1,967 research outputs found
Theoretical X-ray absorption spectroscopy database analysis for oxidised 2D carbon nanomaterials
In this work we provide a proof of principle for a theoretical methodology to identify functionalisation patterns in oxidised carbon 2D nanomaterials. The methodology is based on calculating a large number of X-ray absorption spectra of individually excited carbon atoms in different chemical environments using density functional theory. Since each resulting spectrum gives a fingerprint of the local electronic structure surrounding the excited atom, we may relate each spectrum to the functionalisation pattern of that excited atom up to a desired neighbourhood radius. These functionalisation pattern-specific spectra are collected in a database, that allows fast composition of X-ray absorption spectra for arbitrary structures in density functional theory quality. Finally, we present an exemplary application of the database approach to estimate the relative amount of functional groups in two different experimental samples of carbon nanomaterials
Blockchain for Business Process Enactment: A Taxonomy and Systematic Literature Review
Blockchain has been proposed to facilitate the enactment of
interorganisational business processes. For such processes, blockchain can
guarantee the enforcement of rules and the integrity of execution traces -
without the need for a centralised trusted party. However, the enactment of
interorganisational processes pose manifold challenges. In this work, we ask
what answers the research field offers in response to those challenges. To do
so, we conduct a systematic literature review (SLR). As our guiding question,
we investigate the guarantees and capabilities of blockchain-based enactment
approaches. Based on resulting empirical evidence, we develop a taxonomy for
blockchain-based enactment. We find that a wide range of approaches support
traceability and correctness; however, research focusing on flexibility and
scalability remains nascent. For all challenges, we point towards future
research opportunities.Comment: Preprint, Accepted at BPM 2022, Blockchain Foru
Comments-induced biases in evaluating proprietor content on participatory websites: The robustness of user comment quality's effect across judgment conditions
Current research indicates that the quality of user-generated comments can bias the perceptions of a web page’s proprietary message’s quality (e.g. of a news article). However, this effect could be limited to situations where users judge quality in retrospect, i.e. after website exposure, based on information they can remember. Therefore, two experiments explored whether the effect also occurs under systematically different judgment conditions. The first experiment demonstrates that the effect is also observable under online judgment conditions, i.e. when the proprietor content is perceptible during judgment and the judgment task is known during exposure. The second experiment shows that under these conditions the effect even occurs when users are highly aware of the qualitative dissimilarity of the contents from the different authorial sources, and when they consciously try to shield their judgments from the comments’ influence. More theory development and research is needed to explain the effect under these conditions
ESTER: efficient search on text, entities, and relations
We present ESTER, a modular and highly efficient system for combined full-text and ontology search. ESTER builds on a query engine that supports two basic operations: prefix search and join. Both of these can be implemented very efficiently with a compact index, yet in combination provide powerful querying capabilities. We show how ESTER can answer basic SPARQL graphpattern queries on the ontology by reducing them to a small number of these two basic operations. ESTER further supports a natural blend of such semantic queries with ordinary full-text queries. Moreover, the prefix search operation allows for a fully interactive and proactive user interface, which after every keystroke suggests to the user possible semantic interpretations of his or her query, and speculatively executes the most likely of these interpretations. As a proof of concept, we applied ESTER to the English Wikipedia, which contains about 3 million documents, combined with the recent YAGO ontology, which contains about 2.5 million facts. For a variety of complex queries, ESTER achieves worst-case query processing times of a fraction of a second, on a single machine, with an index size of about 4 GB
The use of weightbearing radiographs to assess the stability of supination-external rotation fractures of the ankle
Background: Isolated lateral malleolar fractures usually result from a supination-external rotation (SER) injury and may include a deltoid ligament rupture. The necessity of operative treatment is based on the recognition of a relevant medial soft-tissue disruption. Currently used tests to assess ankle stability include manual stress radiographs and gravity stress radiographs, but seem to overestimate the need for fracture fixation. Methods: We investigated the use of weightbearing radiographs to distinguish stable and unstable isolated lateral malleolar fractures induced by the SER mechanism in 57 patients. Patients with stable fractures (SER type II according to the Lauge-Hansen classification) were treated non-operatively with varying external support. Forty-seven patients were evaluated by questionnaire and AOFAS ankle-hindfoot score. Follow-up was 18-120months (mean 62). Results: Fifty-one of fifty-seven (90%) patients were found to have stable fractures (SER type II) and were treated non-operatively. The AOFAS score was 96.1 points on average (range 85-100) at latest follow-up. Four patients reported minor complaints. A "moderate” correlation of risk factors (i.e. smoking) to delayed bone healing was found while the correlation of varying external support (i.e. bandage, cast) to the AOFAS score and delayed bone healing was "poor”. Conclusion: The use of weightbearing radiographs is an easy, pain-free, safe and reliable method to exclude the need for operative treatment, with excellent clinical outcome in the majority of the patients seen at latest follow-up. The delay of 3-10days until the decision about surgical treatment is well accepted by the patient
Simultaneous phase, amplitude, and polarization control of femtosecond laser pulses
We present a serial pulse shaper design which allows us to shape the phase,
amplitude, and polarization of fs laser pulses independently and
simultaneously. The capabilities of this setup are demonstrated by
implementing a method for generating parametrically tailored laser pulses.
This method is applied on the ionization of NaK molecules by feedback loop
optimization, employing a temporal sub pulse encoding. Moreover, we introduce
and characterize a further development of this common path pulse shaper scheme
for full control of all light field parameters
Chiral 1D Floquet topological insulators beyond rotating wave approximation
We study one-dimensional (1D) Floquet topological insulators with chiral
symmetry going beyond the standard rotating wave approximation. The occurrence
of many anticrossings between Floquet replicas leads to a dramatic extension of
phase diagram regions with stable topological edge states (TESs). We present an
explicit construction of all TESs in terms of a truncated Floquet Hamiltonian
in frequency space, prove the bulk-boundary correspondence, and analyze the
stability of the TESs in terms of their localization lengths. We propose
experimental tests of our predictions in curved bilayer graphene.Comment: 4+9 page
Indirect Meltdown: Building Novel Side-Channel Attacks from Transient-Execution Attacks
The transient-execution attack Meltdown leaks sensitive information by
transiently accessing inaccessible data during out-of-order execution. Although
Meltdown is fixed in hardware for recent CPU generations, most
currently-deployed CPUs have to rely on software mitigations, such as KPTI.
Still, Meltdown is considered non-exploitable on current systems. In this
paper, we show that adding another layer of indirection to Meltdown transforms
a transient-execution attack into a side-channel attack, leaking metadata
instead of data. We show that despite software mitigations, attackers can still
leak metadata from other security domains by observing the success rate of
Meltdown on non-secret data. With LeakIDT, we present the first cache-line
granular monitoring of kernel addresses. LeakIDT allows an attacker to obtain
cycle-accurate timestamps for attacker-chosen interrupts. We use our attack to
get accurate inter-keystroke timings and fingerprint visited websites. While we
propose a low-overhead software mitigation to prevent the exploitation of
LeakIDT, we emphasize that the side-channel aspect of transient-execution
attacks should not be underestimated.Comment: published at ESORICS 202
Reviving Meltdown 3a
Since the initial discovery of Meltdown and Spectre in 2017, different
variants of these attacks have been discovered. One often overlooked variant is
Meltdown 3a, also known as Meltdown-CPL-REG. Even though Meltdown-CPL-REG was
initially discovered in 2018, the available information regarding the
vulnerability is still sparse. In this paper, we analyze Meltdown-CPL-REG on 19
different CPUs from different vendors using an automated tool. We observe that
the impact is more diverse than documented and differs from CPU to CPU.
Surprisingly, while the newest Intel CPUs do not seem affected by
Meltdown-CPL-REG, the newest available AMD CPUs (Zen3+) are still affected by
the vulnerability. Furthermore, given our attack primitive CounterLeak, we show
that besides up-to-date patches, Meltdown-CPL-REG can still be exploited as we
reenable performance-counter-based attacks on cryptographic algorithms, break
KASLR, and mount Spectre attacks. Although Meltdown-CPL-REG is not as powerful
as other transient-execution attacks, its attack surface should not be
underestimated.Comment: published at ESORICS 202
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