Rapid differentiation between E. coli and Salmonella Typhimurium using metal oxide sensors integrated with pattern recognition

A rapid method to differentiate between E coli and Salmonella Typhimurium was developed. E. coli and S. Typhimurium were separately grown in super broth and incubated at 37 °C. Super broth without inoculation of E. coli or S. Typhimurium was used as control. Numbers of E. coli and S. Typhimurium were followed using a colony counting method. Identification of the volatile metabolites produced by E. coli and S. Typhimurium was determined using solid-phase microextraction coupled with gas chromatography/mass spectrometry. An electronic nose with 12 non-specific metal oxide sensors was used to monitor the volatile profiles produced by E. coli and S. Typhimurium. Principal component analysis (PCA) and back-propagation neural network (BPNN) were used as pattern recognition tools. PCA was used for data exploration and dimensional reduction. PCA could visualize class separation between sample subgroups. The BPNN was shown to be capable of predicting the number of E. coli and S. Typhimurium. Good prediction was possible as measured by a regression coefficient (R² = 0.96) between true and predicted data. Using metal oxide sensors and pattern recognition techniques, it was possible to discriminate between samples containing E. coli from those containing S. Typhimurium.     

Detection of Escherichia coli using CMOS array photo sensor-based enzyme biochip detection system

This work presents optical enzyme detection system based on the CMOS array photo sensor and 1 × 3 polymeric enzyme biochip for detecting Escherichia coli in a one-step procedure. This assay, using 4-methylumbelliferyl-β-d-glucuronide (MUG) as a fluorogenic substrate, had a detection limit of 0.1 U/ml for β-glucuronidase (GUD), which was approximately equal to a cell concentration of 10⁶ CFU/ml of E. coli. MUG was incorporated into lauryl tryptose broth at a final concentration of 100 μg/ml for immediate verification of the presence of E. coli in 1 × 3 polymeric enzyme biochip. The 40 strains of E. coli studied all produced GUD. Of another 36 strains of bacteria tested, one strain (Salmonella choleraesuis subsp. choleraesuis) yielded very small amounts of GUD after 24 h incubation. The optical enzyme detection system was sensitive and rapid.     

Optimal (N,T)-policy for M/G/1 system with cost structures

In this paper, the optimal (N,T)-policy for M/G/1 system with cost structure is studied. The system operates only intermittently. It is shut down when no customers are present. A fixed set-up cost of K>0 is incurred each time the system is reopened. Also, a holding cost of h>0 per unit time is incurred for each customer present. The (N,T)-policy studied for this system is as follows: the system reactivates as soon as N customers are present or the waiting time of the leading customer reaches a predefined time T (see A.S. Alfa, I. Frigui, Eur. J. Oper. Res. 88 (1996) 599-613; Y.N. Doganata, in: E. Arikan (Ed.), Communication, Control, and Signal Processing, 1990, pp. 1663–1669). Later on, as a comparison, the start of the timer count is relaxed as follows: the system reactivates as soon as N customers are present or the time units after the end of the last busy period reaches a predefined time T. For both cases, the explicit optimal policy (N^*,T^*) for minimizing the long-run average cost per unit time are obtained. As extreme cases, we include the simple optimal policies for N-and T-polices. Several counter-intuitive results are obtained about the optimal T-policies for both types of models.     

On pure H reduced-order dynamic controllers: an erratum

There are at least two approaches advocated to obtain a pure H^∞ reduced-order dynamic controller for a given augmented plant. One approach is to eliminate completely the H² aspect from a standard H²/H^∞ setting. A second approach is to equate the H² aspect with the H^∞ aspect in that same setting. This paper invalidates the first approach but affirms the second approach and produces the correct equations resulting therefrom.     

Micro-hotplates for high-throughput thin film processing and in situ phase transformation characterization

This paper presents the use of micro-hotplates (MHPs) as thermal processing and in situ characterization platforms for phase transformations in thin films. MHPs are fabricated by microsystem technology processes and consist of a SiO₂/Si₃N₄ membrane (app. 1 μm) supported by a bulk Si frame. Several embedded Pt thin films serve as heater and electrical measurement electrodes. It is shown that the MHPs have unique properties for the controlled annealing of thin film materials (up to 1270 K), as the annealing temperature and heating/cooling rates can be precisely controlled by in situ measurements. These rates can be extremely high (up to 10⁴ K/s), due to the low thermal mass of MHPs. The high cooling rates are especially useful for the fabrication of metastable phases (e.g. Fe₇₀Pd₃₀) by quenching. By measuring the resistivity of a thin film under test in situ as a function of the MHP temperature, microstructural changes (e.g. phase transformations) can be detected during heating and cooling cycles. In this paper, examples are presented for the determination of phase transitions in thin films using MHPs: the solid–liquid–gas phase transition (Al), the ferromagnetic–paramagnetic phase transition (Fe–Pt) and martensitic transformations (Ni–Ti–Cu, Fe–Pd). Furthermore, it is demonstrated that crystallization processes from amorphous to crystalline (Ni–Ti–Cu) can be detected with this method. Finally the application of MHPs in thin film combinatorial materials science and high-throughput experimentation is described.     

H optimization problem with sign-indefinite quadratic form

This paper presents the solution to min-max control problem arising when the matrix C₁^TC₁ of the cost function in the standard H^∞ control problem (Doyle et al., 1989) is replaced by an arbitrary matrix Q 0. This difference is proved to be sufficient for results obtained in (Doyle et al., 1989) not to cover such the case. Their derivations essentially base on the cost function being H^∞ norm and can not be adjusted to deal with sign-indefinite quadratic form. With some sort of strict frequency condition assumed, state space technique is fruitful to obtain the necessary and sufficient conditions of the solvability of the problem. The solution is given by two Riccati equations and has some difference when compared to that of (Doyle et al., 1989).     

Architecture of electrospun carbon nanofibers–hydroxyapatite composite and its application act as a platform in biosensing

A biofunctional hybrid composite was constructed by assembling hydroxyapatite (HA) onto carboxylic group-functionalized carbon nanofibers (FCNFs). The FCNFs was obtained from acid treatment of carbon nanofibers (CNFs) which were synthesized by the combination of electrospinning and thermal treatment processes. The obtained carbon nanofibers–hydroxyapatite composite (FCNFs–HA) was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and FTIR spectroscopy. Cytochrome c (Cyt c) was successfully immobilized in this three-dimensional FCNFs–HA composite and the electron transfer rate constant (k_s) was evaluated to be 3.66 s⁻¹ according to Laviron's equation. And the surface coverage (Γ*) was estimated to be 8.1 × 10⁻¹⁰ mol cm⁻². Cyt c immobilized in FCNFs–HA composite exhibited a good electrocatalytic activity towards the reduction of hydrogen peroxide (H₂O₂). The catalytic current is linear to the H₂O₂ concentration in the range of 2.0 μM to 8.7 mM (r = 0.9996; n = 28), and the detection limit was 0.3 μM based on the criterion of a signal-to-noise ratio of 3.     

Fabrication of bio/nano interfaces between biological cells and carbon nanotubes using dielectrophoresis

The authors have previously demonstrated the manipulation of bacteria and carbon nanotubes (CNTs) using dielectrophoresis (DEP) and its application for various types of biological and chemical sensors. This paper demonstrates simultaneous DEP handling of bacteria and CNTs, which are mixed and suspended in water. The CNTs were solubilized in water using microplasma-based treatment. When a microelectrode was energized with an ac voltage in the suspension of Escherichia coli (E. coli) cells and multi-walled CNTs (MWCNTs), both of them were simultaneously trapped in the microelectrode gap. Scanning electron microscopy (SEM) images revealed that E. coli cells were trapped on the surface or the tip of MWCNTs, where the electric field strength was intensified due to high aspect ratio of MWCNTs. As a result, bio/nano interfaces between bacteria and MWCNTs were automatically formed in a self-assembly manner. A potential application of the DEP-fabricated bio/nano interfaces is a drug delivery system (DDS), which is realized by transporting drug molecules from CNTs to cells across the cell membrane, which can be electroporated by the local high electric field formed on the CNT surface.     

Direct electrochemistry of cytochrome c and biosensing for hydrogen peroxide on polyaniline grafted multi-walled carbon nanotube electrode

Cytochrome c (cyt c) was immobilized into a matrix consisting of polyaniline (PANI) and multi-walled carbon nanotubes (MWNT) by a new strategy. First, PANI chains were grafted onto MWNT through electropolymerization. Second, the amine groups in PANI chains were oxidized at an applied potential of +0.80 V to acquire positive charges that would effectively immobilize negatively charged cyt C. The ITO/MWNT-g-PANI(O)/cyt c electrode exhibited a pair of redox peaks with a peak potential separation (anodic to cathodic) of 0.25 V (vs Ag/AgCl) in 0.1 M phosphate buffer (pH 7.0). The results demonstrated that ITO/MWNT-g-PANI(O)/cyt c promoted direct electron transfer between cyt c and electrode with a high electron transfer rate constant (17 s⁻¹). The ITO/MWNT-g-PANI(O)/cyt c electrode catalyzes the reduction of H₂O₂. The ITO/MWNT-g-PANI(O)/cyt c biosensor displays an amperometric response to H₂O₂ with a linear concentration range from 0.5 μM to 1.5 mM (r = 0.99, n = 12), a high sensitivity (32.2 μAm M⁻¹) and fast response (9 s) and detection limit of 0.3 μM (S/N = 3).     

(J, J′)-lossless factorization based on conjugation

This paper is concerned with a derivation of the state-space form of the (J, J′)-lossless factorization which contains both the inner-outer factorization and the spectral factorization of positive matrices as special cases. Also, the (J, J′)-lossless factorization gives a unified framework of H^∞ control theory. We use the method of conjugation which makes the derivation much simpler than the previous literature, most of which used the technique of (J, J′)-spectral factorization. A necessary and sufficient condition is represented in terms of two Riccati equations one of which is degenerated.     

Chemiluminescent optical fiber immunosensor detection of Brucella cells presenting smooth-A antigen

Brucellosis is a worldwide distributed zoonotic re-emerging disease, causing abortions in domesticated animals and Malta fever in humans. Currently, the gold standard for confirmation of the existence of the causative agent genus Brucella is the isolation of the bacteria from body or liquid samples, whereas standard serological tests are used for diagnosis. The need for a rapid point of care identification of Brucella organisms has led us to develop a novel chemiluminescent optical fiber immunosensor. The immunosensor based on a conventional enzyme linked immunoassay (ELISA) technique was implemented on optical fibers and its performance was compared to the standard ELISA method. We show that depending on the detecting antibodies used specificity of the assay is achieved. Brucella cells presenting smooth-A O-chain determinant were detected at a minimal protein concentration of 1.098 ng/ml, correlating to 305 cfu/ml, while smooth-M O-chain cells, rough cells and two gram-negative bacteria other than Brucella sp. produced negative results, confirming the high specificity of the technique.     

Necessary and sufficient conditions on Q ( = C( I + PC)) for stabilization of the linear feedback system S(P, C)

We find the following necessary and sufficient conditions for Q (:=C(I+PC)⁻¹) to -stabilize the standard linear time-invariant unity feedback system S(P, C) where P has the l.c.f. (D_pl, N_pl) and the r.c.f. (N_pr, D_pr); and is a principal ideal domain. (i) Q must have elements in (ii) (resp. (iii)) Q must factorize in with D_pr, (resp. D_pl) as a left (resp. right) factor and (iv) (I – QP) must factor in with D_pr, as a left factor.     

TiO2 nanoparticles-enhanced luminol chemiluminescence and its analytical applications in organophosphate pesticide imprinting

This paper reports a surface molecular self-assembly strategy for chlorpyrifos (CPF) imprinting of polymer membranes at the surface of TiO₂ nanoparticles for flow injection chemiluminescence (CL) detection of pesticide CPF which using the character of TiO₂ enhance the chemiluminescence of the luminol–H₂O₂ system. The CL signals produced by the reaction between luminol and H₂O₂, were increased in the presence of CPF imprinting of polymer membranes at the surface of TiO₂ which were eluted from the column through luminol and H₂O₂ injection. The CL enhancement by TiO₂ nanoparticles of the luminol–H₂O₂ system was supposed to originate from the catalysis of TiO₂ nanoparticles and CPF. The CL intensity was linear over the logarithm of concentration of chlorpyrifos ranging from 1.0 × 10⁻¹⁰ to 5.0 × 10⁻⁷ mol/L (r² = 0.996), and the limit of detection was 1.0 × 10⁻¹¹ mol/L (3σ). The detection limit for CPF is lower than other methods. An excellent CL selectivity for CPF over other pesticides was also achieved. The combination of surface molecular self-assembly with polymer molecular imprinting on larger surface area of TiO₂ nanoparticles produce a high ratio of imprinted sites and, thus, provide an ultrasensitive CL detection of CPF.     

FEWZ 2.0: A code for hadronic Z production at next-to-next-to-leading order

We introduce an improved version of the simulation code FEWZ (Fully Exclusive W and Z Production) for hadron collider production of lepton pairs through the Drell–Yan process at next-to-next-to-leading order (NNLO) in the strong coupling constant. The program is fully differential in the phase space of leptons and additional hadronic radiation. The new version offers users significantly more options for customization. FEWZ now bins multiple, user-selectable histograms during a single run, and produces parton distribution function (PDF) errors automatically. It also features a significantly improved integration routine, and can take advantage of multiple processor cores locally or on the Condor distributed computing system. We illustrate the new features of FEWZ by presenting numerous phenomenological results for LHC physics. We compare NNLO QCD with initial ATLAS and CMS results, and discuss in detail the effects of detector acceptance on the measurement of angular quantities associated with Z-boson production. We address the issue of technical precision in the presence of severe phase-space cuts.

Program summary

Program title: FEWZCatalogue identifier: AEJP_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEJP_v1_0.htmlProgram obtainable from: CPC Program Library, Queen?s University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 6 280 771No. of bytes in distributed program, including test data, etc.: 173 027 645Distribution format: tar.gzProgramming language: Fortran 77, C++, PythonComputer: Mac, PCOperating system: Mac OSX, Unix/LinuxHas the code been vectorized or parallelized?: Yes. User-selectable, 1 to 219RAM: 200 Mbytes for common parton distribution functionsClassification: 11.1External routines: CUBA numerical integration library, numerous parton distribution sets (see text); these are provided with the code.Nature of problem: Determination of the Drell–Yan Z/photon production cross section and decay into leptons, with kinematic distributions of leptons and jets including full spin correlations, at next-to-next-to-leading order in the strong coupling constant.Solution method: Virtual loop integrals are decomposed into master integrals using automated techniques. Singularities are extracted from real radiation terms via sector decomposition, which separates singularities and maps onto suitable phase space variables. Result is convoluted with parton distribution functions. Each piece is numerically integrated over phase space, which allows arbitrary cuts on the observed particles. Each sample point may be binned during numerical integration, providing histograms, and reweighted by parton distribution function error eigenvectors, which provides PDF errors.Restrictions: Output does not correspond to unweighted events, and cannot be interfaced with a shower Monte Carlo.Additional comments: !!!!! The distribution file for this program is over 170 Mbytes and therefore is not delivered directly when download or E-mail is requested. Instead a html file giving details of how the program can be obtained is sent.Running time: One day for total cross sections with 0.1% integration errors assuming typical cuts, up to 1 week for smooth kinematic distributions with sub-percent integration errors for each bin.     

The Inf-Sup Condition for the Mapped Q k ?P k?1 disc Element in Arbitrary Space Dimensions

 One of the most popular pairs of finite elements for solving mixed formulations of the Stokes and Navier–Stokes problem is the Q _k −P _k−1 ^disc element. Two possible versions of the discontinuous pressure space can be considered: one can either use an unmapped version of the P _k−1 ^disc space consisting of piecewise polynomial functions of degree at most k−1 on each cell or define a mapped version where the pressure space is defined as the image of a polynomial space on a reference cell. Since the reference transformation is in general not affine but multilinear, the two variants are not equal on arbitrary meshes. It is well-known, that the inf-sup condition is satisfied for the first variant. In the present paper we show that the latter approach satisfies the inf-sup condition as well for k≥2 in any space dimension. Received January 31, 2001; revised May 2, 2002 Published online: July 26, 2002     

On Steiner minimal trees withLp distance

LetL _p be the plane with the distanced _p (A ₁ ,A ₂ ) = (¦x ₁ –x ₂¦ ^p + ¦y₁ –y ₂¦^p)^/1p wherex _i andy _i are the cartesian coordinates of the pointA _i . LetP be a finite set of points inL _p . We consider Steiner minimal trees onP. It is proved that, for 1 <p < , each Steiner point is of degree exactly three. Define the Steiner ratio _p to be inf{L _s (P)/L _m (P)¦PL _p } whereL _s (P) andL _m (P) are lengths of the Steiner minimal tree and the minimal spanning tree onP, respectively. Hwang showed ₁ = 2/3. Chung and Graham proved ₂ > 0.842. We prove in this paper that {} = 2/3 and (2/2)_{12 p} 3/2 for anyp.This work was supported in part by the National Science Foundation of China and the President Foundation of Academia Sinica.     

qwViz: Visualisation of quantum walks on graphs

qwViz is a software package for interactive visualisation of the time-evolution of quantum walks on arbitrarily complex graphs. The package is written in C and uses OpenGL to generate graphics in real-time. The qwViz package can be used to directly simulate discrete-time quantum walks on undirected graphs when provided with the adjacency matrix of the graph. For more detailed studies, qwViz can also be used to visualise externally generated quantum walk data written in an XML-based file format (QWML). Various aspects of the visualisation can be customised and manipulated in real-time, allowing quantum walk dynamics to be probed at various length and time scales.

Program summary

Program title:qwVizCatalogue identifier: AEJN_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEJN_v1_0.htmlProgram obtainable from: CPC Program Library, Queen?s University, Belfast, N. IrelandLicensing provisions: GNU General Public Licence version 3No. of lines in distributed program, including test data, etc.: 42 881No. of bytes in distributed program, including test data, etc.: 97 152Distribution format: tar.gzProgramming language: CComputer: 32-bit and 64-bit workstationOperating system: Linux, Mac OS X 10.5 (and later)RAM: Depends on size of graph, typically less than 50 MBClassification: 4.15, 14External routines: OpenGL, GLUT, Graphviz [1]Nature of problem: Simulation and visualisation of quantum walks on arbitrarily complex undirected graphs.Solution method: The program uses OpenGL to produce 3D visualisations of time-dependent probability distributions arising from quantum walks on graphs. Graph layouts are automatically generated using Graphviz libraries.Restrictions: Graph layouts are two-dimensional, with the third spatial dimension being used to represent the probability of finding the quantum walker at a certain location.Unusual features: The software can be used in active or dual-stereo modes for 3D visualisation of quantum walks. Images and image sequences for movies can be exported in TIFF and TGA formats.Additional comments: Examples of various input files and an XML schema are provided. Source codes written in C and Fortran are also supplied for generating QWML files from external quantum walk simulations.Running time: Computing quantum walk data and graph layout for a 500-step quantum walk on a fifth-generation Sierpinski gasket (366 vertices) took less than 2 seconds on a 2.53 GHz Intel Core 2 Duo processor with 4 GB of RAM and 3 MB L2 shared cache under Mac OS X 10.6.6. The same simulation for a hyper-branched fractal with 1331 vertices took less than 25 seconds. GNU C compiler with optimisation option -O2 was used for these tests. Once data has been computed, the interactive visualisation can be manipulated in real-time.References:

• [1] 

  J. Ellson, E. Gansner, E. Koutsofios, S. North, G. Woodhull, Graphviz and dynagraph – static and dynamic graph drawing tools, in: M. Junger, P. Mutzel (Eds.), Graph Drawing Software, Springer-Verlag, 2003, pp. 127–148.

     

Electron momentum density distribution in Cd3P2

A study of electron momentum density distribution in Cd₃P₂ is reported in this work. The measurement of Compton profile is carried out on a polycrystalline sample using 59.54 keV gamma-rays emanating from an ²⁴¹Am radioisotope. The theoretical calculations are performed using linear combination of atomic orbitals method following the Hartree–Fock and a posteriori density functional theories. The spherically averaged theoretical Compton profiles are in good agreement with the measurement. The best agreement is, however, shown by the Hartree–Fock scheme. Simple ionic model calculations for a number of configurations ₃(Cd+x)₂(P−3x/2) (0.0?x?2.0 in step of 0.2) are also performed utilizing free atom profiles. The ionic model supports transfer of 2.0 electrons per Cd atom from 5s state to 3p state of P.     

Fast GL(n)-Invariant Framework for Tensors Regularization

We propose a novel framework for regularization of symmetric positive-definite (SPD) tensors (e.g., diffusion tensors). This framework is based on a local differential geometric approach. The manifold of symmetric positive-definite (SPD) matrices, P _n , is parameterized via the Iwasawa coordinate system. In this framework distances on P _n are measured in terms of a natural GL(n)-invariant metric. Via the mathematical concept of fiber bundles, we describe the tensor-valued image as a section where the metric over the section is induced by the metric over P _n . Then, a functional over the sections accompanied by a suitable data fitting term is defined. The variation of this functional with respect to the Iwasawa coordinates leads to a set of \frac12n(n+1)\frac{1}{2}n(n+1) coupled equations of motion. By means of the gradient descent method, these equations of motion define a Beltrami flow over P _n . It turns out that the local coordinate approach via the Iwasawa coordinate system results in very simple numerics that leads to fast convergence of the algorithm. Regularization results as well as results of fibers tractography for DTI are presented.