Heterogeneous iodine-organic chemistry fast-tracks marine new particle formation

The gas-phase formation of new particles less than 1 nm in size and their subsequent growth significantly alters the availability of cloud condensation nuclei (CCN, >30–50 nm), leading to impacts on cloud reflectance and the global radiative budget. However, this growth cannot be accounted for by condensation of typical species driving the initial nucleation. Here, we present evidence that nucleated iodine oxide clusters provide unique sites for the accelerated growth of organic vapors to overcome the coagulation sink. Heterogeneous reactions form low-volatility organic acids and alkylaminium salts in the particle phase, while further oligomerization of small α-dicarbonyls (e.g., glyoxal) drives the particle growth. This identified heterogeneous mechanism explains the occurrence of particle production events at organic vapor concentrations almost an order of magnitude lower than those required for growth via condensation alone. A notable fraction of iodine associated with these growing particles is recycled back into the gas phase, suggesting an effective transport mechanism for iodine to remote regions, acting as a “catalyst” for nucleation and subsequent new particle production in marine air.

Marine aerosol formation contributes significantly to the global radiative budget given the high susceptibility of marine stratiform cloud radiative properties to changes in cloud condensation nuclei (CCN) availability. Atmospheric new-particle-formation is thought to involve nucleation of sulfuric acid with water, ammonia, or amines followed by condensation/growth in the presence of organic vapors (1, 2). Unique in the marine boundary layer (MBL), new particle formation involves sequential addition of HIO₃ or clustering of iodine oxides (I_xO_y) (3, 4). In specific source regions such as coastal zones, seaweed beds, or snowpack/pack-ice, iodine oxide nucleation can be a driving force for nucleation (5–7). Over Arctic waters, nonetheless, one study finds insufficient iodic acid vapors to grow nucleated particles to CCN sizes (8), whereas another study finds that both nucleation and growth are almost exclusively driven by iodic acid (9). Over the open ocean, the supply of iodine oxides has been thought to be limited; however, recent measurements suggest that significant reactive iodine chemistry can occur in these regions (10). Moreover, observational evidence exists for open ocean particle formation and growth, especially when oceanic productivity is high (11, 12). An increase in atmospheric iodine levels in the North Atlantic since the mid-20th century has been shown to be driven by growth of anthropogenic ozone and enhanced subice phytoplankton production (13). While the reported IO concentration (0.4–3.1 ppt) in the remote MBL (10, 14, 15) is likely sufficient for formation of prenucleation clusters (∼1 nm), growth of these initial clusters requires the presence of other condensable vapors (16). Since preexisting aerosol particles act as a strong sink for the nucleated clusters, thus inhibiting atmospheric aerosol and CCN formation (17, 18), this early growth phase is essential for their survival. Whereas sulfuric acid vapor is also involved in nucleation, its level in remote open ocean is generally too low (10⁵ molecules cm⁻³) to support subsequent particle growth, leaving organic vapors as the most plausible alternative for particle growth.In the marine atmosphere, condensing organics must originate from the oxidation of marine volatile organic compounds (VOCs), which predominantly comprise C₁–C₅ VOCs (e.g., isoprene) released from phytoplankton. Principal high volatility oxidation products consist of intermediate oxidized organics (IOOs), such as polyhydric alcohols (e.g., tetrols) or polyfunctional carbonyls (e.g., glyoxal) (19–22). Nonetheless, growth of available prenucleation clusters/nanometer particles requires condensing organic molecules of low effective volatilities (i.e., saturation mass concentration, C* < ∼10⁻³ μg m⁻³); otherwise, preferential condensation of the organic mass to larger-diameter particles would occur (23, 24). Formation of such extremely low-volatility organic compounds (ELVOCs) from gas-phase reaction is well established for monoterpene oxidation products (25, 26).A potential pathway for formation of low-volatility organics could also result from particle-phase chemical reactions induced by iodine oxides in the early stages of marine particle formation. When the underlying chemistry is sufficiently fast, kinetic condensation occurs, resulting in particles with diameters smaller than about 50 nm growing at the same rate (e.g., nm h⁻¹) (24). If, however, particle-phase chemistry is preferentially favored in the smallest particles (i.e., stemming from the higher relative concentration of iodine oxides in freshly formed marine particles), growth of the nucleated particles could proceed more rapidly, as compared to that in which gas-phase chemistry is the source of the low-volatility compounds (23).In this paper, we present experimental results from field measurements as well as laboratory studies of nanometer particle growth and derive a plausible chemical mechanism from the results that can explain the observations of ultrafine particle growth in the marine atmosphere. The results suggest that both iodine and condensed organics contribute to particle growth from a nascent nucleation mode into an ultrafine particle mode. Moreover, laboratory studies of the growth of seed iodine oxide particles (IOP) via heterogeneous reactions with organic vapors suggest a hitherto unrecognized mechanism that fast-tracks the growth of nucleation mode clusters into survivable aerosol particles. In this process, a notable fraction of the iodine associated with these growing particles is recycled back to the gas phase, suggesting a transport mechanism for iodine to remote regions.     

Incidence of brain injuries in premature infants with gestational age ≤34 weeks in ten urban hospitals in China

Background

There is a large number (1.5 million per year) of premature births in China. It is necessary to obtain the authentic incidences of intraventricular hemorrhage (IVH) and periventricular leukomalacia (PVL), the common brain injuries, in Chinese premature infants. The present multicenter study aimed to investigate the incidence of brain injuries in premature infants in ten urban hospitals in China.

Methods

The research proposal was designed by the Subspecialty Group of Neonatology of Pediatric Society of the Chinese Medical Association. Ten large-scale urban hospitals voluntarily joined the multicenter investigation. All premature infants with a gestational age ≤34 weeks in the ten hospitals were subjected to routine cranial ultrasound within three days after birth, and then to repeated ultrasound every 3–7 days till their discharge from the hospital from January 2005 to August 2006. A uniform data collection sheet was designed to record cases of brain injuries.

Results

The incidences of overall IVH and severe IVH were 19.7% (305/1551) and 4.6% (72/1551), respectively with 18.4% (56/305) for grade 1, 58.0% (177/305) for grade 2, 17.7% (54/305) for grade 3 and 5.9% (18/305) for grade 4 in nine hospitals. The incidences of overall PVL and cystic PVL were 5.0% (89/1792) and 0.8% (14/1792) respectively, with 84.3% (75/89) for grade 1, 13.5% (12/89) for grade 2, and 2.2% (2/89) for grade 3 in the ten hospitals. The statistically significant risk factors that might aggravate the severity of IVH were vaginal delivery (OR=1.883, 95% CI: 1.099–3.228, P=0.020) and mechanical ventilation (OR=4.150, 95% CI: 2.384–7.223, P=0.000). The risk factors that might result in the development of cystic PVL was vaginal delivery (OR=21.094, 95% CI: 2.650–167.895, P=0.000).

Conclusions

The investigative report can basically reflect the incidence of brain injuries in premature infants in major big cities of China. Since more than 60% of the Chinese population live in the rural areas of China, it is expected to undertake a further multicenter investigation covering the rural areas in the future.     

非穿透性小梁手术超声生物显微镜检查

目的：应用超声生物显微镜（ＵＢＭ）检查技术,探讨非穿透性小梁手术联合透明质酸钠生物胶植入手术区域解剖特点和房水引汉机制。方法：对１４例１６只眼行非穿透性小梁手术联合透明质酸钠生物胶植入的患者,在术后１～３个月内进行手术区域ＵＢＭ检查。检查的指标（项目）包括：巩膜瓣下形成液间腔的大小（宽和高）、透明质酸钠生物胶吸收的情况、剩余角膜小梁膜的厚度以及滤过泡的形态,并对结果进行分析。结果：１６只眼术前平均     

糖尿病患者后房型人工晶状体体植入术眼前段并发症探讨

目的：观察糖尿病患者中行后房型人工晶状体植入术后眼前段并发症及预后。方法：对31例（40只眼）糖尿病组后房型人工晶状体植入与28例（35只眼）对照组老年白内障患者手术效果及并发症进行对比观察。结果：糖尿病组白内障前段手术并发症发生率高于对照组，其术前准备、术中及术后处理均有其特殊性。但总体预后两组并无显著差异。结论：糖尿病患者人工晶状体植入安全可靠、手术预后良好。     

增殖性糖尿病视网膜病变多次手术临床分析

目的：探讨增殖性糖尿病视网膜病变玻璃体切割术后多次手术的原因及处理。方法：回顾性分析3a来因增殖性糖尿病视网膜病变行玻璃体切割术后需要再次手术的患者。结果：患者189眼术后需要再次进行手术的为24例26眼（占总观察眼数13.8%）。分别是：玻璃体再积血3眼,前房积血1眼,视网膜脱离11眼（占总观察眼数5.8%,占再手术眼42.3%,其中3眼合并新生血管性青光眼）,白内障6眼（占总观察眼数3.2%）,单纯硅油取出5眼。189眼中有6眼发生了新生血管性青光眼（3.2%）,6眼均为玻璃体晶状体联合手术或玻璃体切割术后又摘除白内障病例。2次手术19眼,3次或以上手术7眼（其中5眼合并视网膜脱离）。结论：发生视网膜脱离是糖尿病视网膜病变玻璃体切割术后需要多次手术的主要原因;也占据需要3次或以上手术的主要部分。新生血管性青光眼的发生值得重视,出现视网膜脱离时要提高警惕,需要摘除晶状体时必须慎重。     

去卵巢对大鼠泪腺中IL-17A等炎症因子表达的影响

目的建立去卵巢大鼠模型,观察性激素水平改变对泪腺中IL-17A以及IL-1β、IL-6、TNF-α等炎症因子表达的影响。方法实验研究。健康雌性SD大鼠20只随机分为2组,实验组（10只）摘除大鼠双侧卵巢,对照组（10只）为未摘除卵巢的模拟手术组。术前及术后第1个月、第2个月、第3个月时2组均行泪液分泌试验（SIT）、角膜荧光染色检查进行眼表评估。于第3个月时放射免疫分析法分别检测2组大鼠血清雌二醇、睾酮含量,HE染色观察泪腺上皮细胞形态,免疫组化染色法、Western Blot法检测2组泪腺中IL-17A、IL-1β、IL-6、TNF-α的表达。2组性激素质量浓度比较、炎症因子A值表达比较均应用独立样本t检验。2组各时间点的SIT结果比较采用重复测量资料两因素方差分析。结果实验组大鼠去卵巢后第3个月时,体内雌二醇浓度低于对照组（t=-35.37,P<0.01）,睾酮浓度低于对照组（t=-12.13,P<0.01）。2组各时期SIT检查未见泪液分泌减少、均未见角膜荧光染色。HE染色见实验组泪腺腺泡萎缩,排列紊乱,胞质内酶原颗粒明显减少。泪腺IL-17A表达量2组比较实验组高于对照组（免疫组化法：t=7.56,P<0.01;Western Blot法：t=20.90,P<0.01）。余各因子表达量实验组也均高于对照组（免疫组化法：IL-1β：t=13.71,P<0.01;IL-6：t=13.92,P<0.01;TNF-α：t=6.11,P<0.01。Western Blot法：IL-1β：t=16.93,P<0.01;IL-6：t=12.46,P<0.01;TNF-α：t=14.47,P<0.01）。结论大鼠去卵巢3个月时性激素水平降低,未见明显眼表损害。但泪腺中炎症因子IL-17A、IL-1β、IL-6、TNF-α的表达增加。     

人突变Lumican基因转基因小鼠屈光变化特点

目的：探讨人突变Lumican基因转基因小鼠生后不同时间屈光状态及其变化特征。方法实验研究。54只（雄性27只,雌性27只）人突变Lumican基因（cDNA 596T>C）转基因小鼠,于生后3、4、5、6、8、10、12、16、20周共9个时间点分别通过随机数字表法随机选取6只（雄性3只,雌性3只）转基因小鼠,快速散大瞳孔后检影验光测量屈光度数。对比相同时间点转基因小鼠双眼间及雌雄性别间的屈光度数,采用配对t检验;不同时间点转基因小鼠屈光度数的比较采用非参数多个独立样本Kruskal?Wallis H检验,两两组间屈光度数比较采用非参数两个独立样本Mann?Whitney U检验。结果同周龄组转基因小鼠双眼间比较屈光度数差异无统计学意义：第20周转基因小鼠右左眼屈光度均值分别是（1.50±0.45）和（1.25±0.42）D,（t=-0.889,P>0.05）,第3周转基因小鼠右左眼屈光度均值分别是（-2.50±2.59）和（-2.50±4.32）D,（t=0.000,P>0.05）;同周龄组不同性别转基因小鼠眼间比较屈光度数差异无统计学意义：第3周转基因小鼠雌雄性别眼屈光度均值分别是（-0.5±3.83）和（-4.17±1.94）D,（t=2.079,P>0.05）,第12周转基因小鼠雌雄性别眼屈光度均值分别是（1.50±0.84）和（1.50±1.87）D（t=0.000,P>0.05）;不同周龄组转基因小鼠屈光度数差异有统计学意义（H=20.910,P<0.05）;两两组间比较显示转基因小鼠第3周与第6周屈光度数差异有统计学意义（Z=-3.259,P<0.001）,其余各周之间比较屈光度数差异均无统计学意义（P>0.001）。结论人突变Lumican基因转基因小鼠出生后3周时为近视,随时间增加向远视发展,第6周远视屈光度数达到最大,8～20周时远视屈光度数逐渐减小并趋于稳定。（中华眼科杂志,2015,51：527-531）     

白内障超声乳化手术对结膜松弛症患者眼表状况的影响

目的：探讨白内障超声乳化手术对白内障合并结膜松弛症患者眼表状况的影响。

方法：对2014-09/12间在我院接受超声乳化+人工晶状体植入手术的150例200眼白内障患者,根据有无合并结膜松弛症,分为正常组110例140眼和结膜松弛组40例60眼; 随访3～6mo,观察手术前后两组患者泪膜破裂时间、异物感、泪溢及结膜充血等情况以及上述情况恢复到术前状态所用时间,并进行统计学分析。

结果：超声乳化+人工晶状体植入术后,正常组和结膜松弛组患者泪膜破裂时间(BUT)分别与术前比较,差异有统计学意义(t=20.93、19.16,均P =0.00),术后两组患者眼部异物感、泪溢情况、结膜充血情况与术前比较差异有统计学意义(均P =0.00); 比较两组患者BUT、眼部异物感、泪溢和结膜充血等情况恢复到术前状态所用时间,差异有统计学意义(t=17.16、14.18、27.41,均P=0.00)。

结论：超声乳化+人工晶状体植入手术使白内障患者的眼表状况明显变差; 结膜松弛症在白内障术后可显著延迟患者眼表功能的恢复。