According to the traditional wisdom, geomagnetically induced currents (GIC) should occur rarely at mid-to-low latitudes, but in the last decades a growing number of reports have addressed their ...effects on high-voltage (HV) power grids at mid-to-low latitudes. The growing trend to interconnect national power grids to meet regional integration objectives, may lead to an increase in the size of the present energy transmission networks to form a sort of super-grid at continental scale. Such a broad and heterogeneous super-grid can be exposed to the effects of large GIC if appropriate mitigation actions are not taken into consideration. In the present study, we present GIC estimates for the Uruguayan HV power grid during severe magnetic storm conditions. The GIC intensities are strongly dependent on the rate of variation of the geomagnetic field, conductivity of the ground, power grid resistances and configuration. Calculated GIC are analysed as functions of these parameters. The results show a reasonable agreement with measured data in Brazil and Argentina, thus confirming the reliability of the model. The expansion of the grid leads to a strong increase in GIC intensities in almost all substations. The power grid response to changes in ground conductivity and resistances shows similar results in a minor extent. This leads us to consider GIC as a non-negligible phenomenon in South America. Consequently, GIC must be taken into account in mid-to-low latitude power grids as well.
•Initiation of ketogenic diet therapies (KDT) for pediatric epilepsy is usually done on an inpatient basis.•Because (COVID-19) pandemic and the associated lock-down measures, some centers switched to ...telemedicine-based KDT initiation.•We explore the feasibility, effectiveness, and safety of online KDT initiation.•No statistical differences between the two groups regarding efficacy and safety of the diet were found.•Our results support the feasibility and safety of initiating and management of KDT by telemedicine.
Initiation of ketogenic diet therapies (KDT) for pediatric epilepsy is usually done on an inpatient basis and the diet is managed during clinical appointments following a protocol of visits and routine tests. Because of the 2019 coronavirus disease (COVID-19) pandemic and the associated lock-down measures, we switched from outpatient to telemedicine-based KDT initiation.
Objective: To explore the feasibility, effectiveness, and safety of online KDT initiation and follow-up by comparing a group of children with drug-resistant epilepsy that was managed by telemedicine compared to a group that was treated on an outpatient basis.
An observational study was conducted in two groups of patients with drug-resistant epilepsy who initiated KDT and were followed up with an online versus an outpatient modality by the interdisciplinary KDT team of Hospital Pediatria JP Garrahan in Buenos Aires, Argentina. Dietary compliance, ketosis, retention rate, adverse effects, number of contacts, and clinical outcome were evaluated at 1, 3, and 6 months on the diet.
Overall, 37 patients were included, of whom 18 started the KD by telemedicine and 19 on an outpatient basis. Minimum follow-up of the patients was 6 months. All patients received the classic ketogenic diet. No statistical differences between the two groups regarding efficacy and safety of the diet were found.
Our results support the feasibility and safety of initiating and management of KDT by telemedicine. Patients and their families should be carefully selected in order to guarantee a good outcome.
Pinus occidentalis (Swartz) is the primary timber species in the Dominican Republic (DR). Despite its economic importance, studies conducted on this species are scarce, making it difficult to ...estimate current inventory levels. This study aims to enhance the accuracy of estimating the total bole volume of P. occidentalis in different ecological zones (EZs) within La Sierra, evaluating and comparing two established volume equations—combined variable (CV) and Schumacher and Hall (S&H) across nine modeling variants. An indicator variables analysis determined the necessity of distinct equations for two EZs. Fitting included both linear and nonlinear models. Our comprehensive statistical analysis included goodness-of-fit metrics to evaluate each model variant’s performance rigorously. The second modeling variant (SH02) for the SH equation was most effective in the Dry Ecological Zone, showing superior performance in both the fitting and validation phases. Similarly, the third modeling variant (SH03) for the SH equation emerged as the best fit for the Combined Intermediate and Humid Ecological Zones, achieving the lowest overall ranking sum among tested variants. SH02 and SH03 provide reliable and precise volume estimations, allowing for the optimization of forestry management practices for P. occidentalis trees. The SH models outperformed the CV model variants’ consistency in parameter estimation. This tailored approach ensures more accurate volume predictions, which is crucial for sustainable management and conservation efforts.
The discrepancy between cigarette smoking status reported during an interview and measured level of serum cotinine, a nicotine biomarker, was investigated in a representative sample of the US ...population aged >/=17 years (N = 15,357). Data were collected from participants in the Third National Health and Nutrition Examination Survey (1988-1994). Among self-reported smokers, 7.5% (95% confidence interval: 6.3, 8.7) had a serum cotinine level less than or equal to 15.0 ng/ml, the selected cutoff point for identifying nonsmokers. Age (p < 0.01), race/ethnicity (p < 0.01), and average number of cigarettes smoked per day (p < 0.01) were associated with these discrepant findings. Among self-reported nonsmokers, 1.4% (95% confidence interval: 1.1, 1.7) had a serum cotinine level greater than 15.0 ng/ml, the selected cutoff point for identifying smokers. Race/ethnicity (p < 0.01), education (p < 0.01), number of household members who smoked in the home (p = 0.03), and self-reported smoking status from an earlier home interview (p < 0.01) were associated with these discrepant findings. Differences in smoking patterns, including the extent of nicotine dosing, may explain most of the discrepancy observed among self-reported smokers, whereas deception regarding smoking status may explain most of the discrepancy among self-reported nonsmokers. This study provides evidence that self-reported smoking status among adult respondents to a population-based survey conducted in a private medical setting is accurate.
The increase in airborne pollution in large cities since the mid-20th century has had a physiologically proven impact on respiratory health, resulting in the irritation and corrosion of the alveolar ...wall. One of the demographics of the population most affected by this problem is children. This study focuses on the relationship between particulate matter of 2.5 µm (PM2.5) and childhood asthma, which is one of the main respiratory diseases identified in developing countries. The city of Cartagena de Indias, Colombia, is taken as a case study. A relevant correlation between childhood asthma and PM2.5 is found. Incidence series of paediatric asthma on a monthly scale and PM2.5 records in the city of Cartagena are considered. As is common in developing countries, the series was incomplete due to a lack of experts and insufficient economical resources. Therefore, several statistical and analytical processes were applied to provide sufficient quality to the series. An improvement of the time scale of the records was carried out, as well as the completion (statistical imputation) of missing data due to low statistical significance, by applying Rstudio®, PAST® and SPSS®. The last phases consisted of the determination of the main factors that cause childhood asthma incidence, the estimation of the correlation between asthma incidence and PM2.5, as well as the estimation of health impact. A reduction in PM2.5 concentration was simulated using BenMap-CE software to reach safe levels according to the WHO guidelines on air quality to identify preventable cases of childhood asthma, as air pollution has been found to be related to this disease. In addition, a log-linear model was applied to determine the number of hospital visits avoided after reducing the levels of PM2.5 concentration to the maximum levels recommended by WHO. The results showed a good agreement between childhood asthma incidence and PM2.5 pollutants in the spectral analysis (75% coincidence) and Chi2 (85.5% of coincidence) assessments, while visual correlation, mean and linear regression showed lower relations (61.0%, 55.5% and 0.48%, respectively). A reduction to a safe level of 5 µg/m3 would lead to a reduction of 240 annual cases of childhood asthma (95% CI: 137–330).
We estimate the influence of the geomagnetically induced currents (GIC) on the Uruguayan electrical distribution grid. The GIC are related to time variations in the geomagnetic field caused by the ...interaction of the solar wind with the Earth's magnetosphere. These currents may cause several problems in power grids, pipelines, among others. South America is close to the South Atlantic Magnetic Anomaly (SAA). Particle precipitation in the anomaly region could lead to pulsations in the horizontal component of the geomagnetic field, that may contribute to the GIC production. Scarce research has been done to assess the space weather impact on this area.
Due to the lack of magnetic field data at the Uruguayan territory, spherical elementary currents system (SECS) was used to interpolate field values with data available from three magnetic observatories located at Vassouras, Trelew and São Martinho da Serra. The simple topology of the Uruguayan power grid provides some advantages in the calculation of GIC. To calculate these currents, a plane wave method combined with a ground conductivity model was used. Estimated GIC suggest peak currents ca. 15 A, at the earthing points of some substations in a 770 km power line during the Halloween Magnetic Storm on 2003 October 29.
Abstract
We present the first observations of geomagnetically induced currents (GIC) in the Mexican power grid and an improved model to calculate them. The new model comprises ca. 250 substations ...working at various voltage levels, a methodology to estimate geomagnetic disturbances (
δB
) at different points throughout the Mexican territory, and a 1D piecewise model that considers lateral variations in the ground conductivity. This is an improvement of a former uniform conductivity model presented previously to calculate our first GIC estimates (Caraballo et al., 2020). We compared the observed and calculated GIC between August and November 2021 at a coastal 400 kV substation. During this interval, five geomagnetic storms occurred (G1 and G2). The observed GIC exceeded 10 A during the most strong event; this shows a clear grid response even under weak geomagnetic perturbations that occurred during the solar minimum. Further comparison with the results of the former model suggests that the new 1D piecewise model yields better GIC estimates for the Mexican power grid.
Plain Language Summary
We present observations of geomagnetically induced currents (GIC) in the Mexican power grid and an improved model to calculate them. The new model considers multiple operational voltages as well as lateral and vertical variations in ground conductivity. Additionally, we analyzed GIC observations at a given substation from August to November 2021 and the grid response during five geomagnetic storms that occurred during this period. The observed GIC shows a clear grid response even during weak geomagnetic perturbations. Regarding calculated GIC, comparisons with the former model output suggest that the 1D piecewise model can be a valuable tool for providing GIC estimates for the Mexican power grid.
Key Points
We compared geomagnetically induced currents (GIC) observations and estimates for the Mexican power grid during 2021 (near solar cycle minimum)
An improved model to calculate GIC yields better estimates for the Mexican 400/230 kV grid
Measured GIC at a coastal substation exceeded 10 A during a G2 geomagnetic storm that occurred on November 2021
First GIC Estimates for the Mexican Power Grid Caraballo, R.; González‐Esparza, J. A.; Sergeeva, M. ...
Space Weather,
February 2020, 2020-02-00, 20200201, Letnik:
18, Številka:
2
Journal Article
Recenzirano
Odprti dostop
This contribution addresses the first assessment of the impact of geomagnetically induced currents (GIC) on the 400‐kV power grid of Mexico. As an initial approach, we modeled GIC using a uniform ...conductivity for the entire Mexican territory and spatially uniform geomagnetic disturbance. Power grid data were provided by the electric operator of Mexico; the geophysical data were inferred from the main features of Mexican geology. We calculate the power grid response during four geomagnetic storms from Solar Cycles 23 and 24 (i.e., 15 July 2000, 20 October 2003, 17 March 2015, and 7 September 2017), as well as during an extreme scenario (a Carrington‐like event). The results show that the Mexican power grid can be affected by three‐phase GIC ranging from 20 to 75 A during geomagnetic disturbances. According to the model, sites located in coastal areas or close to the edges of the network can experience large GIC during time intervals between 3 and 10 hr, depending on the intensity of the geomagnetic disturbance. It is an interesting result that these sites are of the major economic and strategic significance for the country. In the case of a Carrington‐like event, the power grid could be affected by GIC ranging between 25 and 150 A under a uniform 1 V/km EW geoelectric field. Such an event might produce significant distortions in the grid hardware (i.e., transformers and static VAR compensators), potentially leading to widespread damage.
Key Points
An exploratory model to assess the impact of geomagnetically induced currents (GIC), on the 400‐kV Mexican power grid, is presented
Estimated GIC values are higher at the edges of the Mexican grid
Model results are used to plan the installation of GIC sensors along the power grid
Fe2MnSi fails to follow the Slater-Pauling rule. This phenomenon is thought to originate from either: (i) an antiferromagnetic arrangement of Mn ions at low temperature and/or (ii) chemical disorder. ...An important insight on this issue could be achieved by considering Fe2MnSi1−xGax compounds, thoroughly studied here by means of magnetization, neutron diffraction and density functional calculations (DFT). Our results indicate that chemical disorder (and not the antiferromagnetic arrangement) is responsible for the deviation of the Slater-Pauling rule on Fe2MnSi-based Heusler alloys. Furthermore, evidences suggest that Ga substitution into Si site favors the Fe/Mn disorder, further enhancing the observed deviation.
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