Cultural landmarks and urban landscapes in three contrasting societies

Cultural heritage sites and landscapes are intuitively connected in urban systems. Based on available databases of cultural landmarks, we selected three pairs of cities that are currently dominated by three contrasting religions (Catholic, Buddhist and emerging culture) to compare the long-term changes in cultural landmarks, to quantify their spatial distribution in the current landscape, and to examine the potential influences these landmarks have on landscapes. The landmark database and landscapes were constructed from archived maps, satellite imagery and the UNESCO heritage sites for Barcelona, Bari, Beijing, Vientiane, Shenzhen, and Ulaanbaatar. Roads in Asian cities are mostly constructed in alignment with the four cardinal directions, forming a checkerboard-type landscape, whereas Bari and Barcelona in Europe have examples of roads radiating from major cultural landmarks. We found clear differences in the number of landmarks and surrounding landscape in these cities, supporting our hypothesis that current urban landscapes have been influenced similarly by cultural landmarks, although substantial differences exist among cities. Negative relationships between the number of cultural landmarks and major cover types were found, except with agricultural lands. Clearly, cultural landmarks need to be treated as “natural features” and considered as reference points in urban planning. Major efforts are needed to construct a global database before an overarching conclusion can be made for global cities

Dynamical effects induced by long range activation in a nonequilibrium reaction-diffusion system

We both show experimentally and numerically that the time scales separation introduced by long range activation can induce oscillations and excitability in nonequilibrium reaction-diffusion systems that would otherwise only exhibit bistability. Namely, we show that the Chlorite-Tetrathionate reaction, where autocatalytic species diffuses faster than the substrates, the spatial bistability domain in the nonequilibrium phase diagram is extended with oscillatory and excitability domains. A simple model and a more realistic model qualitatively account for the observed behavior. The latter model provides quantitative agreement with the experiments.Comment: 19 pages + 9 figure

Microbial biomass carbon and enzyme activities of urban soils in Beijing

Introduction To promote rational and sustainable use of soil resources and to maintain the urban soil quality, it is essential to assess urban ecosystem health. In this study, the microbiological properties of urban soils in Beijing and their spatial distribution patterns across the city were evaluated based on measurements of microbial biomass carbon and urease and invertase activities of the soils for the purpose of assessing the urban ecosystem health of Beijing. Materials and methods Grid sampling design, normal Kriging technique, and the multiple comparisons among different land use types were used in soil sampling and data treatment. The inherent chemical characteristics of urban soils in Beijing, e.g., soil pH, electronic conductivity, heavy metal contents, total N, P and K contents, and soil organic matter contents were detected. The size and diversity of microbial community and the extent of microbial activity in Beijing urban soils were measured as the microbial biomass carbon content and the ratio of microbial biomass carbon content to total soil organic carbon. Results and discussion The microbial community health measured in terms of microbial biomass carbon, urease, and invertase activities varied with the organic substrate and nutrient contents of the soils and were not adversely affected by the presence of heavy metals at p < 0.01. It was shown that the older and the biologically more stable part of city exhibited higher microbial activity levels than the more recently developed part of the city and the road areas of heavy traffic. It was concluded that the land use patterns in Beijing urban soils influenced the nature and activities of the microbial communities

152 fs nanotube-mode-locked thulium-doped all-fiber laser.

Ultrafast fiber lasers with broad bandwidth and short pulse duration have a variety of applications, such as ultrafast time-resolved spectroscopy and supercontinuum generation. We report a simple and compact all-fiber thulium-doped femtosecond laser mode-locked by carbon nanotubes. The oscillator operates in slightly normal cavity dispersion at 0.055 ps(2), and delivers 152 fs pulses with 52.8 nm bandwidth and 0.19 nJ pulse energy. This is the shortest pulse duration and the widest spectral width demonstrated from Tm-doped all-fiber lasers based on 1 or 2 dimensional nanomaterials, underscoring their growing potential as versatile saturable absorber materials.We acknowledge funding from the Science and Technology Projects of Shenzhen City (JCYJ20150324140036862, JCYJ20140418095735546), the Natural Science Foundation of Guangdong Province (2015A030310464, 2016A030310049), the Scientific Research Foundation of Shenzhen City (827-000118), the Teknologiateollisuus TT-100, the European Union’s Seventh Framework Programme (REA grant agreement No. 631610), the Academy of Finland (No. 284548), Tekes (OPEC) and Aalto University (Finland). TH acknowledges funding from the Royal Academy of Engineering through a research fellowship (Graphlex).This is the final version of the article. It first appeared from Nature Publishing Group at http://dx.doi.org/10.1038/srep28885

Anomalies in thickness measurements of graphene and few layer graphite crystals by tapping mode atomic force microscopy

Atomic Force Microscopy (AFM) in the tapping (intermittent contact) mode is a commonly used tool to measure the thickness of graphene and few layer graphene (FLG) flakes on silicon oxide surfaces. It is a convenient tool to quickly determine the thickness of individual FLG films. However, reports from literature show a large variation of the measured thickness of graphene layers. This paper is focused on the imaging mechanism of tapping mode AFM (TAFM) when measuring graphene and FLG thickness and we show that at certain measurement parameters significant deviations can be introduced in the measured thickness of FLG flakes. An increase of as much as 1 nm can be observed in the measured height of FLG crystallites, when using an improperly chosen range of free amplitude values of the tapping cantilever. We present comparative Raman spectroscopy and TAFM measurements on selected single and multilayer graphene films, based on which we suggest ways to correctly measure graphene and FLG thickness using TAFM

A Radio Molecular Line Search for Evidence of an O-rich Environment around Binary in Silicate Carbon Stars

We report observations of oxygen-rich (O-rich) radio molecular line tracers, including H2CO, H2O, and HCO+ toward 28 silicate carbon stars (SCSs). SCSs are special evolved star systems that consist of a carbon star associated with peculiar O-rich circumstellar material. Absorption in the 6 cm H2 CO transition was detected from seven SCSs using the Shanghai 65 m Tianma radio telescope. In order to further investigate their O-rich material, several 3 mm molecular lines including HCO+ and CO were also observed with the Purple Mountain Observatory 13.7 m telescope. Double-peak profiles in some of these lines suggest the possible presence of a companion in the SCS system. A negative association between H2O masers and H2CO absorption was found in our sample of SCSs. The H2 O maser sources may correspond to an earlier evolutionary stage when the circumstellar envelope (CSE) material is O-rich and limited to a compact and denser region. As the star evolves the CSE gradually expands and carbon abundance is enhanced, resulting in the H2 O masers disappearing and H2CO absorption arising. © 2020. The American Astronomical Society. All rights reserved.