Quantum phase interference (Berry phase) in single-molecule magnets of Mn12

Magnetization measurements of a molecular clusters Mn12 with a spin ground state of S = 10 show resonance tunneling at avoided energy level crossings. The observed oscillations of the tunnel probability as a function of the magnetic field applied along the hard anisotropy axis are due to topological quantum phase interference of two tunnel paths of opposite windings. Mn12 is therefore the second molecular clusters presenting quantum phase interference.Comment: 3 pages, 4 figures, MMM'01 conference (12-16 Nov.

Sand dune stabilization changes the vegetation characteristics and soil seed bank and their correlations with environmental factors

Currently the amount of data available on the effect of sand dune stabilization on species conservation in inter-dune lowland is very limited, especially for the sand dune systems in semi-arid regions. In this study, we determined whether the characteristics of above-ground vegetation, soil seed bank and their relationships with environmental factors changed with sand dune stabilization in the inter-dune lowlands in Horqin Sandy Land, China. Species composition, abundance and coverage of aboveground vegetation as well as soil seed bank composition and density were surveyed and their correlations with environmental factors (pH, organic matter content, total nitrogen and total phosphorus) were determined. The results showed that changes in the relationship between aboveground vegetation, soil seed bank and soil quality followed the changes in aboveground vegetation and soil seed banks. Aboveground vegetation species richness increased with sand dune stabilization, but soil seed bank species richness declined. The inter-dune lowland of active sand dunes could provide specific habitats for some endemic species and pioneer psammophyte species as indicated by data on aboveground vegetation and soil seed bank. Our results suggested that both active and stabilized sand dunes should be maintained since active sand dunes are essential for the survival of endemic or pioneer species and stabilized sand dunes are important for sustaining species richness

Influence of dry density and wetting–drying cycles on the soil–water retention curve of compacted loess: experimental data and modeling

In this paper, the EC-5 water sensor and the MPS-6 water potential sensor were used to measure water content and suction, respectively, to investigate the evolution of soil–water retention properties of compacted loess samples prepared at different dry densities and subjected to different numbers of wetting–drying cycles. The water retention data were integrated with a detailed microstructural investigation, including morphological analysis (by scanning electron microscopy) and pore size distribution determination (by nuclear magnetic resonance). The microstructural information obtained shed light on the double porosity nature of compacted loess, allowing the identification of the effects of compaction dry density and wetting–drying cycles at both intra- and inter-aggregate levels. The information obtained at the microstructural scale was used to provide a solid physical basis for the development of a simplified version of the water retention model presented in Della Vecchia et al. (Int J Numer Anal Meth Geomech 39: 702–723, 2015). The model, adapted for engineering application to compacted loess, requires only five parameters to capture the water retention properties of samples characterized by different compaction dry densities and subjected to different numbers of wetting–drying cycles. The comparison between numerical simulations and experimental results, both original and from the literature, shows that only one set of parameters is needed to reproduce the effects of dry density variation, while the variation of only one parameter allows the reproduction of the effects of wetting and drying cycles. With respect to the approaches presented in the literature, where ad hoc calibrations are often used to fit density and wetting–drying cycle effects, the model presented here shows a good compromise between simplicity and predictive capabilities, making it suitable for practical engineering applications

When multi-functional landscape meets Critical Zone science: advancing multi-disciplinary research for sustainable human well-being

Environmental degradation has become one of the major obstacles to sustainable development and human well-being internationally. Scientific efforts are being made to understand the mechanism of environmental degradation and sustainability. Critical Zone (CZ) science and research on the multi-functional landscape are emerging fields in earth science that can contribute to such scientific efforts. This paper reviews the progress, similarities and current status of these two scientific research fields, and identifies a number of opportunities for their synergistic integration through functional and multi-functional approaches, process-based monitoring, mechanistic analyses, and dynamic modelling, global long term and networked monitoring, and systematic modeling supported by scaling and deep coupling. These approaches proposed in this paper have the potential to support sustainable human well-being by strengthening a functional orientation that consolidates multi-functional landscape research and CZ science. This is a key challenge for sustainable development and human well-being in the 21st century

Enhanced Expression of Deoxynivalenol-Degrading Enzyme DepB in Bacillus subtilis by Optimizing Expression Elements

A deoxynivalenol-degrading enzyme DepB was successfully expressed in Bacillus subtilis RIK 1285 in this study, but the fermentation level of DepB was low, which hinders its application in food and feed processing. Thus, an integrative strategy of transcriptional and translational regulation was explored to enhance the expression level of DepB. First, nine single strong promoters were selected to replace the original promoter P43, among which the recombinant bacteria mediated by the promoter PspoVG gave the highest enzyme activity of 29.59 U/mL after fermentation. Second, four promoters (P43, PsacB, PspoVG, and PaprE) with relatively high DepB expression levels were chosen to construct a dual-promoter system. DepB mediated by the dual promoter PaprE-PspoVG reached the highest activity of 48.87 U/mL. Moreover, the DepB activity of Mutant-5 with optimized core region (-35 and -10 boxes) of PaprE-PspoVG reached 69.17 U/mL, which was 4.79 times higher than that of the original strain (14.45 U/mL). Finally, DepB expression level was further improved by optimizing the ribosome binding site (RBS) sequence of the promoter PspoVG, and the enzyme activity of RBS15 reached 115.15 U/mL, which was 7.97-fold higher than that of the original strain. The results suggest that combined transcriptional and translational regulation is an effective strategy to improve the fermentation level of recombinant proteins