Cavities and waveguide-cavity coupling in a three-dimensional layer-by-layer photonic crystal

This thesis examines the fundamental characteristics of defect cavities in three-dimensional (3-D) layer-by-layer photonic crystals (PCs). Photonic crystals are engineered materials in which a 3-D periodic variation in the dielectric constant is used to prevent propagation of electromagnetic waves within a range of frequencies, thus creating a photonic band gap. By introducing a cavity defect within the periodic structure of the crystal, narrow transmission bands are formed within the photonic gap. This can be viewed as photonic resonant tunneling, in which photons tunnel through PC cladding layers surrounding the cavity. The transmission modes correspond to the resonant frequencies of the cavity. Using a microwave-scale photonic crystal structure, we studied the effects of changing cladding layer thicknesses on resonant frequencies and the quality factors (Q) of measured transmission peaks. We found that, for a given cavity size, the quality factor increased with increasing cladding thickness, indicative of better photonic confinement within the cavity. Also, the peak transmission level decreased with increasing cladding thickness. Both of these results are consistent with resonant tunneling behavior. We also studied the effect of changing the cavity size, while keeping cladding thicknesses constant. We found that the resonant frequencies changed very little as the cavity sizes changed. Again, this is consistent with the theoretical picture of cavities within PCs. We also studied coupling between waveguides and cavities, in which electromagnetic radiation would travel down a waveguide within a PC, couple to a nearby cavity, which would in turn couple to a second waveguide. By studying variations in the placement of the coupling cavity with respect to the two waveguides, we were able to find conditions that would lead to almost 100% transfer from one waveguide to the other, within a narrow band of frequencies. These results suggest that waveguide-cavity coupling may be a useful component for building complex photonic waveguide networks within a photonic crystal

mRNA Coronavirus Disease 2019 Vaccine-Associated Myopericarditis in Adolescents: A Survey Study

In this survey study of institutions across the US, marked variability in evaluation, treatment, and follow-up of adolescents 12 through 18 years of age with mRNA coronavirus disease 2019 (COVID-19) vaccine-associated myopericarditis was noted. Only one adolescent with life-threatening complications was reported, with no deaths at any of the participating institutions

Cavities and waveguide-cavity coupling in a three-dimensional layer-by-layer photonic crystal

This thesis examines the fundamental characteristics of defect cavities in three-dimensional (3-D) layer-by-layer photonic crystals (PCs). Photonic crystals are engineered materials in which a 3-D periodic variation in the dielectric constant is used to prevent propagation of electromagnetic waves within a range of frequencies, thus creating a photonic band gap. By introducing a cavity defect within the periodic structure of the crystal, narrow transmission bands are formed within the photonic gap. This can be viewed as photonic resonant tunneling, in which photons tunnel through PC cladding layers surrounding the cavity. The transmission modes correspond to the resonant frequencies of the cavity. Using a microwave-scale photonic crystal structure, we studied the effects of changing cladding layer thicknesses on resonant frequencies and the quality factors (Q) of measured transmission peaks. We found that, for a given cavity size, the quality factor increased with increasing cladding thickness, indicative of better photonic confinement within the cavity. Also, the peak transmission level decreased with increasing cladding thickness. Both of these results are consistent with resonant tunneling behavior. We also studied the effect of changing the cavity size, while keeping cladding thicknesses constant. We found that the resonant frequencies changed very little as the cavity sizes changed. Again, this is consistent with the theoretical picture of cavities within PCs. We also studied coupling between waveguides and cavities, in which electromagnetic radiation would travel down a waveguide within a PC, couple to a nearby cavity, which would in turn couple to a second waveguide. By studying variations in the placement of the coupling cavity with respect to the two waveguides, we were able to find conditions that would lead to almost 100% transfer from one waveguide to the other, within a narrow band of frequencies. These results suggest that waveguide-cavity coupling may be a useful component for building complex photonic waveguide networks within a photonic crystal.</p

Optic nerve sheath diameter in glaucoma patients and its correlation with intraocular pressure

Aim: To compare Optic Nerve Sheath Diameter (ONSD) in Primary Open Angle Glaucoma (POAG), Primary Angle Closure Glaucoma (PACG) and Normal Tension Glaucoma (NTG).Material and method: Patients with POAG (n=38), PACG (n=32), NTG (n=18) and Controls (n=48) underwent B-scan ultrasound and Computed Tomography Scan (CT scan) measurement of ONSD. Intraocular pressure (IOP) was measured in all groups and was correlated with ONSD.RESULT: ONSD was significantly (p=&lt;0.001) increased in NTG patients (mean=5.0mm ±0.48SD) compared with POAG (mean=4.20mm±0.32), PACG (mean=4.33mm±0.27) and control (mean=4.21mm±0.31). ONSD showed correlation with IOP in PACG group (r=0.392, p=0.02) while it did not in other groups.Conclusion: ONSD in a group of NTG patients were significantly increased compared with POAG, PACG and controls indicating the role of translaminar cribriform pressure gradient in NTG patients.Indirect measurement of&nbsp; intracranial pressure (ICP) by assessment of ONSD may provide further insight into retrolaminar pressure component and pathophysiology of glaucoma

Comparative study of different formulae for prediction of best fit endotracheal tube size in children

Abstract Background Various formulae have been used to predict appropriate endotracheal tube (ETT) size in children, but there is no consensus regarding the best predictor. Recent use of ultrasonography (USG) to predict the ETT size may not always be feasible leaving the physical parameters as most useful and practical option. The present study was planned to compare age-, height- and weight-based formulae for ETT size prediction in children. Results The accuracy in predicting ETT size was found to be 88.67%, 73.33% and 32.67% for height-based formula (HBF), age-based formula (ABF) and weight-based formula (WBF), respectively. Pearson correlation coefficient was best for HBF (0.968 with 95% CI of 0.937–0.999), followed by ABF (0.942 with 95% CI of 0.887–0.996) and WBF (0.874 with 95% CI of 0.794–0.953). HBF was found to be best suited for children 1–3 years, ≤ 90 cm and weight 98%, while WBF was unsatisfactory across all age, height and weight groups. Conclusions HBF is the best predictor of ETT size across all age groups with marginal superiority over ABF, especially in age group < 3 years. WBF was least effective in predicting ideal ETT size. It is recommended that HBF should be preferred over ABF and WBF for selection of ETT size in paediatric patients. This practice assumes greater importance especially in emergency situations where exact age and weight cannot be ascertained while height is easily obtainable

Systematic review and meta-analysis: influence of smoking cessation on incidence of pneumonia in HIV.

BACKGROUND: Smoking is common in people infected with HIV but cessation support is not a routine part of clinical care. The aim was to assess whether smoking is a risk factor for pneumonia in people with HIV and whether smoking cessation ameliorates excess risk. METHODS: We performed MEDLINE and Embase database searches and included cohort or case-control studies conducted in adult patients infected with HIV extracting a hazard ratio (HR) or odds ratio (OR) that compared the incidence of bacterial pneumonia or pneumonia caused by Pneumocystis jiroveci (PCP) between two smoking categories. Studies were appraised for quality and combined using inverse variance meta-analysis. RESULTS: Fourteen cohort and case-control studies were included. Assessment of outcome was good, but assessment of exposure status was poor. Current smokers were at higher risk of bacterial pneumonia than former smokers: HR 1.37 (95% confidence interval (CI): 1.06, 1.78). There was no evidence that former smokers were at higher risk than never smokers: HR 1.24 (95%CI: 0.96, 1.60). Current smokers were at higher risk of bacterial pneumonia than current non-smokers: HR of 1.73 (95%CI: 1.44, 2.06). There was no evidence that smoking increased the incidence of PCP. The HR for current versus non-smokers was 0.94 (95%CI: 0.79, 1.12), but from case-control studies the OR was 1.76 (95%CI: 1.25, 2.48) with heterogeneity. Confined to higher quality studies, the OR was 0.97 (95%CI: 0.81, 1.16). Residual confounding is possible, but available data suggest this is not an adequate explanation. CONCLUSIONS: Smoking is a risk factor for bacterial pneumonia but not PCP and smoking cessation reduces this risk.See related article: http://www.biomedcentral.com/1741-7015/11/16.</p

mRNA Coronavirus Disease 2019 Vaccine-Associated Myopericarditis&nbsp;in&nbsp;Adolescents: A Survey Study.

In this survey study of institutions across the US, marked variability in evaluation, treatment, and follow-up of adolescents 12 through 18&nbsp;years of age with mRNA coronavirus disease 2019 (COVID-19) vaccine-associated myopericarditis was noted. Only one adolescent with life-threatening complications was reported, with no deaths at any of the participating institutions