集装箱式与池塘养殖草鱼营养品质的分析比较

为比较集装箱式与池塘养殖草鱼鱼肉的食用品质差异,以蒸煮得率、色泽、三磷酸腺苷关联物含量、模拟消化后相对分子质量分布为指标,研究2种养殖方式草鱼生、熟状态下的品质差异;利用感官评价、电子鼻和固相微萃取-气相色谱-质谱分析技术,研究2种养殖方式草鱼在生、熟状态下的气味及挥发性风味物质组成差异.结果表明:1)集装箱式养殖和池...     

固体有机废物堆肥过程中氮的转化

文章论述了固体有机废物堆肥过程中氮的转化过程,主要在氨化、硝化、反硝化、固定和氮以淋洗液和废气的形式排放等方面对环境的影响,并对影响此过程的因素进行了分析,对堆肥过程中氮素的合理调控提出了建议。     

Endotoxin-induced structural transformations in liquid crystalline droplets

The ordering of liquid crystals (LCs) is known to be influenced by surfaces and contaminants. Here, we report that picogram per milliliter concentrations of endotoxin in water trigger ordering transitions in micrometer-size LC droplets. The ordering transitions, which occur at surface concentrations of endotoxin that are less than 10(-5) Langmuir, are not due to adsorbate-induced changes in the interfacial energy of the LC. The sensitivity of the LC to endotoxin was measured to change by six orders of magnitude with the geometry of the LC (droplet versus slab), supporting the hypothesis that interactions of endotoxin with topological defects in the LC mediate the response of the droplets. The LC ordering transitions depend strongly on glycophospholipid structure and provide new designs for responsive soft matter.     

Activation volumes for solid-solid transformations in nanocrystals

The transition between four- and six-coordinate structures in CdSe nanocrystals displays simple transition kinetics as compared with the extended solid, and we determined activation volumes from the pressure dependence of the relaxation times. Our measurements indicate that the transformation takes place by a nucleation mechanism and place strong constraints on the type of microscopic motions that lead to the transformation. The type of analysis presented here is difficult for extended solids, which transform by complicated kinetics and involve ill-defined domain volumes. Solids patterned on the nanoscale may prove to be powerful models for the general study of structural transitions in small systems, as well as in extended solids.     

Phase transformations in carbon fullerenes at high shock pressures

C(60) powders were shock-compressed quasi-isentropically and quenched from pressures in the range 10 to 110 GPa (0.1 to 1.1 Mbar). Recovered specimens were analyzed by Raman spectroscopy and optical microscopy. C(60) fullerenes are stable into the 13- to 17-GPa pressure range. The onset of a fast ( approximately 0.5 micros) reconstructive transformation to graphite occurs near 17 GPa. The graphite recovered from 27 GPa and about 600 degrees C is relatively well ordered with crystal planar domain size of about 100 A. Above 50 GPa a continuous transformation to an amorphous state is observed in recovered specimens. The fast transformation to graphite is proposed to occur by pi-electron rehybridization which initiates breakup of the ball structure and formation of the graphite structure at high density.     

Long-term transformations in the Sundarbans wetlands forests of Bengal

The landscape of the Sundarbans today is a product of two countervailing forces: conversion of wetland forests to cropland vs. sequestration of the forests in reserves to be managed for long-term sustained yield of wood products. For two centures, land-hungry peasants strove to transform the native tidal forest vegetation into an agroecosystem dominated by paddy rice and fish culture. During the colonial period, their reclamation efforts were encouraged by landlords and speculators, who were themselves encouraged by increasingly favorable state policies (land grants, tax incentives, cadastral surveys, and eventually colonization projects and subsidized irrigation) designed by revenue officials to maximize the rate of transformation of wetland forest to taxable agricultural land.In the late nineteenth century, as the rate of agricultural conversion increased, the colonial Forest Department succcessfully sought to preserve large areas of the remaining Sundarbans tidal forest by giving them legal status as Reserved or Protected Forests. These forests were intensively managed to provide a sustainable supply of timber and firewood for the increasing population of southern Bengal. Institutionalization of conflicting policies by the Revenue and Forest Departments reflected the escalating needs for both food and forest products as the colony grew. Today, supplies of some economically valuable trees have been depleted, and some mammals are locally extinct (although the Bengal tiger remains), but government policy in both Bangladesh and India now favors use of the Sundarbans as forest rather than its transformation to agricultural land. Further expansion of cropland to meet the grain demands of the burgeoning Bengali population in both nations has largely taken place outside the boundaries of the Sundarbans. Overexploitation of these forests for wood products remains a possibility, but large-scale clearing for rice paddies is unlikely under present policies.     

天津市个体造林情况调查

个体造林提高了造林成活率有保存率，增加了融资渠道，壮大了集体经济的实力。但个体造林的面积偏小、过于分散，个体造林者缺乏必要的技术管理知识，在品种发展上有一定的盲目性。各级政府部门应在树木采伐上为个体造林者提供优惠政策，并加大技术支持力度。     

冷板式冷藏集装箱换热方式与温度控制的探讨

对冷板的换热方式进行了分析,担子同冷板式冷藏集装箱的温度控制方法和采用对流换热的冷板结构。     

红壤氮转化对土壤水分变化的响应

[目的]土壤水分变化会影响微生物介导的氮转化。探明土壤氮初级转化速率,反映土壤内部氮素动态变化,探索氮转化对土壤水分变化的响应机制。[方法]采用~(15)N成对标记技术,利用数值优化模型,量化不同水分条件(最大持水量的20%、60%、80%、100%)下,有机氮矿化、铵态氮(NH_4~+)微生物同化、自养硝化、异养硝化和硝态氮(NO_3~-)消耗等主要氮转化过程的初级转化速率。[结果]土壤不同氮转化过程对水分变化的响应不同。随土壤含水量上升(从最大持水量的20%升至100%),土壤中易分解有机氮库初级矿化速率(M_(N_(lab)))从1.757 mg·kg~(-1)·d~(-1)增加到2.598 mg·kg~(-1)·d~(-1),难分解有机氮库初级矿化速率(M_(N_(rec)))变化不显著,总初级矿化速率(M,即M_(N_(lab))和M_(N_(rec)))显著上升。初级自养硝化速率(O_(NH_4))随土壤含水量增加而增加,在最大持水量为100%时达到最大值(0.266 mg·kg~(-1)·d~(-1));初级异养硝化速率(O_(N_(rec)))随土壤含水量增加先上升后下降,在最大持水量为60%时达到最大值(0.115 mg·kg~(-1)·d~(-1));土壤在最大持水量为80%和100%时O_(NH_4)显著大于O_(N_(rec)),总初级硝化速率(N,即O_(NH_4)和O_(N_(rec)))随土壤含水量增加而增大。总初级NH_4~+微生物同化速率(I_(NH_4))随土壤含水量增加线性上升,土壤在最大持水量的100 %时达到最大值(1.941 mg·kg~(-1)·d~(-1));初级NO_3~-消耗速率(C_(NO_3))在最大持水量的80%和100%时明显增加,总无机氮消耗速率(I_(NH_4)和C_(NO_3))随土壤含水量增加显著增大,并在最大持水量的80%时超过总氮初级矿化速率。因此,随含水量增加土壤氮净矿化速率先上升到最大值,然后迅速下降为负值。[结论]红壤不同无机氮产生和消耗过程对水分变化的响应不同;适当增加土壤含水量可提高红壤氮素的可利用性。图5表1参48     

Observation of individual chemical reactions in solution

Discrete chemical reaction events occurring in solution have been observed by single photon detection of a bimolecular, chemiluminescent reaction. The reactants were generated from 9,10-diphenylanthracene in acetonitrile with potential pulses applied to an ultramicroelectrode. Electrogenerated radical ions of opposite sign react to yield the excited singlet state of the parent compound. The chemical reactions were restricted to a 20-femtoliter volume adjacent to the electrode by the use of rapid potential pulses. Individual chemical reaction events were stochastic and followed the Poisson distribution, and the interarrival time between successive reaction events was exponentially distributed.     

Visualizing individual nitrogen dopants in monolayer graphene

In monolayer graphene, substitutional doping during growth can be used to alter its electronic properties. We used scanning tunneling microscopy, Raman spectroscopy, x-ray spectroscopy, and first principles calculations to characterize individual nitrogen dopants in monolayer graphene grown on a copper substrate. Individual nitrogen atoms were incorporated as graphitic dopants, and a fraction of the extra electron on each nitrogen atom was delocalized into the graphene lattice. The electronic structure of nitrogen-doped graphene was strongly modified only within a few lattice spacings of the site of the nitrogen dopant. These findings show that chemical doping is a promising route to achieving high-quality graphene films with a large carrier concentration.     

4D visualization of transitional structures in phase transformations by electron diffraction

Complex systems in condensed phases involve a multidimensional energy landscape, and knowledge of transitional structures and separation of time scales for atomic movements is critical to understanding their dynamical behavior. Here, we report, using four-dimensional (4D) femtosecond electron diffraction, the visualization of transitional structures from the initial monoclinic to the final tetragonal phase in crystalline vanadium dioxide; the change was initiated by a near-infrared excitation. By revealing the spatiotemporal behavior from all observed Bragg diffractions in 3D, the femtosecond primary vanadium-vanadium bond dilation, the displacements of atoms in picoseconds, and the sound wave shear motion on hundreds of picoseconds were resolved, elucidating the nature of the structural pathways and the nonconcerted mechanism of the transformation.     

螟纹杀克防治水稻三化螟药效试验

螟纹杀克对 2代三化螟防治效果良好。用量 1 0 50～1 350g/hm2 ,杀虫效果药后 7天在 95.3%以上 ;药后 2 0天的保苗效果在90 .5%～94.9%。     

马铃薯田化学除草与化学调控一体化技术研究

马铃薯田化学除草与化学调控一体化技术研究试验结果表明,应用二甲四氯钠盐和高效益草能混喷,在合理的浓度下,株防效为阔叶类杂草79．76％,单子叶杂草80．94％;鲜重防效为阔叶类杂草84．18％,单子叶杂草71．26％;在盛花期同时喷施2种类型调节剂组合,淀粉含量、干物质含量、Vc含量及产量可分别提高1．97％、3．43％、1．14％、47．33％。该技术的实施对马铃薯种植业的发展具有一定的实用价值。     

苦杏仁化学成分的研究

对陕西永寿县苦杏仁中苦杏仁甙、脂肪、纤维素、蛋白质、糖类、油脂的含量及理化性质,脂肪酸和氨基酸组成,多种微量元素和维生素含量进行了较为系统的分析测定,并与甘肃镇原、内蒙古赤峰、山西晋南和太原等地的苦杏仁成分进行了对比.结果表明,苦杏仁中含有丰富的脂肪、蛋白质、多种微量元素和维生素,其中不饱和脂肪酸的含量很高,氨基酸种类齐全,搭配合理,钾、钙、铁、镁、锌和维生素E的含量高,不同产地苦杏仁的化学成分具有明显的差异.     

Chemical sensing in process analysis

Improvements in process control, which determine production efficiency and product quality, are critically dependent upon on-line process analysis. The technology of the required instrumentation will be substantially expanded by advances in sensing devices. In the future, the hardware will consist of sensor arrays and miniaturized instruments fabricated by microlithography and silicon micromachining. Chemometrics will be extensively used in software to provide error detection, selfcalibration, and correction as well as multivariate data analysis for the determination of anticipated and unanticipated species. A number of examples of monolithically fabricated sensors now exist and more will be forthcoming as the new paradigms and new tools are widely adopted. A trend toward not only on-line but even in-product sensors is becoming discernible.