Primary Aggregation Research Articles

Decline or shifting distribution? A first regional trend assessment for white sharks (Carcharodon carcharias) in South Africa

Unprecedented levels of change in ocean ecosystems bring an ever-increasing need for re-analyses of existing data to explore pressing conservation questions. Substantial declines in white shark (Carcharodon carcharias) presence at two primary aggregation sites have raised concerns about the species’ status throughout South Africa. Using the most comprehensive suite of abundance indices compiled to date, we evaluated temporal trends and the strength of evidence for regional redistribution. Individual indices from all primary aggregation sites in South Africa were highly variable. The overall temporal trend from a log-linear Generalized Additive Model was relatively flat, indicating largely unchanged abundance throughout South Africa since protection in 1991. However, reports of human-shark incidents showed a general shift from the Western to the Eastern Cape. Correlations among individual abundance indices demonstrated that movements were not as simple as animals leaving one site to inhabit another. Further research is needed to explore the effect of movement on monitoring data. Our results reaffirm the need for better standardization in data collection methods to generate abundance indices and to develop long-term monitoring programs on the Eastern Cape. Ideally, environmental or operational factors affecting abundance indices should also be explored in future status assessments at a regional level. Our results provide a baseline for future work, directing research to understand drivers of localized and regional changes and focusing management on reducing anthropogenic sources of mortality within their Southwest Indian Ocean range.

Multi-scale soot formation simulation providing detailed particle morphology in a laminar coflow diffusion flame

The macroscopic simulation of soot production in flames by CFD approaches often assumes of spherical particles or considers ad-hoc formulas in order to take the particle fractal aggregates’ morphology into account. On the other hand, numerically simulated aggregates can be generated by Discrete Element Modeling (DEM) simulations at the nanoscopic scale. However, the change in thermodynamic conditions, surface growth, oxidation, and nucleation mechanisms are commonly neglected by this approach. This work combines these complementary approaches to investigate the detailed morphology of soot along 4 different particle trajectories in a diffusion flame. The proposed multi-scale approach shows remarkably larger and more compact aggregates near the wings of the flame as compared to the centerline, in agreement with previous experimental studies. This approach allows to analyse the particle polydispersity and morphological parameters beyond the fractal dimension, such as anisotropy coefficient and monomers overlapping coefficient. It becomes possible to reveal clear morphological signatures of soot formed along different streamlines in the flame. Finally, we have also observed a positive correlation between primary particle diameter and aggregate gyration diameter due to the predominance of surface reactions over aggregation. The proposed post-processing of CFD results based on DEM methods, bringing new information on soot morphology, is a proof of concept of a more accurate procedure for validating soot models used in CFD codes as compared to existing methods in the literature.

Hydrophobic aggregation via partial Gal removal affects solution characteristics and fine structure of tamarind kernel polysaccharides

The role of molecular aggregation was further investigated on solution and structural characteristics of tamarind kernel polysaccharides (TKPs vs. CTKPs) via partial degalactosylation. In addition to the distinctive aggregation-disaggregation behaviors observed when complexed with Congo red, TKPs and CTKPs in the capillary viscous behaviors behaved as relatively ordered semi-flexible coil, and showed augmented intermolecular interactions during partial degalactosylation. Concretely, the sheet-like structure evolving from ordered architecture contributed more to the conformational asymmetry, where hydrophobic microdomains were sufficiently promoted and solute-solute interactions dominated. Meanwhile, the stiffer semi-flexible primary aggregates with dwindling chain stiffness exhibited stronger and larger-scale hydrophobic aggregations. Considering the multiple interplays of hydrophobic interactions, the role of hydrophobic aggregation could be dissimilar between TKPs and CTKPs, which manifested in the hierarchical change of microstructure as well as susceptibility of structural oligosaccharide motifs to partial degalactosylation, thereby favoring hydrophobic aggregation in varying degrees. Finally, the mechanism of hydrophobic aggregation under partial degalactosylation was further illustrated, which was expected to promote tailored valorizations of tamarind kernel polysaccharide in more potential fields.

Effects of γ-Irradiation, Cation Size, and Salt Concentration on the Aggregation of Boehmite Nanoplatelets

Effects of radiation on the aggregation of nanoplatelets of aluminum oxyhydroxide (boehmite) in slurries of M1+ cation nitrates have been observed using tumbler small- and ultra-small-angle neutron scattering. Nitrate solutions of H, Li, Na, K, and Rb at concentrations of 10–5, 10–3, 10–1, 2, and 4 molal were compared to the results for pure H2O. Primary aggregates consisting of small stacks of boehmite platelets that form immediately after the boehmite is placed in water are smaller for irradiated boehmite than the pristine material. The primary aggregates for irradiated boehmite also appear to have a rougher surface than those observed for unirradiated materials. Both results are possibly due to breaking of the surface OH species and neutralization of the surface. At low salt concentrations, the pH of the irradiated boehmite slurries is lower than that of the corresponding pristine material, indicating that irradiated boehmite adsorbs fewer protons or more hydroxide onto its surface than the pristine boehmite. Increasing the salt concentration decreases the pH to near neutral at 7 due to screening of the electric double layer at the solid/liquid interface. Irradiation does not seem to affect the size of secondary aggregates formed from the aggregation of primary aggregates or the overall size of the primary aggregates.

Investigation of gas transport resistance in fuel cell catalyst layers via hydrogen limiting current measurements of CO-covered catalyst surfaces

The efficiency of fuel cell operation at high power strongly affects the total cost of ownership of fuel cell vehicles. Gas transport resistance at the cathode strongly suppresses efficiency during high-power operation. The resistance comprises Knudsen diffusion resistance in pores formed among the primary carbon aggregates and local gas transport resistance. The former is independent of the electrochemically active Pt surface area per geometrical electrode area (roughness factor: RF). The latter is proportional to the inverse of RF. Separate identification of these resistances in actual catalyst layers remains challenging because of experimental limitations. Herein, we propose a method that can identify the RF-dependent and RF-independent resistances separately using a single sample. RF can be controlled by partially covering the Pt surface by CO. The gas transport resistance can be ascertained from the hydrogen limiting current. Measuring the hydrogen limiting current at controlled CO coverages allows separate identification of the resistances. The RF-dependent resistance is separable further into ionomer/Pt interfacial resistance and permeation resistance through the ionomer thin film by combining the obtained ionomer-to-carbon weight ratio dependence of each resistance component with structural and electrochemical analyses. The separate resistances show the ionomer/Pt interfacial resistance to be dominant in the catalyst layer.

Nanoscale insights into the local structural rearrangements of amyloid-β induced by bexarotene.

A better understanding of the abnormal protein aggregation and the effect of anti-aggregation agents on the fibrillation pathways and the secondary structure of aggregates can determine strategies for the early treatment of dementia. Herein, we present a combination of experimental and theoretical studies providing new insights into the influence of the anti-aggregation drug bexarotene on the secondary structure of individual amyloid-β aggregates and its primary aggregation. The molecular rearrangements and the spatial distribution of β-sheets within individual aggregates were monitored at the nanoscale with infrared nanospectroscopy. We observed that bexarotene limits the parallel β-sheets formation, known to be highly abundant in fibrils at later phases of the amyloid-β aggregation composed of in-register cross-β structure. Moreover, we applied molecular dynamics to provide molecular-level insights into the investigated system. Both theoretical and experimental results revealed that bexarotene slows down the protein aggregation process via steric effects, largely prohibiting the antiparallel to parallel β-sheet rearrangement. We also found that bexarotene interacts not only via the single hydrogen bond formation with the peptide backbone but also with the amino acid side residue via a hydrophobic effect. The studied model of the drug-amyloid-β interaction contributes to a better understanding of the inhibition mechanism of the amyloid-β aggregation by the small molecule drugs. However, our nanoscale findings need to meet in vivo research requiring different analytical approaches.

Evaluating the Rheo-electric Performance of Aqueous Suspensions of Oxidized Carbon Black

HypothesisThe macroscopic properties of carbon black suspensions are primarily determined by the agglomerate microstructure built of primary aggregates. Conferring colloidal stability in aqueous carbon black suspensions should thus have a drastic impact on their viscosity and conductivity. ExperimentsCarbon black was treated with strong acids following a wet oxidation procedure. An analysis of the resulting particle surface chemistry and electrophoretic mobility was performed in evaluating colloidal stability. Changes in suspension microstructure due to oxidation were observed using small-angle X-ray scattering. Utilizing rheo-electric measurements, the evolution of the viscosity and conductivity of the carbon black suspensions as a function of shear rate and carbon content was thoroughly studied. FindingsThe carboxyl groups installed on the carbon black surface through oxidation increased the surface charge density and enhanced repulsive interactions. Electrostatic stability inhibited the formation of the large-scale agglomerates in favor of the stable primary aggregates in suspension. While shear thinning, suspension conductivities were found to be weakly dependent on the shear intensity regardless of the carbon content. Most importantly, aqueous carbon black suspensions formulated from electrostatically repulsive primary aggregates displayed a smaller rise in conductivity with carbon content compared to those formulated from attractive agglomerates.

Abstract 13538: Associations Between Circulating Liver Enzymes and Platelet Reactivity

Introduction: The liver plays an essential role in thrombopoiesis and coagulation, and circulating liver enzymes are associated with altered platelet counts. However, the role of liver enzymes in the modulation of platelet reactivity remains unclear. Methods: A total of 3,429 Framingham Heart Study participants were included in this study. Platelet reactivity to 8 agonists, including adenosine diphosphate (ADP), thromboxane A 2 mimetic (U46619) and arachidonic acid (AA), was measured using light transmission aggregometry (LTA), Multiplate impedance aggregometry and Optimul aggregometry. Platelet counts and platelet-red blood cell aggregates were enumerated using flow cytometry. Levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were also measured. Associations of platelet reactivity phenotypes with liver circulating liver enzyme levels analyzed using linear mixed-effects models and adjusted for sex, age, relatedness, smoking, aspirin-, and statin-use. To correct for multiple testing, a Bonferroni-correction threshold of P<0.0011 was used to account for multiple comparisons. Results: Higher ALT levels were associated with platelet disaggregation in LTA to ADP (β=0.056, SE=0.02, P=3.54E-04), and with decreased platelet reactivity in response to U46619 in Optimul (EC 50 : β=0.064, SE=0.019, P=7.65E-04). Interestingly, higher AST levels were associated with decreased platelet counts (β=-0.082, SE=0.019, P=1.04E-05), platelet reactivity to U46619 (β=-0.069, SE=0.018, P=1.04E-04) and AA (β=-0.047, SE=0.013, P=3.12E-04), and circulating platelet-red blood cell aggregates (β=-0.062, SE=0.018, P=9.54E-04). Conclusion: Our findings suggest that ALT levels could alter primary platelet aggregation. AST may indirectly modulate platelet counts. In addition, lower AST levels may contribute to platelet hyperresponsiveness. Lastly, ALT and AST levels may have antagonistic effects on the formation of platelet and red blood cell aggregates, which may indirectly influence platelet margination within vessels. Additional studies are underway to examine whether liver fat, a marker of fibrosis associated with cardiovascular disease, is also associated with altered platelet function.

Abstract 10885: Integrin β 3 Directly Inhibits Galpha 13 -p115rhogef Interaction and Its Role in Regulating Platelet Exocytosis

G protein-coupled receptors (GPCRs) and adhesion receptor integrins are fundamental to a cell’s response to extracellular stimuli. GPCRs, through Gα q and Gα i , activate integrins and, through the Gα 13 -p115RhoGEF-RhoA pathway, stimulate contractility and integrin-independent exocytosis (granule secretion). Gα 13 also interacts with integrins and mediates outside-in signaling, cell spreading and integrin-dependent exocytosis. However, it was unknown whether there was crosstalk between integrins and the Gα 13 /p115RhoGEF-mediated RhoA signaling pathway. It was also unclear with the role of Gα 13 -integrin interaction in regulating GPCR- and integrin- mediated platelet exocytosis. In this study, we demonstrate that binding of the integrin β 3 cytoplasmic domain to Gα 13 through its ExE motif, directly disrupts the interaction between p115RhoGEF and Gα 13 , thus inhibiting Gα 13 -p115RhoGEF-mediated RhoA activation and signaling. In platelets, this inhibitory effect of integrins greatly reduces GPCR-mediated integrin-independent granule secretion. On the other hand, the Gα 13 -integrin interaction stimulates integrin outside-in signaling and integrin-dependent granule secretion. Furthermore, we demonstrate that the inhibitor peptide derived from the Gα 13 -binding β 3 ExE motif disrupts the β 3 -Gα 13 interaction to inhibit GPCR-induced integrin-independent granule secretion and also inhibits outside-in signaling and integrin-dependent granule secretion. This dual effect results in robust inhibition of granule secretion without affecting primary platelet aggregation, suggesting a new therapeutic approach for the development of selective inhibitors of platelet granule secretion. In conclusion, we have discovered a mechanism underlying direct integrin-GPCR crosstalk that regulates the Gα 13 -p115RhoGEF-RhoA signaling pathway. Our data also demonstrate an approach to potently inhibit platelet granule secretion without impairing primary platelet adhesion/aggregation and hemostasis.

Carbon storage in an arable soil combining field measurements, aggregate turnover modeling and climate scenarios

Quantifying soil structural dynamics and aggregate turnover is important in understanding soil organic carbon (SOC) stocks, particularly over decadal and larger time scales. Until now it has remained unclear clear how soil aggregate size and its associated carbon respond to both long-term soil fertility and climate change. Here, we explore changes in soil structure and aggregate organic C (OC) stocks under different fertilization practices by combining field chronosequence SOC measurements with dynamic and process modeling in a long-term wheat-maize field experiment on the North China Plain. The fertilization practices comprise no fertilization (CK), chemical fertilization (NPK), and combined manure and NPK treatments (MNPK). The experimental measurements included the mass of OC stocks in different soil aggregate size classes. We used this information to calibrate parameters of the Carbon, Aggregation, and Structure Turnover (CAST) model and to predict future changes in aggregate structure and the resulting OC stocks using the RCP2.6 scenarios that were defined by the outputs of five future climate models from IPCC projection. With trends towards a wetter climate and increasing soil moisture under the RCP2.6 scenarios for the region, soil OC stocks will increase in all three treatments, with the strongest increase under MNPK due to exogenous C inputs. The CAST model output further suggests that changes in microaggregate (250–53 μm) OC stocks in the NPK and MNPK treatments accounted for 78.6 % and 75.3 % of the calculated change in total SOC stocks between the early and late 21st century. In conclusion, our combined data and modeling approach describes changes in soil aggregate C, identifies the primary soil aggregate size class of microaggregates involved in C sequestration in an agricultural soil, and predicts the role of Fluvaquent soils on the North China Plain as a future C sink.

Progress of polymer reaction engineering: From process engineering to product engineering

Polymer reaction engineering studies the design, operation, and optimization of reactors for industrial scale polymerization, based on the theory of polymerization kinetics and transfer processes ( e.g. , flow, heat and mass transfer). Although the foundation and development of this discipline are less than 80 years, the global production of polymers has exceeded 400 million tons per annum. It demonstrates that polymer reaction engineering is of vital importance to the polymer industry. Along with the maturity of production processes and market saturation for bulk polymers, emerging industries such as information technology, modern transportation, biomedicine, and new energy have continued to develop. As a result, the research objective for polymer reaction engineering has gradually shifted from maximizing the efficiency of the polymerization process to the precise regulation of high-end product-oriented macromolecules and their aggregation structures, i . e ., from polymer process engineering to polymer product engineering. In this review, the frontiers of polymer reaction engineering are introduced, including the precise regulation of polymer chain structure, the control of primary aggregation structure, and the rational design of polymer products. We narrow down the topic to the polymerization reaction engineering of vinyl monomers. Moreover, the future prospects are provided for the field of polymer reaction engineering.

Effects of ammonia addition on soot formation in ethylene laminar diffusion flames. Part 3. The morphology and nanostructure of soot particles

Ammonia (NH3) fuel has been widely considered a competitive alternative fuel and hydrogen carrier due to its “non-carbon and hydrogen-rich” nature. In this study, the thermophoretic sampling combined with transmission electron microscopy (TEM) analysis was conducted to investigate the effects of NH3 addition with varying ratios (between 0% and 60% by volume fraction while the remainder is argon) on the evolution of morphology and nanostructures of soot particles along the flame axis in the ethylene (40% by volume fraction) co-flow diffusion flames. Results showed that the flame visible height increased with the addition of NH3, and the flame temperature decreased at the height above burner (HAB) below 30 mm while increased at HAB > 30 mm. With NH3 addition, the size of soot (primary particles and aggregates) and the number of soot primary particles contained in the soot aggregates decreased significantly. In addition, the investigation of soot nanostructures showed that the carbon layers with shorter fringe length (Fl) and higher tortuosity (Ft) would be oxidized before it arrived to the flame tip in the NH3-doped flame, resulting in the longer Fl and higher Ft. In general, the inter-fringe spacing (Fd) increased with NH3 addition. The evolution of soot morphology and nanostructures indicated that NH3 would delay the process of particle inception and surface growth.

Floc formation and growth during coagulation removing humic acid: Effect of stirring condition

Number of studies have explored the mechanism of humic acid (HA) removal by coagulation, while studies on the formation and growth mechanism of HA-floc are still limited. In this study, a series of dynamically monitored experiments were carried out and floc characterization techniques were applied to investigate HA-floc growth mechanisms and properties under different stirring conditions. First, HA was removed in the early stages and varied insignificantly during floc growth, and the stirring condition did not affect the removal of HA. Moreover, HA hindered the effective collision, resulting in a slower floc growth rate and a lower fractal dimension. Although stirring condition did not markedly affect the HA removal performance, it had a remarkable effect on floc growth and structure. For example, gentle stirring resulted in larger floc d50 and pore size. Intense stirring accelerated the breakage or aging of flocs, resulting in a reduction in the final floc size at equilibrium. In particular, fast stirring in the early stage of coagulation advanced floc growth, but decreased the zeta potential and active sites of flocs, and reduced the capacity of the primary aggregates to grow into larger flocs. This study provides information on the floc formation and growth mechanism and the properties of flocs formed under different stirring conditions, which are helpful for optimizing the coagulation process on organic matter removal and guide the processes utilizing flocs.

Hydrothermally-assisted recovery of Yttria- stabilized zirconia (YSZ) from end-of-life solid oxide cells

Effective and scalable recycling strategies for the recovery of critical raw materials are yet to be validated for solid oxide cells (SOCs) technologies. The current study aimed at filling this gap by developing optimized recycling processes for the recovery of Yttria-stabilized Zirconia (YSZ) from End-of-Life (EoL) SOC components, in view of using the recovered ceramic phase in cell re-manufacturing. A multi-step procedure, including milling, hydrothermal treatment (HT), and acidic-assisted leaching of nickel from composite Ni-YSZ materials, has been implemented to obtain recovered YSZ powders with defined specifications, in terms of particle size distribution, specific surface area, and chemical purity. The overall optimized procedure includes a pre-milling step (6 h) of the EoL composite materials, and a hydrothermal (HT) treatment at 200 °C for 4 h to further disaggregate the sintered composite, followed by selective oxidative leaching of Ni2+ by HNO3 solution at 80 °C for 2 h. In particular, the intermediate HT step was assessed to play an essential role in promoting the disaggregation of the sintered powders, with a related increase of specific surface area (up to 13 m2 g−1) and the overall reduction of the primary particle aggregates. The acid-assisted leaching allowed to fully extract Nickel from the composite Ni-YSZ powders, with retention of YSZ crystallinity and negligible loss of Zr and Y, as revealed by ICP analysis on the recovered supernatants.The developed multi-step pathway offers a promising strategy to recover valuable YSZ materials for the re-manufacturing of SOCs components, with the aim to boost a circular economy approach in the field of fuel-cell and hydrogen (FCH) technologies.

Market prospects of secondary construction aggregates in Sweden

The transition towards a circular economy is being increasingly envisaged in Europe. Increased utilisation of secondary construction aggregates poses a great opportunity in this regard given its potential to avoid waste disposal, natural resource extraction, and reduce costs. Nevertheless, the Swedish construction aggregates market is dominantly characterised by primary aggregates utilisation. This study employs a qualitative approach to analyse the Swedish construction aggregates market from the user perspective in order to identify the challenges of increased utilisation of secondary aggregates. The dominant and systematic utilisation of primary aggregates is chiefly driven by market processes allowing economic advantages and convenience for the users in doing so, whereas the situational and non-systematic utilisation of secondary aggregates is opportunistically driven by different actors in order to seize opportunities such as avoided costs and improved environmental performance. The realisation of increased secondary aggregates utilisation needs to be first facilitated via changes to the institutional structure that makes such materials a priority issue for the supply chain actors, which necessitates national-level policy interventions and supply chain actor collaborations. Second, the competitiveness of secondary aggregates needs to be lifted to a comparable state to that of primary aggregates, which necessitates the development of specific sectoral application standards and vertical integration of secondary aggregates supply by construction corporations.

Study on Continuous Hydrolysis in a Microchannel Reactor for the Production of Titanium Dioxide by a Sulfuric Acid Process.

The development of a continuous hydrolysis process of titanium sulfate is an innovation to the traditional production process of titanium dioxide by the sulfuric acid process. In the experiment, a microchannel reactor was designed, and the hydrolysis rate of titanium sulfate, the particle size, and particle size distribution of metatitanic acid agglomerates were used as indicators to investigate the effect of operating conditions on the continuous hydrolysis of titanium sulfate. The results have shown that as the amount of dilution water increased, the hydrolysis rate of titanium sulfate decreased, and the particle size of primary aggregates of metatitanic acid increased from 39 to 54 nm. As the alkali mass concentration of dilution water increased, the hydrolysis rate of titanyl sulfate increased, and the particle size of primary aggregates of metastatic acid first decreased and then increased, and the particle size range was 40–48 nm. As the flow rate increased, the hydrolysis rate of titanyl sulfate increased, and the particle size of primary aggregates of metatitanic acid dropped from 59 to 43 nm. Compared with the batch hydrolysis operation, the continuous process has stronger anti-disturbance ability, significantly shorter operation time of the reaction section, and narrower particle size distribution of the product metatitanic acid.

Prognostic Significance of Lymphocyte Infiltrate Localization in Triple-Negative Breast Cancer.

High infiltration by tumor-infiltrating lymphocytes (TILs) is associated with favorable prognosis in different tumor types, but the clinical significance of their spatial localization within the tumor microenvironment is debated. To address this issue, we evaluated the accumulation of intratumoral TILs (itTILs) and stromal TILs (sTILs) in samples from 97 patients with early triple-negative breast cancer (TNBC) in the center (sTIL central) and periphery (sTIL peripheral) of tumor tissues. Moreover, the presence of primary and secondary lymphoid aggregates (LAs) and the expression levels of the cancer testis antigen (CTA), NY-ESO-1, and PD-L1 were explored. High infiltration by itTILs was observed in 12/97 samples (12.3%), unrelated to age, Ki67 expression, tumor size, histologic type and grade, and LA presence. NY-ESO-1 was expressed in tumor cells in 37 samples (38%), with a trend suggesting a correlation with itTIL infiltration (p = 0.0531). PD-L1 expression was detected in immune cells in 47 samples (49%) and was correlated with histologic grade, sTILs, and LA formation. The presence of primary LAs was significantly correlated with better disease-free survival (DFS) (p = 0.027). Moreover, no tumor progression was observed during >40 months of clinical follow up in the 12 patients with high itTILs or in the 14 patients with secondary LAs. Thus, careful evaluation of lymphoid infiltrate intratumoral localization might provide important prognostic information.

Multi-approach LC-MS methods for the characterization of species-specific attributes of monoclonal antibodies from plants

In this work, an analytical platform based on the use of chromatography and mass spectrometry (MS), has been applied to the characterization of Rituximab (RTX) obtained from two plant expression systems (rice and tobacco) in comparison to the mammalian cell-derived reference monoclonal antibody (mAb). Different chromatographic approaches, hyphenated to high resolution MS (HRMS), were applied to RTX structural investigation both at middle- and peptide level. In particular, cation exchange chromatography (CEX), size exclusion chromatography (SEC), reversed phase (RPLC) and hydrophilic interaction liquid chromatographic (HILIC) methods were developed and applied on intact mAbs, IdeS-, and trypsin digests in order to address critical attributes such as primary structure, glycan composition, species-related heterogeneity, glycosylation degree, charge variants, aggregation tendency and enzymatic stability. All the collected data highlight the features and criticalities of each production approach. Production in rice results in a heterogeneous but stable product over time, suggesting the absence of proteases in seeds; while tobacco expression system leads to more homogeneous glycosylation, but protein stability seems to be a critical issue probably due to the presence of proteases. This analytical strategy represents a robust support to scientists in the selection and optimization of the best plant expression system to produce recombinant humanized mAbs.

Integrated and comparative Structural-LCA analysis of unbound and cement-stabilized construction and demolition waste aggregate for subbase road pavement layers formation

A more extensive use of recycled aggregate in road construction is key to meeting the ambitious targets of the EU circular economy action plan. However, scepticism among designers, contractors and road agencies remains a bottleneck. This integrated structural-environmental study demonstrates the advantages of using recycled construction and demolition waste aggregate (CDW-RA) in substitution of primary natural aggregate (NA) for the formation of subbase layers in both flexible and semi-rigid road pavements. The structural responses of different pavements with a 0.30 m subbase layer made up of four materials, i.e., two unbound and two cement-stabilized obtained including NA and CDW-RA, were compared. The environmental-related impacts were also assessed by means of a life cycle assessment (LCA).Laboratory tests and structural design led to pavement structures with the same thickness for the upper hot-mix asphalt layers, i.e., 0.26 and 0.28 m for the two unbound and the two cement-stabilized subbase materials respectively. The pavement with unbound CDW-RA subbase showed the best LCA outcomes because of the more favourable environmental performance of CDW-RA compared to NA. Although the stabilization of NA and CDW-RA reduces the thickness of the top hot-mix asphalt layers by 0.02 m, the environmental benefits are outweighed by the impact associated with the usage of cement. This study encourages the use of CDW-RA in road subbase layers with similar characteristics to those investigated here. The LCA results also support the use of alternative and more environmentally friendly binders that can enhance the environmental sustainability of stabilized materials in road construction.

Bimetallic Organoplatinum(II)‐Ag(I) Cluster Cations with Ag−Pt Interactions Unsupported by Conventional Bridging Ligands

AbstractThe organoplatinum complex of a primary amine and AgClO4 aggregate in methanol to oligonuclear mixed‐metal species. A perchlorate salt 3 with the empirical formula C96H146Ag7Cl13N12O62Pt6 could be isolated and structurally characterized with the help of X‐ray diffraction at the DESY synchrotron. The product contains both a penta‐ and a tetra‐nuclear complex cation in which Ag(I) and Pt(II) alternate, held together without any conventional bridge. The cationic species feature short Ag⋅⋅⋅Pt distances between 2.7 and 2.9 Å and contacts longer than 2.4 Å between Ag and C atoms in aromatic rings. In addition to the interactions with Ag(I) cations, Pt(II) is in a square‐planar arrangement, coordinated by a chelating and a terminal amine and an aqua ligand. The central Ag(I) in the pentanuclear cation is located on a twofold crystallographic axis and not involved in any obvious coordinative bond; it exclusively shows short contacts to the neighboring Pt(II) ions and the Pt‐bonded, formally anionic carbon atoms of the cyclometallated organic ligand. Powder diffraction shows that 3 melts and re‐solidifies without decomposition.