自新冠肺炎疫情以来,全球对一次性医用口罩(disposable medical masks,DMMs)等医疗物资的需求不断攀升,根据流行性传染病专家预判,在未来很长一段时间内,通过佩戴口罩阻隔细菌和病毒等将成为生活常态.如何处理大量废弃DMMs,是全球各个...自新冠肺炎疫情以来,全球对一次性医用口罩(disposable medical masks,DMMs)等医疗物资的需求不断攀升,根据流行性传染病专家预判,在未来很长一段时间内,通过佩戴口罩阻隔细菌和病毒等将成为生活常态.如何处理大量废弃DMMs,是全球各个国家和地区面临的重要课题.本综述从化学升级再造(chemical upcycling)的角度出发,综述和展望了废弃DMMs的主体材料(聚丙烯,PP)回收的现状和未来升级再造的途径,包括机械共混、化学改性、可控降解、物理加工改性等,并分析了各种途径的优劣势,指出将废弃PP通过化学方法有选择性地转换为产品种类单一的相关化学品、燃料和高附加值的相关材料,是实现将废弃DMMs变“废”为“宝”和可持续发展的根本方法.展开更多
Vacuum sealing drainage (VSD) is frequently used in abdominal surgeries. However, relevant guidelines are rare. Chin ese Trauma Surge on Associati on orga nized a committee composed of 28 experts across China in July ...Vacuum sealing drainage (VSD) is frequently used in abdominal surgeries. However, relevant guidelines are rare. Chin ese Trauma Surge on Associati on orga nized a committee composed of 28 experts across China in July 2017, aiming to provide an evidence-based recommendation for the application of VSD in abdominal surgeries.Eleven questions regarding the use of VSD in abdominal surgeries were addressed:(1) which type of materials should be respectively chosen for the intraperitoneal cavity, retroperitoneal cavity and superficial incisions?(2) Can VSD be preventively used for a high-risk abdominal incision w让h primary suture?(3) Can VSD be used in severely contaminated/infected abdominal surgical sites?(4) Can VSD be used for temporary abdominal cavity closure under some special conditions such as severe abdominal trauma, infection, liver transplantation and intra-abdominal volume increment in abdominal compartment syndrome?(5) Can VSD be used in abdominal organ inflammation, injury, or postoperative drainage?(6) Can VSD be used in the treatment of intestinal fistula and pancreatic fistula?(7) Can VSD be used in the treatment of intra-abdominal and extra-peritoneal abscess?(8) Can VSD be used in the treatment of abdominal wall wounds, wound cavity, and defects?(9) Does VSD in crease the risk of bleeding?(10) Does VSD increase the risk of intestinal wail injury?(11) Does VSD increase the risk of peritoneal adhesion? Focusing on these questions, evidence-based recommendations were given accordingly. VSD was strongly recommended regarding the questions 2-4. Weak recommendations were made regarding questions 1 and 5-11. Proper use of VSD in abdominal surgeries can lower the risk of infection in abdominal incisions with primary suture, treat severely contaminated/infected surgical sites and facilitate temporary abdominal cavity closure.展开更多
In wireless sensor networks, sensed information is expected to be reliably and timely delivered to a sink in an ad-hoc way. However, it is challenging to achieve this goal because of the highly dynamic topology induce...In wireless sensor networks, sensed information is expected to be reliably and timely delivered to a sink in an ad-hoc way. However, it is challenging to achieve this goal because of the highly dynamic topology induced from asynchronous duty cycles and temporally and spatially varying link quality among nodes. Currently some opportunistic forwarding protocols have been proposed to address the challenge. However, they involve complicated mechanisms to determine the best forwarder at each hop, which incurs heavy overheads for the resource-constrained nodes. In this paper, we propose a light-weight opportunistic forwarding （LWOF） scheme. Different from other recently proposed opportunistic forwarding schemes, LWOF employs neither historical network information nor a contention process to select a forwarder prior to data transmissions. It confines forwarding candidates to an optimized area, and takes advantage of the preamble in low-power-listening （LPL） MAC protocols and dual-channel communication to forward a packet to a unique downstream node towards the sink with a high probability, without making a forwarding decision prior to data transmission. Under LWOF, we optimize LPL MAC protocol to have a shortened preamble （LWMAC）, based on a theoretical analysis on the relationship among preamble length, delivery probability at each hop, node density and sleep duration. Simulation results show that LWOF, along with LWMAC, can achieve relatively good performance in terms of delivery reliability and latency, as a receiver-based opportunistic forwarding protocol, while reducing energy consumption per packet by at least twice.展开更多
文摘自新冠肺炎疫情以来,全球对一次性医用口罩(disposable medical masks,DMMs)等医疗物资的需求不断攀升,根据流行性传染病专家预判,在未来很长一段时间内,通过佩戴口罩阻隔细菌和病毒等将成为生活常态.如何处理大量废弃DMMs,是全球各个国家和地区面临的重要课题.本综述从化学升级再造(chemical upcycling)的角度出发,综述和展望了废弃DMMs的主体材料(聚丙烯,PP)回收的现状和未来升级再造的途径,包括机械共混、化学改性、可控降解、物理加工改性等,并分析了各种途径的优劣势,指出将废弃PP通过化学方法有选择性地转换为产品种类单一的相关化学品、燃料和高附加值的相关材料,是实现将废弃DMMs变“废”为“宝”和可持续发展的根本方法.
文摘Vacuum sealing drainage (VSD) is frequently used in abdominal surgeries. However, relevant guidelines are rare. Chin ese Trauma Surge on Associati on orga nized a committee composed of 28 experts across China in July 2017, aiming to provide an evidence-based recommendation for the application of VSD in abdominal surgeries.Eleven questions regarding the use of VSD in abdominal surgeries were addressed:(1) which type of materials should be respectively chosen for the intraperitoneal cavity, retroperitoneal cavity and superficial incisions?(2) Can VSD be preventively used for a high-risk abdominal incision w让h primary suture?(3) Can VSD be used in severely contaminated/infected abdominal surgical sites?(4) Can VSD be used for temporary abdominal cavity closure under some special conditions such as severe abdominal trauma, infection, liver transplantation and intra-abdominal volume increment in abdominal compartment syndrome?(5) Can VSD be used in abdominal organ inflammation, injury, or postoperative drainage?(6) Can VSD be used in the treatment of intestinal fistula and pancreatic fistula?(7) Can VSD be used in the treatment of intra-abdominal and extra-peritoneal abscess?(8) Can VSD be used in the treatment of abdominal wall wounds, wound cavity, and defects?(9) Does VSD in crease the risk of bleeding?(10) Does VSD increase the risk of intestinal wail injury?(11) Does VSD increase the risk of peritoneal adhesion? Focusing on these questions, evidence-based recommendations were given accordingly. VSD was strongly recommended regarding the questions 2-4. Weak recommendations were made regarding questions 1 and 5-11. Proper use of VSD in abdominal surgeries can lower the risk of infection in abdominal incisions with primary suture, treat severely contaminated/infected surgical sites and facilitate temporary abdominal cavity closure.
基金This work is supported in part by the International Science and Technology （S＆T） Cooperation Program of China （ISTCP） under Grant No. 2013DFA10690, and the National Natural Science Foundation of China （NSFC） under Grant Nos. 61672498, 61303246 and 61100180.
文摘In wireless sensor networks, sensed information is expected to be reliably and timely delivered to a sink in an ad-hoc way. However, it is challenging to achieve this goal because of the highly dynamic topology induced from asynchronous duty cycles and temporally and spatially varying link quality among nodes. Currently some opportunistic forwarding protocols have been proposed to address the challenge. However, they involve complicated mechanisms to determine the best forwarder at each hop, which incurs heavy overheads for the resource-constrained nodes. In this paper, we propose a light-weight opportunistic forwarding （LWOF） scheme. Different from other recently proposed opportunistic forwarding schemes, LWOF employs neither historical network information nor a contention process to select a forwarder prior to data transmissions. It confines forwarding candidates to an optimized area, and takes advantage of the preamble in low-power-listening （LPL） MAC protocols and dual-channel communication to forward a packet to a unique downstream node towards the sink with a high probability, without making a forwarding decision prior to data transmission. Under LWOF, we optimize LPL MAC protocol to have a shortened preamble （LWMAC）, based on a theoretical analysis on the relationship among preamble length, delivery probability at each hop, node density and sleep duration. Simulation results show that LWOF, along with LWMAC, can achieve relatively good performance in terms of delivery reliability and latency, as a receiver-based opportunistic forwarding protocol, while reducing energy consumption per packet by at least twice.
