Impact of Atmospheric Intraseasonal Oscillations on Multi-Timescale Variability in the Upper Indian Ocean

An ocean general circulation model (the Hybrid Coordinate Ocean Model, HYCOM) is used to examine the impact of atmospheric intraseasonal oscillations (ISOs) on intraseasonal sea surface temperature (SST) during boreal summer, and on seasonal to interannual SST, mixed layer thickness (hm) and upper ocean heat content (uoheat) in the Indian Ocean (IO). In evaluating the intraseasonal SST impacts of atmospheric ISOs, the effects of the Madden- Julian Oscillation (MJO; 30-90 days) and submonthly ISOs are separately examined. The maximum summertime SST variability occurs in the Arabian Sea, the Bay of Bengal, and the eastern equatorial IO. Intraseasonal wind has a much larger impact on intraseasonal SSTs than either shortwave radiation or precipitation. Surface turbulent heat fluxes (THF) and entrainment due to changing intraseasonal wind speeds have a larger impact on SSTs than upwelling or horizontal advection due to changing intraseasonal wind stress in the Arabian Sea and in the Bay of Bengal, while the impacts of wind speed and wind stress are relatively equal in the eastern equatorial IO. Existing studies have shown that ISOs rectify onto low-frequency equatorial surface currents and cross-equatorial transport, suggesting that they may also have important impacts on lowfrequency upper ocean variability. Results indicate that rectification of ISOs onto seasonal and interannual upper ocean variability can be significant, and that it is highly regional. The regions displaying maximum rectification vary between SST, hm, and uoheat, and between seasonal and interannual timescales. Intraseasonal wind speed and wind stress have a much larger impact on seasonal and interannual SST, hm, and uoheat than either intraseasonal shortwave radiation or precipitation. The relative importance of entrainment and THF due to intraseasonal wind speed, and of upwelling and horizontal advection due to intraseasonal wind stress, varies by region

Planar resonant periodic orbits in Kuiper belt dynamics

In the framework of the planar restricted three body problem we study a considerable number of resonances associated to the Kuiper Belt dynamics and located between 30 and 48 a.u. Our study is based on the computation of resonant periodic orbits and their stability. Stable periodic orbits are surrounded by regular librations in phase space and in such domains the capture of trans-Neptunian object is possible. All the periodic orbits found are symmetric and there is evidence for the existence of asymmetric ones only in few cases. In the present work first, second and third order resonances are under consideration. In the planar circular case we found that most of the periodic orbits are stable. The families of periodic orbits are temporarily interrupted by collisions but they continue up to relatively large values of the Jacobi constant and highly eccentric regular motion exists for all cases. In the elliptic problem and for a particular eccentricity value of the primary bodies the periodic orbits are isolated. The corresponding families, where they belong to, bifurcate from specific periodic orbits of the circular problem and seem to continue up to the rectilinear problem. Both stable and unstable orbits are obtained for each case. In the elliptic problem the unstable orbits found are associated with narrow chaotic domains in phase space. The evolution of the orbits, which are located in such chaotic domains, seems to be practically regular and bounded for long time intervals.Comment: preprint, 20 pages, 10 figure

Ground-State Magnetization for Interacting Fermions in a Disordered Potential : Kinetic Energy, Exchange Interaction and Off-Diagonal Fluctuations

We study a model of interacting fermions in a disordered potential, which is assumed to generate uniformly fluctuating interaction matrix elements. We show that the ground state magnetization is systematically decreased by off-diagonal fluctuations of the interaction matrix elements. This effect is neglected in the Stoner picture of itinerant ferromagnetism in which the ground-state magnetization is simply determined by the balance between ferromagnetic exchange and kinetic energy, and increasing the interaction strength always favors ferromagnetism. The physical origin of the demagnetizing effect of interaction fluctuations is the larger number of final states available for interaction-induced scattering in the lower spin sectors of the Hilbert space. We analyze the energetic role played by these fluctuations in the limits of small and large interaction $U$. In the small $U$ limit we do second-order perturbation theory and identify explicitly transitions which are allowed for minimal spin and forbidden for higher spin. These transitions then on average lower the energy of the minimal spin ground state with respect to higher spin. For large interactions $U$ we amplify on our earlier work [Ph. Jacquod and A.D. Stone, Phys. Rev. Lett. 84, 3938 (2000)] which showed that minimal spin is favored due to a larger broadening of the many-body density of states in the low-spin sectors. Numerical results are presented in both limits.Comment: 35 pages, 24 figures - final, shortened version, to appear in Physical Review

Foxa1 Reduces Lipid Accumulation in Human Hepatocytes and Is Down-Regulated in Nonalcoholic Fatty Liver

Triglyceride accumulation in nonalcoholic fatty liver (NAFL) results from unbalanced lipid metabolism which, in the liver, is controlled by several transcription factors. The Foxa subfamily of winged helix/forkhead box (Fox) transcription factors comprises three members which play important roles in controlling both metabolism and homeostasis through the regulation of multiple target genes in the liver, pancreas and adipose tissue. In the mouse liver, Foxa2 is repressed by insulin and mediates fasting responses. Unlike Foxa2 however, the role of Foxa1 in the liver has not yet been investigated in detail. In this study, we evaluate the role of Foxa1 in two human liver cell models, primary cultured hepatocytes and HepG2 cells, by adenoviral infection. Moreover, human and rat livers were analyzed to determine Foxa1 regulation in NAFL. Results demonstrate that Foxa1 is a potent inhibitor of hepatic triglyceride synthesis, accumulation and secretion by repressing the expression of multiple target genes of these pathways (e.g., GPAM, DGAT2, MTP, APOB). Moreover, Foxa1 represses the fatty acid transporter protein FATP2 and lowers fatty acid uptake. Foxa1 also increases the breakdown of fatty acids by inducing peroxisomal fatty acid β-oxidation and ketone body synthesis. Finally, Foxa1 is able to largely up-regulate UCP1, thereby dissipating energy and consistently decreasing the mitochondria membrane potential. We also report that human and rat NAFL have a reduced Foxa1 expression, possibly through a protein kinase C-dependent pathway. We conclude that Foxa1 is an antisteatotic factor that coordinately tunes several lipid metabolic pathways to block triglyceride accumulation in hepatocytes. However, Foxa1 is down-regulated in human and rat NAFL and, therefore, increasing Foxa1 levels could protect from steatosis. Altogether, we suggest that Foxa1 could be a novel therapeutic target for NAFL disease and insulin resistance

Impact of baseline patient characteristics on interventions to reduce diabetes distress: the role of personal conscientiousness and diabetes self-efficacy

AIMS: To improve patient-centred care by determining the impact of baseline levels of conscientiousness and diabetes self-efficacy on the outcomes of efficacious interventions to reduce diabetes distress and improve disease management. METHODS: Adults with Type 2 diabetes with diabetes distress and self-care problems (N=392) were randomized to one of three distress reduction interventions: computer-assisted self-management; computer-assisted self-management plus problem-solving therapy; and health education. The baseline assessment included conscientiousness and self-efficacy, demographics, diabetes status, regimen distress, emotional burden, medication adherence, diet and physical activity. Changes in regimen distress, emotional burden and self-care between baseline and 12 months were recorded and ANCOVA models assessed how conscientiousness and self-efficacy qualified the significant improvements in distress and management outcomes. RESULTS: Participants with high baseline conscientiousness displayed significantly larger reductions in medication adherence and emotional burden than participants with low baseline conscientiousness. Participants with high baseline self-efficacy showed greater improvements in diet, physical activity and regimen distress than participants with low baseline self-efficacy. The impact of conscientiousness and self-efficacy were independent of each other and occurred across all three intervention groups. A significant interaction indicated that those with both high self-efficacy and high conscientiousness at baseline had the biggest improvement in physical activity by 12 months. CONCLUSIONS: Both broad personal traits and disease-specific expectations qualify the outcomes of efficacious interventions. These findings reinforce the need to change from a one-size-fits-all approach to diabetes interventions to an approach that crafts clinical interventions in ways that fit the personal traits and skills of individual people. (Clinical Trials Registry No: NCT-00714441