| 1. |
- Deng, Min, et al.
(author)
-
Genome-wide association analyses in Han Chinese identify two new susceptibility loci for amyotrophic lateral sclerosis
- 2013
-
In: Nature Genetics. - : Nature Publishing Group. - 1061-4036 .- 1546-1718. ; 45:6, s. 697-
-
Journal article (peer-reviewed)abstract
- To identify susceptibility genes for amyotrophic lateral sclerosis (ALS), we conducted a genome-wide association study (GWAS) in 506 individuals with sporadic ALS and 1,859 controls of Han Chinese ancestry. Ninety top SNPs suggested by the current GWAS and 6 SNPs identified by previous GWAS were analyzed in an independent cohort of 706 individuals with ALS and 1,777 controls of Han Chinese ancestry. We discovered two new susceptibility loci for ALS at 1q32 (CAMK1G, rs6703183, P-combined = 2.92 x 10(-8), odds ratio (OR) = 1.31) and 22p11 (CABIN1 and SUSD2, rs8141797, P-combined = 2.35 x 10(-9), OR = 1.52). These two loci explain 12.48% of the overall variance in disease risk in the Han Chinese population. We found no association evidence for the previously reported loci in the Han Chinese population, suggesting genetic heterogeneity of disease susceptibility for ALS between ancestry groups. Our study identifies two new susceptibility loci and suggests new pathogenic mechanisms of ALS.
|
|
| 2. |
|
|
| 3. |
- Weinstein, John N., et al.
(author)
-
The cancer genome atlas pan-cancer analysis project
- 2013
-
In: Nature Genetics. - : Springer Science and Business Media LLC. - 1546-1718 .- 1061-4036. ; 45:10, s. 1113-1120
-
Research review (peer-reviewed)abstract
- The Cancer Genome Atlas (TCGA) Research Network has profiled and analyzed large numbers of human tumors to discover molecular aberrations at the DNA, RNA, protein and epigenetic levels. The resulting rich data provide a major opportunity to develop an integrated picture of commonalities, differences and emergent themes across tumor lineages. The Pan-Cancer initiative compares the first 12 tumor types profiled by TCGA. Analysis of the molecular aberrations and their functional roles across tumor types will teach us how to extend therapies effective in one cancer type to others with a similar genomic profile. © 2013 Nature America, Inc. All rights reserved.
|
|
| 4. |
- Vithanage, Dimali, et al.
(author)
-
Charge carrier dynamics of polymer: Fullerene blends: From geminate to non-geminate recombination
- 2014
-
In: Advanced Energy Materials. - : Wiley. - 1614-6840 .- 1614-6832. ; 4:8
-
Journal article (peer-reviewed)abstract
- The charge carrier dynamics of a new polymer-fullerene blend are examined on the femtosecond to the millisecond time scale. The full time range is globally fitted using a chemical reaction rate model that includes all key processes, charge generation, energy transfer, charge separation, and recombination, over the full 12 orders of magnitude in time and a factor of 33 in light intensity. Particular attention is paid to the charge recombination processes and it is found that they are highly material specific. Comparison of the dynamics to those of a previously studied polymer:fullerene blend reveals that while for one blend the recombination dynamics are mainly controlled by geminate recombination, the charge recombination in the presently studied polymer:fullerene blend are entirely controlled by non-geminate electron-hole recombination. Carrier density dependence of the non-geminate recombination rate is analyzed and a correlated disorder model of site energies is proposed to explain the observed dependency. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
|
|
| 5. |
- Wang, Guo-dong, et al.
(author)
-
The genomics of selection in dogs and the parallel evolution between dogs and humans
- 2013
-
In: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 4, s. 1860-
-
Journal article (peer-reviewed)abstract
- The genetic bases of demographic changes and artificial selection underlying domestication are of great interest in evolutionary biology. Here we perform whole-genome sequencing of multiple grey wolves, Chinese indigenous dogs and dogs of diverse breeds. Demographic analysis show that the split between wolves and Chinese indigenous dogs occurred 32,000 years ago and that the subsequent bottlenecks were mild. Therefore, dogs may have been under human selection over a much longer time than previously concluded, based on molecular data, perhaps by initially scavenging with humans. Population genetic analysis identifies a list of genes under positive selection during domestication, which overlaps extensively with the corresponding list of positively selected genes in humans. Parallel evolution is most apparent in genes for digestion and metabolism, neurological process and cancer. Our study, for the first time, draws together humans and dogs in their recent genomic evolution.
|
|
| 6. |
- Yang, Jia-Xiang, et al.
(author)
-
Facile synthesis, optical properties and theoretical calculation of two novel two-photon absorption chromophores
- 2010
-
In: Journal of Luminescence. - : Elsevier BV. - 0022-2313 .- 1872-7883. ; 130:4, s. 654-659
-
Journal article (peer-reviewed)abstract
- Two heterocycle-based derivatives that can be used as two-photon absorption chromophore, 9-butyl-3-(2,6-diphenylpyridin-4-yl)-9H-carbazole (BDPYC) and 9-butyl-3-(4-(2, 6-diphenylpyridin-4-yl)styryl)-9H-carbazole (BDPSC) have been successfully synthesized and fully characterized by elemental analysis, IR, H-1 NMR, C-13 NMR and MS. The molecules possess D-pi-A structures, but have different pi bridge. The 9-butylcarbazole is used as a donor (D), and the pyridine ring is used as an acceptor (A). One- and two-photon absorption and excited fluorescence properties in various solvents were experimentally investigated. Two-photon initiated optical data recording experiments have been carried Out under 740 nm laser radiation, and the possible mechanism of optical data storage is discussed based on theoretical calculations.
|
|
| 7. |
- Abel, Martin, et al.
(author)
-
Collision-induced absorption by supermolecular complexes from a new potential energy and induced dipole surface, suited for calculations up to thousands of kelvin
- 2010
-
In: 20th International Conference on Spectral Line Shapes. - Melville, NY : American Institute of Physics (AIP). - 9780735408456 ; , s. 251-257
-
Conference paper (peer-reviewed)abstract
- Absorption by pairs of H2 molecules is an important opacity source in the atmospheres of the outer planets, and thus of special astronomical interest. The emission spectra of cool white dwarf stars differ significantly from the expected blackbody spectra, amongst other reasons due to absorption by H2-H2, H2-He, and H2-H collisional complexes in the stellar atmospheres. To model the radiative processes in these atmospheres, which have temperatures of several thousand kelvin, one needs accurate knowledge of the induced dipole (ID) and potential energy surfaces (PES) of such collisional complexes. These come from quantum-chemical calculations with the H2 bonds stretched or compressed far from equilibrium. Laboratory measurements of collision-induced (CI) absorption exist only at much lower temperature. For H2 pairs at room temperature, the calculated spectra of the rototranslational band, the fundamental band, and the first overtone match the experimental data very well. In addition, with the newly obtained IDS it became possible to reproduce the measurements in the far blue wing of the rototranslational spectrum of H2 at 77.5 K, as well as at 300 K. Similarly good agreement between theory and measurement is seen in the fundamental band of molecular deuterium at room temperature. Furthermore, we also show the calculated absorption spectra of H2-He at 600 K and of H2-H2 at 2,000 K, for which there are no experimental data for comparison
|
|
| 8. |
- Asayama, Kei, et al.
(author)
-
Setting Thresholds to Varying Blood Pressure Monitoring Intervals Differentially Affects Risk Estimates Associated With White-Coat and Masked Hypertension in the Population
- 2014
-
In: Hypertension. - 0194-911X .- 1524-4563. ; 64:5, s. 935-942
-
Journal article (peer-reviewed)abstract
- Outcome-driven recommendations about time intervals during which ambulatory blood pressure should be measured to diagnose white-coat or masked hypertension are lacking. We cross-classified 8237 untreated participants (mean age, 50.7 years; 48.4% women) enrolled in 12 population studies, using >= 140/>= 90, >= 130/>= 80, >= 135/>= 85, and >= 120/>= 70 mm Hg as hypertension thresholds for conventional, 24-hour, daytime, and nighttime blood pressure. White-coat hypertension was hypertension on conventional measurement with ambulatory normotension, the opposite condition being masked hypertension. Intervals used for classification of participants were daytime, nighttime, and 24 hours, first considered separately, and next combined as 24 hours plus daytime or plus nighttime, or plus both. Depending on time intervals chosen, white-coat and masked hypertension frequencies ranged from 6.3% to 12.5% and from 9.7% to 19.6%, respectively. During 91 046 person-years, 729 participants experienced a cardiovascular event. In multivariable analyses with normotension during all intervals of the day as reference, hazard ratios associated with white-coat hypertension progressively weakened considering daytime only (1.38; P=0.033), nighttime only (1.43; P=0.0074), 24 hours only (1.21; P=0.20), 24 hours plus daytime (1.24; P=0.18), 24 hours plus nighttime (1.15; P=0.39), and 24 hours plus daytime and nighttime (1.16; P=0.41). The hazard ratios comparing masked hypertension with normotension were all significant (P<0.0001), ranging from 1.76 to 2.03. In conclusion, identification of truly low-risk white-coat hypertension requires setting thresholds simultaneously to 24 hours, daytime, and nighttime blood pressure. Although any time interval suffices to diagnose masked hypertension, as proposed in current guidelines, full 24-hour recordings remain standard in clinical practice.
|
|
| 9. |
- Brguljan-Hitij, Jana, et al.
(author)
-
Risk Stratification by Ambulatory Blood Pressure Monitoring Across JNC Classes of Conventional Blood Pressure
- 2014
-
In: American Journal of Hypertension. - : Oxford University Press (OUP). - 0895-7061 .- 1941-7225. ; 27:7, s. 956-965
-
Journal article (peer-reviewed)abstract
- BACKGROUND Guidelines propose classification of conventional blood pressure (CBP) into normotension (<120/<80 mm Hg), prehypertension (120-139/80-89 mm Hg), and hypertension (>140/>90 mm Hg). METHODS To assess the potential differential contribution of ambulatory blood pressure (ABP) in predicting risk across CBP strata, we analyzed outcomes in 7,826 untreated people recruited from 11 populations. RESULTS During an 11.3-year period, 809 participants died (276 cardiovascular deaths) and 639, 383, and 225 experienced a cardiovascular, cardiac, or cerebrovascular event. Compared with normotension (n = 2,639), prehypertension (n = 3,076) carried higher risk (P <= 0.015) of cardiovascular (+ 41%) and cerebrovascular (+ 92%) endpoints; compared with hypertension (n = 2,111) prehypertension entailed lower risk (P <= 0.005) of total mortality (-14%) and cardiovascular mortality (-29%) and of cardiovascular (-34%), cardiac (-33%), or cerebrovascular (-47%) events. Multivariable-adjusted hazard ratios (HRs) for stroke associated with 24-hour and daytime diastolic ABP (+ 5 mm Hg) were higher (P <= 0.045) in normotension than in prehypertension and hypertension (1.98 vs. 1.19 vs. 1.28 and 1.73 vs. 1.09 vs. 1.24, respectively) with similar trends (0.03 <= P <= 0.11) for systolic ABP (+10 mm Hg). However, HRs for fatal endpoints and cardiac events associated with ABP did not differ significantly (P >= 0.13) across CBP categories. Of normotensive and prehypertensive participants, 7.5% and 29.3% had masked hypertension (daytime ABP >= 135/>= 85 mm Hg). Compared with true normotension (P <= 0.01), HRs for stroke were 3.02 in normotension and 2.97 in prehypertension associated with masked hypertension with no difference between the latter two conditions (P = 0.93). CONCLUSION ABP refines risk stratification in normotension and prehypertension mainly by enabling the diagnosis of masked hypertension.
|
|
| 10. |
|
|
| 11. |
- Fei, Ying, et al.
(author)
-
The combination of a tumor necrosis factor inhibitor and antibiotic alleviates staphylococcal arthritis and sepsis in mice.
- 2011
-
In: The Journal of infectious diseases. - : Oxford University Press (OUP). - 1537-6613 .- 0022-1899. ; 204:3, s. 348-57
-
Journal article (peer-reviewed)abstract
- (See the editorial commentary by Chow, on pages 332-4) Background.Despite advances in medical practices, in recent decades permanent reductions in joint function have not been achieved, and the high mortality rate of patients with staphylococcal septic arthritis has not substantially improved. Methods.We evaluated the effects of a combined tumor necrosis factor (TNF) inhibitor and antibiotic therapy on the course of Staphylococcus aureus arthritis and sepsis in mice. Results.Treatment with the combination of a TNF inhibitor and an antibiotic resulted in a quicker relief of clinical arthritis in mice with septic arthritis, compared with an antibiotic monotherapy. Both histopathologically verified synovitis and the extent of joint destruction were reduced by this combined treatment. Importantly, anti-TNF treatment significantly improved the survival rate of mice with S. aureus sepsis and staphylococcal enterotoxin shock syndrome; this effect might be the result of a partial restoration of the hemostatic balance between coagulation and fibrinolysis. Finally, we demonstrated that anti-TNF treatment downregulates high-mobility group protein B1 in staphylococcal enterotoxin shock syndrome. Conclusions.Thus, simultaneous systemic TNF inhibition and antibiotic therapy has beneficial effects on the outcome of S. aureus arthritis and sepsis in a mouse model, suggesting that the combination of a TNF inhibitor and antibiotics represents a novel therapeutic strategy for the treatment of staphylococcal infections.
|
|
| 12. |
- Feng, Chungang, et al.
(author)
-
A cis-Regulatory Mutation of PDSS2 Causes Silky-Feather in Chickens
- 2014
-
In: PLOS Genetics. - : Public Library of Science (PLoS). - 1553-7390 .- 1553-7404. ; 10:8, s. e1004576-
-
Journal article (peer-reviewed)abstract
- Silky-feather has been selected and fixed in some breeds due to its unique appearance. This phenotype is caused by a single recessive gene (hookless, h). Here we map the silky-feather locus to chromosome 3 by linkage analysis and subsequently fine-map it to an 18.9 kb interval using the identical by descent (IBD) method. Further analysis reveals that a C to G transversion located upstream of the prenyl (decaprenyl) diphosphate synthase, subunit 2 (PDSS2) gene is causing silky-feather. All silky-feather birds are homozygous for the G allele. The silky-feather mutation significantly decreases the expression of PDSS2 during feather development in vivo. Consistent with the regulatory effect, the C to G transversion is shown to remarkably reduce PDSS2 promoter activity in vitro. We report a new example of feather structure variation associated with a spontaneous mutation and provide new insight into the PDSS2 function.
|
|
| 13. |
- Feng, Feng, et al.
(author)
-
Room-temperature large magnetic-dielectric coupling in new phase anatase VTiO4
- 2013
-
In: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 49:89, s. 10462-10464
-
Journal article (peer-reviewed)abstract
- The synthetic new-phase VTiO4, as a new solid solution structure of anatase type, brings a large magnetodielectric ratio (Delta epsilon/epsilon(0)) of 7.2% at 300 K, representing a new simple-oxide structural catalogue exhibiting a room-temperature large magnetic-dielectric effect.
|
|
| 14. |
- Frommhold, Lothar, et al.
(author)
-
Infrared atmospheric emission and absorption by simple molecular complexes, from first principles
- 2010
-
In: Molecular Physics. - : Informa UK Limited. - 0026-8976 .- 1362-3028. ; 108:17, s. 2265-2272
-
Journal article (peer-reviewed)abstract
- Quantum chemical methods are used to obtain the interaction-induced dipole surfaces (IDS) of complexes of two interacting (i.e. colliding) molecules, for example H2–H2, H2–He, etc., collisional complexes, along with their potential energy surfaces (PES). Eight H2 bond distances, from 0.942 to 2.801 bohr, are chosen for each H2 molecule to account for rotovibrational excitations. Rotovibrational matrix elements of these ID and PE surfaces are computed as necessary for the study of supermolecular (‘collision-induced’) absorption spectra of dense hydrogen gas, and of gaseous mixtures of hydrogen and helium, at temperatures up to several thousand kelvin and for frequencies from 0 to those of several H2 overtone bands. Rotovibrational state to state scattering calculations couple the collisional complex perturbatively to single photons. The absorption process causes rotovibrational transitions in one molecule, or simultaneous transitions in both molecules (when H2–H2 collisional complexes are considered). The spectral profiles of tens of thousands of such transitions are computed from first principles. Individual ‘lines’ are very broad so that they overlap substantially, forming a supermolecular quasi-continuum. The comparison of the computed collision-induced absorption (CIA) spectra with existing laboratory measurements at low temperatures (≤ 300 K) shows close agreement so that our results for higher temperatures, where laboratory experiments do not exist, may be used with confidence. Similar calculations of CIA spectra at high temperatures and frequencies are underway for other collisional systems (e.g. H2–H) of interest in astrophysical applications (e.g. ‘cool’ stellar atmospheres). Collision-induced Raman spectra (CIRS) have been similarly obtained; computed Raman spectra also compare favourably with existing laboratory measurements.
|
|
| 15. |
- Ghasemi, Masoomeh, et al.
(author)
-
Bonding in intermetallics may be deceptive – the case of the new type structure Au2InGa2
- 2014
-
In: Intermetallics. - : Elsevier BV. - 0966-9795. ; 46, s. 40-44
-
Journal article (peer-reviewed)abstract
- We have investigated the crystal and the electronic structure of a new ternary phase, Au2InGa2 using powder and single crystal X-Ray Diffraction (XRD) and Stuttgart Tight Binding LMTO-ASA methods, respectively. Complementary methods including Thermo-Gravimetric Differential Thermal Analysis (TG-DTA), Energy Dispersive X-ray Spectroscopy (EDS) and Scanning Electron Microscopy (SEM) were also employed. As a result, the complete structure was determined and the role of homoatomic and heteroatomic bonding is discussed.
|
|
| 16. |
- Jiang, Yi, et al.
(author)
-
Promoting the Activity of Catalysts for the Oxidation of Water with Bridged Dinuclear Ruthenium Complexes
- 2013
-
In: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 52:12, s. 3398-3401
-
Journal article (peer-reviewed)abstract
- Solar fuels: Dinuclear ruthenium catalysts prepared from two covalently bridged monomeric catalytic units show outstanding activities towards the oxidation of water with high turnover numbers up to 43 000 and turnover frequencies up to 40 s-1 (see picture). Direct comparison of the performance parameters indicates that the dimers are significantly more active as catalysts than the monomers.
|
|
| 17. |
- Li, Jian, et al.
(author)
-
Array Comparative Genomic Hybridization of Keratoacanthomas and Squamous Cell Carcinomas: Different Patterns of Genetic Aberrations Suggest Two Distinct Entities
- 2012
-
In: Journal of Investigative Dermatology. - : Elsevier BV. - 1523-1747 .- 0022-202X. ; 132:8, s. 2060-2066
-
Journal article (peer-reviewed)abstract
- Keratoacanthoma (KA) is a benign keratinocytic neoplasm that spontaneously regresses after 3-6 months and shares features with squamous cell carcinomas (SCCs). Furthermore, there are reports of KAs that have metastasized, invoking the question of whether KA is a variant of SCC (Hodak et al., 1993). To date, no reported criteria are sensitive enough to discriminate reliably between KA and SCC, and consequently there is a clinical need for discriminating markers. Our previous study analyzed 132 KAs and 29 SCCs and revealed significantly different regions of genomic aberrations using chromosomal comparative genomic hybridization (CGH). In the present study, we applied array CGH to investigate 98 KAs and 22 SCCs from the above samples. The result shows that all KAs and SCCs have some degree of genetic aberrations. The distribution of numbers of aberrant clones per sample differed significantly between KAs and SCCs (P<0.02), which also demonstrated recurrent aberrations that differed significantly (P<0.001), as illustrated by unsupervised cluster analysis. Classifiers for clinicopathological parameters of KAs were established based on t-test statistics and permutation tests. Tumor size, fibrosis, and inflammation, which are related to the developmental stages of KAs, showed significant (t-test, permutation test) associations with aberrations of selected genomic regions. This suggests chromosomal instability during the whole life cycle of KAs.
|
|
| 18. |
- Li, Xiaoping, et al.
(author)
-
Collision-induced dipoles and polarizabilities of pairs of hydrogen molecules : Ab initio calculations and results from spherical tensor analysis
- 2012
-
In: International Conference of Computational Methods in Sciences and Engineering 2009. - Melville, NY : American Institute of Physics (AIP). - 9780735411227 ; , s. 100-135
-
Conference paper (peer-reviewed)abstract
- New ab initio results are reported for the interaction-induced changes in the dipole moments and polarizabilities of pairs of hydrogen molecules, computed using finite-field coupled-cluster methods in MOLPRO 2000 and GAMESS, with an aug-cc-pV5Z (spdf) basis set. Earlier work by X. Li, C. Ahuja, J. F. Harrison, and K. L. C. Hunt, J. Chem. Phys. 126, 214302 (2007), on collision-induced polarizabilities Δα has been extended with 170 additional geometrical configurations of the H2 pairs. In calculations of Δα, we have used a "random field" technique, with up to 120 different field strengths, having components that range from 0.001 to 0.01 a.u. Numerical tests show that the pair dipoles Δμ can be obtained accurately from calculations limited to 6 values of the field in each direction, so this approach has been used to compute Δμ by X. Li, K. L. C. Hunt, F. Wang, M. Abel, and L. Frommhold, Int. J. Spectroscopy 2010, 371201 (2010). We have evaluated the collision-induced dipoles of H2 pairs for 28 combinations of bond lengths (ranging from 0.942 a.u. to 2.801 a.u.), 7 intermolecular separations R, and 17 different relative orientations. In our work on Δα, the bond lengths are fixed at 1.449 a.u. Our results agree well with the previous ab initio work of W. Meyer, A. Borysow, and L. Frommhold, Phys. Rev. A 40, 6931 (1989), and of Y. Fu, C. G. Zheng and A. Borysow, J. Quant. Spectroscopy and Rad. Transfer, 67, 303 (2000)-where those data exist-for Δμ of H2 pairs. For Δα, our results agree well with the CCSD(T) results obtained by G. Maroulis, J. Phys. Chem. A 104, 4772 (2000) for two pair orientations and fixed R. The pair polarizability anisotropies also agree well with the small-basis self-consistent field results of D. G. Bounds, Mol. Phys. 38, 2099 (1979), although the trace of the polarizability differs by factors of 2 or more from Bounds' results. We have determined the expansion coefficients for Δμ and Δα, expressed as series in the spherical harmonics of the orientation angles of the intermolecular vector and of unit vectors along the molecular axes. The leading coefficients converge at long range to the predictions from perturbation theory, derived by J. E. Bohr and K. L. C. Hunt, J. Chem. Phys. 87, 3821 (1987); T. Bancewicz, W. G.az, and S. Kielich, Chem. Phys. 128, 321 (1988); and X. Li and K. L. C. Hunt, J. Chem. Phys. 100, 7875 (1994); ibid, 9276 (1994). Based on our results for Δμ, we find excellent agreement for the binary rototranslational absorption spectrum of H2 at 297.5 K as calculated by X. Li, K. L. C. Hunt, F. Wang, M. Abel, and L. Frommhold, Int. J. Spectroscopy 2010, 371201 (2010) and as determined experimentally by G. Bachet, E. R. Cohen, P. Dore, and G. Birnbaum, Can. J. Phys. 61, 591 (1983), out to ∼1500 cm-1. We have also calculated the vibrational spectra out to 20,000 cm-1, at T = 600 K, 1000 K, and 2000 K, for which there are no experimental data. We are currently working to extend the temperature range in the calculations to 7000 K, for application in modeling the spectra of cool white dwarf stars. We have used the results for Δα to calculate collision-induced rototranslational Raman spectra for H2 pairs [M. Gustafsson, L. Frommhold, X. Li, and K. L. C. Hunt, J. Chem. Phys. 130, 164314 (2009)]. Experimental results for the Raman spectra have been reported by U. Bafile, M. Zoppi, F. Barocchi, M. S. Brown, and L. Frommhold, Phys. Rev. A 40, 1654 (1989); U. Bafile, L. Ulivi, M. Zoppi, F. Barocchi, M. Moraldi, and A. Borysow, Phys. Rev. A 42, 6916 (1990); and M. S. Brown, S.-K. Wang, and L. Frommhold, Phys. Rev. A 40, 2276 (1989). Agreement between our calculations and experiment is good for both the polarized and depolarized spectra, with the remaining discrepancies probably attributable to the difference between the static (calculated) and frequency-dependent (experimental) values of Δα.
|
|
| 19. |
- Li, Xiao-Fei, et al.
(author)
-
Design of Graphene-Nanoribbon Heterojunctions from First Principles
- 2011
-
In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:25, s. 12616-12624
-
Journal article (peer-reviewed)abstract
- Graphene nanoribbons with armchair and zigzag edges are known to have very different electronic structure and properties. We show here that the fusion of an armchair and a zigzag graphene-nanoribbon (aGNR vertical bar zGNR) can form heterojunctions with remarkable electron transport properties. First-principles calculations reveal that the heterojunction can be either metallic or semiconducting depending on the width of the nanoribbon. A well-defined oscillation of the zero-bias conductance as a function of the ribbon width is observed, which is originated from the resonance and nonresonance of frontier orbitals between aGNR and zGNR We find that the current/voltage characteristics of the aGNR vertical bar zGNR heterojunction possess pronounced rectification effect, and a high rectification ratio can be achieved by tuning the width of the zGNR to minimize the backward current. The unique properties of the proposed heterojunction could be very useful for manufacturing graphene-based electronic devices.
|
|
| 20. |
- Li, Xiao-Fei, et al.
(author)
-
Effects of Interface Roughness on Electronic Transport Properties of Nanotube-Molecule-Nanotube Junctions
- 2010
-
In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114:28, s. 12335-12340
-
Journal article (peer-reviewed)abstract
- We investigate electronic transport properties of molecular junctions constructed by a single conjugated molecule attached in the gap of two broken metallic single walled carbon nanotubes (CNTs). With the help of molecular dynamic simulations (MD), we have provided a realistic description for mechanical stretching processes of different carbon nanotubes and contact structures between the broken CNTs and the conjugated molecule in different junctions. Statistical analysis shows that the molecule generally prefers to be titled inside the junctions with polygonal contact, in particular the apex at the broken ends of tubes. Nonequilibrium Green's function (NEGF) calculations reveal that such realistic CNTs-molecular junctions have very different electron transport properties from junctions with ideal SWCNTs as electrodes. The statistically and energetically favorable CNTs-molecular junctions of different chiralities are found to be always metallic, but their absolute conductance is sensitive to the chirality of the tube. It is suggested that with armchair CNTs as electrodes, a better conductivity can be obtained. The calculated current-voltage characteristics of junctions with realistic contact geometries are in good agreement with experiments.
|
|
| 21. |
- Li, Xiao-Fei, et al.
(author)
-
Electronic transport through zigzag/armchair graphene nanoribbon heterojunctions
- 2012
-
In: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 24:9, s. 095801-
-
Journal article (peer-reviewed)abstract
- The electronic transport properties of a graphene nanoribbon (GNR) are known to be sensitive to its width, edges and defects. We investigate the electronic transport properties of a graphene nanoribbon heterojunction constructed by fusing a zigzag and an armchair graphene nanoribbon (zGNR/aGNR) side by side. First principles results reveal that the heterojunction can be either metallic or semiconducting, depending on the width of the nanoribbons. Intrinsic rectification behaviors have been observed, which are largely sensitive to the connection length between the zGNR and aGNR. The microscopic origins of the rectification behavior have been revealed. We find that the carrier type can alter from electrons to holes with the bias voltage changing from negative to positive; the asymmetrical transmission spectra of electrons and holes induced by the interface defects directly results in the rectification behavior. The results suggest that any methods which can enhance the asymmetry of the transmission spectra between holes and electrons could be used to improve the rectification behavior in the zGNR/aGNR heterojunction. Our findings could be useful for designing graphene based electronic devices.
|
|
| 22. |
- Li, Xiao-Fei, et al.
(author)
-
Strong current polarization and negative differential resistance in chiral graphene nanoribbons with reconstructed (2,1)-edges
- 2012
-
In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 101:7, s. 073101-
-
Journal article (peer-reviewed)abstract
- We investigate electronic structures and transport properties of chiral-graphene-nanoribbons (CGNRs) with reconstructed (2,1)-edges. First principles results reveal that the (2,1)-CGNRs can be either spin non-polarized or polarized, depending on whether the edges are H-saturated or unsaturated. H-saturated systems are semiconductors with width-dependent transmission gap, while unsaturated systems are metallic at non-polarized state or at antiferromagnetic state and they are semiconductors at ferromagnetic state. Moreover, unsaturated systems possess strong current polarizations (nearly 100%) and a striking negative differential resistance behavior (with a peak-to-valley ratio about 105). These remarkable properties suggest the potential application of (2,1)-CGNRs in molectronics and spintronics.
|
|
| 23. |
- Li, Xiao-Fei, et al.
(author)
-
Tuning the Electronic Transport Properties of Zigzag Graphene Nanoribbons via Hydrogenation Separators
- 2011
-
In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:49, s. 24366-24372
-
Journal article (peer-reviewed)abstract
- Hydrogenation technique is known to be useful for opening up the band gap and controlling the electronic properties of the graphene. We have demonstrated with first principles calculations that the hydrogenation can be used to make separators to electrically separate zigzag graphene nanoribbons (zGNR) and tune their transport properties. First principles calculations reveal that each hydrogenation separator can introduce two conducting edge-like states into the subbands around the Fermi level, which can greatly enhance the conductance of the system. We find that the zGNRs with hydrogenation separators are still spin polarized; the distributions of spin densities are mainly located along the two edges of the pristine nanoribbon and the borders of the separators. The current polarization shows a nice oscillation behavior as a function of the position of the separator, which originates from the symmetry dependent transport character of the zGNRs. Moreover, we find that the hydrogenation separators can screen the impact of rough edges, which makes rough-edge zGNRs behave like smooth-edge zGNRs. Our findings could be very useful for designing electronic devices based on the hydrogenation of graphene nanoribbons.
|
|
| 24. |
- Li, Yan, et al.
(author)
-
Ambulatory Hypertension Subtypes and 24-Hour Systolic and Diastolic Blood Pressure as Distinct Outcome Predictors in 8341 Untreated People Recruited From 12 Populations
- 2014
-
In: Circulation. - 0009-7322 .- 1524-4539. ; 130:6, s. 466-474
-
Journal article (peer-reviewed)abstract
- Background-Data on risk associated with 24-hour ambulatory diastolic (DBP24) versus systolic (SBP24) blood pressure are scarce. Methods and Results-We recorded 24-hour blood pressure and health outcomes in 8341 untreated people (mean age, 50.8 years; 46.6% women) randomly recruited from 12 populations. We computed hazard ratios (HRs) using multivariable-adjusted Cox regression. Over 11.2 years (median), 927 (11.1%) participants died, 356 (4.3%) from cardiovascular causes, and 744 (8.9%) experienced a fatal or nonfatal cardiovascular event. Isolated diastolic hypertension (DBP24 >= 80 mm Hg) did not increase the risk of total mortality, cardiovascular mortality, or stroke (HRs <= 1.54; P >= 0.18), but was associated with a higher risk of fatal combined with nonfatal cardiovascular, cardiac, or coronary events (HRs >= 1.75; P <= 0.0054). Isolated systolic hypertension (SBP24 >= 130 mm Hg) and mixed diastolic plus systolic hypertension were associated with increased risks of all aforementioned end points (P <= 0.0012). Below age 50, DBP24 was the main driver of risk, reaching significance for total (HR for 1-SD increase, 2.05; P=0.0039) and cardiovascular mortality (HR, 4.07; P=0.0032) and for all cardiovascular end points combined (HR, 1.74; P=0.039) with a nonsignificant contribution of SBP24 (HR <= 0.92; P >= 0.068); above age 50, SBP24 predicted all end points (HR >= 1.19; P <= 0.0002) with a nonsignificant contribution of DBP24 (0.96 <= HR <= 1.14; P >= 0.10). The interactions of age with SBP24 and DBP24 were significant for all cardiovascular and coronary events (P <= 0.043). Conclusions-The risks conferred by DBP24 and SBP24 are age dependent. DBP24 and isolated diastolic hypertension drive coronary complications below age 50, whereas above age 50 SBP24 and isolated systolic and mixed hypertension are the predominant risk factors.
|
|
| 25. |
- Lou, Fei, et al.
(author)
-
Experimental demonstration of ultra-compact directional couplers based on silicon hybrid plasmonic waveguides
- 2012
-
In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 100:24, s. 241105-
-
Journal article (peer-reviewed)abstract
- Hybrid plasmonic waveguides and directional couplers have been experimentally demonstrated. Using a direct measurement method, the propagation loss of a 170 nm wide waveguide is measured to be 0.08 dB/mu m at 1550 nm when the thickness of low-index region is 56 nm. Ultra-compact directional couplers based on such hybrid plasmonic waveguides are demonstrated with gaps of 140 nm, 185 nm, 235 nm, and 290 nm. The corresponding coupling lengths measured are 1.55 mu m, 2.2 mu m, 3.2 mu m, and 4.8 mu m, respectively, which are in very good agreement with the simulations. These ultra-compact devices can be potentially used in future ultra-dense photonic integrated circuits.
|
|
