高效液相色谱-电喷雾串联质谱法测定畜禽粪便中四环素类抗生素

建立了高效液相色谱-电喷雾串联质谱法(HPLC-MS/MS)测定畜禽粪便中四环素类抗生素的分析方法。样品经甲醇-乙酸-水(体积比6∶3∶1)溶液提取,OASIS HLB小柱净化后,采用Waters Symmetry C18色谱柱(150×3.9mm,5μm)进行分离,以0.3%甲酸水溶液-0.3%甲酸乙腈溶液梯度洗脱,电喷雾正离子模式多反应监测(MRM)模式定量分析。在优化的色谱条件下,四环素、土霉素和金霉素在0.05~1.0mg/L范围内具有良好的线性,其检出限分别为0.025、0.084、0.098mg/kg;样品回收率为80%~103%。实验结果表明,该方法较液相色谱法具有更高的准确性和灵敏度,可满足畜禽粪便中四环素类抗生素残留的检测要求。     

A Hydrogen-Deficient Nickel–Cobalt Double Hydroxide for Photocatalytic Overall Water Splitting

Developing highly efficient and low-cost photocatalysts for overall water splitting has long been a pursuit for converting solar power into clean hydrogen energy. Herein, we demonstrate that a nonstoichiometric nickel–cobalt double hydroxide can achieve overall water splitting by itself upon solar light irradiation, avoiding the consumption of noble-metal co-catalysts. We employed an intensive laser to ablate a NiCo alloy target immersed in alkaline solution, and produced so-called L-NiCo nanosheets with a nonstoichiometric composition and O²⁻/Co³⁺ ions exposed on the surface. The nonstoichiometric composition broadens the band gap, while O²⁻ and Co³⁺ ions boost hydrogen and oxygen evolution, respectively. As such, the photocatalyst achieves a H₂ evolution rate of 1.7 μmol h⁻¹ under AM 1.5G sunlight irradiation and an apparent quantum yield (AQE) of 1.38 % at 380 nm.     

Electrochemical Phase Evolution of Metal-Based Pre-Catalysts for High-Rate Polysulfide Conversion

In situ evolution of electrocatalysts is of paramount importance in defining catalytic reactions. Catalysts for aprotic electrochemistry such as lithium–sulfur (Li-S) batteries are the cornerstone to enhance intrinsically sluggish reaction kinetics but the true active phases are often controversial. Herein, we reveal the electrochemical phase evolution of metal-based pre-catalysts (Co₄N) in working Li-S batteries that renders highly active electrocatalysts (CoS_x). Electrochemical cycling induces the transformation from single-crystalline Co₄N to polycrystalline CoS_x that are rich in active sites. This transformation propels all-phase polysulfide-involving reactions. Consequently, Co₄N enables stable operation of high-rate (10 C, 16.7 mA cm⁻²) and electrolyte-starved (4.7 μL mg_S⁻¹) Li-S batteries. The general concept of electrochemically induced sulfurization is verified by thermodynamic energetics for most of low-valence metal compounds.     

焙烧温度对1,4-丁烯二醇加氢Cu/Raney-Ni催化剂结构和性能影响

在Ni-Al合金粉上浸渍硝酸铜溶液,经不同温度焙烧得到Cu改性Ni-Al合金粉,采用质量分数10%NaOH溶液浸渍上述改性合金粉得Cu/Raney-Ni催化剂。采用EDX、XRD、N_2吸附-脱附、TEM和NH_3-TPD等手段表征了Ni-Al合金粉及相应Raney-Ni催化剂的元素含量、晶体结构、孔结构特征、表面形貌和表面酸碱性,并以1,4-丁烯二醇加氢制1,4-丁二醇为探针反应,考察了焙烧温度对Raney-Ni催化剂加氢性能的影响。表征分析表明,焙烧温度500℃所制备的CRT500催化剂比表面积较大,为64.96m~2/g;弱酸中心比例较高,达81.2%。结果表明,焙烧温度升高,BED可实现完全转化,BDO选择性和收率均先升高后降低。其中,CRT500加氢性能较好,BED转化率为100.00%,BDO选择性为61.88%。进一步升高焙烧温度,催化剂RCT550和RCT600的BDO选择性和收率反而降低,这是由于高温下催化剂易发生团聚或烧结。结合催化剂表征可知,CRT500具有较好的加氢性能,这与该催化剂具有合适的Ni/Al物质的量比(3.84)、弱酸中心所占比例较大和活性组分Ni分散性好等因素有较大关联。     

科学计算应用程序探讨

科学计算应用程序是科学计算研究的成果集成,其研制不同于通常的计算机应用软件.随着科学计算研究的不断深入和高性能计算机的迅猛发展,应用程序越来越依赖于实际应用和高性能计算的交叉融合,迫切需要革新程序的研制思路,发展研制方法.文章简要介绍了科学计算应用程序的主要特征,分析了应用程序面临的主要困难,探讨了研制应用程序的新思路和新方法.     

磁致伸缩-压电联合激励凹筒型发射换能器

设计制作了一种新型磁致伸缩-压电联合激励凹筒型发射换能器,采用稀土超磁致伸缩材料Terfenol-D与PZT压电陶瓷作为联合激励元件,模拟计算与实测结果均表明,与采用单一振子激励的凹筒型发射换能器相比,此种新型换能器在保持尺寸小、频率低等优点的同时,显著拓宽了工作频带并提高了辐射声功率.换能器外型尺寸为φ88 mm×316 mm,水中谐振频率1.30 kHz,-3 dB带通Q值1.43,谐振频率下发射电压响应级135.1 dB.     

The Crystallization of Poly (3-dodecyltbiophene) in an Oriented Solidification Environment

Poly (3-alkylthiophenes) (P3ATs) have made up of a family of conductive polymerswhich are soluble, fusible and processable, since the introduction of flexible alkyl sidechains"'. It is generally accepted that P3ATs can form similar layered structures. inwhich the thiophene rings possess planarity and the side chains act as spacers'-'. Whenthe number. of 'carbon atoms of alkyl side chains is more than 10, some orderlyarrangements will occur for side chains betWeen the' layers'. It has been w…     

流动注射-电感耦合等离子体发射光谱法测定天然水中的钙和镁

本文采用流动注射－电感耦合等离子体发现光谱联用技术测定了天然水中的钙、镁元素。考察了试液的雾化和曝光时间及载气压力等因素对分析信号的影响。通过与气动连续进样的对比，测出了钙、镁在流动注射进样下的分散系数。本法在测定钙、镁含量高的水性时，不需对试样进行稀释处理。对五个水样中钙、镁的分析结果与EDTA络合滴定法相吻合。     

Si-SiO2膜的椭圆偏振光谱

我们建立了椭圆偏振光谱仪装置,提出一种较简便的测定方法(测I_max,I_min,θ_min,算(ψ,Δ)-λ),并对具有不同厚度氧化硅膜的硅样品进行了测量。还在理论上计算了光谱曲线,与实验结果基本相符。最后,对比了测定膜厚的偏振光谱法与消光法。 关键词：     

异种DNA对胚胎发育的影响

有平衡器之东方蝾螈的DNA和无平衡器之黑斑蛙DNA当分别注射至黑斑蛙的受精卵内时.两者都能使受注射卵发育成的有些蝌蚪在左鳃盖上具有类似平衡器的突出物.基于这些事实,可以推论蝌蚪的类似平衡器的突出物既不是由于遗传转化,也不是平衡器的诱导而是DNA对胚胎发育的非特异性效应.