不同滤波方法对超声图像分割的影响

采用各向异性滤波方法以及Gabor滤波方法对乳腺肿瘤超声图像进行处理,再使用snake方法以及levelset方法在设置相同参数的条件下,对过滤的图像分别进行分割。试验结果表明,不同的滤波方法在分害4目标图像的收敛度,边缘圆滑度及整体轮廓提取效果都有较大影响,为分割图像选取适当的滤波器提供了参考。     

直接模糊聚类的截取水平选择及其在植被数量分析中的应用

植被生态研究中常用的聚类法,是着眼于研究区域中植被和环境因子呈间断分布或变化梯度较大的一类情况,对原始数据中各个体按其属性进行归类。直接模糊聚类法则以各个体间的属性相近程度来定义一模糊关系矩阵,然后对矩阵取不同的水平截集,从而得出一等级分类。当模糊关系确定以后,截取水平的选择就成了聚类结果的决定性因素。至目前为止,直接模糊聚类中的截取水平通常由分析者主观给定,或者是以逐步试验,逐步修改的方法确定的。这样,聚类结果就不可避免地带有较大的主观和任意性。笔者认为截取水平应选在模糊关系变化较大之处,使聚类结果尽可能地反映原始数据的结构特征。这一原理已被实施于一通用软件中,实例分析表明,如此选择的截取水平确能比较客观地反映原始数据的特征,从而得出较为合理的聚类结果。     

Influence of Irradiation on the Risk of Transmission of HIV in Bone Grafts Obtained from Appropriately Screened Donors and Followed by Radiation Sterilization

We studied the effects of radiation (electrons of 6.2 MeV) at different temperatures with respect to the inactivation of the human immunodeficiency virus to determine the radiosensitivity of the virus. Using a mathematical model describing the dependence on radiation dose of the proportion of sterile items in a population of bone allografts contaminated by HIV, and subjected to irradiation, we have commented on and explained the calculation of the sterility assurance level in bone transplantation according to different doses of irradiation at different temperatures. Simultaneous application of heat and radiation increases inactivation of HIV. Given the relative imprecision of viral sensitivity curves and the impossibility of knowing the number of viral particles in a patient at a given moment of the disease, irradiation does not authorize bone transplantation without screening. However, irradiation can be considered as a serious adjuvent to decrease the risk of contamination after screening.     

具无穷时滞的积分微分方程组解与平衡解的相交性

得到关于具有无穷时滞的Ｖｏｌｔｅｒｒａ－Ｌｏｔｋａ积分微分方程组全体正解关于正平衡解具有相交性的一组充分条件和两个推论。     

Elimination ofSitotroga cerealella (Olivier) bySitophilus zeamais Motschulsky from mixed laboratory cultures on maize

This paper describes a series of experiments conducted to determine why Sitophilus zeamaisMots . and Sitotroga cerealella (Oliv. ) could not survive together in maize cultures in the laboratory. The effect of S. zeamais on different developmental stages of S. cerealella was investigated. The presence of adult S. zeamais slightly affected moth copulation, egg laying and moth eggs in a mixed culture, but large numbers of developing moths inside maize grains were killed by the adult weevil through feeding on the grains. The major cause of elimination of S. cerealella by S. zeamais from mixed cultures was therefore found to be damage to the immature moths in grain and such moth mortality increased as the developing moths became bigger in the grains. A weevil: grain ratio of approximately 1.4∶1 was found to be the critical weevil density at which the moth disappeared from the mixed cultures.     

Sampling error as a misleading artifact in “key factor analysis”

The influences of sampling error in key factor analysis are investigated statistically. The error involved in the data distorts the results in various misleading ways. In the course of detecting key factors by correlation analysis, the distortion arises in the following two ways: (1) the contributions made by the first and the last components of population trend index (log I or K) to the total variation are overrated as compared with the others; and (2) spurious negative correlation arises between successive two components. The risk of misinterpretation due to such disturbance is usually increased further if the error is concentrated on any particular developmental stages. In the tests to detect density-dependence by using regression analysis, the error consistently acts as if it were a density-dependent factor: under the effect of sampling error, the slope b for the regression of log N_i+1 on log N_i, for example, is expected to become<1 even where there is no density-dependent factor at all. A set of formulas are derived which may serve to check and correct these misleading distortions caused by the error. It is also shown that such undesirable influences can be avoided, at least to a considerable extent, if appropriate sampling plans are adopted for the study. The validity of key factor analysis is discussed in reference to this and some related problems.     

注射硫代乙酰胺及饲喂不同油脂水平饲料建立草鱼肝损伤实验模型

目的通过注射硫代乙酰胺(TAA)及饲喂不同油脂水平饲料建立草鱼肝损伤实验模型。方法 实验草鱼分模型组和对照组,每组分别投喂2.8%油脂组、4.8%油脂组和6.8%油脂组,模型组腹腔注射TAA 300mg/kg,1次/日,注射1 d,共计6个实验组,饲养10周。养殖过程中,于2周、4周和6周对每组实验鱼采血,测定天门冬酸氨基转移酶(AST)、丙氨酸氨基转移酶(ALT)和AST/ALT。结果①模型组特定生长率显著降低了30.5%(P<0.01),成活率平均为73.33%。模型组草鱼肌肉粗脂肪含量显著降低了17.6%,而肝胰脏粗脂肪含量显著增高了13.38%(P<0.01)。②模型组2周、4周和6周时,模型组血清AST/ALT分别为对照组的1.94倍、1.38倍和1.31倍。10周时,模型组草鱼血清AST/ALT增高了10.10%(P>0.05),而血清胆碱酯酶(CHE)降低了6.38%(P>0.05)。模型组草鱼血清超氧化物歧化酶(SOD)活力显著低于对照组8.56%(P<0.05)。③与对照组相比,模型组肝细胞肿胀且边界模糊,肝细胞部分脂肪病变,有部分炎症浸润,并均出现肝纤维化。结论注射TAA及饲喂不同油脂水平饲料可以诱导草鱼肝损伤实验模型,实验模型具备脂肪肝和肝纤维化病理特征。     

Typical values for pediatric interventional cardiology catheterizations: A standardized approach towards Diagnostic Reference Level establishment

PurposeTo define weight-stratified Diagnostic Reference Levels (DRL) typical values for pediatric interventional cardiology (IC) procedures adopting standardized methodologies proposed by ICRP135 and RP185.MethodsProcedures performed at the pediatric catheterization room of the University-Hospital of Padua were analysed. Patients were stratified into body weight (BW) classes and DRL quantities were analysed for the most performed procedures. Typical values are defined as median P_KA and K_a,r. For database consistency, sampling and exclusion methods were precisely defined. The DRL-curve methodology by means of quantile regression median curves was investigated to assess the relationship between P_KA and weight. A like-to-like comparison with literature was made.Results385 procedures were analysed. A large P_KA variability was observed in each weight group. P_KA differences across BW groups were not always statistically significant. When stratifying by procedure, P_KA variability decreased while correlations of P_KA and P_KA/FT with weight increased. The established typical values are generally lower than DRLs published data, whatever stratification method adopted. The highest P_KA median values were observed for Angioplasty (4.9 and 11.6 Gycm² for 5-<15 kg and 15-<30 kg, respectively). The DRL-curve approach shows promising results for Valvuloplasty and Angioplasty.ConclusionsTypical values for pediatric IC DRL quantities were determined according to ICRP135 and RP185 methodologies. Stratification by BW classification does not reduce the variability of the P_KA values, unlike what happens when stratifying by procedure type. Results seem to corroborate that variability and exposure are more affected by procedure type and complexity than by patient weight. DRL-curve is a feasible approach.     

Altered structure and deregulated expression of the tumor suppressor gene retinoblastoma (RB1) in human brain tumors

A total of 40 human brain tumor samples were analyzed for tumor-specific alterations at the RB1 gene locus. Gliomas were more prevalent in younger males and meningiomas in older females. Southern blot analysis revealed loss of heterozygosity (LOH) at the intron 1 locus of RB1 gene in 19.4% of informative cases and this is the first report showing LOH at this locus in human brain tumors. Levels of RB1 mRNA and protein, pRb, and the percentage of hyperphosphorylated form of pRb were also analyzed in these tumors. Normal human fibroblast cell line WI38 was used as control in northern and western analysis. Normal sized RB1 mRNA and protein were present in all the tumor samples. Majority of the gliomas had 2.0-fold or higher levels of RB1 mRNA and most meningiomas had less than 2.0-fold of RB1 mRNA compared to control WI38 cells. The total pRb levels were 2.0-fold or higher in all the tumor samples compared to control. More than 50% of pRb existed in hyperphosphorylated form in all gliomas except two. However, six out of 13 meningiomas had less than 50% of total pRb in the hyperphosphorylated form. These results indicate that the increased percentage of hyperphosphorylated form of pRb in gliomas could provide growth advantage to these tumors. Presence of LOH at the RB1 gene locus and the increased levels of RB1 RNA and protein and increased percentage of hyperphosphorylated form of pRb are indicative of an overall deregulation of pRb pathway in human brain tumors.     

The <Emphasis Type="Italic">Karsteniceras</Emphasis> level: Dysoxic ammonoid beds within the Early Cretaceous (Barremian,Northern Calcareous Alps,Austria)

Summary An Early Cretaceous mass-occurrence of ammonites in the Ternberg Nappe of the Northern Calcareous Alps (Upper Austria) is described for the first time. The mass-occurrence (section KB1-B=Klausrieglerbach 1, section B) dominated by Karsteniceras ternbergense Lukeneder is of Early Barremian age (Moutoniceras moutonianum Zone). The Karsteniceras mass-occurrence comprises eight different genera, each apparently represented by a single species, of which four are identified to species level. About 300 specimens of K. ternbergense between 5 and 37 mm in diameter were investigated. Two groups showing thick main ribs but different maximum size are distinguishable. The latter parameters are suggested to reflect sexual dimorphism within K. ternbergense, a condition that is most probably applicable to the whole leptoceratoid group. The geochemical results indicate that the Karsteniceras mass-occurrence within the described Lower Cretaceous succession was deposited under intermittent oxygen-depleted conditions associated with stable, salinity-stratified water masses. The rhythmicity of laminated black-marly lime-stone layers and light-grey bioturbated, organic-poor lime-stones suggests that the oxic and dysoxic conditions underwent highly dynamic changes. The deposition of the limestones in this interval occurred in an unstable environment and was controlled by short- and long-term fluctuations in oxygen levels. Karsteniceras inhabited areas of stagnant water with low dissolved oxygen; it showed peak abundance during times of oxygen depletion, which partially hindered other invertebrates from settling in such environments. The autochthonous Karsteniceras mass-occurrence can be assigned to the deposition-type of ‘Konservat Lagerst?tte’, which is indicated by the preservation of phosphatic siphuncle structures and proved by the in situ preservation of aptychi within Karsteniceras ternbergense. Based on lithological and geochemical analysis combined with in vestigations of trace fossils, microfossils and macrofossils, an invasion of an opportunistic (r-strategist) Karsteniceras biocoenosis during nonfavorable conditions over the sea bed during the Lower Barremian is proposed for the KB1-B section.