离子平衡的营养学原理及其在畜禽生产中的应用

对离子平衡，电解质平衡和酸碱平衡的概念和相互关系及研究中存在的问题进行了讨论，阐述了动物体内的酸碱来源及其平衡调节，电解质离子的主要营养作用及代谢规律及应用前景，分析比较了动物离子平衡的各种离子平衡公式，同时对日粮离子平衡与动物代谢性疾病的关系。日粮离子平衡与动物正常生长及营养代谢的关系进行了总结，对影响日良离子平衡的主要因素和如何在畜禽生产实践中合理应用离子平衡技术进行了分析。对值得深入研究的问题进行了探讨。     

离子平衡的营养学原理及其在畜禽生产中的应用(续)

对离子平衡、电解质平衡和酸碱平衡的概念和相互关系及研究中存在的问题进行了讨论，阐述了动物体内的酸碱来源及其平衡调节，电解质离子的主要营养作用，代谢规律及应用前景，分析了比较了动物离子平衡的各种离子平衡公式。同时对日粮离子平衡与动物代谢性疾病的关系，日粮离子平衡与动物正常生长及营养代谢的关系进行了总结，对影响日粮离子平衡的主要因素和如何在畜禽生产实践中合理应用离子平衡技术进行了分析，对值得深入研究的问题进行了探讨。     

GRACE measurements of mass variability in the Earth system

Monthly gravity field estimates made by the twin Gravity Recovery and Climate Experiment (GRACE) satellites have a geoid height accuracy of 2 to 3 millimeters at a spatial resolution as small as 400 kilometers. The annual cycle in the geoid variations, up to 10 millimeters in some regions, peaked predominantly in the spring and fall seasons. Geoid variations observed over South America that can be largely attributed to surface water and groundwater changes show a clear separation between the large Amazon watershed and the smaller watersheds to the north. Such observations will help hydrologists to connect processes at traditional length scales (tens of kilometers or less) to those at regional and global scales.     

An amylose antiparallel double helix at atomic resolution

In the crystal structure of the polyiodide complex (p-nitrophenyl-alpha-maltohexaose(2)) . Ba(I(3))(2) . 22H(2)O, the maltohexaose units form an antiparallel, left-handed double helix with O-2 ... O-3 and O-6 ... O-6 hydrogen bonding and a central cavity that encloses two triiodide units. This structure contrasts with the parallel, left-handed double helix with no central cavity proposed for the A-and B-starch helix and the left-handed single helix in V-amylose and may be relevant for the stabilization of glycogen Structure.     

Comet encke: meteor metallic ion identification by mass spectrometer

Metal ions including 23(+) (Na(+)), 24(+) (Mg(+)) 28(+) (Si(+)), 39(+) (K(+)), 40(+) (Ca(+)), 45(+) (Sc(+)), 52(+) Cr(+)). 56(+) (Fe(+)), and 58(+) (Ni(+)) have been detected in the upper atmosphere during the period of the Beta Taurids meteor shower. The abundances of these ions relative to Si(+) show, agreement in most instances with abundances in chondrites. A notable exception is 45(+), which, if it is Sc(+), is 100 times more abundant than neutral scandium found in chondrites.     

Isotopic mass and lattice constant: X-ray standing wave measurements

The molecular volume of crystals depends on their isotopic masses. This influence originates from the zero-point motion and the resulting small differences in lattice constants. This effect was measured with high precision by using an x-ray standing wave. The standing wave is generated during Bragg reflection and thus is in phase with the planes of the substrate crystal, which is covered with a homoepitaxial film that has a different isotopic composition than the substrate. The positions of the surface planes of the film with respect to the substrate planes are revealed by the photoelectrons excited by the maxima of the standing wave. For germanium-76 on natural germanium(111), a difference in lattice constant of -1.1 x 10(-5) and -2.5 x 10(-5) at 300 and 54 kelvin, respectively, was found. The results are in good agreement with theoretical predictions.     

纳米二次离子质谱技术(NanoSIMS)在微生物生态学研究中的应用

超高分辨率显微镜成像技术与同位素示踪技术相结合的纳米二次离子质谱技术(NanoSIMS)具有较高的灵敏度和离子传输效率、极高的质量分辨率和空间分辨率(＜ 50 nm),代表着当今离子探针成像技术的最高水平.利用稳定性或者放射性同位素在原位或者微宇宙条件下示踪目标微生物,然后将样品进行固定、脱水、树脂包埋或者导电镀膜处理,制备成可供二次离子质谱分析的薄片,进一步通过NanoSIMS成像分析,不仅能够在单细胞水平上提供微生物的生理生态特征信息,而且能够准确识别复杂环境样品中的代谢活跃的微生物细胞及其系统分类信息,对于认识微生物介导的元素生物地球化学循环机制具有重要意义.介绍了纳米二次离子质谱技术的工作原理和技术路线,及其与同位素示踪技术、透射电子显微镜(TEM)、扫描电子显微镜(SEM)、荧光原位杂交技术(FISH)、催化报告沉积荧光原位杂交技术(CARD-FISH)、卤素原位杂交技术(Halogen In Situ Hybridization,HISH)等联合使用在微生物生态学研究方面的应用.     

氨基酸平衡性评价指标的比较

为了比较用氨基酸比值系数分(SRC)、氨基酸模式模糊贴近度(FNAAP)评价蛋白质营养价值的合理性,并评估用蛋白质必需氨基酸总含量比值(RTEAA)评价蛋白质营养价值的合理性,用66组文献数据分析了SRC、FNAAP、RTEAA与蛋白质生物价(BV)的相关关系.结果表明,RTEAA与BV极显著相关(ryi.=0.511 6,P<0.001),SRC与BV显著相关(ryi.=0.462 6,P <0.05),FNAAP与BV相关性不显著(P >0.05),由此推断,用SRC评价蛋白质营养价值比用FNAAP合理;RTEAA是评价蛋白质营养价值的合理指标.建议以氨基酸平衡度(degree of essential amino acid balance,DEAAB)这一统计学和生物学含义更为明确的概念替代氨基酸比值系数分(SRC),改用公式DEAAB=1-CVAASs计算氨基酸平衡度,式中CVAASs为氨基酸分(amino acid scores,AASs)的变异系数.     

用于质谱鉴定蛋白质胶内酶解方法的优化

【目的】提高蛋白质胶内酶解效率,减少萃取过程中肽段的损失,增加质谱鉴定的成功率。【方法】在常规胶内酶解方法的基础上,优化脱色、酶解、萃取等步骤,包括：用铁氰化钾和硫代硫酸钠对银染胶块脱色,酶解温度提高至55％,以40mmol／L碳酸氢铵作为酶切缓冲液,使用50％乙腈（ACN）水溶液3步萃取;并使用一步法胶内酶解探索快速胶内酶解方法。【结果】使用铁氰化钾和硫代硫酸钠可在短时间内将银染胶块完全脱色,55℃温浴可使酶切时问由20h减少为2h,以40mmol／I碳酸氢铵作为酶切缓冲液,可省去ZipTip脱盐步骤。优化后,质谱鉴定率提高30．0％（绝对值）,且能明显高酶切效率,使目标肽段更高丰度地呈现出来。【结论】优化后的胶内酶解法可显著提高蛋白质胶内酶解的质谱鉴定成功率和肽段覆盖率,其中一步法胶内酶解法有效减少了胶内酶解时间和步骤,可用于高丰度蛋白质的快速质谱检测。     

Phase separation of lipid membranes analyzed with high-resolution secondary ion mass spectrometry

Lateral variations in membrane composition are postulated to play a central role in many cellular events, but it has been difficult to probe membrane composition and organization on length scales of tens to hundreds of nanometers. We present a high-resolution imaging secondary ion mass spectrometry technique to reveal the lipid distribution within a phase-separated membrane with a lateral resolution of approximately 100 nanometers. Quantitative information about the chemical composition within small lipid domains was obtained with the use of isotopic labels to identify each molecular species. Composition variations were detected within some domains.     

Cassini ion and neutral mass spectrometer: Enceladus plume composition and structure

The Cassini spacecraft passed within 168.2 kilometers of the surface above the southern hemisphere at 19:55:22 universal time coordinated on 14 July 2005 during its closest approach to Enceladus. Before and after this time, a substantial atmospheric plume and coma were observed, detectable in the Ion and Neutral Mass Spectrometer (INMS) data set out to a distance of over 4000 kilometers from Enceladus. INMS data indicate that the atmospheric plume and coma are dominated by water, with significant amounts of carbon dioxide, an unidentified species with a mass-to-charge ratio of 28 daltons (either carbon monoxide or molecular nitrogen), and methane. Trace quantities (<1%) of acetylene and propane also appear to be present. Ammonia is present at a level that does not exceed 0.5%. The radial and angular distributions of the gas density near the closest approach, as well as other independent evidence, suggest a significant contribution to the plume from a source centered near the south polar cap, as distinct from a separately measured more uniform and possibly global source observed on the outbound leg of the flyby.     

Influence of a phase transition of ice on the heat and mass balance of comets

Differences in gas production rates of comets may be explained in part by the phase transition of ice in the comet nuclei.     

Negative differential resistance on the atomic scale: implications for atomic scale devices

Negative differential resistance (NDR) is the essential property that allows fast switching in certain types of electronic devices. With scanning tunneling microscopy (STM) and scanning tunneling spectroscopy, it is shown that the current-voltage characteristics of a diode configuration consisting of an STM tip over specific sites of a boron-exposed silicon(111) surface exhibit NDR. These NDR-active sites are of atomic dimensions ( approximately 1 nanometer). NDR in this case is the result of tunneling through localized, atomic-like states. Thus, desirable device characteristics can be obtained even on the atomic scale.     

Hyperfine zeeman effect atomic absorption spectrometer for mercury

A new type of atomic absorption spectrometer-one that detects trace mercury in host material, based on hyperfine structure lines in a magnetic field-was developed and tested on various substances. This device can detect trace mercury to about 0.04 part per million (40 parts per billion) in about 1 minute. No chemical separation from the host material is necessary.     

Energy balance for ethyl alcohol production from crops

Energy requirements to produce ethyl alcohol from three different crops in Brazil (sugarcane, cassava, and sweet sorghum) were calculated. Figures are presented for the agricultural and industrial phases. The industrial phase is always more energy-intensive, consuming from 60 to 75 percent of the total energy. Sugarcane is the more efficient crop for ethyl alcohol production, followed by sweet sorghum and cassava from a net energy viewpoint. The utilization of sweet sorghum stems might increase the total energy gain from this crop to almost the same level as sugarcane. Cassava has a lower energy gain at the present state of agriculture in Brazil.     

Different sensing techniques for geomorphometric measurements

Solid-state MEMS accelerometers are small and cost-effective new sensors developed within the last decade that have often been used as tilt sensors in non-agricultural environments. In some applications accelerometers can replace electronic clinometers, which are heavily dampened sensors used in common tilt measurements. Our research tested the hypothesis that either sensor can be used as dynamic tilt sensors and accurately map areas with varying topography. Slope is a vector measurement of the rate of change of elevation, and is a soil attribute commonly studied in the geosciences due to the influence it exerts over other soil attributes and crop yield.Mathematical models were used to relate pitch and roll angles of a roving vehicle to field slope gradient and aspect, based on data collected with a dual-axis accelerometer and a dual-axis clinometer in a field test. Benchmark for comparisons were slope values derived from RTK-GPS measurements. Time-domain and spatial-domain filters were applied to the data collected in the field.The coefficient of determination (r²), mean absolute error (MAE), and model efficiency (ME) were used to compare slope gradient results. Slope aspect was evaluated on whether it was correctly classified according to cardinal directions. Results suggest that the accelerometer and the clinometer are accurate enough to be used as dynamic tilt sensors. The MAEs of slope gradient were less than 1° when compared to measurements derived from RTK-GPS, for scales similar to Order I soil maps. The correct classification of slope aspect was higher than 70%. Solid-state MEMS accelerometers represent a new and cost-effective technology that can be successfully used in such measurements. Accelerometers outperform clinometers in cost, speed, and simplicity of use, but not in accuracy.