Stability Of Matrix Research Articles

Flexible and highly pressure-sensitive ternary composites-wrapped polydimethylsiloxane sponge based on synergy of multi-dimensional components

Flexible pressure sensor becomes increasingly important with the development of ultra-sensitive touch technology, electronic skin, and human health monitoring, which requires higher sensitivity. Here, a novel strategy is proposed by designing conductive polymer composites consisting of four components with different dimensions. Through a simple one-step hydrothermal method, the ternary composites of silver-carbon nanotubes-reduced graphene oxide (Ag-CNTs-rGO) were synthesized. The ternary composites-wrapped polydimethylsiloxane (PDMS) sponges, Ag-CNTs-rGO/PDMS, were fabricated by a dip-drying method. The conductive polymer sponges as pressure sensors showed improved sensitivity of 33 kPa−1 in the range of 0–0.05 kPa, which is twelve times higher than that of the conductive sponge without Ag nanoparticles. The uniform coating of Ag nanoparticles on CNTs and rGO not only enhanced the conductivity of the Ag-CNTs-rGO composites but also reduced the contact resistance between carbon materials. The CNTs-rGO matrix accelerated electron transport throughout the conductive sponge. The good flexible stability of the CNTs-rGO matrix and porous PDMS structures enabled the Ag-CNTs-rGO/PDMS sponge to assemble flexible circuits and act as elastic electric contacts. The combination of zero-dimensional metal nanoparticles, one-dimensional CNTs, and two-dimensional graphene as conductive fillers in three-dimensional porous structures provides new insight into acquiring the ultrahigh-performance flexible pressure sensors.

A Deterministic Matrix Design Method Based on the Difference Set Modulo Subgroup for Computational Ghost Imaging

Computational ghost imaging is a novel technique, which has a wide range of applications in many fields. As a key part of computational ghost imaging, the measurement matrix plays an important role in imaging quality and system practicability. To improve the imaging quality of computational ghost imaging and overcome the poor stability and non-negativity of the measurement matrix, we propose a new construction method for the deterministic measurement matrix based on the difference set modulo subgroup. This method uses an efficient simulated annealing algorithm to search for the difference set modulo subgroup. Then a 0–1 binary measurement matrix can be constructed according to the obtained difference set. We can show that the measurement matrix constructed by this method has low coherence and can satisfy the restricted isometry property. The simulation and experimental results showed that the reconstruction quality of the proposed measurement matrix was equivalent to the Sparse random matrix and better than the Toeplitz and Circulant matrices, which indicates the feasibility of the newly proposed measurement matrix.

Preparation of a new Interpenetrating polymer networks IPNS from the waste bottles drinking water PET with epoxy resins and used to remove some toxic ions from water

In this Study, a new polymer IPNS was prepared, From The product of the Glycolysis of Poly(ethylene terephthalate) Waste with epoxy resin, IPNS Networks were characterized using infrared spectroscop(IR (to determine the functional groups, The thermal stability of the polymer matrix was evaluated using Differential Scanning Calorimetry) DSC (and the thermogravimetric analysis (TGA), The efficiency of the IPNS was tested to remove some toxic ions from water such as Cd+2, Pb +2 In different acidic media and at different time periods using flameless atomic absorption technique that the total loading capacity and efficiency of the ions. The adsorption of ions on the polymer network was studied using the Frendlich and Longmuir isotherms, The results showed that the adsorption process follows the Frendlich equation.

Equilibrium-Independent Stability Analysis for Distribution Systems With Lossy Transmission Lines

Power distribution systems are becoming much more active with increased penetration of distributed energy resources. Because of the intermittent nature of these resources, the stability of distribution systems under large disturbances and time-varying conditions is becoming a key issue in practical operations. Because the transmission lines in distribution systems are lossy, standard approaches in power system stability analysis do not readily apply. In this paper, the stability of lossy distribution systems is certified by breaking the network into subsystems. By looking at the equilibrium-independent passivity of each subsystem, the stability of the whole network is implied by the diagonal stability of the interconnection matrix. This analysis scales to large networked systems with time-varying equilibria. The proposed method gracefully extrapolates between lossless and lossy systems, and provides a simple yet effective approach to optimize control efforts with guaranteed stability regions. Case studies verify that the proposed method is much less conservative than existing approaches.

Rapid Prediction of Effect of Ferrous Iron on the Stability of Emulsion Explosives Matrix

Designing an emulsified matrix formulation in the laboratory, the ratios of the emulsifier span-80 and T-152 were 1:0, 2:1, 1:2, 0:1 respectively. Then the preparation was added by 0.04% Fe2+ impurities emulsion matrix. Based on the water-soluble test method, we used ultrasonic instrument to focus on emulsion matrix containing Fe2+ impurities. The results show that the crystallization amount of emulsion matrix by adding Fe2+ is more than that of not adding Fe2+ .Impurities Fe2+ has damaging effects on the stability of its interface membrane. At the same time, ultrasound can accelerate the speed of demulsification of emulsion matrix. As composite emulsifiers span-80: T-152=1:2, the stability of emulsion matrix is the best.

Matrix measures, stability and contraction theory for dynamical systems on time scales

<p style='text-indent:20px;'>This paper is concerned with the study of the stability of dynamical systems evolving on time scales. We first formalize the notion of matrix measures on time scales, prove some of their key properties and make use of this notion to study both linear and nonlinear dynamical systems on time scales. Specifically, we start with considering linear time-varying systems and, for these, we prove a time scale analogous of an upper bound due to Coppel. We make use of this upper bound to give stability and input-to-state stability conditions for linear time-varying systems. Then, we consider nonlinear time-varying dynamical systems on time scales and establish a sufficient condition for the convergence of the solutions. Finally, after linking our results to the existence of a Lyapunov function, we make use of our approach to study certain epidemic dynamics and complex networks. For the former, we give a sufficient condition on the parameters of a SIQR model on time scales ensuring that its solutions converge to the disease-free solution. For the latter, we first give a sufficient condition for pinning synchronization of complex time scale networks and then use this condition to study certain collective opinion dynamics. The theoretical results are complemented with simulations.</p>

Peroxidasin Deficiency Re-programs Macrophages Toward Pro-fibrolysis Function and Promotes Collagen Resolution in Liver.

Background & AimsDuring liver fibrosis, tissue repair mechanisms replace necrotic tissue with highly stabilized extracellular matrix proteins. Extracellular matrix stabilization influences the speed of tissue recovery. Here, we studied the expression and function of peroxidasin (PXDN), a peroxidase that uses hydrogen peroxide to cross-link collagen IV during liver fibrosis progression and regression.MethodsMouse models of liver fibrosis and cirrhosis patients were analyzed for the expression of PXDN in liver and serum. Pxdn-/- and Pxdn+/+ mice were either treated with carbon tetrachloride for 6 weeks to generate toxin-induced fibrosis or fed with a choline-deficient L-amino acid-defined high-fat diet for 16 weeks to create nonalcoholic fatty liver disease fibrosis. Liver histology, quantitative real-time polymerase chain reaction, collagen content, flowcytometry and immunostaining of immune cells, RNA-sequencing, and liver function tests were analyzed. In vivo imaging of liver reactive oxygen species (ROS) was performed using a redox-active iron complex, Fe-PyC3A.ResultsIn human and mouse cirrhotic tissue, PXDN is expressed by stellate cells and is secreted into fibrotic areas. In patients with nonalcoholic fatty liver disease, serum levels of PXDN increased significantly. In both mouse models of liver fibrosis, PXDN deficiency resulted in elevated monocyte and pro-fibrolysis macrophage recruitment into fibrotic bands and caused decreased accumulation of cross-linked collagens. In Pxdn-/- mice, collagen fibers were loosely organized, an atypical phenotype that is reversible upon macrophage depletion. Elevated ROS in Pxdn-/- livers was observed, which can result in activation of hypoxic signaling cascades and may affect signaling pathways involved in macrophage polarization such as TNF-a via NF-kB. Fibrosis resolution in Pxdn-/- mice was associated with significant decrease in collagen content and improved liver function.ConclusionPXDN deficiency is associated with increased ROS levels and a hypoxic liver microenvironment that can regulate recruitment and programming of pro-resolution macrophages. Our data implicate the importance of the liver microenvironment in macrophage programming during liver fibrosis and suggest a novel pathway that is involved in the resolution of scar tissue.

Thermal, mechanical, and electrical properties of difunctional and trifunctional epoxy blends with nanoporous materials

In the present study, the aim is to synthesize the particulate nanocomposites with difunctional and trifunctional epoxy blend as matrix and synthesized nanoporous materials as fillers. Organic/inorganic hybrid networks were prepared by the novel solvent free method. Viscoelastic, thermal, and electrical properties of di- and trifunctional epoxy and the effect of different nanoparticles in the particulate nanocomposites have been studied by dynamic mechanical analyzer, thermogravimetry (TGA), and dielectric strength. Epoxy mixed with different compositions of TGPAP and particulate nanocomposites by the addition of different types of nanomaterials shows higher storage modulus than the pure epoxy. The addition of TGPAP and nanofillers decreases the thermal stability of epoxy matrix. The evolved gas analysis (TG-FTIR) was also done in order to study the products formed during degradation. An increase in dielectric strength and impact strength (4%) was also observed in the particulate nanocomposites.

Development and validation of a simple and sensitive LC-MS/MS method for the quantification of cefazolin in human plasma and its application to a clinical pharmacokinetic study

Cefazolin is widely used during surgery to prevent surgical site infections (SSIs). Although cefazolin redosing is often needed due to its short half-life, the appropriate redosing schedule remains controversial and there is limited information on cefazolin disposition following repeated doses during surgery. In parallel with an ongoing cefazolin redosing clinical study, we have developed and fully validated a simple and robust liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of cefazolin in human plasma. A simple protein precipitation was used for sample preparation. MS/MS analysis was performed using multiple reaction monitoring (MRM) under a positive ionization mode. The lower limit of quantification (LLOQ) for cefazolin was evaluated at 0.25 µg/mL and a linearity ranging from 0.25 to 300 µg/mL. Accuracy was ≤ 114.3% for quality controls and ≤ 118.2% for LLOQ; intra-day and inter-day precision ranging from 1.9% to 14.2% for all quality controls and LLOQ. Matrix effect, extraction recovery, stability testing, dilution integrity, hemolysis effects and whole blood stability have all been investigated. A total of 17 parameters were validated and passed their validation criteria. The method was applied in the quantification of cefazolin in clinical plasma samples and was able to successfully determine the concentrations in patients undergoing various surgeries. In comparison with other prior published methods, our method has a simple sample preparation combined with a short analysis run time, a wide dynamic range and low limit of quantification, and is a fully validated assay that abides by FDA guidance.

Assessing the detectability of the secondary spin in extreme mass-ratio inspirals with fully relativistic numerical waveforms

Extreme mass-ratio inspirals (EMRIs) detectable by the Laser Inteferometric Space Antenna (LISA) are unique probes of astrophysics and fundamental physics. Parameter estimation for these sources is challenging, especially because the waveforms are long, complicated, known only numerically, and slow to compute in the most relevant regime, where the dynamics is relativistic. We perform a time-consuming Fisher-matrix error analysis of the EMRI parameters using fully relativistic numerical waveforms to leading order in an adiabatic expansion on a Kerr background, taking into account the motion of the LISA constellation, higher harmonics, and also including the leading correction from the spin of the secondary in the postadiabatic approximation. We pay particular attention to the convergence of the numerical derivatives in the Fisher matrix and to the numerical stability of the covariance matrix, which for some systems requires computing the numerical waveforms with approximately 90-digit precision. Our analysis confirms previous results (obtained with approximated but much more computationally efficient waveforms) for the measurement errors on the binary's parameters. We also show that the inclusion of higher harmonics improves the errors on the luminosity distance and on the orbital angular momentum angles by one order and two orders of magnitude, respectively, which might be useful to identify the environments where EMRIs live. We particularly focus on the measurability of the spin of the secondary, confirming that, for spin-aligned EMRIs on quasicircular orbits, it cannot be measured with sufficient accuracy. However, due to correlations, its inclusion in the waveform model can deteriorate the accuracy on the measurements of other parameters by orders of magnitude, unless a physically motivated prior on the secondary spin is imposed.

Leader-following consensus of heterogeneous linear multi-agent systems: New results based on linear transformation method

This paper studies the leader-following state consensus problem for heterogeneous linear multi-agent systems under fixed directed communication topologies. First, we propose a consensus protocol consisting of four parts for high-order multi-agent systems, in which different agents are allowed to have different gain matrices so as to increase the degree of design freedom. Then, we adopt a state linear transformation, which is constructed based on the incidence matrix of a directed spanning tree of the communication topology, to equivalently transform the state consensus problem into a partial variable stability problem. Meanwhile, the results of the partial variable stability theory are used to derive a sufficient and necessary consensus criterion, expressed as the Hurwitz stability of a real matrix. Then, this criterion is further expressed as a bilinear matrix inequality condition, and, based on this condition, an iterative algorithm is proposed to find the gain matrices of the protocol. Finally, numerical examples are provided to verify the effectiveness of the proposed protocol design method.

Consensus Conditions for a Class of Fractional-Order Nonlinear Multiagent Systems with Constant and Time-Varying Time Delays

The consensus problem for a class of fractional-order nonlinear multiagent systems with a distributed protocol containing input time delay is investigated in this paper. Consider both cases of constant time delay and time-varying delay, the delay-independent consensus conditions are obtained to achieve the consensus of the systems, respectively, by adopting the linear matrix inequality (LMI) methods and stability theory of fractional-order systems. As illustrated by the numerical examples, the proposed theoretical results work well and accurately.

Novel pH-responsive chitosan/sodium alginate/PEG based hydrogels for release of sodium ceftriaxone

pH-sensitive hydrogels have gained attraction in many biomedical fields. In this study, pH-sensitive hydrogels based on polyelectrolyte complex of chitosan/sodium alginate/PEG with 1,4-diaminobutane as a cross-linking agent were blended by solution casting method. FTIR was conducted to study the interactions among the polymer chains and crosslinker. The influence of the cross-linker concentration on the swelling behavior of the hydrogels was studied. SEM images exhibited the spongy hydrogel matrix and the drug entrapped in the hydrogel is also observed in drug loaded sample. TGA was conducted to check the effect of cross-linking density on the thermal stability of the hydrogel matrix. The release profile of sodium ceftriaxone (CTX) as a model drug in the solutions of PBS, SGF and SIF was investigated. In SGF, drug was released more than 10% in 30 min, while in PBS and SIF, the drug was released in a controlled manner. The comparison of UV spectra of pure and released drug confirmed its chemical stability in the developed hydrogels. The release profile according to the pharmacopeia standards designated the prepared hydrogels as a suitable candidate for drug release applications.

Investigating the active sites in molybdenum anchored nitrogen-doped carbon for alkaline oxygen evolution reaction

Developing durable and efficient non-precious-metal based catalysts for oxygen evolution reaction (OER) is highly desirable in the field of electrocatalysis. In this work, a series of novel Mo anchored N-doped carbon catalysts (denoted as Mo/NC-T) were prepared starting from the zeolitic imidazolate framework 8 (ZIF-8) precursor. Firstly, Mo doped ZIF-8 precursor (Mo/ZIF-8) with a regular polyhedron structure was formed through a simple ion-exchange method process between molybdenum pentachloride (MoCl5) and ZIF-8. Afterward, Mo/ZIF-8 was converted to Mo/NC-T through a two-step calcination process in nitrogen (N2) and ammonia (NH3). The as-synthesized Mo/NC-T samples exhibited superior electrocatalytic OER properties. The optimal sample at 650 °C (Mo/NC-650) presented a low overpotential of 320 mV at 10 mA cm−2, a Tafel slope of 71 mV dec-1, and an outstanding long-term stability for 30 h in 1 M KOH solution. The remarkable OER activity of Mo/NC-T could be ascribed to the structural stability of carbon matrix and the synergistic effect between Mo3+ (derived from Mo-C bonds) and pyridinic N. This work provides a novel perspective on the roles of Mo species in the N-doped carbon electrocatalysts for OER.

The synergistic effect of SiC/R-GO composite on mechanical and tribological properties of thermosetting polyimide

The effective means to solve material wear is to develop self-lubricating composite materials with excellent tribological, thermal, and mechanical properties. Herein, the composites of reduced graphene oxide (r-GO) nanosheet decorated with Silicon Carbide (SiC) were facilely prepared with employing a silane coupling agent, and the corresponding r-GO/SiC/thermosetting polyimide (r-GO/SiC/TPI) nanocomposite films were obtained by in situ polymerization method. The mechanical, tribological, and thermal properties of these nanocomposite films were investigated. When the content of r-GO/SiC was at 1.0 wt%, the compression strength and compression modulus of the composite increased by 37.7% and 47.3%, respectively, which were much higher than that of TPI composites addition of r-GO or SiC alone. Furthermore, r-GO/SiC/TPI composites also exhibited the lowest wear rate and friction coefficient in these reinforced TPI nanocomposites. When the content of r-GO/SiC was 0.8 wt%, particularly, the friction coefficient and wear rate of r-GO/SiC/TPI decreased by 22.8% and 79.8% compared to pure TPI, respectively. Additionally, trace amount r-GO/SiC hybrids also significantly enhance the thermal stability of TPI matrix. Compared to the polyimide composites reinforced by common nano-scale inorganic fillers, the outstanding mechanical and tribological properties of this r-GO/SiC/PI composites could be attributed to the ball on plane structure of GO/SiC, which lead to crack reflection, strength increment. These r-GO/SiC/TPI composites demonstrate the promising potential to be used as high-performance tribological materials in industry applications.

Nitrosylation of tissue transglutaminase enhances fibroblast migration and regulates MMP activation

In wound healing, the TG2 enzyme plays a dual functional role. TG2 has been shown to regulate extracellular matrix (ECM) stabilization by its transamidase activity while increasing cell migration by acting as a cell adhesion molecule. In this process, nitric oxide (NO) plays a particularly important role by nitrosylation of free cysteine ​​residues on TG2, leading to the irreversible inactivation of the catalytic activity.In this study, transfected fibroblasts expressing TG2 under the control of the tetracycline-off promoter were treated with NO donor S-nitroso-N-acetyl penicillamine (SNAP) to analyze the interplay between NO and TG2 in the regulation of cell migration/invasion as well as TGF-β1-dependent MMP activation. Our results demonstrated that inhibition of TG2 cross-linking activity by SNAP promoted the migration and invasion capacity of fibroblasts by hindering TG2-mediated TGF-β1 activation. While the inhibition of TG2 activity by NO downregulated the biosynthesis and activity of MMP-2 and MMP-9, that of MMP-1a and MMP-13 was shown to be upregulated in a TGF-β1-dependent manner under the same conditions. In the presence of SNAP, interaction of TG2 with its cell surface binding partners Integrin-β1 and Syndecan-4 was reduced, which was paralleled by an increase in TG2 and PDGF association. These findings suggests that migratory phenotype of fibroblasts can be regulated by the interplay between nitric oxide and TG2 activity.

Simultaneous determination of fluconazole and ofloxacin in rabbit tear fluid by LC-MS/MS: Application to ocular pharmacokinetic studies

The expansion of polymicrobial keratomycosis (PMK) requires dynamic pharmacotherapy of antimycotics along with antibacterial agents such as fluconazole (FCZ) and ofloxacin (OFX). To effective clinical cure, different microbes require different dosage regimens. A responsive, selective, and fast method for estimation of FCZ and OFX in rabbit tears using high-performance liquid chromatography together with tandem mass spectrometry (LC-MS/MS) was established and validated using ketoconazole as an internal standard (IS). An isocratic separation was achieved using a C18 column with methanol and aqueous 0.2% formic acid (80:20, v/v) as a mobile phase with a total run time and flow rate of 4 min and 400 µL/ min, respectively. The FCZ and OFX were detected utilizing positive ion electrospray ionization (ESI) in multiple reactions monitoring mode. The tear sample extraction was carried out using simple deproteination using methanol. The systematic method validation was carried out according to USFDA regulatory guidelines for selectivity, linearity (r2>0.99), intra-day and inter-day precision and accuracy, matrix effect, dilution integrity, and stability. The validated bioanalytical method was successfully pertained to determine the pharmacokinetics profile of FCZ and OFX marketed formulation in preclinical rabbit tears.

Evaluation of the effect of Shengxian Decoction on doxorubicin-induced chronic heart failure model rats and a multicomponent comparative pharmacokinetic study after oral administration in normal and model rats

Shengxian Decotion (SXT), a well-known Traditional Chinese Medicine (TCM) formula composed of Astragali Radix, Bupleuri Radix, Cimicifugae Rhizoma, Anemarrhenae Rhizoma and Platycodonis Radix, is clinically considered as an effective formula against cardiovascular diseases. However, the exact effective substance of SXT in treating chronic heart failure (CHF) still remains unclear. In the current study, we investigated the benefit of SXT in doxorubicin (DOX)-induced CHF rats and established a UHPLC-MS/MS method to simultaneously determine 18 key compounds in a subsequent comparative pharmacokinetic study in normal and CHF rats. Histopathological studies, transmission electron microscopy, and echocardiography were applied to assess the therapeutic effect of SXT on DOX-induced CHF rats, which indicated that SXT significantly ameliorated DOX-induced CHF, similar to enalapril. In addition, we successfully established a UHPLC-MS/MS method to determine the pharmacokinetics of the components in rat plasma, which was validated with good linearity, inter-day and intra-day precisions and accuracies, matrix effects, extraction recovery, and stability values. Our results showed that only astragaloside IV showed increased plasma exposure in the CHF rats, while saikosaponin A, quercetin, timosaponin B-II, ferulic acid, isoferulic acid and formononetin decreased compared to their pharmacokinetic characteristics in the normal and CHF rats. This study demonstrates that SXT enjoys obvious therapeutic effect on DOX-induced CHF rats, and the altered metabolism of some compounds in SXT is affected by the pathological state of CHF rats. Our findings provide a better understanding of the in vivo exposure to complex compounds of SXT, supporting effective substance screening and further investigation of the therapeutic mechanism.

Diffusion-assisted ultrashort laser pulse induced photothermal growth of core-shell nanoparticles in polymer matrix.

Light-to-heat conversion that occurs when irradiating a metal nanoparticle within a polymer matrix with ultrashort laser pulses initiates photothermal destruction of dissolved precursor molecules just near the nanoparticle. Extracted elementary species deposit on the nanoparticle surface, forming a core-shell structure. We construct an approximate analytical model for this process. The necessary step here is the diffusion of the precursor molecules towards the nanoparticle surface, replacing the broken ones. This diffusion can be a limiting factor for the rate of the shell growth. However, we show that because of the sharp localization of the process the precursor diffusion can successfully supply the growing shell with elementary species at realistic values of the precursor diffusion coefficient if the sample is kept in viscoelastic state at a temperature near the glass transition between the laser pulses. The main restriction on the obtained shell thickness comes from the requirement of matrix stability during the laser processing. Taking this restriction into account, the model allows estimating reachable shell thicknesses depending on the kinetic parameters of the precursor destruction reaction. This paper relies on numerous publications on photo/laser-induced growth of homogeneous metal or semiconductor nanoparticles within polymer matrices; however, this type of growth for compound core-shell nanoparticles is studied for the first time, to our knowledge.

Encapsulation of lactic acid bacteria and Bifidobacteria using starch‐sodium alginate nanofibers to enhance viability in food model

The aim of this study was to nanoencapsulate some probiotic strains of lactic acid bacteria and Bifidobacteria within corn starch (CS) and sodium alginate (SA) nanofiber mats using the electrospinning method to enhance survival and viability in yogurt as a food model. The control and probiotic-containing nanofiber mats had negative zeta potential of −10.83 and −12.57 mV. The SA/CS nanofibers had a greater protective effect on LAB compared to Bifidobacteria in an acidic environment. LAB count within nanofiber mats was reduced by 0.19, 0.85, and 1.05 logCFU, and of Bifidobacteria by 0.27, 0.46, and 1.24 logCFU, at 55, 60, and 65°C, respectively, which was lower than cell loss of free cells. After 20-day storage of yogurt, the count of nanoencapsulated LAB and Bifidobacteria declined 0.19 (97.9% survival) and 0.28 (96.9% survival) logCFU, respectively, while 1.12 (87.7% survival) and 1.25 (86.3% survival) logCFU of cell loss was found for free cells. Practical applications Although probiotic bacteria have a great potential in producing functional metabolites and components with antimicrobial, antioxidant, and health-promoting properties, their survival, and viability during food processing are affected by factors like heat, pH and acidity, food molecular structure, and chemical compounds of the food matrix. To protect probiotics against processing conditions in food preparation, increase their survival and stability in the food matrix, nanoencapsulation techniques are used. The preferred nanoencapsulation methods are those with the least damage to the probiotic cells. So, the results of this study will be useful to design the proper formulations of coatings for probiotics used in food products.