Characterization and evaluation of oil shale based on terahertz spectroscopy: A review

Oil shale is a fine-grained sedimentary rock rich in organic kerogen,which is a national strategic reserve resource and supplementary energy and shale oil and pyrolysis gas can be obtained through carbonization and pyrolysis.Due to the diversity of main components in oil shale and the complexity of the occurrence relationship between organic matter and minerals,the current understanding of the oil generation potential of oil shale and the dy-namic process of organic matter pyrolysis is still unclear,leading to the relatively backward level of its devel-opment technology.The development of new theories and methods for efficient utilization of oil shale resources has great strategic significance.The rotation and vibration frequency of macromolecules in oil shale occur in the terahertz(THz)band,so the THz optical parameters of oil shale can reflect the physical properties of kerogen.In this review,the experimental work progress in THz spectroscopy for characterization and evaluation of oil shale is provided.Oil shale is high anisotropic,resulting that the anisotropy in THz optical parameters strongly depends on the oil yield which is an effective selection for evaluating the oil yield to avoid the problem of environmental pollution in traditional detection.The heterogeneous distributions of organics on the oil shale surface,e.g.,the existence of kerogen-rich and kerogen-poor areas,was evaluated by THz amplitude imaging.In addition,the thermal THz analysis technology was developed to determine the pyrolysis process of kerogen and establish the pyrolysis model of kerogen,and the optimization of oil shale pyrolysis process was realized using THz parameters.Moreover,kerogen in oil shale displays a characteristic absorption peak in the THz range,which provides a new insight into the research of kerogen in the micro and nano scale.The pyrolysis oil shale at high temperature absorbs THz radiation strongly due to the decomposition of pyrite in oil shale.These recent works suggest that THz spectroscopy can realize rapid and non-contact detection of oil shale.At last,we propose the prospects and challenges of the THz technology in future as a new method for optimizing oil shale processing technology and improving the utilization efficiency of oil shale.

山东五莲七宝山铅锌多金属矿床硫化物微量元素分布特征及地质意义

为探讨五莲七宝山铅锌多金属矿中主要硫化物的微量元素分布特征,对矿床成因类型进行约束,在矿床地质研究的基础上,以不同成矿阶段形成的闪锌矿和方铅矿为研究对象,开展矿相学和矿物LA-ICPMS微量元素组成研究。结合野外地质调查和室内矿相学研究,将五莲七宝山铅锌多金属矿床的成矿过程划分为3个成矿阶段,分别是多金属硫化物+碎裂岩阶段(Ⅰ)、多金属硫化物+石英+白云石阶段(Ⅱ)和石英+白云石阶段(Ⅲ)。LA-ICP-MS分析结果表明,主要硫化物中闪锌矿富集Fe、Co、Mn和Cd元素,贫Ge、Se、Te、Re和Tl元素,方铅矿则主要富集Ag和Cd元素;闪锌矿中Cu、Cd、Fe、Mn、Co和In元素以类质同象的方式赋存在矿物中,偶见方铅矿显微包体,方铅矿中Ag元素以类质同象的形式赋存在矿物中,Cu、Zn和As元素则以显微包体的形式赋存在碳酸盐岩化矿石方铅矿中。闪锌矿微量元素成矿温度研究表明,Ⅰ阶段形成的碎裂—角砾岩化矿石以中温为主,Ⅱ阶段形成的碳酸盐岩化矿石则形成于低温环境。结合矿床地质和微量元素分布特征,认为七宝山铅锌多金属矿床属于与岩浆热液作用相关的中—低温热液脉型矿床。

Nanocrystal technology for drug formulation and delivery

With the development of modem technology like high throughput screening, combinatorial chemistry and computer aid drug design, the drug discovery process has been dramatically accelerated. However, new drug candidates often exhibit poor aqueous or even organic medium solubility. Additionally, many of them may have low dissolution velocity and low oral bioavailability. Nanocrystal formulation sheds new light on advanced drug development. Due to small （nano- or micro- meters） sizes, the increased surface-volume ratio leads to drama- tically enhanced drug dissolution velocity and saturation solubility. The simplicity in preparation and the potential for various administration routes allow drug nanocrystals to be a novel drug delivery system for specific diseases （i.e. cancer）. In addition to the comprehensive review of different technologies and methods in drug nanocrystal preparation, suspension, and stabilization, we will also compare nano- and micro-sized drug crystals in pharma- ceutical applications and discuss current nanocrystal drugs on the market and their limitations.

Terahertz-dependent evaluation of water content in high-water-cut crude oil using additive-manufactured samplers

The evaluation of water content in crude oil is of significance to petroleum exploration and transportation.Terahertz(THz) waves are sensitive to fluctuations in the dipole moment of water.However,due to the strong absorption of water in the THz range,it is difficult for the THz spectrum to determine high water content with the common sampler.In this research,micron-grade samplers for THz detection were designed and manufactured using additive manufacturing(AM) technology.Oil-water mixtures with water content from 1.8%to 90.6%were measured with the THz-TDS system using sample cells.In addition,a detailed analysis was performed of the relationships among THz parameters such as signal peak,time delay,and refractive index as well as absorption coefficient and high water content(>60%).Results suggest that the combination of THz spectroscopy and AM technique is effective for water content evaluation in crude oil and can be further applied in the petroleum industry.

Thermal spallation in rock revealed by ultraviolet laser-induced voltage

In the petroleum industry, perforation plays an important role in the exploitation of oil and gas and a considerable number of studies have been conducted with the objective of improving the recovery rates of oil and gas (1,2)Lasers have been used to drill holes in a wide variety of rock types with the advantages of feasibility, cost, benefits, and environmental impact as determined by the Gas Technology Institute [1].

Application of THz technology in oil and gas optics

Fossil fuels currently satisfy^88%of China's energy demands.Oil-gas,known as the hydrocarbon occurred from various types of underground strata,is the most significant part of primary energy sources.Problems in oil-gas exploration,transportation and petrochemical affect the economic viability of the petroleum industry.Recently,the increasing complexity of stratigraphic condition and the fall in oil prices has made the situation more critical.Thus,questing for

Terahertz-dependent PM2.5 monitoring and grading in the atmosphere

Rapid industrialization and economic development have led to serious pollution in the form of fine particulate matter(PM2.5,particulate matter with a diameter of less than 2.5 μm). In China, PM2.5 has been one of the most debated topics in councils of government and issues of public concern. Terahertz(THz) radiation was employed to measure the PM2.5 in the atmosphere from September 2014 to April 2015 in Beijing. Comparison of the PM2.5 level from the website with THz absorbance revealed a significant phenomenon: THz radiation can be used to monitor PM2.5 in the atmosphere. During Asia-Pacific Economic Cooperation(APEC) 2014, "APEC Blue" was also recorded in a THz system. The relationship between absorbance and PM2.5 demonstrates that THz radiation is an effective selection for air pollution grading. Based on the absorbance spectra, the elemental compositions were studied by two-dimensional correlation spectroscopy(2 DCOS) in conjunction with X-ray fluorescence.Several single absorption peaks were revealed and caused by sulphate from coal combustion, vehicle exhaust emissions and secondary reactions. Furthermore, mathematical algorithms, such as the BPANN and SVM, can process the THz absorbance data and greatly improve the precision of the estimation of PM2.5 mass. Our results suggest that THz spectroscopy can not only reveal the component information for pollution source determination, but quantitatively monitor the PM2.5 content for pollution level evaluation. Therefore, the use of THz radiation is a new method for future air pollution monitoring and grading systems.

Non-contacting characterization of oil-gas interface with terahertz wave

Dear Editors,The interface of oil and gas has been a key issue in the process of oil and gas storage and transportation,which is a preparatory work to improve the transport efficiency and prevent oil and gas leaks.There are many methods to characterize the interface of oil and gas,such as the ultrasonic transducers and multi-electrode capacitance level sensors.Recently,the ap-

Evaluation of simulated reservoirs by using the oblique-incidence reflectivity difference technique

Dear Editors,The evaluation of the oil-gas resources’potential depends on the characterization of reservoirs.The geometry of the pore-crack structures and the compositions of the pore walls have influence on hydrocarbon production about capillarity and permeability[1].Besides,it has been known that the adsorption phenomenon in micro-structure plays a significant role in oil-gas reservoirs.Some techniques have been applied to characterize conventional and unconventional reservoirs,

Terahertz assessment of the atmospheric pollution during the first-ever red alert period in Beijing

Haze or smog episodes,which are characterized by the presence of paniculate matter at diameters less than2.5 urn(PM2.5),have attracted increasing attention during the pastfew decades[1].PM2.5 has adverse effects onhuman respiratory health as well as on air visibility[2,3].IntheBeijing-Tianjin-Hebei(BTH)region of China,haze has become especially serious in recent years because of industrial ex-

Non-contacting characterization of PM2.5 in dusty environment with THz-TDS

Dear Editors,Nowadays,many developing countries(such as China)are experiencing severe air pollution due to the rapid urbanization and industrialization.PM2.5,which refers to the particulate matter with an aerodynamic diameter of 2.5mm or less,is the most important causation of air pollution in cities[1].

Characterizing the rock perforation process by laser-induced voltage response

In the petroleum industry,the exploitation of oil and gas is necessarily achieved by perforation,and a considerable number of research studies have been conducted with the objective of improving the recovery rates of oil and gas[1,2].New perforation methods are urgently needed to accelerate the development of energy resources.Drilling rock by laser is a non-contact process that can be used to drill holes in

Quantitative determination of n-heptane and n-octane using terahertz time-domain spectroscopy with chemometrics methods

This paper introduces the terahertz time- domain spectroscopy （THz-TDS） used for the quantitative detection of n-heptane volume ratios in 41 n-heptane and n-octane mixtures with the concentration range of 0-100% at the intervals of 2.5%. Among 41 samples, 33 were used for calibration and the remaining 8 tbr validation. Models of chemometrics methods, including partial least squares （PLS） and back propagation-artificial neural network （BP-ANN）, were built between the THz- TDS and the n-heptane percentage. To evaluate the quality of the built models, we calculated the correlation coefficient （R） and root-mean-square errors （RMSE） of calibration and validation models. R and RMSE of two methods were close to 1 and 0 within acceptable levels, respectively, demonstrating that the combination of THz- TDS and chemometrics methods is a potential and promising tool for further quantitative detection of n- alkanes.

Characterization of the cooling process of solid n-alkanes via terahertz spectroscopy

The terahertz （THz） time-domain spectroscopy technique was used to characterize the cooling process of solid n-alkanes. The THz waveforms of n-octadecane, n- nonadecane, n-eicosane, n-heneicosane, n-docosane, and n-pentacosane were obtained with the cooling time using the aforementioned noncontact optical method. The peak values of the THz signal were found to be related to the cooling temperature of n-alkanes. The THz wave was sensitive to the size and structure of particles in the liquid; therefore, the crystallization process of n-alkanes was monitored. An empirical equation based on signal attenuation was proposed to quantitatively distinguish the content change of structural order in the samples. Results present a new noncontact optical approach for characteriz- ing wax crystallization via THz time-domain spectroscopy.

Characterizing PM2.5 in Beijing and Shanxi Province using terahertz radiation

Particles of aerodynamic diameter〈2.5 pm （PM/.5） caused extremely severe and persistent haze pollution is of concern in many cities. In this study, samples of PM2.5 were collected from atmosphere environment of Beijing and Shanxi Province, and analyzed using terahertz （THz） radiation. The transmission spectrum of PM2.5 in Shanxi Province had two distinct absorption peaks at 6.0 and 6.7 THz, and the curve was increasing on the whole. However, the transmission spectrum of PMa.5 in Beijing had obviously different variation tendency and the absorption peak was studied by monitoring PM2.5 masses in conjunction with two-dimensional correlation spectro- scopy （2DCOS）. By comparing the pollutant species and concentrations of Shanxi Province and Beijing over the time of collecting samples, the concentrations of sulfate and ammonium were similar, which contributed to emerge absorption bands in the same position. While the concentrations of organic matter （OM）, nitrate, chloride and elemental carbon （EC） were different. Furthermore, dust and some other inorganic ion are unique to Shanxi province, which lead to different variation tendency of the transmission spectrum of PM2.5. These results will be of importance for environmental monitoring and for control- ling PM emissions. According to this research, optical techniques, and especially spectral methods, should be considered for PM2.5 monitoring.

Detecting NO3- concentration in nitrate solutions using terahertz time-domain spectroscopy

In this paper, we employed terahertz time domain spectroscopy （THz-TDS） to investigate the nitrate 0 concentration in four types of nitrate solution （sodium nitrate, aluminum nitrate, calcium nitrate and magnesium nitrate）. Their absorption coefficient and refractive index were calculated in 0.2-2.5THz, and a logarithmic relationship was observed between NO3 concentrations and selected optical parameters regardless of the kinds of nitrate solution. Partial least square （PLS） model was built between THz-TDS and NO3 concentration. The correlation coefficient of PLS model was calculated. The results make the quantitative analysis of NO3 concentration possible by THz-TDS and indicate the bright future in practical application.

A proton-catalyzing prodrug for PDT and glycolysis inhibition-synergistic therapy of tumor in spatiotemporal dimensions

The reactive oxygen species(ROS)generation from photosensitizer in photodynamic therapy(PDT)is limited by tumor hypoxia.Even type-I photosensitizers,e.g.,sulfur-substituted Nile blue,still rely on oxygen as the main center for transferring electrons to generate ROS.Cutting off the pathway of oxygen consumption in tumor can help photosensitizers overcome the limitation of low oxygen,in order to efficiently generate more ROS.It is known that glycolysis inhibitor 3-bromopyruvic acid(3-BP),which could specially target mitochondria,can provide more oxygen by inhibiting oxidative phosphorylation.Herein,we successfully designed and synthesized a new 3-BP-coupled sulfur-substituted Nile blue as prodrug(NBBP)for chemical/photodynamic synergistic therapy.Major results indicated that the protons in tumor catalyzed the hydrolysis of NBBP,inhibited photoinduced electron transfer between 3-BP and the photosensitizer in NBBP and further assisted the photosensitizer to be localized in mitochondria,utilizing local oxygen as much as possible and kill tumor cells more efficiently.Moreover,the glycolysis inhibition-induced autophagy was combined with PDT-induced autophagy,which could promote the deaths of tumor cells.Unlike other remedies exploiting nanomaterials,this construction method of NBBP achieves the efficient synergy of photodynamic therapy and glycolysis inhibition,stronger than their theoretical addition,in spatiotemporal dimensions.Our study provides not only a highly efficient platform for tumor therapy but also a design approach for prodrugs with synergistic effects.