Establishment of an animal model of dural venous sinus embolism

BACKGROUND： The pathological mechanism of secondary brain lesion following an embolism remains unclear. The establishment of an animal model that imitates the clinical pathophysiological processes is crucial to better study this disease during a certain time window. OBJECTIVE： To establish a new animal model of dural venous sinus embolism that is simple, has a high success rate, and emulates the pathophysiological course of clinical disease. DESIGN, TIME AND SETTING： A randomized block design trial was performed at the Department of Anatomy, Ningxia Medical College between March and December 2007. MATERIALS： Fifty-eight healthy, adult, Sprague Dawley rats were used in the present study. Plastic emboli, with a total length of 0.4 cm, were self-made. Each plastic embolus had a conical anterior segment; the largest diameter being 0.12 cm. The posterior segment became gradually thin and flat, with a width of 0.2 cm and length of 0.1 cm. METHODS： The fifty-eight rats were randomly divided into three groups： control （n = 6）, embolism （n = 26）, and sham-embolism （n = 26） groups. In the embolism group, a solid embolus was slowly inserted and fixed into the posterior part of the superior sagittal sinus against the flow of blood. The posterior segment was detained outside the superior sagittal sinus for fixing. In the sham-embolism group, rats were subjected only to sinus sagittalis superior exposure. In the control group, rats received no treatments. In both the embolism and the sham-embolism groups, the rat brains were resected at 6 hours, 1, 3, and 5 days post-surgery. MAIN OUTCOME MEASURES： （1） Brain surface appearance in the embolism and sham-embolism groups. （2） Thrombosis in the embolism group. （3） Cerebrospinal fluid content in the above-mentioned two groups. RESULTS： In the embolism group, the model success rate was 92% （24/26）. There was visible thrombosis in the superior sagittal sinus. Cerebral edema was noticeable under a microscope. These changes were visible at 6 hours after embolism and were most obvious at 1 day after surgery. In the embolism group, cerebrospinal fluid content reached a peak level at 6 hours post-surgery and was significantly increased compared with the sham-embolism and the control groups （P 〈 0.05）. At 1 day post-surgery, the amount of cerebrospinal fluid was still greater in the embolism group compared to the control group （P 〈 0.05） CONCLUSION： The method of inserting a solid embolus has many benefits, such as being able to directly observe, short cycle time, and minimal wound. The detained posterior segment prevents movement and perfusion of embolus, which results in a high success rate.

Evaluation of sweet spots and horizontal-well-design technology for shale gas in the basin-margin transition zone of southeastern Chongqing,SW China

The shale gas accumulation conditions in the basin-margin transition zone of southeastern Chongqing in SW China are complex.In order to improve single-well productivity in this area,the geologic characteristics,major factors controlling the occurrence of sweet spots,and drilling/fracturing optimization were investigated in this study.The sweet spot evaluation system and criteria were established,and the horizontal-well-design technology was developed.The following three conclusions were drawn.First,the accumulation and high-productivity-oriented approaches for sweet spot evaluation are proposed and the criteria are established based on screened key indicators.Second,the horizontal well was designed based on:(1)the“six-map”method,to identify both the geology and engineering sweet spots for well locations;and(2)seismic attributes,to predict the development of fractures and cavities,and thus,avoid mud loss and improve the drilling efficiency.The target window,well-azimuth optimization,and the curvature were forecasted to improve the fracturing performances.Third,the Pingqiao anticline,Dongsheng anticline,Jinfo slope,and Wulong syncline were selected as Type I sweet spots.Currently,shale gas has been successfully discovered in the basin-margin transition zone and is being commercially developed.

Simple chemical synthesis and isotropic negative thermal expansion in MHfF_(6)(M=Ca,Mn,Fe,and Co)

The rapid progress of modern technologies has accelerated the prominence of thermal expansion mismatch between materials,and tunable thermal expansion materials will be a powerful safeguard against this challenge.Here,isotropic MHfF_(6)(M=Ca,Mn,Fe,and Co)compounds with tunable thermal expansion have been produced via a low-cost synthetic method and investigated.By utilizing temperature dependent X-ray diffraction(XRD)and Raman spectroscopy,combined with first principles calculations,it was revealed that the transverse thermal vibrations of the F atoms are dominated by low-frequency phonons with negative Grüneisen parameters and are therefore the origin of the negative thermal expansion(NTE).Very interestingly,with the increase of the M atomic number,the metal…F atomic linkages become stiffer,reducing the number of vibrational modes with negative Grüneisen parameters,so that the strong NTE can be gradually adjusted to moderate NTE and to near zero thermal expansion.The present study achieves the tunable thermal expansion in a new compound family and shed light on the internal mechanism from the perspective of lattice vibrational dynamics.

Enrichment mechanism and resource potential of shale-type helium:A case study of Wufeng Formation-Longmaxi Formation in Sichuan Basin

China’s helium resource is highly dependent on overseas imports.Organic-rich and U/Th-rich shale reservoirs generally contain helium,and although the helium content is low,the total reserve is large.Therefore,the effective development and utilisation of shale-type helium resources is a realistic way to improve the security of helium resources in China.In this study,the generation mechanism,helium source and content,migration modes and pathways,controlling factors of enrichment,distribution pattern,and resource potential of the helium were analysed,using the Wufeng-Longmaxi shale in the Sichuan Basin and its periphery.Furthermore,countermeasures were proposed for shale-type helium exploration and development.The results show that the Wufeng-Longmaxi shale has a high content of U and Th and a good ability to generate helium.The helium is generated by a typical crustal source of helium and is characterised by self-generation,self-storage,and wide distribution.The helium resource potential is a product of its content and the resources of the associated natural gas.The continuous supply of helium and effective preservation are the main geological factors that control the enrichment of shale-type helium.The preliminary evaluation results show that the reserves of helium in proven shale gas reserves are 10.8×10^(8)m^(3)in the Sichuan Basin and its periphery,where the extra-large helium fields are likely to be discovered.Additionally,0.0912×10^(8)m^(3)of helium was produced,along with the annual production of shale gas.To avoid the waste of helium and to improve the self-supply ability,it is suggested that research on the resource potential,enrichment mechanism,and distribution pattern of shale-type helium should be carried out as soon as possible,and helium extraction techniques for helium-bearing natural gas should be studied.