Nitrogen fixation is one of the most important issues but a long-standing challenge in chemistry. Here, we propose FeN3-embedded graphene as the catalyst for nitrogen fixation from first-principles calculations. Results show that in view of the chemical coordination, the FeN3 center is highly spin-polarized with a localized magnetic moment substantially to promote N2 adsorption and activate its inert N-N triple bond. The synergy between the graphene and FeN3 equips the system with novel features for the catalytic conversion of the activated N2 into NH3 via a six-proton and six-electron process, following three possible reaction pathways at room temperature. Our findings provide a rational paradigm for catalytic nitrogen fixation that would be conducive to ammonia production.

No abstract

Abstract. Light-absorbing dissolved organic carbon (DOC) constitutes a major part of the organic carbon in glacierized regions, and has important influences on the carbon cycle and radiative forcing of glaciers. However, few DOC data are currently available from the glacierized regions of the Tibetan Plateau (TP). In this study, DOC characteristics of a medium-sized valley glacier (Laohugou Glacier No. 12, LHG) on the northern TP were investigated. Generally, DOC concentrations on LHG were comparable to those in other regions around the world. DOC concentrations in snow pits, surface snow and surface ice (superimposed ice) were 332 ± 132, 229 ± 104 and 426 ± 270 µg L−1, respectively. The average discharge-weighted DOC of proglacial stream water was 238 ± 96 µg L−1, and the annual DOC flux released from this glacier was estimated to be 6949 kg C yr−1, of which 46.2 % of DOC was bioavailable and could be decomposed into CO2 within 1 month of its release. The mass absorption cross section (MAC) of DOC at 365 nm was 1.4 ± 0.4 m2 g−1 in snow and 1.3 ± 0.7 m2 g−1 in ice, similar to the values for dust transported from adjacent deserts. Moreover, there was a significant relationship between DOC and Ca2+; therefore, mineral dust transported from adjacent arid regions likely made important contributions to DOC of the glacierized regions, although contributions from autochthonous carbon and autochthonous/heterotrophic microbial activity cannot be ruled out. The radiative forcing of snow pit DOC was calculated to be 0.43 W m−2, demonstrating that DOC in snow needs to be taken into consideration in accelerating melt of glaciers on the TP.

Background— Coronary guidewires are indispensable during percutaneous coronary interventions. Nowadays, most guidewires have hydrophilic coatings to improve their trackability, allowing easy lesion passage and facilitating balloon and stent positioning. Recent reports, however, have raised concerns about detachment and subsequent embolization of these hydrophilic coatings. Methods and Results— We have retrospectively reviewed the histological samples of the myocardium, obtained during autopsies in the period 2009 to 2013, from all patients who had a history of percutaneous coronary interventions (n=40). Foreign material was observed in the distal myocardium in 4 patients (10%). Furthermore, we have reviewed 205 thrombus specimens which were obtained during thrombus aspiration in the setting of primary percutaneous coronary interventions in the period 2005 to 2009. In 45% of the cases, foreign material was observed within the thrombus. Finally, we have examined the histopathologic appearance of hydrophilic-guidewire coating material ex vivo by embedding the coating in placenta specimen and cut and stain it in exactly the same manner as the myocardium and thrombus specimen. The histopathologic appearance of the hydrophilic coating ex vivo was identical to the foreign material found in vivo. Conclusions— Distal embolization of hydrophilic-coating material was observed in 10% of the patients who had a history of percutaneous coronary interventions. Hydrophilic-coating material was found in 45% of coronary thrombus specimen obtained during thrombus aspiration. These findings suggest that detachment and distal embolization of hydrophilic-coating material from coronary guidewires occur more often than the sparse literature on this topic suggests.

No abstract

C rescentic glomerulonephritis (GN) is a rapidly progressive inflammatory condition affecting the kidneys that can lead to renal failure in humans within days. 1,2 If left untreated, the majority of patients with crescentic GN will die or become dialysis-dependent within 6 months. 3 The central role of CD4 þ T cell-mediated renal injury in nephrotoxic serum nephritis (NTN), a classic experimental anti-glomerular basement membrane antibody-mediated model of crescentic GN, has been well established. 4-10 Several previous studies have elucidated the role of fibroblastic reticular cells (FRCs), the prominent cells that comprise the stromal compartment of the lymph node (LN), in the activation of an immune response. 11-18 FRCs express the membrane glycoprotein podoplanin (PDPN), but they do not express the leukocyte marker CD45 or the vascular marker CD31, a unique cellular signature in the LN. 15 FRCs secrete the chemokines CCL19, CCL21, and CXCL12, which promote the trafficking of naïve T cells into the LN through specialized vasculature known as high endothelial venules (HEVs). 14 FRCs also maintain the integrity of HEVs through interactions between PDPN on the FRCs and C-type lectin-like receptor 2 on platelets. 19 The chemokines secreted by FRCs contain the newly arrived T cells within the paracortex (T-cell zone) of the LN, where the FRCs provide conduits on which these naïve T cells and antigen-presenting cells migrate and interact, resulting in activation of the T cells. 14 Though the kidney has been proven to be a site of recruitment for activated CD4 þ T helper 1 (Th1) and Th17 cells via expression of chemokines such as CCL20 and CXCL9, 10 the role of the kidney lymph node (KLN) as a secondary lymphoid organ where these T cells are also activated in NTN has not yet been explored in depth. 20 CD4 þ T cells are activated in the spleen during NTN, 10 but splenectomy does not affect kidney damage significantly in these mice. 21 This finding raises the hypothesis that the KLN may be the key secondary lymphoid organ responsible for propagation of the immune response in NTN. The objectives of this study are to explore the phenotypic changes that occur to FRCs in the KLN during the early stages of the immune response and examine the effects that modulation of the activity of FRCs has on kidney damage in NTN.

No abstract

No abstract