Clinicopathological correlates in atypical Alzheimer's disease: evaluating anatomical distributions of neurofibrillary tangles and neuropsychological profiles

This study aims to discover whether there is a correlation between atypical clinical presentations of Alzheimer’s disease (AD) and atypical distribution patterns of AD pathology. To provide a measure of the atypical clinical presentations, we obtained standardized neuropsychological test scores for a group of 345 subjects of the Boston University Alzheimer’s Disease Center cohort that had received a clinical or pathological diagnosis of AD. Each of the neuropsychological test scores included in our analyses was classified into one of five cognitive domains, according to the primary domain each test assesses: memory, executive function, attention, visuospatial function, and language. From these test scores, global cognitive performance scores and individual domain performance scores were calculated for a subset of 53 subjects that had brain tissue slides available for pathological analysis. Difference scores were computed for each domain, providing a within-subject comparison of performance between each individual cognitive domain and overall cognitive performance. For these same 53 subjects, tissue slides from six brain regions were obtained and digitally scanned. Neurofibrillary tangle (NFT) quantification was performed for all tissue slides using a computer algorithm modified to recognize AT8 staining patterns. NFT densities were then calculated for five general brain regions (frontal, parietal, temporal, limbic and occipital). In addition, a global NFT density score was computed for each subject, averaging NFT densities across all regions. From these densities, difference scores were calculated for each brain region individually, providing a measure of how each region’s NFT density compares to the overall brain NFT density. Multiple linear regressions analyses were performed with five pairs of cognitive domain difference scores and region NFT density difference scores: memory difference scores and limbic difference scores, executive function difference scores and frontal difference scores, attention difference scores and parietal difference scores, visuospatial difference scores and occipital difference scores, and language difference scores and occipital difference scores. Though we expected to observe significant negative correlations between each of the five difference score pairs, the only statistically significant correlation observed was between memory difference scores and limbic difference scores (β= -0.361, p<0.05). These results suggest that poorer performance in memory-related neuropsychological tests, when compared to global cognitive performance, can predict higher NFT densities in limbic regions when compared to the overall brain pathology. Although no other difference score pairs showed any statistically significant correlations, many study limitations, including small sample size and simplifications in analysis, should be addressed in the future to provide better understanding of these atypical presentations of AD and their underlying pathologies

Identification and analysis of the young population in the starburst galaxy NGC 253

We present a study of the young population in the starburst galaxy NGC 253. In particular, we focused our attention on searching young star groups, obtaining their main properties and studying their hierarchical organization. For this task, we used multiband images and their corresponding photometric data obtained with the Advanced Camera for Surveys of the Hubble Space Telescope (ACS/HST).We have first derived the absorption affecting the different regions of the galaxy. Then, we applied an automatic and objective searching method over the corrected data in order to detect young star groups. We complemented this result with the construction of the stellar density map for the blue young population. A statistical procedure to decontaminate the photometric diagrams from field stars was applied over the detected groups and we estimated their fundamental parameters.As a result, we built a catalog of 875 new identified young groups with their main characteristics, including coordinates, sizes, estimated number of members, stellar densities, luminosity function (LF) slopes and galactocentric distances. We observed these groups delineate different structures of the galaxy, and they are the last step in the hierarchical way in which the young population is organized. From their size distribution, we found they have typical radius of ∼ 40 − 50 pc. These values are consistent with those ones found in others nearby galaxies. We estimated a mean value of the LF slope of 0.21 and an average density of 0.0006 stars/pc³ for the identified young groups taking into account stars earlier than B6.Fil: Rodriguez, Maria Jimena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Baume, Gustavo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Feinstein Baigorri, Carlos. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentin

Experimental verification of democratic particle motions by direct imaging of glassy colloidal systems

We analyze data from confocal microscopy experiments of a colloidal suspension to validate predictions of rapid sporadic events responsible for structural relaxation in a glassy sample. The trajectories of several thousand colloidal particles are analyzed, confirming the existence of rapid sporadic events responsible for the structural relaxation of significant regions of the sample, and complementing prior observations of dynamical heterogeneity. The emergence of relatively compact clusters of mobility allows the dynamics to transition between the large periods of local confinement within its potential energy surface, in good agreement with the picture envisioned long ago by Adam and Gibbs and Goldstein.Comment: 4 pages, 5 figure

Optimal Hyperparameter ϵ\epsilon for Adaptive Stochastic Optimizers through Gradient Histograms

Optimizers are essential components for successfully training deep neural network models. In order to achieve the best performance from such models, designers need to carefully choose the optimizer hyperparameters. However, this can be a computationally expensive and time-consuming process. Although it is known that all optimizer hyperparameters must be tuned for maximum performance, there is still a lack of clarity regarding the individual influence of minor priority hyperparameters, including the safeguard factor $\epsilon$ and momentum factor $\beta$, in leading adaptive optimizers (specifically, those based on the Adam optimizers). In this manuscript, we introduce a new framework based on gradient histograms to analyze and justify important attributes of adaptive optimizers, such as their optimal performance and the relationships and dependencies among hyperparameters. Furthermore, we propose a novel gradient histogram-based algorithm that automatically estimates a reduced and accurate search space for the safeguard hyperparameter $\epsilon$, where the optimal value can be easily found

Hydrometallurgical extraction of Al and Si from kaolinitic clays

Herein is presented the results of a study on the hydrometallurgic extractionand recovery of aluminum and silicon by leaching of kaolinitic clays with HF. Thestudied extraction parameters were: temperature, reaction time, solid/liquid ratio,concentration, and precipitating agent mass. In the leaching process, mineraldissolutions near 100% were obtained when working at 348 K, solid/liquid ratio2% w/v, HF 12% v/v, for 120 minutes. The HF leach liquor generated from thedissolution of kaolinitic clays contains H2SiF6 and H3AlF6. Studies were conductedto recover the two valuable fluorides as K2SiF6 and Na3AlF6 by precipitation withalkaline salts from the leach liquor. Phases of precipitated fluorides were identifiedby XRD and surface morphology by SEM. The purity of the K2SiF6 precipitate was98.8%, whereas for Na3AlF6, it was 89.3%. Also, both synthesized solids are ofhigh commercial value due to their industrial applications.Fil: Pinna, Eliana Guadalupe. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; ArgentinaFil: Suarez, Daniela Silvana. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Universidad Nacional de Cuyo; ArgentinaFil: Rosales, Gustavo Daniel. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; ArgentinaFil: Rodriguez, Mario Humberto. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentin

Analysis of pool-riffle dynamics through numerical morphological modelling

River morphodynamics and sediment transportRiver morphology and morphodynamic

Metabasin dynamics and local structure in supercooled water

We employ the Distance Matrix method to investigate metabasin dynamics in supercooled water. We find that the motion of the system consists in the exploration of a finite region of configuration space (enclosing several distinct local minima), named metabasin, followed by a sharp crossing to a different metabasin. The characteristic time between metabasin transitions is comparable to the structural relaxation time, suggesting that these transitions are relevant for the long time dynamics. The crossing between metabasins is accompanied by very rapid diffusional jumps of several groups of dynamically correlated particles. These particles form relatively compact clusters and act as cooperative relaxing units responsible for the density relaxation. We find that these mobile particles are often characterized by an average coordination larger than four, i.e. are located in regions where the tetrahedral hydrogen bond network is distorted

Development of a nano-Al/CuO based energetic material on silicon substrate

Nanoenergetic materials nEMs have improved performances compared to their bulk counterpart or microcounterpart. The authors propose an approach to synthesize an Al/CuO based nEM that has several advantages over previous investigations such as enhanced contact, reduced impurities and Al oxidation, tailored dimensions, and easier integration into microsystem. CuO nanowires are synthesized by thermally annealing Cu film deposited onto silicon. Nano-Al is integrated with the nanowires to realize an Al/CuO based nEM. The synthesized nEM is characterized by scanning electron microscopy, high resolution transmission electron microscopy, x-ray diffraction, differential thermal analysis, and differential scanning calorimetry