On detection of linear and nonlinear optimization problems

Automatic classification of optimization problems as linear or nonlinear is now being demanded in some modeling and optimization systems to make such systems more user friendly. This requires that the system examine the model and make such determination. On such method of analysis is discussed in this paper.     

Electrochemical sensor for H2O2 using a glassy carbon electrode modified with a nanocomposite consisting of graphene oxide,cobalt(III) oxide,horseradish peroxidase and nafion

Microchimica Acta - The authors describe the synthesis of a nanocomposite consisting of graphene oxide, cobalt(III) oxide and horseradish peroxidase (HRP/GO-Co3O4) in a nafion matrix. The...     

α-Helix-Mimetic Foldamers for Targeting HIV-1 TAR RNA

An oligopyridylamide-based foldamer approach has been employed to target HIV TAR RNA-TAT assembly as a model system to study RNA-protein interactions. The oligopyridylamide scaffold adopts a constrained conformation which presents surface functionalities at distinct spatial locations and mimic the chemical features of the secondary structure of proteins. We have designed a library of oligopyridylamides containing diverse surface functionalities which mimic the side chain residues of the TAT protein domain. The interaction of TAR RNA and TAT plays a pivotal role in facilitating HIV replication. The library was screened using various fluorescent based assays to identify antagonists of the TAR RNA-TAT complex. A tricationic oligopyridylamide ADH-19, possessed the highest affinity towards TAR and efficiently inhibited the TAR RNA-TAT interaction with apparent K_d of 4.1±1.0 μm . Spectroscopic studies demonstrated that ADH-19 interacts with the bulge and the lower bulge regions of TAR RNA, the domains important for TAT interaction. ADH-19 demonstrated appreciable in vivo efficacy (IC₅₀=25±1 μm ) by rescuing TZM-bl cells infected with the pseudovirus HIV-1HXB-2.     

Ring-opening reactions of oxetanes: A review of methodology development and synthetic applications

Ring-opening reactions of oxetanes yield important functionalized products depending upon the nature of nucleophiles as well as substitution pattern on the oxetane ring. Ring opening of oxetanes can be carried out under a variety of reaction conditions. In this review article, an up-to-date overview of major synthetic methodologies involved in the ring opening of oxetanes as well as their synthetic applications has been presented.     

Electrochemical Mechanisms in Potentiometric Phosphate Sensing Using Pure Cobalt,Molybdenum and their Alloy for Environmental Applications

Phosphorus (P) is ubiquitous in the environment, but its measurement is costly and time-consuming. Sensor-based measurement shows potential, but selection of right metal remains the major challenge due to strong P species dependence on pH. This study examined the feasibility of pure cobalt, molybdenum, and their electrodeposited alloy, Co₆₃Mo₄₂ (wt %), as phosphate sensors. The cobalt, molybdenum and alloy exhibited mixed potential, Nernst potential, and oxidation-reduction (red-ox) mechanisms, respectively. Alloy showed good selectivity over a wide pH range, but high limit of detection and long response time (8–14 minutes). Yet, alloy provides a new opportunity for improving electrochemical phosphate sensors.     

An all optical method of implementing a wavelength encoded simultaneous binary full adder-full subtractor unit exploiting nonlinear polarization rotation in semiconductor optical amplifier

Full adders and full subtractors are the basic circuit elements of any digital data processor in electronics as well as in the all optical domain. Again the wavelength dependent encoding/decoding techniques have established itself as a very promising and efficient tool having some inherent and unique advantages relative to the other well known intensity or polarization or phase dependent optical data encoding mechanisms. In this communication, the authors therefore propose a new scheme of implementing a wavelength encoded complete binary full adder-full subtractor unit in the all optical domain using the wavelength conversion by the nonlinear polarization rotation in a single semiconductor optical amplifier. The interacting signals are counter propagating in the semiconductor optical amplifier and hence can be set at the same wavelength. To realize the binary logic wavelength dependent encoding/decoding mechanism is exploited in our proposed scheme of full adder-full subtractor unit. Also the optical add/drop multiplexing employing the special filtering property of the semiconductor optical amplifier is utilized for the designing of the all optical system.     

Injectable hydrogels for targeted delivering of therapeutic molecules for tissue engineering and disease treatment

Hydrogels are cross‐linked three‐dimensional polymeric networks that play a vital role in solving the pharmacological and clinical limitations of the existing systems due to their unique physical properties such as affinity for biological fluids, tunable porous nature, high water content, ease of preparation, flexibility, and biocompatibility. Hydrogel also mimics the living natural tissue, which opens several opportunities for its use in biomedical areas. Injectable hydrogel allows temporal control and exceptional spatial arrangements and can offset hitches with established hydrogel‐based drug delivery systems. Here, we review the recent development of injectable hydrogels and their significance in the delivery of therapeutics such as cells, genes, and drug molecules and how these innovatory systems can complement the current delivery systems.     

Micellar Effect on the Reaction of Chromium(VI) Oxidation of L‐Sorbose in the Presence and Absence of Picolinic Acid in Aqueous Acid Media: A Kinetic Study

The kinetics and mechanism of chromic acid oxidation of L‐sorbose in the presence and absence of picolinic acid (PA) have been studied under the conditions, [L‐sorbose]_T » [PA]_T » [Cr(VI)]_T, at different temperatures. In the absence of PA, the monomeric chromic acid undergoes esterification with the substrate followed by the acid catalysed redox decomposition of the Cr(VI)‐substrate ester through glycol splitting to formaldehyde and the lactone of C₅‐aldonic acid and Cr(IV) which subsequently participates in the faster reactions. In the presence of PA, the Cr(VI)‐PA complex produced in a pre‐equilibrium step experiences a nucleophilic attack by the substrate to produce a ternary complex which decomposes through glycol splitting giving rise to the organic products and Cr(IV)‐PA complex. Both the uncatalysed and PA‐catalysed paths show the first‐order dependence on [L‐sorbose]_T and [Cr(VI)]_T. The PA‐catalysed path is first‐order in [PA]_T and it shows a fractional order in [H⁺]. The uncatalysed path shows a second‐order dependence on [H⁺]. In the presence of the surfactants like N‐cetylpyridinium chloride (CPC, a cationic surfactant) and sodium dodecyl sulfate (SDS, an anionic sulfate), the reaction orders remain unchanged. CPC has been found to inhibit both the uncatalysed and PA‐catalysed paths while SDS shows the rate accelerating effect for both the uncatalysed and PA‐catalysed paths. The observed micellar effects have been rationalised by considering the distribution of the reactants between the micellar and aqueous phases in terms of the proposed reaction mechanism.     

Studies on kinetics and mechanism of oxidation of D‐sorbitol and D‐mannitol by cerium(IV) in aqueous micellar sulfuric acid media

The kinetics and mechanism of cerium(IV) oxidation of hexitols, i.e. D ‐sorbitol and D ‐mannitol, in aqueous sulfuric acid media have been studied in the presence and absence of surfactants. Under the kinetic conditions, [S]_T ? [Ce(IV)]_T, where [S]_T is the total substrate (D ‐sorbitol or D ‐mannitol) concentration, the overall process shows a first‐order dependence on [Ce(IV)]_T and [S]_T. The process is acid catalyzed and inhibited by [HSO]. From the [HSO] dependence, it has been noted that the both Ce(SO₄)²⁺ and Ce(SO₄)₂ have been found kinetically active. The different rate constants in the presence and absence of surfactants have been estimated with the activation parameters. N‐cetylpyridinium chloride has been found to retard the oxidation process of hexitols, whereas sodium dodecyl sulfate has been found to accelerate the rate process. All these findings including the micellar effects have been interpreted in terms of the proposed reaction mechanism and partitioning behavior of the kinetically active different species of Ce(IV) between the aqueous and pseudomicellar phase. © 2008 Wiley Periodicals, Inc. 40: 445–453, 2008     

Mesoporous Porphyrin-Silica Nanocomposite as Solid Acid Catalyst for High Yield Synthesis of HMF in Water

Solid acid catalysts occupy a special class in heterogeneous catalysis for their efficiency in eco-friendly conversion of biomass into demanding chemicals. We synthesized porphyrin containing porous organic polymers (PorPOPs) using colloidal silica as a support. Post-modification with chlorosulfonic acid enabled sulfonic acid functionalization, and the resulting material (PorPOPS) showed excellent activity and durability for the conversion of fructose to 5-hydroxymethyl furfural (HMF) in green solvent water. PorPOPS composite was characterized by N₂ sorption, FTIR, TGA, CHNS, FESEM, TEM and XPS techniques, justifying the successful synthesis of organic networks and the grafting of sulfonic acid sites (5 wt%). Furthermore, a high surface area (260 m²/g) and the presence of distinct mesopores of ~15 nm were distinctly different from the porphyrin containing sulfonated porous organic polymer (FePOP-1S). Surprisingly the hybrid PorPOPS showed an excellent yield of HMF (85%) and high selectivity (>90%) in water as compared to microporous pristine-FePOP-1S (yield of HMF = 35%). This research demonstrates the requirement of organic modification on silica surfaces to tailor the activity and selectivity of the catalysts. We foresee that this research may inspire further applications of biomass conversion in water in future environmental research.