FOREIGN AID AND THE AFRICAN FARMER

International Development,

Coulomb blockade in a Si channel gated by an Al single-electron transistor

We incorporate an Al-AlO_x-Al single-electron transistor as the gate of a narrow (~100 nm) metal-oxide-semiconductor field-effect transistor (MOSFET). Near the MOSFET channel conductance threshold, we observe oscillations in the conductance associated with Coulomb blockade in the channel, revealing the formation of a Si single-electron transistor. Abrupt steps present in sweeps of the Al transistor conductance versus gate voltage are correlated with single-electron charging events in the Si transistor, and vice versa. Analysis of these correlations using a simple electrostatic model demonstrates that the two single-electron transistor islands are closely aligned, with an inter-island capacitance approximately equal to 1/3 of the total capacitance of the Si transistor island, indicating that the Si transistor is strongly coupled to the Al transistor.Comment: 3 pages, 4 figures, 1 table; typos corrected, minor clarifications added; published in AP

An in Situ Technique for Elemental Analysis of Lunar Surfaces

An in situ analytical technique that can remotely determine the elemental constituents of solids has been demonstrated. Laser-Induced Breakdown Spectroscopy (LIBS) is a form of atomic emission spectroscopy in which a powerful laser pulse is focused on a solid to generate a laser spark, or microplasma. Material in the plasma is vaporized, and the resulting atoms are excited to emit light. The light is spectrally resolved to identify the emitting species. LIBS is a simple technique that can be automated for inclusion aboard a remotely operated vehicle. Since only optical access to a sample is required, areas inaccessible to a rover can be analyzed remotely. A single laser spark both vaporizes and excites the sample so that near real-time analysis (a few minutes) is possible. This technique provides simultaneous multielement detection and has good sensitivity for many elements. LIBS also eliminates the need for sample retrieval and preparation preventing possible sample contamination. These qualities make the LIBS technique uniquely suited for use in the lunar environment

High mobility two-dimensional electron system on hydrogen-passivated silicon(111) surfaces

We have fabricated and characterized a field-effect transistor in which an electric field is applied through an encapsulated vacuum cavity and induces a two-dimensional electron system on a hydrogen-passivated Si(111) surface. This vacuum cavity preserves the ambient sensitive surface and is created via room temperature contact bonding of two Si substrates. Hall measurements are made on the H-Si(111) surface prepared in aqueous ammonium fluoride solution. We obtain electron densities up to $6.5 \times 10^{11}$ cm$^{-2}$ and peak mobilities of $\sim 8000$ cm$^{2}$/V s at 4.2 K.Comment: to appear in Applied Physics Letter

Quantum Hall line junction with impurities as a multi-slit Luttinger liquid interferometer

We report on quantum interference between a pair of counterpropagating quantum Hall edge states that are separated by a high quality tunnel barrier. Observed Aharonov-Bohm oscillations are analyzed in terms of resonant tunneling between coupled Luttinger liquids that creates bound electronic states between pairs of tunnel centers that act like interference slits. We place a lower bound in the range of 20-40 $\mu$m for the phase coherence length and directly confirm the extended phase coherence of quantum Hall edge states.Comment: 4 pages, 3 figures, 1 tabl

Transport in Luttinger Liquids

We give a brief introduction to Luttinger liquids and to the phenomena of electronic transport or conductance in quantum wires. We explain why the subject of transport in Luttinger liquids is relevant and fascinating and review some important results on tunneling through barriers in a one-dimensional quantum wire and the phenomena of persistent currents in mesoscopic rings. We give a brief description of our own work on transport through doubly-crossed Luttinger liquids and transport in the Schulz-Shastry exactly solvable Luttinger-like model.Comment: Latex file, 15 pages, four eps figure

Electromagnetic field induced suppression of transport through nn-pp junctions in graphene

We study quasi-particle transmission through an $n$-$p$ junction in a graphene irradiated by an electromagnetic field (EF). In the absence of EF the electronic spectrum of undoped graphene is gapless, and one may expect the perfect transmission of quasi-particles flowing perpendicular to the junction. We demonstrate that the resonant interaction of propagating quasi-particles with the component of EF parallel to the junction induces a \textit{non-equilibrium dynamic gap} $(2\Delta_R)$ between electron and hole bands in the quasi-particle spectrum of graphene. In this case the strongly suppressed quasi-particle transmission is only possible due to interband tunnelling. The effect may be used for controlling transport properties of diverse structures in graphene, like, e.g., $n$-$p$-$n$ transistors, single electron transistors, quantum dots, etc., by variation of the intensity $S$ and frequency $\omega$ of the external radiation.Comment: 5 pages, 3 figure

Tradition and Innovation: The Lives and Music of Women Composers

My Capstone Project, entitled “Tradition and Innovation: The Lives and Music of Women Composers,” is a combination of a creative project and written thesis that explores the struggles that women faced as members of society and composers throughout history. The written portion details the expectations set for women by society and how these expectations had a role in their personal lives and their music. I explore stereotypes and societal values that women lived regularly, including the expectation of women to never perform for a public audience, to obey their fathers and husbands and therefore only receive training with their permission, to raise families, and to only compose in certain genres and for certain instruments. Many of these expectations are deep-rooted in beliefs that women should be passive, silent, and private, and caused great difficulty for aspiring female composers in several different centuries from the 1600s through today. I also create several case studies on women composers, including Amy Beach, Clara Schumann, Fanny Mendelssohn Hensel, Rebecca Clarke, Ethel Smyth, Elisabeth Claude-Jacquet de la Guerre, Libby Larsen, Lili Boulanger, and Cécile Chaminade, in order to determine whether or not they were specifically affected by societal norms, and how they dealt with pressures from expectations. The creative component to my project took place on March 1st, 2008, and was a concert to display the compositions of the composers that I examined in the written portion of my thesis. The goal in creating the concert was to inform an audience of my research and give them a different perspective with which to view the way that we have currently formed our musical canon. I hope that my concert showed my audience the quality of music that women have always been capable of writing, and yet they are still unfortunately not as well-represented as men. I used program notes and a brief lecture to provide my audience with information about the struggles that women faced in different time periods, the types of music they wrote, and whether or not it had a correlation to expectations made for them by society, and how women dealt with their status in their music and their personal lives. The concert included student performers, professors, and guest artists the New York State Baroque. In combining a concert and a written thesis, I hope to bring readers and audience members to the conclusion that I have drawn from researching the world that these women lived in and how it affected their careers and their music. All of the women that I studied were undoubtedly affected in some way by societal expectations. Some of them stayed well within the boundaries set for them during their time, and some broke many of the expectations and became known as leaders for their gender, although even the leaders still were unable to completely escape the challenges of being a female in a patriarchal society. I argue, however, that it is precisely the combination of tradition and innovation portrayed by each of the women that adds depth to their stories and adds beauty and depth to their music