Recursos de colección

CaltechTHESIS (9.323 recursos)

CALIFORNIA INST OF TECH (CIT) Thesis

Type = Thesis

Mostrando recursos 1 - 20 de 8.800

  1. Studies of the Conformational Properties of Dinucleoside Monophosphates and Oligoribonucleotides by Proton Magnetic Resonance

    Nelson, James Henry

    The structural and conformational properties of several dinucleoside monophosphates and oligonucleotides in aqueous solution have been studied by proton magnetic resonance spectroscopy. Specifically, the role of intramolecular base-stacking interactions and other intramolecular forces in the determination of the conformational properties of these molecules has been investigated; and the results of these studies are discussed in relation to the structural properties of biologically significant nucleic acids.

    The proton magnetic resonance spectrum of adenylyl-(3'→5')-adenosine (ApA) was studied as a function of concentration, temperature, solution pH, and concentration of added purine. The results of these studies indicate that the stacking interaction between the two adenine rings in ApA is relatively strong and that the adenine...

  2. I. Synthesis of dl-cis-Tetrahydroeremophilone. II. Studies on Systems Free From Angular Strain

    Murayama, Stanley Tetsu

    I. The total synthesis of racemic cis-tetrahydroeremophilone (17) has been achieved. The key feature of the synthesis was a solvolytic cyclization that proceeded through a symmetrical cation 41 and gave rise to two major products, one of which had the stereochemistry required for the synthesis of tetrahydroeremophilone.

    II. Attempts on the synthesis of the alcohol 1 have been investigated in three related reaction sequences (Schemes 1, 4, 5, and 6). Although none of the reaction sequences gave the desired alcohol 1 that was intended for use in a solvolysis study, an unexpected product, the keto acetate 48, resulted in one sequence and afforded adamantanone (44) upon chromatography on alumina.


  3. Disjointness Preserving Operators

    Hart, Dean Robert

    Let E and F be Archimedian Riesz spaces. A linear operator T : E → F is called disjointness preserving if |f| ∧ |g| = 0 in E implies |Tf| ∧ |Tg| = 0 in F. An order continuous disjointness preserving operator T : E → E is called bi-disjointness preserving if the order closure of |T|E is an ideal in E. If the order dual of E separates the points of E, then every order continuous disjointness preserving operator whose adjoint is disjointness preserving is bi-disjointness preserving. If E is in addition Dedekind complete, then the converse holds.

    DEFINITION. Let...

  4. Observations on the Theory and Characteristics of Electrical Figures on Plates in Air with Particular Reference to their Speed of Growth

    Pleasants, John Gibson
    The fact that electrical figures in air at atmospheric pressure grow with average velocities which lie in the range of from 10 to 103 km./sec., and which may extend beyond this range, depending on the magnitude of the voltage applied and the physical constants of the plate is verified. The velocity decreases with increasing size of the figure. The effect of a variation in the capacitance between surfaces per unit area of the plate has been found to be greater for negative than for positive figures, and has been found to decrease with increasing voltage, for figures at the same stage of development. The maximum current intake has been...

  5. The Hydration of Isobutene. I. The Hydration Rate of Isobutene in Dilute Nitric Acid. II. The Free Energy of Hydration of Isobutene. III. The Hydration of Isobutene in the Presence of Silver Nitrate

    Eberz, William Ferdinand

    The three articles contained in this thesis describe the investigation of the hydration of isobutene.

    In the first paper the rates of hydration of isobutene were measured in dilute nitric acid solutions both with and without other ions present to observe possible catalytic effects.

    In the second paper the equilibrium of the hydration reaction in aqueous solution was determined and, by means of additional data, the standard free energy change and change in heat content of the reaction were calculated.

    In the third part the hydration in the presence of silver ion was investigated and the role of this metal in the reaction was elucidated.


  6. Biochemical and Biophysical Studies on the RNA Species of Sindbis Virus

    Frey, Teryl Kenneth

    Sindbis virus, a togavirus, contains an infectious, single stranded RNA with a molecular weight of 4.3 x 106 (498), which in infected cells serves as a messenger RNA for the translation of the virus onstructural proteins. Also present in infected cells is an RNA with a molecular weight of 1.6 x 106 (268) which consists of the 3' terminal third of the 49S RNA and functions as a messenger RNA for the translation of the virus structural proteins. In this thesis, three features of these RNA species of Sindbis virus are studied: the 3' terminal poly A tracts on the RNAs and the corresponding...

  7. Modulating Biophysical Properties of Insulin with Non-Canonical Mutagenesis at Position B28

    Fang, Katharine Y.

    Non-canonical amino acids are tools for altering the chemical and physical properties of proteins, providing a facile strategy to engineer proteins with novel properties, especially where canonical amino acid mutagenesis has exhausted nearly all avenues for further optimization. Insulin, for example, is one of the most widely studied therapeutic proteins; however, non-canonical insulin engineering is a subfield that has been largely unexplored. To this end, my thesis research has focused on the use of non-canonical amino acids to understand and engineer the biophysical properties of insulin.

    Protein structure and function are sensitive to the smallest of changes; even small differences such...

  8. Electronically Tunable Light Modulation with Graphene and Noble Metal Plasmonics

    Kim, Seyoon

    Graphene is a monolayer of carbon atoms constructing a two-dimensional honeycomb structure, and it has an excellent carrier mobility and a very high thermal conductivity. Remarkably, it has been experimentally demonstrated that a monolayer graphene exhibits an exotic optical properties. To be specific, the plasmonic dispersion relation of a transverse magnetic graphene plasmon is electronically tunable by adjusting carrier density in graphene with external gate bias, and graphene plasmonic nano cavities have been utilized to modulate mid-infrared light.

    In this thesis, we present how to efficiently modulate mid-infrared light by combining graphene plasmonic ribbons with noble metal plasmonic structures.

    First, we propose...

  9. Optics for High-Efficiency Full Spectrum Photovoltaics

    Darbe, Sunita

    While the price of solar energy has dropped dramatically in the last few years, costs must be further reduced to reach wide-scale adoption. One strategy to decrease cost is to increase efficiency. Photovoltaic energy conversion is most efficient for a narrow frequency range. Lack of absorption of low energy photons and thermalization of high-energy photons leads lead to a loss of over 40% of incident solar power on a silicon cell. Current-matching and lattice-matching restrictions limit the efficiency of traditional monolithic multijunction solar cells. In order to avoid these limitations and realize ultrahigh efficiency (close to 50%), this thesis explores...

  10. Wireless Nano and Molecular Scale Neural Interfacing

    Sadek, Akram Sarwat
    Nanoscale circuits and sensors built from silicon nanowires, carbon nanotubes and other devices will require methods for unobtrusive interconnection with the macroscopic world to fully realise their potential; the size of conventional wires precludes their integration into dense, miniature systems. The same wiring problem presents an obstacle in our attempts to understand the brain by means of massively deployed nanodevices, for multiplexed recording and stimulation in vivo. We report on a nanoelectromechanical system that ameliorates wiring constraints, enabling highly integrated sensors to be read in parallel through a single output. Its basis is an effect in piezoelectric nanomechanical resonators that...

  11. Stress, Distribution in Two Circular Cylinders Intersecting at Right Angles Under the Influence of Internal Pressure

    Harmon, Leonard E.

    This investigation is an experimental study of the stress distribution in two circular cylinders intersecting at right angles and acted on by internal pressure. Two specimens of the thick-wall category were tested to rupture and a strain gage analysis was made of critical points. The specifications of the specimens tested were so chosen that this investigation would be the logical beginning of an overall study of intersecting cylinders under the influence of internal pressure.

    The results of two tests are insufficient to indicate trends or establish facts as conclusive. The conclusions reached as a result of this investigation are, therefore,...

  12. Phase Transformations and Entropy of Non-Equilibrium Materials

    Smith, Hillary Leigh

    Time-resolved vibrational spectra through the glass transition in the bulk metallic glass CuZr were acquired with inelastic neutron scattering. Vibrational density of states (DOS) in ranges as small as 4K were extracted from continuous heating through the glass transition. For each temperature interval, the vibrational entropy is calculated from the DOS. This provides a detailed characterization of how the vibrational entropy contributes to the large jump in heat capacity that characterizes the glass transition in amorphous materials. This change in heat capacity has been attributed to combinations of configurational and vibrational entropy. However, the role of vibrational entropy in this...

  13. Computational Enzyme Design

    Sosa Padilla Araujo, Bernardo

    Computational protein design (CPD) is the automated identification of amino acid sequences that will fold into a specified three-dimensional structure. This method has emerged as a promising tool for engineering enzymes. In this thesis, I describe my efforts at improving and applying CPD methods to the design of enzymes.

    Chapter II describes the development and benchmark results for a molecular dynamics (MD) protocol to prescreen enzyme designs. Results indicate that the MD protocol is successful in screening enzymes for enzymatic activity. The protocol is general, reproducible, and excels at discarding false positive designs while predicting the most active enzymes correctly.

    ...

  14. Methodological Developments and Synthetic Applications of Strained Rings and Allylic C–H Functionalization of Hindered Substrates

    O'Connor, Nicholas R.

    Formal dipolar cycloadditions of cyclopropanes and aziridines are useful methods for the formation of carbo- and heterocycles. Given our group’s previous interest in this area, we sought to expand the scope of strained ring cycloadditions by employing heterocumulenes as dipolarophiles. This thesis describes our development of Lewis acid catalyzed formal (3 + 2) cycloadditions between donor–acceptor cyclopropanes and isocyanates, isothiocyanates, and carbodiimides to furnish various five-membered heterocycles. Enantioenriched cycloadducts can be accessed through a stereospecific reaction if enantiopure substrates are employed. We also present a method to access more highly nitrogenated heterocycles by replacing donor–acceptor cyclopropanes with activated aziridines. These...

  15. The Search for Stellar Coronal Mass Ejections

    Villadsen, Jacqueline Rose

    Coronal mass ejections (CMEs) may dramatically impact habitability and atmospheric composition of planets around magnetically active stars, including young solar analogs and many M dwarfs. Theoretical predictions of such effects are limited by the lack of observations of stellar CMEs. This thesis addresses this gap through a search for the spectral and spatial radio signatures of CMEs on active M dwarfs.

    Solar CMEs produce radio bursts with a distinctive spectral signature, narrow-band plasma emission that drifts to lower frequency as a CME expands outward. To search for analogous events on nearby stars, I worked on system design, software, and commissioning for...

  16. Nonlinear Dynamics of Transition Waves in Multi-Stable Discrete and Continuous Media

    Nadkarni, Neel P.
    The concept of phase transitions, i.e., switching between two or more different equilibrium states of a system, is commonly encountered in many physical, chemical and biological phenomena. The exact mechanism of this switching is a highly nonlinear dynamical process that is accommodated by the propagation of a localized wave. The characteristics of the nonlinear wave such as its profile, velocity, energy, and width of transition are governed by the type and specifics of the system that it is propagating through which may be conservative, dissipative, or diffusive in nature. The goal of this thesis is to develop a fundamental understanding...

  17. Microfabricated Tools and Engineering Methods for Sensing Bioanalytes

    Rajagopal, Aditya
    There is a convergence between the needs of the medical community and the capabilities of the engineering community. For example, the scale of biomedical devices and sensors allow for finer, more cost-effective quantification of biological and chemical targets. By using micro-fabrication techniques, we design and demonstrate a variety of microfluidic sensors and actuators that allow us to interact with a biochemical environment. We demonstrate the performance of microfluidic blood-filtrations chips, immune-diagnostic assays, and evaporative coolers. Furthermore, we show how micro-fabricated platinum filaments can be used for highly localized heating and temperature measurement. We demonstrate that these filaments can be used...

  18. Aspects of the Theory of Normed Spaces

    Wiid, Frans Gerhardus Johannes

    The dissertation will be divided into two parts. The first part will, in essence, be a study of weak compactness in a variety of families of normed spaces. Included in this study will be general characterizations of weak compactness in spaces of vector measures and tensor products that contain all known results of this nature as special cases (in particular, we do not need to restrict attention to only those range spaces with strong geometric properties such as, for example, the Radon-Nikodym property). The methods of Nonstandard Analysis constitute a fundamental tool in these investigations.

    The second part of the dissertation...

  19. Theoretical and Experimental Investigation of Phonon Boundary Scattering in Thin Silicon Membranes

    Ravichandran, Navaneetha Krishnan

    The thermal transport properties of thin semiconductor membranes play an important role in the performance of many technologies like micro-electronics and solid-state energy conversion. The dominant resistance to heat flow in thin membranes is offered by the scattering of thermal phonons at the membrane boundaries. In this dissertation, we examine the nature of microscopic phonon boundary scattering processes and their effect on the thermal conductivity of the thin membranes using a pump-probe experimental technique and computationally efficient solutions of the phonon Boltzmann transport equation (BTE).

    First, we investigate the boundary scattering-limited thermal transport in nanostructures using an efficient variance-reduced Monte...

  20. Membrane Potential Dynamics of Hippocampal Neurons During Ripples in Awake Mice

    Hulse, Bradley K.
    During periods of slow wave sleep and quiet wakefulness, the hippocampal formation generates spontaneous population bursts that are organized as a high-frequency “ripple” oscillation. The neurons that participate in these bursts often replay previously experienced activity patterns encoded during alert behavior, and interfering with ripple generation produces deficits in learning and memory tasks. For these reasons, ripples play a prominent role in theories of memory consolidation and retrieval. While spiking during ripples has been extensively studied, our understanding of the subthreshold behavior of hippocampal neurons during these events remains incomplete. Here, we combine in vivo whole-cell recordings with multisite extracellular...

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