Strain Induced One-Dimensional Landau-Level Quantization in Corrugated Graphene

Theoretical research has predicted that ripples of graphene generates effective gauge field on its low energy electronic structure and could lead to zero-energy flat bands, which are the analog of Landau levels in real magnetic fields. Here we demonstrate, using a combination of scanning tunneling microscopy and tight-binding approximation, that the zero-energy Landau levels with vanishing Fermi velocities will form when the effective pseudomagnetic flux per ripple is larger than the flux quantum. Our analysis indicates that the effective gauge field of the ripples results in zero-energy flat bands in one direction but not in another. The Fermi velocities in the perpendicular direction of the ripples are not renormalized at all. The condition to generate the ripples is also discussed according to classical thin-film elasticity theory.Comment: 4 figures, Phys. Rev.

Climate changes reconstructed from a glacial lake in High Central Asiaover the past two millennia

Climatic changes in Arid Central Asia (ACA) over the past two millennia have been widely concerned. However, less attention has been paid to those in the High Central Asia (HCA), where the Asian water tower nurtures the numerous oases by glacier and/or snow melt. Here, we present a new reconstruction of the temperature and precipitation change over the past two millennia based on grain size of a well-dated glacial lake sediment core in the central of southern Tianshan Mountains. The results show that the glacial lake catchment has experienced cold-wet climate conditions during the Dark Age Cold Period (&sim;300&ndash;600 AD; DACP) and the Little Ice Age (&sim;1300&ndash;1870 AD; LIA), whereas warm-dry conditions during the Medieval Warm Period (&sim;700&ndash;1270 AD; MWP). Integration of our results with those of previously published lake sediment records, stalagmite &delta;18O records, ice core net accumulation rates, tree-ring based temperature reconstructions, and mountain glacier activities suggest that there has a broadly similar hydroclimatic pattern over the HCA areas on centennial time scale during the past two millennia. Comparison between hydroclimatic pattern of the HCA and that of the ACA areas suggests a prevailing &#39;warm-dry and cold-wet&#39; hydroclimatic pattern over the whole westerlies-dominated central Asia areas during the past two millennia. We argue that the position and intensity of the westerlies, which are closely related to the phase of the North Atlantic Oscillation (NAO), and the strength of the Siberian High pressure (SH), could have jointly modulated the late Holocene central Asia hydroclimatic changes.<br /

Mixed Organizational Forms - A Generalization and Comparative Case Study on the ETRE Systems of China and the EU

There is a lack of applicable model for understanding stability affected by combination of incentive and direct control for an economic regulation within mixed-forms. The research on stability of an economic regulation has mostly been focused on incentive or direct control in a U-form or M-form dominated organization. Therefore, the purpose of this study has been to discover a universal model for explaining stability affected by combination theory, leading to high mixed-form organizations performance. This dissertation illustrates the relative theories bound to the research topic and moves one step forward into hierarchies, the U-form dominated and M-form dominated mixed forms. And this dissertation puts forward a hypothesis on how to lead an economic regulation to more stable. The suggested theory was empirically tested in a case study and received strong support. The conclusion of the conducted research is that an economic regulation governed by an M-form dominated organization with stronger incentive and less direct control is more stable than a U-form dominated organization with weaker incentive and more direct control

Mixed Organizational Forms - A Generalization and Comparative Case Study on the ETRE Systems of China and the EU

There is a lack of applicable model for understanding stability affected by combination of incentive and direct control for an economic regulation within mixed-forms. The research on stability of an economic regulation has mostly been focused on incentive or direct control in a U-form or M-form dominated organization. Therefore, the purpose of this study has been to discover a universal model for explaining stability affected by combination theory, leading to high mixed-form organizations performance. This dissertation illustrates the relative theories bound to the research topic and moves one step forward into hierarchies, the U-form dominated and M-form dominated mixed forms. And this dissertation puts forward a hypothesis on how to lead an economic regulation to more stable. The suggested theory was empirically tested in a case study and received strong support. The conclusion of the conducted research is that an economic regulation governed by an M-form dominated organization with stronger incentive and less direct control is more stable than a U-form dominated organization with weaker incentive and more direct control

Variations in monsoon precipitation over southwest China during the last 1500 years and possible driving forces

Understanding hydroclimatic patterns and their possible driving mechanisms during distinct climate periods over the last 1500 years-such as the Medieval Warm Period (MWP), the Little Ice Age (LIA), and the Current Warm Period-is crucial for predicting future changes to monsoon precipitation in southwest China under global warming scenarios. In this study, based on Pb-210 and Cs-137 dating of surface sediments and AMS C-14 dating of terrestrial plant residues, we establish a robust age model that covers the last similar to 1500 years (AD 439-2012) at Lake Yihai in southwest China. We use analyses of multiple geochemical proxy indices, including loss on ignition at 550 degrees C, total organic carbon, total nitrogen, C/N ratios, and stable carbon isotopes of organic matter to reconstruct changes in summer monsoon precipitation at Lake Yihai during the last similar to 1500 years. The results show that, over southwest China, warm and dry climate conditions prevailed during the MWP (AD 1000-1400) and the past 200 years, whereas conditions during the LIA (AD 1400-1800) were cold and wet. This is consistent with evidence from other geological records over southwest China, such as stalagmite and lake sediment data. Similar hydroclimatic patterns have occurred over the last 1500 years in adjacent tropical/subtropical monsoon regions where the climate is similarly dominated by the Indian summer monsoon (e.g., South China, the South China Sea, Southeast Asia, Northeast India). We suggest that the meridional migration of the mean position of the Inter-tropical Convergence Zone, and El Nino/Southern Oscillation conditions which are linked to tropical Pacific sea surface temperature, are responsible for centennial-scale hydroclimatic patterns over southwest China and adjacent areas during the last 1500 years

The complete chloroplast genome sequence of Vernonia amygdalina Delile

Vernonia amygdalina Delile is widely used in folkloric medicine for the treatment of various diseases. In this study, the complete chloroplast genome of V. amygdalina Delile was reported, which was assembled and annotated base on genome high-throughput sequencing data. This work provided the clues for the taxonomy of the herb and the potential to utilize the chloroplast genome sequence as a new study target. The length of V. amygdalina Delile chloroplast genome was 153,133bp, with two single-copy regions, each has the length of 84,245bp and 13,152bp respectively. This region were separated by two inverted repeat regions with 27,868bp in length. It was predicted to consist of 131 genes in total, including 86 protein-coding genes, 37 tRNA genes, 8 rRNA genes with GC content at 37.68%. Phylogenetic analysis by RAxML (Random Axelerated Maximum Likelikhood) showed V. amygdalina Delile is closest to Sonchus webbii in Compositae

Late Holocene Indian summer monsoon precipitation history at Lake Lugu, northwestern Yunnan Province, southwestern China

Knowledge of late Holocene precipitation variability in the northwestern Yunnan Province is important for understanding the Indian summer monsoon (ISM) dynamics. In this study, we present a proxy record of the ISM precipitation history at Lake Lugu covering the last 2,900 years based on grain size and carbon/nitrogen (C/N) ratio in the northwestern Yunnan Province. The results show centennial variations in ISM precipitation, with two remarkably dry intervals from 750 to 1167 AD and from 1733 AD to the present and two relatively wet intervals from 898 BC to 750 AD and from 1167 to 1733 AD. A comparison between the record at Lake Lugu and the pollen record at Lake Erhai (both in the northwestern Yunnan Province) suggests that dry climate conditions prevailed during the Medieval Warm Period (MWP) and over the last 100-200 years, whereas relatively humid conditions prevailed during the Little Ice Age (LIA). These characteristics are generally similar to those of the climate patterns in extensive areas dominated by the ISM (e.g., southwestern-southern China, southeastern-southern Tibetan Plateau, northeastern India Himalayas, southern Oman, and equatorial eastern Africa), but anti-phased with the climate patterns in the wide areas dominated by the East Asian summer monsoon (EASM) (e.g., northern-northeastern China and north-central Japan). We speculate that both the variations in the sea surface temperature (SST) over the tropical Indo-Pacific Ocean, the ocean atmosphere coupling processes and the migration of the mean position of the Intertropical Convergence Zone (ITCZ) should be responsible for the hydroclimatic contrasts over the Asian summer monsoon (ASM) region on centennial timescales during the last 2,000 years. (C) 2015 Elsevier B.V. All rights reserved.</p

Temperature Variations and Possible Forcing Mechanisms over the Past 300 Years Recorded at Lake Chaonaqiu in the Western Loess Plateau

Understanding the synchronicity of and discrepancy among temperature variations on the western Loess Plateau (WLP), China, is critical for establishing the drivers of regional temperature variability. Here we present an authigenic carbonate-content timeseries spanning the last 300 years from sediments collected from Lake Chaonaqiu in the Liupan Mountains, WLP, as a decadal-scale record of temperature. Our results reveal six periods of relatively low temperature, during the intervals AD 1743-1750, 1770-1780, 1792-1803, 1834-1898, 1930-1946, and 1970-1995, and three periods of relatively high temperature during 1813-1822, 1910-1928, and since 2000. These findings are consistent with tree-ring datasets from the WLP and correlate well with extreme cold and warm events documented in historical literature. Our temperature reconstruction is also potentially representative of large-scale climate patterns over northern China and more broadly over the Northern Hemisphere. The Pacific Decadal Oscillation (PDO) might be the dominant factor affecting temperature variations over the WLP on decadal timescales.</p

A large carbon pool in lake sediments over the arid/semiaridregion, NW China

Carbon burial in lake sediments is an important component of the global carbon cycle. However, little is known about the magnitude of carbon sequestered in lake sediments over the arid/semiarid region of China(ASAC).In this study, we estimate both organic and inorganic carbon burial since *AD 1800 based on nine lakes in ASAC,and discuss the most plausible factors controlling carbon burial. Our estimates show that the annual organic carbon burial rate(OCBR) ranges from 5.3 to 129.8 g cm-2year-1(weighted mean of 49.9 g cm-2year-1), leading to a standing stock of 1.1&ndash;24.0 kg cm-2(weighted mean of 8.6 kg cm-2)and a regional sum of *108 Tg organic carbon sequestered since *AD 1800. The annual inorganic carbon burial rate(ICBR) ranges from 11.4 to 124.0 g cm-2year-1(weighted mean of 48.3 g cm-2year-1), which is slightly lower than OCBR. The inorganic carbon standing stock ranges from2.4 to 26.0 kg cm-2(weighted mean of 8.1 kg cm-2),resulting in a sum of *101 Tg regional inorganic carbon burial since *AD 1800, which is slightly lower than the organic carbon sequestration. OCBR in ASAC shows a continuously increasing trend since *AD 1950, which is possibly due to the high autochthonous and allochthonous primary production and subsequently high sedimentation rate in the lakes. This increasing carbon burial is possibly related to both climatic changes and enhanced anthropogenic activities, such as land use change, deforestation, and eutrophication in the lake. Furthermore, OCBR and ICBR are expected to continuously increase under the scenario of increasing precipitation and runoff and enhanced anthropogenic activities.The results of this research show that the buried carbon in lake sediments of the ASAC region constitutes a significant and large carbon pool, which should be considered and integrated into the global carbon cycle.</p