[Objective] The aim of this study was to produce Streptomyces avermitilis strain with site-directed mutagenesis in aveD gene,and so as to provide theoretical basis for genetic breeding of S.avermitilis.[Method] PCR-dr...[Objective] The aim of this study was to produce Streptomyces avermitilis strain with site-directed mutagenesis in aveD gene,and so as to provide theoretical basis for genetic breeding of S.avermitilis.[Method] PCR-driven overlap extension was conducted for the site-directed mutagenesis in aveD gene;the mutated aveD gene then was used to construct vector pDC3（pKC1139∷aveD） via molecular manipulations like in vitro enzyme digestion and ligation;the vector pDC3（pKC1139∷aveD） was then introduced to aveD deletion mutant 489 of avermectin-producing strain S.avermitilis 76-9.[Result] Mutant strain 536 of site-directed mutagenesis of S.avermitilis 76-9 was obtained by homologous recombination.The sequencing results show that the sixty-ninth base C in aveD-coding region of mutant 536 was substituted by T,and the corresponding amino acid Thr was mutated to be Ile.[Conclusion] This study laid basis for the development of strains specifically producing avermectin B.展开更多
The sie index lists of the artificia l Laix gmelini and Pinus sykrestris var.mongolica forests in Daxing'an Mountainsregion weie analyzed by the principle of the two-point me thod.The standa rdzed growth model of ...The sie index lists of the artificia l Laix gmelini and Pinus sykrestris var.mongolica forests in Daxing'an Mountainsregion weie analyzed by the principle of the two-point me thod.The standa rdzed growth model of the artificial needle-lea vedforest was set up.According to the model,the ea ch growth-index class and theore tical values ofe ach age-class were calculated,and the standardized sie index list was constiute d.The test of the theore tical values showe d that the standardized site indexlit meet the de ma nd of precision.This study resolved the conversions of site indexes between the same species in diffe rentsite type s and the different spe cies in diffe re nt ste types for nee dle-leave d forests in Da xing'an Moun tains region.展开更多
When patients initially present with atrial fibrillation along with an enlarged heart and heart failure, followed by atrioventricular block, it's essential to consider genetic factors.^([1])Genetic testing can off...When patients initially present with atrial fibrillation along with an enlarged heart and heart failure, followed by atrioventricular block, it's essential to consider genetic factors.^([1])Genetic testing can offer crucial diagnostic evidence, aiding in prognosis assessment and the adoption of appropriate treatment strategies.展开更多
为解决第三代音视频编码标准(audio video coding standard 3,AVS3)帧内预测的耗时问题,提出一种基于最小编码单元(coding unit,CU)代价的帧内预测并行算法。首先,将图像划分为最小CU。然后,利用原始像素作为参考,并行计算所有最小CU的...为解决第三代音视频编码标准(audio video coding standard 3,AVS3)帧内预测的耗时问题,提出一种基于最小编码单元(coding unit,CU)代价的帧内预测并行算法。首先,将图像划分为最小CU。然后,利用原始像素作为参考,并行计算所有最小CU的帧内模式代价。最后,用代价组合的方式快速计算出其他CU的帧内模式优先级,选择最优的15个模式进入粗略模式决策(rough mode decision,RMD)阶段。此外,为减少方法引入的误差,提出了3种优化策略。在预测前对原始像素进行预处理,使其更贴合重构像素;修改帧内预测的代价函数,以更准确地估计每种模式的优先级;大尺寸CU使用顶层的CU代价作为参考,减少CU组合累积的误差。实验结果表明,在码率仅下降0.35%的情况下,整体编码的计算时间减少了27%,有效地减少了帧内预测的耗时并保证了编码质量。展开更多
针对提高4K超高清电视广播视频压缩效率,减少存储空间和网络带宽这一需求,提出应用音视频编码标准3(Audio Video Coding Standard 3,AVS3)视频编解码技术,利用AVS3编解码标准的高效性,提升4K超高清视频内容的编码质量和传输效率。首先,...针对提高4K超高清电视广播视频压缩效率,减少存储空间和网络带宽这一需求,提出应用音视频编码标准3(Audio Video Coding Standard 3,AVS3)视频编解码技术,利用AVS3编解码标准的高效性,提升4K超高清视频内容的编码质量和传输效率。首先,从节目制播环节入手,通过扩展帧内角度预测和信源动态编码,在保持图像质量的同时降低编码比特率,优化编码过程,节省传输带宽;其次,通过视频分层并行解码和音频解码还放声音技术,提升接收解码及呈现的速度和质量;最后,通过应用实验验证AVS3视频编解码技术在4K超高清电视广播领域的实际效果。展开更多
基金Supported by Special Fund for Doctors in Universities in Hebei Province(B2003201)~~
文摘[Objective] The aim of this study was to produce Streptomyces avermitilis strain with site-directed mutagenesis in aveD gene,and so as to provide theoretical basis for genetic breeding of S.avermitilis.[Method] PCR-driven overlap extension was conducted for the site-directed mutagenesis in aveD gene;the mutated aveD gene then was used to construct vector pDC3（pKC1139∷aveD） via molecular manipulations like in vitro enzyme digestion and ligation;the vector pDC3（pKC1139∷aveD） was then introduced to aveD deletion mutant 489 of avermectin-producing strain S.avermitilis 76-9.[Result] Mutant strain 536 of site-directed mutagenesis of S.avermitilis 76-9 was obtained by homologous recombination.The sequencing results show that the sixty-ninth base C in aveD-coding region of mutant 536 was substituted by T,and the corresponding amino acid Thr was mutated to be Ile.[Conclusion] This study laid basis for the development of strains specifically producing avermectin B.
文摘The sie index lists of the artificia l Laix gmelini and Pinus sykrestris var.mongolica forests in Daxing'an Mountainsregion weie analyzed by the principle of the two-point me thod.The standa rdzed growth model of the artificial needle-lea vedforest was set up.According to the model,the ea ch growth-index class and theore tical values ofe ach age-class were calculated,and the standardized sie index list was constiute d.The test of the theore tical values showe d that the standardized site indexlit meet the de ma nd of precision.This study resolved the conversions of site indexes between the same species in diffe rentsite type s and the different spe cies in diffe re nt ste types for nee dle-leave d forests in Da xing'an Moun tains region.
基金Military Healthcare Special Scientific Research Project(25BJZ31, awarded to SHI XM)。
文摘When patients initially present with atrial fibrillation along with an enlarged heart and heart failure, followed by atrioventricular block, it's essential to consider genetic factors.^([1])Genetic testing can offer crucial diagnostic evidence, aiding in prognosis assessment and the adoption of appropriate treatment strategies.
文摘为解决第三代音视频编码标准(audio video coding standard 3,AVS3)帧内预测的耗时问题,提出一种基于最小编码单元(coding unit,CU)代价的帧内预测并行算法。首先,将图像划分为最小CU。然后,利用原始像素作为参考,并行计算所有最小CU的帧内模式代价。最后,用代价组合的方式快速计算出其他CU的帧内模式优先级,选择最优的15个模式进入粗略模式决策(rough mode decision,RMD)阶段。此外,为减少方法引入的误差,提出了3种优化策略。在预测前对原始像素进行预处理,使其更贴合重构像素;修改帧内预测的代价函数,以更准确地估计每种模式的优先级;大尺寸CU使用顶层的CU代价作为参考,减少CU组合累积的误差。实验结果表明,在码率仅下降0.35%的情况下,整体编码的计算时间减少了27%,有效地减少了帧内预测的耗时并保证了编码质量。
文摘针对提高4K超高清电视广播视频压缩效率,减少存储空间和网络带宽这一需求,提出应用音视频编码标准3(Audio Video Coding Standard 3,AVS3)视频编解码技术,利用AVS3编解码标准的高效性,提升4K超高清视频内容的编码质量和传输效率。首先,从节目制播环节入手,通过扩展帧内角度预测和信源动态编码,在保持图像质量的同时降低编码比特率,优化编码过程,节省传输带宽;其次,通过视频分层并行解码和音频解码还放声音技术,提升接收解码及呈现的速度和质量;最后,通过应用实验验证AVS3视频编解码技术在4K超高清电视广播领域的实际效果。
