AIM: To evaluate the safety and efficacy of transepithelial photorefractive keratectomy(t-PRK) with adjuvant mitomycin C(MMC) versus femtosecond laser assisted keratomileusis(Femto-LASIK) in correction of high myopia....AIM: To evaluate the safety and efficacy of transepithelial photorefractive keratectomy(t-PRK) with adjuvant mitomycin C(MMC) versus femtosecond laser assisted keratomileusis(Femto-LASIK) in correction of high myopia.METHODS: Prospective randomized comparative study including 156 eyes of 156 patients with high myopia and a spherical equivalent refraction(SER) <-6.00 D. They were divided randomly into two groups: Group A included 72 eyes treated with t-PRK with adjuvant MMC and Group B included 84 eyes treated with Femto-LASIK. Visual acuity, SER, corneal topography, pachymetry and keratometry were assessed for 12 mo postoperatively.RESULTS: The preoperative mean SER was-8.86±1.81 and-9.25±1.70 D in t-PRK MMC group and Femto-LASIK respectively(P=0.99) which improved to-0.65±0.43 D and-0.69±0.50 D at 12 mo follow up. Mean SER remained stable during the 12 mo of follow-up, with no statistically significant difference between the two groups(P=0.64). In t-PRK MMC group, only six eyes needed retreatment after six months of follow up. And two eyes showed haze(one reversible haze grade 2, while the other had dense irreversible haze grade 4).CONCLUSION: t-PRK MMC provides safe and satisfactory visual outcomes and acceptable risk as Femto-LASIK in patients with high myopia.展开更多
Major causes of haze pollution in Xi＇an City were discussed firstly, and current situation of air pollution caused by vehicle exhaust in Xi＇an City was analyzed. Finally, countermeasures against haze pollution in Xi...Major causes of haze pollution in Xi＇an City were discussed firstly, and current situation of air pollution caused by vehicle exhaust in Xi＇an City was analyzed. Finally, countermeasures against haze pollution in Xi＇an City were put forward, such as strictly implementing I/M （ Inspection/ Maintenance） system of in-use vehicles in Xran City, and paying more attention to in-use vehicles with high pollution to reduce haze.展开更多
在自然界中,甲壳素一般以有序的结晶纳米纤维形式存在,赋予了生物体优异的力学性能。本研究分别采用“常温温和”(常温,Mild condition)和“高温加热”(高温,High temperature condition)两种方法从废弃蟹壳中提取α-甲壳素并制得常温α...在自然界中,甲壳素一般以有序的结晶纳米纤维形式存在,赋予了生物体优异的力学性能。本研究分别采用“常温温和”(常温,Mild condition)和“高温加热”(高温,High temperature condition)两种方法从废弃蟹壳中提取α-甲壳素并制得常温α-甲壳素纳米纤维膜(常温膜)和高温α-甲壳素纳米纤维膜(高温膜),分别对所得两种α-甲壳素纳米纤维样品从微观结构、力学性能、结晶构造、表面特性以及光学性能等方面进行表征,分析对比两种不同提取方法对甲壳素纤维结构及性能的影响,并进一步探究提取制备过程中甲壳素的纤维形态及均匀性对其薄膜力学性能、光学透明性的影响。结果表明,与“高温”提取条件相比,经“常温”条件提取所得α-甲壳素纳米纤维具有较高的长径比且尺寸分布均匀,较好地保留了甲壳素原有的天然结构。其中,常温膜的拉伸强度可达(152±2.56) MPa,断裂伸长率约为10.0%,是高温膜的2.50倍左右,具有较好的柔韧性。同时,常温膜还具备优异的光学及热稳定性能,透光率高达91.0%,雾度低至3.19%,在200℃高温条件下仍能保持性状稳定。综上,“常温”条件下提取的甲壳素纳米纤维由于较好地保留了其天然结构优势,使得制备所得膜材料具备优异的力学强度及透光性等。本工作的研究成果为制备全生物质高强度、低雾度柔性透明膜材料提供了理论依据和技术支持,有望作为柔性透明基材应用于柔性电子元件、电子皮肤、智能标签及柔性传感等研究领域。展开更多
为探究雾霾对高压直流(HVDC)输电线路电晕离子流场的影响规律,提出了雾霾对HVDC输电线路电晕离子流场影响的计算方法。考虑雾霾微粒的荷电特性和湿度对电晕起晕的作用,采用有限元方法计算了±800 k V线路在各种雾霾污染等级下的合...为探究雾霾对高压直流(HVDC)输电线路电晕离子流场的影响规律,提出了雾霾对HVDC输电线路电晕离子流场影响的计算方法。考虑雾霾微粒的荷电特性和湿度对电晕起晕的作用,采用有限元方法计算了±800 k V线路在各种雾霾污染等级下的合成电场强度和离子流密度。计算结果表明:随着雾霾污染程度增加,地面合成电场强度和离子流密度相对于正常天气时的值有所增大,在较大污染程度下,其最大值的增长率随污染浓度增大呈近似线性关系;高湿度雾霾状况下的电晕离子流场随污染程度变化比低湿度雾霾和干霾下更加明显。分析认为:雾霾条件下湿度对电晕起始电场强度的影响及空间悬浮颗粒的荷电行为是地面合成电场和离子流密度变化的主要原因,离子迁移率的减小抑制了地面离子流密度的增大。研究思路对考虑雾霾因素时HVDC输电线路规划设计中电晕效应的分析具有参考价值。展开更多
文摘AIM: To evaluate the safety and efficacy of transepithelial photorefractive keratectomy(t-PRK) with adjuvant mitomycin C(MMC) versus femtosecond laser assisted keratomileusis(Femto-LASIK) in correction of high myopia.METHODS: Prospective randomized comparative study including 156 eyes of 156 patients with high myopia and a spherical equivalent refraction(SER) <-6.00 D. They were divided randomly into two groups: Group A included 72 eyes treated with t-PRK with adjuvant MMC and Group B included 84 eyes treated with Femto-LASIK. Visual acuity, SER, corneal topography, pachymetry and keratometry were assessed for 12 mo postoperatively.RESULTS: The preoperative mean SER was-8.86±1.81 and-9.25±1.70 D in t-PRK MMC group and Femto-LASIK respectively(P=0.99) which improved to-0.65±0.43 D and-0.69±0.50 D at 12 mo follow up. Mean SER remained stable during the 12 mo of follow-up, with no statistically significant difference between the two groups(P=0.64). In t-PRK MMC group, only six eyes needed retreatment after six months of follow up. And two eyes showed haze(one reversible haze grade 2, while the other had dense irreversible haze grade 4).CONCLUSION: t-PRK MMC provides safe and satisfactory visual outcomes and acceptable risk as Femto-LASIK in patients with high myopia.
文摘Major causes of haze pollution in Xi＇an City were discussed firstly, and current situation of air pollution caused by vehicle exhaust in Xi＇an City was analyzed. Finally, countermeasures against haze pollution in Xi＇an City were put forward, such as strictly implementing I/M （ Inspection/ Maintenance） system of in-use vehicles in Xran City, and paying more attention to in-use vehicles with high pollution to reduce haze.
文摘在自然界中,甲壳素一般以有序的结晶纳米纤维形式存在,赋予了生物体优异的力学性能。本研究分别采用“常温温和”(常温,Mild condition)和“高温加热”(高温,High temperature condition)两种方法从废弃蟹壳中提取α-甲壳素并制得常温α-甲壳素纳米纤维膜(常温膜)和高温α-甲壳素纳米纤维膜(高温膜),分别对所得两种α-甲壳素纳米纤维样品从微观结构、力学性能、结晶构造、表面特性以及光学性能等方面进行表征,分析对比两种不同提取方法对甲壳素纤维结构及性能的影响,并进一步探究提取制备过程中甲壳素的纤维形态及均匀性对其薄膜力学性能、光学透明性的影响。结果表明,与“高温”提取条件相比,经“常温”条件提取所得α-甲壳素纳米纤维具有较高的长径比且尺寸分布均匀,较好地保留了甲壳素原有的天然结构。其中,常温膜的拉伸强度可达(152±2.56) MPa,断裂伸长率约为10.0%,是高温膜的2.50倍左右,具有较好的柔韧性。同时,常温膜还具备优异的光学及热稳定性能,透光率高达91.0%,雾度低至3.19%,在200℃高温条件下仍能保持性状稳定。综上,“常温”条件下提取的甲壳素纳米纤维由于较好地保留了其天然结构优势,使得制备所得膜材料具备优异的力学强度及透光性等。本工作的研究成果为制备全生物质高强度、低雾度柔性透明膜材料提供了理论依据和技术支持,有望作为柔性透明基材应用于柔性电子元件、电子皮肤、智能标签及柔性传感等研究领域。
文摘为探究雾霾对高压直流(HVDC)输电线路电晕离子流场的影响规律,提出了雾霾对HVDC输电线路电晕离子流场影响的计算方法。考虑雾霾微粒的荷电特性和湿度对电晕起晕的作用,采用有限元方法计算了±800 k V线路在各种雾霾污染等级下的合成电场强度和离子流密度。计算结果表明:随着雾霾污染程度增加,地面合成电场强度和离子流密度相对于正常天气时的值有所增大,在较大污染程度下,其最大值的增长率随污染浓度增大呈近似线性关系;高湿度雾霾状况下的电晕离子流场随污染程度变化比低湿度雾霾和干霾下更加明显。分析认为:雾霾条件下湿度对电晕起始电场强度的影响及空间悬浮颗粒的荷电行为是地面合成电场和离子流密度变化的主要原因,离子迁移率的减小抑制了地面离子流密度的增大。研究思路对考虑雾霾因素时HVDC输电线路规划设计中电晕效应的分析具有参考价值。
