肺段隔离症的CT表现

目的:了解肺段隔离症的CT表现与诊断价值。方法:对5例肺段隔离症的CT表现进行回顾分析,全部病例均行CT平扫及增强扫描。结果:5例肺段隔离症均位于肺下叶后内基底段,4例位于左下肺,1例位于右下肺;其中2例为增多增粗的异常血管结构,1例为实质性肿块,1例为囊实性肿块,1例为囊性肿块;其中4例病灶周围可见局限性肺气肿;5例均可发现异常供血动脉。结论:肺段隔离症具有典型的CT表现,特别是异常供血动脉的显示在诊断上有重要的定性作用。     

肝硬化的数量化诊断及其影像分型

通过对肝硬化进行量化研究,为临床影像诊断提供依据.选择正常人肝脏横断位CT图片作为对照组,选择肝硬化代偿期组、失代偿期组、肝癌组作为疾病组进行对比研究.利用人体常用解剖轴线作为肝脏测量的基准线.肝脏左叶冠状径(L1)的变化最具有临床意义,肝叶比例不仅存在于肝叶之间也存在于肝叶之内.肝脏各叶测量值对于早期肝硬化的诊断具有重要的意义.     

Effect of prescribed burning on wildfire severity: a landscape-scale case study from the 2003 fires in Victoria

This study examined the effect of previous fuel reduction burning (FRB) on the severity of the >1 million ha 2003 Alpine Fire in eastern Victoria. Sixty-five paired observations (130 total) of fire severity were completed across the broad fire area using GIS (Geographic Information System) analysis. Despite the broad scatter in this large data set, a number of strong trends were evident. A Fire Severity Index (FSI) was calculated from the correlated fire, weather and topographic variables, with a three-factor model using the forest fire danger index (FFDI), fire or FRB age and percentage of north-western aspect, best explaining the variation in measured fire-severity data. The most important finding was that the reduction in fire severity and suppression assistance effects of previous fuel-reduction burning started to decline substantially when the FFDI exceeded 50. Above FFDI 50, landscape-scale fires became ‘weather-dominated’ and variation in fuel and topography became less important to continued fire spread. The greatest effects of previous FRB in reducing wildfire severity and in assisting fire suppression occurred when (1) the FFDI fell to 25 or less (late in the evening and overnight); (2) the age of the FRB was less than 3 years (i.e. when all three components of fuel—surface, bark and elevated material—were still substantially reduced). Some fire-severity reduction effects were still evident for FRBs up to 10 years old, but there was almost no evidence of FRBs older than 10 years having any effect on fire severity. FRBs up to 10 years old also had measurable effects on increasing burnt area patchiness and decreasing canopy loss, both of which have ecological implications. This study provides fire managers planning rotational landscape FRB with important information on likely effects of the burning on fire severity.     

A note on the surface topography of profiled wood decking

Profiled wooden deck-boards with small peaks and grooves machined into their surface are preferred in many countries to flat deck-boards because profiling makes the surface less slippery and prone to checking. Numerous companies manufacture profiled decking, and in this paper we examine the variation in topography of profiled wood decking. The topography of commercial profiled decking used in seven different countries was quantified using confocal profilometry, and principal components analysis was used to explore variability in topography between profiled decking samples and relationships between them. Confocal profilometry was able to measure the topography of profiled decking. We observed large variation in the height and width of profile peaks and also their peak and groove radii. Profiled decking can be classified into three morphological groups using the ratio of radii of surface grooves to those of peaks. Two of these groups, ribbed and rippled decking have been mentioned previously, but we identify and name a third group (ribble profile) with surface topography that lies between those of ribbed and rippled profiles. Our method of classifying profiles makes it possible to identify different types of profiled decking and provides a way of systematically comparing how profile topography influences the ability of profiles to restrict the checking of wood.     

检影验光在圆锥角膜筛查与诊断中的应用研究

[目的]探讨分析利用检影验光在筛查与诊断圆锥角膜中的准确性。[方法]收集2008年11月—2011年11月期间利用检影验光观察瞳孔区影动形态异常方法诊断为疑似圆锥角膜病例32例53只眼,经角膜地形图仪检查明确诊断是否相符,并对诊断不符合病例进行分析。[结果]检影验光筛查诊断为疑似圆锥角膜32例53只眼中,经角膜地形图仪确诊圆锥角膜27例43只眼,不符合5例10只眼,不符合的主要原因为高度近视与散光,高度不规则散光引起的异常检影影动干扰所致。检影验光未诊断为疑似圆锥角膜的11只眼中,经角膜地形图仪确诊圆锥角膜4只眼,不符合的主要原因为圆锥角膜病变程度轻,病变位于周边角膜及散光度数较低,检影异常影动不明显。[结论]在角膜地形图检查对高度近视散光人群普查难以实现时,检影验光中影动形态异常反映了圆锥角膜的主要特征,对筛查圆锥角膜有较高的诊断价值。     

OrbscanⅡ角膜地形图系统筛查亚临床期圆锥角膜

目的研究亚临床期圆锥角膜的角膜地形图改变的特点。方法应用OrbscanⅡ角膜地形图系统检测15例(26只眼)亚临床期圆锥角膜患者的角膜,得到角膜前表面和后表面Diff值、角膜最薄点厚度、角膜中央屈光力及角膜模拟镜差值(SimK值),了解亚临床期圆锥角膜的敏感性指标以及各指标之间的相关关系。结果亚临床期圆锥角膜的角膜前表面Diff值是0.025mm,角膜后表面Diff值为0.050 mm;角膜最薄点厚度(450.65±35.67)μm;SimK值为(4.55±1.09)D;角膜中央屈光力为(47.1±3.5)D。角膜前表面Diff值与角膜后表面Diff值、角膜中央屈光力呈正相关关系;角膜后表面Diff值与角膜中央屈光力呈正相关关系。结论 OrbscanⅡ角膜地形图系统可为早期诊断亚临床期圆锥角膜提供形态学依据。     

Auditory brainstem neural activation patterns are altered in EphA4- and ephrin-B2-deficient mice

Auditory processing requires proper formation of tonotopically ordered projections. We have evaluated the role of an Eph receptor tyrosine kinase and an ephrin ligand in the development of these frequency maps. We demonstrated expression of EphA4 and ephrin-B2 in auditory nuclei and found expression gradients along the frequency axis in neonates. We tested the roles of EphA4 and ephrin-B2 in development of auditory projections by evaluating whether mutations result in altered patterns of expression of the immediate early gene c-fos after exposure to pure tone stimuli. We evaluated two nuclei, the dorsal cochlear nucleus (DCN) and the medial nucleus of the trapezoid body (MNTB), which project in two distinct auditory pathways. The mean number of c-fos-positive neurons in EphA4(-/-) DCN after 8-kHz pure tone stimulation was 42% lower than in wild-type DCN. Along the dorsoventral, tonotopic axis of DCN, the mean position of c-fos-positive neurons was similar for mutant and wild-type mice, but the spread of these neurons along the tonotopic axis was 35% greater for ephrin-B2(lacZ/+) mice than for wild-type mice. We also examined these parameters in MNTB after exposure to 40-kHz pure tones. Both EphA4(-/-) and ephrin-B2(lacZ/+) mice had significantly fewer c-fos-positive cells than wild-type littermates. The labeled band of cells was narrower and laterally shifted in EphA4(-/-) mice compared with wild-type mice. These differences in cell number and distribution suggest that EphA4 and ephrin-B2 signaling influence auditory activation patterns.     

Mechanisms of selective inhibition in visual spatial attention are indexed by alpha-band EEG synchronization

Electroencephalographic studies in humans have demonstrated that orienting of visual attention induces a decrease in oscillatory alpha-band activity (alpha-desynchronization) over cortical areas tuned to the attended visual space. This is interpreted as reflecting intentionally enhanced excitability of these areas to facilitate upcoming visual processing. However, the inverse mechanism might also apply. Brain areas that process task-irrelevant space might be actively suppressed by increased alpha-activity (alpha-synchronization) to protect against input of distracter information. In the present study, we demonstrate that such suppression mechanisms are highly selective and are taking place even without distracters that need to be ignored. During voluntary orienting of attention, we found alpha-synchronization to dominate over desynchronization, to be topographically specific for each of eight attention positions, and to occur over areas processing unattended space in a retinotopically organized pattern. This indicates that alpha-synchronization is an important component of selective attention, serving active suppression of unattended positions during visual spatial orienting.     

GABAergic neuron distribution in the pedunculopontine nucleus defines functional subterritories

γ‐Aminobutyric acid (GABA)ergic neurons are widely distributed in brainstem structures involved in the regulation of the sleep‐wake cycle, locomotion, and attention. These brainstem structures include the pedunculopontine nucleus (PPN), which is traditionally characterized by its population of cholinergic neurons that have local and wide‐ranging connections. The functional heterogeneity of the PPN is partially explained by the topographic distribution of cholinergic neurons, but such heterogeneity might also arise from the organization of other neuronal populations within the PPN. To understand whether a topographical organization is also maintained by GABAergic neurons, we labeled these neurons by in situ hybridization for glutamic acid decarboxylase mRNA combined with immunohistochemistry for choline acetyltransferase to reveal cholinergic neurons. We analyzed their distribution within the PPN by using a method to quantify regional differences based on stereological cell counts. We show that GABAergic neurons of the rat PPN have a rostrocaudal gradient that is opposite to that of cholinergic neurons. Indeed, GABAergic neurons are predominantly concentrated in the rostral PPN; in addition, they form, along with cholinergic neurons, a small, high‐density cluster in the most caudal portion of the nucleus. Thus, we provide evidence of heterogeneity in the distribution of different neuronal populations in the PPN and show that GABAergic and cholinergic neurons define neurochemically distinct areas. Our data suggest that the PPN is neurochemically segregated, and such differences define functional territories. J. Comp. Neurol. 515:397–408, 2009. © 2009 Wiley‐Liss, Inc.