Digestive proteinases and peptidases in the hepatopancreas of the southern brown shrimp (Farfantepenaeus subtilis) in two sub‐adult stages

The aim of this study was to examine proteinases and peptidases from the hepatopancreas of two sub‐adult stages of Farfantepenaeus subtilis: SAS₆ (5.93 ± 0.69 g wet weight) and SAS₁₃ (13.26 ± 0.60 g wet weight). Trypsin and chymotrypsin activity was higher in the extract from the SAS₆ individuals (P < 0.05). The highest activity among aminoacyl‐β‐naphthylamide substrates was found using alanine‐, arginine‐, leucine‐ and lysine‐β‐naphthylamide. There was a positive correlation between the recommended concentration of essential amino acids in penaeid shrimp feed and aminopeptidase activity in both sub‐adult stages. Proteolytic activity of F. subtilis was strongly inhibited by specific trypsin inhibitors. The optimal temperature for trypsin, chymotrypsin and leucine aminopeptidase activity was between 45 and 55 °C. Six and seven bands were found in caseinolytic zymograms for SAS₆ and SAS₁₃ respectively. All bands were inhibited by phenylmethylsulfonyl fluoride in both sub‐adult stages. The use of tosyl‐lysine‐chloromethyl‐ketone and benzamidine caused strong inhibition of the proteolytic bands. Trypsin and chymotrypsin activity was the main difference observed between the protease pattern of SAS₆ and SAS₁₃F. subtilis.     

Passion fruit detection and counting based on multiple scale faster R-CNN using RGB-D images

The accurate and reliable fruit detection in orchards is one of the most crucial tasks for supporting higher level agriculture tasks such as yield mapping and robotic harvesting. However, detecting and counting small fruit is a very challenging task under variable lighting conditions, low-resolutions and heavy occlusion by neighboring fruits or foliage. To robustly detect small fruits, an improved method is proposed based on multiple scale faster region-based convolutional neural networks (MS-FRCNN) approach using the color and depth images acquired with an RGB-D camera. The architecture of MS-FRCNN is improved to detect lower-level features by incorporating feature maps from shallower convolution feature maps for regions of interest (ROI) pooling. The detection framework consists of three phases. Firstly, multiple scale feature extractors are used to extract low and high features from RGB and depth images respectively. Then, RGB-detector and depth-detector are trained separately using MS-FRCNN. Finally, late fusion methods are explored for combining the RGB and depth detector. The detection framework was demonstrated and evaluated on two datasets that include passion fruit images under variable illumination conditions and occlusion. Compared with the faster R-CNN detector of RGB-D images, the recall, the precision and F1-score of MS-FRCNN method increased from 0.922 to 0.962, 0.850 to 0.931 and 0.885 to 0.946, respectively. Furthermore, the MS-FRCNN method effectively improves small passion fruit detection by achieving 0.909 of the F1 score. It is concluded that the detector based on MS-FRCNN can be applied practically in the actual orchard environment.

     

Implementation analysis of transfer of development rights for conserving privately owned built heritage in Hong Kong: A transactions costs perspective

Transfer of development rights (TDR) programs are introduced as an alternative institutional innovation to the traditional regulatory instruments for land development. They meet the demand for development and conservation while balancing the conflicts between public and private interests with minimal use of public funds. Most TDR literature is about nature conservation and there is little focus on the complicated process and diverse stakeholders’ interests of urban land use in dealing with built heritage conservation. Previous studies show that the success of TDR programs depends on various elements, especially policy design and implementation approaches. The design and implementation of TDR programs involves transaction costs that can reduce the efficiency and effectiveness of these programs. This paper aims at developing a framework for analyzing TDR programs. This proposed framework not only takes transactions costs into account, but also provides a basis for decision makers to decipher the process of informal TDR. Using Hong Kong as a case study, three TDR implementation modes are selected to examine how different informal institutional arrangements have resulted in specific transaction costs in practice and hindered TDR projects. Our findings, which are informed by transactions costs economics, provide practical insights in order to improving the efficiency and effectiveness of TDR programs, particularly in informal contexts.     

Detecting the intellectual pathway of resilience thinking in urban and regional studies: A critical reflection on resilience literature

Confronted with increasing natural and anthropogenic crises, sustainable urban and regional development requires a sound understanding of how cities and regions respond to those crises and how that response shapes their continued development. The conceptual ambiguity and missing link among varied perspectives of resilience studies have given rise to a sneaking suspicion about the contribution of resilience thinking. By conducting a network analysis of 1,274 papers published between 1991 and 2019 using CiteSpace, we detect and visualize the intellectual pathway of resilience thinking and argue for its malleability to deepen our understanding about human-environment dynamics. Three major research clusters were identified: adaptive capacity of ecosystems, regional variation in economic resilience, and social resilience of disadvantaged communities. Resistance and recovery of systems are the key concerns in the first two clusters, whereas social resilience emphasizes opportunities and processes of restructuring rather than returning to the pre-crisis status. The extension of resilience thinking to the social realm is a promising area for future research. It calls for a shift of epistemology from the deterministic structure-function hypothesis which is place-less toward a situated understanding of context, relation, and human adaptation despite the methodological challenges ahead.     

鸡滑液支原体乳酸脱氢酶的克隆表达及其表达产物活性研究

根据GenBank中鸡滑液支原体(Mycoplasma synoviae,MS)MS53株的乳酸脱氢酶序列设计一对特异性上下游引物,通过PCR扩增获得MS WVU1853菌株的乳酸脱氢酶基因并将其克隆至pGEM-T Easy载体,测序正确并成功完成点突变后连接表达菌pET-28a(+),将重组表达质粒pET-28a-ldh转化表达菌BL21(DE3)。经IPTG诱导成功表达蛋白rMSLDH并测定其酶促活性。结果显示,重组表达的rMSLDH具有较强酶活性;最适反应温度40℃,最适pH7.5;Al2+和Ba2+可增加酶活性;Cr3+作为该酶的辅因子,在一定浓度内能有效的促进酶促反应进行;Cu2+作用下酶几乎失活,Fe3+、Mn2+、Ni2+、Zn2+对酶产生不同程度的抑制作用;其米氏常数(Km)为0.365 mmol/L,最大反应速率(Vm)为0.98μmol(L●min)。本研究结果为更好地研究鸡滑液支原体乳酸脱氢酶的生物学功能提供了参考。     

山羊卵巢褪黑素信号特异性载体pcDNA3.1-Pro/GDF9-ASMT与pcDNA3.1-Pro/Cyp17-MTNR1A/B的构建

本研究旨在构建褪黑素（melatonin，MLT）合成酶乙酰血清素甲基转移酶（acetylserotonin methytransferase，ASMT）的卵母细胞特异表达载体GDF9-ASMT和MLT受体（MTNR1A与MTNR1B）的颗粒（黄体）细胞特异表达载体Cyp17-MTNR1A、MTNR1B，以期为进一步生产高繁殖力转基因山羊提供载体材料。首先，分别扩增出山羊生长分化因子9（GDF9）与细胞色素P450家族17亚家族A成员1（Cyp17a1）启动子序列备用；然后，扩增ASMT、MTNR1A及MTNR1B基因CDS全长序列，并通过酶切将ASMT连接至GDF9启动子下游，将MTNR1A和MTNR1B连接至Cyp17a1启动子下游，制备出Pro/GDF9-ASMT、Pro/Cyp17-MTNR1A与Pro/Cyp17-MTNR1B表达元件；最后通过酶切连接将上述表达元件整合至pcDNA3.1（+）载体中，从而构建出pcDNA3.1-Pro/GDF9-ASMT、pcDNA3.1-Pro/Cyp17-MTNR1A和pcDNA3.1-Pro/Cyp17-MTNR1B真核表达载体。经测序验证，本研究扩增出的GDF9和Cyp17a1启动子长度分别为2 496和2 497 bp，与GenBank数据库中山羊GDF9和Cyp17a1基因起始密码子上游2 500 bp区域的同源性均为98%；扩增出的ASMT、MTNR1A与MTNR1B的CDS序列长度分别为1 037、1 100和1 130 bp，与GenBank所递交的标准序列同源性分别为98%、98%和99%，氨基酸序列同源性分别为97%、98%和99%。上述载体的成功构建可为进一步生产褪黑素高繁殖力转基因山羊提供参考。     

武汉地区不同杨树品种扦插苗的物候与生长节律

以12个不同杨树品种的1年生扦插苗为试验材料,对其在武汉地区的物候期和生长规律进行了动态测定。结果表明:各品种的物候期存在较大差异,以变异系数来看其中以芽膨大期差异最大,落叶末期差异最小;杨树扦插苗的苗高、地径以及叶片数的生长规律呈递增的变化趋势,符合"S"型生长曲线,杨树苗木的速生期在6月中旬到8月中旬左右。     

低浓度瓜胶压裂液在延长油田的应用

指出了随着低渗油田的开发 ,过去不被注意的压裂液残渣问题 ,引起学者的广泛关注 ,在渗透率越低的油田 ,残渣问题越严重.通过室内试验 ,对多组稠化剂、交联剂种类和加量进行优化 ,确定了交联体系破胶残液中 ,残渣含量仅为原体系的1/3.同时 ,对该体系的耐温耐剪切性能、携砂性能、静态滤失性能进行了综合评价 ,为该体系在延长油田应用提供理论参考.     

短期高温对断乳仔猪心率变异性的影响

试验采用自身配对方法,用ACTI Heart对日龄相同、体况相近的4头受试断乳仔猪在对照期(常温)和试验期(短期高温)条件下心率变异性进行测定,并以时域、频域的方法进行分析,研究高温环境对断乳仔猪心率状况的影响。结果表明,高温条件下,试验个体的窦性心律NN间期的标准差、窦性心律相邻N-N间期差的均方根、高频成分、低频成分显著降低(P0.01),一定程度上反映了高温使动物产生热应激,影响断乳仔猪植物性神经系统与心率变异性。