Tunable light absorption of graphene using topological interface states.

A tunable light absorption of graphene using topological interface states (TISs) is presented. The monolayer graphene is embedded in the interface of asymmetric topological photonic crystals (ATPCs). A strong absorption phenomenon occurs by the excitation of TISs. It is found that the absorption spectra are intensively dependent on the chemical potential of graphene and the periodic number of the ATPCs. Furthermore, the absorption can be rapidly switched in a slight variation of chemical potential, which is modulated by the applied gate voltage on graphene. This study not only opens up a new approach for enhancing light-monolayer graphene interactions, but also provides for practical applications in high absorption optoelectronic devices. This strong absorption phenomenon is different from those in Fabry-Perot resonators, nano-cavities photonic crystal, and traditional topological photonic crystals (TPCs).

Ultra-slow light in one-dimensional Cantor photonic crystals.

Ultra-slow light and complete transmission properties in one-dimensional Cantor photonic crystals are presented. In contrast to traditional dielectric photonic crystals, the proposed structure has large group delay, slower group velocity, and a high quality factor within the same layers and materials. This study shows that larger than 1 µs group delay and slower than 1 m/s group velocity are achieved in the fifth-order Cantor photonic crystal with 52.75 µm length. This ultra-slow-light structure is very promising for application in advanced slow-light devices. A high quality factor of 109 and multiband filters with complete transmission can also be obtained by using this approach.

Sharp resonance with complete transmission in Thue-Morse microring resonators.

We present sharp resonances with complete transmission in the Thue-Morse microring resonator. The quasi-periodic structure attains a better quality of filtering than the traditional periodic structure. This includes the following: (i) the high-Q resonances with complete transmission are obtained in the transmission spectra, (ii) the maximum value of transmittance always remains 1 for an arbitrary proportion of two different radiuses in the major-band regions, and (iii) the complete transmission occurs for arbitrary coupling in the mini-band regions. Moreover, we propose an analytical method to predict the occurrences of resonance peaks in the mini-band regions based on the gap map.

Superradiant modes in resonant quasi-periodic double-period quantum wells.

This paper firstly proposes the existence of superradiant modes in resonant quasi-periodic double-period quantum wells (QWs), which has not been observed from analyzing the structure factor by traditional methods. Using the gap map method, the reflection spectra under the relevant conditions show that there are dips in the middle and the linewidth grows linearly, despite the dips, as the number of QWs increases, which is a direct demonstration of superradiance. It is also found that the relevant conditions are divided into three regions, each of which has a different width of bandgaps.

Extraordinary light absorptance in graphene superlattices.

Extraordinary absorption decrease in graphene superlattices in the visible range is presented. Due to competition between loss and resonant reflection at resonance, the absorption displays non-monotonic behavior. As the period number increases above a certain critical value, absorption decreases with the increase in the period number. This is in contrast to ordinary absorption for a non-resonant condition, which monotonically increases with the period number. Moreover, this extraordinary property can also be controlled by applying a gate voltage to graphene sheets. The results provide not only a new understanding of graphene physics but also an application in nanophotonics and optoelectronics.

High-order micro-ring resonator with perfect transmission using symmetrical Fibonacci structures.

A symmetrical Fibonacci micro-ring resonator (SFMR) has been presented to avoid the coupled resonator optical waveguide (CROW) bottle, which is a bottle-shaped distribution for high orders in transmission spectra. The SFMR features three advantages that improve filtering quality compared to that provided by traditional periodic micro-ring resonators. First, sharper resonances are obtained by eliminating the CROW bottle from the mini gaps that appear in the major-band region. Second, peaks with perfect transmission are always obtained without a radius and coupling modulation in the mini-band regions and major-band regions. Third, the full width at half-maximum of the band-edge peak decreases with the increasing generation order.

Genetic polymorphisms in the prostaglandin pathway genes and risk of head and neck cancer.

OBJECTIVE: Previous studies examining the association between genetic variations in prostaglandin pathway and risk of head and neck cancer (HNC) have only included polymorphisms in the PTGS2 (COX2) gene. This study investigated the association between genetic polymorphisms of six prostaglandin pathway genes (PGDS, PTGDS, PTGES, PTGIS, PTGS1 and PTGS2), and risk of HNC. METHODS: Interviews regarding the consumption of alcohol, betel quid, and cigarette were conducted with 222 HNC cases and 214 controls. Genotyping was performed for 48 tag and functional single-nucleotide polymorphisms (SNPs). RESULTS: Two tag SNPs of PTGIS showed a significant association with HNC risk [rs522962: log-additive odds ratio (OR) = 1.42, 95% confidence interval (CI): 1.01-1.99 and dominant OR = 1.58, 95% CI: 1.02-2.47; rs6125671: log-additive OR = 1.49, 95% CI: 1.08-2.05 and dominant OR = 1.96, 95% CI: 1.16-3.32]. In addition, a region in PTGIS tagged by rs927068 and rs6019902 was significantly associated with risk of HNC (global P = 0.007). Finally, several SNPs interacted with betel quid and cigarette to influence the risk of HNC. CONCLUSIONS: Genetic variations in prostaglandin pathway genes are associated with risk of HNC and may modify the relationship between use of betel quid or cigarette and development of HNC.

Drug-gene interactions and the search for missing heritability: a cross-sectional pharmacogenomics study of the QT interval.

Variability in response to drug use is common and heritable, suggesting that genome-wide pharmacogenomics studies may help explain the 'missing heritability' of complex traits. Here, we describe four independent analyses in 33 781 participants of European ancestry from 10 cohorts that were designed to identify genetic variants modifying the effects of drugs on QT interval duration (QT). Each analysis cross-sectionally examined four therapeutic classes: thiazide diuretics (prevalence of use=13.0%), tri/tetracyclic antidepressants (2.6%), sulfonylurea hypoglycemic agents (2.9%) and QT-prolonging drugs as classified by the University of Arizona Center for Education and Research on Therapeutics (4.4%). Drug-gene interactions were estimated using covariable-adjusted linear regression and results were combined with fixed-effects meta-analysis. Although drug-single-nucleotide polymorphism (SNP) interactions were biologically plausible and variables were well-measured, findings from the four cross-sectional meta-analyses were null (Pinteraction>5.0 × 10(-8)). Simulations suggested that additional efforts, including longitudinal modeling to increase statistical power, are likely needed to identify potentially important pharmacogenomic effects.

Localized modes in one-dimensional symmetric Thue-Morse quasicrystals.

We present occurrence of the strongly localized modes with high transmission in one dimensional symmetric Thue-Morse quasicrystals. This quasicrystal has some interesting properties, including (i) there are strongly localized modes in separated regions which are around odd semi-quarter-wave thickness of the system, (ii) both the frequency of localized mode and the thicknesses of the space layer to appear localized modes are variant for different generation orders of the system, and (iii) the sharpness of the resonant peaks in the transmission spectra increases as the generation order of the system increases.

Exciton photoluminescence in resonant quasi-periodic Thue-Morse quantum wells.

This Letter investigates exciton photoluminescence (PL) in resonant quasi-periodic Thue-Morse quantum wells (QWs). The results show that the PL properties of quasi-periodic Thue-Morse QWs are quite different from those of resonant Fibonacci QWs. The maximum and minimum PL intensities occur under the anti-Bragg and Bragg conditions, respectively. The maxima of the PL intensity gradually decline when the filling factor increases from 0.25 to 0.5. Accordingly, the squared electric field at the QWs decreases as the Thue-Morse QW deviates from the anti-Bragg condition.

Twin extra-high photoluminescence in resonant double-period quantum wells.

Twin extra high photoluminescence (PL) in resonant quasi-periodic double-period quantum wells (DPQWs) for higher-generation orders is demonstrated. In the DPQW, the number of maxima in the maximum values of the PL intensity is two, which is different from other quasi-periodic quantum wells (QWs) and traditional periodic QWs. The maximum PL intensity in a DPQW is also stronger than that in a periodic QW under the anti-Bragg condition and that in a Fibonacci QW. Although the peaks of the squared electric field for the twin PL are both located near the QWs, their field profiles are distinct.

Systematic evaluation of validated type 2 diabetes and glycaemic trait loci for association with insulin clearance.

AIMS/HYPOTHESIS: Insulin clearance is a highly heritable trait, for which few quantitative trait loci have been discovered. We sought to determine whether validated type 2 diabetes and/or glycaemic trait loci are associated with insulin clearance. METHODS: Hyperinsulinaemic-euglycaemic clamps were performed in two Hispanic-American family cohorts totalling 1329 participants in 329 families. The Metabochip was used to fine-map about 50 previously identified loci for type 2 diabetes, fasting glucose, fasting insulin, 2 h glucose or HbA1c. This resulted in 17,930 variants, which were tested for association with clamp-derived insulin clearance via meta-analysis of the two cohorts. RESULTS: In the meta-analysis, 38 variants located within seven loci demonstrated association with insulin clearance (p < 0.001). The top signals for each locus were rs10241087 (DGKB/TMEM195 [TMEM195 also known as AGMO]) (p = 4.4 × 10(-5)); chr1:217605433 (LYPLAL1) (p = 3.25 × 10(-4)); rs2380949 (GLIS3) (p = 3.4 × 10(-4)); rs55903902 (FADS1) (p = 5.6 × 10(-4)); rs849334 (JAZF1) (p = 6.4 × 10(-4)); rs35749 (IGF1) (p = 6.7 × 10(-4)); and rs9460557 (CDKAL1) (p = 6.8 × 10(-4)). CONCLUSIONS/INTERPRETATION: While the majority of validated loci for type 2 diabetes and related traits do not appear to influence insulin clearance in Hispanics, several of these loci do show evidence of association with this trait. It is therefore possible that these loci could have pleiotropic effects on insulin secretion, insulin sensitivity and insulin clearance.

Strong photoluminescence emission from resonant Fibonacci quantum wells.

Strong photoluminescence (PL) emission from a resonant Fibonacci quantum well (FQW) is demonstrated. The maximum PL intensity in the FQW is significantly stronger than that in a periodic QW under the Bragg or anti-Bragg conditions. Moreover, the peaks of the squared electric field in the FQW are located very near each of the QWs. The optimal PL spectrum in the FQW has an asymmetrical form rather than the symmetrical one in the periodic case. The maximum PL intensity and the corresponding thickness filling factor in the FQW become greater with increasing generation order.

High-Q filters with complete transmission by quasi-periodic dielectric multilayers.

A multiple narrow bandpass filter with both high Q factor and complete transmission using quasi-periodic Thue-Morse dielectric multilayers is proposed. The Q factor of the system increases exponentially with the generation order. Even though the Q factor of resonances increases as the generation order of the multilayers increases, these resonances are still complete resonances. The number of resonance peaks for the bandpass filter of the system also increases as the generation order increases. These resonance peaks have a multifractal distribution throughout the frequency range, which is different from that in traditional periodical multilayers.

Quasi-Bragg conditions in Thue-Morse dielectric multilayers.

The existence of quasi-Bragg conditions (QBCs) in Thue-Morse dielectric multilayers (TMDMs), based on high reflectance and large forbidden gap regions in its transmission spectra, is presented. In contrast to a single traditional Bragg condition (TBC) in periodic bilayers, there are three QBCs in TMDMs. The formula for each of these QBCs is derived. The results show that one of these QBCs just overlaps the TBC. However, a singular point with perfect transmission exists in this QBC at the quarter-wave stack, at which high reflection exists in the periodic bilayers.

Insulin clearance: confirmation as a highly heritable trait, and genome-wide linkage analysis.

AIMS/HYPOTHESIS: We have previously documented a high heritability of insulin clearance in a Hispanic cohort. Here, our goal was to confirm the high heritability in a second cohort and search for genetic loci contributing to insulin clearance. METHODS: Hyperinsulinaemic-euglycaemic clamps were performed in 513 participants from 140 Hispanic families. Heritability was estimated for clamp-derived insulin clearance and a two-phase genome-wide linkage scan was conducted using a variance components approach. Linkage peaks were further investigated by candidate gene association analysis in two cohorts. RESULTS: The covariate-adjusted heritability of insulin clearance was 73%, indicating that the majority of the phenotypic variance is due to genetic factors. In the Phase 1 linkage scan, no signals with a logarithm of odds (LOD) score >2 were detected. In the Phase 2 scan, two linkage peaks with an LOD >2 for insulin clearance were identified on chromosomes 15 (LOD 3.62) and 20 (LOD 2.43). These loci harbour several promising candidate genes for insulin clearance, with 12 single nucleotide polymorphisms (SNPs) on chromosome 15 and six SNPs on chromosome 20 being associated with insulin clearance in both Hispanic cohorts. CONCLUSIONS/INTERPRETATION: In a second Hispanic cohort, we confirmed that insulin clearance is a highly heritable trait and identified chromosomal loci that harbour genes regulating insulin clearance. The identification of such genes may improve our understanding of how the body clears insulin, thus leading to improved risk assessment, diagnosis, prevention and therapy of diabetes, as well as of other hyperinsulinaemic disorders, such as the metabolic syndrome and polycystic ovary syndrome.

Shorter telomeres are associated with obesity and weight gain in the elderly.

OBJECTIVE: Obesity and shorter telomeres are commonly associated with elevated risk for age-related diseases and mortality. Whether telomere length (TL) may be associated with obesity or variations in adiposity is not well established. Therefore, we set out to test the hypothesis that TL may be a risk factor for increased adiposity using data from a large population-based cohort study. DESIGN: Levels of adiposity were assessed in six ways (obesity status, body mass index (BMI), the percentage of body fat or % body fat, leptin, visceral and subcutaneous fat mass) in 2721 elderly subjects (42% black and 58% white). Associations between TL measured in leukocytes at baseline and adiposity traits measured at baseline, and three of these traits after 7 years of follow-up were tested using regression models adjusting for important covariates. Additionally, we look at weight changes and relative changes in BMI and % body fat between baseline and follow-up. RESULTS: At baseline, TL was negatively associated with % body fat (ß=-0.35±0.09, P=0.001) and subcutaneous fat (ß=-2.66±1.07, P=0.01), and positively associated with leptin after adjusting for % body fat (ß=0.32±0.14, P=0.001), but not with obesity, BMI or visceral fat. Prospective analyses showed that longer TL was associated with positive percent change between baseline and 7-year follow-up for both BMI (ß=0.48±0.20, P=0.01) and % body fat (ß=0.42±0.23, P=0.05). CONCLUSION: Our study suggests that shorter TL may be a risk factor for increased adiposity. Coupling with previous reports on their reversed roles, the relationship between adiposity and TL may be complicated and may warrant more prospective studies.

Effective Bragg conditions in a one-dimensional quasicrystal.

We present occurrence of the effective Bragg conditions with wide gapwidth and high reflectance in a Fibonacci superlattice, which is a typical one-dimensional quasicrystal. In the Fibonacci material, the number of effective Bragg conditions is two rather than one which appears in traditional periodic structures. Based on the effective Bragg conditions, this study proposes existence of omnidirectional, wideband and high reflectance in the quasiperiodic materials analogous to that in traditional materials.

Simple expressions for the maximum omnidirectional bandgap of bilayer photonic crystals.

We propose three dimensionless approximate expressions to predict the thickness filling factor, gap center, and gap width of the maximum omnidirectional gap (MODG) for various refractive indices in one-dimensional photonic crystals. These expressions are simple and do not include trigonometric or inverse trigonometric functions. It is easy to obtain the MODG from given refractive indices but also to estimate the refractive indices from the MODG based on the results.

Admixture mapping of ankle-arm index: identification of a candidate locus associated with peripheral arterial disease.

BACKGROUND: Peripheral arterial disease (PAD) is associated with significant morbidity and mortality, and has a higher prevalence in African Americans than Caucasians. Ankle-arm index (AAI) is the ratio of systolic blood pressure in the leg to that in the arm, and, when low, is a marker of PAD. METHODS: The authors used an admixture mapping approach to search for genetic loci associated with low AAI. Using data from 1040 African American participants in the observational, population based Health, Aging, and Body Composition Study who were genotyped at 1322 single nucleotide polymorphisms (SNPs) that are informative for African versus European ancestry and span the entire genome, we estimated genetic ancestry in each chromosomal region and then tested the association between AAI and genetic ancestry at each locus. RESULTS: The authors found a region of chromosome 11 that reaches its peak between 80 and 82 Mb associated with low AAI (p<0.001 for rs12289502 and rs9665943, both within this region). 753 African American participants in the observational, population based Cardiovascular Health Study were genotyped at rs9665943 to test the reproducibility of this association, and this association was also statistically significant (odds ratio (OR) for homozygous African genotype 1.59, 95% confidence interval (CI) 1.12 to 2.27). Another candidate SNP (rs1042602) in the same genomic region was tested in both populations, and was also found to be significantly associated with low AAI in both populations (OR for homozygous African genotype 1.89, 95% CI 1.29 to 2.76). CONCLUSION: This study identifies a novel region of chromosome 11 representing an area with a potential candidate gene associated with PAD in African Americans.