Poincare Index与复数滤波相结合的指纹奇异点提取算法

提出了一种使用Poincare Index与复数滤波相结合的方法提取指纹奇异点的方法。首先,使用Poincare Index方法提取指纹图像奇异点,由于Poincare Index易受噪声干扰而提取伪奇异点,使用复数滤波检测备选奇异点的邻近区域,判断该奇异点的可信程度,从而确定奇异点。该方法消除了Poincare Index对噪声敏感、容易提取伪奇异点的缺陷,也弥补了复数滤波无法准确找到奇异点位置的不足。通过实验验证,用该方法提取指纹奇异点取得了很好的效果。     

等离子熔射过程中热传递特性研究

采用红外测温仪检测单位时间内基体温度变化来衡量射流与粒子流(含粉末粒子的射流)的加热效应,实验研究了等离子弧电流、电压、熔射距离以及送粉速率变化对加热效应的影响规律,进而对比分析射流和粒子流与基体/已熔射涂层之间的热传递特性.实验结果表明:等离子熔射过程中的加热效应主要取决于射流引起的对流传热;粒子流的加热效应特点与射流不同,而粉末粒子仅对其沉积区域的温升有贡献;随着熔射距离的增加,射流的加热效应急速下降;等离子弧电流和电压的增大相应地提升了喷枪功率,加大了射流与基体间的对流传热.     

NENP和NINO的电子自旋共振分析

本文在强场框架导出了ｄ８离子基态３Ａ２（Ｆ）自旋哈密顿参量Ｄ、Ｅ和ｇ－因子在斜方对称下的高阶微扰公式；借助于赵等人的参量化ｄ轨道理论，计算ＮＥＮＰ和ＮＩＮＯ的自旋哈密顿参量Ｄ、Ｅ和ｇ－因子，得到了与实验符合很好的结果     

一代Technicolor模型对过程e~+e~-→tc的贡献

在ＬＥＰＩ的能量（Ｓ＝２００ＧｅＶ）下，我们计算了一代Ｔｅｃｈｎｉｃｏｌｏｒ（ＴＣ）模型对过程ｅ＋ｅ－→ｔｃ的贡献．计算结果表明，一代ＴＣ模型对ｅ＋ｅ－→ｔｃ的贡献很小，实验目前还无法观测     

Notch activity acts as a sensor for extracellular calcium during vertebrate left-right determination

During vertebrate embryo development, the breaking of the initial bilateral symmetry is translated into asymmetric gene expression around the node and/or in the lateral plate mesoderm. The earliest conserved feature of this asymmetric gene expression cascade is the left-sided expression of Nodal, which depends on the activity of the Notch signalling pathway. Here we present a mathematical model describing the dynamics of the Notch signalling pathway during chick embryo gastrulation, which reveals a complex and highly robust genetic network that locally activates Notch on the left side of Hensen's node. We identify the source of the asymmetric activation of Notch as a transient accumulation of extracellular calcium, which in turn depends on left-right differences in H+/K+-ATPase activity. Our results uncover a mechanism by which the Notch signalling pathway translates asymmetry in epigenetic factors into asymmetric gene expression around the node.     

Directed evolution of enzymes for biocatalysis and the life sciences

Engineering the specificity and properties of enzymes and proteins within rapid time frames has become feasible with the advent of directed evolution. In the absence of detailed structural and mechanistic information, new functions can be engineered by introducing and recombining mutations, followed by subsequent testing of each variant for the desired new function. A range of methods are available for mutagenesis, and these can be used to introduce mutations at single sites, targeted regions within a gene or randomly throughout the entire gene. In addition, a number of different methods are available to allow recombination of point mutations or blocks of sequence space with little or no homology. Currently, enzyme engineers are still learning which combinations of selection methods and techniques for mutagenesis and DNA recombination are most efficient. Moreover, deciding where to introduce mutations or where to allow recombination is actively being investigated by combining experimental and computational methods. These techniques are already being successfully used for the creation of novel proteins for biocatalysis and the life sciences.Received 8 June 2004; received after revision 22 July 2004; accepted 2 August 2004     

A very energetic supernova associated with the gamma-ray burst of 29 March 2003

Over the past five years evidence has mounted that long-duration (>2 s) gamma-ray bursts (GRBs)-the most luminous of all astronomical explosions-signal the collapse of massive stars in our Universe. This evidence was originally based on the probable association of one unusual GRB with a supernova, but now includes the association of GRBs with regions of massive star formation in distant galaxies, the appearance of supernova-like 'bumps' in the optical afterglow light curves of several bursts and lines of freshly synthesized elements in the spectra of a few X-ray afterglows. These observations support, but do not yet conclusively demonstrate, the idea that long-duration GRBs are associated with the deaths of massive stars, presumably arising from core collapse. Here we report evidence that a very energetic supernova (a hypernova) was temporally and spatially coincident with a GRB at redshift z = 0.1685. The timing of the supernova indicates that it exploded within a few days of the GRB, strongly suggesting that core-collapse events can give rise to GRBs, thereby favouring the 'collapsar' model.     

Construct 2D nanostructure of co-adsorbed dipyridyl derivative by stabilization of hydrogen bond and long alkyl chains

The self-assembled structures of 4, 4‘‘-dionoyl-2,2‘‘-dipyridyl and its co-adsorption with stearic acid on highly oriented pyrolytic graphite (HOPG) have been studied by the scanning tunneling microscopy (STM). As a result, 4,4‘‘-dionoyl-2,2‘‘-dipyridyl forms a planar trans conformation in two cases, and through the co-adsorption with stearic acid, 4,4‘‘-dionoyl-2,2‘‘-dipyridyl and stearic acid form a well-ordered nanostructure.     

河南省残疾人的分布特征与致残因素的研究

河南不仅是全国人口数量最多的省份之一,也是我国残疾人最多的省份.据1987年调查,河南残疾人450.5万人,占全国残疾人8.7%,占河南总人口5.7%.本文从综合观点和生态学角度,论述了河南残疾人的六种类型及其分布规律,以及致残的主要原因,为各级党政领导部制订残疾人有关政策提供了重要科学依据。