Measurement of absolute radius, refractive index and dispersion of a long cylinder

Long cylinders, such as optical fibers, are some of the most widely used photonic devices. The radius and refractive index of these fibers are therefore fundamentally important parameters in determining their performance. We have developed a method to determine the absolute radius, refractive index, and chromatic dispersion of a long cylinder using only the resonance wavelengths of the whispering gallery modes around its circumference for two different polarizations. Since this method only requires the measurement of resonance wavelengths, it is non-destructive and it can be performed using standard equipment. As a proof-of-concept, we demonstrate the method on a $125\mu m$ optical fiber and an $80\mu m$ borosilicate capillary fiber with thick walls, obtaining values for the diameter and the refractive index with an accuracy of $2 nm$ and $2\times 10^{-5}$, respectively.Comment: 10 pages, 5 figures; Correction to name in reference and typo; removed line number

Communication médiatisée et présence sociale : une étude de cas sur des cours entièrement à distance de niveau universitaire

Ce mémoire porte sur les liens entre la communication médiatisée par ordinateur et l'émergence de communautés virtuelles. Plus précisément, il est question de mettre en lien les interactions entre individus dans un contexte virtuel et l'émergence de communautés d'apprentissage dans le cadre de cours en ligne de niveau universitaire. Cette étude de nature quantitative a utilisé le sondage par questionnaire électronique autoadministré comme méthode de collecte de données. L'échantillon est composé des étudiants inscrits à la session d'été 2009 aux cours ComViz et Sexualité et cultures, deux cours offerts entièrement à distance, avec un total de 254 étudiants actifs. Les conclusions mettent en évidence la faiblesse des liens sociaux noués lors des échanges en ligne. Les étudiants utilisent surtout les outils d'interactions pour se présenter et chercher des informations sur des sujets relatifs au cours, mais ne s'engagent pas dans un processus de collaboration reposant sur des objectifs communs

Social support, but not perceived food environment, is associated with diet quality in French-speaking Canadians from the PREDISE study

The objectives were to assess whether social support for healthy eating and perceived food environment are associated with diet quality, and to investigate if sociodemographic characteristics moderate these associations. A probability sample of French-speaking adults from the Province of Québec, Canada, was recruited in the context of the PREDISE study. Participants reported their perceptions of supportive and non-supportive actions related to healthy eating from close others at home and outside of home (n = 952), and of the accessibility to healthy foods (n = 1035). The Canadian Healthy Eating Index (C-HEI) was calculated based on three Web-based 24 h food recalls. Multiple linear regression models showed that supportive (B = 1.50 (95% CI 0.46, 2.54)) and non-supportive (B = −3.06 (95% CI −4.94, −1.18)) actions related to healthy eating from close others at home were positively and negatively associated with C-HEI, respectively, whereas actions from close others outside of home were not. The negative association between non-supportive actions occurring at home and C-HEI was stronger among participants with lower (vs. higher) levels of education (p interaction = 0.03). Perceived accessibility to healthy foods was not associated with C-HEI (p > 0.05). These results suggest that the social environment may have a stronger influence on healthy eating than the perceived physical environment. This adds support for healthy eating promotion programs involving entire families, especially for more socioeconomically disadvantaged individuals, whose efforts to eat healthily may be more easily thwarted by non-supportive household

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Study and Development of Whispering Gallery Mode Resonators for Technological Applications

Whispering gallery mode resonators (WGR) are optical cavities with very low loss. This property makes them particularly interesting for many applications including sensors and nonlinear optics. Despite all the research devoted to these cavities, many basic aspects of WGR are not completely understood and many issues still inhibit these technologies from being used in real world applications. This thesis aims to address some of these issues. First, this thesis presents an attempt of a non-destructive techniques to accurately measure the absolute radius and refractive index of a WGR. In order to do so, instrumental techniques were developed to first accurately determine the mode order number without relying on approximations and, second, determine the axial position where the radius is being measured. Perturbations of the modes are then studied using the interactions of a tapered fiber and optically trapped nanoparticle. An earlier experiment demonstrated a frequency shift occurs when the nanoparticle is in proximity of the tapered fiber. This effect was not observed in our experiment. This thesis then reviews the Pound-Drever-Hall technique and describes an implementation using a single board computer for many of the electrical components. Lastly, packaging was developed to improve the robustness of the tapered fiber and reverse the degradation of the Q factor due to adsorbed water on the surface of silica SNAPs. The packaging is robust enough to transport the fiber to different laboratories but cannot withstand the temperatures required to remove the adsorbed water

THE ROLE OF DECEPTIVE DEFENSE IN CYBER STRATEGY

This thesis examines the role of deceptive defense in cyber strategy and contributes a new practical concept to aid in its implementation. In The Art of War, Sun Tzu stated, “All warfare is based on deception.” Cyber conflict should pose no exception. The ability to operate anonymously in the cyber domain enables attackers to operate with some degree of impunity, as the attribution of their identities is a complex, costly, and imperfect process. However, defenders can utilize cyber deception to improve network security and enhance both forensic and potential retaliatory cyber operations. This work introduces Deceptive Resistance to Adversary Cyber Operations (DRACO), a concept that simulates active network resources while remaining outside of a secure network perimeter. In this respect it differs from traditional “honeypot” deployments that are either within the network or completely detached. DRACO offers a “deception as a service” architecture, requiring limited integration effort and offering cloud hosting potential. During experimentation on a live network, DRACO successfully redirected attacks that were intended for authentic endpoints and revealed insights pertaining to the attack patterns on active and inactive addresses within a network. Additionally, DRACO presents an opportunity to engage with the adversary, which in turn can enable the identification of an ongoing attack, adversary attribution, and assist in the preparation of retaliatory options.Approved for public release. Distribution is unlimited.Outstanding ThesisLieutenant-Colonel, Canadian Arm

Long-term fire history of maple (Acer) forest sites in the central St. Lawrence Lowland, Quebec

In the St-Lawrence lowlands, sugar maple (Acer saccharum) is considered the dominant species of old-growth deciduous forests while red maple (Acer rubrum) tends to dominate sites recently disturbed by logging and agricultural practices. Considering that the long-term influence of fire is not documented for such stands, we reconstructed the postglacial tree composition (as deduced from charcoal species) and fire history of a sugar maple (Ste-Françoise area) and a red maple (Villeroy area) stand located southwest of Quebec City (Canada). The sites are 10 km apart and show contrasting soil and landform features. Using botanical identification andThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Sugar maple (Acer saccharum) at its northeastern range limit: a fire-resilient tree species

The long-standing hypothesis that sugar maple (Acer saccharum) communities are maintained at equilibrium by present climate and small-scale disturbances is questioned as empirical evidence is accumulating about the ability of the species to withstand several stand-scale disturbances. The fire history of a sugar maple site at the northeastern range limit of the species (GaspĂŠ Peninsula, eastern Canada) was documented to test the hypothesis that this forest type is resilient to fire disturbance. The fire history was reconstructed using radiocarbon-dated soil macrocharcoals. Two main fire periods were recorded during the Holocene. The oldest period occurred between 9055 and 8265 cal. years BP, and was characterized by the presence of conifers, including spruce. After 6900 years of fire-free activities, the second period covered the last 1335 years, and was characterized by the presence of sugar maple in the charcoal assemblage. The dominance of sugar maple after more than 1000 years of recurrent fires underlines the species resilience to frequent site disturbances. The soil of the forest stand was heavily disturbed by earthworms. However, the dense seedling and sapling bank of sugar maple suggests that earthworms do not affect negatively the regeneration and survival of the species.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Large antiferromagnetic fluctuation enhancement of the thermopower at a critical doping in magnetic semimetal Cr1+δTe2

Cr 1+ δ Te 2 is a self-intercalated transition metal dichalcogenide that hosts tunable electronic filling and magnetism in its semimetallic band structure. Recent angle-resolved photoemission spectroscopy (ARPES) studies have unveiled a systematic shift in this semimetallic band structure relative to the chemical potential with increased Cr doping. This report presents the temperature and magnetic field dependence of the longitudinal thermopower S xx for different Cr 1+ δ Te 2 compositions. We show that as doping increases, the sign of S xx changes from positive to negative at the critical doping level of δ ~ 0.5. This observed doping-dependent trend in the thermopower is consistent with the evolution of the semimetallic band structure from ARPES. Importantly, an anomalous enhancement of the thermoelectric response near T C is also observed around δ ~ 0.5. Combining information from magnetometry and ARPES measurements, existence of the critical nature of the doping level δ c (~ 0.5) is unveiled in magnetic semimetal Cr 1+ δ Te 2 , where antiferromagnetic fluctuation and near-Fermi-energy pseudogap formation play a potential vital role in enhancing thermoelectric energy conversion