LEAD BASED (PZT) AND LEAD FREE (BZT) COMPOSITES FLEXIBLE FILMS AS LOW-ENERGY PIEZOELECTRIC HARVESTERS

Various alternative renewable sources such as solar, wind, thermal energy and mechanical vibrations are available for the energy generations. For the last decades, energy harvesters based on piezoelectricity from mechanical vibration are explored extensively for its functionality in energy technologies [1,2]. Flexible piezoelectric energy harvesters (FPEHs) and energy storage system were fabricated by employing solid state synthesized lead-free BZT (BaZr0.2Ti0.8O3) and PZT (PbZr0.52Ti0.48O3) nanopowders prepared by autocombustion method with polyvinylidene fluoride (PVDF) in different volume percentage (xBZT/PZT-(1-x)PVDF, x=30, 40, 50). Both flexible films with quite homogeneous distribution of piezo-active filler were confirmed by XRD and SEM analysis. In addition, the remnant polarization (Pr) and dielectric constant are also investigated to evaluate the breakdown strength in flexible films. The improved dielectric loss tangent (< 0.02) and dielectric permittivity of 120 at room temperature and frequency 1 MHz of BZT-PVDF (50- 50) in comparison with neat PVDF films is found beneficial for both energy harvesting and storage. Calculations of storage energies obtained for the investigated materials revealed an increasing trend with increasing amount of active phase (BZT and PZT). The maximum storage energy of 0.11 J/cm3 and 0.13 J/cm3, and energy efficiency (η) of 72% and 39% was obtained for BZT-PVDF (50-50) and PZTPVDF (40-60) films, respectively. Test of the force impact showing similar output voltage of around 4 V for both, BZT and PZT flexible films

MECHANICAL ENERGY HARVESTING POTENTIAL OF BiFeO3-PVDF FLEXIBLE COMPOSITES

Bismuth ferrite (BiFeO3) powders were synthesized by sol-gel methods and incorporated into flexible composites by hot pressing with polyvinylidene fluoride (α-PVDF). Several metal ions with various valances were used to dope BiFeO3 in order to examine their influence on electrical properties. XRD characterization confirmed that almost all of the dopants incorporated very well into the perovskite structure. Microstructural study showed that the composites are homogeneous with thickness of 50 to 140 μm. Dielectric, impedance and ferroelectric properties of composite samples showed that all of the dopants even those with smaller valence than the ions they substitute enhance the capability to handle the electric field. α-PVDF matrix also helped in preventing electrical breakdown comparing to BiFeO3 ceramics, which is usually susceptible to high leakage. Flexible composites were subjected to impact piezoelectric test with the idea to study their potential to collect mechanical energy from the surrounding vibrations

Energy Harvesting Potential of Polymer Composites

Energy is available all around us in different forms and shapes such as from sun, wind, waves, vibrations etc. The enormous amount of mechanical energy released in everyday life by human walking, transportation movement, sound waves and other, represent renewable and safe energy source. Piezoelectric generators exhibit a great potential for powering up low-power portable devices and self-powered electronic systems by extraction of mechanical energy. Employment of lead-free piezoelectric materials will be a breakthrough of a completely new type of safe and harmless production of energy for daily life. Recent challenge in electronics is also utilization of flexible electronics with the ability to bend into diverse shapes which expands the applications of modern electronic devices in different areas.Polymer PVDF/piezoelectric ceramics, flexible composite films were prepared by hot pressing method. The influence of hot pressing method on the formation of electroactive PVDF phases in the polymer was proven by FTIR analysis. DSC analysis have shown the change of PVDF crystallinity degree in the flexible films with addition of ceramics filler particles. The dielectric permittivity value increased with the addition of filler in the polymer matrix while the relaxation processes were governed mostly by the PVDF matrix. Polarization of flexible films enhanced the formation of PVDF electroactive β- phase in the samples. Energy harvesting potential was studied by measuring of voltage output under the impulse hammer load

Altered infective competence of the human gut microbiome in COVID-19

BACKGROUND: Infections with SARS-CoV-2 have a pronounced impact on the gastrointestinal tract and its resident microbiome. Clear differences between severe cases of infection and healthy individuals have been reported, including the loss of commensal taxa. We aimed to understand if microbiome alterations including functional shifts are unique to severe cases or a common effect of COVID-19. We used high-resolution systematic multi-omic analyses to profile the gut microbiome in asymptomatic-to-moderate COVID-19 individuals compared to a control group. RESULTS: We found a striking increase in the overall abundance and expression of both virulence factors and antimicrobial resistance genes in COVID-19. Importantly, these genes are encoded and expressed by commensal taxa from families such as Acidaminococcaceae and Erysipelatoclostridiaceae, which we found to be enriched in COVID-19-positive individuals. We also found an enrichment in the expression of a betaherpesvirus and rotavirus C genes in COVID-19-positive individuals compared to healthy controls. CONCLUSIONS: Our analyses identified an altered and increased infective competence of the gut microbiome in COVID-19 patients. Video Abstract

Clinical Use and Therapeutic Potential of IVIG/SCIG, Plasma-Derived IgA or IgM, and Other Alternative Immunoglobulin Preparations

Intravenous and subcutaneous immunoglobulin preparations, consisting of IgG class antibodies, are increasingly used to treat a broad range of pathological conditions, including humoral immune deficiencies, as well as acute and chronic inflammatory or autoimmune disorders. A plethora of Fab- or Fc-mediated immune regulatory mechanisms has been described that might act separately or in concert, depending on pathogenesis or stage of clinical condition. Attempts have been undertaken to improve the efficacy of polyclonal IgG preparations, including the identification of relevant subfractions, mild chemical modification of molecules, or modification of carbohydrate side chains. Furthermore, plasma-derived IgA or IgM preparations may exhibit characteristics that might be exploited therapeutically. The need for improved treatment strategies without increase in plasma demand is a goal and might be achieved by more optimal use of plasma-derived proteins, including the IgA and the IgM fractions. This article provides an overview on the current knowledge and future strategies to improve the efficacy of regular IgG preparations and discusses the potential of human plasma-derived IgA, IgM, and preparations composed of mixtures of IgG, IgA, and IgM

Three-Level Delta Modulation for Laplacian Source Coding

This paper proposes a novel solution for coding of time varying signals with Laplacian distribution, which is based on delta modulation and three-level quantization. It upgrades the conventional scheme by introducing the quantizer with variable length code. Forward adaptive scheme is used, where the adaptation to the signal variance is performed on frame-by-frame basis. We employ configurations with simple fixed first-order predictor and switched first-order predictor utilizing correlation. Furthermore, we propose different methods for optimizing predictor coefficients. The configurations are tested on speech signal and compared to an adaptive two-level and four-level delta modulation, showing that proposed three-level delta modulation offers performance comparable to a four-level baseline with significant savings in bit rate

Three-Level Delta Modulation with Second-Order Prediction for Gaussian Source Coding

An adaptive three-level delta modulation with a switched second-order linear prediction is proposed in this paper, intended for encoding the time-varying signals modeled by Gaussian distribution. The input signal is processed frame-by-frame, and the adaptation of the quantizer is performed at the frame level. The signal at the output of quantizer is further processed using variable length encoder to decrease the bit rate. The performance is tested in speech coding, showing that the proposed algorithm provides much wider dynamic range and attains higher Signal to Noise Ratio with respect to the baselines, including CFDM, CVSDM and 2-bit Adaptive Delta Modulation