Independent Data Acquisition Research Articles

Modeling of ion beam induced charge sharing experiments for the design of high resolution position sensitive detectors

In a multi-electrode device, the motion of free charge carriers generated by ionizing radiation induces currents on all the electrodes surrounding the active region [1]. The amount of charge induced in each sensitive electrode is a function of the device geometry, the transport parameters and the generation profile. Hence this charge sharing effect allows the signal from each sensitive electrode to provide information about the electrical characteristics of the device, as well as information on the location and the profile of each ionization track.The effectiveness of such approach was recently demonstrated in Ion Beam Induced Charge (IBIC) experiments carried out using a 2MeV He microbeam scanning over a sub-100μm scale silicon device, where the ion strike location point was evaluated through a comparative analysis of the charge induced in two independent surface electrodes coupled to independent data acquisition systems [2].In this report, we show that the Monte Carlo method [3] can be efficiently exploited to simulate this IBIC experiment and to model the experimental data, shedding light on the role played by carrier diffusion, electronic noise and ion beam spot size on the induction of charge in the sensitive electrodes. Moreover, the Monte Carlo method shows that information on the ion strike position can be obtained from the charge signals from the sensitive electrodes.

Receiving And Data Acquisition Systems Of Rt-32 For Vlbi Observations / Rt-32 Uztveršanas Un Datu Reģistrācijas Sistēmas Vlbi Novērojumiem

Abstract Radiotelescope RT-32 is a fully steerable 32-m parabolic antenna located at Irbene and belonging to Ventspils International Radio Astronomy Centre (VIRAC). Currently, the work on upgrading and repair of its receiving hardware and data acquisition systems is of high priority for the VIRAC. One of the main scientific objectives for the VIRAC Radioastronomical observatory is VLBI (very long baseline interferometry) observations in centimetre wavelengths in collaboration with world VLBI networks, such as European VLBI network (EVN), Low Frequency VLBI network (LFVN), and others. During the last years the room in the secondary focus of telescope was reconstructed, and several new receivers were installed. Currently, RT-32 observations are carried out in four different bands: 92 cm, 18 cm, 6 cm, and 2.5 cm. First three of them are already successfully employed in diversified VLBI experiments. The receiver on 2.5 cm band has only one linear polarized chain and is used mainly for the methanol maser single dish observations. The apparatus system of RT-32 is equipped with two independent VLBI data acquisition systems: TN-16, and DBBC in combination with MK5b. Both systems are employed in interferometric observations depending on the purpose of experiment and the enabled radiotelescopes. The current status of RT-32, the availability of its receiving and data acquisition units for VLBI observations and the previous VLBI sessions are discussed.

A novel time stamping technique for distributed data acquisition systems

In this paper, we discuss the design and implementation of a synchronizing technique for data acquisition systems, which can effectively use the normal, standard local area network cables to provide a time stamp, with a range up to 32 days, resolution of 10 ns, and synchronization within ± 5 ns. This system may be used to synchronize data being collected by independent heterogeneous data acquisition modules, that acquire events independently. Such distributed systems are generally designed with a tree-like structure or independent self-triggered acquisition boxes. These leaf edges are connected through branches to the root node, via non-bus based inter-connecting links. The present system has been tested with a set of self-triggered digital signal processing based data acquisition engines, having a 100 MHz analog to digital converter front end.

A Prototype Detector for a Novel High-Resolution PET System: BazookaPET.

We have designed and are developing a novel proof-of-concept PET system called BazookaPET. In order to complete the PET configuration, at least two detector elements are required to detect positron-electron annihilation events. Each detector element of the BazookaPET has two independent data acquisition channels. One side of the scintillation crystal is optically coupled to a 4×4 silicon photomultiplier (SiPM) array and the other side is a CCD-based gamma camera. Using these two separate channels, we can obtain data with high energy, temporal and spatial resolution data by associating the data outputs via several maximum-likelihood estimation (MLE) steps. In this work, we present the concept of the system and the prototype detector element. We focus on characterizing individual detector channels, and initial experimental calibration results are shown along with preliminary performance-evaluation results. We measured energy resolution and the integrated traces of the slit-beam images from both detector channel outputs. A photo-peak energy resolution of ~5.3% FWHM was obtained from the SiPM and ~48% FWHM from the CCD at 662 keV. We assumed SiPM signals follow Gaussian statistics and estimated the 2D interaction position using MLE. Based on our the calibration experiments, we computed the Cramér-Rao bound (CRB) for the SiPM detector channel and found that the CRB resolution is better than 1 mm in the center of the crystal.

Atomic resolution ultrafast scanning tunneling microscope with scan rate breaking the resonant frequency of a quartz tuning fork resonator

We present an ultra-fast scanning tunneling microscope with atomic resolution at 26 kHz scan rate which surpasses the resonant frequency of the quartz tuning fork resonator used as the fast scan actuator. The main improvements employed in achieving this new record are (1) fully low voltage design (2) independent scan control and data acquisition, where the tuning fork (carrying a tip) is blindly driven to scan by a function generator with the scan voltage and tunneling current (I(T)) being measured as image data (this is unlike the traditional point-by-point move and measure method where data acquisition and scan control are switched many times).

Charge sharing in multi-electrode devices for deterministic doping studied by IBIC

Following a single ion strike in a semiconductor device the induced charge distribution changes rapidly with time and space. This phenomenon has important applications to the sensing of ionizing radiation with applications as diverse as deterministic doping in semiconductor devices to radiation dosimetry. We have developed a new method for the investigation of this phenomenon by using a nuclear microprobe and the technique of Ion Beam Induced Charge (IBIC) applied to a specially configured sub-100μm scale silicon device fitted with two independent surface electrodes coupled to independent data acquisition systems. The separation between the electrodes is comparable to the range of the 2MeV He ions used in our experiments. This system allows us to integrate the total charge induced in the device by summing the signals from the independent electrodes and to measure the sharing of charge between the electrodes as a function of the ion strike location as a nuclear microprobe beam is scanned over the sensitive region of the device. It was found that for a given ion strike location the charge sharing between the electrodes allowed the beam-strike location to be determined to higher precision than the probe resolution. This result has potential application to the development of a deterministic doping technique where counted ion implantation is used to fabricate devices that exploit the quantum mechanical attributes of the implanted ions.

Simultaneous eicosanoid profiling and identification by liquid chromatography and hybrid triple quadrupole-linear ion trap mass spectrometry for metabolomic studies in human plasma / Multiparametrische Bestimmung und Identifizierung von Eikosanoiden mit Flüssigchromatographie in Kombination mit Hybrid-Quadrupol/lineare Ionenfallen Massenspektrometrie für Metabolom-Studien in Humanplasma

Abstract Eicosanoids play a key role in many physiological and pathological processes and might therefore serve as interesting diagnostic targets. Methods for the analysis of arachidonic acid metabolites in cells and body fluids require high sensitivity and specificity because of the very low concentrations, similar chemical structures and short half-lives of these metabolites. We established a mass spectrometric method for the simultaneous identification and quantification of arachidonic acid metabolites in human plasma samples using solid phase extraction followed by liquid chromatography (LC) and hybrid triple quadrupole-linear ion trap (QqLIT) mass spectrometry. Quantitative analysis was performed using the 4000 QTrap tandem mass spectrometer in multiple reaction monitoring (MRM) mode. As part of an independent data acquisition experiment MRMs were used as survey scans, which dependently triggered enhanced product ion (EPI) scans. Compound identification was carried out by library search using a library based on EPI spectra of standard components (prostaglandins, thromboxanes, leukotrienes and isoprostanes). The newly developed compound library enables the verification of known and structural elucidation of unknown eicosanoid metabolites in human plasma. In conclusion, our mass spectrometric method allows the simultaneous identification and quantification of arachidonic acid metabolites in one single LC-MS/MS run.

Identification and Quantitation of Newly Synthesized Proteins in Escherichia coli by Enrichment of Azidohomoalanine-labeled Peptides with Diagonal Chromatography

A method is presented to identify and quantify several hundreds of newly synthesized proteins in Escherichia coli upon pulse labeling cells with the methionine analogue azidohomoalanine (azhal). For the first 30 min after inoculation, a methionine-auxotrophic strain grows equally well on azhal as on methionine. Upon a pulse of 15 min and digestion of total protein, azhal-labeled peptides are isolated by a retention time shift between two reversed phase chromatographic runs. The retention time shift is induced by a reaction selective for the azido group in labeled peptides using tris(2-carboxyethyl)phosphine. Selectively modified peptides are identified by reversed phase liquid chromatography and on-line tandem mass spectrometry. We identified 527 proteins representative of all major Gene Ontology categories. Comparing the relative amounts of 344 proteins synthesized in 15 min upon a switch of growth temperature from 37 to 44 degrees C showed that nearly 20% increased or decreased more than 2-fold. Among the most up-regulated proteins many were chaperones and proteases in accordance with the cells response to unfolded proteins due to heat stress. Comparison of our data with results from previous microarray experiments revealed the importance of regulation of gene expression at the level of transcription of the most elevated proteins under heat shock conditions and enabled identification of several candidate genes whose expression may predominantly be regulated at the level of translation. This work demonstrates for the first time the use of a bioorthogonal amino acid for proteome-wide detection of changes in the amounts of proteins synthesized during a brief period upon variations in cellular growth conditions. Comparison of such data with relative mRNA levels enables assessment of the separate contributions of transcription and translation to the regulation of gene expression.

Experimental evaluation of local instantaneous heat transfer characteristics in the combustion chamber of air-cooled direct injection diesel engine

An experimental analysis is conducted investigating the differences between the variations of overall and local instantaneous heat transfer coefficients, during the engine cycle, in the combustion chamber walls of a direct injection (DI), air-cooled diesel engine located at the authors’ laboratory. For this purpose, a novel experimental installation is developed, which separates the engine transient temperature signals into two parts, namely the long- and the short-term response ones, processed in two independent data acquisition systems. Moreover, a new pre-amplification unit for fast response thermocouples, appropriate heat flux sensors and an object-oriented control code for fast data acquisition have been designed and applied. Experimentally obtained cylinder pressure diagrams are used as a basis for the calculation of the overall heat transfer coefficients, whereas one-dimensional heat conduction theory with Fourier analysis techniques, combined with an iterative procedure between calculated and measured temperature data, are implemented in order to calculate the instantaneous local heat transfer coefficients in the engine cylinder. Analysis of the experimental results reveals interesting aspects of transient engine heat transfer. Significant differences are disclosed between the overall and local heat transfer coefficient variations, with the importance of the latter one on engine design being emphasized. The local heat transfer coefficient on the cylinder head is quantified based on the experimental data. The effect of engine speed and load as well as of the air swirling motion on the heat transfer variations are presented. From the analysis results it is concluded that the instantaneous heat transfer variation is non-uniform, unlike its values calculated from standard correlations that assume spatial uniformity, noting that such information, especially for air-cooled diesel engines, seems to be very scarce in the open literature.

Scanning force microscopy three-dimensional modes applied to conductivity measurementsthrough linear-chain organic SAMs

We present here a new approach, based on the use of three-dimensional operation modes ofscanning force microscopy. The protocol used reveals the advantages of independent butsimultaneous data acquisition to discriminate between different interaction regimesand obtain accurate measurements. The procedure is applied to investigate theconducting characteristics of submonolayer linear-chain organic films for whichthe bare metallic substrate provides an excellent in situ reference for molecularlattice periodicity, film thickness determination and conductivity measurements.

Screening for basic drugs in equine urine using direct-injection differential-gradient LC–LC coupled to hybrid tandem MS/MS

A rapid, selective and robust direct-injection LC/hybrid tandem MS method has been developed for simultaneous screening of more than 250 basic drugs in the supernatant of enzyme hydrolysed equine urine. Analytes, trapped using a short HLB extraction column, are refocused and separated on a Sunfire C(18) analytical column using a controlled differential gradient generated by proportional dilution of the first column's eluent with water. Independent data acquisition (IDA) was configured to trigger a sensitive enhanced product ion (EPI) scan when a multiple reaction monitoring (MRM) survey scan signal exceeded the defined criteria. The decision on whether or not to report a sample as a positive result was based upon both the presence of a MRM response within the correct retention time range and a qualitative match between the EPI spectrum obtained and the corresponding reference standard. Ninety seven percent of the drugs targeted by this method met our detection criteria when spiked into urine at 100 ng/ml; 199 were found at 10 ng/ml, 83 at 1 ng/ml and 4 at 0.1 ng/ml.

Quantitative Proteomic Analysis Using Isobaric Protein Tags Enables Rapid Comparison of Changes in Transcript and Protein Levels in Transformed Cells

Isobaric tags for relative and absolute quantitation, an approach to concurrent, relative quantification of proteins present in four cell preparations, have recently been described. To validate this approach using complex mammalian cell samples that show subtle differences in protein levels, a model stem cell-like cell line (FDCP-mix) in the presence or absence of the leukemogenic oncogene TEL/PDGFRbeta has been studied. Cell lysates were proteolytically digested, and peptides within each sample were labeled with one of four isobaric, isotope-coded tags via their N-terminal and/or lysine side chains. The four labeled samples are mixed and peptides separated by two-dimensional liquid chromatography online to a mass spectrometer (LC-MS). Upon peptide fragmentation, each tag releases a distinct mass reporter ion; the ratio of the four reporters therefore gives relative abundances of the given peptide. Relative quantification of proteins is derived using summed data from a number of peptides. TEL/PDGFRbeta leukemic oncogene-mediated changes in protein levels were compared with those seen in microarray analysis of control and transfected FDCP-mix cells. Changes at the protein level in most cases reflected those seen at the transcriptome level. Nonetheless, novel differences in protein expression were found that indicate potential mechanisms for effects of this oncogene.

Three-dimensional (3D) ultrasound--a useful imaging technique in the assessment of neonatal brain.

Clinical application of ultrasound began about fifty years ago. From one-dimensional A-mode, through two-dimensional real time and Doppler examinations, a new era in clinical ultrasonography then began in the late eighties. Development of computer technology enabled introduction of 3D ultrasonography into clinical practice. In obstetrics ultrasound revolutionized fetal follow-up, but it was as important for the detection of intracranial pathology during the neonatal period and infancy. Two-dimensional real time ultrasonography was [table: see text] an exciting method that changed our understanding of the prevalence and pathophysiology of brain pathology in premature and term infants. Will application of 3D ultrasonography bring any substantial improvement to neuroimaging diagnostics in the newborn period? This article attempts to find the answer to this question, despite the limitations set by the short period of application of 3D neurosonography in neonates. The advantages of 3D brain ultrasonography application in neonates are: quicker and observer independent data acquisition, the possibility of off-line data analysis, projection of 3D data on a 2D plane with volumetric, color and power Doppler studies. Unavailability of equipment is the main reason why 3D ultrasonography was performed in only half of the newborns in whom it was indicated. Cost of equipment prevents introduction of 3D as a standard diagnostic procedure in neonates, although its diagnostic value is indisputable.

Experimental instantaneous heat fluxes in the cylinder head and exhaust manifold of an air-cooled diesel engine

An experimental analysis is performed to study the instantaneous heat fluxes, during the engine cycle, in the combustion chamber walls of a direct injection (DI), air cooled, four stroke, Diesel engine located at the authors laboratory. For this purpose, a novel experimental installation has been developed, which separates the engine transient temperature signals into two parts, namely the ‘long’ and the ‘short’ term response ones, followed by their discrete processing in two independent data acquisition systems. Furthermore, a new pre-amplification unit for fast response thermocouples, appropriate heat flux sensors and an innovative, object oriented, control code for fast data acquisition have been designed and developed for the needs of the study. One dimensional heat conduction with Fourier analysis of the raw temperature data are implemented in order to calculate the instantaneous engine cylinder and exhaust pipe heat fluxes. Analysis of the experimental results reveal many interesting aspects of transient engine heat transfer. The effect of engine speed on cylinder head and exhaust manifold heat losses is presented. The simultaneous presentation of heat fluxes on the cylinder head and exhaust manifold, together with the engine indicator diagram, sheds light into the mechanisms governing the transient heat transfer. This is very important, since especially for air cooled Diesel engines, limited information seems to exist in the relevant literature.

Driving Stresses in Fiberglass Pretensioned Piles

Four 25 ft long x 10 inch square fiberglass pretensioned piles, two with steel spirals and two with fiberglass spirals, were driven through dense to very dense sands by a 3-kp drop hammer. Two identical steel pretensioned piles were also driven at the same site to assess the performance of the fiberglass piles. The piles were instrumented by strain gages attached to the prestressing strands and by reusable strain gages/accelerometers attached to the concrete surface near the pile top. Driving stresses were monitored using a pile dynamic analyzer and by an independent data acquisition system. The test results showed that the performance of the fiberglass spirals was inferior to that of the steel.

Structural acoustic laboratories at NRL in Washington, DC

The Physical Acoustics Branch at NRL operates three main laboratories in its prosecution of structural acoustics and related experimental programs. These laboratories serve as the Navy’s principle experimental capability for conducting small scale scattering and radiation studies in water; they are also used for developing advanced sensor technologies such as interferometric fiber optic strain sensors and for conducting some large scale studies. The most recent of these capabilities to come about is NRL’s new LSA (Laboratory for Structural Acoustics) which has several unique features. The heart of this new lab is a one-million-gallon, vibration isolated, temperature-controlled cylindrical tank. It is equipped with two in-water robotic scanners that possess 1-mil repeatability over their 14-×8-×8-ft work spaces, thus allowing for the acquisition of highly precise near-field holographic scattering and radiation data. The NRL laboratories are also equipped with state-of-the-art line and planar sources that allow for the uniform ensonification of test structures, as well as with near-field projection codes for reconstructing surface pressures, normal components of velocity, and far-field information. All laboratories are fully networked and supported by physically independent data acquisition systems that are rigorously maintained to uniform hardware and software standards.

A distributed data-acquisition system for gamma spectral analysis

The neutron-activation analysis staff at Los Alamos National Laboratory's Omega West Reactor has designed and constructed a distributed data-acquisition system for handling a large volume of gamma-ray spectra. Currently the system consists of five independent data-acquisition stations connected to a number of workstations via an Ethernet network. Each data-acquisition station supports up to eight detectors operating simultaneously and is capable of initiating automatic sample manipulation including, but not limited to, sample loading, irradiation, spectrum recording and spectrum storage. Control of the data-acquisition station can be accomplished locally with a computer terminal directly connected to the data-acquisition station or via a workstation connected to the network.

Experimental limit for the circular polarization of the 1081 keV gamma ray in 18F.

A measurement of the circular polarization ${P}_{\ensuremath{\gamma}}$ of the 1081 keV \ensuremath{\gamma}-ray in $^{18}\mathrm{F}$ is reported. The result is ${P}_{\ensuremath{\gamma}}$=(2.7\ifmmode\pm\else\textpm\fi{}5.7)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$. The reaction used was $^{16}\mathrm{O}$${(}^{3}$He,p${)}^{18}$F with a 3.4 MeV $^{3}\mathrm{He}^{+}$ beam of an intensity of 7 \ensuremath{\mu}A impinging on a windowless water target. The circular polarization was measured with a four-prong transmission-type Compton polarimeter. The measurement of the analyzing power of the polarimeter is presented. Gamma rays were detected by means of 130 ${\mathrm{cm}}^{3}$ p-type germanium detectors placed behind the prongs. Four independent data acquisition channels were used: pile-up losses at a counting rate of 60 kcps were kept lower than 15%, owing to the use of trapezoidal shapers. Systematic effects of instrumental origin are discussed and found to give negligible contributions with respect to the statistical uncertainty. The calculation of the asymmetries is performed using different estimators; an extensive comparison of the various methods is presented. The result of the experiment, when averaged with those of the other experiments on $^{18}\mathrm{F}$ carried out until now, gives a grand average ${P}_{\ensuremath{\gamma}}$=(1.2\ifmmode\pm\else\textpm\fi{}3.9)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$. This result is compared with recent theoretical estimates.