Diffusion Limit Research Articles

Analysis of the adhesion structure between the cycloolefin polymer and the copper seed layer formed using medium-vacuum sputtering

We have developed a novel approach for the fabrication of 6G communication antenna substrates by directly sputtering a copper seed layer onto a resin with low dielectric properties and low adhesiveness, without relying on a metal adhesion layer such as titanium. This study presents a detailed analysis of the effects of two surface modification methods—vacuum ultraviolet (VUV) irradiation and oxygen plasma treatment—performed before sputtering the copper seed layer on the interfacial structure between a cycloolefin polymer (COP) film and copper plating layer. Using scanning transmission electron microscopy, energy-dispersive x-ray spectroscopy, and selected area electron diffraction, we confirmed that both surface modification methods promote the formation of polycrystalline Cu2O at the interface between the COP film and the copper plating layer. VUV irradiation enhances the smoothness of the COP surface, resulting in the uniform distribution of hydrophilic functional groups. These functional groups stably interact with the sputtered copper, leading to the oxidation of copper during annealing and the formation of a consistent Cu2O layer. In contrast, oxygen plasma treatment selectively etches regions of the COP surface with high oxygen affinity, creating fine structures and concentrating the hydrophilic functional groups in the recessed areas. After sputtering, copper interacts with these localized functional groups, and during annealing, limited diffusion causes the copper to oxidize and aggregates into a Cu2O particle structure. Thus, this study demonstrates that the structures of polycrystalline Cu2O formed at the interface vary depending on the surface modification methods and elucidates the mechanisms behind these differences through analysis of surface morphology and the distribution of functional groups induced by each method.

Three-dimensional diffractive acoustic tomography

Acoustically probing biological tissues with light or sound, photoacoustic and ultrasound imaging can provide anatomical, functional, and/or molecular information at depths far beyond the optical diffusion limit. However, most photoacoustic and ultrasound imaging systems rely on linear-array transducers with elevational focusing and are limited to two-dimensional imaging with anisotropic resolutions. Here, we present three-dimensional diffractive acoustic tomography (3D-DAT), which uses an off-the-shelf linear-array transducer with single-slit acoustic diffraction. Without jeopardizing its accessibility by general users, 3D-DAT has achieved simultaneous 3D photoacoustic and ultrasound imaging with optimal imaging performance in deep tissues, providing near-isotropic resolutions, high imaging speed, and a large field-of-view, as well as enhanced quantitative accuracy and detection sensitivity. Moreover, powered by the fast focal line volumetric reconstruction, 3D-DAT has achieved 50-fold faster reconstruction times than traditional photoacoustic imaging reconstruction. Using 3D-DAT on small animal models, we mapped the distribution of the biliverdin-binding serpin complex in glassfrogs, tracked gold nanoparticle accumulation in a mouse tumor model, imaged genetically-encoded photoswitchable tumors, and investigated polyfluoroalkyl substances exposure on developing embryos. With its enhanced imaging performance and high accessibility, 3D-DAT may find broad applications in fundamental life sciences and biomedical research.

Numerical analysis of a spherical harmonic discontinuous Galerkin method for scaled radiative transfer equations with isotropic scattering

Abstract In highly diffusion regimes when the mean free path $\varepsilon $ tends to zero, the radiative transfer equation has an asymptotic behavior which is governed by a diffusion equation and the corresponding boundary condition. Generally, a numerical scheme for solving this problem has the truncation error containing an $\varepsilon ^{-1}$ contribution that leads to a nonuniform convergence for small $\varepsilon $. Such phenomenons require high resolutions of discretizations, which degrades the performance of the numerical scheme in the diffusion limit. In this paper, we first provide a priori estimates for the scaled spherical harmonic ($P_{N}$) radiative transfer equation. Then we present an error analysis for the spherical harmonic discontinuous Galerkin (DG) method of the scaled radiative transfer equation showing that, under some additional assumptions, its solutions converge uniformly in $\varepsilon $ to the solution of the scaled radiative transfer equation. We further present an optimal convergence result for the DG method with the upwind flux on Cartesian grids. Error estimates of $\left (1+\mathcal{O}(\varepsilon )\right )h^{k+1}$ (where $h$ is the maximum element length) are obtained when tensor product polynomials of degree at most $k$ are used.

Collective modes in terahertz field response of disordered superconductors

We consider a problem of nonlinear response to an external electromagnetic radiation in conventional disordered superconductors which contain a small amount of weak magnetic impurities. We focus on the diffusive limit and use Usadel equation to analyze the excitation energy and dispersion relation of the collective modes. We determine the resonant frequency and dispersion of both amplitude (Schmidt-Higgs) and phase (Carlson-Goldman) modes for moderate strength of magnetic scattering. We find that the minimum energy required for the excitation of the both of these modes decreases with an increase in spin-flip scattering. Surprisingly we also find that as a result the Carlson-Goldman mode becomes gapless and as a consequence can only be excited at some finite value of the threshold momentum. We thus discover yet another physical realization of a state with gapped momentum dispersion of one of its collective modes. The value of the threshold momentum is determined by the distance between the two consecutive spin-flip scattering events which, in turn, is proportional to the scattering time between two consecutive scattering events. The amplitude mode is diffusive and becomes strongly suppressed with the increase in spin-flip scattering. Possible ways to experimentally verify our results are also discussed.

Phenylboronic acid-modified carbon dot-proteinase K nanohybrids for enhanced photodynamic therapy against bacterial biofilm infections.

Nanohybrids combining phenylboronic acid-modified carbon dots (PCDs) and proteinase K have been engineered for addressing the formidable challenges of antimicrobial photodynamic therapy (aPDT) against bacterial biofilm infections, overcoming biofilm barrier obstruction, the limited diffusion of reactive oxygen species (ROS), and the inadequate ROS generation of traditional photosensitizers. PCDs are formulated for superior water solubility and robust singlet oxygen (1O2) production, mitigating issues related to dispersion and aggregation-induced quenching typical of conventional photosensitizers. The conjugation of phenylboronic acid to CDs not only enhanced 1O2 generation through increased electron-hole separation but also imparted strong bacterial binding capabilities to the PCDs, enabling broad-spectrum sterilization by maximizing the ROS-mediated bacterial destruction. Proteinase K, serving as a structural "glue", actively breaks down biofilms and facilitates the deep penetration of functional PCDs, aiding effective treatment of biofilm infections. In vivo studies confirm that PCDs-proteinase K nanohybrids dramatically accelerate healing in biofilm-infected wounds by synergizing enhanced photosensitization, potent bacterial adherence, and efficient biofilm elimination and penetration. This approach highlights a straightforward strategy to significantly advance aPDT, promoting the clinical adoption of non-antibiotic methods for combating bacterial biofilm infections. STATEMENT OF SIGNIFICANCE: 1) Phenylboronic acid-modified carbon dots (PCDs) were designed for enhanced water solubility and efficient singlet oxygen generation through surface modulation, also suggesting that surface modification can improve the inherent photosensitizing activity of CDs by promoting electron-hole separation; 2) The conjugation of phenylboronic acid endowed PCDs with strong bacterial binding capabilities, enabling highly efficient and broad-spectrum sterilization by maximizing reactive oxygen species-mediated bacterial destruction; 3) Incorporation of proteinase K (PK) leveraged its specific extracellular polymeric substance degrading capability, along with the stimuli-responsive release of PCDs from the PCDs-PK nanohybrids, facilitating biofilm breakdown and enabling deeper penetration of PCDs, thereby improving the treatment of biofilm infections.

Insights into the diverse roles of the terminal oxidases in Burkholderia cenocepacia H111

Burkholderia cenocepacia H111 is an obligate aerobic bacterium which has been isolated from a cystic fibrosis (CF) patient. In CF lungs the environment is considered micro-oxic or even oxygen-depleted due to bacterial activities and limited oxygen diffusion in the mucus layer. To adapt to low oxygen concentrations, bacteria possess multiple terminal oxidases. In this study, we identified six terminal oxidases of B. cenocepacia H111 and constructed reporter strains to monitor their expression in different environments. While the heme-copper oxidase aa3 (cta) was constitutively expressed, the bd-1 oxidase (cyd) was induced under oxygen-limited growth conditions. The cyanide-insensitive bd-type terminal oxidase (cio-1) was mainly expressed in cells grown on the surface of solid medium or in liquid cultures in presence of cyanide, which is known to be produced in the CF lung by the often co-residing CF pathogen Pseudomonas aeruginosa. Indeed, a cio-1 insertional mutant was not able to grow in the presence of cyanide confirming the important role of Cio-1 in cyanide resistance. The caa3 oxidase (caa), was only expressed under nutrient limitation when cells were grown on the surface of solid medium. We also investigated the involvement of two regulatory systems, Anr and RoxS/RoxR, in the expression of cio-1 and cyd. Our data suggest, that, given that Cio-1 is only present in prokaryotes and plays an important role in the defense against cyanide-producing P. aeruginosa, it may be a valuable drug target for treatment of polymicrobial infections in CF patients.

A biophysical basis for the spreading behavior and limited diffusion of Xist.

Xist RNA initiates X inactivation as it spreads in cis across the chromosome. Here, we reveal a biophysical basis for its cis-limited diffusion. Xist RNA and HNRNPK together drive a liquid-liquid phase separation (LLPS) that encapsulates the chromosome. HNRNPK droplets pull on Xist and internalize the RNA. Once internalized, Xist induces a further phase transition and "softens" the HNRNPK droplet. Xist alters the condensate's deformability, adhesiveness, and wetting properties invitro. Other Xist-interacting proteins are internalized and entrapped within the droplet, resulting in a concentration of Xist and protein partners within the condensate. We attribute LLPS to HNRNPK's RGG and Xist's repeat B (RepB) motifs. Mutating these motifs causes Xist diffusion, disrupts polycomb recruitment, and precludes the required mixing of chromosomal compartments for Xist's migration. Thus, we hypothesize that phase transitions in HNRNPK condensates allow Xist to locally concentrate silencing factors and to spread through internal channels of the HNRNPK-encapsulated chromosome.

In Vivo Nanodiamond Quantum Sensing of Free Radicals in Caenorhabditis elegans Models.

Free radicals are believed to play a secondary role in the cell death cascade associated with various diseases. In Huntington's disease (HD), the aggregation of polyglutamine (PolyQ) not only contributes to the disease but also elevates free radical levels. However, measuring free radicals is difficult due to their short lifespan and limited diffusion range. Here, a quantum sensing technique (T1 relaxometry) is used that involves fluorescent nanodiamonds (FND). Nitrogen vacancy (NV) centers within these nanodiamonds change their optical properties in response to magnetic noise, which allows detecting the unpaired electron from free radicals. This method is used to monitor the production of free radicals inside Caenorhabditis elegans models of Huntington's disease in vivo and in real-time. To investigate if radical generation occurs near polyglutamine expansions, a strain expressing Q40 yellow fluorescent protein (Q40::YFP, polyglutamine expansion overexpressed in the muscle) is used. By applying T1 relaxometry on FNDs in the body wall muscle, it is found that the production of free radicals significantly increase when PolyQ is expressed there (compared to the FNDs in intestine). The technique demonstrates the submicrometer localization of free radical information in living animals and direct measurement of their level, which may reveal the relation between oxidative stress and Huntington's disease.

Genipin-crosslinked double PLL membranes overcome the strength-diffusion trade-off in cell encapsulation without compromising biocompatibility.

Cell microencapsulation technologies allow non-autologous implantation of therapeutic cells for sustained drug delivery purposes. The perm-selective membrane of these systems provides resistance to rupture, stablishes the upper molecular weight limit in bidirectional diffusion of molecules, and affects biocompatibility. Thus, despite being a decisive factor to succeed in terms of biosafety and therapeutic efficacy, little progress has been made in its optimization so far. Here we show that, compared to other usually used coating designs, genipin-crosslinked double poly-L-lysine (GDP) membranes are able to simultaneously improve mechanical and mass-transport properties of the microcapsules, without causing any significant increase in the foreign body response when implanted in vivo. In particular, we show that GDP membranes confer capsular integrity under high pressures, both internal and external. Furthermore, this membrane design allows for more efficient bidirectional diffusion of molecules in the 20-40 kDa range while preserving the molecular weight cut-off required for exerting an effective immunobarrier. These findings may also be useful for optimizing the membrane characteristics of multiple drug delivery systems.

Layered double hydroxide modified bismuth vanadate as an efficient photoanode for enhancing photoelectrochemical water splitting.

Photoelectrochemical (PEC) water splitting has attracted significant interest as a promising approach for producing clean and sustainable hydrogen fuel. An efficient photoanode is critical for enhancing PEC water splitting. Bismuth vanadate (BiVO4) is a widely recognized photoanode for PEC applications due to its visible light absorption, suitable valence band position for water oxidation, and outstanding potential for modifications. Nevertheless, sluggish water oxidation rates, severe charge recombination, limited hole diffusion length, and inadequate electron transport properties restrict the PEC performance of BiVO4. To surmount these constraints, incorporating layered double hydroxides (LDHs) onto BiVO4 photoanodes has emerged as a promising approach for enhancing the performance. Herein, the latest advancements in employing LDHs to decorate BiVO4 photoanodes for enhancing PEC water splitting have been thoroughly studied and outlined. Initially, the fundamental principles of PEC water splitting and the roles of LDHs are summarized. Secondly, it covers the development of different composite structures, including BiVO4 combined with bimetallic and trimetallic LDHs, as well as other BiVO4-based composites such as BiVO4/metal oxide, metal sulfide, and various charge transport layers integrated with LDHs. Additionally, LDH composites incorporating materials like graphene, carbon dots, quantum dots, single-atom catalysts, and techniques for surface engineering and LDH exfoliation with BiVO4 are discussed. The research analyzes the design principles of these composites, with a specific focus on how LDHs enhance the performance of BiVO4 by increasing the efficiency and stability through synergistic effects. Finally, challenges and perspectives in future research toward developing efficient and stable BiVO4/LDHs photoelectrodes for PEC water splitting are described.

Intercalating anion and hydrogen-bond network in layered double hydroxide to breakthrough the diffusion limit for unsealing theoretical capacity

Intercalating anion and hydrogen-bond network in layered double hydroxide to breakthrough the diffusion limit for unsealing theoretical capacity

Electrospun microfibers to enhance nutrient supply in bioinks and 3D-bioprinted tissue precursors

3D-bioprinting is a promising technique to mimic the complex anatomy of natural tissues, as it comprises a precise and gentle way of placing bioinks containing cells and hydrogel. Although hydrogels expose an ideal growth environment due to their extracellular matrix (ECM)-like properties, high water amount and tissue like microstructure, they lack mechanical strength and possess a diffusion limit of a couple of hundred micrometers. Integration of electrospun fibers could hereby benefit in multiple ways, for instance by controlling mechanical characteristics, cell orientation, direction of diffusion and anisotropic swelling behavior. The aim of this study was to create an advanced ECM-biomimicking scaffold material for tissue engineering, which offers enhanced diffusion properties. PCL bulk membranes were successfully electrospun and fragmented using a cryo cutting technique. Subsequently, these short single fibers (<400µm in length and ∼5-10µm in diameter) were embedded in an agarose-based hydrogel after hydrophilization of the short single fibers by O2plasma treatment. Fiber-filled bioinks exhibit significantly improved biomolecule diffusion (>500µm), swelling properties (20%-60% of control), and higher mechanical strength, while its viscosity (5-30 mPas*s) and gelation kinetics (28 °C) remained almost unaffected. The diffusion tests indicate a high level of size selectivity, which can be utilized for targeted biomolecule transport in the future. Finally, applying 3D-bioprinting technology (drop-on-demand vs. microextrusion) a print setting dependent post-dispensing orientation of the fibers could be induced, which ultimately paves way for the fabrication of metamaterials with anisotropic material properties. As expected, the fiber-filled bioink was found to be non-cytotoxic in cell culture trials using HUVECs and HepG2 (>80% viability). In summary, microfiber integration holds great promise for 3D-bioprinting of tissue percursors with advanced metamaterial properties and thus offers high applicability in various fields of research, such asin-vitrotissue models, tissue engineered implants or cultivated meat.

Diffusion Limit–Preserving Lumped DFEMs on AMR Meshes

We present sweep-compatible, novel upwinding recipes for the bilinear discontinuous (BLD) finite element method (FEM) that allows lumped BLD to be used on adaptive mesh refinement (AMR) meshes for thick transport applications without adding additional degrees of freedom at hanging nodes that exist on refinement boundaries. We analyze the properties of the upwinding and lumping that are needed for BLD to get the thick diffusion limit on such meshes, present results demonstrating locking with the wrong recipe, and present results showing error convergence and robustness properties for two diffusive problems on a variety of AMR meshes.

Adaptive Compression and Reconstruction for Multidimensional Medical Image Data: A Hybrid Algorithm for Enhanced Image Quality.

Spatial regions within images typically hold greater priority over adjacent areas, especially in the context of medical images (MI) where minute details can have significant clinical implications. This research addresses the challenge of compressing medical image dimensions without compromising critical information by proposing an adaptive compression algorithm. The algorithm integrates a modified image enhancement module, clustering-based segmentation, and a variety of lossless and lossy compression techniques. Edge enhancement contrast limited adaptive histogram equalization (EE-CLAHE) and 2D adaptive anisotropic diffusion filter are employed to enhance and denoise the images, followed by adaptive expectation maximization clustering (AEMC) for segmentation into regions of interest (ROI) and non-ROI. The clustering process is optimized utilizing fuzzy c-means (FCM) and Otsu thresholding. Subsequently, distinct compression schemes are applied to ROI and non-ROI regions, such as Coiflet + Haar, Coiflet + Daubecheis, modified SPIHT Huffman, EZW, and SPIHT algorithms, to ensure effective storage and transmission while preserving diagnostic details. Experimental results demonstrate that the combination of the modified SPIHT Huffman algorithm for ROI and EZW for non-ROI yields superior reconstruction quality across various measures, enabling comprehensive analysis of multi-dimensional images from MRI, CT, and X-ray modalities.

Harmonic balls in Liouville quantum gravity

AbstractHarmonic balls are domains that satisfy the mean‐value property for harmonic functions. We establish the existence and uniqueness of harmonic balls on Liouville quantum gravity (LQG) surfaces using the obstacle problem formulation of Hele–Shaw flow. We show that LQG harmonic balls are neither Lipschitz domains nor LQG metric balls, and that the boundaries of their complementary connected components are Jordan curves. We conjecture that LQG harmonic balls are the scaling limit of internal diffusion limited aggregation on random planar maps. In a companion paper, we prove this in the special case of mated‐CRT maps.

Efficacy of Articaine versus Lignocaine as Local Anesthetic Agents Using Buccal Infiltration Technique for Extraction of Mandibular Premolars

ABSTRACT Introduction: Lignocaine, commonly used for local anesthesia, often results in discomfort during mandibular premolar extractions due to limited tissue diffusion with the buccal infiltration technique. Articaine, with better lipid solubility, promises improved diffusion and patient comfort. This study compares the efficacy of 2% Lignocaine and 4% Articaine in reducing pain during mandibular premolar extractions. Methodology: A split-mouth, randomized, controlled trial included 40 patients, aged between 18 and 40 years, undergoing bilateral mandibular premolar extractions. Each patient received 4% Articaine with adrenaline and 2% Lignocaine with adrenaline on opposite sides at separate appointments. Pain was assessed using the Visual Analog Scale (VAS) and Faces Pain Scale (FPS). Results: Patients in the Articaine group reported significantly lower pain levels (mean FPS: 0.2) compared to the Lignocaine group (mean FPS: 3.6) (P &lt; 0.001). In the Articaine group, 34 out of 40 patients experienced no pain, whereas all patients in the Lignocaine group reported mild to severe pain. Mild pain was reported by 23 patients in the Lignocaine group, and moderate pain by 12 (P &lt; 0.05). No severe pain was recorded in the Articaine group. Conclusion: Articaine demonstrated superior pain control, making it a more effective choice over Lignocaine for mandibular premolar extractions using the buccal infiltration technique.

Psychological Autopsy: A Powerful Tool in Forensic Investigations

Background: A psychological autopsy is a post-mortem investigative tool used to carry out a retrospective reconstruction of a missing subject’s life. The method includes gathering information from all the potentially involved parties, which may indicate the relevant elements directly or indirectly to trace the victim’s experience and identify personality traits, lifestyle, and interpersonal relationships. Discussion: Psychological autopsies are mainly performed during criminal investigations to identify the cause of death and the specific circumstances (natural, accidental, suicidal, or homicidal death). In addition, from an epidemiological point of view, this method aims to collect the relevant information about an individual’s behavior, circumstances, and reasons for their death to identify common risk factors to prevent new suicides. Although less frequently, this tool can also serve other purposes, such as the legal validity estimation of pre-death actions. Moreover, it may be used to assess whether mistakes have been made in treating people undergoing medical or psychological treatment. Conclusions: Currently, this methodology still has a limited diffusion on the Italian and European scenes due to the lack of standardized guidelines and substantial relevant scientific literature. It is the main factor affecting the tool’s reliability, validity, and systematic application in forensic investigations.

Enhancing the emulsification performance of hempseed protein hydrolysate through the incorporation of sugar beet pectin: Role of interaction mechanism and interfacial behavior.

Effects of incorporating sugar beet pectin (SBP) at various pH levels (3.0-7.0) on the conformation, interfacial characteristics, and emulsification performance of hempseed protein hydrolysate (HPH) were explored. The introduction of SBP stimulated the conversion of protein conformation from α-helix and random coil into β-sheet. Besides, the incorporated SBP led to noticeable deformation and disruption of the original granular structure of HPH, and caused a remarkable reduction in surface hydrophobicity and intrinsic fluorescence intensity. FTIR analysis and pH-dependent molecular docking verified that hydrogen bonding, hydrophobic interactions, and electrostatic interactions predominantly drove the interaction between HPH and SBP. Overall, the interaction of HPH with SBP limited protein diffusion to the interface but facilitated their rearrangement at the interface, ultimately contributing to the development of highly viscoelastic interfacial layers with reinforced intermolecular interactions. Consequently, the emulsifying activity and emulsion stability within the acidic pH range (3.0-6.0) were significantly improved by SBP binding, notably at pH5.0. Furthermore, within this pH range, HPH-SBP emulsions exhibited smaller droplet sizes with a more homogeneous distribution and stronger electrostatic repulsion relative to HPH emulsions; yet, the apparent viscosity and elastic modulus of HPH-SBP emulsions were conspicuously elevated in the presence of SBP, conducing to emulsion stabilization.

Absolute calibration-free quantitation of electroactive species on screen-printed electrodes under limited diffusion conditions. A proof of concept

Absolute calibration-free quantitation of electroactive species on screen-printed electrodes under limited diffusion conditions. A proof of concept

Diffusion Mechanism of Waste Crumb Rubber Composite Modified Asphalt Based on Molecular Dynamics Simulation

Waste crumb rubber composite modified asphalt (CRCMA), composed of base asphalt, waste rubber powder, and several additives (softener, activator, and cross-linking agent), has been shown to effectively improve asphalt properties. The interactions between the components in CRCMA are complex, involving molecular diffusion that significantly impacts its performance. The diffusion behavior in asphalt molecules will affect various properties of asphalt and the reasons for the different properties of asphalt can be explained by studying its diffusion mechanism. Therefore, understanding the diffusion mechanism of CRCMA is essential. The molecular dynamics simulation was employed to analyze the factors influencing the diffusion mechanism, using the diffusion coefficient as a key indicator of molecular mobility. The findings showed that the diffusion coefficient of the asphalt system decreased over time but increased with temperature. The rubber composition type also had a significant impact on diffusion, with butadiene rubber (BR) showing the highest coefficient, followed by natural rubber (NR), crumb rubber (CR), and styrene-butadiene rubber (SBR). The diffusion coefficient was the lowest and the diffusion rate was slowest after adding softeners. The diffusion coefficient increased slightly with the addition of CR, and the diffusion rate was slightly accelerated but not significantly. The diffusion coefficient increased rapidly with adding activator and the diffusion rate increased significantly. With the addition of cross-linking agent, the diffusion coefficient began to decrease and the diffusion rate became slower. The CRCMA microscopic performance tests indicated that the swelling effect of CR limits diffusion, while activators promote degradation and desulfurization of CR due to the large molecule structure getting smaller, enhancing diffusion. The S=O bond in the asphalt system was regenerated and re-crosslinked to create a mesh after adding the cross-linking agent. The small molecule structure was transformed into large one. The molecular diffusion was restricted partly and thus the diffusion rate was slowed down.