219 research outputs found
Creating atom-nanoparticle quantum superpositions
A nanoscale object evidenced in a nonclassical state of its center of mass will hugely extend the boundaries of quantum mechanics. To obtain a practical scheme for the same, we exploit a hitherto unexplored coupled system: an atom and a nanoparticle coupled by an optical field. We show how to control the center of mass of a large
âŒ
500
-nm nanoparticle using the internal state of the atom so as to create, as well as detect, nonclassical motional states of the nanoparticle. Specifically, we consider a setup based on a silica nanoparticle coupled to a cesium atom and discuss a protocol for preparing and verifying a Schrödinger-cat state of the nanoparticle that does not require cooling to the motional ground state. We show that the existence of the superposition can be revealed using the Earth's gravitational field using a method that is insensitive to the most common sources of decoherence and works for any initial state of the nanoparticle
VIVO and VIV Species Formed in Aqueous Solution by the Tridentate GlutaroimideâDioxime Ligand â An Instrumental and Computational Characterization
Complexation of VIV in aqueous solution with glutaroimideâdioxime (H3L), a ligand proposed for the possible sequestration of uranium from seawater, was studied by the combined application of spectroscopic (EPR and UV/Vis), spectrometric (ESIâMS), electrochemical (CV), and computational (DFT) techniques. The results indicate that a rare nonâoxido VIV species, with formula [VIVL2]2â, is formed in the pH range 3â5. It transforms into a usual VIVO complex, [VIVOL(OH)]2â, at pH > 6. The nonâoxido species is characterized by a "type 3" EPR spectrum with Az â 126 Ă 10â4 cmâ1 and a UV/Vis signal with Δ > 2000 mâ1âcmâ1 in the visible region. The detection of VV species by ESIâMS spectrometry was related to two possible oxidation processes, the first one in solution and the second one inâsource during the recording of the spectra. The cyclic voltammogram of [VIVL2]2â shows two quasiâreversible processes, at E1/2 = â0.75 V and E1/2 = 0.03 V, assigned to the VIV/VIII reduction and VIV/VV oxidation, respectively. All the experimental results were verified by DFT calculations, which indicated that the geometry of the nonâoxido VIV complex is intermediate between an octahedron and a trigonal prism and allowed us to predict its 51V hyperfine coupling (HFC) tensor A, the electron absorption spectrum, the two redox processes in the cyclic voltammogram, and the electronic structure that, in turn, determines its EPR and UV/Vis behavior
Comparison and optimisation of microRNA extraction from the plasma of healthy pregnant women
Circulating microRNA (miRNA) biomarkers are implicated in the diagnosis, monitoring and prediction of various disease processes. Before embarking upon biomarker discovery, miRNA extraction techniques must first be optimised in the biofluid and population under study. Using plasma from a healthy pregnant woman, it was attempted to optimise and compare the performance of two commercially available miRNA extraction kits; Qiagen (miRNeasy Serum/Plasma) and Promega (MaxwellÂź RSC miRNA from Tissue or Plasma or Serum). Sample miRNA content (concentration and percentage) was assessed using Agilent Bioanalyzer Small RNA chips and reverse transcriptionâquantitative PCR (RTâqPCR) using four constitutively expressed miRNAs (hsaâmiRâ222â3p, hsaâletâ7iâ3p, hsaâmiRâ148â3p and hsaâmiRâ30eâ5p). Quality control spikeâins monitored RNA extraction (UniSp2, 4 and 5) and cDNA synthesis (UniSp6, celâmiRâ39â3p) efficiency. Optimisation approaches included: i) Starting volume of plasma; the addition of ii) Proteinase K; iii) a RNA bacteriophage carrier (MS2); and iv) a glycogen carrier. The two kits exhibited equivalence in terms of miRNA recovery based on Bioanalyzer and RTâqPCR ÎÎCq results. Optimisation attempts for both kits failed to improve upon miRNA content compared with standard methodology. Comparing the standard methodology, the Qiagen kit was more consistent (smaller variance of ÎCq values) compared with the Promega kit. The standard methodology of either kit would be suitable for the investigation of miRNA biomarkers in a healthy pregnant population
Magnetic Reconnection in Extreme Astrophysical Environments
Magnetic reconnection is a basic plasma process of dramatic rearrangement of
magnetic topology, often leading to a violent release of magnetic energy. It is
important in magnetic fusion and in space and solar physics --- areas that have
so far provided the context for most of reconnection research. Importantly,
these environments consist just of electrons and ions and the dissipated energy
always stays with the plasma. In contrast, in this paper I introduce a new
direction of research, motivated by several important problems in high-energy
astrophysics --- reconnection in high energy density (HED) radiative plasmas,
where radiation pressure and radiative cooling become dominant factors in the
pressure and energy balance. I identify the key processes distinguishing HED
reconnection: special-relativistic effects; radiative effects (radiative
cooling, radiation pressure, and Compton resistivity); and, at the most extreme
end, QED effects, including pair creation. I then discuss the main
astrophysical applications --- situations with magnetar-strength fields
(exceeding the quantum critical field of about 4 x 10^13 G): giant SGR flares
and magnetically-powered central engines and jets of GRBs. Here, magnetic
energy density is so high that its dissipation heats the plasma to MeV
temperatures. Electron-positron pairs are then copiously produced, making the
reconnection layer highly collisional and dressing it in a thick pair coat that
traps radiation. The pressure is dominated by radiation and pairs. Yet,
radiation diffusion across the layer may be faster than the global Alfv\'en
transit time; then, radiative cooling governs the thermodynamics and
reconnection becomes a radiative transfer problem, greatly affected by the
ultra-strong magnetic field. This overall picture is very different from our
traditional picture of reconnection and thus represents a new frontier in
reconnection research.Comment: Accepted to Space Science Reviews (special issue on magnetic
reconnection). Article is based on an invited review talk at the
Yosemite-2010 Workshop on Magnetic Reconnection (Yosemite NP, CA, USA;
February 8-12, 2010). 30 pages, no figure
Unruh--DeWitt detectors in spherically symmetric dynamical space-times
In the present paper, Unruh--DeWitt detectors are used in order to
investigate the issue of temperature associated with a spherically symmetric
dynamical space-times. Firstly, we review the semi-classical tunneling method,
then we introduce the Unruh--DeWitt detector approach. We show that for the
generic static black hole case and the FRW de Sitter case, making use of
peculiar Kodama trajectories, semiclassical and quantum field theoretic
techniques give the same standard and well known thermal interpretation, with
an associated temperature, corrected by appropriate Tolman factors. For a FRW
space-time interpolating de Sitter space with the Einstein--de Sitter universe
(that is a more realistic situation in the frame of CDM cosmologies),
we show that the detector response splits into a de Sitter contribution plus a
fluctuating term containing no trace of Boltzmann-like factors, but rather
describing the way thermal equilibrium is reached in the late time limit. As a
consequence, and unlike the case of black holes, the identification of the
dynamical surface gravity of a cosmological trapping horizon as an effective
temperature parameter seems lost, at least for our co-moving simplified
detectors. The possibility remains that a detector performing a proper motion
along a Kodama trajectory may register something more, in which case the
horizon surface gravity would be associated more likely to vacuum correlations
than to particle creation.Comment: 19 pages, to appear on IJTP. arXiv admin note: substantial text
overlap with arXiv:1101.525
A model independent approach to the dark energy equation of state
The consensus of opinion in cosmology is that the Universe is currently
undergoing a period of accelerated expansion. With current and proposed high
precision experiments it offers the hope of being able to discriminate between
the two competing models that are being suggested to explain the observations,
namely a cosmological constant or a time dependent `Quintessence' model. The
latter suffers from a plethora of scalar field potentials all leading to
similar late time behaviour of the universe, hence to a lack of predictability.
In this paper, we develop a model independent approach which simply involves
parameterizing the dark energy equation of state in terms of known observables.
This allows to analyse the impact dark energy has had on cosmology without the
need to refer to particular scalar field models and opens up the possibility
that future experiments will be able to constrain the dark energy equation of
state in a model independent manner.Comment: 6 pages, 5 figures. Final version to appear in PR
Provenance of the Early Mesoproterozoic Radium Creek Group in the northern Mount Painter Inlier: Correlating isotopic signatures to inform tectonic reconstructions
New in situ zircon LA-ICPMS geochronologic and Hf-isotope data from the Radium Creek Group within the Mount Painter Inlier provide important temporal constraints on the Early Mesoproterozoic palaeogeography of eastern Proterozoic Australia. The entire Radium Creek Group was deposited in a single basin forming phase, and has a maximum depositional age of 1595. ±. 3.7. Ma. Detrital zircon from these metasedimentary rocks have U-Pb age populations at ca. 1595. Ma, 1660-1680. Ma, 1710-1780. Ma, ca. 1850. Ma and ca. 2500. Ma. These grains are characterised by isotopically diverse and evolved sources, and have crystallised within predominantly felsic igneous host-rocks. The relative age spectra and isotopic character has more similarity with the Gawler Craton than the Arunta Block, Curnamona Province or the Mount Isa Inlier. These observations suggest that the Mount Painter Province was adjacent to the Gawler Craton in the Early Mesoproterozoic. Our data supports a coherent South Australian Craton at ca. 1595. Ma and a contiguous continental mass that included the North and South Australian cratons. The Mount Painter Inlier occupied a complex plate tectonic setting in the overriding plate of two convergent margins. © 2014 Elsevier B.V
Development of an amplicon-based sequencing approach in response to the global emergence of mpox
The 2022 multicountry mpox outbreak concurrent with the ongoing Coronavirus Disease 2019 (COVID-19) pandemic further highlighted the need for genomic surveillance and rapid pathogen whole-genome sequencing. While metagenomic sequencing approaches have been used to sequence many of the early mpox infections, these methods are resource intensive and require samples with high viral DNA concentrations. Given the atypical clinical presentation of cases associated with the outbreak and uncertainty regarding viral load across both the course of infection and anatomical body sites, there was an urgent need for a more sensitive and broadly applicable sequencing approach. Highly multiplexed amplicon-based sequencing (PrimalSeq) was initially developed for sequencing of Zika virus, and later adapted as the main sequencing approach for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Here, we used PrimalScheme to develop a primer scheme for human monkeypox virus that can be used with many sequencing and bioinformatics pipelines implemented in public health laboratories during the COVID-19 pandemic. We sequenced clinical specimens that tested presumptively positive for human monkeypox virus with amplicon-based and metagenomic sequencing approaches. We found notably higher genome coverage across the virus genome, with minimal amplicon drop-outs, in using the amplicon-based sequencing approach, particularly in higher PCR cycle threshold (Ct) (lower DNA titer) samples. Further testing demonstrated that Ct value correlated with the number of sequencing reads and influenced the percent genome coverage. To maximize genome coverage when resources are limited, we recommend selecting samples with a PCR Ct below 31 Ct and generating 1 million sequencing reads per sample. To support national and international public health genomic surveillance efforts, we sent out primer pool aliquots to 10 laboratories across the United States, United Kingdom, Brazil, and Portugal. These public health laboratories successfully implemented the human monkeypox virus primer scheme in various amplicon sequencing workflows and with different sample types across a range of Ct values. Thus, we show that amplicon-based sequencing can provide a rapidly deployable, cost-effective, and flexible approach to pathogen whole-genome sequencing in response to newly emerging pathogens. Importantly, through the implementation of our primer scheme into existing SARS-CoV-2 workflows and across a range of sample types and sequencing platforms, we further demonstrate the potential of this approach for rapid outbreak response.This publication was made possible by
CTSA Grant Number UL1 TR001863 from the
National Center for Advancing Translational
Science (NCATS), a component of the National
Institutes of Health (NIH) awarded to CBFV. INSA
was partially funded by the HERA project (Grant/
2021/PHF/23776) supported by the European
Commission through the European Centre for
Disease Control (to VB).info:eu-repo/semantics/publishedVersio
Black Hole Thermodynamics and Statistical Mechanics
We have known for more than thirty years that black holes behave as
thermodynamic systems, radiating as black bodies with characteristic
temperatures and entropies. This behavior is not only interesting in its own
right; it could also, through a statistical mechanical description, cast light
on some of the deep problems of quantizing gravity. In these lectures, I review
what we currently know about black hole thermodynamics and statistical
mechanics, suggest a rather speculative "universal" characterization of the
underlying states, and describe some key open questions.Comment: 35 pages, Springer macros; for the Proceedings of the 4th Aegean
Summer School on Black Hole
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