GB Values Research Articles

Evaluation of the applicability of gasification coarse slag as a fine aggregate in controlled low-strength material: preparation, performance, and environmental effect.

Gasification slag (GS) is rich in SiO2, Al2O3, and Fe2O3, and has excellent particle size gradation, which has the potential to be employed as an aggregate in the field of controlled low-strength material (CLSM). Nevertheless, the large-scale application of GS as the fine aggregate for the preparation of CLSM has been scarcely investigated. In the present work, the applicability of replacing part of coal gangue (CG) with gasification coarse slag (GCS) as fine aggregate for the preparation of CLSM was investigated. The results revealed that using GCS as a fine aggregate improved the flowability of CLSM, and increasing the GCS content from 0 to 50 wt% improved the flowability from 250.0 to 280.0 mm. The 28-day compressive strength of all CLSM conformed to the requirements of ACI Committee 229. Compared to the Blank group, the 7- and 28-day compressive strength of the CLSM increased by 23.07% and 26.80%, respectively, at a GCS content of 50 wt%. The increase in compressive strength was mainly due to the pore-filling and hydration-promoting effect of the GCS, which made the structure denser. The dense structure reduced the expansion rate, absorption, and porosity rate of CLSM and increased the wet density. The optimal process parameter was the addition of 10 wt% of GCS. The results of heavy metal ion leaching showed that the optimal sample GS10 leached all heavy metal ions in much less than the limit values of GB 8978-1996 and GB 5085.3-2007. The results will provide new ideas and technical approaches for the large-scale application of GCS as the fine aggregate in CLSM.

Exploring Strategies to Mitigate the Lightness Effect on the Prediction of Soybean Oil Content in Blends of Olive and Avocado Oil Using Smartphone Digital Image Colorimetry.

Extra virgin olive oil (EVOO) and avocado oil (AVO) are recognized for their unique sensory characteristics and bioactive compounds. Declared blends with other vegetable oils are legal, but undeclared mixing is a common type of fraud that can affect product quality and commercialization. In this sense, this study explored strategies to mitigate the influence of lighting in order to make digital image colorimetry (DIC) using a smartphone more robust and reliable for predicting the soybean oil content in EVOO and AVO blends. Calibration models were obtained by multiple linear regression using the images' RGB values. Corrections based on illuminance and white reference were evaluated to mitigate the lightness effect and improve the method's robustness and generalization capability. Lastly, the prediction of the built model from data obtained using a distinct smartphone was assessed. The results showed models with good predictive capacities, R2 > 0.9. Generally, models solely based on GB values showed better predictive performances. The illuminance corrections and blank subtraction improved the predictions of EVOO and AVO samples, respectively, for image acquisition from distinct smartphones and lighting conditions as evaluated by external validation. It was concluded that adequate data preprocessing enables DIC using a smartphone to be a reliable method for analyzing oil blends, minimizing the effects of variability in lighting and imaging conditions and making it a potential technique for oil quality assurance.

Inventory of PCDD/Fs and Fly Ash Characteristics during the e-Waste and Municipal Solid Waste Co-Incineration Process

In the face of a challenging situation for yearly e-waste (EW) increment and disposition, EW co-incineration (EWC) with municipal solid waste (MSW) is a promising solution whose emission characteristics remain unclear. This study is conducted in a 400 tons/day MSW incineration (MSWI) plant to characterize polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and fly ash (FA) properties. Analytical methods include high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) for PCDD/F determination, as well as X-ray diffraction (XRD), X-ray fluorescence (XRF), ion chromatography (IC), and leaching toxicity test for FA. The results indicate that toxic PCDD/F amounts are doubled by EWC in both primary exhaust gas (EG) and FA with international toxic equivalent quantity (I-TEQ) concentrations of 19.00 ± 6.32 ng I-TEQ/Nm3 and 1.33 ± 0.56 ng I-TEQ/g. After the clean-up of the air pollution control system (APCS), emitted PCDD/Fs in solid and gas phases, as well as major air pollutants (CO, NOx, SO2, HCl, and particulate matter), are permissive within the limit values of national standards GB 18485-2014 and GB 16889-2008. Distribution patterns for 136 PCDD/F isomers are analogous in both MSWI and EWC conditions. De novo synthesis is always the major formation route for both EWC and MSWI conditions, while dibenzodioxin/dibenzofuran (DD/DF) chlorination also contributes. The generation of 136 PCDD/Fs is enhanced by EWC, and the correlation coefficients of Cl and Cu in the fuel with the generation of 136 PCDD/F isomers are found to be R = 0.92 and 0.88, respectively. The main components in FA from MSWI and EWC differ less, both containing CaO, SiO2, and Al2O3. However, Cl and Cu contents, as well as leaching toxicity in FA are elevated by EW. Heavy metals, except for Cd, Ni, and Pb, meet the requirement of the standard.

Innovative Alveolar Socket Preservation Procedure Using Demineralized Tooth Dentin as Graft Biomaterial Covered with Three Reabsorbable Membranes: Human Histological Case Series Evaluation

Background: Extracted tooth material has been seen as a valuable alternative to synthetic biomaterials. Aims: A novel flapless alveolar socket preservation (ASP) procedure with demineralized extracted tooth dentin graft material covered by three reabsorbable membranes was histologically and clinically evaluated 4 months after bone healing. Methods: Ten patients were enrolled and separated into two groups. Five post-extractive sites without buccal and/or palatal bone walls were treated with the flapless ASP procedure with demineralized tooth dentin covered with three reabsorbable membranes (Group A—GA). Five patients were treated with primary wound closure covered only with a reabsorbable membrane (Group B—GB). Bone biopsies were performed for histologic and histomorphometric analyses. Results: In both procedures, all clinical outcomes showed good healing of hard and soft tissue and a good maintenance of maxillary architecture. The histological analysis showed no necrosis or inflammatory areas in either group. The histomorphometric analysis showed higher total bone volume in GA (62.78 ± 7.97%) compared to GB (48.04 ± 9.32%), higher vital new bone in GA (57.53 ± 11.16%) compared to GB (42.41 ± 13.06%) and similar values for residual graft in GA (5.24 ± 5.82%) compared to GB (5.29 ± 4.83%). Conclusions: The data obtained show how this novel technique, mixed with the dentin-derived graft material, seems to promote higher bone regeneration.

Effects of Different Inorganic Nitrogen Sources of Iris pseudacorus and Iris japonica on Energy Distribution, Nitrogen, and Phosphorus Removal

High- and low-affinity transport systems are the main pathways for the transportation of NO3– and NH4+ across intracellular membranes. NO3− and NH4+ are assimilated through different metabolic pathways in plants. Fifteen ATP molecules are hydrolyzed in the metabolic process of NO3–; however, only five ATP molecules are hydrolyzed in that of NH4+. In this research, seedlings of Iris pseudacorus and Iris japonica were used as the experimental materials in the NO3–:NH4+ = 30:0, NO3–:NH4+ = 28:2, NO3–:NH4+ = 27:3, NO3–:NH4+ = 15:15, NO3–:NH4+ = 3:27, and NO3–:NH4+ = 0:30 treatments at the 7.5 mmol·L−1 the total nitrogen content (TN). The intracellular free energy was represented by physiological resistance (R) and physiological impedance (Z) according to the Nernst equation and could conveniently and comprehensively determine the cellular metabolic energy (GB). The maximum absorption rate (Vmax) and Michaelis constant (Km) for NH4+ and NO3– uptake were calculated according to the kinetic equation. The results showed that the cellular metabolic energy (GB) of I. pseudacorus was 1 to 1.5 times lower than that of I. japonica at each treatment on the 10th day. The GB values of I. pseudacorus and I. japonica seedlings increased with increasing NH4+ concentration. However, there was a turning point at the NO3–:NH4+ = 15:15 treatment for the cellular metabolic energy of I. pseudacorus and I. japonica. Correlation analysis showed that the value of cellular metabolic energy was negatively correlated with the Vmax and Km for NO3– uptake, whereas it was positively correlated with that for NH4+ uptake. These results demonstrate that the NO3–:NH4+ = 27:3 treatment level was the most suitable for I. pseudacorus and I. japonica. This indicates that the greater cellular metabolic energy is the most suitable for plant growth when the concentration of ammonium or nitrate had no significant difference at treatment. These results provide a simple and rapid solution for removal of nitrogen by determination of cellular metabolic energy.

Performance evaluation of an anaerobic hybrid reactor treating petrochemical effluent

Organic loading rate (OLR), Hydraulic Retention Time (HRT) and up flow velocity are important parameters significantly affecting microbial ecology and characteristics of anaerobic reactors. In this study, Performance of an anaerobic hybrid reactor (UASB/Filter) at mesophilic condition was evaluated in a 15.4 L reactor receiving petrochemical wastewater. The temperature of influent was adjusted by an inline heat exchanger at around 35 ˚C. The reactor was seeded with flocculent sludge from a UASB plant treating dairy wastewater. The sludge was acclimatized to petrochemical wastewater in twostage operation. After 39 weeks, a COD reduction of 70.3% was obtained at OLR=2.0 kg m-3 d-1 and HRT=18 h. Under steady state conditions, experiments were conducted at OLRs of between 0.5 and 24 kg TCOD m-3 d-1 , hydraulic retention times (HRT) of 4-48 h and up flow velocities 0.021-0.25 m h-1. Removal efficiencies in the range of 42-86% were achieved at feed TCOD concentrations of 1000- 4000 mg L-1 . The biogas production data used for determination of biogas production kinetics. The values of Gmax and GB estimated as 11.173 LL-1d -1 and 85.83 g L-1d -1 , respectively.

Electrocatalysis of molecular oxygen reduction reaction at liquid-liquid interface and DFT computational study of proton transfer from the conjugate acid of 2,2'-dipyridylamineto oxygen.

In this study, the catalytic effect of 2,2'-dipyridylamine (DPA) on the reduction of oxygen (O2) at the polarized water/1,2-dichloroethane (DCE) interface was investigated. Ferrocene (Fc) and tetrathiafulvalene (TTF) were weak electron donors used in this study. Slow reduction of O2 at the interface containing Fc and TTF was significantly accelerated upon the addition of DPA. Voltammetry and biphasic shake flask experiments revealed that DPA acts as a proton ionophore to transfer protons between the aqueous and organic phases. The PA, GB, and pKa values of all possible conjugate acids of DPA were calculated. Then, a mechanism was suggested to explain the interaction between protonated DPA and oxygen molecular. The mechanism was computationally analyzed by using density functional theory (DFT). Furthermore, DFT calculations at the B3LYP/6-31G** level of theory showed that the conjugate acid species of DPA transfer proton to O2 at the interface. The results show that DPA-H2+ and DPA-H1+ are the best species to transfer proton to molecular oxygen.

Gas-Phase Protonation Thermodynamics of Biological Lipids: Experiment, Theory, and Implications.

Phospholipids are important to cellular function and are a vital structural component of plasma and organelle membranes. These membranes isolate the cell from its environment, allow regulation of the internal concentrations of ions and small molecules, and host diverse types of membrane proteins. It remains extremely challenging to identify specific membrane protein-lipid interactions and their relative strengths. Native mass spectrometry, an intrinsically gas-phase method, has recently been demonstrated as a promising tool for identifying endogenous protein-lipid interactions. However, to what extent the identified interactions reflect solution- versus gas-phase binding strengths is not known. Here, the "Extended" Kinetic Method and ab initio computations at three different levels of theory are used to experimentally and theoretically determine intrinsic gas-phase basicities (GB, ΔG for deprotonation of the protonated base) and proton affinities (PA, ΔH for deprotonation of the protonated base) of six lipids representing common phospholipid types. Gas-phase acidities (ΔG and ΔH for deprotonation) of neutral phospholipids are also evaluated computationally and ranked experimentally. Intriguingly, it is found that two of these phospholipids, sphingomyelin and phosphatidylcholine, have the highest GB of any small, monomeric biomolecules measured to date and are more basic than arginine. Phosphatidylethanolamine and phosphatidylserine are found to be similar in GB to basic amino acids lysine and histidine, and phosphatidic acid and phosphatidylglycerol are the least basic of the six lipid types studied, though still more basic than alanine. Kinetic Method experiments and theory show that the gas-phase acidities of these phospholipids are high but less extreme than their GB values, with phosphatidylserine and phosphatidylglycerol being the most acidic. These results indicate that sphingomyelin and phosphatidylcholine lipids can act as charge-reducing agents when dissociated from native membrane protein-lipid complexes in the gas phase and provide a straightforward model to explain the results of several recent native mass spectrometry studies of protein-lipid complexes.

On the Basicity of Organic Bases in Different Media

The basicities of simple organic bases – aliphatic and aromatic amines, amidines, phosphazenes, as well as saturated and unsaturated nitrogen heterocycles – are examined in acetonitrile, dimethyl sulfoxide, tetrahydrofuran, water and the gas phase. The basicities (pKaH values) of conjugate acids of a large variety of bases in these media are presented and discussed. Equations employing easily usable structural descriptors have been derived for approximately converting basicities from acetonitrile to other solvents. Recommendations are given on their practical use and a number of pKaH values that are experimentally unavailable are estimated from these relationships. An important part of the minireview is a large compilation of pKaH and GB values of the compounds in solvents and the gas phase, respectively, as well as the revised basicity scale in acetonitrile, now containing more than 270 pKaH values.

Theoretical study of the thermodynamic parameters of (CaO)n nanoclusters with n = 2–16 in the gas and solution phases: proton affinity, molecular basicity, and pKb values

Thermodynamic quantities such as proton affinity (PA) and molecular basicity (GB) for (CaO)n nanoclusters with n = 2–16 have been calculated using three computational models of the density functional theory (DFT) (Becke, 3-parameter, Lee-Yang-Parr (B3LYP), Minnesota 2006, Perdew-Wang 1991 (PW91), Coulomb attenuated method-B3LYP, and ωB97XD functionals); Moller-Plesset perturbation theory; and Hartree-Fock with the cc-PVNZ (n = D and T) basis set in the gas phase. Absolute deviation error (AAD%) indicates that obtained PA and GB values using DFT model and the B3LYP method with mean percentage errors of 0.77 and 0.90%, respectively, have the higher accuracy than the other methods and models. The values obtained for the proton affinity and gas-phase basicity of the nanoclusters were compared to experimental data reported in the literature. In order to confirm basicity properties, quantum descriptors of the molecular electrostatic potential (MEP) and valence natural atomic orbital energies (NAO) have been computed. The MEP and NAO values for species under probe display excellent correlation coefficient. The polarizable continuum model for investigating the solvents effect of water, DMSO, and benzene on the basicity of the CaO nanoclusters has been applied.

Proton irradiation induced defects in β-Ga2O3: A combined EPR and theory study

Proton irradiation of both n-type and semi-insulating bulk samples of β-Ga2O3 leads to the formation of two paramagnetic defects with spin S = 1/2 and monoclinic point symmetry. Their high introduction rates indicate them to be primary irradiation induced defects. The first electron spin resonance (EPR1) has a g-tensor with principal values of gb = 2.0313, gc = 2.0079, and ga* = 2.0025 and quasi-isotropic superhyperfine interaction of 13G with two equivalent Ga neighbors. Under low temperature photoexcitation, this defect is quenched and replaced by a different metastable spin S = 1/2 center of comparable intensity. This second defect (EPR2) has similar principal g-values of gb = 2.0064, gc = 2.0464, and ga* = 2.0024 and shows equally superhyperfine interaction with two equivalent Ga atoms. This EPR2 defect is stable up to T = 100 K, whereas for T > 100 K the initial defect is recovered. Density functional theory calculations of the spin Hamiltonian parameters of various intrinsic defects are carried out using the gauge including projector augmented wave method in order to determine the microscopic structure of these defects. The intuitive models of undistorted gallium monovacancies or self-trapped hole centers are not compatible with neither of these two defects.

The pKa values of amine based solvents for CO2 capture and its temperature dependence—An analysis by density functional theory

A computational chemistry study has been employed to calculate the pKa values of alkylamines (primary, secondary and tertiary) used in the removal of carbon dioxide. A DFT-B3LYP level of theory with 6-311++G (d, p) basis set is used for the computational analysis. The pKa values of amines are of great importance as it has a major role in carbon dioxide capturing mechanism. The temperature dependence of pKa values has also been evaluated and it has been observed that the pKa values of alkylamines shows an inverse relation with the temperature. The Secondary and tertiary amines show maximum and minimum pKa values respectively. The gas phase proton affinity (PA) and gas the phase basicity (GB), which is difficult to measure experimentally, have been computed easily and accurately by this method. It is observed that the PA and GB values increase from primary to tertiary alkylamines. The linear relationship between the pKa values and the free energy of protonation has been computationally verified; the results are in good agreement with the experimental results and the method is simpler and less expensive. The work can be extended to study the carbamate stability and carbon dioxide capture mechanism and there by screening the candidates for the Carbon dioxide Capture and Storage.

Soret and Dufour Effects on Steady Free Convection and Mass Transfer Flow Past a Semi-infinite Flat Plate with Viscous Dissipation

The Soret and Dufour effects on a steady free convection and mass transfer flow past a semi infinite flat plate with viscous dissipation in a porous medium have been studied numerically. The equation governing the flow of heat and mass transfer have been solved by Runge Kutta Gill method with shooting technique. The flow characteristics have been studied for different values of Pr, Gb, Sc, Sr and Du.

Tek Taraflı Dudak Damak Yarıklı Bireylerde Modifiye Gerçek Dikey Çizginin Konumunun Değerlendirilmesi

Objective: To compare the facial anteroposterior projection parameters of unilateral complete cleft lip and palate (UCCLP) patients with non-cleft (NC) individuals having well-balanced faces using Arnett and Gunson Module and determine the capability of modified true vertical line (mTVL) to depict the true extent of retrognathism in UCCLP patients was aimed. Material and Methods: Arnett and Gunson Analysis was used in the evaluation of standard cephalometric headfilms of 30 UCCLP individuals and 30 NC patients with pleasing facial profile between the ages of 17-19 years, taken in natural head position. Projection values relative to true vertical line (TVL, in NC individuals) or modified true vertical line (mTVL, in UCCLP) were measured. Second measurements were done relative to a line that is parallel to the TVL/mTVL but passing through the geometric center of sella turcica (sTVL). Independent samples t-test was used to compare the projections values of the groups. Results: Significantly greater projection values were acquired for Gb, Or, CB, SP, NB, A, Mx1, Md1, LLA, Pog' (p≤0.0001), B' (p≤0.001) and NT (p≤0.05) distances in UCCLP patients (using mTVL) compared to NC individuals (using TVL). On the other hand, projection values of Or, SP, NT, Mx1, ULA (p≤0.0001), A (p≤0.001), NB, A'(p≤0.001) and Gb, CB, Md1, LLA (p≤0.05) showed significant inadequacies in UCCLP patients when measurements were carried out relative to sTVL. Conclusion: This preliminary study showed that mTVL obtained by carrying the subnasale point 3 mm forward was still deficient in varying amounts depending on the severity of the midfacial retrognathism.

Characterization of Serum Carboxylesterase Knockout Mice as a Model for Organophosphorous Nerve Agent Research

Mice are low on the phylogenetic scale and consume fewer resources than other animal models, but one drawback in chemical defense research is their increased resistance to G-type organophosphorus nerve agents (OPs) relative to non-human primates and presumably humans. The protein serum carboxylesterase (sCaE) expressed by the Es-1gene is found in mice and rats, but not in primates; this protein confers increased protection against G-type OPs such as sarin (GB) and soman (GD), but not V-type OPs such as VX. Using standard mating schemes coupled with appropriate genetic and phenotypic monitoring, we are breeding mice lacking the gene Es-1 (sCaE knockout [KO] mice) and wild-type (WT) counterparts, on the C57BL/6 background. sCaE plays no known physiological role in mice, and KO and WT mice are expected to exhibit similar physiological profiles; to confirm this, we compared the overall health, blood chemistry profiles, and CBCs from mice of each background. Additionally, we performed Affymetrix gene chip analyses on multiple organs from KO and WT mice to examine gene expression levels. These data suggest that with the exception of a lack of sCaE activity in their blood, KO mice exhibit similar physiological profiles to WT mice. We have determined LD50 values of VX, GB, and GD in both KO and WT mice using the Dixon and Massey method. LD50 values of GB and GD in the KO mice are 10-20% of those in WT mice, while LD50 values for VX do not differ substantially between KO and WT mice. Bioscavenger enzymes such as BuChE can be administered to the KO mice, and provide protection against 2 X LD50 GB and GD. Together, these data support the hypothesis that sCaE KO mice are a more relevant small animal model for predicting human responses to these OPs than guinea pigs, rats, or WT mice.

Effect of the irreversible A+B →C reaction on the onset and the growth of the buoyancy-driven instability in a porous medium

The effect of irreversible A+B→C reaction on the growth of a buoyancy-driven instability is analyzed theoretically. For the limiting cases of infinitely fast and infinitely slow reaction, new linear stability equations are derived without the quasi-steady state assumption (QSSA) and solved analytically and numerically. The main parameters to explain the present system are the Damköhler number and the dimensionless density difference of chemical species. The present initial growth rate analysis without QSSA shows that the system is initially unconditionally stable regardless of the parameter values of GA, GB and GC, however the previous initial growth rate analysis based on the QSSA predicted the system is unstable if GA>GB (Hejazi and Azaiez, 2012). For time evolving cases, the present growth rates obtained from the spectral analysis and pseudo-spectral method support each other, but quite different from that obtained under the conventional QSSA. Chemical reaction can induce the fingering instability in the physically stable system, and accelerate the growth of instabilities in the physically unstable ones. According to the present analysis without QSSA, even for the physically unstable system,GA>GB, there exists a critical time below which the system is unconditionally stable and therefore, convective motions cannot be expected. Linear stability analysis is confirmed by the nonlinear direct numerical simulations.

Correlative Study of Gall Bladder with Liver in South Indian Cadavers

78 non-pathological Gall Bladders and Livers were studied morphometrically. The length and breadth of GB was compared with that of the respective liver. The measurements were taken by measuring Tape. Morphologically Normal (Pyriform) GBs were 53.2%, cylindrical 11.4%, oval shaped 11.4%, partially intra hepatic 5.1%, intra hepatic 3.8%, hour glass 6.3%, phrygian cap 3.8%, double GB 1.3%, left sided 2.5%. Metrically length and breadth of GB was highly significant (p<0.01). Correlative coefficient values between length of GB and length of Liver was +0.356 and p value was highly significant (p<0.01). Similarly breadth of GB and breadth of Liver correlative coefficient was +0.242 and p value was significant (p<0.05). By these values of GB we can explore the length and breadth of liver. Hence physiological liver can be differentiated from pathological liver (hepatomegaly) especially during the liver transplantation. This study will certainly help anatomists, anthropologists and medico legal experts to compare the south Indian GB and Liver with that of other parts of the country and abroad. Moreover to radiologists and laparoscopic surgeons during cholecystectomy and liver transplantation.

Gas-phase basicity of several common MALDI matrices measured by a simple experimental approach

We present a combined experimental and theoretical study to determine the gas-phase basicity of several relatively small organic molecules that are used as matrices in MALDI: alpha-cyano-4-hydroxycynnamic acid (αCHCA), ferulic acid (FA), 3-hydroxypicolinic acid (HPA), sinapinic acid (SA), and 2,4,6-trihydroxyacetophenone (THAP). Our simple and fast experimental approach utilizes the ability of an electrosonic spray ionization (ESSI) source to produce high densities of gas-phase ions at ambient conditions, so that their gas-phase thermochemical properties can be probed in a bracketing-like experiment at atmospheric pressure, with no need for high vacuum. The reaction between the analyte and reference bases is monitored by a commercial mass spectrometer. We determined the following GB values of the MALDI matrices studied: 908.1 ± 0.8 (αCHCA), 863.8 ± 8.0 (FA), 876.3 ± 10.2 (HPA), 867.4 ± 1.4 (SA), and 864.2 ± 7.6 (THAP) kJ mol−1. A good agreement between the experimentally measured and computationally predicted (DFT-B3LYP, G4MP2) gas-phase basicities for the studied compounds is found, except for αCHCA for which the calculations resulted in approximately 80 kJ mol−1 lower GB. We attribute the observed discrepancy between the measured and calculated values to a gas-phase rearrangement of αCHCA into a heterocyclic aromatic isomer, 7-hydroxyquinoline-3-carboxylic acid (HQA). HQA is thermodynamically more stable and features higher GB than that of αCHCA (calculated at approximately 920 kJ mol−1). The gas-phase basicity values of THAP and HPA are reported for the first time.

Short‐time estimation of biogas and methane potentials from municipal solid wastes

AbstractBiogas (GB) and methane (BMP) potentials are important parameters for the energy potential of the anaerobic digestion of municipal solid wastes (MSW) and to design full‐scale facilities. However, no standard protocol has been defined for this measure. Several samples of mixed MSW and the source‐selected organic fraction of municipal solid waste (OFMSW) obtained at different stages of their mechanical‐biological treatment were analyzed. GB and BMP values obtained at different times were correlated. Biogas potentials calculated at 3, 4, 5, 6, 7, 14, 21, 50 and 100 days correlated well for the OFMSW samples. In the case of the MSW samples, only GB values obtained at times of 14 or more days correlated well with the ultimate biogas production (considered at 100 days). The biogas potential analyzed at 21 days (as proposed in some standard methods) accounted for 77% of the total biogas potential in OFMSW samples and for 71% in the MSW samples. These results are useful for the correct design and operation of anaerobic digestion plants in terms of retention time estimation and expected biogas and methane production. Copyright © 2011 Society of Chemical Industry

Additivity of substituent effects on the proton affinity and gas-phase basicity of pyridines

The change in the proton affinity (PA) and basicity (GB) of pyridine with substituents have been considered by quantum mechanical methods at the B3LYP/6-311++G(d,p) level of theory. The PA and GB values increase by the electron-donating substituents and decrease by the electron-withdrawing substituents. The effects of substituents on the PA and GB are approximately additive. The deviations of changes that are predicted from the additivity of substituent effects are generally lower than 30% from the calculated changes. Linear relationships are observed between the calculated PA values of substituted pyridines and the topological properties of electron density, the molecular electrostatic potentials (MEP), and the N–H bond lengths. In addition, well-defined relations are established between the calculated PA values and the Hammett constants, and the reaction constant ( ρ) has been calculated for the protonation reaction. With some exceptions, the effect of substituents are also additive on the electron density and its Laplacian calculated at N–H BCP, and the MEP values calculated around the N atom.