Quantum Corrections in Quintessence Models

We investigate the impact of quantum fluctuations on a light rolling quintessence field from three different sources, namely, from a coupling to the standard model and dark matter, from its self-couplings and from its coupling to gravity. We derive bounds for time-varying masses from the change of vacuum energy, finding \Delta m_e/m_e << 10^{-11} for the electron and \Delta m_p/m_p << 10^{-15} for the proton since redshift z~2, whereas the neutrino masses could change of order one. Mass-varying dark matter is also constrained. Next, the self-interactions are investigated. For inverse power law potentials, the effective potential does not become infinitely large at small field values, but saturates at a finite maximal value. We discuss implications for cosmology. Finally, we show that one-loop corrections induce non-minimal gravitational couplings involving arbitrarily high powers of the curvature scalar R, indicating that quintessence entails modified gravity effects.Comment: 10 pages + appendix, added reference

Remote Detection of Saline Intrusion in a Coastal Aquifer Using Borehole Measurements of Self-Potential

Funded by NERC CASE studentship . Grant Number: NE/I018417/1Peer reviewedPublisher PD

PENTACYCLIC TRITERPENOIDS FROM THE STEM-BARK OF ALBIZIA CHEVALIERI HAMS (MIMOSACEAE)

Objective: This research is focused towards isolation and identification of pure compounds from the extracts fractions of Albizia chevalieri through the means of gravity column chromatography and other chromatographic processes.Methods: the stem bark was extracted exhaustively with hexane and subsequently with methanol. The methanolic extract was fractionated into ethyl acetate (EA) and n-butanol (NB) soluble parts, after which the hexane extracts were subjected to silica gel gravity column chromatography for the isolation of pure bioactive molecules.The major compounds isolated, were then determined and identified by the use of spectrometric analysis of HR-ESIMS, 1HNMR, [13]CNMR, IR and UV spectra.Results: Investigation of the stem bark hexane extract fraction of A. chevalieri led to the isolation of three known pentacyclic triterpenoids: friedelin (HXC1), Friedelan-3-ol (HXC2) and Lupeol (HXC3), for the first time in the plant.Conclusion: The results obtained will be useful in the evaluation (bioassay) of the isolated compounds against the list of folklore therapeutic claims of A. chevalieri (which include its use as purgative, taenicidal, remedies of cough, dysentery, cancer, diabetes mellitus, tuberculosis and snake bite), and thereby providing scientific basis for its used for treatment of the aforementioned ailments.Keywords: Friedelin, Friedilan-3-ol, Lupeol, Isolation, Spectrometr

Quantum-Well Wavefunction Localization and the Electron-Phonon Interaction in Thin Ag Nanofilms

The electron-phonon interaction in thin Ag-nanofilms epitaxially grown on Cu(111) is investigated by temperature-dependent and angle-resolved photoemission from silver quantum-well states. Clear oscillations in the electron-phonon coupling parameter as a function of the silver film thickness are observed. Different from other thin film systems where quantum oscillations are related to the Fermi-level crossing of quantum-well states, we can identify a new mechanism behind these oscillations, based on the wavefunction localization of the quantum-well states in the film

Understanding the dynamical structure of pulsating stars. HARPS spectroscopy of the delta Scuti stars rho Pup and DX Cet

High-resolution spectroscopy is a powerful tool to study the dynamical structure of pulsating stars atmosphere. We aim at comparing the line asymmetry and velocity of the two delta Sct stars rho Pup and DX Cet with previous spectroscopic data obtained on classical Cepheids and beta Cep stars. We obtained, analysed and discuss HARPS high-resolution spectra of rho Pup and DX Cet. We derived the same physical quantities as used in previous studies, which are the first-moment radial velocities and the bi-Gaussian spectral line asymmetries. The identification of f=7.098 (1/d) as a fundamental radial mode and the very accurate Hipparcos parallax promote rho Pup as the best standard candle to test the period-luminosity relations of delta Sct stars. The action of small-amplitude nonradial modes can be seen as well-defined cycle-to-cycle variations in the radial velocity measurements of rho Pup. Using the spectral-line asymmetry method, we also found the centre-of-mass velocities of rho Pup and DX Cet, V_gamma = 47.49 +/- 0.07 km/s and V_gamma = 25.75 +/- 0.06 km/s, respectively. By comparing our results with previous HARPS observations of classical Cepheids and beta Cep stars, we confirm the linear relation between the atmospheric velocity gradient and the amplitude of the radial velocity curve, but only for amplitudes larger than 22.5 km/s. For lower values of the velocity amplitude (i.e., < 22.5 km/s), our data on rho Pup seem to indicate that the velocity gradient is null, but this result needs to be confirmed with additional data. We derived the Baade-Wesselink projection factor p = 1.36 +/- 0.02 for rho Pup and p = 1.39 +/- 0.02 for DX Cet. We successfully extended the period-projection factor relation from classical Cepheids to delta Scuti stars.Comment: Accepted for publication in A&A (in press

Probing the longitudinal momentum spread of the electron wave packet at the tunnel exit

We present an ellipticity resolved study of momentum distributions arising from strong-field ionization of Helium at constant intensity. The influence of the ion potential on the departing electron is considered within a semi-classical model consisting of an initial tunneling step and subsequent classical propagation. We find that the momentum distribution can be explained by the presence of a longitudinal momentum spread of the electron at the exit from the tunnel. Our combined experimental and theoretical study provides an estimate of this momentum spread

To study and compare the effectiveness of transobturator tape versus Kelly’s repair in the treatment of female stress urinary incontinence

Background: To compare the effectiveness of transobturator tape (TOT) versus Kelly’s repair in the treatment of female stress urinary incontinence.Methods: A retrospective experimental comparative study was conducted in the department of obstetrics and gynaecology in Lokmanya Tilak Municipal General Hospital, Mumbai, India from 2015 to 2016. A cohort of 60 patients was divided in two groups of 30 each. In group 1, patients who underwent transobturator tape fixation were included. In group 2 patients who underwent Kelly’s repair and outcomes were compared with a follow up of 1 year post surgery.Results: Out of 30 patients included in group 1, 29 slings were successful and 1 had a surgical failure in terms of persistence of stress incontinence whereas 3 had persistent symptom in group 2. 2 patients in group 1 and 4 in group 2 had urinary retention in the immediate postoperative phase. Dyspareunia occurred in 1 TOT patient and 3 Kelly’s repair. None had symptoms of overactive bladder in group 1, whereas group 2 had 1 patient with overactive bladder symptoms. None developed erosion in a 1 year follow up period.Conclusions: The transobturator approach is an effective treatment of SUI with higher cure rate, low morbidity, good patient satisfaction and faster recovery

Grid Loss: Detecting Occluded Faces

Detection of partially occluded objects is a challenging computer vision problem. Standard Convolutional Neural Network (CNN) detectors fail if parts of the detection window are occluded, since not every sub-part of the window is discriminative on its own. To address this issue, we propose a novel loss layer for CNNs, named grid loss, which minimizes the error rate on sub-blocks of a convolution layer independently rather than over the whole feature map. This results in parts being more discriminative on their own, enabling the detector to recover if the detection window is partially occluded. By mapping our loss layer back to a regular fully connected layer, no additional computational cost is incurred at runtime compared to standard CNNs. We demonstrate our method for face detection on several public face detection benchmarks and show that our method outperforms regular CNNs, is suitable for realtime applications and achieves state-of-the-art performance.Comment: accepted to ECCV 201

Electron Waiting Times in Mesoscopic Conductors

Electron transport in mesoscopic conductors has traditionally involved investigations of the mean current and the fluctuations of the current. A complementary view on charge transport is provided by the distribution of waiting times between charge carriers, but a proper theoretical framework for coherent electronic systems has so far been lacking. Here we develop a quantum theory of electron waiting times in mesoscopic conductors expressed by a compact determinant formula. We illustrate our methodology by calculating the waiting time distribution for a quantum point contact and find a cross-over from Wigner-Dyson statistics at full transmission to Poisson statistics close to pinch-off. Even when the low-frequency transport is noiseless, the electrons are not equally spaced in time due to their inherent wave nature. We discuss the implications for renewal theory in mesoscopic systems and point out several analogies with energy level statistics and random matrix theory.Comment: 4+ pages, 3 figure