Chemical Transformations of Peat Lignin Subjected to Sonolysis in Aqueous Alkaline Media

2016 ◽  
Vol 24 (1) ◽  
Keyword(s):  
Alkaline Media ◽  
Chemical Transformations

Application of pure, thermostable, alkali-tolerant xylanase in bleaching of oxygen-delignified pine kraft pulp

TAPPI Journal ◽  
2015 ◽  
Vol 14 (11) ◽  
pp. 689-694
Author(s):  
QINGZHI MA ◽  
QI WANG ◽  
CHU WANG ◽  
NIANJIE FENG ◽  
HUAMIN ZHAI
Keyword(s):  
Intrinsic Viscosity ◽  
Chlorine Dioxide ◽  
High Purity ◽  
Kraft Pulp ◽  
Alkaline Media ◽  
Industrial Scale ◽  
Elemental Chlorine ◽  
Effect Of Oxygen ◽  
Alkaline Tolerant ◽  
Ecf Bleaching

The effect of oxygen (O2)-delignified pine kraft pulp pretreatment by high-purity, thermostable, and alkaline-tolerant xylanases on elemental chlorine free (ECF) bleaching of O2-delignification kraft pulp was studied. The study found that xylanase pretreatment preserved the intrinsic viscosity and yield of O2-delignified pulp while causing about 7% of delignification with high delignification selectivity. The xylanases with high purity, higher thermostability (75°C~80°C) in highly alkaline media (pH 8.0~9.5) could be applied on an industrial scale. Pulp pretreatment by the high-purity, thermostable, and alkaline tolerant xylanases could improve pulp brightness or reduce the chlorine dioxide (ClO2) consumption. In a D0ED1D2 bleaching sequence using the same amount of ClO2, the xylanase-pretreated pulp obtained a higher brightness (88.2% vs. 89.7% ISO) at the enzyme dose of 2 U/g pulp; or for the same brightness as control (88.2% ISO), the ClO2 dosage in the D0 stage was reduced by 27%, which represents a 16% savings in total ClO2 used for bleaching.

Enhanced catalytic activity of low-Pt content nanocatalysts supported on hollow carbon spheres for the ORR in alkaline media

MRS Advances ◽  
2020 ◽  
Vol 5 (57-58) ◽  
pp. 2961-2972
Author(s):  
P.C. Meléndez-González ◽  
E. Garza-Duran ◽  
J.C. Martínez-Loyola ◽  
P. Quintana-Owen ◽  
I.L. Alonso-Lemus ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Anion Exchange ◽  
Average Particle Size ◽  
Synthesis Method ◽  
Alkaline Media ◽  
High Catalytic Activity ◽  
Average Particle ◽  
Carbon Spheres ◽  
Hollow Carbon ◽  
Hollow Carbon Spheres

In this work, low-Pt content nanocatalysts (≈ 5 wt. %) supported on Hollow Carbon Spheres (HCS) were synthesized by two routes: i) colloidal conventional polyol, and ii) surfactant-free Bromide Anion Exchange (BAE). The nanocatalysts were labelled as Pt/HCS-P and Pt/HCS-B for polyol and BAE, respectively. The physicochemical characterization of the nanocatalysts showed that by following both methods, a good control of chemical composition was achieved, obtaining in addition well dispersed nanoparticles of less than 3 nm TEM average particle size (d) on the HCS. Pt/HCS-B contained more Pt0 species than Pt/HCS-P, an effect of the synthesis method. In addition, the structure of the HCS remains more ordered after BAE synthesis, compared to polyol. Regarding the catalytic activity for the Oxygen Reduction Reaction (ORR) in 0.5 M KOH, Pt/HCS-P and Pt/HCS-B showed a similar performance in terms of current density (j) at 0.9 V vs. RHE than the benchmark commercial 20 wt. % Pt/C. However, Pt/HCS-P and Pt/HCS-B demonstrated a 6 and 5-fold increase in mass catalytic activity compared to Pt/C, respectively. A positive effect of the high specific surface area of the HCS and its interactions with metal nanoparticles and electrolyte, which promoted the mass transfer, increased the performance of Pt/HCS-P and Pt/HCS-B. The high catalytic activity showed by Pt/HCS-B and Pt/HCS-P for the ORR, even with a low-Pt content, make them promising cathode nanocatalysts for Anion Exchange Membrane Fuel Cells (AEMFC).

BODIPY Fluorophores for Membrane Potential Imaging

2019 ◽  
Author(s):  
Jenna Franke ◽  
Benjamin Raliski ◽  
Steven Boggess ◽  
Divya Natesan ◽  
Evan Koretsky ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Water Solubility ◽  
Water Soluble ◽  
Voltage Sensitivity ◽  
Chemical Transformations ◽  
Direct Modification ◽  
Biological Compatibility ◽  
Meso Position ◽  
Ionizable Groups ◽  
Boron Center

Fluorophores based on the BODIPY scaffold are prized for their tunable excitation and emission profiles, mild syntheses, and biological compatibility. Improving the water-solubility of BODIPY dyes remains an outstanding challenge. The development of water-soluble BODIPY dyes usually involves direct modification of the BODIPY fluorophore core with ionizable groups or substitution at the boron center. While these strategies are effective for the generation of water-soluble fluorophores, they are challenging to implement when developing BODIPY-based indicators: direct modification of BODIPY core can disrupt the electronics of the dye, complicating the design of functional indicators; and substitution at the boron center often renders the resultant BODIPY incompatible with the chemical transformations required to generate fluorescent sensors. In this study, we show that BODIPYs bearing a sulfonated aromatic group at the meso position provide a general solution for water-soluble BODIPYs. We outline the route to a suite of 5 new sulfonated BODIPYs with 2,6-disubstitution patterns spanning a range of electron-donating and -withdrawing propensities. To highlight the utility of these new, sulfonated BODIPYs, we further functionalize them to access 13 new, BODIPY-based voltage-sensitive fluorophores. The most sensitive of these BODIPY VF dyes displays a 48% ΔF/F per 100 mV in mammalian cells. Two additional BODIPY VFs show good voltage sensitivity (≥24% ΔF/F) and excellent brightness in cells. These compounds can report on action potential dynamics in both mammalian neurons and human stem cell-derived cardiomyocytes. Accessing a range of substituents in the context of a water soluble BODIPY fluorophore provides opportunities to tune the electronic properties of water-soluble BODIPY dyes for functional indicators.

Strongly Coupled Redox-Linked Conformational Switching at the Active Site of the Non-Heme Iron-Dependent Dioxygenase, TauD

2019 ◽  
Author(s):  
Christopher John ◽  
Greg M. Swain ◽  
Robert P. Hausinger ◽  
Denis A. Proshlyakov
Keyword(s):  
Active Site ◽  
Structural Model ◽  
Heme Iron ◽  
Chemical Transformations ◽  
Experimental Conditions ◽  
Strongly Coupled ◽  
Non Heme Iron ◽  
Reversible Redox ◽  
Wide Range ◽  
Complex Structural

2-Oxoglutarate (2OG)-dependent dioxygenases catalyze C-H activation while performing a wide range of chemical transformations. In contrast to their heme analogues, non-heme iron centers afford greater structural flexibility with important implications for their diverse catalytic mechanisms. We characterize an <i>in situ</i> structural model of the putative transient ferric intermediate of 2OG:taurine dioxygenase (TauD) by using a combination of spectroelectrochemical and semi-empirical computational methods, demonstrating that the Fe (III/II) transition involves a substantial, fully reversible, redox-linked conformational change at the active site. This rearrangement alters the apparent redox potential of the active site between -127 mV for reduction of the ferric state and 171 mV for oxidation of the ferrous state of the 2OG-Fe-TauD complex. Structural perturbations exhibit limited sensitivity to mediator concentrations and potential pulse duration. Similar changes were observed in the Fe-TauD and taurine-2OG-Fe-TauD complexes, thus attributing the reorganization to the protein moiety rather than the cosubstrates. Redox difference infrared spectra indicate a reorganization of the protein backbone in addition to the involvement of carboxylate and histidine ligands. Quantitative modeling of the transient redox response using two alternative reaction schemes across a variety of experimental conditions strongly supports the proposal for intrinsic protein reorganization as the origin of the experimental observations.

VDM LC-NICKEL 99.2

Alloy Digest ◽  
1996 ◽  
Vol 45 (3) ◽  
Keyword(s):  
Corrosion Resistance ◽  
Physical Properties ◽  
Surface Treatment ◽  
Carbon Content ◽  
Tensile Properties ◽  
Heat Treating ◽  
Alkaline Media ◽  
Excellent Corrosion Resistance

Abstract VDM LC-Nickel 99.2 is unalloyed nickel which offers excellent corrosion resistance in many alkaline media. The metal also has good mechanical, magnetic, and magnetostrictive properties. It has a reduced carbon content to avoid graphitization at temperatures above 570 deg F (300 deg C). This datasheet provides information on composition, physical properties, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: Ni-502. Producer or source: VDM Technologies Corporation.

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