喷孔为节点式微喷带的水力特性初步研究

根据节点式微喷带喷水特点,出水孔以组为单位集中分布,每组喷水孔称为一个节点。根据孔口出流公式导出微喷带喷水孔的压力-流量公式;同时把微喷带看成由不同流量的相同管径短管连接成的管道,在每段管道上用达西—威斯巴赫公式分流态计算其沿程压力损失,在理论分析的基础上加以室内试验数据验证,由此导出微喷带的沿程压力分布公式,并计算沿程出水孔的出流量。对微喷带的生产、使用提供理论支持。     

天然红松林结实与林分因子的关系

本文通过对天然红松林分的调查,掌握了天然红松的结实量和年龄、林分疏密度及和不同林分类型的关系,同时也掌握了红松果实的质量和不同林分类型的关系,对今后天然红松林经营起到一定的作用.     

基于机器学习的青藏高原天然草地盖度时空变化特征研究

草地盖度是评价草地生长状况的重要指标,构建高精度的盖度估测模型是开展天然草地动态监测的关键。本文利用2003—2018年实测数据和地形、土壤等55个指标,建立了4种草地盖度遥感估测模型,通过比较得到研究区草地盖度遥感估测最优模型,并分析了2001—2019年研究区草地盖度时空动态变化。结果表明：由最小绝对压缩变量筛选方法选出10个有较高重要性的变量。其中,比值植被指数与草地植被盖度间的相关性优于其他单因素模型与草地植被盖度间的相关性。在3种机器学习模型中,随机森林优于人工神经网络与支持向量机模型,其R²和均方根误差分别为0.68和12.75%。机器学习方法构建的草地盖度模型优于单因素模型,其R²可提高0.09～0.16,RMSE降低1.52%～2.81%;2001—2019年,研究区草地盖度整体上呈现出自西向东、自北向南增加的趋势,呈增加趋势的面积占比为55.4%,呈减少趋势的面积占比为44.6%。     

Contrast-enhanced ultrasonography for characterization of focal splenic lesions in dogs

Background: Contrast‐enhanced ultrasonography with perflubutane microbubbles improves the diagnostic accuracy to differentiate benign and malignant focal liver lesions in dogs. Hypothesis: Perflubutane microbubbles‐enhanced ultrasonography is useful for differentiation of benign from malignant focal splenic lesions in dogs. Animals: Twenty‐nine clinical dogs with single or multiple focal splenic lesions detected by conventional ultrasonography. Methods: Prospective clinical observational study. Perflubutane microbubbles‐enhanced ultrasonography was performed in 29 dogs with focal splenic lesions. Qualitative assessment of the enhancement pattern was performed in the early vascular, late vascular, and parenchymal phases. Results: In the early vascular phase, a hypoechoic pattern was significantly associated with malignancy (P= .02) with sensitivity of 38% (95% confidence interval [CI], 25–38%) and specificity of 100% (95% CI, 84–100%). In the late vascular phase, a hypoechoic pattern was significantly associated with malignancy (P= .001) with sensitivity of 81% (95% CI, 66–90%) and specificity of 85% (95% CI, 65–95%). There was no significant difference between malignant and benign lesions during the parenchymal phase. Conclusions and Clinical Importance: Hypoechoic splenic nodules in the early and late vascular phases with perflubutane microbubbles‐enhanced ultrasonography are strongly suggestive of malignancy in dogs.     

Development of a large-scale remote sensing ecological index in arid areas and its application in the Aral Sea Basin

The Aral Sea Basin in Central Asia is an important geographical environment unit in the center of Eurasia.It is of great significance to the ecological protection and sustainable development of Central Asia to carry out dynamic monitoring and effective evaluation of the eco-environmental quality of the Aral Sea Basin.In this study,the arid remote sensing ecological index(ARSEI)for large-scale arid areas was developed,which coupled the information of the greenness index,the salinity index,the humidity index,the heat index,and the land degradation index of arid areas.The ARSEI was used to monitor and evaluate the eco-environmental quality of the Aral Sea Basin from 2000 to 2019.The results show that the greenness index,the humidity index and the land degradation index had a positive impact on the quality of the ecological environment in the Aral Sea Basin,while the salinity index and the heat index exerted a negative impact on the quality of the ecological environment.The eco-environmental quality of the Aral Sea Basin demonstrated a trend of initial improvement,followed by deterioration,and finally further improvement.The spatial variation of these changes was significant.From 2000 to 2019,grassland and wasteland(saline alkali land and sandy land)in the central and western parts of the basin had the worst ecological environment quality.The areas with poor ecological environment quality are mainly distributed in rivers,wetlands,and cultivated land around lakes.During the period from 2000 to 2019,except for the surrounding areas of the Aral Sea,the ecological environment quality in other areas of the Aral Sea Basin has been improved in general.The correlation coefficients between the change in the eco-environmental quality and the heat index and between the change in the eco-environmental quality and the humidity index were–0.593 and 0.524,respectively.Climate conditions and human activities have led to different combinations of heat and humidity changes in the eco-environmental quality of the Aral Sea Basin.However,human activities had a greater impact.The ARSEI can quantitatively and intuitively reflect the scale and causes of large-scale and long-time period changes of the eco-environmental quality in arid areas;it is very suitable for the study of the eco-environmental quality in arid areas.     

POSITRON EMISSION TOMOGRAPHY OF THE EQUINE DISTAL LIMB: EXPLORATORY STUDY

Positron emission tomography (PET) is a highly sensitive, noninvasive imaging technique for quantifying biological functions of tissues. However, at the time of this study, PET imaging applications had not been reported in the horse. The aim of this exploratory study was to determine whether a portable high‐resolution PET scanner could be used to image the equine distal limb. Images of the front feet and fetlocks of three research horses, with known lesions localized to the distal front limbs, were acquired under general anesthesia after administration of ¹⁸F‐fluorodeoxyglucose (¹⁸F‐FDG), with doses ranging from 1.5 to 2.9 MBq/kg. The radiation exposure measured during imaging was slightly higher than ^99mTechnetium scintigraphy. However, the use of general anesthesia allowed the proximity and the contact time with the patient to be minimized for the staff involved. ¹⁸F‐FDG uptake was evident throughout the soft tissues, with the highest uptake in the coronary band and the lowest uptake in the tendons. Anatomic structures could be discriminated due to the high contrast between soft tissue and bone. Detected lesions included lysis of the flexor cortex of the navicular bone, lesions of flexor tendons and suspensory ligament, and abnormal uptake through the lamina of a laminitic subject. Findings indicated that tomographic molecular imaging is feasible in the equine distal limb and could be useful as a future diagnostic technique for clinical and research studies, especially those involving tendinopathy/desmopathy and laminitis.     

OSSEOUS LESIONS IN THE METACARPO(TARSO)PHALANGEAL JOINT DIAGNOSED USING LOW-FIELD MAGNETIC RESONANCE IMAGING IN STANDING HORSES

We report the use of low-field standing magnetic resonance imaging in the standing horse for the diagnosis of osseous lesions in the metacarpophalangeal (MCP) or metatarsophalangeal (MTP) joint that were not apparent using standard radiography. Thirteen horses were studied and all had thickening of the subchondral bone plate and abnormal signal intensity in the adjacent spongiosa in either the condyles of metacarpal/metatarsal III or the proximal phalanx or both. Abnormalities were characterized by diffuse decreased signal intensity on T1-weighting adjacent to the subchondral bone and within the spongiosa in at least two imaging planes; in the absence of increases in signal intensity in fat-suppressed images, this change was interpreted as bone sclerosis. Nine horses also had a diffuse decreased signal intensity on T2^*-weighting in the same areas and five had a diffuse increase in signal intensity in fat-suppressed images in conjunction with a decrease in signal intensity on T1- and T2^*-weighted images; the increase in signal intensity in fat-suppressed images was interpreted as fluid accumulation. Five horses had a focal area of change in signal intensity within the subchondral bone with apparent loss of definition between the subchondral bone and the articular cartilage. Eleven horses were available for follow up, of which eight were sound and three remained lame. We conclude that lameness originating from the MCP or MTP joint may be associated with osseous damage in horses of any signalment in the absence of radiographic changes.