微螺钉种植体支抗在成人双颌前突正畸治疗中的临床应用

目的:总结微螺钉种植体支抗在临床中治疗成人双颌前突的经验,评价微螺钉种植体在正畸治疗中作为强支抗内收前牙的有效性.方法:从临床病例中选择12例成人双颌前突患者,矫治设计均为拔除4颗第一前磨牙,在上下颌第一恒磨牙与第二恒磨牙或上下颌第一恒磨牙与第二前磨牙之间的颊侧根尖部植入微螺钉种植体作为强支抗,共48颗,以每侧200g力滑动法关闭间隙.在治疗前后均拍摄头颅定位侧位片及全颌曲面断层片,比较双颌前突患者治疗前后前牙内收情况及第一恒磨牙位置的变化.结果:12例成人双突患者面型均得到明显改善,应用微螺钉种植体支抗顺利完成正畸治疗,第一恒磨牙位置稳定.结论:微螺钉种植体支抗可避免上颌磨牙的前移,能为上下颌前突畸形的矫治提供有效的支抗.     

双颌前突内收后切牙区牙槽骨变化三维影像学研究

目的利用CBCT影像探讨成人双颌前突行种植支抗内收后切牙区牙槽骨的变化.方法选取成人安氏Ⅰ类双颌前突患者20例,采用减数拔除4颗第一前磨牙,种植支抗内收进行矫治.对矫治前后的切牙区牙槽骨进行CBCT影像三维重建,测量矫治前后上下切牙角度、下唇与审美平面的距离,根颈处、根中处及根尖水平处的唇、舌(腭)侧牙槽骨厚度的改变,以及牙根长度的变化.结果 1)矫治后患者上下切牙出现明显内收(P0.01),下唇突度有明显下降(P0.01),侧貌改善明显; 2)与治疗前比较,在唇侧,上颌中切牙和侧切牙牙槽骨厚度在根中水平上增加,差异具有统计学意义(P0.05),在根颈部和根尖部水平上有所减少,但差异无统计学意义(P0.05);与治疗前比较,在舌侧,上颌中切牙和上侧切牙牙槽骨厚度在所有水平上都减少,差异具有统计学意义(P0.05); 3)与治疗前比较,在唇侧,下颌中切牙和侧切牙牙槽骨厚度在根颈、根中、根尖水平均有所下降,但在根中水平差异无统计学意义(P0.05);与治疗前比较,在舌侧,下颌中切牙和侧切牙牙槽骨厚度在根颈、根中、根尖水平均下降,差异均具有统计学意义(P0.01); 4)与治疗前比较,上颌以及下颌中切牙和侧切牙牙根均变短,差异具有统计学意义(P0.05),牙根明显吸收.结论使用CBCT影像可清晰判断成人双颌前突患者种植支抗内收前后切牙牙槽骨的变化情况.     

桩核冠修复下颌第一前磨牙牙颈部应力的三维有限元分析

对桩核冠治疗下颌第一前磨牙的不同修复方式进行三维有限元力学分析,探讨修复方法和应力间联系。采用三维螺旋CT对包埋块进行断层扫描,得到数据采用Mimcs10. 0进行三维建立,再输进ANSYS13. 0三维有限元软件里,创建相应的模型。最大的剪切应力产生于无牙本质肩领以及牙冠360°缺损的状况下;而最大的主应力是在颊舌侧有牙本质同时邻面牙本质破坏的状况下产生。经由三维有限元剖析得出,当牙齿的冠部无牙本质肩领时,不适于采用纤维桩树脂核去做修复;在舌侧牙本质存在宽度缺陷时,需把牙本质肩领的高度提上去,使纤维桩树脂核的修复安全可靠性得到增强。     

物源及沉积体系研究对识别岩性圈闭的意义——以黄骅坳陷歧口凹陷歧南斜坡为例

针对研究区物源波及范围不明确、沉积相带划分证据不充分等问题,首先通过单井资料及地震资料的综合研究,明确了歧南西斜坡区沙三段沉积期的2个物源区位置及砂体分布特征。一是位于西部的羊三木凸起物源区,砂体由凸起向东呈扇形分布,厚度依次减薄;二是东部埕宁隆起物源区,砂体由南向北呈条带状展布。其次,在参考前人研究成果,明确该区古背景、古地形条件下,利用钻井取心、测井及录井等资料,识别出辫状河三角洲、扇三角洲2种主要沉积相类型,结合物源体系综合分析,明确了2个物源区辫状河三角洲前缘水下分流河道砂体在斜坡区内的展布特征:西部砂体受斜坡背景控制,向西斜坡高部位形成上倾尖灭形态,是形成砂岩上倾尖灭岩性油气藏较为有利的目标区;东部砂体位于斜坡相对较低部位,其物源方向由南向北,在区内形成透镜状,是形成砂岩透镜体油气藏的有利目标区。物源及沉积体系研究为歧南西斜坡区沙三段的岩性尖灭圈闭和透镜体圈闭的识别提供了依据,为下一步刻画及评价这2类岩性圈闭油气藏奠定基础。     

脉冲Nd:YAG激光刻蚀牙釉质对牙釉质形态及其抗剪切强度的影响

目的:研究激光刻蚀牙釉质对其形态的影响,测量激光刻蚀釉质后其抗剪切强度能否达到临床要求.方法:选择55颗离体前磨牙,随机分为5组.实验组4组分别接受不同电流强度的激光照射.对照组用体积分数37%磷酸酸蚀.5组每组随机抽取一颗离体牙进行电镜扫描.其余50颗离体牙黏结金属托槽,测量抗剪切强度.结果:对照组釉质表层均匀脱钙,呈凹凸不平的粗糙面,实验组可以看到类似的效果.实验组和对照组两两比较抗剪切强度存在统计学差异(P<0.05).结论:①扫描电子显微镜(SEM)证实激光刻蚀釉质可以获得与体积分数37%磷酸酸蚀相似的微观结构.②激光刻蚀釉质后黏结托槽其抗剪切强度并不能达到临床治疗要求.③激光刻蚀釉质对髓腔温度的影响与其对抗剪切强度的影响成反比关系.     

料层减荷烧结支撑板数值模拟

在烧结台车上安装支撑板,可以支撑起上部烧结饼,减轻下部料层荷重,从而改善下部料层透气性,提高垂直烧结速度,进而提高烧结生产率. 应用ANSYS软件对烧结过程中料层内支撑板的热应力进行模拟. 结果表明:烧结过程中,支撑面中间部位和支撑板窄面中上部是最容易损坏的部位;排矿时,支撑板支脚部位产生应力集中,当支脚厚度大于40 mm时可以满足要求. 料层减荷烧结工业试验验证了模拟结果的正确性.     

西昆仑及邻区岩石圈动力学特征

地球物理资料显示西昆仑地区岩石圈的结构具"厚壳薄幔"特征,热模拟结果表明莫霍面温度偏高;对西昆仑及邻区的重力和地形数据反演推算的岩石圈有效弹性厚度小,说明岩石圈的强度低,有利于均衡调整和快速隆升.研究表明西昆仑地区岩石圈的结构特征、热状态、应力场和岩石圈的强度等动力学因素是相互耦合的.     

急性脑梗死偏瘫患者踝关节运动功能障碍的fMRI研究

目的:利用功能磁共振成像(fMRI)技术,观察急性脑梗死患者的运动相关皮层的激活图,探讨卒中后踝功能障碍及恢复的脑功能相关性改变.方法:采用1.5T磁共振成像系统对10例急性脑梗死患者和5例正常志愿者进行BOLD-fMRI检查,采用健侧、患侧踝关节背伸、趾屈运动作为刺激任务,比较正常志愿者与急性脑梗死患者踝关节运动时脑部激活情况的异同,并采用LI为指标,观察急性脑梗死患者健侧、患侧踝关节运动时脑部激活的差异.结果:正常对照组踝关节运动主要激活对侧SM1区,激活区形态呈斑片状或者不规则状,此外对侧PM区、SMA区也有不同程度的激活.急性脑梗死患者健侧踝关节运动主要激活对侧SM1区,此外对侧PM区、SMA区、颞叶、枕叶、小脑半球、额叶等也有不同程度的激活,与正常对照组激活区相似;患侧踝关节运动(主观运动)时除了对侧半球SM1区激活之外,同侧SM1区、PM区也可见不同程度的激活,对侧半球的激活体积大部分大于同侧.根据公式计算出LI值,结果显示健侧、患侧踝关节运动LI值之间存在显著性差异(P<0.05).结论:fMRI可以客观的显示急性脑梗死后患者大脑运动皮层的激活情况,提示存在脑功能代偿与重组,fMRI作为监测和研究急性脑梗死后运动功能恢复的有用工具,在临床治疗中具有重要的指导意义.     

实验性兔根尖周炎模型的建立

目的:运用内毒素诱导实验性兔根尖周炎模型的建立,探讨建立实验性兔根尖周炎模型的方法.方法:选用6只新西兰大白兔,采用全麻后在其双侧上颌第一、第二磨牙及下颌第一磨牙咬合面开髓,置入内毒素脂多糖后,分别于术后1周、2周、3周各处死2只,制作组织学切片,经HE染色后观察并分析根尖周组织变化的过程.结果:1周后,实验性兔根尖周组织见较明显的炎症细胞浸润;2周后,炎症细胞浸润明显加重;3周后进入慢性炎症期.结论:将内毒素脂多糖封入实验性兔根管后,可成功建立根尖周炎模型,为根尖周病变的研究奠定了基础.     

4种园林植物叶片的解剖结构及抗旱性

采用石蜡切片法观察兰州市甘肃农业大学校园和滨河路两处研究区4种常见园林植物叶片的解剖结构,测定了叶片厚度（T_L）、上（下）角质层厚度(C_TUE、C_TLE)、上（下）表皮细胞厚度、栅栏组织厚度(T_PT)、海绵组织厚度(T_ST)、栅栏组织厚度/海绵组织厚度（P/S）、叶片结构紧密度(T_LS)、疏松度(L_LS)10项叶片结构指标,运用主成分分析法和隶属函数法分析4种园林植物的抗旱能力.结果表明,叶片相对含水量和土壤相对含水量均是甘肃农业大学校园大于滨河路,表明滨河路植物所处的环境较为干旱;叶片解剖结构在两研究区表现出不同程度的差异性,旱柳为等面叶,其余3种植物为异面叶,且植物的T_L、T_PT、P/S、T_LS均是滨河路大于甘肃农业大学校园,而T_ST和L_LS均是滨河路小于甘肃农业大学校园. 10个抗旱性指标在4种园林植物间有较大差异,变异...     

Inference of human population history from individual whole-genome sequences

The history of human population size is important for understanding human evolution. Various studies have found evidence for a founder event (bottleneck) in East Asian and European populations, associated with the human dispersal out-of-Africa event around 60 thousand years (kyr) ago. However, these studies have had to assume simplified demographic models with few parameters, and they do not provide a precise date for the start and stop times of the bottleneck. Here, with fewer assumptions on population size changes, we present a more detailed history of human population sizes between approximately ten thousand and a million years ago, using the pairwise sequentially Markovian coalescent model applied to the complete diploid genome sequences of a Chinese male (YH), a Korean male (SJK), three European individuals (J. C. Venter, NA12891 and NA12878 (ref. 9)) and two Yoruba males (NA18507 (ref. 10) and NA19239). We infer that European and Chinese populations had very similar population-size histories before 10-20?kyr ago. Both populations experienced a severe bottleneck 10-60?kyr ago, whereas African populations experienced a milder bottleneck from which they recovered earlier. All three populations have an elevated effective population size between 60 and 250?kyr ago, possibly due to population substructure. We also infer that the differentiation of genetically modern humans may have started as early as 100-120?kyr ago, but considerable genetic exchanges may still have occurred until 20-40?kyr ago.     

Modelling the recent common ancestry of all living humans

If a common ancestor of all living humans is defined as an individual who is a genealogical ancestor of all present-day people, the most recent common ancestor (MRCA) for a randomly mating population would have lived in the very recent past. However, the random mating model ignores essential aspects of population substructure, such as the tendency of individuals to choose mates from the same social group, and the relative isolation of geographically separated groups. Here we show that recent common ancestors also emerge from two models incorporating substantial population substructure. One model, designed for simplicity and theoretical insight, yields explicit mathematical results through a probabilistic analysis. A more elaborate second model, designed to capture historical population dynamics in a more realistic way, is analysed computationally through Monte Carlo simulations. These analyses suggest that the genealogies of all living humans overlap in remarkable ways in the recent past. In particular, the MRCA of all present-day humans lived just a few thousand years ago in these models. Moreover, among all individuals living more than just a few thousand years earlier than the MRCA, each present-day human has exactly the same set of genealogical ancestors.     

Human presence in the European Arctic nearly 40,000 years ago.

The transition from the Middle to the Upper Palaeolithic, approximately 40,000-35,000 radiocarbon years ago, marks a turning point in the history of human evolution in Europe. Many changes in the archaeological and fossil record at this time have been associated with the appearance of anatomically modern humans. Before this transition, the Neanderthals roamed the continent, but their remains have not been found in the northernmost part of Eurasia. It is generally believed that this vast region was not colonized by humans until the final stage of the last Ice Age some 13,000-14,000 years ago. Here we report the discovery of traces of human occupation nearly 40,000 years old at Mamontovaya Kurya, a Palaeolithic site situated in the European part of the Russian Arctic. At this site we have uncovered stone artefacts, animal bones and a mammoth tusk with human-made marks from strata covered by thick Quaternary deposits. This is the oldest documented evidence for human presence at this high latitude; it implies that either the Neanderthals expanded much further north than previously thought or that modern humans were present in the Arctic only a few thousand years after their first appearance in Europe.     

再论罗家坝遗存

四川宣汉罗家坝遗址二期发掘于2003年3月15日开始,7月上旬结束,取得了突破性成果.对研究古巴人的文化特征,与周边遗址的文化关系及其文化归属提供了可靠的佐证,推测其年代距今约3000-4600年.     

Molecular analysis of Neanderthal DNA from the northern Caucasus

The expansion of premodern humans into western and eastern Europe approximately 40,000 years before the present led to the eventual replacement of the Neanderthals by modern humans approximately 28,000 years ago. Here we report the second mitochondrial DNA (mtDNA) analysis of a Neanderthal, and the first such analysis on clearly dated Neanderthal remains. The specimen is from one of the eastern-most Neanderthal populations, recovered from Mezmaiskaya Cave in the northern Caucasus. Radiocarbon dating estimated the specimen to be approximately 29,000 years old and therefore from one of the latest living Neanderthals. The sequence shows 3.48% divergence from the Feldhofer Neanderthal. Phylogenetic analysis places the two Neanderthals from the Caucasus and western Germany together in a clade that is distinct from modern humans, suggesting that their mtDNA types have not contributed to the modern human mtDNA pool. Comparison with modern populations provides no evidence for the multiregional hypothesis of modern human evolution.     

中亚石器文化研究综述--兼论中亚旧石器时代早期文化

中亚旧石器时代早期文化是指距今300—200万年至30—20万年前的史前人类文化遗址。这表明在很久以前原始人类就开始在中亚地区生息繁衍。在此期间，他们开始制作简单的打制石器，过着采集和狩猎的生活。     

考古学所见四千年前鲁西南地形地貌及自然环境

鲁西南地区是中华民族重要的发祥地之一,远古时代,先民们就居住、繁衍、生息在这块古老的土地上.考古发现表明,四千年前鲁西南的地形地貌及自然环境是河湖交错,林木茂密,气候湿热,水网密布,非常适合人类生存.     

Early human occupation of the Red Sea coast of Eritrea during the last interglacial

The geographical origin of modern humans is the subject of ongoing scientific debate. The 'multiregional evolution' hypothesis argues that modern humans evolved semi-independently in Europe, Asia and Africa between 100,000 and 40,000 years ago, whereas the 'out of Africa' hypothesis contends that modern humans evolved in Africa between 200 and 100 kyr ago, migrating to Eurasia at some later time. Direct palaeontological, archaeological and biological evidence is necessary to resolve this debate. Here we report the discovery of early Middle Stone Age artefacts in an emerged reef terrace on the Red Sea coast of Eritrea, which we date to the last interglacial (about 125 kyr ago) using U-Th mass spectrometry techniques on fossil corals. The geological setting of these artefacts shows that early humans occupied coastal areas and exploited near-shore marine food resources in East Africa by this time. Together with similar, tentatively dated discoveries from South Africa this is the earliest well-dated evidence for human adaptation to a coastal marine environment, heralding an expansion in the range and complexity of human behaviour from one end of Africa to the other. This new, wide-spread adaptive strategy may, in part, signal the onset of modern human behaviour, which supports an African origin for modern humans by 125 kyr ago.     

Significance of enamel thickness in hominoid evolution

Enamel thickness has assumed unique importance in the debate about the hominid status of Ramapithecus, despite the fact that there is little agreement about the meaning of 'thick enamel' or the significance of enamel thickness for hominoid taxonomy. My aim here is to evaluate the usefulness of enamel thickness and microstructure as characteristics for determining the relationships of the later Miocene hominoids, based both on a quantitative study of enamel thickness in extant hominoids and four species of later Miocene Sivapithecus (including 'Ramapithecus') and on scanning electron microscope analysis of enamel microstructure. Four categories of enamel thickness are defined metrically here and have been related to enamel microstructure and developmental rates. Thin fast-formed (pattern 3) enamel represents the ancestral condition in hominoids; it increased developmentally to thick pattern 3 enamel in the great ape and human clade and that condition is primitively retained in Homo and in the fossil hominoid Sivapithecus (including 'Ramapithecus'). Enamel thickness has been secondarily reduced in the African apes and also, although at a different rate and extent, in the orang-utan. Thick enamel, previously the most important characteristic in arguments about the earliest hominid, does not therefore identify a hominid.