Increase In Surface Density Research Articles

Effect of alumina polymorph on the dehydrogenation activity of supported chromia/alumina catalysts

In this work, the effect of surface properties of different alumina supports for CrOx/Al2O3-catalysts on Cr-speciation and dehydrogenation activity was studied. For this purpose, a series of CrOx/Al2O3-catalysts with a monolayer coverage of CrOx (ca. 4.4 at. Cr/nm2) was prepared with γ-, δ-, (δ + θ)-, η-, θ-Al2O3 as supports. Systematic investigation of fresh catalysts with a set of techniques (chemical analysis, N2 adsorption, XRD, Raman and ESR spectroscopy) showed that (i) chemical state distribution of Cr (Cr6+, Cr5+, Cr3+) was the same for all of the catalysts; (ii) CrOx-species were in X-ray amorphous state; (iii) surface chromate species were virtually of the same oligomerization degree. However, aggregation of Cr3+ ions both in calcined and reduced catalysts is support-dependent. ESR data and infrared spectroscopic results of adsorbed CO showed that increase of Lewis acid sites (LAS) surface density on bare aluminas promotes the growth of the relative amount of Cr3+ ions in a relatively large Cr2O3-like clusters in the fresh catalysts. Catalytic testing in a cycling dehydrogenation-regeneration mode leads to catalyst deactivation. Investigation of spent catalysts revealed that deactivation is accompanied with sintering of Cr3+Ox-species with partial migration of Cr3+ ions inside alumina. It was observed that increase of LAS surface density on aluminas promotes the growth of both the initial dehydrogenation activity and stability upon cycling. On the basis of experimental results, it was concluded that (i) Cr3+ ions on the surface of relatively large Cr2O3-like clusters are more active than isolated and poorly agglomerated Cr3+ ions; (ii) increase in LAS concentration on alumina induces growth of surface coverage by Cr2O3-like clusters with concomitant modification of intrinsic activity of active sites through their interaction with support.

Mathematical modelling of phononic nanoplate and its size-dependent dispersion and topological properties

A new model with analysis for the propagation of flexural waves in a phononic plate at nanoscale is developed. The Gurtin-Murdoch theory for surface elasticity is adopted to model the surface heterogeneity. The Mindlin (or first-order) plate theory is further generalized to establish the governing equations for flexural waves in a phononic plate with surface effect, for which the plane wave expansion method is applied to derive the dispersion relation. A numerical model is developed using the finite element method and very good consistency between theory and numerical solution is observed. It is found that the surface density and the surface residual stress play the main role that affects the band structures. The surface effect can be approximately regarded as the competition between frequency decrease due to surface density and frequency increase caused by surface residual stress, which effectively increases the low-frequency bands but decreases the high-frequency bands. The quantum spin Hall effect is observed in the phononic plate at nanoscale, and the surface effect is studied numerically. By applying the k.p perturbation method, a theoretical framework is established to calculate the spin Chern number, which is an important topological invariant that determines the quantum spin Hall effect. Based on the topological analysis, an efficient waveguide with a zig-zag path is designed, in which a topologically protected wave in the interface state can robustly propagate along the path against disorders. The theory and numerical study developed in this paper will help better understand the size-dependent quantum spin Hall effect in nanostructures and it may also provide guidance for the design of topological wave devices at nanoscale.

DNS analysis of boundary layer flashback in turbulent flow with wall-normal pressure gradient

The presence of swirl in combustion systems produces a marked change in their boundary layer flashback behaviour. Two aspects of swirling flow are investigated in this study: the effect of the swirl-generated wall-normal pressure gradient, and the effect of misalignment between the mean flow direction and the direction of flame propagation. The analysis employs Direct Numerical Simulation (DNS) of fuel-lean premixed hydrogen-air flames in turbulent planar channel flow with friction Reynolds number of 180. The effect of swirl on the flashback process is investigated by imposing a wall-normal pressure gradient profile. Analysis of the DNS data shows how the resulting differences in flow field and flame topology contribute to the differences in the overall flashback speed. Misalignment of the flow and propagation directions leads to asymmetry in the flame shape statistics as streaks of high velocity fluid in the boundary layer cleave into the flame front at an angle, yielding an increase in flame surface density away from the wall. Swirl has a stabilising effect on the turbulent flame front during flashback along the centre-body of a swirling annular flow due to the density stratification across the flame front, and produces a reduction in turbulent consumption speed. However the swirl also sets up a hydrostatic pressure difference that drives the flame forward, and the net effect is that the flashback speed is increased. The dominance of hydrostatic effects motivates development of relatively simple modelling for the effect of swirl on flashback speed. A model accounting for the inviscid momentum balance and for confinement effects is presented which adequately describes the effect of swirl on flashback speed observed in previous experimental studies.

The Mass–Size Relation and the Constancy of GMC Surface Densities in the Milky Way

Abstract We use two existing molecular cloud catalogs derived from the same CO survey and two catalogs derived from local dust extinction surveys to investigate the nature of the giant molecular cloud (GMC) mass–size relation in the Galaxy. We find that the four surveys are well described by M GMC ∼ R 2, implying a constant mean surface density, , for the cataloged clouds. However, the scaling coefficients and scatter differ significantly between the CO- and extinction-derived relations. We find that the additional scatter seen in the CO relations is due to a systematic variation in with Galactic radius that is unobservable in the local extinction data. We decompose this radial variation of into two components, a linear negative gradient with Galactic radius and a broad peak coincident with the molecular ring and superposed on the linear gradient. We show that the former may be due to a radial dependence of X CO on metallicity, while the latter likely results from a combination of increased surface densities of individual GMCs and a systematic upward bias in the measurements of due to cloud blending in the molecular ring. We attribute the difference in scaling coefficients between the CO and extinction data to an underestimate of X CO. We recalibrate the CO observations of nearby GMCs using extinction measurements to find that locally X CO = 3.6 ± 0.3 × 1020 cm−2 (K km s−1)−1. We conclude that outside the molecular ring, the GMC population of the Galaxy can be described to relatively good precision by a constant of 35 pc−2.

Relativistic compact stars in the Kuchowicz space-time

We present an anisotropic charged analogue of Kuchowicz (1971) solution of the general relativistic field equations in curvature coordinates by using simple form of electric intensity $E$ and pressure anisotropy factor $\Delta$ that involve charge parameter $K$ and anisotropy parameter $\alpha$ respectively. Our solution is well behaved in all respects for all values of $X$ ( $X$ is related to the radius of the star ) lying in the range $0< X \le 0.6$, $\alpha$ lying in the range $0 \le \alpha \le 1.3$, $K$ lying in the range $0< K \le 1.75$ and Schwarzschild compactness parameter "$u$" lying in the range $0< u \le 0.338$. Since our solution is well behaved for a wide range of the parameters, we can model many different types of ultra-cold compact stars like quark stars and neutron stars. We present some models of super dense quark stars and neutron stars corresponding to $X=0.2,~\alpha=0.2$ and $K=0.5$ for which $u_{max}=0.15$. By assuming surface density $\rho_b=4.6888\times 10^{14}~ g/cc$ the mass and radius are $0.955 M_\odot$ and $9.439 km$ respectively. For $\rho_b=2.7\times 10^{14}~ g/cc$ the mass and radius are $1.259 M_\odot$ and $12.439 km$ respectively and for $\rho_b=2\times 10^{14}~ g/cc$ the mass and radius are $1.463 M_\odot$ and $14.453 km$ respectively. It is also shown that inclusion of more electric charge and anisotropy enhances the static stable configuration under radial perturbations. The $M-R$ graph suggests that the maximum mass of the configuration depends on the surface density {\bf i.e. with the increase of surface density} the maximum mass and corresponding radius decrease. This may be because of existence of exotic matters at higher densities that soften the EoSs.

Influence of surface polymer coating on ballistic impact response of multi-layered fabric composites: Experimental and numerical study

Composites based on aramid fibres are widely used to protect people and vehicles from high-velocity impact threats. Currently, quite a lot of attention is paid to methods for increasing the efficiency of such structures without a significant increase in areal density. The article demonstrates the results of experimental and computational studies of two types of multilayer fabric systems based on Twaron® 709. The first system consisted of dry fabric layers, and the second one was based on the fabric layers with polyvinyl acetate (PVA) surface coating. Experimental studies included quasi-static yarn pull-out tests, high-velocity impact tests of specimens without backing support, and tests on a plasticine block to assess the back face bulging. The results of the experiments showed that thin coatings of PVA contributed to a significant pull-out force increase due to polymer connections between the yarns. This effect led to the fact that specimens based on coated fabrics had a ballistic limit twice as much and showed a three-fold decrease in the depth of the dent on plasticine in comparison with dry fabrics. The total increase in surface density did not exceed 6% while maintaining high flexibility of the package. Also, numerical simulations were used to confirm the results of experiments. It was shown that mesoscale yarn-level models allow to predict plasticine indentation depths of the dry and coated multilayer fabric targets.

PHYSICS OF NANOTRANSISTORS: BALLISTIC INJECTION RATE AND UNIFICATION OF BALLISTIC MODEL WITH THE VIRTUAL SOURCE MODEL

In the sixth one from the line our new tutorial reviews, directed to serve students, university teachers and researchers, the dependence of the electron velocity on the drain voltage in ballistic MOSFETs, as well as its dependence on the gate voltage and on the inversion charge, are considered. At first glance, it seems unusual that in the ballistic MOSFET the speed is saturated with the increase in the drain voltage in the absence of electron scattering, however, the physics of this phenomenon is now quite understandable. In ballistic MOSFET, the electron velocity is saturated not at the drain end of the conduction channel, as in massive transistors, where the electric field is the largest and the scattering intense, but where the source ends and the conduction channel begins, i.e, at the top of the barrier where the electric field is zero.The saturation of the velocity, also known as the ballistic injection rate, is also discussed. It is this speed that is the upper limit of the injection rate in real MOSFETs. If 2 /2 S D n N  , then the ballistic injection rate is constant, however, for 2 / /2 S D n N &gt;  this speed increases with increasing surface density of electrons. Simple calculations of the ballistic injection rate have been made, which can serve as a starting point for more thorough calculations. It is shown how the ballistic model and the virtual source model are interrelated. By simply replacing the traditional mobility, which is limited by scattering, in the virtual source model by ballistic mobility, we obtain the correct course of the ballistic linear current. By replacing the saturation velocity sat v in the massive conduction channel by the ballistic injection rate ball inj v , we obtain the correct value of the ballistic current ON I . It is also shown that the ballistic model predicts larger currents than the experimental data. This is due to the effects of electron scattering, understanding of which is extremely important for modeling nanotransistors.

Increased surface P2X4 receptor regulates anxiety and memory in P2X4 internalization-defective knock-in mice.

ATP signaling and surface P2X4 receptors are upregulated selectively in neurons and/or glia in various CNS disorders including anxiety, chronic pain, epilepsy, ischemia, and neurodegenerative diseases. However, the cell-specific functions of P2X4 in pathological contexts remain elusive. To elucidate P2X4 functions, we created a conditional transgenic knock-in P2X4 mouse line (Floxed P2X4mCherryIN) allowing the Cre activity-dependent genetic swapping of the internalization motif of P2X4 by the fluorescent mCherry protein to prevent constitutive endocytosis of P2X4. By combining molecular, cellular, electrophysiological, and behavioral approaches, we characterized two distinct knock-in mouse lines expressing noninternalized P2X4mCherryIN either exclusively in excitatory forebrain neurons or in all cells natively expressing P2X4. The genetic substitution of wild-type P2X4 by noninternalized P2X4mCherryIN in both knock-in mouse models did not alter the sparse distribution and subcellular localization of P2X4 but increased the number of P2X4 receptors at the surface of the targeted cells mimicking the pathological increased surface P2X4 state. Increased surface P2X4 density in the hippocampus of knock-in mice altered LTP and LTD plasticity phenomena at CA1 synapses without affecting basal excitatory transmission. Moreover, these cellular events translated into anxiolytic effects and deficits in spatial memory. Our results show that increased surface density of neuronal P2X4 contributes to synaptic deficits and alterations in anxiety and memory functions consistent with the implication of P2X4 in neuropsychiatric and neurodegenerative disorders. Furthermore, these conditional P2X4mCherryIN knock-in mice will allow exploring the cell-specific roles of P2X4 in various physiological and pathological contexts.

Mechanical performance and healing process improvement of cement-coir pith particle composites by accelerated carbonation

The accelerated carbonation during the early cure age is a process used to improve the physical and mechanical properties of cement-based composites. In this work, cement-based composites with coir pith particles addition were subjected to the accelerated carbonation process during the first 48 hours of cure in a rich CO2 environment. After curing, the samples were dried and subjected to curing conditions until saturated at 28 days. Thermogravimetric analyses, scanning electron microscopy (SEM) and X-ray diffraction patterns were used to analyze the impact of accelerated carbonation during the early cure age in cement-coir pith composite. The results of the physical properties show an increase in bulk density and surface density of the carbonated samples, as well as reduced water absorption. The reduction of the Ca(OH)2 resulting in the increasing of CaCO3 content was observed by thermogravimetric analysis. The carbonated samples had a 41% increase in compression strength and 28% in the modulus of rupture as compared to non-carbonate samples. The results showed the potential of the accelerated carbonation cure process in cement-based composites with vegetable coconut waste addition. Keywords: Accelerated carbonation, mechanical properties, thermal analysis, cement-based composites, coir pith particles

Is the hepatocyte ultrastructural zonal heterogeneity changed by overnight (16 h) fasting? Morphometric study

ABSTRACTBackground and objectives: Hepatocyte ultra-structure is influenced by feeding status, circadian rhythm, and zone location. The goal of the present study was to study the effect of overnight fasting on the hepatocyte ultrastructure and the zonal heterogeneity and to discuss the functional correlation.Methods: A total of 14 male albino rats were divided into two groups: negative control group fed ad libitum and overnight fasting rats for 16 hours. The different subcellular structures of both centrilobular and periportal hepatocytes in both control and fasted groups were compared by transmission electron microscopy. Morphometric analysis of the electron micrographs was also done using imageJ software.Results: The lysosomes surface density, mitochondrial volume and surface densities were significantly higher in periportal hepatocytes however surface density of smooth endoplasmic reticulum (SER) and peroxisomes were significantly higher in centrilobular hepatocytes of the control group. Fasting caused a significant decrease in the surface density of rough endoplasmic reticulum and glycogen volume density but with significant increase in SER surface density with more mitochondrial fusion and stronger mitochondrial ER contacts, isolation membranes, and autophagosomes. The zonal differences were maintained after fasting. The organelles appeared normal with no signs of degeneration.Conclusion: The organelles appeared normal with no signs of degeneration and the zonal differences were maintained after fasting. The change in hepatocyte ultrastructure after fasting may be related to autophagy.

Tuning the PEG surface density of the PEG-PGA enveloped Octaarginine-peptide Nanocomplexes.

One of the main limitations of protein drugs is their restricted capacity to cross biological barriers. We have previously reported nanostructured complexes of insulin and modified octaarginine (C12-r8), enveloped by a polyethyleneglycol-polyglutamic acid (PEG-PGA) protective shell, and showed their capacity to overcome different barriers associated to the oral modality of administration. The objective of this work was to produce the said nanocomplexes with structurally diverse PEG-PGA shells, i.e. with different chain lengths and PEG substitution degrees, and comparatively analyze their PEG surface density and subsequent impact on their interaction with mucus glycoproteins and Caco-2 cells. The new PEG-PGA enveloped C12-r8-insulin nanocomplexes (ENCPs) exhibited a narrow size distribution (average size of 210-239nm), a neutral surface charge and a 100% insulin association efficiency (final insulin loading of 16.5-29.6% w/w). Proton nuclear magnetic resonance (1H NMR) analysis indicated the possibility to modulate the PEG density on the ENCPs from 6.7 to 44.5 PEG chains per 100nm2. This increase in the ENCPs PEG surface density resulted in their reduced interaction with mucins in vitro, while their interaction with Caco-2 cells in vitro remained unaltered. Overall, these data indicate the capacity to tune the surface characteristics of the ENCPS in order to maximize the capacity of these nanocarriers to overcome barriers associated to mucosal surfaces.

Impact of surface loading on catalytic activity of regular and low micropore SBA‐15 in the Knoevenagel condensation

AbstractThe mesopores of SBA‐15 are well‐suited for immobilizing catalytic aminosilanes for converting substrates for fine chemicals, but these materials have micropores that could impact the observed reaction rate of immobilized catalysts. Materials are synthesized with conventional methods that produce micropores (Regular Micropore SBA‐15; REG) and compared to materials with limited to no micropore volume (NMP SBA‐15). These materials are functionalized with aminosilanes for testing in the Knoevenagel condensation. For low amine loadings, NMP materials have a higher observed reaction rate compared to REG materials, achieving twice the conversion in the same time. As the surface density increases, the reaction rate for NMP materials decreases since organosilane functionalization consumes surface silanols that interact cooperatively with the amine. Regardless of surface density, the NMP materials have higher observed reaction rate than the REG materials. These results demonstrate the importance of reducing micropore volume to create highly active catalytic materials.

Factors influencing the development of diagenetic shrinkage macro-fractures in shale

As an important type of (non-structural) fracture, diagenetic shrinkage fractures of shale play an important role in the storage, seepage, and, in particular, the fracturing production of shale oil and gas. However, there are few studies on this type of fracture. Based on the similarities between desiccation cracks in clayed soil and diagenetic shrinkage macro-fractures in shale (DSMFS), we performed an analogous study on the influence of four factors on DSMFS via experiments using shale core powder. The studies showed that the greater the thickness, the later the time of fracture initiation (TFI) and the higher the critical water content (CWC) of fracture initiation. Additionally, the greater the average fracture length, width, and fracture ratio, the lower the surface density of the fractures. Samples with different water salinities have similar TFIs and CWCs. As water salinity increases, the width, length, and fracture ratio of the DSMFS tend to slightly decrease, and surface density marginally increases. The high content of clay minerals exerts a tremendous influence on the DSMFS. Higher clay minerals result in later TFI and a higher CWC; the fracture length and fracture ratio increase, and in particular, the width increases sharply, whereas the surface density decreases. The influence degrees of each clay mineral are montmorillonite, chlorite, kaolinite, and illite from big to small. With a higher temperature, the TFI, length, width, and fracture ratio decrease; however, the CWC and surface density increase. Therefore, we observed the largest influence of clay mineral content and composition on the DSMFS, followed by the effect of thickness and temperature, whereas water salinity influenced the DSMFS the least. The DSMFS generally has four developmental stages: formation of the main fractures, formation of the sub-fractures, a stabilization, and a fixed stage.

Silver(I) Oxide on Silver–Zinc Alloys: Anodic Formation and Properties

Anodic formation in deoxygenated 0.1 М KOH solution of Ag(I) oxide on Ag–Zn alloys with zinc atomic fraction from 5 to 30 at % and its properties were examined using cyclic voltammetry supplemented by photoelectrochemical measurements. Phase composition of the alloys is confirmed by X-ray diffraction analysis. Surface morphology is studied using scanning electron microscope. Ag(I) oxide anodically formed on silver–zinc alloys is shown possessing n-type conductance, with dominating donor defects. The donor defect concentration in the Ag(I) oxide increases, as the zinc content in the alloy grows, and this leads to a decrease in the maximum photocurrent and to narrowing of the space charge region. With the increasing of the zinc concentration in the alloy, the Ag2O particles’ size decreases and their surface density increases.

Role of surface reconstruction on Cu/TiO2 nanotubes for CO2 conversion

Carbon dioxide hydrogenation to CO via the reverse water gas shift (RWGS) reaction is one route to integrate CO2 utilization into the chemical industry. TiO2 supported Cu catalysts are known to be active for RWGS, but Cu is shown here to behave differently on TiO2 nanotubes (TiNT) vs TiO2 nanoparticles (TiNP). Whereas nanoparticle supports give low rates that are hardly changed by added Cu, the nanotube supports yield much higher activity and three distinct behaviors as the Cu surface density increases. At low surface densities (0.3 Cu/nm2), active Cu-O-Ti sites are created that have low apparent activation energies. At high surface densities (6 Cu/nm2), Cu nanoparticles on TiNT are formed, and reaction barriers are lowered when both Cu and TiNT surfaces are accessible. At intermediate surface densities, metallic Cu domains are engulfed by a TiOx overlayer formed during H2 pretreatment, akin to those formed by classical strong metal support interactions (SMSI). These reduced layers are markedly more active for RWGS than the initial TiNT surfaces, but have similar activation barriers, which are higher than those for which both Cu and TiNP surfaces are exposed. These catalytic findings are supported by computational modeling, in situ IR, UV–vis, and X-ray absorption spectroscopies, and they provide insight into an important reaction for CO2 utilization.

Preparation and Sound Insulation Performance of Superfine Metal Powder/Nitrile-Butadiene Rubber-Polyvinyl Chloride Microcellular Foaming Material

Lightweight sound insulation materials have received much attention. In this study, a series of superfine metal powder (SFM)/nitrile-butadiene rubber (NBR)-polyvinyl chloride (PVC) microcellular foaming materials were prepared with NBR-PVC as matrix and SFM as modifiers by employing the method of molding foaming. Analysis on the morphology of cross section, pore size, and pore distribution possessed by SFM/NBR-PVC was conducted by scanning electron microscopy (SEM), as well as the image processing software of Image-Pro. Then detailed discussion on the effect of SFM with different mass fractions in the matrix on the foaming quality was provided. In the meanwhile, the performance of sound insulation was tested by four-channel impedance tube system. The results show significant improvement for foaming quality and sound insulation performance of NBR-PVC microcellular foaming material through the addition of SFM. In comparison with the pure NBR-PVC materials, the microcellular foaming material exhibits the best performance of foaming quality and sound insulation when the SFM content in matrix is 30 wt%. It is shown that the average pore diameter and the foaming capacity decrease by 60% and 31%, respectively, while the surface density increases by 131%. In the meantime, the sound insulation index of SFM/NBR-PVC microcellular material increases by 7.2 dB to 30.5 dB, which conforms to the requirements of new lightweight sound insulation materials in modern time. Finally, the mechanism of the optimization conducted for sound insulation performance after the addition of SMF is explained.

Constructing surface models of silicate glasses using molecular dynamics to understand the effect of pH on the hydration properties.

In this work, we use realistic silicate glass surface models, with molecular dynamics simulations, and present an algorithm for proper atomic partial charge assignment, consistent with measurable internal dipoles. The immersion energy is calculated for different silicate glass compositions in solutions of varying pH. We use molecular dynamics to elucidate the differences in the structure of water between mono- and divalent cations. The immersion energy of the glass surface is found to increase with an increase in ionic surface density and pH. This can be attributed to the stronger interaction between water and cations, as opposed to the interactions between water and silanol groups. The developed models and methods provide new insights into the structure of glass-solution interfaces and the effect of cation surface density in common nanoscale environments.

Enhanced antibacterial and anticancer properties of Se-NPs decorated TiO2 nanotube film.

Selenium nanoparticle modified surfaces attract increasing attention in the field of tissue engineering. Selenium exhibits strong anticancer, antibacterial and anti-inflammatory properties and it maintains relatively low off-target cytotoxicity. In our paper, we present the fabrication, characterization and cytocompatibility of titanium oxide (TiO2) nanotube surface decorated with various surface densities of chemically synthesized selenium nanoparticles. To evaluate antibacterial and anti-cancer properties of such nanostructured surface, gram negative bacteria E. coli, cancerous osteoblast like MG-63 cells and non-cancerous fibroblast NIH/3T3 were cultured on designed surfaces. Our results suggested that selenium nanoparticles improved antibacterial properties of titanium dioxide nanotubes and confirmed the anticancer activity towards MG-63 cells, with increasing surface density of nanoparticles. Further, the selenium decorated TiO2 nanotubes suggested deteriorating effect on the cell adhesion and viability of non-cancerous NIH/3T3 cells. Thus, we demonstrated that selenium nanoparticles decorated TiO2 nanotubes synthesized using sodium selenite and glutathione can be used to control bacterial infections and prevent the growth of cancerous cells. However, the higher surface density of nanoparticles adsorbed on the surface was found to be cytotoxic for non-cancerous NIH/3T3 cells and thus it might complicate the integration of biomaterial into the host tissue. Therefore, an optimal surface density of selenium nanoparticles must be found to effectively kill bacteria and cancer cells, while remaining favorable for normal cells.

Computational Modeling and Microfluidics Reveal Characteristic Patterns of Regulation of Clot Structure and Mechanics By Tissue Factor Localization

The growth of a blood clot is initiated by tissue factor (TF) exposure and is expected to depend on TF localization (i.e., its level and spatial distribution). We sought to understand how the structural and mechanical properties of clots under flow are shaped by simultaneously varying the surface density of TF and its area of exposure. We used a microfluidic device harboring thrombogenic surfaces that differed in length and TF surface density. We perfused human whole blood through this device and continually measured platelet deposition, thrombin formation, and fibrin accumulation by means of fluorescence microscopy. Using our recently developed, detailed mathematical model of spatial clot growth under flow, we performed computational simulations to gain insights into the connection between the structure of a clot and its mechanical properties, such as resistance to blood flow and flow axial velocity.We detected a non-additive, synergistic influence of the thrombogenic surface length and TF surface density on bulk thrombin and fibrin generation. We found that thrombogenic surface length and TF density controlled not only bulk accumulation, but also the occlusivity of the deposited platelet mass, as well as clot resistance to flow. The extent of this control depended on the blood flow velocity. An increase in the TF surface density resulted in condition-dependent differential acceleration of platelet deposition, thrombin formation, and fibrin accumulation. The viscous resistance of the clot was characterized by spatial variations and was higher in the inner clot region. Notably, despite variations in the intraclot structure, variations in the intraclot flow velocity were minor compared to the abrupt decrease in flow velocity at the boundary of the platelet deposition domain.Our analysis revealed characteristic patterns that describe how the shape, size, internal structure, and viscous resistance of a clot depend on the surface density of TF and its area of exposure. Taken together, our results suggest that the structure and mechanics of a growing clot are correlated, but can differ in their regulation by the distinct aspects of TF localization. These findings provide new insights into how initiating signals can temporally and spatially affect thrombus growth under flow. DISCLAIMERThe opinions and assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the U.S. Army or of the U.S. Department of Defense. This abstract has been approved for public release with unlimited distribution. DisclosuresNo relevant conflicts of interest to declare.

Interpreting competitive adsorption of arsenate and phosphate on nanosized iron (hydr)oxides: effects of pH and surface loading.

Arsenate and phosphate have similar properties due to their electrochemical structures, but their environmental impacts are unique. The abundance and competition of arsenate and phosphate determine their bioavailability and leachability; thus, it is essential to understand their fate in the soil environment. In this study, the effects of pH and surface loading on the competitive adsorption of arsenate and phosphate on four iron (hydr)oxides were evaluated by employing the Langmuir isotherm, competitive sorption ratio (CSR), and competition effect (CE). The stability and transformation of the iron (hydr)oxides were also assessed. Various adsorption patterns were observed in the single and mixed treatments by controlling the addition of oxyanions, pH, surface loading, and type of iron (hydr)oxides. Arsenate was preferentially adsorbed at a low pH, whereas phosphate showed the opposite trend. The CEAs(V),P(V) was close to zero at low surface density (no competition) and sequentially changed to negative or positive values with increasing surface density, indirectly indicating the sequential development of promotive and competitive effects. Transformation in goethite was identified at a high pH with the presence of oxyanions, except that no transformation was observed upon the addition of oxyanions and with pH change. However, the stability of the iron (hydr)oxides decreased at a low pH and with the presence of phosphate, arsenate, or both. The hematite showed a significant promotive effect regardless of the pH. Our study revealed that the pH, surface loading, and type of iron (hydr)oxides are intercorrelated and simultaneously affect the adsorption characteristics of oxyanions and the stability of iron (hydr)oxides.