2,359 research outputs found
The coherent dynamics of photoexcited green fluorescent proteins
The coherent dynamics of vibronic wave packets in the green fluorescent
protein is reported. At room temperature the non-stationary dynamics following
impulsive photoexcitation displays an oscillating optical transmissivity
pattern with components at 67 fs (497 cm-1) and 59 fs (593 cm-1). Our results
are complemented by ab initio calculations of the vibrational spectrum of the
chromophore. This analysis shows the interplay between the dynamics of the
aminoacidic structure and the electronic excitation in the primary optical
events of green fluorescent proteins.Comment: accepted for publication in Physical Review Letter
Some Adventures in the Search for a Modified Gravity Explanation for Cosmic Acceleration
The discovery of cosmic acceleration has raised the intriguing possibility
that we are witnessing the first breakdown of General Relativity on
cosmological scales. In this article I will briefly review current attempts to
construct a theoretically consistent and observationally viable modification of
gravity that is capable of describing the accelerating universe. I will discuss
f(R) models, and their obvious extensions, and the DGP model as an example of
extra-dimensional implementations. I will then briefly describe the Galileon
models and their very recent multifield and curved space extensions - a class
of four-dimensional effective field theories encoding extra dimensional
modifications to gravity. This article is dedicated to the career of my friend
and former colleague, Joshua Goldberg, and is written to appear in his
festschrift.Comment: 17 pages, to appear in a festschrift for Joshua Goldber
Quality Checks Logit Human Reliability (LHR): A New Model to Evaluate Human Error Probability (HEP)
In the years, several approaches for human reliability analysis (HRA) have been developed. The aim of the present research is to propose a hybrid model to evaluate Human Error Probability (HEP). The new approach is based on logit-normal distribution, Nuclear Action Reliability Assessment (NARA), and Performance Shaping Factors (PSFs) relationship. In the research, shortcomings related to literature approaches are analyzed, especially the limitations of the working time. For this reason, PSFs after 8 hours (work standard) during emergency conditions were estimated. Therefore, the correlation between the advantages of these three methodologies allows proposing a HEP analysis during accident scenarios and emergencies; a fundamental issue to ensure the safety and reliability in industrial plants is emergency Mmnagement (EM). Applying EM methodology, two main aspects are analyzed: system reliability and human reliability. System reliability is strongly related to the reliability of its weakest component. During incidental situations, the weakest parts of the whole system are workers (human reliability) and accidental scenarios influence the operator's ability to make decisions. This article proposes a new approach called Logit Human Reliability (LHR) that considers internal and external factors to estimate human reliability during emergencies. LHR has been applied in a pharmaceutical accident scenario, considering 24 hours of working time (more than 8 working hours). The results highlighted that the LHR method gives output data more in conformity with data banks than the conventional methods during the stress phase in an accident scenario
A hybrid model to evaluate human error probability (HEP) in a pharmaceutical plant
The aim of the present research is to propose a hybrid model to evaluate Human Error Probability (HEP) called Logit Human Reliability (LHR). The new approach is based on logit normal distribution, Nuclear Action Reliability Assessment (NARA), and Performance Shaping Factors (PSFs) relationship. The present paper analyzed some shortcomings related to literature approaches, especially the limitations of the working time. We estimated PSFs after 8 hours (work standard) during emergency conditions. Therefore, the correlation between the advantages of these three methodologies allows proposing a HEP analysis during accident scenario and emergencies. The proposed approach considers internal and external factors that affect the operator's ability. LHR has been applied in a pharmaceutical accident scenario, considering 24 hours of working time (more than 8 working hours)
CF-GNNExplainer: Counterfactual Explanations for Graph Neural Networks
Given the increasing promise of graph neural networks (GNNs) in real-world
applications, several methods have been developed for explaining their
predictions. Existing methods for interpreting predictions from GNNs have
primarily focused on generating subgraphs that are especially relevant for a
particular prediction. However, such methods are not counterfactual (CF) in
nature: given a prediction, we want to understand how the prediction can be
changed in order to achieve an alternative outcome. In this work, we propose a
method for generating CF explanations for GNNs: the minimal perturbation to the
input (graph) data such that the prediction changes. Using only edge deletions,
we find that our method, CF-GNNExplainer, can generate CF explanations for the
majority of instances across three widely used datasets for GNN explanations,
while removing less than 3 edges on average, with at least 94\% accuracy. This
indicates that CF-GNNExplainer primarily removes edges that are crucial for the
original predictions, resulting in minimal CF explanations.Comment: Accepted to AISTATS 202
Preliminary realization of an electric-powered hydraulic pump system for a waste compactor truck and a techno-economic analysis
Most industrial trucks are equipped with hydraulic systems designed for specic operations, for which the required power is supplied by the internal combustion engine (ICE). The largest share of the power consumption is required by the hydraulic system during idling operations, and, consequently, the current literature focuses on energy saving strategies for the hydraulic system rather than making the vehicle traction more efficient. This study presents the preliminary realization of an electric-powered hydraulic pump system (e-HPS) that drives the lifting of the dumpster and the garbage compaction in a waste compactor truck, rather than traditional ICE-driven hydraulic pump systems (ICE-HPSs). The different components of the e-HPS are described and the battery pack was modelled using the kinetic battery model. The end-of-life of the battery pack was determined to assess the economic feasibility of the proposed e-HPS for the truck lifespan, using numerical simulations. The aim was twofold: To provide an implementation method to retrofit the e-HPS to a conventional waste compactor truck and to assess its economic feasibility, investigating fuel savings during the use phase and the consequent reduction of CO2 emissions. Results show that the total lifespan cost saving achieved a value of 65,000. Furthermore, total CO2 emissions for the e-HPS were about 80% lower than those of the ICE-HPS, highlighting that the e-HPS can provide significant environmental benefits in an urban context
- …