Digital Commons Network^™

Context-Sensitive Resource Discovery, Guanling Chen, David Kotz

Dartmouth Scholarship

This paper presents the “Solar” system framework that allows resources to advertise context-sensitive names and for applications to make context-sensitive name queries. The heart of our framework is a small specification language that allows composition of “context-processing operators” to calculate the desired context. Resources use the framework to register and applications use the framework to lookup context-sensitive name descriptions. The back-end system executes these operators and constantly updates the context values, adjusting advertised names and informing applications about changes. We report experimental results from a prototype, using a modified version of the Intentional Naming System (INS) as the core directory …

Hydrogenic Spin Quantum Computing In Silicon: A Digital Approach, A. J. Skinner, M. E. Davenport, B. E. Kane

Dartmouth Scholarship

We suggest an architecture for quantum computing with spin-pair encoded qubits in silicon. Electron-nuclear spin-pairs are controlled by a dc magnetic field and electrode-switched on and off hyperfine interaction. This digital processing is insensitive to tuning errors and easy to model. Electron shuttling between donors enables multiqubit logic. These hydrogenic spin qubits are transferable to nuclear spin-pairs, which have long coherence times, and electron spin-pairs, which are ideally suited for measurement and initialization. The architecture is scalable to a highly parallel operation.

Rpb4p, A Subunit Of Rna Polymerase Ii, Mediates Mrna Export During Stress, Marganit Farago, Tal Nahari, Christopher Hammel, Charles N. Cole, Mordechai Choder

Dartmouth Scholarship

Changes in gene expression represent a major mechanism by which cells respond to stress. We and other investigators have previously shown that the yeast RNA polymerase II subunit Rpb4p is required for transcription under various stress conditions, but not under optimal growth conditions. Here we show that, in addition to its role in transcription, Rpb4p is also required for mRNA export, but only when cells are exposed to stress conditions. The roles of Rpb4p in transcription and in mRNA export can be uncoupled genetically by specific mutations in Rpb4p. Both functions of Rpb4p are required to maintain cell viability during …

Observational Constraints On General Relativistic Energy Conditions, Cosmic Matter Density And Dark Energy From X-Ray Clusters Of Galaxies And Type-La Supernovae, P. Schuecker, R. R. Caldwell, H. Böhringer, C. A. Collins

Dartmouth Scholarship

New observational constraints on the cosmic matter density Ωm and an effectively redshift-independent equation

of state parameter wx of the dark energy are obtained while simultaneously testing the strong and null energy conditions of

general relativity on macroscopic scales. The combination of REFLEX X-ray cluster and type-Ia supernova data shows that

for a flat Universe the strong energy condition might presently be violated whereas the null energy condition seems to be

fulfilled. This provides another observational argument for the present accelerated cosmic expansion and the absence of exotic

physical phenomena related to a broken null energy condition. The marginalization of …

Promoters Of The Murine Embryonic Β-Like Globin Genes Ey And Βh1 Do Not Compete For Interaction With The Β-Globin Locus Control Region, Xiao Hu, Michael Bulger, Julia N. Roach, Susan K. Eszterhas, Emmanuel Olivier, Eric Bouhassira, Mark Groudine, Steven Fiering

Dartmouth Scholarship

Mammalian β-globin loci contain multiple β-like genes that are expressed at different times during development. The murine β-globin locus contains two genes expressed during the embryo stage, Ey and βh1, and two genes expressed at both the fetal and postnatal stages, β-major and β-minor. Studies of transgenic human β-like globin loci in mice have suggested that expression of one gene at the locus will suppress expression of other genes at the locus. To test this hypothesis we produced mouse lines with deletions of either the Ey or βh1 promoter in the endogenous murine β-globin locus. Promoter deletion eliminated expression of …

Hierarchy Of Protein Assembly At The Vertex Ring Domain For Yeast Vacuole Docking And Fusion, Li Wang, Alexey J. Merz, Kevin M. Collins, William Wickner

Dartmouth Scholarship

Vacuole tethering, docking, and fusion proteins assemble into a “vertex ring” around the apposed membranes of tethered vacuoles before catalyzing fusion. Inhibitors of the fusion reaction selectively interrupt protein assembly into the vertex ring, establishing a causal assembly hierarchy: (a) The Rab GTPase Ypt7p mediates vacuole tethering and forms the initial vertex ring, independent of t-SNAREs or actin; (b) F-actin disassembly and GTP-bound Ypt7p direct the localization of other fusion factors; (c) The t-SNAREs Vam3p and Vam7p regulate each other’s vertex enrichment, but do not affect Ypt7p localization. The v-SNARE Vti1p is enriched at vertices by a distinct pathway that …

Age, Gender, Biometry, Refractive Error, And The Anterior Chamber Angle Among Alaskan Eskimos, Robert Wojciechowski, Nathan Congdon, William Anninger, Aimee Teo Broman

Dartmouth Scholarship

The prevalence of angle-closure glaucoma (ACG) is greater for Eskimos/Inuit than it is for any other ethnic group in the world. Although it has been suggested that this prevalence may be due to a population tendency toward shallower anterior chamber angles, available evidence for other populations such as Chinese with high rates of ACG has not consistently demonstrated such a tendency.

Rhamnolipid Surfactant Production Affects Biofilm Architecture In Pseudomonas Aeruginosa Pao1, Mary E. Davey, Nicky C. Caiazza, George A. O'Toole

Dartmouth Scholarship

In response to certain environmental signals, bacteria will differentiate from an independent free-living mode of growth and take up an interdependent surface-attached existence. These surface-attached microbial communities are known as biofilms. In flowing systems where nutrients are available, biofilms can develop into elaborate three-dimensional structures. The development of biofilm architecture, particularly the spatial arrangement of colonies within the matrix and the open areas surrounding the colonies, is thought to be fundamental to the function of these complex communities. Here we report a new role for rhamnolipid surfactants produced by the opportunistic pathogen Pseudomonas aeruginosa in the maintenance of biofilm architecture. …

Asymmetry Of The Central Apparatus Defines The Location Of Active Microtubule Sliding In Chlamydomonas Flagella, Matthew J. Wargo, Elizabeth F. Smith

Dartmouth Scholarship

Regulation of ciliary and flagellar motility requires spatial control of dynein-driven microtubule sliding. However, the mechanism for regulating the location and symmetry of dynein activity is not understood. One hypothesis is that the asymmetrically organized central apparatus, through interactions with the radial spokes, transmits a signal to regulate dynein-driven microtubule sliding between subsets of doublet microtubules. Based on this model, we hypothesized that the orientation of the central apparatus defines positions of active microtubule sliding required to control bending in the axoneme. To test this, we induced microtubule sliding in axonemes isolated from wild-type and mutant Chlamydomonas cells, and then …

Richard Goldschmidt: Hopeful Monsters And Other 'Heresies', Michael Dietrich

Dartmouth Scholarship

Richard Goldschmidt is remembered today as one of the most controversial biologists of the twentieth century. Although his work on sex determination and physiological genetics earned him accolades from his peers, his rejection of the classical gene and his unpopular theories about evolution significantly damaged his scientific reputation. This article reviews Goldschmidt's life and work, with an emphasis on his controversial views.

Selberg's Trace Formula On The K-Regular Tree And Applications, Audrey Terras, Dorothy Wallace

Dartmouth Scholarship

We survey graph theoretic analogues of the Selberg trace and pretrace formulas along with some applications. This paper includes a review of the basic geometry of a k-regular tree E (symmetry group, geodesies, horocycles, and the analogue of the Laplace operator). A detailed discussion of the spherical functions is given. The spherical and horocycle transforms are considered (along with three basic examples, which may be viewed as a short table of these transforms). Two versions of the pretrace formula for a finite connected k-regular graph ×□Γ\Ξ are given along with two applications. The first application is to obtain an asymptotic …

A Genetic Lesion That Arrests Plasma Cell Homing To The Bone Marrow, Loren D. Erickson, Ling-Li Lin, Biyan Duan, Laurence Morel, Randolph J. Noelle

Dartmouth Scholarship

The coordinated regulation of chemokine responsiveness plays a critical role in the development of humoral immunity. After antigen challenge and B cell activation, the emerging plasma cells (PCs) undergo CXCL12-induced chemotaxis to the bone marrow, where they produce Ab and persist. Here we show that PCs, but not B cells or T cells from lupus-prone NZM mice, are deficient in CXCL12-induced migration. PC unresponsiveness to CXCL12 results in a marked accumulation of PCs in the spleen of mice, and a concordant decrease in bone marrow PCs. Unlike normal mice, in NZM mice, a majority of the splenic PCs are long-lived. …

The Delphic Boat: What Genomes Tell Us, Michael Dietrich

Dartmouth Scholarship

A review of The Delphic Boat: What Genomes Tell Us by Antoine Danchin Alison Quayle, trans. Harvard University Press, 2003 380 pp. hardcover. ISBN 0-67400-930-4

The Impact Of Pollution On Stellar Evolution Models, Aaron Dotter, Brian Chaboyer

Dartmouth Scholarship

An approach is introduced for incorporating the concept of stellar pollution into stellar evolution models. The approach involves enhancing the metal content of the surface layers of stellar models. In addition, the surface layers of stars in the mass range of 0.5-2.0 M_☉ are mixed to an artificial depth motivated by observations of lithium abundance. The behavior of polluted stellar evolution models is explored assuming the pollution occurs after the star has left the fully convective pre-main-sequence phase. Stellar models polluted with a few Earth masses (M_⊕) of iron are significantly hotter than stars of the …

Boundary Volume And Length Spectra Of Riemannian Manifolds: What The Middle Degree Hodge Spectrum Doesn't Reveal, Carolyn S. Gordon, Juan P. Rossetti

Dartmouth Scholarship

No abstract provided.

Online Detection Of Tonal Pop-Out In Modulating Contexts, Petr Janata, Jeffrey L. Birk, Barbara Tillmann, Jamshed J. Bharucha

Dartmouth Scholarship

We investigated the spontaneous detection of "wrong notes" in a melody that modulated continuously through all 24 major and minor keys. Three variations of the melody were composed, each of which had distributed within it 96 test tones of the same pitch, for example, A2. Thus, the test tones would blend into some keys and pop out in others. Participants were not asked to detect or judge specific test tones; rather, they were asked to make a response whenever they heard a note that they thought sounded wrong or out of place. This task enabled us to obtain subjective measures …

Saru, A Sara Homolog, Is Repressed By Sart And Regulates Virulence Genes In Staphylococcus Aureus, Adhar C. Manna, Ambrose L. Cheung

Dartmouth Scholarship

In searching the Staphylococcus aureus genome, we previously identified sarT, a homolog of sarA, which encodes a repressor for alpha-hemolysin synthesis. Adjacent but transcribed divergently to sarT is sarU, which encodes a 247-residue polypeptide, almost twice the length of SarA. Sequence alignment disclosed that SarU, like SarS, which is another SarA homolog, could be envisioned as a molecule with two halves, with each half being homologous to SarA. SarU, as a member of the SarA family proteins, disclosed conservation of basic residues within the helix-turn-helix motif and within the beta hairpin loop, two putative DNA binding domains within this protein …

Nucleotide Excision Repair- And Polymerase Eta-Mediated Error-Prone Removal Of Mitomycin C Interstrand Cross-Links, H. Zheng, X. Wang, A. J. Warren, R. J. Legerski, Rodney S. Nairn, Joshua W. Hamilton, Lei Li

Dartmouth Scholarship

Interstrand cross-links (ICLs) make up a unique class of DNA lesions in which both strands of the double helix are covalently joined, precluding strand opening during replication and transcription. The repair of DNA ICLs has become a focus of study since ICLs are recognized as the main cytotoxic lesion inflicted by an array of alkylating compounds used in cancer treatment. As is the case for double-strand breaks, a damage-free homologous copy is essential for the removal of ICLs in an error-free manner. However, recombination-independent mechanisms may exist to remove ICLs in an error-prone fashion. We have developed an in vivo …

Simplicity Of Ultragraph Algebras, Mark Tomforde

Dartmouth Scholarship

In this paper we analyze the structure of C*-algebras associated to ultragraphs, which are generalizations of directed graphs. We characterize the simple ultragraph algebras as well as deduce necessary and sufficient conditions for an ultragraph algebra to be purely infinite and to be AF. Using these techniques we also produce an example of an ultragraph algebra which is neither a graph algebra nor an Exel-Laca algebra. We conclude by proving that the C*-algebras of ultragraphs with no sinks are Cuntz-Pimsner algebras.

Linking Dispersal To Local Population Dynamics: A Case Study Using A Headwater Salamander System, Winsor H. Lowe

Dartmouth Scholarship

Dispersal can strongly influence local population dynamics and may be critical to species persistence in fragmented landscapes. Theory predicts that dispersal by resident stream organisms is necessary to offset the loss of individuals to downstream drift. However, there is a lack of empirical data linking dispersal and drift to local population dynamics in streams, leading to uncertainty regarding the general demographic significance of these processes and the power of drift to explain observed dispersal patterns. I assessed the contribution of dispersal along a first-order stream to population dynamics of the headwater salamander Gyrinophilus porphyriticus (Plethodontidae). I conducted mark–recapture surveys of …