142 research outputs found
Ultrafast Relaxation Dynamics of Photoexcited Dirac Fermion in The Three Dimensional Dirac Semimetal Cadmium Arsenide
Three dimensional (3D) Dirac semimetals which can be seen as 3D analogues of
graphene have attracted enormous interests in research recently. In order to
apply these ultrahigh-mobility materials in future electronic/optoelectronic
devices, it is crucial to understand the relaxation dynamics of photoexcited
carriers and their coupling with lattice. In this work, we report ultrafast
transient reflection measurements of the photoexcited carrier dynamics in
cadmium arsenide (Cd3As2), which is one of the most stable Dirac semimetals
that have been confirmed experimentally. By using low energy probe photon of
0.3 eV, we probed the dynamics of the photoexcited carriers that are
Dirac-Fermi-like approaching the Dirac point. We systematically studied the
transient reflection on bulk and nanoplate samples that have different doping
intensities by tuning the probe wavelength, pump power and lattice temperature,
and find that the dynamical evolution of carrier distributions can be retrieved
qualitatively by using a two-temperature model. This result is very similar to
that of graphene, but the carrier cooling through the optical phonon couplings
is slower and lasts over larger electron temperature range because the optical
phonon energies in Cd3As2 are much lower than those in graphene
Dynamical Evolution of Anisotropic Response in Black Phosphorus under Ultrafast Photoexcitation
Black phosphorus has recently emerged as a promising material for high
performance electronic and optoelectronic device for its high mobility, tunable
mid-infrared bandgap and anisotropic electronic properties. Dynamical evolution
of photo excited carriers and its induced change of transient electronic
properties are critical for materials' high field performance, but remains to
be explored for black phosphorus. In this work, we perform angle resolved
transient reflection spectroscopy to study the dynamical evolution of
anisotropic properties of black phosphorus under photo excitation. We find that
the anisotropy of reflectivity is enhanced in the pump induced
quasi-equilibrium state, suggesting an extraordinary enhancement of the
anisotropy in dynamical conductivity in hot carrier dominated regime. These
results raise enormous possibilities of creating high field, angle sensitive
electronic, optoelectronic and remote sensing devices exploiting the dynamical
electronic anisotropic with black phosphorus.Comment: 22 pages,10 figure
Addressing China's grand challenge of achieving food security while ensuring environmental sustainability
China’s increasingly urbanized and wealthy population is driving a growing and changing demand for food, which might not be met without significant increase in agricultural productivity and sustainable use of natural resources. Given the past relationship between lack of access to affordable food and political instability, food security has to be given a high priority on national political agendas in the context of globalization. The drive for increased food production has had a significant impact on the environment, and the deterioration in ecosystem quality due to historic and current levels of pollution will potentially compromise the food production system in China. We discuss the grand challenges of not only producing more food but also producing it sustainably and without environmental degradation. In addressing these challenges, food production should be considered as part of an environmental system (soil, air, water, and biodiversity) and not independent from it. It is imperative that new ways of meeting the demand for food are developed while safeguarding the natural resources upon which food production is based. We present a holistic approach to both science and policy to ensure future food security while embracing the ambition of achieving environmental sustainability in China. It is a unique opportunity for China to be a role model as a new global player, especially for other emerging economies
Industrial Water Use Kuznets Curve: Evidence from Industrialized Countries and Implications for Developing Countries
On the Inapplicability of the Cobb-Douglas Production Function for Estimating the Benefit of Water Use and the Value of Water Resources
Prodrug Strategy for PSMA-targeted Delivery of TGX-221 to Prostate Cancer Cells
TGX-221 is a potent, selective, and cell membrane permeable inhibitor of the PI3K p110β catalytic subunit. Recent studies showed that TGX-221 has anti-proliferative activity against PTEN-deficient tumor cell lines including prostate cancers. The objective of this study was to develop an encapsulation system for parenterally delivering TGX-221 to the target tissue through a prostate-specific membrane aptamer (PSMAa10) with little or no side effects. In this study, PEG-PCL micelles were formulated to encapsulate the drug, and a prodrug strategy was pursued to improve the stability of the carrier system. Fluorescence imaging studies demonstrated that the cellular uptake of both drug and nanoparticles were significantly improved by targeted micelles in a PSMA positive cell line. The area under the plasma concentration time curve of the micelle formulation in nude mice was 2.27-fold greater than the naked drug, and the drug clearance rate was 17.5-fold slower. These findings suggest a novel formulation approach for improving site-specific drug delivery of a molecular-targeted prostate cancer treatment
Quality control and homogenization of daily meteorological data in the trans-boundary region of the Jhelum River basin
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