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Expansion of the Sahara Desert and shrinking of frozen land of the Arctic.
Expansion of the Sahara Desert (SD) and greening of the Arctic tundra-glacier region (ArcTG) have been hot subjects under extensive investigations. However, quantitative and comprehensive assessments of the landform changes in these regions are lacking. Here we use both observations and climate-ecosystem models to quantify/project changes in the extents and boundaries of the SD and ArcTG based on climate and vegetation indices. It is found that, based on observed climate indices, the SD expands 8% and the ArcTG shrinks 16% during 1950-2015, respectively. SD southern boundaries advance 100 km southward, and ArcTG boundaries are displaced about 50 km poleward in 1950-2015. The simulated trends based on climate and vegetation indices show consistent results with some differences probably due to missing anthropogenic forcing and two-way vegetation-climate feedback effect in simulations. The projected climate and vegetation indices show these trends will continue in 2015-2050
High precision predictions for exclusive production at the LHC
We present a resummation-improved prediction for + 0 jets production at
the Large Hadron Collider. We focus on highly-boosted final states in the
presence of jet veto to suppress the background. In this case,
conventional fixed-order calculations are plagued by the existence of large
Sudakov logarithms for
which lead to unreliable predictions as well as large theoretical
uncertainties, and thus limit the accuracy when comparing experimental
measurements to the Standard Model. In this work, we show that the resummation
of Sudakov logarithms beyond the next-to-next-to-leading-log accuracy, combined
with the next-to-next-to-leading order calculation, reduces the scale
uncertainty and stabilizes the perturbative expansion in the region where the
vector bosons carry large transverse momentum. Our result improves the
precision with which Higgs properties can be determined from LHC measurements
using boosted Higgs techniques.Comment: 24 pages, 8 figure
Atomic-Layer-Deposited Al2O3 on Bi2Te3 for Topological Insulator Field-Effect Transistors
We report dual-gate modulation of topological insulator field-effect
transistors (TI FETs) made on Bi2Te3 thin flakes with integration of
atomic-layer-deposited (ALD) Al2O3 high-k dielectric. Atomic force microscopy
study shows that ALD Al2O3 is uniformly grown on this layer-structured channel
material. Electrical characterization reveals that the right selection of ALD
precursors and the related surface chemistry play a critical role in device
performance of Bi2Te3 based TI FETs. We realize both top-gate and bottom-gate
control on these devices, and the highest modulation rate of 76.1% is achieved
by using simultaneous dual gate control.Comment: 4 pages, 3 figure
MoS2 Dual-Gate MOSFET with Atomic-Layer-Deposited Al2O3 as Top-Gate Dielectric
We demonstrate atomic-layer-deposited (ALD) high-k dielectric integration on
two-dimensional (2D) layer-structured molybdenum disulfide (MoS2) crystals and
MoS2 dual-gate n-channel MOSFETs with ALD Al2O3 as top-gate dielectric. Our C-V
study of MOSFET structures shows good interface between 2D MoS2 crystal and ALD
Al2O3. Maximum drain currents using back-gates and top-gates are measured to be
7.07mA/mm and 6.42mA/mm at Vds=2V with a channel width of 3 {\mu}m, a channel
length of 9 {\mu}m, and a top-gate length of 3 {\mu}m. We achieve the highest
field-effect mobility of electrons using back-gate control to be 517 cm^2/Vs.
The highest current on/off ratio is over 10^8.Comment: submitted to IEEE Electron Device Letter
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