Science.gov

Sample records for frequency tuning functions

  1. Tuning the work function of graphene by nitrogen plasma treatment with different radio-frequency powers

    SciTech Connect

    Zeng, Jian-Jhou; Lin, Yow-Jon

    2014-06-09

    Graphene prepared by the chemical vapor deposition method was treated with nitrogen plasma under different radio-frequency (rf) power conditions in order to experimentally study the change in the work function. Control of the rf power could change the work function of graphene from 4.91 eV to 4.37 eV. It is shown that the increased rf power may lead to the increased number of graphitic nitrogen, increasing the electron concentration, and shifting the Fermi level to higher energy. The ability to controllably tune the work function of graphene is essential for optimizing the efficiency of optoelectronic and electronic devices.

  2. Spatial frequency tuning functions and contrast sensitivity at different eccentricities in the visual field

    SciTech Connect

    Chen, H.W.; Aine, C.J.; Flynn, E.R.; Wood, C.C.

    1996-07-01

    The human luminance spatial frequency contrast sensitivity function (CSF) has been well studied using psychophysical measurements by detecting spatial frequency (SF) grating patterns at threshold. Threshold CSFs at different eccentricities have proven to be quite useful in both basic and clinical vision research. However, near threshold, the CSF is measured at a linear area of the saturating contrast-response curve. In contrast, most of our everyday vision may be at suprathreshold levels, and thus may function most of the time at the nonlinear area of the contrast-response curve. In this study, in order to better characterize the CSF at normal contrast levels, we measured the SF tuning functions as well as the CR functions at different suprathreshold contrast levels and different eccentricities of the visual field using noninvasive MEG techniques. In this study, in addition to peak analysis, we have developed more reliable averaged power analysis methods where the average power can be calculated from the entire waveforms.

  3. Apparatuses and methods for tuning center frequencies

    DOEpatents

    Wojciechowski, Kenneth; Olsson, Roy H.

    2016-02-23

    Apparatuses and methods for tuning center frequencies are described herein. Examples of tuning described herein including tuning using feedback from the resonator. Variable gain feedback for tuning of acoustic wave resonators is provided in some examples. An example apparatus may include a resonator and a feedback loop. The resonator may be configured to receive a tuning signal and to provide a feedback signal. The feedback signal may be based on the tuning signal. The feedback loop may be configured to receive the feedback signal from the resonator. The feedback loop further may be configured to provide the tuning signal to actively tune a center frequency of the resonator. The tuning signal may be based on the feedback signal.

  4. The brain frequency tuning function for facial emotion discrimination: An ssVEP study.

    PubMed

    Zhu, Maria; Alonso-Prieto, Esther; Handy, Todd; Barton, Jason

    2016-04-01

    Steady-state visual evoked potentials have only been applied recently to the study of face perception. We used this method to study the spatial and temporal dynamics of expression perception in the human brain and test the prediction that, as in the case of identity perception, the optimal frequency for facial expression would also be in the range of 5-6 Hz. We presented facial expressions at different flickering frequencies (2-8 Hz) to human observers while recording their brain electrical activity. Our modified adaptation paradigm contrasted blocks with varying expressions versus blocks with a constant neutral expression, while facial identity was kept constant. The presentation of different expressions created a larger steady-state response only at 5 Hz, corresponding to a cycle of 200 ms, over right occipito-temporal electrodes. Source localization using a time-domain analysis showed that the effect localized to the right occipito-temporal cortex, including the superior temporal sulcus and fusiform gyrus. PMID:27096944

  5. Stay tuned: active amplification tunes tree cricket ears to track temperature-dependent song frequency.

    PubMed

    Mhatre, Natasha; Pollack, Gerald; Mason, Andrew

    2016-04-01

    Tree cricket males produce tonal songs, used for mate attraction and male-male interactions. Active mechanics tunes hearing to conspecific song frequency. However, tree cricket song frequency increases with temperature, presenting a problem for tuned listeners. We show that the actively amplified frequency increases with temperature, thus shifting mechanical and neuronal auditory tuning to maintain a match with conspecific song frequency. Active auditory processes are known from several taxa, but their adaptive function has rarely been demonstrated. We show that tree crickets harness active processes to ensure that auditory tuning remains matched to conspecific song frequency, despite changing environmental conditions and signal characteristics. Adaptive tuning allows tree crickets to selectively detect potential mates or rivals over large distances and is likely to bestow a strong selective advantage by reducing mate-finding effort and facilitating intermale interactions. PMID:27122007

  6. Spatiotemporal frequency and speed tuning in the owl visual wulst.

    PubMed

    Pinto, Lucas; Baron, Jerome

    2009-10-01

    The avian visual wulst is hodologically equivalent to the mammalian primary visual cortex (V1). In contrast to most birds, owls have a massive visual wulst, which shares striking functional similarities with V1. To provide a better understanding of how motion is processed within this area, we used sinusoidal gratings to characterize the spatiotemporal frequency and speed tuning profiles of 131 neurones recorded from awake burrowing owls. Cells were found to be clearly tuned to both spatial and temporal frequencies, and in a way that is similar to what has been reported in the striate cortex of primates and carnivores. Our results also suggest the presence of spatial frequency tuning domains in the wulst. Speed tuning was assessed by several methods devised to measure the degree of dependence between spatial and temporal frequency tuning. Although many neurones were found to be independently tuned, a significant proportion of cells showed at least some degree of dependence, compatible with the idea that some kind of initial transformation towards an explicit representation of speed is being carried out by the owl wulst. Interestingly, under certain constraints, a higher incidence of spatial frequency-invariant speed tuned profiles was obtained by combining our experimentally measured responses using a recent cortical model of speed tuning. Overall, our findings reinforce the notion that, like V1, the owl wulst is an important initial stage for motion processing, a function that is usually attributed to areas of the tectofugal pathway in lateral-eyed birds. PMID:19788573

  7. ABR frequency tuning curves in dolphins.

    PubMed

    Supin, A Y; Popov, V V; Klishin, V O

    1993-11-01

    Tone-tone masking was used to determine auditory brain-stem response tuning curves in dolphins (Tursiops truncatus) in a simultaneous-masking paradigm. The Q10 of the curves was as large as 16-19 in the frequency range 64-128 kHz. In the range 45-16 kHz, Q10 decreased proportionally to the frequency with the bandwidth of the curves being constant, about 3.5-4 kHz at the 10-dB level. Tuning curves below 45 kHz are supposed to reflect broad spectral bandwidth of the probe's effective part which is no longer than 0.5 ms, irrespective of actual probe duration. Tuning curves above 64 kHz are supposed to reflect the real frequency tuning of the dolphin's auditory system. PMID:8263842

  8. Turbine bucket natural frequency tuning rib

    DOEpatents

    Wang, John Zhiqiang; Norton, Paul Francis; Barb, Kevin Joseph; Jacala, Ariel Caesar-Prepena

    2002-01-01

    A tuning rib is added preferably in the aft cavity of a cored turbine bucket to alter the bucket's natural frequencies. The tuning rib may be a solid rib or a segmented rib and is particularly suited for altering high order frequency modes such as 2T, 4F and 1-3S. As such, detrimental crossings of natural bucket frequencies and gas turbine stimuli can be avoided to thereby improve the reliability of a gas turbine without impacting other features of the bucket that are important to the performance of the gas turbine.

  9. Does Face Inversion Change Spatial Frequency Tuning?

    ERIC Educational Resources Information Center

    Willenbockel, Verena; Fiset, Daniel; Chauvin, Alan; Blais, Caroline; Arguin, Martin; Tanaka, James W.; Bub, Daniel N.; Gosselin, Frederic

    2010-01-01

    The authors examined spatial frequency (SF) tuning of upright and inverted face identification using an SF variant of the Bubbles technique (F. Gosselin & P. G. Schyns, 2001). In Experiment 1, they validated the SF Bubbles technique in a plaid detection task. In Experiments 2a-c, the SFs used for identifying upright and inverted inner facial…

  10. Psychophysical tuning curves at very high frequencies

    NASA Astrophysics Data System (ADS)

    Yasin, Ifat; Plack, Christopher J.

    2005-10-01

    For most normal-hearing listeners, absolute thresholds increase rapidly above about 16 kHz. One hypothesis is that the high-frequency limit of the hearing-threshold curve is imposed by the transmission characteristics of the middle ear, which attenuates the sound input [Masterton et al., J. Acoust. Soc. Am. 45, 966-985 (1969)]. An alternative hypothesis is that the high-frequency limit of hearing is imposed by the tonotopicity of the cochlea [Ruggero and Temchin, Proc. Nat. Acad. Sci. U.S.A. 99, 13206-13210 (2002)]. The aim of this study was to test these hypotheses. Forward-masked psychophysical tuning curves (PTCs) were derived for signal frequencies of 12-17.5 kHz. For the highest signal frequencies, the high-frequency slopes of some PTCs were steeper than the slope of the hearing-threshold curve. The results also show that the human auditory system displays frequency selectivity for characteristic frequencies (CFs) as high as 17 kHz, above the frequency at which absolute thresholds begin to increase rapidly. The findings suggest that, for CFs up to 17 kHz, the high-frequency limitation in humans is imposed in part by the middle-ear attenuation, and not by the tonotopicity of the cochlea.

  11. Frequency tuning of THz quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Qian, Xifeng; Danylov, Andriy A.; Light, Alexander R.; Waldman, Jerry; Erickson, Neal

    2015-03-01

    This paper introduces the continuously tunable THz radiation through sideband generation of a free running and solidnitrogen- cooled THz quantum cascade laser. The 2.324 THz QCL operating in a single longitudinal mode (SLM) in continuous-wave (cw) was mixed with a swept synthesized microwave signal by a THz Schottky-diode-balanced mixer. Through sideband generation, two frequency branches were observed at low and high frequency, characterized with a Fourier-transform spectrometer. At low frequency, the sideband generates frequencies from -50 GHz to +50 GHz. At high frequency, it generates sideband frequencies from 70 GHz to 115 GHz. The total +/-100 GHz tuning range can be further expanded with higher frequency millimeter wave amplifier/multiplier source. The sideband generates total 1 μW of output power at both upper and lower frequency with 200 μW of driven power from the THz QCL, showing a power conversion efficiency of 5 × 10-3. The demonstration of this SM, continuously tunable THz source enables its applications where SM, spatially coherent beam is required.

  12. Automated frequency tuning of SRF cavities at CEBAF

    SciTech Connect

    Chowdhary, M.; Doolittle, L.; Lahti, G.; Simrock, S.N.; Terrell, R.

    1995-12-31

    An automated cavity tuning procedure has been implemented in the CEBAF control system to tune the superconducting RF (SRF) cavities to their operating frequency of 1497 MHz. The capture range for coarse tuning algorithm (Burst Mode) is more than 20 cavity bandwidths (5 kHz). The fine tuning algorithm (Sweep Mode) calibrates the phase offset in the detuning angle measurement. This paper describes the implementation of these algorithms and experience of their operation in CEBAF control system. 3 refs., 5 figs.

  13. Resonant frequency tuning of an industrial vibration energy harvester

    NASA Astrophysics Data System (ADS)

    Toh, T. T.; Wright, S. W.; Mitcheson, P. D.

    2014-11-01

    This paper presents preliminary results of tuning the resonant frequency of two industrial vibration energy harvesters. The VEH-450 from Ferro Solutions and the PMG17-50 from Perpetuum were tested using discrete reactive electrical loads. The former could be tuned to +0.5 Hz and -2 Hz from its natural resonant frequency of 50.5 Hz at 0.1g. The latter, however, has a broadband output power spectrum that spans ±10 Hz and its output voltage saturates at 7 Vrms, thereby rendering it un-tunable using the method presented here. A comparison of output power between a tuned VEH-450 and an un-tuned PMG17-50, normalised by harvester weight, shows that the former outperforms the latter only at a tuned frequency of 49.8 Hz. A discussion of a resonant frequency tuning circuit that can be fitted to an existing harvester without making modifications to the harvester is presented.

  14. Frequency Tuning Feature of a Reditron Oscillator

    NASA Astrophysics Data System (ADS)

    Ling, Genshen; Li, Xiangsheng; Wang, Yong; Li, Chuanlu; Tan, Qimei; Li, Pingping

    1995-08-01

    We report some experimental results which confirm the theoretical analysis of the tuning feature of a reditron oscillator. Here, we produce high power microwave at 10 GHz, and the tuning range of the reditron is 8-13.32 GHz which is controlled by changing both the voltage and the anode-to-cathode separation. We also report a measurement method of the anode-to-cathode distance.

  15. Frequency tuning of piezoelectric energy harvesters by magnetic force

    NASA Astrophysics Data System (ADS)

    Al-Ashtari, Waleed; Hunstig, Matthias; Hemsel, Tobias; Sextro, Walter

    2012-03-01

    A piezoelectric energy harvester is an electromechanical device that converts ambient mechanical vibration into electric power. Most existing vibration energy harvesting devices operate effectively at a single frequency only, dictated by the design of the device. This frequency must match the frequency of the host structure vibration. However, real world structural vibrations rarely have a specific constant frequency. Therefore, piezoelectric harvesters that generate usable power across a range of exciting frequencies are required to make this technology commercially viable. Currently known harvester tuning techniques have many limitations, in particular they miss the ability to work during harvester operation and most often cannot perform a precise tuning. This paper describes the design and testing of a vibration energy harvester with tunable resonance frequency, wherein the tuning is accomplished by changing the attraction force between two permanent magnets by adjusting the distance between the magnets. This tuning technique allows the natural frequency to be manipulated before and during operation of the harvester. Furthermore the paper presents a physical description of the frequency tuning effect. The experimental results achieved with a piezoelectric bimorph fit the calculated results very well. The calculation and experimental results show that using this tuning technique the natural frequency of the harvester can be varied efficiently within a wide range: in the test setup, the natural frequency of the piezoelectric bimorph could be increased by more than 70%.

  16. Frequency Tuning of Hearing in the Beluga Whale.

    PubMed

    Sysueva, Evgeniya V; Nechaev, Dmitry I; Popov, Vladimir V; Supin, Alexander Y

    2016-01-01

    Data on frequency tuning in odontocetes are contradictory: different authors have reported filter qualities from 2 to almost 50. In this study, frequency tuning was measured in a beluga whale (Delphinapterus leucas) using a rippled-noise test stimulus in conjunction with the auditory evoked potential (AEP) technique. The response to ripple reversions was considered to indicate resolvability of the ripple pattern. The limit of ripple-pattern resolution ranged from 20 to 32 ripples per octave (rpo). A model of interaction of the ripple spectrum with frequency-tuned filters suggests that this resolution limit requires a filter quality of 29-46. PMID:26611077

  17. Dynamics of spatial frequency tuning in mouse visual cortex

    PubMed Central

    Vreysen, Samme; Zhang, Bin; Chino, Yuzo M.; Arckens, Lutgarde

    2012-01-01

    Neuronal spatial frequency tuning in primary visual cortex (V1) substantially changes over time. In both primates and cats, a shift of the neuron's preferred spatial frequency has been observed from low frequencies early in the response to higher frequencies later in the response. In most cases, this shift is accompanied by a decreased tuning bandwidth. Recently, the mouse has gained attention as a suitable animal model to study the basic mechanisms of visual information processing, demonstrating similarities in basic neuronal response properties between rodents and highly visual mammals. Here we report the results of extracellular single-unit recordings in the anesthetized mouse where we analyzed the dynamics of spatial frequency tuning in V1 and the lateromedial area LM within the lateral extrastriate area V2L. We used a reverse-correlation technique to demonstrate that, as in monkeys and cats, the preferred spatial frequency of mouse V1 neurons shifted from low to higher frequencies later in the response. However, this was not correlated with a clear selectivity increase or enhanced suppression of responses to low spatial frequencies. These results suggest that the neuronal connections responsible for the temporal shift in spatial frequency tuning may considerably differ between mice and monkeys. PMID:22402662

  18. Squeezing Alters Frequency Tuning of WGM Optical Resonator

    NASA Technical Reports Server (NTRS)

    Mohageg, Makan; Maleki, Lute

    2010-01-01

    Mechanical squeezing has been found to alter the frequency tuning of a whispering-gallery-mode (WGM) optical resonator that has an elliptical shape and is made of lithium niobate. It may be possible to exploit this effect to design reconfigurable optical filters for optical communications and for scientific experiments involving quantum electrodynamics. Some background information is prerequisite to a meaningful description of the squeezing-induced alteration of frequency tuning: The spectrum of a WGM resonator is represented by a comblike plot of intensity versus frequency. Each peak of the comblike plot corresponds to an electromagnetic mode represented by an integer mode number, and the modes are grouped into sets represented by integer mode indices. Because lithium niobate is an electro-optically active material, the WGM resonator can be tuned (that is, the resonance frequencies can be shifted) by applying a suitable bias potential. The frequency shift of each mode is quantified by a tuning rate defined as the ratio between the frequency shift and the applied potential. In the absence of squeezing, all modes exhibit the same tuning rate. This concludes the background information. It has been demonstrated experimentally that when the resonator is squeezed along part of either of its two principal axes, tuning rates differ among the groups of modes represented by different indices (see figure). The differences in tuning rates could be utilized to configure the resonance spectrum to obtain a desired effect; for example, through a combination of squeezing and electrical biasing, two resonances represented by different mode indices could be set at a specified frequency difference something that could not be done through electrical biasing alone.

  19. Estimating cochlear tuning dependence on stimulus level and frequency from the delay of otoacoustic emissions.

    PubMed

    Moleti, Arturo; Sisto, Renata

    2016-08-01

    An objective technique based on the time-frequency analysis of otoacoustic emissions is proposed to get fast and stable estimates of cochlear tuning. Time-frequency analysis allows one to get stable measurements of the delay/frequency function, which is theoretically expected to be a function of cochlear tuning. Theoretical considerations and numerical solutions of a nonlinear cochlear model suggest that the average phase-gradient delay of the otoacoustic emission single-reflection components, weighted, for each frequency, by the amplitude of the corresponding wavelet coefficients, approximately scales as the square root of the cochlear quality factor. The application of the method to human stimulus-frequency and transient-evoked otoacoustic emissions shows that tuning decreases approximately by a factor of 2, as the stimulus level increases by 30 dB in a moderate stimulus level range. The results also show a steady increase of tuning with increasing frequency, by a factor of 2 between 1 and 5 kHz. This last result is model-dependent, because it relies on the assumption that cochlear scale-invariance breaking is only due to the frequency dependence of tuning. The application of the method to the reflection component of distortion product otoacoustic emissions, separated using time-frequency filtering, is complicated by the necessity of effectively canceling the distortion component. PMID:27586727

  20. Frequency tuning with RFQ temperature in China ADS Injector II

    NASA Astrophysics Data System (ADS)

    Jing, Wang; Jian-Long, Huang; Xiao-Qi, Zhang; Bin, Zhang; Yuan, He; Zhou-Li, Zhang; Ai-Min, Shi

    2016-03-01

    A 162.5 MHz four-vane radio frequency quadruple (RFQ) accelerator has been developed at the Institute of Modern Physics (IMP) for Injector II of the China ADS linac. The RFQ will operate in continuous wave mode at 100 kW. For the designed 10 mA beam, the additional RF power dissipation will induce a very large reflection of power. A water-temperature controlling system will be used to reduce the power reflection by tuning the frequency of the RFQ. The tuning capability of the water temperature is studied under different configurations of cooling water. Simulations and experiment are compared in this paper. The experimental results agree well with simulation using ANSYS. This can be used as a reference to tune the RFQ in beam commissioning. Supported by National Natural Science Foundation of China (91026001)

  1. Calibrating the frequency of tuning forks by means of Lissajous figures

    NASA Astrophysics Data System (ADS)

    Quereda, Jorge; Ramón, Marina; Silva, Blanca; Hinarejos, Juan José; Rodrigo, José Gabriel; Farías, Daniel

    2011-05-01

    We produce Lissajous figures by modulating a laser beam along two perpendicular directions by means of two tuning forks. When the ratio of the resonant frequencies of the tuning forks is a small rational number, Lissajous figures are clearly resolved on a screen. Because the ratio of frequencies is never exactly a rational number, a phase drift of the Lissajous figures is observed as a function of time. If the period of this phase drift is measured, variations in the resonant frequencies as small as 0.01 Hz can be detected.

  2. Dynamic functional tuning of nonlinear cortical networks

    NASA Astrophysics Data System (ADS)

    Stetter, Martin

    2006-03-01

    The mammalian neocortex is a highly complex and nonlinear dynamic system. One of its most prominent features is an omnipresent spontaneous neuronal activity. Here the possible functional role of this global background for cognitive flexibility is studied in a prototypic mean-field model area. It is demonstrated that the level of global background current efficiently controls the stimulus-response threshold and the stability and properties of short-term memory states. Moreover, it can dynamically gate arbitrary cortical subnetworks, when applied to parts of the area as a weak bias signal. These results suggest a central functional role of the level of background activation: the dynamic functional tuning of neocortical circuits.

  3. Automatic tuning of the reinforcement function

    SciTech Connect

    Touzet, C.; Santos, J.M.

    1997-12-31

    The aim of this work is to present a method that helps tuning the reinforcement function parameters in a reinforcement learning approach. Since the proposal of neural based implementations for the reinforcement learning paradigm (which reduced learning time and memory requirements to realistic values) reinforcement functions have become the critical components. Using a general definition for reinforcement functions, the authors solve, in a particular case, the so called exploration versus exploitation dilemma through the careful computation of the RF parameter values. They propose an algorithm to compute, during the exploration part of the learning phase, an estimate for the parameter values. Experiments with the mobile robot Nomad 200 validate their proposals.

  4. Size tuning in the absence of spatial frequency tuning in object recognition.

    PubMed

    Fiser, J; Subramaniam, S; Biederman, I

    2001-07-01

    How do we attend to objects at a variety of sizes as we view our visual world? Because of an advantage in identification of lowpass over highpass filtered patterns, as well as large over small images, a number of theorists have assumed that size-independent recognition is achieved by spatial frequency (SF) based coarse-to-fine tuning. We found that the advantage of large sizes or low SFs was lost when participants attempted to identify a target object (specified verbally) somewhere in the middle of a sequence of 40 images of objects, each shown for only 72 ms, as long as the target and distractors were the same size or spatial frequency (unfiltered or low or high bandpassed). When targets were of a different size or scale than the distractors, a marked advantage (pop out) was observed for large (unfiltered) and low SF targets against small (unfiltered) and high SF distractors, respectively, and a marked decrement for the complementary conditions. Importantly, this pattern of results for large and small images was unaffected by holding absolute or relative SF content constant over the different sizes and it could not be explained by simple luminance- or contrast-based pattern masking. These results suggest that size/scale tuning in object recognition was accomplished over the first several images (<576 ms) in the sequence and that the size tuning was implemented by a mechanism sensitive to spatial extent rather than to variations in spatial frequency. PMID:11412885

  5. Natural Focusing Inspection for Pipes by Frequency Tuning

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Rose, Joseph L.; Gavigan, Brian J.

    2005-04-01

    The energy of ultrasonic guided waves may be focused in pipes by utilizing a partially loaded excitation. This focusing technique is called "natural focusing", which can be used to improve a defect's sensitivity to ultrasonic guided waves. However, it is possible that there are a few natural focal points within the inspection range at a particular frequency. Consequently, some defects could be missed. The location of the natural focal points, however, changes with frequency. This phenomenon was theoretically predicted and experimentally confirmed. In this paper, the natural focusing inspection technique is investigated. Although a very limited circumferential length might be covered by a naturally focused profile at a single excitation frequency, the entire cross sectional area of the pipe can be inspected when a range of frequencies is employed. Hence, the natural focusing inspection technique can sufficiently inspect the entire pipe with frequency tuning.

  6. Pump wavelength tuning of optical parametric oscillations and frequency mixing in KTiOAsO4

    NASA Technical Reports Server (NTRS)

    Jani, Mahendra G.; Murray, James T.; Petrin, Roger R.; Powell, Richard C.; Loiacono, D. N.; Loiacono, G. M.

    1992-01-01

    The properties of alexandrite laser-pumped optical parametric oscillators are reported for potassium titanyl arsenate. Near-infrared tuning curves and slope efficiencies were measured as functions of pump wavelength and pump power. In addition, sum frequency mixing of red and infrared wavelengths to produce green emission is also reported.

  7. Dynamic frequency tuning of electric and magnetic metamaterial response

    DOEpatents

    O'Hara, John F; Averitt, Richard; Padilla, Willie; Chen, Hou-Tong

    2014-09-16

    A geometrically modifiable resonator is comprised of a resonator disposed on a substrate, and a means for geometrically modifying the resonator. The geometrically modifiable resonator can achieve active optical and/or electronic control of the frequency response in metamaterials and/or frequency selective surfaces, potentially with sub-picosecond response times. Additionally, the methods taught here can be applied to discrete geometrically modifiable circuit components such as inductors and capacitors. Principally, controlled conductivity regions, using either reversible photodoping or voltage induced depletion activation, are used to modify the geometries of circuit components, thus allowing frequency tuning of resonators without otherwise affecting the bulk substrate electrical properties. The concept is valid over any frequency range in which metamaterials are designed to operate.

  8. Neural tuning matches frequency-dependent time differences between the ears.

    PubMed

    Benichoux, Victor; Fontaine, Bertrand; Franken, Tom P; Karino, Shotaro; Joris, Philip X; Brette, Romain

    2015-01-01

    The time it takes a sound to travel from source to ear differs between the ears and creates an interaural delay. It varies systematically with spatial direction and is generally modeled as a pure time delay, independent of frequency. In acoustical recordings, we found that interaural delay varies with frequency at a fine scale. In physiological recordings of midbrain neurons sensitive to interaural delay, we found that preferred delay also varies with sound frequency. Similar observations reported earlier were not incorporated in a functional framework. We find that the frequency dependence of acoustical and physiological interaural delays are matched in key respects. This suggests that binaural neurons are tuned to acoustical features of ecological environments, rather than to fixed interaural delays. Using recordings from the nerve and brainstem we show that this tuning may emerge from neurons detecting coincidences between input fibers that are mistuned in frequency. PMID:25915620

  9. Spatial cue reliability drives frequency tuning in the barn Owl's midbrain.

    PubMed

    Cazettes, Fanny; Fischer, Brian J; Pena, Jose L

    2014-01-01

    The robust representation of the environment from unreliable sensory cues is vital for the efficient function of the brain. However, how the neural processing captures the most reliable cues is unknown. The interaural time difference (ITD) is the primary cue to localize sound in horizontal space. ITD is encoded in the firing rate of neurons that detect interaural phase difference (IPD). Due to the filtering effect of the head, IPD for a given location varies depending on the environmental context. We found that, in barn owls, at each location there is a frequency range where the head filtering yields the most reliable IPDs across contexts. Remarkably, the frequency tuning of space-specific neurons in the owl's midbrain varies with their preferred sound location, matching the range that carries the most reliable IPD. Thus, frequency tuning in the owl's space-specific neurons reflects a higher-order feature of the code that captures cue reliability. PMID:25531067

  10. Tuning of liquid-crystal birefringence using a square ac variable frequency voltage

    NASA Astrophysics Data System (ADS)

    Hamdi, Rachid; Falih Bendimerad, Djalal; Benkelfat, Badr-Eddine; Vinouze, Bruno

    2015-10-01

    We demonstrate that the birefringence of the liquid-crystal cell (LCC) can be varied by applying different frequency values of a single applied ac square voltage. For the experimental evaluation of the birefringence, associated with a certain wavelength λ, as a function of the frequency F LCC of the electrical signal applied to the LCC, we use, for the first time to our knowledge, what we call here a frequency-dependent transmission technique. It consists in measuring the transmission responses between crossed and parallel polarizers as a function of the frequency F LCC. Experimental tests were carried out using a 7 μm-thick E63 nematic LCC and a laser source emitting at λ = 1.55 μm with a launch power of -3 dBm. The tuning voltage V LCC applied to the LCC is an alternative square wave electrical signal whose frequency ranges from 0.5 to 15 kHz. The peak to peak amplitude of the electrical signal is 5 V. The curve of the measured variations of the optical path difference of the LCC versus the frequency F LCC has a positive slope. Application to the tuning of the center wavelength of the transmission response of a one stage hybrid birefringent filter is shown as a proof-of-principle test.

  11. Frequency selectivity of the human cochlea: Suppression tuning of spontaneous otoacoustic emissions.

    PubMed

    Manley, Geoffrey A; van Dijk, Pim

    2016-06-01

    Frequency selectivity is a key functional property of the inner ear and since hearing research began, the frequency resolution of the human ear has been a central question. In contrast to animal studies, which permit invasive recording of neural activity, human studies must rely on indirect methods to determine hearing selectivity. Psychophysical studies, which used masking of a tone by other sounds, indicate a modest frequency selectivity in humans. By contrast, estimates using the phase delays of stimulus-frequency otoacoustic emissions (SFOAE) predict a remarkably high selectivity, unique among mammals. An alternative measure of cochlear frequency selectivity are suppression tuning curves of spontaneous otoacoustic emissions (SOAE). Several animal studies show that these measures are in excellent agreement with neural frequency selectivity. Here we contribute a large data set from normal-hearing young humans on suppression tuning curves (STC) of spontaneous otoacoustic emissions (SOAE). The frequency selectivities of human STC measured near threshold levels agree with the earlier, much lower, psychophysical estimates. They differ, however, from the typical patterns seen in animal auditory nerve data in that the selectivity is remarkably independent of frequency. In addition, SOAE are suppressed by higher-level tones in narrow frequency bands clearly above the main suppression frequencies. These narrow suppression bands suggest interactions between the suppressor tone and a cochlear standing wave corresponding to the SOAE frequency being suppressed. The data show that the relationship between pre-neural mechanical processing in the cochlea and neural coding at the hair-cell/auditory nerve synapse needs to be reconsidered. PMID:27139323

  12. Tuning of MEMS Devices using Evolutionary Computation and Open-loop Frequency Response

    NASA Technical Reports Server (NTRS)

    Keymeulen, Didier; Fink, Wolfgang; Ferguson, Michael I.; Peay, Chris; Oks, Boris; Terrile, Richard; Yee, Karl

    2005-01-01

    We propose a tuning method for MEMS gyroscopes based on evolutionary computation that has the capacity to efficiently increase the sensitivity of MEMS gyroscopes through tuning and, furthermore, to find the optimally tuned configuration for this state of increased sensitivity. The tuning method was tested for the second generation JPL/Boeing Post-resonator MEMS gyroscope using the measurement of the frequency response of the MEMS device in open-loop operation.

  13. Tuning of SFOAEs Evoked by Low-Frequency Tones Is Not Compatible with Localized Emission Generation.

    PubMed

    Charaziak, Karolina K; Siegel, Jonathan H

    2015-06-01

    Stimulus-frequency otoacoustic emissions (SFOAEs) appear to be well suited for assessing frequency selectivity because, at least on theoretical grounds, they originate over a restricted region of the cochlea near the characteristic place of the evoking tone. In support of this view, we previously found good agreement between SFOAE suppression tuning curves (SF-STCs) and a control measure of frequency selectivity (compound action potential suppression tuning curves (CAP-STC)) for frequencies above 3 kHz in chinchillas. For lower frequencies, however, SF-STCs and were over five times broader than the CAP-STCs and demonstrated more high-pass rather than narrow band-pass filter characteristics. Here, we test the hypothesis that the broad tuning of low-frequency SF-STCs is because emissions originate over a broad region of the cochlea extending basal to the characteristic place of the evoking tone. We removed contributions of the hypothesized basally located SFOAE sources by either pre-suppressing them with a high-frequency interference tone (IT; 4.2, 6.2, or 9.2 kHz at 75 dB sound pressure level (SPL)) or by inducing acoustic trauma at high frequencies (exposures to 8, 5, and lastly 3-kHz tones at 110-115 dB SPL). The 1-kHz SF-STCs and CAP-STCs were measured for baseline, IT present and following the acoustic trauma conditions in anesthetized chinchillas. The IT and acoustic trauma affected SF-STCs in an almost indistinguishable way. The SF-STCs changed progressively from a broad high-pass to narrow band-pass shape as the frequency of the IT was lowered and for subsequent exposures to lower-frequency tones. Both results were in agreement with the "basal sources" hypothesis. In contrast, CAP-STCs were not changed by either manipulation, indicating that neither the IT nor acoustic trauma affected the 1-kHz characteristic place. Thus, unlike CAPs, SFOAEs cannot be considered as a place-specific measure of cochlear function at low frequencies, at least in chinchillas. PMID

  14. Gain and frequency tuning within the mouse cochlear apex

    NASA Astrophysics Data System (ADS)

    Oghalai, John S.; Gao, Simon; Lee, Hee Yoon; Raphael, Patrick D.; Groves, Andrew K.; Zuo, Jian; Applegate, Brian E.

    2015-12-01

    Normal mammalian hearing requires cochlear outer hair cell active processes that amplify the traveling wave with high gain and sharp tuning, termed cochlear amplification. We have used optical coherence tomography to study cochlear amplification within the apical turn of the mouse cochlea. We measured not only classical basilar membrane vibratory tuning curves but also vibratory responses from the rest of the tissues that compose the organ of Corti. Basilar membrane tuning was sharp in live mice and broad in dead mice, whereas other regions of the organ of Corti demonstrated phase shifts consistent with additional filtering beyond that provided by basilar membrane mechanics. We use these experimental data to support a conceptual framework of how cochlear amplification is tuned within the mouse cochlear apex. We will also study transgenic mice with targeted mutations that affect different biomechanical aspects of the organ of Corti in an effort to localize the underlying processes that produce this additional filtering.

  15. Gain and frequency tuning within the mouse cochlear apex

    SciTech Connect

    Oghalai, John S.; Raphael, Patrick D.; Gao, Simon; Lee, Hee Yoon; Groves, Andrew K.; Zuo, Jian; Applegate, Brian E.

    2015-12-31

    Normal mammalian hearing requires cochlear outer hair cell active processes that amplify the traveling wave with high gain and sharp tuning, termed cochlear amplification. We have used optical coherence tomography to study cochlear amplification within the apical turn of the mouse cochlea. We measured not only classical basilar membrane vibratory tuning curves but also vibratory responses from the rest of the tissues that compose the organ of Corti. Basilar membrane tuning was sharp in live mice and broad in dead mice, whereas other regions of the organ of Corti demonstrated phase shifts consistent with additional filtering beyond that provided by basilar membrane mechanics. We use these experimental data to support a conceptual framework of how cochlear amplification is tuned within the mouse cochlear apex. We will also study transgenic mice with targeted mutations that affect different biomechanical aspects of the organ of Corti in an effort to localize the underlying processes that produce this additional filtering.

  16. Tuning the work-function via strong coupling.

    PubMed

    Hutchison, James A; Liscio, Andrea; Schwartz, Tal; Canaguier-Durand, Antoine; Genet, Cyriaque; Palermo, Vincenzo; Samorì, Paolo; Ebbesen, Thomas W

    2013-05-01

    The tuning of the molecular material work-function via strong coupling with vacuum electromagnetic fields is demonstrated. Kelvin probe microscopy extracts the surface potential (SP) changes of a photochromic molecular film on plasmonic hole arrays and inside Fabry-Perot cavities. Modulating the optical cavity resonance or the photochromic film effectively tunes the work-function, suggesting a new tool for tailoring material properties. PMID:23463588

  17. Avalanche-diode oscillator circuit with tuning at multiple frequencies

    NASA Technical Reports Server (NTRS)

    Parker, D.; Ablow, C. M.; Lee, R. E.; Karp, A.; Chambers, D. R.

    1971-01-01

    Detailed theoretical analysis of three different modes or types of high efficiency oscillation in a PIN diode are presented. For the TRAPATT mode in a PIN diode, it is shown that a traveling avalanche zone is not necessary to generate a dense trapped plasma. An economical computer program for TRAPATT oscillations in a PIN diode is described. Typical results of diode power, dc-to-RF conversion efficiency, and required circuit impedances are presented for several different current waveforms. A semianalytical solution for a second type of high efficiency mode in a PIN diode is derived assuming a rectangular current waveform. A quasi-static approximation is employed to derive a semianalytical solution for the voltage across a PIN diode in a third mode, where avalanching occurs during a major portion of a half cycle. Calculations for this mode indicate that the power increases proportionally to the magnitude of the drive current with a small decrease in efficiency relative to the ordinary TRAPATT mode. An analytical solution is also given for a PIN diode, where it is assumed that the ionization coefficient is a step function. It is shown that the step-ionization approximation permits one to draw possible patterns of avalanche region in the depletion layer as a function of time. A rule governing admissible patterns is derived and an example solution given for one admissible pattern. Preliminary experimental results on the high-efficiency oscillations are presented and discussed. Two different experimental circuits, which used channel-dropping filters to provide independent harmonic tuning, are described. Simpler circuits used to produce high-efficiency oscillations are discussed. Results of experiments using inexpensive Fairchild FD300 diodes are given.

  18. Frequency Response and Gap Tuning for Nonlinear Electrical Oscillator Networks

    PubMed Central

    Bhat, Harish S.; Vaz, Garnet J.

    2013-01-01

    We study nonlinear electrical oscillator networks, the smallest example of which consists of a voltage-dependent capacitor, an inductor, and a resistor driven by a pure tone source. By allowing the network topology to be that of any connected graph, such circuits generalize spatially discrete nonlinear transmission lines/lattices that have proven useful in high-frequency analog devices. For such networks, we develop two algorithms to compute the steady-state response when a subset of nodes are driven at the same fixed frequency. The algorithms we devise are orders of magnitude more accurate and efficient than stepping towards the steady-state using a standard numerical integrator. We seek to enhance a given network's nonlinear behavior by altering the eigenvalues of the graph Laplacian, i.e., the resonances of the linearized system. We develop a Newton-type method that solves for the network inductances such that the graph Laplacian achieves a desired set of eigenvalues; this method enables one to move the eigenvalues while keeping the network topology fixed. Running numerical experiments using three different random graph models, we show that shrinking the gap between the graph Laplacian's first two eigenvalues dramatically improves a network's ability to (i) transfer energy to higher harmonics, and (ii) generate large-amplitude signals. Our results shed light on the relationship between a network's structure, encoded by the graph Laplacian, and its function, defined in this case by the presence of strongly nonlinear effects in the frequency response. PMID:24223751

  19. Broad electrical tuning of plasmonic nanoantennas at visible frequencies

    NASA Astrophysics Data System (ADS)

    Hoang, Thang B.; Mikkelsen, Maiken H.

    2016-05-01

    We report an experimental demonstration of electrical tuning of plasmon resonances of optical nanopatch antennas over a wide wavelength range. The antennas consist of silver nanocubes separated from a gold film by a thin 8 nm polyelectrolyte spacer layer. By using ionic liquid and indium tin oxide coated glass as a top electrode, we demonstrate dynamic and reversible tuning of the plasmon resonance over 100 nm in the visible wavelength range using low applied voltages between -3.0 V and 2.8 V. The electrical potential is applied across the nanoscale gap causing changes in the gap thickness and dielectric environment which, in turn, modifies the plasmon resonance. The observed tuning range is greater than the full-width-at-half-maximum of the plasmon resonance, resulting in a tuning figure of merit of 1.05 and a tuning contrast greater than 50%. Our results provide an avenue to create active and reconfigurable integrated nanophotonic components for applications in optoelectronics and sensing.

  20. Spatial cue reliability drives frequency tuning in the barn Owl's midbrain

    PubMed Central

    Cazettes, Fanny; Fischer, Brian J; Pena, Jose L

    2014-01-01

    The robust representation of the environment from unreliable sensory cues is vital for the efficient function of the brain. However, how the neural processing captures the most reliable cues is unknown. The interaural time difference (ITD) is the primary cue to localize sound in horizontal space. ITD is encoded in the firing rate of neurons that detect interaural phase difference (IPD). Due to the filtering effect of the head, IPD for a given location varies depending on the environmental context. We found that, in barn owls, at each location there is a frequency range where the head filtering yields the most reliable IPDs across contexts. Remarkably, the frequency tuning of space-specific neurons in the owl's midbrain varies with their preferred sound location, matching the range that carries the most reliable IPD. Thus, frequency tuning in the owl's space-specific neurons reflects a higher-order feature of the code that captures cue reliability. DOI: http://dx.doi.org/10.7554/eLife.04854.001 PMID:25531067

  1. Electronic structure tuning of diamondoids through functionalization

    NASA Astrophysics Data System (ADS)

    Rander, Torbjörn; Staiger, Matthias; Richter, Robert; Zimmermann, Tobias; Landt, Lasse; Wolter, David; Dahl, Jeremy E.; Carlson, Robert M. K.; Tkachenko, Boryslav A.; Fokina, Natalie A.; Schreiner, Peter R.; Möller, Thomas; Bostedt, Christoph

    2013-01-01

    We investigated the changes in electronic structures induced by chemical functionalization of the five smallest diamondoids using valence photoelectron spectroscopy. Through the variation of three parameters, namely functional group (thiol, hydroxy, and amino), host cluster size (adamantane, diamantane, triamantane, [121]tetramantane, and [1(2,3)4]pentamantane), and functionalization site (apical and medial) we are able to determine to what degree these affect the electronic structures of the overall systems. We show that unlike, for example, in the case of halobenzenes, the ionization potential does not show a linear dependence on the electronegativity of the functional group. Instead, a linear correlation exists between the HOMO-1 ionization potential and the functional group electronegativity. This is due to localization of the HOMO on the functional group and the HOMO-1 on the diamondoid cage. Density functional theory supports our interpretations.

  2. Isotope enrichment by frequency-tripled temperature tuned neodymium laser photolysis of formaldehyde

    DOEpatents

    Marling, John B.

    1977-01-01

    Enrichment of carbon, hydrogen and/or oxygen isotopes by means of isotopically selective photo-predissociation of formaldehyde is achieved by irradiation provided by a frequency-tripled, temperature tuned neodymium laser.

  3. A novel frequency tuned wireless actuator with snake-like motion

    NASA Astrophysics Data System (ADS)

    Zhang, Kewei; Zhu, Qianke; Chai, Yuesheng

    2016-07-01

    In this work, we propose a novel wireless actuator which is composed of magnetostrictive material/copper bi-layer film. The actuator can be controlled to move like a snake bi-directionally along a pipe by tuning the frequency of external magnetic field near its first order resonant frequency. The governing equation for the actuator is established and the vibration mode shape function is derived. Theoretical analysis shows that motion of the actuator is achieved by asymmetric vibration mode shape, specific vibration bending deformation, and effective net total impacting force. The simulation and experimental results well confirm the theoretical analysis. This work provides contribution to the development of wireless micro robots and autonomous magnetostrictive sensors.

  4. Higher-order vibrational mode frequency tuning utilizing fishbone-shaped microelectromechanical systems resonator

    NASA Astrophysics Data System (ADS)

    Suzuki, Naoya; Tanigawa, Hiroshi; Suzuki, Kenichiro

    2013-04-01

    Resonators based on microelectromechanical systems (MEMS) have received considerable attention for their applications for wireless equipment. The requirements for this application include small size, high frequency, wide bandwidth and high portability. However, few MEMS resonators with wide-frequency tuning have been reported. A fishbone-shaped resonator has a resonant frequency with a maximum response that can be changed according to the location and number of several exciting electrodes. Therefore, it can be expected to provide wide-frequency tuning. The resonator has three types of electrostatic forces that can be generated to deform a main beam. We evaluate the vibrational modes caused by each exciting electrodes by comparing simulated results with measured ones. We then successfully demonstrate the frequency tuning of the first to fifth resonant modes by using the algorithm we propose here. The resulting frequency tuning covers 178 to 1746 kHz. In addition, we investigate the suppression of the anchor loss to enhance the Q-factor. An experiment shows that tapered-shaped anchors provide a higher Q-factor than rectangular-shaped anchors. The Q-factor of the resonators supported by suspension beams is also discussed. Because the suspension beams cause complicated vibrational modes for higher frequencies, the enhancement of the Q-factor for high vibrational modes cannot be obtained here. At present, the tapered-anchor resonators are thought to be most suitable for frequency tuning applications.

  5. Low-Frequency Envelope Sensitivity Produces Asymmetric Binaural Tuning Curves

    PubMed Central

    Agapiou, John P.; McAlpine, David

    2008-01-01

    Neurons in the auditory midbrain are sensitive to differences in the timing of sounds at the two ears—an important sound localization cue. We used broadband noise stimuli to investigate the interaural-delay sensitivity of low-frequency neurons in two midbrain nuclei: the inferior colliculus (IC) and the dorsal nucleus of the lateral lemniscus. Noise-delay functions showed asymmetries not predicted from a linear dependence on interaural correlation: a stretching along the firing-rate dimension (rate asymmetry), and a skewing along the interaural-delay dimension (delay asymmetry). These asymmetries were produced by an envelope-sensitive component to the response that could not entirely be accounted for by monaural or binaural nonlinearities, instead indicating an enhancement of envelope sensitivity at or after the level of the superior olivary complex. In IC, the skew-like asymmetry was consistent with intermediate-type responses produced by the convergence of ipsilateral peak-type inputs and contralateral trough-type inputs. This suggests a stereotyped pattern of input to the IC. In the course of this analysis, we were also able to determine the contribution of time and phase components to neurons' internal delays. These findings have important consequences for the neural representation of interaural timing differences and interaural correlation—cues critical to the perception of acoustic space. PMID:18753329

  6. Neural Tuning Functions Underlie Both Generalization and Interference.

    PubMed

    Howard, Ian S; Franklin, David W

    2015-01-01

    In sports, the role of backswing is considered critical for generating a good shot, even though it plays no direct role in hitting the ball. We recently demonstrated the scientific basis of this phenomenon by showing that immediate past movement affects the learning and recall of motor memories. This effect occurred regardless of whether the past contextual movement was performed actively, passively, or shown visually. In force field studies, it has been shown that motor memories generalize locally and that the level of compensation decays as a function of movement angle away from the trained movement. Here we examine if the contextual effect of past movement exhibits similar patterns of generalization and whether it can explain behavior seen in interference studies. Using a single force-field learning task, the directional tuning curves of both the prior contextual movement and the subsequent force field adaptive movements were measured. The adaptation movement direction showed strong directional tuning, decaying to zero by 90° relative to the training direction. The contextual movement direction exhibited a similar directional tuning, although the effect was always above 60%. We then investigated the directional tuning of the passive contextual movement using interference tasks, where the contextual movements that uniquely specified the force field direction were separated by ±15° or ±45°. Both groups showed a pronounced tuning effect, which could be well explained by the directional tuning functions for single force fields. Our results show that contextual effect of past movement influences predictive force compensation, even when adaptation does not require contextual information. However, when such past movement contextual information is crucial to the task, such as in an interference study, it plays a strong role in motor memory learning and recall. This work demonstrates that similar tuning responses underlie both generalization of movement direction

  7. Neural Tuning Functions Underlie Both Generalization and Interference

    PubMed Central

    Howard, Ian S.; Franklin, David W.

    2015-01-01

    In sports, the role of backswing is considered critical for generating a good shot, even though it plays no direct role in hitting the ball. We recently demonstrated the scientific basis of this phenomenon by showing that immediate past movement affects the learning and recall of motor memories. This effect occurred regardless of whether the past contextual movement was performed actively, passively, or shown visually. In force field studies, it has been shown that motor memories generalize locally and that the level of compensation decays as a function of movement angle away from the trained movement. Here we examine if the contextual effect of past movement exhibits similar patterns of generalization and whether it can explain behavior seen in interference studies. Using a single force-field learning task, the directional tuning curves of both the prior contextual movement and the subsequent force field adaptive movements were measured. The adaptation movement direction showed strong directional tuning, decaying to zero by 90° relative to the training direction. The contextual movement direction exhibited a similar directional tuning, although the effect was always above 60%. We then investigated the directional tuning of the passive contextual movement using interference tasks, where the contextual movements that uniquely specified the force field direction were separated by ±15° or ±45°. Both groups showed a pronounced tuning effect, which could be well explained by the directional tuning functions for single force fields. Our results show that contextual effect of past movement influences predictive force compensation, even when adaptation does not require contextual information. However, when such past movement contextual information is crucial to the task, such as in an interference study, it plays a strong role in motor memory learning and recall. This work demonstrates that similar tuning responses underlie both generalization of movement direction

  8. General model with experimental validation of electrical resonant frequency tuning of electromagnetic vibration energy harvesters

    NASA Astrophysics Data System (ADS)

    Zhu, Dibin; Roberts, Stephen; Mouille, Thomas; Tudor, Michael J.; Beeby, Stephen P.

    2012-10-01

    This paper presents a general model and its experimental validation for electrically tunable electromagnetic energy harvesters. Electrical tuning relies on the adjustment of the electrical load so that the maximum output power of the energy harvester occurs at a frequency which is different from the mechanical resonant frequency of the energy harvester. Theoretical analysis shows that for this approach to be feasible the electromagnetic vibration energy harvester’s coupling factor must be maximized so that its resonant frequency can be tuned with the minimum decrease of output power. Two different-sized electromagnetic energy harvesters were built and tested to validate the model. Experimentally, the micro-scale energy harvester has a coupling factor of 0.0035 and an untuned resonant frequency of 70.05 Hz. When excited at 30 mg, it was tuned by 0.23 Hz by changing its capacitive load from 0 to 4000 nF its effective tuning range is 0.15 Hz for a capacitive load variation from 0 to 1500 nF. The macro-scale energy harvester has a coupling factor of 552.25 and an untuned resonant frequency of 95.1 Hz and 95.5 Hz when excited at 10 mg and 25 mg, respectively. When excited at 10 mg, it was tuned by 3.8 Hz by changing its capacitive load from 0 to 1400 nF it has an effective tuning range of 3.5 Hz for a capacitive load variation from 0 to 1200 nF. When excited at 25 mg, its resonant frequency was tuned by 4.2 Hz by changing its capacitive load from 0 to 1400 nF it has an effective tuning range of about 5 Hz. Experimental results were found to agree with the theoretical analysis to within 10%.

  9. Frequency doubling of copper lasers using temperature-tuned ADP

    SciTech Connect

    Molander, W.A.

    1994-03-01

    The ability to generate high average power uv at 255 nm by frequency doubling the green line (510.6 nm) of copper lasers would greatly extend the utility of copper lasers. Material processing and microlithography are two areas of interest. The frequency-doubled copper laser could replace the KrF excimer laser, which has a similar wavelength (248 nm), in some applications. The frequency-doubled copper laser has a narrow linewidth and excellent beam quality at a competitive cost. Other attractive features are high reliability, low operating costs, and the absence of toxic gases. This paper will report recent progress in high-efficiency, high-average-power harmonic generation of the copper laser green line using noncritical phase matching in ADP. Frequency doubling of the yellow line (578.2 nm) and sum-frequency mixing of the two lines are also of interest. These processes, however, cannot be phase-matched in ADP and, therefore, will not be discussed here. The results reported and the issues identified here would be important in these other processes and also in many other frequency conversion schemes in the uv such as 4{omega} conversion of Nd{sup 3+}:YAG lasers.

  10. Frequency tuning curves of the dolphin's hearing: envelope-following response study.

    PubMed

    Popov, V V; Supin, A Y; Klishin, V O

    1996-04-01

    Simultaneous tone-tone masking in conjunction with the envelope-following response (EFR) recording was used to obtain tuning curves in dolphins (Tursiops truncatus). The EFR was evoked by amplitude-modulated probes of various frequencies. A modulation rate of 600 Hz was found to fit the requirement to have a narrow spectrum and evoke EFR of large amplitude. Tuning curves were obtained within the frequency range from 11.2 to 110 kHz. The Q10 values of the obtained tuning curves varied from 12-14 at the 11.2 kHz center frequency to 17-20 at the 64-90 kHz frequencies. PMID:8847667

  11. Self-Tuning Adaptive-Controller Using Online Frequency Identification

    NASA Technical Reports Server (NTRS)

    Chiang, W. W.; Cannon, R. H., Jr.

    1985-01-01

    A real time adaptive controller was designed and tested successfully on a fourth order laboratory dynamic system which features very low structural damping and a noncolocated actuator sensor pair. The controller, implemented in a digital minicomputer, consists of a state estimator, a set of state feedback gains, and a frequency locked loop (FLL) for real time parameter identification. The FLL can detect the closed loop natural frequency of the system being controlled, calculate the mismatch between a plant parameter and its counterpart in the state estimator, and correct the estimator parameter in real time. The adaptation algorithm can correct the controller error and stabilize the system for more than 50% variation in the plant natural frequency, compared with a 10% stability margin in frequency variation for a fixed gain controller having the same performance at the nominal plant condition. After it has locked to the correct plant frequency, the adaptive controller works as well as the fixed gain controller does when there is no parameter mismatch. The very rapid convergence of this adaptive system is demonstrated experimentally, and can also be proven with simple root locus methods.

  12. Gamma Frequency and the Spatial Tuning of Primary Visual Cortex

    PubMed Central

    Fusca, Marco; Rees, Geraint; Schwarzkopf, D. Samuel; Barnes, Gareth

    2016-01-01

    Visual stimulation produces oscillatory gamma responses in human primary visual cortex (V1) that also relate to visual perception. We have shown previously that peak gamma frequency positively correlates with central V1 cortical surface area. We hypothesized that people with larger V1 would have smaller receptive fields and that receptive field size, not V1 area, might explain this relationship. Here we set out to test this hypothesis directly by investigating the relationship between fMRI estimated population receptive field (pRF) size and gamma frequency in V1. We stimulated both the near-center and periphery of the visual field using both large and small stimuli in each location and replicated our previous finding of a positive correlation between V1 surface area and peak gamma frequency. Counter to our expectation, we found that between participants V1 size (and not PRF size) accounted for most of the variability in gamma frequency. Within-participants we found that gamma frequency increased, rather than decreased, with stimulus eccentricity directly contradicting our initial hypothesis. PMID:27362265

  13. Laser frequency stabilization using folded cavity and mirror reflectivity tuning

    NASA Astrophysics Data System (ADS)

    Liu, X.; Cassou, K.; Chiche, R.; Dupraz, K.; Favier, P.; Flaminio, R.; Honda, Y.; Huang, W. H.; Martens, A.; Michel, C.; Pinard, L.; Sassolas, B.; Soskov, V.; Tang, C. X.; Zomer, F.

    2016-06-01

    A new method of laser frequency stabilization using polarization property of an optical cavity is proposed. In a standard Fabry-Perot cavity, the coating layers thickness of cavity mirrors is calculated to obtain the same phase shift for s- and p-wave but a slight detuning from the nominal thickness can produce s- and p-wave phase detuning. As a result, each wave accumulates a different round-trip phase shift and resonates at a different frequency. Using this polarization property, an error signal is generated by a simple setup consisting of a quarter wave-plate rotated at 45°, a polarizing beam splitter and two photodiodes. This method exhibits similar error signal as the Pound-Drever-Hall technique but without need for any frequency modulation. Lock theory and experimental results are presented in this paper.

  14. Surface roughness effects on the frequency tuning performance of a nanoelectromechanical resonator

    PubMed Central

    2013-01-01

    Electrothermal heating is one of radio frequency tuning method in nanoelectromechanical resonators with magnetomotive transduction. This study confirmed that the surface roughness of the nanoresonator affects the electrothermal tuning performance under moderate conditions at room temperature. The effect of surface roughness on electrothermal tuning is complicated and involves interactions of mechanical and electrical properties. In addition, the electrothermal damping varied depending on the nanoscale molecular solid structure. These factors affect the signal-to-noise ratio, the effective stress of the beam, and the quality Q-factor of the nanoresonator. PMID:23742218

  15. Analysis and experiment of self-frequency-tuning piezoelectric energy harvesters for rotational motion

    NASA Astrophysics Data System (ADS)

    Hsu, Jin-Chen; Tseng, Chih-Ta; Chen, Yi-Sheng

    2014-07-01

    Piezoelectric energy harvesting provides a means to harvest the ambient kinetic energy (e.g., vibrations and rotations) of structures for conversion into usable electricity. The technique can be employed to provide power sources for wireless sensors and low-power devices. Most energy harvesting devices developed to date operate most efficiently within a narrow bandwidth because they are resonance-frequency-based designs, although several tunable techniques have been proposed to broaden the efficient frequency range of energy harvesting. However, most efforts have focused on harvesting vibration energy rather than rotational energy. This paper presents the results of a comprehensive design analysis and experimental tests of a passive self-tuning piezoelectric composite cantilever beam for harvesting energy from rotational motion. The piezoelectric beam harvester is mounted on a rotating axis in the radial direction so that the tensile stress induced by the centrifugal force effectively stiffens the beam to passively tune the resonance frequency. A calculation procedure based on a finite element method is developed to analyze the self-frequency-tuning piezoelectric energy harvester, and the results are compared with those obtained from an analytic beam model. The design parameters for the self-tuning characteristics are identified and discussed. Experimental results verify the frequency-tuning energy harvesting behavior and show improved performances for the voltage and power outputs in the bandwidth.

  16. Integrated tuning fork nanocavity optomechanical transducers with high f M Q M product and stress-engineered frequency tuning

    NASA Astrophysics Data System (ADS)

    Zhang, R.; Ti, C.; Davanço, M. I.; Ren, Y.; Aksyuk, V.; Liu, Y.; Srinivasan, K.

    2015-09-01

    Cavity optomechanical systems are being widely developed for precision force and displacement measurements. For nanomechanical transducers, there is usually a trade-off between the frequency (fM) and quality factor (QM), which limits temporal resolution and sensitivity. Here, we present a monolithic cavity optomechanical transducer supporting both high fM and high QM. By replacing the common doubly clamped, Si3N4 nanobeam with a tuning fork geometry, we demonstrate devices with the fundamental f M ≈ 29 MHz and Q M ≈ 2.2 × 10 5 , corresponding to an fMQM product of 6.35 × 10 12 Hz , comparable to the highest values previously demonstrated for room temperature operation. This high fMQM product is partly achieved by engineering the stress of the tuning fork to be 3 times the residual film stress through clamp design, which results in an increase of fM up to 1.5 times. Simulations reveal that the tuning fork design simultaneously reduces the clamping, thermoelastic dissipation, and intrinsic material damping contributions to mechanical loss. This work may find application when both high temporal and force resolution are important, such as in compact sensors for atomic force microscopy.

  17. Adaptive tuning functions arise from visual observation of past movement

    PubMed Central

    Howard, Ian S.; Franklin, David W.

    2016-01-01

    Visual observation of movement plays a key role in action. For example, tennis players have little time to react to the ball, but still need to prepare the appropriate stroke. Therefore, it might be useful to use visual information about the ball trajectory to recall a specific motor memory. Past visual observation of movement (as well as passive and active arm movement) affects the learning and recall of motor memories. Moreover, when passive or active, these past contextual movements exhibit generalization (or tuning) across movement directions. Here we extend this work, examining whether visual motion also exhibits similar generalization across movement directions and whether such generalization functions can explain patterns of interference. Both the adaptation movement and contextual movement exhibited generalization beyond the training direction, with the visual contextual motion exhibiting much broader tuning. A second experiment demonstrated that this pattern was consistent with the results of an interference experiment where opposing force fields were associated with two separate visual movements. Overall, our study shows that visual contextual motion exhibits much broader (and shallower) tuning functions than previously seen for either passive or active movements, demonstrating that the tuning characteristics of past motion are highly dependent on their sensory modality. PMID:27341163

  18. Adaptive tuning functions arise from visual observation of past movement.

    PubMed

    Howard, Ian S; Franklin, David W

    2016-01-01

    Visual observation of movement plays a key role in action. For example, tennis players have little time to react to the ball, but still need to prepare the appropriate stroke. Therefore, it might be useful to use visual information about the ball trajectory to recall a specific motor memory. Past visual observation of movement (as well as passive and active arm movement) affects the learning and recall of motor memories. Moreover, when passive or active, these past contextual movements exhibit generalization (or tuning) across movement directions. Here we extend this work, examining whether visual motion also exhibits similar generalization across movement directions and whether such generalization functions can explain patterns of interference. Both the adaptation movement and contextual movement exhibited generalization beyond the training direction, with the visual contextual motion exhibiting much broader tuning. A second experiment demonstrated that this pattern was consistent with the results of an interference experiment where opposing force fields were associated with two separate visual movements. Overall, our study shows that visual contextual motion exhibits much broader (and shallower) tuning functions than previously seen for either passive or active movements, demonstrating that the tuning characteristics of past motion are highly dependent on their sensory modality. PMID:27341163

  19. Apparatus and Method to Enable Precision and Fast Laser Frequency Tuning

    NASA Technical Reports Server (NTRS)

    Chen, Jeffrey R. (Inventor); Numata, Kenji (Inventor); Wu, Stewart T. (Inventor); Yang, Guangning (Inventor)

    2015-01-01

    An apparatus and method is provided to enable precision and fast laser frequency tuning. For instance, a fast tunable slave laser may be dynamically offset-locked to a reference laser line using an optical phase-locked loop. The slave laser is heterodyned against a reference laser line to generate a beatnote that is subsequently frequency divided. The phase difference between the divided beatnote and a reference signal may be detected to generate an error signal proportional to the phase difference. The error signal is converted into appropriate feedback signals to phase lock the divided beatnote to the reference signal. The slave laser frequency target may be rapidly changed based on a combination of a dynamically changing frequency of the reference signal, the frequency dividing factor, and an effective polarity of the error signal. Feed-forward signals may be generated to accelerate the slave laser frequency switching through laser tuning ports.

  20. Tuning the resonant frequency of resonators using molecular surface self-assembly approach.

    PubMed

    Liu, Wenpeng; Wang, Jingwei; Yu, Yifei; Chang, Ye; Tang, Ning; Qu, Hemi; Wang, Yanyan; Pang, Wei; Zhang, Hao; Zhang, Daihua; Xu, Huaping; Duan, Xuexin

    2015-01-14

    In this work, a new method to tune the resonant frequency of microfabricated resonator using molecular layer-by-layer (LbL) self-assembly approach is demonstrated. By simply controlling the polymer concentration and the number of layers deposited, precisely tuning the frequency of microfabricated resonators is realized. Due to its selective deposition through specific molecular recognitions, such technique avoids the high-cost and complex steps of conventional semiconductor fabrications and is able to tune individual diced device. Briefly, film bulk acoustic resonator (FBAR) is used to demonstrate the tuning process and two types of LbL deposition methods are compared. The film thickness and morphology have been characterized by UV-vis reflection spectra, ellipsometer and AFM. As a result, the maximum resonant frequency shift of FBAR reaches more than 20 MHz, meaning 1.4% tunability at least. The minimum frequency shift is nearly 10 kHZ per bilayer, indicating 7 ppm tuning resolution. Pressure cooker test (PCT) is performed to evaluate the reliability of LbL coated FBAR. Furthermore, applications for wireless broadband communication and chemical sensors of LbL coated FBAR have been demonstrated. PMID:25487349

  1. Molecular Design for Tuning Work Functions of Transparent Conducting Electrodes.

    PubMed

    Koldemir, Unsal; Braid, Jennifer L; Morgenstern, Amanda; Eberhart, Mark; Collins, Reuben T; Olson, Dana C; Sellinger, Alan

    2015-06-18

    In this Perspective, we provide a brief background on the use of aromatic phosphonic acid modifiers for tuning work functions of transparent conducting oxides, for example, zinc oxide (ZnO) and indium tin oxide (ITO). We then introduce our preliminary results in this area using conjugated phosphonic acid molecules, having a substantially larger range of dipole moments than their unconjugated analogues, leading to the tuning of ZnO and ITO electrodes over a 2 eV range as derived from Kelvin probe measurements. We have found that these work function changes are directly correlated to the magnitude and the direction of the computationally derived molecular dipole of the conjugated phosphonic acids, leading to the predictive power of computation to drive the synthesis of new and improved phosphonic acid ligands. PMID:26266603

  2. Wet mammals shake at tuned frequencies to dry

    PubMed Central

    Dickerson, Andrew K.; Mills, Zachary G.; Hu, David L.

    2012-01-01

    In cold wet weather, mammals face hypothermia if they cannot dry themselves. By rapidly oscillating their bodies, through a process similar to shivering, furry mammals can dry themselves within seconds. We use high-speed videography and fur particle tracking to characterize the shakes of 33 animals (16 animals species and five dog breeds), ranging over four orders of magnitude in mass from mice to bears. We here report the power law relationship between shaking frequency f and body mass M to be f ∼ M−0.22, which is close to our prediction of f ∼ M−0.19 based upon the balance of centrifugal and capillary forces. We also observe a novel role for loose mammalian dermal tissue: by whipping around the body, it increases the speed of drops leaving the animal and the ensuing dryness relative to tight dermal tissue. PMID:22904256

  3. Two-dimensional resonance frequency tuning approach for vibration-based energy harvesting

    NASA Astrophysics Data System (ADS)

    Dong, Lin; Prasad, M. G.; Fisher, Frank T.

    2016-06-01

    Vibration-based energy harvesting seeks to convert ambient vibrations to electrical energy and is of interest for, among other applications, powering the individual nodes of wireless sensor networks. Generally it is desired to match the resonant frequencies of the device to the ambient vibration source to optimize the energy harvested. This paper presents a two-dimensionally (2D) tunable vibration-based energy harvesting device via the application of magnetic forces in two-dimensional space. These forces are accounted for in the model separately, with the transverse force contributing to the transverse stiffness of the system while the axial force contributes to a change in axial stiffness of the beam. Simulation results from a COMSOL magnetostatic 3D model agree well with the analytical model and are confirmed with a separate experimental study. Furthermore, analysis of the three possible magnetization orientations between the fixed and tuning magnets shows that the transverse parallel magnetization orientation is the most effective with regards to the proposed 2D tuning approach. In all cases the transverse stiffness term is in general significantly larger than the axial stiffness contribution, suggesting that from a tuning perspective it may be possible to use these stiffness contributions for coarse and fine frequency tuning, respectively. This 2D resonant frequency tuning approach extends earlier 1D approaches and may be particularly useful in applications where space constraints impact the available design space of the energy harvester.

  4. Tuning sum rules with window functions for optical constant evaluation

    NASA Astrophysics Data System (ADS)

    Rodríguez-de Marcos, Luis V.; Méndez, José A.; Larruquert, Juan I.

    2016-07-01

    Sum rules are a useful tool to evaluate the global consistency of a set of optical constants. We present a procedure to spectrally tune sum rules to evaluate the local consistency of optical constants. It enables enhancing the weight of a desired spectral range within the sum-rule integral. The procedure consists in multiplying the complex refractive index with an adapted function, which is named window function. Window functions are constructed through integration of Lorentz oscillators. The asymptotic decay of these window functions enables the derivation of a multiplicity of sum rules akin to the inertial sum rule, along with one modified version of f-sum rule. This multiplicity of sum rules combined with the free selection of the photon energy range provides a double way to tune the spectral contribution within the sum rule. Window functions were applied to reported data of SrF2 and of Al films in order to check data consistency over the spectrum. The use of window functions shows that the optical constants of SrF2 are consistent in a broad spectrum. Regarding Al, some spectral ranges are seen to present a lower consistency, even though the standard sum rules with no window function did not detect inconsistencies. Hence window functions are expected to be a helpful tool to evaluate the local consistency of optical constants.

  5. 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.

  6. Application of bias voltage to tune the resonant frequency of membrane-based electroactive polymer energy harvesters

    NASA Astrophysics Data System (ADS)

    Dong, Lin; Grissom, Michael; Fisher, Frank T.

    2016-05-01

    Vibration-based energy harvesting has been widely investigated to as a means to generate low levels of electrical energy for applications such as wireless sensor networks. However, for optimal performance it is necessary to ensure that resonant frequencies of the device match the ambient vibration frequencies for maximum energy harvested. Here a novel resonant frequency tuning approach is proposed by applying a bias voltage to a pre-stretched electroactive polymer (EAP) membrane, such that the resulting changes in membrane tension can tune the device to match the environmental vibration source. First, a material model which accounts for the change in properties due to the pre-stretch of a VHB 4910 EAP membrane is presented. The effect of the bias voltage on the EAP membrane, which induces an electrostatic pressure and corresponding reduction in membrane thickness, are then determined. The FEM results from ANSYS agree well with an analytical hyperelastic model of the activation response of the EAP membrane. Lastly, through a mass-loaded circular membrane vibration model, the effective resonant frequency of the energy harvester can be determined as a function of changes in membrane tension due to the applied bias voltage. In the case of an EAP membrane, pre-stretch contributes to the pre-stretch stiffness of the system while the applied bias voltage contributes to a change in bias voltage stiffness of the membrane. Preliminary experiments verified the resonant frequencies corresponding to the bias voltages predicted from the appropriate models. The proposed bias voltage tuning approach for the EAP membrane may provide a novel tuning strategy to enable energy harvesting from various ambient vibration sources in various application environments.

  7. Bidirectional frequency tuning of a piezoelectric energy converter based on a cantilever beam

    NASA Astrophysics Data System (ADS)

    Eichhorn, C.; Goldschmidtboeing, F.; Woias, P.

    2009-09-01

    A piezoelectric energy converter is presented, whose resonance frequency can be tuned by applying mechanical stress to its structure. The converter consists of a piezo-polymer cantilever beam with two additional thin arms, which are used to apply an axial preload to the tip of the beam. The compressive or tensile prestress applied through the arms leads to a shift of the beam's resonance frequency. Experiments with this structure indicate a high potential: the resonance frequency of a harvester to which a compressive preload was applied could be altered from 380 Hz to 292 Hz. In another experiment, a harvester with stiffened arms was tuned from 440 Hz to 460 Hz by applying a tensile preload. In combination with automatic control of the applied force, this type of structure could be used to enhance the performance of energy harvesters in vibrating environments with occasional shifts of the vibrational frequency.

  8. Influence of Broad Auditory Tuning on Across-Frequency Integration of Speech Patterns

    ERIC Educational Resources Information Center

    Healy, Eric W.; Carson, Kimberly A.

    2010-01-01

    Purpose: The purpose of the present study was to assess whether diminished tolerance for disruptions to across-frequency timing in listeners with hearing impairment can be attributed to broad auditory tuning. Method: In 2 experiments in which random assignment was used, sentences were represented as 3 noise bands centered at 530, 1500, and 4243…

  9. Fine frequency tuning in sum-frequency generation of continuous-wave single-frequency coherent light at 252 nm with dual-wavelength enhancement.

    PubMed

    Kumagai, Hiroshi

    2007-01-01

    Fine frequency tuning of the deep-ultraviolet single-mode coherent light at 252 nm was conducted through the PID feedback system automatically by changing the temperature of a beta-BaB(2)O(4) (BBO) crystal in a doubly resonant external cavity for the sum-frequency mixing of 373 and 780 nm light. The temperature-dependent frequency tuning rate is 19.3 MHzK(-1), which is sufficiently fine to realize the laser cooling of neutral silicon atoms because the natural width of the laser cooling transition is 28.8 MHz. PMID:17167584

  10. Frequency tuning of the optical delay in cesium D{sub 2} line including hyperfine structure

    SciTech Connect

    Anderson, Monte D.; Perram, Glen P.

    2010-03-15

    The frequency dependence of optical delays in both the wings and core of the cesium 6 {sup 2}S{sub 1/2}-6 {sup 2}P{sub 3/2} transition have been observed and modeled with a Voigt line shape convolved with the six hyperfine components. Tunable delays of 0-37 ns are achieved by tuning the laser frequency through resonance at various vapor pressures of 0.15-5.28 mTorr.

  11. RFQ (radio-frequency quadrupole) accelerator tuning system

    DOEpatents

    Bolie, V.W.

    1988-04-12

    A cooling system is provided for maintaining a preselected operating temperature in a device, which may be an RFQ accelerator, having a variable heat removal requirement, by circulating a cooling fluid through a cooling system remote from the device. Internal sensors in the device enable an estimated error signal to be generated from parameters which are indicative of the heat removal requirement from the device. Sensors are provided at predetermined locations in the cooling system for outputting operational temperature signals. Analog and digital computers define a control signal functionally related to the temperature signals and the estimated error signal, where the control signal is defined effective to return the device to the preselected operating temperature in a stable manner. The cooling system includes a first heat sink responsive to a first portion of the control signal to remove heat from a major portion of the circulating fluid. A second heat sink is responsive to a second portion of the control to remove heat from a minor portion of the circulating fluid. The cooled major and minor portions of the circulating fluid are mixed in responsive to a mixing portion of the control signal, which is effective to proportion the major and minor portions of the circulating fluid to establish a mixed fluid temperature which is effective to define the preselected operating temperature for the remote device. 3 figs., 2 tabs.

  12. Frequency-feedback tuning for single-cell cavity under rf heating

    SciTech Connect

    Stepp, J.D.; Bridges, J.F.

    1993-08-01

    A tuning system is described that is being used to match the source frequency of a high-power klystron on the resonant frequency of the prototype single-cell cavity for the 7-GeV Advance Photon Source (APS) storage ring. Typically a water-cooled piston tuner is required to adjust the reactive component of the cavity`s impedance to minimize reflected power back to the RF drive source. As the cavity watts expand due to RF heating, the resonant frequency decreases. Adjusting the source frequency to follow the cavity resonant frequency is a convenient method used to condition the cavity (for vacuum) at high power levels, in this case, 1 MV gap voltage at 100 kW power level. The tuning system consists of two coupling ports, a phase detector, a digitizing I/O system, and a DC coupled FM-modulated RF source. Proportional Integral Derivative (PID) loop parameters for the Experimental Physics and Industrial Control System (EPICS) software are calculated, and data is presented showing the damped response to peturbations on the loop. The timing system presented here does not need water-cooling, has no moving parts to wear out, and has an inherently faster response time. Its one limitation is the digitizing sampling rate. The only limitation in tuning range is the bandwidth of the RF source.

  13. Electrical laser frequency tuning by three terminal terahertz quantum cascade lasers

    SciTech Connect

    Ohtani, K. Beck, M.; Faist, J.

    2014-01-06

    Electrical laser emission frequency tuning of a three terminal THz quantum cascade laser is demonstrated. A high electron mobility transistor structure is used in a surface plasmon waveguide to modulate the electron density in a channel, controlling the effective refractive index of the waveguide. The threshold current density was modulated by 28% via applying voltage from −3 to 2 V. The observed laser emission frequency shift by electric field was 2 GHz. By using the three terminal devices, pure frequency modulation of the output light is, in principle, achievable.

  14. Investigation of pulsed mode operation with the frequency tuned CAPRICE ECRIS.

    PubMed

    Maimone, F; Tinschert, K; Endermann, M; Hollinger, R; Kondrashev, S; Lang, R; Mäder, J; Patchakui, P T; Spädtke, P

    2016-02-01

    In order to increase the intensity of the highly charged ions produced by the Electron Cyclotron Resonance Ion Sources (ECRISs), techniques like the frequency tuning and the afterglow mode have been developed and in this paper the effect on the ion production is shown for the first time when combining both techniques. Recent experimental results proved that the tuning of the operating frequency of the ECRIS is a promising technique to achieve higher ion currents of higher charge states. On the other hand, it is well known that the afterglow mode of the ECRIS operation can provide more intense pulsed ion beams in comparison with the continuous wave (cw) operation. These two techniques can be combined by pulsing the variable frequency signal driving the traveling wave tube amplifier which provides the high microwave power to the ECRIS. In order to analyze the effect of these two combined techniques on the ion source performance, several experiments were carried out on the pulsed frequency tuned CAPRICE (Compacte source A Plusiers Résonances Ionisantes Cyclotron Electroniques)-type ECRIS. Different waveforms and pulse lengths have been investigated under different settings of the ion source. The results of the pulsed mode have been compared with those of cw operation. PMID:26931930

  15. Tuned range separated hybrid functionals for solvated low bandgap oligomers

    SciTech Connect

    Queiroz, Thiago B. de Kümmel, Stephan

    2015-07-21

    The description of charge transfer excitations has long been a challenge to time dependent density functional theory. The recently developed concept of “optimally tuned range separated hybrid (OT-RSH) functionals” has proven to describe charge transfer excitations accurately in many cases. However, describing solvated or embedded systems is yet a challenge. This challenge is not only computational but also conceptual, because the tuning requires identifying a specific orbital, typically the highest occupied one of the molecule under study. For solvated molecules, this orbital may be delocalized over the solvent. We here demonstrate that one way of overcoming this problem is to use a locally projected self-consistent field diagonalization on an absolutely localized molecular orbital expansion. We employ this approach to determine ionization energies and the optical gap of solvated oligothiophenes, i.e., paradigm low gap systems that are of relevance in organic electronics. Dioxane solvent molecules are explicitly represented in our calculations, and the ambiguities of straightforward parameter tuning in solution are elucidated. We show that a consistent estimate of the optimal range separated parameter (ω) at the limit of bulk solvation can be obtained by gradually extending the solvated system. In particular, ω is influenced by the solvent beyond the first coordination sphere. For determining ionization energies, a considerable number of solvent molecules on the first solvation shell must be taken into account. We demonstrate that accurately calculating optical gaps of solvated systems using OT-RSH can be done in three steps: (i) including the chemical environment when determining the range-separation parameter, (ii) taking into account the screening due to the solvent, and (iii) using realistic molecular geometries.

  16. Possibilities for Continuous Frequency Tuning in Terahertz Gyrotrons with Nontunable Electrodynamic Systems

    NASA Astrophysics Data System (ADS)

    Bratman, V. L.; Savilov, A. V.; Chang, T. H.

    2016-02-01

    Large ohmic losses in the cavities of terahertz gyrotrons may lead to the overlapping of the axial mode spectra. In a number of gyrotron experiments, this effect has been used to provide a fairly broadband frequency tuning by changing appropriately the operating magnetic field and/or accelerating voltage of the gyrotron. Similar to the systems with nonfixed axial structure of the RF electromagnetic field and low diffraction quality, which are due to weak reflections of the operating wave from the collector end of the electrodynamic system, this changing leads to a monotonic change in the axial index of the operating wave and transition from the gyrotron regime to the gyro-BWO regime. According to a theoretical comparison of these two methods performed on the basis of generalization of self-consistent gyrotron equations with allowance for variations in the axial electron momenta, low-reflection systems can provide a higher efficiency and monotonicity of the frequency tuning.

  17. Self-powered resonant frequency tuning for Piezoelectric Vibration Energy Harvesters

    NASA Astrophysics Data System (ADS)

    Ahmed-Seddik, B.; Despesse, G.; Boisseau, S.; Defay, E.

    2013-12-01

    This paper reports on the design, fabrication and testing of an innovative 33-mode piezoelectric vibration energy harvester (VEH). This system is able to change its resonant frequency in real time to follow the main frequency of a vibration source. The system proposed in this paper enables to adapt VEH characteristics (resonant frequency, electrical damping) to vibration parameters variations (frequency and amplitude) in order to optimize the extraction of energy and then the output power at any time. This solution allows up to 40% of resonant frequency tuning ratio; moreover, the adaptation is made in real time and the consumption of the regulation electronic is less than 10% of the VEH output power (480μW@0.1g-276Hz).

  18. Coupling and tuning of modal frequencies in direct current biased microelectromechanical systems arrays

    NASA Astrophysics Data System (ADS)

    Kambali, Prashant N.; Swain, Gyanadutta; Pandey, Ashok Kumar; Buks, Eyal; Gottlieb, Oded

    2015-08-01

    Understanding the coupling of different modal frequencies and their tuning mechanisms has become essential to design multi-frequency MEMS devices. In this work, we fabricate a MEMS beam with fixed boundaries separated from two side electrodes and a bottom electrode. Subsequently, we perform experiments to obtain the frequency variation of in-plane and out-of-plane mechanical modes of the microbeam with respect to both DC bias and laser heating. We show that the frequencies of the two modes coincide at a certain DC bias, which in turn can also be varied due to temperature. Subsequently, we develop a theoretical model to predict the variation of the two modes and their coupling due to a variable gap between the microbeam and electrodes, initial tension, and fringing field coefficients. Finally, we discuss the influence of frequency tuning parameters in arrays of 3, 33, and 40 microbeams, respectively. It is also found that the frequency bandwidth of a microbeam array can be increased to as high as 25 kHz for a 40 microbeam array with a DC bias of 80 V.

  19. Coupling and tuning of modal frequencies in direct current biased microelectromechanical systems arrays

    SciTech Connect

    Kambali, Prashant N.; Swain, Gyanadutta; Pandey, Ashok Kumar; Buks, Eyal; Gottlieb, Oded

    2015-08-10

    Understanding the coupling of different modal frequencies and their tuning mechanisms has become essential to design multi-frequency MEMS devices. In this work, we fabricate a MEMS beam with fixed boundaries separated from two side electrodes and a bottom electrode. Subsequently, we perform experiments to obtain the frequency variation of in-plane and out-of-plane mechanical modes of the microbeam with respect to both DC bias and laser heating. We show that the frequencies of the two modes coincide at a certain DC bias, which in turn can also be varied due to temperature. Subsequently, we develop a theoretical model to predict the variation of the two modes and their coupling due to a variable gap between the microbeam and electrodes, initial tension, and fringing field coefficients. Finally, we discuss the influence of frequency tuning parameters in arrays of 3, 33, and 40 microbeams, respectively. It is also found that the frequency bandwidth of a microbeam array can be increased to as high as 25 kHz for a 40 microbeam array with a DC bias of 80 V.

  20. Breath air measurement using wide-band frequency tuning IR laser photo-acoustic spectroscopy

    NASA Astrophysics Data System (ADS)

    Kistenev, Yury V.; Borisov, Alexey V.; Kuzmin, Dmitry A.; Bulanova, Anna A.; Boyko, Andrey A.; Kostyukova, Nadezhda Y.; Karapuzikov, Alexey A.

    2016-03-01

    The results of measuring of biomarkers in breath air of patients with broncho-pulmonary diseases using wide-band frequency tuning IR laser photo-acoustic spectroscopy and the methods of data mining are presented. We will discuss experimental equipment and various methods of intellectual analysis of the experimental spectra in context of above task. The work was carried out with partial financial support of the FCPIR contract No 14.578.21.0082 (ID RFMEFI57814X0082).

  1. Frequency tuning characteristics of a Q-switched Co:MgF2 laser

    NASA Technical Reports Server (NTRS)

    Lovold, S.; Moulton, P. F.; Killinger, D. K.; Menyuk, N.

    1985-01-01

    A tunable Q-switched Co:MgF2 laser has been developed for atmospheric remote sensing applications. Frequency tuning is provided by a quartz etalon and a specially designed three-element birefringent filter covering the whole gain bandwidth of the Co:MgF2 laser. The laser has good temporal and spectral characteristics, with an emission linewidth of approximately 3 GHz (0.1 per cm).

  2. A new fuzzy self-tuning PD load frequency controller for micro-hydropower system

    NASA Astrophysics Data System (ADS)

    Reyasudin Basir Khan, M.; Jidin, Razali; Pasupuleti, Jagadeesh

    2016-03-01

    This paper presents a new approach for controlling the secondary load bank of a micro-hydropower system using a fuzzy self-tuning proportional-derivative (PD) controller. This technology is designed in order to optimize the micro-hydropower system in a resort island located in the South China Sea. Thus, this technology will be able to mitigate the diesel fuel consumption and cost of electricity supply on the island. The optimal hydropower generation for this system depends on the available stream flow at the potential sites. At low stream flow, both the micro-hydropower system and the currently installed diesel generators are required to feed the load. However, when the hydropower generation exceeds the load demand, the diesel generator is shut down. Meanwhile, the system frequency is controlled by a secondary load bank that absorbs the hydropower which exceeds the consumer demand. The fuzzy rules were designed to automatically tune the PD gains under dynamic frequency variations. Performances of the fuzzy self-tuning PD controller were compared with the conventional PD controller. The result of the controller implementation shows the viability of the proposed new controller in achieving a higher performance and more robust load frequency control than the conventional PD controller.

  3. Design optimizations of phase noise, power consumption and frequency tuning for VCO

    NASA Astrophysics Data System (ADS)

    Nan, Chen; Shengxi, Diao; Lu, Huang; Xuefei, Bai; Fujiang, Lin

    2013-09-01

    To meet the requirements of the low power Zigbee system, VCO design optimizations of phase noise, power consumption and frequency tuning are discussed in this paper. Both flicker noise of tail bias transistors and up-conversion of flicker noise from cross-coupled pair are reduced by improved self-switched biasing technology, leading to low close-in phase noise. Low power is achieved by low supply voltage and triode region biasing. To linearly tune the frequency and get constant gain, distributed varactor structure is adopted. The proposed VCO is fabricated in SMIC 0.18-μm CMOS process. The measured linear tuning range is from 2.38 to 2.61 GHz. The oscillator exhibits low phase noise of -77.5 dBc/Hz and -122.8 dBc/Hz at 10 kHz and 1 MHz offset, respectively, at 2.55 GHz oscillation frequency while dissipating 2.7 mA from 1.2 V supply voltage, which well meet design specifications.

  4. Frequency Modulation Atomic Force Microscopy in Ionic Liquid Using Quartz Tuning Fork Sensors

    NASA Astrophysics Data System (ADS)

    Ichii, Takashi; Fujimura, Motohiko; Negami, Masahiro; Murase, Kuniaki; Sugimura, Hiroyuki

    2012-08-01

    Frequency modulation atomic force microscopy (FM-AFM) imaging in ionic liquids (ILs) were carried out. A quartz tuning fork sensor with a sharpened tungsten tip was used as a force sensor instead of a Si cantilever. Only the tip apex was immersed in ILs and the quality factor of the sensors was kept more than 100 in spite of the high viscosity of ILs. Atomic-resolution topographic imaging was successfully achieved in an IL as well as in an aqueous solution. In addition, frequency shift versus tip-to-sample distance curves were obtained and the structures of local solvation layers were studied.

  5. Observations of the frequency tuning effect in the 14 GHz CAPRICE ion source.

    PubMed

    Celona, L; Ciavola, G; Consoli, F; Gammino, S; Maimone, F; Mascali, D; Spädtke, P; Tinschert, K; Lang, R; Mäder, J; Robbach, J; Barbarino, S; Catalano, R S

    2008-02-01

    A set of measurements with the CAPRICE ion source at the GSI test bench has been carried out to investigate its behavior in terms of intensity and shape of the extracted beam when the microwaves generating the plasma sweep in a narrow range of frequency (+/-40 MHz) around the klystron center frequency (14.5 GHz). Remarkable variations have been observed depending on the source and the beamline operating parameters, confirming that a frequency dependent electromagnetic distribution is preserved even in the presence of plasma inside the source. Moreover, these observations confirm that the frequency tuning is a powerful method to optimize the electron cyclotron resonance ion source performances. A description of the experimental setup and of the obtained results is given in the following. PMID:18315291

  6. Postadsorption Work Function Tuning via Hydrogen Pressure Control

    PubMed Central

    2015-01-01

    The work function of metal substrates can be easily tuned, for instance, by adsorbing layers of molecular electron donors and acceptors. In this work, we discuss the possibility of changing the donor/acceptor mixing ratio reversibly after adsorption by choosing a donor/acceptor pair that is coupled via a redox reaction and that is in equilibrium with a surrounding gas phase. We discuss such a situation for the example of tetrafluoro-1,4-benzenediol (TFBD)/tetrafluoro-1,4-benzoquinone (TFBQ), adsorbed on Cu(111) and Ag(111) surfaces. We use density functional theory and ab initio thermodynamics to show that arbitrary TFBD/TFBQ mixing ratios can be set using hydrogen pressures attainable in low to ultrahigh vacuum. Adjusting the mixing ratio allows modifying the work function over a range of about 1 eV. Finally, we contrast single-species submonolayers with mixed layers to discuss why the resulting inhomogeneities in the electrostatic energy above the surface have different impacts on the interfacial level alignment and the work function. PMID:26692915

  7. Toward tuning the surface functionalization of small ceria nanoparticles

    SciTech Connect

    Huang, Xing; Wang, Binghui; Grulke, Eric A.; Beck, Matthew J.

    2014-02-21

    Understanding and controlling the performance of ceria nanoparticle (CNP) catalysts requires knowledge of the detailed structure and property of CNP surfaces and any attached functional groups. Here we report thermogravimetric analysis results showing that hydrothermally synthesized ∼30 nm CNPs are decorated with 12.9 hydroxyl groups per nm{sup 2} of CNP surface. Quantum mechanical calculations of the density and distribution of bound surface groups imply a scaling relationship for surface group density that balances formal charges in the functionalized CNP system. Computational results for CNPs with only hydroxyl surface groups yield a predicted density of bound hydroxyl groups for ∼30 nm CNPs that is ∼33% higher than measured densities. Quantitative agreement between predicted and measured hydroxyl surface densities is achieved when calculations consider CNPs with both –OH and –O{sub x} surface groups. For this more general treatment of CNP surface functionalizations, quantum mechanical calculations predict a range of stable surface group configurations that depend on the chemical potentials of O and H, and demonstrate the potential to tune CNP surface functionalizations by varying temperature and/or partial pressures of O{sub 2} and H{sub 2}O.

  8. Frequency-tuning input-shaped manifold-based switching control for underactuated space robot equipped with flexible appendages

    NASA Astrophysics Data System (ADS)

    Kojima, Hirohisa; Ieda, Shoko; Kasai, Shinya

    2014-08-01

    Underactuated control problems, such as the control of a space robot without actuators on the main body, have been widely investigated. However, few studies have examined attitude control problems of underactuated space robots equipped with a flexible appendage, such as solar panels. In order to suppress vibration in flexible appendages, a zero-vibration input-shaping technique was applied to the link motion of an underactuated planar space robot. However, because the vibrational frequency depends on the link angles, simple input-shaping control methods cannot sufficiently suppress the vibration. In this paper, the dependency of the vibrational frequency on the link angles is measured experimentally, and the time-delay interval of the input shaper is then tuned based on the frequency estimated from the link angles. The proposed control method is referred to as frequency-tuning input-shaped manifold-based switching control (frequency-tuning IS-MBSC). The experimental results reveal that frequency-tuning IS-MBSC is capable of controlling the link angles and the main body attitude to maintain the target angles and that the vibration suppression performance of the proposed frequency-tuning IS-MBSC is better than that of a non-tuning IS-MBSC, which does not take the frequency variation into consideration.

  9. Active noise control using noise source having adaptive resonant frequency tuning through stress variation

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)

    1995-01-01

    A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by an expandable ring embedded in the noise radiating element. Excitation of the ring causes expansion or contraction of the ring, thereby varying the stress in the noise radiating element. The ring is actuated by a controller which receives input of a feedback signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the ring, causing the ring to expand or contract. Instead of a single ring embedded in the noise radiating panel, a first expandable ring can be bonded to one side of the noise radiating element, and a second expandable ring can be bonded to the other side.

  10. Active noise control using noise source having adaptive resonant frequency tuning through stiffness variation

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)

    1995-01-01

    A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by a plurality of force transmitting mechanisms which contact the noise radiating element. Each one of the force transmitting mechanisms includes an expandable element and a spring in contact with the noise radiating element so that excitation of the element varies the spring force applied to the noise radiating element. The elements are actuated by a controller which receives input of a signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the elements and causes the spring force applied to the noise radiating element to be varied. The force transmitting mechanisms can be arranged to either produce bending or linear stiffness variations in the noise radiating element.

  11. Active noise control using noise source having adaptive resonant frequency tuning through variable ring loading

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)

    1995-01-01

    A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of noise radiating structure is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating structure is tuned by a plurality of drivers arranged to contact the noise radiating structure. Excitation of the drivers causes expansion or contraction of the drivers, thereby varying the edge loading applied to the noise radiating structure. The drivers are actuated by a controller which receives input of a feedback signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the drivers, causing them to expand or contract. The noise radiating structure may be either the outer shroud of the engine or a ring mounted flush with an inner wall of the shroud or disposed in the interior of the shroud.

  12. Tuning fractional PID controllers for a Steward platform based on frequency domain and artificial intelligence methods

    NASA Astrophysics Data System (ADS)

    Copot, Cosmin; Zhong, Yu; Ionescu, Clara; Keyser, Robin

    2013-06-01

    In this paper, two methods to tune a fractional-order PI λ D μ controller for a mechatronic system are presented. The first method is based on a genetic algorithm to obtain the parameter values for the fractionalorder PI λ D μ controller by global optimization. The second method used to design the fractional-order PI λ D μ controller relies on an auto-tuning approach by meeting some specifications in the frequency domain. The real-time experiments are conducted using a Steward platform which consists of a table tilted by six servo-motors with a ball on the top of the table. The considered system is a 6 degrees of freedom (d.o.f.) motion platform. The feedback on the position of the ball is obtained from images acquired by a visual sensor mounted above the platform. The fractional-order controllers were implemented and the performances of the steward platform are analyzed.

  13. Running, hopping and trotting: tuning step frequency to the resonant frequency of the bouncing system favors larger animals.

    PubMed

    Cavagna, Giovanni A; Legramandi, Mario A

    2015-10-01

    A long-lasting challenge in comparative physiology is to understand why the efficiency of the mechanical work done to maintain locomotion increases with body mass. It has been suggested that this is due to a more elastic step in larger animals. Here, we show in running, hopping and trotting animals, and in human running during growth, that the resonant frequency of the bouncing system decreases with increasing body mass and is, surprisingly, independent of species or gait. Step frequency roughly equals the resonant frequency in trotting and running, whereas it is about half the resonant frequency in hopping. The energy loss by elastic hysteresis during loading and unloading the bouncing system from its equilibrium position decreases with increasing body mass. Similarity to a symmetrical bounce increases with increasing body mass and, for a given body mass, seems to be maximal in hopping, intermediate in trotting and minimal in running. We conclude that: (1) tuning step frequency to the resonant frequency of the bouncing system coincides with a lower hysteresis loss in larger, more-compliant animals; (2) the mechanism of gait per se affects similarity with a symmetrical bounce, independent of hysteresis; and (3) the greater efficiency in larger animals may be due, at least in part, to a lower hysteresis loss. PMID:26347555

  14. Layer Specific Sharpening of Frequency Tuning by Selective Attention in Primary Auditory Cortex

    PubMed Central

    O'Connell, Monica Noelle; Barczak, Annamaria; Schroeder, Charles E.

    2014-01-01

    Recent electrophysiological and neuroimaging studies provide converging evidence that attending to sounds increases the response selectivity of neuronal ensembles even at the first cortical stage of auditory stimulus processing in primary auditory cortex (A1). This is achieved by enhancement of responses in the regions that process attended frequency content, and by suppression of responses in the surrounding regions. The goals of our study were to define the extent to which A1 neuronal ensembles are involved in this process, determine its effect on the frequency tuning of A1 neuronal ensembles, and examine the involvement of the different cortical layers. To accomplish these, we analyzed laminar profiles of synaptic activity and action potentials recorded in A1 of macaques performing a rhythmic intermodal selective attention task. We found that the frequency tuning of neuronal ensembles was sharpened due to both increased gain at the preferentially processed or best frequency and increased response suppression at all other frequencies when auditory stimuli were attended. Our results suggest that these effects are due to a frequency-specific counterphase entrainment of ongoing delta oscillations, which predictively orchestrates opposite sign excitability changes across all of A1. This results in a net suppressive effect due to the large proportion of neuronal ensembles that do not specifically process the attended frequency content. Furthermore, analysis of laminar activation profiles revealed that although attention-related suppressive effects predominate the responses of supragranular neuronal ensembles, response enhancement is dominant in the granular and infragranular layers, providing evidence for layer-specific cortical operations in attentive stimulus processing. PMID:25471586

  15. A 2-to-2.4-GHz differentially-tuned fractional-N frequency synthesizer for DVB tuner applications

    NASA Astrophysics Data System (ADS)

    Lingbu, Meng; Lei, Lu; Wei, Zhao; Zhangwen, Tang

    2010-07-01

    This paper describes the design of a fractional-N frequency synthesizer for digital video broadcasting-terrestrial (DVB-T) receivers. Transfer functions in differentially-tuned PLL are derived and loop parameters are designed. In addition, a fully-differential charge pump is presented. An 8/9 high speed prescaler is analyzed and the design considerations for the CML logic are also presented. Test results show that the RMS phase error is less than 0.7° in integer-N mode and less than 1° in fractional-N mode. The implemented frequency synthesizer draws 10 mA from a 1.8-V supply while occupying a die area of about 1-mm2 in a 0.18-μm CMOS process.

  16. Tuning the flexibility in MOFs by SBU functionalization.

    PubMed

    Bon, Volodymyr; Kavoosi, Negar; Senkovska, Irena; Müller, Philipp; Schaber, Jana; Wallacher, Dirk; Többens, Daniel M; Mueller, Uwe; Kaskel, Stefan

    2016-03-14

    A new approach for the fine tuning of flexibility in MOFs, involving functionalization of the secondary building unit, is presented. The "gate pressure" MOF [Zn3(bpydc)2(HCOO)2] was used as a model material and SBU functionalization was performed by using monocarboxylic acids such as acetic, benzoic or cinnamic acids instead of formic acid in the synthesis. The resulting materials are isomorphous to [Zn3(bpydc)2(HCOO)2] in the "as made" form, but show different structural dynamics during the guest removal. The activated materials have entirely different properties in the nitrogen physisorption experiments clearly showing the tunability of the gate pressure, at which the structural transformation occurs, by using monocarboxylic acids with varying backbone structure in the synthesis. Thus, increasing the number of carbon atoms in the backbone leads to the decreasing gate pressure required to initiate the structural transition. Moreover, in situ adsorption/PXRD data suggest differences in the mechanism of the structural transformations: from "gate opening" in the case of formic acid to "breathing" if benzoic acid is used. PMID:26876816

  17. Stochastic Optimally Tuned Range-Separated Hybrid Density Functional Theory.

    PubMed

    Neuhauser, Daniel; Rabani, Eran; Cytter, Yael; Baer, Roi

    2016-05-19

    We develop a stochastic formulation of the optimally tuned range-separated hybrid density functional theory that enables significant reduction of the computational effort and scaling of the nonlocal exchange operator at the price of introducing a controllable statistical error. Our method is based on stochastic representations of the Coulomb convolution integral and of the generalized Kohn-Sham density matrix. The computational cost of the approach is similar to that of usual Kohn-Sham density functional theory, yet it provides a much more accurate description of the quasiparticle energies for the frontier orbitals. This is illustrated for a series of silicon nanocrystals up to sizes exceeding 3000 electrons. Comparison with the stochastic GW many-body perturbation technique indicates excellent agreement for the fundamental band gap energies, good agreement for the band edge quasiparticle excitations, and very low statistical errors in the total energy for large systems. The present approach has a major advantage over one-shot GW by providing a self-consistent Hamiltonian that is central for additional postprocessing, for example, in the stochastic Bethe-Salpeter approach. PMID:26651840

  18. Tuning the functionalities of a mesocrystal via structural coupling

    PubMed Central

    Liu, Heng-Jui; Liu, Yun-Ya; Tsai, Chih-Ya; Liao, Sheng-Chieh; Chen, Ying-Jiun; Lin, Hong-Ji; Lai, Chih-Huang; Hsieh, Wen-Feng; Li, Jiang-Yu; Chen, Chien-Te; He, Qing; Chu, Ying-Hao

    2015-01-01

    In the past decades, mesocrystal, a kind of nanocrystals with specific crystallographic orientation, has drawn a lot of attention due to its intriguing functionalities. While the research community keeps searching for new mesocrystal systems, it is equally crucial to develop new approaches to tune the properties of mesocrystals. In this work, a self-organized two-dimensional mesocrystal composed of highly oriented CoFe2O4 (CFO) nano-crystals with assistance of different perovskite matrices is studied as a model system. We have demonstrated that the strain state and corresponding magnetic properties of the CFO mesocrystal can be modulated by changing the surrounding perovskite matrix through their intimate structural coupling. Interestingly, this controllability is more strongly correlated to the competition of bonding strength between the matrices and the CFO mesocrystals rather than the lattice mismatch. When embedded in a matrix with a higher melting point or stiffness, the CFO mesocrystal experiences higher out-of-plane compressive strain and shows a stronger magnetic anisotropy as well as cation site-exchange. Our study suggests a new pathway to tailor the functionalities of mesocrystals. PMID:26170119

  19. Frequency tuning of hearing in the beluga whale: discrimination of rippled spectra.

    PubMed

    Sysueva, Evgenia V; Nechaev, Dmitry I; Popov, Vladimir V; Supin, Alexander Ya

    2014-02-01

    Frequency tuning was measured in the beluga whale (Delphinapterus leucas) using rippled-noise test stimuli in conjunction with an auditory evoked potential (AEP) technique. The test stimulus was a 2-octave-wide rippled noise with frequency-proportional ripple spacing. The rippled-noise signal contained either a single reversal or rhythmic (1-kHz rate) reversals of the ripple phase. Single or rhythmic phase reversals evoked, respectively, a single auditory brainstem response (ABR) or a rhythmic AEP sequence-the envelope following response (EFR). The response was considered as an indication of resolvability of the ripple pattern. The rhythmic phase-reversal test with EFR recording revealed higher resolution than the single phase-reversal test with single ABR recording. The limit of ripple-pattern resolution with the single phase-reversal test ranged from 17 ripples per octave (rpo) at 32 kHz to 24 rpo at 45 to 64 kHz; for the rhythmic phase-reversal test, the limit ranged from 20 to 32 rpo. An interaction model of a ripple spectrum with frequency-tuned filters suggests that the ripple-pattern resolution limit of 20 to 32 rpo requires a filter quality Q of 29 to 46. Possible causes of disagreement of these estimates with several previously published data are discussed. PMID:25234904

  20. A comparison of spatial frequency tuning for judgments of eye gaze and facial identity.

    PubMed

    Vida, Mark D; Maurer, Daphne

    2015-07-01

    Humans use the direction of eye gaze and facial identity to make important social judgments. We carried out the first measurements of spatial frequency (SF) tuning for judgments of eye gaze, and compared SF tuning for judgments of facial identity and eye gaze. In Experiment 1, participants discriminated between leftward and rightward shifts of gaze, or between two male faces or two female faces. Faces were masked with visual noise that blocked one of 10 SF bands. For each task and masking SF, we measured contrast thresholds for human observers, and used an ideal observer to measure the amount of visual information available to perform the task. As in previous research, low to mid SFs were most important for judgments of facial identity. Mid to high SFs were most important for judgments of eye gaze, and the highest SF important for these judgments was higher than that for identity. In Experiment 2, participants discriminated horizontal and vertical shifts of gaze. The highest SF important for judgments of gaze did not differ between the horizontal and vertical axes. However, SFs above and below this value were more important for judgments of vertical shifts of gaze than for horizontal shifts of gaze. These results suggest that the visual system relies on higher SFs for judgments of eye gaze than for judgments of facial identity, and that SF tuning is broader for judgments of vertical shifts of gaze than for horizontal shifts of gaze. PMID:25982718

  1. Frequency pre-tuning of the niobium-sputtered quarter-wave resonator for HIE-ISOLDE project at CERN

    NASA Astrophysics Data System (ADS)

    Zhang, P.; D`Elia, A.; Venturini Delsolaro, W.; Artoos, K.

    2015-10-01

    Superconducting quarter-wave resonators (QWRs) will be used in the superconducting linac upgrade in the frame of the HIE-ISOLDE project at CERN. The QWRs are made of bulk copper and have their inner surface covered with sputtered niobium. Their resonant frequency is 101.28 MHz at 4.5 K. Each cavity will be equipped with a tuning system to both minimize the forward power and compensate the frequency variations during production and beam operation. After a careful examination of all contributors to the frequency variation, we decomposed them into two components: frequency shift and its uncertainties. A pre-tuning step was subsequently added to the production sequence prior to niobium sputtering to accommodate the frequency shift mainly due to mechanical tolerances during substrate production, substrate surface treatment, niobium sputtering and cooldown process. To this end, the length of the QWR was chosen as a free parameter for the pre-tuning. Consequently the tuning system needs only to compensate the frequency uncertainties and Lorentz force detuning, thus its design has been largely simplified and its production cost was reduced by 80% comparing to its previous version. We have successfully applied this tuning scheme to five HIE-ISOLDE QWRs and the measured tuning error was 2.4 ± 1.9 kHz. This is well consistent with our calculations and well recoverable by the current simplified tuning system. It is worth noticing that the pre-tuning method only involves one-time measurement of the cavity's resonant frequency and its outer conductor length. This paper focuses on HIE-ISOLDE high-β QWR, but the method can be applied to HIE-ISOLDE low-β QWRs and other variants of QWR-like cavities.

  2. Frequency tuning of polarization oscillations in spin-polarized vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Lindemann, Markus; Pusch, Tobias; Michalzik, Rainer; Gerhardt, Nils C.; Hofmann, Martin R.

    2016-04-01

    Controlling the coupled spin-photon dynamics in vertical-cavity surface-emitting lasers (VCSELs) is an attractive opportunity to overcome the limitations of conventional, purely charge based semiconductor lasers. Such spin-controlled VCSELs (spin-VCSELs) offer several advantages, like reduced threshold, spin amplification and polarization control. Furthermore the coupling between carrier spin and light polarization bears the potential for ultrafast polarization dynamics. By injecting spin-polarized carriers, the complex polarization dynamics can be controlled and utilized for high-speed applications. Polarization oscillations as resonance oscillations of the coupled spin- photon system can be generated using pulsed spin injection, which can be much faster than the intensity dynamics in conventional devices. We already demonstrated that the oscillations can be switched in a controlled manner. These controllable polarization dynamics can be used for ultrafast polarization-based optical data communication. The polarization oscillation frequency and therefore the possible data transmission rate is assumed to be mainly determined by the birefringence-induced mode-splitting. This provides a direct tool to increase the polarization dynamics toward higher frequencies by adding a high amount of birefringence to the VCSEL structure. Using this technique, we could recently demonstrate experimentally a birefringence splitting of more than 250 GHz using mechanical strain. Here, we employ the well-known spin-flip model to investigate the tuning of the polarization oscillation frequency. The changing mechanical strain is represented by a linear birefringence sweep to values up to 80πGHz. The wide tuning range presented enables us to generate polarization oscillation frequencies exceeding the conventional intensity modulation frequency in the simulated device by far, mainly dependent on the birefringence in the cavity only.

  3. Frequency tuning of the dolphin's hearing as revealed by auditory brain-stem response with notch-noise masking.

    PubMed

    Popov, V V; Supin, A Y; Klishin, V O

    1997-12-01

    Notch-noise masking was used to measure frequency tuning in a dolphin (Tursiops truncatus) in a simultaneous-masking paradigm in conjunction with auditory brain-stem evoked potential recording. Measurements were made at probe frequencies of 64, 76, 90, and 108 kHz. The data were analyzed by fitting the rounded-exponent model of the auditory filters to the experimental data. The fitting parameter values corresponded to the filter tuning as follows: QER (center frequency divided by equivalent rectangular bandwidths) of 35 to 36.5 and Q10 dB of 18 to 19 at all tested frequencies. PMID:9407671

  4. Fine tuning points of generating function construction for linear recursions

    NASA Astrophysics Data System (ADS)

    Yolcu, Bahar; Demiralp, Metin

    2014-10-01

    Recursions are quite important mathematical tools since many systems are mathematically modelled to ultimately take us to these equations because of their rather easy algebraic natures. They fit computer programming needs quite well in many circumstances to produce solutions. However, it is generally desired to find the asymptotic behaviour of the general term in the relevant sequence for convergence and therefore practicality issues. One of the general tendencies to find the general term asymptotic behaviour, when its ordering number grows unboundedly, is the integral representation over a generating function which does not depend on individual sequence elements. This is tried to be done almost for all types of recursions, even though the linear cases gain more importance than the others because they can be more effectively investigated by using many linear algebraic tools. Despite this may seem somehow to be rather trivial, there are a lot of theoretical fine tuning issues in the construction of true integral representations over true intervals on real axis or paths in complex domains. This work is devoted to focus on this issue starting from scratch for better understanding of the matter. The example cases are chosen to best illuminate the situations to get information for future generalization even though the work can be considered at somehow introductory level.

  5. Tuning the isoelectric point of graphene by electrochemical functionalization

    NASA Astrophysics Data System (ADS)

    Zuccaro, Laura; Krieg, Janina; Desideri, Alessandro; Kern, Klaus; Balasubramanian, Kannan

    2015-07-01

    The ability to control the charge-potential landscape at solid-liquid interfaces is pivotal to engineer novel devices for applications in sensing, catalysis and energy conversion. The isoelectric point (pI)/point of zero charge (pzc) of graphene plays a key role in a number of physico-chemical phenomena occurring at the graphene-liquid interface. Supported by theory, we present here a methodology to identify the pI/pzc of (functionalized) graphene, which also allows for estimating the nature and extent of ion adsorption. The pI of bare graphene (as-prepared, chemical vapor deposition (CVD)-grown) is found to be less than 3.3, which we can continuously modify up to 7.5 by non-covalent electrochemical attachment of aromatic amino groups, preserving the favorable electronic properties of graphene throughout. Modelling all the observed results with detailed theory, we also show that specific adsorption of ions and the substrate play only an ancillary role in our capability to tune the pI of graphene.

  6. Tuning the isoelectric point of graphene by electrochemical functionalization.

    PubMed

    Zuccaro, Laura; Krieg, Janina; Desideri, Alessandro; Kern, Klaus; Balasubramanian, Kannan

    2015-01-01

    The ability to control the charge-potential landscape at solid-liquid interfaces is pivotal to engineer novel devices for applications in sensing, catalysis and energy conversion. The isoelectric point (pI)/point of zero charge (pzc) of graphene plays a key role in a number of physico-chemical phenomena occurring at the graphene-liquid interface. Supported by theory, we present here a methodology to identify the pI/pzc of (functionalized) graphene, which also allows for estimating the nature and extent of ion adsorption. The pI of bare graphene (as-prepared, chemical vapor deposition (CVD)-grown) is found to be less than 3.3, which we can continuously modify up to 7.5 by non-covalent electrochemical attachment of aromatic amino groups, preserving the favorable electronic properties of graphene throughout. Modelling all the observed results with detailed theory, we also show that specific adsorption of ions and the substrate play only an ancillary role in our capability to tune the pI of graphene. PMID:26134956

  7. Tuning the isoelectric point of graphene by electrochemical functionalization

    PubMed Central

    Zuccaro, Laura; Krieg, Janina; Desideri, Alessandro; Kern, Klaus; Balasubramanian, Kannan

    2015-01-01

    The ability to control the charge-potential landscape at solid-liquid interfaces is pivotal to engineer novel devices for applications in sensing, catalysis and energy conversion. The isoelectric point (pI)/point of zero charge (pzc) of graphene plays a key role in a number of physico-chemical phenomena occurring at the graphene-liquid interface. Supported by theory, we present here a methodology to identify the pI/pzc of (functionalized) graphene, which also allows for estimating the nature and extent of ion adsorption. The pI of bare graphene (as-prepared, chemical vapor deposition (CVD)-grown) is found to be less than 3.3, which we can continuously modify up to 7.5 by non-covalent electrochemical attachment of aromatic amino groups, preserving the favorable electronic properties of graphene throughout. Modelling all the observed results with detailed theory, we also show that specific adsorption of ions and the substrate play only an ancillary role in our capability to tune the pI of graphene. PMID:26134956

  8. Riboswitch function: Flipping the switch or tuning the dimmer?

    SciTech Connect

    Baird, Nathan J.; Kulshina, Nadia; Ferré D'Amaré, Adrian R.

    2010-10-08

    Riboswitches are structured mRNA elements involved in gene regulation that respond to the intracellular concentration of specific small molecules. Binding of their cognate ligand is thought to elicit a global conformational change of the riboswitch, in addition to modulating the fine structure of the binding site. X-ray crystallography has produced detailed descriptions of the three-dimensional structures of the ligand-bound conformations of several riboswitches. We have employed small-angle X-ray scattering (SAXS) to generate low-resolution reconstructions of the ligand-free states of the ligand-binding domains of riboswitches that respond to thiamine pyrophosphate (TPP), and cyclic diguanylate (c-di-GMP), a bacterial second messenger. Comparison of the SAXS reconstructions with the crystal structures of these two riboswitches demonstrates that the RNAs undergo dramatic ligand-induced global conformational changes. However, this is not an universal feature of riboswitches. SAXS analysis of the solution behavior of several other riboswitch ligand-binding domains demonstrates a broad spectrum of conformational switching behaviors, ranging from the unambiguous switching of the TPP and c-di-GMP riboswitches to complete lack of switching for the flavin mononucleotide (FMN) riboswitch. Moreover, the switching behavior varies between examples of the same riboswitch from different organisms. The range of observed behaviors suggests that in response to the evolutionary need for precise genetic regulation, riboswitches may be tuned to function more as dimmers or rheostats than binary on/off switches.

  9. The Coefficient of the Voltage Induced Frequency Shift Measurement on a Quartz Tuning Fork

    PubMed Central

    Hou, Yubin; Lu, Qingyou

    2014-01-01

    We have measured the coefficient of the voltage induced frequency shift (VIFS) of a 32.768 KHz quartz tuning fork. Three vibration modes were studied: one prong oscillating, two prongs oscillating in the same direction, and two prongs oscillating in opposite directions. They all showed a parabolic dependence of the eigen-frequency shift on the bias voltage applied across the fork, due to the voltage-induced internal stress, which varies as the fork oscillates. The average coefficient of the VIFS effect is as low as several hundred nano-Hz per millivolt, implying that fast-response voltage-controlled oscillators and phase-locked loops with nano-Hz resolution can be built. PMID:25414971

  10. Bilateral matching of frequency tuning in neural cross-correlators of the owl.

    PubMed

    Fischer, Brian J; Peña, José Luis

    2009-06-01

    Sound localization requires comparison between the inputs to the left and right ears. One important aspect of this comparison is the differences in arrival time to each side, also called interaural time difference (ITD). A prevalent model of ITD detection, consisting of delay lines and coincidence-detector neurons, was proposed by Jeffress (J Comp Physiol Psychol 41:35-39, 1948). As an extension of the Jeffress model, the process of detecting and encoding ITD has been compared to an effective cross-correlation between the input signals to the two ears. Because the cochlea performs a spectrotemporal decomposition of the input signal, this cross-correlation takes place over narrow frequency bands. Since the cochlear tonotopy is arranged in series, sounds of different frequencies will trigger neural activity with different temporal delays. Thus, the matching of the frequency tuning of the left and right inputs to the cross-correlator units becomes a 'timing' issue. These properties of auditory transduction gave theoretical support to an alternative model of ITD-detection based on a bilateral mismatch in frequency tuning, called the 'stereausis' model. Here we first review the current literature on the owl's nucleus laminaris, the equivalent to the medial superior olive of mammals, which is the site where ITD is detected. Subsequently, we use reverse correlation analysis and stimulation with uncorrelated sounds to extract the effective monaural inputs to the cross-correlator neurons. We show that when the left and right inputs to the cross-correlators are defined in this manner, the computation performed by coincidence-detector neurons satisfies conditions of cross-correlation theory. We also show that the spectra of left and right inputs are matched, which is consistent with predictions made by the classic model put forth by Jeffress. PMID:19396457

  11. 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.

  12. Note: Enhanced energy harvesting from low-frequency magnetic fields utilizing magneto-mechano-electric composite tuning-fork.

    PubMed

    Yang, Aichao; Li, Ping; Wen, Yumei; Yang, Chao; Wang, Decai; Zhang, Feng; Zhang, Jiajia

    2015-06-01

    A magnetic-field energy harvester using a low-frequency magneto-mechano-electric (MME) composite tuning-fork is proposed. This MME composite tuning-fork consists of a copper tuning fork with piezoelectric Pb(Zr(1-x)Ti(x))O3 (PZT) plates bonded near its fixed end and with NdFeB magnets attached at its free ends. Due to the resonance coupling between fork prongs, the MME composite tuning-fork owns strong vibration and high Q value. Experimental results show that the proposed magnetic-field energy harvester using the MME composite tuning-fork exhibits approximately 4 times larger maximum output voltage and 7.2 times higher maximum power than the conventional magnetic-field energy harvester using the MME composite cantilever. PMID:26133877

  13. Note: Enhanced energy harvesting from low-frequency magnetic fields utilizing magneto-mechano-electric composite tuning-fork

    NASA Astrophysics Data System (ADS)

    Yang, Aichao; Li, Ping; Wen, Yumei; Yang, Chao; Wang, Decai; Zhang, Feng; Zhang, Jiajia

    2015-06-01

    A magnetic-field energy harvester using a low-frequency magneto-mechano-electric (MME) composite tuning-fork is proposed. This MME composite tuning-fork consists of a copper tuning fork with piezoelectric Pb(Zr1-xTix)O3 (PZT) plates bonded near its fixed end and with NdFeB magnets attached at its free ends. Due to the resonance coupling between fork prongs, the MME composite tuning-fork owns strong vibration and high Q value. Experimental results show that the proposed magnetic-field energy harvester using the MME composite tuning-fork exhibits approximately 4 times larger maximum output voltage and 7.2 times higher maximum power than the conventional magnetic-field energy harvester using the MME composite cantilever.

  14. Stiffness nonlinearity as a means for resonance frequency tuning and enhancing mechanical robustness of vibration power harvesters

    NASA Astrophysics Data System (ADS)

    Loverich, J.; Geiger, R.; Frank, J.

    2008-03-01

    This paper addresses a particular type of power harvesting in which energy in the periodic movement of structures is parasitically converted to stored electric charge. In such applications, tuning of the vibration power harvesters' resonance frequency is often required to match the host structures' forcing frequency. This paper presents a method of adjusting the boundary conditions of nonlinear stiffness elements as a means of tuning the resonance frequency of piezoelectric vibration power harvesters (altering the deformation mode from bending to in-plane stretching). Using this tuning method, the resonance frequency was experimentally varied between 56 and 62 Hz. For a vibration level of 2 mm/s, the harvester has a similar Q to a linear system but its Q is reduced by one third at a vibration level of 10 mm/s. This behavior is important for applications where high sensitivity is required for low vibration levels but mechanical robustness is required for high vibration levels.

  15. The spatial frequency tuning of optic-flow-dependent behaviors in the bumblebee Bombus impatiens

    PubMed Central

    Dyhr, Jonathan P.; Higgins, Charles M.

    2010-01-01

    Insects use visual estimates of flight speed for a variety of behaviors, including visual navigation, odometry, grazing landings and flight speed control, but the neuronal mechanisms underlying speed detection remain unknown. Although many models and theories have been proposed for how the brain extracts the angular speed of the retinal image, termed optic flow, we lack the detailed electrophysiological and behavioral data necessary to conclusively support any one model. One key property by which different models of motion detection can be differentiated is their spatiotemporal frequency tuning. Numerous studies have suggested that optic-flow-dependent behaviors are largely insensitive to the spatial frequency of a visual stimulus, but they have sampled only a narrow range of spatial frequencies, have not always used narrowband stimuli, and have yielded slightly different results between studies based on the behaviors being investigated. In this study, we present a detailed analysis of the spatial frequency dependence of the centering response in the bumblebee Bombus impatiens using sinusoidal and square wave patterns. PMID:20435814

  16. Analysis of Frequency Response and Scale-Factor of Tuning Fork Micro-Gyroscope Operating at Atmospheric Pressure

    PubMed Central

    Ding, Xukai; Li, Hongsheng; Ni, Yunfang; Sang, Pengcheng

    2015-01-01

    This paper presents a study of the frequency response and the scale-factor of a tuning fork micro-gyroscope operating at atmospheric pressure in the presence of an interference sense mode by utilizing the approximate transfer function. The optimal demodulation phase (ODP), which is always ignored in vacuum packaged micro-gyroscopes but quite important in gyroscopes operating at atmospheric pressure, is obtained through the transfer function of the sense mode, including the primary mode and the interference mode. The approximate transfer function of the micro-gyroscope is deduced in consideration of the interference mode and the ODP. Then, the equation describing the scale-factor of the gyroscope is also obtained. The impacts of the interference mode and Q-factor on the frequency response and the scale-factor of the gyroscope are analyzed through numerical simulations. The relationship between the scale-factor and the demodulation phase is also illustrated and gives an effective way to find out the ODP in practice. The simulation results predicted by the transfer functions are in close agreement with the results of the experiments. The analyses and simulations can provide constructive guidance on bandwidth and sensitivity designs of the micro-gyroscopes operating at atmospheric pressure. PMID:25621614

  17. Effect of echolocation behavior-related constant frequency-frequency modulation sound on the frequency tuning of inferior collicular neurons in Hipposideros armiger.

    PubMed

    Tang, Jia; Fu, Zi-Ying; Wei, Chen-Xue; Chen, Qi-Cai

    2015-08-01

    In constant frequency-frequency modulation (CF-FM) bats, the CF-FM echolocation signals include both CF and FM components, yet the role of such complex acoustic signals in frequency resolution by bats remains unknown. Using CF and CF-FM echolocation signals as acoustic stimuli, the responses of inferior collicular (IC) neurons of Hipposideros armiger were obtained by extracellular recordings. We tested the effect of preceding CF or CF-FM sounds on the shape of the frequency tuning curves (FTCs) of IC neurons. Results showed that both CF-FM and CF sounds reduced the number of FTCs with tailed lower-frequency-side of IC neurons. However, more IC neurons experienced such conversion after adding CF-FM sound compared with CF sound. We also found that the Q 20 value of the FTC of IC neurons experienced the largest increase with the addition of CF-FM sound. Moreover, only CF-FM sound could cause an increase in the slope of the neurons' FTCs, and such increase occurred mainly in the lower-frequency edge. These results suggested that CF-FM sound could increase the accuracy of frequency analysis of echo and cut-off low-frequency elements from the habitat of bats more than CF sound. PMID:26026915

  18. Hearing impairment induces frequency-specific adjustments in auditory spatial tuning in the optic tectum of young owls.

    PubMed

    Gold, J I; Knudsen, E I

    1999-11-01

    Bimodal, auditory-visual neurons in the optic tectum of the barn owl are sharply tuned for sound source location. The auditory receptive fields (RFs) of these neurons are restricted in space primarily as a consequence of their tuning for interaural time differences and interaural level differences across broad ranges of frequencies. In this study, we examined the extent to which frequency-specific features of early auditory experience shape the auditory spatial tuning of these neurons. We manipulated auditory experience by implanting in one ear canal an acoustic filtering device that altered the timing and level of sound reaching the eardrum in a frequency-dependent fashion. We assessed the auditory spatial tuning at individual tectal sites in normal owls and in owls raised with the filtering device. At each site, we measured a family of auditory RFs using broadband sound and narrowband sounds with different center frequencies both with and without the device in place. In normal owls, the narrowband RFs for a given site all included a common region of space that corresponded with the broadband RF and aligned with the site's visual RF. Acute insertion of the filtering device in normal owls shifted the locations of the narrowband RFs away from the visual RF, the magnitude and direction of the shifts depending on the frequency of the stimulus. In contrast, in owls that were raised wearing the device, narrowband and broadband RFs were aligned with visual RFs so long as the device was in the ear but not after it was removed, indicating that auditory spatial tuning had been adaptively altered by experience with the device. The frequency tuning of tectal neurons in device-reared owls was also altered from normal. The results demonstrate that experience during development adaptively modifies the representation of auditory space in the barn owl's optic tectum in a frequency-dependent manner. PMID:10561399

  19. Tuning of Kilopixel Transition Edge Sensor Bolometer Arrays with a Digital Frequency Multiplexed Readout System

    NASA Astrophysics Data System (ADS)

    MacDermid, Kevin; Hyland, Peter; Aubin, Francois; Bissonnette, Eric; Dobbs, Matt; Hubmayr, Johannes; Smecher, Graeme; Wairrach, Shahjahen

    2009-12-01

    A digital frequency multiplexing (DfMUX) system has been developed and used to tune large arrays of transition edge sensor (TES) bolometers read out with SQUID arrays for mm-wavelength cosmology telescopes. The DfMUX system multiplexes the input bias voltages and output currents for several bolometers on a single set of cryogenic wires. Multiplexing reduces the heat load on the camera's sub-Kelvin cryogenic detector stage. In this paper we describe the algorithms and software used to set up and optimize the operation of the bolometric camera. The algorithms are implemented on soft processors embedded within FPGA devices operating on each backend readout board. The result is a fully parallelized implementation for which the setup time is independent of the array size.

  20. Increased energy harvesting and reduced accelerative load for backpacks via frequency tuning

    NASA Astrophysics Data System (ADS)

    Xie, Longhan; Cai, Mingjing

    2015-06-01

    In this research, a backpack-based frequency-tuneable harvesting device was developed to harvest part of the human kinetic energy during walking and to relieve part of the accelerative load of the backpack from the bearer. The harvester employed a tuning mechanism to adjust the stretch ratio of the springs to adjust the system's stiffness so that the harvesting device can work in an appropriate status to generate more power and relieve a greater load from the bearer. The analysis indicates that adjusting the stiffness harvesting system to fit well with various external excitation conditions, can not only achieve more power output but also relieve part of the accelerative load from the bearer; and the experimental results agreed with the simulation. Compared with previous work, the harvester in this work had a higher efficiency in energy harvesting and could relieve an increased accelerative load from the bearer.

  1. Tuning the resonant frequencies of a drop by a magnetic field

    NASA Astrophysics Data System (ADS)

    Jamin, Timothée; Djama, Yacine; Bacri, Jean-Claude; Falcon, Eric

    2016-06-01

    We report an experimental study of a magnetic liquid drop deposited on a superhydrophobic substrate and subjected to vertical vibrations in the presence of a static magnetic field. It is well known that a flattened drop of usual liquid displays oscillating lobes at its periphery when vibrated. By adding ferromagnetic nanoparticles to a water drop and varying the strength of the magnetic field, we are experimentally able to efficiently tune the resonant frequencies of the drop. By using conservation energy arguments, we show that the magnetic field contribution is equivalent to adding an effective negative surface tension to the drop. Our model is found to be in good agreement with the experiments with no fitting parameter.

  2. Songbirds tune their vocal tract to the fundamental frequency of their song

    PubMed Central

    Riede, Tobias; Suthers, Roderick A.; Fletcher, Neville H.; Blevins, William E.

    2006-01-01

    In human speech, the sound generated by the larynx is modified by articulatory movements of the upper vocal tract, which acts as a variable resonant filter concentrating energy near particular frequencies, or formants, essential in speech recognition. Despite its potential importance in vocal communication, little is known about the presence of tunable vocal tract filters in other vertebrates. The tonal quality of much birdsong, in which upper harmonics have relatively little energy, depends on filtering of the vocal source, but the nature of this filter is controversial. Current hypotheses treat the songbird vocal tract as a rigid tube with a resonance that is modulated by the end-correction of a variable beak opening. Through x-ray cinematography of singing birds, we show that birdsong is accompanied by cyclical movements of the hyoid skeleton and changes in the diameter of the cranial end of the esophagus that maintain an inverse relationship between the volume of the oropharyngeal cavity and esophagus and the song’s fundamental frequency. A computational acoustic model indicates that this song-related motor pattern tunes the major resonance of the oropharyngeal–esophageal cavity to actively track the song’s fundamental frequency. PMID:16567614

  3. Terahertz beam steering and frequency tuning by using the spatial dispersion of ultrafast laser pulses.

    PubMed

    Maki, Ken-ichiro; Otani, Chiko

    2008-07-01

    We demonstrate a terahertz (THz) beam steering method using difference frequency generation that is based on the principle of phased array antennas. A strip-line photoconductive antenna was illuminated by two spatially dispersed beams produced from an ultrafast laser. THz radiation with a bandwidth of 65 GHz was generated from the overlapping area of the two beams, between which the frequency difference was approximately constant. We confirmed that the THz beam can be steered by tilting one of the incident pump beams so as to change their relative phase relation. The steering range of the THz beam was 29 degrees when the angle between the incident pump beams was only varied within a range of 0.155 degrees, that is, 187 times less. In addition, by laterally shifting one of the pump beams, the frequency of the THz radiation could be tuned from 0.3 to 1.7 THz. This technique can be applied to high-speed terahertz imaging and spectroscopy systems. PMID:18607423

  4. Songbirds tune their vocal tract to the fundamental frequency of their song.

    PubMed

    Riede, Tobias; Suthers, Roderick A; Fletcher, Neville H; Blevins, William E

    2006-04-01

    In human speech, the sound generated by the larynx is modified by articulatory movements of the upper vocal tract, which acts as a variable resonant filter concentrating energy near particular frequencies, or formants, essential in speech recognition. Despite its potential importance in vocal communication, little is known about the presence of tunable vocal tract filters in other vertebrates. The tonal quality of much birdsong, in which upper harmonics have relatively little energy, depends on filtering of the vocal source, but the nature of this filter is controversial. Current hypotheses treat the songbird vocal tract as a rigid tube with a resonance that is modulated by the end-correction of a variable beak opening. Through x-ray cinematography of singing birds, we show that birdsong is accompanied by cyclical movements of the hyoid skeleton and changes in the diameter of the cranial end of the esophagus that maintain an inverse relationship between the volume of the oropharyngeal cavity and esophagus and the song's fundamental frequency. A computational acoustic model indicates that this song-related motor pattern tunes the major resonance of the oropharyngeal-esophageal cavity to actively track the song's fundamental frequency. PMID:16567614

  5. Method for independent and continuous tuning of N lasers phase-locked to the same frequency comb

    NASA Astrophysics Data System (ADS)

    Gunton, Will; Semczuk, Mariusz; Madison, Kirk W.

    2015-09-01

    We present a method of phase-locking any number of continuous-wave lasers to an optical frequency comb (OFC) that enables independent frequency positioning and control of each laser while still maintaining lock to the OFC. The scheme employs an acousto-optic modulator (AOM) in a double pass configuration added to each laser before its light is compared by optical heterodyne with the comb. The only requirement is that the tuning bandwidth of the double pass AOM setup be larger than half the OFC repetition rate. We demonstrate this scheme and achieve an arbitrary frequency tuning precision, a tuning rate of 200~MHz/s and a readout precision at the 1~kHz level.

  6. Speech training alters tone frequency tuning in rat primary auditory cortex

    PubMed Central

    Engineer, Crystal T.; Perez, Claudia A.; Carraway, Ryan S.; Chang, Kevin Q.; Roland, Jarod L.; Kilgard, Michael P.

    2013-01-01

    Previous studies in both humans and animals have documented improved performance following discrimination training. This enhanced performance is often associated with cortical response changes. In this study, we tested the hypothesis that long-term speech training on multiple tasks can improve primary auditory cortex (A1) responses compared to rats trained on a single speech discrimination task or experimentally naïve rats. Specifically, we compared the percent of A1 responding to trained sounds, the responses to both trained and untrained sounds, receptive field properties of A1 neurons, and the neural discrimination of pairs of speech sounds in speech trained and naïve rats. Speech training led to accurate discrimination of consonant and vowel sounds, but did not enhance A1 response strength or the neural discrimination of these sounds. Speech training altered tone responses in rats trained on six speech discrimination tasks but not in rats trained on a single speech discrimination task. Extensive speech training resulted in broader frequency tuning, shorter onset latencies, a decreased driven response to tones, and caused a shift in the frequency map to favor tones in the range where speech sounds are the loudest. Both the number of trained tasks and the number of days of training strongly predict the percent of A1 responding to a low frequency tone. Rats trained on a single speech discrimination task performed less accurately than rats trained on multiple tasks and did not exhibit A1 response changes. Our results indicate that extensive speech training can reorganize the A1 frequency map, which may have downstream consequences on speech sound processing. PMID:24344364

  7. Frequency tuning and intensity coding of sound in the auditory periphery of the lake sturgeon, Acipenser fulvescens

    PubMed Central

    Meyer, Michaela; Fay, Richard R.; Popper, Arthur N.

    2010-01-01

    Acipenser fulvescens, the lake sturgeon, belongs to one of the few extant non-teleost ray-finned (bony) fishes. The sturgeons (family Acipenseridae) have a phylogenetic history that dates back about 250 million years. The study reported here is the first investigation of peripheral coding strategies for spectral analysis in the auditory system in a non-teleost bony fish. We used a shaker system to simulate the particle motion component of sound during electrophysiological recordings of isolated single units from the eighth nerve innervating the saccule and lagena. Background activity and response characteristics of saccular and lagenar afferents (such as thresholds, response–level functions and temporal firing) resembled the ones found in teleosts. The distribution of best frequencies also resembled data in teleosts (except for Carassius auratus, goldfish) tested with the same stimulation method. The saccule and lagena in A. fulvescens contain otoconia, in contrast to the solid otoliths found in teleosts, however, this difference in otolith structure did not appear to affect threshold, frequency tuning, intensity- or temporal responses of auditory afferents. In general, the physiological characteristics common to A. fulvescens, teleosts and land vertebrates reflect important functions of the auditory system that may have been conserved throughout the evolution of vertebrates. PMID:20400642

  8. Hardware platforms for MEMS gyroscope tuning based on evolutionary computation using open-loop and closed -loop frequency response

    NASA Technical Reports Server (NTRS)

    Keymeulen, Didier; Ferguson, Michael I.; Fink, Wolfgang; Oks, Boris; Peay, Chris; Terrile, Richard; Cheng, Yen; Kim, Dennis; MacDonald, Eric; Foor, David

    2005-01-01

    We propose a tuning method for MEMS gyroscopes based on evolutionary computation to efficiently increase the sensitivity of MEMS gyroscopes through tuning. The tuning method was tested for the second generation JPL/Boeing Post-resonator MEMS gyroscope using the measurement of the frequency response of the MEMS device in open-loop operation. We also report on the development of a hardware platform for integrated tuning and closed loop operation of MEMS gyroscopes. The control of this device is implemented through a digital design on a Field Programmable Gate Array (FPGA). The hardware platform easily transitions to an embedded solution that allows for the miniaturization of the system to a single chip.

  9. Resonant tectorial membrane motion in the inner ear: its crucial role in frequency tuning.

    PubMed Central

    Gummer, A W; Hemmert, W; Zenner, H P

    1996-01-01

    The tectorial membrane has long been postulated as playing a role in the exquisite sensitivity of the cochlea. In particular, it has been proposed that the tectorial membrane provides a second resonant system, in addition to that of the basilar membrane, which contributes to the amplification of the motion of the cochlear partition. Until now, technical difficulties had prevented vibration measurements of the tectorial membrane and, therefore, precluded direct evidence of a mechanical resonance. In the study reported here, the vibration of the tectorial membrane was measured in two orthogonal directions by using a novel method of combining laser interferometry with a photodiode technique. It is shown experimentally that the motion of the tectorial membrane is resonant at a frequency of 0.5 octave (oct) below the resonant frequency of the basilar membrane and polarized parallel to the reticular lamina. It is concluded that the resonant motion of the tectorial membrane is due to a parallel resonance between the mass of the tectorial membrane and the compliance of the stereocilia of the outer hair cells. Moreover, in combination with the contractile force of outer hair cells, it is proposed that inertial motion of the tectorial membrane provides the necessary conditions to allow positive feedback of mechanical energy into the cochlear partition, thereby amplifying and tuning the cochlear response. PMID:8710939

  10. Resonance frequency-retuned quartz tuning fork as a force sensor for noncontact atomic force microscopy

    SciTech Connect

    Ooe, Hiroaki; Sakuishi, Tatsuya; Arai, Toyoko; Nogami, Makoto; Tomitori, Masahiko

    2014-07-28

    Based on a two-prong type quartz tuning fork, a force sensor with a high Q factor, which we call a retuned fork sensor, was developed for non-contact atomic force microscopy (nc-AFM) with atomic resolution. By cutting a small notch and attaching an AFM tip to one prong, its resonance frequency can be retuned to that of the other intact prong. In balancing the two prongs in this manner, a high Q factor (>50 000 in ultrahigh vacuum) is obtained for the sensor. An atomic resolution image of the Si(111)-7 × 7 surface was demonstrated using an nc-AFM with the sensor. The dependence of the Q factor on resonance frequency of the sensor and the long-range force between tip and sample were measured and analyzed in view of the various dissipation channels. Dissipation in the signal detection circuit turned out to be mainly limited by the total Q factor of the nc-AFM system.

  11. Term frequency - function of document frequency: a new term weighting scheme for enterprise information retrieval

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Wang, Deqing; Wu, Wenjun; Hu, Hongping

    2012-11-01

    In today's business environment, enterprises are increasingly under pressure to process the vast amount of data produced everyday within enterprises. One method is to focus on the business intelligence (BI) applications and increasing the commercial added-value through such business analytics activities. Term weighting scheme, which has been used to convert the documents as vectors in the term space, is a vital task in enterprise Information Retrieval (IR), text categorisation, text analytics, etc. When determining term weight in a document, the traditional TF-IDF scheme sets weight value for the term considering only its occurrence frequency within the document and in the entire set of documents, which leads to some meaningful terms that cannot get the appropriate weight. In this article, we propose a new term weighting scheme called Term Frequency - Function of Document Frequency (TF-FDF) to address this issue. Instead of using monotonically decreasing function such as Inverse Document Frequency, FDF presents a convex function that dynamically adjusts weights according to the significance of the words in a document set. This function can be manually tuned based on the distribution of the most meaningful words which semantically represent the document set. Our experiments show that the TF-FDF can achieve higher value of Normalised Discounted Cumulative Gain in IR than that of TF-IDF and its variants, and improving the accuracy of relevance ranking of the IR results.

  12. Post-Functionalized Polymer Brushes for Bio-Separation: Tuning GFP Adsorption via Functional Group Display

    NASA Astrophysics Data System (ADS)

    Diamanti, Steve; Arifuzzaman, Shafi; Genzer, Jan; Naik, Rajesh; Vaia, Richard

    2007-03-01

    An inexpensive and robust biosensor platform that can be tuned to separate and/or detect complex mixtures of biomolecules while minimizing reagents would be of great use for military, homeland security, and medical diagnostic applications. Gradient surfaces of poly(2-hydroxyethyl methacrylate) (PHEMA) brushes have been previously shown to spatially localize biomolecule binding, while minimizing non-specific adsorption of the same biomolecule on other regions of the gradient specimen. In order to further improve the specificity and to provide latent functionality for detection of the binding events, post-polymerization modification of PHEMA with various functional groups has been investigated. Using standard succinimide-based coupling, hydroxyl pendants of PHEMA brushes were conjugated to oligo-peptides, alkanes and oligo(ethylene glycol) (OEG) through an alpha-terminus primary amine. Ellipsometry, contact angle, XPS and ER-FTIR spectroscopy indicated that coupling occurred with efficiencies ranging from 10-40%. Post-functionalization of PHEMA with OEG and hexadecane allows manipulation of the hydrophilicity of the surface and thus tuning of Green Fluorescent Protein (GFP) binding.

  13. Methods of reducing low frequency cabin noise and sonically induced stresses, based on the intrinsic structural tuning concept

    NASA Technical Reports Server (NTRS)

    Sengupta, G.

    1977-01-01

    Control of low frequency interior noise has been difficult in all commercial and general aviation aircraft, since the existing sound attenuation techniques are less effective at these frequencies. Therefore low frequency cabin noise and sonically induced stresses can be reduced mainly by a proper design of the fuselage structure. For this purpose, a concept based on intrinsic tuning and damping of fuselage structural elements has been under development at Boeing for the past three years. This paper describes the results of some laboratory and field tests that were conducted for evaluation of the concept.

  14. Note: improving spatial resolution of optical frequency-domain reflectometry against frequency tuning nonlinearity using non-uniform fast Fourier transform.

    PubMed

    Ding, Zhenyang; Liu, Tiegen; Meng, Zhuo; Liu, Kun; Chen, Qinnan; Du, Yang; Li, Dingjie; Yao, X Steve

    2012-06-01

    We propose using non-uniform FFT to minimize the degrading effect of frequency tuning nonlinearity of a tunable laser source (TLS) in an optical frequency-domain reflectometry (OFDR) system. We use an auxiliary interferometer to obtain the required instantaneous optical frequency of the TLS and successfully demonstrate 100 times enhancement in spatial resolution of OFDR with only a 20% increase in computation time. The corresponding measurement reflectivity sensitivity is better than -80 dB, sufficient to detect bending induced index changes in an optical fiber. PMID:22755676

  15. Note: Improving spatial resolution of optical frequency-domain reflectometry against frequency tuning nonlinearity using non-uniform fast Fourier transform

    NASA Astrophysics Data System (ADS)

    Ding, Zhenyang; Liu, Tiegen; Meng, Zhuo; Liu, Kun; Chen, Qinnan; Du, Yang; Li, Dingjie; Yao, X. Steve

    2012-06-01

    We propose using non-uniform FFT to minimize the degrading effect of frequency tuning nonlinearity of a tunable laser source (TLS) in an optical frequency-domain reflectometry (OFDR) system. We use an auxiliary interferometer to obtain the required instantaneous optical frequency of the TLS and successfully demonstrate 100 times enhancement in spatial resolution of OFDR with only a 20% increase in computation time. The corresponding measurement reflectivity sensitivity is better than -80 dB, sufficient to detect bending induced index changes in an optical fiber.

  16. A model for electrical resonance and frequency tuning in saccular hair cells of the bull-frog, Rana catesbeiana.

    PubMed

    Hudspeth, A J; Lewis, R S

    1988-06-01

    1. Electrical resonance in solitary hair cells was examined under several experimental conditions using the tight-seal recording technique in the whole-cell current-clamp mode. 2. Resonance was characterized by the frequency and quality factor of oscillations in membrane potential evoked by depolarizing current pulses. Oscillation frequency increased with depolarization, from about 90 Hz at the resting potential to a limiting value of about 250 Hz. The quality factor of the oscillations was a bell-shaped function of membrane potential that reached a maximum of up to 12.6 at a potential slightly positive to the resting potential. 3. Pharmacological experiments were performed to assess which of three ionic currents participate in electrical resonance. Reduction of the voltage-gated Ca2+ current (ICa) and the Ca2+-activated K+ current (IK(Ca)) by lowering the extracellular Ca2+ concentration, or reduction of IK(Ca) with tetraethylammonium ion (TEA) degraded the resonance. In contrast, blockade of the transient K+ current (IA) with 4-aminopyridine (4-AP) had no significant effect. 4. To test the sufficiency of the Ca2+ and the Ca2+-activated K+ currents to account for resonance, we developed a model using mathematical descriptions of the two currents derived in the preceding paper (Hudspeth & Lewis, 1988), with additional terms for leakage conductance and membrane capacitance. The model correctly predicts the oscillatory responses to applied current pulses, including the non-linear dependences of oscillation frequency and quality factor on membrane potential. 5. Simulations of current-clamp experiments in the presence of a reduced extracellular Ca2+ concentration or of TEA were generated respectively by decreasing the model's values for the maximal Ca2+ or Ca2+-activated K+ conductances. The model's predictions of membrane-potential oscillations under these conditions agree qualitatively with experimental results, providing further support for the model as a

  17. Temporal Frequency Tuning Reveals Interactions between the Dorsal and Ventral Visual Streams.

    PubMed

    Kristensen, Stephanie; Garcea, Frank E; Mahon, Bradford Z; Almeida, Jorge

    2016-09-01

    Visual processing of complex objects is supported by the ventral visual pathway in the service of object identification and by the dorsal visual pathway in the service of object-directed reaching and grasping. Here, we address how these two streams interact during tool processing, by exploiting the known asymmetry in projections of subcortical magnocellular and parvocellular inputs to the dorsal and ventral streams. The ventral visual pathway receives both parvocellular and magnocellular input, whereas the dorsal visual pathway receives largely magnocellular input. We used fMRI to measure tool preferences in parietal cortex when the images were presented at either high or low temporal frequencies, exploiting the fact that parvocellular channels project principally to the ventral but not dorsal visual pathway. We reason that regions of parietal cortex that exhibit tool preferences for stimuli presented at frequencies characteristic of the parvocellular pathway receive their inputs from the ventral stream. We found that the left inferior parietal lobule, in the vicinity of the supramarginal gyrus, exhibited tool preferences for images presented at low temporal frequencies, whereas superior and posterior parietal regions exhibited tool preferences for images present at high temporal frequencies. These data indicate that object identity, processed within the ventral stream, is communicated to the left inferior parietal lobule and may there combine with inputs from the dorsal visual pathway to allow for functionally appropriate object manipulation. PMID:27082048

  18. Tuning the work function of graphene by ultraviolet irradiation

    SciTech Connect

    Lin, Yow-Jon; Zeng, Jian-Jhou

    2013-05-06

    Graphene layers grown by chemical vapor deposition were, respectively, irradiated for 0, 20, 40, and 60 min by an ultraviolet light source in order to experimentally study the change in the work function of graphene. The dependences of the work function and carrier concentration upon ultraviolet irradiation have been found. It is shown that ultraviolet irradiation may lead to oxygen desorption, thus reducing the hole density and work function of graphene. Based on the well-known expression for the Fermi energy of Dirac fermions, the Fermi velocity of graphene was extracted to be about 5.2 Multiplication-Sign 10{sup 5} m/s.

  19. Frequency tuning of a distributed feedback dye laser with two transmission gratings.

    PubMed

    Cui, Y; Ding, T N; Hatten, D L; Hill, W T; Goldhar, J

    1993-11-20

    Distributed feedback dye lasers, which use a holographic grating, present a very simple and reliable way to generate ultrashort pulses. We have developed a new technique for wavelength tuning of this type of laser by projecting the image of a second grating into the dye cell. Single-line operating and tuning was demonstrated with transform-limited output pulses on a picosecond time scale. PMID:20856504

  20. Ih Tunes Theta/Gamma Oscillations and Cross-Frequency Coupling In an In Silico CA3 Model

    PubMed Central

    Neymotin, Samuel A.; Hilscher, Markus M.; Moulin, Thiago C.; Skolnick, Yosef; Lazarewicz, Maciej T.; Lytton, William W.

    2013-01-01

    channels are uniquely positioned to act as neuromodulatory control points for tuning hippocampal theta (4–12 Hz) and gamma (25 Hz) oscillations, oscillations which are thought to have importance for organization of information flow. contributes to neuronal membrane resonance and resting membrane potential, and is modulated by second messengers. We investigated oscillatory control using a multiscale computer model of hippocampal CA3, where each cell class (pyramidal, basket, and oriens-lacunosum moleculare cells), contained type-appropriate isoforms of . Our model demonstrated that modulation of pyramidal and basket allows tuning theta and gamma oscillation frequency and amplitude. Pyramidal also controlled cross-frequency coupling (CFC) and allowed shifting gamma generation towards particular phases of the theta cycle, effected via 's ability to set pyramidal excitability. Our model predicts that in vivo neuromodulatory control of allows flexibly controlling CFC and the timing of gamma discharges at particular theta phases. PMID:24204609

  1. An electrostatic model for the frequency shifts in the carbonmonoxy stretching band of myoglobin: correlation of hydrogen bonding and the stark tuning rate.

    PubMed

    Franzen, Stefan

    2002-11-01

    The effect of internal and applied external electric fields on the vibrational stretching frequency for bound CO (nu(CO)) in myoglobin mutants was studied using density functional theory. Geometry optimization and frequency calculations were carried out for an imidazole-iron-porphine-carbonmonoxy adduct with various small molecule hydrogen-bonding groups. Over 70 vibrational frequency calculations of different model geometries and hydrogen-bonding groups were compared to derive overall trends in the C-O stretching frequency (nu(CO)) in terms of the C-O bond length and Mulliken charge. Simple linear functions were derived to predict the Stark tuning rate using an approach analogous to the vibronic theory of activation.(1) Potential energy calculations show that the strongest interaction occurs for C-H or N-H hydrogen bonding nearly perpendicular to the Fe-C-O bond axis. The calculated frequencies are compared to the structural data available from 18 myoglobin crystal structures, supporting the hypothesis that the vast majority of hydrogen-bonding interactions with CO occur from the side, rather than the end, of the bound CO ligand. The nu(CO) frequency shifts agree well with experimental frequency shifts for multiple bands, known as A states, and site-directed mutations in the distal pocket of myoglobin. The model calculations quantitatively explain electrostatic effects in terms of specific hydrogen-bonding interactions with bound CO in heme proteins. PMID:12405856

  2. Theory of work function tuning via mixed-monolayers on functional surfaces

    NASA Astrophysics Data System (ADS)

    Kotiuga, Michele; Darancet, Pierre; Neaton, Jeffrey B.

    Self-assembled monolayers (SAMs) provide both stability and functionality of surfaces useful in optoelectronic nanoscale devices. The work function, level alignment and other electronic properties of functionalized surfaces can be tuned with the choice of molecule and an even finer control of the properties can be obtained with a SAM comprised of multiple types of molecules. Modeling the effect on electronic properties of mixed-monolayers via ab initio calculations poses a challenge due to the large supercell required to capture a range of relative concentrations between the two types of molecules. Here, we present an implicit model - fit from density functional theory calculations - capturing local electrostatic interactions within the SAM primarily due to depolarization of the induced dipoles formed upon binding. This quantitative model allows us to explore supercells with a large number of molecules and, thus, surface concentrations that are inhomogeneous in nature. We compare to experimental results of thiol terminated carboranes on gold Supported by AFOSR MURI FA9550-12-1-0002 and U.S. DOE under Contract Nos. DE-AC02-06CH1135 & DE-AC02-06CH11231.

  3. Level-dependent auditory tuning: Transducer-based active processes in hearing and best-frequency shifts.

    PubMed

    Nadrowski, Björn; Göpfert, Martin C

    2009-01-01

    Ears boost their sensitivity by means of active, force-generating processes that augment the minute vibrations induced by soft sounds. These processes can alter auditory frequency-tuning in a level-dependent way. In the antennal hearing organ of Drosophila, for example, the active process shifts the best frequency (BF) of the antennal sound receiver when the sound intensity is varied, tuning the receiver to conspecific songs. Here we show that this level-dependent tuning can be reproduced by an active transduction model as proposed for vertebrate hair cells and the Drosophila ear. We further show that the direction of the frequency shift depends on the system to which the molecular modules for auditory transduction connect: If this system is mass-less such as the sensory hair bundles of bullfrog saccular hair cells, the BF of the displacement response will increase as the sound intensity declines. Conversely, BF will decrease with declining intensity if the transduction modules couple to inertial systems such as the fly's antennal sound receiver or cupulae in the fish lateral line. PMID:19704854

  4. Angle-dependent strong-field molecular ionization rates with tuned range-separated time-dependent density functional theory.

    PubMed

    Sissay, Adonay; Abanador, Paul; Mauger, François; Gaarde, Mette; Schafer, Kenneth J; Lopata, Kenneth

    2016-09-01

    Strong-field ionization and the resulting electronic dynamics are important for a range of processes such as high harmonic generation, photodamage, charge resonance enhanced ionization, and ionization-triggered charge migration. Modeling ionization dynamics in molecular systems from first-principles can be challenging due to the large spatial extent of the wavefunction which stresses the accuracy of basis sets, and the intense fields which require non-perturbative time-dependent electronic structure methods. In this paper, we develop a time-dependent density functional theory approach which uses a Gaussian-type orbital (GTO) basis set to capture strong-field ionization rates and dynamics in atoms and small molecules. This involves propagating the electronic density matrix in time with a time-dependent laser potential and a spatial non-Hermitian complex absorbing potential which is projected onto an atom-centered basis set to remove ionized charge from the simulation. For the density functional theory (DFT) functional we use a tuned range-separated functional LC-PBE*, which has the correct asymptotic 1/r form of the potential and a reduced delocalization error compared to traditional DFT functionals. Ionization rates are computed for hydrogen, molecular nitrogen, and iodoacetylene under various field frequencies, intensities, and polarizations (angle-dependent ionization), and the results are shown to quantitatively agree with time-dependent Schrödinger equation and strong-field approximation calculations. This tuned DFT with GTO method opens the door to predictive all-electron time-dependent density functional theory simulations of ionization and ionization-triggered dynamics in molecular systems using tuned range-separated hybrid functionals. PMID:27608987

  5. Hybrid Density Functionals Tuned towards Fulfillment of Fundamental DFT Conditions

    NASA Astrophysics Data System (ADS)

    Scheffler, Matthias

    2014-03-01

    Hybrid exchange-correlation functionals (XC), e.g. PBE0 and HSE, have significantly improved the theoretical description of molecules and solids. Their degree of exact-exchange admixture (α) is in principle a functional of the electron density, but the functional form is not known. In this talk, I will discuss fundamental conditions of exact density-functional theory (DFT) that enable us to find the optimal choice of α for ground-state calculations. In particular, I will discuss the fact that the highest occupied Kohn-Sham level of an N-electron system (ɛHOMO(N)) should be constant for fractional particle numbers between N and N-1 and equals the ionization potential (IP), as given by the total-energy difference. In practice, we realize this in three different ways. XC(α) will be optimized (opt-XC) until it (i) fulfills the condition: ɛHOMO(N) =ɛHOMO (N-1/2) or the Kohn-Sham HOMO agrees with the ionization potential computed in a more sophisticated approach ɛHOMO(N) = IP such as (ii) the G0W0 @opt-XC method or (iii) CCSD(T) or full CI. Using such an opt-XC is essential for describing electron transfer between (organic) molecules, as exemplified by the TTF/TCNQ dimer. It also yields vertical ionization energies of the G2 test set of quantum chemistry with a mean absolute percentage error of only ~3%. Furthermore, our approach removes the starting-point uncertainty of GW calculations and thus bears some resemblance to the consistent starting point scheme and quasiparticle self-consistent GW. While our opt-XC approach yields large α values for small molecules in the gas phase, we find that α needs to be 0.25 or less for organic molecules adsorbed on metals. Work performed in collaboration with V. Atalla, N.A. Richter, S.V. Levchenko, and P. Rinke

  6. Localized electrical fine tuning of passive microwave and radio frequency devices

    DOEpatents

    Findikoglu, Alp T.

    2001-04-10

    A method and apparatus for the localized electrical fine tuning of passive multiple element microwave or RF devices in which a nonlinear dielectric material is deposited onto predetermined areas of a substrate containing the device. An appropriate electrically conductive material is deposited over predetermined areas of the nonlinear dielectric and the signal line of the device for providing electrical contact with the nonlinear dielectric. Individual, adjustable bias voltages are applied to the electrically conductive material allowing localized electrical fine tuning of the devices. The method of the present invention can be applied to manufactured devices, or can be incorporated into the design of the devices so that it is applied at the time the devices are manufactured. The invention can be configured to provide localized fine tuning for devices including but not limited to coplanar waveguides, slotline devices, stripline devices, and microstrip devices.

  7. A Hardware Platform for Tuning of MEMS Devices Using Closed-Loop Frequency Response

    NASA Technical Reports Server (NTRS)

    Ferguson, Michael I.; MacDonald, Eric; Foor, David

    2005-01-01

    We report on the development of a hardware platform for integrated tuning and closed-loop operation of MEMS gyroscopes. The platform was developed and tested for the second generation JPL/Boeing Post-Resonator MEMS gyroscope. The control of this device is implemented through a digital design on a Field Programmable Gate Array (FPGA). A software interface allows the user to configure, calibrate, and tune the bias voltages on the micro-gyro. The interface easily transitions to an embedded solution that allows for the miniaturization of the system to a single chip.

  8. Tuning of noble metal work function with organophosphonate nanolayers

    SciTech Connect

    Ramanath, Ganpati Kwan, Matthew; Chow, P. K.; Quintero, Y. Cardona; Ramprasad, R.; Mutin, P. H.

    2014-08-25

    We demonstrate that weak chemical interactions between untethered moieties in molecular nanolayers on metal surfaces can strongly influence the effective work function Φ{sub eff}. Electron spectroscopy shows that nanolayers of mercaptan-anchored organophosphonates on Au and Pt decrease Φ{sub eff}. The measured Φ{sub eff} shifts correlate with the chemical state of phosphonic acid moieties, and scale with molecular length. These results are contrary to predictions of ab initio calculations of monolayer-capped surfaces, but are consistent with calculations of bilayer-capped surfaces with face-to-face hydrogen-bonded phosphonic acid moieties. Our findings indicate that intra-layer bonding and layering in molecular nanolayers can be key to tailoring heterointerfacial electronic properties for applications.

  9. A quenched study of the Schroedinger functional with chirally rotated boundary conditions: non-perturbative tuning

    SciTech Connect

    Gonzalez-Lopez, Jennifer; Jansen, Karl; Renner, Dru B.; Shindler, Andrea

    2013-02-01

    The use of chirally rotated boundary conditions provides a formulation of the Schroedinger functional that is compatible with automatic O(a) improvement of Wilson fermions up to O(a) boundary contributions. The elimination of bulk O(a) effects requires the non-perturbative tuning of the critical mass and one additional boundary counterterm. We present the results of such a tuning in a quenched setup for several values of the renormalized gauge coupling, from perturbative to non-perturbative regimes, and for a range of lattice spacings. We also check that the correct boundary conditions and symmetries are restored in the continuum limit.

  10. Voltage tuning of the resonance frequency of electroactive polymer membranes over a range of more than 75%

    NASA Astrophysics Data System (ADS)

    Dubois, Philippe; Rosset, Samuel; Niklaus, Muhamed; Shea, Herbert

    2009-05-01

    We report on a novel technique to control the resonance frequency of polymer membranes, without additional external actuators. An electrostatic force is used to apply compressive stress to a dielectric electroactive polymers membrane, consisting of a 25 micron thick, 1 to 4 mm diameter, polydimethylsiloxane (PDMS) film bonded onto patterned silicon or Pyrex wafers. Both sides of the membranes are rendered conductive by low-energy metal ion implantation. Ion implantation is chosen because it stiffens the membrane much less than sputtering a film of similar thickness [1][2]. The initial resonance frequency of the membrane is given by its geometry, the Young's modulus and stress of the composite film. The technique presented here allows tuning the resonance frequency from this initial value down to zero (at the buckling threshold) by adding compressive stress due to a voltage difference applied to the electrodes on both sides of the membrane. We have measured a reduction of the first mode resonance frequency of up to 77% (limited by dielectric breakdown) for ion-implanted membranes [3]. The tuning is repeatable and allows for continuous variation. Excellent agreement was found between our measurements and an analytical model we developed based on the Rayleigh-Ritz theory.

  11. System and method for tuning adjusting the central frequency of a laser while maintaining frequency stabilization to an external reference

    NASA Technical Reports Server (NTRS)

    Livas, Jeffrey (Inventor); Thorpe, James I. (Inventor); Numata, Kenji (Inventor)

    2011-01-01

    A method and system for stabilizing a laser to a frequency reference with an adjustable offset. The method locks a sideband signal generated by passing an incoming laser beam through the phase modulator to a frequency reference, and adjusts a carrier frequency relative to the locked sideband signal by changing a phase modulation frequency input to the phase modulator. The sideband signal can be a single sideband (SSB), dual sideband (DSB), or an electronic sideband (ESB) signal. Two separate electro-optic modulators can produce the DSB signal. The two electro-optic modulators can be a broadband modulator and a resonant modulator. With a DSB signal, the method can introduce two sinusoidal phase modulations at the phase modulator. With ESB signals, the method can further drive the optical phase modulator with an electrical signal with nominal frequency OMEGA(sub 1) that is phase modulated at a frequency OMEGA(sub 2)

  12. Tuned range-separated hybrid functionals in the symmetry-adapted perturbation theory

    SciTech Connect

    Hapka, Michał; Modrzejewski, Marcin; Rajchel, Łukasz; Chałasiński, Grzegorz; Szczęśniak, Małgorzata M.

    2014-10-07

    The aim of this study is to present a performance test of optimally tuned long-range corrected (LRC) functionals applied to the symmetry-adapted perturbation theory (SAPT). In the present variant, the second-order energy components are evaluated at the coupled level of theory. We demonstrate that the generalized Kohn-Sham (GKS) description of monomers with optimally tuned LRC functionals may be essential for the quality of SAPT interaction energy components. This is connected to the minimization of a many-electron self-interaction error and exemplified by two model systems: polyacetylenes of increasing length and stretching of He{sub 3}{sup +}. Next we provide a comparison of SAPT approaches based on Kohn-Sham and GKS description of the monomers. We show that LRC leads to results better or comparable with the hitherto prevailing asymptotically corrected functionals. Finally, we discuss the advantages and possible limitations of SAPT based on LRC functionals.

  13. Analysis of the natural frequency of a quartz double-end tuning fork with a new deformation model

    NASA Astrophysics Data System (ADS)

    Huang, Bo-Shiun; Chang-Chien, Wen-Tien; Hsieh, Fa-Hwa; Chou, Yuan-Fang; Chang, Chia-Ou

    2016-06-01

    The quartz double-end tuning fork is composed of two parallel slender beams with their ends fixed to the proof masses, both ends of which are clamped. The structure is made of a quartz wafer which is anisotropic in stiffness. In anti-phase mode the two slender parallel beams vibrate in opposite directions and can be modelled as an Euler beam. The twist moments caused by the slender beams on the proof mass make the cross-section of the proof mass deform into a warped surface. The objective of this research is to establish the warping deformation model so that we can build up the equation of motion for anisotropic stiffness by using Hamilton’s principle and then perform theoretical analysis. The more realistic warping displacement leads the natural frequency closer to the true one. The purpose of the proof mass is to modulate the frequencies and mode shape of tuning fork beams. The advantage of anti-phase mode is that the centre of mass in unchanged during motion so that the system has a higher signal-to-noise ratio. The theoretically obtained frequency is compared with the experimental one and that obtained by the finite element method.

  14. A short report on voltage-to-frequency conversion for HISTRAP RF system tuning control loops

    SciTech Connect

    Hasanul Basher, A.M.

    1991-09-01

    One of the requirements of the HISTRAP RF accelerating system is that the frequency of the accelerating voltage for the cavity must keep in step with the change in the magnetic field. As the energy of the particle increases, the magnetic field is increased to keep the radius of the particle orbit constant. At the same time, the frequency of the electric field must be changed to insure that it is synchronized with the angular movement of the particle. So we need to generate the frequency of the accelerating voltage in relation to the magnetic field. The frequency generation can be accomplished in two stages. The first stage of frequency generation consists of measuring the magnetic field in terms of voltage which is already developed. The second stage is to convert this voltage into frequency. Final frequency precision can be achieved by deriving a frequency-correcting signal from the beam position. This project is concerned with generating the frequency from the analog voltage. The speed of response required will place very stringent requirements on both hardware and software. Technology is available to carry out this task. A hardware configuration has been established and software has been developed. In the following section, we describe the implementation strategy, the hardware configuration, and the desired specifications. Next, we present the software developed, results obtained, along with capabilities and limitations of the system. Finally, we suggest alternate solutions to overcome some of the limitations toward meeting our goal. In the appendices, we include program listings.

  15. Frequency Selectivity of Voxel-by-Voxel Functional Connectivity in Human Auditory Cortex.

    PubMed

    Cha, Kuwook; Zatorre, Robert J; Schönwiesner, Marc

    2016-01-01

    While functional connectivity in the human cortex has been increasingly studied, its relationship to cortical representation of sensory features has not been documented as much. We used functional magnetic resonance imaging to demonstrate that voxel-by-voxel intrinsic functional connectivity (FC) is selective to frequency preference of voxels in the human auditory cortex. Thus, FC was significantly higher for voxels with similar frequency tuning than for voxels with dissimilar tuning functions. Frequency-selective FC, measured via the correlation of residual hemodynamic activity, was not explained by generic FC that is dependent on spatial distance over the cortex. This pattern remained even when FC was computed using residual activity taken from resting epochs. Further analysis showed that voxels in the core fields in the right hemisphere have a higher frequency selectivity in within-area FC than their counterpart in the left hemisphere, or than in the noncore-fields in the same hemisphere. Frequency-selective FC is consistent with previous findings of topographically organized FC in the human visual and motor cortices. The high degree of frequency selectivity in the right core area is in line with findings and theoretical proposals regarding the asymmetry of human auditory cortex for spectral processing. PMID:25183885

  16. Delocalization error and "functional tuning" in Kohn-Sham calculations of molecular properties.

    PubMed

    Autschbach, Jochen; Srebro, Monika

    2014-08-19

    Kohn-Sham theory (KST) is the "workhorse" of numerical quantum chemistry. This is particularly true for first-principles calculations of ground- and excited-state properties for larger systems, including electronic spectra, electronic dynamic and static linear and higher order response properties (including nonlinear optical (NLO) properties), conformational or dynamic averaging of spectra and response properties, or properties that are affected by the coupling of electron and nuclear motion. This Account explores the sometimes dramatic impact of the delocalization error (DE) and possible benefits from the use of long-range corrections (LC) and "tuning" of functionals in KST calculations of molecular ground-state and response properties. Tuning refers to a nonempirical molecule-specific determination of adjustable parameters in functionals to satisfy known exact conditions, for instance, that the energy of the highest occupied molecular orbital (HOMO) should be equal to the negative vertical ionization potential (IP) or that the energy as a function of fractional electron numbers should afford straight-line segments. The presentation is given from the viewpoint of a chemist interested in computations of a variety of molecular optical and spectroscopic properties and of a theoretician developing methods for computing such properties with KST. In recent years, the use of LC functionals, functional tuning, and quantifying the DE explicitly have provided valuable insight regarding the performance of KST for molecular properties. We discuss a number of different molecular properties, with examples from recent studies from our laboratory and related literature. The selected properties probe different aspects of molecular electronic structure. Electric field gradients and hyperfine coupling constants can be exquisitely sensitive to the DE because it affects the ground-state electron density and spin density distributions. For π-conjugated molecules, it is shown how the

  17. Intelligent Systems for Stabilizing Mode-Locked Lasers and Frequency Combs: Machine Learning and Equation-Free Control Paradigms for Self-Tuning Optics

    NASA Astrophysics Data System (ADS)

    Kutz, J. Nathan; Brunton, Steven L.

    2015-12-01

    We demonstrate that a software architecture using innovations in machine learning and adaptive control provides an ideal integration platform for self-tuning optics. For mode-locked lasers, commercially available optical telecom components can be integrated with servocontrollers to enact a training and execution software module capable of self-tuning the laser cavity even in the presence of mechanical and/or environmental perturbations, thus potentially stabilizing a frequency comb. The algorithm training stage uses an exhaustive search of parameter space to discover best regions of performance for one or more objective functions of interest. The execution stage first uses a sparse sensing procedure to recognize the parameter space before quickly moving to the near optimal solution and maintaining it using the extremum seeking control protocol. The method is robust and equationfree, thus requiring no detailed or quantitatively accurate model of the physics. It can also be executed on a broad range of problems provided only that suitable objective functions can be found and experimentally measured.

  18. The experimental results of a self tuning adaptive controller using online frequency identification. [for Galileo spacecraft

    NASA Technical Reports Server (NTRS)

    Chiang, W.-W.; Cannon, R. H., Jr.

    1985-01-01

    A fourth-order laboratory dynamic system featuring very low structural damping and a noncolocated actuator-sensor pair has been used to test a novel real-time adaptive controller, implemented in a minicomputer, which consists of a state estimator, a set of state feedback gains, and a frequency-locked loop for real-time parameter identification. The adaptation algorithm employed can correct controller error and stabilize the system for more than 50 percent variation in the plant's natural frequency, compared with a 10 percent stability margin in frequency variation for a fixed gain controller having the same performance as the nominal plant condition. The very rapid convergence achievable by this adaptive system is demonstrated experimentally, and proven with simple, root-locus methods.

  19. Method of Tuning Frequency of the Defect Mode in Two-Dimensional Square Photonic Crystals

    NASA Astrophysics Data System (ADS)

    Yan, Shuya; Wu, Fugen; Zhang, Xin; Yao, Yuanwei; Zhong, Huilin; He, Yun; Cheng, Cong

    2013-03-01

    In this paper, we investigate the defect modes created by taking a single rod away from the center of the supercell in two-dimensional photonic crystals. Through theoretical calculation, we find that the defect band can exist in the photonic band gaps, and the position of the defect band frequency intensively depends on the position and radius size of the defect rod. When the radius of the defect rod is bigger than that of the normal rods, the frequency of the defect band can be tunable in a wider range by moving the defect position while the doubly degenerate defect modes may split into two nondegenerate defect modes. The investigation provides a theoretical instruction to design the optical resonator with tunable frequency.

  20. Bivariate flood frequency analyses using Copula function

    NASA Astrophysics Data System (ADS)

    Sraj, Mojca; Bezak, Nejc; Brilly, Mitja

    2013-04-01

    The objective of the study was (1) to perform all steps in flood frequency analyses using Copula approach, (2) to select the most appropriate Copula function and (3) to evaluate the conditional bivariate return periods for the next pairs of variables: peak-volume, volume-duration and peak-duration, respectively. Flood frequency analyses are usually made by univariate distribution functions and in most cases only peaks are considered in analyses. However, hydrological processes are multidimensional, so it is reasonable to consider more than one variable in analyses. Different marginal distributions can be used for Copula modelling. Copula function successfully models dependence between two or more depended variables and determination of marginal distributions and Copula selection are two separate processes. Hydrological station Litija on the Sava river is one of the oldest stations in Slovenia and it lies in eastern part of country. 58 years of annual maximums were used for analyses and three-points graphical method was used for base flow separation. The log-Pearson type 3 distribution was selected as marginal distribution of peaks and durations, the Pearson type 3 distribution was chosen as marginal distribution of volumes. Some frequently used Copula functions from the Archimedean (Gumbel-Hougaard, Frank, Joe, Clayton, BB1 and Ali-Mikhail-Haq), Elliptical (Student-t and Normal) and Extreme value (Galambos, Hüsler-Reiss and Tawn) families were applied to the data. Copula parameters were estimated with the method of moments based on the inversion of Kendall's tau and with the maximum likelihood method. Graphical and statistical test were applied for the comparison of different Copula functions. For the pair peak-duration the Kendall correlation coefficient was negative and only Copulas able to model negative dependence were used. The Gumbel-Hougaard, Frank and Ali-Mikhail-Haq Copulas were selected as optimal based on tests results for the pairs: peak-volume, volume

  1. Spatial frequency tuning reveals interactions between the dorsal and ventral visual systems.

    PubMed

    Mahon, Bradford Z; Kumar, Nicholas; Almeida, Jorge

    2013-06-01

    It is widely argued that the ability to recognize and identify manipulable objects depends on the retrieval and simulation of action-based information associated with using those objects. Evidence for that view comes from fMRI studies that have reported differential BOLD contrast in dorsal visual stream regions when participants view manipulable objects compared with a range of baseline categories. An alternative interpretation is that processes internal to the ventral visual pathway are sufficient to support the visual identification of manipulable objects and that the retrieval of object-associated use information is contingent on analysis of the visual input by the ventral stream. Here, we sought to distinguish these two perspectives by exploiting the fact that the dorsal stream is largely driven by magnocellular input, which is biased toward low spatial frequency visual information. Thus, any tool-selective responses in parietal cortex that are driven by high spatial frequencies would be indicative of inputs from the ventral visual pathway. Participants viewed images of tools and animals containing only low, or only high, spatial frequencies during fMRI. We find an internal parcellation of left parietal "tool-preferring" voxels: Inferior aspects of left parietal cortex are driven by high spatial frequency information and have privileged connectivity with ventral stream regions that show similar category preferences, whereas superior regions are driven by low spatial frequency information. Our findings suggest that the automatic activation of complex object-associated manipulation knowledge is contingent on analysis of the visual input by the ventral visual pathway. PMID:23410033

  2. 750 nm 1.5 W frequency-doubled semiconductor disk laser with a 44 nm tuning range.

    PubMed

    Saarinen, Esa J; Lyytikäinen, Jari; Ranta, Sanna; Rantamäki, Antti; Sirbu, Alexei; Iakovlev, Vladimir; Kapon, Eli; Okhotnikov, Oleg G

    2015-10-01

    We demonstrate 1.5 W of output power at the wavelength of 750 nm by intracavity frequency doubling a wafer-fused semiconductor disk laser diode-pumped at 980 nm. An optical-to-optical efficiency of 8.3% was achieved using a bismuth borate crystal. The wavelength of the doubled emission could be tuned from 720 to 764 nm with an intracavity birefringent plate. The beam quality parameter M2 of the laser output was measured to be below 1.5 at all pump powers. The laser is a promising tool for biomedical applications that can take advantage of the large penetration depth of light in tissue in the 700-800 nm spectral range. PMID:26421536

  3. Spin-torque diode radio-frequency detector with voltage tuned resonance

    NASA Astrophysics Data System (ADS)

    Skowroński, Witold; Frankowski, Marek; Wrona, Jerzy; Stobiecki, Tomasz; Ogrodnik, Piotr; Barnaś, Józef

    2014-08-01

    We report on a voltage-tunable radio-frequency (RF) detector based on a magnetic tunnel junction (MTJ). The spin-torque diode effect is used to excite and/or detect RF oscillations in the magnetic free layer of the MTJ. In order to reduce the overall in-plane magnetic anisotropy of the free layer, we take advantage of the perpendicular magnetic anisotropy at the interface between ferromagnetic and insulating layers. The applied bias voltage is shown to have a significant influence on the magnetic anisotropy, and thus on the resonance frequency of the device. This influence also depends on the voltage polarity. The obtained results are accounted for in terms of the interplay of spin-transfer-torque and voltage-controlled magnetic anisotropy effects.

  4. Spin-torque diode radio-frequency detector with voltage tuned resonance

    SciTech Connect

    Skowroński, Witold Frankowski, Marek; Stobiecki, Tomasz; Wrona, Jerzy; Ogrodnik, Piotr; Barnaś, Józef

    2014-08-18

    We report on a voltage-tunable radio-frequency (RF) detector based on a magnetic tunnel junction (MTJ). The spin-torque diode effect is used to excite and/or detect RF oscillations in the magnetic free layer of the MTJ. In order to reduce the overall in-plane magnetic anisotropy of the free layer, we take advantage of the perpendicular magnetic anisotropy at the interface between ferromagnetic and insulating layers. The applied bias voltage is shown to have a significant influence on the magnetic anisotropy, and thus on the resonance frequency of the device. This influence also depends on the voltage polarity. The obtained results are accounted for in terms of the interplay of spin-transfer-torque and voltage-controlled magnetic anisotropy effects.

  5. Evolution of the electronic spectral function and dynamical conductivity across the disorder-tuned superconductor-insulator transition

    NASA Astrophysics Data System (ADS)

    Trivedi, Nandini

    2015-03-01

    I will discuss the behavior of the single particle electronic spectral function, the bosonic (pair) spectral function P (ω) , and the dynamical conductivity σ (ω) across the superconductor-insulator transition (SIT) calculated using quantum Monte Carlo simulations. The transition is driven by tuning the charging energy relative to the Josephson coupling or by varying the degree of disorder. We identify a prominent Higgs mode in the superconductor, and characteristic energy scales in the insulator, that vanish at the transition due to enhanced quantum phase fluctuations, despite the persistence of a robust fermionic gap across the SIT. Disorder leads to increased absorption at low frequencies compared to the SIT in a clean system. Disorder also expands the quantum critical region, due to a change in the universality class, with an underlying T=0 critical point. Obtaining the conductivity at the transition has been problematical because of analytic continuation of numerical data. We propose a well-defined integrated low-frequency conductivity that can be reliably estimated and discuss its universality. I acknowledge support from DOE DE-FG02-07ER46423.

  6. A Method for Evaluating Tuning Functions of Single Neurons based on Mutual Information Maximization

    NASA Astrophysics Data System (ADS)

    Brostek, Lukas; Eggert, Thomas; Ono, Seiji; Mustari, Michael J.; Büttner, Ulrich; Glasauer, Stefan

    2011-03-01

    We introduce a novel approach for evaluation of neuronal tuning functions, which can be expressed by the conditional probability of observing a spike given any combination of independent variables. This probability can be estimated out of experimentally available data. By maximizing the mutual information between the probability distribution of the spike occurrence and that of the variables, the dependence of the spike on the input variables is maximized as well. We used this method to analyze the dependence of neuronal activity in cortical area MSTd on signals related to movement of the eye and retinal image movement.

  7. Quantitative Reappraisal of the Helmholtz-Guyton Resonance Theory of Frequency Tuning in the Cochlea

    PubMed Central

    Babbs, Charles F.

    2011-01-01

    To explore the fundamental biomechanics of sound frequency transduction in the cochlea, a two-dimensional analytical model of the basilar membrane was constructed from first principles. Quantitative analysis showed that axial forces along the membrane are negligible, condensing the problem to a set of ordered one-dimensional models in the radial dimension, for which all parameters can be specified from experimental data. Solutions of the radial models for asymmetrical boundary conditions produce realistic deformation patterns. The resulting second-order differential equations, based on the original concepts of Helmholtz and Guyton, and including viscoelastic restoring forces, predict a frequency map and amplitudes of deflections that are consistent with classical observations. They also predict the effects of an observation hole drilled in the surrounding bone, the effects of curvature of the cochlear spiral, as well as apparent traveling waves under a variety of experimental conditions. A quantitative rendition of the classical Helmholtz-Guyton model captures the essence of cochlear mechanics and unifies the competing resonance and traveling wave theories. PMID:22028708

  8. Automatic target tracking in forward-looking infrared video sequences using tuned basis functions

    NASA Astrophysics Data System (ADS)

    Bal, Abdullah; Alam, Mohammad S.

    2016-07-01

    Tuned basis function (TBF) is a powerful technique for classification of two classes by transforming them into a new space, where both classes will have complementary eigenvectors. A target discrimination technique can be described based on these complementary eigenvector analyses under two classes: (1) target and (2) background clutter, where basis functions that best represent the desired targets form one class while the complementary basis functions form the second class. Since the TBF does not require pixel-based preprocessing, it provides significant advantages for target tracking applications. Furthermore, efficient eigenvector selection and subframe segmentation significantly reduce the computation burden of the target tracking algorithm. The performance of the proposed TBF-based target tracking algorithm has been tested using real-world forward looking infrared video sequences.

  9. Sensitive Radio-Frequency Measurements of a Quantum Dot by Tuning to Perfect Impedance Matching

    NASA Astrophysics Data System (ADS)

    Ares, N.; Schupp, F. J.; Mavalankar, A.; Rogers, G.; Griffiths, J.; Jones, G. A. C.; Farrer, I.; Ritchie, D. A.; Smith, C. G.; Cottet, A.; Briggs, G. A. D.; Laird, E. A.

    2016-03-01

    Electrical readout of spin qubits requires fast and sensitive measurements, which are hindered by poor impedance matching to the device. We demonstrate perfect impedance matching in a radio-frequency readout circuit, using voltage-tunable varactors to cancel out parasitic capacitances. An optimized capacitance sensitivity of 1.6 aF /√{Hz } is achieved at a maximum source-drain bias of 170 -μ V root-mean-square and with a bandwidth of 18 MHz. Coulomb blockade in a quantum-dot is measured in both conductance and capacitance, and the two contributions are found to be proportional as expected from a quasistatic tunneling model. We benchmark our results against the requirements for single-shot qubit readout using quantum capacitance, a goal that has so far been elusive.

  10. Tuning the acoustic frequency of a gold nanodisk through its adhesion layer

    NASA Astrophysics Data System (ADS)

    Chang, Wei-Shun; Wen, Fangfang; Chakraborty, Debadi; Su, Man-Nung; Zhang, Yue; Shuang, Bo; Nordlander, Peter; Sader, John E.; Halas, Naomi J.; Link, Stephan

    2015-05-01

    To fabricate robust metallic nanostructures with top-down patterning methods such as electron-beam lithography, an initial nanometer-scale layer of a second metal is deposited to promote adhesion of the metal of interest. However, how this nanoscale layer affects the mechanical properties of the nanostructure and how adhesion layer thickness controls the binding strength to the substrate are still open questions. Here we use ultrafast laser pulses to impulsively launch acoustic phonons in single gold nanodisks with variable titanium layer thicknesses, and observe an increase in phonon frequencies as a thicker adhesion layer facilitates stronger binding to the glass substrate. In addition to an all-optical interrogation of nanoscale mechanical properties, our results show that the adhesion layer can be used to controllably modify the acoustic phonon modes of a gold nanodisk. This direct coupling between optically excited plasmon modes and phonon modes can be exploited for a variety of emerging optomechanical applications.

  11. Pressure tuning of anisotropy barrier in Fe8 SMMs probed using high frequency EPR

    NASA Astrophysics Data System (ADS)

    Thirunavukkuarasu, Komalavalli; Beedle, Christopher; Tozer, Stanley; Hill, Stephen

    2014-03-01

    Single-molecule magnets (SMMs) are spin systems with large spin ground state where quantum phenomena such as tunneling of magnetization via a considerable anisotropy barrier manifest. One such SMM that has been extensively studied is [Fe8O2(OH)12(tacn)6]Br8.9H2O, also known as Fe8, with a giant spin ground state of S=10. The eight Fe atoms bridged by the ligands form a butterfly structure where six Fe atoms have spins up and two spins down in the simplest model. This structure in fact gives rise to geometrical spin frustration effects within the cluster. By varying the interaction between the spins, manipulation of quantum tunneling in SMMs may be achieved. Typically, the manipulation of spin interactions is realized using chemical methods. As an alternative approach, we employ high pressure to induce changes in the ligand-field environment of the Fe atoms. In this presentation, the pressure-dependent changes in the anisotropy barrier in single crystal Fe8 SMMs investigated by high frequency electron paramagnetic resonance measurements will be discussed.

  12. Dual-Functional Energy-Harvesting and Vibration Control: Electromagnetic Resonant Shunt Series Tuned Mass Dampers.

    PubMed

    Zuo, Lei; Cui, Wen

    2013-10-01

    This paper proposes a novel retrofittable approach for dual-functional energy-harvesting and robust vibration control by integrating the tuned mass damper (TMD) and electromagnetic shunted resonant damping. The viscous dissipative element between the TMD and primary system is replaced by an electromagnetic transducer shunted with a resonant RLC circuit. An efficient gradient based numeric method is presented for the parameter optimization in the control framework for vibration suppression and energy harvesting. A case study is performed based on the Taipei 101 TMD. It is found that by tuning the TMD resonance and circuit resonance close to that of the primary structure, the electromagnetic resonant-shunt TMD achieves the enhanced effectiveness and robustness of double-mass series TMDs, without suffering from the significantly amplified motion stroke. It is also observed that the parameters and performances optimized for vibration suppression are close to those optimized for energy harvesting, and the performance is not sensitive to the resistance of the charging circuit or electrical load. PMID:23918165

  13. Phosphorylation and calcium antagonistically tune myosin-binding protein C's structure and function.

    PubMed

    Previs, Michael J; Mun, Ji Young; Michalek, Arthur J; Previs, Samantha Beck; Gulick, James; Robbins, Jeffrey; Warshaw, David M; Craig, Roger

    2016-03-22

    During each heartbeat, cardiac contractility results from calcium-activated sliding of actin thin filaments toward the centers of myosin thick filaments to shorten cellular length. Cardiac myosin-binding protein C (cMyBP-C) is a component of the thick filament that appears to tune these mechanochemical interactions by its N-terminal domains transiently interacting with actin and/or the myosin S2 domain, sensitizing thin filaments to calcium and governing maximal sliding velocity. Both functional mechanisms are potentially further tunable by phosphorylation of an intrinsically disordered, extensible region of cMyBP-C's N terminus, the M-domain. Using atomic force spectroscopy, electron microscopy, and mutant protein expression, we demonstrate that phosphorylation reduced the M-domain's extensibility and shifted the conformation of the N-terminal domain from an extended structure to a compact configuration. In combination with motility assay data, these structural effects of M-domain phosphorylation suggest a mechanism for diminishing the functional potency of individual cMyBP-C molecules. Interestingly, we found that calcium levels necessary to maximally activate the thin filament mitigated the structural effects of phosphorylation by increasing M-domain extensibility and shifting the phosphorylated N-terminal fragments back to the extended state, as if unphosphorylated. Functionally, the addition of calcium to the motility assays ablated the impact of phosphorylation on maximal sliding velocities, fully restoring cMyBP-C's inhibitory capacity. We conclude that M-domain phosphorylation may have its greatest effect on tuning cMyBP-C's calcium-sensitization of thin filaments at the low calcium levels between contractions. Importantly, calcium levels at the peak of contraction would allow cMyBP-C to remain a potent contractile modulator, regardless of cMyBP-C's phosphorylation state. PMID:26908872

  14. Towards double-functionalized small diamondoids: selective electronic band-gap tuning

    NASA Astrophysics Data System (ADS)

    Adhikari, Bibek; Fyta, Maria

    2015-01-01

    Diamondoids are nanoscale diamond-like cage structures with hydrogen terminations, which can occur in various sizes and with a diverse type of modifications. In this work, we focus on the structural alterations and the effect of doping and functionalization on the electronic properties of diamondoids, from the smallest adamantane to heptamantane. The results are based on quantum mechanical calculations. We perform a self-consistent study, starting with doping the smallest diamondoid, adamantane. Boron, nitrogen, silicon, oxygen, and phosphorus are chosen as dopants at sites which have been previously optimized and are also consistent with the literature. At a next step, an amine- and a thiol- group are separately used to functionalize the adamantane molecule. We mainly focus on a double functionalization of diamondoids up to heptamantane using both these atomic groups. The effect of isomeration in the case of tetramantane is also studied. We discuss the higher efficiency of a double-functionalization compared to doping or a single-functionalization of diamondoids in tuning the electronic properties, such as the electronic band-gap, of modified small diamondoids in view of their novel nanotechnological applications.

  15. Presynaptic spinophilin tunes neurexin signalling to control active zone architecture and function

    PubMed Central

    Muhammad, Karzan; Reddy-Alla, Suneel; Driller, Jan H; Schreiner, Dietmar; Rey, Ulises; Böhme, Mathias A.; Hollmann, Christina; Ramesh, Niraja; Depner, Harald; Lützkendorf, Janine; Matkovic, Tanja; Götz, Torsten; Bergeron, Dominique D.; Schmoranzer, Jan; Goettfert, Fabian; Holt, Mathew; Wahl, Markus C.; Hell, Stefan W.; Scheiffele, Peter; Walter, Alexander M.; Loll, Bernhard; Sigrist, Stephan J.

    2015-01-01

    Assembly and maturation of synapses at the Drosophila neuromuscular junction (NMJ) depend on trans-synaptic neurexin/neuroligin signalling, which is promoted by the scaffolding protein Syd-1 binding to neurexin. Here we report that the scaffold protein spinophilin binds to the C-terminal portion of neurexin and is needed to limit neurexin/neuroligin signalling by acting antagonistic to Syd-1. Loss of presynaptic spinophilin results in the formation of excess, but atypically small active zones. Neuroligin-1/neurexin-1/Syd-1 levels are increased at spinophilin mutant NMJs, and removal of single copies of the neurexin-1, Syd-1 or neuroligin-1 genes suppresses the spinophilin-active zone phenotype. Evoked transmission is strongly reduced at spinophilin terminals, owing to a severely reduced release probability at individual active zones. We conclude that presynaptic spinophilin fine-tunes neurexin/neuroligin signalling to control active zone number and functionality, thereby optimizing them for action potential-induced exocytosis. PMID:26471740

  16. Presynaptic spinophilin tunes neurexin signalling to control active zone architecture and function.

    PubMed

    Muhammad, Karzan; Reddy-Alla, Suneel; Driller, Jan H; Schreiner, Dietmar; Rey, Ulises; Böhme, Mathias A; Hollmann, Christina; Ramesh, Niraja; Depner, Harald; Lützkendorf, Janine; Matkovic, Tanja; Götz, Torsten; Bergeron, Dominique D; Schmoranzer, Jan; Goettfert, Fabian; Holt, Mathew; Wahl, Markus C; Hell, Stefan W; Scheiffele, Peter; Walter, Alexander M; Loll, Bernhard; Sigrist, Stephan J

    2015-01-01

    Assembly and maturation of synapses at the Drosophila neuromuscular junction (NMJ) depend on trans-synaptic neurexin/neuroligin signalling, which is promoted by the scaffolding protein Syd-1 binding to neurexin. Here we report that the scaffold protein spinophilin binds to the C-terminal portion of neurexin and is needed to limit neurexin/neuroligin signalling by acting antagonistic to Syd-1. Loss of presynaptic spinophilin results in the formation of excess, but atypically small active zones. Neuroligin-1/neurexin-1/Syd-1 levels are increased at spinophilin mutant NMJs, and removal of single copies of the neurexin-1, Syd-1 or neuroligin-1 genes suppresses the spinophilin-active zone phenotype. Evoked transmission is strongly reduced at spinophilin terminals, owing to a severely reduced release probability at individual active zones. We conclude that presynaptic spinophilin fine-tunes neurexin/neuroligin signalling to control active zone number and functionality, thereby optimizing them for action potential-induced exocytosis. PMID:26471740

  17. 1.55-μm mode-locked quantum-dot lasers with 300 MHz frequency tuning range

    SciTech Connect

    Sadeev, T. Arsenijević, D.; Bimberg, D.; Franke, D.; Kreissl, J.; Künzel, H.

    2015-01-19

    Passive mode-locking of two-section quantum-dot mode-locked lasers grown by metalorganic vapor phase epitaxy on InP is reported. 1250-μm long lasers exhibit a wide tuning range of 300 MHz around the fundamental mode-locking frequency of 33.48 GHz. The frequency tuning is achieved by varying the reverse bias of the saturable absorber from 0 to −2.2 V and the gain section current from 90 to 280 mA. 3 dB optical spectra width of 6–7 nm leads to ex-facet optical pulses with full-width half-maximum down to 3.7 ps. Single-section quantum-dot mode-locked lasers show 0.8 ps broad optical pulses after external fiber-based compression. Injection current tuning from 70 to 300 mA leads to 30 MHz frequency tuning.

  18. Metalloprotease OMA1 Fine-tunes Mitochondrial Bioenergetic Function and Respiratory Supercomplex Stability.

    PubMed

    Bohovych, Iryna; Fernandez, Mario R; Rahn, Jennifer J; Stackley, Krista D; Bestman, Jennifer E; Anandhan, Annadurai; Franco, Rodrigo; Claypool, Steven M; Lewis, Robert E; Chan, Sherine S L; Khalimonchuk, Oleh

    2015-01-01

    Mitochondria are involved in key cellular functions including energy production, metabolic homeostasis, and apoptosis. Normal mitochondrial function is preserved by several interrelated mechanisms. One mechanism - intramitochondrial quality control (IMQC) - is represented by conserved proteases distributed across mitochondrial compartments. Many aspects and physiological roles of IMQC components remain unclear. Here, we show that the IMQC protease Oma1 is required for the stability of the respiratory supercomplexes and thus balanced and tunable bioenergetic function. Loss of Oma1 activity leads to a specific destabilization of respiratory supercomplexes and consequently to unbalanced respiration and progressive respiratory decline in yeast. Similarly, experiments in cultured Oma1-deficient mouse embryonic fibroblasts link together impeded supercomplex stability and inability to maintain proper respiration under conditions that require maximal bioenergetic output. Finally, transient knockdown of OMA1 in zebrafish leads to impeded bioenergetics and morphological defects of the heart and eyes. Together, our biochemical and genetic studies in yeast, zebrafish and mammalian cells identify a novel and conserved physiological role for Oma1 protease in fine-tuning of respiratory function. We suggest that this unexpected physiological role is important for cellular bioenergetic plasticity and may contribute to Oma1-associated disease phenotypes in humans. PMID:26365306

  19. A Molecular Surface Functionalization Approach to Tuning Nanoparticle Electrocatalysts for Carbon Dioxide Reduction.

    PubMed

    Cao, Zhi; Kim, Dohyung; Hong, Dachao; Yu, Yi; Xu, Jun; Lin, Song; Wen, Xiaodong; Nichols, Eva M; Jeong, Keunhong; Reimer, Jeffrey A; Yang, Peidong; Chang, Christopher J

    2016-07-01

    Conversion of the greenhouse gas carbon dioxide (CO2) to value-added products is an important challenge for sustainable energy research, and nanomaterials offer a broad class of heterogeneous catalysts for such transformations. Here we report a molecular surface functionalization approach to tuning gold nanoparticle (Au NP) electrocatalysts for reduction of CO2 to CO. The N-heterocyclic (NHC) carbene-functionalized Au NP catalyst exhibits improved faradaic efficiency (FE = 83%) for reduction of CO2 to CO in water at neutral pH at an overpotential of 0.46 V with a 7.6-fold increase in current density compared to that of the parent Au NP (FE = 53%). Tafel plots of the NHC carbene-functionalized Au NP (72 mV/decade) vs parent Au NP (138 mV/decade) systems further show that the molecular ligand influences mechanistic pathways for CO2 reduction. The results establish molecular surface functionalization as a complementary approach to size, shape, composition, and defect control for nanoparticle catalyst design. PMID:27322487

  20. Metalloprotease OMA1 Fine-tunes Mitochondrial Bioenergetic Function and Respiratory Supercomplex Stability

    PubMed Central

    Bohovych, Iryna; Fernandez, Mario R.; Rahn, Jennifer J.; Stackley, Krista D.; Bestman, Jennifer E.; Anandhan, Annadurai; Franco, Rodrigo; Claypool, Steven M.; Lewis, Robert E.; Chan, Sherine S. L.; Khalimonchuk, Oleh

    2015-01-01

    Mitochondria are involved in key cellular functions including energy production, metabolic homeostasis, and apoptosis. Normal mitochondrial function is preserved by several interrelated mechanisms. One mechanism – intramitochondrial quality control (IMQC) – is represented by conserved proteases distributed across mitochondrial compartments. Many aspects and physiological roles of IMQC components remain unclear. Here, we show that the IMQC protease Oma1 is required for the stability of the respiratory supercomplexes and thus balanced and tunable bioenergetic function. Loss of Oma1 activity leads to a specific destabilization of respiratory supercomplexes and consequently to unbalanced respiration and progressive respiratory decline in yeast. Similarly, experiments in cultured Oma1-deficient mouse embryonic fibroblasts link together impeded supercomplex stability and inability to maintain proper respiration under conditions that require maximal bioenergetic output. Finally, transient knockdown of OMA1 in zebrafish leads to impeded bioenergetics and morphological defects of the heart and eyes. Together, our biochemical and genetic studies in yeast, zebrafish and mammalian cells identify a novel and conserved physiological role for Oma1 protease in fine-tuning of respiratory function. We suggest that this unexpected physiological role is important for cellular bioenergetic plasticity and may contribute to Oma1-associated disease phenotypes in humans. PMID:26365306

  1. Functional multilayer coated long period grating tuned in transition region for life science applications

    NASA Astrophysics Data System (ADS)

    Pilla, P.; Malachovská, V.; Borriello, A.; Giordano, M.; Ambrosio, L.; Cutolo, A.; Cusano, A.

    2010-09-01

    We report preliminary results on the development of multilayer coated long period gratings (LPGs) for life science applications. The dip-coating technique and a solvent/nonsolvent strategy were exploited to deposit double-layer polymeric film onto a LPG. A primary coating of atactic polystyrene was used as high refractive index layer to tune the working point of the device in the so-called transition region thus achieving remarkable surrounding medium refractive index sensitivity. A secondary layer of atactic poly(methyl methacrylate-co-methacrylic acid) containing functional carboxyl groups, characterized by a lower refractive index, was deposited onto the primary coating in order to have the desired functional groups on the surface of the device. Commonly used covalent immobilization procedure, NHS/EDC coupling method, was exploited to link streptavidin on the surface of the functionalized coated device. Finally, real-time detection of biotinylated bovine serum albumin affinity binding on immobilized streptavidin was performed by monitoring the shift of the LPG attenuation bands.

  2. Tuning the functional properties of PMN-PT single crystals via doping and thermoelectrical treatments

    NASA Astrophysics Data System (ADS)

    Luo, Laihui; Dietze, Matthias; Solterbeck, Claus-Henning; Luo, Haosu; Es-Souni, Mohammed

    2013-12-01

    Single crystals based on solid solutions of lead-magnesium-niobate (PMN) and lead titanate (PT) have emerged as highly promising multifunctional systems combining piezoelectric, pyroelectric, and electro-optic properties that surpass by far those of the best known lead-zirkonium-titanate ceramics. In this paper we present new findings on how the phase transition temperature and the dielectric and ferroelectric properties can be tuned depending on crystal composition, orientation, and thermoelectrical treatment. Mn-doped and pure 0.72PbMg1/3Nb2/3O3-0.28PbTiO3 (0.72PMN-0.28PT) single crystals with ⟨111⟩ and ⟨001⟩ orientations were investigated. A special attention was devoted to field cooling (FC), i.e., cooling under electric field from different temperatures. The results illustrate different findings that were not reported before: the Curie temperature, i.e., ferroelectric-paraelectric transition temperature, is enhanced after field cooling of the Mn-doped, ⟨001⟩-oriented crystal while such a shift is not observed in the ⟨111⟩-oriented and the non-doped crystals. In addition, substantial polarization suppression occurs in the Mn-doped crystals upon FC from high temperature regardless of orientation. Based on piezoforce microscopy of the domain structure that shows suppression of domain growth following field cooling from 200 °C, we propose a mechanism for polarization suppression based on domain pinning by charged defects. The practical importance of our results lies in showing the opportunity offered by a proper choice of crystal composition and poling conditions for tuning the functional properties of PMN-PT single crystals for a specific application. This should contribute to the understanding of their properties towards advanced sensor and transducers devices.

  3. Tuning the reactivity of semiconductor surfaces by functionalization with amines of different basicity

    PubMed Central

    Bent, Stacey F.; Kachian, Jessica S.; Rodríguez-Reyes, Juan Carlos F.; Teplyakov, Andrew V.

    2011-01-01

    Surface functionalization of semiconductors has been the backbone of the newest developments in microelectronics, energy conversion, sensing device design, and many other fields of science and technology. Over a decade ago, the notion of viewing the surface itself as a chemical reagent in surface reactions was introduced, and adding a variety of new functionalities to the semiconductor surface has become a target of research for many groups. The electronic effects on the substrate have been considered as an important consequence of chemical modification. In this work, we shift the focus to the electronic properties of the functional groups attached to the surface and their role on subsequent reactivity. We investigate surface functionalization of clean Si(100)-2 × 1 and Ge(100)-2 × 1 surfaces with amines as a way to modify their reactivity and to fine tune this reactivity by considering the basicity of the attached functionality. The reactivity of silicon and germanium surfaces modified with ethylamine (CH3CH2NH2) and aniline (C6H5NH2) is predicted using density functional theory calculations of proton attachment to the nitrogen of the adsorbed amine to differ with respect to a nucleophilic attack of the surface species. These predictions are then tested using a model metalorganic reagent, tetrakis(dimethylamido)titanium (((CH3)2N)4Ti, TDMAT), which undergoes a transamination reaction with sufficiently nucleophilic amines, and the reactivity tests confirm trends consistent with predicted basicities. The identity of the underlying semiconductor surface has a profound effect on the outcome of this reaction, and results comparing silicon and germanium are discussed. PMID:21068370

  4. Theoretical study of excited states of DNA base dimers and tetramers using optimally tuned range-separated density functional theory.

    PubMed

    Sun, Haitao; Zhang, Shian; Zhong, Cheng; Sun, Zhenrong

    2016-03-15

    Excited states of various DNA base dimers and tetramers including Watson-Crick H-bonding and stacking interactions have been investigated by time-dependent density functional theory using nonempirically tuned range-separated exchange (RSE) functionals. Significant improvements are found in the prediction of excitation energies and oscillator strengths, with results comparable to those of high-level coupled-cluster (CC) models (RI-CC2 and EOM-CCSD(T)). The optimally-tuned RSE functional significantly outperforms its non-tuned (default) version and widely-used B3LYP functional. Compared to those high-level CC benchmarks, the large mean absolute deviations of conventional functionals can be attributed to their inappropriate amount of exact exchange and large delocalization errors which can be greatly eliminated by tuning approach. Furthermore, the impacts of H-bonding and π-stacking interactions in various DNA dimers and tetramers are analyzed through peak shift of simulated absorption spectra as well as corresponding change of absorption intensity. The result indicates the stacking interaction in DNA tetramers mainly contributes to the hypochromicity effect. The present work provides an efficient theoretical tool for accurate prediction of optical properties and excited states of nucleobase and other biological systems. © 2015 Wiley Periodicals, Inc. PMID:26666212

  5. Tuning the electron transport of molecular junctions by chemically functionalizing anchoring groups: First-principles study

    NASA Astrophysics Data System (ADS)

    Tsukamoto, Shigeru; Caciuc, Vasile; Atodiresei, Nicolae; Blügel, Stefan

    2012-06-01

    In this first-principles study, we present density-functional calculations of the electronic structures and electron transport properties of organic molecular junctions with several anchoring groups containing atoms with different electronegativities, i.e., benzenediboronate (BDB), benzenedicarboxylate (BDC), and dinitrobenzene (DNB) molecular junctions sandwiched between two Cu(110) electrodes. The electronic-structure calculations exhibit a significant difference in the density of states not only at the anchoring groups but also at the aromatic rings of the molecular junctions, suggesting that the electron transport is specific for each system. Our transport calculations show that the BDB and DNB molecular junctions have finite electron transmissions at the zero-bias limit while the BDC molecular junction has a negligible electron transmission. Moreover, for the BDB and DNB systems, the electron transmission channels around the Fermi energy reveal fingerprint features, which provide specific functionalities for the molecular junctions. Therefore, our theoretical results demonstrate the possibility to precisely tune the electron transport properties of molecular junctions by engineering the anchoring groups at the single-atom level.

  6. Dendrites are dispensable for basic motoneuron function but essential for fine tuning of behavior

    PubMed Central

    Ryglewski, Stefanie; Kadas, Dimitrios; Hutchinson, Katie; Schuetzler, Natalie; Vonhoff, Fernando; Duch, Carsten

    2014-01-01

    Dendrites are highly complex 3D structures that define neuronal morphology and connectivity and are the predominant sites for synaptic input. Defects in dendritic structure are highly consistent correlates of brain diseases. However, the precise consequences of dendritic structure defects for neuronal function and behavioral performance remain unknown. Here we probe dendritic function by using genetic tools to selectively abolish dendrites in identified Drosophila wing motoneurons without affecting other neuronal properties. We find that these motoneuron dendrites are unexpectedly dispensable for synaptic targeting, qualitatively normal neuronal activity patterns during behavior, and basic behavioral performance. However, significant performance deficits in sophisticated motor behaviors, such as flight altitude control and switching between discrete courtship song elements, scale with the degree of dendritic defect. To our knowledge, our observations provide the first direct evidence that complex dendrite architecture is critically required for fine-tuning and adaptability within robust, evolutionarily constrained behavioral programs that are vital for mating success and survival. We speculate that the observed scaling of performance deficits with the degree of structural defect is consistent with gradual increases in intellectual disability during continuously advancing structural deficiencies in progressive neurological disorders. PMID:25453076

  7. Frequency analysis via the method of moment functionals

    NASA Technical Reports Server (NTRS)

    Pearson, A. E.; Pan, J. Q.

    1991-01-01

    Several variants are presented of a linear-in-parameters least squares formulation for determining the transfer function of a stable linear system at specified frequencies given a finite set of Fourier series coefficients calculated from transient nonstationary input-output data. The basis of the technique is Shinbrot's classical method of moment functionals using complex Fourier based modulating functions to convert a differential equation model on a finite time interval into an algebraic equation which depends linearly on frequency-related parameters.

  8. Frequency analysis via the method of moment functionals

    NASA Technical Reports Server (NTRS)

    Pearson, A. E.; Pan, J. Q.

    1990-01-01

    Several variants are presented of a linear-in-parameters least squares formulation for determining the transfer function of a stable linear system at specified frequencies given a finite set of Fourier series coefficients calculated from transient nonstationary input-output data. The basis of the technique is Shinbrot's classical method of moment functionals using complex Fourier based modulating functions to convert a differential equation model on a finite time interval into an algebraic equation which depends linearly on frequency-related parameters.

  9. Cochlear microphonic broad tuning curves

    NASA Astrophysics Data System (ADS)

    Ayat, Mohammad; Teal, Paul D.; Searchfield, Grant D.; Razali, Najwani

    2015-12-01

    It is known that the cochlear microphonic voltage exhibits much broader tuning than does the basilar membrane motion. The most commonly used explanation for this is that when an electrode is inserted at a particular point inside the scala media, the microphonic potentials of neighbouring hair cells have different phases, leading to cancelation at the electrodes location. In situ recording of functioning outer hair cells (OHCs) for investigating this hypothesis is exceptionally difficult. Therefore, to investigate the discrepancy between the tuning curves of the basilar membrane and those of the cochlear microphonic, and the effect of phase cancellation of adjacent hair cells on the broadness of the cochlear microphonic tuning curves, we use an electromechanical model of the cochlea to devise an experiment. We explore the effect of adjacent hair cells (i.e., longitudinal phase cancellation) on the broadness of the cochlear microphonic tuning curves in different locations. The results of the experiment indicate that active longitudinal coupling (i.e., coupling with active adjacent outer hair cells) only slightly changes the broadness of the CM tuning curves. The results also demonstrate that there is a π phase difference between the potentials produced by the hair bundle and the soma near the place associated with the characteristic frequency based on place-frequency maps (i.e., the best place). We suggest that the transversal phase cancellation (caused by the phase difference between the hair bundle and the soma) plays a far more important role than longitudinal phase cancellation in the broadness of the cochlear microphonic tuning curves. Moreover, by increasing the modelled longitudinal resistance resulting the cochlear microphonic curves exhibiting sharper tuning. The results of the simulations suggest that the passive network of the organ of Corti determines the phase difference between the hair bundle and soma, and hence determines the sharpness of the

  10. An approximation function for frequency constrained structural optimization

    NASA Technical Reports Server (NTRS)

    Canfield, R. A.

    1989-01-01

    The purpose is to examine a function for approximating natural frequency constraints during structural optimization. The nonlinearity of frequencies has posed a barrier to constructing approximations for frequency constraints of high enough quality to facilitate efficient solutions. A new function to represent frequency constraints, called the Rayleigh Quotient Approximation (RQA), is presented. Its ability to represent the actual frequency constraint results in stable convergence with effectively no move limits. The objective of the optimization problem is to minimize structural weight subject to some minimum (or maximum) allowable frequency and perhaps subject to other constraints such as stress, displacement, and gage size, as well. A reason for constraining natural frequencies during design might be to avoid potential resonant frequencies due to machinery or actuators on the structure. Another reason might be to satisy requirements of an aircraft or spacecraft's control law. Whatever the structure supports may be sensitive to a frequency band that must be avoided. Any of these situations or others may require the designer to insure the satisfaction of frequency constraints. A further motivation for considering accurate approximations of natural frequencies is that they are fundamental to dynamic response constraints.

  11. Tuning the Nanostructure of Highly Functionalized Silica Using Amphiphilic Organosilanes: Curvature Agent Effects.

    PubMed

    Besnard, Romain; Arrachart, Guilhem; Cambedouzou, Julien; Pellet-Rostaing, Stéphane

    2016-05-10

    The self-assembly of amino-undecyl-triethoxysilane (AUT) as micelles in water is considered. The behavior of acid/AUT systems is governed by a complete proton transfer from the acid to the amine, leading to the formation of an ammonium headgroup. This moiety is responsible for the bending of the interface between the organic core of the micelles and the surrounding water. By playing with the size of the acid used as curvature agent, the amphiphilic behavior of the organosilane molecule may be adjusted. We follow the aggregation as the curvature agent size increases. This approach constitutes an efficient and original method in order to tune the nanostructure of highly functionalized silica at the early stage of the elaboration. Small-angle X-ray scattering, wet scanning transmission electron microscopy, dynamic light scattering, and complementary characterization techniques indicate that hybrid organic-inorganic planar objects and vesicles are obtained for smaller curvature agents. Increasing the size of the curvature agent results in a transition of the aggregation geometry from vesicles to cylindrical direct micelles, finally leading to nanofibers organized in a 2D hexagonal network resembling a "reverse MCM-41 structure". A geometrical molecular self-assembly model is finally proposed, considering the dimensions of the surfactant tail and those of the head groups. PMID:27081741

  12. Photofunctional hybrids of lanthanide functionalized bio-MOF-1 for fluorescence tuning and sensing.

    PubMed

    Shen, Xiang; Yan, Bing

    2015-08-01

    A series of luminescent Ln(3+)@bio-MOF-1 (Ln=Eu, Tb, bio-MOF-1=Zn8(ad)4(BPDC)6O⋅2Me2NH2 (ad=adeninate, BPDC=biphenyldicarboxylate)) are synthesized via postsynthetic cation exchange by encapsulating lanthanide ions into an anionic metal-organic framework (MOF), and their photophysical properties are studied. After loading 2-thenoyltrifluroacetone (TTA) as sensitized ligand by a gas diffusion ("ship-in-bottle") method, it is found that the luminescent intensity of Eu(3+) is enhanced. Especially, when loading two different lanthanide cations into bio-MOF-1, the luminescent color can be tuned to close white (light pink) light output. Additionally, bio-MOF-1 and Eu(3+)@bio-MOF-1 are selected as representative samples for sensing metal ions. When bio-MOF-1 is immersed in the aqueous solutions of different metal ions, it shows highly sensitive sensing for Fe(3+) as well as Eu(3+)@bio-MOF-1 immersed in the DMF solutions of different metal ion. The results are benefit for the further application of functionalized bio-MOFs in practical fields. PMID:25881265

  13. Non-covalent functionalization of WS2 monolayer with small fullerenes: tuning electronic properties and photoactivity.

    PubMed

    Luo, Cai-Yun; Huang, Wei-Qing; Hu, Wangyu; Peng, P; Huang, Gui-Fang

    2016-09-14

    Atomically thin two-dimensional transition metal dichalcogenides (TMDCs) heterostructures have recently attracted growing interest due to their massive potential in solar energy applications due to their band gap in the visible spectral range and extremely strong light-matter interactions. Herein, heterostructures composed of WS2 and MoS2 monolayers, as representative TMDCs, with small fullerenes (B12 and C20) are investigated to explore their applications in solar energy conversion using first principles calculations based on density functional theory (DFT). The WS2 (MoS2) monolayer and fullerene form a van der Waals (vdW) heterostructure. Compared to pure monolayers, the heterostructures have a smaller band gap, which favours enhancing visible light absorption. The amount of charge transfer at the interface induced by vdW interactions depends on the type of fullerene. Most importantly, a type-II staggered band alignment is formed between WS2 (MoS2) and fullerene with the latter possessing the higher electron affinity which results in the robust separation of photoexcited charge carriers between them. These results indicate that the electronic properties and photoactivity of TMDCs monolayers can be tuned by non-covalent coupling with small fullerenes, thus meeting the needs of various applications. PMID:27483028

  14. Accurate Ionization Potentials and Electron Affinities of Acceptor Molecules II: Non-Empirically Tuned Long-Range Corrected Hybrid Functionals.

    PubMed

    Gallandi, Lukas; Marom, Noa; Rinke, Patrick; Körzdörfer, Thomas

    2016-02-01

    The performance of non-empirically tuned long-range corrected hybrid functionals for the prediction of vertical ionization potentials (IPs) and electron affinities (EAs) is assessed for a set of 24 organic acceptor molecules. Basis set-extrapolated coupled cluster singles, doubles, and perturbative triples [CCSD(T)] calculations serve as a reference for this study. Compared to standard exchange-correlation functionals, tuned long-range corrected hybrid functionals produce highly reliable results for vertical IPs and EAs, yielding mean absolute errors on par with computationally more demanding GW calculations. In particular, it is demonstrated that long-range corrected hybrid functionals serve as ideal starting points for non-self-consistent GW calculations. PMID:26731340

  15. An exact generalised function approach to frequency response analysis of beams and plane frames with the inclusion of viscoelastic damping

    NASA Astrophysics Data System (ADS)

    Failla, Giuseppe

    2016-01-01

    This paper concerns the frequency response analysis of beams and plane frames with an arbitrary number of Kelvin-Voigt viscoelastic dampers. Typical external and internal dampers are considered, as grounded translational, tuned mass, rotational and axial dampers, for bending and axial vibrations, respectively. Using the theory of generalised functions within a 1D formulation of equations of motion, exact closed-form expressions are derived for beam dynamic Green's functions and frequency response functions under arbitrary polynomial load, for any number of dampers. For a plane frame, exact global frequency response matrix and load vector are built, with size depending only on the number of beam-to-column nodes, for any number of dampers and point/polynomial loads along the frame members. From the nodal displacement solution, the exact frequency response in all frame members is also obtained in closed analytical form. Numerical applications show many of the advantages of the proposed method.

  16. Temporally tuned neuronal differentiation supports the functional remodeling of a neuronal network in Drosophila.

    PubMed

    Veverytsa, Lyubov; Allan, Douglas W

    2012-03-27

    During insect metamorphosis, neuronal networks undergo extensive remodeling by restructuring their connectivity and recruiting newborn neurons from postembryonic lineages. The neuronal network that directs the essential behavior, ecdysis, generates a distinct behavioral sequence at each developmental transition. Larval ecdysis replaces the cuticle between larval stages, and pupal ecdysis externalizes and expands the head and appendages to their adult position. However, the network changes that support these differences are unknown. Crustacean cardioactive peptide (CCAP) neurons and the peptide hormones they secrete are critical for ecdysis; their targeted ablation alters larval ecdysis progression and results in a failure of pupal ecdysis. In this study, we demonstrate that the CCAP neuron network is remodeled immediately before pupal ecdysis by the emergence of 12 late CCAP neurons. All 12 are CCAP efferents that exit the central nervous system. Importantly, these late CCAP neurons were found to be entirely sufficient for wild-type pupal ecdysis, even after targeted ablation of all other 42 CCAP neurons. Our evidence indicates that late CCAP neurons are derived from early, likely embryonic, lineages. However, they do not differentiate to express their peptide hormone battery, nor do they project an axon via lateral nerve trunks until pupariation, both of which are believed to be critical for the function of CCAP efferent neurons in ecdysis. Further analysis implicated ecdysone signaling via ecdysone receptors A/B1 and the nuclear receptor ftz-f1 as the differentiation trigger. These results demonstrate the utility of temporally tuned neuronal differentiation as a hard-wired developmental mechanism to remodel a neuronal network to generate a scheduled change in behavior. PMID:22393011

  17. Tuning the Topology and Functionality of Metal–Organic Frameworks by Ligand Design

    SciTech Connect

    Zhao, Dan; Timmons, Daren J; Yuan, Daqiang; Zhou, Hong-Cai

    2011-02-15

    Metal–organic frameworks (MOFs)—highly crystalline hybrid materials that combine metal ions with rigid organic ligands—have emerged as an important class of porous materials. The organic ligands add flexibility and diversity to the chemical structures and functions of these materials. In this Account, we summarize our laboratory’s experience in tuning the topology and functionality of MOFs by ligand design. These investigations have led to new materials with interesting properties. By using a ligand that can adopt different symmetry conformations through free internal bond rotation, we have obtained two MOFs that are supramolecular stereoisomers of each other at different reaction temperatures. In another case, where the dimerized ligands function as a D₃-Piedfort unit spacer, we achieve chiral (10,3)-a networks. In the design of MOF-based materials for hydrogen and methane storage, we focused on increasing the gas affinity of frameworks by using ligands with different geometries to control the pore size and effectively introduce unsaturated metal centers (UMCs) into the framework. Framework interpenetration in PCN-6 (PCN stands for porous coordination network) can lead to higher hydrogen uptake. Because of the proper alignment of the UMCs, PCN-12 holds the record for uptake of hydrogen at 77 K/760 Torr. In the case of methane storage, PCN-14 with anthracene-derived ligand achieves breakthrough storage capacity, at a level 28% higher than the U.S. Department of Energy target. Selective gas adsorption requires a pore size comparable to that of the target gas molecules; therefore, we use bulky ligands and network interpenetration to reduce the pore size. In addition, with the help of an amphiphilic ligand, we were able to use temperature to continuously change pore size in a 2D layer MOF. Adding charge to an organic ligand can also stabilize frameworks. By ionizing the amine group within mesoMOF-1, the resulting electronic repulsion keeps the network from

  18. Musical experience sharpens human cochlear tuning.

    PubMed

    Bidelman, Gavin M; Nelms, Caitlin; Bhagat, Shaum P

    2016-05-01

    The mammalian cochlea functions as a filter bank that performs a spectral, Fourier-like decomposition on the acoustic signal. While tuning can be compromised (e.g., broadened with hearing impairment), whether or not human cochlear frequency resolution can be sharpened through experiential factors (e.g., training or learning) has not yet been established. Previous studies have demonstrated sharper psychophysical tuning curves in trained musicians compared to nonmusicians, implying superior peripheral tuning. However, these findings are based on perceptual masking paradigms, and reflect engagement of the entire auditory system rather than cochlear tuning, per se. Here, by directly mapping physiological tuning curves from stimulus frequency otoacoustic emissions (SFOAEs)-cochlear emitted sounds-we show that estimates of human cochlear tuning in a high-frequency cochlear region (4 kHz) is further sharpened (by a factor of 1.5×) in musicians and improves with the number of years of their auditory training. These findings were corroborated by measurements of psychophysical tuning curves (PTCs) derived via simultaneous masking, which similarly showed sharper tuning in musicians. Comparisons between SFOAE and PTCs revealed closer correspondence between physiological and behavioral curves in musicians, indicating that tuning is also more consistent between different levels of auditory processing in trained ears. Our findings demonstrate an experience-dependent enhancement in the resolving power of the cochlear sensory epithelium and the spectral resolution of human hearing and provide a peripheral account for the auditory perceptual benefits observed in musicians. Both local and feedback (e.g., medial olivocochlear efferent) mechanisms are discussed as potential mechanisms for experience-dependent tuning. PMID:26900073

  19. Low frequency cabin noise reduction based on the intrinsic structural tuning concept: The theory and the experimental results, phase 2. [jet aircraft noise

    NASA Technical Reports Server (NTRS)

    Sengupta, G.

    1978-01-01

    Low frequency cabin noise and sonically induced stresses in an aircraft fuselage may be reduced by intrinsic tuning of the various structural members such as the skin, stringers, and frames and then applying damping treatments on these members. The concept is also useful in identifying the key structural resonance mechanisms controlling the fuselage response to broadband random excitation and in developing suitable damping treatments for reducing the structural response in various frequency ranges. The mathematical proof of the concept and the results of some laboratory and field tests on a group of skin-stringer panels are described. In the so-called stiffness-controlled region, the noise transmission may actually be controlled by stiffener resonances, depending upon the relationship between the natural frequencies of the skin bay and the stiffeners. Therefore, cabin noise in the stiffness-controlled region may be effectively reduced by applying damping treatments on the stiffeners.

  20. Newton algorithm for fitting transfer functions to frequency response measurements

    NASA Technical Reports Server (NTRS)

    Spanos, J. T.; Mingori, D. L.

    1993-01-01

    In this paper the problem of synthesizing transfer functions from frequency response measurements is considered. Given a complex vector representing the measured frequency response of a physical system, a transfer function of specified order is determined that minimizes the sum of the magnitude-squared of the frequency response errors. This nonlinear least squares minimization problem is solved by an iterative global descent algorithm of the Newton type that converges quadratically near the minimum. The unknown transfer function is expressed as a sum of second-order rational polynomials, a parameterization that facilitates a numerically robust computer implementation. The algorithm is developed for single-input, single-output, causal, stable transfer functions. Two numerical examples demonstrate the effectiveness of the algorithm.

  1. Use of phase information with a stepper motor to control frequency for tuning system of the Front End Test Stand Radio Frequency Quadrupole at Rutherford Appleton Laboratory

    NASA Astrophysics Data System (ADS)

    Alsari, S.; Aslaninejad, M.; Pozimski, J.

    2015-03-01

    For the Front End Test Stand (FETS) linear accelerator project at the Rutherford Appleton Laboratory in the UK, a 4 m, 4 vanes Radio Frequency Quadrupole (RFQ) with a resonant frequency of 324 MHz has been designed. The RF power feeding the RFQ gives rise to the temperature increase in the RFQ, which in turn, results in shifting the resonant frequency of the RFQ. The frequency shift and the stability in the RFQ frequency can be maintained based on the reflected power or signal phase information. We have, however, investigated restoration of the RFQ nominal frequency based on the RF signal phases driving a stepper motor. The concept and the system set-up and electronics are described in detail. Results of the measurements indicating the full restoration of the RFQ nominal frequency based on the RF signal phases and stepper motor are presented. Moreover, measured sensitivity of tuner with respect to its position is given.

  2. Combined dynamic scanning tunneling microscopy and frequency modulation atomic force microscopy investigations on polythiophene chains on graphite with a tuning fork sensor

    NASA Astrophysics Data System (ADS)

    Polesel-Maris, Jérôme; Lubin, Christophe; Thoyer, François; Cousty, Jacques

    2011-04-01

    Polythiophene molecules adsorbed on a highly oriented pyrolytic graphite surface were studied by combined dynamic scanning tunneling microscopy (STM) and frequency modulation atomic force microscopy (FM-AFM) with a quartz tuning fork sensor operating in Qplus mode and equipped with a Pt/Ir tip. Upon completing a careful sub-angström oscillation amplitude calibration of the probe, experiments were conducted in an ultra high vacuum at room temperature. By selecting the tip/surface distance regulation parameter, one can select the type of simultaneous information obtained in an area. For distance regulation based on the mean tunneling current, dynamic STM images together with maps of tip/surface force gradient were obtained. FM-AFM images with maps of the tunneling current were also acquired when the distance regulation was based on the frequency shift. Comparison between these images reveals interesting features. For example the tip which operates in STM mode with ultra low current (<10 pA) generates different interaction forces above molecules or graphite. Changes in energy dissipation processes as small as tens of millielectronvolts per cycle were recorded when the tip oscillates above the polymer or on the graphite surface. Hence data demonstrates that a stiff piezoelectric tuning fork of several kilonewtons/meters working as an AFM/STM probe with sub-angström amplitude can characterize weakly adsorbed molecules.

  3. Frequency importance functions for a feature recognition test material.

    PubMed

    Duggirala, V; Studebaker, G A; Pavlovic, C V; Sherbecoe, R L

    1988-06-01

    The relative importance of different parts of the auditory spectrum to recognition of the Diagnostic Rhyme Test (DRT) and its six speech feature subtests was determined. Three normal hearing subjects were tested twice in each of 70 experimental conditions. The analytical procedures of French and Steinberg [J. Acoust. Soc. Am. 19, 90-119 (1947)] were applied to the data to derive frequency importance functions for each of the DRT subtests and the test as a whole over the frequency range 178-8912 Hz. For the DRT as a whole, the low frequencies were found to be more important than is the case for nonsense syllables. Importance functions for the feature subtests also differed from those for nonsense syllables and from each other as well. These results suggest that test materials loaded with different proportions of particular phonemes have different frequency importance functions. Comparison of the results with those from other studies suggests that importance functions depend to a degree on the available response options as well. PMID:3411027

  4. Planck 2013 results. IV. Low Frequency Instrument beams and window functions

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Aghanim, N.; Armitage-Caplan, C.; Arnaud, M.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bobin, J.; Bock, J. J.; Bonaldi, A.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Bridges, M.; Bucher, M.; Burigana, C.; Butler, R. C.; Cardoso, J.-F.; Catalano, A.; Chamballu, A.; Chiang, L.-Y.; Christensen, P. R.; Church, S.; Colombi, S.; Colombo, L. P. L.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Dickinson, C.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Eriksen, H. K.; Finelli, F.; Forni, O.; Frailis, M.; Franceschi, E.; Gaier, T. C.; Galeotta, S.; Ganga, K.; Giard, M.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Hansen, F. K.; Hanson, D.; Harrison, D.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Jaffe, A. H.; Jaffe, T. R.; Jewell, J.; Jones, W. C.; Juvela, M.; Kangaslahti, P.; Keihänen, E.; Keskitalo, R.; Kiiveri, K.; Kisner, T. S.; Knoche, J.; Knox, L.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Laureijs, R. J.; Lawrence, C. R.; Leahy, J. P.; Leonardi, R.; Lesgourgues, J.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; Lindholm, V.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maino, D.; Mandolesi, N.; Maris, M.; Marshall, D. J.; Martin, P. G.; Martínez-González, E.; Masi, S.; Massardi, M.; Matarrese, S.; Matthai, F.; Mazzotta, P.; Meinhold, P. R.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Moss, A.; Munshi, D.; Naselsky, P.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Novikov, D.; Novikov, I.; O'Dwyer, I. J.; Osborne, S.; Paci, F.; Pagano, L.; Paoletti, D.; Partridge, B.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Platania, P.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Poutanen, T.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Ricciardi, S.; Riller, T.; Rocha, G.; Rosset, C.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Scott, D.; Seiffert, M. D.; Shellard, E. P. S.; Spencer, L. D.; Starck, J.-L.; Stolyarov, V.; Stompor, R.; Sureau, F.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Tavagnacco, D.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Türler, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Varis, J.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; Zacchei, A.; Zonca, A.

    2014-11-01

    This paper presents the characterization of the in-flight beams, the beam window functions, and the associated uncertainties for the Planck Low Frequency Instrument (LFI). Knowledge of the beam profiles is necessary for determining the transfer function to go from the observed to the actual sky anisotropy power spectrum. The main beam distortions affect the beam window function, complicating the reconstruction of the anisotropy power spectrum at high multipoles, whereas the sidelobes affect the low and intermediate multipoles. The in-flight assessment of the LFI main beams relies on the measurements performed during Jupiter observations. By stacking the datafrom multiple Jupiter transits, the main beam profiles are measured down to -20 dB at 30 and 44 GHz, and down to -25 dB at 70 GHz. The main beam solid angles are determined to better than 0.2% at each LFI frequency band. The Planck pre-launch optical model is conveniently tuned to characterize the main beams independently of any noise effects. This approach provides an optical model whose beams fully reproduce the measurements in the main beam region, but also allows a description of the beams at power levels lower than can be achieved by the Jupiter measurements themselves. The agreement between the simulated beams and the measured beams is better than 1% at each LFI frequency band. The simulated beams are used for the computation of the window functions for the effective beams. The error budget for the window functions is estimated from both main beam and sidelobe contributions, and accounts for the radiometer bandshapes. The total uncertainties in the effective beam window functions are: 2% and 1.2% at 30 and 44 GHz, respectively (at ℓ ≈ 600), and 0.7% at 70 GHz (at ℓ ≈ 1000).

  5. The problem of frequency weighting functions and standards for birds

    NASA Astrophysics Data System (ADS)

    Dooling, Robert; Brittan-Powell, Elizabeth; Lauer, Amanda; Dent, Micheal; Noirot, Isabelle

    2005-09-01

    Frequency weighting functions in humans are widely used as a single-figure guess to assess noise problems and aid in making decisions with regard to noise limitations when no other data exist. However, this use of frequency weightings invariably results in a loss of precision in assessing the likelihood of a sound to produce hearing damage or sound annoyance. There is a growing interest in developing frequency weighting functions in animals presumably to assist in judging the risk of hearing damage, interference with acoustic communication, or habitat suitability. Laboratory studies reveal many parallels between humans and animals on a variety of psychoacoustic measures, such as equal loudness contours. However, differences between humans and animals on specific tests argue against using standards developed for humans to gauge the effect of noise on animals. Here we review data which show this same problem exists among birds. That is, the differences in the effects of noise among bird species can be as large as the differences between humans and birds. These results suggest that whereas frequency weighting functions and acoustic standards for a specific species might be useful, generalizing across species is likely not practical.

  6. Planck-LFI radiometers tuning

    NASA Astrophysics Data System (ADS)

    Cuttaia, F.; Mennella, A.; Stringhetti, L.; Maris, M.; Terenzi, L.; Tomasi, M.; Villa, F.; Bersanelli, M.; Butler, R. C.; Cappellini, B.; Cuevas, L. P.; D'Arcangelo, O.; Davis, R.; Frailis, M.; Franceschet, C.; Franceschi, E.; Gregorio, A.; Hoyland, R.; Leonardi, R.; Lowe, S.; Mandolesi, N.; Meinhold, P.; Mendes, L.; Roddis, N.; Sandri, M.; Valenziano, L.; Wilkinson, A.; Zacchei, A.; Zonca, A.; Battaglia, P.; De Nardo, S.; Grassi, S.; Lapolla, M.; Leutenegger, P.; Miccolis, M.; Silvestri, R.

    2009-12-01

    This paper describes the Planck Low Frequency Instrument tuning activities performed through the ground test campaigns, from Unit to Satellite Levels. Tuning is key to achieve the best possible instrument performance and tuning parameters strongly depend on thermal and electrical conditions. For this reason tuning has been repeated several times during ground tests and it has been repeated in flight before starting nominal operations. The paper discusses the tuning philosophy, the activities and the obtained results, highlighting developments and changes occurred during test campaigns. The paper concludes with an overview of tuning performed during the satellite cryogenic test campaign (Summer 2008) and of the plans for the just started in-flight calibration.

  7. Tuning of Strouhal number for high propulsive efficiency accurately predicts how wingbeat frequency and stroke amplitude relate and scale with size and flight speed in birds.

    PubMed Central

    Nudds, Robert L.; Taylor, Graham K.; Thomas, Adrian L. R.

    2004-01-01

    The wing kinematics of birds vary systematically with body size, but we still, after several decades of research, lack a clear mechanistic understanding of the aerodynamic selection pressures that shape them. Swimming and flying animals have recently been shown to cruise at Strouhal numbers (St) corresponding to a regime of vortex growth and shedding in which the propulsive efficiency of flapping foils peaks (St approximately fA/U, where f is wingbeat frequency, U is cruising speed and A approximately bsin(theta/2) is stroke amplitude, in which b is wingspan and theta is stroke angle). We show that St is a simple and accurate predictor of wingbeat frequency in birds. The Strouhal numbers of cruising birds have converged on the lower end of the range 0.2 < St < 0.4 associated with high propulsive efficiency. Stroke angle scales as theta approximately 67b-0.24, so wingbeat frequency can be predicted as f approximately St.U/bsin(33.5b-0.24), with St0.21 and St0.25 for direct and intermittent fliers, respectively. This simple aerodynamic model predicts wingbeat frequency better than any other relationship proposed to date, explaining 90% of the observed variance in a sample of 60 bird species. Avian wing kinematics therefore appear to have been tuned by natural selection for high aerodynamic efficiency: physical and physiological constraints upon wing kinematics must be reconsidered in this light. PMID:15451698

  8. Acoustic Beam Forming Array Using Feedback-Controlled Microphones for Tuning and Self-Matching of Frequency Response

    NASA Technical Reports Server (NTRS)

    Radcliffe, Eliott (Inventor); Naguib, Ahmed (Inventor); Humphreys, Jr., William M. (Inventor)

    2014-01-01

    A feedback-controlled microphone includes a microphone body and a membrane operatively connected to the body. The membrane is configured to be initially deflected by acoustic pressure such that the initial deflection is characterized by a frequency response. The microphone also includes a sensor configured to detect the frequency response of the initial deflection and generate an output voltage indicative thereof. The microphone additionally includes a compensator in electric communication with the sensor and configured to establish a regulated voltage in response to the output voltage. Furthermore, the microphone includes an actuator in electric communication with the compensator, wherein the actuator is configured to secondarily deflect the membrane in opposition to the initial deflection such that the frequency response is adjusted. An acoustic beam forming microphone array including a plurality of the above feedback-controlled microphones is also disclosed.

  9. Simple digital system for tuning and long-term frequency stabilization of a CW Ti:Sapphire laser

    NASA Astrophysics Data System (ADS)

    Beterov, Ilya I.; Markovski, Asparuh G.; Kobtsev, Sergey M.; Yakshina, Elena A.; Entin, Vasily M.; Tretyakov, Denis B.; Baraulya, Vladimir I.; Ryabtsev, Igor I.

    2015-03-01

    We have implemented a simple digital system for long-term frequency stabilization and locking to an arbitrary wavelength of the single-frequency ring CW Ti:Sapphire laser. This system is built using two confocal Fabry-Pérot cavities, one of which is used to narrow the short-term linewidth of the laser and the other to improve the long-term stability of the laser frequency. The length of the second cavity is stabilized using the radiation from an external-cavity diode laser locked to an atomic transition. Our system is an improvement of a commercial Tekhnoscan laser lock. This system has been successfully used in our experiments on high-resolution laser spectroscopy of ultracold rubidium Rydberg atoms.

  10. Cross-stacking aligned carbon-nanotube films to tune microwave absorption frequencies and increase absorption intensities.

    PubMed

    Sun, Hao; Che, Renchao; You, Xiao; Jiang, Yishu; Yang, Zhibin; Deng, Jue; Qiu, Longbin; Peng, Huisheng

    2014-12-23

    Aligned carbon-nanotube (CNT) sheets are used as building blocks to prepare light-weight, frequency-tunable and high-performance microwave absorbers, and the absorption frequency can be accurately controlled by stacking them with different intersectional angles. A remarkable reflection loss of -47.66 dB is achieved by stacking four aligned CNT sheets with an intersectional angle of 90° between two neighboring ones. The incorporation of a second phase such as a metal and a conducting polymer greatly enhances the microwave-absorption capability. PMID:25338951

  11. Online detection of low-frequency functional connectivity

    NASA Astrophysics Data System (ADS)

    Peltier, Scott J.; LaConte, Stephen M.; Hu, Xiaoping

    2004-04-01

    Synchronized oscillations in resting state timecourses have been detected in recent fMRI studies. These oscillations are low frequency in nature (<0.08 Hz), and seem to be a property of symmetric cortices. These fluctuations are important as a pontential signal of interest, which could indicate connectivity between functionally related areas of the brain. It has also been shown that the synchronized oscillations decrease in some spontaneous pathological states (such as cocaine injection). Thus, detection of these functional connectivity patterns may help to serve as a guage of normal brain activity. Currently, functional connectivity detection is applied only in offline post-processing analysis. Online detection methods have been applied to detect task activation in functional MRI. This allows real-time analysis of fMRI results, and could be important in detecting short-term changes in functional states. In this work, we develop an outline algorithm to detect low frequency resting state functional connectivity in real time. This will extend connectivity analysis to allow online detection of changes in "resting state" brain networks.

  12. Frequency doubled AlGaInP-VECSEL with high output power at 331 nm and a large wavelength tuning range in the UV

    NASA Astrophysics Data System (ADS)

    Schwarzbäck, Thomas; Kahle, Hermann; Jetter, Michael; Michler, Peter

    2012-06-01

    We present a non-resonantly pumped vertical external cavity surface-emitting laser in a compact v-shaped cavity configuration. By using intra-cavity frequency doubling in combination with a birefringent filter, a tunable high power UV laser source with an emission wavelength around 335 nm is realized. The fundamental red laser emission is based on a metal-organic vapor-phase epitaxy grown (GaxIn1-x)0.5P0.5/[(AlxGa1-x)yIn1-y]0.5P0.5 (abbr. GaInP/AlGaInP) multi-quantum-well structure. Five quantum well packages with four compressively strained quantum wells are placed in a separate confinement heterostructure in a resonant periodic gain design in strain-compensating quaternary AlGaInP barriers and cladding layers, respectively. The 3 λ cavity is fabricated on a 55 λ/4 pairs Al0.45Ga0.55As/AlAs distributed Bragg reflector. By using a beta barium borate non-linear crystal for second harmonic generation, output powers up to 150mWat a wavelength of 335 nm could be realized. Tuning of the laser resonance was accomplished with a birefringent filter. A tuning of 9 nm in the UV will be shown.

  13. Gold nanoparticle immobilization on ZnO nanorods via bi-functional monolayers: A facile method to tune interface properties

    NASA Astrophysics Data System (ADS)

    Jayaraman, Sundaramurthy; Suresh Kumar, P.; Mangalaraj, D.; Dharmarajan, Rajarathnam; Ramakrishna, Seeram; P Srinivasan, M.

    2015-11-01

    We demonstrated the functionalization of one dimensional (1-D) zinc oxide nanorods (ZnO NRs) using bi-functional organic molecules to create hybrid structures with surface functionalities and tuneable organic/inorganic interface. Bi-functional molecules with carboxylic acid, thiol and silane end groups and amine termination had been employed to functionalize the NRs by forming carboxylate, thiolate and hydroxylation bonds, respectively, with ZnO. The surface textures of NRs were preserved even after functionalization. The functionalized NRs were decorated with gold nanoparticles (AuNPs) and the hybrid structures exhibited a quenched blue shift ultraviolet emission which depended on the distance between the ZnO surface and the AuNPs. The NR functionalization with bi-functional molecules and decoration of NPs, and surface morphologies were analyzed using x-ray photoelectron spectroscopy, field emission scanning electron microscopy and transmission electron spectroscopy. These hybrid structures can play a vital role in tuning the interface properties and have potential applications in future photovoltaics, chemical sensors, biomarkers, and wavelength based biosensors.

  14. A comparative study of rhodopsin function in the great bowerbird (Ptilonorhynchus nuchalis): Spectral tuning and light-activated kinetics.

    PubMed

    van Hazel, Ilke; Dungan, Sarah Z; Hauser, Frances E; Morrow, James M; Endler, John A; Chang, Belinda S W

    2016-07-01

    Rhodopsin is the visual pigment responsible for initiating the phototransduction cascade in vertebrate rod photoreceptors. Although well-characterized in a few model systems, comparative studies of rhodopsin function, particularly for nonmammalian vertebrates are comparatively lacking. Bowerbirds are rare among passerines in possessing a key substitution, D83N, at a site that is otherwise highly conserved among G protein-coupled receptors. While this substitution is present in some dim-light adapted vertebrates, often accompanying another unusual substitution, A292S, its functional relevance in birds is uncertain. To investigate functional effects associated with these two substitutions, we use the rhodopsin gene from the great bowerbird (Ptilonorhynchus nuchalis) as a background for site-directed mutagenesis, in vitro expression and functional characterization. We also mutated these sites in two additional rhodopsins that do not naturally possess N83, chicken and bovine, for comparison. Both sites were found to contribute to spectral blue-shifts, but had opposing effects on kinetic rates. Substitutions at site 83 were found to primarily affect the kinetics of light-activated rhodopsin, while substitutions at site 292 had a larger impact on spectral tuning. The contribution of substitutions at site 83 to spectral tuning in particular depended on genetic background, but overall, the effects of substitutions were otherwise surprisingly additive, and the magnitudes of functional shifts were roughly similar across all three genetic backgrounds. By employing a comparative approach with multiple species, our study provides new insight into the joint impact of sites 83 and 292 on rhodopsin structure-function as well as their evolutionary significance for dim-light vision across vertebrates. PMID:26889650

  15. Tuning the molecular order of C60 functionalized phosphonic acid monolayers.

    PubMed

    Rumpel, Armin; Novak, Michael; Walter, Johannes; Braunschweig, Björn; Halik, Marcus; Peukert, Wolfgang

    2011-12-20

    Mixed self-assembled monolayers (SAM) of alkyl phosphonic acids and C(60) functionalized octadecyl phosphonic acids (C(60)C(18)-PA) are deposited on alumina substrates from solution and are shown to form well-ordered structures with an insulating layer of alkyl chains and a semiconducting layer that comprises mainly C(60). Such an ordered structure is a necessity for the application of SAMs in organic transistors but is difficult to obtain since C(60)C(18)-PA without additional support do self-assemble in dense packaging but not in a well-ordered fashion. To avoid disordering of the SAM and to gain a better control of the interfacial properties we have investigated the stabilizing effects of fluorinated dodecyl phosphonic acids (FC(12)-PA) on the C(60)C(18)-PA monolayer. Vibrational sum-frequency (SFG) spectroscopy, ellipsometry, X-ray photoelectron spectroscopy, and electrical measurements were applied to study the mixed monolayers. Here, we make use of the differently labeled PA to determine surface coverages and molecular properties of the two species independently. Adsorption of FC(12)-PA gives rise to vibrational bands at 1344 cm(-1) and 1376 cm(-1) in SFG spectra, while a pronounced vibrational band centered at 1465 cm(-1) is attributable to C(60) vibrations. The coexistence of the bands is indicative for the presence of a mixed monolayer that is composed of both molecular species. Furthermore, a pronounced maximum in SFG intensity of the C(60) band is observed for SAMs, which are deposited from solutions with ~75% C(60)C(18)-PA and ~25% FC(12)-PA. The intensity maximum originates from successful stabilization of C(60) modified C(60)C(18)-PA by FC(12)-PA and a significantly improved molecular order. Conclusions from SFG spectra are corroborated by electric measurements that show best performance at these concentrations. Our results provide new information on the morphology and composition of C(60) modified SAMs and establish a route to fabricate well

  16. Tunes stuck in your brain: The frequency and affective evaluation of involuntary musical imagery correlate with cortical structure.

    PubMed

    Farrugia, Nicolas; Jakubowski, Kelly; Cusack, Rhodri; Stewart, Lauren

    2015-09-01

    Recent years have seen a growing interest in the neuroscience of spontaneous cognition. One form of such cognition is involuntary musical imagery (INMI), the non-pathological and everyday experience of having music in one's head, in the absence of an external stimulus. In this study, aspects of INMI, including frequency and affective evaluation, were measured by self-report in 44 subjects and related to variation in brain structure in these individuals. Frequency of INMI was related to cortical thickness in regions of right frontal and temporal cortices as well as the anterior cingulate and left angular gyrus. Affective aspects of INMI, namely the extent to which subjects wished to suppress INMI or considered them helpful, were related to gray matter volume in right temporopolar and parahippocampal cortices respectively. These results provide the first evidence that INMI is a common internal experience recruiting brain networks involved in perception, emotions, memory and spontaneous thoughts. PMID:25978461

  17. Functional Role of PPARs in Ruminants: Potential Targets for Fine-Tuning Metabolism during Growth and Lactation

    PubMed Central

    Chen, Shuowen; Khan, Muhammad J.; Loor, Juan J.

    2013-01-01

    Characterization and biological roles of the peroxisome proliferator-activated receptor (PPAR) isotypes are well known in monogastrics, but not in ruminants. However, a wealth of information has accumulated in little more than a decade on ruminant PPARs including isotype tissue distribution, response to synthetic and natural agonists, gene targets, and factors affecting their expression. Functional characterization demonstrated that, as in monogastrics, the PPAR isotypes control expression of genes involved in lipid metabolism, anti-inflammatory response, development, and growth. Contrary to mouse, however, the PPARγ gene network appears to controls milk fat synthesis in lactating ruminants. As in monogastrics, PPAR isotypes in ruminants are activated by long-chain fatty acids, therefore, making them ideal candidates for fine-tuning metabolism in this species via nutrients. In this regard, using information accumulated in ruminants and monogastrics, we propose a model of PPAR isotype-driven biological functions encompassing key tissues during the peripartal period in dairy cattle. PMID:23737762

  18. High frequency of functional extinctions in ecological networks.

    PubMed

    Säterberg, Torbjörn; Sellman, Stefan; Ebenman, Bo

    2013-07-25

    Intensified exploitation of natural populations and habitats has led to increased mortality rates and decreased abundances of many species. There is a growing concern that this might cause critical abundance thresholds of species to be crossed, with extinction cascades and state shifts in ecosystems as a consequence. When increased mortality rate and decreased abundance of a given species lead to extinction of other species, this species can be characterized as functionally extinct even though it still exists. Although such functional extinctions have been observed in some ecosystems, their frequency is largely unknown. Here we use a new modelling approach to explore the frequency and pattern of functional extinctions in ecological networks. Specifically, we analytically derive critical abundance thresholds of species by increasing their mortality rates until an extinction occurs in the network. Applying this approach on natural and theoretical food webs, we show that the species most likely to go extinct first is not the one whose mortality rate is increased but instead another species. Indeed, up to 80% of all first extinctions are of another species, suggesting that a species' ecological functionality is often lost before its own existence is threatened. Furthermore, we find that large-bodied species at the top of the food chains can only be exposed to small increases in mortality rate and small decreases in abundance before going functionally extinct compared to small-bodied species lower in the food chains. These results illustrate the potential importance of functional extinctions in ecological networks and lend strong support to arguments advocating a more community-oriented approach in conservation biology, with target levels for populations based on ecological functionality rather than on mere persistence. PMID:23831648

  19. Frequency-rank correlations of rhodopsin mutations with tuned hydropathic roughness based on self-organized criticality

    NASA Astrophysics Data System (ADS)

    Phillips, J. C.

    2012-11-01

    The behavior of disease-linked mutations of membrane proteins is especially simple in rhodopsin, where they are well-studied, as they are responsible for retinitis pigmentosa, RP (retinal degeneration). Here we show that the frequency of occurrence of single RP mutations is strongly influenced by their transportational survival rates, and that this survival correlates well (82%) with a long-range, non-local hydropathic measure of the roughness of the water interfaces of ex-membrane rhodopsin based on self-organized criticality (SOC). It is speculated that this concept may be generally useful in studying survival rates of many mutated proteins.

  20. Phosphorylated Peptide Functionalization of Lanthanide Upconversion Nanoparticles for Tuning Nanomaterial-Cell Interactions.

    PubMed

    Yao, Chi; Wei, Caiyi; Huang, Zhi; Lu, Yiqing; El-Toni, Ahmed Mohamed; Ju, Dianwen; Zhang, Xiangmin; Wang, Wenning; Zhang, Fan

    2016-03-23

    Peptide modification of nanoparticles with high efficiency is critical in determining the properties and bioapplications of nanoparticles, but the methodology remains a challenging task. Here, by using the phosphorylated linear and cyclic peptide with the arginine-glycine-aspartic acid (RGD) targeting motifs as typical examples, the peptides binding efficiency for the inorganic metal compound nanoparticles was increased significantly after the phosphorylation treatment, and the modification allowed for improving the selectivity and signal-to-noise ratio for cancer targeting and reduced the toxicity derived from nonspecific interactions of nanoparticles with cells owing to the higher amount of phosphopeptide binding. In addition, molecular dynamics (MD) simulations of various peptides on inorganic metal compound surfaces revealed that the peptide adsorption on the surface is mainly driven by electrostatic interactions between phosphate oxygen and the polarized interfacial water layer, consistent with the experimental observation of the strong binding propensity of phosphorylated peptides. Significantly, with the RGD phosphopeptide surface modification, these nanoparticles provide a versatile tool for tuning material-cell interactions to achieve the desired level of autophagy and may prove useful for various diagnostic and therapeutic applications. PMID:26927957

  1. Niobium oxide-polydimethylsiloxane hybrid composite coatings for tuning primary fibroblast functions.

    PubMed

    Young, Matthew D; Tran, Nhiem; Tran, Phong A; Jarrell, John D; Hayda, Roman A; Born, Chistopher T

    2014-05-01

    This study evaluates the potential of niobium oxide-polydimethylsiloxane (PDMS) composites for tuning cellular response of fibroblasts, a key cell type of soft tissue/implant interfaces. In this study, various hybrid coatings of niobium oxide and PDMS with different niobium oxide concentrations were synthesized and characterized using scanning electron microscopy, X-ray photoelectron spectrometry (XPS), and contact angle goniometry. The coatings were then applied to 96-well plates, on which primary fibroblasts were seeded. Fibroblast viability, proliferation, and morphology were assessed after 1, 2, and 3 days of incubation using WST-1 and calcein AM assays along with fluorescent microscopy. The results showed that the prepared coatings had distinct surface features with submicron spherical composites covered in a polymeric layer. The water contact angle measurement demonstrated that the hybrid surfaces were much more hydrophobic than the original pure niobium oxide and PDMS. The combination of surface roughness and chemistry resulted in a biphasic cellular response with maximum fibroblast density on substrate with 40 wt % of niobium oxide. The results of the current study indicate that by adjusting the concentration of niobium oxide in the coating, a desirable cell response can be achieved to improve tissue/implant interfaces. PMID:23776075

  2. The WD40 Domain Protein MSI1 Functions in a Histone Deacetylase Complex to Fine-Tune Abscisic Acid Signaling.

    PubMed

    Mehdi, Saher; Derkacheva, Maria; Ramström, Margareta; Kralemann, Lejon; Bergquist, Jonas; Hennig, Lars

    2016-01-01

    MSI1 belongs to a family of histone binding WD40-repeat proteins. Arabidopsis thaliana contains five genes encoding MSI1-like proteins, but their functions in diverse chromatin-associated complexes are poorly understood. Here, we show that MSI1 is part of a histone deacetylase complex. We copurified HISTONE DEACETYLASE19 (HDA19) with MSI1 and transcriptional regulatory SIN3-like proteins and provide evidence that MSI1 and HDA19 associate into the same complex in vivo. These data suggest that MSI1, HDA19, and HISTONE DEACETYLATION COMPLEX1 protein form a core complex that can integrate various SIN3-like proteins. We found that reduction of MSI1 or HDA19 causes upregulation of abscisic acid (ABA) receptor genes and hypersensitivity of ABA-responsive genes. The MSI1-HDA19 complex fine-tunes ABA signaling by binding to the chromatin of ABA receptor genes and by maintaining low levels of acetylation of histone H3 at lysine 9, thereby affecting the expression levels of ABA receptor genes. Reduced MSI1 or HDA19 levels led to increased tolerance to salt stress corresponding to the increased ABA sensitivity of gene expression. Together, our results reveal the presence of an MSI1-HDA19 complex that fine-tunes ABA signaling in Arabidopsis. PMID:26704384

  3. Wafer-to-wafer transfer process of barium strontium titanate for frequency tuning applications using laser pre-irradiation

    NASA Astrophysics Data System (ADS)

    Samoto, Tetuo; Hirano, Hideki; Somekawa, Toshihiro; Hikichi, Kousuke; Fujita, Masayuki; Esashi, Masayoshi; Tanaka, Shuji

    2015-03-01

    This paper describes laser-assisted film transfer technology for barium strontium titanate (BST) deposited on a sapphire substrate. BST is a promising ferroelectric material for varactors, which are required for frequency-tunable RF applications. However, the deposition temperature of BST (600 ~ 700 °C) is too high for surface acoustic wave (SAW) substrates. In this study, BST grown on a sapphire substrate at 650 °C was transferred at low temperature (140 °C) to a borosilicate glass substrate as well as a LiTaO3 substrate. The transferred BST films were characterized as tunable capacitors. A key process in the BST film transfer technology is the laser pre-irradiation of a buffer Pt layer beneath BST from the backside of the sapphire substrate to weaken the BST-to-Pt adhesion. The mechanism of delamination at the BST/Pt interface is discussed using a simple 1D heat transfer model.

  4. Frequency redistribution function for the polarized two-term atom

    SciTech Connect

    Casini, R.; Landi Degl'Innocenti, M.; Manso Sainz, R.; Landolfi, M.

    2014-08-20

    We present a generalized frequency redistribution function for the polarized two-term atom in an arbitrary magnetic field. This result is derived within a new formulation of the quantum problem of coherent scattering of polarized radiation by atoms in the collisionless regime. The general theory, which is based on a diagrammatic treatment of the atom-photon interaction, is still a work in progress. However, the results anticipated here are relevant enough for the study of the magnetism of the solar chromosphere and of interest for astrophysics in general.

  5. Differentials of a State Reading Assessment: Item Functioning, Distractor Functioning, and Omission Frequency for Disability Categories

    ERIC Educational Resources Information Center

    Kato, Kentaro; Moen, Ross E.; Thurlow, Martha L.

    2009-01-01

    Large data sets from a state reading assessment for third and fifth graders were analyzed to examine differential item functioning (DIF), differential distractor functioning (DDF), and differential omission frequency (DOF) between students with particular categories of disabilities (speech/language impairments, learning disabilities, and emotional…

  6. Tuning the Attempt Frequency of Protein Folding Dynamics via Transition-State Rigidification: Application to Trp-cage

    PubMed Central

    Abaskharon, Rachel M.; Culik, Robert M.; Woolley, G. Andrew; Gai, Feng

    2015-01-01

    The attempt frequency or prefactor (k0) of the transition state rate equation of protein folding kinetics has been estimated to be on the order of 106 s−1, which is many orders of magnitude smaller than that of chemical reactions. Herein, we use the mini-protein Trp-cage to show that it is possible to significantly increase the value of k0 for a protein folding reaction by rigidifying the transition state. This is achieved by reducing the conformational flexibility of a key structural element (i.e., an α-helix) formed in the transition state via photoisomerization of an azobenzene cross-linker. We find that this strategy not only decreases the folding time of the Trp-cage peptide by more than an order of magnitude (to ~100 ns at 25 °C) but also exposes parallel folding pathways, allowing us to provide, to the best of our knowledge, the first quantitative assessment of the curvature of the transition state free energy surface of a protein. PMID:26120378

  7. Solid-state optical absorption from optimally tuned time-dependent range-separated hybrid density functional theory

    NASA Astrophysics Data System (ADS)

    Refaely-Abramson, Sivan; Jain, Manish; Sharifzadeh, Sahar; Neaton, Jeffrey B.; Kronik, Leeor

    We present a framework for obtaining solid-state charge and optical excitations and spectra from optimally tuned range-separated hybrid density functional theory, which allows for the accurate prediction of exciton binding energies. We demonstrate our approach through calculations of one- and two-particle excitations in pentacene, a molecular semiconducting crystal, where we find excellent agreement with experiments and prior computations. We show that with one adjustable parameter, our method accurately predicts band structures and optical spectra of Si and LiF, prototypical covalent and ionic solids. For a range of extended bulk systems, this method may provide a computationally inexpensive alternative to many-body perturbation theory, opening the door to studies of materials of increasing size and complexity [Phys. Rev. B 92, 081204(R), 2015]. This work was supported by DOE.

  8. Solid-state optical absorption from optimally tuned time-dependent range-separated hybrid density functional theory

    NASA Astrophysics Data System (ADS)

    Refaely-Abramson, Sivan; Jain, Manish; Sharifzadeh, Sahar; Neaton, Jeffrey B.; Kronik, Leeor

    2015-08-01

    We present a framework for obtaining reliable solid-state charge and optical excitations and spectra from optimally tuned range-separated hybrid density functional theory. The approach, which is fully couched within the formal framework of generalized Kohn-Sham theory, allows for the accurate prediction of exciton binding energies. We demonstrate our approach through first principles calculations of one- and two-particle excitations in pentacene, a molecular semiconducting crystal, where our work is in excellent agreement with experiments and prior computations. We further show that with one adjustable parameter, set to produce the known band gap, this method accurately predicts band structures and optical spectra of silicon and lithium fluoride, prototypical covalent and ionic solids. Our findings indicate that for a broad range of extended bulk systems, this method may provide a computationally inexpensive alternative to many-body perturbation theory, opening the door to studies of materials of increasing size and complexity.

  9. Assessing vascular endothelial function using frequency and rank order statistics

    NASA Astrophysics Data System (ADS)

    Wu, Hsien-Tsai; Hsu, Po-Chun; Sun, Cheuk-Kwan; Liu, An-Bang; Lin, Zong-Lin; Tang, Chieh-Ju; Lo, Men-Tzung

    2013-08-01

    Using frequency and rank order statistics (FROS), this study analyzed the fluctuations in arterial waveform amplitudes recorded from an air pressure sensing system before and after reactive hyperemia (RH) induction by temporary blood flow occlusion to evaluate the vascular endothelial function of aged and diabetic subjects. The modified probability-weighted distance (PWD) calculated from the FROS was compared with the dilatation index (DI) to evaluate its validity and sensitivity in the assessment of vascular endothelial function. The results showed that the PWD can provide a quantitative determination of the structural changes in the arterial pressure signals associated with regulation of vascular tone and blood pressure by intact vascular endothelium after the application of occlusion stress. Our study suggests that the use of FROS is a reliable noninvasive approach to the assessment of vascular endothelial degeneration in aging and diabetes.

  10. Assigning Quantitative Function to Post-Translational Modifications Reveals Multiple Sites of Phosphorylation That Tune Yeast Pheromone Signaling Output

    PubMed Central

    Pincus, David; Ryan, Christopher J.; Smith, Richard D.

    2013-01-01

    Cell signaling systems transmit information by post-translationally modifying signaling proteins, often via phosphorylation. While thousands of sites of phosphorylation have been identified in proteomic studies, the vast majority of sites have no known function. Assigning functional roles to the catalog of uncharacterized phosphorylation sites is a key research challenge. Here we present a general approach to address this challenge and apply it to a prototypical signaling pathway, the pheromone response pathway in Saccharomyces cerevisiae. The pheromone pathway includes a mitogen activated protein kinase (MAPK) cascade activated by a G-protein coupled receptor (GPCR). We used published mass spectrometry-based proteomics data to identify putative sites of phosphorylation on pheromone pathway components, and we used evolutionary conservation to assign priority to a list of candidate MAPK regulatory sites. We made targeted alterations in those sites, and measured the effects of the mutations on pheromone pathway output in single cells. Our work identified six new sites that quantitatively tuned system output. We developed simple computational models to find system architectures that recapitulated the quantitative phenotypes of the mutants. Our results identify a number of putative phosphorylation events that contribute to adjust the input-output relationship of this model eukaryotic signaling system. We believe this combined approach constitutes a general means not only to reveal modification sites required to turn a pathway on and off, but also those required for more subtle quantitative effects that tune pathway output. Our results suggest that relatively small quantitative influences from individual phosphorylation events endow signaling systems with plasticity that evolution may exploit to quantitatively tailor signaling outcomes. PMID:23554854

  11. Assigning Quantitative Function to Post-Translational Modifications Reveals Multiple Sites of Phosphorylation That Tune Yeast Pheromone Signaling Output

    SciTech Connect

    Pincus, David; Ryan, Christopher J.; Smith, Richard D.; Brent, Roger; Resnekov, Orna; Hakimi, Mohamed Ali

    2013-03-12

    Cell signaling systems transmit information by post-­translationally modifying signaling proteins, often via phosphorylation. While thousands of sites of phosphorylation have been identified in proteomic studies, the vast majority of sites have no known function. Assigning functional roles to the catalog of uncharacterized phosphorylation sites is a key research challenge. Here we present a general approach to address this challenge and apply it to a prototypical signaling pathway, the pheromone response pathway in Saccharomyces cerevisiae. The pheromone pathway includes a mitogen activated protein kinase (MAPK) cascade activated by a G-­protein coupled receptor (GPCR). We used mass spectrometry-based proteomics to identify sites whose phosphorylation changed when the system was active, and evolutionary conservation to assign priority to a list of candidate MAPK regulatory sites. We made targeted alterations in those sites, and measured the effects of the mutations on pheromone pathway output in single cells. Our work identified six new sites that quantitatively tuned system output. We developed simple computational models to find system architectures that recapitulated the quantitative phenotypes of the mutants. Our results identify a number of regulated phosphorylation events that contribute to adjust the input-­output relationship of this model eukaryotic signaling system. We believe this combined approach constitutes a general means not only to reveal modification sites required to turn a pathway on and off, but also those required for more subtle quantitative effects that tune pathway output. Our results further suggest that relatively small quantitative influences from individual regulatory phosphorylation events endow signaling systems with plasticity that evolution may exploit to quantitatively tailor signaling outcomes.

  12. Frequency domain transfer function identification using the computer program SYSFIT

    SciTech Connect

    Trudnowski, D.J.

    1992-12-01

    Because the primary application of SYSFIT for BPA involves studying power system dynamics, this investigation was geared toward simulating the effects that might be encountered in studying electromechanical oscillations in power systems. Although the intended focus of this work is power system oscillations, the studies are sufficiently genetic that the results can be applied to many types of oscillatory systems with closely-spaced modes. In general, there are two possible ways of solving the optimization problem. One is to use a least-squares optimization function and to write the system in such a form that the problem becomes one of linear least-squares. The solution can then be obtained using a standard least-squares technique. The other method involves using a search method to obtain the optimal model. This method allows considerably more freedom in forming the optimization function and model, but it requires an initial guess of the system parameters. SYSFIT employs this second approach. Detailed investigations were conducted into three main areas: (1) fitting to exact frequency response data of a linear system; (2) fitting to the discrete Fourier transformation of noisy data; and (3) fitting to multi-path systems. The first area consisted of investigating the effects of alternative optimization cost function options; using different optimization search methods; incorrect model order, missing response data; closely-spaced poles; and closely-spaced pole-zero pairs. Within the second area, different noise colorations and levels were studied. In the third area, methods were investigated for improving fitting results by incorporating more than one system path. The following is a list of guidelines and properties developed from the study for fitting a transfer function to the frequency response of a system using optimization search methods.

  13. Fine-tuning of CD8(+) T-cell effector functions by targeting the 2B4-CD48 interaction.

    PubMed

    Lissina, Anna; Ambrozak, David R; Boswell, Kristin L; Yang, Wenjing; Boritz, Eli; Wakabayashi, Yoshiyuki; Iglesias, Maria C; Hashimoto, Masao; Takiguchi, Masafumi; Haddad, Elias; Douek, Daniel C; Zhu, Jun; Koup, Richard A; Yamamoto, Takuya; Appay, Victor

    2016-07-01

    Polyfunctionality and cytotoxic activity dictate CD8(+) T-cell efficacy in the eradication of infected and malignant cells. The induction of these effector functions depends on the specific interaction between the T-cell receptor (TCR) and its cognate peptide-MHC class I complex, in addition to signals provided by co-stimulatory or co-inhibitory receptors, which can further regulate these functions. Among these receptors, the role of 2B4 is contested, as it has been described as either co-stimulatory or co-inhibitory in modulating T-cell functions. We therefore combined functional, transcriptional and epigenetic approaches to further characterize the impact of disrupting the interaction of 2B4 with its ligand CD48, on the activity of human effector CD8(+) T-cell clones. In this setting, we show that the 2B4-CD48 axis is involved in the fine-tuning of CD8(+) T-cell effector function upon antigenic stimulation. Blocking this interaction resulted in reduced CD8(+) T-cell clone-mediated cytolytic activity, together with a subtle drop in the expression of genes involved in effector function regulation. Our results also imply a variable contribution of the 2B4-CD48 interaction to the modulation of CD8(+) T-cell functional properties, potentially linked to intrinsic levels of T-bet expression and TCR avidity. The present study thus provides further insights into the role of the 2B4-CD48 interaction in the fine regulation of CD8(+) T-cell effector function upon antigenic stimulation. PMID:26860368

  14. Tuning the work function in transition metal oxides and their heterostructures

    NASA Astrophysics Data System (ADS)

    Zhong, Z.; Hansmann, P.

    2016-06-01

    The development of novel functional materials in experimental labs combined with computer-based compound simulation brings the vision of materials design on a microscopic scale continuously closer to reality. For many applications interface and surface phenomena rather than bulk properties are key. One of the most fundamental qualities of a material-vacuum interface is the energy required to transfer an electron across this boundary, i.e., the work function. It is a crucial parameter for numerous applications, including organic electronics, field electron emitters, and thermionic energy converters. Being generally very resistant to degradation at high temperatures, transition metal oxides present a promising materials class for such devices. We have performed a systematic study for perovskite oxides that provides reference values and, equally important, reports on materials trends and the tunability of work functions. Our results identify and classify dependencies of the work function on several parameters including specific surface termination, surface reconstructions, oxygen vacancies, and heterostructuring.

  15. CYLD - a deubiquitylase that acts to fine-tune microtubule properties and functions.

    PubMed

    Yang, Yunfan; Zhou, Jun

    2016-06-15

    Microtubules are dynamic structures that are crucially involved in a variety of cellular activities. The dynamic properties and functions of microtubules are regulated by various factors, such as tubulin isotype composition and microtubule-binding proteins. Initially identified as a deubiquitylase with tumor-suppressing functions, the protein cylindromatosis (CYLD) has recently been revealed to interact with microtubules, modulate microtubule dynamics, and participate in the regulation of cell migration, cell cycle progression, chemotherapeutic drug sensitivity and ciliogenesis. These findings have greatly enriched our understanding of the roles of CYLD in physiological and pathological conditions. Here, we focus on recent literature that shows how CYLD impacts on microtubule properties and functions in various biological processes, and discuss the challenges we face when interpreting results obtained from different experimental systems. PMID:27173491

  16. Tuning of nanoparticle biological functionality through controlled surface chemistry and characterisation at the bioconjugated nanoparticle surface

    NASA Astrophysics Data System (ADS)

    Hristov, Delyan R.; Rocks, Louise; Kelly, Philip M.; Thomas, Steffi S.; Pitek, Andrzej S.; Verderio, Paolo; Mahon, Eugene; Dawson, Kenneth A.

    2015-12-01

    We have used a silica - PEG based bionanoconjugate synthetic scheme to study the subtle connection between cell receptor specific recognition and architecture of surface functionalization chemistry. Extensive physicochemical characterization of the grafted architecture is capable of capturing significant levels of detail of both the linker and grafted organization, allowing for improved reproducibility and ultimately insight into biological functionality. Our data suggest that scaffold details, propagating PEG layer architecture effects, determine not only the rate of uptake of conjugated nanoparticles into cells but also, more significantly, the specificity of pathways via which uptake occurs.

  17. Tune Measurement in RHIC

    NASA Astrophysics Data System (ADS)

    Brennan, M.; Cameron, P.; Cerniglia, P.; Connolly, R.; Cupolo, J.; Dawson, W.; Degen, C.; DellaPenna, A.; DeLong, J.; Drees, A.; Gassner, D.; Kesselman, M.; Lee, R.; Marusic, A.; Mead, J.; Michnoff, R.; Schultheiss, C.; Sikora, R.; Van Zeijts, J.

    2002-12-01

    Three basic tune measurement methods are employed in RHIC; kicked beam, Schottky, and phase-locked loop. The kicked beam and 2GHz Schottky systems have been in operation since the first commissioning of circulating beam in RHIC in 1999. Preliminary PLL measurements utilizing a commercial off-the-shelf lockin amplifier were completed during that run, and the resonant BPM used in that system also delivered 230MHz Schottky spectra. With encouraging preliminary results and the thought of tune feedback in mind, a PLL tune system was implemented in the FPGA/DSP environment of the RHIC BPM system for the RHIC 2001 run. During that run this system functioned at the level of the present state-of-the-art in tune measurement accuracy and resolution, and was successfully incorporated into a tune feedback system for use during acceleration. Each of the tune measurement systems has particular strengths and weaknesses. We present specific and comparative details of systems design and operation. In addition, we present detailed tune measurements and their utilization in the measurement of chromaticity and the implementation of tune feedback. Finally, we discuss planned upgrades for the RHIC 2003 run.

  18. Local inhibitory plasticity tunes macroscopic brain dynamics and allows the emergence of functional brain networks.

    PubMed

    Hellyer, Peter J; Jachs, Barbara; Clopath, Claudia; Leech, Robert

    2016-01-01

    Rich, spontaneous brain activity has been observed across a range of different temporal and spatial scales. These dynamics are thought to be important for efficient neural functioning. A range of experimental evidence suggests that these neural dynamics are maintained across a variety of different cognitive states, in response to alterations of the environment and to changes in brain configuration (e.g., across individuals, development and in many neurological disorders). This suggests that the brain has evolved mechanisms to maintain rich dynamics across a broad range of situations. Several mechanisms based around homeostatic plasticity have been proposed to explain how these dynamics emerge from networks of neurons at the microscopic scale. Here we explore how a homeostatic mechanism may operate at the macroscopic scale: in particular, focusing on how it interacts with the underlying structural network topology and how it gives rise to well-described functional connectivity networks. We use a simple mean-field model of the brain, constrained by empirical white matter structural connectivity where each region of the brain is simulated using a pool of excitatory and inhibitory neurons. We show, as with the microscopic work, that homeostatic plasticity regulates network activity and allows for the emergence of rich, spontaneous dynamics across a range of brain configurations, which otherwise show a very limited range of dynamic regimes. In addition, the simulated functional connectivity of the homeostatic model better resembles empirical functional connectivity network. To accomplish this, we show how the inhibitory weights adapt over time to capture important graph theoretic properties of the underlying structural network. Therefore, this work presents suggests how inhibitory homeostatic mechanisms facilitate stable macroscopic dynamics to emerge in the brain, aiding the formation of functional connectivity networks. PMID:26348562

  19. miR-17-92 fine-tunes MYC expression and function to ensure optimal B cell lymphoma growth

    PubMed Central

    Mihailovich, Marija; Bremang, Michael; Spadotto, Valeria; Musiani, Daniele; Vitale, Elena; Varano, Gabriele; Zambelli, Federico; Mancuso, Francesco M.; Cairns, David A.; Pavesi, Giulio; Casola, Stefano; Bonaldi, Tiziana

    2015-01-01

    The synergism between c-MYC and miR-17-19b, a truncated version of the miR-17-92 cluster, is well-documented during tumor initiation. However, little is known about miR-17-19b function in established cancers. Here we investigate the role of miR-17-19b in c-MYC-driven lymphomas by integrating SILAC-based quantitative proteomics, transcriptomics and 3′ untranslated region (UTR) analysis upon miR-17-19b overexpression. We identify over one hundred miR-17-19b targets, of which 40% are co-regulated by c-MYC. Downregulation of a new miR-17/20 target, checkpoint kinase 2 (Chek2), increases the recruitment of HuR to c-MYC transcripts, resulting in the inhibition of c-MYC translation and thus interfering with in vivo tumor growth. Hence, in established lymphomas, miR-17-19b fine-tunes c-MYC activity through a tight control of its function and expression, ultimately ensuring cancer cell homeostasis. Our data highlight the plasticity of miRNA function, reflecting changes in the mRNA landscape and 3′ UTR shortening at different stages of tumorigenesis. PMID:26555894

  20. Spectral Tuning of Killer Whale (Orcinus orca) Rhodopsin: Evidence for Positive Selection and Functional Adaptation in a Cetacean Visual Pigment.

    PubMed

    Dungan, Sarah Z; Kosyakov, Alexander; Chang, Belinda S W

    2016-02-01

    Cetaceans have undergone a remarkable evolutionary transition that was accompanied by many sensory adaptations, including modification of the visual system for underwater environments. Recent sequencing of cetacean genomes has made it possible to begin exploring the molecular basis of these adaptations. In this study we use in vitro expression methods to experimentally characterize the first step of the visual transduction cascade, the light activation of rhodopsin, for the killer whale. To investigate the spectral effects of amino acid substitutions thought to correspond with absorbance shifts relative to terrestrial mammals, we used the orca gene as a background for the first site-directed mutagenesis experiments in a cetacean rhodopsin. The S292A mutation had the largest effect, and was responsible for the majority of the spectral difference between killer whale and bovine (terrestrial) rhodopsin. Using codon-based likelihood models, we also found significant evidence for positive selection in cetacean rhodopsin sequences, including on spectral tuning sites we experimentally mutated. We then investigated patterns of ecological divergence that may be correlated with rhodopsin functional variation by using a series of clade models that partitioned the data set according to phylogeny, habitat, and foraging depth zone. Only the model partitioning according to depth was significant. This suggests that foraging dives might be a selective regime influencing cetacean rhodopsin divergence, and our experimental results indicate that spectral tuning may be playing an adaptive role in this process. Our study demonstrates that combining computational and experimental methods is crucial for gaining insight into the selection pressures underlying molecular evolution. PMID:26486871

  1. Commissioning of helium injector for coupled radio frequency quadrupole and separated function radio frequency quadrupole accelerator

    SciTech Connect

    Peng, Shixiang Chen, Jia; Ren, Haitao; Zhao, Jie; Xu, Yuan; Zhang, Tao; Xia, Wenlong; Gao, Shuli; Wang, Zhi; Luo, Yuting; Guo, Zhiyu; Zhang, Ailing; Chen, Jia'er; University of Chinese Academy of Sciences, Beijing 100049

    2014-02-15

    A project to study a new type of acceleration structure has been launched at Peking University, in which a traditional radio frequency quadrupole (RFQ) and a separated function radio frequency quadrupole are coupled in one cavity to accelerate the He+ beam. A helium injector for this project is developed. The injector consists of a 2.45 GHz permanent magnet electron cyclotron resonance ion source and a 1.16 m long low energy beam transport (LEBT). The commissioning of this injector was carried out and an onsite test was held in June 2013. A 14 mA He+ beam with the energy of 30 keV has been delivered to the end of the LEBT, where a diaphragm with the diameter of 7 mm is located. The position of the diaphragm corresponds to the entrance of the RFQ electrodes. The beam emittance and fraction were measured after the 7 mm diaphragm. Its rms emittance is about 0.14 π mm mrad and the fraction of He+ is about 99%.

  2. Nonlinear Trivelpiece-Gould Waves: Frequency, Functional Form, and Stability

    NASA Astrophysics Data System (ADS)

    Dubin, Daniel H. E.

    2015-11-01

    This poster considers the frequency, spatial form, and stability, of nonlinear Trivelpiece- Gould (TG) waves on a cylindrical plasma column of length L and radius rp, treating both traveling and standing waves, and focussing on the regime of experimental interest in which L/rp >> 1. In this regime TG waves are weakly dispersive, allowing strong mode-coupling between Fourier harmonics. The mode coupling implies that linear theory for such waves is a poor approximation even at fairly small amplitudes, and nonlinear theories that include only a small number of harmonics (such as 3-wave parametric resonance theory) fail to fully capture the stability properties of the system. We find that nonlinear standing waves suffer jumps in their functional form as their amplitude is varied continuously. The jumps are caused by nonlinear resonances between the standing wave and nearly linear waves whose frequencies and wave numbers are harmonics of the standing wave. Also, the standing waves are found to be unstable to a multi-wave version of 3-wave parametric resonance, with an amplitude required for instability onset that is much larger than expected from three wave theory. For traveling wave, linearly stability is found for all amplitudes that could be studied, in contradiction to 3-wave theory. Supported by National Science Foundation Grant PHY-1414570, Department of Energy Grants DE-SC0002451and DE-SC0008693.

  3. Coupled vibro-acoustic model updating using frequency response functions

    NASA Astrophysics Data System (ADS)

    Nehete, D. V.; Modak, S. V.; Gupta, K.

    2016-03-01

    Interior noise in cavities of motorized vehicles is of increasing significance due to the lightweight design of these structures. Accurate coupled vibro-acoustic FE models of such cavities are required so as to allow a reliable design and analysis. It is, however, experienced that the vibro-acoustic predictions using these models do not often correlate acceptably well with the experimental measurements and hence require model updating. Both the structural and the acoustic parameters addressing the stiffness as well as the damping modeling inaccuracies need to be considered simultaneously in the model updating framework in order to obtain an accurate estimate of these parameters. It is also noted that the acoustic absorption properties are generally frequency dependent. This makes use of modal data based methods for updating vibro-acoustic FE models difficult. In view of this, the present paper proposes a method based on vibro-acoustic frequency response functions that allow updating of a coupled FE model by considering simultaneously the parameters associated with both the structural as well as the acoustic model of the cavity. The effectiveness of the proposed method is demonstrated through numerical studies on a 3D rectangular box cavity with a flexible plate. Updating parameters related to the material property, stiffness of joints between the plate and the rectangular cavity and the properties of absorbing surfaces of the acoustic cavity are considered. The robustness of the method under presence of noise is also studied.

  4. Hand motor recovery after stroke: tuning the orchestra to improve hand motor function.

    PubMed

    Fregni, Felipe; Pascual-Leone, Alvaro

    2006-03-01

    The motor deficits after stroke are not only the manifestation of the injured brain region, but rather the expression of the ability of the rest of the brain to maintain function. After a lesion in the primary motor cortex, parallel motor circuits might be activated to generate some alternative input to the spinal motoneurons. These parallel circuits may originate from areas such as the contralateral, undamaged primary motor area, bilateral premotor areas, bilateral supplementary motor areas, bilateral somatosensory areas, cerebellum, and basal ganglia. Most importantly, the efferent, cortico-spinal output pathways must be preserved for a desired behavioral result. Most of the recovery of function after a stroke may represent actual relearning of the skills with the injured brain. The main neural mechanisms underlying this relearning process after stroke involve shifts of distributed contributions across a specific neural network (fundamentally the network engaged in skill learning in the healthy). If these notions are indeed correct, then neuromodulatory approaches, such as transcranial magnetic stimulation, targeting these parallel circuits might be useful to limit injury and promote recovery after a stroke. This paper reviews the stroke characteristics that can predict a good recovery and compensations across brain areas that can be implemented after a stroke to accelerate motor function recovery. PMID:16633016

  5. Quasiparticle Spectra from a Nonempirical Optimally Tuned Range-Separated Hybrid Density Functional

    NASA Astrophysics Data System (ADS)

    Refaely-Abramson, Sivan; Sharifzadeh, Sahar; Govind, Niranjan; Autschbach, Jochen; Neaton, Jeffrey B.; Baer, Roi; Kronik, Leeor

    2012-11-01

    We present a method for obtaining outer-valence quasiparticle excitation energies from a density-functional-theory-based calculation, with an accuracy that is comparable to that of many-body perturbation theory within the GW approximation. The approach uses a range-separated hybrid density functional, with an asymptotically exact and short-range fractional Fock exchange. The functional contains two parameters, the range separation and the short-range Fock fraction. Both are determined nonempirically, per system, on the basis of the satisfaction of exact physical constraints for the ionization potential and frontier-orbital many-electron self-interaction, respectively. The accuracy of the method is demonstrated on four important benchmark organic molecules: perylene, pentacene, 3,4,9,10-perylene-tetracarboxylic-dianydride (PTCDA), and 1,4,5,8-naphthalene-tetracarboxylic-dianhydride (NTCDA). We envision that for the outer-valence excitation spectra of finite systems the approach could provide an inexpensive alternative to GW, opening the door to the study of presently out of reach large-scale systems.

  6. Quasiparticle Spectra from a Nonempirical Optimally Tuned Range-Separated Hybrid Density Functional

    NASA Astrophysics Data System (ADS)

    Refaely-Abramson, Sivan; Sharifzadeh, Sahar; Govind, Niranjan; Autschbach, Jochen; Neaton, Jeffrey B.; Baer, Roi; Kronik, Leeor

    2013-03-01

    We present a method for obtaining outer-valence quasiparticle excitation energies from a density-functional-theory-based calculation, with an accuracy that is comparable to that of many-body perturbation theory within the GW approximation. The approach uses a range-separated hybrid density functional, with an asymptotically exact and short-range fractional Fock exchange. The functional contains two parameters, the range separation and the short-range Fock fraction. Both are determined nonempirically, per system, on the basis of the satisfaction of exact physical constraints for the ionization potential and many-electron self-interaction, respectively. The accuracy of the method is demonstrated on four important benchmark organic molecules: perylene, pentacene, 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA), and 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTCDA). We envision that for finite systems the approach could provide an inexpensive alternative to GW, opening the door to the study of presently out of reach large-scale systems (Phys. Rev. Lett., in press).

  7. Quasiparticle spectra from a nonempirical optimally tuned range-separated hybrid density functional.

    PubMed

    Refaely-Abramson, Sivan; Sharifzadeh, Sahar; Govind, Niranjan; Autschbach, Jochen; Neaton, Jeffrey B; Baer, Roi; Kronik, Leeor

    2012-11-30

    We present a method for obtaining outer-valence quasiparticle excitation energies from a density-functional-theory-based calculation, with an accuracy that is comparable to that of many-body perturbation theory within the GW approximation. The approach uses a range-separated hybrid density functional, with an asymptotically exact and short-range fractional Fock exchange. The functional contains two parameters, the range separation and the short-range Fock fraction. Both are determined nonempirically, per system, on the basis of the satisfaction of exact physical constraints for the ionization potential and frontier-orbital many-electron self-interaction, respectively. The accuracy of the method is demonstrated on four important benchmark organic molecules: perylene, pentacene, 3,4,9,10-perylene-tetracarboxylic-dianydride (PTCDA), and 1,4,5,8-naphthalene-tetracarboxylic-dianhydride (NTCDA). We envision that for the outer-valence excitation spectra of finite systems the approach could provide an inexpensive alternative to GW, opening the door to the study of presently out of reach large-scale systems. PMID:23368141

  8. Model updating using correlation analysis of strain frequency response function

    NASA Astrophysics Data System (ADS)

    Guo, Ning; Yang, Zhichun; Jia, You; Wang, Le

    2016-03-01

    A method is proposed to modify the structural parameters of a dynamic finite element (FE) model by using the correlation analysis for strain frequency response function (SFRF). Sensitivity analysis of correlation coefficients is used to establish the linear algebraic equations for model updating. In order to improve the accuracy of updated model, the regularization technique is used to solve the ill-posed problem in model updating procedure. Finally, a numerical study and a model updating experiment are performed to verify the feasibility and robustness of the proposed method. The results show that the updated SFRFs and experimental SFRFs agree well, especially in resonance regions. Meanwhile, the proposed method has good robustness to noise ability and remains good feasibility even the number of measurement locations reduced significantly.

  9. Study on utility of an approximated transfer function of dynamically tuned dry gyro

    NASA Astrophysics Data System (ADS)

    Shingu, H.; Otsuki, M.; Hayano, T.

    The use of a dry gyro in analog rebalance loops is described and a method to improve the static and dynamic characteristics is presented. The transfer function is derived by transforming a generalized equation into the approximated form based on the design specifications of the mechanical parts. This approximation is proved to be reasonable by the result that the differences between the numerical solutions of a generalized equation and those of an approximated equation are less than 1.0%, and their mean values are less than 0.003%. Noninteracting control is analyzed and the stability conditions are investigated. A fundamental design conception for rebalance loops was established.

  10. Tuning and probing interfacial bonding channels for a functionalized organic molecule by surface modification

    NASA Astrophysics Data System (ADS)

    Mercurio, G.; Bauer, O.; Willenbockel, M.; Fiedler, B.; Sueyoshi, T.; Weiss, C.; Temirov, R.; Soubatch, S.; Sokolowski, M.; Tautz, F. S.

    2013-03-01

    The potassium-induced missing row reconstruction of Ag(110) is used to selectively modify the local chemical interaction between the functional anhydride groups of 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) and Ag(110). We find a significant upward shift of the anhydride groups, while the adsorption height of the perylene core is essentially preserved. This demonstrates an attractive perylene/substrate interaction for PTCDA/K:Ag(110), elucidating also the bonding situation for the potassium-free system.