1,149 research outputs found
Topos-Theoretic Extension of a Modal Interpretation of Quantum Mechanics
This paper deals with topos-theoretic truth-value valuations of quantum
propositions. Concretely, a mathematical framework of a specific type of modal
approach is extended to the topos theory, and further, structures of the
obtained truth-value valuations are investigated. What is taken up is the modal
approach based on a determinate lattice \Dcal(e,R), which is a sublattice of
the lattice \Lcal of all quantum propositions and is determined by a quantum
state and a preferred determinate observable . Topos-theoretic extension
is made in the functor category \Sets^{\CcalR} of which base category
\CcalR is determined by . Each true atom, which determines truth values,
true or false, of all propositions in \Dcal(e,R), generates also a
multi-valued valuation function of which domain and range are \Lcal and a
Heyting algebra given by the subobject classifier in \Sets^{\CcalR},
respectively. All true propositions in \Dcal(e,R) are assigned the top
element of the Heyting algebra by the valuation function. False propositions
including the null proposition are, however, assigned values larger than the
bottom element. This defect can be removed by use of a subobject
semi-classifier. Furthermore, in order to treat all possible determinate
observables in a unified framework, another valuations are constructed in the
functor category \Sets^{\Ccal}. Here, the base category \Ccal includes all
\CcalR's as subcategories. Although \Sets^{\Ccal} has a structure
apparently different from \Sets^{\CcalR}, a subobject semi-classifier of
\Sets^{\Ccal} gives valuations completely equivalent to those in
\Sets^{\CcalR}'s.Comment: LaTeX2
Narrow Linewidth 780 nm Distributed Feedback Lasers for Cold Atom Quantum Technology
Cold atom quantum technology systems have a wide range of potential applications which includes atomic clocks, rotational sensors, inertial sensors, quantum navigators, magnetometers and gravimeters. The UK Quantum Technology Hub in Sensors and Metrology has the aim of developing miniature cold atom systems using an approach similar to that pioneered by the chip scale atomic clock where microfabricated vacuum chambers have atomic transitions excited and probed by lasers. Whilst narrow linewidth Ti:Sa and external cavity diode lasers have been required for cooling and control, such lasers are too large, power hungry and expensive for future miniature cold atom systems.
Here we demonstrate 1 mm long 780.24 nm GaAs/AlGaAs distributed feedback (DFB) lasers aimed at 87Rb cold atom systems operating at 20 ĖC with over 50 mW of power and side-mode suppression ratios of 46 dB using sidewall gratings and no regrowth. Rb spectroscopy is used to demonstrate linewidths below the required 6.07 MHz natural linewidth of the 87Rb D2 optical transition used for cooling. Initial packaged fibre-coupled devices demonstrate lifetimes greater than 200 hours. We also investigate the use of integrated semiconductor amplifiers (SOAs) and longer devices to further reduce the linewidths well below 1 MHz. A range of options to control the populations of electrons in the hyperfine split energy levels spaced by 3.417 GHz are examined. Two integrated lasers, integrated electro-absorption modulators (EAMs) and the direct modulation of a single DFB laser approaches are investigated and we will discuss which is best suited to integrated cold atom systems
The Deformable Universe
The concept of smooth deformations of a Riemannian manifolds, recently
evidenced by the solution of the Poincar\'e conjecture, is applied to
Einstein's gravitational theory and in particular to the standard FLRW
cosmology. We present a brief review of the deformation of Riemannian geometry,
showing how such deformations can be derived from the Einstein-Hilbert
dynamical principle. We show that such deformations of space-times of general
relativity produce observable effects that can be measured by four-dimensional
observers. In the case of the FLRW cosmology, one such observable effect is
shown to be consistent with the accelerated expansion of the universe.Comment: 20 pages, LaTeX, 3 figure
Intestinal Inflammation Induced by Soybean Meal Ingestion Increases Intestinal Permeability and Neutrophil Turnover Independently of Microbiota in Zebrafish
IndexaciĆ³n: Scopus.Intestinal inflammation is a condition shared by several intestinal chronic diseases, such as Crohn's disease and ulcerative colitis, with severely detrimental consequences in the long run. Current mammalian models have considerably increased understanding of this pathological condition, highlighting the fact that, in most of the cases, it is a highly complex and multifactorial problem and difficult to deal with. Thus, there is an increasingly evident need for alternative animal models that could offer complementary approaches that have not been exploited in rodents, thereby contributing to a different view on the disease. Here, we report the effects of a soybean mealāinduced intestinal inflammation model on intestinal integrity and function as well as on neutrophil recruitment and microbiota composition in zebrafish. We find that the induced intestinal inflammation process is accompanied by an increase in epithelial permeability in addition to changes in the mRNA levels of different tight junction proteins. Conversely, there was no evidence of damage of epithelial cells nor an increase in their proliferation. Of note, our results show that this intestinal inflammatory model is induced independently of the presence of microbiota. On the other hand, this inflammatory process affects intestinal physiology by decreasing protein absorption, increasing neutrophil replacement, and altering microbiota composition with a decrease in the diversity of cultivable bacteria. Ā© Copyright Ā© 2020 Solis, Hamilton, Caruffo, Garcia-Lopez, Navarrete, Guillemin and Feijoo.https://www.frontiersin.org/articles/10.3389/fimmu.2020.01330/ful
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Sleepwalking into lock-in? Avoiding wrongs to future people in the governance of solar radiation management research
This paper argues for two ways in which we can avoid the reckless endangerment of future people in the governance of solar radiation management (SRM) research, which could happen through lock-in to SRM deployment from research. SRM research is at an early stage, one at which the mechanisms of lock-in could start to operate. However, lock-in fit to endanger future people could be slowed or stopped through targeted governance. This paper argues that governance of SRM research that does not include provisions to detect, slow, or stop lock-in fails the test of an intergenerationally adequate precautionary principle, and that research governed without these provisions cannot itself be justified as a precaution against the impacts of climate change
āO sibling, where art thou?ā ā a review of avian sibling recognition with respect to the mammalian literature
Avian literature on sibling recognition is rare compared to that developed by mammalian researchers. We compare avian and mammalian research on sibling recognition to identify why avian work is rare, how approaches differ and what avian and mammalian researchers can learn from each other. Three factors: (1) biological differences between birds and mammals, (2) conceptual biases and (3) practical constraints, appear to influence our current understanding. Avian research focuses on colonial species because sibling recognition is considered adaptive where āmixing potentialā of dependent young is high; research on a wider range of species, breeding systems and ecological conditions is now needed. Studies of acoustic recognition cues dominate avian literature; other types of cues (e.g. visual, olfactory) deserve further attention. The effect of gender on avian sibling recognition has yet to be investigated; mammalian work shows that gender can have important influences. Most importantly, many researchers assume that birds recognise siblings through ādirect familiarisationā (commonly known as associative learning or familiarity); future experiments should also incorporate tests for āindirect familiarisationā (commonly known as phenotype matching). If direct familiarisation proves crucial, avian research should investigate how periods of separation influence sibling discrimination. Mammalian researchers typically interpret sibling recognition in broad functional terms (nepotism, optimal outbreeding); some avian researchers more successfully identify specific and testable adaptive explanations, with greater relevance to natural contexts. We end by reporting exciting discoveries from recent studies of avian sibling recognition that inspire further interest in this topic
Electric current circuits in astrophysics
Cosmic magnetic structures have in common that they are anchored
in a dynamo, that an external driver converts kinetic energy into internal
magnetic energy, that this magnetic energy is transported as Poynting fl ux across the magnetically dominated structure, and that the magnetic energy
is released in the form of particle acceleration, heating, bulk motion,
MHD waves, and radiation. The investigation of the electric current system is
particularly illuminating as to the course of events and the physics involved.
We demonstrate this for the radio pulsar wind, the solar flare, and terrestrial
magnetic storms
Identical transitions in the strongly deformed Sr-99 and Sr-100
The decay of the very neutron-rich nucleus Rb-100 has been studied by
gamma-spectroscopy of on-line mass-separated samples. Schemes for beta-decay to
Sr-100 and beta-n-decay to Sr-99 are presented. New sets of transitions in
Sr-99 and Sr-100 with identical energies are observed. All identical bands so
far observed in neutron-rich Sr isotopes obey a simple energy rule valid for
even-even, odd-even and odd-odd bands.Comment: 31 pages, 7 figures, Phys. Rev. C, in prin
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