An efficient second‐order accurate cut‐cell method for solving the variable coefficient Poisson equation with jump conditions on irregular domains

A numerical method is presented for solving the variable coefficient Poisson equation on a two‐dimensional domain in the presence of irregular interfaces across which both the variable coefficients and the solution itself may be discontinuous. The approach involves using piecewise cubic splines to represent the irregular interface, and applying this representation to calculate the volume and area of each cut cell. The fluxes across the cut‐cell faces and the interface faces are evaluated using a second‐order accurate scheme. The deferred correction approach is used, resulting in a computational stencil for the discretized Poisson equation on an irregular (complex) domain that is identical to that obtained on a regular (simple) domain. In consequence, a highly efficient multigrid solver based on the additive correction multigrid (ACM) method can be applied to solve the current discretized equation system. Several test cases (for which exact solutions to the variable coefficient Poisson equation with and without jump conditions are known) have been used to evaluate the new methodology for discretization on an irregular domain. The numerical solutions show that the new algorithm is second‐order accurate as claimed, even in the presence of jump conditions across an interface. Copyright © 2006 John Wiley & Sons, Ltd.     

Photooxidation of Methane over TiO2

Fourier‐transform infrared spectroscopy has been employed to investigate the adsorption and photo‐oxidation of CH₄ over powdered TiO₂. The interaction between the CH₄ and TiO₂ surface is weak. It is found that no CH₄ molecules are adsorbed on the surface at 35 °C in a vacuum. Under UV irradiation, CH₄ decomposes to form CO_(a), CO_2(g), H20_(a), and HCOO_(a) in the presence of O₂. The photoreaction rate is retarded and only small amounts of CO_(a) and HCOO_(a) are formed in the absence of O₂. It is observed that the oxygen atoms of O₂ are incorporated into these photoproducts as ¹⁸O₂ is used. The major ¹⁸O‐containing products are C¹⁸O_(a), C¹⁸O_2(g), H₂ ¹⁸O_(a), HC¹⁶O¹⁸O_(a), and HC¹⁸O¹⁸O_(a) after 180 min UV irradiation. However, the extent of ¹⁸O incorporating into the adsorbed formate is dependent on UV irradiation time. In the early stage of UV irradiation HC¹⁶O¹⁶O_(a) is the major formate form indicating the involvement of TiO₂ lattice oxygens for its formation, but HC¹⁸O¹⁸O_(a) becomes the major one after 180 min indicating the involvement of ¹⁸O₂. Formate on TiO₂ further photodecomposes to CO_2(g), but not to CO_(a). CO_(a) formation is directly from CH₄ photodecomposition with the participation of TiO₂ lattice oxygens and O₂.     

Delay-dependent stability criterion for neutral time-delay systems via linear matrix inequality approach

In this paper, the asymptotic stability problem for a class of neutral systems with discrete and distributed delays is considered. Based on linear matrix inequality, a delay-dependent criterion is proposed to guarantee asymptotic stability for such systems. Some numerical examples are given to illustrate our main result.     

Guaranteed Cost Observer–Based Controls for a Class of Uncertain Neutral Time-Delay Systems

In this paper, guaranteed-cost observer-based controls for a class of uncertain neutral time-delay systems are considered. The asymptotic stabilization for the uncertain neutral systems is guaranteed with an observer-based feedback control. The linear matrix inequality (LMI) approach is used to design the observer-based feedback control system. Two classes of observer-based controls are proposed and their guaranteed costs are given. The control and observer gains are given from the LMI feasible solutions. A convex optimization problem with LMIs is formulated to design the optimal guaranteed-cost observer-based controls which minimize the guaranteed cost of the system considered. A numerical example is given to illustrate the results.The research reported here was supported by the National Science Council of Taiwan, ROC under Grant NSC 93-2213-E-214-020     

A new dihydrofurocoumarin from the fruits of Pandanus tectorius Parkinson ex Du Roi

From the fruit of Pandanus tectorius Parkinson ex Du Roi, one new dihydrofurocoumarin, named pandanusin A (1) and 15 known compounds, including one furanocoumarin (2), two coumarins (3, 4), four lignans (5–8), one neolignan (9), two flavonoids (10, 11), three phenolics (12–14), one monoglyceride (15) and one monosaccharide (16) were isolated by various chromatography methods. Among them, compounds (3–5) were obtained from the Pandanus genus for the first time and compounds (9–14, 16) were reported from this species for the first time. Their structures were elucidated by HR–ESI–MS, NMR 1D and 2D experiments and comparison with previous reported data. The α-glucosidase inhibitory activity of all compounds was measured. The isolated compounds (1–12, 14) showed better α-glucosidase inhibitory activity (IC₅₀ = 42.2, 36.5, 84.7, 73.2, 40.8, 26.7, 76.5, 33.8, 68.1, 14.4, 22.1, 81.5, 43.8 μM, respectively) than the standard drug acarbose (IC₅₀ = 214.5 μM).     

Modified screen printed electrode for development of a highly sensitive label-free impedimetric immunosensor to detect amyloid beta peptides

Alzheimer's disease (AD) is a fatal neurodegenerative disease affecting approximately 26 million people world-wide, and the number is increasing as life expectancy increases. Since the only reliable diagnosis for the pathology is histochemical post-mortem examination, there is a rather urgent need for reliable, sensitive and quick detection techniques. Amyloid beta, being one of the established and widely accepted biomarkers of AD is a target biomolecule.     

ISO 15189-accredited laboratories fulfill the JCI Hospital Accreditation Standard requirements for the use of referral laboratories: report of a consensus meeting

Accreditation of healthcare services is recommended to ensure operation according to the highest quality standards. Various initiatives, such as legislation or accreditation by ISO or JCI, may be active to support and improve quality. The growing trend toward JCI hospital accreditation raised the concern of redundancy between JCI requirements for the use of referral laboratories and the ISO 15189 accreditation for medical laboratories. This would result in needless administrative efforts for hospital laboratories to collect and maintain required documentation, as the JCI quality requirements would be guaranteed given that the referral laboratory is ISO 15189 accredited for those examinations. A consensus meeting was organized by the Working Group for Hospital Accreditation of the Belgian Zorgnet-Icuro network, the University Hospitals of Leuven and the Red Cross to discuss the avoidance of any redundancy between both standards and to issue best practice guidelines for referral laboratories. It was concluded that JCI measurable elements for referral laboratories are covered by the ISO 15189 accreditation scope. The article substantiates the consensus that JCI and ISO quality requirements are harmonized and that accurate knowledge and interpretation of prevailing quality standards are essential to avoid redundancy in quality measures.     

Inverse problems for the boundary value problem with the interior nodal subsets

In this paper, inverse nodal problems for Sturm–Liouville equations with boundary conditions polynomially dependent on the spectral parameter were studied. The authors showed that some uniqueness theorems on the potential function hold by the Weyl function, respectively.     

A pressure‐based unstructured grid method for all‐speed flows

An all‐speed algorithm based on the SIMPLE pressure‐correction scheme and the ‘retarded‐density’ approach has been formulated and implemented within an unstructured grid, finite volume (FV) scheme for both incompressible and compressible flows, the latter involving interaction of shock waves. The collocated storage arrangement for all variables is adopted, and the checkerboard oscillations are eliminated by using a pressure‐weighted interpolation method, similar to that of Rhie and Chow [Numerical study of the turbulent flow past an airfoil with trailing edge separation. AIAA Journal 1983; 21 : 1525]. The solution accuracy is greatly enhanced when a higher‐order convection scheme combined with adaptive mesh refinement (AMR) are used. Copyright © 2000 John Wiley & Sons, Ltd.