Search results for "Signal"
showing 10 items of 6924 documents
Intrapulmonary 3He Gas Distribution Depending on Bolus Size and Temporal Bolus Placement
2008
OBJECTIVE: Dynamic ventilation (3)He-MRI is a new method to assess pulmonary gas inflow. As differing airway diameters throughout the ventilatory cycle can influence gas inflow this study intends to investigate the influence of volume and timing of a He gas bolus with respect to the beginning of the tidal volume on inspiratory gas distribution. MATERIALS AND METHODS: An ultrafast 2-dimensional spoiled gradient echo sequence (temporal resolution 100 milliseconds) was used for dynamic ventilation (3)He-MRI of 11 anesthetized and mechanically ventilated pigs. The applied (3)He gas bolus was varied in volume between 100 and 200 mL. A 150-mL bolus was varied in its application time after the beg…
Numerical approach for signal delay in general distributed networks
2003
The authors consider a general network with telegraph equations modelling distributed elements and having, additionally, nonlinear capacitors. A global asymptotic exponential stability of the solution is given. A simple computable upper bound of the delay time is given. Numerical examples illustrate the usefulness of the results. >
Signal integrity studies at optical multiplexer board for TileCal system
2007
6 pages.-- ISI Article Identifier: 000253651800006
Radial properties of high-frequency electrodeless lamps in argon–mercury mixtures
2005
Radial emission properties of high-frequency electrodeless discharge lamps (HFEDLs) in argon–mercury mixtures are investigated both numerically and experimentally. The radial profile of the intensities of the mercury triplet lines 404.7, 435.8 and 546.1 nm are measured for two different values of the high frequency generator power. A model describing physical processes in an HFEDL, including the calculation of radial plasma parameters, is developed. Radial intensity dependences of the lines 404.7, 435.8 and 546.1 nm are calculated and are found to be in good agreement with the experimental measurements.
Improving the performance of acousto-optic tunable filters in imaging applications
2010
Acousto-optic tunable filters (AOTFs) can be used as spectral filters for the implementation of multispectral imaging systems. However, obtaining quality images is challenging. In this work, we propose several improvements that enable the use of these systems in quantitative spectroscopic imaging applications. The improvements are based on three pillars: 1. a finer spectral bandpass shaping by dynamically optimizing the radio frequency (rf) driving signal, 2. an extensive calibration process, and 3. careful image preprocessing that uses calibration data to correct some well known AOTF issues in imaging applications. A novel multispectral imaging instrument is built using commercial off-the-…
Generation of multidimensional random pulses for radioactivity measurements
2000
Multidimensional binary pseudo-random pulses are extremely useful for the set-up calibration and testing of radioactivity measuring equipment. A new method of generation of such signals, based on the parting operation of labeled pulse trains, is presented. The concept of a general coincidence ratio is introduced. Digital window comparators and prohibited or permitted state programmers capable of performing the parting operation and controlling the values of the coincidence ratio are proposed.
Configurable Passband Imaging Spectrometer Based on Acousto-optic Tunable Filter
2008
This work presents a new configurable imaging spectrometer called Autonomous Tunable Filtering System (ATFS). The system can be configured to acquire a single narrow spectral band, a composite multispectral image, or a broad pass-band. This flexibility is given by the use of an Acousto-Optic Tunable Filter (AOTF) driven by a programmable radio frequency (rf) signal generator. The AOTF acts as a light-diffraction element which output wavelength is selected by the frequency of an rf signal applied to it. The designed rf driver is based on a high-speed Digital-to-Analog converter, which can synthesize any composite rf waveform formed by a combination of sine signals. The images are formed thro…
Disease Biomarkers: Modelling MR Spectroscopy and Clinical Applications
2012
Clinical MRS has become a reference technique for in vivo evaluating the metabolism of different tissues, with special application to brain and prostate lesion characterization and tumour’s follow-up. It allows detecting relevant changes that cannot be appreciated in the conventional MR images. Nowadays, MRS has been widely applied in many different brain pathologies with excellent results as a disease biomarker. Since the different diseases and grades have different manifestations in the spectroscopic profile, a deep understanding of the subjacent biology is needed for the signal interpretation. The development of high-field (≥3 T) scanners has permitted the acquisition of high-quality MRS…
The membrane anchor of microsomal epoxide hydrolase from human, rat, and rabbit displays an unexpected membrane topology.
1997
The microsomal epoxide hydrolase (mEH) and cytochrome P450s catalyze the sequential formation of carcinogenic metabolites. According to one algorithm for predicting the membrane topology of proteins, the human, the rabbit, and the rat mEH should adopt a type II topology. The type II topology is also predicted by a recently established neuronal network which is trained to recognize signal peptides with very high accuracy. In contrast to these predictions we find, based on N-glycosylation analysis in a cell-free and in a cellular system, that the membrane anchor of human, rat, and rabbit mEH displays a type I topology. This result is correctly predicted by the positive inside rule in which ne…
Apical transport of osteopontin is independent of N-glycosylation and sialylation.
2002
Studies of how epithelial surface polarity into apical and basolateral domains is generated and maintained have proposed that carbohydrate modifications serve as apical targeting signals for proteins by interacting with lectin sorters. However, the experimental evidence in support of N-glycans, O-glycans and sialic acids mediating apical transport is still very controversial. This could be partly due to the fact that in most studies exogenously expressed proteins were analysed. One has, therefore, examined the role of carbohydrate moieties in apical targeting of the endogenous secretory protein osteopontin in MDCK cells. It was found, however, that sorting of osteopontin does not require N-…