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Full-Text Articles in Physics
Functional Characterization Of Core Promoter Elements: The Downstream Core Element Is Recognized By Taf1, Dong-Hoon Lee, Naum I. Gershenzon, Malavika Gupta, Ilya P. Ioshikhes, Danny Reinberg, Brian A. Lewis
Functional Characterization Of Core Promoter Elements: The Downstream Core Element Is Recognized By Taf1, Dong-Hoon Lee, Naum I. Gershenzon, Malavika Gupta, Ilya P. Ioshikhes, Danny Reinberg, Brian A. Lewis
Physics Faculty Publications
Downstream elements are a newly appreciated class of core promoter elements of RNA polymerase II-transcribed genes. The downstream core element (DCE) was discovered in the human β-globin promoter, and its sequence composition is distinct from that of the downstream promoter element (DPE). We show here that the DCE is a bona fide core promoter element present in a large number of promoters and with high incidence in promoters containing a TATA motif. Database analysis indicates that the DCE is found in diverse promoters, supporting its functional relevance in a variety of promoter contexts. The DCE consists of …
Evidence For Native-Defect Donors In N-Type Zno, David C. Look, Gary C. Farlow, Pakpoom Reunchan, Sukit Limpijumnong, S. B. Zhang, K. Nordlund
Evidence For Native-Defect Donors In N-Type Zno, David C. Look, Gary C. Farlow, Pakpoom Reunchan, Sukit Limpijumnong, S. B. Zhang, K. Nordlund
Physics Faculty Publications
Recent theory has found that native defects such as the O vacancy VO and Zn interstitial ZnI have high formation energies in n-type ZnO and, thus, are not important donors, especially in comparison to impurities such as H. In contrast, we use both theory and experiment to show that, under N ambient, the complex ZnI-NO is a stronger candidate than H or any other known impurity for a 30 meV donor commonly found in bulk ZnO grown from the vapor phase. Since the Zn vacancy is also the dominant acceptor in such material, we must …
Traps In Algan/Gan/Sic Heterostructures Studied By Deep Level Transient Spectroscopy, Z-Q. Fang, David C. Look, D. H. Kim, I. Adesida
Traps In Algan/Gan/Sic Heterostructures Studied By Deep Level Transient Spectroscopy, Z-Q. Fang, David C. Look, D. H. Kim, I. Adesida
Physics Faculty Publications
AlGaN/GaN/SiC Schottky barrier diodes (SBDs), with and without Si3N4 passivation, have been characterized by temperature-dependent current-voltage and capacitance-voltage measurements, and deep level transient spectroscopy (DLTS). A dominant trap A1, with activation energy of 1.0 eV and apparent capture cross section of 2×10−12 cm2, has been observed in both unpassivated and passivated SBDs. Based on the well-known logarithmic dependence of DLTS peak height with filling pulse width for a line-defect related trap, A1, which is commonly observed in thin GaN layers grown by various techniques, is believed to be associated with …
Introduction And Recovery Of Point Defects In Electron-Irradiated Zno, F. Tuomisto, K. Saarinen, David C. Look, Gary C. Farlow
Introduction And Recovery Of Point Defects In Electron-Irradiated Zno, F. Tuomisto, K. Saarinen, David C. Look, Gary C. Farlow
Physics Faculty Publications
We have used positron annihilation spectroscopy to study the introduction and recovery of point defects in electron-irradiated n -type ZnO. The irradiation ( Eel=2MeV , fluence 6×1017cm-2 ) was performed at room temperature, and isochronal annealings were performed from 300 to 600 K. In addition, monochromatic illumination of the samples during low-temperature positron measurements was used in identification of the defects. We distinguish two kinds of vacancy defects: the Zn and O vacancies, which are either isolated or belong to defect complexes. In addition, we observe negative-ion-type defects, which are attributed to O interstitials or …
Role Of Near-Surface States In Ohmic-Schottky Conversion Of Au Contacts To Zno, H. L. Mosbacker, Y. M. Strzhemechny, B. D. White, P. E. Smith, David C. Look, D. C. Reynolds, C. W. Litton, L. J. Brillson
Role Of Near-Surface States In Ohmic-Schottky Conversion Of Au Contacts To Zno, H. L. Mosbacker, Y. M. Strzhemechny, B. D. White, P. E. Smith, David C. Look, D. C. Reynolds, C. W. Litton, L. J. Brillson
Physics Faculty Publications
A conversion from ohmic to rectifying behavior is observed for Au contacts on atomically ordered polar ZnO surfaces following remote, room-temperature oxygen plasma treatment. This transition is accompanied by reduction of the “green” deep level cathodoluminescence emission, suppression of the hydrogen donor-bound exciton photoluminescence and a ∼ 0.75 eV increase in n-type band bending observed via x-ray photoemission. These results demonstrate that the contact type conversion involves more than one mechanism, specifically, removal of the adsorbate-induced accumulation layer plus lowered tunneling due to reduction of near-surface donor density and defect-assisted hopping transport.
Study Of The Photoluminescence Of Phosphorus-Doped P-Type Zno Thin Films Grown By Radio-Frequency Magnetron Sputtering, Dae-Kue Hwang, Hyun-Sik Kim, Jae-Hong Lim, Jin-Yong Y. Oh, Jin-Ho Yang, Seong-Ju Park, Kyong-Kook Kim, David C. Look, Y. S. Park
Study Of The Photoluminescence Of Phosphorus-Doped P-Type Zno Thin Films Grown By Radio-Frequency Magnetron Sputtering, Dae-Kue Hwang, Hyun-Sik Kim, Jae-Hong Lim, Jin-Yong Y. Oh, Jin-Ho Yang, Seong-Ju Park, Kyong-Kook Kim, David C. Look, Y. S. Park
Physics Faculty Publications
Phosphorus-doped p-type ZnO thin films were grown on sapphire by radio-frequency magnetron sputtering. The photoluminescence (PL) spectra revealed an acceptor bound exciton peak at 3.355 eV and a conduction band to the acceptor transition caused by a phosphorus related level at 3.310 eV. A study of the dependence of the excitation laser power density and temperature on the characteristics of the PL spectra suggests that the emission lines at 3.310 and 3.241 eV can be attributed to a conduction band to the phosphorus-related acceptor transition and a donor to the acceptor pair transition, respectively. The acceptor energy level of the …
Computational Technique For Improvement Of The Position-Weight Matrices For The Dna/Protein Binding Sites, Naum I. Gershenzon, Gary D. Stormo, Ilya P. Ioshikhes
Computational Technique For Improvement Of The Position-Weight Matrices For The Dna/Protein Binding Sites, Naum I. Gershenzon, Gary D. Stormo, Ilya P. Ioshikhes
Physics Faculty Publications
Position-weight matrices (PWMs) are broadly used to locate transcription factor binding sites in DNA sequences. The majority of existing PWMs provide a low level of both sensitivity and specificity. We present a new computational algorithm, a modification of the Staden–Bucher approach, that improves the PWM. We applied the proposed technique on the PWM of the GC-box, binding site for Sp1. The comparison of old and new PWMs shows that the latter increase both sensitivity and specificity. The statistical parameters of GC-box distribution in promoter regions and in the human genome, as well as in each chromosome, are presented. The majority …
Ion Cyclotron Waves In The Saturnian Magnetosphere Associated With Cassini's Engine Exhaust, C. T. Russell, J. S. Leisner, K. K. Khurana, M. K. Dougherty, X. Blanco-Cano, Jane L. Fox
Ion Cyclotron Waves In The Saturnian Magnetosphere Associated With Cassini's Engine Exhaust, C. T. Russell, J. S. Leisner, K. K. Khurana, M. K. Dougherty, X. Blanco-Cano, Jane L. Fox
Physics Faculty Publications
Five hours after the orbit insertion maneuver that placed Cassini into orbit about Saturn, a long (90 minute) burst of ion cyclotron waves were seen, very different than any waves on the inbound leg of the orbit or on succeeding orbits. The ion cyclotron waves were left-hand elliptically polarized and propagating at a moderately large angle to the local magnetic field. The waves had a noticeable compressional component consistent with their off angle propagation. The frequency band of the signals was moderately broad and consistent with the singly ionized components of the engine exhaust gases: CO2, N2 …
Effects Of Dissociative Recombination On The Composition Of Planetary Atmospheres, Jane L. Fox
Effects Of Dissociative Recombination On The Composition Of Planetary Atmospheres, Jane L. Fox
Physics Faculty Publications
Because dissociative recombination (DR) reactions of molecular ions are often highly exothermic, in the thermospheres of the Earth and planets DR may be a source of translationally and internally excited fragments. DR is important, therefore, for thermospheric neutral heating; if the excited fragments radiate to space, however, DR may be also a source of thermospheric cooling. DR may produce metastable fragments, which may live long enough to participate in reactions that are not available to ground state species. It is rare, however, for DR to be a significant source of minor species in their ground states. An exception appears to …
Frequency Scanned Interferometer Demonstration System, Jason A. Deibel, Sven Nyberg, Keith Riles, Haijun Yang
Frequency Scanned Interferometer Demonstration System, Jason A. Deibel, Sven Nyberg, Keith Riles, Haijun Yang
Physics Faculty Publications
No abstract provided.
C And C+ In The Venusian Thermosphere/Ionosphere, Jane L. Fox, L. J. Paxton
C And C+ In The Venusian Thermosphere/Ionosphere, Jane L. Fox, L. J. Paxton
Physics Faculty Publications
We have constructed standard low and high solar activity models of the Venus thermosphere, which take into account revised rate coefficients for production and loss processes for C and C+, high-resolution cross sections for photodissociation of CO, and recent solar fluxes from the Solar 2000 v1.24 and v2.22 models of Tobiska [2004]. Among the most important changes is the inclusion of the branching ratio for the channel of dissociative recombination of CO2+ that produces C + O2, which has been measured recently by Seiersen et al. [2003]. We find that unlike Mars, where the …
Thermospheric Distribution Of Fast O(D-1) Atoms, V. Kharchenko, A. Dalgarno, Jane L. Fox
Thermospheric Distribution Of Fast O(D-1) Atoms, V. Kharchenko, A. Dalgarno, Jane L. Fox
Physics Faculty Publications
Detailed calculations are carried out of the sources of energetic metastable O(1D) atoms in the atmosphere at altitudes between 80 km and 200 km, and the corresponding energy distribution functions are derived, taking account of energy transfer and quenching in collisions of the metastable atoms with the ambient atmospheric gas constituents. The energy relaxation of metastable oxygen atoms produced by O2 and O3 photolysis and O2 + dissociative recombination is determined by solving the time-dependent Boltzmann equation. The O(1D) thermalization and quenching times are obtained as functions of the altitude. The steady state …