Showing 2731 - 2740 of 5831 Items
The role of adjuvant in mediating antigen structure and stability
Date: 2012-01-01
Creator: Latoya Jones Braun, Aimee M. Eldridge, Jessica Cummiskey, Kelly K. Arthur, Deborah S., Wuttke
Access: Open access
- The purpose of this study was to probe the fate of a model antigen, a cysteine-free mutant of bacteriophage T4 lysozyme, to the level of fine structural detail, as a consequence of its interaction with an aluminum (Al)-containing adjuvant. Fluorescence spectroscopy and differential scanning calorimetry were used to compare the thermal stability of the protein in solution versus adsorbed onto an Al-containing adjuvant. Differences in accessible hydrophobic surface areas were investigated using an extrinsic fluorescence probe, 8-Anilino-1-naphthalenesulfonic acid (ANS). As has been observed with other model antigens, the apparent thermal stability of the protein decreased following adsorption onto the adjuvant. ANS spectra suggested that adsorption onto the adjuvant caused an increase in exposure of hydrophobic regions of the protein. Electrostatic interactions drove the adsorption, and disruption of these interactions with high ionic strength buffers facilitated the collection of two-dimensional 15N heteronuclear single quantum coherence nuclear magnetic resonance data of protein released from the adjuvant. Although the altered stability of the adsorbed protein suggested changes to the protein's structure, the fine structure of the desorbed protein was nearly identical to the protein's structure in the adjuvant-free formulation. Thus, the adjuvant-induced changes to the protein that were responsible for the reduced thermal stability were not observed upon desorption. © 2011 Wiley Periodicals, Inc.
Measurement of the branching fraction for γ (1S) → τ+τ-
Date: 1994-12-01
Creator: D. Cinabro, T. Liu, M. Saulnier, R. Wilson, H., Yamamoto, T. Bergfeld, B. I. Eisenstein, G. Gollin, B. Ong, M. Palmer, M. Selen, J. J. Thaler, K. W. Edwards, M. Ogg, A. Bellerive, D. I. Britton, E. R.F. Hyatt, D. B. MacFarlane, P. M. Patel, B. Spaan, A. J. Sadoff, R. Ammar, P. Baringer, A. Bean, D. Besson, D. Coppage, N. Copty, R. Davis, N. Hancock, M. Kelly, S. Kotov
Access: Open access
- We have studied the leptonic decay of the γ (1S) resonance into tau pairs using the CLEO II detector. A clean sample of tau pair events is identified via events containing two charged particles where exactly one of the particles is an identified electron. We find B(γ(1S) → τ+τ-) = (2.61±0.12-0.13+0.09)%. The result is consistent with expectations from lepton universality. © 1994.
Determining hilbert modular forms by central values of rankin-selberg convolutions: The level aspect
Date: 2017-12-01
Creator: Alia Hamieh, Naomi Tanabe
Access: Open access
- In this paper, we prove that a primitive Hilbert cusp form g is uniquely determined by the central values of the Rankin-Selberg L-functions (formula presented), where f runs through all primitive Hilbert cusp forms of level q for infinitely many prime ideals q. This result is a generalization of the work of Luo (1999) to the setting of totally real number fields.
Assembly of the precursor and processed light-harvesting chlorophyll a/b protein of Lemna into the light-harvesting complex II of barley etiochloroplasts.
Date: 1986-01-01
Creator: P. R. Chitnis, E. Harel, B. D. Kohorn, E. M. Tobin, J. P., Thornber
Access: Open access
- When the in vitro synthesized precursor of a light-harvesting chlorophyll a/b binding protein (LHCP) from Lemna gibba is imported into barley etiochloroplasts, it is processed to a single form. Both the processed form and the precursor are found in the thylakoid membranes, assembled into the light-harvesting complex of photosystem II. Neither form can be detected in the stromal fraction. The relative amounts of precursor and processed forms observed in the thylakoids are dependent on the developmental stage of the plastids used for uptake. The precursor as well as the processed form can also be detected in thylakoids of greening maize plastids used in similar uptake experiments. This detection of a precursor in the thylakoids, which has not been previously reported, could be a result of using rapidly developing plastids and/or using an heterologous system. Our results demonstrate that the extent of processing of LHCP precursor is not a prerequisite for its inclusion in the complex. They are also consistent with the possibility that the processing step can occur after insertion of the protein into the thylakoid membrane.
Animal-to-animal variability in the phasing of the crustacean cardiac motor pattern: An experimental and computational analysis
Date: 2013-01-01
Creator: Alex H. Williams, Molly A. Kwiatkowski, Adam L. Mortimer, Eve Marder, Mary Lou, Zeeman, Patsy S. Dickinson
Access: Open access
- The cardiac ganglion (CG) of Homarus americanus is a central pattern generator that consists of two oscillatory groups of neurons: "small cells" (SCs) and "large cells" (LCs). We have shown that SCs and LCs begin their bursts nearly simultaneously but end their bursts at variable phases. This variability contrasts with many other central pattern generator systems in which phase is well maintained. To determine both the consequences of this variability and how CG phasing is controlled, we modeled the CG as a pair of Morris-Lecar oscillators coupled by electrical and excitatory synapses and constructed a database of 15,000 simulated networks using random parameter sets. These simulations, like our experimental results, displayed variable phase relationships, with the bursts beginning together but ending at variable phases. The model suggests that the variable phasing of the pattern has important implications for the functional role of the excitatory synapses. In networks in which the two oscillators had similar duty cycles, the excitatory coupling functioned to increase cycle frequency. In networks with disparate duty cycles, it functioned to decrease network frequency. Overall, we suggest that the phasing of the CG may vary without compromising appropriate motor output and that this variability may critically determine how the network behaves in response to manipulations. © 2013 the American Physiological Society.
Third-generation effects on fermion mass predictions in supersymmetric grand unified theories
Date: 1993-01-01
Creator: Stephen G. Naculich
Access: Open access
- Relations among fermion masses and mixing angles at the scale of grand unification are modified at lower energies by renormalization group running induced by gauge and Yukawa couplings. In super-symmetric theories, the b quark and lepton Yukawa couplings, as well as the t quark coupling, may cause significant running if tan, the ratio of Higgs field expectation values, is large. We present approximate analytic expressions for the scaling factors for fermion masses and CKM matrix elements induced by all three third generation Yukawa couplings. We then determine how running caused by the third generation of fermions affects the predictions arising from three possible forms for the Yukawa coupling matrices at the GUT scale: the Georgi-Jarlskog, Giudice, and Fritzsch textures. © 1993 The American Physical Society.
Quantum kinks: Solitons at strong coupling
Date: 1992-01-01
Creator: Stephen G. Naculich
Access: Open access
- We examine solitons in theories with heavy fermions. These "quantum" solitons differ dramatically from semiclassical (perturbative) solitons because fermion loop effects are important when the Yukawa coupling is strong. We focus on kinks in a (1 + 1)-dimensional 4 theory coupled to fermions; a large-N expansion is employed to treat the Yukawa coupling g nonperturbatively. A local expression for the fermion vacuum energy is derived using the WKB approximation for the Dirac eigenvalues. We find that fermion loop corrections increase the energy of the kink and (for large g) decrease its size. For large g, the energy of the quantum kink is proportional to g, and its size scales as 1g, unlike the classical kink; we argue that these features are generic to quantum solitons in theories with strong Yukawa couplings. We also discuss the possible instability of fermions to solitons. © 1992 The American Physical Society.
Digital Authoritarianism in China and Russia: A Comparative Study
Date: 2020-01-01
Creator: Laura H.C. Howells
Access: Open access
- Digital authoritarianism is on the rise around the world and threatens the data privacy and rights of both domestic and international Internet users. However, scholarship on digital authoritarianism remains limited in scope and case study selection. This study contributes a new, more comprehensive analytical framework for the study of Internet governance and applies it to the case studies of China and Russia. Special attention is paid to the still understudied Russian Internet governance model. After thorough literature review and novel data collection and analysis, this paper identifies relative centralization of network infrastructure and the extent and pace of change in governance as the most notable differences between the two models. These points of divergence may be explained by two theories; the varieties of authoritarianism hypothesis posits that different political systems face persistent and unique constraints to governance of the digital realm. The development trajectory theory argues that each country’s technological development path foreshadows the systems’ capacity for and extent of governance. This study is among the first to distinguish between Internet governance strategies of authoritarian regimes.
Phononic rogue waves
Date: 2018-09-13
Creator: E. G. Charalampidis, J. Lee, P. G. Kevrekidis, C. Chong
Access: Open access
- We present a theoretical study of extreme events occurring in phononic lattices. In particular, we focus on the formation of rogue or freak waves, which are characterized by their localization in both spatial and temporal domains. We consider two examples. The first one is the prototypical nonlinear mass-spring system in the form of a homogeneous Fermi-Pasta-Ulam-Tsingou (FPUT) lattice with a polynomial potential. By deriving an approximation based on the nonlinear Schrödinger (NLS) equation, we are able to initialize the FPUT model using a suitably transformed Peregrine soliton solution of the NLS equation, obtaining dynamics that resembles a rogue wave on the FPUT lattice. We also show that Gaussian initial data can lead to dynamics featuring a rogue wave for sufficiently wide Gaussians. The second example is a diatomic granular crystal exhibiting rogue-wave-like dynamics, which we also obtain through an NLS reduction and numerical simulations. The granular crystal (a chain of particles that interact elastically) is a widely studied system that lends itself to experimental studies. This study serves to illustrate the potential of such dynamical lattices towards the experimental observation of acoustic rogue waves.