Sanidine: Predicted and Observed Monoclinic-to-Triclinic Reversible Transformations at High Pressure

High sanidine, (K,Na)AlSi(3)O(8), transforms reversibly to a triclinic phase at high pressure. This is analogous to the high-temperature monalbite transformation. Disordered alkali feldspars of various compositions have unit-cell dimensions which are very similar at the transition (a = 8.30 A, b = 12.97 A, c = 7.14 A, and beta = 116.2 degrees ), indicating that the transformation is structurally controlled. Changes in temperature, pressure, and the sodium/potassium ratio cause similar structural variations: angles between adjacent, rigid tetrahedra vary to accommodate changing effective alkali cation sizes.     

Superconductivity at 45 k in rb/tl codoped c60 and c60/c70 mixtures

The appearance of superconductivity at relatively high temperatures in alkali metal-doped C(60) fullerene provides the challenge to both understand the nature and origin of the superconductivity and to determine the upper limit of the superconducting transition temperature (T(c)). Towards the latter goal, it is shown that doping with potassium-thallium and rubidium-thallium alloys in the 400 to 430 degrees C temperature range increases the T(c) of C(60)/C(70) mixtures to 25.6 K and above 45 K, respectively. Similar increases in T(c) were also observed upon analogous doping of pure C(60). Partial substitution of potassium with thallium in interstitial sites between C(60) molecules is suggested by larger observed unit cell parameters than for the K(3)C(60) and K(4)C(60) phases. Contrary to previous results for C(60) doped with different alkali metals, such expansion does not alone account for the changes in critical temperature.     

Crystal Structures of Titanium, Zirconium, and Hafnium at High Pressures

At high pressures, as determined by x-ray analysis, titanium and zirconium metal have a distorted, body-centered-cubic structure. This phase persists on pressure release. The normal hexagonal close-packed structures are recovered when the metals are heated. An electronic shift must occur in the transition. Hafnium metal showed no such transition.     

Facile splitting of hydrogen and ammonia by nucleophilic activation at a single carbon center

In possessing a lone pair of electrons and an accessible vacant orbital, singlet carbenes resemble transition metal centers and thus could potentially mimic their chemical behavior. Although singlet di(amino)carbenes are inert toward dihydrogen, it is shown that more nucleophilic and electrophilic (alkyl)(amino)carbenes can activate H2 under mild conditions, a reaction that has long been known for transition metals. However, in contrast to transition metals that act as electrophiles toward dihydrogen, these carbenes primarily behave as nucleophiles, creating a hydride-like hydrogen, which then attacks the positively polarized carbon center. This nucleophilic behavior allows these carbenes to activate NH3 as well, a difficult task for transition metals because of the formation of Lewis acid-base adducts.     

达里诺尔湖表层沉积物中Hg、As的形态分布及释放特性

以达里诺尔湖为研究对象,采用七步逐级连续化学提取法,系统开展了表层沉积物中Hg、As的形态分析研究,重点模拟了不同pH下表层沉积物中Hg、As的释放特性。结果表明,达里诺尔湖表层沉积物中Hg的生物有效态主导形态为腐植酸结合或络合态,As的生物有效态主导形态为碳酸盐与铁锰氧化物结合态。在实验pH范围内,碱性或弱碱性环境不利于Hg和As的释放,强碱性环境利于Hg和As的释放;经酸溶液浸提过的沉积物,因金属氧化物的溶解使腐植酸结合或络合态的Hg、As暴露并在碱提取液中释放;经碱溶液浸提过的沉积物,因腐植酸的溶解使铁锰氧化物结合态Hg、As暴露并在酸提取液中释放。保持达里诺尔湖水体偏碱性状态对湖泊的水环境健康和生态安全至关重要。     

长期不同施肥对钙质紫色水稻土重金属累积及有效性的影响

为探讨长期不同施肥对石灰性紫色水稻土重金属累积及有效性的影响,以四川省农业科学院土壤肥料研究所长期定位试验为依托,研究了8种不同施肥条件下[不施肥(CK)、氮肥(N)、氮磷肥(NP)、氮磷钾肥(NPK)、有机肥(M)、有机肥+氮肥(M+N)、有机肥+氮磷肥(M+NP)和有机肥+氮磷钾肥(M+NPK)]土壤理化性质、重金属全量及有效量的变化。结果表明:长期施用氮磷、氮磷钾肥会降低土壤pH、CEC含量,提高土壤有机质、碱解氮及速效磷含量,改善土壤肥力,且与有机肥配施效果更优。长期施用化肥,土壤Fe、Mn、Cu、Zn、Pb和Cd含量变化不明显,有机肥及其与化肥配施后土壤Fe、Mn、Pb含量变化也不明显,Cd略有增加,Cu、Zn含量显著提高,但均低于我国农用地土壤环境质量风险筛选值(GB 15618—2018)。化肥对Cu、Zn、Pb和Cd的有效量影响不明显,磷肥可显著提高有效Fe含量,降低有效Mn含量,而有机肥提高Cu、Pb、Cd有效量,对其有活化效应。相关分析结果表明,土壤重金属有效量与理化性质、元素总量间的相关性因元素的不同而异。研究表明,长期施用化肥及有机肥不会造成石灰性紫色水稻土重金属含量超标的风险。     

Magnetic field-induced superconductivity in the ferromagnet URhGe

In several metals, including URhGe, superconductivity has recently been observed to appear and coexist with ferromagnetism at temperatures well below that at which the ferromagnetic state forms. However, the material characteristics leading to such a state of coexistence have not yet been fully elucidated. We report that in URhGe there is a magnetic transition where the direction of the spin axis changes when a magnetic field of 12 tesla is applied parallel to the crystal b axis. We also report that a second pocket of superconductivity occurs at low temperature for a range of fields enveloping this magnetic transition, well above the field of 2 tesla at which superconductivity is first destroyed. Our findings strongly suggest that excitations in which the spins rotate stimulate superconductivity in the neighborhood of a quantum phase transition under high magnetic field.     

Pressure Dependence of Superconductivity in Single-Phase K3C60

The superconducting compound K(3)C(60) (with transition temperature T(c) = 19.3 kelvin at ambient pressure), formed as a single phase by reaction of alkali vapor with solids of the icosahedral C(60) molecule (buckminsterfullerene), shows a very large decrease of T(c) with increasing pressure. Susceptibility measurements on sintered pellets showing bulk superconductivity are reported up to 21 kilobars of pressure, where T(c) is already less than 8 kelvin. The results are consistent with a piling up of the density of states at the Fermi level.     

The physics of organic superconductors

The upper temperature for superconductivity in organic conductors has increased from 1 kelvin in 1980, when the phenomenon was discovered in the quasi-one-dimensional cation radical salt tetramethyltetraselenafulvalene phosphorus heptafluoride to 12 kelvin in a new series of organic salts that show nearly two-dimensional electronic properties. These superconductors are attracting interest because of the wide range of new phenomena that they exhibit, including the competition between various ground states, the influence of a magnetic field on a quasi-one-dimensional conductor, the quantization of the Hall effect in a three-dimensional material, the giant magnetoresistance effects related to the two-dimensional nature of the Fermi surface of some materials, and the coherent voltage oscillation of a spin-modulated ground state. Furthermore, there is reason to believe that organic conductors with high superconducting transition temperatures could be produced in the near future. The recent finding of superconductivity in "fullerene" doped with alkali metals supports this optimism.     

太湖地区几种水稻土对重金属的缓冲能力的初探

本文采集了太湖地区典型水稻土土种 (黄泥土、白土、乌泥土 ) ,实验室分析了土壤酸碱缓冲能力、土壤中重金属的形态分布特性以及吸附解吸动态与缓冲速率 ,指出不同土种间土壤对重金属污染的缓冲能力差异较大 ,肥力较高的爽水型水稻土 -黄泥土的缓冲能力最强。     

不同土地利用方式下土壤养分特征变化分析

【目的】研究不同土地利用方式下土壤有机质及土壤养分元素特征的变化规律。【方法】在阿克苏地区采集小麦地、枣园、枣麦间作园、荒地枣园和撂荒地等5种典型的土地利用方式下的土壤,运用土壤化学分析方法,测定土壤有机质及氮磷钾等含量。【结果】各土壤养分指标在不同土地利用方式下变异系数为0.92%94.00%,均为中等空间变异性。由农田更替为枣园及枣麦间作后,提高了各层土壤有机质含量,其中020 cm土层各层土壤有机质均显著提高(P<0.05)。由荒地改建为枣园后,各层土壤有机质均有提高,其中010 cm、2030 cm土层显著提高(P<0.05)。0100 cm土层各养分元素含量和有机质含量均随土壤深度的增加而逐渐减少。土壤有机质、全磷、全钾、碱解氮、速效磷和速效钾含量均表现为枣麦间作园>枣园>小麦地>荒地枣园>荒地,全氮表现为枣园>枣麦间作园>小麦>荒地枣园>荒地。土壤有机质与土壤各养分元素之间存在着显著正相关关系。【结论】阿克苏地区农田或荒地改建为枣园或枣麦间作园后,均有利于提高土壤有机质及土壤肥力。     

湖北主产烟区烤烟化学成分的变异分析

以湖北烟区烤烟样品为材料,分析了不同等级、产地和品种间烤烟化学成分的含量状况.结果表明:①湖北烟区烤烟烟碱含量较高,总氮含量较低,糖碱比B2F偏低、C3F适宜、X2F偏高,钾氯比在不同等级均较适宜,石油醚提取物含量较低.②不同产地间烤烟化学成分含量存在广泛的变异,B2F的氯和石油醚提取物总量,C3F的还原糖、糖碱比、总氮、钾、氯、氮碱比和石油醚提取物,以及X2F的总氮、氯和氮碱比在不同产地间差异达显著水平.③不同品种间烤烟化学成分含量亦表现较大变异,B2F的氯离子含量,C3F的烟碱、总氮、石油醚提取物、还原糖、氯离子含量和糖碱比,以及X2F的氯离子、烟碱、总氮、石油醚提取物总量和糖碱比均在品种间存在显著差异.     

对金属化学活泼性的理论讨论

用化学热力学理论和电离能概念对碱金属Li、Na、K、Rb、Cs等元素的化学活泼性进行了探讨，所得的两种规律既有内在联系，又有客观条件上的区别。     

西部干旱区农林复合模式下土壤养分空间变异研究——以新疆泽普县为例

[目的]摸清农林复合模式下土壤养分空间变异情况.[方法]以泽普县为例,采用GIS与地统计学相结合的方法对农林复合模式下耕层土壤(0～20 cm)的有机质、全氮、速效氮、速效磷和速效钾等5种养分要素的空间变异特征进行分析;并与二次土壤普查结果对比分析研究土壤养分变化.[结果]研究区耕层土壤各养分含量呈正态分布,变异性表现为:速效磷＞速效钾＞碱解氮＞全氮＞有机质;全氮、有机质变异函数曲线符合指数模型,碱解氮、速效磷、速效钾的变异函数曲线符合线性无基台模型.从地理位置上看,5种土壤养分含量总体分布呈现西高东低、南北低、中间高的趋势.与1982年相比,除速效钾外,其他4种养分土壤含量都有不同程度的增加,其中速效磷的增加幅度最大.[结论]研究区内土壤养分含量属于中等偏低水平,应增加有机肥的投入,在重视施用氮磷化肥的基础上,也必须重视钾肥施用,培肥土壤,从而保障耕地的可持续利用和发展.     

不同品种烤烟主要品质和安全性指标分析

对烤烟RG17、中烟90、K346、G80的C3F烟叶中水溶性糖、钾、总氮、烟碱、石油醚提取物、总挥发酸和总挥发碱等品质指标和烟气焦油、稠环芳烃化合物等安全指标进行分析．结果表明：K346的烟碱、石油醚提取物、总挥发碱含量相对较高,RG17的钾含量相对较高,G80的总挥发酸含量较高,而总氮含量相对较低．焦油释放量较高的品种为K346,但该品种苯并[α]葸、Chrysene、苯并[α]芘3种稠环芳烃含量最低;中烟90的焦油释放量虽然较低,但其稠环芳烃化合物含量最高．     

脱硫石膏改良碱化土壤对土壤重金属环境的影响

脱硫石膏中的主要成分硫酸钙能与碱性土壤中的交换性Na+进行反应以改良碱性土壤。采集了10个燃煤火力发电厂的脱硫石膏样品进行测试分析,结果表明不同电厂脱硫石膏的硫酸钙含量和砷、汞、铅、铬、镉重金属元素含量存在差异,其硫酸钙含量在51.8~89%之间,重金属含量基本低于适用于耕地的国家土壤环境质量二级标准(GB15618-1995)。利用这些脱硫石膏改良碱化土壤并种植油葵,连续五年监测土壤中的重金属含量,结果表明利用脱硫石膏改良碱化土壤不影响重金属的含量,为今后脱硫石膏改良盐碱地的大面积示范推广提供了安全可靠的依据。     

Solvated electrons in high-temperature melts and glasses of the room-temperature stable electride [Ca₂₄Al₂₈O₆₄]⁴⁺·4e⁻

Solvated electrons in alkali metal-ammonia solutions have attracted attention as a prototype electronic conductor and chemical reducing agent for over a century. However, solvated electrons have not been realized in a high-temperature melt or glass of an oxide system to date. We demonstrated the formation of persistent solvated electrons in both a high-temperature melt and its glass by using the thermally stable electride [Ca(24)Al(28)O(64)](4+)·4e(-) (C12A7:e(-)) and controlling the partial pressure of oxygen. The electrical and structural properties of the resulting melt and glass differ from those of the conventional C12A7:O(2-) oxide, exhibiting metallic and hopping conduction, respectively, and a glass transition temperature that is ~160 kelvin lower than that of C12A7:O(2-) glass. Solvated electrons reside in cage structures in C12A7:e(-) and form a diamagnetic paired state.     

古田水蜜桃园地土壤现状探析

摘要：为了解本县水蜜桃园地作物土壤养分，探讨园地土壤养分供应情况。在水蜜桃作物土壤上,共采集土壤样品2635个。调查结果说明，水蜜桃园地土壤有机质含量为22.7g/kg、碱解氮、有效磷、速效钾的含量分别是136、37.6、66.7mg/kg、微量元素有效硼的含量为0.16mg/kg、土壤pH值为5.0。水蜜桃园地土壤有机质含量丰富水平的占94.2%、碱解氮含量属于的中等水平是94.2%、有效磷含量达丰富水平的占87.3%，84.3％土壤的速效钾缺乏、微量元素有效硼的缺乏样品达96.21％。所以提高有机质含量和改良土壤酸度与增施钾肥适施硼肥，要作为本县水蜜桃园地土壤改善养分供应的最根本措施。     

藏东南地区农业示范园区设施果蔬土壤肥力特性研究

分析藏东南地区农业示范园区设施果蔬土壤有机质、全氮、碱解氮、硝态氮、速效磷、速效钾、土壤酸碱度在不同土层、不同棚龄的累积状况。结果表明：大棚土壤肥力与大田有很大差别,且随着大棚种植年限的增加均有不同程度的增长;大棚有机质、全氮、速效磷含量增加1倍;土壤碱解氮增加2倍,次层土壤硝态氮增加近10倍;土壤速效钾在表层增加;土壤pH逐年下降,有酸化的趋势。     

大理烟区红花大金元烤烟化学成分变异分析

[目的]对大理烟区红花大金元烤烟的主要化学成分进行变异分析。[方法]从区域、年际、部位3个方面分析大理烟区红花大金元烤烟化学成分的变异情况。[结果]大理红花大金元烤烟总糖、还原糖含量总体较高,钾含量较低,氯含量变异性较大;大理烟区红花大金元烤烟化学成分存在地区差异,地区化学稳定性较差;不同年份烤烟的总糖、还原糖含量较稳定,其他指标表现不稳定;不同部位的烤烟总植物碱、钾、糖碱比、氮碱比差异达到极显著水平。[结论]南涧地区红花大金元烤烟化学成分整体比较协调,是大理烟区红花大金元最好的产区;中部叶的化学协调性较好。