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The current methods for detecting myelin changes in ischemic stroke are indirect and cannot accurately reflect their status. This study aimed to develop a novel fluorescent-magnetic resonance dual-modal molecular imaging probe for direct imaging of myelin. Compounds 7a and 7b were synthesized by linking the MeDAS group and Gadolinium (III) 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate. Compound 7a was selected for characterization and further study. Cell uptake, cytotoxicity, and magnetic resonance imaging scans were performed on cells. In vitro experiments on frozen brain sections from 7-day-old, 8-week-old, and ischemic stroke rats were compared with commercially available Luxol Fast Blue staining. After HPLC and MR scanning, brain tissue was soaked in 7a and scanned using T 1 WI and T 1 maps sequences. Spectrophotometer results showed that compounds 7a and 7b had fluorescent properties. MR scans indicated that the compounds had contrast agent properties. Cells could uptake 7a and exhibited high signals in imaging scans. Compound 7a brain tissue staining showed more fluorescence in myelin-rich regions and identified injury sites in ischemic stroke rats. MR scanning of brain sections provided clear myelin contrast. A novel fluorescent-magnetic resonance dual-modal molecular imaging probe for direct imaging of myelin was successfully developed and tested in rats with ischemic stroke. These findings provide new insights for the clinical diagnosis of demyelinating diseases. • Compounds 7a and 7b have fluorescent properties from spectrophotometer results. • Compounds 7a and 7b have MRI contrast agent properties. • Our novel dual-mode probes effectively visualized the rat infarction model. • Our study may provide new ideas for diagnosing demyelinating diseases. [ABSTRACT FROM AUTHOR]

[Display omitted] Demyelination exists in many neurological diseases of nervous system, such as stroke. Currently, magnetic resonance imaging (MRI) has been the main tool for diagnosing and monitoring the myelin related diseases. However, the conventional MRI unable to distinguish demyelinating lesions from other inflammatory lesions. To address this problem, we have designed and prepared a myelin specific magnetic resonance contrast agent, Gd-DTDAS, which was based myelin specific moiety MeDAS g g MeDAS: (E)-4-(4-aminostyryl)- N -methylaniline. and Gd-DTPA h h Gd-DTPA: gadopentetate acid.. In this work, we verified the specificity and sensitivity of Gd-DTDAS to myelin. Moreover, we investigated the specific binding ability of Gd-DTDAS to myelin sheath in the MCAO mice i i MCAO: middle cerebral artery occlusion. models. The in vivo imaging results showed that Gd-DTDAS can bind to the undamaged myelin sheath in the BBB disruption areas, and in turn reduce the relaxation time. The fluorescence images also showed significant fluorescence in the brain right infarct area of the MCAO model mice with administration of Gd-DTDAS. The above results confirmed that Gd-DTDAS could be preferentially distributed in areas with high myelination and can detect focally induced demyelination. [ABSTRACT FROM AUTHOR]

The aromatic hydrocarbon fractions of five crude oils representing a natural sequence of increasing degree of biodegradation from the Liaohe Basin, NE, China, were analyzed using conventional gas chromatography–mass spectrometry (GC–MS) and comprehensive two-dimensional gas chromatography (GC × GC). Because of the limited peak capability and low resolution, compounds in the aromatic fraction of a heavily biodegraded crude oil that were analyzed by GC–MS appeared as unresolved complex mixtures (UCMs) or GC “humps”. They could be separated based on their polarity by GC × GC. UCMs are composed mainly of aromatic biomarkers and aromatic hydrocarbons with branched alkanes or cycloalkanes substituents. The quantitative results achieved by GC × GC-FID were shown that monoaromatic hydrocarbons account for the largest number and mass of UCMs in the aromatic hydrocarbon fraction of heavily biodegraded crude oil, at 45% by mass. The number and mass of diaromatic hydrocarbons ranks second at 33% by mass, followed by the aromatic biomarker compounds, triaromatic, tetraaromatic, and pentaaromatic hydrocarbons, that account for 10%, 6%, 1.5%, and 0.01% of all aromatic compounds by mass, respectively. In the heavily biodegraded oil, compounds with monocyclic cycloalkane substituents account for the largest proportion of mono- and diaromatic hydrocarbons, respectively. The C 4 -substituted compounds account for the largest proportion of naphthalenes and the C 3 -substituted compounds account for the largest proportion of phenanthrenes, which is very different from non-biodegraded, slightly biodegraded, and moderately biodegraded crude oil. It is inferred that compounds of monoaromatic, diaromatic and triaromatic hydrocarbons are affected by biodegradation, that compounds with C 1 -, C 2 -substituents are affected by the increase in degree of biodegradation, and that their relative content decreased, whereas compounds with C 3 -substituents or more were affected slightly or unaffected, and their relative content also increased. The varying regularity of relative content of substituted compounds may be used to reflect the degree of degradation of heavy oil. Moreover, biomarkers for the aromatic hydrocarbons of heavily biodegraded crude oil are mainly aromatic steranes, aromatic secohopanes, aromatic pentacyclotriterpanes, and benzohopanes. According to resultant data, aromatic secohopanes could be used as a specific marker because of their relatively high concentration. This aromatic compound analysis of a series of biodegraded crude oil is useful for future research on the quantitative characterization of the degree of biodegradation of heavy oil, unconventional oil maturity evaluation, oil source correlation, depositional environment, and any other geochemical problems. [ABSTRACT FROM AUTHOR]

In this paper, we analyse the Ordovician condensate in the Tazhong area of the Tarim Basin, NW China, using a new high-resolution comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC × GC-TOFMS). Results show that 4778 compounds at a signal-to-noise ratio of more than 100 were detected, reflecting the advantage of this method in the analysis of condensate. Abundant adamantane series compounds and some diamantane series compounds, as well as a series of sulphur-containing compounds (including the benzothiophene series, and the dibenzothiophene series) were detected for the first time in the study area. Combined with the results of a study on oil and gas sources and migration/accumulation, we address the origin of these compounds. It is implied that the diamondoids were not formed in-situ due to oil cracking (in reservoir approximately 5500 m deep at temperature around 139 °C), whereas the cracking of oil to gas may have occurred in the deeper-buried Cambrian dolomite reservoir at a reservoir temperature of 180–220 °C (8500–11,000 m depth). The oil-cracked gas (secondary cracking product) might have migrated to and accumulated in the shallower-buried Ordovician reservoir, accompanied by abundant diamondoids. The formation of sulphur-containing compounds may be related to thermochemical sulphate reduction (TSR), which, similar to the oil cracking, took place in the deeper-buried Cambrian reservoir. Under high-temperature TSR, SO 4 2− in the formation water is reduced to H 2 S and organic sulphur compounds, leading to the enrichment of sulphur in crude oils (e.g., benzothiophene, and dibenzothiophene series). As such, it is implied that the Tazhong area could potentially be explored for deep-buried oil-cracked gas. [ABSTRACT FROM AUTHOR]

The saturated and aromatic hydrocarbon fractions of crude oil samples have been analyzed by using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-TOFMS) and conventional gas chromatography-mass spectrometry (GC-MS). In order to investigate the consistency and discrepancy of the obtained data from the two instruments, some petroleum geochemical parameters have been compared. A comparison of 23 geochemical parameters indicates that 10 parameters are comparable from the two instruments with less than 5% deviations. Therefore, GC×GC-TOFMS is equivalent to conventional GC-MS in some geochemical parameter acquisitions. However, the other 13 parameters are discrepant, including gammacerane / αβ-hopane, Ts/Tm, 2-ethyl-naphthalene / 1-ethyl-naphthalene (ENR), (2, 6-dimethyl-naphthalene +2,7-dimethyl-naphthalene) / 1,5-dimethyl-naphthalene (DNR), etc. Furthermore, compared to GC×GC-TOFMS, some low concentration compounds could not be detected by the conventional GC-MS, which results in the missing of related geochemical data. Normally, this is caused by the limited separation power and peak capacity of the conventional GC column. Besides, the co-eluting peak integrations are also affected significantly due to the incomplete separation of the compounds. Some low concentration compounds might not be detected because of the interference from the baseline noise or from other substances. GC×GC-TOFMS prevails in compound separation against the conventional GC-MS by avoiding co-elution, which achieves more accurate and precise peak area measurement with the presence of a true baseline. So petroleum geochemical parameters obtained from the GC×GC-TOFMS are more reliable than those from the conventional GC-MS. GC×GC-TOFMS may become one of the most effective analytical tools for the oil and gas geochemical study. [ABSTRACT FROM AUTHOR]

Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GCxGC-TOFMS) is commercially available in the 1990s, with the characteristics of large peak capacity, high resolution, high sensitivity, etc. However, its application to the petroleum and geological analyses is just emerging in China and overseas. In this research, the analytical method for petroleum aromatic fraction using GCxGC-TOFMS is set up, via the choice of the column system and optimization of setting parameters, such as temperature programming, modulation time, hot pulse time, flow rate of carrier gas, data acquisition rate and data processing. The results indicate that different polar compounds of aromatic fraction distribute as bands on structured GCxGC chromatogram. Within each band, homologous compounds appear as a roof-tile structure based on the number of substituent residues. The aromatic compounds are identified and characterized according to the GCxGC chromatogram and mass spectra. According to the polarity and the number of rings, aromatic compounds are spatially present on one chromatogram, which directly reflects the distribution characteristics of complex compounds of aromatic hydrocarbons. In addition, quantitative analysis is favored as some overlapped peaks on traditional GC-MS chromatogram have been separated completely on GCxGC. Some heterocyclic atom aromatic compounds at trace level can be clearly identified using this method, for polarity differences from other interfered aromatic compounds. The development of this method and chromatogram recognition offer petroleum geologists a practical example for the application performance of GCxGC-TOFMS. [ABSTRACT FROM AUTHOR]

The first exploratory well, the ZS1C well, with 158,545 m 3 daily gas production was discovered in 6861–6944 m deep strata of the Cambrian gypsolyte layer of the Tarim Basin, China in 2014. The discovery opens a new target for the Cambrian-reservoired oil and gas exploration, and directly leads to large-scale oil and gas exploration of the deep-reservoired Cambrian oil and gas fields in the Basin. Comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry and a comprehensive two-dimensional gas chromatography–flame ionization detector revealed the presence of abundant adamantane compounds, 2-thiaadamantanes and 2-thiadiamantanes, and a large amount of sulfur-containing compounds in the condensate oil. The formation of organic sulfur-containing compounds, such as 2-thiaadamantanes, is an indication of sulfur incorporation from the gypsum in the stratum into oil and gas in the course of TSR. This reservoir has apparently suffered severe TSR alteration because (1) High content of H 2 S, (2) H 2 S sulfur isotopes, (3) CO 2 carbon isotopes, and others abundant data to support this findings. Similar sulfur isotopic composition of H 2 S, oil condensate and the gypsum in the Cambrian strata indicate that the produced condensate is experienced TSR alteration. Therefore, the deep-accumulated Cambrian oil reservoir has experienced severe TSR alteration, and accumulated natural gas and condensate contains high sulfur content. [ABSTRACT FROM AUTHOR]

A continental condensate field, with the deepest burial depth (7084 m) so far in China, was recently discovered from the Cretaceous sandstone reservoir in the Bozi area of the Kuqa Depression, Tarim Basin. In this paper, we report general features of this field, including geochemistry of the condensates, their origin, and migration and accumulation. General geochemistry of the condensate reflects that it is an over pressured condensate reservoir. Analytical results by newly-developed high-resolution GC × GC–TOFMS method indicate that the condensate is rich in n -alkanes from nC 3 to nC 34 and in diamondoid hydrocarbons with a high content of adamantanes. The condensate has a high abundance of aromatic hydrocarbons. The gas δ 13 C 2 values in these are −23.3‰, which is characteristic of coal-derived gases. Compared with the contents of conventional condensate oils, the BZ1 well has a high content of aromatic hydrocarbons, suggesting that the condensate is in a stage of highly mature cracking. Analyses of oil biomarkers, carbon isotopes, gas compositions, etc., revealed that the condensate is dominantly sourced from the highly mature coals of the Jurassic Qiakemake Formation in the western Kuqa Depression. This set of coal source sequences has generated large quantities of condensate since 3 Ma, when the study area was subjected to a rapid subsidence with sediments over 2000 m and consequently attained at the condensate-generating stage. Such condensates then migrated vertically into the Cretaceous traps along faults. Therefore, the Bozi condensate field is a typical case of large-scale oil/gas field characterized by late-stage accumulation. Multiple elements favor the formation of this large-scale condensate field. The timing of trap formation accords with that of the condensate generation (since 3 Ma). The traps and source rocks are stacked vertically. Faults connect the source rock sequences and the reservoirs. The hydrocarbon charge is strong and efficient. Thick Paleogene gypsum beds act as an excellent cap rock, favoring the accumulation and preservation of the condensate. [ABSTRACT FROM AUTHOR]

The comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC × GC/TOFMS) has been used to characterize a crude oil and a source rock extract sample. During the process, a series of pairwise components between monocyclic alkanes and mono-aromatics have been discovered. After tentative assignments of decahydronaphthalene isomers, a series of alkyl decalin isomers have been synthesized and used for identification and validation of these petroleum compounds. From both the MS and chromatography information, these pairwise compounds were identified as 2-alkyl-decahydronaphthalenes and 1-alkyl-decahydronaphthalenes. The polarity of 1-alkyl-decahydronaphthalenes was stronger. Their long chain alkyl substituent groups may be due to bacterial transformation or different oil cracking events. This systematic profiling of alkyl-decahydronaphthalene isomers provides further understanding and recognition of these potential petroleum biomarkers. [ABSTRACT FROM AUTHOR]

An analytical method for quantifying biomarker compounds of the sterane and the hopane existing in saturated hydrocarbons has been established by using comprehensive two-dimensional gas chromatography-flame ionization detector (GC×GC-FID) with optimized operating parameters. The new method achieves the quantification by using a GC×GC-FID system which is able to completely separate steranes from hopanes. The data obtained by the new method are of good repeatability and reliability. Compared with the original data, the relative standard deviations (RSDs) of 12 reference compounds are less than 5%. The RSDs of the quantitative results of the biomarkers based on seven separate analyses are also less than 5%. Compared with the traditional method of gas chromatography-mass spectrometry (GC-MS), the new method has a number of advantages, such as common internal standards (ISs), high resolution, no co-eluting peak, and no interference caused by diagnostic ion peaks. The new method provides petroleum geologists with an effective and scientific means in future researches. [ABSTRACT FROM AUTHOR]

Highlights: [•] GC×GC–FID and GC×GC–TOFMS were powerful for molecular characterization. [•] Some new long chain alkylated compounds were tentatively detected in condensate. [•] ND1 condensate is of high thermal maturity with moderate degree of thermal cracking. [•] Petroleum is thermally more stable than previously assumed. [•] The exploration potential of ultra-deep reservoir remains high. [ABSTRACT FROM AUTHOR]

Thermal stability of liquid petroleum in the subsurface is closely linked to reservoir temperature. Most oil accumulations occur at temperatures <120 °C. Oil cracks into gas at temperatures >150–160 °C leading to the dominance of gas condensate and free gas accumulations in ultra-deep high-temperature reservoirs. The recently drilled Fuyuan-1 exploration well (northern Tarim basin) produced high-quality non-cracked single-phase (black) oil from a carbonate reservoir located at maximum depth 7711 m and temperature 172 °C. This is the deepest oil discovery in China to date and among the deepest in the world. The oil density (0.825 g/cm 3 at 20 °C or API gravity 40°), relatively low gas/oil ratio (135 m 3 /m 3 or 758 scf/bbl), low variety and abundance of adamantanes as well as lack of thiaadamantanes and dibenzothiophenes indicate that the oil was expelled from a source rock at moderate thermal maturity and has not been cracked. The molecular and isotopic composition of oil-associated gases are consistent with this interpretation. We suggest that the oil remained uncracked because the residence time at temperatures >150-160°C was relatively short (<5 my based on 1D modeling) and apparently insufficient for cracking. We conclude that there is potential for finding unaltered liquid petroleum in other high-temperature reservoirs with relatively low geothermal gradient and recent burial in the Tarim basin and around the world. [ABSTRACT FROM AUTHOR]

The Triassic Chang 7 shale in the Ordos Basin with considerable total organic carbon content (TOC) has been considered as an ideal target for in-situ conversion process (ICP) in China. However, the compositional kinetics for oil and gas generation from the Chang 7 organic matter during heating remain unclear, causing difficulty in the resource evaluation of shale oil and the temperature optimization in future ICP. In this study, the non-isothermal pyrolysis of two Chang 7 kerogens at 2 and 20 ºC/h were conducted to investigate the potential of individual components of products as well as their evolution kinetics. By using a comprehensive two-dimensional gas chromatography (GC×GC), the yields of individual components (including C 1–5 , C 6–14 saturates, C 6–14 aromatics, C 15+ saturates, C 15+ aromatics and NSOs) in pyrolysis products were measured. The maximum yields of oils and C 1–5 from ZK-2 kerogen with hydrogen index (HI) of 471 mg/g TOC were 421.5 and 240.5 mg/g TOC, much higher than those from ZK-1 with HI of 332 mg/g TOC. Relatively, the temperature for giving maximum yield of C 6–14 is significantly higher than those of C 15+ and heteroatomic compounds (NSOs), which were decomposed to re-generate light hydrocarbons in the closed system. It showed that activation energies (Ea) for the generation and cracking of C 6–14 and C 2–5 were distributed in broader ranges compared with NSOs and C 15+ components by kinetic fits. Meanwhile, the mass conversions of oil and gas from the Chang 7 kerogen in ICP at 0.5–10 ºC/d were obtained. The temperatures giving maximum HC yield in ICP were predicted to be 330–368 ºC. The oil and gas generation potentials of the Chang 7 shale in the Ordos Basin giving maximum HC yields were estimated as 542 × 108 t and 89.4 × 108 m3, respectively. Finally, it is elucidated that heated temperatures of about 20 ºC higher than those giving maximum oil yield result in GOR higher than 200 m3/m3. These findings are beneficial for the economic production of shale oil in ICP. • Yields of individual pyrolysis products from the Chang 7 kerogens were determined. • Compositional kinetic models for the evolution of nine components were addressed. • T giving maximum HC yield in ICP at 0.5–10 ºC/d are 330–368 ºC. • ICP at T of 20 ºC higher than those giving maximum oil yield will result in GOR > 200 m3/m3. [ABSTRACT FROM AUTHOR]

In recent years, petroleum exploration has extended from shallow to deep reservoirs in the globle petroliferous basins. In contrast to conventional carbonate reservoirs, the fractures and hydrotherm related karst reservoirs could mainly be developed in deep strata along the tectonic deformation and fault zone. The seismic imaging and tectonic analysis have been combined to identify the scale and features of the deep fault system in the Tarim Basin, NW China. It was found that the tectonic collision and movement generated a prevalent strike-slip fault system, which was conjugated and extended from paleo-uplift to the inside of the Manjar Sag (source kitchen) in the Tarim Basin. The micrograph of cores and images of well logging demonstrated that deep reservoirs are dominated by porosities, fractures, and hydrothermal minerals (e.g., fluorite, pyroxenite). Burial dissolution and thermohydrology along strike-slip fault have greatly contributed to the formation of deep carbonate reservoirs, meanwhile controled the accumulation and hydrocarbon properties in the deep carbonates reservoirs of Tarim Basin. The analysis of adamantane, dibenzothiophene, and carbon isotopes indicated that oil-cracking, thermochemical sulfate reduction (TSR), and gas-washing fractionation could be the main factors to control the sequential accumulation of various hydrocarbons around Manjar Sag. The formation and hydrocarbon accumulation of the deep carbonate reservoirs along this strike-slip fault system could provide important details regarding deep petroleum geological processes from both scientific and practical aspects. These findings could be applied to future studies and the exploration of deep potential marine reserves worldwide. • δ13C 18~19 2,3,6-TMAI ranged −19.81‰ ~ −21.25‰ in North China Mesoproterozoic. • Distribution of Green Sulphur Bacteria exhibited dynamic variations of oceanic redox. • Contributions of GSB to the Xiamaling sedimentary organic matter were limited. [ABSTRACT FROM AUTHOR]