Influence of active structure parameters on resonant frequency of acoustic transducer membranes

The paper presents the results of calculations of the resonant frequency of a multilayer square membrane for ultrasonic microelectromechanical sensors. Various combinations of active layer materials and metal electrodes were taken into account. The dependences of the resonant frequency on the side length of membrane, as well as on the thickness of active piezoelectric layer and metal electrode for SiO2/Ti/ZnO, SiO2/Al/ZnO, SiO2/Ti/PZT and SiO2/Al/PZT structures were ob-tained. According to the calculations, the values of the resonant frequencies are in the ranges of 46.1–498.3 kHz for SiO2/Ti/ZnO; 45.4–477.3 kHz for SiO2/Al/ZnO; 39.4–411.4 kHz for SiO2/Ti/PZT; 38.1–381 kHz for SiO2/Al/PZT. It is shown that the resonant frequency can be increased due to changes in the geometric parameters of the membrane; and the material and dimensions of the piezoelectric layer have the greatest influence. The results of analytical and numerical simulations for particular case of SiO2(1μm)/Ti(1μm)/ZnO(2μm)/Ti(1μm) membrane with a side length of 600 μm are also compared. The obtained results could be used to optimize the design and process technology of microelectrome-chanical ultrasonic sensors.

Recent Advances on Synthesis of 1,4-Benzoxazines and its Derivatives

: 1,4-benzoxazine compounds are an important class of heterocyclic compounds. Ever since 1,4-benzoxazine was discovered in 1959, it has attracted chemists due to its unique physiological activities, and their synthesis and application have been studied. However, the traditional synthesis methods of 1,4-benzoxazines have some drawbacks, such as complicated steps, harsh reaction conditions and low yield. Therefore, it is still a significant direction to develop new and efficient synthesis methods. In this paper, the synthesis methods and reaction mechanisms of these compounds are reviewed, and the application prospect of 1,4- benzoxazine and its derivatives as a dominant active structure in the future is discussed.

Expression of functional eGFP-fused antigen-binding fragment of ranibizumab in Pichia pastoris

Introduction: Ranibizumab is a mouse monoclonal antibody fragment antigen-binding (Fab) against human vascular endothelial growth factor-A (VEGF-A), inhibiting angiogenesis. This antibody is commercially produced in Escherichia coli host and used to treat wet age-related macular degeneration (AMD).Methods: In this study, the heavy and light chains of ranibizumab were expressed in Pichia pastoris. The expressed chains were incubated overnight at 4°C for interaction. The formation of an active structure was evaluated based on the interaction with substrate VEGF-A using an indirect ELISA, and an electrochemical setup. Furthermore, reconstruction of split enhanced green fluorescent protein (eGFP) reporter, chimerized at the C-terminus of the heavy and light chains, was used to characterize chains’ interaction. Results: P. pastoris efficiently expressed designed constructs and secreted them into the culture medium. The anti-Fab antibody detected the constructed Fab structure in western blot analysis. Reconstruction of the split reporter confirmed the interaction between heavy and light chains. The designed ELISA and electrochemical setup results verified the binding activity of the recombinant Fab structure against VEGF-A. Conclusion: In this work, we indicated that the heavy and light chains of ranibizumab Fab fragments (with or without linkage to split parts of eGFP protein) were produced in P. pastoris. The fluorescence of reconstructed eGFP was detected after incubating the equal ratio of chimeric-heavy and light chains. Immunoassay and electrochemical tests verified the bioactivity of constructed Fab. The data suggested that P. pastoris could be considered a potential efficient eukaryotic host for ranibizumab production.

The Pisciarelli main fumarole mechanisms reconstructed by electrical resistivity and induced polarization imaging

Pisciarelli, together with the adjacent Solfatara maar-diatreme, represents the most active structure of the Campi Flegrei caldera (Italy) in terms of degassing and seismic activity. This paper aims to define the structure of the Pisciarelli hydrothermal system (down to a 20 m depth) through electrical resistivity and time-domain-induced polarization tomography and self-potential mapping. The retrieved 3D image of the area helps reconstruct the Pisciarelli subsurface in its area of maximum degassing, containing the main fumarole (“soffione”) and the mud pool. In particular, a channel has been identified in which fluids stored in a deeper reservoir rise toward the surface. Such a structure seems to be surmounted by a clay-cap formation that could govern the circulation of fluids and the abundance of gases/vapors emitted by the soffione. Based on this new reconstruction of the Pisciarelli fumarolic field structural setting, the first conceptual model has been suggested that is capable of simultaneously explaining the mechanisms governing soffione activity and elucidating the role played by the fluid/gas of deeper origin in the shallow fluid circulation system. The proposed model can potentially help to better monitor the processes occurring throughout the Pisciarelli fumarolic field and provide an evaluation of the associated hazards.

Understanding the Failure of the Arab Maghreb Union: A Critical Constructivits Account

The Arab Maghreb Union (AMU), which was established by the countries of the region known as North Africa, also called as the Maghreb, to strengthen regional cooperation, draws attention as an organization that has lost its effectiveness today. This study examines the factors that affect the "failure" of the AMU. The discussions for the AMU to gain an active structure, which was established with the participation of Morocco, Tunisia, Algeria, Mauritania and Libya in the late 1980s, have increased even more with the current political crisis in Libya. The idea of "a united Maghreb" was actually a political argument used to mobilize the people of the region against the colonial powers during their struggle for independence long before the establishment of the AMU. Many reasons can be put forward to explain why the leaders of the region, who used the idea of creating a "united Maghreb" in their discourses, did not show enough will to achieve this dream. This study uses a critical constructivist account of state identity and interest and argues that Maghreb states were not able to develop shared identities and interests. It argues that the creation of the AMU could not pave the way for regional cooperation because Maghreb states consider each other as rivals and articulated their interests on this conception.