Critical pressure for capillary valves in a Lab-on-a-Disk: CFD and flow visualization

Capillary valves are used as pressure barriers to control flow sequencing in microfluidic devices. Influence of valves height on liquid flow pattern and critical pressure are studied through flow visualization and CFD predictions (Gambit® 2.2.30 and FLUENT® 6.2.16). Both hydrophilic and hydrophobic walls are studied. Results show that the surface tension plays a major role in the liquid progress through the microchannel/valve and also in the valve filling process. Critical pressure varies linearly with the valve hydraulic diameter in the range 0.91 < D_h < 3.5 [mm] according to: P = 14.14 · D_h + 47.42 [Pa].     

Modal analysis and modified cascade neural networks in identification of geometrical parameters of circular arches

A hybrid computational system, composed of the finite element method (FEM) and cascade neural network system (CNNs), is applied to the identification of three geometrical parameters of elastic arches, i.e. span l, height f and cross-sectional thickness h. FEM is used in the direct (forward) analysis, which corresponds to the mapping α = {l, f, h} → {ω_j}, where: α – vector of control parameters, ω_j – arch eigenfrequencies. The reverse analysis is related to the identification procedure in which the reverse mapping is performed {ω_j} → {α_i}. For the identification purposes a recurrent, three level CNNs of structure (D^k-H^k-1)_s was formulated, where: k – recurrence step, s = I, II, III-levels of cascade system. The Semi-Bayesian approach is introduced for the design of CNNs applying the MML Maximum Marginal Likelihood) criterion. The computation of hyperparameters is performed by means of the Bayesian procedure evidence. The numerical analysis proves a great numerical efficiency of the proposed hybrid approach for both the perfect (noiseless) values of eigenfrequencies and noisy ones simulated by an added artificial noise.     

Investigation of pollution flashover on high voltage insulators using artificial neural network

High voltage insulators form an essential part of the high voltage electric power transmission systems. Any failure in the satisfactory performance of high voltage insulators will result in considerable loss of capital, as there are numerous industries that depend upon the availability of an uninterrupted power supply. The importance of the research on insulator pollution has been increased considerably with the rise of the voltage of transmission lines. In order to determine the flashover behavior of polluted high voltage insulators and to identify to physical mechanisms that govern this phenomenon, the researchers have been brought to establish a modeling. Artificial neural networks (ANN) have been used by various researches for modeling and predictions in the field of energy engineering systems. In this study, model of V_C = f (H, D, L, σ, n, d) based on ANN which compute flashover voltage of the insulators were performed. This model consider height (H), diameter (D), total leakage length (L), surface conductivity (σ) and number of shed (d) of an insulator and number of chain (n) on the insulator.     

Weyl Closure of a Linear Differential Operator

We study the Weyl closure Cl(L)  = K(x)〈∂〉L ∩ D for an operator L of the first Weyl algebra D = K〈x, ∂〉. We give an algorithm to compute Cl(L) and we describe its initial ideal under the order filtration. Our main application is an algorithm for constructing a Jordan–Hölder series for a holonomic D -module and a formula for its length. Using the closure, we also reproduce a result ofStrömbeck (1978), who described the initial ideals of left ideals of D under the order filtration, and a result ofCannings and Holland (1994), who described the isomorphism classes of right ideals of D.     

Calibration and validation of hyperspectral indices for the estimation of broadleaved forest leaf chlorophyll content,leaf mass per area,leaf area index and leaf canopy biomass

This article aims at finding efficient hyperspectral indices for the estimation of forest sun leaf chlorophyll content (CHL, µg cm_leaf^? 2), sun leaf mass per area (LMA, g_{dry matter} m_leaf^? 2), canopy leaf area index (LAI, m²_leaf m_soil^? 2) and leaf canopy biomass (B_leaf, g_{dry matter} m_soil^? 2). These parameters are useful inputs for forest ecosystem simulations at landscape scale. The method is based on the determination of the best vegetation indices (index form and wavelengths) using the radiative transfer model PROSAIL (formed by the newly-calibrated leaf reflectance model PROSPECT coupled with the multi-layer version of the canopy radiative transfer model SAIL). The results are tested on experimental measurements at both leaf and canopy scales. At the leaf scale, it is possible to estimate CHL with high precision using a two wavelength vegetation index after a simulation based calibration. At the leaf scale, the LMA is more difficult to estimate with indices. At the canopy scale, efficient indices were determined on a generic simulated database to estimate CHL, LMA, LAI and Bleaf in a general way. These indices were then applied to two Hyperion images (50 plots) on the Fontainebleau and Fougères forests and portable spectroradiometer measurements. They showed good results with an RMSE of 8.2 µg cm^? 2 for CHL, 9.1 g m^? 2 for LMA, 1.7 m² m^? 2 for LAI and 50.6 g m^? 2 for Bleaf. However, at the canopy scale, even if the wavelengths of the calibrated indices were accurately determined with the simulated database, the regressions between the indices and the biophysical characteristics still had to be calibrated on measurements. At the canopy scale, the best indices were: for leaf chlorophyll content: ND_chl = (ρ₉₂₅ ? ρ₇₁₀)/(ρ₉₂₅ + ρ₇₁₀), for leaf mass per area: ND_LMA = (ρ₂₂₆₀ ? ρ₁₄₉₀)/(ρ₂₂₆₀ + ρ₁₄₉₀), for leaf area index: D_LAI = ρ₁₇₂₅ ? ρ₉₇₀, and for canopy leaf biomass: ND_Bleaf = (ρ₂₁₆₀ ? ρ₁₅₄₀)/(ρ₂₁₆₀ + ρ₁₅₄₀).     

Dielectric and piezoelectric properties of [0 0 1] and [0 1 1]-poled relaxor ferroelectric PZN–PT and PMN–PT single crystals

The properties of PZN–PT and PMN–PT single crystals of varying compositions and orientations have been investigated. Among the various compositions studied, [0 0 1]-optimally poled PZN-(6–7)%PT and PMN-30%PT exhibit superior dielectric and piezoelectric properties, with K^T ≈ 6800–8000, d₃₃ ≈ 2800 pC/N, d₃₁ ≈ −(1200–1800) pC/N for PZN-(6–7)%PT; and K^T = 7500–9000, d₃₃ = 2200–2500 pC/N and d₃₁ = −(1100–1400) pC/N for PMN-30%PT. These two compositions are also fairly resistant to over-poling. The [0 0 1]-poled electromechanical coupling factors (k₃₃, k₃₁ and k_t) are relatively insensitive to crystal composition. [0 1 1]-optimally poled PZN-7%PT single crystal also exhibits extremely high d₃₁ values of up to −4000 pC/N with k₃₁ ≈ 0.90–0.96. While [0 1 1]-poled PZN-7%PT single crystal becomes over-poled with much degraded properties when poled at and above 0.6 kV/mm, PZN-6%PT crystal shows no signs of over-poling even when poled to 2.0 kV/mm. The presence of a certain amount (i.e., 10–15%) of orthorhombic phase in a rhombohedral matrix has been found to be responsible for the superior transverse piezoelectric properties of [0 1 1]-optimally poled PZN-(6–7)%PT. The present work shows that flux-grown PZN–PT crystals exhibit superior and consistent properties and improved over-poling resistance to flux-grown PMN–PT crystals and that, for or a given crystal composition, flux-grown PMN–PT crystals exhibit superior over-poling resistance to their melt-grown counterparts.     

Curves of Genus 2 with (N,N) Decomposable Jacobians

Let C be a curve of genus 2 and ψ₁: C  −  → E ₁  a map of degree n, from C to an elliptic curveE₁ , both curves defined over C. This map induces a degree n map φ₁:P¹  −  → P ¹  which we call a Frey–Kani covering. We determine all possible ramifications for φ₁. If ψ₁:C  −  → E ₁  is maximal then there exists a maximal map ψ₂: C  −  → E ₂  , of degree n, to some elliptic curveE₂ such that there is an isogeny of degree n²from the JacobianJ_C to E₁ × E₂. We say thatJ_C is (n, n)-decomposable. If the degree n is odd the pair (ψ₂, E₂) is canonically determined. For n =  3, 5, and 7, we give arithmetic examples of curves whose Jacobians are (n, n)-decomposable.     

Systematic profiling of substrate binding response to multidrug-resistant mutations in HIV-1 protease: Implication for combating drug resistance

Human immunodeficiency virus 1 (HIV-1) protease (PR) represents one of the primary targets for developing antiviral agents for the treatment of HIV-infected patients. However, a number of multidrug-resistant mutations in the enzyme have been observed over the past decades, largely limiting the application of PR inhibitors in antiviral therapy. A systematic investigation of the intermolecular interaction between the multidrug-resistant mutants of HIV-1 PR and its substrates would help to establish a complete profile of substrate response to PR mutations and to design new antiviral agents combating drug resistance. Here, we describe an integrative method to profile 6 clinical multidrug-resistant PR mutants against a panel of 16 substrate octapeptides that flank 12 distinct PR cleavage sites in viral precursor polyproteins. It is found that most multidrug-resistant mutations have only a modest or moderate effect on substrate peptide binding, although these mutations would cause a large free energy loss in PR inhibitor binding. Structural analysis reveals that the substrate peptides are loosely bound within PR active pocket to form a wide contact interface between them, and thus mutation of just single or few residues seems not to influence PR–substrate binding considerably. In addition, peptides derived from variable cleavage sites are generally more sensitive to the mutations as compared to those derived from conserved sites, supporting the co-evaluation mechanism of HIV-1 PR and its substrates under drug suppression. We also identify 12 functionally conserved key residues around the enzyme’s active site, which play crucial role in substrate recognition. In vitro fluorescence anisotropy assays confirm that wild-type PR can bind substrate peptides ARVL/AEAM and NLAF/PQGE with a moderately high affinity (K_D = 2 and 16 μM, respectively). In contrast, the key residue mutations N25D/D29N can completely eliminate (K_D = n.d.) or largely reduce (K_D = 32 and 120 μM, respectively) the binding capability of the two peptides, suggesting that these PR residues could be the potential target sites for developing resistance-free anti-HIV agents.     

Red emitting MTiO3 (M = Ca or Sr) phosphors doped with Eu3+ or Pr3+ with some cations as co-dopants

Ca (or Sr)TiO₃:Eu³⁺, M (Li⁺ or Na⁺ or K⁺) and CaTiO₃:Pr³⁺, M (Li⁺ or Na⁺ or Ag⁺ or K⁺ or Gd³⁺ or La³⁺) powders were prepared by combustion synthesis method and the samples were further heated to ～1000 °C to improve the crystallinity. The structure and morphology of materials were examined by X-ray diffraction (XRD) and a scanning electron microscopy (SEM). The morphologies of SrTiO₃:Eu³⁺, CaTiO₃:Eu³⁺ or CaTiO₃:Pr³⁺ powders co-doped with other metal ions were very similar. Small and coagulated particles of nearly cubical shapes with small size distribution having smooth and regular surface were formed. Photo-luminescence spectra of CaTiO₃:Pr³⁺ and co-doped either with Li⁺, Na⁺, K⁺, Ag⁺, La³⁺ or Gd³⁺ ions showed red emissions at 613 nm due to the ¹D₂ → ³H₄ transition of Pr³⁺. The variation of intensity of emission peak with different co-doping follows the order: K⁺ > Ag⁺ > Na⁺ > Li⁺ > La³⁺ > Gd³⁺. The characteristic emissions of CaTiO₃:Eu³⁺ lattices had strong emission at 614 and 620 nm for ⁵D₀ → ⁷F₂ with other weak transitions observed at 580, 592, 654, 705 nm for ⁵D₀ → ⁷F_n transitions where n = 0, 1, 3, 4 respectively in all host lattices. Photoluminescence intensity in SrTiO₃:Eu³⁺ is more than CaTiO₃:Eu³⁺ lattices. A remarkable increase of photoluminescence intensity (in ⁵D₀ → ⁷F₂ transition) was observed if co-doped with Li⁺ ions in CaTiO₃:Eu³⁺ and SrTiO3:Eu³⁺.     

On identifying codes that are robust against edge changes

Assume that G = (V, E) is an undirected graph, and C ⊆ V. For every v ∈ V, denote I_r(G; v) = {u ∈ C: d(u,v) ≤ r}, where d(u,v) denotes the number of edges on any shortest path from u to v in G. If all the sets I_r(G; v) for v ∈ V are pairwise different, and none of them is the empty set, the code C is called r-identifying. The motivation for identifying codes comes, for instance, from finding faulty processors in multiprocessor systems or from location detection in emergency sensor networks. The underlying architecture is modelled by a graph. We study various types of identifying codes that are robust against six natural changes in the graph; known or unknown edge deletions, additions or both. Our focus is on the radius r = 1. We show that in the infinite square grid the optimal density of a 1-identifying code that is robust against one unknown edge deletion is 1/2 and the optimal density of a 1-identifying code that is robust against one unknown edge addition equals 3/4 in the infinite hexagonal mesh. Moreover, although it is shown that all six problems are in general different, we prove that in the binary hypercube there are cases where five of the six problems coincide.     

Design and synthesis of a novel class of carbonic anhydrase-IX inhibitor 1-(3-(phenyl/4-fluorophenyl)-7-imino-3H-[1,2,3]triazolo[4,5d]pyrimidin 6(7H)yl)urea

Carbonic anhydrase IX (CAIX) is a promising target in cancer therapy especially in the case of hypoxia-induced tumors. The selective inhibition of CA isozymes is a challenging task in drug design and discovery process. Here, we performed fluorescence-binding studies and inhibition assay combined with molecular docking and molecular dynamics (MD) simulation analyses to determine the binding affinity of two synthesized triazolo-pyrimidine urea derived (TPUI and TPUII) compounds with CAIX and CAII. Fluorescence binding results are showing that molecule TPUI has an excellent binding-affinity for CAIX (k_D = 0.048 μM). The TPUII also exhibits an appreciable binding affinity (k_D = 7.52 μM) for CAIX. TPUI selectively inhibits CAIX as compared to TPUII in the 4-NPA assay. Docking studies show that TPUI is spatially well-fitted in the active site cavity of CAIX, and is involve in H-bond interactions with His94, His96, His119, Thr199 and Thr200. MD simulation studies revealed that TPUI efficiently binds to CAIX and essential active site residual interaction is consistent during the entire simulation of 40 ns. These studies suggest that TPUI appeared as novel class of CAIX inhibitor, and may be used as a lead molecule for the development of potent and selective CAIX inhibitor for the hypoxia-induced cancer therapy.     

Evaluation of response characteristics of resistive oxygen sensors based on porous cerium oxide thick film using pressure modulation method

In order to reduce the response time of resistive oxygen sensors using porous cerium oxide thick film, it is important to ascertain the factors controlling response. Pressure modulation method (PMM) was used to find the rate-limiting step of sensor response. This useful method measures the amplitude of sensor output (H(f)) for the sine wave modulation of oxygen partial pressure at constant frequency (f). In PMM, “break” response time, which is minimum period in which the sensor responds precisely, can be measured. Three points were examined: (1) simulated calculations of PMM were carried out using a model of porous thick film in which spherical particles are connected in a three-dimensional network; (2) sensor response speed was experimentally measured using PMM; and (3) the diffusion coefficient and surface reaction coefficient were estimated by comparison between experiment and calculation. The plot of log f versus log H(f) in the high f region was found to have a slope of approximately −0.5 for both porous thick film and non-porous thin film, when the rate-limiting step was diffusion. Calculations showed the response time of porous thick film was 1/20 that of non-porous thin film when the grain diameter of the porous thick film was the same as the thickness of non-porous thin film. At 973 K, “break” response time (t_b) of the resistive oxygen sensor was found by experiment to be 109 ms. It was concluded that the response of the resistive oxygen sensor prepared in this study was strongly controlled by diffusion at 923–1023 K, since the experiment revealed that the slope of plot of log f versus log H(f) in the high f region was approximately −0.5. At 923–1023 K, the diffusion coefficient of oxygen vacancy in porous ceria (D_V) was expressed as follows: D_V (m²s⁻¹) = 5.78 × 10⁻⁴ exp(−1.94 eV/kT). At 1023 K, the surface reaction coefficient (K) was found to exceed 10⁻⁴ m/s.     

Evolution of structure,stability, and nonlinear optical properties of the heterodinuclear CNLin (n = 1–10) clusters

The lowest-energy structures and stabilities of the heterodinuclear clusters, CNLi_n (n = 1–10) and relevant CNLi_n⁺ (n = 1–10) cations, are studied using the density functional theory with the 6-311 + G(3df) basis set. The CNLi₆ and CNLi₅⁺ clusters are the first three-dimensional ones in the CNLi_n^0/+ series, respectively, and the CN group always caps the Li_n^0/+ moiety in the CNLi_n^0/+ (n = 1–9) configurations. The CN triple bond is found to be completely cleaved in the CNLi₁₀^0/+ clusters where the C and N atoms are bridged by two Li atoms. The CNLi_n (n = 2–10) clusters are hyperlithiated molecules with delocalized valence electrons and consequently possess low VIP values of 3.780–5.674 eV. Especially, the CNLi₈ and CNLi₁₀ molecules exhibit lower VIPs than that of Cs atom and can be regarded as heterobinuclear superalkali species. Furthermore, these two superalkali clusters show extraordinarily large first hyperpolarizabilities of 19,423 and 42,658 au, respectively. For the CNLi_n⁺ cationic species, the evolution of the energetic and electronic properties with the cluster size shows a special stability for CNLi₂⁺.     

Performance analysis of networks of queues under active queue management scheme

Analysis of networks of queues under repetitive service blocking mechanism has been presented in this paper. Nodes are connected according to an arbitrary configuration and each node in the networks employs an active queue management (AQM) based queueing policy to guarantee certain quality of service for multiple class external traffic. This buffer management scheme has been implemented using queue thresholds. The use of queue thresholds is a well known technique for network traffic congestion control. The analysis is based on a queue-by-queue decomposition technique where each queue is modelled as a GE/GE/1/N queue with single server, R (R ⩾ 2) distinct traffic classes and {N = N₁, N₂, … , N_R} buffer threshold values per class under first-come-first-serve (FCFS) service rule. The external traffic is modelled using the generalised exponential (GE) distribution which can capture the bursty property of network traffic. The analytical solution is obtained using the maximum entropy (ME) principle. The forms of the state and blocking probabilities are analytically established at equilibrium via appropriate mean value constraints. The initial numerical results demonstrate the credibility of the proposed analytical solution.     

Approximate Solutions of Polynomial Equations

In this paper, we introduce “approximate solutions" to solve the following problem: given a polynomial F(x, y) over Q, where x represents an n -tuple of variables, can we find all the polynomials G(x) such that F(x, G(x)) is identically equal to a constant c in Q ? We have the following: let F(x, y) be a polynomial over Q and the degree of y in F(x, y) be n. Either there is a unique polynomial g(x)  ∈ Q [ x ], with its constant term equal to 0, such that F(x, y)  = ∑_j = 0ⁿc_j(y − g(x))^jfor some rational numbers c_j, hence, F(x, g(x)  + a)  ∈ Q for all a ∈ Q, or there are at most t distinct polynomials g₁(x),⋯ , g_t(x), t ≤ n, such that F(x, g_i(x))  ∈ Q for 1  ≤ i ≤ t. Suppose that F(x, y) is a polynomial of two variables. The polynomial g(x) for the first case, or g₁(x),⋯ , g_t(x) for the second case, are approximate solutions of F(x, y), respectively. There is also a polynomial time algorithm to find all of these approximate solutions. We then use Kronecker’s substitution to solve the case of F(x, y).     

Doping effect of Ir(ppy)3 on white-light electrophosphorescent devices based on platinum(II) [1,3-difluoro-4,6-di(2-pyridinyl)benzene] chloride

Phosphorescent white organic light-emitting diodes (WOLEDs) based on single doped platinum(II) [1,3-difluoro-4,6-di(2-pyridinyl)benzene] chloride (Pt-4) emission layers were investigated in this paper. The devices exhibited electroluminescence spectra composed of bluish (λ_max = 480 nm) and reddish (λ_max = 660 nm) emission bands, which corresponding to monomer and excimer emission originated from Pt-4 dopants. With optimized device structures, a maximum current efficiency of 11.5 cd/A was obtained and remained above 10 cd/A even the brightness was over 6000 cd/m². Furthermore, by integrating the fac-tris(2-phenylpyridine) iridium(III) as a complementary emitter and an additional 2,2′,2″-(1,3,5-phenylene)-tris(1-phenyl-1H-benzimidazole) space layer, the device efficiency was further improved, which exhibited a maximum current efficiency of 20.4 cd/A at the luminance of 100 cd/m², and maintained the mild efficiency roll-off that similar to its single Pt-4 doped counterpart.