Ion pairing techniques: compatibility with on-line liquid chromatography--mass spectrometry

The mass spectrometric properties of a series of model ion pairs were examined. In the cases studied it was possible to vaporize the ion pair consituents and to produce spectra corresponding to those of the unpaired materials. These findings offer a convenient means for derivatizing certain ionic compounds and demonstrate the feasibility of analyzing ionic species by on-line liquid chromatography-mass spectrometry.     

Sulfur isotopic composition of cenozoic seawater sulfate

A continuous seawater sulfate sulfur isotope curve for the Cenozoic with a resolution of approximately 1 million years was generated using marine barite. The sulfur isotopic composition decreased from 19 to 17 per mil between 65 and 55 million years ago, increased abruptly from 17 to 22 per mil between 55 and 45 million years ago, remained nearly constant from 35 to approximately 2 million years ago, and has decreased by 0.8 per mil during the past 2 million years. A comparison between seawater sulfate and marine carbonate carbon isotope records reveals no clear systematic coupling between the sulfur and carbon cycles over one to several millions of years, indicating that changes in the burial rate of pyrite sulfur and organic carbon did not singularly control the atmospheric oxygen content over short time intervals in the Cenozoic. This finding has implications for the modeling of controls on atmospheric oxygen concentration.     

根外喷施硫酸镁对水稻淀粉品质的影响

选用寒地穗重型超级稻品种松粳9号、穗数型高产品种龙稻11号与优质品种龙稻18号为试验材料,盆栽条件下通过灌浆成熟期喷施硫酸镁和齐穗期增施氮肥处理及对照处理,系统比较根外喷施硫酸镁对水稻淀粉品质性状、叶片碳氮代谢相关酶活性和基因转录表达量及根系活力变化等的影响。结果表明,灌浆成熟期喷施硫酸镁显著降低稻米蛋白质含量,提高稻米蒸煮食味品质,而齐穗期增施氮肥处理使稻米蛋白质含量提高而降低蒸煮食味品质,硫酸镁处理通过降低稻米蛋白质含量提高稻米黏性和食味品质;灌浆成熟期喷施硫酸镁或齐穗期增施氮肥均显著提高灌浆成熟期叶片全氮含量和叶绿素含量以及灌浆各时期叶片Rubisco亚基基因转录表达量,增强水稻根系活力,促进根系氮素吸收,调控灌浆不同时期叶片和籽粒GS活性,但喷施硫酸镁效果显著优于增施氮肥;叶片全氮含量与GS活性间呈极显著负相关,与叶绿素含量、伤流液含氮化合物总量及Rubisco各亚基基因mRNA表达量呈极显著正相关。减氮同时在灌浆成熟期根外喷施硫酸镁是提高水稻产量和蒸煮食味品质的有效途径,研究为阐明根外喷施硫酸镁对水稻淀粉品质形成的影响和提高优质绿色水稻栽培技术水平提供理论依据。     

Aluminum in seawater: control by biological activity

The distribution and concentration of dissolved aluminum in a vertical hydrographic profile in the Mediterranean Sea near Corsica are controlled by biological activity. The concentrations of dissolved silica and aluminum covary in the profile and exhibit minima coincident with the seasonal thermocline, a nitrate minimum, and an oxygen maximum. These observations support the hypothesis that the silicon and aluminum cycles in the oceans are linked through the activity of diatoms.     

Aluminum in seawater: control by inorganic processes

The distribution of dissolved aluminum in open ocean waters is probably controlled by the solution of aluminum from atmospherically derived particles and bottom sediments balanced against scavenging by siliceous shells of dead organisms. Variations in the aluminum concentration within vertical hydrographic profiles are small as compared to those for other trace metals. Aluminum concentrations in the Atlantic and Pacific are inversely related to the silica contents of these oceans.     

硫酸钾镁肥在葡萄上的应用效果试验

试验结果表明,滨海涂区葡萄施用硫酸钾镁肥具有明显的增产效果,分别比不施硫酸钾镁肥对照和单施硫酸钾处理增产16.0%和10.5%,比单施硫酸钾增加收益达7 560元/hm2。施用硫酸钾镁肥还能提高葡萄果实的着色率,使果实成熟度较为一致,同时提高葡萄的品质,增加果实的含糖量以及可溶性固形物含量,降低总酸含量。     

Synergistic action of potassium chloride and magnesium sulfate on parasitoid wasp oviposition

A dilute solution of potassium chloride and magnesium sulfate induces oviposition in artificial eggs by the egg parasitoids Trichogramma pretiosum and T. minutum. The ability to obtain large numbers of eggs through the use of this inexpensive solution is a major advance toward the development of diets and the large-scale production of Trichogramma spp. in vitro.     

原子吸收光谱法测定小麦品种子粒中钾钠钙镁的含量

采用火焰原子吸收光谱法，测定了6种不同类型的冬小麦品种子粒中钾、钠、钙、镁宏量元素的含量。结果表明：钾、钠、钙、镁元素的相对标准偏差(RSD)分别小于0．77％、7．01％、3．82％、1．63％；并以小麦粉标准样品(GBW08503)进行比较测定。标准样品的测定值与标准值基本一致。该方法简便、快速、准确。     

Chondroitin sulfate: inhibition of synthesis by puromycin

Puromycin reversibly inhibits synthesis of chondroitin sulfate by vertebral chondrocytes from 10-day-old chick embryos. Treatment of these cells with puromycin for 5 hours does not affect viability or capacity to multiply on subsequent release from their matrix. It is suggested that synthesis of this polysaccharide is coupled with that of protein; there may be a feedback control in its synthesis.     

烤烟钾钙镁供应和吸收的关系

通过溶液培养研究了不同钾钙镁供应对烤烟品种K326吸收钾钙镁的影响。结果表明:随着钾钙镁水平的提高,烤烟吸收钾钙镁的量加大;随着生育期推延,烟叶中钾钙镁含量均降低。当K∶Ca∶Mg=468∶240∶60(质量浓度比)时,烟叶中钾钙镁含量较适宜。     

Magnesium ions: activity in seawater

The activity of magnesium ions in seawater was determined from solubility data and found to be between the values determined by Platford and by Garrels and Thompson. Our value may result from extensive formation of magnesium sulfate ion pairs.     

高性能混凝土的抗硫酸盐、镁盐侵蚀研究

结合工程实际，以在4种不同浓度的SO4^2-，Mg^2 侵蚀溶液中浸泡的普通水泥胶砂试件和掺矿渣微粉高性能混凝土胶砂试件为对比试件进行研究，通过测定和观察试件在浸泡期为28d、2个月、4个月、6个月、8个月、10个月、12个月的强度损失和形态形貌变化，用抗折强度和抗蚀系数来评定其抗侵蚀性能。宏观试验结果表明普通水泥胶砂试件在不同浓度的SO4^2-，Mg^2 侵蚀溶液中抗侵蚀性能都很差；掺矿渣微粉高性能混凝土胶砂试件抗侵蚀性能优异，在4种侵蚀溶液中侵蚀龄期均大于1年。     

离子色谱法测定盐卤水中溴离子试验

利用离子色谱法测定盐卤水中的溴离子试验结果表明,该方法大大降低了干扰因素的影响,提高了结果的准确度,缩短了分析时间,提高了工作效率,其加标回收达到93%～104%,精密度相对偏差小于3%。     

Ribosomes: analysis by cesium sulfate gradient centrifugation

Ribosomes from the cytoplasm of a mammalian tissue, HeLa cells, were partially purified and then concentrated into a zone by prolonged centrifugation in Cs(2)SO(4) solution (density, 1.43 grams per milliliter). Ribosomal preparations treated with bentonite prior to density-gradient centrifugation showed single peaks after centrifugation. Material recovered from the peaks represented aggregates of the original 74S particle.     

Peromyscus: effect of early pairing on reproduction

Sibling mating in prairie deer mice (Peromyscus maniculatus bairdi) results in poor reproductive performance. Siblings experimentally paired before puberty exhibit delayed reproduction when adult. A behavioral mechanism is involved in this reproductive delay, since prepubertal familiarity also delays reproduction in nonsibling pairs. Such a reproductive delay may act to reduce inbreeding depression and regulate population growth.     

Chromatographic silica gel: surface area determined by adsorption

The surface area of silicic acid, a form of silica gel, has been determined by adsorption of methanol from a benzene solvent. The method is straightforward, uses inexpensive apparatus, and should be applicable to other particulate adsorbents.     

Atmospheric ammonia: absorption by plant leaves

By monitoring the disappearance of ammonia from an airstream flowing through a small growth chamber containing a single plant seedling, it was discovered that plant leaves absorb significant quantities of ammonia from the air, even at naturally occurring low atmospheric concentrations. The measured absorption rates of ammonia showed large diurnal fluctuations and varied somewhat among species, but differed little with the nitrogen fertility level of plants within a species.