Improvement of dielectric loss of doped Ba0.5Sr0.5TiO3 thin films for tunable microwave devices

Al2O3-Ba0.5Sr0.5TiO3 (Al2O3-BST) thin films, with different Al2O3 contents, were deposited on (100) LaAlO3 substrate by pulsed laser deposition (PLD) technique. The Al2O3-BST films was demosnstrated to be a suitable systems to fabricate ferroelectric thin films with low dielectric loss and higher figure of merit for tunable microwave devices. Pure BST thin films were also fabricated for comparison purpose. The films' structure and morphology were analyzed by X-ray diffractiopn and scanning electron microscopy, respectively; nad showed that the surface roughness for the Al2O3-BST films increased with the Al2O3 content. Apart from that, the broadening in the intensity peak in XRD result indicating the grain size of the Al2O3-BST films reduced with the increasing of Al2O3 dopant. We measured the dielctric properties of Al2O3-BST films with a home-made non-destructive dual resonator method at frequency ~ 7.7 GHZ. The effect of doped Al2O3 into BST thin films significantly reduced the dielectric constant, dielectric loss and tunability compare to pure BST thin film. Our result shows the figure of merit (K), used to compare the films with varied dielectric properties, increased with the Al2O3 content. Therefore Al2O3-BST films show the potential to be exploited in tunable microwave devices.Comment: 8 pages, 4 figures, 1 table. Accepted & tentatively for Feb 15 2004 issue, Journal of Applied Physic

Micro-PIXE with 3.5 MeV protons for the study of low copper concentrations in atherosclerotic artery

The onset and progression of many degenerative diseases including atherosclerosis, have been shown to directly link to the presence/absence of certain metal ions. Consequently, the detection of these ions in tissues may improve the understanding of the driving pathophysiology. The Cu content during atherosclerosis development has not been studied due to its low concentration involved. In this work, the Cu level in atherosclerotic rabbit tissue is determined using PIXE with a 3.5 MeV proton beam. The arteries of three animal groups fed with different diets were studied: group 1, rabbits on normal standard diet, group 2, on High Fat Diet (HFD) and group 3, on HFD + Zinc diet. Zinc supplement has been proven to inhibit the beginning of atherosclerotic lesion. The result of this study shows that the Cu levels in all the atherosclerotic lesions were lower than that in the arterial walls of the samples in HFD groupThis work has been partially funded by a UAM-Banco de Santander Interuniversity Cooperation with Asia Grant (2017–2018) and by the Ministerio de Ciencia, Innovacióny Universidades (CTQ2017-84309-C2-2-R

Using Cold Atoms to Measure Neutrino Mass

We propose a beta decay experiment based on a sample of ultracold atomic tritium. These initial conditions enable detection of the helium ion in coincidence with the beta. We construct a two-dimensional fit incorporating both the shape of the beta-spectrum and the direct reconstruction of the neutrino mass peak. We present simulation results of the feasible limits on the neutrino mass achievable in this new type of tritium beta-decay experiment.Comment: 10 pages, 5 figure

A bound on neutrino masses from baryogenesis

Properties of neutrinos, the lightest of all elementary particles, may be the origin of the entire matter-antimatter asymmetry of the universe. This requires that neutrinos are Majorana particles, which are equal to their antiparticles, and that their masses are sufficiently small. Leptogenesis, the theory explaining the cosmic matter-antimatter asymmetry, predicts that all neutrino masses are smaller than 0.2 eV, which will be tested by forthcoming laboratory experiments and by cosmology.Comment: 8 pages, 2 figure

Technical design and commissioning of the KATRIN large-volume air coil system

The KATRIN experiment is a next-generation direct neutrino mass experiment with a sensitivity of 0.2 eV (90% C.L.) to the effective mass of the electron neutrino. It measures the tritium $\beta$-decay spectrum close to its endpoint with a spectrometer based on the MAC-E filter technique. The $\beta$-decay electrons are guided by a magnetic field that operates in the mT range in the central spectrometer volume; it is fine-tuned by a large-volume air coil system surrounding the spectrometer vessel. The purpose of the system is to provide optimal transmission properties for signal electrons and to achieve efficient magnetic shielding against background. In this paper we describe the technical design of the air coil system, including its mechanical and electrical properties. We outline the importance of its versatile operation modes in background investigation and suppression techniques. We compare magnetic field measurements in the inner spectrometer volume during system commissioning with corresponding simulations, which allows to verify the system's functionality in fine-tuning the magnetic field configuration. This is of major importance for a successful neutrino mass measurement at KATRIN.Comment: 32 pages, 16 figure

Functional connectivity evidence of cortico-cortico inhibition in temporal lobe epilepsy.

Epileptic seizures can initiate a neural circuit and lead to aberrant neural communication with brain areas outside the epileptogenic region. We focus on interictal activity in focal temporal lobe epilepsy and evaluate functional connectivity (FC) differences that emerge as function of bilateral versus strictly unilateral epileptiform activity. We assess the strength of FC at rest between the ictal and non-ictal temporal lobes, in addition to whole brain connectivity with the ictal temporal lobe. Results revealed strong connectivity between the temporal lobes for both patient groups, but this did not vary as a function of unilateral versus bilateral interictal status. Both the left and right unilateral temporal lobe groups showed significant anti-correlated activity in regions outside the epileptogenic temporal lobe, primarily involving the contralateral (non-ictal/non-pathologic) hemisphere, with precuneus involvement prominent. The bilateral groups did not show this contralateral anti-correlated activity. This anti-correlated connectivity may represent a form of protective and adaptive inhibition, helping to constrain epileptiform activity to the pathologic temporal lobe. The absence of this activity in the bilateral groups may be indicative of flawed inhibitory mechanisms, helping to explain their more widespread epileptiform activity. Our data suggest that the location and build up of epilepsy networks in the brain are not truly random, and are not limited to the formation of strictly epileptogenic networks. Functional networks may develop to take advantage of the regulatory function of structures such as the precuneus to instantiate an anti-correlated network, generating protective cortico-cortico inhibition for the purpose of limiting seizure spread or epileptogenesis

Statistical Analysis of future Neutrino Mass Experiments including Neutrino-less Double Beta Decay

We perform a statistical analysis with the prospective results of future experiments on neutrino-less double beta decay, direct searches for neutrino mass (KATRIN) and cosmological observations. Realistic errors are used and the nuclear matrix element uncertainty for neutrino-less double beta decay is also taken into account. Three benchmark scenarios are introduced, corresponding to quasi-degenerate, inverse hierarchical neutrinos, and an intermediate case. We investigate to what extend these scenarios can be reconstructed. Furthermore, we check the compatibility of the scenarios with the claimed evidence of neutrino-less double beta decay.Comment: Matches published version: Europhys.Lett.85:51002 (2009). Format changed suitably for ArXi

On a model with two zeros in the neutrino mass matrix

We consider a Majorana neutrino mass matrix $\mathcal{M}_\nu$ with $(\mathcal{M}_\nu)_{\mu\mu} = (\mathcal{M}_\nu)_{\tau\tau} = 0$, in the basis where the charged-lepton mass matrix is diagonal. We show that this pattern for the lepton mass matrices can be enforced by extending the Standard Model with three scalar SU(2) triplets and by using a horizontal symmetry group \mathbbm{Z}_4. The Ma--Sarkar (type-II seesaw) mechanism leads to very small vacuum expectation values for the triplets, thus explaining the smallness of the neutrino masses; at the same time, that mechanism renders the physical scalars originating in the triplets very heavy. We show that the conditions $(\mathcal{M}_\nu)_{\mu\mu} = (\mathcal{M}_\nu)_{\tau\tau} = 0$ allow both for a normal neutrino mass spectrum and for an inverted one. In the first case, the neutrino masses must be larger than $0.1 {eV}$ and the atmospheric mixing angle $\theta_{23}$ must be practically equal to $45^\circ$. In the second case, the product $\sin{\theta_{13}} | \tan{2 \theta_{23}} |$ must be of order one or larger, thus correlating the large or maximal atmospheric neutrino mixing with the smallness of the mixing angle $\theta_{13}$.Comment: 13 pages, no figures, plain LaTeX; one equation added, published references updated, final version for J. Phys.

Micromachining using focused high energy ion beams

Abstract The combination of deep X-ray lithography with electroforming and micromoulding (i.e., LIGA) has been shown to oer high potential for the production of high aspect-ratio microstructures. The LIGA technique, employing synchrotron light and a suitable X-ray mask, allows production of 3D microstructures in PMMA with aspect ratios around 100. Here we demonstrate that the novel technique of Deep Ion Beam Lithography (DIBL), a direct process utilizing a focused beam of MeV ions scanned in a predetermined pattern over a suitable resist material, can produce three dimensional microstructures with sub-micrometer feature sizes. Microstructures extending up to 100 lm from the substrate with aspect ratios approaching 100 can be produced. Multiple exposures at dierent ion energies allow production of multilayer structures in single resist layers of SU-8, a newly developed, chemically accelerated, negative tone, near UV, photoresist.