The helium question

Helium appears indispensable for certain energy-related uses that may be important 50 years from now, when helium-bearing natural gas, a much cheaper source than air, may be exhausted. Present demand, however, is lower than productive capacity, and much helium is being dissipated into the atmosphere as natural gas is burned for fuel. Controversy over the need for a government-directed helium-conservation program reflects fundamental differences in viewpoints on the economic future of industrial society, on the limits of substitution of labor and capital for a depleting resource, and on intergenerational equity and risk-bearing.     

Quantum reflection of He2 several nanometers above a grating surface

Quantum reflection allows an atom or molecule to be reflected from a solid before it reaches the region where it would encounter the repulsive potential of the surface. We observed nondestructive scattering of the helium dimer (He(2)), which has a binding energy of 10(-7) electron volt, from a solid reflection grating. We scattered a beam containing the dimer as well as atomic helium and larger clusters, but could differentiate the dimer by its diffraction angle. Helium dimers are quantum reflected tens of nanometers above the surface, where the surface-induced forces are too weak to dissociate the fragile bond.     

Synthesis of methylphosphonic acid by marine microbes: a source for methane in the aerobic ocean

Relative to the atmosphere, much of the aerobic ocean is supersaturated with methane; however, the source of this important greenhouse gas remains enigmatic. Catabolism of methylphosphonic acid by phosphorus-starved marine microbes, with concomitant release of methane, has been suggested to explain this phenomenon, yet methylphosphonate is not a known natural product, nor has it been detected in natural systems. Further, its synthesis from known natural products would require unknown biochemistry. Here we show that the marine archaeon Nitrosopumilus maritimus encodes a pathway for methylphosphonate biosynthesis and that it produces cell-associated methylphosphonate esters. The abundance of a key gene in this pathway in metagenomic data sets suggests that methylphosphonate biosynthesis is relatively common in marine microbes, providing a plausible explanation for the methane paradox.     

政府购买公共服务的影响因素及其优化机制——基于合作治理变革趋势的分析视角

当前,政府购买公共服务作为一项制度安排、一种改革工具历久弥新,在实践中得到了广泛的应用.从行政理念、组织结构、政府角色、公共服务的供给方式等多方面阐释了新时期政府购买公共服务的内涵及其价值,分析了政府购买涉及政府、市场、社会组织、公众及外部环境等多重影响因素,进而提出了优化政府的资源整合机制,引入政府购买的问责机制;促进服务市场的有序竞争,优化市场监管机制;加大政府购买的政策扶植力度,着力培育和提升社会组织的参与能力;全面公开政府购买信息,积极探索公众参与监管和评估的机制以及积累社会资本,建立社会信任、互惠规范、多元参与的服务供给机制等路径来提升政府购买公共服务的实践成效.     

Thermal spectrum of uranus: implications for large helium abundance

An analysis of the infrared spectrum of Uranus' disk between 7 micrometers and 3 millimeters suggests a volume mixing ratio for helium in the atmosphere of 40 +/- 20 percent, more than for the sun, Jupiter, or Saturn. Alternative explanations require even more extreme assumptions regarding gas abundances or aerosol vertical distribution and spectral properties. The most serious difficulty with a model containing large amounts of helium is devising a credible evolutionary or chemical model explaining the absence or segregation of so much hydrogen.     

Partial pressure of gases dissolved at great depth

Thermodynamic considerations have been applied to data showing that the solubilities of oxygen, carbon dioxide, and helium in water decrease with increasing pressure and depth. When water is saturated with a given gas at 1 atmosphere absolute, the equilibrium partial pressure of the gas at any depth is equal to the partial pressure of that gas if it were contained in a gas column extending from the surface to that particular depth.     

Isobaric bubble growth: a consequence of altering atmospheric gas

During certain treatments of decompression sickness following dives made with compressed air, the U.S. Navy advocates breathing helium-oxygen mixtures. However, stable nitrogen bubbles created within gelatin by decompression have been found to enlarge when the atmosphere was switched from nitrogen to helium without changing ambient pressure. This suggests that decompression sickness would be worsened by switching from nitrogen to helium in the breathing gas mixture.     

Helium loss, tectonics, and the terrestrial heat budget

It has been known for the last decade that primordial helium incorporated in Earth at the time of its formation is still being degassed during the formation of new ocean crust at spreading ocean ridges. It is now clear that somewhat contrary to expectation, substantial degassing is also taking place through the continental crust. In western Europe the escape of mantle volatiles seems to occur largely where the crust is undergoing active extension. Although it is known that melting is the principal process for extracting and concentrating helium from the mantle at ocean ridges, the equivalent subcontinental process remains poorly understood. The same elements that are responsible for most of Earth's radiogenic heating (uranium and thorium) are also responsible for the generation of radiogenic helium. The present rate of mantle heat loss, however, is out of equilibrium with the rate of helium loss-too large by about a factor of 20. Either radiogenic helium is accumulated in the mantle while heat escapes or current models for the bulk chemistry of Earth are in error and much of the terrestrial heat loss is nonradiogenic.     

激光烧蚀制备纳米Si晶粒的时间飞行动力学分析

针对采用激光诱导荧光(LIF)技术,对真空或不同气压的He、Ar环境下激光烧蚀产生的Si粒子的时间飞行(TOF)进行了测量,并对试验结果进行了数据分析。结果表明,在真空环境下烧蚀形成的Si粒子的速度近似服从麦克斯韦分布律;在气体环境下,其速度偏离麦克斯韦分布律,并且环境气压越大,偏离越明显;Ar环境比相同气压的He下偏离更明显。烧蚀产生的Si粒子在不同种类、不同压强的环境气氛中所受阻力有所不同,其大小与Si粒子速度有关,从而不同速度的Si粒子受到不同大小的阻力,导致速度偏离麦克斯韦分布律。     

天然气水化物储运技术发展综述

天然气水化物的早期研究主要集中在水化物的清除和预防上,其技术无论在原理上还是在应用上均已比较成熟,并已广泛地应用于生产实践。天然气水化物(固态)的体积远远小于天然气的体积,1 m~3的水化物通常可携带150～170 m~3的天然气,国外已较早研究和利用水化物的这一特点来输送天然气。针对当前世界天然气水化物制备、输送和储存技术的研究现状,通过对水化物和液化天然气系列技术的分析和经济比较,指出以水化物的形式进行长距离、跨海洋输送,在技术和经济上有一定的可行性,但离实用尚有差距,需要在技术和经济上进行深入研究。     

"Helium spots": caused by a diapiric magma from the upper mantle

"Helium spots," where a significant amount of helium is present in the soil [up to 350 parts per million with a high (3)He to (4)He ratio of (8.90 +/- 0.31) x 10(-6)], have been found along the fault zone formed by the 1966 Matsushiro swarm earthquakes. The formation of the "helium spots" and the occurrence of the earthquakes are interpreted as the results of a diapiric uprise of a magma approximately 1 kilometer in diameter.     

天然气转变液体燃料技术的应用设想

叙述了国外天然气转变液体燃料技术（ＧＴＬ）的发展动态,评价了这种技术在偏远地区和海上气田及油田伴生气的天然气经济输送、天然气存储和远洋进口天然气等方面的积极作用。提出了在我国塔里木盆地应用ＧＴＬ技术将天然气转化为液体燃料油后与原油和凝析油一起东输的设想,以及ＧＴＬ技术在我国海上气田、天然气进口和煤炭资源转化、运输等方面的可能性。     

Stable compounds of helium and neon: he@c60 and ne@c60

It is demonstrated that fullerenes, prepared via the standard method (an arc between graphite electrodes in a partial pressure of helium), on heating to high temperatures release (4)He and (3)He. The amount corresponds to one (4)He for every 880,000 fullerene molecules. The (3)He/(4)He isotopic ratio is that of tank helium rather than that of atmospheric helium. These results convincingly show that the helium is inside and that there is no exchange with the atmosphere. The amount found corresponds with a prediction from a simple model based on the expected volume of the cavity. In addition, the temperature dependence for the release of helium implies a barrier about 80 kilocalories per mole. This is much lower than the barrier expected from theory for helium passing through one of the rings in the intact structure. Amechanism involving reversibly breaking one or more bonds to temporarily open a "window" in the cage is proposed. A predicted consequence of this mechanism is the incorporation of other gases while the "window" is open. This was demonstrated through the incorporation of (3)He and neon by heating fullerene in their presence.     

水合物技术在天然气储运中的应用

介绍了天然气水合物(NGH)的结构及物理性质.用NGH运输天然气具有安全、可靠和费用低的优点.研究表明,NGH物理性质稳定,除需要绝热条件外,不需要冷却到平衡温度即可投入大规模储运.分析了典型的水合物生成及分解流程,并将NGH储运方法与液化天然气法进行了经济比较.     

食品品牌知名度与质量等级之间的关系研究——以食用油为例

食品品牌代表着企业商誉,是传递质量信号的重要标志.同样,食品质量等级也能够反映出食品的质量好坏.然而在现实生活中,消费者对食品品牌的关注要远高于对食品质量等级的关注.在食品购买的过程中,质量等级有时甚至会被消费者忽视.那么,关于品牌知名度能否作为质量的代名词目前还没有学者给出相关的结论.因此以食用油为例,采用描述性统计的方法,对目前市场上销售的食用油品牌与他们对应的质量等级进行研究,从而验证两者之间是替代的关系还是互补的关系,进而对国家在质量监管和企业的发展战略方面提出相应的建议.     

3种典型烟草薄片热裂解行为的研究

[目的]比较不同温度下3种典型烟草薄片的裂解产物。[方法]利用在线裂解气相色谱/质谱法(PY/GC-MS)研究了3种典型烟草薄片(2种国产薄片,1种进口薄片)的热裂解行为。在氦气氛围中,分别将这3种烟草薄片在300、600、900℃下进行热裂解,并采用气质联用对其裂解产物进行了定性和半定量分析。[结果]3种烟草薄片裂解产物随裂解温度升高而增多,低温下裂解产物主要为酸类等物质,高温下裂解产物种类较复杂。在900℃裂解温度下,3种薄片裂解产物含量最多的均为酸类,其次为酮类,但醇类、芳烃类、醚类和杂环类差异较大。[结论]该研究可为烟草薄片在卷烟生产中的有效应用提供理论依据。     

公益性农技推广服务政府购买的经济绩效评估——基于湖北“以钱养事”改革的准自然实验

提高公益性农技推广服务的供给质量和效率对推进农业供给侧结构性改革、助力乡村振兴具有重要意义。但公益性农技推广服务如何供给学界存在不同观点。采用双重差分法评估公益性农技推广服务政府购买的经济绩效发现,公益性农技推广服务政府购买显著促进了农业经济增长,这一结论在进行各种检验后依然成立;相比于公益性农技推广服务政府购买改革初期,改革后期公益性农技推广服务政府购买对农业经济增长的促进更大。公益性农技推广服务政府购买是一种可行的公益性农技推广服务供给方式,但应通过完善相应制度安排保障其运行机制。     

天然叶黄素及其在水产饲料中的应用

天然叶黄素(Xanthophyll)是指自然界中广泛存在的一大类含氧类胡萝卜素,主要来源于植物和藻类,其中万寿菊(Tagetes erecta L.)花中天然叶黄素含量远高于一般植物,是生产天然叶黄素的优质原料。万寿菊花提取的天然叶黄素通过了国内外权威机构严格的安全性评估,对人体、动物体无害,且有益于机体健康,已广泛应用于食品、医药、饲料等领域。天然叶黄素添加到水产饲料中,不仅能够有效改善水产动物体色,同时在提高水产动物抗氧化能力、作为维生素前体、改善动物健康状况和生长性能方面有一定效果。文章对天然叶黄素及其安全性、在水产饲料中的应用情况进行了综述。     

略论品牌竞争中的文化力作用

在日趋成熟的市场经济中,品牌己由简单意义上的产品标识演化为综合企业形象,产品质量和文化内涵的鲜明标志,成为企业进行市场营销的主力。在激烈的品牌竞争中,品牌中的文化内蕴成为其标志和灵魂,发挥着重要的市场营销的作用,左右着品牌在市场中的地位。这种无形的“文化力”影响可遍及现代社会经济运营的各个方而,深刻的改变着消费者的意识和行为,为企业打造强势品牌,增强品牌竞争力提供有利的支撑。本文通过对企业品牌竞争与品牌文化的关系探讨,品牌内涵演变以及消费者行为变化对品牌文需求的必然性分析,着重论述了企业品牌竞争中的文化力作用。     

土库曼斯坦的天然气工业与出口多元化

土库曼斯坦作为油气资源大国,天然气产业已成为其国民经济的支柱行业,然而受困于产能建设不足及出口通道受阻,土库曼斯坦天然气出口表现出增长乏力的态势。目前,土库曼斯坦已形成北通俄罗斯、南达伊朗、东至中国的天然气出口通道布局,但受地缘政治及经济利益影响,其天然气主力买家仅剩中国。为了摆脱天然气出口困境,土库曼斯坦积极推行天然气出口多元化:一方面拓展新的出口通道,集中推进通往南亚的TAPI项目的落实,同时与各相关方磋商跨里海天然气管道项目;另一方面,充分提升本国天然气的资源化利用,大力发展天然气化工与发电,将现有天然气资源转化为高附加值的产品并出口。土库曼斯坦作为中国进口天然气的主力来源,在中国进口中亚天然气中的地位不可替代,夯实中土天然气贸易合同的履行,谨防土库曼斯坦在供气量上打折扣是当前中土两国关系中最为现实的课题;在将来可探索基于TAPI、IPI项目,建立涵盖中国、伊朗、土库曼斯坦、阿塞拜疆、巴基斯坦、印度的中亚-南亚天然气大管网的可能性。