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The release of Ag+ confined in the cavities of nanoscale inorganic clusters can be selectively triggered by the Na+ present in solutions or biological media for long-lasting bacteriostasis.

The design of Pt-based nanoarchitectures with controllable compositions and morphologies is necessary to enhance their electrocatalytic activity. Herein, we report a rational design and synthesis of anisotropic mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowires for high-efficient electrocatalysis. The catalyst has a uniform core-shell structure with an ultrathin atomic-jagged Pt nanowire core and a mesoporous Pt-skin Pt3Ni framework shell, possessing high electrocatalytic activity, stability and Pt utilisation efficiency. For the oxygen reduction reaction, the anisotropic mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowires demonstrated exceptional mass and specific activities of 6.69 A/mgpt and 8.42 mA/cm2 (at 0.9 V versus reversible hydrogen electrode), and the catalyst exhibited high stability with negligible activity decay after 50,000 cycles. The mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowire configuration combines the advantages of three-dimensional open mesopore molecular accessibility and compressive Pt-skin surface strains, which results in more catalytically active sites and weakened chemisorption of oxygenated species, thus boosting its catalytic activity and stability towards electrocatalysis.

In this Communication, the problem of synthesizing a linearly polarized shaped power pattern with accurate control on both sidelobe and cross-polarization levels is considered. For a user-defined desired polarization direction, the definitions of realizable co-polarization (COP) and cross-polarization (XP) directions for an arbitrary propagation direction in the shaped pattern are presented. With the help of such definitions, the considered problem is formulated as finding appropriate excitations so as to produce a shaped power pattern in which the realizable COP component meets prescribed lower and upper bounds, the realizable XP component and the total power pattern are less than their upper bounds in the regions of interest. The semidefinite relaxation (SDR) method in literature is then extended to solve this vectorial pattern synthesis problem. The proposed method can include the mutual coupling and platform effects by using vectorial active element patterns of an antenna array. A set of synthesis examples with different array geometries and radiation requirements are conducted to validate the effectiveness and advantages of the proposed method. Index Terms-Array pattern synthesis, shaped power pattern, low cross-polarization, semidefinite relaxation(SDR). I. INTRODUCTION A NTENNA arrays with shaped power patterns have been widely applied in various radar and communication systems. In the past decades, many advanced methods concerning the synthesis of shaped power patterns have been developed, for example, in [1]-[9]. Due to the complexity with high nonlinearity of this problem, many shaped power pattern synthesis methods deal with only the array factors, and they lack of considering the mutual coupling between practical antenna elements. Some techniques including genetic algorithms [10], differential evolution algorithms [11], iterative convex optimization [12]-[13] and semidefinite relaxation [14], [15], can deal with an arbitrary antenna array model with different element patterns, and they would be able to include the mutual coupling effect in the pattern synthesis procedure by using the active element patterns [16], [17]. However, these techniques used to consider only the shape distribution of the total radiation power and part of radiation power actually corresponds to the electric field in undesired polarization. This issue becomes significant in some applications when the antenna array is required to radiate the electric field in a particular polarization and thus the cross-polarization level (XPL) should be reduced as much as possible [18]. Usually, the XPL suppression can be realized by choosing appropriate element structure and array arrangement. Nevertheless, using

Hospital-acquired infections are a serious threat to the recovery of patients. To prevent such infections, an antibacterial coating is an effective method to eliminate bacterial colonization on healthcare-related surfaces. Herein, we report an antibacterial hydrogel composed of silver-containing polyoxometalate (AgP5W30 POM) and carboxymethyl chitosan (CMC). The silver ion is encapsulated inside the POM cage and demonstrates long-lasting bacteriostasis after repeated exposure to both Gram-positive and Gram-negative bacteria. The chemical structure of chitosan derivatives, as well as the concentration and pH, is studied to tune the mechanical properties of the hydrogel. The hydrogel undergoes a gel–sol transition above the critical temperature and possesses self-healing ability. This hydrogel can be readily coated on the surface of versatile bulk materials, which is especially convenient for porous objects and resists the growth of Staphylococcus aureus, Escherichia coli, and methicillin-resistant S. aureus (MRSA). In summary, we envision that the AgP5W30-CMC hydrogel has great potential to serve as an antibacterial coating to decrease the prevalence of hospital-acquired infections.

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