分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Even and odd vector modes in optical fibers are represented with linear combinations of orbital angular momentum modes, and considered as single-photon spin-orbit entangled states. It renders generating such states with fiber structures possible.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: In nanoscale imaging technique and ultrafast laser, the reconstruction procedure is normally formulated as a blind phase retrieval (BPR) problem, where one has to recover both the sample and the probe (pupil) jointly from phaseless data. This survey first presents the mathematical formula of BPR, related nonlinear optimization problems and then gives a brief review of the recent iterative algorithms. It mainly consists of three types of algorithms, including the operator-splitting based first-order optimization methods, second order algorithm with Hessian,and subspace methods. The future research directions for experimental issues and theoretical analysis are further discussed.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: The absorption by neutral hydrogen in the intergalactic medium (IGM) produces
the Ly$\alpha$ forest in the spectra of quasars. The Ly$\alpha$ forest
absorbers have a broad distribution of neutral hydrogen column density $N_{\rm
HI}$ and Doppler $b$ parameter. The narrowest Ly$\alpha$ absorption lines (of
lowest $b$) with neutral hydrogen column density above $\sim 10^{13}{\rm
cm^{-2}}$ are dominated by thermal broadening, which can be used to constrain
the thermal state of the IGM. Here we constrain the temperature-density
relation $T=T_0(\rho/\bar{\rho})^{\gamma-1}$ of the IGM at $1.6
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: The absorption by neutral hydrogen in the intergalactic medium (IGM) produces
the Ly$\alpha$ forest in the spectra of quasars. The Ly$\alpha$ forest
absorbers have a broad distribution of neutral hydrogen column density $N_{\rm
HI}$ and Doppler $b$ parameter. The narrowest Ly$\alpha$ absorption lines (of
lowest $b$) with neutral hydrogen column density above $\sim 10^{13}{\rm
cm^{-2}}$ are dominated by thermal broadening, which can be used to constrain
the thermal state of the IGM. Here we constrain the temperature-density
relation $T=T_0(\rho/\bar{\rho})^{\gamma-1}$ of the IGM at $1.6
分类: 医学、药学 >> 基础医学 提交时间: 2017-12-27 合作期刊: 《南方医科大学学报》
摘要: Objective To investigate the protective effects of tea polyphenols (TP) against myocardial ischemia/reperfusion (IR) injuries and explore the possible mechanisms. Methods Langendorff-perfused rat hearts were subjected to ischemia for 30 min followed by reperfusion for another 30 min. Myocardial function indices were measured by a left ventricular cannula via a pressure transducer connected to the polygraph in isolated Langendorff hearts and energy metabolism was measured using 31P nuclear magnetic resonance (NMR) spectroscopy. Whole-cell patch-clamp technique was used to record calcium inward current (ICa-L) in cultured rat cardiac myocytes. Results Compared with the control hearts, the ex vivo rat hearts with 2.5 mg/L TP treatment showed significantly increased left ventricular developed pressure (LVDP), maximal rise rate of LVDP (+ dp/dtmax), maximal fall rate of LVDP (-dp/dtmax), and coronary flow (CF) (P<0.05). During both cardiac ischemia and reperfusion phase, ATP and PCr levels were elevated significantly in TP-treated hearts compared with those in the control hearts (P<0.05). In cultured rat cardiac myocytes, ICa-L was remarkably decreased by TP at the doses of 2.5 and 5.0 mg/L (P<0.01). Conclusion Our results support a possible protective role of TP against myocardial IR injury by improving myocardial energy metabolism and inhibiting ICa-L in the cardiac myocytes.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: We show that, in the pure-quartic systems, modulation instability (MI) undergoes heteroclinic-structure transitions (HSTs) at two critical frequencies of {\omega} c1 and {\omega} c2 ( {\omega} c2 > {\omega} c1 ), which indicates that there are significantchanges of the spatiotemporal behavior in the system. The complicated heteroclinic structure of instability obtained by the mode truncation method reveals all possible dynamic trajectories of nonlinear waves, which allows us to discover the various types of Fermi-Pasta-Ulam (FPU) recurrences and Akhmediev breathers (ABs). When the modulational frequency satisfies {\omega} < {\omega} c2 , the heteroclinic structure encompasses two separatrixes corresponding to the ABs and the nonlinear wave with a modulated final state, which individually separate FPU recurrences into three different regions. Remarkably, crossing critical frequency {\omega} c1 , both the staggered FPU recurrences and ABs essentially switch their patterns. These HST behaviors will give vitality to the study of MI.
分类: 核科学技术 >> 核探测技术与核电子学 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Among different heavy liquid metals (HLMs), lead-bismuth eutectic (LBE) is considered at present as a potential candidate for the coolant of new generation fast reactors (critical and subcritical) and for liquid spallation neutron sources and accelerator driven systems (ADS). A high temperature liquid LBE loop, KYLIN-II-M, has been built to study the characteristics of corrosion and fluidity of LBE at the Institute of Nuclear Energy Safety Technology. However, due to the sensors and execution components of the loop work at high temperatures and in severely corrosive environments, the reliability and security of the data acquisition and control system (DACS) of KYLIN-II-M face challenges during the loop operation. In order to meet the urgent needs for KYLIN-II-Ms long-term stable operation, a virtualization and redundancy control system has been developed. The onsite operation result shows that the DACS is stable and reliable. In this paper, the experimental results are described in detail.
分类: 物理学 >> 地球物理学、天文学和天体物理学 提交时间: 2023-12-15 合作期刊: 《Research in Astronomy and Astrophysics》
摘要: We present an updated catalog of 46,753 radial velocity (RV) standard stars selected from the APOGEE DR17. These stars cover the Northern and Southern Hemispheres almost evenly, with 62% being red giants and 38% being main sequence stars. These RV standard stars are stable on a baseline longer than 200 days (with 54% longer than one year and 10% longer than five years) with a median stability better than 215 m s−1. The average number of observations of those stars is 5 and each observation is required to have signal-to-noise ratio greater than 50 and RV measurement error smaller than 500 m s−1. Based on the new APOGEE RV standard star catalog, we have checked the RV zero-points (RVZPs) for current large-scale stellar spectroscopic surveys including RAVE, LAMOST, GALAH and Gaia. By careful analysis, we estimate their mean RVZP to be +0.149 km s−1, +4.574 km s−1 (for LRS), −0.031 km s−1 and +0.014 km s−1, respectively, for the four surveys. In the RAVE, LAMOST (for MRS), GALAH and Gaia surveys, RVZP exhibits a systematic trend with stellar parameters (mainly [Fe/H], Teff, log g, GBP − GRP and GRVS). The corrections to those small but clear RVZPs are of vital importance for these massive spectroscopic surveys in various studies that require extremely high RV accuracies.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2021-12-31
摘要: Controllable D-D neutron sources have a long service life, low cost, and non-radioactivity. There are favorable prospects for its application in geophysical well logging, since traditional chemical radioactive sources used for well logging pose potential threats to the safety of the human body and environment. This paper presents an improved method to measure formation density that employs a D-D neutron source. In addition, the lithological effect on the measured density was removed to better estimate the formation porosity. First, we investigated the spatial distribution of capture gamma rays through Monte Carlo simulations as well as the relationship between the ratio of capture gamma ray counts and formation density to establish theoretical support for the design of density logging tools and their corresponding data processing methods. Second, we obtained the far to near detector counts of captured gamma rays for an optimized tool structure, and then established its correlation with the density and porosity of three typical formations with pure quartz, calcite, and dolomite minerals. Third, we determined the values for correcting the densities of sandstone and dolomite with the same porosity using limestone data as the reference and established the equations for calculating the correction values, which lays a solid foundation for accurately calculating formation porosity. We observed that the capture gamma ray counts first increased then decreased and varied in different formations; this was especially observed in high-porosity formations. Under the same lithologic conditions (rock matrix), as the porosity increases, the peak value of gamma ray counts moves toward the neutron source. At different detector-source distances, the ratio of the capture gamma ray counts was well correlated with the formation density. An equation of the formation density conversion was established based on the ratio of capture gamma ray counts at the detector-source distances of 30 cm and 65 cm, and the calculated values were consistent with the true values. After correction, the formation density was highly consistent with the true value of the limestone density, and the mean absolute error was -0.013 g/cm3. The calculated porosity values were very close to the true values, and the mean relative error was 2.33%, highlighting the accuracy of the proposed method. These findings provide a new method for developing D-D neutron source logging tools and their well-log data processing methods.
提交时间: 2017-05-02
摘要: Good mechanical properties and large adiabatic temperature change render Heusler-type Ni2FeGa-based magnetic shape memory alloys as a promising candidate material for solid-state mechanical cooling application at ambient conditions. Superelastic behavior
分类: 核科学技术 >> 辐射物理与技术 分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 分类: 光学 >> 计算中的光学 分类: 核科学技术 >> 核科学技术其他学科 提交时间: 2023-06-08
摘要: Owing to the constraints on the fabrication of -ray coding plates with many pixels, few studies have been carried out on -ray computational ghost imaging. Thus, the development of coding plates with fewer pixels is essential to achieve -ray computational ghost imaging. Based on the regional similarity between Hadamard subcoding plates, this study presents an optimization method to reduce the number of pixels of Hadamard coding plates. First, a moving distance matrix was obtained to describe the regional similarity quantitatively. Second, based on the matrix, we used two ant colony optimization arrangement algorithms to maximize the reuse of pixels in the regional similarity area and obtain new compressed coding plates. With full sampling, these two algorithms improved the pixel utilization of the coding plate, and the compression ratio values were 54.2% and 58.9%, respectively. In addition, three undersampled sequences (the Harr, Russian dolls, and cake-cutting sequences) with different sampling rates were tested and discussed. With different sampling rates, our method reduced the number of pixels of all three sequences, especially for the Russian dolls and cake-cutting sequences. Therefore, our method can reduce the number of pixels, manufacturing cost, and difficulty of the coding plate, which is beneficial for the implementation and application of -ray computational ghost imaging.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Irreversible entropy production (IEP) plays an important role in quantum thermodynamic processes. Here we investigate the geometrical bounds of IEP in nonequilibrium thermodynamics by exemplifying a system coupled to a squeezed thermal bath subject to dissipation and dephasing, respectively. We find that the geometrical bounds of the IEP always shift in contrary way under dissipation and dephasing, where the lower and upper bounds turning to be tighter occurs in the situation of dephasing and dissipation, respectively. However, either under dissipation or under dephasing, we may reduce both the critical time of the IEP itself and the critical time of the bounds for reaching an equilibrium by harvesting the benefits of squeezing effects, in which the values of the IEP, quantifying the degree of thermodynamic irreversibility, also becomes smaller. Therefore, due to the nonequilibrium nature of the squeezed thermal bath, the system-bath interaction energy brings prominent impact on the IEP, leading to tightness of its bounds. Our results are not contradictory with the second law of thermodynamics by involving squeezing of the bath as an available resource, which can improve the performance of quantum thermodynamic devices.
分类: 物理学 >> 核物理学 提交时间: 2023-09-13
摘要: Abstract: In this experimental study, involving deuteriumdeuterium fusion neutron emission spectroscopy (NES) measurement on the experimental advanced superconducting tokamak (EAST), a liquid scintillator detector (BC501A) was employed. This decision was based on the detector's superior sensitivity, optimal time-response, and its exceptional n- discrimination capability. This detector emits fast pulse signals that are as narrow as 100 ns, with high count rates that can peak at several Mcps. However, conventional nuclear circuits faced challenges in performing pulse height analysis, n pulse shape discrimination (PSD), and in recording the entire pulse waveform under such high-count-rate conditions. To address these challenges, a high-speed digital pulse signal acquisition and processing system was designed. The system was developed around a micro-telecommunications computing architecture (MTCA). Within this structure, a signal acquisition and processing (SAQP) module communicated through PCI Express (PCIe) links, achieving a bandwidth of up to 1.6 GB/s. To accurately capture the detailed shape of the pulses, four channels of analog-to-digital converters (ADCs) were used, each with a 500-MSPS sampling rate and a 14-bit resolution, ensuring an accuracy that surpassed 11 bits. An n- discrimination algorithm, based on the two-gate integral method, was also developed. Implemented within field programmable gate arrays (FPGA), this algorithm provided a real-time n- discrimination spectrum for pulse height analysis. The system underwent rigorous testing in a laboratory setting and during an EAST experiment. The results confirmed that the innovative SAQP system can satisfy the demanding requirements of high-parameter experiments, manage count rates of up to 2 Mcps, execute real-time n- discrimination algorithms, and record entire pulse waveforms without any data loss.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-08
摘要: Stretchable and flexible conductive polymers have aroused great interest recently because of their applications in the fields of novel electronics, such as smart textiles, artificial electronic skin, flexible electronic displays, etc. In this work, stretchable and flexible conductive thermoplastic polyurethane (TPU)/graphene composite foams have been developed by water vapour induced phase separation. The as-prepared TPU/graphene composite foams exhibited a lower modulus, larger elongation at break, and lower hysteresis during a cycle tensile test than a TPU/graphene composite did. It is expected that the improved elasticity of the TPU/graphene composite foams was caused by the deformation of cells, which partially offset the deformation of the TPU matrix. In addition, the cell walls divided the whole composites into many small parts, which could further restrain plastic deformation of hard segment domains under deformation.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: The fabrication of low-density and compressible polymer/graphene composite (PGC) foams for adjustable electromagnetic interference (EMI) shielding remains a daunting challenge. Herein, ultralightweight and compressible PGC foams have been developed by simple solution dip-coating of graphene on commercial polyurethane (PU) sponges with highly porous network structure. The resultant PU/graphene (PUG) foams had a density as low as ∼0.027−0.030 g/cm3 and possessed good comprehensive EMI shielding performance together with an absorption-dominant mechanism, possibly due to both conductive dissipation and multiple reflections and scattering of EM waves by the inside 3D conductive graphene network. Moreover, by taking advantage of their remarkable compressibility, the shielding performance of the PUG foams could be simply adjusted through a simple mechanical compression, showing promise for adjustable EMI shielding. We believe that the strategy for fabricating PGC foams through a simple dip-coating method could potentially promote the large-scale production of lightweight foam materials for EMI shielding.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: The elastocaloric effect has been investigated by directly measuring temperature change in Ni45Mn44Sn11 metamagnetic shape memory alloys. The stress plateau for magnetostructural transition can be drastically re- duced due to the mechanical training effect. A large temperature change of 4 K was found during compressing the sample with a small transformation strain of 1.3% at 291.5 K. Our results indicate that Ni–Mn–Sn alloys can be a promising candidate for solid-state refrigerants in mechanical cooling application by low deformation level.
分类: 生物学 >> 生物物理学 >> 基因表达调控与表观遗传学 提交时间: 2016-05-11
摘要: FUS-proteinopathies, a group of heterogeneous disorders including ALS-FUS and FTLD-FUS, are characterized by the formation of inclusion bodies containing the nuclear protein FUS in the affected patients. However, the underlying molecular and cellular defects remain unclear. Here we provide evidence for mitochondrial localization of FUS and its induction of mitochondrial damage. Remarkably, FTLD-FUS brain samples show increased FUS expression and mitochondrial defects. Biochemical and genetic data demonstrate that FUS interacts with a mitochondrial chaperonin, HSP60, and that FUS translocation to mitochondria is, at least in part, mediated by HSP60. Down-regulating HSP60 reduces mitochondrially localized FUS and partially rescues mitochondrial defects and neurodegenerative phenotypes caused by FUS expression in transgenic flies. This is the first report of direct mitochondrial targeting by a nuclear protein associated with neurodegeneration, suggesting that mitochondrial impairment may represent a critical event in different forms of FUS-proteinopathies and a common pathological feature for both ALS-FUS and FTLD-FUS. Our study offers a potential explanation for the highly heterogeneous nature and complex genetic presentation of different forms of FUS-proteinopathies. Our data also suggest that mitochondrial damage may be a target in future development of diagnostic and therapeutic tools for FUS-proteinopathies, a group of devastating neurodegenerative diseases.
分类: 生物学 >> 生物物理学 提交时间: 2016-05-11
摘要: Identification and detection of dendritic spines in neuron images are of high interest in diagnosis and treatment of neurological and psychiatric disorders (e.g., Alzheimer's disease, Parkinson's diseases, and autism). In this paper, we have proposed a novel automatic approach using wavelet-based conditional symmetric analysis and regularized morphological shared-weight neural networks (RMSNN) for dendritic spine identification involving the following steps: backbone extraction, localization of dendritic spines, and classification. First, a new algorithm based on wavelet transform and conditional symmetric analysis has been developed to extract backbone and locate the dendrite boundary. Then, the RMSNN has been proposed to classify the spines into three predefined categories (mushroom, thin, and stubby). We have compared our proposed approach against the existing methods. The experimental result demonstrates that the proposed approach can accurately locate the dendrite and accurately classify the spines into three categories with the accuracy of 99.1% for "mushroom" spines, 97.6% for "stubby" spines, and 98.6% for "thin" spines.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We investigate the metal species associated with the Ly$\alpha$ forest in the
eBOSS quasar spectra. Metal absorption lines are revealed in the stacked
spectra from cross-correlating the selected Ly$\alpha$ absorbers in the forest
and the flux fluctuation field. Up to 13 metal species are identified
associated with relatively strong Ly$\alpha$ absorbers (those with flux
fluctuation $-1.0<\delta_{\rm Ly\alpha}<-0.6$ and with neutral hydrogen column
density of ~ $10^{15-16}$ $\rm cm^{-2}$) over absorber redshift range of
$2
分类: 生物学 >> 生物物理学 提交时间: 2016-05-12
摘要: The NLR family apoptosis inhibitory proteins (NAIPs) bind conserved bacterial ligands, such as the bacterial rod protein PrgJ, and recruit NLR family CARD-containing protein 4 (NLRC4) as the inflammasome adapter to activate innate immunity. We found that the PrgJ-NAIP2-NLRC4 inflammasome is assembled into multisubunit disk-like structures through a unidirectional adenosine triphosphatase polymerization, primed with a single PrgJ-activated NAIP2 per disk. Cryo-electron microscopy (cryo-EM) reconstruction at subnanometer resolution revealed a similar to 90 degrees hinge rotation accompanying NLRC4 activation. Unlike in the related heptameric Apaf-1 apoptosome, in which each subunit needs to be conformationally activated by its ligand before assembly, a single PrgJ-activated NAIP2 initiates NLRC4 polymerization in a domino-like reaction to promote the disk assembly. These insights reveal the mechanism of signal amplification in NAIP-NLRC4 inflammasomes.