冰遇盐水实验探究和“融雪剂”问题的反思

从学生的问题出发,引导学生进行有关冰遇盐水的探究实验活动,并与"融雪剂"的问题一起进行反思,发现冰遇盐水是热量传递的过程,而"融雪剂"是与稀溶液的依数性有关。整个探究过程使学生获得学习科学的有效方法。     

利用盐泥制备醋酸钙镁融雪剂

以固废盐泥为主要原料,通过与冰醋酸反应制备了醋酸钙镁(CMA)融雪剂,通过热重-示差扫描量热(TG-DSC)和X射线衍射(XRD)对CMA样品进行了分析。依据国家标准"GB/T 23851-2009"对制备的CMA产品进行相关性能参数的测定,融雪化冰能力、pH和碳钢腐蚀率等指标均能满足要求,该方法为工业化生产低成本CMA融雪剂提供理论依据。     

化学与非致命武器

非致命武器逐渐发展成为一类重要的武器装备。目前非致命武器通常是指可以在不导致人员死亡或大量死亡及设备严重毁坏,对环境破坏程度较小的情况下,实现特定军事或某些非军事目的的武器。这些非致命武器在高技术局部战争和一些特定的反恐怖或维和行动中具有广阔的应用前景。     

贵州兴仁煤砷中毒患者的死因调查与防治

运用高分辨率等离子体质谱法(HRICP-MS)测定了贵州兴仁居民燃用煤中砷含量,并调查了煤砷中毒死者详细资料。结果显示,当地居民燃用煤中砷仍然高度富集,从1976年到2003年,贵州兴仁砷中毒患者共死亡265人,其中死于癌症人数最多,死于肝硬化、腹水的病人其次,其中大部分患者死亡时间集中在1992年以后,说明贵州兴仁煤砷中毒的远期危害逐渐暴露,煤砷中毒的预防与防治应从各个方面全面进行。     

微量元素与心血管疾病

心血管疾病是因为高级神经活动受到障碍而引起的疾病。在美国、英国、日本、挪威等工业发达的国家 ,死于心血管病的人数已列为各种死亡原因的第一位。我国一些城市的初步统计结果也不例外。据 1 972年美国的估计 ,有一百万美国居民死于心血管病 ,占国内整个死亡人数的 3 0 %。而患心血管系统疾病的人有近 3千万之多 ,几乎占全国人口的 1 5%。无论从死亡人数 ,还是从患者人数来看 ,都远远超过其他疾病。经广泛研究发现 ,镉是致高血压的重要因素之一 ;铅可使末梢血管阻力增加 ,与高血压发病有关 ;锌可对抗镉所导致的高血压和动脉硬化症 ,缺锌…     

387例病残儿死亡原因分析

为探讨病残儿死亡原因,提出干预措施,对1992—2005年在本院死亡的387例病残儿病例进行了回顾性分析。结果表明,入住本院的病残儿主要死亡原因前三位分别是出生缺陷、脑瘫和感染性疾病,死亡年龄以3岁以下病残儿为主,占87.59%。提示加强优生优育的健康教育,注意孕妇孕期和围产期保健,减少出生缺陷和脑瘫的发生率,是降低病残儿死亡率的关键。     

新型冠状病毒小分子药物的临床效果及其合成方法概述

冠状病毒是一类广泛存在且对人及家畜具有严重危害的病原体,具有较高的传播性及致死率。2019年末爆发的新型冠状病毒（SARS-CoV-2）所引发的全球疫情持续至今,累计感染人数已经超过三亿,并造成了五百多万的死亡病例。随着病毒不断变异,造成疫苗的防护效率不断下降,时刻威胁着人们的健康安全,因此针对新型冠状病毒的小分子药物的开发就显得尤为必要。本文针对一些重要的新型冠状病毒的小分子药物进行概述,介绍了它们的作用靶点、合成情况、治疗效果以及所处的开发阶段,以期为抗新冠病毒药物的研发和临床研究提供一些参考。     

冷原子吸收光谱法测定鱼体内不同组织中的汞含量

汞在水生生物体中有很强的富集效应,并可通过食物链富集进入人体,具有生物致畸、免疫毒性,神经毒性效应。1956年日本的水俣病就是典型的汞中毒事件,其中多人因误食含汞的鱼肉而死亡。鱼是人们主要的肉类食物之一,对鱼体汞含量的监     

冠状病毒抑制剂的研究进展

冠状病毒是一类广泛存在且对人及家畜具有严重危害的病原体,其中于2003年全球爆发的严重急性呼吸综合征病毒(SARS-CoV)以及2012年被发现并传播的中东呼吸综合征病毒(MERS-CoV)给人们的生命健康以及全球经济造成了严重威胁以及重大损失,特别是2019年末爆发的新型冠状病毒(SARS-CoV-2),截至目前为止已经造成了几百万的感染病例以及几十万人的死亡。可以看出,冠状病毒具有较高的传播性以及较高的致死率,时刻威胁着人们的健康安全,但是针对冠状病毒的感染目前还没有批准上市的有效药物,也没有用于预防的疫苗。本文围绕目前关于冠状病毒的潜在成药性靶点,详细介绍了针对这些靶点的具有代表性的抑制剂的结构设计及其化学合成方法,以期为目前抗冠状病毒药物的研发提供一些参考。     

微量元素与心血管病

心血管病是当前各国人群的主要死亡原因之一。1998年我国心脏病居全国居民病伤死亡的第三位（城市）和第四位（农村）、其死亡率逐年增加，我国每年死于心脏病的人数约为273万人。最常见的心血管疾病分为：     

Optimization design of the road unit in a hydronic snow melting system with porous snow

Hydronic snow melting systems are renewable and reliable to eliminate the slippery conditions on the road. In this study, a hydronic snow melting system was implemented in Harbin, China. The characteristics of porous snow were applied to develop a transient two-dimensional model, according to the experimental results. It is the first time that the snow microstructure was considered in the model for the hydronic snow melting system. Three parameters (embedded pipe depth, embedded pipe spacing, and supplied fluid temperature) were compared and analyzed to optimize the design of the hydronic snow melting system in the cold regions. The results indicated that the snow can be cleared in 4.5 h regardless of the fluctuation of parameters. The rank of influence degree was embedded pipe depth?>?supplied fluid temperature?>?embedded pipe spacing when the target was the maximum melting rate. However, the rank of influence degree changed as supplied fluid temperature?>?embedded pipe depth?>?embedded pipe spacing when the target was the average road surface temperature at the heating time of 6 h. The embedded pipe design should be the embedded pipe depth of 80 mm and embedded pipe spacing of 140 mm at the effects of thermal stress and pipe cost. The control strategy was that the supplied fluid temperature should be 298.15 K in the heating period of 0–1 h, then gradually increased to 308.15 K in the heating period of 1–4 h, and eventually decreased to 298.15 K in the heating period of 4–6 h to save energy. This work can offer a good reference for the optimization and design of hydronic snow melting systems in cold regions.

     

Influence of surface melting effects and availability of reagent ions on LDI‐MS efficiency after UV laser irradiation of Pd nanostructures

In this study, the influence of surface morphology, reagent ions and surface restructuring effects on atmospheric pressure laser desorption/ionization (LDI) for small molecules after laser irradiation of palladium self‐assembled nanoparticular (Pd‐NP) structures has been systematically studied. The dominant role of surface morphology during the LDI process, which was previously shown for silicon‐based substrates, has not been investigated for metal‐based substrates before. In our experiments, we demonstrated that both the presence of reagent ions and surface reorganization effects – in particular, melting – during laser irradiation was required for LDI activity of the substrate. The synthesized Pd nanostructures with diameters ranging from 60 to 180 nm started to melt at similar temperatures, viz. 890–898 K. These materials exhibited different LDI efficiencies, however, with Pd‐NP materials being the most effective surface in our experiments. Pd nanostructures of diameters >400–800 nm started to melt at higher temperatures, >1000 K, making such targets more resistant to laser irradiation, with subsequent loss of LDI activity. Our data demonstrated that both melting of the surface structures and the presence of reagent ions were essential for efficient LDI of the investigated low molecular weight compounds. This dependence of LDI on melting points was exploited further to improve the performance of Pd‐NP‐based sampling targets. For example, adding sodium hypophosphite as reducing agent to Pd electrolyte solutions during synthesis lowered the melting points of the Pd‐NP materials and subsequently gave reduced laser fluence requirements for LDI. Copyright © 2015 John Wiley & Sons, Ltd.     

碱熔-电感耦合等离子体原子发射光谱(ICP-AES)法测定重晶石中的铅

研究了电感耦合等离子体原子发射光谱(ICP-AES)法测定重晶石中的Pb,建立了K2CO_3-Na_2CO_3-Na_2B4O7混合熔剂熔融分解样品,同时以HCl为介质酸化溶解沉淀的方法。同时对比了熔融试剂和熔融时间两个因素的影响,结果表明混合熔剂高温熔融10min就能将重晶石中的Pb释放出来,Pb的检出限为0.033!g/mL,相对标准偏差(RSD,n=7)为0.80%~4.0%,加标回收率在93.55%~107.5%,测定范围是0.10%~10.0%。方法熔样迅速、操作简单,并且能够准确测定重晶石中的铅量,对选矿、冶炼实验有一定的指导意义。     

Spatial and temporal distribution of environmental markers from Coastal to Plateau areas in Antarctica by firn core chemical analysis

The chemical analysis of shallow firn cores sampled in coastal and plateau areas in Northern Victoria Land and along a transect from Talos Dome to Dome C (East Antarctica, Pacific Ocean sector) allowed a global view of spatial and temporal changes in chemical composition of snow depositions over the last 100 years. Variations in concentration of primary (sea spray) and secondary (biogenic emission, atmospheric inputs) source markers were observed and discussed as a function of distance from the sea and altitude.

In the stations characterized by relatively high snow accumulation rates, the sub-sampling resolution was sufficient to obtain a stratigraphic dating by using the periodical variations of seasonal markers. In these stations, a subdivision in “summer” and “winter” samples was carried out in order to study the seasonal changes of the contributions of the measured compounds to the snow composition as elevation and distance from the sea increase.

Some evidence of post-depositional effects which are able to change the original deposition of chloride and nitrate, was observed at stations with low accumulation rates. The reliability of the depth/concentration profile of these substances for reconstructing past deposition was also discussed.     

Influence of ice and snow covers on the UV exposure of terrestrial microbial communities: dosimetric studies

Bacillus subtilis spore biological dosimeters and electronic dosimeters were used to investigate the exposure of terrestrial microbial communities in micro-habitats covered by snow and ice in Antarctica. The melting of snow covers of between 5- and 15-cm thickness, depending on age and heterogeneity, could increase B. subtilis spore inactivation by up to an order of magnitude, a relative increase twice that caused by a 50% ozone depletion. Within the snow-pack at depths of less than approximately 3 cm snow algae could receive two to three times the DNA-weighted irradiance they would receive on bare ground. At the edge of the snow-pack, warming of low albedo soils resulted in the formation of overhangs that provided transient UV protection to thawed and growing microbial communities on the soils underneath. In shallow aquatic habitats, thin layers of heterogeneous ice of a few millimetres thickness were found to reduce DNA-weighted irradiances by up to 55% compared to full-sky values with equivalent DNA-weighted diffuse attenuation coefficients (K(DNA)) of >200 m(-1). A 2-mm snow-encrusted ice cover on a pond was equivalent to 10 cm of ice on a perennially ice covered lake. Ice covers also had the effect of stabilizing the UV exposure, which was often subject to rapid variations of up to 33% of the mean value caused by wind-rippling of the water surface. These data show that changing ice and snow covers cause relative changes in microbial UV exposure at least as great as those caused by changing ozone column abundance.     

An Attempt to Interpret the Spread of Element Concentration in Antarctic Surface Snow: The Same Element in a Given Test Field, Several Elements in Different Sampling Fields

Sampling surface snow on a large test field always leads to a spread of analyte concentration data which partly follows a Gaussian distribution and partly a rectangular one as can be observed from the analysis of literature data. The spread depends on the nonuniformity of the air–snow interface in the field and on the extent of reproducibility of all the procedures used from sampling to analysis. Consequently a sample relevant to a restricted surface might be poorly representative of the surrounding area. Contamination of the sample during the gathering and storing steps is assumed to be the main source of nonrandom results (outliers). Using various statistical tools we were able to evaluate which part of the spread was due to the snow surface nonuniformity in the case of many samples collected in the same test field. In the case of samples gathered in different geographical areas, the possibility of finding correlations among points is greatly enhanced when three or more analytes are considered for each sample. When the same correlation is found for some analytes and a variable tentatively tested, information can be gained about the source of chemical content of snow samples. The use of UV pretreatment of snow samples has been proven to cut down the interference of organics on the electrochemical process in DPASV, allowing one to obtain accurate and reproducible data.     

A new sensitive method for the quantification of glyoxal and methylglyoxal in snow and ice by stir bar sorptive extraction and liquid desorption-HPLC-ESI-MS

In this study, the development of a new sensitive method for the analysis of alpha-dicarbonyls glyoxal (G) and methylglyoxal (MG) in environmental ice and snow is presented. Stir bar sorptive extraction with in situ derivatization and liquid desorption (SBSE-LD) was used for sample extraction, enrichment, and derivatization. Measurements were carried out using high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). As part of the method development, SBSE-LD parameters such as extraction time, derivatization reagent, desorption time and solvent, and the effect of NaCl addition on the SBSE efficiency as well as measurement parameters of HPLC-ESI-MS/MS were evaluated. Calibration was performed in the range of 1–60 ng/mL using spiked ultrapure water samples, thus incorporating the complete SBSE and derivatization process. 4-Fluorobenzaldehyde was applied as internal standard. Inter-batch precision was <12 % RSD. Recoveries were determined by means of spiked snow samples and were 78.9?±?5.6 % for G and 82.7?±?7.5 % for MG, respectively. Instrumental detection limits of 0.242 and 0.213 ng/mL for G and MG were achieved using the multiple reaction monitoring mode. Relative detection limits referred to a sample volume of 15 mL were 0.016 ng/mL for G and 0.014 ng/mL for MG. The optimized method was applied for the analysis of snow samples from Mount Hohenpeissenberg (close to the Meteorological Observatory Hohenpeissenberg, Germany) and samples from an ice core from Upper Grenzgletscher (Monte Rosa massif, Switzerland). Resulting concentrations were 0.085–16.3 ng/mL for G and 0.126–3.6 ng/mL for MG. Concentrations of G and MG in snow were 1–2 orders of magnitude higher than in ice core samples. The described method represents a simple, green, and sensitive analytical approach to measure G and MG in aqueous environmental samples.     

Sigillin A,a Unique Polychlorinated Arthropod Deterrent from the Snow Flea Ceratophysella sigillata

The snow flea Ceratophysella sigillata, a winter‐active species of springtail, produces unique polychlorinated octahydroisocoumarins to repel predators. The structure of the major compound, sigillin A, was elucidated through isolation, spectroscopic analysis, and X‐ray crystallography. Sigillin A showed high repellent activity in a bioassay with predatory ants. A promising approach for the total synthesis of members of this new class of natural compounds was also developed.     

247. Intracatenar cross-linking in gelatin with carbodiimide

Under suitable conditions it is possible to introduce into dissolved denatured gelatin molecules intracatenar cross-links. Working with 2% solutions of commercial gelatin (M_n approximately 40000) at 40° and pH 5,75 and with water-soluble carbodiimid as a condensing agent we succeeded in inserting 7–8 intracatenar amide bonds per molecule. The number of cross-links introduced was determined by the decrease of free ? NH₂ and ? COOH groups. Using 4% solutions a gel melting point of the cross-linked preparations below 0° was obtained as compared with the gel melting point of untreated gelatin at 28°. The low viscosity and the behaviour in gel chromatography on Sepharose 6B show that the cross-linked peptide chains are fixed as rather dense coils. A small amount of the cross-linking reagent remains covalently bound to the protein, as was shown with tritium labeled carbodiimid. The side reactions possibly responsible for this occurrence are discussed. The bonds between reagent and gelatin are fairly stable at acidic pH, but labile at alkaline pH. The results of optical measurements (UV. and CD.) on cross-linked gelatin will be reported in another paper.     

Examination of the correlation of butter spreadability and its fat conformation by DSC

Since the appearance of margarines and spreads on the market, they have been serious competitors with butter. One of the reasons for this was the false nutritional propaganda, but today butterfat has scientifically regained its actual nutritional evaluation. The main disadvantage of butter in comparison to other spreadable tallow is that it does not immediately spread as well when taken out of the refrigerator. One method of obtaining better cold-spreadability is appropriate cream ripening in which a different system known as the corpuscular colloid is created. Recent examinations were conducted during the winter, when the problem of spreadability of butter is the greatest. Simple cold ripening in accordance with the method used in our earlier EPR studies ripened the cream, and by heat-step ripening, then butter was produced from these materials. By deconvolutional analysis of the DSC curves it was established that butter made from the cream ripened by the heat-step method had three characteristic melting peaks as distinct from the two melting peaks of butter made from cold-ripened cream, and the temperature of the second melting peak for butter from heat-step cream was identical to the characteristic melting temperature for fat particles from earlier EPR spectroscope assays. In sum it can be stated that the DSC method clearly shows both the homogeneous and the particle structure characteristic of butter.