Search

The interception of one chemical intermediate with another intermediate is very challenging, as intermediates may be incompatible or too reactive, but could result in a streamlined method of organic synthesis. Here, the authors demonstrate enantioselective four-component reactions via the coupling of two intermediates.

On the basis of analyzing the development of the concept of public welfare packaging, taking the commercial practices of public welfare packaging as examples, the advantages, current situation and problems of food packaging participating in public welfare were analyzed. The design idea of food packaging based on network public welfare communication was put forward. Food public welfare packaging should follow the design principles of commonweal, simplicity, interactivity and communication, and promote the continuous innovation by integrating new media, new materials, new technologies and new contexts, in order to improve public welfare packaging to better serve the enterprise's public welfare communication, so as to achieve win-win results between commercial interests and social benefits.

For a five-phase motor with non-sinusoidal windings arrangement, the electromagnetic torque can be enhanced by injecting third harmonic current. This paper studies the driving system and the fundamental and third harmonic spaces of the five-phase motor with non-sinusoidal windings, proposing a four-dimensional space vector PWM strategy based on modulation function method. According to the relationship of duty circle and modulation function of the periodic midpoint, for a symmetric regular sampling method, the phase modulation function can be obtained. It greatly simplifies the computational complexity and the occupied storage space. To deal with saturation, it only needs to limit the duty cycle or the amplitude of modulation function, which eliminates the complex division operation. To verify the correctness of the proposed method, the simulation and experiment are conducted on MATLAB/Simulink and hardware-in-the-loop simulation platform of RT-LAB/dSPACE, respectively. Finally, the phase current of the motor is analyzed with Fast Fourier Transform (FFT), showing the third harmonic content is basically the same as the set value.

As the third-harmonic air-gap magnetic motive forces (MMFs) can be well utilized to improve the torque density, more and more research has been studying the postfault control for a five-phase permanent-magnet synchronous motor with trapezoidal back electromotive force (EMF). This paper presents a new reduced-order fault-tolerant control (FTC) scheme for the FPMSM with trapezoidal back EMF under single-phase open-circuit fault. Firstly, third reduced-order transformation matrices with third-harmonic current injection, the postfualt five-phase machines can not only realize an undisturbed MMF but also maintain high electromagnetic torque. Finally, the results verify that the proposed FTC strategy on reduced-order model can realize the single-phase open-circuit fault-tolerant and show fast dynamic response capability even under FTC condition.

C22H22N12O4Zn, monoclinic, P21/c (no. 14), a = 9.864(2) Å, b = 8.6657(17) Å, c = 30.803(8) Å, β = 106.67(3)°, V = 2522.3(10) Å3, Z = 4, Rgt(F) = 0.0630, wRref(F2) = 0.1625, T = 293(2) K.

In order to calibrate the stripe precision of a leveling rod, an automatic laser interferometer and a vision measurement system were designed by Xi’an University of Technology in China. The rod was driven by a closed-loop control and the data were collected at the stop state to ensure precision. The laser interferometer provided not only the long distance data but also a position feedback signal in the automatic control loop. CCD camera and a vision measurement method were used to inspect the stripe edge position and defect. A pixel-equivalent self-calibration method was designed to improve precision. ROI (regions of interest) method and an outline tracing method were designed to quickly extract multiple stripe edges. A combination of the image data with the interferometer data reduces control difficulty and ensures the measurement accuracy. The vision measurement method reached sub-pixel precision and the defective edges were reported. The system can automatically calibrate a stripe leveling rod with a high degree of efficiency and precision.

C24H15NO, monoclinic, P21/n (no. 14), a = 10.3161(3) Å, b = 5.53330(10) Å, c = 29.2019(7) Å, β = 97.341(1)°, V = 1653.24(7) Å3, Z = 4, Rgt(F) = 0.0423, wRref(F2) = 0.1344, T = 294(2) K.

BackgroundSingle photon emission computed tomography (SPECT) is an imaging modality that has demonstrated its utility in a number of clinical indications. Despite this progress, a high sensitivity, high spatial resolution, multi-tracer SPECT with a large field of view suitable for whole-body imaging of a broad range of radiotracers for theranostics is not available.PurposeWith the goal of filling this technological gap, we have designed a cadmium zinc telluride (CZT) full-ring SPECT scanner instrumented with a broad-energy tungsten collimator. The final purpose is to provide a multi-tracer solution for brain and whole-body imaging. Our static SPECT does not rely on the dual- and the triple-head rotational SPECT standard paradigm, enabling a larger effective area in each scan to increase the sensitivity. We provide a demonstration of the performance of our design using a realistic model of our detector with simulated body-sized phantoms filled with 99m Tc and 177 Lu.MethodsWe create a realistic model of our detector by using a combination of a Geant4 Application for Tomographic Emission (GATE) Monte Carlo simulation and a finite element model for the CZT response, accounting for low-energy tail effects in CZT that affects the sensitivity and the scatter correction. We implement a modified dual-energy-window scatter correction adapted for CZT. Other corrections for attenuation, detector and collimator response, and detector gaps and edges are also included. The images are reconstructed using the maximum-likelihood expectation-maximization. Detector and reconstruction performance are characterized with point sources, Derenzo phantoms, and a body-sized National Electrical Manufacturers Association (NEMA) Image Quality (IQ) phantom for both 99m Tc and 177 Lu.ResultsOur SPECT design can resolve 7.9 mm rods for 99m Tc (140 keV) and 9.5 mm for 177 Lu (208 keV) in a hot-rod Derenzo phantom with a 3-min exposure and reach an image contrast of 78% for 99m Tc and 57% for 177 Lu using the NEMA IQ phantom with a 6-min exposure. Our modified scatter correction shows an improved contrast-recovery ratio compared to a standard correction.ConclusionsIn this paper, we demonstrate the good performance of our design for whole-body imaging purposes. This adds to our previous demonstration of improved qualitative and quantitative 99m Tc imaging of brain perfusion and 123 I imaging of dopamine transport with respect to state-of-the-art NaI dual-head cameras. We show that our design provides similar IQ and contrast to the commercial full-ring SPECT VERITON for 99m Tc. Regarding 177 Lu imaging of the 208 keV emissions, our design provides similar contrast to that of other state-of-the-art SPECTs with a significant reduction in exposure. The high sensitivity and extended energy range up to 250 keV makes our SPECT design a promising alternative for clinical imaging and theranostics of emerging radionuclides.

Measurement techniques of uranium series nuclides 210Pb, 210Bi and 210Po are relatively independent at present for most cases, and there are still some technical issues that need to be overcome. Joint measurement techniques of these nuclides reported in the literature require expensive testing apparatus and radioactive tracers, or the capacity of resisting disturbance of the deposition conditions is relatively weak and the test period is relatively long. The study conducted of the optimum spontaneous deposition conditions of 210Bi and 210Po on Cu simultaneously and quantitatively is reported in this paper, and the establishment of a new joint measurement technique of 210Pb, 210Bi and 210Po in rock, soil and sediment samples. It was found that 210Bi and 210Po were deposited on Cu foil simultaneously, while 210Pb was not deposited on a 3.14 cm2 Cu foil under the conditions of 0.5 mol/L HCl, 3.5 mol/L NaCl in the total 20 mL solution at 90℃, with a vibration frequency of 120 r/min and vibration amplitude of 20 mm for 70 min. Due to the presence of ascorbic acid, lots of coexisting elements have no interference with target nuclides. The precision of this testing technology was higher than 5% and total recovery rates were 99.5%-100.5%. This new measurement technique has a strong capacity to resist Bi disturbance, the recovery rate is more constant than traditional methods and the test period is short with one set of home-made testing apparatus and no radioactive tracers required. Moreover, this measurement technique is also suitable for the determination of one of these three nuclides separately.

In view of problems that high harmonics of switching frequency of voltage source PWM rectifier pollute power grid and traditional control strategies of voltage source PWM rectifier are all based on two-phase rotating coordinate which has cross coupling member of current and large calculation, the paper proposed a control algorithm of voltage source PWM rectifier based on LCL filter under two-phase static coordinate. The algorithm makes voltage source PWM rectifier system under three-phase static coordinate transform voltage source PWM rectifier system under two-phase static coordinate by use of Clark transform system, which avoids cross coupling member of current under two-phase rotating coordinate; the algorithm uses quasi-resonant regulator to control current of the rectifier, which realizes tracking control for current. The Matlab simulation result proved correctness and feasibility of the algorithm.

Tensor fields are useful for modeling the structure of biological tissues. The challenge to measure tensor fields involves acquiring sufficient data of scalar measurements that are physically achievable and reconstructing tensors from as few projections as possible for efficient applications in medical imaging. In this paper, we present a filtered back-projection algorithm for the reconstruction of a symmetric second-rank tensor field from directional X-ray projections about three axes. The tensor field is decomposed into a solenoidal and irrotational component, each of three unknowns. Using the Fourier projection theorem, a filtered back-projection algorithm is derived to reconstruct the solenoidal and irrotational components from projections acquired around three axes. A simple illustrative phantom consisting of two spherical shells and a 3D digital cardiac diffusion image obtained from diffusion tensor MRI of an excised human heart are used to simulate directional X-ray projections. The simulations validate the mathematical derivations and demonstrate reasonable noise properties of the algorithm. The decomposition of the tensor field into solenoidal and irrotational components provides insight into the development of algorithms for reconstructing tensor fields with sufficient samples in terms of the type of directional projections and the necessary orbits for the acquisition of the projections of the tensor field.

PurposeIn this work, we present tomographic simulations of a new hardware concept for X-ray phase-contrast interferometry wherein the phase gratings are replaced with an array of Fresnel biprisms, and Moiré fringe analysis is used instead of "phase stepping" popular with grating-based setups.MethodsProjections of a phantom consisting of four layers of parallel carbon microfibers is simulated using wave optics representation of X-ray electromagnetic waves. Simulated projections of a phantom with preferential scatter perpendicular to the direction of the fibers are performed to analyze the extraction of small-angle scatter from dark-field projections for the following: (1) biprism interferometry using Moiré fringe analysis; (2) grating interferometry using phase stepping with eight grating steps; and (3) grating interferometry using Moiré fringe analysis. Dark-field projections are modeled as projections of voxel intensities represented by a fixed finite vector basis set of scattering directions. An iterative MLEM algorithm is used to reconstruct, from simulated projection data, the coefficients of a fixed set of seven basis vectors at each voxel representing the small-angle scatter distribution.ResultsResults of reconstructed vector coefficients are shown comparing the three simulated imaging configurations. The single-exposure Moiré fringe analysis shows not only an increase in noise because of one-eighth the number of projection samples but also is obtained with less dose and faster acquisition times. Furthermore, replacing grating interferometry with biprism interferometry provides better contrast-to-noise.ConclusionThe simulations demonstrate the feasibility of the reconstruction of dark-field data acquired with a biprism interferometry system. With the potential of higher fringe visibility, biprism interferometry with Moiré fringe analysis might provide equal or better image quality to that of phase stepping methods with less imaging time and lower dose.

PurposeSingle photon emission computed tomography (SPECT) scanners using cadmium zinc telluride (CZT) offer compact, lightweight, and improved imaging capability over conventional NaI(Tl)-based SPECT scanners. The main purpose in this study is to propose a full-ring SPECT system design with eight large-area CZT detectors that can be used for a broad spectrum of SPECT radiopharmaceuticals and demonstrate the performance of our system in comparison to the reference conventional NaI(Tl)-based two-head Anger cameras.MethodsA newly designed full-ring SPECT system is composed of eight large-area CZT cameras (128 mm × 179.2 mm effective area) that can be independently swiveled around their own axes of rotation independently and can have radial motion for varying aperture sizes that can be adapted to different sizes of imaging volume. Extended projection data were generated by conjoining projections of two adjacent detectors to overcome the limited field-of-view (FOV) by each CZT camera. Using Monte Carlo simulations, we evaluated this new system design with digital phantoms including a Derenzo hot rod phantom and a Zubal brain phantom. Comparison of performance metrics such as spatial resolution, sensitivity, contrast-to-noise ratio (CNR), and contrast-recovery ratio was made between our design and conventional SPECT scanners having different pixel sizes and radii of rotation (one clinically well-known type and two arbitrary types matched to our proposed CZT-SPECT geometries).ResultsThe proposed scanner could result in up to about three times faster in acquisition time over conventional scan time at same acquisition time per step. The spatial resolution improvement, or deterioration, of our proposed scanner compared to the clinical-type scanner was dependent upon the location of the point source. However, there were overall performance improvements over the three different setups of the conventional scanner particularly in volume sensitivity (approximately up to 1.7 times). Overall, we successfully reconstructed the phantom image for both 99m Tc-based perfusion and 123 I-based dopamine transporter (DaT) brain studies simulated for our new design. In particular, the striatal/background contrast-recovery ratio in 3-to-1 reference ratio was over 0.8 for the 123 I-based DaT study.ConclusionsWe proposed a variable-aperture full-ring SPECT system using combined pixelated CZT and energy-optimized parallel-hole collimator modules and evaluated the performance of this scanner using relevant digital phantoms and MC simulations. Our studies demonstrated the potential of our new full-ring CZT-SPECT design, showing reduced acquisition time and improved sensitivity with acceptable CNR and spatial resolution.

Abstract Background The purpose of this study was to investigate the effects and mechanisms of dihydrotestosterone (DHT)-induced expression of sterol regulatory element binding protein-1 (SREBP-1), and the synthesis and secretion of lipids, in HaCaT cells. HaCaT cells were treated with DHT and either the phosphoinositide 3-kinase inhibitor LY294002 or the extracellular-signal-regulated kinase (ERK) inhibitor PD98059. Real time-PCR, Western blot, Oil Red staining and flow cytometry were employed to examine the mRNA and protein expressions of SREBP-1, the gene transcription of lipid synthesis, and lipid secretion in HaCaT cells. Findings We found that DHT upregulated mRNA and protein expressions of SREBP-1. DHT also significantly upregulated the transcription of lipid synthesis-related genes and increased lipid secretion, which can be inhibited by the addition of LY294002. Conclusions Collectively, these results indicate that DHT induces SREBP-1 expression and lipogenesis in HaCaT cells via activation of the phosphoinositide 3-kinase/Akt Pathway.