Differential thermal analysis of low-rank coals

Differential thermal analysis (DTA) of low-rank coals of high lignite to subbituminous rank from coal mines of Pakistan is reported. The studies carried out in dynamic oxygen atmosphere indicate that the exothermic reactions occur between 300 and 650°C and that the samples undergo stepwise oxidation of the organic matter rather than a continuous process as indicated by the pattern of shoulders from 250 to 350°C accompanying the main peak around 450°C. The effect of heating rate, particle size and volatile content was also studied in relation to oxidation. The results show that the increase in heating rate from 10 to 80 deg min⁻¹ results in a marked shift in all the events in the DTA curve towards higher temperatures. As for the effect of particle size, the DTA records of 100–75, 150–100, 250–150 μm and greater than 250 μm fractions show that the magnitude and position of shoulder peaks are more sensitive to changes in particle sizes compared to the main peak. The curves recorded to study the effect of changing volatile content of samples between 30–40% indicate a complex pattern of shoulders accompanying the main peak. In general, the number of shoulder peaks increases with increasing volatile content of samples but their positions do not follow any trend. The DTA curves recorded in nitrogen contain ill-de-fined oxothermic effects over the 300–750°C temperature range. These curves consist of an endothermic peak around 150°C, two exothermic shoulders in the temperature region 300–400°C and a large broad exothermic whip between 500 and 700°C. The heating rates have similar effects as in oxygen while the particle size do not influence the results. It has been concluded that the organic matter in the coals studied here is extremely heterogeneous with different burning characteristics; as a result it is very difficult to quantify energy changes associated with poorly resolved exothermic events along the DTA curve. The effects also dominate in N₂ atmosphere thus making identification of mineral matter difficult. The overall pattern of DTA events in oxygen can be correlated with the heating rate, particle size and volatile content of samples.     

低压气相色谱薄涂柱的热力学特性及应用

本文研究了低压气相色谱固定相新戊二醇己二酸聚酯（NPGA）薄涂柱的热力学特性，测定了最佳色谱条件下的溶解焓（△H）、比保留体积（Vg)气化热（△Hs），并与常压色谱柱进行了比较，应用于污水样品分离，效果良好。     

Pencil sketch graphene films as solid lubricant on steel surface: Observation of transition to grapehene/amorphous carbon

During recent years, graphene as a solid lubrication material have been thoroughly studied under nano or micro scales, but rarely reported at industrial conditions. In present work, graphene films as solid lubricant were prepared on the surface of 201 stainless steel substrates by pencil sketch. And then the friction tests from 5 to 65 N were carried out via a homemade tribo-tester and used GCr15 balls (ø = 5 mm) as friction pairs. Not surprisingly, graphene films cannot bear the loads beyond 5 N, but interestingly, via gradually increasing the loads, graphene films show prominent load performance and steady state of friction coefficients at about 0.12 while the loads varied from 5 to 65 N. Compared with bare steel, the coefficient of graphene films reduced by about 80%, and the wear volume reduced to 1/28 when variable load (from 5 N to 30 N) were applied. Raman spectra shown that the structure of graphene had been changing into diamond-like carbon films with graphene distributed inside, which was confirmed by HRTEM that graphenes were coming with amorphous carbon. Considering the roughness of steel wafers (170 nm), one can speculate that, with graphene films' protection, the steel has no abrasion but plastic deformation instead. It is concluded that the shearing force induced the film densification via sp² to sp³ changing that enforced cross-linking. This cross-linking carbon matrix was responsible for high load bearing and the graphene exfoliated into graphene under shearing force contribute to low steady-state friction. Benefiting from sketch, one can get a lubrication film on any substrates with complex topography, our results shed light on the growth of graphene films for industrial use.     

Hydrogen generation from methanol reforming under unprecedented mild conditions

A homogeneous catalyst [Cp^*Rh(NH₃)(H₂O)₂]³⁺ has been found for the clean conversion of methanol and water to hydrogen and carbon dioxide.The simple and easily available reaction steps can circumvent the formation of CO,therefore,making it possible to avoid inactivating catalysts and contaminating the hydrogen fuel.Different from conventional reforming method for hydrogen production,no additional alkaline or organic substances are required in this method.Valuable hydrogen can be obtained under ambient pressure at 70℃,corresponding TOF is 83.2 h^-1.This is an unprecedented success in reforming methanol to hydrogen.Effects of reaction conditions,such as reaction temperature,initial methanol concentration and the initial pH value of buffer solution on the hydrogen evolution are all systematically investigated.In a certain range,higher reaction temperature will accelerate reaction rate.The slightly acidic condition is conducive to rapid hydrogen production.These findings are of great significance to the present establishment of the carbon-neutral methanol economy.     

新型含酯基结构的具有低线膨胀系数和吸水性的聚酰亚胺的合成

将2种主链中含有酯基结构的二胺单体:二(4-氨基苯基)对苯二甲酸酯(BPTP)和4-氨基苯基-4-氨基对苯甲酸酯(APAB),与几种常见的酸酐聚合,合成了一系列主链中含有酯基结构的新型聚酰亚胺膜材料.结果表明,所制备的聚酰亚胺薄膜表现出优良的热稳定性、机械性能和低吸水性,其中聚合物的表观玻璃化转变温度高达526℃,在空气和N2气气氛下5%的热失重温度分别在498和507℃以上,表明薄膜具有非常优异的热性能.由于聚合物主链中引入酯基结构而表现出低的线膨胀系数和吸水率.     

Low gamma counting for measuring NORM/TENORM with a radon reducing system

A detection system for counting low levels of gamma radiation was built by upgrading an existing rectangular chamber made of 18 metric tonne of steel fabricated before World War II. The internal walls, the ceiling, and the floor of the chamber are covered with copper sheets. The new detection system consists of a stainless steel hollow cylinder with variable circular apertures in the cylindrical wall and in the base, to allow introduction of a NaI (Tl) crystal, or alternatively, a HPGe detector in its interior. This counting system is mounted inside the larger chamber, which in turn is located in a subsurface air-conditioned room. The access to the subsurface room is made from a larger entrance room through a tunnel plus a glass anteroom to decrease the air-exchange rate. Both sample and detector are housed inside the stainless steel cylinder. This cylinder is filled with hyper pure nitrogen gas, before counting a sample, to prevent radon coming into contact with the detector surface. As a consequence, the contribution of the ²¹⁴Bi photopeaks to the background gamma spectra is minimized. The reduction of the gamma radiation background near the detector facilitates measurement of naturally occurring radioactive materials (NORM), and/or technologically enhanced NORM (TENORM), which are usually at concentration levels only slightly higher than those typically found in the natural radioactive background.     

小儿喘息性疾病与低钙血症

用硝苯吡啶治疗了５２例喘息状态并低钙血症病儿，发现不补钙剂也能治愈。     

婴儿低镁血症32例分析

镁是人体内重要的阳离子。报道了南京市第三医院近两年来对３２例婴儿低镁血症的诊断和治疗，并讨论了该症的病因和治疗方法。     

小角躺滴法测定低界面张力

在测定界面张力,特别是测定低界面张力的各种方法中,躺滴法占有相当重要的位置。但一般的躺滴法都要求获得赤道半径(图1中的x_e)数据.故躺滴与基底之间的接触角必须大于90°.这在低界面张力体系中常常难以实现,致使躺滴法的应用受到限制。本文提出一种新的躺滴法,它不依赖于接触角的大小,只需测定躺滴轮廓线上两个相关点的坐标,根据所给数值表即可计算出界面张力,从而为躺滴法应用于低界面张力,特别是     

Synthesis and properties of acceptor-donor-acceptor molecules based on oligothiophenes with tunable and low band gap

A series of acceptor-donor-acceptor molecules (DCN3T, DCN5T and DCN7T) based on oligothiophenes with low band gap are synthesized. The UV-vis absorption spectra of solution show that the introduction of electron-accepting groups results in a shift of the absorption onset towards longer wavelengths. Moreover, the optical spectra of their films show a large bathochromic shift and broadening of the bands with respect to the spectra in solution. The optical band gaps of film of these A-D-A molecules are 1.90, 1.74 and 1.68 eV, respectively. Cyclic voltammetry shows that all these compounds present a reversible first oxidation process whose potential decreases with the lengthening of oligothiophene cores. Electrochemical band gaps are 2.14, 1.88 and 1.71 eV, respectively.     

有应用前景的低感高能炸药研究进展

概述了有应用前景的高能低感炸药的研究成果,从改善现有高能炸药晶体品质和合成新的高能低感炸药方面,总结了大幅度降低炸药冲击波感度的研究现状。     

Novel reduced pressure-balance syringe for chromatographic analysis

When withdrawing a fluid sample (for additional chromatographic analyses) from an apparatus operated at a reduced pressure, a typical syringe proves to be ineffective (even if it is equipped with a gas tight plunger). It simply does not create enough pressure differential to remove a fluid sample from a reduced pressure environment. We encountered such a situation as part of efforts to extend the operation of the advanced distillation curve protocol to reduced pressures. The problem was solved by the development of a pressure balance syringe that allows reliable and precise sampling from an apparatus operating at sub-ambient pressures. This new device uses an external vacuum source to evacuate a syringe barrel, allowing a user to withdraw fluid samples from environments with pressures as low as 0.5kPa. To demonstrate the operation of the newly developed device, distillate analyses were performed on two fluids at low pressure: a predefined validation mixture, and a commercial soy based biodiesel fuel. The pressure balance syringe was used successfully for sampling in both cases. The use of the pressure balance syringe is not limited to reduced pressure distillations; indeed it can be used for a variety of applications in which chemical/compositional analyses are desired on a fluid contained in a reduced pressure environment.     

Heraeus CHN-Rapid元素分析仪的低含量测定

研究用Heraeus CHN-Rapid元素分折仪低含量测定时在样品制备,检测方法和数据处理上的一些改进方法及测定结果。对于含量在0.5%以下样品,绝对误差≤±0.005%,标准偏差≤±0.00%。     

Characterization of a 2.6 μm Kinetex porous shell hydrophilic interaction liquid chromatography column in supercritical fluid chromatography with a comparison to 3 μm totally porous silica

The first systematic study of the performance of a porous shell, hydrophylic interaction liquid chromatography (HILIC) column in supercritical fluid chromatography (SFC) is presented. Observed efficiency on 2.6-μm porous shell particles exceeded all reports using UHPLC on 100-mm long columns packed with <2-μm totally porous particles. A Kinetex 4.6 × 150 mm, 2.6 μm HILIC column significantly outperformed a 3 μm Luna totally porous silica of the same length and diameter. A 17 component, low molecular weight test mix, consisting of a range of small drug-like molecules was separated isocratically on each column, with similar selectivity, but the porous shell column required ½ the time (≈2 min vs. 4 min), with almost 50% higher efficiency. Even little retained compounds (k < 0.5) exhibited more than 30,000 plates under some conditions. Reduced plate heights were higher than previously reported on porous shell particles in both HILIC and rHPLC, with the lowest value of 1.62. Significant fronting was sometimes observed. The cause of the fronting was not determined. The least symmetrical peaks showed the highest apparent efficiency. Pressure drop at optimum velocity (2.5 ml/min) and low modifier concentrations was <60 bar, and only exceeded 250 bar at near double optimum flow and 65% modifier. Peak widths were mostly just over 0.01 min (20 Hz) wide. There was a loss of efficiency when the injection volume was increased. The chromatograph was shown to have extremely low extra-column dispersion, on the order of 5–10 μL², which is also the lowest reported in an SFC, in spite of using standard components. This is likely due to turbulent flow in the tubing and fittings.     

Enrichment of low-abundant serum proteins by albumin/immunoglobulin G immunoaffinity depletion under partly denaturing conditions

We present a simple protocol for affinity depletion to remove the two most abundant serum proteins, albumin and immunoglobulin G (IgG). Under native conditions, albumin/IgG were efficiently removed and several proteins were enriched as shown by two-dimensional electrophoresis (2-DE). Besides that, partly denaturing conditions were established by adding 5 or 20% acetonitrile (ACN) in order to disrupt the binding of low-molecular-weight (LMW) proteins to the carrier proteins albumin/IgG. 2-DE results showed that the total number of detected LMW proteins increased under denaturing conditions when compared to native conditions. Interestingly, the presence of 5% ACN in serum revealed better enrichment of LMW proteins when compared to 20% ACN condition. Seven randomly distributed spots in albumin/IgG depleted serum samples under 5% ACN condition were picked from the 2-DE gels and identified by mass spectrometry (MS). The intensity of five LMW protein spots increased under denaturing conditions when compared to native conditions. Three of the seven identified spots (serum amyloid P, vitamin D-binding protein, and transthyretin) belong to a group of relatively low-abundant proteins, which make up only 1% of all serum proteins. The method presented here improves the resolution of the serum proteome by increasing the number of visualized spots on 2-D gels and allowing the detection and MS identification of LMW proteins and proteins of lower abundance.     

类液体动态界面材料：近期应用进展

类液体表面是接枝了高度柔性分子刷从而表现出类液体特性的表面。典型的类液体表面一般通过在平坦固体表面上共价接枝具有极低玻璃化转变温度的聚合物分子刷（其玻璃化转变温度一般在零下100 ℃以下）制备而成。由于所接枝分子链具有类似流体的高度动态特性,能自由旋转与运动,各种极性或非极性液体在这类被称为“类液体”或“准液体”的表面上粘附力低,易滑落,表现出极低的接触角滞后。传统上,对这类表面的研究主要限于简单的疏水及疏油应用。最近几年,国内外课题组相继报道了关于类液体表面的一些非常独特的界面物理化学特性;对其功能和应用的研究,也从简单的疏水、疏油,拓展到微观无损输运、防垢、除冰、冷凝传热和高性能膜分离等领域。基于类液体表面功能化的类液体动态界面材料也因而成为一类具有广阔应用前景的新兴材料体系。本文将在介绍类液体表面概念的基础上,重点介绍类液体动态界面材料最新的功能和应用研究成果,并对其未来研究和应用空间进行展望。     

Low Bandgap 2D Perovskite Single Crystal with Anomalous-large Charges/ions Collection Ratio for Ultra-sensitive and Stable X-ray Detectors

The low-dimensional halide perovskites have attracted increasing attention due to their improved moisture stability, reduced defects, and suppressed ions migration in many optoelectronic devices such as solar cells, light-emitting diodes, X-ray detectors, and so on. However, they are still limited by their large band gap and short charge carriers’ diffusion length. Here, we demonstrate that the introduction of metal ions into organic interlayers of two-dimensional (2D) perovskite by cross-linking the copper paddle-wheel cluster-based lead bromide ([Cu(O₂C−(CH₂)₃−NH₃)₂]PbBr₄) perovskite single crystals with coordination bonds can not only significantly reduce the perovskite band gap to 0.96 eV to boost the X-ray induced charge carriers, but can also selectively improve the charge carriers’ transport along the out-of-plane direction and blocking the ions motion paths. The [Cu(O₂C−(CH₂)₃−NH₃)₂]PbBr₄ single-crystal device can reach a record charges/ions collection ratio of 1.69×10¹⁸±4.7 % μGy_air⁻¹ s, and exhibit a large sensitivity of 1.14×10⁵±7% μC Gy_air⁻¹ cm⁻² with the lowest detectable dose rate of 56 nGy_air s⁻¹ under 120 keV X-rays irradiation. In addition, [Cu(O₂C−(CH₂)₃−NH₃)₂]PbBr₄ single-crystal detector exposed to the air without any encapsulation shows excellent X-ray imaging capability with long-term operational stability without any attenuation of 120 days.     

氢化物发生-原子荧光光谱法测定低合金钢中微量砷

采用氢化物发生-原子荧光光谱法测定低合金钢中砷的含量。样品经盐酸-硝酸混合酸消解,以盐酸(5+95)溶液为反应介质,15g·L~(-1)硼氢化钾-2g·L~(-1)氢氧化钾的混合溶液为还原剂,采用柠檬酸作为掩蔽剂。砷的质量浓度在60.0μg·L~(-1)以内与荧光强度呈线性关系,方法的检出限(3s/k)为0.023μg·L~(-1)。应用此法对标准钢样进行了分析,测定结果与认定值相符合,可满足钢铁中微量砷(质量分数0.001%～0.04%)的测定要求。     

Low emissivity Ag/Si/glass thin films deposited by sputtering

Si was deposited on the glass substrate as an interlayer for the 2-D growth of Ag thin films because Si has a strong binding energy against Ag and can lead to a negative surface energy change in Ag/glass. The Si interlayer induced an extremely smooth and flat Ag surface, which effectively reduced the resistance and enhanced the reflectance in the IR region. In particular, Ag (9 nm)/Si (3 nm)/glass showed 0.074 emissivity and ∼91% reflectance in the IR region with 67% transmittance in the visible region.     

Low-temperature impedance and dielectric relaxation of NiO nanocrystals

Low-temperatures impedance and dielectric properties of NiO nanocrystals as a function of particle size were investigated by alternative current impedance spectra. It is found that NiO nanocrystals showed distinct bulk and grain boundary conductions at low temperatures, which were almost the same within the experimental error during the decreasing and the subsequent increasing temperature processes. This result indicated that no further protons are formed during these temperature cycles. The conductivities are also highly dependent on the particle size. As the particle size reduced, the conductivities of NiO nanocrystals increased to show a maximum. Further particle size reduction less than 8.9 nm led to a sudden decrease in conductivity. The corresponding activation energies showed a minimum with varying the particle size. These observations were most likely due to the balance between the concentration of charge carriers, holes and protons.