Fraction Of Elements Research Articles

Stability Design Principles of Manganese-Based Oxides in Acid

The use of non-precious catalysts (e.g., transition metal oxides) in electrochemical energy technologies in acid (e.g., proton exchange membrane fuel cells and electrolyzers) has been significantly hampered by the instability of such catalysts at low pHs. While first-row late transition metal oxides based on Fe, Co, and/or Ni have been reported with comparable or higher catalytic activity for the alkaline oxygen reduction and oxygen evolution reactions than their precious-metal-based counterparts (e.g., Pt and IrO2),[1] these oxide catalysts are not stable in acid.[2] Moreover, Mn-based oxides are more acid-stable than those based on late transition metals[1] and can be potentially stabilized by reaching dissolution-deposition equilibrium at moderately acidic pHs,[3] but they still corrode and deactivate in strong acid and after long operation.[4] To tackle this challenge, extensive efforts over the past decades have been focused on combining active, yet unstable metal oxides with corrosion-resistant oxides.[5-7] Nevertheless, having a higher fraction of corrosion-resistant elements results in more acid-stable, yet less active catalysts, indicating an activity-stability trade-off.[2,5,6] To design transition metal oxide catalysts (such as Mn-based oxides) with an optimal trade-off or bypass this limitation, it is critical to establish their stability descriptors in acid. These descriptors can offer a fundamental understanding of oxide dissolution and provide guiding principles to enhance their intrinsic stability. In this work, we employed a library of Mn-based oxides with diverse structures and Mn oxidation states to identify oxide stability descriptors in acid based on intrinsic electronic structure and energetic parameters. Using time-dependent dissolution experiments and density functional theory calculations, greater amounts and faster kinetics of oxide dissolution in acid were correlated with decreased Mn oxidation states, which are accompanied by lowered Mn-O covalency, weakened Mn-O bonds, and reduced barriers for key reaction steps (such as protonation, vacancy formation, and metal ion solvation). Such design principles were shown broadly with a computational screening across a vast chemical space of ~1,000 Mn-based oxides, where an Mn oxidation state of 4+ was found to give rise to the lowest energetic driving force for the dissolution of Mn-based oxides in acid. Moreover, limiting the percentage of ionic metal substituents in oxides and using more acidic substituents were shown to stabilize Mn-based oxides in acid. These findings can provide novel insights into designing acid-stable Mn-based oxides for renewable energy storage and conversion.

Effect of Silicon Element on the Solid Solubility of Carbon in α-Fe

Abstract The VASP (Vienna Ab initio Simulation Package) software package developed by the Hafner team at the University of Vienna was used to calculate the bonding involving the element in the system when silicon is added to a complex of α-Fe and carbon(α-Fe(C)). The interaction energies of silicon with carbon elements in their different neighbor locations in the matrix of α-Fe(C) matrix are obtained, and the electronic structure of a complex composed of α-Fe(C) and silicon(α-Fe(C)-Si) and the interaction between silicon and carbon in the α-Fe matrix are further analyzed. The influence of silicon on the solid solubility of carbon in the α-Fe matrix is analyzed and calculated on this basis. The results show that after a silicon atom is added to α-Fe(C), the silicon atom and iron atoms gain electrons, the carbon atom loses electrons, and bonds among the three are formed. The bonding electrons are mainly provided by iron atoms and the silicon atom. The atomic fraction of carbon element in the range of interaction with the silicon element in the α-Fe(C)-Si system is higher than the average atomic fraction of carbon in the α-Fe(C) system without the silicon element. The results show that the solid solubility of the carbon element in α-Fe increases after the silicon element is added.

The spatial and temporal evolution of mineral discoveries and their impact on mineral rarity

Abstract This paper presents the proceedings of the data analysis of the year and country of mineral discoveries with their Nickel-Strunz classes and rarity to enrich our knowledge of the evolution of mineral discoveries and their spatial distribution during different periods. Based on the dynamic of mineral discovery, three principal periods were identified: (1) Ancient period (up to 1800) of irregular mineral records; (2) Sustainable development period (1800–1949) with regular records and a moderate increase in the total number of minerals; and (3) Modern period (1950–present) of rapid development. It is pointed out that the timeline of mineral discoveries exhibits local anomalies. The positive anomalies were linked to the publications of mineralogical encyclopedias and classifications, while the negative ones were caused mainly by historical events, suppressing scientific activity. The majority of rock-forming and widespread minerals were discovered before the 1980s, while the discovery rate of rare and endemic species still progresses due to the study of hard-to-reach locations and the introduction of high-resolution analytical methods. A comparison of Nickel-Strunz class counts throughout mineral history revealed that the fraction of carbonates, oxides, and elements have drastically decreased during the Sustainable development period and the Modern period with a minor increase of elements during the last period. However, opposite behavior is observed for the phosphates, sulfates, and sulfides, with a sudden decrease in sulfates during the Modern period. On the other hand, the fraction of borates, halides, and silicates remained unchanged during all periods. Spatial analysis of the data showed that the distribution of mineral discoveries on the world map depends not only on the country’s geology but also on the area, population, economic development, and general interest in science.

Thermomechanical treatment influence on strength properties of vanadium alloys of V-Me(Cr, W)-Zr system at different temperatures

The results of a study of the influence of thermomechanical treatment modes and stabilizing annealing temperature on structural-phase state parameters and mechanical properties of disperse-strengthened vanadium alloys of V-Me(Cr, W)-Zr system are presented. The methods of scanning and transmission electron microscopy were used to investigate the grain, defect, and heterophase structure of alloys. The regularities of their structural-phase transformation and fracture were studied depending on the conditions of treatment and tensile deformation. The values of strength properties and plasticity were determined by tension at different temperatures after various treatment modes. It has been established that, regardless of the stabilizing annealing temperature, the use of a modified thermomechanical treatment (TMT-II) provides a higher level of strength properties of the studied alloys both at room and elevated temperatures. The influence of the main factors (elemental composition, volume fraction and dispersion of the second phase particles, parameters of grain and defect structure) on the thermal stability of the structural-phase state and mechanical properties of V-Me(Cr, W)-Zr system alloys is discussed.

Analysis of the main physical and chemical characteristics of the vine shoots of three vine varieties from Veneto (Italy)

In Italy the agricultural residues resulting from pruning of vineyards represent a potential energy resource, in particular for the Veneto region which is the second Italian region by vineyard area. This study is aimed at analyzing the main physical and chemical characteristics of vine shoots from the annual pruning of vineyards. This is for their possible use as wood chips in small-medium size power plants. International and European standards for the analysis of biofuels were used to determine the moisture content, heat value, ash content, micro and macro elemental and fibrous fraction (lignin, cellulose, hemicellulose and extractives). The samples were collected from three different vineyards in the Vicenza area. The varieties analyzed were Chardonnay, Glera and Merlot. For each variety, the three different components of vine shoots were compared: internode, node and pith, to investigate in which part of the vine shoot the greatest accumulation of metallic elements deriving from plant protection products occurs. The results show significant differences among the energy parameters of the three varieties and three vine shoot components. In particular, the pith shows low heat value and high ash content while the woody components are characterized by higher energy values. Analysis of the chemical elements showed a high content of Cu and Zn in the wood components, node and internode, causing the high ash content found. In particular, Cu content exceeds the limits set by the reference standard. As regards the analysis of the fibrous fraction, a high content of extractives was found in the pith. These extractives could be one of the explanations why the pith of the three varieties analyzed, especially in Chardonnay, have less lower heat value on dry basis (LHV0) values and high ash contents. On the contrary, the node and internode components have a higher content of cellulose, hemicellulose and lignin. Overall, the vine shoots analyzed have characteristics suitable for a possible energy use. However, due to the high ash and Cu content, according to EN ISO 17225-9:2021 standard these can only be used as wood chips for industrial purposes in large power plants.

Technology-critical elements in Rhine sediments - A case study on occurrence and spatial distribution

Despite their presence in almost every technical device, little is known about the occurrence, distribution, and fate of technology-critical elements (TCEs) within the environment. Due to high economic demands and short product lifespans as well as low recycling rates, many TCEs appear to become emerging contaminants.Within the scope of this work, 57 sediment samples from the German part of the Rhine river, as well as various tributaries, were collected to study the occurrence and distribution of TCEs. This specific catchment area has consistently been subjected to strong anthropogenic influences over the last century. Hierarchical cluster analysis, as well as principal component analysis were used to gain first insights into the spatial distribution and possible sources of TCEs along the Rhine.Obtained mass fractions in conjunction with corresponding geoaccumulation indices (Igeo) provide first indications of a possible enrichment along the Rhine for the TCEs of interest (Ga, Ge, Nb, In, Te, rare earth elements, and Ta). Especially the mass fractions of Zn, Ge, In, La, Sm, and Gd exhibit significant anthropogenic inputs. For stations characterized by high Ge and In mass fractions, element fingerprints imply possible atmospheric deposition stemming from e.g. combustion processes. Distinct anomalies of La and Sm most likely originate from discharges located at the city of Worms into the Upper Rhine. Statistical analysis of all analyzed 55 elemental mass fractions revealed similar behavior of TCEs compared to classical heavy metals. Diffuse as well as point sources of TCEs are likely. As a result, this study provides further insight into the role of TCEs as potential emerging contaminants in the environment.

A photosensor employing data-driven binning for ultrafast image recognition

Pixel binning is a technique, widely used in optical image acquisition and spectroscopy, in which adjacent detector elements of an image sensor are combined into larger pixels. This reduces the amount of data to be processed as well as the impact of noise, but comes at the cost of a loss of information. Here, we push the concept of binning to its limit by combining a large fraction of the sensor elements into a single “superpixel” that extends over the whole face of the chip. For a given pattern recognition task, its optimal shape is determined from training data using a machine learning algorithm. We demonstrate the classification of optically projected images from the MNIST dataset on a nanosecond timescale, with enhanced dynamic range and without loss of classification accuracy. Our concept is not limited to imaging alone but can also be applied in optical spectroscopy or other sensing applications.

Effect of substrates and voltages on the performance of bio-electrochemical anaerobic digestion

This research study investigates the effect of feedstock chemical composition and voltage supply on methane production from bio-electrochemical anaerobic digestion (BEAD). The experimental work was conducted on batch biomethane potential (BMP) bottles equipped with electrodes and connected to external power. Three substrates with distinct elemental compositions, waste activated sludge (WAS), and cow manure (CM), organic fraction of municipal solid waste (OFMSW), were tested under different voltages (0.7–1.5V). The BMP tests showed that OFMSW had the highest methane yield in the AD control reactors, followed by WAS and CM, which concurred with the estimated theoretical yields. Supplying voltage enhanced the performance of all BEAD reactors, but with different levels of improvement; methane yield, organics removal, and net energy efficiency increased by 7–46%, 16–54%, and 5–37%, respectively, compared to the equivalent controls. The strong relationship between the voltage and substrates with methane production was confirmed statistically through analysis of variance and t-test. Moreover, a regression model was established between the feedstock elemental fractions, power supply, and methane yield, with an adjusted correlation coefficient of 0.9 and a maximum prediction error of 5.4%. The overall findings of this research provide valuable operation and performance insights on the potential bio-electrochemical upgrades to AD systems.

Sparse Bayesian Learning Based Channel Extrapolation for RIS Assisted MIMO-OFDM

Reconfigurable intelligent surface (RIS) is a revolutionary technology and can be used to assist communication systems by adaptively manipulating the wireless environment. In this paper, we propose a novel cascaded channel estimation algorithm for the RIS-assisted multiple-input multiple-output orthogonal frequency division multiplexing systems. Inspired by the channel compression idea, we can obtain a sub-sampled channel by turning off a fraction of RIS elements and then extrapolate it to the complete one, by which the pilot overhead is greatly reduced. The problem of channel extrapolation is transformed into recovering the physical parameters of the cascaded channel from the partial channel observations and is then formulated by the sparse Bayesian learning (SBL) framework. In order to circumvent the curse of high dimensional matrices inversion in the vector-matrix system, we further introduce the tensor structure into the SBL framework. Specially, by leveraging of the channel sparsity over the angle domain and delay domain, we derive the virtual channel expression in tensor form and model a Kronecker-structured prior distribution for the virtual channels. The multi-domain sparse properties of the virtual channel tensor can be effectively captured by a group of low-dimensional hyper-parameters, and thus reduce the computational complexity. In addition, the Cramer-Rao lower bound is derived for the proposed channel extrapolation. Simulation results show the superior performance of the proposed scheme.

Probability of Health Risk, Bioaccumulation, and Geochemical Fractions of Toxic Elements in Soils and Vegetables Impacted by Manures in Nigeria

The intensive application of manures for the improvement of plant yield is a global practice by farmers notwithstanding the associated negative effects. The probability of health risk, bioaccumulation, and speciation of arsenic (As), cadmium (Cd), nickel (Ni), and lead (Pb) in soils and vegetables (Talinum triangulare and Telfairia occidentalis) impacted by untreated wastes from animal farms and inorganic fertilizers used as manures in the oil producing section of Nigeria were investigated. The total metal was determined using spectrophotometric methods while its geochemical fractions were identified following the modified Community Bureau of Reference (BCR) procedures of sequential extraction. The results obtained indicated the following mean concentrations (mg kg-1): 1.64 ± 0.70, 3.17 ± 1.47, 62.22 ± 8.83, and 187 ± 29.73 for As, Cd, Ni, and Pb, respectively. The results revealed that the mean concentrations of all the metals in the studied locations, except As, were above their recommended limits by the Food and Agricultural Organization/World Health Organization (FAO/WHO). The mean values of As and Pb in T. triangulareand T. occidentalis were also above the acceptable limits. Relatively higher levels of the metals were recorded at the studied locations as compared to the control site. The transfer factors of metals determined were generally lower than one; hence, the human exposure rate to these metals may not be high. The sequential extractions of metal indicated that As and Pb existed in the reducible fraction, Cd in the acid extractable fraction, and Ni in the residual fraction. The contamination factor of the metals revealed that As and Ni belong to the low contamination class, while Cd and Pb fall within the very high contamination category. The study showed that all the studied locations were heavily contaminated, with Uyo being the most polluted site. The principal component analysis identified anthropogenic factor as the main contributor to the presence of these metals in the investigated area. Daily intake rates for these metals via vegetable consumption by both the elderly and young populations were generally lower than their recommended oral reference doses. The non-carcinogenic risks obtained for both populations were less than one. However, the consumers of T. triangulare and T. occidentalis from the studied locations were exposed to Pb toxicity, with children being more vulnerable. This study has shown that the application of untreated animal wastes and inorganic fertilizers as manures has the potential to affect human health, bioavailability of metals, and the geochemical fractions of metals in soil over time.

Correlations ofr-process elements in very metal-poor stars as clues to their nucleosynthesis sites

Aims.Various nucleosynthesis studies have pointed out that ther-process elements in very metal-poor (VMP) halo stars might have different origins. By means of familiar concepts from statistics (correlations, cluster analysis, and rank tests of elemental abundances), we look for causally correlated elemental abundance patterns and attempt to link them to astrophysical events. Some of these events produce ther-process elements jointly with iron, while others do not have any significant iron contribution. We try to (a) characterize these different types of events by their abundance patterns and (b) identify them among the existing set of suggestedr-process sites.Methods.The Pearson and Spearman correlation coefficients were used in order to investigate correlations amongr-process elements (X,Y) as well as their relation to iron (Fe) in VMP halo stars. We gradually tracked the evolution of those coefficients in terms of the element enrichments [X/Fe] or [X/Y] and the metallicity [Fe/H]. This approach, aided by cluster analysis to find different structures of abundance patterns and rank tests to identify whether several events contributed to the observed pattern, is new and provides deeper insights into the abundances of VMP stars.Results.In the early stage of our Galaxy, at least threer-process nucleosynthesis sites have been active. The first two produce and eject iron and the majority of the lighterr-process elements. We assign them to two different types of core-collapse events, not identical to regular core-collapse supernovae (CCSNe), which produce only light trans-Fe elements. The third category is characterized by a strongr-process and is responsible for the major fraction of the heavy mainr-process elements without a significant coproduction of Fe. It does not appear to be connected to CCSNe, in fact most of the Fe found in the relatedr-process enriched stars must come from previously occurring CCSNe. The existence of actinide boost stars indicates a further division among strongr-process sites. We assign these two strongr-process sites to neutron star mergers without fast black hole formation and to events where the ejecta are dominated by black hole accretion disk outflows. Indications from the lowest-metallicity stars hint at a connection with massive single stars (collapsars) forming black holes in the early Galaxy.

Status of the Coastal Marine Environment in the Southern Red Sea, Yemen, as Reflected by Elements Accumulated in the Skeletons of Scleractinian (Stony) Corals.

The purpose of this study was to assess the level of anthropogenic contamination as well as to collect more data concerning the mineral composition of scleractinian corals from Southern Red Sea, Hodeidah Governorate, Yemen. The mass fractions of 31 elements were determined in the skeleton of nine coral colonies collected in the vicinity of the south-western coast of Yemen. All measurements were conducted by Instrumental Neutron Activation Analysis (INAA). The final results concerning the distribution of considered elements were comparable and, in some cases, inferior to those reported worldwide. The determined mass fractions of V, Cr, Mn, Fe, Ni, and Zn as Presumably Contaminating Elements (PCE) together with the mass fractions of the same elements previously reported in the literature regarding Red Sea Pleistocene corals permitted calculating the individual Contamination Factor (CF) and collective Pollution Load Index (PLI). In spite of high mass fraction values of Mn and Fe in only a few coral colonies, for all investigated places, the PLI values corresponding to studied areas were less than unit, suggesting the investigated areas could be considered as uncontaminated.

Elemental bioavailability in whey protein supplements

Whey protein (WP) as a dietary supplement for athletes and gym-users is characterized by a content of high-quality amino acids. The benefits of their consumption are well-known and mainly related to the improvements of strength and body composition. Nevertheless, there is a scarce information about the risk associated to their elemental composition. The aim was to evaluate the total content and bioavailability of twenty-five elements in twenty whey protein powder samples, using Inductively Coupled Plasma Mass Spectrometry, and to evaluate the possible risk associated to the excessive daily intake of such products. Results showed that Na, K, Ca and Mg were the most predominant elements. After Hierarchical Cluster Analysis three different groups of whey protein supplements were observed. ANOVA analysis indicates that the concentration of the Na, K and Mg above mentioned elements is the key for the observed classification. The average elemental bioavailable fraction in the stomach is 45 % whereas in the intestine is 64 %. Most of the elements tested (nineteen) show gastric bioavailability higher than 60 %, being Al the lowest (37 %) and Co the highest one (76 %). According to our results, previously published data and recommendations of producers, WP samples can be considered save from the elemental composition point of view.

Reference Materials for the Activity Concentration of Technogenic Radionuclides and the Mass Fraction of Elements Based on the Soil Matrix of the Semipalatinsk Test Site

The application of reference materials for the composition and properties of natural objects with certified characteristics is the main instrument for ensuring the correctness of the obtained analytical information in radioecological, geological, and other studies. The article presents the experience of the branch of the Institute of Radiation Safety and Ecology of the National Nuclear Center of the Republic of Kazakhstan in the development and certification of reference materials containing technogenic radionuclides and mass fractions of elements. The soil selected from the sites of underground and surface nuclear tests at the «Experimental field» and «Balapan» sites of the former Semipalatinsk Test Site, which has a diverse radionuclide composition (natural and technogenic radionuclides) with a wide range of chemical elements, was chosen as the starting material for production of reference materials. The main purpose of the work is the certification of two reference materials: reference material for the activity concentration of 137Cs, 90Sr, the mass fraction of Zn, Cu, Pb, Cd, Co, Fe, Mn, As in the soil cover of the Semipalatinsk Test Site (KZ.04.01.00007–2020) and reference material for the activity concentration of 152Eu, 60Co, the mass fraction of Zn, Cu, Pb, Cd, Co, Fe, Mn, As in the soil cover of the Semipalatinsk Test Site (KZ.04.01.00008–2020).All procedures necessary for the creation of reference materials were carried out: separation of the magnetic fraction from the bulk of the material, grinding of the material, control sieve of the material, as well as homogenization with subsequent analytical studies to certify the parameters of reference materials. The methods of gamma spectrometry, beta spectrometry, mass spectrometry, and combined measurement results processing were applied. The results of an interlaboratory comparative test to determine the certified value of the concentrations of the specified radionuclides and elements are given.Reference materials are soil samples dried to an air-dry state, grinded to a particle size of less than 60 µm, and packaged in hermetically sealed polypropylene containers weighing 200 g. Reference materials have been included in the register of the state system for ensuring the uniformity of measurements and approved as state reference materials of the Republic of Kazakhstan. The scope of reference materials is to provide interlaboratory quality control of tests of analytical laboratories specialized in conducting radioecological complex studies, as well as the development and validation of analytical measurement procedures.

Structures and properties of biocompatible Ti-Zr-Nb-Fe-Mo medium entropy alloys

Biomedical implants require high yield strength, low Young's modulus and high ductility synergistic effect. The “stress shielding” caused by the high Young's modulus of most existing high-entropy alloys limited their applications. In this work, a body-centered cubic solid solution Ti45Zr37Nb16Fe1Mo1 (at.%) medium entropy alloy with low Young's modulus (~63 GPa), high tensile elongation (~25 %), and good corrosion resistance (Ecorr = −264 mV, Icorr = 0.15 μA·cm−2) was designed and fabricated. The admissible elastic strain of cold rolled alloy has increased 50% compared with as-cast alloy (~1.12 %). Furthermore, the coefficient of friction of the cold rolled alloy was higher than the as-cast alloy due to the stress-induced orthorhombic α'' martensite formation. Their mechanical properties can be achieved by tuning the fraction of β-stabilizing elements to obtain a metastable single body-centered cubic phase.

Synthesis, characterization and first hydrogen absorption/desorption of the Mg35Al15Ti25V10Zn15 high entropy alloy

In this work, a novel Mg-containing high entropy alloy (HEA), namely Mg35Al15Ti25V10Zn15, was synthesized, characterized, and the phases formed after synthesis and after first hydrogen absorption/desorption were analyzed. The alloy composition was conceptualized aiming at increasing the atomic fraction of lightweight elements (35 at.% Mg and 15 at.% Al) to increase its gravimetric hydrogen storage capacity. Ti and V were selected to increase the hydrogen affinity of the alloy. Finally, Zn was selected as an alloying element because of its negative enthalpy of mixing with Mg, which could favor the formation of solid solution and avoid Mg segregation. The Mg35Al15Ti25V10Zn15 HEA was synthesized by high-energy ball milling (HEBM) in two different routes: under argon atmosphere (mechanical alloying – MA) and under hydrogen pressure (reactive milling – RM). The sample produced by MA was composed of a body-centered cubic (BCC) phase with an amount of unmixed Mg. When hydrogenated at 375 °C and under 4.0 MPa of H2, the MA sample absorbed about 2.5 wt% of H2 by forming a mixture of MgH2, a face-centered cubic (FCC) hydride, a body-centered tetragonal (BCT) phase and MgZn2. The desorption sequence upon heating was investigated and it was shown that the MgH2 is the first to desorb. The sequence of desorption is completed by the decomposition of the FCC hydride and BCT phase leading to the formation of the BCC phase. On the other hand, the alloy produced by RM was composed of a mixture of an FCC hydride and MgH2. During desorption upon heating, the MgH2 is also the first to desorb. At lower temperatures (below 350 °C), the FCC hydride decomposes partially forming the BCT phase. At higher temperatures, both FCC hydride and BCT phase decomposes forming the BCC phase. The desorption capacity of the RM sample was 2.75 wt% H2.

Arsenic-induced response in roots of arsenic-hyperaccumulator fern and soil enzymatic activity changes

In a pot experiment, arsenic-hyperaccumulating Pteris cretica cv. Albo-lineata plant ferns were cultivated and exposed to low and high doses of arsenate (20 and 100 mg As/kg, respectively) for six months. Physiological and morphological changes of roots, as well as changes in soil quality of the root zone and bulk soil (water-soluble fraction of elements and activity of soil enzymes), were determined. The results showed that the accumulation of inorganic As, mainly in the form of As3+, did not significantly affect the yield of roots, but caused changes in root morphology (deformation of root cell walls due to lignification) and metabolism (decrease of auxin indole-3-acetic acid and 2-oxoindole-3-acetic acid contents). Although the soil quality results varied according to the As dose, there was a clear difference between the root zone and the bulk soil. The activities of enzymes in the root zone were greater that those in the bulk soil. The results showed a significant influence of the high dose of As (100 mg As/kg), which decreased the activity of arylsulfatase, nitrate reductase, and urease in the root zone, while a decrease in acid phosphatase and nitrate reductase was observed in the bulk soil. The water-soluble fractions of As, organic nitrogen, nitrate nitrogen and organic carbon were significantly affected by the high dose of As.

Determination of trace elements in placenta by total reflection X-ray fluorescence spectrometry: effects of sampling and sample preparation

Placental elemental composition can serve as an indicator for neonatal health. Medical studies aiming at revealing such cause-and-effect relationships or studies monitoring potential environmental influences consist of large sample series to ensure statistically sufficient data. Several analytical techniques have been used to study trace metals in human placenta. However, most techniques require provision of clear liquid sample solutions and therefore time- and reagent-consuming total digestion of biological tissue is necessary. In total reflection X-ray fluorescence spectrometry (TXRF)—a straightforward multielement analytical technique—in contrast suspensions of minute sample amounts can be analyzed directly. Therefore, herein we report on a valid method to prepare homogenous sample suspensions for sustainable and fast TXRF analysis of large sample series. The optimized method requires only 10 mg of powdered placental tissue and 1 mL nitric acid. Suspensions are readily prepared within 30 min and the found mass fractions of major, minor, and trace elements are in good agreement in comparison to analysis of digests. In addition, possible effects on fixation time and the exact sampling location, i.e., maternal vs. fetal side of the placenta, were studied applying this method. Thereby, significant differences for fetal placenta tissue compared to maternal or intermediate tissue were observed revealing accumulation of trace elements in the fetal side of the placenta. Furthermore, considerable depletion of up to 60% mass fraction with longer fixation duration occurred in particular in fetal placenta tissue. These findings help to understand the large ranges of mass fraction of elements in placenta reported in the literature and at the same time indicate the necessity for more systematic investigation of non-homogenous elements distributed in placenta taking sampling and stabilization methods into account.Graphical

Chemical speciation and source apportionment of ambient PM2.5 in New Delhi before, during, and after the Diwali fireworks

Diwali is among the most important Indian festivals, and elaborate firework displays mark the evening's festivities. This study assesses the impact of Diwali on the concentration, composition, and sources of ambient PM2.5. We observed the total PM2.5 concentrations to rise to 16 times the pre-firework levels, while each of the elemental, organic, and black carbon fractions of ambient PM2.5 increased by a factor of 46.1, 3.7, and 5.6, respectively. The concentration of species like K, Al, Sr, Ba, S, and Bi displayed distinct peaks during the firework event and were identified as tracers. The average concentrations of potential carcinogens, like As, exceeded US EPA screening levels for industrial air by a factor of ∼9.6, while peak levels reached up to 16.1 times the screening levels. The source apportionment study, undertaken using positive matrix factorization, revealed the fireworks to account for 95% of the total elemental PM2.5 during Diwali. The resolved primary organic emissions, too, were enhanced by a factor of ∼8 during Diwali. Delhi has encountered serious haze events following Diwali in recent years; this study highlights that biomass burning emissions rather than the fireworks drive the poor air quality in the days following Diwali.

What We Talk About When We Talk About "Junk DNA".

“Junk DNA” is a popular yet controversial concept that states that organisms carry in their genomes DNA that has no positive impact on their fitness. Nonetheless, biochemical functions have been identified for an increasing fraction of DNA elements traditionally seen as “Junk DNA”. These findings have been interpreted as fundamentally undermining the “Junk DNA” concept. Here, we reinforce previous arguments that this interpretation relies on an inadequate concept of biological function that does not consider the selected effect of a given genomic structure, which is central to the “Junk DNA” concept. Next, we suggest that another (though ignored) confounding factor is that the discussion about biological functions includes two different dimensions: a horizontal, ecological dimension that reflects how a given genomic element affects fitness in a specific time, and a vertical, temporal dimension that reflects how a given genomic element persisted along time. We suggest that “Junk DNA” should be used exclusively relative to the horizontal dimension, while for the vertical dimension, we propose a new term, “Spam DNA”, that reflects the fact that a given genomic element may persist in the genome even if not selected for on their origin. Importantly, these concepts are complementary. An element can be both “Spam DNA” and “Junk DNA”, and “Spam DNA” can also be recruited to perform evolved biological functions, as illustrated in processes of exaptation or constructive neutral evolution.