With the expansion of hydropower, in‐stream converters, flood‐protection infrastructures, and growing concerns on deltas fragile ecosystems, there is a pressing need to evaluate and monitor bedform ...sediment mass flux. It is critical to estimate real‐time bedform size and migration velocity and provide a theoretical framework to convert easily accessible time histories of bed elevations into spatially evolving patterns. We collected spatiotemporally resolved bathymetries from laboratory flumes and the Colorado River in statistically steady, homogeneous, subcritical flow conditions. Wave number and frequency spectra of bed elevations show compelling evidence of scale‐dependent velocity for the hierarchy of migrating bedforms observed in the laboratory and field. New scaling laws were applied to describe the full range of migration velocities as function of two dimensionless groups based on the bed shear velocity, sediment diameter, and water depth. Further simplification resulted in a mixed length scale model estimating scale‐dependent migration velocities, without requiring bedform classification or identification.
Plain Language Summary
Sand and gravel sediment in river beds often forms wave‐like patterns called ripples or dunes, which are collectively referred to as bedforms. The flow of the river causes bedforms to form and slowly travel downstream, thus contributing to sediment transport, erosion, and deposition along the river and to the evolution of deltas. Predicting how fast bedforms move can improve our ability to estimate sediment load carried by rivers. In this study, experimental measurements of bedforms in a laboratory facility and in the Colorado River are used to better understand bedform movement. This study confirms that smaller bedforms move faster than larger bedforms and provides a simple equation to predict the speed of moving bedforms of different sizes based on the bedform length, the size of the sediment grains, and the depth of the river.
Key Points
Scale‐dependent bedform migration velocities are confirmed using laboratory and field measurements
Bedform velocity depends on stream depth, sediment diameter and shear velocity, reorganized into frictional and bankfull scaling parameters
A mixed length scale is proposed in a simplified predictive model
Background coming from the Formula omittedAr decay chain is considered to be one of the most relevant for the Gerda experiment, which searches for the neutrinoless double beta decay of Formula ...omittedGe. The sensitivity strongly relies on the absence of background around the Q-value of the decay. Background coming from Formula omittedK, a progeny of Formula omittedAr, can contribute to that background via electrons from the continuous spectrum with an endpoint at 3.5 MeV. Research and development on the suppression methods targeting this source of background were performed at the low-background test facility LArGe . It was demonstrated that by reducing Formula omittedK ion collection on the surfaces of the broad energy germanium detectors in combination with pulse shape discrimination techniques and an argon scintillation veto, it is possible to suppress Formula omittedK background by three orders of magnitude. This is sufficient for Phase II of the Gerda experiment.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).The GERmanium Detector Array (Gerda) at the Gran Sasso Underground Laboratory (LNGS) searches for the neutrinoless double ...beta decay (...) of ...Ge. Germanium detectors made of material with an enriched ...Ge fraction act simultaneously as sources and detectors for this decay. During Phase I of theexperiment mainly refurbished semi-coaxial Ge detectors from former experiments were used. For the upcoming Phase II, 30 new ...Ge enriched detectors of broad energy germanium (BEGe)-type were produced. A subgroup of these detectors has already been deployed in Gerda during Phase I. The present paper reviews the complete production chain of these BEGe detectors including isotopic enrichment, purification, crystal growth and diode production. The efforts in optimizing the mass yield and in minimizing the exposure of the ...Ge enriched germanium to cosmic radiation during processing are described. Furthermore, characterization measurements in vacuum cryostats of the first subgroup of seven BEGe detectors and their long-term behavior in liquid argon are discussed. The detector performance fulfills the requirements needed for the physics goals of Gerda Phase II.
Background coming from the 42Ar decay chain is considered to be one of the most relevant for the Gerda experiment, which searches for the neutrinoless double beta decay of 76Ge. The sensitivity ...strongly relies on the absence of background around the Q-value of the decay. Background coming from 42K, a progeny of 42Ar, can contribute to that background via electrons from the continuous spectrum with an endpoint at 3.5 MeV. Research and development on the suppression methods targeting this source of background were performed at the low-background test facility LArGe . It was demonstrated that by reducing 42K ion collection on the surfaces of the broad energy germanium detectors in combination with pulse shape discrimination techniques and an argon scintillation veto, it is possible to suppress 42K background by three orders of magnitude. This is sufficient for Phase II of the Gerda experiment.
An optimisation of the geometrical model of a p-type detector used for material screening was carried out to improve the accuracy of Monte Carlo simulations in reproducing spectrometric measurements. ...Gamma-ray sources were measured to determine the dimensions of the detector dead layer and borehole. An agreement between simulations and measurement within 3% was achieved at energies above 100
keV. In contrast, discrepancies on the order of 23% were encountered using the nominal parameters from the detector manufacturer.
LArGe is a GERDA low-background test facility to study novel background suppression methods in a low-background environment, for future application in the GERDA experiment. Similar to GERDA, LArGe ...operates bare germanium detectors submersed into liquid argon (1 m3, 1.4tons), which in addition is instrumented with photomultipliers to detect argon scintillation light. The light is used in anti-coincidence with the germanium detectors to effectively suppress background events that deposit energy in the liquid argon. The background suppression efficiency was studied in combination with a pulse shape discrimination (PSD) technique using a BEGe detector for various sources, which represent characteristic backgrounds to GERDA. Suppression factors of a few times 103 have been achieved. First background data of LArGe with a coaxial HPGe detector (without PSD) yield a background index of the order 10−2 cts/(keV-kg-y), which is at the level of the GERDA phase I design goal. As a consequence of these results, the development of an active liquid argon veto in GERDA is pursued.
Representatives (AgY, CuY, AgEr, CuDy, MgY and MgCe) of the newly discovered family of ductile stoichiometric B2 intermetallic (metal–rare-earth element, MR) compounds were characterized by X-ray ...diffraction, to determine if their anomalous ductility is related to an exceptional level of phase purity, lack of chemical ordering or a strong crystallographic texture. Brittle NiAl served as an anti-type in this study. We found that all of the rare-earth compounds, except MgY, have a significant volume fraction (∼5–20
vol.%) of second phases (M
2R intermetallics and R
2O
3 oxides), which has not been reported in previous studies of these materials. The most ductile of observed MR compounds, AgY, is highly ordered. A moderate texture was observed in AgY, which may explain its higher ductility (using polycrystal modeling) as compared to other MR compounds. However, the intrinsic polycrystalline ductility of these compounds in the randomly textured state (like that observed in CuY) still has no specific, definitive explanation.
Surgery and radiation are the mainstays of therapy for human gliomas that are the most common primary brain tumors. Most recently, cell culture and animal studies provided the first convincing ...evidence that radiation not only eliminates tumor cells, but also modulates the immune response and likely improves anti-tumor immunotherapy.
We present an in vivo study that analyzes the effects of radiation on the immune response in tumor patients. As readout system, we utilized the reactivity of glioma patients' sera against antigen GLEA2 as the most frequent antigen immunogenic in glioblastoma patients. We established an ELISA assay to analyze reactivity of 24 glioblastoma patients over a period of several months. As control we used 30 sera from healthy donors as well as 30 sera from lung cancer patients. We compared the course of GLEA2 seroreactivity at different times prior, during and after radiation. The GLEA2 seroreactivity was increased by the time of surgery, decreased after surgery, increased again under radiation, and slightly decreased after radiation.
Our results provide in vivo evidence for an increased antibody response against tumor antigens under radiation. Antigens that become immunogenic with an increased antibody response as result of radiation can serve as ideal targets for immunotherapy of human tumors.
In present and future experiments in the field of rare events physics a background index of 10
−3 counts/(keV
kg
a) or better in the region of interest is envisaged. A thorough material screening is ...mandatory in order to achieve this goal. The results of a systematic study of radioactive trace impurities in selected materials using ultra low-level gamma-ray spectrometry in the framework of the GERDA experiment are reported.
Older men have the highest suicide rates worldwide, yet few interventions have been shown effective in reducing suicide risk in middle-age or older men (Lapierre et al., 2011). We developed and ...tested a novel, 12-session Meaning-Centered Men’s Group (MCMG) intervention with 100–120 cognitively-intact, community-residing men 55 years or older who were struggling to adjust to retirement, a transition associated for some with increased suicide risk. The intervention draws on research demonstrating negative associations of Meaning in Life (MIL) with depression and suicide ideation (Heisel & Flett, 2014, 2016), and aims to build camaraderie through group discussions about finding meaning in work, leisure, relationships, and generativity. This paper summarizes findings from this on-going study, including controlled analyses comparing MCMG with a current-events discussion group, and experiences disseminating MCMG to distant sites. Discussion will focus on helping men adjust meaningfully to retirement and preventing the onset or exacerbation of suicide ideation.
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