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摘要:目的 通过对新硫肽类抗生素166A产生菌小单孢菌TMD166进行诱变选育研究,以期获得产166A的高产菌株。方 法 使用多功能等离子体诱变系统(multifunctional plasma mutagenesis system, MPMS)对出发菌株TMD166的孢子进行等离子体-紫 外(MPMS-UV)复合诱变,单孢子悬液经照射处理、涂布培养后获得单菌落,并以牛津杯固体发酵高通量筛选方法对菌株进行初 筛,之后对高产菌株进行摇瓶复筛,利用突变株摇瓶发酵的化学效价筛选出正突变菌株。结果 对比MPMS-UV不同诱变剂量发 现,MPMS105s-UV60s复合诱变剂量获得的正突变率最高,达到41.43%,相应致死率为99.88%。最终筛选出一株166A高产突 变株TMD166-MU1,在培养温度为28℃、210 r/min的条件下,经过96~120 h培养后,166A产量相比出发菌株提高了7.47倍。结 论 采用MPMS-UV复合诱变方式,再结合牛津杯固体发酵高通量筛选方法和摇瓶复筛,可高效筛选获得166A高产菌株。  相似文献   
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《Dental materials》2022,38(4):e69-e82
Objectivestesting if hypothetical transverse centripetal strains due to polymerization contraction of luting materials produce differential alterations in its bonding to luted structures, depending on distances to the center of the luting mass, and if this effect is C-factor related. Two hypotheses were tested: (1) there is a statistically significant decreasing relationship between the bonding strength and the transverse distances to the center of the luting material, and (2) there is a statistically significant difference between bonding strengths among luting spaces with different configuration factors.Methods10 PMMA (15 mm Ø) pairs of cylinders were cemented (Scotchbond Universal adhesive & Relyx Universal, both chemically cured) in a compliant setup under two (20 and 70 N) luting forces forming 2 groups (5 samples each), resulting in different C-factors. Whole samples were sectioned in x and y directions obtaining non-trimmed beams from all along the luting surfaces. Their relative positions in each sample were assessed before separating and categorized (10 categories) according to their distances to the center of the sample. All beams were tested in tension and, because of their uneven bonding areas and to balance its influence, UTS results were transformed into UTSres. First hypothesis was tested trough a linear relationship between UTSres and distances to vertical centers per samples. Second hypothesis was tested using Mann-Whitney U tests to compare UTSres between groups, along all categories. Further Weibull analysis was applied.ResultsANOVA’s p of the regression UTSres – categories were statistically significant for all samples in group 70 N and for all except one in group 20 N: first hypothesis is partially maintained. Although Mann-Whitney tests p comparing UTSres of both groups for all categories but the first were statistically significant this hypothesis was maintained relying in Weibull analysis. Significance: bonded attachment of cemented materials decreases from centers to outbounds in plane, extensive surfaces, and this decrease is C-factor related.  相似文献   
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目的 探讨台式虚拟现实显示器对近距离观看视频所致数字眼疲劳的预防作用。设计 交叉实验研究。研究对象 成年健康受试者31例。方法 受试者随机分两组,第一组先使用手机、后使用台式虚拟显示器观看相同的视频10分钟,中间休息30分钟;第二组使用相反的顺序观看。使用开放式验光仪记录观看视频前、中、后的屈光度,并计算调节误差、调节微波动。选取右眼数据进行统计分析。使用Likert量表记录观看视频前、后的主观视疲劳评分。主要指标 观看视频前后屈光度、调节微波动、调节误差、视疲劳量表评分。结果 观看视频前,采用手机和采用台式虚拟现实显示器者的屈光度分别为(-0.30±0.54)D和(-0.29±0.58)D(P=0.928),调节微波动分别为(0.15±0.07)D和(0.15±0.08)D(P=0.858)。观看视频5分钟时,采用手机者的屈光度为(-3.32±0.68)D,较观看前明显降低(P=0.000);采用台式虚拟现实显示器观看者的屈光度为(-0.39±0.63)D,较观看前未见明显降低(P=0.168);采用手机观看和采用台式虚拟现实显示器观看者的调节微波动分别为(0.33±0.10)D和(0.21±0.10)D(P=0.000);采用手机观看者调节误差为滞后(0.25±0.68)D,采用台式虚拟现实显示器观看者调节误差为超前(0.09±0.63)D(P=0.044)。观看完视频后,采用手机观看者的屈光度为(-0.53±0.56D)D,较观看前明显降低(P=0.000);采用台式虚拟显示器观看者的屈光度为(-0.34±0.61)D,较观看视频前未见明显降低(P=0.335)。观看视频后,采用手机和台式虚拟显示器者的视疲劳量表评分较观看前均增加,分别增加了(8.4±8.3)和(2.5±3.8)(P=0.001)。结论 应用台式虚拟显示器可以预防近距离观看视频引起的数字眼疲劳,这可能与观看时不需要视近调节有关。(眼科,2022, 31: 225-230)  相似文献   
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Amacrine cells of the retina are conspicuously variable in their morphologies, their population demographics, and their ensuing functions. Vesicular glutamate transporter 3 (VGluT3) amacrine cells are a recently characterized type of amacrine cell exhibiting local dendritic autonomy. The present analysis has examined three features of this VGluT3 population, including their density, local distribution, and dendritic spread, to discern the extent to which these are interrelated, using male and female mice. We first demonstrate that Bax-mediated cell death transforms the mosaic of VGluT3 cells from a random distribution into a regular mosaic. We subsequently examine the relationship between cell density and mosaic regularity across recombinant inbred strains of mice, finding that, although both traits vary across the strains, they exhibit minimal covariation. Other genetic determinants must therefore contribute independently to final cell number and to mosaic order. Using a conditional KO approach, we further demonstrate that Bax acts via the bipolar cell population, rather than cell-intrinsically, to control VGluT3 cell number. Finally, we consider the relationship between the dendritic arbors of single VGluT3 cells and the distribution of their homotypic neighbors. Dendritic field area was found to be independent of Voronoi domain area, while dendritic coverage of single cells was not conserved, simply increasing with the size of the dendritic field. Bax-KO retinas exhibited a threefold increase in dendritic coverage. Each cell, however, contributed less dendrites at each depth within the plexus, intermingling their processes with those of neighboring cells to approximate a constant volumetric density, yielding a uniformity in process coverage across the population.SIGNIFICANCE STATEMENT Different types of retinal neuron spread their processes across the surface of the retina to achieve a degree of dendritic coverage that is characteristic of each type. Many of these types achieve a constant coverage by varying their dendritic field area inversely with the local density of like-type neighbors. Here we report a population of retinal amacrine cells that do not develop dendritic arbors in relation to the spatial positioning of such homotypic neighbors; rather, this cell type modulates the extent of its dendritic branching when faced with a variable number of overlapping dendritic fields to approximate a uniformity in dendritic density across the retina.  相似文献   
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A concrete-filled steel tube (CFT) combines the advantages of concrete and steel in construction and structural applications. However, research on the time-dependent deformation of the CFT under long-term sustained loading are still limited, particularly for stress transfer between the steel tube and concrete due to creep. This study investigated the creep behavior of CFT over a long period of 400 days. The creep and shrinkage strain of CFT was significantly lower than those of concrete that was not confined within a steel tube. The vertical strains of the steel tube and concrete core were almost identical, and it was shown that they were well bonded and acted as a composite. The vertical stress of steel increased by 32.7%, whereas the vertical stress of concrete decreased by 15.8% at 375 days. The stress transfer is notable and cannot be neglected in CFT design. Moreover, the results of creep and shrinkage were compared to prediction values of the B4 model and B4-TW model to verify their validity.  相似文献   
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