True IR Research Articles

Rereferencing of clinical EEGs with nonunipolar mastoid reference to infinity reference by REST

ObjectiveConventional electroencephalography (EEG) offline subtraction rereferencing is invalid for many clinical practices when adopting a specific nonunipolar recording montage (e.g., the ipsilateral mastoid (IM) and contralateral mastoid (CM)). Further comparative analyses would thus be blocked due to the lack of a uniform offline reference. Therefore, our goal was to resolve this problem by introducing and assessing the reference electrode standardization technique (REST) to transform nonunipolar mastoid montages into a computational zero reference at infinity (IR) offline. MethodsFor EEG signals and power/connectivity configurations, simulation and clinical schizophrenia resting-state EEG datasets were used to investigate the performance of REST. ResultsREST produced small absolute errors (signal level: 1.21–1.26; power: 0.0057–0.021; connectivity: 0.066–0.088) and high correlations (>0.9) between the IM/CM-IR and true IR references. Using clinical data with the IM online reference, REST revealed valuable changes in spectral and connectivity (P < 0.05) in schizophrenia patients, consistent with previous studies. ConclusionsThese results demonstrated that REST transformation could be adopted to resolve the offline rereferencing of clinical EEGs with specific nonunipolar mastoid references. SignificanceREST could be an effective and robust resolution for nonunipolar clinical EEGs and could therefore retrieve these data for further analysis by deriving a favorable offline reference IR.

Implementation of Statistically-Based Image Reconstruction Algorithms for CT and Numerical Evaluation of Image Quality

[Purpose] Statistically-based image reconstruction (SIR) methods that have been incorporated into commercial CT scanners have succeeded in promoting low-dose CT with high image quality in comparison with scanners using the filtered back-projection (FBP) method. Not only researchers but also medical doctors and technologists engaged in CT studies have an interest in the algorithms of the SIR methods, however, the algorithms have not been made available to users by the CT manufacturers. Kudo reviewed the fundamentals of SIR methods on the basis of the articles published by the joint research group of each manufacturer released before product development (Med Imag Tech 32: 239-248, 2014). He classified the SIR methods into true iterative reconstruction (true IR), hybrid IR, and image space denoising (ISD) methods. His review article has made a significant contribution to the CT community of users. However, the reconstructed images obtained by those methods have not been presented. Our purpose in this study is to implement the mathematical equations of three IR methods, one each of the true IR, hybrid IR and ISD methods, and evaluate their image quality.[Methods] The system matrix of IR methods used in commercial CT scanners uses a physical photon detection process based on the finite size of an X-ray focal spot, the beam width, and the X-ray detector. However, we assumed the X-ray beam was a pencil beam and the system matrix was then given by the line integral of linear attenuation coefficients because we focus on the image quality in the ideal photon detection system equations given by Kudo. Total variation (TV) was used for regularization of the true IR, hybrid IR and ISD methods. Four kinds of numerical phantoms with 256×256 pixels were used as test images. Gaussian noise of 15, 20, 25, and 30 dB was added to the projection data with 256 linear samplings and 256 views over 180°.[Results] Root mean square errors (RMSEs) of the true IR, hybrid IR, and ISD methods were 4.28-5.70, 15.87-16.47, and 16.94-17.17, respectively. RMSE of the FBP method ranged from 27.64-33.02 and that of the FBP method processed with a Gaussian filter of FWHM (full width at half maximum) of 3 pixels ranged from 8.14-17.28. The image quality of the true IR method was superior to that of the hybrid IR and ISD methods and the FBP method.[Discussion] The noise was slightly suppressed by including the variance of projection data; however, the regularization was inevitable even if the noise levels were in the range of 25-30 dB. The noise was not suppressed sufficiently by the hybrid IR and ISD methods because the noise due to the FBP image used as the initial image for these IR methods has a dominating effect in successive reconstruction or denoise processing. Mathematical equations of each IR method were easily realized by observing the intermediate images such as the regularization term of the iteration process. In addition to these equations, the reconstructed images by the SIR methods and their RMSEs presented in this study are useful in CT research.[Conclusions] The fundamental point of SIR methods is the regularization term used in minimizing the object function.

Erratum to: “Synthesis and Properties of Nanosilicon Stabilized by Butyl and Perfluorobutyl Ligands”

257 It was found that in the published paper by L.A. Aslanov, V.N. Zakharov, A.V. Pavlikov, S.V. Sa vilov, V.Yu. Timoshenko, and A.V. Yatsenko “Synthe sis and Properties of Nanosilicon Stabilized by Butyl and Perfluorobutyl Ligands” (Russ. J. Coord. Chem., 2013, vol. 39, no. 6, p. 427), the IR spectrum of sili con nanoparticles with perfluorobutyl ligands exhib its absorption bands for dimethoxyethane (solvent), which is removed only partly during drying of silicon nanoparticles obtained in this solvent. The strongest absorption band at 1101 cm–1 proved to be a superpo sition of the strongest solvent band (1110 cm–1) and the Si–O stretching band (1080 cm–1). The positions of 1200 and 1242 cm–1 bands corresponding to the solvent coincided with the positions of the strongest absorption bands of perfluorobutyl ligands. As a result, the band intensities were distorted. The true IR spectrum of silicon nanoparticles with perfluo robutyl ligands will soon be published. Erratum to: “Synthesis and Properties of Nanosilicon Stabilized by Butyl and Perfluorobutyl Ligands” [Russ. J. Coord. Chem., 39, 6 (2013)]

Complete Elemental Analysis of Low-k a-SiC:H Thin Films by Transmission FTIR Spectroscopy

Fourier transform infrared (FTIR) spectroscopy is a popular technique for qualitatively investigating the chemical bonding of low dielectric constant (low-k) materials utilized in nanoelectronic Cu interconnects. However, quantitative FTIR analysis of low-k materials with widely varying stoichiometry has proven challenging due to numerous optical interference effects, variations in IR absorption strength with optical constants, and a negligible IR activity for homopolar bonds. In this paper, these challenges are overcome to demonstrate full elemental composition analysis by applying multivariate partial least squares (PLS) modeling to the true IR absorbance spectra obtained using previously described methods for eliminating optical interference effects from thin film FTIR spectra. To demonstrate the validity of this approach, transmission FTIR spectra were collected from a series of low-k a-SiC:H thin films with hydrogen content ranging from 25–60%. The elemental concentrations determined from PLS analysis of the corrected low-k a-SiC:H FTIR spectra were found to be in agreement to within ±5% of results obtained from independent nuclear reaction analysis and Rutherford backscattering measurements. These results demonstrate a clear path for establishing transmission FTIR as a quantitative metrology for full compositional analysis (elemental and chemical bond) for a wide range of thin film materials.

Fermion self-energy correction in light-front QED using coherent state basis

We discuss IR divergences in lepton mass renormalization in Light-Front Quantum Electrodynamics (LFQED) in Feynman gauge. We consider LFQED with Pauli-Villars fields and using old-fashioned time ordered perturbation theory (TOPT), we show that our earlier result regarding cancellation of true IR divergences upto $O(e^4)$ in coherent state basis holds in Feynman gauge also.

Mechanism of Hydrogenolysis of an Iridium–Methyl Bond: Evidence for a Methane Complex Intermediate

Evidence for key σ-complex intermediates in the hydrogenolysis of the iridium-methyl bond of (PONOP)Ir(H)(Me)(+) (1) [PONOP = 2,6-bis(di-tert-butylphosphinito)pyridine] has been obtained. The initially formed η(2)-H(2) complex, 2, was directly observed upon treatment of 1 with H(2), and evidence for reversible formation of a σ-methane complex, 5, was obtained through deuterium scrambling from η(2)-D(2) in 2-d(2) into the methyl group of 2 prior to methane loss. This sequence of reactions was modeled by density functional theory calculations. The transition state for formation of 5 from 2 showed significant shortening of the Ir-H bond for the hydrogen being transferred; no true Ir(V) trihydride intermediate could be located. Barriers to methane loss from 2 were compared to those of 1 and the six-coordinate species (PONOP)Ir(H)(Me)(CO)(+) and (PONOP)Ir(H)(Me)(Cl).

IR spectra of cytochrome c denatured with deuterated guanidine hydrochloride show increase in beta sheet.

Attenuated total reflectance Fourier transform IR (ATR-FTIR) spectra are obtained for horse heart ferricytochrome c in solutions of 0-7M guanidine hydrochloride and deuterated guanidine hydrochloride. Substitutions of deuterium for hydrogen in both the denaturant and protein provide resolvable amide I spectra over a wide range of denaturant concentrations. Deuteration enhances the ability to measure the true protein IR spectrum in the amide I region in which the secondary structure can be deduced, because spectra in D(2)O are less prone to spectral distortion upon background denaturant subtraction than spectra in H(2)O. Other investigators studying equilibrium unfolded cytochrome c were limited to guanidine concentrations below 3.0M because of detector saturation. Detector saturation is avoided with the use of ATR-FTIR spectroscopy, allowing one to obtain protein spectra at high denaturant concentrations. Second derivative spectra of samples show reductions in alpha helix and increases in beta sheet at high denaturant concentrations, contrary to expectations of finding primarily a random coil secondary structure. Using this new technique, the protein was estimated to consist of 51% beta sheet and only 15% random coil in the presence of 6.6M deuterated guanidine hydrochloride.

Infrared Photometric Variability of GX 13+1 and GX 17+2

We present infrared photometry of the Galactic bulge X-ray binary systems GX 13+1 and GX 17+2 obtained in 1997 July and August using OSIRIS on the 1.8 m Perkins Telescope at Lowell Observatory. GX 13+1 clearly varies over ~0.6 mag in the K band. Our light curve suggests a modulation on a timescale of ~20 days, which is in agreement with previously proposed orbital periods for the system. The IR counterpart of GX 17+2 is also variable in the K band over ~0.8 mag on a timescale of days to weeks, extending the variability first seen by Naylor, Charles, & Longmore). We discuss the implications our data have for Deutsch et al.'s identification of "star A" as the true IR counterpart of GX 17+2. The variability observed in our photometry of the blend of star A and the foreground star NP Ser implies a ~4 mag intrinsic variation in the K band for GX 17+2.

Adaptive Optics Infrared Imaging Polarimetry and OpticalHSTImaging of Hubble's Variable Nebula (R Monocerotis/NGC 2261): A Close Look at a Very Young Active Herbig Ae/Be star

We present high-resolution (FWHM = 02) near-IR (J, H, and K') adaptive optics images of the Herbig Ae/Be star R Monocerotis. Optical Hubble Space Telescope (HST) WFPC2 PC camera archival images are also presented. For the first time, adaptive optics was utilized to make high-resolution (FWHM = 02) IR-imaging polarimetry maps of R Mon. In addition, the first mid-IR array images (at 11.7 and 20.8 ?m) of R Mon have been obtained. We also present new 3.16, 3.93, and 4.67 ?m images. We have found that R Mon is a 069 binary star with a companion that dereddens onto the classical T Tauri locus. Based on the near-infrared photometry of this companion we believe it is a 1.5 M?, very young ( + 800?280 pc distant based on previous proper-motion and radial velocity measurements of R Mon's jet. Our high-resolution (FWHM ~ 02) adaptive optics infrared polarimetry maps agree with the current interpretation that NGC 2261 is a reflection nebula illuminated by R Mon. Interior to the parabolic shell there is a complex of twisted filaments along the eastern edge. These filaments resemble a double-helical structure which is well described by a power law from ~103 to 105 AU from R Mon. This double helix may trace a twisted magnetic field above R Mon. Based on H I emission-line ratios, we find the direct extinction toward R Mon to be AV = 13.1 mag in the infrared (? > 1.28 ?m), falling to a lower value of AV = 3.6 mag in the optical (? < 1.28 ?m), where scattered light increasingly lowers the effective extinction in the line ratios. The large AV = 13.1 extinction is likely due to the dusty atmosphere of an inclined R ~ 100 AU optically thick accretion disk surrounding R Mon. A simple model of such an accretion disk + star system (with Macc ~ 8 ? 10-5 M? yr-1, M* = 10.4 M?, R* = 2 R?, and T* ~ 3.5 ? 104 K) reproduces the observed dereddened R Mon spectral energy distribution (SED) from the optical (0.4 ?m) to the millimeter region. Consideration of the lower extinction (AV = 3.6) on the path followed by the scattered visible light eliminated any need for an inner gap in the accretion disk model to reproduce the SED. In general, young stellar objects (YSOs) that are obscured in the optical but directly visible in the infrared will have different effective optical and infrared extinctions. Infrared extinctions derived from optical observations dominated by scattered light will be underestimates of the true IR extinction along the direct path. The use of an independent estimator of both the optical and infrared extinctions such as common upper-level H I recombination lines is highly desirable. The utilization of the correct optical and infrared extinctions may relieve the need for optically thin inner-disk gaps to explain YSO near-IR SEDs.

Fourier transform infrared microscopical analysis with synchrotron radiation: The microscope optics and system performance (invited)

When a Fourier transform infrared microspectrometer was first interfaced with the National Synchrotron Light Source in September 1993, there was an instant realization that the performance at the diffraction limit had increased 40–100 times. The synchrotron source transformed the IR microspectrometer into a true IR microprobe, providing high-quality IR spectra for probe diameters at the diffraction limit. The combination of IR microspectroscopy and synchrotron radiation provides a powerful new tool for molecular spectroscopy. The ability to perform IR microspectroscopy with synchrotron radiation is still under development at Brookhaven National Laboratory, but several initial studies have been completed that demonstrate the broad-ranging applications of this technology and its potential for materials characterization.

Coherent states in null-plane QED.

Light front field theories are known to have the usual infra-red divergences of the equal time theories, as wellas new `spurious' infra-red divergences. The formar kind of IR divergences are usually treated by giving a small mass to the gauge particle. An alternative method to deal with these divergences is to calculate the transition matrix elements in a coherent state basis. In this paper we present, as a model calculation the lowest order correction to the three point vertex in QED using a coherent state basis in the light cone formalism. The relevant transition matrix element is shown to be free of the true IR divergences up to $O(e^2)$.