Maximum Achievable Concentrations Research Articles

Hygienic assessment of new pesticides migration from soil into the lower atmospheric air layer

Annotation. A great danger to the environment and the health of the population is the release of chemical substances of technogenic origin, in particular plant protection products into the atmospheric air. The aim of the study was to evaluate the hazard of harmful inhalation impact on the human body of new pesticides: triazolone herbicide amicarbazone, tricetone herbicide bicyclopyrone, and carboxamide fungicide pydiflumetofen, during their migration from soil to the lower atmospheric air layer. Mathematical modeling of the process of evaporation of the studied pesticides from soil to the atmospheric air was carried out and comparison of the maximum achievable concentrations with the average lethal concentration during acute inhalation exposure and hygienic standards in the air environment. Experimental study of the behavior of amicarbazone, bicyclopyrone, and pydiflumetofen in the "soil - atmospheric air" system was carried out in laboratory conditions. The concentrations of the studied substances in the air were determined by the method of high - performance liquid chromatography. It was established that amicarbazone, bicyclopyrone, and pydiflumetofen are non - volatile under saturated vapor pressure and Henry's law constant, and low - risk by the coefficient of possible inhalation poisoning. Acute inhalation poisoning as a result of evaporation from the soil into the lower atmospheric air layer is unlikely. The maximum achievable concentrations of the studied pesticides that can form in the air as a result of evaporation from the soil are significantly lower than their hygienic standards in the working zone. The migration levels of the studied substances from soil to the lower atmospheric air layer depend on their initial concentrations and the type of soil: bicyclopyrone and pydiflumetofen migrate more intensively from sandy soil than from leached chernozem. Threshold concentrations in the soil according to the air – migration indicator of harmfulness: amicarbazone – 0.05 mg/kg, bicyclopyrone – 1.0 mg/kg and pydiflumetofen – 1.2 mg/kg are formed in the plow layer of soil when researched pesticides are introduced according to 1th, 20th and 20th maximum consumption rates. The “soil - atmospheric air” system is not a leading link to the migration of the studied pesticides in the environment. The obtained results were used in the substantiation of hygienic standard of amicarbazone, bicyclopyrone and pydiflumetofen in soil.

Adsorption mechanisms on perfluorooctanoic acid by FeCl3 modified granular activated carbon in aqueous solutions.

Perfluorooctanoic acid (PFOA) is an emerging organic pollutant that is persistent in the environmental, and has been detected in humans, and wildlife. Several technologies, such as activated carbon (AC) adsorption have been used to remove PFOA from water. In this study, Fe-impregnation with/without post-thermal treatment of AC was applied to improve the adsorption of PFOA. The adsorption mechanisms were evaluated using three kinetic models: pseudo-first-order model, pseudo-second-order model, and intra-particle diffusion models. Interpretation of experimental results with the kinetic models revealed that chemical interactions, such as electrostatic attraction or complexation were suggested as the adsorption mechanisms along with physical adsorption. Two isotherm models demonstrated that the modified ACs (171.0-189.9mgg-1) had increases in adsorption capacities than the unmodified AC (164.9mgg-1), which indicated that modification improved the maximum achievable surface concentrations and adsorption affinity to some extent. The evenly distributed iron content on the modified ACs was visualized using an energy dispersive X-ray spectroscopy. The Fe-impregnated AC showed a reduction in the specific surface area and total pore volume; however, post-thermal treatment largely recovered the pore structures. The isotherms normalized by the accessible surface area revealed the importance of the Fe-impregnated surfaces on PFOA adsorption. Comparable pH values of the point of zero charge and chemical compositions of the ACs implied that an increase in Fe-impregnated surface was crucial to improve PFOA adsorption. Thus, substantial enhancement of PFOA removal can be achieved by implementing a proper strategy for AC modification, especially using Fe-impregnation.

Effect of process conditions on generation of hydrochloric acid and lithium hydroxide from simulated lithium chloride solution using bipolar membrane electrodialysis

A feasibility study was carried out on generation of hydrochloric acid and lithium hydroxide from the simulated lithium chloride solution using EX3B model bipolar membrane electrodialysis (BMED). The influence of a series of process parameters, such as feed concentration, initial acid and base concentration in device component, feed solution volume, and current density were investigated. In addition, the maximum achievable concentrations of HCl and LiOH, the average current efficiency, and specific energy consumption were also studied and compared in this paper to the existing literature. Higher LiCl concentrations in the feed solution were found to be beneficial in increasing the final concentrations of HCl and LiOH, as well as improving current efficiency while decreasing specific energy consumption. However, when its concentration was less than 4 g/L, the membrane stack voltage curve of BMED increased rapidly, attributed to the higher solution resistance. Also low initial concentration of acid and base employed in device component can improve the current efficiency. Increasing of the initial concentration of acid and base solution lowered energy consumption. Moreover, a high current density could rapidly increase HCl and LiOH concentration and enhance water movements of BMED process, but reduced the current efficiency. The maximum achievable concentration of HCl and LiOH generated from 130 g/L LiCl solution were close to 3.24 mol/L and 3.57 mol/L, respectively. In summary, the present study confirmed the feasible application for the generation of HCl and LiOH from simulated lithium chloride solution with BMED.

A Review of the Main Considerations for Formulation Development in Preclinical Toxicology Studies.

The main considerations for the development of a formulation for preclinical safety assessment testing are explored. Intravenous, inhalation, oral and dermal dosing are given focus and although different dose routes do present their own individual challenges there are common themes that emerge. In each case it is necessary to maximise exposure to achieve high doses to satisfy regulatory requirements for safety assessment testing. This often involves producing formulations that are at the limits of solubility and maximum volumes possible for administration to different test species by the chosen route. It is concluded that for all routes it is important to thoroughly explore the stability of the test item in the proposed formulation matrix well ahead of dosing any animals, giving careful consideration to which excipients are used and what their underlying toxicity profile may be for the relevant preclinical species. In addition, determining the maximum achievable concentrations and weighing that against the maximum volumes that can be given by the chosen route in all the test species at an early stage will also give a read on whether it would be theoretically possible to achieve suitably high enough doses to support clinical work. Not doing so can cause delays in the development programme and may have ethical repercussions.

Technical support of aerobic fermentation processes

The article shows that aerobic fermentation of sugar-containing media requires the presence of dissolved oxygen in them. In most cases, the latter condition is fulfilled by the introduction and dispersion in the liquid phase of the air, which is compressed to levels corresponding to hydrostatic pressures with some exaggeration. The formation of the dispersed gas phase is accompanied by the interaction of the inlet air and the liquid phase, the efficiency of which is determined by the formed contact surface. The study presents generalizations that relate to the dynamics of biomass growth and correlate with the amount of oxygen introduced into the system. It is important that oxygen refers to gases with limited solubility, and therefore the hydrodynamic state and the interfacial surface are among the factors of intensification of mass transfer processes. It is also shown that the nominal estimation of the hydrodynamic state of gas-liquid media should begin with an assessment of the aeration intensity and it is proposed to take the reduced gas phase velocity as the ratio of the volume air flow to the cross-sectional area of the apparatus. Turning to the indicator of the reduced speed negates the influence of geometrical parameters in the form of the ratio of height and diameter. The results of the process and the efficiency of the equipment used are determined by the performance indicators in the form of concentrations of microorganisms and the output rate of the input power supply. The combination of these requirements leads to the need to combine the maximum achievable concentrations of dissolved oxygen and the minimum concentrations of sugars. The features of the double influence of ambient temperatures in the manifestations of the optimal for microorganisms and for the solubility of gases in accordance with Henry's law are shown, the values of Henry constants are given. The list of factors of influence includes such physical parameters of the environment as viscosity, surface tension, osmotic pressure, hydrostatic pressure, temperature. It is determined that the presence of dissolved nitrogen has an influence on the hydrodynamics of gas-liquid media due to changes in hydrostatic pressure in the circulation circuits.

Electrodialysis-based zero liquid discharge in industrial wastewater treatment.

Over the past few decades, reverse osmosis (RO) has been the dominant technology employed in zero liquid discharge (ZLD) systems for industrial wastewater treatment (WWT). However, RO is limited to a maximum operating salinity of about 75 g kg-1. Electrodialysis (ED) is a potentially attractive option as it can achieve much higher concentrations, thereby reducing the capacity and energy demand of the subsequent evaporation step. Feed-and-bleed experiments were undertaken on a laboratory-scale ED stack using a series of model solutions based on the most common inorganic salts with the aim of determining maximum achievable concentrations. The maximum salt concentration achievable via ED ranged between 104.2 and 267.6 g kg-1, with levels predominantly limited by water transport. In addition, a straightforward review of how ED incorporation can affect ZLD process economics is presented. The operational cost of an ED-based ZLD system for processing RO retentate was almost 20% lower than comparable processes employing high-efficiency RO and disc tubular RO. As the ED-based ZLD system appears economically preferable, and as maximum achievable concentrations greatly exceeded RO operating limits, it would appear to be a promising approach for bridging the gap between RO and evaporation, and may even eliminate the evaporation step altogether.

N- and P- type Doping in Al-rich AlGaN and AlN

Significant challenges in point defect control in AlGaN epitaxy has precluded commercialization of AlGaN based devices. Si is typically employed as n-type dopant in AlGaN and exhibits a low activation energy (<50 meV) in AlxGa1-xN with x<0.8. However, Si doped AlGaN exhibits a “knee behavior” resulting in a conductivity and carrier concentration maxima at a specific Si concentration. Hence a high doping limit exists for Si in AlGaN that lowers the maximum achievable carrier concentrations that are necessary for AlGaN based power electronics. Similarly, a low doping limit (a minimum achievable carrier concentration with a corresponding maximum mobility) exists in AlGaN similar to that in GaN which precludes implementation of AlGaN power electronics that require low doped drift regions. Along the same lines, p-type doping is achieved with Mg, but high activation energies preclude its technological implementation. Following results in GaN, compensating point defects are also expected to play a major role in determining the doping efficiency of Mg, even if methods to “reduce” its activation energy are found. Hence a major “point defect problem” exists in AlGaN that needs to be solved for implementation of AlGaN technology. In this work, we update on three different achievements: (1) identifying and controlling point defects for efficient n-type doping in AlGaN, (2) implantation as a method for achieving high n-type conductivity in AlN and (3) the possibility of high conductivity p-type AlGaN. All these achievements are built upon a point defect control (PDC) framework based on a systematic chemical potential control (CPC) and defect quasi Fermi level control (DQFL). In CPC, the growth environment variables are related to the defect formation energy by determining and controlling the Al,Ga,N and impurity chemical potentials. This helps optimize the growth environment accordingly for minimal point defect incorporation or generation. In DQFL control, the defect quasi Fermi level, the Fermi level describing the probability of the defect level being occupied/unoccupied, is modified by introducing excess minority carriers (by above bandgap illumination). This leads to an increase in the compensating point defect formation energy, reducing their concentration. Both control schemes provide for a theoretical framework that provides a quantitative relationship between point defect formation energies and growth process parameters. CPC based targeted reduction requires knowledge of the defects responsible and accordingly, we identify the point defects responsible for knee behavior in n-type AlGaN as most likely vacancy-silicon complexes and low doping limit as CN. Note that threading dislocations and vacancy-oxygen complexes are also expected to be compensating and contribute to the low doping limit. Utilizing the vacancy-silicon complex and CN in Al0.7Ga0.3N as a case study, we demonstrate control over the knee behavior (improving the peak carrier concentration by impeding the formation VIII-SiIII complexes) and low doping limit (achieving lower carrier concentrations by reducing the compensating impurity (CN) density) in Al0.7Ga0.3N by controlling the chemical potentials of III/N and growth temperature with excellent agreement with quantitative theoretical predictions. These concepts are further used in Si implanted AlN where a reduction in the formation of vacancy-silicon complexes during implantation annealing is necessary. This was achieved by implementing DQFL control during the implantation annealing stage. Such process led to an increase of nearly 3 orders of magnitude in the conductivity of n-type AlN at room temperature. Finally, after recognizing the importance of point defect reduction during doping, significant achievements in p-type AlGaN were realized. Lower Mg activation energies than those previously reported were observed leading to significant p-type conductivity in AlGaN. All these results support our PDC framework and the utility of formation energies from equilibrium formalism typically employed in DFT in predicting defect incorporation in non-equilibrium and high temperature MOCVD growth.

Dissolution performance of binary amorphous drug combinations—Impact of a second drug on the maximum achievable supersaturation

An increased number of amorphous formulations of poorly water soluble drugs are being introduced into the market due to their higher transient solubility and thus faster absorption and higher bioavailability. While most amorphous drug products contain a single drug substance, there is a growing trend towards co-formulating compounds in the same dosage form to improve patient compliance. The purpose of the present work was to evaluate the dissolution behavior and maximum achievable solution concentrations of amorphous solid dispersions of co-formulated ritonavir and lopinavir, and to compare the results with individual amorphous solid dispersion formulations. Dispersions of ritonavir and lopinavir were prepared in polyvinylpyrrolidone (PVP) or hydroxypropylmethylcellulose acetate succinate (HPMCAS) at a 20% (w/w) total drug loading, both alone and in combination, at three different lopinavir:ritonavir weight ratios. Amorphous films containing both drugs, but no polymer, were also prepared. The dissolution behavior of the dispersions and the amorphous films in non-sink conditions was evaluated, using ultracentrifugation to separate any colloidal material from molecularly dissolved drug. Nanoparticle tracking analysis was used to characterize colloidal material formed during the dissolution process. Results from the dissolution study revealed that, although supersaturated solutions resulted following dissolution, the maximum achievable concentration of each drug, when present in combination, was dramatically lower than when the individual dispersions were dissolved. The maximum achievable solution concentration for systems containing both drugs was found to decrease as the mole fraction of the drug in the amorphous phase decreased. The type of polymer used to formulate the dispersion also appeared to influence the dissolution behavior whereby the HPMCAS dispersions dissolved rapidly, resulting in the generation of a nanodroplets, while the PVP dispersions did not produce as many colloidal species. These results highlight the need to consider potential decreases in achievable supersaturation for formulations containing more than one amorphous compound.

Nurse-like cells mediate ibrutinib resistance in chronic lymphocytic leukemia patients

Nurse-like cells mediate ibrutinib resistance in chronic lymphocytic leukemia patients

In vitro activities of levofloxacin, gatifloxacin, moxifloxacin and garenoxacin against Bacteroides fragilis strains evaluated by kill kinetics

This study was designed to investigate the killing activity of levofloxacin, gatifloxacin, moxifloxacin and garenoxacin against 12 Bacteroides fragilis strains by kill kinetics over time. MIC values were determined by Etest and by agar dilution. B. fragilis strains were divided according to their MIC values into two groups: one group with strains with MIC <8.0 µg ml(-1) and one group with strains with MIC ≥ 8.0 µg ml(-1). For kill kinetics over time, the strains with MIC <8.0 µg ml(-1) were incubated with the antibiotics at 0.5, 1, 2 and 4 times their MIC values. The strains with MIC ≥ 8.0 µg ml(-1) were incubated with 0.5, 1, 2, and 4 times the maximum achievable concentrations of the antibiotics in human plasma (Cmax). Among the strains with MIC <8.0 µg ml(-1) levofloxacin and gatifloxacin showed equal efficacy. The growth of the strains with MIC ≥ 8.0 µg ml(-1) was barely affected by levofloxacin, while gatifloxacin had bactericidal action when concentrations of 4 × C max were used. Moxifloxacin was more effective against both groups of strains compared with levofloxacin and gatifloxacin. Garenoxacin was the most active agent against all strains investigated. Due to the varying in vitro activity of the quinolones against obligate anaerobes the treatment with quinolones of patients with intra-abdominal infections needs intensive scrutiny.

EEG-Stadien im Steady State von Xenon-Narkosen

Einleitung: Xenon ist als Inhalationsanästhetikum in Deutschland und in anderen Ländern der Europäischen Union seit 2005 bzw. seit 2007 zugelassen. Es sollte untersucht werden, welche Hypnosetiefe, gemessen am Elektroenzephalogramm (EEG), im Steady State von Xenon-Narkosen erreicht wird.

Effects of Quantum Confinement on the Doping Limit of Semiconductor Nanowires

We have calculated the effects of quantum confinement on maximum achievable free carrier concentrations in semiconductor nanowires. Our calculations are based on the amphoteric defect model, which describes the thermodynamic doping limit in semiconductors in terms of the compensation of external dopants by native defects. We find that the generation of amphoteric native defects strongly limits maximum achievable carrier concentrations for nanowires with small widths where quantum confinement is appreciable. The magnitude of this effect in a given material is found to be determined by two material properties: the effective mass of the free carriers, and the position of the conduction (n-type) or valence band (p-type) edge on the absolute energy scale. These results offer a simple, predictive guideline for designing nanostructure devices and contacts where high doping levels are needed.

Adsorption of Alkylimidazolium and Alkylpyridinium Ionic Liquids onto Natural Soils

The mechanism of ionic liquid sorption onto selected natural soils differing in their organic content, cation exchange capacity, and particle size distribution was investigated in detail. Isotherms were employed to describe sorption. In most cases,the maximum achievable surface concentrations were well above CEC values. This observation may indicate that initially sorbed solutes modify the sorbent, a process favoring further sorption. The experimental data suggest that if a multilayer process occurs, such a mechanism will be applicable to all ionic liquids; but saturation of the second layer occurred only with the longest alkyl chain compound. The shorter alkyl chain cations did not reach saturation in the concentration range investigated here. The influence of the varying pH and ionic strength of an aquifer on sorption strength was also determined.

Surface and interface barriers of InxGa1−xAs binary and ternary alloys

The absolute position of the valence band maxima of the semiconducting InxGa1−xAs alloys relative to the vacuum level, a composition-independent energy level, defined as the Fermi level stabilization energy, EFS, located ∼4.95 eV below the vacuum level, and the energy interval between the composition dependent conduction band minima or valence band maxima determine the equilibrium surface barriers and band offsets of these alloys and their heterostructures. Charged, amphoteric defects, located on EFS, compensate deliberately introduced donor or acceptor impurities and determine the maximum achievable electron or hole concentrations. Experimental measurements made on undoped or on donor-doped metal–semiconductor and on metal–insulator–semiconductor structures of these alloys, indicate that the composition dependence of the equilibrium surface potentials and metal semiconductor barrier heights are consistent with this “vacuum pinning rule.”

Developmental (embryo-fetal toxicity/teratogenicity) toxicity studies of synthetic crystalline lycopene in rats and rabbits

Synthetic crystalline lycopene is a nutritional supplement to increase dietary intake of lycopene, an antioxidant carotenoid. Its potential oral developmental toxicity was studied in rats and rabbits. Each study included 3 control groups (water and matrix for Lycopene 10 CWD or LycoVit® 10%), 3 Lycopene 10 CWD groups [500, 1500 and 3000 (rats)/2000 (rabbits) mg/kg/day] and 1 LycoVit® 10% group [3000 mg/kg/day (rats)/2000 (rabbits)]. The high dosages were at maximum achievable concentrations and dosage volumes (15 and 10 ml/kg for rats and rabbits, respectively) of the highly viscous test material suspensions. Dosages were administered on gestation days (GDs) 6 through 19 (rats) or GDs 6 through 28 (rabbits). Endpoints evaluated included viability, body weight, feed consumption, necropsy observations [GD 20 (rats)/GD 29 (rabbits)], uterine contents and fetal viability, gender, body weight and morphology (skeletons double-stained). Feed consumption and weight gain were essentially unaffected in rats and rabbits, despite intubation problems in both species and reduced gastrointestinal motility and mortality in rabbits attributable to the physical properties of the gels. Neither Lycopene 10 CWD nor LycoVit® 10% caused direct maternal or developmental toxicity in rats or rabbits at dosages as high as 3000 or 2000 mg/kg/day, respectively.

Application of electrodialysis within fine chemistry

Abstract Several fine chemicals and pharmaceutical products are obtained by multi-step processes involving, amongst others, the neutralization of acid and basic solutions which lead to the formation of salts. Two routes using electrodialysis with bipolar membranes (EDBM) can be followed: (i) the conversion of the salt into the corresponding acid and basic solutions, or (ii) the neutralization of the alkali salts of the required organic acid by EDBM instead of carrying out the acid hydrolysis. Within a European Research Program the feasibility of both electrodialysis processes for amino acid production have been studied. The first type of process seemed to be not very attractive because of too high losses of amino acid and because of economical reasons. The second type of ED process was carried out in a batch mode of operation with a fixed current density of 1000 A/m2 until the stack voltage increased to 30 V, then the acidification was continued at a fixed voltage and the current density was decreased to 400 A/m2. The current efficiency found varied between 85 and 97%. The technological aspects are discussed, e.g. how to avoid precipitation of the amino acid in the membrane stack, the maximum achievable concentrations of the neutralized amino acid and of the basic solution produced.

Boron Activation During Solid Phase Epitaxial Regrowth

AbstractTo continue scaling dimensions of transistors, higher dopant concentration levels are needed for ultra-shallow contacts. Therefore studies of dopant activation have been performed in preamorphized silicon wafers with various boron implant conditions to determine the maximum achievable dopant concentrations after Solid Phase Epitaxial Regrowth (SPER) alone. In the first experiment a silicon piece was preamorphized with a 30 keV, 1×1015 cm−2 and 90 keV, 1×1015 cm−2 Si+ implant followed by a 30 keV, 1×1015 cm−2 B+ implant. Solid phase epitaxial regrowth at 500 °C indicates that boron can be activated at low temperatures. Ultra Low Energy (ULE) implants were studied in the second experiment. Silicon wafers were implanted with 2.5 keV, 1×1015 cm−2 Si+ to amorphize and then B+ was implanted at 0.5 keV in the dose range of 1×1015 to 9×1015 cm−2. Samples were annealed in the temperature range of 500 to 650 °C. High concentrations of boron make it difficult to fully regrow amorphous layers and thus yield marginal electrical properties. Much of the boron remains inactive, particularly at the higher dose implants. In both experiments Variable Angle Spectroscopic Ellipsometry (VASE) is used to measure amorphous layer thickness and Hall effect measures active boron dose. For the first experiment, Secondary Ion Mass Spectrometry (SIMS) data compares chemical dose to active dose during the regrowth process. Sheet resistance data is obtained from a four point probe for the ULE implant experiment.

Studies on the use of a thermotolerant strain of Kluyveromyces marxianus in simultaneous saccharification and ethanol formation from cellulose

The thermotolerant yeast strain, Kluyveromyces marxianus IMB3, was found to be capable of ethanol production during growth at 45°C on media containing milled paper and exogenously added commercial cellulase. At maximum achievable cellulose concentrations in shake-flask cultures, ethanol production increased to 6.6 g/l at 45°C, representing an overall level of conversion of 21% of the maximum theoretical yield. Subsequent studies involving variations in added cellulase concentrations to the batch systems demonstrated that ethanol yields could be increased to 10 g/l at 45°C, which represented 39% of the maximum theoretical yield. As a result of ethanol production at 45°C in the systems examined, we suggest that the thermotolerant ethanol-producing yeast strain K. marxianus represents a novel candidate for use in simultaneous saccharification and conversion of the resulting substrates to ethanol.