The intimate relation between the low T/W instability and the co-rotation point

We study the low T/W instability associated with the f-mode of differentially rotating stars. Our stellar models are described by a polytropic equation of state and the rotation profile is given by the standard j-constant law. The properties of the relevant oscillation modes, including the instability growth time, are determined from time evolutions of the linearised dynamical equations in Newtonian gravity. In order to analyse the instability we monitor also the canonical energy and angular momentum. Our results demonstrate that the l=m=2 f-mode becomes unstable as soon as a co-rotation point develops inside the star (i.e. whenever there is a point where the mode's pattern speed matches the bulk angular velocity). Considering various degrees of differential rotation, we show that the instability grows faster deep inside the co-rotation region and deduce an empirical relation that correlates the mode frequency and the star's parameters, which captures the main features of the l=m=2 f-mode growth time. This function is proportional to the product of the kinetic to gravitational energy ratio and the gradient of the star's spin, strengthening further the relationship between the co-rotation point and the low T/W instability. We briefly consider also the l=m=2 r-mode and demonstrate that it never moves far inside the co-rotation region even for significant differential rotation.Comment: 12 pages, 8 figures, 2 tables. Submitted to MNRA

Buoyancy and g-modes in young superfluid neutron stars

We consider the local dynamics of a realistic neutron star core, including composition gradients, superfluidity and thermal effects. The main focus is on the gravity g-modes, which are supported by composition stratification and thermal gradients. We derive the equations that govern this problem in full detail, paying particular attention to the input that needs to be provided through the equation of state and distinguishing between normal and superfluid regions. The analysis highlights a number of key issues that should be kept in mind whenever equation of state data is compiled from nuclear physics for use in neutron star calculations. We provide explicit results for a particular stellar model and a specific nucleonic equation of state, making use of cooling simulations to show how the local wave spectrum evolves as the star ages. Our results show that the composition gradient is effectively dominated by the muons whenever they are present. When the star cools below the superfluid transition, the support for g-modes at lower densities (where there are no muons) is entirely thermal. We confirm the recent suggestion that the g-modes in this region may be unstable, but our results indicate that this instability will be weak and would only be present for a brief period of the star's life. Our analysis accounts for the presence of thermal excitations encoded in entrainment between the entropy and the superfluid component. Finally, we discuss the complete spectrum, including the normal sound waves and, in superfluid regions, the second sound.Comment: 29 pages, 9 figures, submitted to MNRA

TRANS2CARE. Working plans: consciousness and perspective

The project started on 1st April 2011 and will end on 30th September 2014. The project received a budget of \u20ac 2,611,118 from the Italy-Slovenia 2007-2013 Cross-border Cooperation Programme. Seven universities and research institutions, five hospitals and a center for technology transfer distributed over the Programme area constitute the \u201cInterregional network for innovation and technology transfer for health improvement\u201d, which will continuously develop new protocols and biotechnological devices for the prevention, early diagnosis and treatment of neurodegenerative, cardiovascular, orthopaedic and oncological diseases

Materials and devices for spatial multi-dimensional liquid chromatography

In this thesis, the potential of spatial multi-dimensional liquid chromatography is explained, culminating in the “Separation Technologies for A Million Peaks” (STAMP) project. Different kinds of stationary phases were developed and taken into consideration, with the simplicity of the in-situ creation of monoliths being highlighted. Their applications in a hydrophilic-interaction-liquid-chromatography – high-resolution-mass-spectrometry method for the separation of intact proteins and, specifically, intact glycoforms are described in two chapters of this work. Glass, PEEK and titanium were explored as materials for 3D-printing column housings and microfluidic devices, with titanium providing the most successful applications. Titanium devices, with different designs, were successfully used to confine the thermal polymerization of monolithic stationary phases. The most successful design was then implemented in complex microfluidic titanium devices in order to perform spatial multi-dimensional liquid chromatography

On the magnetic field evolution timescale in superconducting neutron star cores

We revisit the various approximations employed to study the long-term evolution of the magnetic field in neutron star cores and discuss their limitations and possible improvements. A recent controversy on the correct form of the induction equation and the relevant evolution timescale in superconducting neutron star cores is addressed and clarified. We show that this ambiguity in the estimation of timescales arises as a consequence of nominally large terms that appear in the induction equation, but which are, in fact, mostly irrotational. This subtlety leads to a discrepancy by many orders of magnitude when velocity fields are absent or ignored. Even when internal velocity fields are accounted for, only the solenoidal part of the electric field contributes to the induction equation, which can be substantially smaller than the irrotational part. We also argue that stationary velocity fields must be incorporated in the slow evolution of the magnetic field as the next level of approximation.Comment: 6 pages, version accepted by MNRA

Tau pathology, microglia activation, and network dysfunction in Alzheimer’s disease

Tau pathology and neuroinflammation are key etio-pathogenetic mediators of Alzheimer’s disease (AD). Network dysfunction has also been reported in AD and linked to cognitive impairment. However, it is unclear how tau pathology and neuroinflammation contribute to network dysfunction and cognitive deficit in AD. I study these issues by combining: 1) positron emission tomography imaging using the [18F-AV]-1451 tracer (measuring in vivo tau pathology) or [11C]PK11195 ligand (indexing in vivo neuroinflammation), with 2) connectivity measures of resting-state functional magnetic resonance imaging. I found increased [18F-AV]-1451 binding (reflecting tau pathology) in AD patients, relative to controls, in the medial/lateral temporal and parietal cortices. In terms of functional connectivity, more strongly connected brain regions accrued more tau pathology. Increasing tau burden was also linked to progressive weakening of the connectivity across the same regions. I also found increased [11C]PK11195 binding (reflecting neuroinflammation) in the medial/lateral temporal and parietal cortices in AD patients, relative to controls. [11C]PK11195 binding in the cuneus/precuneus correlated with episodic memory deficits in AD patients. This pattern of neuroinflammation was linked to large-scale network’ dysfunction and cognitive deficit. AD patients with enhanced neuroinflammation showed more abnormal connectivity across the whole-brain. The expression of a stronger association between altered functional connectivity and high levels of neuroinflammation related to cognitive deficit in AD. My studies have wide-ranging implications that include: 1) the validation of animal models of tau propagation in living patients with AD; 2) improvements in our understanding of the relationship between in vivo tau pathology and brain functioning; 3) evidence for a primary role of neuroinflammation in mediating network dysfunction in AD; 4) support to the notion that immune-therapeutic strategies targeting tau pathology and neuroinflammation may be useful in AD.MRC and NIHR funde