Suspended Medium Research Articles

Sensitive and real-time monitoring of microbial growth using a dielectric sensor with a 65-GHz LC-oscillator array and polytetrafluoroethylene membrane

In this study, we report a sensitive real-time microbial growth monitoring technique using a complementary metal-oxide semiconductor (CMOS) dielectric sensor with a polytetrafluoroethylene (PTFE) membrane. The sensor comprised an LC oscillator array operating at 65-GHz, whose resonant frequency was altered according to the dielectric properties of the region approximately 15 μm from the surface. We previously reported the rapid detection of viable Escherichia coli suspended in a liquid medium using the dielectric sensor; however, sensing growing cells was challenging owing to their tendency to float outside the effective sensing area in the suspended medium. To address this, we propose a new method to enhance the sensitivity of the device using a PTFE membrane that retains cells inside the effective area during measurement. Experiments using Escherichia coli suggested that the use of the membrane more than doubled sensitivity, reducing inspection times for practical applications. Furthermore, experiments with Lactococcus lactis, Staphylococcus epidermidis, and Saccharomyces cerevisiae demonstrated that this method can be used to monitor the growth of various microbes. In addition, variations in the output values of each oscillator facilitated the determination of microbial characteristics, such as cell size and growth distribution. This microbial growth monitoring technique is expected to find applications across a wide range of fields, such as food inspection, environmental hygiene monitoring, antibiotic susceptibility testing, new drug discovery, and the exploration of beneficial microbes.

Influencing Factors and Stimulus-Sensitivity of Chitosan/Polymethacrylic Acid (CS/PMAA) Nanogels as Nanocarriers

ABSTRACT Nanogel, nanosized hydrogel, can contribute to biomedical and pharmaceutical, especially in drug delivery, due to its enthralling properties. Small size, large surface area, hydrophilicity, and stimulus responsiveness of nanogel ameliorate tissue penetration, drug loading capacity, and targeted drug delivery. The current study prepared nanosized, pH-sensitive, biocompatible, and stable chitosan/polymethacrylic acid (CS/PMAA) based nanogels using MBA as a crosslinker and APS as an initiator. FTIR confirmed the reaction between functional groups to synthesize nanogels sufficiently in a spherical shape, as affirmed by a FESEM. DLS data revealed nanosized particles with a size range of 70–170 nm and a range of 6–13 for polydispersity index (PDI). A study showed that 2% of MBA crosslinker is sufficient to achieve the desired crosslinking in 60 minutes reaction time (RT) with nanogel size ~ 92 nm. Increasing RT from 30 to 80 minutes during nanogel synthesis demonstrated a decrease in nanogel sizes from 186–73 nm. Synthesized nanogels have shown pH sensitivity (stimuli responsiveness) in acidic and alkaline mediums with an increase in particle size in pH-2 (~144 nm) and pH-8 (~280 nm) compared to intermediate pHs. The pH sensitivity of nanogels by changing the size per the suspended medium’s pH is crucial for prolonged systemic circulation and targeted drug delivery. Moreover, nanogels have shown good colloidal stability with zeta potential (ZP) +28 mv in acidic and −38 mv alkaline mediums. DSC and XRD results demonstrated thermal stability and amorphous morphology of nanogels, respectively. BET surface analysis revealed the surface area of nanogels in the range of 65–68 cm2/g with an average pore size of 28–32 nm. In-vitro cytotoxicity in the L-929 cell line by MTT assay established the cell viability (>70%) after 24 hours of incubation, substantiating the non-toxicity and biocompatibility of nanogels as nanocarriers for drug delivery.

Estimation of the proximal temperature rise of an excited upconversion particle by detecting the wavefront of emission.

Monitoring the temperature distribution within a local environment at the micro and nanoscale is vital as many processes are solely thermal. Various thermometric techniques have been explored in the community, and out of these, fluorescent nano/micro particle-based mechanisms are accepted widely (fluorescence intensity ratio (FIR) techniques, where the ratio of populations in two consecutive energy levels is compared with Boltzmann distribution). We describe a new technique to account for the temperature rise near an illuminated upconverting particle (UCP) using wavefront imaging, which is more sensitive than the conventional thermometric techniques on the microscale. We rely on a thermo-optical phase microscopic technique by reconstructing the wavefront of emission from an upconverting particle using a Shack-Hartmann wavefront sensor. The wavefront maps the local phase distribution, which is an indicator of the surroundings' optical parameters, particularly the suspended medium's temperature-induced refractive index in the presence of convection currents. We describe how these extracted phase values can provide information about the optical heating due to the particle and hence its local environment along the direction of the emission. Our findings demonstrate the detection of a minimum temperature rise of 0.23 K, while the FIR methods indicate a minimum of 0.3 K rise. This technique is used to study the temperature increase in the backscattered direction for an upconverting particle illuminated on pump resonance. We also estimate the Soret coefficient for an upconverting particle optically trapped on pump resonance and experiencing anisotropic heating across the body.

Inactivation mechanism and kinetics of dielectric barrier discharge plasma against Escherichia coli O157:H7 in phosphate-buffered saline

ABSTRACT This study investigated the inactivation mechanism and kinetics of dielectric barrier discharges (DBD) plasma against Escherichia coli O157:H7. DBD plasma exhibited a remarkable bactericidal effect, and the inactivation kinetics was well described with the Weibull model. Using the ambient air as the working gas, surviving E. coli O157:H7 in phosphate-buffered saline achieved an undetectable level (<10 CFU/mL) after treatment at 18 W for 60 s. DBD plasma altered cell morphology, destructed both the outer and inner membranes, and increased intracellular reactive oxygen species levels. Moreover, DBD plasma significantly decreased the pH of the suspended medium, and increased its oxidation reduction potential and active species levels, which could be mainly responsible for microbial inactivation. The presence of glutathione or N-acetyl-L-cysteine weakened the antibacterial activity of DBD plasma due to their reactive oxygen and nitrogen species (RONS) scavenging capacity, demonstrating that RONS generated by DBD plasma played important roles in decontamination.

In vitro development of gametophytes and sporophytes of critically endangered fern Christella kendujharensis S.K. Behera &amp; S.K. Barik (Thelypteridaceae)

AbstractChristella kendujharensis S.K. Behera &amp; S.K. Barik (family: Thelypteridaceae) is a critically endangered fern endemic to India. We developed its mass propagation protocol through in vitro spore culture in a liquid suspended medium for germination of gametophytes that produced sporophytes subsequently. The spores were monolete, reniform (mean length 36.49 ± 3.6 × breadth 25.67 ± 4.2 μm) to spheroidal with fimbriate and broad‐winged perispore. The maximum germination was in the Parker's and Thompson's (P&amp;TV) medium with 0.1 mg L−1 thiamin, 0.1 mg L−1 riboflavin, 0.1 mg L−1 biotin, 0.1 mg L−1 pyridoxin, 0.5 mg L−1 nicotinic acid, 100 mg L−1 myoinositol, 0.01 mg L−1 folic acid, and 3 mg L−1 glycine. Spore germination was Vittaria type and gametophyte development was Aspidium type. The cordate gametophyte developed archegonia on the 38th day and antheridia on the 42nd day of spore sowing. Both isolate and composite cultures developed sporophytes indicating the presence of intra‐gametophytic selfing. Based on the maximum number of regenerated gametophytes, two combinations, that is, (i) 2 mg L−1 kinetin, and 0.01 mg L−1 2,4‐dichlorophenoxyacetic acid, and (ii) 0.1 mg L−1 naphthaleneacetic acid and 2 mg L−1 kinetin in P&amp;TV media were recommended for mass propagation of C. kendujharensis.

Ultrastructural analysis of zinc oxide nanospheres enhances anti-tumor efficacy against Hepatoma.

Zinc oxide nanomaterial is a potential material in the field of cancer therapy. In this study, zinc oxide nanospheres (ZnO-NS) were synthesized by Sol-gel method using yeast extract as a non-toxic bio-template and investigated their physicochemical properties through various techniques such as FTIR, XR, DLS, and TEM. Furthermore, free zinc ions released from the zinc oxide nanosphere suspended medium were evaluated by using the ICP-AS technique. Therefore, the cytotoxicity of ZnO nanospheres and released Zn ions on both HuH7 and Vero cells was studied using the MTT assay. The data demonstrated that the effectiveness of ZnO nanospheres on HuH7 was better than free Zn ions. Similarly, ZnO-Ns were significantly more toxic to HuH7 cell lines than Vero cells in a concentration-dependent manner. The cell cycle of ZnO-Ns against Huh7 and Vero cell lines was arrested at G2/M. Also, the apoptosis assay using Annexin-V/PI showed that apoptosis of HuH7 and Vero cell lines by ZnO nanospheres was concentration and time-dependent. Caspase 3 assay results showed that the apoptosis mechanism may be intrinsic and extrinsic pathways. The mechanism of apoptosis was determined by applying the RT-PCR technique. The results revealed significantly up-regulated Bax, P53, and Cytochrome C, while the Bcl2 results displayed significant down-regulation and the western blot data confirmed the RT-PCR data. There is oxidative stress of the ZnO nanospheres and free Zn+2 ions. Results indicated that the ZnO nanospheres and free Zn+2 ions induced oxidative stress through increasing reactive oxygen species (ROS) and lipid peroxidation. The morphology of the HuH7 cell line after exposure to ZnO nanospheres at different time intervals revealed the presence of the chromatin condensation of the nuclear periphery fragmentation. Interestingly, the appearance of canonical ultrastructure features of apoptotic morphology of Huh7, Furthermore, many vacuoles existed in the cytoplasm, the majority of which were lipid droplets, which were like foamy cells. Also, there are vesicles intact with membranes that are recognized as swollen mitochondria.

Hydromagnetic Instability of Two Viscoelastic Dusty-Fluids in Porous Medium

An attempt has been made to investigate the instability of the plane interface between two viscoelastic superposed conducting fluids in the presence of suspended particles and variable horizontal magnetic field through porous medium is studied. The cases of two fluids of uniform densities, viscosities, magnetic fields, and suspended particles number densities separated by a horizontal boundary; and of exponentially varying density, viscosity, suspended particles number density, and magnetic field are considered. It is found that the stability criterion is independent of the effects of viscoelasticity, medium porosity, and suspended particles but is dependent on the orientation and magnitude of the magnetic field. The magnetic field succeeds in stabilizing a certain range of wavenumbers which were unstable in the absence of the magnetic field. The system is found to be stable for potentially stable configuration/stratification. The growth rates are found to increase (for certain wavenumbers) and decrease (for other wavenumbers) with the increase in kinematic viscosity, suspended particles number density, magnetic field, medium permeability and stress relaxation time.

Thermodynamic second law analysis of magneto-micropolar fluid flow past nonlinear porous media with non-uniform heat source

This study analyzes the second law of thermodynamic for entropy generation in an irreversible hydromagneto-micropolar flow system with non-homogenous heat generation. The non-symmetric microstructure fluid flow past a stretching sheet with saturated porous non-linear media under magnetic field influence. Ignoring the fluid particle deformation, the microstructure is assumed rigid with the viscous suspended medium. The reduced dimensionless nonlinear formulated model is computationally coded and solved to obtain solutions for the entropy volumetric production, Bejan number and heat transfer magneto-micropolar fluid. The parameter dependent solutions for the flow characteristics and irreversibility processes are plotted and discussed. It is revealed from the study that minimization of entropy generation in a magneto-micropolar flow system is possible by improving the thermodynamic equilibrium with low material variables, viscosity and hysteresis magnetic. Also, it is seen that the terms that encourage internal heat generation reduces the micropolar fluid viscosity in the system.

Some investigations on surface quality indicators for OHNS die steel machined with suspended powder EDM process

The study focuses on the evaluation of surface quality characteristics of oil hardened non shrinking die steel surface machined with suspended powder electrical discharge machining process. Pure copper metal is used as an electrode material, and tungsten powder is used as suspended medium for the purpose. Machining experiments were carried out by varying one parameter at a time. After each test, the machined surface is analysed for evaluating its surface roughness and microhardness values. It is found that combination of 4 A gap current, 12 μs pulse on span and 7 μs pulse off span will result in optimum surface quality indicators for the SPEDM process. Also, dry sliding wear experiments were carried out on the machined surface to evaluate the frictional force and coefficient of friction. Spectroscopic analysis and energy dispersive X-ray diffraction analysis on the machined surface indicate a considerable rise in carbon and tungsten content on the recast white layer of the machined surface. Scanning electron microscopic analysis of the machined surface revealed the presence of compounds of tungsten on the recast white layer. Also, micro-cracks were observed on the machined surface which is due to higher gap current setting during EDM process.

Some investigations on surface quality indicators for OHNS die steel machined with suspended powder EDM process

The study focuses on the evaluation of surface quality characteristics of oil hardened non shrinking die steel surface machined with suspended powder electrical discharge machining process. Pure copper metal is used as an electrode material, and tungsten powder is used as suspended medium for the purpose. Machining experiments were carried out by varying one parameter at a time. After each test, the machined surface is analysed for evaluating its surface roughness and microhardness values. It is found that combination of 4 A gap current, 12 μs pulse on span and 7 μs pulse off span will result in optimum surface quality indicators for the SPEDM process. Also, dry sliding wear experiments were carried out on the machined surface to evaluate the frictional force and coefficient of friction. Spectroscopic analysis and energy dispersive X-ray diffraction analysis on the machined surface indicate a considerable rise in carbon and tungsten content on the recast white layer of the machined surface. Scanning electron microscopic analysis of the machined surface revealed the presence of compounds of tungsten on the recast white layer. Also, micro-cracks were observed on the machined surface which is due to higher gap current setting during EDM process.

Role of physicochemical factors on bacterial attachment in textile fibrous media

AbstractOne of the possible approaches to remove thePseudomonasbacteria from surface water by using textile fibrous media has been studied in this article. The attachment ofPseudomonasbacteria inside textile fibrous media was studied using laboratory column experiment which led to the understanding of the physiochemical interaction between textile surface and the bacteria. Colloid‐filtration theory was used to investigate the effects of various physicochemical factors like pH, ionic strength (M) and mass (g) of the porous media on bacterial attachment. The quantitative assessment of bacterial attachment on the textile surface media was carried out by determining the collision efficiency. The physicochemical factors mentioned above were optimized to obtain maximum collision efficiency so as to achieve maximum bacterial attachment on the textile media surface. Bacterial attachment is found to be directly related to the ionic strength of the suspending medium and the mass of the textile media. A significant improvement in collision efficiency is observed when the ionic strength of the suspended medium is increased. Maximum collision efficiency is achieved at high level of ionic strength and medium level of pH with high level of mass of the textile media.

Synthesis and Characterization of Innovative Type Magneto-Rheological Fluid

This research work is concerned with synthesis of an innovative type of magneto-rheological fluid (MRFluid) using edible low-cost soya bean oil as a carrier liquid with three different concentrations of electrolytic iron powder as a suspended medium and additives as a commercial grease. The field-dependent rheological properties of MRFluid samples were tested under different magnetic field conditions using rheometer. The results of the field-dependent-rheological properties of the prepared MRFluid samples show good agreement with commercial MRFluid. This directly indicates that the proposed innovative type of MRFluid can be used in automotive suspension systems, dampers, vibration control devices and so forth. Sedimentation test is also carried out in order to know the stability of the MRFluids.

On electrophoresis of a pH-regulated nanogel with ion partitioning effects.

The electrophoresis of a polyelectrolyte nanoparticle, whose charge condition depends on the salt concentration and pH of the suspended medium as well as the dielectric permittivity difference, is analyzed. The present nonlinear model for the electrophoresis of this pH-regulated polyelectrolyte (PE) particle is based on the consideration of full set of governing equations of fluid and ion transport coupled with the equation for electric field. The Born energy of the ions are incorporated to account for the difference in the dielectric permittivity of the PE and the electrolyte. The governing equations are computed numerically through a control volume approach. The nonlinear effects are highlighted by comparing with the existing linear model as well as results based on the first-order perturbation analysis valid for a weak applied field. The ion partitioning effect arising due to the difference in self energy of ions between the two media, have a strong impact on the mobility of the PE. The ion partitioning effect attenuates the penetration of counterions in the PE, which enhances the electric force and hence, results in a larger mobility of the PE. The nonlinear effects due to the double layer polarization and relaxation are intensified due to the ion partitioning effect. The ion partitioning effect influences the association/dissociation of PE functional group by tuning the hydrogen/hydroxide ions. Present study shows that the ion partitioning effect is profound for higher salt concentration and/or higher volume density of PE functional groups.

Intellectual properties of a granular nanoporous medium in a non-wetting liquid.

The intellectual properties of a suspension of a granular nanoporous medium in a non-wetting liquid under conditions of a pulsed pressure change are discussed in the work. The characteristic response time (0.1 ÷ 10) ms and the high specific energy intensity of the impact energy conversion (E) (10 ÷ 100) J / g make attractive the use of the such type suspensions in shock / explosion absorption devices. In the process of rapid compression upon impact and when the critical pressure (P0) is reached, the suspension is transformed into a new state with a change in the compressibility (χ = dV / dP) by (2 ÷ 4) of the order. In the new state, the process of volume reduction does not depend on the temperature and viscosity of the liquid, it is practically non-dissipative and at constant pressure. A microscopic mechanism of such a nontrivial nonlinear response is proposed. The intellectual properties of a suspended granular nanoporous medium in a non-wetting liquid under conditions of pulsed pressure changes are considered using of the Libersorb 23-water system as an example.

Nonlinear electrophoresis of a charged polarizable liquid droplet

A numerical study on the electrophoresis of a liquid droplet in an aqueous medium is made by considering the full set of governing equations based on the conservation principle. The surface of the droplet is considered to be charged, and the liquid filling the droplet is nonconducting. The dielectric polarization of the nonconducting droplet is also addressed in the present study. The impact of the surface conduction, double layer polarization, and relaxation effects creates a retardation on the electrophoresis. The occurrence of slip velocity at the droplet surface creates the surface conduction important even at weak electric field and a thin Debye layer for which the double layer polarization and relaxation may become small. The role of the surface conduction, which is measured through the Dukhin number, on the electrophoretic propulsion of the droplet is analyzed. Our numerical solutions for low charge density and thinner Debye length agree well with the existing simplified model and asymptotic analysis. However, a large discrepancy in mobility from these existing results occurs when the droplet size is bigger or droplet viscosity is lower than the suspended liquid medium. The variation of the electrophoretic mobility of a perfectly dielectric droplet as a function of the droplet viscosity, droplet size, and other electrokinetic parameters is analyzed. The dielectric polarization of the droplet and its impact on the electrophoresis are considered in the present work. The drag and the strength of the internal circulation are obtained.

BIOLOGICAL SULFIDE OXIDATION AND ITS IMPACT ON CELL BIOMASS SYNTHESIS BY MESOPHILIC BACTERIUM BACILLUS CERUES (ATCC 14579)

Inhibitory effects of hydrogen sulfide could either be due to toxicity to living tissue or precipitation of sulfide salts which inhibit its utilization for cell growth. Growth, is undoubtedly affected by certain conditions, among which are nutrient types and availability, as well as the operational parameters of the fermenting medium. In this study, Bacillus cereus (ATCC 14579) was tested for potential sulfide biodegradation in a suspended growth medium of orbital shake flasks using a single milieu composition under defined operational parameters. Growth and sulfide oxidation efficiency were measured spectrophotometrically under optimum physical conditions of pH, temperature, acclimatization time and agitation. Sulfide reduction was overwhelmingly recorded at three different sulfide loading rates of 200 ppm S2- L-1 d- 1, 300 ppm S2- L-1 d-1 and 500 ppm S2- L-1 d-1 with corresponding appreciable cell growth measured at OD600 nm. Results indicated that it was possible to realise sulfide removal efficiency of 95% to 99% using this strain in an orbital shake flask within 24 hrs, as well as 65% to 78% within the first 6 hrs of inoculation. Overall, sulfide wasreduced by 95% in 200 ppm and 300 ppm, while 99% in 500 ppm, respectively. While, the corresponding exponential cell growth recorded was 3.91, 3.80 and 3.61 in 200 ppm, 300 ppm and 500 ppm, respectively. This also translate to cell biomass synthesis (cell dry weight) of 0.61 g/L, 0.58 g/L and 0.50 g/L in 200 ppm, 500 ppm and 300 ppm. Based on this finding, it was clear that this inoculum can utilize different sulfide concentration for growth and biosynthesis; thus can be employed to treat sulfide contaminated wastewater in a suspended growth form under simple nutrient composition and operational conditions.

Polychlorinated biphenyls (PCBs) in industrial and municipal effluents: Concentrations, congener profiles, and partitioning onto particulates and organic carbon

Wastewater effluent samples were collected in the summer of 2009 from 16 different locations which included municipal and industrial wastewater treatment plants and petrochemical industrial outfalls in the Houston area. The effluent samples were analyzed for all 209 polychlorinated biphenyls (PCBs) congeners using high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS) using the USEPA method 1668A. The total PCBs (∑209) concentration in the dissolved medium ranged from 1.01 to 8.12ng/L and ranged from 2.03 to 31.2ng/L in the suspended medium. Lighter PCB congeners exhibited highest concentrations in the dissolved phase whereas, in the suspended phase, heavier PCBs exhibited the highest concentrations. The PCB homolog concentrations were dominated by monochlorobiphenyls through hexachlorobiphenyls, with dichlorobiphenyls exhibiting the highest concentration amongst them at most of the effluent outfalls, in the suspended phase. Both total suspended solids (TSS) and various organic carbon fractions played an important role in the distribution of the suspended fractions of PCBs in the effluents. The log Koc values determined in the effluents suggest that effluent PCB loads might have more risk and impact than what standard partitioning models predict.

Performance of submerged membrane bioreactor (SMBR) with and without the addition of the different particle sizes of GAC as suspended medium

In this study the effect of different particle sizes of granular activated carbon (GAC) on the performance of a submerged membrane bioreactor (SMBR) was investigated. The sizes of GAC used were 150-300, 300-600 and 600-1200 μm. The SMBR was operated at a filtration flux of 20 L/m(2)h. The removal of dissolved organic carbon (DOC) and chemical oxygen demand (COD) with the addition of GAC was 95%. The concentration of biopolymers, humic, building block and low molecular weight neutral and acids in the SMBR effluent was reduced by 20%, 66-76%, 20-50%, 30-56%, respectively. It helped to reduce the sludge volume index (SVI) and transmembrane pressure (TMP) development by 30-40% and 58%, respectively. However, the removal of NH₄(+) and PO₄(3-) was relatively low of 35-45% and 34-43%, respectively. The SMBR effluent was rich in PO₄(3-) and was removed/recovered using hydrated ferric oxide (HFO). The removal of PO₄(3-) was almost 90%.

Thermosolutal Instability in Compressible Viscoelastic Dusty Fluid through Porous Medium

Thermosolutal instability in a compressible Walters B’ viscoelastic fluid with suspended particles through a porous medium is considered. Following the linearized stability theory and normal mode analysis, the dispersion relation is obtained. For stationary convection, the Walters B’ viscoelastic fluid behaves like a Newtonian fluid and it is found that suspended particles and medium permeability have a destabilizing effect whereas the stable solute gradient and compressibility have a stabilizing effect on the system. Graphs have been plotted by giving numerical values to the parameters to depict the stability characteristics. The stable solute gradient and viscoelasticity are found to introduce oscillatory modes in the system which are non-existent in their absence.

Nitrification of Municipal Wastewater by Suspended Medium Bioreactor

The performance of Short-HRT suspended medium bioreactor was investigated to treat the municipal effluent from the chemical-biological flocculation plant. The results showed that under the condition of influent ammonia concentration 9.0-15.0 mg/L, carrier filling ratio 30%, optimal air/water ratio and optimal HRT were 2.0 h and 2.7 h, respectively. The removal efficiency of ammonia is 49.7% with ammonia volume load of 0.058 kg/m3•d. Molecular biological method analysis indicated that bacteria species were abundant and could adapt themselves to varied circumstance in the Short-HRT suspended medium bioreactor.