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Interhemispheric coupling, the West Antarctic Ice Sheet and warm Antarctic interglacials
Ice core evidence indicates that even though atmospheric
CO2 concentrations did not exceed 300 ppm at
any point during the last 800 000 years, East Antarctica was
at least 3–4 C warmer than preindustrial (CO2 280 ppm) in each of the last four interglacials. During the previous three interglacials, this anomalous warming was short lived (3000 years) and apparently occurred before the completion of Northern Hemisphere deglaciation. Hereafter, we refer to these periods as “Warmer than Present Transients” (WPTs). We present a series of experiments to investigate the impact of deglacial meltwater on the Atlantic Meridional Overturning Circulation (AMOC) and Antarctic temperature.
It is well known that a slowed AMOC would increase southern
sea surface temperature (SST) through the bipolar seesaw
and observational data suggests that the AMOC remained
weak throughout the terminations precedingWPTs, strengthening rapidly at a time which coincides closely with peak Antarctic temperature. We present two 800 kyr transient simulations using the Intermediate Complexity model GENIE-1 which demonstrate that meltwater forcing generates transient southern warming that is consistent with the timing of WPTs, but is not sufficient (in this single parameterisation) to reproduce the magnitude of observed warmth. In order to investigate model and boundary condition uncertainty, we present three ensembles of transient GENIE-1 simulations across Termination II (135 000 to 124 000 BP) and three snapshot HadCM3 simulations at 130 000 BP. Only with consideration of the possible feedback of West Antarctic Ice Sheet (WAIS)
retreat does it become possible to simulate the magnitude of
observed warming
Remedying the Lose-Lose Game of Compulsive Gambling: Voluntary Exclusions, Mandatory Exclusions, or an Alternative Method?, 40 J. Marshall L. Rev. 1221 (2007)
Generic Finite Size Enhancement of Pairing in Mesoscopic Fermi Systems
The finite size dependent enhancement of pairing in mesoscopic Fermi systems
is studied under the assumption that the BCS approach is valid and that the two
body force is size independent. Different systems are investigated such as
superconducting metallic grains and films as well atomic nuclei. It is shown
that the finite size enhancement of pairing in these systems is in part due to
the presence of a surface which accounts quite well for the data of nuclei and
explains a good fraction of the enhancement in Al grains.Comment: Updated version 17/02/0
Destabilization of the thermohaline circulation by transient perturbations to the hydrological cycle
We reconsider the problem of the stability of the thermohaline circulation as
described by a two-dimensional Boussinesq model with mixed boundary conditions.
We determine how the stability properties of the system depend on the intensity
of the hydrological cycle. We define a two-dimensional parameters' space
descriptive of the hydrology of the system and determine, by considering
suitable quasi-static perturbations, a bounded region where multiple equilibria
of the system are realized. We then focus on how the response of the system to
finite-amplitude surface freshwater forcings depends on their rate of increase.
We show that it is possible to define a robust separation between slow and fast
regimes of forcing. Such separation is obtained by singling out an estimate of
the critical growth rate for the anomalous forcing, which can be related to the
characteristic advective time scale of the system.Comment: 37 pages, 8 figures, submitted to Clim. Dy
Neutron star properties in a chiral SU(3) model
We investigate various properties of neutron star matter within an effective
chiral model. The predictions of this model are
compared with a Walecka-type model. It is demonstrated that the importance of
hyperon degrees are strongly depending on the interaction used, even if the
equation of state near saturation density is nearly the same in both models.
While the Walecka-type model predicts a strange star core with strangeness
fraction , the chiral model allows only for
and predicts that , and will not exist in star, in
contrast to the Walecka-type model.Comment: 13 pages, Revtex, 5 figs include
Acute Hypernatrem ia Increases Functional Connectivity Between the SFO and OVLT: Time Course of the Response
poste
Pharmacology and clinical drug candidates in redox medicine
SIGNIFICANCE
Oxidative stress is suggested to be a disease mechanism common to a wide range of disorders affecting human health. However, so far, the pharmacotherapeutic exploitation of this, for example, based on chemical scavenging of pro-oxidant molecules, has been unsuccessful. Recent Advances: An alternative emerging approach is to target the enzymatic sources of disease-relevant oxidative stress. Several such enzymes and isoforms have been identified and linked to different pathologies. For some targets, the respective pharmacology is quite advanced, that is, up to late-stage clinical development or even on the market; for others, drugs are already in clinical use, although not for indications based on oxidative stress, and repurposing seems to be a viable option.
CRITICAL ISSUES
For all other targets, reliable preclinical validation and drug ability are key factors for any translation into the clinic. In this study, specific pharmacological agents with optimal pharmacokinetic profiles are still lacking. Moreover, these enzymes also serve largely unknown physiological functions and their inhibition may lead to unwanted side effects.
FUTURE DIRECTIONS
The current promising data based on new targets, drugs, and drug repurposing are mainly a result of academic efforts. With the availability of optimized compounds and coordinated efforts from academia and industry scientists, unambiguous validation and translation into proof-of-principle studies seem achievable in the very near future, possibly leading towards a new era of redox medicine
Nuclear Breathing Mode in the Relativistic Mean Field Theory
The breathing-mode giant monopole resonance is studied within the framework
of the relativistic mean-field (RMF) theory. Using a broad range of parameter
sets, an analysis of constrained incompressibility and excitation energy of
isoscalar monopole states in finite nuclei is performed. It is shown that the
non-linear scalar self-interaction and the resulting surface properties
influence the breathing-mode considerably. It is observed that dynamical
surface properties respond differently in the RMF theory than in the Skyrme
approach. A comparison is made with the incompressibility derived from the
semi-infinite nuclear matter and with constrained nonrelativistic Skyrme
Hartree-Fock calculaions.Comment: Latex (12 pages) and 3 figures (available upon request) J. Phys. G
(in press
Assimilative real-time models of HF absorption at high latitudes
Improved real-time HF communications frequency management is required for aircraft on trans-polar routes. Polar cap absorption (PCA) models have therefore been adapted to assimilate real-time measurements of zenithal cosmic radio noise absorption (~ 30 MHz) from a large network of online riometers in Canada and Finland. Two types of PCA model have been developed and improvements to model accuracy following optimisation are quantified. Real-time optimisation is performed by age-weighting riometer measurements in a non-linear regression. This reduces root-mean-square errors (RMSE) from 2-3 dB to less than 1 dB and mean errors to within ±0.2 dB over a wide latitude range. This paper extends previous work by further optimising the models’ dependences on solar-zenith angle to account for differences in the ionospheric response at sunrise and sunset (the Twilight Anomaly). Two models of the rigidity cutoff latitudes are compared and one is optimised in real time by regression to riometer measurements. Whilst measurements from the NASA POES satellites may provide a direct measurement of the rigidity cut-off, it is observed that proton flux measurements from POES often need correcting for relativistic electron contamination for several hours at the start of a PCA event. An optimised real-time absorption model will be integrated into HF ray-tracing propagation predictions relating to measurements of HF signal strengths on a network of HF transmitters and receivers in the high northern latitudes
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