Maximum smoothed likelihood estimation and smoothed maximum likelihood estimation in the current status model

We consider the problem of estimating the distribution function, the density and the hazard rate of the (unobservable) event time in the current status model. A well studied and natural nonparametric estimator for the distribution function in this model is the nonparametric maximum likelihood estimator (MLE). We study two alternative methods for the estimation of the distribution function, assuming some smoothness of the event time distribution. The first estimator is based on a maximum smoothed likelihood approach. The second method is based on smoothing the (discrete) MLE of the distribution function. These estimators can be used to estimate the density and hazard rate of the event time distribution based on the plug-in principle.Comment: Published in at http://dx.doi.org/10.1214/09-AOS721 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Bariatric surgery and brain health: A longitudinal observational study investigating the effect of surgery on cognitive function and gray matter volume

Dietary modifications leading to weight loss have been suggested as a means to improve brain health. In morbid obesity, bariatric surgery (BARS)—including different procedures, such as vertical sleeve gastrectomy (VSG), gastric banding (GB), or Roux-en-Y gastric bypass (RYGB) surgery—is performed to induce rapid weight loss. Combining reduced food intake and malabsorption of nutrients, RYGB might be most effective, but requires life-long follow-up treatment. Here, we tested 40 patients before and six months after surgery (BARS group) using a neuropsychological test battery and compared them with a waiting list control group. Subsamples of both groups underwent structural MRI and were examined for differences between surgical procedures. No substantial differences between BARS and control group emerged with regard to cognition. However, larger gray matter volume in fronto-temporal brain areas accompanied by smaller volume in the ventral striatum was seen in the BARS group compared to controls. RYGB patients compared to patients with restrictive treatment alone (VSG/GB) had higher weight loss, but did not benefit more in cognitive outcomes. In sum, the data of our study suggest that BARS might lead to brain structure reorganization at long-term follow-up, while the type of surgical procedure does not differentially modulate cognitive performance

Generalized Ray Tracing for Axions in Astrophysical Plasmas

Ray tracing plays a vital role in black hole imaging, modeling the emission mechanisms of pulsars, and deriving signatures from physics beyond the Standard Model. In this work we focus on one specific application of ray tracing, namely, predicting radio signals generated from the resonant conversion of axion dark matter in the strongly magnetized plasma surrounding neutron stars. The production and propagation of low-energy photons in these environments are sensitive to both the anisotropic response of the background plasma and curved spacetime; here, we employ a fully covariant framework capable of treating both effects. We implement this both via forward and backward ray tracing. In forward ray tracing, photons are sampled at the point of emission and propagated to infinity, whilst in the backward-tracing approach, photons are traced backwards from an image plane to the point of production. We explore various approximations adopted in prior work, quantifying the importance of gravity, plasma anisotropy, the neutron star mass and radius, and imposing the proper kinematic matching of the resonance. Finally, using a more realistic model for the charge distribution of magnetar magnetospheres, we revisit the sensitivity of current and future radio and sub-mm telescopes to spectral lines emanating from the Galactic Center Magnetar, showing such observations may extend sensitivity to axion masses $m_a \sim \mathcal{O}({\rm few}) \times 10^{-3}$ eV, potentially even probing parameter space of the QCD axion.Comment: 25 pages, 14 figures. Comments welcom

Direct genetic demonstration of Gα13 coupling to the orphan G protein-coupled receptor G2A leading to RhoA-dependent actin rearrangement

G2A is an orphan G protein-coupled receptor (GPCR), expressed predominantly in T and B cells and homologous to a small group of GPCRs of unknown function expressed in lymphoid tissues. G2A is transcriptionally induced in response to diverse stimuli, and its ectopic expression suppresses transformation of B lymphoid precursors by BCR-ABL. G2A induces morphological transformation of NIH 3T3 fibroblasts. Microinjection of constructs encoding G2A into Swiss 3T3 fibroblasts induces actin reorganization into stress fibers that depends on RhoA, but not CDC42 or RAC. G2A elicits RhoA-dependent transcriptional activation of serum response factor. Direct evaluation of RhoA activity demonstrates elevated levels of RhoA-GTP in G2A-expressing cells. Microinjection of embryonic fibroblasts derived from various Galpha knockout mice establishes a requirement for Galpha 13 but not Galpha 12 or Galpha q/11 in G2A-induced actin rearrangement. In conclusion, G2A represents a family of GPCRs expressed in lymphocytes that may link diverse stimuli to cytoskeletal reorganization and transcriptional activation through a pathway involving Galpha 13 and RhoA

From d- to l-Monosaccharide Derivatives via Photodecarboxylation-Alkylation

Photodecarboxylation-alkylation of conformationally locked monosaccharides leads to inversion of stereochemistry at C5. This allows the synthesis of l-sugars from their readily available d-counterparts. Via this strategy, methyl l-guloside was synthesized from methyl d-mannoside in 21% yield over six steps

{\bf τ\tau-Function Evaluation of Gap Probabilities in Orthogonal and Symplectic Matrix Ensembles}

It has recently been emphasized that all known exact evaluations of gap probabilities for classical unitary matrix ensembles are in fact $\tau$-functions for certain Painlev\'e systems. We show that all exact evaluations of gap probabilities for classical orthogonal matrix ensembles, either known or derivable from the existing literature, are likewise $\tau$-functions for certain Painlev\'e systems. In the case of symplectic matrix ensembles all exact evaluations, either known or derivable from the existing literature, are identified as the mean of two $\tau$-functions, both of which correspond to Hamiltonians satisfying the same differential equation, differing only in the boundary condition. Furthermore the product of these two $\tau$-functions gives the gap probability in the corresponding unitary symmetry case, while one of those $\tau$-functions is the gap probability in the corresponding orthogonal symmetry case.Comment: AMS-Late

A Forensic Speaker Identification Study. An Auditory-Acosutic Analysis of Phonetic Features and an Exploration of the "Telephone Effect"

This study investigates the formant, fundamental frequency, and speech tempo parameters in a forensic speaker identification setting and whether these are adequate features to use in an auditory-acoustic analysis. Furthermore, the 'telephone effect' as described by Künzel (2001) is examined and analysed in terms of whether it applies to the aforementioned phonetic features. The results showed that all three parameters proved to be efficient and appropriate for forensic speaker identification practices, but that the articulation rate of the disputed sample was heavily affected by a task-effect. In terms of the intercept recordings, F1 values, especially those of close vowels, were found to be affected, consistent with Künzel's findings (2001). Mean fundamental frequency values were not altered by the intercept sample, but the standard deviation was, resulting in values twice as high compared to direct recordings.Aquest estudi investiga els paràmetres de formant, freqüència fonamental, i velocitat de l'articulació en un entorn de la identificació forense del parlant i si aquests paràmetres són adequats per utilitzar en una anàlisi auditiva-acústica. D'altra banda, 'l'efecte telefònic' descrit per Künzel (2001) és examinat i analitzat pel que fa a si és aplicable a les característiques fonètiques esmentades anteriorment. Els resultats van mostrar que els tres paràmetres són eficients i adequats per a les pràctiques d'identificació forense del parlant, però que la velocitat de l'articulació estava molt afectada per un efecte de tasca. Pel que fa a les gravacions interceptades, els valors de l'F1, especialment els de les vocals tancades, es van trobar afectats, la qual cosa és consistent amb els resultats de l'experiment de Künzel (2001). Els valors mitjans de la freqüència fonamental no van ser alterats per l'enregistrament telefònic, però la desviació estàndar, sí, mostrant valors el doble d'alts comparats amb les gravacions directes

On internal wave breaking and tidal dissipation near the centre of a solar-type star

We study the fate of internal gravity waves, which are excited by tidal forcing by a short-period planet at the interface of convection and radiation zones, approaching the centre of a solar-type star. We study at what amplitude these wave are subject to instabilities. These instabilities lead to wave breaking whenever the amplitude exceeds a critical value. Below this value, the wave reflects perfectly from the centre of the star. Wave breaking results in spinning up the central regions of the star, and the formation of a critical layer, which acts as an absorbing barrier for ingoing waves. As these waves are absorbed, the star is spun up from the inside out. This results in an important amplitude dependence of the tidal quality factor Q'. If the tidal forcing amplitude exceeds the value required for wave breaking, efficient dissipation results over a continuous range of tidal frequencies, leading to Q' \approx 10^5 (P/1day)^(8/3), for the current Sun. This varies by less than a factor of 5 throughout the range of G and K type main sequence stars, for a given orbit. We predict fewer giant planets with orbital periods of less than about 2 days around such stars, if they cause breaking at the centre, due to the efficiency of this process. This mechanism would, however, be ineffective in stars with a convective core, such as WASP-18, WASP-12 and OGLE-TR-56, perhaps partly explaining the survival of their close planetary companions.Comment: 22 pages, 10 figures, accepted in MNRAS, abstract shortened (!