石菖蒲挥发性组分提取方法的对比研究

采用超临界CO2流体萃取（SCFE）与分级分离技术联用提取石菖蒲挥发性组分．并与水蒸气提取（HD）法所得挥发油进行了对比,发现挥发油成分相对含量有所差异。在SCFE挥发油中烯烃单萜、倍半萜类的相对含量高;而含氧单萜、含氧倍半萜类则正好相反．HD法所提挥发油中含氧萜类明显高于SCFE。其主要有效成分口一细辛醚在SCFE和HD所提挥发油中的相对含量分别为52．84％和38．67％,这说明SCFE对口一细辛醚的提取有较好的选择性。     

应用HACCP理念建立食品辐照企业GIP管理体系的探讨

本文应用HACCP基本理念分析了食品辐照加工过程存在的危害因素及质量控制的关键控制点。深入探讨了建立食品辐照加工企业GIP管理体系的原则和方法。     

Molecular mimicry regulates ABA signaling by SnRK2 kinases and PP2C phosphatases

Abscisic acid (ABA) is an essential hormone for plants to survive environmental stresses. At the center of the ABA signaling network is a subfamily of type 2C protein phosphatases (PP2Cs), which form exclusive interactions with ABA receptors and subfamily 2 Snfl-related kinase (SnRK2s). Here, we report a SnRK2-PP2C complex structure, which reveals marked similarity in PP2C recognition by SnRK2 and ABA receptors. In the complex, the kinase activation loop docks into the active site of PP2C, while the conserved ABA-sensing tryptophan of PP2C inserts into the kinase catalytic cleft, thus mimicking receptor-PP2C interactions. These structural results provide a simple mechanism that directly couples ABA binding to SnRK2 kinase activation and highlight a new paradigm of kinase-phosphatase regulation through mutual packing of their catalytic sites.     

Field Scale Mapping of Surface Soil Clay Concentration

The surface soil clay concentration is a useful soil property to map soils, interpret soil properties, and guide irrigation, fertilizer, and agricultural chemical applications. The objective of this study was to determine whether surface soil clay concentrations could be predicted from remotely sensed imagery of bare surface soil or from soil electrical conductivity for a 115 ha field located in Crisp County, Georgia. The soil clay concentrations were determined for soil samples taken at 28 field locations. Three different data sources–an aerial color photograph image, two infrared bands from an ATLAS data set, and the electrical conductivity of the surface soil layer were used in the research. Principal components analysis was applied to the color photograph image, whereas the ratio of two infrared bands was applied to the ATLAS data set. Filtering was applied to both resulting images. The distribution of soil electrical conductivity was derived from the measured soil electrical conductivity data by spatial analysis. Statistical relationships between soil clay concentrations and the principal component 3, the ratio of two ATLAS infrared bands, and the soil electrical conductivity were analyzed, and three linear equations were derived with r ² values 0.83, 0.52, and 0.78, respectively. The distribution of the soil clay concentrations was derived based on these three equations. Six levels of soil clay concentrations were classified in these three methods, and the advantages and disadvantages were discussed. The predicted and measured soil clay concentrations, based on additional soil samples from 30 field locations, were compared using linear regression (r ²=0.76, 0.45, and 0.77 for the three methods). The overall accuracy for these methods were 84%, 66%, and 76%, respectively. The principal components method had the highest accuracy in our research, while the result for the depressional areas is the best from the ratio method.     

双波长分光光度法测定青钱柳总黄酮含量的研究

实验采用三氯化铝显色,双波长分光光度法对青钱柳总黄酮含量进行测定研究.该测定黄酮含量方法简便、准确、快速.     

Utility of on- and off-farm weather records for studies in genetics of heat tolerance

Utility of weather information from on-farm and weather stations was evaluated for the application in studies on the genetics of heat stress. Daily milk yield of 31 primiparous Holstein cows was collected at Tifton, GA, from April 28 to July 19, 1993. Weather information was recorded on-farm and was available from weather stations in Georgia. Analyses used daily average of temperature–humidity index (THI). Effects of threshold of heat stress and the rate of decline in milk after the threshold were estimated. With on-farm weather data, threshold was at THI = 22 and rate of decline was − 1.12 kg of milk per unit of THI measured 2 days before milking. At the Tifton weather station, 3 km away from the farm, the threshold was THI = 20 and the rate was the same. With data from Macon, Columbus, Atlanta, and Athens stations, the threshold was at 20, 21, 20, and 20, respectively, and the rate of decline with a 2 day lag was − 0.88, − 1.02, − 0.90, and − 0.97 kg of milk per unit of THI. Subsequent analysis included 2260 test day records from the same farm from 1993 to 2003 and weather data from Tifton station. The highest rate of decline on milk yield of − 0.22 kg per unit of THI occurred at the threshold of 20 and no lag. For data restricted to 1999–2003, the threshold increased to 22 and the rate to − 0.46 kg per THI unit. Public stations provide satisfactory information for national genetic evaluation for heat stress. Critical parts in such an evaluation are modeling of test days and accounting for changes among farms and weather stations over time.     

Long-term consequences of topsoil mining on select biological and physical characteristics of two New Zealand loessial soils under grazed pasture

Soil chemical, biochemical, biological and structural properties were measured in two New Zealand loessial soils that were topsoil-mined 10 and 25 years ago respectively. Measurements at the 10-year site were compared to some earlier measurements made at this site and the data combined in a chronological sequence for analysis. Topsoil mining had a large, detrimental impact on the soil microbial biomass, the earthworm populations, easily mineralizable N and soil enzyme activities. However, most of these properties substantially recovered, to 80-90 per cent of the levels in unmined soils, within 10-25 years of restoration under pasture. In contrast, while total soil C and N were less affected by topsoil mining, their recovery was much slower. Stabilities of macro-aggregates of soil had fully recovered within 10-25 years after topsoil mining. The apparent changes in all the measured properties between 10 and 25 years of restoration were small in comparison with changes between 0-10 years of restoration after topsoil mining. The total C content of both soils under pasture appeared unlikely to attain the levels present in unmined soils. In soils undergoing restoration, the ratio of microbial C/total soil C may be a useful index of soil ‘biological stability’. Sulphatase activity may reflect the recovery of pasture production.     

Maintaining estuary quality for shorebirds: towards simple guidelines

It is increasingly important to be able to monitor and maintain the quality of estuaries for overwintering shorebirds. Bird numbers alone are not sufficient to indicate quality nor, as recent research shows, can it be assumed that site quality is being maintained simply because there is enough food to meet the birds’ physiological demands; i.e., the amount of food available per bird in autumn needs to be greater than the amount eaten. But how much greater? We used a simple individuals-based and behaviour-based model to explore the factors that affect the relationship between overwinter mortality and the amount of food available per bird in autumn (the food:bird ratio). The aims were to explore how the natural history characteristics of a shorebird species affected the shape of this relationship, in order to identify characteristics of the system that should be included in any monitoring programme of site quality. In all cases there was a minimum threshold food:bird ratio above which mortality did not vary and below which mortality increased steadily. The amount of food per bird required at the threshold varied from one to six times the amount actually consumed by each bird during winter, depending on the amount of realism included in the model. The minimum threshold ratio was most strongly influenced by the shape of the relationship between intake rate and prey density - the functional response - and, when interference competition occurred, by the distribution of the birds’ main food supply. Simulations with realistic spatial distributions of prey predicted that the minimum required amount of food per bird would be between two and five times the amount actually consumed. The threshold approach could provide a simple method of monitoring estuary quality based on food supply and bird numbers. It also provides a potentially clearly-defined and unambiguous measure of the carrying capacity of a site. If applied to a sufficient number of real estuaries, general guidelines for maintaining estuary quality based on estuary characteristics, food supply and bird species might be established.     

Antibiotic Resistance, Gene Transfer, and Water Quality Patterns Observed in Waterways near CAFO Farms and Wastewater Treatment Facilities

We examined water quality indicators (pH, temperature, turbidity, total phosphorus, and fecal coliform density) and bacterial antibiotic resistance (prevalence, conjugative transfer, and genetic linkage of resistance elements) at locations impacted by confined animal feeding operations (CAFOs) and compared them to nearby reference sites. Sites located upstream and downstream of two wastewater treatment facilities were also compared. Sites near CAFO farms had poor water quality (elevated total phosphorus and turbidity), while water quality remained relatively good downstream of wastewater treatment plants. High proportions of antibiotic-resistant bacteria were observed at all study sites, and frequent conjugative transfer of resistance was observed in laboratory assays. Out of a total of 830 environmental bacterial isolates, 77.1% were resistant to only ampicillin, while 21.2% were resistant to combinations of antibiotics including ampicillin (A), kanamycin (K), chlorotetracycline (C), oxytetracycline (O), and streptomycin (S). Multi-drug-resistant bacteria were significantly more common at sites impacted by CAFO farms. In conjugation assays, 83.3% of the environmental isolates transferred one or more antibiotic resistance genes to a laboratory strain of Salmonella typhimurium. A subset of multi-drug-resistant (A, C, and O) isolates was screened for specific tetracycline resistance genes and class I and II integrons. None of the screened isolates (n?=?22) were positive for integrons, while 13 isolates contained resistance genes for tet (B) and tet (C). Our results indicate that CAFO farms not only impair traditional measures of water quality but may also increase the prevalence of multi-drug-resistant bacteria in natural waters.