The effectiveness of the organosolv process in wheat straw delignification optimizing temperature and time reaction

Cellulose - The present study investigates the organosolv treatment of wheat straw, for the optimization of cellulose delignification, which will serve as raw material for the paper industry. The...     

Novel class of hybrid natural products derived from lupeol as antimalarial agents

Thirty-four novel hybrid lupeol derivatives (4-18) were prepared and evaluated for antimalarial activity in vitro against Plasmodium falciparum. Three compounds (13d, 16a and 17a) have shown antimalarial activity at lower dose (10 microg mL(-1)) than lupeol.     

Synthesis of unsymmetrical substituted 1,4-dihydropyridines through thermal and microwave assisted [4+2] cycloadditions of 1-azadienes and allenic esters

Thermal and microwave assisted [4+2] cycloadditions of 1,4-diaryl-1-aza-1,3-butadienes with allenic esters lead to cycloadducts, which after a 1,3-H shift afford variedly substituted unsymmetrical 2-alkyl-1,4-diaryl-3-ethoxycarbonyl-1,4-dihydropyridines in high yields. Reactions carried out under microwave irradiation are cleaner and give higher yields with much shortened reaction times. Density functional theory (DFT) at the B3LYP/6-31G* level has been used to calculate geometric features of the reactants, barrier for s-trans to s-cis and reverse isomerization of azadienes (5a-d, 10a-e), dihedral angles between N(1), C(2), C(3), and C(4) atoms of azadienes along with various indices such as chemical hardness (eta), chemical potential (micro), global electrophilicity (omega), and the difference in global electrophilicity (Deltaomega) between the reacting pairs and Fukui functions (f (+) and f(-)). The results revealed that s-trans is the predominant conformation of azadienes at ambient temperature and the barrier for conversion of the s-trans rotamer of 1-azadienes to s-cis may be the major factor influencing the chemoselectivity, i.e., [4+2] verses [2+2] cycloaddition. The regiochemistry of the observed cycloadditions is collated with the obtained local electrophilicity indices (Fukui functions). Transition states for the formation of both [4+2] and [2+2] cycloadducts as located at the PM3 level indicate that the transition state for the formation of [4+2] cycloadducts has lower energy, again supporting the earlier conclusion that preferred formation of [4+2] cycloaaducts at higher temperature may be a consequence of barrier for s-trans to s-cis transformation of 1-azadienes.     

Moment expansion analysis for time-domain asymptotics

We apply our recently developed distributional technique [2, 3] to study time-domain asymptotics. This enables us to present a rigorous mathematical discussion and extensions of the results given by Chapman [1] and subsequent workers in this field. The present analysis is facilitated by defining functions which are distributionally small at infinity. We find that one of the advantages of using this technique is that multidimensional extensions can be derived very easily. © 1998 B. G. Teubner Stuttgart–John Wiley & Sons Ltd.     

A Critical Review on Pulsed Electric Field: A Novel Technology for the Extraction of Phytoconstituents

Different parts of a plant (seeds, fruits, flower, leaves, stem, and roots) contain numerous biologically active compounds called “phytoconstituents” that consist of phenolics, minerals, amino acids, and vitamins. The conventional techniques applied to extract these phytoconstituents have several drawbacks including poor performance, low yields, more solvent use, long processing time, and thermally degrading by-products. In contrast, modern and advanced extraction nonthermal technologies such as pulsed electric field (PEF) assist in easier and efficient identification, characterization, and analysis of bioactive ingredients. Other advantages of PEF include cost-efficacy, less time, and solvent consumption with improved yields. This review covers the applications of PEF to obtain bioactive components, essential oils, proteins, pectin, and other important materials from various parts of the plant. Numerous studies compiled in the current evaluation concluded PEF as the best solution to extract phytoconstituents used in the food and pharmaceutical industries. PEF-assisted extraction leads to a higher yield, utilizes less solvents and energy, and it saves a lot of time compared to traditional extraction methods. PEF extraction design should be safe and efficient enough to prevent the degradation of phytoconstituents and oils.     

Cosmological analysis of reconstructed $${\mathcal {F}}(T,T_{\mathcal {G}})$$ models

In this paper, we analyze cosmological consequences of the reconstructed generalized ghost pilgrim dark energy \({\mathcal {F}}(T,T_{\mathcal {G}})\) models in terms of redshift parameter z. For this purpose, we consider power-law scale factor, scale factor for two unified phases and intermediate scale factor. We discuss graphical behavior of the reconstructed models and examine their stability analysis. Also, we explore the behavior of equation of state as well as deceleration parameters and \(\omega _{\Lambda }-\omega _{\Lambda }^{'}\) as well as \(r-s\) planes. It is found that all models are stable for pilgrim dark energy parameter 2. The equation of state parameter satisfies the necessary condition for pilgrim dark energy phenomenon for all scale factors. All other cosmological parameters show great consistency with the current behavior of the universe.     

FTIR analysis of natural and synthetic collagen

Collagen is the most abundant protein in humans and animals, comprising of one third of the total proteins that accounts for three quarters of the dry weight skin in humans. Collagen containing a range of proteins has been reported for tissue engineering applications, but, only a small number of studies related to chemical structure evaluation of collagen are found in the literature. Collagen can be obtained from both the natural and synthetic sources and offers a wide range of biomedical applications due to its excellent biocompatibility and low immunogenicity. Hence, it is important to identify chemical structural properties of collagen and Fourier transform infrared (FTIR) appears to be a technique of choice to study their chemical structure. This review aims to highlight the use of FTIR to study collagen-based biomaterials, using it for characterization of collagen extracted from various sources. Characterization of collagen-based materials used in wound healing, skin substitutes, derma fillers, and aging of skin, collagen containing drug delivery agents, collagen-based materials used in tissue engineering, bone regeneration, and osteogenic differentiation is discussed in detail. FTIR analysis of collagen-containing materials used for dental applications, cleft-palate, and in alveolar-ridge preservation has also been highlighted.     

Micellar parameters of diblock copolymers and their interactions with ionic surfactants

The interactions of non-ionic amphiphilic diblock copolymer poly（oxyethylene/oxybutylene）(E₃₉B₁₈) with anionic surfactant sodium dodecyl sulphate（SDS） and cationic surfactant hexadecyltrimethylammonium bromide（CTAB） were studied by using various techniques such as surface tension,conductivity,steady-state fluorescence and dynamic light scattering.Surface tension measurements were used to determine the critical micelle concentration（CMC） and thereby the free energy of micellization(△G_mic),free energy of adsorption(△G_ads),surface excess concentration（Γ） and minimum area per molecule（A）.Conductivity measurements were used to determine the critical micelle concentration（CMC）,critical aggregation concentration（CAC）,polymer saturation point（PSP）,degree of ionization（α） and counter ion binding（β）. Dynamic light scattering experiments were performed to check the changes in physiochemical properties of the block copolymer micelles taken place due to the interactions of diblock copolymers with ionic surfactants.The ratio of the first and third vibronic peaks（I₁/I₃） indicated the polarity of the pyrene micro environment and was used for the detection of micelle as well as polymer-surfactant interactions.Aggregation number（N）,number of binding sites（n） and free energy of binding （△G_b） for pure surfactants as well as for polymer-surfactant mixed micellar systems were determined by the fluorescence quenching method.     

Quantitation of glucosamine sulfate in plasma by HPLC-MS/MS after administration of powder for oral solution formulation

A rapid method for the quantification of glucosamine in human plasma using high‐performance liquid chromatography coupled to tandem mass spectrometry was developed and validated. The sample preparation includes a simple deproteinization step, using d ‐[1‐¹³C] glucosamine hydrochloride as an internal standard. Chromatographic separation was performed on an ACE Ciano column using isocratic elution with acetonitrile and aqueous 2 mm ammonium acetate containing 0.025% formic acid (80:20). Selected reaction monitoring was performed using the transitions m/z 180.1 → m/z 72.1 and m/z 181.0 → m/z 74.6 to quantify glucosamine and internal standard, respectively. The method was validated and proved to be linear, accurate and precise over the range 50–5000 ng/mL of glucosamine. Recovery rates higher than 90% were obtained for both glucosamine and internal standard. No matrix effect was detected in the samples. The validated method was successfully applied to a pharmacokinetic study after oral administration of a powder for oral solution formulation containing glucosamine sulfate. Copyright © 2011 John Wiley & Sons, Ltd.     

Taylor expansions for distributions

We present the Taylor asymptotic expansion of a perturbed distribution of the form is a smooth function defined in ?ⁿ. First we present the one-dimensional theory to illustrate the underlying concepts and then we discuss the multi-dimensional case. We find that various known results follow as special limits of our results.