Application of the split-gradient method to 3D image deconvolution in fluorescence microscopy

The methods of image deconvolution are important for improving the quality of the detected images in the different modalities of fluorescence microscopy such as wide‐field, confocal, two‐photon excitation and 4Pi. Because deconvolution is an ill‐posed problem, it is, in general, reformulated in a statistical framework such as maximum likelihood or Bayes and reduced to the minimization of a suitable functional, more precisely, to a constrained minimization, because non‐negativity of the solution is an important requirement. Next, iterative methods are designed for approximating such a solution. In this paper, we consider the Bayesian approach based on the assumption that the noise is dominated by photon counting, so the likelihood is of the Poisson‐type, and that the prior is edge‐preserving, as derived from a simple Markov random field model. By considering the negative logarithm of the a posteriori probability distribution, the computation of the maximum a posteriori (MAP) estimate is reduced to the constrained minimization of a functional that is the sum of the Csiszár I‐divergence and a regularization term. For the solution of this problem, we propose an iterative algorithm derived from a general approach known as split‐gradient method (SGM) and based on a suitable decomposition of the gradient of the functional into a negative and positive part. The result is a simple modification of the standard Richardson–Lucy algorithm, very easily implementable and assuring automatically the non‐negativity of the iterates. Next, we apply this method to the particular case of confocal microscopy for investigating the effect of several edge‐preserving priors proposed in the literature using both synthetic and real confocal images. The quality of the restoration is estimated both by computation of the Kullback–Leibler divergence of the restored image from the detected one and by visual inspection. It is observed that the noise artefacts are considerably reduced and desired characteristics (edges and minute features as islets) are retained in the restored images. The algorithm is stable, robust and tolerant at various noise (Poisson) levels. Finally, by remarking that the proposed method is essentially a scaled gradient method, a possible modification of the algorithm is briefly discussed in view of obtaining fast convergence and reduction in computational time.     

An open‐source deconvolution software package for 3‐D quantitative fluorescence microscopy imaging

Deconvolution techniques have been widely used for restoring the 3‐D quantitative information of an unknown specimen observed using a wide‐field fluorescence microscope. Deconv , an open‐source deconvolution software package, was developed for 3‐D quantitative fluorescence microscopy imaging and was released under the GNU Public License. Deconv provides numerical routines for simulation of a 3‐D point spread function and deconvolution routines implemented three constrained iterative deconvolution algorithms: one based on a Poisson noise model and two others based on a Gaussian noise model. These algorithms are presented and evaluated using synthetic images and experimentally obtained microscope images, and the use of the library is explained. Deconv allows users to assess the utility of these deconvolution algorithms and to determine which are suited for a particular imaging application. The design of Deconv makes it easy for deconvolution capabilities to be incorporated into existing imaging applications.     

Chemical properties of superfine pulverized coal particles. Part 1. Electron paramagnetic resonance analysis of free radical characteristics

Superfine pulverized coal combustion is a new pulverized coal combustion technology with lots of advantages. A mechanochemical effect exists during the comminution process, which changes the chemical properties of coal significantly. Free radical concentrations and certain functional groups would increase with the decrease of particle sizes. In this paper, we combined electron paramagnetic resonance (EPR) and ¹³C solid-state nuclear magnetic resonance (NMR) techniques to study the free radical characteristics of superfine pulverized coal thoroughly. The final results indicate that the EPR spectra of coal are the superimpositions of several lines induced by different paramagnetic centers, which can be fitted by 1 Gaussian and 3 Lorentzian lines. The influences of coal maturities and particle sizes on EPR parameters, such as g-values, linewidths, and spin concentrations, are analyzed in detail. It is shown that with the decrease of particle sizes, more free radicals are induced through bond cleavages. Mechanical forces initiate the accumulation of free radicals in the fractures and inner pore surfaces of coal. Furthermore, the influence of particle sizes on oxygen-containing radicals (i.e., Lorentzian 1 types) is the greatest. This work provides a primary picture of the occurrence modes and spatial distributions of free radicals in superfine pulverized coal. The findings will help form the basis and provide guidance for further studies on revealing the correlations between the free radical reaction pathways and NO_x formation mechanisms.     

Wavelets: on the virtues and applications of the mathematical microscope

The paper provides a short introduction to wavelets and discusses their main applications in microscopy and biological imaging.     

Detection of loop closure in SLAM: A DeconvNet based approach

The problem of Simultaneous Localization and Mapping(SLAM) suffers from drift in long run odometry and the only way to correct that is by graph optimization based on loop closure detection, where a robot is able to correct its location precisely if it detects that it is at a place which was visited before. The traditional approaches for recognizing known places follow a feature-based bag-of-words model which discards certain geometric and structural information. The proposed methodology represents a scene as low-dimensional vector using a deep deconvolution network. A 12-layer deconvolution net has been proposed that encodes and decodes an image to itself to learn the representation. The use of locally connected autoencoders in the network drastically reduces the dimension without significant loss in retaining the contextual information. Loop closure is identified by comparing such representations. Sequences from KITTI visual odometry dataset and new college dataset are used for evaluation. Performance is compared with state-of-the-art techniques and found satisfactory.     

用Z变换求解离散反卷积

本文介绍了用Z变换求解离散反卷积的方法,并通过实例分析了测量误差(噪声)对反卷积的影响。     

应用离散富氏变换的反褶积方法

应用离散富氏变换(DFT)的反褶积方法,与计算反褶积的Z变换和最小平方法相比,具有以下优点: (1)精度高。(2)运算量少。(3)对地震子波无相位要求。     

用高纯锗γ谱仪测量和分析连续γ射线能谱的方法

本文介绍了一种用高纯锗γ谱仪测量和分析连续γ射线能谱的方法。     

Inversion of microscopic lock-in thermograms in the presence of emissivity contrast

None of the conventionally displayed images of lock-in thermography (in-phase or 0° image, out of phase or −90° image, amplitude image, phase image) is able to become inverted in the presence of emissivity contrast. The phase signal is inherently emissivity-corrected, but here contributions of different heat sources superimpose very nonlinearly, which prevents any meaningful deconvolution. It is shown that the “0°/−90°” image, as an alternative kind of representation of lock-in thermography images, being also inherently emissivity-corrected, is able to be inverted for obtaining, e.g. the lateral power distribution in an electronic device. Blackening the surface by colloidal bismuth also may remove the emissivity contrast.     

Ultrasonic focused waveform generation using time reversal acoustic focusing system

Abstract The concept of Time Reversal Acoustics (TRA) provides an elegant possibility of both temporal and spatial concentrating of acoustic energy in highly inhomogeneous media. We explored the possibility of generating acoustical signals with arbitrary waveforms using the TRA Focusing System (TRA FS). A method has been developed to predict TRA-focused ultrasound waveforms and spatial distribution by using the measurements of transfer function of transfer function relating the signal at the TRA transmitter to that at the focusing point. The developed approach for TRA-focused signal waveform prediction from the results of direct signal measurements was tested on ten-channel TRA FS based on aluminum resonator with glued piezotransducers. The TRA FS operated in the frequency band of 100–1000 kHz. The formation of ultrasonic signals with various envelopes was demonstrated experimentally. The calculated and experimentally measured waveforms and spatial distributions were practically identical. We formed triangular, rectangular, and amplitude modulated tone burst signals with different modulation frequencies in the focal region. The level of side lobes in the generated signals was much lower than that for standard TRA focusing.