Bulk Effects Research Articles

Bulk, overlap and surface effects of swift heavy ions in CeO2

Formation of tracks of swift heavy ions decelerating in the electronic stopping regime in CeO2 was studied, combining the Monte Carlo code TREKIS with molecular dynamics. We show that strong lattice disordering (melting) followed by structure recovery form finally a damaged ion track consisting of a discontinuous crystalline region in CeO2. Normal ion impacts result in appearance of spherical crystalline hillocks on CeO2 surface. The solid-vacuum interface strongly suppresses the recrystallization of the near-surface layers, forming conically shaped tracks with several tens of nanometers lengths. Grazing ion irradiation induces intensive material expulsion from the surface forming finally grooves surrounded by nanohillocks. The processes of surface nanostructures formation is similar to those observed previously in CaF2 which has the similar crystalline structure, however requires much longer recrystallization time. Recent experimental data confirm the simulation results.

A Stable Implementation of a Data‐Driven Scale‐Aware Mesoscale Parameterization

AbstractOcean mesoscale eddies are often poorly represented in climate models, and therefore, their effects on the large scale circulation must be parameterized. Traditional parameterizations, which represent the bulk effect of the unresolved eddies, can be improved with new subgrid models learned directly from data. Zanna and Bolton (2020), https://doi.org/10.1029/2020gl088376 (ZB20) applied an equation‐discovery algorithm to reveal an interpretable expression parameterizing the subgrid momentum fluxes by mesoscale eddies through the components of the velocity‐gradient tensor. In this work, we implement the ZB20 parameterization into the primitive‐equation GFDL MOM6 ocean model and test it in two idealized configurations with significantly different dynamical regimes and topography. The original parameterization was found to generate excessive numerical noise near the grid scale. We propose two filtering approaches to avoid the numerical issues and additionally enhance the strength of large‐scale energy backscatter. The filtered ZB20 parameterizations led to improved climatological mean state and energy distributions, compared to the current state‐of‐the‐art energy backscatter parameterizations. The filtered ZB20 parameterizations are scale‐aware and, consequently, can be used with a single value of the non‐dimensional scaling coefficient for a range of resolutions. The successful application of the filtered ZB20 parameterizations to parameterize mesoscale eddies in two idealized configurations offers a promising opportunity to reduce long‐standing biases in global ocean simulations in future studies.

EFFECT OF PHENOL FORMALDEHYDE RESIN IMPREGNATION ON NANODYNAMIC VISCOELASTICITY OF PINUS MASSONIANA LAMB IN WET STATE

We evaluated the effects of phenol formaldehyde (PF) resin modification on Masson pine (Pinus massoniana Lamb.) wood cell wall in wet states. The penetration degree of PF resin into wood cell was determined using confocal laser scanning microscopy (CLSM). The micromechanical properties of PF-modified wood cell walls in wet state were analyzed by quasi-static nanoindentation and dynamic modulus mapping techniques. Results showed that the PF resin significantly affected the static viscoelasticity and nanodynamic viscoelasticity of wood cell walls in oven-dried and wet states. The cell-wall mechanics increased at a PF resin concentration due to the increased bulking effects, such as decreased crystallinity of cellulose. Furthermore, the microfibrillar angle (MFA) of cell walls was lower than that of the control wood cell wall. The cell-wall mechanics of PF resin-modified sample decreased small than control sample in wet states.

Impregnation Effect of Synthesized Fe3O4 Nanoparticles on the Jabon Wood’s Physical Properties

This study focused on characterizing synthetic magnetite (Fe3O4-NP) and evaluating the impregnated jabon wood’s physical properties. The co-precipitation method used for the synthesis of Fe3O4-NP, namely by mixing the iron solution (n/n Fe2+:Fe3+=1:2) with the strong base of sodium hydroxide (NaOH) (MG-S) and weak base of ammonium hydroxide (NH4OH) (MG-W) as precursors. The impregnation stage uses parameters of a -0.5 bar vacuum for half an hour and 2 bar pressure for 2 hours with magnetite concentrations of 1; 2.5; 5% w/v in a demineralized water solvent. Scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDX) and Fourier transform infrared spectrometry (FTIR) confirmed the presence of Ferrum content and Fe-O functional group in both Fe3O4-NPs produced. The Fe3O4-NP size was also measured via the X-ray diffraction analysis, namely 34.54 nm for the MG-S and 39.24 nm for the MG-W. Magnetic strength obtained was 7.51 mT for the MG-S and 8.58 mT for the MG-W. The impregnated jabon wood’s physical properties also improved with indications of an increase in wood density, weight percent gain (WPG), bulking effect (BE), anti-swelling efficiency (ASE), and a decrease in water absorption (WA). The results showed the best treatments were MG-S 2.5% and MG-W 5%.

Causality Bounds on Dissipative General-Relativistic Magnetohydrodynamics.

We derive necessary and sufficient conditions under which a large class of relativistic generalizations of Braginskii's magnetohydrodynamics with shear, bulk, and heat diffusion effects is causal and strongly hyperbolic in the fully nonlinear regime in curved spacetime. We find that causality severely constrains the size of nonideal effects and the onset of kinetic instabilities. Our results are crucial for assessing the regime of validity of fluid dynamical simulations of plasmas near supermassive black holes.

Measurements and TCAD simulations of guard-ring structures of thin silicon sensors before and after irradiation

The developing of high performing silicon detectors for particle tracking in the next generation of high-energy physics experiments at future colliders (e.g., HL-LHC, FCC) able to operate efficiently up to very high fluence (∼1⋅10171MeVneq/cm2) is of the utmost importance. In order to sustain high voltage values with minimum leakage current injection into the core region of the sensor, the design and optimisation of the Guard-Ring (GR) protection structure is crucial, especially when small substrate thicknesses are used. In a recent R&D batch produced at Fondazione Bruno Kessler (FBK) in the framework of the “eXFlu” project - INFN CSN5 grant for Young Researchers, different optimisation studies of GR structures for thin substrates (45, 30, 20 and 15μm) up to high fluence (2.5⋅10151MeVneq/cm2) have been addressed. These have been enabled thanks to ad-hoc advanced Technology CAD (TCAD) modelling of different GR design strategies, accounting for the comprehensive bulk and surface radiation-induced damage effects, and an extensive test campaign on such GR structures, both before and after irradiation. In this paper the validation of the development framework of the various GR design options before and after irradiation is presented.

Unraveling the negative charge-to-spin conversion in the Heusler alloy Co2FeSi

Recent discoveries of Heusler alloy achieve a strong advantage of the chemically disordered sample in the charge-to-spin conversion and attracted interests for spintronics applications. Here, we observe the negative charge-to-spin conversion in single magnetic layer of Co2FeSi/MgO and prove generations of σy and σx by spin-torque ferromagnetic resonance (ST-FMR). We also report that the change in charge-to-spin conversion efficiency could be controlled by chemical disordering. Furthermore, the thickness dependents of Co2FeSi demonstrated bulk effect is responsible for the generation of spin current. This study contributes to understanding the mechanisms of spin current generation from magnetic full Heusler alloy and also paves the way for the applications of magnetic memory and nonvolatile spin logic technologies.

Effect of Silyl Ether Bulk on Excited-State Intramolecular Proton Transfer-Based Sensing of Extant Hydrogen Fluoride for G-Series Nerve Agent Detection.

Luminescence-based sensing provides a method for the rapid detection of nerve agents. Previous approaches have generally focused on sensing materials containing a nucleophilic group that can react with the electrophilic phosphorus atom found in nerve agents. Herein we report an alternative approach for the detection of phosphonofluoridate-based G-series nerve agents that utilizes the fact they contain hydrogen fluoride. We have developed silylated sensing materials based on an excited-state intramolecular proton transfer (ESIPT) reporter compound, 2-[benzo[d]thiazol-2-yl]phenol. Thin films of differently silylated 2-[benzo[d]thiazol-2-yl]phenol were found to react with the hydrogen fluoride found in di-iso-propyl fluorophosphate (DFP), a simulant of sarin (G-series nerve agent), and turn on the ESIPT emission of the reporter compound. The use of the ESIPT emission reduced the impact of background fluorescence and improved the sensitivity of the detection. The effectiveness of the approach was dependent on the stability of the silyl protecting group used, with the least sterically hindered (trimethylsilyl) found to be too unstable to the ambient environment while the most sterically hindered, e.g., tri-iso-propylsilyl and tert-butyldiphenylsilyl were found to be insufficiently reactive to be useful in a real detection scenario. The sensing material composed of the tert-butyl dimethylsilyl protected 2-[benzo[d]thiazol-2-yl]phenol was found to have the best balance between stability under ambient conditions, and reactivity and selectivity to hydrogen fluoride. In a 3s exposure, it could detect hydrogen fluoride down to a concentration of around 23 ppm in DFP with 99% purity.

Revealing the synergistic effect of bulk and surface co-doped boron on TiO2 for enhanced photocatalytic H2 evolution

Boron(B) doping is considered as a promising modification method for TiO2 photocatalyst due to the facilitation of separation and migration of photogenerated carriers. However, the modification mechanisms of bulk or surface doping modes on photocatalyst are controversial, and the catalytic activity still needs to be improved. Here, a bulk and surface B co-doped TiO2 (B(B&S)-TiO2) derived from B-containing Ti-MOF (MIL-125(B)) precursor was demonstrated, which achieved a H2 evolution rate of 9.56 mmol∙g−1∙h−1 under 365 nm light without co-catalyst. Detailed investigations reveal the synergistic effect between bulk and surface co-doped B, which optimizes the microstructure, activates the 3-coordinated O (O3C) atoms of B-Ti-O structural units as active sites, enhances the transfer of photoelectrons and inhibits the recombination, balances H* adsorption–desorption during the photocatalytic reactions. This work exhibits a novel strategy of bulk and surface B co-doped photocatalysts and highlights the potential for achieving high photocatalytic H2 evolution rate without co-catalyst.

Association in Like-Charged Surfactant-Nanoparticle Systems: Interfacial and Bulk Effects.

The association of similarly charged surfactant molecules and nanoparticles in an aqueous solution remains unresolved, and the understandings reported in the literature are conflicting. To address this issue, we undertake a fundamental study to investigate bulk and interfacial phenomena in binary mixtures of (i) positively charged nanoparticles and cationic surfactants and (ii) negatively charged nanoparticles and anionic surfactants. We find that the surfactant molecules adsorb on the surface of the nanoparticle despite similar charge, leading to supercharging of particles and simultaneously driving more surfactant molecules to the air-dispersion interface. Hence, the properties of the dispersed species, such as the size and zeta potential, and the interfacial properties, such as the surface tension and surface excess concentration, change significantly. This effect is more pronounced at a low surfactant concentration and is observed irrespective of the size of nanoparticles and surfactant-particle combination. Further, we elucidate the important role of electrostatic interactions in the surfactant-particle complexation process by varying the pH of the dispersions. Contrary to changes in the properties of the dispersed species and interface, the presence of particles does not appreciably change the bulk property, such as the critical micelle concentration.

Spin magnetotransport in rare-earth iron garnet (REIG)/Pt: Effects of modulated bulk and REIG/Pt interfaces

The intrinsic magnetization compensation behaviors of rare-earth iron garnets (REIGs) make the material promising for applications in ultrafast spin storage devices. REIG/heavy metal heterostructures such as TbIG/Pt often display two sign crossovers of anomalous Hall effect resistance with varying temperatures. One of these crossovers is attributed to the magnetization compensation of REIG, and the other to the competition between the magnetic proximity effect and the spin Hall effect. Here, we design trilayer REIG heterostructures based on two rare-earth species (Tb and Eu). We modulate the layer stacking of the TbIG/EuIG/TbIG sandwich with a fixed total thickness and explore the contributions of REIG bulk and REIG/Pt interfaces on these two crossover points. As TbIG gradually moves away from Pt, the compensation temperature shows some fluctuations. However, when TbIG is entirely out of contact with Pt, the second crossover point undergoes a change that shows REIG/Pt interface dependency. The results highlight the dominance of REIG bulk on the compensation behavior and the interface sensitivity of the second crossover point. This study provides a reference for designing controllable spintronics devices, such as magnon valve applications.

Performance analysis of perovskite solar cell in presence and absence of defects

Studies of the effect of defects in any solar cell are important in achieving a satisfactory level of its performance. A comparative study with a defect-free against the defect-induced cell carries instant and ready information on laboratory/industry-based fabricated cell performance, which is prone to unavoidably induced defects. In spite of good deal of works on defects of cells such a study in an organized and comparative way remains absent to the knowledge of the authors. Ready and classified presentation of such a study, therefore, is considered to be significant. Present work is a result of motivation to fulfil this gap. This article presents a study of the effects of bulk and interface defects in perovskite solar cells. On examining the effects of deep and shallow defect levels on key performance metrics such as open-circuit voltage, short-circuit current density, and fill factor, the resulting study discusses an analysis of the impact of the defects on cell efficiency. A defect-free cell with optimal perovskite, hole-transport layer (HTL), and electron-transport layer (ETL) dimensions are analysed simultaneously to assess the level at which the defects can degrade the performance of a defect-free cell. It is observed that the defects, particularly in the deep levels, significantly impair the performance of a cell, including the open circuit voltage, short circuit current density, fill factor, and efficiency, compared to those in shallow levels.

In situ monitoring and unveiling of [formula omitted] ions transmembrane process via sensitive fiber-optic plasmonic spectral combs

Potassium ions (K+) transmembrane transport is essential for regulating various physiological processes. Herein, a label-free tilted fiber Bragg grating (TFBG)-assisted plasmonic sensor was proposed and experimentally demonstrated for measuring K+ transmembrane movement in situ and continuously. The sensor was coated with valinomycin-modified vesicular liposome, providing an exceptional capability for selectively capturing and transporting K+ through the liposome’s bilayer membrane. A differential demodulation method was proposed, by which great advancements were achieved in unveiling K+ transmembrane process showing three stages in real time. In particular, not only does the sensor sensitively detect low K+ level (detection limit down to 8.5 pM) but also successively decouple bulk and surface effects involved in transmembrane dynamics, along with additional advantage of resistance to temperature and light power fluctuations. These advancements represent great progress in revealing K+ transmembrane movement and highlight the potential for monitoring transmembrane-related cellular signaling pathways like cell proliferation and apoptosis.

Near-infrared Spectroscopy for Remote Sensing of Porosity, Density, and Cubicity of Crystalline and Amorphous H2O Ices in Astrophysical Environments

We present laboratory spectra of pure amorphous and crystalline H2O ices in the near-infrared (NIR, 1–2.5 μm/10,000–4000 cm−1) at 80–180 K. The aim of this study is to provide spectroscopic reference data that allow remotely accessing ice properties for icy objects such as icy moons, cometary ice, or Saturn rings. Specifically, we identify new spectral markers for assessing three important properties of ices in space: (i) porosity/fluffiness, (ii) bulk density of amorphous ice, and (iii) cubicity in crystalline ice. The analysis is based on the first OH-stretching overtone (2ν OH) and the combinational band at 5000 cm−1/2 μm, which are potent spectral markers for these properties. By comparison of vapor-deposited, microporous amorphous solid water, pore-free low-, high-, and very-high-density amorphous ice, we are able to separate the effect of (bulk) density from the effect of porosity on NIR-spectra of amorphous ices. This allows for clarifying a longstanding inconsistency about the density of amorphous ice vapor-deposited at low temperatures, first brought up by Jenniskens & Blake. Direct comparison of NIR spectra with powder X-ray diffractograms allows us to correlate spectral features with the number of cubic stacking layers in stacking-disordered ice Isd, ranging from fully cubic ice Ic to fully hexagonal ice Ih. We show that exposure times for instruments on the James Webb Space Telescope are in the hour range to distinguish these properties, demonstrating the usefulness of the neglected NIR spectral range for identifying ices in space.

Effects of agricultural mulch film on swine manure composting: Film degradation and nitrogen transformation

The utilization of biodegradable mulch films (bio-MFs) is essential for agricultural safety. This study explored the effects of no MF (CK), aging bio-MF (BM), non-aging bio-MF (NBM), and aging polyethylene (PE)-MF (PEM) on swine manure composting. The results demonstrated that outdoor aging (45 days) accelerated the macroscopic degradation of bio-MF in the BM. A reduction in NH4+-N and NH3 emissions in the initial composting was observed owing to an increase in the carbon source or the bulking effect provided by the MFs. N2O emissions from days 9 to 21 were higher in the PEM than other treatments because of the formation of anaerobic zone in the MF-based aggregates. An obvious increase of amoA in PEM indicated a promoted nitrification during the maturation phase, meanwhile the increase of NO2−-N and aggregate promoted denitrification. Altogether, MF influenced composting through the synergistic effects of increasing the carbon source, bulking effect, and aggregates.

High-Entropy Ceramics Enhanced Droplet Electricity Generator for Energy Harvesting and Bacterial Detection.

The droplet electricity generator (DEG) is a solid-liquid triboelectric nanogenerator with transistor-inspired bulk effect, which is regarded as an effective strategy for raindrop energy harvesting. However, further enhancement of DEG output voltage is necessary to enable its widespread applications. Here, high-entropy ceramics are integrated into the design of DEG intermediate layer for the first time, achieving a high output voltage of 525 V. High-entropy ceramics have colossal dielectric constant, which can help to reduce the triboelectric charge decay for DEG. Furthermore, the effect of factors on DEG output performance when employing high-entropy ceramics as the intermediate layer is extensively analyzed, and the underlying mechanisms and mathematical models are explored. Finally, the enhanced output voltage of DEG not only facilitates faster energy harvesting but also develops a novel method for rapid bacterial detection. This work successfully integrates high-entropy ceramics into DEG design, significantly enhances the output voltage, and offers a novel direction for DEG development.

Scrutinizing transport phenomena and recombination mechanisms in thin film Sb2S3 solar cells

The Schockley–Quisser (SQ) limit of 28.64% is distant from the Sb2S3 solar cells’ record power conversion efficiency (PCE), which is 8.00%. Such poor efficiency is mostly owing to substantial interface-induced recombination losses caused by defects at the interfaces and misaligned energy levels. The endeavor of this study is to investigate an efficient Sb2S3 solar cell structure via accurate analytical modeling. The proposed model considers different recombination mechanisms such as non-radiative recombination, Sb2S3/CdS interface recombination, Auger, SRH, tunneling-enhanced recombination, and their combined impact on solar cell performance. This model is verified against experimental work (Glass/ITO/CdS/Sb2S3/Au) where a good coincidence is achieved. Several parameters effects such as thickness, doping, electronic affinity, and bandgap are scrutinized. The effect of both bulk traps located in CdS and Sb2S3 on the electrical outputs of the solar cell is analyzed thoroughly. Besides, a deep insight into the effect of interfacial traps on solar cell figures of merits is gained through shedding light into their relation with carriers’ minority lifetime, diffusion length, and surface recombination velocity. Our research findings illuminate that the primary contributors to Sb2S3 degradation are interfacial traps and series resistance. Furthermore, achieving optimal band alignment by fine-tuning the electron affinity of CdS to create a Spike-like conformation is crucial for enhancing the immunity of the device versus the interfacial traps. In our study, the optimized solar cell configuration (Glass/ITO/CdS/Sb2S3/Au) demonstrates remarkable performance, including a high short-circuit current (JSC) of 47.9 mA/cm2, an open-circuit voltage (VOC) of 1.16 V, a fill factor (FF) of 54%, and a notable improvement in conversion efficiency by approximately 30% compared to conventional solar cells. Beyond its superior performance, the optimized Sb2S3 solar cell also exhibits enhanced reliability in mitigating interfacial traps at the CdS/Sb2S3 junction. This improved reliability can be attributed to our precise control of band alignment and the fine-tuning of influencing parameters.

Second-Generation Chiral Amino Acid Derivatives Afford High Stereoselectivity and Stability in Aqueous RNA Acylation.

Activated acyl species have proven versatile in the esterification of 2'-OH groups in RNA, enabling structure mapping, caging, profiling, and labeling of the biopolymer. Nearly all reagents developed for this reaction have been achiral; however, a recent study reported that simple chiral amino acid acylimidazole derivatives could yield diastereoselective reactions at RNA 2'-OH in water, enabling up to 4:1 selectivity in screening. Here, we investigated the effect of steric bulk on the stereoselectivity of RNA reaction and on the stability of adducts with a library of 36 chiral acylimidazole scaffolds with increasing steric demand. The results document the highest stereoselectivity yet achieved in RNA acylation reactions, with as high as >99:1 diastereoselectivity at >70% conversion. Also notably, the bulky adducts were found to have markedly improved stability on RNA.

From interface effect to bulk effect: Probing the capacitive coupling enhancement mechanism to achieve high performance DC droplet-based nanogenerator

The DC droplet-based nanogenerator (DNG) technology has opened up a new avenue for high-entropy water energy harvesting. However, the conventional DC DNG relies on the interface effect to generate a limited surface charge density, which severely restricts its electrical performance. Here, inspired by the MOS transistors, a novel total current DNG (TC-DNG) platform with back-gate modulation structure is developed, successfully realizing the transform from interface effect to bulk effect. By using the rationally patterned DNG as triboelectric probe, an intriguing capacitive coupling enhancement mechanism is discovered. With such a mechanism, the nanogenerator could employ both the capacitive coupling effect of the back-gate electrode and the self-exciting effect of droplet charge-shuttles to achieve a significantly enhanced performance in both charge transfer and voltage output. As a result, this TC-DNG provides a transferred charge of 30 nC per droplet and an output voltage of 800 V and is capable of illuminating 480 high-brightness LEDs without using any power management circuit. In addition, this TC-DNG could easily adapt to a wide range of application scenarios owing to the interchangeability of the back-gate material. This work could inspire further innovations in energy transfer mechanism and harvesting technology at the liquid-solid interface.

Thermal entanglement in conformal junctions

We consider a quantum junction described by a 1+1-dimensional boundary conformal field theory (BCFT). Our analysis focuses on correlations emerging at finite temperature, achieved through the computation of entanglement measures. Our approach relies on characterizing correlation functions of twist fields using BCFT techniques. We provide non-perturbative predictions for the crossover between low and high temperatures. An intriguing interplay between bulk and boundary effects, associated with the bulk/boundary scaling dimensions of the fields above, is found. In particular, the entanglement entropy is primarily influenced by bulk thermal fluctuations, exhibiting extensiveness for large system sizes with a prefactor independent of the scattering properties of the defect. In contrast, negativity is governed by fluctuations across the entangling points only, adhering to an area law; its value depends non-trivially on the defect, and it diverges logarithmically as the temperature is decreased. To validate our predictions, we numerically check them for free fermions on the lattice, finding good agreement.