Positive Results Research Articles

On the Effect of Driving Turbulent-like Fluctuations on a Harris Current Sheet Configuration and the Formation of Plasmoids

Energy dissipation in collisionless plasmas is one of the most outstanding open questions in plasma physics. Magnetic reconnection and turbulence are two phenomena that can produce the conditions for energy dissipation. These two phenomena are closely related to each other in a wide range of plasmas. Turbulent fluctuations can emerge in critical regions of reconnection events, and magnetic reconnection can occur as a product of the turbulent cascade. In this study, we perform 2D particle-in-cell simulations of a reconnecting Harris current sheet in the presence of turbulent fluctuations to explore the effect of turbulence on the reconnection process in collisionless nonrelativistic pair plasmas. We find that the presence of a turbulent field can affect the onset and evolution of magnetic reconnection. Moreover, we observe the existence of a scale-dependent amplitude of magnetic field fluctuations above which these fluctuations are able to disrupt the growing of magnetic islands. These fluctuations provide thermal energy to the particles within the current sheet and preferential perpendicular thermal energy to the background population.

The Fatigue Behavior of Narrow Single-body Titanium Implants in Saline and Acidic Media.

The objective of this study was to examine how the saline and acidic environment affects the mechanical integrity of narrow single-body titanium implants for oral rehabilitation. Thirty titanium-base alloy implants with 2.5 mm diameter were placed into a polyacetal holder and coupled to a stainless-steel prosthetic cap for fatigue testing in three different environments, as follows: dry air; saline solution (pH at 7.6); and lactic acid solution (pH at 3.4). The fracture surfaces were analyzed using a Scanning Electron Microscope (SEM). Also, finite element analysis was carried out to estimate the maximum von Mises stresses. The fatigue resistance was higher in the group tested in dry air (60%), followed by saline solution (30%) and lactic acid (10%). Regardless of the environment, fracture occurred at the same region of the failed specimens in line with the highest stress concentration spots, according to the finite element analysis. SEM analyses revealed two distinct failure regions, both with the presence of fatigue streaks: fatigue and overload. A high incidence of secondary cracks was also noticed on the specimens exposed to the solutions. The present study revealed that both saline and acidic solutions significantly affect the fatigue resistance of narrow dental implants. Critical regions of the narrow implants were also susceptible to cracks and plastic deformation that should be taken into consideration in planning for oral rehabilitation.

Dynamic Loss Weighting for Multiorgan Segmentation in Medical Images.

Deep neural networks often suffer from performance inconsistency for multiorgan segmentation in medical images; some organs are segmented far worse than others. The main reason might be organs with different levels of learning difficulty for segmentation mapping, due to variations such as size, texture complexity, shape irregularity, and imaging quality. In this article, we propose a principled class-reweighting algorithm, termed dynamic loss weighting, which dynamically assigns a larger loss weight to organs if they are discriminated as more difficult to learn according to the data and network's status, for forcing the network to learn from them more to maximally promote the performance consistency. This new algorithm uses an extra autoencoder to measure the discrepancy between the segmentation network's output and the ground truth and dynamically estimates the loss weight of organs per the contribution of the organ to the new updated discrepancy. It can capture the variation in organs' learning difficult during training, and it is neither sensitive to data's property nor dependent on human priors. We evaluate this algorithm in two multiorgan segmentation tasks: abdominal organs and head-neck structures, on publicly available datasets, with positive results obtained from extensive experiments which confirm the validity and effectiveness. Source codes are available at: https://github.com/YouyiSong/Dynamic-Loss-Weighting.

ASTM International Subcommittee E07.02 on Reference Radiological Images: A brief history and update of recent work

Radiographic interpretation is a combination of art and science. The radiograph interpreter must be well versed in x-ray physics, conditions of the exposure, characteristics of the source and image detector, the design of the part, its specifications, and potential flaws. But there is also an art to interpretation that is gained over years of looking at many radiographs taken in many different conditions. As an aid to interpretation, reference radiographs have been developed and well accepted as means of identifying different types of indications and grading those indications for accept/reject decisions. Industrial radiography began in 1922 under the direction of HH Lester at the US Army Watertown Arsenal. The first radiography standards and reference radiographs appeared in the 1930s. ASTM International Committee E07 on Nondestructive Testing was formed out of Committee E04 on Metallography X-ray Methods subcommittee in 1938 when ASTM was the American Society for Testing Materials. An ASTM Subcommittee on Reference Radiographs was formed in 1950 and immediately adopted some of these first reference films as consensus standards. Since those first reference radiograph standards ASTM has developed both film and digital radiograph standards for 11 types of castings and 3 types of welds, several radiographic parameter demonstration films, a standard film for measuring film digitization performance, and films for evaluating visual acuity of radiograph interpreters. This paper discusses the history of reference films and the recent development of digital reference images, film digitizer performance film, and the visual acuity standard. The just-approved ASTM E3168 Standard Practice for Determining Low-Contrast Visual Acuity of Radiographic Interpreters is the first standard containing actual radiographic images of varying sharpness, contrast, and noise that can be used to evaluate interpreters and/or interpretation environments. This paper documents the initial statistical study performed on the visual acuity standard films.

Assessing the Sources of the O+ in the Plasma Sheet

AbstractTo study the average contributions of the cusp outflow through the lobes and of the nightside auroral outflow to the O+ in the plasma sheet (PS), we performed a statistical study of tailward streaming O+ in the lobes, plasma sheet boundary layer|the plasma sheet boundary layer (PSBL) and the PS, using MMS/Hot Plasma Composition Analyzer (HPCA) data from 2017 to 2020. Similar spatial patterns illustrate the entry of cusp‐origin O+ from the lobes to the PS through the PSBL. There is an YGSM‐dependent energy pattern for the lobe O+, with low‐energy O+ streaming closer to the tail center and high energy (1–3 keV) O+ streaming near the flanks. Low energy (1–100 eV) O+ from the nightside auroral oval is identified in the near‐Earth PSBL/PS with high‐density (>0.02 cm−3), and energetic (>3 keV) streaming O+ with similar density (∼0.013 cm−3) is observed further out on the duskside of the PSBL/PS. The rest of the nightside auroral O+ in the PSBL is mixed with O+ coming in from the lobe, making it difficult to distinguish the source. We estimated the contributions of the different sources of H+ and O+ ions through the PS between 7 and 17 RE, using estimates from this work and data extracted from previous studies. We conclude that, during quiet times, the majority of the near‐Earth PS H+ are from the cusps, the polar wind and Earthward convection from the distant tail. Similarly, while the O+ in the same region has a mixed source, cusp origin outflow provides the highest contribution.

Two sunspot group populations and Gnevyshev-Waldmeier rule

Based on the materials of the Royal Greenwich Observatory catalog, the study of two different sunspot group populations continued: LLG – large long-lived, and SSG – small short-lived groups. The task of achieving a higher accuracy of the population separation parameter than before (Nagovitsyn & Pevtsov 2016, 2021) is being solved. A procedure for randomizing the lifetimes of sunspot groups observed once a day is proposed, which allows for statistical studies to achieve a higher time resolution. The form of the Gnevyshev-Waldmeier Rule is taken, which linearly connects the logarithm of the logS area and the lifetime of the sunspot group LT (over limited time intervals). It is shown that it has coefficients significantly different for SSG and LLG populations. The range of values of the group lifetime parameter separating the populations was found as LT∗=4.75±0.53 days, which is in agreement with the threshold values obtained earlier for the number of days of sunspot group observation: mSSG⩽5 days and mLLG>5 days. It is shown that the parameters of the bilognormal distribution of the sunspot group areas, obtained from their common grouped sample statistically by Levenberg–Marquardt method and with a preliminary division into lognormal distributions by lifetime, correspond to each other. It was clarified that, with an accuracy of up to a tenth of a day, the SSG population corresponds to the lifetimes of groups ⩽4.6 days, and the LLG population corresponds to times ⩾4.7 days. The results obtained make it possible to study various physical properties of SSG and LLG populations independently of each other in order to compare them and study their nature.

A Statistical Study of the CME Properties Based on Angular Width during the Solar Cycle 24

A Statistical Study of the CME Properties Based on Angular Width during the Solar Cycle 24

A statistical study of precipitation on the eastern Antarctic plateau (Dome-C) using remote sensing and in-situ instrumentation.

Studying precipitation at very high latitudes is a challenge, particularly during the polar winter. Direct monitoring of ice habit and size in high latitude precipitation is crucial for validating the algorithms used to derive precipitation from radar, and for improving the climatological modeling of polar areas. The high plateau lacks long-term direct observations of precipitation. In this work, carried out at Concordia Station (Dome-C (DC), -75°S, 123°E, 3233 m a.m.s.l), the use of a depolarization LIDAR, a flatbed scanner (ICECAMERA), a microwave profiler (HAMSTRAD) and meteorological instrumentation made possible the study, over the period 2014-2021, of shape, size, height and temperature of formation of precipitation. The precipitation sources were classified into four types: ice fogs, liquid fogs, mixed-phase clouds, and cirrus. Ten representative ice habits for Dome-C were chosen. The size distribution for every habit was calculated, allowing for the estimation of the corresponding radar reflectivity. The use of W-band radars, such as CLOUDSAT, with a sensitivity of -28dB, resulted in capturing all the crystals observed in Concordia. A positive trend was observed between grain size and height in ice habits that are typical of cloud precipitation. North West (NW) and North East (NE) winds at cloud height, blowing from coastal regions, caused the majority of precipitation from clouds. The study also examined the height trend of the ice habit composition of precipitation. The ice habit composition for each of the four types of precipitation source was analyzed, and the possibility of determining the source by simply observing the precipitation was explored. This work marks the first comprehensive investigation of precipitation on the eastern Antarctic plateau.

MeV Electron Precipitation During Radiation Belt Dropouts

AbstractTo gain deeper insights into radiation belt loss into the atmosphere, a statistical study of MeV electron precipitation during radiation belt dropout events is undertaken. During these events, electron intensities often drop by an order of magnitude or more within just a few hours. For this study, dropouts are defined as a decrease by at least a factor of five in less than 8 hours. Van Allen probe measurements are employed to identify dropouts across various parameters, complemented by precipitation data from the CALorimetric Electron Telescope instrument on the International Space Station. A temporal analysis unveils a notable increase in precipitation occurrence and intensity during dropout onset, correlating with the decline of SYM‐H, the north‐south component of the interplanetary magnetic field, and the peak of the solar wind dynamic pressure. Moreover, dropout occurrences show correlations with the solar cycle, exhibiting maxima at the spring and autumn equinoxes. This increase during equinoxes reflects the correlation between equinoxes and the SYM‐H index, which itself exhibits a correlation with precipitation during dropouts. Spatial analysis reveals that dropouts with precipitation penetrate into lower L‐star regions, mostly reaching L‐star <4, while most dropouts without precipitation don't penetrate deeper than L‐star 5. This is consistent with the larger average dimensions of dropouts associated with precipitation. During dropouts, precipitation is predominantly observed in the dusk‐midnight sector, coinciding with the most intense precipitation events. The results of this study provide insight into the contribution of precipitation to radiation belt dropouts by deciphering when and where precipitation occurred.

A statistical study of the impact of the stream interaction regions on the heliospheric current sheet

The heliospheric current sheet (HCS) serves as the boundary that separates two sectors in which the interplanetary magnetic field lines diverge in opposite directions. In this study, we conducted a statistical analysis of 216 HCS events, utilizing data from the Wind spacecraft to examine the impact of stream interaction regions (SIRs) on the HCSs. Our findings revealed that out of all the HCS events, 153 (70.8%) were succeeded by a SIR within 36 h. Conversely, 63 HCS events (29.2%) were not followed by any SIR. The occurrence of HCSs accompanied by SIRs displayed a rough anti-correlation with solar sunspots. The statistical results further indicated that the presence of a SIR exerts some influence on the preceding HCS. Specifically, the thickness of the HCS is significantly reduced by the trailing SIR, and the subsequent SIR can cause the leading HCS to stand more vertically to the ecliptic plane and more aligned with the Sun–Earth line (a smaller angle between the normal of the HCS and the Earth's dawn–dusk line in the ecliptic plane).

Nonlinear Drift‐Bounce Resonance Between Charged Particles and Ultralow Frequency Waves

AbstractUltra‐low frequency (ULF) waves contribute significantly to the dynamic evolution of Earth's magnetosphere by accelerating and transporting charged particles within a wide energy range. A substantial excitation mechanism of these waves is their drift‐bounce resonant interactions with magnetospheric particles. Here, we extend the conventional drift‐bounce resonance theory to formulate the nonlinear particle trapping in the ULF wave‐carried potential well, which can be approximately described by a pendulum equation. We also predict the observable signatures of the nonlinear drift‐bounce resonance, and compare them with spacecraft observations. We further discuss potential drivers of the pendulum including the convection electric field and the magnetospheric dayside compression, which lead to additional particle acceleration or deceleration depending on magnetic longitude. These drivers indicate preferred regions for nonlinear ULF wave growth, which are consistent with previous statistical studies.

Statistical Study of Groundwater Salinity at Lake Dayet Erroumi, Morocco

Statistical Study of Groundwater Salinity at Lake Dayet Erroumi, Morocco

JWST COMPASS: A NIRSpec/G395H Transmission Spectrum of the Sub-Neptune TOI-836c

Planets between the sizes of Earth and Neptune are the most common in the Galaxy, bridging the gap between the terrestrial and giant planets in our solar system. Now that we are firmly in the era of JWST, we can begin to measure, in more detail, the atmospheres of these ubiquitous planets to better understand their evolutionary trajectories. The two planets in the TOI-836 system are ideal candidates for such a study, as they fall on either side of the radius valley, allowing for direct comparisons of the present-day atmospheres of planets that formed in the same environment but had different ultimate end states. We present results from the JWST NIRSpec G395H transit observation of the larger and outer of the planets in this system, TOI-836c (2.587 R ⊕, 9.6 M ⊕, T eq ∼ 665 K). While we measure average 30-pixel binned precisions of ∼24 ppm for NRS1 and ∼43 ppm for NRS2 per spectral bin, we do find residual correlated noise in the data, which we attempt to correct using the JWST Engineering Database. We find a featureless transmission spectrum for this sub-Neptune planet and are able to rule out atmospheric metallicities <175× solar in the absence of aerosols at ≲1 mbar. We leverage microphysical models to determine that aerosols at such low pressures are physically plausible. The results presented herein represent the first observation from the COMPASS (Compositions of Mini-Planet Atmospheres for Statistical Study) JWST program, which also includes TOI-836b and will ultimately compare the presence and compositions of atmospheres for 12 super-Earths/sub-Neptunes.

Statistical Study of Coronal Mass Ejections of the 23rd and 24th Solar Cycles Based on Their Angular Width

Statistical Study of Coronal Mass Ejections of the 23rd and 24th Solar Cycles Based on Their Angular Width

Statistical Study of Hot Flow Anomaly Induced Ground Magnetic Ultra‐Low Frequency Oscillations

AbstractPc5 ULF waves play an important role in transporting energy and particles in the coupled magnetospheric and ionospheric system. They are known to be initiated by dynamic pressure fluctuations upstream of the magnetopause, including those induced by hot flow anomalies (HFAs). However, the role of HFAs in generating magnetospheric and ground magnetic Pc5 ULF oscillations has not been investigated statistically yet. Thus, in this paper, we investigate the contribution of HFAs to ground magnetic Pc5 ULF oscillations and analyze how the characteristics of HFAs influence these oscillations, based on the coordinated observations between the THEMIS probes and the ground magnetometers at high latitudes during the years 2008, 2009 and 2019. We find that HFAs can serve as a notable source of ground magnetic Pc5 ULF oscillations, with about 18.9% of Interplanetary Magnetic Field (IMF) discontinuity‐induced HFAs associated with discernible enhancements in Pc5 ULF wave power, whereas spontaneous HFAs play a comparatively minor role in generating these oscillations. Furthermore, we observe that the cores of HFAs are likely to contribute more significantly to modulating the induced ground magnetic Pc5 ULF oscillations than their compressed boundaries. More dynamic pressure reductions within HFA cores correspond to stronger ground magnetic Pc5 ULF oscillations. Additionally, HFAs can propagate with the IMF discontinuity along the bow shock, continuously generating ground magnetic Pc5 ULF oscillations during their propagation. This research sheds light on the mechanisms underlying Pc5 ULF wave generation and underscores the role of HFAs in driving magnetospheric‐ionospheric interactions.

The project of Magdalena Gutiérrez: the poetics of living in the Atacama Desert. The four modes of climate management

This study addresses the issue of living in fragile ecological environments, such as oases in deserts. Currently, the oasis of San Pedro de Atacama is experiencing a decrease in its agricultural area due to urbanization and tourism, affecting the sustainability of traditional farming practices and putting at risk the ecological and cultural balance of this Atacamenian locale. The article presents sustainable design strategies for contemporary living in fragile environments, examining thermal qualities and climate control strategies applied to the “Workshop House” or Casa Taller of Magdalena Gutiérrez. Using the principles of Lisa Heschong and Eva Horn, the review also includes Reyner Banham's climate management modes. The methodology combines architectural and ethnographic analysis, structured in three stages: selection of works, construction of the conceptual framework, and analysis and systematization. Models, photographs, maps, and diagrams were used to contrast theories and thermal and cultural qualities with evidence from the work. Classification criteria included evaluating characteristics such as the degree of privacy of areas and rooms, ventilation, lighting, thermal insulation, and heating methods, with a binary rating employed for systematic evaluation. The results highlighted that Casa Taller manifests poetic living in the exteriority of the Atacama Desert, suggesting a vocation for community activities. The lighting qualities revealed a strategic design that maximizes controlled daylight, utilizing openings and skylights. It was concluded that the Casa Taller represents an expression of "Revisited Critical Regionalism." The "site-form" relationship is fundamental in this approach, balancing local techniques with cultural and natural surroundings. This work offers a sustainable model for living in fragile environments, where architectural design is appropriately integrated with the place’s climatic and cultural conditions.

Mapping the molecular landscape of Lotus japonicus nodule organogenesis through spatiotemporal transcriptomics

Legumes acquire nitrogen-fixing ability by forming root nodules. Transferring this capability to more crops could reduce our reliance on nitrogen fertilizers, thereby decreasing environmental pollution and agricultural production costs. Nodule organogenesis is complex, and a comprehensive transcriptomic atlas is crucial for understanding the underlying molecular events. Here, we utilized spatial transcriptomics to investigate the development of nodules in the model legume, Lotus japonicus. Our investigation has identified the developmental trajectories of two critical regions within the nodule: the infection zone and peripheral tissues. We reveal the underlying biological processes and provide gene sets to achieve symbiosis and material exchange, two essential aspects of nodulation. Among the candidate regulatory genes, we illustrate that LjNLP3, a transcription factor belonging to the NIN-LIKE PROTEIN family, orchestrates the transition of nodules from the differentiation to maturation. In summary, our research advances our understanding of nodule organogenesis and provides valuable data for developing symbiotic nitrogen-fixing crops.

Cell-type-specific effects of autism-associated 15q duplication syndrome in the human brain

Recurrent copy-number variation represents one of the most well-established genetic drivers in neurodevelopmental disorders, including autism spectrum disorder. Duplication of 15q11-q13 (dup15q) is a well-described neurodevelopmental syndrome that increases the risk of autism more than 40-fold. However, the effects of this duplication on gene expression and chromatin accessibility in specific cell types in the human brain remain unknown. To identify the cell-type-specific transcriptional and epigenetic effects of dup15q in the human frontal cortex, we conducted single-nucleus RNA sequencing and multi-omic sequencing on dup15q-affected individuals (n= 6) as well as individuals with non-dup15q autism (n= 7) and neurotypical control individuals (n= 7). Cell-type-specific differential expression analysis identified significantly regulated genes, critical biological pathways, and differentially accessible genomic regions. Although there was overall increased gene expression across the duplicated genomic region, cellular identity represented an important factor mediating gene-expression changes. As compared to other cell types, neuronal subtypes showed greater upregulation of gene expression across a critical region within the duplication. Genes that fell within the duplicated region and had high baseline expression in control individuals showed only modest changes in dup15q, regardless of cell type. Of note, dup15q and autism had largely distinct signatures of chromatin accessibility but shared the majority of transcriptional regulatory motifs, suggesting convergent biological pathways. However, the transcriptional binding-factor motifs implicated in each condition implicated distinct biological mechanisms: neuronal JUN and FOS networks in autism vs. an inflammatory transcriptional network in dup15q microglia. This work provides a cell-type-specific analysis of how dup15q changes gene expression and chromatin accessibility in the human brain, and it finds evidence of marked cell-type-specific effects of this genetic driver. These findings have implications for guiding therapeutic development in dup15q syndrome, as well as understanding the functional effects of copy-number variants more broadly in neurodevelopmental disorders.

Comparing amoxicillin and trimethoprim: Overall performance in combating Escherichia coli-causing urinary tract infection

Urinary Tract Infection (UTI) is one of the most prevalent bacterial infections in the world, and 80% of reported UTI cases are derived by gram negative bacteria Escherichia coli. Uropathogenic Escherichia coli is strongly adaptive and resilient against immune response, forming Intracellular Bacterial Communities (IBC) inside uroepithelium cells that constitute the urethra and the bladder. Their rapid absorption of cellular nutrients enables them to advance upward toward the kidney and cause inflammation. Hence, based on the perceived severity of UTI, multiple antibiotics are used to treat UPEC-causing UTI. This article provides a detailed review on the contemporary performance of amoxicillin and trimethoprim, both widely used to treat UPEC-causing UTI for decades. Amoxicillin is a penicillin-derivative that produces bactericidal by inhibiting transpeptidase to disrupt peptidoglycan synthesis, causing rapid-growing bacteria to lyse. It is a well-tolerated drug that can be used on pregnant patients. Resistant UPEC develop beta-lactamase to counter amoxicillin. Trimethoprim, on the other hand, is a dihydropyrimidine antibiotic that impedes the production of tetrahydrofolic acids, producing either bacteriostatic or bactericidal effects. Resistant UPEC transforms the shape of tetrahydrofolic acids-producing enzyme, dihydrofolic reductase, to resist trimethoprim. Although amoxicillin and trimethoprim are competitive inhibitors are effective against a variety of gram-positive and gram-negative species, trimethoprim, in statistical study, is proven to be more effective than amoxicillin in treating gram-negative UTI. Today, the wide-spread resistant strains of UPEC exists for both drugs. Thus, amoxicillin and trimethoprim are implemented mainly through combination therapies, amoxicillin/clavulanate and trimethoprim sulfamethoxazole, respectively. These combinations are more effective than the drugs to be used alone and are able to counter some resistant strains, but UPEC that are resistant to combinations also exists. Regardless, both amoxicillin and trimethoprim are still used as first-line antibiotics, while more powerful antibiotics are reserved for special multi-resistant superbugs.

Influence of Doping Engineering in 1 μm Drift Layer Quasi‐Vertical Fin Field‐Effect Transistor for Achieving &gt;139 V Breakdown Voltage

A quasi‐vertical gallium nitride (GaN) fin field effect transistor (FinFET) is designed and analyzed to assess the performance of electrical parameters. The device is deployed on a silicon carbide (SiC) substrate and analyzed using technology computer‐aided design (TCAD). The donor concentration in the critical regions is identified as a significant limiting factor for FinFET electrical properties. Hence, the influence of channel and drift layer doping concentrations (Nd) on performance characteristics is investigated in this work. The electrical characteristics such as threshold voltage, ION/IOFF ratio, subthreshold swing (SS), specific ON‐resistance, and breakdown voltage (VBV) are evaluated for various doping profiles. The doping profile with channel and drift layer concentration of 4 × 1015 cm−3 for a 300 nm fin width and 1 μm thick drift layer exhibits normally OFF behavior with a threshold voltage (Vt) of 1.5 V. It also demonstrates a VBV of 139 V. The corresponding doping profile reveals a low SS of 61 mV dec−1, which is comparable to other similar power devices. This demonstrates the significant potential of the device for medium‐power switching applications.