[en] We study the pressureless Euler equations with nonlocal alignment interactions, which arises as a macroscopic representation of the Cucker–Smale model on animal flocks. For the Euler-alignment system with bounded interactions, a critical threshold phenomenon is proved in Tadmor and Tan (2014 Phil. Trans. R. Soc. A 372 20130401), where global regularity depends on initial data. With strongly singular interactions, global regularity is obtained in Do et al (2018 Arch. Ration. Mech. Anal. 228 1–37), for all initial data. We consider the remaining case when the interaction is weakly singular. We show a critical threshold, similar to the system with bounded interaction. However, different global behaviors may happen for critical initial data, which reveals the unique structure of the weakly singular alignment operator. (paper)

[en] Highlights: • The a³Δ_1,2 and A¹Δ low-lying states of TaN molecule observed. • The equilibrium vibrational constants for the X¹Σ⁺ and a³Δ_1,2 states determined. • Theory and experiment shows good agreement for term energy and molecular constants. Laser-induced dispersed fluorescence spectra of TaN molecules, produced in a free-jet apparatus, have been studied. Two spin components of the lowest-lying a³Δ state along with their vibrational structure have been observed. The A¹Δ state, which was predicted earlier by ab initio calculation has also been observed. The X¹Σ⁺ ground state vibrational progression up to v = 9 has been recorded. The experimentally determined term energies and vibrational constants at equilibrium for the ground and a³Δ states are in fairly good agreement with the ab initio values reported earlier.

No abstract available

[en] (1−x)(Bi_0.5Na_0.5)TiO₃-xBa(Ni_0.5Nb_0.5)O₃ (x = 0–0.04) lead-free ceramics (abbreviated as (1−x)BNT-xBNN) were synthesized by a conventional solid-state reaction method. The effect of BNN contents on phase structure, microstructure, ferroelectric, dielectric, pyroelectric properties and thermal stability of (1−x)BNT-xBNN ceramics were systematically investigated. The pyroelectric coefficient (p) at room temperature increased gradually from 3.01 × 10⁻⁸ C cm⁻²K⁻¹ at x = 0 to 5.94 × 10⁻⁸ C cm⁻²K⁻¹ at x = 0.04. The dielectric loss (tan δ) and dielectric constant (ε _r) decreased first with the small amount of BNN content, then increased slightly with further BNN addition, acquiring the minimum tan δ and ε _r at x = 0.02. When x = 0.02, the optimal over-all properties were observed with pyroelectric figure of merit (FOMs) of F _v = 3.82 × 10⁻² m² C⁻¹ and figure of merit of F _d = 2.74 × 10⁻⁵ P a ^−1/2. More importantly, the depolarization temperature (T_d) of 0.98BNT-0.02BNN ceramics is up to ∼195 °C which is higher than most other reported BNT-based ferroelectric ceramics. In addition, it can be exposed to temperature up to ∼145 °C with negligible deterioration of pyroelectric properties, showing excellent thermal stability. The overall properties reveal that 0.98BNT-0.02BNN ceramics is a promising pyroelectric material for infrared detectors. (paper)

[en] A tantalum/tantalum nitride (Ta/TaN) multilayered coating is deposited on plasma-nitridedAZ91 Mg alloy. The top TaN layer undergoes O₂ + Ar plasma etching to improve the antibacterial properties and Mg plasma immersion ion implantation (MgPIII) is performed to enhance the biocompatibility and wound healing capability. A uniform, compact, homogeneous, and columnar nanostructured MgPIII and plasma-etched TaN layer with a cluster size of about 17 nm, surface roughness of 0.28 nm, and needle morphology is observed. Although, plasma etching increases the corrosion current density (i _corr) from 0.02 to 0.19 µA cm⁻² due to larger surface roughness and different potentials between sharp points and smooth points, MgPIII decreases i _corr from 0.19 to 0.02 µA cm⁻² besides a more positive corrosion potential. The amounts of Mg⁺² released to the simulated body fluid (SBF) diminishes from 89.63 ± 0.54 to 60.30 ± 0.47 mg l⁻¹ cm⁻² indicating improved corrosion resistance. Under fever conditions (40 °C), i _corr decreases by 63%, but the open circuit potential does not change due to the constant chemical composition of the surface as well as thicker double layer and less defects, as confirmed by the larger amount of Mg⁺² of 71.49 ± 0.22 mg l⁻¹ cm⁻² leached to the SBF. In the self-healing process which occurs via the reactions between the tantalum intermediate layer and electrolytes and penetrating ions through the defects as well as formation of oxide compounds, creation and propagation of defects are deterred as shown the 24 h destructive polarization test in SBF. The combination of plasma etching and MgPIII enhance not only the bacterial resistance and biocompatibility of the super-hard TaN layer by providing the rougher surface on TaN–P–Mg, but also the nano-mechanical properties and anticorrosion properties. As a result, the hardness increases by 7%, elastic modulus decreases by 19%, and the stiffness increases by 21%. (paper)

No abstract available

[en] The synthesis of polynitrogen compounds is of great importance due to their potential as high-energy-density materials (HEDM), but because of the intrinsic instability of these compounds, their synthesis and stabilization is a fundamental challenge. Polymeric nitrogen units which may be stabilized in compounds with metals at high pressure are now restricted to non-branched chains with an average N-N bond order of 1.25, limiting their HEDM performances. Herein, we demonstrate the synthesis of a novel polynitrogen compound TaN${}_5$ via a direct reaction between tantalum and nitrogen in a diamond anvil cell at circa 100 GPa. TaN${}_5$ is the first example of a material containing branched all-single-bonded nitrogen chains [N${}_5$${}^{5-<!--\; ???\; -->}$]${}_{\mathrm{\infty <!--\; ???\; -->}}$. Apart from that we discover two novel Ta-N compounds: TaN${}_4$ with finite N${}_4$${}^{4-<!--\; ???\; -->}$ chains and the incommensurately modulated compound TaN${}_{2-<!--\; ???\; -->x}$, which is recoverable at ambient conditions. (© 2021 Wiley-VCH GmbH)

[en] The shadowing effect is one of the most urgent issues yet to be solved in high-volume manufacturing using extreme ultraviolet lithography (EUVL). Many studies have been conducted to mitigate the unexpected results caused by shadowing effects. The simplest way to mitigate the shadowing effect is to reduce the thickness of the absorber. Since nickel has high extinction coefficients in the EUV wavelengths, it is one of more promising absorber material candidates. A Ni based absorber exhibited imaging performance comparable to a Tantalum nitride absorber. However, the Ni-based absorber showed a dramatic reduction in horizontal-vertical critical dimension (H-V CD) bias. Therefore, limitations in fabricating a EUV mask can be mitigated by using the Ni based absorber.

[en] The influence of a variable oxygen concentration in HfO_x (x < 2) layers on the forming process and resistive switching of TaN/HfO_x/Ni ReRAM cells is investigated. We demonstrate that resistive switching is possible only for those cells for which the Hf/O ratio in a HfO_x layer corresponds to a narrow range for which x ≈ 1.8. The decrease of oxygen concentration in the oxide layer is shown to lead to, on the one hand, the decrease in the I _ON/I _OFF ratio and, on the other hand, to the elimination of the forming process. The analysis of XPS spectra of HfO_x films for a wide range of compositions revealed that the range of x, for which resistive switching is possible, corresponds to a maximum concentration of the Hf₄O₇ phase. The influence of HfO_x phase composition on resistive switching is discussed. (paper)

[en] We reconsider the all-optical weak homodyne-measurement based experimental schemes aimed at revealing Bell nonclassicality (‘nonlocality’) of a single photon. We focus on the schemes put forward by Tan et al (TWC, 1991) and Hardy (1994). In our previous work we show that the TWC experiment can be described by a local hidden variable model, hence the claimed nonclassicality is apparent. The nonclassicality proof proposed by Hardy remains impeccable. We investigate which feature of the Hardy’s approach is crucial to disclose the nonclassicality. There are consequential differences between TWC and Hardy setups: (i) the initial state of Hardy is a superposition of a single photon excitation with vacuum in one of the input modes of a 50–50 beamsplitter. In the TWC case there is no vacuum component. (ii) In the final measurements of Hardy’s proposal the local settings are specified by the presence or absence of a local oscillator field (on/off). In the TWC case the auxiliary fields are constant, only phases are varied. We show that in Hardy’s setup the violation of local realism occurs due to the varying strength of the local oscillators. Still, one does not need to operate in the fully on/off detection scheme. Thus, the nonclassicality in a Hardy-like setup cannot be attributed to the single-photon state alone. It is a consequence of its interference with the photons from auxiliary local fields. Neither can it be attributed to the joint state of the single photon excitation and the local oscillator modes, as this state is measurement setting dependent. Despite giving spurious violations of local realism, the TWC scheme can serve as an entanglement indicator, for the TWC state. Nevertheless an analogue indicator based on intensity rates rather than just intensities overperforms it. (paper)