University of Arkansas

About: University of Arkansas is a education organization based out in Fayetteville, Arkansas, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 17225 authors who have published 33329 publications receiving 941102 citations. The organization is also known as: Arkansas & UA.

Understanding the high-electrocatalytic performance of two-dimensional MoS2 nanosheets and their composite materials

Abstract: Two-dimensional (2D) layered molybdenum disulfide (MoS2) materials have attracted a wide range of attention due to their unique physical and chemical properties as well as their tunable electronic structures. Nowadays, hydrogen evolution reaction (HER) in water splitting is crucial to the cost-effective production of the pure hydrogen fuel, while oxygen reduction reaction (ORR) in fuel cells has been suffering from sluggish reaction kinetics even if a high loading of platinum is applied. In this context, it is of great urgency to develop new catalysts comparable to traditional noble metal catalysts in electrocatalytic activity but composed of earth-abundant elements. In the past decade, 2D layered MoS2-based materials have demonstrated great potential as non-noble metal catalysts for both HER and ORR to meet the two aforementioned requirements. To this end, we conduct this survey aimed at summarizing the recent efforts in addressing electrocatalytic issues involved in HER and ORR activities using 2D MoS2 materials. Starting from an introduction on the superiorities of MoS2-based electrocatalysts for HER and ORR in this review, we then discuss the critical obstacles faced by MoS2 nanosheets with respect to their catalytic activities. Subsequently, we summarize the recent strategies for improving the catalytic activity of MoS2-based materials and the updated advances. In the end, we suggest potential pathways for high-catalytic performance comparable to those of their noble-metal counterparts and give some perspectives on practical applications of MoS2-based materials in the future. The insightful views from this review are believed to be greatly beneficial for accomplishing a better understanding on 2D layered MoS2-based material catalysts in electrocatalytic activities.

Carcinogen substrate specificity of human COX-1 and COX-2.

Abstract: The activation of carcinogenic aromatic and heterocyclic amines and benzo[a]pyrene-7,8-diol to intracellular electrophiles by prostaglandin H synthase (COX) is well documented for ovine sources of this enzyme. Here, the arachidonic acid-dependent activation of substrates by human (h)COX-1 and-2 is examined, utilizing recombinant enzymes. The COX-dependent activation of benzidine (BZ), 4-aminobiphenyl, (+)benzo[a]pyrene-7,8-diol, (+)benzo[a]pyrene-7,8-diol, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3-methylimidazo [4,5-f]quinoline (IQ), 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP), and 4,4'-methylenebis(2-chloroaniline) (MOCA) is assessed by means of COX-catalyzed, covalent DNA binding. The hCOX isozymes activated all substrates tested, activation varied from barely detectable for IQ (0.76 and 1.52 pmol bound/mg DNA for COX-1 and -2, respectively) to a high of 65 and 117 pmol bound/mg DNA for COX-1 and -2, respectively, for the activation of MOCA. BZ, which is an excellent peroxidase substrate, did not exhibit high DNA binding levels in hCOX assays and this phenomenon was found to be due to high levels of binding to protein, which effectively competed with the DNA for binding in the assay. The demonstrated ability of the COX enzymes to activate a variety of environmental and dietary carcinogens indicates a potential role for COX in the activation pathway of aromatic and heterocyclic amines and polycyclic hydrocarbons at extra-hepatic sites during early or late stages of carcinogenesis.

Subcritical Water and Sulfured Water Extraction of Anthocyanins and Other Phenolics from Dried Red Grape Skin

Abstract: Water, an inexpensive and environmentally friendly solvent is an ideal solvent for industrial extraction of phenolics, but its use is limited due to poor extraction efficiency at low temperatures. In this study, subcritical water (SW) and subcritical sulfured water (SSW) (containing 1400 μg/mL sodium metabisulfite) extractions of grape skin phenolics were conducted over the temperature range of 100 to 160°C in 10°C increments for a short time (40 s), and compared with conventional hot water or aqueous 60% (v/v) methanol extractions (50°C, 1 h). The composition and contents of anthocyanins, flavonols, hydroxycinnamates, phenolic acids, and antioxidant capacities (Oxygen Radical Absorbing Capacity [ORAC]) in the extracts were determined. Increasing SW extraction temperature from 100 to 160°C resulted in a linear increase in ORAC values, but extraction temperatures > 110°C resulted in decreased contents of individual and total anthocyanins. Subcritical sulfured water extracts had higher levels of total anthocyanins and total phenolics than SW extracts. The SW and SSW extracts had comparable or higher levels of anthocyanins and ORAC values than extracts obtained using conventional hot water or 60% methanol. Subcritical water at 100 to 110°C appears to be an excellent alternative to organic solvents to extract anthocyanins and other phenolics from dried red grape skin and possibly other grape processing byproducts.

Extended performance GeSn/Si(100) p-i-n photodetectors for full spectral range telecommunication applications

Abstract: First-generation n-i-GeSn/p-Si(100) photodiode detectors with Ge0.98Sn0.02 active layers were fabricated under complementary metal oxide semiconductor compatible conditions. It is found that, even at this low Sn concentration, the detector quantum efficiencies are higher than those in comparable pure-Ge device designs processed at low temperature. Most significantly, the spectral range of the GeSn device responsivity is dramatically increased—to at least 1750 nm—well beyond the direct band gap of Ge (1550 nm). This allows coverage of all telecommunication bands using entirely group IV materials.