[en] We investigate the benefit of incorporating a priori assumptions about cardiac motion in a fully four-dimensional (4D) reconstruction algorithm for gated cardiac SPECT. Previous work has shown that non-motion-specific 4D Gibbs priors enforcing smoothing in time and space can control noise while preserving resolution. In this paper, we evaluate methods for incorporating known heart motion in the Gibbs prior model. The new model is derived by assigning motion vectors to each 4D voxel, defining the movement of that volume of activity into the neighboring time frames. Weights for the Gibbs cliques are computed based on these open-quotes most likelyclose quotes motion vectors. To evaluate, we employ the mathematical cardiac-torso (MCAT) phantom with a new dynamic heart model that simulates the beating and twisting motion of the heart. Sixteen realistically-simulated gated datasets were generated, with noise simulated to emulate a real Tl-201 gated SPECT study. Reconstructions were performed using several different reconstruction algorithms, all modeling nonuniform attenuation and three-dimensional detector response. These include ML-EM with 4D filtering, 4D MAP-EM without prior motion assumption, and 4D MAP-EM with prior motion assumptions. The prior motion assumptions included both the correct motion model and incorrect models. Results show that reconstructions using the 4D prior model can smooth noise and preserve time-domain resolution more effectively than 4D linear filters. We conclude that modeling of motion in 4D reconstruction algorithms can be a powerful tool for smoothing noise and preserving temporal resolution in gated cardiac studies

[en] Exploration of novel hard metastable phases of silicon nitride was performed using a recently developed particle-swarm optimization method within the CALYPSO software package. Three potential hard metastable phases of t-Si_3N_4, m-Si_3N_4, and o-Si_3N_4 were predicted. These phases are mechanically and dynamically stable at ambient pressure based on their elastic constants and phonon dispersions. t-Si_3N_4 and m-Si_3N_4 exhibit lower energies than γ-Si_3N_4 at pressures below 2.5 GPa and 2.9 GPa, respectively, which promise that the formers could be obtained by quenching from γ-Si_3N_4. o-Si_3N_4 is a better high-pressure metastable phase than CaTi_2O_4-type Si_3N_4 proposed by Tatsumi et al. and it can come from the transition of γ-Si_3N_4 under 198 GPa. The theoretical band gaps of t-Si_3N_4, m-Si_3N_4, and o-Si_3N_4 at ambient pressure were 3.15 eV, 3.90 eV, and 3.36 eV, respectively. At ambient pressure, the Vickers hardness values of t-Si_3N_4 (32.6 GPa), m-Si_3N_4 (31.5 GPa), and o-Si_3N_4 (36.1 GPa) are comparable to β-Si_3N_4 and γ-Si_3N_4. With the pressure increasing, t-Si_3N_4, m-Si_3N_4, and o-Si_3N_4 will change from the brittle to ductile state at about 15.7 GPa, 7.3 GPa and 28.9 GPa, respectively. - Graphical abstract: This figure shows the crystal structures of three Si_3N_4 predicted in this manuscript, and left to right: t-Si_3N_4, m-Si_3N_4 and o-Si_3N_4. - Highlights: • We explored three metastable phases of Si_3N_4 — t-Si_3N_4, m-Si_3N_4, and o-Si_3N_4. • The enthalpies of t and m- are much lower than that of γ at ambient pressure. • ois one further high pressure phase than γ. • o-Si_3N_4 is the most hardest phase in Si_3N4 system. • Increasing pressure will change them from brittle to ductile state

[en] Highlights: • The transformations of heavy metals during lignite SCWG were investigated. • The risks of heavy metals in lignite and residues after SCWG were evaluated. • The effects of experimental conditions on corrosion during SCWG were studied. - Abstract: Transformation characteristics of heavy metals during lignite supercritical water gasification (SCWG) were studied. A sequential extraction procedure (modified Tessier method) was used to selectively extract different fractions of Pb, Cd, Cr, Mn, Cu, Ni, and Zn. Heavy metals transformed into more stable fractions after SCWG. For Pb, Cd, Mn, Cu, and Zn, SCWG reduced the bioavailability and the risks posed by heavy metals in lignite. Under the experimental conditions, the conversion rates for Pb and Cd were 16.0%–25.2% and 16.3%–23.4%, respectively, whereas those for Mn, Cu, and Zn were much lower. Solid products enriched with Pb, Cd, Mn, Cu, and Zn were obtained after SCWG; the contents of these metals varied slightly in the liquid products under different experimental conditions. Excess Cr and Ni that did not originate from lignite were found in the residues, owing to reactor corrosion during lignite SCWG. Higher temperatures alleviated corrosion, whereas higher pressures and equivalence ratios (ER) had the opposite effect. None of the heavy metals were detected in the gas phase under the experimental conditions used in the present study. The correlation between the distributions of heavy metals and the experimental conditions were also studied. The transformation pathways of Pb, Cd, Mn, Cu, and Zn during SCWG were deduced according to the experimental results.

[en] In 23 normal subjects, 37 CAD-NMI and 14 CAD-MI, left ventricular function was assessed using an automatic method from equilibrium radionuclide ventriculography. Early diastolic function was measured for evaluating its clinical value in coronary artery diseases. The results showed that PFR was more sensitive than the others for detecting ischaemic heart disease. There were significant difference on PFR between normal subjects and CAD-NMI group (p < 0.01) and PFR values of 35 in 37 CAD-NMI were lower than that of normal subjects. The order of sensitivity in other indices were TPFR(20/37, p<0.01)=PER(20/37, p<0.01)>TPER(17/37, p<0.05)>EF(16/37, p>0.05). There were also significant difference in PFR, PER and EF between CAD-NMI and CAD-MI (p<0.01), while there was no difference in TPFR and TPER(p>0.05)

[en] The interaction between flower-like CdSe nanostructure particles (CdSe NP) and bovine serum albumin (BSA) was investigated from a spectroscopic angle under simulative physiological conditions. Under pH 7.4, CdSe NP could effectively quench the intrinsic fluorescence of BSA via static quenching. The binding constant (K_A) was 6.38, 3.27, and 1.90x10⁴ M^-1 at 298, 304, and 310 K, respectively and the number of binding sites was 1.20. According to the Van't Hoff equation, the thermodynamic parameters (ΔH^o=-77.48 kJ mol^-1, ΔS^o=-168.17 J mol^-1 K^-1) indicated that hydrogen bonds and van der Waals forces played a major role in stabilizing the BSA-CdSe complex. Besides, UV-vis and circular dichroism (CD) results showed that the addition of CdSe NP changed the secondary structure of BSA and led to a decrease in α-helix. These results suggested that BSA underwent substantial conformational changes induced by flower-like CdSe nanostructure particles. - Highlights: → Estimate the binding of flower-like CdSe NP to BSA by spectroscopic methods. → Hydrogen bonds and van der Waals forces were the major forces. →Addition of CdSe changed the micro-environmentl of BSA. → Decrease in α-helix of BSA secondary structure induced by CdSe.

[en] Objective: To investigate the feasibility of the unilateral laminotomy for bilateral decompression (ULBD) in the treatment of degenerative lumbar spinal stenosis by anatomical study. Methods: 10 adult formalin-fixed spine corpse specimens were selected, then the ULBD were performed with the posterior ligaments complex almost intact. CT scans were performed, and the parameters including the maximum anterior-posterior diameter the maximum transverse diameter, and the vertebral spinal canal area were detected before and after operation. Results: Compared with before operation, the maximum anterior-posterior diameter and the maximum transverse diameter and the vertebral spinal canal area of corpses after operation were increased (P < O.01). Conclusion: With the posterior ligaments complex almost intact, the ULBD could enlarge the lumbar spinal canal and decompress the nerve effectively. (authors)

[en] Highlights: → A nitrite sensor fabricated based on copper calcined layered double hydroxides and gold nanoparticles modified electrode. → This sensor exhibited excellent electrocatalytic oxidation to nitrite. → This nitrite sensor exhibited very good analytical performance with low cost, convenient preparation and rapid detection. - Abstract: In this paper, a novel nitrite sensor was constructed based on electrodeposition of gold nanoparticles (AuNPs) on a copper calcined layered double hydroxide (Cu-CLDH) modified glassy carbon electrode. Electrochemical experiments showed that AuNPs/CLDH composite film exhibited excellent electrocatalytic oxidation activity with nitrite due to the synergistic effect of the Cu-CLDH with AuNPs. The fabricated sensor exhibited excellent performance for nitrite detection within a wide concentration interval of 1-191 μM and with a detection limit of 0.5 μM. The superior electrocatalytic response to nitrite was mainly attributed to the large surface area, minimized diffusion resistance, and enhanced electron transfer of the Cu-CLDH and AuNPs composition film. This platform offers a novel route for nitrite sensing with wide analytical applications and will supply the practical applications for a variety of simple, robust, and easy-to-manufacture analytical approaches in the future.

[en] In this paper, an efficient boundary condition is applied to solve the photoionization rate, and a two-dimensional numerical simulation is carried out for the development and propagation of an air streamer at low temperature and sub-atmospheric pressure. The results show that the new boundary condition improves the calculation accuracy, but the influence of photoionization on the streamer discharge process is not obvious. The discharge current in the development of streamer discharge is defined, and the corresponding expression of the positive and negative streamer discharge current is given. The influence of the electric field exceeding the threshold value on the discharge process is preliminarily introduced. In the process of discharge, only the propagation velocity of the streamer is obviously higher than that of normal temperature and pressure, and the trend of the other parameters is basically the same as that described in the previous paper. The above results give us a deeper understanding of the discharge characteristics under low temperature and sub-atmospheric pressure, which has certain significance for the development of aviation and high voltage engineering. (paper)

[en] In this paper, we report external electric field manipulates sequential and super-exchange charge transfer in donor-bridge-acceptor (D-B-A) system in two-photon absorption (TPA). Our results reveal that the orientation and absorption strength of sequential and super-exchange charge transfer excitons can be well manipulated in D-B-A system in TPA. The energy levels and absorption intensity of electronic transitions in one-photon absorption (OPA), as the intermediate state in TPA, are strongly influenced by external electric field, which provides a great opportunity for strong absorption with different charge transfer characteristics in TPA of D-B-A. Also, the optical properties of lowest charge transfer excited state under different external electric fields are also investigated in OPA. Our results can provide deeper understanding of external electric field in controlling sequential and super-exchange charge transfer in D-B-A system in TPA.

[en] Highlights: • A brief literature review on particle deposition in flue gas cooling is presented. • A particle reduction mechanism based on wet deposition is explored. • Fouling of wet deposition can be solved by condensate auto-cleaning and scrubber. • Variable analysis, technical feasibility, and economic evaluation are discussed. Coal-fired boilers tend to be equipped with considerable pollutant control equipment given the increase in environmental protection standard, thereby continuously increasing operating cost and decreasing the output rate of coal resources. Synergistic capture of pollutants may be a potential solution. In this work, a method for installing a cooling heat exchanger at the outlet of wet flue gas desulfurization scrubber is proposed to recover waste heat and capture fine particles. The cooling process of this method uses wet atmosphere, thereby indicating that this work differs from previous relevant works that are mainly based on dry deposition. Accordingly, the activity of particle reduction in the exchanger is also considered different. Thus, relevant mechanisms are recently explored on the basis of wet deposition through experiments. In addition to diffusiophoretic and thermophoretic depositions, particle growth or agglomeration is considered a dominant factor. Moreover, condensed water is crucial for cleaning, which may resolve the risk of fouling. Variable analysis of the influences of flue gas temperature drop, trapping surface area, initial particle concentration, and flue gas flow rate are also addressed in this work to provide references for engineering applications. Technical feasibility and economic evaluation of this method are discussed, through which possible measures for improvement are proposed. Furthermore, an applicable mode for heat recovery and a synergistic particle capture are presented, and an acceptable economic performance is estimated.