Ms Frame Research Articles

Routing of information flow by selective visual attention in LFPs of monkey area V4

Routing of information flow by selective visual attention in LFPs of monkey area V4

Trajectory analysis of single molecules exhibiting non-Brownian motion

Four techniques for analyzing single molecule tracking data--confinement level analysis, time series analysis and statistical analysis of lateral diffusion, multistate kinetics, and a newly developed method, radius of gyration evolution analysis--are compared using a set of sample fluorophore trajectories obtained from the lipophilic carbocyanine dye 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine, DiIC(18), partitioned into surface tethered poly(n-isopropylacrylamide). The purpose here is two-fold: first to test that these techniques can be applied to single molecules trajectories, which typically contain a smaller total number of frames than those obtained from other particles, e.g. quantum dots or gold nanoparticles; and second to critically compare the information obtained from each method against the others. A set of five SMT trajectories, ranging in length from 41 to 273 steps with a 30 ms frame transfer exposure, were all successfully analyzed by all four techniques, provided two important criteria were met: enough steps to define the motion were acquired in the trajectory, generally on the order of 50 steps, and the fast and slow diffusion coefficients differ by at least a factor of 5. Beyond that the four trajectory analysis methods studied provide partially confirmatory and partially complementary information. SMT data resulting from more complex physical behavior may well benefit from using these techniques in succession to identify and sort populations.

Predictability matters for multiple object tracking

Most accounts of multiple object tracking (MOT) suggest that only the spatial arrangement of objects at any one time is important for explaining performance. In contrast, we argue that observers predict future target positions. Previously this proposition was tested by studying the recovery of targets after a period of invisibility (Fencsik, Klieger, & Horowitz, 2007; Keane & Pylyshyn, 2006). Here, we test the predictive hypothesis in a continuous tracking paradigm. In two experiments, we asked observers to track three out of twelve moving disks for three to six seconds, and varied the average turn angle. We held speed constant at 8°/s, but direction for each disk changed with probability .025 on each 13.33 ms frame. Observers marked all targets at the end of the trial. Experiment 1 used turn angles of 0°, 30°, and 90°, while Experiment 2 used 0°, 15°, 30°, 45°, 60°, 75°, and 90°. Turn angle was fixed for all objects within a trial but varied across trials. In both experiments, accuracy was maximal at 0° and declined as turn angle increased (Exp 1: p = .001; Exp 2: p = .001). In Experiment 2, the steepest decline in accuracy was from 0° to 30°, while accuracy was roughly constant from 45° to 90°. These data demonstrate that it is easier to track predictably moving targets. Since velocity, density, and other factors known to affect MOT performance were constant, this suggests that observers predict target motion online to improve tracking. Furthermore, the pattern of data in Experiment 2 is compatible with a model in which the visual system assumes that target trajectories will vary only within a narrow 30° band.

Detective quantum efficiency, modulation transfer function and energy resolution comparison between CdTe and silicon sensors bump-bonded to XPAD3S

XPAD3S is a single-photon-counting chip developed in collaboration by SOLEIL Synchrotron, the Institut Louis Néel and the Centre de Physique de Particules de Marseille. The circuit, designed in the 0.25 microm IBM technology, contains 9600 square pixels with 130 microm side giving a total size of 1 cm x 1.5 cm. The main features of each pixel are: single threshold adjustable from 4.5 keV up to 35 keV, 2 ms frame rate, 10(7) photons s(-1) mm(-2) maximum local count rate, and a 12-bit internal counter with overflow allowing a full 27-bit dynamic range to be reached. The XPAD3S was hybridized using the flip-chip technology with both a 500 microm silicon sensor and a 700 microm CdTe sensor with Schottky contacts. Imaging performances of both detectors were evaluated using X-rays from 6 keV up to 35 keV. The detective quantum efficiency at zero line-pairs mm(-1) for a silicon sensor follows the absorption law whereas for CdTe a strong deficit at low photon energy, produced by an inefficient entrance layer, is measured. The modulation transfer function was evaluated and it was shown that both detectors present an ideal modulation transfer function at 26 keV, limited only by the pixel size. The influence of the Cd and Te K-edges of the CdTe sensor was measured and simulated, establishing that fluorescence photons reduce the contrast transfer at the Nyquist frequency from 60% to 40% which remains acceptable. The energy resolution was evaluated at 6% with silicon using 16 keV X-rays, and 8% with CdTe using 35 keV X-rays. A 7 cm x 12 cm XPAD3 imager, built with eight silicon modules (seven circuits per module) tiled together, was successfully used for X-ray diffraction experiments. A first result recently obtained with a new 2 cm x 3 cm CdTe imager is also presented.

Adaptive Long-Term Coding of LSF Parameters Trajectories for Large-Delay/Very- to Ultra-Low Bit-Rate Speech Coding

This paper presents a model-based method for coding the LSF parameters of LPC speech coders on a basis, that is, beyond the usual 20-30 ms frame duration. The objective is to provide efficient LSF quantization for a speech coder with large delay but very- to ultra-low bit-rate (i.e., below 1 kb/s). To do this, speech is first segmented into voiced/unvoiced segments. A Discrete Cosine model of the time trajectory of the LSF vectors is then applied to each segment to capture the LSF interframe correlation over the whole segment. Bi-directional transformation from the model coefficients to a reduced set of LSF vectors enables both efficient sparse coding (using here multistage vector quantizers) and the generation of interpolated LSF vectors at the decoder. The proposed method provides up to 50% gain in bit-rate over frame-by-frame quantization while preserving signal quality and competes favorably with 2D-transform coding for the lower range of tested bit rates. Moreover, the implicit time-interpolation nature of the long-term coding process provides this technique a high potential for use in speech synthesis systems.

Contact-Mode High-Resolution High-Speed Atomic Force Microscopy Movies of the Purple Membrane

High-speed atomic force microscopy (HS-AFM) is becoming a reference tool for the study of dynamic biological processes. The spatial and time resolutions of HS-AFM are on the order of nanometers and milliseconds, respectively, and allow structural and functional characterization of biological processes at the single-molecule level. In this work we present contact-mode HS-AFM movies of purple membranes containing two-dimensional arrays of bacteriorhodopsin (bR). In high-resolution movies acquired at a 100 ms frame acquisition time, the substructure on individual bR trimers was visualized. In regions in between different bR arrays, dynamic topographies were observed and interpreted as motion of the bR trimers. Similarly, motion of bR monomers in the vicinity of lattice defects in the purple membrane was observed. Our findings indicate that the bR arrays are in a mobile association-dissociation equilibrium. HS-AFM on membranes provides novel perspectives for analyzing the membrane diffusion processes of nonlabeled molecules.

A comparative analysis of diesel fuel injection parameters in piezoelectric and electromagnetic fuel injectors

The paper presents the results of a comparative analysis of the changes in the injection spray shape and penetration and its vertex angle during the injection through piezoelectric and electromagnetic fuel injectors. The results of the observation of the fuel spray with the use of high speed camera (100 ms frame frequency) have been presented. Moreover, the parameterization and digital processing (including its automation) of the obtained image have too been presented. The influence of the pressure and the timing of the injection on the variable-in-time spray parameters have been shown. A mathematical model describing these relations has been proposed.

A combination of data mining method with decision trees building for Speech/Music discrimination

Nowadays the applications in multimedia domain require that the Speech/Music classifier has many other merits in addition to the accuracy, such as short-time delay and low complexity. Here, we endeavor to form a Speech/Music classifier by using different data mining methods. The main contributions of this paper are to obtain a system by analyzing the inherent validity of diverse features extracted from the audio, building a hierarchical structure of oblique decision trees (HODT) to maintain optimal performances, and applying a novel context-based state transform (ST) strategy to refine the classification results. The proposed algorithm is evaluated by a set of 5–11 min 702 audio files, which are made from 54 speech or music files according to different Signal-to-Noise Ratio (SNR) levels and diverse noise types. The experiment results show that our proposed classifier outperforms AMR-WB+ by achieving 97.9% and 95.9% in classification rate at the 10 ms frame level in pure and high SNR (> = 20 dB) environment, respectively. The post-processing ST strategy further enhances the system performance, particularly at low SNR circumstances (10 dB), with 5.6% up in the accuracy rate. In addition, the complexity of the proposed system is lower than 1WMOPS which make it easily adaptable to many scenarios.

3D Particle Trajectories Observed by Orthogonal Tracking Microscopy

We demonstrate high-resolution, high-speed 3D nanoparticle tracking using angled micromirrors. When angled micromirrors are introduced into the field of view of an optical microscope, reflected side-on views of a diffusing nanoparticle are projected alongside the usual direct image. The experimental design allows us to find the 3D particle trajectory using fast, centroid-based image processing, with no nonlinear computing operations. We have tracked polystyrene particles of 190 nm diameter with position measurement precision <20 nm in 3D with 3 ms frame duration (i.e., at an imaging rate >330 frames per second). Because the image processing requires only approximately 1 ms per frame, this technique could enable real-time feedback-controlled nanoparticle assembly applications with nanometer precision.

The temporal dynamics of selective attention of the visual periphery as measured by classification images

This study estimates the temporal dynamics of selective attention with classification images, a technique assessing observer information use by tracking how responses are correlated with external noise added to the stimulus. Three observers performed a yes/no discrimination of a Gaussian signal that could appear at one of eight locations (eccentricity-4.6 degrees ). During the stimulus duration (300 ms), a peripheral cue indicated the potential signal location with 100% validity, and stimuli were presented in frames (37.5 ms/frame) of independently sampled Gaussian luminance image noise. Stimuli were presented either with or without a succeeding masking display (100 ms) of high-contrast image noise, with mask presence having little effect. The results from the classification images suggest that observers were able to use information at the cued location selectively (relative to the uncued locations), starting within the first (0-37.5 ms) or second (37.5-75 ms) frame. This suggests a selective attention effect earlier than those found in previous behavioral and event-related potential (ERP) studies, which generally have estimated the latency for selective attention effects to be 75-100 ms. We present a deconvolution method using the known temporal impulse response of early vision that indicates how the classification image results might relate to previous behavioral and ERP results. Applying the model to the classification images suggests that accounting for the known temporal dynamics could explain at least part of the difference in results between classification images and the previous studies.

Combustion front dynamics in the combustion synthesis of refractory metal carbides and di-borides using time-resolved X-ray diffraction

A compact diffraction-reaction chamber, using a 2-inch photodiode array detector, has been employed to investigate the chemical dynamics at the combustion front of a selected series of refractory metal carbides and di-borides from their constituent element reactants as well as binary products from B4C as a reactant. These systems are denoted as (i) M + C --> MC; (ii) M + 2B --> MB2; and (iii) 3M + B4C --> 2MB2 + MC, where M = Ti, Zr, Nb, Hf or Ta. Time-resolved X-ray diffraction using intense synchrotron radiation at frame rates up to 10 frames s(-1) (or 100 ms frame(-1)) was employed. The combustion reactions were found to complete within 200-400 ms. In contrast to the Ta + C --> TaC combustion system studied earlier, in which a discernible intermediate sub-carbide phase was first formed, reacted further and disappeared to yield the final TaC product, no intermediate sub-carbide or sub-boride was detected in the current systems. Combustion for the Ti, Zr and Hf systems involved a liquid phase, in which the adiabatic temperatures Tad are well above the melting points of the respective reactant metals and have a typical combustion front velocity of 5-6 mm s(-1). The Nb and Ta systems have lower Tad, involving no liquid phase. These are truly solid combustion systems and have a lower combustion front velocity of 1-2 mm s(-1). The current study opens up a new avenue to chemical dynamics and macrokinetic investigations of high-temperature solid-state reactions.

Analysis of the channel bit-rate detection process in WCDMA

A critical task within receivers for third-generation W-CDMA systems is the detection of the respective channel parameters and bit-rate on the basis of decoding the transport format combination indicator (TFCI) bits associated with each 10 ms frame. Evaluation of hard and soft decoding of the TFCI bits is therefore the focus of this work. The probability of erroneous rate detection for each case is computed and supported by simulation results obtained in realistic scenarios specified by the 3GPP standardisation forum. It is shown that the improved performance provided by soft decoding over hard detection is in the range of 2 to 3 dB for a wide range of signal-to-interference-plus-noise ratios, and that for low data rates, where fewer TFCI bits are transmitted per slot, the decoding performance is inferior to that in high data rates.

Edge-enhanced radiology with broadband synchrotron X-rays

Broadband synchrotron X-rays with limited coherence can be used for high resolution phase contrast radiology. Our experimental results confirm the prediction that the extreme spatial coherence of third-generation synchrotron sources although helpful but not strictly necessary for refraction-based or diffraction-based edge enhancement. Source with rather limited lateral coherence can produce Fresnel diffraction fringes. The direct observation of the same fringes using broadband synchrotron lights demonstrates that high time coherence is also not required. Broadband light produces a high photon flux and high average photon energy, that was exploited for real-time radiology (5 ms frame) studies with high lateral resolution (1 μm) and excellent contrast, without using a sophisticated detecting system. These results enhance the potential impact of phase contrast on medical X-ray applications, materials science and other domains.

Shared time division duplexing: an approach to low-delay high-quality wireless digital speech communications

Various strategies to provide low-delay high-quality digital speech communications in a high-capacity wireless network are examined. Various multiple access schemes based on time-division and packet reservation are compared in terms of their statistical multiplexing capabilities, sensitivity to speech packet dropping, delay, robustness to lossy packet environments, and overhead efficiency. In particular, a low-delay multiple access scheme, called shared time-division duplexing (STDD) is proposed. This scheme allows both the uplink and downlink traffic to share a common channel, thereby achieving high statistical multiplexing gain even with a low population of simultaneous conversations. The authors also propose a choice of low delay, high quality speech coding and digital modulation systems based on adaptive DPCM, with QDPSK or pseudo-analog transmission (skewed DPSK), for use in conjunction with the STDD multiple access protocol. The choice of the alternative systems depends on required end-to-end delay, recovered speech quality and bandwidth efficiency. Typically, with a total capacity of 1 MBaud, 2 ms frame and 8 kBaud speech coding rate, low delay STDD is able to support 48 pairs of users compared to 38, 35, and 16 for TDMA with speech activity detection, basic TDMA and PRMA respectively. This corresponds to respective gains of 26%, 37% and 200%.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

One-pass, speaker-independent, isolated digit recognition system

The system described in this paper is an outgrowth of one presented earlier [J. Acoust. Soc. Am. Suppl. 1 72, S30 (1982)]. It is a combination of deterministic and probabilistic approaches to isolated word recognition. The most distinguishing features of the new system are a real-time, one-pass algorithm and the use of telephone-quality speech rather than broadband microphone speech. This new version is targeted to a single chip implementation with the requirement that the system uses no more than 256 bytes of RAM and 8000 bytes of ROM. The system makes decisions based on a single 20 ms frame often features (with no long term storage of previous frames). Preliminary segmentation and matching are combined to significantly reduce both the number of confusable words at each recognition point as well as the memory requirement for references obtained during the multispeaker training. The system was evaluated on a ten digit vocabulary (1000 tokens, 21 talkers) and showed an accuracy of 94.4% with a 3.1% error rate, and a 2.5% rejection rate. The effects of using a one-pass algorithm on total performance are also discussed.

The use of tracking rules in automatic formant analysis of speech

The J.S.R.U. computer‐simulated automatic formant analyser uses analysis by synthesis to achieve high reliability and accuracy in the matching of synthetic formants to the peaks of pitch synchronous short term spectra of natural speech [P.M. Seeviour, J. N. Holmes and M. W. Judd, IEEE Int. Conf. Acoust., Speech, Signal Processing, Philadelphia, PA, pp. 609–693 (1976)]. However, analysis by synthesis does not of itself necessarily provide consistent labeling of the peaks of the natural spectrum. The specific case of this problem as it appears in the J.S.R.U. formant analyser will be discussed. The task is to choose, for each 10 ms frame of speech, from among a number of attempts to produce a synthetic match to the natural spectrum. The restrictions on the algorithm, particularly the need to avoid excessive smoothing of formant movement, will be mentioned. Simple heuristic rules currently in use will be described and the performance obtainable with such rules will be illustrated by means of spectrograms and audio tape recordings.