Carbon monoxide: residence time in the atmosphere

A lower limit of 0.1 year for the residence time of carbon monIoxide in the atmosphere is derived from radiocarbon measurements. The action of certain microorganisms and atmospheric photochemical reactions are possible mechanisms for the removal of carbon monoxide. This value can be compared with 2.7 years, a value deduced from estimated rates of carbon monoxide production and global measurements of atmospheric concentrations of carbon monoxide.     

Diel periodicity of photosynthesis in polar phytoplankton: influence on primary production

In the Southern Ocean, primary production estimated from seasonal chemical and geochemical changes is two to four times greater than the value calculated from carbon-14 uptake. Since carbon uptake had typically been measured only during midday incubations, the influence of diel periodicity of photosynthesis on daily productions was not considered. Phytoplankton from McMurdo Sound, Antarctica, exhibited distinct, but seasonally variable diel patterns of light-saturated and light-limited photosynthesis. Maximum photosynthetic capacity occurred about noon in early September, and its occurrence progressively shifted to about midnight by late October. This shift was accompanied by a concomitant phase shift in the occurrence of minimum photosynthetic capacity from midnight to midday. Daily production estimated from time-of-day corrected photosynthetic characteristics and from 24-hour incubations was 2.5 to 4 times greater than that predicted from 6-hour midday incubations. If similar diel periodicity in photosynthesis occurs in other polar oceans, primary production would be significantly higher than previously estimated from carbon-14 uptake measurements.     

Small interannual variability of global atmospheric hydroxyl

The oxidizing capacity of the global atmosphere is largely determined by hydroxyl (OH) radicals and is diagnosed by analyzing methyl chloroform (CH(3)CCl(3)) measurements. Previously, large year-to-year changes in global mean OH concentrations have been inferred from such measurements, suggesting that the atmospheric oxidizing capacity is sensitive to perturbations by widespread air pollution and natural influences. We show how the interannual variability in OH has been more precisely estimated from CH(3)CCl(3) measurements since 1998, when atmospheric gradients of CH(3)CCl(3) had diminished as a result of the Montreal Protocol. We infer a small interannual OH variability as a result, indicating that global OH is generally well buffered against perturbations. This small variability is consistent with measurements of methane and other trace gases oxidized primarily by OH, as well as global photochemical model calculations.     

Erosion of galilean satellite surfaces by jovian magnetosphere particles

The Galilean satellites of Jupiter-Io (J1), Europa (J2), Ganymede (J3), and Callisto (J4)-are embedded in the intense ion and electron fluxes of the Jovian magnetosphere. The effect of these particles on the icy surfaces of the outer three satellites depends on the fluxes and the efficiency of the sputtering of water ice by such particles. Recent laboratory measurements provided data on the erosion of water ice by energetic particles and showed that it occurs much faster than would be expected from normal sputtering theory. The Voyager spacecraft encounters with Jupiter provided the first measurements of ion fluxes (energies greater, similar 30 kiloelectron volts) in the vicinity of the Galilean satellites. Using the laboratory sputtering data together with particle measurements from the Voyager 1 low-energy charged particle experiment, the effects of erosion on the surfaces of J2 to J4 are estimated. It is shown that the surface of Europa could be eroded by as much as 100 meters over an eon (10(9) years). Column densities of water vapor that could be produced around the three satellites from particle bombardment of their surfaces are also calculated, and the sources and losses of oxygen in the gravitationally bound gas produced by sputtering or sublimation are estimated.     

种猪现实育种值的估测

取杭州市种猪试验场2000-2002年共1 443头长白猪个体性能测定资料,用4种方法估测了90kg体重校正背膘厚估计上代亲本公猪的育种值,其中用25头以上后裔平均值与同期群体平均值之差的2倍定义为现实育种值.结果表明:现实育种值的数值和方向与后裔测定育种值十分一致,与一次测定值的育种值差很大,现实育种值的方向与BLUP值比较一致.现实育种值不受表型值的影响,是猪真正育种值的最佳估计值.估测青年公猪的育种值,用BLUP法比较好.     

大白猪生产和繁殖性状遗传趋势的分析

配合混合模型,用非求导的REML方法（DF-REML）分析估计了大白猪生产和繁殖性状的表型和遗传趋势。165日龄体重、90kg体重平均背膘厚和总产仔数的表型趋势分别为1.64、-0.23和0.11,遗传趋势分别为0.76、-0.14和0.01。结果表明,大白猪品系选择试验的165日龄体重和90kg体重背膘厚两个主选性状的选择是显著有效的,生长速度逐代提高,背膘厚逐代下降。辅助的体型选择使得大白猪体型结构逐渐向结实型发展。产仔数的遗传趋势是弱的有利变化,表明在对生长速度与背膘厚合并选择时,对繁殖性能的影响很小。     

Correlation between surface free energy and surface constitution

Self-assembled monolayers (SAMs) of alkylsiloxanes on elastomeric PDMS (polydimethylsiloxane) were used as model systems to study interactions between surfaces. Surface free energies (gammasv) of these chemically modified surfaces were estimated by measuring the deformations that resulted from the contact between small semispherical lenses and flat sheets of the elastomer under controlled loads. The measured surface free energies correlated with the surface chemical compositions of the SAMs and were commensurate with the values estimated from the measurements of contact angles. This study provides direct experimental evidence for the validity of estimates of the surface free energies of low-energy solids obtained from contact angles.     

后金融危机时代财务会计计量模式的选择

会计目标的多元化要求会计计量属性的多元化,虚拟经济与实体经济并存要求公允价值计量与历史成本计量（含摊余成本计量）并存。金融危机的启示是,历史成本计量与公允价值计量各有优劣,谁也不能取代另一方而独立存在。后金融危机时代的会计计量模式必然是历史成本计量与公允价值计量相融合的双重计量模式,这是历史的选择,也是理性的选择。     

Thin Membranes of Parlodion

Parlodion membranes 50 to 1000 A A thick have been prepared by deposition of isoamyl acetate solutions on the air-water interface under conditions of controlled evaporation. Capacitance and resistance measurements have established the integrity of large areas of these membranes. The former also provides corroboration of the thickness estimated from the amounts of parlodion deposited.     

Limits on sensitivity of large silicon bolometers for solar neutrino detection

Estimates are given for ultimate limits on background in proposed direct-counting measurements of neutrino scattering from large silicon crystals. Methods of background reduction are discussed. In the best case, the limiting backgrounds due to activities from cosmic-ray spallation of silicon would be less than the expected true event rate for reactor neutrino measurements of coherent neutral-current scattering from silicon nuclei. Considerable reduction of the estimated high-energy backgrounds would be required for a good signal-to-noise ratio in solar neutrino detection.     

应用BLUP法估测种公猪平均日增重的育种值

用BLUP法估测了10头二花脸种公猪自初生至六月龄平均日增重的育种值,同时用最小二乘常数和离差法作对照。结果表明:用BLUP法所得的819号公猪的育种值为0.0132公斤/天,名列第一;15号公猪的育种值为-0.01公斤/天,名列第十;819号公猪的最小二乘常数为0.0207公斤/天,也名列第一;用离差法所得的育种值为0.0067公斤/天,也名列第一。三种方法所得的结果数值上差别较大,但在名次排列上却十分一致。BLUP法与最小二乘常数,BLUP法与离差法在名次排列上的顺位相关系数分别为0.964和0.952,表明它们之间的相关十分密切。用三种方法所得的结果具有相同的趋势,但BLUP法估测误差较低,精确性较高。     

Ages estimated from a diffusion equation model for scarp degradation

The diffusion equation derived from the continuity equation for hillslopes is applied to scarp erosion in unconsolidated materials. Solutions to this equation allow direct calculation of the product of the rate coefficient and the age of the scarp from measurements of scarp morphology. Where the rate coefficient can be estimated or can be derived from scarps of known age, this method allows direct calculation of unknown ages of scarps.     

Exploitation of spatial information in high resolution digital imagery to map leaf area index

Crop responses to management practices and the environment, as quantified by leaf area index (LAI), provide decision-making criteria for the delineation of crop management zones. The objective of this work was to investigate whether spatial correlations inferred from remotely sensed imagery can be used to interpolate and map LAI using a relatively small number of ground-based LAI measurements. Airborne imagery was recorded with the Airborne Imaging Spectrometer for Applications (AISA) radiometer over a 3.2 ha corn field. Spectral vegetation indexes (SVI) were derived from the image and aggregated to cells of 2 × 2 m², 4 × 4 m², and 8 × 8 m² resolution. The residual maximum likelihood method was used to estimate the LAI variogram parameters. A generalized least squares regression was used to relate ground truth LAI data and collocated image pixels. This regression result was then used to convert variograms from the imagery to LAI units as well as to interpolate and map LAI. The decrease in resolution by merging pixels led to an increase in the value of the r ² and to a decrease in root mean-squared error (RMSE) values. The accuracy of kriged estimates from the variogram of the measured LAI and that from the image derived variograms was estimated by cross-validation. There was no difference in the accuracy of the estimates using either variograms from measured LAI values or from those of converted SVIs. Maps of LAI from ground-based measurements made by kriging the data with image-derived variogram parameters were similar to those obtained by with kriging with the variogram of measured LAI. Similar coarse spatial trends of high, medium and low LAI were evident for both maps. Variogram parameters from ground-based measurements of LAI compared favorably with those derived from remotely sensed imagery and could be used to provide reasonable results for the interpolation of LAI measurements.     

Evaluation of the precision of the rising plate meter for measuring compressed sward height on heterogeneous grassland swards

Accurate estimation of herbage mass (HM) is essential for optimising grass utilisation and increasing profit for pasture-based livestock agriculture. The rising plate meter (RPM) is used for predicting HM based on average compressed sward height (CSH). Sampling resolution and distribution are primary parameters in determining spatial heterogeneity of HM. There is no definitive sampling protocol for the RPM. The objectives of this study were to: investigate spatial variation of HM within pastures, determine the number of RPM measurements required to accurately predict mean HM, and assess the precision of the RPM in terms of measurement repeatability. Intensive CSH measurements and HM reference cuts were carried out on controlled plots and grazed paddocks over two grazing seasons. Sward heterogeneity was estimated as the coefficient of variation (CV) of CSH and compared to empirically derived ‘true’ sward heterogeneity in terms of HM CV. Retrospective analysis simulations were performed to identify the effect of various reduced measurement resolutions on estimated mean CSH error. Repeated measures analysis was performed on grass samples to determine RPM measurement system precision. Results indicated that pasture heterogeneity varied by 36% across the growing season and was affected by grazing, fertilisation, sward composition and seasonality. Mean CSH could be estimated to within 5% relative prediction error by recording 24 measurements per ha in a random stratified manner. The standard deviation of RPM measurement repeatability was calculated to be 4.34 mm. The findings of this study will be used to inform the implementation of a more optimum grass measurement protocol.

     

Europium-155 in debris from nuclear weapons

The lithium-drifted germanium detector enables determination of europium-155 on a routine basis in environmental samples contaminated with debris from nuclear weapons. From measurements of europium-155, cesium-144, and strontium-90 in air filters collected between 1961 and 1966, the yield of europium-155 from weapons was estimated at 1400 atoms per 10(6) fissions, which is close to the yield of europium-155 from fast fission of uranium-238.     

金华猪胴体分离方法改进的研究

根据金华猪胴体分离资料进行了相关和多元回归分析,获得了根据不同胴体性状估计瘦肉率的估测公式.结果还表明在猪胴体的分离中只要把皮脂和骨肉分开,利用皮脂率就可估测出准确度较高的胴体瘦肉率,实测值与估测值的绝对差值在0.578～0.865个百分点之间(P＞0.05),完全可以在试验研究的胴体估测中使用.     

Water diversion and agricultural production: Evidence from China

Water diversion can alleviate water shortages caused by the uneven distribution of water resources.  China’s South-to-North Water Diversion Project (SNWD) is the largest water diversion project worldwide.  Based on the prefecture-level data of China’s Huang-Huai-Hai Plain from 2000 to 2020, this study employs an empirical strategy of Differences-in-Differences (DID) to analyze the impact of SNWD on agricultural production.  The results show that SNWD has significantly increased agricultural production, measured by the agricultural value added.  The estimated results of the benchmark model remain robust when the contemporaneous policy is addressed, an alternative outcome is used, subsamples are estimated, and alternative estimation techniques are employed.  This study argues that the potential impact mechanism may be that SNWD significantly increases the acreage for cash crops but reduces that for grain crops.  Heterogeneity analysis shows that in prefectures with high temperature or land potential, SNWD’s impact on agricultural value added is relatively low.  In contrast, in areas with prolonged sunshine or high slopes, SNWD’s impact on agricultural value added is relatively large.  Given the low added value of grain crops, the government should consider strengthening food security by subsidizing water supply to sustain grain production.     

Satellite gravity measurements confirm accelerated melting of Greenland ice sheet

Using time-variable gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) satellite mission, we estimate ice mass changes over Greenland during the period April 2002 to November 2005. After correcting for the effects of spatial filtering and limited resolution of GRACE data, the estimated total ice melting rate over Greenland is -239 +/- 23 cubic kilometers per year, mostly from East Greenland. This estimate agrees remarkably well with a recent assessment of -224 +/- 41 cubic kilometers per year, based on satellite radar interferometry data. GRACE estimates in southeast Greenland suggest accelerated melting since the summer of 2004, consistent with the latest remote sensing measurements.     

Venus: topography revealed by radar data

Surface height variations over the entire equatorial region on Venus have been estimated from extended series of measurements of interplanetary radar echo delays. Most notable is a mountainous section of about 3-kilometer peak height located at a longitude of 100 degrees (International Astronomical Union coordinate system). The eastern edge has an average inclination of about 0.5 degrees, which is unusually steep for a large-scale slope on Venus. The resolution of the radar measurements along the surface of Venus varied between about 200 and 400 kilometers with a repeatability in altitude determination generally between 200 and 500 meters. The mean equatorial radius was found to be 6050.0+/-0.5 kilometers.     

应用Taylors指数法则进行种间与种内分布格局的分析与数据转换

Taylor＇s指数法则中的b值因种而有不同,表现十分稳定。但在有些情况下,在生活习性相近的不同种之间,b值却相同。另外,Taylor＇s参数b值尚因种在不同时期和虫态的种群而表现差异。