• Studies of an Event Building algorithm of the readout system for the twin TPCs in HFR

    分类: 物理学 >> 核物理学 提交时间: 2024-02-26

    摘要: The High Energy Fragment Separator (HFRS), which is currently under construction, is a leading international radioactive beam device. Multiple sets of position-sensitive Twin Time Projection Chamber (TPC)
    detectors are distributed on HFRS for particle identification and beam monitoring. The twin TPCs’ readout
    electronics system operates in a trigger-less mode due to its high counting rate, leading to a challenge of handling large amounts of data. To address this problem, we introduced an event-building algorithm. This algorithm
    employs a hierarchical processing strategy to compress data during transmission and aggregation. In addition,
    it reconstructs twin TPCs’ events online and stores only the reconstructed particle information, which significantly reduces the burden on data transmission and storage resources. Simulation studies demonstrated that the
    algorithm accurately matches twin TPCs’ events and reduces more than 98% of the data volume at a counting
    rate of 500 kHz/channel.

  • HIRFL-CSR 外靶实验终端 Veto 探测器的刻度

    分类: 核科学技术 >> 核探测技术与核电子学 分类: 物理学 >> 核物理学 提交时间: 2024-02-26

    摘要: 使用宇宙射线对兰州重离子加速器冷却储存环 (HIRFL-CSR) 外靶实验终端 (ETF) 的 Veto 探测器开展了
    件的依据,可为中子墙探测器物理目标的实现提供重要支持。在刻度过程中,得到了 Veto 探测器的位置分辨
    半高全宽 (FWHM) 为 2.53 cm,所有单元条时间归一后的时间分辨 FWHM 为 1.09 ns。

  • Design and test for the CEPC muon subdetector based on extruded scintillator and SiPM

    分类: 核科学技术 >> 核探测技术与核电子学 提交时间: 2024-02-25

    A combination of scintillator, wavelength shifting (WLS) fiber, and silicon photomultiplier (SiPM) shows excellent performance in the `KL and μ detector (KLM)' of the Belle II experiment. We describe the R&D for a similar detection technology with a new scintillator and SiPM, which can be implemented for a muon detector for the proposed CEPC experiment and the upgrade of KLM in Belle II. The R&D contains the study of the performance of a new scintillator with a length of 150 cm, the NDL SiPM with a sensitive surface of 3 mm × 3 mm or the Hamamatsu MPPC with a sensitive surface of 1.3 mm × 1.3 mm, the construction of a detector strip, and the methods to achieve excellent light collection. The cosmic ray tests show good photon collections by NDL SiPM or MPPC, efficiencies well above 90% with a threshold of 8 p.e., and time resolutions of better than 1.7 ns for the hits at the far end of a scintillator strip. The performance shows a good option for an excellent muon detector for CEPC and the possible upgrade of Belle II KLM.

  • Reevaluating GPR30: A Paradigm Shift from Estrogen Receptor to Unique Hydrophilic Ligand Activation

    分类: 药物科学 >> 结构生物学 提交时间: 2024-02-24

    摘要: The orphan receptor GPR30, previously classified as a G protein-coupled estrogen receptor (GPER), has been a subject of debate regarding its ligand specificity. Through an integrative approach combining structure elucidation, biochemical binding, and cell signaling assays, we demonstrate that estrogen does not directly bind to or activate GPR30. Cryo-EM structures of GPR30 reveal an unexpected hydrophilic ligand-binding pocket, with striking differences from classical hydrophobic steroid-binding sites, inconsistent with estrogen binding. We further confirmed hydrophilic agonists like Lys05 as true activators of GPR30, providing structural insights into their binding mechanism and receptor activation. Our findings necessitate a paradigm shift in defining GPR30's role in estrogen signaling, indicating that its activation occurs through mechanisms independent of estrogen binding. This study opens new avenues for developing targeted GPR30 ligands and reinterpreting its role in estrogen-mediated processes.

  • Isotopic dependence of the yield ratios of light fragments from different projectiles and their unified neutron skin thicknesses

    分类: 物理学 >> 核物理学 提交时间: 2024-02-24

    摘要: The yield ratios of neutron-proton (R(n/p)) and 3H-3He (R(3H/3He)) with reduced rapidity from 0 to 0.5 were simulated for 50 MeV/u even-even 36-56Ca + 40Ca, even-even 48-78Ni + 58Ni and 100-139Sn (every third isotopes) + 112Sn at full reduced impact parameters using the isospin-dependent quantum molecular dynamics (IQMD) model. The neutron and proton density distributions and root-mean-square radii of the reaction systems were obtained using the Skyrme-Hartree-Fock model, which was used for the phase space initialization of the projectile and target in IQMD. We defined the unified neutron skin thickness as ΔRnp=2>n1/2-2>p1/2, which was negative for neutron-deficient nuclei. The unified ΔRnp values for nuclei with the same relative neutron excess from different isotopic chains were nearly equal, except for extreme neutron-rich isotopes, which is a type of scaling behavior. The yield ratios of the three isotopic chains-induced reactions, which dependent on the reduced impact parameter and the unified neutron skin thickness, were studied. The results show that both R(n/p) and R(3H/3He) decreased with a reduced impact parameter for extreme neutron-deficient isotopes; however, they increased with reduced impact parameters for extreme neutron-rich isotopes, and increased with the ΔRnp of the projectiles for all reduced impact parameters. In addition, a scaling phenomena was observed between ΔRnp and the yield ratios in peripheral collisions from different isotopic chain projectiles (except for extreme neutron-rich isotopes). Thus, R(n/p) and R(3H/3He) from peripheral collisions were suggested as experimental probes for extracting the neutron or proton skin thicknesses of non-extreme neutron-rich nuclei from different isotopic chains.

  • 多重物理约束下 Duflo-Zuker 核质量模型的研究

    分类: 物理学 >> 核物理学 提交时间: 2024-02-23

    摘要: 原子核质量在核物理和核天体研究中扮演着十分重要的角色。尽管当前的理论模型可较好的描述已知核素的质量,但不同模型在外推上仍然存在许多争议,尤其是丰中子区的预言。本文回顾了我们近年来在核质量模型外推研究的主要成果,即使用严格的多目标优化算法将核素质量差 𝛼 衰变能和局域质量关系作为限制条件,缓和质量模型中的过拟合问题,在一定程度上提升模型的外推能力。

  • Design and performance evaluation of a large field-of-view dual-particle time-encoded imager based on a depth-of-interaction detector

    分类: 核科学技术 >> 核探测技术与核电子学 提交时间: 2024-02-23

    摘要: Time-encoded imaging is useful for identifying potential special nuclear materials and other radioactive sources at a distance. In this study, a large field-of-view time-encoded imager was developed for gamma-ray and neutron source hotspot imaging based on a depth-of-interaction (DOI) detector. The imager primarily consists of a DOI detector system and a rotary dual-layer cylindrical coded mask. An EJ276 plastic scintillator coupled with two SiPMs was designed as the DOI detector to increase the field of view and improve the imager performance. The difference in signal time at both ends and the log of the signal amplitude ratio were used to calculate the interaction position resolution. The position resolution of the DOI detector was calibrated using a collimated Cs-137 source, and the full width at half maximum of the reconstruction position of the Gaussian fitting curve was approximately 4.4 cm. The DOI detector can be arbitrarily divided into several units to independently reconstruct the source distribution images. The unit length was optimized via Am-Be source-location experiments. A multidetector filtering method is proposed for image denoising. This method can effectively reduce image noise caused by poor DOI detector position resolution. The vertical field of view of the imager was (-55°, 55°) when the detector was placed in the center of the coded mask. A DT neutron source at 20 m standoff could be located within 2400 s with an angular resolution of 3.5°.

  • 代数上的拓扑结构及其完备化

    分类: 数学 >> 代数与数论 提交时间: 2024-02-23

    摘要: 本文以拓扑Abel群的完备化为基础, 定义了拓扑$k$-代数及其完备化, 并从射影极限的角度对完备化的进行了代数解释.

  • Summary of evidence for the use of Chinese medicine nursing in symptom management of lung cancer patients

    分类: 护理学 >> 护理学 提交时间: 2024-02-22

    摘要: Objectives 
    To search and summarize the best evidence of traditional Chinese medicine nursing in symptom management of lung cancer patients, so as to provide reference for medical staff to implement traditional Chinese medicine characteristic symptom management for lung cancer patients.
    Patients with lung cancer often have treatment-related symptoms during treatment, which greatly reduces the quality of life of patients and increases the treatment cost of patients. Traditional Chinese medicine nursing technology plays a role in reducing adverse reactions, improving tumor complications and improving the quality of life.
    An integrative review of the study.
    All evidence from guideline collaborative networks, professional association websites, and well-known domestic and international databases in the last 10 years was searched. Literature quality evaluation tools were used to evaluate the quality of the included literature, and evidence was extracted from those that met the quality requirements.The PRISMA checklist was used to evaluate the current study.
     A total of 34 best evidences of  the use of Chinese medicine nursing in symptom management of lung cancer patients were obtained.  They are from three aspects: symptom management, emotions, and diet.
    The existing evidence shows that traditional Chinese medicine nursing has certain curative effect in the symptom management of lung cancer patients. In order to promote the standardized application of traditional Chinese medicine nursing, more clinical research, systematic evaluation and other evidence are still needed in the future.
    Relevance to Clinical Practice
    This study summarizes the evidence for the use of Chinese medicine nursing in symptom management of lung cancer patients and provides clinical decision-making for clinical nursing staff to carry out traditional Chinese medicine nursing in the management of lung cancer symptoms.
    Patient or Public Contribution/s
    There are no patient or public contributions to this study.

  • 紫癜性肾炎患儿纤维蛋白原与国际小儿肾脏病研究组病理分级及肾单位微观病变的关系研究

    分类: 医学、药学 >> 临床医学 提交时间: 2024-02-22 合作期刊: 《中国全科医学》

    摘要: 背景 临床中紫癜性肾炎(HSPN)患儿多存在纤维蛋白原(FIB)升高现象,但 FIB 与肾脏病变相关性的研究较少。目的 探讨 HSPN 患儿 FIB 与国际小儿肾脏病研究组(ISKDC)病理分级及肾单位部分微观病理变化的相关性,明确 FIB 能否评估 HSPN 患儿肾损伤轻重。方法 收集 2017 年 12 月—2022 年 12 月在河南中医药大学第一附属医院儿科肾病病区住院同时行肾活检的紫癜性肾炎患儿 922 例,汇总其做肾活检期间的临床信息、FIB 及肾脏病理信息,并依据 FIB 水平将患儿分为 A 组(偏低)<2.38 g/L、B 级(标准)2.38~4.98 g/L、C 级(偏高)>4.98 g/L。采用 Spearman 秩相关分析探究 FIB 与 ISKDC 病理分级、肾小球系膜增生比例、新月体比例的相关性;再通过受试者工作特征(ROC)曲线分析 FIB 对肾单位微观病理变化的预测情况。结果 922 例已做肾活检的 HSPN 患儿中,FIB 为(3.48±1.01)g/L。A 组 113 例,FIB 偏低率 12.26%;B 组 734 例,FIB 标准率占 79.61%;C 组 75 例,FIB 偏高率占 8.13%。ISKDC 病理分级中Ⅱ a 型 173 例(18.76%)、Ⅱ b 型 29 例(3.15%)、Ⅲ a 型 466 例(50.54%)、Ⅲ b 型 232 例(25.16%)、Ⅳ型及以上 22 例(2.39%)(其中Ⅳ a 型 2 例,Ⅳ b 型 18 例,V 型 2 例)。Spearman 秩相关分析结果显示,HSPN 患儿 FIB 及 FIB 分组与肾脏病理 ISKDC 分级(rs=0.146,P<0.001;rs=0.129,P<0.001)呈正相关性。922 例 HSPN 患儿中有 911 例(98.9%)存在系膜细胞增生,655 例(71.04%)存在新月体增生。Spearman 秩相关分析结果显示,FIB、FIB 分组均与系膜细胞增生率呈弱正相关性(rs=0.092,P=0.005;rs=0.096,P=0.003),与新月体增生率呈正相关性(rs=0.132,P<0.001;rs=0.83,P=0.012)。922 例 HSPN 患儿中肾小球急性病变 763 例(82.75%)、急慢性病变 97 例(10.52%)、慢性病变 62 例(6.73%)。HSPN 患儿 FIB 与肾小球病变的急慢性情况呈正相关(rs=0.145,P<0.001)。同时,HSPN患儿部分肾活检指标病变(新月体形成、系膜增生分叶、肾小球硬化、球囊粘连、小管炎或再生、小管细胞颗粒变性、小管间质水肿、小管炎性细胞浸润、小管萎缩、小管间质纤维化、小管腔红细胞管型、肾间质血管)与 FIB 比较,差异有统计学意义(P<0.05)。ROC 曲线显示,FIB 对肾小球硬化的灵敏度最高(灵敏度 =0.900,特异度 =0.303),FIB最佳截断值为 2.835 mg/L;FIB 对小管间质纤维化正向预测的 ROC 曲线下面积(AUC)=0.623,对小管细胞颗粒变性反向预测的 AUC=0.641。结论 FIB 可作为一项反映 HSPN 患儿肾脏病理变化轻重的实验室检查指标,能反映肾脏病理分级的轻重,与肾小球硬化、球囊粘连等肾单位微观指标关系密切,可协助临床诊断和治疗。

  • 卡托普利抑制试验在原发性醛固酮增多症诊断、分型以及临床转归中的应用

    分类: 医学、药学 >> 临床医学 提交时间: 2024-02-22 合作期刊: 《中国全科医学》

    摘要: 背景 原发性醛固酮增多症(PA)作为继发性高血压中发病率最高、心脑血管危害大但手术后治愈率高的疾病,已被各大高血压指南推荐扩大筛查、早期诊断和治疗。但该类患者的确诊、分型和治疗后临床转归判定方式繁多且存在较多争议。卡托普利抑制试验(CCT)因其便捷、安全可直接用于社区、门诊进行,期望 CCT 能对 PA患者进行全程管理以改善预后。目的 探究 CCT 对 PA 的诊断效能、分型判定以及临床转归的判断能力。方法 选取2020-10-01 至 2022-12-30 在四川大学华西医院内分泌代谢科接受内分泌性高血压病因筛查并登记的 824 例患者为研究对象。经筛选后最终 370 例患者纳入研究,其中 123 例原发性高血压(EH)患者纳入 EH 组,247 例 PA 患者分别纳入单侧醛固酮瘤(APA)组 81 例、特发性醛固酮增多症(IHA)组 55 例和未分型 PA(u-PA)组 111 例。比较 4 组间差异并绘制 CCT 后各指标及联合诊断 PA 的受试者工作特征(ROC)曲线,确定最佳截断值。其次绘制 CCT 后各指标诊断 APA 和 IHA 亚型的 ROC 曲线,计算 ROC 曲线下面积(AUC)评估 CCT 对 APA 和 IHA 的分型判断能力。最后根据术后临床结局将单侧肾上腺切除患者分为 3 组:未缓解组 11 例、临床改善组 27 例和临床缓解组 54 例,比较 3 组间差异并判断 CCT 对 APA 患者术后临床转归的判断能力。结果 CCT 后血浆醛固酮浓度(PAC)对 PA 的诊断效能最高(AUC=0.921,95%CI=0.893~0.950),最佳截断值为 11.7 ng/dL,灵敏度、特异度分别为 84.6% 和 86.0%;CCT 后醛固酮 / 肾素比值(ARR)对 PA 也有较好的诊断效能(AUC=0.868,95%CI=0.823~0.923),最佳截断值为 2.8(ng/dL)/(mU/L),灵敏度、特异度分别为 82.2% 和 81.0%。CCT 后 PAC>17.0 ng/dL 可协助诊断 APA 亚型,CCT 后PAC<11.7 ng/dL 同时 ARR<2.8(ng/dL)/(mU/L)的患者可排除 APA 亚型。CCT 后 PAC 抑制率和术后 PAC 较基线下降率对判断患者生化缓解情况效能低,CCT 后 PAC 或 CCT 后 ARR 更能反应术后生化缓解情况。结论 CCT 可全程用于 PA 患者的诊断、分型和临床转归评价,CCT 后 PAC 及 CCT 后 ARR 诊断 PA 的最佳截断值分别为 11.7 ng/dL 和 2.8(ng/dL)/(mU/L),也可用于 APA 的分型判断以及术后生化缓解的判断。CCT 前采血检验临床意义小,可适当简化流程。

  • 我国城乡高中一、二年级学生体质健康测试状况的调查研究

    分类: 医学、药学 >> 临床医学 提交时间: 2024-02-22 合作期刊: 《中国全科医学》

    摘要: 背景 目前有关高中生体质健康测试成绩的研究以各省、市内局部地区较为多见,多中心大样本量的全域研究成果甚少。各类学校在普遍开展线上与线下混合式教学时,势必延长了高中生本已较长的静坐时间。这种趋势是否对高中生的体质健康产生一定的影响,亟待开展全域范围的调查研究。目的 调查并分析我国七大地区城乡高中一、二年级学生的体质健康测试成绩水平及相关影响因素,探索出高中一、二年级学生的体质健康水平均衡的提升的赋能路径。方法 采用分层随机整群抽样方法,于 2019 年 1—3 月在我国 31 个省(直辖市、自治区)七大地区(华东、华南、华北、华中、西北、西南、东北)高中学校按照市区县与乡镇村进行分层抽样,然后随机整群分别选取市区县高中学校和乡镇村高中学校各 1 所共 62 所学校 42 523 名在读的高一、高二年级学生进行调研,同时收集学生的体质健康测试成绩数据(BMI 反映身体发育水平,肺活量反映身体机能,坐位体前屈反映躯体柔韧度,引体向上、50 m 跑、立定跳远反映上下肢爆发力量水平,1 min 仰卧起坐反映躯体核心力量水平,800 m 跑、1 000 m 跑反映心肺耐力水平),并运用非参数检验及多重线性回归分析探讨体质健康测试成绩水平的影响因素性。结果 42 523 名高中生的中位年龄为 16.00(16.00,17.00)岁;男生 20 074 名(47.2%)、女生 22 449 名(52.8%),市县区 21 725 名(51.1%)、镇乡村 20 798 名(48.9%)。七大地区高中生性别、城乡分布比较,差异有统计学意义(P<0.05)。七大地区高中男生各项体质健康测试成绩比较,差异均有统计学意义(P<0.05);各项体质健康测试成绩前三的地区如下:身高(华北 >东北 > 华中)、体质量(东北 > 华北 > 华中)、BMI(华中 > 东北 > 华北)、肺活量(东北 > 华中 > 华南)、50 m 跑(华南 > 华中 > 华东)、立定跳远(华南 > 华北 > 西北)、坐位体前屈(华南 > 西南 > 华中)、引体向上(华南 > 西南 > 西北)、1 000 m 跑(华南 > 华中 > 西南)。市县区高中男生的肺活量成绩高于镇乡村,50 m 跑、立定跳远、坐位体前屈、引体向上、1 000 m 跑成绩低于镇乡村(P<0.001)。七大地区高中女生各项体质健康测试成绩比较,差异均有统计学意义(P<0.05);各项体质健康测试成绩前三的地区如下:身高(华北 > 东北 > 西北)、体质量(东北 >华北 > 西北)、BMI(东北 > 华北 > 西北)、肺活量(东北 > 华南 > 华中)、50 m 跑(华南 > 华中 > 华东)、立定跳远(华南 > 华北 > 华中)、坐位体前屈(东北 > 华中 > 华南)、1 min 仰卧起坐(华北 > 华中 > 华东 = 西南)、800 m跑(东北 > 华中 > 华南)。市县区高中女生的身高、体质量、BMI 成绩高于镇乡村,肺活量、50 m 跑、立定跳远、坐位体前屈、1 min 仰卧起坐、800 m 跑成绩低于镇乡村(P<0.001)。多重线性回归分析结果显示,男生引体向上成绩与 BMI、1 000 m 跑成绩呈负相关,与 50 m 跑、立定跳远、坐位体前屈成绩呈正相关(P<0.05),坐位体前屈为最主要的影响因素,1 000 m 跑次之;1 000 m 跑成绩与 BMI、引体向上成绩呈负相关,与 50 m 跑、立定跳远、坐位体前屈成绩呈正相关(P<0.05),引体向上为最主要的影响因素,坐位体前屈次之。女生 1 min 仰卧起坐成绩与 BMI、肺活量、立定跳远、800 m 跑成绩呈正相关,与 50 m 跑、坐位体前屈成绩呈负相关(P<0.05),BMI 为最主要的影响因素,坐位体前屈次之;800 m 跑成绩与 BMI、50 m 跑、坐位体前屈成绩呈负相关,与立定跳远、1 min 仰卧起坐成绩呈正相关(P<0.05),坐位体前屈为最主要的影响因素,BMI 次之。结论 我国市县区高中一、二年级男生的身体发育水平与镇乡村相当,但市县区高中一、二年级女生的身体发育水平高于镇乡村女生。市县区高中一、二年级学生的上下肢爆发力量、躯体核心力量、心肺耐力水平均显著低于镇乡村。除身体发育水平以外,华南地区的高中一、二年级男生的体质健康各项测试成绩水平的优势十分明显。

  • 低能N+-He 碰撞中的态选择单电子俘获研究

    分类: 物理学 >> 核物理学 分类: 物理学 >> 原子与分子物理学 提交时间: 2024-02-22

    摘要: 利用反应显微成像谱仪,采用二重符合方法,实验测量了0.64 keV/u N+ 与He 单电子俘获产生的反冲离子He+ 三维动量,获得了电子俘获到炮弹离子不同量子态的态选择截面和角分布。实验结果表明:基态的 炮弹离子N+(1s22s22p2 3P) 俘获He 靶的一个1s 电子主要布居到2p 壳层,也可以看到布居到更高壳层的贡献; 亚稳态的炮弹离子N+(1s22s2p3 5S) 俘获He 靶的一个1s 电子主要布居到2s 壳层,几乎看不到布居到更高壳层 的贡献。利用NHe+ 准分子离子的势能曲线定性地解释了实验结果,但分子库仑过垒模型的反应窗预测与实 验存在较大差别。在亚稳态炮弹离子N+(1s22s2p3 5S) 俘获靶电子到2s 轨道的过程中,角微分截面出现了明显 的振荡结构, 这很可能来自Demkov 型跃迁。

  • Besov Estimates for Sub-elliptic Equations in the Heisenberg Group

    分类: 数学 >> 应用数学 提交时间: 2024-02-22

    摘要: 本文研究Heisenberg群上非退化散度型次椭圆方程弱解的正则性。基于系数矩阵更一般的假设,本文针对齐次与非齐次两种情形,建立弱解在Besov空间中的水平Calderon-Zygmund估计。本文的研究将丰富发展Heisenberg群上非线性Calderon-Zygmund正则性理论。

  • POLAR2/LPD探测器的校准和校正算法

    分类: 物理学 >> 核物理学 提交时间: 2024-02-21

    摘要: 气体X射线偏振测量是指一类用于测量软X射线偏振的探测器。这些探测器的系统效应会引入残余调制,导致源的偏振检测结果出现系统偏差。本文讨论了这些系统效应及其在Polar2/低能X射线偏振探测器(LPD)的气体微通道像素探测器(GMPD)原型中的校准和校正。此外,我们提出了一种算法,该算法将参数化与蒙特卡洛模拟和贝叶斯迭代相结合,以消除残余调制。数据校正后,不同能量点的残余调制已降至1%以下,并观察到偏振度与调制度之间存在良好的线性关系。校正后调制度的改善范围为2%至15%,结果超过了5 keV以上的IXPE。

  • Structural Insights into Ligand Recognition, Selectivity and Activation of the human Bombesin Receptor Subtype-3

    分类: 药物科学 >> 结构生物学 提交时间: 2024-02-21

    摘要: Bombesin receptor subtype-3 (BRS3) is an important orphan G protein-coupled receptor that regulates energy homeostasis and insulin secretion. As a member of the bombesin receptor (BnR) family, which includes neuromedin B receptor (NMBR) and gastrin-releasing peptide receptor (GRPR), the lack of known endogenous ligands and high-resolution structure has impeded understanding of BRS3 signaling and function. Here, we present cryogenic electron microscopy (cryo-EM) structures of BRS3 in complex with heterotrimeric Gq protein in three states: apo, bound to the pan-BnR agonist, BA1, and bound to the synthetic BRS3-specific agonist MK-5046. These structures reveal the architecture of the orthosteric ligand pocket underpinning molecular recognition. Comparisons with BnR members provide insights into the structural basis for BRS3’s selectivity and low affinity for bombesin peptides. Examination of conserved micro-switches suggests a shared activation mechanism among BnRs. Together our results enable deeper exploration of BRS3’s ligand selectivity, signaling, and therapeutic targeting for diabetes and obesity.

  • Formation and ecological response of sand patches in the protection system of Shapotou section of the Baotou-Lanzhou railway, China

    分类: 地球科学 >> 地理学 提交时间: 2024-02-21 合作期刊: 《干旱区科学》

    摘要: The development of bare patches typically signifies a process of ecosystem degradation. Within the protection system of Shapotou section of the Baotou-Lanzhou railway, the extensive emergence of bare sand patches poses a threat to both stability and sustainability. However, there is limited knowledge regarding the morphology, dynamic changes, and ecological responses associated with these sand patches. Therefore, we analyzed the formation and development process of sand patches within the protection system and its effects on herbaceous vegetation growth and soil nutrients through field observation, survey, and indoor analysis methods. The results showed that sand patch development can be divided into three stages, i.e., formation, expansion, and stabilization, which correspond to the initial, actively developing, and semi-fixed sand patches, respectively. The average dimensions of all sand patch erosional areas were found to be 7.72 m in length, 3.91 m in width, and 0.32 m in depth. The actively developing sand patches were the largest, and the initial sand patches were the smallest. Throughout the stage of formation and expansion, the herbaceous community composition changed, and the plant density decreased by more than 50.95%. Moreover, the coverage and height of herbaceous plants decreased in the erosional area and slightly increased in the depositional lobe; and the fine particles and nutrients of soils in the erosional area and depositional lobe showed a decreasing trend. In the stabilization phases of sand patches, the area from the inlet to the bottom of sand patches becomes initially covered with crusts. Vegetation and 0–2 cm surface soil condition improved in the erosional area, but this improvement was not yet evident in the depositional lobe. Factors such as disturbance, climate change, and surface resistance to erosion exert notable influences on the formation and dynamics of sand patches. The results can provide evidence for the future treatment of sand patches and the management of the protection system of Shapotou section of the Baotou-Lanzhou railway.

  • Effects of drip and flood irrigation on carbon dioxide exchange and crop growth in the maize ecosystem in the Hetao Irrigation District, China

    分类: 农、林、牧、渔 >> 农业基础学科 提交时间: 2024-02-21 合作期刊: 《干旱区科学》

    摘要: Drip irrigation and flood irrigation are major irrigation methods for maize crops in the Hetao Irrigation District, Inner Mongolia Autonomous Region, China. This research delves into the effects of these irrigation methods on carbon dioxide (CO2) exchange and crop growth in this region. The experimental site was divided into drip and flood irrigation zones. The irrigation schedules of this study aligned with the local commonly used irrigation schedule. We employed a developed chamber system to measure the diurnal CO2 exchange of maize plants during various growth stages under both drip and flood irrigation methods. From May to September in 2020 and 2021, two sets of repeated experiments were conducted. In each experiment, a total of nine measurements of CO2 exchange were performed to obtain carbon exchange data at different growth stages of maize crop. During each CO2 exchange measurement event, CO2 flux data were collected every two hours over a day-long period to capture the diurnal variations in CO2 exchange. During each CO2 exchange measurement event, the biological parameters (aboveground biomass and crop growth rate) of maize and environmental parameters (including air humidity, air temperature, precipitation, soil water content, and photosynthetically active radiation) were measured. The results indicated a V-shaped trend in net ecosystem CO2 exchange in daytime, reducing slowly at night, while the net assimilation rate (net primary productivity) exhibited a contrasting trend. Notably, compared with flood irrigation, drip irrigation demonstrated significantly higher average daily soil CO2 emission and greater average daily CO2 absorption by maize plants. Consequently, within the maize ecosystem, drip irrigation appeared more conducive to absorbing atmospheric CO2. Furthermore, drip irrigation demonstrated a faster crop growth rate and increased aboveground biomass compared with flood irrigation. A strong linear relationship existed between leaf area index and light utilization efficiency, irrespective of the irrigation method. Notably, drip irrigation displayed superior light use efficiency compared with flood irrigation. The final yield results corroborated these findings, indicating that drip irrigation yielded higher harvest index and overall yield than flood irrigation. The results of this study provide a basis for the selection of optimal irrigation methods commonly used in the Hetao Irrigation District. This research also serves as a reference for future irrigation studies that consider measurements of both carbon emissions and yield simultaneously.

  • Effects of landscape fragmentation of plantation forests on carbon storage in the Loess Plateau, China

    分类: 农、林、牧、渔 >> 林学 提交时间: 2024-02-21 合作期刊: 《干旱区科学》

    摘要: Tree plantation and forest restoration are the major strategies for enhancing terrestrial carbon sequestration and mitigating climate change. The Grain for Green Project in China has positively impacted global carbon sequestration and the trend towards fragmentation of plantation forests. Limited studies have been conducted on changes in plantation biomass and stand structure caused by fragmentation, and the effect of fragmentation on the carbon storage of plantation forests remains unclear. This study evaluated the differences between carbon storage and stand structure in black locust forests in fragmented and continuous landscape in the Ansai District, China and discussed the effects of ecological significance of four landscape indices on carbon storage and tree density. We used structural equation modelling to explore the direct and indirect effects of fragmentation, edge, abiotic factors, and stand structure on above-ground carbon storage. Diameter at breast height (DBH) in fragmented forests was 53.3% thicker, tree density was 40.9% lower, and carbon storage was 49.8% higher than those in continuous forests; for all given DBH>10 cm, the trees in fragmented forests were shorter than those in continuous forests. The patch area had a negative impact on carbon storage, i.e., the higher the degree of fragmentation, the lower the density of the tree; and fragmentation and distance to edge (DTE) directly increased canopy coverage. However, canopy coverage directly decreased carbon storage, and fragmentation directly increased carbon storage and tree density. In non-commercial forests, fragmentation reduces the carbon storage potential of plantation, and the influence of patch area, edge, and patchy connection on plantation should be considered when follow-up trees are planted and for the plantation management. Thus, expanding the area of plantation patches, repairing the edges of complex-shaped patches, enhancing the connectivity of similar patches, and applying nutrients to plantation forests at regular intervals are recommended in fragmented areas of the Loess Plateau.

  • Land use and cover change and influencing factor analysis in the Shiyang River Basin, China

    分类: 地球科学 >> 地理学 提交时间: 2024-02-21 合作期刊: 《干旱区科学》

    摘要: Land use and cover change (LUCC) is the most direct manifestation of the interaction between anthropological activities and the natural environment on Earth's surface, with significant impacts on the environment and social economy. Rapid economic development and climate change have resulted in significant changes in land use and cover. The Shiyang River Basin, located in the eastern part of the Hexi Corridor in China, has undergone significant climate change and LUCC over the past few decades. In this study, we used the random forest classification to obtain the land use and cover datasets of the Shiyang River Basin in 1991, 1995, 2000, 2005, 2010, 2015, and 2020 based on Landsat images. We validated the land use and cover data in 2015 from the random forest classification results (this study), the high-resolution dataset of annual global land cover from 2000 to 2015 (AGLC-2000-2015), the global 30 m land cover classification with a fine classification system (GLC_FCS30), and the first Landsat-derived annual China Land Cover Dataset (CLCD) against ground-truth classification results to evaluate the accuracy of the classification results in this study. Furthermore, we explored and compared the spatiotemporal patterns of LUCC in the upper, middle, and lower reaches of the Shiyang River Basin over the past 30 years, and employed the random forest importance ranking method to analyze the influencing factors of LUCC based on natural (evapotranspiration, precipitation, temperature, and surface soil moisture) and anthropogenic (nighttime light, gross domestic product (GDP), and population) factors. The results indicated that the random forest classification results for land use and cover in the Shiyang River Basin in 2015 outperformed the AGLC-2000-2015, GLC_FCS30, and CLCD datasets in both overall and partial validations. Moreover, the classification results in this study exhibited a high level of agreement with the ground truth features. From 1991 to 2020, the area of bare land exhibited a decreasing trend, with changes primarily occurring in the middle and lower reaches of the basin. The area of grassland initially decreased and then increased, with changes occurring mainly in the upper and middle reaches of the basin. In contrast, the area of cropland initially increased and then decreased, with changes occurring in the middle and lower reaches. The LUCC was influenced by both natural and anthropogenic factors. Climatic factors and population contributed significantly to LUCC, and the importance values of evapotranspiration, precipitation, temperature, and population were 22.12%, 32.41%, 21.89%, and 19.65%, respectively. Moreover, policy interventions also played an important role. Land use and cover in the Shiyang River Basin exhibited fluctuating changes over the past 30 years, with the ecological environment improving in the last 10 years. This suggests that governance efforts in the study area have had some effects, and the government can continue to move in this direction in the future. The findings can provide crucial insights for related research and regional sustainable development in the Shiyang River Basin and other similar arid and semi-arid areas.