1,544 research outputs found
Climate-Vegetation-Feedbacks as a Mechanism for Accelerated Climate Change: The onset of the African Humid Period
Paleo-environmental records and models indicate that the African Humid Period (AHPabruptly ended about 5000-4000 years before present (BP). Some proxies indicate alsan abrupt onset of the AHP between 14,000 and 11,000 BP. How important are local orbitaforcing, ice-sheet forcing, greenhouse gas forcing, and the reorganization of the AtlantiMeridional Overturning Circulation (AMOC) for changes in the African Monsoon/vegetatiosystem? Here we use transient simulations with climate-vegetation models of differencomplexity to identify the factors that control the onset of the African Monsoon/VegetationWe test the following hypothesis:(1) There is no indication for insolation-thresholds for the onset/break of the AHP.(2) Forcing from CO2/ice-sheets significantly controls the climate of North Africa.(3) CO2 fertilization contributes to the vegetation changes over North Africa.(4) A shutdown of the AMOC is as important as orbital insolation for the African Monsoon
Preserving the measure of compatibility between quantum states
In this paper after defining the abstract concept of compatibility-like
functions on quantum states, we prove that every bijective transformation on
the set of all states which preserves such a function is implemented by an
either unitary or antiunitary operator.Comment: 11 pages, submitted for publicatio
Correction to: The hidden therapist: evidence for a central role of music in psychedelic therapy.
The article The hidden therapist: evidence for a central role of music in psychedelic therapy, written by Mendel Kaelen, Bruna Giribaldi, Jordan Raine, Lisa Evans, Christopher Timmerman, Natalie Rodriguez, Leor Roseman, Amanda Feilding, David Nutt, Robin Carhart-Harris, was originally published electronically on the publisher's internet portal
Globally clustered chimera states in delay--coupled populations
We have identified the existence of globally clustered chimera states in
delay coupled oscillator populations and find that these states can breathe
periodically, aperiodically and become unstable depending upon the value of
coupling delay. We also find that the coupling delay induces frequency
suppression in the desynchronized group. We provide numerical evidence and
theoretical explanations for the above results and discuss possible
applications of the observed phenomena.Comment: Accepted in Phys. Rev. E as a Rapid Communicatio
Turmeric inhibits parathyroid hormone-related protein (PTHrP) secretion from human rheumatoid synoviocytes
Excessive production of parathyroid hormone-related protein (PTHrP) by tumor-like synoviocytes contributes to joint destruction in rheumatoid arthritis (RA). Having previously demonstrated that curcuminoid-only and essential oil-only fractions of turmeric prevent joint destruction in an animal model of RA, we hypothesized that synoviocyte PTHrP production could be one signaling pathway targeted by turmeric (Curcuma longa L.) in RA
The Ratio of Ortho- to Para-H2 in Photodissociation Regions
We discuss the ratio of ortho- to para-H2 in photodissociation regions
(PDRs). We draw attention to an apparent confusion in the literature between
the ortho-to-para ratio of molecules in FUV-pumped vibrationally excited
states, and the H2 ortho-to-para abundance ratio. These ratios are not the same
because the process of FUV-pumping of fluorescent H2 emission in PDRs occurs
via optically thick absorption lines. Thus, gas with an equilibrium ratio of
ortho- to para-H2 equal to 3 will yield FUV-pumped vibrationally excited
ortho-to-para ratios smaller than 3, because the ortho-H2 pumping rates are
preferentially reduced by optical depth effects. Indeed, if the ortho and para
pumping lines are on the ``square root'' part of the curve-of-growth, then the
expected ratio of ortho and para vibrational line strengths is the square root
of 3, ~ 1.7, close to the typically observed value. Thus, contrary to what has
sometimes been stated in the literature, most previous measurements of the
ratio of ortho- to para-H2 in vibrationally excited states are entirely
consistent with a total ortho-to-para ratio of 3, the equilibrium value for
temperatures greater than 200 K. We present an analysis and several detailed
models which illustrate the relationship between the total ratios of ortho- to
para-H2 and the vibrationally excited ortho-to-para ratios in PDRs. Recent
Infrared Space Observatory (ISO) measurements of pure rotational and
vibrational H2 emissions from the PDR in the star-forming region S140 provide
strong observational support for our conclusions.Comment: 23 pages (including 5 figures), LaTeX, uses aaspp4.sty, accepted for
publication in Ap
Anaphylatoxin C5a receptor mRNA is strongly expressed in Kupffer and stellate cells and weakly in sinusoidal endothelial cells but not in hepatocytes of normal rat liver
AbstractAnaphylatoxins (C5a and C3a), which are generated during complement activation, have recently been shown to increase glucose output from hepatocytes (HC) in perfused rat liver. They did not act directly on HC but indirectly by prostanoid release from non-parenchymal cells (NPC), probably Kupffer cells (KC). In order to corroborate this mechanism, the distribution of anaphylatoxin receptors in the different cell types of rat liver was determined by quantitative RT-PCR with primers specific for the rat C5a receptor (rC5aR) using RNA isolated from KC, sinusoidal endothelial cells (SEC), hepatic stellate cells (HSC) and HC. In line with functional data, C5aR mRNA was detected in freshly isolated NPC but not in HC of rat liver. Mainly KC but also HSC clearly expressed C5aR mRNA, while SEC did so only weakly. KC expressed up to 10-fold more C5aR mRNA than HSC and these in turn up to 10-fold more than SEC. These results support the proposed indirect action of anaphylatoxins on HC
A propensity criterion for networking in an array of coupled chaotic systems
We examine the mutual synchronization of a one dimensional chain of chaotic
identical objects in the presence of a stimulus applied to the first site. We
first describe the characteristics of the local elements, and then the process
whereby a global nontrivial behaviour emerges. A propensity criterion for
networking is introduced, consisting in the coexistence within the attractor of
a localized chaotic region, which displays high sensitivity to external
stimuli,and an island of stability, which provides a reliable coupling signal
to the neighbors in the chain. Based on this criterion we compare homoclinic
chaos, recently explored in lasers and conjectured to be typical of a single
neuron, with Lorenz chaos.Comment: 4 pages, 3 figure
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