Theoretical study of the ammonia nitridation rate on an Fe (100) surface: A combined density functional theory and kinetic Monte Carlo study

Ammonia (NH[subscript 3]) nitridation on an Fe surface was studied by combining density functional theory (DFT) and kinetic Monte Carlo (kMC) calculations. A DFT calculation was performed to obtain the energy barriers (E[subscript b]) of the relevant elementary processes. The full mechanism of the exact reaction path was divided into five steps (adsorption, dissociation, surface migration, penetration, and diffusion) on an Fe (100) surface pre-covered with nitrogen. The energy barrier (E[subscript b]) depended on the N surface coverage. The DFT results were subsequently employed as a database for the kMC simulations. We then evaluated the NH[subscript 3] nitridation rate on the N pre-covered Fe surface. To determine the conditions necessary for a rapid NH[subscript 3] nitridation rate, the eight reaction events were considered in the kMC simulations: adsorption, desorption, dissociation, reverse dissociation, surface migration, penetration, reverse penetration, and diffusion. This study provides a real-time-scale simulation of NH[subscript 3] nitridation influenced by nitrogen surface coverage that allowed us to theoretically determine a nitrogen coverage (0.56 ML) suitable for rapid NH[subscript 3] nitridation. In this way, we were able to reveal the coverage dependence of the nitridation reaction using the combined DFT and kMC simulations.Korea (South). Ministry of Education, Science and Technology (MEST) (National Research Foundation of Korea. 2011-0028612

Wolff-Parkinson-White syndrome in young people, from childhood to young adulthood: relationships between age and clinical and electrophysiological findings

PurposeThe aim of the present study was to evaluate the characteristics of electrophysiologic studies (EPS) and radiofrequency ablation (RFA) performed in subjects aged less than 30 years with Wolff-Parkinson-White (WPW) syndrome, particularly pediatric patients under 18 years of age, based on our experience.MethodsTwo hundred and one consecutive patients with WPW syndrome were recruited and divided to 3 groups according to age: group 1, 6 to 17 years; group 2, 18 to 29 years; and group 3, 30 to 60 years. The clinical, electrophysiological, and therapeutic data for these patients were evaluated by a retrospective medical record review.ResultsA total of 73 (36%) of these patients were <30 years of age. Although there were more males than females in group 2 (male:female, 31:11), there was no sex difference in group 1 (male:female, 16:15). Left accessory pathway was detected less frequently in group 1 (32%, 10/31) than in group 2 (57%, 24/42) and group 3 (63%, 81/128) (P=0.023 and P=0.002, respectively).ConclusionThe present study describes several different electrophysiological characteristics in children and adolescents with WPW syndrome. Therefore, when EPS and RFA are performed in children and adolescence with WPW syndrome, we recommend that these characteristics be considered

Electronic Structural Origin of the Catalytic Activity Trend of Transition Metals for Electrochemical Nitrogen Reduction

As an alternative to the conventional Haber–Bosch process for NH₃ synthesis that operates under harsh conditions, an electrochemical process has recently been pursued. Here, using a joint experiment–density functional calculation approach, we determine the activity trend of four transition metals (TMs) (Fe, Ru, Rh, and Pd) for N₂ reduction to NH₃: Fe > Ru > Pd > Rh, where the protonation step of *N₂ to form *N₂H (* indicates surface sites) is a potential determining step (PDS). The activity trend of the electrocatalysts is determined by the ability of the adsorbate (*N₂) over the catalyst surfaces to easily obtain electrons at the PDS with an assumption of a scaling relationship between the activation energy barrier and the free energy difference. In electronic structures, the ability can be estimated by the energy difference between the lowest unoccupied molecular orbital (LUMO) of the adsorbed N₂ on the TM surfaces and the fermi energy (E_F). For early TMs (e.g., Sc and Ti) where the PDS is *NH protonation reaction to form *NH₂, the activity of the TMs can be similarly explained with an electronic structural feature that is the energy difference between the LUMO of the *NH and the E_F. Based on the origin, we additionally consider 10 TMs (Ni, Cr, Mn, Co, Cu, Mo, Ag, W, Pt, and Au) and then determine the activity trend of the total 16 diverse TMs for NH₃ synthesis. We expect that this work could pave the way to novel alloy catalysts with a high activity for electrochemical NH₃ synthesis

Hearing Abilities at Ultra-High Frequency in Patients with Tinnitus

ObjectivesTo compare tinnitus patients who have normal hearing between 250 Hz and 8 kHz with normal controls with regard to the ability of each group to hear extended high-frequency pure tone thresholds.MethodsWe enrolled 18 tinnitus patients, each of whom had a threshold of HL <25 dB and threshold differences of <10 dB between ears at frequencies of 250 and 500 Hz and 1, 2, 4, and 8 kHz. We also enrolled age- and gender-matched normal volunteers (10 ears), for each patient. Extended high frequency pure tone audiometry was performed, and the mean hearing thresholds at 10, 12, 14, and 16 kHz of each tinnitus ear were compared with those of the 10 age- and sex-matched normal ears.ResultsOf the 18 patients with tinnitus, 12 had significantly increased hearing thresholds at more than one of the four high frequencies, compared with the normal group. When we assessed results according to frequency, we found that 8 patients had decreased hearing ability at 10 kHz, 10 at 12 kHz, 8 at 14 kHz, and 4 at 16 kHz.ConclusionSome patients with tinnitus who have normal hearing below 8 kHz have decreased hearing ability at extended high-frequencies. Thus, the proportion of patients with tinnitus who have normal hearing over the entire audible range is smaller than in previous reports

Dissimilar anisotropy of electron versus hole bulk transport in anatase TiO2: Implications for photocatalysis

Recent studies on crystal facet manipulation of anatase TiO2 in photocatalysis have revealed that reduction and oxidation reactions preferably occur on (100)/(101) and (001) facets, respectively; however, a fundamental understanding of their origin is lacking. Here, as a result of first-principles calculations, we suggest that a dissimilar trend in the anisotropy of electron vs hole bulk transport in anatase TiO2 can be a dominant underlying mechanism for the difference in photochemical activity. Photoexcited electrons and holes are driven to different facets, i.e., electrons on (100)/(101) and holes on (001), leading to the observed preference for either reduction or oxidation. This trend of electrons vs holes found in pure TiO2 applies even for cases where a variety of dopants or defects is introduced.clos

Activation of AMP-activated protein kinase stimulates the nuclear localization of glyceraldehyde 3-phosphate dehydrogenase in human diploid fibroblasts

In addition to its well-known glycolytic activity, GAPDH displays multiple functions, such as nuclear RNA export, DNA replication and repair, and apoptotic cell death. This functional diversity depends on its intracellular localization. In this study, we explored the signal transduction pathways involved in the nuclear translocation of GAPDH using confocal laser scanning microscopy of immunostained human diploid fibroblasts (HDFs). GAPDH was present mainly in the cytoplasm when cultured with 10% FBS. Serum depletion by culturing cells in a serum-free medium (SFM) led to a gradual accumulation of GAPDH in the nucleus, and this nuclear accumulation was reversed by the re-addition of serum or growth factors, such as PDGF and lysophosphatidic acid. The nuclear export induced by the re-addition of serum or growth factors was prevented by LY 294002 and SH-5, inhibitors of phosphoinositide 3-kinase (PI3K) and Akt/protein kinase B, respectively, suggesting an involvement of the PI3K signaling pathway in the nuclear export of GAPDH. In addition, 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR), an activator of AMP-activated protein kinase (AMPK), stimulated the nuclear translocation of GAPDH and prevented serum- and growth factor-induced GAPDH export. AMPK inhibition by compound C or AMPK depletion by siRNA treatment partially prevented SFM- and AICAR-induced nuclear translocation of GAPDH. Our data suggest that the nuclear translocation of GAPDH might be regulated by the PI3K signaling pathway acting mainly as a nuclear export signal and the AMPK signaling pathway acting as a nuclear import signal.Peairs A, 2009, CLIN EXP IMMUNOL, V156, P542, DOI 10.1111/j.1365-2249.2009.03924.xChen Z, 2009, CIRC RES, V104, P496, DOI 10.1161/CIRCRESAHA.108.187567Cao C, 2008, J BIOL CHEM, V283, P28897, DOI 10.1074/jbc.M804144200Li XX, 2008, ARTERIOSCL THROM VAS, V28, P1789, DOI 10.1161/ATVBAHA.108.172452Lombardi M, 2008, J CELL BIOL, V182, P327Sen N, 2008, NAT CELL BIOL, V10, P866, DOI 10.1038/ncb1747Kim HS, 2008, J BIOL CHEM, V283, P3731, DOI 10.1074/jbc.M704432200Du ZX, 2007, ENDOCRINOLOGY, V148, P4352, DOI 10.1210/en.2006-1511Harada N, 2007, J BIOL CHEM, V282, P22651, DOI 10.1074/jbc.M610724200Goirand F, 2007, J PHYSIOL-LONDON, V581, P1163, DOI 10.1113/jphysiol.2007.132589Barbini L, 2007, MOL CELL BIOCHEM, V300, P19, DOI 10.1007/s11010-006-9341-1Hurley RL, 2006, J BIOL CHEM, V281, P36662, DOI 10.1074/jbc.M606676200Hara MR, 2006, CELL MOL NEUROBIOL, V26, P527, DOI 10.1007/s10571-006-9011-6Tisdale EJ, 2006, J BIOL CHEM, V281, P8436, DOI 10.1074/jbc.M513031200Rattan R, 2005, J BIOL CHEM, V280, P39582, DOI 10.1074/jbc.M507443200Hara MR, 2005, NAT CELL BIOL, V7, P665, DOI 10.1038/ncb1268Sirover MA, 2005, J CELL BIOCHEM, V95, P45, DOI 10.1002/jcb.20399Jones RG, 2005, MOL CELL, V18, P283, DOI 10.1016/j.molcel.2005.03.027Tisdale EJ, 2004, J BIOL CHEM, V279, P54046, DOI 10.1074/jbc.M409472200Hardie DG, 2004, J CELL SCI, V117, P5479, DOI 10.1242/jcs.01540Li J, 2004, AM J PHYSIOL-ENDOC M, V287, pE834, DOI 10.1152/ajpendo.00234.2004Cooray S, 2004, J GEN VIROL, V85, P1065, DOI 10.1099/vir.0.1977-0Brown VM, 2004, J BIOL CHEM, V279, P5984, DOI 10.1074/jbc.M307071200Tisdale EJ, 2003, J BIOL CHEM, V278, P52524, DOI 10.1074/jbc.M309343200HAWLEY SA, 2003, J BIOL, V2, P28Schmitz HD, 2003, CELL BIOL INT, V27, P511, DOI 10.1011/S1065-6995(03)00096-9Tisdale EJ, 2002, J BIOL CHEM, V277, P3334, DOI 10.1074/jbc.M109744200Schmitz HD, 2001, EUR J CELL BIOL, V80, P419Dastoor Z, 2001, J CELL SCI, V114, P1643Yeo EJ, 2000, MOL CELLS, V10, P415Stein SC, 2000, BIOCHEM J, V345, P437Sirover MA, 1999, BBA-PROTEIN STRUCT M, V1432, P159Shashidharan P, 1999, NEUROREPORT, V10, P1149Rameh LE, 1999, J BIOL CHEM, V274, P8347Sawa A, 1997, P NATL ACAD SCI USA, V94, P11669Vincent MF, 1996, BIOCHEM PHARMACOL, V52, P999Reiss N, 1996, BIOCHEM MOL BIOL INT, V38, P711CORTON JM, 1995, EUR J BIOCHEM, V229, P558KAWAMOTO RM, 1986, BIOCHEMISTRY-US, V25, P657BOYCE ST, 1983, J INVEST DERMATOL S, V81, P33

Spirulina

Skin regeneration is a complex process involving massive proliferation and alignment of cells, where there are obstacles to completion of regeneration, the main one being excessive generation of reactive oxygen species (ROS) from inflammation or infection. Spirulina, blue-green algae that has antioxidant and anti-inflammatory activities, has been used to relieve such ROS stress. In this study, Spirulina extract loaded PCL (Spirulina-PCL) nanofiber was evaluated as a cutaneous wound dressing in view of antioxidative mechanism. In addition to increasing fibroblast viability, the Spirulina extract and its dressing modulated intra- and extracellular ROS by enhancing antioxidant mechanism of fibroblast under oxidative stress. Finally, in vivo assays confirmed that Spirulina-PCL helps regenerate wounds and enhance regeneration. Taken together, the results of this study indicate that Spirulina and nanofiber have the potential for application to cutaneous wound to facilitate skin regeneration