Differential Sedimentation Research Articles

Quantification of the hetero-contact formation process for a CuO/CeO2 hetero-aggregate model system prepared by double flame spray pyrolysis

In hetero-aggregates, different materials form sintered hetero-contacts, which lead to new material properties. In this study, the influence of process parameters on the formation of hetero-contacts in Double Flame Spray Pyrolysis (DFSP) was quantified. The mixing of jets was monitored by Particle Image Velocimetry (PIV) measurements as well as by thermocouples and compared to the single flame setting. Overlap of the jets was evaluated using tracers to visualize the mixing zone. Ten CuO/CeO2 model material samples were prepared with different flame inclination angles, nozzle distances and different particle volume fractions. Mixing on hetero-aggregate level was quantified using Convolutional Neural Network (CNN) evaluations of STEM images, Temperature-Programmed Reduction (TPR) and Differential Centrifugal Sedimentation (DCS) disk centrifugation to determine cluster sizes and hetero-coordination numbers as mixing quantifiers. Here, good correlations between the differently measured quantifiers were observed.

Conversion of Ultrasmall Glutathione-Coated Silver Nanoparticles during Dispersion in Water into Ultrasmall Silver Sulfide Nanoparticles.

Ultrasmall silver nanoparticles (2 nm) were prepared by reduction with sodium borohydride (NaBH4) and stabilized by the ligand glutathione (a tripeptide: glycine-cysteine-glutamic acid). NMR spectroscopy and optical spectroscopy (UV and fluorescence) revealed that these particles initially consist of silver nanoparticles and fluorescing silver nanoclusters, both stabilized by glutathione. Over time, the silver nanoclusters disappear and only the silver nanoparticles remain. Furthermore, the capping ligand glutathione eliminates hydrogen sulfide (H2S) from the central cysteine and is released from the nanoparticle surface as tripeptide glycine-dehydroalanine-glutamic acid. Hydrogen sulfide reacts with the silver core to form silver sulfide. After four weeks in dispersion at 4 °C, this process is completed. These processes cannot be detected by transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), or differential centrifugal sedimentation (DCS) as these methods cannot resolve the mixture of nanoparticles and nanoclusters or the nature of the nanoparticle core. X-ray photoelectron spectroscopy showed the mostly oxidized state of the silver nanoparticle core, Ag(+I), both in freshly prepared and in aged silver nanoparticles. These results demonstrate that ultrasmall nanoparticles can undergo unnoticed changes that considerably affect their chemical, physical, and biological properties. In particular, freshly prepared ultrasmall silver nanoparticles are much more toxic against cells and bacteria than aged particles because of the presence of the silver clusters.

Quantitative evaluation of particle–binder interactions in ceramic slurries via differential centrifugal sedimentation

In diverse materials science spanning from fine ceramics to lithium-ion batteries and fuel cells, the particle–binder interactions in slurries play a crucial role in governing the ultimate performance. Despite numerous efforts to date, quantitatively elucidating these hidden interactions has remained a longstanding challenge. Here, we demonstrate a dynamic approach to evaluate adsorptive interactions between ceramic particles and polymeric binders entangled in a slurry utilizing differential centrifugal sedimentation (DCS). Particles settling under a centrifugal force field impart significant viscous resistance on the adsorbed binder, leading to its detachment, influenced by particle size and density. This behaviour directly reflects the particle–binder interactions, and detailed DCS spectrum analysis enables the quantitative assessment of nano-Newton-order adsorption forces. An important finding is the strong correlation of these forces with the mechanical properties of the moulded products. Our results provide insight that forming a flexible network structure with appropriate interactions is essential for desirable formability.

Value of proprotein convertase subtilisin/kexin type 9 and inflammatory markers in the diagnosis of carotid atherosclerosis in hypertensive men

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is involved in lipid metabolism, has local and systemic effects in immunoregulation and atherogenesis in hypertensive patients.Aim. To personalize cardiovascular risk (CVR) stratification taking into account the diagnostic value of PCSK9 and inflammatory markers in men with hypertension and carotid atherosclerosis.Material and methods. The study included 162 males with stage I-III hypertension of various CVR. All patients underwent collection of complaints and medical history, physical examination with anthropometry. The following laboratory test were performed: complete blood count with white blood cell differential and erythrocyte sedimentation rate, assessment of fibrinogen, C-reactive protein (CRP), total cholesterol, low-density lipoprotein cholesterol, triglycerides, blood glucose, serum creatinine level. Glomerular filtration rate and microalbuminuria were also evaluated. Serum PCSK9, interleukins-8, 10 (IL-8, 10) were determined by enzyme immunoassay. In addition, 24-hour blood pressure monitoring, extracranial artery ultrasound with determination of intima-media thickness and carotid stenosis severity were performed. Patients were divided into 3 groups according to PCSK9 level.Results. Analysis of conventional cardiovascular factors and cytokine status (IL-8 and IL-10) in patients showed an inverse relationship between age and IL-8 (r=-0,230; p=0,036), IL-8/IL-10 (r=-0,309; p=0,005); heredity and IL-8/IL-10 (r=-0,423; p=0,001). There were following relationships between CVR factors and PCSK9: direct relationship between men's age (r=0,220, p=0,032), systolic and diastolic blood pressure (r=0,230, p=0,033; r=0,260, p=0,015) and PCSK9; inverse relationship between PCSK9 and heredity (r=-0,286, p=0,011). C-reactive protein and erythrocyte sedimentation rate were associated with IL-10 levels, which are associated with anti-inflammatory activity (r=0,78; p=0,02; r=0,78; p=0,02, respectively). The IL-8/IL-10 cytokine imbalance was most pronounced in patients with a night-peaker 24-hour systolic blood pressure profile (p=0,02). Patients with intima-media thickening and plaques had a highest level of PCSK9 (p=0,006). IL-8 levels were significantly higher with unchanged intima-media thickness (p=0,01).Conclusion. In patients with high levels of PCSK9, there is a close relationship between risk factors for hypertension and cytokine imbalance. The severity of extra­cranial artery atherosclerosis significantly depends on the increase in the levels of PCSK9 (p=0,006) and inflammatory markers (IL-10) (p=0,044).

Increased Cytotoxicity of Bimetallic Ultrasmall Silver-Platinum Nanoparticles (2 nm) on Cells and Bacteria in Comparison to Silver Nanoparticles of the Same Size.

Ultrasmall nanoparticles (diameter 2 nm) of silver, platinum, and bimetallic nanoparticles (molar ratio of Ag:Pt 0:100; 20:80; 50:50; 70:30; 100:0), stabilized by the thiolated ligand glutathione, were prepared and characterized by transmission electron microscopy, differential centrifugal sedimentation, X-ray photoelectron spectroscopy, small-angle X-ray scattering, X-ray powder diffraction, and NMR spectroscopy in aqueous dispersion. Gold nanoparticles of the same size were prepared as control. The particles were fluorescently labeled by conjugation of the dye AlexaFluor-647 via copper-catalyzed azide-alkyne cycloaddition after converting amine groups of glutathione into azide groups. All nanoparticles were well taken up by HeLa cells. The cytotoxicity was assessed with an MTT test on HeLa cells and minimal inhibitory concentration (MIC) tests on the bacteria Escherichia coli and Staphylococcus xylosus. Notably, bimetallic AgPt nanoparticles had a higher cytotoxicity against cells and bacteria than monometallic silver nanoparticles or a physical mixture of silver and platinum nanoparticles. However, the measured release of silver ions from monometallic and bimetallic silver nanoparticles in water was very low despite the ultrasmall size and the associated high specific surface area. This is probably due to the surface protection by a dense layer of thiolated ligand glutathione. Thus, the enhanced cytotoxicity of bimetallic AgPt nanoparticles is caused by the biological environment in cell culture media, together with a polarization of silver by platinum.

Long-read subcellular fractionation and sequencing reveals the translational fate of full-length mRNA isoforms during neuronal differentiation.

Alternative splicing (AS) alters the cis-regulatory landscape of mRNA isoforms, leading to transcripts with distinct localization, stability, and translational efficiency. To rigorously investigate mRNA isoform-specific ribosome association, we generated subcellular fractionation and sequencing (Frac-seq) libraries using both conventional short reads and long reads from human embryonic stem cells (ESCs) and neural progenitor cells (NPCs) derived from the same ESCs. We performed de novo transcriptome assembly from high-confidence long reads from cytosolic, monosomal, light, and heavy polyribosomal fractions and quantified their abundance using short reads from their respective subcellular fractions. Thousands of transcripts in each cell type exhibited association with particular subcellular fractions relative to the cytosol. Of the multi-isoform genes, 27% and 19% exhibited significant differential isoform sedimentation in ESCs and NPCs, respectively. Alternative promoter usage and internal exon skipping accounted for the majority of differences between isoforms from the same gene. Random forest classifiers implicated coding sequence (CDS) and untranslated region (UTR) lengths as important determinants of isoform-specific sedimentation profiles, and motif analyses reveal potential cell type-specific and subcellular fraction-associated RNA-binding protein signatures. Taken together, our data demonstrate that alternative mRNA processing within the CDS and UTRs impacts the translational control of mRNA isoforms during stem cell differentiation, and highlight the utility of using a novel long-read sequencing-based method to study translational control.

Geochemical characteristics and hydrocarbon generation modeling of the Paleogene source rocks in the Qinnan Depression, Bohai Bay Basin, China

Introduction: The Qinnan Depression in the Bohai Bay Basin is lowly explored, where hydrocarbon generation potential of source rocks is required detailed investigation to identify hydrocarbon exploration potential and direction.Methods: This study is based on organic geochemical analysis performed on the Paleogene source rocks. After that, the burial, thermal maturity, and hydrocarbon generation histories of the Paleogene source rocks at various sags were reconstructed on BasinMod software based on reasonable geological models and geological parameters derived from geological analogy.Results: Results show that the 3rd member (Es3) and 1st member (Es1) of the Eocene Shahejie Formation are high-quality source rocks with a mixture of type I and II kerogen, whose organic matter was originated from aquatic organisms under a reducing environment. The 3rd member (Ed3) of the Oligocene Dongying Formation are fair-quality source rocks with type II kerogen and are dominated by mixed organic matter depositing in a weakly reducing environment. Clear differences in hydrocarbon generation were observed in these three source rocks owing to differential subsidence and sedimentation among the Eastern, Southeastern, and Western sags. Source rocks at the Eastern Sag were maturated early and lasted for a long time, which were currently at late mature (1.0–1.3%Ro) to high mature (1.3–2.0%Ro) stages. Two hydrocarbon generation events occurred in the Oligocene and Miocene, respectively, with intensive hydrocarbon generation capacity. Source rocks at the Southeastern Sag were maturated late and lasted for a short period, which were currently at a medium mature (0.7–1.0%Ro) stage. The major hydrocarbon generation event had occurred since the late Miocene, with intensive hydrocarbon generation capacity. Source rocks at the Western Sag were at an early mature (0.5–0.7%Ro) stage and began to generate hydrocarbon in the Pliocene, with weak hydrocarbon generation capacity. The hydrocarbon generation capacity of the Paleogene source rocks is as follows: Es3>Es1>Ed3.Discussion: The Qinnan Depression has high oil and gas exploration potential, where exploration activities should focus on effective traps around depression and slope zones located at the Eastern and Southeastern sags.

The Molecular Footprint of Peptides on the Surface of Ultrasmall Gold Nanoparticles (2 nm) Is Governed by Steric Demand.

Ultrasmall gold nanoparticles were functionalized with peptides of two to seven amino acids that contained one cysteine molecule as anchor via a thiol-gold bond and a number of alanine residues as nonbinding amino acid. The cysteine was located either in the center of the molecule or at the end (C-terminus). For comparison, gold nanoparticles were also functionalized with cysteine alone. The particles were characterized by UV spectroscopy, differential centrifugal sedimentation (DCS), high-resolution transmission electron microscopy (HRTEM), and small-angle X-ray scattering (SAXS). This confirmed the uniform metal core (2 nm diameter). The hydrodynamic diameter was probed by 1H-DOSY NMR spectroscopy and showed an increase in thickness of the hydrated peptide layer with increasing peptide size (up to 1.4 nm for heptapeptides; 0.20 nm per amino acid in the peptide). 1H NMR spectroscopy of water-dispersed nanoparticles showed the integrity of the peptides and the effect of the metal core on the peptide. Notably, the NMR signals were very broad near the metal surface and became increasingly narrow in a distance. In particular, the methyl groups of alanine can be used as probe for the resolution of the NMR spectra. The number of peptide ligands on each nanoparticle was determined using quantitative 1H NMR spectroscopy. It decreased with increasing peptide length from about 100 for a dipeptide to about 12 for a heptapeptide, resulting in an increase of the molecular footprint from about 0.1 to 1.1 nm2.

The influence of lithospheric inheritance and Cenozoic magmatism on Phanerozoic rock cooling in the São Francisco Craton and adjacent orogens

The South American Platform encompasses the São Francisco Craton (SFC) and the Araçuaí-Ribeira orogenic system (AROS) located in the eastern Brazil. These geologic domains hold records of differential exhumation, sedimentation, volcanic activity, and post-rift reactivation of faults and shear zones. Therefore, these terranes provide outstanding opportunities for studying the dynamics of lithospheric processes, particularly in their interaction zones, characterized by the transition from cratonic to orogenic lithosphere. To investigate the processes involved in the contrasting behavior of the upper crust, we provide 23 new apatite fission track (AFT) ages and thermal histories from the northern segment of the AROS and from the eastern area of the SFC. The AFT ages range from 154.4 ± 20.1 and 37.1 ± 3.0 Ma and the mean track lengths range from 10.9 and 13.2 μm. We compiled thermal information from previous thermochronological analysis from 357 sites and constructed inverse distance weighted maps that depict the spatial distribution of AFT ages and the temperature evolution from 360 to 30 Ma. The results indicate that the SFC experienced its final exhumation within the apatite partial annealing zone (APAZ) at temperatures ranging from 110 °C to 60 °C during the late Paleozoic. In contrast, the AROS went through its last cooling within the APAZ during the Mesozoic or even in the Cenozoic. This suggests that reactivation and reheating, possibly associated with the South Atlantic rift, influenced the orogenic basement of the passive margin. We highlight that the reheating associated to the Abrolhos magmatic province in the northern segment of the AROS caused the youngest AFT ages of the study area. Our work demonstrates the importance of considering contrasting rheology when analyzing regional exhumation patterns, the structural fabric of orogens through reactivation of crustal discontinuities generating heating and exhumation, and how volcanism can disrupt the thermal record, inducing crustal reheating.

Improved Characterization of Aqueous Single-Walled Carbon Nanotube Dispersions Using Dynamic Light Scattering and Analytical Centrifuge Methods.

Aqueous dispersions of single-walled carbon nanotubes (SWCNTs) with a surfactant were studied by using a combination of differential sedimentation and dynamic light scattering methods. When applied to elongated particles like SWCNTs, the differential sedimentation method makes it possible to measure their diameters in dispersions, while the dynamic light scattering method allows to measure their lengths. Both methods have logarithmic dependence on the ratio between the length and diameter of the particles, and their simultaneous use improves the accuracy of measuring particles' dimensions. It was shown that sonication of dispersions leads not only to unbundling of agglomerates into individual nanotubes but also to a decrease in their lengths and the appearance of new defects detectable in increasing the D/G ratio in the Raman spectra. Unbundling into individual nanotubes occurs after exposure to 1 kWh/L energy density, and the single nanotube diameter with SDBS is ca. 3.3 nm larger than that of the naked nanotubes. Conductivity of thin SWCNT films made out of individual nanotubes demonstrates a power law dependence with the exponent close to the theoretical one for rigid rods.

Ultrastructure and Surface Composition of Glutathione-Terminated Ultrasmall Silver, Gold, Platinum, and Alloyed Silver-Platinum Nanoparticles (2 nm).

Alloyed ultrasmall silver-platinum nanoparticles (molar ratio Ag:Pt = 50:50) were prepared and compared to pure silver, platinum, and gold nanoparticles, all with a metallic core diameter of 2 nm. They were surface-stabilized by a layer of glutathione (GSH). A comprehensive characterization by high-resolution transmission electron microscopy (HRTEM), electron diffraction (ED), X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), differential centrifugal sedimentation (DCS), and UV spectroscopy showed their size both in the dry and in the water-dispersed state (hydrodynamic diameter). Solution NMR spectroscopy (1H, 13C, COSY, HSQC, HMBC, and DOSY) showed the nature of the glutathione shell including the number of GSH ligands on each nanoparticle (about 200 with a molecular footprint of 0.063 nm2 each). It furthermore showed that there are at least two different positions for the GSH ligand on the gold nanoparticle surface. Platinum strongly reduced the resolution of the NMR spectra compared to silver and gold, also in the alloyed nanoparticles. X-ray photoelectron spectroscopy (XPS) showed that silver, platinum, and silver-platinum particles were at least partially oxidized to Ag(+I) and Pt(+II), whereas the gold nanoparticles showed no sign of oxidation. Platinum and gold nanoparticles were well crystalline but twinned (fcc lattice) despite the small particle size. Silver was crystalline in electron diffraction but not in X-ray diffraction. Alloyed silver-platinum nanoparticles were almost fully amorphous by both methods, indicating a considerable internal disorder.

The Efficacy and Safety of Adding Chlorpromazine to Atazanavir/Ritonavir Regimen in the Treatment of Moderate COVID-19 Patients, a Randomized Double-blind Clinical Trial

Background: According to COVID-19 mutation and no defined treatment, it is necessary to find effective treatment. Chlorpromazine, a phenothiazine antipsychotic drug, has been shown in animal studies to have antiviral effects by inhibiting clathrin-mediated endocytosis. The aim of this study was to evaluate the effectiveness of adding chlorpromazine to the atazanavir/ritonavir regimen in the treatment of moderate COVID-19 patients. Methods: In this randomized double-blind clinical trial, sixty hospitalized patients with moderate COVID-19 confirmed by CT findings or polymerase chain reaction (PCR) were enrolled. All patients received atazanavir/ritonavir 300mg/100mg once daily. In two parallel groups, chlorpromazine 25 mg three times a day or a placebo was administered for up to 14 days. Complete blood count with differential, C-reactive protein (CRP), liver enzymes, and erythrocyte sedimentation rate was measured on days 1, 3, 5, 7, and 10. The primary outcome was the improvement of oxygen saturation and the secondary outcome was the duration of hospitalization and conversion of PCR test results. Results: Oxygen saturation during the hospitalization was not different among the two groups. The mean duration of hospitalization in the chlorpromazine group was 7.4±2.7 days and in the placebo was 8.2±3 days (P=0.2). Compared to baseline, both groups showed an increase in white blood cell count (P=0.04) and polymorphonuclear cells (P=0.04) but lymphocyte count decreased. At the end of the study, the PCR test was negative in 100% of patients in the chlorpromazine group and 95% of patients in the placebo group. Conclusion: In adult hospitalized patients with moderate symptomatic COVID-19, adding chlorpromazine to the atazanavir/ritonavir regimen did not improve outcomes.

A mini review on manipulation of carbohydrate for better use in surimi and surimi products: modification and compounding.

Carbohydrate is widely used in the production of surimi and surimi products to improve their qualities, such as anti-freezing capability, gelling ability, nutrition, flavor and 3D printability. More and more native carbohydrates have been modified through physical methods (e.g., ball milling, irradiation and differential sedimentation), chemical method (e.g., deacetylation, hydroxypropylation and acetic acid esterification) or enzymatic method (e.g., chitosanase) before being used in the processing of surimi and surimi products in recent years. At the same time, different carbohydrates are compounded and applied to surimi and surimi products. The modified and compounded carbohydrates in surimi have been proved to improve quality of surimi and surimi products more pronouncedly than native carbohydrates. Therefore, this review summarizes the manipulation of carbohydrate by modification and compounding to improve the qualities of surimi and surimi products. Moreover, the prospects for carbohydrate modification and compounding for use in surimi and surimi products are discussed. © 2023 Society of Chemical Industry.

The Uptake of Engineered Nanoparticles by Sludge Particulates

The aim of the study was to understand the removal characteristics of engineered nanoparticles (ENP) from sludge treatment processes in wastewater treatment plants (WWTP). Removal of ENP (TiO2, ZnO) was tested on primary and secondary sludge, using differential sedimentation experiments to quantify the attachment of ENP to sludge particulates. To better understand the attachment characteristics, aquatic conditions such as mixed liquid suspended solid concentration, and Ionic strength of the wastewater, were varied to replicate different field conditions of WWTPs. Results showed different degrees of multilayer attachment to sludge surfaces based on the experimental conditions. To verify the effect of ENP surface characters with the sludge attachment, SiO2, ZnO, and TiO2 were tested, showing SiO2 with the highest amount of attachment regardless of its surface charge. With the variation of sludge concentration, up to four degrees of magnitude in sorption was observed. Salt concentrations also showed high impacts on the sorption, where the sorption is decreased by half when doubling the salt concentration. The findings of the current research may aid in understanding the fate of engineered nanoparticles in wastewater treatment plants.

α-Amino Acids as Reducing and Capping Agents in Gold Nanoparticles Synthesis Using the Turkevich Method.

Amino acid-capped gold nanoparticles (AuNPs) are a promising tool for various applications, including therapeutics and diagnostics. Most often, amino acids are used to cap AuNPs synthesized with other reducing agents. However, only a few studies have been dedicated to using α-amino acids as reducing and capping agents in AuNPs synthesis. Hence, there are still several gaps in understanding their role in reducing gold salts. Here, we used 20 proteinogenic α-amino acids and one non-proteinogenic α-amino acid in analogy to sodium citrate as reducing and capping agents in synthesizing AuNPs using the Turkevich method. Only four of the twenty-one investigated amino acids have not yielded gold nanoparticles. The shape, size distribution, stability, and optical properties of synthesized nanoparticles were characterized by scanning electron microscopy, differential centrifugal sedimentation, the phase analysis light scattering technique, and UV-vis spectroscopy. The physicochemical characteristics of synthesized AuNPs varied with the amino acid used for the reduction. We proposed that in the initial stage of gold salts reduction most of the used α-amino acids behave similarly to citrate in the Turkevich method. However, their different physicochemical properties resulting from differences in their chemical structures significantly influence the outcomes of reactions.

Combining orthogonal measurements to unveil diclofenac encapsulation into polymeric and lipid nanocarriers

The quantification of the drug associated to nanoparticle carriers, often expressed in terms of encapsulation efficiency, is a regulatory requirement. The establishment of independent methods to evaluate this parameter provides a means for measurement validation, which is critical in providing confidence in the methods and enabling the robust characterization of nanomedicines. Chromatography is traditionally used to measure drug encapsulation into nanoparticles. Here, we describe an additional independent strategy based on analytical centrifugation. The encapsulation of diclofenac into nanocarriers was quantified based on the mass difference between placebo (i.e. unloaded) and loaded nanoparticles. This difference was estimated using particle densities measured by differential centrifugal sedimentation (DCS) and size and concentration values measured by particle tracking analysis (PTA). The proposed strategy was applied to two types of formulations, namely poly(lactic-co-glycolic acid) (PLGA) nanoparticles and nanostructured lipid carriers, which were analysed by DCS operated in sedimentation and flotation modes, respectively. The results were compared to those from high performance liquid chromatography (HPLC) measurements. Additionally, X-ray photoelectron spectroscopy analysis was used to elucidate the surface chemical composition of the placebo and loaded nanoparticles. The proposed approach enables the monitoring of batch-to-batch consistency and the quantification of diclofenac association to PLGA nanoparticles from 0.7 ng to 5 ng of drug per 1 μg of PLGA, with good linear correlation between DCS and HPLC results (R2 = 0.975). Using the same approach, similar quantification in lipid nanocarriers was possible for a loading of diclofenac ≥1.1 ng per 1 μg of lipids, with results in agreement with the HPLC method (R2 = 0.971).Hence, the strategy proposed here expands the analytical tools available for evaluating nanoparticles encapsulation efficiency, being thus significant for increasing the robustness of drug-delivery nanocarriers characterization.

Factors controlling the morphology and internal sediment architecture of moats and their associated contourite drifts

ABSTRACTThe interaction of sedimentary systems with oceanographic processes in deep‐water environments is not well understood yet, despite its importance for palaeoenvironmental reconstructions, and for a full understanding of source‐to‐sink sediment transport. The aim of this study is to improve the understanding of how contourite moats, elongated depressions formed by bottom currents associated with contourite drifts, develop and of the link between moat‐drift system morphology and bottom current dynamics. This study provides a systematic comparison of 185 cross‐sections of moat‐drift systems distributed at 39 different locations worldwide, and a detailed analysis of the morphology of six moats that cover a wide range of typical geological and hydrodynamic settings. Additionally, in situ measured current data were analysed to better link hydrodynamics to moat morphology. The median of all profiles across all moat‐drift systems reveals a 50 m relief, a width of 2.3 km, a relief to width ratio of 0.022, a slope angle of 6°, a drift angle of 3° and a concave‐up shaped morphology. Moats can be over 100 km long. Some moats are driven by sediment erosion while others are depositional and primarily exist due to differential sedimentation inside the moat compared to the drift alongside the moat. A new sub‐classification of moat‐drift systems based on their stratigraphy is proposed. This classification distinguishes moats depending on the degree of erosion versus deposition. No relation is found between latitude and moat‐drift morphology or stratigraphy in the analysed examples. The combined data indicate that a steeper slope focuses the current more than a gentle slope, resulting in an increase of the relief–width ratio and drift angle. Thus, this study provides new insights into the interaction of ocean currents with sedimentary morphology, which thereby affects the evolution of a poorly understood deep‐water sedimentary system.

Sensitivity of convectively driven tropical tropopause cirrus properties to ice habits in high-resolution simulations

Abstract. Cirrus clouds that form in the tropical tropopause layer (TTL) can play a key role in vertical transport through the upper troposphere and lower stratosphere, which can significantly impact the radiative energy budget and stratospheric chemistry. However, the lack of realistic representation of natural ice cloud habits in microphysical parameterizations can lead to uncertainties in cloud-related processes and cloud–climate feedbacks. The main goal of this study is to investigate the role of different cloud regimes and the associated ice habits in regulating the properties of the TTL. We compare aircraft measurements from the StratoClim field campaign to a set of numerical experiments at the scale of large-eddy simulations (LESs) for the same case study that employ different microphysics schemes. Aircraft measurements over the southern slopes of the Himalayas captured high ice water content (HIWC) up to 2400 ppmv and ice particle aggregates exceeding 700 µm in size with unusually long residence times. The observed ice particles were mainly of liquid origin, with a small amount formed in situ. The corresponding profile of ice water content (IWC) from the ERA5 reanalysis corroborates the presence of HIWC detrained from deep-convective plumes in the TTL but underestimates HIWC by an order of magnitude. In the TTL, only the scheme that predicts ice habits can reproduce the observed HIWC, ice number concentration, and bimodal ice particle size distribution. The lower range of particle sizes is mostly represented by planar and columnar habits, while the upper range is dominated by aggregates. Large aggregates with sizes between 600 and 800 µm have fall speeds of less than 20 cm s−1, which explains the long residence time of the aggregates in the TTL. Planar ice particles of liquid origin contribute substantially to HIWC. The columnar and aggregate habits are in the in situ range with lower IWC and number concentrations. For all habits, the ice number concentration increases with decreasing temperature. For the planar ice habit, relative humidity is inversely correlated with fall speed. This correlation is less evident for the other two ice habits. In the lower range of supersaturation with respect to ice, the columnar habit has the highest fall speed. The difference in ice number concentration across habits can be up to 4 orders of magnitude, with aggregates occurring in much smaller numbers. We demonstrate and quantify the linear relationship between the differential sedimentation of pristine ice crystals and the size of the aggregates that form when pristine crystals collide. The slope of this relationship depends on which pristine ice habit sediments faster. Each simulated ice habit is associated with distinct radiative and latent heating rates. This study suggests that a model configuration nested down to LES scales with a microphysical parameterization that predicts ice shape evolution is crucial to provide an accurate representation of the microphysical properties of TTL cirrus and thus the associated (de)hydration process.

Effects of Salinity on Abiotic Aggregation of Organic Matter and Subsequent Microbial Responses.

Studies of marine aggregation have focused on determining formation rates of larger particles from small particles. However, it has been shown that particles can form from the dissolved phase, which includes colloidal material. The purpose of this study was to investigate the effect of aggregation on the chemical composition of both the dissolved and particulate phases in two salinity regimes: (1) the coast of Avery Point, Connecticut, USA (AP; salinity of 30.1 psu); (2) the estuary of Thames River, Connecticut, USA (TR; salinity of 5.0 psu). The samples were incubated on a roller table for two days in the dark at a speed of 8 rpm. The mixed collision mechanism of shear and differential sedimentation provided by the roller table enhanced the gross aggregation of particulate organic carbon (POC; 0.75 µM d-1 and 1.04 µM d-1 in AP and TR, respectively). Subsequent microbial degradation led to a negative net aggregation of POC (-5.20 µM d-1 and -1.19 µM d-1 in AP and TR, respectively). Although bacterial abundance remained in a narrow range in this study, the aggregation of organic matter (OM) enhanced planktonic community respiration (CR; CR increased 5.1 mg-C m-3 d-1 and 205.4 mg-C m-3 d-1 in AP and TR, respectively). The collision also led to a gross aggregation of uncharacterized particulate organic matter (POM) transferred from uncharacterized dissolved organic matter (DOM; 0.62 µM-C d-1 and 0.56 µM-C d-1 in AP and TR, respectively). The aggregated, uncharacterized POM could be biologically refractory. The C- and N-yields and enrichment factor (EF) analysis indicated that the organic substrate dynamics in this study were complicated.

Study of thermal decomposition of hay-based activated biocarbons modified with nanolayers of ionic polyacrylamide

The thermal behaviour of hay-based activated carbons modified with adsorption nanolayers of ionic polymers were investigated. The anionic and cationic forms of polyacrylamides (PAM) with different contents of ionizable groups were applied. Using spectrophotometry, potentiometric titration, microelectrophoresis, DCS (Differential Centrifugal Sedimentation) and thermal analysis methods, the adsorption and electrokinetic, properties, as well as thermal stability of studied activated biocarbons—PAM systems were established. It was shown that PAM adsorbed amounts on the activated biocarbon surfaces were considerably higher for cationic polyacrylamides than for anionic ones. The conducted TG-DSC-FTIR/MS analysis in helium showed a significant influence of the synthesis conditions on the content of oxygen surface groups of activated biocarbons obtained in conventional or microwave muffle furnace. The measurements carried out in the oxidizing atmosphere for the polymer-modified samples showed similarity to the original materials and were characterized by three main stages of decomposition: dehydration, decomposition of surface functional groups and, at high temperatures—combustion process. The main decomposition products were CO2 and H2O.