A simple model for the evolution of multi-stranded coronal loops

We develop and analyze a simple cellular automaton (CA) model that reproduces the main properties of the evolution of soft X-ray coronal loops. We are motivated by the observation that these loops evolve in three distinguishable phases that suggest the development, maintainance, and decay of a self-organized system. The model is based on the idea that loops are made of elemental strands that are heated by the relaxation of magnetic stress in the form of nanoflares. In this vision, usually called "the Parker conjecture" (Parker 1988), the origin of stress is the displacement of the strand footpoints due to photospheric convective motions. Modeling the response and evolution of the plasma we obtain synthetic light curves that have the same characteristic properties (intensity, fluctuations, and timescales) as the observed cases. We study the dependence of these properties on the model parameters and find scaling laws that can be used as observational predictions of the model. We discuss the implications of our results for the interpretation of recent loop observations in different wavelengths.Comment: 2010, accepted for publication in Ap

Are constant loop widths an artifact of the background and the spatial resolution?

We study the effect of the coronal background in the determination of the diameter of EUV loops, and we analyze the suitability of the procedure followed in a previous paper (L\'opez Fuentes, Klimchuk & D\'emoulin 2006) for characterizing their expansion properties. For the analysis we create different synthetic loops and we place them on real backgrounds from data obtained with the Transition Region and Coronal Explorer (\textit{TRACE}). We apply to these loops the same procedure followed in our previous works, and we compare the results with real loop observations. We demonstrate that the procedure allows us to distinguish constant width loops from loops that expand appreciably with height, as predicted by simple force-free field models. This holds even for loops near the resolution limit. The procedure can easily determine when loops are below resolution limit and therefore not reliably measured. We find that small-scale variations in the measured loop width are likely due to imperfections in the background subtraction. The greatest errors occur in especially narrow loops and in places where the background is especially bright relative to the loop. We stress, however, that these effects do not impact the ability to measure large-scale variations. The result that observed loops do not expand systematically with height is robust.Comment: Accepted for publication in Ap

Evidence of Nanoflare Heating in Coronal Loops Observed with Hinolde-XRT and SDO-AIA

We study a series of coronal loop lightcurves from X-ray and EUV observations. In search for signatures of nanoflare heating, we analyze the statistical properties of the observed lightcurves and compare them with synthetic cases obtained with a 2D cellular-automaton model based on nanoflare heating driven by photospheric motions. Our analysis shows that the observed and the model lightcurves have similar statistical properties. The asymmetries observed in the distribution of the intensity fluctuations indicate the possible presence of widespread cooling processes in sub-resolution magnetic strands

Hot topics, urgent priorities, and ensuring success for racial/ethnic minority young investigators in academic pediatrics.

BackgroundThe number of racial/ethnic minority children will exceed the number of white children in the USA by 2018. Although 38% of Americans are minorities, only 12% of pediatricians, 5% of medical-school faculty, and 3% of medical-school professors are minorities. Furthermore, only 5% of all R01 applications for National Institutes of Health grants are from African-American, Latino, and American Indian investigators. Prompted by the persistent lack of diversity in the pediatric and biomedical research workforces, the Academic Pediatric Association Research in Academic Pediatrics Initiative on Diversity (RAPID) was initiated in 2012. RAPID targets applicants who are members of an underrepresented minority group (URM), disabled, or from a socially, culturally, economically, or educationally disadvantaged background. The program, which consists of both a research project and career and leadership development activities, includes an annual career-development and leadership conference which is open to any resident, fellow, or junior faculty member from an URM, disabled, or disadvantaged background who is interested in a career in academic general pediatrics.MethodsAs part of the annual RAPID conference, a Hot Topic Session is held in which the young investigators spend several hours developing a list of hot topics on the most useful faculty and career-development issues. These hot topics are then posed in the form of six "burning questions" to the RAPID National Advisory Committee (comprised of accomplished, nationally recognized senior investigators who are seasoned mentors), the RAPID Director and Co-Director, and the keynote speaker.Results/conclusionsThe six compelling questions posed by the 10 young investigators-along with the responses of the senior conference leadership-provide a unique resource and "survival guide" for ensuring the academic success and optimal career development of young investigators in academic pediatrics from diverse backgrounds. A rich conversation ensued on the topics addressed, consisting of negotiating for protected research time, career trajectories as academic institutions move away from an emphasis on tenure-track positions, how "non-academic" products fit into career development, racism and discrimination in academic medicine and how to address them, coping with isolation as a minority faculty member, and how best to mentor the next generation of academic physicians

Effects of spatial resolution of terrain models on modelled discharge and soil loss in Oaxaca, Mexico

The effect of the spatial resolution of digital terrain models (DTMs) on topography and soil erosion modelling is well documented for low resolutions. Nowadays, the availability of high spatial resolution DTMs from unmanned aerial vehicles (UAVs) opens new horizons for detailed assessment of soil erosion with hydrological models, but the effects of DTM resolution on model outputs at this scale have not been systematically tested. This study combines plot-scale soil erosion measurements, UAV-derived DTMs, and spatially explicit soil erosion modelling to select an appropriate spatial resolution based on allowable loss of information. During 39 precipitation events, sediment and soil samples were collected on five bounded and unbounded plots and four land covers (forest, fallow, maize, and eroded bare land). Additional soil samples were collected across a 220ha watershed to generate soil maps. Precipitation was collected by two rain gauges and vegetation was mapped. A total of two UAV campaigns over the watershed resulted in a 0.60m spatial-resolution DTM used for resampling to 1, 2, 4, 8, and 15m and a multispectral orthomosaic to generate a land cover map. The OpenLISEM model was calibrated at plot level at 1m resolution and then extended to the watershed level at the different DTM resolutions. Resampling the 1m DTM to lower resolutions resulted in an overall reduction in slope. This reduction was driven by migration of pixels from higher to lower slope values; its magnitude was proportional to resolution. At the watershed outlet, 1 and 2m resolution models exhibited the largest hydrograph and sedigraph peaks, total runoff, and soil loss; they proportionally decreased with resolution. Sedigraphs were more sensitive than hydrographs to spatial resolution, particularly at the highest resolutions. The highest-resolution models exhibited a wider range of predicted soil loss due to their larger number of pixels and steeper slopes. The proposed evaluation method was shown to be appropriate and transferable for soil erosion modelling studies, indicating that 4m resolution (<5% loss of slope information) was sufficient for describing soil erosion variability at the study site

Looking for Crumbs in the Obesity Forest: Anti-obesity Interventions and Obesity-Associated Cardiometabolic Traits in the Mexican Population. History and Systematic Review With Meta-Analyses

Mexicans and Mexican Americans share culture, genetic background, and predisposition for chronic complications associated with obesity and diabetes making imperative efficacious treatments and prevention. Obesity has been treated for centuries focused-on weight loss while other treatments on associated conditions like gout, diabetes (T2D), and hypertriglyceridemia. To date, there is no systematic review that synthesizes the origin of obesity clinics in Mexico and the efforts to investigate treatments for obesity tested by randomized clinical trials (RCT). We conducted systematic searches in Pubmed, Scopus, and Web of Science to retrieve anti-obesity RCT through 2019 and without an inferior temporal limit. The systematic review included RCT of anti-obesity treatments in the Mexican adult population, covering alternative medicine, pharmacological, nutritional, behavioral, and surgical interventions reporting metabolism-associated traits such as BMI, weight, waist circumference, triglycerides, glucose, among others. Only the studies with at least 3 months of treatment were included in the meta-analyses in order to reduce placebo effects. We found 634 entries, after removal of duplicates and screening the studies based on eligibility criteria, we analyzed 43 national, and 2 multinational-collaborative studies. Most of the national studies had small sample sizes, and the implemented strategies do not have replications in the population. The nutrition/behavioral interventions were difficult to blind, and most studies have medium-to-high risk of bias. Nutritional/behavioral interventions and medications showed effects on BMI, waist circumference, and blood pressure. Simple measures like pure water instead of sweet beverages decrease triglycerides and systolic blood pressure. Dark chocolate showed the highest effect for BMI and high blood pressure, and treatment with insulin increased weight in those with T2D. The study of obesity in Mexico has been on-going for more than four decades, the interest on RCT just increased until this millennium, but with small sample sizes and lack of replication. The interventions affect different cardiometabolic associated traits, which should be analyzed in detail in the population living near the Mexico-U.S. border; therefore, bi-national collaboration is desirable to disentangle the cultural effects on this population\u27s treatment response

Randomized Clinical Trials of obesity treatments in Mexican population. Systematic Review and Meta-Analysis

Background: Mexicans and Mexican Americans share similar culture, genetic background, and predisposition for obesity and diabetes. Randomized clinical trials (RCT) assessing obesity treatments (ObT) are reliable to assess efficacy. To date, there is no systematic review to investigate ObT tested by RCT in Mexican adults. Methods: We conducted systematic searches in Pubmed, Scopus, and Web of Science to retrieve ObT RCT from 1990 to 2019. The ObT included alternative medicine, pharmacological, nutritional, behavioral, and surgical interventions. The analyzed RCT were at least three months of duration, and reported: BMI, weight, waist circumference, triglycerides, glucose and blood pressure. Results: We found 634 entries; after removal of duplicates and exclusions based on eligibility criteria, we analyzed 43 and 2 multinational-collaborative studies. Most of the national studies had small sample sizes, and did not have replications from other studies. The nutrition/behavioral interventions were difficult to blind, and most studies had medium to high risk of bias. Random effects meta-analysis of nutritional/behavioral interventions and medications showed effects on BMI, waist circumference, and blood pressure. Simple measures like plain water instead of sweet beverages decreased triglycerides and systolic blood pressure. Participants with obesity and hypertension had beneficial effects with antioxidants, and the treatment with insulin increased weight in those with T2D. Conclusions: The RCT’s in Mexico reported effects on metabolic components despite small sample sizes and lack of replication. In the future we should analyze ObT in population living on the U.S.-Mexico border; therefore, bi-national collaboration is desirable to disentangle cultural effects on ObT response

Reduced Levels of Membrane-Bound Alkaline Phosphatase Are Common to Lepidopteran Strains Resistant to Cry Toxins from Bacillus thuringiensis

Development of insect resistance is one of the main concerns with the use of transgenic crops expressing Cry toxins from the bacterium Bacillus thuringiensis. Identification of biomarkers would assist in the development of sensitive DNA-based methods to monitor evolution of resistance to Bt toxins in natural populations. We report on the proteomic and genomic detection of reduced levels of midgut membrane-bound alkaline phosphatase (mALP) as a common feature in strains of Cry-resistant Heliothis virescens, Helicoverpa armigera and Spodoptera frugiperda when compared to susceptible larvae. Reduced levels of H. virescens mALP protein (HvmALP) were detected by two dimensional differential in-gel electrophoresis (2D-DIGE) analysis in Cry-resistant compared to susceptible larvae, further supported by alkaline phosphatase activity assays and Western blotting. Through quantitative real-time polymerase chain reaction (qRT-PCR) we demonstrate that the reduction in HvmALP protein levels in resistant larvae are the result of reduced transcript amounts. Similar reductions in ALP activity and mALP transcript levels were also detected for a Cry1Ac-resistant strain of H. armigera and field-derived strains of S. frugiperda resistant to Cry1Fa. Considering the unique resistance and cross-resistance phenotypes of the insect strains used in this work, our data suggest that reduced mALP expression should be targeted for development of effective biomarkers for resistance to Cry toxins in lepidopteran pests

DESARROLLO DE UN PROTOCOLO DE MULTIPLICACIÓN DE BAMBÚ GUADUA ANGUSTIFOLIA USANDO BIORREACTORES DE INMERSIÓN TEMPORAL BITS, CON FINES DE REFORESTACIÓN

The Bamboo Guadua angustifolia has great economic and environmental importance, but its traditional methods of propagation are inefficient. The objective of the study was to develop an efficient micropropagation protocol for Guadua, using Temporary Immersion Bioreactors BITs. For the establishment, disinfected nodal segments and Murashige &amp; Skoog MS medium + 2 mg L-1 of benzylaminopurine BAP were used. For micropropagation, 5 doses of BAP 2, 3, 4, 5 and 6 mg L-1 were tested. In the multiplication phase in BITs, MS was used with 3 doses of BAP 3, 4, 5 mg L-1 and immersion frequencies every 3, 6 and 8 hours. For rooting in BITs, MS + 2.5 mg L-1 of adenine sulfate was used. The results showed that using 2 mg L-1 of BAP, one shoot per explant was obtained, while with 3, 4, 5 and 6 mg L-1 of BAP, 2 shoots were obtained. In BIT multiplication, 3.5, 7.5 and 10.4 shoots per explant were obtained with doses of 3, 4 and 5 mg L-1 of BAP, respectively. Using immersion frequencies every 3, 6, and 8 hours, 7.5, 8.7, and 13.6 shoots per plant were obtained, respectively. The number of roots was 11.3, 4.0 and 4.3 with immersion frequencies of 3, 6 and 8 hours. The best results in BITs were obtained using 3 mg L-1 of BAP and immersion frequency every 3 hours The results show significant advances in bamboo micropropagation and applicable to other species.El Bambú Guadua angustifolia posee gran importancia económica y ambiental, pero sus métodos tradicionales de propagación son ineficientes. El objetivo del estudio fue desarrollar un eficiente protocolo de micropropagación para Guadua, utilizando Biorreactores de Inmersión Temporal BITs. Para el establecimiento se utilizaron segmentos nodales desinfectados y medio Murashige &amp; Skoog MS + 2 mg L-1 de bencilaminopurina BAP. Para la micropropagación se ensayaron 5 dosis de BAP 2, 3, 4, 5 y 6 mg L-1. En fase de multiplicación en BITS se utilizó MS con 3 dosis de BAP 3, 4, 5 mg L-1 y frecuencias de inmersión cada 3, 6 y 8 horas. Para enraizamiento en BITs se utilizó MS + 2.5 mg L-1 de sulfato de adenina. Los resultados mostraron que usando 2 mg L-1 de BAP, se obtuvo un brote por explante, mientras que con 3, 4, 5 y 6 mg L-1 de BAP se obtuvieron 2 brotes. En multiplicación BIT se obtuvieron 3.5, 7.5 y 10.4 brotes por explante con dosis de 3, 4 y 5 mg L-1 de BAP, respectivamente. Usando frecuencias de inmersión cada 3, 6 y 8 horas, se obtuvieron 7.5, 8.7 y 13.6 brotes por plantas, respectivamente. El número de raíces fue de 11.3, 4.0 y 4.3 con frecuencias de inmersiones de 3, 6 y 8 horas. Los mejores resultados en BITs se obtuvieron usando 3 mg L-1 de BAP y frecuencia de inmersión cada 3 horas. Los resultados muestran avances significativos en micropropagación de bambú y aplicable a otras especies

The little skate genome and the evolutionary emergence of wing-like fins

Skates are cartilaginous fish whose body plan features enlarged wing-like pectoral fins, enabling them to thrive in benthic environments1,2. However, the molecular underpinnings of this unique trait remain unclear. Here we investigate the origin of this phenotypic innovation by developing the little skate Leucoraja erinacea as a genomically enabled model. Analysis of a high-quality chromosome-scale genome sequence for the little skate shows that it preserves many ancestral jawed vertebrate features compared with other sequenced genomes, including numerous ancient microchromosomes. Combining genome comparisons with extensive regulatory datasets in developing fins—including gene expression, chromatin occupancy and three-dimensional conformation—we find skate-specific genomic rearrangements that alter the three-dimensional regulatory landscape of genes that are involved in the planar cell polarity pathway. Functional inhibition of planar cell polarity signalling resulted in a reduction in anterior fin size, confirming that this pathway is a major contributor to batoid fin morphology. We also identified a fin-specific enhancer that interacts with several hoxa genes, consistent with the redeployment of hox gene expression in anterior pectoral fins, and confirmed its potential to activate transcription in the anterior fin using zebrafish reporter assays. Our findings underscore the central role of genome reorganization and regulatory variation in the evolution of phenotypes, shedding light on the molecular origin of an enigmatic trait