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2012

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Articles 1 - 30 of 1978

Full-Text Articles in Physics

Extension To Pv Optics To Include Front Electrode Design In Solar Cells, Debraj Guhabiswas Dec 2012

Extension To Pv Optics To Include Front Electrode Design In Solar Cells, Debraj Guhabiswas

Dissertations

Proper optical designing of solar cells and modules is of paramount importance towards achieving high photovoltaic conversion efficiencies. Modeling softwares such as PV OPTICS, BIRANDY and SUNRAYS have been created to aid such optical designing of cells and modules; but none of these modeling packages take the front metal electrode architecture of a solar cell into account.

A new model, has been developed to include the front metal electrode architecture to finished solar cells for optical calculations. This has been implemented in C++ in order to add a new module to PV OPTICS (NREL’s photovoltaic modeling tool) to include ...


Theoretical Studies Of Structural And Electronic Properties In Transition Metal Oxides, Tsezar F. Seman Dec 2012

Theoretical Studies Of Structural And Electronic Properties In Transition Metal Oxides, Tsezar F. Seman

Dissertations

The following studies are presented: theory of K-edge resonant inelastic x-ray scattering and its application for La0.5Sr1.5MnO4, effects of rare earth ion size on the stability of the coherent Jahn-Teller distortions in undoped perovskite manganites, and symmetry-mode-based classical and quantum mechanical formalism of lattice dynamics.

The formula based on tight-binding approach for the calculation of K-edge resonant inelastic x-ray scattering (RIXS) spectrum for transition metal oxides is presented first, by extending the previous existing result to include explicit momentum dependence and a basis with multiple core-hole sites. This formula is applied to layered ...


Dark Matter With Density-Dependent Interactions, Kimberly K. Boddy, Sean M. Carroll, Mark Trodden Dec 2012

Dark Matter With Density-Dependent Interactions, Kimberly K. Boddy, Sean M. Carroll, Mark Trodden

Department of Physics Papers

The decay and annihilation cross sections of dark matter particles may depend on the value of a chameleonic scalar field that both evolves cosmologically and takes different values depending on the local matter density. This possibility introduces a separation between the physics relevant for freeze-out and that responsible for dynamics and detection in the late universe. We investigate how such dark sector interactions might be implemented in a particle physics Lagrangian and consider how current and upcoming observations and experiments bound such dark matter candidates. A specific simple model allows for an increase in the annihilation cross section by a ...


Correct Spectral Conversion Between Surface‐Enhanced Raman And Plasmon Resonance Scattering From Nanoparticle Dimers For Single‐Molecule Detection, Kyuwan Lee Dec 2012

Correct Spectral Conversion Between Surface‐Enhanced Raman And Plasmon Resonance Scattering From Nanoparticle Dimers For Single‐Molecule Detection, Kyuwan Lee

Kyuwan Lee

Simultaneous measurement of surface-enhanced Raman scattering (SERS) and localized surface plasmon resonance (LSPR) in nanoparticle dimers presents outstanding opportunities in molecular identification and in the elucidation of physical properties, such as the size, distance, and deformation of target species. SERS–LSPR instrumentation exists and has been used under limited conditions, but the extraction of SERS and LSPR readouts from a single measurement is still a challenge. Herein, the extraction of LSPR spectra from SERS signals is reported and a tool for measuring the interparticle distance from Raman enhancement data by the standardization of the SERS signal is proposed. The SERS ...


Testing Diagnostics Of Nuclear Activity And Star Formation In Galaxies At Z > 1, Jonathan R. Trump, Nicholas P. Konidaris, Guillermo Barro, David C. Koo, Dale D. Kocevski, Stéphanie Juneau, Benjamin J. Weiner, S. M. Faber, Ian S. Mclean, Renbin Yan, Pablo G. Pérez-González, Victor Villar Dec 2012

Testing Diagnostics Of Nuclear Activity And Star Formation In Galaxies At Z > 1, Jonathan R. Trump, Nicholas P. Konidaris, Guillermo Barro, David C. Koo, Dale D. Kocevski, Stéphanie Juneau, Benjamin J. Weiner, S. M. Faber, Ian S. Mclean, Renbin Yan, Pablo G. Pérez-González, Victor Villar

Physics and Astronomy Faculty Publications

We present some of the first science data with the new Keck/MOSFIRE instrument to test the effectiveness of different AGN/SF diagnostics at z ~ 1.5. MOSFIRE spectra were obtained in three H-band multi-slit masks in the GOODS-S field, resulting in 2 hr exposures of 36 emission-line galaxies. We compare X-ray data with the traditional emission-line ratio diagnostics and the alternative mass-excitation and color-excitation diagrams, combining new MOSFIRE infrared data with previous HST/WFC3 infrared spectra (from the 3D-HST survey) and multiwavelength photometry. We demonstrate that a high [O III]/Hβ ratio is insufficient as an active galactic ...


Matter Radii Of 29-35Mg, H Terry Fortune, R. Sherr Dec 2012

Matter Radii Of 29-35Mg, H Terry Fortune, R. Sherr

Department of Physics Papers

We have computed matter radii for the ground states of 29–35Mg for a variety of reasonable assumptions about the structure of the relevant states. For cases in which the dominant configuration is generally agreed, our computed radii are in good agreement with experimental ones. For cases in which the dominant configuration is unknown or ambiguous, comparisons between the calculated and experimental Rm do not allow a decision as to the preferred configuration.


Hydrostatic And Uniaxial Pressure Dependence Of Superconducting Transition Temperature Of Kfe2as2 Single Crystals, Sergey L. Bud'ko, Yong Liu, Thomas A. Lograsso, Paul C. Canfield Dec 2012

Hydrostatic And Uniaxial Pressure Dependence Of Superconducting Transition Temperature Of Kfe2as2 Single Crystals, Sergey L. Bud'ko, Yong Liu, Thomas A. Lograsso, Paul C. Canfield

Ames Laboratory Publications

We present heat capacity, c-axis thermal expansion and pressure-dependent, low-field, temperature-dependent magnetization for pressures up to ∼12 kbar, data for KFe2As2 single crystals. Tc decreases under pressure with dTc/dP≈−0.10 K/kbar. The inferred uniaxial, c-axis, pressure derivative is positive, dTc/dpc≈0.11 K/kbar. The data are analyzed in comparison with those for overdoped Fe-based superconductors. Arguments are presented that superconductivity in KFe2As2 may be different from the other overdoped, Fe-based materials in the 122 family.


The Central Molecular Gas Structure In Liners With Low-Luminosity Active Galactic Nuclei: Evidence For Gradual Disappearance Of The Torus, F. Müller-Sánchez, M. A. Prieto, M. Mezcua, R. I. Davies, M. A. Malkan, Moshe Elitzur Dec 2012

The Central Molecular Gas Structure In Liners With Low-Luminosity Active Galactic Nuclei: Evidence For Gradual Disappearance Of The Torus, F. Müller-Sánchez, M. A. Prieto, M. Mezcua, R. I. Davies, M. A. Malkan, Moshe Elitzur

Physics and Astronomy Faculty Publications

We present observations of the molecular gas in the nuclear environment of three prototypical low-luminosity active galactic nuclei (LLAGNs), based on VLT/SINFONI AO-assisted integral-field spectroscopy of H2 1-0 S(1) emission at angular resolutions of ~0.''17. On scales of 50-150 pc, the spatial distribution and kinematics of the molecular gas are consistent with a rotating thin disk, where the ratio of rotation (V) to dispersion (σ) exceeds unity. However, in the central 50 pc, the observations reveal a geometrically and optically thick structure of molecular gas (V/σ < 1 and N H > 1023 cm–2) that is likely ...


Transforming Fabry-Pérot Resonances Into A Tamm Mode, Maxim Durach, Anastasia Rusina Dec 2012

Transforming Fabry-Pérot Resonances Into A Tamm Mode, Maxim Durach, Anastasia Rusina

Physics Faculty Publications

We propose an optical structure composed of two metal nanolayers enclosing a distributed Bragg reflector (DBR) mirror. The structure is an open photonic system whose bound modes are coupled to external radiation. We apply the special theoretical treatment based on inversion symmetry of the structure to classify its resonances. We show that the structure supports resonances transitional between Fabry-Pérot modes and Tamm plasmons. When the dielectric contrast of the DBR is removed these modes are a pair of conventional Fabry-Pérot resonances. They spectrally merge into a Tamm mode at high contrast. The optical properties of the structure in the frequency ...


Petawatt-Laser-Driven Wakefield Acceleration Of Electrons To 2 Gev In 10^{17} Cm^{-3} Plasma, Xiaoming Wang, Rafal B. Zgadzaj, Neil Fazel, Sunghwan A. Yi, X. Zhang, Watson Henderson, Yen-Yu Zhang, Rick Korzekwa, Hai-En Tsai, C.-H. Pai, Zhengyan Li, Hernan Quevedo, Gilliss Dyer, Erhard W. Gaul, Mikael Martinez, Aaron Bernstein, Ted Borger, M. Spinks, M. Donovan, Serguei Y. Kalmykov, Vladimir N. Khudik, Gennady Shvets, Todd Ditmire, Michael C. Downer Dec 2012

Petawatt-Laser-Driven Wakefield Acceleration Of Electrons To 2 Gev In 10^{17} Cm^{-3} Plasma, Xiaoming Wang, Rafal B. Zgadzaj, Neil Fazel, Sunghwan A. Yi, X. Zhang, Watson Henderson, Yen-Yu Zhang, Rick Korzekwa, Hai-En Tsai, C.-H. Pai, Zhengyan Li, Hernan Quevedo, Gilliss Dyer, Erhard W. Gaul, Mikael Martinez, Aaron Bernstein, Ted Borger, M. Spinks, M. Donovan, Serguei Y. Kalmykov, Vladimir N. Khudik, Gennady Shvets, Todd Ditmire, Michael C. Downer

Serge Youri Kalmykov

Electron self-injection into a laser-plasma accelerator (LPA) driven by the Texas Petawatt (TPW) laser is reported at plasma densities 1.7 - 6.2 x 10^{17} cm^{-3}. Energy and charge of the electron beam, ranging from 0.5 GeV to 2 GeV and tens to hundreds of pC, respectively, depended strongly on laser beam quality and plasma density. Angular beam divergence was consistently around 0.5 mrad (FWHM), while shot-to-shot pointing fluctuations were limited to ±1.4 mrad rms. Betatron x-rays with tens of keV photon energy are also clearly observed.


Sub-Millimeter-Scale, 100-Mev-Class Quasi-Monoenergetic Laser Plasma Accelerator Based On All-Optical Control Of Dark Current In The Blowout Regime, Serguei Y. Kalmykov, Xavier Davoine, Bradley A. Shadwick Dec 2012

Sub-Millimeter-Scale, 100-Mev-Class Quasi-Monoenergetic Laser Plasma Accelerator Based On All-Optical Control Of Dark Current In The Blowout Regime, Serguei Y. Kalmykov, Xavier Davoine, Bradley A. Shadwick

Serge Youri Kalmykov

It is demonstrated that by negatively chirping the frequency of a 20-fs, 15-TW driving laser pulse with an ultrabroad bandwidth (corresponding to a sub-2-cycle transform-limited duration it is possible to prevent early compression of the pulse into an optical shock, thus reducing expansion of the accelerating plasma bucket (electron density "bubble") and delaying dephasing of self-injected and accelerated electrons. These features help suppress unwanted continuous self-injection (dark current) in the blowout regime, making possible to use the entire dephasing length to generate low-background, quasi-monoenergetic 200-MeV-scale electron beams from sub-mm-length, dense plasmas (n_{e0} = 1.3 x 10^{19} cm^{−3}).


One-Phase Problems For Discontinuous Heat Transfer In Fractal Media, Yang Xiaojun Dec 2012

One-Phase Problems For Discontinuous Heat Transfer In Fractal Media, Yang Xiaojun

Xiao-Jun Yang

We first propose the fractal models for the one-phase problems of discontinuous transient heat transfer.The models are taken in sense of local fractional differential operator and used to describe the (dimensionless)melting of fractal solid semi-infinite materials initially at their melt temperatures.


Measures Of Centrality Based On The Spectrum Of The Laplacian, Scott D. Pauls, Daniel Remondini Dec 2012

Measures Of Centrality Based On The Spectrum Of The Laplacian, Scott D. Pauls, Daniel Remondini

Open Dartmouth: Faculty Open Access Scholarship

We introduce a family of new centralities, the k-spectral centralities. k-Spectral centrality is a measurement of importance with respect to the deformation of the graph Laplacian associated with the graph. Due to this connection, k-spectral centralities have various interpretations in terms of spectrally determined information.

We explore this centrality in the context of several examples. While for sparse unweighted net- works 1-spectral centrality behaves similarly to other standard centralities, for dense weighted net- works they show different properties. In summary, the k-spectral centralities provide a novel and useful measurement of relevance (for single network elements as well as whole subnetworks ...


Passive Ranging Using A Dispersive Spectrometer And Optical Filters, Jacob A. Martin Dec 2012

Passive Ranging Using A Dispersive Spectrometer And Optical Filters, Jacob A. Martin

Theses and Dissertations

Monocular passive ranging using atmospheric oxygen absorption has been demonstrated in the past using an FTS. These instruments are very sensitive to vibration making them di cult to use on an airborne platform. This work focuses on whether passive ranging can be done with instruments that are easier to deploy. Two potential instruments are tested and compared: a diffraction grating spectrometer and optical filters. A grating spectrometer was able to estimate range to within 5% for a static solid rocket motor ring at a distance of 910 m using the NIR absorption band of oxygen. Testing at shorter ranges produced ...


Atacama Cosmology Telescope: A Measurement Of The Thermal Sunyaev-Zel’Dovich Effect Using The Skewness Of The Cmb Temperature Distribution, Michael J. Wilson, Blake D. Sherwin, J. Colin Hill, Graeme Addison, Nick Battaglia, J. Richard Bond, Sudeep Das, Mark J. Devlin, Erik D. Reese, Daniel S. Swetz Dec 2012

Atacama Cosmology Telescope: A Measurement Of The Thermal Sunyaev-Zel’Dovich Effect Using The Skewness Of The Cmb Temperature Distribution, Michael J. Wilson, Blake D. Sherwin, J. Colin Hill, Graeme Addison, Nick Battaglia, J. Richard Bond, Sudeep Das, Mark J. Devlin, Erik D. Reese, Daniel S. Swetz

Department of Physics Papers

We present a detection of the unnormalized skewness 3(n̂)> induced by the thermal Sunyaev-Zel’dovich (tSZ) effect in filtered Atacama Cosmology Telescope (ACT) 148 GHz cosmic microwave background temperature maps. Contamination due to infrared and radio sources is minimized by template subtraction of resolved sources and by constructing a mask using outlying values in the 218 GHz (tSZ-null) ACT maps. We measure 3(n̂)>=-31±6  μK3 (Gaussian statistics assumed) or ±14  μK3 (including non-Gaussian corrections) in the filtered ACT data, a 5σ detection. We show that the skewness is a sensitive probe of σ8, and ...


Oscillator Strength Measurements Of The 5s6s 1s0→5snp 1p1 Rydberg Transitions Of Strontium, S. U. Haq, M. A. Kalyar, M. Rafiq, R. Ali, Naveed K. Piracha, M. A. Baig Dec 2012

Oscillator Strength Measurements Of The 5s6s 1s0→5snp 1p1 Rydberg Transitions Of Strontium, S. U. Haq, M. A. Kalyar, M. Rafiq, R. Ali, Naveed K. Piracha, M. A. Baig

Naveed K. Piracha

We report the experimentally determined oscillator strengths for the 5s6s 1S0→5snp 1P1 Rydberg transitions of strontium using two-step excitation in conjunction with a thermionic diode ion detector. The absolute photoionization cross section from the 5s6s 1S0 excited state has been determined by adjusting the polarization vector of the ionizing laser beam parallel, perpendicular, and at the magic angle with respect to that of the exciting dye laser. The measured absolute value of the photoionization cross section 0.9±0.2 Mb at the 5s threshold is used to extract the f values of the 5s6s 1S0→5snp 1P1 (26 ...


Spatial And Orientational Control Of Liquid Crystal Alignment Using A Surface Localized Polymer Layer, Lu Lu, Tatiana Sergan, Vassili Sergan, Philip J. Bos Dec 2012

Spatial And Orientational Control Of Liquid Crystal Alignment Using A Surface Localized Polymer Layer, Lu Lu, Tatiana Sergan, Vassili Sergan, Philip J. Bos

Chemical Physics Publications

We present an alignment method for the surface contacting liquid crystal (LC) director. This method allows complete control of the polar pretilt angle as a function of position in a liquid crystal device, and has the potential of controlling the azimuthal orientation of LC. Important considerations of this method are to form a thin layer of reactive monomers at the LC cell interior surface, and to control the deleterious effects of flow due to polymerization induced concentration gradients. To achieve these, the voltage and frequency of the applied electric field and the UV intensity during the polymerization process are significant.


Interferometric Synthetic Aperture Sonar Signal Processing For Autonomous Underwater Vehicles Operating Shallow Water, Patricia E. Giardina Dec 2012

Interferometric Synthetic Aperture Sonar Signal Processing For Autonomous Underwater Vehicles Operating Shallow Water, Patricia E. Giardina

University of New Orleans Theses and Dissertations

The goal of the research was to develop best practices for image signal processing method for InSAS systems for bathymetric height determination. Improvements over existing techniques comes from the fusion of Chirp-Scaling a phase preserving beamforming techniques to form a SAS image, an interferometric Vernier method to unwrap the phase; and confirming the direction of arrival with the MUltiple SIgnal Channel (MUSIC) estimation technique. The fusion of Chirp-Scaling, Vernier, and MUSIC lead to the stability in the bathymetric height measurement, and improvements in resolution. This method is computationally faster, and used less memory then existing techniques.


Fibroblast Growth Factor Homologous Factor 1 Interacts With Nemo To Regulate Nf-Κb Signaling In Neurons., Hans-Georg König, Beau J. Fenner, Jennifer C. Byrne, Robert F. Schwamborn, Tytus Bernas, Caroline A. Jefferies, Jochen Hm Prehn Dec 2012

Fibroblast Growth Factor Homologous Factor 1 Interacts With Nemo To Regulate Nf-Κb Signaling In Neurons., Hans-Georg König, Beau J. Fenner, Jennifer C. Byrne, Robert F. Schwamborn, Tytus Bernas, Caroline A. Jefferies, Jochen Hm Prehn

Physiology and Medical Physics Articles

Neuronal survival and plasticity critically depend on constitutive activity of the transcription factor nuclear factor-κB (NF-κB). We here describe a role for a small intracellular fibroblast growth factor homologue, the fibroblast growth factor homologous factor 1 (FHF1/FGF12), in the regulation of NF-κB activity in mature neurons. FHFs have previously been described to control neuronal excitability, and mutations in FHF isoforms give rise to a form of progressive spinocerebellar ataxia. Using a protein-array approach, we identified FHF1b as a novel interactor of the canonical NF-κB modulator IKKγ/NEMO. Co-immunoprecipitation, pull-down and GAL4-reporter experiments, as well as proximity ligation assays, confirmed ...


Toward High-Performance Nanostructured Thermoelectric Materials: The Progress Of Bottom-Up Solution Chemistry Approaches, Yixin Zhao, Jeffrey S. Dyck, Clemens Burda Dec 2012

Toward High-Performance Nanostructured Thermoelectric Materials: The Progress Of Bottom-Up Solution Chemistry Approaches, Yixin Zhao, Jeffrey S. Dyck, Clemens Burda

Jeffrey Dyck

Significant research effort has recently gone into the synthesis of thermoelectric nanomaterials through different chemical approaches since nanomaterials chemistry became a promising strategy for improving thermoelectric performance. Different thermoelectric nanocrystals, especially PbTe, Bi2Te3 and CoSb3, with various compositions and morphologies have been successfully prepared by solvo/hydrothermal, electrochemical, and ligand-based synthesis methods. Such nanoscale materials show not only substantial reduction in thermal conductivity due to increased phonon scattering at nanoscale grain boundaries and lower densities of phonon states but possibly also an enhancement in thermopower due to electronic quantum size effects. More recently, the notoriously low power factors of thermoelectric ...


Structure Inhomogeneities, Shallow Defects, And Charge Transport In The Series Of Thermoelectric Materials K2bi8−Xsbxse13, Jeffrey S. Dyck, T. Kyratski, E. Hatzikraniotis, K. M. Paraskevopoulos, C. D. Malliakas, C. Uher, M. G. Kanatzidis Dec 2012

Structure Inhomogeneities, Shallow Defects, And Charge Transport In The Series Of Thermoelectric Materials K2bi8−Xsbxse13, Jeffrey S. Dyck, T. Kyratski, E. Hatzikraniotis, K. M. Paraskevopoulos, C. D. Malliakas, C. Uher, M. G. Kanatzidis

Jeffrey Dyck

The charge transport properties of the low-dimensional thermoelectric materials K2Bi8-xSbxSe13 (02Bi8-xSbxSe13 was analyzed on the basis of the classical semiconductor theory and discussed in the context of recent band calculations. The results suggest that the K2Bi8-xSbxSe13 materials possess coexisting domains with semimetallic and semiconducting characters whose ratio is influenced by the value of x and by local defects. The extent and relative distribution of these domains control the charge transport properties. Electron diffraction experiments performed on samples of K2Bi8-xSbxSe13 with x=1.6 show evidence for such domains by indicating regions with long range ordering of K+/Bi3+ atoms and ...


No-Go Theorems For Generalized Chameleon Field Theories, Junpu Wang, Lam Hui, Justin Khoury Dec 2012

No-Go Theorems For Generalized Chameleon Field Theories, Junpu Wang, Lam Hui, Justin Khoury

Department of Physics Papers

The chameleon, or generalizations thereof, is a light scalar that couples to matter with gravitational strength, but whose manifestation depends on the ambient matter density. A key feature is that the screening mechanism suppressing its effects in high-density environments is determined by the local scalar field value. Under very general conditions, we prove two theorems limiting its cosmological impact: (i) the Compton wavelength of such a scalar can be at most ≃1 MPc at the present cosmic density, which restricts its impact to nonlinear scales; and (ii) the conformal factor relating Einstein- and Jordan-frame scale factors is essentially constant over ...


Fast Absolute Quantification Of In Vivo Water And Fat Content With Magnetic Resonance Imaging, Yifan Cui Dec 2012

Fast Absolute Quantification Of In Vivo Water And Fat Content With Magnetic Resonance Imaging, Yifan Cui

Electronic Thesis and Dissertation Repository

Quantitative water fat imaging offers a non-invasive method for monitoring and staging diseases associated with changes in either water or fat content in tissue. In this work absolute water and fat mass density measurement with in vivo Magnetic Resonance Imaging (MRI) is demonstrated. T1 independent, T2* corrected chemical shift based water-fat separated images are acquired. By placing a phantom with known mass density in the field of view for signal intensity calibration, absolute water or fat mass density can be computed, assuming the B1+ (transmit) and B1- (receive) fields can be measured. Phantom experiments with known ...


Epr And Endor Studies Of Point Defects In Lithium Tetraborate Crystals, Douglas A. Buchanan Dec 2012

Epr And Endor Studies Of Point Defects In Lithium Tetraborate Crystals, Douglas A. Buchanan

Theses and Dissertations

Lithium tetraborate (Li2B4O7 or LTB) is a promising material for both radiation dosimetry and neutron detection applications. LTB crystals can be grown pure or doped with different impurities including transition-metal and rare-earth ions. Research in this dissertation focuses on undoped LTB crystals and LTB crystals doped with copper and silver. Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) are used to characterize point defects in the lithium tetraborate crystals. Thermoluminescence (TL), photoluminescence (PL), photoluminescence excitation (PLE), and optical absorption (OA) are also used. An intrinsic hole trap associated with lithium vacancies is characterized with EPR and ENDOR and its ...


Data Curation Is For Everyone! The Case For Master's And Baccalaureate Institutional Engagement With Data Curation, Yasmeen Shorish Dec 2012

Data Curation Is For Everyone! The Case For Master's And Baccalaureate Institutional Engagement With Data Curation, Yasmeen Shorish

Yasmeen Shorish

This article describes the fundamental challenges to data curation, how these challenges may be compounded for smaller institutions, and how data management is an essential and manageable component of data curation. Data curation is often discussed within the confines of large, research universities. As a result, master’s and baccalaureate institutions may be left with the impression that they cannot engage with data curation. However, by proactively engaging with faculty, libraries of all sizes can build closer relationships and help educate faculty on data documentation and organization best practices. Experiences from one master’s comprehensive institution as it engages with ...


Branching Ratio Of 18Ne(7.06 Mev, 4+), H Terry Fortune Dec 2012

Branching Ratio Of 18Ne(7.06 Mev, 4+), H Terry Fortune

Department of Physics Papers

The recently reported branching ratio (BR) for the 4+ state in 18Ne at Ex = 7.06 MeV strongly disagrees with the BR computed using the known properties of this state.


A Comparison Of Short-Range Molecular Order In Bent-Core And Rod-Like Nematic Liquid Crystals, S. Chakraborty, J. T. Gleeson, Antal Jákli, Samuel Sprunt Dec 2012

A Comparison Of Short-Range Molecular Order In Bent-Core And Rod-Like Nematic Liquid Crystals, S. Chakraborty, J. T. Gleeson, Antal Jákli, Samuel Sprunt

Antal Jakli

Thermotropic liquid crystals exhibit strongly temperature-dependent positional correlations among molecules in the nematic phase above the transition to a smectic-A or C phase. However, even in the absence of a lower temperature smectic phase, nematics composed of reduced symmetry molecules (bent-core mesogens, for example) reveal small angle X-ray scattering (SAXS) patterns with features similar to those associated with pretransitional smectic order. We report on a quantitative analysis and comparison of two-dimensional SAXS data on a bent-core nematic compound (lacking a smectic phase) and a rod-like nematic (exhibiting a nematic to smectic-C transition). This analysis demonstrates that a nanostructure based on ...


The Shape And Mechanics Of Curved Fold Origami Structures, Marcelo A. Dias, Christian Santangelo Dec 2012

The Shape And Mechanics Of Curved Fold Origami Structures, Marcelo A. Dias, Christian Santangelo

Christian Santangelo

We develop recursion equations to describe the three-dimensional shape of a sheet upon which a series of concentric curved folds have been inscribed. In the case of no stretching outside the fold, the three-dimensional shape of a single fold prescribes the shape of the entire origami structure. To better explore these structures, we derive continuum equations, valid in the limit of vanishing spacing between folds, to describe the smooth surface intersecting all the mountain folds. We find that this surface has negative Gaussian curvature with magnitude equal to the square of the fold's torsion. A series of open folds ...


Cold-Nuclear-Matter Effects On Heavy-Quark Production In D+Au Collisions At Root S-Nn=200 Gev, Andrew Adare, Alan Dion, John C. Hill, Todd Kempel, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, H. Pei, Marzia Rosati, C. L. Silva, Feng Wei, Et Al., Phenix Collaboration Dec 2012

Cold-Nuclear-Matter Effects On Heavy-Quark Production In D+Au Collisions At Root S-Nn=200 Gev, Andrew Adare, Alan Dion, John C. Hill, Todd Kempel, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, H. Pei, Marzia Rosati, C. L. Silva, Feng Wei, Et Al., Phenix Collaboration

Physics and Astronomy Publications

The PHENIX experiment has measured electrons and positrons at midrapidity from the decays of hadrons containing charm and bottom quarks produced in d + Au and p + p collisions at root S-NN = 200 GeV in the transverse-momentum range 0.85 <= p(T)(e) <= 8.5 GeV/c. In central d + Au collisions, the nuclear modification factor R-dA at 1.5 < p(T) < 5 GeV/c displays evidence of enhancement of these electrons, relative to those produced in p + p collisions, and shows that the mass-dependent Cronin enhancement observed at the Relativistic Heavy Ion Collider extends to the heavy D meson family. A comparison with the neutral-pion data suggests that the difference in cold-nuclear-matter effects on light- and heavy-flavor mesons could contribute to the observed differences between the pi(0) and heavy-flavor-electron nuclear modification factors R-AA.


Investigation Of Low-Stress Silicon Nitride As A Replacement Material For Beryllium X-Ray Windows, David B. Brough Dec 2012

Investigation Of Low-Stress Silicon Nitride As A Replacement Material For Beryllium X-Ray Windows, David B. Brough

Theses and Dissertations

The material properties of low stress silicon nitride make it a possible replacement material for beryllium in X-ray windows. In this study, X-ray windows made of LPCVD deposited low stress silicon nitride are fabricated and characterized. The Young's modulus of the LPCVD low stress silicon nitride are characterized and found to be 226±23 GPa. The residual stress is characterized using two different methods and is found to be 127±25 MPa and 141±0.28 MPa. Two support structure geometries for the low stress silicon nitride X-ray windows are used. X-ray windows with thicknesses of 100 nm and ...