• Characteristics and hazards of different snow avalanche types in a continental snow climate region in the Central Tianshan Mountains

    分类: 地球科学 >> 地理学 提交时间: 2021-04-30 合作期刊: 《干旱区科学》

    摘要:Snow avalanches are a common natural hazard in many countries with seasonally snow-covered mountains. The avalanche hazard varies with snow avalanche type in different snow climate regions and at different times. The ability to understand the characteristics of avalanche activity and hazards of different snow avalanche types is a prerequisite for improving avalanche disaster management in the mid-altitude region of the Central Tianshan Mountains. In this study, we collected data related to avalanche, snowpack, and meteorology during four snow seasons (from 2015 to 2019), and analysed the characteristics and hazards of different types of avalanches. The snow climate of the mid-altitude region of the Central Tianshan Mountains was examined using a snow climate classification scheme, and the results showed that the mountain range has a continental snow climate. To quantify the hazards of different types of avalanches and describe their situation over time in the continental snow climate region, this study used the avalanche hazard degree to assess the hazards of four types of avalanches, i.e., full-depth dry snow avalanches, full-depth wet snow avalanches, surface-layer dry snow avalanches, and surface-layer wet snow avalanches. The results indicated that surface-layer dry snow avalanches were characterized by large sizes and high release frequencies, which made them having the highest avalanche hazard degree in the Central Tianshan Mountains with a continental snow climate. The overall avalanche hazard showed a single peak pattern over time during the snow season, and the greatest hazard occurred in the second half of February when the snowpack was deep and the temperature increased. This study can help the disaster and emergency management departments rationally arrange avalanche relief resources and develop avalanche prevention strategies.

  • Layer-specific response properties of the human lateral geniculate nucleus and superior colliculus

    分类: 生物学 >> 生物物理学 >> 神经科学 提交时间: 2016-05-12

    摘要:The human LGN and SC consist of distinct layers, but their layer-specific response properties remain poorly understood. In this fMRI study, we characterized visual response properties of the magnocellular (M) and parvocellular (P) layers of the human LGN, as well as at different depths in the SC. Results show that fMRI is capable of resolving layer-specific signals from the LGN and SC. Compared to the P layers of the LGN, the M layers preferred higher temporal frequency, lower spatial frequency stimuli, and their responses saturated at lower contrast. Furthermore, the M layers are colorblind while the P layers showed robust response to both chromatic and achromatic stimuli. Visual responses in the SC were strongest in the superficial voxels, which showed similar spatiotemporal and contrast response properties as the M layers of the LGN, but were sensitive to color and responded strongly to isoluminant color stimulus. Thus, the non-invasive fMRI measures show that the M and P layers of human LGN have similar response properties as that observed in non-human primates and the superficial layers of the human SC prefer transient inputs but are not colorblind. (C) 2015 Elsevier Inc. All rights reserved.