Computation of ~7Be solar neutrino flux

1. Introduction J. N. Bahcall computed 7Be electron-capture consi-dering only the capture of continuum electrons and neglecting the plasma screening by the ionized gas of the star [1] . While I. Iben et al. thought that there is a finite probability that 7Be exists as an atom with one or two bound K-shell electrons [2]. They computed the capture rate of bound electron in 7Be3+ and 7Be4+ using Debye-Huckel approximation to estimate the screening effect of the ionized plasma on the rate of b…     

Neutrinos and our sun — Part 2

In this part we describe the chain of nuclear reactions that fuse protons into helium nuclei in the centres of stars. Neutrinos play an important role in the proton-proton chain and detection of these neutrinos is important for a direct insight into the processes taking place at the centre of the sun. Experiments for the detection of solar neutrinos and the emerging result from them, known as the Solar Neutrino Puzzle, are described. The puzzle refused to go away even with very carefully designed experiments. Its solution came from physics, by reviving the idea of neutrino oscillations, speculated many decades ago. Recent experiments have confirmed these ideas and have enriched our knowledge of these fundamental particles.     

Application of least squares vector machines in modelling water vapor and carbon dioxide fluxes over a cropland

INTRODUCTION Modelling the variation in surface-atmosphericexchange of water vapor and carbon dioxide fluxesand how they are influenced by a complex combina-tion of environment variables and plant physiology iscrucial for assessing the annual water and carbonbudget for cropland. Biophysical or process-basedmodels such as soil-vegetation-atmosphere transfer(SVAT) (Franks et al., 1997; Franks and Beven, 1999Mo and Beven, 2004), Simultaneous Heat and Water(SHAW) (Flerchinger et al., 1…     

Atmospheric corrosion mapping of copper surfaces from diffuse light scattering measurements by an optoelectronic sensor system

A novel light scattering technique for mapping metal surface corrosion is presented and its results on copper exposed to atmosphere are reported. The front end of the instrument is made up of a sensor module comprising a thin beam light emitting diode （LED） illuminating a small spot on the metal surface, and a matched pair of photodetectors, one for capturing the reflected light and the other for sampling the scattered light. The analog photocurrent signals are digitized and processed online by a per- sonal computer （PC） to determine the corrosion factor defined in terms of the two current values. By scanning the sample surface using the light beam and by computing the corrosion factor values simultaneously, a three dimensional graph and a two dimensional contour map are generated in the PC using Matlab tools. The values of the corrosion factor measured in different durations of exposure to atmosphere, which obey a bilogarithmic law, testify to the validity of our mathematical model.     

Effects of continuous casting mould fluxes on reducing longitudinal and star cracks on a slab surface

1.IntroductionAstothecurrenttechnologyofcontinuouscastingofsteel,itisanemergencyformouldfluxestoharmonizetheconflictsbetweenheattransferandlubricationforslabcasting.Whenstructuralsteelwhosemassfractionofcarbonwcis0.09%to0.15%andhighstrengthlowalloysteel(HSLA)whosewcis0.14%to0.25%arecontinuouslycast,itisnecessarytocontroltheheatfluxfromtheslabshelltothecoppermouldnottoexceed1.7?06W/m2becauseofthebigandcoarseausteniticcrystalsintheinitialsolidifiedslabshell[1].Otherwise,longitudinalcrackstendt…     

采用常压室温等离子体诱变技术获得一株高产雄甾-4-烯-3,17-二酮的突变菌株 Mycobacterium neoaurum ZADF-4

目的：获得一株高产雄甾-4-烯-3,17-二酮（ AD ）的Mycobacterium neoaurum突变株。
　　创新点：获得了一株3-甾酮-Δ1-脱氢酶（KSDD）酶活缺陷型的高产 AD的诱变菌株 Mycobacterium neo-aurum ZADF-4,并采用菌落显色法筛选 KSDD酶活缺陷型M. neoaurum突变株。
　　方法：（1）诱变方法：采用常压室温等离子体（ARTP）诱变技术来处理出发菌株 M. neoaurum ZAD。ARTP 诱变条件如下：功率40 W ,气流量12.5 L/min,辐射距离1 cm,样品体积10μl,辐射时间为60、90、120、150和180 s;致死率统计优化后,最适辐射时间为150 s,致死率为90%~96%。（2）筛选方法：将ARTP诱变处理后的菌株点种在硝酸纤维滤膜上,30°C培养2 d,然后将长有菌落的滤膜小心取出并漂浮在4 mg/ml二氯靛酚（DCPIP）溶液（0.1 mmol/L磷酸缓冲液pH 7.0）,30°C培养1 d直到全部菌落染成蓝色。然后将该滤膜取出,漂浮在250 mmol/L AD溶液（2%甲醇和50 mmol/L Tris pH 7.0缓冲液）,室温放置15 min左右,观察菌落颜色变化。KSDD在底物 AD 存在时会脱氢产生雄甾-1,4-二烯-3,17-二酮（ADD）和H+,H+可以使被DCPIP染成蓝色的菌株褪色。因此,酶活缺陷型的菌株会仍保持蓝色,而酶活高的菌株会褪色为黄色（图3）。（3）对获得的潜在的高产AD菌株进行进一步的酶活检测以及产量验证,以期获得最优的突变株。
　　结论：获得了4株具有潜在的高产AD能力的菌株,其中,最优的突变株ZADF-4的KSDD酶活相较于出发菌株ZAD下降了81.2%（图4）,活性胶也证明其KSDD酶活相较于出发菌株下降明显（图5）。薄层色谱法（TLC）和高效液相色谱法（HPLC）实验证明突变株 ZADF-4中,AD的产量有了明显的提高（图6和图7）,提高到了(6.28±0.11) g/L, AD/ADD提高到8：1,AD的摩尔产率达到60.3%（表1）。对出发菌株ZAD和突变株ZADF-4的ksdd基因进行克隆和序列比对,发现ZADF-4的ksdd序列在5'端缺失9个核苷酸（atgttctac）,导致3个氨基酸（MFY）的缺失;还发生了两个点突变,其中一个是无义突变（g.15a>6t）,另一个是有义突变（g.413c>404t）,并引起了相应位置上的氨基酸变化（p.138S>135L）。上述的基因突变及其引起的氨基酸序列的变化可能是引起M. neoaurum ZADF-4中KSDD酶活降低及AD产量提高的主要原因。     

运用表观热惯量遥感地表蒸散——以河北省易县崇陵流域为例

现有遥感地表蒸散的方法是基于地表热量平衡方程,先求出地表净辐射通量、土壤热通量和显热通量,再用余项法求出潜热通量。地表净辐射通量和显热通量的计算需空气温度、风速和地表粗糙度等非遥感参数,并且涉及到空间插值问题,由此增加了估算的复杂性并降低了估算的精度。引入反映地物固有热特性的物理参数一表现热惯量,结合地表辐射温度,充分利用遥感较易获取的这两个参数来估算地表蒸散,可弥补上述不足。利用河北省易县崇陵流域卫星过境同步观测的地面资料,以2007年5月28日过境的LANDSAT／TM作为数据源,尝试利用表现热惯量来遥感地表蒸散的新途径。首先根据像元表现热惯量和地表辐射温度等遥感参数反演出像元的大气下行辐射,进而估算出地表净辐射通量;其次,利用表现热惯量估算出波文比,再根据波文比时地表净辐射通量进行切割,然后代入地表热量平衡方程中,直接估算出地表潜热通量;最后,计算出崇陵流域日地表蒸散量,并获取其空间分布图。这种方法避开了估算显热通量的中闻环节,可操作性更强。     

“大气物理学”混合式教学实施策略与实践反思

依托自建的校级优秀SPOC示范课程,针对不同专业和首次任职方向的本科学员,开展“大气物理学”线上线下混合式教学实践探索,逐步形成了基于目标先行、重在课堂面授、遵循结果导向、倡导学科融合的“校本特色混合模式”,提升了混合课程的教学效果,加之反思和总结实践经验及存在的问题,以期为混合式教学改革提供经验交流和实施策略。     

中微子与泡利

在众多的亚原子粒子家族中,中微子是最令人捉摸不定的基本态粒子。它们虽然只参与弱相互作用,但它们似乎具有许多独特的性质,它们与粒子物理和天体物理的基本理论有着广泛的和至关重要的联系。泡利是第一个预言中微子存在的理论物理学家,他有着和中微子一样的迷,既琢磨不透,又魅力无穷。