Solar Grand Minima and random fluctuations in dynamo parameters

We consider to what extent the long-term dynamics of cyclic solar activity in the form of Grand Minima can be associated with random fluctuations of the parameters governing the solar dynamo. We consider fluctuations of the alpha-coefficient in the conventional Parker migratory dynamo, and also in slightly more sophisticated dynamo models, and demonstrate that they can mimic the gross features of the phenomenon of the occurrence of Grand Minima over a suitable parameter range. The temporal distribution of these Grand Minima appears chaotic, with a more or less exponential waiting time distribution, typical of Poisson processes. In contrast however, the available reconstruction of Grand Minima statistics based on cosmogenic isotope data demonstrates substantial deviations from this exponential law. We were unable to reproduce the non-Poissonic tail of the waiting time distribution either in the framework of a simple alpha-quenched Parker model, or in its straightforward generalization, nor in simple models with feedback on the differential rotation. We suggest that the disagreement may only be apparent and is plausibly related to the limited observational data, and that the observations and results of numerical modeling can be consistent and represent physically similar dynamo regimes.Comment: Solar Physics, in prin

Bromine soil/sediment enrichment in tidal salt marshes as a potential indicator of climate changes driven by solar activity: New insights from W coast Portuguese estuaries

This paper aims at providing insight about bromine (Br) cycle in four Portuguese estuaries: Minho, Lima (in the NW coast) and Sado, Mira (in the SW coast). The focus is on their tidal marsh environments, quite distinct with regard to key biophysicochemical attributes. Regardless of the primary bromide (Br-) common natural source, i.e., seawater, the NW marshes present relatively higher surface soil/sediment Br concentrations than the ones from SW coast. This happens in close connection with organic matter (OM) content, and is controlled by their main climatic contexts. Yet, the anthropogenic impact on Br concentrations cannot be discarded. Regarding [Br] spatial patterns across the marshes, the results show a general increase from tidal flat toward high marsh. Maxima [Br] occur in the upper driftline zone, at transition from highest low marsh to high marsh, recognized as a privileged setting for OM accumulation. Based on the discovery of OM ubiquitous bromination in marine and transitional environments, it is assumed that this Br occurs mainly as organobromine. Analysis of two dated sediment cores indicates that, despite having the same age (AD ~1300), the Caminha salt marsh (Minho estuary) evidences higher Br enrichment than the Casa Branca salt marsh (Mira estuary). This is related to a greater Br storage ability, which is linked to OM build-up and rate dynamics under different climate scenarios. Both cores evidence a fairly similar temporal Br enrichment pattern, and may be interpreted in light of the sun-climate coupling. Thereby, most of the well-known Grand Solar Minima during the Little Ice Age appear to have left an imprint on these marshes, supported by higher [Br] in soils/sediments. Besides climate changes driven by solar activity and impacting marsh Br biogeodynamics, those Br enrichment peaks might also reflect inputs of enhanced volcanic activity covarying with Grand Solar Minima.This work was partly supported by IDL through the UID/GEO/50019/2013 program, by C2 TN through the UID/Multi/04349/2013 program, and is a contribution of the project WestLog (PTDC/CTE/105370/2008), funded by the Fundação para a Ciência e a Tecnologia (FCT). João Moreno benefits from a FCT PhD grant (SFRH/BD/87995/2012). J.J. Gómez-Navarro acknowledges the funding provided through the contract for the return of experienced researches, resolution R-735/2015 of the University of Murcia.info:eu-repo/semantics/publishedVersio

Application of Interferometry in Ultrasonic System for Vibration

International audienceVibration signals are important state parameters for mechanical equipments’ status monitoring and fault diagnosis. In this paper, in order to overcome the limitations of the traditional vibration measurement med1ods and instrument, a new non-contacting vibration method based on ultrasonic for vibration detection in special environment was presented. The mainly researched in this paper were the circuit for ultrasonic transmitting, receiving, algorithm and the module based on LabVIEW for signal analysis and processing. New algorithm was adopted in the system design. The measurement for vibration signals, which may have higher accuracy, was based on ultrasonic wave of different frequency. Experiments were carried on for proving the theory and the result was expected, verifying the reliability and feasibility of the system

SIRT6 modulates paclitaxel and epirubicin resistance and survival in breast cancer

In this study, we report the identification of a novel role of SIRT6 in both epirubicin and paclitaxel resistance in breast cancer. We found that SIRT6 protein levels are elevated in paclitaxel- and epirubicin-resistant MCF-7 cells compared with the parental sensitive cells. SIRT6 knockout and depletion sensitized cells to both paclitaxel and epirubicin treatment, whereas SIRT6 ectopic overexpression led to increased resistance to paclitaxel and epirubicin. Moreover, our data suggest that SIRT6 could be mediating epirubicin resistance through enhancing the DNA repair response to epirubicin-induced DNA damage. Clonogenic assays also revealed that mouse embryonic fibroblasts (MEFs) lacking SIRT6 have decreased long-term viability in response to epirubicin. The tumour suppressor FOXO3a increases its levels of acetylation in MEFs depleted of SIRT6, whereas its induction by epirubicin is attenuated in breast cancer cells overexpressing SIRT6. Further cell viability studies demonstrate that deletion of FOXO1/3/4 in MEFs can confer sensitivity to both paclitaxel and epirubicin, suggesting that SIRT6 reduces paclitaxel and epirubicin sensitivity, at least in part, through modulating FOXO acetylation and expression. Consistently, immunohistochemical analysis of 118 breast cancer patient samples revealed that high SIRT6 nuclear staining is significantly associated with poorer overall survival (P = 0.018; Kaplan-Meier analysis). Multivariate Cox analysis demonstrated that nuclear SIRT6 staining remained associated with death after correcting for tumour stage and lymph-node involvement (P = 0.033). Collectively, our data suggest that SIRT6 has a role in paclitaxel and epirubicin sensitivity via targeting FOXO proteins and that SIRT6 could be a useful biomarker and therapeutic target for paclitaxel- and epirubicin-resistant cancer.Cancer Research UKThe Royal Thai Government ScholarshipImperial College Healthcare NHS TrustBreast Cancer CampaignDepto. de Biología CelularFac. de Ciencias BiológicasTRUEpu