Simple Form Research Articles

Terrain Analysis According to Multiscale Surface Roughness in the Taklimakan Desert

Surface roughness, interpreted in the wide sense of surface texture, is a generic term referring to a variety of aspects and scales of spatial variability of surfaces. The analysis of solid earth surface roughness is useful for understanding, characterizing, and monitoring geomorphic factors at multiple spatiotemporal scales. The different geomorphic features characterizing a landscape exhibit specific characteristics and scales of surface texture. The capability to selectively analyze specific roughness metrics at multiple spatial scales represents a key tool in geomorphometric analysis. This research presents a simplified geostatistical approach for the multiscale analysis of surface roughness, or of image texture in the case of images, that is highly informative and interpretable. The implemented approach is able to describe two main aspects of short-range surface roughness: omnidirectional roughness and roughness anisotropy. Adopting simple upscaling approaches, it is possible to perform a multiscale analysis of roughness. An overview of the information extraction potential of the approach is shown for the analysis of a portion of the Taklimakan desert (China) using a 30 m resolution DEM derived from the Copernicus Glo-30 DSM. The multiscale roughness indexes are used as input features for unsupervised and supervised learning tasks. The approach can be refined both from the perspective of the multiscale analysis as well as in relation to the surface roughness indexes considered. However, even in its present, simplified form, it can find direct applications in relation to multiple contexts and research topics.

Exact planetary waves and jet streams

We investigate exact nonlinear waves on surfaces locally approximating the rotating sphere for two-dimensional inviscid incompressible flow. Our first system corresponds to a $\beta$ -plane approximation at the equator, and the second to a $\gamma$ approximation, with the latter describing flow near the poles. We find exact wave solutions in the Lagrangian reference frame that cannot be written down in closed form in the Eulerian reference frame. The wave particle trajectories, contours of potential vorticity and Lagrangian mean velocity take relatively simple forms. The waves possess a non-trivial Lagrangian mean flow that depends on the amplitude of the waves and on a particle label that characterizes values of constant potential vorticity. The mean flow arises due to potential vorticity conservation on fluid particles. Solutions over the entire space are generated by assuming that the flow far from the origin is zonal and there is a region of uniform potential vorticity between this zonal flow and the waves. In the $\gamma$ approximation, a class of waves is found that, based on analogous solutions on the plane, we call Ptolemaic vortex waves. The mean flow of some of these waves, which we can describe in highly nonlinear scenarios due to the exact nature of the solutions, resembles polar jet streams. Several illustrative solutions are used as initial conditions in the fully spherical rotating Navier–Stokes equations, where integration is performed via the numerical scheme presented in Salmon & Pizzo (Atmosphere, vol. 14, issue 4, 2023, 747). The potential vorticity contours found from these numerical experiments vary between stable permanent progressive form and fully turbulent flows generated by wave breaking.

Adaptive quantized finite-time fault-tolerant control for uncertain multi-input multi-output systems and its application

The article proposes a novel state-feedback control method for a multiple-input multiple-output (MIMO) nonlinear system with actuator faults and input quantization. The innovation of the design approach lies in the utilization of fuzzy logic systems (FLSs) to approximate the uncertain intermediate virtual control laws, thereby achieving a simplified virtual control design form. Additionally, finite-time control is employed to enhance the system’s response speed. Different from the existing literatures, the adaptive control scheme of partial loss fault gain is integrated with input quantization, which completes the unknown gain estimation and avoids the assumption condition of unknown control gain. The theoretical analysis combined with Lyapunov stability analysis shows that the tracking error can converge regardless of whether the system experiences a fault, while the closed-loop signal remains stably bounded for a finite time. Finally, the simulation results of the quadrotor unmanned aerial vehicle (UAV) attitude system indicate that this control scheme is effective.

A Review of Drug Abuse, Misuse, and Related Laboratory Challenges.

Various definitions can be considered for drugs and substance abuse. According to the National Institute on Abuse, the use of an over-the-counter drug in a different way than that prescribed to experience or arouse emotion is a simple form of drug abuse. The World Health Organization (WHO) also defines drug abuse as the persistent or sporadic use of drugs that are incompatible or unrelated to acceptable medical practice. With the increasing non-therapeutic use of prescription drugs, serious related consequences have also increased. Therefore, there is a need to know more precisely about the types of substances and drug abuse, which is the most important part of diagnosis and recognizing the tests that cause false positive and negative results. The purpose of this review article is to collect and summarize the most important and more common types of drugs of abuse and review the drugs that cause false results in screening tests. In addition, the most common detection methods of the drug will be reviewed and the advantages and drawbacks of each method will be discussed. In this article, we aimed to point out all the facts about the emerging problems in drug abuse, the methods of screening, and the possible false results in addition to troubleshooting strategies.

Zero-dimensional simulations of DC ns-pulsed plasma jet in N2 at near atmospheric pressure: validation of the vibrational kinetics

Abstract A Direct Current (DC) nanosecond (ns)-pulsed plasma jet fed with N2 at near atmospheric pressure (20 000 Pa) is studied using a transient zero-dimensional (0-D) model coupled with a two-term Boltzmann equation solver. Good agreement is observed between the simulated and measured plasma properties: including the electron density and the ratios of the N2(v = 1, 2, 3, 4) densities to the gas density. A variety of theoretical approaches are considered to determine the Vibrational-Vibrational (V-V) and Vibrational-Translational (V-T) rate coefficients. For the V-V kinetics, the simple form of an Harmonic Oscillator (sfHO), the Schwartz–Slawsky–Herzfeld (SSH) and the Forced Harmonic Oscillator (FHO) approaches are used. The SSH approach used in this study is an improved version based on the pure SSH approach. For the V-T kinetics, the sfHO, a fit function of the Semi-Classical (ffSC) calculations and a fit function of the Quasi-Classical Trajectory (ffQCT) calculations are used. The influence of these different approaches on the calculated temporal evolution profiles of the vibrational distribution functions (VDFs) within one pulse modulation cycle is revealed. It is observed that the use of these different approaches does not strongly affect the densities of the low vibrational levels (v < 5), whereas larger influences on the higher level densities are found. In addition, it is found that the simulated evolution of the VDFs are sensitive to the probabilities of the neutral wall reaction N2(v) + wall → N2(v − 1) in the range of 1 × 10−2 to 1 × 10−4. A further analysis of the wall quenching probabilities of N2(0 < v < 58) is of importance for a more accurate prediction of the VDFs.

Amphipods (Gammarus pseudolimnaeus) do not demonstrate a left-right preference in a 3-D printed aquatic T-maze

Crustaceans are increasingly used as research subjects in experiments investigating learning in invertebrates. While many of these species may be useful models it is essential to document the presence or absence of behavioral laterality, especially considering the long-held belief that functional lateralization was unique to humans or other vertebrate species. Neglecting this fundamental step weakens the applicability of results and may unnecessarily complicate experimental design. Amphipods (Gammarus pseudolimnaeus) may be a useful invertebrate for studying simple discriminations or escape behavior, but research on their potential behavioral laterality is absent. The current study investigated whether amphipods demonstrate a left-right bias when navigating an aquatic T-maze by placing them in the maze and recording their choices across multiple trials. Our results suggested that amphipods do not show a strong left-right bias during initial navigation of an aquatic T-maze. These findings may encourage other researchers to test invertebrates for behavioral laterality, utilize amphipods in studies of simple forms of learning, and potentially simplify future experimental design.

Formulation and Sensory Evaluation of Symbiotic Kulfi with Lactobacillus lactis, Banana (Musa paradisiaca) Powder and Flaxseed (Linum usitatissimum) Powder as a Functional Ingredients

Kulfi was one of the old frozen dessert earlier which was popular in rural area, nowadays that scope increased in both rural and urban area. Many probiotic dairy products are present in market but probiotic ice cream extending their space widely, some alterations were made to slight increase the viability of probiotic microorganisms that provide wide health benefits to consumers and peoples were more sensitive lactose intolerance by breakdown of complex sugars into simpler form. In this study made to production of symbiotic kulfi by incorporation of probiotic culture lactobacillus lactis (0.05g/100g), Banana powder (musa paradisiaca) (8g, 16g. 24g), and Flax seed (Linum usitatissimum) powder as a prebiotic source (2g, 4g, 6g). Banana powder and flax seed powder, not only act as prebiotic source along with provides good texture and taste with increased color and appearance of the kulfi samples. The effect of banana powder and flax seed powder reveals the survivability of probiotic microorganisms, variation in nutritional composition and sensory property. Viability of probiotic microorganisms was slight decreased by increasing in days of storage at freeze condition. In comparison of C1, P1, P2, P3 the acidity was decreased (0.22, 0.20, 0.16), Total soluble solid (50.1, 57.1, 62.5) and total carbohydrate increased. The increase in prebiotic concentration, saturated fat (5.30, 4.80, 4.30), total fat and sodium concentration was decreased. By comparing all kulfi samples, P1 sample got the highest score in both sensory attributes and nutritional analysis.

Sodelovanje in vztrajanje bolnikov z multiplo sklerozo pri zdravljenju z zdravili

Multiple sclerosis (MS) is a chronic, inflammatory, and demyelinating disease of the central nervous system that presents the second highest cause of disability among young adults in their thirties. Medication treatments are based on parenteral and novel oral disease-modifying therapies (DMTs) for their simple dosage form, increased efficacy, and safety. Medication adherence (MA) assesses the extent to which patients’ medication administration corresponds with the agreed-upon treatment recommendations from health-care providers. Medication persistence (MP) is part of the MA continuum and defined as the interval between the initiation and last dose of the applied medication immediately preceding discontinuation. Adherence measures are based on medication availability and gaps over the period it is dispensed. Medication adherence in persons with MS is complex due to disease chronicity and more demanding routes of administration. Adherence is higher in patients on oral compared to older injectable parenteral treatment. Younger age, female gender, and longer disease course are key risk factors leading to lower adherence, which declines substantially after six months of treatment. The association of disability with adherence remains unknown. The major adherence barriers in the course of treatment are adverse effects, injectophobia, and dosage frequency. Common non-adherence reasons among patients are forgetfulness, depression, and fatigue. Medication non-adherence is associated with lower health and economic outcomes. Interventions for increasing MA in persons with MS are complex and individualized. Overcoming adherence barriers in MS should be aimed at injectophobia, coping with adverse effects, and increasing beliefs towards treatment necessity.

Solution of the problem with a small parameter in suspension filtration in a porous medium

Relevance. The necessity to calculate the changes in filtration properties during injection of suspensions for subsequent forecasting of technological parameters of wells. This calculation is complicated by the presence of different-scale effects, since the penetration depth of dispersed particles is orders of magnitude smaller than the characteristic dimensions of the formation. These effects have not been studied in detail before. Aim. To analyze the effect of a small parameter on the behavior of flow characteristics using a mathematical model of suspension filtration in a porous medium. Objects. Colmatation coefficient, filtration coefficient, distribution of concentration of dispersed particles in the formation, porosity, mathematical model of deep-bed suspension migration into a porous medium. Methods. Numerical modeling, explicit finite-difference scheme, solution of a problem with a small parameter, introduction of dimensionless parameters, method of characteristics. Results and conclusions. It is shown that the processes of conformance control and colmatation of a porous medium are described within the framework of a unified system of equations of deep-bed suspension migration into a porous medium. It is identified that the concentration of retained particles is a small parameter that allows reducing the complete system of equations of deep-bed suspension migration into a porous medium to a simplified form, in which the solution can be obtained analytically using the method of characteristics. The authors compared the solutions of the complete and simplified systems of equations of deep-bed suspension migration into a porous medium, indicating their compliance with an error of less than 4 %. They obtained the distributions of the concentration of dispersed particles and porosity in the reservoir during colmatation, showing that over time the colmatation front propagates at a constant rate. It is shown that the colmatation coefficient is a small parameter that significantly determines the nature of oil displacement by water, and a decrease in the colmatation coefficient leads to a decrease in the rate of colmatation and the appearance and growth of the size of the stabilized zone near the displacement front.

Present simple forms in the written work of Bangladeshi EFL learners

This paper presents an investigation on plausible causes of similarities and differences of present simple tense features in the written work of Bangladeshi EFL learners. It endeavours to compare between British Standard English (BSE) present simple tense features found in different standard sources and the same used by the Bangladeshi EFL learners. In doing so, content analysis is employed on written compositions of a specific topic and these are collected from 30 postgraduate advance level Bangladeshi EFL learners with a special focus on the use of present simple form. Atlas.ti software is used to analyse the collected data. It is found that the features of present simple tense are the mostly used form and also a complex part of the learner’s written work. The study has found that one of the major causes of similarities and dissimilarities between the two standards are the cross-linguistic influence (CLI). This influence may be a ‘positive transfer’ that refers to the facilitating effects of one language in acquiring another; or a ‘negative transfer’ i.e. the divergences due to some differences between the target language and the native one of the learners (Odlin, 2013). For the similar features between the Bangladeshi native language, Bengali (L1) and English present tense, the learners can easily adopt the features; contrarily, they make occasional mistakes in writing or do not use in the cases of dissimilar features. Thus, based on current CLI and second language acquisition (SLA) theories, the study has hopefully contributed to the theoretical development of cross-linguistic study in written English in Bangladesh.

Converging profile relationships for offshore wind speed and turbulence intensity

Abstract. This paper reduces uncertainty in the quantification of offshore wind speed and turbulence intensity. A range of industry standard relationships, including those from International Electrotechnical Commission (IEC) and International Organization for Standardization (ISO), are compared with an extensive set of met mast data collected offshore northwestern Europe over recent decades. Analysis initially focused on over 1000 independent storm peak events identified within the 10 min mean wind speed data. Time series and coherent vertical profiles were subjected to detailed scrutiny and analysis, considering wind speeds at various averaging periods, turbulence intensity and gust factors. Most peak events were associated with neutral atmospheric conditions, so they were well represented by the ISO Frøya profile, with a shear close to the IEC power law exponent of α= 0.11. A new pragmatic approximation of atmospheric stability in terms of relative shear is outlined, bringing together key elements of the IEC and ISO standards. New empirical relationships to quantify offshore wind ambient turbulence intensity are described. A simple generalised form of gust factor relationship is adopted, with a coefficient that varies with averaging period. Distinct recommendations are made for estimating peak 10 min mean winds from peaks in 1 or 3 h mean winds. Finally, a simplified workflow for the estimation of extreme offshore winds is used to show how IEC and ISO relationships can be effectively combined.

Cloud droplet size distributions governed by condensation, collision–coalescence, and sedimentation. Part 2: Analytical expressions for size distribution shape and asymptotic behavior for large-droplet tails

Abstract Droplet growth via condensation and collision-coalescence has been investigated in the limit of very weak coalescence growth: a collector-mode approximation emerges for coalescence growth that consists solely of droplets in the tail collecting droplets near the main mode of the cloud droplet size distribution, and that does not deplete the mode. In this second part, the approximation is formalized, leading to a simplified form of the collision-coalescence term in the equation governing the evolution of the droplet size distribution. This form allows for analytical solutions for transient growth and for steady-state distributions representing a balance between condensation, collision-coalescence growth, and removal by sedimentation. The solutions lead to an expression for the drizzle growth time, formally, the finite time in which a droplet approaches infinite size. The drizzle growth time is related to a transition radius at which droplet growth switches from condensation-dominated to coalescence-dominated. The solutions also provide a dimensionless group that governs the steady-state distribution shape, which is referred to as the drizzle number. The solutions are checked by comparing to a Monte Carlo model developed in Part 1, and it is found that the analytical solution is excellent when the drizzle number is much greater than unity, which is the typical situation for the microphysical conditions achievable in a convection-cloud chamber. The steady-state size distribution has the form of a modified gamma distribution, with a transition to power-law tail at sufficiently large radius. The solutions are formally valid for a convection-cloud chamber, but can also be extended to shallow, mixed-layer clouds such as mixing fogs.

CD36 deficiency protects lipopolysaccharide-induced sepsis via inhibiting CerS6-mediated endoplasmic reticulum stress

The type 2 scavenger receptor CD36 functions not only as a long chain fatty acid transporter, but also as a pro-inflammatory mediator. Ceramide is the simple N-acylated form of sphingosine and exerts distinct biological activity depending on its acyl chain length. Six ceramide synthases (CerS) in mammals determine the chain length of ceramide species, and CerS6 mainly produces C16-ceramide. Endotoxin-induced septic shock shows high mortality, but the pathophysiologic role of sphingolipids involved in this process has been hardly investigated. This paper aims to highlight the different role of CerS isoforms in endotoxin-induced inflammatory responses and the regulatory role of CD36 in CerS6 protein degradation with an emphasis as the potential therapeutic candidates in humans. Lipopolysaccharide (LPS), the endotoxin of the Gram-negative bacterial cell wall, was treated to induce endotoxin-induced inflammation both in vitro and in vivo. CerS6-derived C16-ceramide propagated LPS-induced inflammatory responses activating various intracellular signaling pathways, such as mitogen-activated protein kinase and nuclear factor-κB, resulting in the formation of inflammasome complex and pro-inflammatory cytokines. Mechanistically, CerS6-derived C16-ceramide augmented inflammatory responses via endoplasmic reticulum stress, and CerS6 protein stability was regulated by CD36. Finally, CerS6 protein expression and LPS-induced lethality were strikingly reduced in CD36 knockout mice. Collectively, our findings show that CerS6-derived C16-ceramide plays a pivotal role in endotoxin-induced inflammation and suggest CerS6 and its regulator CD36 as possible targets for therapy under life-threatening inflammation such as septic shock.

Patient-completed online “follow-up form” to assess continuation of anti-CGRP(r) antibody therapy in patients with chronic migraine: A pilot project

BackgroundThe introduction of new drugs that target the Calcitonin Gene-Related Peptide (CGRP) system has provided significant hope for patients with otherwise treatment-resistant migraine, but also resulted in significant capacity issues at the point of delivery, as patients require follow-up at certain timepoints. AimPilot a patient-completed “follow-up form” (FuF) to replace direct patient contact at the time of 1-year treatment review in patients receiving anti-CGRP (receptor (r)) antibody therapy for chronic migraine. MethodsPatients with chronic migraine already receiving anti-CGRP(r) antibody therapy and due for 1-year review were contacted by telephone and recruited into the project. Patients completed a simple online form, which mirrored questions asked at 1-year follow-up, and a patient satisfaction survey. ResultsThirty-nine (78 %) of 50 patients completed the FuF, which resulted in further telephone contact in 3 (8 %) patients. Over 90 % strongly agreed that the FuF was easy to understand and complete. 80 % strongly agreed that they felt confident in decision making regarding continuation or cessation of anti-CGRP(r) antibody therapy. Overall, 88 % rated their experience of the online form as “Excellent” and 12 % as “Good”. ConclusionsWithin our headache service, we have demonstrated that an appropriately designed online patient-completed form has the potential to replace direct patient contact at 1-year review in patients already receiving anti-CGRP(r) antibody therapy for chronic migraine.

Taking relations as known conditions: A tagging based method for relational triple extraction

Relational triple extraction refers to extracting entities and relations from natural texts, which is a crucial task in the construction of knowledge graph. Recently, tagging based methods have received increasing attention because of their simple and effective structural form. Among them, the two-step extraction method is easy to cause the problem of category imbalance. To address this issue, we propose a novel two-step extraction method, which first extracts subjects, generates a fixed-size embedding for each relation, and then regards these relations as known conditions to extract the objects directly with the identified subjects. In order to eliminate the influence of irrelevant relations when predicting objects, we use a relation-special attention mechanism and a gate unit to select appropriate relations. In addition, most current models do not account for two-way interaction between tasks, so we design a feature interactive network to achieve bidirectional interaction between subject and object extraction tasks and enhance their connection. Experimental results on NYT, WebNLG, NYT⋆ and WebNLG⋆ datasets show that our model is competitive among joint extraction models.

Walking pace is a protective factor for rheumatoid arthritis: a mendelian randomization study

Walking pace is a simple and functional form of exercise and a strong predictor of health, but little is known about its causal association with rheumatoid arthritis. This study aimed to investigate the causal effect of WP on the developing RA using Mendelian randomization analysis. The genetic variation associated with WP was selected as an instrumental variable from the latest genome-wide association studies. Summary-level data for the outcomes were obtained from the corresponding GWAS. The inverse-variance weighted method was used as the primary MR analysis. The results were further tested using a multivariable MR approach based on Bayesian model averaging. Confounders (BMI, SMK, HBP, TD) with close associations with RA were included in the analysis. An observational study with individual data from UK Biobank was performed to reinforce our findings. The MR results indicated the significant inverse associations of WP with the risk of RA (odds ratio (OR), 0.31; 95% confidence interval (CI), 0.15, 0.62; p = 1.05 × 10 −3). After adjusting for the risk factors, the associations for WP and RA did not change substantially. Observational study results demonstrated the same effect of WP on reducing the risk of RA. The Mendelian randomization analysis and observational study provide evidence suggesting that walking pace is a protective factor for rheumatoid arthritis. Given its simple measurement, walking pace may be a pragmatic target for interventions.

Research on fractional-order memory system signals based on Loop-By-Loop Progressive Iterative Method

This article abandons the traditional Laplace transform and proposes a new method for studying fractional-order circuits, which is the Loop-By-Loop Progressive Iterative Method(LPIM). Firstly, in order to demonstrate the correctness of LPIM, the fractance circuit, which is a relatively mature and simple form in fractional-order circuits, was chosen as the research object. The output signals of fractance circuit were studied for the first time using Laplace transform and LPIM, respectively. The results showed that the conclusions obtained by LPIM were completely consistent with those obtained by Laplace transform method and existing theories, thus verifying the correctness of LPIM. Then, a brand new Fractional-Order Memory Systems (FMS) model is constructed, and based on this model, LPIM is used for the first time to simulate the output signal of Flux-Controlled Fractional-Order Memory Systems (FFMS) that has not been studied so far. The results show that when a sine signal is used as the excitation signal, the output signal of the FFMS intersects at two points, and the output signal is modulated by the frequency of the excitation signal. Finally, combining existing theories, predict the output commonalities of FMS.

Approximation Algorithms for Dynamic Inventory Management on Networks

We provide the first approximation algorithm for dynamic inventory management on a network with stochastic demand and backlogging. Specifically, under a mild cost condition, we prove the cost of a specially designed base-stock policy is less than 1.618 times the cost of an optimal policy. We develop a novel stochastic programming analysis to prove this result: We carefully calibrate two stochastic programs (providing upper and lower bounds on the optimal policy), and compare their objectives. The upper bound arises from a new class of base-stock policies we define to address the currently unresolved issue of how to assign and fulfill backlogs in a system with fulfillment flexibility. We show the optimal policy in this class takes a simple and intuitive form: backlogs are assigned to their lowest cost activities for replenishment, and the ordered resources for those activities are committed to the backlogs for fulfillment. Next, the lower bound stochastic program is derived through a novel cost accounting scheme that captures the tradeoff between current inventory decisions and future backlog decisions. We then exploit this tradeoff to bound the ratio of the two stochastic program objectives and prove our main result. We also demonstrate our policy’s practicality with numerical simulations that show it performs within 1% of optimal on average across a wide range of problem instances. Finally, we show that our techniques and results extend to more general settings, demonstrating their potential for broader applicability. Importantly, our approach extends to problems with lead times, where we prove an approximation guarantee for base-stock policies that is independent of both the lead time and network structure. Thus, our work provides the new managerial insight that properly designed base-stock policies can be effective in network settings. This paper was accepted by Victor Martínez-de-Albéniz, operations management. Supplemental Material: The online appendix and data files are available at https://doi.org/10.1287/mnsc.2022.02965 .

A Study on the Development of Information and Communication Technology-Based Oral Functional Rehabilitation Exercise Program Content for Elderly People.

Background/Objectives: This study was conducted to develop information and communication technology (ICT)-based oral functional rehabilitation exercise (OFRE) program content to effectively improve the oral function of the elderly people. Methods: After selecting evidence-based effective OFRE items through systematic review, the final items were constructed through the validity evaluation of detailed items through an expert Delphi survey. The items were composed in a simple content form that can be performed directly and applied to ICT-based mobile applications. Results: The final content items consisted of an oral functional motor-ability measurement, oral Pilates videos, and games. The first is to measure the maximum opening amount before and after exercise, and the opening amount was designed to be measured by eating the fruit displayed on the screen by opening and closing the lips. The second one consisted of eight exercises in the video, and each exercise was to be performed at least three times a day, with a total of two sets. The third is a salivary secretion function exercise that stimulates the salivary glands to stimulate the user's interest and enable them to perform oral movements on their own. It consists of a lip and respiratory muscle exercise that inflates the cheeks and bursts a balloon, and the image disappears when the word in the image presented on the screen is pronounced correctly. It consists of pronunciation exercises. Conclusions: This content development attempt can be expanded into new convergence research linked to ICT and can be used as basic data when developing related content as part of digital care for the elderly in the future.

Soft-gluon exchange matters: Isotropic screening in QCD kinetic theory

QCD kinetic theory simulations are a prominent tool for studying the nonequilibrium initial stages in heavy-ion collisions. Despite their success, all implementations rely on approximations of the hard thermal loop (HTL) screened matrix elements in the collision terms. In this paper, we present our results for different isotropic screening prescriptions in the elastic collision term for gluons. In particular, we go beyond the simple Debye-like screening form that is used in all current implementations and apply the isotropic HTL matrix element instead. For isotropic systems, the evolution is nearly unchanged, but when studying the equilibration process in a Bjorken expanding plasma, we find qualitative and quantitative differences in a range of moments of the distribution function, such as a decrease in the maximum pressure anisotropy by up to 50%. In contrast, we find no significant qualitative impact on the jet quenching parameter or on the late-time hydrodynamization dynamics of anisotropic plasmas, but observe systematically smaller values of η/s by about 10% that coincide with perturbative calculations at small couplings. Our study reveals that the choice of the screening prescription can lead to large corrections at early times, but is less important close to equilibrium. Published by the American Physical Society 2024