367 research outputs found
Constraints on the nature of dust particles by infrared observations
The far-infrared (FIR) emissivity of dust is an important parameter
characterizing the physical properties of the grains. With the availability of
stellar databases and far-infrared data from Infrared Space Observatory (ISO)
it is possible to compare the optical and infrared properties of dust, and
derive the far-infrared emissivity with respect to the optical extinction.
In this paper we present the results of a systematic analysis of the FIR
emissivity of interstellar clouds observed with ISOPHOT (the photometer onboard
ISO) at least at two infrared wavelengths, one close to ~100um and one at
200um. We constructed FIR emission maps, determined dust temperatures, created
extinction maps using 2MASS survey data, and calculated far-infrared emissivity
for each of these clouds. We present the largest homogeneously reduced database
constructed so far for this purpose. During the data analysis special care was
taken on possible systematic errors. We find that far-infrared emissivity has a
clear dependence on temperature.
The emissivity is enhanced by a factor of usually less than 2 in the low dust
temperature regime of 12K<=T_d<=14K. This result suggests larger grain sizes in
those regions. However, the emissivity increase of typically below 2 restricts
the possible grain growth processes to ice-mantle formation and coagulation of
silicate grains, and excludes the coagulation of carbonaceous particles on the
scales of the regions we investigated.
In the temperature range 14K<=T_d<=16K a systematic decrease of emissivity is
observed with respect to the values of the diffuse interstellar matter.
Possible scenarios for this behaviour are discussed in the paper.Comment: Accepted for publication in MNRA
Determinants of risk: Exposure and vulnerability
Many climate change adaptation efforts aim to address the implications of potential changes in the frequency, intensity, and duration of weather and climate events that affect the risk of extreme impacts on human society. That risk is determined not only by the climate and weather events (the hazards) but also by the exposure and vulnerability to these hazards. Therefore, effective adaptation and disaster risk management strategies and practices also depend on a rigorous understanding of the dimensions of exposure and vulnerability, as well as a proper assessment of changes in those dimensions. This chapter aims to provide that understanding and assessment, by further detailing the determinants of risk as presented in Chapter 1.
The first sections of this chapter elucidate the concepts that are needed to define and understand risk, and show that risk originates from a combination of social processes and their interaction with the environment (Sections 2.2 and 2.3), and highlight the role of coping and adaptive capacities (Section 2.4). The following section (2.5) describes the different dimensions of vulnerability and exposure as well as trends therein. Given that exposure and vulnerability are highly context-specific, this section is by definition limited to a general overview (a more quantitative perspective on trends is provided in Chapter 4). A methodological discussion (Section 2.6) of approaches to identify and assess risk provides indications of how the dimensions of exposure and vulnerability can be explored in specific contexts, such as adaptation planning, and the central role of risk perception and risk communication. The chapter concludes with a cross-cutting discussion of risk accumulation and the nature of disasters
"Last-Mile" preparation for a potential disaster
Extreme natural events, like e.g. tsunamis or earthquakes, regularly lead to catastrophes with dramatic consequences. In recent years natural disasters caused hundreds of thousands of deaths, destruction of infrastructure, disruption of economic activity and loss of billions of dollars worth of property and thus revealed considerable deficits hindering their effective management: Needs for stakeholders, decision-makers as well as for persons concerned include systematic risk identification and evaluation, a way to assess countermeasures, awareness raising and decision support systems to be employed before, during and after crisis situations. The overall goal of this study focuses on interdisciplinary integration of various scientific disciplines to contribute to a tsunami early warning information system. In comparison to most studies our focus is on high-end geometric and thematic analysis to meet the requirements of small-scale, heterogeneous and complex coastal urban systems. Data, methods and results from engineering, remote sensing and social sciences are interlinked and provide comprehensive information for disaster risk assessment, management and reduction. In detail, we combine inundation modeling, urban morphology analysis, population assessment, socio-economic analysis of the population and evacuation modeling. The interdisciplinary results eventually lead to recommendations for mitigation strategies in the fields of spatial planning or coping capacity
Observations and radiative transfer modelling of a massive dense cold core in G333
Cold massive cores are one of the earliest manifestations of high mass star
formation. Following the detection of SiO emission from G333.125-0.562, a cold
massive core, further investigations of the physics, chemistry and dynamics of
this object has been carried out. Mopra and NANTEN2 molecular line profile
observations, Australia Telescope Compact Array (ATCA) line and continuum
emission maps, and Spitzer 24 and 70 \mum images were obtained. These new data
further constrain the properties of this prime example of the very early stages
of high mass star formation. A model for the source was constructed and
compared directly with the molecular line data using a 3D molecular line
transfer code - MOLLIE. The ATCA data reveal that G333.125-0.562 is composed of
two sources. One of the sources is responsible for the previously detected
molecular outflow and is detected in the Spitzer 24 and 70 \mum band data.
Turbulent velocity widths are lower than other more active regions of G333
which reflects the younger evolutionary stage and/or lower mass of this core.
The molecular line modelling requires abundances of the CO isotopes that
strongly imply heavy depletion due to freeze-out of this species onto dust
grains. The principal cloud is cold, moderately turbulent and possesses an
outflow which indicates the presence of a central driving source. The secondary
source could be an even less evolved object as no apparent associations with
continuum emissions at (far-)infrared wavelengths.Comment: 10 pages, accepted to MNRA
JWST/NIRSpec Observations of the Coldest Known Brown Dwarf
We present 1-5um spectroscopy of the coldest known brown dwarf, WISE
J085510.83-071442.5 (WISE 0855), performed with the Near-Infrared Spectrograph
(NIRSpec) on board the James Webb Space Telescope (JWST). NIRSpec has
dramatically improved the measurement of spectral energy distribution of WISE
0855 in terms of wavelength coverage, signal-to-noise ratios, and spectral
resolution. We have performed preliminary modeling of the NIRSpec data using
the ATMO 2020 models of cloudless atmospheres, arriving at a best fitting model
that has T_eff=285 K. That temperature is ~20 K higher than the value derived
by combining our luminosity estimate with evolutionary models (i.e., the radius
in the model fit to the SED is somewhat smaller than expected from evolutionary
models). Through comparisons to the model spectra, we detect absorption in the
fundamental band of CO, which is consistent with an earlier detection in a
ground-based spectrum and indicates the presence of vertical mixing. Although
PH_3 is expected in Y dwarfs that experience vertical mixing, it is not
detected in WISE 0855. Previous ground-based M-band spectroscopy of WISE 0855
has been cited for evidence of H_2O ice clouds, but we find that the NIRSpec
data in that wavelength range are matched well by our cloudless model. Thus,
clear evidence of H_2O ice clouds in WISE 0855 has not been identified yet, but
it may still be present in the NIRSpec data. The physical properties of WISE
0855, including the presence of H_2O clouds, can be better constrained by more
detailed fitting with both cloudless and cloudy models and the incorporation of
unpublished 5-28um data from the Mid-infrared Instrument on JWST.Comment: Astronomical Journal, in pres
"Last-Mile" preparation for a potential disaster - Interdisciplinary approach towards tsunami early warning and an evacuation information system for the coastal city of Padang, Indonesia
Extreme natural events, like e.g. tsunamis or earthquakes, regularly lead to catastrophes with dramatic consequences. In recent years natural disasters caused hundreds of thousands of deaths, destruction of infrastructure, disruption of economic activity and loss of billions of dollars worth of property and thus revealed considerable deficits hindering their effective management: Needs for stakeholders, decision-makers as well as for persons concerned include systematic risk identification and evaluation, a way to assess countermeasures, awareness raising and decision support systems to be employed before, during and after crisis situations. The overall goal of this study focuses on interdisciplinary integration of various scientific disciplines to contribute to a tsunami early warning information system. In comparison to most studies our focus is on high-end geometric and thematic analysis to meet the requirements of smallscale, heterogeneous and complex coastal urban systems. Data, methods and results from engineering, remote sensing and social sciences are interlinked and provide comprehensive information for disaster risk assessment, management and reduction. In detail, we combine inundation modeling, urban morphology analysis, population assessment, socioeconomic analysis of the population and evacuation modeling. The interdisciplinary results eventually lead to recommendations for mitigation strategies in the fields of spatial planning or coping capacity.DFG/03G0666A-
Detection of Prion Protein Particles in Blood Plasma of Scrapie Infected Sheep
Prion diseases are transmissible neurodegenerative diseases affecting humans and animals. The agent of the disease is the prion consisting mainly, if not solely, of a misfolded and aggregated isoform of the host-encoded prion protein (PrP). Transmission of prions can occur naturally but also accidentally, e.g. by blood transfusion, which has raised serious concerns about blood product safety and emphasized the need for a reliable diagnostic test. In this report we present a method based on surface-FIDA (fluorescence intensity distribution analysis), that exploits the high state of molecular aggregation of PrP as an unequivocal diagnostic marker of the disease, and show that it can detect infection in blood. To prepare PrP aggregates from blood plasma we introduced a detergent and lipase treatment to separate PrP from blood lipophilic components. Prion protein aggregates were subsequently precipitated by phosphotungstic acid, immobilized on a glass surface by covalently bound capture antibodies, and finally labeled with fluorescent antibody probes. Individual PrP aggregates were visualized by laser scanning microscopy where signal intensity was proportional to aggregate size. After signal processing to remove the background from low fluorescence particles, fluorescence intensities of all remaining PrP particles were summed. We detected PrP aggregates in plasma samples from six out of ten scrapie-positive sheep with no false positives from uninfected sheep. Applying simultaneous intensity and size discrimination, ten out of ten samples from scrapie sheep could be differentiated from uninfected sheep. The implications for ante mortem diagnosis of prion diseases are discussed
Developing an impact library for forecasting surface water flood risk
During surface water flooding events, emergency responders require detailed information on the risks posed in order to provide an appropriate and effective response. Few early warning systems quantitatively estimate the risk and impacts of surface water flooding. Improvements in computational processing capability, availability of new datasets and developments in forecasting models means that the forecasting information currently being supplied by the Flood Forecasting Centre can be improved upon through the application of a timely, impact‐based model. This article presents a novel approach to collating receptor datasets into a pre‐calculated Impact Library for use in a Hazard Impact Model (HIM) that will operate using real‐time probabilistic rainfall and surface runoff forecasts for England and Wales. The HIM provides an approach suitable for modelling flood impacts. Initial results are presented for a case study covering the 2012 floods in the North East of England. Information generated by the HIM provides additional benefits beyond current methods. Features include operator access to 1 km 15 min spatial–temporal data, analysis of individual impact criteria and modular refinement of the Impact Library to suit different situations. The HIM has been developed in partnership via the Natural Hazards Partnership
Global vulnerability hotspots: differences and agreement between international indicator-based assessments
Climate change impacts and their consequences are determined not only by the intensity and frequency of different climatic hazards but also by the vulnerability of the system, society or community exposed. While general agreement exists about the importance of assessing vulnerability to understand climate risks, there is still a tendency to neglect global and regional vulnerability patterns because they are hard to quantify, despite their value in informing adaptation, disaster risk and development policies. Several approaches to quantifying global vulnerability exist. These differ in terms of the indicators they use and how they classify countries or regions into vulnerability classes. The paper presents the structure of selected approaches and explores two indices in depth. The aim of this paper is to assess the level of agreement between selected international indicator-based assessments of vulnerability, at the level of climate regions. Results suggest that the two major global vulnerability assessments analysed largely agree on the location of the most and least vulnerable regions when these assessments are aggregated to a regional scale using the IPCC’s climate regions. The paper then discusses the robustness of the information derived and its usefulness for adaptation, disaster risk and development policies. Measuring progress towards reducing vulnerability to climate change and hazards is key for various agencies and actors in order to be able to develop informed policies and strategies for managing climate risks and to promote enabling conditions for achieving the SDGs and building resilience
Transiting Exoplanet Studies and Community Targets for JWST's Early Release Science Program
The James Webb Space Telescope will revolutionize transiting exoplanet
atmospheric science due to its capability for continuous, long-duration
observations and its larger collecting area, spectral coverage, and spectral
resolution compared to existing space-based facilities. However, it is unclear
precisely how well JWST will perform and which of its myriad instruments and
observing modes will be best suited for transiting exoplanet studies. In this
article, we describe a prefatory JWST Early Release Science (ERS) program that
focuses on testing specific observing modes to quickly give the community the
data and experience it needs to plan more efficient and successful future
transiting exoplanet characterization programs. We propose a multi-pronged
approach wherein one aspect of the program focuses on observing transits of a
single target with all of the recommended observing modes to identify and
understand potential systematics, compare transmission spectra at overlapping
and neighboring wavelength regions, confirm throughputs, and determine overall
performances. In our search for transiting exoplanets that are well suited to
achieving these goals, we identify 12 objects (dubbed "community targets") that
meet our defined criteria. Currently, the most favorable target is WASP-62b
because of its large predicted signal size, relatively bright host star, and
location in JWST's continuous viewing zone. Since most of the community targets
do not have well-characterized atmospheres, we recommend initiating preparatory
observing programs to determine the presence of obscuring clouds/hazes within
their atmospheres. Measurable spectroscopic features are needed to establish
the optimal resolution and wavelength regions for exoplanet characterization.
Other initiatives from our proposed ERS program include testing the instrument
brightness limits and performing phase-curve observations.(Abridged)Comment: This is a white paper that originated from an open discussion at the
Enabling Transiting Exoplanet Science with JWST workshop held November 16 -
18, 2015 at STScI (http://www.stsci.edu/jwst/science/exoplanets). Accepted
for publication in PAS
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