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Physics

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Articles 91 - 119 of 119

Full-Text Articles in Astrophysics and Astronomy

Small-Scale Structures In Three-Dimensional Magnetohydrodynamic Turbulence, P. D. Mininni, A. G. Pouquet, D. C. Montgomery Dec 2006

Small-Scale Structures In Three-Dimensional Magnetohydrodynamic Turbulence, P. D. Mininni, A. G. Pouquet, D. C. Montgomery

Dartmouth Scholarship

We investigate using direct numerical simulations with grids up to 15363 points, the rate at which small scales develop in a decaying three-dimensional MHD flow both for deterministic and random initial conditions. Parallel current and vorticity sheets form at the same spatial locations, and further destabilize and fold or roll up after an initial exponential phase. At high Reynolds numbers, a self-similar evolution of the current and vorticity maxima is found, in which they grow as a cubic power of time; the flow then reaches a finite dissipation rate independent of the Reynolds number.

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Casimir Forces And Non-Newtonian Gravitation, Roberto Onofrio Oct 2006

Casimir Forces And Non-Newtonian Gravitation, Roberto Onofrio

Dartmouth Scholarship

The search for non-relativistic deviations from Newtonian gravitation can lead to new phenomena signalling the unification of gravity with the other fundamental interactions. Various recent theoretical frameworks indicate a possible window for non-Newtonian forces with gravitational coupling strength in the micrometre range. The major expected background in the same range is attributable to the Casimir force or variants of it if dielectric materials, rather than conducting ones, are considered. Here we review the measurements of the Casimir force performed so far in the micrometre range and how they determine constraints on non-Newtonian gravitation, also discussing the dominant sources of false …

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The Viscous Catenary, John Koulakis Apr 2006

The Viscous Catenary, John Koulakis

Pomona Senior Theses

Variational techniques are used to develop a theory for the time evolution of a thin strand of viscous fluid suspended from two points. The shape of the strand is approximated to be a parabola and energy conservation is used to derive a differential equation modeling the change in height over time. Data is collected with a high resolution camera and a strobe light to obtain the position and shape of the strand over multiple intervals of time. Three very different and unexpected types of behaviors are observed depending on the initial thickness and shape of the filament. The approximation fits …

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Investigation Of Carbon Nanotube Growth Using A Nozzle Cvd Method, James Mcfarland Apr 2006

Investigation Of Carbon Nanotube Growth Using A Nozzle Cvd Method, James Mcfarland

Pomona Senior Theses

This work uses a modification of the chemical vapor deposition (CVD) technique to study the effects of source gas flow geometry (and the corresponding parameters) on carbon nanotube growth. Our approach is to flow the carbon-containing source gas through a nozzle, projecting the gas stream onto targeted regions of the substrate. This technique not only allows the potential for localized nanotube growth, but also offers an interesting opportunity to provide an experimental test of theoretical nanotube growth models.

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Unfolding The Labyrinth: Open Problems In Physics, Mathematics, Astrophysics, And Other Areas Of Science, Florentin Smarandache, Victor Christianto, Fu Yuhua, Radi Khrapko, John Hutchison Jan 2006

Unfolding The Labyrinth: Open Problems In Physics, Mathematics, Astrophysics, And Other Areas Of Science, Florentin Smarandache, Victor Christianto, Fu Yuhua, Radi Khrapko, John Hutchison

Branch Mathematics and Statistics Faculty and Staff Publications

The reader will find herein a collection of unsolved problems in mathematics and the physical sciences. Theoretical and experimental domains have each been given consideration. The authors have taken a liberal approach in their selection of problems and questions, and have not shied away from what might otherwise be called speculative, in order to enhance the opportunities for scientific discovery. Progress and development in our knowledge of the structure, form and function of the Universe, in the true sense of the word, its beauty and power, and its timeless presence and mystery, before which even the greatest intellect is awed …

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Limits Of Quintessence, R. R. Caldwell, Eric V. Linder Sep 2005

Limits Of Quintessence, R. R. Caldwell, Eric V. Linder

Dartmouth Scholarship

We present evidence that the simplest particle-physics scalar-field models of dynamical dark energy can be separated into distinct behaviors based on the acceleration or deceleration of the field as it evolves down its potential towards a zero minimum. We show that these models occupy narrow regions in the phase plane of w and w′, the dark energy equation of state and its time derivative in units of the Hubble time. Restricting an energy scale of the dark energy microphysics limits how closely a scalar field can resemble a cosmological constant. These results, indicating a desired measurement resolution of order σ(w′)≈(1+w), …

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Deep-Uv Light Emitting Diodes: An Experimental Investigation Of Characterization And Optimization Techniques, Eric M. Fraser May 2005

Deep-Uv Light Emitting Diodes: An Experimental Investigation Of Characterization And Optimization Techniques, Eric M. Fraser

Pomona Senior Theses

Light emitting diodes (LEDs) and laser diodes (LDs) have many advantages over conventional light sources. Current commercial LEDs span the spectrum from IR to near- UV. There are a variety of applications for devices that extend into the deep-UV, including biological agent detection and optical storage. The nitride material system is a set of semiconducting compounds that have wavelengths that span a broad range, from yellow to deep-UV. AlGaN has a direct bandgap that extends into the deep-UV range; we will try to grow device-quality material, deposited epitaxially using metalorganic chemical vapor deposition on sapphire substrates.

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Deep-Uv Light Emitting Diodes: An Experimental Investigation Of Characterization And Optimization Techniques, Eric M. Fraser May 2005

Deep-Uv Light Emitting Diodes: An Experimental Investigation Of Characterization And Optimization Techniques, Eric M. Fraser

Pomona Senior Theses

Light emitting diodes (LEDs) and laser diodes (LDs) have many advantages over conventional light sources. Current commercial LEDs span the spectrum from IR to near- UV. There are a variety of applications for devices that extend into the deep-UV, including biological agent detection and optical storage. The nitride material system is a set of semiconducting compounds that have wavelengths that span a broad range, from yellow to deep-UV. AlGaN has a direct bandgap that extends into the deep-UV range; we will try to grow device-quality material, deposited epitaxially using metalorganic chemical vapor deposition on sapphire substrates.

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Today's Take On Einstein’S Relativity: Proceedings Of The Conference Of 18 Feb 2005, Florentin Smarandache, Homer B. Tilton Jan 2005

Today's Take On Einstein’S Relativity: Proceedings Of The Conference Of 18 Feb 2005, Florentin Smarandache, Homer B. Tilton

Branch Mathematics and Statistics Faculty and Staff Publications

Non Sequiturs in Relativity Four in number at this point Dr. Smith of "Lost in Space" had a knack of easing out of binds that he'd gotten himself into. Dr. Einstein was a little like that. Einstein originally declared that the distortions of special relativity reflect real changes to the objects being remotely observed, then reconsidered. The first non sequitur is quoted here from Sachs:[1] In a lecture that Einstein gave to the Prussian Academy of Sciences in 1921, he said the following: "Geometry predicates nothing about relations of real things, but only geometry together with the purport of physical …

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Patterning Polymer Thin Films: Lithographically Induced Self Assembly And Spinodal Dewetting, Regina C. Carns May 2004

Patterning Polymer Thin Films: Lithographically Induced Self Assembly And Spinodal Dewetting, Regina C. Carns

Pomona Senior Theses

In an age in which the microchip is ubiquitous, the rewards for novel methods of microfabrification are great, and the vast possibilities of nanotechnology lie just a little ahead. Various methods of microlithography offer differing benefits, and even as older techniques such as optical lithography are being refined beyond what were once considered their upper limits of resolution, new techniques show great promise for going even further once they reach their technological maturity. Recent developments in optical lithography may allow it to break the 100-nm limit even without resorting to x-rays.

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Riemann Tensor Of The Ambient Universe, The Dilaton, And Newton’S Constant, Rossen Ivanov, Emil Prodanov Jan 2004

Riemann Tensor Of The Ambient Universe, The Dilaton, And Newton’S Constant, Rossen Ivanov, Emil Prodanov

Articles

We investigate a four-dimensional world, embedded into a five-dimensional spacetime, and find the five-dimensional Riemann tensor via generalisation of the Gauss (--Codacci) equations. We then derive the generalised equations of the four-dimensional world and also show that the square of the dilaton field is equal to the Newton's constant. We find plausable constant and non-constant solutions for the dilaton. Comment: 5 pages, revtex

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Steps Toward The Creation Of A Carbon Nanotube Single Electron Transistor, R. Matthew Ferguson May 2003

Steps Toward The Creation Of A Carbon Nanotube Single Electron Transistor, R. Matthew Ferguson

Pomona Senior Theses

This report details work toward the fabrication of a single-electron transistor created from a single-walled carbon nanotube (SWNT). Specifically discussed is a method for growing carbon nanotubes (CNTs) via carbon vapor deposition (CVD). The growth is catalyzed by a solution of 0.02g Fe(NO3)3·9H2O, 0.005g MoO2(acac)2, and 0.015g of alumina particles in 15mL methanol. SWNT diameter ranges from 0.6 to 3.0 nm. Also discussed is a method to control nanotube growth location by patterning samples with small islands of catalyst. A novel “maskless” photolithographic process is used to focus light from a lightweight commercial digital projector through a microscope. Catalyst islands …

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Maskless Projection Lithography, J. David Musgraves May 2003

Maskless Projection Lithography, J. David Musgraves

Pomona Senior Theses

Photolithography is a key element of the modem integrated circuit process. It is photolithography, combined with metal deposition, that allows a three dimensional circuit to be built up on a two dimensional surface. Since it is such an important part of the semiconductor manufacturing industry, a massive base of research in this area already exists. The problem with this pre-existing research is that it is geared solely toward industrial purposes, as opposed to more academic research areas. The goal of my research is to move this industrial process into the academic setting of Pomom College.

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Steps Toward The Creation Of A Carbon Nanotube Single Electron Transistor, R. Matthew Ferguson May 2003

Steps Toward The Creation Of A Carbon Nanotube Single Electron Transistor, R. Matthew Ferguson

Pomona Senior Theses

This report details work toward the fabrication of a single-electron transistor created from a single-walled carbon nanotube (SWNT). Specifically discussed is a method for growing carbon nanotubes (CNTs) via carbon vapor deposition (CVD). The growth is catalyzed by a solution of 0.02g Fe(NO3)3·9H2O, 0.005g MoO2(acac)2, and 0.015g of alumina particles in 15mL methanol. SWNT diameter ranges from 0.6 to 3.0 nm. Also discussed is a method to control nanotube growth location by patterning samples with small islands of catalyst. A novel “maskless” photolithographic process is used to focus light from a lightweight commercial digital projector through a microscope. Catalyst islands …

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Bouncing Branes, Emil Prodanov Jan 2002

Bouncing Branes, Emil Prodanov

Articles

Two classical scalar fields are minimally coupled to gravity in the Kachru-Shulz-Silverstein scenario with a rolling fifth radius. A Tolman wormhole solution is found for a R x S^3 brane with Lorentz metric and for a R x AdS_3 brane with positive definite metric.

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A Solar Comparison, Larry Weinstein Jan 2000

A Solar Comparison, Larry Weinstein

Physics Faculty Publications

[First paragraph] Gilbert Ward [Phys.Teach 38, 333 (Sept. 2000)] states, "You emit more than 7000 times as much heat per unit mass as the Sun does." This difference was pointed out to me much more graphically by Brian Quinn many years ago as, "If the sun were made out of gerbils, the Earth would be incinerated."

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A First Principles Warm Inflation Model That Solves The Cosmological Horizon And Flatness Problems, Arjun Berera, Marcelo Gleiser, Rudnei O. Ramos Jul 1999

A First Principles Warm Inflation Model That Solves The Cosmological Horizon And Flatness Problems, Arjun Berera, Marcelo Gleiser, Rudnei O. Ramos

Dartmouth Scholarship

A quantum field theory warm inflation model is presented that solves the horizon and flatness problems. The model obtains, from the elementary dynamics of particle physics, cosmological scale factor trajectories that begin in a radiation dominated regime, enter an inflationary regime, and then smoothly exit back into a radiation dominated regime, with non-negligible radiation throughout the evolution.

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Strong Dissipative Behavior In Quantum Field Theory, Arjun Berera, Marcelo Gleiser, Rudnei O. Ramos Nov 1998

Strong Dissipative Behavior In Quantum Field Theory, Arjun Berera, Marcelo Gleiser, Rudnei O. Ramos

Dartmouth Scholarship

We study the conditions under which an overdamped regime can be attained in the dynamic evolution of a quantum field configuration. Using a real-time formulation of finite temperature field theory, we compute the effective evolution equation of a scalar field configuration, quadratically interacting with a given set of other scalar fields. We then show that, in the overdamped regime, the dissipative kernel in the field equation of motion is closely related to the shear viscosity coefficient, as computed in scalar field theory at finite temperature. The effective dynamics is equivalent to a time-dependent Ginzburg-Landau description of the approach to equilibrium …

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Basic Astronomy Labs, Terry L. Smith, Michael D. Reynolds, Jay S. Huebner Jan 1996

Basic Astronomy Labs, Terry L. Smith, Michael D. Reynolds, Jay S. Huebner

Physics Faculty Research and Scholarship

Providing the tools and know-how to apply the principles of astronomy first-hand, these 43 laboratory exercises each contain an introduction that clearly shows budding astronomers why the particular topic of that lab is of interest and relevant to astronomy. About one-third of the exercises are devoted solely to observation, and no mathematics is required beyond simple high school algebra and trigonometry.Organizes exercises into six major topics—sky, optics and spectroscopy, celestial mechanics, solar system, stellar properties, and exploration and other topics—providing clear outlines of what is involved in the exercise, its purpose, and what procedures and apparatus are to be used. …

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Neuron-Proton Scattering At 23.6 Mev, Jerome G. Beery Jun 1963

Neuron-Proton Scattering At 23.6 Mev, Jerome G. Beery

Physics & Astronomy ETDs

The angular distribution for neutron-proton scattering was measured at a neutron energy of m3.6 MeV. The measurement was made using the Los Alamos Variable Energy Cyclotron and a liquid hydrogen bubble chamber. The angular distribution was normalized to a total n-p cross section of 408 mb.

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The Diffraction Of Polarized Light From A Laser By A Straight Edge, Robert Lawrence Berger Jun 1963

The Diffraction Of Polarized Light From A Laser By A Straight Edge, Robert Lawrence Berger

Physics & Astronomy ETDs

The purpose of this experiment was to determine the effect of the polarized light from a highly coherent light source on the diffraction pattern of a metallic straight edge.

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Fast Neutron Induced Fission Of U238, Michael J. Bennett Jun 1963

Fast Neutron Induced Fission Of U238, Michael J. Bennett

Physics & Astronomy ETDs

This work describes an experimental study of the energetics of the fission of U238 performed with solid state detectors. The fissions were produced by fission-spectrum neutrons from a reactor. The procedure used for calibrating the detector response is described and the effects of some experimental uncertainties, such as pulse height defect and neutron emission, are discussed.

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Absorbance Of The Oh Radical In A Specific Wavelength Interval Near 309a, Paul F. Bird May 1961

Absorbance Of The Oh Radical In A Specific Wavelength Interval Near 309a, Paul F. Bird

Physics & Astronomy ETDs

The absorbance of the OH radical as a function of optical density was studied by computing the absorbance for an incident radiation in the wavelength interval 3089A-3097A. The absorbance was studied for 3 different temperatures and various values of the parameters specifying the line shapes and magnitude of the spectral absorption coefficient.

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Characteristics And Calibration Of A Large Liquid Scintillator, James R. Barcus Jun 1959

Characteristics And Calibration Of A Large Liquid Scintillator, James R. Barcus

Physics & Astronomy ETDs

It is the purpose of this thesis to present in some detail the method and results of the calibration -- in particular, the determination of the single particle pulse height which is crucial to any meaningful interpretation of the observational data.

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On The Relation Between The Cosmic Ray Air Shower Spectrum And The Pulse Height Spectrum Of A Large Scintillator, Robert T. Barton Jun 1958

On The Relation Between The Cosmic Ray Air Shower Spectrum And The Pulse Height Spectrum Of A Large Scintillator, Robert T. Barton

Physics & Astronomy ETDs

The purpose of this paper is to study other lateral distribution functions proposed by various authors, to select an alternative to the one used previously, to repeat the calculations of the required quantities using the alternative function, and to comment on the relative merits of the different choices. Since an empirical formula was used in the original work it seemed desirable to use a theoretical relation for comparison if a suitable one were available.

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The Motion Of A Charged Particle In Homogenous Time-Varying Magnetic Field, Thomas R. Bates May 1956

The Motion Of A Charged Particle In Homogenous Time-Varying Magnetic Field, Thomas R. Bates

Physics & Astronomy ETDs

This paper will discuss the motion of a non-relativistic, non-radiating charged particle in an infinite homogeneous magnetic field which varies linearly with time. We shall assume the motion to be confined to a plane perpendicular to the magnetic field.

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Diffuse Reflection Of Light, Francis L. Bentsen May 1954

Diffuse Reflection Of Light, Francis L. Bentsen

Physics & Astronomy ETDs

This thesis describes an attempt to determine the feasibility of measuring the ozone content in the air by absorption of light over a long path.

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The Intensity Of Zodiacal Light, Allan F. Beck Feb 1951

The Intensity Of Zodiacal Light, Allan F. Beck

Physics & Astronomy ETDs

The study of the intensities measured in the region of the zodiacal light, the second most important contributor to this light of the night sky after starlight has been subtracted, is the purpose of this paper.

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Some Contributions Of Pure Math To Science, Herbert B.E. Case Jan 1897

Some Contributions Of Pure Math To Science, Herbert B.E. Case

Student and Lippitt Prize Essays

An examination of the connection between math and science through discoveries in the subjects of astronomy, mechanics, physics and chemistry.

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