Analysis of surface plasmon excitation at terahertz frequencies with highly-doped graphene sheets via attenuated total reflection

Excitation of surface plasmons supported by doped graphene sheets at terahertz frequencies is investigated numerically. To alleviate the momentum mismatch between the highly-confined plasmon modes and the incident radiation, it is proposed to increase the surface conductivity of graphene through high doping levels or with few-layer graphene. For currently achievable doping levels, our analysis shows that surface plasmons on monolayer graphene may be excited at operating frequencies up to about 10 THz (~ 41.3 meV) with a high-index coupling prism, and higher frequencies/energies are possible for few-layer graphene. These highly-confined surface modes are promising for sensing and waveguiding applications in the terahertz regime

Proposal for compact solid-state III-V single-plasmon sources

We propose a compact single-plasmon source operating at near-infrared wavelengths on an integrated III-V semiconductor platform, with a thin ridge waveguide serving as the plasmon channel. By attaching an ultra-small cavity to the channel, it is shown that both the plasmon generation efficiency ({\beta}) and the spontaneous-decay rate into the channel can be significantly enhanced. An analytical model derived with the Lorentz reciprocity theorem captures the main physics involved in the design of the source and yields results in good agreement with fully-vectorial simulations of the device. At resonance, it is predicted that the ultra-small cavity increases the {\beta}-factor by 70% and boosts the spontaneous decay rate by a factor 20. The proposed design could pave the way towards integrated and scalable plasmonic quantum networks. Comparison of the present design with other fully-dielectric competing approaches is addressed.Comment: 8 pages, 4 figure

Role of quasicylindrical waves and surface plasmon polaritons on beam shaping with resonant nanogratings in the infrared

Journal ArticleThe role of quasicylindrical waves and surface plasmon polaritons in beam shaping with resonant nanogratings is investigated. It is shown that the field on the grating surface can be strongly influenced by plasmons and quasicylindrical waves in the infrared. A method that combines far-field measurements with the fast Fourier transform to map the field amplitude at the grating surface is demonstrated. For samples with a small degree of geometric asymmetry, it is shown that the imaginary part of the transform (with null zeroth-order component) can better map the amplitude of the resonant surface waves than the full complex-valued transform. Our results will impact the study, design, and footprint of resonant nanogratings. © 2014 American Physical Society.Engineering and Physical Sciences Research Council (EPSRC

The discriminative power of the EuroQol visual analog scale is sensitive to survey language in Singapore

<p>Abstract</p> <p>Background</p> <p>Existing evidence for validity of the visual analog scale of the EQ-5D-3L questionnaire (EQ-VAS) is weak in Chinese-speaking respondents in Singapore. We therefore investigated the validity of the Chinese (Singapore) version of EQ-VAS in patients with diabetes.</p> <p>Methods</p> <p>In a cross-sectional survey, patients with type 2 diabetes seen in a primary care facility completed an identical Chinese or English questionnaire containing the EQ-5D-3L and questions assessing other health and disease-related characteristics. Convergent and known-groups validity of the EQ-VAS was examined for Chinese- and English-speaking respondents separately.</p> <p>Results</p> <p>The EQ-VAS was correlated with the EQ-5D-3L health index and a 5-point Likert-type scale for assessing global health in both Chinese-speaking (N = 335) and English-speaking respondents (N = 298), suggesting convergent validity. The mean EQ-VAS scores differed between English-speaking patients with differing duration of diabetes (< 10 years versus ≥ 10 years), comorbidity status (absence versus presence), and complications of diabetes (absence versus presence), providing evidence for known-groups validity. However, the EQ-VAS scores for Chinese-speaking respondents known to differ in these characteristics were similar, even among subgroups of relatively younger patients or those with formal school education.</p> <p>Conclusions</p> <p>Chinese- and English-speaking Singaporeans respond differently to the EQ-VAS. The Chinese version of EQ-VAS appears less sensitive than its English version for measuring global health in patient populations in Singapore.</p

Unravelling the genome of long chain N-acylhomoserine lactone-producing Acinetobacter sp. strain GG2 and identification of its quorum sensing synthase gene

Myriad proteobacteria use N-acyl homoserine lactone (AHL) molecules as quorum-sensing (QS) signals to regulate different physiological functions, including virulence, antibiotic production and biofilm formation. Many of these proteobacteria possess LuxI/LuxR system as the QS mechanism. Recently, we reported the 3.89 Mb genome of Acinetobacter sp. strain GG2. In this work, the genome of this long chain AHL-producing bacterium was unravelled which led to the molecular characterization of luxI homlogue, designated as aciI. This 552 bp gene was cloned and overexpressed in Escherichia coli BL21(DE3). The purified protein was approximately 20.5 kDa and is highly similar to several autoinducer proteins of LuxI family among Acinetobacter species. To verify the AHL synthesis activity of this protein, high resolution liquid chromatography-mass spectrometry analysis revealed the production of 3-oxo-dodecanoyl homoserine lactone and 3-hydroxy dodecanoyl homoserine lactone from induced E.coli harboring the recombinant AciI. Our data show for the first time, the cloning and characterization of the luxI homologue from Acinetobacter sp. strain GG2, and confirmation of its AHLs production. These data are of great significance as the annotated genome of strain GG2 has provided a valuable insight in the study of autoinducer molecules and its roles in QS mechanism of the bacterium

Essays on information revelation and political institutions

This dissertation examines how political institutions shape incentives for the transmission of policy-relevant private information. The first two chapters present theoretical frameworks to examine strategic information transmission to political candidates by a biased adviser. The third explores the causal impact of gender representation on municipal outcomes in the United States. In Chapter One, I examine a model of "cheap talk" lobbying with no commitment. A biased adviser seeks to influence the policy outcome of a Downsian election by sending messages to the two candidates before they announce their policy platforms. I show that the adviser may credibly reveal some information on voter preferences, but only privately to one candidate. Political competition has a disciplining effect; the adviser prefers extreme policies, but instead recommends a pragmatic policy --- one that is just close enough to voters' preference. In some situations, the presence of the biased adviser benefits the median voter. The second chapter presents a model of informational lobbying with full commitment. The biased adviser strategically designs informative signals on voter preferences that will be observed by each of the two candidates. In contrast to the cheap talk context, the optimal signal structure is shown to involve only public signals that are observed by both candidates. In particular, candidates receive precise information about how extreme voter preferences are, but not whether voters lean right or left. Consequently, both candidates choose the same biased policy, as a result of which the median voter is always worse off. Chapter Three investigates the effect of gender representation on municipal outcomes in the United States between 2008 and 2016. Using novel data, the analysis exploits close elections between male and female candidates to measure the impact of an exogenous increase in the number of female council members. Consistent with the existing literature, we find evidence of decreased per capita expenditure, which, we argue, is not driven by revenue constraints but by increased disagreement or "gridlock" within the council. We also find no significant effect of gender representation on the composition of municipal spending or on other women's political aspirations

Medicinal plants in Sabah (North Borneo) exhibit antipancreatic lipase, anti-amylase, and antioxidant properties

Medicinal plants have been widely used for their notable health benefits and help in disease prevention for generations. In recent years, obesity has become among the risk factors of hyperglycemia and oxidation stress. This study aims to investigate the potential of plants in Sabah, North Borneo to inhibit the key enzymes involved in obesity, hyperglycemia and oxidative stress. A total of 46 plant extracts were subjected to anti-pancreatic lipase, α-amylase inhibition and antioxidant assays. It was observed that S43 (Lantana camara) exhibited the greatest IC50 of anti-pancreatic lipase activity (mean of IC50 (±S.D.) = 0.20 mg mL-1 ± 0.010). Cinnamomum sp. (S42) has the most substantial α-amylase activity with a mean IC50 (±S.D.) = 2.68 mg mL-1 ± 0.471. S19 (Glochidion rubrum) was the most effective antioxidants (mean of IC50 (±S.D.) = 0.011 mg mL-1 ± 0.004) among all the investigated samples. Interestingly, three plant extracts were found (S6-Buchanania sp.; S22-Vitex negundo and S42-Cinnamomum sp.) to exhibit inhibition activity in ant pancreatic lipase, α-amylase and antioxidant assays. The bioactivities of plant extracts have been closely related to the content of phytochemicals, as in earlier studies. Thus, plants have the potential to serve as supplements and nutraceuticals for obesity and other related complications