Values Of Spectral Parameter Research Articles

Design of separable-denominator variable 2-D digital filters with guaranteed stability

Stability guarantee is the most important issue in designing variable recursive digital filters since unstable variable filters cannot be applied in signal processing applications. This paper proposes a technique for designing separable-denominator variable two-dimensional (2-D) digital filters having variable magnitude characteristics, and the stability of the designed variable recursive 2-D filters is always guaranteed. The method assumes each coefficient of the variable 2-D recursive digital filter as a polynomial of the spectral parameters that specify different variable magnitude responses. Since the filter coefficients are represented by different polynomials, substitution of different values of the spectral parameters into the polynomials gives different filter coefficients and thus different magnitude responses. To guarantee the stability, we first perform coefficient transformations on the denominator coefficients of the recursive transfer function such that the stability conditions of the recursive filter are always satisfied for arbitrary values of the new coefficients. Then both the denominator and the numerator coefficients are determined as the polynomials of the spectral parameters. The proposed technique is effective in designing separable-denominator variable 2-D digital filters with guaranteed stability.

Baxter'sQ-operator for the homogeneousXXXspin chain

Applying the Pasquier-Gaudin procedure we construct the Baxter's Q-operator for the homogeneous XXX model as integral operator in standard representation of SL(2). The connection between Q-operator and local Hamiltonians is discussed. It is shown that operator of Lipatov's duality symmetry arises naturally as leading term of the asymptotic expansion of Q-operator for large values of spectral parameter.

In vitro diagnosis of axillary lymph node metastases in breast cancer by spectrum analysis of radio frequency echo signals

Axillary lymph node status is of particular importance for staging and managing breast cancer. Currently, axillary lymph node dissection is performed routinely in cases of invasive breast cancer because of the lack of accurate noninvasive methods for diagnosing lymph node metastasis. We investigated the diagnostic ability of ultrasonic tissue characterization based on spectrum analysis of backscattered echo signals to detect axillary lymph node metastasis in breast cancer in vitro compared with in vitro B-mode imaging. Immediately after surgery, individual lymph nodes were isolated from axillary tissue. Each lymph node was scanned in a water bath using a 10-MHz instrument, and radio frequency data and B-mode images were acquired. Spectral parameter values were calculated, and discriminant analysis was performed to classify metastatic and nonmetastatic lymph nodes. Forty histologically characterized axillary lymph nodes were enrolled in this study, including 25 nonmetastatic and 15 metastatic lymph nodes. A significant difference existed in the spectral parameter values (slope and intercept) for metastatic and nonmetastatic lymph nodes. Spectral parameter-based discriminant function classification of metastatic vs. nonmetastatic lymph nodes provided a sensitivity of 93.3%, specificity of 92.0%, and overall accuracy of 92.5%. In comparison, B-mode ultrasound images of in vitro lymph nodes provided a sensitivity of 73.3%, specificity of 84.0%, and overall accuracy of 80.0%. Receiver operating characteristic (ROC) analysis comparing the efficacy of both methods gave an ROC curve area of 0.9888 for spectral methods, which was greater than the area of 0.8980 for B-mode ultrasound. Hence, this in vitro study suggests that the diagnostic ability of spectrum analysis may prove to be markedly superior to that of B-mode ultrasound in detecting axillary lymph node metastasis in breast cancer. Because of these encouraging results, we intend to conduct an investigation of the ability of spectral methods to classify metastatic axillary lymph nodes in vivo.

Design of variable 2-D linear phase recursive digital filters with guaranteed stability

This paper proposes a new technique for designing variable two-dimensional (2-D) linear phase recursive digital filters, the stability of which is always guaranteed. The method finds each variable filter coefficient as a multidimensional (M-D) polynomial of a few parameters. The parameters specify different frequency responses, thus they are called the spectral parameters. In applying the resulting variable filters, substituting different spectral parameter values into the M-D polynomials will obtain different filter coefficients and, thus, different frequency responses. To guarantee the stability, we first perform denominator coefficient transformations such that they satisfy the stability conditions. Then, both denominator and numerator coefficients are determined as M-D polynomials.

Three-dimensional prostate imaging and tissue typing

Three-dimensional (3-D) depictions of ultrasonic scan data have been developed in our laboratories for visualizing tissue properties and structure in several medical applications including characterization of prostatic and ophthalmic tissues. Data for 3-D depictions are acquired as a set of parallel ultrasonic scans and are displayed as volume or surface renderings or as interactively dissectable blocks. Acquired data consist of digitized radio-frequency (rf) echo signals. Tissue-typing information is based on parameters derived from linear-regression analyses of normalized power spectra of the digitized rf echo-signal data. Tissue properties, such as scatterer size, are computed from spectral parameter values. Tissue typing is performed by comparing computed parameter values from an unknown tissue with database values associated with known tissue types. Images portraying spectral parameter values, scatterer properties, or most-likely tissue type have been developed. Three-dimensional presentations are generated from sets of scan-plane data using desktop computers or imaging workstations. Volumes can be examined in several ways, e.g., by dynamically presenting the entire 3-D volume as a tilting or a rotating transparent rendering. Three-dimensional images of the prostate gland facilitate visualization of cancerous regions warranting biopsy. [Research supported, in part, by the National Cancer Institute and the National Eye Institute.]

The N-Methylpropionamide-Water System. Study of Intermolecular Interactions

Abstract The 1H-NMR spectra of liquid binary mixtures, N-methylpropionamide (NMP)-water, were recorded at 298 K over a wide range of mixed solvent compositions. From these data the values of spectral parameter, Δδ(NMP-H2O) were found. The densities (d 12) and viscosities (η12) of mixed solvent were measured at 298.15K, as well as the dielectric permittivities (ε12) at 293.15K, 298.15K and 303.15K. From these new parent data, the values of molar volumes (V 12) and their deviations from “ideality” were calculated. Additionally, the values of temperature coefficient of dielectric permittivities (ε12) were found. These structural parameters as functions of concentration suggest the formation of the structures such as clathrate hydrates and the most stable “complexes” (sub-units) of the NMP·2H2O and 3NMP·2H2O types.

Measurement of Respiratory Acoustical Signals: Comparison of Sensors

We assessed the performance of three air-coupled and four contact sensors under standardized conditions of lung sound recording. Recordings were obtained from three of the investigators at the best site on the posterior lower chest as determined by auscultation. Lung sounds were band-pass filtered between 100 and 2,000 Hz and sampled simultaneously with calibrated airflow at a rate of 10 kHz. Fourier techniques were used for power spectral analysis. Average spectra for inspiratory sounds at flows of 2 +/- 0.5 L/s were referenced against background noise at zero flow. Air-coupled and contact sensors had comparable maximum signal-to-noise ratios and gave similar values for most spectral parameters. Unexpectedly, less sensitivity (lower signal-to-noise ratio) at high frequencies was observed in the air-coupled devices. Sensor performance needs to be characterized in studies of lung sounds. We suggest that lung sound spectra should be averaged at known airflows over several breaths and that all measurements should be reported relative to sounds recorded at zero flow.

Absorption Difference and Comparative Absorption Spectrophotometry of Neodymium(III) Haloacetates in Non-Aqueous Media and in Crystalline State

Abstract Neodymium(III) haloacetates (monochloro-, dichloro-, trichloro- and trifluoro acetates) gave 1:3 adducts with alcohols, while yield mixed solvato complexes with dimethyl formamide and dimethyl sulphoxide of the type Nd(solv)x (OOCR)3 where x = 4 or 6 depending upon the time given for the reaction. Absorption difference and comparative absorption spectrophotometry were used to study the coordination geometry of metal ion in Nd(III) haloacetates both in crystalline and in non-aqueous (DMF, Methanol, Methanol-DMF, and Isobutanol-DMF equimolar binary mixtures) solvents. The computed values of spectral parameters and the variation of these parameters were used to supplement comparative absorption study. The transitions 4I9/2→4G7/2, 4F7/2, 4F5/2 and 4F3/2 and which have generally been regarded almost linsensitive towards coordination environment, have been found tp be substantially sensitive and thus been referred to as Pseudohypersensitive transitions and observation has been given the name “Ligand Me...

Spectral mass sum rules for interacting fermi fields

Spectral representations and recursive equations among Schwinger functions are exploited to obtain nonperturbative relations—spectral mass sum rules—involving mean values of spectral masses and physical parameters of the theory in interacting Fermi fields models. For the Yukawa model in two space-time dimensions, the finite part of the mass sum rule is extracted, and upper bounds (mean-field-like) on the average spectral mass and on the physical mass are obtained.

Hot plasma parameters in Neptune's magnetosphere

This paper presents values of particle spectral parameters and estimates of plasma densities, temperatures, and beta parameters, obtained with the Low Energy Charged Particle instrument during the Voyager 2 encounter with Neptune on August 24-25, 1989. In addition, trapped electron intensities are compared with the whistler mode stably trapped limits. The results revealed a very good inbound-outbound symmetry for both the proton and the electron profiles, suggesting that there was little dynamical activity in Neptune's magnetosphere during the Voyager encounter. The similarities and differences observed between Neptune and Uranus in the values of plasma density, pressure, and beta are discussed.

13C and 119Sn NMR spectra of diphenyl- and dibenzyltin(IV) compounds and their complexes

13C and 119Sn NMR spectra of diphenyl- and dibenzyltin(IV) compounds have been studied in solutions of coordinating and non-coordinating solvents. Regions of values of the δ(119Sn) chemical shifts have been determined which characterize individual types of coordination of the central tin atom. The values of 13C NMR spectral parameters, the δ(13C) chemical shifts and nJ(119Sn, 13C) coupling constants, have been used to describe the real shapes of coordination sphere of the central tin atom and to discuss the internal structure of the organic substituents and of the nature of their bonding linkage to the tin atom.

13C and 119Sn NMR spectra of divinyltin(IV) compounds

The 13C and 119Sn NMR spectra of a set of divinyltin(IV) compounds in coordinating and non-coordinating solvents have been studied. The obtained results are discussed in terms of relations between the values of NMR spectral parameters and the geometries of coordination polyhedra of molecules of the divinyltin(IV) compounds and their complexes.

Identification of marine organisms using kinetic and spectral properties of their bioluminescence

We have used a polychromator consisting of six photomultiplier tubes, each filtered to a different wavelength with narrow band-pass interference-filters, to study bioluminescence. Spectral and kinetic data collected from ten marine species in the laboratory describe their luminous flashes. These data suggest that the concept of luminous signatures, within the limits of our studies, is a valid one, with potential uses for future biological studies both in the laboratory and in situ. The kinetic parameters considered were rise time (RT), decay time (DT) and total time (TT), while the spectral parameters consisted of ratios of light intensities at 480 and 520 nm to the intensity at 500nm. Oneway analysis of variance (ANOVA) demonstrated significant heterogeneity among species for all variables. A posteriori analysis performed with the ANOVA for TT indicated that mean TT for most species is significantly different from all other species. Canonical discriminant analysis was performed to estimate the value of kinetic and spectral parameters for species' identification. Kinetic data were somewhat more valuable in species' classification than spectral data. Discriminant analysis with RT and DT alone gave 83.1% correct species-classifications. Classification success based only on relative intensities at 480 and 520 nm was 77.5%. When all four variables were included, classification success was 100%.

Gas exchange across an air‐water interface: Experimental results and modeling of bubble contribution to transfer

Gas exchange experiments have been performed in a wind‐water tunnel filled with fresh water or seawater. Transfer velocities have been measured for nitrous oxide and argon in a range of wind speeds extending from 3 m/s to 14 m/s. The air‐liquid interface was covered either with only normally developed wind waves or with mechanically generated waves in addition. For u<9 m/s a linear variation of the transfer velocity, kL, with wind speed (and also friction velocity) is observed for both gases. Two distinct relationships link kL and u, depending on the presence of artificially generated waves. In this last case, a mean enhancement of the order of 30% is observed. The ratio of the transfer velocities measured for Ar and N2O is equal to 0.93. This figure does not allow the precise determination of the dependence of kL on the Schmidt number of the gas since molecular diffusivities of Ar and N2O in water are close and not precisely known. For higher wind speeds (u>9 m/s), a jump of the values of kL up to a factor of 3 is observed first for Ar and then for N2O, the ratio kL Ar/kL being highly variable. This observation is interpreted as being the result of the onset of breaking waves which create bubbles through which mass transfer takes place. No difference for gas exchange either in fresh water or in seawater has been identified from the whole set of experiments. A theoretical model is developed to compute the contribution of bubbles to gas exchange. The transport equations, derived for a single bubble, take into account the diffusive mass flux exchanged between the bubble and the liquid, the hydrodynamic pressure, and the presence of two gaseous components inside the bubble. The equations used to represent the dynamics take care of the orbital motion of water associated with waves. A relation to link sources and spectra of bubble populations is derived. Numerical values for spectral parameters are taken from the literature. It is found that the results of experiments run at 9 m/s and 10 m/s are well explained for N2O and for Ar. A unique distribution of bubbles explains the excess of gas transfer associated with the presence of breaking waves. In a further step the theoretical treatment is extended to compute the transfer velocity kB for gas exchange through bubbles as a function of the concentration gradient in atmosphere and water for three gases, helium, argon, and nitrous oxide. It is shown that in wind tunnel conditions, kB is independent of the concentration gradient. This does not hold at the atmosphere‐ocean interface. The transfer velocity kB is highly dependent on the gas concentrations in air and water when they are close to solubility equilibrium. It is demonstrated that equilibrium must occur at the ocean surface for supersaturation conditions. The higher saturation anomalies and the larger transfer velocities are computed for the less soluble gas. This conclusion is in good agreement with observations made at sea.

Spectral analysis with short data batches (photon correlation spectroscopy)

This paper studies the limiting accuracy with which power spectra and the values of spectral parameters for random signals can be achieved from short batches of data. Initially, general expressions for arbitrary data are derived; these are then restricted for simplicity to wide-band signals. In addition, comparison is made with computer simulation for two well defined models, namely, photodetection of light of constant intensity and heterodyne photodetection of narrow-band Gaussian-Lorentzian light. It is shown that there is no analytical difference between operation in time or frequency space for batch data, and also that long data sets can be analysed at least as well, in terms of the accuracy with which spectral parameters can be determined by fitting, by averaging over many short batches as by processing the set as a whole.

Estimation of amino acid residue side-chain absorption in the infrared spectra of protein solutions in heavy water.

AbstractThe values of maximum frequencies, intensities, and other spectral parameters of the main absorption bands of amino acid residue side‐chain groups have been obtained in the 1500–1800‐cm−1 region for solutions in heavy water at pD 1–12. It is shown that absorption of residues of asparagine, glutamine, aspartic and glutamic acids, arginine, and tyrosine must be taken into account in quantitative studies of the infrared spectra of polypeptide and protein solutions in heavy water. Examples of separating out the amide I band for ribonuclease A in heavy water are given.

The influence of a photospheric spectrum of turbulence on the profiles of weak Fraunhofer lines

We assume that the motion field in the solar photosphere is described by a spectrum of turbulence, defined by suitably chosen parameters. For various values of the spectral parameters we compute average (i.e. averaged over a sufficiently large part of the photosphere) profiles of weak Fraunhofer lines. The resulting profiles which represent the distribution function of line-of-sight velocity components as modified by the transfer of radiation through the atmosphere, are thereupon still broadened by a function representing the influence of the distribution function of the granulation cell sizes. The resulting functions should be compared with the distribution function of line-of-sight velocity components as derived from observations, in order to arrive at an observational derivation of the parameters of the photospheric spectrum of turbulence.

Proton‐proton coupling constants in the unsubstituted pyrylium cation

AbstractAn iterative analysis of the PMR spectrum of the title compound was performed and the calculated values of spectral parameters, relative chemical shifts, proton‐proton and direct carbon‐proton couplings are compared with those of pyridine.