19,329 research outputs found
Electric field modulation of topological order in thin film semiconductors
We propose a method that can consecutively modulate the topological orders or
the number of helical edge states in ultrathin film semiconductors without a
magnetic field. By applying a staggered periodic potential, the system
undergoes a transition from a topological trivial insulating state into a
non-trivial one with helical edge states emerging in the band gap. Further
study demonstrates that the number of helical edge state can be modulated by
the amplitude and the geometry of the electric potential in a step-wise
fashion, which is analogous to tuning the integer quantum Hall conductance by a
megntic field. We address the feasibility of experimental measurement of this
topological transition.Comment: 4 pages, 4 figure
Human Neutrophil Elastase Degrades SPLUNC1 and Impairs Airway Epithelial Defense against Bacteria
Background:Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) are a significant cause of mortality of COPD patients, and pose a huge burden on healthcare. One of the major causes of AECOPD is airway bacterial (e.g. nontypeable Haemophilus influenzae [NTHi]) infection. However, the mechanisms underlying bacterial infections during AECOPD remain poorly understood. As neutrophilic inflammation including increased release of human neutrophil elastase (HNE) is a salient feature of AECOPD, we hypothesized that HNE impairs airway epithelial defense against NTHi by degrading airway epithelial host defense proteins such as short palate, lung, and nasal epithelium clone 1 (SPLUNC1).Methodology/Main Results:Recombinant human SPLUNC1 protein was incubated with HNE to confirm SPLUNC1 degradation by HNE. To determine if HNE-mediated impairment of host defense against NTHi was SPLUNC1-dependent, SPLUNC1 protein was added to HNE-treated primary normal human airway epithelial cells. The in vivo function of SPLUNC1 in NTHi defense was investigated by infecting SPLUNC1 knockout and wild-type mice intranasally with NTHi. We found that: (1) HNE directly increased NTHi load in human airway epithelial cells; (2) HNE degraded human SPLUNC1 protein; (3) Recombinant SPLUNC1 protein reduced NTHi levels in HNE-treated human airway epithelial cells; (4) NTHi levels in lungs of SPLUNC1 knockout mice were increased compared to wild-type mice; and (5) SPLUNC1 was reduced in lungs of COPD patients.Conclusions:Our findings suggest that SPLUNC1 degradation by neutrophil elastase may increase airway susceptibility to bacterial infections. SPLUNC1 therapy likely attenuates bacterial infections during AECOPD. Ā© 2013 Jiang et al
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Natural and anthropogenic forest fires recorded in the Holocene pollen record from a Jinchuan peat bog, northeastern China
Pollen and charcoal particles from a Jinchuan peat (northeastern China) were examined to investigate the fire origin and interaction between
climate, vegetation, fire and human activity during the Holocene. Pollen results show that: (i) a broadleaved deciduous forest was dominant during
the early Holocene; (ii) from ~5500 cal. yr B.P. there was a gradual increase in coniferous trees (mainly Pinus), and a decrease in broadleaved
deciduous trees (e.g. Quercus, Juglans, and UlmusāZelkova); (iii) after ~4200 cal. yr B.P., the deciduous forest was replaced by a mixed forest of
coniferous and deciduous trees; (iv) coniferous trees including Pinus, Abies and Picea further increased after ~2000 cal. yr B.P., reflecting a
cooler and drier climate after ~5500ā4200 cal. yr B.P. Two layers of abundant microfossil charcoal particles (250ā10 Ī¼m) and the coexistence of
macrofossil particles (N2 mm) suggest two local fires: fire event 1 (5120Ā±66 cal. yr B.P.) and fire event 2 (1288Ā±8 cal. yr B.P., AD 662Ā±8).
Charcoal layer 1, with a large amount of Monolete psilate spores, is superimposed on the long-term trend of vegetation changes, indicating a
natural origin for fire event 1 that was probably facilitated by drying environmental conditions since the mid-Holocene. Cerealia-type pollen and a
low percentage of Monolete psilate spores were observed in charcoal layer 2, indicating that fire event 2 was caused by clearing. We suggest that
fire event 2 may be related to the spread of the Han farming culture accompanied by the territorial expansion of the Tang Dynasty to the studied
area in AD 668
Lexicalization, Separation and transitivity: A comparative study of Mandarin VO compound Variations
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