学习向量量化神经网络用于胃癌组织样品分类识别的研究

将lvq神经网络(Learn ing Vector Quantization Neural Networks)用于胃癌组织样品的分类识别,根据胃癌组织及相应正常组织的FTIR光谱的主要特征吸收峰值(包括vas(CH3)、vs(CH2)、δ(CH2)、v(C-O)、vs(PO2-)、vas(PO2-)和vs(核酸,细胞蛋白及膜脂))全部或部分作为网络输入向量,对未知的胃组织样品进行分类识别,结果显示:i)以上述全部七个谱峰为输入向量时,网络经训练学习后,其平均识别正确率最高(达89.3%),表明该网络对胃癌组织样品的分类识别是满意的,完全可作为临床医学的辅助诊断手段;ii)总体上,当作为输入向量的FTIR特征谱峰越多时,则网络的平均分类识别正确率越高;iii)作为输入的FTIR特征谱峰不同时,则网络的平均分类识别正确率也不同。     

支持向量机和线性判别分析用于禽流感病毒编码蛋白识别

以支持向量机(SVM)和线性判别分析(LDA)对200条禽流感病毒、100条B型流感和100条C型流感病毒蛋白共400条为训练集样本,从表征序列的200个整体与局部变量中以逐步(stepwise)方法选取24个变量作为LDA模型的输入建立线性识别模型,病毒蛋白总识别率达99.8%,留一法交互检验总识别率为99.4%.从原始200变量中经主成分分析得16个主成分作为SVM的输入,以径向基核函数(RBF)SVM建立非线性识别模型,病毒蛋白总识别率为99.8%,留一法交互检验总识别率为99.2%.以100条禽流感、50条B型流感和50条C型流感病毒编码蛋白质共200条为测试集样本,得LDA模型,对其总识别正确率为95.4%,SVM模型对其总识别正确率为96.5%.识别结果表明,两个模型都可较好识别禽流感病毒蛋白,并且SVM对禽流感病毒蛋白的识别结果优于LDA.     

BP神经网络与正交变换结合的研究

1引言本文将输入向量采用奇异值分解方式进行正交变换,再与BP神经网络相结合用于测定配伍输液中的甲硝唑、头了解唑啉钠与维生素B6,结果令人满意。2原理2．1BP神经网络原理BP（backpropagation）神经网络是多层前馈神经网络,由一个输入层、一个输出层和几个隐含层构成。一通常采用三层结构,二个输入层,一个隐含层,一个输出层。设Aj为输入向量,j＝1,2,…l。l为输入节点数,C输出层的输出向量,Oi为隐蔽层的输出向量,i＝1,2,…。,S为隐节点数,Wij为输入展与隐蔽层的连接权。为隐蔽层与输出层的连接权,F()则取Sigmoid函数…     

基于三维荧光光谱的枸杞鉴别方法

以枸杞干果为研究对象,将三维荧光光谱技术与平行因子分析法、BP神经网络相结合,建立枸杞定性鉴别模型。采用固体样品支架测得枸杞粉末样品的三维荧光光谱,利用平行因子分析方法对预处理后的三维荧光矩阵进行三线性分解得到2个主因子的浓度得分,然后将浓度得分作为BP神经网络的输入向量,建立枸杞的人工神经网络鉴别模型。利用所建模型对待测样品进行预测,预测正确率为100%。结果表明,平行因子分析结合BP神经网络建立的枸杞产地鉴别模型,能够快速准确地鉴别宁夏枸杞。     

芳香族化合物生物降解性的QSBR研究

分别采用线性基团贡献法和人工神经网络法对芳香族化合物的生物降解最大去除率QTOD进行QSBR研究。得到不同基团对生物降解性的贡献顺序为 :C6H5>COOH >OH >CO >CH3 >C1 >NH2>NO2 。线性基团贡献法对于训练组和测试组的预测正确率分别为 86%和 80 % ,总的预测正确率达85 % ;而人工神经网络法的预测正确率分别为 94%、80 %和 92 %。结果表明 ,线性基团贡献法和神经网络法的预测效果均很好 ,而神经网络法的预测更精确。     

He(2~3S)与CH_3l和CH_3Br在流动余辉中传能的解离激发反应

本文利用流动余辉技术研究了亚稳态He(2~3S)与CH_3I和CH_3Br传能时分子的解离激发过程.实验中测定了产物的相对分布、CH(A,υ′=O)的转动布居和主要碎片的形成速率常数.     

固定化金属离子亲和发光二氧化硅纳米粒子的制备及其用于磷酸化蛋白免疫印迹标记

发展了一种能够识别磷酸化蛋白的固定化金属离子亲和发光二氧化硅纳米粒子用于免疫印迹(Western Blot)磷酸化蛋白的标记。首先通过反相微乳液Stöber方法合成了掺杂异硫氰酸荧光素硅烷化衍生物的发光二氧化硅(FITC@SiO₂)球形纳米粒子,粒子平均粒径为60 nm。然后通过共聚反应在FITC@SiO₂纳米粒子表面生成一层聚合物用于保护纳米粒子,并引入N,N-(双羧甲基)-L-赖氨酸功能基团用于螯合金属离子,从而实现固定化金属离子亲和作用。以α-酪蛋白作为实验模型,用高效液相色谱-质谱研究了螯合不同金属离子的发光纳米粒子对磷酸化蛋白的识别作用。结果表明,螯合了Ti⁴⁺金属离子的发光二氧化硅FITC@SiO₂纳米粒子对α-酪蛋白酶解液中的磷酸化肽段的富集作用最强。利用这种发光二氧化硅FITC@SiO₂纳米粒子对磷酸化肽段的特异性识别性能,可用于Western Blot实验中标记磷酸化蛋白的条带。结果显示,α-酪蛋白的电泳条带可以被亲和发光二氧化硅FITC@SiO₂纳米粒子标记,而作为对照的牛血清白蛋白则没有被标记。     

人工神经网络法预测炸药组分的色谱保留值参数

 以分子拓扑指数作为炸药组分的结构描述符 ,利用反向传播算法 (BP)人工神经网络 ,以Sigmoid函数为传递函数 ,分子连接性指数0 χ ,1χ ,2 χ与边邻接指数 (ε)为输入向量 ,反相高效液相色谱保留值参数logkw 和S为输出向量 ,将输入向量归一化至 - 3～ 3区间 ,输出向量归一化至 0～ 1区间 ,网络精度取 0 5 ,学习步长 η的初始值取0 2 ,动量因子α取 0 5 ,通过对 2 0种炸药的网络模型进行训练 ,建立了炸药分子结构与logkw 和S之间的定量模型。结果表明 ,该模型较好地反映了炸药分子结构与保留值之间的关系。     

基于随机森林与Chemistry Development Kit描述符的P-gp底物识别

应用随机森林方法、开放源代码软件-CDK(Chemistry Development Kit)描述符与170个化合物的训练数据集[其中96个为磷糖蛋白(P-gp)底物], 建立了P-gp底物的识别模型. 研究了CDK描述符与P-gp底物识别的关系, 结果表明, 原子极化性和电荷偏面积等分子属性对P-gp底物识别起到重要作用. 该模型对训练集的预测正确率为99.42%; 对外部测试集(42个化合物, 其中24个为P-gp底物)的预测结果为P-gp底物、非底物及总测试集的识别正确率分别为87.50%, 83.33%和85.71%. 212个化合物数据集上的Leave-One-Out交叉验证识别正确率为77.4%.     

8-羟基喹啉衍生物对某些阴离子的双重光谱响应

本文以5-甲酰基-8-羟基喹啉(5M8Q)作为阴离子识别探针,通过紫外、荧光等光谱仪考察其对阴离子识别作用。实验显示:在乙腈溶液中5M8Q对F-、CH3COO-和H2PO4-等阴离子有灵敏的识别作用:F-、CH3COO-和H2PO4-可诱导5M8Q吸收光谱红移,吸收峰位置由322nm红移至400nm。当F-、CH3COO-和H2PO4-浓度为5M8Q两倍当量时,5M8Q荧光显著增强且分别增强至103、60和13倍。结果表明:5M8Q对F-、CH3COO-和H2PO4-有灵敏的双重光谱响应,并且表现出荧光增强型识别性质。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.