Ammonium pyrrolidine dithiocarbamate (APDTC) monolayer was self-assembled on fresh copper surface obtained after oxidation–reduction cycle treatment in 0.1
mol
L
−
1
potassium chloride solution at ...ambient temperature. The APDTC self-assembled monolayer (SAM) on copper surface was investigated by surface enhanced Raman scattering spectroscopy and the results show that APDTC SAM is chemisorbed on copper surface by its sulfur atoms with perpendicular orientation. The optimum immersing period for SAM formation is 4
h at 0.01
mol
L
−
1
concentration of APDTC. The impedance results indicate that APDTC SAM has good corrosion inhibition effects for copper in 0.5
mol
L
−
1
hydrochloric acid solution and its maximum inhibition efficiency could reach 95%. Quantum chemical calculations show that APDTC has relatively small Δ
E between the highest occupied molecular orbital and the lowest unoccupied molecular orbital and large negative charge in its two sulfur atoms, which facilitate formation of an insulating Cu/APDTC film on copper surface.
► DDTC is of low toxicity. ► DDTC SAM had good corrosion inhibition effects on copper in 3% NaCl solution. ► DDTC SAM was chemisorbed on copper surface by its S atoms.
Sodium diethyldithiocarbamate ...(DDTC) self-assembled monolayer (SAM) on copper surface has been investigated by SERS and EDS and the results show that DDTC SAM is chemisorbed on copper surface by its S atoms with tilted orientation. Corrosion inhibition ability of DDTC SAM was measured in 3% NaCl solution using electrochemical methods. The impedance results indicate that the maximum inhibition efficiency of DDTC SAM can reach 99%. Quantum chemical calculations show that DDTC has relatively small Δ
E between HOMO and LUMO and large negative charge in its two sulfur atoms, which facilitates the formation of a DDTC SAM on copper surface.
This paper presents an active aerodynamic control method of flutter oscillation for long-span suspension bridges with a newly designed twin-winglet system. The key point of this paper is to establish ...the theoretical framework for active control of bridge flutter by a pair of rotatable winglets beyond the deck, of which motions are determined by the feedback control algorithm. Through utilizing aerodynamic forces generated by these winglets, this active control system can improve aerodynamic stability of long-span suspension bridges to some extent. The modeling and control of this system mainly focus on practical feasibility, in which the relative rotations rather than driving forces of both winglets are selected as the control variables in the paper. State space expression of the control system is proposed to handle problems of high order terms elimination and decoupling for control variables. Since the unobservability of aerodynamic states, model reduction technique is adopted in the design of observer and controller. The active control algorithm presented in this paper is verified by numerical simulations, and the stabilizing mechanism and energy consumption are discussed as well. It shows good effectiveness and robustness of this active aerodynamic control device in a wide range of wind speeds for flutter suppression.
•A theoretical framework for active control of bridge flutter by a twin-winglet system is established.•Relative rotations rather than driving forces of the winglets are used in the modeling for practical considerations, using optimal feedback control principles.•Effectiveness, robustness and mechanism of the twin-winglet system are discussed by numerical examples.
We report a localized surface plasmon enhanced upconversion luminescence in Au/SiO2/Y2O3:Yb3+,Er3+ nanoparticles when excited at 980 nm. By adjusting the silica spacer's thickness, a maximum ...9.59-fold enhancement of the green emission was obtained. Effect of the spacer distance on the Au-Y2O3:Yb3+, Er3+ green upconversion mechanism was numerically simulated and experimentally demonstrated. In theory for radiative decay and excitation rates, they can be largely enhanced at the spacer thicknesses of less than 70 and 75 nm, respectively, and the quenching can be caused by the non-radiative energy transferring at the distance of less than 55 nm.
ABSTRACT
The close correlation observed between emission state and spin-down rate change of pulsars has many implications both for the magnetospheric physics and the neutron star interior. The ...middle-aged pulsar PSR J0738-4042, which had been observed to display variations in the pulse profile associated with its spin-down rate change due to external effects, is a remarkable example. In this study, based on the 12.5 yr combined public timing data from UTMOST and Parkes, we have detected a new emission-rotation correlation in PSR J0738-4042 concurrent with a glitch. A glitch that occurred at MJD 57359 (5) (2015 December 3) with Δν/ν ∼ 0.36(4) × 10−9 is the first glitch event observed in this pulsar, and is probably the underlying cause of the emission-rotation correlation. Unlike the usual post-glitch behaviours, the braking torque on the pulsar has continued to increase over 1380 d, corresponding to a significant decrease in $\ddot{\nu }$. As for changes in the pulse profile after the glitch, the relative amplitude of the leading component weakens drastically, while the middle component becomes stronger. A combined model of crustquake induced platelet movement and vortex creep response is invoked to account for this rare correlation. In this scenario, magnetospheric state-change is naturally linked to the pulsar-intrinsic processes that give rise to a glitch.
The mechanism of structural evolution and phase formation for in-situ bulk metallic glass composites (BMGCs) remains unclear and needs to be described via a comprehensive strategy. Herein, four ...chemical compositions (named as ZN10, ZN30, ZN50, and ZN70, respectively) were designed and used as base alloys for exploring the microstructures and mechanical properties from the thermodynamic and structural points of view. A pseudo-binary (ZrNb)-(CuNiAl) phase diagram was constructed to predict the relationship between structural evolutions and chemical compositions. Phase formation and composition distributions of bulk metallic glasses (BMGs) and in-situ BMGCs were carefully investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) equipped with an energy-dispersive spectrometer (EDS). Based on experimental results, the structural evolutions were analyzed and discussed in details, showing the evolution from the atomic-scale ordered clusters to micro-scale phase precipitation in the supercooled liquid. Furthermore, the compressive mechanical tests of as-cast samples were performed to unveil the correlation between microstructures and deformation behaviors of different alloys. It is believed that the proposed strategy and experimental results can deepen the understanding of the formation of BMGs and in-situ BMGCs associated with atomic-scale ordered structures, and provide new insights to design in-situ BMGCs from the structural perspective.
•In-situ BMGCs were successfully designed and prepared from a multi-cluster competition strategy.•A pseudo-binary (ZrNb)-(CuNiAl) phase diagram was constructed to predict the mechanism of structural evolution.•Icosahedral-like and crystal-like clusters are responsible for different crystallization tendencies.•The features of mechanical properties have been carefully investigated.
Summary
Precipitates and solute enrich in aged ferritic steel containing copper were examined using high‐resolution electron microscopy, high‐angle annular dark‐field scanning transmission electron ...microscopy and energy‐dispersive X‐ray spectroscopy. Two ledges with one‐atom and two‐atom layers height in the 9R/3R interface were observed. The enrichment of copper into two successive closed‐packed planes with an interval of Fe‐rich close‐packed plane was detected. The passage of the Shockley partial, or the shearing, changes the stacking sequence of closed‐packed planes. Finally, 9R Cu variant transformed into 3R Cu variant.
Abstract
How animals assess information encoded in individual color patches have been extensively studied, yet the role of both individual color patches and gross color pattern (i.e., the combination ...of color patches) remains understudied. We tested the functioning of both individual color patches and gross color pattern in sexual selection using the jumping spider Siler semiglaucus as a study system. We first quantified sexual dimorphism in S. semiglaucus in both individual patches and gross color pattern using the newly developed quantitative color pattern analysis (QCPA) framework. After detecting sexual differences in color coverage and pattern contrast, we manipulated the abdomen color pattern of males and had them engage in both female mate choice and male contest trials. Females spent more time watching males with lower pattern contrast and greater red coverage during mate assessment, suggesting that they evaluate information from both individual patches and gross color pattern of males. However, male color pattern had no significant effect on the outcomes of male contests. Thus, we suggest that the observed sexual color pattern dimorphism evolved primarily through female mate choice in S. semiglaucus. This is the first study to use QCPA framework to quantify sexual dimorphism in within-pattern conspicuousness from an intraspecific perspective in invertebrates. Our study also highlights the importance of both individual color patches and gross color pattern in sexual selection.
Males and females are strikingly different in color patterns, which is likely sexually selected. However, it is difficult to quantify such a difference. By applying a newly developed quantitative color pattern analysis framework, we quantify sexual dimorphism in color patterns in a jumping spider. We find that male abdomen color pattern is shaped exclusively by female mate choice. Our study sheds new light on the importance of global color patterns in sexual selection.
Ti-28 at.%Ta powders were produced by rapid solidification via plasma rotating electrode process (PREP). It is found that microstructure, morphology and phase constituents of Ti-28Ta powders are ...particle size dependent. Small powder particle exhibit the formation of predominant martensitic α” and minor metastable β, whilst large particles consist of primary metastable β with minor martensitic α” phase. The amount of martensitic α” increases while the amount of metastable β phase decreases with decreasing the particle size. The martensitic α” lath with the size of about 50 nm wide and 1 μm long are formed preferentially at the β grain boundaries. The martensitic transformation start temperature (Ms) and peak temperature (Mp) are ∼390 °C and ∼340 °C respectively for the Ti-28Ta powders with the particle size between 40 and 65 μm. An increased Vickers micro-hardness is obtained and is associated with decreasing particle size.
•We investigated the particle size effect on the microstructures of the Ti-28Ta powders.•The cooling rate has a significant effect on α”/β ratio in powders dependent on the particle size.•The α” martensitic plates were preferentially formed at the grain boundaries.
Co-receptor tropism has been identified to correlate with HIV-1 transmission and the disease progression in patients. A molecular epidemiology investigation of co-receptor tropism is important for ...clinical practice and effective control of HIV-1. In this study, we investigated the co-receptor tropism on HIV-1 variants of 85 antiretroviral-naive patients with Geno2pheno algorithm at a false-positive rate of 10%. Our data showed that a majority of the subjects harboured the CCR5-tropic virus (81.2%, 69/85). No significant differences in gender, age, baseline CD4+ T-cell counts and transmission routes were observed between subjects infected with CXCR4-tropic or CCR5-tropic virus. The co-receptor tropism appeared to be associated with the virus genotype; a significantly more CXCR4-use was predicted in CRF01_AE infections whereas all CRF07_BC and CRF08_BC were predicted to use CCR5 co-receptor. Sequences analysis of V3 revealed a higher median net charge in the CXCR4 viruses over CCR5 viruses (4.0 vs. 3.0, P < 0.05). The predicted N-linked glycosylation site between amino acids 6 and 8 in the V3 region was conserved in CCR5 viruses, but not in CXCR4 viruses. Besides, variable crown motifs were observed in both CCR5 and CXCR4 viruses, of which the most prevalent motif GPGQ existed in both viral tropism and almost all genotypes identified in this study except subtype B. These findings may offer important implications for clinical practice and enhance our understanding of HIV-1 biology.
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