High Time Resolution DPWMs based on the Rolling Subtraction Algorithm

Positron emission tomography (PET) with high resolution and high sensitivity is desirable for detecting cancers and neurological diseases. In this work, a depth-of-interaction (DOI)-time-of-flight (TOF) PET has been attempted to achieve both high spatial and high timing resolution. Dual-ended readout is a simple technique that can provide excellent timing and DOI resolutions and consistent signal arrival times, regardless of the DOI position along the scintillation crystal, as a mean-time method is used. A dual-ended readout DOI-TOF PET module consisting of a 6 × 6 array of 2 × 2 × 20 mm3 saw-cut cerium-doped lutetium-yttrium oxyorthosilicate (LYSO) crystals is constructed. Both ends of the LYSO crystal array are optically coupled to a multi-pixel photon counter (MPPC) with 4 × 4 channels. The sixteen MPPC outputs are reduced to four position signals using a charge division circuit (CDC) board, and the timing signal is extracted from the common cathode of the MPPC. The four position signals from the MPPC are digitized by a DRS4-based high-speed waveform digitizer with a sampling rate of 5 GSa/s. A 22Na source is placed in front of a reference detector and at the side of the dual-ended readout DOI-TOF PET module in five steps of 2 mm, 6 mm, 10 mm, 14 mm, and 18 mm to measure the DOI, coincidence timing resolutions (CTRs), and mean-times. The full-width-half-maximums (FWHMs) of DOI resolutions and CTRs varied from 3.0 mm to 3.8 mm, with an average of 3.5 mm, and from 333 ps to 367 ps, with an average of 349 ps, respectively. The average of the slopes of the mean-time versus DOI position, for the 36 crystals, was −0.60 ± 1.68 ps/nm, which was consistent with the null value. The dual-ended readout DOI-TOF PET module based on the mean-time method produced both good DOI and CTRs, and consistent signal arrival times. The found solution would be the most advantageous in the small aperture PET systems, such as those for brain and breast imaging.

High time resolution and extreme radiation hardness are key for detectors to be operated in future particle accelerators and in space or medical applications. With respect to these relevant properties, we report here on performances of pixel sensors prepared on mono- and poly-crystalline synthetic Chemical Vapor Deposited (CVD) diamonds, by fast laser modification via multiphoton absorption from a 50 fs, 800 nm, Ti:Sa source. The research has been carried out in the framework of the Timespot experiment of the Italian National Institute for Nuclear Physics (INFN) aimed to achieve both high spatial resolution (55 μm pitch) and very high time resolution (tens of picoseconds) with very radiation tolerant detectors. Timespot exploits the recent 3D electrode architecture to enhance both time resolution and radiation hardness with respect to standard planar silicon and diamond detectors. We present here a major step forward in material engineering and fabrication procedure, yielding a time resolution improvement of our devices from the initial 280 ps to the present 80 ps, bringing this figure of merit very close to that allowed by the more mature 3D silicon technology. Recent results will be presented, and strategies for further improvements will be discussed. Since diamond is known to be a very radiation-tolerant material, it is considered very promising for implementing devices planned for very fast response and radiation hardness. We present results on a thorough study of polycrystalline and monocrystalline diamond sensors irradiated up to a fluence level of 1016 neq (1 MeV)/cm2. The superior radiation hardness of the 3D architecture is demonstrated with respect to the planar detectors. We have also verified that the radiation hardness increases with increasing bulk electrode density. The results are discussed and compared with other radiation hardness studies carried out on 3D diamond sensors.

Advanced factor analysis for multiple time resolution aerosol composition data

A 2-D multichannel interferometer designed for tomographically inferring contours of electron density in the WT-3 tokamak plasmas (Rs0.65 m, as0.2 m, B τ ≤1.75 T) with high time resolution is described. A frequency shift of w lF e1.45 MHz for a local beam splitted from a 337 μm HCN laser beam is obtained by use of a super rotating grating /1/, which allows the time resolution of the density measurements as fast as τs10 μsec.

The duty cycle in digital pulse width modulation (DPWM) whose time resolution is as high as hundreds of picosecond will be increased since the propagation delays of internal logics and interconnects are superimposed on the on-time. The duty-cycle-increment phenomenon affects the regulation performance of converters, especially when the delays are the same magnitude level as switching period. In this paper, a compensation method based on tool command language commands is used to offset the propagation delays. Furthermore, the DPWM applies a counter, phase locked loop, and carry chain to constitute segmented delay-line, while it maintains a wide duty cycle range and a high time resolution. This DPWM is implemented by a low-cost field-programmable gate array Cyclone IV. It achieves a good linearity where R2 is 0.9949 for an 11-bit, 9.375 MHz switching frequency DPWM. The duty cycle range is from 1.52% to 97.81%. Meanwhile, the time resolution and average duty difference are 53 ps and 3.08%, respectively.

This paper presents a novel digital pulse width modulator (DPWM) structure with higher time resolution and lower input clock frequency, which is especially suitable for high frequency digitally controlled DC-DC switching converters. For the proposed DPWM, two multi-phase clock arrays are generated which have relatively close frequencies, and the time-inserting method is also utilized. The FPGA based simulation results show that, the proposed DPWM can achieve the time resolution of around 30ps and the equivalent 12-bits precision when the input dual-clock frequencies are 100MHz and 105MHz at 5MHz switching frequency.

view Abstract Citations (64) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Angular Diameters and Fluxes of Magellanic Cloud Planetary Nebulae. II. High-Speed Direct Imaging Wood, P. R. ; Meatheringham, S. J. ; Dopita, M. A. ; Morgan, D. H. Abstract Images and fluxes of Magellanic Cloud planetary nebulae have been obtained with a time resolution of 1/60 s. The high time resolution was used to remove translational seeing effects. Angular diameters greater than 0arcsec.7 have been obtained for 20 Magellanic Cloud planetary nebulae, and fluxes in Hβ or [O III] λ5007 or both have been obtained for 80 nebulae. Masses have been derived for 18 nebulae from the angular diameters and Hβ fluxes. The ionized masses of typical Magellanic Cloud planetary nebulae increase with radius R roughly as R3/2 to R5/3 until R ≈ 0.1 pc; thereafter, the ionized mass has a maximum value of ≡0.5 M_sun;. Bolometric luminosities have been estimated for the central stars of those objects for which Hβ fluxes were obtained. Publication: The Astrophysical Journal Pub Date: September 1987 DOI: 10.1086/165533 Bibcode: 1987ApJ...320..178W Keywords: Magellanic Clouds; Planetary Nebulae; Speckle Interferometry; Stellar Evolution; Stellar Mass; Cassegrain Optics; High Resolution; Spatial Resolution; Stellar Luminosity; Astrophysics; NEBULAE: PLANETARY; GALAXIES: MAGELLANIC CLOUDS; STARS: EVOLUTION; STARS: MASS LOSS full text sources ADS | data products SIMBAD (64) NED (2) Related Materials (1) Part 1: 1986ApJ...311..632W

Presynaptic calcium influx at the inhibitor of the crayfish neuromuscular junction was investigated by measuring fluorescence transients generated by calcium-sensitive dyes. This approach allowed us to correlate presynaptic calcium influx with transmitter release at a high time resolution. Systematic testing of the calcium indicators showed that only low-affinity dyes, with affinities in the range of micromolar, should be used to avoid saturation of dye binding and interference with transmitter release. Presynaptic calcium influx was regulated by slowly increasing the duration of the action potential through progressive block of potassium channels. The amplitude of the calcium transient, measured from a cluster of varicosities, was linearly related to the duration of the action potential with a slope of 1.2. Gradual changes in potassium channel block allowed us to estimate the calcium cooperativity of transmitter release over a 10-fold range in presynaptic calcium influx. Calcium cooperativity measured here exhibited one component with an average value of 3.1. Inspection of simultaneously recorded presynaptic calcium transients and inhibitory postsynaptic currents (IPSCs) showed that prolonged action potentials were associated with a slow rising phase of presynaptic calcium transients, which were matched by a slow rate of rise of IPSCs. The close correlation suggests that fluorescence transients provide information on the rate of calcium influx. Because there is an anatomic mismatch between the presynaptic calcium transient, measured from a cluster of varicosities, and IPSC, measured with two-electrode voltage clamp, macropatch recording was used to monitor inhibitory postsynaptic responses from the same cluster of varicosities from which the calcium transient was measured. Inhibitory postsynaptic responses recorded with the macropatch method exhibited a faster rising phase than that recorded with two-electrode voltage clamp. This difference could be attributed to slight asynchrony of transmitter release due to action potential conduction along fine branches. In conclusion, this report shows that fluorescence transients generated by calcium-sensitive dyes can provide insights to the properties of presynaptic calcium influx, and its correlation with transmitter release, at a high time resolution.

Neutron flux measurement provides essential data for the diagnostic tools that control plasma combustion, equipment maintenance, and radiation safety and reveals key information on plasma physics, machine protection, and control issues. To obtain rapid change of the neutron emission rate by magnetohydrodynamic instabilities, a fast neutron flux measurement system with high time resolution (~10 ) was developed on the HL-2M tokamak (located at Southwestern Institute of Physics, China). The system includes four EJ-410 detectors and four digitizers that we developed ourselves with dedicated field-programmable gate array firmware, including a waveform recording function, real-time count rate measurement, and real-time integration measurement. The simulation results show that the throughput rate of the readout electronics is 96.7% when the input counting rate is 1 mega count per second (Mcps) and the throughput rate could achieve 63.8% when the input counting rate is 6 Mcps. Moreover, when the input counting rate increases further to 10 Mcps, the integration model may be used. Given that this measurement system is highly portable and has a high time resolution, it is suitable for the fast neutron flux diagnostic on the HL-2A tokamak.

<bold>Background</bold>Time resolution is crucial in positron annihilation lifetime measurement techniques, directly affecting the detection accuracy of microstructural defects in materials. Improving time resolution remains a key development direction for positron lifetime spectrometers.<bold>Purpose</bold>This study aims to develop a novel two-dimensional positron annihilation lifetime measurement method with high time resolution and high peak-to-valley ratio for enhanced characterization of material microstructures.<bold>Methods</bold>A three-detector coincidence system was constructed using BaF₂ scintillators coupled with photomultiplier tubes, where all gamma rays from a single annihilation event were simultaneously detected. Firstly, the system measured positron lifetimes through both "A-Start &amp; B-Stop" and "A-Start &amp; C-Stop" detector combinations to obtain two-dimensional lifetime spectra with <italic>T</italic>₁ and <italic>T</italic>₂ as coordinate axes. Then, time resolution functions were extracted by analyzing the distribution perpendicular to the <italic>T</italic>₁ = <italic>T</italic>₂ diagonal line. Finally, the two-dimensional spectra were diagonalized to convert into one-dimensional lifetime spectra for comparison with conventional methods.<bold>Results</bold>Experimental results show that the time resolution for detecting 0.511 MeV annihilation gamma rays reaches 142 ps (Full width at Half Maximum, FWHM), representing a 29% improvement over conventional single-photon detection. The system time resolution achieves 156 ps compared to 188 ps for conventional two-channel coincidence methods, showing a 87% enhancement factor that matches theoretical predictions. The peak-to-valley ratio of the diagonalized two-dimensional lifetime spectrum reaches 2.3×10⁴, representing a 40% improvement over triple-detector coincidence measurements.<bold>Conclusion</bold>The two-dimensional positron annihilation lifetime measurement method proposed in this study significantly enhances both time resolution and peak-to-valley ratio through comprehensive detection of temporal and lifetime information from all gamma rays in annihilation events. The achieved time resolution improvement of 15% and peak-to-valley ratio enhancement of 40% provide new capabilities for high-performance spectrometer development and accurate characterization of material microdefects.

Time-Frequency (TF) analyses have been widely used to analyze some nonstationary signals like speech and biological signals. Cohen's class TF distribution has a high resolution in time and frequency and becomes a powerful tool for nonstationary signal analysis. In order to apply the TF analysis using a novel kernel to biological signals, the authors investigated a higher resolution kernel for the ultrasound Doppler signal. The authors would like to apply the TF analysis to blood flow signal analysis. They measured the ultrasound Doppler signal which was obtained in olive oil with a steel ball moving to and fro in the continuous ultrasound. The movement of the steel ball was controlled by various functions. The authors used three kinds of kernel: (1) the Wigner distribution, (2) the Choi-Williams distribution (ED), and (3) the authors' new kernel (named eight figure-kernel), that has high resolution. The results show that the demodulation accuracy with the authors' new kernel is higher and the negative components are smaller than the ED, which makes the cross-term small.

Abstract. PM1 (particulate matter with an aerodynamic diameter &lt;1 μm) non-refractory components and black carbon were measured continuously together with additional air quality and atmospheric parameters at an urban background site in Barcelona, Spain, during March 2009 (campaign DAURE, Determination of the sources of atmospheric Aerosols in Urban and Rural Environments in the western Mediterranean). Positive matrix factorization (PMF) was conducted on the organic aerosol (OA) data matrix measured by an aerosol mass spectrometer, on both unit mass (UMR) and high resolution (HR) data. Five factors or sources could be identified: LV-OOA (low-volatility oxygenated OA), related to regional, aged secondary OA; SV-OOA (semi-volatile oxygenated OA), a fresher oxygenated OA; HOA (hydrocarbon-like OA, related to traffic emissions); BBOA (biomass burning OA) from domestic heating or agricultural biomass burning activities; and COA (cooking OA). LV-OOA contributed 28% to OA, SV-OOA 27%, COA 17%, HOA 16%, and BBOA 11%. The COA HR spectrum contained substantial signal from oxygenated ions (O:C: 0.21) whereas the HR HOA spectrum had almost exclusively contributions from chemically reduced ions (O:C: 0.03). If we assume that the carbon in HOA is fossil while that in COA and BBOA is modern, primary OA in Barcelona contains a surprisingly high fraction (59%) of non-fossil carbon. This paper presents a method for estimating cooking organic aerosol in ambient datasets based on the fractions of organic mass fragments at m/z 55 and 57: their data points fall into a V-shape in a scatter plot, with strongly influenced HOA data aligned to the right arm and strongly influenced COA data points aligned to the left arm. HR data show that this differentiation is mainly driven by the oxygen-containing ions C3H3O+ and C3H5O+, even though their contributions to m/z 55 and 57 are low compared to the reduced ions C4H7+ and C4H9+. A simple estimation method based on the markers m/z 55, 57, and 44 is developed here and allows for a first-order-estimation of COA in urban air. This study emphasizes the importance of cooking activities for ambient air quality and confirms the importance of chemical composition measurements with a high mass and time resolution.

The generation of spectral mutants of the green fluorescent protein (GFP) set the stage for multiple-color imaging in living cells. However, the use of this technique has been limited by a spectral overlap of the available GFP mutants and/or by insufficient resolution in both time and space. Using a new setup for dual-color imaging, we demonstrate here the visualization of small, fast moving vesicular structures with a high time resolution. Two GFP-fusion proteins were generated: human chromogranin B, a secretory granule matrix protein, and phogrin, a secretory granule membrane protein. They were tagged with enhanced yellow fluorescent protein (EYFP) and enhanced cyan fluorescent protein (ECFP), respectively. Both fusion proteins were cotransfected in Vero cells, a cell line from green monkey kidney. EYFP and ECFP were excited sequentially at high time rates using a monochromator. Charged coupled device (CCD)-based image acquisition resulted in 5-8 dual-color images per second, with a resolution sufficient to detect transport vesicles in mammalian cells. Under these conditions, a fully automated time-resolved analysis of the movement of color-coded objects was achieved. The development of specialized software permitted the analysis of the extent of colocalization between the two differentially labeled sets of cellular structures over time. This technical advance will provide an important tool to study the dynamic interactions of subcellular structures in living cells.

The importance of reactive halogen species (particularly halogen oxides) in the troposphere is due to their strong effect on tropospheric ozone levels, which has been first discovered during surface ozone depletion episodes in the polar boundary layer after polar sunrise (bromine oxide, BrO). Halogen oxides have also been reported from mid-latitude coastal sites (iodine oxide, IO and iodine dioxide, OIO) and from the Dead Sea basin (BrO). Results from the field studies performed in framework of this thesis at Arctic and mid- latitude locations are presented here. BrO and its vertical profile near the ground has been observed during surface ozone destruction in the Canadian high and low Arctic. First simultaneous measurements of BrO and IO in the Arctic boundary layer were performed by ground-based MAX-DOAS, which was developed within this work. The measurements at the Hudson Bay represent the southernmost and first direct observations of Arctic surface ozone losses due to BrO and allowed for the first time to study the day and nighttime chemistry of BrO at high time resolution. Molecular bromine was inferred to be a major reservoir compound during the night, initiating sunrise ozone destruction upon photolysis. The first simultaneous measurements of BrO and gas phase elemental mercury at high time resolution in the Canadian Arctic support the proposed key role of BrO as oxidant for mercury in the gas phase during polar springtime. Further measurements of halogen oxides at clean and moderately polluted mid-latitude coastal sites yielded new field data on halogen oxide concentrations and upper limits at different pollution levels.

A spatial and temporal fluctuation microscope (STFM) was developed for fast imaging as well as the measurement and visualisation of mobilites and interactions of fluorescently labeled particles. The instrument extends the concept of a point confocal laser-scanning microscope to illumination and detection along a line. For the construction and application of the STFM, theoretical descriptions of the beam geometry, the point spread functions and the fluorescence auto- and cross-correlation fit functions were derived. The final system provids fast confocal imaging up to 30 images per second and allows for the spatially resolved detection of particle concentration fluctuations down to 15 μs time resolution at hundreds of points in parallel. An optical resolution of 200 x 380 x 700 nm in x-, y- and z-direction was determined experimentally, and the spatially resolved fluctuations of fluorescent quantum dots were evaluated. Finally, the capabilities of the STFM in terms of fast imaging and mobility measurements were applied to studies of PML nuclear bodies and green fluorescent protein in living cells. Both the in vitro and the in vivo fluorescence correlation spectroscopy experiments conducted with the STFM were compared to single point measurements with a commercial point-confocal microscope and FCS setup. The results demonstrate the unique capabilities of the STFM for the characterisation of position-dependent diffusive translocations of macromolecules in the cell with very high time resolution.