Increase In Electron Density Research Articles

Investigation of plasma decay in BP-HiPIMS discharges

Abstract Investigation of the plasma decay mechanism from energy and density temporal/spatial evolutions together is important and urgent in the novel bipolar-pulse high power impulse magnetron sputtering (BP-HiPIMS) discharge for adjusting the deposited ion energy flux. In this work, temporal and spatial characteristics of the electron energy distribution function (EEDF) have been systematically investigated using a time-resolved (250 ns) Langmuir probe to obtain the plasma decay process clearly. The plasma decay has a typical characteristic of three-step during the positive pulse. At the initial period of positive pulse (Step 1), the existence of hot electrons and potential gradient force can accelerate the plasma density decay even up to ~1015 m-3/μs. As the electron energy are cooled to several eVs, the plasma decay is dominated by the density gradient pressure with an ion sound velocity (0.5－0.7 kms-1), which can increase the downstream electron density (Step 2). As the redistribution of plasma density in the whole discharge domain, the electron density decay is exponential (Step 3) and the maximum decay rate is near the target due to the higher density gradient, while the maximum electron temperature is away from the target. Along the density gradient diffusion, the relation between electron density and temperature in BP-HiPIMS satisfies the well-known Boltzmann relation ne＝n0exp(eVp/kTe). In addition, the EEDF characteristics in the BP-HiPIMS operated with an auxiliary anode and solenoid coil have also been investigated in this work, where an increase in electron density and plasma diffusion mobility has been observed after applying the anode or solenoid coil. These temporal and spatial EEDFs allow us to understand the complex plasma physics in the emerged BP-HiPIMS discharge clearly, especially with the view of high-energy and low-energy electron loss and balance.

Electroreduction-Driven Formation and Connectivity of Polyoxometalate Coordination Networks.

We present the synthesis of metal oxide coordination networks based on Preyssler-type polyoxoanions ([NaP5W30O110]14- and [NaP5MoW29O110]14-) bridged with metal-aquo complexes ([M(H2O)n]m+, Mm+ = Co2+, Ni2+, Zn2+, Y3+), induced by electrochemical reduction. Networks bridged with first-row transition metals are isostructural with a previously reported Co-bridged structure, while the Y3+-bridged structure is new. All networks feature an uncommon binding motif of the metal cation to the oxygen atoms at cap positions, which we hypothesize is due to increased electron density at the cap upon reduction. Oxidation of a Zn2+-bridged network resulted in a new structure in which Zn2+-Ocap bonds are lost, indicating the importance of reduction in the connectivity of these polyoxometalate-based coordination networks.

Cost-Effective RuNi Solid Solutions Prepared by Electrodeposition for Efficient Alkaline Hydrogen Evolution.

The development of efficient hydrogen evolution reaction (HER) catalysts is crucial for water electrolysis. Currently, Ru-based catalysts are considered top contenders, but issues with stability, activity, and cost remain. In this work, RuNi alloys possessing a solid solution structure within the Ru lattice are prepared via straightforward electrodeposition on various substrates and assessed as HER catalysts in alkaline media. A RuNi solid solution containing 9.8 at. % Ni deposited on Ti substrate, wherein the Ni content greatly surpasses the solubility limit of Ni in Ru at room temperature, exhibits a considerably low overpotential of 28mV at a current density of 10mA cm- 2, along with good long-term stability (less than 100mV increase in overpotential after 600 h). The enhancement in HER performance results from the increased electron density around Ru atoms due to Ni coordination, which facilitates the desorption of H* from the catalyst surface to produce H2. Concurrently, incorporating Ni reduces the Ru usage, rendering the RuNi alloy a viable cost-effective HER catalyst for practical applications.

Proton dose deposition in heterogeneous media: A TOPAS Monte Carlo simulation study.

This study investigated the influence of tissue electron density on proton beam dose distribution using TOPAS Monte Carlo simulation. Heterogeneous tissue models composed of 14 materials were constructed to simulate the dose deposition process of a 169.23MeV proton beam. The study analyzed the relationships between electron density and key parameters such as maximum dose, total dose, and dose distribution. Results showed that increasing electron density led to higher local maximum dose, lower total dose, and decreased Bragg peak depth, range, penumbra width, and full width at half maximum (FWHM). High-density tissues caused a sharp, concentrated Bragg peak at shallower depths, while low-density tissues caused a backward shift and widening of the Bragg peak. Differences in proton energy deposition in various tissues were the fundamental reasons for dose distribution variations. This study quantified the relationship between electron density and proton beam dose distribution, providing a reference for accurate dose calculation and optimization in proton therapy.

Deciphering the Basis of Enhanced Na+ Storage Induced by Halogen Doping in Na2VTi(PO4)3

AbstractElemental doping is a widely adopted strategy to enhance the electrochemical performance of electrode materials, yet limited studies have explored the resulting variations in the bonding environments and the interactions between dopant atoms and their neighboring atoms. In this study, halogen‐doped (fluorine, chlorine, and bromine) polyanionic phosphates are synthesized to investigate the effects of halogen doping on the fine crystal structure, chemical micro‐environment, and electronic structure of Na2VTi(PO4)3 for Na ion storage. Density functional theory analysis reveals that halogen doping strengthens interactions at the Na sites while disrupting their symmetry, thereby promoting Na+ conductivity. Simultaneously, the increased electron density and expanded electron cloud potentially bridge the electron clouds previously isolated by [PO4] tetrahedra, facilitating electron transport. As a result, the doped samples demonstrate improved performance in rate capability, capacity, and cycling stability. This study provides deeper insights into the influence of elemental doping on electrode materials properties.

Performance Study of Ultraviolet AlGaN/GaN Light-Emitting Diodes Based on Superlattice Tunneling Junction.

In this study, we aim to enhance the internal quantum efficiency (IQE) of AlGaN-based ultraviolet (UV) light-emitting diodes (LEDs) by using the short-period AlGaN/GaN superlattice as a tunnel junction (TJ) to construct polarized structures. We analyze in detail the effect of this polarized TJ on the carrier injection efficiency and investigate the increase in hole and electron density caused by the formation of 2D hole gas (2DHG) and 2D electron gas (2DEG) in the superlattice structure. In addition, a dielectric layer is introduced to evaluate the effect of stress changes on the tunneling probability and current spread in TJ. At a current of 140 mA, this method demonstrates effective current expansion. Our results not only improve the performance of UV LEDs but also provide an important theoretical and experimental basis for future research on UV LEDs based on superlattice TJ. In addition, our study also highlights the key role of group III nitride materials in achieving efficient UV luminescence, and the polarization characteristics and band structure of these materials are critical for optimizing carrier injection and recombination processes.

Rapid prediction model of terahertz transmission in hypersonic plasma sheath under different flight speeds for different vehicle types

Abstract This work clarifies the systematic relationship and difference mechanism between flight speed, plasma sheath and terahertz transmission under different vehicle types by joint simulation model of hypersonic plasma flow and improved scattering matrix method. Significant differences in plasma sheath and terahertz transmission characteristics are observed in different vehicle types. Radio Attenuation Measurement C (RAM C) vehicle has a larger collision frequency and sheath thickness, resulting in higher terahertz attenuation than Hypersonic International Flight Research Experimentation (HIFiRE) vehicle. With the increase of flight speed, electron density, collision frequency and terahertz attenuation of the two different types of vehicles all show a significant increase, and the sheath thickness shows an opposite trend. However, the impact of flight speed on HIFiRE vehicle is much smaller than that on RAM C vehicle, which means that flight parameters have higher control accuracy for RAM C vehicle. On this basis, the systematic relationship between plasma sheath distribution and flight speed is further determined, and a rapid prediction model for terahertz transmission attenuation of different types of vehicle is developed based on a large amount of plasma sheath data. The rapid prediction model greatly reduces the calculation time and resources compared with traditional numerical methods, and its related prediction coefficients show significant differences on different vehicle types.

Spectroscopic Insight on Neodymium Solvation in Lithium Borohydride-Supported Electrolyte.

Borohydride-based electrolytes have recently emerged as promising media for the electrodeposition of electropositive metals, including rare earth (RE) elements. While the presence of supporting alkali metal cations and RE counteranions provides essential electrochemical conductivity for achieving fast metal electrodeposition, interactions between the host ligand and solvated neodymium (Nd) complexes remain unclear. This study provides insights into the coordination structure of a concentrated and directly solvated Nd salt in a lithium borohydride-supported electrolyte. Our spectroscopic results indicate that the RE coordination environment is significantly influenced by the solvation mechanism, which can vary between metathesis and complexation pathways, primarily dictated by stoichiometric factors. Under dilute conditions, nearly complete metathesis of anions leads to a high coordination number for the host ligand (borohydride), consistent with the previously reported solvated Nd speciation in chlorine-free electrolytes. In contrast, concentrated dissolution of the Nd salt in the supported electrolyte is dominated by a complexation pathway featuring a Li-ion-paired complex with a low coordination number of the host ligand. Density functional theory (DFT) calculations indicated that the observed blue shift in the borohydride vibration was the result of an increase in electron density drawn into the terminal B-H interbond region from the hydride as the coordination changed from Li to Nd. In conjunction with DFT results, vibrational analyses allowed correlation of the experimental shifts associated with changes in Nd ligation and coordination spheres, further consolidating the prevalence of highly chloride-coordinated species under concentrated conditions. The outcomes of this work illuminate the distinctive and heterogeneous coordination structures that the electroactive RE species can adopt at high concentrations in lithium borohydride-supported electrolytes, as a key step to comprehend the reported metal electrodeposition performance in these media.

Crystalline-amorphous hybrid CoNi layered double hydroxides for high areal energy density supercapacitor.

Crystalline-amorphous hybrid materials have garnered significant attention in the realm of energy storage, yet simultaneously regulating the morphological and electronic structure of crystalline-amorphous hybrid remains a challenge. Herein, crystalline-amorphous hybrid CoNi-layered double hydroxides (CA-CoNi-LDHs) were constructed by a facile chronoamperometry (i-t) electrochemical activation strategy, which allows for dual modulation of both structural transformations and electronic structure of CoNi-layered double hydroxides (CoNi-LDHs). Experimental results demonstrate that the construction of a crystalline-amorphous hybrid can effectively optimize both the morphological and electronic structure of CoNi-LDHs, expose abundant defects, and raise the concentration of active Ni2+ and Co3+ species, which are conducive to increasing the active sites for energy storage. The reduced adsorption energy for OH-, the increased electron density near the Fermi energy level, coupled with the narrowed bandgap energy of CA-CoNi-LDHs are favorable for accelerating electron transfer and enhancing reaction kinetic. Consequently, the CA-CoNi-LDHs@CC electrode with high mass loading (18.8mgcm-2) delivers an impressive areal capacitance of 13,070mFcm-2 at 5mAcm-2, along with exceptional cycling stability. Moreover, the assembled asymmetric supercapacitor based on CA-CoNi-LDHs@CC possesses a high areal energy density of 0.71mWhcm-2 at a power density of 3.95mWcm-2. This work proves that construction of crystalline-amorphous hybrid materials is a viable strategy for achieving high energy density storage.

Effects of a Solar Flare on Global Propagation of Extremely Low Frequency Waves

AbstractSolar flares have profound impacts on the lower ionosphere and long‐distance radio propagation. Extremely low frequency (ELF: 3–3,000 Hz) waves are challenging to observe and experience unique interactions with the lower ionosphere. The primary natural sources of ELF waves are thunderstorm lightnings across the globe. Using a newly developed azimuth determination technique and improved observation hardware we show that ELF attenuation in the Earth‐Ionosphere spherical cavity decreases and propagation velocity increases under the influence of an M‐class solar flare. Using a two‐parameter model of the lower ionosphere, the observations are shown to be consistent with increased electron density and sharper gradients in the D‐region resulting from X‐ray radiation. The sharper electron density gradient is primarily responsible for the propagation velocity increase, suggesting a unique capability that ELF observations can bring to global remote sensing of the lower ionosphere under space weather perturbations.

Low-coordinated Fe−N3 single atom with rapid protonation for boosting oxygen reduction reactions

Accurately constructing the coordination environment of single-atom catalysts (SACs) is an available avenue to promote multistep tandem catalytic reactions, but challenging. Herein, we construct a Fe SAC with low-coordinated Fe − N3 configuration for efficient oxygen reduction reaction (ORR). Low-coordinated Fe − N3 successfully breaks the electron distribution symmetry of the Fe − N4 unit to optimize the adsorption strength of the reactive species on it. In situ characterization techniques directly observed the bond stretching and increased electron density of Fe − N3 configuration facilitates the dissociation of *OOH intermediates and protonation of *O, thus accelerating the four-electron reaction kinetics. Therefore, this designed Fe − N3 catalyst exhibits a mass activity of 619 A gmetal-1 at 0.85 V, nearly 39 times higher than commercial Pt/C (16 A gmetal-1), and a high four-electron selectivity of 99.1 %. Furthermore, the catalyst shows high power density (125.3 mW cm−2) in zinc-air batteries (ZABs), indicating its promising application potential. This work provides a new insight to construct well-defined SACs with coordination environment for efficient catalytic reactions.

Unraveling the mechanistic effects of oxidation and ionization on polydopamine-Pb(Ⅱ) interaction: MD and DFT study

Polydopamine (PDA), recognized for its straightforward synthesis and multifunctional groups, serves as an effective adsorbent for lead ions (Pb(II)). The structures of PDA are affected by different oxidation and ionization degrees, consequently influencing the adsorption performance for Pb(Ⅱ). Despite its extensive use, the detailed microscopic mechanisms by which these modifications affect Pb(II) adsorption remain poorly understood. In this study, all-atom molecular dynamics (AAMD) and density functional theory (DFT) simulations were employed to elucidate the interactions between PDA and Pb(II) under varying conditions of PDA’s ionization and oxidation. Enhancing PDA's ionization and oxidation degrees can effectively boost Pb(II)'s adsorption capacity. Specifically, heightened ionization significantly amplifies adsorption, as evidenced by the transfer of PDA monomer to the 6p vacant orbital of Pb(II), fostering strong coordination bonds through increased electron density. Meanwhile, escalated oxidation levels of PDA facilitate enhanced aggregation among polydopamine monomers, forming a more porous structure. Furthermore, oxidation activates inner orbital electrons within the polydopamine monomer, elevating electron transfer efficiency between PDA and Pb(II). These insights clarify the role of ionization and oxidation in optimizing PDA's performance as a Pb(II) adsorbent and provide valuable guidance for the design of advanced materials for heavy metal removal.

Machine-learning-accelerated density functional theory screening of Cu-based high-entropy alloys for carbon dioxide reduction to ethylene

Computational screening of high-entropy alloy (HEA) catalysts as alternatives to the typical Cu electrocatalyst for CO2 reduction reaction (CO2RR) has been extensively focused on C1 products, but C2+ products have received significantly less attention. This work optimized CuZnPdAgAu HEA catalyst composition for CO2RR to ethylene via density functional theory and supervised machine learning regression techniques. Candidates were identified from 106,045 HEA data for enthalpy of adsorption of *CO2, *H, *HOCCOH, and *C2H4 species, and the Gibbs free energy of *H. The electrocatalytic properties during the reaction were examined on the surface of the optimized HEA candidate – Cu0.36Zn0.18Pd0.10Ag0.18Au0.18 benchmarked to Cu (111). The Pd site of such a candidate functions as the active site for the CO2 activation step. In terms of catalytic activity, it showed lower Gibbs free energy for the potential determining step – the *OCCOH formation step compared to that on the Cu (111). Insight into electronic properties demonstrated that the candidate reduces the uphill reaction energy for *HOCCOH production pathway due to increased electron density in the C–C bond, donated from two Cu sites. It is shown that the HEA catalyst candidate has the potential for CO2RR targeting ethylene, an alternative to a common Cu catalyst.

Glyphosate and glyphosate-based herbicides induce Poecilia reticulata to maintain redox equilibrium during and after coexposure to iron oxide nanoparticles (y-Fe2O3)

Iron oxide nanoparticles (IONPs) are being increasingly recognized as viable materials for environmental remediation due to their capacity to adsorb contaminants such as glyphosate (GLY) on their surfaces. Nevertheless, the ecotoxicological implications of IONPs associated with GLY necessitate thorough evaluation to ascertain the safety of such remediation strategies. In this context, the present investigation was conducted to examine hepatic biomarkers pertinent to the redox system, as well as ultrastructural hepatic alterations in Poecilia reticulata, following a 21-day exposure to environmentally relevant concentrations of IONPs, iron ions (Fe), and glyphosate in its pure form (GLY) as well as a commercial glyphosate-based herbicide (GBH). After this exposure, the fish underwent a 21-day recovery in uncontaminated water. The results indicated an increase in the activity of catalase (CAT) and glutathione S-transferase (GST) and in the concentration of glutathione (GSH) in the animals subjected to IONP+GBH and IONP+GLY treatments. This biochemical response persisted for the duration of both the exposure and recovery phases. Concurrently, hepatocytes displayed mitochondria with increased electron density, augmented lipid droplet accumulation, and expanded necrotic areas within the hepatic tissue. In contrast, fish exposed solely to IONPs exhibited sustained redox homeostasis throughout the investigative timeline. These findings suggest that the coexposure toxicity of IONP+GLY and IONP+GBH is attributable to the agent adsorbed onto the IONPs and that P. reticulata could maintain an active antioxidant defense mechanism throughout the entire study period.

Boosted triboelectric performance in stretchable nanogenerators via 2D MXene-Driven electron accumulation and LiNbO₃-assisted charge transfer

The development of piezoelectrically enhanced triboelectric hybrid nanogenerators (PET-HNGs) has garnered considerable attention for their potential in energy harvesting. However, their performance in stretchable applications across diverse environments, such as air and water, remains limited due to the lack of high-performance, stretchable material compositions and a comprehensive understanding of the charge transfer mechanism involved. To address these challenges, we have designed a high-performance, stretchable nano-/micro-composite film by embedding 2D MXene nanosheets and piezoelectric LiNbO3 microparticles into an Ecoflex polymer matrix. Quantum mechanical calculations revealed that MXene nanosheets significantly increase electron density near the Fermi level, while LiNbO3 microparticles enhance electron transfer during contact electrification with polydimethylsiloxane (PDMS). This synergistic effect resulted in a substantial enhancement of the triboelectric energy harvesting performance, with the composite film exhibiting a 355 % increase in voltage, a 324 % increase in current, and a 100 % boost in power output density compared to systems using pure Ecoflex based TENGs. The fabricated PET-HNG demonstrated remarkable output metrics, including a voltage of 455 V, current of 140 μA, power output density of 15.6 W m−2, and an energy conversion efficiency of 78.5 %, all while maintaining exceptional performance stability even under mechanical stretching.This stretchable nanogenerator shows great potential as a self-powered wearable sensor for real-time biomechanical monitoring in various environments, including air and underwater. This innovation paves the way for the development of next-generation wearable electronics and energy harvesting devices.

Exciton-Exciton Interaction in Monolayer MoSe2 from Mutual Screening of Coulomb Binding.

Excitons in two-dimensional (2D) semiconductors are particularly exciting, as reduced screening and dimensional confinement foster their pronounced many-body interactions. Optical pumping is typically used to create excitons so as to study their properties, but at the same time such pumping can also create unbound charge carriers. This makes experimental determination of the exciton-exciton interactions difficult. Most importantly, the two effects of band gap renormalization and Coulomb screening on the individual exciton resonance energy counteract each other. Here by comparing the influences of exciton and electron density on the exciton ground and excited states energies of monolayer MoSe2 using photoluminescence spectroscopy, we are able to distinctly identify the screening of Coulomb binding by the neutral excitons and by charge carriers. The energy difference between exciton ground state (A-1s) and excited state (A-2s) red-shifts by 5.5 meV when the neutral exciton density increases from 0 to 4 × 1011 cm-2, in contrast to the blue shifts with the increase of either electron or hole density. This energy difference change is attributed to the mutual screening of Coulomb binding of neutral excitons, a many-body effect that is over 5 times magnitude stronger than the conventional estimate of exciton-exciton interactions. From this mutual Coulomb screening we extract an exciton polarizability of α2Dexciton = 2.5 × 10-17 eV(m/V)2. Our finding uncovers a mechanism that dominates the repulsive part of many-body interaction between neutral excitons.

Effects of Tube Diameter and Gas Flow Rate on the Discharge Dynamics Characteristics and Reactive Species of Nanosecond Pulsed Discharge Plasma in Contact With Water

ABSTRACTThe use of millimeter quartz tubes to generate non‐thermal plasma in contact with liquid is widely applied in medicine, such as the effective disinfection of catheter tubes and tooth cavities. Here, the effects of tube diameter and gas flow rate on discharge dynamics and reactive species characteristics of nanosecond pulse needle‐water discharge are studied using an ICCD camera and optical emission spectra. The discharge diffusion is increased significantly by an appropriate combination of tube diameter and gas flow rate. Besides, the discharge intensity, emission spectra intensities of reactive species, gas temperature, and electron density increase with the increase of quartz tube diameter and gas flow rate, which contributes to enhance the production of OH and H2O2 species in aqueous samples.

Theoretical study of particle and energy balance equations in locally bounded plasmas

In this study, new particle and energy balance equations have been developed to predict the electron temperature and density in locally bounded plasmas. Classical particle and energy balance equations assume that all plasma within a reactor is completely confined only by the reactor walls. However, in industrial plasma reactors for semiconductor manufacturing, the plasma is partially confined by internal reactor structures. We predict the effect of the open boundary area ( ) and ion escape velocity ( ) on electron temperature and density by developing new particle and energy balance equations. Theoretically, we found a low ion escape velocity ( / ) and high open boundary area ( ) to result in an approximately 38% increase in electron density and an 8% decrease in electron temperature compared to values in a fully bounded reactor. Additionally, we suggest that the velocity of ions passing through the open boundary should exceed under the condition .

Kinetics of optical phonons and DP depolarization of spins in drift transport: Hot carrier spin effect in semiconductors

<p>Spin-<strong>c</strong>onserving transport of carriers is an essential requirement for the practical semiconductor-based spintronic devices. Kinetics of optical phonons and Dyakonov-Perel (DP) depolarization of spins in drift transport in semiconductor gallium arsenide (GaAs) is theoretically investigated<strong>. </strong>We consider electrons in <em>n</em>-type bulk GaAs subjected to a strong electric field, where the electron distribution is assumed to be drifted Maxwellian. The momentum drift of this distribution results in the enhanced drift velocity, and electrons with the corresponding energy emit optical hot phonons in the drifting process. The hot phonons are incorporated via the longitudinal polar optical phonon (POP) mechanism in the momentum relaxation. It is found that a finite phonon lifetime can reduce the momentum relaxation rate, which results in a delay in the runaway to higher fields, where the effect increases with the electron density. The electron spin is found to relax with the DP relaxation frequencies, and the DP spin lifetimes are found to decrease with increasing the drift field. However, a high field completely depolarizes the electron spin due to an increase of the DP spin precession frequency of the hot electrons in the POP scattering process. It is also found that the DP spin precession frequency decreases with decreasing electron temperature or increasing electron density in the moderate range. However, the findings resulting from this investigation demonstrate the hot carrier effect in the spin transport in semiconductors. The results are discussed in comparison with those obtained in earlier experimental and theoretical studies with different approaches.</p>

Ionospheric Disturbances Observed Over the Peruvian Sector During the Mother's Day Storm (G5‐Level) on 10–12 May 2024

AbstractThis article presents the recent extreme and rare G5‐level geomagnetic storm (Mother's Day Storm) effects on the equatorial and low‐latitude ionosphere observed at the Peruvian sector by the Jicamarca (11.9°S, 76.8°W, magnetic dip 1°N) incoherent scatter radar and associated instruments. This storm was produced by multiple Earth‐directed coronal mass ejections, which generated significant modifications in the Earth's magnetic field, leading to the Sym‐H of ∼−518 nT. On the dayside, due to the strong eastward penetration electric field, vertical plasma drift and equatorial electrojet (EEJ) enhanced for 2–3 hr and remained consistent at values of ∼95 m/s and 260 nT between 1700 and 1900 UT (1200 and 1400 LT). At the same time, vertical E B plasma drift uplifted the equatorial ionosphere, producing the dusk‐side super plasma fountain and transferring electron density to higher latitudes. A huge increase (∼1,325%) in electron density (from 11 to 142 TECu) is observed at low and mid‐latitudes from ∼20°S to 50°S between 2000 and 0400 UT (1500–2300 LT). The strong westward penetration electric field suppressed pre‐reversal enhancement, leading to downward plasma drift (∼−96 m/s) at around 2400 UT (1900 LT). Overnight, vertical plasma drift fluctuated between ±90 m/s, and the combined effect of penetration and disturbance dynamo electric fields caused a significant increase (∼530 km) in ionospheric virtual height. In the main and early recovery phase, consistent short‐ and long‐duration electric field disturbances persisted for approximately 30 hr, with periods of ∼48 and 90 min.