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Addressing the H_0 tension through matter with pressure and no early dark energy
No full textWe propose that the Hubble tension arises due to an unaccounted-for additional component that behaves as matter with pressure.
We aim to demonstrate that this fluid remains subdominant compared to both dust and radiation throughout the entire expansion history of the Universe. Specifically, the additional fluid satisfies the Zel'dovic limit with a constant equation of state, ω_s > 0, and quite a small normalized energy density, Ω_s.
This component modifies both the sound horizon and the background expansion rate, acting quite differently from early dark-energy models, without significantly affecting the other cosmological parameters. To show this, we performed a Markov chain Monte Carlo analysis of our model, hereafter dubbed the Λ_ω_s cold dark matter (Λ_ω_sCDM) paradigm, using the publicly available Boltzmann code. CLASS
Our results confirm the presence of this fluid, with properties that closely resemble those of radiation. We find best-fit values that satisfy ω_s łesssim ω_γ and a relative energy density of Ω_s / Ω_γ = 0.33, with ω_γ and Ω_γ being the equation of state and density of photons, respectively. The additional fluid may be interpreted either as a thermalized scalar field, plausibly associated with the quasi-quintessence model, or as Proca-type vector fields, albeit we did not exclude a priori more exotic possibilities, i.e., dark radiation, axions, and so on. Physical implications of our results were analyzed in detail, indicating a statistical preference for the Λ_ω_sCDM scenario over the conventional ΛCDM background
Differences between economical, ecological and societal optimal designs of solar parks due to feed-in restrictions
No full textWith increasing market share of distributed, renewable electricity generation, challenges like net congestion, become increasingly relevant. Solar parks in northwest Europe are generating electrical energy homogeneously over the full capacity range. To increase the utilisation of the grid connection, the AC:DC ratio, the grid export limit relative to installed DC capacity, of solar parks is reduced which clips the high production hours. In this work, we investigate how such an external force changes the optimal design of solar parks for lowest levelised cost of electricity and average capture price and how it depends on other factors such as module price and land cost. We show that costs and a low AC:DC ratio shift the optimal design to low angle and high ground coverage ratio. On the other hand, energy yield per panel and ecological considerations favour higher tilt angles and lower ground coverage ratio
A reduced model for droplet dynamics with interfacial viscosity
No full textWe propose an extension of the phenomenological Maffettone-Minale (MM) model (Maffetton
FAMEπ: A Practical Full-Stack System Architecture for Empowering Secure Digital Finance
No full textThe rapid advancement of digital technologies and the growing complexity of financial systems have amplified the uncertainty, heterogeneity, and interconnectedness of modern financial problems. Traditional digital finance methods, which typically focus on single scenarios, isolated user groups, or narrowly defined tasks, struggle to address today’s hybrid financial environments characterized by cross-scenario demands, multi-stakeholder interactions, and tightly coupled functional and security requirements. To bridge this gap, we first propose a novel taxonomy of digital finance research encompassing five macro perspectives (Application, Model, Element, Platform Infrastructure, and Facility) providing a systematic coordinate system for positioning and analyzing existing studies. Building on this foundation, we introduce FAMEπ, a practical full-stack system architecture designed to empower secure, scalable, and holistic digital finance. FAMEπ co-designs and integrates diverse financial applications, a broad spectrum of models, theories of full-element aggregation optimization and trustworthy computation, and a unified intelligent computing platform. Unlike fragmented or patchwork solutions, FAMEπ achieves cross-layer interoperability and system-level optimization, enabling resilient, robust, and inherently secure digital finance across all major scenarios. This work thus establishes both a conceptual blueprint and an architectural path toward next-generation full-stack digital finance systems
A study of runaway stars originating in the Scorpius-Centaurus-Lupus association
No full textRunaway stars are OB-type stars with an unusually high space velocity, and they originate in a stellar cluster. OB runaways are produced by dynamical ejection or by a supernova explosion in a multiple system, and a hybrid scenario is also possible.
Being the closest OB association to Earth, the Scorpius-Centaurus-Lupus association is an extraordinarily interesting subject of research, and it has been identified as the parent cluster of several known runaway stars. Our aim with this work is to find new runaway candidates originating in the Scorpius-Centaurus-Lupus association and its recently found subgroups using new data. Gaia
By tracing back in time the flight paths of all known OB-type stars within a radius around the Sun and those of the individual subgroups of Scorpius-Centaurus-Lupus, we intend to find close encounters between runaway candidates and the studied subgroups in order to find the likeliest parent group(s) for each candidate. As input data, we largely use DR3 and astrometry as well as radial velocities from the literature. 1.7 įlo Gaia Hipparcos
We present eight runaway candidates originating from Scorpius-Centaurus-Lupus (3D space velocity 20- ), of which at least three were previously known as such. Additionally, we find 22 walkaway stars (10- ), i.e., ``slower'' runaway stars that may have been ejected from their parent group by the same mechanisms as their faster counterparts. 67 įlo 20 įlo
We identified five new runaway stars. Among the total number of eight runaway stars (including one, ζ Oph, that is likely produced by the binary supernova scenario), up to two might have been ejected dynamically, whereas most were produced in a binary-supernova scenario. Further traceback studies may find some of the neutron stars born in these supernovae, and some of them are possibly responsible for the 60 Fe found in Earth's crust. We confirm that the runaway star ζ Oph and pulsar PSR1706 originated from Scorpius-Centaurus-Lupus in a recent nearby binary supernova, most probably from subgroup SigMA 15, which has more than one thousand member stars
Asymptotic power spectra and visibilities of damped mixed modes
No full textRecent observational studies of red giant stars have estimated the visibility of their mixed oscillation modes, which is a proxy of the average energy of these modes. Among other things, they demonstrated that although the damping rate of the oscillations in the core of many red giants appears to be negligible, other red giants exhibit high core damping rates that are sometimes consistent with the infinite value limit. Up until now, it has not been possible to link the mixed mode visibilities to core damping rates in a quantitative way. In this study, we use the progressive wave picture to derive an analytical function expressing the approximate resonance pattern of red giants up to a proportionality factor. This function can model the influence of the damping on the oscillations, as well as take into account other effects such as mode asymmetries. In particular, this expression can be used to obtain a quantitative estimate for the visibility of mixed modes and to predict the detectability of mixed mode and multiplet signatures under different core damping rates. Here, we conduct a parameter study to investigate how the damping processes affect these aspects. We find that the visibility approaches the value expected for an infinite core damping rate already at finite values. Furthermore, we find that both the mixed mode and the multiplet signatures disappear at finite core damping rates. This implies that the observational characteristics of red giants with finite core damping rates can appear as if their core damping rate were infinite, providing an explanation for the observed populations. Moreover, we have used our method to quantitatively estimate the core damping rates of red giants with unusually low mixed mode amplitudes from their observed visibilities. The analytical function describing the power spectrum developed in the present work is a flexible tool with many possible applications, which will be further explored in future studies
Co-combustion of
No full textFossil-based solid fuel dependency is characterized by supply scarcity and environmental hazards, underscoring the need for cleaner, renewable energy sources. Spirulina (Arthrospira) platensis (SP) cyanobacterium is a promising source of energy due to its abundance and high calorific value. However, co-combustion is one of several methods to reduce environmental impact by utilizing unmanaged plastic or synthetic waste (SW) with high volatility and combining it with SP. Circulating fluidized bed combustor (CFBC) technology is one of the effective thermal methods to convert various types of feedstocks into a heat source. There is limited study about the co-combustion of microalgae and plastic waste in CFBC. This study aims to examine the ash characteristics of 30% SP and 70% SW. Ash characterization is important to mitigate ash buildup and evaluate its potential for valorization. Morphology analysis showed that combustion significantly alters the feedstock's physical structure, resulting in more porous, coarser ash. The main compositions of ash are O, Si, Cl, P, Na, and Fe. Fourier transform infrared (FTIR) spectroscopy revealed the loss of specific peaks in the 3700-2000 cm⁻1 region after combustion, indicating the decomposition of proteins and lipids from SP, whereas the SW component showed significant polymer degradation
Synthesis of KOH-activated carbon through sonication for adsorption in soap production from used cooking oil
No full textUsed cooking oil (UCO) is a waste generated from frying processes in both household and industrial sectors. One way to utilize UCO is by processing it into soap. However, before being used as a raw material, purification is required because UCO contains reaction products formed during frying. This study aims to purify UCO using corn cob–based activated carbon (AC), which was activated with KOH and assisted by ultrasonic irradiation, and to evaluate its feasibility as a raw material for liquid soap production. The purification process of UCO was carried out in several stages, including degumming, neutralization, and adsorption using AC. The AC was carbonized and activated with varying KOH concentrations (10% to 60%) under ultrasonic irradiation times of 20, 40, and 60 minutes, followed by characterization using FTIR, XRD, SEM, and BET. The results showed that AC prepared with 40% KOH and 40 minutes of ultrasonic irradiation exhibited the highest iodine adsorption capacity of 1065 mg/g. The purification process from degumming to adsorption successfully reduced the free fatty acid content to 0.144%, peroxide value to 9.8 meQ O₂/kg, and moisture content to 0.07%. The purified UCO was then applied as a raw material to produce high-quality liquid soap
Evaluation of draw solution for enhanced microalgae harvesting via forward osmosis
No full textMicroalgae have attracted increasing attention as a renewable resource with potential applications in biofuels, wastewater treatment, and environmental remediation. However, large-scale harvesting remains a critical challenge due to the high energy requirements and cost inefficiencies of conventional techniques such as centrifugation and chemical flocculation. This study investigates forward osmosis (FO) as a sustainable alternative for microalgae harvesting, with sodium chloride (NaCl) evaluated as the draw solution (DS). A cellulose triacetate (CTA) FO membrane was employed to concentrate Chlorella vulgaris cultures using draw solution concentrations ranging from 2M to 7M. System performance was assessed based on water flux, electrical conductivity (EC), and total solids (TS) recovery under varying operating conditions. Results showed that water flux depended strongly on DS concentration, with higher NaCl molarity enhancing osmotic pressure and initial flux. The 6M NaCl DS produced the highest water flux (12.7 L/m2·h), although performance declined over time due to dilution effects and membrane fouling. The 4M NaCl solution provided the best balance between efficiency and cost, yielding the highest TS recovery (18.4%). FO effectively concentrated biomass, with the final concentration dependent on initial culture density and operational settings. FESEM analysis confirmed the presence of fouling layers on the membrane surface, which were manageable with periodic cleaning. Overall, the results highlight the importance of draw-solution optimisation to balance concentration efficiency, operational stability, and salt diffusion in FO-based microalgae harvesting systems
Hardcarbon Synthesis From Nipah Palm (
No full textLithium-ion batteries are among the most widely used energy storage systems. The negative electrode (anode) material plays a crucial role in determining their electrochemical performance. However, graphite anodes face several drawbacks, including high cost. Hard carbon has emerged as a promising alternative due to its high storage capacity and cycling stability. This study aims to synthesize and characterize hard carbon derived from nipah palm shell waste as a sustainable anode material. Nipah biomass was selected as the precursor because of its high cellulose (36.5%) and lignin (27.3%) content, which are essential for forming a robust hard carbon structure. The conversion process was carried out through a one-stage pyrolysis method consisting of three steps: pre-treatment, pyrolysis, and activation. The nipah shells were washed, dried, and pyrolyzed at 800 °C under a nitrogen atmosphere. The resulting hard carbon was activated using acidic and basic solutions (HCl, KOH, and NaOH), rinsed with deionized water until neutral pH, and subsequently dried. SEM–EDX analysis revealed that HCl activation produced a morphology most like commercial hard carbon. XRD analysis showed a strong peak near 2θ = 23° and a weaker peak at 2θ = 41°. FTIR spectra confirmed the presence of oxygen-containing functional groups (C–O and C=O), with absorption peaks around 1050 cm⁻1 (C–O stretching) and 1600 cm⁻1 (C=C/C=O stretching), typical of biomass-derived hard carbon. The HCl-activated sample exhibited weaker oxygen-related bands compared to NaOH- and KOH-activated samples, indicating a cleaner carbon surface and supporting its closer similarity to commercial hard carbon. Electrochemical evaluation demonstrated that HCl-activated hard carbon delivered a specific capacity of ~28 mAh g⁻1 at 0.5C, maintained stable capacity up to 3C, and achieved 78.79% retention after 20 cycles. These findings confirm the successful conversion of nipah palm shell waste into hard carbon and highlight its potential as a sustainable anode material for lithium-ion batteries