Drift Effects Research Articles

Small towns limit dispersal and reduce genetic diversity in populations of Texas horned lizards.

There is a general expectation that urban populations will be fragmented and the movement of individuals will be restricted leading to low effective population sizes, low genetic diversity, higher inbreeding, and higher differentiation than populations living in more continuous habitat. In this study, we compare the genetic diversity and differentiation of Texas horned lizards that are found in four small towns (Kenedy, Karnes City, Rockdale, and Smithville) in Texas and at Tinker Air Force Base, Oklahoma to populations that occur in 16 natural areas and to an introduced population in South Carolina. We also present more detailed spatial genetic data and home range data for several of the towns. Texas horned lizards (Phrynosoma cornutum) living in small towns have lower genetic diversity, higher differentiation, and smaller effective population sizes than populations located in more natural areas. There was evidence for human-mediated movement of lizards into town; however, it has not been enough to counteract the effects of drift. Home range size is smaller in town than in more natural areas. Genetic patterns suggest dispersal occurs over short distances and is inhibited across areas with a high percent of impervious surface and major roads. These data suggest that effective planning to maintain suitable habitat and corridors to facilitate movement is critical to maintaining small terrestrial species like the Texas horned lizard and must be integrated into the early stages of urban development.

Field-domain rapid-scan EPR at 240 GHz for studies of protein functional dynamics at room temperature

We present field-domain rapid-scan (RS) electron paramagnetic resonance (EPR) at 8.6T and 240GHz. To enable this technique, we upgraded a home-built EPR spectrometer with an FPGA-enabled digitizer and real-time processing software. The software leverages the Hilbert transform to recover the in-phase (I) and quadrature (Q) channels, and therefore the raw absorptive and dispersive signals, χ′ and χ′′, from their combined magnitude (I2+Q2). Averaging a magnitude is simpler than real-time coherent averaging and has the added benefit of permitting long-timescale signal averaging (up to at least 2.5×106 scans) because it eliminates the effects of source-receiver phase drift. Our rapid-scan (RS) EPR provides a signal-to-noise ratio that is approximately twice that of continuous wave (CW) EPR under the same experimental conditions, after scaling by the square root of acquisition time. We apply our RS EPR as an extension of the recently reported time-resolved Gd-Gd EPR (TiGGER) [Maity et al., 2023], which is able to monitor inter-residue distance changes during the photocycle of a photoresponsive protein through changes in the Gd-Gd dipolar couplings. RS, opposed to CW, returns field-swept spectra as a function of time with 10ms time resolution, and thus, adds a second dimension to the static field transients recorded by TiGGER. We were able to use RS TiGGER to track time-dependent and temperature-dependent kinetics of AsLOV2, a light-activated phototropin domain found in oats. The results presented here combine the benefits of RS EPR with the improved spectral resolution and sensitivity of Gd chelates at high magnetic fields. In the future, field-domain RS EPR at high magnetic fields may enable studies of other real-time kinetic processes with time resolutions that are otherwise difficult to access in the solution state.

An adversarial network used for drift correction in electronic nose

The electronic nose (E-nose) is an important means for machines to sense odor signals, but it faces a serious problem that limits its development: sensor drift. Drift refers to the long-time and irregular changes in the response signal of the gas sensor to the same analyte, and it will bring serious performance degradation to the E-nose. To reduce the effect of drift, we proposed an entropy minimization model based on adversarial networks (EMAD) which reduced the distribution difference between data with and without drift through adversarial training. EMAD consists of a generator and a classifier. To simplify the structure and improve the prediction diversity, the classifier is reused as a discriminator for adversarial training while learning the domain invariant features from the source domain. EMAD reduced the distribution difference between original data and drift data while preserving the features for classification. Experiment results on the public dataset showed that EMAD effectively eliminated the performance degradation caused by drift and achieved the highest classification accuracy compared with other advanced methods.

High performance power handling in the absence of an H-mode edge in negative triangularity DIII-D plasmas

Experiments performed during strongly-shaped high-power diverted negative triangularity (NT) experiments in DIII-D achieved detached divertor conditions and a transient-free edge, showcasing the potential for application of NT to a core-edge integrated reactor-like scenario and providing the first characterization of the parametric dependencies for detachment onset. Detached divertor conditions will be required in future devices to mitigate divertor heat fluxes. Access to dissipative divertor conditions was investigated via an increase in upstream density. Detachment onset at the outer strike point was achieved with H-mode level confinement H98−y2∼1 and reactor-relevant normalized pressures βN∼2 . Confinement degradation was observed with deeper detachment, associated with the loss of an electron temperature pedestal. Differences in geometry, radial transport, impact of cross field drifts are discussed to explain differences in access to detachment in NT discharges. Higher normalized densities, with respect to equivalent discharges in positive triangularity, were necessary to achieve detachment, partially explained by the shorter parallel connection length to the targets. The effect of cross-field particle drifts (E×B, B ×∇ B) on access to detachment was demonstrated by the lower upstream density needed to access detachment with ion B ×∇ B drift directed outside of the active divertor (Greenwald fraction fGw∼ 0.9–1.0 vs fGw∼ 1.3). The upstream density at detachment onset was observed to increase linearly with plasma current with ion B ×∇ B drift into the divertor, consistent with the observed narrowing of the scrape-off layer heat flux width λ q . Edge fluid simulations capture separatrix densities needed to achieve detachment in NT plasma and their dependence on drift direction. The ability to reproduce detachment dynamics in NT plasma increases the confidence in future design studies for NT divertors.

The role of divertor pumping combined with full drifts in particle exhaust and divertor plasma

The effect of drifts combined with pumping on particle exhaust is assessed using the SOLPS-ITER code package, considering full drifts. Both drift and pumping speed S can affect particle exhaust. Drifts change the neutral density by influencing plasma flow and the resulting particle recycling. This leads to the accumulation of neutral particles either far away or close to the pump opening location. The particle exhaust is enhanced as S rises. When the pump opening is positioned at the common flux region (CFR) of the outer divertor (referred to as Pump CFR/OD), particle exhaust is suppressed by drifts in forward Bt , while it is enhanced by drifts in reversed Bt , with fixed S. On the other hand, when the pump is situated in the private flux region (PFR) of the OD (referred to as Pump PFR/OD), particle exhaust is enhanced by drifts in both reversed and forward Bt compared to the case without drifts. Moreover, the effective pumping in reversed Bt is stronger than in forward Bt . In the same Bt direction, Pump PFR/OD has a higher effective pumping than Pump CFR/OD. Increased S results in higher particle exhaust in all Bt direction and pump location cases. The plasma detachment is affected by drift, S and pump opening location, respectively. For the specified Bt direction and pump opening location case, higher S suppresses plasma detachment. For identical particle exhaust rates, stronger pumping capacity can promote plasma detachment. Therefore, Pump PFR/OD can more easily achieve OD detachment than Pump CFR/OD in the same Bt direction. Overall, placing the pump at the PFR side of the OD while running in reversed Bt is the best option from the divertor particle exhaust and plasma detachment point of view.

Efficient and scalable covariate drift detection in machine learning systems with serverless computing

As machine learning models are increasingly deployed in production, robust monitoring and detection of concept and covariate drift become critical. This paper addresses the gap in the widespread adoption of drift detection techniques by proposing a serverless-based approach for batch covariate drift detection in ML systems. Leveraging the open-source OSCAR framework and the open-source Frouros drift detection library, we develop a set of services that enable parallel execution of two key components: the ML inference pipeline and the batch covariate drift detection pipeline. To this end, our proposal takes advantage of the elasticity and efficiency of serverless computing for ML pipelines, including scalability, cost-effectiveness, and seamless integration with existing infrastructure. We evaluate this approach through an edge ML use case, showcasing its operation on a simulated batch covariate drift scenario. Our research highlights the importance of integrating drift detection as a fundamental requirement in developing robust and trustworthy AI systems and encourages the adoption of these techniques in ML deployment pipelines. In this way, organizations can proactively identify and mitigate the adverse effects of covariate drift while capitalizing on the benefits offered by serverless computing.

Plasma rotation and diamagnetic drift effects on the resistive wall modes in the negative triangularity tokamaks

It was found previously that the negative triangularity (NT) configuration is more MHD-unstable for low n modes than the positive triangularity (PT) case, although the situation is reversed for intermediate n modes and the NT configuration becomes more stable for intermediate n modes ( n=3−10 ) (Zheng et al 2021 Nucl. Fusion 61 116014). Here, n is the toroidal mode number. In this work, we extend the studies to include the rotation effects, as well as the diamagnetic drift effects, to see how the resistive wall modes (RWMs) in the NT configuration are affected as compared with the PT configuration. This is particularly motivated by noting that the wall interface with the plasma is quite different between the NT and PT configurations. It affects the plasma rotation and diamagnetic drift effects on the low n RWM. We consider the DIII-D-NT-experiment equilibrium reconstructed by the EFIT code. Based on the equilibrium g-file, the extended equilibria are constructed with the VMEC code by varying the beta values while keeping the pressure and poloidal current flux profiles basically unchanged. The bootstrap current contribution to the equilibria is taken into account with the Sauter formula. The MHD stability is then computed using the AEGIS code with the rotation and diamagnetic drift effects taken into account. We found that, although the NT configuration is less stable for n = 1 MHD modes, the rotation and diamagnetic drift stabilization effects on RWMs are more effective in the NT configuration than in the PT one. Note that even in the PT case, the stabilization of RWMs by the rotation and kinetic effects is critical. Because the low-n RWMs in the regular NT case are more unstable, the rotation and diamagnetic drift stabilization effects found in this research are important for the NT tokamak concept.

A new lysine biosynthetic enzyme from a bacterial endosymbiont shaped by genetic drift and genome reduction.

The effect of population bottlenecks and genome reduction on enzyme function is poorly understood. Candidatus Liberibacter solanacearum is a bacterium with a reduced genome that is transmitted vertically to the egg of an infected psyllid-a population bottleneck that imposes genetic drift and is predicted to affect protein structure and function. Here, we define the function of Ca. L. solanacearum dihydrodipicolinate synthase (CLsoDHDPS), which catalyzes the committed branchpoint reaction in diaminopimelate and lysine biosynthesis. We demonstrate that CLsoDHDPS is expressed in Ca. L. solanacearum and expression is increased ~2-fold in the insect host compared to in planta. CLsoDHDPS has decreased thermal stability and increased aggregation propensity, implying mutations have destabilized the enzyme but are compensated for through elevated chaperone expression and a stabilized oligomeric state. CLsoDHDPS uses a ternary-complex kinetic mechanism, which is to date unique among DHDPS enzymes, has unusually low catalytic ability, but an unusually high substrate affinity. Structural studies demonstrate that the active site is more open, and the structure of CLsoDHDPS with both pyruvate and the substrate analogue succinic-semialdehyde reveals that the product is both structurally and energetically different and therefore evolution has in this case fashioned a new enzyme. Our study suggests the effects of genome reduction and genetic drift on the function of essential enzymes and provides insights on bacteria-host co-evolutionary associations. We propose that bacteria with endosymbiotic lifestyles present a rich vein of interesting enzymes useful for understanding enzyme function and/or informing protein engineering efforts.

Effect of symmetry-breaking on the MHD edge stability limit of tokamak plasmas

We demonstrate for the first time that symmetry-breaking in tokamak plasmas reduces the window of stable edge operational space, leading to a lower achievable edge pressure gradient. Predictive simulations with the linear magnetohydrodynamic stability code CASTOR3D show a reduction of the critical pressure gradient by up to 30%, in agreement with experimental observations. The analysis has been extended to experimental plasmas considering, for the first time, ion diamagnetic drift effects in realistic non-axisymmetric (3D) tokamak geometry. The 3D geometry in plasmas with edge localised modes (ELMs) increases the growth rate of edge instabilities compared to the axisymmetric case. Further reducing the edge pressure gradient eliminates the instabilities corresponding to an experiment with suppressed ELMs, reproducing the empirically observed threshold for ELM suppression. Our findings highlight the importance of predictions of the ELM occurrence in full 3D geometry for future tokamak devices with intentionally and unintentionally broken axisymmetry.

Drift potential and coverage ratio analysis of an air induction nozzle under an agricultural drone with various operating condition; an indoor test

Delivering pesticides in the agricultural field has been a venturing advancement in the past decades with the aim of target spraying. Agricultural drones have been introduced as useful assets for target spraying, however, the turbulent downwash flow generated by the drone blades accelerates the atomization process that attributes to the drift potential. In this experimental study, the effect of downwash flow on an air induction nozzle is compared to that of a conventional flat fan XR nozzle under various drone operating conditions to evaluate the best working condition. The test was carried out in an indoor facility in which the effect of environmental parameters can be minimized. The 2D patternation of the droplet deposition known as coverage ratio was evaluated using water-sensitive papers with the change of operating conditions, including nozzle type, drone speed, flying height, and blade rotational speed. As the drone flight speed, height, rotational speed, and nozzle position changed, alterations in droplet size and coverage uniformity were observed along with propagation in the drift effect. In addition, the coverage ratio of the AI nozzle was higher than that of the XR nozzle.

Super-X and conventional divertor configurations in MAST-U ohmic L-mode; a comparison facilitated by interpretative modelling

Measurements are presented, alongside corresponding interpretative SOLPS-ITER simulations, of the first MAST-U experiments comparing ohmically heated L-mode fuelling scans in Conventional divertor (CD) and Super-X divertor (SXD) configurations. In experiment, at comparable outer mid-plane separatrix electron density, ne,sep,OMP , the maximum lower outer target heat load was found to be a factor 16 ±7 lower in SXD compared to CD. In simulation, a factor 26.8 reduction was found (slightly higher than the experimental range), suggesting an additional reduction in SXD compared to the factor 9.3 expected from geometric considerations alone. According to the simulations, this additional reduction in the SXD is due to a net radial transport of the energy remaining downstream of the Te=5 eV location. This energy is carried out of the critical (highest heat load) flux tube by deuterium atoms, demonstrating the importance of a longer legged divertor which provides space for this to occur. Importantly, in both simulation and experiment, the SXD has minimal impact on the upstream ne and Te profiles. Spectral inferences of detachment front movement in SXD compare well between simulation and experiment. In regions of high magnetic field gradient, the parallel movement of the front towards the X-point becomes less sensitive to increasing ne,sep,OMP , in qualitative agreement with simplified models and previous predictive simulations. Additional aspects, regarding the target ion flux rollover, upstream separatrix temperature and drift effects, are also presented and discussed.

Wearable Loops for Dynamic Monitoring of Joint Flexion: A Machine Learning Approach

We present a machine learning driven system to monitor joint flexion angles during dynamic motion, using a wearable loop-based sensor. Our approach uses wearable loops to collect transmission coefficient data and an Artificial Neural Network (ANN) with fine-tuned parameters to increase accuracy of the measured angles. We train and validate the ANN for sagittal plane flexion of a leg phantom emulating slow motion, walking, brisk walking, and jogging. We fabricate the loops on conductive threads and evaluate the effect of fabric drift via measurements in the absence and presence of fabric. In the absence of fabric, our model produced a root mean square error (RMSE) of 5.90°, 6.11°, 5.90°, and 5.44° during slow motion, walking, brisk walking, and jogging. The presence of fabric degraded the RMSE to 8.97°, 7.21°, 9.41°, and 7.79°, respectively. Without the proposed ANN method, errors exceeded 35.07° for all scenarios. Proof-of-concept results on three human subjects further validate this performance. Our approach empowers feasibility of wearable loop sensors for motion capture in dynamic, real-world environments. Increasing speed of motion and the presence of fabric degrade sensor performance due to added noise. Nevertheless, the proposed framework is generalizable and can be expanded upon in the future to improve upon the reported angular resolution.

Optimization design and evaluation of composited fiber optic sensors for monitoring ammonia gas with relative error calibration unit

In this paper, a relative error calibration unit has been designed to analyze and calibrate the common relative errors in optical fiber gas detection system based on directly absorption spectrum (DAS) technology. The ammonia gas was successfully encapsulated in one cut of hollow core fiber as the closed micro-cavity reference cell by dipping saturated solution and cascade-fusing fibers. Through the difference algorithm, the maximum relative error caused by the power fluctuation of the light source is reduced by 85.3 %; to reduce the temperature drift effect caused by optical fiber structure and ammonia absorbance, the calibration equation is obtained by fitting and inversion calculation. The temperature relative error decreases by 95 %. The proposed self-referencing hollow fiber gas sensing probe has a compact structure and can be used for precise monitoring of harmful gases in harsh environments such as narrow space, strong electromagnetic interference, high temperature and humidity.

Suggested mechanism of CCR5Δ32, CCR2-64I and SDF 1-3'A allele frequency change in Polish and Lithuanian gene pools from the perspective of passing time.

The study aimed to determine the frequency of the alleles associated with hereditary immune response in 16 historical populations and assess which evolutionary forces may have contributed to the observed frequency fluctuation. The analysed polymorphic sites are located in three genes - CCR5, CCR2 and SDF 1 (CXCL12). Protein products are involved in the innate immune response and are also involved in various types of infections, autoimmune diseases and tumours. The frequency of the alleles found in the DNA of the studied individuals was determined by the Sanger methodology and was compared with the data obtained for modern populations. To confirm the authenticity of the obtained results, mtDNA HVRI haplotypes of all the studied samples were obtained and compared with the genetic database of the laboratory personnel who came into contact with the studied material. Based on the variability of allele frequency, advanced biostatistical analysis was used to distinguish the effect of natural selection from genetic drift, i.e. the forces operating on the polymorphic sites studied. All procedures were performed according to the guidelines for working with ancient DNA to avoid contamination with modern DNA molecules. 681 samples from 39 archaeological sites in Poland and Lithuania dated to the 40th century BC and the 19th century were studied. The biostatistical analysis showed that the fluctuations in the frequency of CCR5Δ32 in the analysed time interval could be mainly the effect of genetic drift. Nevertheless, for CCR2-64I and SDF 1-3'A, the results confirm the suggestion of negative selection as the mechanism involved. Since all the polymorphic sites encode the elements of innate immune response that are indirectly associated with the process of an HPV infection and the development of cervical cancer, the human papillomavirus may be a good candidate for a selection coefficient affecting the frequency of CCR2-64I and SDF 1-3'A. However, for CCR5Δ32, selection was not detected despite its proven role in the molecular mechanism involved in the response to an HPV infection. The presented work seems to be the first in which the problem of the pattern of CCR5Δ32, CCR2-64I and SDF 1-3'A frequency fluctuations in a temporal perspective was discussed, proposing HPV as a factor influencing the occurrence of the CCR2 and SDF1 alleles.

A novel method for calculating broadband electrical performance of high-speed aircraft radome under thermo-mechanical-electrical coupling

The electrical performance of radomes on high-speed aircraft can be influenced by the thermal and mechanical loads produced during high-speed flight, which can affect the detection distance and accuracy of the guidance system. This paper presents a new method that uses the Finite Difference Time Domain (FDTD) method to calculate the electrical performance of radomes under Thermo-Mechanical-Electrical (TME) coupling. This method can accurately characterize the effects of material dielectric temperature drift and structural deformation on the electrical performance of the radome under flight conditions, enabling high-precision full-wave calculations of the broadband electrical performance of the radome. The method initiates by utilizing a Finite Element Grid Model (FE-GM) of the radome to sequentially acquire the radome’s response temperature field and structural deformation field through thermal and mechanical simulations. Subsequently, spatial mapping techniques are developed to accurately incorporate the dielectric temperature drift and structural deformation of the radome into its Yee grid Electromagnetic (EM) simulation model. A verification case was designed to test the proposed method, and the results confirmed its high computational accuracy. Additionally, the effectiveness and necessity of the method were further demonstrated by analyzing the electrical performance of a fused silica ceramic radome used on a high-speed aircraft.

Effect of Argo Salinity Drift since 2016 on the Estimation of Regional Steric Sea Level Change Rates

Since 2016, the Argo (Array for Real-Time Geostrophic Oceanography) ocean salinity data has exhibited significant drift, directly affecting the accurate quantification of the global steric sea level (SSL) rates. To further investigate how salinity drift affects the estimation of SSL rates in different depths and regions, we divide the 0–2000 m into three layers (0–300 m, 300–1000 m and 1000–2000 m) and select five open oceans (the South and North Pacific, the South and North Atlantic, and the Indian Ocean) for discussion. By comparing the SSL rates between the periods of 2005–2015 and 2005–2019, we can evaluate the impact of salinity drift. Taking the estimated results from the IPRC (provided by the International Pacific Research Center at the University of Hawaii) and BOA (provided by the Second Institute of Oceanography, China) data as examples, we find that the effect of salinity drift is the largest at the depth of 1000–2000 m, about 29% for IPRC data and about 18% for BOA data. Moreover, the South Atlantic is susceptible to the effects of salinity drift, with an approximately 13% impact for IPRC data and 21% for BOA data.

The City as an Evolutionary Hothouse—The Search for Rapid Evolution in Urban Settings

Cities are ubiquitous and, though a novel phenomenon by evolutionary standards, provide a home for many species and exert particularly strong and novel selection pressures on them. They thus offer a unique opportunity to study rapid evolutionary processes. We conducted a scoping review of published studies documenting evolutionary processes in urban environments, focusing primarily on more recent work. Unfortunately, cities have not been attractive environments for biological research and thus remain poorly studied, despite slowly growing interest in recent years. Nonetheless, we found studies documenting the effects of mutation, genetic drift, and selection in cities. However, studies show some geographic bias and were not always as conclusive as might be desired. There is even support for incipient urban speciation. Evidence across the board is less abundant and less conclusive than desirable, suggesting the need for more data collection. The urban setting, with its stronger selection, more common intermixing, and abundance of both human and widespread potential non-human zoonosis hosts and human-associated species offers great opportunities to further document evolution in action and explore its conservation implications.

Cycle-to-cycle switching endurance variability in vertically aligned nanocrystalline molybdenum disulfide: computational insights

We propose a model to depict abrupt transient changes in the endurance test results of a resistive switching device comprising vertically oriented layers of nanocrystalline transition metal dichalcogenide layers with respect to the substrate. We aim to relate and understand the so-called resistance drift occurring in the endurance test results with our model, which is further tested using density functional theory simulations. We conclude that the relationship between resistance drift and skin effect is dominated by alternating electric current resistance and surface resistance. These results are crucial for understanding the resistance drift occurring in several resistive switching devices operating based on defects and ions.

A Synergistic, Cultivator Model of De Novo Gene Origination.

The origin and fixation of evolutionarily young genes is a fundamental question in evolutionary biology. However, understanding the origins of newly evolved genes arising de novo from noncoding genomic sequences is challenging. This is partly due to the low likelihood that several neutral or nearly neutral mutations fix prior to the appearance of an important novel molecular function. This issue is particularly exacerbated in large effective population sizes where the effect of drift is small. To address this problem, we propose a regulation-focused, cultivator model for de novo gene evolution. This cultivator-focused model posits that each step in a novel variant's evolutionary trajectory is driven by well-defined, selectively advantageous functions for the cultivator genes, rather than solely by the de novo genes, emphasizing the critical role of genome organization in the evolution of new genes.

Fourier transform-based post-processing drift compensation and calibration method for scanning probe microscopy

Scanning probe microscopy (SPM) is ubiquitous in nanoscale science allowing the observation of features in real space down to the angstrom resolution. The scanning nature of SPM, wherein a sharp tip rasters the surface during which a physical setpoint is maintained via a control feedback loop, often implies that the image is subject to drift effects, leading to distortion of the resulting image. While there are in-operando methods to compensate for the drift, correcting the residual linear drift in obtained images is often neglected. In this paper, we present a reciprocal space-based technique to compensate the linear drift in atomically-resolved scanning probe microscopy images without distinction of the fast and slow scanning directions; furthermore this method does not require the set of SPM images obtained for the different scanning directions. Instead, the compensation is made possible by the a priori knowledge of the lattice parameters. The method can also be used to characterize and calibrate the SPM instrument.