农户参与农地股份合作制意愿的影响因素研究——基于湖北省三汊镇的农户调查

农地股份合作制作为一种新的土地流转方式,在实践过程中极大地显示了其制度的优越性。通过对湖北省三汊镇农户的入户调查,采用Logistic模型,实证分析了影响农户土地入股意愿的内部因素,并加以规范分析找出了影响农户入股意愿的主要外部因素。研究结果表明,农户入股意愿主要受户主的职业、家庭主要收入来源和家庭人口数量等内部因素和劳保福利、完善的社保等外部因素的影响,并据此提出了相应的促进农地股份合作制的建议。最后,对其前景进行了展望。     

以“食品微生物学”为例探索基于工程认证的学生自主实践教学模式

针对"食品微生物学"实践教学,倡导以学生为中心、自主实践的教学理念,培养自主学习意识和科学素养,对实验课程的教学模式、考核评价等进行改革,优化考核评价体系,从而提高实验课堂效果,加强学生动手能力的培养。为解决复杂工程问题打下坚实的基础,有力支撑工程教育认证对课程教学指标点达成的要求。其他食品类基础实验也可借鉴"食品微生物学",不断完善食品科学与工程专业基础实验教学模式。     

Mercury distribution and speciation in floodplain soils and uptake into native earthworms (Diplocardia spp.)

Historically as part of its national security mission, the U.S. Department of Energy's Y-12 National Security Facility in Oak Ridge, TN acquired a significant fraction of the world's supply of elemental mercury. During the 1950s and 1960s, a large amount of elemental mercury escaped confinement and is still present in the watershed surrounding the Y-12 facility. Earthworms are key components in natural food chains, providing a food source for many small mammals and important food sources for small birds. The objectives of this study were to investigate the current status of mercury distribution and speciation and determination of mercury bioavailability to native earthworms in floodplain soils of East Fork Poplar Creek (EFPC) after decades of U.S. Department of Energy's remediation. The present study clearly shows that the total mercury in a tested floodplain field of EFPC was significantly below the US Department of Energy target 400 mg Hg/kg. The major mercury form in the current floodplain soils of EFPC is mainly the non-cinnabar mercury bound form in soil silicates (4 M HNO₃-extractable residual fraction). The results show strong linear relationships between mercury concentrations in native earthworms (both mature and immature groups) and the non-cinnabar mercury form. Native earthworms may be used as a potential mercury ecological bio-indicator (bio-marker) for demonstrating mercury bioavailability and ecotoxicity in the ecosystem.     

Purification, cloning, and immunological characterization of arginine kinase, a novel allergen of Octopus fangsiao

Arginine kinase (AK) is an important enzyme participating in energy metabolism in invertebrates, but, to date, there have been no reports that AK from octopus is an allergen. In this study, octopus AK was purified, and its molecular biological, immunological, and physicochemical characterizations were analyzed. The results showed that octopus AK was purified and confirmed by mass spectrometry for the first time, and its molecular mass was 38 kDa. The full-length gene sequence of octopus AK encompassed 1209 bp and was predicted to encode a protein with 348 amino acid residues. The homology of octopus AK and crustacean AK was about 54%, but the similarity between their three-dimensional structures was high. Octopus AK could react with mouse anti-shrimp AK and rabbit anti-crab AK polyclonal antibody singly. Octopus AK could also react with specific IgE of the sera from octopus-allergic patients effectively, whereas crab AK could inhibit the reaction between them. Finally, the IgE-binding activity of octopus AK could be reduced in the processes of thermal or acid-alkali treatment. In summary, AK was identified as a novel allergen in octopus, which had a sensitizing ability similar to that of crustacean AK. This is significant in allergy diagnosis and the treatment of octopus-allergic disorders.     

Whey protein nanofibrils: the environment-morphology-functionality relationship in lyophilization, rehydration, and seeding

Amyloid-like fibrils from β-lactoglobulin have potential as efficient thickening and gelling agents for food and biomedical applications, but the link between fibril morphology and bulk viscosity is poorly understood. We examined how lyophilization and rehydration affects the morphology and rheological properties of semiflexible (i.e., straight) and highly flexible (i.e., curly) fibrils, the latter made with 80 mM CaCl(2). Straight fibrils were fractured into short rods by lyophilization and rehydration, whereas curly fibrils sustained little damage. This was reflected in the viscosities of rehydrated fibril dispersions, which were much lower for straight fibrils than for curly fibrils. Lyophilized straight or curly fibrils seeded new fibril growth, but viscosity enhancement due to seeding was negligible. We believe that the increase in fibril concentration caused by seeding was counterbalanced by a decrease in fibril length, reducing the ability of fibrils to form physical entanglement networks.     

Isolation and characterization of an oxygen radical absorbance activity peptide from defatted peanut meal hydrolysate and its antioxidant properties

Defatted peanut meal hydrolysate (DPMH) was purified using ultrafiltration, gel filtration chromatography, and high-performance liquid chromatography. A tripeptide with strong oxygen radical absorbance capacity (ORAC) was isolated and identified as Tyr-Gly-Ser by ESI-MS/MS. It was then synthesized to measure its antioxidant properties in different systems. The ORAC value of Tyr-Gly-Ser was 3-fold higher than that of glutathione (GSH), and it displayed a stronger protective effect on linoleic acid peroxidation and H(2)O(2)-induced oxidative injury in rat pheochromocytoma line PC12 cells than GSH (p < 0.05). However, Tyr-Gly-Ser showed negligible DPPH radical scavenging activity, reducing power, and no metal chelating ability. The results suggested that Tyr-Gly-Ser displayed antioxidant activity via the hydrogen atom transfer mechanism, and the Tyr at the N-terminal was the hydrogen donor. The ORAC assay was recommended as a reliable and effective method to measure the antioxidant activity in the course of antioxidant peptide isolation.     

Matrix effects in analysis of β-agonists with LC-MS/MS: influence of analyte concentration, sample source, and SPE type

The synergistic influences of analyte concentration, sample source, and solid-phase extraction (SPE) type on matrix effects in the multiresidue analyses of eight β-agonists with LC-ESI-MS/MS were evaluated. Porcine muscle and liver extracts and urine from diverse sources were purified by strong or mixed-mode cation exchange and molecularly imprinted polymer SPE cartridges, respectively. Three spiked concentrations (2, 10, and 20 ng/mL) of eight β-agonists in the purified matrices and the different sample sources were analyzed. The results show that for most β-agonists there are significant differences in matrix effects between analyte concentrations or sample sources (P < 0.05), whereas there is no significant difference in matrix effects between different SPE cartridges (P > 0.05). Results from main effects testing indicated that analyte concentration was the main effector.     

Rapid Determination of Mercury in Contaminated Soil and Plant Samples Using Portable Mercury Direct Analyzer without Sample Preparation, a Comparative Study

The objective of this study was to determine the efficiency of a portable total mercury analyzer (OhioLumex RA-915+) in comparison with traditional analytical methods, such as inductively coupled plasma atomic emission spectrometry and cold vapor atomic absorption. The quick mercury analytical procedure with the direct mercury analyzer without sample pretreatment (such as sample digestion) was optimized for a variety of environmental samples, including contaminated soil and plant samples. The efficiency was evaluated using practical parameters, such as time required for analysis, sample amount, mercury species, accuracy, and precision/reproducibility, as well as using statistical analysis. Our results demonstrate that these three instrumental methods yielded similar mercury concentration values and statistical data, while the mercury direct analyzer had the advantages of not requiring for sample digestion and only requiring a small quantity of samples for distribution of mercury in a single root, a single root hair, and sub-regions of a single leaf of plants. These factors are used to justify use of the portable direct mercury analyzer under field conditions and validation of the results.     

唐皇城含光门土遗址盐分病害分析与研究

唐皇城含光门土遗址中微溶-可溶盐导致地泛白、酥粉、片状脱落等病害极为严重。通过对土壤含水率、酸碱度(pH)、电导率测定以及微溶-可溶盐的X射线粉末衍射(XRD)、能谱(EDX)、扫描电子显微镜(SEM)分析,结果表明:唐皇城含光门东展厅土遗址微溶-可溶盐主要以硫酸钙类和硫酸钠类为主;西展厅五期断面土遗址主要以硫酸钙类、碳酸钙类为主。不同部位含盐量与水分的运移密切相关,随着距离水平地面高度的增加,含水率的的降低,微溶-可溶盐的含量降低。通过扫描电子显微镜观察发现,硫酸钙类是导致土遗址酥粉、脱落病害的主要原因。     

高功率密度柴油机的排气流通特性

为了分析柴油机功率密度提高后排气流动特征的变化,建立单缸柴油机一维热动力模型,对转速为3000r/min时柴油机的控制参数和热动力参数进行仿真,计算结果与试验值吻合良好。应用校准的模型分析柴油机提高功率密度对排气流动的影响。结果表明,随转速提高超临界排气持续曲轴转角明显增加,在转速为4200r/min时达128°;活塞排气指示功明显增大。排气流通面积成为影响高功率密度柴油机排气流动性能的主要因素,增大排气门喉口直径,可缩短超临界排气,减小排气指示功绝对值。为高功率密度柴油机排气系统的优化设计提供理论参考。