The significance of pockmarks to understanding fluid flow processes and geohazards

Underwater gas and liquid escape from the seafloor has long been treated as a mere curiosity. It was only after the advent of the side‐scan sonar and the subsequent discovery of pockmarks that the scale of fluid escape and the moon‐like terrain on parts of the ocean floor became generally known. Today, pockmarks ranging in size from the ‘unit pockmark’ (1–10 m wide, < 0.6 m deep) to the normal pockmark (10–700 m wide, up to 45 m deep) are known to occur in most seas, oceans, lakes and in many diverse geological settings. In addition to indicating areas of the seabed that are ‘hydraulically active’, pockmarks are known to occur on continental slopes with gas hydrates and in association with slides and slumps. However, possibly their potentially greatest significance is as an indicator of deep fluid pressure build‐up prior to earthquakes. Whereas only a few locations containing active (bubbling) pockmarks are known, those that become active a few days prior to major earthquakes may be important precursors that have been overlooked. Pockmark fields and individual pockmarks need to be instrumented with temperature and pressure sensors, and monitoring should continue over years. The scale of such research calls for a multinational project in several pockmark fields in various geological settings.     

文化冲突与跨国迁移群体的适应策略——以南非中国新移民群体为例

论文运用田野调查的方法,选择南非的中国新移民作为研究对象,介绍了20世纪90年代以来南非中国新移民群体的概况,阐释了中国新移民在南非遭遇的文化冲突以及他们的适应策略。研究发现,中国新移民在基本价值、家庭观念、消费观念等方面与南非人有明显的冲突,新移民群体对＂南非文化＂持一种＂保持距离＂的态度。具体体现在居住区域、社会交往和通婚等方面。同时,同质性强的中国新移民身处介于同质与异质之间的社会空间,对南非文化仍有明显的隔阂。     

The coastal landslides of Shetland

Little is known of hard-rock coastal landsliding in Scotland. We identify 128 individual coastal landslides or landslide complexes >50 m wide along the coasts of Shetland. Most are apparently translational slides characterized by headscarps, displaced blocks and/or debris runout, but 13 deep-seated failures with tension cracks up to 200 m inland from cliff crests were also identified. Thirty-one sites exhibit evidence of at least localized recent activity. Landslide distribution is primarily determined by the distribution of coastal cliffs >30 m high, and they are preferentially developed on metasedimentary rocks. Analysis of 16 landslides on Fetlar (NE Shetland) indicates that most are translational dip-slip failures; 3 represent deep-seated failures and several exhibit active frontal erosion attributable to basal sapping by storm waves. As these landslides terminate in shallow water, failure was probably initiated when rising sea level resulted in footslope erosion and upslope propagation of instability, causing downslope displacement of landslide blocks on upper slopes. ¹⁰Be exposure dating of two headscarps yielded ages of 4.8?±?0.2 ka and 4.4?±?0.2 ka, consistent with the onset of footslope erosion as sea level rose. Our results suggest that landslides have played a hitherto undocumented but important role in retreat of cliffed coastlines in Scotland.     

The Sherrington–Cushing connection: A bench to bedside collaboration at the dawn of the twentieth century

ABSTRACT

British physiologist Charles Sherrington (1857–1952) and American neurosurgeon Harvey Cushing (1869–1939) were seminal figures in the history of neuroscience. The two came from different worlds, one laboratory-based and the other largely clinical. Their scientific intersection, beginning in July 1901, provides a glimpse into a nascent form of “bench to bedside” collaboration, which carried with it the potential to extend the arm of neurophysiological experimentation from Sherrington’s laboratory to Cushing’s operatory. I reviewed extensive primary source materials archived at Yale University School of Medicine Library. Sherrington viewed Cushing’s bedside work as an opportunity, in humans, to extend his bench-side physiological observations on higher primates, at times almost directing Cushing in the clinic. Cushing would indeed take Sherrington’s observations on apes and extend them to his patients, and the work would eventually overturn the prevailing notion that the motor and sensory cortex were intermixed across the Rolandic fissure.