信息技术支持下中学数学教学实践与思考

1 何谓信息技术与数学教学的整合 信息技术与数学教学的整合是教育信息化中一个重要的课题.比较而言,信息技术与数学教学的整合要比掌握信息技术的一般技能困难得多.所谓"整合"不是把数学教学整合到信息技术中,而是把信息技术有机地融入数学教学中去支持数学教学.因此,必须考虑结合学科教学的特点才能实现整合.     

Comparison of the sensitivities for atom interferometers in two different operation methods

We investigated the sensitivities of atom interferometers in the usual fringe-scanning method(FSM) versus the fringelocking method(FLM). The theoretical analysis shows that for typical noises in atom interferometers, the FSM will degrade the sensitivity while the FLM does not. The sensitivity-improvement factor of the FLM over the FSM depends on the type of noises, which is validated by numerical simulations. The detailed quantitative analysis on this fundamental issue is presented, and our analysis is readily extendable to other kinds of noises as well as other fringe shapes in addition to a cosine one.     

阴沟肠杆菌固氮调节操纵子nifLA启动子的结构及其氧敏感性

阴沟肠杆菌E26带有与肺炎克氏杆菌同源的、排列类似的固氮基因簇。我们测定了E26固氮调节操纵子nifLA启动子区的核甘酸序列及其转录起始点。据此,构建一个E26 nifL’-lacZ翻译水平融合质粒,在大肠杆菌中测定其表达调节。结果表明,有氧培养条件下,E26 nifLA启动子的活性受到抑制,与肺炎克氏杆菌nifLA启动子相似。比较E26与肺炎克氏杆菌nifLA启动子区的核苷酸序列,显示出它们具有保守的σ~(54)启动子-24/-12区,转录起始点下游NifA结合区,以及类似的NtrC结合区结构。此外,在NtrC结合区和-24/-12区之间,揭示出一段11bp的保守序列。推测11bp保守区也许与nifLA启动子氧敏感有关。     

Common-mode noise rejection using fringe-locking method in WEP test by simultaneous dual-species atom interferometers

We theoretically investigate the application of the fringe-locking method(FLM) in the dual-species quantum test of the weak equivalence principle(WEP).With the FLM,the measurement is performed invariably at the midfringe,and the extraction of the phase shift for atom interferometers is linearized.For the simultaneous interferometers,this linearization enables a good common-mode rejection of vibration noise,which is usually the main limit for high precision WEP tests of the dual-species kind.We note that this method also allows for an unbiased determination of the gravity accelerations difference,which meanwhile is ready to be implemented.     

Three-dimensional hexapole focusing of pulsed molecular beam for state selection

We theoretically investigate three-dimensional(3D) focusing of pulsed molecular beam using a series of hexapoles with different orientations. Transversely oriented hexapoles provide both the transverse and longitudinal focusing force and a longitudinally oriented one provides only the transverse force. The hexapole focusing position are designed to realize the simultaneous focusing in three directions. The additional longitudinal focusing compared with the conventional hexapole can suppress the effect of chromatic aberration induced by the molecular longitudinal velocity spread, thus improving the state-selection purity as well as the beam density. Performance comparison of state selection between this 3D focusing hexapole and a conventional one is made using numerical trajectory simulations, choosing CHF_3 molecules as a tester. It is confirmed that our proposal can improve the state-selection purity from 68.2% to 96.1% and the beam density by a factor of 2.3.