Single stage purification of flax,hemp, and milkweed stem and their physical and morphological properties

Agriculture biomass is an alternative possible solution for the extraction of cellulose, compared to the classical soft and hard wood. However, the valorization of cellulose is challenging for the researchers as it involves multiple steps. In the present study, the raw fibers of flax, hemp, and milkweed stem fibers were purified in single step using hydrogen peroxide in water. By this method authors successfully extracted the purified cellulose fibers without damaging the fiber length. The purified fibers were characterized to understand the thermal, functional, crystalline, and morphological properties by thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The FTIR results showed the effective removal of lignin and significant improvement in thermal stability was observed by TGA. Evidently, the SEM results showed significant improvement in the morphology compared to that of the raw fibers. XRD results showed that the treatment does not affect the crystallinity of the fibers.     

Methode calorimetrique de mesure des enthalpies de formation des alliages liquides a forte tension de vapeur

The heat effects corresponding to the dissolution of solid PbSe in liquid Pb-Se alloys starting from pure Pb were measured with a direct reaction calorimeter. The partial enthalpy of formation of PbSe in the melt and the integral enthalpy of formation of the Pb-PbSe system in the liquid state referred the liquid Pb and PbSe were deduced. Then, from a very simple change of reference state, and in the knowledge of the enthalpy of PbSe, the integral enthalpy of formation of Pb-Se liquid alloys with reference to pure liquid components could be derived. The results agreed very well with those obtained previously on the dissolution of Se in Pb. The method used can be applied whenever the component to be added to the bath has a high vapor pressure.

---

Zusammenfassung Die bei der Überführung von festem PbSe in flüssige Pb-Se-Legierungen auftretenden Wärmeeffekte wurden mittels direkter Reaktionskalorimetrie bestimmt. Die auf flüssiges Pb und PbSe bezogene partielle Bildungsenthalpie des Pb-PbSe-Systems im flüssigen Zustand wurde ermittelt. Durch eine geringfügige Veränderung des Referenzzustandes konnte bei Kenntnis der Enthalpie von PbSe die integrale Bildungsenthalpie von flüssigen Pb-Se-Legierungen in Bezug auf die reinen Komponenten abgeleitet werden. Die Ergebnisse stimmen gut mit denen überein, die früher für die Auflösung von Se in Pb erhalten wurden. Die Methode ist anwendbar, wenn dem Bade zuzugebende Komponenten einen hohen Dampfdruck haben.

---

Pb-Se Pb-Se, . Pb-Se Pb-PbSe Pb Pb-Se. PbSe, Pb-Se . , . , .

     

Molecular dynamics effects on luminescence properties of oligothiophene derivatives: a molecular mechanics-response theory study based on the CHARMM force field and density functional theory

CHARMM force field parameter values for a class of oligothiophene derivatives have been derived with reference to density functional theory/B3LYP potential energy surfaces. The force field parametrization of these luminescent conjugated polyelectrolytes includes the electronic ground state as well as the strongly light absorbing first excited state. In conjunction with quantum chemical response theory calculations of transition state properties, a molecular dynamical model of the Stokes shift is obtained. The theoretical model is benchmarked against experimental data recorded at room temperature which refer to sodium salts of p-HTAA and p-FTAA with distilled water as a solvent. For p-HTAA the theoretically predicted Stokes shift of 112 nm is in good agreement with the experimental result of 124 nm, given the approximations about exciton localization that were introduced to obtain a force field for the excited state.     

Electrochemical reduction of oxygen catalyzed by a wide range of bacteria including Gram-positive

Most bacteria known to be electrochemically active have been harvested in the anodic compartments of microbial fuel cells (MFCs) and are able to use electrodes as electron acceptors. The reverse phenomenon, i.e. using solid electrodes as electron donors, is not so widely studied. To our knowledge, most of the electrochemically active bacteria are Gram-negative. The present study implements a transitory electrochemical technique (cyclic voltammetry) to study the microbial catalysis of the electrochemical reduction of oxygen. It is demonstrated that a wide range of aerobic and facultative anaerobic bacteria are able to catalyze oxygen reduction. Among these electroactive bacteria, several were Gram-positive. The transfer of electrons was direct since no activity was obtained with the filtrate. These findings, showing a widespread property among bacteria including Gram-positive ones, open new and interesting routes in the field of electroactive bacteria research.     

Very general formation of tetrahydropterin cation radicals during reaction of iron porphyrins with tetrahydropterins: model for the corresponding NO-synthase reaction

Electron transfer from tetrahydropterins to iron porphyrins, with formation of intermediate tetrahydropterin cation radicals, is a very general reaction that was shown to occur not only with tetrahydrobiopterin, as originally found in NO-synthases, but also with another important biological cofactor, tetrahydrofolate, and various iron porphyrins, either in their ferric state, or in the Fe(II)O(2) state, as in the first model of the corresponding NO-synthase reaction described in this paper.     

Mechanisms of ATPases--a multi-disciplinary approach

ATPases are important molecular machines that convert the chemical energies stored in ATP to mechanical actions within the cell. ATPases are among the most abundant proteins with diverse functions involved in almost every cellular pathway. The well characterised ATPases include the various motor proteins responsible for cargo transfers, cell motilities, and muscle contractions; the protein degradation machinery - the proteasome; the ATP synthase, F-ATPase; and the chaperone systems. Other ATPases include DNA helicases and DNA replication complex; proteins responsible for protein/complex disassembly; and certain gene regulators. It is beyond the scope of this review to cover the complete range of ATPases. Instead, we will focus on a few representative ATPases, chosen based on their diverse mechanisms and properties. Furthermore, this review is by no means trying to cover comprehensively the literature for each ATPase nor the historical aspects in each field. We will focus on describing the various techniques being employed to derive the mechanisms and properties of the chosen ATPases. Among them, high and low resolution structural studies combined with biochemical assays seem to be the dominant technical advances adapted to reveal mechanisms for most of the ATPases except the bacterial sigma54 activators, whose mechanism of action is mostly derived from large amount of biochemical studies. A number of them, especially the F-ATPase and motor proteins, have been studied successfully by various single molecule and imaging techniques. We will therefore discuss them in greater details in order to describe the wide range techniques being utilised.     

A slowly relaxing rigid biradical for efficient dynamic nuclear polarization surface-enhanced NMR spectroscopy: expeditious characterization of functional group manipulation in hybrid materials

A new nitroxide-based biradical having a long electron spin-lattice relaxation time (T(1e)) has been developed as an exogenous polarization source for DNP solid-state NMR experiments. The performance of this new biradical is demonstrated on hybrid silica-based mesostructured materials impregnated with 1,1,2,2-tetrachloroethane radical containing solutions, as well as in frozen bulk solutions, yielding DNP enhancement factors (ε) of over 100 at a magnetic field of 9.4 T and sample temperatures of ~100 K. The effects of radical concentration on the DNP enhancement factors and on the overall sensitivity enhancements (Σ(?)) are reported. The relatively high DNP efficiency of the biradical is attributed to an increased T(1e), which enables more effective saturation of the electron resonance. This new biradical is shown to outperform the polarizing agents used so far in DNP surface-enhanced NMR spectroscopy of materials, yielding a 113-fold increase in overall sensitivity for silicon-29 CPMAS spectra as compared to conventional NMR experiments at room temperature. This results in a reduction in experimental times by a factor >12,700, making the acquisition of (13)C and (15)N one- and two-dimensional NMR spectra at natural isotopic abundance rapid (hours). It has been used here to monitor a series of chemical reactions carried out on the surface functionalities of a hybrid organic-silica material.     

Concentration landscape generators for shear free dynamic chemical stimulation

In this paper we first introduce a novel fabrication process, which allows for easy integration of thin track-etched nanoporous membranes, within 2D or 3D microchannel networks. In these networks, soluble chemical compounds can diffuse out of the channels through well-defined and spatially organized microfabricated porous openings. Interestingly, multiple micron-scale porous areas can be integrated in the same device and each of these areas can be connected to a different microfluidic channel and reservoir. We then present and characterize several membrane-based microdevices and their use for the generation of stable diffusible concentration gradients and complex dynamic chemical landscapes under shear free conditions. We also demonstrate how a simple flow-focusing geometry can be used to generate "on-demand" concentration profiles. In turn, these devices should provide an ideal experimental framework for high throughput cell-based assays: long term high-resolution video microscopy experiments can be performed, under multiple spatially and temporally controlled chemical conditions, with simple protocols and in a cell-friendly environment.