Enrichment of adenosine using thermally responsive chromatographic materials under friendly pH conditions

A thermally responsive boronate affinity chromatographic material, which showed thermal sensitivity, had been successfully applied for the enrichment and separation of cis‐diol‐containing compounds, and the capture and release process could be facilitated by adjusting the temperature. However, in this system, the pH of the mobile phase must be higher than 9.8, and alkaline media can lead to the degradation of labile compounds; the use of silica beads also limits its use. In this study, thermally responsive boronate affinity chromatographic material, namely poly(N‐isopropylacrylamide‐co‐N‐acryloyl‐3‐aminophenylboronic acid) grafted silica, was successfully prepared by atom transfer radical polymerization. Its structure was confirmed by IR spectroscopy and the graft ratio was 20.8%, determined by thermogravimetric analysis. Furthermore, the capture/release of adenosine, a cis‐diol, was performed from pH 5.0–9.0 and 10–50°C. The elution of adenosine was remarkably retarded at decreased temperatures and adenosine could be captured completely at 10°C at pH values of 5.0–9.0. The enrichment of adenosine could be achieved by simply changing the temperature from 10 to 50°C. Therefore, this material not only improved the stability of the silica, but was also suitable for the capture of oxidation‐sensitive biological analytes. Moreover, it could be used for the enrichment of cis‐diol‐containing compounds in LC with MS.     

15N/14N Isotopic Exchange in the Dissociative Adsorption of N2 on Tantalum Nitride Cluster Anions Ta3N3-

Adsorption and activation of dinitrogen (N₂) is an indispensable process in nitrogen fixation. Metal nitride species continue to attract attention as a promising catalyst for ammonia synthesis. However, the detailed mechanisms at a molecular level between reactive nitride species and N₂ remain unclear at elevated temperature, which is important to understand the temperature effect and narrow the gap between the gas phase system and condensed phase system. Herein, the ¹⁴N/¹⁵N isotopic exchange in the reaction between tantalum nitride cluster anions Ta₃¹⁴N₃^- and ¹⁵N₂ leading to the regeneration of ¹⁴N₂/¹⁴N¹⁵N was observed at elevated temperature (393-593 K) using mass spectrometry. With the aid of theoretical calculations, the exchange mechanism and the effect of temperature to promote the dissociation of N₂ on Ta3N3? were elucidated. A comparison experiment for Ta₃¹⁴N₄^-/¹⁵N₂ couple indicated that only desorption of ¹⁵N₂ from Ta₃¹⁴N₄¹⁵N₂^- took place at elevated temperature. The different exchange behavior can be well understood by the fact that nitrogen vacancy is a requisite for the dinitrogen activation over metal nitride species. This study may shed light on understanding the role of nitrogen vacancy in nitride species for ammonia synthesis and provide clues in designing effective catalysts for nitrogen fixation.     

Understanding the thermal stability of human serum proteins with the related near-infrared spectral variables selected by Monte Carlo-uninformative variable elimination

Understanding the thermal stability of the proteins in human serum is essential since human serum is the important source of pharmaceutical proteins. Near-infrared (NIR) spectroscopy was applied to the investigation of thermal changes in secondary structure and hydration of human serum proteins. However, as a multicomponent system, the overlap of the broad NIR bands makes the structural analysis very difficult directly using the spectra of serum samples. Therefore, continuous wavelet transform (CWT) was used to improve the resolution of NIR spectra, and Monte Carlo-uninformative variable elimination (MC-UVE) method was applied to the selection of the variables associated with the proteins for the structural analysis. The variables (5956, 5867, 5815, 5747, 4525, 4401, 4359 and 4328 cm^-1) related to protein secondary structures and those (7074, 6951, 6827 and 6700 cm^-1) connected with water species were selected. Then, the thermal stability was analyzed through the intensity variations of the selected variables with temperature from 30 ℃ to 80 ℃. It was found that the variation of the spectral variables related to both α-helix and β-sheetchanges apparently around 60 ℃, indicating the beginning of the thermal denaturation and the transition from α-helix to β-sheet. Moreover, an obvious change was found around 60 ℃ for the content of the water specie S₃, i.e., the water cluster containing three hydrogen bonds. The result demonstrates that MC-UVE can identify the protein-related NIR spectral variables, and the water species may be a marker for investigation of the structural change of proteins in biochemical systems.     

Broadband reflective liquid crystal films induced by facile temperature-dependent coexistence of chiral nematic and TGB phase

A wide pitch gradient covering the near infrared region (750.0–2500.0 nm) were facilely obtained by simple controlling temperature difference to LC mixtures with a twist grain boundary (TGB)–N* phase transition. After the pitch gradient formed, the structure of broad reflective bandwidth was fixed through polymerisation of monomers in mixtures by UV irradiation. It was found that the temperature difference between the up and down side of the samples was critical to form wide-pitch gradient distribution. Additionally, the reflection wavelength and bandwidth of films could be adjusted by the applied temperature difference with the widest bandwidth up to 1750 nm. This simple method for the preparation of broad reflective films was expected to be used in the fields like architectural energy conservation or infrared shield.     

ZIF-8衍生的具有可控氧空位的ZnO对光催化去除NO的增强及毒性NO2形成的抑制

氧化锌作为一种半导体材料,具有合适的能带结构位置,高催化效率,低成本和环境可持续性,因而广泛用于光催化领域.然而,由于氧化锌的宽带隙,可见光吸收能力差以及光生电子-空穴对的快速复合,极大地影响了其光催化效率.通过引入氧空位调控光催化剂的结构被证明是一种可以改善光生载流子的分离,从而提高光催化性能的有效方法.本文以ZIF-8为前驱体,采用两步煅烧法合成了具有不同浓度氧空位分布的ZnO纳米光催化剂,通过X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、紫外-可见漫反射光谱(UV-Vis DRS)、X射线光电子能谱(XPS)、电子顺磁共振(EPR)、荧光光谱仪(PL)等手段系统地分析了合成的光催化剂的理化性质,并评价了它们在可见光下光催化氧化去除NO反应性能.EPR结果表明,样品中氧空位的浓度取决于温度处理的过程.通过两步煅烧法得到氧化锌中氧空位的含量高于一步直接煅烧法所得的样品.此外,随着煅烧温度升高,合成的氧化锌晶格越完好,其氧空位含量越少.UV-Vis DRS结果表明,两步煅烧法合成的ZnO与商业的ZnO及一步法直接煅烧合成的ZnO相比,其吸光范围从紫外光拓展到了可见光,表现出了更加优异的吸光性能.光催化反应结果表明,与商业氧化锌和一步直接煅烧法所得样品相比,两步煅烧法合成的样品表现出了更优异的光催化去除NO性能,并抑制了中间产物毒性NO2的产生,促进了NO的深度氧化.具体反应路径为:在光照过程中,光生电子很容易被氧空位俘获,与O2反应产生更多的超氧自由基(·O2^-),从而将NO氧化成最终的产物硝酸盐.尤其有趣的是,先在350 ℃煅烧2小时再400℃煅烧1小时的两步法样品Z 350-400的NO去除效率分别比一步法样品Z 400(400℃煅烧)和商用ZnO高出1.5和4.6倍.这表明以MOF材料衍生的具有适当量氧空位的金属氧化物为一种高效去除NO的光催化剂具有很好的应用前景.     

Pressure-dependent viscosity of powder injection moulding compounds

A single piston capillary rheometer was modified by the addition of a second chamber with a restricting valve (developed at the Polymer Centre, Zlín, Czech Republic), which provides backpressure and increasing the pressure in the melted material during the flow through the die. The Carreau–Yasuda model was employed to fit the measured viscosity data and determine the temperature and pressure coefficients for polyolefin based binder and its compounds with carbide powder. Both temperature and pressure sensitivity coefficients are largely dependent on the structure of a polymer, which should be taken into account for binder-formation’s development. Increasing the loading level of the powder in the compound diminishes the pressure sensitivity of their flow properties.     

Temperature spectra from a turbulent thermal plume by ultrasound scattering

This paper reports the results of a study on temperature inhomogeneities conducted on a thermal plume by using ultrasound scattering as a non-intrusive measurement technique. The plume rises from a metallic disk which can be heated up to 800 °C. The working fluid is air at atmospheric pressure. In the measurement technique, an incoming ultrasound wave is emitted towards the thermal plume. The incident wave is scattered because of non-linear couplings with the flow instabilities present in the measurement region. The scattered wave carries information about those flow instabilities. The technique allows for the retrieving of this information. The shape of the obtained spectrum of temperature fluctuations as a function of wave vector modulus is consistent with previous theoretical analysis. Three qualitatively different regions were identified: first, a production region characterized by a q² law; secondly, a region with behavior as per q⁻³ associated with a buoyancy region and; finally, a dissipation region associated with a q⁻⁷ law. These spectral regions characterize the energy transfers mechanisms among the length scales of flow investigated here. A coefficient of anisotropy γ was defined to analyze anisotropic features of the flow.     

沿垂等温平板的自然对流问题的近似解析解

本文用加权残值得到了沿垂等温平板的自然对流问题的近似解析解。和已有准确解的比较表明，在平板表面附近，近似解有很好的精度，而且速度场的精度比温度场更好一些。文末还对配域法的准收敛问题作了说明。     

软土地区人工冻土无侧限瞬时抗压强度的试验研究

冻结法施工在上海隧道建设中(如隧道旁通道、地下泵房等的设计与施工)得到广泛应用,也曾引发过严重的地质灾害(如上海地铁4号线外滩段的地质灾害)。因此安全、经济、合理地将冻结法用于上海软土地区隧道建设中已经成为上海工程建设中的一个重要的研究课题。本文以上海复兴东路越江隧道旁通道冻结法施工中遇到的第⑥层粉质粘土及第⑦层粉细砂为研究对象,针对设计冻结壁重要强度参数无侧限瞬时抗压强度,进行了室内试验研究,揭示了两种土的冻结强度随温度的变化关系,同时研究了粉细砂的冻结强度随含水率的变化规律。     

Limitations of temperature measurements with holographic interferometry in the presence of pressure variations

In recent years oscillatory flows have shown to be a promising strategy to enhance heat transfer. However, the mechanisms underlying oscillatory heat transfer enhancement are not yet completely understood. One problem, when investigating heat transfer in oscillatory flows experimentally, is to resolve the temperature distribution as a function of time. This is one reason that most studies reported in the literature so far were restricted to frequencies of a few hertz. As shown in this paper, an appropriate tool to investigate oscillatory heat transfer phenomena at higher frequencies (1000 Hz) is real time holographic interferometry (HI) combined with high-speed cinematography. In the present paper HI was applied to study acoustically driven flow. To apply HI to such a physical situation it was necessary to expand its applicability to cases where changes in the refractive index are caused not only by temperature changes but also by pressure variations. For this purpose a new evaluation formula that accounts for pressure variations was derived. On the example of the acoustic field, we discuss the impact of the pressure variations on temperature measurements. Additionally, an image processing algorithm was developed that allows the measurement of time dependent temperature distributions. The uncertainties of the temperature measurements introduced by the image processing algorithm were found to be in the range of thermocouple measurements.