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Commensurable twisted bilayers can drastically change the magnetic properties of chromium trihalide layered compounds, which opens novel opportunities for tuning magnetic states through layer rotations. Here, we introduce a mathematical approach to obtain moir�� patterns in twisted hexagonal bilayers by performing a certain commensurable rotation $��$ over one layer. To test our approach, we apply it to find moir�� structures with $��=21.79^{\circ}$ and $32.20^{\circ}$ in the phases R$\bar{3}$ and C2/m of CrI$_{3}$. For comparison purposes, we also consider a non-shifted CrI$_{3}$ structure. Electronic and magnetic properties of the so-obtained systems are computed by \textit{Ab-Initio} methodologies. Results show the presence of rotation-angle-dependent magnetic configurations and steep modifications of the dispersion bands due to variations in the nearest and next nearest distances among layers of Cr atoms. Modifications obtained from these commensurable rotations are discussed on the basis of competition among different energy contributions due to changes in the atomic arrangements., 10 pages, 6 figures

Background: Over the past decade, visual short-term memory (VSTM) binding tests have been shown to be one of the most sensitive behavioral indicators of Alzheimer’s disease (AD), especially when they require the binding of multiple features (e.g., color and shape). Recently, it has become possible to directly measure amyloid and tau levels in vivo via positron emission tomography (PET). To this point, these behavioral and neurochemical markers have not been compared in humans with AD or at risk for it. Methods: In a cross-sectional study, we compared VSTM performance to tau and amyloid concentrations, measured by PET, in individuals certain to develop AD by virtue of their inheritance of the presenilin-1 E280A mutation. These included 21 clinically unimpaired subjects and 7 subjects with early mild cognitive impairment (MCI), as well as 30 family members who were not carriers of the mutation. Results: We found that VSTM performance correlated strongly with tau in entorhinal cortex and inferior temporal lobe, and also with amyloid when examining asymptomatic carriers only. The condition requiring binding was not preferentially linked to tau—in fact, the non-binding “shape only” condition showed a stronger relationship. Conclusions: The results confirm VSTM’s status as an early marker of AD pathology, and raise interesting questions as to the course of binding-specific versus non-binding aspects of VSTM in early AD.

Background Parkinson's disease is the second most common neurodegenerative disorder and affects people from all ethnic backgrounds, yet little is known about the genetics of Parkinson's disease in non-European populations. In addition, the overall identification of copy number variants at a genome-wide level has been understudied in Parkinson's patients. The objective of this study was to understand the genome-wide burden of copy number variants in Latinos and its association with Parkinson's disease. Methods We used genome-wide genotyping data from 747 Parkinson's disease patients and 632 controls from the Latin American Research Consortium on the Genetics of Parkinson's disease. Results Genome-wide copy number burden analysis showed that patients were significantly enriched for copy number variants overlapping known Parkinson's disease genes compared with controls (odds ratio, 3.97; 95%CI, 1.69-10.5; P = 0.018). PRKN showed the strongest copy number burden, with 20 copy number variant carriers. These patients presented an earlier age of disease onset compared with patients with other copy number variants (median age at onset, 31 vs 57 years, respectively; P = 7.46 × 10-7 ). Conclusions We found that although overall genome-wide copy number variant burden was not significantly different, Parkinson's disease patients were significantly enriched with copy number variants affecting known Parkinson's disease genes. We also identified that of 250 patients with early-onset disease, 5.6% carried a copy number variant on PRKN in our cohort. Our study is the first to analyze genome-wide copy number variant association in Latino Parkinson's disease patients and provides insights about this complex disease in this understudied population. © 2020 International Parkinson and Movement Disorder Society.

[EN] This paper analyzes the reflectance obtained with a series of Landsat images processed with LEDAPS model in a region of the Colombian Andes. A total of 38 images of TM and ETM sensors were calibrated to surface reflectance using LEDAPS in order to determine difference among bands of the same sensor, difference between sensors and analyze temporal patterns. Exact nonparametric statistics allow to conclude that: a) surface reflectance for band 1–5 and 7 were significantly different and this difference remains among images of different dates; b) there are statistical similarities between the TM and ETM sensors bands; c) temporal variations on surface reflectance from the years 1986 to 2013 with the sensors studied are not statistically significant. These results are supported by the implementation of robust modeling with various methods resistant to unusual observations and other typical problems of the classical least squares modeling., [ES] En este trabajo se hace un análisis de la reflectividad obtenida con una serie de imágenes Landsat procesa-das con el modelo LEDAPS en una región de los Andes Colombianos. Fueron calibradas 38 imágenes de los sensores TM y ETM con el modelo LEDAPS con el fin de evaluar las diferencias de reflectividad entre las bandas de un mismo sensor, las diferencias entre sensores, y los patrones temporales. Se utilizaron pruebas estadísticas no paramétricas exactas que permitieron concluir: a) la reflectividad superficial entre bandas (1-5 y 7) es distinta y que esta diferencia se mantiene entre escenas de fechas distintas; b) al comparar las bandas de igual longitud de onda entre los sensores TM y ETM+ hay altas similitudes estadísticas entre las bandas; c) las variaciones temporales en reflectividad desde el año 1986 a 2013 con los sensores estudiados no son significativas. Estos resultados están sustentados con la implementación de modelación robusta con varios métodos resistentes a observaciones inusuales y otros problemas típicos de la modelación de mínimos cuadrados clásicos

Presenilin-1 (PSEN1) mutations are the most common cause of familial early onset Alzheimer's disease (AD). The PSEN1 E280A (E280A) mutation has an autosomal dominant inheritance and is involved in the production of amyloid-ß. The largest family group of carriers with E280A mutation is found in Antioquia, Colombia. The study of mutation carriers provides a unique opportunity to identify brain changes in stages previous to AD. Electroencephalography (EEG) is a low cost and minimally invasiveness technique that enables the following of brain changes in AD.

INTRODUCTION: Differences in the prevalence of dementia among populations and in the effect of apolipoprotein E (APOE) on the emergence of Alzheimer disease (AD), which is the main type of dementia, have been reported. METHODS: This study estimated the ancestry of a group of individuals with late-onset Alzheimer disease (LOAD) (N=280) and established whether there were any differences when compared with a control group (N=357) in a sample of the Colombian population. RESULTS: When the analyses were adjusted for known risk factors such as age, sex, presence of APOE[Latin Small Letter Open E]4, socioeconomic status, educational attainment, and place of birth, African ancestry was associated with an increased LOAD risk (odds ratio: 1.55; 95% confidence interval, 1.09-2.03; P=0.029), whereas Native American ancestry was associated with lower risk (odds ratio: 0.75; 95% confidence interval, 0.61-0.98; P=0.046), for every 10% increase in ancestry. In addition, there were significant differences in the proportion of Native American ancestry between carriers and noncarriers of the APOE[Latin Small Letter Open E]4 allele (Mann-Whitney U test, P=0.047), with noncarriers having higher mean Native American ancestry when compared with carriers. CONCLUSIONS: Our results are consistent with the presence of variants of African origin in the genome of the Colombian population and different from APOE[Latin Small Letter Open E]4 that represents a risk factor for the development of LOAD, whereas variants of Native American origin may be conferring protection. However, unknown environmental factors or epigenetic differences among continental groups could also explain the observed associations.

Biopercular syndrome is a labio-facio-pharyngeal-laryngeal-gloso-masticatory diplegia, with automatic dissociation of movements. Ischemia is the most common etiology when it occurs bilaterally in the opercular area, but it has been also described in patients with bilateral subcortical lesions. There are few cases described with unilateral lesions. We report a 76-year-old woman who developed a biopercular syndrome caused by unilateral ischemic lesion of the right middle cerebral artery confirmed by magnetic resonance imaging and cerebral SPECT.

Introduction: Even though less than 1% of Alzheimer’s disease (AD) is of hereditary origin, FAD is used as a reference for its natural history and as a framework for the development of animal models and therapies for the disease. Given that all known mutations for FAD occur in proteins involved[for full text, please go to the a.m. URL], 60th Annual Meeting of the German Society for Neuropathology and Neuroanatomy (DGNN)

Recent evidence suggests that rare genetic variants within the TREM2 gene are associated with increased risk of Alzheimer's disease. TREM2 mutations are the genetic basis for a condition characterized by polycystic lipomembranous osteodysplasia with sclerosing leukoencephalopathy (PLOSL) and an early-onset dementia syndrome. TREM2 is important in the phagocytosis of apoptotic neuronal cells by microglia in the brain. Loss of function might lead to an impaired clearance and to accumulation of necrotic debris and subsequent neurodegeneration. In this study, we investigated a consanguineous family segregating autosomal recessive behavioral variant FTLD from Antioquia, Colombia. Exome sequencing identified a nonsense mutation in TREM2 (p.Trp198X) segregating with disease. Next, using a cohort of clinically characterized and neuropathologically verified sporadic AD cases and controls, we report replication of the AD risk association at rs75932628 within TREM2 and demonstrate that TREM2 is significantly overexpressed in the brain tissue from AD cases. These data suggest that a mutational burden in TREM2 may serve as a risk factor for neurodegenerative disease in general, and that potentially this class of TREM2 variant carriers with dementia should be considered as having a molecularly distinct form of neurodegenerative disease. © 2013 Elsevier Inc.

Short-term memory binding is a memory function that underpins the temporary retention of complex objects (e.g. shapes with colours). In the verbal domain, this function has been found to be impaired in sporadic Alzheimer’s disease. Whether short-term memory binding is also impaired in familial Alzheimer’s disease, whether this impairment extends to the visual domain and whether it could be detected earlier than other cognitive deficits are issues yet to be investigated. Twenty two patients with familial Alzheimer’s disease caused by the E280A single presenilin-1 mutation, thirty carriers of the mutation who did not meet Alzheimer’s disease criteria (asymptomatic carriers) and 30 healthy relatives (non-carrier healthy controls) were assessed with a visual short-term memory task and a neuropsychological battery. The short-term memory task assessed the recognition of shapes, colours or shape-colour bindings presented in two consecutive arrays (i.e. study and test). Changes, which always occurred in the test array, consisted of new features replacing studied features (single feature conditions) or of features swapping across items (the binding condition). The neuropsychological battery comprised tests of associative and non-associative memory, attention, language, visuospatial and executive functions. Patients with Alzheimer’s disease and asymptomatic carriers performed significantly worse than healthy controls in the feature binding condition only. Group comparisons between asymptomatic carriers and healthy controls on standard neuropsychological tasks revealed no significant differences. Classification and area under the curve analyses confirmed that the binding task combines more sensitivity and specificity for patients with Alzheimer’s disease and most notably for asymptomatic carriers of the mutation than other traditional neuropsychological measures. This suggests that visual short-term memory binding deficits may be a preclinical marker for familial Alzheimer’s disease.

En este artículo se presenta un método simple para determinar el campo magnético generado por líneas de transmisión. El cálculo del campo magnético tiene en cuenta los efectos de mitigación de bucles pasivos, incluyendo su ubicación óptima en la línea mediante la aplicación de algoritmos genéticos. Los resultados de los cálculos son validados mediante reportes de casos publicados en el IEEE, software de análisis de campo electromagnético y datos experimentales arrojados de una implementación realizada en las líneas de alimentación de las torres de iluminación en un estadio. Luego del análisis, se demuestra la validez del método y la factibilidad de aplicarlo en líneas de transmisión del sistema de potencia. A simple method to determine the magnetic field generated by transmission lines is presented in this paper. The magnetic field calculation takes into account the mitigating effects of passive loops, including their optimal position in the line by applying genetic algorithms. Calculations results are validated by case reports published in the IEEE Transactions, software package for electromagnetic field analysis, and experimental data obtained from an implementation made in the power lines at a stadium lighting tower. After the analysis, the method’s validity and feasibility of its application to transmission lines power systems are demonstrated.

En este trabajo desarrollamos un breve estudio sobre la función cuantil y su estimación según un determinado método en el caso de utilizar información auxiliar. Presentamos el método de estimación de la función cuantil que va acompañado de la estimación de la función de distribución. Consideradas dos características de esa población, definimos un estimador ratio simple de la función cuantil que nos va a servir para poder analizar la relación de proporcionalidad que pueda existir entre ambas, observando que cuanto mayor es esta relación más se aproxima el estimador ratio a la función cuantil de la población, coincidiendo ambas en el caso de que esta relación de proporcionalidad sea total. Se acompaña dicho estudio de una simulación realizada sobre una población donde hemos analizado las dos características.

Esta comunicaación pretende cuantificar en unidades monetarias el riesgo inherentes a las operaciones financieras aleatorias y logicamente, dicha cantidad estará referida al momento de su disponibilidad. Por lo tanto el análisis y valoración del riesgo, que clásicamente se hace a través de las desviaciones típicas, lo completamos mediante la valoración de dichas desviaciones mediante una ley finanicera; para ello utilizamos como función de distribución la función de desviación típica de los procesos estocásticos de prestación y contraprestación.