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Plasmon–molecule hybrid systems provide platforms for studying light–matter interactions. It is of great interest for systems where both strong and weak plasmon–molecule couplings exist and can tra...

Convergence of ultrasonic energy is of great importance in the medical and engineering fields. In this work, ultrasonic focusing based on circular Airy-like beam (CALB) is numerically and experimentally demonstrated. The CALB focusing can be achieved simply using a planar resin ring lens immersed in water. At 2 MHz, the acoustic intensity at the focus can reach 257 times that for the incident wave. Arising from the self-healing feature of Airy beams, the CALB focusing can be well maintained even if there exists an obstacle in the acoustic path. Meanwhile, the focusing behaviour is well performed in a broad frequency range of 1.5 MHz to 3.1 MHz due to the simple and non-resonant design. By adjusting the frequency of the incident waves, the focal length can be modified without changing the lens structure. The CALB focusing and the corresponding planar lens may promote wide applications in ultrasound imaging, non-destructive testing, acoustic tweezing and medical diagnostic techniques.

Non-Hermitian systems with parity-time $(\mathcal{P}\mathcal{T})$ symmetry have attracted increasing interest due to their intriguing properties and associated applications. Inspired by that, we propose here an acoustic anti-parity-time $(\mathrm{A}\text{\ensuremath{-}}\mathcal{P}\mathcal{T})$ symmetric structure with metamaterials featuring balanced positive and negative indices, together with equal gain/loss. According to the derived scattering matrix, we demonstrate its extraordinary scattering properties. For example, the spontaneous phase transition of the scattering matrix is observed, by simply modulating the frequency, gain/loss, or geometric width. In the absence of gain/loss, the $\mathrm{A}\text{\ensuremath{-}}\mathcal{P}\mathcal{T}$ symmetric structure degrades into a pair of complementary media, resulting in bidirectional total transmission. At the zero and pole of the scattering matrix, the structure behaves as an acoustic coherent perfect absorber and equivalent laser, respectively, which can perfectly absorb two-port coherent incident waves and radiate two coherent output waves with extensive and equal amplitudes. Different from that in the $\mathcal{P}\mathcal{T}$ symmetric structure, these three effects based on the $\mathrm{A}\text{\ensuremath{-}}\mathcal{P}\mathcal{T}$ symmetric structure are all achieved in the symmetric phase of the scattering matrix, resulting in the symmetric intensity distributions. Besides, the coherent perfect absorption and lasing modes of the $\mathrm{A}\text{\ensuremath{-}}\mathcal{P}\mathcal{T}$ symmetric structure are continuous and symmetric in the parameter space, which may facilitate further experimental realizations. The proposed $\mathrm{A}\text{\ensuremath{-}}\mathcal{P}\mathcal{T}$ symmetric structure provides an alternative method to demonstrate the physics of the non-Hermitian Hamiltonian, and may offer an alternative approach to design acoustic functional devices such as absorbers, sensors, and amplifiers.

Broadband absorption of low-frequency sound waves via a deep subwavelength structure is of great and ongoing interest in research and engineering. Here, we numerically and experimentally present a design of a broadband low-frequency absorber based on an acoustic metaporous composite (AMC). The AMC absorber is constructed by embedding a single metamaterial resonator into a porous layer. The finite element simulations show that a high absorption (absorptance A > 0.8) can be achieved within a broad frequency range (from 290 Hz to 1074 Hz), while the thickness of AMC is 1/13 of the corresponding wavelength at 290 Hz. The broadband and high-efficiency performances of the absorber are attributed to the coupling between the two resonant absorptions and the trapped mode. The numerical simulations and experimental results are obtained to be in good agreement with each other. Moreover, the high broadband absorption can be maintained under random incident acoustic waves. The proposed absorber provides potential applications in low-frequency noise reduction especially when limited space is demanded.

We present the analytical derivation and numerical simulation for the wavefront manipulation of reflected waves at a lossy surface. It is found that the incident plane wave can be reflected in the desired direction or conversed to the trapped surface mode without parasitic scatterings by introducing acoustic energy loss at the surface. To realize the lossy inhomogeneous surface, holey-structured acoustic metamaterial arrays with decoupled reflection amplitude and phase are used. Anomalous reflection phenomena, including non-specular reflection, negative reflection, and conversion of the propagating wave into the surface wave, are achieved by modulating the decoupled amplitude and phase. Our results provide a practical and straightforward way to manipulate the reflected waves, which can also be extended to the three-dimensional wave propagation.

The passive lossless acoustic metasurfaces (AMs) usually use nonlocal behaviors to realize high-efficiency acoustic field manipulation. However, nonlocal behaviors always need complicated unit-cell designs or structure optimizations. In this work, a simple passive lossless AM without nonlocal responses is proposed to perfectly manipulate multi-order diffraction beams. We demonstrate theoretically that the proposed AM can efficiently split an incident acoustic wave into desired reflected directions with arbitrary power flow ratio. Then two examples of two-beam and three-beam lossless AM splitters are constructed with well-designed rigidly ended tubes. Simulation results verify that nearly 100% reflection efficiency can be achieved in the two AM splitters and the power flow distributions are in accord with the designed values. Finally, we fabricate the two-beam AM splitter and confirm experimentally that it can achieve high-efficiency reflection splitting with arbitrary power distribution. Our proposed AM may contribute to designing devices for different applications in energy harvesting and communication.

Acoustic ventilation barriers (AVBs) constructed from metamaterials can effectively insulate sound waves while maintaining airflow, but previous schemes suffer from complex geometric structures. Here, we propose a reconfigurable AVB with subwavelength thickness (0.15λ), which is composed of simple zigzag structures with regular intervals and can be assembled into a full enclosure with an arbitrary shape. It is the interaction between the scattered wave of the zigzag structure and the un-scattered wave through the air channel that leads to a transmission dip and hence a sound insulation. Numerical simulations and experimental demonstrations consistently verify that the AVB possesses excellent omnidirectional sound insulation, while the width of the air channel can reach three times the unit width. As the number of cavity increases, the acoustic insulation bandwidth is broadened from 0.875/λ to 2.75/λ. As an example, a circle AVB is further demonstrated to shield acoustic waves emitting from either the interior or exterior. Experimental measurements indicate that the average sound transmission losses can reach roughly 19 dB and 15 dB, respectively. We believe that the proposed AVB may find potential applications in architectural acoustics, room acoustics, and duct noise control.

The sound absorption of vegetation with embedded periodic metamaterials is investigated numerically and experimentally. Acoustical property of the vegetation can be described as that in a porous material. The physical parameters of vegetation in the numerical study are obtained by fitting the measured reflection and transmission coefficients with the simulated results. The embedded metamaterial is composed of two-layer oppositely oriented split tubes, which can achieve two resonant absorption peaks at wavelengths much larger than its thickness. Both absorption peaks can be easily controlled by adjusting the width of the metamaterial while keeping its thickness unchanged. It is demonstrated that the absorption performance can be significantly enhanced by embedding periodic metamaterials into the vegetation. The results can be explained by coupling the viscous and thermal losses of vegetations with the resonance phenomenon arising from the metamaterials. Moreover, sound absorption increases with increased incidence angles and vegetation thickness. When more than one metamaterial per spatial period is considered, additional absorption peaks are observed which can further broaden the effective absorption bandwidth.

The sound absorption via an absorber constructed by a vegetation layer and a metasurface substrate (MS) is numerically and experimentally investigated. By combining the vegetation and MS, high-efficiency sound absorption (>90%) can be achieved in a broader frequency range (from 0.93 kHz to 1.15 kHz). The MS subunit is composed of two 180°-twisted ellipse-shaped split tubes, which can achieve high absorption at the resonance frequency. According to the applications, the resonance absorption peak can be controlled by adjusting the length of the semi-major axis of the elliptical subunit. The acoustical properties of the vegetation layer can be described as a porous material, and its parameters in the simulation are obtained by fitting the measured sound absorption coefficients. Integrating the vegetation layer into the proposed absorber can further improve the absorptions in a wide frequency range of interest while it does not affect the resonance frequency of the MS subunit. Five different subunits are selected to form a deep-subwavelength MS array which can extend the absorption bandwidth. The broadband sound absorption of the absorber is robust under oblique incidence even at large incident angles. The proposed absorber has potential applications in acoustic engineering such as traffic and building noise control as well as green facades and green walls.

We design and build an acoustic invisible medium (AIM) based on first principles. Isotropic, inhomogeneous mass density and bulk modulus profiles of the AIM are derived from scattering-free conditions. Acoustic invisibility is illustrated by two types of examples: the AIM under plane-wave incidence and point sound sources. It is found that an AIM of arbitrary shape is invisible to plane waves of any incident angle. The invisibility of the AIM holds for any sound source sitting anywhere except for in the AIM region. Acoustic field distributions show that the acoustic wave enters the AIM from one side and recovers its initial shape at the other side. The designed AIMs are numerically verified by the finite element method, and are highly consistent with theoretical results. This work offers an alternative strategy to achieve a scattering-free AIM and could be extendable to the three-dimensional cases.

Acoustic needle focusing, which features elongated depth of focusing and narrow lateral size, is of great importance in applications requiring acoustic convergence in a large region, such as acoustic fast imaging. Here, a method is proposed to design an acoustic metasurface lens (AML) composed of space-coiling subunits for shaping a needle focusing. By manipulating the transmitted phase delay, the designed AML can generate two symmetrical parabolic accelerating beams along the designed convex trajectories, finally forming the acoustic needle focusing. Numerical simulations demonstrate that the focal intensity can reach roughly 17 times that of the incident wave while keeping the depth of focusing 18.2 times the wavelength. The working bandwidth of the highly efficient needle focusing is from 3.042 to 3.842 kHz. In addition, the focal intensity, depth and position of needle focusing can be freely modulated by simply changing the incident direction or tailoring the trajectory of two accelerating beams. The proposed acoustic needle focusing may have potential applications in acoustic imaging, acoustic energy delivering and particles trapping and manipulation.

Acoustic bottle-beams have been realized by acoustic metasurfaces (AMs) composed of space-coiling subunits. By manipulating the transmitted acoustical phase, the special AM can generate two intersecting accelerating beams along the designed convex trajectories, forming the acoustic bottle-beam. The transmitted acoustic bottle-beams are investigated theoretically and demonstrated numerically. We find that the shape and area of the acoustic bottle-beam could be statically controlled by designing the AM as well as dynamically modulated by the incident angles. In addition, the highly efficient acoustic focusing could be obtained at the convergence point of the bottle-beams, which also could be adjusted dynamically by the incident angles. It is further found that this focusing is robust against the obstacle scattering. The realization and manipulation of acoustic bottle-beams may have potential applications in biomedical imaging/therapy and non-destructive evaluation.

An acoustic anisotropic lens (AAL) based on large mass-density modulation depth (LMMD) medium is proposed for subwavelength imaging. The underlying mechanism for converting evanescent components into propagating waves is attributed to the strong suppression of the transverse velocity field component in LMMD medium. In addition, the proposed lens can operate in a broadband manner, which is more flexible in practical applications. Both transfer matrix method and finite element method are used to corroborate the subwavelength imaging capabilities of the proposed lens. The numerical simulations demonstrate that the proposed lens can clearly distinguish two Gaussian sources with equal width of λ0/25 and separation of λ0/5 in a broad frequency bandwidth. Medium losses decrease the transmission but cannot compromise the resolution of the lens.

An acoustic asymmetric phase modulation metasurface (APMM) has been proposed theoretically and demonstrated numerically. We find that the proposed APMM could realize the asymmetric transmission of the acoustic wave and the conversion of the propagating wave into the surface wave. The underlying mechanism is based on an asymmetric phase modulation by coupling an acoustic gradient index metasurface (AGIM) and a near-zero-index medium (ZIM). The AGIM and ZIM are implemented by only employing the coiling-up-space structures. Numerical simulations also show that the APMM could provide the high transmission contrast for the asymmetric transmission. The subwavelength thickness and flat geometry of the APMM may be useful for the further actual applications in the acoustic artificial device.

We investigate the electronic and magnetic properties of Fe2MnGa1−x Si x alloy (x = 0, 0.25, 0.5, 0.75, and 1) using first-principles density functional theory within the generalized gradient approximation method. The lattice constant decreases linearly whereas bulk modulus increases with increasing Si content. The total magnetic moment varies linearly with increasing Si content, which follows the Slater-Pauling rule. Electronic band structure calculations indicate that the Fe2MnGa1−x Si x exhibits half-metallic character for all the concentrations studied and the spin polarization and the spin-down band gap both increase with the Si content. Based on the magnetic properties calculations, the Heisenberg exchange coupling parameters give Fe-Mn ferromagnetic coupling and Mn-Mn antiferromagnetic coupling. The T C first decreases and then increases with Si content, which is in well agreement with the experimental results.

Binary acoustic metasurfaces (AMs) are proposed and demonstrated with the goal of perfect anomalous reflection and refraction. The AMs require only two subunits per period, thereby greatly improving the fabrication accuracy and reducing the design process. Theoretical analysis gives the range of incident and diffracted angles for the case of only two propagating modes, one of which can be suppressed by designing the two subunits to have opposite phases, thereby achieving perfect anomalous reflection/refraction. Moreover, the reflection- and refraction-type binary AMs are realized using two types of space-coiling structures. Finite-element simulations show the realization of anomalous reflection and refraction, the energy efficiencies of which can reach almost 100%. The present work provides a simple and straightforward way to design high-efficiency and practical AMs that enable nearly ideal manipulation of reflected/transmitted waves.

Broadband absorption of the audible sound wave at low frequency has been achieved by using periodic acoustic metamaterial resonators (AMRs) embedded inside a porous layer. A single AMR embedded in a porous layer could reach perfect absorption (PA) at the resonance frequency, and it can be easily tuned by adjusting the inner radius of AMR. With four AMRs in the porous layer, a high absorption (>80%) is obtained in the frequency range from 180 Hz to 550 Hz, while the thickness of the porous layer is only 1 / 10 of the relevant wavelength at 300 Hz. The broadband and high absorption performances are due to the interferences of the low-frequency resonances of the AMRs and the energy trapping between the AMRs and the rigid backings. The finite element simulations are experimentally validated. Moreover, the broadband low-frequency absorption is robust under various oblique incidence even at large incident angles. The effects of the acoustic parameters of the porous layer on the absorption properties are also discussed. The absorbers should have high potential for the practical applications in buildings, aircrafts and automobiles due to their ease of fabrication, ultra-thin, and robust high-efficiency.

Focused acoustic vortex (FAV) beams can steadily trap particles in three-dimensions. Previous FAV emitters are mainly based on the active device arrays. Here, we design a passive artificial structure engraved with two sets of discrete Archimedean spiral slits to generate the FAV in water. The acoustic intensity and phase distributions of FAVs are investigated theoretically and demonstrated using the finite element method. The constructive interference between two transmitted acoustic vortices through the inner and outer spiral parts achieves the FAV. It is found that the focal length and depth of the FAV can be modulated by simply changing the initial radius of the Archimedean spiral. Furthermore, we implement the Schlieren imaging experiment to verify the generation of the FAV by the artificial structure. Our design may offer potential applications in particle trapping, biomedical therapy, and medical imaging.Focused acoustic vortex (FAV) beams can steadily trap particles in three-dimensions. Previous FAV emitters are mainly based on the active device arrays. Here, we design a passive artificial structure engraved with two sets of discrete Archimedean spiral slits to generate the FAV in water. The acoustic intensity and phase distributions of FAVs are investigated theoretically and demonstrated using the finite element method. The constructive interference between two transmitted acoustic vortices through the inner and outer spiral parts achieves the FAV. It is found that the focal length and depth of the FAV can be modulated by simply changing the initial radius of the Archimedean spiral. Furthermore, we implement the Schlieren imaging experiment to verify the generation of the FAV by the artificial structure. Our design may offer potential applications in particle trapping, biomedical therapy, and medical imaging.

A 3D acoustic metasurface carpet cloak (AMCC) based on groove structure units is proposed and investigated. The key idea behind this acoustic invisibility is the phase compensation via local phase modulation, and thus a cloak with a thickness of only of a half wavelength could be designed for objects with arbitrary geometric shapes and sizes. We first demonstrate the cloaking effect of hiding a conical object numerically, and find that the working bandwidth of the designed AMCC is from 6200–7500 Hz. Further experimental results are in good agreement with the numerical simulations, verifying that the AMCC works well for the normal incident wave and the small-angled incident waves. As another example, we also confirm that the proposed AMCC can hide a semispherical object. The present AMCC is thin, has a simple geometrical structure, and is easy to implement, which benefits future realistic applications.

We propose an acoustic waveguide consisting of periodic parity-time-symmetric zero-index metamaterials separated by layers of passive medium. Consistent analytical derivations and numerical simulations show that a rich variety of extraordinary scattering effects can be achieved. For example, unidirectional transparency is found to occur at an exceptional point. At singular points, the system behaves as an acoustic coherent perfect absorber (CPA) laser. Bidirectional transparency, induced by the Fabry-Perot resonance or balanced dissipation and amplification, is also observed. In contrast to the previous scheme without structural periodicity, the proposed periodic structure allows a greater number of conditions under which the CPA laser behavior and bidirectional transparency can be achieved, which may facilitate the experimental realization of such extraordinary effects.

Ultrathin Bi films have been theoretically predicted to be an elemental two-dimensional topological insulator recently. Investigation on phonon properties in topological insulators, especially down to a few-layer regime, is an interesting topic. In this paper, the evolution of structures and phonon properties of ultrathin Bi (111) films with thickness is studied from first-principles calculations by including spin–orbit coupling. The calculations of lattice dynamics show that both two Raman modes A1g and Eg in ultrathin Bi (111) films harden compared with those in bulk, which is contrary to other nanomaterials. The possible origin of this anomalous phonon behavior is discussed by considering the peculiar semimetallicity of Bi. With increasing thickness, the frequencies of these two Raman modes decrease gradually toward the values in the bulk. Our calculations also show that the softening and hardening of surface phonon modes coexist in ultrathin Bi films.

We have investigated the electronic and magnetic properties of the doped Heusler alloys Co2Fe1−xV xAl ( x = 0 , 0.25, 0.5, 0.75, 1) using first-principles density functional theory within the generalized gradient approximation (GGA) scheme. The calculated results reveal that with increasing V content the lattice parameter slightly increases. The magnetic moment of the Fe sites increases while the magnetic moment of the Co sites decreases with V doping; the total spin moment of these compounds linearly decreases. We also have performed the electronic structure calculations for Co2Fe1−xV xAl with positional disorder of Co–Fe(V) type and Al–Fe(V) type. It is found that formation of Al–Fe(V)-type disorder is more favorable than that of Co–Fe(V)-type disorder in Co2Fe1−xV xAl alloys. Furthermore, we found that the spin polarization increases with V doping in Co2Fe1−xV xAl with ordered L 2 1 and disordered B2 structures. Detailed calculations show that the stability of the L 2 1 structure will be enhanced with increasing V content. The results are compatible with experiments.

We propose a coded acoustic metasurface (CAM) to generate Airy-like beams (ALBs) in air. A space-folding structure is designed to act as the bit “1” unit of the CAM, and an air unit with the same size is used as the bit “0”. Finite-element simulations demonstrate that the ALBs generated by this simple CAM have excellent self-accelerating, self-healing, and non-diffracting features. It is found that the bit “1” unit works well in a large frequency range of 6–9 kHz, and the CAM, therefore, generates a broadband ALB. Furthermore, two symmetrical CAMs are employed to compose a lens for realizing the acoustic focusing in the frequency range of 6–9 kHz, and the focal length of the CAM lens is sensitive to the working frequency. The work presented here could greatly benefit acoustic imaging, particle trapping and manipulation, and broadband acoustical devices.

We design an asymmetric transmission system (ATS) with two flat acoustic metasurfaces (AMs) to yield bidirectional asymmetric acoustic focusing (BAAF). The acoustic waves could be focused on both sides of the ATS with different focal lengths and intensities. To achieve high intensity energy concentration, the accelerating acoustic beams are selected to realize the BAAF. The working bandwidth of the BAAF based on our ATS could reach ~ 0.4 kHz. It is found that by adjusting the distance between two flat AMs, the focal length and intensity of the bidirectional focusing could easily be modulated. Because the distance between two flat AMs is large enough, the BAAF even could be converted into a unidirectional acoustic focusing. The proposed BAAF may find applications in non-destructive evaluation, biomedical imaging and medical diagnosis.

Patients with esophageal cancer are often diagnosed at advanced stages, leading to poor prognosis. Biomarkers are needed to enable earlier detection as well as to aid in the prediction of prognosis, but to date these tools remain scarce. Thymidine kinase (TK1) has been shown to exhibit altered expression levels in esophageal tumor cells, therefore this study sought to determine whether serum TK1 levels are also altered and, if so, to assess the utility of TK1 as a biomarker in esophageal squamous cell carcinoma. Eighty patients with esophageal squamous cell carcinoma were included as the case group and 80 healthy persons were selected as the control group. Serum TK1 levels, postoperatively for cancer patients, were detected by chemiluminescence. Follow-up was performed for cancer patients to determine the progression free survival (PFS) and overall survival (OS). Serum TK1 levels were significantly higher in cases of esophageal cancer than in healthy control individuals (t=7.235, P0.05). When cancer cases were sub-divided into lower and higher serum TK1 levels, based on the mean level of 3.38 pmol/L, statistically significant differences in TNM stage, tumor differentiation, and lymph node metastasis were observed between patients with ≥3.38 pmol/L and3.38 pmol/L (χ(2)=28.134, 3.187, 7.234, P0.05). The average OS of all esophageal cancer patients was 30.13 months, and the average PFS was 24.73 months. However, when the cases were divided by serum TK1 level, average OS of those with higher serum TK1 (≥3.38 pmol/L) was significantly lower (23.98 mo) than those with lower serum TK1 (32.96 mo) (χ(2)=5.439, P0.05). Similarly, average PFS was significantly lower in patients with higher serum TK1 (17.65 mo versus 27.62) (χ(2)=4.640, P0.05). OS was correlated with TNM stage (hazard ratio, HR=3.116), degree of tumor differentiation (HR=0.427), lymph node metastasis (HR=0.535), and serum TK1 level (HR=1.913) (Wald χ(2)=6.782, 6.228, 4.562, 5.681, P0.05). Similarly, PFS was correlated with TMN stage (HR=2.153), degree of tumor differentiation (HR=0.627), and serum TK1 level (HR=1.632) (Wald χ(2)=7.035, 5.335, 4.887, P0.05). Thus, patients with esophageal squamous cell carcinoma exhibit higher circulating TK1 levels, consistent with findings of increased TK1 expression in tumor cells. Further, the correlation of serum TK1 levels with clinical features of esophageal cancer and with patient survival suggest that serum TK1 may serve as a valuable biomarker for predicting patient prognosis.

Induction of larval diapause is a photoperiodically controlled event in the life history of the moth Pseudopidorus fasciata. In the present study, the photoperiodic counter of diapause induction has been systematically investigated. The required day number (RDN) for a 50% response was determined by transferring from a short night (LD 16:8) to a long night (LD 12:12) or vice versa at different times after hatching, The RND differed significantly between short- and long-night cycles at different temperatures. The RDN for long-night cycles at 20, 22, 25 and 28 degrees C was 11.5, 9.5, 7.5 and 8.5 days, respectively. The RDN for short-night cycles was 3 days at 22 degrees C and 5 days at 20 degrees C indicating that the effect of one short night was equivalent to the effect of 2-3 long nights effect. Night-interruption experiments of 24h photoperiods by a 1 h light pulse showed that the most crucial event for the photoperiodic time measurement in this moth was whether the length of pre-interruption (D(1)) or the post-interruption (D(2)) scotophases exceeded the critical night length (10.5 h). If D(1) or D(2) exceeded 10.5 h diapause was induced. The diapause-averting effect of a single short-night cycle (LD 16:8) against a background of long nights (LD 12:12) showed that the photoperiodic sensitivity was greatest during the first 7 days of the larval period and the highest sensitivity was on the fourth day. Both non-24 and 24 h light-dark cycle experiments revealed that the photoperiodic counter in P. fasciata is able to accumulate both long and short nights during the photosensitive period, but in different ways. The information from short-night cycles seems to be accumulated one by one in contrast to long-night cycles where six successive cycles were necessary for about 50% diapause induction and eight cycles for about 90% diapause. These results suggest the accumulation of long-night and short-night cycles may be based on different mechanisms.

An acoustic metasurface (AM) composed of space-coiling subunits is proposed to generate acoustic Airy-like beams (ALBs) by manipulating the transmitted acoustic phase. The self-accelerating, self-healing, and non-diffracting features of ALBs are demonstrated using finite element simulations. We further employ two symmetrical AMs to realize two symmetrical ALBs, resulting in highly efficient acoustic focusing. At the working frequency, the focal intensity can reach roughly 20 times that of the incident wave. It is found that the highly efficient acoustic focusing can circumvent obstacles in the propagating path and can be maintained in a broad frequency bandwidth. In addition, simply changing the separation between the two AMs can modulate the focal length of the proposed AM lens. ALBs generated by AMs and the corresponding AM lens may benefit applications in medical ultrasound imaging, biomedical therapy, and particle trapping and manipulation.

Acoustic zero-index metamaterials (ZIMs) with extremely large phase velocity can be used to manipulate the acoustic transmission by introducing various kinds of defects. However, previous works are based on ideal effective zero-index materials and are restricted to cylindrical defects to predigest the model complexity, which may hamper the practical applications. Here, we theoretically and numerically investigate the acoustic transmission through a ZIM waveguide structure embedded with a rectangular defect. The consistent results demonstrate that the total reflection, total transmission, and cloaking effect can be achieved by introducing suitable rectangular defect into the ideal ZIM. Moreover, the labyrinthine metamaterial, whose effective mass density and reciprocal modulus are simultaneously near zero in a certain frequency region, is further employed to implement a practical ZIM. Numerical simulations show that the transmission amplitude of the labyrinthine ZIM waveguide can cover an entire range of [...

A first-principles method is introduced to design and achieve perfect monochromatic acoustic anti-reflection (AR) at any frequency. We established the relationship between the mass density and bulk modulus of the AR coating, which enabled the removal of any impedance mismatch. Perfect acoustic AR was realized by designing explicit conditions for the impedance matching. Theoretical results were numerically obtained using the finite element method. Importantly, perfect monochromatic acoustic AR was even realized for an ultra-thin AR layer at a deep subwavelength scale. We further approximated a multilayered AR coating with varying bulk moduli, which could provide perfect AR at any frequency. This ultra-thin multilayered AR structure may be beneficial for the minimization and integration of related acoustic devices.

The geometric and electronic structures of the ethylene oxide (EO) molecule adsorbed on Si(100)-[Formula: see text] surface were investigated by using the density-functional theory calculations. All possible adsorbed structures were considered and it was found that only four adsorption structures are stable. The calculations of the formation energy revealed the most stable conformation and demonstrated that the nature of Si–O bond significantly affects the stability of adsorption systems. The analysis of corresponding electronic structures showed that two adsorbed structures are still semiconductor compounds but the other two are not. In particular, the EO after adsorbing was found to be connected via a ring-opening reaction where the molecule forms a five-membered ring together with the surface of dimer silicon atoms, and the produced five-membered ring is almost perpendicular to the silicon surface.

To investigate the selection of recipients, operative technique, and perioperative management of lung transplantation for silicosis.Lung transplantations (LTx) were performed for five end-stage silicosis in our hospital who were diagnosed in accordance with recommendations of the local Prophylactic Therapeutic Institution for Occupational Diseases. The chest roentgenogram and high resolution CT showed somewhat pulmonary interstitial fibrosis, pulmonary emphysema and massive opacities. The mean pulmonary artery pressure (mPAP) was30mmHg, NYHA III or IV. Two patients received thoracic surgery prior to LTx, one patient was ventilator-dependent. One patient received bilateral sequence lung transplantation (BSLT) under extracorporeal membrane oxygenation (ECMO) support. Four patients received single lung transplantation (SLT), 3 under ECMO support.Patient five died of multiple organ failure on postoperative day 8, the remaining four patients were discharged from hospital. During follow up, patient three died of severe infection 7 month postoperatively, the remaining three patients were alive for 5 years, 3 years and 2 years respectively, and lived good quality of life, especially with lower mPAP and improved lung function. Although our patients suffered low-grade chronic rejection with the manifestation of bronchiolitis obliterative syndrome (BOS).Lung transplantation is a viable option for patients with end-stage silicosis, providing acceptable quality of life and survival. Both SLT and BSLT are satisfactory approach for end-stage silicosis,and long-term survival requires further investigations.

The diffusion is of great significance in many applications when the impurities are employed to tune the semiconductor's electrical or optical properties. It is necessary to understand how dopant defects diffuse in semiconductors. Using first-principles calculations, we consider interstitial diffusion mechanisms and calculate the migration barrier energies of interstitial Cu, Ag and Au atoms in II–VI compounds ZnTe. We find that the relative size of dopant and bulk atoms is an important factor which affects the diffusion behavior. The high symmetry Tc site, which is tetrahedrally coordinated by four cation atoms, is the global minimum energy location for Ag and Au interstitials. The size of Cu adatom is small, so Cu is more stable when it locates at the Ta site which is tetrahedrally coordinated by four anion atoms. But the global minimum energy location for Cu interstitials is M site which is of smaller space than Ta. Cu adatoms show an asymmetric curve of energy diffusion barrier with two energetically distinct extremum in the pathway. Ag diffuses along nearly straight line paths along [111] or equivalent directions. Diffusion for Cu or Au deviates from the straight line paths along 〈111〉 avoiding high symmetric sites.

The diffusion plays an important role in many applications when the impurities are employed to tune the semiconductor's electrical or optical properties, which make it essential to understand theoretically the microscopic mechanisms governing how dopant defects diffuse. Using first-principles calculations, we compare the diffusion behaviors and migration barriers of interstitial Cu , Ag , and Au atoms in II–VI compounds ZnSe . We consider interstitial diffusion mechanisms and calculate the corresponding activation energies. For noble atoms, we find that the interstitial mediated mechanism is the dominant one. We also find that the relative size of dopant atoms and constituent atoms of II–VI compounds is an important factor affecting the diffusion behaviors. The coupling in ZnSe between Cu d levels and unoccupied host s levels is not as strong as that in CdTe .