Orientations of graphs avoiding given lists on out-degrees

Let $G$ be a graph and $F:V\left(G\right)\to 2^{\mathbb{N}}$ be a mapping. The graph $G$ is said to be $F$- avoiding if there exists an orientation $O$ of $G$ such that $d_O^{+}\left(v\right)\notin F\left(v\right)$ for every $v\in V\left(G\right)$, where $d_O^{+}\left(v\right)$ denotes the out-degree of $v$ in the directed graph $G$ with respect to $O$. In this paper it is shown that if $G$ is bipartite and $\mid F\left(v\right)\mid \le d_G\left(v\right)/2$ for every $v\in V\left(G\right)$, then $G$ is $F$-avoiding. The bound $\mid F\left(v\right)\mid \le d_G\left(v\right)/2$ is best possible. For every graph $G$, we conjecture that if $\mid F\left(v\right)\mid \le \frac{1}{2}\left(d_G\left(v\right)-1\right)$ for every $v\in V\left(G\right)$, then $G$ is $F$-avoiding. We also argue about this conjecture for the best possibility of the conditions and also show some partial solutions.     

Enhanced Heterotrophic Denitrification: Effect of Dairy Industry Sludge Acclimatization and Operating Conditions

Heterotrophic denitrification of drinking water was enhanced by selection of an anoxic sludge taken from a dairy industry among the sludges taken from various industries, and the effect of carbon sources was examined. Acclimatization to high nitrate concentration was then carried out in a five-stage process. Considering removals of both nitrate and nitrite, the sludge taken from anoxic unit of Tehran Pegah dairy industry was shown to be the superior microbial culture, with ethanol as carbon source as compared to acetate. To enhance the rate of denitrification, acclimatization to nitrate (at 100, 200, 400, 800, and 1,600 mg N-NO₃/L) was carried out in sequencing batch reactors over a 3-month period under anoxic condition, and comparisons were made between the performances of acclimated and non-acclimated sludges at each stage. It was found that acclimatization up to the fourth stage enhanced the specific denitrification rate to a high value of 29.6 mg N-NO₃/h/g mixed liquor suspended solids (MLSS), with no significant nitrite accumulation. Additionally, the effect of initial pH (6, 6.5, 7, and 7.5) and carbon-to-nitrogen (C/N) ratio (1, 1.5, 2, and 3) on the performance of this final acclimated sludge was assessed, where initial pH of 7 and C/N ratio of 1.5 resulted in the best performances considering both nitrate and nitrite removal.     

An improved particle shifting technique for incompressible smoothed particle hydrodynamics methods

The smoothed particle hydrodynamics (SPH) method is one of the powerful Lagrangian tools for modeling free surface flows. However, it suffers from particle disorder, which leads to interpolation and numerical errors. To overcome this problem, several techniques have been introduced until now, among which the particle shifting technique (PST) based on Fick's law is an efficient one. The current form of this method needs tuning parameters to fulfill numerical stability criteria. In this study, to eliminate calibration factors, a new shifting coefficient is derived theoretically based on particle positions before and after shifting, regardless of other parameters such as velocity, pressure, time step intervals, etc. The only required input is particle positions, and the main concern is conserving particle densities in their updated positions. In addition to the proposed PST, a new distribution index (DI) is introduced for measuring the spatial uniformity of particles. Furthering the research, some novel treatments are also studied to improve particle movements near free surface boundary. The proposed idea is only assessed for ISPH method in this study, and its performance in other SPH schemes needs more investigations. Following this innovative method, it is validated by modeling different cases including dam break flow, paddle movement, and elliptical water drop. In all cases, particle arrangements have been improved by means of the modified shifting method. In that sense, good agreements between simulation results with experimental data, analytical solutions, and other numerical methods approve the ability of the developed method in simulating free surface flows.     

Electrochemical sensor for ultrasensitive determination of ceftazidime using hollow platinum nanoparticles/reduced graphene oxide/pencil graphite electrode

In this paper, an electrochemical sensor was prepared based on the modification of pencil graphite electrode (PGE) by hollow platinum nanoparticles/reduced graphene oxide (HPtNPs/rGO/PGE) for determination of ceftazidime (CFZ). Initially, rGO was electrodeposited on the electrode surface, and then, hollow platinum nanoparticles were placed on the electrode surface via galvanic displacement reaction of Pt(IV) ions with cobalt nanoparticles (CoNPs) that had electrodeposited on the electrode surface. Several significant parameters controlling the performance of the HPtNPs/rGO/PGE were examined and optimized using central composite design as one optimization methodology. The surface morphology and elemental characterization of the bare PGE, rGO/PGE, CoNPs/rGO/PGE, and HPtNPs/rGO/PGE-modified electrodes was analyzed by field-emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and electrochemical impedance spectroscopy. The electrochemical activity of CFZ on resulting modified electrode was investigated by cyclic voltammetry (CV) and adsorptive differential pulse voltammetry (AdDPV). Adsorptive differential pulse voltammetry indicates that peak current increases linearly with respect to increment in CFZ concentration. CFZ was determined in the linear dynamic range of 5.0 × 10^?13 to 1.0 × 10^?9 M, and the detection limit was determined as 2.2 × 10^?13 M using AdDPV under optimized conditions. The results showed that modified electrode has high selectivity and very high sensitivity. The method was used to determine of CFZ in drug injection and plasma samples.     

The effect of rib shape on the behavior of laminar flow of oil/MWCNT nanofluid in a rectangular microchannel

Journal of Thermal Analysis and Calorimetry - In this research, the laminar and forced flow and heat transfer of oil/multi-walled carbon nanotubes nanofluid in a microchannel have been numerically...     

Improved DNA fragment length estimation in capillary electrophoresis

In CE the charged DNA strands are fractionated according to fragment lengths as they migrate through the capillary, since shorter DNA fragments pass through the sieving matrix faster. Multiplexed internal size standards are used to estimate the size of unknown DNA fragments. In the literature there are statements about migration abnormalities for the 250 and 340 bp fragments in the GeneScan-500 (GS500) internal size standards. Such anomalous migration of size standards could obviously introduce errors in the estimation of unknown fragments. Therefore, a number of analysis programs simply exclude some of these fragments. In the present work we first evaluate the effect of excluding each of the fragments in the internal size standards used in CE. Next, a method which is based on estimating the true values of the anomalous fragments is presented. The results obtained by the new method indicate a significant improvement compared to results obtained when one (or both) of the anomalous fragments in GS500 is (are) excluded or included when estimating the size of unknown DNA fragments. In the higher-molecular-weight region, the average error is reduced from 1.91 bp in ABI GeneMapper (excluding 250 bp) to 0.15 bp in the new method (using the estimated values for 250 and 340 bp). In the lower-molecular-weight region, excluding both fragments will improve the results by an average of 0.74 bp compared to ABI GeneMapper.     

A full-wave three-dimensional analysis of open dielectric waveguides and periodic structures using an equivalent network model

An accurate fully vectorial wave analysis to calculate the propagation characteristics and field distribution of open dielectric waveguides and optical integrated circuits is presented. Based on the periodic repetition concept and using an equivalent network model, a method to analyze wave propagation in these guides is developed, which is able to take the simultaneous presence of mixed polarizations into account. Compared with conventional approaches like mode matching as well as with other numerical methods, the presented three-dimensional (3D) method shows individual advantages like accuracy, simplicity, and numerical efficiency. To show both validity and usefulness of this approach, some fundamental structures are investigated and the obtained numerical results are presented.     

A sulfonic acid functionalized ionic liquid as a homogeneous and recyclable catalyst for the one-pot synthesis of α-aminophosphonates

A sulfonic acid functionalized ionic liquid is used as a Brønsted acid catalyst for the one-pot, three-component synthesis of α-aminophosphonates from aldehydes and ketones at room temperature in water. This homogeneous catalytic procedure is simple and efficient and the catalyst can be reused at least six times without any noticeable decrease in catalytic activity.     

Some relations between rank, chromatic number and energy of graphs

The energy of a graph G, denoted by E(G), is defined as the sum of the absolute values of all eigenvalues of G. Let G be a graph of order n and be the rank of the adjacency matrix of G. In this paper we characterize all graphs with . Among other results we show that apart from a few families of graphs, , where n is the number of vertices of G, and χ(G) are the complement and the chromatic number of G, respectively. Moreover some new lower bounds for E(G) in terms of are given.