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The targeted concentration of acoustic waves has significant implications for industrial nondestructive testing, ultrasound diagnosis, and medical treatment. Most conventional sound-focusing metasurfaces suffer from an untunable focus, narrow bandwidth, and fixed geometric configurations, which severely constrain their practical utility. In this paper, we propose a reconfigurable acoustic coding metasurface composed of two coding units with high transmittance and transmitted phases of 0 and π for realizing tunable and broadband sound focusing. Through the straightforward manipulation of each unit structure and alterations in the coding sequences, precise control of the focus position across the entire working plane is attainable, enabling both tunable axial-axis and off-axis sound-focusing effects. Moreover, the sound-focusing performance of the proposed metasurface is excellent within a broad frequency range from 3000 to 5500 Hz. The experimental results are consistent with theoretical expectations and numerical simulations. This work lays a practical foundation for the design of acoustic devices for tunable and broadband sound focusing. [ABSTRACT FROM AUTHOR]

Aims: Both hypercapnia and hypocapnia are common in patients with acute heart failure (AHF), but the association between partial pressure of arterial carbon dioxide (PaCO2) and AHF prognosis remains unclear. The objective of this study was to investigate the connection between PaCO2 within 24 h after admission to the intensive care unit (ICU) and mortality during hospitalization and at 1 year in AHF patients. Methods and results: AHF patients were enrolled from the Medical Information Mart for Intensive Care IV database. The patients were divided into three groups by PaCO2 values of <35, 35–45, and >45 mmHg. The primary outcome was to investigate the connection between PaCO2 and in‐hospital mortality and 1 year mortality in AHF patients. The secondary outcome was to assess the prediction value of PaCO2 in predicting in‐hospital mortality and 1 year mortality in AHF patients. A total of 2374 patients were included in this study, including 457 patients in the PaCO2 < 35 mmHg group, 1072 patients in the PaCO2 = 35–45 mmHg group, and 845 patients in the PaCO2 > 45 mmHg group. The in‐hospital mortality was 19.5%, and the 1 year mortality was 23.9% in the PaCO2 < 35 mmHg group. Multivariate logistic regression analysis showed that the PaCO2 < 35 mmHg group was associated with an increased risk of in‐hospital mortality [hazard ratio (HR) 1.398, 95% confidence interval (CI) 1.039–1.882, P = 0.027] and 1 year mortality (HR 1.327, 95% CI 1.020–1.728, P = 0.035) than the PaCO2 = 35–45 mmHg group. The PaCO2 > 45 mmHg group was associated with an increased risk of in‐hospital mortality (HR 1.387, 95% CI 1.050–1.832, P = 0.021); the 1 year mortality showed no significant difference (HR 1.286, 95% CI 0.995–1.662, P = 0.055) compared with the PaCO2 = 35–45 mmHg group. The Kaplan–Meier survival curves showed that the PaCO2 < 35 mmHg group had a significantly lower 1 year survival rate. The area under the receiver operating characteristic curve for predicting in‐hospital mortality was 0.591 (95% CI 0.526–0.656), and the 1 year mortality was 0.566 (95% CI 0.505–0.627) in the PaCO2 < 35 mmHg group. Conclusions: In AHF patients, hypocapnia within 24 h after admission to the ICU was associated with increased in‐hospital mortality and 1 year mortality. However, the increase in 1 year mortality may be influenced by hospitalization mortality. Hypercapnia was associated with increased in‐hospital mortality. [ABSTRACT FROM AUTHOR]

The lack of efficient and non-precious metal catalysts poses a challenge for electrochemical water splitting in hydrogen and oxygen evolution reactions. Here, we report on the preparation of growing Ni(OH)2 nanosheets in situ on a Ni and graphene hybrid using supergravity electrodeposition and the hydrothermal method. The obtained catalyst displays outstanding performance with small overpotentials of 161.7 and 41 mV to acquire current densities of 100 and 10 mA cm−2 on hydrogen evolution reaction, overpotentials of 407 and 331 mV to afford 100 and 50 mA cm−2 on oxygen evolution reaction, and 10 mA·cm−2 at a cell voltage of 1.43 V for water splitting in 1 M KOH. The electrochemical activity of the catalyst is higher than most of the earth-abundant materials reported to date, which is mainly due to its special hierarchical structure, large surface area, and good electrical conductivity. This study provides new tactics for enhancing the catalytic performance of water electrolysis. [ABSTRACT FROM AUTHOR]

The mode manipulation of Lamb waves plays an important role in damage detection and identification of damage types, location, and size. In this paper, we propose a composite phononic crystal (PC) plate with antisymmetric and symmetric PCs for realizing mode conversion from A0 to S0 mode of Lamb waves. The theoretical analysis, numerical simulations, and experimental validation are introduced and the mode conversion mechanism of the composite PC plate is systematically investigated. The effect of geometrical parameters on band structures of antisymmetric and symmetric PCs is first discussed. Then multi-physics field simulation models are developed and in-plane displacement fields are obtained in numerical simulations, which shows that the mode conversion is enhanced when the period number of the antisymmetric PC decreases and that of symmetric the PC increases. The composite PC plate specimens are fabricated with precision wire cutting technology for experimental measurements and the self-designed polyvinylidene fluoride (PVDF) comb transducer is used to stimulate the Lamb waves. The experimental results are consistent with the numerical simulations, which demonstrate that the proposed composite PC plate can achieve the mode conversion from A0 to S0 mode of Lamb waves. Our proposed structures have applicable values for the mode manipulation of Lamb waves in damage detection. [ABSTRACT FROM AUTHOR]

NiFe-layered double hydroxides (NiFe-LDH) have been reported to possess exceptional oxygen evolution reaction (OER) activity. However, maintaining the stability of high activity over a long time remains a critical challenge that needs to be addressed for their practical application. Here, we report a custom-sized deep recombination of 2D graphene oxide with NiFe-LDH (NiFe-LDH/GO/NF) through a simple electrodeposition method that improves OER activity and achieves excellent stability. The excellent performance of the catalyst mainly comes from the three-phase interface and electron transport channel dredged by the three-dimensional structure constructed by the deep composite, which can not only significantly reduce its charge and electron transfer resistance, improving the material conductivity, but it also effectively increases the specific surface area, inhibits aggregation, and exposes rich active sites. In addition, GO with good conductivity not only supports NiFe-LDH well but also increases the heterogeneous interface, putting the NiFe-LDH/GO composites in close contact with Ni foam and increasing the electrocatalytic stability of the NiFe-LDH/GO/NF. The experimental results show that the overpotential of NiFe-LDH/20,000GO/NF is only 295 mV at a current density of 100 mA cm−2; the Tafel slope is 52 mV dec−1, and the charge transfer resistance (Rct) is only 0.601 Ω in 1 M KOH. This indicates that GO has excellent potential to assist in constructing geometric and electronic structures of NiFe-LDH in long-term applications. [ABSTRACT FROM AUTHOR]

In this work, a compact low-frequency sound absorption metastructure composed of multiple resonators with embedded wavy bending necks is proposed. By arranging this metastructure in parallel and optimizing the parameters, it exhibits excellent broadband sound absorption capability in low-frequency range and has a much more compact volume. Compared with the traditional resonators, an individual resonator of this metastructure can move down the absorption frequency about 120 Hz while maintaining the same thickness. Furthermore, different resonator units are combined into a sound absorption array by employing appropriate design techniques. We first built a small metastructure composed of four units to demonstrate the correctness and accuracy of our design method. Both theoretical models and finite element simulation models are built and experimental results show good agreement between them. To achieve the same absorption value and frequency range, the thickest resonator in the traditional resonator array must be 30% thicker than the one in the wavy bending neck resonator array, which means the overall size of the structure is 30% larger. Following this design method, perfect sound absorption within the frequency range of 248 Hz–420 Hz is achieved with a compact volume of 53 mm in radius and 47 mm in height. The design strategy presents a new approach to achieve perfect broadband low-frequency sound absorption. [ABSTRACT FROM AUTHOR]