Multimode pulsation of the ZZ Ceti star GD 154

We present the results of a comparative period search on different time-scales and modelling of the ZZ Ceti (DAV) star GD 154. We determined six frequencies as normal modes and four rotational doublets around the ones having the largest amplitude. Two normal modes at 807.62 and 861.56 microHz have never been reported before. A rigorous test revealed remarkable intrinsic amplitude variability of frequencies at 839.14 and 861.56 microHz over a 50 d time-scale. In addition, the multimode pulsation changed to monoperiodic pulsation with an 843.15 microHz dominant frequency at the end of the observing run. The 2.76 microHz average rotational split detected led to a determination of a 2.1 d rotational period for GD 154. We searched for model solutions with effective temperatures and log g close to the spectroscopically determined ones. The best-fitting models resulting from the grid search have M_H between 6.3 x 10^-5 and 6.3 x 10^-7 M*, which means thicker hydrogen layer than the previous studies suggested. Our investigations show that mode trapping does not necessarily operate in all of the observed modes and the best candidate for a trapped mode is at 2484 microHz.Comment: 11 pages, 11 figures, accepted for publication in MNRA

Educate, Empower, Employ

Since the start of the Syrian Civil War in 2011, Lebanon is estimated to have taken in more than two million Syrian refugees. Due to policy and security obstacles, many of these refugees are considered by the Lebanese government to be living in Lebanon illegally, which restricts, among other aspects, their ability to continue employment or education. Based on field research conducted in-country through interviews, surveys, and focus groups, the authors have identified areas where innovative and inclusive higher education opportunities can be provided for Syrian refugees in Lebanon to allow them to move forward with their lives in self-sufficiency and dignity. The research aimed to answer the following questions: Where are the intersections of the interests and expectations of Syrian refugees in Lebanon with higher education and employment opportunities? How do individual characteristics such as gender, age, time in exile, and class affect refugees’ perceptions of their higher education needs and ambitions? What are the current barriers to accessing higher education, and what is the necessary support needed to overcome the barriers? Where are the opportunities for universities to fill the gaps in programming or resources

Low and high beta band activity in the primary sensorimotor cortex is diminished by ipsilateral subthalamic stimulation in Parkinsonian patients [Abstract]

Objective: We analyzed how change of the low and high beta power in the primary sensorimotor cortex relates to different levels of subthalamic stimulation; we hypothesized that it is a suitable biomarker for a closed-loop system. Background: Beta power in the motor system is shown to indicate the kinetic state in Parkinson’s disease. Method: We recruited 20 Parkinsonian patients. Bradykinesia of the most affected hand was measured first with Kinesia motion sensor system (Great Lakes NeuroTechnologies) in medication withdrawal; and four levels of contralateral stimulation (0: OFF, 1-3: decreasing symptoms to ON state) was individually selected. We performed 64-channel electroencephalography (EEG) measurement during a resting state with the four levels of stimulation settings mentioned above. We stimulated the usually used contacts during the whole study, and the ipsilateral stimulation remained ON and unchanged. The 2 minutes long EEG segments were cleaned from DBS artifacts by in-house algorithms. We performed line-noise removal; eye blinks and muscle artifacts were eliminated using ICA analyses. We calculated spectral power at the low (13-20Hz) and high (21-30Hz) beta frequency bands at the sensorimotor cortical region both sides using a beamformer algorithm called the Dynamic Imaging of Coherent Sources. We used repeated measures ANOVA to compare power values in the different locations and stimulation conditions in the two frequency bands. The Medical Research Council in Hungary provided ethical approval. (080958/2015/OTIG). Results: Resting state low- and high-frequency beta power in the primary sensorimotor cortex gradually decreased with the elevation of the ipsilateral stimulation level. In the continuously stimulated contralateral hemisphere, beta power remained at the baseline level. The beta power values measured in the two hemispheres were significantly different in stimulation levels 0-2 but not in level 3 (p < 0.05) both in the low- and high-frequency bands. Conclusion: The change of beta power in the primary sensorimotor cortex during STN-DBS is strictly ipsilateral, and depends on the level of stimulation. Beta power in the sensorimotor cortex could be a potential biomarker for closed-loop DBS. The support of Medtronic Inc. for this project is gratefully acknowledged

Pseudo-Hermitian Hamiltonians, indefinite inner product spaces and their symmetries

We extend the definition of generalized parity $P$, charge-conjugation $C$ and time-reversal $T$ operators to nondiagonalizable pseudo-Hermitian Hamiltonians, and we use these generalized operators to describe the full set of symmetries of a pseudo-Hermitian Hamiltonian according to a fourfold classification. In particular we show that $TP$ and $CTP$ are the generators of the antiunitary symmetries; moreover, a necessary and sufficient condition is provided for a pseudo-Hermitian Hamiltonian $H$ to admit a $P$-reflecting symmetry which generates the $P$-pseudounitary and the $P$-pseudoantiunitary symmetries. Finally, a physical example is considered and some hints on the $P$-unitary evolution of a physical system are also given.Comment: 20 page

Cyclone-induced surface ozone and HDO depletion in the Arctic

Ground-based, satellite, and reanalysis datasets were used to identify two similar cyclone-induced surface ozone depletion events at Eureka, Canada (80.1° N, 86.4° W), in March 2007 and April 2011. These two events were coincident with observations of hydrogen deuterium oxide (HDO) depletion, indicating that condensation and sublimation occurred during the transport of the ozone-depleted air masses. Ice clouds (vapour and crystals) and aerosols were detected by lidar and radar when the ozone- and HDO-depleted air masses arrived over Eureka. For the 2007 event, an ice cloud layer was coincident with an aloft ozone depletion layer at 870 m altitude on 2–3 March, indicating this ice cloud layer contained bromine-enriched blowing-snow particles. Over the following 3 days, a shallow surface ozone depletion event (ODE) was observed at Eureka after the precipitation of bromine-enriched particles onto the local snowpack. A chemistry–climate model (UKCA) and a chemical transport model (pTOMCAT) were used to simulate the surface ozone depletion events. Incorporating the latest surface snow salinity data obtained for the Weddell Sea into the models resulted in improved agreement between the modelled and measured BrO concentrations above Eureka. MERRA-2 global reanalysis data and the FLEXPART particle dispersion model were used to study the link between the ozone and HDO depletion. In general, the modelled ozone and BrO showed good agreement with the ground-based observations; however, the modelled BrO and ozone in the near-surface layer are quite sensitive to the snow salinity. HDO depletion observed during these two blowing-snow ODEs was found to be weaker than pure Rayleigh fractionation. This work provides evidence of a blowing-snow sublimation process, which is a key step in producing bromine-enriched sea-salt aerosol

Bitangential interpolation in generalized Schur classes

Bitangential interpolation problems in the class of matrix valued functions in the generalized Schur class are considered in both the open unit disc and the open right half plane, including problems in which the solutions is not assumed to be holomorphic at the interpolation points. Linear fractional representations of the set of solutions to these problems are presented for invertible and singular Hermitian Pick matrices. These representations make use of a description of the ranges of linear fractional transformations with suitably chosen domains that was developed in a previous paper.Comment: Second version, corrected typos, changed subsection 5.6, 47 page

Scattering theory for Klein-Gordon equations with non-positive energy

We study the scattering theory for charged Klein-Gordon equations: \{{array}{l} (\p_{t}- \i v(x))^{2}\phi(t,x) \epsilon^{2}(x, D_{x})\phi(t,x)=0,[2mm] \phi(0, x)= f_{0}, [2mm] \i^{-1} \p_{t}\phi(0, x)= f_{1}, {array}. where: \epsilon^{2}(x, D_{x})= \sum_{1\leq j, k\leq n}(\p_{x_{j}} \i b_{j}(x))A^{jk}(x)(\p_{x_{k}} \i b_{k}(x))+ m^{2}(x), describing a Klein-Gordon field minimally coupled to an external electromagnetic field described by the electric potential $v(x)$ and magnetic potential $\vec{b}(x)$. The flow of the Klein-Gordon equation preserves the energy: h[f, f]:= \int_{\rr^{n}}\bar{f}_{1}(x) f_{1}(x)+ \bar{f}_{0}(x)\epsilon^{2}(x, D_{x})f_{0}(x) - \bar{f}_{0}(x) v^{2}(x) f_{0}(x) \d x. We consider the situation when the energy is not positive. In this case the flow cannot be written as a unitary group on a Hilbert space, and the Klein-Gordon equation may have complex eigenfrequencies. Using the theory of definitizable operators on Krein spaces and time-dependent methods, we prove the existence and completeness of wave operators, both in the short- and long-range cases. The range of the wave operators are characterized in terms of the spectral theory of the generator, as in the usual Hilbert space case