Bayesian filtering of speckled images

Speckle noise arises in imaging systems that use coherent or partially coherent illumination. We demonstrate that such noise may be reduced by use of bayesian filters. The usual assumption that speckle noise is approximately equivalent to multiplicative image noise is replaced with an exact analysis.     

In vivo dynamic turnover of cerebral 13C isotopomers from [U-13C]glucose

An INEPT-based (13)C MRS method and a cost-effective and widely available 11.7 Tesla 89-mm bore vertical magnet were used to detect dynamic (13)C isotopomer turnover from intravenously infused [U-(13)C]glucose in a 211 microL voxel located in the adult rat brain. The INEPT-based (1)H-->(13)C polarization transfer method is mostly adiabatic and therefore minimizes signal loss due to B(1) inhomogeneity of the surface coils used. High quality and reproducible data were acquired as a result of combined use of outer volume suppression, ISIS, and the single-shot three-dimensional localization scheme built in the INEPT pulse sequence. Isotopomer patterns of both glutamate C4 at 34.00 ppm and glutamine C4 at 31.38 ppm are dominated first by a doublet originated from labeling at C4 and C5 but not at C3 (with (1)J(C4C5) = 51 Hz) and then by a quartet originated from labeling at C3, C4, and C5 (with (1)J(C3C4) = 35 Hz). A lag in the transition of glutamine C4 pattern from doublet-dominance to quartet dominance as compared to glutamate C4 was observed, which provides an independent verification of the precursor-product relationship between neuronal glutamate and glial glutamine and a significant intercompartmental cerebral glutamate-glutamine cycle between neurons and glial cells.     

Transfer of1H and13C dynamic nuclear polarization from immobilized nitroxide radicals to flowing liquids

In this study,¹H and¹³C dynamic nuclear polarization (DNP) was generated at a magnetic field strength of 0.33 T utilizing silica phase immobilized nitroxide (SPIN) samples. The polarization was subsequently transferred to flowing liquids and monitored at a magnetic field strength of 4.7 T. These solid/liquid intermolecular transfer (SLIT) experiments provide efficient polarization transfer without the necessity of the free radical system present in the monitoring fluid. Specifically, ultimate¹H SLIT DNP Overhauser enhancements of ?56 and ?110 have been observed for benzene and chloroform in the presence of SPIN system 2, respectively. The¹³C SLIT DNP enhancement for benzene is dominated by three-spin effects and poor leakage factors (f _c). However, a particularly favorable case is the chloroform/SPIN 2 system which exhibits a scalar dominated enhancement. For this case, positive enhancements 40–60 times the¹³C thermal Boltzmann magnetization at 4.7 T have been observed. The large scalar dominated¹³C DNP enhancement for this system represents one of the largest experimental enhancements reported to date. The¹³C DNP spectra for other samples which exhibit favorable scalar¹³C dominated enhancements (e.g., Freon 113) are also presented. Three different SPIN systems were also prepared and characterized in the present study.     

Inverse polarization transfer for detecting in vivo 13C magnetization transfer effect of specific enzyme reactions in 1H spectra

The wide chemical shift dispersion and long T(1) of (13)C have allowed determination of in vivo magnetization transfer effects caused by aspartate aminotransferase and lactate dehydrogenase reactions using (13)C magnetic resonance spectroscopy. In this report, we demonstrate that these effects can be observed in the proton spectra by transferring the equilibrium magnetization of (13)C via the one-bond scalar coupling between (13)C and (1)H using an inverse insensitive nuclei enhanced by polarization transfer-based heteronuclear polarization transfer method. This inverse method allows a combination of the advantages of the long (13)C T(1) for maximum magnetization transfer and the high sensitivity of proton detection. The feasibility of this in vivo inverse polarization transfer approach was evaluated for detecting the (13)C magnetization transfer effect of aspartate aminotransferase and lactate dehydrogenase reactions from a 72.5-microl voxel in the rat brain at 11.7 T.     

1H and 13C NMR Determination of 1-Naphtyl-Polymethoxylated Diphenylwiethanes

The complete structural analysis of 1-[(4-methoxyphenyl)-(3,4,5-trimethoxyphe- nyl)methyl]naphtalene 5a and 1-[(2,5-dimethoxyphenyl)-(3,4,5-trimethoxyphenyl) methyljnaphtalene 5b, prepared by alkylation of 1-[chloro-(3,4,5-trimethoxyphenyl) methyl]naphtalene without by-products such as benzofluorene 2, may be accurately determined by ¹H, ¹³C NMR and 2D NMR analysis.     

1H AND 13C NMR Assignments of Artheethers

The ¹H and ¹³C nmr assignments for all hydrogen and carbon atoms were made for β and α arteethers (5 and 6) based on chemical shift theory and 2D-nmr techniques (COSY and HETCOR).     

Bayesian estimation of relaxation times T(1) in MR images of irradiated Fricke-agarose gels

The authors present a novel method for processing T(1)-weighted images acquired with Inversion-Recovery (IR) sequence. The method, developed within the Bayesian framework, takes into account a priori knowledge about the spatial regularity of the parameters to be estimated. Inference is drawn by means of Markov Chains Monte Carlo algorithms. The method has been applied to the processing of IR images from irradiated Fricke-agarose gels, proposed in the past as relative dosimeter to verify radiotherapeutic treatment planning systems. Comparison with results obtained from a standard approach shows that signal-to noise ratio (SNR) is strongly enhanced when the estimation of the longitudinal relaxation rate (R1) is performed with the newly proposed statistical approach. Furthermore, the method allows the use of more complex models of the signal. Finally, an appreciable reduction of total acquisition time can be obtained due to the possibility of using a reduced number of images. The method can also be applied to T(1) mapping of other systems.     

Neuronal integration of dynamic sources: Bayesian learning and Bayesian inference

One of the brain's most basic functions is integrating sensory data from diverse sources. This ability causes us to question whether the neural system is computationally capable of intelligently integrating data, not only when sources have known, fixed relative dependencies but also when it must determine such relative weightings based on dynamic conditions, and then use these learned weightings to accurately infer information about the world. We suggest that the brain is, in fact, fully capable of computing this parallel task in a single network and describe a neural inspired circuit with this property. Our implementation suggests the possibility that evidence learning requires a more complex organization of the network than was previously assumed, where neurons have different specialties, whose emergence brings the desired adaptivity seen in human online inference.     

Bayesian estimation of a dynamic structure's response

This study focuses on the estimation of uncertainty associated with the stress/strain prediction procedures from dynamic test data of structural systems. An accurate prediction of the maximum response levels for physical components during in-field operating conditions is essential for evaluating their performance and life characteristics, as well as for investigating their behavior in light of system design and reliability assessment. Stress/strain inference for a dynamic system is based on the combination of experimental data and results from the analytical/numerical model of the component under consideration. Both modeling challenges and testing limitations contribute to the introduction of various sources of uncertainty within the given estimation procedure with consequent reduced confidence in the predicted response.The objective of this work is to quantify the uncertainties present in the current response estimation process by means of a Bayesian-network representation of the modeling process which allows for a rigorous synthesis of modeling assumptions and information from experimental data, as it takes into account the multi-directional nature of uncertainty propagation. More specifically, the focus is on the residual uncertainty associated with the system's inferred response, and its dependence upon the amount of test data being included in the estimation analysis.Both discrete and linear Gaussian networks were investigated with a focus on their training accuracy and performance in the presence of nonlinear relationships among the physical quantities, weak cause-effect nodal links, as well as different sensitivity levels with respect to infused evidence.     

Gibbs distribution-based Bayesian segmentation of electron microscopy nanostructure images

The use of Gibbs distribution-based Bayesian segmentation of electron microscopy images for visualizing nanostructures is investigated. Bayesian segmentation involves dividing an image into nonoverlapping areas that correspond as closely as possible to the observed image. A quantitative characteristic of this correspondence is the a posteriori probability of one variant of division or another. The most likely version is always the division with the greatest a posteriori probability. The Metropolis algorithm for stochastic relaxation is used to obtain Bayesian estimates of the a posteriori probability of a division. Our study of Bayesian segmentation requires visualization of nanostructures on an electron microscopy image of a film made of NiW nanocrystalline alloy.     

Detection and tracking of targets in infrared images using Bayesian techniques

Simple yet robust techniques for detecting targets in infrared (IR) images are an important component of automatic target recognition (ATR) systems. In our previous works, we have developed IR target detection and tracking algorithms based on image correlation and intensity. In this paper, we discuss these algorithms, their performances and problems associated with them and then propose novel algorithms to alleviate these problems. Our proposed target detection and tracking algorithms are based on frequency domain correlation and Bayesian probabilistic techniques, respectively. The proposed algorithms are found to be suitable for real-time detection and tracking of static or moving targets, while accommodating for detrimental affects posed by the clutter and background noise. Finally, limitations of all these algorithms are discussed.     

2,4,6-三甲氧基苯-1-O-D葡萄糖苷的核磁共振谱的理论研究

应用规范不变原子轨道GIAO法,分别在HF/6-311+G(2d,p)//B3LYP/6-31G(d)和HF/6-311+G(2d,p)//B3LYP/6-31G(d,p)水平上,计算了从卫茅科南蛇藤属植物苦皮藤中分离鉴定出的2,4,6-三甲氧基苯-1-O-D葡萄糖苷(化合物1)的α和β分子构型的1HNMR和13CNMR的化学位移值,并对理论计算值与实验值的误差进行了统计分析,其中β分子构型的计算值与实验值较为接近,结合α和β分子构型的总能量计算值,预测化合物1分子应择型于β构型,即为2,4,6-三甲氧基苯-1-O-β-D葡萄糖苷,这与根据糖的端基质子化学位移和耦合常数实验值(δH=4.81,J=7.3Hz)推断的结论相吻合,进一步说明理论计算的合理性.     

1H MRS detection of glycine residue of reduced glutathione in vivo

Glutathione (GSH) is a powerful antioxidant found inside different kinds of cells, including those of the central nervous system. Detection of GSH in the human brain using ¹H MR spectroscopy is hindered by low concentration and spectral overlap with other metabolites. Previous MRS methods focused mainly on the detection of the cysteine residue (GSH-Cys) via editing schemes. This study focuses on the detection of the glycine residue (GSH-Gly), which is overlapped by glutamate and glutamine (Glx) under physiological pH and temperature. The first goal of the study was to obtain the spectral parameters for characterization of the GSH-Gly signal under physiological conditions. The second goal was to investigate a new method of separating GSH-Gly from Glx in vivo. The characterization of the signal was carried out by utilization of numerical simulations as well as experiments over a wide range of magnetic fields (4.0–14 T). The proposed separation scheme utilizes J-difference editing to quantify the Glx contribution to separate it from the GSH-Gly signal. The presented method retains 100% of the GSH-Gly signal. The overall increase in signal to noise ratio of the targeted resonance is calculated to yield a significant SNR improvement compared to previously used methods that target GSH-Cys residue. This allows shorter acquisition times for in vivo human clinical studies.     

1H dynamic nuclear polarization in supercritical ethylene at 1.4 T

(1)H dynamic nuclear polarization (DNP) has been measured in supercritical ethylene in the pressure range 60-300 bar in an external field of 1.4 T. A single-cell sapphire tube was used as a high-pressure cell, and powdered 1,3-bisdiphenylene-2-phenyl allyl (BDPA) free radicals were added and distributed at the wall of the cell. At all pressures the dominant DNP mechanism was a positive Overhauser enhancement, caused by proton-electron contact interactions at the fluid/solid radical interface. The observed enhancements varied from 12 at 60 bar to 17 at 300 bar. Besides the Overhauser enhancement, small solid state and thermal mixing enhancements also were observed, indicating that part of the ethylene was adsorbed at the radical surface for a prolonged time. The impacts of the experimental conditions on the Overhauser enhancement factors are discussed, and enhancements of at least 40-60 are estimated when the EPR saturation factor and the leakage factor become maximal. These data indicate that DNP-enhanced NMR has the potential of extending the impact of NMR in research areas involving supercritical fluids.     

吉士脱酮的1H及13C NMR研究

Gestodene是避孕药物18甲基炔诺酮的衍生物,动物实验表明它的孕激素活性为18甲基炔诺酮的3~5倍.本文采用各种2D NMR技术,包括:¹H-¹H COSY,¹H-¹³C COSY和HMBC等,归属了它的¹H和¹³C的谱线,并得到了有关质子间的偶合常数.     

多取代(口山)酮及其糖甙(口山)酮的1H和13C NMR研究

总结了作者所测定过的多取代(口山)酮及其糖甙类衍生物的¹H和¹³C NMR位移数据,着重就取代基与结构的关系进行了探讨,认为多取代(口山)酮1位和8位取代情况直接影响着其他位置的化学位移数值,这一现象可以直接用于该类化合物的结构鉴定.     

Quantification of human brain metabolites from in vivo 1H NMR magnitude spectra using automated artificial neural network analysis

Long echo time (TE=270 ms) in vivo proton NMR spectra resembling human brain metabolite patterns were simulated for lineshape fitting (LF) and quantitative artificial neural network (ANN) analyses. A set of experimental in vivo 1H NMR spectra were first analyzed by the LF method to match the signal-to-noise ratios and linewidths of simulated spectra to those in the experimental data. The performance of constructed ANNs was compared for the peak area determinations of choline-containing compounds (Cho), total creatine (Cr), and N-acetyl aspartate (NAA) signals using both manually phase-corrected and magnitude spectra as inputs. The peak area data from ANN and LF analyses for simulated spectra yielded high correlation coefficients demonstrating that the peak areas quantified with ANN gave similar results as LF analysis. Thus, a fully automated ANN method based on magnitude spectra has demonstrated potential for quantification of in vivo metabolites from long echo time spectroscopic imaging.     

1H and C-13 Nuclear Magnetic Resonance of Tiaprofenic Acid

¹H-NMR spectrum of tiaprofenic acid in CDCI3 was obtained and proton chemical shifts from tetramethylsilane were assigned to each proton and set of equivalent protons of the molecule. The hydroxy proton of the carboxylic acid group was confirmed by deuterium exchange. The natural abundance C-13 nuclear magnetic resonance spectrum of the compound in CDCI3 was recorded using Fourier transorm technique. The chemical shifts of carbon resonances have been assigned on the basis of the chemical shift additivity theory and the signal multiplicity observed in the single frequency off-resonance decoupled (SFORD) spectrum. Also comparison with carbon chemical shifts of model compounds were useful.     

The Assignment of Long-Range 13C-1H Coupling Constants in Pyrazoles 13C NMR,Selective Decoupling

Although quite a few papers have been devoted to the ¹³C NMR study of pyrazoles, there is one problem that has not yet been satisfactorily solved, namely the assignment of the ²JCH and ³JCH coupling constants. In general, the ³C chemical shifts and ¹JCH coupling constants can be easily attributed, but the assigment of the long-range ²JCH and ³JCH coupling constants is not straight forward. In N- substituted pyrazoles, where annular tautomerism is prevented, each carbon atom can have two long-range coupling constants with the ring protons.     

Intermolecular interactions of benzene and carbon tetrachloride with selected free radicals in solution as studied by 13C and 1H dynamic nuclear polarization

Intermolecular hyperfine coupling between ¹³C nuclei and free-radical unpaired electron spins has been examined for six combinations of three free radicals and two solvent molecules. From magnetic field and temperature-dependent dynamic nuclear polarization measurements, scalar and dipolar coupling contributions have been separated. Interpretation of these results in terms of a modified diffusion model revealed scalar spectral density functions with two or three frequency components, each characterized by a distinct contact time. Collisions with the shortest time constant were found to be nearly independent of the system and accounted for approximately 90 per cent of all radical-receptor collisions and 30 per cent of the scalar relaxation rate. These have been related to random elastic collisions. In contrast, collisions with long contact times were found to be highly system dependent. Although few in number, they accounted for a relatively large fraction of the scalar relaxation rate because of their long duration. These have been interpreted as stereospecific collisions which reflect the tendency of the colliding partners to form weak transient complexes. Lastly, relative scalar coupling energies were obtained and related to the availability of the unpaired electron and to the structure of both colliding molecules.