[en] The tektites in China are distributed on the north part of Australia - Southeastern Asia strewfield of tektite: Leizhou Peninsula of Guangdong Province and Hainan Island, and located exactly at the boundary between Zanjiang Formation and Beihai Formation. A new hypothesis is suggested: During the end of Lower Pleistocene, a comet of special components from the outer part of the Solar System approached the Earth, and then it was captured by the Earth, when it came approximately to the Roche's limit. It was crushed into countless fragments, detritus and dusts, which rotated around the Earth, probably far above the Earth's atmosphere, as a cloud ring. Under the action of crushing energy they could be in the situation of liquid-melt drop in the almost vacuum circumstances and the flow and bubble structure were formed. During their rotation the climate became anomalous and the violet Fe-Si concentration were formed on the surface of sediments. After a rather short time of rotation the unstable ring was broken and the fragments impacted on the hard ground instantaneously

[en] In this paper we focus on the dynamics of the overdamped limit case of the Frenkel–Kontorova (F–K) model with irrational mean spacing. We extend the results of Baesens and MacKay on rational mean spacing case to irrational case: there exists a depinning force F_d ≥ 0 such that the F–K model possesses an equilibrium with a given mean spacing if the constant driving force F in [0, F_d] or it admits a uniform sliding solution provided F > F_d. Moreover, the average velocity of the particles exists and is unique, and it is non-decreasing and continuous with respect to F in [0, +∞). In particular, we prove that the average velocity depends continuously upon the mean spacing

[en] The magnetization process in nanocrystalline Fe_85.1Mo_0.5Zr_3.3Nb_3.3B_6.8Cu₁ alloy was studied by varying the AC and/or DC magnetic field amplitude in the frequency range from 0.1 kHz to 1 MHz. When a small magnetic field is applied, the magnetization process is dominated by the domain wall bulging; and when the applied field is over the threshold field (H_p), the magnetization process is dominated by the domain wall bulging and displacement. A small longitudinally DC magnetic field will lead to an increase in the magnetization process, a high DC field produces a decrease in the magnetization process

[en] Effects of applied DC fields on the domain wall magnetization processes of Fe₈₂Nb₇B₁₀Cu₁ soft magnetic nanocrystalline ribbons at low frequencies were researched by impedance spectroscopy. Results show that small longitudinal DC fields help the domain wall unpin from the pinning field and large longitudinal DC fields increase the pinning field and damp the domain wall motion, while the transverse DC fields have little influence on the pinning field

[en] Talc is a potential filler for enhancing mechanical and thermal performance of polymers. In this study, a novel kind of filler based on black talc and dye (Direct contact 28) was synthesized and characterized. The stained black talc was filled into acrylonitrile–butadiene–styrene at different content levels, and their mechanical, thermal and colorimetric properties were investigated. Furthermore, samples filled with talc were prepared in the same way. The particle size of stained black talc located both within and at the interface of acrylonitrile–butadiene–styrene was larger than that of the talc which was ascribed to agglomeration. As black talc can increase toughness and strength of acrylonitrile–butadiene–styrene in low filler loading, and the dye can improve compatibility between black talc and acrylonitrile–butadiene–styrene, so mechanical and thermal properties of stained black talc/acrylonitrile–butadiene–styrene have been enhanced. Within a certain amount of filler loading, acrylonitrile–butadiene–styrene can be colored by stained black talc, and its color deepened as filler loading increased. However, it can absorb part of incident light as some filler existed in the form of solid particles in acrylonitrile–butadiene–styrene matrix, which led to acrylonitrile–butadiene–styrene dimmed with increment of filler loading. This filler achieved modification, filling, enhancement and colorability; the optimum filler concentrations were less than 10 wt%. This study opens a new approach to utilizing black talc and to fabricating polymer fillers.

[en] We extend Mather's work (1985 Comment. Math. Helv. 60 508–57) to high-dimensional cylinder maps defined by monotone recurrence relations, e.g. the generalized Frenkel–Kontorova model with finite range interactions. We construct uncountably many Denjoy minimal sets provided that the Birkhoff minimizers with some irrational rotation number ω do not form a foliation. (paper)

[en] Objective: To investigate whether the average fractional anisotropy (FA) of the corticospinal tracts is statistically different between patients with relapsing-remitting multiple sclerosis (RRMS) and normal volunteers by using diffusion tensor tractography (DTF), and to determine whether this index correlated with expanded disability status scale (EDSS) in RRMS patients. Methods: Thirty-six volunteers and 64 patients with RRMS underwent diffusion tensor imaging. Then the corticospinal tracts were reconstructed, and the FA values of them were computed. The difference of FA of the corticospinal tracts between RRMS patients and normal volunteers was investigated, and the correlation of this index with EDSS and pyramidal score was also determined. Results: There was no sex (male: 0.501±0.026, female: 0.493±0.024) and side (left: 0.500±0.031, right: 0.494±0.024) differences of FA on corticospinal tracts (P>0.05). The average FA of the corticospinal tracts (0.472±O.037) of RRMS group was significantly lower than that of normal control group (0.497±0.028) (P<0.001). However, the average FA of cerebral type (0.469±0.038) of RRMS had no statistical difference with that (0.476±0.035) of spinal type (P>0.05). The average FA of the corticospinal tracts correlated with EDSS (r=-0.193, P<0.05) and pyramidal score (mean value=2.0) (r= -0.218, P<0.05). Among them, the FA of the corticospinal tracts of the cerebral type of RRMS correlated more with EDSS (mean value=3.1) (r=-0.273, P<0.05) and pyramidal score (mean value r=-2.1) (r=-0.268, P<0.05), but this correlation was not found in the spinal type (P>0.05). Conclusion: The average FA of the corticospinal tracts of RRMS patients is significantly abnormal and this index may be suitable in evaluating the functional status of the cerebral type of RRMS patients. (authors)

[en] Objective: To investigate the value of macrophage activity imaging (MAI) in the diagnosis of brain and spinal cord lesions in rat model of multiple sclerosis (MS). Methods: Twenty LEW rats were divided into 15 model rats and 5 control rats. MS animal model, experimental autoimmune encephalomyelitis (EAE) was induced by the injection of peptide 35-55 of myelin oligodendrocyte glycoprotein (MOG_35-55), MRI was performed on the third day of the acute stage of disease. The brain and spinal cord of' rats were scanned by 3.0 T MR scanner (Siemens Trio Tim) with quadrature wrist joint coil. The T₂W and T₁W images, Gadolinium enhanced T₁W images in 3D volume were obtained respectively. The MAI were obtained at 24 hours after intravenous injection of ultra small superparamagnetic iron oxide (USPIO) as contrast medium on T₂WI. The workstation with special software was used for the reconstruction images of brain and spinal cord of rat in multiple orientations. Results: Fifteen MOG35₅5-EAE rats model of' MS were successfully induced. The great majority lesions of central nervous system in acute stage were located in the brain (58/63) and less in the spinal cord (5/63). The main manifestation of EAE lesions presented was hyperintensity on T₂WI and hypointensity on T₁WI, and some lesions had enhancement after Gd-DTPA injection. The EAE lesions presented as hypointensity on MAI images, but some of them were found to be isointensity on T₂WI. The enhancement pattern was discrepant between USPIO and Gd-DTPA. The sensitivity of depicting lesions of MOG_35-55-EAE rat at acute stage were higher on T₂WI (14/15) and MAI (13/15), and the detection rate was 100% (15/15) if they were combined. Gd-DTPA enhanced T₁WI had a lower sensitivity (7/15). All the MAI findings were negative in the control rats. Conclusions: MAI can complement the drawback of conventional MRI techniques by continuously monitoring the inflammatory activity of EAE lesions, and it could raise the detection rate of EAE lesions by combining with T₂WI. Gd-DTPA enhanced T₁WI monitors the breakdown of the blood brain barrier. MAI and Gd-DTPA enhanced MR imaging are complementary in the diagnosis and monitoring of EAE lesions. (authors)

[en] Experimental observations shows that the oxide formed on Zr alloys are strongly textured. The texture and grain-boundary characteristics of oxide are dependent on the texture of metal substrate. Computer simulation and thermodynamic modeling clarify the effect of metal substrate on structure of oxide film, and intrinsic factors affecting the microstructure. Models of diffusion process of hydrogen atoms and oxygen diffusion through oxide are presented. Both intra-granular and inter-granular hydrides were found following (0001)_α-Zr//(111)_δ-ZrH1.5 relationship. The through-thickness texture inhomogeneity in cladding tubes, the effects of hoop stress on the hydride orientation and the formation of interlinked hydride structure were studied. A thermodynamic model was developed to analyze the nucleation and the stress-induced reorientation of intergranular hydrides. These works provide a framework for understanding the oxidation, the hydrogen ingress and the hydride formation in Zr alloys. (author)

[en] Objective: To establish a rat model of multiple sclerosis (MS) for clinical MRI study. Methods: The Lewis (LEW) rats were immunized by myelin oligodendrocyte glycoprotein peptide 35-55 (MOG_35-55) emulsified with complete Freunds adjuvant/incomplete Freunds adjuvant. Twenty LEW rats were selected. Group A rats were 5, group B rats were 10 and control group rats were 5. MRI and histopathology analysis were observed on group A and control group, and clinical course were observed on group B. The clinical course was observed and the brain and spinal cord of EAE rats were scanned on 3.0 T MR system with quadrature wrist joint coil on the third day of the acute stage of disease. The T₂/T₁ weighted images and Gadolinium enhanced T₁ weighted images in 3D volume were obtained respectively. The magnetization transfer ratio (MTR) images were calculated with special software in workstation. Rats were sacrificed within 24 h after MRI, and the histopathological changes of central nervous system were observed. Results: Twice immunization of MOG_35-55 was used and a rat model of MS was successfully induced with all the rats. The model had varied clinical symptoms. The lesions of central nervous system at acute stage on group A (5 rats) were depicted on MRI. The lesions located in the brain and the spinal cord with main manifestation of hyperintensity on T₂ weighed images and hypointensity on T₁ weighted images. Some lesions had Gd-DTPA enhancement, and the value of MTR decreased. The infiltration of mononuclear cells around blood vessels and the extensive distribution of lesions of demyelination in brain and spinal cord were verified by histological examination. Conclusions: Twice immunization of MOG_35-55 could produce a rat model which mimics MS. The model is stable with higher incidence, and the antigen is cheap and obtained easily. The intravital monitoring of brain and spinal cord lesions in MOG_35-55 induced rat model is possible on 3.0 T clinical whole- body MR scanner with a quadrature wrist joint coil. MOG_35-55induced rat model is an ideal MS model for clinical MRI study. (authors)