Progressive Cenozoic cooling and the demise of Antarctica's last refugium

The Antarctic Peninsula is considered to be the last region of Antarctica to have been fully glaciated as a result of Cenozoic climatic cooling. As such, it was likely the last refugium for plants and animals that had inhabited the continent since it separated from the Gondwana supercontinent. Drill cores and seismic data acquired during two cruises (SHALDRIL I and II) in the northernmost Peninsula region yield a record that, when combined with existing data, indicates progressive cooling and associated changes in terrestrial vegetation over the course of the past 37 million years. Mountain glaciation began in the latest Eocene (approximately 37-34 Ma), contemporaneous with glaciation elsewhere on the continent and a reduction in atmospheric CO(2) concentrations. This climate cooling was accompanied by a decrease in diversity of the angiosperm-dominated vegetation that inhabited the northern peninsula during the Eocene. A mosaic of southern beech and conifer-dominated woodlands and tundra continued to occupy the region during the Oligocene (approximately 34-23 Ma). By the middle Miocene (approximately 16-11.6 Ma), localized pockets of limited tundra still existed at least until 12.8 Ma. The transition from temperate, alpine glaciation to a dynamic, polythermal ice sheet took place during the middle Miocene. The northernmost Peninsula was overridden by an ice sheet in the early Pliocene (approximately 5.3-3.6 Ma). The long cooling history of the peninsula is consistent with the extended timescales of tectonic evolution of the Antarctic margin, involving the opening of ocean passageways and associated establishment of circumpolar circulation.     

后极性白内障的超声乳化手术治疗

目的:探讨后极性白内障的临床特点及超声乳化手术的手术技巧。方法:连续收集2009-10/2011-03在本院诊治的后极性白内障患者12例17眼,所有病例均接受详尽的病史采集,以及视力、裂隙灯显微镜检查,B型超声波及间接检眼镜检查,所有患眼在球周浸润麻醉下行超声乳化白内障摘除及折叠人工晶状体植入,总结手术技巧、术前术后视力及术中并发症。结果:所有患眼均植入折叠人工晶状体。术中11眼后囊膜完整透明,2眼后囊膜破裂,其中1眼发生在分核时,另1眼发生在核周壳吸除时;4眼术中发现后囊膜混浊需后期行YAG激光后囊膜切开术。15眼折叠人工晶状体植入囊袋内,2眼植入睫状沟。术后1mo最佳矫正视力≥0.5者16眼,0.4者1眼。结论:超声乳化联合折叠型人工晶状体植入是治疗后极性白内障安全有效的方法。应用连续环形撕囊、轻柔谨慎的水分层而不做水分离,低能量、低吸力、低流量的超声乳化参数设置,手动吸除核周壳和皮质等手术技巧,可以减少手术并发症。     

Inverse horse-shoe technique for the phacoemulsification of posterior polar cataract

Objective: To study a new technique of controlled hydrodelineation followed by viscodelineation and viscodissection during phacoemulsification in eyes with posterior polar cataracts and to report its effectiveness in preserving the posterior capsule.Design: Prospective interventional study.Participants: Twenty-eight eyes of 22 patients with posterior polar cataracts.Methods: All patients underwent phacoemulsification under topical anaesthesia with controlled hydrodelineation, viscodelineation, and viscodissection with minimal stress on the posterior capsule. Hydrodissection was not done. The preoperative complications and visual outcome were recorded.Results: The mean follow-up time was 8 months (range 2-24 months). Posterior capsule rupture occurred only in 2 eyes (7.1%); neither of the 2 had any vitreous prolapse, so anteriorvitrectomy was not required. Mean visual acuity improved significantly after surgery (p = 0.0001, paired t test). The causes of the low postoperative visual acuity were amblyopia in 3 eyes (10.7%) and age-related macular degeneration in 1 (3.6%).Conclusions: This inverse horse-shoe technique of controlled viscodelineation and viscodissection markedly reduced the risk of posterior capsule rupture. Moreover, if it occurred, the anterior vitreous face remained intact, so the IOL could be implanted in the sulcus without resorting to anterior vitrectomy.     

表皮生长因子调节小鼠生发泡期卵母细胞发育成熟的实验研究

目的 :观察表皮生长因子 ( EGF)对生发泡期 ( GV期 )卵母细胞生发泡破裂( GVBD)、第一极体 ( FP)形成的影响。方法 :体外培养的昆明种雌性小鼠 GV期卵母细胞分为卵丘卵母细胞复合体 ( COC)组及去卵丘裸卵 ( DO)组 ,观察不同浓度 ( 0、2、5、1 0、1 5μg/ L ) EGF对体外培养 0、4、8、1 2、2 4、3 6、48h COC、DO各组 GVBD、FP形成的影响。结果 :( 1 ) EGF可促进 DO组的卵母细胞成熟分裂 ,培养 48h EGF各组与对照组相比 ,有显著性差异 ( P<0 .0 5) ;( 2 ) COC组培养 3 6h后 EGF各组成熟率均显著大于对照组 ( P<0 .0 5) ;( 3 )不论是否存在 EGF,COC组成熟分裂率均显著高于 DO组 ( P<0 .0 5) ;( 4)EGF作用呈剂量依赖性。结论 :EGF不仅可促进 COC组 GVBD发生、FP形成 ,而且可不通过卵丘细胞直接刺激卵母细胞成熟 ,EGF对 COC促进作用强于 DO,并呈剂量依赖性。     

Initiating Mechanism of the Anionic Polymerization of Methacrylates with t‐BuOK and the Synthesis of ABA Type Triblock Copolymers

Using potassium tert‐butoxide (t‐BuOK) as initiator, anionic polymerization and copolymerization of the methacrylate monomers are carried out in tetrahydrofuran at 0 °C or above. The polymers are characterized by gel permeation chromatography (GPC), proton nuclear magnetic resonance (¹H‐NMR), Fourier transform infrared (FTIR), and dynamic mechanical analyzer (DMA). There is a critical concentration of the active species in t‐BuOK, above which no matter how much more t‐BuOK is added, it has no initiation activity. Among the active species of t‐BuOK, the main part possesses large average vibration distance between anion–cation pairs, which can initiate all methacrylate monomers in this study. While another part of the active species possesses the small average vibration distance, which can only initiate the polymerization of methyl methacrylate at slow rate. It provides an supporting evidence for the “channel idea” proposed previously. Finally, poly(methyl methacrylate)‐b‐poly(lauryl methacrylate)‐b‐poly(methyl methacrylate) (PMMA‐b‐PLMA‐b‐PMMA) three‐block copolymer is synthesized. This study paves the way for the synthesis of thermoplastic elastomers with full polar monomers and full saturated chains by anionic polymerization.     

Relation between thallium-201/iodine 123-BMIPP subtraction and fluorine 18 deoxyglucose polar maps in patients with hypertrophic cardiomyopathy

BACKGROUND: Clinical studies have shown discrepancies in the distribution of thallium-201 and iodine 123-beta-methyl-iodophenylpentadecanoic acid (BMIPP) in patients with hypertrophic cardiomyopathy (HCM). Myocardial uptake of fluorine 18 deoxyglucose (FDG) is increased in the hypertrophic area in HCM. METHODS AND RESULTS: We examined whether the distribution of a Tl-201/BMIPP subtraction polar map correlates with that of an FDG polar map. We normalized to maximum count each Tl-201 and BMIPP bull's-eye polar map of 6 volunteers and obtained a standard Tl-201/BMIPP subtraction polar map by subtracting a normalized BMIPP bull's-eye polar map from a normalized Tl-201 bull's-eye polar map. The Tl-201/BMIPP subtraction polar map was then applied to 8 patients with HCM (mean age 65+/-12 years) to evaluate the discrepancy between Tl-201 and BMIPP distribution. We compared the Tl-201/BMIPP subtraction polar map with an FDG polar map. In patients with HCM, the Tl-201/BMIPP subtraction polar map showed a focal uptake pattern in the hypertrophic area similar to that of the FDG polar map. By quantitative analysis, the severity score of the Tl-201/BMIPP subtraction polar map was significantly correlated with the percent dose uptake of the FDG polar map. CONCLUSION: These results suggest that this new quantitative method may be an alternative to FDG positron emission tomography for the routine evaluation of HCM.     

活细胞工作站技术在小鼠卵母细胞实时观察中的应用

摘要：目的：将活细胞工作站（LCS）应用于实时观察小鼠卵母细胞后期成熟和极体排放过程。 方法：运用LCS技术平台,利用hoechst 33342标记DNA,同时结合明场观察,实时记录小鼠卵母细胞后期成熟和第二极体排放过程。 结果：在建立最适工作条件后,成功将LCS技术平台应用于小鼠卵母细胞观察,获得了第二极体排放的实时影像。 结论：LCS技术可成功地应用于小鼠卵母细胞观察,为进一步扩展LCS应用范围,获得卵母细胞及早期胚胎生长发育过程的实时影像打下良好的基础。