Thickness-dependent anisotropic transport of phonons and charges in few-layered PdSe2.

So far, layered PdSe2 has attracted much attention due to its completely tunable band-gap with varying layer numbers, yet the thickness-dependent transporting properties have been rarely studied. We have systematically studied the electronic structures, phonon and charge transport properties, and thermoelectric properties of few-layered (from 1L to 4L) and bulk PdSe2 by first-principles calculations and Boltzmann transport theory. As the thickness increases, the energy levels of band edges relative to 4s of selenium move oppositely due to their different bonding states, leading to the power-law decrease of the band-gap. Meanwhile, the electron effective mass decreases rapidly while the hole effective mass increases significantly compared with those unperturbed. Calculations on elastic constants reveal that both bulk and few-layered PdSe2 are mechanically stable, and the bulk is ductile with a Poisson's ratio of 0.27. The shifts of Raman active modes with respect to the thickness as well as their Gruneisen parameters are analyzed and the underlying physics is discussed. At room temperature, the thermal conductivities of the bulk are 7.7, 10.1 and 0.9 W m-1 K-1 along the a, b and c axes, respectively. It is found that the low-frequency modes (<2.0 THz) contribute about 80% of in-plane thermal conductivities. Due to the enhanced contribution from the ZA mode, the thermal conductivity of few-layered PdSe2 is much larger than that of the bulk. The ZA mode is mainly scattered by itself and the Umklapp scattering dominates in the process as the thickness increases. Calculations on charge transport reveal that the electron mobility increases from 2.5-13.2 (1L) to 121.9-167.8 (4L) cm2 V-1 s-1 with the decreasing anisotropy µb/µa, while the hole mobility remains to be ∼20 cm2 V-1 s-1, which is in good agreement with the experimental results. Calculations on the thermoelectric properties reveal that the ZT value as well as the power factor increases largely as the thickness increases and it gets to be optimum for the triple layer. Interestingly, the transport of electrons and phonons is decoupled along the out-of-plane direction, which makes bulk PdSe2 exhibit good thermoelectric performance along the c axis.

mRNA expression change of myelin gene in hippocampus following cerebral ischemia / 中华急诊医学杂志

Objective To study the mRNA expression of myelin basic protein (MBP) and myelin oligodendregha glyeoprotein (MOG) in hippocampus of rats following global brain ischemia.Method The four- vessel occlusion animal model in the Sprague-Dawley rats was used in this study.The mRNA expression levels of MBP and MOG in the hippocampus of rats were analyzed by reverse transcription polymerase chain reaction (RT- PCR) at day 2,4,7,14 and 28 days after global brain ischemia.There were eight rats at each time-point and sham operated group.Results The mRNA expression of both MBP and MOG in hippocampus of rats decreased at 2 days after global brain ischemia.The gene expression of myelin gene decreased significantly at 7 days and it reached to the lowest level at 28 days.Compared with sham operated group,the gene expression of MBP and MOG in hippocampus of rats decreased significantly at 7,14 and 28 days after global brain ischemia (P

Analysis of 994(G--> T) mutation in the plasma platelet-activating factor acetylhydrolase gene in the patients with cerebral infarction / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To investigate the relationship between plasma platelet-activating factor acetylhydrolase (PAF-AH) gene 994(G--> T) mutation in exon 9 and the patients with cerebral infarction in Chinese Hans.</p><p><b>METHODS</b>The authors conducted a case-control study including 108 patients in three groups (atherosclerotic cerebral infarction group, lacunar infarction group and cerebral embolism group) and 215 normal subjects as controls. Genomic DNA was analyzed for the mutant allele by a specific polymerase chain reaction.</p><p><b>RESULTS</b>The frequency of the mutant genotype in the 102 patients with cerebral infarction was 35.19%(32.41% heterozygotes and 2.78% homozygotes), and was 38.10%(34.92% heterozygotes and 3.18% homozygotes) in the atherosclerotic cerebral infarction group, being all significantly higher than the control group's 20.46% (18.60% heterozygotes and 1.86% homozygotes)(P< 0.01); however, the frequencies of the mutant genotype in the lacunar infarction group and cerebral embolism group were 32.35% (29.41% heterozygotes and 2.94% homozygotes) and 27.27% (27.27% heterozygotes and 0 homozygotes) respectively, being not statistically different from those of the controls (P> 0.05).</p><p><b>CONCLUSION</b>These findings show that the 994(G--> T) mutation of plasma PAF-AH gene may be an independent risk for atherosclerotic cerebral infarction, but not for lacunar infarction.</p>

Decreased treatment gap in epilepsy after intervention in five rural areas of China / 中华神经科杂志

Objective To evaluate the change of treatment gap of epilepsy after intervention in rural areas of China.Method Six months after being stopped from the intervention project in 2004,using the same method as the first survey at the baseline,a door-to-door epidemiological survey was conducted again in 5 rural areas where the intervention measures had been carried out for about 3 years.Results Three hundred and twenty cases of epilepsy were diagnosed in the total sample population,yielding a prevalence rate of 0.62% and the prevalence of active epilepsy 0.44%.The prevalence and the active prevalence of epilepsy in the survey in 2000 were 0.70% and 0.46% respectively.Of the people with epilepsy,39.1% were treated regularly which increased about 14% than that in the baseline survey (24.8%).The treatment gap for active epilepsy was 49.8%,which decreased by 12.8% than that in the first survey (62.6%). Conclusion The treatment gap of epilepsy in the demonstration areas has decreased remarkably,proving that the intervention measures used in the study are effective and feasible in rural areas of China.