Asymptotic Stability Conditions and Estimates of Solutions for Nonlinear Multiconnected Time-Delay Systems

This paper examines certain classes of multiconnected (complex) systems with time-varying delay. Delay-independent stability conditions and estimates of the convergence rate of solutions to the origin for those systems are derived. It is shown that the exponents in the obtained estimates depend on the parameters of Lyapunov functions constructed for the corresponding isolated subsystems. The problem of computing parameter values that provide the most precise estimates is investigated. Some examples are presented to demonstrate the effectiveness of the proposed approaches.     

COVID-19 crisis impact on the stability between parties in crowdfunding and crowdsourcing

This research reviews challenges in building sustainable relationships between the parties involved in the crowdfunding and crowdsourcing projects, which are running in extreme situations, such as the COVID-19 pandemic. This study aims to solve problems that generate the crowdsourcing concerns and to find better alternatives to increase trust for crowdfunding among donors, as this impacts their strategic sustainability in the conditions of turbulence and COVID-induced financial crisis. It was found that factors influence donor decisions in different ways, yet the common tendency for donor activity is non-monotonicity. Future development in the field of sustainable relationships should focus on creating a donor classification system.

     

Three-dimensional optical data storage through multi-photon confocal microscopy and imaging

Three dimensional optical data storage is one of the most promising tools to respond to the always growing demand for high data storage capacity. Here, we focused a femtosecond laser source by means of a confocal microscope onto different transparent recording media. The purpose of the study is to probe the capability of the system to independently address different data layers within the storage medium achieving thus three dimensional data storage. We demonstrated the possibility to write superposed independent layers of data due to either multiphoton excitation or to local optical breakdown and the performances observed in the different types of media used are compared.     

Improved CO2 Capture from Flue Gas by Basic Sites,Charge Gradients,and Missing Linker Defects on Nickel Face Cubic Centered MOFs

The adsorptive properties of the isoreticular series [Ni₈(OH)₄(H₂O)₂(BDP_X)₆] (H₂BDP_X = 1,4‐bis(pyrazol‐4‐yl)benzene‐4‐X with X = H (1), OH (2), NH₂ (3)) can be enhanced by postsynthetic treatment with an excess of KOH in ethanol. In the case of X = H, NH₂, this treatment leads to partial removal of the organic linkers, deprotonation of coordinated water molecules and introduction of extraframework cations, giving rise to materials of K[Ni₈(OH)₅(EtO)‐(H₂O)₂(BDP_X)_5.5] (1@KOH, 3@KOH) formulation, in which the original framework topology is maintained. By contrast, the same treatment with KOH in the [Ni₈(OH)₄(H₂O)₂(BDP_OH)₆] (2) system, enclosing the more acidic phenol residues, leads to a new material containing a larger fraction of missing linker defects and extra‐framework cations as well as phenolate residues, giving rise to the material K₃[Ni₈(OH)₃(EtO)(H₂O)₆(BDP_O)₅] (2@KOH), which also conserves the original face cubic centered (fcu) topology. It is noteworthy that the introduction of missing linker defects leads to a higher accessible pore volume with a concomitant increased adsorption capacity. Moreover, the creation of coordinatively unsaturated metal centers, charge gradients, and phenolate nucleophilic sites in 2@KOH gives rise to a boosting of CO₂ capture features with increased adsorption heat and adsorption capacity, as proven by the measurement of pulse gas chromatography and breakthrough curve measurements of simulated flue gas.     

Test and Reliability in Approximate Computing

This paper presents an overview of test and reliability approaches for approximate computing architectures. We focus on how specific methods for test and reliability can be used to improve the characteristics of approximate computing in terms of power consumption, area, life expectancy and precision. This paper does not address specification and design of approximate hardware/software/algorithms, but provides an in-depth knowledge on how the reliability and test related techniques can be efficiently used to maximize the benefits of approximate computing.     

A 3D Cell-Free Bone Model Shows Collagen Mineralization is Driven and Controlled by the Matrix

Osteons, the main organizational components of human compact bone, are cylindrical structures composed of layers of mineralized collagen fibrils, called lamellae. These lamellae have different orientations, different degrees of organization, and different degrees of mineralization where the intrafibrillar and extrafibrillar minerals are intergrown into one continuous network of oriented crystals. While cellular activity is clearly the source of the organic matrix, recent in vitro studies call into question whether the cells are also involved in matrix mineralization and suggest that this process could be simply driven by the interactions of the mineral with extracellular matrix. Through the remineralization of demineralized bone matrix, the complete multiscale reconstruction of the 3D structure and composition of the osteon without cellular involvement are demonstrated. Then, this cell-free in vitro system is explored as a realistic, functional model for the in situ investigation of matrix-controlled mineralization processes. Combined Raman and electron microscopy indicate that glycosaminoglycans (GAGs) play a more prominent role than generally assumed in the matrix–mineral interactions. The experiments also show that the organization of the collagen is in part a result of its interaction with the developing mineral.     

Polycarbonate films metalized with a single component molecular conductor suited to strain and stress sensing applications

The paper reports all-organic strain and stress sensitive films that use electrical monitoring approach. The films were prepared by self-metallizing polycarbonate films with the single component molecular conductor [Au(α-tpdt)₂]⁰ (tpdt = 2,3-thiophenedithiolate). It was shown that [Au(α-tpdt)₂]⁰ by its nature is able to form metallic solid material with low crystallinity. Electromechanical tests demonstrated that the developed films are strain-resistive materials with advanced elastic properties: their electrical resistance varies linearly with uniaxial elongation up to relative strain being of 1.0% that is about five times larger than that for conventional metals. The gauge factor of the films is 4.4 and stress sensitivity is 30 Ω/bar. The processing characteristics of polycarbonate films, self-metalized with a metallic [Au(α-tpdt)₂]⁰-based layer, make them potentially useful for engineering flexible, lightweight, strain and pressure sensors. Due to electromechanical characteristics these films are suited to strain sensing applications requiring miniature strain control in a wide deformation range.     

Functionalization of Nanostructured Hematite Thin‐Film Electrodes with the Light‐Harvesting Membrane Protein C‐Phycocyanin Yields an Enhanced Photocurrent

The integration of light‐harvesting proteins and other photosynthetic molecular machinery with semiconductor surfaces plays an important role in improving their performance as solar‐cell materials. Phycocyanin is one such protein that can be employed for this purpose. Phycocyanins have light‐harvesting properties and belong to the phycobilisome protein family. They are present in cyanobacteria, which capture light energy and funnel it to reaction centers during photosynthesis. Here, a way of increasing the photocurrent of hematite by covalent cross‐coupling with phycocyanin is reported. For this, a hematite–phycocyanin integrated system is assembled by consecutive adsorption and cross‐coupling of protein molecules, separated by an agarose layer and a linker molecule, on the top of a mesoporous hematite film. The hematite–phycocyanin assembly shows a two‐fold increased photocurrent in comparison with pristine hematite film. The increase in the photocurrent is attributed to the enhanced light absorption of the hematite film after integration with the protein, as is evident from the UV–vis spectra and from the photocurrent‐action spectrum. The assembly shows long‐term stability and thus constitutes a promising hybrid photoanode for photo‐electrochemical applications.     

Difference frequency magneto-acousto-electrical tomography (DF-MAET): application of ultrasound-induced radiation force to imaging electrical current density

Magneto-acousto-electrical tomography (MAET) is a potential imaging modality which can provide high-spatial-resolution images of the impedance of conductive media. In MAET, the impedance is reconstructed from the mapped current density distribution J(ab)(r) that would exist in a sample if a current/voltage source were to be applied through measurement electrodes a and b. To map J(ab)(r) without applying a current/voltage source, the sample is placed in a static magnetic field and a focused ultrasonic pulse is directed to a point r to generate a point-like dipole source via the Lorentz force mechanism. The MAET voltage U(ab), which is directly proportional to J(ab)(r), is measured through electrodes a and b for each scanning point. To reconstruct the electrical impedance, we need to map the current density distribution at every point inside the sample. However, with the MAET experimental setup reported in our previous paper on MAET, the MAET signal from a homogenous interior of the sample is undetectable because of the spatially-oscillating nature of the ultrasound field inside the sample. In this paper, we propose to use dual-frequency ultrasound to generate the MAET signal at the difference frequency through the ultrasound radiation force mechanism. The dynamic radiation force causes vibrations inside the sample (and consequently, generates the electric field) with a wavelength much larger than the dimension of the sample along the transducer's axis. Therefore, the MAET signal caused by the radiation force will not be canceled out. We create a dynamic radiation force by applying an amplitude-modulated signal with a modulation frequency fm of several kilohertz and a carrier frequency f(0) of 2.25 MHz to drive the transducer. The dependence of the DF-MAET signal in experiments on the modulation frequency and on the density of the sample agrees with the prediction based on the radiation force mechanism. The spatial resolution of DF-MAET is also studied to verify the radiation force mechanism. Finally, we will prove that the parametric effect in the coupling oil is not a significant source of the DF-MAET signal by imaging a sample at different distances from the transducer. Potential improvements to the present DF-MAET experimental configuration are also discussed.