913 research outputs found
Standard Model physics at the LHC
In this contribution to the volume "From My Vast Repertoire -- The Legacy of
Guido Altarelli" I discuss selected topics of Standard Model (SM) physics at
the LHC and their connection to the work of Guido Altarelli. An overarching
connection is given by Guido's fundamental contributions to our understanding
of the strong force, parton distribution functions and their evolution, and
techniques to calculate theoretical predictions through perturbative Quantum
Chromodynamics. The increasingly precise LHC measurements of diverse processes
can be confronted with SM predictions relying on these foundations to test the
SM and contribute to the knowledge of the proton structure. The LHC experiments
have also started to perform precise measurements of SM parameters, such as the
mass of the W boson, and have measured a variety of processes sensitive to
interactions of multiple electroweak bosons. The discovery of the Higgs boson
in 2012 and the measurements of its properties are crucial to establish the
nature of the mechanism of electroweak symmetry breaking and the status of
these studies is summarised.Comment: Contribution to the volume "From my Vast Repertoire - the Legacy of
Guido Altarelli" : 24 pages, 13 figure
Improving the representation of Arctic clouds in atmospheric models across scales using observations
With a nearly twice as strongly pronounced temperature increase compared to that of the Northern Hemisphere, the Arctic is especially susceptible to global climate change. The effect of clouds on the Arctic warming is especially uncertain, which is caused by misrepresented cloud microphysical processes in atmospheric models. This thesis aims at employing a scale- and definition-aware comparison of models and observations and will propose changes how to better parameterize Arctic clouds in atmospheric models.
In the first part of this thesis, ECHAM6, which is the atmospheric component of the MPI-ESM global climate model, is compared to spaceborne lidar observations of clouds from the CALIPSO satellite. This comparison shows that ECHAM6 overestimates Arctic low-level, liquid containing clouds over snow- and ice-covered surfaces, which consequently leads to an overestimated amount of radiative energy received by the surface. Using sensitivity studies, it is shown that the probable cause of the model biases in cloud amount and phase is related to misrepresented cloud microphysical parameterization (i.e., parameterization of the Wegener-Bergeron-Findeisen process and of the cloud cover scheme) in ECHAM6. By revising those processes, a better representation of cloud amount and cloud phase is achieved, which helps to more accurately simulated the amount of radiative energy received by the Arctic in ECHAM6.
The second part of this thesis will focus on a comparison of kilometer-scale simulation with the ICON model to aircraft observations from the ACLOUD campaign that took place in May/June 2017 over the sea ice-covered Arctic Ocean north of Svalbard, Norway. By comparing measurements of solar and terrestrial surface irradiances during ACLOUD flights to the respective quantities in ICON, it is shown that the model systematically overestimates the transmissivity of the mostly liquid clouds during the campaign. This model bias is traced back to the way cloud condensation nuclei get activated into cloud droplets in the two-moment, bulk microphysical scheme used. By parameterizing subgrid-scale vertical motion as a function of turbulent kinetic energy, a more realistic CCN activation into cloud droplets is achieved. This consequently results in an improved representation of cloud optical properties in the ICON simulations.
Furthermore, the results of two studies to which contributions have been made during the Ph.D. will be summarized. In Petersik et al. 2018, the impact of subgrid-scale variability in clear-sky relative humidity on hygroscopic growth of aerosols in the aerosol-climate model ECHAM6-HAM2 has been explored. It was shown that the revised parameterization of hygroscopic growth of aerosols resulted in a stronger swelling of aerosol particles, which consequently causes an increased backscattering of solar radiation. In the study of Costa-Suros et al. 2019, it is explored whether it is possible to detect and attribute aerosol-cloud interactions in large-eddy simulation over Germany. It was shown that an increase in cloud droplet number concentration could be attributed to an increased aerosol load, while such an attribution was not possible for other cloud micro- and macrophysical variables
Electroweak Measurements with the ATLAS and CMS Experiments
Highlights of ATLAS and CMS measurements involving the production of heavy
electroweak gauge bosons, W and Z, at the LHC are presented. Cross sections of
single W and Z bosons are studied with very high precision and differential in
various kinematic variables. The rapidity differential measurements are shown
to have a so far unique impact on our knowledge of proton structure with
regards to the strange quark density. The production in association with one or
more light or heavy flavour jets is studied. Furthermore measurements of {\tau}
final states, W polarisation and the weak mixing angle sin2{\theta}W are
presented. Various di-boson measurements are presented and measurements are in
general found to be well described by the Standard Model predictions. These
measurements test the non-Abelian gauge structure and limits on anomalous
triple gauge couplings are derived, which are of impact comparable to the
corresponding LEP and Tevatron results.Comment: 8 pages, 12 figures. To appear in the proceedings of the 47th
Recontres de Moriond, EW session, 201
Prediction of Retention Indices and Response Factors of Oxygenates for GC-FID by Multilinear Regression
The replacement of fossil carbon sources with green bio-oils promotes the importance of several hundred oxygenated hydrocarbons, which substantially increases the analytical effort in catalysis research. A multilinear regression is performed to correlate retention indices (RIs) and response factors (RFs) with structural properties. The model includes a variety of possible products formed during the hydrodeoxygenation of bio-oils with good accuracy (RRF2 0.921 and RRI2 0.975). The GC parameters are related to the detailed hydrocarbon analysis (DHA) method, which is commonly used for non-oxygenated hydrocarbons. The RIs are determined from a paraffin standard (C5–C15), and the RFs are calculated with ethanol and 1,3,5-trimethylbenzene as internal standards. The method presented here can, therefore, be used together with the DHA method and be expanded further. In addition to the multilinear regression, an increment system has been developed for aromatic oxygenates, which further improves the prediction accuracy of the response factors with respect to the molecular constitution (R2 0.958). Both predictive models are designed exclusively on structural factors to ensure effortless application. All experimental RIs and RFs are determined under identical conditions. Moreover, a folded Plackett–Burman screening design demonstrates the general applicability of the datasets independent of method- or device-specific parameters
a simple robust scaleinvariant text feature detector
In this paper we present SITT, a simple robust scaleinvariant text feature
detector for document mosaicing. Digital image stitching has been studied for
several decades. SIFT-Features in combination with RANSAC algorithm are
established to produce good panoramas. The main problem of realtime text
document stitching is the size of the feature set created by SIFT-Features. We
introduce SITT-Features to solve this problem. Our experiments denote that for
document images SITT-Features produce faster good results than SIFT-Features
Timeliness of notification systems for infectious diseases: A systematic literature review.
Timely notification of infectious diseases is crucial for prompt response by public health services. Adequate notification systems facilitate timely notification. A systematic literature review was performed to assess outcomes of studies on notification timeliness and to determine which aspects of notification systems are associated with timely notification
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Publication of Atmospheric Model Data using the ATMODAT Standard
Scientific data should be published in a way so that other scientists can benefit from these data, enabling further research. The FAIR Data Principles are defining the basic prerequisite for a good data publication: data should be Findable, Accessible, Interoperable, and Reusable. Increasingly, research communities are developing discipline-specific data publication standards under consideration of the FAIR Data Principles. A very comprehensive yet strict data standard has been developed for the climate model output within the Climate Model Intercomparison Project (CMIP), which largely builds upon the Climate and Forecast Metadata Conventions (CF conventions). There are, however, many areas of atmospheric modelling where data cannot be standardised according to the CMIP data standard because, e.g., the data contain specific variables which are not covered by the CMIP standard. Furthermore, fulfilling the strict CMIP data standard for smaller Model Intercomparison Projects (MIPs) requires much effort (in time and manpower) and hence the outcome of these MIPs often remains non-standardised. For innovative model diagnostics, preexisting standards are also not flexible enough. For that reason, the ATMODAT standard, a quality guideline for atmospheric model data, was created. The ATMODAT standard defines a set of requirements that aim at ensuring the high reusability of atmospheric model data publications. The requirements include the use of the netCDF file format, the application of the CF conventions, rich and standardised file metadata, and the publication of the data with a DataCite DOI. Additionally, a tool for checking the conformity of data and metadata to this standard, the atmodat data checker, was developed and is available on GitHub under an open licence. By using the more flexible ATMODAT standard, the publication of standardised datasets is simplified for smaller MIPs. This standardisation process is presented as an example using the data of an aerosol-climate model from the AeroCOM MIP. Furthermore, the landing pages of ATMODAT-compliant data publications can be highlighted with the EASYDAB logo. EASYDAB (Earth System Data Branding) is a newly developed quality label for carefully curated and highly standardised data publications. The ATMODAT data standardisation can easily be transferred to data from other disciplines and contribute to their improved reusability
Organic Food Claims in Europe
Better regulatory guidelines, improved testing methods, and additional research into product quality criteria are needed to further develop the European organic food market
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