Formic Acid as a Potential Pretreatment Agent for the Conversion of Sugarcane Bagasse to Bioethanol

In recent years, growing attention has been focused on the use of lignocellulosic biomass as a feedstock for the production of ethanol, a possible renewable alternative to fossil fuels. Several pretreatment processes have been developed for decreasing the biomass recalcitrance, but only a few of them seem to be promising. In this study, effect of various organic solvents and organic acids on the pretreatment of sugarcane bagasse was studied. Among the different organic acids and organic solvents tested, formic acid was found to be effective. Optimization of process parameters for formic acid pretreatment was carried out. The structural changes before and after pretreatment was investigated by scanning electron microscopy, X-ray diffraction (XRD), and Fourier transform infrared (FTIR) analysis. The X-ray diffraction profile showed that the degree of crystallinity was more for pretreated biomass than that of untreated. The FTIR spectra shown at the stretching of hydrogen bonds of pretreated sugarcane bagasse arose at higher number. It also revealed that the cellulose content in the solid residue increased because the hemicelluloses fraction in raw materials was released by acid hydrolytic reaction.     

Synthesis,Characterization, and Antibacterial Studies of Oxovanadium(IV) Complexes with Thiazole-Derived Schiff Bases

Oxovanadium(IV) complexes of Schiff bases, derived from 2-amino-4-phenyl thiazole/substituted 2-amino-4-phenyl thiazoles and thiophene-2-aldehyde have been synthesized and characterized on the basis of elemental analysis, molar conductance measurements, magnetic susceptibility data, and UV-visible, and IR spectral studies. All the complexes are monomeric possessing a 1:2 (metal:ligand) stoichiometry. On the basis of these data, a square pyramidal geometry has been assigned for the complexes. A few complexes have been subjected to thermal decomposition studies. The ligands and their metal complexes have been screened for their antibacterial activities.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

An Efficient Synthesis of [(Tosylamino)alkyl]naphthalenols by Nucleophilic Addition of Naphthalen‐2‐ol with N‐Tosyl Imines Using Boron Trifluoride Etherate as Catalyst

[(Tosylamino)alkyl]naphthalenols have efficiently been synthesized by nucleophilic addition of naphthalen‐2‐ol with N‐tosyl imines (derived from both aromatic and aliphatic aldehydes) in the presence of BF₃?OEt₂ as a catalyst at room temperature. The products are formed within 5–9 h in high yields (72–91%).     

A Linear Hybridization of Dai-Yuan and Hestenes-Stiefel Conjugate Gradient Method for Unconstrained Optimization

Conjugate gradient methods are interesting iterative methods that solve large scale unconstrained optimization problems. A lot of recent research has thus focussed on developing a number of conjugate gradient methods that are more effective. In this paper, we propose another hybrid conjugate gradient method as a linear combination of Dai-Yuan (DY) method and the Hestenes-Stiefel (HS) method. The sufficient descent condition and the global convergence of this method are established using the generalized Wolfe line search conditions. Compared to the other conjugate gradient methods, the proposed method gives good numerical results and is effective.     

Stability of superparamagnetic iron oxide nanoparticles at different pH values: experimental and theoretical analysis

The detection of superparamagnetic nanoparticles using NMR logging has the potential to provide enhanced contrast in oil reservoir rock formations. The stability of the nanoparticles is critical because the NMR relaxivity (R(2) ≡ 1/T(2)) is dependent on the particle size. Here we use a molecular theory to predict and validate experimentally the stability of citric acid-coated/PEGylated iron oxide nanoparticles under different pH conditions (pH 5, 7, 9, 11). The predicted value for the critical surface coverage required to produce a steric barrier of 5k(B)T for PEGylated nanoparticles (MW 2000) was 0.078 nm(-2), which is less than the experimental value of 0.143 nm(-2), implying that the nanoparticles should be stable at all pH values. Dynamic light scattering (DLS) measurements showed that the effective diameter did not increase at pH 7 or 9 after 30 days but increased at pH 11. The shifts in NMR relaxivity (from R(2) data) at 2 MHz agreed well with the changes in hydrodynamic diameter obtained from DLS data, indicating that the aggregation behavior of the nanoparticles can be easily and quantitatively detected by NMR. The unexpected aggregation at pH 11 is due to the desorption of the surface coating (citric acid or PEG) from the nanoparticle surface not accounted for in the theory. This study shows that the stability of the nanoparticles can be predicted by the theory and detected by NMR quantitatively, which suggests the nanoparticles to be a possible oil-field nanosensor.     

Rietveld refinement and impedance spectroscopy of calcium titanate

Single phase perovskite CaTiO₃ has been synthesized by conventional solid state reaction technique. The ceramic was characterized by XRD at room temperature and its Rietveld refinement inferred orthorhombic crystal structure with the space group Pbnm. The field dependence of dielectric relaxation and conductivity was measured over a wide frequency range from room temperature to 673 K. Analysis of Nyquist plots of CaTiO₃ revealed the contribution of many electrically active regions corresponding to bulk mechanism, distribution of grain boundaries and electrode processes. The dc conductivity depicted a semiconductor to metal type transition. Frequency dependence of dielectric constant (ε′) and tangent loss (tan δ) show a dispersive behavior at low frequencies and is explained on basis of Maxwell-Wagner model and Koop's theory. Both conductivity and electric modulus formalisms have been employed to study the relaxation dynamics of charge carriers. The variation of ac conductivity with frequency at different temperatures obeys the universal Jonscher's power law (σ_ac α ω^s). The values of exponent ‘s’ lie in the range 0.13 ≤ s ≤ 0.33, which in light of CBH model suggest a large polaron hopping type of conduction mechanism.     

A facile three-component reaction of dicarbomethoxycarbene, aldehydes and o-quinones: synthesis of novel spiro-dioxolanes

Successful trapping of the carbonyl ylides generated from dicarbomethoxycarbene and aldehydes with 1,2-diones is described.     

Polarographic determination of lead in drinking water samples of Western U.P. districts with 3-hydroxypyridine-2-thiol

The polarographic determination of lead in presence of 3-hydroxypyridine-2-thiol (HPT) has been investigated. The method was applied to the determination of the lead concentration in drinking water samples from Western U.P. (Province) of India.     

Synthesis and magneto-spectral investigations of some six and nine coordinated complexes of lanthanides(III) derived from 4[N-(2′-hydroxy-1′-naphthalidene) amino]antipyrinethiosemicarbazone

The present work describes the synthesis and characterization of some six and nine coordinated complexes of trivalent lanthanide(III) with 4[N-(2′-hydroxy-1′-naphthalidene)amino]antipyrinethiosemicarbazone (HNAAPTS). All the complexes have the general composition LnX₃.n(HNAAPTS) (X = NO₃ ^?, n = 1; X = NCS^? or ClO₄ ^?, n = 2). The complexes were characterized through elemental analyses, molar mass, conductivity measurements, magnetic susceptibilities, and infrared and electronic spectra. Infrared spectra revealed that HNAAPTS acts as a neutral tridentate (N,N,S) donor. The coordination number in these complexes is either six or nine depending on the nature of the anionic ligand.