三嗪成炭剂和聚磷酸铵协同阻燃动态硫化热塑性弹性体阻燃性能及成炭机制

将三嗪成炭剂(CFA)与聚磷酸铵(APP)复配成膨胀型阻燃剂(IFR),采用极限氧指数、垂直燃烧和锥形量热等测试研究了不同CFA和APP的比例对动态硫化热塑性弹性体(TPV)阻燃性能和力学性能的影响;并用扫描电子显微镜、拉曼光谱、X射线衍射和红外光谱分析了残炭的形貌和结构,进一步研究了其成炭机制。研究结果表明,当CFA和APP的质量比为1∶3,总添加量为40%(质量分数)时,TPV/IFR复合材料具有最佳的阻燃性能,LOI达到26.4%,且通过UL-94 V-0级;锥形量热测试表明,TPV/IFR复合材料具有优异的阻燃和抑烟性能;力学性能测试表明,TPV/IFR复合材料仍具有优异的力学性能,其拉伸强度和断裂伸长率分别为4.19 MPa和391.06%;残炭的形貌和结构分析表明,TPV/IFR复合材料以凝聚相成炭阻燃作用为主,燃烧后形成含有P-O-C和P-O-P交联结构的致密石墨焦炭层,起到隔热隔氧的作用,提高了材料的阻燃性能。

Nerve transfer helps repair brachial plexus injury by increasing cerebral cortical plasticity

In the treatment of brachial plexus injury, nerves that are functionally less important are transferred onto the distal ends of damaged crucial nerves to help recover neuromuscular function in the target region. For example, intercostal nerves are transferred onto axillary nerves, and accessory nerves are transferred onto suprascapular nerves, the phrenic nerve is transferred onto the musculocutaneous nerves, and the contralateral C7 nerve is transferred onto the median or radial nerves. Nerve transfer has become a major method for reconstructing the brachial plexus after avulsion injury. Many experiments have shown that nerve transfers for treatment of brachial plexus injury can help reconstruct cerebral cortical function and increase cortical plasticity. In this review article, we summarize the recent progress in the use of diverse nerve transfer methods for the repair of brachial plexus injury, and we discuss the impact of nerve transfer on cerebral cortical plasticity after brachial plexus injury.

Efficient oxidation of ethylbenzene catalyzed by cobalt zeolitic imidazolate framework ZIF-67 and NHPI

Efficient catalytic oxidation of ethylbenzene to acetophenone was realized using the catalytic system of cobalt zeolitic imidazolate framework ZIF-67/N-hydroxyphthalimide （NHPI） under mild conditions. 95.2% conversion of ethylbenzene with 90.3% selectivity to acetophenone could be obtained at 373 K under 0.3 MPa 02 for 9 h. The results show that there exists synergetic effect between ZIF-67 and NHPI. 1-Phenylethyl hydroperoxide （PEHP） was generated via a radical process involving the hydrogen abstraction from ethylbenzene by phthalimide N-oxyl, and subsequently effectively decomposed to acetophenone by ZIF-67.

赏析等价转化思想在解决几何问题时的应用

立体几何体积问题是高考的重要考点,很多学生不擅长用等价转化的数学思想解决它.根据转化方式的不同,本文通过例析并点评了线段中点在平面外的转化、线段中点在平面内的转化、线面平行时线上点面距离的转化、不规则几何体体积的转化,来让大家充分认识等价转化思想在求体积时化难为易,灵活巧妙地应用.

Diurnal variation of nitrated polycyclic aromatic hydrocarbons in PM_(10) at a roadside site in Xiamen,China

Intensive daytime and nighttime sampling was carried out from 23 Oct to 31 Dec 2008 to investigate the occurrence of nitrated polycyclic aromatic hydrocarbons （NPAHs） in PM1o at a roadside site in Xiamen, China. At the same time, six PMt0 samples were collected from a nearby roadway tunnel for comparison. Six NPAHs, namely 9-nitroanthracene, 2- and 3-nitrofluoranthene, 1- nitropyrene, 7-nitrobenz[a]anthracene, and 6-nitrobenzo[a]pyrene, were identified and quantified using GC/MS in negative ion chemical ionization mode. The average total concentration of six NPAHs （~NPAHs） in the cold season （26 Nov-31 Dec） was 2.3 （daytime） and 9.9 （nighttime） times higher than those in the warm season. Significant statistical difference （p 〈 0.01, 2-tailed） of ∑NPAHs between daytime and nighttime was found during both the warm and cold seasons. NPAHs were significantly positively correlated with their parent PAHs and nitrogen dioxide but negatively correlated with ambient temperature. The ratio of 2 ＋ 3-nitrofluoranthene to 1- nitropyrene exhibited a similar diurnal pattern as ZNPAHs and was generally greater than 5, indicating the importance of secondary atmospheric formation. The diurnal variations of NPAHs were all influenced by the diurnal variations of PAHs, nitrogen dioxide, sunlight, and temperature. The daily inhalable exposure to the six NPAHs in the tunnel was much higher than the roadside values in the warm season but only slightly higher than those in the cold season.

Microstructure and high-temperature properties of Fe-Ti-Cr-Mo-B-C-Y2O3 laser cladding coating

Fe-based composite coatings were fabricated on 5 CrNiMo die steel by laser beam melting a precursor mixture of ferrotitanium,ferrochromium,ferromolybdenum,B4 C and Y2 O3 powders.Micro structure and properties of the coatings were studied by X-ray diffraction(XRD),scanning electron microscopy(SEM),energy-dispersive spectrometer(EDS),resistance furnace and high-temperature tribometer.The results show that(Ti,Mo)C particles with flower-like and(Ti,Mo)B2 with block-like shapes are in situ formed during laser cladding.Volume faction of multiple ceramic particles increases with the increasing of Y2 O3.The cumulative oxidation mass of the coating with 2 wt% Y2 O3 is decreased by one-third than that of the coating without Y2 O3.The oxidation layer of the coating with Y2 O3 is getting smooth.Meanwhile,high temperature wear volume loss of the coating with 2 wt% Y2 O3 is about 40% that of the coating without Y2 O3.The coating with 2 wt% Y2 O3 shows a smoother wear scar and few flat grooves are observed after high temperature wear test.

Effectiveness of intravenous r- tPA versus UK for acute ischaemic stroke: a nationwide prospective Chinese registry study

Background Intravenous recombinant tissue plasminogen activator(r-tPA)and urokinase(UK)are both recommended for the treatment of acute ischaemic stroke(AIS)in China,but with few comparative outcome data being available.We aimed to compare the outcomes of these two thrombolytic agents for the treatment of patients within 4.5 hours of onset of AIS in routine clinical practice in China.Methods A pre-planned,prospective,nationwide,multicentre,real-world registry of consecutive patients with AIS(age≥18 years)who received r-tPA or UK within 4.5 hours of symptom onset according to local decision-making and guideline recommendations during 2017-2019.The primary effectiveness outcome was the proportion of patients with an excellent functional outcome(defined by modified Rankin scale scores 0 to 1)at 90 days.The key safety endpoint was symptomatic intracranial haemorrhage according to standard definitions.Multivariable logistic regression was used for comparative analysis,with adjustment according to propensity scores to ensure balance in baseline characteristics.Results Overall,4130 patients with AIS were registered but 320 had incomplete or missing data,leaving 3810 with available data for analysis of whom 2666 received r-tPA(median dose 0.88(IQR 0.78-0.90)mg/kg)and 1144 received UK(1.71(1.43-2.00)×104 international unit per kilogram).There were several significant intergroup differences in patient characteristics:r-tPA patients were more educated,had less history of stroke,lower systolic blood pressure,greater neurological impairment and shorter treatment times from symptom onset than UK patients.However,in adjusted analysis,the frequency of excellent outcome(OR 1.18,95%CI 1.00 to 1.40,p=0.052)and symptomatic intracranial haemorrhage(OR 0.70,95%CI 0.33 to 1.47,p=0.344)were similar between groups.Conclusions UK may be as effective and carry a similar safety profile as r-tPA in treating mild to moderate AIS within guidelines in China.Registration http://www.clinicaltrials.gov.unique identifier:NCT02854592.

Antiplatelet Therapy in Acute Mild-Moderate Ischemic Stroke(ATAMIS):a parallel,randomised,open-label,multicentre,prospective study

Background A recent study shows that dual antiplatelet therapy with clopidogrel plus aspirin is superior to aspirin monotherapy for minor stroke,which is defined as a National Institutes of Health Stroke Scale(NIHSS)score of≤3.However,acute mild-moderate ischaemic stroke(4≤NIHSS≤10)still needs aggressive antiplatelet intervention to prevent deterioration and recurrence of stroke.The efficacy and safety of dual antiplatelet therapy versus aspirin monotherapy in the population are not clear.A multicentre clinical trial is designed to evaluate the efficacy and safety of clopidogrel plus aspirin therapy versus aspirin monotherapy within 48 hours of symptom onset of mild-moderate ischaemic stroke.Methods/Design The study is a randomised,open-label,multicentre,prospective trial with a target enrolment of 2700 patients from 60 centres in Northeast China.A treatment allocation identification number to each enrolled patient will be provided by a random number generator.The follow-up time for the clopidogrel plus aspirin and aspirin monotherapy groups is 90 days.The primary efficacy endpoint is a stroke progression event,which is defined as≥4 point increase in the NIHSS score in 48 hours.The second efficacy endpoints include new ischaemic stroke within 90 days,change in the NIHSS score within 14 days,modified Rankin Scale score on day 90 and other vascular or death events within 90 days.The safety endpoints include mucocutaneous haemorrhage,organ haemorrhage and intracranial haemorrhage,adverse events and severe adverse events.χ^(2)test,t-test(or Mann-Whitney test),survival analysis and Cox proportional hazards models will be conducted.The findings of the study may provide an important evidence for clinical practice for these patients.Discussion The trial will be conducted under a rational design and will provide valuable evidence on the appropriate treatment for this population.Ethics and dissemination The study was reviewed and approved by the Ethics Committee of the General Hospital of Shen-Yang Military Region(no K(2016)6).Trial registration number NCT02869009;Pre-results.

Sulfur mediated heavy metal biogeochemical cycles in coastal wetlands:From sediments,rhizosphere to vegetation

The interactions and mechanisms between sulfur and heavy metals are a growing focus of biogeochemical studies in coastal wetlands.These issues underline the fate of heavy metals bound in sediments or released into the system through sediments.Despite the fact that numerous published studies have suggested sulfur has a significant impact on the bioavailability of heavy metals accumulated in coastal wetlands,to date,no review article has systematically summarized those studies,particularly from the perspective of the three major components of wetland ecosystems(sediments,rhizosphere,and vegetation).The present review summarizes the studies published in the past four decades and highlights the major achievements in this field.Research and studies available thus far indicate that under anaerobic conditions,most of the potentially bioavailable heavy metals in coastal wetland sediments are fixed as precipitates,such as metal sulfides.However,fluctuations in physicochemical conditions may affect sulfur cycling,and hence,directly or indirectly lead to the conversion and migration of heavy metals.In the rhizosphere,root activities and microbes together affect the speciation and transformation of sulfur which in turn mediate the migration of heavy metals.As for plant tissues,tolerance to heavy metals is enhanced by sulfur-containing compounds via promoting a series of chelation and detoxification processes.Finally,to further understand the interactions between sulfur and heavy metals in coastal wetlands,some major future research directions are proposed.