分类： 生物学 >> 生物物理学 分类： 化学 >> 物理化学 分类： 生物学 >> 生物物理学 提交时间： 2024-04-16
摘要： Transcription factor (TF) are proteins that regulates the transcription of genetic information from DNA to messenger RNA by binding to a specific DNA sequence.Nucleic acid-protein interactions are crucial in regulating transcription in biological systems. This work presents a quick and convenient method for constructing tight-binding models and offers physical insights into the electronic structure properties of transcription factor complexes and DNA motifs. The tight binding Hamiltonian parameters are generated using the random forest regression algorithm, which reproduces the given ab-initiolevel calculations with reasonable accuracy. We present a library of residue-level parameters derived from extensive electronic structure calculations over various possible combinations of nucleobases and amino acid side chains from high-quality DNA-protein complex structures. As an example, our approach can reasonably generate the subtle electronic structure details for the orthologous transcription factors human AP-1 and Epstein-Barr virus Zta within a few seconds on a laptop. This method potentially enhances our understanding of the electronic structure variationsof gene-protein interaction complexes, even those involving dozens of proteins and genes. We hope this study offers a powerful tool for analyzing transcription regulation mechanisms at an electronic structural level.
分类： 生物学 >> 植物学 >> 应用植物学 提交时间： 2024-04-17 合作期刊: 《广西植物》
摘要： 膨胀素（expansin，EXP）通过调控细胞壁的松弛在植物应对环境胁迫过程中起着 重要作用。为研究EXP 基因在大豆应对非生物胁迫过程中的作用，对大豆中的两个EXP 基 因（GmEXPB5 和GmEXPB7）及其蛋白序列进行生物信息学分析，通过实时荧光定量PCR （qRT-PCR）检测基因表达量。结果表明：(1) GmEXPB5 和GmEXPB7 分别位于大豆第10 和12 号染色体上，编码的蛋白序列长度分别为272 和267 个氨基酸。GmEXPB5 蛋白分子 量为29.07 kD，理论等电点为7.51；GmEXPB7 蛋白分子量为29.09 kD，理论等电点为8.66。 GmEXPB5 和GmEXPB7 均为稳定的亲水蛋白且定位于细胞壁中。GmEXPB5 和GmEXPB7 蛋白均含有一段信号肽序列和一个保守的DPBB_1 结构域。(2) GmEXPB5 蛋白与鹰嘴豆 CaEXPB15 蛋白亲缘关系最近，GmEXPB7 蛋白与密花豆、赤豆和豇豆的EXPB3 蛋白有着 较近的亲缘关系。(3) GmEXPB5 和GmEXPB7 在大豆根、茎和叶中均表达且它们在根和叶中 的表达量均显著高于茎中的表达量。(4) GmEXPB5 和GmEXPB7 在大豆幼苗中可以响应盐、 干旱和低温胁迫。(5) GmEXPB5 启动子区域含有两种与逆境相关的顺式作用元件（ABRE 和 ARE）；GmEXPB7 启动子区域含有五种与逆境相关的顺式作用元件（ABRE、ARE、 CGTCA-motif、TC-rich repeats 和MBS）。上述结果表明，GmEXPB5 和GmEXPB7 能够参 与大豆对非生物胁迫的应答。
分类： 图书馆学、情报学 >> 情报资料的处理 提交时间： 2024-04-18
摘要： 目的/意义 ：本研究旨在系统地分析突发事件微博舆情的主题演化趋势，可视化舆情发展过程中的焦点主题，为后续网络舆情的引导提供实践参考依据。 方法/过程 ：采用BERTopic主题提取模型识别舆情发展不同阶段的主题，并采用余弦相似度度量主题间的相似性，可视化主题的演化路径。以新浪微博“东航Mu5735空难事件”为例，进行突发事件网络舆情的主题演化研究。 结果/结论： 实证研究结果表明，基于BERTopic主题模型对舆情事件建模得到高效且可观性较高的主题识别结果，准确把握舆情发展每个阶段中热点主题，揭示了舆情传播过程中主题演变过程。 创新/局限 ：本研究提出了一种基于 BERTopic 模型对短文本突发事件微博舆情主题演化分析的总体框架，对主题提取后的结果进行主题内容演化分析并进行可视化展示。本研究的局限性在于当前选用的数据来源仅来源于微博平台，后续可提高数据来源的多样性。
分类： 天文学 >> 天文学史 分类： 天文学 >> 天文仪器与技术 提交时间： 2024-04-10
摘要： 中国古代保留着丰富的天文观测记录，其中尤为宝贵的是大量实测的恒星观测数据。然而，确定这些观测数据的年代是一个相当复杂的问题。本文以宋元时代的两组观测数据为基础，运用广义霍夫变换的技术手段对数据进行计算和分析。我们成功地获得了对恒星观测年代的较为准确的估算结果。这一方法为未来分析更多古代天文星表数据提供了新的途径和视角。
分类： 图书馆学、情报学 >> 情报学 提交时间： 2024-04-16
摘要： 数字经济时代最特殊的一种资产就是数据，数据作为生产要素和企业资产，已成为新时代我国的生产核心要素，是数字经济的核心引擎，数据要素不仅推动传统生产要素革命性聚变与裂变进而产生倍增效应，而且提高了传统要素的配置效率，驱动经济加快创新发展。然而数据流通交易作为数据要素市场化配置的关键环节却缺乏有效实践，本文从信息管理的角度出发，以上海数据交易所为例，从制度保障、基础设施建设以及平台运营机制这三个方面为企业数据资产化的实现路径提供一个样本参考，通过这一研究，旨在提高企业更加重视数据要素的意识，重视数据资产的价值挖掘和使用，致力于有效实现资源统筹优化，从而有效推动我国经济高质量发展。
分类： 物理学 >> 凝聚态:电子结构、电、磁和光学性质 提交时间： 2024-04-17
Shuqiang He
Yi-Feng Zheng
Guosheng Shi
Yi-Jie Xiang
Meihui Xiao
Qituan Zhang
Yue-Yu Zhang
Haiping Fang
摘要： The identification of new materials with superconducting properties is the pursuit in the realm of superconductivity research. Here, excitedly, we show that the simplest salt daily used can be made a superconductor at normal pressure only by adjusting its stoichiometry of Na and Cl as Na3Cl at normal pressure based on first-principles calculations. This bulk stable abnormal Na-Cl stoichiometric crystal of 3:1, the first ‘magic’ ratio, includes metallic (Na) atoms in the core as well as hybridization of ionic and metallic bonding, facilitating the electron-phonon-coupling for superconductivity with a critical temperature Tc of 0.13 K. The flat bands and van Hove singularities near the Fermi level produce large densities of states, similar to H3S and LaH10, which is beneficial for the emergence of superconductivity. The crystal composed of with abnormal Na-Cl magic stoichiometry is a precisely tunable, purely sodium and chloride-based, three-dimensional bulk superconductor, which is therefore an ideal material for designing and understanding abnormal stoichiometric crystals. The methodology of constructing this bulk abnormal crystal may be general to almost all elements, which could lead to insights into the physics of other conventional superconductors and even high-critical-temperature superconductors.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Correlated red noise recently reported from pulsar timing observations may be an indication of stochastic gravitational waves emitted by cosmic strings that formed during a primordial phase transition near the Grand Unification energy scale. Unfortunately, known probes of cosmic strings, namely the Cosmic Microwave Background anisotropies and string lensing of extragalactic galaxies, are not sensitive enough for low string tensions of $G\mu = 10^{-10}-10^{-7}$ that are needed to explain this putative signal. We show that strong gravitational lensing of Fast Radio Bursts (FRBs) by cosmic strings is a potentially unambiguous avenue to probe that range of string tension values. The image pair of string lensing are expected to have identical magnification factor and parity, and have a typical time delay of $\sim 10^2\,\,(G\,\mu/10^{-8})^2$ seconds. The unique spectral fingerprint of each FRB, as well as the possibility to detect correlations in the time series of the electric field of the radio waves, will enable verification of the string lensing interpretation. Very-Long-Baseline Interferometry (VLBI) observations can spatially resolve the image pair and provide a lower bound on the string tension based on the image separation. We calculate the FRB lensing rate as a function of FRB detection number for several different models of the FRB redshift distribution. We find that a survey detecting $\sim 10^5$ FRBs, in line with estimates for the detection rate of the forthcoming survey CHORD, can uncover a strong lensing event for a string tension of $G\mu \simeq 10^{-7}$. Larger FRB surveys, such as Phase 2 of the Square Kilometre Array (SKA), have the potential to significantly improve the sensitivity on the string tension to $G\mu \simeq 10^{-9}$.
分类： 生物学 >> 植物学 >> 应用植物学 提交时间： 2024-04-17 合作期刊: 《广西植物》
摘要： 为探讨外源多胺（PAs）对荔枝胚性愈伤组织（EC）增殖及体胚分化的影响机制， 该研究以“妃子笑”荔枝EC 为材料，采用单因素法在增殖培养基中添加腐胺（Put）、亚 精胺（Spd）及精胺（Spm），分析了不同PAs 处理后EC 形态、结构、内源PAs 含量及相 关酶指标的变化。结果表明：（1）外源Put、Spd 和Spm 处理均显著提高了EC 增殖率，降 低了体胚诱导及萌发数量。经外源PAs 处理增殖的EC 胚性细胞大小较一致，染色深且均匀， 多细胞原胚减少，可见已经分化完全的早期子叶胚。（2）外源PAs 处理均显著提高了EC 中内源PAs 含量，其中Put 处理EC 中各类内源PAs 及总PAs 含量最高；当在含外源PAs 培养基上增殖的EC 转入不含外源PAs 的培养基上增殖时（恢复培养），EC 中的Put 含量 仍然显著高于对照，内源Spd 和Spm 则显著降低。（3）外源Put 处理显著提高了EC 中的 鸟氨酸脱羧酶（ODC）、精氨酸脱羧酶（ADC）和二胺氧化酶（DAO）活性，而外源Spd、 Spm 处理显著降低了EC 中的ODC 及ADC 活性，外源Spd 显著提高了多胺氧化酶（PAO） 活性；恢复培养后，EC 中ADC 和DAO 活性比恢复培养前显著降低，ODC、PAO 无显著 性差异。综上认为，外源PAs 可以通过调节PAs 代谢相关酶活性影响内源PAs 含量，进而 影响荔枝EC 增殖和体胚诱导。该研究结果为进一步研究PAs 调节荔枝体胚发生机制，提高 荔枝离体再生效率提供了基础。
分类： 生物学 >> 植物学 >> 应用植物学 提交时间： 2024-04-17 合作期刊: 《广西植物》
摘要： 为研究和明确贵州兔眼蓝莓不同品种的果实香气成分及含量，该研究采用顶空固相 微萃取和气相色谱-气质联用（HS-SPME/GC-MS）方法，对贵州主栽兔眼蓝莓‘杰兔’‘灿烂’ ‘顶峰’‘梯芙蓝’和‘粉蓝’等品种的果实香气组分含量进行检测分析。结果表明：（1）5 个品种共检测出7 大类46 种香气成分，其中醇类有8 种、萜类有13 种、苯环类有9 个、醛 类仅3 种、酯类5 种、烷烃类有4 种、其他类有4 种。（2）‘顶峰’的香气成分最多，有33 种，‘粉蓝’最少，仅24 种；各品种香气组分中，醛类占比最大，其次为苯环类，‘灿烂’醛 类含量最高（59.32%），‘粉蓝’苯环类含量最高（42.58%）。（3）5 个品种中，‘杰兔’的香气 成分总含量最高，为172 872.20 ng‧g-1，其次是‘灿烂’，为162 200.87 ng‧g-1；‘顶峰’和‘粉 蓝’的香气成分总含量较低，分别为91 284.45 ng‧g-1 和97 511.10 ng‧g-1。5 个兔眼蓝莓品种在 香气成分和含量上表现出显著差异，这些差异为蓝莓品种的优选和深加工原料的选择提供了 重要依据。
分类： 图书馆学、情报学 >> 读者工作 提交时间： 2024-04-16
摘要： 本文探讨近年来国内外图书馆读者荐购的研究热点并分析现有读者荐购服务的痛点和挑战，并对未来荐购管理模式创新和荐购系统建设提出设想，以期提高图书馆读者荐购服务质量，推动传统图书馆服务向智慧化转型。采用文献计量法，对国内外图书馆读者荐购相关研究进行梳理，分析了国内外读荐购的最新研究成果并对发文主体进行概述分析。采用SWOT法对读者荐购进行分析，探讨现行荐购管理模式的优缺点。研究发现，传统的荐购模式已不能完全适应智慧图书馆建设的要求。图书馆应着力利用资源优势围绕用户需求搭建智能化、个性化荐购平台，将信息技术运用于读者荐购服务场景中。
分类： 护理学 >> 护理学 提交时间： 2024-04-14
摘要： 目的 总结TCD发泡试验在缺血性脑卒中患者人群中应用的操作及护理经验。方法 回顾性分析2023年1月-2023年7月，我院40名神经内科缺血性脑卒中患者群体进行TCD发泡试验的资料，分析总结对缺血性脑卒中患者人群的操作及护理要点。结果 40例患者中11名患者为卵圆孔未闭，TCD发泡试验阳性，结论 TCD发泡试验可及时发现患者潜在脑梗死危险因素，对预防脑梗死的复发、提高患者的生活质量具有重大意义。对患者进行针对性护理可有效缓解患者在试验中的紧张情绪，提高患者配合程度。
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We measure for the first time the outermost edges of the Milky Way (MW) halo in terms of the depletion and turnaround radii. The inner depletion radius, $r_\mathrm{id}$, identified at the location of maximum infall velocity, separates a growing halo from the draining environment, while the turnaround radius, $r_\mathrm{ta}$, marks the outermost edge of infalling material towards the halo, both of which are located well outside the virial radius. Using the motions of nearby dwarf galaxies within $3\mathrm{Mpc}$, we obtain a marginal detection of the infall zone around the MW with a maximum velocity of $v_\mathrm{inf, max}=-46_{-39}^{+24}\mathrm{km s^{-1}}$. This enables us to measure $r_\mathrm{id}=559\pm 107 \mathrm{kpc}$ and $r_\mathrm{ta}=839\pm 121 \mathrm{kpc}$. The measured depletion radius is about 1.5 times the MW virial radius ($R_\mathrm{200m}$) measured from internal dynamics. Compared with halos in the cosmological simulation Illustris TNG100, the factor 1.5 is consistent with that of halos with similar masses and dynamical environments to the MW but slightly smaller than typical values of Local Group analogs, potentially indicating the unique evolution history of the MW. These measurements of halo edges directly quantify the ongoing evolution of the MW outer halo and provide constraints on the current dynamical state of the MW that are independent from internal dynamics.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The Solar System's orbital structure is thought to have been sculpted by an episode of dynamical instability among the giant planets. However, the instability trigger and timing have not been clearly established. Hydrodynamical modeling has shown that while the Sun's gaseous protoplanetary disk was present the giant planets migrated into a compact orbital configuration in a chain of resonances. Here we use dynamical simulations to show that the giant planets' instability was likely triggered by the dispersal of the gaseous disk. As the disk evaporated from the inside-out, its inner edge swept successively across and dynamically perturbed each planet's orbit in turn. The associated orbital shift caused a dynamical compression of the exterior part of the system, ultimately triggering instability. The final orbits of our simulated systems match those of the Solar System for a viable range of astrophysical parameters. The giant planet instability therefore took place as the gaseous disk dissipated, constrained by astronomical observations to be a few to ten million years after the birth of the Solar System. Terrestrial planet formation would not complete until after such an early giant planet instability; the growing terrestrial planets may even have been sculpted by its perturbations, explaining the small mass of Mars relative to Earth.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： A general covariant local field theory of the holographic dark energy model is presented. It turns out the low energy effective theory of the holographic dark energy is the massive gravity theory whose graviton has 3 polarisations, including one scalar mode and two tensor modes. The Compton wavelength is the size of the future event horizon of the universe. The UV-IR correspondence in the holographic dark energy model stems from the scalar graviton's strong coupling at the energy scale that marks the breaking down of the effective field theory.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Thermoelastic loss is one of the main energy dissipation mechanisms in resonant systems. A careful analysis of the thermoelastic loss is critical to design low-noise resonators for high-precision applications, such as gravitational-wave detectors. This paper presents an analytical solution to the thermoelastic loss in multimaterial coated finite substrates with realistic assumptions on the model structure and the elastic fields. The mechanism responsible for thermoelastic loss is taken as a function of material properties, operating temperature and frequency, and other design parameters. We calculate the thermoelastic loss for specific applications over a wide range of frequencies (1 Hz to 10 GHz) and temperatures (1 K to 300 K), and for a variety of substrate and coating materials. The result is relevant for gravitational-wave detectors and for experiments sensitive to mechanical dissipation.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Potential features in the primordial power spectrum have been searched for in galaxy surveys in recent years since these features can assist in understanding the nature of inflation. The null detection to date suggests that any such features should be fairly weak, and next-generation galaxy surveys, with their unprecedented sizes and precisions, are in a position to place stronger constraints than before. However, even if such primordial features once existed in the early Universe, they would have been significantly damped in the nonlinear regime at low redshift due to structure formation, which makes them difficult to be directly detected in real observations. A potential way to tackle this challenge for probing the features is to undo the cosmological evolution, i.e., using reconstruction to obtain an approximate linear density field. By employing a set of N-body simulations, here we show that a recently-proposed nonlinear reconstruction algorithm can effectively retrieve damped oscillatory features from halo catalogues and improve the accuracy of the measurement of feature parameters (assuming that such primordial features do exist). We do a Fisher analysis to forecast how nonlinear reconstruction affects the constraining power, and find that it can lead to significantly more robust constraints on the feature amplitude for a DESI-like survey. Comparing nonlinear reconstruction with other ways of improving constraints, such as increasing the survey volume and range of scales, this shows that it is possible to achieve what the latter do, but at a lower cost.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Building accurate and predictive models of the underlying mechanisms of celestial motion has inspired fundamental developments in theoretical physics. Candidate theories seek to explain observations and predict future positions of planets, stars, and other astronomical bodies as faithfully as possible. We use a data-driven learning approach, extending that developed in Lu et al. ($2019$) and extended in Zhong et al. ($2020$), to a derive stable and accurate model for the motion of celestial bodies in our Solar System. Our model is based on a collective dynamics framework, and is learned from the NASA Jet Propulsion Lab's development ephemerides. By modeling the major astronomical bodies in the Solar System as pairwise interacting agents, our learned model generate extremely accurate dynamics that preserve not only intrinsic geometric properties of the orbits, but also highly sensitive features of the dynamics, such as perihelion precession rates. Our learned model can provide a unified explanation to the observation data, especially in terms of reproducing the perihelion precession of Mars, Mercury, and the Moon. Moreover, Our model outperforms Newton's Law of Universal Gravitation in all cases and performs similarly to, and exceeds on the Moon, the Einstein-Infeld-Hoffman equations derived from Einstein's theory of general relativity.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Presolar grains are microscopic dust grains that formed in the stellar winds or explosions of ancient stars that died before the formation of the solar system. The majority (~90% in number) of presolar silicon carbide (SiC) grains, including types mainstream (MS), Y, and Z, came from low-mass C-rich asymptotic giant branch (AGB) stars, which is supported by the ubiquitous presence of SiC dust observed in the circumstellar envelope of AGB stars and the signatures of slow neutron-capture process preserved in these grains. Here, we review the status of isotope studies of presolar AGB SiC grains with an emphasis on heavy-element isotopes and highlight the importance of presolar grain studies for nuclear astrophysics. We discuss the sensitives of different types of nuclei to varying AGB stellar parameters and how their abundances in presolar AGB SiC grains can be used to provide independent, detailed constraints on stellar parameters, including 13C formation, stellar temperature, and nuclear reaction rates.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Simple climate models have been around for more than a century but have recently come back into fashion: they are useful for explaining global warming and the habitability of extrasolar planets. The Climate App (https://www.climateapp.ca) is an interactive web-based application that describes the radiative transfer governing planetary climate. The App is currently available in French and English and is suitable for teaching high-school through college students, or public outreach. The beginner version can be used to explore the greenhouse effect and planetary albedo, sufficient for explaining anthropogenic climate change, the Faint Young Sun Paradox, the habitability of TRAPPIST planets and other simple scenarios. There is also an advanced option with more atmospheric layers and incorporating the absorption and scattering of shortwave radiation for students and educators wishing a deeper dive into atmospheric radiative transfer. A number of pedagogical activities are being beta tested and rolled out.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The Messenger Interface Monte-Carlo Mappings V (M^3) is a photoionization code adopting the fully self-consistent Monte-Carlo radiative transfer technique, which presents a major advance over previous photoionization models with simple geometries. M^3 is designed for modeling nebulae in arbitrary three-dimensional geometries. In this paper, we describe the Monte-Carlo radiative transfer technique and the microphysics implemented in M^3, including the photoionization, collisional ionization, the free-free and free-bound recombination, and two-photon radiation. We put M^3 through the Lexington/Meudon benchmarks to test the reliability of the new code. We apply M^3 to three HII region models with fiducial geometries, demonstrating that M^3 is capable of dealing with nebulae with complex geometries. M^3 is a promising tool for understanding emission-line behavior in the era of SDSS-V/LVM and JWST, which will provide high-quality data of spatially-resolved nearby HII regions and highly turbulent local and high-redshift HII regions.
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