Bulk Fractions Research Articles

Fire effects on C and H isotopic composition in plant biomass and soil: Bulk and particle size fractions

This work studies carbon (C) and hydrogen (H) isotope composition of plant biomass and soil organic matter (SOM) in an attempt to assess both, changes exerted by fire and possible inputs of charred materials to the soil after a wildfire. Isotope composition of bulk soil, soil particle size fractions and biomass of the dominant standing vegetation in the area (Quercus suber) from Doñana National Park (SW-Spain) were studied by isotope ratio mass spectrometry (IRMS). SOM C isotope composition indicates the occurrence of two SOM pools with different degree of alteration. Coarse soil fractions (>0.5 mm) were found 13C depleted with δ13C values close to those in leaf biomass, pointing to a predominance of poorly transformed SOM. Conversely, fine fractions (<0.1 mm) were found enriched in 13C as corresponds to a more humified SOM. The fire produced no changes in this trend, although a consistent 13C enrichment (c. 1‰) was observed in all soil fractions with decreasing size. Concerning H isotopes, the coarse fractions (>0.5 mm) displayed significant lower δ2H values than the intermediate and fine ones (<0.5 mm), again similar to those in leaf biomass (c. -80‰), whereas the fine fractions were found deuterium (2H)-enriched with significant higher δ2H values (c. 50‰), suggesting physical speciation of H depending on soil particle size. The fire produced a significant 2H depletion (Δ2H c. -10‰) in the finer fractions (<0.1 mm). The study of stable isotope analysis added new information and complements the results obtained by other proxies to better understand the effect of fire on SOM.

NMR Relaxometry and Diffusometry Analysis of Dynamics in Ionic Liquids and Ionogels for Use in Lithium-Ion Batteries.

We have investigated the charge transport dynamics of a novel solid-like electrolyte material based on mixtures of the ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM] TFSI) and various concentrations of lithium salt bis(trifluoromethylsulfonyl)imide (LiTFSI) confined within a SiO2 matrix, prepared via a sol-gel method. The translational diffusion coefficients of BMIM+, TFSI-, and Li+ in ILs and confined ILs (ionogels, IGs) with different concentrations of lithium salt have been measured at variable temperatures, covering the 20-100 °C range, using nuclear magnetic resonance (NMR) pulsed field gradient diffusion spectroscopy. The mobility of BMIM+, TFSI-, and Li+ was found to increase with the [BMIM] TFSI/LiTFSI ratio, exhibiting an almost liquid-like mobility in IGs. Additionally, the effect of confinement on IL rotational dynamics has been analyzed by measuring 1H, 19F, and 7Li spin-lattice relaxation rate dispersions of IGs at different temperatures, using fast field-cycling NMR relaxometry. The analysis of the experimental data was performed assuming the existence of two fractions of the liquid: a bulk fraction (at least several ionic radii from the silica particles) and a surface fraction (close to the silica particles) and using two different models based on translational and rotational diffusion and reorientation mediated by translational displacements. The existence and weighting of these two fractions of ions were obtained from the direct diffusion measurements. The results show that the ion dynamics slowed only modestly under confinement, which evidences that IGs preserve IL transport properties, and this behavior is an encouraging indication for using IGs as a solid electrolyte for Li+ batteries.

Clay mineral assemblages as tracers of fireplaces in Pleistocene archaeological sites (Cueva del Ángel, Spain)

The mineralogical characterization (bulk and clay fraction) of the endokarstic deposit from Cueva del Ángel site, Lucena (Córdoba, Spain) has been carried out. The samples of the surroundings (within an approximate radius of 25 km) and one sample (A-1) from non-archaeological zone in the cave was also studied in order to perform a mineralogical correspondence with the samples of the sedimentary record. Samples of three different profiles and Stratigraphic Units (J/K: Units I, II, III; J/7: Units I, II; 7/8: Unit I) were considered. The mineralogical composition of the samples from the three profiles is similar. Calcite, phyllosilicates and phosphates (mostly apatite group), with minor quartz and dolomite, constitute the mineralogical association of the sediment. The surroundings samples have a similar bulk mineralogical composition than profiles of the sedimentary record, except for the absence of phosphates (associated with the deposit). On the contrary, significant differences were observed in the clay minerals assemblages of the three studied profiles, and also between the Stratigraphic Units. Stratigraphic Unit III of J/K profile and 7/8 profile are dominated by a clay mineral assemblage consisting of smectite, illite and kaolinite. In these samples, the phyllosilicates show a higher degree of ordering, and they are similar to the surroundings samples. The same clay minerals are detected in samples of Stratigraphic Units II of J/7 and J/K profiles (in the last one kaolinite only appears in traces), but the degree of ordering of phyllosilicates is lower. The phyllosilicates present in Stratigraphic Units I from J/K and J/7 profiles exhibited a high degree of degradation, being impossible their identification. This fact could be related to a thermal effect in this zone of the sedimentary record. In fact, X-ray patterns of sample A-1 (located in a non-archaeological zone in the cave) heated to 600 °C and 1000 °C are similar to the XRD of degraded samples from Stratigraphic Units I from J/K and J/7 profiles. SEM study confirms the heating action on phyllosilicates present in some zones of the sedimentary record, where evidences of cracking due to thermal events can be observed on aluminium silicates belonging to Stratigraphic Unit I from J/K and J/7 profiles. Considering the clay mineralogical study, the areas of the sedimentary record affected by fire have been delimited. Therefore, the clay mineralogy study could be used as fireplace tracers in sedimentary records.

Strategies to improve the prediction of bulk soil and fraction organic carbon in Brazilian samples by using an Australian national mid-infrared spectral library

At present, organic carbon (OC) levels are measured using techniques that can be very expensive and time-consuming or can generate toxic residue. Mid-infrared (MIR) spectroscopy, which is an inexpensive and safe technique, can be used for OC prediction; however, appropriate modeling is required. This study aimed to evaluate different strategies for MIR modeling calibration in order to improve the accuracy and cost-effectiveness of OC prediction in bulk soils and fractions (e.g., particulate OC, POC; humic OC, HOC; resistant OC, ROC). We used regional topsoil samples (i.e. 0–20 cm) from Brazil (BRreL) and an existing Australian national library (AUnaL) to calibrate different models, which were used to predict OC content in target samples (i.e. subset of the Brazilian sample set). In total, eight strategies were tested, including the use of different soil libraries, different chemometric approaches (i.e. common multivariate regression and local-type modeling), and spiking. The highest accuracy for OC prediction in Brazilian regional target samples for both bulk soils (RPIQ = 5.86; RMSE = 3.17 g kg−1) and fractions (RPIQ = 1.58, 5.72, and 5.21 for POC, HOC, and ROC, respectively) was obtained when the BRreL was used to calibrate a partial least square regression. When AUnaL was used alone as the calibration set, the OC prediction accuracy sharply decreased and even the local-type models Cubist and spectrum-based learning, in general, were not able to achieve high OC predictions accuracy. With this strategy, the averaged RPIQ values (among the three models) were 2.92, 0.55, 2.17, and 0.65 for bulk OC, POC, HOC, and ROC, respectively. However, when 20 Brazilian regional samples (representing 8 and 42% of the original calibration samples used for total and fraction OC, respectively) were spiked to the AUnaL, the OC predictions accuracy markedly improved for all OC pools, regardless of the modeling approach used. With this strategy, the averaged RPIQ values were 4.74, 1.35, 4.49, and 2.29 for bulk OC, POC, HOC, and ROC, respectively. In addition, high OC prediction accuracy (RPIQ = 4.49 for bulk OC; RPIQ = 1.58, 6.87, and 4.26 for POC, HOC, and ROC, respectively) was obtained when models were calibrated with the 20-spiking subset only. Our results suggest that a proper selection of a small calibration set, that could be used alone or to augment an existing library, is critical and could make feasible the OC prediction in bulk soils and fractions by MIR spectroscopy.

Illite distribution and morphology explaining basinal variations in reservoir properties of Upper Jurassic sandstones, Danish North Sea

Abstract Growth of fibrous illite may destroy an otherwise promising sandstone reservoir, even sandstones characterized by microquartz coatings. Therefore detailed petrographical and diagenetic investigations were performed in order to understand the factors that control illite precipitation and other factors affecting the reservoir properties in the Upper Jurassic Heno Formation. The Heno Formation is encountered in large parts of the Danish Central Graben, where its lower part – the Gert Member – was mainly deposited in back-barrier environments and its upper part – the Ravn Member – was deposited in a shoreface environment. In total, 215 core samples from 15 wells were investigated petrographically by optical and scanning electron microscopy. This was supplemented by plug porosity and permeability measurements and X-ray diffraction of bulk and clay fraction. The investigations show, among other things, that microquartz coatings may help to preserve porosity and permeability, whereas the permeability is reduced when microquartz occurs combined with fibrous illite. Illite precipitation is largely governed by the amounts of K-feldspar present during burial. Consequently, the initial abundance of K-feldspar (in the sediment source area) and its alteration during and immediately after deposition, in particular during subaerial exposure (at sequence boundaries), has a major influence on the final reservoir properties of the sandstones. The risk of illite precipitation can largely be predicted from the available sediment source material, depositional environment and burial depth.

Palladium-Coated Platinum Powders with Tunable, Nanostructured Surfaces for Applications in Catalysis

Simultaneous control of nanoscale surface morphology and composition remains a challenge in preparing bimetallic catalysts, particularly at the large scale required for industrial application and with high-surface-area substrates. Atomic layer electroless deposition (ALED) is a scalable approach to prepare surface-modified metal powders in which elements more noble than the surface hydrides of the substrate metal are deposited layer-by-layer in a surface-limited fashion. Herein we demonstrate that high-surface-area Pt powder is a viable substrate for controlled deposition of Pd adlayers using this technique, with the potential for large-scale preparation, for use in electrocatalytic and catalytic applications such as fuel cells and functionalization of petrochemical feedstocks. Two different growth mechanisms have been proposed based on bulk and surface Pd atomic fractions obtained from atomic absorption spectroscopy and X-ray photoelectron spectroscopy, respectively. Further, spectral simulations were pe...

The Metabolic Enzyme Hexokinase 2 Localizes to the Nucleus in AML and Normal Hematopoietic Stem/Progenitor Cells to Maintain Stemness

Hematopoietic cells are arranged in a hierarchy where mature blood cells arise from stem and progenitor precursors. AML is also hierarchical with differentiated blasts arising from leukemic stem/progenitor cells. Recent studies show that metabolites can affect epigenetic marks; however, it is unknown whether metabolic enzymes can directly localize to the nucleus to regulate stemness in AML and normal hematopoietic cells. Here, we discovered that the mitochondrial enzyme, Hexokinase 2, localizes to the nucleus in AML and normal hematopoietic stem cells to maintain stemness. Metabolic enzymes that localize to nucleus of stem cells were identified by evaluating stem and bulk fractions of OCI-AML-8227 leukemia cells, which are arranged in a hierarchy with functionally defined stem cells. We separated OCI-AML-8227 cells into CD34+38- and CD34-38+ populations by FACS and prepared nuclear and cytoplasmic lysates. Immunoblotting of the lysates revealed that the metabolic enzyme Hexokinase 2 (HK2) was increased in the nuclear fraction of 8227 stem cells compared to bulk cells. In contrast, other mitochondrial enzymes such as Enolase1, Aconitase2, and Succinate Dehydrogenase A &amp; B, were not detected in the nuclear lysates. HK2 is an outer mitochondrial membrane protein that phosphorylates glucose to glucose-6-phosphate, initiating glycolysis. We confirmed nuclear HK2 in OCI-AML-8227 stem cells by confocal microscopy and also demonstrated nuclear HK2 in AML cell lines (OCI-AML2, NB4, K563, and MV411) and in 7 of 9 primary AML samples. We FACS sorted normal cord blood into populations of stem/progenitor (HSC, MPP, MLP, CMP, GMP and MEP) and differentiated (Monocytes, Granulocytes, B, T, and NK) cells. The localization of HK2 in these cells was analysed and quantified by immunofluorescence. Nuclear HK2 was detected in the stem/progenitor cells and progressively declined to minimal levels as cells matured. Next, we explored mechanisms that regulate nuclear localization of HK2. AKT-mediated phosphorylation of HK2 promoted localization to mitochondria while inhibition of phosphorylation increased its nuclear levels. Moreover, the nuclear import of HK2 was dependent on IPO5, a member of b-importin family that imports protein to the nucleus; CRM1 was responsible for HK2 nuclear export. We tested whether the nuclear localization of HK2 was functionally important to maintain stemness. We overexpressed HK2 tagged with nuclear localizing signals (PKKKRKV or PAAKRVKLD) in 8227 and NB4 leukemia cells. Selective overexpression of HK2 in the nucleus did not alter the rate of proliferation of the cells, however there was enhanced clonogenic growth and inhibition of retinoic acid-mediated cell differentiation. Conversely, we selectively reduced nuclear HK2 by expressing HK2 with an outer mitochondrial localization signal while knocking down endogenous HK2 with shRNA targeting the 3'UTR of HK2. Selective depletion of nuclear HK2 in AML cells did not alter growth rate, but did reduce clonogenic growth and increased differentiation after treatment with retinoic acid. To determine whether nuclear HK2 maintains stemness through its kinase activity, we over-expressed a kinase dead double mutant of nuclear HK2(D209A D657A). Nuclear kinase dead HK2 increased clonogenic growth and inhibited differentiation after retinoic acid treatment, demonstrating that HK2 maintains stemness independent of kinase function. To understand nuclear functions of HK2, we used proximity-dependent biotin labeling (BioID) and mass spectrometry to identify proteins that interact with nuclear HK2. A top hit in our screen was Exonuclease 3'-5' domain containing 2 (EXD2), involved in DNA repair. Of note, DNA damage induces differentiation of AML cells. In 8227 cells, nuclear EXD2 was higher in the stem cell fraction compared to the bulk fraction. Moreover, knockdown of EXD2 reduced AML growth, clonogenic growth and decreased nuclear HK2 levels. Finally, nuclear HK2 overexpression conferred resistance to the PARP inhibitor, olaparib. In summary, we discovered that unphosphorylated HK2 localizes to the nucleus in malignant and normal hematopoietic stem cells. Through mechanisms independent of its kinase function, nuclear HK2 maintains AML cells in their stem/progenitor state potentially by regulating DNA damage and repair. Thus, we define a new role for a mitochondrial enzyme in the regulation of stemness and differentiation. Disclosures Minden: Trillium Therapetuics: Other: licensing agreement. Schimmer:Medivir Pharmaceuticals: Research Funding; Otsuka Pharmaceuticals: Consultancy; Novartis Pharmaceuticals: Consultancy; Jazz Pharmaceuticals: Consultancy.

IPO11 Is Upregulated in Relapsed AML and Supports Survival of Leukemic Stem Cells

Patients with relapsed AML (Acute Myeloid Leukemia) have a poor prognosis and few therapeutic options. Therefore, it remains critical to identify biological vulnerabilities in relapsed AML cells. To identify such vulnerabilities, we analyzed mRNA expression by RNA sequencing of 11 paired diagnosis and relapsed AML samples and identified 34 genes that were upregulated at FDR &lt;= 0.01 at relapse. In parallel, we conducted a genome-wide CRISPR screen of 91,320 barcoded gRNA in human OCI-AML2 AML cells and identified 570 genes that reduced growth and viability with a negative FDR (false discovery rate) of 0.01 or less. We then compared the upregulated genes at relapse with the genes necessary for AML growth and viability through the CRISPR screen and identified only one hit, IPO11. IPO11 is a member of the importin-β family of proteins functions that facilitate the import of protein cargo into the nucleus. To date, 10 importin-β family members have been identified, but only IPO11 was upregulated at AML relapse, although, importin β1, TNPO3 AND IPO13 were also hits in the CRISPR screen and necessary for AML growth and viability. Therefore, we focused our study on IPO11. Using independent databases of gene expression, we confirmed that IPO11 mRNA was upregulated in LSC+ (engrafting) vs. LSC- (non-engrafting) samples (rank 125, FDR &lt;=0.05, GSE76008), CD34+ vs CD34- LSC (rank 42, FDR &lt;=0.05, GSE76008) and undifferentiated cluster (M0) vs. myeloid cluster M4/M5 (rank 648, FDR &lt;=0.05, TCGA-LAML). To verify that IPO11 protein was also increased in AML stem cells, we separated 8227 low passage primary AML cells into functionally defined stem (CD34+CD38-) and bulk (CD34-CD38+) fractions. IPO11 protein was only detected in AML stem cells compared to bulk cells as measured by immunoblotting. To determine whether IPO11 is necessary for AML growth and viability, we knocked down IPO11 in OCI-AML2, TEX and NB4 leukemia cells with shRNA in lentiviral vectors. Knockdown of IPO11 induced cell cycle arrest with reduced AML growth and viability by 80-90%. In contrast, knockdown of another importin-β family member, IPO5, that was not a hit in our CRIPSR screen did not reduce AML growth and viability. In addition, we demonstrated that knockdown of IPO11 increased differentiation of AML cells as evidenced by increased CD11b expression and staining with non-specific esterase. Finally, knockdown of IPO11 reduced the clonogeneic growth of the above-mentioned AML cell lines and engraftment of TEX cells and the low passage primary AML sample 8227 cells into immune deficient mice by over 90%. To identify cargos of IPO11 whose nuclear import is necessary for AML survival, we compared IPO11 cargo identified through a Bio-ID mass spectrometry protein-protein interaction screen with hits identified from our CRISPR screen. Through this analysis, we identified 7 hits in common to both screens, including RFC5 (replication fork complex unit 5). RFC5 is an essential DNA polymerase accessory protein, involved in telomere maintenance, DNA replication and mismatch repair. Knockdown of IPO11 decreased the nuclear localization of RFC5 in AML cells. In addition, knockdown of RFC5 in AML cells decreased AML growth and decreased clonogeneic growth. Thus, in summary, comparing genes that are upregulated in paired diagnosis and relapse AML samples to our CRISPR screen we identified IPO11 as a single hit. IPO11 knockdown reduced growth and viability, promoted differentiation, reduced CFU generation of several AML cells lines. In a mouse model we show that IPO11 knockdown dramatically reduced engraftment of leukemic cells. We further identify RFC5, a protein involved in replication and DNA damage response as one of the cargos of IPO11. Our study suggests IPO11 supports LSC survival and relapse and provides a new target for novel therapeutic intervention. Disclosures Schimmer: Otsuka Pharmaceuticals: Consultancy; Medivir Pharmaceuticals: Research Funding; Jazz Pharmaceuticals: Consultancy; Novartis Pharmaceuticals: Consultancy.

Thermodynamic model of fast pyrolysis bio-oil advanced distillation curves

Fast pyrolysis bio-oil (FPBO) is a complex organic liquid with over 1000 organic compounds. Therefore, little research exists on the prediction and modelling of liquid physicochemical properties and vapour-liquid phase behaviour. A thermodynamic model of the FPBO vapour-liquid equilibrium (VLE) in distillation will improve the understanding of bulk and FPBO fraction properties, and therefore, aid in the enhancement of FPBO for desired applications, such as condensation of pyrolysis vapours, fractionation, and evaporation during combustion. FPBO produced at 450 °C from softwood sawmill residues at a feed rate of 4 kg/h (~20 s residence time) in a pilot-scale auger reactor was distilled in an advanced distillation curve (ADC) apparatus at atmospheric pressure and at a vacuum of 5 kPa (abs). The ADC equipment allows for the data collection of true thermodynamic state points, including vapour phase composition data. UNIQUAC was the selected equation of states (EoS) to model FPBO distillation VLEs in a 20–flash series in VMGSim™. A surrogate mixture of water, 3,4,4′-biphenoltriol (pyrolytic lignin), inert solids, and multiple organic components was used to model and predict the VLE and consequently bulk physicochemical properties. It was found that GC-FID composition data (in area%), water content (Karl Fisher titration), distillation residue, and solid content were sufficient to inform the model (surrogate composition). This work improved the understanding of FPBO phase behaviour, composition, and bulk properties. The method allows for the identification of target components and fractions to enhance FPBO quality for desired applications.

Soil organic matter and glomalin-related soil protein contents do not explain soil aggregate stability after freeze-thaw cycles at contrasting soil moisture contents

ABSTRACT Soil organic carbon (SOC) and glomalin-related soil protein (GRSP) contributes to the formation and stability of soil aggregates, but it remains unknown whether the frequency of freeze-thaw cycles (FTCs) and soil moisture content (SMC) at freezing changes aggregate stability and whether SOC and GRSP regulate these changes. Effects of FTCs (0, 1, 3 and 9 times) and initial SMC (40% and 80% field capacity) on aggregate distribution, SOC, and easily extractable, difficultly extractable and total GRSP content in soil aggregates (> 2000 μm, 250–2000 μm, and <250 μm) were evaluated in Chinese pine forest soil. FTCs significantly reduced MWD by disrupting large macro-aggregates. On the other hand, higher SMC increased MWD by binding soil particles, the effect of which was much greater than the disruptive effects of FTCs. SOC in bulk soil and aggregate fractions slightly decreased with the frequency of FTCs. Bulk and aggregate-associated GRSP fractions first decreased, and then increased with the frequency of FTCs. SOC and GRSP fractions correlated insignificantly with MWD. Our results indicated that increasing SMC could augment soil aggregate stability, and that SOC and GRSP might not be the primary control on aggregate stabilization during freeze-thaw conditions in Chinese pine forest soil.

Microbial Diversity in Bulk and Rhizosphere Soil of Ranunculus glacialis Along a High-Alpine Altitudinal Gradient.

Serving as “natural laboratories”, altitudinal gradients can be used to study changes in the distribution of microorganisms in response to changing environmental conditions that typically occur over short geographical distances. Besides, rhizosphere zones of plants are known to be hot-spots for microbial diversity and to contain different microbial communities when compared with surrounding bulk soil. To discriminate the effects of altitude and plants, we investigated the microbial communities in the rhizosphere of Ranunculus glacialis and bulk soil along a high-alpine altitudinal gradient (2,600–3,400 m a.s.l.). The research area of this study was Mount (Mt.) “Schrankogel” in the Central Alps of Tyrol (Austria). Our results point to significantly different microbial diversities and community compositions in the different altitudinal belts. In the case of prokaryotes, environmental parameters could explain 41% of the total variation of soil communities, with pH and temperature being the strongest influencing factors. Comparing the effects derived from fraction (bulk vs. rhizosphere soil) and environmental factors, the effects of the roots of R. glacialis accounted for about one third of the explained variation. Fungal communities on the other hand were nearly exclusively influenced by environmental parameters accounting for 37.4% of the total variation. Both, for altitudinal zones as well as for bulk and rhizosphere fractions a couple of very specific biomarker taxa could be identified. Generally, the patterns of abundance of several taxa did not follow a steady increased or decreased trend along the altitudinal gradient but in many cases a maximal or minimal occurrence was established at mid-altitudes (3,000–3,100 m). This mid-altitudinal zone is a transition zone (the so-called alpine-nival ecotone) between the (lower) alpine grassland/tundra zone and the (upper) sparsely vegetated nival zone and was shown to correspond with the summer snow line. Climate change and the associated increase in temperature will shift this transition zone and thus, might also shift the described microbial patterns and biomarkers.

Diversity, distribution and multi-functional attributes of bacterial communities associated with the rhizosphere and endosphere of timothy (Phleum pratense L.).

To characterize the bacterial communities of the rhizosphere and endosphere of the forage grass timothy (Phleum pratense L.) and evaluate the functional attributes with respect to growth promotion properties, antimicrobial and biosurfactant capacities. A total of 254 culturable bacteria were identified using 16S rRNA sequencing and grouped into 16 taxa that shared high homology of 98-99% with other known sequences. A majority of the isolates were recovered from the rhizosphere soil fraction and leaf and crown tissues. Bacillus genus was the most abundant in the bulk and rhizosphere soil fractions. Isolates belonging to the Methylobacterium genus were exclusively found in leaves making them tissue-specific. A majority of the bacterial isolates exhibited multi-functional growth promotion attributes and plant stress improvement related to the production of indole 3-acetic acid, VOC and siderophores and polymer-degrading enzymes and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activities. Some demonstrated antimicrobial properties such as hydrogen cyanide and biosurfactant production and activities of fungal cell wall degrading enzymes. The internalization and spread of selected bacterial isolates in timothy seedlings under gnotobiotic conditions was confirmed using the culture-dependent method and SEM microscopy in proof-of-concept experiments. The attributes of some isolates with respect to growth promotion abilities, biocontrol potential and efficient colonization of timothy make them desirable for future development as potential biofertilizer tools. This study provides the first evidence of bacterial endophytes that have the necessary functional attributes to protect cool-season forage grasses against abiotic stress.

Maxwell–Stefan diffusion coefficient model derived from entropy generation minimization principle for binary liquid mixtures

A new model for the Maxwell–Stefan (MS) diffusion coefficient was developed in this study. The entropy generation minimization principle was used to derive the expression of the MS diffusion coefficient, which has a similar form as Eyring’s model. Molar excess internal energy based on two-liquid theory was derived to correct the error induced by the linear mixing rule. The local surface area fraction was used to replace the bulk fraction by considering the intermolecular friction force exerting on the molecular surfaces. The new model was applied to calculate the Fick diffusion coefficients for four binary systems, which were measured experimentally by digital holographic interferometry. Comparison of the experimental and calculation results indicated that the proposed model has a good performance for calculating the diffusion coefficients for the mentioned binary systems.

Millennial-scale evolution of elemental ratios in bulk sediments from the western Philippine Sea and implications for chemical weathering in Luzon since the Last Glacial Maximum

To reconstruct the chemical weathering history in Luzon, Philippines, since the Last Glacial Maximum (LGM), major and trace elements (Ti, Al, Fe, K, Ba, Rb, V, Sc, Cr, and Th) and grain size were determined for core MD06-3054 as well as the bulk and detrital fractions of three core-top samples from the western Philippine Sea (WPS). In combination with previously published Sr-Nd isotopes, our new results indicate that Ti-normalized elemental ratios in the study samples were not controlled by the quantity of biogenic, authigenic, or diagenetic materials, sediment provenance, or grain size. Instead, variations in Ti-normalized elemental ratios mainly reflect changes in chemical weathering intensity, with lower values representing stronger chemical weathering in Luzon. To assess long-term integrated chemical weathering patterns, we defined a stacked chemical weathering index (SCWI) based on all elemental ratios in the study core. Downcore SCWI records indicate that sediments deposited during the LGM underwent a degree of chemical weathering equal to that during the Holocene, and sediments deposited during the last deglaciation exhibit rapid changes in chemical weathering, with higher intensity during the Heinrich event 1 (H1) and Younger Dryas (YD), and lower intensity during the Bølling-Allerød (B/A) in the WPS. These observations are in excellent agreement with chemical weathering proxies, such as the K/Al ratios and chemical index of alteration when applied to the same core. We infer that persistent sea-level lowstand and induced reworking of poorly consolidated sediments on the eastern Luzon continental shelf during the LGM accounted for equal or slightly stronger chemical weathering for the LGM sediments relative to the Holocene sediments. Rainfall, rather than air temperature, in Luzon was responsible for the rapid changes in chemical weathering during the last deglaciation, with higher precipitation generating stronger chemical weathering during the H1 and YD than during the B/A. Our observations, combined with existing data, suggest that strong weathering of marine sediments during colder intervals of the middle–late Quaternary is likely to be a general feature of the tropical West Pacific, although the mechanism that underlies this phenomenon remains controversial.

Geochemical investigations in bulk and clay size fractions from lower Krishna river sediments, southern India: implications of elemental fractionation during weathering, transportation and deposition

Major and trace elements, including rare earth elements (REEs) geochemistry of bed sediments from the lower reaches of Krishna river suggest their origin mainly from weathering of Deccan basalts and Precambrian rocks of the southern India. The elemental compositions indicate evidence of sedimentary sorting during weathering, transportation and deposition. Highly depleted Na2O and high values of Chemical Index of Alteration (CIA) are suggestive of moderate to strong chemical weathering environment in lower reaches of Krishna river. Major, trace and REE concentrations of bulk sediments suggest marginal variations in relative contribution from mafic and felsic minerals. The bed sediments contain significantly low concentrations of trace elements like Ba, Sr, La, Ce and Nd and moderately low concentrations of V, Zr, Rb, Zn, Ni and Cr relative to upper continental crust (UCC) composition. Most of the other trace elements and REEs are almost similar to UCC indicating their origin from weathering of mixed rock types in catchment areas of Krishna river. Strong relationships of ΣREEs with Ti and Zr in bed sediments suggest that REEs are mainly controlled by heavy minerals such as titanite and zircon. A marked increase in REEs in clay fractions of sediments indicates their adsorption and/or substitution on clay lattice.

Detrital record of the denudation of volcanic islands under sub-tropical climate (Cape Verde)

This research is focused on the composition of the sediments produced in volcanic islands when the climate does not favour weathering. The XRD mineralogy (bulk sample and fraction finer than 63 μm), petrography and geochemistry of a set of bedload stream and beach samples collected in the “old” Maio and the “young” Fogo islands of Cape Verde archipelago are used to investigate the compositional transformations promoted by exogenous processes during island denudation. The main factor responsible for the variability in sediment composition is the incorporation of biogenic material derived from the evolving shelves; it largely exceeds the effects of the exhumation of different volcanic and basement units. Given the arid climate (and steep land surface in Fogo), only the most labile components of basaltic rocks, such as volcanic glass, are decomposed. The incipient weathering and sorting processes are responsible for the depletion of Al in bedload deposits. The same happens with other elements usually regarded as non-mobile (namely, Nb, Th, REE, etc.), while Mg is concentrated. Thus, weathering indices grounded on the premise that “mobile” elements are lost and “non-mobile” elements are enriched via weathering are useless in Cape Verde bedload sediments. With time, weathering is able to promote Na leaching and the formation of secondary minerals, which tend to retain non-mobile elements released in the earlier stages of alteration (e.g., LREE, Th, Y, Nb, Ta etc.). Sorting processes are responsible for the selective removal of less-dense grains, explaining local differences between beach and stream deposits. Beach placers are enriched in augitic clinopyroxene (occasionally also in olivine in the Fogo island), and Sc, Cr and Co. Niobium and Ta must be hosted in fine-grained particles that are easily windblown and their abundances in dusts may reveal Cape Verde as a source of airborne material crossing the Atlantic Ocean.

Carbonate drifts as marine archives of aeolian dust (Santaren Channel, Bahamas)

AbstractSediment data from the Bahamian Santaren carbonate drift reveal the variability of trans‐Atlantic Saharan dust transport back to about 100 ka bp (Marine Isotope Stage 5·3) and demonstrate that carbonate drifts are a valuable pelagic archive of aeolian dust flux. Carbonate drift bodies are common around tropical carbonate platforms; they represent large‐scale accumulations of ocean‐current transported material, which originates from the adjacent shallow‐water carbonate factory as well as from pelagic production, i.e. periplatform ooze. Subordinately, there is a clay‐size to silt‐size non‐carbonate fraction, which typically amounts to less than 10% of the sediment volume and originates from aeolian and fluvial input. Sedimentation rates in the 5·42 m long core GeoHH‐M95‐524 recovered 25 km west of Great Bahama Bank in the Santaren Channel ranges from 1·5 to 24·5 cm ka−1 with lowest values during the last glacial lowstand and highest values following platform re‐flooding around 8 ka bp. These sedimentation rates imply that carbonate drifts have not only the potential to resolve long‐term environmental changes on orbital timescales, but also millennial to centennial fluctuations during interglacials. The sediment core has been investigated with the aim of characterizing the lithogenic dust fraction. Laboratory analyses included X‐ray fluorescence core scanning, determination of carbonate content and grain‐size analyses (of bulk and terrigenous fraction), as well as visual inspections of the lithogenic residue; the age model is based on oxygen isotopes and radiocarbon ages. Data show that the input of aeolian dust in the periplatform ooze as indicated by Ti/Al and Fe/Al element ratios abruptly increases at 57 ka bp, stays elevated during glacial times, and reaches a Holocene minimum around 6·5 ka bp, contemporary to the African Humid Period. Subsequently, there is a gradual increase in dust flux which almost reaches glacial levels during the last centuries. Grain‐size data show that the majority of dust particles fall into the fine silt range (below 10 μm); however, there is a pronounced coarse dust fraction in the size range up to 63 μm and individual ‘giant’ dust particles are up to 515 μm in size. Total dust flux and the relative amounts of fine and coarse dust are decoupled. The time‐variable composition of the grain‐size spectrum is interpreted to reflect different dust transport mechanisms: fine dust particles are delivered by the trade winds and the geostrophic winds of the Saharan Air Layer, whereas coarse dust particles travel with convective storm systems. This mode of transport ensures continuous re‐suspension of large particles and results in a prolonged transport. In this context, grain‐size data from the terrigenous fraction of carbonate drifts provide a measure for past coarse dust transport, and consequently for the frequency of convective storm systems over the dust source areas and the tropical Atlantic.

Trace metals and PAHs in topsoils of the University campus in the megacity of São Paulo, Brazil.

The aim of this study is to discuss the concentration distribution, composition and possible sources of trace metals and 13 PAHs in topsoils of the University campus, in the city of São Paulo, the largest city of South America. Mineralogy and granulometry of topsoils (0-10 cm) samples, were determined and As, Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, Sb, V, Zn, Hg, Pt, Pd and PAHs concentrations were quantified in the bulk fraction. The average clay content of soils was 221±61.8 g kg-1 and total carbon was low (mean of 25 g kg-1). Concentrations of metals were generally lower than the reference value established by the São Paulo State Environmental Agency and other studies in the São Paulo urban area, except for Cd, Ni, Pb, Cr and Zn. The mean concentration of the sum of 13 PAHs was 0.33 mg kg-1 and fluorene, indeno(1,2,3-cd)pyrene, anthracene, pyrene and benzo(ghi)perylene were the most abundant compounds. PAHs and trace metals variability were constrained in PMF analysis and showed an association with exhaust and non-exhaust vehicular emissions. The results also pointed out a spatial pattern in the campus area related to traffic conditions and intensity and terrain slope.

Paleoenvironmental considerations based on geochemistry and mineralogy of a Miocene lacustrine calcrete, southern Portugal

A lacustrine carbonate facies has been investigated in Middle Miocene successions of the western side of the Moura-Marmelar basin, Southern Portugal in order to evaluate paleoenvironments in which carbonates formed, by using geochemistry and mineralogy. The studied formation corresponds to a recent unearthed section of a calcrete with an homogeneous carbonate facies comprising fine, whitish, and powdery material, and the only detected difference is a slightly hardness decrease towards the top, as well as an increase of weathered rock fragments (schist). The calcrete is calcium rich, even some magnesium enrichment was observed at the middle level, which is differentiated by a general depletion of all chemical elements, particularly REE, in both the bulk and clay-size fraction. Regarding the mineralogy, calcite prevails, and dolomite is only present in the middle level of the calcrete, together with a smectite enrichment, suggesting changes to more alkaline and low drainage, lacustrine and arid to semi-arid conditions.

The Metabolic Enzyme Hexokinase 2 Localizes to the Nucleus in AML and Normal Hematopoietic Stem/Progenitor Cells to Maintain Stemness

Hematopoietic cells are arranged in a hierarchy where stem and progenitor cells differentiate into mature blood cells. Likewise, AML (Acute Myeloid Leukemia) is also hierarchical with leukemic stem and progenitor cells giving rise to more mature and differentiated blasts. Recent studies have shown that mitochondrial enzymes such as IDH2 can regulate AML stemness by altering metabolites that affect epigenetic marks. However, it is unknown whether mitochondrial metabolic enzymes can directly localize to the nucleus to regulate stemness in AML and normal hematopoietic cells. Here, we show that the mitochondrial enzyme, Hexokinase 2, localizes to the nucleus in AML and normal hematopoietic stem cells to maintain stemness.We sought to identify mitochondrial metabolic enzymes that localize to the nucleus of stem cells, by evaluating the stem and bulk fractions from 8227 leukemia cells. 8227 leukemia cells are arranged in a hierarchy with functionally defined stem cells present in the CD34+CD38- fraction. We separated 8227 cells into CD34+CD38- and CD34-CD38+ populations by FACS sorting and prepared lysates of the nuclear and cytoplasmic fractions from each population. Using immunoblotting, we measured levels of mitochondrial enzymes in the subcellular fractions of each population. We discovered that the metabolic enzyme Hexokinase 2 (HK2) was increased in the nuclear fraction of 8227 stem cells compared to bulk cells. In contrast, other mitochondrial enzymes such as Aconitase 2 and Succinate Dehydrogenase B were not detected in the nuclear fractions. HK2 is an outer mitochondrial membrane protein that phosphorylates glucose to glucose-6-phosphate, thereby initiating glycolysis and the entry of glucose metabolites into the TCA cycle in the mitochondria. The nuclear localization of HK2 in mammalian cells has not been previous reported. We confirmed that 8227 cells have nuclear HK2 by confocal fluorescent microscopy and also demonstrated nuclear HK2 in AML cell lines (OCI-AML2, NB4, K562, and MV411) and primary AML samples.We also FACS sorted normal cord blood into populations of stem/progenitor (HSC, MPP, MLP, CMP, GMP and MEP) and differentiated (B cells, T cells, NK cells, Monocytes and Granulocytes) cells. The localization of HK2 in these cell fractions was measured by immunofluorescence and quantified by Metamorph and Imaris. Nuclear HK2 was detected in the stem/progenitor cells and progressively declined to minimal levels as the cells matured (Fig 1A).The mitochondrial localization of HK2 is dependent on AKT-mediated phosphorylation of Thr-473 and inhibited by dephosphorylation by the phosphatase PHLPP1. We asked whether phosphorylation of HK2 regulates the nuclear abundance of HK2. Using AML2 cells, we showed that knockdown of PHLPP1 decreased the abundance of nuclear HK2, while inhibition of AKT increased HK2 in the nucleus.Finally, we tested whether the nuclear localization of HK2 was functionally important to maintain stemness. We over-expressed HK2 tagged with nuclear localizing signals (PKKKRKV and PAAKRVKLD) in 8227 and NB4 leukemia cells. We confirmed the selective over-expression of HK2 in the nucleus of these cells by immunoblotting and immunofluorescence. Increasing nuclear HK2 did not alter the proliferation of the cells under basal conditions. However, increasing nuclear HK2 enhanced clonogenic growth and blocked retinoic acid-mediated cell differentiation.In summary, we discovered that the unphosphorylated form of the metabolic enzyme HK2 localizes to the nucleus in malignant and normal hematopoietic stem cells and is functionally important to maintain stem/progenitor state. Thus, we define a new role for mitochondrial enzymes in the regulation of stemness and differentiation. [Display omitted] DisclosuresSchimmer:Medivir AB: Research Funding; Jazz Pharmaceuticals: Consultancy; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Otsuka Pharmaceuticals: Consultancy.