BioCARS, a NIH‐supported national user facility for macromolecular time‐resolved X‐ray crystallography at the Advanced Photon Source (APS), has recently completed commissioning of an upgraded ...undulator‐based beamline optimized for single‐shot laser‐pump X‐ray‐probe measurements with time resolution as short as 100 ps. The source consists of two in‐line undulators with periods of 23 and 27 mm that together provide high‐flux pink‐beam capability at 12 keV as well as first‐harmonic coverage from 6.8 to 19 keV. A high‐heat‐load chopper reduces the average power load on downstream components, thereby preserving the surface figure of a Kirkpatrick–Baez mirror system capable of focusing the X‐ray beam to a spot size of 90 µm horizontal by 20 µm vertical. A high‐speed chopper isolates single X‐ray pulses at 1 kHz in both hybrid and 24‐bunch modes of the APS storage ring. In hybrid mode each isolated X‐ray pulse delivers up to ∼4 × 1010 photons to the sample, thereby achieving a time‐averaged flux approaching that of fourth‐generation X‐FEL sources. A new high‐power picosecond laser system delivers pulses tunable over the wavelength range 450–2000 nm. These pulses are synchronized to the storage‐ring RF clock with long‐term stability better than 10 ps RMS. Monochromatic experimental capability with Biosafety Level 3 certification has been retained.
Processing Al alloys by combining aging and deformation have attracted considerable interests recently. However, contrary to the well defined precipitation-hardening in Al alloys obtained by ...conventional artificial aging, the strengthening mechanism in these alloys is still poorly understood. In this report, a thermo-mechanical route proceeding by solution treatment, water quenching, natural aging, cold-rolling and post-annealing was implemented to produce an Al–Mg–Si alloy sheet with significant improvement in strength and a comparable ductility to conventional T6 treated alloy. A relatively complete physical metallurgical picture of this Al–Mg–Si sheet alloy processed by deformation and aging was established based on electron microscopy. During post-annealing, the deformed structures underwent a considerable decrease in dislocation density and extensive sub-grains as well as nano-grains formed. At the same time, nano-sized wall-like precipitates that were rather different with those in traditionally aged Al–Mg–Si alloys formed with the mediation of lattice defects. Observing in the longitudinal plane, the sheet possessed a banded microstructure consisted of sub-lamellas with a thickness of about 100–200nm. The hierarchical nanostructures achieved by deformation and aging due to concurrent precipitation and defects annihilation can enhance the capacity of the alloy to accommodate dislocations under tension deformation and thus led to a ductile failure. The combination of strength and ductility in our hierarchically nanostructured Al–Mg–Si alloy was discussed.
Transition metal compounds containing nickel and copper have been investigated as electrode materials for energy storage. (Ni,Cu)(OH)2CO3 and α-Ni(OH)2 with different Ni/Cu ratios are synthesized by ...a simple hydrothermal method. All the samples show the similar dandelion-like morphology. It is demonstrated that the mole ratio of Ni to Cu is a key factor to influence the phase and electrochemical performances of the products. Carbonate anions will be intercalated into nickel copper layered double hydroxides with a hydrotalcite structure when the sample is nickel-rich, which will lead to much better electrochemical properties compared with the copper-rich samples with crystalline (Ni,Cu)(OH)2CO3 structure. Among all the materials, sample (Ni0.89Cu0.11)2(OH)2CO3 can deliver the highest specific capacitance of 1017.3 F g−1 at 1 A g−1 and retain 68.5% of the original value after 4000 cycles at 5 A g−1. Meanwhile, an asymmetric capacitor which is assembled by using the optimized material as a positive electrode and activated carbon as a negative electrode exhibits a high energy density of 38.56 Wh kg−1 at a power density of 850.01 W kg−1 and a high power density of 8407.4 W kg−1 at an energy density of 21.7 Wh kg−1. Based on the above results, nickel copper carbonate hydroxides are of potential application for energy storage.
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•(Ni,Cu)2(OH)2CO3 with different Ni/Cu ratios are synthesized by hydrothermal method.•Ni/Cu molar ratio is a key factor to phase and electrochemical performances.•Carbonate anions will intercalate into the space of layered double hydroxides for nickel-rich sample.•The optimized material delivers a high specific capacitance.
Flexible integrated circuits with complex functionalities are the missing link for the active development of wearable electronic devices. Here, we report a scalable approach to fabricate self-aligned ...graphene microwave transistors for the implementation of flexible low-noise amplifiers and frequency mixers, two fundamental building blocks of a wireless communication receiver. A devised AlO x T-gate structure is used to achieve an appreciable increase of device transconductance and a commensurate reduction of the associated parasitic resistance, thus yielding a remarkable extrinsic cutoff frequency of 32 GHz and a maximum oscillation frequency of 20 GHz; in both cases the operation frequency is an order of magnitude higher than previously reported. The two frequencies work at 22 and 13 GHz even when subjected to a strain of 2.5%. The gigahertz microwave integrated circuits demonstrated here pave the way for applications which require high flexibility and radio frequency operations.
The Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope has commenced science observations of the Sun starting in late 2016. Since the Sun is much larger than the field of view of ...individual ALMA dishes, the ALMA interferometer is unable to measure the background level of solar emission when observing the solar disk. The absolute temperature scale is a critical measurement for much of ALMA solar science, including the understanding of energy transfer through the solar atmosphere, the properties of prominences, and the study of shock heating in the chromosphere. In order to provide an absolute temperature scale, ALMA solar observing will take advantage of the remarkable fast-scanning capabilities of the ALMA 12 m dishes to make single-dish maps of the full Sun. This article reports on the results of an extensive commissioning effort to optimize the mapping procedure, and it describes the nature of the resulting data. Amplitude calibration is discussed in detail: a path that uses the two loads in the ALMA calibration system as well as sky measurements is described and applied to commissioning data. Inspection of a large number of single-dish datasets shows significant variation in the resulting temperatures, and based on the temperature distributions, we derive quiet-Sun values at disk center of 7300 K at
λ
=
3
mm
and 5900 K at
λ
=
1.3
mm
. These values have statistical uncertainties of about 100 K, but systematic uncertainties in the temperature scale that may be significantly larger. Example images are presented from two periods with very different levels of solar activity. At a resolution of about
25
″
, the 1.3 mm wavelength images show temperatures on the disk that vary over about a 2000 K range. Active regions and plages are among the hotter features, while a large sunspot umbra shows up as a depression, and filament channels are relatively cool. Prominences above the solar limb are a common feature of the single-dish images.
Many nanoparticle-based carriers to atherosclerotic plaques contain peptides, lipoproteins, and sugars, yet the application of DNA-based nanostructures for targeting plaques remains infrequent. In ...this work, we demonstrate that DNA-coated superparamagnetic iron oxide nanoparticles (DNA-SPIONs), prepared by attaching DNA oligonucleotides to poly(ethylene glycol)-coated SPIONs (PEG-SPIONs), effectively accumulate in the macrophages of atherosclerotic plaques following an intravenous injection into apolipoprotein E knockout (ApoE–/–) mice. DNA-SPIONs enter RAW 264.7 macrophages faster and more abundantly than PEG-SPIONs. DNA-SPIONs mostly enter RAW 264.7 cells by engaging Class A scavenger receptors (SR-A) and lipid rafts and traffic inside the cell along the endolysosomal pathway. ABS-SPIONs, nanoparticles with a similarly polyanionic surface charge as DNA-SPIONs but bearing abasic oligonucleotides also effectively bind to SR-A and enter RAW 264.7 cells. Near-infrared fluorescence imaging reveals evident localization of DNA-SPIONs in the heart and aorta 30 min post-injection. Aortic iron content for DNA-SPIONs climbs to the peak (∼60% ID/g) 2 h post-injection (accompanied by profuse accumulation in the aortic root), but it takes 8 h for PEG-SPIONs to reach the peak aortic amount (∼44% ID/g). ABS-SPIONs do not appreciably accumulate in the aorta or aortic root, suggesting that the DNA coating (not the surface charge) dictates in vivo plaque accumulation. Flow cytometry analysis reveals more pronounced uptake of DNA-SPIONs by hepatic endothelial cells, splenic macrophages and dendritic cells, and aortic M2 macrophages (the cell type with the highest uptake in the aorta) than PEG-SPIONs. In summary, coating nanoparticles with DNA is an effective strategy of promoting their systemic delivery to atherosclerotic plaques.
The Binchang area of southwestern Ordos Basin is one of the most promising areas for low-rank coalbed methane (CBM) in China. This work investigates the Jurassic Yanan Formation coal and CBM geology ...and accumulation characteristics of CBM in the southwestern Ordos Basin based on data from 46 wells and laboratory measurements of 14 coal samples from 7 mines. The results show that coal rank in the Binchang area is mainly sub-bituminous A and high-volatile C bituminous (0.46%–0.73%Ro). Coals are dominated by inertinite (14.7–85.6%); less abundant are vitrinite (8.5–77.7%) and liptinite (1.5–15.2%). Minerals are found only in small amounts (0.4–8.3%). Permeability is between 0.04 and 25.3mD, and porosity ranges from 2.4% to 20.1%. Most coal pores are less than 100nm in diameter, making them favorable for gas adsorption but unfavorable for gas permeability. Pore morphology is represented mainly by micro- and mesopores with a well-connected and ink-bottle shaped (narrow throat and wide body) morphology. These coals are characterized by a high adsorption volume of more than 3.0×10−3ml/g. Methane isothermal adsorption measurements of 12 coal samples revealed that their maximum adsorption capacity (on a dry and ash-free basis) varies from 5.06 to 13.37m3/t, depending on moisture content. However, under the influence of gas preservation conditions, the in-place gas content is generally 0.11–6.26m3/t. Finally, based on a comprehensive analysis of coal thickness, gas content, hydrogeology conditions, roof, floor, and depth properties, this study indicated that the best prospective target areas for CBM production are forecasted to be the Tingnan and Dafosi areas, which are located in the syncline, central south part of the study area.
► The physical properties of low-rank CBM reservoirs are characterized. ► The low-rank CBM enrichment and accumulation model is provided. ► The favorable exploration areas of low-rank CBM are pointed out.
Androgen has been shown to regulate male physiological activities and cancer proliferation. It is used to antagonize estrogen-induced proliferative effects in breast cancer cells. However, evidence ...indicates that androgen can stimulate cancer cell growth in estrogen receptor (ER)-positive and ER-negative breast cancer cells via different types of receptors and different mechanisms. Androgen-induced cancer growth and metastasis link with different types of integrins. Integrin αvβ3 is predominantly expressed and activated in cancer cells and rapidly dividing endothelial cells. Programmed death-ligand 1 (PD-L1) also plays a vital role in cancer growth. The part of integrins in action with androgen in cancer cells is not fully mechanically understood. To clarify the interactions between androgen and integrin αvβ3, we carried out molecular modeling to explain the potential interactions of androgen with integrin αvβ3. The androgen-regulated mechanisms on PD-L1 and its effects were also addressed.
High-density memory arrays require selector devices, which enable selection of a specific memory cell within a memory array by suppressing leakage current through unselected cells. Such selector ...devices must have highly nonlinear current–voltage characteristics and excellent endurance; thus selectors based on a tunneling mechanism present advantages over those based on the physical motion of atoms or ions. Here, we use two-dimensional (2D) materials to build an ultrathin (three-monolayer-thick) tunneling-based memory selector. Using a sandwich of h-BN, MoS2, and h-BN monolayers leads to an “H-shaped” energy barrier in the middle of the heterojunction, which nonlinearly modulates the tunneling current when the external voltage is varied. We experimentally demonstrate that tuning the MoS2 Fermi level can improve the device nonlinearity from 10 to 25. These results provide a fundamental understanding of the tunneling process through atomically thin 2D heterojunctions and lay the foundation for developing high endurance selectors with 2D heterojunctions, potentially enabling high-density non-volatile memory systems.
► The random sequential packing model of dodecahedra is simulated. ► The microstructure of fresh cement paste is characterized by stereological theory. ► Effects of particle shape and PSD on the ...microstructure are quantitatively evaluated. ► The statistical results are verified by the theoretical results.
At the microscopic scale, fresh cement paste is composed of random packing of irregular cement particles and their packing behavior plays an important role in microstructure evolution. The characterization of fresh cement paste microstructure is of particular interest in its physical properties, such as mechanical and transport properties. The preponderance of previous work has focused on the microstructure model by random packing of ellipsoidal particles, and little is known about three-dimensional (3D) non-ellipsoidal particles. In this paper, a modified cement particle size distribution function is used to facilitate particle size distribution of dodecahedral particles. Based on a random sequential algorithm, the microstructure model of fresh cement paste is simulated by the random sequential packing of dodecahedral particles with various sizes. Applying stereological tools and a serial sectioning analysis technique, the simulated microstructure composed of multi-sized dodecahedral cement particles is characterized and compared with that of ellipsoidal cement particles developed by the preliminary work to evaluate the influence of cement particle shape on the microstructure of fresh cement paste. Moreover, the random packings of multi-sized dodecahedral particles satisfied with three specified particle size distribution functions, respectively, are investigated to assess the effect of particle size distribution on the random packing of the dodecahedral particles. Finally, the reliability of the statistical results is verified by theoretical solutions.
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