Additional Modes Research Articles

Monomers Versus Prenucleation Clusters En Route to Polymorphism of Supramolecular Polymers.

Polymorphism in supramolecular polymers is strongly correlated with the polymerization pathways underlying their formation. To effectively control emerging polymorphs, a comprehensive understanding of nucleation pathways and mechanisms is essential. Herein, a coronene-dipeptide conjugate (Cr-o-FFOEt) is introduced and its self-assembly into two different stable 1D supramolecular polymorphs (Agg 1 and 2f) is observed in the same solvent composition (water/THF, 7:3 v/v) and same concentration at room temperature, following two competitive self-assembly pathways. The difference in the mode of solvent addition triggers the two self-assembly pathways. Furthermore, the isolated intermediate Agg 2i is found to transform into Agg 1 or Agg 2f under controlled experimental conditions. The supramolecular aggregates of Cr-o-FFOEt are thoroughly examined with the help of optical, chiroptical, and morphological techniques to understand the subtle difference in choosing the self-assembling pathways. The studies reveal that the nanotube formation of Agg 1 follows a classical nucleation-elongation supramolecular polymerization mechanism (involving monomers). In contrast, the helical fibers of Agg 2f are formed by the involvement of preorganized oligomers (nonclassical process). The observation highlights the underappreciated role of prenucleation clusters in pathway complexity and polymorphism of supramolecular 1D polymers.

Superorders and terahertz acoustic modes in multiferroic BiFeO3/LaFeO3 superlattices

Superlattices are materials created by the alternating growth of two chemically different materials. The direct consequence of creating a superlattice is the folding of the Brillouin zone, which gives rise to additional electronic bands and phonon modes. This phenomenon has been successfully exploited to achieve new transport and optical properties in semiconductor superlattices. Here, we show that multiferroic BiFeO3/LaFeO3 superlattices exhibit several structural orders parallel and perpendicular to the growth direction, not existing in individual bulk materials. Using transmission electron microscopy, x-ray diffraction, and first-principles calculations, we reveal in particular a new long-range order of tilted FeO6 octahedra, with a period along the growth direction about twice that of the chemical supercell, i.e., a superorder. The effect of this new structural order on the phonon dynamics is studied with ultrafast optical pump-probe experiments. While a folded-mode at 1.2 THz is attributed solely to the chemical modulation of the superlattice, the existence of another 0.7 THz mode seems to be explained only by a double Brillouin zone folding in agreement with the structural out-of-plane superorder. Our work shows that multiferroic BiFeO3/LaFeO3 superlattices can be used to tune the spectrum of coherent THz phonons, and potentially that of magnons or electromagnons.

Aligning fermentation conditions with non-canonical amino acid addition strategy is essential for Nε-((2-azidoethoxy)carbonyl)-L-lysine uptake and incorporation into the target protein

Protein engineering with non-canonical amino acids (ncAAs) holds great promises for diverse applications, however, there are still limitations in the implementation of this technology at manufacturing scale. The know-how to efficiently produce ncAA-incorporated proteins in a scalable manner is still very limited. In the present study, we incorporated the ncAA N6-[(2-azidoethoxy)carbonyl]-L-lysine (Azk) into an antigen binding fragment (Fab) in Escherichia coli. We used the orthogonal pyrrolysyl-tRNA synthetase/suppressor tRNACUAPyl pair from Methanosarcina mazei to incorporate Azk site-specifically. We characterized Azk uptake and Fab production at bench-scale under different fermentation conditions, varying timing and mode of Azk addition, Azk-to-cell ratio and induction time. Our results indicate that Azk uptake is comparatively efficient in the batch phase. We discovered that the time between Azk uptake and inducing its incorporation into the Fab must be kept short, which suggests that intracellular Azk is consumed and/or degraded. The results obtained in this study are an important step towards the development of efficient production methods for Azk-incorporated proteins in E. coli. The developed process is scalable and provides excellent yields of 2.95 mg functionalized Fab per g CDM, which corresponds to 80% of yield obtained with the wild type Fab. We also identified the cellular uptake of Azk being dependent on the physiological state of the cell as a potential bottleneck in production.

Dislocation‐induced local symmetry reduction in single‐crystal KNbO3 observed by Raman spectroscopy

AbstractIn recent years, dislocation‐tuned functionalized ceramics have become one of the focal points of modern materials research due to their outstanding properties. These range from improved electrical conductivity and ferroelectric properties to dislocation‐enhanced toughening and superconductivity, caused by local strain fields. The aim of this work is to investigate the dislocation‐induced structural changes in single‐crystal KNbO3 by micro‐Raman spectroscopy. Dislocation‐rich regions with tailored densities have been generated using the Brinell indenter scratching method. The influence of the dislocations on the single‐crystal structure can be observed in the Raman spectra. The activation of additional Raman modes is observed, which does not occur in regions of low dislocation density. This observation is confirmed by DFT calculations of vibrational modes and is attributed to a reduction in the crystal symmetry due to increased defect densities in plastically deformed KNbO3. In addition, an increase in compressive stress at higher dislocation densities can be demonstrated by a blueshift in Raman mode positions.

An Ultra‐Thin Dual‐Polarized Bandpass Frequency Selective Surface for 2.45‐/5.8‐GHz ISM Bands

ABSTRACTThis paper presents the design of a single‐layer, double‐sided frequency selective surface (FSS) with bandpass characteristics at the S‐band (2.45 GHz) and C band (5.8 GHz) for sub‐6‐GHz Industrial Scientific and Medical (ISM) bands. The proposed FSS is based on the concept of complementary FSS that produces additional resonant modes. The FSS is constructed using an ultra‐thin microwave laminate with a thickness of 0.00076λeff calculated at the C‐band. The solid patch on the front side of the FSS unit cell is composed of an octagonal ring connected to four spiral arms while the slotted region on the rear side is complementary to the geometry on the front side. The unit cell size of the proposed FSS element is 0.087λeff × 0.087λeff. The FSS has an ultra‐low profile with at least 40% size reduction compared to the state‐of‐the‐art. The FSS element offers 11.12% (288 MHz) and 11.45% (650 MHz) at 2.45 GHz and 5.8 GHz, respectively, at x‐polarization while 5.8% (142 MHz) and 5.9% (342 MHz) bandwidth in the y‐polarization. The FSS element has a rotational symmetric structure offering enhanced polarization stability and angular independent operation for oblique incidences up to 80°. Furthermore, FSS operation is stable, which is evaluated and presented. The prototype bandpass FSS is fabricated, and the simulation results are validated in real‐time using experiments.

Dearomative Carbonylations of Arenes via Bifunctional Coordination to Cr(CO)3

Carbonylation reactions serve as powerful tools to construct useful carbonyl compounds with high efficiency and atom economy. Compared with the well-developed carbonylation chemistry for alkenes, the dearomative carbonylation of arenes is largely underexplored, possibly owing to the severe challenge in overcoming resonance stabilization of arene π-systems. Bifunctional coordination to tricarbonylchromium not only offers a reliable strategy to activate inert benzene π-bonds towards dearomatizations but also provides the CO source for the carbonylation process. Herein, we highlight the recent progress in dearomative carbonylations of chromium-bound arenes through either conventional nucleophile-electrophile addition mode or newly-developed umpolung-enabled nucleophile-nucleophile addition mode under mild CO-gas-free conditions. Given the great abundance and diversity of arene substrates, we hope this review will attract more attention to this new direction of carbonylation chemistry.

N─N Bond Oxidative Addition‐Promoted Diaziridinone Activation: A Mechanistic Study

AbstractDensity functional theory (DFT) calculation has been used to reveal palladium‐catalyzed mode of diaziridinone ring activation. Our theoretical studies found that oxidative addition of di‐tert‐butyldiaziridinone to Pd(II) can give a high valent Pd(IV) intermediate, along with the cleavage of N─N bond in di‐tert‐butyldiaziridinone through a concerted three‐membered‐cyclic transition state. Subsequent transformations via reductive elimination and β‐N elimination give the desired indolo[3,2‐b]indole product. The competitive activation modes such as metathesis and migratory insertion can be excluded in our selected model reaction. The rate‐determining step of this reaction is the oxidative addition of di‐tert‐butyldiaziridinone step. Distortion‐interaction analysis was conducted to reveal that the oxidative addition mode of di‐tert‐butyldiaziridinone is superior to the metathesis mode due to the lower interaction energy.

Efficient Computation of Overlap Reduction Functions for Pulsar Timing Arrays.

Pulsar timing arrays seek and study gravitational waves (GWs) through the angular two-point correlation function of timing residuals they induce in pulsars. The two-point correlation function induced by the standard transverse-traceless GWs is the famous Hellings-Downs curve, a function only of the angle between the two pulsars. Additional polarization modes (vector or scalar) that may arise in alternative-gravity theories have different angular correlation functions. Furthermore, anisotropy, linear, or circular polarization in the stochastic GW background gives rise to additional structure in the two-point correlation function that cannot be written simply in terms of the angular separation of the two pulsars. In this Letter, we provide a simple formula for the most general two-point correlation function-or overlap reduction function (ORF)-for a gravitational-wave background with an arbitrary polarization state, possibly containing anisotropies in its intensity and polarization (linear and/or circular). We provide specific expressions for the ORFs sourced by the general-relativistic transverse-traceless GW modes as well as vector (or spin-1) modes that may arise in alternative-gravity theories.

Ion Association and Hydration of Some Heavy-Metal Nitrate Salts in Aqueous Solution.

Aqueous solutions of four heavy-metal nitrate salts (AgNO3, TlNO3, Cd(NO3)2 and Pb(NO3)2) have been studied at 25 °C using broadband dielectric relaxation spectroscopy (DRS) at frequencies 0.27 ≤ ν/GHz ≤ 115 over the approximate concentration range 0.2 ≲ c/mol L-1 ≲ 2.0 (0.08 ≲ c/mol L-1 ≲ 0.4 for the less-soluble TlNO3). The spectra for AgNO3, TlNO3, and Pb(NO3)2 were best described by assuming the presence of three relaxation processes. These consisted of one solute-related Debye mode centered at ∼2 GHz and two higher-frequency solvent-related modes: one an intense Cole-Cole mode centered at ∼18 GHz and the other a small-amplitude Debye mode at ∼500 GHz. These modes can be assigned, respectively, to the rotational diffusion of contact ion pairs (CIPs), the cooperative relaxation of solvent water molecules, and its preceding fast H-bond flip. For Cd(NO3)2 solutions an additional solute-related Debye mode of small-amplitude, centered at ∼0.5 GHz, was required to adequately fit the spectra. This mode was consistent with the presence of small amounts of solvent-shared ion pairs. Detailed analysis of the solvent modes indicated that all the cations are strongly solvated with, at infinite dilution, effective total hydration numbers (Zt0 values) of irrotationally bound water molecules of ∼5 for both Ag+ and Tl+, ∼10 for Pb2+, and ∼20 for Cd2+. These results clearly indicate the presence of a partial second hydration shell for Pb2+(aq) and an almost complete second shell for Cd2+(aq). However, the hydration numbers decline considerably with increasing solute concentration due to ion-ion interactions. Association constants for the formation of contact ion pairs indicated weak complexation that varies in the order: Tl+ < Ag+ < Pb2+ < Cd2+, consistent with the charge/radius ratios of the cations and their Gibbs energies of hydration. Where comparisons were possible the present constants mostly agreed well with the rather uncertain literature values.

Summary of the 11th Conference on Magnetic Confined Fusion Theory and Simulation

This conference report summarizes recent progress in plasma theory and simulation that was presented in contributed papers and discussions at the 11th Conference on Magnetic Confined Fusion Theory and Simulation (CMCFTS) held in Chengdu, China, 27–30 October, 2023. Progress in various fields has been achieved. For example, results on zonal flow generation by mode coupling, simulations of the key physics of divertor detachment, energetic particle effects on magnetohydrodynamic (MHD) modes in addition to ion- and electron-scale turbulence, physics of edge coherent modes and edge-localized modes, and the optimization of ion heating schemes as well as confinement scenarios using advanced integrated modeling are presented at the conference. In this conference, the scientific research groups were organized into six categories: (a) edge and divertor physics; (b) impurity, heating, and current drive; (c) energetic particle physics; (d) turbulent transport; (e) MHD instability; and (f) integrated modeling and code development. A summary of the highlighted progress in these working groups is presented.

Numerical Investigation of Piezoelectric Energy Harvesting From a Multi-Mode T-Shaped Structure

In this work, energy harvesting from a proposed three-mode T-shaped structure, composed of a vertical beam, two horizontal beams, a center mass, and tip masses, is investigated to expand the frequency bandwidth for energy harvesting, without compromising the power density due to the additional mass of the structure, as is the case with most multi-mode harvesters. The aim is to cleverly use and position the additional mass to help induce higher and more uniform strain levels throughout the piezoelectric patch, leading to greater power generation to help counteract the added mass. A numerical model was developed to analyze the structure, to obtain voltage and power frequency responses, taking into effect the load resistance modeling and the accurate evaluation of resonance peaks by estimating each mode damping ratio. The validity of the model was confirmed by comparisons with previous experiments involving other structures, which demonstrated strong agreement. The excitation load was strategically applied to induce maximum displacement of the center and tip masses relative to the fixed ends in each mode. The outcomes reveal that the T-shaped configuration exhibits the capacity to generate higher maximum strain and a more uniform strain distribution across the piezoelectric patch when compared to previous L-shaped and traditional cantilever harvesters' designs. These characteristics yielded a power density higher than that of the L-shaped structure by approximately 70% with only around 20% addition in structure mass. Additionally, the multi-mode T-shaped structure boasts a significantly broader harvesting bandwidth due to the additional mode, without compromising power density, as was the case with L-shaped structures. Furthermore, the positioning of the tip mass was systematically altered to assess its impact on the frequency bandwidth and power output of the horizontal and vertical beams in the three bending modes, demonstrating great robustness and tuning capabilities.

Spontaneous ignition and flame propagation in hydrogen/methane wrinkled laminar flames at reheat conditions: Effect of pressure and hydrogen fraction

Direct numerical simulations (DNS) with detailed chemical kinetics and chemical explosive mode analysis (CEMA) are performed to investigate the effect of operating pressure and hydrogen–methane blending on laminar wrinkled flames at reheat combustion conditions. Building upon previous three-dimensional DNS datasets of reheat hydrogen flames, the present work considers two-dimensional configurations that render computationally-feasible simulations of high-pressure combustion and significantly more complex hydrocarbon chemistry. A geometrically-simplified representation of the reheat combustor is adopted and the thermodynamic states considered in the simulations are carefully chosen to mimic gas turbine operation conditions, which are constrained to achieve a target flame position and flame temperature. The two-dimensional DNS results are first assessed against the available three-dimensional data and then analyzed to extract the main trends exhibited by the reheat combustion process with respect to the fraction of the fuel consumed by spontaneous ignition and flame propagation, for increasing pressures and hydrogen fractions. Due to significant differences in the characteristic features of the velocity and thermal boundary layers between the three-dimensional and the two-dimensional configurations, a different global flame shape is observed (V-shaped flame vs W-shape flame) together with a ∼10% bias in the fraction of fuel consumed by spontaneous ignition. Crucially, results from the scaling studies reveal very clear trends with a significant decrease in the fuel consumption by spontaneous ignition for increasing pressures and hydrogen fractions, at the conditions investigated. Finally, this study highlights the important role that first-principle direct numerical simulations, even when conducted in computationally affordable two-dimensional simplified geometrical configurations, can play in obtaining detailed insights and quantitative trends useful for the characterization of complex reactive flows.Novelty and significanceThe reheat burners of the two-stage sequential gas turbine combustors are designed to stabilize flames primarily due to spontaneous ignition. However, prior numerical simulations revealed the presence of an additional assisted-ignition mode aided by recirculation zones. In this study, we used practically feasible two-dimensional direct numerical simulations of premixed hydrogen–air mixtures under lean conditions to quantify the roles of the two flame stabilization modes at different operating pressures. Achieving fundamental understanding of the effect of pressure and hydrogen fraction on flame stabilization is crucial to the development of two-stage sequential combustion and the present two-dimensional calculations provide important new insights. We show that at high pressures, both modes consume fuel to a similar extent. We also investigated the effect of methane blending on flame stabilization. This study also discusses how two-dimensional direct numerical simulations can be leveraged in the design optimization of reheat burners at low technology readiness levels.

EmojiChat: Toward Designing Emoji-Driven Social Interaction in VR Museums

Museums have traditionally been places of learning, evolving into spaces that also facilitate socializing. This shift is particularly evident in virtual reality (VR) museums, which have become popular venues for activities like friend gatherings. However, education has long established the social norm that museums need to “maintaining silence.” Even in virtual environments, this can influence visitor behavior. This perception often prevents people from using verbal communication, leading them to prefer quieter forms of interaction. In museums, including the VR museums that now largely replicate the layout of physical museums, this preference may be reinforced by specific features, such as spaciousness, quietness, and block-based layouts, which may create visual obstructions, restricting interaction modes dependent on shared view, such as gesture interaction. These limitations necessitate the introduction of an additional interaction mode. Emojis, with their capacity for rapid message exchange and adjustable positioning, emerge as a suitable interaction mode in this context. Thus, we introduce EmojiChat, an innovative VR museum experience designed to respect the social norms of traditionally keeping quiet while promoting natural interaction. We first design and iterate a customized emoji set for the museum context through semi-structured interviews, participatory design, and an online survey. Then, this emoji set is integrated into a VR museum to facilitate interaction between visitors. Finally, we conduct a comparative study to evaluate the performance of EmojiChat. Our results show that the integration of emojis can improve communication enjoyment and efficiency. Additionally, we identify usage patterns for interaction modes and the advantages offered by emojis. We also identify several challenges that point toward future directions for enhancing emoji integration and facilitating social interaction.

(Invited) Collective Radial Breathing Modes in Homogeneous Nanotube Bundles

Carbon nanotubes (CNTs) exist in many atomic structures typically grow as mixtures of of many chiralities with a vast variety of properties. Identical CNTs that are arranged into two-dimensional hexagonal lattices, their vibrational properties have been predicted to change with additional low-frequency modes appearing in the Raman spectrum. [1] Up to now, the experimental study of collective vibrations has been limited by a lack of pure homogeneous chirality bundles. We overcome this challenge by employing a self-coil mechanism of a very long CNT that loop into itself during the growth process resulting in a tightly packed hexagonal stack [2]. This lattice is perfectly homogeneous in terms of diameter, chiral twist, and even handedness of the tube. By characterizing and comparing the physical properties of the coil with respect to its tails, the bundling effects are clearly visible. We report on two breathing-like modes for quasi-infinite bundles, compared to the single radial breathing mode characteristic for isolated tubes. The exciton-phonon coupling in these modes is probed with resonant Raman spectroscopy, revealing the same resonance energy for both breathing-like peaks. Additionally, we study the dependence of vibrational coupling on the tube diameter by analysing different tube’s diameter coils and other bundling geometries. Our experimental findings align well with previously reported theoretical studies, demonstrating a 1/d scaling for all modes, as well as confirming the relative shift of the modes dependent on intertube interaction. These vibrations provide insight into the role of intertube lattice dynamics in two-dimensional THz-range phononic crystals.[1] Popov, V. N.; Henrard, L. Evidence for the existence of two breathinglike phonon modes in infinite bundles of single-walled carbon nanotubes. Phys. Rev. B 2001, 63, 233407[2] Nakar, D.; Gordeev, G.; Machado, L. D.; Popovitz-Biro, R.; Rechav, K.; Oliveira, E. F.; Kusch, P.; Jorio, A.; Galvao, D. S.; Reich, S.; others Few-wall Carbon Nanotube Coils. Nano Letters 2019, 20, 953–962.

(Invited) Design of Reduced Shear Force Cu Cleaning Processes Via α-β-Unsaturated Chemistries for Enhanced BTA Residue Removal

As integrated circuit and logic devices continue to decrease, limiting induced defectivity during Chemical Mechanical Planarization (CMP) processes (polishing and substrate cleaning) is imperative. Defects resulting from the CMP process can be classified as mechanical (i.e., scratching), chemical (i.e., corrosion), or physiochemical (i.e., adsorbed contaminants) according to the mechanism of formation. Traditionally, a contact cleaning method implements a polyvinyl alcohol (PVA) brush to transfer cleaning chemistry to the substrate of interest and provides the necessary mechanical energy for defect removal. While this process effectively removes contaminants, its reliance on shear forces can induce secondary defect modes, such as scratching. One major challenge for the post-CMP cleaning of Cu substrates is the polymeric residue film comprised of BTA-Cu+ complexes that propagate during the CMP polishing process. The current and most effective mode to mitigate this “residue defect” is coupling brush-induced shear force with additives that promote interfacial redox reactions to remove residues through an undercutting mechanism. This work focuses on developing a “softer” and additive structure-based approach that drives less aggressive interfacial shear between the brush and wafer substrate. More specifically, α-β-unsaturated additives with diverse functionality (i.e., -unsaturated carboxylic acids, carboxylic acids, and unsaturated benzaldehydes) will be tested to evaluate their efficacy to “overcut” the organic residue via a proposed aza-Michael addition reaction pathway. This “overcutting” mechanism relies on additional modes of interaction (i.e., p-stacking, H-bonding, conformational relationships, etc.) with the BTA- Cu+ polymeric residue film. A suite of dynamic techniques (i.e., Tafel analysis, OCP vs. time, contact angle, additive diffusion analysis, and shear force) will attempt to correlate the additive structure and reaction mechanism to organic residue removal efficiency and measured interfacial shear forces. Initial results have shown that implementing an “overcutting” mechanism will decrease the overall shear force and significantly reduce the generation of secondary defects without sacrificing overall defect removal efficiency.

Magnetic field enhanced terahertz generation from shape-dependent metallic nanoparticles

Abstract This communication deals with the analytical study of terahertz (THz) generation via frequency-difference mechanism using two circularly symmetric Gaussian laser beams with slightly different frequencies ω 1 and ω 2 and wave vectors k → 1 and k → 2 simultaneously propagating through a mixture of spatially corrugated noble-metal nanoparticles. The mixture, consisting of spherical nanoparticles (SNPs) and cylindrical nanoparticles (CNPs), is placed in a host medium under the influence of an externally applied static magnetic field. The two co-propagating laser beams impart a nonlinear ponderomotive force on the electrons of the NPs, causing them to experience nonlinear oscillatory velocity. Furthermore, the consequent nonlinear current density excites THz radiation at the beat frequency ω ( = ω 1 − ω 2 ) . Magnetic fields influence the surface plasmon resonance condition associated with electrons of the nanoparticles due to enhancement in ponderomotive nonlinearities, thereby causing an increment in the amplitude of the generated THz field. It is observed that the generated THz radiation has a strong dependence on the shape and size of the NPs in addition to the magnetic field strength. CNPSs provide greater THz amplitude than SNPs due to additional resonance modes, and combining both kinds of nanostructures further enhances the amplitude. THz radiation plays an important role in biomedical and pharmaceutical fields, communications, security and THz spectroscopy.

Improving the safety of radiotherapy treatment processes via incident-driven FMEA feedback loops.

Failure mode and effects analysis (FMEA) is a valuable tool for radiotherapy risk assessment, yet its outputs might be unreliable due to failures not being identified or due to a lack of accurate error rates. A novel incident reporting system (IRS) linked to an FMEA database was tested and evaluated. The study investigated whether the system was suitable for validating a previously performed analysis and whether it could provide accurate error rates to support the expert occurrence ratings of previously identified failure modes. Twenty-three pre-identified failure modes of our external beam radiotherapy process, covering the process steps from patient admission to treatment delivery, were proffered on dedicated FMEA feedback and incident reporting terminals generated by the IRS. The clinical setting involved a computed tomography scanner, dosimetry, and five linacs. Incoming reports were used as basis to identify additional failure modes or confirm initial ones. The Kruskal-Wallis H test was applied to compare the risk priorities of the retrospective and prospective failure modes. Wald's sequential probability ratio test was used to investigate the correctness of the experts' occurrence ratings by means of the number of incoming reports. Over a 15-month period, 304 reports were submitted. There were 0.005 (confidence interval [CI], 0.0014-0.0082) reported incidents per imaging study and 0.0006 (CI, 0.0003-0.0009) reported incidents per treatment fraction. Sixteen additional failure modes could be identified, and their risk priorities did not differ from those of the initial failure modes (p=0.954). One failure mode occurrence rating could be increased, whereas the other 22 occurrence ratings could not be disproved. Our approach is suitable for validating FMEAs and deducing additional failure modes on a continual basis. Accurate error rates can only be provided if a sufficient number of reports is available.

Removal of organic matter from food wastewater using anaerobic digestion at low temperatures enhanced by exogenous signaling molecule N-hexanoyl-homoserine lactone enhancement: Insight to extracellular polymeric substances and key functional genes

This experiment aimed to study the effects of adding the exogenous signaling molecule N-hexanoyl-homoserine lactone (C6-HSL) on the anaerobic digestion of food wastewater at low temperature (15 °C). Daily addition of 0.4 μmol C6-HSL increased the average chemical oxygen demand removal from 45.98% to 94.92%, while intermittent addition (adding 2 μmol C6-HSL every five days) increased it from 45.98% to 72.44%. These two modes of C6-HSL addition increased protease and acetate kinase activity by 47.99%/8.04% and 123.26%/127.91% respectively, and increased coenzyme F420 concentrations by 15.79% and 63.16%, respectively. The regulation of loosely bound extracellular polymeric substances synthesis was influenced by C6-HSL, which increased protein and polysaccharide content in sludge. The relative abundance of Firmicutes and Bacteroidetes increased following addition of C6-HSL. After continuous addition of C6-HSL, the relative abundance of related functional genes such as amy, apgM, aceE, and accC increased, indicating that methanogens obtained sufficient substrate. The abundance of glycolysis-related functional genes such as glk, pfk, pgi, tpiA, gap, pgk, gpmA, eno, and pyk increased after the addition of C6-HSL, ensuring the efficient transformation and absorption of organic matter by anaerobic sludge at low temperatures. This study provides new comprehensive insights into the mechanism behind the enhancement of food wastewater anaerobic digestion by C6-HSL at low temperature.

In Vitro Wear of Titanium Reinforced Hydroxyapatite Coatings in Simulated Body Fluid

Abstract Titanium-reinforced hydroxyapatite (Ti-HAP) coatings have been deposited over 254 SMO stainless steel using a low-velocity oxygen fuel technique. FESEM, XRD, Vickers microhardness, and shear strength tests have been performed to characterize the developed coatings. Further, in vitro wear behaviors of the coatings were evaluated using a pin-on-disc wear tester in simulated body fluid. The results reveal that 40Ti-HAP coating possesses superior wear resistance compared to 60Ti-HAP, Ti, and HAP coatings, attributed to higher surface hardness and higher shear strength values. Amongst the tested samples, the friction coefficient was lower for Ti coating, followed by 60Ti-HAP composite coating. The surface roughness was a prominent factor in reducing the friction coefficient of coating samples. Local detachment and brittle fracture were the dominant wear modes in Ti-HAP coating, whereas an additional micro-plowing wear mode was observed in pure hydroxyapatite and titanium coating.

A relativistic scalar model for fractional interaction between dark matter and gravity

Abstract In a series of recent papers we put forward a “fractional gravity”&amp;#xD;framework striking an intermediate course between a modified gravity theory and an&amp;#xD;exotic dark matter (DM) scenario, which envisages the DM component in virialized&amp;#xD;halos to feel a non-local interaction mediated by gravity. The remarkable success&amp;#xD;of this model in reproducing several aspects of DM phenomenology motivates us to&amp;#xD;look for a general relativistic extension. Specifically, we propose a theory, dubbed&amp;#xD;Relativistic Scalar Fractional Gravity or RSFG, in which the trace of the DM stressenergy tensor couples to the scalar curvature via a non-local operator constructed with&amp;#xD;a fractional power of the d’Alembertian. We derive the field equations starting from&amp;#xD;an action principle, and then we investigate their weak field limit, demonstrating that&amp;#xD;in the Newtonian approximation the fractional gravity setup of our previous works is&amp;#xD;recovered. We compute the first-order post-Newtonian parameter γ and its relation&amp;#xD;with weak lensing, showing that although in RSFG the former deviates from its GR&amp;#xD;values of unity, the latter is unaffected. We also perform a standard scalar-vectortensor-decomposition of RSFG in the weak field limit, to highlight that gravitational&amp;#xD;waves propagate at the speed of light, though also an additional scalar mode becomes&amp;#xD;dynamical. Finally, we derive the modified conservation laws of the DM stress energy&amp;#xD;tensor in RSFG, showing that a new non-local force emerges, and hence that the DM&amp;#xD;fluid deviates from the geodesic solutions of the field equations.