Simultaneous determination of N-acetylcysteine and acetaminophen by voltammetric method using N-(3,4-dihydroxyphenethyl)-3,5-dinitrobenzamide modified multiwall carbon nanotubes paste electrode

A new dopamine-derivative, i.e. N-(3,4-dihydroxyphenethyl)-3,5-dinitrobenzamide (N-DHPB), was synthesized and its application was investigated for the simultaneous determination of N-acetylcysteine (NAC) and acetaminophen (AC) using modified multiwall carbon nanotubes paste electrode. This modified electrode exhibited a potent and persistent electron mediating behavior followed by well separated oxidation peaks of NAC and AC. The peaks current of differential pulse voltammograms of NAC and AC increased linearly with their concentration in the ranges of 0.5-200 μmol L⁻¹ NAC and 15.0-270 μmol L⁻¹ AC. The detection limits for NAC and AC were 0.2 μmol L⁻¹ and 10.0 μmol L⁻¹, respectively. The relative standard deviation for seven successive assays of 1.0 and 30.0 μmol L⁻¹ NAC and AC were 1.7% and 2.2%, respectively. The proposed sensor was successfully applied for the determination of NAC in human urine, tablet, and serum samples.     

Red tide detection and tracing using MODIS fluorescence data: A regional example in SW Florida coastal waters

Near real-time data from the MODIS satellite sensor was used to detect and trace a harmful algal bloom (HAB), or red tide, in SW Florida coastal waters from October to December 2004. MODIS fluorescence line height (FLH in W m^− 2 μm^− 1 sr^− 1) data showed the highest correlation with near-concurrent in situ chlorophyll-a concentration (Chl in mg m^− 3). For Chl ranging between 0.4 to 4 mg m^− 3 the ratio between MODIS FLH and in situ Chl is about 0.1 W m^− 2 μm^− 1 sr^− 1 per mg m^− 3 chlorophyll (Chl = 1.255 (FLH × 10)^0.86, r = 0.92, n = 77). In contrast, the band-ratio chlorophyll product of either MODIS or SeaWiFS in this complex coastal environment provided false information. Errors in the satellite Chl data can be both negative and positive (3-15 times higher than in situ Chl) and these data are often inconsistent either spatially or temporally, due to interferences of other water constituents. The red tide that formed from November to December 2004 off SW Florida was revealed by MODIS FLH imagery, and was confirmed by field sampling to contain medium (10⁴ to 10⁵ cells L^− 1) to high (> 10⁵ cells L^− 1) concentrations of the toxic dinoflagellate Karenia brevis. The FLH imagery also showed that the bloom started in mid-October south of Charlotte Harbor, and that it developed and moved to the south and southwest in the subsequent weeks. Despite some artifacts in the data and uncertainty caused by factors such as unknown fluorescence efficiency, our results show that the MODIS FLH data provide an unprecedented tool for research and managers to study and monitor algal blooms in coastal environments.     

Development of an optical sensor for determination of zinc by application of PC-ANN

A very sensitive and reversible optical chemical sensor based on dithizone as chromoionophore immobilized within a plasticized carboxylated PVC film for Zn²⁺ determination is described. At optimum conditions (i.e. pH 5.0), the proposed sensor displays a linear response to Zn²⁺ over 5.0 × 10⁻⁸-5.0 × 10⁻⁶ mol L⁻¹ range. This range was improved to 2.5 × 10⁻⁸-5.8 × 10⁻⁵ mol L⁻¹ range by applying principle component-feed forward artificial neural network with back-propagation training algorithm (PC-ANNB). Detection limit of 8.0 × 10⁻⁹ mol L⁻¹ was obtained. The sensor is fully reversible within the dynamic range and the response time (t_95%) is approximately 4 min under batch conditions. In addition to its high stability and reproducibility, the sensor shows good selectivity towards Zn²⁺ ion with respect to common metal cations. The sensor was successfully applied for determination of Zn²⁺ ion in hair sample.     

Development of molecularly imprinted electrochemical sensor with titanium oxide and gold nanomaterials enhanced technique for determination of 4-nonylphenol

4-Nonylphenol (4-NP) was reported to affect the health of wildlife and humans through altering endocrine function. A novel electrochemical sensor for sensitive and fast determination of 4-NP was developed. Titanium oxide (TiO₂) nanoparticles and gold nanoparticles (AuNPs) were introduced for the enhancement of electron conduction and sensitivity. 4-NP-imprinted functionalized AuNPs composites with specific binding sites for 4-NP was modified on electrode. The resulting electrodes were characterized by cyclic voltammetry (CV). Rebinding experiments were carried out to determine the specific binding capacity and selective recognition. The linear range was over the range from 4.80 × 10⁻⁴ to 9.50 × 10⁻⁷ mol L⁻¹, with the detection limit of 3.20 × 10⁻⁷ mol L⁻¹ (S/N = 3). The sensor was successfully employed to detect 4-NP in real samples.     

A (4n − 9)/3 diagnosis algorithm on n-dimensional cube network

As a generalization of the precise and pessimistic diagnosis strategies of system-level diagnosis of multicomputers, the t/k diagnosis strategy can significantly improve the self-diagnosing capability of a system at the expense of no more than k fault-free processors (nodes) being mistakenly diagnosed as faulty. In the case k ? 2, to our knowledge, there is no known t/k diagnosis algorithm for general diagnosable system or for any specific system. Hypercube is a popular topology for interconnecting processors of multicomputers. It is known that an n-dimensional cube is (4n − 9)/3-diagnosable. This paper addresses the (4n − 9)/3 diagnosis of n-dimensional cube. By exploring the relationship between a largest connected component of the 0-test subgraph of a faulty hypercube and the distribution of the faulty nodes over the network, the fault diagnosis of an n-dimensional cube can be reduced to those of two constituent (n − 1)-dimensional cubes. On this basis, a diagnosis algorithm is presented. Given that there are no more than 4n − 9 faulty nodes, this algorithm can isolate all faulty nodes to within a set in which at most three nodes are fault-free. The proposed algorithm can operate in O(N log₂ N) time, where N = 2ⁿ is the total number of nodes of the hypercube. The work of this paper provides insight into developing efficient t/k diagnosis algorithms for larger k value and for other types of interconnection networks.     

Direct electrochemistry of cytochrome P450 6A1 in mimic bio-membrane and its application for pesticides sensing

The direct electrochemistry of house fly cytochrome P4506A1 (CYP6A1) confined in dioctadecyl dimethyl ammonium bromide (DDAB) film was achieved. The immobilized CYP6A1 displayed a pair of redox peaks with a formal potential of −0.36 mV in pH 7.0 O₂-free phosphate buffers at scan rate of 1 V s⁻¹ and the direct electron transfer of CYP6A1 was characterized by voltammetry. The CYP6A1 in the DDAB film retained its bioactivity and could catalyze the reduction of dissolved oxygen. Upon addition of its substrate aldrin or heptachlor to the air-saturated solution, the reduction peak current of dissolved oxygen increased, which indicates the catalytic behavior of CYP6A1 to its substrates. By amperometry a calibration linear range was obtained to be 9.08 × 10⁻⁶-4.54 × 10⁻⁵ mol L⁻¹ with a sensitivity of 80 μA mM⁻¹ for aldrin or 8.91 × 10⁻⁶-4.46 × 10⁻⁵ mol L⁻¹ with a sensitivity of 66 μA mM⁻¹ for heptachlor. The apparent Michaelis-Menten constant for the electrocatalytic activity of CYP6A1 was found to be 7.468 × 10⁻⁵ mol L⁻¹ for aldrin and 4.316 × 10⁻⁵ mol L⁻¹ for heptachlor. The bioelectrocatalytic products were analysed using gas chromatography (GC) and electron ionization-mass spectrometry (EI-MS). The results confirmed that epoxidation was the main pathways of CYP6A1-mediated organochlorine pesticides oxidation.     

Per-6-ammonium-β-cyclodextrin/p-nitrophenol complex as a colorimetric sensor for phosphate and pyrophosphate anions in water

Using per-6-ammonium-β-cyclodextrin (per-6-NH₃⁺-β-CD) as an anion binding site and p-nitrophenol as a spectroscopic probe, a colorimetric sensor is developed for phosphate and pyrophosphate anions in water. Per-6-NH₃⁺-β-CD forms a 1:2 inclusion complex with p-nitrophenol as characterized by NOESY and ESI-MS spectra and it undergoes a distinct color change from colorless to intense yellow upon exposure to phosphate or pyrophosphate anions over other anions including perchlorate, ATP²⁻, ADP²⁻ and AMP²⁻. The seven ammonium groups of 1, bind phosphate (characterized by ESI-MS) or pyrophosphate anions specifically by electrostatic interaction. This naked eye sensing is significant for very low concentration (5 × 10⁻⁵ M) of anion with 1:2 ratio of host and guest.     

Embedding meshes into locally twisted cubes

As a newly introduced interconnection network for parallel computing, the locally twisted cube possesses many desirable properties. In this paper, mesh embeddings in locally twisted cubes are studied. Let LTQ_n(V, E) denote the n-dimensional locally twisted cube. We present three major results in this paper: (1) For any integer n ? 1, a 2 × 2ⁿ⁻¹ mesh can be embedded in LTQ_n with dilation 1 and expansion 1. (2) For any integer n ? 4, two node-disjoint 4 × 2ⁿ⁻³ meshes can be embedded in LTQ_n with dilation 1 and expansion 2. (3) For any integer n ? 3, a 4  × (2ⁿ⁻² − 1) mesh can be embedded in LTQ_n with dilation 2. The first two results are optimal in the sense that the dilations of all embeddings are 1. The embedding of the 2 × 2ⁿ⁻¹ mesh is also optimal in terms of expansion. We also present the analysis of 2p × 2q mesh embedding in locally twisted cubes.     

Electrochemical genosensor based on modified octadecanethiol self-assembled monolayer for Escherichia coli detection

An electrochemical genosensor based on 1-fluoro-2-nitro-4-azidobenzene (FNAB) modified octadecanethiol (ODT) self-assembled monolayer (SAM) has been fabricated for Escherichia coli detection. The results of electrochemical response measurements investigated using methylene blue (MB) as a redox indicator reveal that this nucleic acid sensor has 60 s of response time, high sensitivity (0.5 × 10⁻¹⁸ M) and linearity as 0.5 × 10⁻¹⁸-1 × 10⁻⁶ M. The sensor has been found to be stable for about four months and can be used about ten times. It is shown that water borne pathogens like Klebsiella pneumonia, Salmonella typhimurium and other gram-negative bacterial samples has no significant effects in the response of this sensor.     

Comments on “Generalised finite Radon transform for N × N images”

In Kingston and Svalbe [1], a generalized finite Radon transform (FRT) that applied to square arrays of arbitrary size N × N was defined and the Fourier slice theorem was established for the FRT. Kingston and Svalbe asserted that “the original definition by Matúš and Flusser was restricted to apply only to square arrays of prime size,” and “Hsung, Lun and Siu developed an FRT that also applied to dyadic square arrays,” and “Kingston further extended this to define an FRT that applies to prime-adic arrays”. It should be said that the presented generalized FRT together with the above FRT definitions repeated the known concept of tensor representation, or tensor transform of images of size N × N which was published earlier by Artyom Grigoryan in 1984-1991 in the USSR. The above mentioned “Fourier slice theorem” repeated the known tensor transform-based algorithm of 2-D DFT [5-11], which was developed for any order N₁ × N₂ of the transformation, including the cases of N × N, when N = 2^r, (r > 1), and N = L^r, (r ≥ 1), where L is an odd prime. The problem of “over-representation” of the two-dimensional discrete Fourier transform in tensor representation was also solved by means of the paired representation in Grigoryan [6-9].     

Adaptive reversible image watermarking scheme

This paper presents an adaptive block sized reversible image watermarking scheme. A reversible watermarking approach recovers the original image from a watermarked image after extracting the embedded watermarks. Without loss of generality, the proposed scheme segments an image of size 2^N × 2^N adaptively to blocks of size 2^L × 2^L, where L starts from a user-defined number to 1, according to their block structures. If possible, the differences between central ordered pixel and other pixels in each block are enlarged to embed watermarks. The embedded quantity is determined by the largest difference in a block and watermarks are embedded into LSB bits of above differences. Experimental results show that the proposed adaptive block size scheme has higher capacity than conventional fixed block sized method.     

Edge-bipancyclicity of the k-ary n-cubes with faulty nodes and edges

The k-ary n-cube has been one of the most popular interconnection networks for massively parallel systems. In this paper, we investigate the edge-bipancyclicity of k-ary n-cubes with faulty nodes and edges. It is proved that every healthy edge of the faulty k-ary n-cube with f_v faulty nodes and f_e faulty edges lies in a fault-free cycle of every even length from 4 to kⁿ − 2f_v (resp. kⁿ − f_v) if k ? 4 is even (resp. k ? 3 is odd) and f_v + f_e ? 2n − 3. The results are optimal with respect to the number of node and edge faults tolerated.     

An electrochemical sensor for trace uranium determination based on 6-O-palmitoyl-l-ascorbic acid-modified graphite electrodes

The development of a preconcentrating sensor based on 6-O-palmitoyl-l-ascorbic acid (PAA)-modified graphite (GRA) electrodes for the determination of uranium is described. PAA, a water insoluble compound of ascorbic acid, was immobilized onto the surface of the GRA electrodes through physical adsorption from acetone solutions. Uranium was accumulated by heterogeneous complexation (10 min, in 0.1 M H₃BO₃, pH 4.3) and then, it was reduced by means of a differential pulse voltammetric scan in 0.1 M H₃BO₃, pH 3.4. Alternatively, the performance of both preconcentration and voltammetric steps in a single run, at 0.1 M H₃BO₃, pH 3.65, was also examined; however, in this case the observed current signals were lower by 30%. The experimental variables were investigated and under the selected conditions, a linear calibration curve in the range 2.7-67.5 μg L⁻¹ U(VI) was constructed (r² = 0.9981). The 3σ limit of detection and the relative standard deviation of the method were 1.8 μg L⁻¹ U(VI) and 8% (n = 5, 20 μg L⁻¹ U(VI), preconcentration time 10 min), respectively. By increasing the preconcentration time to 30 min, a limit of detection as low as 0.26 μg L⁻¹ U(VI) can be achieved. The effect of potential interferences was also examined. The accuracy of the method was established by recovery studies in inoculated tap and lake water samples. A simple and fast procedure based on filtering of the sample through a C-18 microcolumn was successfully used to remove the organic matter from the lake water samples.     

Embedding meshes into crossed cubes

Crossed cubes are important variants of hypercubes. In this paper, we consider embeddings of meshes in crossed cubes. The major research findings in this paper are: (1) For any integer n ? 1, a 2 × 2ⁿ⁻¹ mesh can be embedded in the n-dimensional crossed cube with dilation 1 and expansion 1. (2) For any integer n ? 4, two node-disjoint 4 × 2ⁿ⁻³ meshes can be embedded in the n-dimensional crossed cube with dilation 1 and expansion 2. The obtained results are optimal in the sense that the dilations of the embeddings are 1. The embedding of the 2 × 2ⁿ⁻¹ mesh is also optimal in terms of expansion because it has the smallest expansion 1.     

Augmented k-ary n-cubes

We define an interconnection network AQ_n,k which we call the augmented k-ary n-cube by extending a k-ary n-cube in a manner analogous to the existing extension of an n-dimensional hypercube to an n-dimensional augmented cube. We prove that the augmented k-ary n-cube AQ_n,k has a number of attractive properties (in the context of parallel computing). For example, we show that the augmented k-ary n-cube AQ_n,k: is a Cayley graph, and so is vertex-symmetric, but not edge-symmetric unless n = 2; has connectivity 4n − 2 and wide-diameter at most max{(n − 1)k − (n − 2), k + 7}; has diameter , when n = 2; and has diameter at most , for n ? 3 and k even, and at most , for n ? 3 and k odd.     

Electrochemical studies of bovine serum albumin immobilization onto the poly-o-phenylenediamine and carbon-coated nickel composite film and its interaction with papaverine

A biosensor based on bovine serum albumin (BSA) and poly-o-phenylenediamine (PoPD)/carbon-coated nickel (C-Ni) nanobiocomposite film modified electrode has been developed to study the interaction of BSA with papaverine (PAP). The well-dispersed C-Ni nanoparticles were dripped onto the glassy carbon electrode (GCE) surface firstly, and PoPD films were subsequently electropolymerized by cyclic voltammetry (CV) to prepare PoPD/C-Ni/GCE. Finally, the BSA was easily immobilized on the PoPD films via electrostatic adsorption. The morphology and the electrochemical properties of the fabricated composite electrodes were examined by scanning electron microscope (SEM) and electrochemical impedance spectroscopy (EIS), respectively. The interaction of PAP with BSA was monitored by differential pulse voltammetry (DPV), using PoPD as the electrochemical indicator. The binding constant (K), obtained by DPV, was 1.7 × 10⁴ L/mol, which was consistent with the fluorescence analysis. This constructed biosensor also exhibited a fine linear correlation with PAP concentration range of 2.5 × 10⁻⁹-4.5 × 10⁻⁵ mol/L and a detection limit of 8.3 × 10⁻¹⁰ mol/L was achieved by DPV.     

Constructing vertex-disjoint paths in (n, k)-star graphs

This work describes a novel routing algorithm for constructing a container of width n − 1 between a pair of vertices in an (n, k)-star graph with connectivity n − 1. Since Lin et al. [T.C. Lin, D.R. Duh, H.C. Cheng, Wide diameter of (n, k)-star networks, in: Proceedings of the International Conference on Computing, Communications and Control Technologies, vol. 5, 2004, pp. 160-165] already calculated the wide diameters in (n, n − 1)-star and (n, 1)-star graphs, this study only considers an (n, k)-star with 2 ? k ? n − 2. The length of the longest container among all constructed containers serves as the upper bound of the wide diameter of an (n, k)-star graph. The lower bound of the wide diameter of an (n, k)-star graph with 2 ? k ? ⌊n/2⌋ and the lower bound of the wide diameter of a regular graph with a connectivity of 2 or above are also computed. Measurement results indicate that the wide diameter of an (n, k)-star graph is its diameter plus 2 for 2 ? k ? ⌊n/2⌋, or its diameter plus a value between 1 and 2 for ⌊n/2⌋ + 1 ? k ? n − 2.     

High sensitive optode for selective determination of Ni based on the covalently immobilized thionine in agarose membrane

A novel Ni²⁺ optode was prepared by covalent immobilization of thionine, 3,7-diamine-5-phenothiazoniom thionineacetate, in a transparent agarose membrane. Influences of various experimental parameters on Ni²⁺ sensing, including the reaction time, the solution pH and the concentration of reagents were investigated. Under the optimized conditions, a linear response was obtained for Ni²⁺ concentrations ranging from 1.00 × 10⁻¹⁰ to 1.00 × 10⁻⁷ mol l⁻¹ with an R² value of 0.9985. The detection limit (3σ) of the method for Ni²⁺ was 9.30 × 10⁻¹¹ mol l⁻¹. The influence of several potentially interfering ions such as Ag⁺, Hg²⁺, Cd²⁺, Zn²⁺, Pb²⁺, Cu²⁺, Mn²⁺, Co³⁺, Cr³⁺, Al³⁺ and Fe³⁺ on the determination of Ni²⁺ was studied and no significant interference was observed. The membrane showed a good durability and short response time with no evidence of reagent leaching. The membrane was successfully applied for the determination of Ni²⁺ in environmental water samples.     

One-pot electrodeposition of 3-aminopropyltriethoxysilane-chitosan hybrid gel film to immobilize glucose oxidase for biosensing

We report on the electrodeposition of a 3-aminopropyltriethoxysilane-chitosan (APTES-CS) hybrid gel film for in situ immobilization of glucose oxidase (GOx) on an Au or platinized Au (Pt_nano/Au) electrode for biosensing of glucose. Controllable electroreduction of p-benzoquinone is used to lift the electrode-surface pH for the GOx-APTES-CS codeposition, which was monitored by an electrochemical quartz crystal microbalance. The fabrication procedures of the biosensor and the parameters influencing the biosensing performance were optimized. The prepared porous GOx-APTES-CS/Pt_nano/Au and GOx-APTES-CS/Au electrodes can be used to detect the enzymatically generated H₂O₂ at 0.5 and 0.7 V vs SCE, respectively. The enzyme electrodes exhibited linear responses to glucose concentration from 0.2 μM to 8.2 mM (R = 0.998, at Pt_nano/Au substrate) and from 0.2 μM to 5.5 mM (R = 0.998, at Au substrate), with current sensitivities of 69.5 (Pt_nano/Au) and 65 (Au) μA mM⁻¹ cm⁻², respectively, and a detection limit of 0.2 μM (S/N = 3) was achieved for each electrode. The response time was less than 5 (Pt_nano/Au) or 8 (Au) s. It is striking that the enzyme electrodes remained their initial response sensitivity after storage for 5 (Au) and >6 (Pt_nano/Au) months in 0.10 M PBS (pH 7.0) at 4 °C.     

A dynamic programming algorithm for simulation of a multi-dimensional torus in a crossed cube

The torus is a popular interconnection topology and several commercial multicomputers use a torus as the basis of their communication network. Moreover, there are many parallel algorithms with torus-structured and mesh-structured task graphs have been developed. If one network can embed a mesh or torus network, the algorithms with mesh-structured or torus-structured can also be used in this network. Thus, the problem of embedding meshes or tori into networks is meaningful for parallel computing. In this paper, we prove that for n ? 6 and 1 ? m ? ⌈n/2⌉ − 1, a family of 2^m disjoint k-dimensional tori of size 2^s₁×2^s₂×?×2^s_k each can be embedded in an n-dimensional crossed cube with unit dilation, where each s_i ? 2, , and max_1?i?k{s_i} ? 3 if n is odd and ; otherwise, max_1?i?k{s_i} ? n − 2m − 1. A new concept, cycle skeleton, is proposed to construct a dynamic programming algorithm for embedding a desired torus into the crossed cube. Furthermore, the time complexity of the algorithm is linear with respect to the size of desired torus. As a consequence, a family of disjoint tori can be simulated on the same crossed cube efficiently and in parallel.