Strontium-90: concentrations in surface waters of the Atlantic Ocean

From the large body of analyses of strontium-90 in surface waters of the Atlantic Ocean, annual average concentrations (from 10 degrees N to 70 degrees N) have been compared to those predicted. The data indicate higher fall-out over ocean than over land and confirm the rapid rates of down-mixing shown by most studies of subsurface strontium-90.     

Radionuclide concentrations in surface air: direct relationship to global fallout

By relating the average monthly hemispheric concentrations of radionuclides in the suirface air to the monthly hemispheric fallout of these nuclides, we have derived proportionility constants. For every disintegration per minutte of a radioactive nutclide per 1000 cubic meters of the suirface air in the Northern Hemisphere, 3.3 kilocuirics of that nutclide will be deposited on the surface; in the Soluthern Hemisphere, 5.0 kilocutries will deposit for every disintegration per minutte per 1000 cuibic meters. Oni the basis of thlese factors, the global deposition of radionuclides can be estimated from a relatively small numbnber of measurements of the radioactivity in the surface air.     

Gravitational effects on concentrations and partial pressures in solutions: a thermodynamic analysis

Thermodynamic analysis establishes the equilibrium relationships between the concentrations and partial pressures of the components of liquid and gaseous solutions in the presence of a gravitational field. The conditions of equilibrium between a column of gas and gas-saturated water and the conditions of equilibrium governing a model of the distribution of radioactive heat sources in surface rocks are deduced from the theory.     

Microtubule formation in vitro in solutions containing low calcium concentrations

Isolated rat brain tubulin can be repolymerized in vitro in solutions containing adenosine triphosphate or guanosine triphosphate, magnesium ions, and a good calcium chelator. The extreme sensitivity of tubulin to calcium ions explains the failure of previous efforts to obtain polymerization and suggests a possible mechanism for regulation of microtubule polymerization in vivo.     

渭南农业结构调整的思路浅析

陕西省渭南市在长期计划经济体制下形成的传统农业结构模式,在社会主义市场经济体制条件下,同时受到国内、外农产品市场两个方面的巨大冲击.在严峻形势面前,渭南农业结构调整优化的紧迫性已愈来愈引起广大农民、农业科技人员和各级政府的极大关注,积极探索在市场经济条件下适合渭南农业实际的现代农业结构模式,对推动和优化渭南市的农业结构,促进渭南农业生产和农村经济的进一步发展有积极意义.但从渭南农业和农村经济发展的客观要求来讲,要实现渭南农业结构的根本变革,无疑还是有很大的差距.作者根据长期的农业科研和农技推广工作实践,就渭南市农业结构调整的思路提出几点看法,愿同农业科技同行进行商榷.     

Enhanced immunogenicity of the pre-S region of hepatitis B surface antigen

The 55 codons upstream of the gene sequence encoding the hepatitis B surface antigen (HBsAg) are called the pre-S(2) region. It has been proposed that polypeptides of high molecular weight that contain the pre-S(2) region should be included in future hepatitis B virus (HBV) vaccines. The pre-S(2) region and the S gene product [25 kilodalton (kD)] together compose a polypeptide of high molecular weight (33 kD). As an initial attempt to determine the relevance of the 33-kD polypeptide to development of an HBV vaccine, the murine immune response to pre-S(2)-encoded determinants as compared to S-encoded determinants on the same polypeptide was examined. The results indicate (i) the pre-S(2) region is significantly more immunogenic than the S region of HBsAg, (ii) the 26 amino acid residues at the NH2-terminus of the 33-kD polypeptide represent a dominant antibody binding site on the pre-S(2) region, (iii) the immune response to the pre-S(2) region is regulated by H-2-linked genes distinct from those that regulate the response to the S region, and (iv) immunization of an S region nonresponder strain with HBV envelope particles that contain both the pre-S(2) and S regions can circumvent nonresponsiveness to the S region.     

烷基三甲基溴化铵碳氢链长对其水溶液表面活性的影响

实验结果表明,在ｎｃ＝１０～１６范围内,烷基三甲基溴化铵表面活性剂在水溶液表面的吸附和在水溶液中的胶团化作用均随着其碳氢链长的增加而呈不同程度的增强．在实际应用中,结合使用效果和经济效益,当强调表面吸附时,以Ｃ１２ＴＡＢ较好;若希望利用其胶团性质,则应更多地使用价廉的Ｃ１６ＴＡＢ．     

Lead aerosols in the atmosphere: increasing concentrations

The concentrations of atmospheric lead around San Diego, California, have been determined and their geographic and seasonal variations are explained. The lead aerosol concentration at San Diego is increasing at a rate of 5 percent per year. The isotopic composition of lead aerosols is similar to that of the lead additives isolated from gasoline, which are the largest contributors to atmospheric lead pollution.     

小麦生长季节太湖地区土壤溶液中氮磷浓度的变化

利用原状土柱通过人工灌溉，研究了不同施肥处理下太湖地区典型水稻土（黄泥土）在小麦生长季节中表层和底层土壤溶液中不同形态氮磷浓度的变化。氮磷钾肥的施用按基肥、拔节肥、穗肥5：3：2的比例分次施用。结果表明，在小麦分蘖期、拔节期、抽穗期，表层土壤溶液中总磷浓度和铵态氮浓度逐渐提高；表层土壤溶液中硝态氮浓度和底层土壤溶液中各形态氮和磷的浓度均没有显变化；土壤溶液中氮磷形态以有机态氮和无机态磷为主。提示：太湖地区小麦生长季节土壤氮磷向水体迁移的环境风险在小麦微穗期后相对较高。     

轮虫休眠卵用不同浓度盐溶液处理后卵壳的扫描电镜观察

对萼花臂尾轮虫(Brachionus calyciflorus）、壶状臂尾轮虫（B.urceus）、褶皱臂尾轮虫（B.plicatilis）和卜氏晶囊轮虫（Asplanchna brightwelli）的休眠卵用不同浓度食盐溶液处理后卵壳进行了扫描电镜观察,发现不同种轮虫休眠卵的外表超微结构有明显的差异,大部分表面有孔,卵壳有不同程度的龟裂。新鲜休眠卵用盐度为10的食盐溶液处理后,龟裂不明显;隔年休眠卵经饱和食盐水处理,龟裂明显。     

轮虫休眠卵用不同浓度盐溶液处理后卵壳的扫描电镜观察

对萼花臂尾轮虫 (Brachionuscalyciflorus)、壶状臂尾轮虫 (B urceus)、褶皱臂尾轮虫 (B plicatilis)和卜氏晶囊轮虫 (Asplanchnabrightwelli)的休眠卵用不同浓度食盐溶液处理后的卵壳进行了扫描电镜观察 ,发现不同种轮虫休眠卵的外表超微结构有明显的差异 ,大部分表面有孔 ,卵壳有不同程度的龟裂。新鲜休眠卵用盐度为 1 0的食盐溶液处理后 ,龟裂不明显 ;隔年休眠卵经饱和食盐水处理后 ,龟裂明显     

用曲面拟合法确定平原区域正常高的方法

对应用GPS技术结合几何水准测量资料确定正常高的方法进行了研究,针对测区地形特点,选择合理的曲面拟合数学模型,并以此为基础建立计算其他GPS点高程异常和正常高的方程。同时,结合工程实践对上述求解方程进行了验证,其拟合结果的标准差为1.1cm,达到了四等水准测量的要求。研究证明,采用一定密度及合理分布的GPS水准高程联测点,选择曲面函数模型拟合区域大地水准面,是平原区域确定正常高的一种行之有效的方法。     

干旱区精河流域地表温度的模型反演研究

以精河流域绿洲为研究区,使用Landsat ETM⁺数据,采用单窗算法和普适性单通道算法对研究区地表温度进行反演,并将这两种算法的反演结果与研究区MODIS温度产品(MODIS LST)进行比较。结果表明：(1) 单窗算法和普适性单通道算法反演的结果总体趋势比较接近,研究区整体的平均温度相差约2k;(2) 采用改进型土壤调整植被指数(MSAVI)代替归一植被指数(NDVI)计算地表比辐射率可有效提高反演精度,并且同等条件下单窗算法的反演精度高于普适性单通道算法,两种算法的反演结果与MODIS LST的相关系数分别是0.9255和0.8651;(3) 在城镇区域,普适性单通道算法反演结果与MSAVI的相关性高于单窗算法,相关系数为0.8136,说明普适性单通道算法更适合干旱区大范围城镇地表温度的反演研究。     

Deletion in cysteine-rich region of LDL receptor impedes transport to cell surface in WHHL rabbit

The Watanabe heritable hyperlipidemic (WHHL) rabbit, an animal with familial hypercholesterolemia, produces a mutant receptor for plasma low-density lipoprotein (LDL) that is not transported to the cell surface at a normal rate. Cloning and sequencing of complementary DNA's from normal and WHHL rabbits, shows that this defect arises from an in-frame deletion of 12 nucleotides that eliminates four amino acids from the cysteine-rich ligand binding domain of the LDL receptor. A similar mutation, detected by S1 nuclease mapping of LDL receptor messenger RNA, occurred in a patient with familial hypercholesterolemia whose receptor also fails to be transported to the cell surface. These findings suggest that animal cells may have fail-safe mechanisms that prevent the surface expression of improperly folded proteins with unpaired or improperly bonded cysteine residues.     

Search for organic and volatile inorganic compounds in two surface samples from the chryse planitia region of Mars

Two surface samples collected from the Chryse Planitia region of Mars were heated to temperatures up to 500 degrees C, and the volatiles that they evolved were analyzed with a gas chromatograph-mass spectrometer. Only water and carbon dioxide were detected. This implies that organic compounds have not accumulated to the extent that individual components could be detected at levels of a few parts in 10(9) by weight in our samples. Proposed mechanisms for the accumulation and destruction of organic compounds are discussed in the light of this limit.     

Microtus: A Simple Method of Recording Time Spent in the Nest

A prairie vole, Microtus ochrogaster, was tagged with a radioactive label, a survey meter was placed over its nest, and the presence or absence of the animal in the nest was recorded on tape.     

Mascons: lunar mass concentrations

Lunar Orbiter tracking data have been processed to supply a qualitatively consistent gravimetric map of the lunar nearside. While a simplified model was employed, the results indicate that there are large mass concentrations under the lunar ringed maria. These mass concentrations may have important implications for the various theories regarding lunar history.     

Acetylcholine concentrations in rat brain: diurnal oscillation

A diurnal oscillation of acetylcholine concentrations in rat brain has been demonstrated by gas chromatography. Peak concentrations occur at 2 hours of light, and a trough is seen at 6 hours of darkness. This pattern is observed only in grouped rats, and emerges after at least 18 days of prior conditioning in an environment with controlled light, humidity, and temperature.     

Atmospheric aerosols: increased concentrations during the last decade

Atmospheric turbidity values calculated each month from solar radiation observations at MaunaLoa Observatory, Hawaii, show an increase of aerosols from 1958 through the present. These data indicate that either the effects of the Mount Agung eruption are still being observed or a longer-term trend of increasing turbidity is in evidence.     

Alpha-ketoglutaramate: increased concentrations in the cerebrospinal fluid of patients in hepatic coma

alpha-Ketoglutaramate, a deaminated metabolite of glutamine not previously identified in biological tissues, was measured in the cerebrospinal fluid of human subjects and found to be increased three- to tenfold in patients with hepatic coma. When perfused into the cerebral lateral ventricles of rats, alpha-ketoglutaramate (10 mM) depressed the animals' nocturnal locomotor activity, and at higher doses induced circling behavior and myoclonus. The concentration of alpha-ketoglutaramate in cerebrospinal fluid appears to be a reliable diagnostic indicator of hepatic coma, and its accumulation may contribute to the pathogenesis of this disease.