653 research outputs found
Scalable Online Conformance Checking Using Incremental Prefix-Alignment Computation
Conformance checking techniques aim to collate observed process behavior with
normative/modeled process models. The majority of existing approaches focuses
on completed process executions, i.e., offline conformance checking. Recently,
novel approaches have been designed to monitor ongoing processes, i.e., online
conformance checking. Such techniques detect deviations of an ongoing process
execution from a normative process model at the moment they occur. Thereby,
countermeasures can be taken immediately to prevent a process deviation from
causing further, undesired consequences. Most online approaches only allow to
detect approximations of deviations. This causes the problem of falsely
detected deviations, i.e., detected deviations that are actually no deviations.
We have, therefore, recently introduced a novel approach to compute exact
conformance checking results in an online environment. In this paper, we focus
on the practical application and present a scalable, distributed implementation
of the proposed online conformance checking approach. Moreover, we present two
extensions to said approach to reduce its computational effort and its
practical applicability. We evaluate our implementation using data sets
capturing the execution of real processes
How do we accelerate while running?
Running biomechanics are well established in terms of lower extremity joint kinetics as is the direct relationship between these variables and running speed. Many studies have investigated the differences in these variables when running velocity was increased in discrete increments but investigations of accelerated running in which velocity is continually increasing are almost non-existent. One investigation of the acceleration phase of running showed that joint torques did not increase while accelerating. These results cannot be aligned with the fully established results of running biomechanics at different speeds. We expected the joint torques to increase in magnitude for each step during the acceleration phase based on the previous research investigating increases in running velocity. The purpose of this study was to quantify lower extremity joint torques and powers during constant speed running and during running while accelerating at two rates of acceleration between a baseline velocity of 2.50 ms�¹ to a maximal velocity of 6.00 ms�¹. It was hypothesized that lower extremity sagittal plane joint torques and joint powers would positively and linearly increase throughout the acceleration phase of running. 15 young, healthy runners (n = 8 females) between the ages of 18 and 22 were analyzed on an instrumented treadmill while accelerating at 0.40 ms�² (A1) and 0.80 ms�² (A2) from the initial to final velocities. Inverse dynamics were used to determine lower limb joint torques and powers using ground reaction forces and kinematic data collected by 3D motion capture. Correlation and regression analyses were used to identify the relationships between mean, maximum hip, knee, and ankle torques and power to step number during the constant velocity and acceleration phase. The results of this study showed a significant increase in the joint torques and joint powers per step in both conditions A1 and A2 at the hip, knee, and ankle joints during the acceleration phase when the regression beta weights and correlation coefficients were tested for significance (p < 0.05). It was also observed that the knee and ankle joint torques and the hip, knee, and ankle joint powers had significantly greater increases per step in condition A2. There was no significant difference in the beta weights in hip joint torque between conditions A1 and A2. The constant state, pre- and post-acceleration phases had no relationship between joint torque and step number and joint power and step number in almost every variable, with three exceptions. There was a significant, direct increase in magnitude in hip joint power during the pre-acceleration period of condition A1, as well as hip joint torque during the post-acceleration period of condition A2. Additionally, a significant inverse relationship was seen in ankle joint power in condition A2 in the post-acceleration period. Finally, it was observed that the hip and ankle are the primary contributors to accelerating while running based on the magnitude of the beta weights of these variables, with the knee also contributing but not as much as the hip and ankle. In conclusion, in contrast to a previous study, our data suggest that hip, knee, and ankle torques doincrease during accelerated running on a step by step basis as do hip, knee, and ankle joint powers. Therefore, the tested hypothesis was supported based on the results of this study.M.S
Modeling, Analysis and Simulation Approaches Used in Development of the National Aeronautics and Space Administration Max Launch Abort System
The National Aeronautics and Space Administration (NASA) Engineering and Safety Center was chartered to develop an alternate launch abort system (LAS) as risk mitigation for the Orion Project. Its successful flight test provided data for the design of future LAS vehicles. Design of the flight test vehicle (FTV) and pad abort trajectory relied heavily on modeling and simulation including computational fluid dynamics for vehicle aero modeling, 6-degree-of-freedom kinematics models for flight trajectory modeling, and 3-degree-of-freedom kinematics models for parachute force modeling. This paper highlights the simulation techniques and the interaction between the aerodynamics, flight mechanics, and aerodynamic decelerator disciplines during development of the Max Launch Abort System FTV
Towards Debiasing Fact Verification Models
Fact verification requires validating a claim in the context of evidence. We
show, however, that in the popular FEVER dataset this might not necessarily be
the case. Claim-only classifiers perform competitively with top evidence-aware
models. In this paper, we investigate the cause of this phenomenon, identifying
strong cues for predicting labels solely based on the claim, without
considering any evidence. We create an evaluation set that avoids those
idiosyncrasies. The performance of FEVER-trained models significantly drops
when evaluated on this test set. Therefore, we introduce a regularization
method which alleviates the effect of bias in the training data, obtaining
improvements on the newly created test set. This work is a step towards a more
sound evaluation of reasoning capabilities in fact verification models.Comment: EMNLP IJCNLP 201
Optimizing the α1B-adrenergic receptor for solution NMR studies
Sample preparation for NMR studies of G protein-coupled receptors faces special requirements: Proteins need to be stable for prolonged measurements at elevated temperatures, they should ideally be uniformly labeled with the stable isotopes 13C, 15N, and all carbon-bound protons should be replaced by deuterons. In addition, certain NMR experiments require protonated methyl groups in the presence of a perdeuterated background. All these requirements are most easily satisfied when using Escherichia coli as the expression host. Here we describe a workflow, starting from a temperature-stabilized mutant of the α1B-adrenergic receptor, obtained using the CHESS methodology, into an even more stable species, in which flexible parts from termini were removed and the intracellular loop 3 (ICL3) was stabilized against proteolytic cleavage. The yield after purification corresponds to 1–2 mg/L of D2O culture. The final purification step is ligand-affinity chromatography to ensure that only well-folded ligand-binding protein is isolated. Proper selection of detergent has a remarkable influence on the quality of NMR spectra. All optimization steps of sequence and detergent are monitored on a small scale by monitoring the melting temperature and long-term thermal stability to allow for screening of many conditions. The stabilized mutant of the α1B-adrenergic receptor was additionally incorporated in nanodiscs, but displayed slightly inferior spectra compared to a sample in detergent micelles. Finally, both [15N,1H]- as well as [13C,1H]- HSQC spectra are shown highlighting the high quality of the final NMR sample. Importantly, the quality of [13C,1H]-HSQC spectra indicates that the so prepared receptor could be used for studying side-chain dynamics
The Wyoming Survey for H-alpha. I. Initial Results at z ~ 0.16 and 0.24
The Wyoming Survey for H-alpha, or WySH, is a large-area, ground-based,
narrowband imaging survey for H-alpha-emitting galaxies over the latter half of
the age of the Universe. The survey spans several square degrees in a set of
fields of low Galactic cirrus emission. The observing program focuses on
multiple dz~0.02 epochs from z~0.16 to z~0.81 down to a uniform
(continuum+line) luminosity at each epoch of ~10^33 W uncorrected for
extinction (3sigma for a 3" diameter aperture). First results are presented
here for 98+208 galaxies observed over approximately 2 square degrees at
redshifts z~0.16 and 0.24, including preliminary luminosity functions at these
two epochs. These data clearly show an evolution with lookback time in the
volume-averaged cosmic star formation rate. Integrals of Schechter fits to the
extinction-corrected H-alpha luminosity functions indicate star formation rates
per co-moving volume of 0.009 and 0.014 h_70 M_sun/yr/Mpc^3 at z~0.16 and 0.24,
respectively. The formal uncertainties in the Schechter fits, based on this
initial subset of the survey, correspond to uncertainties in the cosmic star
formation rate density at the >~40% level; the tentative uncertainty due to
cosmic variance is 25%, estimated from separately carrying out the analysis on
data from the first two fields with substantial datasets.Comment: To appear in the Astronomical Journa
Apolipoprotein E mediates evasion from hepatitis C virus−neutralizing antibodies
Background & Aims
Efforts to develop an effective vaccine against hepatitis C virus (HCV) have been hindered by the propensity of the virus to evade host immune responses. HCV particles in serum and in cell culture associate with lipoproteins, which contribute to viral entry. Lipoprotein association has also been proposed to mediate viral evasion of the humoral immune response, though the mechanisms are poorly defined.
Methods
We used small interfering RNAs to reduce levels of apolipoprotein E (apoE) in cell culture−derived HCV−producing Huh7.5-derived hepatoma cells and confirmed its depletion by immunoblot analyses of purified viral particles. Before infection of naïve hepatoma cells, we exposed cell culture−derived HCV strains of different genotypes, subtypes, and variants to serum and polyclonal and monoclonal antibodies isolated from patients with chronic HCV infection. We analyzed the interaction of apoE with viral envelope glycoprotein E2 and HCV virions by immunoprecipitation.
Results
Through loss-of-function studies on patient-derived HCV variants of several genotypes and subtypes, we found that the HCV particle apoE allows the virus to avoid neutralization by patient-derived antibodies. Functional studies with human monoclonal antiviral antibodies showed that conformational epitopes of envelope glycoprotein E2 domains B and C were exposed after depletion of apoE. The level and conformation of virion-associated apoE affected the ability of the virus to escape neutralization by antibodies.
Conclusions
In cell-infection studies, we found that HCV-associated apoE helps the virus avoid neutralization by antibodies against HCV isolated from chronically infected patients. This method of immune evasion poses a challenge for the development of HCV vaccines
Retrievals of Aerosol Optical and Microphysical Properties from Imaging Polar Nephelometer Scattering Measurements
A method for the retrieval of aerosol optical and microphysical properties from in situ light-scattering measurements is presented and the results are compared with existing measurement techniques. The Generalized Retrieval of Aerosol and Surface Properties (GRASP) is applied to airborne and laboratory measurements made by a novel polar nephelometer. This instrument, the Polarized Imaging Nephelometer (PI-Neph), is capable of making high-accuracy field measurements of phase function and degree of linear polarization, at three visible wavelengths, over a wide angular range of 3 to 177. The resulting retrieval produces particle size distributions (PSDs) that agree, within experimental error, with measurements made by commercial optical particle counters (OPCs). Additionally, the retrieved real part of the refractive index is generally found to be within the predicted error of 0.02 from the expected values for three species of humidified salt particles, with a refractive index that is well established. The airborne measurements used in this work were made aboard the NASA DC-8 aircraft during the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) field campaign, and the inversion of this data represents the first aerosol retrievals of airborne polar nephelometer data. The results provide confidence in the real refractive index product, as well as in the retrieval's ability to accurately determine PSD, without assumptions about refractive index that are required by the majority of OPCs
Clustering of red galaxies around the z=1.53 quasar 3C270.1
In the paradigm of hierarchical galaxy formation, luminous radio galaxies
mark mass assembly peaks that should contain clusters of galaxies. Observations
of the z=1.53 quasar 3C270.1 with the Spitzer Space Telescope at 3.6-24 micron
and with the 6.5-m MMT in the z'- and Y-bands allow detection of potential
cluster members via photometric redshifts. Compared with nearby control fields,
there is an excess of 11 extremely red objects (EROs) at 1.33 < z_phot < 1.73,
consistent with a proto-cluster around the quasar. The spectral energy
distributions (SEDs) of 3/4 of the EROs are better fitted with passive
elliptical galaxies than withdust-reddened starbursts, and of four sources
well-detected on an archival HST snapshot image, all have undisturbed
morphologies. However, one ERO, not covered by the HST image, is a double
source with 0.8" separation on the z' image and a marginal (2sigma) 24 micron
detection indicating a dust-enshrouded starburst. The EROs are more luminous
than L* (H = -23.6 AB mag at z=1.5).Comment: 12 pages, 7 figures, accepted by Ap
Interference and interaction effects in multi-level quantum dots
Using renormalization group techniques, we study spectral and transport
properties of a spinless interacting quantum dot consisting of two levels
coupled to metallic reservoirs. For strong Coulomb repulsion and an applied
Aharonov-Bohm phase , we find a large direct tunnel splitting
between the levels of
the order of the level broadening . As a consequence we discover a
many-body resonance in the spectral density that can be measured via the
absorption power. Furthermore, for , we show that the system can be
tuned into an effective Anderson model with spin-dependent tunneling.Comment: 5 pages, 4 figures included, typos correcte
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