Existence Of Synergistic Effects Research Articles

Adsorption and reduction of Cr(VI) by N, S co-doped porous carbon from sewage sludge and low-rank coal: Combining experiments and theoretical calculations

Herein, a novel N, S co-doped porous carbon (S5C5-AC) for Cr(VI) removal was prepared by co-hydrothermal carbonization (HTC) of sewage sludge (SS) and low-rank coal (LC) combining with KOH modification. The results showed that S5C5-AC had excellent adsorption performance on Cr(VI), and lower pH value, higher initial concentration and longer contact time were beneficial for Cr(VI) adsorption. The adsorption kinetics and isotherms revealed that Cr(VI) adsorption by S5C5-AC was homogeneous and dominated by chemisorption. The adsorption isotherm showed that the maximum equilibrium adsorption capacity of S5C5-AC for Cr(VI) was 382.04 mg/g at 25 °C. Furthermore, the results showed that the main mechanisms for Cr(VI) removal were the pore filling, electrostatic interaction and reduction. Moreover, the electron transfer mechanism during the adsorption and reduction process was further explored at the molecular and electronic levels by density functional theory (DFT) and front orbital theory (FOT) simulations. The analysis of DFT and FOT indicated that the synergistic effect between S and N functional groups was exhibited during the Cr(VI) removal process. Considering the existence of synergistic effects between N and S functional groups during adsorption, the S and N content and form were modified collaboratively. Increasing the relative content of pyrrolic N may be the most effective pathway for improving removal performance. Besides that, S5C5-AC exhibited excellent adsorption capacity over a high coexisting ion concentration range and various actual water bodies and regeneration performance, which indicated that S5C5-AC had promising potential for the remediation of wastewater in industrial applications.

Thermogravimetric analysis and kinetic modeling of the co-pyrolysis of a bituminous coal and poplar wood

The co-pyrolysis of coal and biomass has proven to be a promising route to produce liquid and gaseous fuels as well as specific value-added chemicals while contributing to mitigating CO2 emissions. The interactions between the co-processed feedstocks, however, need to be elucidated to support the development of such a thermochemical conversion process. In this context, the present work covers the kinetic analysis of the co-pyrolysis of a bituminous coal with poplar wood. In this research, biomass was blended with coal at two different mass ratios (10% (mass) and 20% (mass)). Thermogravimetric analyses were carried out with pure and blended samples at four heating rates (5, 10, 15 and 30 °C·min−1). A direct comparison of experimental and theoretical results (based on a simple additivity rule) failed to yield a clear-cut conclusion regarding the existence of synergistic effects. Kinetic analyses have therefore been achieved using two model-free methods (the Ozawa–Flynn–Wall and Kissinger–Akahira–Sunose models) to estimate the rate constant parameters related to the pyrolysis process. A significant decrease of the activation energy has thus been observed when adding wood to coal (activation energies associated with the blend containing 20% (mass) of biomass being even lower than those estimated for pure wood at low conversion degrees). This trend was attributed to the possible presence of synergies whose related mechanisms are discussed. The rate constant parameters derived by means of the two tested models were finally used to simulate the evolution of the conversion degree of each sample as a function of the temperature, thus leading to a satisfying agreement between measured and simulated data.

Assessing short-term effects of ambient air pollution on respiratory diseases in Guwahati, India with the application of the generalized additive model

Research studies connecting air pollution and its effect on health are much needed by the policymakers in India. Generalized additive model (GAM) was applied to quantify the effect of air pollutants on hospital visits related to respiratory diseases for an Indian city, Guwahati. A total of 6335 patients visited the only medical college and hospital in the city for respiratory diseases during 2016-2018. The multi-pollutant GAM models indicate the existence of synergistic effects of particulate matter less than 2.5 µm in diameter (PM2.5), nitrogen dioxide (NO2), and carbon monoxide (CO) on hospital visits of the patients due to respiratory diseases. The ambient PM2.5 concentrations have a strong link with hospital visits in all 6 single lag days. However, the effect of CO on hospital visits due to respiratory diseases was more robust. The percent change of hospital visits associated with each 1 unit increase in CO concentrations at lag 1 day was 15.7% (RR = 1.157; 95% CI 0.929, 1.442), which was enhanced to as high as 40.8% (RR = 1.408; 1.130,1.755) at lag3. The rise of each 10 units of concentrations of PM2.5 and 1 unit of CO at cumulative lag0-6 day was associated with the percentage change in hospital visits of 6.67% and 62.36% respectively. Single-pollutant GAM models indicate that the risk percentage of PM2.5 causing respiratory disease increased in combination with other pollutants.

Synergistic Effect of Co-utilization of Coal and Biomass Char: An Overview

Global concerns on impact of greenhouse gases emission, mostly released from coal-fired power plant, and the depletion of fossil fuel particularly coal, has led the production of electricity from alternatives resources such as co-utilization technologies. Previous studies proved that the co-utilization of coal and biomass/biomass chars has significantly reduced the emission of greenhouse gases either during the pyrolysis, combustion or gasification process in laboratories, pilots as well as in the industrial scales. Interestingly, most of the studies reported the presence of synergistic effect during the co-utilization processes particularly between coal and biomass char while some are not. Biomass chars were found to have porous and highly disorder carbon structure and belong to the class of most reactive carbon material, resulting to be more reactive than those hard coal and lignite. Up to date, microwave assisted pyrolysis is one of the best and latest techniques employed to produce better quality of biomass chars and it is also reduce the processing cost. Lot of works has been done regarding on the existence of synergistic effects during its co-utilization. However, the knowledge is limited to thermal and product characteristics so far. Even so, the specific reasons behind its existence are yet to understand well. Therefore, in this paper, the emphasis will be given on the synergistic effects on emission characteristics of co-utilization of coal and biomass chars so that it can be apply in energy-based industries to help in reduction of the greenhouse gases emission.

Existence of Synergistic Effects During Co-pyrolysis of Petroleum Coke and Wood Pellet

Abstract This study attempts to comprehend the thermal degradation behaviour of different blends of petroleum coke (denoted as PC) and wood pellets (denoted as WP) (1:0, 3:1, 1:1. 1:3 and 0:1) using thermogravimetric (denoted as TG) analysis under N2 atmosphere with constant particle size range of 500–850 µm and at constant heating rate of 5 °C/min. TG experiments indicated that it is difficult to predict the pyrolysis characteristics of their blends accurately based on individual components and blending ratios. The non-additive behaviour of TG curves of the blends indicates presence of synergistic effects which could further promote the volatile yields during the co-pyrolysis process. The mixed model including homogeneous reaction model (denoted as HRM) and shrinking core model (denoted as SCM) models were used to predict the variation in kinetic parameters (activation energy and pre-exponential factor) with different blend ratios. The most obvious synergistic effects were observed when the blending ratio was 25 % on account of maximum mass loss rate from the differential thermogravimetry (denoted as DTG), maximum deviation based on root mean square (denoted as RMS) value as well as divergence in the differential thermogravimetric analysis (denoted as DTA) curve.

Self-assembled polymeric vectors mixtures: characterization of the polymorphism and existence of synergistic effects in photodynamic therapy

The objective of this work was to assess the relation between the purity of polymeric self-assemblies vectors solution and their photodynamic therapeutic efficiency. For this, several amphiphilic block copolymers of poly(ethyleneoxide-b-ε-caprolactone) have been used to form self-assemblies with different morphologies (micelles, worm-like micelles or vesicles). In a first step, controlled mixtures of preformed micelles and vesicles have been characterized both by dynamic light scattering and asymmetrical flow field flow fractionation (AsFlFFF). For this, a custom-made program, STORMS, was developed to analyze DLS data in a thorough manner by providing a large set of fitting parameters. This showed that DLS only sensed the larger vesicles when the micelles/vesicles ratio was 80/20 w/w. On the other hand, AsFlFFF allowed clear detection of the presence of micelles when this same ratio was as low as 10/90. Subsequently, the photodynamic therapy efficiency of various controlled mixtures was assessed using multicellular spheroids when a photosensitizer, pheophorbide a, was encapsulated in the polymer self-assemblies. Some mixtures were shown to be as efficient as monomorphous systems. In some cases, mixtures were found to exhibit a higher PDT efficiency compared to the individual nano-objects, revealing a synergistic effect for the efficient delivery of the photosensitizer. Polymorphous vectors can therefore be superior in therapeutic applications.

Advances in Voltammetric Sensors Using Combinations of Phthalocyanines with Nanoparticles and/or Biomolecules in LB and LbL Films

Electrochemical sensors have been prepared using a range of materials and using a variety of methods. The selection of phthalocyanines or nanoparticles as sensing materials in electrochemical sensors was inspired in their electrocatalytic properties1. In turn, nanostructured sensors prepared using the Langmuir-Blodgett (LB) or the electrostatic Layer-by-Layer (LbL) techniques have the advantage of the enhanced number of active sites that has a reflect in the increase in the intensity. The control of molecular architectures afforded by these techniques can led to the development of a variety of devices where synergy is achieved by combining distinct materials, including organic-inorganic hybrids2. In this work combinations of phthalocyanines with nanoparticles and/or biomolecules in LB and LbL films have been developed and their structures have been analyzed. The films have been used as voltammetric sensors for the detection of compounds of interest in the food industry (i.e. phenols or organic acids). The role of the molecular interactions in the electrocatalytic properties or as biomimetic systems to immobilize biomolecules has been studied and the existence of synergistic effects has been evidenced. For instance, the combination of phthalocyanines with gold nanoparticles in LB films produced an increase in the sensitivity towards phenols and detection limits of 10-7 mol.L-1 were attained. Similar detection limits could be obtained by combining phthalocyanines with silver nanoparticles in LbL films. LB and LbL films combining phthalocyanines and amphiphilic molecules provided biomimetic environments where enzymes could preserve their functionality. Detection limits as low as 10-8 mol.L-1 towards phenols were attained.

Selection of strains from Bacillus thuringiensis genes containing effective in the control of Spodoptera frugiperda.

The bacterium Bacillus thuringiensis (Berliner) is an important entomopathogen that can replace chemical pesticides in crops. In addition to the endotoxins found in B. thuringiensis , new proteins have been studied recently, such as Vip and Chitinase, which can enhance toxic effects by acting synergistically. Thus, the objectives of this work were to select new B. thuringiensis isolates carrying cry1Fa, vip3Aa , and chi ; to verify polymorphisms based on PCR-RFLP analysis; and to evaluate mortality and existence of synergistic effects of these genes on Spodoptera frugiperda larvae. A total of 114 isolates were subjected to screening via PCR to detect the vip3Aa , cry1Fa , and chi genes . Neonatal larvae of S. frugiperda were bioassayed using isolates containing one, two or all three genes and were compared to the standard strains . The PCR-RFLP analysis showed the absence of polymorphisms in these gene regions. The B. thuringiensis isolates from different regions of Brazil contained different combinations of the cry1Fa, vip3Aa , and chi genes. The presence of vip3Aa appeared to act synergistically with chi , and the combination of all three genes caused increased mortality in S. frugiperda larvae. Due to their insecticidal potential, these isolates are a prospective source of genes that can be used to genetically modify crops to increase the efficacy of pest control.

Comparing models of the combined-stimulation advantage for speech recognition

The "combined-stimulation advantage" refers to an improvement in speech recognition when cochlear-implant or vocoded stimulation is supplemented by low-frequency acoustic information. Previous studies have been interpreted as evidence for "super-additive" or "synergistic" effects in the combination of low-frequency and electric or vocoded speech information by human listeners. However, this conclusion was based on predictions of performance obtained using a suboptimal high-threshold model of information combination. The present study shows that a different model, based on Gaussian signal detection theory, can predict surprisingly large combined-stimulation advantages, even when performance with either information source alone is close to chance, without involving any synergistic interaction. A reanalysis of published data using this model reveals that previous results, which have been interpreted as evidence for super-additive effects in perception of combined speech stimuli, are actually consistent with a more parsimonious explanation, according to which the combined-stimulation advantage reflects an optimal combination of two independent sources of information. The present results do not rule out the possible existence of synergistic effects in combined stimulation; however, they emphasize the possibility that the combined-stimulation advantages observed in some studies can be explained simply by non-interactive combination of two information sources.

Environmental cumulative effects of coal underground mining

More than 70% of primary energy production and consumption in China is occupied by coal. The exploitation quantity has been about 35 billion tons since 1949, over 95% of which is by underground mining. In 2008, the coal production has reached 2.72 billion tons. Long-time and intensive mining has caused spatiotemporal cumulative effects on soil, water, air environment, and ecosystem, which include ground subsidence, hydrodynamics change, land use change, soil pollution, air pollution, and ecosystem evolution etc. In this study, the cumulative sources, paths, and main performances of the environmental cumulative effects on underground coal mining region are analyzed. Moreover, the existence of synergistic effects among all environmental factors is pointed out, with some suggestions proposed for future research.

Growth of Ti and TiSi 2 films on Si(111) by low energy Ti + beam deposition

The deposition of titanium and titanium disilicide thin films on Si(111) by low-energy (10–500 eV) Ti + beams in the temperature range 25–700°C has been investigated by in-situ Auger electron spectroscopy (AES) and reflection high-energy electron diffraction (RHEED) as well as ex-situ depth profile X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and transmission electron diffraction (TED). Small XPS chemical shifts in the Si 2p and Ti 2p peaks and changes in the AES line shapes originating from elemental silicon and titanium and the titanium disilicide compound have been resolved. The XPS shifts were used for resolution of the silicide layer in the depth profiles. This interfacial silicide layer is formed even at 25°C, and its characteristics are dependent on both Ti + energy and Si temperature. The RHEED and TED results confirm the growth of a polycrystalline Ti film for T≤500°C, the C49–TiSi 2 phase for T∼600°C, the C54–TiSi 2 phase for T∼700°C or above, and the existence of synergistic effects between the substrate temperature and Ti + kinetic energy on the crystalline quality of the films. The AFM images exhibit a broad range of morphologies as a function of growth conditions. The effects of energetic ions and temperature in Ti and TiSi 2 film deposition are discussed accordingly.