基于碳纳米管／壳聚糖／纳米金活性界面的辣根过氧化物酶传感器研制

利用壳聚糖(Chitosan)的成膜性能以及碳纳米管在其中良好的分散性,在玻碳电极表面首先形成碳纳米管/壳聚糖膜,通过膜表面丰富的氨基与纳米金的强静电吸附,在玻碳电极表面获得稳定的纳米Au修饰层,吸附固定辣根过氧化物酶(HRP),制得无需电子媒介的H2O2生物传感器.循环伏安曲线显示,当加入H2O2溶液后,阴极峰电流增大,而阳极电流相应减少,表明通过碳纳米管/壳聚糖/纳米金活性界面固定在玻碳电极表面的HRP与电极之间有良好的直接电子传导能力,对H2O2的还原具有良好的电催化活性,H2O2的测定线性范围为5×10-5～2.7×10-3mol/L.     

辣根过氧化物酶在巯基丁二酸铜（II）自组装单分子层修饰电极表面的固定及对H2O2传感研究

利用气相沉积技术制备TiO2凝胶膜,将辣根过氧化酶固定在巯基丁二酸铜(II)(CuL-SH)自组装单分子层修饰金电极表面,制得测定H2O2 的电流型生物传感器.金电极表面的CuL-SH同时作为电子媒介体.研究了各种因素如pH、工作电位等对传感器响应电流的影响.传感器对H2O2的还原显示出快速电催化响应(＜10 s),计时电流法测定H2O2的线性范围为2.2 μmol/L -0.6 mmol/L(R = 0.999),检出限为1.0×10-6mol/L.测得酶催化动力学参数米氏常数KMapp＝0.56 mmol/L.传感器的稳定性好,60 d 其响应值仍保持90 %.对其灵敏度和选择性进行了研究,并应用于实际样品测定.     

辣根过氧化物酶修饰电极的直接电化学行为研究

采用预混合自组装方法将辣根过氧化物酶修饰到玻碳电极表面,运用循环伏安法(CV)、电化学阻抗法(EIS)等方法研究了该电极的电化学行为.讨论了H2O2在GC/PDDA/PSS-HRP/PDDA修饰电极上的响应.在最佳实验条件下,修饰电极对H2O2在1.66×10-6～1.14×10-4 mol/L浓度范围内与电流呈线性关系,检测极限为9.76×10-7 mol/L.     

基于壳聚糖-纳米TiO2复合膜／CdSe固定血红蛋白的过氧化氢生物传感器的研究

以壳聚糖/nano-TiO2复合膜为基底固载量子点硒化镉(CdSe)和血红蛋白(Hb)制备过氧化氢生物传感器.用循环伏安法对修饰电极进行了表征,并用计时电流法对过氧化氢(H2O2)生物传感器的性能进行了研究.结果表明,在优化的实验条件下,该传感器的响应电流与其浓度在3.9×10-6～1.2×10-2mol/L范围内呈良好的线性关系,检出限为1.0×10-6mol/L.该传感器的米氏常数为1.65mmol/L,表明所固定的酶具有较高的生物活性.     

电聚合二氧化锆固载辣根过氧化物酶的第三代生物传感器的研制

利用生物相容性良好的无机材料二氧化锆(ZrO2)对辣根过氧化物酶(HRP)进行直接固定,用交流阻抗法对修饰电极进行了表征,并用循环伏安法和计时电流法对过氧化氢(H2O2)生物传感器的性能进行了研究.结果表明,该法成功的制备了以电聚合ZrO2为载体的无介体第三代电流型生物传感器.其线性范围为1.00×10-6～1.87×10-3mol/L,线性回归方程为:ip(μA)=0.002 3 c(μmol/L)+2.9324,相关系数r为0.996 8,检测限为2.86×10-7 mol/L.     

基于铂纳米颗粒修饰碳纳米管Nafion膜电极的葡萄糖传感器

将分散在Nafion溶液中的多壁碳纳米管(MWNT)修饰玻碳电极(GCE),再在该膜上电沉积一层铂纳米粒子,制成铂纳米颗粒修饰的碳纳米管Nafion膜电极(Nafion-MWNT-Pt/GCE),并吸附固定葡萄糖氧化酶(GOD),构建电流型葡萄糖生物传感器。考察了Nafion-MWNT-Pt/GCE的电化学特性,发现沉积铂纳米粒子后,Fe(CN)6-3/-4电对在Nafion-MWNT-Pt/GCE上的氧化峰和还原蜂之间的电势差(ΔE)为179mV,小于未修饰铂纳米粒子的碳纳米管Nafion膜电极的ΔE(190mV),表明碳纳米管上电沉积的铂纳米粒子可加速电极的电子传递,电化学反应具有良好的可逆性。此外,铂纳米粒子尚具有良好的催化H2O2氧化的特性,H2O2在Nafion-MWNT-Pt/GCE上的计时电流响应明显增大。基于Nafion-MWNT-Pt/GCE的葡萄糖生物传感器显示了良好的传感性能,其检测线性范围为2.1×10-5～7.6×10-3mol/L,检测下限为1.0×10-6mol/L。     

基于DNA-Hb修饰的聚合二氧化锆/金电极过氧化氢生物传感器的研究

以聚合二氧化锆(ZrO2)薄膜修饰的金电极为基底,通过在二氧化锆修饰电极表面滴涂DNA和血红蛋白(Hb)溶液制备了性能优良的DNA-Hb/ZrO2/Au过氧化氢传感器.该传感器对H2O2的还原显示出较好的电催化响应,固定在电极表面的Hb在0.1 mol/L(pH5.0)PBS中对过氧化氢响应灵敏度高,检测范围宽(1.7×10-7～3.0×10-3～mol/L),检测下限低(8.0×10-8～tool/L),并且表现出良好的热稳定性和高选择性.     

基于金纳米-植酸胶束混合组装的过氧化氢传感器的电化学研究

采用混合组装技术,利用植酸胶束(IP6micelles)的磷酸酯键络合辣根过氧化物酶(HRP)和金纳米粒子(GNPs),形成了具有生物亲和性的纳米复合材料,保持了辣根过氧化物酶的生物活性,并利用金纳米粒子的高电子密度、介电特性和催化性能,实现了HRP与玻碳电极(GCE)表面的直接电子转移。Nafion膜的滴加能提高电极的选择性和稳定性。实验过程中借助紫外-可见吸收光谱和透射电子显微镜进行表征,实验结果证明:GNPs的高导电和高催化性能,结合植酸胶束的优良生物相容性和对酶的高负载量的特点,使得吸附在其上的HRP保持活性,制备的生物传感器能对H2O2进行电催化还原。Nafion/HRP-IP6micelles-GNPs/GCE对H2O2的线性浓度范围为5×10-7～1.15×10-5mol/L(线性相关系数r=0.993,n=9),最低检测限为0.1μmol/L(信噪比S/N=3),米氏常数为0.002 4 mmol/L。     

基于石墨烯-海藻酸钠复合材料的辣根过氧化物酶传感器研究

构建了一种以海藻酸钠-石墨烯(SA-GR)为基底的新型过氧化氢电化学酶传感器。利用滴涂法将生物相容性良好的海藻酸钠-石墨烯复合物固定在玻碳电极表面,再通过酰胺键将HRP连接在SA-GR复合膜上,从而制备出了性能良好的过氧化氢电化学酶传感器。该传感器重现性好、灵敏度较高,并且响应速度快(3 s),米氏常数较低(Km=0.663),对H2O2检测的线性范围为1.0×10-4～1.2×10-3mol/L,检测下限为5.7×10-6mol/L。     

基于多壁碳纳米管负载镍的无酶葡萄糖传感器

文中采用水热法合成负载镍纳米碳管(MWCNTs)复合材料,以Nafion为固定剂将复合材料修饰于玻碳电极的表面制备了一种新型葡萄糖传感器,并用于血清样品中葡萄糖的测定。实验发现,合成在纳米碳管表面的镍为纳米级,并分散均匀。复合材料修饰的电极对葡萄糖响应电流明显大于镍圆盘电极,而且受抗坏血酸和尿酸干扰较小。实验采用安培法测定葡萄糖,线性范围为2×10-6mol/L～1.2×10-3mol/L,检测下限达到了5×10-7mol/L。     

Negation as Failure as Resolution

Providing a clean procedural semantics of the Negation As Failure rule in Logic Programming has been an open problem for some time now. This rule has been treated as a technique in nonmonotonic reasoning, not as a rule in classical logic. This paper contains a demonstration of the negation as failure rule as a resolution procedure in first-order logic. We present a sound and complete resolution scheme for negation as failure rule for the larger class of constraint logic programs. The approach is to consider a canonical partition of the completion of a definite (constraint) program into the IF and the FI programs. We show that a negated goal, provable from the completed definite program is provable from just the FI part. The clauses in this program have a structure dual to that of definite Horn clauses. We describe a sound and complete linear resolution rule for this fragment, and show that a resolution proof of the negated goal from the FI part corresponds to a finite failure tree resulting from classical linear resolution applied to the goal on the If part of the original definite program. Our work shows that negation as failure rule can be computationally efficient in the sense that the SLD-resolution on the If part of a definite program along with the negation as failure rule is more efficient than a direct resolution procedure on the completion of that program.     

WLAN as easy as GSM

The WLAN Smart Card Consortium has released a comprehensive smart card specification — WLAN-SIM V0.1 — to allow hot spot operators to extend SIM technology for use in WLAN authentication. The purpose of the specification is to ensure interoperability between smart card providers, which is a key element for operators to provide roaming between hot spot providers.This is a short news story only. Visit www.compseconline.com for the latest computer security industry news.     

IMS--是机遇也是挑战

随着数据业务的发展，网络运营商面临着是做IP电信运营商还是做IP通道提供商的选择。对于IP通道提供商．主要工作是IP包的传输，业务由第三方提供；而对于IP电信运营商来说．其责任不仅仅是宽带接入、应用和业务提供、费用的收取，甚至是最终内容的提供也在运营商的经营范同之列。     

解析拥塞控制的算法

归纳了基于路由器网络拥塞控制算法,此算法以网络中流量守恒为原则,根据复用统计的方法将路由器的输入输出流量作比较,参照比较结果将路由器的工作状态分为空闲状态、正常状态、轻度拥塞状态、重度拥塞状态。分别在路由器不同状态下实施拥塞控制算法,当网络为轻度拥塞时,在路由器处采用改进的RED的算法并进行数据流管理;当网络出现重度拥塞时,再结合ECN算法进行拥塞控制。     

There are planar graphs almost as good as the complete graphs and almost as cheap as minimum spanning trees

Let S be a set ofn points in the plane. For an arbitrary positive rationalr, we construct a planar straight-line graph onS that approximates the complete Euclidean graph onS within the factor (1 + 1/r)[2π/3 cos(π/6)], and it has length bounded by 2r + 1 times the length of a minimum Euclidean spanning tree onS. Given the Deiaunay triangulation ofS, the graph can be constructed in linear time.     

There are planar graphs almost as good as the complete graphs and almost as cheap as minimum spanning trees

Let S be a set ofn points in the plane. For an arbitrary positive rationalr, we construct a planar straight-line graph onS that approximates the complete Euclidean graph onS within the factor (1 + 1/r)[2/3 cos(/6)], and it has length bounded by 2r + 1 times the length of a minimum Euclidean spanning tree onS. Given the Deiaunay triangulation ofS, the graph can be constructed in linear time.