomalous behavior of the electrodynamic system response to the gravitational - wave affect is being discussed. On the basis of the rich experimental material have been investigated the frequencies of gravitational-wave radiation of a number of binary systems: J0700+6418, J1012+5307, J1537+1155, J1959+2048, J2130+1210, J1915+1606. The work is carried out with supporting of RFFI No. 14-07-97510, State Task to Universities on 2014-2016.

Process and application of shock compression by nanosecond pulses of frequency-doubled Nd:YAG laser

NASA Astrophysics Data System (ADS)

Sano, Yuji; Kimura, Motohiko; Mukai, Naruhiko; Yoda, Masaki; Obata, Minoru; Ogisu, Tatsuki

2000-02-01

The authors have developed a new process of laser-induced shock compression to introduce a residual compressive stress on material surface, which is effective for prevention of stress corrosion cracking (SCC) and enhancement of fatigue strength of metal materials. The process developed is unique and beneficial. It requires no pre-conditioning for the surface, whereas the conventional process requires that the so-called sacrificial layer is made to protect the surface from damage. The new process can be freely applied to water- immersed components, since it uses water-penetrable green light of a frequency-doubled Nd:YAG laser. The process developed has the potential to open up new high-power laser applications in manufacturing and maintenance technologies. The laser-induced shock compression process (LSP) can be used to improve a residual stress field from tensile to compressive. In order to understand the physics and optimize the process, the propagation of a shock wave generated by the impulse of laser irradiation and the dynamic response of the material were analyzed by time-dependent elasto-plastic calculations with a finite element program using laser-induced plasma pressure as an external load. The analysis shows that a permanent strain and a residual compressive stress remain after the passage of the shock wave with amplitude exceeding the yield strength of the material. A practical system materializing the LSP was designed, manufactured, and tested to confirm the applicability to core components of light water reactors (LWRs). The system accesses the target component and remotely irradiates laser pulses to the heat affected zone (HAZ) along weld lines. Various functional tests were conducted using a full-scale mockup facility, in which remote maintenance work in a reactor vessel could be simulated. The results showed that the system remotely accessed the target weld lines and successfully introduced a residual compressive stress. After sufficient training for operational personnel, the system was applied to the core shroud of an existing nuclear power plant.

Study of Pulsed vs. RF Plasma Properties for Surface Processing Applications

NASA Astrophysics Data System (ADS)

Tang, Ricky; Hopkins, Matthew; Barnat, Edward; Miller, Paul

2015-09-01

The ability to manipulate the plasma parameters (density, E/N) was previously demonstrated using a double-pulsed column discharge. Experiments extending this to large-surface plasmas of interest to the plasma processing community were conducted. Differences between an audio-frequency pulsed plasma and a radio-frequency (rf) discharge, both prevalent in plasma processing applications, were studied. Optical emission spectroscopy shows higher-intensity emission in the UV/visible range for the pulsed plasma comparing to the rf plasma at comparable powers. Data suggest that the electron energy is higher for the pulsed plasma leading to higher ionization, resulting in increased ion density and ion flux. Diode laser absorption measurements of the concentration of the 1S5 metastable and 1S4 resonance states of argon (correlated with the plasma E/N) provide comparisons between the excitation/ionization states of the two plasmas. Preliminary modeling efforts suggest that the low-frequency polarity switch causes a much more abrupt potential variation to support interesting transport phenomena, generating a ``wave'' of higher temperature electrons leading to more ionization, as well as ``sheath capture'' of a higher density bolus of ions that are then accelerated during polarity switch.

Polarized linewidth-controllable double-trapping electromagnetically induced transparency spectra in a resonant plasmon nanocavity

PubMed Central

Wang, Luojia; Gu, Ying; Chen, Hongyi; Zhang, Jia-Yu; Cui, Yiping; Gerardot, Brian D.; Gong, Qihuang

2013-01-01

Surface plasmons with ultrasmall optical mode volume and strong near field enhancement can be used to realize nanoscale light-matter interaction. Combining surface plasmons with the quantum system provides the possibility of nanoscale realization of important quantum optical phenomena, including the electromagnetically induced transparency (EIT), which has many applications in nonlinear quantum optics and quantum information processing. Here, using a custom-designed resonant plasmon nanocavity, we demonstrate polarized position-dependent linewidth-controllable EIT spectra at the nanoscale. We analytically obtain the double coherent population trapping conditions in a double-Λ quantum system with crossing damping, which give two transparent points in the EIT spectra. The linewidths of the three peaks are extremely sensitive to the level spacing of the excited states, the Rabi frequencies and detunings of pump fields, and the Purcell factors. In particular the linewidth of the central peak is exceptionally narrow. The hybrid system may have potential applications in ultra-compact plasmon-quantum devices. PMID:24096943

Measurement potential of laser speckle velocimetry

NASA Technical Reports Server (NTRS)

Adrian, R. J.

1982-01-01

Laser speckle velocimetry, the measurement of fluid velocity by measuring the translation of speckle pattern or individual particles that are moving with the fluid, is described. The measurement is accomplished by illuminating the fluid with consecutive pulses of Laser Light and recording the images of the particles or the speckles on a double exposed photographic plate. The plate contains flow information throughout the image plane so that a single double exposure may provide data at hundreds or thousands of points in the illuminated region of the fluid. Conventional interrogation of the specklegram involves illuminating the plate to form Young's fringes, whose spacing is inversely proportional to the speckle separation. Subsequently the fringes are digitized and analyzed in a computer to determine their frequency and orientation, yielding the velocity magnitude and orientation. The Young's fringe technique is equivalent to performing a 2-D spatial correlation of the double exposed specklegram intensity pattern, and this observation suggests that correlation should be considered as an alternative processing method. The principle of the correlation technique is examined.

Reflection and backscattering of microwaves under doubling of the plasma density and displacement of the gyroresonance region during electron cyclotron resonance heating of plasma in the l-2M stellarator

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

Batanov, G. M.; Borzosekov, V. D.; Vasilkov, D. G.

Reflection and backscattering of high-power (400 kW) gyrotron radiation creating and heating plasma at the second harmonic of the electronic cyclotron frequency in the L-2M stellarator have been investigated experimentally. The effect of the displacement of the gyroresonance region from the axis of the plasma column under doubling of the plasma density on the processes of reflection and backscattering of microwave radiation has been examined. A near doubling of short-wavelength (k{sub ⊥} ≈ 30 cm{sup –1}) turbulent density fluctuations squared is observed. The change in the energy confinement time under variations of plasma parameters and characteristics of short-wavelength turbulence ismore » discussed. A discrepancy between the measured values of the reflection coefficient from the electron cyclotron resonance heating region and predictions of the one-dimensional model is revealed.« less

Equivalent mismatch negativity deficits across deviant types in early illness schizophrenia-spectrum patients.

PubMed

Hay, Rachel A; Roach, Brian J; Srihari, Vinod H; Woods, Scott W; Ford, Judith M; Mathalon, Daniel H

2015-02-01

Neurophysiological abnormalities in auditory deviance processing, as reflected by the mismatch negativity (MMN), have been observed across the course of schizophrenia. Studies in early schizophrenia patients have typically shown varying degrees of MMN amplitude reduction for different deviant types, suggesting that different auditory deviants are uniquely processed and may be differentially affected by duration of illness. To explore this further, we examined the MMN response to 4 auditory deviants (duration, frequency, duration+frequency "double deviant", and intensity) in 24 schizophrenia-spectrum patients early in the illness (ESZ) and 21 healthy controls. ESZ showed significantly reduced MMN relative to healthy controls for all deviant types (p<0.05), with no significant interaction with deviant type. No correlations with clinical symptoms were present (all ps>0.05). These findings support the conclusion that neurophysiological mechanisms underlying processing of auditory deviants are compromised early in illness, and these deficiencies are not specific to the type of deviant presented. Copyright © 2015 Elsevier B.V. All rights reserved.

Extraction-controlled terahertz frequency quantum cascade lasers with a diagonal LO-phonon extraction and injection stage.

PubMed

Han, Y J; Li, L H; Grier, A; Chen, L; Valavanis, A; Zhu, J; Freeman, J R; Isac, N; Colombelli, R; Dean, P; Davies, A G; Linfield, E H

2016-12-12

We report an extraction-controlled terahertz (THz)-frequency quantum cascade laser design in which a diagonal LO-phonon scattering process is used to achieve efficient current injection into the upper laser level of each period and simultaneously extract electrons from the adjacent period. The effects of the diagonality of the radiative transition are investigated, and a design with a scaled oscillator strength of 0.45 is shown experimentally to provide the highest temperature performance. A 3.3 THz device processed into a double-metal waveguide configuration operated up to 123 K in pulsed mode, with a threshold current density of 1.3 kA/cm² at 10 K. The QCL structures are modeled using an extended density matrix approach, and the large threshold current is attributed to parasitic current paths associated with the upper laser levels. The simplicity of this design makes it an ideal platform to investigate the scattering injection process.

Surprising performance for vibrational frequencies of the distinguishable clusters with singles and doubles (DCSD) and MP2.5 approximations

NASA Astrophysics Data System (ADS)

Kesharwani, Manoj K.; Sylvetsky, Nitai; Martin, Jan M. L.

2017-11-01

We show that the DCSD (distinguishable clusters with all singles and doubles) correlation method permits the calculation of vibrational spectra at near-CCSD(T) quality but at no more than CCSD cost, and with comparatively inexpensive analytical gradients. For systems dominated by a single reference configuration, even MP2.5 is a viable alternative, at MP3 cost. MP2.5 performance for vibrational frequencies is comparable to double hybrids such as DSD-PBEP86-D3BJ, but without resorting to empirical parameters. DCSD is also quite suitable for computing zero-point vibrational energies in computational thermochemistry.

Electronic Circuit Experiments and SPICE Simulation of Double Covering Bifurcation of 2-Torus Quasi-Periodic Flow in Phase-Locked Loop Circuit

NASA Astrophysics Data System (ADS)

Kamiyama, Kyohei; Endo, Tetsuro; Imai, Isao; Komuro, Motomasa

2016-06-01

Double covering (DC) bifurcation of a 2-torus quasi-periodic flow in a phase-locked loop circuit was experimentally investigated using an electronic circuit and via SPICE simulation; in the circuit, the input radio-frequency signal was frequency modulated by the sum of two asynchronous sinusoidal baseband signals. We observed both DC and period-doubling bifurcations of a discrete map on two Poincaré sections, which were realized by changing the sample timing from one baseband sinusoidal signal to the other. The results confirm the DC bifurcation of the original flow.

Power spectrum model of visual masking: simulations and empirical data.

PubMed

Serrano-Pedraza, Ignacio; Sierra-Vázquez, Vicente; Derrington, Andrew M

2013-06-01

In the study of the spatial characteristics of the visual channels, the power spectrum model of visual masking is one of the most widely used. When the task is to detect a signal masked by visual noise, this classical model assumes that the signal and the noise are previously processed by a bank of linear channels and that the power of the signal at threshold is proportional to the power of the noise passing through the visual channel that mediates detection. The model also assumes that this visual channel will have the highest ratio of signal power to noise power at its output. According to this, there are masking conditions where the highest signal-to-noise ratio (SNR) occurs in a channel centered in a spatial frequency different from the spatial frequency of the signal (off-frequency looking). Under these conditions the channel mediating detection could vary with the type of noise used in the masking experiment and this could affect the estimation of the shape and the bandwidth of the visual channels. It is generally believed that notched noise, white noise and double bandpass noise prevent off-frequency looking, and high-pass, low-pass and bandpass noises can promote it independently of the channel's shape. In this study, by means of a procedure that finds the channel that maximizes the SNR at its output, we performed numerical simulations using the power spectrum model to study the characteristics of masking caused by six types of one-dimensional noise (white, high-pass, low-pass, bandpass, notched, and double bandpass) for two types of channel's shape (symmetric and asymmetric). Our simulations confirm that (1) high-pass, low-pass, and bandpass noises do not prevent the off-frequency looking, (2) white noise satisfactorily prevents the off-frequency looking independently of the shape and bandwidth of the visual channel, and interestingly we proved for the first time that (3) notched and double bandpass noises prevent off-frequency looking only when the noise cutoffs around the spatial frequency of the signal match the shape of the visual channel (symmetric or asymmetric) involved in the detection. In order to test the explanatory power of the model with empirical data, we performed six visual masking experiments. We show that this model, with only two free parameters, fits the empirical masking data with high precision. Finally, we provide equations of the power spectrum model for six masking noises used in the simulations and in the experiments.

Picosecond pulsed micro-module emitting near 560 nm using a frequency doubled gain-switched DBR ridge waveguide semiconductor laser

NASA Astrophysics Data System (ADS)

Kaltenbach, André; Hofmann, Julian; Seidel, Dirk; Lauritsen, Kristian; Bugge, Frank; Fricke, Jörg; Paschke, Katrin; Erdmann, Rainer; Tränkle, Günther

2017-02-01

A miniaturized picosecond pulsed semiconductor laser source in the spectral range around 560nm is realized by integrating a frequency doubled distributed Bragg reflector ridge waveguide laser (DBR-RWL) into a micromodule. Such compact laser sources are suitable for mobile application, e.g. in microscopes. The picosecond optical pulses are generated by gain-switching which allows for arbitrary pulse repetition frequencies. For frequency conversion a periodically poled magnesium doped lithium niobate ridge waveguide crystal (PPLN) is used to provide high conversion efficiency with single-pass second harmonic generation (SHG). The coupling of the pulsed radiation into the PPLN crystal is realized by a GRIN-lens. Such types of lenses collect the divergent laser radiation and focus it into the crystal waveguide providing high coupling efficiency at a minimum of space compared to the usage of fast axis collimator(FAC)/slow axis collimator (SAC) lens combinations. The frequency doubled output pulses show a pulse width of about 60 ps FWHM and a spectral width around 0.06nm FWHM at a central wavelength of 557nm at 15Å. The pulse peak power could be determined to be more than 300mW at a repetition frequency of 40 MHz.

Tunable KTA Stokes laser based on stimulated polariton scattering and its intracavity frequency doubling.

PubMed

Zang, Jie; Cong, Zhenhua; Chen, Xiaohan; Zhang, Xingyu; Qin, Zengguang; Liu, Zhaojun; Lu, Jianren; Wu, Dong; Fu, Qiang; Jiang, Shiqi; Zhang, Shaojun

2016-04-04

This paper presents the tunable Stokes laser characteristics of KTiOAsO₄ (KTA) crystal based on stimulated polariton scattering (SPS). When the pumping laser wavelength is 1064.2 nm, the KTA Stokes wave can be discontinuously tuned from 1077.9 to 1088.4 nm with four gaps from 1079.0 to 1080.1 nm, from 1080.8 to 1082.8 nm, from 1083.6 to 1085.5 nm, and from 1085.8 to 1086.8 nm. When a frequency doubling crystal LiB₃O₅ (LBO) is inserted into the Stokes laser cavity, the frequency-doubled wave can be discontinuously tuned from 539.0 to 539.5 nm, from 540.1 to 540.4 nm, from 541.3 to 541.8 nm, from 542.7 to 542.9 nm and from 543.4 to 544.2 nm. With a pumping pulse energy of 130.0 mJ and an output coupler reflectivity of about 30%, the obtained maximum Stokes laser pulse energy at 1078.6 nm is 33.9 mJ and the obtained maximum frequency-doubled laser pulse energy at 543.8 nm is 15.7 mJ. By using the most probably coupled transverse optical modes obtained from the literature, the polariton refractive indexes, and the simplified polariton Sellmeier equations, the polariton dispersion curve is obtained. The formation of the Stokes frequency gaps is explained.

Power enhanced frequency conversion system

NASA Technical Reports Server (NTRS)

Sanders, Steven (Inventor); Lang, Robert J. (Inventor); Waarts, Robert G. (Inventor)

2001-01-01

A frequency conversion system includes at least one source providing a first near-IR wavelength output including a gain medium for providing high power amplification, such as double clad fiber amplifier, a double clad fiber laser or a semiconductor tapered amplifier to enhance the power output level of the near-IR wavelength output. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Ra-man/Brillouin amplifier or oscillator between the high power source and the NFM device.

Organic materials with nonlinear optical properties

DOEpatents

Stupp, Samuel I.; Son, Sehwan; Lin, Hong-Cheu

1995-01-01

The present invention is directed to organic materials that have the ability to double or triple the frequency of light that is directed through the materials. Particularly, the present invention is directed to the compound 4-[4-(2R)-2-cyano-7-(4'-pentyloxy-4-biphenylcarbonyloxy)phenylheptylidene) phenylcarbonyloxy]benzaldehyde, which can double the frequency of light that is directed through the compound. The invention is also directed to the compound (12-hydroxy-5,7-dodecadiynyl) 4'-[(4'-pentyloxy-4-biphenyl)carbonyloxy]-4-biphenylcarboxylate, and its polymeric form. The polymeric form can triple the frequency of light directed through it.

Organic materials with nonlinear optical properties

DOEpatents

Stupp, S.I.; Son, S.; Lin, H.C.

1995-05-02

The present invention is directed to organic materials that have the ability to double or triple the frequency of light that is directed through the materials. Particularly, the present invention is directed to the compound 4-[4-(2R)-2-cyano-7-(4{prime}-pentyloxy-4-biphenylcarbonyloxy)phenylheptylidenephenylcarbonyloxy]benzaldehyde, which can double the frequency of light that is directed through the compound. The invention is also directed to the compound (12-hydroxy-5,7-dodecadiynyl)-4{prime}-[(4{prime}-pentyloxy-4-biphenyl)carbonyloxy]-4-biphenylcarboxylate, and its polymeric form. The polymeric form can triple the frequency of light directed through it. 4 figs.

On the numerical investigation of sound transmission through double-walled structures with membrane-type acoustic metamaterials.

PubMed

Marinova, Polina; Lippert, Stephan; von Estorff, Otto

2017-10-01

Acoustic metamaterials appear to be of great help in the design of reliable and effective noise reduction measures in the low frequency range. The current contribution is concerned with the modeling of a low-frequency noise shield, based on a double wall arrangement, which includes membrane-type acoustic metamaterials (MAMs), considered as the most promising approach when it comes especially to the tonal noise at frequencies below 300 Hz. MAMs consist of small-sized membranes loaded with a mass. Due to their robustness and relatively simple production, MAMs have been proven to decrease the sound transmission in frequency ranges, for which poro-elastic materials have a rather negligible effect. A simulation model of a double wall panel, whose acoustic cavity is furnished with layers of metamaterials, has been developed and the sound transmission loss (STL) through the structure was calculated, using the finite element method. In order to validate the modelling approach, the STL estimation from the finite element analysis was compared to experimental measurements. The achieved results indicate a noise-decreasing possibility in tunable narrow bands as well as a broadband noise reduction for frequencies less than 300 Hz without significantly adding to the panel mass.

The physical characteristics of human proteins in different biological functions.

PubMed

Wang, Tengjiao; Tang, Hailin

2017-01-01

The physical properties of gene products are the foundation of their biological functions. In this study, we systematically explored relationships between physical properties and biological functions. The physical properties including origin time, evolution pressure, mRNA and protein stability, molecular weight, hydrophobicity, acidity/alkaline, amino acid compositions, and chromosome location. The biological functions are defined from 4 aspects: biological process, molecular function, cellular component and cell/tissue/organ expression. We found that the proteins associated with basic material and energy metabolism process originated earlier, while the proteins associated with immune, neurological system process etc. originated later. Tissues may have a strong influence on evolution pressure. The proteins associated with energy metabolism are double-stable. Immune and peripheral cell proteins tend to be mRNA stable/protein unstable. There are very few function items with double-unstable of mRNA and protein. The proteins involved in the cell adhesion tend to consist of large proteins with high proportion of small amino acids. The proteins of organic acid transport, neurological system process and amine transport have significantly high hydrophobicity. Interestingly, the proteins involved in olfactory receptor activity tend to have high frequency of aromatic, sulfuric and hydroxyl amino acids.

The physical characteristics of human proteins in different biological functions

PubMed Central

Tang, Hailin

2017-01-01

The physical properties of gene products are the foundation of their biological functions. In this study, we systematically explored relationships between physical properties and biological functions. The physical properties including origin time, evolution pressure, mRNA and protein stability, molecular weight, hydrophobicity, acidity/alkaline, amino acid compositions, and chromosome location. The biological functions are defined from 4 aspects: biological process, molecular function, cellular component and cell/tissue/organ expression. We found that the proteins associated with basic material and energy metabolism process originated earlier, while the proteins associated with immune, neurological system process etc. originated later. Tissues may have a strong influence on evolution pressure. The proteins associated with energy metabolism are double-stable. Immune and peripheral cell proteins tend to be mRNA stable/protein unstable. There are very few function items with double-unstable of mRNA and protein. The proteins involved in the cell adhesion tend to consist of large proteins with high proportion of small amino acids. The proteins of organic acid transport, neurological system process and amine transport have significantly high hydrophobicity. Interestingly, the proteins involved in olfactory receptor activity tend to have high frequency of aromatic, sulfuric and hydroxyl amino acids. PMID:28459865

Polarized micro Raman spectroscopy of bilayer graphene

NASA Astrophysics Data System (ADS)

Moon, Hyerim; Yoon, Duhee; Son, Young-Woo; Cheong, Hyeonsik

2009-03-01

The frequency of Raman 2D band of the graphite depends on the excitation laser energy. This phenomenon is explained with double resonance Raman process. In polarized micro-Raman spectroscopy of single layer graphene, Raman G band (˜1586 cm-1) is isotropic, and 2D band (˜2686 cm-1) strongly depends on relative polarizations of the incident and scattered photons. This strong polarization dependence originates from inhomogeneous optical absorption and emission mediated by resonant electron-phonon interaction. In bi-layer graphene, Raman 2D band can be decomposed into four Lorenztian peaks which can be interpreted in terms of the four transition paths in the double resonance Raman process. We investigated the polarization dependence of each Lorenztian peak in the Raman 2D band of bi-layer graphene for different excitation laser energies. Strong polarization dependence of the Raman 2D band, similar to the case of single layer graphene, is observed. The excitation energy dependence of the polarized Raman scattering is analyzed in terms of the band structure of bi-layer graphene.

Methods Development for Spectral Simplification of Room-Temperature Rotational Spectra

NASA Astrophysics Data System (ADS)

Kent, Erin B.; Shipman, Steven

2014-06-01

Room-temperature rotational spectra are dense and difficult to assign, and so we have been working to develop methods to accelerate this process. We have tested two different methods with our waveguide-based spectrometer, which operates from 8.7 to 26.5 GHz. The first method, based on previous work by Medvedev and De Lucia, was used to estimate lower state energies of transitions by performing relative intensity measurements at a range of temperatures between -20 and +50 °C. The second method employed hundreds of microwave-microwave double resonance measurements to determine level connectivity between rotational transitions. The relative intensity measurements were not particularly successful in this frequency range (the reasons for this will be discussed), but the information gleaned from the double-resonance measurements can be incorporated into other spectral search algorithms (such as autofit or genetic algorithm approaches) via scoring or penalty functions to help with the spectral assignment process. I.R. Medvedev, F.C. De Lucia, Astrophys. J. 656, 621-628 (2007).

Contribution of inter-muscular synchronization in the modulation of tremor intensity in Parkinson's disease.

PubMed

He, Xin; Hao, Man-Zhao; Wei, Ming; Xiao, Qin; Lan, Ning

2015-12-01

Involuntary central oscillations at single and double tremor frequencies drive the peripheral neuromechanical system of muscles and joints to cause tremor in Parkinson's disease (PD). The central signal of double tremor frequency was found to correlate more directly to individual muscle EMGs (Timmermann et al. 2003). This study is aimed at investigating what central components of oscillation contribute to inter-muscular synchronization in a group of upper extremity muscles during tremor in PD patients. 11 idiopathic, tremor dominant PD subjects participated in this study. Joint kinematics during tremor in the upper extremity was recorded along with EMGs of six upper arm muscles using a novel experimental apparatus. The apparatus provided support for the upper extremity on a horizontal surface with reduced friction, so that resting tremor in the arm can be recorded with a MotionMonitor II system. In each subject, the frequencies of rhythmic firings in upper arm muscles were determined using spectral analysis. Paired and pool-averaged coherence analyses of EMGs for the group of muscles were performed to correlate the level of inter-muscular synchronization to tremor amplitudes at shoulder and elbow. The phase shift between synchronized antagonistic muscle pairs was calculated to aid coherence analysis in the muscle pool. Recorded EMG revealed that rhythmic firings were present in most recorded muscles, which were either synchronized to form phase-locked bursting cycles at a subject specific frequency, or unsynchronized with a random phase distribution. Paired coherence showed a stronger synchronization among a subset of recorded arm muscles at tremor frequency than that at double tremor frequency. Furthermore, the number of synchronized muscles in the arm was positively correlated to tremor amplitudes at elbow and shoulder. Pool-averaged coherence at tremor frequency also showed a better correlation with the amplitude of resting tremor than that of double tremor frequency, indicating that the neuromechanical coupling in peripheral neuromuscular system was stronger at tremor frequency. Both paired and pool-averaged coherences are more consistent indexes to correlate to tremor intensity in a group of upper extremity muscles of PD patients. The central drive at tremor frequency contributes mainly to synchronize peripheral muscles in the modulation of tremor intensity.

Spin current and second harmonic generation in non-collinear magnetic systems: the hydrodynamic model

NASA Astrophysics Data System (ADS)

Karashtin, E. A.; Fraerman, A. A.

2018-04-01

We report a theoretical study of the second harmonic generation in a noncollinearly magnetized conductive medium with equilibrium spin current. The hydrodynamic model is used to unravel the mechanism of a novel effect of the double frequency signal generation that is attributed to the spin current. According to our calculations, this second harmonic response appears due to the ‘non-adiabatic’ spin polarization of the conduction electrons induced by the oscillations in the non-uniform magnetization forced by the electric field of the electromagnetic wave. Together with the linear velocity response this leads to the generation of the double frequency spin current. This spin current is converted to the electric current via the inverse spin Hall effect, and the double-frequency electric current emits the second harmonic radiation. Possible experiment for detection of the new second harmonic effect is proposed.

SEM investigations of the cementum surface after irradiation with a frequency-doubled Alexandrite laser

NASA Astrophysics Data System (ADS)

Rechmann, Peter; Hennig, Thomas

1996-04-01

During prior studies it could be demonstrated while engaging a frequency doubled Alexandrite-laser (wavelength 380 nm, pulse duration 100 ns, fluence 1 J/cm2, pulse repetition rate 110 Hz) a fast and strictly selective ablation of supra- and subgingival calculus is possible. Even the removal of unstained microbial plaque was observed. First conclusions were drawn after light microscopical investigations on undecalcified sections of irradiated teeth. In the present study the cementum surface after irradiation with a frequency doubled Alexandrite-laser was observed by means of a Scanning Electron Microscope. After irradiation sections of teeth were dried in alcohol and sputtered with gold. In comparison irradiated cementum surfaces of unerupted operatively removed wisdom teeth and tooth surfaces after the selective removal of calculus were investigated. A complete removal of calculus was observed as well as a remaining smooth surface of irradiated cementum.

A Double-Negative Metamaterial-Inspired Mobile Wireless Antenna for Electromagnetic Absorption Reduction.

PubMed

Alam, Touhidul; Faruque, Mohammad Rashed Iqbal; Islam, Mohammad Tariqul

2015-07-29

A double-negative metamaterial-inspired antenna is presented for mobile wireless applications. The antenna consists of a semi-circular radiating patch and a 3 × 4 hexagonal shaped metamaterial unit cell array in the ground plane. The antenna is fed with a 50 Ω microstrip feed line. The electric dimensions of the proposed antenna are 0.20λ × 0.26λ × 0.004λ, at the low-end frequency. The proposed antenna achieves a -10 dB impedance with a bandwidth of 2.29 GHz at the lower band and 1.28 GHz at the upper band and can operate for most of the mobile applications such as upper GSM bands, WiMAX, Bluetooth, and wireless local area network (WLAN) frequency bands. The focused novelties of the proposed antenna are its small size, multi-standard operating bands, and electromagnetic absorption reduction at all the operating frequencies using the double-negative metamaterial ground plane.

303 nm continuous wave ultraviolet laser generated by intracavity frequency-doubling of diode-pumped Pr3+:LiYF4 laser

NASA Astrophysics Data System (ADS)

Zhu, Pengfei; Zhang, Chaomin; Zhu, Kun; Ping, Yunxia; Song, Pei; Sun, Xiaohui; Wang, Fuxin; Yao, Yi

2018-03-01

We demonstrate an efficient and compact ultraviolet laser at 303 nm generated by intracavity frequency doubling of a continuous wave (CW) laser diode-pumped Pr3+:YLiF4 laser at 607 nm. A cesium lithium borate (CLBO) crystal, cut for critical type I phase matching at room temperature, is used for second-harmonic generation (SHG) of the fundamental laser. By using an InGaN laser diode array emitting at 444.3 nm with a maximum incident power of 10 W, as high as 68 mW of CW output power at 303 nm is achieved. The output power stability in 4 h is better than 2.85%. To the best of our knowledge, this is high efficient UV laser generated by frequency doubling of an InGaN laser diode array pumped Pr3+:YLiF4 laser.

Double Brillouin frequency spaced multiwavelength Brillouin-erbium fiber laser with 50 nm tuning range

NASA Astrophysics Data System (ADS)

Zhao, J. F.; Liao, T. Q.; Zhang, C.; Zhang, R. X.; Miao, C. Y.; Tong, Z. R.

2012-09-01

A 50 nm tuning range multiwavelength Brillouin-erbium fiber laser (MWBEFL) with double Brillouin frequency spacing is presented. Two separated gain blocks with symmetrical architecture, consisted by erbium-doped fiber amplifiers (EDFAs) and Brillouin gain media, are used to generate double Brillouin frequency spacing. The wider tuning range is realized by eliminating the self-lasing cavity modes existing in conventional MWBEFLs because of the absence of the physical mirrors at the ends of the linear cavity. The Brillouin pump (BP) is preamplified by the EDFA before entering the single-mode fiber (SMF), which leads to the reduction of threshold power and the generation enhancement of Brillouin Stokes (BS) signals. Four channels with 0.176 nm spacing are achieved at 2 mW BP power and 280 mW 980 nm pump power which can be tuned from 1525 to 1575 nm.

Analytic double product integrals for all-frequency relighting.

PubMed

Wang, Rui; Pan, Minghao; Chen, Weifeng; Ren, Zhong; Zhou, Kun; Hua, Wei; Bao, Hujun

2013-07-01

This paper presents a new technique for real-time relighting of static scenes with all-frequency shadows from complex lighting and highly specular reflections from spatially varying BRDFs. The key idea is to depict the boundaries of visible regions using piecewise linear functions, and convert the shading computation into double product integrals—the integral of the product of lighting and BRDF on visible regions. By representing lighting and BRDF with spherical Gaussians and approximating their product using Legendre polynomials locally in visible regions, we show that such double product integrals can be evaluated in an analytic form. Given the precomputed visibility, our technique computes the visibility boundaries on the fly at each shading point, and performs the analytic integral to evaluate the shading color. The result is a real-time all-frequency relighting technique for static scenes with dynamic, spatially varying BRDFs, which can generate more accurate shadows than the state-of-the-art real-time PRT methods.

Real-time volcano monitoring using GNSS single-frequency receivers

NASA Astrophysics Data System (ADS)

Lee, Seung-Woo; Yun, Sung-Hyo; Kim, Do Hyeong; Lee, Dukkee; Lee, Young J.; Schutz, Bob E.

2015-12-01

We present a real-time volcano monitoring strategy that uses the Global Navigation Satellite System (GNSS), and we examine the performance of the strategy by processing simulated and real data and comparing the results with published solutions. The cost of implementing the strategy is reduced greatly by using single-frequency GNSS receivers except for one dual-frequency receiver that serves as a base receiver. Positions of the single-frequency receivers are computed relative to the base receiver on an epoch-by-epoch basis using the high-rate double-difference (DD) GNSS technique, while the position of the base station is fixed to the values obtained with a deferred-time precise point positioning technique and updated on a regular basis. Since the performance of the single-frequency high-rate DD technique depends on the conditions of the ionosphere over the monitoring area, the ionospheric total electron content is monitored using the dual-frequency data from the base receiver. The surface deformation obtained with the high-rate DD technique is eventually processed by a real-time inversion filter based on the Mogi point source model. The performance of the real-time volcano monitoring strategy is assessed through a set of tests and case studies, in which the data recorded during the 2007 eruption of Kilauea and the 2005 eruption of Augustine are processed in a simulated real-time mode. The case studies show that the displacement time series obtained with the strategy seem to agree with those obtained with deferred-time, dual-frequency approaches at the level of 10-15 mm. Differences in the estimated volume change of the Mogi source between the real-time inversion filter and previously reported works were in the range of 11 to 13% of the maximum volume changes of the cases examined.

Computational infrared and two-dimensional infrared photon echo spectroscopy of both wild-type and double mutant myoglobin-CO proteins.

PubMed

Choi, Jun-Ho; Kwak, Kyung-Won; Cho, Minhaeng

2013-12-12

The CO stretching mode of both wild-type and double mutant ( T67R / S92D ) MbCO (carbonmonoxymyoglobin) proteins is an ideal infrared (IR) probe for studying the local electrostatic environment inside the myoglobin heme pocket. Recently, to elucidate the conformational switching dynamics between two distinguishable states, extensive IR absorption, IR pump-probe, and two-dimensional (2D) IR spectroscopic studies for various mutant MbCO's have been performed by the Fayer group. They showed that the 2D IR spectroscopy of the double mutant, which has a peroxidase enzyme activity, reveals a rapid chemical exchange between two distinct states, whereas that of the wild-type does not. Despite the fact that a few simulation studies on these systems were already performed and reported, such complicated experimental results have not been fully reproduced nor described in terms of conformational state-to-state transition processes. Here, we first develop a distributed vibrational solvatochromic charge model for describing the CO stretch frequency shift reflecting local electric potential changes. Then, by carrying out molecular dynamic simulations of the two MbCO's and examining their CO frequency trajectories, it becomes possible to identify a proper reaction coordinate consisting of His64 imidazole ring rotation and its distance to the CO ligand. From the 2D surfaces of the resulting potential of mean forces, the spectroscopically distinguished A1 and A3 states of the wild-type as well as two more substates of the double mutant are identified and their vibrational frequencies and distributions are separately examined. Our simulated IR absorption and 2D IR spectra of the two MbCO's are directly compared with the previous experimental results reported by the Fayer group. The chemical exchange rate constants extracted from the two-state kinetic analyses of the simulated 2D IR spectra are in excellent agreement with the experimental values. On the basis of the quantitative agreement between the simulated spectra and experimental ones, we further examine the conformational differences in the heme pockets of the two proteins and show that the double mutation, T67R / S92D , suppresses the A1 population, restricts the imidazole ring rotation, and increases hydrogen-bond strength between the imidazole Nε-H and the oxygen atom of the CO ligand. It is believed that such delicate change of distal His64 imidazole ring dynamics induced by the double mutation may be responsible for its enhanced peroxidase catalytic activity as compared to the wild-type myoglobin.

Tracking Second Thoughts: Continuous and Discrete Revision Processes during Visual Lexical Decision

PubMed Central

Barca, Laura; Pezzulo, Giovanni

2015-01-01

We studied the dynamics of lexical decisions by asking participants to categorize lexical and nonlexical stimuli and recording their mouse movements toward response buttons during the choice. In a previous report we revealed greater trajectory curvature and attraction to competitors for Low Frequency words and Pseudowords. This analysis did not clarify whether the trajectory curvature in the two conditions was due to a continuous dynamic competition between the response alternatives or if a discrete revision process (a "change of mind") took place during the choice from an initially selected response to the opposite one. To disentangle these two possibilities, here we analyse the velocity and acceleration profiles of mouse movements during the choice. Pseudowords' peak movement velocity occurred with 100ms delay with respect to words and Letters Strings. Acceleration profile for High and Low Frequency words and Letters Strings exhibited a butterfly plot with one acceleration peak at 400ms and one deceleration peak at 650ms. Differently, Pseudowords' acceleration profile had double positive peaks (at 400 and 600ms) followed by movement deceleration, in correspondence with changes in the decision from lexical to nonlexical response buttons. These results speak to different online processes during the categorization of Low Frequency words and Pseudowords, with a continuous competition process for the former and a discrete revision process for the latter. PMID:25699992

Cyclically optimized electrochemical processes

NASA Astrophysics Data System (ADS)

Ruedisueli, Robert Louis

It has been frequently observed in experiment and industry practice that electrochemical processes (deposition, dissolution, fuel cells) operated in an intermittent or cyclic (AC) mode show improvements in efficiency and/or quality and yield over their steady (DC) mode of operation. Whether rationally invoked by design or empirically tuned-in, the optimal operating frequency and duty cycle is dependent upon the dominant relaxation time constant for the process in question. The electrochemical relaxation time constant is a function of: double-layer and reaction intermediary pseudo-capacitances, ion (charge) transport via electrical migration (mobility), and diffusion across a concentration gradient to electrode surface reaction sites where charge transfer and species incorporation or elimination occurs. The rate determining step dominates the time constant for the reaction or process. Electrochemical impedance spectroscopy (EIS) and piezoelectric crystal electrode (PCE) response analysis have proven to be useful tools in the study and identification of reaction mechanisms. This work explains and demonstrates with the electro-deposition of copper the application of EIS and PCE measurement and analysis to the selection of an optimum cyclic operating schedule, an optimum driving frequency for efficient, sustained cyclic (pulsed) operation.

Interest of the attenuation coefficient in multiparametric high frequency ultrasound investigation of whole blood coagulation process.

PubMed

Callé, Rachel; Plag, Camille; Patat, Frédéric; Ossant, Frédéric

2009-01-01

Previous studies [R. Libgot, F. Ossant, Y. Gruel, P. Lermusiaux, and F. Patat, Proc.-IEEE Utrason. Symp. 4, 2259-2262 (2005); R. Libgot-Calle, F. Ossant, Y. Gruel, P. Lermusiaux, and F. Patat, Ultrasound Med. Biol. 34, 252-264 (2008); F. Ossant, R. Libgot, P. Coupe, P. Lermusiaux, and F. Patat, Proc.-IEEE Ultrason. Symp. 2, 846-849 (2004)] showed the potential of an in vitro high frequency ultrasound (beyond 20 MHz) device to describe the blood clotting process. The parameters were simultaneously estimated in double transmission (DT) with the calculation of the velocity of longitudinal waves and in backscattering (BS) modes with the estimation of the integrated BS coefficient and the effective scatterer size. The aim of the present study was to show how the integrated attenuation coefficient (IAC) assessed in DT mode could provide additional information on this process, especially regarding the fibrin polymerization which is an important part of the coagulation process. A characteristic time t(a) of the variations in IAC that could be linked to fibrin formation was identified.

Hormone replacement therapy in women with epilepsy: a randomized, double-blind, placebo-controlled study.

PubMed

Harden, Cynthia L; Herzog, Andrew G; Nikolov, Blagovest G; Koppel, Barbara S; Christos, Paul J; Fowler, Kristen; Labar, Douglas R; Hauser, W Allen

2006-09-01

Previous reports have suggested that hormone replacement therapy (HRT) could increase seizure activity in women with epilepsy. We sought to determine whether adding HRT to the medication regimen of postmenopausal women with epilepsy was associated with an increase in seizure frequency. This was a randomized, double-blind, placebo-controlled trial of the effect of HRT on seizure frequency in postmenopausal women with epilepsy, taking stable doses of antiepileptic drugs (AEDs), and within 10 years of their last menses. After a 3-month prospective baseline, subjects were randomized to placebo, Prempro (0.625 mg of conjugated equine estrogens plus 2.5 mg of medroxyprogesterone acetate or CEE/MPA) daily, or double-dose CEE/MPA daily for a 3-month treatment period. Twenty-one subjects were randomized after completing baseline. The subjects' ages ranged from 45 to 62 years (mean, 53 years; SD, +/-5), and the number of AEDs used ranged from none to three (median, one). Five (71%) of seven subjects taking double-dose CEE/MPA had a worsening seizure frequency of at least one seizure type, compared with four (50%) of eight taking single-dose CEE/MPA and one (17%) of six taking placebo (p = 0.05). An increase in seizure frequency of the subject's most severe seizure type was associated with increasing CEE/MPA dose (p = 0.008). An increase in complex partial seizure frequency also was associated with increasing CEE/MPA dose (p = 0.05). Two subjects taking lamotrigine had a decrease in lamotrigine levels of 25-30% while taking CEE/MPA. CEE/MPA is associated with a dose-related increase in seizure frequency in postmenopausal women with epilepsy. CEE/MPA may decrease lamotrigine levels.

Single-Receiver GPS Phase Bias Resolution

NASA Technical Reports Server (NTRS)

Bertiger, William I.; Haines, Bruce J.; Weiss, Jan P.; Harvey, Nathaniel E.

2010-01-01

Existing software has been modified to yield the benefits of integer fixed double-differenced GPS-phased ambiguities when processing data from a single GPS receiver with no access to any other GPS receiver data. When the double-differenced combination of phase biases can be fixed reliably, a significant improvement in solution accuracy is obtained. This innovation uses a large global set of GPS receivers (40 to 80 receivers) to solve for the GPS satellite orbits and clocks (along with any other parameters). In this process, integer ambiguities are fixed and information on the ambiguity constraints is saved. For each GPS transmitter/receiver pair, the process saves the arc start and stop times, the wide-lane average value for the arc, the standard deviation of the wide lane, and the dual-frequency phase bias after bias fixing for the arc. The second step of the process uses the orbit and clock information, the bias information from the global solution, and only data from the single receiver to resolve double-differenced phase combinations. It is called "resolved" instead of "fixed" because constraints are introduced into the problem with a finite data weight to better account for possible errors. A receiver in orbit has much shorter continuous passes of data than a receiver fixed to the Earth. The method has parameters to account for this. In particular, differences in drifting wide-lane values must be handled differently. The first step of the process is automated, using two JPL software sets, Longarc and Gipsy-Oasis. The resulting orbit/clock and bias information files are posted on anonymous ftp for use by any licensed Gipsy-Oasis user. The second step is implemented in the Gipsy-Oasis executable, gd2p.pl, which automates the entire process, including fetching the information from anonymous ftp

Frequency of glove perforation and the protective effect of double gloves in gynecological surgery.

PubMed

Murta, Eddie F C; Silva, Cléber S; Júnior, Odilon R A

2003-06-01

The purposes of this prospective study were to verify the frequency of glove perforation during gynecological operations and to evaluate the efficacy of double gloving in preventing damage to the inner glove. From May 2000 to May 2001, three house staff and 12 residents were asked to place their used gloves in bags labeled with the following information: procedure performed, presence of a recognized glove perforation, and role in operating team (surgeon, first or second assistant, and instrumentalist). All glove sets were tested using the method of water pression. Damaged gloves were excluded from that analysis. In all, 35 and 51 operations were utilized with single and double gloves, respectively. There were 240 single gloves and 792 double gloves tested. Perforation occurred in 10.4% of the single gloves and 9.8% of the outer double gloves. There were no cases of perforation in the inner double gloves. In cases of operating time that lasted more than 2 h, 56% of the surgeries that used single gloves had perforation vs 58.5% of the double gloves. The first assistant had the major risk for glove perforation with the use of single or double gloves. The indicator finger of the non-dominant hand was the major risk for perforation. In conclusion, we recommend double gloving in all gynecological surgery to reduce the risk of contracting blood-borne diseases.

Operation of the CAPRICE electron cyclotron resonance ion source applying frequency tuning and double frequency heating.

PubMed

Maimone, F; Tinschert, K; Celona, L; Lang, R; Mäder, J; Rossbach, J; Spädtke, P

2012-02-01

The properties of the electromagnetic waves heating the electrons of the ECR ion sources (ECRIS) plasma affect the features of the extracted ion beams such as the emittance, the shape, and the current, in particular for higher charge states. The electron heating methods such as the frequency tuning effect and the double frequency heating are widely used for enhancing the performances of ECRIS or even for the routine operation during the beam production. In order to better investigate these effects the CAPRICE ECRIS has been operated using these techniques. The ion beam properties for highly charged ions have been measured with beam diagnostic tools. The reason of the observed variations of this performance can be related to the different electromagnetic field patterns, which are changing inside the plasma chamber when the frequency is varying.

Photonics-based microwave frequency measurement using a double-sideband suppressed-carrier modulation and an InP integrated ring-assisted Mach-Zehnder interferometer filter.

PubMed

Fandiño, Javier S; Muñoz, Pascual

2013-11-01

A photonic system capable of estimating the unknown frequency of a CW microwave tone is presented. The core of the system is a complementary optical filter monolithically integrated in InP, consisting of a ring-assisted Mach-Zehnder interferometer with a second-order elliptic response. By simultaneously measuring the different optical powers produced by a double-sideband suppressed-carrier modulation at the outputs of the photonic integrated circuit, an amplitude comparison function that depends on the input tone frequency is obtained. Using this technique, a frequency measurement range of 10 GHz (5-15 GHz) with a root mean square value of frequency error lower than 200 MHz is experimentally demonstrated. Moreover, simulations showing the impact of a residual optical carrier on system performance are also provided.

Diffraction-limited 577 nm true-yellow laser by frequency doubling of a tapered diode laser

NASA Astrophysics Data System (ADS)

Christensen, Mathias; Vilera, Mariafernanda; Noordegraaf, Danny; Hansen, Anders K.; Buß, Thomas; Jensen, Ole B.; Skovgaard, Peter M. W.

2018-02-01

A wide range of laser medical treatments are based on coagulation of blood by absorption of the laser radiation. It has, therefore, always been a goal of these treatments to maximize the ratio of absorption in the blood to that in the surrounding tissue. For this purpose lasers at 577 nm are ideal since this wavelength is at the peak of the absorption in oxygenated hemoglobin. Furthermore, 577 nm has a lower absorption in melanin when compared to green wavelengths (515 - 532 nm), giving it an advantage when treating at greater penetration depth. Here we present a laser system based on frequency doubling of an 1154 nm Distributed Bragg Reflector (DBR) tapered diode laser, emitting 1.1 W of single frequency and diffraction limited yellow light at 577 nm, corresponding to a conversion efficiency of 30.5%. The frequency doubling is performed in a single pass configuration using a cascade of two bulk non-linear crystals. The system is power stabilized over 10 hours with a standard deviation of 0.13% and the relative intensity noise is measured to be 0.064 % rms.

Discharge-pumped cw gas lasers utilizing 'dressed-atom' gain media

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

Sorokin, P.P.; Glownia, J.H.; Hodgson, R.T.

The possibility of realizing an efficient gaseous laser-beam-generating medium that utilizes {lambda}-type coherently phased (i.e., 'dressed') atoms for the active laser species, but that does not inherently require the use of external laser beams for pumping, is explored. Specifically, it is investigated if multiphoton stimulated hyper-Raman scattering (SHRS) processes driven by fluorescence radiation generated in a continuous electrical discharge present within the vapor-containing cell could produce continuous-wave (cw) optical gain at the {lambda}-atom resonance frequencies {omega}{sub o} and {omega}{sub o}{sup '}. It is deduced that such gain could result from n-photon (n{>=}4) SHRS processes only if absorption of fluorescence pumpmore » light occurs in the first three transitions of the n-photon sequence representing the process unit step. Estimates of the amount of optical gain that could be produced in such a system indicate that it should be sufficient to allow multiwatt cw laser operation to occur on one set of {lambda} transitions connecting levels in a 'double-{lambda}' structure, with the pump light being discharge-produced fluorescence centered about the transitions of the other {lambda} pair. However, to initiate operation of such a device would require injection into the laser optical cavity of intense 'starter' laser pulses at both lasing frequencies. What should be an optimal experimental configuration for determining feasibility of the proposed laser device is described. In the suggested configuration, Cs-atom 6S{sub 1/2}-6P{sub 1/2} transitions form the double-{lambda} structure.« less

Near-infrared lasers and self-frequency-doubling in Nd:YCOB cladding waveguides.

PubMed

Ren, Yingying; Chen, Feng; Vázquez de Aldana, Javier R

2013-05-06

A design of cladding waveguides in Nd:YCOB nonlinear crystals is demonstrated in this work. Compact Fabry-Perot oscillation cavities are employed for waveguide laser generation at 1062 nm and self-frequency-doubling at 531 nm, under optical pump at 810 nm. The waveguide laser shows slope efficiency as high as 55% at 1062 nm. The SFD green waveguide laser emits at 531 nm with a maximum power of 100 μW.

Frequency-Comb Based Double-Quantum Two-Dimensional Spectrum Identifies Collective Hyperfine Resonances in Atomic Vapor Induced by Dipole-Dipole Interactions

NASA Astrophysics Data System (ADS)

Lomsadze, Bachana; Cundiff, Steven T.

2018-06-01

Frequency-comb based multidimensional coherent spectroscopy is a novel optical method that enables high-resolution measurement in a short acquisition time. The method's resolution makes multidimensional coherent spectroscopy relevant for atomic systems that have narrow resonances. We use double-quantum multidimensional coherent spectroscopy to reveal collective hyperfine resonances in rubidium vapor at 100 °C induced by dipole-dipole interactions. We observe tilted and elongated line shapes in the double-quantum 2D spectra, which have never been reported for Doppler-broadened systems. The elongated line shapes suggest that the signal is predominately from the interacting atoms that have a near zero relative velocity.

Effects of Weight and Syntactic Priming on the Production of Cantonese Verb-Doubling

ERIC Educational Resources Information Center

Francis, Elaine J.; Matthews, Stephen; Wong, Reace Wing Yan; Kwan, Stella Wing Man

2011-01-01

Verb-doubling, where a copy of the main verb occurs both before and after the direct object, is a structure commonly used in Chinese in sentences containing a frequency or duration phrase. In Cantonese, verb-doubling is highly optional and therefore problematic for existing syntactic, semantic, and pragmatic accounts of its distribution in…

Multi-frequency electrical impedance tomography as a non-invasive tool to characterize and monitor crop root systems

NASA Astrophysics Data System (ADS)

Weigand, Maximilian; Kemna, Andreas

2017-02-01

A better understanding of root-soil interactions and associated processes is essential in achieving progress in crop breeding and management, prompting the need for high-resolution and non-destructive characterization methods. To date, such methods are still lacking or restricted by technical constraints, in particular the charactization and monitoring of root growth and function in the field. A promising technique in this respect is electrical impedance tomography (EIT), which utilizes low-frequency (< 1 kHz)- electrical conduction- and polarization properties in an imaging framework. It is well established that cells and cell clusters exhibit an electrical polarization response in alternating electric-current fields due to electrical double layers which form at cell membranes. This double layer is directly related to the electrical surface properties of the membrane, which in turn are influenced by nutrient dynamics (fluxes and concentrations on both sides of the membranes). Therefore, it can be assumed that the electrical polarization properties of roots are inherently related to ion uptake and translocation processes in the root systems. We hereby propose broadband (mHz to hundreds of Hz) multi-frequency EIT as a non-invasive methodological approach for the monitoring and physiological, i.e., functional, characterization of crop root systems. The approach combines the spatial-resolution capability of an imaging method with the diagnostic potential of electrical-impedance spectroscopy. The capability of multi-frequency EIT to characterize and monitor crop root systems was investigated in a rhizotron laboratory experiment, in which the root system of oilseed plants was monitored in a water-filled rhizotron, that is, in a nutrient-deprived environment. We found a low-frequency polarization response of the root system, which enabled the successful delineation of its spatial extension. The magnitude of the overall polarization response decreased along with the physiological decay of the root system due to the stress situation. Spectral polarization parameters, as derived from a pixel-based Debye decomposition analysis of the multi-frequency imaging results, reveal systematic changes in the spatial and spectral electrical response of the root system. In particular, quantified mean relaxation times (of the order of 10 ms) indicate changes in the length scales on which the polarization processes took place in the root system, as a response to the prolonged induced stress situation. Our results demonstrate that broadband EIT is a capable, non-invasive method to image root system extension as well as to monitor changes associated with the root physiological processes. Given its applicability on both laboratory and field scales, our results suggest an enormous potential of the method for the structural and functional imaging of root systems for various applications. This particularly holds for the field scale, where corresponding methods are highly desired but to date are lacking.

Study of the field-sequential modulation of Nd:YVO4/MgO:PPLN based intra-cavity frequency doubling green laser

NASA Astrophysics Data System (ADS)

Zhang, Bin; Gan, Yi; Xu, Chang-Qing

2018-06-01

The field sequential modulation of a Nd:YVO4/MgO:PPLN intra-cavity, frequency doubling green laser was studied. The modulation frequency was set at 1 kHz and the duty cycle was changed from 20% to CW operation. It was shown that the quasi-phase matched (QPM) temperature decreases with an increase of the modulation duty cycle, and in turn causing the peak efficiency to rise. It was found that the temperature change in MgO:PPLN and the thermal lens effect in Nd:YVO4 crystal were the respective origins of these observed experimental phenomena.

Improvement of the energy resolution via an optimized digital signal processing in GERDA Phase I

NASA Astrophysics Data System (ADS)

Agostini, M.; Allardt, M.; Bakalyarov, A. M.; Balata, M.; Barabanov, I.; Barros, N.; Baudis, L.; Bauer, C.; Becerici-Schmidt, N.; Bellotti, E.; Belogurov, S.; Belyaev, S. T.; Benato, G.; Bettini, A.; Bezrukov, L.; Bode, T.; Borowicz, D.; Brudanin, V.; Brugnera, R.; Budjáš, D.; Caldwell, A.; Cattadori, C.; Chernogorov, A.; D'Andrea, V.; Demidova, E. V.; Vacri, A. di; Domula, A.; Doroshkevich, E.; Egorov, V.; Falkenstein, R.; Fedorova, O.; Freund, K.; Frodyma, N.; Gangapshev, A.; Garfagnini, A.; Grabmayr, P.; Gurentsov, V.; Gusev, K.; Hegai, A.; Heisel, M.; Hemmer, S.; Heusser, G.; Hofmann, W.; Hult, M.; Inzhechik, L. V.; Janicskó Csáthy, J.; Jochum, J.; Junker, M.; Kazalov, V.; Kihm, T.; Kirpichnikov, I. V.; Kirsch, A.; Klimenko, A.; Knöpfle, K. T.; Kochetov, O.; Kornoukhov, V. N.; Kuzminov, V. V.; Laubenstein, ********************M.; Lazzaro, A.; Lebedev, V. I.; Lehnert, B.; Liao, H. Y.; Lindner, M.; Lippi, I.; Lubashevskiy, A.; Lubsandorzhiev, B.; Lutter, G.; Macolino, C.; Majorovits, B.; Maneschg, W.; Medinaceli, E.; Misiaszek, M.; Moseev, P.; Nemchenok, I.; Palioselitis, D.; Panas, K.; Pandola, L.; Pelczar, K.; Pullia, A.; Riboldi, S.; Rumyantseva, N.; Sada, C.; Salathe, M.; Schmitt, C.; Schneider, B.; Schönert, S.; Schreiner, J.; Schütz, A.-K.; Schulz, O.; Schwingenheuer, B.; Selivanenko, O.; Shirchenko, M.; Simgen, H.; Smolnikov, A.; Stanco, L.; Stepaniuk, M.; Ur, C. A.; Vanhoefer, L.; Vasenko, A. A.; Veresnikova, A.; von Sturm, K.; Wagner, V.; Walter, M.; Wegmann, A.; Wester, T.; Wilsenach, H.; Wojcik, M.; Yanovich, E.; Zavarise, P.; Zhitnikov, I.; Zhukov, S. V.; Zinatulina, D.; Zuber, K.; Zuzel, G.

2015-06-01

An optimized digital shaping filter has been developed for the Gerda experiment which searches for neutrinoless double beta decay in Ge. The Gerda Phase I energy calibration data have been reprocessed and an average improvement of 0.3 keV in energy resolution (FWHM) corresponding to 10 % at the value for decay in Ge is obtained. This is possible thanks to the enhanced low-frequency noise rejection of this Zero Area Cusp (ZAC) signal shaping filter.

Super-Resolution of Multi-Pixel and Sub-Pixel Images for the SDI

DTIC Science & Technology

1993-06-08

where the phase of the transmitted signal is not needed. The Wigner - Ville distribution ( WVD ) of a real signal s(t), associated with the complex...B. Boashash, 0. P. Kenny and H. J. Whitehouse, "Radar imaging using the Wigner - Ville distribution ", in Real-Time Signal Processing, J. P. Letellier...analytic signal z(t), is a time- frequency distribution defined as-’- 00 W(tf) Z (~t + ) t- -)exp(-i2nft) . (45) Note that the WVD is the double Fourier

The in-process control of PVC sheath of a double core cable

NASA Astrophysics Data System (ADS)

Galeeva, N. S.; Redko, V. V.; Redko, L. A.

2018-01-01

In this work the possibility of the sheath hermiticity testing by measuring of the cable capacity per unit length variation during spark testing is considered. The research object is 2×0.75 HO3VVH2-F cable. According to the physical modelling it is proved that such defect of sheath as pinhole through the whole thickness of sheath can be registered for the test length 10 cm with test voltage frequencies 1kHz and 10kHz.

The Evolutionary Biology of Poxviruses

PubMed Central

Hughes, Austin L.; Irausquin, Stephanie; Friedman, Robert

2009-01-01

The poxviruses (family Poxviridae) are a family of double-stranded viruses including several species that infect humans and their domestic animals, most notably Variola virus (VARV), the causative agent of smallpox. The evolutionary biology of these viruses poses numerous questions, for which we have only partial answers at present. Here we review evidence regarding the origin of poxviruses, the frequency of host transfer in poxvirus history, horizontal transfer of host genes to poxviruses, and the population processes accounting for patterns of nucleotide sequence polymorphism. PMID:19833230

Experiments with Lasers and Frequency Doublers

NASA Technical Reports Server (NTRS)

Bachor, H.-A.; Taubman, M.; White, A. G.; Ralph, T.; McClelland, D. E.

1996-01-01

Solid state laser sources, such as diode-pumped Nd:YAG lasers, have given us CW laser light of high power with unprecedented stability and low noise performance. In these lasers most of the technical sources of noise can be eliminated allowing them to be operated close to the theoretical noise limit set by the quantum properties of light. The next step of reducing the noise below the standard limit is known as squeezing. We present experimental progress in generating reliably squeezed light using the process of frequency doubling. We emphasize the long term stability that makes this a truly practical source of squeezed light. Our experimental results match noise spectra calculated with our recently developed models of coupled systems which include the noise generated inside the laser and its interaction with the frequency doubler. We conclude with some observations on evaluating quadrature squeezed states of light.

Stochastic P-bifurcation and stochastic resonance in a noisy bistable fractional-order system

NASA Astrophysics Data System (ADS)

Yang, J. H.; Sanjuán, Miguel A. F.; Liu, H. G.; Litak, G.; Li, X.

2016-12-01

We investigate the stochastic response of a noisy bistable fractional-order system when the fractional-order lies in the interval (0, 2]. We focus mainly on the stochastic P-bifurcation and the phenomenon of the stochastic resonance. We compare the generalized Euler algorithm and the predictor-corrector approach which are commonly used for numerical calculations of fractional-order nonlinear equations. Based on the predictor-corrector approach, the stochastic P-bifurcation and the stochastic resonance are investigated. Both the fractional-order value and the noise intensity can induce an stochastic P-bifurcation. The fractional-order may lead the stationary probability density function to turn from a single-peak mode to a double-peak mode. However, the noise intensity may transform the stationary probability density function from a double-peak mode to a single-peak mode. The stochastic resonance is investigated thoroughly, according to the linear and the nonlinear response theory. In the linear response theory, the optimal stochastic resonance may occur when the value of the fractional-order is larger than one. In previous works, the fractional-order is usually limited to the interval (0, 1]. Moreover, the stochastic resonance at the subharmonic frequency and the superharmonic frequency are investigated respectively, by using the nonlinear response theory. When it occurs at the subharmonic frequency, the resonance may be strong and cannot be ignored. When it occurs at the superharmonic frequency, the resonance is weak. We believe that the results in this paper might be useful for the signal processing of nonlinear systems.

Advances in dual-tone development for pitch frequency doubling

NASA Astrophysics Data System (ADS)

Fonseca, Carlos; Somervell, Mark; Scheer, Steven; Kuwahara, Yuhei; Nafus, Kathleen; Gronheid, Roel; Tarutani, Shinji; Enomoto, Yuuichiro

2010-04-01

Dual-tone development (DTD) has been previously proposed as a potential cost-effective double patterning technique1. DTD was reported as early as in the late 1990's2. The basic principle of dual-tone imaging involves processing exposed resist latent images in both positive tone (aqueous base) and negative tone (organic solvent) developers. Conceptually, DTD has attractive cost benefits since it enables pitch doubling without the need for multiple etch steps of patterned resist layers. While the concept for DTD technique is simple to understand, there are many challenges that must be overcome and understood in order to make it a manufacturing solution. Previous work by the authors demonstrated feasibility of DTD imaging for 50nm half-pitch features at 0.80NA (k1 = 0.21) and discussed challenges lying ahead for printing sub-40nm half-pitch features with DTD. While previous experimental results suggested that clever processing on the wafer track can be used to enable DTD beyond 50nm halfpitch, it also suggest that identifying suitable resist materials or chemistries is essential for achieving successful imaging results with novel resist processing methods on the wafer track. In this work, we present recent advances in the search for resist materials that work in conjunction with novel resist processing methods on the wafer track to enable DTD. Recent experimental results with new resist chemistries, specifically designed for DTD, are presented in this work. We also present simulation studies that help and support identifying resist properties that could enable DTD imaging, which ultimately lead to producing viable DTD resist materials.

Intracavity frequency doubling of a continuous wave Ti:sapphire ring laser and application in resonance Raman spectroscopy of heme protein dynamics

NASA Astrophysics Data System (ADS)

Buchter, Scott C.; Williams, Curtis; Schulte, Alfons; Alekel, Theodore, III; Mizell, Gregory J.; Fay, William R.

1995-04-01

Noncritical temperature-tuned phase-matching and large nonlinear coefficients make potassium niobate an attractive material for frequency doubling tuneable near-infrared radiation. We have mounted a KNbO3 crystal intracavity in an argon ion pumped, continuous wave Ti:Sapphire ring laser to increase the power level of the second harmonic. Wavelength selection at the fundamental frequency is accomplished with a birefringent filter. By using the crystal orientation that defines the d32 coefficient of KNbO3 we have obtained a blue second harmonic output tuneable from 425-445 nm. The laser is also characterized by the narrow linewidth of the Ti:Sapphire ring oscillator and good temporal stability. A continuous wave, frequency doubled Ti:sapphire laser is well suited to excite the resonance Raman spectrum in heme proteins with strong absorption bands in the range of 400 to 450 nm. We demonstrate the feasibility of such a setup for Raman studies of ligand binding to myoglobin. The Raman bands yield information on the reaction dynamics and on conformational changes near the linkage between the heme and the protein. In particular, a shift of the stretch frequency of the iron- histidine bond with high pressure may be attributed to a protein conformational change.

Physiological and harmonic components in neural and muscular coherence in Parkinsonian tremor.

PubMed

Wang, Shouyan; Aziz, Tipu Z; Stein, John F; Bain, Peter G; Liu, Xuguang

2006-07-01

To differentiate physiological from harmonic components in coherence analysis of the tremor-related neural and muscular signals by comparing power, cross-power and coherence spectra. Influences of waveform, burst-width and additional noise on generating harmonic peaks in the power, cross-power and coherence spectra were studied using simulated signals. The local field potentials (LFPs) of the subthalamic nucleus (STN) and the EMGs of the contralateral forearm muscles in PD patients with rest tremor were analysed. (1) Waveform had significant effect on generating harmonics; (2) noise significantly decreased the coherence values in a frequency-dependent fashion; and (3) cross-spectrum showed high resistance to harmonics. Among six examples of paired LFP-EMG signals, significant coherence appeared at the tremor frequency only, both the tremor and double tremor frequencies and the double-tremor frequency only. In coherence analysis of neural and muscular signals, distortion in waveform generates significant harmonic peaks in the coherence spectra and the coherence values of both physiological and harmonic components are modulated by extra noise or non-tremor related activity. The physiological or harmonic nature of a coherence peak at the double tremor frequency may be differentiated when the coherence spectra are compared with the power and in particular the cross-power spectra.

Near-IR, blue, and UV generation by frequency conversion of a Tm:YAP laser

NASA Astrophysics Data System (ADS)

Cole, Brian; Goldberg, Lew; Chinn, Steve

2018-02-01

We describe generation of near-infrared (944nm, 970nm), blue (472nm, 485nm), and UV (236 nm) light by frequency up-conversion of 2 μm output of a compact and efficient passively Q-switched Tm:YAP laser. The Tm:YAP laser source was near diffraction limited with maximum Q-switched pulse peak power of 190 kW. For second harmonic generation (SHG) of NIR, both periodically poled lithium niobate (PPLN) and lithium tri-borate (LBO) were evaluated, with 58% conversion efficiency and 3.1 W of 970 nm power achieved with PPLN. The PPLN 970nm emission was frequency doubled in 20mm long type I LBO, generating 1.1 W at 485nm with a conversion efficiency of 34%. With LBO used for frequency doubling of 2.3 W of 1888 nm Tm:YAP output to 944nm, 860mW was generated, with 37% conversion efficiency. Using a second LBO crystal to generate the 4th harmonic, 545mW of 472nm power was generated, corresponding to 64% conversion efficiency. To generate the 8th harmonic of Tm:YAP laser emission, the 472nm output of the second LBO was frequency doubled in a 7mm long BBO crystal, generating 110 mW at 236nm, corresponding to 21% conversion efficiency.

Soft X-ray holographic grating beam splitter including a double frequency grating for interferometer pre-alignment.

PubMed

Liu, Ying; Tan, Xin; Liu, Zhengkun; Xu, Xiangdong; Hong, Yilin; Fu, Shaojun

2008-09-15

Grating beam splitters have been fabricated for soft X-ray Mach- Zehnder interferometer using holographic interference lithography. The grating beam splitter consists of two gratings, one works at X-ray laser wavelength of 13.9 nm with the spatial frequency of 1000 lines/mm as the operation grating, the other works at visible wavelength of 632.8 nm for pre-aligning the X-ray interferometer with the spatial frequency of 22 lines/mm as the pre-alignment grating. The two gratings lie vertically on the same substrate. The main feature of the beam splitter is the use of low-spatial- frequency beat grating of a holographic double frequency grating as the pre-alignment grating of the X-ray interferometer. The grating line parallelism between the two gratings can be judged by observing the diffraction patterns of the pre-alignment grating directly.

High-efficiency and multi-frequency polarization converters based on graphene metasurface with twisting double L-shaped unit structure array

NASA Astrophysics Data System (ADS)

Chen, Ming; Xiao, Xiaofei; Chang, Linzi; Wang, Congyun; Zhao, Deping

2017-07-01

In this work, a high-efficiency and tunable dual-frequency reflective polarization converter composed of graphene metasurface with twisting double L-shaped unit is firstly realized. Numerical results demonstrate that the device can convert a linearly polarized wave to its cross-polarized wave, and meantime it can also convert to a circularly polarized wave. Subsequently, one thickness of 500 nm SiO2 layer sandwiched by two graphene metasurfaces with similar pattern is stacked on the top of the two-layered structure, a four-frequency efficient reflective polarization converters is realized. Above all, those working frequencies can also be dynamically tuned within a large frequency range by adjusting the Fermi energy of the graphene, without reoptimizing and refabricating the nanostructures, which paves a novel way toward developing a controllable polarization converter for mid-infrared applications.

Red-green-blue (RGB) light generator using tapered fiber pumped with a frequency-doubled Yb-fiber laser.

PubMed

Rusu, M; Kivistö, Samuli; Gawith, C; Okhotnikov, O

2005-10-17

We report on successful realization of a picosecond visible-continuum source embedding a single mode fiber taper. The output of ytterbium mode-locked fiber laser was frequency doubled in a periodically-polled lithium niobate (PPLN) crystal to produce green pump light. Spectral brightness of the white light generated in the tapered fiber was improved by limiting the broadening just to the visible wavelengths. The influence of taper parameters, particularly the dispersion, on white light spectrum has been studied.

Red-green-blue (RGB) light generator using tapered fiber pumped with a frequency-doubled Yb-fiber laser

NASA Astrophysics Data System (ADS)

Rusu, M.; Kivistö, Samuli; Gawith, C. B. E.; Okhotnikov, O. G.

2005-10-01

We report on successful realization of a picosecond visible-continuum source embedding a single mode fiber taper. The output of ytterbium mode-locked fiber laser was frequency doubled in a periodically-polled lithium niobate (PPLN) crystal to produce green pump light. Spectral brightness of the white light generated in the tapered fiber was improved by limiting the broadening just to the visible wavelengths. The influence of taper parameters, particularly the dispersion, on white light spectrum has been studied.

Analysis of Thickness and Quality factor of a Double Paddle Oscillator at Room Temperature.

PubMed

Shakeel, Hamza; Metcalf, Thomas H; Pomeroy, J M

2016-01-01

In this paper, we evaluate the quality (Q) factor and the resonance frequency of a double paddle oscillator (DPO) with different thickness using analytical, computational and experimental methods. The study is carried out for the 2 nd anti-symmetric resonance mode that provides extremely high experimental Q factors on the order of 10 5 . The results show that both the Q factor and the resonance frequency of a DPO increase with the thickness at room temperature.

Design of a solar-pumped frequency-doubled 532 nm Nd:YVO4 laser

NASA Astrophysics Data System (ADS)

Kittiboonanan, P.; Putchana, W.; Deeudomand, M.; Ratanavis, A.

2017-09-01

During the last year we have made progresson a development of a frequency-doubled 532 nm Nd:YVO4 laser pumped by solar light. The research aimed to demonstrate solar pumped lasers consisting of the optically contracted Nd:YVO4 crystal and KTP crystal with a system of laser mirrors deposited onto crystal sides. The Cassegrain reflector is used as the configuration. This solar pumped laser system is appealing for a variety applications including laser communication, imaging and defense applications.

Continuous-wave laser at 440 nm based on frequency-doubled diode-pumped Nd:GdVO(4) crystal.

PubMed

Castaing, Marc; Balembois, François; Georges, Patrick

2008-09-01

We present for the first time, to the best of our knowledge, a frequency-doubled Nd:GdVO(4) laser operating in a cw on the pure three-level laser line at 880 nm. We obtained 300 mW at 440 nm for 23 W of incident pump power at 808 nm. Moreover, with a 25% output coupler we obtained a cw power of 1.9 W at the fundamental wavelength at 880 nm.

The design and performance of the nano-carbon based double layers flexible coating for tunable and high-efficiency microwave absorption

NASA Astrophysics Data System (ADS)

Zhang, Danfeng; Hao, Zhifeng; Qian, Yannan; Zeng, Bi; Zhu, Haiping; Wu, Qibai; Yan, Chengjie; Chen, Muyu

2018-05-01

Nanocarbon-based materials are outstanding microwave absorbers with good dielectric properties. In this study, double-layer silicone resin flexible absorbing coatings, composed of carbon-coated nickel nanoparticles (Ni@C) and carbon nanotubes (CNTs), with low loading and a total thickness of 2 mm, were prepared. The reflection loss (RL) of the double-layer absorbing coatings has measured for frequencies between 2 and 18 GHz using the Arch reflecting testing method. The effects of the thickness and electromagnetic parameters of each layer and of the layer sequence on the absorbing properties were investigated. It is found that the measured bandwidth (RL ≤ - 10 dB) of the optimum double-layer structure in our experiment range achieves 3.70 GHz. The results indicated that the double coating structure composed of different materials has greater synergistic absorption effect on impedance matching than that of same materials with different loading. The maximum RL of S1 (5 wt% CNTs)/S3 (60 wt% Ni@C) double-layer absorbing coating composed of different materials (S1 and S3) was larger than the one achieved using either S1 or S3 alone with the same thickness. This was because double-layer coating provided a suitable matching layer and improve the interfacial impedance. It was also shown that absorbing peak value and frequency position can be adjusted by double-layer coating structure.

Specializations for aerial hawking in the echolocation system of Molossus molossus (Molossidae, Chiroptera).

PubMed

Mora, E C; Macías, S; Vater, M; Coro, F; Kössl, M

2004-07-01

While searching for prey, Molossus molossus broadcasts narrow-band calls of 11.42 ms organized in pairs of pulses that alternate in frequency. The first signal of the pair is at 34.5 kHz, the second at 39.6 kHz. Pairs of calls with changing frequencies were only emitted when the interpulse intervals were below 200 ms. Maximum duty cycles during search phase are close to 20%. Frequency alternation of search calls is interpreted as a mechanism for increasing duty cycle and thus the temporal continuity of scanning, as well as increasing the detection range. A neurophysiological correlate for the processing of search calls was found in the inferior colliculus. 64% of neurons respond to frequencies in the 30- to 40-kHz range and only in this frequency range were closed tuning curves found for levels below 40 dB SPL. In addition, 15% of the neurons have double-tuned frequency-threshold curves with best thresholds at 34 and 39 kHz. Differing from observations in other bats, approach calls of M. molossus are longer and of higher frequencies than search calls. Close to the roost, the call frequency is increased to 45.0-49.8 kHz and, in addition, extremely broadband signals are emitted. This demonstrates high plasticity of call design.

CFD modeling and experimental verification of oscillating flow and heat transfer processes in the micro coaxial Stirling-type pulse tube cryocooler operating at 90-170 Hz

NASA Astrophysics Data System (ADS)

Zhao, Yibo; Yu, Guorui; Tan, Jun; Mao, Xiaochen; Li, Jiaqi; Zha, Rui; Li, Ning; Dang, Haizheng

2018-03-01

This paper presents the CFD modeling and experimental verifications of oscillating flow and heat transfer processes in the micro coaxial Stirling-type pulse tube cryocooler (MCSPTC) operating at 90-170 Hz. It uses neither double-inlet nor multi-bypass while the inertance tube with a gas reservoir becomes the only phase-shifter. The effects of the frequency on flow and heat transfer processes in the pulse tube are investigated, which indicates that a low enough frequency would lead to a strong mixing between warm and cold fluids, thereby significantly deteriorating the cooling performance, whereas a high enough frequency would produce the downward sloping streams flowing from the warm end to the axis and almost puncturing the gas displacer from the warm end, thereby creating larger temperature gradients in radial directions and thus undermining the cooling performance. The influence of the pulse tube length on the temperature and velocity when the frequencies are much higher than the optimal one are also discussed. A MCSPTC with an overall mass of 1.1 kg is worked out and tested. With an input electric power of 59 W and operating at 144 Hz, it achieves a no-load temperature of 61.4 K and a cooling capacity of 1.0 W at 77 K. The changing tendencies of tested results are in good agreement with the simulations. The above studies will help to thoroughly understand the underlying mechanism of the inertance MCSPTC operating at very high frequencies.

Strategy for improved frequency response of electric double-layer capacitors

NASA Astrophysics Data System (ADS)

Wada, Yoshifumi; Pu, Jiang; Takenobu, Taishi

2015-10-01

We propose a strategy for improving the response speed of electric double-layer capacitors (EDLCs) and electric double-layer transistors (EDLTs), based on an asymmetric structure with differently sized active materials and gate electrodes. We validate the strategy analytically by a classical calculation and experimentally by fabricating EDLCs with asymmetric Au electrodes (1:50 area ratio and 7.5 μm gap distance). The performance of the EDLCs is compared with that of conventional symmetric EDLCs. Our strategy dramatically improved the cut-off frequency from 14 to 93 kHz and this improvement is explained by fast charging of smaller electrodes. Therefore, this approach is particularly suitable to EDLTs, potentially expanding the applicability to medium speed (kHz-MHz) devices.

Design and measure of a tunable double-band metamaterial absorber in the THz spectrum

NASA Astrophysics Data System (ADS)

Guiming, Han

2018-04-01

We demonstrate and measure a hybrid double-band tunable metamaterial absorber in the terahertz region. The measured metamaterial absorber contains of a hybrid dielectric layer structure: a SU-8 layer and a VO2 layer. Near perfect double-band absorption performances are achieved by optimizing the SU-8 layer thickness at room temperature 25 °C. Measured results show that the phase transition can be observed when the measured temperature reaches 68 °C. Further measured results indicate that the resonance frequency and absorption amplitude of the proposed metamaterial absorber are tunable through increasing the measured temperature, while structural parameters unchanged. The proposed hybrid metamaterial absorber shows many advantages, such as frequency agility, absorption amplitude tunable, and simple fabrication.

A Double-Negative Metamaterial-Inspired Mobile Wireless Antenna for Electromagnetic Absorption Reduction

PubMed Central

Alam, Touhidul; Faruque, Mohammad Rashed Iqbal; Islam, Mohammad Tariqul

2015-01-01

A double-negative metamaterial-inspired antenna is presented for mobile wireless applications. The antenna consists of a semi-circular radiating patch and a 3 × 4 hexagonal shaped metamaterial unit cell array in the ground plane. The antenna is fed with a 50 Ω microstrip feed line. The electric dimensions of the proposed antenna are 0.20λ × 0.26λ × 0.004λ, at the low-end frequency. The proposed antenna achieves a −10 dB impedance with a bandwidth of 2.29 GHz at the lower band and 1.28 GHz at the upper band and can operate for most of the mobile applications such as upper GSM bands, WiMAX, Bluetooth, and wireless local area network (WLAN) frequency bands. The focused novelties of the proposed antenna are its small size, multi-standard operating bands, and electromagnetic absorption reduction at all the operating frequencies using the double-negative metamaterial ground plane. PMID:28793474

The effect of gravity modulation on thermosolutal convection in an infinite layer of fluid

NASA Astrophysics Data System (ADS)

Saunders, B. V.; Murray, B. T.; McFadden, G. B.; Coriell, S. R.; Wheeler, A. A.

1992-06-01

The effect of time-periodic vertical gravity modulation on the onset of thermosolutal convection in an infinite horizontal layer with stress-free boundaries is investigated using Floquet theory for the linear stability analysis. Situations for which the fluid layer is stably stratified in either the fingering or diffusive regimes of double-diffusive convection are considered. Results are presented both with and without steady background acceleration. Modulation may stabilize an unstable base solution or destabilize a stable base solution. In addition to synchronous and subharmonic response to the modulation frequency, instability in the double diffusive system can occur via a complex conjugate mode. In the diffusive regime, where oscillatory onset occurs in the unmodulated system, regions of resonant instability occur and exhibit strong coupling with the unmodulated oscillatory frequency. The response to modulation of the fundamental instability of the unmodulated system is described both analytically and numerically; in the double-diffusive system this mode persists under subcritical conditions as a high-frequency lobe.

The effect of gravity modulation on thermosolutal convection in an infinite layer of fluid

NASA Technical Reports Server (NTRS)

Saunders, B. V.; Murray, B. T.; Mcfadden, G. B.; Coriell, S. R.; Wheeler, A. A.

1992-01-01

The effect of time-periodic vertical gravity modulation on the onset of thermosolutal convection in an infinite horizontal layer with stress-free boundaries is investigated using Floquet theory for the linear stability analysis. Situations for which the fluid layer is stably stratified in either the fingering or diffusive regimes of double-diffusive convection are considered. Results are presented both with and without steady background acceleration. Modulation may stabilize an unstable base solution or destabilize a stable base solution. In addition to synchronous and subharmonic response to the modulation frequency, instability in the double diffusive system can occur via a complex conjugate mode. In the diffusive regime, where oscillatory onset occurs in the unmodulated system, regions of resonant instability occur and exhibit strong coupling with the unmodulated oscillatory frequency. The response to modulation of the fundamental instability of the unmodulated system is described both analytically and numerically; in the double-diffusive system this mode persists under subcritical conditions as a high-frequency lobe.

Laser diode and pumped Cr:Yag passively Q-switched yellow-green laser at 543 nm

NASA Astrophysics Data System (ADS)

Yao, Y.; Ling, Zhao; Li, B.; Qu, D. P.; Zhou, K.; Zhang, Y. B.; Zhao, Y.; Zheng, Q.

2013-03-01

Efficient and compact yellow green pulsed laser output at 543 nm is generated by frequency doubling of a passively Q-switched end diode-pumped Nd:YVO4 laser at 1086 nm under the condition of sup-pressing the higher gain transition near 1064 nm. With 15 W of diode pump power and the frequency doubling crystal LBO, as high as 1.58 W output power at 543 nm is achieved. The optical to optical conversion efficiency from the corresponding Q-switched fundamental output to the yellow green output is 49%. The peak power of the Q-switched yellow green pulse laser is up to 30 kW with 5 ns pulse duration. The output power stability over 8 hours is better than 2.56% at the maximum output power. To the best of our knowledge, this is the highest watt-level laser at 543 nm generated by frequency doubling of a passively Q-switched end diode pumped Nd:YVO4 laser at 1086 nm.

1W frequency-doubled VCSEL-pumped blue laser with high pulse energy

NASA Astrophysics Data System (ADS)

Van Leeuwen, Robert; Chen, Tong; Watkins, Laurence; Xu, Guoyang; Seurin, Jean-Francois; Wang, Qing; Zhou, Delai; Ghosh, Chuni

2015-02-01

We report on a Q-switched VCSEL side-pumped 946 nm Nd:YAG laser that produces high average power blue light with high pulse energy after frequency doubling in BBO. The gain medium was water cooled and symmetrically pumped by three 1 kW 808 nm VCSEL pump modules. More than 1 W blue output was achieved at 210 Hz with 4.9 mJ pulse energy and at 340 Hz with 3.2 mJ pulse energy, with 42% and 36% second harmonic conversion efficiency respectively. Higher pulse energy was obtained at lower repetition frequencies, up to 9.3 mJ at 70 Hz with 52% conversion efficiency.

Quench-induced breathing mode of one-dimensional Bose gases.

PubMed

Fang, Bess; Carleo, Giuseppe; Johnson, Aisling; Bouchoule, Isabelle

2014-07-18

We measure the position- and momentum-space breathing dynamics of trapped one-dimensional Bose gases at finite temperature. The profile in real space reveals sinusoidal width oscillations whose frequency varies continuously through the quasicondensate to ideal Bose gas crossover. A comparison with theoretical models taking temperature into account is provided. In momentum space, we report the first observation of a frequency doubling in the quasicondensate regime, corresponding to a self-reflection mechanism due to the repulsive interactions. Such a mechanism is predicted for a fermionized system, and has not been observed to date. The disappearance of the frequency doubling through the crossover is mapped out experimentally, giving insights into the dynamics of the breathing evolution.

Quench-Induced Breathing Mode of One-Dimensional Bose Gases

NASA Astrophysics Data System (ADS)

Fang, Bess; Carleo, Giuseppe; Johnson, Aisling; Bouchoule, Isabelle

2014-07-01

We measure the position- and momentum-space breathing dynamics of trapped one-dimensional Bose gases at finite temperature. The profile in real space reveals sinusoidal width oscillations whose frequency varies continuously through the quasicondensate to ideal Bose gas crossover. A comparison with theoretical models taking temperature into account is provided. In momentum space, we report the first observation of a frequency doubling in the quasicondensate regime, corresponding to a self-reflection mechanism due to the repulsive interactions. Such a mechanism is predicted for a fermionized system, and has not been observed to date. The disappearance of the frequency doubling through the crossover is mapped out experimentally, giving insights into the dynamics of the breathing evolution.

A frequency doubled pressure-tunable oscillator-amplifier dye laser system

NASA Technical Reports Server (NTRS)

Moriarty, A.; Heaps, W.; Davis, D. D.

1976-01-01

A tunable high-repetition-rate oscillator-amplifier dye-laser system is reported. The dye laser described was longitudinally pumped with the second harmonic of a Nd-YAG laser operating at 10 Hz. Using three Faraday-Perot etalons and pressure tuning, a maximum fundamental output power of the order of 6 MW with a corresponding spectral width of less than 0.003 nm at 564 nm was obtained. The fundamental at 564 nm was frequency doubled to give a maximum power level of 0.6 MW of second-harmonic output power with a spectral width less than 0.0015 nm at 282 nm. Frequency stability could be maintained to within approximately 15% of the line-width.

Microelectromechanical systems (MEMS) sensors based on lead zirconate titanate (PZT) films

NASA Astrophysics Data System (ADS)

Wang, Li-Peng

2001-12-01

In this thesis, modeling, fabrication and testing of microelectromechanical systems (MEMS) accelerometers based on piezoelectric lead zirconate titanate (PZT) films are investigated. Three different types of structures, cantilever beam, trampoline, and annular diaphragm, are studied. It demonstrates the high-performance, miniaturate, mass-production-compatible, and potentially circuitry-integratable piezoelectric-type PZT MEMS devices. Theoretical models of the cantilever-beam and trampoline accelerometers are derived via structural dynamics and the constitutive equations of piezoelectricity. The time-dependent transverse vibration equations, mode shapes, resonant frequencies, and sensitivities of the accelerometers are calculated through the models. Optimization of the silicon and PZT thickness is achieved with considering the effects of the structural dynamics, the material properties, and manufacturability for different accelerometer specifications. This work is the first demonstration of the fabrication of bulk-micromachined accelerometers combining a deep-trench reactive ion etching (DRIE) release strategy and thick piezoelectric PZT films deposited using a sol-gel method. Processing challenges which are overcome included materials compatibility, metallization, processing of thick layers, double-side processing, deep-trench silicon etching, post-etch cleaning and process integration. In addition, the processed PZT films are characterized by dielectric, ferroelectric (polarization electric-field hysteresis), and piezoelectric measurements and no adverse effects are found. Dynamic frequency response and impedance resonance measurements are performed to ascertain the performance of the MEMS accelerometers. The results show high sensitivities and broad frequency ranges of the piezoelectric-type PZT MEMS accelerometers; the sensitivities range from 0.1 to 7.6 pC/g for resonant frequencies ranging from 44.3 kHz to 3.7 kHz. The sensitivities were compared to theoretical values and a reasonable agreement (˜36% difference) is obtained.

Vlasov simulations of electron acceleration by radio frequency heating near the upper hybrid layer

NASA Astrophysics Data System (ADS)

Najmi, A.; Eliasson, B.; Shao, X.; Milikh, G.; Sharma, A. S.; Papadopoulos, K.

2017-10-01

It is shown by using a combination of Vlasov and test particles simulations that the electron distribution function resulting from energization due to Upper Hybrid (UH) plasma turbulence depends critically on the closeness of the pump wave to the double resonance, defined as ω ≈ ωUH ≈ nωce, where n is an integer. For pump frequencies, away from the double resonance, the electron distribution function is very close to Maxwellian, while as the pump frequency approaches the double resonance, it develops a high energy tail. The simulations show turbulence involving coupling between Lower Hybrid (LH) and UH waves, followed by excitation of Electron Bernstein (EB) modes. For the particular case of a pump with frequency between n = 3 and n = 4, the EB modes cover the range from the first to the 5th mode. The simulations show that when the injected wave frequency is between the 3rd and 4th harmonics of the electron cyclotron frequency, bulk electron heating occurs due to the interaction between the electrons and large amplitude EB waves, primarily on the first EB branch leading to an essentially thermal distribution. On the other hand, when the frequency is slightly above the 4th electron cyclotron harmonic, the resonant interaction is predominantly due to the UH branch and leads to a further acceleration of high-velocity electrons and a distribution function with a suprathermal tail of energetic electrons. The results are consistent with ionospheric experiments and relevant to the production of Artificial Ionospheric Plasma Layers.

A generalization of the double-corner-frequency source spectral model and its use in the SCEC BBP validation exercise

USGS Publications Warehouse

Boore, David M.; Di Alessandro, Carola; Abrahamson, Norman A.

2014-01-01

The stochastic method of simulating ground motions requires the specification of the shape and scaling with magnitude of the source spectrum. The spectral models commonly used are either single-corner-frequency or double-corner-frequency models, but the latter have no flexibility to vary the high-frequency spectral levels for a specified seismic moment. Two generalized double-corner-frequency ω2 source spectral models are introduced, one in which two spectra are multiplied together, and another where they are added. Both models have a low-frequency dependence controlled by the seismic moment, and a high-frequency spectral level controlled by the seismic moment and a stress parameter. A wide range of spectral shapes can be obtained from these generalized spectral models, which makes them suitable for inversions of data to obtain spectral models that can be used in ground-motion simulations in situations where adequate data are not available for purely empirical determinations of ground motions, as in stable continental regions. As an example of the use of the generalized source spectral models, data from up to 40 stations from seven events, plus response spectra at two distances and two magnitudes from recent ground-motion prediction equations, were inverted to obtain the parameters controlling the spectral shapes, as well as a finite-fault factor that is used in point-source, stochastic-method simulations of ground motion. The fits to the data are comparable to or even better than those from finite-fault simulations, even for sites close to large earthquakes.

Augmenting Transport versus Increasing Cold Storage to Improve Vaccine Supply Chains

PubMed Central

Haidari, Leila A.; Connor, Diana L.; Wateska, Angela R.; Brown, Shawn T.; Mueller, Leslie E.; Norman, Bryan A.; Schmitz, Michelle M.; Paul, Proma; Rajgopal, Jayant; Welling, Joel S.; Leonard, Jim; Chen, Sheng-I; Lee, Bruce Y.

2013-01-01

Background When addressing the urgent task of improving vaccine supply chains, especially to accommodate the introduction of new vaccines, there is often a heavy emphasis on stationary storage. Currently, donations to vaccine supply chains occur largely in the form of storage equipment. Methods This study utilized a HERMES-generated detailed, dynamic, discrete event simulation model of the Niger vaccine supply chain to compare the impacts on vaccine availability of adding stationary cold storage versus transport capacity at different levels and to determine whether adding stationary storage capacity alone would be enough to relieve potential bottlenecks when pneumococcal and rotavirus vaccines are introduced by 2015. Results Relieving regional level storage bottlenecks increased vaccine availability (by 4%) more than relieving storage bottlenecks at the district (1% increase), central (no change), and clinic (no change) levels alone. Increasing transport frequency (or capacity) yielded far greater gains (e.g., 15% increase in vaccine availability when doubling transport frequency to the district level and 18% when tripling). In fact, relieving all stationary storage constraints could only increase vaccine availability by 11%, whereas doubling the transport frequency throughout the system led to a 26% increase and tripling the frequency led to a 30% increase. Increasing transport frequency also reduced the amount of stationary storage space needed in the supply chain. The supply chain required an additional 61,269L of storage to relieve constraints with the current transport frequency, 55,255L with transport frequency doubled, and 51,791L with transport frequency tripled. Conclusions When evaluating vaccine supply chains, it is important to understand the interplay between stationary storage and transport. The HERMES-generated dynamic simulation model showed how augmenting transport can result in greater gains than only augmenting stationary storage and can reduce stationary storage needs. PMID:23717590

Augmenting transport versus increasing cold storage to improve vaccine supply chains.

PubMed

Haidari, Leila A; Connor, Diana L; Wateska, Angela R; Brown, Shawn T; Mueller, Leslie E; Norman, Bryan A; Schmitz, Michelle M; Paul, Proma; Rajgopal, Jayant; Welling, Joel S; Leonard, Jim; Chen, Sheng-I; Lee, Bruce Y

2013-01-01

When addressing the urgent task of improving vaccine supply chains, especially to accommodate the introduction of new vaccines, there is often a heavy emphasis on stationary storage. Currently, donations to vaccine supply chains occur largely in the form of storage equipment. This study utilized a HERMES-generated detailed, dynamic, discrete event simulation model of the Niger vaccine supply chain to compare the impacts on vaccine availability of adding stationary cold storage versus transport capacity at different levels and to determine whether adding stationary storage capacity alone would be enough to relieve potential bottlenecks when pneumococcal and rotavirus vaccines are introduced by 2015. Relieving regional level storage bottlenecks increased vaccine availability (by 4%) more than relieving storage bottlenecks at the district (1% increase), central (no change), and clinic (no change) levels alone. Increasing transport frequency (or capacity) yielded far greater gains (e.g., 15% increase in vaccine availability when doubling transport frequency to the district level and 18% when tripling). In fact, relieving all stationary storage constraints could only increase vaccine availability by 11%, whereas doubling the transport frequency throughout the system led to a 26% increase and tripling the frequency led to a 30% increase. Increasing transport frequency also reduced the amount of stationary storage space needed in the supply chain. The supply chain required an additional 61,269L of storage to relieve constraints with the current transport frequency, 55,255L with transport frequency doubled, and 51,791L with transport frequency tripled. When evaluating vaccine supply chains, it is important to understand the interplay between stationary storage and transport. The HERMES-generated dynamic simulation model showed how augmenting transport can result in greater gains than only augmenting stationary storage and can reduce stationary storage needs.

High-efficiency frequency doubling of continuous-wave laser light.

PubMed

Ast, Stefan; Nia, Ramon Moghadas; Schönbeck, Axel; Lastzka, Nico; Steinlechner, Jessica; Eberle, Tobias; Mehmet, Moritz; Steinlechner, Sebastian; Schnabel, Roman

2011-09-01

We report on the observation of high-efficiency frequency doubling of 1550 nm continuous-wave laser light in a nonlinear cavity containing a periodically poled potassium titanyl phosphate crystal (PPKTP). The fundamental field had a power of 1.10 W and was converted into 1.05 W at 775 nm, yielding a total external conversion efficiency of 95±1%. The latter value is based on the measured depletion of the fundamental field being consistent with the absolute values derived from numerical simulations. According to our model, the conversion efficiency achieved was limited by the nonperfect mode matching into the nonlinear cavity and by the nonperfect impedance matching for the maximum input power available. Our result shows that cavity-assisted frequency conversion based on PPKTP is well suited for low-decoherence frequency conversion of quantum states of light.

Recognition memory for low- and high-frequency-filtered emotional faces: Low spatial frequencies drive emotional memory enhancement, whereas high spatial frequencies drive the emotion-induced recognition bias.

PubMed

Rohr, Michaela; Tröger, Johannes; Michely, Nils; Uhde, Alarith; Wentura, Dirk

2017-07-01

This article deals with two well-documented phenomena regarding emotional stimuli: emotional memory enhancement-that is, better long-term memory for emotional than for neutral stimuli-and the emotion-induced recognition bias-that is, a more liberal response criterion for emotional than for neutral stimuli. Studies on visual emotion perception and attention suggest that emotion-related processes can be modulated by means of spatial-frequency filtering of the presented emotional stimuli. Specifically, low spatial frequencies are assumed to play a primary role for the influence of emotion on attention and judgment. Given this theoretical background, we investigated whether spatial-frequency filtering also impacts (1) the memory advantage for emotional faces and (2) the emotion-induced recognition bias, in a series of old/new recognition experiments. Participants completed incidental-learning tasks with high- (HSF) and low- (LSF) spatial-frequency-filtered emotional and neutral faces. The results of the surprise recognition tests showed a clear memory advantage for emotional stimuli. Most importantly, the emotional memory enhancement was significantly larger for face images containing only low-frequency information (LSF faces) than for HSF faces across all experiments, suggesting that LSF information plays a critical role in this effect, whereas the emotion-induced recognition bias was found only for HSF stimuli. We discuss our findings in terms of both the traditional account of different processing pathways for HSF and LSF information and a stimulus features account. The double dissociation in the results favors the latter account-that is, an explanation in terms of differences in the characteristics of HSF and LSF stimuli.

Four-wave mixing in an asymmetric double quantum dot molecule

NASA Astrophysics Data System (ADS)

Kosionis, Spyridon G.

2018-06-01

The four-wave mixing (FWM) effect of a weak probe field, in an asymmetric semiconductor double quantum dot (QD) structure driven by a strong pump field is theoretically studied. Similarly to the case of examining several other nonlinear optical processes, the nonlinear differential equations of the density matrix elements are used, under the rotating wave approximation. By suitably tuning the intensity and the frequency of the pump field as well as by changing the value of the applied bias voltage, a procedure used to properly adjust the electron tunneling coupling, we control the FWM in the same way as several other nonlinear optical processes of the system. While in the weak electron tunneling regime, the impact of the pump field intensity on the FWM is proven to be of crucial importance, for even higher rates of the electron tunneling it is evident that the intensity of the pump field has only a slight impact on the form of the FWM spectrum. The number of the spectral peaks, depends on the relation between specific parameters of the system.

[The risk of surgical glove perforations].

PubMed

Hagen, Gerd Ødegård; Arntzen, Halvard

2007-03-29

The increasing prevalence of blood-borne viral diseases has drawn attention to the barrier between the surgical personnel's hands and the patients body fluids during surgery. At present, the typical practice is to use double gloving in orthopaedic surgery, and single gloving in other types of surgery. The main purpose of our study was to estimate and compare the perforation risk in different categories of surgery. In a series of 655 surgical operations covering 5 main categories of surgery, all detected glove perforations were recorded and analysed. Perforations were found in 203 out of 655 operations (31%). The observed perforation frequency was 44.5% in gastrointestinal surgery, 34.7% in orthopaedic surgery, 31.1% in gynaecology, 18.6% in vascular surgery and 9.2% in general surgery. In some subcategories, the frequencies were even higher. In several categories of surgery, we found high perforation frequencies. Perforations in single gloves are often not detected during operations. This may increase the risk of transmission of blood-borne infections, particularly because the time of exposure may be long. Double indicator gloves make the intra-operative detection of perforations easier. Also double gloving is known to significantly reduce the perforation risk. The use of double indicator gloves is recommended in all categories of surgery.

Design and construction of a novel 1H/19F double-tuned coil system using PIN-diode switches at 9.4T.

PubMed

Choi, Chang-Hoon; Hong, Suk-Min; Ha, YongHyun; Shah, N Jon

2017-06-01

A double-tuned 1 H/ 19 F coil using PIN-diode switches was developed and its performance evaluated. The is a key difference from the previous developments being that this design used a PIN-diode switch in series with an additionally inserted inductor in parallel to one of the capacitors on the loop. The probe was adjusted to 19 F when the reverse bias voltage was applied (PIN-diode OFF), whilst it was switched to 1 H when forward current was flowing (PIN-diode ON). S-parameters and Q-factors of single- and double-tuned coils were examined and compared with/without a phantom on the bench. Imaging experiments were carried out on a 9.4T preclinical scanner. All coils were tuned at resonance frequencies and matched well. It is shown that the Q-ratio and SNR of double-tuned coil at 19 F frequency are nearly as good as those of a single-tuned coil. Since the operating frequency was tuned to 19 F when the PIN-diodes were turned off, losses due to PIN-diodes were substantially lower resulting in the provision of excellent image quality of X-nuclei. Copyright © 2017 Elsevier Inc. All rights reserved.

Sustained multi-kHz flamefront and 3-component velocity-field measurements for the study of turbulent flames

NASA Astrophysics Data System (ADS)

Boxx, I.; Stöhr, M.; Carter, C.; Meier, W.

2009-04-01

We describe an approach of imaging the dynamic interaction of the flamefront and flowfield. Here, a diode-pumped Nd:YLF laser operating at 5 kHz is used to pump a dye laser, which is then frequency doubled to 283 nm to probe flamefront OH, while a dual cavity diode-pumped Nd:YAG system produces pulse-pairs for particle image velocimetry (PIV). CMOS digital cameras are used to detect both planar laser-induced fluorescence (PLIF) and particle scattering (in a stereo arrangement) such that a 5 kHz measurement frequency is attained. This diagnostic is demonstrated in lifted-jet and swirl-stabilized flames, wherein the dynamics of the flame stabilization processes are seen. Nonperiodic effects such as local ignition and/or extinction, lift-off and flashback events, and their histories can be captured by this technique. As such, this system has the potential to significantly extend our understanding of nonstationary combustion processes relevant to industrial and technical applications.

Double checking: a second look

PubMed Central

Chreim, Samia; Forster, Alan

2015-01-01

Abstract Rationale, aims and objectives Double checking is a standard practice in many areas of health care, notwithstanding the lack of evidence supporting its efficacy. We ask in this study: ‘How do front line practitioners conceptualize double checking? What are the weaknesses of double checking? What alternate views of double checking could render it a more robust process?’ Method This is part of a larger qualitative study based on 85 semi‐structured interviews of health care practitioners in general internal medicine and obstetrics and neonatology; thematic analysis of the transcribed interviews was undertaken. Inductive and deductive themes are reported. Results Weaknesses in the double checking process include inconsistent conceptualization of double checking, double (or more) checking as a costly and time‐consuming procedure, double checking trusted as an accepted and stand‐alone process, and double checking as preventing reporting of near misses. Alternate views of double checking that would render it a more robust process include recognizing that double checking requires training and a dedicated environment, Introducing automated double checking, and expanding double checking beyond error detection. These results are linked with the concepts of collective efficiency thoroughness trade off (ETTO), an in‐family approach, and resilience. Conclusion(s) Double checking deserves more questioning, as there are limitations to the process. Practitioners could view double checking through alternate lenses, and thus help strengthen this ubiquitous practice that is rarely challenged. PMID:26568537

Green frequency-doubled laser-beam propagation in high-temperature hohlraum plasmas.

PubMed

Niemann, C; Berger, R L; Divol, L; Froula, D H; Jones, O; Kirkwood, R K; Meezan, N; Moody, J D; Ross, J; Sorce, C; Suter, L J; Glenzer, S H

2008-02-01

We demonstrate propagation and small backscatter losses of a frequency-doubled (2omega) laser beam interacting with inertial confinement fusion hohlraum plasmas. The electron temperature of 3.3 keV, approximately a factor of 2 higher than achieved in previous experiments with open geometry targets, approaches plasma conditions of high-fusion yield hohlraums. In this new temperature regime, we measure 2omega laser-beam transmission approaching 80% with simultaneous backscattering losses of less than 10%. These findings suggest that good laser coupling into fusion hohlraums using 2omega light is possible.

Generation of 369.4 nm Radiation by Efficient Doubling of a Diode Laser

NASA Technical Reports Server (NTRS)

Williams, A.; Seidel, D. J.; Maleki, J.

1993-01-01

A resonant cavity second harmonic generation system has been developed to produce 369.4 nm radiation from a 738.8 nm diode laser with 10 mW nominal output power. This system utilizes a polarization technique to lock the cavity to the laser frequency. In this paper we report on an evaluation of the system using a Titanium:Sapphire laser as the input source, and preliminary results with a diode laser source. To our knowledge, this is the deepest uv light ever produced by frequency-doubling a diode laser.

Generation of high-energy sub-20 fs pulses tunable in the 250-310 nm region by frequency doubling of a high-power noncollinear optical parametric amplifier.

PubMed

Beutler, Marcus; Ghotbi, Masood; Noack, Frank; Brida, Daniele; Manzoni, Cristian; Cerullo, Giulio

2009-03-15

We report on the generation of powerful sub-20 fs deep UV pulses with 10 microJ level energy and broadly tunable in the 250-310 nm range. These pulses are produced by frequency doubling a high-power noncollinear optical parametric amplifier and compressed by a pair of MgF2 prisms to an almost transform-limited duration. Our results provide a power scaling by an order of magnitude with respect to previous works.

Upstream ionization instability associated with a current-free double layer.

PubMed

Aanesland, A; Charles, C; Lieberman, M A; Boswell, R W

2006-08-18

A low frequency instability has been observed using various electrostatic probes in a low-pressure expanding helicon plasma. The instability is associated with the presence of a current-free double layer (DL). The frequency of the instability increases linearly with the potential drop of the DL, and simultaneous measurements show their coexistence. A theory for an upstream ionization instability has been developed, which shows that electrons accelerated through the DL increase the ionization upstream and are responsible for the observed instability. The theory is in good agreement with the experimental results.

A 160 W single-frequency laser based on an active tapered double-clad fiber amplifier

NASA Astrophysics Data System (ADS)

Trikshev, A. I.; Kurkov, A. S.; Tsvetkov, V. B.; Filatova, S. A.; Kertulla, J.; Filippov, V.; Chamorovskiy, Yu K.; Okhotnikov, O. G.

2013-06-01

We present a CW single-frequency laser at 1062 nm (linewidth <3 MHz) with 160 W of total output power based on a two stage fiber amplifier. A GTWave fiber is used for the first stage of the amplifier. A tapered double-clad fiber (T-DCF) is used for the second stage of the amplifier. The high output power is achieved due to the amplified spontaneous emission (ASE) filtering and increased stimulated Brillouin scattering (SBS) threshold inherent to the axially non-uniform geometry.

Characterization the microstructure of pulsed Nd:YAG welding method in low frequencies; correlation with tensile and fracture behavior in laser-welded nitinol joints

NASA Astrophysics Data System (ADS)

Shojaei Zoeram, Ali; Rahmani, Aida; Asghar Akbari Mousavi, Seyed Ali

2017-05-01

The precise controllability of heat input in pulsed Nd:YAG welding method provided by two additional parameters, frequency and pulse duration, has made this method very promising for welding of alloys sensitive to heat input. The poor weldability of Ti-rich nitinol as a result of the formation of Ti2Ni IMC has deprived us of the unique properties of this alloy. In this study, to intensify solidification rate during welding of Ti-rich nitinol, pulsed Nd:YAG laser beam in low frequency was employed in addition to the employment of a copper substrate. Specific microstructure produced in this condition was characterized and the effects of this microstructure on tensile and fracture behavior of samples welded by two different procedures, full penetration and double-sided method with halved penetration depth for each side were investigated. The investigations revealed although the combination of low frequencies, the use of a high thermal conductor substrate and double-sided method eliminated intergranular fracture and increased tensile strength, the particular microstructure, built in the pulsed welding method in low frequencies, results to the formation of the longitudinal cracks during the first stages of tensile test at weld centerline. This degrades tensile strength of welded samples compared to base metal. The results showed samples welded in double-sided method performed much better than samples welded in full penetration mode.

Regulatory role of NKG2D+ NK cells in intestinal lamina propria by secreting double-edged Th1 cytokines in ulcerative colitis

PubMed Central

Lin, Xue; Chang, Ying; Liu, Jing; Zhou, Rui; Nie, Jia-Yan; Dong, Wei-Guo; Zhao, Qiu; Li, Jin

2017-01-01

The role of intestinal lamina propria (LP) NKG2D+ NK cells is unclear in regulating Th1/Th2 balance in ulcerative colitis (UC). In this study, we investigated the frequency of LP NKG2D+ NK cells in DSS-induced colitis model and intestinal mucosal samples of UC patients, as well as the secretion of Th1/Th2/Th17 cytokines in NK cell lines after MICA stimulation. The role of Th1 cytokines in UC was validated by bioinformatics analysis. We found that DSS-induced colitis in mice was characterized by a Th2-mediated process. In acute phrase, the frequency of LP NKG2D+ lymphocytes increased significantly and decreased in remission, while the frequency of LP NKG2D+ NK cells decreased significantly in acute phase and increased in remission. No obvious change was found in the frequency of total LP NK cells. Similarly, severe UC patients had a higher expression of mucosal NKG2D and a lower number of NKG2D+ NK cells than mild to moderate UC. In NK cell lines, the MICA stimulation could induce a predominant secretion of Th1 cytokines (TNF, IFN-γ). Furthermore, in bioinformatics analysis, mucosal Th1 cytokine of TNF, showed a double-edged role in UC when compared to the Th1-mediated disease of Crohn's colitis. In conclusion, LP NKG2D+ NK cells partially played a regulatory role in UC through secreting Th1 cytokines to regulate the Th2-predominant Th1/Th2 imbalance, despite of the concomitant pro-inflammatory effects of Th1 cytokines. PMID:29228739

Proton decoupling and recoupling under double-nutation irradiation in solid-state NMR

NASA Astrophysics Data System (ADS)

Takeda, Kazuyuki; Wakisaka, Asato; Takegoshi, K.

2014-12-01

The effect of 1H decoupling in magic-angle spinning solid-state NMR is studied under radiofrequency irradiation causing simultaneous nutations around a pair of orthogonal axes. Double-nutation with an arbitrary pair of nutation frequencies is implemented through modulation of the amplitude, phase, and frequency of the transmitting pulses. Similarity and difference of double-nutation decoupling and two-pulse phase-modulation decoupling schemes [A. E. Bennett, C. M. Rienstra, M. Auger, K. V. Lakshmi, and R. G. Griffin, J. Chem. Phys. 103, 6951-6958 (1995) and I. Scholz, P. Hodgkinson, B. H. Meier, and M. Ernst, J. Chem. Phys. 130, 114510 (2009)] are discussed. The structure of recoupling bands caused by interference of the 1H spin nutation with sample spinning is studied by both experiments and numerical simulations.

Robustness analysis of elastoplastic structure subjected to double impulse

NASA Astrophysics Data System (ADS)

Kanno, Yoshihiro; Takewaki, Izuru

2016-11-01

The double impulse has extensively been used to evaluate the critical response of an elastoplastic structure against a pulse-type input, including near-fault earthquake ground motions. In this paper, we propose a robustness assessment method for elastoplastic single-degree-of-freedom structures subjected to the double impulse input. Uncertainties in the initial velocity of the input, as well as the natural frequency and the strength of the structure, are considered. As fundamental properties of the structural robustness, we show monotonicity of the robustness measure with respect to the natural frequency. In contrast, we show that robustness is not necessarily improved even if the structural strength is increased. Moreover, the robustness preference between two structures with different values of structural strength can possibly reverse when the performance requirement is changed.

Solid-state switch increases switching speed

NASA Technical Reports Server (NTRS)

Mcgowan, G. F.

1966-01-01

Solid state switch for commutating capacitors in an RC commutated network increases switching speed and extends the filtering or commutating frequency spectrum well into the kilocycle region. The switch is equivalent to the standard double- pole double-throw /DPDT/ relay and is driven from digital micrologic circuits.

Acoustic contributions of a sound absorbing blanket placed in a double panel structure: absorption versus transmission.

PubMed

Doutres, Olivier; Atalla, Noureddine

2010-08-01

The objective of this paper is to propose a simple tool to estimate the absorption vs. transmission loss contributions of a multilayered blanket unbounded in a double panel structure and thus guide its optimization. The normal incidence airborne sound transmission loss of the double panel structure, without structure-borne connections, is written in terms of three main contributions; (i) sound transmission loss of the panels, (ii) sound transmission loss of the blanket and (iii) sound absorption due to multiple reflections inside the cavity. The method is applied to four different blankets frequently used in automotive and aeronautic applications: a non-symmetric multilayer made of a screen in sandwich between two porous layers and three symmetric porous layers having different pore geometries. It is shown that the absorption behavior of the blanket controls the acoustic behavior of the treatment at low and medium frequencies and its transmission loss at high frequencies. Acoustic treatment having poor sound absorption behavior can affect the performance of the double panel structure.

RGB generation by four-wave mixing in small-core holey fibers

NASA Astrophysics Data System (ADS)

Horak, Peter; Dupriez, Pascal; Poletti, Francesco; Petrovich, Marco N.; Jeong, Yoonchan; Nilsson, Johan; Richardson, David J.; Payne, David N.

2007-09-01

We report the generation of white light comprising red, green, and blue spectral bands from a frequency-doubled fiber laser in submicron-sized cores of microstructured holey fibers. Picosecond pulses of green light are launched into a single suspended core of a silica holey fiber where energy is transferred by an efficient four-wave mixing process into a red and blue sideband whose wavelengths are fixed by birefringent phase matching due to a slight asymmetry of the structure arising during the fiber fabrication. Numerical models of the fiber structure and of the nonlinear processes confirm our interpretation. Finally, we discuss power scaling and limitations of this white light source.

Collision and radiative processes in emission of atmospheric carbon dioxide

NASA Astrophysics Data System (ADS)

Smirnov, B. M.

2018-05-01

The peculiarities of the spectroscopic properties of CO2 molecules in air due to vibration-rotation radiative transitions are analyzed. The absorption coefficient due to atmospheric carbon dioxide and other atmospheric components is constructed within the framework of the standard atmosphere model, on the basis of classical molecular spectroscopy and the regular model for the spectroscopy absorption band. The radiative flux from the atmosphere toward the Earth is represented as that of a blackbody, and the radiative temperature for emission at a given frequency is determined with accounting for the local thermodynamic equilibrium, a small gradient of the tropospheric temperature and a high optical thickness of the troposphere for infrared radiation. The absorption band model with an absorption coefficient averaged over the frequency and line-by-line model are used for evaluating the radiative flux from the atmosphere to the Earth which values are nearby for these models and are equal W m‑2 for the contemporary concentration of atmospheric CO2 molecules and W m‑2 at its doubled value. The absorption band model is not suitable to calculate the radiative flux change at doubling of carbon dioxide concentration because averaging over oscillations decreases the range where the atmospheric optical thickness is of the order of one, and just this range determines this change. The line-by-line method gives the change of the global temperature K as a result of doubling the carbon dioxide concentration. The contribution to the global temperature change due to anthropogenic injection of carbon dioxide in the atmosphere, i.e. resulted from combustion of fossil fuels, is approximately 0.02 K now.

Single-stage high frequency coaxial pulse tube cryocooler with base temperature below 30 K

NASA Astrophysics Data System (ADS)

Yang, L. W.; Xun, Y. Q.; Thummes, G.; Liang, J. T.

2010-05-01

This paper introduces two single-stage high frequency coaxial pulse tube cryocoolers (PTCs) with base temperature below 30 K. One has reached the lowest temperature of 26.1 K with an electric power of 250 W, which is the reported lowest temperature for single-stage high frequency PTC without multi-bypass. Using nozzle for double-inlet instead of need valves, the second PTC has achieved the temperature of 28.6 K with an electric power of 235 W. The analysis result is coinciding with experiments in general. The paper shows the advantage of the cooperated phase adjustment method of inertance tube and double-inlet, they might be the best choice when low temperature PTC is required.

Strain-induced three-photon effects

NASA Astrophysics Data System (ADS)

Jeong, Jae-Woo; Shin, Sung-Chul; Lyubchanskii, I. L.; Varyukhin, V. N.

2000-11-01

Strain-induced three-photon effects such as optical second-harmonic generation and hyper-Rayleigh light scattering, characterized by electromagnetic radiation at the double frequency of an incident light, are phenomenologically investigated by adopting a nonlinear photoelastic interaction. The relations between the strain and the nonlinear optical susceptibility for crystal surfaces with point symmetries of 4mm and 3m are described by a symmetry analysis of the nonlinear photoelastic tensor. We theoretically demonstrate a possibility of determining the strain components by measuring the rotational anisotropy of radiation at the second-harmonic frequency. Hyper-Rayleigh light scattering by dislocation strain is also described using a nonlinear photoelastic tensor. The angular dependencies of light scattered at the double frequency of an incident light for different scattering geometries are analyzed.

Solid-state-based laser system as a replacement for Ar⁺ lasers.

PubMed

Beck, Tobias; Rein, Benjamin; Sörensen, Fabian; Walther, Thomas

2016-09-15

We report on a solid-state-based laser system at 1028 nm. The light is generated by a diode laser seeded ytterbium fiber amplifier. In two build-up cavities, its frequency is doubled and quadrupled to 514 nm and 257 nm, respectively. At 514 nm, the system delivers up to 4.7 W of optical power. In the fourth harmonic, up to 173 mW are available limited by the nonlinear crystal. The frequency of the laser is mode-hop-free tunable by 16 GHz in 10 ms in the UV. Therefore, the system is suitable as a low maintenance, efficient, and tunable narrowband replacement for frequency doubled Ar⁺ laser systems.

Diode-side-pumped intracavity frequency-doubled Nd:YAG/BaWO4 Raman laser generating average output power of 3.14 W at 590 nm.

PubMed

Li, Shutao; Zhang, Xingyu; Wang, Qingpu; Zhang, Xiaolei; Cong, Zhenhua; Zhang, Huaijin; Wang, Jiyang

2007-10-15

We report a linear-cavity high-power all-solid-state Q-switched yellow laser. The laser source comprises a diode-side-pumped Nd:YAG module that produces 1064 nm fundamental radiation, an intracavity BaWO(4) Raman crystal that generates a first-Stokes laser at 1180 nm, and a KTP crystal that frequency doubles the first-Stokes laser to 590 nm. A convex-plane cavity is employed in this configuration to counteract some of the thermal effect caused by high pump power. An average output power of 3.14 W at 590 nm is obtained at a pulse repetition frequency of 10 kHz.

Continuous-wave yellow-green laser at 0.56  μm based on frequency doubling of a diode-end-pumped ceramic Nd:YAG laser.

PubMed

Yao, Wenming; Gao, Jing; Zhang, Long; Li, Jiang; Tian, Yubing; Ma, Yufei; Wu, Xiaodong; Ma, Gangfei; Yang, Jianming; Pan, Yubai; Dai, Xianjin

2015-06-20

We present what is, to the best of our knowledge, the first report on yellow-green laser generation based on the frequency doubling of the 1.1 μm transitions in Nd:YAG ceramics. By employing an 885 nm diode laser as the end-pumping source and a lithium triborate crystal as the frequency doubler, the highest continuous wave output powers of 1.4, 0.5, and 1.1 W at 556, 558, and 561 nm are achieved, respectively. These result in optical-to-optical efficiencies of 6.9%, 2.5%, and 5.4% with respect to the absorbed pump power, respectively.

Measurements of thermal conductivity and the coefficient of thermal expansion for polysilicon thin films by using double-clamped beams

NASA Astrophysics Data System (ADS)

Liu, Haiyun; Wang, Lei

2018-01-01

In this paper, a test structure for simultaneously determining thermal conductivity and the coefficient of thermal expansion (CTE) of polysilicon thin film is proposed. The test structure consists of two double-clamped beams with different lengths. A theoretical model for extracting thermal conductivity and CTE based on electrothermal analysis and resonance frequency approach is developed. Both flat and buckled beams are considered in the theoretical model. The model is confirmed by finite element software ANSYS. The test structures are fabricated by surface micromachined fabrication process. Experiments are carried out in our atmosphere. Thermal conductivity and CTE of polysilicon thin film are obtained to be (29.96  ±  0.92) W · m · K-1 and (2.65  ±  0.03)  ×  10-6 K-1, respectively, with temperature ranging from 300-400 K.

Increased upstream ionization due to formation of a double layer.

PubMed

Thakur, S Chakraborty; Harvey, Z; Biloiu, I A; Hansen, A; Hardin, R A; Przybysz, W S; Scime, E E

2009-01-23

We report observations that confirm a theoretical prediction that formation of a current-free double layer in a plasma expanding into a chamber of larger diameter is accompanied by an increase in ionization upstream of the double layer. The theoretical model argues that the increased ionization is needed to balance the difference in diffusive losses upstream and downstream of the expansion region. In our expanding helicon source experiments, we find that the upstream plasma density increases sharply at the same antenna frequency at which the double layer appears.

SPECIAL ISSUE ON OPTICAL PROCESSING OF INFORMATION: Optical information processing with transformation of the spatial coherence of light

NASA Astrophysics Data System (ADS)

Bykovskii, Yurii A.; Markilov, A. A.; Rodin, V. G.; Starikov, S. N.

1995-10-01

A description is given of systems with spatially incoherent illumination, intended for spectral and correlation analysis, and for the recording of Fourier holograms. These systems make use of transformation of the degree of the spatial coherence of light. The results are given of the processing of images and signals, including those transmitted by a bundle of fibre-optic waveguides both as monochromatic light and as quasimonochromatic radiation from a cathode-ray tube. The feasibility of spatial frequency filtering and of correlation analysis of images with a bipolar impulse response is considered for systems with spatially incoherent illumination where these tasks are performed by double transformation of the spatial coherence of light. A description is given of experimental systems and the results of image processing are reported.

Subwavelength and directional control of flexural waves in zone-folding induced topological plates

NASA Astrophysics Data System (ADS)

Chaunsali, Rajesh; Chen, Chun-Wei; Yang, Jinkyu

2018-02-01

Inspired by the quantum spin Hall effect shown by topological insulators, we propose a plate structure that can be used to demonstrate the pseudospin Hall effect for flexural waves. The system consists of a thin plate with periodically arranged resonators mounted on its top surface. We extend a technique based on the plane-wave expansion method to identify a double Dirac cone emerging due to the zone-folding in frequency band structures. This particular design allows us to move the double Dirac cone to a lower frequency than the resonating frequency of local resonators. We then manipulate the pattern of local resonators to open subwavelength Bragg band gaps that are topologically distinct. Building on this method, we verify numerically that a waveguide at an interface between two topologically distinct resonating plate structures can be used for guiding low-frequency, spin-dependent one-way flexural waves along a desired path with bends.

Phase locking of a semiconductor double-quantum-dot single-atom maser

NASA Astrophysics Data System (ADS)

Liu, Y.-Y.; Hartke, T. R.; Stehlik, J.; Petta, J. R.

2017-11-01

We experimentally study the phase stabilization of a semiconductor double-quantum-dot (DQD) single-atom maser by injection locking. A voltage-biased DQD serves as an electrically tunable microwave frequency gain medium. The statistics of the maser output field demonstrate that the maser can be phase locked to an external cavity drive, with a resulting phase noise L =-99 dBc/Hz at a frequency offset of 1.3 MHz. The injection locking range, and the phase of the maser output relative to the injection locking input tone are in good agreement with Adler's theory. Furthermore, the electrically tunable DQD energy level structure allows us to rapidly switch the gain medium on and off, resulting in an emission spectrum that resembles a frequency comb. The free running frequency comb linewidth is ≈8 kHz and can be improved to less than 1 Hz by operating the comb in the injection locked regime.

On sound transmission through double-walled cylindrical shells lined with poroelastic material: Comparison with Zhou's results and further effect of external mean flow

NASA Astrophysics Data System (ADS)

Liu, Yu; He, Chuanbo

2015-12-01

In this discussion, the corrections to the errors found in the derivations and the numerical code of a recent analytical study (Zhou et al. Journal of Sound and Vibration 333 (7) (2014) 1972-1990) on sound transmission through double-walled cylindrical shells lined with poroelastic material are presented and discussed, as well as the further effect of the external mean flow on the transmission loss. After applying the corrections, the locations of the characteristic frequencies of thin shells remain unchanged, as well as the TL results above the ring frequency where BU and UU remain the best configurations in sound insulation performance. In the low-frequency region below the ring frequency, however, the corrections attenuate the TL amplitude significantly for BU and UU, and hence the BB configuration exhibits the best performance which is consistent with previous observations for flat sandwich panels.

Double negative acoustic metastructure for attenuation of acoustic emissions

NASA Astrophysics Data System (ADS)

Kumar, Sanjay; Bhushan, Pulak; Prakash, Om; Bhattacharya, Shantanu

2018-03-01

Acoustic metamaterials hold great potential for attenuation of low frequency acoustic emissions. However, a fundamental challenge is achieving high transmission loss over a broad frequency range. In this work, we report a double negative acoustic metastructure for absorption of low frequency acoustic emissions in an aircraft. This is achieved by utilizing a periodic array of hexagonal cells interconnected with a neck and mounted with an elastic membrane on both ends. An average transmission loss of 56 dB under 500 Hz and an overall absorption of over 48% have been realized experimentally. The negative mass density is derived from the dipolar resonances created as a result of the in-phase movement of the membranes. Further, the negative bulk modulus is ascribed to the combined effect of out-of-phase acceleration of the membranes and the Helmholtz resonator. The proposed metastructure enables absorption of low frequency acoustic emissions with improved functionality that is highly desirable for varied applications.

Transfer functions of double- and multiple-cavity Fabry-Perot filters driven by Lorentzian sources.

PubMed

Marti, J; Capmany, J

1996-12-20

We derive expressions for the transfer functions of double- and multiple-cavity Fabry-Perot filters driven by laser sources with Lorentzian spectrum. These are of interest because of their applications in sensing and channel filtering in optical frequency-division multiplexing networks.

Transfer functions of double- and multiple-cavity Fabry Perot filters driven by Lorentzian sources

NASA Astrophysics Data System (ADS)

Marti, Javier; Capmany, Jose

1996-12-01

We derive expressions for the transfer functions of double- and multiple-cavity Fabry Perot filters driven by laser sources with Lorentzian spectrum. These are of interest because of their applications in sensing and channel filtering in optical frequency-division multiplexing networks.

Double resonator cantilever accelerometer

DOEpatents

Koehler, Dale R.

1984-01-01

A digital quartz accelerometer includes a pair of spaced double-ended tuning forks fastened at one end to a base and at the other end through a spacer mass. Transverse movement of the resonator members stresses one and compresses the other, providing a differential frequency output which is indicative of acceleration.

100μJ-level single frequency linearly-polarized nanosecond pulsed laser at 775 nm (Conference Presentation)

NASA Astrophysics Data System (ADS)

Shi, Wei; Fang, Qiang; Fan, Jingli; Cui, Xuelong; Zhang, Zhuo; Li, Jinhui; Zhou, Guoqing

2017-02-01

We report a single frequency, linearly polarized, near diffraction-limited, pulsed laser source at 775 nm by frequency doubling a single frequency nanosecond pulsed all fiber based master oscillator-power amplifier, seeded by a fiber coupled semiconductor DFB laser diode at 1550 nm. The laser diode was driven by a pulsed laser driver to generate 5 ns laser pulses at 260 Hz repetition rate with 50 pJ pulse energy. The pulse energy was boosted to 200 μJ using two stages of core-pumped fiber amplifiers and two stages of cladding-pumped fiber amplifiers. The multi-stage synchronous pulse pumping technique was adopted in the four stages of fiber amplifiers to mitigate the ASE. The frequency doubling is implemented in a single pass configuration using a periodically poled lithium niobate (PPLN) crystal. The crystal is 3 mm long, 1.4 mm wide, 1 mm thick, with a 19.36 μm domain period chosen for quasi-phase matching at 33°C. It was AR coated at both 1550 nm and 775 nm. The maximum pulse energy of 97 μJ was achieved when 189 μJ fundamental laser was launched. The corresponding conversion efficiency is about 51.3%. The pulse duration was measured to be 4.8 ns. So the peak power of the generated 775 nm laser pulses reached 20 kW. To the best of our knowledge, this is the first demonstration of a 100 μJ-level, tens of kilowatts-peak-power-level single frequency linearly polarized 775 nm laser based on the frequency doubling of the fiber lasers.

35-GHz radar sensor for automotive collision avoidance

NASA Astrophysics Data System (ADS)

Zhang, Jun

1999-07-01

This paper describes the development of a radar sensor system used for automotive collision avoidance. Because the heavy truck may have great larger radar cross section than a motorcyclist has, the radar receiver may have a large dynamic range. And multi-targets at different speed may confuse the echo spectrum causing the ambiguity between range and speed of target. To get more information about target and background and to adapt to the large dynamic range and multi-targets, a frequency modulated and pseudo- random binary sequences phase modulated continuous wave radar system is described. The analysis of this double- modulation system is given. A high-speed signal processing and data processing component are used to process and combine the data and information from echo at different direction and at every moment.

Analysis of multiple time scales in a transistor amplifier.

PubMed

Armstead, Douglas N; Carroll, Thomas L

2005-03-01

It was shown previously in an experiment that when high frequency signals (on the order of 1 MHz) were injected into this low frequency amplifier, the nonlinearities of the pn junctions caused period doubling, chaos, and very low frequency oscillations (on the order of 1 Hz). In this paper we present theory and simulations to explain the existence of the low frequency oscillations.

Investigation of the Mössbauer Spectrum Quality as a Dependence on the Frequency of the Velocity Signal

NASA Astrophysics Data System (ADS)

Pechousek, J.; Prochazka, R.; Cuda, J.; Frydrych, J.; Jancik, D.

2010-07-01

This paper is focused on a quality characterizing the Mössbauer spectra measured for various frequencies of the velocity signal. Standard electromechanical double-loudspeaker drive and digital PID velocity controller were used for calibration spectra measurement in the frequency interval from 4 up to 100 Hz. Several parameters were evaluated for recommendation of the suitable velocity signal frequency.

Comparison and characterization of efficient frequency doubling at 397.5 nm with PPKTP, LBO and BiBO crystals

NASA Astrophysics Data System (ADS)

Wen, Xin; Han, Yashuai; Wang, Junmin

2016-04-01

A continuous-wave Ti:sapphire laser at 795 nm is frequency doubled in a bow-tie type enhancement four-mirror ring cavity with LiB3O5 (LBO), BiB3O6 (BiBO), and periodically polled KTiOPO4 (PPKTP) crystals, respectively. The properties of 397.5 nm ultra-violet (UV) output power, beam quality, stability for these different nonlinear crystals are investigated and compared. For PPKTP crystal, the highest doubling efficiency of 58.1% is achieved from 191 mW of 795 nm mode-matched fundamental power to 111 mW of 397.5 nm UV output. For LBO crystal, with 1.34 W of mode-matched 795 nm power, 770 mW of 397.5 nm UV output is achieved, implying a doubling efficiency of 57.4%. For BiBO crystal, with 323 mW of mode-matched 795 nm power, 116 mW of 397.5 nm UV output is achieved, leading to a doubling efficiency of 35.9%. The generated UV radiation has potential applications in the fields of quantum physics.

Design and analysis of a double superimposed chamber valveless MEMS micropump.

PubMed

Zordan, E; Amirouche, F

2007-02-01

The newly designed micropump model proposed consists of a valveless double chamber pump completely simulated and optimized for drug delivery conditions. First, the inertia force and viscous loss in relation to actuation, pressure, and frequency is considered, and then a model of the nozzle/diffuser elements is introduced. The value of the flowrate obtained from the first model is then used to determine the loss coefficients starting from geometrical properties and flow velocity. From the developed model IT analysis is performed to predict the micropump performance based on the actuation parameters and no energy loss. A single-chamber pump with geometrical dimensions equal to each of the chambers of the double-chamber pump was also developed, and the results from both models are then compared for equally applied actuation pressure and frequency. Results show that the proposed design gives a maximum flow working frequency that is about 30 per cent lower than the single chamber design, with a maximum flowrate that is 140 per cent greater than that of the single chamber. Finally, the influences of geometrical properties on flowrate, maximum flow frequency, loss coefficients, and membrane strain are examined. The results show that the nozzle/ diffuser initial width and chamber side length are the most critical dimensions of the design.

Resonance line transfer calculations by doubling thin layers. I - Comparison with other techniques. II - The use of the R-parallel redistribution function. [planetary atmospheres

NASA Technical Reports Server (NTRS)

Yelle, Roger V.; Wallace, Lloyd

1989-01-01

A versatile and efficient technique for the solution of the resonance line scattering problem with frequency redistribution in planetary atmospheres is introduced. Similar to the doubling approach commonly used in monochromatic scattering problems, the technique has been extended to include the frequency dependence of the radiation field. Methods for solving problems with external or internal sources and coupled spectral lines are presented, along with comparison of some sample calculations with results from Monte Carlo and Feautrier techniques. The doubling technique has also been applied to the solution of resonance line scattering problems where the R-parallel redistribution function is appropriate, both neglecting and including polarization as developed by Yelle and Wallace (1989). With the constraint that the atmosphere is illuminated from the zenith, the only difficulty of consequence is that of performing precise frequency integrations over the line profiles. With that problem solved, it is no longer necessary to use the Monte Carlo method to solve this class of problem.

Light and scanning electron microscope investigations comparing calculus removal using an Er:YAG laser and a frequency-doubled alexandrite laser

NASA Astrophysics Data System (ADS)

Rechmann, Peter; Hennig, Thomas; Sadegh, Hamid M. M.; Goldin, Dan S.

1997-05-01

With respect to lasers emitting within the mid-IR spectral domain fiber applicators are being developed. Intended is the use of these lasers in periodontal therapy and their application inside the gingival pocket. Aim of the study presented here is to compare the effect of an Er:YAG laser on dental calculus with the results following irradiation with a frequency doubled Alexandrite laser. The surface of freshly extracted wisdom teeth and of extracted teeth suffering from severe periodontitis were irradiated with both laser wavelengths using a standardized application protocol. Calculus on the enamel surface, at the enamel cementum junction and on the root surface was irradiated. For light microscope investigations undecalcified histological sections were prepared after treatment. For the scanning electron microscope teeth were dried in alcohol and sputtered with gold. Investigations revealed that with both laser systems calculus can be removed. Using the frequency doubled Alexandrite laser selective removal of calculus is possible while engaging the Er:YAG laser even at lowest energies necessary for calculus removal healthy cementum is ablated without control.

Selective ablation of dental calculus with a frequency-doubled Alexandrite laser

NASA Astrophysics Data System (ADS)

Rechmann, Peter; Hennig, Thomas

1996-01-01

The aim of the study was the selective removal of dental calculus by means of pulsed lasers. In a first approach the optical characteristics of subgingival calculus were calculated using fluorescence emission spectroscopy (excitation laser: N2-laser, wavelength 337 nm, pulse duration 4 ns). Subgingival calculus seems to absorb highly in the ultraviolet spectral region up to 420 nm. According to these measurements a frequency doubled Alexandrite-laser (wavelength 377 nm, pulse duration 100 ns, repetition rate 110 Hz) was used to irradiate calculus located on enamel, at the cementum enamel junction and on the root surface (located on dentin or on cementum). Irradiation was performed perpendicular to the root surface with a laser fluence of 1 Jcm-2. During the irradiation procedure an effective water cooling-system was engaged. Histological investigations were done on undecalcified sections. As a result, engaging low fluences allows a fast and strictly selective removal of subgingival calculus. Even more the investigations revealed that supragingival calculus can be removed in a strictly selective manner engaging a frequency doubled Alexandrite-laser. No adverse side effects to the surrounding tissues could be found.

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

Zhang, Hailong; Vibration Control Lab, School of Electrical and Automation Engineering, Nanjing Normal University, Nanjing 210042; Zhang, Ning

Magneto-rheological (MR) damper possesses inherent hysteretic characteristics. We investigate the resulting nonlinear behaviors of a two degree-of-freedom (2-DoF) MR vibration isolation system under harmonic external excitation. A MR damper is identified by employing the modified Bouc-wen hysteresis model. By numerical simulation, we characterize the nonlinear dynamic evolution of period-doubling, saddle node bifurcating and inverse period-doubling using bifurcation diagrams of variations in frequency with a fixed amplitude of the harmonic excitation. The strength of chaos is determined by the Lyapunov exponent (LE) spectrum. Semi-physical experiment on the 2-DoF MR vibration isolation system is proposed. We trace the time history and phasemore » trajectory under certain values of frequency of the harmonic excitation to verify the nonlinear dynamical evolution of period-doubling bifurcations to chaos. The largest LEs computed with the experimental data are also presented, confirming the chaotic motion in the experiment. We validate the chaotic motion caused by the hysteresis of the MR damper, and show the transitions between distinct regimes of stable motion and chaotic motion of the 2-DoF MR vibration isolation system for variations in frequency of external excitation.« less

Broadband reflective multi-polarization converter based on single-layer double-L-shaped metasurface

NASA Astrophysics Data System (ADS)

Mao, Chenyang; Yang, Yang; He, Xiaoxiang; Zheng, Jingming; Zhou, Chun

2017-12-01

In this paper, a broadband reflective multi-polarization converter based on single-layer double-L-shaped metasurface is proposed. The proposed metasurface can effectively convert linear-polarized (TE/TM) incident wave into the reflected wave with three different polarizations within the frequency bands of 5.5-22.75 GHz. Based on the electric and magnetic resonant features of the double-L-shaped structure, the proposed metasurface can convert linearly polarized waves into cross-polarized waves at three resonant frequency bands. Furthermore, the incident linearly polarized waves can be effectively converted into left/right handed circular-polarized (LHCP and RHCP) waves at other four non-resonance frequency bands. Thus, the proposed metasurface can be regarded as a seven-band multi-polarization converter. The prototype of the proposed polarization converter is analyzed and measured. Both simulated and measured results show the 3-dB axis ratio bandwidth of circular polarization bands and the high polarization conversion efficiency of cross-polarization bands when the incident wave changes from 0° to 30° at both TE and TM modes.

Wireless multichannel biopotential recording using an integrated FM telemetry circuit.

PubMed

Mohseni, Pedram; Najafi, Khalil; Eliades, Steven J; Wang, Xiaoqin

2005-09-01

This paper presents a four-channel telemetric microsystem featuring on-chip alternating current amplification, direct current baseline stabilization, clock generation, time-division multiplexing, and wireless frequency-modulation transmission of microvolt- and millivolt-range input biopotentials in the very high frequency band of 94-98 MHz over a distance of approximately 0.5 m. It consists of a 4.84-mm2 integrated circuit, fabricated using a 1.5-microm double-poly double-metal n-well standard complementary metal-oxide semiconductor process, interfaced with only three off-chip components on a custom-designed printed-circuit board that measures 1.7 x 1.2 x 0.16 cm3, and weighs 1.1 g including two miniature 1.5-V batteries. We characterize the microsystem performance, operating in a truly wireless fashion in single-channel and multichannel operation modes, via extensive benchtop and in vitro tests in saline utilizing two different micromachined neural recording microelectrodes, while dissipating approximately 2.2 mW from a 3-V power supply. Moreover, we demonstrate successful wireless in vivo recording of spontaneous neural activity at 96.2 MHz from the auditory cortex of an awake marmoset monkey at several transmission distances ranging from 10 to 50 cm with signal-to-noise ratios in the range of 8.4-9.5 dB.

Efficient frequency conversion by stimulated Raman scattering in a sodium nitrate aqueous solution

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

Ganot, Yuval, E-mail: yuvalga@sapir.ac.il, E-mail: ibar@bgu.ac.il; Bar, Ilana, E-mail: yuvalga@sapir.ac.il, E-mail: ibar@bgu.ac.il

2015-09-28

Frequency conversion of laser beams, based on stimulated Raman scattering (SRS) is an appealing technique for generating radiation at new wavelengths. Here, we investigated experimentally the SRS due to a single pass of a collimated frequency-doubled Nd:YAG laser beam (532 nm) through a saturated aqueous solution of sodium nitrate (NaNO{sub 3}), filling a 50 cm long cell. These experiments resulted in simultaneous generation of 1st (564 nm) and 2nd (599 nm) Stokes beams, corresponding to the symmetric stretching mode of the nitrate ion, ν{sub 1}(NO{sub 3}{sup −}), with 40 and 12 mJ/pulse maximal converted energies, equivalent to 12% and 4% efficiencies, respectively, for a 340more » mJ/pulse pump energy. The results indicate that the pump and SRS beams were thermally defocused and that four-wave mixing was responsible for the second order Stokes process onset.« less

Transient regime in second harmonic generation

NASA Astrophysics Data System (ADS)

Szeftel, Jacob; Sandeau, Laure; Sandeau, Nicolas; Delezoide, Camille; Khater, Antoine

2013-09-01

The time growth of the electromagnetic field at the fundamental and double frequencies is studied from the very onset of the second harmonic generation (SHG) process for a set of dipoles lacking a symmetry centre and exhibiting a nonresonant coupling with a classical electromagnetic field. This approach consists first of solving the Schrödinger equation by applying a generalised Rabi rotation to the Hamiltonian describing the light-dipole interaction. This rotation has been devised for the resulting Hamiltonian to show up time-independent for both components of the electromagnetic field at the fundamental frequency and the second harmonic one. Then an energy conservation argument, derived from the Poynting theorem, is introduced to work out an additional relationship between the electromagnetic field and its associated electric polarisation. Finally this analysis yields the full time behaviour of all physical quantities of interest. The calculated results reproduce accurately both the observed spatial oscillations of the SHG intensity (Maker's fringes) and its power law dependence on the intensity of the incoming light at the fundamental frequency.

On the vibrational characteristics of single- and double-walled carbon nanotubes containing ice nanotube in aqueous environment

NASA Astrophysics Data System (ADS)

Ansari, R.; Ajori, S.; Ameri, A.

2015-10-01

The properties and behavior of carbon nanotubes (CNTs) in aqueous environment due to their considerable potential applications in nanobiotechnology and designing nanobiosensors have attracted the attention of researchers. In this study, molecular dynamics simulations are carried out to investigate the vibrational characteristics of single- and double-walled CNTs containing ice nanotubes (a new phase of ice) in vacuum and aqueous environments. The results demonstrate that formation of ice nanotubes inside the CNTs reduces the natural frequency of pure CNTs. Moreover, it is demonstrated that increasing the number of walls considerably reduces the sensitivity of frequency to the presence of ice nanotube inside CNT. Additionally, it is shown that increasing the length decreases the effect of ice nanotube on reducing the frequency. The calculation of natural frequency of CNTs in aqueous media demonstrates that the interaction of CNTs with water molecules considerably reduces the natural frequency up to 50 %. Finally, it is demonstrated that in the case of CNTs with one free end in aqueous environment, the CNT does not vibrate in its first mode, and its frequency is between the frequencies of first and second modes of vibration.

Electron Heating Mode Transitions in Nitrogen (13.56 and 40.68) MHz RF-CCPs

NASA Astrophysics Data System (ADS)

Erozbek Gungor, Ummugul; Bilikmen, Sinan Kadri; Akbar, Demiral

2015-09-01

Capacitively coupled radio frequency plasmas (RF-CCPs) are commonly used in plasma material processing. Parametrical structure of the plasma determines the demands of processing applications. For example; high density plasmas in gamma mode are mostly preferred for etching applications while stabile plasmas in gamma mode are usually used in sputtering applications. For this reason, characterization of the plasma is very essential before surface modification of the materials. In this work, analysis of electron heating mode transition in high frequency (40.68 MHz) RF-CCP was deeply investigated. The plasma was generated in a home-made (500 × 400 mm2) stainless steel cylindrical reactor in which two identical (200 mm in diameter) electrodes were placed with 40 mm interval. In addition, L-type automatic matching network system was connected to the 40.68 MHz RF generator to get high accuracy. Moreover, the pure (99.995 %) nitrogen was used as an activation gas on account of having an appreciable impression in plasma processing applications. Furthermore, diagnostic measurements of the plasma were done by using the Impedans Langmuir single and double probe systems. It was found that two transition points; α- γ (pressure dependent) and γ- α (RF power dependent) were observed in both medium and high RF-CCPs. As a result, the α- γ pressure transition increased, whereas the γ- α power transition remained constant by changing the RF frequency sources.

Frequency-Stable Ionic-Type Hybrid Gate Dielectrics for High Mobility Solution-Processed Metal-Oxide Thin-Film Transistors

PubMed Central

Heo, Jae Sang; Choi, Seungbeom; Jo, Jeong-Wan; Kang, Jingu; Park, Ho-Hyun; Kim, Yong-Hoon; Park, Sung Kyu

2017-01-01

In this paper, we demonstrate high mobility solution-processed metal-oxide thin-film transistors (TFTs) by using a high-frequency-stable ionic-type hybrid gate dielectric (HGD). The HGD gate dielectric, a blend of sol-gel aluminum oxide (AlOx) and poly(4-vinylphenol) (PVP), exhibited high dielectric constant (ε~8.15) and high-frequency-stable characteristics (1 MHz). Using the ionic-type HGD as a gate dielectric layer, an minimal electron-double-layer (EDL) can be formed at the gate dielectric/InOx interface, enhancing the field-effect mobility of the TFTs. Particularly, using the ionic-type HGD gate dielectrics annealed at 350 °C, InOx TFTs having an average field-effect mobility of 16.1 cm2/Vs were achieved (maximum mobility of 24 cm2/Vs). Furthermore, the ionic-type HGD gate dielectrics can be processed at a low temperature of 150 °C, which may enable their applications in low-thermal-budget plastic and elastomeric substrates. In addition, we systematically studied the operational stability of the InOx TFTs using the HGD gate dielectric, and it was observed that the HGD gate dielectric effectively suppressed the negative threshold voltage shift during the negative-illumination-bias stress possibly owing to the recombination of hole carriers injected in the gate dielectric with the negatively charged ionic species in the HGD gate dielectric. PMID:28772972

Poisson-process generalization for the trading waiting-time distribution in a double-auction mechanism

NASA Astrophysics Data System (ADS)

Cincotti, Silvano; Ponta, Linda; Raberto, Marco; Scalas, Enrico

2005-05-01

In this paper, empirical analyses and computational experiments are presented on high-frequency data for a double-auction (book) market. Main objective of the paper is to generalize the order waiting time process in order to properly model such empirical evidences. The empirical study is performed on the best bid and best ask data of 7 U.S. financial markets, for 30-stock time series. In particular, statistical properties of trading waiting times have been analyzed and quality of fits is evaluated by suitable statistical tests, i.e., comparing empirical distributions with theoretical models. Starting from the statistical studies on real data, attention has been focused on the reproducibility of such results in an artificial market. The computational experiments have been performed within the Genoa Artificial Stock Market. In the market model, heterogeneous agents trade one risky asset in exchange for cash. Agents have zero intelligence and issue random limit or market orders depending on their budget constraints. The price is cleared by means of a limit order book. The order generation is modelled with a renewal process. Based on empirical trading estimation, the distribution of waiting times between two consecutive orders is modelled by a mixture of exponential processes. Results show that the empirical waiting-time distribution can be considered as a generalization of a Poisson process. Moreover, the renewal process can approximate real data and implementation on the artificial stocks market can reproduce the trading activity in a realistic way.

Modelling the nonlinear behaviour of double walled carbon nanotube based resonator with curvature factors

NASA Astrophysics Data System (ADS)

Patel, Ajay M.; Joshi, Anand Y.

2016-10-01

This paper deals with the nonlinear vibration analysis of a double walled carbon nanotube based mass sensor with curvature factor or waviness, which is doubly clamped at a source and a drain. Nonlinear vibrational behaviour of a double-walled carbon nanotube excited harmonically near its primary resonance is considered. The double walled carbon nanotube is harmonically excited by the addition of an excitation force. The modelling involves stretching of the mid plane and damping as per phenomenon. The equation of motion involves four nonlinear terms for inner and outer tubes of DWCNT due to the curved geometry and the stretching of the central plane due to the boundary conditions. The vibrational behaviour of the double walled carbon nanotube with different surface deviations along its axis is analyzed in the context of the time response, Poincaré maps and Fast Fourier Transformation diagrams. The appearance of instability and chaos in the dynamic response is observed as the curvature factor on double walled carbon nanotube is changed. The phenomenon of Periodic doubling and intermittency are observed as the pathway to chaos. The regions of periodic, sub-harmonic and chaotic behaviour are clearly seen to be dependent on added mass and the curvature factors in the double walled carbon nanotube. Poincaré maps and frequency spectra are used to explicate and to demonstrate the miscellany of the system behaviour. With the increase in the curvature factor system excitations increases and results in an increase of the vibration amplitude with reduction in excitation frequency.

Estimating frame bulk and shear moduli of two double porosity layers by ultrasound transmission.

PubMed

Bai, Ruonan; Tinel, Alain; Alem, Abdellah; Franklin, Hervé; Wang, Huaqing

2016-08-01

The acoustic plane wave transmission by water saturated double porosity media is investigated. Two samples of double porosity media assumed to obey Berryman and Wang (BW) extension (Berryman and Wang, 1995, 2000) of Biot's theory in the low frequency regime are under consideration: ROBU® (pure binder-free borosilicate glass 3.3 manufactured to form the individual grains) and Tobermorite 11Å (the individual porous cement grains show irregular shapes). The de facto gap existing between theoretical and experimental data can be minimized by modifying adequately two of the parameters estimated from triaxial tests: the frame bulk and shear moduli. The frequency dependent imaginary parts that follow necessary from the minimization are in relation with the energy losses due to contact relaxation and friction between grains. Copyright © 2016 Elsevier B.V. All rights reserved.

Proton decoupling and recoupling under double-nutation irradiation in solid-state NMR

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

Takeda, Kazuyuki, E-mail: takezo@kuchem.kyoto-u.ac.jp; Wakisaka, Asato; Takegoshi, K.

The effect of {sup 1}H decoupling in magic-angle spinning solid-state NMR is studied under radiofrequency irradiation causing simultaneous nutations around a pair of orthogonal axes. Double-nutation with an arbitrary pair of nutation frequencies is implemented through modulation of the amplitude, phase, and frequency of the transmitting pulses. Similarity and difference of double-nutation decoupling and two-pulse phase-modulation decoupling schemes [A. E. Bennett, C. M. Rienstra, M. Auger, K. V. Lakshmi, and R. G. Griffin, J. Chem. Phys. 103, 6951–6958 (1995) and I. Scholz, P. Hodgkinson, B. H. Meier, and M. Ernst, J. Chem. Phys. 130, 114510 (2009)] are discussed. The structuremore » of recoupling bands caused by interference of the {sup 1}H spin nutation with sample spinning is studied by both experiments and numerical simulations.« less

Yellow light generation by frequency doubling of a fiber oscillator

NASA Astrophysics Data System (ADS)

Bacher, Christoph; Oliveira, Ricardo; Nogueira, Rogério N.; Romano, Valerio; Ryser, Manuel

2016-04-01

Laser sources with light-emission in the yellow spectral range around 577nm are very favorable for a variety of applications. These include applications in astronomy, in ophthalmology or in quantum optics. The generation and amplification of 1154 nm light is not straight forward when using Yb-doped optical fibers, since lasing occurs preferentially around the gain-maximum of 1030 nm. We generate the radiation within a fiber Bragg grating (FBG) based cavity and focused on reducing the amplified spontaneous emission (ASE). After the cavity, the output is frequency doubled to 577nm by using a second harmonic crystal.

Study of the spectral bandwidth of a double-pass acousto-optic system [Invited].

PubMed

Champagne, Justine; Kastelik, Jean-Claude; Dupont, Samuel; Gazalet, Joseph

2018-04-01

Acousto-optic tunable filters are known as efficient instruments for spectral and spatial filtering of light. In this paper, we analyze the bandwidth dependence of a double-pass filter. The interaction geometry chosen allows the simultaneous diffraction of the ordinary and the extraordinary optical modes by a single ultrasonic frequency. We present the main parameters of a custom device (design, optical range, driving frequency) and experimental results concerning the angular deviation of the beams including the effect of optical birefringence. The spectral resolution and the side lobes' significance are discussed. Spectral bandwidth of such a system is analyzed.

Frequency-doubled passively Q-switched microchip laser producing 225  ps pulses at 671  nm.

PubMed

Nikkinen, Jari; Korpijärvi, Ville-Markus; Leino, Iiro; Härkönen, Antti; Guina, Mircea

2016-11-15

We report a 671 nm laser source emitting 225 ps pulses with an average power of 55 mW and a repetition rate of 444 kHz. The system consists of a 1342 nm SESAM Q-switched Nd:YVO₄ microchip master oscillator and a dual-stage Nd:YVO₄ power amplifier. The 1342 nm signal was frequency-doubled to 671 nm using a periodically poled lithium niobate crystal. This laser source provides a practical alternative for applications requiring high energy picosecond pulses, such as time-gated Raman spectroscopy.

Synchronous optical pumping of quantum revival beats for atomic magnetometry

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

Seltzer, S. J.; Meares, P. J.; Romalis, M. V.

2007-05-15

We observe quantum beats with periodic revivals due to nonlinear spacing of Zeeman levels in the ground state of potassium atoms, and demonstrate their synchronous optical pumping by double modulation of the pumping light at the Larmor frequency and the revival frequency. We show that synchronous pumping increases the degree of spin polarization by a factor of 4. As a practical example, we explore the application of this double-modulation technique to atomic magnetometers operating in the geomagnetic field range, and find that it can increase the sensitivity and reduce magnetic-field-orientation-dependent measurement errors endemic to alkali-metal magnetometers.

Analytical solutions to the free vibration of a double-walled carbon nanotube carrying a bacterium at its tip

NASA Astrophysics Data System (ADS)

Storch, Joel A.; Elishakoff, Isaac

2013-11-01

We calculate the natural frequencies and mode shapes of a cantilevered double-walled carbon nanotube carrying a rigid body—representative of a bacterium or virus—at the tip of the outer nanotube. By idealizing the nanotubes as Bernoulli-Euler beams, we are able to obtain exact expressions for both the mode shapes and characteristic frequency equation. Separate analyses are performed for the special case of a concentrated tip mass and the more complicated situation where the tip body also exhibits inertia and mass center offset from the beam tip.

Frequency Analysis of the RRc Variables of the MACHO Database for the LMC

NASA Astrophysics Data System (ADS)

Kovács, G.; Alcock, C.; Allsman, R.; Alves, D.; Axelrod, T.; Becker, A.; Bennett, D.; Clement, C.; Cook, K. H.; Drake, A.; Freeman, K.; Geha, M.; Griest, K.; Kurtz, D. W.; Lehner, M.; Marshall, S.; Minniti, D.; Nelson, C.; Peterson, B.; Popowski, P.; Pratt, M.; Quinn, P.; Rodgers, A.; Rowe, J.; Stubbs, C.; Sutherland, W.; Tomaney, A.; Vandehei, T.; Welch, D. L.; MACHO Collaboration

We present the first massive frequency analysis of the 1200 first overtone RR Lyrae stars in the Large Magellanic Cloud observed in the first 4.3 yr of the MACHO project. Besides the many new double-mode variables, we also discovered stars with closely spaced frequencies. These variables are most probably nonradial pulsators.

Millimeter-band oscillations based on resonant tunneling in a double-barrier diode at room temperature

NASA Technical Reports Server (NTRS)

Brown, E. R.; Sollner, T. C. L. G.; Goodhue, W. D.; Parker, C. D.

1987-01-01

A double-barrier diode at room temperature has yielded oscillations with fundamental frequencies up to 56 GHz and second harmonics up to 87 GHz. The output powers at these frequencies were about 60 and 18 microW, respectively. These results are attributed to a recent improvement in the material parameters of the device and to the integration of the device into a waveguide resonator. The most successful diode to date has thin (about 1.5 nm) AlAs barriers, a 4.5-nm-wide GaAs quantum well, and 2 x 10 to the 17th/cu cm doping concentration in the n-GaAs outside the barriers. This particular diode is expected to oscillate at frequencies higher than those achieved by any reported p-n tunnel diode.

Generation of 46 W green-light by frequency doubling of 96 W picosecond unpolarized Yb-doped fiber amplifier

NASA Astrophysics Data System (ADS)

Qi, Yaoyao; Yu, Haijuan; Zhang, Jingyuan; Zhang, Ling; He, Chaojian; Lin, Xuechun

2018-05-01

We demonstrated a high efficiency and high average power picosecond green light source based on SHG (second harmonic generation) of an unpolarized ytterbium-doped fiber amplifier chain. Using single-pass frequency doubling in two temperature-tuned type-I phase-matching LBO crystals, we were able to generate 46 W, >70 ps pulses at 532 nm from a fundamental beam at 1064 nm, whose output is 96 W, 4.8 μJ, with a repetition frequency of 20 MHz and nearly diffraction limited. The optical conversion efficiency was ∼48% in a highly compact design. To the best of our knowledge, this is the first reported on ps green source through SHG of an unpolarized fiber laser with such a high output and high efficiency.

The use of acoustically tuned resonators to improve the sound transmission loss of double-panel partitions

NASA Astrophysics Data System (ADS)

Mason, J. M.; Fahy, F. J.

1988-07-01

Double-leaf partitions are often utilized in situations requiring low weight structures with high transmission loss, an example of current interest being the fuselage walls of propeller-driven aircraft. In this case, acoustic excitation is periodic and, if one of the frequencies of excitation lies in the region of the fundamental mass-air-mass frequency of the partition, insulation performance is considerably less than desired. The potential effectiveness of tuned Helmholtz resonators connected to the partition cavity is investigated as a method of improving transmission loss. This is demonstrated by a simple theoretical model and then experimentally verified. Results show that substantial improvements may be obtained at and around the mass-air-mass frequency for a total resonator volume 15 percent of the cavity volume.

Double-wavelet approach to study frequency and amplitude modulation in renal autoregulation

NASA Astrophysics Data System (ADS)

Sosnovtseva, O. V.; Pavlov, A. N.; Mosekilde, E.; Holstein-Rathlou, N.-H.; Marsh, D. J.

2004-09-01

Biological time series often display complex oscillations with several interacting rhythmic components. Renal autoregulation, for instance, involves at least two separate mechanisms both of which can produce oscillatory variations in the pressures and flows of the individual nephrons. Using double-wavelet analysis we propose a method to examine how the instantaneous frequency and amplitude of a fast mode is modulated by the presence of a slower mode. Our method is applied both to experimental data from normotensive and hypertensive rats showing different oscillatory patterns and to simulation results obtained from a physiologically based model of the nephron pressure and flow control. We reveal a nonlinear interaction between the two mechanisms that regulate the renal blood flow in the form of frequency and amplitude modulation of the myogenic oscillations.

Photonic microwave waveforms generation based on pulse carving and superposition in time-domain

NASA Astrophysics Data System (ADS)

Xia, Yi; Jiang, Yang; Zi, Yuejiao; He, Yutong; Tian, Jing; Zhang, Xiaoyu; Luo, Hao; Dong, Ruyang

2018-05-01

A novel photonic approach for various microwave waveforms generation based on time-domain synthesis is theoretically analyzed and experimentally investigated. In this scheme, two single-drive Mach-Zehnder modulators are used for pulses shaping. After shifting the phase and implementing envelopes superposition of the pulses, desired waveforms can be achieved in time-domain. The theoretic analysis and simulations are presented. In the experimental demonstrations, a triangular waveform, square waveform, and half duty cycle sawtooth (or reversed-sawtooth) waveform are generated successfully. By utilizing time multiplexing technique, a frequency-doubled sawtooth (or reversed-sawtooth) waveform with 100% duty cycle can be obtained. In addition, a fundamental frequency sawtooth (or reversed-sawtooth) waveform with 100% duty cycle can also be achieved by the superposition of square waveform and frequency-doubled sawtooth waveform.

Accuracy enhanced distance measurement system using double-sideband modulated frequency scanning interferometry

NASA Astrophysics Data System (ADS)

Chen, Xilun; Wang, Xiangchuan; Pan, Shilong

2017-03-01

An implementation of a distance measurement system using double-sideband with suppressed carrier modulation (DSB-SC) frequency scanning interferometry is proposed to reduce the variations in the optical path and improve the measurement accuracy. In this proposed system, the electro-optic DSB-SC is used to create dual-swept signals with opposite scanning directions. For each swept signal, the relative distance between the reference arm and the measuring arm is determined by the beat frequency of signals from two arms. By multiplying both beat signals, measurement errors caused by variations in the optical path can be greatly reduced. As an experimental demonstration, a vibration was introduced in the optical path length. The experimental results show that the variations can be suppressed for over 19.9 dB.

Processes governing transient responses of the deep ocean buoyancy budget to a doubling of CO2

NASA Astrophysics Data System (ADS)

Palter, J. B.; Griffies, S. M.; Hunter Samuels, B. L.; Galbraith, E. D.; Gnanadesikan, A.

2012-12-01

Recent observational analyses suggest there is a temporal trend and high-frequency variability in deep ocean buoyancy in the last twenty years, a phenomenon reproduced even in low-mixing models. Here we use an earth system model (GFDL's ESM2M) to evaluate physical processes that influence buoyancy (and thus steric sea level) budget of the deep ocean in quasi-steady state and under a doubling of CO2. A new suite of model diagnostics allows us to quantitatively assess every process that influences the buoyancy budget and its temporal evolution, revealing surprising dynamics governing both the equilibrium budget and its transient response to climate change. The results suggest that the temporal evolution of the deep ocean contribution to sea level rise is due to a diversity of processes at high latitudes, whose net effect is then advected in the Eulerian mean flow to mid and low latitudes. In the Southern Ocean, a slowdown in convection and spin up of the residual mean advection are approximately equal players in the deep steric sea level rise. In the North Atlantic, the region of greatest deep steric sea level variability in our simulations, a decrease in mixing of cold, dense waters from the marginal seas and a reduction in open ocean convection causes an accumulation of buoyancy in the deep subpolar gyre, which is then advected equatorward.

A Bowtie Antenna Coupled Tunable Photon-Assisted Tunneling Double Quantum Well (DQW) THz Detector

DTIC Science & Technology

2002-01-01

Proc. Vol. 692 © 2002 Materials Research Society H4.2 A Bowtie Antenna Coupled Tunable Photon-Assisted Tunneling Double Quantum Well (DQW) THz Detector ...on photon-assisted tunneling (PAT) between the two electron layers in a double quantum well (DQW) heterostructure, will be explained. The detector is...the frequency and strength of that radiation. The THz detector discussed in this paper makes use of photon- assisted tunnelling (PAT) between multiple

Comparison of various decentralised structural and cavity feedback control strategies for transmitted noise reduction through a double panel structure

NASA Astrophysics Data System (ADS)

Ho, Jen-Hsuan; Berkhoff, Arthur

2014-03-01

This paper compares various decentralised control strategies, including structural and acoustic actuator-sensor configuration designs, to reduce noise transmission through a double panel structure. The comparison is based on identical control stability indexes. The double panel structure consists of two panels with air in between and offers the advantages of low sound transmission at high frequencies, low heat transmission, and low weight. The double panel structure is widely used, such as in the aerospace and automotive industries. Nevertheless, the resonance of the cavity and the poor sound transmission loss at low frequencies limit the double panel's noise control performance. Applying active structural acoustic control to the panels or active noise control to the cavity has been discussed in many papers. In this paper, the resonances of the panels and the cavity are considered simultaneously to further reduce the transmitted noise through an existing double panel structure. A structural-acoustic coupled model is developed to investigate and compare various structural control and cavity control methods. Numerical analysis and real-time control results show that structural control should be applied to both panels. Three types of cavity control sources are presented and compared. The results indicate that the largest noise reduction is obtained with cavity control by loudspeakers modified to operate as incident pressure sources.

Vibro-acoustic modelling of aircraft double-walls with structural links using Statistical Energy Analysis

NASA Astrophysics Data System (ADS)

Campolina, Bruno L.

The prediction of aircraft interior noise involves the vibroacoustic modelling of the fuselage with noise control treatments. This structure is composed of a stiffened metallic or composite panel, lined with a thermal and acoustic insulation layer (glass wool), and structurally connected via vibration isolators to a commercial lining panel (trim). The goal of this work aims at tailoring the noise control treatments taking design constraints such as weight and space optimization into account. For this purpose, a representative aircraft double-wall is modelled using the Statistical Energy Analysis (SEA) method. Laboratory excitations such as diffuse acoustic field and point force are addressed and trends are derived for applications under in-flight conditions, considering turbulent boundary layer excitation. The effect of the porous layer compression is firstly addressed. In aeronautical applications, compression can result from the installation of equipment and cables. It is studied analytically and experimentally, using a single panel and a fibrous uniformly compressed over 100% of its surface. When compression increases, a degradation of the transmission loss up to 5 dB for a 50% compression of the porous thickness is observed mainly in the mid-frequency range (around 800 Hz). However, for realistic cases, the effect should be reduced since the compression rate is lower and compression occurs locally. Then the transmission through structural connections between panels is addressed using a four-pole approach that links the force-velocity pair at each side of the connection. The modelling integrates experimental dynamic stiffness of isolators, derived using an adapted test rig. The structural transmission is then experimentally validated and included in the double-wall SEA model as an equivalent coupling loss factor (CLF) between panels. The tested structures being flat, only axial transmission is addressed. Finally, the dominant sound transmission paths are identified in the 100 Hz to 10 kHz frequency range for double-walls under diffuse acoustic field and under point-force excitations. Non-resonant transmission is higher at low frequencies (frequencies lower than 1 kHz) while the structure-borne and the airborne paths dominate at mid- and high-frequencies, around 1 kHz and higher, respectively. An experimental validation on double-walls shows that the model is able to predict changes in the overall transmission caused by different structural couplings (rigid coupling, coupling via isolators and structurally uncoupled). Noise reduction means adapted to each transmission path, such as absorption, dissipation and structural decoupling, may be then derived. Keywords: Statistical energy analysis, Vibration isolator, Double-wall, Transfer path analysis, Transmission Loss.

Design and Fabrication of 1D and 2D Micro Scanners Actuated by Double Layered Lead Zirconate Titanate (PZT) Bimorph Beams

NASA Astrophysics Data System (ADS)

Tsaur, Jiunnjye; Zhang, Lulu; Maeda, Ryutaro; Matsumoto, Sohei; Khumpuang, Sommawan

2002-06-01

Micro scanners including 1D scanner beams and 2D scanning micromirrors are designed and fabricated. In order to yield large bending force, the sol-gel derived double layered lead zirconate titanate (PZT) structures are developed to be the actuator components. In our developed fabrication process, the use of thermal treatment and the addition of one platinium/titanium film played an important role to yield the well-crystallized perovskite phase and decrease the residual strss of total cantilever structures successfully. In the case of 1D scanner beams with the size of 750× 230 μm2, the optical scanning angle was 41.2 deg with respect to actuation with AC 5 V at 2706 Hz. Under the applied bias of 10 V, the bimorph beam bended upward and the deflection angle of 34.3 deg was measured. A 2D scanning micromirror supported by four suspended double layered PZT actuators was designed to rotate around two orthogonal axes by the operation at different resonant frequencies. While resonating with AC 7.5 V at 3750 Hz and 5350 Hz, the maximum scanning area of 24\\circ× 26\\circ was obtained.

Frequency and variability of dental morphology in deciduous and permanent dentition of a Nasa indigenous group in the municipality of Morales, Cauca, Colombia.

PubMed

Díaz, Eider; García, Lorena; Hernández, Michelle; Palacio, Lesly; Ruiz, Diana; Velandia, Nataly; Villavicencio, Judy; Moreno, Freddy

2014-01-01

To determine the frequency, variability, sexual dimorphism and bilateral symmetry of fourteen dental crown traits in the deciduous and permanent dentition of 60 dental models (35 women and 25 men) obtained from a native, indigenous group of Nasa school children of the Musse Ukue group in the municipality of Morales, Department of Cauca, Colombia. This is a quantitative, descriptive, cross-sectional study that characterizes dental morphology by means of the systems for temporary dentition from Dahlberg (winging), and ASUDAS (crowding, reduction of hypocone, metaconule and cusp 6), Hanihara (central and lateral incisors in shovel-shape and cusp 7), Sciulli (double bit, layered fold protostylid, cusp pattern and cusp number) and Grine (Carabelli trait); and in permanent dentition from ASUDAS (Winging, crowding, central and lateral incisors in shovel-shape and double shovel-shape, Carabelli trait, hypocone reduction, metaconule, cusp pattern, cusp number, layered fold protostylid, cusp 6 and cusp 7). The most frequent dental crown features were the shovel-shaped form, grooved and fossa forms of the Carabelli trait, metaconule, cusp pattern Y6, layered fold, protostylid (point P) and cusp 6. Sexual dimorphism was not observed and there was bilateral symmetry in the expression of these features. The sample studied presented a great affinity with ethnic groups belonging to the Mongoloid Dental Complex due to the frequency (expression) and variability (gradation) of the tooth crown traits, upper incisors, the Carabelli trait, the protostylid, cusp 6 and cusp 7. The influence of the Caucasoide Dental Complex associated with ethno-historical processes cannot be ruled out.

[Echolocation calls of free-flying Himalayan swiftlets (Aerodramus brevirostris)].

PubMed

Wang, Bin; Ma, Jian-Zhang; Chen, Yi; Tan, Liang-Jing; Liu, Qi; Shen, Qi-Qi; Liao, Qing-Yi; Zhang, Li-Biao

2013-02-01

Here, we present our findings of free-flying echolocation calls of Himalayan swiftlets (Aerodramus brevirostris), which were recorded in Shenjing Cave, Hupingshan National Reserve, Shimen County, Hunan Province in June 2012, using Avisoft-UltraSoundGate 116(e). We noted that after foraging at dusk, the Himalayan swiftlets flew fast into the cave without clicks, and then slowed down in dark area in the cave, but with sounds. The echolocation sounds of Himalayan swiftlets are broadband, double noise burst clicks, separated by a short pause. The inter-pulse intervals between double clicks (99.3±3.86 ms)were longer than those within double clicks (6.6±0.42 ms) (P<0.01). With the exception of peak frequency, between 6.2±0.08 kHz and 6.2±0.10 kHz, (P>0.05) and pulse duration 2.9±0.12 ms, 3.2±0.17 ms, (P>0.05) between the first and second, other factors-maximum frequency, minimum frequency, frequency bandwidth, and power-were significantly different between the clicks. The maximum frequency of the first pulse (20.1±1.10 kHz) was higher than that of second (15.4±0.98 kHz) (P<0.01), while the minimum frequency of the first pulse (3.7±0.12 kHz) was lower than that of second (4.0±0.09 kHz) (P<0.05); resulting in the frequency bandwidth of the first pulse (16.5±1.17 kHz) longer than that of second (11.4±1.01 kHz) (P<0.01). The power of the first pulse (-32.5±0.60 dB) was higher than that of second (-35.2±0.94 dB) (P<0.05). More importantly, we found that Himalayan swiftlets emitted echolocation pulses including ultrasonic sound, with a maximum frequency reaching 33.2 kHz.

Holographic cinematography and its applications

NASA Astrophysics Data System (ADS)

Smigielski, P.; Fagot, H.; Albe, F.

1986-08-01

Recording of single-exposure cineholograms of living bodies on 126-mm films, at a repetition rate of 25 holograms per second with the help of a frequency-doubled pulse YAG-laser; and recording of double-exposure cineholograms of reflecting moving objects for medical and industrial applications are reported. Limitations of 3D movies are described.

2H{ 19F} REDOR for distance measurements in biological solids using a double resonance spectrometer

NASA Astrophysics Data System (ADS)

Grage, Stephan L.; Watts, Jude A.; Watts, Anthony

2004-01-01

A new approach for distance measurements in biological solids employing 2H{ 19F} rotational echo double resonance was developed and validated on 2H, 19F- D-alanine and an imidazopyridine based inhibitor of the gastric H +/K +-ATPase. The 2H- 19F double resonance experiments presented here were performed without 1H decoupling using a double resonance NMR spectrometer. In this way, it was possible to benefit from the relatively longer distance range of fluorine without the need of specialized fluorine equipment. A distance of 2.5 ± 0.3 Å was measured in the alanine derivative, indicating a gauche conformation of the two labels. In the case of the imidazopyridine compound a lower distance limit of 5.2 Å was determined and is in agreement with an extended conformation of the inhibitor. Several REDOR variants were compared, and their advantages and limitations discussed. Composite fluorine dephasing pulses were found to enhance the frequency bandwidth significantly, and to reduce the dependence of the performance of the experiment on the exact choice of the transmitter frequency.

Frequency-dependent learning achieved using semiconducting polymer/electrolyte composite cells

NASA Astrophysics Data System (ADS)

Dong, W. S.; Zeng, F.; Lu, S. H.; Liu, A.; Li, X. J.; Pan, F.

2015-10-01

Frequency-dependent learning has been achieved using semiconducting polymer/electrolyte composite cells. The cells composed of polymer/electrolyte double layers realized the conventional spike-rate-dependent plasticity (SRDP) learning model. These cells responded to depression upon low-frequency stimulation and to potentiation upon high-frequency stimulation and presented long-term memory. The transition threshold θm from depression to potentiation varied depending on the previous stimulations. A nanostructure resembling a bio-synapse in its transport passages was demonstrated and a random channel model was proposed to describe the ionic kinetics at the polymer/electrolyte interface during and after stimulations with various frequencies, accounting for the observed SRDP.Frequency-dependent learning has been achieved using semiconducting polymer/electrolyte composite cells. The cells composed of polymer/electrolyte double layers realized the conventional spike-rate-dependent plasticity (SRDP) learning model. These cells responded to depression upon low-frequency stimulation and to potentiation upon high-frequency stimulation and presented long-term memory. The transition threshold θm from depression to potentiation varied depending on the previous stimulations. A nanostructure resembling a bio-synapse in its transport passages was demonstrated and a random channel model was proposed to describe the ionic kinetics at the polymer/electrolyte interface during and after stimulations with various frequencies, accounting for the observed SRDP. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02891d

Analysis of different techniques to improve sound transmission loss in cylindrical shells

NASA Astrophysics Data System (ADS)

Oliazadeh, Pouria; Farshidianfar, Anooshiravan

2017-02-01

In this study, sound transmission through double- and triple-walled shells is investigated. The structure-acoustic equations based on Donnell's shell theory are presented and transmission losses calculated by this approach are compared with the transmission losses obtained according to Love's theory. An experimental set-up is also constructed to compare natural frequencies obtained from Donnell and Love's theories with experimental results in the high frequency region. Both comparisons show that Donnell's theory predicts the sound transmission characteristics and vibrational behavior better than Love's theory in the high frequency region. The transmission losses of the double- and triple-walled construction are then presented for various radii and thicknesses. Then the effects of air gap size as an important design parameter are studied. Sound transmission characteristics through a circular cylindrical shell are also computed along with consideration of the effects of material damping. Modest absorption is shown to greatly reduce the sound transmission at ring frequency and coincidence frequency. Also the effects of five common gases that are used for filling the gap are investigated.

Validation of a Polyimide Foam Model for Use in Transmission Loss Applications

NASA Technical Reports Server (NTRS)

Hong, Kwanwoo; Bolton, J. Stuart; Cano, Roberto J.; Weiser, Erik S.; Jensen, Brian J.; Silcox, Rich; Howerton, Brian M.; Maxon, John; Wang, Tongan; Lorenzi, Tyler

2010-01-01

The work described in this paper was focused on the use of a new polyimide foam in a double wall sound transmission loss application. Recall that polyimide foams are functionally attractive, compared to polyurethane foams, for example, owing to their fire resistance. The foam considered here was found to have a flow resistivity that was too high for conventional acoustical applications, and as a result, it was processed by partial crushing to lower the flow resistivity into an acceptable range. Procedures for measuring the flow resistivity and Young s modulus of the material have been described, as was an inverse characterization procedure for estimating the remaining Biot parameters based on standing wave tube measurements of transmission loss and absorption coefficient. The inverse characterization was performed using a finite element model implementation of the Biot poro-elastic material theory. Those parameters were then used to predict the sound transmission loss of a double panel system lined with polyimide foam, and the predictions were compared with full-scale transmission loss measurements. The agreement between the two was reasonable, especially in the high and low frequency limits; however, it was found that the SEA model resulted in an under-prediction of the transmission loss in the mid-frequency range. Nonetheless, it was concluded that the performance of polyimide foam could be predicted using conventional poro-elastic material models and that polyimide foam may offer an attractive alternative to other double wall linings in certain situations: e.g., when fire resistance is a key issue. Future work will concentrate on reducing the density of the foam to values similar to those used in current aircraft sidewall treatments, and developing procedures to improve the performance of the foam in transmission loss applications.

Development of a Hydrogen Gas Sensor Using a Double Saw Resonator System at Room Temperature

PubMed Central

Yunusa, Zainab; Hamidon, Mohd Nizar; Ismail, Alyani; Isa, Maryam Mohd; Yaacob, Mohd Hanif; Rahmanian, Saeed; Ibrahim, Siti Azlida; Shabaneh, Arafat A.A

2015-01-01

A double SAW resonator system was developed as a novel method for gas sensing applications. The proposed system was investigated for hydrogen sensing. Commercial Surface Acoustic Wave (SAW) resonators with resonance frequencies of 433.92 MHz and 433.42 MHz were employed in the double SAW resonator system configuration. The advantages of using this configuration include its ability for remote measurements, and insensitivity to vibrations and other external disturbances. The sensitive layer is composed of functionalized multiwalled carbon nanotubes and polyaniline nanofibers which were deposited on pre-patterned platinum metal electrodes fabricated on a piezoelectric substrate. This was mounted into the DSAWR circuit and connected in parallel. The sensor response was measured as the difference between the resonance frequencies of the SAW resonators, which is a measure of the gas concentration. The sensor showed good response towards hydrogen with a minimum detection limit of 1%. PMID:25730480

Electrocapillarity and zero-frequency differential capacitance at the interface between mercury and ionic liquids measured using the pendant drop method.

PubMed

Nishi, Naoya; Hashimoto, Atsunori; Minami, Eiji; Sakka, Tetsuo

2015-02-21

The structure of ionic liquids (ILs) at the electrochemical IL|Hg interface has been studied using the pendant drop method. From the electrocapillarity (potential dependence of interfacial tension) differential capacitance (Cd) at zero frequency (in other words, static differential capacitance or differential capacitance in equilibrium) has been evaluated. The potential dependence of zero-frequency Cd at the IL|Hg interface exhibits one or two local maxima near the potential of zero charge (Epzc), depending on the cation of the ILs. For 1-ethyl-3-methylimidazolium tetrafluoroborate, an IL with the cation having a short alkyl chain, the Cdvs. potential curve has one local maximum whereas another IL, 1-octyl-3-methylimidazolium tetrafluoroborate, with the cation having a long alkyl chain, shows two maxima. These behaviors of zero-frequency Cd agree with prediction by recent theoretical and simulation studies for the electrical double layer in ILs. At negative and positive potentials far from Epzc, the zero-frequency Cd increases for both the ILs studied. The increase in zero-frequency Cd is attributable to the densification of ionic layers in the electrical double layer.

Problems in mechanistic theoretical models for cell transformation by ionizing radiation

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

Chatterjee, A.; Holley, W.R.

1991-10-01

A mechanistic model based on yields of double strand breaks has been developed to determine the dose response curves for cell transformation frequencies. At its present stage the model is applicable to immortal cell lines and to various qualities (X-rays, Neon and Iron) of ionizing radiation. Presently, we have considered four types of processes which can lead to activation phenomena: (1) point mutation events on a regulatory segment of selected oncogenes, (2) inactivation of suppressor genes, through point mutation, (3) deletion of a suppressor gene by a single track, and (4) deletion of a suppressor gene by two tracks.

Patients double-seropositive for ANCA and anti-GBM antibodies have varied renal survival, frequency of relapse, and outcomes compared to single-seropositive patients.

PubMed

McAdoo, Stephen P; Tanna, Anisha; Hrušková, Zdenka; Holm, Lisa; Weiner, Maria; Arulkumaran, Nishkantha; Kang, Amy; Satrapová, Veronika; Levy, Jeremy; Ohlsson, Sophie; Tesar, Vladimir; Segelmark, Mårten; Pusey, Charles D

2017-09-01

Co-presentation with both ANCA and anti-GBM antibodies is thought to be relatively rare. Current studies of such 'double-positive' cases report small numbers and variable outcomes. To study this further we retrospectively analyzed clinical features and long-term outcomes of a large cohort of 568 contemporary patients with ANCA-associated vasculitis, 41 patients with anti-GBM disease, and 37 double-positive patients with ANCA and anti-GBM disease from four European centers. Double-positive patients shared characteristics of ANCA-associated vasculitis (AAV), such as older age distribution and longer symptom duration before diagnosis, and features of anti-GBM disease, such as severe renal disease and high frequency of lung hemorrhage at presentation. Despite having more evidence of chronic injury on renal biopsy compared to patients with anti-GBM disease, double-positive patients had a greater tendency to recover from being dialysis-dependent after treatment and had intermediate long-term renal survival compared to the single-positive patients. However, overall patient survival was similar in all three groups. Predictors of poor patient survival included advanced age, severe renal failure, and lung hemorrhage at presentation. No single-positive anti-GBM patients experienced disease relapse, whereas approximately half of surviving patients with AAV and double-positive patients had recurrent disease during a median follow-up of 4.8 years. Thus, double-positive patients have a truly hybrid disease phenotype, requiring aggressive early treatment for anti-GBM disease, and careful long-term follow-up and consideration for maintenance immunosuppression for AAV. Since double-positivity appears common, further work is required to define the underlying mechanisms of this association and define optimum treatment strategies. Copyright © 2017 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.

Frequent PIK3CA Mutations in Colorectal and Endometrial Cancer with Double Somatic Mismatch Repair Mutations

PubMed Central

Cohen, Stacey A.; Turner, Emily H.; Beightol, Mallory B.; Jacobson, Angela; Gooley, Ted A.; Salipante, Stephen J.; Haraldsdottir, Sigurdis; Smith, Christina; Scroggins, Sheena; Tait, Jonathan F.; Grady, William M.; Lin, Edward H.; Cohn, David E.; Goodfellow, Paul J.; Arnold, Mark W.; de la Chapelle, Albert; Pearlman, Rachel; Hampel, Heather; Pritchard, Colin C.

2016-01-01

Background & Aims Double somatic mutations in mismatch repair (MMR) genes have recently been described in colorectal and endometrial cancers with microsatellite instability (MSI) not attributable to MLH1 hypermethylation or germline mutation. We sought to define the molecular phenotype of this newly recognized tumor subtype. Methods From two prospective Lynch syndrome screening studies, we identified patients with colorectal and endometrial tumors harboring ≥2 somatic MMR mutations, but normal germline MMR testing (“double somatic”). We determined the frequencies of tumor PIK3CA, BRAF, KRAS, NRAS, and PTEN mutations by targeted next-generation sequencing and used logistic-regression models to compare them to: Lynch syndrome, MLH1 hypermethylated, and microsatellite stable (MSS) tumors. We validated our findings using independent datasets from The Cancer Genome Atlas (TCGA). Results Among colorectal cancer cases, we found that 14/21 (67%) of double somatic cases had PIK3CA mutations vs. 4/18 (22%) Lynch syndrome, 2/10 (20%) MLH1 hypermethylated, and 12/78 (15%) MSS tumors; p<0.0001. PIK3CA mutations were detected in 100% of 13 double somatic endometrial cancers (p=0.04). BRAF mutations were absent in double somatic and Lynch syndrome colorectal tumors. We found highly similar results in a validation cohort from TCGA (113 colorectal, 178 endometrial cancer), with 100% of double somatic cases harboring a PIK3CA mutation (p<0.0001). Conclusions PIK3CA mutations are present in double somatic mutated colorectal and endometrial cancers at substantially higher frequencies than other MSI subgroups. PIK3CA mutation status may better define an emerging molecular entity in colorectal and endometrial cancers, with the potential to inform screening and therapeutic decision making. PMID:27302833

Hypersonic Induced Interactions of Plasma and Non-Plasma Jets

DTIC Science & Technology

2006-06-12

kHz, and an output transformer cascade which transforms the voltage to up to 76 kVpp. The burst pulses of the pulse control board are controlled by a...flow condition have imposed the use of a double- pulse laser system with a pulse separation time in the microsecond range. The PIV image acquisition...system utilises a double-cavity Nd:YAG Litron Laser with a pulse energy of 2 x 200 mJ. The beams are frequency doubled to a wavelength of 532 nm and

Effective conductivity and permittivity of unsaturated porous materials in the frequency range 1 mHz–1GHz

PubMed Central

Revil, A

2013-01-01

A model combining low-frequency complex conductivity and high-frequency permittivity is developed in the frequency range from 1 mHz to 1 GHz. The low-frequency conductivity depends on pore water and surface conductivities. Surface conductivity is controlled by the electrical diffuse layer, the outer component of the electrical double layer coating the surface of the minerals. The frequency dependence of the effective quadrature conductivity shows three domains. Below a critical frequency fp, which depends on the dynamic pore throat size Λ, the quadrature conductivity is frequency dependent. Between fp and a second critical frequency fd, the quadrature conductivity is generally well described by a plateau when clay minerals are present in the material. Clay-free porous materials with a narrow grain size distribution are described by a Cole-Cole model. The characteristic frequency fd controls the transition between double layer polarization and the effect of the high-frequency permittivity of the material. The Maxwell-Wagner polarization is found to be relatively negligible. For a broad range of frequencies below 1 MHz, the effective permittivity exhibits a strong dependence with the cation exchange capacity and the specific surface area. At high frequency, above the critical frequency fd, the effective permittivity reaches a high-frequency asymptotic limit that is controlled by the two Archie's exponents m and n like the low-frequency electrical conductivity. The unified model is compared with various data sets from the literature and is able to explain fairly well a broad number of observations with a very small number of textural and electrochemical parameters. It could be therefore used to interpret induced polarization, induction-based electromagnetic methods, and ground penetrating radar data to characterize the vadose zone. PMID:23576823

The improvement of a simple theoretical model for the prediction of the sound insulation of double leaf walls.

PubMed

Davy, John L

2010-02-01

This paper presents a revised theory for predicting the sound insulation of double leaf cavity walls that removes an approximation, which is usually made when deriving the sound insulation of a double leaf cavity wall above the critical frequencies of the wall leaves due to the airborne transmission across the wall cavity. This revised theory is also used as a correction below the critical frequencies of the wall leaves instead of a correction due to Sewell [(1970). J. Sound Vib. 12, 21-32]. It is found necessary to include the "stud" borne transmission of the window frames when modeling wide air gap double glazed windows. A minimum value of stud transmission is introduced for use with resilient connections such as steel studs. Empirical equations are derived for predicting the effective sound absorption coefficient of wall cavities without sound absorbing material. The theory is compared with experimental results for double glazed windows and gypsum plasterboard cavity walls with and without sound absorbing material in their cavities. The overall mean, standard deviation, maximum, and minimum of the differences between experiment and theory are -0.6 dB, 3.1 dB, 10.9 dB at 1250 Hz, and -14.9 dB at 160 Hz, respectively.

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.

On the vibrational behavior of single- and double-walled carbon nanotubes under the physical adsorption of biomolecules in the aqueous environment: a molecular dynamics study.

PubMed

Ajori, S; Ansari, R; Darvizeh, M

2016-03-01

The adsorption of biomolecules on the walls of carbon nanotubes (CNTs) in an aqueous environment is of great importance in the field of nanobiotechnology. In this study, molecular dynamics (MD) simulations were performed to understand the mechanical vibrational behavior of single- and double-walled carbon nanotubes (SWCNTs and DWCNTs) under the physical adsorption of four important biomolecules (L-alanine, guanine, thymine, and uracil) in vacuum and an aqueous environment. It was observed that the natural frequencies of these CNTs in vacuum reduce under the physical adsorption of biomolecules. In the aqueous environment, the natural frequency of each pure CNT decreased as compared to its natural frequency in vacuum. It was also found that the frequency shift for functionalized CNTs as compared to pure CNTs in the aqueous environment was dependent on the radius and the number of walls of the CNT, and could be positive or negative.

A tunable, double-wavelength heterodyne detection interferometer with frequency-locked diode-pumped Nd:YAG sources for absolute measurements

NASA Astrophysics Data System (ADS)

Gelmini, E.; Minoni, U.; Docchio, F.

1995-08-01

A double heterodyne interferometric instrument using a tunable synthetic wavelength for the absolute measurements of distance and position is presented. The optical synthetic wavelength is generated by a pair of PZT-tunable diode-pumped Nd:YAG lasers operating at 1.064 μm. Based on a closed-loop scheme, a suitable electronic circuit has been developed to implement the frequency locking of the two lasers. A digital frequency comparator provides an error signal, used to control the slave laser, by comparing the laser beat frequency to a reference oscillator. Demodulation of the superheterodyne signals is obtained by a rf detector followed by low-pass filtering. Distance measurements are obtained by a digital phase meter gauging the phase difference between the demodulated signals from a measuring interferometer and from a reference interferometer. The paper presents the optical and the electronic layouts of the instrument as well as experimental results from a laboratory prototype.

Double frequency of difference frequency signals for optical Doppler effect measuring velocity

NASA Astrophysics Data System (ADS)

Yang, Xiufang; Zhou, Renkui; Wei, W. L.; Wang, Xiaoming

2005-12-01

The mathematical model for measuring moving objects (including fluid body, rolled steel materials in the steel works, turbulent flow, vibration body, etc.) velocity or speed by non-contact method is established using light-wave Doppler effect in this paper. In terms of concrete conditions of different optical circuits, and with the correlated conditions substituted, it is easy to obtain the measurement velocity formulas related to optical circuits. An optical circuit layout of difference Doppler effect measuring velocity is suggested in this paper. The fine beam of light emitted by laser is divided into parallel two beam by spectroscope and mirror They are focused on the object point p by a condenser lens respectively. The object point p become a diffuse source. It scatter rays to every aspect. Some rays scattered by the diffuse source p are collected by a lens. Photoelectric detecter receive the lights collected by the lens. This optical circuit layout can realize the double frequency of difference frequency signals in a novel way.

Phlebitis induced by parenteral treatment with flucloxacillin and cloxacillin: a double-blind study.

PubMed Central

Svedhem, A; Alestig, K; Jertborn, M

1980-01-01

Two studies were performed on a total of 54 patients with staphylococcal infections. Study I compares with phlebitogenic properties of flucloxacillin after intravenous infusions when either saline or sterile water was used as a solvent. No difference was observed between the two solvents, and the frequency of phlebitis for the total material without respect to solvents was 5% after 1 day of treatment and 13% after 2 days. Study II was a double-blind comparison of phlebitis caused by intravenous infusions of either flucloxacillin or cloxacillin. The frequencies of phlebitis were found to be 18 and 13%, respectively. After 2 days of treatment the frequency of phlebitis increased dramatically for both drugs. All infusions were given through a plastic cannula of 5-cm length and 1.2-mm diameter. PMID:7447412

Low-frequency gravitational wave detection via double optical clocks in space

NASA Astrophysics Data System (ADS)

Su, Jianfeng; Wang, Qiang; Wang, Qinghua; Jetzer, Philippe

2018-04-01

We propose a Doppler tracking system for gravitational wave detection via double optical clocks in space (DOCS). In this configuration two spacecrafts (each containing an optical clock) are launched to space for Doppler shift observations. Compared to the similar attempt of gravitational wave detection in the Cassini mission, the radio signal of DOCS that contains the relative frequency changes avoids completely noise effects due for instance to troposphere, ionosphere, ground-based antenna and transponder. Given the high stabilities of the two optical clocks (Allan deviation  ∼ 4.1× 10-17 @ 1000 s), an overall estimated sensitivity of 5 × 10-19 could be achieved with an observation time of 2 yr, and would allow to detect gravitational waves in the frequency range from  ∼10‑4 Hz to  ∼10‑2 Hz.

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

Fayolle, M.; Yamaguchi, M.; Ohto, T.

Organic magnetoresistance (OMAR) can be caused by either single carrier (bipolaron) or double carriers (electron-hole)-based mechanisms. In order to consider applications for OMAR, it is important to control the mechanism present in the device. In this paper, we report the effect of traps on OMAR resulting of disorder at the interface between the organic active layer with the hole injection layer [poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate): PEDOT:PSS]. It has been found that while the single carriers OMAR is enhanced by the presence of traps, the double carriers OMAR is totally removed in a sample with a high interface trap density. The reasons formore » these results are discussed based on the impedance spectroscopy measurements. First, the mechanism (single or double carriers) responsible of the OMAR was determined with the support of the capacitance measurement. Then, the influence of traps was discussed with the Nyquist diagrams and phase angle-frequency plots of the samples. The results suggested that with a rough interface and thus high disorder, the presence of traps enhanced the bipolaron formation. Traps also acted as recombination centers for electron-hole pairs, which prevented the double carriers OMAR in devices with a rough interface. On the other hand, with a low trap density, i.e., with a smooth surface, the single carrier OMAR decreased, and double carriers OMAR appeared. The sign of the OMAR could then be controlled by simply sweeping the bias voltage. This work demonstrated that the roughness at the interface is important for controlling OMAR and its reproducibility, and that the combination of OMAR measurement and impedance spectroscopy is helpful for clarifying the processes at the interface.« less

Nanosecond pulse shaping at 780 nm with fiber-based electro-optical modulators and a double-pass tapered amplifier

DOE PAGES

Rogers, III, C. E.; Gould, P. L.

2016-02-01

Here, we describe a system for generating frequency-chirped and amplitude-shaped pulses on time scales from sub-nanosecond to ten nanoseconds. The system starts with cw diode-laser light at 780 nm and utilizes fiber-based electro-optical phase and intensity modulators, driven by an arbitrary waveform generator, to generate the shaped pulses. These pulses are subsequently amplified to several hundred mW with a tapered amplifier in a delayed double-pass configuration. Frequency chirps up to 5 GHz in 2 ns and pulse widths as short as 0.15 ns have been realized.

Multi-wavelength generation based on cascaded Raman scattering and self-frequency-doubling in KTA

NASA Astrophysics Data System (ADS)

Zhong, K.; Li, J. S.; Xu, D. G.; Ding, X.; Zhou, R.; Wen, W. Q.; Li, Z. Y.; Xu, X. Y.; Wang, P.; Yao, J. Q.

2010-04-01

A multi-wavelength laser is developed based on cascaded stimulated Raman scattering (SRS) and self-frequency-doubling in an x-cut KTA crystal pumped by an A-O Q-switched Nd:YAG laser. The generation of 1178 nm from cascaded SRS of 234 and 671 cm-1 Raman modes is observed. The six wavelengths, including the fundamental 1064 nm, four Stokes waves at 1091, 1120, 1146, 1178 nm, and the second harmonic generation (SHG) of 1146 nm, are tens to hundreds of millwatts for each at 10 kHz, corresponding to a total conversion efficiency of 8.72%.

Harmonic mode-locking using the double interval technique in quantum dot lasers.

PubMed

Li, Yan; Chiragh, Furqan L; Xin, Yong-Chun; Lin, Chang-Yi; Kim, Junghoon; Christodoulou, Christos G; Lester, Luke F

2010-07-05

Passive harmonic mode-locking in a quantum dot laser is realized using the double interval technique, which uses two separate absorbers to stimulate a specific higher-order repetition rate compared to the fundamental. Operating alone these absorbers would otherwise reinforce lower harmonic frequencies, but by operating together they produce the harmonic corresponding to their least common multiple. Mode-locking at a nominal 60 GHz repetition rate, which is the 10(th) harmonic of the fundamental frequency of the device, is achieved unambiguously despite the constraint of a uniformly-segmented, multi-section device layout. The diversity of repetition rates available with this method is also discussed.

Nanosecond pulse shaping at 780 nm with fiber-based electro-optical modulators and a double-pass tapered amplifier.

PubMed

Rogers, C E; Gould, P L

2016-02-08

We describe a system for generating frequency-chirped and amplitude-shaped pulses on time scales from sub-nanosecond to ten nanoseconds. The system starts with cw diode-laser light at 780 nm and utilizes fiber-based electro-optical phase and intensity modulators, driven by an arbitrary waveform generator, to generate the shaped pulses. These pulses are subsequently amplified to several hundred mW with a tapered amplifier in a delayed double-pass configuration. Frequency chirps up to 5 GHz in 2 ns and pulse widths as short as 0.15 ns have been realized.

Highly efficient single-pass frequency doubling of a continuous-wave distributed feedback laser diode using a PPLN waveguide crystal at 488 nm.

PubMed

Jechow, Andreas; Schedel, Marco; Stry, Sandra; Sacher, Joachim; Menzel, Ralf

2007-10-15

A continuous-wave distributed feedback diode laser emitting at 976 nm was frequency doubled by the use of a periodically poled lithium niobate waveguide crystal with a channel size of 3 microm x 5 microm and an interaction length of 10 mm. A laser to waveguide coupling efficiency of 75% could be achieved resulting in 304 mW of incident infrared light inside the waveguide. Blue laser light emission of 159 mW at 488 nm has been generated, which equals to a conversion efficiency of 52%. The resulting wall plug efficiency was 7.4%.

Diode-pumped continuous-wave and femtosecond Cr:LiCAF lasers with high average power in the near infrared, visible and near ultraviolet.

PubMed

Demirbas, Umit; Baali, Ilyes; Acar, Durmus Alp Emre; Leitenstorfer, Alfred

2015-04-06

We demonstrate continuous-wave (cw), cw frequency-doubled, cw mode-locked and Q-switched mode-locked operation of multimode diode-pumped Cr:LiCAF lasers with record average powers. Up to 2.54 W of cw output is obtained around 805 nm at an absorbed pump power of 5.5 W. Using intracavity frequency doubling with a BBO crystal, 0.9 W are generated around 402 nm, corresponding to an optical-to-optical conversion efficiency of 12%. With an intracavity birefringent tuning plate, the fundamental and frequency-doubled laser output is tuned continuously in a broad wavelength range from 745 nm to 885 nm and from 375 to 440 nm, respectively. A saturable Bragg reflector is used to initiate and sustain mode locking. In the cw mode-locked regime, the Cr:LiCAF laser produces 105-fs long pulses near 810 nm with an average power of 0.75 W. The repetition rate is 96.4 MHz, resulting in pulse energies of 7.7 nJ and peak powers of 65 kW. In Q-switched mode-locked operation, pulses with energies above 150 nJ are generated.

Clearance of yellow tattoo ink with a novel 532-nm picosecond laser.

PubMed

Alabdulrazzaq, Hamad; Brauer, Jeremy A; Bae, Yoon-Soo; Geronemus, Roy G

2015-04-01

Although technology and tattoo removal methods continue to evolve, yellow pigment clearance continues to be challenging and usually unsuccessful. We describe a case series of six tattoos containing yellow ink, successfully treated with a frequency-doubled Nd:YAG 532-nm picosecond laser. Case series with six subjects participating for the treatment of multicolored tattoos that contain yellow pigment. Treatments performed with a frequency-doubled Nd:YAG 532-nm picosecond laser at 6-8 week intervals. One subject achieved complete clearance of the treated site after one session, and five subjects required 2-4 treatments to achieve over 75% clearance. Minimal downtime was experienced, and no scarring or textural skin changes were observed in any of the treated sites. This is the first case series that demonstrates effective and consistent reduction of yellow tattoo ink using a frequency doubled Nd:YAG 532-nm laser with a picosecond pulse duration. Treatments were well tolerated and subjects had positive outcomes. This is a small observational case series from an ongoing clinical trial, and studies with a larger sample size and comparative group are needed in the future. © 2015 Wiley Periodicals, Inc.

A high-finesse Fabry-Perot cavity with a frequency-doubled green laser for precision Compton polarimetry at Jefferson Lab

DOE PAGES

Rakhman, A.; Hafez, Mohamed A.; Nanda, Sirish K.; ...

2016-03-31

Here, a high-finesse Fabry-Perot cavity with a frequency-doubled continuous wave green laser (532 nm) has been built and installed in Hall A of Jefferson Lab for high precision Compton polarimetry. The infrared (1064 nm) beam from a ytterbium-doped fiber amplifier seeded by a Nd:YAG nonplanar ring oscillator laser is frequency doubled in a single-pass periodically poled MgO:LiNbO 3 crystal. The maximum achieved green power at 5 W infrared pump power is 1.74 W with a total conversion efficiency of 34.8%. The green beam is injected into the optical resonant cavity and enhanced up to 3.7 kW with a corresponding enhancementmore » of 3800. The polarization transfer function has been measured in order to determine the intra-cavity circular laser polarization within a measurement uncertainty of 0.7%. The PREx experiment at Jefferson Lab used this system for the first time and achieved 1.0% precision in polarization measurements of an electron beam with energy and current of 1.0 GeV and 50 μA.« less

Negative group velocity Lamb waves on plates and applications to the scattering of sound by shells

NASA Astrophysics Data System (ADS)

Marston, Philip L.

2003-05-01

Symmetric Lamb waves on plates exhibit anomalies for certain regions of frequency. The phase velocity appears to be double-valued [M. F. Werby and H. Überall, J. Acoust. Soc. Am. 111, 2686-2691 (2002)] with one of the branches having a negative group velocity relative to the corresponding phase velocity. The classification of the symmetric plate modes for frequencies appearing to have a double-valued phase velocity is reviewed here. The complication of a double-valued velocity is avoided by examining mode orthogonality and the complex wave-number spectra. Various authors have noted an enhancement in the backscattering of sound by elastic shells in water that occurs for frequencies where symmetric leaky Lamb waves (generalized to case of a shell) have contra-directed group and phase velocities. The ray diagram for negative group velocity contributions to the scattering by shells [G. Kaduchak, D. H. Hughes, and P. L. Marston, J. Acoust. Soc. Am. 96, 3704-3714 (1994)] is unusual since for this type of mode the energy on the shell flows in the opposite direction of the wave vector. Circumnavigation of the shell is not required for the leaky ray to be backward directed.

Unraveling Cell Processes: Interference Imaging Interwoven with Data Analysis

PubMed Central

Brazhe, A. R.; Pavlov, A. N.; Erokhova, L. A.; Yusipovich, A. I.; Maksimov, G. V.; Mosekilde, E.; Sosnovtseva, O. V.

2006-01-01

The paper presents results on the application of interference microscopy and wavelet-analysis for cell visualization and studies of cell dynamics. We demonstrate that interference imaging of erythrocytes can reveal reorganization of the cytoskeleton and inhomogenity in the distribution of hemoglobin, and that interference imaging of neurons can show intracellular compartmentalization and submembrane structures. We investigate temporal and spatial variations of the refractive index for different cell types: isolated neurons, mast cells and erythrocytes. We show that the refractive dynamical properties differ from cell type to cell type and depend on the cellular compartment. Our results suggest that low frequency variations (0.1–0.6 Hz) result from plasma membrane processes and that higher frequency variations (20–26 Hz) are related to the movement of vesicles. Using double-wavelet analysis, we study the modulation of the 1 Hz rhythm in neurons and reveal its changes under depolarization and hyperpolarization of the plasma membrane. We conclude that interference microscopy combined with wavelet analysis is a useful technique for non-invasive cell studies, cell visualization, and investigation of plasma membrane properties. PMID:19669463

Enhancement of signal-to-noise ratio in Brillouin optical time domain analyzers by dual-probe detection

NASA Astrophysics Data System (ADS)

Iribas, Haritz; Loayssa, Alayn; Sauser, Florian; Llera, Miguel; Le Floch, Sébastien

2017-04-01

We demonstrate a simple technique to enhance the signal-to-noise ratio (SNR) in Brillouin optical time-domain analysis sensors by the addition of gain and loss processes. The technique is based on the shift of the pump pulse optical frequency in a double-sideband probe system, so that the gain and loss processes take place at different frequencies. In this manner, the loss and the gain do not cancel each other out, and it makes possible to take advantage of both informations at the same time, obtaining an improvement of 3 dB on the SNR. Furthermore, the technique does not need an optical filtering, so that larger improvement on SNR and a simplification of the setup are obtained. The method is experimentally demonstrated in a 101 km fiber spool, obtaining a measurement uncertainty of 2.6 MHz (2σ) at the worst-contrast position for 2 m spatial resolution. This leads, to the best of our knowledge, to the highest figure-of-merit in a BOTDA without using coding or raman amplification.

Solar actinic flux spectroradiometry: a technique for measuring photolysis frequencies in the atmosphere.

PubMed

Hofzumahaus, A; Kraus, A; Müller, M

1999-07-20

A spectroradiometer has been developed for direct measurement of the solar actinic UV flux (scalar intensity) and determination of photolysis frequencies in the atmosphere. The instrument is based on a scanning double monochromator with an entrance optic that exhibits an isotropic angular response over a solid angle of 2pi sr. Actinic flux spectra are measured at a resolution of 1 nm across a range of 280-420 nm, which is relevant for most tropospheric photolysis processes. The photolysis frequencies are derived from the measured radiation spectra by use of published absorption cross sections and quantum yields. The advantage of this technique compared with the traditional chemical actinometry is its versatility. It is possible to determine the photolysis frequency for any photochemical reaction of interest provided that the respective molecular photodissociation parameters are known and the absorption cross section falls within a wavelength range that is accessible by the spectroradiometer. The instrument and the calibration procedures are described in detail, and problems specific to measurement of the actinic radiation are discussed. An error analysis is presented together with a discussion of the spectral requirements of the instrument for accurate measurements of important tropospheric photolysis frequencies (J(O(1))(D), J(NO(2)), J(HCHO)). An example of measurements from previous atmospheric chemistry field campaigns are presented and discussed.

Statistics and classification of the microwave zebra patterns associated with solar flares

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

Tan, Baolin; Tan, Chengming; Zhang, Yin

2014-01-10

The microwave zebra pattern (ZP) is the most interesting, intriguing, and complex spectral structure frequently observed in solar flares. A comprehensive statistical study will certainly help us to understand the formation mechanism, which is not exactly clear now. This work presents a comprehensive statistical analysis of a big sample with 202 ZP events collected from observations at the Chinese Solar Broadband Radio Spectrometer at Huairou and the Ondŕejov Radiospectrograph in the Czech Republic at frequencies of 1.00-7.60 GHz from 2000 to 2013. After investigating the parameter properties of ZPs, such as the occurrence in flare phase, frequency range, polarization degree,more » duration, etc., we find that the variation of zebra stripe frequency separation with respect to frequency is the best indicator for a physical classification of ZPs. Microwave ZPs can be classified into three types: equidistant ZPs, variable-distant ZPs, and growing-distant ZPs, possibly corresponding to mechanisms of the Bernstein wave model, whistler wave model, and double plasma resonance model, respectively. This statistical classification may help us to clarify the controversies between the existing various theoretical models and understand the physical processes in the source regions.« less

Holographic Cinematography And Its Applications

NASA Astrophysics Data System (ADS)

Smigielski, P.; Fagot, H.; Albe, F.

1988-01-01

Important progresses were achieved for the first time: 1) recording of single-exposure cineholograms of living bodies on 126-mm films, at a repetition rate of 25 holograms per second with the help of a frequency-doubled pulse YAG-laser; 2) recording of double-exposure cineholograms of reflecting moving objects for medical and industrial applications. Limitations of 3-D movies are described.

First measurements of electron temperature in the D region with a symmetric double probe

NASA Technical Reports Server (NTRS)

Szuszczewicz, E. P.

1973-01-01

Measurement of the altitude profile of electron temperature in the ionospheric D region with the aid of a symmetric double probe flown on a Nike-Cajun payload launched on Oct. 13, 1971. The procedure for determining the electron temperature from the parameters of the double probe's current-voltage characteristic under conditions of nonnegligible ion-atom collision frequencies is described. It is shown that in its first lower ionospheric application the technique of the symmetric double probe has yielded the lowest values of electron temperature yet measured and has provided the very first direct measurement of electron temperature in the D region.

47 CFR 73.322 - FM stereophonic sound transmission standards.

Code of Federal Regulations, 2010 CFR

2010-10-01

... frequency in a transmission system meeting the following parameters: (1) The modulating signal for the main... frequency modulate the main carrier between the limits of 8 and 10 percent. (3) One stereophonic subcarrier... stereophomic subcarriers are not precluded. (4) Double sideband, suppressed-carrier, amplitude modulation of...

New perspectives on self-similarity for shallow thrust earthquakes

NASA Astrophysics Data System (ADS)

Denolle, Marine A.; Shearer, Peter M.

2016-09-01

Scaling of dynamic rupture processes from small to large earthquakes is critical to seismic hazard assessment. Large subduction earthquakes are typically remote, and we mostly rely on teleseismic body waves to extract information on their slip rate functions. We estimate the P wave source spectra of 942 thrust earthquakes of magnitude Mw 5.5 and above by carefully removing wave propagation effects (geometrical spreading, attenuation, and free surface effects). The conventional spectral model of a single-corner frequency and high-frequency falloff rate does not explain our data, and we instead introduce a double-corner-frequency model, modified from the Haskell propagating source model, with an intermediate falloff of f-1. The first corner frequency f1 relates closely to the source duration T1, its scaling follows M0∝T13 for Mw<7.5, and changes to M0∝T12 for larger earthquakes. An elliptical rupture geometry better explains the observed scaling than circular crack models. The second time scale T2 varies more weakly with moment, M0∝T25, varies weakly with depth, and can be interpreted either as expressions of starting and stopping phases, as a pulse-like rupture, or a dynamic weakening process. Estimated stress drops and scaled energy (ratio of radiated energy over seismic moment) are both invariant with seismic moment. However, the observed earthquakes are not self-similar because their source geometry and spectral shapes vary with earthquake size. We find and map global variations of these source parameters.

Comparison of symmetric and asymmetric double quantum well extended-cavity diode lasers for broadband passive mode-locking at 780  nm.

PubMed

Christopher, Heike; Kovalchuk, Evgeny V; Wenzel, Hans; Bugge, Frank; Weyers, Markus; Wicht, Andreas; Peters, Achim; Tränkle, Günther

2017-07-01

We present a compact, mode-locked diode laser system designed to emit a frequency comb in the wavelength range around 780 nm. We compare the mode-locking performance of symmetric and asymmetric double quantum well ridge-waveguide diode laser chips in an extended-cavity diode laser configuration. By reverse biasing a short section of the diode laser chip, passive mode-locking at 3.4 GHz is achieved. Employing an asymmetric double quantum well allows for generation of a mode-locked optical spectrum spanning more than 15 nm (full width at -20  dB) while the symmetric double quantum well device only provides a bandwidth of ∼2.7  nm (full width at -20  dB). Analysis of the RF noise characteristics of the pulse repetition rate shows an RF linewidth of about 7 kHz (full width at half-maximum) and of at most 530 Hz (full width at half-maximum) for the asymmetric and symmetric double quantum well devices, respectively. Investigation of the frequency noise power spectral density at the pulse repetition rate shows a white noise floor of approximately 2100  Hz 2 /Hz and of at most 170  Hz 2 /Hz for the diode laser employing the asymmetric and symmetric double quantum well structures, respectively. The pulse width is less than 10 ps for both devices.

Modulation of human time processing by subthalamic deep brain stimulation.

PubMed

Wojtecki, Lars; Elben, Saskia; Timmermann, Lars; Reck, Christiane; Maarouf, Mohammad; Jörgens, Silke; Ploner, Markus; Südmeyer, Martin; Groiss, Stefan Jun; Sturm, Volker; Niedeggen, Michael; Schnitzler, Alfons

2011-01-01

Timing in the range of seconds referred to as interval timing is crucial for cognitive operations and conscious time processing. According to recent models of interval timing basal ganglia (BG) oscillatory loops are involved in time interval recognition. Parkinsońs disease (PD) is a typical disease of the basal ganglia that shows distortions in interval timing. Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is a powerful treatment of PD which modulates motor and cognitive functions depending on stimulation frequency by affecting subcortical-cortical oscillatory loops. Thus, for the understanding of BG-involvement in interval timing it is of interest whether STN-DBS can modulate timing in a frequency dependent manner by interference with oscillatory time recognition processes. We examined production and reproduction of 5 and 15 second intervals and millisecond timing in a double blind, randomised, within-subject repeated-measures design of 12 PD-patients applying no, 10-Hz- and ≥ 130-Hz-STN-DBS compared to healthy controls. We found under(re-)production of the 15-second interval and a significant enhancement of this under(re-)production by 10-Hz-stimulation compared to no stimulation, ≥ 130-Hz-STN-DBS and controls. Milliseconds timing was not affected. We provide first evidence for a frequency-specific modulatory effect of STN-DBS on interval timing. Our results corroborate the involvement of BG in general and of the STN in particular in the cognitive representation of time intervals in the range of multiple seconds.

Modulation of Human Time Processing by Subthalamic Deep Brain Stimulation

PubMed Central

Timmermann, Lars; Reck, Christiane; Maarouf, Mohammad; Jörgens, Silke; Ploner, Markus; Südmeyer, Martin; Groiss, Stefan Jun; Sturm, Volker; Niedeggen, Michael; Schnitzler, Alfons

2011-01-01

Timing in the range of seconds referred to as interval timing is crucial for cognitive operations and conscious time processing. According to recent models of interval timing basal ganglia (BG) oscillatory loops are involved in time interval recognition. Parkinsońs disease (PD) is a typical disease of the basal ganglia that shows distortions in interval timing. Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is a powerful treatment of PD which modulates motor and cognitive functions depending on stimulation frequency by affecting subcortical-cortical oscillatory loops. Thus, for the understanding of BG-involvement in interval timing it is of interest whether STN-DBS can modulate timing in a frequency dependent manner by interference with oscillatory time recognition processes. We examined production and reproduction of 5 and 15 second intervals and millisecond timing in a double blind, randomised, within-subject repeated-measures design of 12 PD-patients applying no, 10-Hz- and ≥130-Hz-STN-DBS compared to healthy controls. We found under(re-)production of the 15-second interval and a significant enhancement of this under(re-)production by 10-Hz-stimulation compared to no stimulation, ≥130-Hz-STN-DBS and controls. Milliseconds timing was not affected. We provide first evidence for a frequency-specific modulatory effect of STN-DBS on interval timing. Our results corroborate the involvement of BG in general and of the STN in particular in the cognitive representation of time intervals in the range of multiple seconds. PMID:21931767

Widely tunable and monochromatic terahertz difference frequency generation with organic crystal 2-(3-(4-hydroxystyryl)-5,5-dime-thylcyclohex-2-enylidene) malononitrile

NASA Astrophysics Data System (ADS)

Liu, Pengxiang; Zhang, Xinyuan; Yan, Chao; Xu, Degang; Li, Yin; Shi, Wei; Zhang, Guochun; Zhang, Xinzheng; Yao, Jianquan; Wu, Yicheng

2016-01-01

We report an experimental study on widely tunable terahertz (THz) wave difference frequency generation (DFG) with hydrogen-bonded crystals 2-(3-(4-hydroxystyryl)-5,5-dime-thylcyclohex-2-enylidene) malononitrile (OH1). The organic crystals were pumped by a ˜1.3 μm double-pass KTiOPO4 optical parametric oscillator. A tuning range of 0.02-20 THz was achieved. OH1 crystals offer a long effective interaction length (also high output) for the generation below 3 THz, owing to the low absorption and favorable phase-matching. The highest energy of 507 nJ/pulse was generated at 1.92 THz with a 1.89-mm-thick crystal. Comprehensive explanations were provided, on the basis of theoretical calculations. Cascading phenomenon during the DFG process was demonstrated. The photon conversion efficiency could reach 2.9%.

Widely tunable and monochromatic terahertz difference frequency generation with organic crystal 2-(3-(4-hydroxystyryl)-5,5-dime-thylcyclohex-2-enylidene) malononitrile

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

Liu, Pengxiang; The Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, School of Physics and TEDA Applied Physics Institute, Nankai University, Tianjin 300071; Zhang, Xinyuan

2016-01-04

We report an experimental study on widely tunable terahertz (THz) wave difference frequency generation (DFG) with hydrogen-bonded crystals 2-(3-(4-hydroxystyryl)-5,5-dime-thylcyclohex-2-enylidene) malononitrile (OH1). The organic crystals were pumped by a ∼1.3 μm double-pass KTiOPO{sub 4} optical parametric oscillator. A tuning range of 0.02–20 THz was achieved. OH1 crystals offer a long effective interaction length (also high output) for the generation below 3 THz, owing to the low absorption and favorable phase-matching. The highest energy of 507 nJ/pulse was generated at 1.92 THz with a 1.89-mm-thick crystal. Comprehensive explanations were provided, on the basis of theoretical calculations. Cascading phenomenon during the DFG process wasmore » demonstrated. The photon conversion efficiency could reach 2.9%.« less

Influence of CdS nanoparticles grain morphology on laser-induced absorption

NASA Astrophysics Data System (ADS)

Ebothé, Jean; Michel, Jean; Kityk, I. V.; Lakshminarayana, G.; Yanchuk, O. M.; Marchuk, O. V.

2018-06-01

Using external illumination of a 7 nanosecond (ns) doubled frequency Nd: YAG laser emitting at λ = 532 nm with frequency repetition 10 Hz it was established a possibility of significant changes of the absorption at the probing wavelength 1150 nm of continuous wave (cw) He-Ne laser for the CdS nanoparticles embedded into the PVA polymer matrix. The effect is observed only during the two beam laser coherent treatment and this effect is a consequence of interference of two coherent beams. It is shown a principal role of the grain morphology in the efficiency of the process, which is more important than the nanoparticle sizes. The photoinduced absorption is manifested in the space distribution of the probing laser beam. The principal role of the grain interfaces between the nanoparticle interfaces and the surrounding polymer matrix is shown. The effect is almost independent of the nanoparticle sizes. It may be used for laser operation by nanocomposites.

A 220-GHz SIS Mixer Tightly Integrated With a Sub-Hundred-Microwatt SiGe IF Amplifier

NASA Astrophysics Data System (ADS)

Montazeri, Shirin; Grimes, Paul K.; Tong, Cheuk-Yu Edward; Bardin, Joseph C.

2016-01-01

Future kilopixel-scale heterodyne focal plane arrays based on superconductor-insulator-superconductor (SIS) mixers will require submilliwatt power consumption low-noise amplifiers (LNAs) which are tightly integrated with the mixers. In this paper, an LNA that is optimized for direct connection to a 220-GHz SIS mixer chip and requires less than 100 μW of dc power is reported. The amplifier design process is described, and measurement results are presented. It is shown that, when pumped at local oscillator frequencies between 214 and 226 GHz, the mixer/amplifier module achieves a double-sideband system noise temperature between 35 and 50 K over the 3.3-6 GHz IF frequency range while requiring just 90 μW of dc power. Moreover, the potential to further reduce the power consumption is explored and successful operation is demonstrated for LNA power consumption as low as 60 μW.

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

Sobottka, Marcelo, E-mail: sobottka@mtm.ufsc.br; Hart, Andrew G., E-mail: ahart@dim.uchile.cl

Highlights: {yields} We propose a simple stochastic model to construct primitive DNA sequences. {yields} The model provide an explanation for Chargaff's second parity rule in primitive DNA sequences. {yields} The model is also used to predict a novel type of strand symmetry in primitive DNA sequences. {yields} We extend the results for bacterial DNA sequences and compare distributional properties intrinsic to the model to statistical estimates from 1049 bacterial genomes. {yields} We find out statistical evidences that the novel type of strand symmetry holds for bacterial DNA sequences. -- Abstract: Chargaff's second parity rule for short oligonucleotides states that themore » frequency of any short nucleotide sequence on a strand is approximately equal to the frequency of its reverse complement on the same strand. Recent studies have shown that, with the exception of organellar DNA, this parity rule generally holds for double-stranded DNA genomes and fails to hold for single-stranded genomes. While Chargaff's first parity rule is fully explained by the Watson-Crick pairing in the DNA double helix, a definitive explanation for the second parity rule has not yet been determined. In this work, we propose a model based on a hidden Markov process for approximating the distributional structure of primitive DNA sequences. Then, we use the model to provide another possible theoretical explanation for Chargaff's second parity rule, and to predict novel distributional aspects of bacterial DNA sequences.« less

Radiation-induced chromosomal instability in BALB/c and C57BL/6 mice: the difference is as clear as black and white

NASA Technical Reports Server (NTRS)

Ponnaiya, B.; Cornforth, M. N.; Ullrich, R. L.

1997-01-01

Genomic instability has been proposed to be the earliest step in radiation-induced tumorigenesis. It follows from this hypothesis that individuals highly susceptible to induction of tumors by radiation should exhibit enhanced radiation-induced instability. BALB/c white mice are considerably more sensitive to radiation-induced mammary cancer than C57BL/6 black mice. In this study, primary mammary epithelial cell cultures from these two strains were examined for the "delayed" appearance of chromosomal aberrations after exposure to 137Cs gamma radiation, as a measure of radiation-induced genomic instability. As expected, actively dividing cultures from both strains showed a rapid decline of initial asymmetrical aberrations with time postirradiation. However, after 16 population doublings, cells from BALB/c mice exhibited a marked increase in the frequency of chromatid-type breaks and gaps which remained elevated throughout the time course of the experiment (28 doublings). No such effect was observed for the cells of C57BL/6 mice; after the rapid clearance of initial aberrations, the frequency of chromatid-type aberrations in the irradiated population remained at or near those of nonirradiated controls. These results demonstrate a correlation between the latent expression of chromosomal damage in vitro and susceptibility for mammary tumors, and provide further support for the central role of radiation-induced instability in the process of tumorigenesis.

Clinical relevance of IgG antibodies against food antigens in Crohn's disease: a double-blind cross-over diet intervention study.

PubMed

Bentz, S; Hausmann, M; Piberger, H; Kellermeier, S; Paul, S; Held, L; Falk, W; Obermeier, F; Fried, M; Schölmerich, J; Rogler, G

2010-01-01

Environmental factors are thought to play an important role in the development of Crohn's disease (CD). Immune responses against auto-antigens or food antigens may be a reason for the perpetuation of inflammation. In a pilot study, 79 CD patients and 20 healthy controls were examined for food immunoglobulin G (IgG). Thereafter, the clinical relevance of these food IgG antibodies was assessed in a double-blind cross-over study with 40 patients. Based on the IgG antibodies, a nutritional intervention was planned. The interferon (IFN)gamma secretion of T cells was measured. Eosinophil-derived neurotoxin was quantified in stool. The pilot study resulted in a significant difference of IgG antibodies in serum between CD patients and healthy controls. In 84 and 83% of the patients, respectively, IgG antibodies against processed cheese and yeast were detected. The daily stool frequency significantly decreased by 11% during a specific diet compared with a sham diet. Abdominal pain reduced and general well-being improved. IFNgamma secretion of T cells increased. No difference for eosinophil-derived neurotoxin in stool was detected. A nutritional intervention based on circulating IgG antibodies against food antigens showed effects with respect to stool frequency. The mechanisms by which IgG antibodies might contribute to disease activity remain to be elucidated.

Acute effects of delta-9-tetrahydrocannabinol, cannabidiol and their combination on facial emotion recognition: a randomised, double-blind, placebo-controlled study in cannabis users.

PubMed

Hindocha, Chandni; Freeman, Tom P; Schafer, Grainne; Gardener, Chelsea; Das, Ravi K; Morgan, Celia J A; Curran, H Valerie

2015-03-01

Acute administration of the primary psychoactive constituent of cannabis, Δ-9-tetrahydrocannabinol (THC), impairs human facial affect recognition, implicating the endocannabinoid system in emotional processing. Another main constituent of cannabis, cannabidiol (CBD), has seemingly opposite functional effects on the brain. This study aimed to determine the effects of THC and CBD, both alone and in combination on emotional facial affect recognition. 48 volunteers, selected for high and low frequency of cannabis use and schizotypy, were administered, THC (8mg), CBD (16mg), THC+CBD (8mg+16mg) and placebo, by inhalation, in a 4-way, double-blind, placebo-controlled crossover design. They completed an emotional facial affect recognition task including fearful, angry, happy, sad, surprise and disgust faces varying in intensity from 20% to 100%. A visual analogue scale (VAS) of feeling 'stoned' was also completed. In comparison to placebo, CBD improved emotional facial affect recognition at 60% emotional intensity; THC was detrimental to the recognition of ambiguous faces of 40% intensity. The combination of THC+CBD produced no impairment. Relative to placebo, both THC alone and combined THC+CBD equally increased feelings of being 'stoned'. CBD did not influence feelings of 'stoned'. No effects of frequency of use or schizotypy were found. In conclusion, CBD improves recognition of emotional facial affect and attenuates the impairment induced by THC. This is the first human study examining the effects of different cannabinoids on emotional processing. It provides preliminary evidence that different pharmacological agents acting upon the endocannabinoid system can both improve and impair recognition of emotional faces. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

Acute effects of delta-9-tetrahydrocannabinol, cannabidiol and their combination on facial emotion recognition: A randomised, double-blind, placebo-controlled study in cannabis users

PubMed Central

Hindocha, Chandni; Freeman, Tom P.; Schafer, Grainne; Gardener, Chelsea; Das, Ravi K.; Morgan, Celia J.A.; Curran, H. Valerie

2015-01-01

Acute administration of the primary psychoactive constituent of cannabis, Δ-9-tetrahydrocannabinol (THC), impairs human facial affect recognition, implicating the endocannabinoid system in emotional processing. Another main constituent of cannabis, cannabidiol (CBD), has seemingly opposite functional effects on the brain. This study aimed to determine the effects of THC and CBD, both alone and in combination on emotional facial affect recognition. 48 volunteers, selected for high and low frequency of cannabis use and schizotypy, were administered, THC (8 mg), CBD (16 mg), THC+CBD (8 mg+16 mg) and placebo, by inhalation, in a 4-way, double-blind, placebo-controlled crossover design. They completed an emotional facial affect recognition task including fearful, angry, happy, sad, surprise and disgust faces varying in intensity from 20% to 100%. A visual analogue scale (VAS) of feeling ‘stoned’ was also completed. In comparison to placebo, CBD improved emotional facial affect recognition at 60% emotional intensity; THC was detrimental to the recognition of ambiguous faces of 40% intensity. The combination of THC+CBD produced no impairment. Relative to placebo, both THC alone and combined THC+CBD equally increased feelings of being ‘stoned’. CBD did not influence feelings of ‘stoned’. No effects of frequency of use or schizotypy were found. In conclusion, CBD improves recognition of emotional facial affect and attenuates the impairment induced by THC. This is the first human study examining the effects of different cannabinoids on emotional processing. It provides preliminary evidence that different pharmacological agents acting upon the endocannabinoid system can both improve and impair recognition of emotional faces. PMID:25534187

Design and Implementation of an RTK-Based Vector Phase Locked Loop

PubMed Central

Shafaati, Ahmad; Lin, Tao; Broumandan, Ali; Lachapelle, Gérard

2018-01-01

This paper introduces a novel double-differential vector phase-locked loop (DD-VPLL) for Global Navigation Satellite Systems (GNSS) that leverages carrier phase position solutions as well as base station measurements in the estimation of rover tracking loop parameters. The use of double differencing alleviates the need for estimating receiver clock dynamics and atmospheric delays; therefore, the navigation filter consists of the baseline dynamic states only. It is shown that using vector processing for carrier phase tracking leads to a significant enhancement in the receiver sensitivity compared to using the conventional scalar-based tracking loop (STL) and vector frequency locked loop (VFLL). The sensitivity improvement of 8 to 10 dB compared to STL, and 7 to 8 dB compared to VFLL, is obtained based on the test cases reported in the paper. Also, an increased probability of ambiguity resolution in the proposed method results in better availability for real time kinematic (RTK) applications. PMID:29533994

A comparative study between different approaches to improve the RCS of a compact double-layer absorber

NASA Astrophysics Data System (ADS)

El-Hakim, H. A.; Mahmoud, K. R.

2017-10-01

In this paper, straightforward and efficient techniques have been addressed into double-layer structure to enlarge the operating bandwidth to include the X, Ku and K bands, in addition to increase the electromagnetic wave absorption for wide varieties of incident angles and both polarization types. To increase the band-stop resonating frequency up to 26 GHz, an additional layer of meta-surface, circuit analog radar absorber material (CAR), or a thin radar absorber material (RAM) layer is engineered. The synthesized layers are designed based on optimization process with genetic algorithm (GA) through numerical technique (Ansoft design software HFSS) for both transmission line (T.L) and the free space method to get optimal material properties suitable for the design. For different approaches, the designed structures achieved a reflectivity value less than -16 dB on average in the desired bandwidth from 8 to 26 GHz for TE/TM modes with incidence angle up to 50o.

Single-longitudinal-mode, narrow bandwidth double-ring fiber laser stabilized by an efficiently taper-coupled high roundness microsphere resonator

NASA Astrophysics Data System (ADS)

Wan, Hongdan; Liu, Linqian; Ding, Zuoqin; Wang, Jie; Xiao, Yu; Zhang, Zuxing

2018-06-01

This paper proposes and demonstrates a single-longitudinal-mode, narrow bandwidth fiber laser, using an ultra-high roundness microsphere resonator (MSR) with a stabilized package as the single-longitudinal-mode selector inside a double-ring fiber cavity. By improving the heating technology and surface cleaning process, MSR with high Q factor are obtained. With the optimized coupling condition, light polarization state and fiber taper diameter, we achieve whispering gallery mode (WGM) spectra with a high extinction ratio of 23 dB, coupling efficiency of 99.5%, a 3 dB bandwidth of 1 pm and a side-mode-suppression-ratio of 14.5 dB. The proposed fiber laser produces single-longitudinal-mode laser output with a 20-dB frequency linewidth of about 340 kHz, a signal-to-background ratio of 54 dB and a high long-term stability without mode-hopping, which is potential for optical communication and sensing applications.

Chromosome territories reposition during DNA damage-repair response

PubMed Central

2013-01-01

Background Local higher-order chromatin structure, dynamics and composition of the DNA are known to determine double-strand break frequencies and the efficiency of repair. However, how DNA damage response affects the spatial organization of chromosome territories is still unexplored. Results Our report investigates the effect of DNA damage on the spatial organization of chromosome territories within interphase nuclei of human cells. We show that DNA damage induces a large-scale spatial repositioning of chromosome territories that are relatively gene dense. This response is dose dependent, and involves territories moving from the nuclear interior to the periphery and vice versa. Furthermore, we have found that chromosome territory repositioning is contingent upon double-strand break recognition and damage sensing. Importantly, our results suggest that this is a reversible process where, following repair, chromosome territories re-occupy positions similar to those in undamaged control cells. Conclusions Thus, our report for the first time highlights DNA damage-dependent spatial reorganization of whole chromosomes, which might be an integral aspect of cellular damage response. PMID:24330859

Recent changes in the fire regime across the North American boreal region-Spatial and temporal patterns of burning across Canada and Alaska

NASA Astrophysics Data System (ADS)

Kasischke, Eric S.; Turetsky, Merritt R.

2006-05-01

We used historic records from 1959-99 to explore fire regime characteristics at ecozone scales across the entire North American boreal region (NABR). Shifts in the NABR fire regime between the 1960s/70s and the 1980s/90s were characterized by a doubling of annual burned area and more than a doubling of the frequency of larger fire years because of more large fire events (>1,000 km2). The proportion of total burned area from human-ignited fires decreased over this same time period, while the proportion of burning during the early and late- growing-seasons increased. Trends in increased burned area were consistent across the NABR ecozones, though the western ecozones experienced greater increases in larger fire years compared to the eastern ecozones. Seasonal patterns of burning differed among ecozones. Along with the climate warming, changes in the fire regime characteristics may be an important driver of future ecosystem processes in the NABR.

Precise and long-term stabilization of the carrier-envelope phase of femtosecond laser pulses using an enhanced direct locking technique.

PubMed

Yu, Tae Jun; Hong, Kyung-Han; Choi, Hyun-Gyug; Sung, Jae Hee; Choi, Il Woo; Ko, Do-Kyeong; Lee, Jongmin; Kim, Junwon; Kim, Dong Eon; Nam, Chang Hee

2007-06-25

We demonstrate a long-term operation with reduced phase noise in the carrier-envelope-phase (CEP) stabilization process by employing a double feedback loop and an improved signal detection in the direct locking technique [Opt. Express 13, 2969 (2005)]. A homodyne balanced detection method is employed for efficiently suppressing the dc noise in the f-2f beat signal, which is converted into the CEP noise in the direct locking loop working at around zero carrier-envelope offset frequency (f(ceo)). In order to enhance the long-term stability, we have used the double feedback scheme that modulates both the oscillator pump power for a fast control and the intracavity-prism insertion depth for a slow and high-dynamic-range control. As a result, the in-loop phase jitter is reduced from 50 mrad of the previous result to 29 mrad, corresponding to 13 as in time scale, and the long-term stable operation is achieved for more than 12 hours.

Double-push skating versus V2 and V1 skating on uphill terrain in cross-country skiing.

PubMed

Stöggl, Thomas; Kampel, Wolfgang; Müller, Erich; Lindinger, Stefan

2010-01-01

The aims of the study were a) to compare the double-push skating technique with the V2 and the V1 skating techniques on an uphill terrain by a kinematic and kinetic analysis, b) to provide kinetic and kinematic data of the V1 technique at maximal skiing speeds, and c) to test the hypotheses that the double-push skating technique is faster compared with the V2 and the V1 skating techniques. Six elite skiers performed maximum speed sprints over a 60-m uphill section (7 degrees -10 degrees) using the double-push, the V2, and the V1 techniques. Pole and plantar forces and cycle characteristics were analyzed. The double-push skating technique was approximately 4.3% faster (P < 0.05) compared with the V2 skating technique and equally fast compared with the V1 skating technique. The double-push and the V2 techniques demonstrated longer cycle lengths, lower cycle rates (both P < 0.05), and equal poling frequencies and pole forces compared with the V1 technique. Cycle length, peak foot force, and knee extension ranges of motion and velocities were higher in the double-push technique compared with the V2 technique (all P values <0.05). Center of pressure was located more laterally in the double-push technique compared with the other two techniques (P < 0.05). All measured skiing speeds were drastically higher compared with former studies. The higher skiing speeds of the V1 and the double-push techniques compared with the V2 technique stress the mechanical advantage of those techniques on uphill terrain. Because of larger cycle lengths, lower cycle rate, longer recovery times, and equal poling frequency, the double-push technique might be seen as more economic on steep uphills compared with the V1 technique. From a tactical point of view compared with the V1 technique, the double-push technique needs less space due to less lateral displacement, and no technique transitions are necessary when entering and leaving an uphill section.

Method for double-sided processing of thin film transistors

DOEpatents

Yuan, Hao-Chih; Wang, Guogong; Eriksson, Mark A.; Evans, Paul G.; Lagally, Max G.; Ma, Zhenqiang

2008-04-08

This invention provides methods for fabricating thin film electronic devices with both front- and backside processing capabilities. Using these methods, high temperature processing steps may be carried out during both frontside and backside processing. The methods are well-suited for fabricating back-gate and double-gate field effect transistors, double-sided bipolar transistors and 3D integrated circuits.

PIF1 disruption or NBS1 hypomorphism does not affect chromosome healing or fusion resulting from double-strand breaks near telomeres in murine embryonic stem cells.

PubMed

Reynolds, Gloria E; Gao, Qing; Miller, Douglas; Snow, Bryan E; Harrington, Lea A; Murnane, John P

2011-11-10

Telomerase serves to maintain telomeric repeat sequences at the ends of chromosomes. However, telomerase can also add telomeric repeat sequences at DNA double-strand breaks (DSBs), a process called chromosome healing. Here, we employed a method of inducing DSBs near telomeres to query the role of two proteins, PIF1 and NBS1, in chromosome healing in mammalian cells. PIF1 was investigated because the PIF1 homolog in Saccharomyces cerevisiae inhibits chromosome healing, as shown by a 1000-fold increase in chromosome in PIF1-deficient cells. NBS1 was investigated because the functional homolog of NBS1 in S. cerevisiae, Xrs2, is part of the Mre11/Rad50/Xrs2 complex that is required for chromosome healing due to its role in the processing of DSBs and recruitment of telomerase. We found that disruption of mPif1 had no detectable effect on the frequency of chromosome healing at DSBs near telomeres in murine embryonic stem cells. Moreover, the Nbs1(ΔB) hypomorph, which is defective in the processing of DSBs, also had no detectable effect on the frequency of chromosome healing, DNA degradation, or gross chromosome rearrangements (GCRs) that result from telomeric DSBs. Although we cannot rule out small changes in chromosome healing using this system, it is clear from our results that knockout of PIF1 or the Nbs1(ΔB) hypomorph does not result in large differences in chromosome healing in murine cells. These results represent the first genetic assessment of the role of these proteins in chromosome healing in mammals, and suggest that murine cells have evolved mechanisms to ensure the functional redundancy of Pif1 or Nbs1 in the regulation of chromosome healing. Copyright © 2011 Elsevier B.V. All rights reserved.

Multiple nonlinear Bragg diffraction of femtosecond laser pulses in a {\\chi^{(2)}} photonic lattice with hexagonal domains

NASA Astrophysics Data System (ADS)

Vyunishev, A. M.; Arkhipkin, V. G.; Baturin, I. S.; Akhmatkhanov, A. R.; Shur, V. Ya; Chirkin, A. S.

2018-04-01

The frequency doubling of femtosecond laser pulses in a two-dimensional (2D) rectangular nonlinear photonic lattice with hexagonal domains is studied experimentally and theoretically. The broad fundamental spectrum enables frequency conversion under nonlinear Bragg diffraction for a series of transverse orders at a fixed longitudinal quasi-phase-matching order. The consistent nonstationary theory of the frequency doubling of femtosecond laser pulses is developed using the representation based on the reciprocal lattice of the structure. The calculated spatial distribution of the second-harmonic spectral intensity agrees well with the experimental data. The condition for multiple nonlinear Bragg diffraction in a 2D nonlinear photonic lattice is offered. The hexagonal shape of the domains contributes to multibeam second harmonic excitation. The maximum conversion efficiency for a series of transverse orders in the range 0.01%-0.03% is obtained.

Proposed Cavity for Reduced Slip-Stacking Loss

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

Eldred, J.; Zwaska, R.

This paper employs a novel dynamical mechanism to improve the performance of slip-stacking. Slip-stacking in an accumulation technique used at Fermilab since 2004 which nearly double the proton intensity. During slip-stacking, the Recycler or the Main Injector stores two particles beams that spatially overlap but have different momenta. The two particle beams are longitudinally focused by two 53 MHz 100 kV RF cavities with a small frequency difference between them. We propose an additional 106 MHz 20 kV RF cavity, with a frequency at the double the average of the upper and lower main RF frequencies. In simulation, we findmore » the proposed RF cavity significantly enhances the stable bucket area and reduces slip-stacking losses under reasonable injection scenarios. We quantify and map the stability of the parameter space for any accelerator implementing slip-stacking with the addition of a harmonic RF cavity.« less

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.

Structural parameter effect of porous material on sound absorption performance of double-resonance material

NASA Astrophysics Data System (ADS)

Fan, C.; Tian, Y.; Wang, Z. Q.; Nie, J. K.; Wang, G. K.; Liu, X. S.

2017-06-01

In view of the noise feature and service environment of urban power substations, this paper explores the idea of compound impedance, fills some porous sound-absorption material in the first resonance cavity of the double-resonance sound-absorption material, and designs a new-type of composite acoustic board. We conduct some acoustic characterizations according to the standard test of impedance tube, and research on the influence of assembly order, the thickness and area density of the filling material, and back cavity on material sound-absorption performance. The results show that the new-type of acoustic board consisting of aluminum fibrous material as inner structure, micro-porous board as outer structure, and polyester-filled space between them, has good sound-absorption performance for low frequency and full frequency noise. When the thickness, area density of filling material and thickness of back cavity increase, the sound absorption coefficient curve peak will move toward low frequency.

Fast coupled-cluster singles and doubles for extended systems: Application to the anharmonic vibrational frequencies of polyethylene in the Γ approximation

NASA Astrophysics Data System (ADS)

Keçeli, Murat; Hirata, So

2010-09-01

The mod- n scheme is introduced to the coupled-cluster singles and doubles (CCSD) and third-order Møller-Plesset perturbation (MP3) methods for extended systems of one-dimensional periodicity. By downsampling uniformly the wave vectors in Brillouin-zone integrations, this scheme accelerates these accurate but expensive correlation-energy calculations by two to three orders of magnitude while incurring negligible errors in their total and relative energies. To maintain this accuracy, the number of the nearest-neighbor unit cells included in the lattice sums must also be reduced by the same downsampling rate (n) . The mod- n CCSD and MP3 methods are applied to the potential-energy surface of polyethylene in anharmonic frequency calculations of its infrared- and Raman-active vibrations. The calculated frequencies are found to be within 46cm-1 (CCSD) and 78cm-1 (MP3) of the observed.

Information content of the space-frequency filtering of blood plasma layers laser images in the diagnosis of pathological changes

NASA Astrophysics Data System (ADS)

Ushenko, A. G.; Boychuk, T. M.; Mincer, O. P.; Bodnar, G. B.; Kushnerick, L. Ya.; Savich, V. O.

2013-12-01

The bases of method of the space-frequency of the filtering phase allocation of blood plasma pellicle are given here. The model of the optical-anisotropic properties of the albumen chain of blood plasma pellicle with regard to linear and circular double refraction of albumen and globulin crystals is proposed. Comparative researches of the effectiveness of methods of the direct polarized mapping of the azimuth images of blood plasma pcllicle layers and space-frequency polarimetry of the laser radiation transformed by divaricate and holelikc optical-anisotropic chains of blood plasma pellicles were held. On the basis of the complex statistic, correlative and fracta.1 analysis of the filtered frcquencydimensional polarizing azimuth maps of the blood plasma pellicles structure a set of criteria of the change of the double refraction of the albumen chains caused by the prostate cancer was traced and proved.

Removal of particulate matter emitted from a subway tunnel using magnetic filters.

PubMed

Son, Youn-Suk; Dinh, Trieu-Vuong; Chung, Sang-Gwi; Lee, Jai-Hyo; Kim, Jo-Chun

2014-01-01

We removed particulate matter (PM) emitted from a subway tunnel using magnetic filters. A magnetic filter system was installed on the top of a ventilation opening. Magnetic field density was increased by increasing the number of permanent magnet layers to determine PM removal characteristics. Moreover, the fan's frequency was adjusted from 30 to 60 Hz to investigate the effect of wind velocity on PM removal efficiency. As a result, PM removal efficiency increased as the number of magnetic filters or fan frequency increased. We obtained maximum removal efficiency of PM10 (52%), PM2.5 (46%), and PM1 (38%) at a 60 Hz fan frequency using double magnetic filters. We also found that the stability of the PM removal efficiency by the double filter (RSD, 3.2-5.8%) was higher than that by a single filter (10.9-24.5%) at all fan operating conditions.

Design of Measurement Apparatus for Electromagnetic Shielding Effectiveness Using Flanged Double Ridged Waveguide

NASA Astrophysics Data System (ADS)

Kwon, Jong Hwa; Choi, Jae Ick; Yook, Jong Gwan

In this paper, we design and manufacture a flanged double ridged waveguide with a tapered section as a sample holder for measuring the electromagnetic shielding effectiveness (SE) of planar material in broadband frequency ranges up to 10GHz. The proposed technique overcomes the limitations of the conventional ASTM D4935 test method at high frequencies. The simulation results for the designed sample holders agree well with the fabricated ones in consideration of the design specification of S11 < -20dB within the frequency range of 1-10GHz. To verify the proposed measurement apparatus, the measured SE data of the commercial shielding materials from 1 to 10GHz were indirectly compared with those obtained from the ASTM D4935 from 30MHz to 1GHz. We observed that the SE data obtained by using both experimental techniques agree with each other.

Surface laser marking optimization using an experimental design approach

NASA Astrophysics Data System (ADS)

Brihmat-Hamadi, F.; Amara, E. H.; Lavisse, L.; Jouvard, J. M.; Cicala, E.; Kellou, H.

2017-04-01

Laser surface marking is performed on a titanium substrate using a pulsed frequency doubled Nd:YAG laser ( λ= 532 nm, τ pulse=5 ns) to process the substrate surface under normal atmospheric conditions. The aim of the work is to investigate, following experimental and statistical approaches, the correlation between the process parameters and the response variables (output), using a Design of Experiment method (DOE): Taguchi methodology and a response surface methodology (RSM). A design is first created using MINTAB program, and then the laser marking process is performed according to the planned design. The response variables; surface roughness and surface reflectance were measured for each sample, and incorporated into the design matrix. The results are then analyzed and the RSM model is developed and verified for predicting the process output for the given set of process parameters values. The analysis shows that the laser beam scanning speed is the most influential operating factor followed by the laser pumping intensity during marking, while the other factors show complex influences on the objective functions.

Instantaneous Doppler Global Velocimetry Measurements of a Rotor Wake: Lessons Learned

NASA Technical Reports Server (NTRS)

Meyers, James; Fleming, Gary A.; Gorton, Susan Althoff; Berry, John D.

1998-01-01

A combined Doppler Global Velocimetry (DGV) and Projection Moir Interferometry (PMI) investigation of a helicopter rotor wake flow field and rotor blade deformation is presented. The three-component DGV system uses a single-frequency, frequency-doubled Nd:YAG laser to obtain instantaneous velocity measurements in the flow. The PMI system uses a pulsed laser-diode bar to obtain blade bending and twist measurements at the same instant that DGV measured the flow. The application of pulse lasers to DGV and PMI in large-scale wind tunnel applications represents a major step forward in the development of these technologies. As such, a great deal was learned about the difficulties of using these instruments to obtain instantaneous measurements in large facilities. Laser speckle and other image noise in the DGV data images were found to be traceable to the Nd:YAG laser. Although image processing techniques were used to virtually eliminate laser speckle noise, the source of low-frequency image noise is still under investigation. The PMI results agreed well with theoretical predictions of blade bending and twist.

Achromatic phase-matching second harmonic generation for a tunable laser

DOEpatents

Jacobson, A.G.; Bisson, S.; Trebino, R.

1998-01-20

An optical system uses a nonlinear optical medium to alter the frequency of a relatively narrow band light source tunable over a plurality of different frequencies using an optical system for passively directing light to the nonlinear medium at a correct phase matching angle. In this manner, the light from the tunable light source can be efficiently frequency-doubled or frequency-tripled without the need of moving parts. An all prism design provides a system of optimal efficiency. 6 figs.

Achromatic phase-matching second harmonic generation for a tunable laser

DOEpatents

Jacobson, Alexander Gerson; Bisson, Scott; Trebino, Rick

1998-01-01

An optical system uses a nonlinear optical medium to alter the frequency of a relatively narrow band light source tunable over a plurality of different frequencies using an optical system for passively directing light to the nonlinear medium at a correct phase matching angle. In this manner, the light from the tunable light source can be efficiently frequency-doubled or frequency-tripled without the need of moving parts. An all prism design provides a system of optimal efficiency.

The effect of global warming on lightning frequencies

NASA Technical Reports Server (NTRS)

Price, Colin; Rind, David

1990-01-01

The first attempt to model global lightning distributions by using the Goddard Institute for Space Studies (GISS) GCM is reported. Three sets of observations showing the relationship between lightning frequency and cloud top height are shown. Zonally averaged lightning frequency observed by satellite are compared with those calculated using the GISS GCM, and fair agreement is found. The change in lightning frequency for a double CO2 climate is calculated and found to be nearly 2.23 x 10 exp 6 extra lightning flashes per day.

Holographic Cinematography And Its Applications

NASA Astrophysics Data System (ADS)

Smigielski, Paul

1987-09-01

We describe several applications of cineholography to objects scattering light by reflection: single-exposure cineholograms on 126-mm films at a repetition rate of 25 holograms per second for 3-D movies and for flight simulators applications, double-exposure cineholograms for medical and industrial applications (NDT). Limitations of cineholography are also described. The light source used for cineholograms recording is a frequency-doubled pulse YAG-laser.

Parametric nonfeedback resonance in period doubling systems

NASA Astrophysics Data System (ADS)

Pisarchik, A. N.; Corbalán, R.

1999-02-01

Slow periodic modulation of a control parameter in a period doubling system leads to an interaction between stable and unstable periodic orbits. This causes a resonance in the system response at the modulation frequency. The conditions for this resonance are studied through numerical simulations of quadratic map and laser equations. The results are confirmed by experiments in a CO2 laser with modulated losses.

Coherent wave packet dynamics in a double-well potential in cavity

NASA Astrophysics Data System (ADS)

Zheng, Li; Li, Gang; Ding, Ming-Song; Wang, Yong-Liang; Zhang, Yun-Cui

2018-02-01

We investigate the coherent wave packet dynamics of a two-level atom trapped in a symmetric double-well potential in a near-resonance cavity. Prepared on one side of the double-well potential, the atom wave packet oscillates between the left and right wells, while recoil induced by the emitted photon from the atom entangles the atomic internal and external degrees of freedom. The collapse and revival of the tunneling occurs. Adjusting the width of the wave packets, one can modify the tunneling frequency and suppress the tunneling.

Double Charge Exchange Reactions and Double Beta Decay

NASA Astrophysics Data System (ADS)

Auerbach, N.

2018-05-01

The subject of this presentation is at the forefront of nuclear physics, namely double beta decay. In particular one is most interested in the neutrinoless process of double beta decay, when the decay proceeds without the emission of two neutrinos. The observation of such decay would mean that the lepton conservation symmetry is violated and that the neutrinos are of Majorana type, meaning that they are their own anti-particles. The life time of this process has two unknowns, the mass of the neutrino and the nuclear matrix element. Determining the nuclear matrix element and knowing the cross-section well will set limits on the neutrino mass. There is a concentrated effort among the nuclear physics community to calculate this matrix element. Usually these matrix elements are a very small part of the total strength of the transition operators involved in the process. There is no simple way to “calibrate” the nuclear double beta decay matrix element. The double beta decay is a double charge exchange process, therefore it is proposed that double charge exchange reactions using ion projectiles on nuclei that are candidates for double beta decay, will provide additional necessary information about the nuclear matrix elements.

Frequency and variability of dental morphology in deciduous and permanent dentition of a Nasa indigenous group in the municipality of Morales, Cauca, Colombia

PubMed Central

Díaz, Eider; García, Lorena; Hernández, Michelle; Palacio, Lesly; Ruiz, Diana; Velandia, Nataly; Villavicencio, Judy

2014-01-01

Objectives: To determine the frequency, variability, sexual dimorphism and bilateral symmetry of fourteen dental crown traits in the deciduous and permanent dentition of 60 dental models (35 women and 25 men) obtained from a native, indigenous group of Nasa school children of the Musse Ukue group in the municipality of Morales, Department of Cauca, Colombia. Methods: This is a quantitative, descriptive, cross-sectional study that characterizes dental morphology by means of the systems for temporary dentition from Dahlberg (winging), and ASUDAS (crowding, reduction of hypocone, metaconule and cusp 6), Hanihara (central and lateral incisors in shovel-shape and cusp 7), Sciulli (double bit, layered fold protostylid, cusp pattern and cusp number) and Grine (Carabelli trait); and in permanent dentition from ASUDAS (Winging, crowding, central and lateral incisors in shovel-shape and double shovel-shape, Carabelli trait, hypocone reduction, metaconule, cusp pattern, cusp number, layered fold protostylid, cusp 6 and cusp 7). Results: The most frequent dental crown features were the shovel-shaped form, grooved and fossa forms of the Carabelli trait, metaconule, cusp pattern Y6, layered fold, protostylid (point P) and cusp 6. Sexual dimorphism was not observed and there was bilateral symmetry in the expression of these features. Conclusions: The sample studied presented a great affinity with ethnic groups belonging to the Mongoloid Dental Complex due to the frequency (expression) and variability (gradation) of the tooth crown traits, upper incisors, the Carabelli trait, the protostylid, cusp 6 and cusp 7. The influence of the Caucasoide Dental Complex associated with ethno-historical processes cannot be ruled out. PMID:24970955

A simple method for the computation of first neighbour frequencies of DNAs from CD spectra

PubMed Central

Marck, Christian; Guschlbauer, Wilhelm

1978-01-01

A procedure for the computation of the first neighbour frequencies of DNA's is presented. This procedure is based on the first neighbour approximation of Gray and Tinoco. We show that the knowledge of all the ten elementary CD signals attached to the ten double stranded first neighbour configurations is not necessary. One can obtain the ten frequencies of an unknown DNA with the use of eight elementary CD signals corresponding to eight linearly independent polymer sequences. These signals can be extracted very simply from any eight or more CD spectra of double stranded DNA's of known frequencies. The ten frequencies of a DNA are obtained by least square fit of its CD spectrum with these elementary signals. One advantage of this procedure is that it does not necessitate linear programming, it can be used with CD data digitalized using a large number of wavelengths, thus permitting an accurate resolution of the CD spectra. Under favorable case, the ten frequencies of a DNA (not used as input data) can be determined with an average absolute error < 2%. We have also observed that certain satellite DNA's, those of Drosophila virilis and Callinectes sapidus have CD spectra compatible with those of DNA's of quasi random sequence; these satellite DNA's should adopt also the B-form in solution. PMID:673843

Local vibrational modes of the formic acid dimer - the strength of the double hydrogen bond

NASA Astrophysics Data System (ADS)

Kalescky, R.; Kraka, E.; Cremer, D.

2013-07-01

The 24 normal and 24 local vibrational modes of the formic acid dimer formed by two trans formic acid monomers to a ring (TT1) are analysed utilising preferentially experimental frequencies, but also CCSD(T)/CBS and ωB97X-D harmonic vibrational frequencies. The local hydrogen bond (HB) stretching frequencies are at 676 cm-1 and by this 482 and 412 cm-1 higher compared to the measured symmetric and asymmetric HB stretching frequencies at 264 and 194 cm-1. The adiabatic connection scheme between local and normal vibrational modes reveals that the lowering is due to the topology of dimer TT1, mass coupling, and avoided crossings involving the HṡṡṡOC bending modes. The HB local mode stretching force constant is related to the strength of the HB whereas the normal mode stretching force constant and frequency lead to an erroneous underestimation of the HB strength. The HB in TT1 is stabilised by electron delocalisation in the O=C-O units fostered by forming a ring via double HBs. This implies that the CO apart from the OH local stretching frequencies reflect the strength of the HB via their red or blue shifts relative to their corresponding values in trans formic acid.

The effect of external mean flow on sound transmission through double-walled cylindrical shells lined with poroelastic material

NASA Astrophysics Data System (ADS)

Zhou, Jie; Bhaskar, Atul; Zhang, Xin

2014-03-01

Sound transmission through a system of double shells, lined with poroelastic material in the presence of external mean flow, is studied. The porous material is modeled as an equivalent fluid because shear wave contributions are known to be insignificant. This is achieved by accounting for the energetically most dominant wave types in the calculations. The transmission characteristics of the sandwich construction are presented for different incidence angles and Mach numbers over a wide frequency range. It is noted that the transmission loss exhibits three dips on the frequency axis as opposed to flat panels where there are only two such frequencies—results are discussed in the light of these observations. Flow is shown to decrease the transmission loss below the ring frequency, but increase this above the ring frequency due to the negative stiffness and the damping effect added by the flow. In the absence of external mean flow, porous material provides superior insulation for most part of the frequency band of interest. However, in the presence of external flow, this is true only below the ring frequency—above this frequency, the presence of air gap in sandwich constructions is the dominant factor that determines the acoustic performance. In the absence of external flow, an air gap always improves sound insulation.

Scale-dependent effects on wave propagation in magnetically affected single/double-layered compositionally graded nanosize beams

NASA Astrophysics Data System (ADS)

Ebrahimi, Farzad; Barati, Mohammad Reza

2018-04-01

This article deals with the wave propagation analysis of single/double layered functionally graded (FG) size-dependent nanobeams in elastic medium and subjected to a longitudinal magnetic field employing nonlocal elasticity theory. Material properties of nanobeam change gradually according to the sigmoid function. Applying an analytical solution, the acoustical and optical dispersion relations are explored for various wave number, nonlocality parameter, material composition, elastic foundation constants, and magnetic field intensity. It is found that frequency and phase velocity of waves propagating in S-FGM nanobeam are significantly affected by these parameters. Also, presence of cut-off and escape frequencies in wave propagation analysis of embedded S-FGM nanobeams is investigated.

Semi-monolithic cavity for external resonant frequency doubling and method of performing the same

NASA Technical Reports Server (NTRS)

Hemmati, Hamid (Inventor)

1999-01-01

The fabrication of an optical cavity for use in a laser, in a frequency doubling external cavity, or any other type of nonlinear optical device, can be simplified by providing the nonlinear crystal in combination with a surrounding glass having an index of refraction substantially equal to that of the nonlinear crystal. The closed optical path in this cavity is formed in the surrounding glass and through the nonlinear crystal which lies in one of the optical segments of the light path. The light is transmitted through interfaces between the surrounding glass in the nonlinear crystal through interfaces which are formed at the Brewster-angle to minimize or eliminate reflection.

Double-Edge Molecular Measurement of Lidar Wind Profiles at 355 nm

NASA Technical Reports Server (NTRS)

Flesia, Cristina; Korb, C. Laurence; Hirt, Christian; Einaudi, Franco (Technical Monitor)

2000-01-01

We built a direct detection Doppler lidar based on the double-edge molecular technique and made the first molecular based wind measurements using the eyesafe 355 nm wavelength. Three etalon bandpasses are obtained with Step etalons on a single pair of etalon plates. Long-term frequency drift of the laser and the capacitively stabilized etalon is removed by locking the etalon to the laser frequency. We use a low angle design to avoid polarization effects. Wind measurements of 1 to 2 m/s accuracy are obtained to 10 km altitude with 5 mJ of laser energy, a 750s integration, and a 25 cm telescope. Good agreement is obtained between the lidar and rawinsonde measurements.

Bright light therapy decreases winter binge frequency in women with bulimia nervosa: a double-blind, placebo-controlled study.

PubMed

Braun, D L; Sunday, S R; Fornari, V M; Halmi, K A

1999-01-01

The study objective was to determine the effect of winter bright light therapy on binge and purge frequencies and depressive symptoms in subjects with bulimia nervosa. Thirty-four female bulimic outpatients were treated with either 10,000 lux bright white light or 50 lux dim red light (placebo control) during the winter months. In this double-blind study, the placebo group (n = 18) and the bright light group (n = 16) were matched for age, degree of seasonality (measured by the Seasonal Patterns Assessment Questionnaire [SPAQ]), and concurrent depression (measured by Structured Clinical Interview for DSM-IV [SCID]). Three weeks of baseline data collection were followed by 3 weeks of half-hour daily morning light treatment and 2 weeks of follow-up evaluation. There was a significant light-treatment by time interaction (Wilks' lambda = .81, F(2,28) = 3.31, P = .05). The mean binge frequency decreased significantly more from baseline to the end of treatment for the bright light group (F(1,29) = 6.41, P = .017) than for the placebo group. The level of depression (measured by daily Beck Depression Inventory [BDI] scores) did not significantly differ between the groups during any phase, and neither depression nor seasonality affected the response to light treatment. In this double-blind study, bulimic women who received 3 weeks of winter bright light treatment reported a reduced binge frequency between baseline and the active treatment period in comparison to subjects receiving dim red light.

Doubling of coastal flooding frequency within decades due to sea-level rise

USGS Publications Warehouse

Vitousek, Sean; Barnard, Patrick L.; Fletcher, Charles H.; Frazer, Neil; Erikson, Li; Storlazzi, Curt D.

2017-01-01

Global climate change drives sea-level rise, increasing the frequency of coastal flooding. In most coastal regions, the amount of sea-level rise occurring over years to decades is significantly smaller than normal ocean-level fluctuations caused by tides, waves, and storm surge. However, even gradual sea-level rise can rapidly increase the frequency and severity of coastal flooding. So far, global-scale estimates of increased coastal flooding due to sea-level rise have not considered elevated water levels due to waves, and thus underestimate the potential impact. Here we use extreme value theory to combine sea-level projections with wave, tide, and storm surge models to estimate increases in coastal flooding on a continuous global scale. We find that regions with limited water-level variability, i.e., short-tailed flood-level distributions, located mainly in the Tropics, will experience the largest increases in flooding frequency. The 10 to 20 cm of sea-level rise expected no later than 2050 will more than double the frequency of extreme water-level events in the Tropics, impairing the developing economies of equatorial coastal cities and the habitability of low-lying Pacific island nations.

Cavity ring-down spectroscopy (CRDS) system for measuring atmospheric mercury using differential absorption

NASA Astrophysics Data System (ADS)

Pierce, A.; Obrist, D.; Moosmuller, H.; Moore, C.

2012-04-01

Atmospheric elemental mercury (Hg0) is a globally pervasive element that can be transported and deposited to remote ecosystems where it poses — particularly in its methylated form — harm to many organisms including humans. Current techniques for measurement of atmospheric Hg0 require several liters of sample air and several minutes for each analysis. Fast-response (i.e., 1 second or faster) measurements would improve our ability to understand and track chemical cycling of mercury in the atmosphere, including high frequency Hg0 fluctuations, sources and sinks, and chemical transformation processes. We present theory, design, challenges, and current results of our new prototype sensor based on cavity ring-down spectroscopy (CRDS) for fast-response measurement of Hg0 mass concentrations. CRDS is a direct absorption technique that implements path-lengths of multiple kilometers in a compact absorption cell using high-reflectivity mirrors, thereby improving sensitivity and reducing sample volume compared to conventional absorption spectroscopy. Our sensor includes a frequency-doubled, dye-laser emitting laser pulses tunable from 215 to 280 nm, pumped by a Q-switched, frequency tripled Nd:YAG laser with a pulse repetition rate of 50 Hz. We present how we successfully perform automated wavelength locking and stabilization of the laser to the peak Hg0 absorption line at 253.65 nm using an external isotopically-enriched mercury (202Hg0) cell. An emphasis of this presentation will be on the implementation of differential absorption measurement whereby measurements are alternated between the peak Hg0 absorption wavelength and a nearby wavelength "off" the absorption line. This can be achieved using a piezo electric tuning element that allows for pulse-by-pulse tuning and detuning of the laser "online" and "offline" of the Hg absorption line, and thereby allows for continuous correction of baseline extinction losses. Unexpected challenges with this approach included different efficiencies of laser performance (e.g., frequency doubling) at the two wavelengths and temperature dependence. We will discuss improvements on the control of our system to eliminate drift due to conversion efficiency and temperature dependence. We will detail complications with operating this instrument from a mobile platform for in situ measurements in the field. Finally, we will present data acquisition and processing approaches along with results of calibration curves, and comparisons to conventional mercury analyzers (i.e., a Tekran 2537 mercury vapor analyzer) during ambient air measurements.

Efficient flattop ultra-wideband wavelength converters based on double-pass cascaded sum and difference frequency generation using engineered chirped gratings.

PubMed

Tehranchi, Amirhossein; Morandotti, Roberto; Kashyap, Raman

2011-11-07

High-efficiency ultra-broadband wavelength converters based on double-pass quasi-phase-matched cascaded sum and difference frequency generation including engineered chirped gratings in lossy lithium niobate waveguides are numerically investigated and compared to the single-pass counterparts, assuming a large twin-pump wavelength difference of 75 nm. Instead of uniform gratings, few-section chirped gratings with the same length, but with a small constant period change among sections with uniform gratings, are proposed to flatten the response and increase the mean efficiency by finding the common critical period shift and minimum number of sections for both single-pass and double-pass schemes whilst for the latter the efficiency is remarkably higher in a low-loss waveguide. It is also verified that for the same waveguide length and power, the efficiency enhancement expected due to the use of the double-pass scheme instead of the single-pass one, is finally lost if the waveguide loss increases above a certain value. For the double-pass scheme, the criteria for the design of the low-loss waveguide length, and the assignment of power in the pumps to achieve the desired efficiency, bandwidth and ripple are presented for the optimum 3-section chirped-gratings-based devices. Efficient conversions with flattop bandwidths > 84 nm for lengths < 3 cm can be obtained.

Application of the Undifferenced GNSS Precise Positioning in Determining Coordinates in National Reference Frames

NASA Astrophysics Data System (ADS)

Krzan, Grzegorz; Stępniak, Katarzyna

2017-09-01

In high-accuracy positioning using GNSS, the most common solution is still relative positioning using double-difference observations of dual-frequency measurements. An increasingly popular alternative to relative positioning are undifferenced approaches, which are designed to make full use of modern satellite systems and signals. Positions referenced to global International Terrestrial Reference Frame (ITRF2008) obtained from Precise Point Positioning (PPP) or Undifferenced (UD) network solutions have to be transformed to national (regional) reference frame, which introduces additional bases related to the transformation process. In this paper, satellite observations from two test networks using different observation time series were processed. The first test concerns the positioning accuracy from processing one year of dual-frequency GPS observations from 14 EUREF Permanent Network (EPN) stations using NAPEOS 3.3.1 software. The results were transformed into a national reference frame (PL-ETRF2000) and compared to positions from an EPN cumulative solution, which was adopted as the true coordinates. Daily observations were processed using PPP and UD multi-station solutions to determine the final accuracy resulting from satellite positioning, the transformation to national coordinate systems and Eurasian intraplate plate velocities. The second numerical test involved similar processing strategies of post-processing carried out using different observation time series (30 min., 1 hour, 2 hours, daily) and different classes of GNSS receivers. The centimeter accuracy of results presented in the national coordinate system satisfies the requirements of many surveying and engineering applications.

Frequency tripling of convergent beam employing crystals tiling in large-aperture high-energy laser facilities

NASA Astrophysics Data System (ADS)

Wang, Junhua; Li, Dazhen; Wang, Bo; Yang, Jing; Yang, Houwen; Wang, Xiaoqian; Cheng, Wenyong

2017-11-01

In inertial confinement fusion, ultraviolet laser damage of the fused silica lens is an important limiting factor for load capability of the laser driver. To solve this problem, a new configuration of frequency tripling is proposed in this paper. The frequency tripling crystal is placed on downstream of the focusing lens, thus sum frequency generation of fundamental frequency light and doubling frequency light occurs in the beam convergence path. The focusing lens is only irradiated by fundamental light and doubling frequency lights. Thus, its damage threshold will increase. LiB3O5 (LBO) crystals are employed as frequency tripling crystals for its larger acceptance angle and higher damage threshold than KDP/DKDP crystals'. With the limitation of acceptance angle and crystal growth size are taken into account, the tiling scheme of LBO crystals is proposed and designed optimally to adopt to the total convergence angle of 36.0 mrad. Theoretical results indicate that 3 LBO crystals titling with different cutting angles in θ direction can meet the phase matching condition. Compared with frequency tripling of parallel beam using one LBO crystal, 83.8% (93.1% with 5 LBO crystals tiling) of the frequency tripling conversion efficiency can be obtained employing this new configuration. The results of a principle experiment also support this scheme. By employing this new design, not only the load capacity of a laser driver will be significantly improved, but also the fused silica lens can be changed to K9 glass lens which has the mature technology and low cost.

Young's double-slit interference with two-color biphotons.

PubMed

Zhang, De-Jian; Wu, Shuang; Li, Hong-Guo; Wang, Hai-Bo; Xiong, Jun; Wang, Kaige

2017-12-12

In classical optics, Young's double-slit experiment with colored coherent light gives rise to individual interference fringes for each light frequency, referring to single-photon interference. However, two-photon double-slit interference has been widely studied only for wavelength-degenerate biphoton, known as subwavelength quantum lithography. In this work, we report double-slit interference experiments with two-color biphoton. Different from the degenerate case, the experimental results depend on the measurement methods. From a two-axis coincidence measurement pattern we can extract complete interference information about two colors. The conceptual model provides an intuitional picture of the in-phase and out-of-phase photon correlations and a complete quantum understanding about the which-path information of two colored photons.

Practical design of a 4 Tesla double-tuned RF surface coil for interleaved 1H and 23Na MRI of rat brain.

PubMed

Alecci, M; Romanzetti, S; Kaffanke, J; Celik, A; Wegener, H P; Shah, N J

2006-08-01

MRI is proving to be a very useful tool for sodium quantification in animal models of stroke, ischemia, and cancer. In this work, we present the practical design of a dual-frequency RF surface coil that provides (1)H and (23)Na images of the rat head at 4 T. The dual-frequency RF surface coil comprised of a large loop tuned to the (1)H frequency and a smaller co-planar loop tuned to the (23)Na frequency. The mutual coupling between the two loops was eliminated by the use of a trap circuit inserted in the smaller coil. This independent-loop design was versatile since it enabled a separate optimisation of the sensitivity and RF field distributions of the two coils. To allow for an easy extension of this simple double-tuned coil design to other frequencies (nuclei) and dimensions, we describe in detail the practical aspects of the workbench design and MRI testing using a phantom that mimics in vivo conditions. A comparison between our independent-loop, double-tuned coil and a single-tuned (23)Na coil of equal size obtained with a phantom matching in vivo conditions, showed a reduction of the (23)Na sensitivity (about 28 %) because of signal losses in the trap inductance. Typical congruent (1)H and (23)Na rat brain images showing good SNR ((23)Na: brain 7, ventricular cerebrospinal fluid 11) and spatial resolution ((23)Na: 1.25 x 1.25 x 5mm(3)) are also reported. The in vivo SNR values obtained with this coil were comparable to, if not better than, other contemporary designs in the literature.

Practical design of a 4 Tesla double-tuned RF surface coil for interleaved 1H and 23Na MRI of rat brain

NASA Astrophysics Data System (ADS)

Alecci, M.; Romanzetti, S.; Kaffanke, J.; Celik, A.; Wegener, H. P.; Shah, N. J.

2006-08-01

MRI is proving to be a very useful tool for sodium quantification in animal models of stroke, ischemia, and cancer. In this work, we present the practical design of a dual-frequency RF surface coil that provides 1H and 23Na images of the rat head at 4 T. The dual-frequency RF surface coil comprised of a large loop tuned to the 1H frequency and a smaller co-planar loop tuned to the 23Na frequency. The mutual coupling between the two loops was eliminated by the use of a trap circuit inserted in the smaller coil. This independent-loop design was versatile since it enabled a separate optimisation of the sensitivity and RF field distributions of the two coils. To allow for an easy extension of this simple double-tuned coil design to other frequencies (nuclei) and dimensions, we describe in detail the practical aspects of the workbench design and MRI testing using a phantom that mimics in vivo conditions. A comparison between our independent-loop, double-tuned coil and a single-tuned 23Na coil of equal size obtained with a phantom matching in vivo conditions, showed a reduction of the 23Na sensitivity (about 28 %) because of signal losses in the trap inductance. Typical congruent 1H and 23Na rat brain images showing good SNR ( 23Na: brain 7, ventricular cerebrospinal fluid 11) and spatial resolution ( 23Na: 1.25 × 1.25 × 5 mm 3) are also reported. The in vivo SNR values obtained with this coil were comparable to, if not better than, other contemporary designs in the literature.

An analytical study of the free and forced vibration response of a ribbed plate with free boundary conditions

NASA Astrophysics Data System (ADS)

Lin, Tian Ran; Zhang, Kai

2018-05-01

An analytical study to predict the vibration response of a ribbed plate with free boundary conditions is presented. The analytical solution was derived using a double cosine integral transform technique and then utilized to study the free and forced vibration of the ribbed plate, as well as the effect of the rib on the modal response of the uniform plate. It is shown that in addition to the three zero-frequency rigid body modes of the plate, the vibration modes of the uniform plate can be classified into four mode groups according to the symmetric properties of the plate with respect to the two orthogonal middle lines parallel to the plate edges. The four mode groups correspond to a double symmetric group, a double anti-symmetric group and two symmetric/anti-symmetric groups. Whilst the inclusion of the rib to the plate is shown to cause distortion to the distribution of vibration modes, most modes can still be traced back to the original modes of the uniform plate. Both the mass and stiffness of the rib are shown to affect the modal vibration of the uniform plate, whereby a dominant effect from the rib mass leads to a decrease in the modal frequency of the plate, whereas a dominant effect from the rib stiffness leads to an increase in plate modal frequency. When the stiffened rib behaves as an effective boundary to the plate vibration, an original plate mode becomes a pair of degenerate modes, whereby one mode has a higher frequency and the other mode has a lower frequency than that of the original mode.

Building of nested components by a double-nozzle droplet deposition process

NASA Astrophysics Data System (ADS)

Li, SuLi; Wei, ZhengYing; Du, Jun; Zhao, Guangxi; Wang, Xin; Lu, BingHeng

2016-07-01

According to the nested components jointed with multiple parts,a double-nozzle droplet deposition process was put forward in this paper, and the experimental system was developed. Through the research on the properties of support materials and the process of double-nozzle droplet deposition, the linkage control of the metal droplet deposition and the support material extrusion was realized, and a nested component with complex construction was fabricated directly. Compared with the traditional forming processes, this double-nozzle deposition process has the advantages of short cycle, low cost and so on. It can provide an approach way to build the nested parts.

Moment tensor inversion with three-dimensional sensor configuration of mining induced seismicity (Kiruna mine, Sweden)

NASA Astrophysics Data System (ADS)

Ma, Ju; Dineva, Savka; Cesca, Simone; Heimann, Sebastian

2018-06-01

Mining induced seismicity is an undesired consequence of mining operations, which poses significant hazard to miners and infrastructures and requires an accurate analysis of the rupture process. Seismic moment tensors of mining-induced events help to understand the nature of mining-induced seismicity by providing information about the relationship between the mining, stress redistribution and instabilities in the rock mass. In this work, we adapt and test a waveform-based inversion method on high frequency data recorded by a dense underground seismic system in one of the largest underground mines in the world (Kiruna mine, Sweden). A stable algorithm for moment tensor inversion for comparatively small mining induced earthquakes, resolving both the double-couple and full moment tensor with high frequency data, is very challenging. Moreover, the application to underground mining system requires accounting for the 3-D geometry of the monitoring system. We construct a Green's function database using a homogeneous velocity model, but assuming a 3-D distribution of potential sources and receivers. We first perform a set of moment tensor inversions using synthetic data to test the effects of different factors on moment tensor inversion stability and source parameters accuracy, including the network spatial coverage, the number of sensors and the signal-to-noise ratio. The influence of the accuracy of the input source parameters on the inversion results is also tested. Those tests show that an accurate selection of the inversion parameters allows resolving the moment tensor also in the presence of realistic seismic noise conditions. Finally, the moment tensor inversion methodology is applied to eight events chosen from mining block #33/34 at Kiruna mine. Source parameters including scalar moment, magnitude, double-couple, compensated linear vector dipole and isotropic contributions as well as the strike, dip and rake configurations of the double-couple term were obtained. The orientations of the nodal planes of the double-couple component in most cases vary from NNW to NNE with a dip along the ore body or in the opposite direction.

Moment Tensor Inversion with 3D sensor configuration of Mining Induced Seismicity (Kiruna mine, Sweden)

NASA Astrophysics Data System (ADS)

Ma, Ju; Dineva, Savka; Cesca, Simone; Heimann, Sebastian

2018-03-01

Mining induced seismicity is an undesired consequence of mining operations, which poses significant hazard to miners and infrastructures and requires an accurate analysis of the rupture process. Seismic moment tensors of mining-induced events help to understand the nature of mining-induced seismicity by providing information about the relationship between the mining, stress redistribution and instabilities in the rock mass. In this work, we adapt and test a waveform-based inversion method on high frequency data recorded by a dense underground seismic system in one of the largest underground mines in the world (Kiruna mine, Sweden). Stable algorithm for moment tensor inversion for comparatively small mining induced earthquakes, resolving both the double couple and full moment tensor with high frequency data is very challenging. Moreover, the application to underground mining system requires accounting for the 3D geometry of the monitoring system. We construct a Green's function database using a homogeneous velocity model, but assuming a 3D distribution of potential sources and receivers. We first perform a set of moment tensor inversions using synthetic data to test the effects of different factors on moment tensor inversion stability and source parameters accuracy, including the network spatial coverage, the number of sensors and the signal-to-noise ratio. The influence of the accuracy of the input source parameters on the inversion results is also tested. Those tests show that an accurate selection of the inversion parameters allows resolving the moment tensor also in presence of realistic seismic noise conditions. Finally, the moment tensor inversion methodology is applied to 8 events chosen from mining block #33/34 at Kiruna mine. Source parameters including scalar moment, magnitude, double couple, compensated linear vector dipole and isotropic contributions as well as the strike, dip, rake configurations of the double couple term were obtained. The orientations of the nodal planes of the double-couple component in most cases vary from NNW to NNE with a dip along the ore body or in the opposite direction.

Continuous quantum measurement with independent detector cross correlations.

PubMed

Jordan, Andrew N; Büttiker, Markus

2005-11-25

We investigate the advantages of using two independent, linear detectors for continuous quantum measurement. For single-shot measurement, the detection process may be quantum limited if the detectors are twins. For weak continuous measurement, cross correlations allow a violation of the Korotkov-Averin bound for the detector's signal-to-noise ratio. The joint weak measurement of noncommuting observables is also investigated, and we find the cross correlation changes sign as a function of frequency, reflecting a crossover from incoherent relaxation to coherent, out of phase oscillations. Our results are applied to a double quantum-dot charge qubit, simultaneously measured by two quantum point contacts.

Overlay metrology for double patterning processes

NASA Astrophysics Data System (ADS)

Leray, Philippe; Cheng, Shaunee; Laidler, David; Kandel, Daniel; Adel, Mike; Dinu, Berta; Polli, Marco; Vasconi, Mauro; Salski, Bartlomiej

2009-03-01

The double patterning (DPT) process is foreseen by the industry to be the main solution for the 32 nm technology node and even beyond. Meanwhile process compatibility has to be maintained and the performance of overlay metrology has to improve. To achieve this for Image Based Overlay (IBO), usually the optics of overlay tools are improved. It was also demonstrated that these requirements are achievable with a Diffraction Based Overlay (DBO) technique named SCOLTM [1]. In addition, we believe that overlay measurements with respect to a reference grid are required to achieve the required overlay control [2]. This induces at least a three-fold increase in the number of measurements (2 for double patterned layers to the reference grid and 1 between the double patterned layers). The requirements of process compatibility, enhanced performance and large number of measurements make the choice of overlay metrology for DPT very challenging. In this work we use different flavors of the standard overlay metrology technique (IBO) as well as the new technique (SCOL) to address these three requirements. The compatibility of the corresponding overlay targets with double patterning processes (Litho-Etch-Litho-Etch (LELE); Litho-Freeze-Litho-Etch (LFLE), Spacer defined) is tested. The process impact on different target types is discussed (CD bias LELE, Contrast for LFLE). We compare the standard imaging overlay metrology with non-standard imaging techniques dedicated to double patterning processes (multilayer imaging targets allowing one overlay target instead of three, very small imaging targets). In addition to standard designs already discussed [1], we investigate SCOL target designs specific to double patterning processes. The feedback to the scanner is determined using the different techniques. The final overlay results obtained are compared accordingly. We conclude with the pros and cons of each technique and suggest the optimal metrology strategy for overlay control in double patterning processes.

Evolution of the Novalux extended cavity surface-emitting semiconductor laser (NECSEL)

NASA Astrophysics Data System (ADS)

McInerney, John G.

2016-03-01

Novalux Inc was an enterprise founded by Aram Mooradian in 1998 to commercialise a novel electrically pumped vertical extended cavity semiconductor laser platform, initially aiming to produce pump lasers for optical fiber telecommunication networks. Following successful major investment in 2000, the company developed a range of single- and multi-mode 980 nm pump lasers emitting from 100-500 mW with excellent beam quality and efficiency. This rapid development required solution of several significant problems in chip and external cavity design, substrate and DBR mirror optimization, thermal engineering and mode selection. Output coupling to single mode fiber was exceptional. Following the collapse of the long haul telecom market in late 2001, a major reorientation of effort was undertaken, initially to develop compact 60-100 mW hybrid monolithically integrated pumplets for metro/local amplified networks, then to frequency-doubled blue light emitters for biotech, reprographics and general scientific applications. During 2001-3 I worked at Novalux on a career break from University College Cork, first as R&D Director managing a small group tasked with producing new capabilities and product options based on the NECSEL platform, including high power, pulsed and frequency doubled versions, then in 2002 as Director of New Product Realization managing the full engineering team, leading the transition to frequency doubled products.

Study on the ternary mixed ligand complex of palladium(II)-aminophylline-fluorescein sodium by resonance Rayleigh scattering, second-order scattering and frequency doubling scattering spectrum and its analytical application.

PubMed

Chen, Peili; Liu, Shaopu; Liu, Zhongfang; Hu, Xiaoli

2011-01-01

The interaction between palladium(II)-aminophylline and fluorescein sodium was investigated by resonance Rayleigh scattering, second-order scattering and frequency doubling scattering spectrum. In pH 4.4 Britton-Robinson (BR) buffer medium, aminophylline (Ami) reacted with palladium(II) to form chelate cation([Pd(Ami)]2+), which further reacted with fluorescein sodium (FS) to form ternary mixed ligand complex [Pd(Ami)(FS)2]. As a result, resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling scattering spectrum (FDS) were enhanced. The maximum scattering wavelengths of [Pd(Ami)(FS)2] were located at 300 nm (RRS), 650 nm (SOS) and 304 nm (FDS). The scattering intensities were proportional to the Ami concentration in a certain range and the detection limits were 7.3 ng mL(-1) (RRS), 32.9 ng mL(-1) (SOS) and 79.1 ng mL(-1) (FDS), respectively. Based on it, the new simple, rapid, and sensitive scattering methods have been proposed to determine Ami in urine and serum samples. Moreover, the formation mechanism of [Pd(Ami)(FS)2] and the reasons for enhancement of RRS were fully discussed. Crown Copyright © 2010. Published by Elsevier B.V. All rights reserved.

Nonlinear theory of the narrow-band generation and detection of terahertz radiation in resonant tunneling heterostructures

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

Kapaev, V. V., E-mail: kapaev@lebedev.ru

The nonlinear regime of high-frequency response for resonant tunneling structures in a time-periodic electric field has been investigated using a technique for solving the time-dependent Schrödinger equation based on a Floquet mode expansion of the wave functions. The dependences of current harmonic amplitudes on ac signal amplitude have been calculated and the limiting values of the generated field have been determined for singleand double-well resonant tunneling structures. The dynamic Stark effect is shown to play an important role in the formation of response. It leads to a quadratic (in ac field amplitude) shift in the positions of resonances E{sub r}more » in single-well structures and in double-well ones in the nonresonant case and to a splitting at resonance hν ≈ E{sub r2}–E{sub r1} (ν is the signal frequency, E{sub r1} and E{sub r2} are the energies of the size-quantization levels) in double-well structures proportional to the ac signal amplitude. The phenomenon of ac signal detection by resonant tunneling structures has been investigated. The effect of resonant direct-current amplification in double-well structures has been detected at a signal frequency satisfying the condition hν ≈ E{sub r2}–E{sub r1}. In asymmetric systems, detection is shown to be possible in the absence of a dc bias, which allows zero-biased detectors based on them to be created.« less

Spatial filtering velocimeter for vehicle navigation with extended measurement range

NASA Astrophysics Data System (ADS)

He, Xin; Zhou, Jian; Nie, Xiaoming; Long, Xingwu

2015-05-01

The idea of using spatial filtering velocimeter is proposed to provide accurate velocity information for vehicle autonomous navigation system. The presented spatial filtering velocimeter is based on a CMOS linear image sensor. The limited frame rate restricts high speed measurement of the vehicle. To extend measurement range of the velocimeter, a method of frequency shifting is put forward. Theoretical analysis shows that the frequency of output signal can be reduced and the measurement range can be doubled by this method when the shifting direction is set the same with that of image velocity. The approach of fast Fourier transform (FFT) is employed to obtain the power spectra of the spatially filtered signals. Because of limited frequency resolution of FFT, a frequency spectrum correction algorithm, called energy centrobaric correction, is used to improve the frequency resolution. The correction accuracy energy centrobaric correction is analyzed. Experiments are carried out to measure the moving surface of a conveyor belt. The experimental results show that the maximum measurable velocity is about 800deg/s without frequency shifting, 1600deg/s with frequency shifting, when the frame rate of the image is about 8117 Hz. Therefore, the measurement range is doubled by the method of frequency shifting. Furthermore, experiments were carried out to measure the vehicle velocity simultaneously using both the designed SFV and a laser Doppler velocimeter (LDV). The measurement results of the presented SFV are coincident with that of the LDV, but with bigger fluctuation. Therefore, it has the potential of application to vehicular autonomous navigation.

Digital image processing techniques for the analysis of fuel sprays global pattern

NASA Astrophysics Data System (ADS)

Zakaria, Rami; Bryanston-Cross, Peter; Timmerman, Brenda

2017-12-01

We studied the fuel atomization process of two fuel injectors to be fitted in a new small rotary engine design. The aim was to improve the efficiency of the engine by optimizing the fuel injection system. Fuel sprays were visualised by an optical diagnostic system. Images of fuel sprays were produced under various testing conditions, by changing the line pressure, nozzle size, injection frequency, etc. The atomisers were a high-frequency microfluidic dispensing system and a standard low flow-rate fuel injector. A series of image processing procedures were developed in order to acquire information from the laser-scattering images. This paper presents the macroscopic characterisation of Jet fuel (JP8) sprays. We observed the droplet density distribution, tip velocity, and spray-cone angle against line-pressure and nozzle-size. The analysis was performed for low line-pressure (up to 10 bar) and short injection period (1-2 ms). Local velocity components were measured by applying particle image velocimetry (PIV) on double-exposure images. The discharge velocity was lower in the micro dispensing nozzle sprays and the tip penetration slowed down at higher rates compared to the gasoline injector. The PIV test confirmed that the gasoline injector produced sprays with higher velocity elements at the centre and the tip regions.

Hot-electron bolometer terahertz mixers for the Herschel Space Observatory.

PubMed

Cherednichenko, Sergey; Drakinskiy, Vladimir; Berg, Therese; Khosropanah, Pourya; Kollberg, Erik

2008-03-01

We report on low noise terahertz mixers (1.4-1.9 THz) developed for the heterodyne spectrometer onboard the Herschel Space Observatory. The mixers employ double slot antenna integrated superconducting hot-electron bolometers (HEBs) made of thin NbN films. The mixer performance was characterized in terms of detection sensitivity across the entire rf band by using a Fourier transform spectrometer (from 0.5 to 2.5 THz, with 30 GHz resolution) and also by measuring the mixer noise temperature at a limited number of discrete frequencies. The lowest mixer noise temperature recorded was 750 K [double sideband (DSB)] at 1.6 THz and 950 K DSB at 1.9 THz local oscillator (LO) frequencies. Averaged across the intermediate frequency band of 2.4-4.8 GHz, the mixer noise temperature was 1100 K DSB at 1.6 THz and 1450 K DSB at 1.9 THz LO frequencies. The HEB heterodyne receiver stability has been analyzed and compared to the HEB stability in the direct detection mode. The optimal local oscillator power was determined and found to be in a 200-500 nW range.

Estimation of automobile-driver describing function from highway tests using the double steering wheel

NASA Technical Reports Server (NTRS)

Delp, P.; Crossman, E. R. F. W.; Szostak, H.

1972-01-01

The automobile-driver describing function for lateral position control was estimated for three subjects from frequency response analysis of straight road test results. The measurement procedure employed an instrumented full size sedan with known steering response characteristics, and equipped with a lateral lane position measuring device based on video detection of white stripe lane markings. Forcing functions were inserted through a servo driven double steering wheel coupling the driver to the steering system proper. Random appearing, Gaussian, and transient time functions were used. The quasi-linear models fitted to the random appearing input frequency response characterized the driver as compensating for lateral position error in a proportional, derivative, and integral manner. Similar parameters were fitted to the Gabor transformed frequency response of the driver to transient functions. A fourth term corresponding to response to lateral acceleration was determined by matching the time response histories of the model to the experimental results. The time histories show evidence of pulse-like nonlinear behavior during extended response to step transients which appear as high frequency remnant power.

Transmitted spectral modulation of double-ring resonator using liquid crystals in terahertz range

NASA Astrophysics Data System (ADS)

Sun, Huijuan; Zhou, Qingli; Wang, Xiumin; Li, Chenyu; Wu, Ani; Zhang, Cunlin

2013-12-01

Metamaterials with subwavelength structural features show unique electromagnetic responses that are unattainable with natural materials. Recent research on these artificial materials has been pushed forward to the terahertz region because of potential applications in biological fingerprinting, security imaging, remote sensing, and high frequency magnetic and electric resonant devices. Active control of their properties could further facilitate and open up new applications in terms of modulation and switching. Liquid crystals, which have been the subject of research for more than a century, have the unique properties for the development of many other optical components such as light valves, tunable filters and tunable lenses. In this paper, we investigated the transmitted spectral modulation in terahertz range by using liquid crystals (5CB and TEB300) covering on the fabricated double-ring resonators to realize the shift of the resonance frequency. Our obtained results indicate the low frequency resonance shows the obvious blue-shift, while the location of high frequency resonance is nearly unchanged. We believe this phenomenon is related to not only the refractive index of the covering liquid crystals but also the resonant mechanism of both resonances.

Experimental quantification of the true efficiency of carbon nanotube thin-film thermophones.

PubMed

Bouman, Troy M; Barnard, Andrew R; Asgarisabet, Mahsa

2016-03-01

Carbon nanotube thermophones can create acoustic waves from 1 Hz to 100 kHz. The thermoacoustic effect that allows for this non-vibrating sound source is naturally inefficient. Prior efforts have not explored their true efficiency (i.e., the ratio of the total acoustic power to the electrical input power). All previous works have used the ratio of sound pressure to input electrical power. A method for true power efficiency measurement is shown using a fully anechoic technique. True efficiency data are presented for three different drive signal processing techniques: standard alternating current (AC), direct current added to alternating current (DCAC), and amplitude modulation of an alternating current (AMAC) signal. These signal processing techniques are needed to limit the frequency doubling non-linear effects inherent to carbon nanotube thermophones. Each type of processing affects the true efficiency differently. Using a 72 W(rms) input signal, the measured efficiency ranges were 4.3 × 10(-6) - 319 × 10(-6), 1.7 × 10(-6) - 308 × 10(-6), and 1.2 × 10(-6) - 228 × 10(-6)% for AC, DCAC, and AMAC, respectively. These data were measured in the frequency range of 100 Hz to 10 kHz. In addition, the effects of these processing techniques relative to sound quality are presented in terms of total harmonic distortion.

Frequency Variation of the Polarimetric Scattering Mechanisms of Forests and its Consequences on Biomass Estimation using InSAR

NASA Astrophysics Data System (ADS)

Thirion-Lefevre, L.; Guinvarc'h, R.

2016-12-01

InSAR provides forest height estimation that can be used to evaluate the aboveground biomass (AGB). This estimation depends on frequency, polarization and forest structure. If the forest is dense, high frequency gives a good estimation of the AGB whatever the polarization. For other forests, the response is a mix of scattering mechanisms with different phase centers. For instance at P-band, more information can be obtained on the structure thanks to a deeper penetration. However, double bounce mechanism can be strong with its phase center closer to the ground. As a consequence, AGB is underestimated. Quantifying double bounce mechanism can therefore help to assess this estimation. This mechanism can actually be significantly lowered using the Double Brewster Effect (DBE). The latter occurs for a dielectric dihedral and results in a reduced VV component by more than 10 dB for a large angular bandwidth, typically from 20° to 70° (HH is not affected). It consists in two successive Brewster effects, one for the ground, one for the trunk. This DBE is then dependent on the frequency and on the properties of the scatterers (moisture, ground composition, etc). It gives a new light on the interpretation of InSAR height estimation, based on a phenomenology study. We will first quantify this effect on real data at P- and L-bands. We will then present the relation between DBE and the interferometric height using a coherent scattering electromagnetic model previously validated on forests at P- and L-bands. Actually, the interferometric coherence of a forest can be modeled for each polarization by a simple summation of the coherence of the main scattering mechanisms (single and double bounce scattering), weighted by their respective magnitude. Thus, at HH, the resulting height will be determined by the relative weight of the scattering mechanisms. At VV, if DBE is strong, then the interferometric height will depend on the single scattering only.

Comparing Sexual Harassment Subtypes among Black and White Women by Military Rank: Double Jeopardy, the Jezebel, and the Cult of True Womanhood

ERIC Educational Resources Information Center

Buchanan, NiCole T.; Settles, Isis H.; Woods, Krystle C.

2008-01-01

Drawing upon feminist analyses of double jeopardy and the cult of true womanhood, we examine race, rank, sexual harassment frequency, and psychological distress for Black and White female military personnel (N= 7,714). Results indicated that White women reported more overall sexual harassment, gender harassment, and crude behavior, whereas Black…

The double burden household in sub-Saharan Africa: maternal overweight and obesity and childhood undernutrition from the year 2000: results from World Health Organization Data (WHO) and Demographic Health Surveys (DHS).

PubMed

Wojcicki, Janet M

2014-10-31

Previous studies have characterized an increasing trend of double burden households, or households with individuals experiencing both undernutrition and obesity, in countries undergoing a nutrition transition. Although most prior studies indicate the prevalence of double burden households is highest in middle-income countries, there is some support for an increase in double burden households in sub-Saharan African countries as well. Using data from the Demographic Health Surveys (DHS) and the World Health Organization (WHO), the prevalence of double burden households in sub-Saharan African countries was calculated and the associations between prevalence of overweight/obese adults and underweight, stunted and wasted children were evaluated at the country and household (DHS only) levels. Restricted analyses and frequencies were calculated using urban-only datasets. Surveys from 28 African countries were available using WHO data and 26 from the DHS surveys. Only surveys that were conducted after 2000 were included in analyses. Using the WHO datasets, there were inverse associations between the prevalence of overweight and obesity in adults and underweight, stunting and wasting in children. Correspondingly, there were positive associations between adult underweight and child underweight, stunting and wasting. These associations were not significant in a smaller sample size using urban-only surveys. The prevalence of double burden households in DHS datasets was low: under 5 percent for obese mothers and underweight, stunted or wasted child pairs with a slightly higher percentage for overweight mothers and children with undernutrition. Restricting the analysis to urban only populations did not increase the frequencies of double burden households significantly. There was a low prevalence of double burden households in recent data from sub-Saharan Africa. Countries that have a high prevalence of child undernutrition correspondingly have a high prevalence of adult underweight and low prevalence of adult overweight and obesity.

Characteristics of seismic noises excited from three typhoons in the western Pacific

NASA Astrophysics Data System (ADS)

Park, S.; Choi, E.; Hong, T. K.

2017-12-01

Typhoons play an important role in the atmospheric circulation. Strong winds from typhoons excite ocean waves that accompany seismic noises. The primary and double frequency microseisms are dominant in frequencies of 0.05-0.1 Hz and 0.1-0.4 Hz. We investigate the characteristics of seismic noises from three typhoons that include Son-tinh in October 2012, Bopha in November 2012, and Soulik in July 2013. The peak wind speeds were 148-184 km/h, and the central atmospheric pressures reached 925-955 hPa. The typhoons passed through the western Pacific to South China Sea. We analyzed the temporal changes in spectral amplitudes of seismic noises during typhoon periods. The amplitude of seismic noises increases with decreasing distance between typhoon and seismic station. We observe large spectral amplitudes in frequencies of 0.1-0.4 Hz, which corresponds to the dominant frequencies of the double frequency microseism. The seismic energy in the frequency band of the primary frequency microseism was relatively weak. The seismic-noise amplitudes displays high correlation with the equivalent pressures on ocean bottom from Wave Watch III model. The observation suggests that the seismic noises may be originated from the ocean waves. The dominant frequency of seismic noises generally increases after passage across the stations due to the dispersion of ocean waves. Also, the dominant frequencies of seismic noises from the typhoons in the South China Sea appear to be higher than those from the typhoons in the Pacific. This feature may allow us to identify the origin of seismic noises and the nature of typhoons.

Visual and tactile information in double bass intonation control.

PubMed

Lage, Guilherme Menezes; Borém, Fausto; Vieira, Maurílio Nunes; Barreiros, João Pardal

2007-04-01

Traditionally, the teaching of intonation on the non-tempered orchestral strings (violin, viola, cello, and double bass) has resorted to the auditory and proprioceptive senses only. This study aims at understanding the role of visual and tactile information in the control of the non-tempered intonation of the acoustic double bass. Eight musicians played 11 trials of an atonal sequence of musical notes on two double basses of different sizes under different sensorial constraints. The accuracy of the played notes was analyzed by measuring their frequencies and comparing them with respective target values. The main finding was that the performance which integrated visual and tactile information was superior in relation to the other performances in the control of double bass intonation. This contradicts the traditional belief that proprioception and hearing are the most effective feedback information in the performance of stringed instruments.

Simulation of double-pass stimulated Raman backscattering

NASA Astrophysics Data System (ADS)

Wu, Z.; Chen, Q.; Morozov, A.; Suckewer, S.

2018-04-01

Experiments on Stimulated Raman Backscattering (SRBS) in plasma have demonstrated significantly higher energy conversion in a double-pass amplifier where the laser pulses go through the plasma twice compared with a single-pass amplifier with double the plasma length of a single pass. In this paper, the improvement in understanding recent experimental results is presented by considering quite in detail the effects of plasma heating on the modeling of SRBS. Our simulation results show that the low efficiency of single-pass amplifiers can be attributed to Landau damping and the frequency shift of Langmuir waves. In double-pass amplifiers, these issues can be avoided, to some degree, because pump-induced heating could be reduced, while the plasma cools down between the passes. Therefore, double-pass amplifiers yield considerably enhanced energy transfer from the pump to the seed, hence the output pulse intensity.

Microstructure and fatigue resistance of high strength dual phase steel welded with gas metal arc welding and plasma arc welding processes

NASA Astrophysics Data System (ADS)

Ahiale, Godwin Kwame; Oh, Yong-Jun; Choi, Won-Doo; Lee, Kwang-Bok; Jung, Jae-Gyu; Nam, Soo Woo

2013-09-01

This study presents the microstructure and high cycle fatigue performance of lap shear joints of dual phase steel (DP590) welded using gas metal arc welding (GMAW) and plasma arc welding (PAW) processes. High cycle fatigue tests were conducted on single and double lap joints under a load ratio of 0.1 and a frequency of 20 Hz. In order to establish a basis for comparison, both weldments were fabricated to have the same weld depth in the plate thickness. The PAW specimens exhibited a higher fatigue life, a gentle S-N slope, and a higher fatigue limit than the GMAW specimens. The improvement in the fatigue life of the PAW specimens was primarily attributed to the geometry effect that exhibited lower and wider beads resulting in a lower stress concentration at the weld toe where cracks initiate and propagate. Furthermore, the microstructural constituents in the heat-affected zone (HAZ) of the PAW specimens contributed to the improvement. The higher volume fraction of acicular ferrite in the HAZ beneath the weld toe enhanced the PAW specimen's resistance to fatigue crack growth. The double lap joints displayed a higher fatigue life than the single lap joints without changing the S-N slope.

RNA interference by feeding in vitro synthesized double-stranded RNA to planarians: methodology and dynamics

PubMed Central

Rouhana, Labib; Weiss, Jennifer A.; Forsthoefel, David J.; Lee, Hayoung; King, Ryan S.; Inoue, Takeshi; Shibata, Norito; Agata, Kiyokazu; Newmark, Phillip A.

2013-01-01

Background The ability to assess gene function is essential for understanding biological processes. Currently, RNA interference (RNAi) is the only technique available to assess gene function in planarians, in which it has been induced via injection of double-stranded RNA (dsRNA), soaking, or ingestion of bacteria expressing dsRNA. Results We describe a simple and robust RNAi protocol, involving in vitro synthesis of dsRNA that is fed to the planarians. Advantages of this protocol include the ability to produce dsRNA from any vector without subcloning, resolution of ambiguities in quantity and quality of input dsRNA, as well as time, and ease of application. We have evaluated the logistics of inducing RNAi in planarians using this methodology in careful detail, from the ingestion and processing of dsRNA in the intestine, to timing and efficacy of knockdown in neoblasts, germline, and soma. We also present systematic comparisons of effects of amount, frequency, and mode of dsRNA delivery. Conclusions This method gives robust and reproducible results and is amenable to high-throughput studies. Overall, this RNAi methodology provides a significant advance by combining the strengths of current protocols available for dsRNA delivery in planarians and has the potential to benefit RNAi methods in other systems. PMID:23441014

A Two-Color Fourier Transform Mm-Wave Spectrometer for Gas Analysis Operating from 260-295 GHZ

NASA Astrophysics Data System (ADS)

Steber, Amanda L.; Harris, Brent J.; Lehmann, Kevin K.; Pate, Brooks H.

2013-06-01

We have designed a two-color mm-wave spectrometer for Fourier transform mm-wave spectroscopy that uses consumer level components for the tunable synthesizers, digital control of the pulse modulators, and digitization of the coherent free induction decay (FID). The excitation pulses are generated using an x24 active multiplier chain (AMC) that produces a peak power of 30 mW. The microwave input to the AMC is generated in a frequency up conversion circuit that accepts a microwave input frequency from about 2-4 GHz. This circuit also generates the input to the mm-wave subhamonic mixer that creates the local oscillator from a separate 2-4 GHz microwave input. Excitation pulses at two independently tunable frequencies are generated using a dual-channel source based on a low-cost, wideband synthesizer integrated circuit (Valon Technology Model 5008). The outputs of the synthesizer are pulse modulated using a PIN diode switch that is driven using the arbitrary waveform generator (AWG) output of a USB-controlled high-speed digitizer / arbitrary waveform generator combination unit (Tie Pie HS-5 530 XM). The two pulses are combined using a Wilkinson power divider before input to the up conversion circuit. The FID frequency is down converted in a two-stage mixing process to 65 MHz. The two LO frequencies used in the receiver are provided by a second Valon 5008. The FID is digitized at 200 MSamples/s using the 12-bit Tie Pie digitizer. The digital oscilloscope (and its AWG channel) and the two synthesizers use a 10 MHz reference signal from a Rubidium clock to permit time-domain signal averaging. A key feature of the digital oscilloscope is its deep memory of 32 Mpts (complemented by the 64 Mpt memory in the 240 MS/s AWG). This makes it possible to perform several one- and two-color coherent measurements, including pulse echoes and double-resonance spectroscopy, in a single "readout" experiment to speed the analysis of mm-wave rotational spectra. The spectrometer sensitivity and frequency accuracy are illustrated by high-speed measurements of OCS rotational transitions for low-abundance isotopes. Examples of pulse echo measurements to determine the collisional relaxation rate and two-color double-resonance measurements to confirm the presence of a molecular species will be illustrated using OCS as the room-temperature gas sample.

Anomalous visual experiences, negative symptoms, perceptual organization and the magnocellular pathway in schizophrenia: a shared construct?

PubMed

Kéri, Szabolcs; Kiss, Imre; Kelemen, Oguz; Benedek, György; Janka, Zoltán

2005-10-01

Schizophrenia is associated with impaired visual information processing. The aim of this study was to investigate the relationship between anomalous perceptual experiences, positive and negative symptoms, perceptual organization, rapid categorization of natural images and magnocellular (M) and parvocellular (P) visual pathway functioning. Thirty-five unmedicated patients with schizophrenia and 20 matched healthy control volunteers participated. Anomalous perceptual experiences were assessed with the Bonn Scale for the Assessment Basic Symptoms (BSABS). General intellectual functions were evaluated with the revised version of the Wechsler Adult Intelligence Scale. The 1-9 version of the Continuous Performance Test (CPT) was used to investigate sustained attention. The following psychophysical tests were used: detection of Gabor patches with collinear and orthogonal flankers (perceptual organization), categorization of briefly presented natural scenes (rapid visual processing), low-contrast and frequency-doubling vernier threshold (M pathway functioning), isoluminant colour vernier threshold and high spatial frequency discrimination (P pathway functioning). The patients with schizophrenia were impaired on test of perceptual organization, rapid visual processing and M pathway functioning. There was a significant correlation between BSABS scores, negative symptoms, perceptual organization, rapid visual processing and M pathway functioning. Positive symptoms, IQ, CPT and P pathway measures did not correlate with these parameters. The best predictor of the BSABS score was the perceptual organization deficit. These results raise the possibility that multiple facets of visual information processing deficits can be explained by M pathway dysfunctions in schizophrenia, resulting in impaired attentional modulation of perceptual organization and of natural image categorization.

Improved Electrochemical Cycling Durability in a Nickel Oxide Double-Layered Film.

PubMed

Hou, Shuai; Zhang, Xiang; Tian, Yanlong; Zhao, Jiupeng; Geng, Hongbin; Qu, Huiying; Zhang, Hangchuan; Zhang, Kun; Wang, Binsheng; Gavrilyuk, Alexander; Li, Yao

2017-11-16

For the first time, a crystalline-amorphous double-layered NiO x film has been prepared by reactive radio frequency magnetron sputtering. This film has exhibited improved electrochemical cycling durability, whereas other electrochromic parameters have been maintained at the required level, namely, a short coloration/bleaching time (0.8 s/1.1 s) and an enhanced transmittance modulation range (62.2 %) at λ=550 nm. Additionally, the double-layered film has shown better reversibility than that of amorphous and crystalline single-layered films. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dynamic modelling of a double-pendulum gantry crane system incorporating payload

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

Ismail, R. M. T. Raja; Ahmad, M. A.; Ramli, M. S.

The natural sway of crane payloads is detrimental to safe and efficient operation. Under certain conditions, the problem is complicated when the payloads create a double pendulum effect. This paper presents dynamic modelling of a double-pendulum gantry crane system based on closed-form equations of motion. The Lagrangian method is used to derive the dynamic model of the system. A dynamic model of the system incorporating payload is developed and the effects of payload on the response of the system are discussed. Extensive results that validate the theoretical derivation are presented in the time and frequency domains.

Overlapping double potential wells in a single optical microtube cavity with vernier-scale-like tuning effect

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

Madani, A.; Schmidt, O. G.; Material Systems for Nanoelectronics, Chemnitz University of Technology, Reichenhainer Str. 70, 09107 Chemnitz

2016-04-25

Spatially and temporally overlapping double potential wells are realized in a hybrid optical microtube cavity due to the coexistence of an aggregate of luminescent quantum dots embedded in the tube wall and the cone-shaped tube's geometry. The double potential wells produce two independent sets of optical modes with different sets of mode numbers, indicating phase velocity separation for the modes overlapping at the same frequency. The overlapping mode position can be tuned by modifying the tube cavity, where these mode sets shift with different magnitudes, allowing for a vernier-scale-like tuning effect.

Detection of internal fields in double-metal terahertz resonators

DOE PAGES

Mitrofanov, Oleg; Han, Zhanghua; Ding, Fei; ...

2017-02-06

(THz) plasmonic double-metal resonators enable enhanced light-matter coupling by utilizing strong localization of the resonant field. The closed resonator design however restricts investigations of the light-matter interaction effects. We propose and demonstrate a method for spatial mapping and spectroscopic analysis of the internal resonant THz fields in plasmonic double-metal THz resonators. We use the aperture-type scanning near-field THz time-domain microscopy and the concept of image charges to probe the THz fields confined within the resonator. The experimental method opens doors to studies of light-matter coupling in deeply sub-wavelength volumes at THz frequencies.

Dynamic near-field optical interaction between oscillating nanomechanical structures

DOE PAGES

Ahn, Phillip; Chen, Xiang; Zhang, Zhen; ...

2015-05-27

Near-field optical techniques exploit light-matter interactions at small length scales for mechanical sensing and actuation of nanomechanical structures. Here, we study the optical interaction between two mechanical oscillators—a plasmonic nanofocusing probe-tip supported by a low frequency cantilever, and a high frequency nanomechanical resonator—and leverage their interaction for local detection of mechanical vibrations. The plasmonic nanofocusing probe provides a confined optical source to enhance the interaction between the two oscillators. Dynamic perturbation of the optical cavity between the probe-tip and the resonator leads to nonlinear modulation of the scattered light intensity at the sum and difference of their frequencies. This double-frequencymore » demodulation scheme is explored to suppress unwanted background and to detect mechanical vibrations with a minimum detectable displacement sensitivity of 0.45pm/Hz 1/2, which is limited by shot noise and electrical noise. We explore the demodulation scheme for imaging the bending vibration mode shape of the resonator with a lateral spatial resolution of 20nm. We also demonstrate the time-resolved aspect of the local optical interaction by recording the ring-down vibrations of the resonator at frequencies of up to 129MHz. The near-field optical technique is promising for studying dynamic mechanical processes in individual nanostructures.« less

Compact intra-cavity frequency doubled line beam green laser by a laser diode array pumped

NASA Astrophysics Data System (ADS)

Yan, Boxia; Qi, Yan; Wang, Yanwei

2016-10-01

Compact, high power, and low-cost green laser light sources are needed in projection-related applications such as digital cinema, rear-projection television, simulators, and command and control stations. We report a LD array directly pumped intracavity SHG Nd:YVO4/PPMgLN laser without lens or waveguide in this letter. A compact 3.12 W green laser was demonstrated by intra-cavity frequency doubled using a PPMgLN bulk crystal by a 19-emitter LD array pumped(single bar), the conversion efficiency from input LD array was 9.2%. A line-beam output suitable for laser projectors was generated, which has the potential to be scalable to small volumes and low costs for laser projection displays.

Analog of electromagnetically induced transparency at terahertz frequency based on a bilayer-double-H-metamaterial

NASA Astrophysics Data System (ADS)

Wang, Yue'e.; Li, Zhi; Hu, Fangrong

2018-01-01

We designed a bilayer-double-H-metamaterials (BDHM) composed of two layers of metal and two layers of dielectric to analog a spectral response of electromagnetically induced transparency (EIT) at terahertz frequency. By changing the incident angle, the BDHM exhibits an EIT-like spectral response. The tunable spectral performances and modulation mechanism of the transparent peak are theoretically investigated using full-wave electromagnetic simulation software. The physical mechanism of the EIT-like effect is based on the constructive and destructive interference between the induced electrical dipoles. Our work provides a new way to realize the EIT-like effect only by changing the incident angles of the metamaterials. The potential applications include tunable filters, sensors, attenuators, switches, and so on.

Continuous-wave ultraviolet generation at 320 nm by intracavity frequency doubling of red-emitting Praseodymium lasers

NASA Astrophysics Data System (ADS)

Richter, A.; Pavel, N.; Heumann, E.; Huber, G.; Parisi, D.; Toncelli, A.; Tonelli, M.; Diening, A.; Seelert, W.

2006-04-01

We describe a new approach for the generation of coherent ultraviolet radiation. Continuous-wave ultraviolet light at 320 nm has been obtained by intracavity frequency doubling of red-emitting Praseodymium lasers. Lasing at the 640-nm fundamental wavelength in Pr:LiYF4 and Pr:BaY2F8 was realized by employing an optically pumped semiconductor laser at 480 nm as pump source.Using LiB3O5 as nonlinear medium, ~19 mW of ultraviolet radiation with ~9% optical efficiency with respect to absorbed power was reached for both laser crystals; the visible-to-ultraviolet conversion efficiency was 26% and 35% for Pr:LiYF4 and Pr:BaY2F8, respectively.

Visualization of vortex structures and analysis of frequency of PVC

NASA Astrophysics Data System (ADS)

Gesheva, E. S.; Shtork, S. I.; Alekseenko, S. V.

2018-03-01

The paper presents the results of the study of large-scale vortex structures in a model chamber. Methods of forming quasi-stationary vortices of various shapes by changing the geometric parameters of the chamber have been proposed. In the model chamber with a tangential swirl of the flow, a rectilinear vortex, single helical and double helical vortices were obtained. The double helical structure of the vortex is unique due to its immovability around the axis of the chamber. The resulting structures slowly oscillate around their own axes, which is called the vortex core precession; while the oscillation frequency depends linearly on the liquid flow rate. The use of stationary vortex structures in power plants will increase the efficiency of combustion chambers and reduce slagging.

Phonon self-energy corrections to non-zero wavevector phonon modes in single-layer graphene

NASA Astrophysics Data System (ADS)

Araujo, Paulo; Mafra, Daniela; Sato, Kentaro; Saito, Richiiro; Kong, Jing; Dresselhaus, Mildred

2012-02-01

Phonon self-energy corrections have mostly been studied theoretically and experimentally for phonon modes with zone-center (q = 0) wave-vectors. Here, gate-modulated Raman scattering is used to study phonons of a single layer of graphene (1LG) in the frequency range from 2350 to 2750 cm-1, which shows the G* and the G'-band features originating from a double-resonant Raman process with q 0. The observed phonon renormalization effects are different from what is observed for the zone-center q = 0 case. To explain our experimental findings, we explored the phonon self-energy for the phonons with non-zero wave-vectors (q 0) in 1LG in which the frequencies and decay widths are expected to behave oppositely to the behavior observed in the corresponding zone-center q = 0 processes. Within this framework, we resolve the identification of the phonon modes contributing to the G* Raman feature at 2450 cm-1 to include the iTO+LA combination modes with q 0 and the 2iTO overtone modes with q = 0, showing both to be associated with wave-vectors near the high symmetry point K in the Brillouin zone.

Coupling Ocean Models and Satellite Derived Optical Fields to Estimate LIDAR Penetration and Detection Performance

DTIC Science & Technology

2012-01-01

34Laser oscillations in nd-doped yttrium aluminum , yttrium gallium and gadolinium garnets ," Applied Physics Letters (10): 182. doi:10.1063/1.1753928...Aluminium Garnet ) Nd:YAG lasers, and inherent of this material is its fundamental 1064nm frequency that is frequency doubled to 532 nm to penetrate

Double ionization in R -matrix theory using a two-electron outer region

NASA Astrophysics Data System (ADS)

Wragg, Jack; Parker, J. S.; van der Hart, H. W.

2015-08-01

We have developed a two-electron outer region for use within R -matrix theory to describe double ionization processes. The capability of this method is demonstrated for single-photon double ionization of He in the photon energy region between 80 and 180 eV. The cross sections are in agreement with established data. The extended R -matrix with time dependence method also provides information on higher-order processes, as demonstrated by the identification of signatures for sequential double ionization processes involving an intermediate He+ state with n =2 .

Oscillations up to 712 GHz in InAs/AlSb resonant-tunneling diodes

NASA Technical Reports Server (NTRS)

Brown, E. R.; Parker, C. D.; Mahoney, L. J.; Molvar, K. M.; Soderstrom, J. R.

1991-01-01

Oscillations have been obtained at frequencies from 100 to 712 GHz in InAs/AlSb double-barrier resonant-tunneling diodes at room temperature. The measured power density at 360 GHz was 90 W/sq cm, which is 50 times that generated by GaAs/AlAs diodes at essentially the same frequency. The oscillation at 712 GHz represents the highest frequency reported to date from a solid-state electronic oscillator at room temperature.

Ordering of the O-O stretching vibrational frequencies in ozone

NASA Technical Reports Server (NTRS)

Scuseria, Gustavo E.; Lee, Timothy J.; Scheiner, Andrew C.; Schaefer, Henry F., III

1989-01-01

The ordering of nu1 and nu3 for O3 is incorrectly predicted by most theoretical methods, including some very high level methods. The first systematic electron correlation method based on one-reference configuration to solve this problem is the coupled cluster single and double excitation method. However, a relatively large basis set, triple zeta plus double polarization is required. Comparison with other theoretical methods is made.

Effectiveness evaluation of double-layered satellite network with laser and microwave hybrid links based on fuzzy analytic hierarchy process

NASA Astrophysics Data System (ADS)

Zhang, Wei; Rao, Qiaomeng

2018-01-01

In order to solve the problem of high speed, large capacity and limited spectrum resources of satellite communication network, a double-layered satellite network with global seamless coverage based on laser and microwave hybrid links is proposed in this paper. By analyzing the characteristics of the double-layered satellite network with laser and microwave hybrid links, an effectiveness evaluation index system for the network is established. And then, the fuzzy analytic hierarchy process, which combines the analytic hierarchy process and the fuzzy comprehensive evaluation theory, is used to evaluate the effectiveness of the double-layered satellite network with laser and microwave hybrid links. Furthermore, the evaluation result of the proposed hybrid link network is obtained by simulation. The effectiveness evaluation process of the proposed double-layered satellite network with laser and microwave hybrid links can help to optimize the design of hybrid link double-layered satellite network and improve the operating efficiency of the satellite system.

A double-inverted pendulum model for studying the adaptability of postural control to frequency during human stepping in place.

PubMed

Breniere, Y; Ribreau, C

1998-10-01

In order to analyze the influence of gravity and body characteristics on the control of center of mass (CM) oscillations in stepping in place, equations of motion in oscillating systems were developed using a double-inverted pendulum model which accounts for both the head-arms-trunk (HAT) segment and the two-legged system. The principal goal of this work is to propose an equivalent model which makes use of the usual anthropometric data for the human body, in order to study the ability of postural control to adapt to the step frequency in this particular paradigm of human gait. This model allows the computation of CM-to-CP amplitude ratios, when the center of foot pressure (CP) oscillates, as a parametric function of the stepping in place frequency, whose parameters are gravity and major body characteristics. Motion analysis from a force plate was used to test the model by comparing experimental and simulated values of variations of the CM-to-CP amplitude ratio in the frontal plane versus the frequency. With data from the literature, the model is used to calculate the intersegmental torque which stabilizes the HAT when the Leg segment is subjected to a harmonic torque with an imposed frequency.

A double-panel active segmented partition module using decoupled analog feedback controllers: numerical model.

PubMed

Sagers, Jason D; Leishman, Timothy W; Blotter, Jonathan D

2009-06-01

Low-frequency sound transmission has long plagued the sound isolation performance of lightweight partitions. Over the past 2 decades, researchers have investigated actively controlled structures to prevent sound transmission from a source space into a receiving space. An approach using active segmented partitions (ASPs) seeks to improve low-frequency sound isolation capabilities. An ASP is a partition which has been mechanically and acoustically segmented into a number of small individually controlled modules. This paper provides a theoretical and numerical development of a single ASP module configuration, wherein each panel of the double-panel structure is independently actuated and controlled by an analog feedback controller. A numerical model is developed to estimate frequency response functions for the purpose of controller design, to understand the effects of acoustic coupling between the panels, to predict the transmission loss of the module in both passive and active states, and to demonstrate that the proposed ASP module will produce bidirectional sound isolation.

Sound transmission through a double-panel construction lined with poroelastic material in the presence of mean flow

NASA Astrophysics Data System (ADS)

Zhou, Jie; Bhaskar, Atul; Zhang, Xin

2013-08-01

This paper investigates the sound transmission characteristics through a system of double-panel lined with poroelastic material in the core. The panels are surrounded by external and internal fluid media where a uniform external mean flow exists on one side. Biot's theory is used to model the porous material. Three types of constructions—bonded-bonded, bonded-unbonded and unbonded-unbonded—are considered. The effect of Mach number of the external flow on the sound transmission over a wide frequency range in a diffuse sound field is examined. External mean flow is shown to give a modest increase in transmission loss at low frequency, but a significant increase at high frequency. It is brought out that calculations based on static air on the incidence side provide a conservative estimate of sound transmission through the sandwich structure. The acoustic performance of the sandwich panel for different configurations is presented. The effect of curvature of the panel is also brought out by using shallow shell theory.

Harmonic Generation in InAs Nanowire Double Quantum Dots

NASA Astrophysics Data System (ADS)

Schroer, M. D.; Jung, M.; Petersson, K. D.; Petta, J. R.

2012-02-01

InAs nanowires provide a useful platform for investigating the physics of confined electrons subjected to strong spin-orbit coupling. Using tunable, bottom-gated double quantum dots, we demonstrate electrical driving of single spin resonance.ootnotetextS. Nadj-Perge et al., Nature 468, 1084 (2010)^,ootnotetextM.D. Schroer et al., Phys. Rev. Lett. 107, 176811 (2011) We observe a standard spin response when the applied microwave frequency equals the Larmour frequency f0. However, we also observe an anomalous signal at frequencies fn= f0/ n for integer n up to n ˜5. This is equivalent to generation of harmonics of the spin resonance field. While a f0/2 signal has observed,ootnotetextE.A. Laird et al., Phys. Rev. Lett. 99, 246601 (2007) we believe this is the first observation of higher harmonics in spin resonance. Possible mechanisms will be discussed.ootnotetextE.I. Rashba, arXiv:1110.6569 (2011) Acknowledgements: Research supported by the Sloan and Packard Foundations, the NSF, and Army Research Office.

Somatic cell mutations at the glycophorin A locus in erythrocytes of atomic bomb survivors: Implications for radiation carcinogenesis

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

Kyoizumi, Seishi; Akiyama, Mitoshi; Tanabe, Kazumi

To clarify the relationship between somatic cell mutations and radiation exposure, the frequency of hemizygous mutant erythrocytes at the glycophorin A (GPA) locus was measured by flow cytometry for 1,226 heterozygous atomic bomb (A-bomb) survivors in HIroshima and Nagasaki. For statistical analysis, both GPA mutant frequency and radiation dose were log-transformed to normalize skewed distributions of these variables. The GPA mutant frequency increased slightly but significantly with age at testing and with the number of cigarettes smoked. Also, mutant frequency was significantly higher in males than in females even with adjustment for smoking and was higher to Hiroshima than inmore » Nagasaki. These characteristics of background GPA mutant frequency are qualitatively similar to those of background solid cancer incidence or mortality obtained from previous epidemiological studies of survivors. An analysis of the mutant frequency dose response using a descriptive model showed that the doubling dose is about 1.20 Sv [95% confidence interval (CI): 0.95-1.56], whereas the minimum dose for detecting a significant increase in mutant frequency is about 0.24 Sv (95% CI: 0.041-0.51). No significant effects of sex, city or age at the time of exposure on the dose response were detected. Interestingly, the doubling dose of the GPA mutant frequency was similar to that of solid cancer incidence in A-bomb survivors. This observation is in line with the hypothesis that radiation-induced somatic cell mutations are the major cause of excess cancer risk after radiation. 49 refs., 6 figs., 2 tabs.« less

A double tuned rail damper—increased damping at the two first pinned-pinned frequencies

NASA Astrophysics Data System (ADS)

Maes, J.; Sol, H.

2003-10-01

Railway-induced vibrations are a growing matter of environmental concern. The rapid development of transportation, the increase of vehicle speeds and vehicle weights have resulted in higher vibration levels. In the meantime vibrations that were tolerated in the past are now considered to be a nuisance. Numerous solutions have been proposed to remedy these problems. The majority only acts on a specific part of the dynamic behaviour of the track. This paper presents a possible solution to reduce the noise generated by the 'pinned-pinned' frequencies. Pinned-pinned frequencies correspond with standing waves whose nodes are positioned exactly at the sleeper supports. The two first pinned-pinned frequencies are situated approximately at 950 and 2200 Hz (UIC60-rail and sleeper spacing of 0.60 m). To attenuate these vibrations, the Department of MEMC at the VUB has developed a dynamic vibration absorber called the Double Tuned Rail Damper (DTRD). The DTRD is mounted between two sleepers on the rail and is powered by the motion of the rail. The DTRD consists of two major parts: a steel plate which is connected to the rail with an interface of an elastic layer, and a rubber mass. The two first resonance frequencies of the steel plate coincide with the targeted pinned-pinned frequencies of the rail. The rubber mass acts as a motion controller and energy absorber. Measurements at a test track of the French railway company (SNCF) have shown considerable attenuation of the envisaged pinned-pinned frequencies. The attenuation rate surpasses 5 dB/m at certain frequency bands.

Cytogenetic studies of mice chronically fed carcinogens

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

Director, A.E.; Ramsey, M.J.; Tucker, J.D.

1997-10-01

Over the past few years, we have carried out chronic feeding studies in C57BL/6 female mice. These experiments examined the effect of the chronic ingestion of a single chemical carcinogen on chromosomes. The carcinogens studied were PhIP,MeIQx, cyclophosphamide and urethane. These studies used traditional assays, such as SCEs and MN, as well as chromosome painting. In all four cases, the traditional assays showed an increase in the frequency of lesions, demonstrating that the chemicals, and/or their reactive metabolites, reached the target nuclei. This, however, seemed at odds with the data obtained from chromosome painting, which did not show an increasemore » in the frequency of stable chromosome aberrations. This discrepancy between traditional assays and chromosome painting may be due to the nature of the lesions that each assay identifies. The traditional assays tend to identify lesions on the chromatid level, where as chromosome painting identifies lesions on the chromosome level requires two or more DNA double strand breaks occurring proximally in both time and space. In other words, for exposure to a chemical carcinogen to induce an increase in chromosome aberrations as measured by chromosome painting, the chemical, or its metabolites, would have to cause a large number of double strand breaks. By applying this logic to the data obtained from the four chronic feeding studies, one can infer that the chronic ingestion of chemical carcinogens does not result in the frequent formation of double strand breaks and therefore, does not result in the frequent formation of double strand breaks and therefore, does not result in increased frequencies of stable chromosome aberrations. We must, therefore, look elsewhere for the mechanism(s) underlying carcinogenesis due to chronic exposure to chemical carcinogens.« less

Laboratory observation of multiple double layer resembling space plasma double layer

NASA Astrophysics Data System (ADS)

Alex, Prince; Arumugam, Saravanan; Sinha, Suraj

2017-10-01

Perceptible double layer consisting of more than one layers were produced in laboratory using a double discharge plasma setup. The confinement of oppositely charged particles in each layer with sharply defined luminous boarder is attributed to the self-organization scenario. This structure is generated in front of a positively biased electrode when the electron drift velocity (νd) exceeds 1.3 times the electron thermal velocity (νte) . Stable multiple double layer structures were observed only between 1.3 νte <=νd <= 3 νte. At νd = 1.3 νte, oscillations were excited in the form of large amplitude burst followed by a high frequency stable oscillation. Beyond νd = 3 νte, multiple double layer begins to collapse which is characterized by an emergence in turbulence. Long range dependence in the corresponding electrostatic potential fluctuations indicates the role of self-organized criticality in the emergence of turbulence. The algebraic decaying tale of the autocorrelation function and power law behavior in the power spectrum are consistent with the observation.

The nature of pulsar radio emission

NASA Astrophysics Data System (ADS)

Dyks, J.; Rudak, B.; Demorest, P.

2010-01-01

High-quality averaged radio profiles of some pulsars exhibit double, highly symmetric features both in emission and in absorption. It is shown that both types of feature are produced by a split fan beam of extraordinary-mode curvature radiation that is emitted/absorbed by radially extended streams of magnetospheric plasma. With no emissivity in the plane of the stream, such a beam produces bifurcated emission components (BFCs) when our line of sight passes through the plane. An example of a double component created in this way is present in the averaged profile of the 5-ms pulsar J1012+5307. We show that the component can indeed be very well fitted by the textbook formula for the non-coherent beam of curvature radiation in the polarization state that is orthogonal to the plane of electron trajectory. The observed width of the BFC decreases with increasing frequency at a rate that confirms the curvature origin. Likewise, the double absorption features (double notches) are produced by the same beam of the extraordinary-mode curvature radiation, when it is eclipsed by thin plasma streams. The intrinsic property of curvature radiation to create bifurcated fan beams explains the double features in terms of a very natural geometry and implies the curvature origin of pulsar radio emission. Similarly, the `double conal' profiles of class D result from a cut through a wider stream with finite extent in magnetic azimuth. Therefore, their width reacts very slowly to changes of viewing geometry resulting from geodetic precession. The stream-cut interpretation implies a highly non-orthodox origin of both the famous S-swing of polarization angle and the low-frequency pulse broadening in D profiles. The azimuthal structure of polarization modes in the curvature radiation beam provides an explanation for the polarized `multiple imaging' and the edge depolarization of pulsar profiles.

Optimization of A 2-Micron Laser Frequency Stabilization System for a Double-Pulse CO2 Differential Absorption Lidar

NASA Technical Reports Server (NTRS)

Chen, Songsheng; Yu, Jirong; Bai, Yingsin; Koch, Grady; Petros, Mulugeta; Trieu, Bo; Petzar, Paul; Singh, Upendra N.; Kavaya, Michael J.; Beyon, Jeffrey

2010-01-01

A carbon dioxide (CO2) Differential Absorption Lidar (DIAL) for accurate CO2 concentration measurement requires a frequency locking system to achieve high frequency locking precision and stability. We describe the frequency locking system utilizing Frequency Modulation (FM), Phase Sensitive Detection (PSD), and Proportional Integration Derivative (PID) feedback servo loop, and report the optimization of the sensitivity of the system for the feed back loop based on the characteristics of a variable path-length CO2 gas cell. The CO2 gas cell is characterized with HITRAN database (2004). The method can be applied for any other frequency locking systems referring to gas absorption line.

Single-sideband modulator for frequency domain multiplexing of superconducting qubit readout

NASA Astrophysics Data System (ADS)

Chapman, Benjamin J.; Rosenthal, Eric I.; Kerckhoff, Joseph; Vale, Leila R.; Hilton, Gene C.; Lehnert, K. W.

2017-04-01

We introduce and experimentally characterize a superconducting single-sideband modulator compatible with cryogenic microwave circuits and propose its use for frequency domain multiplexing of superconducting qubit readout. The monolithic double-balanced modulators that comprise the device are formed with purely reactive elements (capacitors and Josephson junction inductors) and require no microwave-frequency control tones. Microwave signals in the 4 to 8 GHz band, with power up to -85 dBm, are converted up or down in frequency by as much as 120 MHz. Spurious harmonics in the device can be suppressed by up to 25 dB for select probe and modulation frequencies.

Red laser based on intra-cavity Nd:YAG/CH4 frequency doubled Raman lasers

NASA Astrophysics Data System (ADS)

Wang, Yanchao; Wang, Pengyuan; Liu, Jinbo; Liu, Wanfa; Guo, Jingwei

2017-01-01

Stimulated Raman scattering (SRS) is a powerful tool for the extension of the spectral range of lasers. To obtain efficient Raman conversion in SRS, many researchers have studied different types of Raman laser configurations. Among these configurations, the intra-cavity type is particularly attractive. Intra-cavity SRS has the advantages of high intra-cavity laser intensity, low-SRS threshold, and high Raman conversion efficiency. In this paper, An Q-switched intra-cavity Nd: YAG/CH4 frequency-doubled Raman lasers is reported. A negative branch confocal resonator with M= 1.25 is used for the frequency-doubling of Nd: YAG laser. The consequent 532nm light is confined in intra- cavity SRS with travelling wave resonator, and the focal of one mirror of cavity is overlap with the center of the other mirror of the cavity. We found this design is especially efficient to reduce the threshold of SRS, and increase conversion efficiency. The threshold is measured to be 0.62 MW, and at the pump energy of 16.1 mJ, the conversion efficiency is 34%. With the smaller magnification M, the threshold could further decrease, and the conversion efficiency could be improved further. This is a successful try to extend the spectral range of a laser to the shorter wavelength by SRS, and this design may play an important role in the fulfillment of high power red lasers.

Trans-Lesion DNA Polymerases May Be Involved in Yeast Meiosis

PubMed Central

Arbel-Eden, Ayelet; Joseph-Strauss, Daphna; Masika, Hagit; Printzental, Oxana; Rachi, Eléanor; Simchen, Giora

2013-01-01

Trans-lesion DNA polymerases (TLSPs) enable bypass of DNA lesions during replication and are also induced under stress conditions. Being only weakly dependent on their template during replication, TLSPs introduce mutations into DNA. The low processivity of these enzymes ensures that they fall off their template after a few bases are synthesized and are then replaced by the more accurate replicative polymerase. We find that the three TLSPs of budding yeast Saccharomyces cerevisiae Rev1, PolZeta (Rev3 and Rev7), and Rad30 are induced during meiosis at a time when DNA double-strand breaks (DSBs) are formed and homologous chromosomes recombine. Strains deleted for one or any combination of the three TLSPs undergo normal meiosis. However, in the triple-deletion mutant, there is a reduction in both allelic and ectopic recombination. We suggest that trans-lesion polymerases are involved in the processing of meiotic double-strand breaks that lead to mutations. In support of this notion, we report significant yeast two-hybrid (Y2H) associations in meiosis-arrested cells between the TLSPs and DSB proteins Rev1-Spo11, Rev1-Mei4, and Rev7-Rec114, as well as between Rev1 and Rad30. We suggest that the involvement of TLSPs in processing of meiotic DSBs could be responsible for the considerably higher frequency of mutations reported during meiosis compared with that found in mitotically dividing cells, and therefore may contribute to faster evolutionary divergence than previously assumed. PMID:23550131

Effective removal of equine arteritis virus from stallion semen.

PubMed

Morrell, J M; Geraghty, R M

2006-05-01

A method of removing equine arteritis virus (EAV) from equine semen used for artificial insemination is urgently needed. Recent medical studies suggest that a double semen processing technique of density gradient centrifugation followed by a 'swim-up' can provide virus-free sperm preparations for assisted reproduction. To investigate the use of the double semen processing technique to obtain virus-free sperm preparations from stallion semen containing EAV. Aliquots of an ejaculate from an uninfected stallion were spiked with virus and processed by the double processing technique. The sperm preparations were tested by PCR for the presence of EAV. The procedure was repeated using an ejaculate from a known shedding stallion, testing processed and unprocessed aliquots by PCR and virus isolation. Virus-free sperm preparations were obtained using the double sperm processing technique. The 'swim-up' step is apparently required to ensure complete virus removal. The double semen processing technique is potentially a useful and simple tool for the removal of EAV from the semen of shedding stallions. The inclusion of density gradient centrifugation and 'swim-up' in protocols for the processing of semen for artificial insemination could help prevent the transmission of viral diseases carried in semen, such as EAV.

Experimental observation and determination of the laser-induced frequency shift of hyperfine levels of ultracold polar molecules

NASA Astrophysics Data System (ADS)

Liu, Wenliang; Wang, Xiaofeng; Wu, Jizhou; Su, Xingliang; Wang, Shen; Sovkov, Vladimir B.; Ma, Jie; Xiao, Liantuan; Jia, Suotang

2017-08-01

We report on the experimental observation and quantitative determination of the laser-induced frequency shift (LIFS) of the ultracold polar molecules formed by photoassociation (PA). The experiments are performed by detecting a series of double PA spectra with a molecular hyperfine structure, which are induced by two PA lasers with a precise and adjustable frequency reference. We find that the LIFS of the molecular hyperfine levels shows a linear dependence on PA laser intensity.

Power Scaling and Frequency Stabilization of an Injection-Locked Laser

DTIC Science & Technology

2000-05-01

In Chapter 4,1 alter the well -documented theory of locking a laser to a Fabry- Perot by performing the PDH error signal derivation in a new manner...the well -documented modulation transfer scheme to lock the frequency-doubled NPRO to a hyperfine component of an electronic transition in I2. 33 I...generally true at very low noise frequencies, well within the feedback loop bandwidth. However, when G0L(V„) « 1 and thus GCL(vn) « 1, Equation 3.9

Single reflector interference spectrometer and drive system therefor

NASA Technical Reports Server (NTRS)

Schindler, R. A. (Inventor)

1974-01-01

In a Fourier interference spectrometer of the doublepass retroreflector type, a single mirror is employed in the path of both split beams of an incoming ray to cause them to double back through separate retroreflectors. Changes in optical path length are achieved by linear displacement of both retroreflectors using a motor driven lead screw on one for large, low frequency changes, a moving-coil actuator on the other for smaller, mid-frequency changes and a piezoelectric actuator on one of these two for small, high frequency changes.

A Survey of Scattering, Attenuation, and Size Spectra Studies of Bubble Layers and Plumes Beneath the Air-Sea Interface.

DTIC Science & Technology

1991-08-30

authors exploit the spatial resolution benefits of nonlinear bubble response (at the sum frequency) to the double frequency excitation by two...interaction method is the computational require- ment. Although exact runtimes for MIM are not given, and it apparently does have speed advantages over...Frequencies," J. Acoust. Soc. Am. 75(5), 1473-1477 (1984). (136] T.D.K. Ngoc, E.R. Franchi , and B.B. Adams, "Modeling of Ocean Surface Spectrum and

Noncontact, Low Frequency Ultrasound as an Effective Therapy against Pseudomonas aeruginosa-infected Biofilm Wounds

DTIC Science & Technology

2013-03-01

venous ulcers: themes and stories about their impact on quality of life. Ostomy Wound Manage 1998; 44: 38–49. 4. Mustoe TA, O’Shaughnessy K, Kloeters...double-blind, controlled, multi- center study. Ostomy Wound Manage 2005; 51: 24–39. 29. Ennis WJ, Valdes W, Gainer M, Meneses P. Evaluation of clini...frequency, nonthermal ultrasound in burn care. Ostomy Wound Manage 2008; 54: 66–9. 33. Kavros SJ, Schenck EC. Use of noncontact low-frequency ultrasound in

Design and Measurement of Self-Matched, Dual-Frequency Coplanar-Waveguide-Fed Slot Antennas

NASA Technical Reports Server (NTRS)

Omar, Amjad A.; Scardelletti, Maxmilian C.; Hejazi, Zuhair M.; Dib, Nihad

2007-01-01

This report presents two new designs of dual-frequency, coplanar-waveguide-fed, double-folded slot antennas. An important advantage of these antennas is that, because they are self-matched to the feeding coplanar waveguide, they do not need an external matching circuit. This reduces the antenna size and simplifies its design. To verify the designs, the authors measured and compared the return loss and radiation patterns with those obtained using available commercial software with good agreement. Dual-frequency slot antennas;

High speed photodiodes in standard nanometer scale CMOS technology: a comparative study.

PubMed

Nakhkoob, Behrooz; Ray, Sagar; Hella, Mona M

2012-05-07

This paper compares various techniques for improving the frequency response of silicon photodiodes fabricated in mainstream CMOS technology for fully integrated optical receivers. The three presented photodiodes, Spatially Modulated Light detectors, Double, and Interrupted P-Finger photodiodes, aim at reducing the low speed diffusive component of the photo generated current. For the first photodiode, Spatially Modulated Light (SML) detectors, the low speed current component is canceled out by converting it to a common mode current driving a differential transimpedance amplifier. The Double Photodiode (DP) uses two depletion regions to increase the fast drift component, while the Interrupted-P Finger Photodiode (IPFPD) redirects the low speed component towards a different contact from the main fast terminal of the photodiode. Extensive device simulations using 130 nm CMOS technology-parameters are presented to compare their performance using the same technological platform. Finally a new type of photodiode that uses triple well CMOS technology is introduced that can achieve a bandwidth of roughly 10 GHz without any process modification or high reverse bias voltages that would jeopardize the photodetector and subsequent transimpedance amplifier reliability.

Meiotic recombination hotspots - a comparative view.

PubMed

Choi, Kyuha; Henderson, Ian R

2015-07-01

During meiosis homologous chromosomes pair and undergo reciprocal genetic exchange, termed crossover. Meiotic recombination has a profound effect on patterns of genetic variation and is an important tool during crop breeding. Crossovers initiate from programmed DNA double-stranded breaks that are processed to form single-stranded DNA, which can invade a homologous chromosome. Strand invasion events mature into double Holliday junctions that can be resolved as crossovers. Extensive variation in the frequency of meiotic recombination occurs along chromosomes and is typically focused in narrow hotspots, observed both at the level of DNA breaks and final crossovers. We review methodologies to profile hotspots at different steps of the meiotic recombination pathway that have been used in different eukaryote species. We then discuss what these studies have revealed concerning specification of hotspot locations and activity and the contributions of both genetic and epigenetic factors. Understanding hotspots is important for interpreting patterns of genetic variation in populations and how eukaryotic genomes evolve. In addition, manipulation of hotspots will allow us to accelerate crop breeding, where meiotic recombination distributions can be limiting. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

Estimation of satellite position, clock and phase bias corrections

NASA Astrophysics Data System (ADS)

Henkel, Patrick; Psychas, Dimitrios; Günther, Christoph; Hugentobler, Urs

2018-05-01

Precise point positioning with integer ambiguity resolution requires precise knowledge of satellite position, clock and phase bias corrections. In this paper, a method for the estimation of these parameters with a global network of reference stations is presented. The method processes uncombined and undifferenced measurements of an arbitrary number of frequencies such that the obtained satellite position, clock and bias corrections can be used for any type of differenced and/or combined measurements. We perform a clustering of reference stations. The clustering enables a common satellite visibility within each cluster and an efficient fixing of the double difference ambiguities within each cluster. Additionally, the double difference ambiguities between the reference stations of different clusters are fixed. We use an integer decorrelation for ambiguity fixing in dense global networks. The performance of the proposed method is analysed with both simulated Galileo measurements on E1 and E5a and real GPS measurements of the IGS network. We defined 16 clusters and obtained satellite position, clock and phase bias corrections with a precision of better than 2 cm.

Ends-in Vs. Ends-Out Recombination in Yeast

PubMed Central

Hastings, P. J.; McGill, C.; Shafer, B.; Strathern, J. N.

1993-01-01

Integration of linearized plasmids into yeast chromosomes has been used as a model system for the study of recombination initiated by double-strand breaks. The linearized plasmid DNA recombines efficiently into sequences homologous to the ends of the DNA. This efficient recombination occurs both for the configuration in which the break is in a contiguous region of homology (herein called the ends-in configuration) and for ``omega'' insertions in which plasmid sequences interrupt a linear region of homology (herein called the ends-out configuration). The requirements for integration of these two configurations are expected to be different. We compared these two processes in a yeast strain containing an ends-in target and an ends-out target for the same cut plasmid. Recovery of ends-in events exceeds ends-out events by two- to threefold. Possible causes for the origin of this small bias are discussed. The lack of an extreme difference in frequency implies that cooperativity between the two ends does not contribute to the efficiency with which cut circular plasmids are integrated. This may also be true for the repair of chromosomal double-strand breaks. PMID:8307337

Quasinormal Modes of Charged Dilaton Black Holes and Their Entropy Spectra

NASA Astrophysics Data System (ADS)

Sakalli, I.

2013-08-01

In this study, we employ the scalar perturbations of the charged dilaton black hole (CDBH) found by Chan, Horne and Mann (CHM), and described with an action which emerges in the low-energy limit of the string theory. A CDBH is neither asymptotically flat (AF) nor non-asymptotically flat (NAF) spacetime. Depending on the value of its dilaton parameter a, it has both Schwarzschild and linear dilaton black hole (LDBH) limits. We compute the complex frequencies of the quasinormal modes (QNMs) of the CDBH by considering small perturbations around its horizon. By using the highly damped QNM in the process prescribed by Maggiore, we obtain the quantum entropy and area spectra of these black holes (BHs). Although the QNM frequencies are tuned by a, we show that the quantum spectra do not depend on a, and they are equally spaced. On the other hand, the obtained value of undetermined dimensionless constant ɛ is the double of Bekenstein's result. The possible reason of this discrepancy is also discussed.

Kerr hysteresis loop tracer with alternate driving magnetic field up to 10 kHz

NASA Astrophysics Data System (ADS)

Callegaro, Luca; Fiorini, Carlo; Triggiani, Giacomo; Puppin, Ezio

1997-07-01

A magneto-optical Kerr loop tracer for hysteresis loop measurements in thin films with field excitation frequency f0 from 10 mHz to 10 kHz is described. A very high sensitivity is obtained by using an ultrabright light-emitting diode as a low-noise light source and a novel acquisition process. The field is generated with a coil driven by an audio amplifier connected to a free-running oscillator. The conditioned detector output constitutes the magnetization signal (M); the magnetic field (H) is measured with a fast Hall probe. The acquisition electronics are based on a set of sample-and-hold amplifiers which allow the simultaneous sampling of M, H, and dH/dt. Acquisition is driven by a personal computer equipped with a multifunction I/O board. Test results on a 120 nm Fe film on Si substrate are shown. The coercive field of the film increases with frequency and nearly doubles at 10 kHz with respect to dc.

Radio frequency measurements of tunnel couplings and singlet–triplet spin states in Si:P quantum dots

PubMed Central

House, M. G.; Kobayashi, T.; Weber, B.; Hile, S. J.; Watson, T. F.; van der Heijden, J.; Rogge, S.; Simmons, M. Y.

2015-01-01

Spin states of the electrons and nuclei of phosphorus donors in silicon are strong candidates for quantum information processing applications given their excellent coherence times. Designing a scalable donor-based quantum computer will require both knowledge of the relationship between device geometry and electron tunnel couplings, and a spin readout strategy that uses minimal physical space in the device. Here we use radio frequency reflectometry to measure singlet–triplet states of a few-donor Si:P double quantum dot and demonstrate that the exchange energy can be tuned by at least two orders of magnitude, from 20 μeV to 8 meV. We measure dot–lead tunnel rates by analysis of the reflected signal and show that they change from 100 MHz to 22 GHz as the number of electrons on a quantum dot is increased from 1 to 4. These techniques present an approach for characterizing, operating and engineering scalable qubit devices based on donors in silicon. PMID:26548556

Double-bundle anterior cruciate ligament reconstruction is superior to single-bundle reconstruction in terms of revision frequency: a study of 22,460 patients from the Swedish National Knee Ligament Register.

PubMed

Svantesson, Eleonor; Sundemo, David; Hamrin Senorski, Eric; Alentorn-Geli, Eduard; Musahl, Volker; Fu, Freddie H; Desai, Neel; Stålman, Anders; Samuelsson, Kristian

2017-12-01

Studies comparing single- and double-bundle anterior cruciate ligament (ACL) reconstructions often include a combined analysis of anatomic and non-anatomic techniques. The purpose of this study was to compare the revision rates between single- and double-bundle ACL reconstructions in the Swedish National Knee Ligament Register with regard to surgical variables as determined by the anatomic ACL reconstruction scoring checklist (AARSC). Patients from the Swedish National Knee Ligament Register who underwent either single- or double-bundle ACL reconstruction with hamstring tendon autograft during the period 2007-2014 were included. The follow-up period started with primary ACL reconstruction, and the outcome measure was set as revision surgery. An online questionnaire based on the items of the AARSC was used to determine the surgical technique implemented in the single-bundle procedures. These were organized into subgroups based on surgical variables, and the revision rates were compared with the double-bundle ACL reconstruction. Hazard ratios (HR) with 95% confidence interval (CI) was calculated and adjusted for confounders by Cox regression. A total of 22,460 patients were included in the study, of which 21,846 were single-bundle and 614 were double-bundle ACL reconstruction. Double-bundle ACL reconstruction had a revision frequency of 2.0% (n = 12) and single-bundle 3.2% (n = 689). Single-bundle reconstruction had an increased risk of revision surgery compared with double-bundle [adjusted HR 1.98 (95% CI 1.12-3.51), p = 0.019]. The subgroup analysis showed a significantly increased risk of revision surgery in patients undergoing single-bundle with anatomic technique using transportal drilling [adjusted HR 2.51 (95% CI 1.39-4.54), p = 0.002] compared with double-bundle ACL reconstruction. Utilizing a more complete anatomic technique according to the AARSC lowered the hazard rate considerably when transportal drilling was performed but still resulted in significantly increased risk of revision surgery compared with double-bundle ACL reconstruction [adjusted HR 1.87 (95% CI 1.04-3.38), p = 0.037]. Double-bundle ACL reconstruction is associated with a lower risk of revision surgery than single-bundle ACL reconstruction. Single-bundle procedures performed using transportal femoral drilling technique had significantly higher risk of revision surgery compared with double-bundle. However, a reference reconstruction with transportal drilling defined as a more complete anatomic reconstruction reduces the risk of revision surgery considerably. III.

Ligand protons in a frozen solution of copper histidine relax via a T1e-driven three-spin mechanism

NASA Astrophysics Data System (ADS)

Stoll, S.; Epel, B.; Vega, S.; Goldfarb, D.

2007-10-01

Davies electron-nuclear double resonance spectra can exhibit strong asymmetries for long mixing times, short repetition times, and large thermal polarizations. These asymmetries can be used to determine nuclear relaxation rates in paramagnetic systems. Measurements of frozen solutions of copper(L-histidine)2 reveal a strong field dependence of the relaxation rates of the protons in the histidine ligand, increasing from low (g‖) to high (g⊥) field. It is shown that this can be attributed to a concentration-dependent T1e-driven relaxation process involving strongly mixed states of three spins: the histidine proton, the Cu(II) electron spin of the same complex, and another distant electron spin with a resonance frequency differing from the spectrometer frequency approximately by the proton Larmor frequency. The protons relax more efficiently in the g⊥ region, since the number of distant electrons able to participate in this relaxation mechanism is higher than in the g‖ region. Analytical expressions for the associated nuclear polarization decay rate Teen-1 are developed and Monte Carlo simulations are carried out, reproducing both the field and the concentration dependences of the nuclear relaxation.

Radio frequency switching network: a technique for infrared sensing

NASA Astrophysics Data System (ADS)

Mechtel, Deborah M.; Jenkins, R. Brian; Joyce, Peter J.; Nelson, Charles L.

2016-10-01

This paper describes a unique technique that implements photoconductive sensors in a radio frequency (RF) switching network designed to locate in real-time the position and intensity of IR radiation incident on a composite structure. In the implementation described here, photoconductive sensors act as rapid response switches in a two-layer RF network embedded in an FR-4 laminate. To detect radiation, phosphorous-doped silicon photoconductive sensors are inserted in GHz range RF transmission lines. By permitting signal propagation only when a sensor is illuminated, the RF signals are selectively routed from lower layer transmission lines to upper layer lines, thereby pinpointing the location and strength of incident radiation. Simulations based on a high frequency three-dimensional planar electromagnetics model are presented and compared to the experimental results. The experimental results are described for GHz range RF signal control for 300- and 180-mW incident energy from 975- to 1060-nm wavelength lasers, respectively, where upon illumination, RF transmission line signal output power doubled when compared to nonilluminated results. The experimental results are also reported for 100-W incident energy from a 1060-nm laser. Test results illustrate real-time signal processing would permit a structure to be controlled in response to incident radiation.