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Encéfalo , Imagen por Resonancia Magnética , Humanos , Encéfalo/diagnóstico por imagen , Encéfalo/metabolismo , Encéfalo/patología , Hierro/metabolismo , Proteínas Mitocondriales/metabolismo , Enfermedades Neurodegenerativas/diagnóstico por imagen , Enfermedades Neurodegenerativas/metabolismo , Masculino , Distrofias Neuroaxonales , Trastornos del Metabolismo del HierroRESUMEN
BACKGROUND: Data on the prevalence of non-communicable diseases (NCDs) in TB household contacts (HHCs) are limited, yet important to inform integrated screening and care for NCD within contact investigations. It is also unclear if screening these contacts reveals more people with NCDs than individuals in the same neighbourhood. METHOD: We conducted a pilot cross-sectional study in South Africa and Tanzania, enrolling adult HHCs of TB and individuals in neighbourhood households (controls). We inquired about known NCD and systematically measured blood pressure, and tested for spot blood glucose and haemoglobin A1c. RESULTS: We enrolled 203 adult contacts of 111 persons with TB and 160 controls. Among contacts, respectively 12.2% (95% CI 8.3-17.6) and 39.7% (95% CI 33.1-46.7) had diabetes and hypertension, compared to 14.1% (95% CI 9.2-21.0) and 44.7% (95% CI 36.9-52.7) among controls. More than half of NCDs were newly identified. We did not find a significant difference in the prevalence of at least one NCD between the two groups (OR 0.85, 95% CI 0.50-1.45, adjusted for age and sex). CONCLUSIONS: We found a high prevalence of undiagnosed NCDs among contacts, suggesting a potential benefit of integrating NCD screening and care within contact investigations. Screening in the same community might similarly find undiagnosed NCDs.
CONTEXTE: Les données sur la prévalence des maladies non transmissibles (NCD, pour l'anglais « non-communicable diseases ¼) chez les contacts familiaux (HHC, pour l'anglais « household contacts ¼) de personnes atteintes de TB sont restreintes, mais elles revêtent une grande importance pour le dépistage et la prise en charge intégrée des NCD dans le cadre des enquêtes sur les contacts. De plus, on ignore si le dépistage de ces contacts permet de détecter davantage de personnes atteintes de NCD par rapport aux les individus résidant dans le même quartier. MÉTHODE: Nous avons réalisé une étude pilote transversale en Afrique du Sud et en Tanzanie, au cours de laquelle nous avons recruté des adultes HHC de personnes atteintes de TB et des individus vivant dans les ménages voisins (témoins). Nous les avons interrogés sur les NCD connues et avons systématiquement mesuré la pression artérielle, ainsi que réalisé des tests de de glycémie et d'hémoglobine glyquée. RÉSULTATS: Un total de 203 contacts adultes de 111 personnes atteintes de TB et 160 témoins ont été répertoriés. Parmi ces contacts, respectivement 12,2% (IC à 95% 8,317,6) et 39,7% (IC à 95% 33,146,7) souffraient de diabète et d'hypertension, contre 14,1% (IC à 95% 9,221,0) et 44,7% (IC à 95% 36,952,7) chez les témoins. Plus de la moitié des NCD ont été récemment découvertes. Aucune disparité significative n'a été observée dans la prévalence d'au moins une NCD entre les deux groupes (OR 0,85 ; 95% CI 0,501,45, ajusté pour l'âge et le sexe). CONCLUSIONS: Nous avons observé une fréquence élevée de NCDs non diagnostiquées parmi les contacts, ce qui indique qu'il pourrait être potentiellement bénéfique d'inclure le dépistage et les soins des NCD dans les enquêtes sur les contacts. Le dépistage au sein de la même communauté pourrait également révéler des NCD non diagnostiquées.
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BACKGROUND: Hepatocellular carcinoma (HCC) is a unique cancer allowing tumor diagnosis with identification of definitive patterns of enhancement on contrast-enhanced imaging, avoiding invasive biopsy. However, it is still unclear to what extent Contrast-Enhanced Ultrasound (CEUS) is a clinically useful additional step when Computed tomography (CT) or Magnetic resonance imaging (MRI) are inconclusive. METHODS: A prospective international multicenter validation study for CEUS Liver Imaging Reporting and Data System (LI-RADS) was conducted between January 2018 and August 2021. 646 patients at risk for HCC with focal liver lesions were enrolled. CEUS was performed using an intravenous ultrasound contrast agent within 4 weeks of CT/MRI. Liver nodules were categorized based on LI-RADS (LR) criteria. Histology or one-year follow-up CT/MRI imaging results were used as the reference standard. The diagnostic performance of CEUS was evaluated for inconclusive CT/MRI scan in two scenarios for which the AASLD recommends repeat imaging or imaging follow-up: observations deemed non-characterizable (LR-NC) or with indeterminate probability of malignancy (LR-3). RESULTS: 75 observations on CT or MRI were categorized as LR-3 (n = 54) or LR-NC (n = 21) CEUS recategorization of such observations into a different LR category (namely, into one among LR-1, LR-2, LR-5, LR-M, or LR-TIV) resulted in management recommendation changes in 33.3% (25/75) and in all but one (96.0%, 24/25) observation, the new management recommendations were correct. CONCLUSION: CEUS LI-RADS resulted in management recommendations change in substantial number of liver observations with initial indeterminate CT/MRI characterization, identifying both non-malignant lesions and HCC, potentially accelerating the diagnostic process and alleviating the need for biopsy or follow-up imaging. CLINICALTRIALS: gov number, NCT03318380.
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Carcinoma Hepatocelular , Medios de Contraste , Neoplasias Hepáticas , Imagen por Resonancia Magnética , Tomografía Computarizada por Rayos X , Ultrasonografía , Humanos , Neoplasias Hepáticas/diagnóstico por imagen , Carcinoma Hepatocelular/diagnóstico por imagen , Masculino , Imagen por Resonancia Magnética/métodos , Femenino , Tomografía Computarizada por Rayos X/métodos , Estudios Prospectivos , Ultrasonografía/métodos , Persona de Mediana Edad , Anciano , Adulto , Anciano de 80 o más AñosRESUMEN
Plasmon polaritons, or plasmons, are coupled oscillations of electrons and electromagnetic fields that can confine the latter into deeply subwavelength scales, enabling novel polaritonic devices. While plasmons have been extensively studied in normal metals or semimetals, they remain largely unexplored in correlated materials. In this paper, we report infrared (IR) nano-imaging of thin flakes of CsV3Sb5, a prototypical layered Kagome metal. We observe propagating plasmon waves in real-space with wavelengths tunable by the flake thickness. From their frequency-momentum dispersion, we infer the out-of-plane dielectric function ϵ c that is generally difficult to obtain in conventional far-field optics, and elucidate signatures of electronic correlations when compared to density functional theory (DFT). We propose correlation effects might have switched the real part of ϵ c from negative to positive values over a wide range of middle-IR frequencies, transforming the surface plasmons into hyperbolic bulk plasmons, and have dramatically suppressed their dissipation.
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INTRODUCTION: Children with underlying comorbidities and infants are most severely affected by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection, including in low- and middle-income countries with a high prevalence of HIV and TB. We describe the clinical presentation of SARS-CoV-2 infection in children during the Omicron wave, in Cape Town, South Africa. METHODS: We analysed routine care data from a prospective cohort of children aged 0-13 years, with a positive SARS-CoV-2 real-time reverse-transcription polymerase chain reaction (rRT-PCR) or SARS-CoV-2 antigen test, admitted to Tygerberg Hospital between 1 November 2021 until 1 March 2022. Risk factors for severity of disease were assessed. RESULTS: Ninety-five children tested positive for SARS-CoV-2, of whom 87 (91.6%) were symptomatic. Clinical data were available for 86 children. The median age was 11 months (IQR 3.0-60.0), 37 (43.0%) were females, 21 (24.7%) were HIV-exposed and 7 (8.1%) were living with HIV (CLHIV). In total, 44 (51.2%) children had at least one underlying comorbidity. TB co-infection was seen in 11 children, 6 children were newly diagnosed and 5 children were already on TB treatment at the time of admission. CONCLUSION: There was no evidence of more severe disease in children living with HIV or TB.
INTRODUCTION: Les enfants et les nourrissons présentant des comorbidités sous-jacentes sont les plus gravement touchés par l'infection par le coronavirus-2 du syndrome respiratoire aigu sévère (SARS-CoV-2), y compris dans les pays à revenu faible ou intermédiaire où la prévalence du VIH et de la TB est élevée. Nous décrivons la présentation clinique de l'infection par le SARS-CoV-2 chez les enfants pendant la vague Omicron, au Cap, en Afrique du Sud. MÉTHODES: Nous avons analysé les données de soins de routine d'une cohorte prospective d'enfants âgés de 0 à 13 ans, avec un test positif de réaction en chaîne de la polymérase de transcription inverse en temps réel (rRT-PCR) ou d'antigène du SARS-CoV-2, admis à l'hôpital Tygerberg entre le 1er novembre 2021 et le 1er mars 2022. Les facteurs de risque de gravité de la maladie ont été évalués. RÉSULTATS: Quatre-vingt-quinze enfants ont été testés positifs au SARS-CoV-2, dont 87 (91,6%) étaient symptomatiques. Des données cliniques étaient disponibles pour 86 enfants. L'âge médian était de 11 mois (IQR 3,060,0), 37 (43,0%) étaient des filles, 21 (24,7%) étaient exposés au VIH et 7 (8,1%) vivaient avec le VIH (CLHIV). Au total, 44 (51,2%) enfants présentaient au moins une comorbidité sous-jacente. La co-infection par la TB a été observée chez 11 enfants, 6 enfants ont été nouvellement diagnostiqués et 5 enfants étaient déjà sous traitement antituberculeux au moment de l'admission. CONCLUSION: Il n'y a pas de preuve d'une maladie plus grave chez les enfants vivant avec le VIH ou la TB.
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Additive manufacturing is a technique that allows the construction of prototypes and has evolved a lot in the last 20 years, innovating industrial fabrication processes in several areas. In chemistry, additive manufacturing has been used in several functionalities, such as microfluidic analytical devices, energy storage devices, and electrochemical sensors. Theophylline and paracetamol are important pharmaceutical drugs where overdosing can cause adverse effects, such as tachycardia, seizures, and even renal failure. Therefore, this paper aims at the development of miniaturized electrochemical sensors using 3D printing and polylactic acid-based conductive carbon black commercial filament for theophylline and paracetamol detection. Electrochemical characterizations of the proposed sensor were performed to prove the functionality of the device. Morphological characterizations were carried out, in which chemical treatment could change the surface structure, causing the improvement of the analytical signal. Thus, the detection of theophylline at a linear range of 5.00-150 µmol L-1 with a limit of detection of 1.2 µmol L-1 was attained, and the detection of paracetamol at a linear range of 1.00-200 µmol L-1 with a limit of detection of 0.370 µmol L-1 was obtained, demonstrating the proposed sensor effectively detected pharmaceutical drugs.
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Acetaminofén , Técnicas Electroquímicas , Poliésteres , Hollín , Teofilina , Acetaminofén/análisis , Hollín/química , Técnicas Electroquímicas/métodos , Teofilina/análisis , Poliésteres/química , Límite de Detección , Impresión Tridimensional , MiniaturizaciónRESUMEN
The protection of Earth's stratospheric ozone (O3) is an ongoing process under the auspices of the universally ratified Montreal Protocol and its Amendments and adjustments. A critical part of this process is the assessment of the environmental issues related to changes in O3. The United Nations Environment Programme's Environmental Effects Assessment Panel provides annual scientific evaluations of some of the key issues arising in the recent collective knowledge base. This current update includes a comprehensive assessment of the incidence rates of skin cancer, cataract and other skin and eye diseases observed worldwide; the effects of UV radiation on tropospheric oxidants, and air and water quality; trends in breakdown products of fluorinated chemicals and recent information of their toxicity; and recent technological innovations of building materials for greater resistance to UV radiation. These issues span a wide range of topics, including both harmful and beneficial effects of exposure to UV radiation, and complex interactions with climate change. While the Montreal Protocol has succeeded in preventing large reductions in stratospheric O3, future changes may occur due to a number of natural and anthropogenic factors. Thus, frequent assessments of potential environmental impacts are essential to ensure that policies remain based on the best available scientific knowledge.
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Ozono Estratosférico , Rayos Ultravioleta , Humanos , Ozono Estratosférico/análisis , Rayos Ultravioleta/efectos adversos , Ozono/química , Cambio ClimáticoRESUMEN
Fibroblastic reticular cells (FRCs) are stromal cells (SCs) that can be isolated from lymph node (LN) biopsies. Studies have shown that these nonhematopoietic cells have the capacity to shape and regulate adaptive immunity and can become a form of personalized cell therapy. Successful translational efforts, however, require the cells to be formulated as injectable units, with their native architecture preserved. The intrinsic reticular organization of FRCs, however, is lost in the monolayer cultures. Organizing FRCs into three-dimensional (3D) clusters would recapitulate their structural and functional attributes. Herein, we report a scaffolding method based on the self-assembling peptide (SAP) EAKII biotinylated at the N-terminus (EAKbt). Cross-linking with avidin transformed the EAKbt fibrils into a dense network of coacervates. The combined forces of fibrillization and bioaffinity interactions in the cross-linked EAKbt likely drove the cells into a cohesive 3D reticula. This facile method of generating clustered FRCs (clFRCs) can be completed within 10 days. In vitro clFRCs attracted the infiltration of T cells and rendered an immunosuppressive milieu in the cocultures. These results demonstrate the potential of clFRCs as a method for stromal cell delivery.
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Materiales Biocompatibles , Fibroblastos , Humanos , Fibroblastos/citología , Materiales Biocompatibles/química , Ensayo de Materiales , Tamaño de la Partícula , Células Cultivadas , Células del Estroma/citología , Células del Estroma/metabolismo , Péptidos/químicaAsunto(s)
Implantación de Pene , Humanos , Masculino , Implantación de Pene/efectos adversos , Implantación de Pene/métodos , Complicaciones Posoperatorias/prevención & control , Complicaciones Posoperatorias/etiología , Pene/irrigación sanguínea , Pene/cirugía , Pene/lesiones , Disfunción Eréctil/etiología , Prótesis de PeneRESUMEN
Antimony (Sb) is an poorly understood, increasingly common pollutant, especially in soils susceptible to waterlogging. We investigated the impact of waterlogging on Sb release, methylation, and volatilization from an organic-rich wetland soil and an iron (Fe)-rich floodplain soil in a 27-day microcosm experiment. The release of Sb into the porewaters of the organic-rich soil was environmentally relevant and immediate with waterlogging (3.2 to 3.5 mg L-1), and likely associated with a complex interplay of sulfide precipitation, sorption with organic matter and manganese (Mn) (oxyhydr)oxides in the soil. The release of Sb from the Fe-rich soil was likely associated with Fe-(oxyhydr)oxide reduction and immobilized due to co-precipitation with Fe-sulfides or as Sb-sulfides. Volatile Sb was produced from the soils after waterlogging. The organic-rich soil produced more volatile Sb (409 to 835 ng kgsoil-1), but the Fe-rich soil volatilized Sb more efficiently. The negligible association of Sb volatilization with soil parameters indicates a more complex underlying, potentially microbial, mechanism and that antimony volatilization could be ubiquitous and not dependent on specific soil properties. Future works should investigate the microbial and physiochemical drivers of Sb volatilization in soils as it may be an environmentally relevant part of the biogeochemical cycle.
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A critical measure of the quality of pharmaceutical proteins is the preservation of native conformations of the active pharmaceutical ingredients. Denaturation of the active proteins in any step before administration into patients could lead to loss of potency and/or aggregation, which is associated with an increased risk of immunogenicity of the products. Interfacial stress enhances protein instability as their adsorption to the air-liquid and liquid-solid interfaces are implicated in the formation of denatured proteins and aggregates. While excipients in protein formulations have been employed to reduce the risk of aggregation, the roles of albumin as a stabilizer have not been reviewed from practical and theoretical standpoints. The amphiphilic nature of albumin makes it accumulate at the interfaces. In this review, we aim to bridge the knowledge gap between interfacial instability and the influence of albumin as a surface-active excipient in the context of reducing the immunogenicity risk of protein formulations.
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Visual detection is a fundamental natural task. Detection becomes more challenging as the similarity between the target and the background in which it is embedded increases, a phenomenon termed 'similarity masking'. To test the hypothesis that V1 contributes to similarity masking, we used voltage sensitive dye imaging (VSDI) to measure V1 population responses while macaque monkeys performed a detection task under varying levels of target-background similarity. Paradoxically, we find that during an initial transient phase, V1 responses to the target are enhanced, rather than suppressed, by target-background similarity. This effect reverses in the second phase of the response, so that in this phase V1 signals are positively correlated with the behavioral effect of similarity. Finally, we show that a simple model with delayed divisive normalization can qualitatively account for our findings. Overall, our results support the hypothesis that a nonlinear gain control mechanism in V1 contributes to perceptual similarity masking.
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Macaca , Primates , Animales , Enmascaramiento Perceptual , Imagen de Colorante Sensible al VoltajeRESUMEN
Subunit vaccines are an important platform for controlling current and emerging infectious diseases. The lymph nodes are the primary site generating the humoral response and delivery of antigens to these sites is critical to effective immunization. Indeed, the duration of antigen exposure within the lymph node is correlated with the antibody response. While current licensed vaccines are typically given through the intramuscular route, injecting vaccines subcutaneously allows for direct access to lymphatic vessels and therefore can enhance the transfer of antigen to the lymph nodes. However, protein subunit antigen uptake into the lymph nodes is inefficient, and subunit vaccines require adjuvants to stimulate the initial immune response. Therefore, formulation strategies have been developed to enhance the exposure of subunit proteins and adjuvants to the lymph nodes by increasing lymphatic uptake or prolonging the retention at the injection site. Given that lymph node exposure is a crucial consideration in vaccine design, in depth analyses of the pharmacokinetics of antigens and adjuvants should be the focus of future preclinical and clinical studies. This review will provide an overview of formulation strategies for targeting the lymphatics and prolonging antigen exposure and will discuss pharmacokinetic evaluations which can be applied toward vaccine development.
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Vasos Linfáticos , Vasos Linfáticos/metabolismo , Antígenos , Vacunas de Subunidad , Vacunación , Ganglios Linfáticos , Adyuvantes Inmunológicos/metabolismo , Desarrollo de VacunasRESUMEN
Chronic wasting disease (CWD) is a highly contagious, fatal neurodegenerative disease caused by infectious prions (PrPCWD) affecting wild and captive cervids. Although experimental feeding studies have demonstrated prions in feces of crows (Corvus brachyrhynchos), coyotes (Canis latrans), and cougars (Puma concolor), the role of scavengers and predators in CWD epidemiology remains poorly understood. Here we applied the real-time quaking-induced conversion (RT-QuIC) assay to detect PrPCWD in feces from cervid consumers, to advance surveillance approaches, which could be used to improve disease research and adaptive management of CWD. We assessed recovery and detection of PrPCWD by experimental spiking of PrPCWD into carnivore feces from 9 species sourced from CWD-free populations or captive facilities. We then applied this technique to detect PrPCWD from feces of predators and scavengers in free-ranging populations. Our results demonstrate that spiked PrPCWD is detectable from feces of free-ranging mammalian and avian carnivores using RT-QuIC. Results show that PrPCWD acquired in natural settings is detectable in feces from free-ranging carnivores, and that PrPCWD rates of detection in carnivore feces reflect relative prevalence estimates observed in the corresponding cervid populations. This study adapts an important diagnostic tool for CWD, allowing investigation of the epidemiology of CWD at the community-level.
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Coyotes , Ciervos , Enfermedades Neurodegenerativas , Priones , Enfermedad Debilitante Crónica , Animales , Heces , Enfermedad Debilitante Crónica/diagnóstico , Enfermedad Debilitante Crónica/epidemiologíaRESUMEN
MVA-BN is an orthopoxvirus vaccine that provides protection against both smallpox and mpox. In June 2022, Canada launched a publicly-funded vaccination campaign to offer MVA-BN to at-risk populations including men who have sex with men (MSM) and sex workers. The safety of MVA-BN has not been assessed in this context. To address this, the Canadian National Vaccine Safety Network (CANVAS) conducted prospective safety surveillance during public health vaccination campaigns in Toronto, Ontario and in Vancouver, British Columbia. Vaccinated participants received a survey 7 and 30 days after each MVA-BN dose to elicit adverse health events. Unvaccinated individuals from a concurrent vaccine safety project evaluating COVID-19 vaccine safety were used as controls. Vaccinated and unvaccinated participants that reported a medically attended visit on their 7-day survey were interviewed. Vaccinated participants and unvaccinated controls were matched 1:1 based on age group, gender, sex and provincial study site. Overall, 1,173 vaccinated participants completed a 7-day survey, of whom 75 % (n = 878) also completed a 30-day survey. Mild to moderate injection site pain was reported by 60 % of vaccinated participants. Among vaccinated participants 8.4 % were HIV positive and when compared to HIV negative vaccinated individuals, local injection sites were less frequent in those with HIV (48 % vs 61 %, p = 0.021), but health events preventing work/school or requiring medical assessment were more frequent (7.1 % vs 3.1 %, p = 0.040). Health events interfering with work/school, or requiring medical assessment were less common in the vaccinated group than controls (3.3 % vs. 7.1 %, p < 0.010). No participants were hospitalized within 7 or 30 days of vaccination. No cases of severe neurological disease, skin disease, or myocarditis were identified. Our results demonstrate that the MVA-BN vaccine appears safe when used for mpox prevention, with a low frequency of severe adverse events and no hospitalizations observed.
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Infecciones por VIH , Mpox , Minorías Sexuales y de Género , Vacuna contra Viruela , Humanos , Masculino , Colombia Británica , Homosexualidad Masculina , Inmunización , Estudios Prospectivos , Factores de Riesgo , Vacuna contra Viruela/efectos adversos , Vacunación/efectos adversos , Vacunas AtenuadasRESUMEN
Rett syndrome (RTT) is the rare neurodevelopmental disorder caused by mutations in methyl CpG binding protein 2 (MECP2) gene with a prevalence of 1:10,000 worldwide. The hallmark clinical features of RTT are developmental delay, microcephaly, repetitive behaviours, gait abnormalities, respiratory abnormalities and seizures. Still, the understanding on the diagnosis of RTT among clinicians are less. The aim of our work was to study various clinical manifestations and a spectrum of MECP2 genetic heterogeneity in RTT patients from South Indian population. We screened 208 autistic patients and diagnosed 20 RTT patients, who were further divided into classical RTT (group I; N = 11) and variant RTT (group II; N = 9). The clinical severity of RTT was measured using RSSS, RSBQ, SSI, SSS and RTT gross motor scale. The biochemical analysis showed that thyroid-stimulating hormone (TSH), plasma dopamine and cholesterol levels were higher in group I when compared to group II, whereas the level of blood pressure, calcium, ferritin and high-density lipoprotein levels were significantly decreased in both RTT groups, when compared to the control group. The genetic mutational spectrum of MECP2 mutations were found in 12/20 of RTT patients, which revealed the occurrence of 60% pathogenic mutation and 20% unknown mutation and it was correlated with the clinical finding of respiratory dysfunction, scoliosis and sleeping problems. The significant results of this study provided clinical and genetic aspects of RTT diagnosis and proposed the clinicians to screen abnormal cholesterol, calcium and TSH levels tailed with MECP2 gene mutations for early prognosis of disease severity.
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Progresión de la Enfermedad , Proteína 2 de Unión a Metil-CpG , Mutación , Síndrome de Rett , Humanos , Síndrome de Rett/genética , Femenino , India/epidemiología , Proteína 2 de Unión a Metil-CpG/genética , Niño , Mutación/genética , Preescolar , Inestabilidad Genómica/genética , Adolescente , Masculino , Adulto , Adulto JovenRESUMEN
ABSTRACT Spodoptera cosmioides (Walker, 1858) is an economically relevant polyphagous moth, widely distributed in the Neotropics and part of the Spodoptera latifascia (Walker, 1856) species group. In this study, we used extensive sampling from different regions to describe the spatial distribution of S. cosmioides in Brazil and evaluate its variability both from morphological and molecular perspectives. Variable coloration and several morphological similarities were found among S. cosmioides and congeners of the S. latifascia complex, diverging from each 0.5 to 3.5% of mitochondrial DNA. The genetic divergence at the species level of S. cosmioides was 0.5% throughout Brazil, and a geographic structure was absent, including shared haplotypes with S. descoinsi Lalanne-Cassou & Silvain, 1994. Spodoptera cosmioides was found in all six biomes of Brazil, with the highest abundance recorded in the Cerrado, followed by the Amazon, Atlantic Rainforest, Caatinga, Pantanal, and Pampa.
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When detecting targets under natural conditions, the visual system almost always faces multiple, simultaneous, dimensions of extrinsic uncertainty. This study focused on the simultaneous uncertainty about target amplitude and background contrast. These dimensions have a large effect on detection and vary greatly in natural scenes. We measured the human performance for detecting a sine-wave target in white noise and natural-scene backgrounds for two levels of prior probability of the target being present. We derived and tested the ideal observer for white-noise backgrounds, a special case of a template-matching observer that dynamically moves its criterion with the background contrast (the DTM observer) and two simpler models with a fixed criterion: the template-matching (TM) observer and the normalized template-matching (NTM) observer that normalizes template response by background contrast. Simulations show that, when the target prior is low, the performance of the NTM observer is near optimal and the TM observer is near chance, suggesting that manipulating the target prior is valuable for distinguishing among models. Surprisingly, we found that the NTM and DTM observers better explain human performance than the TM observer for both target priors in both background types. We argue that the visual system most likely exploits contrast normalization, rather than dynamic criterion adjustment, to deal with simultaneous background contrast and target amplitude uncertainty. Finally, our findings show that the data collected under high levels of uncertainty have a rich structure capable of discriminating between models, providing an alternative approach for studying high dimensions of uncertainty.
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Incertidumbre , Humanos , ProbabilidadRESUMEN
A number of recent studies have been directed at measuring and modeling detection of targets at specific locations in natural backgrounds, a key subtask of visual search in natural environments. A useful approach is to bin natural background patches into joint histograms with bins along specific background dimensions. By measuring psychometric functions in a sparse subset of these bins, it is possible to estimate how the included dimensions jointly affect detectability over the whole space of natural backgrounds. In previous studies, we found that threshold is proportional to the product of the background luminance, contrast, and similarity; a result predicted by a simple template-matching observer with divisive normalization along each of the dimensions. The measure of similarity was the cosine similarity of the amplitude spectra of the target and background (SA)-a phase-invariant measure. Here, we investigated the effect of the cosine similarity of the target and background images (SI|A)-a phase-dependent measure. We found that threshold decreases monotonically with SI|A in agreement with a recent study (Rideaux et al., 2022). In contrast, the template-matching observer predicts threshold to be a U-shaped function of SI|A reaching a minimum when the target and background are orthogonal (SI|A = 0). Surprisingly, when the template-matching observer includes a small amount of intrinsic position uncertainty (measured in a separate experiment) the pattern of thresholds is explained.