Extremal GG-invariant eigenvalues of the Laplacian of GG-invariant metrics

The study of extremal properties of the spectrum often involves restricting the metrics under consideration. Motivated by the work of Abreu and Freitas in the case of the sphere $S^2$ endowed with $S^1$-invariant metrics, we consider the subsequence $\lambda_k^G$ of the spectrum of a Riemannian manifold $M$ which corresponds to metrics and functions invariant under the action of a compact Lie group $G$. If $G$ has dimension at least 1, we show that the functional $\lambda_k^G$ admits no extremal metric under volume-preserving $G$-invariant deformations. If, moreover, $M$ has dimension at least three, then the functional $\lambda_k^G$ is unbounded when restricted to any conformal class of $G$-invariant metrics of fixed volume. As a special case of this, we can consider the standard O(n)-action on $S^n$; however, if we also require the metric to be induced by an embedding of $S^n$ in $\mathbb{R}^{n+1}$, we get an optimal upper bound on $\lambda_k^G$.Comment: To appear in Mathematische Zeitschrif

Bounding the eigenvalues of the Laplace-Beltrami operator on compact submanifolds

We give upper bounds for the eigenvalues of the La-place-Beltrami operator of a compact $m$-dimensional submanifold $M$ of $\R^{m+p}$. Besides the dimension and the volume of the submanifold and the order of the eigenvalue, these bounds depend on either the maximal number of intersection points of $M$ with a $p$-plane in a generic position (transverse to $M$), or an invariant which measures the concentration of the volume of $M$ in $\R^{m+p}$. These bounds are asymptotically optimal in the sense of the Weyl law. On the other hand, we show that even for hypersurfaces (i.e., when $p=1$), the first positive eigenvalue cannot be controlled only in terms of the volume, the dimension and (for $m\ge 3$) the differential structure.Comment: To appear, London Math Societ

Development of a portable leaf photosynthesis and volatile organic compounds emission system.

Understanding how plant carbon metabolism responds to environmental variables such as light is central to understanding ecosystem carbon cycling and the production of food, biofuels, and biomaterials. Here, we couple a portable leaf photosynthesis system to an autosampler for volatile organic compounds (VOCs) to enable field observations of net photosynthesis simultaneously with emissions of VOCs as a function of light. Following sample collection, VOCs are analyzed using automated thermal desorption-gas chromatograph-mass spectrometry (TD-GC-MS). An example is presented from a banana plant in the central Amazon with a focus on the response of photosynthesis and the emissions of eight individual monoterpenes to light intensity. Our observations reveal that banana leaf emissions represent a 1.1 +/- 0.1% loss of photosynthesis by carbon. Monoterpene emissions from banana are dominated by trans-β-ocimene, which accounts for up to 57% of total monoterpene emissions at high light. We conclude that the developed system is ideal for the identification and quantification of VOC emissions from leaves in parallel with CO2 and water fluxes.The system therefore permits the analysis of biological and environmental sensitivities of carbon metabolism in leaves in remote field locations, resulting in the emission of hydrocarbons to the atmosphere.•A field-portable system is developed for the identification and quantification of VOCs from leaves in parallel with leaf physiological measurements including photosynthesis and transpiration.•The system will enable the characterization of carbon and energy allocation to the biosynthesis and emission of VOCs linked with photosynthesis (e.g. isoprene and monoterpenes) and their biological and environmental sensitivities (e.g. light, temperature, CO2).•Allow the development of more accurate mechanistic global VOC emission models linked with photosynthesis, improving our ability to predict how forests will respond to climate change. It is our hope that the presented system will contribute with critical data towards these goals across Earth's diverse tropical forests

Cancer stem cells and macrophages: Implications in tumor biology and therapeutic strategies

This work was supported by a Ramón y Cajal Merit Award from the Ministerio de Economía y Competitividad, Spain (Bruno Sainz Jr.), a Clinic and Laboratory Integration Program (CLIP) grant from the Cancer Research Institute, NY (Bruno Sainz Jr.), and an NIH/NCI R00 (CA154605, Heather L. Machad

Hubble Asteroid Hunter: II. Identifying strong gravitational lenses in HST images with crowdsourcing

The Hubble Space Telescope (HST) archives constitute a rich dataset of high resolution images to mine for strong gravitational lenses. While many HST programs specifically target strong lenses, they can also be present by coincidence in other HST observations. We aim to identify non-targeted strong gravitational lenses in almost two decades of images from the ESA it Hubble Space Telescope archive (eHST), without any prior selection on the lens properties. We used crowdsourcing on the Hubble Asteroid Hunter (HAH) citizen science project to identify strong lenses, alongside asteroid trails, in publicly available large field-of-view HST images. We visually inspected 2354 objects tagged by citizen scientists as strong lenses to clean the sample and identify the genuine lenses. We report the detection of 252 strong gravitational lens candidates, which were not the primary targets of the HST observations. 198 of them are new, not previously reported by other studies, consisting of 45 A grades, 74 B grades and 79 C grades. The majority are galaxy-galaxy configurations. The newly detected lenses are, on average, 1.3 magnitudes fainter than previous HST searches. This sample of strong lenses with high resolution HST imaging is ideal to follow-up with spectroscopy, for lens modelling and scientific analyses. This paper presents an unbiased search of lenses, which enabled us to find a high variety of lens configurations, including exotic lenses. We demonstrate the power of crowdsourcing in visually identifying strong lenses and the benefits of exploring large archival datasets. This study shows the potential of using crowdsourcing in combination with artificial intelligence for the detection and validation of strong lenses in future large-scale surveys such as ESA's future mission Euclid or in JWST archival images.Comment: 24 page, 14 figures, 5 tables, accepted for publication in A&A June 28 202

Inventário de Flow no Trabalho: Evidências de Validade da Versão Brasileira

Flow in work is constituted by the positive experiences and mental state experienced during the day-to-day occupational activities. This study aims to adapt and assess the psychometric properties of the Brazilian Version of the Work Related Flow Inventory (WOLF). Participants were a nationwide sample of 640 professional (74% women), aged 19 to 73 years (M = 35.9, SD = 10.5). Confirmatory factor analyses (CFA) supported the oblique three-factor structure (absorption, work enjoyment and intrinsic work motivation) as being the most reliable to the data. Multigroup CFA achieved full measurement invariance for the gender and employment status (autonomous and non-autonomous). Flow dimensions were positively related to occupational selfefficacy and job satisfaction. WOLF presented adequate psychometric properties, suggesting its usefulness in evaluating flow at work in the Brazilian context.Flow no trabalho constitui-se pelas experiências positivas e estado mental vivenciados durante as atividades ocupacionais do dia a dia. Este estudo tem como objetivo adaptar e avaliar as propriedades psicométricas da versão Brasileira do Inventário de Flow no Trabalho (WOLF). Os participantes desta pesquisa foram uma amostra nacional de 640 profissionais (74% mulheres), idades entre 19 a 73 anos (M = 35,9, DP = 10,5). A análise fatorial confirmatória (AFC) evidenciou a estrutura de três fatores oblíquos (absorção, envolvimento e motivação intrínseca) como a mais adequada aos dados. A AFC Multigrupo demonstrou a invariância da escala para sexo e situação de trabalho (autônomo e não-autônomo). As dimensões de flow estiveram positivamente relacionadas à autoeficácia ocupacional e satisfação no trabalho. WOLF apresentou propriedades psicométricas satisfatórias, sugerindo a sua utilidade para avaliar flow no contexto brasileiro.El flow en trabajo comprende una experiencia positiva y estado mental que pueden ocurrir durante las actividades laborales. Este estudio pretende adaptar y evaluar las propiedades psicométricas de la versión brasilera del Inventario de Flow en trabajo (WOLF). Los participantes fueron una muestra nacional de 640 profesionales (74% mujeres) con edades entre 19 a 73 años (M = 35,9, DE = 10,5). El análisis factorial confirmatorio (AFC) respaldó que la estructura oblicua de tres factores (absorción, implicación y motivación intrínseca) es la más confiable. El AFC multigrupo alcanzó invariancia de medida completa para sexo y status de empleo (autónomo y no autónomo). Las dimensiones del flow se relacionaron positivamente con autoeficacia ocupacional y satisfacción laboral. El WOLF presentó propiedades psicométricas adecuadas, lo que sugiere su utilidad en evaluar flow en el contexto brasilero

EEG theta dynamics within frontal and parietal cortices for error processing during reaching movements in a prism adaptation study altering visuo-motor predictive planning

Modulation of frontal midline theta (fmθ) is observed during error commission, but little is known about the role of theta oscillations in correcting motor behaviours. We investigate EEG activity of healthy partipants executing a reaching task under variable degrees of prism-induced visuo-motor distortion and visual occlusion of the initial arm trajectory. This task introduces directional errors of different magnitudes. The discrepancy between predicted and actual movement directions (i.e. the error), at the time when visual feedback (hand appearance) became available, elicits a signal that triggers on-line movement correction. Analysis were performed on 25 EEG channels. For each participant, the median value of the angular error of all reaching trials was used to partition the EEG epochs into high- and low-error conditions. We computed event-related spectral perturbations (ERSP) timelocked either to visual feedback or to the onset of movement correction. ERSP time-locked to the onset of visual feedback showed that fmθ increased in the high-but not in the lowerror condition with an approximate time lag of 200 ms. Moreover, when single epochs were sorted by the degree of motor error, fmθ started to increase when a certain level of error was exceeded and, then, scaled with error magnitude. When ERSP were time-locked to the onset of movement correction, the fmθ increase anticipated this event with an approximate time lead of 50 ms. During successive trials, an error reduction was observed which was associated with indices of adaptations (i.e., aftereffects) suggesting the need to explore if theta oscillations may facilitate learning. To our knowledge this is the first study where the EEG signal recorded during reaching movements was time-locked to the onset of the error visual feedback. This allowed us to conclude that theta oscillations putatively generated by anterior cingulate cortex activation are implicated in error processing in semi-naturalistic motor behaviours. © 2016 Arrighi et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Detection of European Strain of \u3ci\u3eEchinococcus multilocularis\u3c/i\u3e in North America

To the Editor: In 2009, an alveolar hydatid cyst, the intermediate stage of the cestode Echinococcus multilocularis, was detected in the liver of a dog from Quesnel, British Columbia (BC), Canada, 600 km west of the nearest known record of this parasite in central North America. Alveolar hydatid cysts normally occur in rodent intermediate hosts. However, humans can serve as aberrant intermediate hosts; cysts generally originate in the liver and, in about one third of cases, metastasize throughout the body. Detection of the larval stage of this pathogen in an unusual host in a new geographic region required application of multiple molecular epidemiologic techniques to determine if this was range expansion of a native strain or introduction of a new strain of veterinary and public health concern. The possible establishment of a European strain in North American wildlife, with spillover into domestic dogs, may have implications for public health and require increased vigilance by medical and veterinary personnel in the newly endemic region. Compared with native North American strains, European strains of E. multilocularis appear to have greater potential to cause alveolar hydatid disease (AHD) in humans. These strains are emerging worldwide (increasing in both prevalence and distribution) as a result of changes in landscape, climate, and wildlife–human interfaces. In Europe, human AHD can be fatal (definite or probable cause of death in 23.5% of 119 recent cases) and has low cure rates (5% of 408 recent cases). As of 2000, in Europe and Asia, the estimated cost per case of AHD was US $100,000–$300,000. Therefore, better understanding of the distribution, genetic diversity, and pathogenicity of strains of E. multilocularis is needed to assess risks and mitigate costs for public and veterinary health, as well as to provide evidence for the regulation and screening of imported domestic animals and translocated wildlife

Novel inhibition mechanism and potent antiviral activity of translocation-deficient reverse transcriptase inhibitors [abstract]

Abstract only availableNucleoside RT inhibitors (NRTIs) are among the most potent anti-HIV agents and act as chain terminators because they lack a 3'OH. However, this feature can reduce affinity for RT compared to the analogous dNTP substrate, as well as reduced intracellular conversion to the active dNTP. To overcome this, it was shown that certain nucleosides that retain the 3'OH and have substitutions at the 4' ribose and 2 position of the base have exceptional antiviral properties. One of these compounds, 4'-ethynyl, 2-fluoro deoxy-adenosine (4'E-2FdA) is the most potent NRTI inhibitor against wild-type and multi-drug resistant HIV viruses described to date. We have recently reported that 4'E-2FdA acts as a chain terminator despite the presence of an accessible 3'OH. We show that after 4'E-2FdA-MP incorporation, RT does not bind the next incoming dNTP. We analyzed RT translocation on different sequences terminated with 4'E-2FdA-MP, and found that even at sequences when RT is naturally found post-translocated, the inhibitor prevents translocation. This decrease in translocation efficiency explains the reduced binding of the next incoming dNTP and the termination of elongation. While the inhibitor stabilizes the pre-translocated 4'E-2FdA-MP-terminated primer, the pyrophosphate-dependent excision rate of 4'E-2FdA-MP was not very high compared to ddAMP. In conclusion, this highly potent chain termination activity arises from difficulty of the primer 3'-terminus to translocate following incorporation of the compound, and not from simple steric hindrance due to the 4' substitution. Therefore, we propose that 4'E-2FdA is a Translocation-Deficient Reverse Transcriptase Inhibitor (TDRTI) that acts by a novel mechanism.NIH grant to S. Sarafiano