Absorption of proteins and peptides in the far ultraviolet

An absorption peak for the peptide bond at 187 nanometers has been confirmed; a protein assay at this wavelength allows quantitation of proteins in aqueous solution at concentrations between 0.1 and 25 micrograms per milliliter. Assays are conducted at 6 degrees C to take advantage of the reduction of end-absorption of water with temperature.     

谷维素在甲醇中的溶解度研究

研究温度和溶液pH值对甲醇中谷维素溶解度的影响。结果表明,相同pH值条件下,谷维素的溶解度随温度的升高而迅速增大,但当温度上升到40℃以上时,溶解度的增大幅度趋缓;相同温度条件下,当溶液的pH值达到11时,谷维素的溶解度达到最大值。     

Doubly ionized carbon observed in the plasma tail of comet Kudo-Fujikawa

Comet C/2002 X5 (Kudo-Fujikawa) was observed near its perihelion of 0.19 astronomical unit by the Ultraviolet Coronagraph Spectrometer aboard the Solar and Heliospheric Observatory spacecraft. Images of the comet reconstructed from high-resolution spectra reveal a quasi-spherical cloud of neutral hydrogen and a variable tail of C+ and C2+ that disconnects from the comet and subsequently regenerates. The high abundance of C2+ and C+, at least 24% relative to water, cannot be explained by photodissociation of carbon monoxide and is instead attributed to the evaporation and subsequent photoionization of atomic carbon from organic refractory compounds present in the cometary dust grains. This result serves to strengthen the connection between comets and the material from which the Solar System formed.     

石榴贮藏技术

造成石榴贮藏中损失的三大原因为:腐烂、果皮褐变以及由失水引起的果皮干瘪、籽粒皱缩。解决石榴贮藏中存在的问题,要从5个方面入手,即选择耐藏品种;进行精心的田间管理,获得优质、健康的石榴;采收注意适时无伤;采后处理尤其要注意充分预贮,使其失去3%~5%的水分,使果皮变得有弹性;贮藏期间的管理主要是初期温度要降下来,腐烂果要及时剔除。5个方面系统、协调进行可有效控制石榴贮藏中存在的问题。     

紫外光谱法测定发酵液中的透明质酸

利用透明质酸在196 nm波长紫外光下有吸收峰,并且透明质酸在0～1.0 g/L的质量浓度范围内与吸光度有良好的线性关系,采用紫外光谱法测定了发酵法生产透明质酸发酵液中透明质酸的浓度.结果表明,发酵液中透明质酸质量浓度为0.98 g/L,平均回收率为100.45%,相对标准偏差为0.78%,认为紫外光谱法是一种可准确测定透明质酸浓度的方法.     

试论农业人口城镇化是解决“三农”问题的关键

我国改革开发 2 0多年以来城市已经汇入了现代化和国际化的潮流 ,而农村却出现了边缘化倾向 ,有的还相当原始和封闭。一方面是城市呈现出一种欣欣向荣的景象 ,而另一方面却是农村显出破败和凋蔽 ,农业、农村、农民被习称为”三农”的问题。“三农”的核心是农民 ,而农民问题的核心是农民收入 ,考察我国实际国情以及借鉴国际经验 ,我们认为增加农民收入的根本出路是减少农民 ,其方法则是加快城市化进程。     

农业环境纠纷的多元化处理机制探讨

随着我国社会经济的高速发展,农业环境污染和环境破坏也不断加剧并引发各种纠纷。但现有环境纠纷解决的方式以行政裁决和诉讼为主且存在各种弊端,难以适应农业环境纠纷处理实践的需要。为了更好地处理农业环境纠纷,实现环境正义,建设环境友好型社会,应建立由和解、调解、行政裁决、仲裁和诉讼等多元化的农业环境纠纷处理机制,并针对该多元化的纠纷处理机制,采取相应措施完善这5种纠纷处理方式,以便更加有效、和谐地处理农业环境纠纷,化解各种因农业环境纠纷引发的社会矛盾,为建设环境友好型社会提供法律支撑。     

土地整理在解决土地供需矛盾中的应用——以北京市通州区为例

土地整理作为一项涉及资源环境、社会经济、政策制度的系统工程,是我国社会经济发展过程中解决土地利用问题的必然选择。以北京市通州区土地整理项目为例,介绍了土地整理在解决土地供需矛盾中的应用。     

远红光对玉米叶片叶绿素荧光的影响

以玉米杂交种先玉335(X-335)和玉米杂交种郑单958(Z-958)为供试材料,研究远红光对玉米叶片叶绿素荧光的影响,结果表明:远红光环境下,玉米叶片的光合作用所产生的有机物量和叶片胞间CO2浓度均下降,叶片蒸腾速率减弱,叶片气孔导度减小,光合电子传递效率下降,但PSⅡ原初光能转化效率提高,非光化学淬灭系数上升;X-335光化学淬灭系数上升,Z-958下降;两个玉米品种在远红光环境下光系统的功能都下降。     

Kinetic isotope effects for the reactions of muonic helium and muonium with H2

The neutral muonic helium atom may be regarded as the heaviest isotope of the hydrogen atom, with a mass of ~4.1 atomic mass units ((4.1)H), because the negative muon almost perfectly screens one proton charge. We report the reaction rate of (4.1)H with (1)H(2) to produce (4.1)H(1)H + (1)H at 295 to 500 kelvin. The experimental rate constants are compared with the predictions of accurate quantum-mechanical dynamics calculations carried out on an accurate Born-Huang potential energy surface and with previously measured rate constants of (0.11)H (where (0.11)H is shorthand for muonium). Kinetic isotope effects can be compared for the unprecedentedly large mass ratio of 36. The agreement with accurate quantum dynamics is quantitative at 500 kelvin, and variational transition-state theory is used to interpret the extremely low (large inverse) kinetic isotope effects in the 10(-4) to 10(-2) range.     

Possible mechanism for the antiarrhythmic effect of helium in anesthetized dogs

Breathing a mixture of 75 percent helium and 25 percent oxygen instead of 75 percent nitrogen and 25 percent oxygen reduced the occurrence of dangerous cardiac arrhythmias after ligation of the circumflex coronary artery in open-chest dogs anesthetized with pentobarbital. In dogs not subjected to circumflex ligation, the sensitivity of blood pressure, heart rate, and extrasystoles to epinephrine injected intravenously was not altered by the substitution of helium for nitrogen; however, helium did reduce the baseline heart rate and the concentration of endogenous plasma catecholamines. The antiarrhythmic effect of helium may thus be mediated by changes in sympathetic activity.     

A remarkable auroral event on jupiter observed in the ultraviolet with the hubble space telescope

Two sets of ultraviolet images of the Jovian north aurora were obtained with the Faint Object Camera on board the Hubble Space Telescope. The first series shows an intense discrete arc in near corotation with the planet. The maximum apparent molecular hydrogen emission rate corresponds to an electron precipitation of approximately 1 watt per square meter, which is about 30,000 times larger than the solar heating by extreme ultraviolet radiation. Such a particle heating rate of the auroral upper atmosphere of Jupiter should cause a large transient temperature increase and generate strong thermospheric winds. Twenty hours after initial observation, the discrete arc had decreased in brightness by more than one order of magnitude. The time scale and magnitude of the change in the ultraviolet aurora leads us to suggest that the discrete Jovian auroral precipitation is related to large-scale variations in the current system, as is the case for Earth's discrete aurorae.     

农民利益诉求表达障碍及其对策

阐述了当前农民利益诉求表达存在的渠道不畅问题,提出了建立农民利益诉求机制的对策。     

A reservoir of ionized gas in the galactic halo to sustain star formation in the Milky Way

Without a source of new gas, our Galaxy would exhaust its supply of gas through the formation of stars. Ionized gas clouds observed at high velocity may be a reservoir of such gas, but their distances are key for placing them in the galactic halo and unraveling their role. We have used the Hubble Space Telescope to blindly search for ionized high-velocity clouds (iHVCs) in the foreground of galactic stars. We show that iHVCs with 90 ≤ |v(LSR)| ? 170 kilometers per second (where v(LSR) is the velocity in the local standard of rest frame) are within one galactic radius of the Sun and have enough mass to maintain star formation, whereas iHVCs with |v(LSR)| ? 170 kilometers per second are at larger distances. These may be the next wave of infalling material.     

论解决我国农村剩余劳动力问题的对策

要顺利完成我国农村剩余劳动力的转移,必须针对我国存在的特殊问题,采取相应的对策,调整农业和农村经济结构,使农村剩余劳动力在农村内部得到转移;消除体制障碍,促使劳动力的合理流动;坚持因地制宜的城镇化战略,使城镇化与农村就业有效的结合起来。     

白藜芦醇与牛血清白蛋白相互作用的研究

采用荧光猝灭光谱、同步荧光光谱和紫外-可见吸收光谱,研究了白藜芦醇与牛血清白蛋白(BSA)的相互作用。结果表明白藜芦醇对BSA有较强的荧光猝灭作用,荧光猝灭机理属于二者形成复合物所引起的静态猝灭和非辐射能量转移;根据不同温度下防己诺林碱对BSA的荧光猝灭作用,利用Stern-Volmer方程处理实验数据,得到白藜芦醇与BSA之间的结合常数KA为6.11×104(25℃)、4.46×104(35℃)和3.84×104(45℃)。根据F rster非辐射能量转移理论,求出了白藜芦醇与BSA之间的结合距离为2.36 nm(25℃)、2.73 nm(35℃)和2.48 nm(45℃)。通过计算热力学参数,可知该药物与牛血清白蛋白的相互作用是一个吉布斯自由能降低的自发过程,且二者之间的主要作用力类型为疏水作用力,同时用同步荧光光谱探讨了白藜芦醇对BSA构象的影响。     

油茶北缘分布区芽苗砧嫁接育苗轻基质筛选

为了筛选油茶北缘分布区油茶芽苗砧嫁接育苗最佳轻基质配方,选择5种适宜油茶生长的轻基质配方在信阳市光山县开展筛选研究.测定了各种轻基质化学性质及一年生苗木的生长指标.结果表明,不同轻基质对苗木地下部分的影响较大;油茶地径、节间长、根系体积、地下部鲜重及总生物量等指标在不同轻基质间存在显著差异.从中筛选出适宜油茶北缘分布区...     

Pioneer 10 observations of the ultraviolet glow in the vicinity of jupiter

A two-channel ultraviolet photometer aboard Pioneer 10 has made several observations of the ultraviolet glow in the wavelength range from 170 to 1400 angstroms in the vicinity of Jupiter. Preliminary results indicate a Jovian hydrogen (1216 angstrom) glow with a brightness of about 1000 rayleighs and a helium (584 angstrom) glow with a brightness of about 10 to 20 rayleighs. In addition, Jupiter appears to have an extensive hydrogen torus surrounding it in the orbital plane of Io. The mean diameter of the torus is about equal to the diameter of the orbit of Io. Several observations of the Galilean satellites have also occurred but only a rather striking Io observation has been analyzed to date. If the observed Io glow is predominantly that of Lyman-alpha, the surface brightness is about 10,000 rayleighs.     

Isolating the spectroscopic signature of a hydration shell with the use of clusters: superoxide tetrahydrate

Cluster spectroscopy, aided by ab initio theory, was used to determine the detailed structure of a complete hydration shell around an anion. Infrared spectra of size-selected O(2)-. (H(2)O)(n) (n = 1 to 4) cluster ions were obtained by photoevaporation of an argon nanomatrix. Four water molecules are required to complete the coordination shell. The simple spectrum of the tetrahydrate reveals a structure in which each water molecule is engaged in a single hydrogen bond to one of the four lobes of the pi* orbital of the superoxide, whereas the water molecules bind together in pairs. This illustrates how water networks deform upon accommodating a solute ion to create a distinct supramolecular species.