5,455 research outputs found
Simulation of the Burridge-Knopoff Model of Earthquakes with Variable Range Stress Transfer
Simple models of earthquake faults are important for understanding the
mechanisms for their observed behavior, such as Gutenberg-Richter scaling and
the relation between large and small events, which is the basis for various
forecasting methods. Although cellular automaton models have been studied
extensively in the long-range stress transfer limit, this limit has not been
studied for the Burridge-Knopoff model, which includes more realistic friction
forces and inertia. We find that the latter model with long-range stress
transfer exhibits qualitatively different behavior than both the long-range
cellular automaton models and the usual Burridge-Knopoff model with nearest
neighbor springs, depending on the nature of the velocity-weakening friction
force. This result has important implications for our understanding of
earthquakes and other driven dissipative systems.Comment: 4 pages, 5 figures, published on Phys. Rev. Let
Earthquake swarm in the Santa Barbara Channel, California, 1968
Sixty-three minor earthquakes (maximum magnitude = 5.2) occurred in the Santa Barbara Channel during the period June 26 to August 3 1968. The epicenters form a shot-scatter pattern upon a broad, high-standing fault block in the channel midway between Santa Cruz Island and the City of Santa Barbara. Focal mechanism studies indicate that oblique-slip movement occurred along a northwest-striking fault even though the major folds and faults strike nearly east-west. Preliminary studies of the areal hydrocarbon production data show no compelling evidence for a causal relationship with the swarm
The Keck Aperture Masking Experiment: spectro-interferometry of 3 Mira Variables from 1.1 to 3.8 microns
We present results from a spectro-interferometric study of the Miras o Cet, R
Leo and W Hya obtained with the Keck Aperture Masking Experiment from 1998 Sep
to 2002 Jul. The spectrally dispersed visibility data permit fitting with
circularly symmetric brightness profiles such as a simple uniform disk. The
stellar angular diameter obtained over up to ~ 450 spectral channels spaning
the region 1.1-3.8 microns is presented. Use of a simple uniform disk
brightness model facilitates comparison between epochs and with existing data
and theoretical models. Strong size variations with wavelength were recorded
for all stars, probing zones of H2O, CO, OH, and dust formation. Comparison
with contemporaneous spectra extracted from our data show a strong
anti-correlation between the observed angular diameter and flux. These
variations consolidate the notion of a complex stellar atmosphere consisting of
molecular shells with time-dependent densities and temperatures. Our findings
are compared with existing data and pulsation models. The models were found to
reproduce the functional form of the wavelength vs. angular diameter curve
well, although some departures are noted in the 2.8-3.5 micron range.Comment: 10 pages, 10 figures Accepted to Ap
Self-Similarity of Friction Laws
The change of the friction law from a mesoscopic level to a macroscopic level
is studied in the spring-block models introduced by Burridge-Knopoff. We find
that the Coulomb law is always scale invariant. Other proposed scaling laws are
only invariant under certain conditions.}Comment: Plain TEX. Figures not include
Observations of Mira stars with the IOTA/FLUOR interferometer and comparison with Mira star models
We present K'-band observations of five Mira stars with the IOTA
interferometer. The interferograms were obtained with the FLUOR fiber optics
beam combiner, which provides high-accuracy visibility measurements in spite of
time-variable atmospheric conditions. For the M-type Miras X Oph, R Aql, RU
Her, R Ser, and the C-type Mira V CrB we derived the uniform-disk diameters
11.7mas, 10.9mas, 8.4mas, 8.1mas, and 7.9mas (+/- 0.3mas), respectively.
Simultaneous photometric observations yielded the bolometric fluxes. The
derived angular Rosseland radii and the bolometric fluxes allowed the
determination of effective temperatures. For instance, the effective
temperature of R Aql was determined to be 2970 +/- 110 K. A linear Rosseland
radius for R Aql of (250 +100/-60) Rsun was derived from the angular Rosseland
radius of 5.5mas +/- 0.2mas and the HIPPARCOS parallax of 4.73mas +/- 1.19mas.
The observations were compared with theoretical Mira star models of Bessel et
al. (1996) and Hofmann et al. (1998). The effective temperatures of the M-type
Miras and the linear radius of R Aql indicate fundamental mode pulsation.Comment: 12 pages, 4 postscript figure
Clinical outcome and long-term follow-up after liposuction procedures
Liposuction is one of the most common aesthetic procedure used in plastic surgery. Reports are available on the results, the probable complications, and the feedback of patients. However, systematic studies dealing with these aspects using reliable large-enough data are still needed. The data comprised 116 procedures during a 6-year period up to 2005. The data were processed and categories of results were formed. Furthermore, a follow-up examination and a survey on the feedback of patients were carried out. Significant differences were identified in indications, results, and complications. The follow-up examinations and the survey showed satisfying results. In the majority of cases, surgeons were satisfied with the operations. In conclusion, if conducted by qualified surgeons in appropriate surgical conditions and postoperative care possibilities, liposuction may be considered as a reliable surgical procedure. The success of this procedure depends, however, on suitable infrastructure and operative competenc
Near mean-field behavior in the generalized Burridge-Knopoff earthquake model with variable range stress transfer
Simple models of earthquake faults are important for understanding the
mechanisms for their observed behavior in nature, such as Gutenberg-Richter
scaling. Because of the importance of long-range interactions in an elastic
medium, we generalize the Burridge-Knopoff slider-block model to include
variable range stress transfer. We find that the Burridge-Knopoff model with
long-range stress transfer exhibits qualitatively different behavior than the
corresponding long-range cellular automata models and the usual
Burridge-Knopoff model with nearest-neighbor stress transfer, depending on how
quickly the friction force weakens with increasing velocity. Extensive
simulations of quasiperiodic characteristic events, mode-switching phenomena,
ergodicity, and waiting-time distributions are also discussed. Our results are
consistent with the existence of a mean-field critical point and have important
implications for our understanding of earthquakes and other driven dissipative
systems.Comment: 24 pages 12 figures, revised version for Phys. Rev.
Detection of Bursts from FRB 121102 with the Effelsberg 100-m Radio Telescope at 5 GHz and the Role of Scintillation
FRB 121102, the only repeating fast radio burst (FRB) known to date, was
discovered at 1.4 GHz and shortly after the discovery of its repeating nature,
detected up to 2.4 GHz. Here we present three bursts detected with the 100-m
Effelsberg radio telescope at 4.85 GHz. All three bursts exhibited frequency
structure on broad and narrow frequency scales. Using an autocorrelation
function analysis, we measured a characteristic bandwidth of the small-scale
structure of 6.41.6 MHz, which is consistent with the diffractive
scintillation bandwidth for this line of sight through the Galactic
interstellar medium (ISM) predicted by the NE2001 model. These were the only
detections in a campaign totaling 22 hours in 10 observing epochs spanning five
months. The observed burst detection rate within this observation was
inconsistent with a Poisson process with a constant average occurrence rate;
three bursts arrived in the final 0.3 hr of a 2 hr observation on 2016 August
20. We therefore observed a change in the rate of detectable bursts during this
observation, and we argue that boosting by diffractive interstellar
scintillations may have played a role in the detectability. Understanding
whether changes in the detection rate of bursts from FRB 121102 observed at
other radio frequencies and epochs are also a product of propagation effects,
such as scintillation boosting by the Galactic ISM or plasma lensing in the
host galaxy, or an intrinsic property of the burst emission will require
further observations.Comment: Accepted to ApJ. Minor typos correcte
Reducing preventable adverse events in obstetrics by improving interprofessional communication skills - Results of an intervention study.
BACKGROUND: Progress in medicine involves the structured analysis and communication of errors. Comparability between the individual disciplines is only possible to a limited extent and obstetrics plays a special role: the expectation of a self-determined and joyful event meets with possibly serious complications in highly complex care situations. This must be managed by an interdisciplinary team with an increasingly condensed workload. Adverse events cannot be completely controlled. However, taking controllable risk factors into account and with a focused communication a reduction of preventable adverse events is possible. In the present study, the effect of interprofessional team training on preventable adverse events in an obstetric department was investigated. METHODS: The training consisted of a 4-h interdisciplinary training session based on psychological theories. Preventable adverse events were defined in six categories according to potential patterns of causation. 2,865 case records of a refence year (2018) and 2,846 case records of the year after the intervention (2020) were retrospectively evaluated. To determine the communication training effect, the identified preventable adverse events of 2018 and 2020 were compared according to categories and analyzed for obstetrically relevant controllable and uncontrollable risk factors. Questionnaires were used to identify improvements in self-reported perceptions and behaviors. RESULTS: The results show that preventable adverse events in obstetrics were significantly reduced after the intervention compared to the reference year before the intervention (13.35% in the year 2018 vs. 8.83% in 2020, p < 0.005). Moreover, obstetrically controllable risk factors show a significant reduction in the year after the communication training. The questionnaires revealed an increase in perceived patient safety (t(28) = 4.09, p < .001), perceived communication behavior (t(30) = -2.95, p = .006), and self-efficacy to cope with difficult situations (t(28) = -2.64, p = .013). CONCLUSIONS: This study shows that the communication training was able to reduce preventable adverse events and thus increase patient safety. In the future, regular trainings should be implemented alongside medical emergency trainings in obstetrics to improve patient safety. Additionally, this leads to the strengthening of human factors and ultimately also to the prevention of second victims. Further research should follow up implementing active control groups and a randomized-controlled trail study design. TRIAL REGISTRATION: The study was approved by the Ethics Committee of University Hospital (protocol code 114/19-FSt/Sta, date of approval 29 May 2019), study registration: NCT03855735
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