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11.
Guangyuan Wang Jimin Shen Shengyue Wei Daxing Cai Jinde Liu 《Molecules (Basel, Switzerland)》2022,27(22)
This study identified and detected the existence of major pollutants in northeast China. As an alpine region and an agricultural base, this region has representative significance in pollution research. We selected 56 samples from drinking water sources of typical villages and towns, focusing on the analysis of heavy metals and organic micropollutants in northeast China. The analysis results showed that Fe and Mn were the main metal elements exceeding the standard. The exceeding rates were 17.9% and 19.6%. Experiments showed that there were 19 kinds of pesticides, 6 kinds of OPEs, 2 kinds of PAEs, 22 kinds of PPCPs. The detection rate of these 49 kinds of organic micro-pollutants were 1.79~82.14%. The characteristics of organic pollution were extensive and varied. Many underground water samples had high level of micropollutants. The water quality parameters of drinking water sources in villages and towns showed close relation to local geological conditions and agricultural activities. Actions must be taken to control these parameters from the source of pollution. 相似文献
12.
Valery A. Isidorov Jolanta Maslowiecka Lukasz Szoka Naldo Pellizzer Dora Miranda Ewa Olchowik-Grabarek Monika Zambrzycka Izabela Swiecicka 《Molecules (Basel, Switzerland)》2022,27(22)
The chemical composition of propolis of four species of stingless bees (SLBs) from Argentina was determined, and its antibacterial and anticancer activity was evaluated on selected types of microbes and cancer cell lines. Volatile secretions of all propolis samples are formed by 174 C2–C15 organic compounds, mainly mono- and sesquiterpenes and their derivatives. The chromatograms of ether extracts showed 287 peaks, of which 210 were identified. The most representative groups in the extracts of various propolis samples were diterpenoids (mainly resin acids), triterpenoids and phenolic compounds: long-chain alkenyl phenols, resorcinols and salicylates. The composition of both volatile and extractive compounds turned out to be species-specific; however, in both cases, the pairwise similarity of the propolis of Scaptotrigona postica and Tetragonisca fiebrigi versus that of Tetragona clavipes and Melipona quadrifasciata quadrifasciata was observed, which indicated the similarity of the preferences of the respective species when choosing plant sources of resin. The composition of the studied extracts completely lacked flavonoids and phenolcarboxylic acids, which are usually associated with the biological activity and medicinal properties of propolis. However, tests on selected microbial species and cancer cell lines showed such activity. All propolis samples tested against Paenibacillus larvae, two species of Bacillus and E. coli showed biofilm inhibition unrelated to the inhibition of bacterial growth, leading to a decrease in their pathogenicity. Testing the anticancer activity of ether extracts using five types of cell cultures showed that all four types of propolis studied inhibit the growth of cancer cells in a dose- and time-dependent manner. Propolis harvested by T. clavipes demonstrated the highest cytotoxicity on all tested cell lines. 相似文献
13.
Despoina-Eleni Zacharioudaki Ioannis Fitilis Melina Kotti 《Molecules (Basel, Switzerland)》2022,27(15)
Fluorescence spectroscopy is an optical spectroscopic method that has been applied for the assessment of environmental quality extensively during the last 20 years. Most of the earlier works have used conventional light sources in spectrofluorometers to assess quality. Many recent works have used laser sources of light for the same purpose. The improvement of the energy sources and of the higher resolution spectrometers has led to a tremendous increase in applications. The motivation for the present review study is the increasing use of laser sources in environmental applications. The review is divided in two parts. The fundamental principles of fluorescence spectroscopy are described in the first part. The environmental applications are described in the second part. 相似文献
14.
文章是以作者和刘惠春教授多年合作的研究工作为基础写成的,主要内容为太赫兹(THz)半导体器件及其通信和成像应用,以此深切缅怀刘惠春教授。近十年来,THz科学与技术已取得了长足进步,它在物理学、材料科学、生命科学、天文学、信息技术和国防安全等多个领域的应用也已初现端倪。在这些应用中,半导体THz器件的发展起着举足轻重的作用。文章着重介绍了作者近年来在半导体THz器件与应用方面的研究进展,主要内容包括基于负有效质量的电子学THz振荡器、飞秒激光泵浦半导体THz辐射源、基于量子阱子带间跃迁的THz量子级联激光器和THz量子阱探测器,以及基于这些器件的THz无线通信和成像应用研究。此外,文章还对未来THz技术的发展进行了简要的探讨。 相似文献
15.
单光子源是实现量子密匙分配、线性光学量子计算的基本单元。作者回顾了单光子源在量子信息科学发展中的作用,讨论了光子的统计特性,分析了具有类似原子二能级结构的半导体量子点作为单光子发射源的特点,介绍了微腔与二能级系统的耦合以及微腔量子电动力学基本原理。在弱耦合区,Purcell效应导致微腔中量子点激子复合寿命降低,因此可用微腔来改善量子点单光子发射效率。文章总结了近年来在半导体微腔增强量子点单光子发射领域的进展,探讨了分布式布拉格反射微腔、柱状微腔和光子晶体微腔等结构对改善半导体量子点单光子发射和收集效率、光子极化以及光子全同性等方面的作用,并对未来半导体量子点单光子源的发展进行了展望。 相似文献
16.
17.
D. Widory 《Combustion Theory and Modelling》2013,17(5):831-841
Stable (i.e. non-radioactive) carbon-isotope composition (δ13C) in fuels has been extensively used as an indicator of the processes leading to the generation of their parent crude-oil. With the example of those used in Paris (France), this preliminary study isotopically characterizes fuels and combustibles, as well as the isotopic relations existing with their combustion by-products, i.e. gases (CO2) and particles (bulk carbon). Results show that δ13C in fuels is clearly related to their physical state, with natural gas being strongly depleted in 13C while coal yields the highest δ13C, and liquid fuels display intermediate values. This relation is also valid for combustion gases, although δ13C values of combustion particles form a homogeneous range within which no clear distinction is observed. Combustion processes are accompanied by carbon-isotope fractionation (noted Δ13C) resulting from the combustion being incomplete. Carbon-isotope fractionation is strictly negative (Δ13C = ?1.3‰) during the formation of combustion gases, but generally positive in particle formation even if values close to zero are observed. Using simple mixing equations for describing the closed system formed by fuel, CO2 and carbonaceous particles, we discuss the carbon budget for spark-ignition (unleaded gasoline) and diesel engines. Stable carbon isotopes corroborate the already-proved superior efficiency of diesel combustion mode compared with spark ignition, as carbon is preferentially transformed into CO2. 相似文献
18.
J. Nassar J. Goldbach 《International journal of environmental analytical chemistry》2013,93(2):145-159
Abstract The problem of determining the concentration changes of reactive hydrocarbon immissions as a function of time was solved by means of an automatic gas chromatograph which, without enrichment, could record ethylene and acetylene in ppb concentrations. At the same time various other pollutants were covered, so that by a mutual allocation of the individual components it was possible to identify certain emitter groups. The results clearly show that ethylene and acetylene primarily originate from the combustion processes of the automobiles, while the handling and storage of petroleum products and their processing do not exert any influence on the immission of the two components. By way of time series measurements during a summer week in 1976 with very intensive solar radiation it was possible to show indirect secondary photochemical reactions. 相似文献
19.
Industrially advanced countries and inereasingly also agricultural countries today use radioisotopes as labelled compounds or scaled sources in order to solve their scientific and technological problems. 相似文献
20.
K. Irmer 《Isotopes in environmental and health studies》2013,49(10):417-418
Bei der kontinuierlichen Durchstrahlungsprüfung von Werkstücken werden überwiegend Meßeinrichtungen, bestehend aus 60Co-Strahlungsquelle, Szintillationsdetektor und schreibendem Meßgerät, verwendet 1. 相似文献