1,116 research outputs found
Population of bound excited states in intermediate-energy fragmentation reactions
Fragmentation reactions with intermediate-energy heavy-ion beams exhibit a
wide range of reaction mechanisms, ranging from direct reactions to statistical
processes. We examine this transition by measuring the relative population of
excited states in several sd-shell nuclei produced by fragmentation with the
number of removed nucleons ranging from two to sixteen. The two-nucleon removal
is consistent with a non-dissipative process whereas the removal of more than
five nucleons appears to be mainly statistical.Comment: 5 pages, 6 figure
Atomistic modelling of large-scale metal film growth fronts
We present simulations of metallization morphologies under ionized sputter
deposition conditions, obtained by a new theoretical approach. By means of
molecular dynamics simulations using a carefully designed interaction
potential, we analyze the surface adsorption, reflection, and etching reactions
taking place during Al physical vapor deposition, and calculate their relative
probability. These probabilities are then employed in a feature-scale
cellular-automaton simulator, which produces calculated film morphologies in
excellent agreement with scanning-electron-microscopy data on ionized sputter
deposition.Comment: RevTeX 4 pages, 2 figure
Equation of state for polymer liquid crystals: theory and experiment
The first part of this paper develops a theory for the free energy of
lyotropic polymer nematic liquid crystals. We use a continuum model with
macroscopic elastic moduli for a polymer nematic phase. By evaluating the
partition function, considering only harmonic fluctuations, we derive an
expression for the free energy of the system. We find that the configurational
entropic part of the free energy enhances the effective repulsive interactions
between the chains. This configurational contribution goes as the fourth root
of the direct interactions. Enhancement originates from the coupling between
bending fluctuations and the compressibility of the nematic array normal to the
average director. In the second part of the paper we use osmotic stress to
measure the equation of state for DNA liquid crystals in 0.1M to 1M NaCl
solutions. These measurements cover 5 orders of magnitude in DNA osmotic
pressure. At high osmotic pressures the equation of state, dominated by
exponentially decaying hydration repulsion, is independent of the ionic
strength. At lower pressures the equation of state is dominated by fluctuation
enhanced electrostatic double layer repulsion. The measured equation of state
for DNA fits well with our theory for all salt concentrations. We are able to
extract the strength of the direct electrostatic double layer repulsion. This
is a new and alternative way of measuring effective charge densities along
semiflexible polyelectrolytes.Comment: text + 5 figures. Submitted to PR
Zum biochemischen Wirkungsmechanismus des adrenocorticotropen Hormons
Es wird eine Übersicht über zwei Hypothesen und die dazugehörigen Befunde zum Wirkungsmechanismus des adrenocorticotropen Hormons gegeben: 1. Der Gehalt der Nebenniere an cyclischem Adenosinmonophosphat wird durch ACTH erhöht, die stimulierende Wirkung des Hormons auf die Corticoidsynthese wird durch cyclisches Adenosinmonophosphat imitiert. Die Beschleunigung der Corticoidsynthese dürfte allerdings nicht durch eine Aktivierung der Phosphorylase in der Nebenniere erfolgen. 2. Befunde zum biochemischen Mechanismus der Stimulation der Proteinsynthese in der Nebenniere durch ACTH werden referiert. Die Intaktheit der Proteinsynthese der Nebenniere scheint für den steroidogenen Effekt des ACTH Voraussetzung zu sein.Two current hypotheses on the mechanism of action of ACTH are reviewed: 1. The content of cyclic 3,5-adenosine monophosphate of the adrenals is increased by ACTH, and cyclic AMP or ACTH enhance corticoid synthesis. However, stimulation of corticoid synthesis presumably is not mediated by activation of adrenal phosphorylase. 2. Experiments dealing with the biochemical mechanism of the stimulation of adrenal protein synthesis are reviewed. The integrity of the adrenal protein synthesis appears to be necessary for the enhancement of corticoid synthesis by ACTH
Twilight zone observation network: a distributed observation network for sustained, real-time interrogation of the ocean’s twilight zone
© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Thorrold, S. R., Adams, A., Bucklin, A., Buesseler, K., Fischer, G., Govindarajan, A., Hoagland, P., Jin, D., Lavery, A., Llopez, J., Madin, L., Omand, M., Renaud, P. G., Sosik, H. M., Wiebe, P., Yoerger, D. R., & Zhang, W. Twilight zone observation network: a distributed observation network for sustained, real-time interrogation of the Ocean’s Twilight Zone. Marine Technology Society Journal, 55(3), (2021): 92–93, https://doi.org/10.4031/MTSJ.55.3.46.The ocean's twilight zone (TZ) is a vast, globe-spanning region of the ocean. Home to myriad fishes and invertebrates, mid-water fishes alone may constitute 10 times more biomass than all current ocean wild-caught fisheries combined. Life in the TZ supports ocean food webs and plays a critical role in carbon capture and sequestration. Yet the ecological roles that mesopelagic animals play in the ocean remain enigmatic. This knowledge gap has stymied efforts to determine the effects that extraction of mesopelagic biomass by industrial fisheries, or alterations due to climate shifts, may have on ecosystem services provided by the open ocean. We propose to develop a scalable, distributed observation network to provide sustained interrogation of the TZ in the northwest Atlantic. The network will leverage a “tool-chest” of emerging and enabling technologies including autonomous, unmanned surface and underwater vehicles and swarms of low-cost “smart” floats. Connectivity among in-water assets will allow rapid assimilation of data streams to inform adaptive sampling efforts. The TZ observation network will demonstrate a bold new step towards the goal of continuously observing vast regions of the deep ocean, significantly improving TZ biomass estimates and understanding of the TZ's role in supporting ocean food webs and sequestering carbon.This research is part of the Woods Hole Oceanographic Institution’s Ocean Twilight Zone Project, funded as part of The Audacious Project housed at TED
The Ethics of Care: Normative Structures and Empirical Implications
In this article I argue that the ethics of care provides us with a novel reading of human relations, and therefore makes possible a fresh approach to several empirical challenges. In order to explore this connection, I discuss some specific normative features of the ethics of care—primarily the comprehension of the moral agent and the concept of care—as these two key elements contribute substantially to a new ethical outlook. Subsequently, I argue that the relational and reciprocal mode of thinking with regard to the moral agent must be extended to our understanding of care. I term this comprehension “mature care”. Citing conflicts of interests as examples, I demonstrate how this conceptualization of care may further advance the ethics of care’s ability to take on empirical challenges. Finally, I discuss political implications that may emanate from the ethics of care and the concept of mature care
Biotransfer possibilities of selenium from plants used in phytoremediation
We are investigating the biotransfer of accumulated Se by the plant in several
phytoremediation systems. In study I, we evaluated the biotransfer of Se from Indian
mustard, a Brassica species, to the insect-cabbage looper (Trichoplusia ni); mortality,
deterrence, and biomagnification of Se were examined. We determined that
feeding behavior of food chain consumers was affected not only by the plant
concentration of Se, but also by the mobility of the insects and choice of feed
available. In study II, we examined the survival and development of beet armyworm
(Spodoptera exigua) fed Se-enriched plant tissues from different lines of saltbush
(Atriplex spp.) After feeding on lines of saltbush that produced high biomass and
accumulated high concentrations of Se, insect growth and survival was reduced. In
studies III, IV, and V, lambs, dairy cows, and rabbits were fed Se-enriched Brassica
and Medicago (alfalfa) plants as part of their feed ration. None of the tested animals
exhibited any Se toxicity symptoms, but they had increased levels of Se in most
tissues sampled (e.g., organs, blood, urine, feces), excluding milk. In study VI, we
evaluated biotransfer of Se from broccoli to rats to determine efficacy of Se for
reducing colon cancer. We found that Se-enriched plant material was more effective
than inorganic sources of Se for preventing precancerous colon lesions. Results from
all studies clearly show that Se absorbed by plants can be transferred biologically in
an intentional or unintentional manner to insects and animals
Practicing Imperfect Forgiveness
Forgiveness is typically regarded as a good thing - even a virtue - but acts of forgiveness can vary widely in value, depending on their context and motivation. Faced with this variation, philosophers have tended to reinforce everyday concepts of forgiveness with strict sets of conditions, creating ideals or paradigms of forgiveness. These are meant to distinguish good or praiseworthy instances of forgiveness from problematic instances and, in particular, to protect the self-respect of would-be forgivers. But paradigmatic forgiveness is problematic for a number of reasons, including its inattention to forgiveness as a gendered trait. We can account for the values and the risks associated with forgiving far better if we treat it as a moral practice and not an ideal
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