Micro bimorph cantilever switches for tuning integrated optical systems

We propose to use a self aligning technology (Figure 1) to integrate micro bimorph cantilevers with tips with respect to e.g. the holes in a photonic band gap (PBG) microresonator coupling section in order to perturb its evanescent field [1]. Using a simplified process, we first fabricated bimorph cantilevers on top of silicon, by surface micromachining techniques in which the upper electrode is a thin layer of Chromium on the top of a thick layer of dielectric material which is Silicon Rich Nitride (SiN). The resonance frequencies and pull in voltages of these electrostatically actuated bimorph cantilevers with off-state deflection [2] are analysed and it is found that the higher resonance frequencies come at the price of larger switching voltages (Figure 2-3). This allows for fabrication of relative stiff cantilevers with resonance frequencies in the MHz range to interact with the evanescent field of PBG crystals in which the mechanical elements start to play a role typically with a distance <400 nanometers. We have also fabricated bimorph cantilevers without tips, integrated on top of various optical systems like ring resonators, photonic crystals and planar waveguides. Analytical and numerical models are developed to predict the resonance frequencies and the pull-in voltages of these switches, including the effect of undercut and validated it with experimental data. We have observed selective wavelength on/off switching by perturbing the near band edge resonance of a waveguide grating with a 20 μm wide silicon nitride AFM cantilever, without using its tip area (Figure 4). The observed mechanical perturbation allows 15 dB on/off switching of a specific wavelength and a wavelength tuning of approximately 60 pm. In conclusion, here we describe the technology for fabricating integrated bimorph switches, the optimization studies of the cantilever designs and measurements of mechano-optical interactions using an AFM based cantilever. These optical switches have potential application in the field of elecommunication networks

Qatar's national mental health study—the world mental health Qatar

Background We provide an overview of Qatar's first epidemiological study on prevalence, predictors, and treatment contact for mood and anxiety disorders. Aims We highlight the importance of the three-pronged study, its aims, and its key components. Materials & Methods The first component comprised a probability-based representative survey of Qatari and non-Qatari (Arab) adult males and females recruited from the general population and interviewed using the International Diagnostic Interview (CIDI version 3.3). The second component, a clinical reappraisal study, assessed concordance between diagnoses based on the CIDI and independent clinical assessments conducted by trained clinical interviewers. The third component comprised a resting-state functional magnetic resonance imaging study of healthy survey respondents who were matched to patients with psychosis. Results 5000 survey interviews provided data on prevalence and treatment of common mental disorders. Clinical re-interviews (N = 485) provided important diagnostic validity data. Finally, state-of-the art structural and functional brain markers for psychosis were also collected (N = 100). Discussion Descriptive epidemiological data were collected to inform future mental health priorities in Qatar and situates these within a global context. Conclusion The study fills important gaps in regional and global estimates and establish necessary baseline to develop comprehensive risk estimates for mental health in Qatar’s young population

Mechanical tuning of optical race-track ring resonators

This paper presents the fabrication and mechanical characterization of electrostatically actuated micro bimorphs integrated with race-track ring resonators, for optical tuning applications. The bimorphs, having an upward deflection in the off-state, are integrated by surface micromachining techniques with race-track ring resonators fabricated on Silicon On Insulator (SOI) wafers. Using electrostatic actuation, these bimorphs are pulled into the evanescent field of the ring resonator thereby modulating the propagation properties. Pull-in voltages of the bimorphs have been measured statically and the effect of electrostatic spring softening (ESS) on the resonance frequency has been measured dynamically. The resonance wavelength of the optical ring resonator could be tuned by 50 pm by applying an 8.5 V DC voltage to a 40 μm long bimorph, bringing it into close proximity of the ring resonator waveguide. To the best of our knowledge, this is the first experimental demonstration of tuning of race track ring resonators by integrated, electrostatically actuated bimorphs.\ud \u

Mathematical modeling of temperature effect on algal growth for biodiesel application

Microalgae biomass is promising feedstock for the industrial production of biodiesel. Hence, research and development are required in various domains especially optimizations of growth conditions including temperature effect for mass scale operation (production of biomass, harvesting, extraction of lipid, etc). Since in middle east region, seasonal temperature variation and more rapid daily fluctuations are amenable to alter the growth kinetics of microalgae in outdoor culture and hence affect algae biomass production efficiency. Therefore, in this study, a mathematical model was developed to calculate how the algae sp. (Chlorella kessleri) will react at different temperatures. The model integrates Monod model and Arrhenius equation, and as such it describes the relationship of algal growth rate with culturing temperature and limiting nutrient concentration. The apparent activation energy and pre-exponential factors were calculated to be 2537 cal/mol and 0.0077 day−1, respectively. The developed models could be useful to anticipate the effective impacts of temperature on outdoor algae culture

Stress testing and non-invasive coronary angiography in patients with suspected coronary artery disease: time for a new paradigm

Diagnosis and management of coronary artery disease represents major challenges to our health care system, affecting millions of patients each year. Until recently, the diagnosis of coronary artery disease was possible only through cardiac catheterization and invasive coronary angiography. To avoid the risks of an invasive procedure, stress testing is often employed for an initial assessment of patients with suspected coronary artery disease, serving as a gatekeeper for cardiac catheterization. With the emergence of non-invasive coronary angiography, the question arises if such a strategy is still sensible, particularly, in view of only a modest agreement between stress testing results and the presence of coronary artery disease established by cardiac catheterization. Much data in support of the diagnostic accuracy and prognostic value of non-invasive coronary angiography by computed tomography have emerged within the last few years. These data challenge the role of stress testing as the initial imaging modality in patients with suspected coronary artery disease. This article reviews the clinical utility, limitations, as well as the hazards of stress testing compared with non-invasive coronary artery imaging by computed tomography. Finally, the implications of this review are discussed in relation to clinical practice

Selective Exposure to Berita Harian Online and Utusan Malaysia Online: The Roles of Surveillance Motivation, Website Usability and Website Attractiveness

News media allows audiences to be selective in determining both their news sources and type of news stories they read. This study examined factors influencing selective exposure to the online editions of two mainstream Malaysian newspapers, Berita Harian and Utusan Malaysia. Using selective exposure theory as the theoretical lens, this study compared both newspapers in terms of their audiences’ level of surveillance motivation, and how audiences rate the newspapers’ websites with respect to usability and attractiveness. This study used a within-subject experimental research design that exposed 51 subjects to both Berita Harian and Utusan Malaysia online newspapers. The results of the experiment indicate that Berita Harian and Utusan Malaysia online were significantly different in terms of website usability; however, no significant differences were found in terms of surveillance motivation or website attractiveness between the two newspapers. Further analysis indicate that the only significant predictor of selective exposure was website usability. This study highlights the importance of website usability for online newspapers wanting to harness audience selectivity

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Integration of Micro-cantilevers with Photonic Structures for Mechano-optical Wavelength Selective Devices

This thesis deals with the fabrication technology and mechano-optical characterisation of compact integrated wavelength selective optical devices for use in telecommunication applications. Upon electrostatic actuation, a mechanical element perturbs the optical evanescent field of a guided wave providing electro mechano-optical modulation of light. The silicon-on-insulator (SOI) based optical devices are fabricated in a silicon photonics fabrication platform called ePIXfab using deep-UV lithography. Further, using surface micromaching techniques, the mechanical elements are monolithically integrated with the optical devices in the MESA+ Cleanroom. Mechanooptical modulation is investigated in three different types of optical devices, viz. a microring resonator, a photonic crystal slab waveguide and a photonic crystal microcavity based device. Owing to their ease of fabrication and low power consumption, electrostatically actuated curled micro-bimorph cantilevers are chosen as the mechanical perturbing element. The thesis concentrates on the characterisation of the mechanical elements, the development of integration technologies and mechano-optical characterisation of the integrated devices