对干酪乳杆菌群(Lactobacillus casei group)内5个种和4个亚种的23个代表菌株的苯丙氨酰-tRNA合成酶α亚基基因(pheS)序列和18个16S rRNA基因序列进行系统发育学分析,探索pheS基因序列分析在干酪乳杆菌群种水平鉴定中应用的可行性。分...对干酪乳杆菌群(Lactobacillus casei group)内5个种和4个亚种的23个代表菌株的苯丙氨酰-tRNA合成酶α亚基基因(pheS)序列和18个16S rRNA基因序列进行系统发育学分析,探索pheS基因序列分析在干酪乳杆菌群种水平鉴定中应用的可行性。分析结果表明,pheS基因序列群内种间的差异率在6.8%～34%之间,种内最大差异率可达3%,其变异率远高于16S rRNA基因,可作为该群内种水平鉴定的重要手段。展开更多
The nucleotide scquence of tRNAphe gene of Carp mitochondria was determined. Sequence comparisons made among Whale,Human,Xenopus laevis, Bovine, Mouse,Chicken and Carp revealed a novel conservative structure in the D....The nucleotide scquence of tRNAphe gene of Carp mitochondria was determined. Sequence comparisons made among Whale,Human,Xenopus laevis, Bovine, Mouse,Chicken and Carp revealed a novel conservative structure in the D. stem (dihydrouridine stem),which is known to vary in other vertebrate mitochondrial and eytoplasmic tRNA genes.This conservative structure contains 13 bp. When the first 7 bp of the conserviative structure were compared with the A domain recognized by RNA Pol III, we noticed partial homology between these two kinds of sequences among different species. In view of the tRNAphe gene's close position to the D loop,it is reasonable to expect extraordinary functions in this novel conservation structure.展开更多
Channel flows of Plate Heat Exchangers (PHEs) were assessed by experiments with three different chevron angle arrangements in turbulent regime. Two chevron angles were selected to assess low and high pressure drop cha...Channel flows of Plate Heat Exchangers (PHEs) were assessed by experiments with three different chevron angle arrangements in turbulent regime. Two chevron angles were selected to assess low and high pressure drop channels, besides a third mixed configuration as to achieve in-between results regarding hydraulic performance. Friction factor correlations were provided with the channel Reynolds number ranging from 1175 to 8325. Two-dimensional (2D) mean velocity field was obtained by Particle Tracking Velocimetry (PTV) with Reynolds number equal to 3450. To the best of our knowledge, this is the first experimental study that quantified the complete 2D velocity field of a typical PHE channel. This value allowed comparison with literature results of Plate and Shell Heat Exchanger (PSHE) channels with the same Reynolds number. PSHE mean velocity field is highly heterogeneous as compared to the one obtained for PHE channels. Peak velocity magnitude in the PSHE center is 50% higher than its bulk velocity, whereas this value is only 15% higher in the PHE center. Pressure drop in PHE mixed channels cannot be approximated by averaging chevron angles: furrow flow prevailed in the specified conditions. The axial velocity is asymmetric regarding the vertical plane. Smooth streamlines prevail in the channel inlet. Recirculation zones at the channel exit affect pipe flow in the manifold outlet with swirling flow structures. The necessary length to obtain fully developed pipe flow at the channel outlet was estimated. Significant velocity components occur in the distribution areas and can limit the heat exchanger performance. The results reported herein are essential to understand how the PHE channel geometry affects the velocity field and, therefore, local heat transfer and dissipation processes.展开更多
文摘对干酪乳杆菌群(Lactobacillus casei group)内5个种和4个亚种的23个代表菌株的苯丙氨酰-tRNA合成酶α亚基基因(pheS)序列和18个16S rRNA基因序列进行系统发育学分析,探索pheS基因序列分析在干酪乳杆菌群种水平鉴定中应用的可行性。分析结果表明,pheS基因序列群内种间的差异率在6.8%～34%之间,种内最大差异率可达3%,其变异率远高于16S rRNA基因,可作为该群内种水平鉴定的重要手段。
文摘The nucleotide scquence of tRNAphe gene of Carp mitochondria was determined. Sequence comparisons made among Whale,Human,Xenopus laevis, Bovine, Mouse,Chicken and Carp revealed a novel conservative structure in the D. stem (dihydrouridine stem),which is known to vary in other vertebrate mitochondrial and eytoplasmic tRNA genes.This conservative structure contains 13 bp. When the first 7 bp of the conserviative structure were compared with the A domain recognized by RNA Pol III, we noticed partial homology between these two kinds of sequences among different species. In view of the tRNAphe gene's close position to the D loop,it is reasonable to expect extraordinary functions in this novel conservation structure.
文摘Channel flows of Plate Heat Exchangers (PHEs) were assessed by experiments with three different chevron angle arrangements in turbulent regime. Two chevron angles were selected to assess low and high pressure drop channels, besides a third mixed configuration as to achieve in-between results regarding hydraulic performance. Friction factor correlations were provided with the channel Reynolds number ranging from 1175 to 8325. Two-dimensional (2D) mean velocity field was obtained by Particle Tracking Velocimetry (PTV) with Reynolds number equal to 3450. To the best of our knowledge, this is the first experimental study that quantified the complete 2D velocity field of a typical PHE channel. This value allowed comparison with literature results of Plate and Shell Heat Exchanger (PSHE) channels with the same Reynolds number. PSHE mean velocity field is highly heterogeneous as compared to the one obtained for PHE channels. Peak velocity magnitude in the PSHE center is 50% higher than its bulk velocity, whereas this value is only 15% higher in the PHE center. Pressure drop in PHE mixed channels cannot be approximated by averaging chevron angles: furrow flow prevailed in the specified conditions. The axial velocity is asymmetric regarding the vertical plane. Smooth streamlines prevail in the channel inlet. Recirculation zones at the channel exit affect pipe flow in the manifold outlet with swirling flow structures. The necessary length to obtain fully developed pipe flow at the channel outlet was estimated. Significant velocity components occur in the distribution areas and can limit the heat exchanger performance. The results reported herein are essential to understand how the PHE channel geometry affects the velocity field and, therefore, local heat transfer and dissipation processes.
