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Fractional-Period Excitations In Continuum Periodic Systems, H E. Nistazakis, Mason A. Porter, Pg Kevrekidis, Dj Frantzeskakis, N Nicolin, Jk Chin

Panos Kevrekidis

We investigate the generation of fractional-period states in continuum periodic systems. As an example, we consider a Bose-Einstein condensate confined in an optical-lattice potential. We show that when the potential is turned on nonadiabatically, the system explores a number of transient states whose periodicity is a fraction of that of the lattice. We illustrate the origin of fractional-period states analytically by treating them as resonant states of a parametrically forced Duffing oscillator and discuss their transient nature and potential observability.

Sigma Exchange In The Nuclear Force And Effective Field Theory, John Donoghue

John Donoghue

In the phenomenological description of the nuclear interaction a crucial role is traditionally played by the exchange of a scalar I=0 meson, the sigma, of mass 500-600 MeV, which however is not seen clearly in the particle spectrum and which has a very ambiguous status in QCD. I show that a remarkably simple and reasonably controlled combination of ingredients can reproduce the features of this part of the nuclear force. The use of chiral perturbation theory calculations for two pion exchange supplemented by the Omnes function for pion rescattering suffices to reproduce the magnitude and shape of the exchange of …

Possible Nonconductive Role Of Geobacter Sulfurreducens Pilus Nanowires In Biofilm Formation, Gemma Reguera, Rachael B. Pollina, Julie S. Nicoll, Derek Lovley

Derek Lovley

Geobacter sulfurreducens required expression of electrically conductive pili to form biofilms on Fe(III) oxide surfaces, but pili were also essential for biofilm development on plain glass when fumarate was the sole electron acceptor. Furthermore, pili were needed for cell aggregation in agglutination studies. These results suggest that the pili of G. sulfurreducens also have a structural role in biofilm formation.

Roots & Routes: A Re-Imagining Of Refugee Identity Constructions And The Implications For Schooling, Jacqueline Mosselson

Jacqueline Mosselson

The ways in which refugees are assumed to adapt to United States society have serious consequences on their enjoyment and fulfillment in their schooling experiences. This is further compounded by the incorporation of refugees under a more general umbrella of "immigrant" studies. Here, excerpts are shared from an experiential study of fifteen adolescent Bosnian female refugees in New York City schools to articulate an alternative identity paradigm, roots & routes, which captures the ways in which refugees consciously balance their ethnic and new national identities in understanding themselves, their lives, and how they represent themselves to others. This paradigm enables …

Stability Of Discrete Solitons In The Presence Of Parametric Driving, H. Susanto, Q. E. Hoq, Panos Kevrekidis

Panos Kevrekidis

In this Brief Report, we consider parametrically driven bright solitons in the vicinity of the anticontinuum limit. We illustrate the mechanism through which these solitons become unstable due to the collision of the phase mode with the continuous spectrum, or eigenvalues bifurcating thereof. We show how this mechanism typically leads to complete destruction of the bright solitary wave.

A Framework For New Generation Transportation Simulation, Daiheng Ni

Daiheng Ni

This paper discussed the evolution and future trend of simulation in general domain and in transportation. Some challenges facing transportation modeling and simulation were identified. As an effort to address these challenges, a framework of new generation transportation simulation was developed. The framework is envisioned to be multi- scale in resolution, parallel in execution, and driven by ob- jects. The paper further discussed strategies of transporta- tion simulation at a nanoscopic level which offers a level of modeling detail beyond the state-of-the-art.

Incongruence Between Genetic And Morphological Diversity In Microcebus Griseorufus On Beza Mahafaly, Laurie Godfrey, K. L. Heckman, E. Rasoazanabary, E. Machlin, A. D. Yoder

Laurie R. Godfrey

Background - The past decade has seen a remarkable increase in the number of recognized mouse lemur species (genus Microcebus). As recently as 1994, only two species of mouse lemur were recognized according to the rules of zoological nomenclature. That number has now climbed to as many as fifteen proposed species. Indeed, increases in recognized species diversity have also characterized other nocturnal primates – galagos, sportive lemurs, and tarsiers. Presumably, the movement relates more to a previous lack of information than it does to any recent proclivity for taxonomic splitting. Due to their nocturnal habits, one can hypothesize that mouse …

Bmc Infectious Diseases, Frances Cirino, Wilmore C. Webley, Corrie West, Nancy L. Croteau, Chester Andrzejewski Jr, Elizabeth S. Stuart

Wilmore C Webley

No abstract provided.

Criticality For The Gehring Link Problem, Jason Cantarella, Joseph H.G. Fu, Robert Kusner, John M. Sullivan, Nancy C. Wrinkle

Robert Kusner

In 1974, Gehring posed the problem of minimizing the length of two linked curves separated by unit distance. This constraint can be viewed as a measure of thickness for links, and the ratio of length over thickness as the ropelength. In this paper we refine Gehring’s problem to deal with links in a fixed link-homotopy class: we prove ropelength minimizers exist and introduce a theory of ropelength criticality.

Our balance criterion is a set of necessary and sufficient conditions for criticality, based on a strengthened, infinite-dimensional version of the Kuhn–Tucker theorem. We use this to prove that every critical link …

A Genomic Approach To Identify Regulatory Nodes In The Transcriptional Network Of Systemic Acquired Resistance In Plants, Dong Wang, Nita Amornsiripanitch, Xinnian Dong

Dong Wang

Many biological processes are controlled by intricate networks of transcriptional regulators. With the development of microarray technology, transcriptional changes can be examined at the whole-genome level. However, such analysis often lacks information on the hierarchical relationship between components of a given system. Systemic acquired resistance (SAR) is an inducible plant defense response involving a cascade of transcriptional events induced by salicylic acid through the transcription cofactor NPR1. To identify additional regulatory nodes in the SAR network, we performed microarray analysis on Arabidopsis plants expressing the NPR1-GR (glucocorticoid receptor) fusion protein. Since nuclear translocation of NPR1-GR requires dexamethasone, we were able …

Vortex Matter, Effective Magnetic Charges, And Generalizations Of Dipolar Superfluidity Concept In Layered Systems, Egor Babaev

Egor Babaev

In the first part of this letter we discuss electrodynamics of an excitonic condensate in a bilayer. We show that under certain conditions the system has a dominant energy scale and is described by the effective electrodynamics with "planar magnetic charges". In the second part of the paper we point out that a vortex liquid state in bilayer superconductors also possesses dipolar superfluid modes and establish equivalence mapping between this state and a dipolar excitonic condensate. We point out that a vortex liquid state in an N-layer superconductor possesses multiple topologically coupled dipolar superfluid modes and therefore represents a generalization …

Marriage: The Good, The Bad, And The Greedy, Naomi R. Gerstel, Natalia Sarkisian

Naomi R. Gerstel

Even good marriages can have some bad side effects, taking people away from other social connections.

Reconstitution Of Protein Targeting To The Inner Envelope Membrane Of Chloroplasts, Ming Li, Danny Schnell

Danny Schnell

The chloroplast envelope plays critical roles in the synthesis and regulated transport of key metabolites, including intermediates in photosynthesis and lipid metabolism. Despite this importance, the biogenesis of the envelope membranes has not been investigated in detail. To identify the determinants of protein targeting to the inner envelope membrane (IM), we investigated the targeting of the nucleus-encoded integral IM protein, atTic40. We found that pre-atTic40 is imported into chloroplasts and processed to an intermediate size (int-atTic40) before insertion into the IM. Int-atTic40 is soluble and inserts into the IM from the internal stromal compartment. We also show that atTic40 and …

Gaining Perspective With Refworks, David Mac Court

David Mac Court

Conference abstract: RefWorks receives rave reviews on the UMass Amherst campus. Reference librarians Madeleine Charney and Dave Mac Court outline the glories and the pitfalls of this online product and how it manages citations and generates bibliographies. Learn about “teaching moments” that occur during a session. The program also describes the various stages of librarians’ involvement and the evolution of RefWorks instruction, and is sponsored by ALS and ACRL/NEC.

Role Of Red Gsu In Stress Response And Fe(Iii) Reduction In Geobacter Sulfurreducens, Laurie N. Didonato, Sara A. Sullivan, Barbara A. Methѐ, Kelly P. Nevin, Reg England, Derek Lovley

Kelly Nevin

Geobacter species are key members of the microbial community in many subsurface environments in which dissimilatory metal reduction is an important process. The genome of Geobacter sulfurreducens contains a gene designated relGsu, which encodes a RelA homolog predicted to catalyze both the synthesis and the degradation of guanosine 3′,5′-bispyrophosphate (ppGpp), a regulatory molecule that signals slow growth in response to nutrient limitation in bacteria. To evaluate the physiological role of RelGsu in G. sulfurreducens, a relGsu mutant was constructed and characterized, and ppGpp levels were monitored under various conditions in both the wild-type and relGsu mutant strains. In the wild-type …

Role Of Red Gsu In Stress Response And Fe(Iii) Reduction In Geobacter Sulfurreducens, Laurie N. Didonato, Sara A. Sullivan, Barbara A. Methѐ, Kelly P. Nevin, Reg England, Derek Lovley

Derek Lovley

Geobacter species are key members of the microbial community in many subsurface environments in which dissimilatory metal reduction is an important process. The genome of Geobacter sulfurreducens contains a gene designated relGsu, which encodes a RelA homolog predicted to catalyze both the synthesis and the degradation of guanosine 3′,5′-bispyrophosphate (ppGpp), a regulatory molecule that signals slow growth in response to nutrient limitation in bacteria. To evaluate the physiological role of RelGsu in G. sulfurreducens, a relGsu mutant was constructed and characterized, and ppGpp levels were monitored under various conditions in both the wild-type and relGsu mutant strains. In the wild-type …

On A Notion Of Maps Between Orbifolds Ii. Homotopy And Cw-Complex, Weimin Chen Chen

Weimin Chen

This is the second of a series of papers which are devoted to a comprehensive theory of maps between orbifolds. In this paper, we develop a basic machinery for studying homotopy classes of such maps. It contains two parts: (1) the construction of a set of algebraic invariants – the homotopy groups, and (2) an analog of CW-complex theory. As a corollary of this machinery, the classical Whitehead theorem which asserts that a weak homotopy equivalence is a homotopy equivalence is extended to the orbifold category.

Implicating An Introduced Generalist Parasitoid In The Invasive Browntail Moth's Enigmatic Demise, Joseph Elkinton, D. Parry, G. Boettner

Joseph Elkinton

Recent attention has focused on the harmful effects of introduced biological control agents on nontarget species. The parasitoid Compsilura concinnata is a notable example of such biological control gone wrong. Introduced in 1906 primarily for control of gypsy moth, Lymantria dispar, this tachinid fly now attacks more than 180 species of native Lepidoptera in North America. While it did not prevent outbreaks or spread of gypsy moth, we present reanalyzed historical data and experimental findings suggesting that parasitism by C. concinnata is the cause of the enigmatic near-extirpation of another of North America's most successful invaders, the browntail moth (Euproctis …

Remarks On The Combinatorial Intersection Cohomology Of Fans, Tom Braden

Tom Braden

No abstract provided.

Cardiac Myosin Missense Mutations Cause Dilated Cardiomyopathy In Mouse Models And Depress Molecular Motor Function, Joachim Schmitt, Edward Debold, Ferhaan Ahmad, Amy Armstrong, Andrea Frederico, David Conner, Ulrike Mende, Martin Lohse, David Warshaw, Christine Seidman, J. Seidman

Edward P. Debold

Dilated cardiomyopathy (DCM) leads to heart failure, a leading cause of death in industrialized nations. Approximately 30% of DCM cases are genetic in origin, with some resulting from point mutations in cardiac myosin, the molecular motor of the heart. The effects of these mutations on myosin's molecular mechanics have not been determined. We have engineered two murine models characterizing the physiological, cellular, and molecular effects of DCM-causing missense mutations (S532P and F764L) in the α-cardiac myosin heavy chain and compared them with WT mice. Mutant mice developed morphological and functional characteristics of DCM consistent with the human phenotypes. Contractile function …

Radiationless Travelling Waves In Saturable Nonlinear Schrödinger Lattices, T. R. O. Melvin, A. R. Champneys, Panos Kevrekidis, J. Cuevas

Panos Kevrekidis

The long-standing problem of moving discrete solitary waves in nonlinear Schrödinger lattices is revisited. The context is photorefractive crystal lattices with saturable nonlinearity whose grand-canonical energy barrier vanishes for isolated coupling strength values. Genuinely localized traveling waves are computed as a function of the system parameters for the first time. The relevant solutions exist only for finite velocities.

The Structure Of Escherichia Coli Signal Recognition Particle Revealed By Scanning Transmission Electron Microscopy, Lain L. Mainprize, Daniel R. Beniac, Elena Falkovskaia, Robert M. Cleverley, Lila Gierasch, F. Peter Ottensmeyer, David W. Andrews

Lila Gierasch

Structural studies on various domains of the ribonucleoprotein signal recognition particle (SRP) have not converged on a single complete structure of bacterial SRP consistent with the biochemistry of the particle. We obtained a three-dimensional structure for Escherichia coli SRP by cryoscanning transmission electron microscopy and mapped the internal RNA by electron spectroscopic imaging. Crystallographic data were fit into the SRP reconstruction, and although the resulting model differed from previous models, they could be rationalized by movement through an interdomain linker of Ffh, the protein component of SRP. Fluorescence resonance energy transfer experiments determined interdomain distances that were consistent with our …

Biofilm And Nanowire Production Leads To Increased Current In Geobacter Sulfurreducens Fuel Cells, Gemma Reguera, Kelly P. Nevin, Julie S. Nicoll, Sean F. Covalla, Trevor L. Woodard, Derek Lovley

Derek Lovley

Geobacter sulfurreducens developed highly structured, multilayer biofilms on the anode surface of a microbial fuel cell converting acetate to electricity. Cells at a distance from the anode remained viable, and there was no decrease in the efficiency of current production as the thickness of the biofilm increased. Genetic studies demonstrated that efficient electron transfer through the biofilm required the presence of electrically conductive pili. These pili may represent an electronic network permeating the biofilm that can promote long-range electrical transfer in an energy-efficient manner, increasing electricity production more than 10-fold.

Biofilm And Nanowire Production Leads To Increased Current In Geobacter Sulfurreducens Fuel Cells, Gemma Reguera, Kelly P. Nevin, Julie S. Nicoll, Sean F. Covalla, Trevor L. Woodard, Derek Lovley

Kelly Nevin

Geobacter sulfurreducens developed highly structured, multilayer biofilms on the anode surface of a microbial fuel cell converting acetate to electricity. Cells at a distance from the anode remained viable, and there was no decrease in the efficiency of current production as the thickness of the biofilm increased. Genetic studies demonstrated that efficient electron transfer through the biofilm required the presence of electrically conductive pili. These pili may represent an electronic network permeating the biofilm that can promote long-range electrical transfer in an energy-efficient manner, increasing electricity production more than 10-fold.

The Nuclear Central Force In The Chiral Limit, John Donoghue

John Donoghue

Chiral perturbation theory supplemented by the Omnes function is employed to study the strength of the isoscalar central nuclear interaction, G_S, in the chiral limit vs the physical case. A very large modification is seen, i.e. eta_s = G_S ~ chiral /G_S ~ physical = 1.37 +- 0.10 . This large effect is seen to arise dominantly at low energy from the extra contributions made by massless pions at energies near the physical threshold where the physical spectral function must vanish kinematically. The slope away from the chiral limit, d_S, is also calculated and is correspondingly large. I also explain …

On The Nondegeneracy Of Constant Mean Curvature Surfaces, Nick Korevaar, Robert Kusner, Jesse Ratzkin

Robert Kusner

We prove that many complete, noncompact, constant mean curvature (CMC) surfaces $f:\Sigma \to \R^3$ are nondegenerate; that is, the Jacobi operator Δf+|Af|2 has no L2 kernel. In fact, if Σ has genus zero and f(Σ) is contained in a half-space, then we find an explicit upper bound for the dimension of the L2 kernel in terms of the number of non-cylindrical ends. Our main tool is a conjugation operation on Jacobi fields which linearizes the conjugate cousin construction. Consequences include partial regularity for CMC moduli space, a larger class of CMC surfaces to use in gluing constructions, and a surprising …

Undulated Cylinders Of Charged Diblock Copolymers, Gregory M. Grason, Christian Santangelo

Christian Santangelo

We study the cylinder to sphere morphological transition of diblock copolymers in aqueous solution with a hydrophobic block and a charged block. We find a metastable undulated cylinder configuration for a range of charge and salt concentrations which, nevertheless, occurs above the threshold where spheres are thermodynamically favorable. By modeling the shape of the cylinder ends, we find that the free-energy barrier for the transition from cylinders to spheres is quite large and that this barrier falls significantly in the limit of high polymer charge and low solution salinity. This suggests that observed undulated cylinder phases are kinetically trapped structures.

Spectral Methods Based On Prolate Spheroidal Wave Functions For Hyperbolic Pdes, Qian-Yong Chen, D. Gottlieb, J. S. Hesthaven

Qian-Yong Chen

We examine the merits of using prolate spheroidal wave functions (PSWFs) as basis functions when solving hyperbolic PDEs using pseudospectral methods. The relevant approximation theory is reviewed and some new approximation results in Sobolev spaces are established. An optimal choice of the band-limit parameter for PSWFs is derived for single-mode functions. Our conclusion is that one might gain from using the PSWFs over the traditional Chebyshev or Legendre methods in terms of accuracy and efficiency for marginally resolved broadband solutions.

Community Saves Farm From Jaws Of Development —Feeds Self Instead, Madeleine K. Charney

Madeleine K. Charney

Amherst, Massachusetts community members join forces to form a non-profit landtrust and launch the North Amherst Community Farm.

Regression Analysis With Categorized Regression Calibrated Exposure: Some Interesting Findings, Ingvild Dalen, John Buonaccorsi, Petter Laake, Anette Hjartaker, Magne Thorese

John Buonaccorsi

Background: Regression calibration as a method for handling measurement error is becoming increasingly well-known and used in epidemiologic research. However, the standard version of the method is not appropriate for exposure analyzed on a categorical (e.g. quintile) scale, an approach commonly used in epidemiologic studies. A tempting solution could then be to use the predicted continuous exposure obtained through the regression calibration method and treat it as an approximation to the true exposure, that is, include the categorized calibrated exposure in the main regression analysis. Methods: We use semi-analytical calculations and simulations to evaluate the performance of the proposed approach …