Novel Streptococcus infantarius subsp. infantarius variants harboring lactose metabolism genes homologous to Streptococcus thermophilus

Streptococcus infantarius subsp. infantarius belongs to the Streptococcus bovis/Streptococcus equinus complex (SBSEC) commonly associated with human and animal infections. We elucidated the lactose metabolism of S. infantarius subsp. infantarius predominant in African fermented milk products. S. infantarius subsp. infantarius isolates (n = 192) were identified in 88% of spontaneously fermented camel milk suusac samples (n = 24) from Kenya and Somalia at log₁₀ 8.2–8.5 CFU mL⁻¹. African S. infantarius isolates excreted stoichiometric amounts of galactose when grown on lactose, exhibiting a metabolism similar to Streptococcusthermophilus and distinct from their type strain. African S. infantarius subsp. infantarius CJ18 harbors a regular gal operon with 99.7–100% sequence identity to S. infantarius subsp. infantarius ATCC BAA-102^T and a gal-lac operon with 91.7–97.6% sequence identity to S. thermophilus, absent in all sequenced SBSEC strains analyzed. The expression and functionality of lacZ was demonstrated in a β-galactosidase assay. The gal-lac operon was identified in 100% of investigated S. infantarius isolates (n = 46) from suusac samples and confirmed in Malian fermented cow milk isolates. The African S. infantarius variant potentially evolved through horizontal gene transfer of an S. thermophilus-homologous lactose pathway. Safety assessments are needed to identify any putative health risks of this novel S. infantarius variant.     

多晶硅隧道压阻模型*

基于陷阱模型,分析了多晶硅能带结构和导电机理,给出了解释隧道压阻效应的等效电路,说明了构成多晶硅压阻效应的内在因素以及隧道压阻效应在其中的作用。综合晶界区域和晶粒中性区两方面压阻效应建立了新的压阻模型——隧道压阻模型。结果表明,掺杂浓度在1020cm-3以上,复合晶界的压阻系数不但大于晶粒中性区的压阻系数,而且随掺杂浓度增加而增大,从而揭示了多晶硅纳米薄膜在重掺杂情况下出现应变因子随掺杂浓增加而增大的重要实验现象的内在机理。     

Natural attenuation of nitrogen loading from septic effluents: Spatial and environmental controls

We assess the role of septic systems as potential nitrogen (N) sources to coastal open water bodies. To quantify the potential role of septic tanks, we document the distribution pattern and functionality of septic tanks in McIntosh County in Georgia, USA, and examine factors governing the mitigation of septic N loading in coastal groundwater. Employing a field calibrated 2D variable-density reaction-transport model, we focus on the role of setback distance of a leaky septic source from the receiving surface waters, on transport and biogeochemical characteristics of the subsurface environment, and on leachate composition and reactivity. We conclude that the removal of bioavailable nitrogen via denitrification may be increased by increasing the septic system setback distance, in particular in brackish and saline coastal settings where sulfide produced in sulfate reduction can limit N₂ production.     

KG型矿用过渡轨道的设计及应用

通过设计矿用过渡轨道，提出了掘进巷道临时车场轨道闭合的新途径，并对矿用过渡轨道的应用效果进行了评价。     

Lactic acid bacteria diversity of African raw and fermented camel milk products reveals a highly competitive,potentially health-threatening predominant microflora

The microflora of 59 East African camel milk samples of unfermented raw milk supply chains and spontaneously fermented milk (suusac) was analyzed to describe the diversity of predominant lactic acid bacteria (LAB), identify potential health risks and study bacteriocin-like inhibitory substance (BLIS) production. Bacterial isolates (n = 532) were identified using a genotypic approach incorporating rep-PCR, 16S rRNA gene sequencing, and species-specific PCR assays. The bacterial numbers on MRS and M17 agar exceeded log₁₀ 6.5 colony forming units (CFU) mL^?1 for raw milk supply chain samples and log₁₀ 8 CFU mL^?1 for suusac. Streptococcus agalactiae and Staphylococcus spp. were predominant in unfermented products, while suusac contained predominantly Streptococcus infantarius subsp. infantarius followed by Lactococcus lactis subsp. lactis, Streptococcus thermophilus, and lactobacilli. Fifty per cent of S. infantarius subsp. infantarius isolates originating from 15 out of 24 suusac samples produced a BLIS active against other LAB or Listeria and representing a potential selective advantage during fermentation. This study provides a detailed insight at the genotypic level into the LAB diversity of previously unstudied dairy products. It indicates potential health risks for consumers and the need for hygienic and manufacturing interventions and reports a potentially novel BLIS produced by S. infantarius subsp. infantarius.     

Improvement of Acoustic Doppler Velocimetry in steady and unsteady turbulent open-channel flows by means of seeding with hydrogen bubbles

Velocimetry is used in various fields of research. In hydraulics, Ultrasonic Velocimetry based on the Doppler Shift effect can accurately resolve the quasi-instantaneous flow field [Takeda Y. Velocity profile measurement by Ultrasonic Doppler method. Experimental Thermal and Fluid Science 1995;10:444–53; Takeda Y. Ultrasonic Doppler method for flow measurement. In: International symposium on advanced fluid information. 2002. p. 69–76] if the acoustic scattering level is sufficiently high. But Ultrasonic velocity instruments are known to perform poorly in clear water with low acoustic scattering level, such as often found in laboratory applications.

Artificial seeding of the flow can be used to increase the acoustic scattering level. Blanckaert and Lemmin [Blanckaert K, Lemmin U. Means of noise reduction in acoustic turbulence measurements. Journal of Hydraulic Research IAHR 2006;44:3–17] have proposed a technique to seed the flow with micro hydrogen bubbles generated by means of electrolysis. This technique is optimized under steady flow conditions and subsequently applied to measure the flow characteristics around the front of a surge wave.     

海洋水质监测用新型过滤器的研制

应海洋调查和海洋污染监测的需要研制成功的二种新型过滤器，具有多功能性，可满足不同样品水的过滤需要，并能同时有效地防止空气的二次污染，避免了过滤水样过程中的许多宏观上对样品的沾污因素。因此不仅适应性和实用性大大提高，而且大大提高了其监测数据的准确性和可靠性。     

Numerische Simulation der Strömung in Anlaufstrecken von Grenzschichtwindkanälen für bauwerksaerodynamische Untersuchungen

Zusammenfassung In der vorliegenden Arbeit wird die dreidimensionale turbulente Str?mung in Anlaufstrecken von Grenzschichtwindkan?len mit rechteckigem Querschnitt unter Berücksichtigung der Sekund?rstr?mung zweiter Art berechnet. Die Brauchbarkeit des Verfahrens wird durch Vergleich mit Messungen und Berechnungsergebnissen anderer Autoren für Str?mungen in Kan?len mit glatten und rauhen W?nden gezeigt, und anschlie?end werden die Ergebnisse für einen Grenzschichtwindkanal besprochen.     

LTE-A空口监测分析仪中PDSCH解资源映射的设计与实现

针对增强型长期演进（LTE-A）物理层传统解资源映射方法中重复计算资源映射位置造成的计算量冗余问题,提出一种新型架构的物理下行共享信道（PDSCH）解资源映射方法,为LTE-A空口监测分析仪相关物理层处理提供支持。首先,在物理层下行信号和信道解资源映射之前,产生单天线端口0模式、发射分集模式、单流波束赋形以及双流波束赋形下各个信号和信道的资源索引;然后,在物理层解资源映射时根据资源索引直接定位各信号和信道资源的时频位置;最后,把PDSCH信道解资源映射模块放在整个LTE-A链路级仿真平台中,给出四种传输模式下的仿真,得出不同传输模式下的误码率以及吞吐量的对比图,为最终的硬件实现提供理论参考。同时通过与传统架构下的解资源映射模块进行对比表明,该新型架构下的解资源映射模块比传统架构下的解资源映射仿真所花费的时间减少了33.33%,降低了解资源映射时的运算量和设备资源消耗。