291 research outputs found
The Impact of Temperature on Mortality in Tianjin, China: A Case-Crossover Design with a Distributed Lag Nonlinear Model
Background: Although interest in assessing the impacts of temperature on mortality has increased, few studies have used a case-crossover design to examine nonlinear and distributed lag effects of temperature on mortality. Additionally, little evidence is available on the temperature–mortality relationship in China or on what temperature measure is the best predictor of mortality
Semimetal Contacts to Monolayer Semiconductor: Weak Metalization as an Effective Mechanism to Schottky Barrier Lowering
Recent experiment has uncovered semimetal bismuth (Bi) as an excellent
electrical contact to monolayer MoS with ultralow contact resistance. The
contact physics of the broader semimetal/monolayer-semiconductor family beyond
Bi/MoS, however, remains largely unexplored thus far. Here we perform a
comprehensive first-principle density functional theory investigation on the
electrical contact properties between six archetypal two-dimensional (2D)
transition metal dichalcogenide (TMDC) semiconductors, i.e. MoS, WS,
MoSe, WSe, MoTe and WTe, and two representative types of
semimetals, Bi and antimony (Sb). As Bi and Sb work functions energetically
aligns well with the TMDC conduction band edge, Ohmic or nearly-Ohmic -type
contacts are prevalent. The interlayer distance of semimetal/TMDC contacts are
significantly larger than that of the metal/TMDC counterparts, which results in
only weak metalization of TMDC upon contact formation. Intriguingly, such weak
metalization generates semimetal-induced gap states (MIGS) that extends below
the conduction band minimum, thus offering an effective mechanism to reduce or
eliminate the -type Schottky barrier height (SBH) while still preserving the
electronic structures of 2D TMDC. A modified Schottky-Mott rule that takes into
account SMIGS, interface dipole potential, and Fermi level shifting is
proposed, which provides an improved agreement with the DFT-simulated SBH. We
further show that the tunneling-specific resistivity of Sb/TMDC contacts are
generally lower than the Bi counterparts, thus indicating a better charge
injection efficiency can be achieved through Sb contacts. Our findings reveal
the promising potential of Bi and Sb as excellent companion electrode materials
for advancing 2D semiconductor device technology.Comment: 12 pages, 7 figure
Enhancing the specificity and efficiency of polymerase chain reaction using polyethyleneimine-based derivatives and hybrid nanocomposites
There is a general necessity to improve the specificity and efficiency of the polymerase chain reaction (PCR), and exploring the PCR-enhancing mechanism still remains a great challenge. In this paper we report the use of branched polyethyleneimine (PEI)-based derivatives and hybrid nanocomposites as a novel class of enhancers to improve the specificity and efficiency of a nonspecific PCR system. We show that the surface-charge polarity of PEI and PEI derivatives plays a major role in their effectiveness to enhance the PCR. Positively charged amine-terminated pristine PEI, partially (50%) acetylated PEI (PEI-Ac50), and completely acetylated PEI (PEI-Ac) are able to improve PCR efficiency and specificity with an optimum concentration order of PEI < PEI-Ac50 < PEI-Ac, whereas negatively charged carboxyl-terminated PEI (PEI-SAH; SAH denotes succinamic acid groups) and neutralized PEI modified with both polyethylene glycol (PEG) and acetyl (Ac) groups (PEI-PEG-Ac) are unable to improve PCR specificity and efficiency even at concentrations three orders of magnitude higher than that of PEI. Our data clearly suggests that the PCR-enhancing effect is primarily based on the interaction between the PCR components and the PEI derivatives, where electrostatic interaction plays a major role in concentrating the PCR components locally on the backbones of the branched PEI. In addition, multiwalled carbon nanotubes modified with PEI and PEI-stabilized gold nanoparticles are also able to improve the PCR specificity and efficiency with an optimum PEI concentration less than that of the PEI alone, indicating that the inorganic component of the nanocomposites may help improve the interaction between PEI and the PCR components. The developed PEI-based derivatives or nanocomposites may be used as efficient additives to enhance other PCR systems for different biomedical applications
Progress in strategies for sequence diversity library creation for directed evolution
Protein engineering has been the most attractive strategy for biologists to redesign enzymes. As the simplest technique of protein engineering, directed evolution has been applied to many fields, such as industry, agriculture and medicine. An experiment of directed evolution comprises mutant libraries creation and screening or selection for enzyme variants with desired properties. Therefore, a successful application of directed evolution depends on whether or not one can generate a quality library and perform effective screening to find the desired properties. Directed evolution is already increasingly used in many laboratories to improve protein stability and activity, alter enzyme substrate specificity, or design new activities. Meanwhile, many more effective novel strategies of mutant library generation and screening or selection have emerged in recent years, and will continue to be developed. Combining computational/rational design with directed evolution has been developed as more available means to redesign enzymes.Keywords: Protein engineering, directed evolution, sequence diversity creation, novel strategy, computational design, rational desig
Projecting Fine Particulate Matter-related Mortality in East China
China is suffering from severe air pollution from fine particulate matter [≤ 2.5 μm in aerodynamic diameter (PM)], especially East China. But its future trends and potential health impacts remain unclear. The study objectives were to project future trends of PM and its short-term effect on mortality in East China by 2030. First, daily changes in PM concentrations between 2005 and 2030 were projected under the "current legislation" scenario (CLE) and the "maximum technically feasible reduction" scenario (MFR). Then, they were linked to six population projections, two mortality rate projections, and PM-mortality associations to estimate the changes in PM-related mortality in East China between 2005 and 2030. Under the CLE scenario, the annual mean PM concentration was projected to decrease by 0.62 μg/m in East China, which could cause up to 124 000 additional deaths, when considering the population growth. Under the MFR scenario, the annual mean PM concentration was projected to decrease by 20.41 μg/m in East China. At least 230 000 deaths could be avoided by such a large reduction in PM concentration under MFR scenario, even after accounting for the population growth. Therefore, our results suggest that reducing PM concentration substantially in East China would benefit the public health. Otherwise, it may still remain as a great health risk in the future, especially when the population keeps growing
Advances, Mechanisms and Applications in Oxygen Evolution Electrocatalysis of Gold- driven
© 2024 The Authors. Published by Elsevier B.V. This is an open access article under the Creative Commons Attribution-Non Commercial-No Derivatives CC BY-NC-ND licence, https://creativecommons.org/licenses/by-nc-nd/4.0/The oxygen evolution reaction (OER) plays a crucial role in electrochemical energy storage and conversion. Among different metal elements, gold (Au) stands out due to its high electronegativity and remarkable catalytic properties, especially in nanoscale size. In this review, we aim to comprehensively analyze the oxygen electrocatalytic performance of nanosized Au, including the influence of the crystal surface, morphology, substrate materials of Au nanoparticles, size and ligands of Au nanoclusters, and Au single atoms on oxygen electrocatalysis. By exploring the catalytic performance of noble metals, non-noble metals, oxides, hydroxides/oxyhydroxides/layered double hydroxides, sulfides, phosphides, nitrides, and selenides through the integration of nanosized Au, which offers valuable insights for enhancing the OER efficiency. These effects can be attributed to two mechanisms: i) adsorbate evolution mechanism (AEM) and ii) lattice oxygen mechanism (LOM), where the nanosized Au changed the electronic structure of the catalysts and improved the adsorption of reaction intermediates to accelerate electron transfer process or exerts the synergistic effect between metallic Au and oxygen vacancies. For instance, Au-driven OER catalysts can be widely used in zinc-air batteries and water splitting in the future.Peer reviewe
Laser-assisted synthesis of two-dimensional transition metal dichalcogenides: a mini review
The atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDCs) have attracted the researcher’s interest in the field of flexible electronics due to their high mobility, tunable bandgaps, and mechanical flexibility. As an emerging technique, laser-assisted direct writing has been used for the synthesis of TMDCs due to its extremely high preparation accuracy, rich light–matter interaction mechanism, dynamic properties, fast preparation speed, and minimal thermal effects. Currently, this technology has been focused on the synthesis of 2D graphene, while there are few literatures that summarize the progress in direct laser writing technology in the synthesis of 2D TMDCs. Therefore, in this mini-review, the synthetic strategies of applying laser to the fabrication of 2D TMDCs have been briefly summarized and discussed, which are divided into top-down and bottom-up methods. The detailed fabrication steps, main characteristics, and mechanism of both methods are discussed. Finally, prospects and further opportunities in the booming field of laser-assisted synthesis of 2D TMDCs are addressed
2D Janus Niobium Oxydihalide NbO: Multifunctional High-Mobility Piezoelectric Semiconductor for Electronics, Photonics and Sustainable Energy Applications
Two-dimensional (2D) niobium oxydihalide NbOI has been recently
demonstrated as an excellent in-plane piezoelectric and nonlinear optical
materials. Here we show that Janus niobium oxydihalide, NbO (X, Y = Cl, Br,
I and XY), is a multifunctional anisotropic semiconductor family with
exceptional piezoelectric, electronic, photocatalytic and optical properties.
NbO are stable and mechancially flexible monolayers with band gap around
the visible light regime of eV. The anisotropic carrier mobility of
NbO lies in the range of cmVs, which
represents some of the highest among 2D semiconductors of bandgap
eV. Inversion symmetry breaking in Janus NbO generates sizable out-of-plane
piezoelectric response while still retaining a strong in-plane
piezoelectricity. Remarkably, NbO exhibits an additional out-of-plane
piezoelectric response, as large as 0.55 pm/V. GW-BSE
calculation further reveals the strong linear optical dichroism of NbO in
the visible-to-ultraviolet regime. The optical absorption peaks with
\% in the deep UV regime ( eV), outperforming the vast majority of
other 2D materials. The high carrier mobility, strong optical absorption,
sizable built-in electric field and band alignment compatible with overall
water splitting further suggest the strengths of NbO in energy conversion
application. We further propose a directional stress sensing device to
demonstrate how the out-of-plane piezoelectricity can be harnessed for
functional device applications. Our findings unveil NbO as an exceptional
multifunctional 2D semiconductor for flexible electronics, optoelectronics, UV
photonics, piezoelectric and sustainable energy applications.Comment: 16 Pages, 7 Figures, 3 Table
A Truncated IL‐17RC Peptide Ameliorates Synovitis and Bone Destruction of Arthritic Mice
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134880/1/adhm201600668_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134880/2/adhm201600668-sup-0001-S1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134880/3/adhm201600668.pd
Adaptive Steered Molecular Dynamics Combined With Protein Structure Networks Revealing the Mechanism of Y68I/G109P Mutations That Enhance the Catalytic Activity of D-psicose 3-Epimerase From Clostridium Bolteae
The scarcity, richness, and other important physiological functions of D-psicose make it crucial to increase the yield of D-psicose. The production of D-psicose can be accomplished by D-psicose 3-epimerase (DPEase) from Clostridium bolteae (CbDPEase) catalyzing the substrate D-fructose. Although the catalytic efficiency of the CbDPEase has been raised via using the site-directed mutagenesis (Y68I/G109P) technique, structure-activity relationship in the wild-type CbDPEase and Y68I/G109P mutant is currently poorly understood. In our study, a battery of molecular modeling methods [homology modeling, adaptive steered molecular dynamics (ASMD) simulations, and Molecular Mechanics/Generalized Born Surface Area (MM-GB/SA)], combined with protein structure networks, were employed to theoretically characterize the reasons for the differences in the abilities of the D-fructose catalyzed by the wild-type CbDPEase and Y68I/G109P mutant. Protein structure networks demonstrated that site-directed mutagenesis enhanced the connectivity between D-fructose and CbDPEase, leading to the increased catalytic efficiency mediated by the functional residues with high betweenness. During the dissociation of the D-fructose from the Y68I/G109P mutant, planes of benzene rings of F248 and W114 could be continuously parallel to the stretching direction of D-fructose. It made the tunnel have an open state and resulted in the stable donor-π interactions between D-fructose and the benzene rings around 18Å. The stronger substrate-protein interactions were detected in the Y68I/G109P mutant, instead of in the wild-type CbDPEase, which were consistent with the binding free energy and Potential Mean of Force (PMF) results. The theoretical results illustrated the reasons that Y68I/G109P mutations increased the catalytic efficiency of CbDPEase and could be provided the new clue for further DPEase engineering
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