136 research outputs found
Grenseområdene Norge-Russland. Luft- og nedbørkvalitet, april 2014-mars 2015.
Smelteverkene på russisk side av den norsk-russiske grense slipper ut store mengder svoveldioksid (SO2) og tungmetaller. Dette gir forhøyede konsentrasjoner også på norsk side. Denne rapporten inngår i kartlegging av miljøbelastningen i grenseområdene og omfatter målinger av luftkvalitet, nedbørkvalitet og meteorologi
Infection by a foliar endophyte elicits novel arabidopside-based plant defence reactions in its host, Cirsium arvense
Endophytic fungi live asymptomatically within plants. They are usually regarded as non-pathogenic or even mutualistic, but whether plants respond antagonistically to their presence remains unclear, particularly in the little-studied associations between endophytes and nong-raminoid herbaceous plants.
We investigated the effects of the endophyte Chaetomium cochlioides on leaf chemistry in Cirsium arvense. Plants were sprayed with spores; leaf material from both subsequent new growth and the sprayed leaves was analysed 2 wk later. Infection frequency was 91% and63% for sprayed and new growth, respectively, indicating that C. cochlioides rapidly infects new foliage.
Metabolomic analyses revealed marked changes in leaf chemistry with infection, especially in new growth. Changes in several novel oxylipin metabolites were detected, including arabi-dopsides reported here for the first time in a plant species other than Arabidopsis thaliana,and a jasmonate-containing galactolipid.
The production of these metabolites in response to endophyte presence, particularly in newly infected foliage, suggests that endophytes elicit similar chemical responses in plants to those usually produced following wounding, herbivory and pathogen invasion. Whether en-dophytes benefit their hosts may depend on a complex series of chemically mediated interactions between the plant, the endophyte, other microbial colonists and natural enemies
Use of sedimentary algal pigment analyses to infer past lake-water total phosphorus concentrations
AbstractWe tested the feasibility of using sedimentary algal pigment analyses by spectral deconvolution to infer past lake-water total phosphorus concentrations. We established equations that link lake-water nutrient concentrations and sediment pigment concentrations, using a combination of calibration in both space and time, with a training set of 31 Swedish lakes. The calibration dataset yielded a significant positive relationship between total carotenoid concentrations and lake-water total phosphorus concentrations. We also compared sediment-pigment-based nutrient inferences with time series of water column monitoring data to evaluate whether temporal changes in total phosphorus concentrations are well captured by analysis of sedimentary pigments. We found that changes in pigment preservation through time can alter the relationship between concentrations of lake-water nutrients and sedimentary pigments, thus limiting the reliability of historical ecological conditions inferred from pigments in the sediment. Our data suggested that ratios of Chlorophyll derivatives to total carotenoids (CD/TC ratio) and Chlorophyll a to Chlorophyll derivatives (CPI) can be used as proxies for pigment preservation. Using our approach, inferred temporal changes in water-column total phosphorus concentrations in lakes are promising, but require further development, specifically with respect to the influence of pigment degradation in both the water column and sediments, as well as the factors that control such degradation.</jats:p
Cerebellar mutism syndrome in children with brain tumours of the posterior fossa
Background: Central nervous system tumours constitute 25% of all childhood cancers; more than half are located in the posterior fossa and surgery is usually part of therapy. One of the most disabling late effects of posterior fossa tumour surgery is the cerebellar mutism syndrome (CMS) which has been reported in up to 39% of the patients but the exact incidence is uncertain since milder cases may be unrecognized. Recovery is usually incomplete. Reported risk factors are tumour type, midline location and brainstem involvement, but the exact aetiology, surgical and other risk factors, the clinical course and strategies for prevention and treatment are yet to be determined. Methods: This observational, prospective, multicentre study will include 500 children with posterior fossa tumours. It opened late 2014 with participation from 20 Nordic and Baltic centres. From 2016, five British centres and four Dutch centres will join with a total annual accrual of 130 patients. Three other major European centres are invited to join from 2016/17. Follow-up will run for 12 months after inclusion of the last patient. All patients are treated according to local practice. Clinical data are collected through standardized online registration at pre-determined time points pre- and postoperatively. Neurological status and speech functions are examined pre- operatively and postoperatively at 1-4 weeks, 2 and 12 months. Pre- and postoperative speech samples are recorded and analysed. Imaging will be reviewed centrally. Pathology is classified according to the 2007 WHO system. Germline DNA will be collected from all patients for associations between CMS characteristics and host genome variants including pathway profiles. Discussion: Through prospective and detailed collection of information on 1) differences in incidence and clinical course of CMS for different patient and tumour characteristics, 2) standardized surgical data and their association with CMS, 3) diversities and results of other therapeutic interventions, and 4) the role of host genome variants, we aim to achieve a better understanding of risk factors for and the clinical course of CMS - with the ultimate goal of defining strategies for prevention and treatment of this severely disabling condition.Peer reviewe
Refining the prediction for OJ 287 next impact flare arrival epoch
The bright blazar OJ~287 routinely parades high brightness bremsstrahlung
flares which are explained as being a result of a secondary supermassive black
hole (SMBH) impacting the accretion disk of a primary SMBH in a binary system.
We begin by showing that these flares occur at times predicted by a simple
analytical formula, based on the Kepler equation, which explains flares since
1888. The next impact flare, namely the flare number 26, is rather peculiar as
it breaks the typical pattern of two impact flares per 12 year cycle. This will
be the third bremsstrahlung flare of the current cycle that follows the already
observed 2015 and 2019 impact flares from OJ~287. Unfortunately, astrophysical
considerations make it difficult to predict the exact arrival epoch of the
flare number 26. In the second part of the paper, we describe our recent OJ~287
observations. They show that the pre-flare light curve of flare number 22,
observed in 2005, exhibits similar activity as the pre-flare light curve in
2022, preceding the expected flare number 26 in our model. We argue that the
pre-flare activity most likely arises in the primary jet whose activity is
modulated by the transit of the secondary SMBH through the accretion disk of
the primary. Observing the next impact flare of OJ~287 in October 2022 will
substantiate the theory of disk impacts in binary black hole systems.Comment: 16 pages, 2 figure
Refining the 2022 OJ 287 impact flare arrival epoch
The bright blazar OJ~287 routinely parades high brightness bremsstrahlung
flares, which are explained as being a result of a secondary supermassive black
hole (SMBH) impacting the accretion disc of a more massive primary SMBH in a
binary system. The accretion disc is not rigid but rather bends in a calculable
way due to the tidal influence of the secondary. Below we refer to this
phenomenon as a variable disc level. We begin by showing that these flares
occur at times predicted by a simple analytical formula, based on general
relativity inspired modified Kepler equation, which explains impact flares
since 1888.
The 2022 impact flare, namely flare number 26, is rather peculiar as it
breaks the typical pattern of two impact flares per 12-year cycle. This is the
third bremsstrahlung flare of the current cycle that follows the already
observed 2015 and 2019 impact flares from OJ~287.
It turns out that the arrival epoch of flare number 26 is sensitive to the
level of primary SMBH's accretion disc relative to its mean level in our model.
We incorporate these tidally induced changes in the level of the accretion disc
to infer that the thermal flare should have occurred during July-August 2022,
when it was not possible to observe it from the Earth. Thereafter, we explore
possible observational evidence for certain pre-flare activity by employing
spectral and polarimetric data from our campaigns in 2004/05 and 2021/22. We
point out theoretical and observational implications of two observed
mini-flares during January-February 2022.Comment: 29 pages, 6 figures, 1 table. arXiv admin note: text overlap with
arXiv:2209.0836
On the need of an ultramassive black hole in OJ 287
The highly variable blazar OJ~287 is commonly discussed as an example of a
binary black hole system. The 130 year long optical light curve is well
explained by a model where the central body is a massive black hole of
18.3510 solar mass that supports a thin accretion disc. The
secondary black hole of 0.1510 solar mass impacts the disc twice
during its 12 year orbit, and causes observable flares. Recently, it has been
argued that an accretion disc with a typical AGN accretion rate and above
mentioned central body mass should be at least six magnitudes brighter than
OJ~287's host galaxy and would therefore be observationally excluded. Based on
the observations of OJ~287's radio jet, detailed in Marscher and Jorstad
(2011), and up-to-date accretion disc models of Azadi et al. (2022), we show
that the V-band magnitude of the accretion disc is unlikely to exceed the host
galaxy brightness by more than one magnitude, and could well be fainter than
the host. This is because accretion power is necessary to launch the jet as
well as to create electromagnetic radiation, distributed across many
wavelengths, and not concentrated especially on the optical V-band. Further, we
note that the claimed V-band concentration of accretion power leads to serious
problems while interpreting observations of other Active Galactic Nuclei.
Therefore, we infer that the mass of the primary black hole and its accretion
rate do not need to be smaller than what is determined in the standard model
for OJ~287
miR-126 Regulates Distinct Self-Renewal Outcomes in Normal and Malignant Hematopoietic Stem Cells
SummaryTo investigate miRNA function in human acute myeloid leukemia (AML) stem cells (LSC), we generated a prognostic LSC-associated miRNA signature derived from functionally validated subpopulations of AML samples. For one signature miRNA, miR-126, high bioactivity aggregated all in vivo patient sample LSC activity into a single sorted population, tightly coupling miR-126 expression to LSC function. Through functional studies, miR-126 was found to restrain cell cycle progression, prevent differentiation, and increase self-renewal of primary LSC in vivo. Compared with prior results showing miR-126 regulation of normal hematopoietic stem cell (HSC) cycling, these functional stem effects are opposite between LSC and HSC. Combined transcriptome and proteome analysis demonstrates that miR-126 targets the PI3K/AKT/MTOR signaling pathway, preserving LSC quiescence and promoting chemotherapy resistance
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