Fourier Analysis Research Papers - Academia.edu (original) (raw)

O f all birth defects, congenital heart defects are the most frequent cause of death among infants in the US. The state-of-the-art approach to repair congenital heart defects is open heart reconstructive surgery in the neonatal period.... more

O f all birth defects, congenital heart defects are the most frequent cause of death among infants in the US. The state-of-the-art approach to repair congenital heart defects is open heart reconstructive surgery in the neonatal period. Complications that can occur as a result of these complex surgeries are sinus node dysfunction or atrioventricular block arising from trauma to the sinoatrial node (SAN) and atrioventricular node (AVN), respectively. These complications are associated with significant morbidity and mortality. 2 Patients with persistent complications require short-term or chronic cardiac rhythm management using implantable pacemakers. The need for permanent pacemakers after repair for congenital cardiac defects ranges from 1% to 3% for ventricular septal defect to as high as 27% to 45% for congenitally corrected transposition of the great arteries. The SAN, AVN, and other tissues of the conduction pathways are not visible using surgical loupes or microscopes. These instruments are based on reflection of light from the tissue surface and do not provide visual information from within the tissue, where nodal tissue resides. The localization of SAN and AVN tissue during surgery is based on their relative proximity to anatomic landmarks. The SAN is usually located proximal to the crista terminalis in the right atrium. The AVN is adjacent to the atrioventricular septum of the heart. Commonly, the AVN is identified from the triangle of Koch, which is defined as the space between the septal leaflet of the tricuspid valve, coronary sinus, and the tendon of Todaro. In hearts with congenital defects this localization is made more difficult by individual variations in the spatial relationship of landmarks to nodal structures. The aforementioned postoperative complications can arise as a result of this imprecise methodology for localization of nodal tissue. Thus, imaging Background-Risks associated with pediatric reconstructive heart surgery include injury of the sinoatrial node (SAN) and atrioventricular node (AVN), requiring cardiac rhythm management using implantable pacemakers. These injuries are the result of difficulties in identifying nodal tissues intraoperatively. Here we describe an approach based on confocal microscopy and extracellular fluorophores to quantify tissue microstructure and identify nodal tissue. Methods and Results-Using conventional 3-dimensional confocal microscopy we investigated the microstructural arrangement of SAN, AVN, and atrial working myocardium (AWM) in fixed rat heart. AWM exhibited a regular striated arrangement of the extracellular space. In contrast, SAN and AVN had an irregular, reticulated arrangement. AWM, SAN, and AVN tissues were beneath a thin surface layer of tissue that did not obstruct confocal microscopic imaging. Subsequently, we imaged tissues in living rat hearts with real-time fiber-optics confocal microscopy. Fiber-optics confocal microscopy images resembled images acquired with conventional confocal microscopy. We investigated spatial regularity of tissue microstructure from Fourier analysis and second-order image moments. Fourier analysis of fiber-optics confocal microscopy images showed that the spatial regularity of AWM was greater than that of nodal tissues (37.5±5.0% versus 24.3±3.9% for SAN and 23.8±3.7% for AVN; P<0.05). Similar differences of spatial regularities were revealed from second-order image moments (50.0±7.3% for AWM versus 29.3±6.7% for SAN and 27.3±5.5% for AVN; P<0.05). Conclusions-The study demonstrates feasibility of identifying nodal tissue in living heart using extracellular fluorophores and fiber-optics confocal microscopy. Application of the approach in pediatric reconstructive heart surgery may reduce risks of injuring nodal tissues. (Circ Cardiovasc Imaging. 2013;6:739-746.

Cognition is thought to result from interactions within large-scale networks of brain regions. Here we propose a method to identify these large-scale networks using functional magnetic resonance imaging (fMRI). Regions belonging to such... more

Cognition is thought to result from interactions within large-scale networks of brain regions. Here we propose a method to identify these large-scale networks using functional magnetic resonance imaging (fMRI). Regions belonging to such networks are defined as sets of strongly interacting regions, each of which showing an homogeneous temporal activity. Our method of large-scale network identification (LSNI) proceeds by first detecting functionally homogeneous regions. The networks of functional interconnections are then found by comparing the correlations among these regions against a model of the correlations in the noise.

time of day effects on EEG spectral parameters. PHYSIOL BEHAV 54(2) 283-287, 1993.--Electroencephalographic (EEG) recordings were obtained from nine male subjects at sea level and again following rapid ascent to high altitude (4300... more

time of day effects on EEG spectral parameters. PHYSIOL BEHAV 54(2) 283-287, 1993.--Electroencephalographic (EEG) recordings were obtained from nine male subjects at sea level and again following rapid ascent to high altitude (4300 meters) at 0900, 1600, and 1830 h. Electroencephalographic data were subjected to Fast Fourier Transformation and analyzed for beta, spindle, alpha, theta, delta, and total amplitudes. Total amplitude increased from baseline to altitude while relative theta (absolute theta/total amplitude) decreased from baseline to altitude. Amplitude for absolute and relative spindle and total amplitude increased across the day.

FT-IR spectroscopy has traditionally been used to determine the degree of conversion of dental resins. FT-Raman scattering provided an alternate method of obtaining degrees of conversion for these systems and was particularly useful for... more

FT-IR spectroscopy has traditionally been used to determine the degree of conversion of dental resins. FT-Raman scattering provided an alternate method of obtaining degrees of conversion for these systems and was particularly useful for measuring spectra of materials without any sample preparation. Raman and FT-Raman spectroscopy gave identical results, but the latter technique was preferred for the highly fluorescent samples often encountered in commercial composites. Linear calibration curves were obtained for the aromatic mixtures Bis-GMA/TEGDMA and BisphenoI-A/TEGDMA using C=C/O, and for the wholly aliphatic mixture EGDMA/EGDA using C=C/C=O, over a wide range of mole ratios. If both the mole and intensity ratios {C=C/O or C=C/C=O} were known for an uncured dental resin, then the degrees of conversion could be obtained for the cured materials using Raman spectroscopy. However, if the mole ratios for the uncured resin were unknown, then the degree of conversion depended on the calibration curve, since the Raman scattering cross section of the vibrational modes depended on the molecules to which they were attached.

The secondary structure of six bovine lens protein fractions (two a, three f3 and one y-crystallin) are examined in solution and in solid forms for the first time using FTIR spectroscopy. Films of the nuclear and cortical regions of the... more

The secondary structure of six bovine lens protein fractions (two a, three f3 and one y-crystallin) are examined in solution and in solid forms for the first time using FTIR spectroscopy. Films of the nuclear and cortical regions of the bowine lens are also examined. The structure is quantitatively estimated from the vibrational analysis of the resolution-enhanced amide-I profile achieved by Fourier self-deconvolution and linear least-squares curve-fit algorithm. All the protein fractions fold predominantly in a f3-pleated sheet structure with little or no a-helical domains in solution or in lyophilized solid form. These proteins also retain their predominant f3-sheet conformation in the cellular phospholipid environment of the lens, in conformity with the structure obtained for all the mammalian species examined to date. Despite structural homology, vibrational data indicate 'subtle structural differences within each class of the crystallins probably due to presence of several minor substructures/subconforma tions. Substantial high amounts of turns (approx. 40%) observed in the f3-fractions may have a fundamental implication in stabilizing the tertiary structure of the uniquely folded-proteins vital for the transparency of the lens. These proteins in solid KBr-matrix undergo a major structural change, induced primarily by ionic interactions which refold them in a helical conformation. IR spectroscopy together with band-narrowing procedures has proven to be an effective tool to obtain structural information of proteins in solution, as solid substrates or in a complex biological tissue, such as ocular lens.

The most commonly encountered form of echo planar spectroscopy (EPS) involves oscillating gradients in one spatial dimension during readout. Data are consequently not sampled on a Cartesian grid. A fast gridding algorithm applicable to... more

The most commonly encountered form of echo planar spectroscopy (EPS) involves oscillating gradients in one spatial dimension during readout. Data are consequently not sampled on a Cartesian grid. A fast gridding algorithm applicable to this particular situation is presented. The method is optimal, i.e., it performs as well as the full discrete Fourier transform (DFT) for band limited signals while allowing for use of the fast Fourier transform (FFT). The method is demonstrated for reconstruction of data that are partially undersampled in the time domain. The advantages of undersampling are lower hardware requirements or fewer interleaves per acquisition. The method is of particular interest when large bandwidths are needed (eg., for high field scanning) and for scanners with limited gradient performance. The unavoidable artifacts resulting from undersampling are demonstrated to be acceptable for spectroscopy with long echo times.

Objective: An analysis of EEG synchrony between homologous early visual areas tested the hypothesis that interhemispheric functional connectivity during visual stimulation is reduced in children with autism compared to controls. Methods:... more

Objective: An analysis of EEG synchrony between homologous early visual areas tested the hypothesis that interhemispheric functional connectivity during visual stimulation is reduced in children with autism compared to controls. Methods: EEG power and coherence within and between two homologous regions of the occipital cortex were measured during long latency flash visual evoked potentials. Measures were compared between two groups of children (5.5-8.5 years), one with autism spectrum disorders and the other with typical development.

The Fourier phase spectrum plays a central role regarding where in an image contours occur, thereby defining the spatial relationship between those structures in the overall scene. Only a handful of studies have demonstrated... more

The Fourier phase spectrum plays a central role regarding where in an image contours occur, thereby defining the spatial relationship between those structures in the overall scene. Only a handful of studies have demonstrated
psychophysically the relevance of the Fourier phase spectrum with respect to human visual processing, and none have demonstrated the relative amount of local cross-scale spatial phase alignment needed to perceptually
extract meaningful structure from an image. We investigated the relative amount of spatial phase alignment needed for humans to perceptually match natural scene image structures at three different spatial frequencies [3, 6, and 12 cycles per degree (cpd)] as a function of the number of structures within the image (i.e., “structural sparseness”). The results showed that (1) the amount of spatial phase alignment needed to match structures depends on structural sparseness, with a bias for matching structures at 6 cpd and (2) the ability to match partially phase-randomized images at a given spatial frequency is independent of structural sparseness at other spatial frequencies. The findings of the current study are discussed in terms of a network of feature integrators in the human visual system.

Consider a conducting disk surrounded by a thin dielectric layer submitted to an electric field at the pulsation ω. The conductivity of the layer grows like ω 1−γ , γ ∈ [0, 1], when the pulsation ω tends to infinity. Using a... more

Consider a conducting disk surrounded by a thin dielectric layer submitted to an electric field at the pulsation ω. The conductivity of the layer grows like ω 1−γ , γ ∈ [0, 1], when the pulsation ω tends to infinity. Using a pseudodifferential approach on the torus, we build an equivalent boundary condition with the help of an appropriate factorization of Helmholtz operator in the layer. This generalized impedance condition approximates the thin membrane in the high frequency limit for small thickness of the layer. L 2 -error estimates are given and we illustrate our results with numerical simulations. This work extends, in the circular geometry, previous works of Lafitte and Lebeau [7], [8], in which γ identically equals zero.

Alterations in autonomic activity caused by anaesthesia can be assessed by spectral analysis of heart rate variability (HRVA This study examined the effects of ketamine and midazolam on HRV. Thirty patients of ASA PS 1 were studied.... more

Alterations in autonomic activity caused by anaesthesia can be assessed by spectral analysis of heart rate variability (HRVA This study examined the effects of ketamine and midazolam on HRV. Thirty patients of ASA PS 1 were studied. Fifteen were given ketamine (2 mg" kg -t) and 15 received midazolam (0.3 rag" kg-~), iv. The RR intervals of ECG were measured before and after induction of anaesthesia for ten minutes during spontaneous respiration. Power spectral density of the data was computed using fast Fourier transform. The spectral peaks within each measurement were calculated" low frequency area , high frequency area , and totai power (TP, 0.04-0.5 Hz~ Normalized unit power was derived as follows: low frequency area (nuLF/~" LF[ TP X lOOT6 high frequency area (nuHF~" HF/ TP X 100%. Both ketamine and midazolam caused reductions in all measurements of HRV power (P < 0.05). However, ketamine increased nuLF from 64 + 14% to 75 =1= 13% (P < 0.05) and decreased nuHF from 36 :t= 14% to 25 4, 13% (P < 0.05), while midazolam decreased nuLF from 66 4-15% to 54 + 14% (P < 0.05) and increased nuHF from 34 4, 15% to 46 4, 14% (P < 0.05). These results documented that both ketamine and midazolam reduced the total power and all frequency components of power in spite Beat-to-beat variations in heart rate (HR) reflect the dynamic responses of the cardiovascular control system to naturally occurring physiological perturbations. The autonomic nervous system (ANS) is an intricate feedback CAN J ANAESTH 1995 / 4.

We present an analytical solution for the magnetic field, induced eddy currents, and the corresponding losses generated in the rotor of a slotless permanent-magnet (PM) motor. The field excitation is a current sheet placed at the stator... more

We present an analytical solution for the magnetic field, induced eddy currents, and the corresponding losses generated in the rotor of a slotless permanent-magnet (PM) motor. The field excitation is a current sheet placed at the stator interior surface. The solution is based on an analytical solution of the diffusion equation using double Fourier series and in the complex domain. The first and the second Fourier series correspond to the time and space harmonics, respectively. We have analyzed the effect of each time harmonic in detail, and verified the results with FEM software.

Time-frequency distribution methods are being widely used for the analysis of a variety of biomedical signals. Recently, they have been applied also to study otoacoustic emissions (OAE&#39;s), the active acoustic response of the... more

Time-frequency distribution methods are being widely used for the analysis of a variety of biomedical signals. Recently, they have been applied also to study otoacoustic emissions (OAE&#39;s), the active acoustic response of the hearing end organ. Click-evoked otoacoustic emissions (CEOAE&#39;s) are time-varying signals with a clear frequency dispersion along with the time axis. Analysis of CEOAE&#39;s is of considerable interest due to their close relation with cochlear mechanisms. In this paper, several basic time-frequency distribution methods are considered and compared on the basis of both simulated signals and real CEOAE&#39;s. The particular structure of CEOAE&#39;s requires a method with both a satisfactory time and frequency resolution. Results from simulations and real CEOAE&#39;s revealed that the wavelet approach is highly suitable for the analysis of such signals. Some examples of the application of the wavelet transform to CEOAE&#39;s are provided here. Applications range from the extraction of normative data from adult and neonatal OAE&#39;s to the extraction of quantitative parameters for clinical purposes.

Tau proteins and amyloid-␤ (A␤) peptides are the current recognized cerebrospinal fluid (CSF) biomarkers used as an aid in the diagnosis of Alzheimer's disease (AD). However, there is no consensus on their clinical use due to... more

Tau proteins and amyloid-␤ (A␤) peptides are the current recognized cerebrospinal fluid (CSF) biomarkers used as an aid in the diagnosis of Alzheimer's disease (AD). However, there is no consensus on their clinical use due to non-qualified cutoff values, probably related to the observed high pre-analytical and analytical variability. Standardized pre-analytical protocols have therefore been proposed. Importantly, these recommend the use of polypropylene collection/sampling tubes while, to date, no broad comparison of these types of tubes has been conducted. In this study, we first compared, as part of a real clinical workflow, the impact of four different collection tubes on the CSF concentration of A␤ peptides (A␤ 42 ,A␤ 40) and total (hTau) and phosphorylated (P-Tau181P) tau proteins measured using routine ELISA kits. We then extended this study to 11 polypropylene tubes used by different clinical laboratories, and investigated their plastic polymer composition using differential scanning calorimetry and Fourier Transformed Infrared spectroscopy. Significant concentration variations linked solely to the use of different types of tubes were observed. This was particularly marked for A␤ peptides, with >50% disparity occurring in less than five minutes.

Sounds convey information about the materials composing an object. Stimuli were synthesized using a computer model of impacted plates that varied their material properties: viscoelastic and thermoelastic damping and wave velocity ͑related... more

Sounds convey information about the materials composing an object. Stimuli were synthesized using a computer model of impacted plates that varied their material properties: viscoelastic and thermoelastic damping and wave velocity ͑related to elasticity and mass density͒. The range of damping properties represented a continuum between materials with predominant viscoelastic and thermoelastic damping ͑glass and aluminum, respectively͒. The perceptual structure of the sounds was inferred from multidimensional scaling of dissimilarity judgments and from their categorization as glass or aluminum. Dissimilarity ratings revealed dimensions that were closely related to mechanical properties: a wave-velocity-related dimension associated with pitch and a damping-related dimension associated with timbre and duration. When asked to categorize sounds, however, listeners ignored the cues related to wave velocity and focused on cues related to damping. In both dissimilarity-rating and identification experiments, the results were independent of the material of the mallet striking the plate ͑rubber or wood͒. Listeners thus appear to select acoustical information that is reliable for a given perceptual task. Because the frequency changes responsible for detecting changes in wave velocity can also be due to changes in geometry, they are not as reliable for material identification as are damping cues.

Longitudinal (T,) and apparent transverse relaxation times (TJ of choline-containing compounds (Cho), creatinelphosphocreatine (Cr/PCr), and N-acetyl aspartate (NAA) were measured in vivo in human brain at 4 Tesla. Measurements were... more

Longitudinal (T,) and apparent transverse relaxation times (TJ of choline-containing compounds (Cho), creatinelphosphocreatine (Cr/PCr), and N-acetyl aspartate (NAA) were measured in vivo in human brain at 4 Tesla. Measurements were performed using a water suppressed stimulated echo pulse sequence with complete outside volume presaturation to improve volume localization at short echo times. T,-values of Cho (1.2 fi 0.1 s), Cr (1.6 f 0.3 s), and NAA (1.6 f 0.2 s) at 4 Tesla in occipital brain were only slightly larger than those reported in the literature at 1.5 Tesla. Thus, TR will not adversely affect the expected enhancement of signal-to-noise at 4 Tesla. Surprisingly, apparent T,-values of Cho (142 i 34 ms), Cr (140 -c 13 ms), and NAA (185 f 24 ms) at 4 Tesla were significantly smaller than those at 1.5 Tesla and further decreased when increasing the mixing interval TM. Potential contributing factors, such as diffusion in local susceptibility related gradients, dipolar relaxation due to intracellular paramagnetic substances and motion effects are discussed. The results suggest that short echo time spectroscopy is advantageous to maintain signal to noise at 4 Tesla.

The idea that sex differences in the execution of different mental tasks mean a different cerebral organization met contradictory results. Sex differences in brain electrical activity were reported by various authors. The EEG coherences... more

The idea that sex differences in the execution of different mental tasks mean a different cerebral organization met contradictory results. Sex differences in brain electrical activity were reported by various authors. The EEG coherences show functional and anatomical interrelation, so they may reveal differences in brain organization. This paper tries to demonstrate how sex differences are manifested in EEG coherences, in 42 right-handed control children, 18 girls and 24 boys, aged 7.6 to 13.3. Since the effect of age is high on EEG measurements, regression against age was calculated and eliminated. The Z-transformed coherence values were compared by Student's t-test. The results obtained showed that girls had higher right intrahemispheric coherence values than boys in all bands. These sex differences were more numerous in the theta band. The interhemispheric differences were slight and girls had higher coherences in all bands except for the alpha band, where boys had higher interhemispheric coherence than girls. These results show slight but consistent differences in the functional organization of the right hemisphere by sex and reveal the necessity to elaborate separated EEG norms for boys and girls. PMID: 8225795 [PubMed -indexed for MEDLINE]

In this contribution it is proven mathematically that it is in principle impossible to determine the magnetic charge distribution inside a magnetic material by a method which measures the stray field outside the sample, such as magnetic... more

In this contribution it is proven mathematically that it is in principle impossible to determine the magnetic charge distribution inside a magnetic material by a method which measures the stray field outside the sample, such as magnetic force microscopy (MFM). A general source of stray field, E N , is defined and it is shown that different solutions can be found for E N that result in the same stray field. It is also shown how both a perpendicular and a longitudinal medium can be described with the same E N . Using the equations for stray field, resulting from E N , it is also proven that performing the same MFM measurement at different scanning heights does not provide any new information on the stray field for sample; from a measurement at one (constant) height, the stray field at all other heights can be calculated. Moreover, the component of the field parallel to the same plane can be obtained from a measurement of the field component perpendicular to the sample plane.

The catalase-peroxidase encoded by katG of Mycobacterium tuberculosis is a more effective activator of the antibiotic isoniazid than is the equivalent enzyme from Escherichia coli. The environment of the heme iron was investigated using... more

The catalase-peroxidase encoded by katG of Mycobacterium tuberculosis is a more effective activator of the antibiotic isoniazid than is the equivalent enzyme from Escherichia coli. The environment of the heme iron was investigated using X-ray absorption spectroscopy to determine if differences in this region were associated with the differences in reactivity. The variation in the distal side Fe^ligand distances between the two enzymes was the same within experimental error indicating that it was not the heme iron environment that produced the differences in reactivity. Analysis of variants of the E. coli catalase-peroxidase containing changes in active site residues Arg102 and His106 revealed small differences in Fe^water ligand distance including a shorter distance for the His106Tyr variant. The Arg102Leu variant was 5-coordinate, but His106Cys and Arg102Cys variants showed no changes within experimental error. These results are compared with those reported for other peroxidases. ß 2001 Elsevier Science B.V. All rights reserved.

Sulfonamide antibiotics are persistent pollutants of aquatic bodies, known to induce high levels of bacterial resistance. We investigated the adsorption of sulfadiazine, sulfamethazine, and sulfachloropyridazine sulfonamides into a highly... more

Sulfonamide antibiotics are persistent pollutants of aquatic bodies, known to induce high levels of bacterial resistance. We investigated the adsorption of sulfadiazine, sulfamethazine, and sulfachloropyridazine sulfonamides into a highly dealuminated faujasite zeolite (Y) with cage window sizes comparable to sulfonamide dimensions. At maximal solubility the antibiotics were almost completely (>90%) and quickly (t < 1 min) removed from the water by zeolite. The maximal amount of sulfonamides adsorbed was 18-26% DW of dry zeolite weight, as evidenced by thermogravimetric analyses and accounted for about one antibiotic molecule per zeolitic cage. The presence of this organic inside the cage was revealed by unit cell parameter variations and structural deformations obtained by X-ray structure analyses carried out using the Rietveld method on exhausted zeolite. The most evident deformation effects were the lowering of the Fd-3m real symmetry in the parent zeolite to Fd-3 and the remarkable deformations which occurred in the 12-membered ring cage window after sulfadiazine or sulfachloropyridazine adsorption. After sulfamethazine adsorption, zeolite deformation caused a lowering in symmetry up to the monoclinic P2/m space group. The effective and irreversible adsorption of sulfonamides into organophylic Y zeolite makes this cheap and environmentally friendly material a suitable candidate for removing sulfonamides from water.

A new FFT-accelerated projection matching method is presented and tested. The electron microscopy images are represented by their Fourier-Bessel transforms and the 3D model by its expansion in spherical harmonics, or more specifically in... more

A new FFT-accelerated projection matching method is presented and tested. The electron microscopy images are represented by their Fourier-Bessel transforms and the 3D model by its expansion in spherical harmonics, or more specifically in terms of symmetry-adapted functions. The rotational and translational properties of these representations are used to quickly access all the possible 2D projections of the 3D model, which allow an exhaustive inspection of the whole five-dimensional domain of parameters associated to each particle.

Present work illustrates a scheme of quantitative description of the shape of the skull outlines of temnospondyl amphibians using bilaterally symmetric closed Fourier curves. Some special points have been identified on the Fourier fits of... more

Present work illustrates a scheme of quantitative description of the shape of the skull outlines of temnospondyl amphibians using bilaterally symmetric closed Fourier curves. Some special points have been identified on the Fourier fits of the skull outlines, which are the local maxima, or minima of the distances from the centroid of the points at the skull outline. These points denotes break in curvature of the outline and their positions can be compared to differentiate the skull shapes. The ratios of arc-lengths of the posterior and lateral outline of 58 temnospondyl skulls have been plotted to generate a triaguarity series of the skulls. This series grades different families, some of their genera and species as well as some individuals according to their posterior and lateral skull length ratios. This model while comparing different taxa, takes into account the entire arc-length of the outline of the temnospondyl skulls, and does not depend on few geometric or biological points used by earlier workers for comparing skull shapes.

The statistics of low-frequency, long-range acoustic transmissions in the North Pacific Ocean are presented. Broadband signals at center frequencies of 28, 75, and 84 Hz are analyzed at propagation ranges of 3252 to 5171 km, and... more

The statistics of low-frequency, long-range acoustic transmissions in the North Pacific Ocean are presented. Broadband signals at center frequencies of 28, 75, and 84 Hz are analyzed at propagation ranges of 3252 to 5171 km, and transmissions were received on 700 and 1400 m long vertical receiver arrays with 35 m hydrophone spacing. In the analysis we focus on the energetic ''finale'' region of the broadband time front arrival pattern, where a multipath interference pattern exists. A Fourier analysis of 1 s regions in the finale provide narrowband data for examination as well. Two-dimensional ͑depth and time͒ phase unwrapping is employed to study separately the complex field phase and intensity. Because data sampling occured in 20 or 40 min intervals followed by long gaps, the acoustic fields are analyzed in terms of these 20 and 40 min and multiday observation times. An analysis of phase, intensity, and complex envelope variability as a function of depth and time is presented in terms of mean fields, variances, probability density functions ͑PDFs͒, covariance, spectra, and coherence. Observations are compared to a random multipath model of frequency and vertical wave number spectra for phase and log intensity, and the observations are compared to a broadband multipath model of scintillation index and coherence.

The applicability of models based on fractal geometry to characterize thin-film surfaces is investigated. The fractal geometry of sputtered chromium nitride and silicon nitride thin film surfaces is described using Fourier profile... more

The applicability of models based on fractal geometry to characterize thin-film surfaces is investigated. The fractal geometry of sputtered chromium nitride and silicon nitride thin film surfaces is described using Fourier profile analysis of scanning tunneling microscopy images and a box counting method. The CrN x -and SiN xcoatings were deposited on silicon wafers by reactive magnetron sputtering. The columnar structure of the amorphous silicon nitride varied with deposition similarly to the stucture of the polycrystalline chromium nitride films. For quantitative comparison of film morphology, an average column diameter has been used as a characteristic. The average column diameter increases with increasing gas pressure because of shadowing processes during deposition. The fractal dimension decreases with increasing pressure. Films with fine columnar structures are characterized by a larger fractal dimension than films with a coarse columnar structure. The fractal dimension determined by Fourier analysis is larger than the dimension calculated by the box counting method. The reason may be the limited pixel density of digitized images.

Acoustical measures of vocal function are routinely used in the assessments of disordered voice, and for monitoring the patient's progress over the course of voice therapy. Typically, acoustic measures are extracted from sustained vowel... more

Acoustical measures of vocal function are routinely used in the assessments of disordered voice, and for monitoring the patient's progress over the course of voice therapy. Typically, acoustic measures are extracted from sustained vowel stimuli where short-term and long-term perturbations in fundamental frequency and intensity, and the level of "glottal noise" are used to characterize the vocal function. However, acoustic measures extracted from continuous speech samples may well be required for accurate prediction of abnormal voice quality that is relevant to the client's "real world" experience. In contrast with sustained vowel research, there is relatively sparse literature on the effectiveness of acoustic measures extracted from continuous speech samples. This is partially due to the challenge of segmenting the speech signal into voiced, unvoiced, and silence periods before features can be extracted for vocal function characterization. In this paper we propose a joint time-frequency approach for classifying pathological voices using continuous speech signals that obviates the need for such segmentation. The speech signals were decomposed using an adaptive time-frequency transform algorithm, and several features such as the octave max, octave mean, energy ratio, length ratio, and frequency ratio were extracted from the decomposition parameters and analyzed using statistical pattern classification techniques. Experiments with a database consisting of continuous speech samples from 51 normal and 161 pathological talkers yielded a classification accuracy of 93.4%.

A signal-processing algorithm has been developed where a filter function is extracted from degraded data through mathematical operations. The filter function can then be used to restore much of the degraded content of the data through use... more

A signal-processing algorithm has been developed where a filter function is extracted from degraded data through mathematical operations. The filter function can then be used to restore much of the degraded content of the data through use of a deconvolution algorithm. This process can be performed without prior knowledge of the detection system, a technique known as blind deconvolution. The extraction process, designated self-deconvolving data reconstruction algorithm, has been used successfully to restore digitized photographs, digitized acoustic waveforms, and other forms of data. The process is noniterative, computationally efficient, and requires little user input. Implementation is straightforward, allowing inclusion into many types of signal-processing software and hardware. The novelty of the invention is the application of a power law and smoothing function to the degraded data in frequency space. Two methods for determining the value of the power law are discussed. The first method assumes the power law is frequency dependent. The function derived comparing the frequency spectrum of the degraded data with the spectrum of a signal with the desired frequency response. The second method assumes this function is a constant of frequency. This approach requires little knowledge of the original data or the degradation.

Microelectrocorticography (µECoG) provides insights into the cortical organization with high temporal and spatial resolution desirable for better understanding of neural information processing. Here we evaluated the use of µECoG for... more

Microelectrocorticography (µECoG) provides insights into the cortical organization with high temporal and spatial resolution desirable for better understanding of neural information processing. Here we evaluated the use of µECoG for detailed cortical recording of somatosensory evoked potentials (SEPs) in an ovine model. The approach to the cortex was planned using an MRI-based 3D model of the sheep's brain. We describe a minimally extended surgical procedure allowing placement of two different µECoG grids on the somatosensory cortex. With this small craniotomy, the frontal sinus was kept intact, thus keeping the surgical site sterile and making this approach suitable for chronic implantations. We evaluated the procedure for chronic implantation of an encapsulated µECoG recording system. During acute and chronic recordings, significant SEP responses in the triangle between the ansate, diagonal, and coronal sulcus were identified in all animals. Stimulation of the nose, upper lip,...

Este artículo esboza algunas claves para pensar los procesos que configuran el ordenamiento corporal en las ciudades capitalistas. Indaga la relación entre cuerpos, estructura urbana y estructura social en dos configuraciones... more

Este artículo esboza algunas claves para pensar los procesos que configuran el ordenamiento corporal en las ciudades capitalistas. Indaga la relación entre cuerpos, estructura urbana y estructura social en dos configuraciones socio-espaciales particulares: la Venecia Shakesperiana y el Falansterio de Charles Fourier. Primero, se retoman fragmentos de El Mercader de Venecia, enfatizando los modos en que el extrañamiento y la distancia social repercuten en (y son subsidiarios de) la configuración de los espacios reservados a esos cuerpos extraños recluidos dentro de los muros del ghetto judío. Seguidamente, se discute el proyecto del Falansterio, orientado a la reconfiguración del vínculo social sobre la base del placer y los deseos reprimidos por el imperio de la razón industrial de comienzos del siglo XIX.

Investigation of underwater electrical wire explosions occurring in the time scale of few microseconds requires a measurement of pressure waves with nanosecond rise time and microsecond fall time. Various types of pressure gauges are used... more

Investigation of underwater electrical wire explosions occurring in the time scale of few microseconds requires a measurement of pressure waves with nanosecond rise time and microsecond fall time. Various types of pressure gauges are used for this purpose, however, none of them seems to be suitable for the task since the frequency range of the pressure waves lies between 10 7 and 10 9 Hz, whereas all types of mechanical gauges have a bandwidth below 10 7 Hz. Therefore, a mathematical processing of measurements is required for reconstruction of the actual pressure wave forms. In this article, a signal processing algorithm, based on energy conservation requirements and Fourier analysis, for reconstruction of the wave form of the pressure wave generated under water by electrical explosion of wires is proposed. The gauge used in the experiments is a PCB 119A12 type pressure gauge with a bandwidth below 1 MHz produced by Piezo-Electronics, Inc. Pressure waves were produced by underwater electrical explosion of a thin wire made of Cu by a current pulse with an amplitude of 30-60 kA having a rise time of a 3 s. It is shown that the error of the gauge in the measurement of the peak pressure is more than 100%, which leads to an error in the estimation of the energy of almost 300%.

This study describes the application of a novel quantitative method for classifying patterns of EEG activity that are associated with the predominant sleep-states of newborn infants. Periods in which there are bursts of high-voltage slow... more

This study describes the application of a novel quantitative method for classifying patterns of EEG activity that are associated with the predominant sleep-states of newborn infants. Periods in which there are bursts of high-voltage slow wave activity in the EEG that alternate with periods of low-voltage activity are termed Tracé-alternant. During active or REM sleep, Tracé-alternant is absent and EEG activity is characterized by a variable mixture of frequencies including intermittent high frequency activity superimposed on (10-20 Hz) slower frequencies. Results show that an analytic method previously developed in fetal baboons for identifying EEG segments with and without Tracé-alternant successfully distinguishes homologous patterns of EEG activity in preterm infants. This method provides an excellent objective approach for monitoring changes in EEG patterns that are coincident with behaviorally defined sleep states.

Simulation results on dynamic yaw stability derivatives of a gull bird by means of computational fluid dynamics are presented. Two different kinds of motions are used for determining the dynamic yaw stability derivatives CNr and CNbeta .... more

Simulation results on dynamic yaw stability derivatives of a gull bird by means of computational fluid dynamics are presented. Two different kinds of motions are used for determining the dynamic yaw stability derivatives CNr and CNbeta . Concerning the first one, simple lateral translation and yaw rotary motions in yaw are considered. The second one consists of combined motions. To determine dynamic yaw stability derivatives of the bird, the simulation of an unsteady flow with a bird model showing a harmonic motion is performed. The unsteady flow solution for each time step is obtained by solving unsteady Euler equations based on a finite volume approach for a smaller reduced frequency. Then, an evaluation of unsteady forces and moments for one cycle is conducted using harmonic Fourier analysis. The results on the dynamic yaw stability derivatives for both simulations of the model motion show a good agreement.

In this paper, we have proposed a fingerprint orientation model based on 2D Fourier expansions (FOMFE) in the phase plane. The FOMFE does not require prior knowledge of singular points (SPs). It is able to describe the overall ridge... more

In this paper, we have proposed a fingerprint orientation model based on 2D Fourier expansions (FOMFE) in the phase plane. The FOMFE does not require prior knowledge of singular points (SPs). It is able to describe the overall ridge topology seamlessly, including the SP regions, even for noisy fingerprints. Our statistical experiments on a public database show that the proposed FOMFE can significantly improve the accuracy of fingerprint feature extraction and thus that of fingerprint matching. Moreover, the FOMFE has a low-computational cost and can work very efficiently on large fingerprint databases. The FOMFE provides a comprehensive description for orientation features, which has enabled its beneficial use in feature-related applications such as fingerprint indexing. Unlike most indexing schemes using raw orientation data, we exploit FOMFE model coefficients to generate the feature vector. Our indexing experiments show remarkable results using different fingerprint databases.

This paper addresses a forensic tool used to assess audio authenticity. The proposed method is based on detecting phase discontinuity of the power grid signal; this signal, referred to as electric network frequency (ENF), is sometimes... more

This paper addresses a forensic tool used to assess audio authenticity. The proposed method is based on detecting phase discontinuity of the power grid signal; this signal, referred to as electric network frequency (ENF), is sometimes embedded in audio signals when the recording is carried out with the equipment connected to an electrical outlet or when certain microphones are in an ENF magnetic field. After down-sampling and band-filtering the audio around the nominal value of the ENF, the result can be considered a single tone such that a high-precision Fourier analysis can be used to estimate its phase. The estimated phase provides a visual aid to locating editing points (signalled by abrupt phase changes) and inferring the type of audio editing (insertion or removal of audio segments). From the estimated values, a feature is used to quantify the discontinuity of the ENF phase, allowing an automatic decision concerning the authenticity of the audio evidence. The theoretical background is presented along with practical implementation issues related to the proposed technique, whose performance is evaluated on digitally edited audio signals.

Recently, joint Spectral and Time domain Optical Coherence Tomography (joint STdOCT) has been proposed to measure ocular blood flow velocity. Limitations of CCD technology allowed only for twodimensional imaging at that time. In this... more

Recently, joint Spectral and Time domain Optical Coherence Tomography (joint STdOCT) has been proposed to measure ocular blood flow velocity. Limitations of CCD technology allowed only for twodimensional imaging at that time. In this paper we demonstrate fast threedimensional STdOCT based on ultrahigh speed CMOS camera. Proposed method is straightforward, fully automatic and does not require any advanced image processing techniques. Three-dimensional distributions of axial velocity components of the blood in human eye vasculature are presented: in retinal and, for the first time, in choroidal layer. Different factors that affect quality of velocity images are discussed. Additionally, the quantitative measurement allows to observe a new interesting optical phenomenon -random Doppler shift in OCT signals that forms a vascular pattern at the depth of sclera.

The properties of magnetic material are normally described by the permeability tensor, while the magnetically nonlinear properties of electromagnetic devices (EMDs) can be described by the current-dependent characteristics of flux... more

The properties of magnetic material are normally described by the permeability tensor, while the magnetically nonlinear properties of electromagnetic devices (EMDs) can be described by the current-dependent characteristics of flux linkages. This paper presents and evaluates different experimental methods appropriate for determining the magnetically nonlinear characteristics of EMDs. The tested device is supplied by a controlled voltage source. Sinusoidal voltages, sinusoidal voltages with offset, and stepwise changing voltages are applied. Current-dependent characteristics of flux linkages are determined from the measured voltages and currents, either by numerical integration or by Fourier analysis and calculation of impedances.

Abstract. In this article we will give a characterization of so-lutions for the equation ∂2 ∂t2 u + ∆xu − 2x · ∇xu = 0 which are Poisson-Hermite integral of Lp(γn)-functions, 1 ≤ p ≤ ∞, follow-ing the classical case of characterization of... more

Abstract. In this article we will give a characterization of so-lutions for the equation ∂2 ∂t2 u + ∆xu − 2x · ∇xu = 0 which are Poisson-Hermite integral of Lp(γn)-functions, 1 ≤ p ≤ ∞, follow-ing the classical case of characterization of harmonic functions as Poisson ...

The European green crab Carcinus maenas is a widely spread invasive species. Studying the most recently introduced population of the species in the Atlantic coast off Patagonia, it became apparent to us that carapaces (the dorsal cover of... more

The European green crab Carcinus maenas is a widely spread invasive species. Studying the most recently introduced population of the species in the Atlantic coast off Patagonia, it became apparent to us that carapaces (the dorsal cover of the visceral-cavity detaching from the rest of the exoskeleton after ecdysis) accumulated on the intertidal may be used as a valuable complementary material to analyze the size structure of crabs. However, since growth rate (and consequently size at instar) of crabs differs between males and females, finding a method to distinguish crab sex by observation of carapace morphology was necessary to allow the construction of independent size frequency distributions for each sex. In this work, we examined the shape of the carapaces from both sexes of C. maenas, and using Elliptical Fourier Analysis successfully identified sexual dimorphism. Thus, a reliable method to identify sexes by visual observation of the carapace was developed. Based on our results, we discuss the evolutionary significance of carapace form differentiation of both sexes.

As an open source platform, Android provides freedom to developers to make contribution towards the rapid growth of the Android market. On the other hand, users of Android devices might not be familiar with the privacy and security... more

As an open source platform, Android provides freedom to developers to make contribution towards the rapid growth of the Android market. On the other hand, users of Android devices might not be familiar with the privacy and security implications of installing mobile application on their cell phones. Users might assume that a device that is password locked protects their personal information, but the devices might preserve the personal information on the devices in ways the end users might not be aware of. This research focuses on one of these applications 'WhatsApp®', a very popular social networking mobile application. This research outlines the ways forensic investigators can extract valuable information from WhatsApp and from similar mobile applications installed on the Android platform. The major focus is the extraction and analysis of the data of the application user from non-volatile external storage and the volatile memory (RAM) of an Android device.

Water energy which is very good to be used as a source of electrical energy in underdeveloped areas has not been reached by electricity. The purpose of this research is to utilize water energy for the generation of electrical energy is to... more

Water energy which is very good to be used as a source of electrical energy in underdeveloped areas has not been reached by electricity. The purpose of this research is to utilize water energy for the generation of electrical energy is to choose a four nozzle cross flow water turbine. The method used is to test a Cross Flow turbine with four nozzles as a micro-scale hydroelectric power generator. The results showed that a cross flow turbine with four nozzles is very good as a permanent magnet Direct Current generator that can work at a flow that is not too high. At a water discharge of 4.2x 10-3 m 3 /s and an outer diameter of 200 mm cross flow turbine with 24 blades, it can produce Cross Flow Turbine power with four nozzles is 3.251 Watt and generator power is 1.528 Watt.

The ␤-cyclodextrin (␤-CD) polyiodide inclusion complex (␤-CD) 2 •Co 0.5 •I 7 •21H 2 O has been synthesized, characterized and further investigated via FT-Raman spectroscopy in the temperature range of 30-120 • C. The experimental results... more

The ␤-cyclodextrin (␤-CD) polyiodide inclusion complex (␤-CD) 2 •Co 0.5 •I 7 •21H 2 O has been synthesized, characterized and further investigated via FT-Raman spectroscopy in the temperature range of 30-120 • C. The experimental results point to the coexistence of I − 7 units (I 2 •I − 3 •I 2) that seem not to interact with the Co 2+ ions and I − 7 units that display such interactions. The former units exhibit a disorder-order transition of both their I 2 molecules above 60 • C due to a symmetric charge-transfer interaction with the central I − 3 [I 2 ← I − 3 → I 2 ], whereas in the latter units only one of the two I 2 molecules becomes well-ordered above 30 • C. The other I 2 molecule remains disordered presenting no charge-transfer phenomena. The Co 2+ ion induces a considerable asymmetry on the geometry of the I − 3 anion and a significant modification of its Lewis base character. Complementary dielectric measurements suggest no important involvement of H•••I contacts in the observed modification of the I − 3 electron-transfer properties.

Rationale: Stimulant medications are the most commonly used treatments for attention deficit/hyperactivity disorder (ADHD) in North America and Australia, although it is still not entirely known how these medications work. Objectives:... more

Rationale: Stimulant medications are the most commonly used treatments for attention deficit/hyperactivity disorder (ADHD) in North America and Australia, although it is still not entirely known how these medications work. Objectives: This study aimed to investigate the effects of stimulant medications on the EEG of children with the Combined subtype of ADHD. Method: An initial EEG was recorded during an eyes-closed resting condition and Fourier transformed to provide absolute and relative power estimates for the delta, theta, alpha and beta bands. Theta/alpha and theta/beta ratios were also calculated. Subjects were placed on a 6-month trial of a stimulant and a second EEG was recorded at the end of the trial. Results: The ADHD group had significantly greater absolute delta and theta, less posterior absolute beta, more relative theta, and less relative alpha than the control group, which is typical of EEG studies of children with ADHD. The use of stimulant medications resulted in normalisation of the EEG, primarily evident in changes in the theta and beta bands. Conclusions: These results suggest that stimulants act to increase cortical arousal in children with ADHD, normalising their brain activity.

Dissolved organic matter (DOM) in sediment pore water is a complex molecular mixture reflecting various sources and biogeochemical processes. In order to constrain those sources and processes, molecular variations of pore water DOM in... more

Dissolved organic matter (DOM) in sediment pore water is a complex molecular mixture reflecting various sources and biogeochemical processes. In order to constrain those sources and processes, molecular variations of pore water DOM in surface sediments from the NW Iberian shelf were analyzed by ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and compared to river and marine water column DOM. Weighted average molecular element ratios of oxygen to carbon ((O/C) wa ) and hydrogen to carbon ((H/C) wa ) provided general information about DOM sources. DOM in local rivers was more oxygenated ((O/C) wa 0.52) and contained less hydrogen ((H/C) wa 1.15) than marine pore water DOM (mean (O/C) wa 0.50, mean (H/C) wa 1.26). The relative abundance of specific compound groups, such as highly oxygenated aromatic compounds or nitrogen-bearing compounds with low H/C ratios, correspond to a high concentration of lignin phenols (160 lg/g sediment dry weight) and a high TOC/TN ratio (13.3) in the sedimentary organic matter and were therefore assigned to terrestrial sources. The lower degree of unsaturation and a higher relative abundance of nitrogen-bearing compounds in the pore water DOM reflected microbial activity within the sediment. One sampling site on the shelf with a high sediment accumulation, and a humic-rich river sample showed a wide range of sulfur compounds in the DOM, accompanied by a higher abundance of lipid biomarkers for sulfate-reducing bacteria, probably indicating early diagenetic sulfurization of organic matter.