3,445 research outputs found
Optical loss compensation in a bulk left-handed metamaterial by the gain in quantum dots
A bulk left-handed metamaterial with fishnet structure is investigated to
show the optical loss compensation via surface plasmon amplification, with the
assistance of a Gaussian gain in PbS quantum dots. The optical resonance
enhancement around 200 THz is confirmed by the retrieval method. By exploring
the dependence of propagation loss on the gain coefficient and metamaterial
thickness, we verify numerically that the left-handed response can endure a
large propagation thickness with ultralow and stable loss under a certain gain
coefficient.Comment: 6 pages with 4 figure
Phylogenetic structure and formation mechanism of shrub communities in arid and semiarid areas of the Mongolian Plateau
The mechanisms of species coexistence within a community have always been the focus in ecological research. Community phylogenetic structure reflects the relationship of historical processes, regional environments, and interactions between species, and studying it is imperative to understand the formation and maintenance mechanisms of community composition and biodiversity. We studied the phylogenetic structure of the shrub communities in arid and semiarid areas of the Mongolian Plateau. First, the phylogenetic signals of four plant traits (height, canopy, leaf length, and leaf width) of shrubs and subshrubs were measured to determine the phylogenetic conservation of these traits. Then, the net relatedness index (NRI) of shrub communities was calculated to characterize their phylogenetic structure. Finally, the relationship between the NRI and current climate and paleoclimate (since the Last Glacial Maximum, LGM) factors was analyzed to understand the formation and maintenance mechanisms of these plant communities. We found that desert shrub communities showed a trend toward phylogenetic overdispersion; that is, limiting similarity was predominant in arid and semiarid areas of the Mongolian Plateau despite the phylogenetic structure and formation mechanisms differing across habitats. The typical desert and sandy shrub communities showed a significant phylogenetic overdispersion, while the steppified desert shrub communities showed a weak phylogenetic clustering. It was found that mean winter temperature (i.e., in the driest quarter) was the major factor limiting steppified desert shrub phylogeny distribution. Both cold and drought (despite having opposite consequences) differentiated the typical desert to steppified desert shrub communities. The increase in temperature since the LGM is conducive to the invasion of shrub plants into steppe grassland, and this process may be intensified by global warming
A Small Molecule Compound Targeting STAT3 DNA-Binding Domain Inhibits Cancer Cell Proliferation, Migration, and Invasion
Signal transducer and activator of
transcription 3 (STAT3) plays
important roles in multiple aspects of cancer aggressiveness including
migration, invasion, survival, self-renewal, angiogenesis, and tumor
cell immune evasion by regulating the expression of multiple downstream
target genes. STAT3 is constitutively activated in many malignant
tumors and its activation is associated with high histological grade
and advanced cancer stages. Thus, inhibiting STAT3 promises an attracting
strategy for treatment of advanced and metastatic cancers. Herein,
we identified a STAT3 inhibitor, inS3-54, by targeting the DNA-binding
domain of STAT3 using an improved virtual screening strategy. InS3-54
preferentially suppresses proliferation of cancer over non-cancer
cells and inhibits migration and invasion of malignant cells. Biochemical
analyses show that inS3-54 selectively inhibits STAT3 binding to DNA
without affecting the activation and dimerization of STAT3. Furthermore,
inS3-54 inhibits expression of STAT3 downstream target genes and STAT3
binding to chromatin in situ. Thus, inS3-54 represents a novel probe
for development of specific inhibitors targeting the DNA-binding domain
of STAT3 and a potential therapeutic for cancer treatments
Balance Fatigue Design of Cast Steel Nodes in Tubular Steel Structures
Cast steel nodes are being increasingly popular in steel structure joint application as their advanced mechanical performances and flexible forms. This kind of joints improves the structural antifatigue capability observably and is expected to be widely used in the structures with fatigue loadings. Cast steel node joint consists of two parts: casting itself and the welds between the node and the steel member. The fatigue resistances of these two parts are very different; the experiment results showed very clearly that the fatigue behavior was governed by the welds in all tested configurations. This paper focuses on the balance fatigue design of these two parts in a cast steel node joint using fracture mechanics and FEM. The defects in castings are simulated by cracks conservatively. The final crack size is decided by the minimum of 90% of the wall thickness and the value deduced by fracture toughness. The allowable initial crack size could be obtained through the integral of Paris equation when the crack propagation life is considered equal to the weld fatigue life; therefore, the two parts in a cast steel node joint will have a balance fatigue life
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