We present a systematic study of the time and band-resolved scintillation in xenon-based time projection chambers (TPCs), performed simultaneously for the primary (S1) and secondary (S2) components ...in a small, purity-controlled, setup. We explore a range of conditions of general academic interest, focusing on those of relevance to contemporary TPCs: pressure range 1–10 bar, pressure-reduced electric fields of 0–100 V/cm/bar in the drift region (S1) and up to the proportional scintillation regime in the multiplication region (S2), and wavelength bands 145–250/250–400/400–600 nm, for both
α
and
β
particles. Attention is paid to the possibility of non-conventional scintillation mechanisms such as the 3rd continuum emission, recombination light from
β
-electrons at high pressure (for S1), emission from high-lying excited states and neutral bremsstrahlung (for S2). Time constants and, specially, scintillation yields have been obtained as a function of electric field and pressure, the latter aided by Geant4 simulations.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The photoreceptor phytochrome B (PHYB) and the homeodomain protein BEL5 are involved in the response of potato tuber induction to the photoperiod. However, whether they act in the same tuberization ...pathway is unknown. Here we show the effect of a microRNA, miR172 , on this developmental event. miR172 levels are higher under tuber-inducing short days than under non-inductive long days and are upregulated in stolons at the onset of tuberization. Overexpression of this microRNA in potato promotes flowering, accelerates tuberization under moderately inductive photoperiods and triggers tuber formation under long days. In plants with a reduced abundance of PHYB, which tuberize under long days, both BEL5 mRNA and miR172 levels are reduced in leaves and increased in stolons. This, together with the presence of miR172 in vascular bundles and the graft transmissibility of its effect on tuberization, indicates that either miR172 might be mobile or it regulates long-distance signals to induce tuberization. Consistent with this, plants overexpressing miR172 show increased levels of BEL5 mRNA, which has been reported to be transmissible through grafts. Furthermore, we identify an APETALA2 -like mRNA containing a miR172 binding site, which is downregulated in plants overexpressing miR172 and plants in which PHYB is silenced. Altogether, our results suggest that miR172 probably acts downstream of the tuberization repressor PHYB and upstream of the tuberization promoter BEL5 and allow us to propose a model for the control of tuberization by PHYB, miR172 and BEL5.
Clustering of magnetic nanoparticles can drastically change their collective magnetic properties, which in turn may influence their performance in technological or biomedical applications. Here, we ...investigate a commercial colloidal dispersion (FeraSpinTMR), which contains dense clusters of iron oxide cores (mean size around 9 nm according to neutron diffraction) with varying cluster size (about 18-56 nm according to small angle x-ray diffraction), and its individual size fractions (FeraSpinTMXS, S, M, L, XL, XXL). The magnetic properties of the colloids were characterized by isothermal magnetization, as well as frequency-dependent optomagnetic and AC susceptibility measurements. From these measurements we derive the underlying moment and relaxation frequency distributions, respectively. Analysis of the distributions shows that the clustering of the initially superparamagnetic cores leads to remanent magnetic moments within the large clusters. At frequencies below 105 rad s−1, the relaxation of the clusters is dominated by Brownian (rotation) relaxation. At higher frequencies, where Brownian relaxation is inhibited due to viscous friction, the clusters still show an appreciable magnetic relaxation due to internal moment relaxation within the clusters. As a result of the internal moment relaxation, the colloids with the large clusters (FS-L, XL, XXL) excel in magnetic hyperthermia experiments.
Studies on switching to tenofovir alafenamide (TAF)-based regimens raise concerns about a worse metabolic profile in people with HIV, even though most received tenofovir disoproxil fumarate (TDF) in ...their previous regimen. This study aims to evaluate changes in lipid fractions, glucose, and serum markers for hepatic steatosis (HS) after switching from a TDF- or TAF-sparing regimen to bictegravir/emtricitabine/TAF (B/F/TAF).
We performed a retrospective cohort study of people with HIV who switched to B/F/TAF from TDF- or TAF-sparing regimens between January 2019 and May 2022 with at least 6 months of follow-up. The primary endpoint was the absolute change in lipid fractions at 6 months. Secondary outcomes were changes in lipid fractions at 12 months and changes in other metabolic parameters (glucose, creatinine, and HS based on the triglyceride-to-glucose TyG ratio at 6 and 12 months). Changes were analysed using mixed linear regression models with random intercept and time as a fixed effect.
The study included 259 people with HIV (median age 55 interquartile range (IQR) 47-60 years; 80% male; 88% Caucasian; CD4+ T-cell count 675 IQR 450-880 cells/mm
; 84.3% HIV-RNA <50 copies/mL). In total, 63 patients (30%) had hypertension, 93 (44%) dyslipidaemia, 30 (14%) diabetes, and 45% obesity/overweight. Most (60%) switched from integrase inhibitor-based regimens, and 21% switched from a boosted regimen. At 6 months, significant reductions were observed in total cholesterol (-7.64 mg/dL 95% confidence interval (CI) -13.52 to -1.76; p = 0.002), triglycerides (-23.4 95% CI -42.07 to -4.65; p = 0.003), and TyG ratio (-0.14 95% CI -0.23 to -0.05; p < 0.001).
In our real-life cohort, the effect of switching TDF-/TAF-sparing regimens to triple therapy with B/F/TAF improved total cholesterol, triglycerides, and serum markers of HS at 6 months and was neutral for the remaining metabolic parameters at 12 months.
Local dwarf spheroidal galaxies (dSphs) are nearby dark-matter dominated systems, making them excellent targets for searching for gamma rays from particle dark matter interactions. If dark matter ...annihilates or decays directly into two gamma rays (or a gamma ray and a neutral particle), a monochromatic spectral line is created. At TeV energies, no other process is predicted to produce spectral lines, making this a very clean indirect dark matter search channel. With the development of event-by-event energy reconstruction, we can now search for spectral lines with the High Altitude Water Cherenkov (HAWC) Observatory. HAWC is a wide field of view survey instrument located in central Mexico that observes gamma rays from ∼ 200 GeV to ∼ 200 TeV . In this work we present results from a recent search for spectral lines from local, dark matter dominated, dwarf galaxies using 1038 days of HAWC data. We also present updated limits on several continuum channels that were reported in a previous publication. Our gamma-ray spectral line limits are the most constraining obtained so far from 20 TeV to 100 TeV.
We performed a time-resolved spectroscopic study of the VUV/UV scintillation of gaseous argon as a function of pressure and electric field, by means of a wavelength sensitive detector operated with ...different radioactive sources. Our work conveys new evidence of distinctive features of the argon light which are in contrast with the general assumption that, for particle detection purposes, the scintillation can be considered to be largely monochromatic at 128 nm (second continuum). The wavelength and time-resolved analysis of the photon emission reveal that the dominant component of the argon scintillation during the first tens of ns is in the range 160, 325 nm. This light is consistent with the third continuum emission from highly charged argon ions/molecules. This component of the scintillation is field-independent up to 25 V/cm/bar and shows a very mild dependence with pressure in the range 1, 16 bar. The dynamics of the second continuum emission is dominated by the excimer formation time, whose variation as a function of pressure has been measured. Additionally, the time and pressure-dependent features of electron-ion recombination, in the second continuum band, have been measured. This study opens new paths toward a novel particle identification technique based on the spectral information of the noble-elements scintillation light.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
ABSTRACT
We present the results of a continuum reverberation mapping study of the radio-quiet type 1 Seyfert galaxy IRAS 09149−6206. The analysis was performed using X-ray, ultraviolet (UV), and ...optical observations made with the Swift telescope between 2017 January and December. The time delays between different light curves were measured using three different algorithms: PyI2CCF, PyROA, and JAVELIN. Our results show that the time delays increase with wavelength after τ ∝ λ4/3, as predicted for a geometrically thin and optically thick accretion disc, but only after accounting for significant diffuse continuum emission from the broad-line region. However, the measured size of the accretion disc can be up to five times larger than that predicted by standard theory. To our surprise, the strong increase in soft X-ray fluxes is delayed by about 15 d compared to the optical UV fluctuations, which challenges the prediction of the lamp-post model. Our analysis of the X-ray variability reveals the presence of a non-variable spectral component at 0.3–6.0 keV along with variable excess emission at 2.0–3.0 keV, which could be partly related to relativistic reflection in the inner region of the accretion disc. IRAS 09149−6206 joins the list of objects for which the traditional lamp-post model cannot explain the observed time delays. A scenario that incorporates other geometric considerations into the lamp-post model, e.g. an extended corona along a scattering source, might be better suited to explain the observed long time delays.
CONSTANS (CO) is involved in the photoperiodic control of plant developmental processes, including flowering in several species and seasonal growth cessation and bud set in trees. It has been ...proposed that CO could also affect the day‐length regulation of tuber induction in Solanum tuberosum (potato), a plant of great agricultural relevance. To address this question, we examined the role of CO in potato. A potato CO‐like gene, StCO, was identified and found to be highly similar to a previously reported potato gene of unknown function. Potato plants overexpressing StCO tuberized later than wild‐type plants under a weakly inductive photoperiod. StCO silencing promoted tuberization under both repressive and weakly inductive photoperiods, but did not have any effect under strongly inductive short days, demonstrating that StCO represses tuberization in a photoperiod‐dependent manner. The effect of StCO on tuber induction was transmitted through grafts. In addition, StCO affected the mRNA levels of StBEL5 – a tuberization promoter, the mRNA of which moves long distances in potato plants – and StFT/StSP6A, a protein highly similar to FLOWERING LOCUS T (FT), which is a key component of systemic flowering signals in other species. We also found that StFT/StSP6A transcript levels correlate with the induction of tuber formation in wild‐type plants. These results show that StCO plays an important role in photoperiodic tuberization and, together with the recent demonstration that StFT/StSP6A promotes tuberization, indicate that the CO/FT module participates in controlling this process. Moreover, they support the notion that StCO is involved in the expression of long‐distance regulatory signals in potato, as CO does in other species.
Neutral bremsstrahlung in TPCs Amedo, P.; González-Díaz, D.; Jones, B.J.P.
Journal of instrumentation,
02/2022, Letnik:
17, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Abstract
Traditionally, it has been assumed that electroluminescence (EL) in time projection chambers was purely an excimer-based emission. This idea changed when neutral bremsstrahlung (NBrS) was ...observed first in argon and subsequently in xenon a few years ago. In this work we explore further the framework used to explain these observations, presenting results for noble gas-based mixtures, as well as mixtures including small fractions of a molecular additive (‘quencher’). Spectral content and yields are discussed in some cases of contemporary interest, together with their pressure-scalings.
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