190 research outputs found
Wind-induced drift of objects at sea: the leeway field method
A method for conducting leeway field experiments to establish the drift
properties of small objects (0.1-25 m) is described. The objective is to define
a standardized and unambiguous procedure for condensing the drift properties
down to a set of coefficients that may be incorporated into existing stochastic
trajectory forecast models for drifting objects of concern to search and rescue
operations and other activities involving vessels lost at sea such as
containers with hazardous material.
An operational definition of the slip or wind and wave-induced motion of a
drifting object relative to the ambient current is proposed. This definition
taken together with a strict adherence to 10 m wind speed allows us to refer
unambiguously to the leeway of a drifting object. We recommend that all objects
if possible be studied using what we term the direct method, where the object's
leeway is studied directly using an attached current meter.
We divide drifting objects into four categories, depending on their size. For
the smaller objects (less than 0.5 m), an indirect method of measuring the
object's motion relative to the ambient current must be used. For larger
objects, direct measurement of the motion through the near-surface water masses
is strongly recommended. Larger objects are categorized according to the
ability to attach current meters and wind monitoring systems to them.
The leeway field method proposed here is illustrated with results from field
work where three objects were studied in their distress configuration; a 1:3.3
sized model of a 40-ft Shipping container, a World War II mine and a 220 l
(55-gallon) oil drum.Comment: 33 pages, 12 figures, 3 table
Emergent statistical mechanics from properties of disordered random matrix product states
The study of generic properties of quantum states has led to an abundance of
insightful results. A meaningful set of states that can be efficiently prepared
in experiments are ground states of gapped local Hamiltonians, which are well
approximated by matrix product states. In this work, we introduce a picture of
generic states within the trivial phase of matter with respect to their
non-equilibrium and entropic properties: We do so by rigorously exploring
non-translation-invariant matrix product states drawn from a local i.i.d.
Haar-measure. We arrive at these results by exploiting techniques for computing
moments of random unitary matrices and by exploiting a mapping to partition
functions of classical statistical models, a method that has lead to valuable
insights on local random quantum circuits. Specifically, we prove that such
disordered random matrix product states equilibrate exponentially well with
overwhelming probability under the time evolution of Hamiltonians featuring a
non-degenerate spectrum. Moreover, we prove two results about the entanglement
Renyi entropy: The entropy with respect to sufficiently disconnected subsystems
is generically extensive in the system-size, and for small connected systems
the entropy is almost maximal for sufficiently large bond dimensions.Comment: 11 page
The Leeway of Shipping Containers at Different Immersion Levels
The leeway of 20-foot containers in typical distress conditions is
established through field experiments in a Norwegian fjord and in open-ocean
conditions off the coast of France with wind speed ranging from calm to 14 m/s.
The experimental setup is described in detail and certain recommendations given
for experiments on objects of this size. The results are compared with the
leeway of a scaled-down container before the full set of measured leeway
characteristics are compared with a semi-analytical model of immersed
containers. Our results are broadly consistent with the semi-analytical model,
but the model is found to be sensitive to choice of drag coefficient and makes
no estimate of the cross-wind leeway of containers. We extend the results from
the semi-analytical immersion model by extrapolating the observed leeway
divergence and estimates of the experimental uncertainty to various realistic
immersion levels. The sensitivity of these leeway estimates at different
immersion levels are tested using a stochastic trajectory model. Search areas
are found to be sensitive to the exact immersion levels, the choice of drag
coefficient and somewhat less sensitive to the inclusion of leeway divergence.
We further compare the search areas thus found with a range of trajectories
estimated using the semi-analytical model with only perturbations to the
immersion level. We find that the search areas calculated without estimates of
crosswind leeway and its uncertainty will grossly underestimate the rate of
expansion of the search areas. We recommend that stochastic trajectory models
of container drift should account for these uncertainties by generating search
areas for different immersion levels and with the uncertainties in crosswind
and downwind leeway reported from our field experiments.Comment: 25 pages, 11 figures and 5 tables; Ocean Dynamics, Special Issue on
Advances in Search and Rescue at Sea (2012
The Lyman alpha reference sample. VII. Spatially resolved H kinematics
We present integral field spectroscopic observations with the Potsdam Multi
Aperture Spectrophotometer of all 14 galaxies in the Lyman Alpha
Reference Sample (LARS). We produce 2D line of sight velocity maps and velocity
dispersion maps from the Balmer (H) emission in our data
cubes. These maps trace the spectral and spatial properties of the LARS
galaxies' intrinsic Ly radiation field. We show our kinematic maps
spatially registered onto the Hubble Space Telescope H and Lyman
(Ly) images. Only for individual galaxies a causal connection
between spatially resolved H kinematics and Ly photometry can
be conjectured. However, no general trend can be established for the whole
sample. Furthermore, we compute non-parametric global kinematical statistics --
intrinsic velocity dispersion , shearing velocity ,
and the ratio -- from our kinematic maps. In
general LARS galaxies are characterised by high intrinsic velocity dispersions
(54\,km\,s median) and low shearing velocities (65\,km\,s
median). values range from 0.5 to 3.2 with an
average of 1.5. Noteworthy, five galaxies of the sample are dispersion
dominated systems with and are thus
kinematically similar to turbulent star forming galaxies seen at high redshift.
When linking our kinematical statistics to the global LARS Ly
properties, we find that dispersion dominated systems show higher Ly
equivalent widths and higher Ly escape fractions than systems with
. Our result indicates that turbulence in
actively star-forming systems is causally connected to interstellar medium
conditions that favour an escape of Ly radiation.Comment: 26 pages, 15 figures, accepted for publication in A&
From gradual spreading to catastrophic collapse - Reconstruction of the 1888 Ritter Island volcanic sector collapse from high-resolution 3D seismic data
Volcanic island flank collapses have the potential to trigger devastating tsunamis threatening coastal communities and infrastructure. The 1888 sector collapse of Ritter Island, Papua New Guinea (in the following called Ritter) is the most voluminous volcanic island flank collapse in historic times. The associated tsunami had run-up heights of more than 20 m on the neighboring islands and reached settlements 600 km away from its source. This event provides an opportunity to advance our understanding of volcanic landslide-tsunami hazards. Here, we present a detailed reconstruction of the 1888 Ritter sector collapse based on high-resolution 2D and 3D seismic and bathymetric data covering the failed volcanic edifice and the associated mass-movement deposits. The 3D seismic data reveal that the catastrophic collapse of Ritter
occurred in two phases: (1) Ritter was first affected by deep-seated, gradual spreading over a long time period, which is manifest in pronounced compressional deformation within the volcanic edifice and the adjacent seafloor sediments. A scoria cone at the foot of Ritter acted as a buttress, influencing the displacement and deformation of the western flank of the volcano and causing shearing within the volcanic edifice. (2) During the final, catastrophic phase of the collapse, about 2.4 kmÂł of Ritter disintegrated almost entirely and travelled as a highly energetic mass flow, which incised the underlying sediment. The irregular topography west of Ritter is a product of both compressional deformation and erosion. A crater-like depression underlying the recent volcanic cone and eyewitness accounts suggest that an explosion may have accompanied the catastrophic collapse. Our findings demonstrate that volcanic sector collapses may transform from slow gravitational deformation to catastrophic collapse. Understanding the processes involved in such a transformation is crucial for assessing the hazard potential of other volcanoes with slowly deforming flanks such as Mt. Etna or Kilauea
Patient recruitment into clinical studies of solid malignancies during the COVID-19 pandemic in a tertiary cancer center
Background and purpose: To analyze clinical trial activities and patient recruitment numbers into prospective clinical studies for solid malignancies during the COVID-19 pandemic in a tertiary cancer center.
Materials and methods: Patient recruitment numbers in prospective clinical studies of solid malignancies were retrospectively analyzed for the years 2019 â 2021 at the Comprehensive Cancer Center Zurich (CCCZ). Changes in recruitment numbers were tested for association with organ-specific subunits, as well as organizational and treatment-related trial characteristics. To assess differences between categorical variables, Chi-squared test was used. For uni- and multivariate analysis, Cox proportional hazards were calculated.
Results: In 2019, there were a total of 107 studies (registry trials, clinical phase I-III trials, and translational studies) recruiting 304 patients at the CCCZ. During the COVID-19 pandemic in 2020 and 2021, there were 120 and 125 active trials with a total recruitment of 355 and 666 patients, respectively. No significant differences between the subunits and study characteristics in changes of patient recruitment in clinical phase I-III trials were identified when the year prior to the COVID-19 pandemic (2019) was compared to the first year of the pandemic (2020) and to 2020-2021.
Conclusions: Despite healthcare systems around the world have experienced significant disruption due to the COVID-19 pandemic, data from our tertiary cancer center showed that clinical trial activities were maintained at a high level during the pandemic
Mechanistic insights into an engineered riboswitch: a switching element which confers riboswitch activity
While many different RNA aptamers have been identified that bind to a plethora of small molecules only very few are capable of acting as engineered riboswitches. Even for aptamers binding the same ligand large differences in their regulatory potential were observed. We address here the molecular basis for these differences by using a set of unrelated neomycin-binding aptamers. UV melting analyses showed that regulating aptamers are thermally stabilized to a significantly higher degree upon ligand binding than inactive ones. Regulating aptamers show high ligand-binding affinity in the low nanomolar range which is necessary but not sufficient for regulation. NMR data showed that a destabilized, open ground state accompanied by extensive structural changes upon ligand binding is important for regulation. In contrast, inactive aptamers are already pre-formed in the absence of the ligand. By a combination of genetic, biochemical and structural analyses, we identified a switching element responsible for destabilizing the ligand free state without compromising the bound form. Our results explain for the first time the molecular mechanism of an engineered riboswitch
Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory
The Auger Engineering Radio Array (AERA) is part of the Pierre Auger
Observatory and is used to detect the radio emission of cosmic-ray air showers.
These observations are compared to the data of the surface detector stations of
the Observatory, which provide well-calibrated information on the cosmic-ray
energies and arrival directions. The response of the radio stations in the 30
to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of
the incoming electric field. For the latter, the energy deposit per area is
determined from the radio pulses at each observer position and is interpolated
using a two-dimensional function that takes into account signal asymmetries due
to interference between the geomagnetic and charge-excess emission components.
The spatial integral over the signal distribution gives a direct measurement of
the energy transferred from the primary cosmic ray into radio emission in the
AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air
shower arriving perpendicularly to the geomagnetic field. This radiation energy
-- corrected for geometrical effects -- is used as a cosmic-ray energy
estimator. Performing an absolute energy calibration against the
surface-detector information, we observe that this radio-energy estimator
scales quadratically with the cosmic-ray energy as expected for coherent
emission. We find an energy resolution of the radio reconstruction of 22% for
the data set and 17% for a high-quality subset containing only events with at
least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO
Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy
We measure the energy emitted by extensive air showers in the form of radio
emission in the frequency range from 30 to 80 MHz. Exploiting the accurate
energy scale of the Pierre Auger Observatory, we obtain a radiation energy of
15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV
arriving perpendicularly to a geomagnetic field of 0.24 G, scaling
quadratically with the cosmic-ray energy. A comparison with predictions from
state-of-the-art first-principle calculations shows agreement with our
measurement. The radiation energy provides direct access to the calorimetric
energy in the electromagnetic cascade of extensive air showers. Comparison with
our result thus allows the direct calibration of any cosmic-ray radio detector
against the well-established energy scale of the Pierre Auger Observatory.Comment: Replaced with published version. Added journal reference and DOI.
Supplemental material in the ancillary file
- âŠ