Low Threshold Concentrations Research Articles

Lethal and Sublethal Toxicity of Nanosilver and Carbon Nanotube Composites to Hydra vulgaris-A Toxicogenomic Approach.

The increasing use of nanocomposites has raised concerns about the potential environmental impacts, which are less understood than those observed with individual nanomaterials. The purpose of this study was to investigate the toxicity of nanosilver carbon-walled nanotube (AgNP-CWNT) composites in Hydra vulgaris. The lethal and sublethal toxicity was determined based on the characteristic morphological changes (retraction/loss of tentacles and body disintegration) for this organism. In addition, a gene expression array was optimized for gene expression analysis for oxidative stress (superoxide dismutase, catalase), regeneration and growth (serum response factor), protein synthesis, oxidized DNA repair, neural activity (dopamine decarboxylase), and the proteasome/autophagy pathways. The hydras were exposed for 96 h to increasing concentrations of single AgNPs, CWNTs, and to 10% AgNPs-90% CWNTs, and 50% AgNPs-50% CNWT composites. Transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) analysis revealed the presence of AgNPs attached to the carbon nanotubes and AgNP aggregates. The data revealed that the AgNP-CWNT composites were more toxic than their counterparts (AgNPs and CNWT). The sublethal morphological changes (EC50) were strongly associated with oxidative stress and protein synthesis while lethal morphological changes (LC50) encompassed changes in dopamine activity, regeneration, and proteasome/autophagic pathways. In conclusion, the toxicity of AgNP-CWNT composites presents a different pattern in gene expression, and at lower threshold concentrations than those obtained for AgNPs or CWNTs alone.

Enhancing the properties of epoxidized natural rubber-graphene nanocomposites through crosslinking with imidazole-activated dicarboxylic acid-cured system

The epoxidized natural rubber containing 25 mol% epoxide (ENR-25) was cured through crosslinking reactions with dodecanedioic acid (DA), both with and without activation by 1,2-dimethylimidazole (DMI). Analysis of the Fourier Transform Infrared (FTIR) spectroscopy of the DMI-activated DA-cured ENR revealed new absorption peaks at 1440 cm−1 and 1505 cm−1, indicating the presence of C-N stretching vibrations and carboxylate ions compared to samples without DMI activation. Additionally, ENR-graphene (GP) nanocomposites with various GP loadings were investigated, which revealed the formation of inter- and intramolecular hydrogen and covalent bonds within the ENR and GP networks. Furthermore, DMI activation of ENR cured with dicarboxylic acid accelerated the crosslinking reaction, reducing scorch and cure times while enhancing properties such as tensile strength, toughness, and 100 % modulus. Moreover, the incorporation and increased loading of GP in ENR nanocomposites synergistically enhanced strength properties, delta torque, crosslink density, initial relaxation modulus, thermal resistance, and electrical conductivity. This enhancement is attributed to interactions between the polar functional groups on GP surfaces and the functional groups of ENR adducts cured with DMI-activated dicarboxylic acid. Moreover, the ENR-GP nanocomposites exhibited a low percolation threshold concentration at 1.25 phr, enabling the formation of fully conductive GP networks within the ENR matrix. The significance of this study is to simplify the curing and production processes of ENR composites, offering promising self-healing capabilities and potential for reuse and recycling.

Sub-grid Variability and its Impact on Exposure in Regional Scale Air Quality and Integrated Assessment Models: Application of the uEMEP Downscaling Model

Regional scale air quality and integrated assessment models are necessarily limited in their spatial resolution, particularly when applied to larger regions such as Europe or for global applications. The EMEP MSC-W chemical transport model and the GAINS integrated assessment model, which makes use of source receptor information precalculated by the EMEP MSC-W model, use resolutions of 0.1°×0.1° and 0.3°×0.2°. These resolutions cannot account for variability at finer scales. Variability within grids, both concentration and population distributions, can be significant. To improve exposure calculations that take into account the sub-grid variability, the uEMEP model has been applied in this study to provide suitable parameterisations of the sub-grid variability within an EMEP MSC-W grid. The uEMEP model is applied on a European domain at 250 × 250 m2. This provides roughly 7000 sub-grids within each EMEP MSC-W 0.3°×0.2° grid to analyse the sub-grid variability in exposure. The analysis derives an exposure correction factor (ECF) for each source sector in each EMEP MSC-W grid. This factor provides information on the impact of sub-grid resolution on the population weighted concentrations within each grid. The population weighted standard deviation is also calculated, providing information on sub-grid variability to derive frequency distributions and parameterised forms of the sub-grid variability suitable for health risk assessments. The impact of sub-grid variability is assessed for the pollutants PM2.5, NOX and NO2. For NO2, additional chemistry calculations are carried out on the NOX frequency distributions. We show that the parameterised form of the sub-grid variability provides close to equivalent results as the original uEMEP calculations. Exposure to PM2.5 increases by around 13% when the sub-grid variability is taken into account for a 2030 emission scenario. For NO2, this increase is around 31% for the same scenario. A similar increase is found in the health risk indicator ’population attributable fraction’ when no lower concentration threshold is used in the concentration–response function. When applying the World Health Organizations recommended threshold value we find that including the sub-grid variability increases the calculated population attributable fraction by 32% and 46% for PM2.5 and NO2 respectively. We conclude that sub-grid variability should be taken into account in future exposure calculations for regional scale modelling and impact assessments.

Effects of silver nanowires and their surface modification on electromagnetic interference, transport and mechanical properties of an aerospace grade epoxy

The aerospace industry has progressively grown its use of composites. Electrically conductive nanocomposites are among important modern materials for this sector. We report on a bulk composite containing silver nanowires (AgNW) and an aerospace grade epoxy for use in carbon fiber reinforced polymers (CFRPs). AgNWs’ surfaces were also modified to enhance their ability to be dispersed in epoxy. Composites were obtained by use of three-roll milling which is of major interest for industrial applications, especially for the aerospace sector, since the process is scalable and works for aerospace grade resins with high curing temperatures. Our main objective is to improve the electromagnetic interference (EMI) shielding performance of CFRPs via improving the properties of the resin material. The addition of AgNWs did not considerably alter the flexural strength of the epoxy, however the composite with surface-modified AgNWs has a 46 % higher flexural strength. Adding AgNWs over a low threshold concentration of 0.05 wt% significantly enhanced the electrical conductivity. Conductivities above the percolation threshold lie around 102 S/m. At a concentration of 5 wt% AgNW, the EMI shielding efficiency (SE) of epoxy increased from 3.49 to 12.31 dB. Moreover, the thermal stability of the epoxy was unaffected by AgNWs. As a result, it was discovered that (surface modified) AgNWs improved the (multifunctional) capabilities of the aerospace grade epoxy resin which might be used in CFRPs to further enhance properties of composites parts, demonstrating suitability of AgNWs’ as a reinforcement material in aerospace applications.

Recombinant silk protein condensates show widely different properties depending on the sample background.

There is an increasing understanding that condensation is a crucial intermediate step in the assembly of biological materials and for a multitude of cellular processes. To apply and to understand these mechanisms, in vitro biophysical characterisation techniques are central. The formation and biophysical properties of protein condensates depend on a multitude of factors, such as protein concentration, pH, temperature, salt concentration, and presence of other biomolecules as well as protein purification and storage conditions. Here we show how critical the procedures for preparing protein samples for in vitro studies are. We compare two purification methods of the recombinant spider silk protein CBM-AQ12-CBM and study the effect of background molecules, such as DNA, on the formation and properties of the condensates. We characterize the condensates using aggregation induced emitters (AIEs), coalescence studies, and micropipette aspiration. The condensated sample containing background molecules exhibit a lower threshold concentration for condensate formation accompanied by a lower surface tension and longer coalescence time when compared to the pure protein condensates. Furthermore, the partitioning of small AIEs is enhanced in the presence of background molecules. Our results highlight that the purification method and remaining background molecules strongly affect the biophysical properties of spider silk condensates. Using the acquired knowledge about spider silk protein purification we derive guidelines for reproducible condensate formation that will foster the use of spider silk proteins as adhesives or carriers for biomedical applications.

Novel and Simple Method for Quantification of 2,4,6-Trichlorophenol with Microbial Conversion to 2,4,6-Trichloroanisole.

Contamination with 2,4,6-trichloroanisole (TCA) often causes taste and odor (T&O) problems in drinking water due to its low odor threshold concentration. Microbial O-methylation of the precursor 2,4,6-trichlorophenol (TCP) would be the dominant mechanism for TCA formation. Simple and rapid measurement of TCP in the low concentration range is necessary to control the problems induced by TCA. In this study, the combination of microbial conversion and instrumental analysis was proposed as a method of TCP quantification. Fungi and bacteria were isolated from various water samples and examined for their ability to produce TCA from TCP. As a result, a strain exhibiting quantitative TCA production and a high growth rate was obtained and named Mycolicibacterium sp. CB14. The conversion rate of TCP to TCA by this strain was found to be high and stable (85.9 ± 5.3%), regardless of the applied TCP concentration, although within the range of 0.1-10 µg/L. The limits of detection and quantification for TCP by this proposed method were determined to be 5.2 ng/L and 17.3 ng/L, respectively. By improving the methods, Mycolicibacterium sp. CB14 could be used for the quantification of TCP at very low concentration levels, which is sufficient to manage the T&O problem caused by TCA.

Dimensional Reduction for Single-Molecule Imaging of DNA and Nucleosome Condensation by Polyamines, HP1α and Ki-67.

Macromolecules organize themselves into discrete membrane-less compartments. Mounting evidence has suggested that nucleosomes as well as DNA itself can undergo clustering or condensation to regulate genomic activity. Current in vitro condensation studies provide insight into the physical properties of condensates, such as surface tension and diffusion. However, methods that provide the resolution needed for complex kinetic studies of multicomponent condensation are desired. Here, we use a supported lipid bilayer platform in tandem with total internal reflection microscopy to observe the two-dimensional movement of DNA and nucleosomes at the single-molecule resolution. This dimensional reduction from three-dimensional studies allows us to observe the initial condensation events and dissolution of these early condensates in the presence of physiological condensing agents. Using polyamines, we observed that the initial condensation happens on a time scale of minutes while dissolution occurs within seconds upon charge inversion. Polyamine valency, DNA length, and GC content affect the threshold polyamine concentration for condensation. Protein-based nucleosome condensing agents, HP1α and Ki-67, have much lower threshold concentrations for condensation than charge-based condensing agents, with Ki-67 being the most effective, requiring as low as 100 pM for nucleosome condensation. In addition, we did not observe condensate dissolution even at the highest concentrations of HP1α and Ki-67 tested. We also introduce a two-color imaging scheme where nucleosomes of high density labeled in one color are used to demarcate condensate boundaries and identical nucleosomes of another color at low density can be tracked relative to the boundaries after Ki-67-mediated condensation. Our platform should enable the ultimate resolution of single molecules in condensation dynamics studies of chromatin components under defined physicochemical conditions.

Stretchable conductive nanocomposites of low electrical percolation threshold for washable high-performance-interconnects

We report a rationally designed stretchable conductive composite of low Ag percolation threshold concentration with the aid of boron nitride (BN) as a non-conductive auxiliary filler.

SARS-CoV-2 Spike Protein Induces Hemagglutination: Implications for COVID-19 Morbidities and Therapeutics and for Vaccine Adverse Effects

Experimental findings for SARS-CoV-2 related to the glycan biochemistry of coronaviruses indicate that attachments from spike protein to glycoconjugates on the surfaces of red blood cells (RBCs), other blood cells and endothelial cells are key to the infectivity and morbidity of COVID-19. To provide further insight into these glycan attachments and their potential clinical relevance, the classic hemagglutination (HA) assay was applied using spike protein from the Wuhan, Alpha, Delta and Omicron B.1.1.529 lineages of SARS-CoV-2 mixed with human RBCs. The electrostatic potential of the central region of spike protein from these four lineages was studied through molecular modeling simulations. Inhibition of spike protein-induced HA was tested using the macrocyclic lactone ivermectin (IVM), which is indicated to bind strongly to SARS-CoV-2 spike protein glycan sites. The results of these experiments were, first, that spike protein from these four lineages of SARS-CoV-2 induced HA. Omicron induced HA at a significantly lower threshold concentration of spike protein than the three prior lineages and was much more electropositive on its central spike protein region. IVM blocked HA when added to RBCs prior to spike protein and reversed HA when added afterward. These results validate and extend prior findings on the role of glycan bindings of viral spike protein in COVID-19. They furthermore suggest therapeutic options using competitive glycan-binding agents such as IVM and may help elucidate rare serious adverse effects (AEs) associated with COVID-19 mRNA vaccines, which use spike protein as the generated antigen.

Oligomeric ethylene-glycol brush functionalized graphene oxide with exceptional interfacial properties for versatile applications

Graphene oxide (GO) has continued to prompt fantastic discoveries and applications; however, the highly extended two-dimensional π-conjugation of pristine graphene sheets leads to the aggregation of GO sheets in strong brine, which impairs the applications of GO. In this work GO with covalently-bound oligomeric ethylene–glycol brushes (termed as GOC) was prepared using graphite oxide as a raw material. The synthesized GOC was investigated by a holistic combination of experimental characterizations and molecular dynamic simulations. Our results showed that GOC behaves like a highly anisotropic colloid that well dispersed in various organic solvents, and retained high dispersion stability in strong brine even after storage at high temperature (e.g, 90 ℃). The GOC can sharply decrease surface tension after reaching a very low threshold concentration of 0.04 mg/mL; on account of that, it successfully generated water-in-oil Pickering emulsions with an internal water content of as high as 90 vol%. The GOC also functions as a liquid crystal at the oil–water interface without the need of external assistances/stimuli. We envisage that the prepared multifunctional GOC materials will stimulate a broad range of its applications when exceptional interfacial properties are required such as in the field of food, cosmetics, and petroleum industries.

Tuning reactivity of Bi2MoO6 nanosheets sensors toward NH3 via Ag doping and nanoparticle modification

Noble metal-doping and modification are proved effective in improving the gas-response performance of semiconductor sensors. In this study, we developed a promising Bi2MoO6 (BMO)-based gas sensor capable of sensing ppb-level NH3 at room temperature via introducing silver (Ag). The BMO samples with different Ag doping and modification ratios were successfully formed via one-step solvothermal and glucose reduction techniques, respectively, which could be confirmed by the results of X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) techniques. Compared to bare BMO, the gas-sensing properties of both Ag-doped and Ag surface-modified BMO samples were improved to various extents, respectively. In particular, the 5% Ag-modified BMO sensor with the highest response (Gg/Ga = 37.6 to 200 ppb NH3), long-term stability, and low threshold concentration (50 ppb) at 20% RH. Based on the spillover effect and metal–semiconductor junctions of Ag nanoparticles, the enhanced sensing response towards NH3 can be thoroughly illustrated. Combined with the first-principles calculations, the adsorption energy, density of states, and charge transfer of Ag-modified BMO were further performed to demonstrate the high sensing response and ultra-low detection limit.

Metabolism of Carotenoids and β-Ionone Are Mediated by Carotenogenic Genes and PpCCD4 Under Ultraviolet B Irradiation and During Fruit Ripening.

Carotenoids are essential pigments widely distributed in tissues and organs of higher plants, contributing to color, photosynthesis, photoprotection, nutrition, and flavor in plants. White- or yellow-fleshed colors in peach were determined by expression of carotenoids cleavage dioxygenase (PpCCD) genes, catalyzing the degradation of carotenoids. The cracked volatile apocarotenoids are the main contributors to peach aroma and flavor with low sensory threshold concentration. However, the detailed regulatory roles of carotenoids metabolism genes remained unclear under UV-B irradiation. In our study, metabolic balance between carotenoids and apocarotenoids was regulated by the expression of phytoene synthase (PSY), β-cyclase (LCY-B), ε-cyclase (LCY-E), and PpCCD4 under UV-B irradiation. The transcript levels of PpPSY, PpLCY-B, PpLCY-E, and PpCHY-B were elevated 2- to 10-fold compared with control, corresponding to a nearly 30% increase of carotenoids content after 6 h UV-B irradiation. Interestingly, the total carotenoids content decreased by nearly 60% after 48 h of storage, while UV-B delayed the decline of lutein and β-carotene. The transcript level of PpLCY-E increased 17.83-fold compared to control, partially slowing the decline rate of lutein under UV-B irradiation. In addition, the transcript level of PpCCD4 decreased to 30% of control after 48 h UV-B irradiation, in accordance with the dramatic reduction of apocarotenoid volatiles and the delayed decrease of β-carotene. Besides, β-ionone content was elevated by ethylene treatment, and accumulation dramatically accelerated at full ripeness. Taken together, UV-B radiation mediated the metabolic balance of carotenoid biosynthesis and catabolism by controlling the transcript levels of PpPSY, PpLCY-B, PpLCY-E, and PpCCD4 in peach, and the transcript level of PpCCD4 showed a positive relationship with the accumulation of β-ionone during the ripening process. However, the detailed catalytic activity of PpCCD4 with various carotenoid substrates needs to be studied further, and the key transcript factors involved in the regulation of metabolism between carotenoids and apocarotenoids need to be clarified.

OC-06: Identification of predictive hemostatic biomarkers for cancer diagnosis: results from the HYPERCAN study

ABL1 kinase T315I positive chronic myelogenous leukemia (CML) is treated with the tyrosine kinase inhibitor (TKI) ponatinib. However, its use is associated with a high incidence (29%) of arterial occlusive events.Determine the molecular basis of ponatinib-induced thrombosis.A C57BL/6 mouse model of ponatinib-induced rose bengal thrombosis was created. We characterized ponatinib or combined ponatinib with pioglitazone and measured aortic ROS and apoptosis with antibodies to nitrotyrosine and caspase 3, respectively, using immunohistoperoxidase. The influence of ponatinib influence on collagen-rich peptide (CRP)- and thrombin-induced JON/A and P-selectin expression and ADP-induced fibrinogen binding was examined. Aorta RNAseq studies were performed.Treatment of 20-week old mice with >3 mg/kg oral ponatinib daily for 14 days shortened carotid artery thrombosis times (18.7+3.7 min) compared to control (32.3+4.8 min, p<0.0001) (see Blood Adv. 3 (2019) 2312). Ponatinib-treated mice have normal CBCs, PT, aPTT, and contact- and tissue factor-induced TGT. Aortic adventitia of ponatinib-treated mice express increased nitrotyrosine and caspase 3. Treated mice have shortened tail bleeding times (55+12 min) versus untreated mice (102+9.3 min). CRP- or thrombin-induced JON/A and P-selectin occurred at lower threshold concentrations in ponatinib-treated mice. Concurrent pioglitazone treatment corrected ponatinib-induced thrombosis, aortic ROS and caspase 3 expression, and CRP-induced platelet hyper-reactivity. The mechanism for ponatinib-induced thrombosis and its correction by pioglitazone was sought. Aorta RNAseq data was examined on Reactome’s Hemostasis Enrichment Gene Set. Ponatinib-treated mice have 293/488 up-regulated gene sets (see Fig. 1). The most up-regulated aortic gene is F5. Other up-regulated aortic genes with ponatinib treatment include F8, F2, F10, and F7 and APBB1P, SERPINB2 (PAI-3), and TIMP. Additionally, related integrins (ITGB2, ITGA2B, ITGAL, are ITGAX), receptors (MPL, GP5, GP9), and adhesive proteins (SELL and AMICA1) also are increased. Further, the kinases of the GPVI activation cascade (LCK, LAT, SYK, LYN, FYN) were elevated. Combining pioglitazone with ponatinib treatment reduced the upregulation of 100 gene sets seen with ponatinib alone. Pioglitazone corrected the ponatinib-induced prothrombotic phenotype. F8, F2 and the genes of and Lyn were knocked off the list of top genes expressed.These investigations indicate that ponatinib treatment increases gene expression of aortic prothrombotic and platelet signalling genes that promote GPVI activation. Addition of pioglitazone reduces the prothrombotic characteristics conferred by ponatinib treatment. These data indicate that cancer-associated thrombosis can be managed by non-anticoagulant pharmacologic agents.

Metal Organic Frameworks: Desulfurization Process by Engineered Novel Adsorbents

AbstractRemoval of sulfur‐containing compounds from liquid and gas steams originated from various processes of chemical industries would be essential, since these compounds can be the principal sources of deterioration and environmental degradation, and pollution even at low threshold concentration levels. The metal‐organic frameworks (MOFs) compromise a wide‐ranging of chemical structure designs with adjustable pore size and high promising surface area for the desulfurization process. In this review study, the current published studies and researches about sulfur removal in liquid and gas purification processes using MOFs as highly effective adsorbents and catalysts are systematically gathered and compared. According to the broad contextual information for sulfur removal using different MOFs in this study, it is called for new insight windows opened for the advance progresses in this area and the project of new and more effective MOF‐based sorbents.

Thallium cycling in pore waters of intertidal beach sediments

Pore water data of thallium (Tl) in marine environments are scarce. It has been suggested that anoxic sediments are a sink for dissolved Tl likely due to its incorporation into Fe sulfides. However, recent studies indicated that Tl is removed from solution prior to the onset of sulfidic conditions and that Tl is involved in biological cycles in coastal seawater. To assess the Tl behavior in marine sediments, pore waters of a high energy beach (Spiekeroog Island, Germany) were sampled during different seasons and on different spatial scales. The study site provides a perfect set of samples to assess trace metal behavior under various redox conditions.Samples were analyzed for the dissolved trace metals Tl, molybdenum (Mo), uranium (U), and rhenium (Re). Additionally, sediments were incubated to monitor trace metal removal or release under controlled conditions. On-site redox conditions were characterized using dissolved oxygen (O2), manganese (Mn), and iron (Fe) concentrations.Our results indicated high enrichments of Tl in pore waters concurrently to aerobic organic matter (OM) degradation, exceeding seawater concentrations up to 6-fold. In contrast, Tl was completely removed in weakly reducing pore water characterized by more than 1 µM Mn or Fe. The spatial Tl distribution in intertidal pore waters responded to the present dissolved Mn and Fe level, which varied in space and with season. We suggest, Tl release to be attributed to OM degradation, particle desorption, or reoxidation, whereas Tl removal is likely related to the presence of trace amounts of dissolved sulfide.In conclusion, the fast reaction kinetics of Tl led to fast and complete removal in comparison to Mo, U, and Re and we suggest the following order of removal: Tl > Re > U > Mo. The removal behavior as well as the high enrichments of Tl in pore waters implicate that sinks and sources in the marine environment are not yet fully understood. Although the intertidal sediments form an overall sink for Tl (U and Re), especially under mostly anoxic conditions in summer, sediments turn into a Tl net source in winter, when sediments are more oxic.For global marine Tl balances, Tl fluxes have been estimated based on pore water Tl/Mn ratios. Contrastingly, Tl removal from pore waters at low threshold concentrations of Mn at our site indicated that these Tl flux estimations may not be applicable in permeable sandy beach sediments and in many other types of sediments, which host mildly sulfidic conditions.

Role of Dislocations in the Process of Degradation of Semiconductor Lasers with Electronic Energy Pumping. Experimental Research

Light self-destruction-degradation of the second type has been observed in samples of semiconductor lasers with electronic energy pumping with high optical homogeneity and good quality of surface treatment. In these samples, damage appeared in the form of cords perpendicular to the ends of the resonator. According to the current understanding of the passage of powerful light streams through various media, the emergence of narrow light channels is due to the phenomenon of self-focusing. It refers to the fundamental physical mechanisms of propagation of laser radiation and is caused by nonlinear phenomena arising in a medium under the influence of high-power laser radiation. The physical reason for self-focusing is an increase in the refractive index n in a strong light field. Thermal self-focusing is the most probable cause of radiation redistribution in the active region of the crystal. However, it is possible that in the initial stage of the appearance of light channels a certain role is played by the growth of the intensity of radiation in certain sections of the crystal because of the instability of generation or small fluctuations in the pump current density. Then the process acquires an avalanche character, since the localization of the ray in the channel increases the density of light radiation which can lead to overheating of the substance and the activation of the thermal self-focusing mechanism. The experiments performed in this paper have shown that optically homogeneous crystals possess maximum resistance to degradation processes. In them, the critical power of light destruction is determined by the self-focusing threshold of radiation in a material. Since the nonlinear addition to the refractive index Δn = n2E2 at the self-focusing threshold is determined by the change in the concentration of non-equilibrium carriers ΔN(E2), the value of the maximum fluctuation DΔNmax itself is proportional to the value of the non-equilibrium carrier concentration at the generation threshold ΔNpores and the relative excess of the generation threshold J = (j – jn)/jn. Thus, a low threshold concentration of non-equilibrium carriers is one of the conditions for increasing material resistance to degradation processes. In doped crystals ΔNpores is less than in pure materials. This, perhaps, explains the rather higher value of Pcritial in the optimally doped homogeneous n-GaAs. Smaller values of Pcritial in p-type samples doped with zinc can be associated not only with the inhomogeneity of these crystals, but also with large generation thresholds. In addition, the cross section for absorption of radiation by holes is about 3–4 times larger than by electrons, which can also reduce the self-destruction threshold of lasers. At Т = 300 K, the lasing thresholds are higher that naturally reduces the value of the self-focusing threshold.

Analysis of Separation Distances under Varying Odour Emission Rates and Meteorology: A WWTP Case Study

A wide variability of odour impact criteria is found around the world. The objective of this research work was to evaluate the influence of the uncertainties related to some individual stages of odour impact assessment in the application of regulatory criteria. The evaluation procedure was established by following the guidelines of the Northern Italian regions. A wastewater treatment plant located in Northern Italy was considered as a case study. Odour dispersion modelling was carried out with the CALPUFF model. The study focused on two phases of the assessment. The first phase was the selection of the meteorology datasets. For low odour concentration thresholds (CT = 1 OU m−3), the results showed that two different years (2018 and 2019) provided similar patterns of the separation distances. The difference between the two years tended to increase by increasing the value of the concentration threshold (CT = 3 OU m−3 and CT = 5 OU m−3). The second phase of the assessment was the selection of the open field correction method for wind velocity used in the calculation of odour emission rates (OERs). Three different relationships were considered: the power law, the logarithmic law and the Deaves–Harris (D–H) law. The results showed that OERs and separation distances varied depending on the selected method. Taking the power law as the reference, the average variability of the separation distances was between −7% (D–H law) and +10% (logarithmic law). Higher variability (up to 25%) was found for single transport distances. The present study provides knowledge towards a better alignment of the concept of the odour impact criteria.

Application of solid phase extraction (SPE) coupled to dispersive liquid–liquid micro-extraction (DLLME) and sensory evaluation technique for the study of taste and odor active compounds in water

Abstract Short-chain carbonyls could cause taste and odor issues in drinking water due to their very low odour threshold concentrations (OTCs). Several techniques such as 2,4-dinitrophenylhydrazine (DNPH) derivatization-HPLC and solid-phase micro-extraction (SPME) have been applied for trace short-chain aldehydes analysis in water. However, to study the taste and odor contributors in drinking water, it would be helpful to obtain an extract with representative odor from water samples for further studies, such as GC-olfactometry analysis or sensory test. Therefore, the above techniques still have some constraints due to the derivatization process or complex operating procedures. In this work, we developed a solid-phase extraction (SPE) coupled to dispersive liquid–liquid micro-extraction (DLLME) method to study short-chain aldehydes in ozonated water samples (LOQ = 1 ppb, RSD% = 12–45%). This method enables us to obtain an extract with representative odor from water for further volatile components analysis and sensory evaluation. Pair-wise nose clip sensory evaluation on the taste and odor of ozonated water indicated a high correlation between odor and taste of ozonated water. The SPE-DLLME method enabled a reliable study, for the first time, on correlations of volatile carbonyls and taste &amp; odor performance for ozonated water by applying a series of statistical models.

Roles of Organohalide-Respiring Dehalococcoidia in Carbon Cycling.

The class Dehalococcoidia within the Chloroflexi phylum comprises the obligate organohalide-respiring genera Dehalococcoides, Dehalogenimonas, and "Candidatus Dehalobium." Knowledge of the unique ecophysiology and biochemistry of Dehalococcoidia has been largely derived from studies with enrichment cultures and isolates from sites impacted with chlorinated pollutants; however, culture-independent surveys found Dehalococcoidia sequences in marine, freshwater, and terrestrial biomes considered to be pristine (i.e., not impacted with organohalogens of anthropogenic origin). The broad environmental distribution of Dehalococcoidia, as well as other organohalide-respiring bacteria, supports the concept of active halogen cycling and the natural formation of organohalogens in various ecosystems. Dechlorination reduces recalcitrance and renders organics susceptible to metabolic oxidation by diverse microbial taxa. During reductive dechlorination, hydrogenotrophic organohalide-respiring bacteria, in particular Dehalococcoidia, can consume hydrogen to low consumption threshold concentrations (<0.3 nM) and enable syntrophic oxidation processes. These functional attributes and the broad distribution imply that Dehalococcoidia play relevant roles in carbon cycling in anoxic ecosystems.

Experimental study on volatile sulfur compound inhibition using a single-chamber membrane-free microbial electrolysis cell

Odor emissions from sewer systems and wastewater treatment plants have attracted much attention due to the potential negative effects on human health. A single-chamber membrane-free microbial electrolysis cell was proposed for the removal of sulfides in a sewer system. The feasibility of the use of volatile sulfur compounds and their removal efficiency in liquid and headspace gas phases were investigated using synthetic wastewater with real sewer sediment and Ru/Ir-coated titanium electrodes. The results indicate that hydrogen sulfide and volatile organic sulfur compounds were effectively inhibited in the liquid phase upon electrochemical treatment at current densities of 1.55, 2.06, and 2.58mA/cm2, and their removal rates reached up to 86.2-100%, except for dimethyl trisulfide, the amount of which increased greatly at 1.55mA/cm2. In addition, the amount of volatile sulfur compounds in the headspace decreased greatly; however, the total theoretical odor concentration was still high, and methanethiol and ethanethiol greatly contributed to the total strength of the odor concentration due to their low odor threshold concentrations. The major pathway for sulfide removal in the single-chamber membrane-free microbial electrolysis cell is biotic oxidation, the removal rate of which was 0.4-0.5mg/min, 4-5 times that of indirect electrochemical oxidation.