215 research outputs found

    Patches in a side-by-side configuration: a description of the flow and deposition fields

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    In the last few decades, a lot of research attention has been paid to flow-vegetation interactions. Starting with the description of the flow field around uniform macrophyte stands, research has evolved more recently to the description of flow fields around individual, distinct patches. However, in the field, vegetation patches almost never occur in isolation. As such, patches will influence each other during their development and interacting, complex flow fields can be expected. In this study, two emergent patches of the same diameter (D = 22 cm) and a solid volume fraction of 10% were placed in a side-by-side configuration in a lab flume. The patches were built as an array of wooden cylinders, and the distance between the patches (gap width Delta) was varied between Delta = 0 and 14 cm. Flow measurements were performed by a 3D Vectrino Velocimeter (Nortek AS) at mid-depth of the flow. Deposition experiments of suspended solids were performed for selected gap widths. Directly behind each patch, the wake evolved in a manner identical to that of a single, isolated patch. On the centerline between the patches, the maximum velocity U-max was found to be independent of the gap width Delta. However, the length over which this maximum velocity persists, the potential core L-j, increased linearly as the gap width increased. After the merging of the wakes, the centerline velocity reaches a minimum value U-min. The minimum centerline velocity decreased in magnitude as the gap width decreased. The velocity pattern within the wake is reflected in the deposition patterns. An erosion zone occurs on the centerline between the patches, where the velocity is elevated. Deposition occurs in the low velocity zones directly behind each patch and also downstream of the patches, along the centerline between the patches at the point of local velocity minimum. This downstream deposition zone, a result of the interaction of neighbouring patch wakes, may facilitate the establishment of new vegetation, which may eventually inhibit flow between the upstream patches and facilitate patch merger

    Dynamic drag modeling of submerged aquatic vegetation canopy flows

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    Vegetation has a profound effect on flow and sediment transport processes in natural rivers, by increasing both skin friction and form drag. The increase in drag introduces a drag discontinuity between the in-canopy flow and the flow above, which leads to the development of an inflection point in the velocity profile, resembling a free shear layer. Therefore, drag acts as the primary driver for the entire canopy system. Most current numerical hydraulic models which incorporate vegetation rely either on simple, static plant forms, or canopy-scaled drag terms. However, it is suggested that these are insufficient as vegetation canopies represent complex, dynamic, porous blockages within the flow, which are subject to spatially and temporally dynamic drag forces. Here we present a dynamic drag methodology within a CFD framework. Preliminary results for a benchmark cylinder case highlight the accuracy of the method, and suggest its applicability to more complex cases

    Investigating the Mini and Giant Radio Flare Episodes of Cygnus X-3

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    The microquasar Cygnus X-3 underwent a giant radio flare in 2017 April, reaching a maximum flux of similar to 16.5 Jy at 8.5 GHz. We present results from a long monitoring campaign carried out with Medicina at 8.5, 18.6, and 24.1 GHz, parallel to the Metsahovi radio telescope at 37 GHz, from 2017 April 4 to 11. We observe a spectral steepening from alpha = 0.2 to 0.5 (with S-nu proportional to nu(-alpha)) within 6 hr of the epoch of the flare's peak maximum, and rapid changes in the spectral slope in the following days during brief enhanced emission episodes while the general trend of the radio flux density indicated the decay of the giant flare. We further study the radio orbital modulation of Cyg X-3 emission associated with the 2017 giant flare and with six mini-flares observed in 1983, 1985, 1994, 1995, 2002, and 2016. The enhanced emission episodes observed during the decline of the giant flare at 8.5 GHz coincide with the orbital phase phi similar to 0.5 (orbital inferior conjunction). On the other hand, the light curves of the mini-flares observed at 15-22 GHz peak at phi similar to 0, except for the 2016 light curve, which is shifted 0.5 w.r.t. the other ones. We attribute the apparent phase shift to the variable location of the emitting region along the bent jet. This might be explained by the different accretion states of the flaring episodes (the 2016 mini-flare occurred in the hypersoft X-ray state)

    Autoimmunity in gestational diabetes mellitus in Sardinia: a preliminary case-control report

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    <p>Abstract</p> <p>Background</p> <p>We previously reported a high prevalence (22.3%) of gestational diabetes mellitus (GDM) in a large group of Sardinian women, in contrast with the prevalence of Type 2 diabetes. Sardinia has an unusual distribution of haplotypes and genotypes, with the highest population frequency of HLA DR3 in the world, and after Finland, the highest prevalence of Type 1 diabetes and Autoimmune-related Diseases. In this study we preliminarily tested the prevalence of serological markers of Type 1 diabetes in a group of Sardinian GDM patients.</p> <p>Methods</p> <p>We determined glutamic decarboxylase antibodies (anti-GAD65), protein tyrosine phosphatase ICA 512 (IA2) antibodies (anti-IA2), and IAA in 62 GDM patients, and in 56 controls with matching age, gestational age and parity.</p> <p>Results</p> <p>We found a high prevalence and very unusual distribution of antibodies in GDM patients (38.8%), the anti-IA2 being the most frequent antibody. Out of all our GDM patients, 38.8% (24 of 62) were positive for at least one antibody. Anti-IA2 was present in 29.0 % (18 out of 62) vs. 7.1% (4 out of 56) in the controls (P < 0.001). IAA was present in 14.5% (9 out of 62) of our GDM patients, and absent in the control subjects (P < 0.001). Anti-GAD65 was also present in GDM patients, with a prevalence of 3.2% (2 out of 62) while it was absent in the control group (P = NS). Pre-gestational weight was significantly lower (57.78 Ā± 9.8 vs 65.9 Ā± 17.3 <it>P </it>= 0.04) in auto-antibodies- positive GDM patients.</p> <p>Conclusion</p> <p>These results are in contrast with the very low prevalence of all antibodies reported in Italy. If confirmed, they could indicate that a large proportion of GDM patients in Sardinia have an autoimmune origin, in accordance with the high prevalence of Type 1 diabetes.</p

    Characterization of TEM1/endosialin in human and murine brain tumors

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    <p>Abstract</p> <p>Background</p> <p><it>TEM1/endosialin </it>is an emerging microvascular marker of tumor angiogenesis. We characterized the expression pattern of <it>TEM1/endosialin </it>in astrocytic and metastatic brain tumors and investigated its role as a therapeutic target in human endothelial cells and mouse xenograft models.</p> <p>Methods</p> <p><it>In situ </it>hybridization (ISH), immunohistochemistry (IH) and immunofluorescence (IF) were used to localize <it>TEM1/endosialin </it>expression in grade II-IV astrocytomas and metastatic brain tumors on tissue microarrays. Changes in <it>TEM1/endosialin </it>expression in response to pro-angiogenic conditions were assessed in human endothelial cells grown <it>in vitro</it>. Intracranial U87MG glioblastoma (GBM) xenografts were analyzed in nude <it>TEM1/endosialin </it>knockout (KO) and wildtype (WT) mice.</p> <p>Results</p> <p><it>TEM1/endosialin </it>was upregulated in primary and metastatic human brain tumors, where it localized primarily to the tumor vasculature and a subset of tumor stromal cells. Analysis of 275 arrayed grade II-IV astrocytomas demonstrated <it>TEM1/endosialin </it>expression in 79% of tumors. Robust <it>TEM1/endosialin </it>expression occurred in 31% of glioblastomas (grade IV astroctyomas). <it>TEM1/endosialin </it>expression was inversely correlated with patient age. TEM1/endosialin showed limited co-localization with CD31, Ī±SMA and fibronectin in clinical specimens. <it>In vitro</it>, <it>TEM1/endosialin </it>was upregulated in human endothelial cells cultured in matrigel. Vascular <it>Tem1/endosialin </it>was induced in intracranial U87MG GBM xenografts grown in mice. <it>Tem1/endosialin </it>KO vs WT mice demonstrated equivalent survival and tumor growth when implanted with intracranial GBM xenografts, although <it>Tem1/endosialin </it>KO tumors were significantly more vascular than the WT counterparts.</p> <p>Conclusion</p> <p><it>TEM1/endosialin </it>was induced in the vasculature of high-grade brain tumors where its expression was inversely correlated with patient age. Although lack of <it>TEM1/endosialin </it>did not suppress growth of intracranial GBM xenografts, it did increase tumor vascularity. The cellular localization of <it>TEM1/endosialin </it>and its expression profile in primary and metastatic brain tumors support efforts to therapeutically target this protein, potentially via antibody mediated drug delivery strategies.</p

    Overexpression of c-erbB2 is a negative prognostic factor in anaplastic astrocytomas

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    The epidermal growth factor receptor (EGFR) family, consisting of four tyrosine kinase receptors, c-erbB1-4, seems to be influential in gliomagenesis. The aim of this study was to investigate EGFR gene amplification and expression of c-erbB1-4 receptor proteins in human anaplastic astrocytomas. Formalin-fixed and paraffin-embedded sections from 31 cases were investigated by standard immunohistochemical procedures for expression of c-erbB1-4 receptor proteins using commercial antibodies. EGFR gene amplification was studied by fluorescence in situ hybridization using paraffin-embedded tissues. Two monoclonal antibodies, NCL-EGFR-384 and NCL-EGFR, were used for EGFR detection and they displayed positive immunoreactivity in 97% and 71%, respectively. For c-erbB2 detection three monoclonal antibodies, CB11, 3B5, and 5A2, were applied and they displayed positive immunoreactivity in 45%, 100%, and 52%, respectively. Positive immunostaining for c-erbB3 and c-erbB4 was encountered in 97% and 74%, respectively. The EGFR gene was amplified in 9 out of 31 tumors (29%). After adjusting for age, Karnofsky performance status, and extent of surgical resection, Cox multiple regression analysis with overall survival as the dependent variable revealed that c-erbB2 overexpression detected by the monoclonal antibody clone CB11 was a statistically significant poor prognostic factor (P = 0.004). This study shows the convenience and feasibility of immunohistochemistry when determining the expression of receptor proteins in tissue sections of human astrocytomas. The synchronous overexpression of c-erbB1-4 proteins in anaplastic astrocytomas supports their role in the pathogenesis of these tumors. Further, c-erbB2 overexpression seems to predict aggressive behaviour

    Delineating the molecular and phenotypic spectrum of the SETD1B-related syndrome

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    Purpose Pathogenic variants in SETD1B have been associated with a syndromic neurodevelopmental disorder including intellectual disability, language delay, and seizures. To date, clinical features have been described for 11 patients with (likely) pathogenic SETD1B sequence variants. This study aims to further delineate the spectrum of the SETD1B-related syndrome based on characterizing an expanded patient cohort. Methods We perform an in-depth clinical characterization of a cohort of 36 unpublished individuals with SETD1B sequence variants, describing their molecular and phenotypic spectrum. Selected variants were functionally tested using in vitro and genome-wide methylation assays. Results Our data present evidence for a loss-of-function mechanism of SETD1B variants, resulting in a core clinical phenotype of global developmental delay, language delay including regression, intellectual disability, autism and other behavioral issues, and variable epilepsy phenotypes. Developmental delay appeared to precede seizure onset, suggesting SETD1B dysfunction impacts physiological neurodevelopment even in the absence of epileptic activity. Males are significantly overrepresented and more severely affected, and we speculate that sex-linked traits could affect susceptibility to penetrance and the clinical spectrum of SETD1B variants. Conclusion Insights from this extensive cohort will facilitate the counseling regarding the molecular and phenotypic landscape of newly diagnosed patients with the SETD1B-related syndrome

    Hunting for the nature of the enigmatic narrow-line Seyfert 1 galaxy PKS 2004-447

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    Narrow-line Seyfert 1 (NLS1) galaxies are a class of active galactic nuclei (AGN) that, in some cases, can harbor powerful relativistic jets. One of them, PKS 2004-447, shows gamma-ray emission, and underwent its first recorded multifrequency flare in 2019. However, past studies revealed that in radio this source can be classified as a compact steep-spectrum source (CSS), suggesting that, unlike other gamma-ray sources, the relativistic jets of PKS 2004-447 have a large inclination with respect to the line of sight. We present here a set of spectroscopic observations of this object, aimed at carefully measuring its black hole mass and Eddington ratio, determining the properties of its emission lines, and characterizing its long term variability. We find that the black hole mass is (1.5 +/- 0.2)x10(7) M-circle dot, and the Eddington ratio is 0.08. Both values are within the typical range of NLS1s. The spectra also suggest that the 2019 flare was caused mainly by the relativistic jet, while the accretion disk played a minor role during the event. In conclusion, we confirm that PKS 2004-447 is one of the rare examples of gamma-ray emitting CSS/NLS1s hybrid, and that these two classes of objects are likely connected in the framework of AGN evolution
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