252 research outputs found
O1 Serogroup Cholera Vibrios Isolated from the Rostov-on-Don Water Bodies in the Course of Surveillance in 2008–2012
Identified are the peculiarities of biological properties and origin of cholera vibrio O1 serogroup strains isolated from the Rostov-on-Don water bodies in the course of surveillance in 2008–2012. 41 atoxigenic V. cholerae O1 strains have been isolated from 767 water samples and investigated. Stable tendency of isolation of increased numbers of atoxigenic V. cholerae O1 strains over time has been demonstrated. In addition, in the strains under study detected have been the genes of additional pathogenicity factors, by PCR genotyping using specific primers for 45 nucleotide sequences associated with V. cholerae pathogenicity. The strains have also been classified according to 19 VNTR-genotypes grouped into 6 clusters based on VNTR-typing using exclusive copyright locus-specific primers. Discovered have been the strains with similar genotypes though isolated at different points both throughout the year and over the period of several years. These ones have probably been imported. They are characterized by a capacity to persist in ambient water bodies for a certain period of time
Improved functionalization of oleic acid-coated iron oxide nanoparticles for biomedical applications
Superparamagnetic iron oxide nanoparticles
can providemultiple benefits for biomedical applications
in aqueous environments such asmagnetic separation or
magnetic resonance imaging. To increase the colloidal
stability and allow subsequent reactions, the introduction
of hydrophilic functional groups onto the particles’
surface is essential. During this process, the original
coating is exchanged by preferably covalently bonded
ligands such as trialkoxysilanes. The duration of the
silane exchange reaction, which commonly takes more
than 24 h, is an important drawback for this approach. In
this paper, we present a novel method, which introduces
ultrasonication as an energy source to dramatically
accelerate this process, resulting in high-quality waterdispersible nanoparticles around 10 nmin size. To prove
the generic character, different functional groups were
introduced on the surface including polyethylene glycol
chains, carboxylic acid, amine, and thiol groups. Their
colloidal stability in various aqueous buffer solutions as
well as human plasma and serum was investigated to
allow implementation in biomedical and sensing
applications.status: publishe
Directionality of nuclear recoils in a liquid argon time projection chamber
The direct search for dark matter in the form of weakly interacting massive
particles (WIMP) is performed by detecting nuclear recoils (NR) produced in a
target material from the WIMP elastic scattering. A promising experimental
strategy for direct dark matter search employs argon dual-phase time projection
chambers (TPC). One of the advantages of the TPC is the capability to detect
both the scintillation and charge signals produced by NRs. Furthermore, the
existence of a drift electric field in the TPC breaks the rotational symmetry:
the angle between the drift field and the momentum of the recoiling nucleus can
potentially affect the charge recombination probability in liquid argon and
then the relative balance between the two signal channels. This fact could make
the detector sensitive to the directionality of the WIMP-induced signal,
enabling unmistakable annual and daily modulation signatures for future
searches aiming for discovery. The Recoil Directionality (ReD) experiment was
designed to probe for such directional sensitivity. The TPC of ReD was
irradiated with neutrons at the INFN Laboratori Nazionali del Sud, and data
were taken with 72 keV NRs of known recoil directions. The direction-dependent
liquid argon charge recombination model by Cataudella et al. was adopted and a
likelihood statistical analysis was performed, which gave no indications of
significant dependence of the detector response to the recoil direction. The
aspect ratio R of the initial ionization cloud is estimated to be 1.037 +/-
0.027 and the upper limit is R < 1.072 with 90% confidence levelComment: 20 pages, 10 figures, submitted to Eur. Phys. J.
Study on cosmogenic activation above ground for the DarkSide-20k project
The activation of materials due to the exposure to cosmic rays may become an
important background source for experiments investigating rare event phenomena.
DarkSide-20k is a direct detection experiment for galactic dark matter
particles, using a two-phase liquid argon time projection chamber filled with
49.7 tonnes (active mass) of Underground Argon (UAr) depleted in 39Ar. Here,
the cosmogenic activity of relevant long-lived radioisotopes induced in the
argon and other massive components of the set-up has been estimated; production
of 120 t of radiopure UAr is foreseen. The expected exposure above ground and
production rates, either measured or calculated, have been considered. From the
simulated counting rates in the detector due to cosmogenic isotopes, it is
concluded that activation in copper and stainless steel is not problematic.
Activation of titanium, considered in early designs but not used in the final
design, is discussed. The activity of 39Ar induced during extraction,
purification and transport on surface, in baseline conditions, is evaluated to
be 2.8% of the activity measured in UAr from the same source, and thus
considered acceptable. Other products in the UAr such as 37Ar and 3H are shown
to not be relevant due to short half-life and assumed purification methods
Measurement of isotopic separation of argon with the prototype of the cryogenic distillation plant Aria for dark matter searches
The Aria cryogenic distillation plant, located in Sardinia, Italy, is a key component of the DarkSide-20k experimental program for WIMP dark matter searches at the INFN Laboratori Nazionali del Gran Sasso, Italy. Aria is designed to purify the argon, extracted from underground wells in Colorado, USA, and used as the DarkSide-20k target material, to detector-grade quality. In this paper, we report the first measurement of argon isotopic separation by distillation with the 26 m tall Aria prototype. We discuss the measurement of the operating parameters of the column and the observation of the simultaneous separation of the three stable argon isotopes: 36Ar , 38Ar , and 40Ar . We also provide a detailed comparison of the experimental results with commercial process simulation software. This measurement of isotopic separation of argon is a significant achievement for the project, building on the success of the initial demonstration of isotopic separation of nitrogen using the same equipment in 2019
Sensitivity projections for a dual-phase argon TPC optimized for light dark matter searches through the ionization channel
Dark matter lighter than 10 GeV/c encompasses a promising range of
candidates. A conceptual design for a new detector, DarkSide-LowMass, is
presented, based on the DarkSide-50 detector and progress toward DarkSide-20k,
optimized for a low-threshold electron-counting measurement. Sensitivity to
light dark matter is explored for various potential energy thresholds and
background rates. These studies show that DarkSide-LowMass can achieve
sensitivity to light dark matter down to the solar neutrino floor for GeV-scale
masses and significant sensitivity down to 10 MeV/c considering the Migdal
effect or interactions with electrons. Requirements for optimizing the
detector's sensitivity are explored, as are potential sensitivity gains from
modeling and mitigating spurious electron backgrounds that may dominate the
signal at the lowest energies
Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET
The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR
Relationship of edge localized mode burst times with divertor flux loop signal phase in JET
A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM
RNA localization in neurite morphogenesis and synaptic regulation: current evidence and novel approaches
It is now generally accepted that RNA localization in the central nervous system conveys important roles both during development and in the adult brain. Of special interest is protein synthesis located at the synapse, as this potentially confers selective synaptic modification and has been implicated in the establishment of memories. However, the underlying molecular events are largely unknown. In this review, we will first discuss novel findings that highlight the role of RNA localization in neurons. We will focus on the role of RNA localization in neurotrophin signaling, axon outgrowth, dendrite and dendritic spine morphogenesis as well as in synaptic plasticity. Second, we will briefly present recent work on the role of microRNAs in translational control in dendrites and its implications for learning and memory. Finally, we discuss recent approaches to visualize RNAs in living cells and their employment for studying RNA trafficking in neurons
Sensitivity projections for a dual-phase argon TPC optimized for light dark matter searches through the ionization channel
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