86 GHz Very Long Baseline Polarimetry of 3C273 and 3C279 with the Coordinated Millimeter VLBI Array

86 GHz Very Long Baseline Polarimetry probes magnetic field structures within the cores of Active Galactic Nuclei at higher angular resolutions and a spectral octave higher than previously achievable. Observations of 3C273 and 3C279 taken in April 2000 with the Coordinated Millimeter VLBI Array have resulted in the first total intensity (Stokes I) and linear polarization VLBI images reported of any source at 86 GHz. These results reveal the 86 GHz electric vector position angles within the jets of 3C273 and 3C279 to be orthogonal to each other, and the core of 3C273 to be unpolarized. If this lack of polarization is due to Faraday depolarization alone, the dispersion in rotation measure is >=90000 rad/m^2 for the core of 3C273.Comment: AASTeX v5.02; 10 pages; 4 figures; accepted for publication in the Astrophysical Journal Letter

ROSAT and ASCA observations of the Crab-Like Supernova Remnant N157B in the Large Magellanic Cloud

We report the results of ROSAT and ASCA X-ray observations of the supernova remnant N157B (or 30 Dor B, SNR 0539-69.1) in the Large Magellanic Cloud. For comparison, we also briefly describe the results on SNR 0540-69.3, the only confirmed Crab-like remnant in the Cloud. The X-ray emission from N157B can be decomposed into a bright comet-shaped feature, superimposed on a diffuse emission region of a dimension $\sim 20$ pc. The flat and nearly featureless spectrum of the remnant is distinctly different from those of young shell-like remnants, suggesting a predominantly Crab-like nature of N157B. Characterized by a power law with an energy slope $\sim 1.5$, the spectrum of N157B above $\sim 2$ keV is, however, considerably steeper than that of SNR 0540-69.3, which has a slope of $\sim 1.0$. At lower energies, the spectrum of N157B presents marginal evidence for emission lines, which if real most likely arise in hot gas of the diffuse emission region. The hot gas has a characteristic thermal temperature of 0.4-0.7 keV. No significant periodic signal is detected from N157B in the period range of $3 \times 10^{-3}-2000$ s. The pulsed fraction is $\lesssim 9$ (99% confidence) in the $2-7$ keV range. We discuss the nature of the individual X-ray components. In particular, we suggest that the synchrotron radiation of relativistic particles from a fast-moving ($\sim 10^3 km s^{-1}$) pulsar explains the size, morphology, spectrum, and energetics of the comet-shaped X-ray feature. We infer the age of the remnant as $\sim 5 \times 10^3$ yrs. The lack of radio polarization of the remnant may be due to Faraday dispersion by foreground \ion{H}{2} gas.Comment: To be published in The Astrophysical Journal, 21 pages, plus 11 images in the PS, GIF, or jpeg format. Postscript files of images are available at http://www.astro.nwu.edu/astro/wqd/paper/n157b

Temperature dependence of the triplet diffusion and quenching rates in films of an Ir(ppy)(3)-cored dendrimer

We study photoluminescence and triplet-triplet exciton annihilation in a neat film of a fac-tris(2-phenylpyridyl)iridium(III) [Ir(ppy)(3)]-cored dendrimer and in its blend with a 4,4(')-bis(N-carbazolyl)biphenyl host for the temperature range of 77-300 K. The nearest neighbor hopping rate of triplet excitons is found to increase by a factor of 2 with temperature between 150 and 300 K and is temperature independent at lower temperature. The intermolecular quenching rate follows the Arrhenius law with an activation energy of 7 meV, which can be explained by stronger dipole-dipole interactions with the donor molecule in the higher triplet substate. The results indicate that energy disorder has no significant effect on triplet transport and quenching in these materials

A water budget dichotomy of rocky protoplanets from 26^{26}Al-heating

In contrast to the water-poor inner solar system planets, stochasticity during planetary formation and order of magnitude deviations in exoplanet volatile contents suggest that rocky worlds engulfed in thick volatile ice layers are the dominant family of terrestrial analogues among the extrasolar planet population. However, the distribution of compositionally Earth-like planets remains insufficiently constrained, and it is not clear whether the solar system is a statistical outlier or can be explained by more general planetary formation processes. Here we employ numerical models of planet formation, evolution, and interior structure, to show that a planet's bulk water fraction and radius are anti-correlated with initial $^{26}$Al levels in the planetesimal-based accretion framework. The heat generated by this short-lived radionuclide rapidly dehydrates planetesimals prior to accretion onto larger protoplanets and yields a system-wide correlation of planet bulk abundances, which, for instance, can explain the lack of a clear orbital trend in the water budgets of the TRAPPIST-1 planets. Qualitatively, our models suggest two main scenarios of planetary systems' formation: high-$^{26}$Al systems, like our solar system, form small, water-depleted planets, whereas those devoid of $^{26}$Al predominantly form ocean worlds, where the mean planet radii between both scenarios deviate by up to about 10%.Comment: Preprint version; free-to-read journal version at https://rdcu.be/bmdlw; blog article at https://t.co/p6SValG1i

Triplet exciton diffusion and phosphorescence quenching in Iridium(III)-Centered dendrimers

A study of triplet-triplet exciton annihilation and nonradiative decay in films of iridium(III)-centered phosphorescent dendrimers is reported. The average separation of the chromophore was tuned by the molecular structure and also by blending with a host material. It was found that triplet exciton hopping is controlled by electron exchange interactions and can be over 600 times faster than phosphorescence quenching. Nonradiative decay occurs by weak dipole-dipole interactions and is independent of exciton diffusion, except in very thin films

Anxiety and anxious-depression in Parkinson's disease over a 4-year period: A latent transition analysis

Background: Depression and anxiety in Parkinson's disease are common and frequently co-morbid, with significant impact on health outcome. Nevertheless, management is complex and often suboptimal. The existence of clinical subtypes would support stratified approaches in both research and treatment. Method: Five hundred and thirteen patients with Parkinson's disease were assessed annually for up to 4 years. Latent transition analysis (LTA) was used to identify classes that may conform to clinically meaningful subgroups, transitions between those classes over time, and baseline clinical and demographic features that predict common trajectories. Results: In total, 64.1% of the sample remained in the study at year 4. LTA identified four classes, a 'Psychologically healthy' class (approximately 50%), and three classes associated with psychological distress: one with moderate anxiety alone (approximately 20%), and two with moderate levels of depression plus moderate or severe anxiety. Class membership tended to be stable across years, with only about 15% of individuals transitioning between the healthy class and one of the distress classes. Stable distress was predicted by higher baseline depression and psychiatric history and younger age of onset of Parkinson's disease. Those with younger age of onset were also more likely to become distressed over the course of the study. Conclusions: Psychopathology was characterized by relatively stable anxiety or anxious-depression over the 4-year period. Anxiety, with or without depression, appears to be the prominent psychopathological phenotype in Parkinson's disease suggesting a pressing need to understanding its mechanisms and improve management

Ultrafast depolarization of the fluorescence in a conjugated polymer

The effect of the extent of pi electron conjugation on the primary photophysics in semiconducting polymers is reported. A rapid depolarization of photoluminescence and transient absorption, which indicates a reorientation of the transition dipole moment by similar to 30 degrees on a sub-100 fs time scale, is observed in the fully conjugated polymer poly[2-(2'-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene] (MEH-PPV). In contrast, partially conjugated polymers exhibit a much slower depolarization. The results reveal rapid changes of exciton delocalization in the fully conjugated MEH-PPV driven by structural relaxation

Motor phenotypes, medication and mood: further associations with impulsive behaviours in Parkinson's disease

BACKGROUND: Dopaminergic drugs are the primary risk factor for Impulse Control Behaviours (ICB) in Parkinson's disease (PD), others being early-onset disease and gender. OBJECTIVE: This report further explores ICB symptom relationships with motor and mood phenotypes, the complex relationship with dopaminergic medications, and hypothesizes a model with potential clinical implications. METHODS: Data from 500 PD patients were analyzed. Hypersexuality, gambling and shopping behaviour were assessed using selected questions from the Minnesota Impulsive Disorders Interview questionnaire. Local questions assessed hobbyism. Motor characteristics considered were akinetic-rigid/gait disturbance (PIGD) and 'non-PIGD' phenotypes, motor severity, motor progression, and presence/absence of motor fluctuations. Other variables included anxiety, depression, current levodopa and agonist use, age, gender and cognition. RESULTS: Overall, ICB symptom frequency was 17.8%. There was no relationship between PIGD/non-PIGD motor phenotypes and ICB symptoms. Those with ICB symptoms had higher total combined levodopa/agonist equivalent intake, but not current agonist-only equivalent intake. ICB symptoms were reported by 23.1% of those taking combined levodopa and agonist compared to 19.2% on agonist monotherapy and 11.6% levodopa monotherapy. Compared with non-ICB patients, patients with ICB symptoms were more likely to show an anxious mood phenotype, reported more motor fluctuations, and were younger. CONCLUSIONS: Both PIGD and non-PIGD phenotypes are equally affected. Dose-related risk applies to total anti-parkinsonian medication and not just current agonist-only. Anxious mood phenotypes may carry increased risk. A role of anxiety, either as a marker of risk, indirect causal factor, or maintaining factor is incorporated into a preliminary model. We discuss implications for clinical management

Non-Bloch-Siegert-type power-induced shift of two-photon electron paramagnetic resonances of charge-carrier spin states in an OLED

We present Floquet theory-based predictions and electrically detected magnetic resonance (EDMR) experiments scrutinizing the nature of two-photon magnetic resonance shifts of charge-carrier spin states in the perdeuterated $\pi$-conjugated polymer poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene] (d-MEH-PPV) under strong magnetic resonant drive conditions (radiation amplitude $B_1$ ~ Zeeman field $B_0$). Numerical calculations show that the two-photon resonance shift with power is nearly drive-helicity independent. This is in contrast to the one-photon Bloch-Siegert shift that only occurs under non-circularly polarized strong drive conditions. We therefore treated the Floquet Hamiltonian analytically under arbitrary amplitudes of the co- and counter-rotating components of the radiation field to gain insight into the nature of the helicity dependence of multi-photon resonance shifts. In addition, we tested Floquet-theory predictions experimentally by comparing one-photon and two-photon charge-carrier spin resonance shifts observed through room-temperature EDMR experiments on d-MEH-PPV-based bipolar injection devices [i.e., organic light emitting diode structures (OLEDs)]. We found that under the experimental conditions of strong, linearly polarized drive, our observations consistently agree with theory, irrespective of the magnitude of $B_1$, and therefore underscore the robustness of Floquet theory in predicting nonlinear magnetic resonance behaviors.Comment: 22 pages, 5 figure

Teaching mathematics for search using a tutorial style of delivery

Understanding of mathematics is needed to underpin the process of search, either explicitly with Exact Match (Boolean logic, adjacency) or implicitly with Best match natural language search. In this paper we outline some pedagogical challenges in teaching mathematics for information retrieval (IR) to postgraduate information science students. The aim is to take these challenges either found by experience or in the literature, to identify both theoretical and practical ideas in order to improve the delivery of the material and positively affect the learning of the target audience by using a tutorial style of teaching. Results show that there is evidence to support the notion that a more pro-active style of teaching using tutorials yield benefits both in terms of assessment results and student satisfaction