Bacterial Reduction Rates Research Articles

Physical covering for control of Escherichia coli O157:H7 and Salmonella spp. in static and windrow composting processes.

This study investigated the effect of a 30-cm covering of finished compost (FC) on survival of Escherichia coli O157:H7 and Salmonella spp. in active static and windrow composting systems. Feedstocks inoculated with E. coli O157:H7 (7.41 log CFU/g) and Salmonella (6.46 log CFU/g) were placed in biosentry tubes (7.5-cm diameter, 30-cm height) at three locations: (i and ii) two opposing sides at the interface between the FC cover layer (where present) and the feedstock material (each positioned approximately 10 cm below the pile's surface) and (iii) an internal location (top) (approximately 30 cm below the surface). On specific sampling days, surviving populations of inoculated E. coli O157:H7 and Salmonella, generic E. coli, and coliforms in compost samples were determined. Salmonella spp. were reduced significantly within 24 h in windrow piles and were below the detection limit after 3 and 7 days at internal locations of windrow and static piles containing FC covering, respectively. Likewise, E. coli O157:H7 was undetectable after 1 day in windrow piles covered with finished compost. Use of FC as a covering layer significantly increased the number of days that temperatures in the windrows remained ≥55°C at all locations and in static piles at internal locations. These time-temperature exposures resulted in rapid reduction of inoculated pathogens, and the rate of bacterial reduction was rapid in windrow piles. The sample location significantly influenced the survival of these pathogens at internal locations compared to that at interface locations of piles. Finished compost covering of compost piles aids in the reduction of pathogens during the composting process.

Synthesis of ZnO nanoparticles by PNP and its application on the functional finishing of cotton fabrics

This paper presents a facile and novel approach for the synthesis of ZnO nanoparticles in aqueous solution based on a one-step reaction between a modified hyperbranched polymer (PNP) and zinc nitrate. The prepared ZnO nanoparticles polymeric hybrid was characterized and its antibacterial activity was investigated. The results indicated that the ZnO nanoparticles have an average size about 6 nm and well dispersed in aqueous medium. The minimum inhibitory concentration (MIC) of them was 20 ppm and 60 ppm against S. aureus and E. coli, respectively. For the functional finishing of cotton fabrics by these ZnO nanoparticles, a microwave assisted in situ fabrication method was employed. Scanning electron microscope (SEM), energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) measurements confirmed that the ZnO nanoparticles in situ generated in cotton fabrics successfully. Fourier transform infrared (FT-IR) spectroscopic investigation demonstrated that the ZnO nanoparticles were fixed on the cotton fibers by PNP. The treated cotton fabrics exhibited excellent UV protective properties and antibacterial activities. When ZnO content of cotton fabric was 1.49 %, the UPF value of treated cotton fabric exceeded 125 and the bacterial reduction rate against S. aureus and E. coli reached 99.97 % and 98.40 %, respectively.

Humanized tissue pharmacodynamics of cefazolin against commonly isolated pathogens in skin and skin structure infections.

The objective of this study was to assess the efficacy of humanized cefazolin tissue concentrations against methicillin-susceptible Staphylococcus aureus (MSSA) and Enterobacteriaceae in an in vitro pharmacodynamic model. Nine clinical isolates [five MSSA (cefazolin MIC range 0.5-2.0 mg/L), two Escherichia coli (cefazolin MICs 1.0 and 2.0 mg/L) and two Klebsiella pneumoniae (cefazolin MICs of 1.0 and 2.0 mg/L)] were evaluated with a starting inoculum (0 h) of 10(6) cfu/mL. Time-kill curves were built and the area under the bacterial killing and regrowth curve (AUBC) was calculated. The starting inoculum had a mean ± SD of 6.3 ± 0.28 log10 cfu/mL. Cefazolin human simulated targets for peak, trough and half-life were 13.0 mg/L, 2.6 mg/L and 2.6 h, respectively. Control isolates grew to 8.5 ± 0.2 log10 cfu/mL. Against MSSA, cefazolin achieved a reduction from 0 h of -1.18 ± 0.67 and -3.58 ± 1.24 log10 cfu/mL, at 4 and 24 h, respectively. Cefazolin achieved a reduction in bacterial density of -3.45 ± 0.35 and -2.68 ± 0.99 log10 cfu/mL at 4 and 24 h, respectively, when tested against Enterobacteriaceae. No significant difference was observed when comparing AUBC based on MIC values. The rate of initial bacterial reduction of Enterobacteriaceae was rapid, with a decrease of >3 log10 cfu/mL by 4 h, while MSSA exhibited a gradual reduction in bacterial density over one dosing interval. The observed antibacterial effects of cefazolin support its continued utility against susceptible S. aureus, E. coli and K. pneumoniae in skin and skin structure infections.

Rates of bacterial sulfate reduction and their response to experimental temperature changes in coastal sediments of Qi’ao Island, Zhujiang River Estuary in China

Subtropical sediment cores (QA09-1 and QA12-9) from the coastal zone of Qi’ao Island in the Zhujiang River Estuary were used to determine the rates of sulfate reduction and their response to experimental temperature changes. The depth distribution of the sulfate reduction rates was measured from whole-core incubations with radioactive tracer 35SO42−, and peaks of 181.19 nmol/(cm3·d) and 107.49 nmol/(cm3·d) were exhibited at stations QA09-1 and QA12-9, respectively. The profiles of the pore water methane and sulfate concentrations demonstrated that anaerobic oxidation of methane occurred in the study area, which resulted in an increase in the sulfate reduction rate at the base of the sulfate-reducing zone. Meanwhile, the sulfate concentration was not a major limiting factor for controlling the rates of sulfate reduction. In addition, the incubation of the sediment slurries in a block with a temperature gradient showed that the optimum temperature for the sulfate reduction reaction was 36°C. The Arrhenius plot was linear from the lowest temperature to the optimum temperature, and the activation energy was at the lower end of the range of previously reported values. The results suggested that the ambient temperature regime of marine environments probably selected for the microbial population with the best-suited physiology for the respective environment.

Synthesis of silver nanoparticles with sericin and functional finishing to cotton fabrics

This research presents a novel strategy to fabricate multi-functional cotton textiles. In this study, silver nanoparticles-sericin (Ag NPS-sericin) hybrid colloid has been prepared using sericin as reducing agent and dispersing agent. Cotton fabrics was oxidized selectively with sodium periodate (NaIO4) to generate oxidized cotton fabrics, and which has then been finished using Ag NPS-sericin hybrid colloid prepared to obtain multi-functional cotton textiles. The finished cotton fabric not only possessed excellent antibacterial activity, but also it was modified functionally by sericin protein, which endowed antibacterial cotton fabrics relatively smooth surface and good wear ability. Fourier transform infrared spectrogram confirmed that sericin protein was grafted onto cellulose fibers. Ag NPs were characterized by UV-Vis spectroscopy, transmission electron microscope (TEM) and X-ray powder diffraction (XRD). The results of SEM, X-ray photoelectron spectroscopy (XPS) and EDS confirmed that silver nanoparticles and sericin been loaded successfully on the surface of cotton fabrics. The antibacterial experiments showed bacterial reduction rates of S.aureus and E.coli were able to reach above 99 %. After washing 20 times, it showed still good antibacterial activity at over 95 % against S.aureus and E.coli.

Si nanowire directly grown on a liquid metal substrate—towards wafer scale transferable nanowire arrays with improved visible-light sterilization

Integrating vertically aligned nanowires (NWs) on a functional substrate is important for the application of NWs in wafer scale assemblies and functional devices. However, vertically aligned NWs via the current epitaxial growth route can only be prepared on crystalline wafers. A convenient method is thus presented to overcome NW substrate limitations. Liquid metal is proposed to serve as a substrate for the initial growth of vertically aligned NWs. NWs could then be harvested from the growth substrate and integrated with functional substrates. Fabricated vertically aligned silicon NWs (SiNWs) were grown on molten Sn and then integrated into a flexible transparent poly(dimethylsiloxane) film to obtain a SiNW/functional substrate device. The device showed enhanced visible-light absorption ability and refreshable visible-light bactericidal activities with a bacterial reduction rate of close to 100%, indicating that growth with molten metal as a substrate could be a promising approach for extending the function and application of NWs.

Antibacterial Efficacy Testing of a Bioelectric Wound Dressing Against Clinical Wound Pathogens

Silver-based wound dressings have been developed for the control of bioburden in wounds. However, the popularity and extensive use of silver-based dressings has been associated with emerging microbial resistances to silver. In this study we examined in vitro antibacterial efficacy of a bioelectric dressing containing silver and zinc against various wound pathogens. Antibiotic-sensitive clinical wound isolates showed a 100% reduction in bacterial growth, except that Enterococcus faecalis isolate was shown to survive with a bacterial log10 reduction rate of less than 102 CFU. We also investigated antibacterial efficacy against the extended spectrum β-lactamase (ESBL) bacteria, multidrug-resistant (MDR) bacteria, and methicillin-resistant Staphylococcus aureus (MRSA). The bioelectric dressing was effective in killing wound pathogens including ESBL, MDR, and MRSA in vitro. Furthermore, based on the primary results against E. faecalis, we carried out extensive studies against several nosocomial Enterococcus species including vancomycin-resistant species. Overall, the vancomycin-sensitive or -resistant Enterococcus species were resistant to this dressing at up to 48 h, except for the vancomycin-resistant Enterococcus raffinosus isolate only showing a 100% bacterial reduction at 48 h, but not at 24 h. The results demonstrated the effective bactericidal activity of a bioelectric dressing against antibiotic-sensitive and MDR strains, but Enterococcus species are bacteriostatic.

단삼과 소목을 이용한 견직물의 복합염색

The purpose of this research is to analyze the effects of Dansam and Sappan wood extract to perform combination dyeing on silk fabrics, with respect to color changes, fastness (washing, dry cleaning, perspiration, rubbing and light fastness), and functionality (antibacterial activity and deodorization). Combination dyeing was performed by first combining Dansam with Sappan wood, then Sappan wood with Dansam, in these orders. Given the changes in the combination ratio, pre-mordant treatment was performed. Looking at the surface colors of each dye, Dansam generally produces YR color series, while Sappan wood produces YR, R, and RP color series. The effects of changing the order in which combination dying was performed on the surface colors were as follows. First, combination dyeing (A) was performed by using Dansam before Sappan wood, to produce YR and R color series. Then combination dyeing (B) was performed by using Sappan wood before Dansam, to produce YR, R, and RP color series. By visual inspections, more similar color changes of the combination dyeing were noticed with the post-dyeing material rather than the pre-dyeing material. Therefore, it was presumably confirmed that surface color changes of combination dyeing were greatly influenced by the post-dyeing color. Individual dyeing tests for fastness showed that Dansam was comparatively superior to Sappan wood, which demonstrated lower fastness to washing, dry cleaning, perspiration, and light, relatively. The fastness of combination dyed samples was shown middle, but similar fastness to the post-dye material, The fastness of (B) method was higher than (A) method in the washing and light fastness. This confirms that color fastness from combination dyeing was considerably influenced by the post-dye material. It was found that all dyed samples had a very high bacterial reduction rate of 99.9% and high deodorization rate of 95%.

Fabrication of ZnO Nanoparticles by Hyperbranched Polymer and their Application on the Functional Finishing of Cotton Fabric

A novel ZnO nanoparticles aqueous solution was prepared through a one-step reaction between a modified hyperbranched polymer-PNP and zinc nitrate. During the reaction process, PNP not only acted as the reagent to produce ZnO nanoparticles, but also controlled the size of the synthesized ZnO nanoparticles and stabilize them after reaction. The size of ZnO nanoparticles were about 6 nm with narrow size distribution. Then the ZnO nanoparticles were utilized for the functional finishing of cotton fabrics by in situ generation and deposition method. Scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) measurements confirmed the ZnO nanoparticles coated on the cotton fibers. The treated cotton fabrics exhibited excellent UV protective properties and antibacterial activities. When the ZnO content in cotton fabric was 2.23 %, the UPF value of treated cotton fabric reached 114.4 and the bacterial reduction rates againstStaphylococcus aureus(S. aureus) andEscherichia coli(E. coli) both exceeded 98 %.

Fabrication of Antibacterial and UV Protective Silk Fabrics via <i>in Situ</i> Generating ZnO Nanoparticles by Hyperbranched Polymer

This paper presents a method of fabricating ZnO nanoparticles coated silk fabrics via a one-step in situ generation and deposition reaction. In this procedure, amino terminated hyperbranched polymer (HBP-NH2) and zinc nitrate were used as the precursors without any other binders. The results indicated that UV protective properties and antibacterial activities of treated silk fabrics grew in quantity with increase of the concentration of precursors in this reaction process. When the concentration of HBP-NH2and zinc nitrate were 24 g/L and 17.85g/L respectively, the UPF value of treated silk fabric was 131 and the bacterial reduction rates againstStaphylococcus aureusandEscherichia coliboth exceeded 99%. Moreover, the treated silk fabrics were characterized by FESEM, EDS and XRD which demonstrated that the ZnO nanoparticles coated on the silk fibers successfully and well dispersed with diameter around 90nm.

Stable isotope (S, C) chemostratigraphy and hydrocarbon biomarkers in the Ediacaran upper section of Sierras Bayas Group, Argentina

The Neoproterozoic sedimentary successions of the Sierras Bayas Group (SBG) are situated within the Tandilia Belt, Buenos Aires Province, Argentina. The Loma Negra Formation (LNF) from the upper part of the SBG has been investigated using a combination of inorganic, organic and isotopic geochemical methods in order to determine the stable isotope composition of carbonates (δ13Ccar, δ18Ocar), kerogen (δ13Cker), pyrite and carbonate associated sulfur (δ34Spy, δ34SCAS). Concentrations of major, trace and rare earth elements and hydrocarbon distributions were also investigated. This data set was used to further the understanding of the interactions between paleo-biodiversity and paleoenvironmental conditions for terminal Ediacaran (post-Gaskiers) shelf deposits. The high δ34Spy values exceeding the coeval δ34SCAS values in green micritic limestones of the lower LNF may be explained by a combination of different events such as globally low seawater sulfate concentrations, an increased rate of bacterial sulfate reduction, and a decrease in sulfate levels in the near-bottom deepest water layer inherited from glaciations. Negative Ce anomalies in the dark grey micritic limestones of the upper LNF suggest they were deposited under oxidizing conditions. However, higher concentrations of Fe, Mo, Zn and REE, and the occurrence of authigenic 34S-enriched pyrite suggest that the sediments were maintained under reducing conditions. The distributions of hydrocarbon biomarkers (e.g. hopanes maximizing at C29) are in line with this hypothesis and indicate a diverse microbial community including primary producers such as cyanobacteria (e.g. terminally-branched monomethyl alkanes, hopanoid distribution), phototrophic bacteria (e.g. acyclic isoprenoids C<21) and green bacteria (e.g. n-C18≫Phytane). The unsteady Δ13Ccar-ker values reflect changes in primary biomass due to relative contributions of bacterial microorganisms using different photosynthetic carbon-fixation pathways. The lowest Δ13Ccar-ker values coincided with the latest biomarker signal interpreted as the signature of green non-sulfur bacteria using a less 13C fractionation pathway. The combined biogeochemical features of the Loma Negra Formation, indicated a well-stratified water column with oxygenated surface waters, oxygen-poor bottom waters and anoxic sediments which helped to refine a correlation with the Polanco Formation from the Arroyo del Soldado Group in Uruguay.

In situ generation and deposition of nano-ZnO on cotton fabric by hyperbranched polymer for its functional finishing

Due to the advantage of hyperbranched polymers on controlling synthesis of nanoparticles (NPs), this paper presents a method to fabricate ZnO NPs coated cotton fabrics via in situ generation and deposition in one-step reaction with amino-terminated hyperbranched polymer (HBP-NH2) to explore its application in textile finishing. Firstly, the mechanism of this reaction was proposed in detail. The treated cotton fabrics were then characterized by field emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD), and the ultraviolet (UV) protective properties and antibacterial activities of the fabrics were measured. The results indicated that ZnO NPs with a diameter around 80 nm dispersed on the surface of the cotton fabric well, the ultraviolet protection factor (UPF) value of the treated cotton fabric was 136 and the bacterial reduction rates against Staphylococcus aureus and Escherichia coli both exceeded 99%, when the concentration of HBP-NH2 and zinc nitrate were 16 g/L and 96 mM respectively.

Gas Flow Effect on E. coli and B. subtilis Bacteria Inactivation in Water Using a Pulsed Dielectric Barrier Discharge

This paper presents an experimental study of the inactivation in water of two representative classes of bacteria, Gram-negative Escherichia coli and Gram-positive Bacillus subtilis, using pulsed dielectric barrier discharges (PDBDs) in a coaxial arrangement. To this purpose, an adjustable plasma source supplies 25-kV/500-Hz pulses, 30 μs long, at atmospheric pressure, with total energy consumption estimated at about 100 mJ/pulse. The inactivation effect of a PDBD on these types of microorganisms has been previously studied in dependence on an oxygen gas flow mode (null, continuous, and modulate). The results have shown a significant bacterial reduction rate from 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> to 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> cells/mL with E. coli and from 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> to 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> cells/mL with B. subtilis. The inactivation effectiveness is substantially similar in both kinds of bacteria, although some data suggest a greater susceptibility of the Gram-negative E. coli to plasma exposure. Plasma diagnostics was carried out using optical emission spectroscopy whereby the OH radical and reactive oxygen species formation rates in solution were found and the level of ozone produced by the discharge was monitored. Finally, a kinetics model was developed to characterize the chemical species taking place in nonthermal plasma inactivation processes in water.

Utilization of Bamboo Leaves as a New Resource of Natural Green Colorants

The objective of this study was to find an appropriate method and process for protecting the green color in bamboo leaves and subsequent extraction of the green colorants, chlorophyll. Various inorganic salts including cupric sulfate, ferric sulfate, and zinc chloride were employed as green color protectors. Accordingly, the effects of metal salts and treatment conditions on color protection were investigated to find appropriate protector and conditions. And also, the efficacy of bamboo colorants as a natural green dye was evaluated through dyeing and colorfastness tests. Antimicrobial activity of dyed fabrics was measured by shake flask method in terms of bacterial reduction rate using Staphylococcus aureus(ATCC 6538). On the basis of experimental results for stabilizing bamboo leaves colorants, it was confirmed that Cu was the most appropriate metal type considering dye uptake, photostability and light fastness, and its optimum concentration was 0.025%. After the stabilization, the colorants were extracted efficiently at NaOH aqueous solution of 1.00%. It was concluded that bamboo leave has a high potentiality as new resources to produce a natural green dye with antimicrobial functionality.

Antibacterial cotton fabric grafted with silver nanoparticles and its excellent laundering durability

In order to fabricate antibacterial cotton fabric with excellent antibacterial property and laundering durability, amino functional silver nanoparticles (Ag NPs) were prepared by one-step reaction with amino-terminated hyperbranched polymer (HBP-NH2) and grafted on the oxidized cotton fabric subsequently. The synthesized amino functional Ag NPs and Ag NPs grafted oxidized cotton fabric (Ag-GOCF) were characterized which indicated that the average size of Ag NPs was 10.8nm with narrow size distribution and the Ag NPs have been grafted on the cotton fabric. 99.43% and 99.45% bacterial reduction rates were obtained for Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) respectively in case the cotton fabric was treated with 10mg/L Ag NPs solution to produce Ag-GOCF with 149.88mg/kg Ag content. After 50 washing cycles, the Ag content of this Ag-GOCF was maintained at 116.08mg/kg with its antibacterial activity at over 96% reduction level.

Bacterial Reduction as Means for Colonic Drug Delivery: Can Other Chemical Groups Provide an Alternative to the Azo Bond?

We compared the rate of colonic bacterial reduction of disulfide and nitro bonds to that of an azo counterpart. The disulfide and nitro reduction rates are comparable to that of azo having a similar molecular structure. We further explored QSAR of bacterial reduction of different nitro compounds giving a Hammett correlation with ρ=0.553, R2=0.97. We conclude that disulfide and nitro compounds have an unexploited potential for use in prodrugs and drug delivery systems targeted to the colon.

In situ synthesis of silver nanoparticles on silk fabric with PNP for antibacterial finishing

This research presents a generic strategy to fabricate antibacterial textile through in situ synthesis of silver nanoparticles on the fabric with smart polymeric molecules. Silk fabric and polyamide network polymer (PNP) were chosen for this study. PNP which has numerous amino groups and three-dimensional structure was applied to entrap silver ions into silk fabric. The pretreated silk fabrics were heated by steam method to make silver nanoparticles synthesized in situ on them without any other reductant and linker to provide silk fabric with antibacterial properties. The results indicated that the treated silk fabrics had excellent antibacterial activity and laundering durability. The quantitative bacterial tests showed the bacterial reduction rates of Staphylococcus aureus and Escherichia coli were able to reach above 99 % with not more than 0.05 mmol/L of AgNO3. The whiteness of silk fabric only changed from 90.47 to 86.49. The antibacterial activity of the treated silk fabric was maintained at 98.86 % reduction even after being exposed to 30 consecutive home laundering conditions. In addition, the results of scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy confirmed that silver nanoparticles had generated and dispersed well in Ag0 form on the surface of silk fibers. The understanding acquired from this work will allow one to work with the preparation of other silver nanoparticles functional textiles with excellent antibacterial activities and laundering durability through this facile, eco-friendly in situ synthesis method.

Geochemical characteristics of the barite deposits at cold seeps from the northern Gulf of Mexico continental slope

Although less common than the occurrence of authigenic carbonate, barite has been observed frequently at cold seeps on continental margins worldwide. It is understood that barite forms by the interaction of barium-rich and sulfate-free seeping fluids with dissolved sulfate of pore water near the seafloor, but questions remain about the geochemical processes and mode(s) of the barite formation. Here, we report geochemical characteristics of barite deposits at 11 cold seep locations from the northern Gulf of Mexico continental slope. Samples from these sites of fluid and gas expulsion provide environmental information on barite formation. Seafloor observations and samples acquired indicate that barites occur as chimneys, cones, crusts, irregular mound-like buildups up to 2-meters high, and as a material disseminated in host sediment. Most barite samples are white-to-gray and usually have a porous fabric and layered internal structure. Mineralogically, samples of barite may contain a significant amounts of carbonate minerals, such as calcite and dolomite, but aragonite is absent in all samples analyzed in this study. Negative δ 13C values (as low as − 46.4‰ V-PDB) of the associated carbonates strongly suggests that methane is the primary carbon source. The δ 34S and δ 18O values of the barites have large variations, ranging from 18‰ to 80.4‰ V-CDT, and 7.5‰ to 26.7‰ V-SMOW, respectively. On δ 34S versus δ 18O plots, many barite deposits show a linear trend that projects down toward the isotopic composition of seawater sulfate. The trend suggests that barite formed from seawater sulfate that has been isotopically modified to varying degrees by biological sulfate reduction. The δ 34S/δ 18O ratios vary between 2.4 and 4.1. The variations are interpreted to reflect local controls on the flux of barium-rich seep fluids, changes in the rate of bacterial sulfate reduction, and/or the openness of pore fluid system. The 87Sr/ 86Sr values of the barites indicate that within-site variation is small (< 0.00026) although there is a considerable range of Sr isotopic variations across multiple geographic sites (from 0.70782 to 0.71005). The observed variations probably reflect local controls on the source(s) and diagenetic evolution of seeping fluids. Strong deviation of the Sr isotope ratios of barites from coeval seawater ( 87Sr/ 86Sr = 0.70917) is interpreted as the modification of the strontium from less radiogenic sources like older marine sediments or more radiogenic terrigenous material such as basinal brine and/or meteoric water. The new results further offer a better understanding of the origin and geochemical history of barite deposits that occur in geological record on the basis of δ 34S and δ 18O compositions.

Finite-element model simulation of nitrate transport behaviour in saturated fractured porous media

Abstract A finite-element reactive transport model is developed and applied to study the transport behaviour of nitrate under the effect of denitrification in saturated fractured media. The reduction of nitrate is considered to be undertaken by a heterotrophic population of bacteria present on the fracture walls and in the pore space of the porous matrix. The bacterial metabolic activity is controlled by the availability of an electron donor (organic matter) and electron acceptors (nitrate and oxygen). Model equations are developed assuming 1D advective–dispersive transport in a set of parallel fractures with 2D diffusive transport in the adjacent porous matrix. The bacterial reaction in these equations is represented by dual Monod kinetic terms and the bacterial growth is represented by a single linear kinetic equation. The equations are discretized by the finite-element Galerkin method and the resultant set of non-linear algebraic equations is solved by an iterative scheme. The model is used to explore the effect of denitrification on fracture and porous matrix nitrate concentration profiles for different values of fracture aperture size, advective velocity, porous matrix width, porosity, and dispersion and diffusion coefficients. The effect of the presence of oxygen in limiting rates of bacterial nitrate reduction is also assessed. Overall, it is concluded that in fractured media with good porous matrix diffusion properties and favourable properties for bacterial growth, denitrification in the porous matrix can be more significant than in the fracture set in the reduction of nitrate mass.

감국 추출액으로 염색한 키토산/나노실버 복합편성물의 염착특성

This study examines the dyeability, light fastness, washing fastness, and antibacterial activity of chitosan and nano silver composite knit fabrics dyed with extracted solution from Chrysanthemum Indicum Linn. The results show that <TEX>${\Delta}E$</TEX> values of chitosan and nano silver composite knit fabrics were higher than cotton 100% knit fabrics in dyed condition with extracted solution from Chrysanthemum Indicum Linn, and mordant treatments influenced the chrominance change. Chrysanthemum indicum Linn confirmed that this could be a polygenetic colors. <TEX>${\Delta}E$</TEX> values of post-mordant treatments knit fabrics were higher than pre-mordant treatments knit fabrics in dyed condition with extracted solution from Chrysanthemum Indicum Linn., and mordant treatments method influenced the chrominance change. The dyeability of chitosan and nano silver composite knit fabrics was increased by mordant treatment. The fastness of the chitosan and nano silver composite knit fabrics was better than cotton 100% knit fabrics. In the result of antibacterial activity, the bacterial reduction rate of chitosan and nano silver composite knit fabrics was 99.9% to Staphylococcus aureus and Klebsiella pneumoniae.