Kinetic speciation of Co(II), Ni(II), Cu(II), and Zn(II) in model solutions and freshwaters: lability and the d electron configuration

The kinetic speciation of Co(II), Ni(II), Cu(II), and Zn(II) in model solutions of a well-characterized fulvic acid (Laurentian fulvic acid), freshwater samples from the Rideau River (Ottawa, Ontario), and freshwater samples from the Sudbury (Ontario) area were investigated by the competing ligand exchange method using Chelex 100 as the competing ligand and by inductively coupled plasma-mass spectrometry to measure the dissociation kinetics. The metal species were quantitatively characterized by the rate coefficient for the first-order dissociation of metal complex to free metal ion. This technique can be applied to almost all elements and represents an important advance in our ability to investigate the kinetic availability of metal species in the freshwater environment. The order of the lability of the metal complexes, Co(II) > Ni(II) > Cu(II) < Zn(II), follows the reverse order of the ligand field stabilization energy with the exception of Cu(II); the behavior of Cu(II) is also due to the Jahn-Teller effect, which shortens the equatorial bonds and lengthens the axial bonds of a tetragonally distorted Cu(II)-L6 complex. This study has demonstrated a relationship between the lability of metal-DOM complexes of the 3d transition metals in freshwaters and their d electron configuration. This is the first time that the importance of the d electron configuration on the lability of metal complexes in the freshwater environment has been demonstrated. The slow complexation kinetics of both Ni(II) and Cu(II) suggestthatthe usual equilibrium assumption for freshwaters may be invalid.     

Prediction of viscoelastic behavior of interphase in polypropylene‐chopped rice husk composites for β‐relaxation domain

The effect of chopped rice husk (CRH) content on viscoelastic properties and crystallinity of polypropylene (PP) composites was investigated. Composites containing 0, 20, and 40 part per hundred plastics (php) of CRH into PP were prepared by twin‐screw extruder, with maleic anhydride‐grafted PP as the coupling agent. The viscoelastic behavior and the crystallinity of these composites have been studied by dynamic mechanical analysis as well as differential scanning calorimetry, respectively. By the incorporation of CRH into PP, the storage modulus (E′) was found to be increased progressively, whereas the mechanical loss factor (tan δ) decreased in a nonlinear manner. A self‐consistent analysis was proposed for the prediction of viscoelastic response of the interphase between PP matrix and CRH particles. A three‐phase model was applied in a reverse mode, and the viscoelastic behavior of the interphase was extracted and compared with the unfilled matrix. Differential scanning calorimetry results indicated that CRH influences crystallization temperature as well as the degree of crystallinity of the composites. An entrapped polymer within CRH filler and PP matrix was detected by scanning electron microscope, which can be attributed to the interfacial layer with a good adhesion between the main components. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A New Model of Charging Demand Related to Plug-in Hybrid Electric Vehicles Aggregation

This paper offers a comprehensive and exact model for Plug-in Hybrid Electric Vehicle (PHEV) aggregation based on the real statistics. For this purpose, available transportation and technical reports are analyzed to extract Cumulative Distribution Functions and accurate modeling of PHEVs charging load profile. We can study PHEVs effects on the distribution system by analyzing available registered data; however, the main problem is that such data, due to the low penetration of PHEVs, are not accessible, and expensive monitoring equipment such as Global Positioning Systems are needed to collect such data. Therefore, due to the lack of access to such data, researchers have offered different estimations for the charging load profile of PHEVs using statistical methods. In this study, a new model for the initial state of charge (SOC) is introduced that it is a function of fuel consumption of the vehicles. The driving behaviors such as speed and road slope have been considered in the proposed model. Simulation results show the impressiveness effectiveness and accuracy of the proposed methodology.     

Transthoracic Doppler echocardiography of normally originating coronary arteries in children

Transthoracic Doppler color flow and spectral velocity patterns of normal coronary arteries in children have not been well studied. We designed this study to evaluate coronary artery flow velocity characteristics in normal and hypertrophied hearts. Sixty-eight children with optimal two-dimensional echocardiographic images of the left coronary artery (LCA) and right coronary artery (RCA) were prospectively studied. The heart was normal in 45 children, and 23 had left and/or right ventricular hypertrophy assessed by echocardiography (mean age 5.8 versus 5.2 years, p = NS). Color flow signals were detected in the LCA in 63(92%) of the 68 children studied, and pulsed Doppler spectral waveforms were recorded in 47 (69%). The latter were recorded in 26 (58%) of 45 normal children and in 21 (91%) of 23 children with left ventricular hypertrophy. Diastolic RCA flow signals were detected mostly in those with right ventricular hypertrophy (10 of 10). Higher levels of LCA maximum diastolic velocity (42 +/- 23 versus 24 +/- 6 cm/sec, p = 0.0004), increased diastolic flow (16 +/- 15 versus 6 +/- 4 ml/min, p = 0.01), and delayed time to peak diastolic velocity expressed as a percentage of diastolic spectral duration (38% +/- 14% versus 20% +/- 8%, p = 0.0001) were observed in children with left ventricular hypertrophy than in those in normal children. A strong correlation was present between Doppler-derived LCA flow and left ventricular mass/m2 (r = 0.7, p = 0.001). In normal hearts, LCA spectral velocity pattern did not change with increasing age, but the time velocity integral became progressively larger, resulting in a strong correlation with weight (p < 0.001, r = 0.78). This study demonstrates (1) LCA flow signals can be detected and quantitated in the majority of children with and those without left ventricular hypertrophy. (2) Left ventricular hypertrophy is associated with increased LCA flow, higher diastolic velocity, and delayed peak diastolic velocity. (3) RCA flow signals are mostly detected when there is right ventricular hypertrophy. Studies on larger groups of patients are needed to further confirm our observations and to enhance understanding of coronary artery flow reserve.     

Discovery of novel anticancer compounds based on a quinoxalinehydrazine pharmacophore

Quinoxalinehydrazines represent a novel class of compounds with excellent potency in a panel of cancer cell lines. A prototype compound, SC144, showed significant in vivo efficacy in mice xenograft models of human breast cancer cells. The subsequent structure-activity relationship study resulted in the discovery of SC161 with better potency in cancer cell lines. Further exploring the possible conformational space by a 10 ns molecular dynamics simulation as presented herein, resulted in various pharmacophore orientations. The trajectory analysis indicated that in most of the simulation time, the molecule stays favorably in a compact planarlike orientation. We therefore built a pharmacophore model based on the cluster containing the highest number of frames to represent the most probable orientation. The model was used to screen a subset of our small molecule database containing 350,000 compounds. We selected 35 compounds for the initial cytotoxicity screen. Seventeen compounds belonging to oxadiazolopyrazine and quinoline class displayed cytotoxicity in various cancer cell lines. Five of them, compounds 2, 6, 15, 16, and 19, all bearing an oxadiazolopyrazine scaffold, showed IC(50) values <3 muM in certain tumor cell lines. The most potent compound, 2, showed IC(50) values <2 muM in HCT116 p53(+/+), HCT116 p53(-/-), and HEY cells, and 8 muM in NIH3T3 cells. This study shows that conformational sampling of a lead small molecule followed by representative pharmacophore model development is an efficient approach for the rational design of novel anticancer agents with similar or better potency than the original lead but with different physicochemical properties.     

Fast coding unit partitioning method based on edge detection for HEVC intra-coding

High efficiency video coding (HEVC) standard is the latest video coding standard generation. It employs powerful coding tools to obtain improved compression efficiency. To better exploit the redundancies, HEVC adopts a very flexible quad-tree coding structure, allowing the encoder to use a block partition that matches the image features. This exhaustive technique may achieve a higher coding efficiency; however, it induces a significant computational complexity in the encoding engine. This paper proposes a new texture parameter for classifying digital videos as a first contribution and then introduces an efficient coding unit (CU) partitioning algorithm based on the early defined texture parameter in order to speed up the encoding process. In fact, the proposed technique is based on edge detection by performing SOBEL filtering in order to decide the appropriate CU size. Compared to the original HEVC, the average execution time-saving is about 31 % while maintaining almost the same output video quality.     

Effect of single-walled carbon nanotubes on morphology and mechanical properties of NBR/PVC blends

Dynamically vulcanized thermoplastic elastomer based on Nitrile butadiene-rubber (NBR)/PVC with functionalized single-walled carbon nanotubes (f-SWNTs) and non-functionalized single-walled carbon nanotubes (SWNTs) were prepared using a brabender internal mixer. Effects of two types of SWNTs (functionalized and non-functionalized) on morphology and mechanical properties of NBR/PVC blends were studied. Results showed that the mechanical properties of NBR/PVC/SWNTs nanocomposites improved with the increasing of SWNTs content and in particular with the increase of f-SWNTs content. Moreover, the enhancement of mechanical properties of NBR/PVC blends reinforced with functionalized SWNT was higher than that of NBR/PVC blends with non-functionalized SWNT. Dispersion of SWNTs and morphology of NBR/PVC/SWNT nanocomposites were determined by scanning electron microscopy and transmission electron microscopy (TEM) techniques. TEM images illustrated that f-SWNTs were dispersed uniformly in NBR/PVC matrix while non-functionalized SWNTs showed much aggregation. Dynamic mechanical thermal analysis of NBR/PVC/SWNTs nanocomposites was also studied. The outcomes indicated that in the case of f-SWNTs, the intensity of tan ?? peak was lower than that in the case of non-functionalized SWNTs. Meanwhile, the intensity of tan ?? peak reduced when the content of f-SWNTs was increased.