Reversals in nature and the nature of reversals

The asymmetric shape of reversals of the Earth's magnetic field indicates a possible connection with relaxation oscillations as they were early discussed by van der Pol. A simple mean-field dynamo model with a spherically symmetric $\alpha$ coefficient is analysed with view on this similarity, and a comparison of the time series and the phase space trajectories with those of paleomagnetic measurements is carried out. For highly supercritical dynamos a very good agreement with the data is achieved. Deviations of numerical reversal sequences from Poisson statistics are analysed and compared with paleomagnetic data. The role of the inner core is discussed in a spectral theoretical context and arguments and numerical evidence is compiled that the growth of the inner core might be important for the long term changes of the reversal rate and the occurrence of superchrons.Comment: 24 pages, 12 figure

Peran Dependency, Commitment, Trust Dan Communication Terhadap Kolaborasi Rantai Pasok Dan Kinerja Perusahaan: Studi Pendahuluan

. Supply Chain Collaboration plays a significant role to the effectiveness of organizations. This preliminary study aims to identify social psychology factors that might influence collaborative relationship within a supply chain network, in the context of medium-sized food manufacturing enterprise. The supply chain collaboration practice and its impact of implementation on firm's performance, both operational and financial, were investigated. Based on this purposes, a survey within a case study approach was conducted. The data were collected from one medium scale food manufacturing enterprise. A partial least squares-path modeling (PLS-PM) was proposed for conceptualizing and measuring the effects of dependence, commitment, trust, and communication on supply chain collaboration. The effect of supply chain collaboration on firm's performance was also measured and quantified. From buyer's perspective, the study reveals that commitment and trust positively affect supply chain collaboration and that supply chain collaboration has a considerable effect on firm's performance. Meanwhile, dependence influences the collaboration indirectly through commitment, while communication influences the collaboration indirectly through trust

5D Einstein-Maxwell solitons and concentric rotating dipole black rings

We discuss the application of the solitonic techniques to the 5D Einstein-Maxwell gravity. As an illustration we construct an exact solution describing two concentric rotating dipole black rings. The properties of the solution are investigated.Comment: 19 pages, 1 figur

The Cheeger problem in abstract measure spaces

We consider nonnegative (Formula presented.) -finite measure spaces coupled with a proper functional (Formula presented.) that plays the role of a perimeter. We introduce the Cheeger problem in this framework and extend many classical results on the Cheeger constant and on Cheeger sets to this setting, requiring minimal assumptions on the pair measure space perimeter. Throughout the paper, the measure space will never be asked to be metric, at most topological, and this requires the introduction of a suitable notion of Sobolev spaces, induced by the coarea formula with the given perimeter

Green Root Collective Action for Conservation of Agri-Bio Diversity: a Case Study in Tuscany

The literature on environmental policy shows that institutional arrangements are key in designing effective environmental policies. Besides regulation and market (Coasian) solutions, grass root collective action has been advocated as a possible solution for the provision of agro-environmental public goods. We gauge that the same institutional arrangement can be found in many territorially integrated food chains that aims at re-embedding food production in the local society. Building on this literature, we present a case study - a short supply chain for bread production from ancient local wheat landraces in Tuscany – emphasizing the role played by collective action in maintaining high quality production in a context of severe information asymmetries

The influence of current collectors on Tayler instability and electro-vortex flows in liquid metal batteries

The Tayler instability is a kink-type flow instability which occurs when the electrical current through a conducting fluid exceeds a certain critical value. Originally studied in the astrophysical context, the instability was recently shown to be also a limiting factor for the upward scalability of liquid metal batteries. In this paper, we continue our efforts to simulate this instability for liquid metals within the framework of an integro-differential equation approach. The original solver is enhanced by multi-domain support with Dirichlet-Neumann partitioning for the static boundaries. Particular focus is laid on the detailed influence of the axial electrical boundary conditions on the characteristic features of the Tayler instability, and, secondly, on the occurrence of electro-vortex flows and their relevance for liquid metal batteries.Comment: 26 pages, 16 figure

Homovanillic acid in CSF of mild stage Parkinson's disease patients correlates with motor impairment.

In Parkinson's disease (PD), several efforts have been spent in order to find biochemical parameters able to identify the progression of the pathological processes at the basis of the disease. It is already known that advanced PD patients manifesting dyskinesia are featured by the high homovanillic acid (HVA)/dopamine (DA) ratio, suggesting the increased turnover of DA in these patients. Less clear is whether similar changes affect mild and moderate stages of the disease (between 1 and 2.5 of Hoehn & Yahr -H&Y- stage). Hence, here we tested whether cerebrospinal fluid (CSF) concentrations of DA and its major metabolites, either 3,4-dihydroxyphenylacetic acid (DOPAC) or HVA, correlate with motor performance in mild and moderate PD patients. CSF samples were collected after 2 days of anti-PD drugs washout, via lumbar puncture (LP) performed 130 min following administration of oral levodopa (LD) dose (200 mg). LP timing was determined in light of our previous tests clarifying that 2 h after oral LD administration CSF DA concentration reaches a plateau, which was un-respective of PD stage or duration. DA, DOPAC and HVA were assayed by high performance liquid chromatography in a group of 19 patients, distributed in two groups on the basis of the H&Y stage with a cut-off of 1.5. In these PD patients, HVA was correlated with DOPAC (R = 0,56, p < 0,01) and both HVA and DOPAC CSF levels increased in parallel with the motor impairment. More importantly, HVA correlated with motor impairment measured by the Unified Parkinson's Disease Score -III (UPDRS) (R = 0.61; p < 0.0001). The present findings showed the early alteration of the DA pre-synaptic machinery, as documented by the progressive increase of CSF HVA concentrations, which also correlated with PD motor impairment. Therefore, we suggest the potential use of measuring the CSF HVA level as a possible biomarker of PD stage changes in order to monitor the effectiveness of PD-modifying pharmacological therapies

Helicity detection of the astrophysical magnetic fields from radio emission statistics

We discuss inverse problem of detection turbulence magnetic field helical properties using radio survey observations statistics. In this paper, we present principal solution which connects magnetic helicity and correlation between Faraday rotation measure and polarization degree of radio synchrotron emission. The effect of depolarization plays the main role in this problem and allows to detect magnetic helicity for certain frequency range of observable radio emission. We show that the proposed method is mainly sensitive to a large-scale magnetic field component.Comment: 5 pages, 6 figure

Acute inactivation of the medial forebrain bundle imposes oscillations in the SNr: a challenge for the 6-OHDA model?

It has been recently shown that the substantia nigra pars reticulata (SNr) of 6-hydroxydopamine (6-OHDA)-lesioned rats, under urethane anaesthesia, manifests a prominent low frequency oscillation (LFO) of around 1Hz, synchronized with cortical slow wave activity (SWA). Nevertheless, it is poorly understood whether these electrophysiological alterations are correlated only with severe dopamine depletion or may also play a relevant pathogenetic role in the early stages of the dopamine denervation. Hence, here we recorded SNr single units and electrocorticogram (ECoG) in two models of dopamine denervation: (i) acute dopamine denervated rats, obtained by injection of tetrodotoxin (TTX), (ii) chronic dopamine depleted rats, 2 weeks after 6-OHDA lesioning. Both TTX and 6-OHDA were infused into the medial forebrain bundle (MFB). The acute TTX-mediated dopamine depletion caused a fast developing occurrence of a SNr/ECoG coherence, peaking between 0.48 and 1.22 Hz, parallel with a consistent decrease of firing rate (from 22.61 \ub1 7.04 to 15.35 \ub1 9.04 Hz) homolateraly to the infusion. Strikingly, this abnormal 1 Hz synchronization, TTX-mediated was qualitatively similar to the ECoG/SNr synchronization detectable in the 6-OHDA lesioned hemisphere (LH). In addition, TTX infusion in the un-lesioned hemispheres (UH) of 6-OHDA treated rats, produced ECoG/SNr synchronization qualitatively similar to that recordable in the LH. Hence, our data support the proposition that LFO, is tightly correlated to cortex, and represent a critical hallmark of a basal ganglia (BG) failure from the early stages of dopamine denervation