202 research outputs found
Generalized Hermite-Gauss decomposition of the two-photon state produced by spontaneous parametric down-conversion
We provide a general decomposition of the two-photon state produced by
spontaneous parametric down-conversion in Hermite-Gaussian modes, in the case
that the pump beam is described by a Hermite-Gaussian beam of any order. We
show that the spatial correlations depend explicitly on the order of the pump
beam, as well as other experimental parameters. We use the decomposition to
demonstrate a few interesting cases. Our results are applicable to the
engineering of two-photon spatial entanglement, in particular for non-Gaussian
states.Comment: 14 page draft, 5 figure
Extended polarized semiclassical model for quantum-dot cavity QED and its application to single-photon sources
We present a simple extension of the semi-classical model for a two-level
system in a cavity, in order to incorporate multiple polarized transitions,
such as those appearing in neutral and charged quantum dots (QDs), and two
nondegenerate linearly polarized cavity modes. We verify the model by exact
quantum master equation calculations, and experimentally using a neutral QD in
a polarization non-degenerate micro-cavity, in both cases we observe excellent
agreement. Finally, the usefulness of this approach is demonstrated by
optimizing a single-photon source based on polarization postselection, where we
find an increase in the brightness for optimal polarization conditions as
predicted by the model.Comment: 8 pages, for simple code see https://doi.org/10.5281/zenodo.347666
Circular material flow in the intensive care unit-environmental effects and identification of hotspots
PurposeThe healthcare sector is responsible for 6–7% of CO2 emissions. The intensive care unit (ICU) contributes to these CO2 emissions and a shift from a linear system to a circular system is needed. The aim of our research was to perform a material flow analysis (MFA) in an academic ICU. Secondary aims were to obtain information and numbers on mass, carbon footprint, agricultural land occupation and water usage and to determine so-called “environmental hotspots” in the ICU.MethodsA material flow analysis was performed over the year 2019, followed by an environmental footprint analysis of materials and environmental hotspot identification.Results2839 patients were admitted to our ICU in 2019. The average length of stay was 4.6 days. Our MFA showed a material mass inflow of 247,000 kg in 2019 for intensive care, of which 50,000 kg is incinerated as (hazardous) hospital waste. The environmental impact per patient resulted in 17 kg of mass, 12 kg CO2 eq, 300 L of water usage and 4 m2 of agricultural land occupation per day. Five hotspots were identified: non-sterile gloves, isolation gowns, bed liners, surgical masks and syringes (including packaging).ConclusionThis is the first material flow analysis that identified environmental risks and its magnitude in the intensive care unit
Kinematics of the ring-like nebula SuWt 2
We present the first detailed spatio-kinematical analysis and modelling of
the Southern planetary nebula SuWt 2. This object presents a problem for
current theories of planetary nebula formation and evolution, as it is not
known to contain a central post-main sequence star.
Deep narrowband [NII]6584 images reveal the presence of faint bipolar lobes
emanating fromthe edges of the nebular ring. Longslit observations of the
H-alpha and [NII]6584 emission lines were obtained using EMMI on the 3.6-m
ESO-NTT. The spectra reveal the nebular morphology as a bright torus encircling
the waist of an extended bipolar structure. By deprojection, the inclination of
the ring is found to be 68\degr 2\degr (c.f. ~90\degr for the
double A-type binary believed to lie at the centre of the nebula), and the ring
expansion velocity is found to be 28 km/s.
Our findings are discussed with relation to possible formation scenarios for
SuWt 2. Through comparison of the nebular heliocentric systemic velocity, found
here to be -25 5 km/s, and the heliocentric systemic velocity of the
double A-type binary, we conclude that neither component of the binary could
have been the nebular progenitor. However, we are unable to rule out the
presence of a third component to the system, which would have been the nebula
progenitor.Comment: 7 pages, 4 figures. Accepted for publication in MNRA
Herschel Planetary Nebula Survey (HerPlaNS) - First Detection of OH+ in Planetary Nebulae
We report the first detections of OH emission in planetary nebulae (PNe).
As part of an imaging and spectroscopy survey of 11 PNe in the far-IR using the
PACS and SPIRE instruments aboard the Herschel Space Observatory, we performed
a line survey in these PNe over the entire spectral range between 51 and
672m to look for new detections. OH rotational emission lines at
152.99, 290.20, 308.48, and 329.77m were detected in the spectra of three
planetary nebulae: NGC 6445, NGC 6720, and NGC 6781. Excitation temperatures
and column densities derived from these lines are in the range of 27 to 47 K
and 210 to 4 10 cm, respectively. In PNe,
the OH+ rotational line emission appears to be produced in the
photodissociation region (PDR) in these objects. The emission of OH+ is
observed only in PNe with hot central stars (T > 100000 K), suggesting
that high-energy photons may play a role in the OH+ formation and its line
excitation in these objects, as it seems to be the case for ultraluminous
galaxies.Comment: 9 pages, 7 figures; accepted for publication in A&
Herschel observations of nebulae ejected by massive evolved stars
We have obtained far-infrared Herschel PACS imaging and spectroscopic observations of nebulae associated to massive evolved stars. The study of these nebulae is crucial to understand the evolution of these stars as it can reveal the mass-loss history.
The infrared images along with available data at other wavelengths give a complete view of their morphology. The dust modeling provides the dust parameters, such as the temperature, the mass and the composition of dust. The spectroscopic analysis provides the gas C,N,O abundances and mass. Based on these observations, the evolutionary status of the star at the time of the nebula ejection can be constrained.
We present here selected results of an ongoing exhaustive study of nebulae around low- and high-luminosity LBVs (AG Car, HR Car, WRAY 15-751, G79.29+0.46, HD168625), WN stars (NGC6888, M1-67, He3-519) and Of stars (NGC6164/5)
Two-photon speckle as a probe of multi-dimensional entanglement
We calculate the statistical distribution P_2(I_2) of the speckle pattern
produced by a photon pair current I_2 transmitted through a random medium, and
compare with the single-photon speckle distribution P_1(I_1). We show that the
purity Tr rho^2 of a two-photon density matrix rho can be directly extracted
from the first two moments of P_1 and P_2. A one-to-one relationship is derived
between P_1 and P_2 if the photon pair is in an M-dimensional entangled pure
state. For M>>1 the single-photon speckle disappears, while the two-photon
speckle acquires an exponential distribution. The exponential distribution
transforms into a Gaussian if the quantum entanglement is degraded to a
classical correlation of M>>1 two-photon states. Two-photon speckle can
therefore discriminate between multi-dimensional quantum and classical
correlations.Comment: 5 pages, 2 figure
The Herschel Planetary Nebula Survey (HerPlaNS) I. Data Overview and Analysis Demonstration with NGC 6781
This is the first of a series of investigations into far-IR characteristics
of 11 planetary nebulae (PNs) under the Herschel Space Observatory Open Time 1
program, Herschel Planetary Nebula Survey (HerPlaNS). Using the HerPlaNS data
set, we look into the PN energetics and variations of the physical conditions
within the target nebulae. In the present work, we provide an overview of the
survey, data acquisition and processing, and resulting data products. We
perform (1) PACS/SPIRE broadband imaging to determine the spatial distribution
of the cold dust component in the target PNs and (2) PACS/SPIRE
spectral-energy-distribution (SED) and line spectroscopy to determine the
spatial distribution of the gas component in the target PNs. For the case of
NGC 6781, the broadband maps confirm the nearly pole-on barrel structure of the
amorphous carbon-richdust shell and the surrounding halo having temperatures of
26-40 K. The PACS/SPIRE multi-position spectra show spatial variations of
far-IR lines that reflect the physical stratification of the nebula. We
demonstrate that spatially-resolved far-IR line diagnostics yield the (T_e,
n_e) profiles, from which distributions of ionized, atomic, and molecular gases
can be determined. Direct comparison of the dust and gas column mass maps
constrained by the HerPlaNS data allows to construct an empirical gas-to-dust
mass ratio map, which shows a range of ratios with the median of 195+-110. The
present analysis yields estimates of the total mass of the shell to be 0.86
M_sun, consisting of 0.54 M_sun of ionized gas, 0.12 M_sun of atomic gas, 0.2
M_sun of molecular gas, and 4 x 10^-3 M_sun of dust grains. These estimates
also suggest that the central star of about 1.5 M_sun initial mass is
terminating its PN evolution onto the white dwarf cooling track.Comment: 27 pages, 16 figures, accepted for publication in A&
European marine omics biodiversity observation network: a strategic outline for the implementation of omics approaches in ocean observation
Marine ecosystems, ranging from coastal seas and wetlands to the open ocean, accommodate a wealth of biological diversity from small microorganisms to large mammals. This biodiversity and its associated ecosystem function occurs across complex spatial and temporal scales and is not yet fully understood. Given the wide range of external pressures on the marine environment, this knowledge is crucial for enabling effective conservation measures and defining the limits of sustainable use. The development and application of omics-based approaches to biodiversity research has helped overcome hurdles, such as allowing the previously hidden community of microbial life to be identified, thereby enabling a holistic view of an entire ecosystem’s biodiversity and functioning. The potential of omics-based approaches for marine ecosystems observation is enormous and their added value to ecosystem monitoring, management, and conservation is widely acknowledged. Despite these encouraging prospects, most omics-based studies are short-termed and typically cover only small spatial scales which therefore fail to include the full spatio-temporal complexity and dynamics of the system. To date, few attempts have been made to establish standardised, coordinated, broad scaled, and long-term omics observation networks. Here we outline the creation of an omics-based marine observation network at the European scale, the European Marine Omics Biodiversity Observation Network (EMO BON). We illustrate how linking multiple existing individual observation efforts increases the observational power in large-scale assessments of status and change in biodiversity in the oceans. Such large-scale observation efforts have the added value of cross-border cooperation, are characterised by shared costs through economies of scale, and produce structured, comparable data. The key components required to compile reference environmental datasets and how these should be linked are major challenges that we address.</jats:p
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