Physical Sciences and Mathematics Commons^™

Solution Scattering And Fret Studies Of Nucleosomes Reveal Dna: Unwrapping Effects Of H3 And H4 Tail Removal, Kurt Andresen, Isabel Jimenez-Useche, Steven C. Howell, Chongli Yuan, Xiangyun Qiu

Physics and Astronomy Faculty Publications

Using a combination of small-angle X-ray scattering (SAXS) and fluorescence resonance energy transfer (FRET) measurements we have determined the role of the H3 and H4 histone tails, independently, in stabilizing the nucleosome DNA terminal ends from unwrapping from the nucleosome core. We have performed solution scattering experiments on recombinant wild-type, H3 and H4 tail-removed mutants and fit all scattering data with predictions from PDB models and compared these experiments to complementary DNA-end FRET experiments. Based on these combined SAXS and FRET studies, we find that while all nucleosomes exhibited DNA unwrapping, the extent of this unwrapping is increased for nucleosomes …

Fearless: Heather Ipsen, Heather Ipsen

SURGE

In celebration of Sustainability Week on campus, we proudly feature Heather Ipsen ’16 who has fearlessly raised awareness for the environmental issues about which she’s passionate and started a group on campus to better facilitate dialogue between sustainability groups. [excerpt]

Fearless: Adrienne Ellis, Adrienne M. Ellis

SURGE

Taking the initiative to change college policies related to LGBTQ issues, restructuring a sustainable community garden in Gettysburg over the summer, and continually being motivated to change and challenge the powers that be through her love of people, Adrienne Ellis ’14 fearlessly fights for what she believes to help the people she loves— everybody. [excerpt]

Number Of Sialic Acid Residues In Ganglioside Headgroup Affects Interactions With Neighboring Lipids, Shelli L. Frey, Ka Yee C. Lee

Chemistry Faculty Publications

Monolayers of binary mixtures of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and asialo-(GA₁), disialo-(GD_1b) and trisialo-(GT_1b) gangliosides were used to determine the effect of ganglioside headgroup charge and geometry on its interactions with the neighboring zwitterionic lipid. Surface pressure versus molecular area isotherm measurements along with concurrent fluorescence microscopy of the monolayers at the air-water interface were complemented with atomic force microscopy imaging of monolayers deposited on solid substrates. Results were used to further develop a proposed geometric packing model that the complementary geometry of DPPC and monosialoganglioside GM₁ headgroups affects their close molecular packing, …

First Observation Of 15be, J. Snyder, T. Baumann, G. Christian, R. A. Haring-Kaye, P. A. Deyoung, Z. Kohley, B. Luther, M. Mosby, S. Mosby, A. Simon, J. K. Smith, A. Spyrou, Sharon L. Stephenson, M. Thoennessen

Physics and Astronomy Faculty Publications

The neutron-unbound nucleus 15Be was observed for the first time. It was populated using neutron transfer from a deuterated polyethylene target with a 59 MeV/u 14Be beam. Neutrons were measured in coincidence with outgoing 14Be particles and the reconstructed decay energy spectrum exhibits a resonance at 1.8(1) MeV. This corresponds to 15Be being unbound by 0.45 MeV more then 16Be thus significantly hindering the sequential two-neutron decay of 16Be to 14Be through this state.

Ion Competition In Condensed Dna Arrays In The Attractive Regime, Xiangyun Qiu, John Giannini, Steven C. Howell, Qi Xia, Fuyou Ke, Kurt Andresen

Physics and Astronomy Faculty Publications

Physical origin of DNA condensation by multivalent cations remains unsettled. Here, we report quantitative studies of how one DNA-condensing ion (Cobalt³⁺ Hexammine, or Co³⁺Hex) and one nonDNA-condensing ion (Mg²⁺) compete within the interstitial space in spontaneously condensed DNA arrays. As the ion concentrations in the bath solution are systematically varied, the ion contents and DNA-DNA spacings of the DNA arrays are determined by atomic emission spectroscopy and x-ray diffraction, respectively. To gain quantitative insights, we first compare the experimentally determined ion contents with predictions from exact numerical calculations based on nonlinear Poisson-Boltzmann equations. Such calculations …

Elucidating Internucleosome Interactions And The Roles Of Histone Tails, Steven C. Howell, Kurt Andresen, Isabel Jimenez-Useche, Chongli Yuan, Xiangyun Qiu

Physics and Astronomy Faculty Publications

The nucleosome is the first level of genome organization and regulation in eukaryotes where negatively charged DNA is wrapped around largely positively charged histone proteins. Interaction between nucleosomes is dominated by electrostatics at long range and guided by specific contacts at short range, particularly involving their flexible histone tails. We have thus quantified how internucleosome interactions are modulated by salts (KCl, MgCl₂) and histone tail deletions (H3, H4 N-terminal), using small-angle x-ray scattering and theoretical modeling. We found that measured effective charges at low salts are ∼1/5th of the theoretically predicted renormalized charges and that H4 tail deletion …

Indigenous Film Festivals As Eco-Testimonial Encounter: The 2011 Native Film + Video Festival, Salma Monani

Environmental Studies Faculty Publications

In struggles for political and cultural recognition many Indigenous groups employ visual media to make their concerns heard. Amongst these various channels for media activism are Indigenous film festivals which, in the words of festival coordinator Amalia Cόrdova, work to convey ‘a sense of solidarity with Indigenous struggles’. Cόrdova’s essay on Indigenous film festivals appears in the collection Film Festivals and Activism (2012). In the introduction to the collection co-editor Leshu Torchin writes about activist festivals as testimonial encounters or fields of witnessing where the films offer testimony and the audiences serve as witnessing publics, ‘viewers [who] take responsibility …

Fearless: Kevin Lugo, Kevin B. Lugo

SURGE

This summer, recent graduate Kevin Lugo will bike over 4,000 miles across the country to benefit the Ulman Cancer Fund for Young Adults. His choice to bike for seventy days from Baltimore to Seattle makes him fearless! His goal is to raise $7,476 for the organization, and he reached that goal last night (although more donations are always welcome in support of fighting cancer)! Kevin explains that when he studied abroad in Denmark in the fall of 2011, he “fell in love with sustainable transportation, especially cycling.” Not only does his fearless endeavor raise money to fight cancer, but he …

Coble And Eisenhart: Two Gettysburgians Who Led Mathematics, Darren B. Glass

Math Faculty Publications

In 1895, there were 134 students at Gettysburg College, which was then called Pennsylvania College. Of these students, two of them went on to become president of the American Mathematical Society. In this article, we look at the lives of these two men, Arthur Coble and Luther Eisenhart, and their contributions to mathematics and higher education, as well as look at what mathematics was like at Gettysburg at the end of the nineteenth century.

Fearless: Painted Turtle Farm, Center For Public Service

SURGE

For the last seven years, the student-run organic farm has provided vegetables that were utilized both at Servo, the Campus Kitchen at Gettysburg College, and the food pantry to create meals that are both healthy and locally grown, providing sustainable and environmentally sound alternatives to other sources of herbs and vegetables. [excerpt]

Fearless: Mike Altman, Michael A. Altman

SURGE

After participating in the 2011 Heston Internship in Uganda working in a community on clean water projects, Mike gained a new interest in Global Health. His interest grew and a few months ago he started an internship with charity: water, an organization working to bring access to clean water throughout the world in a way that attempts to break the traditional donation model. At charity: water, Mike is part of a greater group that is working to more closely connect people to specific water projects through financial transparency and innovative fundraising campaigns. [excerpt]

Fearless: Steph Adamczak, Stephanie K. Adamczak

SURGE

Steph Adamczak ’15 has been shaking things up on campus by having some fearless conversations about the current investments Gettysburg College is making in fossil fuels. Steph hopes that by opening these important conversations, the college will consider divesting from these specific investments, especially with increased support from the Gettysburg College student body. [excerpt]

The Status Of A Pa Endangered Bird- The Upland Sandpiper, Paul A. Di Salvo, Kalley S. Hansel, Jessica L. Zupancic, Andrew M. Wilson

Student Publications

The upland sandpiper (Bartramia Longuardia) has experienced a steep population decline in the northeastern U.S. since the mid-20^th Century. In Pennsylvania it was found in less than 0.5% of atlas blocks during the Second Atlas of Breeding Birds in Pennsylvania project (2^nd PBBA; 2004-09) and breeding was confirmed at only two locations. Due to continued declines and a small population size, the upland sandpiper was listed as PA endangered in 2012. During May 2012 the areas around 15 2^nd PBBA upland sandpiper sightings were resurveyed by Gettysburg College students and volunteer birdwatchers. The aim was …

Equilibrating Temperaturelike Variables In Jammed Granular Subsystems, James G. Puckett, Karen E. Daniels

Physics and Astronomy Faculty Publications

Although jammed granular systems are athermal, several thermodynamiclike descriptions have been proposed which make quantitative predictions about the distribution of volume and stress within a system and provide a corresponding temperaturelike variable. We perform experiments with an apparatus designed to generate a large number of independent, jammed, two-dimensional configurations. Each configuration consists of a single layer of photoelastic disks supported by a gentle layer of air. New configurations are generated by cyclically dilating, mixing, and then recompacting the system through a series of boundary displacements. Within each configuration, a bath of particles surrounds a smaller subsystem of particles with a …

Environmental Film Festivals: Beginning Explorations At The Intersections Of Film Festival Studies And Ecocritical Studies, Salma Monani

Environmental Studies Faculty Publications

Drawing from the burgeoning field of film festival studies and its engagement with public sphere theory, I examine environmental film festivals to suggest that their festival terrain is bounded by three end-member festival types, that of the official public sphere, the alternative public sphere, and the corporate or trade-show sphere. Few environmental festivals fall neatly into a single end-member category. Analyzing how they construct their identities suggests the complex ways in which these festivals work to negotiate their presence in a heterogeneous environmental and media landscape and makes room for continued attention to these unique sites of ecocinema engagement.

Imaginenative 2012: Ecocinema And The Indigenous Film Festival, Salma Monani, Miranda Brady

Environmental Studies Faculty Publications

Much scholarship points to how ecological concerns are never far from Indigenous struggles for political sovereignty and public participation. In this paper we turn to the Indigenous film festival as a relatively understudied yet rich site to explore such ecological concerns. Specifically, we highlight the ImagineNATIVE 2012 film festival based in Toronto, Canada.

Solitary Wave And Shock Wave Solutions Of The Variants Of Boussinesq Equations, Houria Triki, Abhinandan Chowdhury, Anjan Biswas

Math Faculty Publications

This paper obtains the solitary wave as well as the shock wave solutions of the variants of the Boussinesq equations in both (1+1) and (1+2) dimensions. The domain restrictions are also identified in the process.

A State-Dependent Delay Equation With Negative Feedback And ‘Mildly Unstable’ Rapidly Oscillating Periodic Solutions, Benjamin B. Kennedy

Math Faculty Publications

We consider state-dependent delay equations of the form x′(t)=f(x(t−d(x(t)))) where d is smooth and f is smooth, bounded, nonincreasing, and satisfies the negative feedback condition xf(x)x≠0. We identify a special family of such equations each of which has a ``rapidly oscillating" periodic solution p. The initial segment p0 of p is the fixed point of a return map R that is differentiable in an appropriate setting.

We show that, although all the periodic solutions p we consider are unstable, the stability can be made arbitrarily mild in the sense that, given ϵ>0, we can choose f and d such …

Pointless Hyperelliptic Curves, Ryan P. Becker, Darren B. Glass

Math Faculty Publications

In this paper we consider the question of whether there exists a hyperelliptic curve of genus g which is defined over but has no rational points over for various pairs . As an example of such a result, we show that if p is a prime such that is also prime then there will be pointless hyperelliptic curves over of every genus.