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2007

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Articles 6031 - 6060 of 6763

Full-Text Articles in Physical Sciences and Mathematics

Experimental Study Of Exclusive ²H(E,E'P)N Reaction Mechanisms At High Q², S. E. Kuhn, M. J. Amaryan, H. Bagdasaryan, M. Bektasoglu, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, N. Guler, C. E. Hyde-Wright, H. G. Juengst, N. Kalantarians, A. Klein, M. R. Niroula, R. A. Niyazov, S. Tkachenko, L. B. Weinstein, J. Zhang, Et. Al., Clas Collaboration Jan 2007

Experimental Study Of Exclusive ²H(E,E'P)N Reaction Mechanisms At High Q², S. E. Kuhn, M. J. Amaryan, H. Bagdasaryan, M. Bektasoglu, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, N. Guler, C. E. Hyde-Wright, H. G. Juengst, N. Kalantarians, A. Klein, M. R. Niroula, R. A. Niyazov, S. Tkachenko, L. B. Weinstein, J. Zhang, Et. Al., Clas Collaboration

Physics Faculty Publications

The reaction 2H(e,e(')p)n has been studied with full kinematic coverage for photon virtuality 1.75 < Q2< 5.5 GeV2. Comparisons of experimental data with theory indicate that for very low values of neutron recoil momentum (pn< 100 MeV/c) the neutron is primarily a spectator and the reaction can be described by the plane-wave impulse approximation. For 100 < pn< 750 MeV/c, proton-neutron rescattering dominates the cross section, while Delta production followed by the NΔ → NN transition is the primary contribution at higher momenta.

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Quark Contribution To The Small-𝔁 Evolution Of Color Dipole, Ian Balitsky Jan 2007

Quark Contribution To The Small-𝔁 Evolution Of Color Dipole, Ian Balitsky

Physics Faculty Publications

The small-𝔁 deep inelastic scattering in the saturation region is governed by the nonlinear evolution of Wilson-lines operators. In the leading logarithmic approximation it is given by the Balitsky-Kovchegov (BK) equation for the evolution of color dipoles. In the next-to-leading order (NLO) the nonlinear equation gets contributions from quark and gluon loops. In this paper I calculate the quark-loop contribution to small-𝔁 evolution of Wilson lines in the NLO. It turns out that there are no new operators at the one-loop level—just as at the tree level, the high-energy scattering can be described in terms of Wilson lines. In addition, …

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Low And Medium Β Superconducting Cavities And Accelerators, Jean R. Delayen Jan 2007

Low And Medium Β Superconducting Cavities And Accelerators, Jean R. Delayen

Physics Faculty Publications

No abstract provided.

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A General Model Of Resistive Wall Instability In Linear Accelerators, Jean R. Delayen Jan 2007

A General Model Of Resistive Wall Instability In Linear Accelerators, Jean R. Delayen

Physics Faculty Publications

A general model for wakefield-generated instabilities in linear accelerators, originally developed for cumulative beam breakup [1], is applied to the resistive wall instability. The general solution for various bunch charge distributions and application to various accelerator configurations are presented.

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All-Optical Regeneration For Phase-Shift Keyed Optical Communication Systems, Kevin Croussore Jan 2007

All-Optical Regeneration For Phase-Shift Keyed Optical Communication Systems, Kevin Croussore

Electronic Theses and Dissertations

All-optical signal processing techniques for phase-shift keyed (PSK) systems were developed theoretically and demonstrated experimentally. Nonlinear optical effects in fibers, in particular four-wave mixing (FWM) that occurs via the ultra-fast Kerr nonlinearity, offer a flexible framework within which numerous signal processing functions can be accomplished. This research has focused on the regenerative capabilities of various FWM configurations in the context of processing PSK signals. Phase-preserving amplitude regeneration, phase regeneration, and phase-regenerative wavelength conversion are analyzed and demonstrated experimentally. The single-pump phase-conjugation process was used to regenerate RZ-DPSK pulse amplitudes with different input noise distributions, and the impact on output phase …

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Two-Dimensional Guided Mode Resonant Structures For Spectral Filtering Applications, Sakoolkan Boonruang Jan 2007

Two-Dimensional Guided Mode Resonant Structures For Spectral Filtering Applications, Sakoolkan Boonruang

Electronic Theses and Dissertations

Guided mode resonant (GMR) structures are optical devices that consist of a planar waveguide with a periodic structure either imbedded in or on the surface of the structure. The resonance anomaly in GMR structures has many applications as dielectric mirrors, tunable devices, sensors,and narrow spectral band reflection filters. A desirable response from a resonant grating filter normally includes a nearly 100% narrowband resonant spectral reflection (transmission), and a broad angular acceptance at either normal incidence or an oblique angle of incidence. This dissertation is a detailed study of the unique nature of the resonance anomaly in GMR structures with two-dimensional …

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Optimizing The High Dynamic Range Imaging Pipeline, Ahmet Oguz Akyuz Jan 2007

Optimizing The High Dynamic Range Imaging Pipeline, Ahmet Oguz Akyuz

Electronic Theses and Dissertations

High dynamic range (HDR) imaging is a rapidly growing field in computer graphics and image processing. It allows capture, storage, processing, and display of photographic information within a scene-referred framework. The HDR imaging pipeline consists of the major steps an HDR image is expected to go through from capture to display. It involves various techniques to create HDR images, pixel encodings and file formats for storage, tone mapping for display on conventional display devices and direct display on HDR capable screens. Each of these stages have important open problems, which need to be addressed for a smoother transition to an …

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Modeled And Observed N2 Lyman-Birge-Hopfield Band Emissions Earth's Dayglow: A Comparison, Donald Murray Jan 2007

Modeled And Observed N2 Lyman-Birge-Hopfield Band Emissions Earth's Dayglow: A Comparison, Donald Murray

Electronic Theses and Dissertations

Ultraviolet (UV) spectra obtained from Earth’s dayglow contain important information for understanding the thermosphere, and the N2 Lyman-Birge-Hopfield (LBH) bands are possibly the most useful emission. To be useful, a thorough understanding of how the LBH band emission varies with altitude and latitude is essential to present and future use of this emission by space-based remote sensors. Excited by photoelectron impact on N2 leading to transitions from the a 1Πg state to the ground state, the LBH emissions radiate between 1270 and 2400 Å. In addition to being populated by electron impact excitation, the a 1Πg state is populated by …

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Discrete Surface Solitons, Sergiy Suntsov Jan 2007

Discrete Surface Solitons, Sergiy Suntsov

Electronic Theses and Dissertations

Surface waves exist along the interfaces between two different media and are known to display properties that have no analogue in continuous systems. In years past, they have been the subject of many studies in a diverse collection of scientific disciplines. In optics, one of the mechanisms through which optical surface waves can exist is material nonlinearity. Until recently, most of the activity in this area was focused on interfaces between continuous media but no successful experiments have been reported. However, the growing interest that nonlinear discrete optics has attracted in the last two decades has raised the question of …

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Effects Of Polarization And Coherence On The Propagation And The Detection Of Stochastic Electromagnetic Beams, Mohamed Fouad Salem Jan 2007

Effects Of Polarization And Coherence On The Propagation And The Detection Of Stochastic Electromagnetic Beams, Mohamed Fouad Salem

Electronic Theses and Dissertations

Most of the physically realizable optical sources are radiating in a random manner given the random nature of the radiation of a large number of atoms that constitute the source. Besides, a lot of natural and synthetic materials are fluctuating randomly. Hence, the optical fields that one encounters, in most of the applications are fluctuating and must be treated using random or stochastic functions. Within the framework of the scalar-coherence theory, one can describe changes of the properties of any stochastic field such as the spectral density and the spectral degree of coherence on propagation in any linear medium, deterministic …

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Performance Analysis Of Security Aspects In Uml Models, Dorin Bogdan Petriu, Dorina C. Petriu, C Murray Woodside, Jing Xiu, Toqeer A. Israr, Geri Georg, Robert B. France, James M. Bieman, Siv Holde Houmb, Jan Jurjens Jan 2007

Performance Analysis Of Security Aspects In Uml Models, Dorin Bogdan Petriu, Dorina C. Petriu, C Murray Woodside, Jing Xiu, Toqeer A. Israr, Geri Georg, Robert B. France, James M. Bieman, Siv Holde Houmb, Jan Jurjens

Faculty Research & Creative Activity

The focus of the paper is on the analysis of performance effects of different security solutions modeled as aspects in UML. Aspect oriented modeling (AOM) allows software designers to isolate and separately address solutions for crosscutting concerns, which are defined as distinct UML aspect models, then are composed with the primary UML model of the system under development. For performance analysis we use techniques developed previously in the PUMA project, which take as input UML models annotated with the standard UML Profile for Schedulability, Performance and Time (SPT), and transform them first into Core Scenario Model (CSM) and then into …

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Comment On “Wave-Breaking Limits For Relativistic Electrostatic Waves In A One-Dimensional Warm Plasma” [Phys. Plasmas 13, 123102 (2006)], Carl B. Schroeder, Eric Esarey, Bradley Allan Shadwick Jan 2007

Comment On “Wave-Breaking Limits For Relativistic Electrostatic Waves In A One-Dimensional Warm Plasma” [Phys. Plasmas 13, 123102 (2006)], Carl B. Schroeder, Eric Esarey, Bradley Allan Shadwick

Department of Physics and Astronomy: Faculty Publications

In this Comment, several incorrect and misleading claims made by Trines and Norreys (TN) in Ref. 1 are addressed.

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Acoustic Analog To Quantum Mechanical Level Splitting, Shawn A. Hilbert, Herman Batelaan Jan 2007

Acoustic Analog To Quantum Mechanical Level Splitting, Shawn A. Hilbert, Herman Batelaan

Department of Physics and Astronomy: Faculty Publications

A simple physical system is discussed that mirrors the quantum mechanical infinite square well with a central delta well potential. The physical realization consists of a continuous sound wave traveling in a pair of tubes separated by an adjustable diaphragm. The equivalence between the quantum system and the acoustic system is explored. The analytic solution to the quantum system exhibits level splitting as does the acoustic system.

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A Macroscopic Test Of The Aharonov-Bohm Effect, Adam Caprez, Brett E. Barwick, Herman Batelaan Jan 2007

A Macroscopic Test Of The Aharonov-Bohm Effect, Adam Caprez, Brett E. Barwick, Herman Batelaan

Department of Physics and Astronomy: Faculty Publications

The Aharonov-Bohm (AB) effect is a purely quantum mechanical effect. The original (classified as Type-I) AB-phase shift exists in experimental conditions where the electromagnetic fields and forces are zero. It is the absence of forces that makes the ABeffect entirely quantum mechanical. Although the AB-phase shift has been demonstrated unambiguously, the absence of forces in Type-I AB-effects has never been shown. Here, we report the observation of the absence of time delays associated with forces of the magnitude needed to explain the AB-phase shift for a macroscopic system.

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Impact Of Computers On Cultures In Third World Countries: A Case Of Computers In Education, James R. Ochwa-Echel Jan 2007

Impact Of Computers On Cultures In Third World Countries: A Case Of Computers In Education, James R. Ochwa-Echel

James R. Ochwa-Echel

No abstract provided.

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Programming With Perltex, Andrew Mertz, William Slough Jan 2007

Programming With Perltex, Andrew Mertz, William Slough

Faculty Research and Creative Activity

PerlTEX couples two well-known worlds—the Perl programming language and the LATEX typesetting system. The resulting system provides users with a way to augment LATEX macros with Perl code, thereby adding programming capabilities to LATEX that would otherwise be difficult to express. In this paper, we illus- trate the use of PerlTEX with a variety of examples and explain the associated Perl code. Although Perl may perhaps be best known for its string manipula- tion capabilities, we demonstrate how PerlTEX indirectly provides support for “programming” graphics through the use of additional packages such as TikZ.

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Borazans:  Tunable Fluorophores Based On 2-(Pyrazolyl)Aniline Chelates Of Diphenylboron, Brendan J. Liddle, Rosalice M. Silva, Tyler James Morin, Felipe P. Macedo, Ruchi Shukla, Sergey V. Lindeman, James R. Gardinier Jan 2007

Borazans:  Tunable Fluorophores Based On 2-(Pyrazolyl)Aniline Chelates Of Diphenylboron, Brendan J. Liddle, Rosalice M. Silva, Tyler James Morin, Felipe P. Macedo, Ruchi Shukla, Sergey V. Lindeman, James R. Gardinier

Chemistry Faculty Research and Publications

The reaction between 2-pyrazolyl-4-X-anilines, H(pzAnX), (X = para-OMe (L1), Me (L2), H (L3), Cl (L4), CO2Et (L5), CF3 (L6), CN (L7)) and triphenylboron in boiling toluene affords the respective, highly emissive N,N‘-boron chelate complexes, BPh2(pzAnX) (X = para-OMe (1), Me (2), H (3), Cl (4), CO2Et (5), CF3 (6), CN (7)) in high yield. The …

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A ‘Metallic Tape’ Stabilized By An Unprecedented Μ5-Κ2,Κ2,Κ2,Κ1,Κ1-) Scorpionate Binding Mode, James R. Gardinier, Rosalice M. Silva, Chengeto Gwengo, Sergey V. Lindeman Jan 2007

A ‘Metallic Tape’ Stabilized By An Unprecedented Μ5-Κ2,Κ2,Κ2,Κ1,Κ1-) Scorpionate Binding Mode, James R. Gardinier, Rosalice M. Silva, Chengeto Gwengo, Sergey V. Lindeman

Chemistry Faculty Research and Publications

The Janus scorpionate ligand, tris(mercaptothiadiazolyl)borate, exhibits extraordinary coordination capacity and versatility, binding from two up to five metal cations as demonstrated by its thallium(I) salt, a compound that serves as a model for metal–surface binding.

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Chemistry And Biology Of Streptogramin A Antibiotics, Fahim Ahmed, William Donaldson Jan 2007

Chemistry And Biology Of Streptogramin A Antibiotics, Fahim Ahmed, William Donaldson

Chemistry Faculty Research and Publications

The streptogramin A antibiotics have proven to be highly active against Gram positive bacteria, particularly methicillin-resistant Staphylococcus aureus. Members of this group of compounds are characterized by a 23-membered macrocycles containing polyene, oxazole, amide and ester functionality. The chemistry and biology of these valuable antimicrobial agents is covered.

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Initial Studies On A Novel Target-Promoted Dna Alkylation System, Ting Xu Jan 2007

Initial Studies On A Novel Target-Promoted Dna Alkylation System, Ting Xu

Theses and Dissertations

A novel target-promoted DNA alkylation system was designed, which consists of a DNA intercalating/alkylating quinone methide (QM) precursor, a removable amine linker, and a sequence-specific delivery. The QM in this system was regenerated by eliminating the amino linker promoted by the hydrophobic interaction between the target DNA and the intercalating QM precursor. Three alkylation model systems (methoxyl polycyclic system, intramolecular hydrogen bonding system and biaryl system) were proposed and synthesized. The potential DNA QM alkylation was investigated by deoxyadenosine (dA) and deoxyguanosine (dG) alkylation with the biaryl system. Only one deoxynucleoside adduct was observed when dA or dG reacted with …

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Cafm Studies Of Epitaxial Lateral Overgrowth Gan Films, Vishal P. Kasliwal Jan 2007

Cafm Studies Of Epitaxial Lateral Overgrowth Gan Films, Vishal P. Kasliwal

Theses and Dissertations

This thesis uses the techniques of atomic force microscopy (AFM) and conductiveAFM (CAFM) to study defect sites on GaN films. In particular, these defect sites demonstrate current leakage under reverse-bias conditions that are detrimental to device fabrication. Two growth techniques that were used to improve this leakage behavior for samples in this study included: epitaxial lateral overgrowth (ELO) and nano-ELO using a Si3N4 film. Both techniques decrease defects such as threading dislocations by controlling the nucleation and growth behavior of the GaN films. The EL0 technique uses a patterned dielectric film to laterally grow micron-wide regions (referred to as 'wings') …

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Practical Synthesis Of Unsymmetrical Tetraarylethylenes And Their Application For The Preparation Of [Triphenylethylene−Spacer−Triphenylethylene] Triads, Moloy Banerjee, Susanna J. Emond, Sergey V. Lindeman, Rajendra Rathore Jan 2007

Practical Synthesis Of Unsymmetrical Tetraarylethylenes And Their Application For The Preparation Of [Triphenylethylene−Spacer−Triphenylethylene] Triads, Moloy Banerjee, Susanna J. Emond, Sergey V. Lindeman, Rajendra Rathore

Chemistry Faculty Research and Publications

We have demonstrated that reactions of diphenylmethyllithium with a variety of substituted benzophenones produces corresponding tertiary alcohols that are easily dehydrated, without any need for purification, to produce various unsymmetrical and symmetrical tetraarylethylenes in excellent yields. The simplicity of the method allows for the preparation of a variety of ethylenic derivatives in multigram (10−50 g) quantities with great ease. The methodology was successfully employed for the preparation of various triphenylethylene (TPE)-based triads (i.e., TPE−spacer−TPE) containing polyphenylene and fluoranyl-based spacers. The ready availability of various substituted tetraarylethylenes allowed us to shed light on the effect of substituents on the oxidation potentials …

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Hexabenzo[4.4.4]Propellane:  A Helical Molecular Platform For The Construction Of Electroactive Materials, Paromita Debroy, Sergey V. Lindeman, Rajendra Rathore Jan 2007

Hexabenzo[4.4.4]Propellane:  A Helical Molecular Platform For The Construction Of Electroactive Materials, Paromita Debroy, Sergey V. Lindeman, Rajendra Rathore

Chemistry Faculty Research and Publications

Helical hexabenzo[4.4.4]propellane (a relative of hexaphenylethane) and its derivatives are synthesized and their structures are established by X-ray crystallography. Isolation and X-ray crystallographic characterization of a robust trication-radical salt of hexamethoxypropellane derivative confirms that its framework is stable toward oxidative (aliphatic) C−C bond cleavage. It is also demonstrated that propellane can be easily brominated at the 4,4‘-positions of the biphenyl linkages for its usage as a molecular platform for the preparation of electroactive materials.

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Electron Transfer Prompted Ejection Of A Tightly Bound K+ From The Ethereal Cavity Of A Hexaarylbenzene-Based Receptor, Ruchi Shukla, Sergey V. Lindeman, Rajendra Rathore Jan 2007

Electron Transfer Prompted Ejection Of A Tightly Bound K+ From The Ethereal Cavity Of A Hexaarylbenzene-Based Receptor, Ruchi Shukla, Sergey V. Lindeman, Rajendra Rathore

Chemistry Faculty Research and Publications

Synthesis of a pair of rotamers (9u/9s) of a hexaarylbenzene derivative containing six (cofacially arranged) electroactive 2,5-dimethoxytolyl groups is described. The toroidal electronic stabilization due to the circular arrangement of aryl groups in 9u/9s leads to the observation of multiple (reversible) oxidation waves and lowering of their Eox1 by ∼250 mV relative to model compounds. The binding of K+ to symmetrical rotamer 9s was monitored by an electrochemical method and further confirmed by X-ray crystallography.

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Impact Of Computers On Cultures In Third World Countries: A Case Of Computers In Education, James R. Ochwa-Echel Jan 2007

Impact Of Computers On Cultures In Third World Countries: A Case Of Computers In Education, James R. Ochwa-Echel

Faculty Research and Creative Activity

No abstract provided.

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Impact Of Computers On Cultures In Third World Countries: A Case Of Computers In Education, James Ochwa-Echel Jan 2007

Impact Of Computers On Cultures In Third World Countries: A Case Of Computers In Education, James Ochwa-Echel

Faculty Research and Creative Activity

No abstract provided.

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Dna Multiplex Hybridization On Microarrays And Thermodynamic Stability In Solution: A Direct Comparison, Daniel J. Fish, M. Todd Horne, Greg P. Brewood, Jim P. Goodarzi, Saba Alemayehu, Ashwini Bhandiwad, Robert P. Searles, Albert S. Benight Jan 2007

Dna Multiplex Hybridization On Microarrays And Thermodynamic Stability In Solution: A Direct Comparison, Daniel J. Fish, M. Todd Horne, Greg P. Brewood, Jim P. Goodarzi, Saba Alemayehu, Ashwini Bhandiwad, Robert P. Searles, Albert S. Benight

Chemistry Faculty Publications and Presentations

Hybridization intensities of 30 distinct short duplex DNAs measured on spotted microarrays, were directly compared with thermodynamic stabilities measured in solution. DNA sequences were designed to promote formation of perfect match, or hybrid duplexes containing tandem mismatches. Thermodynamic parameters DeltaH degrees , DeltaS degrees and DeltaG degrees of melting transitions in solution were evaluated directly using differential scanning calorimetry. Quantitative comparison with results from 63 multiplex microarray hybridization experiments provided a linear relationship for perfect match and most mismatch duplexes. Examination of outliers suggests that both duplex length and relative position of tandem mismatches could be important factors contributing to …

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Modular Polyketide Synthases And Cis Double Bond Formation:  Establishment Of Activated Cis-3-Cyclohexylpropenoic Acid As The Diketide Intermediate In Phoslactomycin Biosynthesis, Mamoun M. Alhamadsheh, Nadaraj Palaniappan, Suparna Daschouduri, Kevin A. Reynolds Jan 2007

Modular Polyketide Synthases And Cis Double Bond Formation:  Establishment Of Activated Cis-3-Cyclohexylpropenoic Acid As The Diketide Intermediate In Phoslactomycin Biosynthesis, Mamoun M. Alhamadsheh, Nadaraj Palaniappan, Suparna Daschouduri, Kevin A. Reynolds

Chemistry Faculty Publications and Presentations

The majority of modular polyketide synthase (PKS) systems which generate unsaturated products do so with trans double bonds. Phoslactomycin B (PLM B) presents a class of antitumor and antiviral natural polyketide products that have unique structural features, including a linear unsaturated backbone with one trans and three cis double bonds. There is substantial evidence that trans double bonds are established by ketoreductase-dehydratase (KR-DH) didomains within a PKS module. In cases where modules containing these didomains appear to generate product containing a cis double bond there is no experimental evidence to determine if they do so directly, or if they also …

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Probing Reactivity And Substrate Specificity Of Both Subunits Of The Dimeric Mycobacterium Tuberculosis Fabh Using Alkyl-Coa Disulfide Inhibitors And Acyl-Coa Substrates, Sarbjot Sachdeva, Faik Musayev, Mamoun M. Alhamadsheh, J. Neel Scarsdale, H. Tonie Wright, Kevin A. Reynolds Jan 2007

Probing Reactivity And Substrate Specificity Of Both Subunits Of The Dimeric Mycobacterium Tuberculosis Fabh Using Alkyl-Coa Disulfide Inhibitors And Acyl-Coa Substrates, Sarbjot Sachdeva, Faik Musayev, Mamoun M. Alhamadsheh, J. Neel Scarsdale, H. Tonie Wright, Kevin A. Reynolds

Chemistry Faculty Publications and Presentations

The dimeric Mycobacterium tuberculosis FabH (mtFabH) catalyses a Claisen-type condensation between an acyl-CoA and malonyl-acyl carrier protein (ACP) to initiate the Type II fatty acid synthase cycle. To analyze the initial covalent acylation of mtFabH with acyl-CoA, we challenged it with mixture of C6-C20 acyl-CoAs and the ESI-MS analysis showed reaction at both subunits and a strict specificity for C12 acyl CoA. Crystallographic and ESI-MS studies of mtFabH with a decyl-CoA disulfide inhibitor revealed a decyl chain bound in acyl-binding channels of both subunits through disulfide linkage to the active site cysteine. These data provide the first unequivocal evidence that …

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A Critical Review On Electromagnetic Precursors And Earthquake Prediction, Levent Sevgi̇ Jan 2007

A Critical Review On Electromagnetic Precursors And Earthquake Prediction, Levent Sevgi̇

Turkish Journal of Electrical Engineering and Computer Sciences

Seismo-electromagnetic precursory-based earthquake prediction studies are criticized in terms of their scientific content, problem complexity, signal excitation and propagation, causal relations with earthquakes, and public awareness and expectations. One aim is to trigger a new debate on this hot topic in the Electromagnetic Society.

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