Summer Magic

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Studying creation of bulk elementary excitation by heaters in superfluid helium-Ⅱ at low temperatures

In this paper, the obtained experimental results concerning creation of bulk elementary excitations （BEEs） in isotopically pure liquid ^4He at low temperatures -60 mK are discussed. Positive rotons＇ （R^＋-rotons） creation by a pulsed heater was studied. Signals were recorded for the following quantum processes： quantum evaporation of ^4He-atoms from the free liquid-helium surface by the BEEs of the liquid helium-Ⅱ, and BEEs reflection from the free surface back into the bulk liquid. Typical signals are shown, and ratios of signal amplitudes are evaluated. For long heater pulses from 5 to 10 μs, appearance of the second atomic cloud consisting of evaporated ^4He-atoms was observed in addition to the first atomic cloud. It is thought that the first atomic cloud of the evaporated helium atoms consists of very fast ^4He-atoms with energies ～35 K evaporated by positive rotons with the special energies ～17 K （～2ER～2×8.6 K with ER representing the roton minimum energy） corresponding to the third non-dispersive Zakharenko wave. The second cloud of slower ^4He-atoms was created by surface elementary excitations （SEEs or ripplons） possessing the special energies ～7.15 K representing the binding energy. It was assumed that such SEEs can be created by phonons incoming to the liquid surface with special energies ～6.2 K corresponding to the first non-dispersive Zakharenko wave which can interact at the liquid surface with the same phonons already reflected from the surface for long heater pulses. Also, some pulsed-heater characteristics were studied in order to better understand the features of such heaters in low temperature experiments.     

心路历程--建议

Dear Friends,Giving advice is one of the most popular pastimes known to mankind. Everyone has some advice to give to everyone else. It is easier to give advice than it is to take advice. Most of us have been given more advice than we can possibly use.I am drawn to this topic because many of our readers ask me to give them advice on a variety(变化,多样性)of different prob-lems.This can be very flattering(讨人喜欢的), and I appreciate your willingness to ask me. I respond to your questions, and I feel free to give my opinions and my comments on any subject. These comments     

Origins of individual differences in theory of mind: from nature to nurture?

In this study of the origins of individual differences in theory of mind (ToM), the Environmental Risk (E-Risk) Longitudinal Twin Study sample of 1,116 sixty-month-old twin pairs completed a comprehensive battery of ToM tasks. Individual differences in ToM were striking and strongly associated with verbal ability. Behavioral genetic models of the data showed that environmental factors explained the majority of the variance in ToM performance in this sample. Shared environmental influences on verbal ability had a common impact on ToM and explained more than half the phenotypic correlation between these two skills. Possible underlying proximal mechanisms are discussed, including maternal speech and mind-mindedness, sibling interactions, and peer influences.     

论生物課中各种不同教学方法的运用

千篇一律的上課方式是目前中学生物学教学中一个最大的缺点,这种上課方式的特点是:在口头检查学生的家庭作业后,教师講解新教材,演示直观教具,巩固新教材,布置家庭作业。这样的上課結構在有些場合下还可运用,但不能经常如此。如果在上課时运用各种不同的教学方法,特別是让学生独立地研究所分发的材料、活的植物和教科书上的插图的話,学生將能更好地掌握教材。当教师在进行生物学課时所采用的教学方法时应遵循些什么原則呢? 首先,应明确,生物学課程具有那些教学方法,按我們的意見,大致有以下一些:講解法,談話法,中学性的演講法,学生独立工作法,实驗,閱讀教科     

我们怎样研究工厂史

我校历史小组研究"共产国际"造船厂史,已经两年了.历史小组开始活动的那天,正好是我市生活中极有意义的日子——赫尔松市这家历史最长久的企业开办150年纪念日.在小组成立不久的一次会议上,我简扼地给学生们讲了这家工厂的历史和该厂工人革命与生产的光荣传统.我的讲述使孩子们发生了兴趣.有一位组员问我:     

苏霍姆林斯基论教师的备课

苏霍姆林斯基从自己的教育生涯一开始就十分重视改进课堂教学的问题。在他有关教学论问题的许多文章中,在《把正个心灵献给孩子们》、《帕夫雷什中学》、《公民的诞生》、《给教师的一百条建议》、《和青年校长的谈话》等著作的章节里都含有关于改进课堂教学的途径和条件的宝贵思想。同样,保存在基洛夫格勒州帕夫雷什村《苏霍姆林斯基教育纪念馆》里的未发表过的他的文章、材料和文件也有很大的重要意义。在纪念馆的藏书中有帕夫雷什中学二十多年来的校务会议的记录、1965—1970年间教师心理学讲习班会议的记录、若干期帕夫雷什中学教师手写的刊物《教育思想》、学校的工作计划等。在帕夫雷什的纪念馆里保存着三十一本苏霍姆林斯基在担任帕夫雷什中学校长的二十二年期间听课的分析笔记。他从担任校长的头几天起至生命的最后几天止,每天都听本校教师的课二——三节,听课时,通常他把笔记本的纸折成二部分,一侧是扼要的课堂记载,另一侧记下给教师的建议、局部的结论和深刻的总结。     

大气物理和大气化学

气候是由复杂的大气—洋—海—冰—陆地—生物圈的相互作用决定的。为了弄清楚对人类生活具有生死悠关的重要性的气候形成的因素及其变化的原因,人们必须研究:(a)与太阳能转化为各种形式的热能以及与水从一种形态转化为另一种形态有关的大量物理过程和化学过程;(b)空气流-海流的相互作用;(c)大洋表面和深层之间的交换;和(d)大气层中的大量化学转化。在这篇文章中,考虑到对气候和气候变化有关的基本物理过程和化学过程。     

微生物资源中心:农业培训与开发的催化工具

微生物资源中心(MIRCENs)全球网络是由联合国教科文组织建立的,包括五个有关生物固氮方面的中心。这些中心分别在:肯尼亚,巴西,美国和塞内加尔,负责培训根瘤菌接种方法方面的专门人材。根瘤菌剂应用于一定的豆科植物常常能代替粮食生产对昂贵的化学氮肥的需求。MIRCENs可称得上是国际科学合作的典范。     

单宁对杨梅汁花色苷稳定性的影响

分析了单宁对增加杨梅汁花色苷稳定性的效果。在pH=4.5和pH=3.2时加入单宁使杨梅汁最大吸收波长和最大吸光度增大。在pH为1.0时单宁浓度增大导致杨梅汁最大吸收波长增大，但最大吸光度没有增加。单宁和杨梅汁花色苷的辅助色素反应为放热反应，其△H等于-8.481kJ/mol, △S为7.286J/mol。温度的升高促进辅助色素反应向分解方向进行。