83 research outputs found

    Structure and stability of 7-mercapto-4-methylcoumarin self-assembled monolayers on gold: an experimental and computational analysis

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    Self-assembled monolayers (SAM) of 7-mercapto-4-methylcoumarin (MMC) on a flat gold surface were studied by molecular dynamics (MD) simulations, reference-free grazing incidence X-ray fluorescence (GIXRF) and X-ray photoelectron spectroscopy (XPS), to determine the maximum monolayer density and to investigate the nature of the molecule/surface interface. In particular, the protonation state of the sulfur atom upon adsorption was analyzed, since some recent literature presented evidence for physisorbed thiols (preserving the S-H bond), unlike the common picture of chemisorbed thiyls (losing the hydrogen). MD with a specifically tailored force field was used to simulate either thiol or thiyl monolayers with increasing number of molecules, to determine the maximum dynamically stable densities. This result was refined by computing the monolayer chemical potential as a function of the density with the bennet acceptance ratio method, based again on MD simulations. The monolayer density was also measured with GIXRF, which provided the absolute quantification of the number of sulfur atoms in a dense self-assembled monolayer (SAM) on flat gold surfaces. The sulfur core level binding energies in the same monolayers were measured by XPS, fitting the recorded spectra with the binding energies proposed in the literature for free or adsorbed thiols and thiyls, to get insight on the nature of the molecular species present in the layer. The comparison of theoretical and experimental SAM densities, and the XPS analysis strongly support the picture of a monolayer formed by chemisorbed, dissociated thiyls

    Unveiling a Rich System of Faint Dwarf Galaxies in the Next Generation Fornax Survey

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    We report the discovery of 158 previously undetected dwarf galaxies in the Fornax cluster central regions using a deep coadded u,gu, g and ii-band image obtained with the DECam wide-field camera mounted on the 4-meter Blanco telescope at the Cerro Tololo Interamerican Observatory as part of the {\it Next Generation Fornax Survey} (NGFS). The new dwarf galaxies have quasi-exponential light profiles, effective radii 0.1 ⁣< ⁣re ⁣< ⁣2.80.1\!<\!r_e\!<\!2.8 kpc and average effective surface brightness values 22.0 ⁣< ⁣μi ⁣< ⁣28.022.0\!<\!\mu_i\!<\!28.0 mag arcsec2^{-2}. We confirm the existence of ultra-diffuse galaxies (UDGs) in the Fornax core regions that resemble counterparts recently discovered in the Virgo and Coma galaxy clusters.~We also find extremely low surface brightness NGFS dwarfs, which are several magnitudes fainter than the classical UDGs. The faintest dwarf candidate in our NGFS sample has an absolute magnitude of Mi ⁣= ⁣8.0M_i\!=\!-8.0\,mag. The nucleation fraction of the NGFS dwarf galaxy sample appears to decrease as a function of their total luminosity, reaching from a nucleation fraction of > ⁣75%>\!75\% at luminosities brighter than Mi ⁣ ⁣15.0M_i\!\simeq\!-15.0 mag to 0%0\% at luminosities fainter than Mi ⁣ ⁣10.0M_i\!\simeq\!-10.0 mag. The two-point correlation function analysis of the NGFS dwarf sample shows an excess on length scales below  ⁣100\sim\!100 kpc, pointing to the clustering of dwarf galaxies in the Fornax cluster core.Comment: 6 pages, 3 figures. Accepted for publication in The Astrophysical Journal Letters. Download the high-resolution version of the paper from the following link: https://www.dropbox.com/s/xb9vz8s29wlzjgf/ms.pdf?dl=

    New-onset myasthenia gravis after mRNA SARS-CoV-2 vaccination: a case series

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    Background Myasthenia gravis (MG) is an autoimmune disease that targets acetylcholine receptor (AChR) of the neuromuscular junction. New-onset MG after SARS-CoV-2 vaccination has rarely been reported. Case presentation We report about three patients who presented new-onset myasthenia gravis after receiving mRNA SARSCoV-2 vaccination. The patients were all males and older than 55 years. All the patients presented with ocular and bulbar symptoms. The interval between vaccine administration and MG onset ranged from 3 days after the frst dose to 10 days after the second dose. All the patients had elevated serum AChR antibodies and responded to pyridostigmine. Two out of three patients were successfully treated with IVIG or plasma exchange and with long-term immunosuppression. Conclusions MG is a rare disease; clinicians should be aware of possible new-onset MG after SARS-CoV-2 vaccination, especially with the current recommendation of booster doses. The hyperstimulation of the innate immune system or the exacerbation of a subclinical pre-existing MG could be possible explanations

    Pregnancy in patients with tuberculosis: A TBNET cross-sectional survey

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    BACKGROUND: Objectives: To determine whether the incidence of tuberculosis with pregnancy is more common than would be expected from the crude birth rate; to see whether there is significant delay in the diagnosis of tuberculosis during pregnancy. METHOD: Design: A cross-sectional survey. SETTING: 13 tuberculosis clinics within different European countries and the USA. POPULATION/SAMPLE: All patients with tuberculosis seen at these clinics for a period\u2009>\u20091 year. INSTRUMENT: Questionnaire survey based on continuous data collection. MAIN OUTCOME MEASURES: number and proportion of women with tuberculosis who were pregnant; timing of diagnosis in relation to pregnancy, including those who were pregnant or delivered in the 3 months prior to the diagnosis of TB and those who developed TB within 3 months after delivery. RESULTS: Pregnancy occurred in 224 (1.5 %) of 15,217 TB patients and followed the expected rate predicted from the crude birth rate for the clinic populations. TB was diagnosed more commonly in the 3 months after delivery (n\u2009=\u2009103) than during pregnancy (n\u2009=\u200968; \u3c7 2\u2009=\u200925.1, P\u2009<\u20090.001). CONCLUSIONS: TB is diagnosed more frequently after delivery, despite variations in local TB incidence and healthcare systems

    VEGAS: A VST Early-type GAlaxy Survey. II. Photometric study of giant ellipticals and their stellar halos

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    Observations of diffuse starlight in the outskirts of galaxies are thought to be a fundamental source of constraints on the cosmological context of galaxy assembly in the Λ\LambdaCDM model. Such observations are not trivial because of the extreme faintness of such regions. In this work, we investigate the photometric properties of six massive early type galaxies (ETGs) in the VEGAS sample (NGC 1399, NGC 3923, NGC 4365, NGC 4472, NGC 5044, and NGC 5846) out to extremely low surface brightness levels, with the goal of characterizing the global structure of their light profiles for comparison to state-of-the-art galaxy formation models. We carry out deep and detailed photometric mapping of our ETG sample taking advantage of deep imaging with VST/OmegaCAM in the g and i bands. By fitting the light profiles, and comparing the results to simulations of elliptical galaxy assembly, we identify signatures of a transition between "relaxed" and "unrelaxed" accreted components and can constrain the balance between in situ and accreted stars. The very good agreement of our results with predictions from theoretical simulations demonstrates that the full VEGAS sample of 100\sim 100 ETGs will allow us to use the distribution of diffuse light as a robust statistical probe of the hierarchical assembly of massive galaxies.Comment: Accepted for publication in Astronomy & Astrophysic

    COVID-19-associated Guillain-Barré syndrome in the early pandemic experience in Lombardia (Italy)

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    Objective To estimate the incidence and describe clinical characteristics and outcome of GBS in COVID-19 patients (COVID19-GBS) in one of the most hit regions during the frst pandemic wave, Lombardia. Methods Adult patients admitted to 20 Neurological Units between 1/3–30/4/2020 with COVID19-GBS were included as part of a multi-center study organized by the Italian society of Hospital Neuroscience (SNO). Results Thirty-eight COVID19-GBS patients had a mean age of 60.7 years and male frequency of 86.8%. CSF albuminocytological dissociation was detected in 71.4%, and PCR for SARS-CoV-2 was negative in 19 tested patients. Based on neurophysiology, 81.8% of patients had a diagnosis of AIDP, 12.1% of AMSAN, and 6.1% of AMAN. The course was favorable in 76.3% of patients, stable in 10.5%, while 13.2% worsened, of which 3 died. The estimated occurrence rate in Lombardia ranges from 0.5 to 0.05 GBS cases per 1000 COVID-19 infections depending on whether you consider positive cases or estimated seropositive cases. When we compared GBS cases with the pre-pandemic period, we found a reduction of cases from 165 to 135 cases in the 2-month study period in Lombardia. Conclusions We detected an increased incidence of GBS in COVID-19 patients which can refect a higher risk of GBS in COVID-19 patients and a reduction of GBS events during the pandemic period possibly due to a lower spread of more common respiratory infectious diseases determined by an increased use of preventive measures

    Common and rare variant association analyses in amyotrophic lateral sclerosis identify 15 risk loci with distinct genetic architectures and neuron-specific biology

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    A cross-ancestry genome-wide association meta-analysis of amyotrophic lateral sclerosis (ALS) including 29,612 patients with ALS and 122,656 controls identifies 15 risk loci with distinct genetic architectures and neuron-specific biology. Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with a lifetime risk of one in 350 people and an unmet need for disease-modifying therapies. We conducted a cross-ancestry genome-wide association study (GWAS) including 29,612 patients with ALS and 122,656 controls, which identified 15 risk loci. When combined with 8,953 individuals with whole-genome sequencing (6,538 patients, 2,415 controls) and a large cortex-derived expression quantitative trait locus (eQTL) dataset (MetaBrain), analyses revealed locus-specific genetic architectures in which we prioritized genes either through rare variants, short tandem repeats or regulatory effects. ALS-associated risk loci were shared with multiple traits within the neurodegenerative spectrum but with distinct enrichment patterns across brain regions and cell types. Of the environmental and lifestyle risk factors obtained from the literature, Mendelian randomization analyses indicated a causal role for high cholesterol levels. The combination of all ALS-associated signals reveals a role for perturbations in vesicle-mediated transport and autophagy and provides evidence for cell-autonomous disease initiation in glutamatergic neurons

    Genome-wide Analyses Identify KIF5A as a Novel ALS Gene

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    To identify novel genes associated with ALS, we undertook two lines of investigation. We carried out a genome-wide association study comparing 20,806 ALS cases and 59,804 controls. Independently, we performed a rare variant burden analysis comparing 1,138 index familial ALS cases and 19,494 controls. Through both approaches, we identified kinesin family member 5A (KIF5A) as a novel gene associated with ALS. Interestingly, mutations predominantly in the N-terminal motor domain of KIF5A are causative for two neurodegenerative diseases: hereditary spastic paraplegia (SPG10) and Charcot-Marie-Tooth type 2 (CMT2). In contrast, ALS-associated mutations are primarily located at the C-terminal cargo-binding tail domain and patients harboring loss-of-function mutations displayed an extended survival relative to typical ALS cases. Taken together, these results broaden the phenotype spectrum resulting from mutations in KIF5A and strengthen the role of cytoskeletal defects in the pathogenesis of ALS.Peer reviewe
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