Signals of primordial phase transitions on CMB maps

The analysis of the CMB anisotropies is a rich source of cosmological informations. In our study, we simulated the signals produced by the relics of a first order phase transition occured during an inflationary epoch in the early Universe. These relics are bubbles of true vacuum that leave a characteristic non-Gaussian imprint on the CMB. We use different statistical estimators in order to evaluate this non-Gaussianity. We obtain some limits on the allowed values of the bubble parameters comparing our results with the experimental data. We also predict the possibility to detect this signal with the next high resolution experiments.Comment: 2 pages, submitted to Proceedings of 9th Marcel Grossmann meetin

Present limits to cosmic bubbles from the COBE-DMR three point correlation function

The existence of large scale voids in several galaxy surveys suggests the occurence of an inflationary first order phase transition. This process generates primordial bubbles that, before evolving into the present voids, leave at decoupling a non-Gaussian imprint on the CMB. I this paper we evaluate an analytical expression of the collapsed three point correlation function from the bubble temperature fluctuations. Comparing the results with COBE-DMR measures, we obtain upper limits on the allowed non-Gaussianity and hence on the bubble parameters.Comment: 4 pages, 3 figures; submitted to MNRA

Multiscale mass-spring models of carbon nanotube foams

This article is concerned with the mechanical properties of dense, vertically aligned CNT foams subject to one-dimensional compressive loading. We develop a discrete model directly inspired by the micromechanical response reported experimentally for CNT foams, where infinitesimal portions of the tubes are represented by collections of uniform bi-stable springs. Under cyclic loading, the given model predicts an initial elastic deformation, a non-homogeneous buckling regime, and a densification response, accompanied by a hysteretic unloading path. We compute the dynamic dissipation of such a model through an analytic approach. The continuum limit of the microscopic spring chain defines a mesoscopic dissipative element (micro-meso transition) which represents a finite portion of the foam thickness. An upper-scale model formed by a chain of non-uniform mesoscopic springs is employed to describe the entire CNT foam. A numerical approximation illustrates the main features of the proposed multiscale approach. Available experimental results on the compressive response of CNT foams are fitted with excellent agreement

Detecting stable massive neutral particles through particle lensing

Stable massive neutral particles emitted by astrophysical sources undergo deflection under the gravitational potential of our own galaxy. The deflection angle depends on the particle velocity and therefore non-relativistic particles will be deflected more than relativistic ones. If these particles can be detected through neutrino telescopes, cosmic ray detectors or directional dark matter detectors, their arrival directions would appear aligned on the sky along the source-lens direction. On top of this deflection, the arrival direction of non-relativistic particles is displaced with respect to the relativistic counterpart also due to the relative motion of the source with respect to the observer; this induces an alignment of detections along the sky projection of the source trajectory. The final alignment will be given by a combination of the directions induced by lensing and source proper motion. We derive the deflection-velocity relation for the Milky Way halo and suggest that searching for alignments on detection maps of particle telescopes could be a way to find new particles or new astrophysical phenomena.Comment: 17 pages, 7 figures. Accepted by PR

Can You Hear Me Now: The Myths Surrounding Cell Phone Use While Driving and Connecticut\u27s Failed Attempt at a Remedy Note

The use of cell phones while driving has been demonized by many as a predominant cause of automobile accidents attributed to distracted driving. While there is no doubt that distracted driving is dangerous, and increases the risk of being involved in an automobile accident, this Note contends that cell phone use does not play as prominent a role in distracted driving as is typically portrayed. Many other distractive stimuli pose a more significant threat, and often occur more regularly than cell phone use. Unlike cell phone use, however, these other distractive stimuli have not been characterized as negatively, or singled out by legislative bans. In particular, Connecticut’s legislation banning cell phone use while driving is neither a direct nor a particularly effective means of achieving its purported purpose of increasing the safety of Connecticut’s roadways. This Note advocates utilizing a graded negligence methodology which directly addresses the root of the problem—the conduct of the driver—by focusing on remedying all distractive driving practices. The graded negligence standard concentrates on the quality of conduct exhibited in the presence of a distractive influence, weighed with the level of negligence displayed in the conduct, combined with several other factors

Observational Constraints on Silent Quartessence

We derive new constraints set by SNIa experiments (`gold' data sample of Riess et al.), X-ray galaxy cluster data (Allen et al. Chandra measurements of the X-ray gas mass fraction in 26 clusters), large scale structure (Sloan Digital Sky Survey spectrum) and cosmic microwave background (WMAP) on the quartessence Chaplygin model. We consider both adiabatic perturbations and intrinsic non-adiabatic perturbations such that the effective sound speed vanishes (Silent Chaplygin). We show that for the adiabatic case, only models with equation of state parameter $|\alpha |\lesssim 10^{-2}$ are allowed: this means that the allowed models are very close to \LambdaCDM. In the Silent case, however, the results are consistent with observations in a much broader range, -0.3<\alpha<0.7.Comment: 7 pages, 12 figures, to be submitted to JCA

YouTube Atherectomy Videos: What Industry is Telling Us About this Endovascular Procedure

BACKGROUND: Patients are turning to the Internet and YouTube for information about their providers, disease states and potential interventions. Endovascular atherectomy is a common procedure undertaken in the treatment of peripheral vascular disease especially in outpatient treatment centers despite its cost. Little is known how this procedure is portrayed in online video content. We set forth to search YouTube to gain insight to how industry and non-industry portrays this endovascular technology. METHODS: YouTube (www.youtube.com) website was accessed in July 2017 with a cleared cached web browser for the key search word “atherectomy”. The top 100 videos with greater than 100 views were examined. All results were separated into two categories - industry (I) or non-industry (NI) sources. The duration of video, age of video, total video views, academic information, cost information and if outpatient treatment center focused care were also collected. RESULTS: A total of 100 videos were examined. The videos were separated into two groups: Industry (n=20) and Non-Industry (n=80). Videos from Industry and Non-Industry were similar in content in terms of duration (4.8 ± 4.5 and 5.6 ± 4.4 minutes), creation time (3.3 ± 2.2 and 3.4 ± 1.9 years), and total views (7386 ± 14,593 and 5560 ± 13,181). Proportions of videos from each group that contained educational content were also similar (70% and 70%). However, only 7% (n=7) of the videos reference the procedure being linked to care in outpatient treatment center. Only 3% (n=3) mentioned the cost of the procedure. All of these videos from each of these categories were from non-industry sources. Conclusion: In our sampling of “Atherectomy” YouTube videos, we find similar video content in terms of duration, creation time, total views and educational content. Interestingly, the cost and its association with outpatient treatment labs is mentioned in only a minority of the videos and only from non-industry sources. These data should inform the vascular surgery community the lack of public understanding of this endovascular technology as evidenced in YouTube videos