| 1. |
- Clark, Andrew G., et al.
(författare)
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Evolution of genes and genomes on the Drosophila phylogeny
- 2007
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 450:7167, s. 203-218
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Tidskriftsartikel (refereegranskat)abstract
- Comparative analysis of multiple genomes in a phylogenetic framework dramatically improves the precision and sensitivity of evolutionary inference, producing more robust results than single-genome analyses can provide. The genomes of 12 Drosophila species, ten of which are presented here for the first time (sechellia, simulans, yakuba, erecta, ananassae, persimilis, willistoni, mojavensis, virilis and grimshawi), illustrate how rates and patterns of sequence divergence across taxa can illuminate evolutionary processes on a genomic scale. These genome sequences augment the formidable genetic tools that have made Drosophila melanogaster a pre-eminent model for animal genetics, and will further catalyse fundamental research on mechanisms of development, cell biology, genetics, disease, neurobiology, behaviour, physiology and evolution. Despite remarkable similarities among these Drosophila species, we identified many putatively non-neutral changes in protein-coding genes, non-coding RNA genes, and cis-regulatory regions. These may prove to underlie differences in the ecology and behaviour of these diverse species.
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| 2. |
- Ablikim, M., et al.
(författare)
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Measurements of (XcJ)-> K+K-K+K- decays
- 2006
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 642:3, s. 197-202
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Tidskriftsartikel (refereegranskat)abstract
- Using 14M psi(2S) events taken with the BESII detector, chi(cJ) -> 2(K+K-) decays are studied. For the four-kaon final state, the branching fractions are B(chi(c0,1,2) ->.2(K+K-)) = (3.48 +/- 0.23 +/- 0.47) x 10(-3), (0.70 +/- 0.13 +/- 0.10) x 10(-3), and (2.17 +/- 0.20 +/- 0.31) x 10(-3). For the phi K+K- final state, the branching fractions, which are measured for the first time, are B(chi(c0,1,2) -> phi K+K-) = (1.03 +/- 0.22 +/- 0.15) x 10(-3), (0.46 +/- 0.16 +/- 0.06) x 10(-3), and (1.67 +/- 0.26 +/- 0.24) x 10(-4). For the phi phi final state, B(chi(c0,2) -> phi phi) = (0.94 +/- 0.21 +/- 0.13) x 10(-3) and (1.70 +/- 0.30 +/- 0.25) x 10(-3).
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| 3. |
- Abazov, V. M., et al.
(författare)
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The upgraded DO detector
- 2006
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 565:2, s. 463-537
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Tidskriftsartikel (refereegranskat)abstract
- The DO experiment enjoyed a very successful data-collection run at the Fermilab Tevatron collider between 1992 and 1996. Since then, the detector has been upgraded to take advantage of improvements to the Tevatron and to enhance its physics capabilities. We describe the new elements of the detector, including the silicon microstrip tracker, central fiber tracker, solenoidal magnet, preshower detectors, forward muon detector, and forward proton detector. The uranium/liquid -argon calorimeters and central muon detector, remaining from Run 1, are discussed briefly. We also present the associated electronics, triggering, and data acquisition systems, along with the design and implementation of software specific to DO.
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| 4. |
- Birney, Ewan, et al.
(författare)
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Prepublication data sharing
- 2009
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 461:7261, s. 168-170
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Tidskriftsartikel (refereegranskat)abstract
- Rapid release of prepublication data has served the field of genomics well. Attendees at a workshop in Toronto recommend extending the practice to other biological data sets.
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| 5. |
- Gao, Bin, et al.
(författare)
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Studies of bromine modified single-walled carbon nanotubes using photoelectron spectroscopy and density-functional theory
- 2006
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X .- 1879-0895. ; 75:11, s. 1939-1942
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Tidskriftsartikel (refereegranskat)abstract
- Many applications based on single-walled carbon nanotubes (SWNTs) require chemical modification of carbon nanotube to optimize the functionalities of the device. In this contribution we discuss the properties of SWNTs immersed in a hydrobromic acid (HBr) solution. Changes of atomic and electronic structures of bromine modified SWNTs were investigated using photoelectron spectroscopy (PES). Spectra of SWNTs before and after immersion in the HBr solution exhibit different features. To understand the mechanism of interaction between SWNTs and bromine, we performed density-functional theory calculations to reveal the structural changes, adsorption energy and chemical bonding information of SWNTs interacting with bromine. In addition, based on the Gelius model, from the molecular orbitals (MOs), we calculated ultraviolet photoelectron spectra (UPS) of SWNTs with and without functionalizing and compared them with the experiment. The present study is a first step in the understanding of the functionalization mechanism of carbon nanotubes.
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| 6. |
- Li, Liyuan, et al.
(författare)
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An Efficient Sequential Approach to Tracking Multiple Objects through Crowds for Real-Time Intelligent CCTV Systems
- 2008
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Ingår i: IEEE Transactions on Systems, Man and Cybernetics Part B: Cybernetics. - 1083-4419. ; 38:5, s. 1254-1269
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Tidskriftsartikel (refereegranskat)abstract
- Efficiency and robustness are the two most important issues for multi-object tracking algorithms in real-time intelligent video surveillance systems. We propose a novel2 1/2 D approach to real time multi-object tracking in crowds, which is formulated as a MAP estimation problem and is approximated through an “assignment” step and a “location” step. Observing that the occluding object is usually less affected by the occluded objects, sequential solutions for the assignment and the location are derived. A novel dominant color histogram (DCH) is proposed as an efficient object model. The DCH can be regarded as a generalized color histogram, where dominant colors are selected based on a given distance measure. Comparing with conventional color histograms, DCH only requires a few color components (31 in average). Further, our theoretical analysis and evaluation on real data have shown that DCHs are robust to illumination changes. Using DCH, efficient implementations of sequential solutions for the assignment and the location steps are proposed. The "Assignment" step includes the estimation of depth order for the objects in a dispersing group, one-by-one assignment, and feature exclusion from the group representation. The "Location" step includes the depth order estimation for the objects in a new group, two-phase mean-shift location, and the exclusion of tracked objects from the new position in the group. Multi-object tracking results and evaluation from public datasets are presented. Experiments on image sequences captured from crowded public environments have shown good tracking results, where about 90% of objects have been successfully tracked with the correct identification numbers by the proposed method. Our results and evaluation have indicated that the method is efficient and robust for tracking multiple objects (large than or equal to 3) in complex occlusions for real world surveillance scenarios.
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| 7. |
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| 8. |
- Luo, Ruijiang, et al.
(författare)
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Efficient Adaptive Background Subtraction based on Multi-Resolution Background Modelling and Updating
- 2007
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Ingår i: to appear in Proc. of Pacific-RIM Conf. on Multimedia (PCM'07), Dec. 11-14, Hong Kong, 2007.
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Konferensbidrag (refereegranskat)abstract
- Adaptive background subtraction (ABS) is a fundamental step for foreground object detection in many real-time video surveillance systems. In many ABS methods, a pixel-based statistical model is used for the background and each pixel is updated online to adapt to various background changes. As a result, heavy computation and memory consumption are required. In this paper, we propose an efficient methodology for implementation of ABS algorithms based on multi-resolution background modelling and sequential sampling for updating background. Experiments and quantitative evaluation are conducted on two open data sets (PETS2001 and PETS2006) and scenarios captured in some public places, and some results are included. Our results have shown that the proposed method requires a significant reduction in memory and CPU usage, meanwhile maintaining a similar foreground segmentation performance as compared with the corresponding single resolution methods.
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| 9. |
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| 10. |
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| 11. |
- Ren, Guobin, et al.
(författare)
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Design of all-solid bandgap fiber with improved confinement and bend losses
- 2006
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Ingår i: IEEE Photonics Technology Letters. - : IEEE. - 1041-1135 .- 1941-0174. ; 18:24, s. 2560-2562
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Tidskriftsartikel (refereegranskat)abstract
- We propose a new design of low-contrast all-solid bandgap fiber with low confinement and bend losses within low-order bandgaps. By introducing an index depressed layer around the high index rod in fiber cladding, we theoretically predict that the confinement loss of the proposed all-solid bandgap fiber would be significantly improved. Due to the enlarged index mismatch of the guided core mode and the edge of the bandgaps, the critical bend radius of the proposed fiber is remarkably reduced.
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| 12. |
- Tian, Chao, et al.
(författare)
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Overexpression of connective tissue growth factor WISP-1 in Chinese primary rectal cancer patients
- 2007
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Ingår i: World Journal of Gastroenterology. - 1007-9327 .- 2219-2840. ; 13:28, s. 3878-3882
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Tidskriftsartikel (refereegranskat)abstract
- Aim: To clarify the expression change of Wnt-induced secreted protein-1 (WISP-1) in human rectal cancer and to determine whether it is correlated with invasion and metastasis of human rectal cancer. Methods: Eighty-six paired samples of rectal cancer and surgically resected distant normal rectal tissue were collected and allocated into cancer group and control group respectively. WISP-1 mRNA was detected by relative quantitative real-time RT-PCR and WISP-1 protein was examined by immunohistochemical staining. Results: WISP-1 gene overexpression was found in 65% (56/86) primary rectal cancers, 2-30 times that of the level in normal matched rectal tissues (P = 0.001). The mRNA expression level was correlated with Duke's staging, histological differentiation grade and lymph node status. The WISP-1 protein expression was in accordance with mRNA expression level. The positive degree of immunohistochemical staining in the cancer group (1.40 ± 0.35) was different from that in control group (1.04 ± 0.08, P < 0.001). Moreover, in cancer group the positive staining degree in high-level mRNA cancers (1.46 ± 0.37, n = 56) was higher than that in low-level mRNA (1.28 ± 0.28, n = 30, P = 0.018). Conclusion: Aberrant levels of WISP-1 expression may play a role in rectal tumorigenesis. WISP-1 may be used as a specific clinical diagnosis and prognosis marker in rectal cancer. © 2007 WJG. All rights reserved.
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| 13. |
- Wang, Chuan-Kui, et al.
(författare)
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Breakdown of optical power limiting and dynamical two-photon absorption for femtosecond laser pulses in molecular medium
- 2007
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 24:9, s. 2436-2442
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Tidskriftsartikel (refereegranskat)abstract
- We solve numerically the Maxwell-Bloch equations using an iterative predictor-corrector finite-difference time-domain technique to study the propagation of femtosecond laser pulses in a strong two-photon absorption (TPA) organic molecular medium [4,4'-bis(dimethylamino) stilbene]. The hybrid density functional theory is used to calculate electronic structures of the compound. The molecular system is described by a three-level model in an optical regime and has demonstrated a good optical power limiting behavior in a certain intensity region. Thresholds for the breakdown of optical power limiting are observed that are dependent on the input pulse width and, slightly, the propagation distance. The dynamical two-photon absorption cross section is obtained, which is almost a linearly increasing function of the pulse width in the femtosecond time domain. The propagation distance also has an obvious influence on the measurement of the TPA cross section, and non-monotonic dependence of the TPA cross section on propagation distance is observed. The input pulse width and the thickness of the molecular samples thus should be taken into account when the TPA cross section is measured.
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| 14. |
- Wang, Lin, et al.
(författare)
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Synthesis and high pressure induced amorphization of C60 nanosheets
- 2007
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 91:10, s. 103112-
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Tidskriftsartikel (refereegranskat)abstract
- C-60 nanosheets with thicknesses in the nanometer range were synthesized by a simple method. Compared to bulk C-60, the lattice of the nanosheets is expanded by about 0.4%. In situ Raman spectroscopy and energy-dispersive x-ray diffraction under high pressures have been employed to study the structure of the nanosheets. The studies indicate that the bulk modulus of the C-60 nanosheets is significantly larger than that of bulk C-60. The C-60 cages in nanosheets can persist at pressures over 30 GPa, 3 GPa higher than for bulk C-60. These results suggest that C-60 crystals in even small size will be a potential candidate of superhard materials.
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| 15. |
- Xiao, Kai, et al.
(författare)
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Photoelectrical characteristics of a C/CNx multiwalled nanotube
- 2007
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Ingår i: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 17:15, s. 2842-2846
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Tidskriftsartikel (refereegranskat)abstract
- A nanotube diode fabricated from a single C/CNx multiwalled nanotube exhibits a large photocurrent and a large photovoltage under illumination. The current-voltage (I-V) characteristics of the diode indicate a clear rectification effect. By comparing the I-V characteristics of C, CNx, and C/CNx nanotube diodes, we show that the rectifying characteristics of the C/CNx diode arises from the molecular junction formed at the C/CNx interface where the C and CNx segments are chemically bonded. External radiation photochernically generates electrons and holes in the C/CNx nanotube, producing a large photocurrent because of the influence of the strong electric field in the vicinity of the C/CNx junction. These unique photoresponsive characteristics of C/CNx, nanotube junction diodes points to potential applications such as photovoltaic devices and photodiodes.
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| 16. |
- Yu, G., et al.
(författare)
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Structures, electronic states, photoluminescence, and carrier transport properties of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles
- 2005
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 127:17, s. 6335-6346
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Forskningsöversikt (refereegranskat)abstract
- The excellent electroluminescent (EL) properties of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles, 1-methyl-1,2,3,4,5-pentaphenylsilole (MPPS), and 1,1,2,3,4,5-hexaphenylsilole (HPS) have been found. Despite some studies devoted to these materials, very little is known about the real origin of their unique EL properties. Therefore, we investigated the structures, photoluminescence (PL), and charge carrier transport properties of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles as well as the effect of substituents on these characteristics. The single crystals of the three siloles involving 1,1-dimethyl-2,3,4,5-tetraphenylsilole (DMTPS), MPPS, and HIPS were grown and their crystal structures were determined by X-ray diffraction. Three siloles have nonplanar molecular structures. The substituents at 1,1-positions enhance the steric hindrance and have predominant influence on the twisted degree of phenyl groups at ring carbons. This nonplanar structure reduces the intermolecular interaction and the likelihood of excimer formation, and increases PL efficiency in the solid state. The silole films show high fluorescence quantum yields (75-85%), whereas their dilute solutions exhibit a faint emission. The electronic structures of the three siloles were investigated using quantum chemical calculations. The highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUMOs) are mainly localized on the silole ring and two phenyl groups at 2,5-positions in all cases, while the LUMOs have a significant orbital density at two exocyclic Si-C bonds. The extremely theoretical studies of luminescent properties were carried out. We calculated the nonradiative decay rate of the first excited state as well as the radiative one. It is found that the faint emission of DMTPS in solutions mainly results from the huge nonradiative decay rate. In solid states, molecular packing can remarkably restrict the intramolecular rotation of the peripheral side phenyl ring, which has a large contribution to the nonradiative transition process. This explains why the 1,1-disubstituted 2,3,4,5-tetraphenylsiloles in the thin films exhibit high fluorescence quantum yields. The charge carrier mobilities of the MPPS and HPS films were measured using a transient EL technique. We obtained a mobility of 2.1 x 10(-6) cm(2)/V(.)s in the MPPS film at an electric field of 1.2 x 10(6) V/cm. This mobility is comparable to that of Alq(3), which is one of the most extensively used electron transport materials in organic light-emitting diodes (LEDs), at the same electric field. The electron mobility of the HPS film is about similar to 1.5 times higher than that of the MPPS film. To the best of our knowledge, this kind of material is one of the most excellent emissive materials that possess both high charge carrier mobility and high PL efficiency in the solid states simultaneously. The excellent EL performances of MPPS and HPS are presumably ascribed to these characteristics.
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| 17. |
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| 18. |
- Yu, X., et al.
(författare)
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Theoretical investigation of highly birefringent all-solid photonic bandgap fiber with elliptical cladding rods
- 2006
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Ingår i: IEEE Photonics Technology Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1041-1135 .- 1941-0174. ; 18:11, s. 1243-1245
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Tidskriftsartikel (refereegranskat)abstract
- We theoretically study for the first time the waveguiding properties of an all-solid photonic bandgap fiber with elliptical cladding rods. High birefringence in the order of 10 -3 is easily achievable in such fibers. The contributions of the cladding rod's ellipticity, the lattice ratio of the cladding microstructure as well as the index contrast of two soft glasses to the birefringence are systematically evaluated. The evolutions of birefringence with the structure and material variations show that our highly birefringent fiber design can be tailored.
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| 19. |
- Zhao, K., et al.
(författare)
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Studies on two-photon absorption cross-sections of 1,4-dimethoxy-2,5-divinyl-benzene derivatives
- 2005
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Ingår i: Wuli xuebao. - : Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences. - 1000-3290. ; 54:6, s. 2662-2668
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Tidskriftsartikel (refereegranskat)abstract
- The one-photon and two-photon absorption properties of a series of 1, 4-dimethoxy-2, 5-divinyl-benzene derivatives are investigated by use of the analytic response theory at HF level. The one-photon and two-photon fluorescence spectra of E, E-2-5Bis[4'-(N, N-di-n-butylamino) styryl]-1 4-dimenthoxybenzene are measured. The numerical results show that these molecules have strong two-photon absorption cross sections. In the visible light region, the maximal one-photon absorption strengths of the molecules occur in the first excited state. Furthermore, the maximal two-photon absorption cross sections of the D-pi-A typed molecules still appear in the first state, but for D-pi-D typed molecules the second excited state has the maximal two-photon absorption cross-section. The optical properties of the molecules are closely related to the electric property of the donor and acceptor. The symmetrically substituted molecules can not be determined to have a larger two-photon absorption cross section than the asymmetrically substituted molecules for such a kind of pi-center. The charge-transfer process for the charge-transfer states is displayed, and then the mechanism of photopolymerization is discussed qualitatively.
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