Ferroelectric properties of PZT/BFO multilayer thin films prepared using the sol-gel method

In this study, Pb(Zr0.52Ti0.48)O3/BiFeO3 [PZT/BFO] multilayer thin films were fabricated using the spin-coating method on a Pt(200 nm)/Ti(10 nm)/SiO2(100 nm)/p-Si(100) substrate alternately using BFO and PZT metal alkoxide solutions. The coating-and-heating procedure was repeated several times to form the multilayer thin films. All PZT/BFO multilayer thin films show a void-free, uniform grain structure without the presence of rosette structures. The relative dielectric constant and dielectric loss of the six-coated PZT/BFO [PZT/BFO-6] thin film were approximately 405 and 0.03%, respectively. As the number of coatings increased, the remanent polarization and coercive field increased. The values for the BFO-6 multilayer thin film were 41.3 C/cm2 and 15.1 MV/cm, respectively. The leakage current density of the BFO-6 multilayer thin film at 5 V was 2.52 × 10-7 A/cm2

Broad humoral and cellular immunity elicited by one-dose mRNA vaccination 18 months after SARS-CoV-2 infection

Practical guidance is needed regarding the vaccination of coronavirus disease 2019 (COVID-19) convalescent individuals in resource-limited countries. It includes the number of vaccine doses that should be given to unvaccinated patients who experienced COVID-19 early in the pandemic. We recruited COVID-19 convalescent individuals who received one or two doses of an mRNA vaccine within 6 or around 18 months after a diagnosis of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection. Their samples were assessed for IgG-binding or neutralizing activity and cell-mediated immune responses against SARS-CoV-2 wild-type and variants of concern. A total of 43 COVID-19 convalescent individuals were analyzed in the present study. The results showed that humoral and cellular immune responses against SARS-CoV-2 wild-type and variants of concern, including the Omicron variant, were comparable among patients vaccinated within 6 versus around 18 months. A second dose of vaccine did not significantly increase immune responses. One dose of mRNA vaccine should be considered sufficient to elicit a broad immune response even around 18 months after a COVID-19 diagnosis.This work was supported in part by the Bio & Medical Technology Develop‑ ment Program of the National Research Foundation (NRF) & funded by the Korean government (MSIT) (2021M3A9I2080496, to H.-R. Kim & W. B. Park), the Creative-Pioneering Researchers Program through Seoul National University (to C.-H. Lee), and the Seoul National University Hospital Research Fund (112021-5050 to P. G. Choe and 800-20220110 to C.-H. Lee)

MICROPROBE METHOD FOR STUDYING GAS-LIQUID OXYGEN TRANSFER IN VARIOUS SURFACTANT SYSTEMS.

Abstract not availabl

Electrical properties of lead-free 0.98(Na0.5K0.5)NbO3-0.02Ba(Zr0.52Ti0.48)O3 piezoelectric ceramics by optimizing sintering temperature

Lead-free 0.98(Na(0.5)K(0.5))NbO(3)-0.02Ba(Zr(0.52)Ti(0.48))O(3 )[0.98NKN-0.02BZT] ceramics were fabricated by the conventional mixed oxide method with sintering temperature at 1,080°C to 1,120°C. The results indicate that the sintering temperature obviously influences the structural and electrical properties of the sample. For the 0.98NKN-0.02BZT ceramics sintered at 1,080°C to 1,120°C, the bulk density increased with increasing sintering temperature and showed a maximum value at a sintering temperature of 1,090°C. The dielectric constant, piezoelectric constant [d(33)], electromechanical coupling coefficient [k(p)], and remnant polarization [P(r)] increased with increasing sintering temperature, which might be related to the increase in the relative density. However, the samples would be deteriorated when they are sintered above the optimum temperature. High piezoelectric properties of d(33 )= 217 pC/N, k(p )= 41%, dielectric constant = 1,951, and ferroelectric properties of P(r )= 10.3 μC/cm(2 )were obtained for the 0.98NKN-0.02BZT ceramics sintered at 1,090°C for 4 h

DENSIFICATION AND FERROELECTRIC PROPERTIES OF PZT(60/40) THICK FILMS FABRICATED BY SCREEN-PRINTING METHOD

Ferroelectric PbZr0.6Ti0.4O3 (PZT) thick films were fabricated using a combination of screen-printing method and PZT precursor sol coating process (M. Koch, N. Harris, R. Maas, A. G. R. Evans, N. M. White and A. Brunnschweiler, Meas. Sci. Technol. 8 (1997) 49; Y. S. Yoon, J. Korean. Phys. Soc. 47 (2005) 321). Structural and electrical properties of the PZT thick films with the treatment of sol coating were investigated. The porosity decreased and the densification was enhanced with increasing the number of sol coatings. All PZT thick films showed the typical X-ray diffraction patterns of a perovskite polycrystalline structure. The thickness of all thick films was approximately 60–61 μm. The relative dielectric constant increased and dielectric loss decreased with increasing the number of sol coatings, and the values of the six-layer PZT-6 film were 167.8, 0.78% at 1 kHz, respectively. The remanent polarization and coercive field of the 6-coated PZT-6 thick films were 14.1 μC/cm2 and 20.3 kV/cm, respectively.Sol–gel, thick films, PZT, densification, ferroelectric

Practical RSA-PAKE for Low-Power Device in Imbalanced Wireless Networks

For enhancing the security of ubiquitous communication, we have to consider three keywords: mobility , wireless , and low computing capability . In this paper, we study one of suitable security protocols for the ubiquitous communication environment. We discuss RSA-based password-authenticated key exchange (RSA-PAKE) protocols for imbalanced wireless networks where a party uses a low-power device to communicate with another party equipped with a powerful computing device. For imbalanced wireless network applications, it is important to reduce the cost of communication for a low-power device even though the cost for powerful devices is increasing. The most power-consuming operation in RSA-PAKE protocols is the reliability test of unauthorized RSA public keys. Hence, it is important to design an efficient reliability test method to construct an efficient RSA-PAKE protocol. In this paper, we propose a new reliability test technique and design a provably secure RSA-PAKE protocol using the technique. Our protocol is suitable for securing the communications conducted over imbalanced wireless networks since the operations computed by one communicating party are efficient enough to be implemented on most low-power devices such as mobile phones and PDAs. The cost of a low-power device is reduced by 84.25% compared with CEKEP, the most efficient RSA-PAKE protocol. We prove the security of our protocol under a firmly formalized security model

Photoinactivation of Photosystem II in leaves

Photoinactivation of Photosystem II (PS II), the light-induced loss of ability to evolve oxygen, inevitably occurs under any light environment in nature, counteracted by repair. Under certain conditions, the extent of photoinactivation of PS II depends on the photon exposure (light dosage, x), rather than the irradiance or duration of illumination per se, thus obeying the law of reciprocity of irradiance and duration of illumination, namely, that equal photon exposure produces an equal effect. If the probability of photoinactivation (p) of PS II is directly proportional to an increment in photon exposure (p = kΔx, where k is the probability per unit photon exposure), it can be deduced that the number of active PS II complexes decreases exponentially as a function of photon exposure: N = Noexp(-kx). Further, since a photon exposure is usually achieved by varying the illumination time (t) at constant irradiance (I), N = Noexp(-kI t), i.e., N decreases exponentially with time, with a rate coefficient of photoinactivation kI, where the product kI is obviously directly proportional to I. Given that N = Noexp(-kx), the quantum yield of photoinactivation of PS II can be defined as -dN/dx = kN, which varies with the number of active PS II complexes remaining. Typically, the quantum yield of photoinactivation of PS II is ca. 0.1μmol PS II per mol photons at low photon exposure when repair is inhibited. That is, when about 107 photons have been received by leaf tissue, one PS II complex is inactivated. Some species such as grapevine have a much lower quantum yield of photoinactivation of PS II, even at a chilling temperature. Examination of the longer-term time course of photoinactivation of PS II in capsicum leaves reveals that the decrease in N deviates from a single-exponential decay when the majority of the PS II complexes are inactivated in the absence of repair. This can be attributed to the formation of strong quenchers in severely-photoinactivated PS II complexes, able to dissipate excitation energy efficiently and to protect the remaining active neighbours against damage by light