Dilution Percentage Research Articles

Testing for drugs in formalin-fixed tissues: About a complex medicolegal case involving midazolam and oxycodone

Establish the analytical and interpretation criteria when the body has been subjected to formalin preservation techniques. Death is accompanied by various body modifications: lividities, rigidity, cyanosis, swelling, etc. Thanatopraxy refers to all the techniques that can delay the degradation of a body and keep it in a state close to living. This operation aims to stop the invasive bacterial evolution and to slow down the decomposition. Formalin and methanol (used to stabilize formalin) may change the characteristics of xenobiotics present in the body, modify the pH and dilute the compounds. The toxicological results are therefore not characteristic of the moment of death. The difficulty lies in the interpretation of the results since neither the exact volume of conservation liquid injected nor the volume of blood removed are known. The authors report the case of a 35-year-old man who died as a result of cancer. The body was embalmed the day after his death, at the request of his family, and buried. After a deeper investigation of the facts, it was envisaged that Mr. X. died as a result of an overdose of oxycodone, due to a dilution error of the pump, not correctly fixed by his nurse. A complete toxicological analysis was therefore requested to measure the concentrations, as the subject was simultaneously under midazolam and oxycodone. A standard analysis of blood was performed, using validated laboratory procedures. In addition, stability studies of oxycodone and midazolam were conducted in the presence of formalin to determine possible influence. A 30 mL pool of blank blood containing 1 mg/L of oxycodone and midazolam was prepared and then aliquoted into 30 tubes of 1 mL. Except for the first tube, 20 μL of formalin (20%) was added to each tube. The tubes were stored at + 4 °C until analysis. On day 1, the first set of tubes (without formalin) was extracted and analyzed on ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS ® , Waters). The stability studies were spread over 21 days, and each analysis was done three times ( n = 3). The femoral blood analyzes showed the presence of methanol (1.31 g/L) but no ethanol, midazolam at therapeutic concentration (74 ng/mL) and oxycodone at a toxic concentration (152 ng/mL). No other compound was detected. It can be concluded that the concentrations measured in blood were certainly lower than those at the time of death, without being able to evaluate the percentage of degradation and/or dilution. The stability study of oxycodone showed a rapid and complete degradation of the molecule, in contact with formalin (−99% in 9 days). Midazolam was less affected, although instability was evident (−48% and −73% in 9 and 21 days, respectively). These results should be taken into account when interpreting the concentrations. The results of the stability studies prove the degradation of both midazolam and oxycodone in the presence of formalin. It is therefore assumed that the victim was exposed to higher concentration of oxycodone, confirming the mistake of the nurse. This was also documented when evaluating the oxycodone pump records. The concentrations obtained during the toxicological analyzes are therefore underestimated in relation to the concentrations at the time of death, but the level of variation cannot be quantified. Formalin preservation techniques have negative consequences for toxicological analyses and their interpretations. Stability studies of oxycodone and midazolam were instrumental in understanding the probable causes of death of Mr. X. These observations constitute the first stability studies of these two compounds in the presence of formalin.

EXPERIMENTAL DETERMINATION OF LAMINAR BURNING VELOCITY OF BIOGAS AT PRESSURES UP TO 5 BAR

This paper presents a very detailed description of a new cylindrical constant volume combustion chamber designed for laminar burning velocity determination of gaseous mixtures at ambient temperature and initial pressure up to 6 bar. The experimental setup, the experimental procedure and the determination of the range of flame radius for laminar burning determination are all described in details. The laminar burning velocity of twelve synthetic biogas mixtures has been studied. Initial pressure varying between 1 and 5 bar, equivalence ratios, f, between 0.7 and 1.1 and percentage dilution, with a mixture of CO2 and N2, between 35 and 55% have been considered. Five experiments were run for each mixture providing a maximum percentage standard deviation of 8.11%. However, for two third of the mixtures this value is lower than 3.55%. A comparison with simulation using PREMIX for both GRI-Mech 3.0 and San Diego mechanisms has provided closer agreement for mixtures with equivalence ratio closer to stoichiometry whereas for f = 0.7 the deviation is larger than 15% for all pressures. Mixtures with lower equivalence ratio, higher dilution percentage and higher initial pressure presents the lower values of laminar burning velocity.

Effect of weld dilution on post-weld thermal conductivity of austenitic stainless steel clad layers

Cladding austenitic stainless steels are trendy these days in pressure vessels to enhance surface qualities. In this work, austenitic stainless steel clad layers deposited by flux cored arc welding process on structural steel plates used in boiler construction are investigated. To facilitate this, composite clad layers are produced with 316L stainless steel deposits on low carbon structural steel plates based on the design of experiments. Results exhibit an incremental trend of thermal conductivity with respect to percentage of weld dilution. A linear mathematical relationship is established between the percentage of weld dilution and post-weld thermal conductivity of clad layers for the prediction of thermal conductivity of clad layer deposits. These results could be supportive in the fabrication industries for producing energy efficient thermal equipment.

Combining the assessment of apical endpoints and gene expression in the freshwater snail Physa acuta after exposure to reclaimed water

Post-treatment wastewater reuses are diverse. Recreational and environmental restoration uses of reclaimed water (RW) can be potentially harmful to aquatic organisms. In this work the freshwater snail Physa acuta was exposed to RW (100%) and its dilution (RW 50%). A simple laboratory mixture of three emerging pollutants was used to address the complex problem of mixture toxicity of RW. Hence fortified reclaimed water (FRW), obtained by adding fluoxetine (400 μg FLX/L), perfluorooctane sulphonic acid (90 μg PFOS/L) and methylparaben (9 μg MP/L), was tested at two dilution percentages: 100% and 50%. The effects of the laboratory mixture of FLX, PFOS and MP on the test medium were also studied. Long-lasting effects, together with early molecular responses, were assessed. Fecundity (cumulative egg production) over 21 days and the hatching of produced eggs (F1) after another 21-day embryonic exposure were monitored. The gene expression of three genes was analysed after 24 h of exposure: two endocrine-related nuclear receptors (ERR and RXR) and one stress protein gene (Hsp70). This reproduction test, with additional assessments of the F1 recovered eggs' hatching success, showed that both RW and FRW significantly reduced fecundity. F1 hatching was affected only by FRW. The gene expression results showed that the RXR response was strikingly similar to the fecundity response, which suggests that this nuclear receptor is involved in the reproductive pathways of gastropods. ERR remained virtually unaltered. Hsp70 was overexpressed by the laboratory mixture in the test medium, but no effect was observed in the fortification of RW. This opposite effect and lack of response for F1 hatching produced by the laboratory mixture in the test medium highlighted the difficulty of predicting mixture effects. The experimental approach allowed us to test the effects caused by RW on P. acuta at different biological organisation levels. Thus, the combination of molecular biomarkers and ecological relevant endpoints is a good strategy to test complex mixtures like RW as it provides a framework to link mechanisms of action and whole organism effects when it is almost impossible to detect the pollutant(s) that cause toxic effects.

A Study of Mechanical Properties of Vibration Assisted Arc Welding Joint

Welding is one of the major aspects of manufacturing as well as mechanical engineering. The strength of the metal joint depends on the type of welding used. Quality of metal joining strength can be improved with a few changes in the regular welding process. A few factors that improve metal jointing strength during the arc welding process had been studied in this paper. Research in welding process shows that Vibration can improve mechanical properties of the joining section. However, welding joint quality varies with different ranges of parameters in different conditions. To analyze those ranges of parameters in some selected conditions, a study has been performed in this paper. Some input parameters like vibration amplitude, vibration frequency, welding speed and electrode angle are selected to analyze the variation in the welded joint. For analyzing the results, output parameters –bending strength and dilution rate are calculated. It has been found that if all input parameters are kept in a selected range then output parameters –bending strength, the percentage of dilution increases than the regular case. Finally, it can be shown that Bending strength and percentage of dilution of a metal joint assisted with vibration shows the better result than without vibration.

A Study of Mechanical Properties of Vibration Assisted Arc Welding Joint

Welding is one of the major aspects of manufacturing as well as mechanical engineering. The strength of the metal joint depends on the type of welding used. Quality of metal joining strength can be improved with a few changes in the regular welding process. A few factors that improve metal jointing strength during the arc welding process had been studied in this paper. Research in welding process shows that Vibration can improve mechanical properties of the joining section. However, welding joint quality varies with different ranges of parameters in different conditions. To analyze those ranges of parameters in some selected conditions, a study has been performed in this paper. Some input parameters like vibration amplitude, vibration frequency, welding speed and electrode angle are selected to analyze the variation in the welded joint. For analyzing the results, output parameters –bending strength and dilution rate are calculated. It has been found that if all input parameters are kept in a selected range then output parameters –bending strength, the percentage of dilution increases than the regular case. Finally, it can be shown that Bending strength and percentage of dilution of a metal joint assisted with vibration shows the better result than without vibration.

Correlating Hardness and Welding Dilution with the Abrasion Mass Loss of Hardfacings Welded with Different Currents and Polarities

The correlation of hardness, microstructure, and dilution with the abrasion mass loss of hardfaced samples deposited using different currents (500 and 600 A) and polarities (AC and DC+) was studied. Four different welding conditions were considered for submerged arc welding using a martensitic hardfacing electrode and austenitic buffer electrode. Single-layer hardfacing was applied over the single-layer buffer. The microstructure of hardfacing was observed by an optical microscope. The micro-Vickers hardness across a single-layer hardfacing and dilution percentage were also measured. A dry-sand–rubber wheel abrasion test was conducted according to ASTM G65 procedure A to record the abrasive mass loss of the samples. The use of higher current and DC+ polarity resulted in the highest mass loss because of the deepest dilution and lowest hardness. Dilution affects the hardness and microstructure of hardfacing. The lowest abrasive mass loss, shallowest dilution, and highest hardness were obtained for the sample welded with lower current and AC polarity.

Ore Dilution Estimation Model in Tanzania Southern Highland Zone: A Case of New Luika Gold Mine

This paper brings about understanding of the effect of ore dilution to the economics of mine and reveals that, mining ore dilution is one among factors affecting the economy of mining projects. Dilution factor varies within a single mine for different benches and zones due to changes seen in grade distribution and shape of ore body, also varies based on commodity price obtained. It was necessary to make sure that these variations were taken into account during designing or evaluating a mine. The study identified suitable methods that are supposed to be used for estimation of ore dilution level which are: Geological review method, loading and haulage methods. By checking the number of dilution from the data, the percentage of dilution, the total tons of ore and total tons of waste was computed by the formula of dilution, the computed average dilution estimation was found to be 64% which was then used in determination of an increase level of ore dilution by comparing obtained results to the standards ore dilution used by the company. Normally the company estimated 20% up to 23% as standard ore dilution which brings about the average of 21.5% standard ore dilution. Upon considering the factor of standard planned ore dilution in the Company, the finding proved that there is an increase by 42.5% ore dilution during operation each day. Upon considering factors concerned with the process of comminuting, the results shows that grade from grade control is 4.73 g/t and grade of the final product is 3.95 g/t and the grade difference is 0.78 g/t where by factors like, leakage, slurry overflow, some other chemical agents in the CIL tanks that take place in the process like (CIL) Carbon In Leach process, crushing and grinding are taking into consideration. The study shows that, the dilution per hour in a given bench is above standard planned ore dilution. By checking the line graph from the findings it shows the dilution per hour in a given bench is higher than standard planned by the company which is 29%.

Study of the hot-wire TIG process with AISI-316L filler material, analysing the effect of magnetic arc blow on the dilution of the weld bead

The TIG process with hot-wire addition is described as a highly productive process in comparison with conventional TIG process with cold-wire and achieves large deposition rates and low dilution percentages, characteristics that permit to the process to be an optimum alternative for cladding applications. There are many options of electrical circuit configurations to heat the addition wire in the TIG Hot-Wire process, highlighting the utilization of the continuous pulsed current and the alternating current. In the present paper were studied two configurations of the electrical circuit for heating the addition materials, which in theory provoke different behaviours in the welding arc, and therefore, in the geometrical properties of the welding bead too. A first analysis done on the welding arc, which demonstrates that to heat the wire with continuous constant current generates a permanent magnetic blow over the arc. According to trials made, the direction and intensity of the magnetic blow will depend on the polarity and on the current value to heat the wire. A macrographic analysis of the weld beads demonstrated that the best results were for the tests made with hot-wire, achieving dilutions up to 2% for a wire velocity of 7.5 m/min, 1 kW of power for to heat the wire and using a welding velocity of 30 cm/min.

The use of CO2 as an additive for ignition delay and pollutant control in CH4/air autoignition

The effect of CO2 dilution on the adiabatic and isochoric autoignition of CH4/air mixtures is analyzed with Computational Singular Perturbation (CSP) algorithmic tools, with a particular emphasis on the determination of the features of the chemical dynamics that control ignition delay and emission formation. Increasing CO2 dilution causes longer ignition delays, lower final temperatures and decreased formation of NO and CO. These effects of CO2 dilution are shown to be entirely thermal, contrary to what happens with dilution with H2O, which also has chemical activity and can reduce ignition delay. For the same initial mole fraction of the diluent, the decrease in final temperature and in NO concentration is larger in the CO2 case whereas the decrease in CO is larger in the H2O case. The thermal effect of CO2 is entirely analogous with those of dilution with the chemically inert Ar, only stronger for the same percentage of initial dilution, because of the larger specific heat of CO2. The reactions that have the largest contribution to the characteristic explosive time scale of the system during ignition delay (H2O2(+M)→OH+OH(+M), CH3O2+CH2O→CH3O2H+HCO, CH4+CH3O2→CH3+CH3O2H, H+O2→O+OH, etc.) are not substantially affected by CO2 dilution, neither are the species that are pointed by CSP (CH3O2, H2O2, CH2O, etc.) as having the largest impact on the this timescale. The same holds for the modes that control CO and NO formation. The results point to the possibility of cold exhaust gas recirculation being used in order to produce mixtures with longer ignition delays and therefore substantial resistance to uncontrolled ignition.

NO formation of opposed-jet syngas diffusion flames: Strain rate and dilution effects

The NO formation characteristics and reaction pathways of opposed-jet H2/CO syngas diffusion flames were analyzed with a revised OPPDIF program which coupled a narrowband radiation model with detailed chemical kinetics in this work. The effects of strain rates ranging from 0.1 to 1000 s−1 and diluents including CO2, H2O and N2 on NO production rates were investigated for three typical syngas compositions. The numerical results demonstrated that NO is produced primary through NNH-intermediate route and thermal route at high strain rates, where the reaction of NH + O = NO + H (R51) also become more active. Near the strain rate of 10 s−1, the flame temperature is the highest and thermal route is the dominant NO formation route, but NO would be consumed by reburn route where NO is converted to NH through HNO, especially for H2-rich syngas. At low strain rates, radiative heat loss results in a lower flame temperature and further reduce NO formation, while the reaction of N + CO2 = NO + CO (R140) become more important, especially for CO-rich syngas. With the diluents, NO production rates decreased with increasing dilution percentages. When the flame temperature is very high as the thermal route is dominant near strain rate of 10 s−1, CO2 dilution makes flame temperature and NO production rate the lowest. Toward both lower and higher strain rates, adding H2O is more effective in reducing NO because R140 and NNH-intermediate route are suppressed the most by H2O dilution respectively.

An RCM experimental and modeling study on CH4 and CH4/C2H6 oxidation at pressures up to 160 bar

The oxidation of CH4 and CH4/C2H6 mixtures were studied at pressures relevant to knocking in large bore natural gas engines. The experiments were carried out in a rapid compression machine (RCM) at end of compression (EOC) temperatures ranging between 885 and 940K at compressed gas pressures of 105, 125, 150, and 160bar at varying equivalence ratios (0.417, 0.526, and 1.0) and dilution percentages (0, 10, and 30% Exhaust Gas Recirculation – EGR) that were defined in a test matrix. This study describes the method and limitations of performing high-pressure experiments of this magnitude in an RCM, modeling, and validation of the kinetic mechanism against experimental data. While the recently published AramcoMech 2.0 could well predict the ignition delay times (IDTs) for CH4 within the uncertainty ranges at comparatively higher pressures and lower temperatures (885–940K), the predicted reactivity is, in general, lower than that of AramcoMech 1.3 as shown in our previous screening study. Based on the comparison between both mechanisms as well as sensitivity analysis on the predicted IDTs, the reaction rate constant for Ḣ-atom abstraction from CH4 by HȮ2 radical was optimized in order to achieve better agreement with the new data while maintaining the agreement to the previous data sets. The modified mechanism predicts well the IDTs and the trend of their variation caused by the change in pressure, equivalence ratio, dilution percentage, and mixture variation with C2H6.

Study the Effect of Cold and Hot Water Extracts of Parsley Plant Petroselinumcrispum on the Growth of some Enterobacteriaceae

This study was conducted to determine the effect of hot and cold water extractsof parsley leaves on five genus of bacteria belong toenterobacteriaceae familynomely; E.coli, Enterobacter, Klebsiella, Shigellaand Salmonella after 24 or 48 hrs of incubation where the number of growth colonies on macConkey agar appears. The efficiency of these extractsto prevent bacteria from growthwas indicated by using the percentage ofdilution value. The resultsshowed that the hot water extract was more efficientin most treated bacteria compared with cold water extract. Also resultsindicated that both Salmonella andEnterobacterwere more sensitive toward both extracts incomparsion with other studied bacteria, such asKlebsiellashowed higher resistance toward both extracts. Additionally, significant differencesbetween number of colonies grown on MacConkeymedium that treated with hot or cold water extracts were recorded.

Methodology for optimization of coefficient for ore recovery in sublevel caving mining method

Ore recovery and ore dilution have an important role for efficient operation of a mine. With each increase in percentage of ore dilution and reduced ore recovery there is negative impact on the economic value of the ore reserves. These parameters are mainly controlled with quality mining project and in situ analysis. The primary goal of this science paper is to present the methodology for optimization of coefficient for ore recovery and ore dilution in sublevel caving mining method. The optimization will be carried out through economic parameters, ie by calculating the net present value (NPV).

Investigation of powder dynamics in silane-argon discharge using impedance analyser

We report the growth of powder formation in Argon (Ar) diluted Silane (SiH4) plasma using 27.12 MHz assisted Plasma Enhanced Chemical Vapor Deposition process with the approach of plasma diagnosis. The appearance of powder during processing contaminates the process chamber which further can alter the film properties; hence plasma diagnosis was vital towards detecting this variation. This work presents for the first time a diagnosis of powder in the plasma using Impedance Analyser (V/I probe) at various concentrations of Argon dilution (10%–90%), chamber pressure (0.3 Torr–0.6 Torr), and applied power (4 W–20 W). Efforts were made to understand the different phases of powder formation (i.e., chain and accumulation process, coalescence phase and α → γ′ transition (powder zone)) by monitoring and evaluating the plasma characteristics such as discharge voltage and current (Vrms and Irms), Impedance (Z), phase angle (ϕ), electron density (ne), bulk field (Eb), and sheath width (ds). From the results of plasma characterization, the coalescence phase can be well diagnosed by the low amplitude of Irms, ϕ, ne, and ds in combination with a high amplitude of Vrms and Eb whereas α → γ′ transition regime diagnose by a lower value of Vrms, Z, ϕ, Eb, and ds with a higher value of Irms and ne which signifies the presence of powder in the plasma. It was also observed that with the increase of applied power, the coalescence phase gets shifted towards the lower Ar dilution percentage. Conversely, the phase transition region from amorphous (a-Si:H) to microcrystalline (μc-Si:H) thin film will observe at the onset of powder formation thus on account of plasma results, deposition of silicon thin films was carried out, and the film properties are in good agreement with plasma characteristics.

Low pH, high salinity: Too much for microbial fuel cells?

Twelve single chambered, air-cathode Tubular Microbial Fuel Cells (TMFCs) have been filled up with fruit and vegetable residues. The anodes were realized by means of a carbon fiber brush, while the cathodes were realized through a graphite-based porous ceramic disk with Nafion membranes (117 Dupont). The performances in terms of polarization curves and power production were assessed according to different operating conditions: percentage of solid substrate water dilution, adoption of freshwater and a 35mg/L NaCl water solution and, finally, the effect of an initial potentiostatic growth.All TMFCs operated at low pH (pH=3.0±0.5), as no pH amendment was carried out. Despite the harsh environmental conditions, our TMFCs showed a Power Density (PD) ranging from 20 to 55mW/m2kgwaste and a maximum CD of 20mA/m2kgwaste, referred to the cathodic surface.COD removal after a 28-day period was about 45%.The remarkably low pH values as well as the fouling of Nafion membrane very likely limited TMFC performances. However, a scale-up estimation of our reactors provides interesting values in terms of power production, compared to actual anaerobic digestion plants. These results encourage further studies to characterize the graphite-based porous ceramic cathodes and to optimize the global TMFC performances, as they may provide a valid and sustainable alternative to anaerobic digestion technologies.

Multiple effects of a commercial Roundup® formulation on the soil filamentous fungus Aspergillus nidulans at low doses: evidence of an unexpected impact on energetic metabolism.

Soil microorganisms are highly exposed to glyphosate-based herbicides (GBH), especially to Roundup® which is widely used worldwide. However, studies on the effects of GBH formulations on specific non-rhizosphere soil microbial species are scarce. We evaluated the toxicity of a commercial formulation of Roundup® (R450), containing 450g/L of glyphosate (GLY), on the soil filamentous fungus Aspergillus nidulans, an experimental model microorganism. The median lethal dose (LD50) on solid media was between 90 and 112mg/L GLY (among adjuvants, which are also included in the Roundup® formulation), which corresponds to a dilution percentage about 100 times lower than that used in agriculture. The LOAEL and NOAEL (lowest- and no-observed-adverse-effect levels) associated to morphology and growth were 33.75 and 31.5mg/L GLY among adjuvants, respectively. The formulation R450 proved to be much more active than technical GLY. At the LD50 and lower concentrations, R450 impaired growth, cellular polarity, endocytosis, and mitochondria (average number, total volume and metabolism). In contrast with the depletion of mitochondrial activities reported in animal studies, R450 caused a stimulation of mitochondrial enzyme activities, thus revealing a different mode of action of Roundup® on energetic metabolism. These mitochondrial disruptions were also evident at a low dose corresponding to the NOAEL for macroscopic parameters, indicating that these mitochondrial biomarkers are more sensitive than those for growth and morphological ones. Altogether, our data indicate that GBH toxic effects on soil filamentous fungi, and thus potential impairment of soil ecosystems, may occur at doses far below recommended agricultural application rate.

Effect of welding parameters on microstructure of Fe-based nanostructured weld overlay deposited through FCAW-S

Lately, modern hardfacing tubular wires for semiautomatic welding with gas protection and without it have been developed. These wires deposit Fe-based nanostructured alloys with high abrasive wear resistance. The information on these new consumables is scarce, especially about the effect that the welding parameters (heat input, shielding gas, arc voltage, current intensity, etc.) have on the deposit, its microstructure and, consequently, its wear behaviour. For this reason, in this article, we study the effect of heat input (voltage, intensity of current and welding velocity) on the properties of a flux-cored arc welding Fe-based nanostructured deposit obtained without gas protection. This study is a continuation of a previous one in which the same consumable was used under shielding gas. Bead on plate samples were welded using heat inputs between 0.5 and 3.5 k/mm. The dimensional study was performed on the beads, chemical composition was determined and the microstructure was analysed using optical and electronic microscopy and X-ray diffraction. Microhardness, crystallite size and dilution percentage were also measured. An important influence of the welding parameters on the bead geometry and the microstructure was observed. The operational behaviour of this wire, welded without shielding gas, was very good.

Performance of high temperature PEM fuel cell materials. Part 1: Effects of temperature, pressure and anode dilution

High temperature proton exchange membrane (HT-PEM) fuel cells operate most effectively at temperatures 160 °C or greater and can tolerate high carbon monoxide concentrations in fuel feeds. For practical mobile fuel cell systems, the ability to tolerate high levels of carbon monoxide enables a simplified integrated reformer fuel cell design, where a one-step reforming process can directly feed the fuel cell. This creates the potential for practical fuel cell systems to be designed that are capable of operating using an on-board hydrocarbon fuel. Hydrocarbon reforming processes (i.e., partial oxidation, steam reforming, or autothermal reforming) generate effluent gas compositions that typically contain various amounts of hydrogen, carbon monoxide, carbon dioxide, nitrogen, and water. While there are several studies that have examined the effects of CO dilution on HT-PEM fuel cell performance, there are very few that have examined the effects of other common reformate species, particularly while operating at varying temperatures and pressures. This work aims to fill the research gap in published data through evaluation of the performance exhibited by two HT-PEM membrane-electrode assembly (MEA) types, Advent's TPS©-based MEA and the BASF Celtec series MEA, based on acid-doped polybenzimidazole (PBI). In Part I of this series, the effects of temperature and pressure for various percentages of anode dilution were investigated. Temperatures and pressures were varied from 160 to 200 °C and 101.3–200 kPa, respectively. The effect of hydrogen diluted with nitrogen in the anode feed was examined with nitrogen concentrations up to 70%. Overall, the PBI MEA provided greater performance than the TPS for all tested conditions. Our results show that the performance loss due to high dilution levels can be wholly mitigated through an increase in operating temperature, pressure, or a combination thereof. For example, even at a dilution level containing 70% nitrogen, operating the cell at 200 °C and at 200 kPa provides the same power output as running the cell on pure hydrogen at 160 °C and at atmospheric pressure. This data can be used to model the performance effect of high diluent concentrations in the anode gas feed when developing an integrated reformer/fuel cell system.

Comparative evaluation of antibacterial activity of caffeic acid phenethyl ester and PLGA nanoparticle formulation by different methods

The aim of the present study was to evaluate the antimicrobial activity of nanoparticle and free formulations of the CAPE compound using different methods and comparing the results in the literature for the first time. In parallel with this purpose, encapsulation of CAPE with the PLGA nanoparticle system (CAPE-PLGA-NPs) and characterization of nanoparticles were carried out. Afterwards, antimicrobial activity of free CAPE and CAPE-PLGA-NPs was determined using agar well diffusion, disk diffusion, broth microdilution and reduction percentage methods. P. aeroginosa, E. coli, S. aureus and methicillin-resistant S. aureus (MRSA) were chosen as model bacteria since they have different cell wall structures. CAPE-PLGA-NPs within the range of 214.0 ± 8.80 nm particle size and with an encapsulation efficiency of 91.59 ± 4.97% were prepared using the oil-in-water (o–w) single-emulsion solvent evaporation method. The microbiological results indicated that free CAPE did not have any antimicrobial activity in any of the applied methods whereas CAPE-PLGA-NPs had significant antimicrobial activity in both broth dilution and reduction percentage methods. CAPE-PLGA-NPs showed moderate antimicrobial activity against S. aureus and MRSA strains particularly in hourly measurements at 30.63 and 61.25 μg ml−1 concentrations (both p < 0.05), whereas they failed to show antimicrobial activity against Gram-negative bacteria (P. aeroginosa and E. coli, p > 0.05). In the reduction percentage method, in which the highest results of antimicrobial activity were obtained, it was observed that the antimicrobial effect on S. aureus was more long-standing (3 days) and higher in reduction percentage (over 90%). The appearance of antibacterial activity of CAPE-PLGA-NPs may be related to higher penetration into cells due to low solubility of free CAPE in the aqueous medium. Additionally, the biocompatible and biodegradable PLGA nanoparticles could be an alternative to solvents such as ethanol, methanol or DMSO. Consequently, obtained results show that the method of selection is extremely important and will influence the results. Thus, broth microdilution and reduction percentage methods can be recommended as reliable and useful screening methods for determination of antimicrobial activity of PLGA nanoparticle formulations used particularly in drug delivery systems compared to both agar well and disk diffusion methods.